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Sample records for anodic niobium oxides

  1. Influence of electropolishing and anodic oxidation on morphology, chemical composition and corrosion resistance of niobium

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    Sowa, Maciej; Greń, Katarzyna [Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego Street 6, 44-100 Gliwice (Poland); Kukharenko, Andrey I. [Institute of Metal Physics, Russian Academy of Sciences-Ural Division, S. Kovalevskoi Street 18, 620990 Yekaterinburg (Russian Federation); Ural Federal University, Mira Street 19, 620002 Yekaterinburg, Mira str. 19 (Russian Federation); Korotin, Danila M. [Institute of Metal Physics, Russian Academy of Sciences-Ural Division, S. Kovalevskoi Street 18, 620990 Yekaterinburg (Russian Federation); Michalska, Joanna [Faculty of Materials Engineering and Metallurgy, Silesian University of Technology, Krasińskiego Street 8, 40-019 Katowice (Poland); Szyk-Warszyńska, Lilianna; Mosiałek, Michał [Jerzy Haber Institute of Catalysis and Surface Chemistry PAS, Niezapominajek Street 8, 30-239 Kraków (Poland); Żak, Jerzy [Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego Street 6, 44-100 Gliwice (Poland); Pamuła, Elżbieta [AGH University of Science and Technology, Faculty of Materials Science and Ceramics, Mickiewicza Avenue 30, 30-059 Kraków (Poland); Kurmaev, Ernst Z. [Institute of Metal Physics, Russian Academy of Sciences-Ural Division, S. Kovalevskoi Street 18, 620990 Yekaterinburg (Russian Federation); Cholakh, Seif O. [Ural Federal University, Mira Street 19, 620002 Yekaterinburg, Mira str. 19 (Russian Federation); Simka, Wojciech, E-mail: wojciech.simka@polsl.pl [Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego Street 6, 44-100 Gliwice (Poland)

    2014-09-01

    The work presents results of the studies performed on electropolishing of pure niobium in a bath that contained: sulphuric acid, hydrofluoric acid, ethylene glycol and acetanilide. After the electropolishing, the specimens were subjected to anodic passivation in a 1 mol dm{sup −3} phosphoric acid solution at various voltages. The surface morphology, thickness, roughness and chemical composition of the resulting oxide layers were analysed. Thusly prepared niobium samples were additionally investigated in terms of their corrosion resistance in Ringer's solution. The electropolished niobium surface was determined to be smooth and lustrous. The anodisation led to the growth of barrier-like oxide layers, which were enriched in phosphorus species. - Highlights: • Pure niobium was electropolished and subsequently anodised in a H{sub 3}PO{sub 4} solution. • Phosphorus was successfully introduced into the oxide layers after the treatment. • Corrosion resistance of niobium in Ringer's solution was improved after anodising.

  2. Аnodic formation of nanoporous crystalline niobium oxide

    Directory of Open Access Journals (Sweden)

    LEONID SKATKOV

    2014-05-01

    Full Text Available The research results of anodic deposition of crystalline niobium oxide are presented in this work. The factors that have an impact on crystalline phase nucleation and its primary growth are revealed. Dependence of morphology and properties of nanoporous niobium oxide on modes of its formation is shown.

  3. Anodic oxidation

    CERN Document Server

    Ross, Sidney D; Rudd, Eric J; Blomquist, Alfred T; Wasserman, Harry H

    2013-01-01

    Anodic Oxidation covers the application of the concept, principles, and methods of electrochemistry to organic reactions. This book is composed of two parts encompassing 12 chapters that consider the mechanism of anodic oxidation. Part I surveys the theory and methods of electrochemistry as applied to organic reactions. These parts also present the mathematical equations to describe the kinetics of electrode reactions using both polarographic and steady-state conditions. Part II examines the anodic oxidation of organic substrates by the functional group initially attacked. This part particular

  4. Fabrication of superhydrophobic niobium pentoxide thin films by anodization

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Bong-Yong [Future Convergence Ceramic Division, Korea Institute of Ceramic Engineering and Technology, Seoul 153-801 (Korea, Republic of); Jung, Eun-Hye [Future Convergence Ceramic Division, Korea Institute of Ceramic Engineering and Technology, Seoul 153-801 (Korea, Republic of); Department of Chemical Engineering, Inha University, Incheon 402-024 (Korea, Republic of); Kim, Jin-Ho, E-mail: jhkim@kicet.re.kr [Electronic and Optic Materials Division, Korea Institute of Ceramic Engineering and Technology, Seoul 153-801 (Korea, Republic of)

    2014-07-01

    We report a simple method to fabricate a niobium oxide film with a lotus-like micro–nano surface structure. Self-assembled niobium pentoxide (Nb{sub 2}O{sub 5}) films with superhydrophobic property were fabricated by an anodization and a hydrophobic treatment. This process has several advantages such as low cost, simplicity and easy coverage of a large area. The surface of fabricated Nb{sub 2}O{sub 5} film was changed from hydrophilic to superhydrophobic surface by a treatment using fluoroaldyltrimethoxysilane (FAS) solution. This value is considered to be the lowest surface free energy of any solid, based on the alignment of -CF{sub 3} groups on the surface. In particular, among FAS coated surfaces, the micro–nano complex cone structured Nb{sub 2}O{sub 5} film showed the highest water-repellent property with a static contact angle of ca. 162°. This study gives promising routes from biomimetic superhydrophobic surfaces.

  5. Anode properties of magnesium hydride catalyzed with niobium oxide for an all solid-state lithium-ion battery.

    Science.gov (United States)

    Ikeda, Suguru; Ichikawa, Takayuki; Kawahito, Koji; Hirabayashi, Kazuhiro; Miyaoka, Hiroki; Kojima, Yoshitsugu

    2013-08-18

    The anode properties of pristine MgH2 and MgH2 catalyzed with Nb2O5 have been investigated for an all solid-state lithium-ion battery. The catalytic effect stabilizes the plateau voltage as a result of kinetic improvement of the hydrogen transfer from the Mg phase to the Li phase.

  6. Niobium-doped titanium oxide anode and ionic liquid electrolyte for a safe sodium-ion battery

    Science.gov (United States)

    Usui, Hiroyuki; Domi, Yasuhiro; Shimizu, Masahiro; Imoto, Akinobu; Yamaguchi, Kazuki; Sakaguchi, Hiroki

    2016-10-01

    The anode properties of Nb-doped rutile TiO2 electrodes were investigated in an ionic liquid electrolyte comprised of N-methyl-N-propylpyrrolidinium cation and bis(fluorosulfonyl)amide anion for use in a safe Na-ion battery. Although the electrolyte's conductivity was lower than that of a conventional organic electrolyte at 30 °C, it showed high conductivity comparable to that of the organic electrolyte at 60 °C. The Nb-doped TiO2 electrode showed excellent cyclability in the ionic liquid electrolyte at 60 °C: a high capacity retention of 97% was observed even at the 350th cycle, which is comparable to value in the organic electrolyte (91%). In a non-flammability test in a closed system, no ignition was observed with the ionic liquid electrolyte even at 300 °C. These results indicate that combination of a Nb-doped TiO2 anode and ionic liquid electrolyte gives not only an excellent cyclability but also high safety for a Na-ion battery operating at a temperature below the sodium's melting point of 98 °C.

  7. Electron beam niobium oxide powder deposition

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, D.S. [Centro Tecnico Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil); Nono, M.C.A. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Silva, C.R.M. [Universidade de Brasilia (UnB), Brasilia, DF (Brazil)

    2009-07-01

    Full text: Zirconium oxide applied by Electron Beam –Physical Vapor Deposition can produce high quality coatings for high temperature blades. In this work niobium, yttrium and zirconium oxides were applied on metallic substrates, using EB-PVD, aiming thermal conductivity reduction. Coating characterization has been performed by X-ray diffractometry and scanning electron microscopy. X-ray diffractometry shows only tetragonal phase for the composition range evaluated, with tetragonality increase for higher niobium oxide amounts. Higher amounts of niobium promote reduction of ceramic coating theoretical density and thermal conductivity. (author)

  8. Electrical analysis of niobium oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Graça, M.P.F., E-mail: mpfg@ua.pt [I3N & Physics Department, Aveiro University, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Saraiva, M. [I3N & Physics Department, Aveiro University, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Freire, F.N.A. [Mechanics Engineering Department, Ceará Federal University, Fortaleza (Brazil); Valente, M.A.; Costa, L.C. [I3N & Physics Department, Aveiro University, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal)

    2015-06-30

    In this work, a series of niobium oxide thin films was deposited by reactive magnetron sputtering. The total pressure of Ar/O{sub 2} was kept constant at 1 Pa, while the O{sub 2} partial pressure was varied up to 0.2 Pa. The depositions were performed in a grounded and non-intentionally heated substrate, resulting in as-deposited amorphous thin films. Raman spectroscopy confirmed the absence of crystallinity. Dielectric measurements as a function of frequency (40 Hz–110 MHz) and temperature (100 K–360 K) were performed. The dielectric constant for the film samples with thickness (d) lower than 650 nm decreases with the decrease of d. The same behaviour was observed for the conductivity. These results show a dependence of the dielectric permittivity with the thin film thickness. The electrical behaviour was also related with the oxygen partial pressure, whose increment promotes an increase of the Nb{sub 2}O{sub 5} stoichiometry units. - Highlights: • Niobium oxide thin films were deposited by reactive magnetron sputtering. • XRD showed a phase change with the increase of the P(O{sub 2}). • Raman showed that increasing P(O{sub 2}), Nb{sub 2}O{sub 5} amorphous increases. • Conductivity tends to decrease with the increase of P(O{sub 2}). • Dielectric analysis indicates the inexistence of preferential grow direction.

  9. Oxidation Behavior of Binary Niobium Alloys

    Science.gov (United States)

    Barrett, Charles A.; Corey, James L.

    1960-01-01

    This investigation concludes a study to determine the effects of up to 25 atomic percent of 55 alloying additions on the oxidation characteristics of niobium. The alloys were evaluated by oxidizing in an air atmosphere for 4 hours at 1000 C and 2 hours at 1200 C. Titanium and chromium improved oxidation resistance at both evaluation conditions. Vanadium and aluminum improved oxidation resistance at 1000 C, even though the V scale tended to liquefy and the Al specimens became brittle and the scale powdery. Copper, cobalt, iron, and iridium improved oxidation resistance at 1200 C. Other investigations report tungsten and molybdenum are protective up to about 1000 C, and tantalum at 1100 C. The most important factor influencing the rate of oxidation was the ion size of the alloy additions. Ions slightly smaller than the Nb(5+) ion are soluble in the oxide lattice and tend to lower the compressive stresses in the bulk scale that lead to cracking. The solubility of the alloying addition also depends on the valence to some extent. All of the elements mentioned that improve the oxidation resistance of Nb fit this size criterion with the possible exception of Al, whose extremely small size in large concentrations would probably lead to the formation of a powdery scale. Maintenance of a crack-free bulk scale for as long as possible may contribute to the formation of a dark subscale that ultimately is rate- controlling in the oxidation process. The platinum-group metals, especially Ir, appear to protect by entrapment of the finely dispersed alloying element by the incoming Nb2O5 metal-oxide interface. This inert metallic Ir when alloyed in a sufficient amount with Yb appears to give a ductile phase dispersed in the brittle oxide. This scale would then flow more easily to relieve the large compressive stresses to delay cracking. Complex oxide formation (which both Ti and Zr tend to initiate) and valence effects, which probably change the vacancy concentration in the scale

  10. Niobium-doped strontium titanates as SOFC anodes

    DEFF Research Database (Denmark)

    Blennow Tullmar, Peter; Kammer Hansen, Kent; Wallenberg, L. Reine;

    2008-01-01

    been synthesized with a recently developed modified glycine-nitrate process. The synthesized powders have been calcined and sintered in air or in 9% H(2) / N(2) between 800 - 1400 degrees C. After calcination the samples were single phase Nb-doped strontium titanate with grain sizes of less than 100 nm...... in diameter on average. The phase purity, defect structure, and microstructure of the materials have been analyzed with SEM, XRD, and TGA. The electrical conductivity of the Nb-doped titanate decreased with increasing temperature and showed a phonon scattering conduction mechanism with sigma > 120 S...... ability of the Nb-doped titanates to be used as a part of a SOFC anode. However, the catalytic activity of the materials was not sufficient and it needs to be improved if titanate based materials are to be realized as constituents in SOFC anodes....

  11. Stress dependent oxidation of sputtered niobium and effects on superconductivity

    Science.gov (United States)

    David Henry, M.; Wolfley, Steve; Monson, Todd; Clark, Blythe G.; Shaner, Eric; Jarecki, Robert

    2014-02-01

    We report on the suppression of room temperature oxidation of DC sputtered niobium films and the effects upon the superconductive transition temperature, Tc. Niobium was sputter-deposited on silicon dioxide coated 150 mm wafers and permitted to oxidize at room temperature and pressure for up to two years. Resistivity and stress measurements indicate that tensile films greater than 400 MPa resist bulk oxidation with measurements using transmission electron microscope, electron dispersive X-ray spectroscopy, x-ray photoelectric spectroscopy, and secondary ion mass spectrometry confirming this result. Although a surface oxide, Nb2O5, consumed the top 6-10 nm, we measure less than 1 at. % oxygen and nitrogen in the bulk of the films after the oxidation period. Tc measurements using a SQUID magnetometer indicate that the tensile films maintained a Tc approaching the dirty superconductive limit of 8.4 K after two years of oxidation while maintaining room temperature sheet resistance. This work demonstrates that control over niobium film stress during deposition can prevent bulk oxidation by limiting the vertical grain boundaries ability to oxidize, prolonging the superconductive properties of sputtered niobium when exposed to atmosphere.

  12. Synthesis and Characterization of Niobium-doped TiO2 Nanotube Arrays by Anodization of Ti-20Nb Alloys

    Institute of Scientific and Technical Information of China (English)

    Zhengchao Xu; Qi Li; Shian Gao; Jianku Shangi

    2012-01-01

    Well crystallized niobium-doped TiO; nanotube arrays (TiNbO-NT) were successfully synthesized via the anodization of titanium/niobium alloy sheets, followed with a heat treatment at 550 ℃ for 2 h. Morphology analysis results demonstrated that both the titanium/niobium alloy microstructure and the dissolution strength of electrolyte played major roles in the formation of nanotube structure. A single-phase microstructure was more favorable to the formation of uniform nanotube arrays, while modulating the dissolution strength of electrolyte was required to obtain nanotube arrays from the alloys with multi-phase microstructures. X-ray diffraction (XRD) and X-ray photoelectron (XPS) analysis results clearly demonstrated that niobium dopants (Nb^5+) were successfully doped into TiO2 anatase lattice by substituting Ti^4+ in this approach.

  13. Plasma Niobium Surface Alloying of Pure Titanium and its Oxidation at 900 ℃

    Institute of Scientific and Technical Information of China (English)

    WANG Wen-bo; ZHONG Xu; HE Zhi-yong; WANG Zhen-xia; ZHANG Ping-ze

    2007-01-01

    A niobium-modified layer on pure titanium surface was obtained by means of double glow plasma surface alloying technique. The modified layer was uniform, continuous, compact and well adhered to the substrate. The niobium composition in the modified layer decreased gradually from the surface to the substrate. The oxidation behavior of the niobium-modified layer was investigated and compared with the untreated surface at 900 ℃ for 100 h. Characterization of the layers was performed using X-ray diffraction and scanning electron microscope, respectively. The test results show that the oxidation behavior of pure titanium was improved by niobium alloying process. Niobium has a positive influence on the oxidation resistance.

  14. Evaluation of niobium dimethylamino-ethoxide for chemical vapour deposition of niobium oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Dabirian, Ali [Laboratory for Photonic Materials and Characterization, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 17, 1015 Lausanne (Switzerland); Kuzminykh, Yury, E-mail: yury.kuzminykh@empa.ch [Laboratory for Photonic Materials and Characterization, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 17, 1015 Lausanne (Switzerland); Laboratory for Advanced Materials Processing, Empa, Swiss Federal Laboratories for Materials Science and Technology, Feuerwerkerstrasse 39, 3602 Thun (Switzerland); Wagner, Estelle; Benvenuti, Giacomo [3D-Oxides, 70 Rue G. Eiffel Technoparc, 01630 St Genis Pouilly (France); ABCD Technology, 12 route de Champ-Colin, 1260 Nyon (Switzerland); Rushworth, Simon [Tyndall National Institute, Lee Maltings, Dyke Parade, Cork (Ireland); Hoffmann, Patrik, E-mail: patrik.hoffmann@empa.ch [Laboratory for Photonic Materials and Characterization, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 17, 1015 Lausanne (Switzerland); Laboratory for Advanced Materials Processing, Empa, Swiss Federal Laboratories for Materials Science and Technology, Feuerwerkerstrasse 39, 3602 Thun (Switzerland)

    2014-11-28

    Chemical vapour deposition (CVD) processes depend on the availability of suitable precursors. Precursors that deliver a stable vapour pressure are favourable in classical CVD processes, as they ensure process reproducibility. In high vacuum CVD (HV-CVD) process vapour pressure stability of the precursor is of particular importance, since no carrier gas assisted transport can be used. The dimeric Nb{sub 2}(OEt){sub 10} does not fulfil this requirement since it partially dissociates upon heating. Dimethylamino functionalization of an ethoxy ligand of Nb(OEt){sub 5} acts as an octahedral field completing entity and leads to Nb(OEt){sub 4}(dmae). We show that Nb(OEt){sub 4}(dmae) evaporates as monomeric molecule and ensures a stable vapour pressure and, consequently, stable flow. A set of HV-CVD experiments were conducted using this precursor by projecting a graded molecular beam of the precursor onto the substrate at deposition temperatures from 320 °C to 650 °C. Film growth rates ranging from 8 nm·h{sup −1} to values larger than 400 nm·h{sup −1} can be obtained in this system illustrating the high level of control available over the film growth process. Classical CVD limiting conditions along with the recently reported adsorption–reaction limited conditions are observed and the chemical composition, and microstructural and optical properties of the films are related to the corresponding growth regime. Nb(OEt){sub 4}(dmae) provides a large process window of deposition temperatures and precursor fluxes over which carbon-free and polycrystalline niobium oxide films with growth rates proportional to precursor flux are obtained. This feature makes Nb(OEt){sub 4}(dmae) an attractive precursor for combinatorial CVD of niobium containing complex oxide films that are finding an increasing interest in photonics and photoelectrochemical water splitting applications. The adsorption–reaction limited conditions provide extremely small growth rates comparable to an

  15. Novel borothermal process for the synthesis of nanocrystalline oxides and borides of niobium.

    Science.gov (United States)

    Jha, Menaka; Ramanujachary, Kandalam V; Lofland, Samuel E; Gupta, Govind; Ganguli, Ashok K

    2011-08-21

    A new process has been developed for the synthesis of nanocrystalline niobium oxide and niobium diboride using an amorphous niobium precursor obtained via the solvothermal route. On varying the ratio of niobium precursor to boron and the reaction conditions, pure phases of nanostructured niobium oxides (Nb(2)O(5), NbO(2)), niobium diboride (NbB(2)) and core-shell nanostructures of NbB(2)@Nb(2)O(5) could be obtained at normal pressure and low temperature of 1300 °C compared to a temperature of 1650 °C normally used. The above borothermal process involves the in situ generation of B(2)O(2) to yield either oxide or diboride. The niobium oxides and borides have been characterized in detail by XRD, HRTEM and EDX studies. The core-shell structure has been investigated by XPS depth profiling, EFTEM and EELS (especially to characterize the presence of boron and the shell thickness). The niobium diboride nanorods (with high aspect ratio) show a superconducting transition with the T(c) of 6.4 K. In the core-shell of NbB(2)@Nb(2)O(5), the superconductivity of NbB(2) is masked by the niobium oxide shell and hence no superconductivity was observed. The above methodology has the benefits of realizing both oxides and borides of niobium in nanocrystalline form, in high purity and at much lower temperatures.

  16. THE INFLUENCE OF NIOBIUM ON THE ACIDITY AND STRUCTURE OF GAMMA-ALUMINA-SUPPORTED VANADIUM OXIDES

    Directory of Open Access Journals (Sweden)

    M.N.B. Sathler

    1998-06-01

    Full Text Available Gamma-alumina-supported niobium oxide was used as a support for vanadium oxides. The influence of the addition of niobium oxide was studied by looking for changes in the structure and acid-base character of superficial species. Vanadium oxide was deposited using the continuous adsorption method; niobium oxide was impregnated using the incipient wetness method. The catalysts were characterized by XPS, UV-visible and IR spectroscopy. Catalytic tests were performed using propane oxidation reaction at 400oC. For coverage below the monolayer, both vanadium and niobium oxides were observed in slightly condensed superficial species. The presence of vanadium oxide on the support was found to increase the Lewis acidity and create some Bronsted acidity. Higher catalytic activity and selectivity for propene were associated with vanadium oxides. The presence of niobium did not contribute to the modification of the chemical properties of superficial vanadium but did decrease the adsorption of vanadium on the alumina.

  17. High temperature oxidation resistance in titanium–niobium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tegner, B.E. [School of Physics, SUPA and CSEC, The University of Edinburgh, Edinburgh EH9 3JZ (United Kingdom); Zhu, L. [School of Physics, SUPA and CSEC, The University of Edinburgh, Edinburgh EH9 3JZ (United Kingdom); School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Siemers, C. [Technische Universitat Braunschweig, Institut fur Werkstoffe, Langer Kamp 8, 38106 Braunschweig (Germany); Saksl, K. [Slovak Academy of Sciences, Institute of Materials Research, Watsonova 47, 04353 Kosice (Slovakia); Ackland, G.J., E-mail: gjackland@ed.ac.uk [School of Physics, SUPA and CSEC, The University of Edinburgh, Edinburgh EH9 3JZ (United Kingdom)

    2015-09-15

    Highlights: • The conventional explanation for oxidation resistance is disproven, an alternative presented. • A generic analytic diffusion model for oxidation resistance is presented. • We develop a class of oxidation resistant niobium–titanium alloys. • Calculation, microscopy, spectroscopy and diffraction analysis of the alloys. • The theory is verified in oxidation tests. - Abstract: Titanium alloys are ideally suited for use as lightweight structural materials, but their use at high temperature is severely restricted by oxidation. Niobium is known to confer oxidation-resistance, and here we disprove the normal explanation, that Nb{sup 5+} ions trap oxygen vacancies. Using density functional theory calculation, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) we show that Nb is insoluble in TiO{sub 2}. In fact, the Ti–Nb surface has three-layer structure: the oxide itself, an additional Nb-depleted zone below the oxide and a deeper sublayer of enhanced Nb. Microfocussed X-ray diffraction also demonstrates recrystallization in the Nb-depleted zone. We interpret this using a dynamical model: slow Nb-diffusion leads to the build up of a Nb-rich sublayer, which in turn blocks oxygen diffusion. Nb effects contrast with vanadium, where faster diffusion prevents the build up of equivalent structures.

  18. Nanostructures Using Anodic Aluminum Oxide

    Science.gov (United States)

    Valmianski, Ilya; Monton, Carlos M.; Pereiro, Juan; Basaran, Ali C.; Schuller, Ivan K.

    2013-03-01

    We present two fabrication methods for asymmetric mesoscopic dot arrays over macroscopic areas using anodic aluminum oxide templates. In the first approach, metal is deposited at 45o to the template axis to partially close the pores and produce an elliptical shadow-mask. In the second approach, now underway, nanoimprint lithography on a polymer intermediary layer is followed by reactive ion etching to generate asymmetric pore seeds. Both these techniques are quantified by an analysis of the lateral morphology and lattice of the pores or dots using scanning electron microscopy and a newly developed MATLAB based code (available for free download at http://ischuller.ucsd.edu). The code automatically provides a segmentation of the measured area and the statistics of morphological properties such as area, diameter, and eccentricity, as well as the lattice properties such as number of nearest neighbors, and unbiased angular and radial two point correlation functions. Furthermore, novel user defined statistics can be easily obtained. We will additionally present several applications of these methods to superconducting, ferromagnetic, and organic nanostructures. This work is supported by AFOSR FA9550-10-1-0409

  19. Microfabrication of an anodic oxide film by anodizing laser-textured aluminium

    OpenAIRE

    2007-01-01

    A simple method for the fabrication of microstructures of an aluminium anodic oxide film (anodic alumina) by anodizing laser-textured aluminium is demonstrated. In the process, the aluminium substrate was first textured by a low power laser beam, and then the textured aluminium was subjected to anodizing, to develop a continuous, thick porous layer on the textured surface. Microstructures with a depth of a few to several tens of micrometres were fabricated successfully on the anodic oxide fil...

  20. Oxide anode materials for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Fergus, Jeffrey W. [Auburn University, Materials Research and Education Center, 275 Wilmore Laboratories, Auburn, AL 36849 (United States)

    2006-07-15

    A major advantage of solid oxide fuel cells (SOFCs) over polymer electrolyte membrane (PEM) fuel cells is their tolerance for the type and purity of fuel. This fuel flexibility is due in large part to the high operating temperature of SOFCs, but also relies on the selection and development of appropriate materials - particularly for the anode where the fuel reaction occurs. This paper reviews the oxide materials being investigated as alternatives to the most commonly used nickel-YSZ cermet anodes for SOFCs. The majority of these oxides form the perovskite structure, which provides good flexibility in doping for control of the transport properties. However, oxides that form other crystal structures, such as the cubic fluorite structure, have also shown promise for use as SOFC anodes. In this paper, oxides are compared primarily in terms of their transport properties, but other properties relative to SOFC anode performance are also discussed. (author)

  1. Optical Transmittance of Anodically Oxidized Aluminum Alloy

    Science.gov (United States)

    Saito, Mitsunori; Shiga, Yasunori; Miyagi, Mitsunobu; Wada, Kenji; Ono, Sachiko

    1995-06-01

    Optical transmittance and anisotropy of anodic oxide films that were made from pure aluminum and an aluminum alloy (A5052) were studied. The alloy oxide film exhibits an enhanced polarization function, particularly when anodization is carried out at a large current density. It was revealed by chemical analysis that the alloy oxide film contains a larger amount of unoxidized aluminum than the pure-aluminum oxide film. The polarization function can be elucidated by considering unoxidized aluminum particles that are arranged in the columnar structure of the alumina film. Electron microscope observation showed that many holes exist in the alloy oxide film, around which columnar cells are arranged irregularly. Such holes and irregular cell arrangement cause the increase in the amount of unoxidized aluminum, and consequently induces scattering loss.

  2. Synthesis, characterization, and catalytic application of ordered mesoporous carbon–niobium oxide composites

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Juan-Li; Gao, Shuang; Liu, Chun-Ling; Liu, Zhao-Tie; Dong, Wen-Sheng, E-mail: wsdong@snnu.edu.cn

    2014-11-15

    Graphical abstract: The ordered mesoporous carbon–niobium oxide composites have been synthesized by a multi-component co-assembly method associated with a carbonization process. - Highlights: • Ordered mesoporous carbon–niobium oxide composites were synthesized. • The content of Nb{sub 2}O{sub 5} in the composites could be tuned from 38 to 75%. • Niobium species were highly dispersed in amorphous carbon framework walls. • The composites exhibited good catalytic performance in the dehydration of fructose. - Abstract: Ordered mesoporous carbon–niobium oxide composites have been synthesized by a multi-component co-assembly method associated with a carbonization process using phenolic resol as carbon source, niobium chloride as precursor and amphiphilic triblock copolymer Pluronic F127 as template. The resulting materials were characterized using a combination of techniques including differential scanning calorimetry–thermogravimetric analysis, N{sub 2} physical adsorption, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results show that with increasing the content of Nb{sub 2}O{sub 5} from 38 to 75% the specific surface area decreases from 306.4 to 124.5 m{sup 2} g{sup −1}, while the ordered mesoporous structure is remained. Niobium species is well dispersed in the amorphous carbon framework. The mesoporous carbon–niobium oxide composites exhibit high catalytic activity in the dehydration of fructose to 5-hydroxymethylfurfural. A 100% conversion of fructose and a 76.5% selectivity of 5-hydroxymethylfurfural were obtained over the carbon–niobium oxide composite containing 75% Nb{sub 2}O{sub 5} under the investigated reaction conditions.

  3. Ellipsometric investigation of anodic zirconium oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Patrito, E.M.; Macagno, V.A. (Univ. Nacional de Cordoba, Cordoba (Argentina). Dept. de Fisicoquimica)

    1993-06-01

    The anodic oxidation of zirconium was studied by in situ ellipsometry together with capacity measurements. The oxides were grown under potentiodynamic, galvanostatic, and potentiostatic conditions up to final potentials of 100 V in 0.5M H[sub 2]SO[sub 4] solution. The refractive index of the oxides changes depending on the growth current. The films were slightly absorbing but their absorption coefficient was independent of the oxide growth conditions. Different methods of surface preparation including etching in hydrofluoric acid-based mixtures, electropolishing and mechanical polishing were used. The surfaces and oxides were characterized by SEM examination and XPS measurements. The surface pretreatment affects both the substrate and the oxide optical constants as well as the rate of oxide growth. The density and dielectric constant of the oxides were calculated performing simultaneous ellipsometric, coulometric, and capacity measurements.

  4. Fabrication of anodic aluminum oxide with incorporated chromate ions

    Science.gov (United States)

    Stępniowski, Wojciech J.; Norek, Małgorzata; Michalska-Domańska, Marta; Bombalska, Aneta; Nowak-Stępniowska, Agata; Kwaśny, Mirosław; Bojar, Zbigniew

    2012-10-01

    The anodization of aluminum in 0.3 M chromic acid is studied. The influence of operating conditions (like anodizing voltage and electrolyte's temperature) on the nanoporous anodic aluminum oxide geometry (including pore diameter, interpore distance, the oxide layer thickness and pores density) is thoroughly investigated. The results revealed typical correlations of the anodic alumina nanopore geometry with operating conditions, such as linear increase of pore diameter and interpore distance with anodizing voltage. The anodic aluminum oxide is characterized by a low pores arrangement, as determined by Fast Fourier transforms analyses of the FE-SEM images, which translates into a high concentration of oxygen vacancies. Moreover, an optimal experimental condition where chromate ions are being successfully incorporated into the anodic alumina walls, have been determined: the higher oxide growth rate the more chromate ions are being trapped. The trapped chromate ions and a high concentration of oxygen vacancies make the anodic aluminum oxide a promising luminescent material.

  5. A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °C

    Science.gov (United States)

    Li, Mengran; Zhao, Mingwen; Li, Feng; Zhou, Wei; Peterson, Vanessa K.; Xu, Xiaoyong; Shao, Zongping; Gentle, Ian; Zhu, Zhonghua

    2017-01-01

    The slow activity of cathode materials is one of the most significant barriers to realizing the operation of solid oxide fuel cells below 500 °C. Here we report a niobium and tantalum co-substituted perovskite SrCo0.8Nb0.1Ta0.1O3-δ as a cathode, which exhibits high electroactivity. This cathode has an area-specific polarization resistance as low as ~0.16 and ~0.68 Ω cm2 in a symmetrical cell and peak power densities of 1.2 and 0.7 W cm-2 in a Gd0.1Ce0.9O1.95-based anode-supported fuel cell at 500 and 450 °C, respectively. The high performance is attributed to an optimal balance of oxygen vacancies, ionic mobility and surface electron transfer as promoted by the synergistic effects of the niobium and tantalum. This work also points to an effective strategy in the design of cathodes for low-temperature solid oxide fuel cells.

  6. The Influence of Oxide on the Electrodeposition of Niobium from Alkali Fluoride Melts

    DEFF Research Database (Denmark)

    Christensen, Erik; Wang, Xingdong; Barner, Jens H. Von;

    1994-01-01

    , average oxidation states close to five were obtained. Cyclic voltammetry showed that NbF72- is reduced in two steps. A mechanism Nb(V) --> Nb(IV) --> Nb(0) is proposed. When oxide is present, new waves due to reduction of niobium mono-oxofluoro and dioxofluoro complexes are observed at -0.6 and -0.74 V...

  7. Structural engineering of nanoporous anodic aluminium oxide by pulse anodization of aluminium.

    Science.gov (United States)

    Lee, Woo; Schwirn, Kathrin; Steinhart, Martin; Pippel, Eckhard; Scholz, Roland; Gösele, Ulrich

    2008-04-01

    Nanoporous anodic aluminium oxide has traditionally been made in one of two ways: mild anodization or hard anodization. The first method produces self-ordered pore structures, but it is slow and only works for a narrow range of processing conditions; the second method, which is widely used in the aluminium industry, is faster, but it produces films with disordered pore structures. Here we report a novel approach termed "pulse anodization" that combines the advantages of the mild and hard anodization processes. By designing the pulse sequences it is possible to control both the composition and pore structure of the anodic aluminium oxide films while maintaining high throughput. We use pulse anodization to delaminate a single as-prepared anodic film into a stack of well-defined nanoporous alumina membrane sheets, and also to fabricate novel three-dimensional nanostructures.

  8. Fabrication of titanium oxide nanotube arrays by anodic oxidation

    Science.gov (United States)

    Zhao, Jianling; Wang, Xiaohui; Chen, Renzheng; Li, Longtu

    2005-06-01

    The formation of titanium oxide nanotube arrays on titanium substrates was investigated in HF electrolytes. Under optimized electrolyte and oxidation conditions, well-ordered nanotubes of titania were fabricated. Topologies of the anodized titanium change remarkably along with the changing of applied voltages, electrolyte concentration and oxidation time. Electrochemical determination and scanning electron microscope indicate the nanotubes are formed due to the competition of titania formation and dissolution under the assistance of electric field. A possible growth mechanism has also been presented.

  9. Photoluminescence from Nd Doped Anodic Aluminium Oxide

    Institute of Scientific and Technical Information of China (English)

    ZHOU Zhang-Kai; PENG Xiao-Niu; SU Xiong-Rui; HAO Zhong-Hua

    2009-01-01

    We prepare Nd doped anodic aluminium oxide (Nd:AAO) template by using Nd doped aluminium foils through two-step anodization processes. Photoluminescence (PL) from the Nd:AAO template with the annealing temper-ature higher than 400℃ is observed, and the PL intensity enhanced with the increasing annealing temperature is found. We investigate the crystallization of Nd:AAO template and the excitation wavelength dependence of PL intensity, showing that the PL results from the Nd doped in the template. The approach presented may probably facilitate the fabricating of AAO with good light-emitting property, which can be used in fabrication of multifunctional nanosized films and may find applications in photonic devices.

  10. Growth behavior of anodic oxide formed by aluminum anodizing in glutaric and its derivative acid electrolytes

    Science.gov (United States)

    Nakajima, Daiki; Kikuchi, Tatsuya; Natsui, Shungo; Suzuki, Ryosuke O.

    2014-12-01

    The growth behavior of anodic oxide films formed via anodizing in glutaric and its derivative acid solutions was investigated based on the acid dissociation constants of electrolytes. High-purity aluminum foils were anodized in glutaric, ketoglutaric, and acetonedicarboxylic acid solutions under various electrochemical conditions. A thin barrier anodic oxide film grew uniformly on the aluminum substrate by glutaric acid anodizing, and further anodizing caused the film to breakdown due to a high electric field. In contrast, an anodic porous alumina film with a submicrometer-scale cell diameter was successfully formed by ketoglutaric acid anodizing at 293 K. However, the increase and decrease in the temperature of the ketoglutaric acid resulted in non-uniform oxide growth and localized pitting corrosion of the aluminum substrate. An anodic porous alumina film could also be fabricated by acetonedicarboxylic acid anodizing due to the relatively low dissociation constants associated with the acid. Acid dissociation constants are an important factor for the fabrication of anodic porous alumina films.

  11. New porous titanium–niobium oxide for photocatalytic degradation of bromocresol green dye in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Chaleshtori, Maryam Zarei, E-mail: mzarei@utep.edu [Materials Research and Technology Institute (MRTI), University of Texas at El Paso, 500W. University Ave., El Paso, TX 79968 (United States); Hosseini, Mahsa; Edalatpour, Roya [Materials Research and Technology Institute (MRTI), University of Texas at El Paso, 500W. University Ave., El Paso, TX 79968 (United States); Masud, S.M. Sarif [Department of Chemistry, University of Texas at El Paso, 500W. University Ave., El Paso, TX 79968 (United States); Chianelli, Russell R., E-mail: chianell@utep.edu [Materials Research and Technology Institute (MRTI), University of Texas at El Paso, 500W. University Ave., El Paso, TX 79968 (United States)

    2013-10-15

    Graphical abstract: The photocatalytic activity of different porous titanium–niobium oxides was evaluated toward degradation of bromocresol green (BG) under UV light. A better catalytic activity was observed for all samples at lower pH. Catalysts have a stronger ability for degradation of BG in acid media than in alkaline media. - Highlights: • Different highly structured titanium–niobium oxides have been prepared using improved methods of synthesis. • Photo-degradation of bromocresol green dye (BG) with nanostructure titanium–niobium oxide catalysts was carried out under UV light. • The photo-catalytic activity of all catalysts was higher in lower pH. • Titanium–niobium oxide catalysts are considerably stable and reusable. - Abstract: In this study, high surface area semiconductors, non porous and porous titanium–niobium oxides derived from KTiNbO{sub 5} were synthesized, characterized and developed for their utility as photocatalysts for decontamination with sunlight. These materials were then used in the photocatalytic degradation of bromocresol green dye (BG) in aqueous solution using UV light and their catalytic activities were evaluated at various pHs. For all catalysts, the photocatalytic degradation of BG was most efficient in acidic solutions. Results show that the new porous oxides have large porous and high surface areas and high catalytic activity. A topotactic dehydration treatment greatly improves catalyst performance at various pHs. Stability and long term activity of porous materials (topo and non-topo) in photocatalysis reactions was also tested. These results suggest that the new materials can be used to efficiently purify contaminated water.

  12. Advanced hybrid supercapacitor based on a mesoporous niobium pentoxide/carbon as high-performance anode.

    Science.gov (United States)

    Lim, Eunho; Kim, Haegyeom; Jo, Changshin; Chun, Jinyoung; Ku, Kyojin; Kim, Seongseop; Lee, Hyung Ik; Nam, In-Sik; Yoon, Songhun; Kang, Kisuk; Lee, Jinwoo

    2014-09-23

    Recently, hybrid supercapacitors (HSCs), which combine the use of battery and supercapacitor, have been extensively studied in order to satisfy increasing demands for large energy density and high power capability in energy-storage devices. For this purpose, the requirement for anode materials that provide enhanced charge storage sites (high capacity) and accommodate fast charge transport (high rate capability) has increased. Herein, therefore, a preparation of nanocomposite as anode material is presented and an advanced HSC using it is thoroughly analyzed. The HSC comprises a mesoporous Nb2O5/carbon (m-Nb2O5-C) nanocomposite anode synthesized by a simple one-pot method using a block copolymer assisted self-assembly and commercial activated carbon (MSP-20) cathode under organic electrolyte. The m-Nb2O5-C anode provides high specific capacity with outstanding rate performance and cyclability, mainly stemming from its enhanced pseudocapacitive behavior through introduction of a carbon-coated mesostructure within a voltage range from 3.0 to 1.1 V (vs Li/Li(+)). The HSC using the m-Nb2O5-C anode and MSP-20 cathode exhibits excellent energy and power densities (74 W h kg(-1) and 18,510 W kg(-1)), with advanced cycle life (capacity retention: ∼90% at 1000 mA g(-1) after 1000 cycles) within potential range from 1.0 to 3.5 V. In particular, we note that the highest power density (18,510 W kg(-1)) of HSC is achieved at 15 W h kg(-1), which is the highest level among similar HSC systems previously reported. With further study, the HSCs developed in this work could be a next-generation energy-storage device, bridging the performance gap between conventional batteries and supercapacitors.

  13. Niobium Carbide Synthesis from Niobium Oxide: Study of the Synthesis Conditions, Kinetics, and Solid-State Transformation Mechanism

    Science.gov (United States)

    Teixeira da Silva, V. L. S.; Schmal, M.; Oyama, S. T.

    1996-04-01

    The carburization of B-niobium oxide (B-Nb2O5) to niobium carbide (NbC) in 20% (v/v) CH4/H2was studied at temperature-programmed conditions. The reaction required high temperatures, greater than 1370 K, and variations of heating rate (0.04-0.17 K s-1) and molar space velocity (400-1600 h-1) had only a minor effect on the product specific surface area (Sg). In the course of the transformationSgincreased from 1 m2g-1to about 20 m2g-1, and scanning electron microscopy showed the development of macropores of about 100 nm. The progress of the reaction was followed by mass spectroscopic analysis of the gaseous products, which identified two distinct stages. X-ray diffraction analysis of reaction intermediates showed that in the first stage B-Nb2O5was reduced to NbO2, and in the second stage NbO2was simultaneously reduced and carburized to NbC. The first reduction occurred by a nucleation mechanism with an activation energy of 100 kJ mol-1. Independent experiments with NbO indicated that it was not involved in the reaction pathway. However, X-ray photoelectron spectroscopy revealed the presence of an oxycarbide phase which was probably the intermediate in the final transformation. Overall the reaction took place by the following steps:[formula]The oxycarbide phase transformed rapidly to the product NbC and was not observable as a bulk phase by XRD.

  14. Formation and Morphology of Anodic Oxide Films of Ti

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The morphology and structure of the oxide films of Ti in H3PO4 were investigated by galvanostatic anodization, SEM and XRD. The oxide film grew from some pores in the grooves to layered microdomains as increasing anodizing voltage. The crystallinity of the oxide films decreased with the increase of the concentration of the electrolyte. The model has been proposed for the growth of the oxide films by two steps, i.e. by uniform thickening and by local deposition.

  15. Redox Stable Anodes for Solid Oxide Fuel Cells

    Directory of Open Access Journals (Sweden)

    Guoliang eXiao

    2014-06-01

    Full Text Available Solid oxide fuel cells (SOFCs can convert chemical energy from the fuel directly to electrical energy with high efficiency and fuel flexibility. Ni-based cermets have been the most widely adopted anode for SOFCs. However, the conventional Ni-based anode has low tolerance to sulfur-contamination, is vulnerable to deactivation by carbon build-up (coking from direct oxidation of hydrocarbon fuels, and suffers volume instability upon redox cycling. Among these limitations, the redox instability of the anode is particularly important and has been intensively studied since the SOFC anode may experience redox cycling during fuel cell operations even with the ideal pure hydrogen as the fuel. This review aims to highlight recent progresses on improving redox stability of the conventional Ni-based anode through microstructure optimization and exploration of alternative ceramic-based anode materials.

  16. Functionalization of niobium electrodes for the construction of impedimetric biosensors

    Energy Technology Data Exchange (ETDEWEB)

    Helali, S. [Unite de recherche de Physique des Semiconducteurs et Capteurs, IPEST, La Marsa (Tunisia)], E-mail: salwahleli@yahoo.fr; Abdelghani, A.; Hafaiedh, I. [Unite de recherche de Physique des Semiconducteurs et Capteurs, IPEST, La Marsa (Tunisia); Martelet, C. [Centre de Genie Electrique de Lyon, CEGELY, ECL, 69134 Ecully cedex (France); Prodromidis, M.I.; Albanis, T. [Department of Chemistry, University of Ioannina, 45110 Ioannina (Greece); Jaffrezic-Renault, N. [Laboratoire des Sciences Analytiques, CNRS UMR 5180, Batiment Raulin, Universite de Claude Bernard, 69622 Villeurbanne Cedex (France)

    2008-07-01

    This paper describes the development of an impedimetric immunosensor, based on niobium/niobium oxide (Nb/NbOxHy) electrodes, for the detection of atrazine. Niobium oxide was anodically formed onto niobium electrodes at 25 V in 1 M H{sub 2}SO{sub 4}. Hydrous oxide layers were then silanized with APTES, and using glutaraldehyde as a cross linker, Fab fragment k47 antibody was covalently immobilized onto the surface of the electrodes. Electrochemical impedance spectroscopy (EIS) was used to characterize the building-up of the immunosensors as well as the binding of atrazine to its specific antibody. In presence of ferricyanide redox species and under a cathodic polarization voltage (- 1.2 V versus SCE), the relationship between the concentration of atrazine and the change of the electron transfer resistance value was studied.

  17. Titanium-Niobium Oxides as Non-Noble Metal Cathodes for Polymer Electrolyte Fuel Cells

    OpenAIRE

    Akimitsu Ishihara; Yuko Tamura; Mitsuharu Chisaka; Yoshiro Ohgi; Yuji Kohno; Koichi Matsuzawa; Shigenori Mitsushima; Ken-ichiro Ota

    2015-01-01

    In order to develop noble-metal- and carbon-free cathodes, titanium-niobium oxides were prepared as active materials for oxide-based cathodes and the factors affecting the oxygen reduction reaction (ORR) activity were evaluated. The high concentration sol-gel method was employed to prepare the precursor. Heat treatment in Ar containing 4% H2 at 700–900 °C was effective for conferring ORR activity to the oxide. Notably, the onset potential for the ORR of the catalyst prepared at 700 °C was a...

  18. MEASUREMENT OF THE HIGH-FIELD Q-DROP IN A LARGE-GRAIN NIOBIUM CAVITY FOR DIFFERENT OXIDATION PROCESSES

    Energy Technology Data Exchange (ETDEWEB)

    Gianluigi Ciovati; Peter Kneisel; Alex Gurevich

    2008-01-23

    In this contribution, we present the results from a series of RF tests at 1.7 K and 2.0 K on a single-cell cavity made of high-purity large (with area of the order of few cm2) grain niobium which underwent various oxidation processes. After initial buffered chemical polishing, anodization, baking in pure oxygen atmosphere and baking in air up to 180 °C was applied with the objective of clearly identifying the role of oxygen and the oxide layer on the Q-drop. During each rf test a temperature mapping system was used allowing to measure the local temperature rise of the cavity outer surface due to RF losses, which gives information about the losses location, their field dependence and space distribution on the RF surface. The results confirmed that the depth affected by baking is about 20 – 30 nm from the surface and showed that the Q-drop did not re-appear in a previously baked cavity by further baking at 120 °C in pure oxygen atmosphere or in air up to 180 °C. A statistic of the position of the “hot-spots” on the cavity surface showed that grain-boundaries are not the preferred location. An interesting correlation was found between the Q-drop onset, the quench field and the low-field energy gap, which supports the hypothesis of thermo-magnetic instability governing the Q-drop and the baking effect.

  19. Self-ordering behavior of nanoporous anodic aluminum oxide (AAO) in malonic acid anodization

    Energy Technology Data Exchange (ETDEWEB)

    Lee, W; Nielsch, K; Goesele, U [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Germany)

    2007-11-28

    The self-ordering behavior of anodic aluminum oxide (AAO) has been investigated for anodization of aluminum in malonic acid (H{sub 4}C{sub 3}O{sub 4}) solution. In the present study it is found that a porous oxide layer formed on the surface of aluminum can effectively suppress catastrophic local events (such as breakdown of the oxide film and plastic deformation of the aluminum substrate), and enables stable fast anodic oxidation under a high electric field of 110-140 V and {approx}100 mA cm{sup -2}. Studies on the self-ordering behavior of AAO indicated that the cell homogeneity of AAO increases dramatically as the anodization voltage gets higher than 120 V. Highly ordered AAO with a hexagonal arrangement of the nanopores could be obtained in a voltage range 125-140 V. The current density (i.e., the electric field strength (E) at the bottom of a pore) is an important parameter governing the self-ordering of the nanopores as well as the interpore distance (D{sub int}) for a given anodization potential (U) during malonic acid anodization.

  20. Anodic aluminium oxide catalytic membranes for asymmetric epoxidation.

    Science.gov (United States)

    Cho, So-Hye; Walther, Nolan D; Nguyen, SonBinh T; Hupp, Joseph T

    2005-11-14

    Catechol-functionalized (salen)Mn complexes can be supported on mesoporous anodized aluminium oxide disks to yield catalytic membranes that are highly active in the enantioselective epoxidation of olefins when being deployed in a forced-through-flow reactor.

  1. Effect of tungsten doping on catalytic properties of niobium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Cardoso, Franciane P.; Nogueira, Andre E. [Departamento de Quimica, Universidade Federal de Lavras, Lavras-MG (Brazil); Patricio, Patricia S.O., E-mail: patriciapatricio@cefetmg.br [Centro Federal de Educacao Tecnologica, CEFET, Belo Horizonte, MG (Brazil); Oliveira, Luiz C.A. [Departamento de Quimica, ICEx, Universidade Federal de Minas Gerais, Belo Horizonte, MG (Brazil)

    2012-04-15

    A novel material based on niobia (Nb{sub 2}O{sub 5}) was synthesized to oxidize an organic compound in aqueous medium in the presence of H{sub 2}O{sub 2} after chemical modifications. Niobia was modified by doping with tungsten and also treating with H{sub 2}O{sub 2} in order to maximize the oxidative properties of this oxide. The analysis of the products from methylene blue dye oxidation with electro spray ionization mass spectrometry (ESI-MS) showed that the dye was successively oxidized to different intermediate compounds. The successive hydroxylation during this oxidation strongly suggests that highly reactive hydroxyl radicals are generated involving H{sub 2}O{sub 2} on the W-doped niobia grain surface. These results strongly suggest that the H{sub 2}O{sub 2} can regenerate in situ the peroxo group remaining active the system. (author)

  2. Effect of processing on structural features of anodic aluminum oxides

    Science.gov (United States)

    Erdogan, Pembe; Birol, Yucel

    2012-09-01

    Morphological features of the anodic aluminum oxide (AAO) templates fabricated by electrochemical oxidation under different processing conditions were investigated. The selection of the polishing parameters does not appear to be critical as long as the aluminum substrate is polished adequately prior to the anodization process. AAO layers with a highly ordered pore distribution are obtained after anodizing in 0.6 M oxalic acid at 20 °C under 40 V for 5 minutes suggesting that the desired pore features are attained once an oxide layer develops on the surface. While the pore features are not affected much, the thickness of the AAO template increases with increasing anodization treatment time. Pore features are better and the AAO growth rate is higher at 20 °C than at 5 °C; higher under 45 V than under 40 V; higher with 0.6 M than with 0.3 M oxalic acid.

  3. The oxidation of TaBe sub 12 and NbBe sub 12 coatings on niobium

    Energy Technology Data Exchange (ETDEWEB)

    Courtright, E.L.

    1990-01-01

    The oxidation behavior of tantalum and niobium beryllide coatings on niobium were evaluated. Intermetallic bond layers consisting of Ir{sub 3}Ta and Ir{sub 3}Nb were used to butter the large thermal expansion mismatch between the beryllide coatings and underlying niobium substrate. All coatings were applied by Triode Sputtering except for a final environmental protection layer of stabilized zirconia deposited by RF Diode using a ceramic target. Severe delamination and spalling occurred during cyclic oxidation exposure, even at temperatures as low as 925{degrees}C, indicating that the bond layer did not prevent the differential expansion stresses from reaching the delamination failure threshold, particularly at the edges and corners. Hot pressed samples of the two beryllide compounds were also exposed to a similar cyclic oxidation history, but, in contrast to the coatings, exhibited excellent oxidation resistance to temperatures as high as 1370{degrees}C. 9 refs., 8 figs., 1 tab.

  4. Tunable structural color of anodic tantalum oxide films

    Institute of Scientific and Technical Information of China (English)

    Sheng Cui-Cui; Cai Yun-Yu; Dai En-Mei; Liang Chang-Hao

    2012-01-01

    Tantalum (Ta) oxide films with tunable structural color were fabricated easily using anodic oxidation.The structure,components,and surface valence states of the oxide filns were investigated by using gazing incidence X-ray diffractometry,X-ray photoelectron microscopy,and surface analytical techniques.Their thickness and optical properties were studied by using spectroscopic ellipsometry and total reflectance spectrum.Color was accurately defined using L*a*b* scale.The thickness of compact Ta2O5 films was linearly dependent on anodizing voltage.The film color was tunable by adjusting the anodic voltage.The difference in color appearance resulted from the interference behavior between the interfaces of air-oxide and oxide-metal.

  5. A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °C

    Science.gov (United States)

    Li, Mengran; Zhao, Mingwen; Li, Feng; Zhou, Wei; Peterson, Vanessa K.; Xu, Xiaoyong; Shao, Zongping; Gentle, Ian; Zhu, Zhonghua

    2017-01-01

    The slow activity of cathode materials is one of the most significant barriers to realizing the operation of solid oxide fuel cells below 500 °C. Here we report a niobium and tantalum co-substituted perovskite SrCo0.8Nb0.1Ta0.1O3−δ as a cathode, which exhibits high electroactivity. This cathode has an area-specific polarization resistance as low as ∼0.16 and ∼0.68 Ω cm2 in a symmetrical cell and peak power densities of 1.2 and 0.7 W cm−2 in a Gd0.1Ce0.9O1.95-based anode-supported fuel cell at 500 and 450 °C, respectively. The high performance is attributed to an optimal balance of oxygen vacancies, ionic mobility and surface electron transfer as promoted by the synergistic effects of the niobium and tantalum. This work also points to an effective strategy in the design of cathodes for low-temperature solid oxide fuel cells. PMID:28045088

  6. A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °C.

    Science.gov (United States)

    Li, Mengran; Zhao, Mingwen; Li, Feng; Zhou, Wei; Peterson, Vanessa K; Xu, Xiaoyong; Shao, Zongping; Gentle, Ian; Zhu, Zhonghua

    2017-01-03

    The slow activity of cathode materials is one of the most significant barriers to realizing the operation of solid oxide fuel cells below 500 °C. Here we report a niobium and tantalum co-substituted perovskite SrCo0.8Nb0.1Ta0.1O3-δ as a cathode, which exhibits high electroactivity. This cathode has an area-specific polarization resistance as low as ∼0.16 and ∼0.68 Ω cm(2) in a symmetrical cell and peak power densities of 1.2 and 0.7 W cm(-2) in a Gd0.1Ce0.9O1.95-based anode-supported fuel cell at 500 and 450 °C, respectively. The high performance is attributed to an optimal balance of oxygen vacancies, ionic mobility and surface electron transfer as promoted by the synergistic effects of the niobium and tantalum. This work also points to an effective strategy in the design of cathodes for low-temperature solid oxide fuel cells.

  7. Fabrication of anodic aluminium oxide templates on curved surfaces.

    Science.gov (United States)

    Yin, Aijun; Guico, Rodney S; Xu, Jimmy

    2007-01-24

    Aluminium anodization provides a simple and inexpensive way to obtain nanoporous templates with uniform and controllable pore diameters and periods over a wide range. Moreover, one of the interesting possibilities afforded by the anodization process is that the anodization can take place on arbitrary surfaces, such as curved surfaces, which has not yet been well studied or applied in nanofabrication. In this paper, we characterize the anodization of Al films on silicon substrates with a curved top surface. The structures of the resultant anodic aluminium oxide (AAO) films are examined by scanning electron microscopy. Unique features including cessation, bending, and branching of pore channels are observed in the curved area. Possible growth mechanisms are proposed, which can also contribute to the understanding of the self-organization mechanism in the formation of porous AAO membranes. The new structures may open new opportunities in optical, electronic and electrochemical applications.

  8. Fabrication of anode supported PEN for solid oxide fuel cell

    Institute of Scientific and Technical Information of China (English)

    谢淑红; 崔崑; 夏风; 肖建中

    2004-01-01

    Fabrication process for anode supported planar PEN of intermediate temperature solid oxide fuel cell (SOFC) was introduced, in which tape casting and screen printing methods were used. Gd2O3 doped CeO2(GDC) powders were prepared by solid reaction method. Anode tape was produced by tape casting. Electrolyte and cathode were produced by screen printing. The GDC powder's component, thermal expand coefficient, the porosity, density and microstructure of anode and electrolyte were investigated . It was shown that an bi-layer with dense thin electrolyte film and porous anode support and with good coherency of the electrolyte film to the anode could be realized after co-sintering the green tape at 1 350℃ by optimizing the power characteristics of the starting materials in the slurry.

  9. Formation and Thermal Stability of Large Precipitates and Oxides in Titanium and Niobium Microalloyed Steel

    Institute of Scientific and Technical Information of China (English)

    ZHUO Xiao-jun; WOO Dae-hee; WANG Xin-hua; LEE Hae-geon

    2008-01-01

    As-cast CC slabs of microalloyed steels are prone to surface and sub-surface cracking. Precipitation phenomena in-itiated during solidification reduce ductility at high temperature. The unidirectional solidification unit is employed to sim-ulate the solidification process during continuous casting. Precipitation behavior and thermal stability are systemati-cally investigated. Samples of adding titanium and niobium to steels have been examined using field emission scanning electron microscope (FE-SEM), electron probe X-ray microanalyzer (EPMA), and transmission electron microscope (TEM). It has been found that the addition of titanium and niobium to high-strength low-alloyed (HSLA) steel resuited in undesirable large precipitation in the steels, i. e. , precipitation of large precipitates with various morphologies. The composition of the large precipitates has been determined. The effect of cooling rate on (Ti, Nb)(C, N) precipitate formation is investigated. With increasing the cooling rate, titanium-rich (Ti,Nb)(C, N) precipitates are transformed to niobium-rich (Ti,Nb)(C,N) precipitates. The thermal stability of these large precipitates and oxides have been assessed by carrying out various heat treatments such as holding and quenching from temperature at 800 and 1 200 ℃. It has been found that titanium-rich (Ti,Nb)(C,N) precipitate is stable at about 1 200 ℃ and niobi-um-rich (Ti,Nb)(C,N) precipitate is stable at about 800 ℃. After reheating at 1 200 ℃ for 1 h, (Ca, Mn)S and TiN are precipitated from Ca-Al oxide. However, during reheating at 800 ℃ for 1 h, Ca-Al-Ti oxide in specimens was stable. The thermodynamic calculation of simulating the thermal process is employed. The calculation results are in good agreement with the experimental results.

  10. Formation of anodic aluminum oxide with serrated nanochannels.

    Science.gov (United States)

    Li, Dongdong; Zhao, Liang; Jiang, Chuanhai; Lu, Jia G

    2010-08-11

    We report a simple and robust method to self-assemble porous anodic aluminum oxide membranes with serrated nanochannels by anodizing in phosphoric acid solution. Due to high field conduction and anionic incorporation, an increase of anodizing voltage leads to an increase of the impurity levels and also the field strength across barrier layer. On the basis of both experiment and simulation results, the initiation and formation of serrated channels are attributed to the evolution of oxygen gas bubbles followed by plastic deformation in the oxide film. Alternating anodization in oxalic and phosphoric acids is applied to construct multilayered membranes with smooth and serrated channels, demonstrating a unique way to design and construct a three-dimensional hierarchical system with controllable morphology and composition.

  11. Mesoporous Niobium Oxide Spheres as an Effective Catalyst for the Transamidation of Primary Amides with Amines

    KAUST Repository

    Ghosh, Subhash Chandra

    2014-02-06

    Mesoporous niobium oxide spheres (MNOS), conveniently prepared by a novel antisolvent precipitation approach, have been shown to be an effective catalyst for the transamidation of primary amides with amines. This novel transamidation can be efficiently carried out under solvent-free conditions and is applicable to a wide range of primary amides and amines to provide N-alkyl amides in good to excellent yields. The catalyst is highly stable and reusable. The application of this transamidation reaction has been demonstrated in the synthesis of antidepressant drug moclobemide and other druglike compounds. © 2014 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.

  12. ELLIPSOMETRIC INVESTIGATION OF THE SILICON / ANODIC-OXIDE INTERFACE

    OpenAIRE

    Palik, E.; Bermudez, V.

    1983-01-01

    Ellipsometric measurements have been carried out during growth and etch back of anodic oxides on Si in 2M KOH. Pronounced variations in ψ and Ɗ occur as etching proceeds through the SiO2/Si interface and also during the initial stages of re-anodization. The results are interpreted in terms of changes in the stoichiometry and thickness of an SiOx (0⩽x⩽2) connective layer.

  13. Progress in Nano-Engineered Anodic Aluminum Oxide Membrane Development

    Directory of Open Access Journals (Sweden)

    Gerrard Eddy Jai Poinern

    2011-02-01

    Full Text Available The anodization of aluminum is an electro-chemical process that changes the surface chemistry of the metal, via oxidation, to produce an anodic oxide layer. During this process a self organized, highly ordered array of cylindrical shaped pores can be produced with controllable pore diameters, periodicity and density distribution. This enables anodic aluminum oxide (AAO membranes to be used as templates in a variety of nanotechnology applications without the need for expensive lithographical techniques. This review article is an overview of the current state of research on AAO membranes and the various applications of nanotechnology that use them in the manufacture of nano-materials and devices or incorporate them into specific applications such as biological/chemical sensors, nano-electronic devices, filter membranes and medical scaffolds for tissue engineering.

  14. Impact of anode microstructure on solid oxide fuel cells.

    Science.gov (United States)

    Suzuki, Toshio; Hasan, Zahir; Funahashi, Yoshihiro; Yamaguchi, Toshiaki; Fujishiro, Yoshinobu; Awano, Masanobu

    2009-08-14

    We report a correlation between the microstructure of the anode electrode of a solid oxide fuel cell (SOFC) and its electrochemical performance for a tubular design. It was shown that the electrochemical performance of the cell was extensively improved when the size of constituent particles was reduced so as to yield a highly porous microstructure. The SOFC had a power density of greater than 1 watt per square centimeter at an operating temperature as low as 600 degrees C with a conventional zirconia-based electrolyte, a nickel cermet anode, and a lanthanum ferrite perovskite cathode material. The effect of the hydrogen fuel flow rate (linear velocity) was also examined for the optimization of operating conditions. Higher linear fuel velocity led to better cell performance for the cell with higher anode porosity. A zirconia-based cell could be used for a low-temperature SOFC system under 600 degrees C just by optimizing the microstructure of the anode electrode and operating conditions.

  15. Anodic oxidation of stilbenes bearing electron-withdrawing ring substituents

    Energy Technology Data Exchange (ETDEWEB)

    Halas, Summer M.; Okyne, Kwame; Fry, Albert J

    2003-06-15

    A number of disubstituted stilbenes bearing either two strong electron-withdrawing groups or one electron-withdrawing and one electron-donating group were synthesized and anodically oxidized in a divided cell in methanol at a carbon anode. A variety of types of products were obtained, most of which have never been observed upon oxidation of alkenes not bearing electron-withdrawing groups. A mechanistic scheme involving 2-methoxy-1,2-diarylethyl cations as key intermediates can account for all of the observed products. The nature of the products from each alkene is strongly correlated with the sum of the Hammett {sigma}{sup +} values of the ring substituents.

  16. Anodic oxidation with doped diamond electrodes: a new advanced oxidation process

    Energy Technology Data Exchange (ETDEWEB)

    Kraft, Alexander; Stadelmann, Manuela; Blaschke, Manfred

    2003-10-31

    Boron-doped diamond anodes allow to directly produce OH{center_dot} radicals from water electrolysis with very high current efficiencies. This has been explained by the very high overvoltage for oxygen production and many other anodic electrode processes on diamond anodes. Additionally, the boron-doped diamond electrodes exhibit a high mechanical and chemical stability. Anodic oxidation with diamond anodes is a new advanced oxidation process (AOP) with many advantages compared to other known chemical and photochemical AOPs. The present work reports on the use of diamond anodes for the chemical oxygen demand (COD) removal from several industrial wastewaters and from two synthetic wastewaters with malic acid and ethylenediaminetetraacetic (EDTA) acid. Current efficiencies for the COD removal between 85 and 100% have been found. The formation and subsequent removal of by-products of the COD oxidation has been investigated for the first time. Economical considerations of this new AOP are included.

  17. Anodic oxide growth on Zr in neutral aqueous solution

    Indian Academy of Sciences (India)

    Z Tun; J J Noël; D W Shoesmith

    2008-10-01

    Anodization and subsequent cathodic reactions on a thin-film sample of Zr were studied with in-situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS). The NR results during anodization showed the originally 485 Å thick Zr film generally behaved similar to a bulk electrode in neutral solution. The anodization ratio measured at applied potentials increased in steps of 0.5 V was somewhat higher than the value determined by coulometry, while the Pilling Bedworth ratio is in good agreement with published data. Thickening of the oxide layer, accelerated immediately after each potential increase, gradually decreased over several hours, but remained non-zero even after ∼ 12 h. The thickened oxide eventually cracked when its thickness reached ∼ 120 Å, causing loss of passivation. Surprisingly, neither the anodization ratio nor the Pilling Bedworth ratio showed any discontinuity at the time of oxide cracking, and the EIS behaviour remained qualitatively as before. This observation is taken as the evidence that the cracked and intact regions of the electrode behave more or less independently as parallel electrodes. When the potential was eventually switched to cathodic polarity, NR shows, as expected, that the effects of oxide cracking were irreversible. However, the electrode resistance recovered partially suggesting the cracks were rapidly plugged with newly formed oxide.

  18. Anodes for Solid Oxide Fuel Cells Operating at Low Temperatures

    DEFF Research Database (Denmark)

    Abdul Jabbar, Mohammed Hussain

    An important issue that has limited the potential of Solid Oxide Fuel Cells (SOFCs) for portable applications is its high operating temperatures (800-1000 ºC). Lowering the operating temperature of SOFCs to 400-600 ºC enable a wider material selection, reduced degradation and increased lifetime....... On the other hand, low-temperature operation poses serious challenges to the electrode performance. Effective catalysts, redox stable electrodes with improved microstructures are the prime requisite for the development of efficient SOFC anodes. The performance of Nb-doped SrT iO3 (STN) ceramic anodes...... at 400ºC. The potential of using WO3 ceramic as an alternative anode materials has been explored. The relatively high electrode polarization resistance obtained, 11 Ohm cm2 at 600 ºC, proved the inadequate catalytic activity of this system for hydrogen oxidation. At the end of this thesis...

  19. Raman and photoelectron spectroscopic investigation of high-purity niobium materials: Oxides, hydrides, and hydrocarbons

    Science.gov (United States)

    Singh, Nageshwar; Deo, M. N.; Nand, Mangla; Jha, S. N.; Roy, S. B.

    2016-09-01

    We present investigations of the presence of oxides, hydrides, and hydrocarbons in high-purity (residual resistivity ratio, ˜300) niobium (Nb) materials used in fabrication of superconducting radio frequency (SRF) cavities for particle accelerators. Raman spectroscopy of Nb materials (as-received from the vendor as well as after surface chemical- and thermal processing) revealed numerous peaks, which evidently show the presence of oxides (550 cm-1), hydrides (1277 and 1385 cm-1: ˜80 K temperature), and groups of hydrocarbons (1096, 2330, 2710, 2830, 2868, and 3080 cm-1). The present work provides direct spectroscopic evidence of hydrides in the electropolished Nb materials typically used in SRF cavities. Raman spectroscopy thus can provide vital information about the near-surface chemical species in niobium materials and will help in identifying the cause for the performance degradation of SRF cavities. Furthermore, photoelectron spectroscopy was performed on the Nb samples to complement the Raman spectroscopy study. This study reveals the presence of C and O in the Nb samples. Core level spectra of Nb (doublet 3d5/2 and 3d3/2) show peaks near 206.6 and 209.4 eV, which can be attributed to the Nb5+ oxidation state. The core level spectra of C 1 s of the samples are dominated by graphitic carbon (binding energy, 284.6 eV), while the spectra of O 1 s are asymmetrically peaked near binding energy of ˜529 eV, and that indicates the presence of metal-oxide Nb2O5. The valence-band spectra of the Nb samples are dominated by a broad peak similar to O 2p states, but after sputtering (for 10 min) a peak appears at ˜1 eV, which is a feature of the elemental Nb atom.

  20. Formation of Anodic Aluminum Oxide with Branched and Meshed Pores.

    Science.gov (United States)

    Kim, Byeol; Lee, Jin Seok

    2016-06-01

    Anodic aluminum oxide (AAO), with a self-ordered hexagonal array, is important for various applications in nanofabrication including as the fabrication of nanotemplates and other nanostructures. With the consideration, there have been many efforts to control the characteristic parameters of porous anodic alumina by adjustment of the anodizing conditions such as the electrolyte, temperature, applied potential, and Al purity. In particular, impurities in Al are changing the morphology of an alumina film; however, the formation mechanism has not yet been explained. In this work, we anodized a high purity (99.999%, Al(high)) and low purity (99.8%, Al(low)) aluminum foil by a two-step anodization process in an oxalic acid solution or phosphoric acid. It was found that the purity of aluminum foil has influenced the morphology of the alumina film resulting in branched and meshed pores. Also, electrochemical analysis indicated that the branched and meshed pores in the low-purity Al foil formed by the presence of impurities. Impurities act as defects and change the general growth mechanism for pore formation by inducing an electric field imbalance during anodization. This work contributes to the research field of topographical chemistry and applied fields including nanofabrication.

  1. A review of liquid metal anode solid oxide fuel cells

    Directory of Open Access Journals (Sweden)

    ALIYA TOLEUOVA

    2013-06-01

    Full Text Available This review discusses recent advances in a solid oxide fuel cell (SOFC variant that uses liquid metal electrodes (anodes with the advantage of greater fuel tolerance and the ability to operate on solid fuel. Key features of the approach are discussed along with the technological and research challenges that need to be overcome for scale-up and commercialisation.

  2. Investigation of anodic oxide coatings on zirconium after heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Sowa, Maciej [Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego Street 6, 44-100 Gliwice (Poland); Dercz, Grzegorz [Institute of Materials Science, University of Silesia, 75 Pułku Piechoty Street 1 A, 41-500 Chorzów (Poland); Suchanek, Katarzyna [The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego Street 152, 31-342 Krakow (Poland); Simka, Wojciech, E-mail: wojciech.simka@polsl.pl [Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego Street 6, 44-100 Gliwice (Poland)

    2015-08-15

    Highlights: • Oxide layers prepared via PEO of zirconium were subjected to heat treatment. • Surface characteristics were determined for the obtained oxide coatings. • Heat treatment led to the partial destruction of the anodic oxide layer. • Pitting corrosion resistance of zirconium was improved after the modification. - Abstract: Herein, results of heat treatment of zirconium anodised under plasma electrolytic oxidation (PEO) conditions at 500–800 °C are presented. The obtained oxide films were investigated by means of SEM, XRD and Raman spectroscopy. The corrosion resistance of the zirconium specimens was evaluated in Ringer's solution. A bilayer oxide coatings generated in the course of PEO of zirconium were not observed after the heat treatment. The resulting oxide layers contained a new sublayer located at the metal/oxide interface is suggested to originate from the thermal oxidation of zirconium. The corrosion resistance of the anodised metal was improved after the heat treatment.

  3. Niobium-gallium oxide with a high concentration of Cr3+ ions: Photoluminescence and structural characteristics

    Science.gov (United States)

    Costa, G. K. B.; Pedro, S. S.; López, A.; Carvalho, I. C. S.; Cella, N.; Sosman, L. P.

    2016-10-01

    This work presents photoluminescence data for gallium-niobium oxide with chromium ion as an impurity. The samples were obtained by the solid-state method (SSM) and the wet-chemical method (WCM) and investigated by X-ray diffraction, photoluminescence, excitation, and photoacoustic and X-ray fluorescence. The color of the sample obtained by the SSM was pink, while the color of the sample prepared by the WCM was green. This dramatic difference was associated with Cr3+ concentration and with the neighborhood of the doping ions, obtained from crystallographic data, which is strongly dependent on the preparation method. The difference between the samples was also verified in the photoacoustic and excitation spectra, in which the energy bands were located at different energy levels; on the other hand, in the photoluminescence spectra, no band shift was observed. All spectra were assigned to chromium ions at nonequivalent octahedral sites.

  4. Ultrafine Nb2O5 Nanocrystal Coating on Reduced Graphene Oxide as Anode Material for High Performance Sodium Ion Battery.

    Science.gov (United States)

    Yan, Litao; Chen, Gen; Sarker, Swagotom; Richins, Stephanie; Wang, Huiqiang; Xu, Weichuan; Rui, Xianhong; Luo, Hongmei

    2016-08-31

    Ultrafine niobium oxide nanocrystals/reduced graphene oxide (Nb2O5 NCs/rGO) was demonstrated as a promising anode material for sodium ion battery with high rate performance and high cycle durability. Nb2O5 NCs/rGO was synthesized by controllable hydrolysis of niobium ethoxide and followed by heat treatment at 450 °C in flowing forming gas. Transmission electron microscopy images showed that Nb2O5 NCs with average particle size of 3 nm were uniformly deposited on rGO sheets and voids among Nb2O5 NCs existed. The architecture of ultrafine Nb2O5 NCs anchored on a highly conductive rGO network can not only enhance charge transfer and buffer the volume change during sodiation/desodiation process but also provide more active surface area for sodium ion storage, resulting in superior rate and cycle performance. Ex situ XPS analysis revealed that the sodium ion storage mechanism in Nb2O5 could be accompanied by Nb(5+)/Nb(4+) redox reaction and the ultrafine Nb2O5 NCs provide more surface area to accomplish the redox reaction.

