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Sample records for anodic niobium oxides

  1. Micro-length anodic porous niobium oxide for lithium-ion thin film battery applications

    International Nuclear Information System (INIS)

    Yoo, Jeong Eun; Park, Jiyoung; Cha, Gihoon; Choi, Jinsub

    2013-01-01

    The anodization of niobium in an aqueous mixture of H 3 PO 4 and HF in the potential range from 2.5 to 30 V for 2 h at 5 °C was performed, demonstrating that anodic porous niobium oxide film with a thickness of up to 2000 nm, including a surface dissolution layer, can be obtained by controlling the applied potential and composition of the electrolytes. Specifically, surface dissolution-free porous niobium oxide film with a thickness of 800 nm can be prepared in a low electrolyte concentration. The surface dissolution is observed when the concentration ratio of HF (wt.%):H 3 PO 4 (M) was more than 2:1. The discontinuous layers in the niobium oxide film were observed when the thickness was higher than 500 nm, which was ascribed to the large volume expansion of the niobium oxide grown from the niobium metal. The anodic porous niobium oxide film was used as the cathode for lithium-ion batteries in the potential range from 1.2 to 3.0 V at a current density of 7.28 × 10 − 6 A cm −2 . The first discharge capacity of ca. 53 μA h cm − 2 was obtained in 800 nm thick niobium oxide without a surface dissolution layer. - Highlights: ► Anodic porous niobium oxide film with a thickness of 2000 nm was obtained. ► Surface dissolution-free porous niobium oxide film was prepared. ► The niobium oxide film was used as the cathode for lithium-ion batteries

  2. Niobium oxide nanocolumns formed via anodic alumina with modulated pore diameters

    Science.gov (United States)

    Pligovka, A.; Zakhlebayeva, A.; Lazavenka, A.

    2018-03-01

    Niobium oxide nanocolumns with modulated diameters were formed for the first