  5. Impurity-defect structure of anodic aluminum oxide produced by two-sided anodizing in tartaric acid

    Science.gov (United States)

    Chernyakova, K. V.; Vrublevsky, I. A.; Ivanovskaya, M. I.; Kotsikau, D. A.

    2012-03-01

    Porous aluminum oxide is prepared in a 0.4 M aqueous solution of tartaric acid by two-sided anodizing. Fourier Transform IR spectroscopy (FTIR) data reveal the presence, in the alumina, of unoxidized tartarate ions, as well as products of their partial (radical organic products and CO) and complete (CO2) oxidation. Carboxylate ions and elemental carbon contained in the anodic oxide impart a gray color to the films.

  6. Titanium-Niobium Oxides as Non-Noble Metal Cathodes for Polymer Electrolyte Fuel Cells

    Directory of Open Access Journals (Sweden)

    Akimitsu Ishihara

    2015-07-01

    Full Text Available In order to develop noble-metal- and carbon-free cathodes, titanium-niobium oxides were prepared as active materials for oxide-based cathodes and the factors affecting the oxygen reduction reaction (ORR activity were evaluated. The high concentration sol-gel method was employed to prepare the precursor. Heat treatment in Ar containing 4% H2 at 700–900 °C was effective for conferring ORR activity to the oxide. Notably, the onset potential for the ORR of the catalyst prepared at 700 °C was approximately 1.0 V vs. RHE, resulting in high quality active sites for the ORR. X-ray (diffraction and photoelectron spectroscopic analyses and ionization potential measurements suggested that localized electronic energy levels were produced via heat treatment under reductive atmosphere. Adsorption of oxygen molecules on the oxide may be governed by the localized electronic energy levels produced by the valence changes induced by substitutional metal ions and/or oxygen vacancies.

  7. Measurement of the high-field Q-drop in a high-purity large-grain niobium cavity for different oxidation processes

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi; Kneisel, Peter; gurevich, alex

    2007-06-01

    The most challenging issue for understanding the performance of superconducting radio-frequency (rf) cavities made of high-purity (residual resistivity ratio > 200) niobium is due to a sharp degradation (“Q-drop”) of the cavity quality factor Q0(Bp) as the peak surface magnetic field (Bp) exceeds about 90 mT, in the absence of field emission. In addition, a low-temperature (100 – 140 C) “in-situ” baking of the cavity was found to be beneficial in reducing the Q-drop. In this contribution, we present the results from a series of rf tests at 1.7 K and 2.0 K on a single-cell cavity made of high-purity large (with area of the order of few cm2) grain niobium which underwent various oxidation processes, after initial buffered chemical polishing, such as anodization, baking in pure oxygen atmosphere and baking in air up to 180 °C, with the objective of clearly identifying the role of oxygen and the oxide layer on the Q-drop. During each rf test a temperature mapping system allows measuring the local temperature rise of the cavity outer surface due to rf losses, which gives information about the losses location, their field dependence and space distribution. The results confirmed that the depth affected by baking is about 20 – 30 nm from the surface and showed that the Q-drop did not re-appear in a previously baked cavity by further baking at 120 °C in pure oxygen atmosphere or in air up to 180 °C. These treatments increased the oxide thickness and oxygen concentration, measured on niobium samples which were processed with the cavity and were analyzed with Transmission Electron Microscope (TEM) and Secondary Ion Mass Spectroscopy (SIMS). Nevertheless, the performance of the cavity after air baking at 180 °C degraded significantly and the temperature maps showed high losses, uniformly distributed on the surface, which could be completely recovered only by a post-purification treatment at 1250 °C. A statistic of the position of the “hot-spots” on the

  8. Fabrication and Characterization of Graded Anodes for Anode-Supported Solid Oxide Fuel Cells by Tape Casting and Lamination

    DEFF Research Database (Denmark)

    Beltran-Lopez, J.F.; Laguna-Bercero, M.A.; Gurauskis, Jonas

    2014-01-01

    Graded anodes for anode-supported solid oxide fuel cells (SOFCs) are fabricated by tape casting and subsequent cold lamination of plates using different compositions. Rheological parameters are adjusted to obtain stable suspensions for tape casting. The conditions for the tape casting and laminat...

  9. Alternative anode materials for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Goodenough, John B.; Huang, Yun-Hui [Texas Materials Institute, ETC 9.102, 1 University Station, C2200, The University of Texas at Austin, Austin, TX 78712 (United States)

    2007-11-08

    The electrolyte of a solid oxide fuel cell (SOFC) is an O{sup 2-}-ion conductor. The anode must oxidize the fuel with O{sup 2-} ions received from the electrolyte and it must deliver electrons of the fuel chemisorption reaction to a current collector. Cells operating on H{sub 2} and CO generally use a porous Ni/electrolyte cermet that supports a thin, dense electrolyte. Ni acts as both the electronic conductor and the catalyst for splitting the H{sub 2} bond; the oxidation of H{sub 2} to H{sub 2}O occurs at the Ni/electrolyte/H{sub 2} triple-phase boundary (TPB). The CO is oxidized at the oxide component of the cermet, which may be the electrolyte, yttria-stabilized zirconia, or a mixed oxide-ion/electron conductor (MIEC). The MIEC is commonly a Gd-doped ceria. The design and fabrication of these anodes are evaluated. Use of natural gas as the fuel requires another strategy, and MIECs are being explored for this application. The several constraints on these MIECs are outlined, and preliminary results of this on-going investigation are reviewed. (author)

  10. Downscaled anodic oxidation process for aluminium in oxalic acid

    Science.gov (United States)

    Sieber, M.; Morgenstern, R.; Kuhn, D.; Hackert-Oschätzchen, M.; Schubert, A.; Lampke, T.

    2017-03-01

    The increasing multi-functionality of parts and assemblies in several fields of engineering demands, amongst others, highly functionalised surfaces. For the different applications, on the one hand, there is a need to scale up surface modification processes originating in the nano- and micro-scale. On the other hand, conventional macro-scale surface refinement methods offer a huge potential for application in the said nano- and micro-scale. The anodic oxidation process, which is established especially for aluminium and its alloys, allows the formation of oxide ceramic layers on the surface. The build-up of an oxide ceramic coating comes along with altered chemical, tribological and electrical surface properties. As a basis for further investigations regarding the use of the anodic oxidation process for micro-scale-manufacturing, the scale effects of oxalic acid anodising on commercially pure aluminium as well as on the AlZn5.5MgCu alloy are addressed in the present work. The focus is on the amount of oxide formed during a potentiostatic process in relation to the exchanged amount of charge. Further, the hardness of the coating as an integral measure to assess the porous oxide structure is approached by nano-indentation technique.

  11. Barrier and porous anodic oxides on InSb

    Energy Technology Data Exchange (ETDEWEB)

    Suleiman, A.; Hashimoto, T. [Corrosion and Protection Centre, School of Materials, University of Manchester, P.O. Box 88, Manchester M60 1QD (United Kingdom); Skeldon, P. [Corrosion and Protection Centre, School of Materials, University of Manchester, P.O. Box 88, Manchester M60 1QD (United Kingdom)], E-mail: peter.skeldon@manchester.ac.uk; Thompson, G.E. [Corrosion and Protection Centre, School of Materials, University of Manchester, P.O. Box 88, Manchester M60 1QD (United Kingdom); Echeverria, F. [Dpto de Ing. Metalurgica y de Materiales, Universidad de Antioquia, Oficina 18-240, Calle 67 No. 53-108, A.A. 1226, Medellin (Colombia); Graham, M.J.; Sproule, G.I.; Moisa, S. [Institute for Microstructural Sciences, National Research Council of Canada, Montreal Road, Ottawa, K1A 0R6 (Canada); Habazaki, H. [Graduate Engineering School, Hokkaido University, N13 W8, Kita-ku, Sapporo 060-8628 (Japan); Bailey, P.; Noakes, T.C.Q. [Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom)

    2008-05-15

    Anodizing of InSb at 5 mA cm{sup -2} in sodium tungstate electrolyte is shown to produce barrier-type amorphous oxide at relatively low voltages, to about 40 V, and porous-type amorphous oxide at increased voltages. The barrier-type amorphous oxide, consisting of units of In{sub 2}O{sub 3} and Sb{sub 2}O{sub 3}, distributed relatively uniformly throughout the film, develops at a formation ratio of 2.2 {+-} 0.2 nm V{sup -1}. The outer 15-20% of the film also contains tungsten species. The relatively high efficiency of barrier film growth reduces significantly with transition to porous oxide, which is associated additionally with generation of oxygen at the film surface. The final oxide, at 65 V, comprises pores, of typical diameter 80 nm, orientated approximately normal to the substrate and extending from a barrier region to the film surface.

  12. Synthesis and characterization of anodized titanium-oxide nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Michael Z. [ORNL; Lai, Peng [University of Cincinnati; Bhuiyan, Md S [ORNL; Tsouris, Costas [ORNL; Gu, Baohua [ORNL; Paranthaman, Mariappan Parans [ORNL; Gabitto, Jorge [Prairie View A& M University; Harrison, L. D. [Prairie View A& M University

    2009-01-01

    Anodized titanium-oxide containing highly ordered, vertically oriented TiO2 nanotube arrays is a nanomaterial architecture that shows promise for diverse applications. In this paper, an anodization synthesis using HF-free aqueous solution is described. The anodized TiO2 film samples (amorphous, anatase, and rutile) on titanium foils were characterized with scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Additional characterization in terms of photocurrent generated by an anode consisting of a titanium foil coated by TiO2 nanotubes was performed using an electrochemical cell. A platinum cathode was used in the electrochemical cell. Results were analyzed in terms of the efficiency of the current generated, defined as the ratio of the difference between the electrical energy output and the electrical energy input divided by the input radiation energy, with the goal of determining which phase of TiO2 nanotubes leads to more efficient hydrogen production. It was determined that the anatase crystalline structure converts light into current more efficiently and is therefore a better photocatalytic material for hydrogen production via photoelectrochemical splitting of water.

  13. Radiopacity and cytotoxicity of Portland cement associated with niobium oxide micro and nanoparticles

    Directory of Open Access Journals (Sweden)

    Leticia Boldrin MESTIERI

    2014-12-01

    Full Text Available Objective Mineral Trioxide Aggregate (MTA is composed of Portland Cement (PC and bismuth oxide (BO. Replacing BO for niobium oxide (NbO microparticles (Nbµ or nanoparticles (Nbη may improve radiopacity and bioactivity. The aim of this study was to evaluate the radiopacity and cytotoxicity of the materials: 1 PC; 2 White MTA; 3 PC+30% Nbµ; 4 PC+30% Nbη. Material and Methods For the radiopacity test, specimens of the different materials were radiographed along an aluminum step-wedge. For cell culture assays, Saos-2 osteoblastic-cells (ATCC HTB-85 were used. Cell viability was evaluated through MTT assay, and bioactivity was assessed by alkaline phosphatase activity assay. Results The results demonstrated higher radiopacity for MTA, followed by Nbµ and Nbη, which had similar values. Cell culture analysis showed that PC and PC+NbO associations promoted greater cell viability than MTA. Conclusions It was concluded that the combination of PC+NbO is a potential alternative for composition of MTA.

  14. Sol-Gel Synthesis and Characterization of Cubic Bismuth Zinc Niobium Oxide Nanopowders

    Directory of Open Access Journals (Sweden)

    Ganchimeg Perenlei

    2014-01-01

    Full Text Available Bismuth zinc niobium oxide (BZN was successfully synthesized by a diol-based sol-gel reaction utilizing metal acetate and alkoxide precursors. Thermal analysis of a liquid suspension of precursors suggests that the majority of organic precursors decompose at temperatures up to 150°C, and organic free powders form above 350°C. The experimental results indicate that a homogeneous gel is obtained at about 200°C and then converts to a mixture of intermediate oxides at 350–400°C. Finally, single-phased BZN powders are obtained between 500 and 900°C. The degree of chemical homogeneity as determined by X-ray diffraction and EDS mapping is consistent throughout the samples. Elemental analysis indicates that the atomic ratio of metals closely matches a Bi1.5ZnNb1.5O7 composition. Crystallite sizes of the BZN powders calculated from the Scherrer equation are about 33–98 nm for the samples prepared at 500–700°C, respectively. The particle and crystallite sizes increase with increased sintering temperature. The estimated band gap of the BZN nanopowders from optical analysis is about 2.60–2.75 eV at 500-600°C. The observed phase formations and measured results in this study were compared with those of previous reports.

  15. Coloration and bleaching mechanism of niobium oxide electrochromic thin films; Sanka niobu electromic usumaku no chakushoshoku mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimura, K.; Miki, T.; Tazawa, M.; Jin, P.; Igarashi, K.; Tanemura, S. [National Industrial Research Institute of Nagoya, Nagoya (Japan)

    1997-11-25

    In order to search for the coloration and bleaching mechanism of niobium oxide, considerations were given on optical properties and electron conditions in niobium oxide thin films (glass plates as substrates coated with ITO) prepared by using the reactive DC magnetron sputtering process. The films were so grown that their thickness will all be 100 nm to facilitate data comparison. Coloration and bleaching of the grown test films were conducted by cyclic voltammetry. Electron spectra were measured by using XPS, and electron energy was analyzed. Coloration of niobium oxide occurs as a result of change in valency electron state from an Nb {sup 5+} state to an Nb {sup 4+} state, while change in the XPS spectra also corresponds with the above change. However, the XPS spectra differ greatly between crystalline samples and amorphous samples. The coloration and bleaching mechanism of the crystallized Nb2O5 film can be explained by a reaction formula similar to that for WO3. However, with regard to the amorphous Nb2O5 film, an independent reaction involving water in the film seems to occur together with the same reaction as in the crystallized film. 9 refs., 5 figs.

  16. Structural transformation of nickel hydroxide films during anodic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Crocker, R.W.; Muller, R.H.

    1992-05-01

    The transformation of anodically formed nickel hydroxide/oxy-hydroxide electrodes has been investigated. A mechanism is proposed for the anodic oxidation reaction, in which the reaction interface between the reduced and oxidized phases of the electrode evolves in a nodular topography that leads to inefficient utilization of the active electrode material. In the proposed nodular transformation model for the anodic oxidation reaction, nickel hydroxide is oxidized to nickel oxy-hydroxide in the region near the metal substrate. Since the nickel oxy-hydroxide is considerably more conductive than the surrounding nickel hydroxide, as further oxidation occurs, nodular features grow rapidly to the film/electrolyte interface. Upon emerging at the electrolyte interface, the reaction boundary between the nickel hydroxide and oxy-hydroxide phases spreads laterally across the film/electrolyte interface, creating an overlayer of nickel oxy-hydroxide and trapping uncharged regions of nickel hydroxide within the film. The nickel oxy-hydroxide overlayer surface facilitates the oxygen evolution side reaction. Scanning tunneling microscopy of the electrode in its charged state revealed evidence of 80 {endash} 100 Angstrom nickel oxy-hydroxide nodules in the nickel hydroxide film. In situ spectroscopic ellipsometer measurements of films held at various constant potentials agree quantitatively with optical models appropriate to the nodular growth and subsequent overgrowth of the nickel oxy-hydroxide phase. A two-dimensional, numerical finite difference model was developed to simulate the current distribution along the phase boundary between the charged and uncharged material. The model was used to explore the effects of the physical parameters that govern the electrode behavior. The ratio of the conductivities of the nickel hydroxide and oxy-hydroxide phases was found to be the dominant parameter in the system.

  17. Characterization of Human Gingival Fibroblasts on Zirconia Surfaces Containing Niobium Oxide

    Directory of Open Access Journals (Sweden)

    Young-Dan Cho

    2015-09-01

    Full Text Available It was indicated that tetragonal zirconia polycrystal (TZP containing yttria (Y2O3 and niobium oxide (Nb2O5 ((Y,Nb-TZP could be an adequate dental material to be used at esthetically important sites. The (Y,Nb-TZP was also proved to possess its osteogenic potential comparable with those conventional dental implant material, titanium (Ti. The objective of the current study was to characterize cellular response of human gingival fibroblasts (HGFs to smooth and rough surfaces of the (Y,Nb-TZP disc, which were obtained by polishing and sandblasting, respectively. Various microscopic, biochemical, and molecular techniques were used to investigate the disc surfaces and cellular responses for the experimental (Y,Nb-TZP and the comparing Ti groups. Sandblasted rough (Y,Nb-TZP (Zir-R discs had the highest surface roughness. HGFs cultured on polished (Y,Nb-TZP (Zir showed a rounded cell morphology and light spreading at 6 h after seeding and its proliferation rate significantly increased during seven days of culture compared to other surfaces. The mRNA expressions of type I collagen, integrin α2 and β1 were significantly stimulated for the Zir group at 24 h after seeding. The current findings, combined with the previous results, indicate that (Y,Nb-TZP provides appropriate surface condition for osseointegration at the fixture level and for peri-implant mucosal sealing at the abutment level producing a suitable candidate for dental implantation with an expected favorable clinical outcome.

  18. Preparation and characterization of Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3} composite oxide formed by cathodic electroplating and anodizing

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Joo-Hee; Kim, Tae-Yoo; Kim, Nam-Jeong; Lee, Chang-Hyoung; Park, Eun-Mi [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, Chan [Division of Materials Science and Engineering, Pukyong National University, Busan 608-739 (Korea, Republic of); Suh, Su-Jeong, E-mail: suhsj@skku.ac.kr [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Advanced Materials and Process Research Center for IT, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2011-11-15

    Highlights: > We fabricate Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3}/Al film for high performance thin film capacitor. > The optimum condition of electrolyte composition will coat NbO{sub x} on Al without corrosion of Al during the cathodic electroplating. > Increasing annealing temperature will form Nb{sub 2}O{sub 5} crystalline. > The Al{sub 2}O{sub 3} layer will form between Nb{sub 2}O{sub 5} layer and metal Al after anodizing and the thin film capacitor with Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3}/Al improve dielectric properties. - Abstract: Al foil was coated with niobium oxide by cathodic electroplating and anodized in a neutral boric acid solution to achieve high capacitance in a thin film capacitor. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) revealed the niobium oxide layer on Al to be a hydroxide-rich amorphous phase. The film was crystalline and had stoichiometric stability after annealing at temperatures up to 600 deg. C followed by anodizing at 500 V, and the specific capacitance of the Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3} composite oxide was approximately 27% higher than that of Al{sub 2}O{sub 3} without a Nb{sub 2}O{sub 5} layer. The capacitance was quite stable to the resonance frequency. Overall, the Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3} composite oxide film is a suitable material for thin film capacitors.

  19. Ammonium removal from landfill leachate by anodic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Cabeza, Adelaida [Department of Chemical Engineering, University of Cantabria, Avda. de los Castros s/n. 39005 Santander (Spain); Urtiaga, Ane [Department of Chemical Engineering, University of Cantabria, Avda. de los Castros s/n. 39005 Santander (Spain)]. E-mail: urtiaga@unican.es; Rivero, Maria-Jose [Department of Chemical Engineering, University of Cantabria, Avda. de los Castros s/n. 39005 Santander (Spain); Ortiz, Inmaculada [Department of Chemical Engineering, University of Cantabria, Avda. de los Castros s/n. 39005 Santander (Spain)

    2007-06-18

    The feasibility of removing ammonium from landfill leachates by electrochemical oxidation was studied. Raw leachates and biologically/physico-chemically pretreated leachates from a municipal landfill site were treated. Boron doped diamond was used as anode and stainless steel as cathode, both electrodes with an area of 70 cm{sup 2}. The effects of the applied current density (15-90 mA cm{sup -2}), the initial ammonium concentration (480-2000 mg L{sup -1}), and the initial chloride concentration were experimentally studied. Total ammonium removal was obtained after 360 min of processing and almost half of the initial ammonium nitrogen was oxidized to nitrate. On the other hand, the concentration of chloride enhanced the rate of ammonium oxidation. In addition, the amount of N-NH{sub 4} {sup +} transformed into N-NO{sub 3} {sup -} decreased when additional chloride was provided.

  20. Electrochemical degradation of clofibric acid in water by anodic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Sires, Ignasi [Laboratori de Ciencia i Tecnologia Electroquimica de Materials, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Cabot, Pere Lluis [Laboratori de Ciencia i Tecnologia Electroquimica de Materials, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Centellas, Francesc [Laboratori de Ciencia i Tecnologia Electroquimica de Materials, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Garrido, Jose Antonio [Laboratori de Ciencia i Tecnologia Electroquimica de Materials, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Rodriguez, Rosa Maria [Laboratori de Ciencia i Tecnologia Electroquimica de Materials, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Arias, Conchita [Laboratori de Ciencia i Tecnologia Electroquimica de Materials, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Brillas, Enric [Laboratori de Ciencia i Tecnologia Electroquimica de Materials, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain)]. E-mail: brillas@ub.edu

    2006-10-05

    Aqueous solutions containing the metabolite clofibric acid (2-(4-chlorophenoxy)-2-methylpropionic acid) up to close to saturation in the pH range 2.0-12.0 have been degraded by anodic oxidation with Pt and boron-doped diamond (BDD) as anodes. The use of BDD leads to total mineralization in all media due to the efficient production of oxidant hydroxyl radical ({center_dot}OH). This procedure is then viable for the treatment of wastewaters containing this compound. The effect of pH, apparent current density, temperature and metabolite concentration on the degradation rate, consumed specific charge and mineralization current efficiency has been investigated. Comparative treatment with Pt yields poor decontamination with complete release of stable chloride ion. When BDD is used, this ion is oxidized to Cl{sub 2}. Clofibric acid is more rapidly destroyed on Pt than on BDD, indicating that it is more strongly adsorbed on the Pt surface enhancing its reaction with {center_dot}OH. Its decay kinetics always follows a pseudo-first-order reaction and the rate constant for each anode increases with increasing apparent current density, being practically independent of pH and metabolite concentration. Aromatic products such as 4-chlorophenol, 4-chlorocatechol, 4-chlororesorcinol, hydroquinone, p-benzoquinone and 1,2,4-benzenetriol are detected by gas chromatography-mass spectrometry (GC-MS) and reversed-phase chromatography. Tartronic, maleic, fumaric, formic, 2-hydroxyisobutyric, pyruvic and oxalic acids are identified as generated carboxylic acids by ion-exclusion chromatography. These acids remain stable in solution using Pt, but they are completely converted into CO{sub 2} with BDD. A reaction pathway for clofibric acid degradation involving all these intermediates is proposed.

  1. Controlling interferometric properties of nanoporous anodic aluminium oxide.

    Science.gov (United States)

    Kumeria, Tushar; Losic, Dusan

    2012-01-26

    A study of reflective interference spectroscopy [RIfS] properties of nanoporous anodic aluminium oxide [AAO] with the aim to develop a reliable substrate for label-free optical biosensing is presented. The influence of structural parameters of AAO including pore diameters, inter-pore distance, pore length, and surface modification by deposition of Au, Ag, Cr, Pt, Ni, and TiO2 on the RIfS signal (Fabry-Perot fringe) was explored. AAO with controlled pore dimensions was prepared by electrochemical anodization of aluminium using 0.3 M oxalic acid at different voltages (30 to 70 V) and anodization times (10 to 60 min). Results show the strong influence of pore structures and surface modifications on the interference signal and indicate the importance of optimisation of AAO pore structures for RIfS sensing. The pore length/pore diameter aspect ratio of AAO was identified as a suitable parameter to tune interferometric properties of AAO. Finally, the application of AAO with optimised pore structures for sensing of a surface binding reaction of alkanethiols (mercaptoundecanoic acid) on gold surface is demonstrated.

  2. Microstructure and optical appearance of anodized friction stir processed Al - Metal oxide surface composites

    DEFF Research Database (Denmark)

    Gudla, Visweswara Chakravarthy; Jensen, Flemming; Bordo, Kirill

    2014-01-01

    Multiple-pass friction stir processing (FSP) was employed to impregnate Ti, Y and Ce oxide powders into the surface of an Aluminium alloy. The FSP processed surface composite was subsequently anodized with an aim to develop optical effects in the anodized layer owing to the presence of incorporated...... oxide particles which will influence the scattering of light. This paper presents the investigations on relation between microstructure of the FSP zone and optical appearance of the anodized layer due to incorporation of metal oxide particles and modification of the oxide particles due to the anodizing...

  3. Structural features of anodic oxide films formed on aluminum substrate coated with self-assembled microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Asoh, Hidetaka [Department of Applied Chemistry, Faculty of Engineering, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015 (Japan)], E-mail: asoh@cc.kogakuin.ac.jp; Uchibori, Kota; Ono, Sachiko [Department of Applied Chemistry, Faculty of Engineering, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015 (Japan)

    2009-07-15

    The structural features of anodic oxide films formed on an aluminum substrate coated with self-assembled microspheres were investigated by scanning electron microscopy and atomic force microscopy. In the first anodization in neutral solution, the growth of a barrier-type film was partially suppressed in the contact area between the spheres and the underlying aluminum substrate, resulting in the formation of ordered dimple arrays in an anodic oxide film. After the subsequent second anodization in acid solution at a voltage lower than that of the first anodization, nanopores were generated only within each dimple. The nanoporous region could be removed selectively by post-chemical etching using the difference in structural dimensions between the porous region and the surrounding barrier region. The mechanism of anodic oxide growth on the aluminum substrate coated with microspheres through multistep anodization is discussed.

  4. Comparative study on ammonia oxidation over Ni-based cermet anodes for solid oxide fuel cells

    Science.gov (United States)

    Molouk, Ahmed Fathi Salem; Yang, Jun; Okanishi, Takeou; Muroyama, Hiroki; Matsui, Toshiaki; Eguchi, Koichi

    2016-02-01

    In the current work, we investigate the performance of solid oxide fuel cells (SOFCs) with Ni‒yttria-stabilized zirconia (Ni-YSZ) and Ni‒gadolinia-dope ceria (Ni-GDC) cermet anodes fueled with H2 or NH3 in terms of the catalytic activity of ammonia decomposition. The cermet of Ni-GDC shows higher catalytic activity for ammonia decomposition than Ni-YSZ. In response to this, the performance of direct NH3-fueled SOFC improved by using Ni-GDC anode. Moreover, we observe further enhancement in the cell performance and the catalytic activity for ammonia decomposition with applying Ni-GDC anode synthesised by the glycine-nitrate combustion process. These results reveal that the high performance of Ni-GDC anode for the direct NH3-fueled SOFC results from its mixed ionic-electronic conductivity as well as high catalytic activity for ammonia decomposition.

  5. Evaluation of nickel-titanium oxide-niobium pentoxide metal ceramic composite as interconnect for solid oxide fuel cell

    Science.gov (United States)

    Budur, Abhijith

    With increasing importance for clean energy, fuel cells have gained great significance in recent decades. Solid oxide fuel cells are easy to transport due to presence of solid electrolyte and also have requisite electrical properties,but have been obstructed by their limitation to be used at only temperatures greater than 6000C and less than 8000C. To construct a stack of cells, materials that are good electrical conductors and having necessary mechanical strengths at that temperatures are being considered as interconnects between the cells. Evaluation of Nickel-Titanium dioxide-Niobium pentoxide (NTN) as interconnect and comparison to Stainless Steel 441 alloy has been made in this research. The criteria for evaluation are the resistance, long-term stability and the power density characteristics of the cell for each interconnect. Electrical measurements by impedance spectroscopy techniques were conducted at variousworking temperatures using a gas mixture of 10 % hydrogen and 90% nitrogen to evaluate both interconnect materials in the working range of fuel cells. Scanning Electron Microscopy images of Lanthanum Strontium Manganite paste before and after the fuel cell measurements are shown.The results showed that both NTN and Stainless Steel 441 interconnects exhibit similar electrical properties under operating conditions of the fuel cell. Since theNTN interconnect is less prone to corrosion and does not have the effect of chromium poisoning, it can be considered as a viable interconnect material for solid oxide fuel cells.

  6. Anodic deposition of hydrous ruthenium oxide for supercapacitors

    Science.gov (United States)

    Hu, Chi-Chang; Liu, Ming-Jue; Chang, Kuo-Hsin

    This communication demonstrates the success in the anodic deposition of hydrous ruthenium oxide (denoted as RuO 2· xH 2O) from RuCl 3· xH 2O in aqueous media with/without adding acetate ions (CH 3COO -, AcO -) as the complex agent. The benefits of as-deposited RuO 2· xH 2O include the low electron-hopping resistance and the low contact resistance at the Ti-RuO 2· xH 2O interface which are clarified in electrochemical impedance spectroscopic (EIS) studies. The cycling stability, specific capacitance, and power performance of as-deposited RuO 2· xH 2O are further improved by annealing in air at 150 °C for 2 h. The morphologies of as-deposited and annealed RuO 2· xH 2O films, examined by scanning electron microscopy (SEM), are very similar to that of thermally decomposed RuO 2. The high onset frequencies of 660 and 1650 Hz obtained from EIS spectra for the as-deposited and annealed RuO 2· xH 2O films, respectively, definitely illustrate the high-power merits of both oxide films prepared by means of the anodic deposition without considering the advantages of its simplicity, one-step, reliability, low cost, and versatility for electrode preparation.

  7. Preparation of Aluminum Nanomesh Thin Films from an Anodic Aluminum Oxide Template as Transparent Conductive Electrodes

    Science.gov (United States)

    Li, Yiwen; Chen, Yulong; Qiu, Mingxia; Yu, Hongyu; Zhang, Xinhai; Sun, Xiao Wei; Chen, Rui

    2016-02-01

    We have employed anodic aluminum oxide as a template to prepare ultrathin, transparent, and conducting Al films with a unique nanomesh structure for transparent conductive electrodes. The anodic aluminum oxide template is obtained through direct anodization of a sputtered Al layer on a glass substrate, and subsequent wet etching creates the nanomesh metallic film. The optical and conductive properties are greatly influenced by experimental conditions. By tuning the anodizing time, transparent electrodes with appropriate optical transmittance and sheet resistance have been obtained. The results demonstrate that our proposed strategy can serve as a potential method to fabricate low-cost TCEs to replace conventional indium tin oxide materials.

  8. Solid oxide fuel cell power plant with an anode recycle loop turbocharger

    Energy Technology Data Exchange (ETDEWEB)

    Saito, Kazuo; Skiba, Tommy; Patel, Kirtikumar H.

    2016-09-27

    An anode exhaust recycle turbocharger (100) has a turbocharger turbine (102) secured in fluid communication with a compressed oxidant stream within an oxidant inlet line (218) downstream from a compressed oxidant supply (104), and the anode exhaust recycle turbocharger (100) also includes a turbocharger compressor (106) mechanically linked to the turbocharger turbine (102) and secured in fluid communication with a flow of anode exhaust passing through an anode exhaust recycle loop (238) of the solid oxide fuel cell power plant (200). All or a portion of compressed oxidant within an oxidant inlet line (218) drives the turbocharger turbine (102) to thereby compress the anode exhaust stream in the recycle loop (238). A high-temperature, automotive-type turbocharger (100) replaces a recycle loop blower-compressor (52).

  9. Formation and dielectric properties of anodic oxide films on Zr–Al alloys

    OpenAIRE

    Koyama, Shun; Aoki, Yoshitaka; Nagata, Shinji; Habazaki, Hiroki

    2011-01-01

    Zr–Al alloys containing up to 26 at.% aluminum, prepared by magnetron sputtering, have been anodized in 0.1 mol dm−3 ammonium pentaborate electrolyte, and the structure and dielectric properties of the resultant anodic oxide films have been examined by grazing incidence X-ray diffraction, transmission electron microscopy, Rutherford backscattering spectroscopy, and AC impedance spectroscopy. The anodic oxide film formed on zirconium consists of monoclinic and tetragonal ZrO2 with the fo...

  10. Formation of crystalline TiO2 by anodic oxidation of titanium

    Institute of Scientific and Technical Information of China (English)

    Zixue Su; Linjie Zhang; Feilong Jiang; Maochun Hongn

    2013-01-01

    Formation of crystalline TiO2 (anatase) films by anodic oxidation of titanium foils in ethylene glycol (EG) based electrolytes at room temperature has been investigated. By varying the anodizing parameters such as the amounts of water and NH4F added, applied voltage and anodization time, anodic TiO2 films with different crystalline structures were obtained. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray powder diffraction (XRD) characterizations were employed to determine the morphologies and crystalline structures of as-prepared anodic TiO2 films. The results indicate that crystallization of anodic TiO2 films was generally facilitated by high fluoride concentration, high applied voltage and longer anodization time, and the formation of anodic TiO2 films with best crystallinity could only be achieved when optimized amounts of water were added.

  11. OXIDATION OF DRY HYDROCARBONS AT HIGH-POWER DENSITY ANODES

    Energy Technology Data Exchange (ETDEWEB)

    K.Krist; O. Spaldon-Stewart; R. Remick

    2004-03-01

    This work builds upon discoveries by the University of Pennsylvania and others pertaining to the oxidation of dry hydrocarbon fuels in high temperature solid oxide fuel cells. The work reported here was restricted primarily to dry methane and confirms that YSZ-based cells, having ceria in the anode as a catalyst and copper in the anode as a current collector, can operate on dry methane for extended periods. Thirty-three lab-scale cells of various designs were fabricated and operated under a variety of conditions. The longest-lived cell gave stable performance on dry methane at 800 C for over 305 hours. Only slight carbon deposition was noted at the completion of the test. A corresponding nickel/YSZ-based anode would have lasted for less than an hour under these test conditions (which included open circuit potential measurements) before carbon fouling essentially destroyed the cell. The best performing cell achieved 112 mW/cm{sub 2} on dry methane at 800 C. Several problems were encountered with carbon fouling and declining open circuit voltages in many of the test cells after switching from operation on hydrogen to dry methane. Although not rigorously confirmed by experimentation, the results suggested that air infiltration through less than perfect perimeter seals or pinholes in the electrolytes, or both gave rise to conditions that caused the carbon fouling and OCV decline. Small amounts of air reacting with methane in a partial oxidation reaction could produce carbon monoxide that, in turn, would deposit the carbon. If this mechanism is confirmed, it implies that near perfect hardware is required for extended operation. Some evidence was also found for the formation of electrical shorts, probably from carbon deposits bridging the electrolyte. Work with odorized methane and with methane containing 100-ppm hydrogen sulfide confirmed that copper is stable at 800 C in dry hydrocarbon fuels in the presence of sulfur. In a number of cases, but not exclusively, the

  12. AFM based anodic oxidation and its application to oxidative cutting and welding of CNT

    Institute of Scientific and Technical Information of China (English)

    JIAO NianDong; WANG YueChao; XI Ning; DONG ZaiLi

    2009-01-01

    Probe anodic oxidation by atomic force microscope (AFM) is one of the most important techniques in fabricating nano structures and devices.The technique was further studied in this paper.By analyzing the distribution of the electric field on substrate surface the dependence of oxide characters on field was discussed.The impacts of various parameters on oxide fabrication were experimentally studied.Based on these studies, we realized the oxidative cutting and welding of carbon nanotube (CNT) by the AFM based oxidation technique and provided a novel technique for the assembly and fabrication of CNT based nano devices.

  13. AFM based anodic oxidation and its application to oxidative cutting and welding of CNT

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Probe anodic oxidation by atomic force microscope (AFM) is one of the most important techniques in fabricating nano structures and devices. The technique was further studied in this paper. By analyzing the distribution of the electric field on substrate surface the dependence of oxide characters on field was discussed. The impacts of various parameters on oxide fabrication were experimentally studied. Based on these studies, we realized the oxidative cutting and welding of carbon nanotube (CNT) by the AFM based oxidation technique and provided a novel technique for the assembly and fabrication of CNT based nano devices.

  14. Possible influence of surface oxides on the optical response of high-purity niobium material used in the fabrication of superconducting radio frequency cavity

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Nageshwar [Magnetic and Superconducting Materials Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India); Deo, M.N. [High Pressure & Synchrotron Radiation Physics Division, BARC, Mumbai 400085 (India); Roy, S.B. [Magnetic and Superconducting Materials Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India)

    2016-09-11

    We have investigated the possible influence of surface oxides on the optical properties of a high-purity niobium (Nb) material for fabrication of superconducting radio frequency (SCRF) cavities. Various peaks in the infrared region were identified using Fourier transform infrared and Raman spectroscopy. Optical response functions such as complex refractive index, dielectric and conductivity of niobium were compared with the existing results on oxides free Nb and Cu. It was observed that the presence of a mixture of niobium-oxides, and probably near other surface impurities, appreciably influence the conducting properties of the material causing deviation from the typical metallic characteristics. In this way, the key result of this work is the observation, identification of vibrational modes of some of surface complexes and study of its influences on the optical responses of materials. This method of spectroscopic investigation will help in understanding the origin of degradation of performance of SCRF cavities.

  15. Possible influence of surface oxides on the optical response of high-purity niobium material used in the fabrication of superconducting radio frequency cavity

    Science.gov (United States)

    Singh, Nageshwar; Deo, M. N.; Roy, S. B.

    2016-09-01

    We have investigated the possible influence of surface oxides on the optical properties of a high-purity niobium (Nb) material for fabrication of superconducting radio frequency (SCRF) cavities. Various peaks in the infrared region were identified using Fourier transform infrared and Raman spectroscopy. Optical response functions such as complex refractive index, dielectric and conductivity of niobium were compared with the existing results on oxides free Nb and Cu. It was observed that the presence of a mixture of niobium-oxides, and probably near other surface impurities, appreciably influence the conducting properties of the material causing deviation from the typical metallic characteristics. In this way, the key result of this work is the observation, identification of vibrational modes of some of surface complexes and study of its influences on the optical responses of materials. This method of spectroscopic investigation will help in understanding the origin of degradation of performance of SCRF cavities.

  16. Characterization and Tribological Properties of Hard Anodized and Micro Arc Oxidized 5754 Quality Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    M. Ovundur

    2015-03-01

    Full Text Available This study was initiated to compare the tribological performances of a 5754 quality aluminum alloy after hard anodic oxidation and micro arc oxidation processes. The structural analyses of the coatings were performed using XRD and SEM techniques. The hardness of the coatings was determined using a Vickers micro-indentation tester. Tribological performances of the hard anodized and micro arc oxidized samples were compared on a reciprocating wear tester under dry sliding conditions. The dry sliding wear tests showed that the wear resistance of the oxide coating generated by micro arc oxidation is remarkably higher than that of the hard anodized alloy.

  17. Electrode Reaction Pathway in Oxide Anode for Solid Oxide Fuel Cells

    Science.gov (United States)

    Li, Wenyuan

    Oxide anodes for solid oxide fuel cells (SOFC) with the advantage of fuel flexibility, resistance to coarsening, small chemical expansion and etc. have been attracting increasing interest. Good performance has been reported with a few of perovskite structure anodes, such as (LaSr)(CrMn)O3. However, more improvements need to be made before meeting the application requirement. Understanding the oxidation mechanism is crucial for a directed optimization, but it is still on the early stage of investigation. In this study, reaction mechanism of oxide anodes is investigated on doped YCrO 3 with H2 fuel, in terms of the origin of electrochemical activity, rate-determining steps (RDS), extension of reactive zone, and the impact from overpotential under service condition to those properties. H2 oxidation on the YCs anodes is found to be limited by charge transfer and H surface diffusion. A model is presented to describe the elementary steps in H2 oxidation. From the reaction order results, it is suggested that any models without taking H into the charge transfer step are invalid. The nature of B site element determines the H2 oxidation kinetics primarily. Ni displays better adsorption ability than Co. However, H adsorption ability of such oxide anode is inferior to that of Ni metal anode. In addition, the charge transfer step is directly associated with the activity of electrons in the anode; therefore it can be significantly promoted by enhancement of the electron activity. It is found that A site Ca doping improves the polarization resistance about 10 times, by increasing the activity of electrons to promote the charge transfer process. For the active area in the oxide anode, besides the traditional three-phase boundary (3PB), the internal anode surface as two-phase boundary (2PB) is proven to be capable of catalytically oxidizing the H2 fuel also when the bulk lattice is activated depending on the B site elements. The contribution from each part is estimated by switching

  18. Investigation of top-emitting OLEDs using molybdenum oxide as anode buffer layer

    Institute of Scientific and Technical Information of China (English)

    LIN Hui; YU Jun-sheng; ZHANG Wei

    2012-01-01

    A high-effective bottom anode is essential for high-performance top-emitting organic light-emitting devices (OLEDs).In this paper,Ag-based top-emitting OLEDs are investigated.Ag has the highest reflectivity for visible light among all metals,yet its hole-injection properties are not ideal for anodes of top-emitting OLED.The performance of the devices is significantly improved using the molybdenum oxide as anode buffer layer at the surface of Ag.By introducing the molybdenum oxide,the hole injection from Ag anodes into top-emitting OLED is largely enhanced with rather high reflectivity retained.

  19. Fabrication of YBCO nanowires with anodic aluminum oxide (AAO) template

    Energy Technology Data Exchange (ETDEWEB)

    Dadras, Sedigheh, E-mail: dadras@alzahra.ac.ir; Aawani, Elaheh

    2015-10-15

    We have fabricated YBCO nanowires by using anodic aluminum oxide (AAO) template and sol–gel method, to investigate the fundamental properties of the one-dimensional nanostructure YBCO high-temperature superconductor and enhance its applications. The field-emission scanning electron microscopy and X-ray diffraction pattern results have shown forming of Y-123 nanowires in the template. As an outcome, the YBCO nanowires, prepared by dipping AAO template into YBCO sol method, have average diameter of about 38 nm and length of 1 μm; this is an optimum nanowire sample with larger diameter and length. The resistance–temperature measurement indicates that the onset critical temperature of these samples occurs at 91 K, and the resistance of the optimum sample at onset transition is 10 times lower than the other sample.

  20. Fabrication of Nanostructured PLGA Scaffolds Using Anodic Aluminum Oxide Templates

    CERN Document Server

    Hsueh, Cheng-Chih; Hsu, Shan-Hui; Hung, Huey-Shan

    2008-01-01

    PLGA (poly(lactic-co-glycolic acid)) is one of the most used biodegradable and biocompatible materials. Nanostructured PLGA even has great application potentials in tissue engineering. In this research, a fabrication technique for nanostructured PLGA membrane was investigated and developed. In this novel fabrication approach, an anodic aluminum oxide (AAO) film was use as the template ; the PLGA solution was then cast on it ; the vacuum air-extraction process was applied to transfer the nano porous pattern from the AAO membrane to the PLGA membrane and form nanostures on it. The cell culture experiments of the bovine endothelial cells demonstrated that the nanostructured PLGA membrane can double the cell growing rate. Compared to the conventional chemical-etching process, the physical fabrication method proposed in this research not only is simpler but also does not alter the characteristics of the PLGA. The nanostructure of the PLGA membrane can be well controlled by the AAO temperate.

  1. Electrical transport through single-wall carbon nanotube-anodic aluminum oxide-aluminum heterostructures

    Science.gov (United States)

    Kukkola, Jarmo; Rautio, Aatto; Sala, Giovanni; Pino, Flavio; Tóth, Géza; Leino, Anne-Riikka; Mäklin, Jani; Jantunen, Heli; Uusimäki, Antti; Kordás, Krisztián; Gracia, Eduardo; Terrones, Mauricio; Shchukarev, Andrey; Mikkola, Jyri-Pekka

    2010-01-01

    Aluminum foils were anodized in sulfuric acid solution to form thick porous anodic aluminum oxide (AAO) films of thickness ~6 µm. Electrodes of carboxyl-functionalized single-wall carbon nanotube (SWCNT) thin films were inkjet printed on the anodic oxide layer and the electrical characteristics of the as-obtained SWCNT-AAO-Al structures were studied. Nonlinear current-voltage transport and strong temperature dependence of conduction through the structure was measured. The microstructure and chemical composition of the anodic oxide layer was analyzed using transmission and scanning electron microscopy as well as x-ray photoelectron spectroscopy. Schottky emission at the SWCNT-AAO and AAO-Al interfaces allowed by impurity states in the anodic aluminum oxide film together with ionic surface conduction on the pore walls of AAO gives a reasonable explanation for the measured electrical conduction. Calcined AAO is proposed as a dielectric material for SWCNT-field effect transistors.

  2. Effect of intermetallic phases on the anodic oxidation and corrosion of 5A06 aluminum alloy

    Science.gov (United States)

    Li, Song-mei; Li, Ying-dong; Zhang, You; Liu, Jian-hua; Yu, Mei

    2015-02-01

    Intermetallic phases were found to influence the anodic oxidation and corrosion behavior of 5A06 aluminum alloy. Scattered intermetallic particles were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) after pretreatment. The anodic film was investigated by transmission electron microscopy (TEM), and its corrosion resistance was analyzed by electrochemical impedance spectroscopy (EIS) and Tafel polarization in NaCl solution. The results show that the size of Al-Fe-Mg-Mn particles gradually decreases with the iron content. During anodizing, these intermetallic particles are gradually dissolved, leading to the complex porosity in the anodic film beneath the particles. After anodizing, the residual particles are mainly silicon-containing phases, which are embedded in the anodic film. Electrochemical measurements indicate that the porous anodic film layer is easily penetrated, and the barrier plays a dominant role in the overall protection. Meanwhile, self-healing behavior is observed during the long immersion time.

  3. Antisolvent Precipitation for the Synthesis of Monodisperse Mesoporous Niobium Oxide Spheres as Highly Effective Solid Acid Catalysts

    KAUST Repository

    Li, Cheng Chao

    2012-03-20

    We have developed a low-cost reaction protocol to synthesize mesoporous Nb 2O 5-based solid acid catalysts with external shape control. In the synthesis, monodisperse glycolated niobium oxide spheres (GNOS) were prepared by means of a simple antisolvent precipitation approach and subsequently converted to mesoporous niobium oxide spheres (MNOS) with a large surface area of 312m 2g -1 by means of the hydrothermal treatment. The antisolvent acetone used to obtain GNOS was recovered through distillation at high purity. The obtained mesoporous MNOS were functionalized further with sulfate anions at different temperatures or incorporated with tungstophosphoric acid to obtain recyclable solid acid catalysts. These MNOS-based catalysts showed excellent performance in a wide range of acid-catalyzed reactions, such as Friedel-Crafts alkylation, esterification, and hydrolysis of acetates. As they are monodisperse spheres with diameters in the submicrometer range, the catalysts can be easily separated and reused. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Anode Supported Solid Oxide Fuel Cells - Deconvolution of Degradation into Cathode and Anode Contributions

    DEFF Research Database (Denmark)

    Hagen, Anke; Liu, Yi-Lin; Barfod, Rasmus;

    2007-01-01

    The degradation of anode supported cells was studied over 1500 h as function of cell polarization either in air or oxygen on the cathode. Based on impedance analysis, contributions of anode and cathode to the increase of total resistance were assigned. Accordingly, the degradation rates of the ca...

  5. Silicon oxide based high capacity anode materials for lithium ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Haixia; Han, Yongbong; Masarapu, Charan; Anguchamy, Yogesh Kumar; Lopez, Herman A.; Kumar, Sujeet

    2017-03-21

    Silicon oxide based materials, including composites with various electrical conductive compositions, are formulated into desirable anodes. The anodes can be effectively combined into lithium ion batteries with high capacity cathode materials. In some formulations, supplemental lithium can be used to stabilize cycling as well as to reduce effects of first cycle irreversible capacity loss. Batteries are described with surprisingly good cycling properties with good specific capacities with respect to both cathode active weights and anode active weights.

  6. Friction stir processed Al - Metal oxide surface composites: Anodization and optical appearance

    DEFF Research Database (Denmark)

    Gudla, Visweswara Chakravarthy; Jensen, Flemming; Canulescu, Stela

    2014-01-01

    Multiple-pass friction stir processing (FSP) was employed to impregnate metal oxide (TiO2, Y2O3 and CeO2) particles into the surface of an Aluminium alloy. The surface composites were then anodized in a sulphuric acid electrolyte. The effect of anodizing parameters on the resulting optical...... dark to greyish white. This is attributed to the localized microstructural and morphological differences around the metal oxide particles incorporated into the anodic alumina matrix. The metal oxide particles in the FSP zone electrochemically shadowed the underlying Al matrix and modified the local...

  7. Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying

    DEFF Research Database (Denmark)

    Canulescu, Stela; Rechendorff, K.; Borca, C. N.;

    2014-01-01

    The band structure of pure and Ti-alloyed anodic aluminum oxide has been examined as a function of Ti concentration varying from 2 to 20 at. %. The band gap energy of Ti-alloyed anodic Al oxide decreases with increasing Ti concentration. X-ray absorption spectroscopy reveals that Ti atoms...... are not located in a TiO2 unit in the oxide layer, but rather in a mixed Ti-Al oxide layer. The optical band gap energy of the anodic oxide layers was determined by vacuum ultraviolet spectroscopy in the energy range from 4.1 to 9.2 eV (300–135 nm). The results indicate that amorphous anodic Al2O3 has a direct...

  8. Nickel/Yttria-stabilised zirconia cermet anodes for solid oxide fuel cells

    NARCIS (Netherlands)

    Primdahl, Søren

    1999-01-01

    This thesis deals with the porous Ni/yttria-stabilized zirconia (YSZ) cermet anode on a YSZ electrolyte for solid oxide fuel cells (SOFC). Such anodes are predominantly operated in moist hydrogen at 700°C to 1000°C, and the most important technological parameters are the polarization resistance and

  9. Ni modified ceramic anodes for direct-methane solid oxide fuel cells

    Science.gov (United States)

    Xiao, Guoliang; Chen, Fanglin

    2016-01-19

    In accordance with certain embodiments of the present disclosure, a method for fabricating a solid oxide fuel cell is described. The method includes synthesizing a composition having a perovskite present therein. The method further includes applying the composition on an electrolyte support to form an anode and applying Ni to the composition on the anode.

  10. FIB-SEM investigation of trapped intermetallic particles in anodic oxide films on AA1050 aluminium

    DEFF Research Database (Denmark)

    Jariyaboon, Manthana; Møller, Per; Dunin-Borkowski, Rafal E.;

    2011-01-01

    Purpose - The purpose of this investigation is to understand the structure of trapped intermetallics particles and localized composition changes in the anodized anodic oxide film on AA1050 aluminium substrates. Design/methodology/approach - The morphology and composition of Fe-containing intermet...

  11. Photoluminescence emission of nanoporous anodic aluminum oxide films prepared in phosphoric acid

    Science.gov (United States)

    Nourmohammadi, Abolghasem; Asadabadi, Saeid Jalali; Yousefi, Mohammad Hasan; Ghasemzadeh, Majid

    2012-12-01

    The photoluminescence emission of nanoporous anodic aluminum oxide films formed in phosphoric acid is studied in order to explore their defect-based subband electronic structure. Different excitation wavelengths are used to identify most of the details of the subband states. The films are produced under different anodizing conditions to optimize their emission in the visible range. Scanning electron microscopy investigations confirm pore formation in the produced layers. Gaussian analysis of the emission data indicates that subband states change with anodizing parameters, and various point defects can be formed both in the bulk and on the surface of these nanoporous layers during anodizing.

  12. Platinum-Niobium(V Oxide/Carbon Nanocomposites Prepared By Microwave Synthesis For Ethanol Oxidation

    Directory of Open Access Journals (Sweden)

    Virginija KEPENIENĖ

    2016-05-01

    Full Text Available In the present work, Pt nanoparticles were deposited by means of microwave synthesis on the primary carbon supported Nb2O5 composite which was prepared in two different ways: (A by dispersion of Nb2O5 and carbon with the mass ratio equal to 1:1 in a 2-propanol solution by ultrasonication for 30 min. with further desiccation of the mixture and (B by heating the Nb2O5/C composite obtained according to the procedure (A at 500 °C for 2 h. The transmission electron microscopy was used to determine the shape and the size of catalyst particles. X-ray diffraction and inductively coupled plasma optical emission spectroscopy were employed to characterize the structure and composition of the synthesized catalysts. The electrocatalytic activity of the synthesized catalysts towards the oxidation of ethanol in an alkaline medium was investigated by means of cyclic voltammetry.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.8609

  13. Anodic Oxidation of Carbon Steel at High Current Densities and Investigation of Its Corrosion Behavior

    Science.gov (United States)

    Fattah-Alhosseini, Arash; Khan, Hamid Yazdani

    2017-02-01

    This work aims at studying the influence of high current densities on the anodization of carbon steel. Anodic protective coatings were prepared on carbon steel at current densities of 100, 125, and 150 A/dm2 followed by a final heat treatment. Coatings microstructures and morphologies were analyzed using X-ray diffraction (XRD) and scanning electron microscope (SEM). The corrosion resistance of the uncoated carbon steel substrate and the anodic coatings were evaluated in 3.5 wt pct NaCl solution through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results showed that the anodic oxide coatings which were prepared at higher current densities had thicker coatings as a result of a higher anodic forming voltage. Therefore, the anodized coatings showed better anti-corrosion properties compared to those obtained at lower current densities and the base metal.

  14. Synthesis of silver nanotubes by electroless deposition in porous anodic aluminium oxide templates.

    Science.gov (United States)

    Zhang, Shu-Hong; Xie, Zhao-Xiong; Jiang, Zhi-Yuan; Xu, Xin; Xiang, Juan; Huang, Rong-Bin; Zheng, Lan-Sun

    2004-05-07

    An electroless deposition method has been employed for the synthesis of silver nanotubes using porous anodic aluminium oxide as templates, by which high-yield silver nanotubes with length over ten microns have been synthesized.

  15. CNTs tuning and vertical alignment in anodic aluminium oxide membrane

    Institute of Scientific and Technical Information of China (English)

    Maria Sarno; Diana Sannino; Caterina Leone; Paolo Ciambelli

    2012-01-01

    Anodic aluminium oxide (AAOM) membranes were used for template growth of carbon nanotubes (CNT) inside their pores by chemical vapour deposition (CVD) of different hydrocarbons,in the absence of transition metal catalyst.A composite material,containing one nanotube for each channel,having the same length as the membrane thickness and the external diameter close to the diameter of the membrane holes,was obtained.Yield,selectivity,and quality of CNTs in terms of diameter (up to very thin CNT),carbon order,length,arrangement (i.e.number of tubes for each channel),purity,that are critical requisites for several applications were optimized by investigating the effect of changing the hydrocarbon feedstock gas,also in the presence of hydrogen.The samples produced using methane as a feedstock have a well ordered structure.The role of the alumina channels surface during the CNT growth has been investigated and its catalytic activity has been proved for the first time.

  16. Facile fabrication of nanofluidic diode membranes using anodic aluminium oxide.

    Science.gov (United States)

    Wu, Songmei; Wildhaber, Fabien; Vazquez-Mena, Oscar; Bertsch, Arnaud; Brugger, Juergen; Renaud, Philippe

    2012-09-21

    Active control of ion transport plays important roles in chemical and biological analytical processes. Nanofluidic systems hold the promise for such control through electrostatic interaction between ions and channel surfaces. Most existing experiments rely on planar geometry where the nanochannels are generally very long and shallow with large aspect ratios. Based on this configuration the concepts of nanofluidic gating and rectification have been successfully demonstrated. However, device minimization and throughput scaling remain significant challenges. We report here an innovative and facile realization of hetero-structured Al(2)O(3)/SiO(2) (Si) nanopore array membranes by using pattern transfer of self-organized nanopore structures of anodic aluminum oxide (AAO). Thanks to the opposite surface charge states of Al(2)O(3) (positive) and SiO(2) (negative), the membrane exhibits clear rectification of ion current in electrolyte solutions with very low aspect ratios compared to previous approaches. Our hetero-structured nanopore arrays provide a valuable platform for high throughput applications such as molecular separation, chemical processors and energy conversion.

  17. Nanoporous Pirani sensor based on anodic aluminum oxide

    Science.gov (United States)

    Jeon, Gwang-Jae; Kim, Woo Young; Shim, Hyun Bin; Lee, Hee Chul

    2016-09-01

    A nanoporous Pirani sensor based on anodic aluminum oxide (AAO) is proposed, and the quantitative relationship between the performance of the sensor and the porosity of the AAO membrane is characterized with a theoretical model. The proposed Pirani sensor is composed of a metallic resistor on a suspended nanoporous membrane, which simultaneously serves as the sensing area and the supporting structure. The AAO membrane has numerous vertically-tufted nanopores, resulting in a lower measurable pressure limit due to both the increased effective sensing area and the decreased effective thermal loss through the supporting structure. Additionally, the suspended AAO membrane structure, with its outer periphery anchored to the substrate, known as a closed-type design, is demonstrated using nanopores of AAO as an etch hole without a bulk micromachining process used on the substrate. In a CMOS-compatible process, a 200 μm × 200 μm nanoporous Pirani sensor with porosity of 25% was capable of measuring the pressure from 0.1 mTorr to 760 Torr. With adjustment of the porosity of the AAO, the measurable range could be extended toward lower pressures of more than one decade compared to a non-porous membrane with an identical footprint.

  18. Growth of porous type anodic oxide films at micro-areas on aluminum exposed by laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, Tatsuya [Graduate School of Engineering, Hokkaido University, N13-W8, Kita-Ku, Sapporo 060-8628 (Japan)], E-mail: kiku@eng.hokudai.ac.jp; Sakairi, Masatoshi [Graduate School of Engineering, Hokkaido University, N13-W8, Kita-Ku, Sapporo 060-8628 (Japan); Takahashi, Hideaki [Asahikawa National College of Technology, Syunkohdai, 2-2, 1-6, Asahikawa 071-8142 (Japan)

    2009-11-30

    Aluminum covered with pore-sealed anodic oxide films was irradiated with a pulsed Nd-YAG laser to remove the oxide film at micro-areas. The specimen was re-anodized for long periods to examine the growth of porous anodic oxide films at the area where substrate had been exposed by measuring current variations and morphological changes in the oxide during the re-anodizing. The chemical dissolution resistance of the pore-sealed anodic oxide films in an oxalic acid solution was also examined by measuring time-variations in rest potentials during immersion. The resistance to chemical dissolution of the oxide film became higher with increasing pore-sealing time and showed higher values at lower solution temperatures. During potentiostatic re-anodizing at five 35-{mu}m wide and 4-mm long lines for 72 h after the film was removed the measured current was found to increase linearly with time. Semicircular columnar-shaped porous type anodic oxide was found to form during the re-anodizing at the laser-irradiated area, and was found to grow radially, thus resulting in an increase in the diameter. After long re-anodizing, the central and top parts of the oxide protruded along the longitudinal direction of the laser-irradiated area. The volume expansion during re-anodizing resulted in the formation of cracks, parallel to the lines, in the oxide film formed during the first anodizing.

  19. Sub-100 fJ and sub-nanosecond thermally driven threshold switching in niobium oxide crosspoint nanodevices.

    Science.gov (United States)

    Pickett, Matthew D; Williams, R Stanley

    2012-06-01

    We built and measured the dynamical current versus time behavior of nanoscale niobium oxide crosspoint devices which exhibited threshold switching (current-controlled negative differential resistance). The switching speeds of 110 × 110 nm(2) devices were found to be Δt(ON) = 700 ps and Δt(OFF) = 2:3 ns while the switching energies were of the order of 100 fJ. We derived a new dynamical model based on the Joule heating rate of a thermally driven insulator-to-metal phase transition that accurately reproduced the experimental results, and employed the model to estimate the switching time and energy scaling behavior of such devices down to the 10 nm scale. These results indicate that threshold switches could be of practical interest in hybrid CMOS nanoelectronic circuits.

  20. Photocatalytic activity of porous TiO2 films prepared by anodic oxidation

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; TAO Jie; WANG Tao; WANG Ling

    2007-01-01

    Anatase titanium dioxide is an active photocatalyst, however, it is difficult to be immobilized on the substrate.The crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation. The film was then used for photocatalysis via the methyl orange degradation method. The effects of anodization voltage, pH value, TiO2 film area and degradation time on the photocatalyst were investigated respectively by UV-visible spectrum. It was indicated that the TiO2 film prepared by anodic oxidation at 140 V had the best photocatalysis capability and the degradation of methyl orange was accelerated with acid addition.

  1. Microstructural characterization of oxide film formed on NiTi by anodization in acetic acid

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, F.T. [Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong)]. E-mail: apaftche@polyu.edu.hk; Shi, P. [Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Department of Materials and Chemical Engineering, Liaoning Institute of Technology, Jinzhou, Liaoning (China); Pang, G.K.H. [Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Wong, M.H. [Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Man, H.C. [Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong)

    2007-07-12

    NiTi was galvanostatically anodized in acetic acid aiming at forming an anodic film for improving corrosion resistance. While the corrosion behavior of anodized NiTi in Hanks' solution was reported elsewhere [P. Shi, F.T. Cheng, H.C. Man, Mater. Lett., submitted for publication], the present work reports the microstructural characterization of the anodic film formed. Bright-field image of the sample cross-section captured by transmission electron microscopy (TEM) revealed an oxide film of about 20 nm thick, which was smooth and free of defects. The surface roughness R {sub a} of the film, determined by atomic force microscopy (AFM), was about 1.45 nm. Analysis by X-ray photoelectron spectroscopy (XPS) along the depth of the anodic film indicated that the oxidation state of Ti varied from +4 (corresponding to TiO{sub 2}) at the surface to lower oxidation states (corresponding to Ti suboxides) beneath. A small amount of Ni in the metallic and oxidized states was also present. The Ni/Ti atomic ratio was about 0.04 at the surface of the anodic film, which was much lower than the corresponding value of 0.30 for the mechanically polished samples. Selected-area diffraction (SAD) patterns and high-resolution TEM image of the anodic film showed that the film was amorphous.

  2. Stabilisation of composite LSFCO-CGO based anodes for methane oxidation in solid oxide fuel cells

    Science.gov (United States)

    Sin, A.; Kopnin, E.; Dubitsky, Y.; Zaopo, A.; Aricò, A. S.; Gullo, L. R.; Rosa, D. La; Antonucci, V.

    A La 0.6Sr 0.4Fe 0.8Co 0.2O 3-Ce 0.8Gd 0.2O 1.9 (LSFCO-CGO) composite anode material was investigated for the direct electrochemical oxidation of methane in intermediate temperature solid oxide fuel cells (IT-SOFCs). A maximum power density of 0.17 W cm -2 at 800 °C was obtained with a methane-fed ceria electrolyte-supported SOFC. A progressive increase of performance was recorded during 140 h operation with dry methane. The anode did not show any structure degradation after the electrochemical testing. Furthermore, no formation of carbon deposits was detected by electron microscopy and elemental analysis. Alternatively, this perovskite material showed significant chemical and structural modifications after high temperature treatment in a dry methane stream in a packed-bed reactor. It is derived that the continuous supply of mobile oxygen anions from the electrolyte to the LSFCO anode, promoted by the mixed conductivity of CGO electrolyte at 800 °C, stabilises the perovskite structure near the surface under SOFC operation and open circuit conditions.

  3. Performance of alternative oxide anodes for the electrochemical oxidation of hydrogen and methane in solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Tu, H.; Apfel, H.; Stimming, U. [Department of Physics E19, Technical University of Munich, James-Franck-Strasse 1, D-85748 Garching (Germany)

    2006-07-15

    The electrode performances of the alternative oxides: La{sub 0.05}Ca{sub 0.95}Cr{sub 0.05}Ti{sub 0.95}O{sub 3-{delta}}-8YSZ and Ce{sub 0.8}TM{sub 0.2}O{sub 2-{delta}}(TM=Mn, Co) for the direct electrochemical oxidation of methane are investigated to assess their potential as anode materials for efficient methane conversion in a SOFC. The electrochemical oxidation of hydrogen was also studied, for comparison. The oxides are characterised electrochemically with impedance spectroscopy in the frequency range from 10 mHz to 1MHz, using a three-electrode geometry. They are compared to a standard Ni/8YSZ anode for the electrochemical oxidation of hydrogen. It is found that La{sub 0.05}Ca{sub 0.95}Cr{sub 0.05}Ti{sub 0.95}O{sub 3-{delta}}-8YSZ demonstrates a poor electrochemical activity in both hydrogen and methane. However, the electrochemical activity of Ce{sub 0.8}Mn{sub 0.2}O{sub 2-{delta}} is promising, but the electronic conductivity needs to be increased, e.g., by adding a conducting oxide, before it can be used as an anode material in a SOFC. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  4. Evolution of Anode Porosity under Air Oxidation: The Unveiling of the Active Pore Size

    Directory of Open Access Journals (Sweden)

    Francois Chevarin

    2017-03-01

    Full Text Available The carbon anode, used in aluminum electrolysis (Hall–Héroult process, is over-consumed by air oxidation and carboxy-reaction (with CO2. Several anode features may affect this over-consumption, such as impurity content, graphitization level and anode porosity features (e.g., porosity volume fraction or pore size distribution. The two first parameters are basically related to the quality of raw materials and coke calcination conditions. Anode porosity is, however, greatly affected by anode manufacturing conditions, and is possible to be modified, to some extent, by adjusting the anode recipe and the processing parameters. This work aims to investigate the effect of anode porosity on its air reactivity. Baked anode samples were prepared in laboratory scale and then crushed into powder form (−4760 + 4000 µm. The recipe for anode preparation was similar to a typical industrial recipe, except that in the lab scale no butt particles were used in the recipe. Anode particles were then gasified at six different conversion levels (0, 5, 15, 25, 35 and 50 wt % under air at 525 °C. The porosity was characterized in several pore size ranges, measured by nitrogen adsorption and mercury intrusion (0.0014–0.020, 0.002–0.025, 0.025–0.100, 0.1–40.0 and superior at 40 µm. The volume variation of each pore range, as a function of carbon conversion, was assessed and used to determine the size of the most active pores for air oxidation. The most active pore size was found to be the pores inferior at 40 µm before 15 wt % of gasification and pores superior at 40 µm between 15 and 50 wt % of carbon conversion. Limitation of pore size range could be used as an additional guideline, along with other targets such as high homogeneity and density, to set the optimum anode manufacturing parameters.

  5. The surface treatment on oxide film of pure titanium Part 1. The effect of Anodic oxidation

    Institute of Scientific and Technical Information of China (English)

    Ge Wang; Xiangrong Cheng

    2006-01-01

    目的:研究阳极氧化对纯钛种植材料氧化膜的影响.方法:5片直径9 mm厚2 mm的纯钛在升压速度为7~8 v/min、电流密度≤10 mA/cm2的条件下分别进行阳极氧化处理,(A)10 v 10 min,(B)24 v 10 min,(C) 40 v 10 min,(D)24 v 40 min,(E) 24 v 2 h.用potentiostat仪检测以上样品在生理盐水和人造海水中的电化学行为.结果:以上样品的颜色呈:A蓝色,B淡黄色,C粉红色,D金黄色,E深黄色.随着电压的升高和作用时间的延长,2.55峰渐渐强化,2.34峰弱化.在生理盐水中,阳极氧化膜的开路电势稳定于0 mV,而自然氧化膜则很快从-50上升到-40 mV,极化电流比自然氧化膜的低100倍.在人造海水中,阳极氧化膜的开路电势稳定在-90 mV,自然氧化膜则从-480 mV快速上升到-310 mV,且活化电流明显高于阳极氧化膜.结论:阳极氧化膜的颜色可能和膜的厚度有关,而颜色对种植体上的修复体有影响,因此,金黄色被选为理想的颜色.2.55和2.34峰的变化规律尚无法解释.阳极氧化膜的稳定性和耐腐蚀性远远高于自然氧化膜.因此,阳极氧化法是一种提高纯钛氧化膜耐腐蚀性的好方法.%Objectives: To study the oxide film of pure titanium implant material treated by anodic oxidation. Methods: Five commercially pure (CP) titanium sheets (9mm in diameter and 2mm thick) were treated by the speed of 7-8 v/min of potential, the current density ≤10mA/cm2 to (A) 10v for 10min, (B) 24v for 10min, (C) 40v for 10min, (D) 24v for 40min, (E) 24v for 2hr in Kawahara's electrochemical solution. The electro-chemical behavior of anodic oxide film and natural oxide film was studied using a potentiostat. Results: The samples color changed from white to the following sequence blue, light gold, pink, media gold and dark gold. Along with potential and time going on, XRD patterns showed that the peak 2.55 strengthened, and peak 2.34 weakened. The voltage-time curve in physiological salt solution (PSS) showed

  6. Other Oxides Pre-removed from Bangka Tin Slag to Produce a High Grade Tantalum and Niobium Oxides Concentrate

    Science.gov (United States)

    Permana, S.; Soedarsono, J. W.; Rustandi, A.; Maksum, A.

    2016-05-01

    Indonesia, as the second largest tin producer in the world, has a byproduct from the production of tin. This byproduct is in the forms of tin slag containing tantalum pentoxide (Ta2O5) and niobium pentoxide (Nb2O5). This study focuses on the recovery of tantalum pentoxide and niobium pentoxide from the tin slag. In the process, one part of the tin slag sample was sieved only (BTS), and the other was roasted at 900°C, water quenched and then sieved (BTS-RQS). Samples BTS and BTS-RQS were characterized by thermo gravimetric analysis (TGA) and X-ray flourence (XRF). One part of BTS-RQS sample was dissolved in hydrofluoric acid (HF) and the other was dissolved in hydrochloric acid (HCl), washed with distilled water, then dissolved into sodium hydroxide (NaOH). Each sample was characterized by using XRF. The BTS sample produced the highest recovery of 0.3807 and 0.6978% for Ta2O5 and Nb2O5, respectively, from the particle size of -1.00+0.71 and a fraction of 47.29%, while BTS-RQS produced the highest recovery of 0.3931 and 0.8994% for Ta2O5 and Nb2O5, respectively, on the particle size of -0.71+0350 and a fraction of 21%. BTS-RQS, dissolved with 8% hydro fluoride acid, yields tantalum pentoxide and niobium pentoxide with a ratio of 2.01 and 2.09, respectively. For the sample BTS-RQS dissolve first with 6M hydrochloric acid, washed with distilled water, then dissolved with sodium hydroxide 10M, the yield ratios are 1.60 and 1.84 for tantalum pentoxide and niobium pentoxide, respectively. In this study, it is found that the dissolution by using hydrofluoric acid 8% yields the best ratio.

  7. Facile synthesis of reduced graphene oxide-porous silicon composite as superior anode material for lithium-ion battery anodes

    Science.gov (United States)

    Jiao, Lian-Sheng; Liu, Jin-Yu; Li, Hong-Yan; Wu, Tong-Shun; Li, Fenghua; Wang, Hao-Yu; Niu, Li

    2016-05-01

    We report a new method for synthesizing reduced graphene oxide (rGO)-porous silicon composite for lithium-ion battery anodes. Rice husks were used as a as a raw material source for the synthesis of porous Si through magnesiothermic reduction process. The as-obtained composite exhibits good rate and cycling performance taking advantage of the porous structure of silicon inheriting from rice husks and the outstanding characteristic of graphene. A considerably high delithiation capacity of 907 mA h g-1 can be retained even at a rate of 16 A g-1. A discharge capacity of 830 mA h g-1 at a current density of 1 A g-1 was delivered after 200 cycles. This may contribute to the further advancement of Si-based composite anode design.

  8. Electrophoretic deposition of PTFE particles on porous anodic aluminum oxide film and its tribological properties

    Science.gov (United States)

    Zhang, Dongya; Dong, Guangneng; Chen, Yinjuan; Zeng, Qunfeng

    2014-01-01

    Polytetrafluoroethylene (PTFE) composite film was successfully fabricated by depositing PTFE particles into porous anodic aluminum oxide film using electrophoretic deposition (EPD) process. Firstly, porous anodic aluminum oxide film was synthesized by anodic oxidation process in sulphuric acid electrolyte. Then, PTFE particles in suspension were directionally deposited into the porous substrate. Finally, a heat treatment at 300 °C for 1 h was utilized to enhance PTFE particles adhesion to the substrate. The influence of anodic oxidation parameters on the morphology and micro-hardness of the porous anodic aluminum oxide film was studied and the PTFE particles deposited into the pores were authenticated using energy-dispersive spectrometer (EDS) and scanning electron microscopy (SEM). Tribological properties of the PTFE composite film were investigated under dry sliding. The experimental results showed that the composite film exhibit remarkable low friction. The composite film had friction coefficient of 0.20 which deposited in 15% PTFE emulsion at temperature of 15 °C and current density of 3 A/dm2 for 35 min. In addition, a control specimen of porous anodic aluminum oxide film and the PTFE composite film were carried out under the same test condition, friction coefficient of the PTFE composite film was reduced by 60% comparing with the control specimen at 380 MPa and 100 mm/s. The lubricating mechanism was that PTFE particles embedded in porous anodic aluminum oxide film smeared a transfer film on the sliding path and the micro-pores could support the supplement of solid lubricant during the sliding, which prolonged the lubrication life of the aluminum alloys.

  9. Electrophoretic deposition of PTFE particles on porous anodic aluminum oxide film and its tribological properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Dongya; Dong, Guangneng, E-mail: donggn@mail.xjtu.edu.cn; Chen, Yinjuan; Zeng, Qunfeng

    2014-01-30

    Polytetrafluoroethylene (PTFE) composite film was successfully fabricated by depositing PTFE particles into porous anodic aluminum oxide film using electrophoretic deposition (EPD) process. Firstly, porous anodic aluminum oxide film was synthesized by anodic oxidation process in sulphuric acid electrolyte. Then, PTFE particles in suspension were directionally deposited into the porous substrate. Finally, a heat treatment at 300 °C for 1 h was utilized to enhance PTFE particles adhesion to the substrate. The influence of anodic oxidation parameters on the morphology and micro-hardness of the porous anodic aluminum oxide film was studied and the PTFE particles deposited into the pores were authenticated using energy-dispersive spectrometer (EDS) and scanning electron microscopy (SEM). Tribological properties of the PTFE composite film were investigated under dry sliding. The experimental results showed that the composite film exhibit remarkable low friction. The composite film had friction coefficient of 0.20 which deposited in 15% PTFE emulsion at temperature of 15 °C and current density of 3 A/dm{sup 2} for 35 min. In addition, a control specimen of porous anodic aluminum oxide film and the PTFE composite film were carried out under the same test condition, friction coefficient of the PTFE composite film was reduced by 60% comparing with the control specimen at 380 MPa and 100 mm/s. The lubricating mechanism was that PTFE particles embedded in porous anodic aluminum oxide film smeared a transfer film on the sliding path and the micro-pores could support the supplement of solid lubricant during the sliding, which prolonged the lubrication life of the aluminum alloys.

  10. Impact of nanostructured anode on low-temperature performance of thin-film-based anode-supported solid oxide fuel cells

    Science.gov (United States)

    Park, Jung Hoon; Han, Seung Min; Yoon, Kyung Joong; Kim, Hyoungchul; Hong, Jongsup; Kim, Byung-Kook; Lee, Jong-Ho; Son, Ji-Won

    2016-05-01

    The impact of a nanostructured Ni-yttria-stabilized zirconia (Ni-YSZ) anode on low-temperature solid oxide fuel cell (LT-SOFC) performance is investigated. By modifying processing techniques for the anode support, anode-supported SOFCs based on thin-film (∼1 μm) electrolytes (TF-SOFCs) with and without the nanostructured Ni-YSZ (grain size ∼100 nm) anode are fabricated and a direct comparison of the TF-SOFCs to reveal the role of the nanostructured anode at low temperature is made. The cell performance of the nanostructured Ni-YSZ anode significantly increases as compared to that of the cell without it, especially at low temperatures (500 °C). The electrochemical analyses confirm that increasing the triple-phase boundary (TPB) density near the electrolyte and anode interface by the particle-size reduction of the anode increases the number of sites available for charge transfer. Thus, the nanostructured anode not only secures the structural integrity of the thin-film components over it, it is also essential for lowering the operating temperature of the TF-SOFC. Although it is widely considered that the cathode is the main factor that determines the performance of LT-SOFCs, this study directly proves that anode performance also significantly affects the low-temperature performance.

  11. Effects of Complex Structured Anodic Oxide Dielectric Layer Grown in Pore Matrix for Aluminum Capacitor.

    Science.gov (United States)

    Shin, Jin-Ha; Yun, Sook Young; Lee, Chang Hyoung; Park, Hwa-Sun; Suh, Su-Jeong

    2015-11-01

    Anodization of aluminum is generally divided up into two types of anodic aluminum oxide structures depending on electrolyte type. In this study, an anodization process was carried out in two steps to obtain high dielectric strength and break down voltage. In the first step, evaporated high purity Al on Si wafer was anodized in oxalic acidic aqueous solution at various times at a constant temperature of 5 degrees C. In the second step, citric acidic aqueous solution was used to obtain a thickly grown sub-barrier layer. During the second anodization process, the anodizing potential of various ranges was applied at room temperature. An increased thickness of the sub-barrier layer in the porous matrix was obtained according to the increment of the applied anodizing potential. The microstructures and the growth of the sub-barrier layer were then observed with an increasing anodizing potential of 40 to 300 V by using a scanning electron microscope (SEM). An impedance analyzer was used to observe the change of electrical properties, including the capacitance, dissipation factor, impedance, and equivalent series resistance (ESR) depending on the thickness increase of the sub-barrier layer. In addition, the breakdown voltage was measured. The results revealed that dielectric strength was improved with the increase of sub-barrier layer thickness.

  12. Anode protection system for shutdown of solid oxide fuel cell system

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bob X; Grieves, Malcolm J; Kelly, Sean M

    2014-12-30

    An Anode Protection Systems for a SOFC system, having a Reductant Supply and safety subsystem, a SOFC anode protection subsystem, and a Post Combustion and slip stream control subsystem. The Reductant Supply and safety subsystem includes means for generating a reducing gas or vapor to prevent re-oxidation of the Ni in the anode layer during the course of shut down of the SOFC stack. The underlying ammonia or hydrogen based material used to generate a reducing gas or vapor to prevent the re-oxidation of the Ni can be in either a solid or liquid stored inside a portable container. The SOFC anode protection subsystem provides an internal pressure of 0.2 to 10 kPa to prevent air from entering into the SOFC system. The Post Combustion and slip stream control subsystem provides a catalyst converter configured to treat any residual reducing gas in the slip stream gas exiting from SOFC stack.

  13. Nanopatterning of Crystalline Silicon Using Anodized Aluminum Oxide Templates for Photovoltaics

    Science.gov (United States)

    Chao, Tsu-An

    A novel thin film anodized aluminum oxide templating process was developed and applied to make nanopatterns on crystalline silicon to enhance the optical properties of silicon. The thin film anodized aluminum oxide was created to improve the conventional thick aluminum templating method with the aim for potential large scale fabrication. A unique two-step anodizing method was introduced to create high quality nanopatterns and it was demonstrated that this process is superior over the original one-step approach. Optical characterization of the nanopatterned silicon showed up to 10% reduction in reflection in the short wavelength range. Scanning electron microscopy was also used to analyze the nanopatterned surface structure and it was found that interpore spacing and pore density can be tuned by changing the anodizing potential.

  14. The simulation of the temperature effects on the microhardness of anodic alumina oxide layers

    Directory of Open Access Journals (Sweden)

    M. Gombár

    2014-01-01

    Full Text Available In order to improve the mechanical properties of the layer deposited by anodic oxidation of aluminum on the material EN AW-1050 H24, in the contribution was investigated the microhardness of the deposited layer as a function of the physic-chemical factors affecting in the process of anodic oxidation at the constant anodic current density J = 3 A.dm-2 in electrolyte formed by sulfuric acid and oxalic acid, with the emphasis on the influence of electrolyte temperature in the range – 1,78 °C to 45,78 °C. The model of the studied dependence was compiled based on mathematical and statistical analysis of matrix from experimental obtained data from composite rotation plan of experiment with five independent variable factors (amount of sulfuric acid in the electrolyte, the amount of oxalic acid in the electrolyte, electrolyte, anodizing time and applied voltage.

  15. Modelling the growth process of porous aluminum oxide film during anodization

    Science.gov (United States)

    Aryslanova, E. M.; Alfimov, A. V.; Chivilikhin, S. A.

    2015-11-01

    Currently it has become important for the development of metamaterials and nanotechnology to obtain regular self-assembled structures. One such structure is porous anodic alumina film that consists of hexagonally packed cylindrical pores. In this work we consider the anodization process, our model takes into account the influence of layers of aluminum and electrolyte on the rate of growth of aluminum oxide, as well as the effect of surface diffusion. In present work we consider those effects. And as a result of our model we obtain the minimum distance between centers of alumina pores in the beginning of anodizing process.

  16. The electrochemical oxidation of H{sub 2} and CO at patterned Ni anodes of SOFCs

    Energy Technology Data Exchange (ETDEWEB)

    Utz, Annika

    2011-07-01

    In this work, a deeper understanding of the electrochemical oxidation at SOFC anodes was gained by the experimental characterization of patterned Ni anodes in H{sub 2}-H{sub 2}O and CO-CO{sub 2} atmosphere. By high resolution data analysis, the Line Specific Resistance attributed to charge transfer and its dependencies on gas composition, temperature and polarization voltage were identified. Furthermore, the comparison of the performance of patterned and cermet anodes was enabled using a transmission line model. (orig.)

  17. Biocatalytic anode for glucose oxidation utilizing carbon nanotubes for direct electron transfer with glucose oxidase

    Energy Technology Data Exchange (ETDEWEB)

    Vaze, Abhay; Hussain, Nighat; Tang, Chi [Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060 (United States); Leech, Donal [School of Chemistry, National University of Ireland, Galway (Ireland); Rusling, James [Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060 (United States); Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06032 (United States); School of Chemistry, National University of Ireland, Galway (Ireland)

    2009-10-15

    Covalently linked layers of glucose oxidase, single-wall carbon nanotubes and poly-L-lysine on pyrolytic graphite resulted in a stable biofuel cell anode featuring direct electron transfer from the enzyme. Catalytic response observed upon addition of glucose was due to electrochemical oxidation of FADH{sub 2} under aerobic conditions. The electrode potential depended on glucose concentration. This system has essential attributes of an anode in a mediator-free biocatalytic fuel cell. (author)

  18. In-situ IR spectroscopy to study anodic oxidation of Si(111) in KOH solution

    NARCIS (Netherlands)

    Philipsen, H.G.G.; Chazalviel, J.-N.; Allongue, P.; Ozanam, F.; Kelly, J.J.

    2007-01-01

    Fourier Transform Infrared (FTIR) spectroscopy was used to study in-situ the anodic oxidation of n-type Si(111) in KOH solution. Changes in surface chemistry were followed during oxide growth. The results are considered on the basis of a model developed from electrochemical measurements.

  19. Development and Testing of High Surface Area Iridium Anodes for Molten Oxide Electrolysis

    Science.gov (United States)

    Shchetkovskiy, Anatoliy; McKechnie, Timothy; Sadoway, Donald R.; Paramore, James; Melendez, Orlando; Curreri, Peter A.

    2010-01-01

    Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400-1600?C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form? process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

  20. Anodic oxidized nanotubular titanium implants enhance bone morphogenetic protein-2 delivery.

    Science.gov (United States)

    Bae, In-Ho; Yun, Kwi-Dug; Kim, Hyun-Seung; Jeong, Byung-Chul; Lim, Hyun-Pil; Park, Sang-Won; Lee, Kwang-Min; Lim, Young-Chai; Lee, Kyung-Ku; Yang, Yunzhi; Koh, Jeong-Tae

    2010-05-01

    Implant failure has been attributed to loosening of an implant from the host bone possibly due to poor osseointegration. One promising strategy for improving osseointegration is to develop a functional implant surface that promotes osteoblast differentiation. In this study, a titanium (Ti) surface was functionalized by an anodic oxidation process and was loaded with recombinant human bone morphogenetic protein-2 (rhBMP-2). The following four groups of Ti surfaces were prepared: machined (M), anodized machined (MA), resorbable blast medium (RBM), and anodized RBM (RBMA). The surfaces were characterized by scanning electron microscopy and contact angle measurements. The results showed that a Ti oxide layer (TiO(2)) was observed in the anodized surfaces in the form of nanotubes, approximately 100 nm in diameter and 500 nm in length. The hydrophilic properties of the anodized surfaces were significantly improved. The adsorbed rhBMP-2 loaded on the nonanodized surfaces and lyophilized showed spherical particle morphology. However, the adsorbed rhBMP-2 showed a dispersed pattern over the anodized surfaces. The velocity of the rhBMP-2 released from the surfaces was measured to determine if the anodized surface can improve in delivery efficiency. The results showed that the release velocity of the rhBMP-2 from the anodized surfaces was sustained when compared with that of the nonanodized surfaces. In addition, the rhBMP-2 released from the surface was found to be bioactive according to the alkaline phosphatase activity and the level of calcium mineral deposition. These results suggest that the TiO(2) nanotubular structure formed by anodizing is a promising configuration for sustained rhBMP-2 delivery.

  1. Air-Impregnated Nanoporous Anodic Aluminum Oxide Layers for Enhancing the Corrosion Resistance of Aluminum.

    Science.gov (United States)

    Jeong, Chanyoung; Lee, Junghoon; Sheppard, Keith; Choi, Chang-Hwan

    2015-10-13

    Nanoporous anodic aluminum oxide layers were fabricated on aluminum substrates with systematically varied pore diameters (20-80 nm) and oxide thicknesses (150-500 nm) by controlling the anodizing voltage and time and subsequent pore-widening process conditions. The porous nanostructures were then coated with a thin (only a couple of nanometers thick) Teflon film to make the surface hydrophobic and trap air in the pores. The corrosion resistance of the aluminum substrate was evaluated by a potentiodynamic polarization measurement in 3.5 wt % NaCl solution (saltwater). Results showed that the hydrophobic nanoporous anodic aluminum oxide layer significantly enhanced the corrosion resistance of the aluminum substrate compared to a hydrophilic oxide layer of the same nanostructures, to bare (nonanodized) aluminum with only a natural oxide layer on top, and to the latter coated with a thin Teflon film. The hydrophobic nanoporous anodic aluminum oxide layer with the largest pore diameter and the thickest oxide layer (i.e., the maximized air fraction) resulted in the best corrosion resistance with a corrosion inhibition efficiency of up to 99% for up to 7 days. The results demonstrate that the air impregnating the hydrophobic nanopores can effectively inhibit the penetration of corrosive media into the pores, leading to a significant improvement in corrosion resistance.

  2. Direct methane solid oxide fuel cells based on catalytic partial oxidation enabling complete coking tolerance of Ni-based anodes

    Science.gov (United States)

    Lee, Daehee; Myung, Jaeha; Tan, Jeiwan; Hyun, Sang-Hoon; Irvine, John T. S.; Kim, Joosun; Moon, Jooho

    2017-03-01

    Solid oxide fuel cells (SOFCs) can oxidize diverse fuels by harnessing oxygen ions. Benefited by this feature, direct utilization of hydrocarbon fuels without external reformers allows for cost-effective realization of SOFC systems. Superior hydrocarbon reforming catalysts such as nickel are required for this application. However, carbon coking on nickel-based anodes and the low efficiency associated with hydrocarbon fueling relegate these systems to immature technologies. Herein, we present methane-fueled SOFCs operated under conditions of catalytic partial oxidation (CPOX). Utilizing CPOX eliminates carbon coking on Ni and facilitates the oxidation of methane. Ni-gadolinium-doped ceria (GDC) anode-based cells exhibit exceptional power densities of 1.35 W cm-2 at 650 °C and 0.74 W cm-2 at 550 °C, with stable operation over 500 h, while the similarly prepared Ni-yttria stabilized zirconia anode-based cells exhibit a power density of 0.27 W cm-2 at 650 °C, showing gradual degradation. Chemical analyses suggest that combining GDC with the Ni anode prevents the oxidation of Ni due to the oxygen exchange ability of GDC. In addition, CPOX operation allows the usage of stainless steel current collectors. Our results demonstrate that high-performance SOFCs utilizing methane CPOX can be realized without deterioration of Ni-based anodes using cost-effective current collectors.

  3. Influence of anodization parameters on the volume expansion of anodic aluminum oxide formed in mixed solution of phosphoric and oxalic acids

    Science.gov (United States)

    Kao, Tzung-Ta; Chang, Yao-Chung

    2014-01-01

    The growth of anodic alumina oxide was conducted in the mixed solution of phosphoric and oxalic acids. The influence of anodizing voltage, electrolyte temperature, and concentration of phosphoric and oxalic acids on the volume expansion of anodic aluminum oxide has been investigated. Either anodizing parameter is chosen to its full extent of range that allows the anodization process to be conducted without electric breakdown and to explore the highest possible volume expansion factor. The volume expansion factors were found to vary between 1.25 and 1.9 depending on the anodizing parameters. The variation is explained in connection with electric field, ion transport number, temperature effect, concentration, and activity of acids. The formation of anodic porous alumina at anodizing voltage 160 V in 1.1 M phosphoric acid mixed with 0.14 M oxalic acid at 2 °C showed the peak volume expansion factor of 1.9 and the corresponding moderate growth rate of 168 nm/min.

  4. Mechanical and Abrasive Wear Properties of Anodic Oxide Layers Formed on Aluminium

    Institute of Scientific and Technical Information of China (English)

    W.Bensalah; K.Elleuch; M.Feki; M.Wery; H.F.Ayedi

    2009-01-01

    Aluminium oxide coatings were formed on aluminium substrates in oxalic acid-sulphuric acid bath. Abrasion tests of the obtained anodic layers were carried out on a pin-on-disc machine in accordance with the ISO/DP 825 specifications. The Vickers microhardness, D (HV0.2). and the abrasion weight loss, Wa (mg) were measured. Influence of oxalic acid concentration (Cox), bath temperature (T) and anodic current density (J) on D and Wa has been examined, and the sulphuric acid concentration (Caul) was maintained at 160 g.L-1. It was found that high microhardness and abrasive wear resistance of oxide layers were produced under low temperatures and high current densities with the addition of oxalic acid. The morphology and the composition of the anodic oxide layer were examined by scanning electron microscopy (SEM), atomic force microscopy (AFM), optical microscopy and glow-discharge optical emission spectroscopy (GDOES). It was found that the chemistry of the anodizing electrolyte, temperature, and current density are the controlling factors of the mechanical properties of the anodic oxide layer.

  5. A new anode material for oxygen evolution in molten oxide electrolysis.

    Science.gov (United States)

    Allanore, Antoine; Yin, Lan; Sadoway, Donald R

    2013-05-16

    Molten oxide electrolysis (MOE) is an electrometallurgical technique that enables the direct production of metal in the liquid state from oxide feedstock, and compared with traditional methods of extractive metallurgy offers both a substantial simplification of the process and a significant reduction in energy consumption. MOE is also considered a promising route for mitigation of CO2 emissions in steelmaking, production of metals free of carbon, and generation of oxygen for extra-terrestrial exploration. Until now, MOE has been demonstrated using anode materials that are consumable (graphite for use with ferro-alloys and titanium) or unaffordable for terrestrial applications (iridium for use with iron). To enable metal production without process carbon, MOE requires an anode material that resists depletion while sustaining oxygen evolution. The challenges for iron production are threefold. First, the process temperature is in excess of 1,538 degrees Celsius (ref. 10). Second, under anodic polarization most metals inevitably corrode in such conditions. Third, iron oxide undergoes spontaneous reduction on contact with most refractory metals and even carbon. Here we show that anodes comprising chromium-based alloys exhibit limited consumption during iron extraction and oxygen evolution by MOE. The anode stability is due to the formation of an electronically conductive solid solution of chromium(iii) and aluminium oxides in the corundum structure. These findings make practicable larger-scale evaluation of MOE for the production of steel, and potentially provide a key material component enabling mitigation of greenhouse-gas emissions while producing metal of superior metallurgical quality.

  6. Fabrication of diameter-modulated and ultrathin porous nanowires in anodic aluminum oxide templates

    Energy Technology Data Exchange (ETDEWEB)

    Sulka, Grzegorz D., E-mail: Sulka@chemia.uj.edu.pl [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany); Department of Physical Chemistry and Electrochemistry, Jagiellonian University, Ingardena 3, 30060 Krakow (Poland); Brzozka, Agnieszka [AGH University of Science and Technology, Faculty of Non-Ferrous Metals, Al. Mickiewicza 30, Krakow 30-059 (Poland); Liu, Lifeng [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany)

    2011-05-30

    Graphical abstract: Display Omitted Highlights: > AAO templates with modulated pore diameter were fabricated by pulse anodization. > HA pulse duration tunes the shape of pores and the structure of AAO channels. > Au, Ag, Ni and Ag-Au diameter-modulated nanowires were synthetized. > Porous ultrathin Au nanowires were obtained by dealloying Ag-Au nanowires. - Abstract: Anodic aluminum oxide (AAO) membranes with modulated pore diameter were synthesized by pulse anodization in 0.3 M sulfuric acid at 1 deg. C. For AAO growth, a typical combination of alternating mild anodizing (MA) and hard anodizing (HA) pulses with applied potential pulses of 25 V and 35 V was applied. The control of the duration of HA pulses will provide an interesting way to tune the shape of pores and the structure of AAO channels. It was found that a non-uniform length of HA segments in cross section of AAO is usually observed when the HA pulse duration is shorter than 1.2 s. The pulse anodization performed with longer HA pulses leads to the formation of AAO templates with periodically modulated pore diameter and nearly uniform length of segments. Various diameter-modulated metallic nanowires (Au, Ag, Ni and Ag-Au) were fabricated by electrodeposition in the pores of anodic alumina membranes. A typical average nanowire diameter was about 30 nm and 48 nm for MA and HA nanowire segments, respectively. After a successful dealloying silver from Ag-Au nanowires, porous ultrathin Au nanowires were obtained.

  7. A novel Ni/ceria-based anode for metal-supported solid oxide fuel cells

    Science.gov (United States)

    Rojek-Wöckner, Veronika A.; Opitz, Alexander K.; Brandner, Marco; Mathé, Jörg; Bram, Martin

    2016-10-01

    For optimization of ageing behavior, electrochemical performance, and sulfur tolerance of metal-supported solid oxide fuel cells a new anode concept is introduced, which is based on a Ni/GDC cermet replacing the established Ni/YSZ anodes. In the present work optimized processing parameters compatible with MSC substrates are specified by doing sintering studies on pressed bulk specimen and on real porous anode structures. The electrochemical performance of the Ni/GDC anodes was characterized by means of symmetrical electrolyte supported model-type cells. In this study, three main objectives are pursued. Firstly, the effective technical realization of the Ni/GDC concept is demonstrated. Secondly, the electrochemical behavior of Ni/GDC porous anodes is characterized by impedance spectroscopy and compared with the current standard Ni/YSZ anode. Further, a qualitative comparison of the sulfur poisoning behavior of both anode types is presented. Thirdly, preliminary results of a successful implementation of the Ni/GDC cermet into a metal-supported single cell are presented.

  8. Losses in superconducting Niobium Films caused by Interface Tunnel Exchange

    CERN Document Server

    Junginger, Tobias; Welsch, Carsten

    2012-01-01

    Identifying the loss mechanisms of niobium film cavities enables an accurate determination of applications for future accelerator projects and points to research topics required to mitigate their limitations. Measurements on samples show that the electric field is a dominant loss mechanism for niobium films, acting through interface tunneling between localized states in surface oxides and delocalized states in the superconducting niobium.

  9. Formation of Al-Si Composite Oxide Film by Hydrolysis Precipitation and Anodizing

    Institute of Scientific and Technical Information of China (English)

    Zhe-Sheng Feng; Ying-Jie Xia; Jia Ding; Jin-Ju Chen

    2007-01-01

    This paper presents a new technique in the high dielectric constant composite oxide film preparation.On the basis of nanocompsite high dielectric constant aluminum oxide film growth technology, a new idea of adulterating Si oxide species into the aluminum composite film was proposed. As a result, the specific capacitance and withstanding voltage of the composite oxide film formed at the anodizing voltage of 20V are enhanced, and the leakage current of the aluminum composite oxide film is reduced through incorporation of Si oxide species.

  10. Surface characteristics and electrochemical corrosion behavior of a pre-anodized microarc oxidation coating on titanium alloy.

    Science.gov (United States)

    Cui, W F; Jin, L; Zhou, L

    2013-10-01

    A porous bioactive titania coating on biomedical β titanium alloy was prepared by pre-anodization followed by micro arc oxidation technology. The effects of pre-anodization on the phase constituent, morphology and electrochemical corrosion behavior of the microarc oxidation coating were investigated. The results show that pre-anodization has less influence on the phase constituent and the surface morphology of the microarc oxidation coating, but improves the inner layer density of the microarc oxidation coating. The decrease of plasma discharge strength due to the presence of the pre-anodized oxide film contributes to the formation of the compact inner layer. The pre-anodized microarc oxidation coating effectively inhibits the penetration of the electrolyte in 0.9% NaCl solution and thus increases the corrosion resistance of the coated titanium alloy in physiological solution.

  11. Evolution of insoluble eutectic Si particles in anodic oxidation films during adipic-sulfuric acid anodizing processes of ZL114A aluminum alloys

    Science.gov (United States)

    Hua, Lei; Liu, Jian-hua; Li, Song-mei; Yu, Mei; Wang, Lei; Cui, Yong-xin

    2015-03-01

    The effects of insoluble eutectic Si particles on the growth of anodic oxide films on ZL114A aluminum alloy substrates were investigated by optical microscopy (OM) and scanning electron microscopy (SEM). The anodic oxidation was performed at 25°C and a constant voltage of 15 V in a solution containing 50 g/L sulfuric acid and 10 g/L adipic acid. The thickness of the formed anodic oxidation film was approximately 7.13 μm. The interpore distance and the diameters of the major pores in the porous layer of the film were within the approximate ranges of 10-20 nm and 5-10 nm, respectively. Insoluble eutectic Si particles strongly influenced the morphology of the anodic oxidation films. The anodic oxidation films exhibited minimal defects and a uniform thickness on the ZL114A substrates; in contrast, when the front of the oxide oxidation films encountered eutectic Si particles, defects such as pits and non-uniform thickness were observed, and pits were observed in the films.

  12. Studies on anodic oxide coating with low absorptance and high emittance on aluminum alloy 2024

    Energy Technology Data Exchange (ETDEWEB)

    Siva Kumar, C. [Department of Post-graduate studies in Chemistry, Central College, Bangalore (India); Sharma, A.K. [Thermal Process Section, ISRO Satellite Centre, Vimanapura Post, Bangalore (India); Mahendra, K.N.; Mayanna, S.M. [Department of Post-graduate studies in Chemistry, Central College, Bangalore (India)

    2000-01-01

    Anodization of AA 2024 in sulfuric acid bath containing glycerol, lactic acid and ammonium metavenadate has been studied to develop white anodic oxide coating. Investigation on the influence of various operating parameters - coating thickness, current density and ammonium metavenadate concentration on the optical properties was carried out to optimize the process. Infrared, atomic absorption spectroscopic techniques and scanning electron micrograph were used to characterize the coating. The obtained oxide coating provides a ratio of solar absorptance ({alpha}) to infrared emittance ({epsilon}), as low as 0.2. The optical properties and hardness values measured under optimum experimental conditions support its use as a thermal control coating.

  13. Laser-Doping through Anodic Aluminium Oxide Layers for Silicon Solar Cells

    OpenAIRE

    2015-01-01

    This paper demonstrates that silicon can be locally doped with aluminium to form localised p+ surface regions by laser-doping through anodic aluminium oxide (AAO) layers formed on the silicon surface. The resulting p+ regions can extend more than 10 μm into the silicon and the electrically active p-type dopant concentration exceeds 1020 cm−3 for the first 6-7 μm of the formed p+ region. Anodic aluminium oxide layers can be doped with other impurities, such as boron and phosphorus, by anodisin...

  14. Durability Prediction of Solid Oxide Fuel Cell Anode Material under Thermo-Mechanical and Fuel Gas Contaminants Effects

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Gulfam; Guo, Hua; Kang , Bruce S.; Marina, Olga A.

    2011-01-10

    Solid Oxide Fuel Cells (SOFCs) operate under harsh environments, which cause deterioration of anode material properties and service life. In addition to electrochemical performance, structural integrity of the SOFC anode is essential for successful long-term operation. The SOFC anode is subjected to stresses at high temperature, thermal/redox cycles, and fuel gas contaminants effects during long-term operation. These mechanisms can alter the anode microstructure and affect its electrochemical and structural properties. In this research, anode material degradation mechanisms are briefly reviewed and an anode material durability model is developed and implemented in finite element analysis. The model takes into account thermo-mechanical and fuel gas contaminants degradation mechanisms for prediction of long-term structural integrity of the SOFC anode. The proposed model is validated experimentally using a NexTech ProbostatTM SOFC button cell test apparatus integrated with a Sagnac optical setup for simultaneously measuring electrochemical performance and in-situ anode surface deformation.

  15. Hierarchically oriented macroporous anode-supported solid oxide fuel cell with thin ceria electrolyte film.

    Science.gov (United States)

    Chen, Yu; Zhang, Yanxiang; Baker, Jeffrey; Majumdar, Prasun; Yang, Zhibin; Han, Minfang; Chen, Fanglin

    2014-04-09

    Application of anode-supported solid oxide fuel cell (SOFC) with ceria based electrolyte has often been limited by high cost of electrolyte film fabrication and high electrode polarization. In this study, dense Gd0.1Ce0.9O2 (GDC) thin film electrolytes have been fabricated on hierarchically oriented macroporous NiO-GDC anodes by a combination of freeze-drying tape-casting of the NiO-GDC anode, drop-coating GDC slurry on NiO-GDC anode, and co-firing the electrolyte/anode bilayers. Using 3D X-ray microscopy and subsequent analysis, it has been determined that the NiO-GDC anode substrates have a porosity of around 42% and channel size from around 10 μm at the electrolyte side to around 20 μm at the other side of the NiO-GDC (away from the electrolyte), indicating a hierarchically oriented macroporous NiO-GDC microstructure. Such NiO-GDC microstructure shows a tortuosity factor of ∼1.3 along the thickness direction, expecting to facilitate gas diffusion in the anode during fuel cell operation. SOFCs with such Ni-GDC anode, GDC film (30 μm) electrolyte, and La0.6Sr0.4Co0.2Fe0.8O3-GDC (LSCF-GDC) cathode show significantly enhanced cell power output of 1.021 W cm(-2) at 600 °C using H2 as fuel and ambient air as oxidant. Electrochemical Impedance Spectroscopy (EIS) analysis indicates a decrease in both activation and concentration polarizations. This study has demonstrated that freeze-drying tape-casting is a very promising approach to fabricate hierarchically oriented porous substrate for SOFC and other applications.

  16. Direct determination of fluorine in niobium oxide using slurry sampling electrothermal high-resolution continuum source molecular absorption spectrometry

    Science.gov (United States)

    Huang, Mao Dong; Becker-Ross, Helmut; Okruss, Michael; Geisler, Sebastian; Florek, Stefan; Richter, Silke; Meckelburg, Angela

    Aiming for a round-robin test, a new method for the direct determination of fluorine in niobium oxide has been developed. It is based on the use of high-resolution molecular absorption spectra of calcium mono-fluoride (CaF) generated in the graphite tube, combined with the slurry sampling technique. The absorption measurement was performed at the 606.44 nm CaF rotational line. By using graphite tubes with zirconium carbide (ZrC) modified platform, the molecular absorption sensitivity of CaF has been improved by a factor of 20, and no additional chemical modifier was necessary. Generally, non-spectral interferences were observed in the presence of HCl, H2SO4, and H3PO4. For HCl, additional spectral interference occurred due to an overlap of the absorption spectra of CaF and CaCl. However, due to the absence of these mentioned substances in the current material, such interferences do not exist for this application. The characteristic mass found for the CaF 606.44 nm line was 0.1 ng; the limit of detection was 5 mg fluorine per kg solid sample (3σ criterion). The results obtained by the method were within the range of certified values. Comparing to the classical method such as the pyrohydrolysis-photometric method, the developed new method showed clear advantages regarding sensitivity and specificity. The time requirement for one sample analysis was strongly shortened from several hours to only some minutes.

  17. Optimizing Hydrogen Storage by Doping the LiBH4 +MgH2 Reaction with Various Niobium Based Oxides

    Science.gov (United States)

    Hornung, Paul; Walko, Robert; Wenzel, Andrew; Wright, Richard; Dobbins, Tabbetha

    In this study, the effects of doping the dehydrogenation reaction of MgH2 + 2LiBH4 was combined with 5 mole% of three different Niobium based oxides (Nb2O5, NbO2, and LiNbO3). The compounds were mixed using high energy ball milling, and then heated using an air tight heating stage. We looked for changes in the Raman spectra as temperature increased (up to 350C) as an indication of hydrogen desorption reaction. We found that milled LiBH4 undergoes significant changes in Raman spectra during heating to 130C. MgH2 undergoes significant changes when comparing before and after milling--but in each case, the spectral peaks remain unchanged during heating to 350C. The sample with LiNbO3 exhibited a concrete change in Raman spectrum at 300 C while the sample doped with Nb2O5 underwent a change in spectra at 170C. The sample doped with NbO2 showed little change in spectra when the samples were heated up to 350C. Further studies are underway to examine the nature of the changes in the Raman spectra using X-ray diffraction and residual gas analysis.

  18. Preparation and analysis of anodic aluminum oxide films with continuously tunable interpore distances

    Science.gov (United States)

    Qin, Xiufang; Zhang, Jinqiong; Meng, Xiaojuan; Deng, Chenhua; Zhang, Lifang; Ding, Guqiao; Zeng, Hao; Xu, Xiaohong

    2015-02-01

    Nanoporous anodic aluminum oxides are often used as templates for preparation of nanostructures such as nanodot, nanowire and nanotube arrays. The interpore distance of anodic aluminum oxide is the most important parameter in controlling the periodicity of these nanostructures. Herein we demonstrate a simple and yet powerful method to fabricate ordered anodic aluminum oxides with continuously tunable interpore distances. By using mixed solution of citric and oxalic acids with different molar ratio, the range of anodizing voltages within which self-ordered films can be formed were extended to between 40 and 300 V, resulting in the interpore distances change from 100 to 750 nm. Our work realized very broad range of interpore distances in a continuously tunable fashion and the experiment processes are easily controllable and reproducible. The dependence of the interpore distances on acid ratios in mixed solutions was discussed through analysis of anodizing current and it was found that the effective dissociation constant of the mixed acids is of great importance. The interpore distances achieved are comparable to wavelengths ranging from UV to near IR, and may have potential applications in optical meta-materials for photovoltaics and optical sensing.

  19. Preparation and crystalline phase of a TiO2 porous film by anodic oxidation

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; TAO Jie; ZHANG Weiwei; TAO Haijun; WANG Ling

    2005-01-01

    Anatase titanium dioxide is an active photocatalyst, but it is difficult to immobilize on the substrate. A crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation in this work. Constant voltage and constant current anodic oxidation were adopted with sulphuric acid used as the electrolyte, pure titanium as the anode and copper as the cathode. The morphology and structure of the porous film on the substrate were analyzed with the aid of Field Emission Scanning Electron Microscopy (FESEM) and X-ray Diffraction (XRD). The effects of the parameters of anodic oxidation (such as voltage, the concentration of sulphuric acid, anodization time and current density) on the aperture and the crystalline phase of the TiO2 porous film were systematically investigated. The results indicate that the increase of current density facilitates the augment of the aperture and the generation of anatase and rutile. In addition, the forming mechanism of anatase and rutile TiO2 porous films was discussed.

  20. The Catalysis of NAD+ on Methanol Anode Oxidation Electrode for Direct Methanol Fuel Cell

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ping; PAN Mu; YUAN Run-zhang

    2004-01-01

    A tentative idea of developing a liquid-catalytic system on methanol anode oxidation was proposed by analyzing the characteristics of methanol anode oxidation in direct methanol fuel cell. The kinetics of methanol oxidation at a glassy carbon electrode in the presence of nicotinamide adenine dinucleotide (NAD+) was investigated. It is found that the current density of methanol oxidation increases greatly and the electrochemical reaction impedance reduces obviously in the presence of NAD+ compared with those in the absence of NAD+. The catalytic activity of NAD+ is sensitive to temperature. When the temperature preponderates over 45℃, NAD+ is out of function of catalysis for methanol oxidation, which is probably due to the denaturation of NAD+ at a relatively high temperature.

  1. Nanoporous anodic aluminum oxide with a long-range order and tunable cell sizes by phosphoric acid anodization on pre-patterned substrates.

    Science.gov (United States)

    Surawathanawises, Krissada; Cheng, Xuanhong

    2014-01-20

    Nanoporous anodic aluminum oxide (AAO) has been explored for various applications due to its regular cell arrangement and relatively easy fabrication processes. However, conventional two-step anodization based on self-organization only allows the fabrication of a few discrete cell sizes and formation of small domains of hexagonally packed pores. Recent efforts to pre-pattern aluminum followed with anodization significantly improve the regularity and available pore geometries in AAO, while systematic study of the anodization condition, especially the impact of acid composition on pore formation guided by nanoindentation is still lacking. In this work, we pre-patterned aluminium thin films using ordered monolayers of silica beads and formed porous AAO in a single-step anodization in phosphoric acid. Controllable cell sizes ranging from 280 nm to 760 nm were obtained, matching the diameters of the silica nanobead molds used. This range of cell size is significantly greater than what has been reported for AAO formed in phosphoric acid in the literature. In addition, the relationships between the acid concentration, cell size, pore size, anodization voltage and film growth rate were studied quantitatively. The results are consistent with the theory of oxide formation through an electrochemical reaction. Not only does this study provide useful operational conditions of nanoindentation induced anodization in phosphoric acid, it also generates significant information for fundamental understanding of AAO formation.

  2. Nanoporous anodic aluminum oxide with a long-range order and tunable cell sizes by phosphoric acid anodization on pre-patterned substrates

    Science.gov (United States)

    Surawathanawises, Krissada; Cheng, Xuanhong

    2014-01-01

    Nanoporous anodic aluminum oxide (AAO) has been explored for various applications due to its regular cell arrangement and relatively easy fabrication processes. However, conventional two-step anodization based on self-organization only allows the fabrication of a few discrete cell sizes and formation of small domains of hexagonally packed pores. Recent efforts to pre-pattern aluminum followed with anodization significantly improve the regularity and available pore geometries in AAO, while systematic study of the anodization condition, especially the impact of acid composition on pore formation guided by nanoindentation is still lacking. In this work, we pre-patterned aluminium thin films using ordered monolayers of silica beads and formed porous AAO in a single-step anodization in phosphoric acid. Controllable cell sizes ranging from 280 nm to 760 nm were obtained, matching the diameters of the silica nanobead molds used. This range of cell size is significantly greater than what has been reported for AAO formed in phosphoric acid in the literature. In addition, the relationships between the acid concentration, cell size, pore size, anodization voltage and film growth rate were studied quantitatively. The results are consistent with the theory of oxide formation through an electrochemical reaction. Not only does this study provide useful operational conditions of nanoindentation induced anodization in phosphoric acid, it also generates significant information for fundamental understanding of AAO formation. PMID:24535886

  3. Oxidation of phenol and chlorophenols on platinized titanium anodes in an acidic medium

    Science.gov (United States)

    Mokbel, Saleh Mohammed; Kolosov, E. N.; Mikhalenko, I. I.

    2016-06-01

    A comparative study of oxidation of phenol, 3-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenol on Pt/Ti and Ce,Pt/Ti electrocatalysts is performed via cyclic voltammetry. It is shown that the surface morphology and roughness of the anode do not change after modification with cerium. The formal kinetic orders of electrooxidation of all compounds are found to be less than one. It is shown that the β temperature coefficients of the rate of oxidation of chlorophenols grow by 10 to 50% when the Ce,Pt/Ti anode is used at a substrate concentration of 1 mM. A tenfold increase in concentration reduces the effect of cerium additive, except for 3-chlorophenol: the latter exhibits a 250% increase in the β value, compared to the Pt/Ti anode.

  4. Influence of Anodic Conditions on Self-ordered Growth of Highly Aligned Titanium Oxide Nanopores

    Directory of Open Access Journals (Sweden)

    Hernández-Vélez M

    2007-01-01

    Full Text Available AbstractSelf-aligned nanoporous TiO2templates synthesized via dc current electrochemical anodization have been carefully analyzed. The influence of environmental temperature during the anodization, ranging from 2 °C to ambient, on the structure and morphology of the nanoporous oxide formation has been investigated, as well as that of the HF electrolyte chemical composition, its concentration and their mixtures with other acids employed for the anodization. Arrays of self-assembled titania nanopores with inner pores diameter ranging between 50 and 100 nm, wall thickness around 20–60 nm and 300 nm in length, are grown in amorphous phase, vertical to the Ti substrate, parallel aligned to each other and uniformly disordering distributed over all the sample surface. Additional remarks about the photoluminiscence properties of the titania nanoporous templates and the magnetic behavior of the Ni filled nanoporous semiconductor Ti oxide template are also included.

  5. The application of the barrier-type anodic oxidation method to thickness testing of aluminum films

    Science.gov (United States)

    Chen, Jianwen; Yao, Manwen; Xiao, Ruihua; Yang, Pengfei; Hu, Baofu; Yao, Xi

    2014-09-01

    The thickness of the active metal oxide film formed from a barrier-type anodizing process is directly proportional to its formation voltage. The thickness of the consumed portion of the metal film is also corresponding to the formation voltage. This principle can be applied to the thickness test of the metal films. If the metal film is growing on a dielectric substrate, when the metal film is exhausted in an anodizing process, because of the high electrical resistance of the formed oxide film, a sudden increase of the recorded voltage during the anodizing process would occur. Then, the thickness of the metal film can be determined from this voltage. As an example, aluminum films are tested and discussed in this work. This method is quite simple and is easy to perform with high precision.

  6. A Review of RedOx Cycling of Solid Oxide Fuel Cells Anode

    Directory of Open Access Journals (Sweden)

    Jan Van herle

    2012-08-01

    Full Text Available Solid oxide fuel cells are able to convert fuels, including hydrocarbons, to electricity with an unbeatable efficiency even for small systems. One of the main limitations for long-term utilization is the reduction-oxidation cycling (RedOx cycles of the nickel-based anodes. This paper will review the effects and parameters influencing RedOx cycles of the Ni-ceramic anode. Second, solutions for RedOx instability are reviewed in the patent and open scientific literature. The solutions are described from the point of view of the system, stack design, cell design, new materials and microstructure optimization. Finally, a brief synthesis on RedOx cycling of Ni-based anode supports for standard and optimized microstructures is depicted.

  7. Preparation and Evaluation of Multi-Layer Anodes of Solid Oxide Fuel Cell

    Science.gov (United States)

    Santiago, Diana; Farmer, Serene C.; Setlock, John A.

    2012-01-01

    The development of an energy device with abundant energy generation, ultra-high specific power density, high stability and long life is critical for enabling longer missions and for reducing mission costs. Of all different types of fuel cells, the solid oxide fuel cells (SOFC) is a promising high temperature device that can generate electricity as a byproduct of a chemical reaction in a clean way and produce high quality heat that can be used for other purposes. For aerospace applications, a power-to-weight of (is) greater than 1.0 kW/kg is required. NASA has a patented fuel cell technology under development, capable of achieving the 1.0 kW/kg figure of merit. The first step toward achieving these goals is increasing anode durability. The catalyst plays an important role in the fuel cells for power generation, stability, efficiency and long life. Not only the anode composition, but its preparation and reduction are key to achieving better cell performance. In this research, multi-layer anodes were prepared varying the chemistry of each layer to optimize the performance of the cells. Microstructure analyses were done to the new anodes before and after fuel cell operation. The cells' durability and performance were evaluated in 200 hrs life tests in hydrogen at 850 C. The chemistry of the standard nickel anode was modified successfully reducing the anode degradation from 40% to 8.4% in 1000 hrs and retaining its microstructure.

  8. Effect of Graphene-Graphene Oxide Modified Anode on the Performance of Microbial Fuel Cell

    Directory of Open Access Journals (Sweden)

    Na Yang

    2016-09-01

    Full Text Available The inferior hydrophilicity of graphene is an adverse factor to the performance of the graphene modified anodes (G anodes in microbial fuel cells (MFCs. In this paper, different amounts of hydrophilic graphene oxide (GO were doped into the modification layers to elevate the hydrophilicity of the G anodes so as to further improve their performance. Increasing the GO doped ratio from 0.15 mg·mg−1 to 0.2 mg·mg−1 and 0.25 mg·mg−1, the static water contact angle (θc of the G-GO anodes decreased from 74.2 ± 0.52° to 64.6 ± 2.75° and 41.7 ± 3.69°, respectively. The G-GO0.2 anode with GO doped ratio of 0.2 mg·mg−1 exhibited the optimal performance and the maximum power density (Pmax of the corresponding MFC was 1100.18 mW·m−2, 1.51 times higher than that of the MFC with the G anode.

  9. Fracture toughness of solid oxide fuel cell anode substrates determined by a double-torsion technique

    Science.gov (United States)

    Pećanac, G.; Wei, J.; Malzbender, J.

    2016-09-01

    Planar solid oxide fuel cell anode substrates are exposed to high mechanical loads during assembly, start-up, steady-state operation and thermal cycling. Hence, characterization of mechanical stability of anode substrates under different oxidation states and at relevant temperatures is essential to warrant a reliable operation of solid oxide fuel cells. As a basis for mechanical assessment of brittle supports, two most common anode substrate material variants, NiO-3YSZ and NiO-8YSZ, were analyzed in this study with respect to their fracture toughness at room temperature and at a typical stack operation temperature of 800 °C. The study considered both, oxidized and reduced materials' states, where also an outlook is given on the behavior of the re-oxidized state that might be induced by malfunctions of sealants or other functional components. Aiming at the improvement of material's production, different types of warm pressed and tape cast NiO-8YSZ substrates were characterized in oxidized and reduced states. Overall, the results confirmed superior fracture toughness of 3YSZ compared to 8YSZ based composites in the oxidized state, whereas in the reduced state 3YSZ based composites showed similar fracture toughness at room temperature, but a higher value at 800 °C compared to 8YSZ based composites. Complementary microstructural analysis aided the interpretation of mechanical characterization.

  10. Bacterial nanometric amorphous Fe-based oxide: a potential lithium-ion battery anode material.

    Science.gov (United States)

    Hashimoto, Hideki; Kobayashi, Genki; Sakuma, Ryo; Fujii, Tatsuo; Hayashi, Naoaki; Suzuki, Tomoko; Kanno, Ryoji; Takano, Mikio; Takada, Jun

    2014-04-23

    Amorphous Fe(3+)-based oxide nanoparticles produced by Leptothrix ochracea, aquatic bacteria living worldwide, show a potential as an Fe(3+)/Fe(0) conversion anode material for lithium-ion batteries. The presence of minor components, Si and P, in the original nanoparticles leads to a specific electrode architecture with Fe-based electrochemical centers embedded in a Si, P-based amorphous matrix.

  11. The Effect of Anodic Surface Treatment on the Oxidation of Catechols at Ultrasmall Carbon Ring Electrodes

    Science.gov (United States)

    1991-07-09

    selectivity. A model of the surface formed following anodic oxidation is consistent with previous models involving both surface cleanliness and carbon...involving both surface cleanliness and carbon structure orientation. 2 INTRODUCTION Because of the vast electroanalytical utility of carbon electrodes...of the electron transfer rate following treatment are a function of the surface cleanliness and the orientation of the carbon structure

  12. Bimodal spatial distribution of pores in anodically oxidized aluminum thin films

    Science.gov (United States)

    Behnke, J. F.; Sands, T.

    2000-12-01

    Though porous anodic aluminum oxide has been the subject of considerable research since the 1950s, little attention has been devoted to the characterization of the self-organization of the pore structures, and fewer of these studies have focused on anodization of thin films. The degree to which these structures self-organize, however, could play a vital role in future applications of porous anodic aluminum oxide. In this study a model is developed to describe pore ordering in thin anodized aluminum films. The model is based on a radial distribution function approach to describe the interpore spacings. Idealized one-dimensional and two-dimensional (2D) radial distribution functions are combined by linear superposition to approximate experimental radial distribution functions. Using these radial distribution functions, an order parameter is developed and an improved definition of pore spacing is constructed. This method confirms that the oxide initially forms with a highly frustrated porous structure and reorganizes toward greater 2D order as the oxide grows into the film.

  13. High-performance anode-supported solid oxide fuel cell with impregnated electrodes

    Science.gov (United States)

    Osinkin, D. A.; Bogdanovich, N. M.; Beresnev, S. M.; Zhuravlev, V. D.

    2015-08-01

    The 61%NiO + 39%Zr0.84Y0.16O1.92 (NiO-YSZ) and 56%NiO + 44%Zr0.83Sc0.16Ce0.01O1.92 (NiO-CeSSZ) composite powders have been prepared using two-steps and one-step combustion synthesis, respectively. The Ni-YSZ anode substrate with a low level of electrical resistance (less than 1 mOhm cm) and porosity of about 53% in the reduced state was fabricated. The functional layer of the anode with the high level of electrochemical activity was made of NiO-CeSSZ. The single anode-supported solid oxide fuel cell with the bi-layer Ni-cermet anode, Zr0.84Sc0.16O1.92 film electrolyte and the Pt + 3% Zr0.84Y0.16O1.92 cathode was fabricated. The power density and the U-I curves of the fuel cell at initial state and after impregnation of the cathode and anode by praseodymium and cerium oxides, respectively, have been measured at different temperatures. The maximum of power density of the initial fuel cell was 0.35 W cm-2 at conditions of wet hydrogen (air) supply to the anode (cathode) at 900 °C. After the electrodes were impregnated, the value of power density increased by seven times and was approximately 2.4 W cm-2 at 0.6 V. It was suggested that after the electrodes impregnation the polarization resistance of the fuel cell was determined by the gas diffusion in the supported anode.

  14. Anodic oxidation of oxytetracycline: Influence of the experimental conditions on the degradation rate and mechanism

    Directory of Open Access Journals (Sweden)

    Annabel Fernandes

    2014-12-01

    Full Text Available The anodic oxidation of oxytetracycline was performed with success using as anode a boron-doped diamond electrode. The experiments were conducted in batch mode, using two different electrochemical cells: an up-flow cell, with recirculation, that was used to evaluate the influence of recirculation flow rate; and a stirred cell, used to determine the influence of the applied current density. Besides oxytetracyclin electrodegradation rate and mineralization extent, oxidation by-products were also assessed. Both the flow rate and the applied current density have shown positive influence on the oxytetracycline oxidation rate. On the other hand, the mineralization degree presented the highest values at the lowest flow rate and the lowest current density tested. The main oxidation by-products detected were oxalic, oxamic and maleic acids.

  15. Effect of rhenium on short term oxidation of niobium based alloys for high temperature applications

    Science.gov (United States)

    Sierra, Ruth M.

    The effect of adding Re to Nb-based alloys and is intended to analyze in depth the microstructures of Nb based alloys with Re, Si and Cr additions, in atomic percentages. The binary alloys (Nb-5Re, Nb-5Si and Nb-5Cr) reveal the formation of a single phase, NbSS, NbSS + Nb3Si and NbSS+NbCr2 respectively. The formation of the single phase was confirmed by TEM studies for the Nb-5Re alloy. Addition of Re to form ternary alloys, has helped in the formation of Nb5Si 3 and (Nb, Re) Cr2, in Nb-5Re- 5Si and Nb-5Re-5Cr respectively. Quaternary alloy Nb-5Re-5Si-5Cr has Nb5Si3, NbCr2 and NbSS. The oxidation behavior has been studied and the formation of the oxides has been characterized using XRD, SEM, EDS. Nb-Re-Si-Cr-X (Al, B, W) alloy system has been examined at temperatures between 700 and 1400°C in air. The continued work was to develop and discover a new materials system capable of replacing nickel based super alloys. Additions of aluminum were found to provide limited oxidation resistance. A discontinuous layer of Al2O3 and SiO2 was observed to form at all temperatures adapted for this study. Alloy containing aluminum additions were observed to suffer from pest oxidation at intermediate temperatures due to the development of Nb2O5. Poor oxidation resistance at intermediate temperatures for alloys with aluminum additions was attributed to a transformation in the structure of Nb2O5 formed. Pesting was observed at 900°C, consuming the metal completely. Additions of chromium were observed to increase oxidation resistance through the development of a layered oxide structure containing SiO2 and CrNbO4. Internal oxidation layer was observed to develop oxides in the midst of the phases formed. Boron addition has helped in the formation of the 3, 5 silicides, NbSS, and Laves phase. The combination of oxides of Nb2O5, CrNbO4 and SiO2 has helped improve the oxidation resistance of the alloy. Rhenium in this alloy has been a major element in terms of forming Re-oxides which has

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

    DEFF Research Database (Denmark)

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

    1994-01-01

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

  17. Facile hydrothermal preparation of niobium pentaoxide decorated reduced graphene oxide nanocomposites for supercapacitor applications

    Science.gov (United States)

    Murugan, M.; Kumar, R. Mohan; Alsalme, Ali; Alghamdi, Abdulaziz; Jayavel, R.

    2016-04-01

    Facile synthesis of graphene-Nb2O5 composite has been reported. Graphene oxide was prepared by the modified Hummer's method. The metal oxide (Nb2O5) was introduced to the graphene to form the composite by the hydrothermal method. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared (FTIR) and thermo gravimetric analysis (TGA). SEM and TEM results revealed that the metal oxide particles are uniformly dispersed on the surface of thin sheets of well-defined multilayered graphene structure. Thermal stability of the graphene metal oxide nanocomposites was also investigated. The CV measurements reveal a significant enhancement in the specific capacitance reaching 321 Fg-1 at a scan rate of 10 mV s-1. With promising electrochemical characteristics, Nb2O5 decorated graphene nanocomposite are explored as potential electrode material for supercapacitor applications.

  18. Effects of the Use of Pore Formers on Performance of an Anode supported Solid Oxide Fuel Cell

    Energy Technology Data Exchange (ETDEWEB)

    Haslam, J J; Pham, A; Chung, B W; DiCarlo, J F; Glass, R S

    2003-12-04

    The effects of amount of pore former used to produce porosity in the anode of an anode supported planar solid oxide fuel cell were examined. The pore forming material utilized was rice starch. The reduction rate of the anode material was measured by Thermogravimetric Analysis (TGA) to qualitatively characterize the gas transport within the porous anode materials. Fuel cells with varying amounts of porosity produced by using rice starch as a pore former were tested. The performance of the fuel cell was the greatest with an optimum amount of pore former used to create porosity in the anode. This optimum is believed to be related to a trade off between increasing gas diffusion to the active three-phase boundary region of the anode and the loss of performance due to the replacement of active three-phase boundary regions of the anode with porosity.

  19. Purification of Niobium by Electron Beam Melting

    Science.gov (United States)

    Sankar, M.; Mirji, K. V.; Prasad, V. V. Satya; Baligidad, R. G.; Gokhale, A. A.

    2016-06-01

    Pure niobium metal, produced by alumino-thermic reduction of niobium oxide, contains various impurities which need to be reduced to acceptable levels to obtain aerospace grade purity. In the present work, an attempt has been made to refine niobium metals by electron beam drip melting technique to achieve purity confirming to the ASTM standard. Input power to the electron gun and melt rate were varied to observe their combined effect on extend of refining and loss of niobium. Electron beam (EB) melting is shown to reduce alkali metals, trace elements and interstitial impurities well below the specified limits. The reduction in the impurities during EB melting is attributed to evaporation and degassing due to the combined effect of high vacuum and high melt surface temperature. The % removal of interstitial impurities is essentially a function of melt rate and input power. As the melt rate decreases or input power increases, the impurity levels in the solidified niobium ingot decrease. The EB refining process is also accompanied by considerable amount of niobium loss, which is attributed to evaporation of pure niobium and niobium sub-oxide. Like other impurities, Nb loss increases with decreasing melt rate or increase in input power.

  20. Synthesis of self-ordered titanium oxide nanotubes by anodization of titanium

    Science.gov (United States)

    Krishnan, A. Yaadhav; Sivabalan, S.; Subhachandhar, S.; Balakrishnan, M.; Narayanan, R.

    2012-07-01

    Self-ordered arrays of titanium oxide nanotubes were prepared by anodization of Ti in sodium sulphate solution containing sodium fluoride. The dimensions of the nanotubes (diameter: 20-100 nm and length: 1000-1500 nm) could be tuned by changing the synthesis parameters. The as-anodized nanotubes showed amorphous structure which upon annealing at 500°C in oxygen atmosphere turned crystalline, according to XRD analysis. The pit morphologies show that pit initiation occurs due to NaF content in the electrolyte and nanotube formation starts after pit growth terminates.

  1. Synthesis and characterization of nanoporous anodic oxide film on aluminum in H3PO4 + KMnO4 electrolyte mixture at different anodization conditions

    Science.gov (United States)

    Verma, Naveen; Jindal, Jitender; Singh, Krishan Chander; Mari, Bernabe

    2016-04-01

    The micro structural properties of nanoporous anodic oxide film formed in H3PO4 were highly influenced by addition of a low concentration of KMnO4 (0.0005 M) in 1 M H3PO4 solution. The KMnO4 as additive enhanced the growth rate of oxide film formation as well as thickness of pore walls. Furthermore the growth rate was found increased with increase in applied current density. The increase in temperature and lack of stirring during anodization causes the thinness of pore wall which leads to increase in pore volume. With the decrease in concentration of H3PO4 in anodizing electrolyte from 1M to 0.3 M, keeping all other conditions constant, the decrease in porosity was observed. This might be due to the dissolution of aluminium oxide film in highly concentrated acidic solution.

  2. Anodic oxidation of o-nitrophenol on BDD electrode: Variable effects and mechanisms of degradation

    Energy Technology Data Exchange (ETDEWEB)

    Rabaaoui, Nejmeddine, E-mail: chimie_tunisie@yahoo.fr [Materials, Environment and Energy Laboratory (06/UR/12-01), Science Faculty of Gafsa, 2112, University of Gafsa (Tunisia); Saad, Mohamed El Khames [Materials, Environment and Energy Laboratory (06/UR/12-01), Science Faculty of Gafsa, 2112, University of Gafsa (Tunisia); Moussaoui, Younes [Materials, Environment and Energy Laboratory (06/UR/12-01), Science Faculty of Gafsa, 2112, University of Gafsa (Tunisia); Physical Organic Chemistry Laboratory, Science Faculty of Sfax, University of Sfax (Tunisia); Allagui, Mohamed Salah [Science Faculty of Gafsa, University of Gafsa (Tunisia); Bedoui, Ahmed [Materials, Environment and Energy Laboratory (06/UR/12-01), Science Faculty of Gafsa, 2112, University of Gafsa (Tunisia); Science Faculty of Gabes, 6072, University of Gabes (Tunisia); Elaloui, Elimame [Materials, Environment and Energy Laboratory (06/UR/12-01), Science Faculty of Gafsa, 2112, University of Gafsa (Tunisia); Science Faculty of Gafsa, University of Gafsa (Tunisia)

    2013-04-15

    Highlights: ► Anodic oxidation is an effective method for degrading o-nitrophenol. ► The effect of operating parameters on the degradation was investigated. ► The main intermediate products were determined by HPLC technique. ► A plausible degradation pathway of o-nitrophenol was proposed. -- Abstract: The electrochemical oxidation of pesticide, o-nitrophenol (ONP) as one kind of pesticide that is potentially dangerous and biorefractory, was studied by galvanostatic electrolysis using boron-doped diamond (BDD) as anode. The influence of several operating parameters, such as applied current density, supporting electrolyte, and initial pH value, was investigated. The best degradation occurred in the presence of Na{sub 2}SO{sub 4} (0.05 M) as conductive electrolyte. After 8 h, nearly complete degradation of o-nitrophenol was achieved (92%) using BDD electrodes at pH 3 and at current density equals 60 mA cm{sup −2}. The decay kinetics of o-nitrophenol follows a pseudo-first-order reaction. Aromatic intermediates such as catechol, resorcinol, 1,2,4-trihydroxybenzene, hydroquinone and benzoquinone and carboxylic acids such as maleic glycolic, malonic, glyoxilic and oxalic, have been identified and followed during the ONP treatment by chromatographic techniques. From these anodic oxidation by-products, a plausible reaction sequence for ONP mineralization on BDD anodes is proposed.

  3. Effect of impregnation phases on the performance of Ni-based anodes for low temperature solid oxide fuel cells

    Science.gov (United States)

    Liu, Zhangbo; Ding, Dong; Liu, Beibei; Guo, Weiwei; Wang, Wendong; Xia, Changrong

    2011-10-01

    Impregnated nanoparticles are very effective in improving the electrochemical performance of solid oxide fuel cell (SOFC) anodes possibly due to the extension of reaction sites and/or the enhancement of catalytic activity. In this work, samaria-doped ceria (SDC), pure ceria, samaria, and alumina oxides impregnated Ni-based anodes are fabricated to compare the site extending and the catalytic effects. Except for alumina, the impregnation of the other three nano-sized oxides could substantially enhance the performance of the anodes for the hydrogen oxidation reactions. Moreover, single cells with CeO2 and Sm2O3 impregnated anodes could exhibit as great performance as those with SDC impregnated anodes. When the impregnation loading reached the optimal value, 1.7 mmol cm-3, these cells exhibit very high performance, with peak power densities around 750 mW cm-2. The high performance of CeO2 and Sm2O3 impregnated anodes demonstrates that the improved performance are mainly attributed to the significantly improved electrochemical activities of the anodes, but not to the extension of triple-phase-boundary, and wet impregnation is indeed an alternative and effective technique to introduce these nano-sized catalytic active oxides into the anode configuration of SOFCs to enhance cell performance, stability and reliability.

  4. Binder-free graphene and manganese oxide coated carbon felt anode for high-performance microbial fuel cell.

    Science.gov (United States)

    Zhang, Changyong; Liang, Peng; Yang, Xufei; Jiang, Yong; Bian, Yanhong; Chen, Chengmeng; Zhang, Xiaoyuan; Huang, Xia

    2016-07-15

    A novel anode was developed by coating reduced graphene oxide (rGO) and manganese oxide (MnO2) composite on the carbon felt (CF) surface. With a large surface area and excellent electrical conductivity, this binder-free anode was found to effectively enhance the enrichment and growth of electrochemically active bacteria and facilitate the extracellular electron transfer from the bacteria to the anode. A microbial fuel cell (MFC) equipped with the rGO/MnO2/CF anode delivered a maximum power density of 2065mWm(-2), 154% higher than that with a bare CF anode. The internal resistance of the MFC with this novel anode was 79Ω, 66% lower than the regular one's (234Ω). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses affirmed that the rGO/MnO2 composite significantly increased the anodic reaction rates and facilitated the electron transfer from the bacteria to the anode. The findings from this study suggest that the rGO/MnO2/CF anode, fabricated via a simple dip-coating and electro-deposition process, could be a promising anode material for high-performance MFC applications.

  5. Assessment of the performance of Ni-yttria-stabilized zirconia anodes in anode-supported Solid Oxide Fuel Cells operating on H 2-CO syngas fuels

    Science.gov (United States)

    Ye, Xiao-Feng; Wang, S. R.; Zhou, J.; Zeng, F. R.; Nie, H. W.; Wen, T. L.

    Anode-supported Solid Oxide Fuel Cells (SOFCs) with Ni-yttria-stabilized zirconia (YSZ) anode have been fabricated and studied using H 2-CO syngas fuels. Syngas fuels with different compositions of H 2-CO are supplied and the cell performance is measured at 750 °C. A high CO content has caused carbon deposition and crack formation in the Ni-YSZ anode after long-term operation, even though it is diluted with H 2O and N 2. However, it was found that a Cu-CeO 2 coating on Ni-YSZ can greatly improve the anode stability in syngas by facilitating the water gas shift reaction. The optimized single cell has run in sygas with a composition of 65%H 2-32%CO-3%H 2O for 1050 h without obvious degradation of its performance.

  6. Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices

    Science.gov (United States)

    Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

    2010-03-02

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

  7. New roots to formation of nanostructures on glass surface through anodic oxidation of sputtered aluminum

    Directory of Open Access Journals (Sweden)

    Satoru Inoue, Song-Zhu Chu, Kenji Wada, Di Li and Hajime Haneda

    2003-01-01

    Full Text Available New processes for the preparation of nanostructure on glass surfaces have been developed through anodic oxidation of sputtered aluminum. Aluminum thin film sputtered on a tin doped indium oxide (ITO thin film on a glass surface was converted into alumina by anodic oxidation. The anodic alumina gave nanometer size pore array standing vertically on the glass surface. Kinds of acids used in the anodic oxidation changed the pore size drastically. The employment of phosphoric acid solution gave several tens nanometer size pores. Oxalic acid cases produced a few tens nanometer size pores and sulfuric acid solution provided a few nanometer size pores. The number of pores in a unit area could be changed with varying the applied voltage in the anodization and the pore sizes could be increased by phosphoric acid etching. The specimen consisting of a glass substrate with the alumina nanostructures on the surface could transmit UV and visible light. An etched specimen was dipped in a TiO2 sol solution, resulting in the impregnation of TiO2 sol into the pores of alumina layer. The TiO2 sol was heated at ~400 °C for 2 h, converting into anatase phase TiO2. The specimens possessing TiO2 film on the pore wall were transparent to the light in UV–Visible region. The electro deposition technique was applied to the introduction of Ni metal into pores, giving Ni nanorod array on the glass surface. The removal of the barrier layer alumina at the bottom of the pores was necessary to attain smooth electro deposition of Ni. The photo catalytic function of the specimens possessing TiO2 nanotube array was investigated in the decomposition of acetaldehyde gas under the irradiation of UV light, showing that the rate of the decomposition was quite large.

  8. Electrospun carbon-tin oxide composite nanofibers for use as lithium ion battery anodes.

    Science.gov (United States)

    Bonino, Christopher A; Ji, Liwen; Lin, Zhan; Toprakci, Ozan; Zhang, Xiangwu; Khan, Saad A

    2011-07-01

    Composite carbon-tin oxide (C-SnO(2)) nanofibers are prepared by two methods and evaluated as anodes in lithium-ion battery half cells. Such an approach complements the long cycle life of carbon with the high lithium storage capacity of tin oxide. In addition, the high surface-to-volume ratio of the nanofibers improves the accessibility for lithium intercalation as compared to graphite-based anodes, while eliminating the need for binders or conductive additives. The composite nanofibrous anodes have first discharge capacities of 788 mAh g(-1) at 50 mA g(-1) current density, which are greater than pure carbon nanofiber anodes, as well as the theoretical capacity of graphite (372 mAh g(-1)), the traditional anode material. In the first protocol to fabricate the C-SnO(2) composites, tin sulfate is directly incorporated within polyacrylonitrile (PAN) nanofibers by electrospinning. During a thermal treatment the tin salt is converted to tin oxide and the polymer is carbonized, yielding carbon-SnO(2) nanofibers. In the second approach, we soak the nanofiber mats in tin sulfate solutions prior to the final thermal treatment, thereby loading the outer surfaces with SnO(2) nanoparticles and raising the tin content from 1.9 to 8.6 wt %. Energy-dispersive spectroscopy and X-ray diffraction analyses confirm the formation of conversion of tin sulfate to tin oxide. Furthermore, analysis with Raman spectroscopy reveals that the additional salt soak treatment from the second fabrication approach increases in the disorder of the carbon structure, as compared to the first approach. We also discuss the performance of our C-SnO(2) compared with its theoretical capacity and other nanofiber electrode composites previously reported in the literature.

  9. Reduced Graphene Oxide/Tin-Antimony Nanocomposites as Anode Materials for Advanced Sodium-Ion Batteries.

    Science.gov (United States)

    Ji, Liwen; Zhou, Weidong; Chabot, Victor; Yu, Aiping; Xiao, Xingcheng

    2015-11-11

    Reduced graphene oxides loaded with tin-antimony alloy (RGO-SnSb) nanocomposites were synthesized through a hydrothermal reaction and the subsequent thermal reduction treatments. Transmission electron microscope images confirm that SnSb nanoparticles with an average size of about 20-30 nm are uniformly dispersed on the RGO surfaces. When they were used as anodes for rechargeable sodium (Na)-ion batteries, these as-synthesized RGO-SnSb nanocomposite anodes delivered a high initial reversible capacity of 407 mAh g(-1), stable cyclic retention for more than 80 cycles and excellent cycle stability at ultra high charge/discharge rates up to 30C. The significantly improved performance of the synthesized RGO-SnSb nanocomposites as Na-ion battery anodes can be attributed to the synergetic effects of RGO-based flexible framework and the nanoscale dimension of the SnSb alloy particles (batteries.

  10. Model of porous aluminium oxide growth during initial stage of anodization

    Science.gov (United States)

    Aryslanova, E. M.; Alfimov, A. V.; Chivilikhin, S. A.

    2014-10-01

    Currently, the development of nanotechnology and metamaterials requires the ability to obtain regular self-assembled structures with different parameters. One such structure is porous alumina in which the pores grow perpendicular to the substrate and are hexagonally packed. Pore size and the distance between them can be varied depending on the anodization voltage, the electrolyte and the anodization time (pore diameter - from 2 to 350 nm, the distance between the pores - from 5 to 50 nm). At the moment, there are different models describing the process of anodizing aluminum, in this paper we propose a model that takes into account the effect of layers of aluminum, aluminum oxide, and the electrolyte, as well as the influence of the effect of surface diffusion.

  11. The effect of different oxide layers on the sensing properties of anodic alumina nanoporous film

    Directory of Open Access Journals (Sweden)

    H. Abbasian

    2014-03-01

    Full Text Available In the present work, anodized aluminum oxide template was prepared by accelerated mild anodization technique in 0.6M phosphoric aside and 175 V, anodization voltage. Pore widening was performed by chemical etching in 0.5M phosphoric acid for 8, 16, 32, 40 minutes. Scanning Electron Microscopy (SEM images showed the pores, diameter exponentially increases with etching time. By depositing silver contacts on the prepared samples and using an RC circuit for applying impedance spectroscopy, the characteristics of the humidity sensor based on constructed samples were investigated. The maximum response was seen for the sample etched for 40 minutes. For this sample, the detectable threshold of relative moisture was 30% and the response and the recovery time were 8, 2 seconds, respectively

  12. Optimization of dry reforming of methane over Ni/YSZ anodes for solid oxide fuel cells

    Science.gov (United States)

    Guerra, Cosimo; Lanzini, Andrea; Leone, Pierluigi; Santarelli, Massimo; Brandon, Nigel P.

    2014-01-01

    This work investigates the catalytic properties of Ni/YSZ anodes as electrodes of Solid Oxide Fuel Cells (SOFCs) to be operated under direct dry reforming of methane. The experimental test rig consists of a micro-reactor, where anode samples are characterized. The gas composition at the reactor outlet is monitored using a mass spectrometer. The kinetics of the reactions occurring over the anode is investigated by means of Isotherm reactions and Temperature-programmed reactions. The effect of the variation of temperature, gas residence time and inlet carbon dioxide-methane volumetric ratio is analyzed. At 800 °C, the best catalytic performance (in the carbon safe region) is obtained for 1.5 dry reforming and cracking reactions, respectively. In other ranges, dry reforming and reverse water gas shift are the dominant reactions and the inlet feed reaches almost the equilibrium condition provided that a sufficient gas residence time is obtained.

  13. Biogas Catalytic Reforming Studies on Nickel-Based Solid Oxide Fuel Cell Anodes

    DEFF Research Database (Denmark)

    Johnson, Gregory B.; Hjalmarsson, Per; Norrman, Kion;

    2016-01-01

    Heterogeneous catalysis studies were conducted on two crushed solid oxide fuel cell (SOFC) anodes in fixed-bed reactors. The baseline anode was Ni/ScYSZ (Ni/scandia and yttria stabilized zirconia), the other was Ni/ScYSZ modified with Pd/doped ceria (Ni/ScYSZ/Pd-CGO). Three main types...... of Pd-CGO helped to mitigate sulfur deactivation effect; e.g. lowering the onset temperature (up to 190°C) for CH4 conversion during temperature-programmed reactions. Both Ni/ScYSZ and Ni/ScYSZ/Pd-CGO anode catalysts were more active for dry reforming of biogas than they were for steam reforming....... Deactivation of reforming activity by sulfur was much more severe under steam reforming conditions than dry reforming; a result of greater sulfur retention on the catalyst surface during steam reforming....

  14. Oxygen release and exchange in niobium oxide MEHPPV hybrid solar cells

    DEFF Research Database (Denmark)

    Lira-Cantu, M.; Norrman, K.; Andreasen, J.W.;

    2006-01-01

    exchange was demonstrated using O-18(2)-isotopic labeling in combination with time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging analysis of devices and oxide substrates. TOF-SIMS depth profiling confirmed O-18 incorporation throughout the device in hybrid solar cells. The results...

  15. In situ luminescence and IR study of porous silicon during and after anodic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Dubin, V.M. [Laboratoire de Physique de la Matiere Condensee, CNRS, Ecole Polytechnique, F-91128 Palaiseau Cedex (France); Ozanam, F. [Laboratoire de Physique de la Matiere Condensee, CNRS, Ecole Polytechnique, F-91128 Palaiseau Cedex (France); Chazalviel, J.N. [Laboratoire de Physique de la Matiere Condensee, CNRS, Ecole Polytechnique, F-91128 Palaiseau Cedex (France)

    1995-01-15

    When porous silicon is transferred into a non-fluoride electrolyte and anodically oxidized, the onset of red electroluminescence during anodic oxidation appears correlated with a decrease in the OH IR absorption bands, indicating significant electrolyte removal from the pores. The electron states whose population is affected by carrier injection or light excitation have been investigated using in situ electromodulated or photomodulated IR spectroscopy. The modulated IR absorption of red-luminescent electro-oxidized porous silicon exhibits an extra absorption of localized carriers in the 1000-2500cm{sup -1} region, suggesting that the red luminescence occurs through carriers trapped in localized states. The localization process may be efficiently affected by the dielectric constant of the medium surrounding the silicon nanocrystallites. ((orig.))

  16. Investigations into the interactions between sulfur and anodes for solid oxide fuel cells

    Science.gov (United States)

    Cheng, Zhe

    Solid oxide fuel cells (SOFCs) are electrochemical devices based on solid oxide electrolytes that convert chemical energy in fuels directly into electricity via electrode reactions. SOFCs have the advantages of high energy efficiency and low emissions and hold the potential to be the power of the future especially for small power generation systems (1-10 kW). Another unique advantage of SOFCs is the potential to directly utilize hydrocarbon fuels such as natural gas through internal reforming. However, all hydrocarbon fuels contain some sulfur compounds, which transform to hydrogen sulfide (H2S) in the reforming process and dramatically degrade the performance of the existing SOFCs. In this study, the interactions between sulfur contaminant (in the form of H2S) and the anodes for SOFCs were systematically investigated in order to gain a fundamental understanding of the mechanism of sulfur poisoning and ultimately to achieve rational design of sulfur-tolerant anodes. The sulfur poisoning behavior of the state-of-the-art Ni-YSZ cermet anodes was characterized using electrochemical measurements performed on button cells (of different structures) under various operating conditions, including H2S concentration, temperature, cell current density/terminal voltage, and cell structure. Also, the mechanisms of interactions between sulfur and the Ni-YSZ cermet anode were investigated using both ex situ and in situ characterization techniques such as Raman spectroscopy. Results suggest that the sulfur poisoning of Ni-YSZ cermet anodes at high temperatures in fuels with ppm-level H2S is due not to the formation of multi-layer conventional nickel sulfides but to the adsorption of sulfur on the nickel surface. In addition, new sulfur-tolerant anode materials were explored in this study. Thermodynamic principles were applied to predict the stability of candidate sulfur-tolerant anode materials and explain complex phenomena concerning the reactivity of candidate materials with

  17. Layered reduced graphene oxide with nanoscale interlayer gaps as a stable host for lithium metal anodes

    Science.gov (United States)

    Lin, Dingchang; Liu, Yayuan; Liang, Zheng; Lee, Hyun-Wook; Sun, Jie; Wang, Haotian; Yan, Kai; Xie, Jin; Cui, Yi

    2016-07-01

    Metallic lithium is a promising anode candidate for future high-energy-density lithium batteries. It is a light-weight material, and has the highest theoretical capacity (3,860 mAh g-1) and the lowest electrochemical potential of all candidates. There are, however, at least three major hurdles before lithium metal anodes can become a viable technology: uneven and dendritic lithium deposition, unstable solid electrolyte interphase and almost infinite relative dimension change during cycling. Previous research has tackled the first two issues, but the last is still mostly unsolved. Here we report a composite lithium metal anode that exhibits low dimension variation (˜20%) during cycling and good mechanical flexibility. The anode is composed of 7 wt% ‘lithiophilic’ layered reduced graphene oxide with nanoscale gaps that can host metallic lithium. The anode retains up to ˜3,390 mAh g-1 of capacity, exhibits low overpotential (˜80 mV at 3 mA cm-2) and a flat voltage profile in a carbonate electrolyte. A full-cell battery with a LiCoO2 cathode shows good rate capability and flat voltage profiles.

  18. Ceramic Lithium Ion Conductor to Solve the Anode Coking Problem of Practical Solid Oxide Fuel Cells.

    Science.gov (United States)

    Wang, Wei; Wang, Feng; Chen, Yubo; Qu, Jifa; Tadé, Moses O; Shao, Zongping

    2015-09-07

    For practical solid oxide fuel cells (SOFCs) operated on hydrocarbon fuels, the facile coke formation over Ni-based anodes has become a key factor that limits their widespread application. Modification of the anodes with basic elements may effectively improve their coking resistance in the short term; however, the easy loss of basic elements by thermal evaporation at high temperatures is a new emerging problem. Herein, we propose a new design to develop coking-resistant and stable SOFCs using Li(+) -conducting Li0.33 La0.56 TiO3 (LLTO) as an anode component. In the Ni/LLTO composite, any loss of surface lithium can be efficiently compensated by lithium diffused from the LLTO bulk under operation. Therefore, the SOFC with the Ni/LLTO anode catalyst layer yields excellent power outputs and operational stability. Our results suggest that the simple adoption of a Li(+) conductor as a modifier for Ni-based anodes is a practical and easy way to solve the coking problem of SOFCs that operate on hydrocarbons.

  19. Large Scale Inert Anode for Molten Oxide Electrolysis Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Molten oxide electrolysis is a demonstrated laboratory-scale process for producing oxygen from the JSC-1a lunar simulant; however, critical subsystems necessary for...

  20. Analysis of peel strength of consisting of an aluminum sheet, anodic aluminum oxide and a copper foil laminate composite

    Science.gov (United States)

    Shin, Hyeong-Won; Lee, Hyo-Soo; Jung, Seung-Boo

    2017-01-01

    Laminate composites consisting of an aluminum sheet, anodic aluminum oxide, and copper foil have been used as heat-spreader materials for high-power light-emitting diodes (LEDs). These composites are comparable to the conventional structure comprising an aluminum sheet, epoxy adhesives, and copper foil. The peel strength between the copper foil and anodic aluminum oxide should be more than 1.0 kgf/cm in order to be applied in high-power LED products. We investigated the effect of the anodic aluminum oxide morphology and heat-treatment conditions on the peel strength of the composites. We formed an anodic aluminum oxide layer on a 99.999% pure aluminum sheet using electrochemical anodization. A Ti/Cu seed layer was formed using the sputtering direct bonding copper process in order to form a copper circuit layer on the anodic aluminum oxide layer by electroplating. The developed heat spreader, composed of an aluminum layer, anodic aluminum oxide, and a copper circuit layer, showed peel strengths ranging from 1.05 to 3.45 kgf/cm, which is very suitable for high-power LED applications.

  1. Highly durable anode supported solid oxide fuel cell with an infiltrated cathode

    Science.gov (United States)

    Samson, Alfred Junio; Hjalmarsson, Per; Søgaard, Martin; Hjelm, Johan; Bonanos, Nikolaos

    2012-10-01

    An anode supported solid oxide fuel cell with an La0.6Sr0.4Co1.05O3-δ (LSC) infiltrated-Ce0.9Gd0.1O1.95 (CGO) cathode that shows a stable performance has been developed. The cathode was prepared by screen printing a porous CGO backbone on top of a laminated and co-fired anode supported half cell, consisting of a Ni-yttria stabilized zirconia (YSZ) anode support, a Ni-scandia-doped yttria-stabilized zirconia (ScYSZ) anode, a ScYSZ electrolyte, and a CGO barrier layer. LSC was introduced into the CGO backbone by multiple infiltrations of an aqueous nitrate solution followed by firing. The cell was tested at 700 °C under a current density of 0.5 A cm-2 for 1500 h using air as oxidant and humidified hydrogen as fuel. The electrochemical performance of the cell was analyzed by impedance spectroscopy and current-voltage relationships. No measurable degradation in the cell voltage or increase in the resistance from the recorded impedance was observed during long term testing. The power density reached 0.79 W cm-2 at a cell voltage of 0.6 V at 750 °C. Post test analysis of the LSC infiltrated-CGO cathode by scanning electron microscopy revealed no significant micro-structural difference to that of a nominally identical untested counterpart.

  2. Electrochemical oxidation of polyethylene glycol in electroplating solution using paraffin composite copper hexacyanoferrate modified (PCCHM) anode.

    Science.gov (United States)

    Bejankiwar, Rajesh S; Basu, Abir; Cementi, Max

    2004-01-01

    Electrochemical oxidation of polyethylene glycol (PEG) in an acidic (pH 0.18 to 0.42) and high ionic strength electroplating solution was investigated. The electroplating solution is a major source of wastewater in the printing wiring board industry. A paraffin composite copper hexacyanoferrate modified (PCCHM) electrode was used as the anode and a bare graphite electrode was used as the cathode. The changes in PEG and total organic carbon (TOC) concentrations during the course of the reaction were monitored. The efficiency of the PCCHM anode was compared with bare graphite anode and it was found that the former showed significant electrocatalytic property for PEG and TOC removal. Chlorides present in the solution were found to contribute significantly in the overall organic removal process. Short chain organic compounds like acetic acid, oxalic acid, formic acid and ethylene glycol formed during electrolysis were identified by HPLC method. Anode surface area and applied current density were found to influence the electro-oxidation process, in which the former was found to be dominating. Investigations of the kinetics for the present electrochemical reaction suggested that the two stage first-order kinetic model provides a much better representation of the overall mechanism of the process if compared to the generalized kinetic model.

  3. Electrochemical oxidation of polyethylene glycol in electroplating solution using paraffin composite copper hexacyanoferrate modified (PCCHM) anode

    Institute of Scientific and Technical Information of China (English)

    Rajesh S. Bejankiwar; Abir Basu; Max Cementi

    2004-01-01

    Electrochemical oxidation of polyethylene glycol(PEG) in an acidic(pH 0.18 to 0.42) and high ionic strength electroplating solution was investigated. The electroplating solution is a major source of wastewater in the printing wiring board industry. A paraffin composite copper hexacyanoferrate modified(PCCHM) electrode was used as the anode and a bare graphite electrode was used as the cathode. The changes in PEG and total organic carbon(TOC) concentrations during the course of the reaction were monitored. The efficiency of the PCCHM anode was compared with bare graphite anode and it was found that the former showed significant electrocatalytic property for PEG and TOC removal. Chlorides present in the solution were found to contribute significantly in the overall organic removal process. Short chain organic compounds like acetic acid, oxalic acid, formic acid and ethylene glycol formed during electrolysis were identified by HPLC method. Anode surface area and applied current density were found to influence the electro-oxidation process, in which the former was found to be dominating. Investigations of the kinetics for the present electrochemical reaction suggested that the two stage first-order kinetic model provides a much better representation of the overall mechanism of the process if compared to the generalized kinetic model.

  4. Electrochemical Characteristics of Tin Oxide-Graphite as Anode Material for Lithium-ion Cells

    Science.gov (United States)

    Hasanaly, Siti Munirah

    2010-03-01

    Tin oxide anode materials used in lithium-ion cells experience large volume changes during charging and discharging which cause substantial losses in capacity. In this work, the tin oxide-graphite composite is proposed as an alternative anode material to overcome this problem. The composite was synthesised from a solution of tin chloride dihydrate and graphite powders with citric acid as the chelating agent. In this sol-gel method, a solid phase is formed through a chemical reaction in a liquid phase at moderate temperature. The technique offers several advantages compared to the solid state synthesis technique such as the ability to maintain the homogeneous mixture of precursors during synthesis and to produce small particles. The electrochemical behaviour of the anode material was investigated by means of galvanostatic charge discharge technique. An initial reversible capacity of 748 mAh/g is obtained and nearly 600 mAh/g was retained upon the reaching the fifth cycle. This study shows that the presence of graphite is able to minimise the agglomeration of tin particles that causes large volume changes during cycling, thereby improving cyclability of the anode material.

  5. Treatment of methyl orange dye wastewater by cooperative electrochemical oxidation in anodic-cathodic compartment.

    Science.gov (United States)

    Pang, L; Wang, H; Bian, Z Y

    2013-01-01

    Electrochemical oxidation of methyl orange wastewater was studied using Ti/IrO(2)/RuO(2) anode and a self-made Pd/C O(2)-fed cathode in the divided cell with a terylene diaphragm. The result indicated that the appropriate rate of feeding air improved the methyl orange removal efficiency. The discoloration efficiency of methyl orange in the divided cell increased with increasing current density. The initial pH value had some effect on the discoloration of methyl orange, which became not obvious when the pH ranged from 2 to 10. However, the average removal efficiency of methyl orange wastewater in terms of total organic carbon (TOC) can reach 89.3%. The methyl orange structure had changed in the electrolytic process, and the characteristic absorption peak of methyl orange was about 470 nm. With the extension of electrolysis time, the concentration of methyl orange gradually reduced; wastewater discoloration rate increased gradually. The degradation of methyl orange was assumed to be cooperative oxidation by direct or indirect electrochemical oxidation at the anode and H(2)O(2), ·OH, O(2)(-)· produced by oxygen reduction at the cathode in the divided cell. Therefore, the cooperative electrochemical oxidation of methyl orange wastewater in the anodic-cathodic compartment had better degradation effects.

  6. Synthesis of Coral-Like Tantalum Oxide Films via Anodization in Mixed Organic-Inorganic Electrolytes

    Science.gov (United States)

    Yu, Hongbin; Zhu, Suiyi; Yang, Xia; Wang, Xinhong; Sun, Hongwei; Huo, Mingxin

    2013-01-01

    We report a simple method to fabricate nano-porous tantalum oxide films via anodization with Ta foils as the anode at room temperature. A mixture of ethylene glycol, phosphoric acid, NH4F and H2O was used as the electrolyte where the nano-porous tantalum oxide could be synthesized by anodizing a tantalum foil for 1 h at 20 V in a two–electrode configuration. The as-prepared porous film exhibited a continuous, uniform and coral-like morphology. The diameters of pores ranged from 30 nm to 50 nm. The pores interlaced each other and the depth was about 150 nm. After calcination, the as-synthesized amorphous tantalum oxide could be crystallized to the orthorhombic crystal system. As observed in photocatalytic experiments, the coral-like tantalum oxide exhibited a higher photocatalytic activity for the degradation of phenol than that with a compact surface morphology, and the elimination rate of phenol increased by 66.7%. PMID:23799106

  7. Synthesis of coral-like tantalum oxide films via anodization in mixed organic-inorganic electrolytes.

    Directory of Open Access Journals (Sweden)

    Hongbin Yu

    Full Text Available We report a simple method to fabricate nano-porous tantalum oxide films via anodization with Ta foils as the anode at room temperature. A mixture of ethylene glycol, phosphoric acid, NH4F and H2O was used as the electrolyte where the nano-porous tantalum oxide could be synthesized by anodizing a tantalum foil for 1 h at 20 V in a two-electrode configuration. The as-prepared porous film exhibited a continuous, uniform and coral-like morphology. The diameters of pores ranged from 30 nm to 50 nm. The pores interlaced each other and the depth was about 150 nm. After calcination, the as-synthesized amorphous tantalum oxide could be crystallized to the orthorhombic crystal system. As observed in photocatalytic experiments, the coral-like tantalum oxide exhibited a higher photocatalytic activity for the degradation of phenol than that with a compact surface morphology, and the elimination rate of phenol increased by 66.7%.

  8. Effect of Oxide Inclusions on Electrochemical Properties of Aluminium Sacrificial Anodes

    Institute of Scientific and Technical Information of China (English)

    M. Emamy; A. Keyvani; M. Mahta; J. Campbell

    2009-01-01

    Oxide films are incorporated into melts by an entrainment process, and are expected to be present in most metals, but particularly cast Al alloys. The oxides are necessarily present as folded-over double films (bifilms) that are effectively cracks. Their effect on the electrochemical behaviour of cast Al-5Zn-0.02ln sacrificial anodes was studied in 3 wt pct sodium chloride solution using the NACE efficiency evaluation. Three methods were employed to entrain progressive amounts of oxide in the alloy, including the addition of Al-Zn-ln maching chips to the charge, increasing the pouring height, and agitating the melt. The introduction of oxide bifilms in the cast alloy resulted in the deterioration of the electrochemical properties of the sacrificial anodes, such as current capacity and anode efficiency, and introduced increasing variability in these properties. The results suggest that corrosion behaviour is strongly related to the presence of bifilms suspended in the liquid alloy because bifilms provide crack paths allowing the corrodant to penetrate deeply into the metal matrix, and simultaneously provide localized galvanic cells because of the precipitation of Fe rich intermetallic compounds on their outer surfaces.

  9. The Effect of Anodic Oxide Films on the Nickel-Aluminum Reaction in Aluminum Braze Sheet

    Science.gov (United States)

    Tadgell, Colin A.; Wells, Mary A.; Corbin, Stephen F.; Colley, Leo; Cheadle, Brian; Winkler, Sooky

    2017-03-01

    The influence of an anodic oxide surface film on the nickel-aluminum reaction at the surface of aluminum brazing sheet has been investigated. Samples were anodized in a barrier-type solution and subsequently sputtered with nickel. Differential scanning calorimetry (DSC) and metallography were used as the main investigative techniques. The thickness of the anodic film was found to control the reaction between the aluminum substrate and nickel coating. Solid-state formation of nickel-aluminum intermetallic phases occurred readily when a relatively thin oxide film (13 to 25 nm) was present, whereas intermetallic formation was suppressed in the presence of thicker oxides ( 60 nm). At an intermediate oxide film thickness of 35 nm, the Al3Ni phase formed shortly after the initiation of melting in the aluminum substrate. Analysis of DSC traces showed that formation of nickel-aluminum intermetallic phases changed the melting characteristics of the aluminum substrate, and that the extent of this change can be used as an indirect measure of the amount of nickel incorporated into the intermetallic phases.

  10. Acetalization of acetone with glycerol catalyzed by niobium-aluminum mixed oxides synthesized by a sol–gel process

    NARCIS (Netherlands)

    Rodrigues, Raphael; Mandelli, Dalmo; Gonçalves, Norberto S.; Pescarmona, Paolo P.; Carvalho, Wagner A.

    2016-01-01

    Niobium-aluminum-based catalysts were synthesized by a sol–gel process and successfully applied to the reaction of acetalization of acetone with glycerol yielding 2,2-dimethyl-1,3-dioxolane-4-methanol (solketal) and 2,2-dimethyl-1,3-dioxan-5-ol. The synthesis procedure was developed using high-throu

  11. The effect of porosity gradient in a Nickel/Yttria Stabilized Zirconia anode for an anode-supported planar solid oxide fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    An, Chung Min; Sammes, Nigel [Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO (United States); Song, Jung-Hoon [RIST, Pohang (Korea); Kang, Inyong [Department of Chemical Engineering, Colorado School of Mines, Golden, CO (United States)

    2010-02-01

    In this paper, a graded Ni/YSZ cermet anode, an 8 mol.%YSZ electrolyte, and a lanthanum strontium manganite (LSM) cathode were used to fabricate a solid oxide fuel cell (SOFC) unit. An anode-supported cell was prepared using a tape casting technique followed by hot pressing lamination and a single step co-firing process, allowing for the creation of a thin layer of dense electrolyte on a porous anode support. To reduce activation and concentration overpotential in the unit cell, a porosity gradient was developed in the anode using different percentages of pore former to a number of different tape-slurries, followed by tape casting and lamination of the tapes. The unit cell demonstrated that a concentration distribution of porosity in the anode increases the power in the unit cell from 76 mW cm{sup -2} to 101 mW cm{sup -2} at 600 C in humidified hydrogen. Although the results have not been optimized for good performance, the effect of the porosity gradient is quite apparent and has potential in developing superior anode systems. (author)

  12. Formation of Ultrafine Metal Particles and Metal Oxide Precursor on Anodized Al by Electrolysis Deposition

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Nickel was deposited by ac electrolysis deposition in the pores of the porous oxide film of Al produced by anodizing in phosphoric acid. Ultrafine rod-shaped Ni particles were formed in the pores. At the same time a film of Ni oxide precursor was developed on the surface of the porous oxide film. The Ni particles and the Ni oxide precursor were examined by SEM, TEM and X-ray diffraction. The thickness of the barrier layer of the porous oxide film was thin and it attributed to the formation of the metal particles, while the formation of the oxide precursor was associated with the surface pits which were developed in the pretreatment of Al.

  13. Dependence of Performance of Organic Light-emitting Devices on Sheet Resistance of Indium-tin-oxide Anodes

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The dependence of the performance of organic light-emitting devices(OLEDs) on the sheet resistance of indium-tin-oxide(ITO) anodes was investigated by measuring the steady state current density brightness voltage characteristics and the electroluminescent spectra. The device with a higher sheet resistance anode shows a lower current density, a lower brightness level, and a higher operation voltage. The electroluminescence(EL) efficiencies of the devices with the same structure but different ITO anodes show more complicated differences. Furthermore, the shift of the light-emitting zone toward the anode was found when an anode with a higher sheet resistance was used. These performance differences are discussed and attributed to the reduction of hole injection and the increase in voltage drop over ITO anode with the increase in sheet resistance.

  14. Comparison of different structures of niobium oxide blocking layer for dye-sensitized solar cells.

    Science.gov (United States)

    Chun, Jae Hwan; Kim, Jong Sung

    2014-08-01

    In this study, four different types of Nb2O5 thin layers were prepared using sol-gel process to improve energy conversion efficiency of dye sensitized solar cells (DSSCs). Nb2O5 layer was prepared on the fluorine-doped tin oxide (FTO) layer, TiO2 electrode layer, and inside of TiO2 layer, respectively. The Nb2O5 layer was used to reduce the recombination of photo induced electrons and holes. The DSSCs were assembled with platinum (Pt) coated counter electrode, ruthenium dye, and iodine based electrolyte. The photocurrent-voltage (I-V) characteristics of DSSCs with different types of Nb2O5 were studied. The efficiency depends not only on the structure of DSSCs but also on the initial compositions for the preparation of Nb2O5.

  15. Bioactive titanium metal surfaces with antimicrobial properties prepared by anodic oxidation treatment

    Institute of Scientific and Technical Information of China (English)

    YUE ChongXia; YANG BangCheng; ZHANG XingDong

    2009-01-01

    In order to endow titanium metals with bioactivity and antimicrobial properties,titanium plates were subjected to anodic oxidation treatment in NaCI solutions in this study.The treated titanium metals could induce apatite formation in the fast calcification solution,and osteoblasts on the treated titanium surfaces proliferated well as those on the untreated titanium metal surfaces.The treated metals could inhibit S.aureus growth in the microbial culture experiments.It was assumed that Ti-OH groups and Ti-CI groups formed on the treated titanium surface were responsible for the bioactivity and antimicrobial properties of the metals.The anodic oxidation treatment was an effective way to prepare bioactive titanium surfaces with antimicrobial properties.

  16. Fabrication of polymeric nano-batteries array using anodic aluminum oxide templates.

    Science.gov (United States)

    Zhao, Qiang; Cui, Xiaoli; Chen, Ling; Liu, Ling; Sun, Zhenkun; Jiang, Zhiyu

    2009-02-01

    Rechargeable nano-batteries were fabricated in the array pores of anodic aluminum oxide (AAO) template, combining template method and electrochemical method. The battery consisted of electropolymerized PPy electrode, porous TiO2 separator, and chemically polymerized PAn electrode was fabricated in the array pores of two-step anodizing aluminum oxide (AAO) membrane, based on three-step assembling method. It performs typical electrochemical battery behavior with good charge-discharge ability, and presents a capacity of 25 nAs. AFM results show the hexagonal array of nano-batteries' top side. The nano-battery may be a promising device for the development of Micro-Electro-Mechanical Systems (MEMS), and Nano-Electro-Mechanical Systems (NEMS).

  17. Growth Kinetics of Anodic Oxide Films Formed on Zircaloy-2 in Various Electrolytes

    Directory of Open Access Journals (Sweden)

    V. Jeevana Jyothi

    2009-01-01

    Full Text Available The Kinetics of anodic oxidation of zircaloy-2 have been studied at current densities ranging from 4 to 12 mA cm-2 at room temperature in order to investigate the dependence of ionic current density on the field across the oxide film. Thickness of the anodic films was estimated from capacitance data. The formation rate, current efficiency and differential field were found to increase with increase in the ionic current density for zircaloy-2. Plots of logarithm of formation rate vs. logarithm of current density is fairly linear. From linear plots of logarithm of ionic current density vs. differential field and applying the Cabrera - Mott theory, the half - jump distance (a and height of energy barrier (W were deduced.

  18. Transformation and removal of arsenic in groundwater by sequential anodic oxidation and electrocoagulation

    Science.gov (United States)

    Zhang, Peng; Tong, Man; Yuan, Songhu; Liao, Peng

    2014-08-01

    Oxidation of As(III) to As(V) is generally essential for the efficient remediation of As(III)-contaminated groundwater. The performance and mechanisms of As(III) oxidation by an as-synthesized active anode, SnO2 loaded onto Ti-based TiO2 nanotubes (Ti/TiO2NTs/Sb-SnO2), were investigated. The subsequent removal of total arsenic by electrocoagulation (EC) was further tested. The Ti/TiO2NTs/Sb-SnO2 anode showed a high and lasting electrochemical activity for As(III) oxidation. 6.67 μM As(III) in synthetic groundwater was completely oxidized to As(V) within 60 min at 50 mA. Direct electron transfer was mainly responsible at the current below 30 mA, while hydroxyl radicals contributed increasingly with the increase in the current above 30 mA. As(III) oxidation was moderately inhibited by the presence of bicarbonate (20 mM), while was dramatically increased with increasing the concentration of chloride (0-10 mM). After the complete oxidation of As(III) to As(V), total arsenic was efficiently removed by EC in the same reactor by reversing electrode polarity. The removal efficiency increased with increasing the current but decreased by the presence of phosphate and silica. Anodic oxidation represents an effective pretreatment approach to increasing EC removal of As(III) in groundwater under O2-limited conditions.

  19. Anodic aluminium oxide membranes used for the growth of carbon nanotubes.

    Science.gov (United States)

    López, Vicente; Morant, Carmen; Márquez, Francisco; Zamora, Félix; Elizalde, Eduardo

    2009-11-01

    The suitability of anodic aluminum oxide (AAO) membranes as template supported on Si substrates for obtaining organized iron catalyst for carbon nanotube (CNT) growth has been investigated. The iron catalyst was confined in the holes of the AAO membrane. CVD synthesis with ethylene as carbon source led to a variety of carbon structures (nanotubes, helices, bamboo-like, etc). In absence of AAO membrane the catalyst was homogeneously distributed on the Si surface producing a high density of micron-length CNTs.

  20. Electrocatalytic Oxidation of Cellulose to Gluconate on Carbon Aerogel Supported Gold Nanoparticles Anode in Alkaline Medium

    OpenAIRE

    Hanshuang Xiao; Meifen Wu; Guohua Zhao

    2015-01-01

    The development of high efficient and low energy consumption approaches for the transformation of cellulose is of high significance for a sustainable production of high value-added feedstocks. Herein, electrocatalytic oxidation technique was employed for the selective conversion of cellulose to gluconate in alkaline medium by using concentrated HNO3 pretreated carbon aerogel (CA) supported Au nanoparticles as anode. Results show that a high gluconate yield of 67.8% and sum salts yield of 88.9...

  1. Invalidation manner and mechanism of new type NbO electrolytic capacitor anode

    Institute of Scientific and Technical Information of China (English)

    LI Jian; YI Dan-qing; WEN Jun-jie; LIU Hui-qun; ZHONG Hui

    2005-01-01

    Niobium suboxide powder was pressed and sintered in vacuum into NbO electrolytic capacitor sintered anode..High voltage and constant current formation experiment was performed on NbO electrolytic capacitor anode,during which electrolyte was 0.01 % Ha PO4 solution, temperature was 90 C and current was 50 mA per gram sample. Through the relationship between anode voltage and time and scanning electron microscopy(SEM) images of invalidated anode and normal forming anode, invalidation manner and mechanism of NbO electrolytic capacitor anode were discussed. The results show that, the main invalidation manner of NbO electrolytic capacitor anode is not short circuit but open circuit, which is different to that of traditional Ta electrolytic capacitor anode. The reason of invalidation is that anode oxide film whose thickness increases gradually penetrates the "connection neck" among anode powder particles, which leads to the open circuit invalidation of anode. Compared with Ta electrolytic capacitor,NbO electrolytic capacitor has better security.

  2. Aluminum oxide as a dual-functional modifier of Ni-based anodes of solid oxide fuel cells for operation on simulated biogas

    Science.gov (United States)

    Wang, Feng; Wang, Wei; Ran, Ran; Tade, Moses O.; Shao, Zongping

    2014-12-01

    Al2O3 and SnO2 additives are introduced into the Ni-YSZ cermet anode of solid oxide fuel cells (SOFCs) for operation on simulated biogas. The effects of incorporating Al2O3/SnO2 on the electrical conductivity, morphology, coking resistance and catalytic activity for biogas reforming of the cermet anode are systematically studied. The electrochemical performance of the internal reforming SOFC is enhanced by introducing an appropriate amount of Al2O3 into the anode, but it becomes worse with excess alumina addition. For SnO2, a negative effect on the electrochemical performance is demonstrated, although the coking resistance of the anode is improved. For fuel cells operating on biogas, stable operation under a polarization current for 130 h at 750 °C is achieved for a cell with an Al2O3-modified anode, while cells with unmodified or SnO2-modified Ni-YSZ anodes show much poorer stability under the same conditions. The improved performance of the cell with the Al2O3-modified anode mainly results from the suppressed coking and sintering of the anode and from the formation of NiAl2O4 in the unreduced anode. In sum, modifying the anode with Al2O3 may be a useful and facile way to improve the coking resistance and electrochemical performance of the nickel-based cermet anodes for SOFCs.

  3. Laser-Doping through Anodic Aluminium Oxide Layers for Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Pei Hsuan Doris Lu

    2015-01-01

    Full Text Available This paper demonstrates that silicon can be locally doped with aluminium to form localised p+ surface regions by laser-doping through anodic aluminium oxide (AAO layers formed on the silicon surface. The resulting p+ regions can extend more than 10 μm into the silicon and the electrically active p-type dopant concentration exceeds 1020 cm−3 for the first 6-7 μm of the formed p+ region. Anodic aluminium oxide layers can be doped with other impurities, such as boron and phosphorus, by anodising in electrolytes containing the extrinsic impurities in ionic form. The ions become trapped in the formed anodic oxide during anodisation, therefore enabling the impurity to be introduced into the silicon, with aluminium, during laser-doping. This codoping process can be used to create very heavily doped surface layers which can reduce contact resistance on metallisation, whilst the deeper doping achieved by the intrinsic aluminium may act to shield the surface from minority carriers. laser-doping through AAO layers can be performed without introducing any voids in the silicon or fumes which may be harmful to human health.

  4. Characterization of calcium phosphate deposited on valve metal by anodic oxidation with polarity inversion.

    Science.gov (United States)

    Okawa, Seigo; Homma, Kikuo; Kanatani, Mitsugu; Watanabe, Kouichi

    2009-07-01

    Electrochemical deposition of calcium phosphate (CAP) on valve metals such as Ta, Nb, and Zr, was performed by anodic oxidation with alternate polarity inversion at an applied 20 VDC. A saturated hydroxyapatite(HAP)-phosphoric acid solution (pH 3) was used as the electrolyte. FTIR, XRD, and XPS were employed to investigate the detailed characteristics of the deposition. HAP was precipitated on Ta; HAP including brushite and monetite on Nb; and HAP and monetite on Zr. The Ca/P atomic ratios were 1.3-1.5 by XPS, and HPO(4)(2- )bands were detected on Ta by FTIR. Therefore, the HAP precipitated on Ta was a Ca-deficient HAP. In addition, the XPS spectra of the specimens showed that phosphate ions were incorporated into the anodic oxide film. Deposits with nano-grain size were observed by AFM. The results confirmed that CAP with nano-grain size was deposited on valve metals by the anodic oxidation with polarity inversion.

  5. The Microstructure and Capacitance Characterizations of Anodic Titanium Based Alloy Oxide Nanotube

    Directory of Open Access Journals (Sweden)

    Po Chun Chen

    2013-01-01

    Full Text Available This paper presents a simple anodization process to fabricate ordered nanotubes (NTs of titanium and its alloys (Ti-Mo and Ti-Ta. TiO2, MoO3, and Ta2O5 are high dielectric constant materials for ultracapacitor application. The anodic titanium oxide contains a compact layer on the NT film and a barrier layer under the NT film. However, the microstructure of oxide films formed by anodic Ti-Mo and Ti-Ta alloys contains six layers, including a continuous compact layer, a continuous partial porous layer, a porous layer, a net layer, an ordering NT film, and an ordering compact barrier layer. There are extra layers, which are a partial porous layer and a porous layer, not presented on the TiO2 NT film. In this paper, we fabricated very high surface area ordered nanotubes from Ti and its alloys. Based on the differences of alloys elements and compositions, we investigated and calculated the specific capacitance of these alloys oxide nanotubes.

  6. Oxidation of H2 and CO in a fuel cell with a Platinum-tin Anode

    Directory of Open Access Journals (Sweden)

    Javier González

    2010-06-01

    Full Text Available This report describes the construction and evolution of a fuel cell with a bi-metallic anode of Pt-Sn supported on carbon, as catalysts for oxidation of pure hydrogen, pure CO and a 2% CO in H2 mixture. Both, cathode and anode were made with a structure composed by a diffusive layer and a catalytic layer. The diffusive layer was made with a carbon cloth while the catalytic layer contained the platinum and tin supported on carbon. To test the performance of the catalytic mixture, a proton exchange membrane fuel cell (PEMFC was developed with an original design for the gas distributation plates. The reactants were feed to ambient temperature and 3 psig in the anode side, while 5 psig pure oxygen was used in the cathode. The anode catalytic load was 0.57 mg/cm2 of platinum and 0.08 mg/cm2 of tin. The catalytic load in cathode was 0.85 mg/cm2 of pure platinum. It was found that this caralytic mixture is tolerant to CO presence.

  7. Growth control of carbon nanotubes using by anodic aluminum oxide nano templates.

    Science.gov (United States)

    Park, Yong Seob; Choi, Won Seek; Yi, Junsin; Lee, Jaehyeong

    2014-05-01

    Anodic Aluminum Oxide (AAO) template prepared in acid electrolyte possess regular and highly anisotropic porous structure with pore diameter range from five to several hundred nanometers, and with a density of pores ranging from 10(9) to 10(11) cm(-2). AAO can be used as microfilters and templates for the growth of CNTs and metal or semiconductor nanowires. Varying anodizing conditions such as temperature, electrolyte, applied voltage, anodizing and widening time, one can control the diameter, the length, and the density of pores. In this work, we deposited Al thin film by radio frequency magnetron sputtering method to fabricate AAO nano template and synthesized multi-well carbon nanotubes on a glass substrate by microwave plasma-enhanced chemical vapor deposition (MPECVD). AAO nano-porous templates with various pore sizes and depths were introduced to control the dimension and density of CNT arrays. The AAO nano template was synthesize on glass by two-step anodization technique. The average diameter and interpore distance of AAO nano template are about 65 nm and 82 nm. The pore density and AAO nano template thickness are about 2.1 x 10(10) pores/cm2 and 1 microm, respectively. Aligned CNTs on the AAO nano template were synthesized by MPECVD at 650 degrees C with the Ni catalyst layer. The length and diameter of CNTs were grown 2 microm and 50 nm, respectively.

  8. Large Aperture Low Threshold Current 980nm VCSELs Fabricated with Pulsed Anodic Oxidation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Pulsed anodic oxidation technique, a new way of forming current blocking layers, was successfully used in ridge-waveguide QW laser fabrication. This method was applied in 980 nm VCSELs fabrication to form a high-quality native oxide current blocking layer, which simplifies the device process. A significant reduction of threshold current and a distinguished device performance are achieved. The 500 μm diameter device has a current threshold as low as 0.48 W. The maximum CW operation output power at room tempe...

  9. Nano-hardness and elastic modulus of anodic aluminium oxide based Poly (2-hydroxyethylmethacrylate composite membranes

    Directory of Open Access Journals (Sweden)

    Gérrard Eddy Jai Poinern

    2014-07-01

    Full Text Available In this study we determine the elastic and hardness properties of electrochemically engineered porous anodic aluminium oxide (AAO membranes and AAO membranes infiltrated with Poly (2-hydroxyethylmethacrylate to form a unique biologically compatible AAO/polymer composite. The electrochemically-synthesised membranes have a nanometre scale porous oxide structure with a mean pore diameter of 100 nm. The membranes were characterized using field emission scanning electron microscopy before and after polymer infiltration. The polymer treated and untreated membranes were then examined using the nano-indentation technique to measure the hardness and subsequently determine the membrane elasticity.

  10. Oxidation of organic pollutants on BDD anodes using modulated current electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Panizza, M. [Department of Chemical and Process Engineering, University of Genoa, P.le J.F. Kennedy 1, 16129 Genova (Italy)], E-mail: marco.panizza@unige.it; Kapalka, Agnieszka [Institute of Chemical Sciences and Engineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Comninellis, Ch. [Institute of Chemical Sciences and Engineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)], E-mail: christos.comninellis@epfl.ch

    2008-01-01

    In this paper, a theoretical model is presented for organic pollutants mineralization at high current efficiency (close to 100%) and low energy consumption on boron-doped diamond electrodes. The model is formulated for a perfect mixed electrochemical reactor operated as a batch recirculation system under multiple current steps, in which the applied current is adjusted during the electrolysis to be close to the limiting value. An experimental validation with the anodic oxidation of 3,4,5-trihydroxybenzoic acid is also provided. The results have shown that multiple current steps electrolysis and continuous current control allowed obtaining high oxidation rate and current efficiency.

  11. Role of aluminum doping on phase transformations in nanoporous titania anodic oxides

    Energy Technology Data Exchange (ETDEWEB)

    Bayata, Fatma [Istanbul Bilgi University, Department of Mechanical Engineering, 34060, Eyup, Istanbul (Turkey); Ürgen, Mustafa, E-mail: urgen@itu.edu.tr [Istanbul Technical University, Department of Metallurgical and Materials Engineering, 34469, Maslak, Istanbul (Turkey)

    2015-10-15

    The role of aluminium doping on anatase to rutile phase transformation of nanoporous titanium oxide films were investigated. For this purpose pure and aluminum doped metal films were deposited on alumina substrates by cathodic arc physical deposition. The nanoporous anodic oxides were prepared by porous anodizing of pure and aluminum doped titanium metallic films in an ethylene glycol + NH{sub 4}F based electrolyte. Nanoporous amorphous structures with 60–80 nm diameter and 2–4 μm length were formed on the surfaces of alumina substrates. The amorphous undoped and Al-doped TiO{sub 2} anodic oxides were heat-treated at different temperatures in the range of 280–720 °C for the investigation of their crystallization behavior. The combined effects of nanoporous structure and Al doping on crystallization behavior of titania were investigated using X-ray diffraction (XRD) and micro Raman analysis. The results indicated that both Al ions incorporated into the TiO{sub 2} structure and the nanoporous structure retarded the rutile formation. It was also revealed that presence or absence of metallic film underneath the nanopores has a major contribution to anatase-rutile transformation. - Highlights: • Al-doped TiO{sub 2} nanopores were grown on alumina substrates using anodization method. • The crystallization behavior of nanoporous Al-doped TiO{sub 2} were investigated. • Al doping into nanoporous TiO{sub 2} retarded the anatase-rutile transformation. • Nanostructuring has significant role in controlling rutile formation temperature. • The absence of the metallic film under the nanopores delayed the rutile formation.

  12. Nanosegregated bimetallic oxide anode catalyst for proton exchange membrane electrolyzer

    Science.gov (United States)

    Danilovic, Nemanja; Kang, Yijin; Markovic, Nenad; Stamenkovic, Vojislav; Myers, Deborah J.; Subbaraman, Ram

    2016-08-23

    A surface segregated bimetallic composition of the formula Ru.sub.1-xIr.sub.x wherein 0.1.ltoreq.x.ltoreq.0.75, wherein a surface of the material has an Ir concentration that is greater than an Ir concentration of the material as a whole is provided. The surface segregated material may be produced by a method including heating a bimetallic composition of the formula Ru.sub.1-xIr.sub.x, wherein 0.1.ltoreq.x.ltoreq.0.75, at a first temperature in a reducing environment, and heating the composition at a second temperature in an oxidizing environment. The surface segregated material may be utilized in electrochemical devices.

  13. Graphite coated with manganese oxide/multiwall carbon nanotubes composites as anodes in marine benthic microbial fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Yubin, E-mail: ffyybb@ouc.edu.cn; Yu, Jian; Zhang, Yelong; Meng, Yao

    2014-10-30

    Highlights: • MnO{sub 2}/MWCNTs composites anode exhibits faster reaction kinetics. • The surfaces of MnO{sub 2}/MWCNTs composites anode exhibits better wettability. • A BMFC using the modified anode have excellent power output. - Abstract: Improving anode performance is of great significance to scale up benthic microbial fuel cells (BMFCs) for its marine application to drive oceanography instruments. In this study, manganese oxide (MnO{sub 2})/multiwall carbon nanotubes (MWCNTs) composites are prepared to be as novel anodes in the BMFCs via a direct redox reaction between permanganate ions (MnO{sub 4}{sup −}) and MWCNTs. The results indicate that the MnO{sub 2}/MWCNTs anode has a better wettability, greater kinetic activity and higher power density than that of the plain graphite (PG) anode. It is noted that the MnO{sub 2} (50% weight percent)/MWCNTs anode shows the highest electrochemical performance among them and will be a promising material for improving bioelectricity production of the BMFCs. Finally, a synergistic mechanism of electron transfer shuttle of Mn ions and their redox reactions in the interface between modified anode and bacteria biofilm are proposed to explain its excellent electrochemical performance.

  14. Adhesive strength of medical polymer on anodic oxide nanostructures fabricated on biomedical β-type titanium alloy.

    Science.gov (United States)

    Hieda, Junko; Niinomi, Mitsuo; Nakai, Masaaki; Cho, Ken; Mohri, Tomoyoshi; Hanawa, Takao

    2014-03-01

    Anodic oxide nanostructures (nanopores and nanotubes) were fabricated on a biomedical β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), by anodization in order to improve the adhesive strength of a medical polymer, segmented polyurethane (SPU), to TNTZ. TNTZ was anodized in 1.0M H3PO4 solution with 0.5 mass% NaF using a direct-current power supply at a voltage of 20V. A nanoporous structure is formed on TNTZ in the first stage of anodization, and the formation of a nanotube structure occurs subsequently beneath the nanoporous structure. The nanostructures formed on TNTZ by anodization for less than 3,600s exhibit higher adhesive strengths than those formed at longer anodization times. The adhesive strength of the SPU coating on the nanoporous structure formed on top of TNTZ by anodization for 1,200s improves by 144% compared to that of the SPU coating on as-polished TNTZ with a mirror surface. The adhesive strength of the SPU coating on the nanotube structure formed on TNTZ by anodization for 3,600s increases by 50%. These improvements in the adhesive strength of SPU are the result of an anchor effect introduced by the nanostructures formed by anodization. Fracture occurs at the interface of the nanoporous structure and the SPU coating layer. In contrast, in the case that SPU coating has been performed on the nanotube structure, fracture occurs inside the nanotubes.

  15. Electrochemical Oxidation of Ammonia on Ir Anode in Potential Fixed Electrochemical Sensor

    Institute of Scientific and Technical Information of China (English)

    HAN Yi-ping; LUO Peng; CAI Chen-xin; XIE Lei; LU Tian-hong

    2008-01-01

    Ir catalyst possesses a good electrocatalytic activity and selectivity for the oxidation of NH3 and/or NH4OH at Ir anode in the potential fixed electrochemical sensor with the neutral solution.Owing to the same electrochemical behavior of NH3 and NH4OH in a NaCIO4 solution,NH4OH can be used instead of NH3 for the experimental convenience.It was found that the potential of the oxidation peak of NH4OH at the Ir/GC electrode in NaCIO4 solutions is at about 0.85 V,and the current density of the oxidation peak of NH4OH is linearly proportional to the concentration of NH4OH.The electrocatalytic oxidation of NH4OH is diffusion-controlled.Especially,Ir has no electrocatalytic activity for the CO oxidation,illustrating that CO does not interfere in the measurement of NH4OH and the potential fixed electrochemical NH3 sensor with the neutral solution,and the anodic Ir catalyst possesses a good selectivity.Therefore,lr may have practical application in the potential fixed electrochemical NH3 sensor with the neutral solution.

  16. Identification of a Methane Oxidation Intermediate on Solid Oxide Fuel Cell Anode Surfaces with Fourier Transform Infrared Emission.

    Science.gov (United States)

    Pomfret, Michael B; Steinhurst, Daniel A; Owrutsky, Jeffrey C

    2013-04-18

    Fuel interactions on solid oxide fuel cell (SOFC) anodes are studied with in situ Fourier transform infrared emission spectroscopy (FTIRES). SOFCs are operated at 800 °C with CH4 as a representative hydrocarbon fuel. IR signatures of gas-phase oxidation products, CO2(g) and CO(g), are observed while cells are under load. A broad feature at 2295 cm(-1) is assigned to CO2 adsorbed on Ni as a CH4 oxidation intermediate during cell operation and while carbon deposits are electrochemically oxidized after CH4 operation. Electrochemical control provides confirmation of the assignment of adsorbed CO2. FTIRES has been demonstrated as a viable technique for the identification of fuel oxidation intermediates and products in working SOFCs, allowing for the elucidation of the mechanisms of fuel chemistry.

  17. Influence of niobium, neodymium and praseodymium oxides percentage on the Si{sub 3} N{sub 4} sintering; Influencia da percentagem de niobia, neodimia e praseodimia, na sinterizacao do Si{sub 3} N{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Cosme Roberto Moreira da; Martins, Joao Renato Santos; Piorino Neto, Francisco; Melo, Francisco Cristovao Lourenco de; Folgueras, Luiza de Castro [Centro Tecnico Aeroespacial, Sao Jose dos Campos, SP (Brazil). Inst. de Atividades Espaciais

    1995-12-31

    The objective of this work was to study the influence of mixtures of neodymium, niobium and praseodymium oxides, as sintering aids for silicon nitride. Samples were sintered in temperatures between 1700 deg C and 1750 deg C, during 30 minutes. Microstructure, intergranular phases and additives effects on {alpha}-{beta} transformation were evaluated. (author) 10 refs., 2 figs., 8 tabs.

  18. Rational design of metal oxide nanocomposite anodes for advanced lithium ion batteries

    Science.gov (United States)

    Li, Yong; Yu, Shenglan; Yuan, Tianzhi; Yan, Mi; Jiang, Yinzhu

    2015-05-01

    Metal-oxide anodes represent a significant future direction for advanced lithium ion batteries. However, their practical applications are still seriously hampered by electrode disintegration and capacity fading during cycling. Here, we report a rational design of 3D-staggered metal-oxide nanocomposite electrode directly fabricated by pulsed spray evaporation chemical vapor deposition, where various oxide nanocomponents are in a staggered distribution uniformly along three dimensions and across the whole electrode. Such a special design of nanoarchitecture combines the advantages of nanoscale materials in volume change and Li+/electron conduction as well as uniformly staggered and compact structure in atom migration during lithiation/delithiation, which exhibits high specific capacity, good cycling stability and excellent rate capability. The rational design of metal-oxide nanocomposite electrode opens up new possibilities for high performance lithium ion batteries.

  19. OBTENTION OF POROUS TITANIUM DIOXIDE COATINGS BY ANODIC OXIDATION FOR PHOTOCATALYTIC APPLICATIONS

    Directory of Open Access Journals (Sweden)

    Hernán D. Traid

    2016-03-01

    Full Text Available Titanium dioxide is one of the most used materials in heterogeneous photocatalysis process due its low cost, low toxicity and high photocatalytic activity. In the present work, porous TiO2 coatings are obtained by anodic oxidation, starting at constant current density and continuing at constant potential of 120 V in spark discharge conditions. After the oxidation, the coatings received a thermal treatment. The studied variable was the current density. The curves of current density and potential showed characteristics fluctuations of spark discharge. Micrographs of the oxides showed an average pore diameter of 100 nm. Diffractograms showed, in all cases, the presence of the anatase and rutile phases of TiO2, showing an increase of the rutile fraction when the current density was higher. The synthesized oxides showed favorable characteristics as potential materials for heterogeneous catalysis processes for water treatment.

  20. Electrochemical combustion of indigo at ternary oxide coated titanium anodes

    Directory of Open Access Journals (Sweden)

    María I. León

    2014-12-01

    Full Text Available The film of iridium and tin dioxides doped with antimony (IrO2-SnO2–Sb2O5 deposited on a Ti substrate (mesh obtained by Pechini method was used for the formation of ·OH radicals by water discharge. Detection of ·OH radicals was followed by the use of the N,N-dimethyl-p-nitrosoaniline (RNO as a spin trap. The electrode surface morphology and composition was characterized by SEM-EDS. The ternary oxide coating was used for the electrochemical combustion of indigo textile dye as a model organic compound in chloride medium. Bulk electrolyses were then carried out at different volumetric flow rates under galvanostatic conditions using a filter-press flow cell. The galvanostatic tests using RNO confirmed that Ti/IrO2-SnO2-Sb2O5 favor the hydroxyl radical formation at current densities between 5 and 7 mA cm-2, while at current density of 10 mA cm-2 the oxygen evolution reaction occurs. The indigo was totally decolorized and mineralized via reactive oxygen species, such as (·OH, H2O2, O3 and active chlorine formed in-situ at the Ti/IrO2-SnO2-Sb2O5 surface at volumetric flow rates between 0.1-0.4 L min-1 and at fixed current density of 7 mA cm-2. The mineralization of indigo carried out at 0.2 L min-1 achieved values of 100 %, with current efficiencies of 80 % and energy consumption of 1.78 KWh m-3.

  1. Methane Steam Reforming over an Ni-YSZ Solid Oxide Fuel Cell Anode in Stack Configuration

    Directory of Open Access Journals (Sweden)

    D. Mogensen

    2014-01-01

    Full Text Available The kinetics of catalytic steam reforming of methane over an Ni-YSZ anode of a solid oxide fuel cell (SOFC have been investigated with the cell placed in a stack configuration. In order to decrease the degree of conversion, a single cell stack with reduced area was used. Measurements were performed in the temperature range 600–800°C and the partial pressures of all reactants and products were varied. The obtained rates could be well fitted with a power law expression (r ∝PCH40.7. A simple model is presented which is capable of predicting the methane conversion in a stack configuration from intrinsic kinetics of the anode support material. The predictions are compared with the stack measurements presented here, and good agreement is observed.

  2. Synthesis and properties of iridescent Zn-containing anodic aluminum oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Xiaoxuan; Sun, Huiyuan, E-mail: huiyuansun@126.com; Liu, Lihu; Hou, Xue; Liu, Huiyuan

    2015-07-01

    A simple method of fabricating Zn-containing anodic aluminum oxide films for multifunctional anticounterfeit technology is reported. The resulting membranes were characterized with UV–vis illumination studies, natural light illumination color experiments, and electron microscopy analysis. Deposition of Zn in the nanopore region can enhance the color saturation of the thin alumina film with different colors dramatically. Both the anodization time and etching time have great influence on the structural color. The mechanisms for the emergence of this phenomenon are discussed and theoretical analysis further demonstrates the experimental results. - Highlights: • Iridescent PAA@Zn nanocomposite films were successfully fabricated. • A simple organics-assisted method is applied to making a series of fancy and multicolor patterns. • The color varies with the angle of incidence of the light used to view the film as is expected with Bragg–Snell formula. • Such colored films could be used in multifunctional anti-counterfeiting applications.

  3. Anodic oxides on InAlP formed in sodium tungstate electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Suleiman, A. [Corrosion and Protection Centre, School of Materials, University of Manchester, P.O. Box 88, Manchester M60 1QD (United Kingdom); Skeldon, P. [Corrosion and Protection Centre, School of Materials, University of Manchester, P.O. Box 88, Manchester M60 1QD (United Kingdom)], E-mail: p.skeldon@manchester.ac.uk; Thompson, G.E. [Corrosion and Protection Centre, School of Materials, University of Manchester, P.O. Box 88, Manchester M60 1QD (United Kingdom); Echeverria, F. [Corrosion and Protection Group, University of Antioquia, Medellin (Colombia); Graham, M.J.; Sproule, G.I.; Moisa, S.; Quance, T. [Institute for Microstructural Sciences, National Research Council of Canada, Montreal Road, Ottawa K1A 0R6 (Canada); Habazaki, H. [Graduate Engineering School, Hokkaido University, N13 W8, Kita-ku, Sapporo 060-8628 (Japan)

    2010-02-15

    Amorphous anodic oxide films on InAlP have been grown at high efficiency in sodium tungstate electrolyte. The films are shown to comprise an outer layer containing indium species, an intermediate layer containing indium and aluminium species and an inner layer containing indium, aluminium and phosphorus species{sub .} The layering correlates with the influence on cation migration rates of the energies of In{sup 3+}-O, Al{sup 3+}-O and P{sup 5+}-O bonds, which increase in this order. The film surface becomes increasingly rough with increase of the anodizing voltage as pores develop in the film, which appear to be associated with generation of oxygen gas.

  4. Sulfur Poisoning of the Water Gas Shift Reaction on Anode Supported Solid Oxide Fuel Cells

    DEFF Research Database (Denmark)

    Hagen, Anke

    2013-01-01

    Investigation of fuels containing sulfur impurities is important regarding durability of solid oxide fuel cells (SOFC) because they are present in various potential fuels for SOFC applications. The effect of H2S in the ppm range on the performance of state-of-the-art anode supported SOFC at 850...... and 750°C is evaluated in either hydrogen/steam or hydrogen/steam/CO fuel. It was found that the poisoning effect is more severe in H2/H2O/CO vs. H2/H2O fuel. Only ∼8 ppm H2S can be allowed in the CO containing fuel without risking damage to the anode, whereas 90 ppm (or even more) is possible in H2/H2O...

  5. Characterization of Anodic Aluminum Oxide Membrane with Variation of Crystallizing Temperature for pH Sensor.

    Science.gov (United States)

    Yeo, Jin-Ho; Lee, Sung-Gap; Jo, Ye-Won; Jung, Hye-Rin

    2015-11-01

    We fabricated electrolyte-dielectric-metal (EDM) device incorporating a high-k Al2O3 sensing membrane from a porous anodic aluminum oxide (AAO) using a two step anodizing process for pH sensors. In order to change the properties of the AAO template, the crystallizing temperature was varied from 400 degrees C to 700 degrees C over 2 hours. The structural properties were observed by field emission scanning electron microscopy (FE-SEM). The pH sensitivity increased with an increase in the crystallizing temperature from 400 degrees C to 600 degrees C. However at 700 degrees C, deformation occurred. The porous AAO sensor with a crystallizing temperature of 600 degrees C displayed the good sensitivity and long-term stability and the values were 55.7 mV/pH and 0.16 mV/h, respectively.

  6. Highly durable anode supported solid oxide fuel cell with an infiltrated cathode

    DEFF Research Database (Denmark)

    Samson, Alfred Junio; Hjalmarsson, Per; Søgaard, Martin

    2012-01-01

    An anode supported solid oxide fuel cell with an La0.6Sr0.4Co1.05O3_δ (LSC) infiltrated-Ce0.9Gd0.1O1.95 (CGO) cathode that shows a stable performance has been developed. The cathode was prepared by screen printing a porous CGO backbone on top of a laminated and co-fired anode supported half cell...... in the resistance from the recorded impedance was observed during long term testing. The power density reached 0.79Wcm-2 at a cell voltage of 0.6 V at 750 deg. C. Post test analysis of the LSC infiltrated-CGO cathode by scanning electron microscopy revealed no significant micro-structural difference...

  7. The role of stress in self-ordered porous anodic oxide formation and corrosion of aluminum

    Science.gov (United States)

    Capraz, Omer Ozgur

    The phenomenon of plastic flow induced by electrochemical reactions near room temperature is significant in porous anodic oxide (PAO) films, charging of lithium batteries and stress-corrosion cracking (SCC). As this phenomenon is poorly understood, fundamental insight into flow from our work may provide useful information for these problems. In-situ monitoring of the stress state allows direct correlation between stress and the current or potential, thus providing fundamental insight into technologically important deformation and failure mechanisms induced by electrochemical reactions. A phase-shifting curvature interferometry was designed to investigate the stress generation mechanisms on different systems. Resolution of our curvature interferometry was found to be ten times more powerful than that obtained by state-of-art multiple deflectometry technique and the curvature interferometry helps to resolve the conflicting reports in the literature. During this work, formation of surface patterns during both aqueous corrosion of aluminum and formation of PAO films were investigated. Interestingly, for both cases, stress induced plastic flow controls the formation of surface patterns. Pore formation mechanisms during anodizing of the porous aluminum oxide films was investigated . PAO films are formed by the electrochemical oxidation of metals such as aluminum and titanium in a solution where oxide is moderately soluble. They have been used extensively to design numerous devices for optical, catalytic, and biological and energy related applications, due to their vertically aligned-geometry, high-specific surface area and tunable geometry by adjusting process variables. These structures have developed empirically, in the absence of understanding the process mechanism. Previous experimental studies of anodizing-induced stress have extensively focused on the measurement of average stress, however the measurement of stress evolution during anodizing does not provide

  8. LOW-TEMPERATURE, ANODE-SUPPORTED HIGH POWER DENSITY SOLID OXIDE FUEL CELLS WITH NANOSTRUCTURED ELECTRODES

    Energy Technology Data Exchange (ETDEWEB)

    Anil V. Virkar

    2001-09-26

    Anode-supported solid oxide fuel cells with Ni + yttria-stabilized zirconia (YSZ) anode, YSZ-samaria-doped ceria (SDC) bi-layer electrolyte and Sr-doped LaCoO{sub 3} (LSC) + SDC cathode were fabricated. Fuel used consisted of H{sub 2} diluted with He, N{sub 2}, H{sub 2}O or CO{sub 2}, mixtures of H{sub 2} and CO, and mixtures of CO and CO{sub 2}. Cell performance was measured at 800 C with above-mentioned fuel gas mixtures and air as oxidant. For a given concentration of the diluent, the cell performance was higher with He as the diluent than with N{sub 2} as the diluent. Mass transport through porous Ni-YSZ anode for H{sub 2}-H{sub 2}O, CO-CO{sub 2} binary systems and H{sub 2}-H{sub 2}O-diluent gas ternary systems was analyzed using multicomponent gas diffusion theory. At high concentrations of the diluent, the maximum achievable current density was limited by the anodic concentration polarization. From this measured limiting current density, the corresponding effective gas diffusivity was estimated. Highest effective diffusivity was estimated for fuel gas mixtures containing H{sub 2}-H{sub 2}O-He mixtures ({approx}0.34 cm{sup 2}/s), and the lowest for CO-CO{sub 2} mixtures ({approx}0.07 cm{sup 2}/s). The lowest performance was observed with CO-CO{sub 2} mixture as a fuel, which in part was attributed to the lowest effective diffusivity of the fuels tested.

  9. Novel Size and Surface Oxide Effects in Silicon Nanowires as Lithium Battery Anodes

    KAUST Repository

    McDowell, Matthew T.

    2011-09-14

    With its high specific capacity, silicon is a promising anode material for high-energy lithium-ion batteries, but volume expansion and fracture during lithium reaction have prevented implementation. Si nanostructures have shown resistance to fracture during cycling, but the critical effects of nanostructure size and native surface oxide on volume expansion and cycling performance are not understood. Here, we use an ex situ transmission electron microscopy technique to observe the same Si nanowires before and after lithiation and have discovered the impacts of size and surface oxide on volume expansion. For nanowires with native SiO2, the surface oxide can suppress the volume expansion during lithiation for nanowires with diameters <∼50 nm. Finite element modeling shows that the oxide layer can induce compressive hydrostatic stress that could act to limit the extent of lithiation. The understanding developed herein of how volume expansion and extent of lithiation can depend on nanomaterial structure is important for the improvement of Si-based anodes. © 2011 American Chemical Society.

  10. Effect of Anodisation Parameters on the Formation of Porous Anodic Oxide on Ti, Zr and W

    Energy Technology Data Exchange (ETDEWEB)

    Lockman, Zainovia; Ismail, Syahriza; Razak, Khairunisak Abdul; Lee, Lim Shu, E-mail: zainovia@eng.usm.my [School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia)

    2011-02-15

    Ti, Zr and W foils were anodized in 85% glycerol + 15% water electrolyte added to it 0.5wt%NH{sub 4}F (pH {approx} 6) at 20V. Self-ordered nanotubular oxide structure was found on Ti and Zr whereas oxide on W is comprised of dual layer with compact inner layer and oxide precipitates as the outer layer. The mechanism of the formation of the nanotubes is discussed. The formation of bi-layer on W is attributed to the high degree of dissolution and precipitation of WO{sub 3} on the surface of the anodic oxide in the viscous glycerol solution. In aqueous bath, the precipitation is much reduced revealing WO{sub 3} with a more ordered porous structure. On Zr foil nanotubes formed are much smaller than on Ti with diameter of < 40 nm compared to 100 nm on Ti. The length of the nanotubes is in the range of 1-2({mu}m for both zirconia and titania nanotubes. Increasing the voltage increases the diameter of the nanotubes marginally and there exists a maximum voltage which could be applied on the foils before the nanotubular structure is destroyed. In 85% glycerol, the voltage must be kept at < 30V for both samples.

  11. Effect of Anodisation Parameters on the Formation of Porous Anodic Oxide on Ti, Zr and W

    Science.gov (United States)

    Lockman, Zainovia; Ismail, Syahriza; Razak, Khairunisak Abdul; Shu Lee, Lim

    2011-02-01

    Ti, Zr and W foils were anodized in 85% glycerol + 15% water electrolyte added to it 0.5wt%NH4F (pH ~ 6) at 20V. Self-ordered nanotubular oxide structure was found on Ti and Zr whereas oxide on W is comprised of dual layer with compact inner layer and oxide precipitates as the outer layer. The mechanism of the formation of the nanotubes is discussed. The formation of bi-layer on W is attributed to the high degree of dissolution and precipitation of WO3 on the surface of the anodic oxide in the viscous glycerol solution. In aqueous bath, the precipitation is much reduced revealing WO3 with a more ordered porous structure. On Zr foil nanotubes formed are much smaller than on Ti with diameter of nanotubes is in the range of 1-2(μm for both zirconia and titania nanotubes. Increasing the voltage increases the diameter of the nanotubes marginally and there exists a maximum voltage which could be applied on the foils before the nanotubular structure is destroyed. In 85% glycerol, the voltage must be kept at < 30V for both samples.

  12. Iron oxide-decorated carbon for supercapacitor anodes with ultrahigh energy density and outstanding cycling stability.

    Science.gov (United States)

    Guan, Cao; Liu, Jilei; Wang, Yadong; Mao, Lu; Fan, Zhanxi; Shen, Zexiang; Zhang, Hua; Wang, John

    2015-05-26

    Supercapacitor with ultrahigh energy density (e.g., comparable with those of rechargeable batteries) and long cycling ability (>50000 cycles) is attractive for the next-generation energy storage devices. The energy density of carbonaceous material electrodes can be effectively improved by combining with certain metal oxides/hydroxides, but many at the expenses of power density and long-time cycling stability. To achieve an optimized overall electrochemical performance, rationally designed electrode structures with proper control in metal oxide/carbon are highly desirable. Here we have successfully realized an ultrahigh-energy and long-life supercapacitor anode by developing a hierarchical graphite foam-carbon nanotube framework and coating the surface with a thin layer of iron oxide (GF-CNT@Fe2O3). The full cell of anode based on this structure gives rise to a high energy of ∼74.7 Wh/kg at a power of ∼1400 W/kg, and ∼95.4% of the capacitance can be retained after 50000 cycles of charge-discharge. These performance features are superior among those reported for metal oxide based supercapacitors, making it a promising candidate for the next generation of high-performance electrochemical energy storage.

  13. Characterization and quantification of oxides generated by anodization on titanium for implantation purposes

    Science.gov (United States)

    Aloia Games, L.; Pastore, J.; Bouchet, A.; Ballarre, J.

    2011-12-01

    The use of titanium as implant material is widely known in the surgery field. The formation of natural or artificial compact and protective oxide is a convenient tool for metal protection and a good way to generate phosphate deposits to enhance biocompatibility and bone fixation with the existing tissue. The present work has the aim of superficially modify commercially pure titanium sheets used in orthopedics and odontology, with a potencistatic anodization process with an ammonium phosphate and ammonium fluoride solution as electrolyte. The objective is to generate titanium oxides doped with phosphorous on the surface, to promote bioactivity. The characterization and quantification of the generated deposits is presented as a starting point for the future application of these materials. The applied characterization methods are X ray diffraction, micro-Raman spectroscopy analysis for evaluating the chemical and phase composition on the modified surface and PDI image analysis techniques that allow the segmentation of SEM images and the measurement and quantification of the oxides generated by the anodization process. The samples with polished treated surface at 30V have the deposit of a phosphate rich thick layer covering almost all the surface and spherical-shaped titanium oxide crystals randomly placed (covering more than 20% of the surface area).

  14. Anodic oxidation of salicylic acid on BDD electrode: Variable effects and mechanisms of degradation

    Energy Technology Data Exchange (ETDEWEB)

    Rabaaoui, Nejmeddine, E-mail: chimie_tunisie@yahoo.fr [Faculte des Sciences de Sfax, Departement de Chimie, 3038 Sfax (Tunisia); Allagui, Mohamed Salah [Faculte des Sciences de Gafsa, Campus Universitaire Sidi Ahmed Zarrouk, 2112 Gafsa (Tunisia)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer Oxidation with BDD is a powerful electrochemical method able to mineralize. Black-Right-Pointing-Pointer SA is oxidized to aromatic compounds then CO{sub 2} and H{sub 2}O. Black-Right-Pointing-Pointer Polymeric intermediate products were formed. - Abstract: The degradation of 100 mL of solution with salicylic acid (SA) in the pH range 3.0-10.0 has been studied by anodic oxidation in a cell with a boron-doped diamond (BDD) anode and a stainless steel cathode, both of 3 cm{sup 2} area, by applying a current of 100, 300 and 450 mA at 25 Degree-Sign C. Completed mineralization is always achieved due to the great concentration of hydroxyl radical ({center_dot}OH) generated at the BDD surface. The mineralization rate increases with increasing applied current, but decreases when drug concentration rises from 200 mg L{sup -1}. Nevertheless, the pH effect was not significant. During oxidation it was observed that catechol, 2,5-dihydroxylated benzoic acid, 2,3-dihydroxylated benzoic acid and hydroquinone were formed as aromatic intermediates. In addition, ion-exclusion chromatography allowed the detection of fumaric, maleic, oxalic and formic as the ultimate carboxylic acid.

  15. Growth Mechanism of γ-MnS Nanorod-Arrays by Hydrothermal Method on Anodic Aluminum Oxide Template

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jianming; Liu, Weifeng; Lv, Yong; Yao, Lianzeng [Chinese Academy of Science, Hefei, Anhui (China)

    2010-09-15

    Hydrothermal method is a general, low-cost and convenience method which was utilized for synthesis of nanomaterials. Our research group has reported that oriented MnS nanorods on anodic aluminum oxide template were synthesized under a hydrothermal condition and demonstrated the effect of precursor content on the morphology evolution of as-samples. In order to research the growth mechanism of the arrays, herein we synthesized MnS nanorod arrays by combination of anodic aluminum oxide template and hydrothermal method on different substrates. Through-hole anodic aluminum oxide templates were prepared using Al foil (99.999%) via a two-step anodization process as described in literature. To investigate the effect of different substrates on the morphology of the-products, different substrates including anodic aluminum oxide template (sample A), one-step anodization Al foil (sample B, which was prepared by first anodizing Al foil for 10h and then removing the alumina layer with the mixed acid (0.6 M H{sub 3}PO{sub 4} and 0.15 M H{sub 2}CrO{sub 4}), where the foil still kept the close-packed concave nano-pits consistently with the nanopole of anodic aluminum oxide template), Al foil (sample C, dipped in HNO{sub 3} solution and covered by a compact alumina layer), Si wafer (sample D) respectively were put into Teflon-lined stainless steel autoclaves of 20 mL capacity filled with 16 mL mixed solution consisting of 2 mol/L MnCl{sub 4} and 2 mol/L thiourea. We kept the reaction at 150 .deg. C for 20 h. When reactions completed the products were washed three times with distilled water and absolute ethanol, respectively. Then the products were dried in an oven at 60 .deg. C.

  16. LOW-TEMPERATURE, ANODE-SUPPORTED HIGH POWER DENSITY SOLID OXIDE FUEL CELLS WITH NANOSTRUCTURED ELECTRODES

    Energy Technology Data Exchange (ETDEWEB)

    Professor Anil V. Virkar

    2003-05-23

    This report summarizes the work done during the entire project period, between October 1, 1999 and March 31, 2003, which includes a six-month no-cost extension. During the project, eight research papers have, either been, published, accepted for publication, or submitted for publication. In addition, several presentations have been made in technical meetings and workshops. The project also has provided support for four graduate students working towards advanced degrees. The principal technical objective of the project was to analyze the role of electrode microstructure on solid oxide fuel cell performance. Prior theoretical work conducted in our laboratory demonstrated that the particle size of composite electrodes has a profound effect on cell performance; the finer the particle size, the lower the activation polarization, the better the performance. The composite cathodes examined consisted of electronically conducting perovskites such as Sr-doped LaMnO{sub 3} (LSM) or Sr-doped LaCoO{sub 3} (LSC), which is also a mixed conductor, as the electrocatalyst, and yttria-stabilized zirconia (YSZ) or rare earth oxide doped CeO{sub 2} as the ionic conductor. The composite anodes examined were mixtures of Ni and YSZ. A procedure was developed for the synthesis of nanosize YSZ by molecular decomposition, in which unwanted species were removed by leaching, leaving behind nanosize YSZ. Anode-supported cells were made using the as-synthesized powders, or using commercially acquired powders. The electrolyte was usually a thin ({approx}10 microns), dense layer of YSZ, supported on a thick ({approx}1 mm), porous Ni + YSZ anode. The cathode was a porous mixture of electrocatalyst and an ionic conductor. Most of the cell testing was done at 800 C with hydrogen as fuel and air as the oxidant. Maximum power densities as high as 1.8 W/cm{sup 2} were demonstrated. Polarization behavior of the cells was theoretically analyzed. A limited amount of cell testing was done using liquid

  17. The impact of NiO on microstructure and electrical property of solid oxide fuel cell anode

    Institute of Scientific and Technical Information of China (English)

    LI Yan; LUO Zhong-yang; YU Chun-jiang; LUO Dan; XU Zhu-an; CEN Ke-fa

    2005-01-01

    Ni-Ce0.8Sm0.2O1.9 (Ni-SDC) cermet was selected as anode material for reduced temperature (800 ℃) solid oxide fuel cells in this study. The influence of NiO powder fabrication methods for Ni-SDC cermets on the electrode performance was investigated so that the result obtained can be applied to make high-quality anode. Three kinds of NiO powder were synthesized with a fourth kind being available in the market. Four types of anode precursors were fabricated with these NiO powders and Ce0.sSm0.2O1.9 (SDC), and then were reduced to anode wafers for sequencing measurement. The electrical conductivity of the anodes was measured and the effect ofmicrostructure was investigated. It was found that the anode electrical conductivity depends strongly on the NiO powder morphologies, microstructure of the cermet anode and particle sizes, which are decided by NiO powder preparation technique. The highest electrical conductivity is obtained for anode cermets with NiO powder synthesized by NiCO3·2Ni(OH)2.4H2O or Ni(NO3)2.6H2O decomposition technique.

  18. Modern Trends in Anodic Oxidation of Titanium Implant%钛种植体阳极氧化的研究

    Institute of Scientific and Technical Information of China (English)

    王婷婷; 王丽娜(综述); 范震(审校)

    2016-01-01

    如何对钛种植体进行表面改性,提高钛种植体表面物理性能、化学性能和生物性能一直是国内外学者研究的热点。钛表面阳极氧化技术可增加钛表面氧化膜厚度,增加表面粗糙度,增强耐腐蚀性和抗菌性,使钛表面着色。细胞黏附实验显示,经阳极氧化后的钛表面生物活性提高,骨结合能力增强。根据氧化条件的不同,阳极氧化又可以分为一般阳极氧化、微弧氧化、二氧化钛纳米管的形成。本文将对钛表面阳极氧化的研究进展做一综述。%Anodic oxidation is used for the surface treatment of commercial implants to improve their functional (physi-cal, chemical, and biological) properties for clinical success. The anodic oxidation technique on the titanium can increase the thickness of titanium surface oxidation film and the surface roughness, enhance the corrosion resistance and antimicro-bial properties, change the color of titanium surface. Cell adhesion experiments have shown that titanium surface is more bioactive for initial bone bonding after anodic oxidation. According to different oxidation conditions, anodic oxidation can be divided into general anodic oxidation, micro arc oxidation, the formation of titanium dioxide nanotubes. This article re-views the impact of titanium and titanium alloy anodic oxidation technology on dental implant.

  19. Nanostructured metal oxide-based materials as advanced anodes for lithium-ion batteries.

    Science.gov (United States)

    Wu, Hao Bin; Chen, Jun Song; Hng, Huey Hoon; Lou, Xiong Wen David

    2012-04-21

    The search for new electrode materials for lithium-ion batteries (LIBs) has been an important way to satisfy the ever-growing demands for better performance with higher energy/power densities, improved safety and longer cycle life. Nanostructured metal oxides exhibit good electrochemical properties, and they are regarded as promising anode materials for high-performance LIBs. In this feature article, we will focus on three different categories of metal oxides with distinct lithium storage mechanisms: tin dioxide (SnO(2)), which utilizes alloying/dealloying processes to reversibly store/release lithium ions during charge/discharge; titanium dioxide (TiO(2)), where lithium ions are inserted/deinserted into/out of the TiO(2) crystal framework; and transition metal oxides including iron oxide and cobalt oxide, which react with lithium ions via an unusual conversion reaction. For all three systems, we will emphasize that creating nanomaterials with unique structures could effectively improve the lithium storage properties of these metal oxides. We will also highlight that the lithium storage capability can be further enhanced through designing advanced nanocomposite materials containing metal oxides and other carbonaceous supports. By providing such a rather systematic survey, we aim to stress the importance of proper nanostructuring and advanced compositing that would result in improved physicochemical properties of metal oxides, thus making them promising negative electrodes for next-generation LIBs.

  20. Production of planar copper-based anode supported intermediate temperature solid oxide fuel cells cosintered at 950 °C

    Science.gov (United States)

    De Marco, Vincenzo; Grazioli, Alberto; Sglavo, Vincenzo M.

    2016-10-01

    Copper-based anode supported planar Intermediate Temperature Solid Oxide Fuel Cells are produced and characterized in the present work. The most important advancement is related to the use of copper within the anodic layer, this giving promising results for feeding Intermediate Temperature Solid Oxide Fuel Cells with carbon and sulphur containing fuels. Both anode and Li2O containing-Gadolinia Doped Ceria based electrolyte are produced by water based tape casting process. The supporting anode is coupled to the electrolyte by thermopressing, the cathode being obtained by screen printing. A 3 h isotherm at 950 °C allows to obtain the cosintering of the three layers. The electrochemical test performed on such cells reveals a 0.8 V open circuit voltage and a power density higher than 26 mW cm-2 at 650 °C.

  1. Effect of surface treatments on anodic oxide film growth and electrochemical properties of tantalum used for biomedical applications.

    Science.gov (United States)

    Silva, R A; Silva, I P; Rondot, B

    2006-07-01

    Self-expandable nitinol (nickel-titanium) alloys and 316L stainless steel are the most commonly used materials in the production of coronary stents. However, tantalum (Ta) has already been used to make stents for endovascular surgery and may constitute an alternative to other materials because of its better electrochemical performance, namely its higher corrosion resistance, as well as its radio-opacity. The characterization of wet polished, chemically polished, wet polished anodized, and chemically polished anodized Ta electrodes has been performed in a 0.15 M NaCl solution (simulated body fluid) using Ucorr = f(t) measurements, anodic polarizations, capacity measurements, anodic oxidations, and atomic force microscopy (AFM) imaging. Anodic polarization curves have shown that the abnormal current density peak with a maximum value around 1.65 V (critical applied potential, Uc) disappeared for the anodized electrodes indicating a probable relationship between the surface states and the film growth. These results are confirmed by capacity measurements. The behavior of wet polished and chemically polished electrodes during anodic oxidations seemingly indicated that for these particular treatments the film growth is different. The AFM images and roughness measurements have shown that chemical polishing produced smoother electrodes, a fact probably related to the differences in film growth.

  2. Nickel/Yttria-stabilised zirconia cermet anodes for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Primdahl, S.

    1999-08-01

    This thesis deals with the porous Ni/yttria-stabilized zirconia (YSZ) cermet anode on a YSZ electrolyte for solid oxide fuel cells (SOFC). Such anodes are predominantly operated in moist hydrogen at 700 deg. C to 1000 deg. C, and the most important technological parameters are the polarization resistance and the long-term stability. The polarization resistance can be measured by a number of techniques, in the present work impedance spectroscopy has been used extensively. By impedance spectroscopy limiting processes in the anode polarization resistance may often be separated and characterized individually, provided they have a reasonable separation in time constants. Three limiting processes are recognized in impedance spectra obtained on technological Ni/YSZ cermet anodes characterized against a stable reference electrode atmosphere. By parameter studies and illustrative experiments, the two contributions at low and medium frequency have been identified as gas conversion and diffusion limitations, respectively. Both of these effects are concentration limitations relating to the inefficient exchange of fuel gas in the test setup outside the porous cermet. A test setup geometry where these concentration effects are avoided for high-performance electrodes is recommended. The high frequency limitation is demonstrated to relate to the cermet structure. The dependence on gas composition, temperature, adsorbed species (sulfur), isotopes (H/D), sintering temperature and cermet thickness is investigated. Despite these studies and several similar studies by others, the exact chemical or physical nature of the limiting step has not been incontestably identified. However, these is a general consensus in literature about the hydrogen oxidation process taking place on or near to the triple phase boundary (TPB) line, where open gas-filled pores, the continuous electrolyte phase (oxide ion cunductor) and the continuous Ni phase (electronic conductor) meet. The physical thickness

  3. Morphology of Platinum Nanowire Array Electrodeposited Within Anodic Aluminium Oxide Template Characterized by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    孔令斌; 陆梅; 李梦轲; 郭新勇; 力虎林

    2003-01-01

    Uniform platinum nanowires were synthesized by electrodepositing the platinum under a very low altering current frequency (20Hz) and increasing voltage (5-15 V) in the pores of anodic aluminium oxide (AAO) template.Atomic force microscopy observation indicates that the template membranes we obtained have hexagonally closepacked nanochannels. The platinum nanowires have highly ordered arrays after partially dissolving the aluminium oxide membrane. With the increasing dissolving time, the platinum nanowire array collapsed. A concave topography of the aluminium substrate was observed after the aluminium oxide membrane was dissolved completely and the platinum nanowires were released from the template. Platinum nanowires were also characterized by transmission electron microscopy and the phase structure of the Al/AAO/Pt composite was proven by x-ray diffraction.

  4. Vanadium Sulfide on Reduced Graphene Oxide Layer as a Promising Anode for Sodium Ion Battery.

    Science.gov (United States)

    Sun, Ruimin; Wei, Qiulong; Li, Qidong; Luo, Wen; An, Qinyou; Sheng, Jinzhi; Wang, Di; Chen, Wei; Mai, Liqiang

    2015-09-23

    As an alternative system of rechargeable lithium ion batteries, sodium ion batteries revitalize researchers' interest due to the low cost, abundant sodium resources, and similar storage mechanism to lithium ion batteries. VS4 has emerged as a promising anode material for SIBs due to low cost and its unique linear chains structure that can offer potential sites for sodium storage. Herein, we present the growth of VS4 on reduced graphene oxide (rGO) as SIBs anode for the first time. The VS4/rGO anode exhibits promising performance in SIBs. It delivers a reversible capacity of 362 mAh g(-1) at 100 mA g(-1) and a good rate performance. We also investigate the sodium storage behavior of the VS4/rGO. Different than most transition metal sulfides, the VS4/rGO composite experiences a three-step separation mechanism during the sodiation process (VS4 to metallic V and Na2S, then the electrochemical mechanism is akin to Na-S). The VS4/rGO composite proves to be a promising material for rechargeable SIBs.

  5. Fabrication and optical properties of platinum nanowire arrays on anodic aluminium oxide templates

    Institute of Scientific and Technical Information of China (English)

    高铁仁; 陈子瑜; 彭勇; 李发伸

    2002-01-01

    Arrays of Pt nanowires, fabricated by electrodepositing Pt metal into nanoporous anodic aluminium oxide (AAO)templates, exhibit a preferable optical absorption band in the ultraviolet-visible (UV-VIS) spectra and present a blueshift as the wire aspect ratio increases or its radius decreases. This type of optical property of Pt nanowire/porous alumina composites has been theoretically explored using Maxwell-Garnett (MG) effective medium theory. The MG theory,however, is only applicable to nanowires with an infinitesimally small radius relative to the wavelength of an incident light. The nanowire radius is controlled by the pore radius of the host alumina, which depends on anodizing conditions such as the selected electrolyte, anodizing time, temperature and voltage. The nanowire aspect ratios depend on the amount of Pt deposited into the nanopores of AAO films. The optical absorption properties of the arrays of Pt nanowires with diameters of 24, 55 and 90nm have been investigated by the UV-VIS spectra, which show that the extinction maximum (λmax) shifts to shorter wavelength side as the wire aspect ratio increases or its radius decreases.The results are qualitatively consistent with those calculated based on the MG theory.

  6. Ru nanostructure fabrication using an anodic aluminum oxide nanotemplate and highly conformal Ru atomic layer deposition.

    Science.gov (United States)

    Kim, Woo-Hee; Park, Sang-Joon; Son, Jong-Yeog; Kim, Hyungjun

    2008-01-30

    We fabricated metallic nanostructures directly on Si substrates through a hybrid nanoprocess combining atomic layer deposition (ALD) and a self-assembled anodic aluminum oxide (AAO) nanotemplate. ALD Ru films with Ru(DMPD)(EtCp) as a precursor and O(2) as a reactant exhibited high purity and low resistivity with negligible nucleation delay and low roughness. These good growth characteristics resulted in the excellent conformality for nanometer-scale vias and trenches. Additionally, AAO nanotemplates were fabricated directly on Si and Ti/Si substrates through a multiple anodization process. AAO nanotemplates with various hole sizes (30-100 nm) and aspect ratios (2:1-20:1) were fabricated by controlling the anodizing process parameters. The barrier layers between AAO nanotemplates and Si substrates were completely removed by reactive ion etching (RIE) using BCl(3) plasma. By combining the ALD Ru and the AAO nanotemplate, Ru nanostructures with controllable sizes and shapes were prepared on Si and Ti/Si substrates. The Ru nanowire array devices as a platform for sensor devices exhibited befitting properties of good ohmic contact and high surface/volume ratio.

  7. Fabrication of solid oxide fuel cell anode electrode by spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lin; Kim, Gap-Yong; Chandra, Abhijit [Iowa State University, Department of Mechanical Engineering, 2034 Black Engineering Building, Ames, IA 50011 (United States)

    2010-10-15

    Large triple phase boundaries (TPBs) and high gas diffusion capability are critical in enhancing the performance of a solid oxide fuel cell (SOFC). In this study, ultrasonic spray pyrolysis has been investigated to assess its capability in controlling the anode microstructure. Deposition of porous anode film of nickel and Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} on a dense 8 mol.% yttria stabilized zirconia (YSZ) substrate was carried out. First, an ultrasonic atomization model was utilized to predict the deposited particle size. The model accurately estimated the deposited particle size based on the feed solution condition. Second, effects of various process parameters, which included the precursor solution feed rate, precursor solution concentration and deposition temperature, on the TPB formation and porosity were investigated. The deposition temperature and precursor solution concentration were the most critical parameters that influenced the morphology, porosity and particle size of the anode electrode. Ultrasonic spray pyrolysis achieved homogeneous distribution of constitutive elements within the deposited particles and demonstrated capability to control the particle size and porosity in the range of 2-17 {mu}m and 21-52%, respectively. (author)

  8. Fabrication of solid oxide fuel cell anode electrode by spray pyrolysis

    Science.gov (United States)

    Liu, Lin; Kim, Gap-Yong; Chandra, Abhijit

    Large triple phase boundaries (TPBs) and high gas diffusion capability are critical in enhancing the performance of a solid oxide fuel cell (SOFC). In this study, ultrasonic spray pyrolysis has been investigated to assess its capability in controlling the anode microstructure. Deposition of porous anode film of nickel and Ce 0.9Gd 0.1O 1.95 on a dense 8 mol.% yttria stabilized zirconia (YSZ) substrate was carried out. First, an ultrasonic atomization model was utilized to predict the deposited particle size. The model accurately estimated the deposited particle size based on the feed solution condition. Second, effects of various process parameters, which included the precursor solution feed rate, precursor solution concentration and deposition temperature, on the TPB formation and porosity were investigated. The deposition temperature and precursor solution concentration were the most critical parameters that influenced the morphology, porosity and particle size of the anode electrode. Ultrasonic spray pyrolysis achieved homogeneous distribution of constitutive elements within the deposited particles and demonstrated capability to control the particle size and porosity in the range of 2-17 μm and 21-52%, respectively.

  9. Accelerated creep in solid oxide fuel cell anode supports during reduction

    Science.gov (United States)

    Frandsen, H. L.; Makowska, M.; Greco, F.; Chatzichristodoulou, C.; Ni, D. W.; Curran, D. J.; Strobl, M.; Kuhn, L. T.; Hendriksen, P. V.

    2016-08-01

    To evaluate the reliability of solid oxide fuel cell (SOFC) stacks during operation, the stress field in the stack must be known. During operation the stress field will depend on time as creep processes relax stresses. The creep of reduced Ni-YSZ anode support at operating conditions has been studied previously. In this work a newly discovered creep phenomenon taking place during the reduction is reported. This relaxes stresses at a much higher rate (∼×104) than creep during operation. The phenomenon was studied both in three-point bending and uniaxial tension. Differences between the two measurements could be explained by newly observed stress promoted reduction. Finally, samples exposed to a small tensile stress (∼0.004 MPa) were observed to expand during reduction, which is in contradiction to previous literature. These observations suggest that release of internal residual stresses between the NiO and the YSZ phases occurs during reduction. The accelerated creep should practically eliminate any residual stress in the anode support in an SOFC stack, as has previously been indirectly observed. This phenomenon has to be taken into account both in the production of stacks and in the simulation of the stress field in a stack based on anode supported SOFCs.

  10. Cycle Life of Commercial Lithium-Ion Batteries with Lithium Titanium Oxide Anodes in Electric Vehicles

    Directory of Open Access Journals (Sweden)

    Xuebing Han

    2014-07-01

    Full Text Available The lithium titanium oxide (LTO anode is widely accepted as one of the best anodes for the future lithium ion batteries in electric vehicles (EVs, especially since its cycle life is very long. In this paper, three different commercial LTO cells from different manufacturers were studied in accelerated cycle life tests and their capacity fades were compared. The result indicates that under 55 °C, the LTO battery still shows a high capacity fade rate. The battery aging processes of all the commercial LTO cells clearly include two stages. Using the incremental capacity (IC analysis, it could be judged that in the first stage, the battery capacity decreases mainly due to the loss of anode material and the degradation rate is lower. In the second stage, the battery capacity decreases much faster, mainly due to the degradation of the cathode material. The result is important for the state of health (SOH estimation and remaining useful life (RUL prediction of battery management system (BMS for LTO batteries in EVs.

  11. Assessment of the Morphological, Biochemical, and Kinetic Properties for Candida rugosa Lipase Immobilized on Hydrous Niobium Oxide to Be Used in the Biodiesel Synthesis

    Directory of Open Access Journals (Sweden)

    Michele Miranda

    2011-01-01

    Full Text Available Lipase from Candida rugosa (CRL was immobilized by covalent attachment on hydrous niobium oxide. The matrix could effectively be attached to the enzyme with high retention of activity and prevent its leakage. Following immobilization, CRL exhibited improved storage stability and performed better at higher incubation temperatures. In addition, the enzyme retained most of its catalytic efficiency after successive operational cycles. The immobilized derivative was also fully characterized with respect to its morphological properties: particle size, surface specific area, and pore size distribution. Structural integrity and conformational changes, such as surface cavities in the support, set by the lipase procedure, were observed by Scanning Electron Microscopy. Additionally, a comparative study between free and immobilized lipases was provided in terms of pH, temperature, and thermal stability. CRL derivative was evaluated for the synthesis of biodiesel employing babassu oil and short chain alcohols. The process was feasible only for oil and butanol reaction system.

  12. Niobium(v) chloride and imidazolium bromides as efficient dual catalyst systems for the cycloaddition of carbon dioxide and propylene oxide

    KAUST Repository

    Wilhelm, Michael E.

    2014-02-19

    The application of niobium(v) chloride and several imidazolium bromides as catalyst systems for the cycloaddition of propylene oxide (PO) with carbon dioxide to propylene carbonate (PC) is reported. A set of 31 different imidazolium bromides has been synthesized with varying substituents at all five imidazolium ring atoms, of which 17 have not been reported before. The impact of different substitution patterns (steric and electronic changes and solubility in PO) at the imidazolium ring on the catalytic activity was investigated. The optimisation of the catalyst structure allows for the valorisation of carbon dioxide under mild reaction conditions with high reaction rates in very good yield and selectivity for PC. This journal is © the Partner Organisations 2014.

  13. Niobium(v) chloride and imidazolium bromides as efficient dual catalyst systems for the cycloaddition of carbon dioxide and propylene oxide

    KAUST Repository

    Wilhelm, Michael E.

    2014-01-01

    The application of niobium(v) chloride and several imidazolium bromides as catalyst systems for the cycloaddition of propylene oxide (PO) with carbon dioxide to propylene carbonate (PC) is reported. A set of 31 different imidazolium bromides has been synthesized with varying substituents at all five imidazolium ring atoms, of which 17 have not been reported before. The impact of different substitution patterns (steric and electronic changes and solubility in PO) at the imidazolium ring on the catalytic activity was investigated. The optimisation of the catalyst structure allows for the valorisation of carbon dioxide under mild reaction conditions with high reaction rates in very good yield and selectivity for PC. This journal is © the Partner Organisations 2014.

  14. Boehmite nanostructures preparation by hydrothermal method from anodic aluminium oxide membrane.

    Science.gov (United States)

    Yang, X; Wang, J Y; Pan, H Y

    2009-02-01

    Boehmite nanostructures were successfully synthesized from porous anodic aluminium oxide (AAO) membrane by a simple and efficient hydro-thermal method. The experiment used high purity alumina as raw material, and the whole reaction process avoided superfluous impurities to be introduced. Thus, the purity of Boehmite products was ensured. The examinations of the morphology and structure were carried out by atomic force microscope (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Composition of the specimens was analyzed using energy dispersive X-ray spectroscope (EDX) and X-ray diffraction (XRD). Based on these observations the growth process was analyzed.

  15. Methane Steam Reforming over an Ni-YSZ Solid Oxide Fuel Cell Anode in Stack Configuration

    DEFF Research Database (Denmark)

    Mogensen, David; Grunwaldt, Jan-Dierk; Hendriksen, Peter Vang;

    2014-01-01

    The kinetics of catalytic steam reforming of methane over an Ni-YSZ anode of a solid oxide fuel cell (SOFC) have been investigated with the cell placed in a stack configuration. In order to decrease the degree of conversion, a single cell stack with reduced area was used. Measurements were...... performed in the temperature range 600-800 degrees C and the partial pressures of all reactants and products were varied. The obtained rates could be well fitted with a power law expression (r proportional to P-CH4(0.7)). A simple model is presented which is capable of predicting the methane conversion...

  16. Selective-Area Growth of Transferable InN Nanocolumns by Using Anodic Aluminum Oxide Nanotemplates

    Science.gov (United States)

    Wang, Xiao; Zhang, Guozhen; Xu, Yang; Wu, Hao; Liu, Chang

    2017-02-01

    InN nanocolumn arrays were grown on c-plane sapphire with and without anodic aluminum oxide (AAO) nanotemplates. The crystalline quality of InN nanocolumns was significantly improved by selective-area growth (SAG) using AAO templates, as verified by X-ray diffraction measurements. Then, InN nanocolumns were transferred onto p-type silicon substrates after etching off the AAO templates. Current-voltage characteristic of the transferred n-InN/p-Si heterojunctions shows on/off ratio as high as 4.65 × 103 at 2 V. This work offers a potential way to grow transferable devices with improving performances.

  17. Surface and interface analysis of poly-hydroxyethylmethacrylate-coated anodic aluminium oxide membranes

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Nurshahidah [School of Engineering and Information Technology, Murdoch University, WA 6150 (Australia); Murdoch Applied Nanotechnology Research Group, Murdoch University, WA 6150 (Australia); Duan, Xiaofei [School of Chemistry, The University of Melbourne, VIC 3010 (Australia); Jiang, Zhong-Tao, E-mail: Z.Jiang@murdoch.edu.au [School of Engineering and Information Technology, Murdoch University, WA 6150 (Australia); Goh, Bee Min [School of Engineering and Information Technology, Murdoch University, WA 6150 (Australia); Lamb, Robert [School of Chemistry, The University of Melbourne, VIC 3010 (Australia); Tadich, Anton [Australian Synchrotron, Clayton, VIC 3086 (Australia); Poinern, Gérrard Eddy Jai; Fawcett, Derek [Murdoch Applied Nanotechnology Research Group, Murdoch University, WA 6150 (Australia); Chapman, Peter [Department of Chemistry, Curtin University, WA 6102 (Australia); Singh, Pritam [School of Engineering and Information Technology, Murdoch University, WA 6150 (Australia)

    2014-01-15

    The surface and interface of poly (2-hydroxyethylmethacrylate) (PHEMA) and anodic aluminium oxide (AAO) membranes were comprehensively investigated using Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. It was found that 1s→π* (C=O) and 1s→σ* (C-O) transitions were dominant on the surface of both bulk PHEMA polymer and PHEMA-surface coated AAO (AAO–PHEMA) composite. Findings from NEXAFS, Fourier-Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) analyses suggest the possibility of chemical interaction between carbon from the ester group of polymer and AAO membrane.

  18. Study on the influences of reduction temperature on nickel-yttria-stabilized zirconia solid oxide fuel cell anode using nickel oxide-film electrode

    Science.gov (United States)

    Jiao, Zhenjun; Ueno, Ai; Suzuki, Yuji; Shikazono, Naoki

    2016-10-01

    In this study, the reduction processes of nickel oxide at different temperatures were investigated using nickel-film anode to study the influences of reduction temperature on the initial performances and stability of nickel-yttria-stabilized zirconia anode. Compared to conventional nickel-yttria-stabilized zirconia composite cermet anode, nickel-film anode has the advantage of direct observation at nickel-yttria-stabilized zirconia interface. The microstructural changes were characterized by scanning electron microscopy. The reduction process of nickel oxide is considered to be determined by the competition between the mechanisms of volume reduction in nickel oxide-nickel reaction and nickel sintering. Electrochemical impedance spectroscopy was applied to analyze the time variation of the nickel-film anode electrochemical characteristics. The anode performances and microstructural changes before and after 100 hours discharging and open circuit operations were analyzed. The degradation of nickel-film anode is considered to be determined by the co-effect between the nickel sintering and the change of nickel-yttria-stabilized zirconia interface bonding condition.

  19. Novel light-weight, high-performance anode-supported microtubular solid oxide fuel cells with an active anode functional layer

    Science.gov (United States)

    Liu, Tong; Wang, Yao; Ren, Cong; Fang, Shumin; Mao, Yating; Chen, Fanglin

    2015-10-01

    Influence of the air-gap, the distance from the tube-in-orifice spinneret to the upper surface of the external coagulant bath during the extrusion/phase-inversion process, on the microstructure of nickel - yttria-stabilized zirconia (Ni-YSZ) hollow fibers has been systematically studied. When the air-gap is 0 cm, the obtained Ni-YSZ hollow fiber has a sandwich microstructure. However, when the air-gap is increased to 15 cm, a bi-layer Ni-YSZ hollow fiber consisting of a thin layer with small pores and a thick support with highly porous fingerlike macrovoids has been achieved. The output power density of microtubular solid oxide fuel cells (MT-SOFCs) with a cell configuration of Ni-YSZ/YSZ/YSZ-LSM increases from 594 mW cm-2 for the cells with the Ni-YSZ anode of sandwich microstructure to 832 mW cm-2 for the cells with the Ni-YSZ anode of bi-layer microstructure at 750 °C, implying that to achieve the same output power density, the weight of the cells with the bi-layer anode support can be reduced to 41.5% compared with that of the cells with the sandwich anode support. Thermal-cycling test shows no obvious degradation on the open-circuit-voltage (OCV), indicating that the MT-SOFCs have robust resistance to thermal cycling.

  20. Local anodic oxidation on hydrogen-intercalated graphene layers: oxide composition analysis and role of the silicon carbide substrate

    Science.gov (United States)

    Colangelo, Francesco; Piazza, Vincenzo; Coletti, Camilla; Roddaro, Stefano; Beltram, Fabio; Pingue, Pasqualantonio

    2017-03-01

    We investigate nanoscale local anodic oxidation (LAO) on hydrogen-intercalated graphene grown by controlled sublimation of silicon carbide (SiC). Scanning probe microscopy was used as a lithographic and characterization tool in order to investigate the local properties of the nanofabricated structures. The anomalous thickness observed after the graphene oxidation process is linked to the impact of LAO on the substrate. Micro-Raman (μ-Raman) spectroscopy was employed to demonstrate the presence of two oxidation regimes depending on the applied bias. We show that partial and total etching of monolayer graphene can be achieved by tuning the bias voltage during LAO. Finally, a complete compositional characterization was achieved by scanning electron microscopy and energy dispersive spectroscopy.

  1. Local anodic oxidation on hydrogen-intercalated graphene layers: oxide composition analysis and role of the silicon carbide substrate.

    Science.gov (United States)

    Colangelo, Francesco; Piazza, Vincenzo; Coletti, Camilla; Roddaro, Stefano; Beltram, Fabio; Pingue, Pasqualantonio

    2017-03-10

    We investigate nanoscale local anodic oxidation (LAO) on hydrogen-intercalated graphene grown by controlled sublimation of silicon carbide (SiC). Scanning probe microscopy was used as a lithographic and characterization tool in order to investigate the local properties of the nanofabricated structures. The anomalous thickness observed after the graphene oxidation process is linked to the impact of LAO on the substrate. Micro-Raman (μ-Raman) spectroscopy was employed to demonstrate the presence of two oxidation regimes depending on the applied bias. We show that partial and total etching of monolayer graphene can be achieved by tuning the bias voltage during LAO. Finally, a complete compositional characterization was achieved by scanning electron microscopy and energy dispersive spectroscopy.

  2. Degradation of 1-hydroxy-2,4-dinitrobenzene from aqueous solutions by electrochemical oxidation: role of anodic material.

    Science.gov (United States)

    Quiroz, Marco A; Sánchez-Salas, José L; Reyna, Silvia; Bandala, Erick R; Peralta-Hernández, Juan M; Martínez-Huitle, Carlos A

    2014-03-15

    Electrochemical oxidation (ECOx) of 1-hydroxy-2,4-dinitrobenzene (or 2,4-dinitrophenol: 2,4-DNP) in aqueous solutions by electrolysis under galvanostatic control was studied at Pb/PbO2, Ti/SnO2, Ti/IrxRuySnO2 and Si/BDD anodes as a function of current density applied. Oxidative degradation of 2,4-DNP has clearly shown that electrode material and the current density applied were important parameters to optimize the oxidation process. It was observed that 2,4-DNP was oxidized at few substrates to CO2 with different results, obtaining good removal efficiencies at Pb/PbO2, Ti/SnO2 and Si/BDD anodes. Trends in degradation way depend on the production of hydroxyl radicals (OH) on these anodic materials, as confirmed in this study. Furthermore, HPLC results suggested that two kinds of intermediates were generated, polyhydroxylated intermediates and carboxylic acids. The formation of these polyhydroxylated intermediates seems to be associated with the denitration step and substitution by OH radicals on aromatic rings, this being the first proposed step in the reaction mechanism. These compounds were successively oxidized, followed by the opening of aromatic rings and the formation of a series of carboxylic acids which were at the end oxidized into CO2 and H2O. On the basis of these information, a reaction scheme was proposed for each type of anode used for 2,4-D oxidation.

  3. Anode materials for hydrogen sulfide containing feeds in a solid oxide fuel cell

    Science.gov (United States)

    Roushanafshar, Milad

    SOFCs which can directly operate under high concentration of H2S would be economically beneficial as this reduces the cost of gas purification. H2S is highly reactive gas specie which can poison most of the conventional catalysts. As a result, developing anode materials which can tolerate high concentrations of H2S and also display high activity toward electrochemical oxidation of feed is crucial and challenging for this application. The performance of La0.4Sr0.6TiO3+/-delta -Y0.2Ce0.8O2-delta (LST-YDC) composite anodes in solid oxide fuel cells significantly improved when 0.5% H2 S was present in syngas (40% H2, 60% CO) or hydrogen. Gas chromatography and mass spectrometry analyses revealed that the rate of electrochemical oxidation of all fuel components improved when H2S containing syngas was present in the fuel. Electrochemical stability tests performed under potentiostatic condition showed that there was no power degradation for different feeds, and that there was power enhancement when 0.5% H2S was present in various feeds. The mechanism of performance improvement by H2S was discussed. Active anodes were synthesized via wet chemical impregnation of different amounts of La0.4Ce0.6O1.8 (LDC) and La 0.4Sr0.6TiO3 (L4ST) into porous yttria-stabilized zirconia (YSZ). Co-impregnation of LDC with LS4T significantly improved the performance of the cell from 48 mW.cm-2 (L4ST) to 161 mW.cm -2 (LDC-L4ST) using hydrogen as fuel at 900 °C. The contribution of LDC to this improvement was investigated using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). EIS measurements using symmetrical cells showed that the polarization resistance decreased from 3.1¦O.cm 2 to 0.5 O.cm2 when LDC was co-impregnated with LST, characterized in humidified H2 (3% H2O) at 900 °C. In addition, the microstructure of the cell was modified when LDC was impregnated prior to L4ST into the porous YSZ. TEM and SEM

  4. Fabrication of highly ordered porous nickel oxide anode materials and their electrochemical characteristics in lithium storage

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Fengjuan [College of Communications and Electronics Engineering, Qiqihar University, 42 Wenhua Street, Qiqihar, Heilongjiang 161006 (China); National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China); Li, Qianqian [College of Communications and Electronics Engineering, Qiqihar University, 42 Wenhua Street, Qiqihar, Heilongjiang 161006 (China); Tao, Bairui, E-mail: tbr_sir@163.com [Computer Center, Qiqihar University, 42 Wenhua Street, Qiqihar, Heilongjiang 161006 (China); National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China); Chu, Paul K. [Department of Physics and Material Sciences, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

    2014-05-01

    Highlights: • NiO/Si-MCP nanocomposites electrocatalysts as anodes in lithium ion batteries. • Si MCP itself is an excellent support for electrocatalyst. • The structure with high surface to volume ratio endows higher mass NiO nanopatricles. • The ordered channel and mesoporous structure permits liquid electrolyte flow easily. • This research may provide a meaning way in integratable lithium-ion batteries. - Abstract: The structure and electrochemical properties of silicon microchannel plates (MCP)-supported NiO nanocomposites (NiO/Si-MCP) synthesized by silicon micromachining, electroless plating, and thermal annealing are investigated as anodes in lithium ion batteries. Galvanostatic charge and discharge results indicate that the NiO/Si-MCP is capable of delivering a higher capacity than the bare nickel-oxide film. At a 1 C current, the NiO/Si-MCP nanocomposite film shows an enormous first discharge capacity of about 3190 mA g{sup −1} and charge capacity of 1977 mA g{sup −1}. After 15 cycles, the NiO/Si-MCP nanocomposite retains a reversible capacity of 1531 mA g{sup −1} with 63.7% of the capacity maintained in the 2nd cycle. The lithium storage capacity is maintained at ∼880 mA h g{sup −1} after 50 discharge/charge cycles and it is much larger than that of NiO and its composites. The enhanced electrochemical performance of the highly ordered three-dimensional materials is attributed to the synergistic effects offered by the silicon microchannel plates in the nickel oxide film subsequently facilitating electrolyte penetration, diffusion, and migration. The structure is promising anode materials in lithium-ion batteries.

  5. Investigation into the diffusion and oxidation behavior of the interface between a plasma-sprayed anode and a porous steel support for solid oxide fuel cells

    Science.gov (United States)

    Zhang, Shan-Lin; Li, Cheng-Xin; Li, Chang-Jiu; Liu, Meilin; Yang, Guan-Jun

    2016-08-01

    Porous metal-supported solid oxide fuel cells (SOFCs) have attracted much attention because their potential to dramatically reduce the cost while enhancing the robustness and manufacturability. In particular, 430 ferritic steel (430L) is one of the popular choice for SOFC support because of its superior performance and low cost. In this study, we investigate the oxidation and diffusion behavior of the interface between a Ni-based anode and porous 430L support exposed to a humidified (3% H2O) hydrogen atmosphere at 700 °C. The Ni-GDC (Ce0.8Gd0.2O2-δ) cermet anodes are deposited on the porous 430L support by atmospheric plasma spraying (APS). The effect of exposure time on the microstructure and phase structure of the anode and the supports is studied and the element diffusion across the support/anode interface is characterized. Results indicate that the main oxidation product of the 430L support is Cr2O3, and that Cr and Fe will diffuse to the anode and the diffusion thickness increases with the exposure time. The diffusion thickness of Cr and Fe reach about 5 and 2 μm, respectively, after 1000 h exposure. However, the element diffusion and oxidation has little influence on the area-specific resistance, indicating that the porous 430L steel and plasma sprayed Ni-GDC anode are promising for durable SOFCs.

  6. Steam reforming of methanol over copper loaded anodized aluminum oxide (AAO) prepared through electrodeposition

    Science.gov (United States)

    Linga Reddy, E.; Karuppiah, J.; Lee, Hyun Chan; Kim, Dong Hyun

    2014-12-01

    In order to study the steam reforming of methanol (SRM) to produce hydrogen for fuel cells, porous γ-alumina support is developed on Al substrate using anodic oxidation process and copper catalyst particles are deposited homogeneously over anodic aluminum oxide (AAO) surface by electrodeposition method. We investigated the effect of electrodeposition time and hot water treatment (HWT) on the activity of catalysts for SRM reaction in the temperature range between 160 and 360 °C. The experimental results indicate that the SRM activity, CO2 and dimethyl ether (DME) selectivity's over Cu catalysts increased as the electrodeposition time increased from 30 to 120 s, further increment in deposition time of Cu have no significant effect on it. The rates of SRM conversion are found to be higher for the catalysts made from the supports obtained after HWT, which may be due to the enhancement in the surface area of AAO support. It is found that the SRM activity and CO2 selectivity strongly depended upon the free exposed copper sites available for methanol adsorption and reaction, and DME in products is mainly observed in the reaction temperature range between 300 and 350 °C and it is higher for the catalysts with low Cu content.

  7. Degradation of thiamethoxam by the synergetic effect between anodic oxidation and Fenton reactions.

    Science.gov (United States)

    Meijide, J; Gómez, J; Pazos, M; Sanromán, M A

    2016-12-05

    In this work, a comparative study using anodic oxidation, Fenton and electro-Fenton treatments was performed in order to determine the synergic effect for the removal of thiamethoxan. The results determined that electro-Fenton process showed high efficiency in comparison with Fenton or anodic oxidation. After that, this hybrid process was optimized and the influence of iron catalyst concentration and applied current intensity on the degradation and mineralization were evaluated. Degradation profiles were monitored by high performance liquid chromatography (HPLC) being satisfactorily described by pseudo-first order kinetic model. At the optimal experimental conditions (300mA and 0.2mM Fe(+2)), the complete degradation of thiamethoxam was achieved after 10min. On the other hand, mineralization of thiamethoxam was monitored by total organic carbon (TOC) decay reaching more than 92% of TOC removal after 8h. Furthermore, a plausible mineralization pathway for the thiamethoxam degradation was proposed based on the identification of by-products such as aromatic intermediates, carboxylic acids and inorganic ions released throughout electro-Fenton process.

  8. Identification of chlorinated oligomers formed during anodic oxidation of phenol in the presence of chloride

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Linxi; Campo, Pablo; Kupferle, Margaret J., E-mail: margaret.kupferle@uc.edu

    2015-02-11

    Graphical abstract: - Highlights: • By-products from anodic oxidation of phenol in the presence of chloride are investigated. • Chlorinated oligomer formation is demonstrated by LC-QTOF-MS. • They have structures similar to triclosan and polychlorinated dibenzo-p-dioxins. - Abstract: Chlorinated oligomer intermediates formed during the anodic electrochemical oxidation of phenol with a boron-doped diamond electrode were studied at two different concentrations of chloride (5 mM and 50 mM). Under the same ionic strength, with sodium sulfate being the make-up ion, a 10-fold increase in Cl{sup −} led to removal rates 10.8, 1.5, and 1.4 times higher for phenol, TOC, and COD, respectively. Mono-, di- and trichlorophenols resulting from electrophilic substitution were the identified by-products. Nevertheless, discrepancies between theoretical and measured TOC values along with gaps in the mass balance of chlorine-containing species indicated the formation of unaccounted-for chlorinated by-products. Accurate mass measurements by liquid chromatography quadrupole time-of-flight mass spectrometry and MS-MS fragmentation spectra showed that additional compounds formed were dimers and trimers of phenol with structures similar to triclosan and polychlorinated dibenzo-p-dioxins.

  9. Anodic aluminum oxide with fine pore size control for selective and effective particulate matter filtering

    Science.gov (United States)

    Zhang, Su; Wang, Yang; Tan, Yingling; Zhu, Jianfeng; Liu, Kai; Zhu, Jia

    2016-07-01

    Air pollution is widely considered as one of the most pressing environmental health issues. Particularly, atmospheric particulate matters (PM), a complex mixture of solid or liquid matter suspended in the atmosphere, are a harmful form of air pollution due to its ability to penetrate deep into the lungs and blood streams, causing permanent damages such as DNA mutations and premature death. Therefore, porous materials which can effectively filter out particulate matters are highly desirable. Here, for the first time, we demonstrate that anodic aluminum oxide with fine pore size control fabricated through a scalable process can serve as effective and selective filtering materials for different types of particulate matters (such as PM2.5, PM10). Combining selective and dramatic filtering effect, fine pore size control and a scalable process, this type of anodic aluminum oxide templates can potentially serve as a novel selective filter for different kinds of particulate matters, and a promising and complementary solution to tackle this serious environmental issue.

  10. Calcination/acid-activation treatment of an anodic oxidation TiO2/Ti film catalyst

    Institute of Scientific and Technical Information of China (English)

    YAO Zhongping; JIANG Yanli; JIANG Zhaohua; ZHU Hongkui; BAI Xuefeng

    2009-01-01

    The aim of this work was to investigate the effects of calcination/acid-activation on the composition, structure, and photocatalytic (PC) re-duction property of an anodic oxidation TiO2/Ti film catalyst. The surface morphology and phase composition were examined by scanning electron microscopy and X-ray diffraction. The catalytic property of the film catalysts was evaluated through the removal rate of potassium chromate during the PC reduction process. The results showed that the film catalysts were composed of anatase and mtile TiO2 with a mi-cro-porous surface structure. The calcination treatment increased the content of TiO2 in the film, changed the relative ratio of anatase and rutile TiO2, and decreased the size of the micro pores of the film cat.a/ysts. The removal rate of potassium chromate was related to the tech-nique parameters of calcination/acid-activation treatment. When the anodic oxidation TiO2Ti film catalyst was calcined at 873 K for 30 min and then acid-activated in the concentrated H2SO4 for 60 min, it presented the highest catalytic property, with the removal rate of potassium chromate of 96.3% during the PC reduction process under the experimental conditions.

  11. Light extraction enhancement of organic light-emitting diodes using aluminum zinc oxide embedded anodes.

    Science.gov (United States)

    Hsu, Ching-Ming; Lin, Bo-Ting; Zeng, Yin-Xing; Lin, Wei-Ming; Wu, Wen-Tuan

    2014-12-15

    Aluminum zinc oxide (AZO) has been embedded onto indium tin oxide (ITO) anode to enhance the light extraction from an organic light-emitting diode (OLED). The embedded AZO provides deflection and scattering interfaces on the newly generated AZO/organics and AZO/ITO interfaces rather than the conventional ITO/organic interface. The current efficiency of AZO embedded OLEDs was enhanced by up to 64%, attributed to the improved light extraction by additionally created reflection and scattering of emitted light on the AZO/ITO interfaces which was roughed in AZO embedding process. The current efficiency was found to increase with the increasing AZO embedded area ratio, but limited by the accompanying increases in haze and electrical resistance of the AZO embedded ITO film.

  12. Large Aperture Low Threshold Current 980 nm VCSELs Fabricated with Pulsed Anodic Oxidation

    Institute of Scientific and Technical Information of China (English)

    CUI Jin-jiang; NING Yong-qiang; LI Te; LIU Guang-yu; ZHANG Yan; PENG Biao; SUN Yan-fang; WANG Li-jun

    2007-01-01

    Pulsed anodic oxidation technique, a new way of forming current blocking layers, was successfully used in ridge-waveguide QW laser fabrication. This method was applied in 980 nm VCSELs fabrication to form a high-quality native oxide current blocking layer, which simplifies the device process. A significant reduction of threshold current and a distinguished device performance are achieved. The 500 μm diameter device has a current threshold as low as 048 W. The maximum CW operation output power at room temperature is 1.48 W. The lateral divergence angle θ‖ and vertical divergence angle θ⊥ are as low as 15.3° and 13.8° without side-lobes at a current of 6 A.

  13. Anodic aluminium oxide membranes for immunoisolation with sufficient oxygen supply for pancreatic islets.

    Science.gov (United States)

    Cho, Siwoo; Lee, Sangmin; Jeong, Seong Hee; Kim, Yeongae; Kim, Song Cheol; Hwang, Woonbong; Park, Jaesung

    2013-05-01

    Immunoisolation membranes have been developed for various cell encapsulations for therapeutic purposes. However effective encapsulation systems have been hindered by low oxygen (O2) permeability or imperfect immunoisolation caused by either low porosity or non-uniform pore geometry. Here, we report an encapsulation method that uses an anodic aluminum oxide membrane formed by polyethylene oxide self-assembly to obtain nanochannels with both high selectivity in excluding immune molecules and high permeability of nutrients such as glucose, insulin, and O2. The extracorporeal encapsulation system composed of these membranes allows O2 flux to meet the O2 demand of pancreatic islets of Langerhans and provides excellent in vitro viability and functionality of islets.

  14. Effect of electrolyte temperature on the thickness of anodic aluminium oxide (AAO layer

    Directory of Open Access Journals (Sweden)

    P. Michal

    2016-07-01

    Full Text Available Effect of electrolyte temperature on the thickness of resulting oxide layer has been studied. Unlike previous published studies this article was aimed to monitor the relationship between electrolyte temperature and resulting AAO layer thickness in interaction with other input factors affecting during anodizing process under special process condition, i.e. lower concentration of sulphuric acid, oxalic acid, boric acid and sodium chloride. According to Design of Experiments (DOE 80 individual test runs of experiment were carried out. Using statistical analysis and artificial intelligence for evaluation, the computational model predicting the thickness of oxide layer in the range from 5 / μm to 15 / μm with tolerance ± 0,5 / μm was developed.

  15. Hydrometallurgical process for the recycling of copper using anodic oxidation of cuprous ammine complexes and flow-through electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Oishi, T.; Yaguchi, M.; Koyama, K.; Tanaka, M. [Metals Recycling Group, Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569 (Japan); Lee, J.-C. [Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), 30 Gajeong-dong, Yuseong-ku, Daejeon 305-350 (Korea)

    2008-01-01

    Flow-through electrolysis for copper electrowinning from cuprous ammine complex was studied in order to develop a hydrometallurgical copper recycling process using an ammoniacal chloride solution, focusing on the anodic oxidation of cuprous to cupric ammine complexes. The current efficiency of this anodic oxidation was 96% at a current density of 200 A m{sup -2} under a batch condition. In a flow-through electrolysis using a sub-liter cell and a carbon felt anode, the anodic current efficiency increased with the flow rate and was typically higher than 97%. This tendency was explained by the backward flow of the cupric ammine complex, which was formed on the anode, through the diaphragm. The anodic overpotential was lower than 0.3 V even at an apparent current density of 1500 A m{sup -2}. A similar current efficiency and overpotential were also achieved in a liter scale cell, which indicates the scale flexibility of this electrolysis. The power consumption requirements for copper electrowinning in this cell were 460 and 770 kWh t{sup -1} at the current densities of 250 and 500 A m{sup -2}, respectively, which were much lower than that of the conventional copper electrowinning despite the longer interpolar distance. (author)

  16. Ni coarsening in the three-phase solid oxide fuel cell anode - a phase-field simulation study

    CERN Document Server

    Chen, Hsun-Yi; Cronin, J Scott; Wilson, James R; Barnett, Scott A; Thornton, Katsuyo

    2012-01-01

    Ni coarsening in Ni-yttria stabilized zirconia (YSZ) solid oxide fuel cell anodes is considered a major reason for anode degradation. We present a predictive, quantative modeling framework based on the phase-field approach to systematically examine coarsening kinetics in such anodes. The initial structures for simulations are experimentally acquired functional layers of anodes. Sample size effects and error analysis of contact angles are examined. Three phase boundary (TPB) lengths and Ni surface areas are quantatively identified on the basis of the active, dead-end, and isolated phase clusters throughout coarsening. Tortuosity evolution of the pores is also investigated. We find that phase clusters with larger characteristic length evolve slower than those with smaller length scales. As a result, coarsening has small positive effects on transport, and impacts less on the active Ni surface area than the total counter part. TPBs, however, are found to be sensitive to local morphological features and are only i...

  17. A Stability Study of Ni/Yttria-Stabilized Zirconia Anode for Direct Ammonia Solid Oxide Fuel Cells.

    Science.gov (United States)

    Yang, Jun; Molouk, Ahmed Fathi Salem; Okanishi, Takeou; Muroyama, Hiroki; Matsui, Toshiaki; Eguchi, Koichi

    2015-12-30

    In recent years, solid oxide fuel cells fueled with ammonia have been attracting intensive attention. In this work, ammonia fuel was supplied to the Ni/yttria-stabilized zirconia (YSZ) cermet anode at 600 and 700 °C, and the change of electrochemical performance and microstructure under the open-circuit state was studied in detail. The influence of ammonia exposure on the microstructure of Ni was also investigated by using Ni/YSZ powder and Ni film deposited on a YSZ disk. The obtained results demonstrated that Ni in the cermet anode was partially nitrided under an ammonia atmosphere, which considerably roughened the Ni surface. Moreover, the destruction of the anode support layer was confirmed for the anode-supported cell upon the temperature cycling test between 600 and 700 °C because of the nitriding phenomenon of Ni, resulting in severe performance degradation.

  18. 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.

  19. Ceria-Based Anodes for Next Generation Solid Oxide Fuel Cells

    Science.gov (United States)

    Mirfakhraei, Behzad

    Mixed ionic and electronic conducting materials (MIECs) have been suggested to represent the next generation of solid oxide fuel cell (SOFC) anodes, primarily due to their significantly enhanced active surface area and their tolerance to fuel components. In this thesis, the main focus has been on determining and tuning the physicochemical and electrochemical properties of ceria-based MIECs in the versatile perovskite or fluorite crystal structures. In one direction, BaZr0.1Ce0.7Y0.1 M0.1O3-delta (M = Fe, Ni, Co and Yb) (BZCY-M) perovskites were synthesized using solid-state or wet citric acid combustion methods and the effect of various transition metal dopants on the sintering behavior, crystal structure, chemical stability under CO2 and H 2S, and electrical conductivity, was investigated. BZCY-Ni, synthesized using the wet combustion method, was the best performing anode, giving a polarization resistance (RP) of 0.4 O.cm2 at 800 °C. Scanning electron microscopy and X-ray diffraction analysis showed that this was due to the exsolution of catalytic Ni nanoparticles onto the oxide surface. Evolving from this promising result, the effect of Mo-doped CeO 2 (nCMO) or Ni nanoparticle infiltration into a porous Gd-doped CeO 2 (GDC) anode (in the fluorite structure) was studied. While 3 wt. % Ni infiltration lowered RP by up to 90 %, giving 0.09 O.cm2 at 800 °C and exhibiting a ca. 5 times higher tolerance towards 10 ppm H2, nCMO infiltration enhanced the H2 stability by ca. 3 times, but had no influence on RP. In parallel work, a first-time study of the Ce3+ and Ce 4+ redox process (pseudocapacitance) within GDC anode materials was carried out using cyclic voltammetry (CV) in wet H2 at high temperatures. It was concluded that, at 500-600 °C, the Ce3+/Ce 4+ reaction is diffusion controlled, probably due to O2- transport limitations in the outer 5-10 layers of the GDC particles, giving a very high capacitance of ca. 70 F/g. Increasing the temperature ultimately

  20. Flame oxidation of stainless steel felt enhances anodic biofilm formation and current output in bioelectrochemical systems.

    Science.gov (United States)

    Guo, Kun; Donose, Bogdan C; Soeriyadi, Alexander H; Prévoteau, Antonin; Patil, Sunil A; Freguia, Stefano; Gooding, J Justin; Rabaey, Korneel

    2014-06-17

    Stainless steel (SS) can be an attractive material to create large electrodes for microbial bioelectrochemical systems (BESs), due to its low cost and high conductivity. However, poor biocompatibility limits its successful application today. Here we report a simple and effective method to make SS electrodes biocompatible by means of flame oxidation. Physicochemical characterization of electrode surface indicated that iron oxide nanoparticles (IONPs) were generated in situ on an SS felt surface by flame oxidation. IONPs-coating dramatically enhanced the biocompatibility of SS felt and consequently resulted in a robust electroactive biofilm formation at its surface in BESs. The maximum current densities reached at IONPs-coated SS felt electrodes were 16.5 times and 4.8 times higher than the untreated SS felts and carbon felts, respectively. Furthermore, the maximum current density achieved with the IONPs-coated SS felt (1.92 mA/cm(2), 27.42 mA/cm(3)) is one of the highest current densities reported thus far. These results demonstrate for the first time that flame oxidized SS felts could be a good alternative to carbon-based electrodes for achieving high current densities in BESs. Most importantly, high conductivity, excellent mechanical strength, strong chemical stability, large specific surface area, and comparatively low cost of flame oxidized SS felts offer exciting opportunities for scaling-up of the anodes for BESs.

  1. 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

    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...

  2. Comparison of reduction products from graphite oxide and graphene oxide for anode applications in lithium-ion batteries and sodium-ion batteries.

    Science.gov (United States)

    Sun, Yige; Tang, Jie; Zhang, Kun; Yuan, Jinshi; Li, Jing; Zhu, Da-Ming; Ozawa, Kiyoshi; Qin, Lu-Chang

    2017-02-16

    Hydrazine-reduced graphite oxide and graphene oxide were synthesized to compare their performances as anode materials in lithium-ion batteries and sodium-ion batteries. Reduced graphite oxide inherits the layer structure of graphite, with an average spacing between neighboring layers (d-spacing) of 0.374 nm; this exceeds the d-spacing of graphite (0.335 nm). The larger d-spacing provides wider channels for transporting lithium ions and sodium ions in the material. We showed that reduced graphite oxide as an anode in lithium-ion batteries can reach a specific capacity of 917 mA h g(-1), which is about three times of 372 mA h g(-1), the value expected for the LiC6 structures on the electrode. This increase is consistent with the wider d-spacing, which enhances lithium intercalation and de-intercalation on the electrodes. The electrochemical performance of the lithium-ion batteries and sodium-ion batteries with reduced graphite oxide anodes show a noticeable improvement compared to those with reduced graphene oxide anodes. This improvement indicates that reduced graphite oxide, with larger interlayer spacing, has fewer defects and is thus more stable. In summary, we found that reduced graphite oxide may be a more favorable form of graphene for the fabrication of electrodes for lithium-ion and sodium-ion batteries and other energy storage devices.

  3. Fabrication of TiO2 Crystalline Coatings by Combining Ti-6Al-4V Anodic Oxidation and Heat Treatments

    Science.gov (United States)

    Schvezov, Carlos Enrique; Ares, Alicia Esther

    2015-01-01

    The bio- and hemocompatibility of titanium alloys are due to the formation of a TiO2 layer. This natural oxide may have fissures which are detrimental to its properties. Anodic oxidation is used to obtain thicker films. By means of this technique, at low voltages oxidation, amorphous and low roughness coatings are obtained, while, above a certain voltage, crystalline and porous coatings are obtained. According to the literature, the crystalline phases of TiO2, anatase, and rutile would present greater biocompatibility than the amorphous phase. On the other hand, for hemocompatible applications, smooth and homogeneous surfaces are required. One way to obtain crystalline and homogeneous coatings is by heat treatments after anodic oxidation. The aim of this study is to evaluate the influence of heat treatments on the thickness, morphology, and crystalline structure of the TiO2 anodic coatings. The characterization was performed by optical and scanning electron microscopy, X-ray diffraction, and X-ray reflectometry. Coatings with different colors of interference were obtained. There were no significant changes in the surface morphology and roughness after heat treatment of 500°C. Heat treated coatings have different proportions of the crystalline phases, depending on the voltage of anodic oxidation and the temperature of the heat treatment. PMID:25784939

  4. Fabrication of TiO2 Crystalline Coatings by Combining Ti-6Al-4V Anodic Oxidation and Heat Treatments

    Directory of Open Access Journals (Sweden)

    María Laura Vera

    2015-01-01

    Full Text Available The bio- and hemocompatibility of titanium alloys are due to the formation of a TiO2 layer. This natural oxide may have fissures which are detrimental to its properties. Anodic oxidation is used to obtain thicker films. By means of this technique, at low voltages oxidation, amorphous and low roughness coatings are obtained, while, above a certain voltage, crystalline and porous coatings are obtained. According to the literature, the crystalline phases of TiO2, anatase, and rutile would present greater biocompatibility than the amorphous phase. On the other hand, for hemocompatible applications, smooth and homogeneous surfaces are required. One way to obtain crystalline and homogeneous coatings is by heat treatments after anodic oxidation. The aim of this study is to evaluate the influence of heat treatments on the thickness, morphology, and crystalline structure of the TiO2 anodic coatings. The characterization was performed by optical and scanning electron microscopy, X-ray diffraction, and X-ray reflectometry. Coatings with different colors of interference were obtained. There were no significant changes in the surface morphology and roughness after heat treatment of 500°C. Heat treated coatings have different proportions of the crystalline phases, depending on the voltage of anodic oxidation and the temperature of the heat treatment.

  5. Carbon nanotube/nanofiber embedded nanoporous anodized aluminium oxide surface and its tribological properties.

    Science.gov (United States)

    Kushwaha, M K; Sil, Anjan; Ray, S

    2008-08-01

    Nanoporous alumina has been prepared by anodization of pure aluminium using phosphoric acid electrolyte. Carbon nanotubes/nanofibres (CNTs/CNFs) are grown within the pores by chemical vapour deposition technique, using acetylene gas as carbon precursor. Such synthesis of nanostructured carbonaceous materials within the nanoporous oxide template has high potential for many applications (e.g., electronics, magnetic, etc.) in nanotechnology. Possibility of using such material combination for engineering systems where abrasion resistance coupled with self-lubrication (at comparatively higher loads) are the key requirements, has been explored through the present work. Pore structure has been characterized by SEM/FE-SEM in this study and CNTs/CNFs have been examined by TEM, FE-SEM and Raman spectroscopy. While the pore diameters are found to lie in the range of 180-220 nm, the CNTs/CNFs diameter are observed to be in the range of 50 to 220 nm. The CNTs/CNFs growing from bottom of the pores are found to replicate the pore diameter, while those grown above the surface are varying significantly in diameter and probably matching the diameter of the catalyst, which remains adsorbed on the top surface and inner walls of the pores. On comparing friction and wear properties of both materials (viz. anodized alumina and CNTs/CNFs embedded anodized alumina) as determined by pin-on-disc machine using hardened steel disc as counterface, it is found that wear rate and coefficient of friction of CNTs embedded composite surface is significantly lower which is attributed to formation of transfer layer of hard wear resistant alumina mechanically mixed with graphitic CNTs/CNFs.

  6. Quasi-solid state rechargeable Na-CO2 batteries with reduced graphene oxide Na anodes.

    Science.gov (United States)

    Hu, Xiaofei; Li, Zifan; Zhao, Yaran; Sun, Jianchao; Zhao, Qing; Wang, Jianbin; Tao, Zhanliang; Chen, Jun

    2017-02-01

    Na-CO2 batteries using earth-abundant Na and greenhouse gas CO2 are promising tools for mobile and stationary energy storage, but they still pose safety risks from leakage of liquid electrolyte and instability of the Na metal anode. These issues result in extremely harsh operating conditions of Na-CO2 batteries and increase the difficulty of scaling up this technology. We report the development of quasi-solid state Na-CO2 batteries with high safety using composite polymer electrolyte (CPE) and reduced graphene oxide (rGO) Na anodes. The CPE of PVDF-HFP [poly(vinylidene fluoride-co-hexafluoropropylene)]-4% SiO2/NaClO4-TEGDME (tetraethylene glycol dimethyl ether) has high ion conductivity (1.0 mS cm(-1)), robust toughness, a nonflammable matrix, and strong electrolyte-locking ability. In addition, the rGO-Na anode presents fast and nondendritic Na(+) plating/stripping (5.7 to 16.5 mA cm(-2)). The improved kinetics and safety enable the constructed rGO-Na/CPE/CO2 batteries to successfully cycle in wide CO2 partial pressure window (5 to 100%, simulated car exhaust) and especially to run for 400 cycles at 500 mA g(-1) with a fixed capacity of 1000 mA·hour g(-1) in pure CO2. Furthermore, we scaled up the reversible capacity to 1.1 A·hour in pouch-type batteries (20 × 20 cm, 10 g, 232 Wh kg(-1)). This study makes quasi-solid state Na-CO2 batteries an attractive prospect.

  7. Quasi–solid state rechargeable Na-CO2 batteries with reduced graphene oxide Na anodes

    Science.gov (United States)

    Hu, Xiaofei; Li, Zifan; Zhao, Yaran; Sun, Jianchao; Zhao, Qing; Wang, Jianbin; Tao, Zhanliang; Chen, Jun

    2017-01-01

    Na-CO2 batteries using earth-abundant Na and greenhouse gas CO2 are promising tools for mobile and stationary energy storage, but they still pose safety risks from leakage of liquid electrolyte and instability of the Na metal anode. These issues result in extremely harsh operating conditions of Na-CO2 batteries and increase the difficulty of scaling up this technology. We report the development of quasi–solid state Na-CO2 batteries with high safety using composite polymer electrolyte (CPE) and reduced graphene oxide (rGO) Na anodes. The CPE of PVDF-HFP [poly(vinylidene fluoride-co-hexafluoropropylene)]–4% SiO2/NaClO4–TEGDME (tetraethylene glycol dimethyl ether) has high ion conductivity (1.0 mS cm−1), robust toughness, a nonflammable matrix, and strong electrolyte-locking ability. In addition, the rGO-Na anode presents fast and nondendritic Na+ plating/stripping (5.7 to 16.5 mA cm−2). The improved kinetics and safety enable the constructed rGO-Na/CPE/CO2 batteries to successfully cycle in wide CO2 partial pressure window (5 to 100%, simulated car exhaust) and especially to run for 400 cycles at 500 mA g−1 with a fixed capacity of 1000 mA·hour g−1 in pure CO2. Furthermore, we scaled up the reversible capacity to 1.1 A·hour in pouch-type batteries (20 × 20 cm, 10 g, 232 Wh kg−1). This study makes quasi–solid state Na-CO2 batteries an attractive prospect. PMID:28164158

  8. Corrosion Behavior of Anodic Oxidized TiO2 Film in Seawater

    Institute of Scientific and Technical Information of China (English)

    WANG Min; WANG Wei; HE Benlin; SUN Mingliang; YIN Yansheng; LIU Lan; ZOU Wuyuan; XU Xuefei

    2010-01-01

    TiO2 films were formed on metallic titanium substrates by the anodic oxidation method in H2SO4 solution under the 80V D.C..Phase component and microstructure were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM).Water contact angles on titanium oxide film surface were measured under both dark and sunlight illumination conditions.Corrosion tests were carried out in seawater under different illumination conditions by electrochemistry impedance spectrum(EIS)and polarization curves.The result showed that the TiO2 film prepared by the anodic oxidation method was anatase with a uniform structure and without obvious pores or cracks on its surface.The average water contact angle of the film was 116.4 ° in dark,in contrast to an angle of 42.7 ° under the UV illumination for 2 hours,which demonstrates good hydrophobic property.The anti-corrosion behavior of the TiO2 film was declining with the extended immersion time.Under dark conditions,however,the hydrophobic TiO2 film retarded the water infiltrating into the substrate.The impedance changed slowly and the corrosion current density was 2 orders of magnitude lower than that with the film illuminated by sunlight.All of those mentioned above indicate that the TiO2 film possesses much better performance under dark condition,and it can be applied as an engineering material under dark seawater environment.

  9. Pilot scale performance of the electro-oxidation of landfill leachate at boron-doped diamond anodes.

    Science.gov (United States)

    Anglada, Angela; Urtiaga, Ane; Ortiz, Inmaculada

    2009-03-15

    During the electrochemical oxidation of real wastewaters, the different species present in the effluent may interact creating complex scenarios making the prediction of the behavior of the whole system difficult. In this paper the different phenomena that occur during the electro-oxidation process of landfill leachate at a pilot plant scale with boron-doped diamond (BDD) anodes are elucidated. The total BDD anode area of the pilot plant was 1.05 m2. The evolution of the concentration of chloride ions, chlorate, and inorganic carbon and the value of pH and redox potential were found to be inter-related. In turn, the concentration of chloride affected the oxidation of ammonia, which took place through indirect oxidation by active chlorine. Moreover, chloride ions competed with organic matter to be oxidized at the anode. The effect of current density was also investigated. Organic matter and ammonia oxidation were highly influenced by the applied current density value. A change in the mechanism of organic matter oxidation was observed when high current densities were applied. Two mathematical models, previously applied to the oxidation of synthetic wastewaters in the literature, were able to predict the evolution of chemical oxygen demand and ammonia for low current density values.

  10. Doped Yttrium Chromite-Ceria Composite as a Redox-Stable and Sulfur-Tolerant Anode for Solid Oxide Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Kyung J.; Coyle, Christopher A.; Marina, Olga A.

    2011-12-11

    A Ca- and Co-doped yttrium chromite (YCCC) - samaria-doped ceria (SDC) composite was studied in relation to a potential use as a solid oxide fuel cell (SOFC) anode material. Tests performed using the yttria-stabilized zirconia (YSZ) electrolyte-supported cells revealed that the electrocatalytic activity of the YCCC-SDC anode towards hydrogen oxidation at 800 C was comparable to that of the Ni-YSZ anode. In addition, the YCCC-SDC anode exhibited superior sulfur tolerant characteristics showing less than 10% increase in a polarization resistance, fully reversible, upon exposure to 20 ppm H2S at 800 C. No performance degradation was observed during multiple reduction-oxidation (redox) cycles when the anode was intentionally exposed to the air environment followed by the reduction in hydrogen. The redox tolerance of the YCCC-SDC anode was attributed to the dimensional and chemical stability of the YCCC exhibiting minimal isothermal chemical expansion upon redox cycling.

  11. Buffered Electrochemical Polishing of Niobium

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Tian, Hui [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States); Corcoran, Sean [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

    2011-03-01

    The standard preparation of superconducting radio-frequency (SRF) cavities made of pure niobium include the removal of a 'damaged' surface layer, by buffered chemical polishing (BCP) or electropolishing (EP), after the cavities are formed. The performance of the cavities is characterized by a sharp degradation of the quality factor when the surface magnetic field exceeds about 90 mT, a phenomenon referred to as 'Q-drop.' In cavities made of polycrystalline fine grain (ASTM 5) niobium, the Q-drop can be significantly reduced by a low-temperature (? 120 °C) 'in-situ' baking of the cavity if the chemical treatment was EP rather than BCP. As part of the effort to understand this phenomenon, we investigated the effect of introducing a polarization potential during buffered chemical polishing, creating a process which is between the standard BCP and EP. While preliminary results on the application of this process to Nb cavities have been previously reported, in this contribution we focus on the characterization of this novel electrochemical process by measuring polarization curves, etching rates, surface finish, electrochemical impedance and the effects of temperature and electrolyte composition. In particular, it is shown that the anodic potential of Nb during BCP reduces the etching rate and improves the surface finish.

  12. Improvement of output performance of solid oxide fuel cell by optimizing Ni/samaria-doped ceria anode functional layer

    Energy Technology Data Exchange (ETDEWEB)

    Ai, Na; Lue, Zhe; Chen, Kongfa; Huang, Xiqiang [Center for Condensed Matter Science and Technology, Harbin Institute of Technology, Harbin 150001 (China); Tang, Jinke [Department of Physics, University of New Orleans, New Orleans, LA 70148 (United States); Su, Wenhui [Center for Condensed Matter Science and Technology, Harbin Institute of Technology, Harbin 150001 (China); International Center for Material Physics, Academia, Shenyang 110015 (China)

    2008-10-15

    Anode functional layers (AFLs) were fabricated using slurry spin coating method on anode substrates to improve the performance of cells based on samaria-doped ceria (SDC) films. The effects of the chemical compositions of AFL and AFL thickness on the performance of solid oxide fuel cell anodes were investigated by studying their effect on the ohmic loss, electrode overpotential, and output performance of cells in different atmospheres. With humidified hydrogen used as fuel and oxygen as oxidant, the cell with an 8-{mu}m-thick AFL (NiO:SDC = 6:4) exhibited excellent maximum power densities of 3.41, 2.89, 1.46 and 0.80 W cm{sup -2} at 650, 600, 550 and 500 C, respectively. (author)

  13. Effect of Samarium Oxide on the Electrical Conductivity of Plasma-Sprayed SOFC Anodes

    Science.gov (United States)

    Panahi, S. N.; Samadi, H.; Nemati, A.

    2016-10-01

    Solid oxide fuel cells (SOFCs) are rapidly becoming recognized as a new alternative to traditional energy conversion systems because of their high energy efficiency. From an ecological perspective, this environmentally friendly technology, which produces clean energy, is likely to be implemented more frequently in the future. However, the current SOFC technology still cannot meet the demands of commercial applications due to temperature constraints and high cost. To develop a marketable SOFC, suppliers have tended to reduce the operating temperatures by a few hundred degrees. The overall trend for SOFC materials is to reduce their service temperature of electrolyte. Meanwhile, it is important that the other components perform at the same temperature. Currently, the anodes of SOFCs are being studied in depth. Research has indicated that anodes based on a perovskite structure are a more promising candidate in SOFCs than the traditional system because they possess more favorable electrical properties. Among the perovskite-type oxides, SrTiO3 is one of the most promising compositions, with studies demonstrating that SrTiO3 exhibits particularly favorable electrical properties in contrast with other perovskite-type oxides. The main purpose of this article is to describe our study of the effect of rare-earth dopants with a perovskite structure on the electrical behavior of anodes in SOFCs. Sm2O3-doped SrTiO3 synthesized by a solid-state reaction was coated on substrate by atmospheric plasma spray. To compare the effect of the dopant on the electrical conductivity of strontium titanate, different concentrations of Sm2O3 were used. The samples were then investigated by x-ray diffraction, four-point probe at various temperatures (to determine the electrical conductivity), and a scanning electron microscope. The study showed that at room temperature, nondoped samples have a higher electrical resistance than doped samples. As the temperature was increased, the electrical

  14. Cadmium, lead and silver adsorption in hydrous niobium oxide(V) prepared by precipitation in homogeneous solution method; Adsorcao de chumbo, cadmio e prata em oxido de niobio(V) hidratado preparado pelo metodo da precipitacao em solucao homogenea

    Energy Technology Data Exchange (ETDEWEB)

    Tagliaferro, Geronimo V.; Pereira, Paulo Henrique F.; Rodrigues, Liana Alvares; Silva, Maria Lucia Caetano Pinto da, E-mail: fernandes_eng@yahoo.com.b [Universidade de Sao Paulo (USP), Lorena, SP (Brazil). Escola de Engenharia. Dept. de Engenharia Quimica

    2011-07-01

    This paper describes the adsorption of heavy metals ions from aqueous solution by hydrous niobium oxide. Three heavy metals were selected for this study: cadmium, lead and silver. Adsorption isotherms were well fitted by Langmuir model. Maximum adsorption capacity (Q{sub 0}) for Pb{sup 2+}, Ag{sup +} and Cd{sup 2+} was found to be 452.5, 188.68 and 8.85 mg g{sup -1}, respectively. (author)

  15. Photo- and electroluminescence properties of lanthanide tungstate-doped porous anodic aluminum oxide

    Science.gov (United States)

    Staninski, Krzysztof; Piskuła, Zbigniew; Kaczmarek, Małgorzata

    2017-02-01

    A new cathode material for the potential use in light-emitting devices, based on porous anodic alumina (PAA), aluminum and ITO layers has been synthesized. Porous alumina samples with ordered pore arrays were prepared electrochemically from high purity Al sheet in H2SO4 and H3PO4. To be able to apply the matrix obtained in the electroluminescence cell, the thickness of the barrier layer of aluminum oxide was decreased by slow reduction of the anodization voltage to zero. The luminescence and electroluminescence (EL) properties of the Al2O3 matrix admixtured with Eu3+ and Tb3+ ions as well as europium and terbium tungstates, were determined. The particles of inorganic luminophore were synthesized on the walls of the matrix cylindrical nanopores in the two-step process of immersion in solutions of TbCl3 or EuCl3 and Na2WO4. The effect of the nanopores diameter and the thickness of the porous Al2O3 layer on the intensity and relative yield of electroluminescence was analyzed, the best results were obtained for 80-90 μm PAA layers with 140 nm nanopores.

  16. Electrochemical incineration of dimethyl phthalate by anodic oxidation with boron-doped diamond electrode

    Institute of Scientific and Technical Information of China (English)

    HOU Yining; QU Jiuhui; ZHAO Xu; LIU Huijuan

    2009-01-01

    The anodic oxidation of aqueous solutions containing dimethyl phthalate (DMP) up to 125 mg/L with sodium sulfate (Na2SO4) as supporting electrolyte within the pH range 2.0-10.0 was studied using a one-compartment batch reactor employing a boron-doped diamond (BDD) as anode. Electrolyses were carried out at constant current density (1.5-4.5 mA/cm2). Complete mineralization was always achieved owing to the great concentration of hydroxyl radical (·OH) generated at the BDD surface. The effect of pH, apparent current density and initial DMP concentration on the degradation rate of DMP, the specific charge required for its total mineralization and mineralization current efficiency was investigated systematically. The mineralization rate of DMP was found to be pH-independent and to increase with increasing applied current density. Results indicated that this electrochemical process was subjected, at least partially, to the mass transfer of organics onto the BDD surface. Kinetic analysis of the temporal change of DMP concentration during electrolysis determined by High Performance Liquid Chromatography (HPLC) revealed that DMP decay under all tested conditions followed a pseudo first-order reaction. Aromatic intermediates and generated carboxylic acids were identified by Gas Chromatography-Mass Spectrometry (GC-MS) and a general pathway for the electrochemical incineration of DMP on BDD was proposed.

  17. Growth and Magnetic Characterization of 1D Permalloy Nanowires Using Self Developed Anodic Aluminium Oxide Templates.

    Science.gov (United States)

    Singh, Ashutosh K; Mandal, Kalyan

    2016-01-01

    1D Permalloy refers to arrays of nanowires (NWs) made of an alloy of Ni and Fe with 80 and 20 at% composition respectively. In the present work 1 D Permalloy NWs arrays were fabricated into the pores of self engineered Anodic Aluminium Oxide (AAO) templates by a simple electrodeposition technique (EDT). By varying the anodization voltage and parameters of the electrolyte solutions we developed AAO templates with different average pore diameters (40 nm to 70 nm) and developed 1D Permalloy NWs within them. Structural characterization of AAO templates and 1D Permalloy NWs were performed by Transmission and Scanning Electron Microscopy (TEM and SEM respectively). X-ray diffraction (XRD) studies of 1D Permalloy NWs showed their fcc crystalline structure and the AAO template was found to be amorphous in nature. Magnetic studies showed the 1D Permalloy NWs arrays to have strong shape anisotropy, and the easy axis was found to be parallel to the NWs axis. We studied the angular dependence of magnetic properties of the NWs. Coercivity (Hc) and remanence (Mr/Ms) measured along the NWs axis were found to be higher than those measured in a direction perpendicular to the NWs axis. 1D Permalloy NWs developed in this work have the potential to be used in magnetic recording devices.

  18. Realization of tin oxide like anode for the manufacture of the organic solar cells

    Directory of Open Access Journals (Sweden)

    Khelil A.

    2012-06-01

    Full Text Available The transparent oxides such as SnO2, In2O3 and ZnO continue to arouse a private interest for their various applications. The objective of the various studies being to carry out the layers which are simultaneously most transparent and most conducting possible. Thus in the field of the solar spectrum, the transmission of the layers must be higher than 80% and their conductivity exceeding 103 (Ohm.cm-1. Their transparency which is related to the value of their forbidden band must be higher than 3.7 e V. Their electric properties as for them depend on the composition of the layers and a possible doping. In this work, one characterized layers of SnO2 deposited by chemical pulverization, one carried out measurements by, electronic scan microscopy, diffraction of x-rays and also of the optical measurements and electronic. It results from it that the layers are conducting and transparent in the visible one but they are relatively rough, following its characterizations, one carried out organic photovoltaic cells using these layers of SnO2 and also of the commercial ITO like anode in these components. More particularly one was interested in the influence of the presence of a fine layer of gold between the anode and organic material.

  19. Facile design of ultra-thin anodic aluminum oxide membranes for the fabrication of plasmonic nanoarrays

    Science.gov (United States)

    Hao, Qi; Huang, Hao; Fan, Xingce; Hou, Xiangyu; Yin, Yin; Li, Wan; Si, Lifang; Nan, Haiyan; Wang, Huaiyu; Mei, Yongfeng; Qiu, Teng; Chu, Paul K.

    2017-03-01

    Ultra-thin anodic aluminum oxide (AAO) membranes are efficient templates for the fabrication of patterned nanostructures. Herein, a three-step etching method to control the morphology of AAO is described. The morphological evolution of the AAO during phosphoric acid etching is systematically investigated and a nonlinear growth mechanism during unsteady-state anodization is revealed. The thickness of the AAO can be quantitatively controlled from ∼100 nm to several micrometers while maintaining the tunablity of the pore diameter. The AAO membranes are robust and readily transferable to different types of substrates to prepare patterned plasmonic nanoarrays such as nanoislands, nanoclusters, ultra-small nanodots, and core–satellite superstructures. The localized surface plasmon resonance from these nanostructures can be easily tuned by adjusting the morphology of the AAO template. The custom AAO template provides a platform for the fabrication of low-cost and large-scale functional nanoarrays suitable for fundamental studies as well as applications including biochemical sensing, imaging, photocatalysis, and photovoltaics.

  20. Stability of the anodic growth porous tungsten oxide in different solutions

    Energy Technology Data Exchange (ETDEWEB)

    Chai, Y.; Yam, F. K.; Hassan, Z. [Nano-Optoelectronic Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia)

    2015-05-15

    This article presents the study of the stability of the anodic growth porous tungsten oxide (WO{sub 3}) film in different solutions. As-anodized films are relatively stable in acidic electrolytes like sulphuric acid (H{sub 2}SO{sub 4}), hydrochloric acid (HCl) but not in oxalic acid. In higher pH solution, rate of dissolution of the WO{sub 3} film is higher. Annealing at 400 °C for 2 h transform the as-grown sample from amorphous phase to the crystalline phase and this significantly improve the stability of the film in high pH solution. Photocurrent measurements reveal that there is no significant difference of the electrolyte used (0.5 M H{sub 2}SO{sub 4}, 0.33 M H{sub 3}PO{sub 4}, 0.1 M sodium sulfate (Na{sub 2}SO{sub 4})) on the photocurrent. As-annealed films exhibit good stablility for the long photoelectrochemical (PEC) measurements (1700 s) in 0.5 M H{sub 2}SO{sub 4} and 0.1 M Na{sub 2}SO{sub 4}. There is no effect on the photocurrent for the variation of the concentration of the acidic solution (H{sub 2}SO{sub 4}). However, lower photocurrent was obtained as the concentration of Na{sub 2}SO{sub 4} was increased.

  1. Synthesis of bismuth (III oxide films based anodes for electrochemical degradation of reactive blue 19 and crystal violet

    Directory of Open Access Journals (Sweden)

    Petrović Milica M.

    2014-01-01

    Full Text Available The Bi2O3 films-based anodes were synthesized by electrodeposition of Bi on stainless steel substrate at constant current density and during different deposition times, fallowed by calcination, forming Bi2O3. The thickness of the films was determined by two methods: the observation under the microscope and by calculation from mass difference. Electrochemical proceses at the anodes were ivestigated by linear sweep voltammetry. At the anodes obtained within 2, 5, 10 and 15 minutes of deposition, two dyes, namely: Reactive Blue 19 and Crystal Violet, were decolorized by oxidation with •OH radical, generated from H2O2 decomposition at the anodes. Decoloration times of the anodes varied, and the shortest one was achieved with the anode obtained during 5 minutes of deposition, with the film thickness of 2.5±0.3 μm. The optimal H2O2 concentration for the dyes degradation was found to be 10 mmol dm-3. [Projekat Ministarstva nauke Republike Srbije, br. ТR 34008

  2. Direct Logistic Fuel JP-8 Conversion in a Liquid Tin Anode Solid Oxide Fuel Cell (LTA-SOFC)

    Science.gov (United States)

    2008-04-09

    demonstrated the ability of the Liquid Tin Anode Solid Oxide Fuel Cell (LTA SOFC) to direct convert logistic fuel, JP-8. The demonstration of direct JP-8...conversion without fuel processing or reforming was unprecedented in fuel cell technology. The DOD has a broad interest in power generation using

  3. A modified anode/electrolyte structure for a solid oxide electrochemical cell and a method for making said structure

    DEFF Research Database (Denmark)

    2013-01-01

    -stabilised zirconium oxide electrolyte and (c) a metallic and/or a ceramic electrocatalyst in the shape of interlayers incorporated in the interface between the anode and the electrolyte. This assembly is first sintered at a given temperature and then at a lower temperature in reducing gas mixtures. These heat...

  4. Accelerated creep in solid oxide fuel cell anode supports during reduction

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lund; Makowska, Malgorzata Grazyna; Greco, Fabio

    2016-01-01

    To evaluate the reliability of solid oxide fuel cell (SOFC) stacks during operation, the stress field in the stack must be known. During operation the stress field will depend on time as creep processes relax stresses. The creep of reduced Ni-YSZ anode support at operating conditions has been...... studied previously. In this work a newly discovered creep phenomenon taking place during the reduction is reported. This relaxes stresses at a much higher rate (∼ x104) than creep during operation. The phenomenon was studied both in three-point bending and uniaxial tension. Differences between the two...... measurements could be explained by newly observed stress promoted reduction. Finally, samples exposed to a small tensile stress (∼ 0.004 MPa) were observed to expand during reduction, which is in contradiction to previous literature. These observations suggest that release of internal residual stresses between...

  5. Micromechanical Modeling of Solid Oxide Fuel Cell Anode Supports based on Three-dimensional Reconstructions

    DEFF Research Database (Denmark)

    Kwok, Kawai; Jørgensen, Peter Stanley; Frandsen, Henrik Lund

    2014-01-01

    The efficiency and lifetime of solid oxide fuel cells (SOFCs) is compromised by mechanical failure of cells in the system. Improving the mechanical reliability is a major step in ensuring feasibility of the technology. To quantify the stress in a cell, mechanical properties of the different layers...... need to be accurately known. Since the mechanical properties are heavily dependent on the microstructures of the materials, it is highly advantageous to understand the impact of microstructures and to be able to determine accurate effective mechanical properties for cell or stack scale analyses...... are computed by the finite element method. The macroscopic creep response of the porous anode support is determined based on homogenization theory. It is shown that micromechanical modeling provides an effective tool to study the effect of microstructures on the macroscopic properties....

  6. Anodized Aluminum Oxide Templated Synthesis of Metal-Organic Frameworks Used as Membrane Reactors.

    Science.gov (United States)

    Yu, Yifu; Wu, Xue-Jun; Zhao, Meiting; Ma, Qinglang; Chen, Junze; Chen, Bo; Sindoro, Melinda; Yang, Jian; Han, Shikui; Lu, Qipeng; Zhang, Hua

    2017-01-09

    The incorporation of metal-organic frameworks (MOFs) into membrane-shaped architectures is of great importance for practical applications. The currently synthesized MOF-based membranes show many disadvantages, such as poor compatibility, low dispersity, and instability, which severely limit their utility. Herein, we present a general, facile, and robust approach for the synthesis of MOF-based composite membranes through the in situ growth of MOF plates in the channels of anodized aluminum oxide (AAO) membranes. After being used as catalysis reactors, they exhibit high catalytic performance and stability in the Knoevenagel condensation reaction. The high catalytic performance might be attributed to the intrinsic structure of MOF-based composite membranes, which can remove the products from the reaction zone quickly, and prevent the aggregation and loss of catalysts during reaction and recycling process.

  7. Enhanced Elastic Modulus of Regenerated Silk Fibroin by Geometric Confinement in Anodized Aluminum Oxide Templates

    Science.gov (United States)

    Li, Jiankang; Li, Liang

    2017-02-01

    Geometric confinement is a promising method for the reconstruction of silk fibroin to form diversified structures with excellent mechanical properties. To accomplish geometric confinement, a water vapor assistant embossing process is used with porous anodic aluminum oxide templates, yielding silk fibroin nanopillars with diameters ranging from 40 nm to 130 nm. The elastic modulus of the regenerated silk fibroin nanopillars is investigated with atomic force microscopy nanoindentation analysis. Compared to films with the same treatment conditions, geometric confinement provided a twofold increase in elastic modulus in embossed silk fibroin nanopillars, indicating that β-sheet crystal ordering occurred during the water vapor assistant embossing process. These results demonstrate the feasibility and mechanical property enhancement of the embossing method to fabricate silk nanostructures, and will be useful in designing miniaturized devices.

  8. Solid oxide fuel cell anode image segmentation based on a novel quantum-inspired fuzzy clustering

    Science.gov (United States)

    Fu, Xiaowei; Xiang, Yuhan; Chen, Li; Xu, Xin; Li, Xi

    2015-12-01

    High quality microstructure modeling can optimize the design of fuel cells. For three-phase accurate identification of Solid Oxide Fuel Cell (SOFC) microstructure, this paper proposes a novel image segmentation method on YSZ/Ni anode Optical Microscopic (OM) images. According to Quantum Signal Processing (QSP), the proposed approach exploits a quantum-inspired adaptive fuzziness factor to adaptively estimate the energy function in the fuzzy system based on Markov Random Filed (MRF). Before defuzzification, a quantum-inspired probability distribution based on distance and gray correction is proposed, which can adaptively adjust the inaccurate probability estimation of uncertain points caused by noises and edge points. In this study, the proposed method improves accuracy and effectiveness of three-phase identification on the micro-investigation. It provides firm foundation to investigate the microstructural evolution and its related properties.

  9. Optical properties of one-dimensional photonic crystals based on porous films of anodic aluminum oxide

    Science.gov (United States)

    Gorelik, V. S.; Klimonsky, S. O.; Filatov, V. V.; Napolskii, K. S.

    2016-04-01

    The optical properties of one-dimensional photonic crystals based on porous anodic aluminum oxide films have been studied by measuring transmittance and specular reflectance spectra in the visible and UV spectral regions. Angular dependences of the spectral positions of optical stop bands are obtained. It is shown that the reflectance within the first stop band varies from point to point on the sample surface, reaching a level of 98-99% at some points. The dispersion relation for electromagnetic waves in the model of infinite periodic structure is calculated for the samples under study. The possibility of using models with an infinite or finite number of layers to calculate reflectance spectra near the first optical stop band is discussed.

  10. Combining adsorption with anodic oxidation as an innovative technique for removal and destruction of organics.

    Science.gov (United States)

    Brown, N W; Roberts, E P L

    2013-01-01

    Coupling of adsorption with electrochemical oxidation is a novel approach to the treatment of aqueous organics that has demonstrated a number of key benefits over the individual application of these processes. This is based on a highly conducting adsorbent material, developed under the trade name Nyex™, that is able to rapidly adsorb the organics and anodically oxidise them within a single treatment unit. Successful scale up of the process (in both continuous and batch operation) has been achieved for the polishing of two separate groundwaters (one containing relatively simple petrol, diesel and their degradation products and the other with a range of more complex organics). Treatment showed that low discharge consents can be achieved, including the removal of more complex and difficult to treat compounds to below the limits of detection. Energy consumption for electrochemical regeneration was relatively low (down to 0.5 kWh/m(3)) suggesting that the process could be a practical alternative approach for effluent polishing.

  11. Science Letters:Anodic oxidation of salicylic acid at Ta/BDD electrode

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Boron-doped diamond (BDD) film electrodes using Ta as substrates were employed for anodic oxidation of salicylic acid (SA). The effects of operational variables including initial concentration, current density, temperature and pH were examined.The results showed that BDD films deposited on the Ta substrates had high electrocatalytic activity for SA degradation. There was little effect of pH on SA degradation. The current efficiency (CE) was found to be dependent mainly on the initial SA concentration,current density and temperature. Chemical oxygen demand (COD) was reduced from 830 mg/L to 42 mg/L under a current density of 200 A/m2 at 30 ℃.

  12. Electrically conductive anodized aluminum coatings

    Science.gov (United States)

    Alwitt, Robert S. (Inventor); Liu, Yanming (Inventor)

    2001-01-01

    A process for producing anodized aluminum with enhanced electrical conductivity, comprising anodic oxidation of aluminum alloy substrate, electrolytic deposition of a small amount of metal into the pores of the anodized aluminum, and electrolytic anodic deposition of an electrically conductive oxide, including manganese dioxide, into the pores containing the metal deposit; and the product produced by the process.

  13. Coordination Compounds of Niobium(IV) Oxide Dihalides Including the Synthesis and the Crystallographic Characterization of NHC Complexes.

    Science.gov (United States)

    Bortoluzzi, Marco; Ferretti, Eleonora; Marchetti, Fabio; Pampaloni, Guido; Pinzino, Calogero; Zacchini, Stefano

    2016-05-01

    The 1:1 molar reactions of NbOX3 with SnBu3H, in toluene at 0 °C in the presence of oxygen/nitrogen donors, resulted in the formation of NbOX2L2 (X = Cl, L2 = dme, 2a; X = Br, L2 = dme, 2b; X = Cl, L = thf, 2c; X = Cl, L = NCMe, 2d; dme = 1,2-dimethoxyethane, thf = tetrahydrofuran), in good yields. The 1:2 reactions of freshly prepared 2d and 2b with the bulky NHC ligands 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, Imes, and 1,3-bis(2,6-dimethylphenyl)imidazol-2-ylidene, Ixyl, respectively, afforded the complexes NbOCl2(Imes)2, 3, and NbOBr2(Ixyl)2, 4, in 50-60% yields. The reactions of 2b with NaOR, in tetrahydrofuran, gave NbOCl(OR) (R = Ph, 5; R = Me, 6) in about 60% yields. All the products were characterized by analytical and spectroscopic techniques; moreover DFT calculations were carried out in order to shed light on synthetic and structural features. Compounds 3 and 4, whose molecular structures have been ascertained by X-ray diffraction, represent very rare examples of crystallographically characterized niobium-NHC systems.

  14. Electrocatalytic Oxidation of Cellulose to Gluconate on Carbon Aerogel Supported Gold Nanoparticles Anode in Alkaline Medium

    Directory of Open Access Journals (Sweden)

    Hanshuang Xiao

    2015-12-01

    Full Text Available The development of high efficient and low energy consumption approaches for the transformation of cellulose is of high significance for a sustainable production of high value-added feedstocks. Herein, electrocatalytic oxidation technique was employed for the selective conversion of cellulose to gluconate in alkaline medium by using concentrated HNO3 pretreated carbon aerogel (CA supported Au nanoparticles as anode. Results show that a high gluconate yield of 67.8% and sum salts yield of 88.9% can be obtained after 18 h of electrolysis. The high conversion of cellulose and high selectivity to gluconate could be attributed to the good dissolution of cellulose in NaOH solution which promotes its hydrolysis, the surface oxidized CA support and Au nanoparticles catalyst which possesses high amount of active sites. Moreover, the bubbled air also plays important role in the enhancement of cellulose electrocatalytic conversion efficiency. Lastly, a probable mechanism for electrocatalytic oxidation of cellulose to gluconate in alkaline medium was also proposed.

  15. Pyrite oxidation in the presence of hematite and alumina: II. Effects on the cathodic and anodic half-cell reactions.

    Science.gov (United States)

    Tabelin, Carlito Baltazar; Veerawattananun, Suchol; Ito, Mayumi; Hiroyoshi, Naoki; Igarashi, Toshifumi

    2017-03-01

    The oxidative dissolution of pyrite is an important process in the redox recycling of iron (Fe) and is well-known for its role in the formation of acid mine drainage (AMD), which is considered as the most serious and widespread problem after the closure of mines and mineral processing operations. Because this process requires the movement of electrons, common metal oxides in nature that have either semiconducting (e.g., hematite) or insulating (e.g., alumina) properties may have strong effects on it. In this study, changes in the electrochemical behavior of pyrite in the presence of hematite and alumina were investigated. Results showed that the formation of surface-bound species directly influenced the anodic and cathodic half-cell reactions as well as the transfer of electrons between these sites. Pyrite pretreated in the air became anodically more reactive than that pretreated in oxygenated water, but the type of oxidizing media had little effect on the cathodic half-cell reaction. The presence of hematite and alumina during pretreatment also had strong effects on the electrochemical properties of pyrite. Chronoamperometry measurements suggest that hematite and alumina enhanced the anodic half-cell reaction but suppressed the cathodic half-cell reaction of pyrite oxidation. Increased anodic half-cell reaction in the presence of hematite could be attributed to electron "bridging" and catalytic effects of this mineral. In contrast, the effects of alumina on the anodic half-cell reaction were indirect and could be explained by the formation of Fe(3+)-oxyhydroxide surface species during pretreatment. Suppression of the cathodic half-cell reaction by both minerals was attributed to their "protective" effect on cathodic sites. Our results also point to the cathodic half-cell reaction as the rate determining-step of the overall oxidative dissolution process.

  16. Anodic oxides on a beta type Nb-Ti alloy and their characterization by electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Woldemedhin, Michael Teka; Hassel, Achim Walter [Max Planck Institut fuer Eisenforschung GmbH, Duesseldorf (Germany); Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University, Linz (Austria); Raabe, Dierk [Max Planck Institut fuer Eisenforschung GmbH, Duesseldorf (Germany)

    2010-04-15

    Anodic oxides were grown on the surface of an electropolished (Ti-30 at% Nb) beta-titanium ({beta}-Ti) alloy by cyclic voltammetry. The scan rate was 100 mV s{sup -1} between 0 and 8 V in increments of l V in an acetate buffer of pH 6.0. Electrochemical impedance spectroscopy was carried out right after each anodic oxide growth increment to study the electronic properties of the oxide/electrolyte interface in a wide frequency range from 100 kHz to 10 MHz with an AC perturbation voltage of 10 mV. A film formation factor of 2.4 nm V{sup -1} was found and a relative permittivity number (dielectric constant) of 42.4 was determined for the oxide film formed. Mott-Schottky analysis on a potentiostatically formed 7 nm thick oxide film was performed to assess the semiconducting properties of the mixed anodic oxide grown on the alloy. A flat band potential of -0.47 V (standard hydrogen electrode, SHE) was determined, connected to a donor density of 8.2 x 10{sup 17} cm{sup -3}. {beta}-Ti being highly isotropic in terms of mechanical properties should be superior to the stiffer {alpha}-Ti compound. Its application, however, requires a passivation behaviour comparable or better than {alpha}-Ti which in fact is found. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  17. Multi-electrolyte-step anodic aluminum oxide method for the fabrication of self-organized nanochannel arrays

    Science.gov (United States)

    2012-01-01

    Nanochannel arrays were fabricated by the self-organized multi-electrolyte-step anodic aluminum oxide [AAO] method in this study. The anodization conditions used in the multi-electrolyte-step AAO method included a phosphoric acid solution as the electrolyte and an applied high voltage. There was a change in the phosphoric acid by the oxalic acid solution as the electrolyte and the applied low voltage. This method was used to produce self-organized nanochannel arrays with good regularity and circularity, meaning less power loss and processing time than with the multi-step AAO method. PMID:22333268

  18. Insights of ibuprofen electro-oxidation on metal-oxide-coated Ti anodes: Kinetics, energy consumption and reaction mechanisms.

    Science.gov (United States)

    Wang, Chong; Yu, Yanxin; Yin, Lifeng; Niu, Junfeng; Hou, Li-An

    2016-11-01

    Electrochemical degradation of ibuprofen (IBP) was performed on three types of Ti-based metal oxide electrodes. The degradation of IBP followed pseudo-first-order kinetics and the electrochemical degradation rate constant (k) over Ti/SnO2-Sb/Ce-PbO2 (9.4 × 10(-2) min(-1)) was 2.0 and 1.7 times of the values over Ti/Ce-PbO2 (4.7 × 10(-2) min(-1)) and Ti/SnO2-Sb (5.6 × 10(-2) min(-1)), respectively. The removal of total organic carbon and the energy consumption per order for IBP degradation were 93.2% and 13.1 Wh L(-1), respectively, under the optimal conditions using Ti/SnO2-Sb/Ce-PbO2 anode. Six aromatic intermediate products of IBP were identified by ultra-high-performance liquid chromatography coupled with a quadrupole time-of-flight mass spectrometer. The electrochemical mineralization mechanism of IBP was proposed. It was supposed that OH radicals produced on the surface of anode attacked IBP to form hydroxylated IBP derivatives that were then followed by a series of hydroxylation, loss of isopropanol and isopropyl, decarboxylation and benzene ring cleavage processes to form simple linear carboxylic acids. By successive hydroxylation, these carboxylic acids were then oxidized to CO2 and H2O, achieving the complete mineralization of IBP.

  19. Highly Ordered Zinc Oxide Nanotubules Synthesized within the Anodic Aluminum Oxide Template

    Institute of Scientific and Technical Information of China (English)

    WANG; Zhen

    2001-01-01

    Zinc oxide (ZnO) is a wide-band-gap semiconductor, which has a broad range of applications, e.g., in pigment, rubber additives, gas sensors, varistors and transducers1. It has recently been demonstrated that nanophase zinc oxide can be used in photocells of the Gatzel type2, which results in improved current generation efficiency. The properties of high aspect ratios and small sizes of zinc oxide nanotubules or nanowires are expected to improve the luminescence efficiency of the electro-optical devices and the sensitivity of the chemical sensors3.  ……

  20. Highly Ordered Zinc Oxide Nanotubules Synthesized within the Anodic Aluminum Oxide Template

    Institute of Scientific and Technical Information of China (English)

    WANG Zhen; LI HuLin

    2001-01-01

    @@ Zinc oxide (ZnO) is a wide-band-gap semiconductor, which has a broad range of applications, e.g., in pigment, rubber additives, gas sensors, varistors and transducers1. It has recently been demonstrated that nanophase zinc oxide can be used in photocells of the Gatzel type2, which results in improved current generation efficiency. The properties of high aspect ratios and small sizes of zinc oxide nanotubules or nanowires are expected to improve the luminescence efficiency of the electro-optical devices and the sensitivity of the chemical sensors3.

  1. Carbon monoxide tolerant platinum electrocatalysts on niobium doped titania and carbon nanotube composite supports

    Science.gov (United States)

    Rigdon, William A.; Huang, Xinyu

    2014-12-01

    In the anode of electrochemical cells operating at low temperature, the hydrogen oxidation reaction is susceptible to poisoning from carbon monoxide (CO) which strongly adsorbs on platinum (Pt) catalysts and increases activation overpotential. Adsorbed CO is removed by oxidative processes such as electrochemical stripping, though cleaning can also cause corrosion. One approach to improve the tolerance of Pt is through alloying with less-noble metals, but the durability of alloyed electrocatalysts is a critical concern. Without sacrificing stability, tolerance can be improved by careful design of the support composition using metal oxides. The bifunctional mechanism is promoted at junctions of the catalyst and metal oxides used in the support. Stable metal oxides can also form strong interactions with catalysts, as is the case for platinum on titania (TiOx). In this study, niobium (Nb) serves as an electron donor dopant in titania. The transition metal oxides are joined to functionalized multi-wall carbon nanotube (CNT) supports in order to synthesize composite supports. Pt is then deposited to form electrocatalysts which are characterized before fabrication into anodes for tests as an electrochemical hydrogen pump. Comparisons are made between the control from Pt-CNT to Pt-TiOx-CNT and Pt-Ti0.9Nb0.1Ox-CNT in order to demonstrate advantages.

  2. A colorimetric sensor based on anodized aluminum oxide (AAO) substrate for the detection of nitroaromatics.

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y.; Wang, H. H.; Indacochea, J. E.; Wang, M. L. (Materials Science Division); (Northeastern Univ.); (Univ. of Illinois at Chicago)

    2011-12-15

    Simple and low cost colorimetric sensors for explosives detection were explored and developed. Anodized aluminum oxide (AAO) with large surface area through its porous structure and light background color was utilized as the substrate for colorimetric sensors. Fabricated thin AAO films with thickness less than {approx} 500 nm allowed us to observe interference colors which were used as the background color for colorimetric detection. AAO thin films with various thickness and pore-to-pore distance were prepared through anodizing aluminum foils at different voltages and times in dilute sulfuric acid. Various interference colors were observed on these samples due to their difference in structures. Accordingly, suitable anodization conditions that produce AAO samples with desired light background colors for optical applications were obtained. Thin film interference model was applied to analyze the UV-vis reflectance spectra and to estimate the thickness of the AAO membranes. We found that the thickness of produced AAO films increased linearly with anodization time in sulfuric acid. In addition, the growth rate was higher for AAO anodized using higher voltages. The thin film interference formulism was further validated with a well established layer by layer deposition technique. Coating poly(styrene sulfonate) sodium salt (PSS) and poly(allylamine hydrochloride) (PAH) layer by layer on AAO thin film consistently shifted its surface color toward red due to the increase in thickness. The red shift of UV-vis reflectance was correlated quantitatively to the number of layers been assembled. This sensitive red shift due to molecular attachment (increase in thickness) on AAO substrate was applied toward nitroaromatics detection. Aminopropyltrimethoxysilane (APTS) which can be attached onto AAO nanowells covalently through silanization and attract TNT molecules was coated and applied for TNT detection. UV-vis spectra of AAO with APTS shifted to the longer wavelength side due to

  3. Synergetic antibacterial activity of reduced graphene oxide and boron doped diamond anode in three dimensional electrochemical oxidation system

    Science.gov (United States)

    Qi, Xiujuan; Wang, Ting; Long, Yujiao; Ni, Jinren

    2015-05-01

    A 100% increment of antibacterial ability has been achieved due to significant synergic effects of boron-doped diamond (BDD) anode and reduced graphene oxide (rGO) coupled in a three dimensional electrochemical oxidation system. The rGO, greatly enhanced by BDD driven electric field, demonstrated strong antibacterial ability and even sustained its excellent performance during a reasonable period after complete power cut in the BDD-rGO system. Cell damage experiments and TEM observation confirmed much stronger membrane stress in the BDD-rGO system, due to the faster bacterial migration and charge transfer by the expanded electro field and current-carrying efficiency by quantum tunnel. Reciprocally the hydroxyl-radical production was eminently promoted with expanded area of electrodes and delayed recombination of the electron-hole pairs in presence of the rGO in the system. This implied a huge potential for practical disinfection with integration of the promising rGO and the advanced electrochemical oxidation systems.

  4. Structural characterization of niobium oxide thin films grown on SrTiO3 (111) and (La,Sr)(Al,Ta)O3 (111) substrates

    Science.gov (United States)

    Dhamdhere, Ajit R.; Hadamek, Tobias; Posadas, Agham B.; Demkov, Alexander A.; Smith, David J.

    2016-12-01

    Niobium oxide thin films have been grown by molecular beam epitaxy on SrTiO3 (STO) (111) and (La0.18Sr0.82)(Al0.59Ta0.41)O3 (LSAT) (111) substrates. Transmission electron microscopy (TEM) confirmed the formation of high quality films with coherent interfaces. Films grown with higher oxygen pressure on STO (111) resulted in a (110)-oriented NbO2 phase with a distorted rutile structure, which can be described as body-centered tetragonal. The a lattice parameter of NbO2 was determined to be ˜13.8 Å in good agreement with neutron diffraction results published in the literature. Films grown on LSAT (111) at lower oxygen pressure produced the NbO phase with a defective rock salt cubic structure. The NbO lattice parameter was determined to be a ≈ 4.26 Å. The film phase/structure identification from TEM was in good agreement with in situ x-ray photoelectron spectroscopy measurements that confirmed the dioxide and monoxide phases, respectively. The atomic structure of the NbO2/STO and NbO/LSAT interfaces was determined based on comparisons between high-resolution electron micrographs and image simulations.

  5. OPERATION OF SOLID OXIDE FUEL CELL ANODES WITH PRACTICAL HYDROCARBON FUELS

    Energy Technology Data Exchange (ETDEWEB)

    Scott A. Barnett; Jiang Liu; Yuanbo Lin

    2004-07-30

    This work was carried out to achieve a better understanding of how SOFC anodes work with real fuels. The motivation was to improve the fuel flexibility of SOFC anodes, thereby allowing simplification and cost reduction of SOFC power plants. The work was based on prior results indicating that Ni-YSZ anode-supported SOFCs can be operated directly on methane and natural gas, while SOFCs with novel anode compositions can work with higher hydrocarbons. While these results were promising, more work was clearly needed to establish the feasibility of these direct-hydrocarbon SOFCs. Basic information on hydrocarbon-anode reactions should be broadly useful because reformate fuel gas can contain residual hydrocarbons, especially methane. In the Phase I project, we have studied the reaction mechanisms of various hydrocarbons--including methane, natural gas, and higher hydrocarbons--on two kinds of Ni-containing anodes: conventional Ni-YSZ anodes and a novel ceramic-based anode composition that avoid problems with coking. The effect of sulfur impurities was also studied. The program was aimed both at achieving an understanding of the interactions between real fuels and SOFC anodes, and providing enough information to establish the feasibility of operating SOFC stacks directly on hydrocarbon fuels. A combination of techniques was used to provide insight into the hydrocarbon reactions at these anodes during SOFC operation. Differentially-pumped mass spectrometry was be used for product-gas analysis both with and without cell operation. Impedance spectroscopy was used in order to understand electrochemical rate-limiting steps. Open-circuit voltages measurements under a range of conditions was used to help determine anode electrochemical reactions. Life tests over a wide range of conditions were used to establish the conditions for stable operation of anode-supported SOFC stacks directly on methane. Redox cycling was carried out on ceramic-based anodes. Tests on sulfur tolerance of

  6. Three-Dimensional Crumpled Reduced Graphene Oxide/MoS2 Nanoflowers: A Stable Anode for Lithium-Ion Batteries.

    Science.gov (United States)

    Xiong, Fangyu; Cai, Zhengyang; Qu, Longbing; Zhang, Pengfei; Yuan, Zefang; Asare, Owusu Kwadwo; Xu, Wangwang; Lin, Chao; Mai, Liqiang

    2015-06-17

    Recently, layered transition-metal dichalcogenides (TMDs) have gained great attention for their analogous graphite structure and high theoretical capacity. However, it has suffered from rapid capacity fading. Herein, we present the crumpled reduced graphene oxide (RGO) decorated MoS2 nanoflowers on carbon fiber cloth. The three-dimensional framework of interconnected crumpled RGO and carbon fibers provides good electronic conductivity and facile strain release during electrochemical reaction, which is in favor of the cycling stability of MoS2. The crumpled RGO decorated MoS2 nanoflowers anode exhibits high specific capacity (1225 mAh/g) and excellent cycling performance (680 mAh/g after 250 cycles). Our results demonstrate that the three-dimensional crumpled RGO/MoS2 nanoflowers anode is one of the attractive anodes for lithium-ion batteries.

  7. Investigation of Metal Oxide/Carbon Nano Material as Anode for High Capacity Lithium-ion Cells

    Science.gov (United States)

    Wu, James Jianjun; Hong, Haiping

    2014-01-01

    NASA is developing high specific energy and high specific capacity lithium-ion battery (LIB) technology for future NASA missions. Current state-of-art LIBs have issues in terms of safety and thermal stability, and are reaching limits in specific energy capability based on the electrochemical materials selected. For example, the graphite anode has a limited capability to store Li since the theoretical capacity of graphite is 372 mAh/g. To achieve higher specific capacity and energy density, and to improve safety for current LIBs, alternative advanced anode, cathode, and electrolyte materials are pursued under the NASA Advanced Space Power System Project. In this study, the nanostructed metal oxide, such as Fe2O3 on carbon nanotubes (CNT) composite as an LIB anode has been investigated.

  8. Degradation behavior of anode-supported solid oxide fuel cell using LNF cathode as function of current load

    Energy Technology Data Exchange (ETDEWEB)

    Komatsu, Takeshi; Yoshida, Yoshiteru; Watanabe, Kimitaka; Chiba, Reiichi; Taguchi, Hiroaki; Orui, Himeko; Arai, Hajime [NTT Energy and Environment Systems Laboratories, Atsugi-shi, Kanagawa 243-0198 (Japan)

    2010-09-01

    We investigated the effect of current loading on the degradation behavior of an anode-supported solid oxide fuel cell (SOFC). The cell consisted of LaNi{sub 0.6}Fe{sub 0.4}O{sub 3} (LNF), alumina-doped scandia stabilized zirconia (SASZ), and a Ni-SASZ cermet as the cathode, electrolyte, and anode, respectively. The test was carried out at 1073 K with constant loads of 0.3, 1.0, 1.5, and 2.3 A cm{sup -2}. The degradation rate, defined by the voltage loss during a fixed period (about 1000 h), was faster at higher current densities. From an impedance analysis, the degradation depended mainly on increases in the cathodic resistance, while the anodic and ohmic resistances contributed very little. The cathode microstructures were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). (author)

  9. Anode gas recirculation for improving the performance and cost of a 5-kW solid oxide fuel cell system

    Science.gov (United States)

    Torii, Ryohei; Tachikawa, Yuya; Sasaki, Kazunari; Ito, Kohei

    2016-09-01

    Solid oxide fuel cells (SOFCs) have the potential to efficiently convert chemical energy into electricity and heat and are expected to be implemented in stationary combined heat and power (CHP) systems. This paper presents the heat balance analysis for a 5-kW medium-sized integrated SOFC system and the evaluation of the effect of anode gas recirculation on the system performance. The risk of carbon deposition on an SOFC anode due to anode gas recirculation is also assessed using the C-H-O diagram obtained from thermodynamic equilibrium calculations. These results suggest that a higher recirculation ratio increases net fuel utilization and improves the electrical efficiency of the SOFC system. Furthermore, cost simulation of the SOFC system and comparison with the cost of electricity supply by a power grid indicates that the capital cost is sufficiently low to popularize the SOFC system in terms of the total cost over one decade.

  10. Nanoporous palladium anode for direct ethanol solid oxide fuel cells with nanoscale proton-conducting ceramic electrolyte

    Science.gov (United States)

    Li, Yong; Wong, Lai Mun; Xie, Hanlin; Wang, Shijie; Su, Pei-Chen

    2017-02-01

    In this work, we demonstrate the operation of micro-solid oxide fuel cells (μ-SOFCs) with nanoscale proton-conducting Y-BaZrO3 (BZY) electrolyte to avoid the fuel crossover problem for direct ethanol fuel cells (DEFCs). The μ-SOFCs are operated with the direct utilisation of ethanol vapour as a fuel and Pd as anode at the temperature range of 300-400 °C. The nanoporous Pd anode is achieved by DC sputtering at high Ar pressure of 80 mTorr. The Pd-anode/BYZ-electrolyte/Pt-cathode cell show peak power densities of 72.4 mW/cm2 using hydrogen and 15.3 mW/cm2 using ethanol at 400 °C. No obvious carbon deposition is seen from XPS analysis after fuel cell test with ethanol fuel.

  11. Direct solid-sampling electrothermal atomic absorption spectrometry methods for the determination of silicon in oxides of niobium, titanium and zirconium

    Science.gov (United States)

    Dong, Huang Mao; Krivan, Viliam

    2001-09-01

    An electrothermal atomic absorption spectrometer with a transversely heated graphite tube and a solid sampling system based on the boat technique was used for the development of methods for direct determination of silicon in powdered niobium pentoxide, titanium dioxide and zirconium dioxide. In the analysis of niobium pentoxide, serious matrix-caused non-spectral interferences and background were avoided by conversion of the niobium pentoxide matrix into the thermally stable niobium carbide using a methane atmosphere during the pyrolysis stage. For all three materials, calibration procedures using aqueous standard solutions were developed. For titanium dioxide and zirconium dioxide, the accuracy was checked by comparison of the results with those of independent methods, whereby good agreement was achieved. Owing to the high applicable sample amount per atomization (3-15 mg) and almost complete freedom of interference from the blank, limits of detection at the 10-ng g -1 level were achieved.

  12. Novel Mg-Doped SrMoO3 Perovskites Designed as Anode Materials for Solid Oxide Fuel Cells

    Directory of Open Access Journals (Sweden)

    Vanessa Cascos

    2016-07-01

    Full Text Available SrMo1−xMxO3−δ (M = Fe and Cr, x = 0.1 and 0.2 oxides have been recently described as excellent anode materials for solid oxide fuel cells at intermediate temperatures (IT-SOFC with LSGM as the electrolyte. In this work, we have improved their properties by doping with aliovalent Mg ions at the B-site of the parent SrMoO3 perovskite. SrMo1−xMgxO3−δ (x = 0.1, 0.2 oxides have been prepared, characterized and tested as anode materials in single solid-oxide fuel cells, yielding output powers near 900 mW/cm−2 at 850 °C using pure H2 as fuel. We have studied its crystal structure with an “in situ” neutron power diffraction (NPD experiment at temperatures as high as 800 °C, emulating the working conditions of an SOFC. Adequately high oxygen deficiencies, observed by NPD, together with elevated disk-shaped anisotropic displacement factors suggest a high ionic conductivity at the working temperatures. Furthermore, thermal expansion measurements, chemical compatibility with the LSGM electrolyte, electronic conductivity and reversibility upon cycling in oxidizing-reducing atmospheres have been carried out to find out the correlation between the excellent performance as an anode and the structural features.

  13. Kinetics of the electrolytic Fe+2/Fe+3 oxidation on various anode materials

    Directory of Open Access Journals (Sweden)

    Cifuentes, L.

    2003-08-01

    Full Text Available The kinetics of the electrolytic Fe+2/Fe+3 oxidation, relevant to hydro-electrometallurgical processing, have been studied on lead, platinum, ruthenium oxide, iridium oxide and graphite anodes in ferrous sulfate-sulfuric acid solutions. The oxidation rate depends on ferrous sulfate concentration, solution temperature and degree of agitation. Potentiodynamic studies show that: a the highest oxidation rate is obtained on platinum; b lead is unsuitable as anodic material for the said reaction; c the remaining anode materials show a similar and satisfactory performance.

    Se ha estudiado la cinética de la oxidación electrolítica Fe+2/Fe+3 -relevante para el procesamiento hidroelectrometalúrgico- sobre plomo, platino, óxido de rutenio, óxido de iridio y grafito en soluciones de sulfato ferroso en ácido sulfúrico. La velocidad de oxidación depende de la concentración de sulfato ferroso, la temperatura de la solución y el grado de agitación. Estudios potenciodinámicos demuestran que: a las mayores velocidades de oxidación se obtienen sobre platino; b el plomo es inadecuado como material anódico para la reacción mencionada; c los materiales anódicos restantes exhiben un desempeño similar y satisfactorio.

  14. The effect of H2S on the performance of Ni-YSZ anodes in solid oxide fuel cells

    DEFF Research Database (Denmark)

    Rasmussen, Jens Foldager Bregnballe; Hagen, Anke

    2009-01-01

    Biomass-derived fuel, e.g. biogas, is a potential fuel for solid oxide fuel cells (SOFCs). At operating temperature (850 °C) reforming of the carbon-containing biogas takes place over the Ni-containing anode. However, impurities in the biogas, e.g. H2S, can poison both the reforming...... and the electrochemical activity of the anode. Tests of single anode-supported planar SOFCs were carried out in the presence of H2S under current load at 850 °C. The cell voltage dropped as we periodically added 2–100 ppm H2S to an H2-containing fuel in 24 h intervals, but it regenerated to the initial value after we...... turned off the H2S. Evaluation of the changes of the cell voltage suggests that saturation coverage was reached at approximately 40 ppm H2S. A front-like movement of S-poisoning over the anode was seen by monitoring the in-plane voltage in the anode. Furthermore, impedance spectra showed that mainly...

  15. Nonradical oxidation from electrochemical activation of peroxydisulfate at Ti/Pt anode: Efficiency, mechanism and influencing factors.

    Science.gov (United States)

    Song, Haoran; Yan, Linxia; Ma, Jun; Jiang, Jin; Cai, Guangqiang; Zhang, Wenjuan; Zhang, Zhongxiang; Zhang, Jiaming; Yang, Tao

    2017-03-21

    Electrochemical activation of peroxydisulfate (PDS) at Ti/Pt anode was systematically investigated for the first time in this work. The synergistic effect produced from the combination of electrolysis and the addition of PDS demonstrates that PDS can be activated at Ti/Pt anode. The selective oxidation towards carbamazepine (CBZ), sulfamethoxazole (SMX), propranolol (PPL), benzoic acid (BA) rather than atrazine (ATZ) and nitrobenzene (NB) was observed in electrochemical activation of PDS process. Moreover, addition of excess methanol or tert-butanol had negligible impact on CBZ (model compound) degradation, demonstrating that neither sulfate radical (SO4(-)) nor hydroxyl radical (HO) was produced in electrochemical activation of PDS process. Direct oxidation (PDS oxidation alone and electrolysis) and nonradical oxidation were responsible for the degradation of contaminants. The results of linear sweep voltammetry (LSV) and chronoamperometry suggest that electric discharge may integrate PDS molecule with anode surface into a unique transition state structure, which is responsible for the nonradical oxidation in electrochemical activation of PDS process. Adjustment of the solution pH from 1.0 to 7.0 had negligible effect on CBZ degradation. Increase of either PDS concentration or current density facilitated the degradation of CBZ. The presence of chloride ion (Cl(-)) significantly enhanced CBZ degradation, while addition of bicarbonate (HCO3(-)), phosphate (PO4(3-)) and humic acid (HA) all inhibited CBZ degradation with the order of HA > HCO3(-) > PO4(3-). The degradation products of CBZ and chlorinated products were also identified. Electrochemical activation of PDS at Ti/Pt anode may serve as a novel technology for selective oxidation of organic contaminants in water and soil.

  16. Boosting the local anodic oxidation of silicon through carbon nanofiber atomic force microscopy probes

    Directory of Open Access Journals (Sweden)

    Gemma Rius

    2015-01-01

    Full Text Available Many nanofabrication methods based on scanning probe microscopy have been developed during the last decades. Local anodic oxidation (LAO is one of such methods: Upon application of an electric field between tip and surface under ambient conditions, oxide patterning with nanometer-scale resolution can be performed with good control of dimensions and placement. LAO through the non-contact mode of atomic force microscopy (AFM has proven to yield a better resolution and tip preservation than the contact mode and it can be effectively performed in the dynamic mode of AFM. The tip plays a crucial role for the LAO-AFM, because it regulates the minimum feature size and the electric field. For instance, the feasibility of carbon nanotube (CNT-functionalized tips showed great promise for LAO-AFM, yet, the fabrication of CNT tips presents difficulties. Here, we explore the use of a carbon nanofiber (CNF as the tip apex of AFM probes for the application of LAO on silicon substrates in the AFM amplitude modulation dynamic mode of operation. We show the good performance of CNF-AFM probes in terms of resolution and reproducibility, as well as demonstration that the CNF apex provides enhanced conditions in terms of field-induced, chemical process efficiency.

  17. Boosting the local anodic oxidation of silicon through carbon nanofiber atomic force microscopy probes.

    Science.gov (United States)

    Rius, Gemma; Lorenzoni, Matteo; Matsui, Soichiro; Tanemura, Masaki; Perez-Murano, Francesc

    2015-01-01

    Many nanofabrication methods based on scanning probe microscopy have been developed during the last decades. Local anodic oxidation (LAO) is one of such methods: Upon application of an electric field between tip and surface under ambient conditions, oxide patterning with nanometer-scale resolution can be performed with good control of dimensions and placement. LAO through the non-contact mode of atomic force microscopy (AFM) has proven to yield a better resolution and tip preservation than the contact mode and it can be effectively performed in the dynamic mode of AFM. The tip plays a crucial role for the LAO-AFM, because it regulates the minimum feature size and the electric field. For instance, the feasibility of carbon nanotube (CNT)-functionalized tips showed great promise for LAO-AFM, yet, the fabrication of CNT tips presents difficulties. Here, we explore the use of a carbon nanofiber (CNF) as the tip apex of AFM probes for the application of LAO on silicon substrates in the AFM amplitude modulation dynamic mode of operation. We show the good performance of CNF-AFM probes in terms of resolution and reproducibility, as well as demonstration that the CNF apex provides enhanced conditions in terms of field-induced, chemical process efficiency.

  18. Mild oxidation treatment of graphite anode for Li-ion batteries

    Institute of Scientific and Technical Information of China (English)

    GUO Hua-jun; LI Xin-hai; WANG Zhi-xing; PENG Wen-jie; GUO Yong-xing

    2005-01-01

    The graphite was modified by mild oxidation, and the effects of modification temperature and soaking time on the characteristics of graphite were investigated. The structure and characteristics of the graphite were determined by X-ray diffraction, scanning electron microscopy, BET surface area, particle size analysis and electrochemical measurements. The results show that the modified graphite has a better-developed crystallite structure, larger average particle diameter, smaller surface area, and better electrochemical characteristics than the untrented graphite. The sample mild-oxidized at 600 ℃ for 3 h has the best electrochemical performances with a reversible capacity of 304.5 mA·h/g, a irreversible capacity of 66.4 mA·h/g, and a initial coulombic efficiency of 82.1%. The charge/discharge properties and a cycling stability of the prototype lithium ion batteries with modified graphite as anodes are improved. Its capacity retention ratio at the 200th cycle is enhanced from 66.75% to 90.15%.

  19. Fabrication of Orderly Copper Particle Arrays on a Multi-Electrolyte-Step Anodic Aluminum Oxide Template

    Directory of Open Access Journals (Sweden)

    Chun-Ko Chen

    2013-01-01

    Full Text Available A multi-electrolyte-step (MES anodic aluminum oxide (AAO method was used to achieve nanochannel arrays with good circularity and periodic structure. The nano-channel array fabrication process included immersion in a phosphoric acid solution with a 120–150 bias voltage. Bowl-shaped structures were then formed by removing the walls of the nano-channel arrays. The nano-channel arrays were grown from the bottom of the bowl structure in an oxalic solution using a 50 V bias voltage. A comparison of this new MES process with the one-step and five-step AAO process showed a 50% improvement in the circularity over the one-step process. The standard deviation of the average period in the MES array was 25 nm which is less than that of one-step process. This MES method also took 1/4 of the growing time of the five-step process. The orderliness of the nano-channel arrays for the five-step and MES process was similar. Finally, Cu nanoparticle arrays with a 200 nm period were grown using an electroplating process inside the MES nano-channel arrays on fluorine doped tin oxide glass. Stronger surface plasmon resonance absorption from 550 nm to 750 nm was achieved with the MES process than was possible with the one-step process.

  20. Molybdenum oxide nanosheets prepared by an anodizing-exfoliation process and observation of photochromic properties

    Science.gov (United States)

    Ranjbar, M.; Delalat, F.; Salamati, H.

    2017-02-01

    Anodizing-exfoliation of molybdenum foil was performed in 0.02 M HCl electrolyte at 30 V. In this process, the electrolyte rapidly turned into a blue colloidal solution of molybdenum oxide nanosheets with fragmented edges observed on transmission electron microscope (TEM). X-ray Diffraction (XRD) pattern of particles was free of peak while annealing at a temperature range of 100-500 °C led to formation of monoclinic (for T 300 °C) phases of MoO3. Moreover, addition of PdCl2 (0.2 g/l) salt solution caused a spontaneous bleaching of the initial blue colloid. Annealing of powders extracted from these bleached solutions with different PdCl2 concentrations at 500 °C led to a preferential growth of (0k0) orientation. X-ray photoelectron spectroscopy (XPS) revealed that the blue nanosheets solution contains mainly Mo5+ with slightly Mo6+ oxidation states and each of annealing or salt bleaching procedures can entirely convert Mo5+ to Mo6+. When the bleached solutions was exposed to KrF laser beam (λ = 248 nm) a strong photochromic coloration with a deep blue color was occurred. Regardless of Pd:Mo ratio, the primary and laser irradiated solutions showed analogues optical absorption bands in the 1-3 nm photon energy range while the photochromic process led to a broader absorption band.

  1. H2 and CO oxidation process at the three-phase boundary of Cu-ceria cermet anode for solid oxide fuel cell

    Science.gov (United States)

    Zheng, Minghao; Wang, Shuang; Li, Mei; Xia, Changrong

    2017-03-01

    Cu-ceria cermets have been widely investigated as the anode materials for solid oxide fuel cells (SOFCs) that operated with hydrocarbon fuels. However, the anode reaction processes are not clear yet, especially those at the ceria-Cu-gas three phase boundary (3 PB). This work investigates samaria-doped ceria (SDC)-Cu-gas 3 PB reaction kinetics for the oxidation of H2 and CO, the products from hydrocarbons via external and internal reforming. Electrochemical conductivity relaxation measurement demonstrates that Cu is a synergistic catalyst that can significantly increase the reaction rate. The reaction at 3 PB contributes 81.3/66.8% of H2/CO oxidation when 5.4% SDC surface is covered with Cu particles. Combining with AC impedance analysis, elementary steps are proposed for the reaction at 3 PB. Water vapor combining to oxygen vacancy and carbon monoxide transforming to carbonate are the rate-determining steps for the oxidation of H2 and CO, respectively. Cu-SDC has shown much higher catalytic activity, i.e. about fivefold reaction rate, for the oxidation of CO than H2. In addition, Cu-SDC electrodes exhibit lower interfacial polarization resistance and lower activation energy for the electrochemical oxidation of CO than H2. Consequently, CO is easier to be oxidized than H2 when the Cu-ceria anode is fueled with syngas, the reforming product from hydrocarbons.

  2. Effect of sodium tartrate concentrations on morphology and characteristics of anodic oxide film on titanium alloy Ti–10V–2Fe–3Al

    Directory of Open Access Journals (Sweden)

    Ma Kun

    2016-08-01

    Full Text Available The effect of sodium tartrate concentrations on morphology and characteristics of anodic oxide film on titanium alloy was investigated. The alloy substrates were anodized in different concentration solutions of sodium tartrate with the addition of PTFE emulsion and their morphology and characteristics were analyzed. The anodic oxide film presented a uniform petaloid drums and micro-cracks morphology. Additionally, micro-cracks dramatically swelled with the increase of the tartrate concentrations. The thickness of the anodic oxide film increased with the concentrations until the concentration reached 15 g/L. The results of Raman analysis illustrate that all samples have similarity in the crystal structure, consisting of mainly amorphous TiO2, some anatase TiO2 and a small amount of rutile TiO2. And the ratios of anatase TiO2 and rutile TiO2 increase with the concentrations until it reaches 15 g/L. Furthermore, the intensity of the peaks increases with enhanced concentrations until the concentration reaches 15 g/L. The corrosion resistance of the anodic oxide film is increased by the sodium tartrate with higher concentrations before 15 g/L. The coefficient of friction of the anodic oxide film reduces with the concentrations until the concentration reaches 15 g/L, then the coefficient of friction of the anodic oxide film increases with the concentrations.

  3. Mineralization of the recalcitrant oxalic and oxamic acids by electrochemical advanced oxidation processes using a boron-doped diamond anode.

    Science.gov (United States)

    Garcia-Segura, Sergi; Brillas, Enric

    2011-04-01

    Oxalic and oxamic acids are the ultimate and more persistent by-products of the degradation of N-aromatics by electrochemical advanced oxidation processes (EAOPs). In this paper, the kinetics and oxidative paths of these acids have been studied for several EAOPs using a boron-doped diamond (BDD) anode and a stainless steel or an air-diffusion cathode. Anodic oxidation (AO-BDD) in the presence of Fe(2+) (AO-BDD-Fe(2+)) and under UVA irradiation (AO-BDD-Fe(2+)-UVA), along with electro-Fenton (EF-BDD), was tested. The oxidation of both acids and their iron complexes on BDD was clarified by cyclic voltammetry. AO-BDD allowed the overall mineralization of oxalic acid, but oxamic acid was removed much more slowly. Each acid underwent a similar decay in AO-BDD-Fe(2+) and EF-BDD, as expected if its iron complexes were not attacked by hydroxyl radicals in the bulk. The faster and total mineralization of both acids was achieved in AO-BDD-Fe(2+)-UVA due to the high photoactivity of their Fe(III) complexes that were continuously regenerated by oxidation of their Fe(II) complexes. Oxamic acid always released a larger proportion of NH(4)(+) than NO(3)(-) ion, as well as volatile NO(x) species. Both acids were independently oxidized at the anode in AO-BDD, but in AO-BDD-Fe(2+)-UVA oxamic acid was more slowly degraded as its content decreased, without significant effect on oxalic acid decay. The increase in current density enhanced the oxidation power of the latter method, with loss of efficiency. High Fe(2+) contents inhibited the oxidation of Fe(II) complexes by the competitive oxidation of Fe(2+) to Fe(3+). Low current densities and Fe(2+) contents are preferable to remove more efficiently these acids by the most potent AO-BDD-Fe(2+)-UVA method.

  4. Effect of niobium alloying level on the oxidation behavior of titanium aluminides at 850°C

    Science.gov (United States)

    Banu, Alexandra; Marcu, Maria; Petrescu, Simona; Ionescu, Nicolae; Paraschiv, Alexandru

    2016-12-01

    This work addresses the alloying of titanium aluminides used in aircraft engine applications and automobiles. The oxidation resistance behavior of two titanium aluminides of α2 + γ(Ti3Al + TiAl) and orthorhombic Ti2NbAl, recognized as candidates for high-temperature applications, was investigated by exposure of the alloys for 100 h in air. Thus, oxidation resistance was expressed as the mass gain rate, whereas surface aspects were analyzed using scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy, and the type of oxidation products was analyzed by X-ray diffraction and Raman spectroscopy. The orthorhombic Ti2NbAl alloy was embrittled, and pores and microcracks were formed as a result of oxygen diffusion through the external oxide layer formed during thermal oxidation for 100 h.

  5. Effect of niobium alloying level on the oxidation behavior of titanium aluminides at 850°C

    Institute of Scientific and Technical Information of China (English)

    Alexandra Banu; Maria Marcu; Simona Petrescu; Nicolae Ionescu; Alexandru Paraschiv

    2016-01-01

    This work addresses the alloying of titanium aluminides used in aircraft engine applications and automobiles. The oxidation resis-tance behavior of two titanium aluminides ofα2+γ (Ti3Al + TiAl) and orthorhombic Ti2NbAl, recognized as candidates for high-temperature applications, was investigated by exposure of the alloys for 100 h in air. Thus, oxidation resistance was expressed as the mass gain rate, whereas surface aspects were analyzed using scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy, and the type of oxidation products was analyzed by X-ray diffraction and Raman spectroscopy. The orthorhombic Ti2NbAl alloy was embrittled, and pores and microcracks were formed as a result of oxygen diffusion through the external oxide layer formed during thermal oxidation for 100 h.

  6. Anode regeneration following carbon depositions in an industrial-sized anode supported solid oxide fuel cell operating on synthetic diesel reformate

    Science.gov (United States)

    Subotić, Vanja; Schluckner, Christoph; Mathe, Jörg; Rechberger, Jürgen; Schroettner, Hartmuth; Hochenauer, Christoph

    2015-11-01

    Carbon deposition is a primary concern during operation of solid oxide fuel cells (SOFCs) fueled with carbon-containing fuels. It leads to cell degradation and thus reduces SOFC sustained operation and durability. This paper reports on an experimental investigation of carbon formation on the nickel/yttria-stabilized zirconia (Ni/YSZ) anode of an anode-supported SOFC and its regeneration. The cell was fueled with a synthetically produced diesel reformate to investigate and simulate the cell behavior under real operating conditions. For this purpose the cell was operated under load to determine the critical operating time. Rapid carbon generation, such as at open circuit voltage (OCV), can be prevented when the cell is under load. Carbon depositions were detected using scanning electron microscopy (SEM) and further analyzed by Raman spectroscopy. Industrial-size cells suitable for commercial applications were studied. This study proves the reversibility of carbon formation and the reproducibility of the regeneration process. It shows that carbon formations can be recognized and effectively, fully and cell-protecting regenerated. It indicates the excellent possibility of using SOFCs in the automotive industry as an auxiliary power unit (APU) or combined power-heat unit, operated with diesel reformate, without danger from cell degradation caused by carbon-containing fuels.

  7. The fabrication of high sensitivity gold nanorod H2S gas sensors utilizing the highly uniform anodic aluminum oxide template

    Science.gov (United States)

    Li, Chien-Yu; Li, Ciao-Yu; Wu, You-Lin; Hsu, Chung-Ping; Lee, Ming-Ching; Houng, Mau-Phon

    2016-12-01

    Gold nanorod were fabricated using anodic alumina oxide template for H2S gas detection. The nanorod gas sensor exhibits high surface density and contact area, which can increase detection sensitivity. The anodic alumina oxide template contains an array of pores, with a width of 70 nm and a length of 27 μ m . Au nanorod were obtained through electro-deposition under a pulse bias of -1 V. The resistance of the Au nanorod was recorded upon exposure to various concentrations of H2S. The resistance could be attributed to the high electron affinity between sulfide and Au nanorod. Au-sulfide bonds provide strong bonding, which could alter the conductivity of the sensor. The gas sensor exhibits high sensitivity and short response time for H2S detection at room temperature.

  8. The fabrication of high sensitivity gold nanorod H2S gas sensors utilizing the highly uniform anodic aluminum oxide template

    Directory of Open Access Journals (Sweden)

    Chien-Yu Li

    2016-12-01

    Full Text Available Gold nanorod were fabricated using anodic alumina oxide template for H2S gas detection. The nanorod gas sensor exhibits high surface density and contact area, which can increase detection sensitivity. The anodic alumina oxide template contains an array of pores, with a width of 70 nm and a length of 27μm. Au nanorod were obtained through electro-deposition under a pulse bias of −1 V. The resistance of the Au nanorod was recorded upon exposure to various concentrations of H2S. The resistance could be attributed to the high electron affinity between sulfide and Au nanorod. Au–sulfide bonds provide strong bonding, which could alter the conductivity of the sensor. The gas sensor exhibits high sensitivity and short response time for H2S detection at room temperature.

  9. Synthesis of ozone from air via a polymer-electrolyte-membrane cell with a doped tin oxide anode

    OpenAIRE

    Wang, YH; Cheng, S; Chan, KY

    2006-01-01

    The generation of ozone from air using an electrochemical cell consisting of an air cathode, a polymer-electrolyte-membrane (PEM), and a doped tin oxide anode is reported. This synthesis is environmentally friendly compared to the conventional high-voltage corona discharge process since NOx formation is eliminated; a higher ozone concentration is generated; and lower energy may be required. © The Royal Society of Chemistry 2006.

  10. Novel synthesis of tin oxide/graphene aerogel nanocomposites as anode materials for lithium ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Zheyu [College of Material Science and Engineering, Liaoning Technical University, Fuxin 123000 (China); Energy & Materials Engineering Centre, College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387 (China); Li, Xifei, E-mail: xfli2011@hotmail.com [Energy & Materials Engineering Centre, College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387 (China); Tai, Limin, E-mail: tailimin@163.com [College of Material Science and Engineering, Liaoning Technical University, Fuxin 123000 (China); Song, Haoze; Zhang, Yiyan; Yan, Bo; Fan, Linlin; Shan, Hui [Energy & Materials Engineering Centre, College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387 (China); Li, Dejun, E-mail: dli1961@126.com [Energy & Materials Engineering Centre, College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387 (China)

    2015-10-15

    A novel method of mechanical exfoliation followed by hydrothermal approach was proposed to synthesize the tin oxide/graphene aerogels (SnO{sub 2}/GAs) nanocomposites. Homogeneous distribution of SnO{sub 2} nanocrystals on GAs was confirmed by SEM, XRD and TEM characterization. It was found that optimized exfoliation of the SnS{sub 2} is the key factor to obtain high electrochemical lithiation/delithiation performance of the anodes. The as-prepared SnO{sub 2}/GA nanocomposites exhibited high reversible capacity (up to 1086.7 mAh g{sup −1} after 100 cycles) and excellent cycling stability. The improved rate capability was also obtained, for instance, the reversible capacity at a current density of 800 mA g{sup −1} is over 447.9 mAh g{sup −1}, and then recovered to as high as 784.4 mAh g{sup −1} at a current density of 100 mA g{sup −1}. - Highlights: • A novel approach was employed to synthesize the SnO{sub 2}/GA nanocomposites. • The designed SnO{sub 2}/GAs exhibited high reversible capacity and excellent cycling stability. • The volume change challenge of SnO{sub 2} was markedly alleviated by the GA matrix. • The novel synthesis method can be extended for other materials in lithium ion batteries.

  11. Nanowires: properties, applications and synthesis via porous anodic aluminium oxide template

    Indian Academy of Sciences (India)

    Jaya Sarkar; Gobinda Gopal Khan; A Basumallick

    2007-06-01

    Quasi one-dimensional nanowires possess unique electrical, electronic, thermoelectrical, optical, magnetic and chemical properties, which are different from that of their parent counterpart. The physical properties of nanowires are influenced by the morphology of the nanowires, diameter dependent band gap, carrier density of states etc. Nanowires hold lot of promises for different applications. Basic electronic devices like junction diodes, transistors, FETs and logic gates can be fabricated by using semiconductor and superlattice nanowires. Thermoelectric cooling system can be fabricated by using metallic nanowires. Semiconductor nanowire junctions can be used for different opto-electronic applications. Moreover, periodic arrays of magnetic nanowires hold high potential for recording media application. Nanowires are also potential candidates for sensor and bio-medical applications. In the present article, the physical and chemical properties of nanowires along with their probable applications in different fields have been reviewed in detail. The review also includes highlights of the synthesis of nanowires via porous anodic aluminium oxide template since the technique is simple, cost-effective and a low temperature technique.

  12. Role of Iron Anode Oxidation on Transformation of Chromium by Electrolysis

    Science.gov (United States)

    Sarahney, Hussam; Mao, Xuhui; Alshawabkeh, Akram N.

    2012-01-01

    The potential for chemical reduction of hexavalent chromium Cr(VI) in contaminated water and formation of a stable precipitate by Zero Valent Iron (ZVI) anode electrolysis is evaluated in separated electrodes system. Oxidation of iron electrodes produces ferrous ions causing the development of a reducing environment in the anolyte, chemical reduction of Cr(VI) to Cr(III) and formation of stable iron-chromium precipitates. Cr(VI) transformation rates are dependent on the applied electric current density. Increasing the electric current increases the transformation rates; however, the process is more efficient under lower volumetric current density (for example 1.5 mA L−1 in this study). The transformation follows a zero order rate that is dependent on the electric current density. Cr(VI) transformation occurs in the anolyte when the electrodes are separated as well as when the electrolytes (anolyte/catholyte) are mixed, as used in electrocoagulation. The study shows that the transformation occurs in the anolyte as a result of ferrous ion formation and the product is a stable Fe15Cr5(OH)60 precipitate. PMID:23284182

  13. Role of Iron Anode Oxidation on Transformation of Chromium by Electrolysis.

    Science.gov (United States)

    Sarahney, Hussam; Mao, Xuhui; Alshawabkeh, Akram N

    2012-12-30

    The potential for chemical reduction of hexavalent chromium Cr(VI) in contaminated water and formation of a stable precipitate by Zero Valent Iron (ZVI) anode electrolysis is evaluated in separated electrodes system. Oxidation of iron electrodes produces ferrous ions causing the development of a reducing environment in the anolyte, chemical reduction of Cr(VI) to Cr(III) and formation of stable iron-chromium precipitates. Cr(VI) transformation rates are dependent on the applied electric current density. Increasing the electric current increases the transformation rates; however, the process is more efficient under lower volumetric current density (for example 1.5 mA L(-1) in this study). The transformation follows a zero order rate that is dependent on the electric current density. Cr(VI) transformation occurs in the anolyte when the electrodes are separated as well as when the electrolytes (anolyte/catholyte) are mixed, as used in electrocoagulation. The study shows that the transformation occurs in the anolyte as a result of ferrous ion formation and the product is a stable Fe(15)Cr(5)(OH)(60) precipitate.

  14. Electrochemical Fabrication of Pd-Ag Alloy Nanowire Arrays in Anodic Alumina Oxide Template

    Institute of Scientific and Technical Information of China (English)

    Erhong YUE; Gang YU; Yuejun OUYANG; Baicheng WENG; Weiwei SI; Liyuan YE

    2008-01-01

    The synthesis of Pd-Ag alloy nanowires in nanopores of porous anodic aluminum oxide (AAO) template by electrochemical deposition technique was reported.Pd-Ag alloy nanowires with 16%-25% Ag content are expected to serve as candidates of useful nanomaterials for the hydrogen sensors.Scanning electron microscopy (SEM) and energy dispersed X-ray spectroscopy (EDX) were employed to characterize the morphologies and compositions of the Pd-Ag nanowires.X-ray diffraction (XRD) was used to characterize the phase properties of the Pd-Ag nanowires.Pd-Ag alloy nanowire arrays with 17.28%-23.76% Ag content have been successfully fabricated by applying potentials ranging from -0.8 to -1.0 V (vs SCE).The sizes of the alloy nanowires are in agreement with the diameter of AAO nanopores.The underpotential deposition of Ag+ on Pd and Au plays an important role in producing an exceptionally high Ag content in the alloy.Alloy compositions can still be controlled by adjusting the ion concentration ratio of Pd2+ and Ag+ and the electrodeposition processes.XRD shows that nanowires obtained are in the form of alloy of Pd and Ag.

  15. Sorption of hydrophilic dyes on anodic aluminium oxide films and application to pH sensing.

    Science.gov (United States)

    Silina, Yuliya E; Kuchmenko, Tatyana A; Volmer, Dietrich A

    2015-02-07

    The sorption of selected hydrophilic pH-sensitive dyes (bromophenol blue, bromothymol blue, bromocresol purple, alizarin red, methyl orange, congo red, rhodamine 6G) on films of anodized aluminium oxide (AAO) was investigated in this study. Depth and pore structure of the AAO channels were adjusted by changing electrolysis time and current density during treatment of aluminium foil in oxalic acid, sulfosalycilic acid and sulfuric acid at concentration levels between 0.2 and 0.6 M. The dyes were immobilized on the AAO surface by direct saturation of the films in dye solutions. It was shown by scanning electron microscopy and X-ray spectral analysis that the dyes penetrated into the AAO channels by more than 1.5 μm, even at static saturation conditions. The anionic dyes linked to the porous AAO surface exhibited differential shifts of the UV absorption bands in their acidic/basic forms. By combining several dyes, the films have an application range between pH = 0.5-9 in aqueous media. The dye-modified AAO film was a simple, portable, inexpensive and reusable pH sensor with very fast response time and clear colour transitions.

  16. Anodic oxidation of textile dyehouse effluents on boron-doped diamond electrode

    Energy Technology Data Exchange (ETDEWEB)

    Tsantaki, Eleni; Velegraki, Theodora; Katsaounis, Alexandros [Department of Environmental Engineering, Technical University of Crete, Polytechneioupolis, GR-73100 Chania (Greece); Mantzavinos, Dionissios, E-mail: mantzavi@mred.tuc.gr [Department of Environmental Engineering, Technical University of Crete, Polytechneioupolis, GR-73100 Chania (Greece)

    2012-03-15

    The electrochemical oxidation of textile effluents over a boron-doped diamond anode was investigated in the present study. Experiments were conducted with a multi-component synthetic solution containing seventeen dyes and other auxiliary inorganics, as well as an actual effluent from a textile dyeing process. The effect of varying operating parameters, such as current density (4-50 mA/cm{sup 2}), electrolyte concentration (0.1-0.5 M HClO{sub 4}), initial solution pH (1-12.3) and temperature (22-43 Degree-Sign C), on process efficiency was investigated following changes in total organic carbon (TOC), chemical oxygen demand (COD) and color. Complete decolorization accompanied by significant mineralization (up to 85% depending on the conditions) could be achieved after 180 min of treatment. Performance was improved at higher electrolyte concentrations and lower pH values, while the effect of temperature was marginal. Energy consumption per unit mass of COD removed was favored at lower current densities, since energy was unnecessarily wasted to side reactions at higher densities.

  17. Liquid crystal alignment in nanoporous anodic aluminum oxide layer for LCD panel applications.

    Science.gov (United States)

    Hong, Chitsung; Tang, Tsung-Ta; Hung, Chi-Yu; Pan, Ru-Pin; Fang, Weileun

    2010-07-16

    This paper reports the implementation and integration of a self-assembled nanoporous anodic aluminum oxide (np-AAO) film and liquid crystal (LC) on an ITO-glass substrate for liquid crystal display (LCD) panel applications. An np-AAO layer with a nanopore array acts as the vertical alignment layer to easily and uniformly align the LC molecules. Moreover, the np-AAO nanoalignment layer provides outstanding material properties, such as being inorganic with good transmittance, and colorless on ITO-glass substrates. In this application, an LCD panel, with the LC on the np-AAO nanoalignment layer, is successfully implemented on an ITO-glass substrate, and its performance is demonstrated. The measurements show that the LCD panel, consisting of an ITO-glass substrate and an np-AAO layer, has a transmittance of 60-80%. In addition, the LCD panel switches from a black state to a bright state at 3 V(rms), with a response time of 62.5 ms. In summary, this paper demonstrates the alignment of LC on an np-AAO layer for LCD applications.

  18. Electrodeposited porous metal oxide films with interconnected nanoparticles applied as anode of lithium ion battery

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Anguo, E-mail: hixiaoanguo@126.com; Zhou, Shibiao; Zuo, Chenggang; Zhuan, Yongbing; Ding, Xiang

    2014-12-15

    Highlights: • Highly porous NiO film is prepared by a co-electrodeposition method. • Porous NiO film is composed of interconnected nanoparticles. • Porous structure is favorable for fast ion/electron transfer. • Porous NiO film shows good lithium ion storage properties. - Abstract: Controllable synthesis of porous metal oxide films is highly desirable for high-performance electrochemical devices. In this work, a highly porous NiO film composed of interconnected nanoparticles is prepared by a simple co-electrodeposition method. The nanoparticles in the NiO film have a size ranging from 30 to 100 nm and construct large-quantity pores of 20–120 nm. As an anode material for lithium ion batteries, the highly porous NiO film electrode delivers a high discharge capacity of 700 mA h g{sup −1} at 0.2 C, as well as good high-rate performance. After 100 cycles at 0.2 C, a specific capacitance of 517 mA h g{sup −1} is attained. The good electrochemical performance is attributed to the interconnected porous structure, which facilitates the diffusion of ion and electron, and provides large reaction surface area leading to improved performance.

  19. Electrodeposition of photocatalytic TiO2 film on surface of alumina prepared by anodic oxidation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xin-yu; CHEN Tie-qun

    2004-01-01

    A new electrochemical method to prepare photocatalytic TiO2 thin film was developed, by which the TiO2 was electrodeposited on surface of alumina by AC electrolysis in solution consisting of K2 [TiO(C2O4 )2] and C2H2O4. The deposited TiO2 thin film was primarily characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and energy dispersive spectrum (EDS) methods. The photocatalytic properties of this film were also studied by the photocatalytic degradation of methyl orange. The results show that the TiO2 film electrodeposited by this method is mainly in amorphous and with a little crystalline component mixed anatase and rutile. The surface of the alumina prepared by anodic oxidation is porous and the TiO2 electrodeposited on it is scattered and incompact. TiO2 thin film fixed on the surface of alumina shows photocatalytic activity to the degradation of methyl orange.

  20. Electrically conducting polymer nanostructures confined in anodized aluminum oxide templates (AAO

    Directory of Open Access Journals (Sweden)

    I. Blaszczyk-Lezak

    2016-03-01

    Full Text Available Intrinsically or extrinsically conducting polymers are considered good candidates for replacement of metals in specific applications. In order to further expand their applications, it seems necessary to examine the influence of confinement effects on the electric properties of nanostructured conducting polymers in comparison to the bulk. The present study reports a novel way to fabricate and characterize high quality and controllable one-dimensional (1D polymer nanostructures with promising electrical properties, with the aid of two examples polyaniline (PANI and poly(vinylidene fluoride with multiwall carbon nanotubes (PVDF-MWCNT as representative of intrinsically and extrinsically conducting polymers, respectively. In this work, porous anodic aluminum oxide (AAO templates have been used both as a nanoreactor to synthesize 1D PANI nanostructures by polymerization of the ANI monomer and as a nanomold to prepare 1D PVDFMWCNT nanorods by melt infiltration of the precursor PVDF-MWCNT film. The obtained polymer nanostructures were morphologically and chemically characterized by SEM and Confocal Raman Spectroscopy, respectively, and the electrical properties determined by Broadband Dielectric Spectroscopy (BDS in a non-destructive way. SEM study allowed to establish the final nanostructure of PANI and PVDF-MWCNT and confirmed, in both cases, the well-aligned and uniform rodlike polymer nanostructures. Confocal Raman Microscopy has been performed to study the formation of the conducting emeraldine salt of PANI through all the length of AAO nanocavities. Finally, the electrical conductivity of both types of polymer nanostructures was easily evaluated by means of Dielectric Spectroscopy.

  1. Anodic deposition of colloidal iridium oxide thin films from hexahydroxyiridate(IV) solutions.

    Science.gov (United States)

    Zhao, Yixin; Vargas-Barbosa, Nella M; Hernandez-Pagan, Emil A; Mallouk, Thomas E

    2011-07-18

    A facile, in-situ deposition route to stable iridium oxide (IrO(x)·nH(2)O) nanoparticle thin films from [Ir(OH)(6)](2-) solutions is reported. The [Ir(OH)(6)](2-) solution, made by alkaline hydrolysis of [IrCl(6)](2-), is colorless and stable near neutral pH, and forms blue IrO(x)·nH(2)O nanoparticle suspensions once it is adjusted to acidic or basic conditions. IrO(x)·nH(2)O nanoparticle thin films are grown anodically on glassy carbon, fluorine-doped tin oxide, and gold electrodes by electrolyzing [Ir(OH)(6)](2-) solutions at +1.0-1.3 V versus Ag/AgCl. The thickness of the IrO(x)·nH(2)O films can be controlled by varying the concentration of [Ir(OH)(6)](2-) , the deposition potential, and/or the deposition time. These thin films are stable between pH 1 and 13 and have the lowest overpotential (η) for the oxygen evolution reaction (OER) of any yet reported. Near neutral pH, the Tafel slope for the OER at a IrO(x)·nH(2)O film/Au rotating disk electrode was 37-39 mV per decade. The exchange current density for the OER was 4-8 × 10(-10) A cm(-2) at a 4 mC cm(-2) coverage of electroactive Ir.

  2. Niobium based coatings for dental implants

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, G., E-mail: enggiova@hotmail.com [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior s/n, CU, Mexico D.F. 04510 (Mexico); Facultad de Quimica, Departamento de Ingenieria Quimica, Universidad Nacional Autonoma de Mexico, Mexico D.F. 04510 (Mexico); Rodil, S.E. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior s/n, CU, Mexico D.F. 04510 (Mexico); Arzate, H. [Laboratorio de Biologia Celular y Molecular, Facultad de Odontologia, Universidad Nacional Autonoma de Mexico, CU, Mexico D.F. 04510 (Mexico); Muhl, S. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior s/n, CU, Mexico D.F. 04510 (Mexico); Olaya, J.J. [Unidad de Materiales, Departamento de Ingenieria Mecanica y Mecatronica, Universidad Nacional de Colombia, Cra. 30 45-03 Bogota (Colombia)

    2011-01-15

    Niobium based thin films were deposited on stainless steel (SS) substrates to evaluate them as possible biocompatible surfaces that might improve the biocompatibility and extend the life time of stainless steel dental implants. Niobium nitride and niobium oxide thin films were deposited by reactive unbalanced magnetron sputtering under standard deposition conditions without substrate bias or heating. The biocompatibility of the surfaces was evaluated by testing the cellular adhesion and viability/proliferation of human cementoblasts during different culture times, up to 7 days. The response of the films was compared to the bare substrate and pieces of Ti6Al4V; the most commonly used implant material for orthopedics and osteo-synthesis applications. The physicochemical properties of the films were evaluated by different means; X-ray diffraction, Rutherford backscattering spectroscopy and contact angle measurements. The results suggested that the niobium oxide films were amorphous and of stoichiometric Nb{sub 2}O{sub 5} (a-Nb{sub 2}O{sub 5}), while the niobium nitride films were crystalline in the FCC phase (c-NbN) and were also stoichiometric with an Nb to N ratio of one. The biological evaluation showed that the biocompatibility of the SS could be improved by any of the two films, but neither was better than the Ti6Al4V alloy. On the other hand, comparing the two films, the c-NbN seemed to be a better surface than the oxide in terms of the adhesion and proliferation of human cemetoblasts.

  3. Effects of Anodic Voltages on Microstructure and Properties of Plasma Electrolytic Oxidation Coatings on Biomedical NiTi Alloy

    Institute of Scientific and Technical Information of China (English)

    Jilin Xu; Fu Liu; Junming Luo; Liancheng Zhao

    2013-01-01

    Plasma electrolytic oxidation (PEO) coatings,formed under various anodic voltages (320-440 V) on biomedical NiTi alloy,are mainly composed of γ-Al2O3 crystal phase.The evolution of discharging sparks during the PEO process under different anodic voltages was observed.The surface and cross-sectional morphologies,composition,bonding strength,wear resistance and corrosion resistance of the coatings were investigated by scanning electron microscopy (SEM),thin-film X-ray diffraction (TF-XRD),energy dispersive X-ray spectrometry (EDS),surface roughness,direct pull-off test,ball-on-disk friction and wear test and potentiodynamic polarization test,respectively.The results showed that the evolution of discharging sparks during the PEO process directly influenced the microstructure of the PEO coatings and further influences the properties.When the anodic voltage increased from 320 V to 400 V,the corrosion resistance and wear resistance of the coatings slowly increased,and all the bonding strength was higher than 60 MPa; further increasing the anodic voltages,especially up to 440 V,although the thickness and γ-Al2O3 crystallinity of the coatings further increased,the microstructure and properties of the coatings were obviously deteriorated.

  4. Nano Ru Impregnated Ni-YSZ Anode as Carbon Resistance Layer for Direct Ethanol Solid Oxide Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    SUN; Liangliang; ZHENG; Tao; HU; Zhimin; LUO; Linghong; WU; Yefan; XU; Xu; CHENG; Liang; SHI; Jijun

    2015-01-01

    Carbon formation on conventional Ni and Y2O3 stabilized zirconia(Ni/YSZ) anodes is a major problem for direct ethanol solid oxide fuel cells(DE-SOFC). A nanostructure Ru layer was grown in Ni/YSZ anodes through wet impregnation method with RuC l3 solvent at pH =4. Anode-supported Ni-YSZ/YSZ/(La0.8Sr0.2)0.98 MnO 3±δ(LSM) and Ru-Ni-YSZ/YSZ/LSM fuel cells were compared in terms of the performance and carbon formation with ethanol fuel. X-ray diffraction, scanning electron microscopy, energy disperse spectroscopy and electrochemical workstation were used to study the morphology and fuel cell performance. The results indicate that a nano structured and pearl like Ru layer was well dispersed on the surface of Ni-YSZ materials. The single cell with Ru-impregnated Ni/YSZ showed a maximum power density of 369 m W/cm at 750°C, which was higher than Ni-YSZ/YSZ/LSM. Specifically, no carbon was formed in the anode after 1000 min operation. Fuel cell performance and carbon resistance were enhanced with the addition of the Ru layer.

  5. Combined Theoretical and Experimental Investigation and Design of H2S Tolerant Anode for Solid Oxide Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Gerardine G. Botte; Damilola Daramola; Madhivanan Muthuvel

    2009-01-07

    A solid oxide fuel cell (SOFC) is a high temperature fuel cell and it normally operates in the range of 850 to 1000 C. Coal syngas has been considered for use in SOFC systems to produce electric power, due to its high temperature and high hydrogen and carbon monoxide content. However, coal syngas also has contaminants like carbon dioxide (CO{sub 2}) and hydrogen sulfide (H{sub 2}S). Among these contaminants, H{sub 2}S is detrimental to electrode material in SOFC. Commonly used anode material in SOFC system is nickel-yttria stabilized zirconia (Ni-YSZ). The presence of H{sub 2}S in the hydrogen stream will damage the Ni anode and hinder the performance of SOFC. In the present study, an attempt was made to understand the mechanism of anode (Ni-YSZ) deterioration by H{sub 2}S. The study used computation methods such as quantum chemistry calculations and molecular dynamics to predict the model for anode destruction by H{sub 2}S. This was done using binding energies to predict the thermodynamics and Raman spectroscopy to predict molecular vibrations and surface interactions. On the experimental side, a test stand has been built with the ability to analyze button cells at high temperature under syngas conditions.

  6. Nickel-based anode with water storage capability to mitigate carbon deposition for direct ethanol solid oxide fuel cells.

    Science.gov (United States)

    Wang, Wei; Su, Chao; Ran, Ran; Zhao, Bote; Shao, Zongping; Tade, Moses O; Liu, Shaomin

    2014-06-01

    The potential to use ethanol as a fuel places solid oxide fuel cells (SOFCs) as a sustainable technology for clean energy delivery because of the renewable features of ethanol versus hydrogen. In this work, we developed a new class of anode catalyst exemplified by Ni+BaZr0.4Ce0.4Y0.2O3 (Ni+BZCY) with a water storage capability to overcome the persistent problem of carbon deposition. Ni+BZCY performed very well in catalytic efficiency, water storage capability and coking resistance tests. A stable and high power output was well maintained with a peak power density of 750 mW cm(-2) at 750 °C. The SOFC with the new robust anode performed for seven days without any sign of performance decay, whereas SOFCs with conventional anodes failed in less than 2 h because of significant carbon deposition. Our findings indicate the potential applications of these water storage cermets as catalysts in hydrocarbon reforming and as anodes for SOFCs that operate directly on hydrocarbons.

  7. Nano Ru Impregnated Ni-YSZ Anode as Carbon Resistance Layer for Direct Ethanol Solid Oxide Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    SUN Liangliang; ZHENG Tao; HU Zhimin; LUO Linghong; WU Yefan; XU Xu; CHENG Liang; SHI Jijun

    2015-01-01

    Carbon formation on conventional Ni and Y2O3stabilized zirconia (Ni/YSZ) anodes is a major problem for direct ethanol solid oxide fuel cells (DE-SOFC). A nanostructure Ru layer was grown in Ni/YSZ anodes through wet impregnation method with RuCl3solvent at pH=4. Anode-supported Ni-YSZ/YSZ/(La0.8Sr0.2)0.98MnO3±δ(LSM) and Ru-Ni-YSZ/YSZ/LSM fuel cells were compared in terms of the performance and carbon formation with ethanol fuel. X-ray diffraction, scanning electron microscopy,energy disperse spectroscopy and electrochemical workstation were used to study the morphology and fuel cell performance. The results indicate that a nano structured and pearl like Ru layer was well dispersed on the surface of Ni-YSZ materials. The single cell with Ru-impregnated Ni/YSZ showed a maximum power density of 369 mW/cmat 750°C, which was higher than Ni-YSZ/YSZ/LSM. Specifically, no carbon was formed in the anode after 1000 min operation. Fuel cell performance and carbon resistance were enhanced with the addition of the Ru layer.

  8. Efficiency analysis of a hydrogen-fueled solid oxide fuel cell system with anode off-gas recirculation

    Science.gov (United States)

    Peters, Roland; Deja, Robert; Engelbracht, Maximilian; Frank, Matthias; Nguyen, Van Nhu; Blum, Ludger; Stolten, Detlef

    2016-10-01

    This study analyzes different hydrogen-fueled solid oxide fuel cell (SOFC) system layouts. It begins with a simple system layout without any anode off-gas recirculation, continues with a configuration equipped with off-gas recirculation, including steam condensation and then considers a layout with a dead-end anode off-gas loop. Operational parameters such as stack fuel utilization, as well as the recirculation rate, are modified, with the aim of achieving the highest efficiency values. Drawing on experiments and the accumulated experience of the SOFC group at the Forschungszentrum Jülich, a set of operational parameters were defined and applied to the simulations. It was found that anode off-gas recirculation, including steam condensation, improves electrical efficiency by up to 11.9 percentage-points compared to a layout without recirculation of the same stack fuel utilization. A system layout with a dead-end anode off-gas loop was also found to be capable of reaching electrical efficiencies of more than 61%.

  9. Fabrication and characterization of anode-supported micro-tubular solide oxide fuel cell by phase inversion method

    Science.gov (United States)

    Ren, Cong

    Nowadays, the micro-tubular solid oxide fuel cells (MT-SOFCs), especially the anode supported MT-SOFCs have been extensively developed to be applied for SOFC stacks designation, which can be potentially used for portable power sources and vehicle power supply. To prepare MT-SOFCs with high electrochemical performance, one of the main strategies is to optimize the microstructure of the anode support. Recently, a novel phase inversion method has been applied to prepare the anode support with a unique asymmetrical microstructure, which can improve the electrochemical performance of the MT-SOFCs. Since several process parameters of the phase inversion method can influence the pore formation mechanism and final microstructure, it is essential and necessary to systematically investigate the relationship between phase inversion process parameters and final microstructure of the anode supports. The objective of this study is aiming at correlating the process parameters and microstructure and further preparing MT-SOFCs with enhanced electrochemical performance. Non-solvent, which is used to trigger the phase separation process, can significantly influence the microstructure of the anode support fabricated by phase inversion method. To investigate the mechanism of non-solvent affecting the microstructure, water and ethanol/water mixture were selected for the NiO-YSZ anode supports fabrication. The presence of ethanol in non-solvent can inhibit the growth of the finger-like pores in the tubes. With the increasing of the ethanol concentration in the non-solvent, a relatively dense layer can be observed both in the outside and inside of the tubes. The mechanism of pores growth and morphology obtained by using non-solvent with high concentration ethanol was explained based on the inter-diffusivity between solvent and non-solvent. Solvent and non-solvent pair with larger Dm value is benefit for the growth of finger-like pores. Three cells with different anode geometries was

  10. Dual-cut graphene transistors with constant-current regions fabricated by the atomic force microscope anode oxidation

    Science.gov (United States)

    Wu, Chong-Rong; Dou, Kun Peng; Wang, Cheng-Hung; Chang, Chung-En; Kaun, Chao-Cheng; Wu, Chao-Hsin; Lin, Shih-Yen

    2017-01-01

    Graphene bandgap opening is an important issue for the application of this material. We have demonstrated that by atomic force microscope (AFM) anode oxidation, long nonconductive oxidation lines can be fabricated on graphene surfaces. By using this fabrication technique with the dual-cut transistor architecture, the phenomenon of constant-current regions near the Dirac point can be observed in devices at room temperature when the cut separation is smaller than 100 nm. The results may provide evidence of the phenomenon of graphene bandgap opening at room temperature. The theoretical bandgap values are further estimated by density-function-derived tight-binding calculations.

  11. Fracture strength of micro-tubular solid oxide fuel cell anode in redox cycling experiments

    Energy Technology Data Exchange (ETDEWEB)

    Pusz, Jakub; Smirnova, Alevtina; Mohammadi, Alidad; Sammes, Nigel M. [Department of Chemical, Materials, and Biomolecular Engineering, University of Connecticut, 44 Weaver Road, Storrs, CT 06269 (United States)

    2007-01-01

    The maximum fracture strength of Ni/8YSZ anodes exposed to several redox cycles is compared. The anodes were fabricated using fine and coarse particle size powders. Fine-structured powders show a 77% increase in mechanical strength after exposure to three redox cycles. The coarse-structured material did not produce similar results and redox cycling resulted in gradual decrease in the mechanical stability of the supports. The impact of redox cycling on the microstructure was evaluated using SEM. Fine-structured anodes tend to agglomerate leading to decreased porosity. Coarse anodes did not show any significant changes in microstructure while exposed to redox cycling. The electrochemical performance evaluated under load conditions, and after the first redox cycle, indicates a 40% improvement for the cell fabricated using a fine-structured anode powder. The increase in performance is believed to be due to better adhesion between the anode material and the Ni current collector. The cell fabricated using a coarse-structured anode powder did not recover after the redox cycle. (author)

  12. Conical tungsten stamps for the replication of pore arrays in anodic aluminium oxide films.

    Science.gov (United States)

    LeClere, D J; Thompson, G E; Derby, B

    2009-06-17

    A tungsten master stamp has been generated by applying a novel procedure that includes two-step anodizing, followed by sequential anodizing and pore widening to develop nominally funnelled pores. These conical-shaped pores were filled with tungsten by sputter coating to manufacture a master stamp. Under a pressure of 65 MPa, the master stamp successfully embossed the surface of annealed and electropolished aluminium. The embossed surface was then used to control the position of pores created by anodizing under the conditions used to produce the original pore array.

  13. Nucleophile-directed selectivity towards linear carbonates in the niobium pentaethoxide-catalysed cycloaddition of CO2 and propylene oxide

    KAUST Repository

    Dutta, Barnali

    2014-01-01

    Homoleptic Nb-complexes combined with selected organic nucleophiles generate very active catalytic systems for the cycloaddition of propylene oxide and CO2 under ambient conditions. An unprecedented reaction pathway towards an acyclic organic carbonate is observed when extending the study to [Nb(OEt)5] in combination with 4-dimethylamino-pyridine (DMAP) or tetra-n-butylammonium bromide (TBAB). Mechanistic insights of the reaction are provided based on experimental and spectroscopic evidences. This journal is © the Partner Organisations 2014.

  14. Recent advances in nanostructured Nb-based oxides for electrochemical energy storage

    Science.gov (United States)

    Yan, Litao; Rui, Xianhong; Chen, Gen; Xu, Weichuan; Zou, Guifu; Luo, Hongmei

    2016-04-01

    For the past five years, nanostructured niobium-based oxides have emerged as one of the most prominent materials for batteries, supercapacitors, and fuel cell technologies, for instance, TiNb2O7 as an anode for lithium-ion batteries (LIBs), Nb2O5 as an electrode for supercapacitors (SCs), and niobium-based oxides as chemically stable electrochemical supports for fuel cells. Their high potential window can prevent the formation of lithium dendrites, and their rich redox chemistry (Nb5+/Nb4+, Nb4+/Nb3+) makes them very promising electrode materials. Their unique chemical stability under acid conditions is favorable for practical fuel-cell operation. In this review, we summarized recent progress made concerning the use of niobium-based oxides as electrodes for batteries (LIBs, sodium-ion batteries (SIBs), and vanadium redox flow batteries (VRBs)), SCs, and fuel cell applications. Moreover, crystal structures, charge storage mechanisms in different crystal structures, and electrochemical performances in terms of the specific capacitance/capacity, rate capability, and cycling stability of niobium-based oxides are discussed. Insights into the future research and development of niobium-based oxide compounds for next-generation electrochemical devices are also presented. We believe that this review will be beneficial for research scientists and graduate students who are searching for promising electrode materials for batteries, SCs, and fuel cells.

  15. Fabrication of Acrylonitrile-Butadiene-Styrene Nanostructures with Anodic Alumina Oxide Templates, Characterization and Biofilm Development Test for Staphylococcus epidermidis.

    Directory of Open Access Journals (Sweden)

    Camille Desrousseaux

    Full Text Available Medical devices can be contaminated by microbial biofilm which causes nosocomial infections. One of the strategies for the prevention of such microbial adhesion is to modify the biomaterials by creating micro or nanofeatures on their surface. This study aimed (1 to nanostructure acrylonitrile-butadiene-styrene (ABS, a polymer composing connectors in perfusion devices, using Anodic Alumina Oxide templates, and to control the reproducibility of this process; (2 to characterize the physico-chemical properties of the nanostructured surfaces such as wettability using captive-bubble contact angle measurement technique; (3 to test the impact of nanostructures on Staphylococcus epidermidis biofilm development. Fabrication of Anodic Alumina Oxide molds was realized by double anodization in oxalic acid. This process was reproducible. The obtained molds present hexagonally arranged 50 nm diameter pores, with a 100 nm interpore distance and a length of 100 nm. Acrylonitrile-butadiene-styrene nanostructures were successfully prepared using a polymer solution and two melt wetting methods. For all methods, the nanopicots were obtained but inside each sample their length was different. One method was selected essentially for industrial purposes and for better reproducibility results. The flat ABS surface presents a slightly hydrophilic character, which remains roughly unchanged after nanostructuration, the increasing apparent wettability observed in that case being explained by roughness effects. Also, the nanostructuration of the polymer surface does not induce any significant effect on Staphylococcus epidermidis adhesion.

  16. Effects of the buffer layer inserted between the transparent conductive oxide anode and the organic electron donor

    Energy Technology Data Exchange (ETDEWEB)

    Godoy, A.; Kouskoussa, B.; Benchouk, K.; Khelil, A. [Facultad Ciencias de la Salud, Universidad Diego Portales, Ejercito 141, Santiago de Chile (Chile); Cattin, L.; Soto, G.M. [Universite de Nantes, Nantes Atlantique Universites, Institut des Materiaux Jean Rouxel (IMN)-CNRS, Faculte des Sciences et Techniques, 2 rue de la Houssiniere, BP 92208, Nantes F-44000 (France); Toumi, L. [LPCM2E, Universite d' Oran Es-Senia, LPCM2E (Algeria); Diaz, F.R.; del Valle, M.A. [Laboratorio de Polimeros, Facultad de Quimica, Pontificia Universidad Catolica de Chile, Casilla 306, Correo 22, Santiago (Chile); Morsli, M.; Bernede, J.C. [Universite de Nantes, Nantes Atlantique Universites, LAMP, Faculte des Sciences et Techniques, 2 rue de la Houssiniere, BP 92208, Nantes F-44000 (France)

    2010-04-15

    In optoelectronic devices, the work function of the transparent conductive oxide, which is used as anode, does not match well the highest occupied molecular orbital of the organic material, which induces the formation of a barrier opposed to hole exchange at this interface. Therefore a thin buffer layer is often used to achieve good matching of the band structure at the interface. From experimental results it can be deduced that the main effects of the buffer layer consist in a better matching of the band structure at the interface anode/organic material and in a more homogeneous organic layer growth. We show that, whatever the nature of the buffer layer-metal, oxide, organic material - the classical Schottky-Mott model allows to anticipate, at least roughly, the behaviour of the contact, even if some dipole effect are often present. A good correlation between the ''metal/buffer layer'' work function and the barrier {phi}{sub b} for hole exchange at anode/organic electron donor interfaces is obtained, as expected by the model. (author)

  17. Fabrication of anodized tantalum oxide integrated capacitors on singulated chips with active devices

    Science.gov (United States)

    Wasef, Mohammed Aziz

    The purpose of this project was to determine the feasibility and processability of fabricating anodized tantalum oxide integrated capacitors on singulated chips. Using high-resolution transparencies to pattern the metals during the photolithographic process, capacitors as large as 0.25 cm2 were fabricated successfully with the yield being higher for capacitors smaller than 0.1 cm2. Several capacitor designed were attempted and final designed was selected on the basis of ease of alignment and prevention of shorts. The next step in the project involved utilizing this design to fabricate capacitors on 2.2 mm by 2.2 mm silicon dummy chips. In order to accomplish this task, a support wafer technique was used. A silicon wafer with holes etched all the way through was attached to a non-etched silicon wafer to provide a base for the dummy chips that were placed in the holes of the support wafer, thus making the top of the chips co-planar with a wafer that could be put through standard wafer processing equipment. The chips were glued to the wafer using a thermoplastic as an adhesive. The design specified for this project called for five 100 pF capacitors and a single 50 pF capacitor. Since the chips had to be individually placed in the holes, all the masks used in the project had to be individually designed for reach run. The capacitors had a bottom plate thickness of 2500 A of tantalum which was anodized at 120 V and 0.5 mA/cm2 to an oxide thickness of 1920 A. The top plate was 2 mum of aluminum and the insulating ring around the bottom plate was made of 5 mum of benzocyclobutene. After fabrication, testing of the capacitors provided a yield of 97% for the 100 pF capacitors with average capacitance of 98.3 pF +/- 3.6 pF and 75% for the 50 pF capacitors with an average capacitance of 50 pF +/- 1.65 pF. The inductance of the capacitors was less than 20 pH and resistance was about 110 O. The resistance was brought down to 1 O when a 2 mum sublayer of aluminum was deposited

  18. Synthesis and electrochemical properties of stannous oxide clinopinacoid as anode material for lithium ion batteries.

    Science.gov (United States)

    Iqbal, M Zubair; Wang, Fengping; Rafique, M Yasir; Ali, Shujaat; Din, Rafi Ud; Farooq, M Hassan; Khan, Matiullah; Ali, Murad

    2013-03-01

    Tin monoxide is a significant functional semiconductor material which employed to a wide area of applications especially optical and energy storage devices. Presently, template free hydrothermal technique has been employing to synthesize stannous oxide (SnO) clinopinacoid type controlled morphology using SnCl2 x 2H2O, NH3, and H2O as raw materials. The crystalline phase, morphology, particle size and component were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and field-emission scanning electron microscopy (FESEM). FESEM results exhibited the large scale homogeneous growth of clinopinacoid architecture with the obvious size of 5 - 7 micrometers. The XRD results showed that the average crystallite size of the tetragonal phase romarchite SnO was about 29 nm calculated from the FWHM of X-ray diffraction pattern. The dominant Raman active modes A(1g) = 205 cm(-1), B(1g) = 105-107 cm(-1) and about 6 cm(-1) redshift were observed by the Raman spectroscopy, which further confirmed the existence of the nano tetragonal phase SnO. The electrochemical performance of as-synthesized SnO clinopinacoid structure as the anode material for lithium ion batteries was investigated. It was observed that the first discharge capacity of the two samples could reach a very high value of 1502 mA h g(-1) and 1422 mA h g(-1) respectively. The effect of nitrogen concentration on morphology as well as cyclic performance of Li-Ion-batteries was also discussed.

  19. Facile synthesis of binder-free reduced graphene oxide/silicon anode for high-performance lithium ion batteries

    Science.gov (United States)

    Zhang, Wei; Zuo, Pengjian; Chen, Cheng; Ma, Yulin; Cheng, Xinqun; Du, Chunyu; Gao, Yunzhi; Yin, Geping

    2016-04-01

    A novel binder-free reduced graphene oxide/silicon (RGO/Si) composite anode has been fabricated by a facile doctor-blade coating method. The relatively low C/O ratio plays an important role for the fabrication of the bind-free multilayered RGO/Si electrode with silicon nanoparticles encapsulating among the RGO sheet layers. The RGO provides the electron transport pathway and prevents the electrode fracture caused by the volume changes of active silicon particles during cycling. The RGO/Si composite anode with a silicon content of 66.7% delivers a reversible capacity of 1931 mAh g-1 at 0.2 A g-1 and still remains 92% of the initial capacity after 50 cycles.

  20. Fabrication of Pd Micro-Membrane Supported on Nano-Porous Anodized Aluminum Oxide for Hydrogen Separation.

    Science.gov (United States)

    Kim, Taegyu

    2015-08-01

    In the present study, nano-porous anodized aluminum oxide (AAO) was used as a support of the Pd membrane. The AAO fabrication process consists of an electrochemical polishing, first/second anodizing, barrier layer dissolving and pores widening. The Pd membrane was deposited on the AAO support using an electroless plating with ethylenediaminetetraacetic acid (EDTA) as a plating agent. The AAO had the regular pore structure with the maximum pore diameter of ~100 nm so it had a large opening area but a small free standing area. The 2 µm-thick Pd layer was obtained by the electroless plating for 3 hours. The Pd layer thickness increased with increasing the plating time. However, the thickness was limited to ~5 µm in maximum. The H2 permeation flux was 0.454 mol/m2-s when the pressure difference of 66.36 kPa0.5 was applied at the Pd membrane under 400 °C.

  1. Silver nanoparticles deposited on anodic aluminum oxide template using magnetron sputtering for surface-enhanced Raman scattering substrate

    Energy Technology Data Exchange (ETDEWEB)

    Wong-ek, Krongkamol [Nanoscience and Technology Program, Chulalongkorn University, Bangkok 10330 (Thailand); Eiamchai, Pitak; Horprathum, Mati; Patthanasettakul, Viyapol [National Electronics and Computer Technology Center, 112 Thailand Science Park, Phahonyothin Rd., Klong Luang, Pathumthani 12120 (Thailand); Limnonthakul, Puenisara [Department of Physics, Faculty of Science, King Mongkut' s University of Technology Thonburi, Bangkok 10140 (Thailand); Chindaudom, Pongpan [National Electronics and Computer Technology Center, 112 Thailand Science Park, Phahonyothin Rd., Klong Luang, Pathumthani 12120 (Thailand); Nuntawong, Noppadon, E-mail: noppadon.nuntawong@nectec.or.t [National Electronics and Computer Technology Center, 112 Thailand Science Park, Phahonyothin Rd., Klong Luang, Pathumthani 12120 (Thailand)

    2010-09-30

    Low-cost and highly sensitive surface-enhanced Raman scattering (SERS) substrates have been fabricated by a simple anodizing process and a magnetron sputtering deposition. The substrates, which consist of silver nanoparticles embedded on anodic aluminum oxide (AAO) templates, are investigated by a scanning electron microscope and a confocal Raman spectroscopy. The SERS activities are demonstrated by Raman scattering from adsorbed solutions of methylene blue and pyridine on the SERS substrate surface. The most optimized SERS substrate contains the silver nanoparticles, with a size distribution of 10-30 nm, deposited on the AAO template. From a calculation, the SERS enhancement factor is as high as 8.5 x 10{sup 7}, which suggests strong potentials for direct applications in the chemical detection and analyses.

  2. Performance of Electrolyte Supported Solid Oxide Fuel Cells with STN Anodes

    DEFF Research Database (Denmark)

    Veltzé, Sune; Reddy Sudireddy, Bhaskar; Jørgensen, Peter Stanley

    2013-01-01

    In order to replace the state of the art Ni-cermet as SOFC anode, electrolyte supported cells comprising CGO/Ni infiltrated Nbdoped SrTiO3 anodes, and LSM/YSZ cathodes have been developed and tested as single 5 x 5 cm2 cells. The initial performance reached 0.4 W/cm2 at 850 C. Further tests under...

  3. Niobium doped lanthanum calcium ferrite perovskite as a novel electrode material for symmetrical solid oxide fuel cells

    Science.gov (United States)

    Kong, Xiaowei; Zhou, Xiaoliang; Tian, Yu; Wu, Xiaoyan; Zhang, Jun; Zuo, Wei

    2016-09-01

    Development of cost-effective and efficient electrochemical catalysts for the fuel cells electrode is of prime importance to emerging renewable energy technologies. Here, we report for the first time the novel La0.9Ca0.1Fe0.9Nb0.1O3-δ (LCFNb) perovskite with good potentiality for the electrode material of the symmetrical solid oxide fuel cells (SSOFC). The Sc0.2Zr0.8O2-δ (SSZ) electrolyte supported symmetrical cells with impregnated LCFNb and LCFNb/SDC (Ce0.8Sm0.2O2-δ) electrodes achieve relatively high power outputs with maximum power densities (MPDs) reaching up to 392 and 528.6 mW cm-2 at 850 °C in dry H2, respectively, indicating the excellent electro-catalytic activity of LCFNb towards both hydrogen oxidation and oxygen reduction. Besides, the MPDs of the symmetrical cells with LCFNb/SDC composite electrodes in CO and syngas (CO: H2 = 1:1) are almost identical to those in H2, implying that LCFNb material has similar catalytic activities to carbon monoxide compared with hydrogen. High durability in both H2, CO and syngas during the short term stability tests for 50 h are also obtained, showing desirable structure stability, and carbon deposition resistance of LCFNb based electrodes. The present results indicate that the LCFNb perovskite with remarkable cell performance is a promising electrode material for symmetrical SOFCs.

  4. Development of Plasma-Sprayed Molybdenum Carbide-Based Anode Layers with Various Metal Oxides for SOFC

    Science.gov (United States)

    Faisal, N. H.; Ahmed, R.; Katikaneni, S. P.; Souentie, S.; Goosen, M. F. A.

    2015-12-01

    Air plasma-sprayed (APS) coatings provide an ability to deposit a range of novel fuel cell materials at competitive costs. This work develops three separate types of composite anodes (Mo-Mo2C/Al2O3, Mo-Mo2C/ZrO2, Mo-Mo2C/TiO2) using a combination of APS process parameters on Hastelloy®X for application in intermediate temperature proton-conducting solid oxide fuel cells. Commercially available carbide of molybdenum powder catalyst (Mo-Mo2C) and three metal oxides (Al2O3, ZrO2, TiO2) was used to prepare three separate composite feedstock powders to fabricate three different anodes. Each of the modified composition anode feedstock powders included a stoichiometric weight ratio of 0.8:0.2. The coatings were characterized by scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction, nanoindentation, and conductivity. We report herein that three optimized anode layers of thicknesses between 200 and 300 µm and porosity as high as 20% for Mo-Mo2C/Al2O3 (250-µm thick) and Mo-Mo2C/TiO2 (300 µm thick) and 17% for Mo-Mo2C/ZrO2 (220-µm thick), controllable by a selection of the APS process parameters with no addition of sacrificial pore-forming material. The nanohardness results indicate the upper layers of the coatings have higher values than the subsurface layers in coatings with some effect of the deposition on the substrate. Mo-Mo2C/ZrO2 shows high electrical conductivity.

  5. Catalytic activity of Ni-YSZ anodes in a single-chamber solid oxide fuel cell reactor

    Science.gov (United States)

    Savoie, Sylvio; Napporn, Teko W.; Morel, Bertrand; Meunier, Michel; Roberge, Réal

    The importance of heterogeneous catalysis in single-chamber solid oxide fuel cells (SC-SOFC) is universally recognized, but little studied. This work presents a thorough investigation of the catalytic activity of three Ni-YSZ half-cells in a well-described single-chamber reactor. One in-house electrolyte-supported and two commercially available anode-supported half-cells composed of anodes with thicknesses ranging from 50 μm to 1.52 mm are investigated. They are exposed to methane and oxygen gas mixtures within CH 4:O 2 flow rate ratios (R in) of 0.8-2.0 and furnace temperatures of 600-800 °C. The conversion of methane always results in the formation of syngas species (H 2 and CO). However, their yields vary considerably based on the individual anode, the operating temperature, and R in. The SC-reactor design and the presence of hot-spots at the reactor entrance bring the methane and oxygen conversion rates well above the limit expected from experiments carried out with anode half-cells only. Major variations in the H 2/CO ratio are observed. In lowering the temperature from 800 °C to 600 °C, it spreads from well below to well above the stoichiometric value of 2.0 expected for the partial oxidation reaction. To optimize the SC-SOFC any further, the findings stress the need to undertake even more catalytic studies of its electrode materials under actual structure and morphology as well as final reactor configuration.

  6. Fabrication of TiO2 Cathodes by Anodic Oxidation for Hydrogen Generation from Electrolysis of Water

    Directory of Open Access Journals (Sweden)

    *İ. Koyuncu

    2014-09-01

    Full Text Available In this investigation, titanium oxide plates were used as cathode for hydrogen production in the aqueous solutions of sulfuric acid, potassium hydroxide, acetic acid and ammonia hydroxides electrolytes separately. Gaseous hydrogen was produced at the cathode and oxygen at the anode. For this purpose, titanium plates were fabricated in acid solution by anodic oxidation. Microstructure of TiO2 nanorod observation was conducted with scanning electron microscopy (SEM. The effects of operating conditions and the electrochemical test parameters, such as electrolytes concentration, temperature, and cell voltage were investigated. Also the performance of TiO2 cathode was compared to zirconium oxide and graphite electrodes. The results show that the highly rated, hydrogen production performance on TiO2 cathode has better than the other electrodes. The maximum rate of hydrogen production is by TiO2 cathode 8.18 ml/ (h. cm2. The cell efficiency for water electrolysis was reached 95% using titanium oxide electrode in 1.5 M H2SO4.

  7. Fluorine-Doped Tin Oxide Nanocrystal/Reduced Graphene Oxide Composites as Lithium Ion Battery Anode Material with High Capacity and Cycling Stability.

    Science.gov (United States)

    Xu, Haiping; Shi, Liyi; Wang, Zhuyi; Liu, Jia; Zhu, Jiefang; Zhao, Yin; Zhang, Meihong; Yuan, Shuai

    2015-12-16

    Tin oxide (SnO2) is a kind of anode material with high theoretical capacity. However, the volume expansion and fast capability fading during cycling have prevented its practical application in lithium ion batteries. Herein, we report that the nanocomposite of fluorine-doped tin oxide (FTO) and reduced graphene oxide (RGO) is an ideal anode material with high capacity, high rate capability, and high stability. The FTO conductive nanocrystals were successfully anchored on RGO nanosheets from an FTO nanocrystals colloid and RGO suspension by hydrothermal treatment. As the anode material, the FTO/RGO composite showed high structural stability during the lithiation and delithiation processes. The conductive FTO nanocrystals favor the formation of stable and thin solid electrolyte interface films. Significantly, the FTO/RGO composite retains a discharge capacity as high as 1439 mAhg(-1) after 200 cycles at a current density of 100 mAg(-1). Moreover, its rate capacity displays 1148 mAhg(-1) at a current density of 1000 mAg(-1).

  8. Study on Improving the Oxidation Efficiency of Lead Anode Slime%提高铅阳极泥氧化效率的研究

    Institute of Scientific and Technical Information of China (English)

    程永强

    2014-01-01

    影响铅阳极泥氧化的因素较多,本试验主要研究了温度及湿度对阳极泥氧化的影响。通过控制不同的温度和阳极泥含水量,对阳极泥氧化过程进行了监测。当温度在21~35℃范围时,阳极泥氧化速度较快,最佳的氧化温度为21~25℃。在采取保湿措施的同时,减少氧化过程中水分的蒸发,有利于阳极泥的氧化,最佳的湿度条件为阳极泥含水15%~25%。%T here are many influence factors in the oxidation of anode alime . T his test mainly studies the influence of temperature and humidity on the oxidation of anode slime . By controlling the different temperature and anode alime water content , the anode alime oxidation process is monitored . When the temperature is in the range of 21℃ to 35℃ , Anode slime oxidation speed is faster , the best oxidation temperature is 21℃ to 25℃ . As the same time of taking moisturizing measures , water evaporation is reduced in the oxidation process . This is good for the oxidation of anode slime;the best humidity condition is anode alime water content 15% to 25% .

  9. The impact of steam and current density on carbon formation from biomass gasification tar on Ni/YSZ, and Ni/CGO solid oxide fuel cell anodes

    Science.gov (United States)

    Mermelstein, Joshua; Millan, Marcos; Brandon, Nigel

    The combination of solid oxide fuel cells (SOFCs) and biomass gasification has the potential to become an attractive technology for the production of clean renewable energy. However the impact of tars, formed during biomass gasification, on the performance and durability of SOFC anodes has not been well established experimentally. This paper reports an experimental study on the mitigation of carbon formation arising from the exposure of the commonly used Ni/YSZ (yttria stabilized zirconia) and Ni/CGO (gadolinium-doped ceria) SOFC anodes to biomass gasification tars. Carbon formation and cell degradation was reduced through means of steam reforming of the tar over the nickel anode, and partial oxidation of benzene model tar via the transport of oxygen ions to the anode while operating the fuel cell under load. Thermodynamic calculations suggest that a threshold current density of 365 mA cm -2 was required to suppress carbon formation in dry conditions, which was consistent with the results of experiments conducted in this study. The importance of both anode microstructure and composition towards carbon deposition was seen in the comparison of Ni/YSZ and Ni/CGO anodes exposed to the biomass gasification tar. Under steam concentrations greater than the thermodynamic threshold for carbon deposition, Ni/YSZ anodes still exhibited cell degradation, as shown by increased polarization resistances, and carbon formation was seen using SEM imaging. Ni/CGO anodes were found to be more resilient to carbon formation than Ni/YSZ anodes, and displayed increased performance after each subsequent exposure to tar, likely due to continued reforming of condensed tar on the anode.

  10. Cyanide oxidation by singlet oxygen generated via reaction between H2O2 from cathodic reduction and OCl(-) from anodic oxidation.

    Science.gov (United States)

    Tian, Shichao; Li, Yibing; Zeng, Huabin; Guan, Wei; Wang, Yan; Zhao, Xu

    2016-11-15

    Cyanide is widely present in electroplating wastewater or metallurgical effluents. In the present study, the electrochemical destruction of cyanide with various anode and cathode compositions under alkaline conditions was investigated. The results indicated that the electrochemical system using RuO2/Ti as anode and activated carbon fiber (ACF) as cathode in the presence of sodium chloride was efficient for the cyanide removal. In this system, in situ generation of HClO by anodic oxidation of Cl(-) at RuO2/Ti anode occurred with the H2O2 generation by O2 reduction at ACF cathode. As confirmed by the electron spin resonance technique, the reaction between HClO and H2O2 led to the generation of singlet oxygen, which was responsible for the cyanide removal. Further experiment indicated that the cyanide removal efficiency increased with the increase of the current density or the sodium chloride concentration. Cyanate was identified as main product in the system. Besides, the system exhibited good stability for the cyanide removal, which was beneficial to its practical application.

  11. Influence of voltage waveform on anodic film of AZ91 Mg alloy via plasma electrolytic oxidation: Microstructural characteristics and electrochemical responses

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Young Gun [School of Materials Science and Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Lee, Eung Seok [Department of Metallurgy and Materials Engineering, Hanyang University, Ansan 426-791 (Korea, Republic of); Shin, Dong Hyuk, E-mail: dhshin@hanyang.ac.kr [Department of Metallurgy and Materials Engineering, Hanyang University, Ansan 426-791 (Korea, Republic of)

    2014-02-15

    Highlights: • The effect of voltage waveform on the anodic film structure is significant. • The anodic film by asymmetric-sine wave is denser than that by half-sine wave. • Asymmetric-sine wave results in excellent electrochemical properties. -- Abstract: The present study investigated how the voltage waveform influenced the microstructural characteristics and electrochemical responses of the anodic film on AZ91 Mg alloy coated by plasma electrolytic oxidation (PEO). PEO coatings of AZ91 Mg alloy were performed for 600 s in an alkaline silicate electrolyte with respect to the voltage waveform such as half-sine and asymmetric-sine waveforms. Microstructural observations on cross section of the anodic film utilizing scanning electron microscope revealed that the anodic film formed via asymmetric-sine wave was much denser in structure than that via half-sine counterpart since the occurrence of the cathodic breakdown between the anodic pulses could effectively suppress the formation of the micro-pores and discharge channels in the anodic films. Thereby, the hardness and corrosion properties of the anodic film formed by asymmetric-sine wave were found to be superior to those by half-sine wave. In addition, electrochemical responses were interpreted in relation to the equivalent circuit model consisting of resistor and capacitor elements within an electrical cell.

  12. Soft chemical synthesis and electrochemical properties of tin oxide-based materials as anodes for lithium ion batteries

    Institute of Scientific and Technical Information of China (English)

    何则强; 李新海; 熊利芝; 吴显明; 刘恩辉; 侯朝辉; 邓凌峰

    2004-01-01

    A novel soft chemical approach was developed to synthesize tin oxide-based powders. The microstructure, morphology, and electrochemical performance of the materials were investigated by X-ray diffraction, scanning electron microscope and electrochemical methods. The results show that the particles of tin oxide-based materials form an interconnected network structure like mesoporous material. The average size of the particles is about 200 nm. The materials deliver a charge capacity of more than 570 mA*h*g-1. And the capacity loss per cycle is about 0.15% after being cycled for 30 times. The good electrochemical performance indicates that tin oxide-based materials are promising anodes for lithium ion batteries.

  13. Application of 8YSZ Nanopowder Synthesized by the Modified Solvothermal Process for Anode Supported Solid Oxide Fuel Cells.

    Science.gov (United States)

    Meepho, Malinee; Wattanasiriwech, Suthee; Angkavatana, Pavadee; Wattanasiriwech, Darunee

    2015-03-01

    Thin electrolyte yttria-stabilized zirconia (8YSZ) films were coated on the porous solid oxide fuel cell (SOFC) anode substrates for the use at an intermediate temperature range. Nano-8YSZ powder with a particle size of about 5 nm was synthesized using the modified solvothermal process. The electrolyte suspension was prepared by dispersion the synthesized 8YSZ nanopowder in ethanol, with PVB and 1,3-propanediol as a binder and a charging agent respectively. The 8YSZ suspension was subsequently deposited on the pre-sintered NiO-YSZ porous substrates by the electrophoretic deposition (EPD) technique. In order to obtain high quality electrolyte films, preparation process was optimized through two strategic approaches; (i) adjustment of suspension's rheological property and (ii) compatibility of anode-electrolyte sintering shrinkage. Rheological property of the suspension was improved with an addition of 1,3-propanediol. The zeta potential of this suspension was increased and reached the value of +24 mV so the well-dispersed slurry was finally obtained. The second approach was achieved by using a proper composite anode powders. Dense and uniform 8YSZ electrolyte films with a thickness of about 1 thickness successfully be formed on the NiO-YSZ porous substrates after co-sintering at 1400 °C for 2 h.

  14. Building one-dimensional oxide nanostructure arrays on conductive metal substrates for lithium-ion battery anodes.

    Science.gov (United States)

    Jiang, Jian; Li, Yuanyuan; Liu, Jinping; Huang, Xintang

    2011-01-01

    Lithium ion battery (LIB) is potentially one of the most attractive energy storage devices. To meet the demands of future high-power and high-energy density requirements in both thin-film microbatteries and conventional batteries, it is challenging to explore novel nanostructured anode materials instead of conventional graphite. Compared to traditional electrodes based on nanostructure powder paste, directly grown ordered nanostructure array electrodes not only simplify the electrode processing, but also offer remarkable advantages such as fast electron transport/collection and ion diffusion, sufficient electrochemical reaction of individual nanostructures, enhanced material-electrolyte contact area and facile accommodation of the strains caused by lithium intercalation and de-intercalation. This article provides a brief overview of the present status in the area of LIB anodes based on one-dimensional nanostructure arrays growing directly on conductive inert metal substrates, with particular attention to metal oxides synthesized by an anodized alumina membrane (AAM)-free solution-based or hydrothermal methods. Both the scientific developments and the techniques and challenges are critically analyzed.

  15. Electrophoretic deposition of multi-walled carbon nanotubes on porous anodic aluminum oxide using ionic liquid as a dispersing agent

    Science.gov (United States)

    Hekmat, F.; Sohrabi, B.; Rahmanifar, M. S.; Jalali, A.

    2015-06-01

    Multi-wall carbon nanotubes (MW-CNTs) have been arranged in nanochannels of anodic aluminum oxide template (AAO) by electrophoretic deposition (EPD) to make a vertically-aligned carbon nanotube (VA-CNT) based electrode. Well ordered AAO templates were prepared by a two-step anodizing process by applying a constant voltage of 45 V in oxalic acid solution. The stabilized CNTs in a water-soluble room temperature ionic liquid (1-methyl-3-octadecylimidazolium bromide), were deposited in the pores of AAO templates which were conductive by deposition of Ni nanoparticles in the bottom of pores. In order to obtain ideal results, different EPD parameters, such as concentration of MWCNTs and ionic liquid on stability of MWCNT suspensions, deposition time and voltage which are applied in EPD process and also optimal conditions for anodizing of template were investigated. The capacitive performance of prepared electrodes was analyzed by measuring the specific capacitance from cyclic voltammograms and the charge-discharge curves. A maximum value of 50 Fg-1 at the scan rate of 20 mV s-1was achieved for the specific capacitance.

  16. Growth of Anodic Aluminum Oxide Templates and the Application in Fabrication of the BiSbTe-Based Thermoelectric Nanowires

    Directory of Open Access Journals (Sweden)

    Chin-Guo Kuo

    2014-01-01

    Full Text Available A two-step electrochemical anodization was used to form the anodic aluminum oxide (AAO thin films with nanotube arrays of self-organized honeycomb structure. Al foil was anodized in 10% sulfuric acid (H2SO4 and 3% oxalic acid (H2C2O4 at 25°C at constant voltage of 40 V for 60 min for two times. Ethylene glycol (C2H6O2 was used as a solution and 0.3 M potassium iodide (KI was used to improve the solution’s conductivity. Different electrolyte concentrations of Bi(NO33-5H2O, SbCl3, and TeCl4 were added into KI-C2H6O2 solution and the cyclic voltammetry experiment was used to find the reduced voltages of Bi3+, Sb3+, and Te4+ ions. The potentiostatic deposition and pulse electrodeposition (PED processes were used to deposit the (Bi,Sb2−xTe3+x-based materials. Field-emission scanning electron microscope and energy dispersive spectrometers were used to analyze the compositions of the deposited (Bi,Sb2−xTe3+x-based materials. After finding the optimal deposition parameter of the PED process the AAO nanotube arrays were used as the templates to deposit the (Bi,Sb2−xTe3+x-based thermoelectric nanowires.

  17. Electro oxidation of Phenol on a Ti/RuO{sub 2} anode: effect of some electrolysis parameters

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Iranildes D. dos; Dutra, Achilles J.B. [Universidade Federal do Rio de Janeiro (PEMM/COPPE/UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-Graduacao de Engenharia. Programa de Engenharia Metalurgica e de Materiais; Afonso, Julio C., E-mail: julio@iq.ufrj.b [Universidade Federal do Rio de Janeiro (IQ/UFRJ), RJ (Brazil). Inst. de Quimica. Dept. de Quimica Analitica

    2011-07-01

    The influences of electrolysis time, anodic area, current density and supporting electrolyte on phenol and its byproducts degradation on a Ti/RuO{sub 2} anode were investigated. It was observed that phenol and its byproducts were rapidly broken down in the presence of chloride ions. Gas chromatography/mass spectrometry (GC/MS) data have shown that the presence of chloride ions lead to chlorophenols formation, due to reactions with Cl{sub 2} and/or OCl{sup -} generated during electrolysis. However, these intermediate products were also degraded later by the oxidizing agents. The standards established by the CONAMA (Brazilian National Council for the Environment) for phenols and chlorophenols in effluents were achieved after 360 min of electrolysis with a current density of 10 mA cm-2. Cyclic voltammograms obtained with the anodes before and after 436 h of electrolysis under severe salinity conditions (2 mol L-1) and current density (800 mA cm-2) showed that Ti/RuO{sub 2} did not lose its electrocatalytic properties. This fact indicates that Ti/RuO{sub 2} can be used for the treatment of effluents containing phenols in a chloride environment. (author)

  18. Controlled hydrodynamic conditions on the formation of iron oxide nanostructures synthesized by electrochemical anodization: Effect of the electrode rotation speed

    Science.gov (United States)

    Lucas-Granados, Bianca; Sánchez-Tovar, Rita; Fernández-Domene, Ramón M.; García-Antón, Jose

    2017-01-01

    Iron oxide nanostructures are of particular interest because they can be used as photocatalysts in water splitting due to their advantageous properties. Electrochemical anodization is one of the best techniques to synthesize nanostructures directly on the metal substrate (direct back contact). In the present study, a novel methodology consisting of the anodization of iron under hydrodynamic conditions is carried out in order to obtain mainly hematite (α-Fe2O3) nanostructures to be used as photocatalysts for photoelectrochemical water splitting applications. Different rotation speeds were studied with the aim of evaluating the obtained nanostructures and determining the most attractive operational conditions. The synthesized nanostructures were characterized by means of Raman spectroscopy, Field Emission Scanning Electron Microscopy, photoelectrochemical water splitting, stability against photocorrosion tests, Mott-Schottky analysis, Electrochemical Impedance Spectroscopy (EIS) and band gap measurements. The results showed that the highest photocurrent densities for photoelectrochemical water splitting were achieved for the nanostructure synthesized at 1000 rpm which corresponds to a nanotubular structure reaching ∼0.130 mA cm-2 at 0.54 V (vs. Ag/AgCl). This is in agreement with the EIS measurements and Mott-Schottky analysis which showed the lowest resistances and the corresponding donor density values, respectively, for the nanostructure anodized at 1000 rpm.

  19. Performance evaluation of a liquid tin anode solid oxide fuel cell operating under hydrogen, argon and coal

    Science.gov (United States)

    Khurana, Sanchit; LaBarbera, Mark; Fedkin, Mark V.; Lvov, Serguei N.; Abernathy, Harry; Gerdes, Kirk

    2015-01-01

    A liquid tin anode solid oxide fuel cell is constructed and investigated under different operating conditions. Electrochemical Impedance Spectroscopy (EIS) is used to reflect the effect of fuel feed as the EIS spectra changes significantly on switching the fuel from argon to hydrogen. A cathode symmetric cell is used to separate the impedance from the two electrodes, and the results indicate that a major contribution to the charge-transfer and mass-transfer impedance arises from the anode. The OCP of 0.841 V for the cell operating under argon as a metal-air battery indicates the formation of a SnO2 layer at the electrolyte/anode interface. The increase in the OCP to 1.1 V for the hydrogen fueled cell shows that H2 reduces the SnO2 film effectively. The effective diffusion coefficients are calculated using the Warburg element in the equivalent circuit model for the experimental EIS data, and the values of 1.9 10-3 cm2 s-1 at 700 °C, 2.3 10-3 cm2 s-1 at 800 °C and 3.5 10-3 cm2 s-1 at 900 °C indicate the system was influenced by diffusion of hydrogen in the system. Further, the performance degradation over time is attributed to the irreversible conversion of Sn to SnO2 resulting from galvanic polarization.

  20. Ultrahigh capacity anode material for lithium ion battery based on rod gold nanoparticles decorated reduced graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Atar, Necip, E-mail: necipatar@gmail.com [Department of Chemical Engineering, Pamukkale University, Denizli (Turkey); Eren, Tanju [Department of Chemical Engineering, Pamukkale University, Denizli (Turkey); Yola, Mehmet Lütfi [Department of Metallurgical and Materials Engineering, Sinop University, Sinop (Turkey)

    2015-09-01

    In this study, we report the synthesis of rod shaped gold nanoparticles/2-aminoethanethiol functionalized reduced graphene oxide composite (rdAuNPs/AETrGO) and its application as an anode material for lithium-ion batteries. The structure of the rdAuNPs/AETrGO composite was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The electrochemical performance was investigated at different current rates by using a coin-type cell. It was found that the rod shaped gold nanoparticles were highly dispersed on the reduced graphene oxide sheets. Moreover, the rdAuNPs/AETrGO composite showed a high specific gravimetric capacity of about 1320 mAh g{sup −1} and a long-term cycle stability. - Highlights: • We prepared rod shaped gold nanoparticles functionalized reduced graphene oxide. • The nanocomposite was used as an anode material for lithium-ion batteries. • The nanocomposite showed a high specific gravimetric capacity of about 1320 mAh g{sup −1}. • The nanocomposite exhibited a long-term cycle stability.

  1. Influence of oxidative nanopatterning and anodization on the fatigue resistance of commercially pure titanium and Ti-6Al-4V.

    Science.gov (United States)

    Ketabchi, Amirhossein; Weck, Arnaud; Variola, Fabio

    2015-04-01

    With an increasingly aging population, a significant challenge in implantology is the creation of biomaterials that actively promote tissue integration and offer excellent mechanical properties. Engineered surfaces with micro- and nanoscale topographies have shown great potential to control and direct biomaterial-host tissue interactions. Two simple yet efficient chemical treatments, oxidative nanopatterning and anodization, have demonstrated the ability to confer exciting new bioactive capacities to commercially pure titanium and Ti-6Al-4V alloy. However, the resulting nanoporous and nanotubular surfaces require careful assessment in regard to potential adverse effects on the fatigue resistance, a factor which may ultimately cause premature failure of biomedical implants. In this work, we have investigated the impact of oxidative nanopatterning and anodization on the fatigue resistance of commercially pure titanium and Ti-6Al-4V. Quantitative (e.g., S-N curves) and qualitative analyses were carried out to precisely characterize the fatigue response of treated metals and compare it to that of polished controls. Scanning electron microscopy (SEM) imaging revealed the effects of cyclic loading on the fracture surface and on the structural integrity of chemically grown nanostructured oxides. Results from this study reinforce the importance of mechanical considerations in the development and optimization of micro- and nanoscale surface treatments for metallic biomedical implants.

  2. Novel Combination of Efficient Perovskite Solar Cells with Low Temperature Processed Compact TiO2 Layer via Anodic Oxidation.

    Science.gov (United States)

    Du, Yangyang; Cai, Hongkun; Wen, Hongbin; Wu, Yuxiang; Huang, Like; Ni, Jian; Li, Juan; Zhang, Jianjun

    2016-05-25

    In this work, a facile and low temperature processed anodic oxidation approach is proposed for fabricating compact and homogeneous titanium dioxide film (AO-TiO2). In order to realize morphology and thickness control of AO-TiO2, the theory concerning anodic oxidation (AO) is unveiled and the influence of relevant parameters during the process of AO such as electrolyte ingredient and oxidation voltage on AO-TiO2 formation is observed as well. Meanwhile, we demonstrate that the planar perovskite solar cells (p-PSCs) fabricated in ambient air and utilizing optimized AO-TiO2 as electron transport layer (ETL) can deliver repeatable power conversion efficiency (PCE) over 13%, which possess superior open-circuit voltage (Voc) and higher fill factor (FF) compared to its counterpart utilizing conventional high temperature processed compact TiO2 (c-TiO2) as ETL. Through a further comparative study, it is indicated that the improvement of device performance should be attributed to more effective electron collection from perovskite layer to AO-TiO2 and the decrease of device series resistance. Furthermore, hysteresis effect about current density-voltage (J-V) curves in TiO2-based p-PSCs is also unveiled.

  3. Method of surface preparation of niobium

    Science.gov (United States)

    Srinivasan-Rao, Triveni; Schill, John F.

    2003-01-01

    The present invention is for a method of preparing a surface of niobium. The preparation method includes polishing, cleaning, baking and irradiating the niobium surface whereby the resulting niobium surface has a high quantum efficiency.

  4. A Preliminary Study on WO3‐Infiltrated W–Cu–ScYSZ Anodes for Low Temperature Solid Oxide Fuel Cells

    DEFF Research Database (Denmark)

    Abdul Jabbar, Mohammed Hussain; Reddy Sudireddy, Bhaskar; Høgh, Jens Valdemar Thorvald

    2012-01-01

    Preparation and electrochemical characterization of WO3‐infiltrated 0.48W–0.52Cu–ScYSZ (WCS) anode for solid oxide fuel cell are reported. The DC conductivity of a WO3 ceramic was 1,200 and 24 S cm–1 in reducing and oxidizing atmospheres, respectively, at 650 °C. WCS porous backbones in the form ...

  5. Phase separation of a binary liquid in anodic aluminium oxide templates: a structural study by small angle neutron scattering.

    Science.gov (United States)

    Lefort, R; Duvail, J-L; Corre, T; Zhao, Y; Morineau, D

    2011-07-01

    The radial nanostructure of the binary liquid triethylamine/water confined in 60 nm diameter independent cylindrical pores of anodic aluminium oxide membranes is studied by small angle neutron scattering. It is shown that composition inhomogeneities are present in the confined mixtures well below the bulk critical point. An analysis of the neutron scattering form factor reveals the existence of an adsorbed water layer of a few nanometers at the liquid/alumina interface, coexisting with a TEA-rich phase in the core.

  6. New nanotube synthesis strategy--application of sodium nanotubes formed inside anodic aluminium oxide as a reactive template.

    Science.gov (United States)

    Wang, Lung-Shen; Lee, Chi-Young; Chiu, Hsin-Tien

    2003-08-07

    Formation of Na nanotubes inside the channels of anodic aluminium oxide (AAO) membranes has been achieved by decomposing NaH thermally on AAO. The as-produced material, Na@AAO, is applied as a reactive template to prepare other tubular materials. Reacting Na@AAO with gaseous C6Cl6 generates carbon nanotubes (ca. 250 nm, wall thickness of 20 nm, tube length of 60 microm) inside the AAO channels. Highly aligned bundles of nearly amorphous carbon nanotubes are isolated after AAO is removed.

  7. Nanoscale carbon tubules deposited in anodic aluminium oxide template:a study of soft x-ray transmission

    Institute of Scientific and Technical Information of China (English)

    Liu Li-Feng; Zhou Zhen-Ping; Yuan Hua-Jun; Ci Li-Jie; Liu Dong-Fang; Gao Yan; Wang Jian-Xiong; Wang Gang; Zhou Wei-Ya; Zhu Pei-Ping; Cui Ming-Qi; Zheng Lei; Zhu Jie; Zhao Yi-Dong; Song Li; Yan Xiao-Qin

    2004-01-01

    Well-aligned, catalyst-free nanoscale carbon tubules array was prepared by organic compound vapour deposition method using anodic aluminium oxide (AAO) as a template. The experiment of soft x-ray channelling in such carbon tubules array deposited in AAO template was performed at Beijing Synchrotron Radiation Facility. The transmission of x-rays in carbon tubules array with AAO template support was found even higher than that in bare AAO template at high-energy part of energy spectrum though the porous area of the former was smaller than that of the latter. A qualitative explanation is presented to interpret our results.

  8. Ferrite-based perovskites as cathode materials for anode-supported solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Mai, Andreas; Haanappel, Vincent A.C.; Uhlenbruck, Sven; Tietz, Frank; Stoever, Detlev [Institute for Materials and Processes in Energy Systems, Forschungszentrum Juelich, IWV-1, D-52425 Juelich (Germany)

    2005-05-12

    The properties and the applicability of iron- and cobalt-containing perovskites were evaluated as cathodes for solid oxide fuel cells (SOFCs) in comparison to state-of-the-art manganite-based perovskites. The materials examined were La{sub 1-x-y}Sr{sub x}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (x=0.2 and 0.4; y=0-0.05), La{sub 0.8}Sr{sub 0.2}FeO{sub 3-{delta}}, La{sub 0.7}Ba{sub 0.3}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} and Ce{sub 0.05}Sr{sub 0.95}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}}. The main emphasis was placed on the electrochemical properties of the materials, which were investigated on planar anode-supported SOFCs with 8 mol% yttria-stabilised zirconia (8YSZ) electrolytes. An interlayer of the composition Ce{sub 0.8}Gd{sub 0.2}O{sub 2-{delta}} was placed between the electrolyte and the cathode to prevent undesired chemical reactions between the materials. The sintering temperatures of the cathodes were adapted for each of the materials to obtain similar microstructures. In comparison to the SOFCs with state-of-the-art manganite-based cathodes, SOFCs with La{sub 1-x-y}Sr{sub x}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} cathodes achieved much higher current densities. Small A-site deficiency and high strontium content had a particularly positive effect on cell performance. The measured current densities of cells with these cathodes were as high as 1.76 A/cm{sup 2} at 800 {sup o}C and 0.7 V, which is about twice the current density of cells with LSM/YSZ cathodes. SOFCs with La{sub 0.58}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} cathodes have been operated for more than 5000 h in endurance tests with a degradation of 1.0-1.5% per 1000 h.

  9. Free-standing reduced graphene oxide/MnO2-reduced graphene oxide-carbon nanotube nanocomposite flexible membrane as an anode for improving lithium-ion batteries.

    Science.gov (United States)

    Li, Yong; Ye, Daixin; Shi, Bin; Liu, Wen; Guo, Rui; Pei, Haijuan; Xie, Jingying

    2017-01-09

    To solve the barriers of poor rate capability and inferior cycling stability for the MnO2 anode in lithium ion batteries, we present a highly flexible membrane anode employing two-dimensional (2D) reduced graphene oxide sheets (rGO) and a three-dimensional (3D) MnO2-reduced graphene oxide-carbon nanotube nanocomposite (MGC) by a vacuum filtration and thermal annealing approach. All the components in the 2D/3D thin film anode have a synergistic effect on the improved performance. The initial discharge specific capacity of the electrode with the MnO2 content of 56 wt% was 1656.8 mA h g(-1) and remains 1172.5 mA h g(-1) after 100 cycles at a density of 100 mA g(-1). On enhancing the density to 200 mA g(-1), the membrane-electrode still exhibits a large reversible discharging capacity of ∼948.9 mA h g(-1) after 300 cycles. Moreover, the flexible Li-ion battery with a large area also shows excellent electrochemical performance in different bending positions, which provides the potential for wearable energy storage devices.

  10. Characterization of Niobium Platings Obtained from NaCl-KCl Melts

    DEFF Research Database (Denmark)

    Gillesberg, Bo; Barner, Jens H. Von; Bjerrum, Niels

    1998-01-01

    oxidation of metallic niobium with NiCl2. The initial valency of niobium was found to 3 when a NaCl-KCl melt was applied as solvent. The deposits were characterised by X-ray analy-sis and Scanning Electron Microscopy (SEM) combined with EDX analysis. From both NaCl-KCl and LiCl-KCl melts dense and coherent...

  11. Fracture properties of nickel-based anodes for solid oxide fuel cells

    DEFF Research Database (Denmark)

    Goutianos, Stergios; Frandsen, Henrik Lund; Sørensen, Bent F.

    2010-01-01

    such as the anode material (NiO–YSZ) in a fuel cell. The approach involves a new specimen geometry which consists of a thin ceramic glued onto thick steel beams to form a double cantilever beam (DCB) specimen. The fracture toughness values, measured from truly sharp cracks, are obtained over a range of applied...

  12. Characterisation of the Ni/ScYSZ interface in a model solid oxide fuel cell anode

    DEFF Research Database (Denmark)

    Schmidt, Michael Stenbæk; Hansen, Karin Vels; Norrman, Kion;

    2008-01-01

    A nickel point electrode setup was used as a model of an SOFC anode on three slightly different electrolytes of zirconia stabilised by co-doping with scandia and yttria. The effect of electrolyte impurities on the electrode polarisation resistance was investigated by correlating electrochemical i...

  13. Vapor-phase fabrication of β-iron oxide nanopyramids for lithium-ion battery anodes.

    Science.gov (United States)

    Carraro, Giorgio; Barreca, Davide; Cruz-Yusta, Manuel; Gasparotto, Alberto; Maccato, Chiara; Morales, Julián; Sada, Cinzia; Sánchez, Luis

    2012-12-01

    The other polymorph: A vapor-phase route for the fabrication of β-Fe(2)O(3) nanomaterials on Ti substrates at 400-500 °C is reported. For the first time, the β polymorph is tested as anode for lithium batteries, exhibiting promising performances in terms of Li storage and rate capability.

  14. Nano integrated lithium polymer electrolytes based on anodic aluminum oxide (AAO) templates

    Science.gov (United States)

    Bokalawela, Roshan S. P.

    Since their discovery in the 1970s, polymer electrolytes have been actively studied because they have properties important for many device applications. However, even after 40 years, the detailed mechanisms of conductivity in these electrolytes are still not completely understood. Moreover, the conductivity in polymer electrolytes is one of the limiting factors of these devices so that different methods to enhance conductivity are actively being explored. One proposed method of enhancing the conductivity is to confine the polymer electrolyte in the nanoscale, but the study of material properties at the nanoscale is challenging in this area. In this work, we confine poly(ethylene oxide) lithium triflate (PEO:LiTf)(X:1)X=10,30 polymer electrolytes in carefully fabricated nanometer-diameter anodized aluminum oxide (AAO) pore structures. We demonstrate two orders of magnitude higher conductivity in the confined structures versus that of bulk films. Using x-ray characterization we show that this increased conductivity is associated with ordered PEO polymer chains aligned in the template pore direction. The activation energy of the AAO-confined polymer electrolyte is found to be smaller than that of the unconfined melt and about half that of the unconfined solid. This result indicates that not only is the room-temperature confined polymer ordered, but that this order persists at temperatures where the nano-confined polymer electrolyte is expected to be a liquid. The geometric bulk resistances of the electrolytes were obtained by AC-impedance spectra, from which the ionic conductivities were calculated. The Arrhenius plots of temperature dependent ionic conductivities showed that the usual melting temperature of the PEO phase in confined PEO:LiTf(X:1) X=10,30 is suppressed and a single activation energy was evident throughout the temperature range 25--90 °C. Wide-angle x-ray scattering (WAXS) patterns show that the polymer chains in both the pure PEO and PEO:LiTf(10

  15. Kinetics of Carbon Monoxide Electro-Oxidation in Solid-Oxide Fuel Cells from Ni-YSZ Patterned-Anode Measurements

    KAUST Repository

    Hanna, J.

    2013-04-17

    A mathematical model is developed around the framework of a reduced mechanism describing electrochemical oxidation of carbon monoxide on Ni-YSZ patterned anodes. The electro-oxidation mechanism involves three reactions, one describing adsorption/ desorption of COonNi, and two single-electron charge-transfer steps inwhich the surface adsorbate CO(Ni) participates directly. These steps are coupled with surface transport in a reaction-diffusion model for which analytic equilibrium and steady-state solutions are derived. As much as possible, we make use of existing, independent, published information about heterogeneous chemistry, surface transport, and other model parameters. The only unknowns in our model are taken to be the kinetic rate constants of the electrochemical reactions, which we evaluate by fitting the model predictions to previously published patterned-anode experiments [B. Habibzadeh, Ph.D. Thesis, University of Maryland, College Park, MD, USA (2007)]. The results show that diffusion of CO on the Ni surface to the three-phase boundary is the rate-controlling process for CO electro-oxidation. Moreover, from a reaction standpoint, the charge-transfer process is dominated by a slow step involving CO(Ni). These findings collectively demonstrate the critical dependence of the electro-oxidation process to the direct participation of CO. © 2013 The Electrochemical Society. All rights reserved.

  16. Synthesis and electrochemical performance of ruthenium oxide-coated carbon nanofibers as anode materials for lithium secondary batteries

    Science.gov (United States)

    Hyun, Yura; Choi, Jin-Yeong; Park, Heai-Ku; Lee, Chang-Seop

    2016-12-01

    In this study, ruthenium oxide (RuO2) coated carbon nanofibers (CNFs) were synthesized and applied as anode materials of Li secondary batteries. The CNFs were grown on Ni foam via chemical vapor deposition (CVD) method after CNFs/Ni foam was put into the 0.01 M RuCl3 solution. The ruthenium oxide-coated CNFs/Ni foam was dried in a dryer at 80 °C. The morphologies, compositions, and crystal quality of RuO2/CNFs/Ni foam were characterized by SEM, EDS, XRD, Raman spectroscopy, and XPS. The electrochemical characteristics of RuO2/CNFs/Ni foam as anode of Li secondary batteries were investigated using three-electrode cell. The RuO2/CNFs/Ni foam was directly employed as a working electrode without any binder, and lithium foil was used as the counter and reference electrodes. LiClO4 (1 M) was employed as electrolyte and dissolved in a mixture of propylene carbonate (PC): ethylene carbonate (EC) in a 1:1 volume ratio. The galvanostatic charge/discharge cycling and cyclic voltammetry measurements were carried out at room temperature by using a battery tester. In particular, synthesized RuO2/CNFs/Ni foam showed the highest retention rate (47.4%). The initial capacity (494 mAh/g) was reduced to 234 mAh/g after 30 cycles.

  17. Microstructural degradation of Ni-YSZ anodes for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Thyden, K.

    2008-03-15

    Ni-YSZ cermets have been used as anode materials in SOFCs for more than 20 years. Despite this fact, the major cause of degradation within the Ni-YSZ anode, namely Ni sintering / coarsening, is still not fully understood. Even if microstructural studies of anodes in tested cells are of technological relevance, it is difficult to identify the effect from isolated parameters such as temperature, fuel gas composition and polarization. Model studies of high temperature aged Ni-YSZ cermets are generally performed in atmospheres containing relatively low concentrations of H2O. In this work, the microstructural degradation in both electrochemically longterm tested cells and high-temperature aged model materials are studied. Since Ni particle sintering / coarsening is attributed to be the major cause of anode degradation, this subject attains the primary focus. A large part of the work is focused on improving microstructural techniques and shows that the application of low acceleration voltages (<= 1 kV) in a FE-SEM makes it possible to obtain two useful types of contrast between the phases in Ni-YSZ composites. By changing between the ordinary lateral SE detector and the inlens detector, using similar microscope settings, two very different sample characteristics are probed: 1) The difference in secondary emission coefficient, delta, between the percolating and non-percolating Ni is maximized in the low-voltage range due to a high delta for the former and the suppression of delta by a positive charge for the latter. This difference yields a contrast between the two phases which is picked up by an inlens secondary electron detector. 2) The difference in backscatter coefficient, eta, between Ni and YSZ is shown to increase with decreasing voltage. The contrast is illustrated in images collected by the normal secondary detector since parts of the secondary signals are generated by backscattered electrons. High temperature aging experiments of model Ni-YSZ anode cermets show

  18. Preparation and application of a titanium dioxide/graphene oxide anode material for lithium-ion batteries

    Science.gov (United States)

    Siwińska-Stefańska, Katarzyna; Kurc, Beata

    2015-12-01

    This paper describes the synthesis and physicochemical properties of a new type of titania/graphene oxide (TA/GO) composite. Titania powder was synthesized via the sol-gel method, and its surface was functionalized with N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AAPTS) to increase its adhesion to graphene oxide. Transmission electron microscopy (TEM), non-invasive back scattering (NIBS), porous structure parameters (low-temperature nitrogen sorption), degree of modification of titania and TA/GO determined by Fourier-transform infrared spectroscopy (FT-IR), impedance analysis, charging/discharging and cyclic voltammetry were carried out. At a current density of 50 mA g-1, the good cyclability exhibited by the TA/GO anode can be readily retained at 370 mAh g-1 after 50 cycles, which is outstanding among the TiO2 composites reported in the literature.

  19. Preparation of 3D nanoporous copper-supported cuprous oxide for high-performance lithium ion battery anodes.

    Science.gov (United States)

    Liu, Dequan; Yang, Zhibo; Wang, Peng; Li, Fei; Wang, Desheng; He, Deyan

    2013-03-01

    Three-dimensional (3D) nanoporous architectures can provide efficient and rapid pathways for Li-ion and electron transport as well as short solid-state diffusion lengths in lithium ion batteries (LIBs). In this work, 3D nanoporous copper-supported cuprous oxide was successfully fabricated by low-cost selective etching of an electron-beam melted Cu(50)Al(50) alloy and subsequent in situ thermal oxidation. The architecture was used as an anode in lithium ion batteries. In the first cycle, the sample delivered an extremely high lithium storage capacity of about 2.35 mA h cm(-2). A high reversible capacity of 1.45 mA h cm(-2) was achieved after 120 cycles. This work develops a promising approach to building reliable 3D nanostructured electrodes for high-performance lithium ion batteries.

  20. Apatite Formation and Biocompatibility of a Low Young's Modulus Ti-Nb-Sn Alloy Treated with Anodic Oxidation and Hot Water.

    Directory of Open Access Journals (Sweden)

    Hidetatsu Tanaka

    Full Text Available Ti-6Al-4V alloy is widely prevalent as a material for orthopaedic implants because of its good corrosion resistance and biocompatibility. However, the discrepancy in Young's modulus between metal prosthesis and human cortical bone sometimes induces clinical problems, thigh pain and bone atrophy due to stress shielding. We designed a Ti-Nb-Sn alloy with a low Young's modulus to address problems of stress disproportion. In this study, we assessed effects of anodic oxidation with or without hot water treatment on the bone-bonding characteristics of a Ti-Nb-Sn alloy. We examined surface analyses and apatite formation by SEM micrographs, XPS and XRD analyses. We also evaluated biocompatibility in experimental animal models by measuring failure loads with a pull-out test and by quantitative histomorphometric analyses. By SEM, abundant apatite formation was observed on the surface of Ti-Nb-Sn alloy discs treated with anodic oxidation and hot water after incubation in Hank's solution. A strong peak of apatite formation was detected on the surface using XRD analyses. XPS analysis revealed an increase of the H2O fraction in O 1s XPS. Results of the pull-out test showed that the failure loads of Ti-Nb-Sn alloy rods treated with anodic oxidation and hot water was greater than those of untreated rods. Quantitative histomorphometric analyses indicated that anodic oxidation and hot water treatment induced higher new bone formation around the rods. Our findings indicate that Ti-Nb-Sn alloy treated with anodic oxidation and hot water showed greater capacity for apatite formation, stronger bone bonding and higher biocompatibility for osteosynthesis. Ti-Nb-Sn alloy treated with anodic oxidation and hot water treatment is a promising material for orthopaedic implants enabling higher osteosynthesis and lower stress disproportion.

  1. Intermediate-Temperature Solid-Oxide Fuel Cells with a Gadolinium-Doped Ceria Anodic Functional Layer Deposited via Radio-Frequency Sputtering.

    Science.gov (United States)

    Tanveer, Waqas Hassan; Ji, Sanghoon; Yu, Wonjong; Cho, Gu Young; Lee, Yoon Ho; Cha, Suk Won

    2015-11-01

    We investigated the effects of the insertion of a gadolinium-doped ceria (GDC) anodic functional layer (AFL) on the electrochemical performance of intermediate-temperature solid-oxide fuel cells (SOFCs). Fully stabilized yttria-stabilized zirconia (YSZ) was used as an oxygen-ion-conducting and support material. Nickel-Samaria-doped ceriathin film was used as an anode material, while screen-printed lanthanum strontium magnetite served as a cathode material. In order to enhance the interfacial reaction on the anode side, a GDC-AFL with a thickness of about 140 nm, deposited via radio-frequency sputtering, was inserted into the anode-electrolyte interface. SOFCs with and without a GDC-AFL were electrochemically characterized. In an intermediate temperature range of about 700 - 800 degrees C, the application of the GDC-AFL led to an increase in the peak power density of approximately 16%.

  2. Nanocrystalline ceria coatings on solid oxide fuel cell anodes: the role of organic surfactant pretreatments on coating microstructures and sulfur tolerance.

    Science.gov (United States)

    Wu, Chieh-Chun; Tang, Ling; De Guire, Mark R

    2014-01-01

    Treatments with organic surfactants, followed by the deposition of nanocrystalline ceria coatings from aqueous solution, were applied to anodes of solid oxide fuel cells. The cells were then operated in hydrogen/nitrogen fuel streams with H2S contents ranging from 0 to 500 ppm. Two surfactant treatments were studied: immersion in dodecanethiol, and a multi-step conversion of a siloxy-anchored alkyl bromide to a sulfonate functionality. The ceria coatings deposited after the thiol pretreatment, and on anodes with no pretreatment, were continuous and uniform, with thicknesses of 60-170 nm and 100-140 nm, respectively, and those cells exhibited better lifetime performance and sulfur tolerance compared to cells with untreated anodes and anodes with ceria coatings deposited after the sulfonate pretreatment. Possible explanations for the effects of the treatments on the structure of the coatings, and for the effects of the coatings on the performance of the cells, are discussed.

  3. Triple-phase boundary and power density enhancement in thin solid oxide fuel cells by controlled etching of the nickel anode.

    Science.gov (United States)

    Ebrahim, Rabi; Yeleuov, Mukhtar; Issova, Ainur; Tokmoldin, Serekbol; Ignatiev, Alex

    2014-01-01

    Fabrication of microporous structures for the anode of a thin film solid oxide fuel cell (SOFC(s)) using controlled etching process has led us to increased power density and increased cell robustness. Micropores were etched in the nickel anode by both wet and electrochemical etching processes. The samples etched electrochemically showed incomplete etching of the nickel leaving linked nickel islands inside the pores. Samples which were wet- etched showed clean pores with no nickel island residues. Moreover, the sample with linked nickel islands in the anode pores showed higher output power density as compared to the sample with clean pores. This enhancement is related to the enlargement of the surface of contact between the fuel-anode-electrolyte (the triple-phase boundary).

  4. Nanocrystalline ceria coatings on solid oxide fuel cell anodes: the role of organic surfactant pretreatments on coating microstructures and sulfur tolerance

    Science.gov (United States)

    Wu, Chieh-Chun; Tang, Ling

    2014-01-01

    Summary Treatments with organic surfactants, followed by the deposition of nanocrystalline ceria coatings from aqueous solution, were applied to anodes of solid oxide fuel cells. The cells were then operated in hydrogen/nitrogen fuel streams with H2S contents ranging from 0 to 500 ppm. Two surfactant treatments were studied: immersion in dodecanethiol, and a multi-step conversion of a siloxy-anchored alkyl bromide to a sulfonate functionality. The ceria coatings deposited after the thiol pretreatment, and on anodes with no pretreatment, were continuous and uniform, with thicknesses of 60–170 nm and 100–140 nm, respectively, and those cells exhibited better lifetime performance and sulfur tolerance compared to cells with untreated anodes and anodes with ceria coatings deposited after the sulfonate pretreatment. Possible explanations for the effects of the treatments on the structure of the coatings, and for the effects of the coatings on the performance of the cells, are discussed. PMID:25383282

  5. Growth of Hollow Transition Metal (Fe, Co, Ni) Oxide Nanoparticles on Graphene Sheets through Kirkendall Effect as Anodes for High-Performance Lithium-Ion Batteries.

    Science.gov (United States)

    Yu, Xianbo; Qu, Bin; Zhao, Yang; Li, Chunyan; Chen, Yujin; Sun, Chunwen; Gao, Peng; Zhu, Chunling

    2016-01-26

    A general strategy based on the nanoscale Kirkendall effect has been developed to grow hollow transition metal (Fe, Co or Ni) oxide nanoparticles on graphene sheets. When applied as lithium-ion battery anodes, these hollow transition metal oxide-based composites exhibit excellent electrochemical performance, with high reversible capacities and long-term stabilities at a high current density, superior to most transition metal oxides reported to date.

  6. Carbon Materials Metal/Metal Oxide Nanoparticle Composite and Battery Anode Composed of the Same

    Science.gov (United States)

    Hung, Ching-Cheh (Inventor)

    2006-01-01

    A method of forming a composite material for use as an anode for a lithium-ion battery is disclosed. The steps include selecting a carbon material as a constituent part of the composite, chemically treating the selected carbon material to receive nanoparticles, incorporating nanoparticles into the chemically treated carbon material and removing surface nanoparticles from an outside surface of the carbon material with incorporated nanoparticles. A material making up the nanoparticles alloys with lithium.

  7. Partial oxidation of dimethyl ether using the structured catalyst Rh/Al2O3/Al prepared through the anodic oxidation of aluminum.

    Science.gov (United States)

    Yu, B Y; Lee, K H; Kim, K; Byun, D J; Ha, H P; Byun, J Y

    2011-07-01

    The partial oxidation of dimethyl ether (DME) was investigated using the structured catalyst Rh/Al2O3/Al. The porous Al2O3 layer was synthesized on the aluminum plate through anodic oxidation in an oxalic-acid solution. It was observed that about 20 nm nanopores were well developed in the Al2O3 layer. The thickness of Al2O3 layer can be adjusted by controlling the anodizing time and current density. After pore-widening and hot-water treatment, the Al2O3/Al plate was calcined at 500 degrees C for 3 h. The obtained delta-Al2O3 had a specific surface area of 160 m2/g, making it fit to be used as a catalyst support. A microchannel reactor was designed and fabricated to evaluate the catalytic activity of Rh/Al2O3/Al in the partial oxidation of DME. The structured catalyst showed an 86% maximum hydrogen yield at 450 degrees C. On the other hand, the maximum syngas yield by a pack-bed-type catalyst could be attained by using a more than fivefold Rh amount compared to that used in the structured Rh/Al2O3/Al catalyst.

  8. Kinetics of niobium carbide coating produced on AISI 1040 steel by thermo-reactive deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Ugur

    2004-07-15

    There are a lot of technologically interesting characteristics of niobium carbide coating deposited by pack method which is the production of hard, wear-resistant, oxidation and corrosion resistant coating layer on the steel substrates. In the present study, the growth kinetics of niobium carbide layer deposited by thermo-reactive diffusion techniques in a solid medium on steel samples was reported. Niobium carbide coating treatment was performed on AISI 1040 steels in the powder mixture consisting of ferro-niobium, ammonium chloride and alumina at 1073, 1173 and 1273 K for 1-4 h. The presence of NbC and Nb{sub 2}C phases formed on the surface of the steel substrates was confirmed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analyses. Niobium carbide layer thickness ranges from 3.42{+-}0.52 to 11.78{+-}2.29 {mu}m depending upon the treatment time and temperature. Layer growth kinetics was analyzed by measuring the depth of niobium carbide layer as a function of time and temperature. The kinetics of niobium carbide coating by pack method shows a parabolic relationship between carbide layer thickness and treatment time, and the activation energy for the process is estimated to be 91.257 kJ mol{sup -1}. Moreover, an attempt was made to investigate the possibility of predicting the contour diagram of niobium carbide layer variation and to establish some empirical relationships between process parameters and niobium carbide layer thickness.

  9. Cytotoxic, hematologic and histologic effects of niobium pentoxide in Swiss mice.

    Science.gov (United States)

    Dsouki, Nuha Ahmad; de Lima, Maurício Pereira; Corazzini, Roseli; Gáscon, Thaís Moura; Azzalis, Ligia Ajaime; Junqueira, Virgínia Berlanga Campos; Feder, David; Fonseca, Fernando Luiz Affonso

    2014-05-01

    The use of metal devices in medical application is increasing but it remains incompletely understood the physiological effects of component degradation. Niobium (Nb) alloys have already been investigated in the 1980's and recent studies demonstrated the potential of Nb as an implant material. The purpose of this study was to determine cytotoxic, hematologic and histologic effects of niobium in Swiss mice. Animals were treated with a single dose of 3 % niobium oxide (Nb2O5) diluted in PBS, i.p. Cytotoxic assay, hematologic and histologic evaluation were done 3, 7 and 12 days after niobium treatment. Data have shown increased number of cells after niobium treatment, but there was no difference in cell viability. Furthermore, it was not observed hematological modification 3, 7 or 12 days after niobium treatment. Despite the fact that animals treated with niobium for 3 and 7 days showed mild degeneration in hepatocytes, mice kept alive for 12 days showed liver cells regeneration. Our results suggested that niobium cytotoxicity was not progressive because 12 days after treatment there was an evident liver regeneration. Data obtained indicated that niobium may be promising alternatives to biomedical applications.

  10. Low temperature solid oxide fuel cells with proton-conducting Y:BaZrO{sub 3} electrolyte on porous anodic aluminum oxide substrate

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Seungbum [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); School of Mechanical and Aerospace Engineering, Seoul National University, Daehak-dong, Gwanak-gu, Seoul 151–742 (Korea, Republic of); Su, Pei-Chen [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Ji, Sanghoon [Graduate School of Convergence Science and Technology, Seoul National University, Daehak-dong, Gwanak-gu, Seoul 151–742 (Korea, Republic of); Cha, Suk Won, E-mail: swcha@snu.ac.kr [School of Mechanical and Aerospace Engineering, Seoul National University, Daehak-dong, Gwanak-gu, Seoul 151–742 (Korea, Republic of)

    2013-10-01

    This paper presents the architecture of a nano thin-film yttrium-doped barium zirconate (BYZ) solid-oxide fuel cell that uses nanoporous anodic aluminum oxide (AAO) as a supporting and gas-permeable substrate. The anode was fabricated by sputtering 300 nm platinum thin film that partially covered the AAO surface pores, followed by an additional conformal platinum coating to tune the pore size by atomic layer deposition. Two different nano-porous anode structures with a pore size of 10 nm or 50 nm were deposited. Proton-conducting BYZ ceramic electrolyte with increasing thicknesses of 300, 600, and 900 nm was deposited on top of the platinum anode by pulsed laser deposition, followed by a 200 nm layer of porous Pt sputtered on BYZ electrolyte as a cathode. The open circuit voltage (OCV) of the fuel cells was characterized at 250 °C with 1:1 volumetric stoichiometry of a methanol/water vapor mixture as the fuel. The OCVs were 0.17 V with a 900 nm-thick BYZ electrolyte on 50 nm pores and 0.3 V with a 600 nm-thick BYZ electrolyte on 10 nm pores, respectively, but it increased to 0.8 V for a 900 nm-thick BYZ electrolyte on 10 nm pores, indicating that increasing the film thickness and decreasing a surface pore size help to reduce the number of electrolyte pinholes and the gas leakage through the electrolyte. A maximum power density of 5.6 mW/cm{sup 2} at 250 °C was obtained from the fuel cell with 900 nm of BYZ electrolyte using methanol vapor as a fuel. - Highlights: • A low temperature ceramic fuel cell on nano-porous substrate was demonstrated. • A thin-film yttrium doped barium zirconate (BYZ) was deposited as an electrolyte. • An open circuit voltage (OCV) was measured to verify the BYZ film quality. • An OCV increased by increasing BYZ film thickness and decreasing pore size of anode. • The current–voltage performance was measured using vaporized methanol fuel at 250 °C.

  11. V{sub 2}O{sub 5}-ZrO{sub 2} catalysts for the oxidative dehydrogenation of propane - influence of the niobium oxide doping

    Energy Technology Data Exchange (ETDEWEB)

    Albrecht, S.; Hallmeier, K.H.; Wendt, G. [Leipzig Univ. (Germany). Fakultaet fuer Chemie und Mineralogie; Lippold, G. [Leipzig Univ. (Germany). Fakultaet fuer Physik und Geowissenschaften

    1998-12-31

    The oxidative dehydrogenation (ODH) of light alkanes is an alternative way for the production of olefins. A wide variety of catalytic systems has been investigated. Vanadium oxide based catalysts were described in the literature as effective catalysts for the ODH of propane. The catalytic activity and selectivity depend on the kind of support material, the kind of dopants and the formation of complex metal oxide phases. In recent papers it was claimed that both orthovanadate and/or pyrovanadate species are selective for the ODH of propane. Niobia based materials were investigated as catalysts for acidic and selective oxidation type reactions. In the ODH of propane niobia exhibited a high selectivity to propene but the conversion of propane was low. V{sub 2}O{sub 5}-Nb{sub 2}O{sub 5} catalysts proved to be catalytically active and selective and showed no formation of oxygenates. In the present study the influence of the niobia dopant of the catalytic properties of V{sub 2}O{sub 5}-ZrO{sub 2} catalysts in the ODH of propane was examined. The structural and textural properties of the catalysts were investigated using several methods. (orig.)

  12. Surface Modification of a MCFC Anode by Electrochemical Alloying

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Considering the properties of the valve metal alloys with specific corrosion resistance and electrocatalytic ac tivity, an investigation was made to examine if nickel-niobium alloy could serve as the anode material for molten carbo nate fuel cell (MCFC). An attempt was made to produce nickel-niobium surface alloy by an electrochemical process in the molten fluorides and to testify its performance required by the MCFC anode. Experimental results indicated that the corrosion resistance as well as polarization performance of the nickel electrode was improved by the surface alloying.As far as the corrosion resistance and polarization performance is concerned, the nickel-niobium surface alloy can be considered as a candidate material for the anode of MCFC.

  13. SRF niobium characterization using SIMS and FIB-TEM

    Energy Technology Data Exchange (ETDEWEB)

    Stevie, F. A. [Analytical Instrumentation Facility, North Carolina State University, 2410 Campus Shore Dr., Raleigh, NC 27695, US (United States)

    2015-12-04

    Our understanding of superconducting radio frequency (SRF) accelerator cavities has been improved by elemental analysis at high depth resolution and by high magnification microscopy. This paper summarizes the technique development and the results obtained on poly-crystalline, large grain, and single crystal SRF niobium. Focused ion beam made possible sample preparation using transmission electron microscopy and the images obtained showed a very uniform oxide layer for all samples analyzed. Secondary ion mass spectrometry indicated the presence of a high concentration of hydrogen and the hydrogen content exhibited a relationship with improvement in performance. Depth profiles of carbon, nitrogen, and oxygen did not show major differences with heat treatment. Niobium oxide less than 10 nm thick was shown to be an effective hydrogen barrier. Niobium with titanium contamination showed unexpected performance improvement.

  14. SRF niobium characterization using SIMS and FIB-TEM

    Science.gov (United States)

    Stevie, F. A.

    2015-12-01

    Our understanding of superconducting radio frequency (SRF) accelerator cavities has been improved by elemental analysis at high depth resolution and by high magnification microscopy. This paper summarizes the technique development and the results obtained on poly-crystalline, large grain, and single crystal SRF niobium. Focused ion beam made possible sample preparation using transmission electron microscopy and the images obtained showed a very uniform oxide layer for all samples analyzed. Secondary ion mass spectrometry indicated the presence of a high concentration of hydrogen and the hydrogen content exhibited a relationship with improvement in performance. Depth profiles of carbon, nitrogen, and oxygen did not show major differences with heat treatment. Niobium oxide less than 10 nm thick was shown to be an effective hydrogen barrier. Niobium with titanium contamination showed unexpected performance improvement.

  15. Large grain cavities from pure niobium ingot

    Science.gov (United States)

    Myneni, Ganapati Rao [Yorktown, VA; Kneisel, Peter [Williamsburg, VA; Cameiro, Tadeu [McMurray, PA

    2012-03-06

    Niobium cavities are fabricated by the drawing and ironing of as cast niobium ingot slices rather than from cold rolled niobium sheet. This method results in the production of niobium cavities having a minimum of grain boundaries at a significantly reduced cost as compared to the production of such structures from cold rolled sheet.

  16. Performance and life-time behaviour of NiCu-CGO anodes for the direct electro-oxidation of methane in IT-SOFCs

    Science.gov (United States)

    Sin, A.; Kopnin, E.; Dubitsky, Y.; Zaopo, A.; Aricò, A. S.; La Rosa, D.; Gullo, L. R.; Antonucci, V.

    An anodic cermet of NiCu alloy and gadolinia doped ceria has been investigated for CH 4 electro-oxidation in IT-SOFCs. Polarization curves have been recorded in the temperature range from 650 to 800 °C. A maximum power density of 320 mW cm -2 at 800 °C has been obtained in the presence of dry methane in an electrolyte-supported cell. The electrochemical behaviour during 1300 h operation in dry methane and in the presence of redox-cycles has been investigated at 750 °C; variation of the electrochemical properties during these experiments have been interpreted in terms of anode morphology modifications. The methane cracking process at the anode catalyst has been investigated by analysing the oxidative stripping of deposited carbon species.

  17. Performance and life-time behaviour of NiCu-CGO anodes for the direct electro-oxidation of methane in IT-SOFCs

    Energy Technology Data Exchange (ETDEWEB)

    Sin, A.; Kopnin, E.; Dubitsky, Y.; Zaopo, A. [Pirelli Labs S.p.A., Viale Sarca 222, I-20126 Milan (Italy); Arico, A.S.; La Rosa, D.; Gullo, L.R.; Antonucci, V. [CNR-ITAE, Via Salita Santa Lucia Sopra Contesse 5, I-98125 Messina (Italy)

    2007-01-10

    An anodic cermet of NiCu alloy and gadolinia doped ceria has been investigated for CH{sub 4} electro-oxidation in IT-SOFCs. Polarization curves have been recorded in the temperature range from 650 to 800{sup o}C. A maximum power density of 320mWcm{sup -2} at 800{sup o}C has been obtained in the presence of dry methane in an electrolyte-supported cell. The electrochemical behaviour during 1300h operation in dry methane and in the presence of redox-cycles has been investigated at 750{sup o}C; variation of the electrochemical properties during these experiments have been interpreted in terms of anode morphology modifications. The methane cracking process at the anode catalyst has been investigated by analysing the oxidative stripping of deposited carbon species. (author)

  18. 阳极氧化法制备多孔氧化铝膜的形成过程研究%Investigation on the growth sequence of porous anodic aluminum oxide films by two-step anodization

    Institute of Scientific and Technical Information of China (English)

    刘海凤; 路丙强; 梁冬林; 魏水强; 苟凯佩; 王凡; 文衍宣

    2012-01-01

    采用阳极氧化技术,研究了电压对多孔氧化铝膜生长过程的影响.使用扫描电镜( SEM)对在草酸-水-乙醇体系中形成的多孔氧化铝膜形貌进行观测.结果表明,在第二步氧化过程中,在40V氧化电压下,多孔氧化铝膜的有序度和孔径随反应时间延长而降低;在80 V下,经过长时间反应,AAO膜表面腐蚀严重,难以获得平整的多孔结构.预氧化过程所形成的薄氧化层有效保护了多孔氧化铝表面,同时对多孔结构具有短距离诱导作用.改变氧化电压、电解质浓度和反应时间,有序孔排列的结构参数也有所改变.高电场下,孔道的相互作用促进了其生长分化,形成了两种不同的孔道结构.%The detailed growth processes of porous anodic aluminum oxide films influenced by the applied voltage were studied via anodization method. The appearance of the porous anodic aluminum oxide films formed in oxalic acid-water-ethanol solution was studied by SEM. At the second anodization step, the ordering degree and pore size of oxide films decreased at 40 V, while the rough surface of AAO by severe corrosion was obtained at 80 V. Whereas, the surface oxide layer generated by pre-anodization provided effective protection at the early stage of high-voltage anodization, and guided the formation of ordered pores array in short range. The structural parameters of ordered pores array were dependent on the applied voltage, electrolyte concentration and reaction time. At high applied voltage, the cause of interaction forces between neighboring pores enhances the differentiation of pore growth, and hence two different pores growth behaviors in the internal and surface of AAO membrane are observed.

  19. Anodic oxidation of ketoprofen-An anti-inflammatory drug using boron doped diamond and platinum electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Murugananthan, M., E-mail: muruga.chem@gmail.com [National Metallurgical Laboratory Madras Centre, CSIR Madras Complex, Taramani, Chennai 600 113 (India); Latha, S.S.; Bhaskar Raju, G. [National Metallurgical Laboratory Madras Centre, CSIR Madras Complex, Taramani, Chennai 600 113 (India); Yoshihara, S. [Department of Advanced Interdisciplinary Science, Graduate School of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya, Tochigi 321-8585 (Japan)

    2010-08-15

    The mineralization of ketoprofen (KP) by anodic oxidation was studied by employing boron doped diamond (BDD) and Pt electrodes. The redox behavior of KP molecule, fouling of electrodes, generation of oxygen and active chlorine species were studied by cyclic voltammetry. The effect of electrolyte, pH of aqueous medium and applied current density on the mineralization behavior of KP was also investigated. The degradation and mineralization were monitored by UV-vis spectrophotometer and total organic carbon analyzer, respectively. The results were explained in terms of in situ generation of hydroxyl radical ({center_dot}OH), peroxodisulfate (S{sub 2}O{sub 8}{sup 2-}), and active chlorine species (Cl{sub 2}, HOCl, OCl{sup -}). The physisorbed {center_dot}OH on BDD was observed to trigger the combustion of KP in to CO{sub 2} and H{sub 2}O. The poor mineralization at both BDD and Pt anodes in the presence of NaCl as supporting electrolyte was ascribed to the formation of chlorinated organic compounds which are refractory. Complete mineralization of KP molecule was achieved using Na{sub 2}SO{sub 4} as supporting electrolyte.

  20. A silicon nanowire-reduced graphene oxide composite as a high-performance lithium ion battery anode material.

    Science.gov (United States)

    Ren, Jian-Guo; Wang, Chundong; Wu, Qi-Hui; Liu, Xiang; Yang, Yang; He, Lifang; Zhang, Wenjun

    2014-03-21

    Toward the increasing demands of portable energy storage and electric vehicle applications, silicon has been emerging as a promising anode material for lithium-ion batteries (LIBs) owing to its high specific capacity. However, serious pulverization of bulk silicon during cycling limits its cycle life. Herein, we report a novel hierarchical Si nanowire (Si NW)-reduced graphene oxide (rGO) composite fabricated using a solvothermal method followed by a chemical vapor deposition process. In the composite, the uniform-sized [111]-oriented Si NWs are well dispersed on the rGO surface and in between rGO sheets. The flexible rGO enables us to maintain the structural integrity and to provide a continuous conductive network of the electrode, which results in over 100 cycles serving as an anode in half cells at a high lithium storage capacity of 2300 mA h g(-1). Due to its [111] growth direction and the large contact area with rGO, the Si NWs in the composite show substantially enhanced reaction kinetics compared with other Si NWs or Si particles.

  1. Influence of Nanowire Diameter on Structural and Optical Properties of cu Nanowire Synthesized in Anodic Aluminium Oxide Film

    Science.gov (United States)

    Cetinel, A.; Özcelik, Z.

    2016-11-01

    Copper (Cu) nanowire arrays embedded in anodic aluminium oxide films (AAO) on aluminium substrate have been synthesized by alternating current electrochemical deposition. Two-step anodization process has been performed to get the through-hole AAO with ordered nanochannels in 0.3M oxalic acids at DC voltages 30, 40, 50 and 60V, respectively. Structural characterization of the Cu nanowires has been analyzed by scanning electron microscopy (SEM) and X-ray diffraction (or) X-ray diffractometer (XRD). Our SEM analysis has revealed that the diameters of vertically oriented Cu nanowires are 15, 25, 45 and 60nm and the length of Cu nanowires having high packing density is about 15μm. XRD measurement has indicated that polycrystalline Cu nanowires prefer growth orientation along the (111) direction. Optical measurements show that reflection of the Cu nanowires/AAO on aluminium reduces with decreasing diameter of the Cu nanowires. This effect can be associated with increased light scattering from metal nanoparticles near their localized plasmon resonance frequency depending on the size and shape of the nanoparticles.

  2. Fabrication of a Ni nano-imprint stamp for an anti-reflective layer using an anodic aluminum oxide template.

    Science.gov (United States)

    Park, Eun-Mi; Lim, Seung-Kyu; Ra, Senug-Hyun; Suh, Su-Jung

    2013-11-01

    Aluminum anodizing can alter pore diameter, density distribution, periodicity and layer thickness in a controlled way. Because of this property, porous type anodic aluminum oxide (AAO) was used as a template for nano-structure fabrication. The alumina layer generated at a constant voltage increased the pore size from 120 nm to 205 nm according to an increasing process time from 60 min to 150 min. The resulting fabricated AAO templates had pore diameters at or less than 200 nm. Ni was sputtered as a conductive layer onto this AAO template and electroplated using DC and pulse power. Comparing these Ni stamps, those generated from electroplating using on/reverse/off pulsing had an ordered pillar array and maintained the AAO template morphology. This stamp was used for nano-imprinting on UV curable resin coated glass wafer. Surface observations via electron microscopy showed that the nano-imprinted patterned had the same shape as the AAO template. A soft mold was subsequently fabricated and nano-imprinted to form a moth-eye structure on the glass wafer. An analysis of the substrate transmittance using UV-VIS/NIR spectroscopy showed that the transmittance of the substrate with the moth-eye structure was 5% greater that the non-patterned substrate.

  3. Impedance spectroscopy of highly ordered nano-porous electrodes based on Au-AAO (anodic aluminum oxide) structure.

    Science.gov (United States)

    Ahn, Jaehwan; Cho, Sungbo; Min, Junhong

    2013-11-01

    Electrochemical measurements using the microelectrodes are increasingly utilized for the label-free detection of the small amount of biological materials such as DNA, protein, and cells. However, the interfacial electrode impedance increases and may hinder the detection of weak signals as the size of electrode decreases. To enhance the measurement sensitivity while reducing the electrode size, in this study, microelectrodes employing a nanoporous structure were fabricated and characterized by using electrical impedance spectroscopy. We made the highly ordered honeycomb nanoporous structure of Anodic Aluminum Oxide (AAO) by electrochemical anodizing and formed Au layer on the surface of AAO (Au/AAO) by electroless Au plating method. The electrical characteristics of the fabricated Au/AAO electrodes were evaluated by using de Levie's model derived for the pore electrodes. As a result, the interfacial electrode impedance of the fabricated Au/AAO electrodes was 2-3 order lower than the value of the planar electrodes at frequencies below 1 kHz. It implies this nanoporous electrode could be directly applied to label free detection of biomaterials.

  4. Solid oxide fuel cell anode degradation by the effect of hydrogen chloride in stack and single cell environments

    Science.gov (United States)

    Madi, Hossein; Lanzini, Andrea; Papurello, Davide; Diethelm, Stefan; Ludwig, Christian; Santarelli, Massimo; Van herle, Jan

    2016-09-01

    The poisoning effect by hydrogen chloride (HCl) on state-of-the-art Ni anode-supported solid oxide fuel cells (SOFCs) at 750 °C is evaluated in either hydrogen or syngas fuel. Experiments are performed on single cells and short stacks and HCl concentration in the fuel gas is increased from 1 ppm(v) up to 1000 ppm(v) at different current densities. Characterization methods such as cell voltage monitoring vs. time and electrochemical impedance response analysis (distribution of relaxation times (DRT), equivalent electrical circuit) are used to identify the prevailing degradation mechanism. Single cell experiments revealed that the poisoning is more severe when feeding with hydrogen than with syngas. Performance loss is attributed to the effects of HCl adsorption onto nickel surfaces, which lowered the catalyst activity. Interestingly, in syngas HCl does not affect stack performance even at concentrations up to 500 ppm(v), even when causing severe corrosion of the anode exhaust pipe. Furthermore, post-test analysis suggests that chlorine is present on the nickel particles in the form of adsorbed chlorine, rather than forming a secondary phase of nickel chlorine.

  5. Enhancing Sulfur Tolerance of Ni-Based Cermet Anodes of Solid Oxide Fuel Cells by Ytterbium-Doped Barium Cerate Infiltration.

    Science.gov (United States)

    Li, Meng; Hua, Bin; Luo, Jing-Li; Jiang, San Ping; Pu, Jian; Chi, Bo; Li, Jian

    2016-04-27

    Conventional anode materials for solid oxide fuel cells (SOFCs) are Ni-based cermets, which are highly susceptible to deactivation by contaminants in hydrocarbon fuels. Hydrogen sulfide is one of the commonly existed contaminants in readily available natural gas and gasification product gases of pyrolysis of biomasses. Development of sulfur tolerant anode materials is thus one of the critical challenges for commercial viability and practical application of SOFC technologies. Here we report a viable approach to enhance substantially the sulfur poisoning resistance of a Ni-gadolinia-doped ceria (Ni-GDC) anode through impregnation of proton conducting perovskite BaCe0.9Yb0.1O3-δ (BCYb). The impregnation of BCYb nanoparticles improves the electrochemical performance of the Ni-GDC anode in both H2 and H2S containing fuels. Moreover, more importantly, the enhanced stability is observed in 500 ppm of H2S/H2. The SEM and XPS analysis indicate that the infiltrated BCYb fine particles inhibit the adsorption of sulfur and facilitate sulfur removal from active sites, thus preventing the detrimental interaction between sulfur and Ni-GDC and the formation of cerium sulfide. The preliminary results of the cell with the BCYb+Ni-GDC anode in methane fuel containing 5000 ppm of H2S show the promising potential of the BCYb infiltration approach in the development of highly active and stable Ni-GDC-based anodes fed with hydrocarbon fuels containing a high concentration of sulfur compounds.

  6. Porphyrin Dye-Sensitized Zinc Oxide Aggregated Anodes for Use in Solar Cells

    Directory of Open Access Journals (Sweden)

    Yu-Kai Syu

    2016-08-01

    Full Text Available Porphyrin YD2-o-C8-based dyes were employed to sensitize room-temperature (RT chemical-assembled ZnO aggregated anodes for use in dye-sensitized solar cells (DSSCs. To reduce the acidity of the YD2-o-C8 dye solution, the proton in the carboxyl group of a porphyrin dye was replaced with tetrabuthyl ammonium (TBA+ in this work. The short-circuit current density (Jsc of the YD2-o-C8-TBA-sensitized ZnO DSSCs is higher than that of the YD2-o-C8-sensitized cells, resulting in the improvement of the efficiency of the YD2-o-C8-based ZnO DSSCs. With an appropriate incorporation of chenodeoxycholic acid (CDCA as coadsorbate, the Jsc and efficiency of the YD2-o-C8-TBA-sensitized ZnO DSSC are enhanced due to the improvement of the incident-photon-to-current efficiency (IPCE values in the wavelength range of 400–450 nm. Moreover, a considerable increase in Jsc is achieved by the addition of a light scattering layer in the YD2-o-C8-TBA-sensitized ZnO photoanodes. Significant IPCE enhancement in the range 475–600 nm is not attainable by tuning the YD2-o-C8-TBA sensitization processes for the anodes without light scattering layers. Using the RT chemical-assembled ZnO aggregated anode with a light scattering layer, an efficiency of 3.43% was achieved in the YD2-o-C8-TBA-sensitized ZnO DSSC.

  7. Methane steam reforming kinetics over Ni-YSZ anode materials for Solid Oxide Fuel Cells

    DEFF Research Database (Denmark)

    Mogensen, David

    energy. The overall efficiency of a fuel cell system operating on natural gas can be significantly improved by having part of the steam reforming take place inside the SOFC stack. In order to avoid large temperature gradients as a result of the highly endothermal steam reforming reaction, the amount...... of internal reforming has to be carefully controlled. The objective of this thesis is to make such a careful control possible by examining the rate of internal steam reforming in SOFCs. The catalytic steam reforming activity of Ni-YSZ anode material was tested both in a packed bed reactor to determine...

  8. Modeling mass transfer in solid oxide fuel cell anode: II. H2/CO co-oxidation and surface diffusion in synthesis-gas operation

    Science.gov (United States)

    Bao, Cheng; Jiang, Zeyi; Zhang, Xinxin

    2016-08-01

    Following the previous work on comparing performance of Fickian, Stefan-Maxwell and dusty-gas model for mass transfer in single fuel system, this article is focused on the electrochemistry and transport in the anode of solid oxide fuel cell using H2sbnd H2Osbnd COsbnd CO2sbnd N2 hybrid fuel. Under the standard framework of the dusty-gas model combined with the Butler-Volmer equation, it carries out a macroscopic area-specific modeling work. More specifically, two variables of hydrogen current fraction and enhancement factor are well defined and solved for the electrochemical co-oxidation of H2 and CO, and the diffusion equivalent circuit model is introduced to describe more comprehensively the resistance of mass transfer including molecular/Knudsen diffusion and surface diffusion. The model has been validated well in full region of Vsbnd I performance of an experimental anode-supported button cell. An approximate analytical solution of the hydrogen current fraction is also presented for explicit computation. Comparison between the results by different approaches for the effective diffusivity shows the importance of right mass-transfer modeling.

  9. Anodic-Aluminium-Oxide Template-Assisted Growth of ZnO Nanodots on Si (100) at Low Temperature

    Institute of Scientific and Technical Information of China (English)

    XU Tian-Ning; WU Hui-Zhen; LAO Yan-Feng; QIU Dong-Jiang; CHEN Nai-Bo; DAI Ning

    2004-01-01

    ZnO nanodots have been grown on Si (100) assisted by anodic aluminium oxide (AAO) template at low temperature (350℃). Regular arrangement to a certain extent in local for ZnO nanodots is observed, and the average diameter of nanodots is about 9. 7nm. Photoluminescence studies at room temperature for photon energy between 2.0 and 3.6 eV reveal a strong single exciton peak at 3.274 eV (378.8 nm) with the green emission fully quenched.Narrow full width at half maximum (FWHM) of the UV emission band (0.14 eV) suggests the as-grown ZnO nanodots have a narrow size distribution.

  10. Biocompatibility and in vitro antineoplastic drug-loaded trial of titania nanotubes prepared by anodic oxidation of a pure titanium

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    TiO2 nanotube (NT) arrays have been prepared by anodic oxidation of a Ti sheet,and carbon-deposited TiO2 NT arrays have been prepared by annealing TiO2 NT arrays in carbon atmosphere. The biocompatibility of the as-prepared NT arrays was investigated by observing the growth of osteosarcoma (MG-63) cells on the NT arrays. The application of the TiO2 NT arrays as a drug delivery vehicle was investigated. Both the TiO2 NTs and the carbon-modified TiO2 NTs have good biocompatibility supporting the normal growth and adhesion of MG-63 cells with no need of extracellular matrix protein coating. The one end-opened TiO2 NTs can be easily filled with drugs,working as an efficient drug delivery vehicle.

  11. Fabrication and characterization of anodic oxide films on a Ti-10V-2Fe-3Al titanium alloy

    Institute of Scientific and Technical Information of China (English)

    Jian-hua Liu; Jun-lan Yi; Song-mei Li; Mei Yu; Yong-zhen Xu

    2009-01-01

    Anodic oxide films of the titanium alloy Ti-10V-2Fe-3Al in ammonium tartrate electrolyte without hydrofluoric acid or fluoride were fabricated.The morphology,components,and microstructure of the films were characterized by scanning electron mi-croscopy (SEM),X-ray photoelectron spectroscopy (XPS),X-ray diffraction (XRD),and Raman spectroscopy.The results showed that the films were thick,uniform,and nontransparent.Such films exhibited sedimentary morphology,with a thickness of about 3 μm,and the pore diameters of the deposits ranged from several hundred nanometers to 1.5 μm.The films were mainly titanium dioxide.Some coke-like deposits,which may contain or be changed by OH,NH,C-C,C-O,and C=O groups,were doped in the firms.The films were mainly amorphous with a small amount of anatase and rutile phase.

  12. Direct observation of anodic dissolution and filament growth behavior in polyethylene-oxide-based atomic switch structures

    Science.gov (United States)

    Krishnan, Karthik; Tsuruoka, Tohru; Aono, Masakazu

    2016-06-01

    We directly observed anodic dissolution and subsequent filament growth behavior in a planar atomic switch structure with Ag salt incorporated polyethylene oxide (Ag-PEO) film using in situ optical microscopy and ex situ scanning electron microscopy. The high ionic conductivities of Ag-PEO films enable the investigation of filament formation under voltage bias, even in micrometer-scaled devices. It was found that the filament formation changes from unidirectional growth to dendritic growth, depending on its distance from the grounded electrode. Based on this understanding of filament growth dynamics in planar devices, highly stable resistive switching was achieved in an Ag/Ag-PEO/Pt stacked device with an Ag-PEO film thickness of 100 nm. The device showed repeated switching operations for more than 102 sweep cycles, with a high ON/OFF resistance ratio of 105.

  13. Improved light extraction of LYSO scintillator by the photonic structure from a layer of anodized aluminum oxide

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Zhichao [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Liu, Bo, E-mail: lbo@tongji.edu.cn [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Cheng, Chuanwei; Zhang, Haifeng; Wu, Shuang; Gu, Mu; Chen, Hong [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Chen, Liang; Liu, Jinliang; Ouyang, Xiaoping [Northwest Institute of Nuclear Technology, Xi’an 710024 (China)

    2015-06-21

    As a promising scintillator in the field of medical imaging systems, LYSO with its high refractive index suffers from a low light extraction efficiency due to the total internal reflection. Here, we demonstrate that a photonic structure formed by an anodized aluminum oxide layer can enhance the light extraction efficiency by the outcoupling the light trapped in the crystal. An enhancement of light output by 25% can be achieved by an AAO layer covered on the surface of LYSO. The imperfect periodicity of AAO can lead to a consistent enhancement for the entire range of emission wavelength and directionality. Such enhanced light output is practical and attractive for use in the scintillation detection systems. It is important to note that the fabrication method of AAO is simple and low-cost for the large area applications, which is obviously advantageous over the expensive traditional methods such as electron beam lithography.

  14. Wetting characteristics of the anodic aluminum oxide template and fabrication of cracks using ultraviolet curable resin solution

    Science.gov (United States)

    Sung Yoon, Jae; Phuong, NguyenThi; Hwan Kim, Jeong; Choi, Doo-Sun; Whang, Kyung-hyun; Yoo, Yeong-eun

    2014-03-01

    We have investigated the wetting characteristics of the anodic aluminum oxide (AAO) template with ultraviolet curable polymer resin. The wettability of the template depends on the pore size on the surface, where it is improved with smaller pores and vice versa. Plasma treatment on the surface of the template is used to improve the wettability and the adhesion of the cured polymer to the template. And we also introduce the cracks on the polymer layer for possible application as nano-sized cavities. The resin within the pore is cleaved during the curing process so that cavities or cracks could be made which are much smaller than the original pores of the AAO template.

  15. Preparation of thin hexagonal highly-ordered anodic aluminum oxide (AAO) template onto silicon substrate and growth ZnO nanorod arrays by electrodeposition

    Science.gov (United States)

    Chahrour, Khaled M.; Ahmed, Naser M.; Hashim, M. R.; Elfadill, Nezar G.; Qaeed, M. A.; Bououdina, M.

    2014-12-01

    In this study, anodic aluminum oxide (AAO) templates of Aluminum thin films onto Ti-coated silicon substrates were prepared for growth of nanostructure materials. Hexagonally highly ordered thin AAO templates were fabricated under controllable conditions by using a two-step anodization. The obtained thin AAO templates were approximately 70 nm in pore diameter and 250 nm in length with 110 nm interpore distances within an area of 3 cm2. The difference between first and second anodization was investigated in details by in situ monitoring of current-time curve. A bottom barrier layer of the AAO templates was removed during dropping the voltage in the last period of the anodization process followed by a wet etching using phosphoric acid (5 wt%) for several minutes at ambient temperature. As an application, Zn nanorod arrays embedded in anodic alumina (AAO) template were fabricated by electrodeposition. Oxygen was used to oxidize the electrodeposited Zn nanorods in the AAO template at 700 °C. The morphology, structure and photoluminescence properties of ZnO/AAO assembly were analyzed using Field-emission scanning electron microscope (FESEM), Energy dispersive X-ray spectroscopy (EDX), Atomic force microscope (AFM), X-ray diffraction (XRD) and photoluminescence (PL).

  16. Degradation of trans-ferulic acid in acidic aqueous medium by anodic oxidation, electro-Fenton and photoelectro-Fenton.

    Science.gov (United States)

    Flores, Nelly; Sirés, Ignasi; Garrido, José Antonio; Centellas, Francesc; Rodríguez, Rosa María; Cabot, Pere Lluís; Brillas, Enric

    2016-12-01

    Solutions of pH 3.0 containing trans-ferulic acid, a phenolic compound in olive oil mill wastewater, have been comparatively degraded by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF). Trials were performed with a BDD/air-diffusion cell, where oxidizing OH was produced from water discharge at the BDD anode and/or in the solution bulk from Fenton's reaction between cathodically generated H2O2 and added catalytic Fe(2+). The substrate was very slowly removed by AO-H2O2, whereas it was very rapidly abated by EF and PEF, at similar rate in both cases, due to its fast reaction with OH in the bulk. The AO-H2O2 process yielded a slightly lower mineralization than EF, which promoted the accumulation of barely oxidizable products like Fe(III) complexes. In contrast, the fast photolysis of these latter species under irradiation with UVA light in PEF led to an almost total mineralization with 98% total organic carbon decay. The effect of current density and substrate concentration on the performance of all treatments was examined. Several solar PEF (SPEF) trials showed its viability for the treatment of wastewater containing trans-ferulic acid at larger scale. Four primary aromatic products were identified by GC-MS analysis of electrolyzed solutions, and final carboxylic acids like fumaric, acetic and oxalic were detected by ion-exclusion HPLC. A reaction sequence for trans-ferulic acid mineralization involving all the detected products is finally proposed.

  17. Effect of the Electrolyte Temperature and the Current Density on a Layer Microhardness Generated by the Anodic Aluminium Oxidation

    Directory of Open Access Journals (Sweden)

    Emil Spišák

    2015-01-01

    Full Text Available The paper investigates the influence of the chemical composition and temperature of electrolyte, the oxidation time, voltage, and the current density on Vickers microhardness of aluminium oxide layers, at the same time. The layers were generated in the electrolytes with different concentrations of sulphuric and oxalic acids and surface current densities 1 A·dm−2, 3 A·dm−2, and 5 A·dm−2. The electrolyte temperature varied from −1.78°C to 45.78°C. The results have showed that while increasing the electrolyte temperature at the current density of 1 A·dm−2, the increase in the layer microhardness values is approximately by 66%. While simultaneously increasing the molar concentration of H2SO4 in the electrolyte, the growth rate of the microhardness value decreases. At the current density of 3 A·dm−2, by increasing the electrolyte temperature, a reduction in the microhardness of the generated layer occurs with the anodic oxidation time less than 25 min. The electrolyte temperature is not significant with the changing values of the layer microhardness at voltages less than 10.5 V.

  18. Elementary kinetic modelling applied to solid oxide fuel cell pattern anodes and a direct flame fuel cell system

    Energy Technology Data Exchange (ETDEWEB)

    Vogler, Marcel

    2009-05-27

    In the course of this thesis a model for the prediction of polarisation characteristics of solid oxide fuel cells (SOFC) was developed. The model is based on an elementary kinetic description of electrochemical reactions and the fundamental conservation principles of mass and energy. The model allows to predict the current-voltage relation of an SOFC and offers ideal possibilities for model validation. The aim of this thesis is the identification of rate-limiting processes and the determination of the elementary pathway during charge transfer. The numerical simulation of experiments with model anodes allowed to identify a hydrogen transfer to be the most probable charge-transfer reaction and revealed the influence of diffusive transport. Applying the hydrogen oxidation kinetics to the direct flame fuel cell system (DFFC) showed that electrochemical oxidation of CO is possible based on the same mechanism. Based on the quantification of loss processes in the DFFC system, improvements on cell design, predicting 80% increase of efficiency, were proposed. (orig.)

  19. Preparation of mesoporous alumina films by anodization: Effect of pretreatments on the aluminum surface and MTBE catalytic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez, A.L., E-mail: avazquezd@ipn.m [Departamento de Ingenieria Metalurgica, ESIQIE-IPN, AP 75-876, Mexico, D.F. (Mexico); Programa de Ingenieria Molecular, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, C.P. 07730, Mexico, D.F. (Mexico); Carrera, R. [Departamento de Ingenieria Metalurgica, ESIQIE-IPN, AP 75-876, Mexico, D.F. (Mexico); Programa de Ingenieria Molecular, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, C.P. 07730, Mexico, D.F. (Mexico); Arce, E. [Departamento de Ingenieria Metalurgica, ESIQIE-IPN, AP 75-876, Mexico, D.F. (Mexico); Castillo, N. [CINVESTAV, Departamento de Fisica. Av. IPN 2508, 07360, Mexico, D.F (Mexico); Castillo, S. [Departamento de Ingenieria Metalurgica, ESIQIE-IPN, AP 75-876, Mexico, D.F. (Mexico); Programa de Ingenieria Molecular, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, C.P. 07730, Mexico, D.F. (Mexico); Moran-Pineda, M. [Programa de Ingenieria Molecular, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, C.P. 07730, Mexico, D.F. (Mexico)

    2009-08-26

    Mesoporous materials are both scientifically and technologically important because of the presence of voids of controllable dimensions at atomic, molecular, and nanometric scales. Over the last decade, there has been both an increasing interest and research effort in the synthesis and characterization of these types of materials. The purposes of this work are to study the physical and chemical changes in the properties of mesoporous alumina films produced by anodization in sulphuric acid by different pretreatments on the aluminium surface such as mechanical polishing [MP] and electropolishing [EP]; and to compare their properties such as morphology, structure and catalytic activity with those present in commercial alumina. The morphologic and physical characterizations of the alumina film samples were carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The chemical evaluations were performed by the oxidation of methyl-tert-butyl-ether (MTBE) at 400 deg. C under O{sub 2}/He oxidizing conditions (Praxair, 2.0% O{sub 2}/He balance). According to the results, the samples that presented higher activities than those in Al{sub 2}O{sub 3}/Al [MP] and commercial alumina in the MTBE oxidation (69%), were those prepared by Al{sub 2}O{sub 3}/Al [EP]. The average mesoporous diameter was 17 nm, and the morphological shape was equiaxial; thus, that pore distribution was the smallest of all with a homogeneous distribution.

  20. Synthesis of praseodymium doped cerium oxides by the polymerization-combustion method for application as anodic component in SOFC devices

    Science.gov (United States)

    Cruz Pacheco, A. F.; Gómez Cuaspud, J. A.; López, E. Vera

    2016-02-01

    This work reports the synthesis and the characterization of six oxides; it is based on Ce1-xPrxO2 (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) system, which is obtained by the polymerization- combustion technique for potential applications on design of advanced electrodic components, for solid oxide fuel cells (SOFC). Initially the solid precursors are characterized by infrared spectroscopy (FTIR) and thermal analysis (TGA-DTA), allowing to determine the formation of prevalent citrate species and the optimal temperature for the consolidation of the desired crystalline phases. The X-ray diffraction (XRD) and the transmission electron microscopy analysis (TEM) are performed over calcined samples which provided information about the formation of a fluorite phase with grain distribution, surface, textural and morphological properties consistent with the nanometric obtaining crystallites (30nm), it is oriented along the (1 1 1) facet, with d spacings of 0.31nm for the main diffraction signal. These results indicate the effectiveness of the proposed synthesis method for potential applications in the design of advanced anodic materials for solid oxide fuel cells.

  1. Anodic Stripping Determination of Pt (IV) Based on the Anodic Oxidation of Cu from the Intermetallic Phase of Cu[3]Pt

    OpenAIRE

    Ustinova, Elvira Maratovna; Kolpakova, Nina Alexandrovna

    2014-01-01

    It is shown that platinum can be determined by anodic stripping voltammetry at the peak of selective electrooxidation of copper from intermetallic phase with platinum of Cu[3]Pt composition. The composition of intermetallic copper-platinum phase formed on the electrode during pre-electrolysis was calculated on the amount of potential displacement (delta Е) of copper electrooxidation.

  2. Recovery of Niobium and Zirconium from the Cyclone Discharge of Chlorination Plant Producing Titanium Tetrachloride

    Directory of Open Access Journals (Sweden)

    V. S. Gireesh

    2014-03-01

    Full Text Available This paper describes a method for recovering niobium and zirconium from the cyclone solid residues arising from chlorination of titaniferrous ores. The residue contains beneficiated ilmenite (BI fines, calcined petroleum coke (CPC and metal chlorides of niobium, aluminium, zirconium, iron, manganese, vanadium etc. The BI fines and CPC present in the residue were removed by soaking the residue with water and by separating the insoluble fraction contain BI and CPC by filtration. The filtrate containing the soluble metal chlorides was acidified with hydrochloric acid followed by agitation and heating in the presence of sulphate ions (sulphuric acid to precipitate niobium and zirconium as their oxo sulphate which is filtered, dried and calcined to convert niobium and zirconium oxides. The optimum amount of sulphuric acid was found to be 3 % and the optimum pH and temperature for precipitation of niobium and zirconium is 0.5 and 90 oC respectively.

  3. In-Situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes

    Science.gov (United States)

    2010-12-28

    Fuel Cells " Ann. Rev. Anal. Chem., 3 151-174 (2010). 2. B. C. Eigenbrodt1, M. B. Pomfret, D. A. Steinhurst, J. C. Owrutsky and R. A. Walker "Direct...in situ optical studies of solid oxide fuel cells operating with methanol and methane" J. Phys. Chem. C available online at ASAP. (Content from...Mapping of Surface Electrolyte Oxide Concentration in Solid Oxide Fuel Cells " submitted to Analytical Methods, accepted pending revisions. 4. J. D

  4. Characterization of Metal Oxide-Based Gas Nanosensors and Microsensors Fabricated via Local Anodic Oxidation Using Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Bráulio S. Archanjo

    2013-01-01

    Full Text Available This work reports on nanoscale and microscale metal oxide gas sensors, consisting of metal-semiconductor-metal barriers designed via scanning probe microscopy. Two distinct metal oxides, molybdenum and titanium oxides, were tested at different temperatures using CO2 and H2 as test gases. Sensitivities down to ppm levels are demonstrated, and the influence of dry and humid working atmospheres on these metal oxide conductivities was studied. Furthermore, the activation energy was evaluated and analyzed within working sensor temperature range. Finally, full morphological, chemical, and structural analyses of the oxides composites are provided allowing their identification as MoO3 and Ti.

  5. The electrochemical oxidation of dimethyl disulfide-Anodic methylsulfanylation of phenols and aromatic ethers

    Energy Technology Data Exchange (ETDEWEB)

    Quang Tho Do [Laboratoire d' Electrochimie et Environnement, CEREA, Universite Catholique de l' Ouest, BP 10808, 49008 ANGERS Cedex 01 (France); Elothmani, Driss [Laboratoire GRAPPE, Ecole Superieure d' Agriculture d' Angers, BP 30748, 49007 ANGERS Cedex 01 (France); Simonet, Jacques [Laboratoire d' Electrochimie Moleculaire (UMR CNRS 6510), Universite de RENNES 1, 35042 RENNES Cedex (France); Guillanton, Georges Le [Laboratoire d' Electrochimie et Environnement, CEREA, Universite Catholique de l' Ouest, BP 10808, 49008 ANGERS Cedex 01 (France)]. E-mail: gleguill@uco.fr

    2005-08-30

    The electrochemical oxidation of dimethyl disulfide was investigated in acetonitrile and dichloromethane. The nature of the oxidation strongly depends on the nucleophilicity of the solvent. In acetonitrile a one-electron oxidation is observed and the consecutive species did not exhibit any reactivity towards aromatic compounds subject to electrophile substitution. On the contrary, the oxidation of dimethyl disulfide in methylene chloride afforded a two-electron process with the formation of a species consistent with CH{sub 3} -S{sup +}. Its reactivity towards phenols and aromatic ethers was confirmed and showed a selective monomethylsulfanylation in most of the cases.

  6. Electron microscopic studies of anodic oxide films on the AZ91HP alloy

    Directory of Open Access Journals (Sweden)

    D. Peixoto Barbosa

    2003-01-01

    Full Text Available A Mg-9wt.Al-1wt.%Zn-alloy was anodized up to 90 V with constant current/constant voltage in an electrolyte which contained the compounds of the HAE-process (KOH, Al(OH3, KF, Na3PO4 and KMnO4. Electron microscopic examinations revealed a highly porous and irregular film structure. The distribution of the elements in the film was measured with energy dispersive spectrometry on specimens prepared in cross section for the transmission electron microscope. The main characteristic found was a fluoride-enriched zone of about 100 nm thickness at the metal / film interface. Practically no manganese from the permanganate was detected in this fluoride-enriched zone.

  7. Microstructural degradation of Ni-YSZ anodes for solid oxide fuel cells

    DEFF Research Database (Denmark)

    Thydén, Karl Tor Sune

    2008-01-01

    are of technological relevance, it is difficult to identify the effect from isolated parameters such as temperature, fuel gas composition and polarization. Model studies of high temperature aged Ni-YSZ cermets are generally performed in atmospheres containing relatively low concentrations of H2O. In this work......, the microstructural degradation in both electrochemically longterm tested cells and high-temperature aged model materials are studied. Since Ni particle sintering / coarsening is attributed to be the major cause of anode degradation, this subject attains the primary focus. A large part of the work is focused......-reforming catalysis. In the context of electrochemically tested and technologically relevant cells, the majority of the microstructural work is performed on a cell tested at 850°C under relatively severe conditions for 17,500 hours. It is demonstrated that the major Ni rearrangements take place at the interface...

  8. Favorable binding effect for improving the electrochemical performance of cobalt oxide anode for lithium ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wan Lin; Nguyen, Van Hiep; Gu, Hal-Bon, E-mail: kuku-linlin@hotmail.com

    2014-01-01

    Electrochemical characteristics of CoO anode are highly dependent on the use of binders. Its electrochemical reversibility is drastically improved by using poly(acrylic acid) (PAA) as a binder in comparison with the commonly used poly(vinylidene fluoride) (PVdF) binder. PAA can effectively buffer the volume expansion of the CoO electrode during the lithium insertion and extraction, resulting in improving electrochemical characteristics of the electrode. The cyclic stability of CoO electrode with PAA binder is remarkably improved. Impedance of CoO electrode with PAA binder is much smaller than that of PVdF binder. Moreover, the reversible capacity reaches 860 mA h g{sup −1} at a current density of 50 mA g{sup −1}.

  9. Anode supported single chamber solid oxide fuel cells operating in exhaust gases of thermal engine

    Science.gov (United States)

    Briault, Pauline; Rieu, Mathilde; Laucournet, Richard; Morel, Bertrand; Viricelle, Jean-Paul

    2014-12-01

    This project deals with the development and the electrochemical characterization of anode supported single chamber SOFC in a simulated environment of thermal engine exhaust gas. In the present work, a gas mixture representative of exhaust conditions is selected. It is composed of hydrocarbons (HC: propane and propene), oxygen, carbon monoxide, carbon dioxide, hydrogen and water. Only oxygen content is varied leading to different gas mixtures characterized by three ratios R = HC/O2. Concerning the cell components, a cermet made of nickel and an electrolyte material, Ce0.9Gd0.1O1.95 (CGO) is used as anode and two cathode materials, La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and Pr2NiO4+δ (PNO), are evaluated. The prepared cells are investigated in the various gas mixtures for temperatures ranging from 450 °C to 600 °C. Ni-CGO/CGO/LSCF-CGO cell has delivered a maximum power density of 15 mW cm-2 at 500 °C with R = HC/O2 = 0.21, while lower power densities are obtained for the other ratios, R = 0.44 and R = 0.67. Afterwards, LSCF and PNO cathode materials are compared and LSCF is found to deliver the highest power densities. Finally, by improving the electrolyte microstructure, some cells presenting a maximum power density of 25 mW cm-2 at 550 °C are produced. Moreover, up to 17% of initial HC are eliminated in the gas mixture.

  10. Influence of terminal electron acceptor availability to the anodic oxidation on the electrogenic activity of microbial fuel cell (MFC).

    Science.gov (United States)

    Srikanth, S; Venkata Mohan, S

    2012-11-01

    The electrogenic activity of microbial fuel cell (MFC) with the function of anode placement from the terminal electron acceptor (TEA) was evaluated. Shorter anode distances from TEA showed higher electrogenesis due to the feasibility of higher electron acceptance as well as their discharge towards TEA. Substrate degradation was also higher at shorter anode placements from TEA due to the optimum substrate availability to the anodic biofilm. Bio-electro kinetics showed significant variation in the catalytic currents and exchange current densities with the function of anode placement indicating its role in electron acceptance and their transfer to the cathode. Anode placement of 3cm showed higher electrogenesis (406.38mW/m(2)) and substrate degradation (63.12%) along with significantly reduced polarization (6.72Ω) and charge transfer resistances compared to other anodic placements. The spacing between electrodes is crucial in accepting electrons as well as their discharge towards TEA which ultimately governs the power generation efficacy.

  11. Oxidation of Fe-W Alloy Electrodeposits for Application to Anodes as Lithium Ion Batteries

    Science.gov (United States)

    Su, Changwei; Ye, Mengchao; Zhon, Linxing; Hou, Jianping; Li, Junmin; Guo, Junming

    2016-12-01

    A citrate-ammonia bath was selected to electrodeposit Fe-W alloys, which exhibit a crystalline structure even if the content of W in the Fe-W alloy is up to 37.8wt%. Those alloys could be oxidized partly at 700∘C. Resultant oxides were composed of Fe2O3, Fe3O4 and amorphous products. The composite oxides presented better electrochemical properties than those of the Fe2O3 and Fe3O4 composite formed by oxidation of Fe deposits. For instance, such an electrode demonstrates the reversible capacity of up to 2438.3mAhg-1 (in terms of incremental oxygen) after 100 charge-discharge cycles, while the electrodes of Fe2O3 and Fe3O4 composites formed by oxidation of Fe deposits were of only 667.5mAhg-1.

  12. Size-Controlled Synthesis of Copper Oxide Particles on Reduced Graphene Oxide for Lithium-Ion Battery Anode Applications.

    Science.gov (United States)

    Jang, Haneul; Kim, Kyungbae; Chang, Hyejung; Kim, Jae-Hun; Choi, Hyunjoo

    2015-11-01

    Copper oxide/reduced graphene oxide (rGO) hybrids have been successfully synthesized by attaching copper ions onto the functional groups of GO by means of a solution process, which causes precipitation and agglomeration of copper oxides during subsequent thermal reduction of the GO. The resulting copper oxide/rGO hybrid exhibited improved electrochemical performance compared to monolithic CuO, which is presumed to be due to rGO acting as a mechanical support that buffers the volume change in copper oxides that occurs as a result of the conversion reaction during charge/discharge cycling. Furthermore, it was found that the size of the copper oxide particles can be optimized by adjusting the annealing time, with a hybrid annealed for 30 min achieving a reversible capacity of 544 mA h g(-1) and an initial coulombic efficiency of 62.7%.

  13. Study for preparation of nanoporous titania on titanium by anodic oxidation; Estudo da preparacao de titania nanoporosa sobre titanio por oxidacao anodica

    Energy Technology Data Exchange (ETDEWEB)

    Passos, Alessandra Pires

    2014-07-01

    Currently titanium is the most common material used in dental, orthopedic implants and cardiovascular applications. In the mid 1960s, prof. Braenemark and coworkers developed the concept of osseointegration, meaning the direct structural and functional connection between living bone and the surface of artificial implant. Thus, studies on the modification of the implant surface are widely distributed among them are the acid attack, blasting with particles of titanium oxide or aluminum oxide, coating with bioactive materials such as hydroxyapatite, and the anodic oxidation. The focus of this work was to investigate the treatment of titanium surface by anodic oxidation. The aim was to develop a nanoporous titanium oxide overlay with controlled properties over titanium substrates. Recent results have shown that such surface treatment improves the biological interaction at the interface bone-implant besides protecting the titanium further oxidation and allow a faster osseointegration. The anodizing process was done in the potentiostatic mode, using an electrolyte composed of 1.0 mol/L H{sub 3}PO{sub 4} and HF 0.5% m/I. The investigated process parameters were the electrical potential (Va) and the process time (T). The electric potential was varied from 10 V to 30 V and the process time was defined as 1.0 h, 1.5 h or 2.0 h. The treated Ti samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive spectroscopy X-ray (EDS), and X-ray diffraction (XRD). The results showed the formation of nanoporous titanium oxide by anodizing with electric potential (Va) in the range of 20 V to 30 V and process time in the range of 1 to 2 hours. The average pore diameter was in the range 94-128 nm. Samples anodized in electric potential lower than 20 V did not show the formation of the nanoporous surface. In the case of Va above 30 V, it was observed the formation of agglomerates of TiO{sub 2}. The results obtained in this study

  14. Structural investigation of SiSn/(reduced graphene oxide) nanocomposite powder for Li-ion battery anode applications

    Science.gov (United States)

    Kawasaki, Masahiro; Laokawee, Viratchara; Sarakonsri, Thapanee; Hashizume, Takashi; Shiojiri, Makoto

    2016-11-01

    We synthesized SiSn/(reduced graphene oxide (rGO)) nanocomposite powder for a Li-ion battery material and characterized the structure by transmission electron microscopy (TEM) and analytical scanning transmission electron microscopy (STEM). Graphene oxide was prepared by Hummers method. The graphene oxide powder processed by heat treatment was added together with Si powder into a solution of SnCl2 ṡ 2(H2O) dissolved in N2 bubbled ethylene glycol, and the solution was reacted with NaBH4. The product had a nominal atomic ratio of Si: Sn: C = 14: 3.5: 100. High-resolution TEM/STEM analysis revealed that the powder consisted of crystalline particles of Sn, Si, and SiO as well as thin reduced graphene oxide (rGO) lamellae of amorphous-like graphite with distorted lattices that were often found in areas as local as a few nm2. The aggregated Si and SiO particles grew up to several hundred nm across. Sn particles grew as large as a few tens of nm while those as small as a few nm were scattered on the (0001) rGO surface with some epitaxial relations. Si, SiO, and Sn particles were found hanging on at the edges of the rGO lamellae. An electrochemical test was performed for this nanocomposite powder. The result suggested that the SiSn/rGO powder would be a promising anode material for lithium-ion batteries with high capacity.

  15. Niobium and tantalum: indispensable twins

    Science.gov (United States)

    Schulz, Klaus; Papp, John

    2014-01-01

    Niobium and tantalum are transition metals almost always paired together in nature. These “twins” are difficult to separate because of their shared physical and chemical properties. In 1801, English chemist Charles Hatchett uncovered an unknown element in a mineral sample of columbite; John Winthrop found the sample in a Massachusetts mine and sent it to the British Museum in London in 1734. The name columbium, which Hatchet named the new element, came from the poetic name for North America—Columbia—and was used interchangeably for niobium until 1949, when the name niobium became official. Swedish scientist Anders Ekberg discovered tantalum in 1802, but it was confused with niobium, because of their twinned properties, until 1864, when it was recognized as a separate element. Niobium is a lustrous, gray, ductile metal with a high melting point, relatively low density, and superconductor properties. Tantalum is a dark blue-gray, dense, ductile, very hard, and easily fabricated metal. It is highly conductive to heat and electricity and renowned for its resistance to acidic corrosion. These special properties determine their primary uses and make niobium and tantalum indispensable.

  16. Fabrication of Polymeric Antireflection Film Manufactured by Anodic Aluminum Oxide Template on Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Jenn-Kai Tsai

    2017-03-01

    Full Text Available In this study, high energy conversion efficient dye-sensitized solar cells (DSSCs were successfully fabricated by attaching a double anti-reflection (AR layer, which is composed of a subwavelength moth-eye structured polymethyl methacrylate (PMMA film and a polydimethylsiloxane (PDMS film. An efficiency of up to 6.79% was achieved. The moth-eye structured PMMA film was fabricated by using an anodic aluminum oxide (AAO template which is simple, low-cost and scalable. The nano-pattern of the AAO template was precisely reproduced onto the PMMA film. The photoanode was composed of Titanium dioxide (TiO2 nanoparticles (NPs with a diameter of 25 nm deposited on the fluorine-doped tin oxide (FTO glass substrate and the sensitizer N3. The double AR layer was proved to effectively improve the short-circuit current density (JSC and conversion efficiency from 14.77 to 15.79 mA/cm2 and from 6.26% to 6.79%, respectively.

  17. Novel synthesis of holey reduced graphene oxide (HRGO) by microwave irradiation method for anode in lithium-ion batteries

    Science.gov (United States)

    Alsharaeh, Edreese; Ahmed, Faheem; Aldawsari, Yazeed; Khasawneh, Majdi; Abuhimd, Hatem; Alshahrani, Mohammad

    2016-07-01

    In this work, holey reduced graphene oxide (HRGO) was synthesized by the deposition of silver (Ag) nanoparticles onto the reduced graphene oxide (RGO) sheets followed by nitric acid treatment to remove Ag nanoparticles by microwave irradiation to form a porous structure. The HRGO were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), ultra violet-visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA), and Raman spectroscopy. These novel HRGO exhibited high rate capability with excellent cycling stability as an anode material for lithium-ion batteries. The results have shown an excellent electrochemical response in terms of charge/discharge capacity (423 mAh/g at 100 mA/g). The cyclic performance was also exceptional as a high reversible capacity (400 mAh/g at 100 mA/g) was retained for 100 charge/discharge cycles. This fascinating electrochemical performance can be ascribed to their specific porous structure (2–5 nm pores) and high surface area (457 m2/g), providing numerous active sites for Li+ insertion, high electrical conductivity, low charge-transfer resistance across the electrolyte–electrode interface, and improved structural stability against the local volume change during Li+ insertion–extraction. Such electrodes are envisioned to be mass scalable with relatively simple and low-cost fabrication procedures, thereby providing a clear pathway toward commercialization.

  18. Influência do agente precipitante na preparação do óxido de nióbio (V hidratado pelo método da precipitação em solução homogênea Influence of precipitating agent in the preparation of hydrous niobium oxide by the method of homogeneous precipitation

    Directory of Open Access Journals (Sweden)

    Geronimo Virginio Tagliaferro

    2005-03-01

    Full Text Available This work reports the preparation, characterization and study of the ion exchange behavior of hydrous niobium oxide prepared by a homogeneous precipitation method. The precipitating agent was obtained in aqueous solution by thermal decomposition of urea or ammonium carbonate. The compounds were chemically and physically characterized by X-ray diffractometry, thermal analysis (TG/DTG, surface area measurements and ion exchange behavior with sodium. The materials prepared with ammonium carbonate presented a higher degree of crystallinity and better ion exchange capacity with sodium than materials prepared with urea. In the homogeneous precipitation method, materials were obtained with specific surface area of 123 - 224 m² g-1. A variation of the preparation process produced hydrous niobium oxide with a different degree of hydration and specific surface area. This provided materials with different physico-chemical properties.

  19. Zinc oxide nanostructures by chemical vapour deposition as anodes for Li-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Laurenti, M., E-mail: marco.laurenti@iit.it [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento, 21, 10129 Turin (Italy); Department of Applied Science and Technology – DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin (Italy); Garino, N. [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento, 21, 10129 Turin (Italy); Porro, S.; Fontana, M. [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento, 21, 10129 Turin (Italy); Department of Applied Science and Technology – DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin (Italy); Gerbaldi, C., E-mail: claudio.gerbaldi@polito.it [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento, 21, 10129 Turin (Italy); Department of Applied Science and Technology – DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin (Italy)

    2015-08-15

    Highlights: • ZnO nanostructures are grown by simple chemical vapour deposition. • Polycrystalline nanostructured porous thin film is obtained. • Film exhibits stable specific capacity (∼400 mA h g{sup −1}) after prolonged cycling. • CVD-grown ZnO nanostructures show promising prospects as Li-ion battery anode. - Abstract: ZnO nanostructures are grown by a simple chemical vapour deposition method directly on a stainless steel disc current collector and successfully tested in lithium cells. The structural/morphological characterization points out the presence of well-defined polycrystalline nanostructures having different shapes and a preferential orientation along the c-axis direction. In addition, the high active surface of the ZnO nanostructures, which accounts for a large electrode/electrolyte contact area, and the complete wetting with the electrolyte solution are considered to be responsible for the good electrical transport properties and the adequate electrochemical behaviour, as confirmed by cyclic voltammetry and galvanostatic charge/discharge cycling. Indeed, despite no binder or conducting additives are used, when galvanostatically tested in lithium cells, after an initial decay, the ZnO nanostructures can provide a rather stable specific capacity approaching 70 μA h cm{sup −2} (i.e., around 400 mA h g{sup −1}) after prolonged cycling at 1 C, with very high Coulombic efficiency and an overall capacity retention exceeding 62%.

  20. Synthesis of copper hydroxide and oxide nanostructures via anodization technique for efficient photocatalytic application.

    Science.gov (United States)

    Hyam, Rajeshkumar Shankar; Lee, Jongseok; Cho, Eunju; Khim, Jeehyeong; Lee, Haigun

    2012-11-01

    We have demonstrated a facile protocol for synthesizing CuO and Cu2O mixed-phase nanostructures by anodization of copper hydroxide (Cu(OH)2) nanoneedles and their heat treatment in different atmospheres, which affect photocatalytic degradation efficiency. The oxygen annealed sample had relatively small (100 nm) lamellar, spherical nanoparticulate structures on the substrate surface, which showed better photocatalytic degradation of reactive black 5 dye resulting from the appropriate morphology and phase formation, compared to the samples annealed in different atmospheres and vacuum. The pseudo first-order rate constant (k) of the oxygen annealed sample was 0.0054/min, which was relatively high due to the formation of a CuO-Cu2O heterojunction with matching band potentials. Air, nitrogen, argon and vacuum annealing resulted in bigger particles and different morphologies, which led to pseudo first-order rate constants (k) of 0.0032/min (air-annealed); 0.0021/min (N2-annealed); 0.0033/min (Ar-annealed); and 0.0027/min (vacuum-annealed), which resulted in poor photocatalytic degradation of the reactive black 5 dye.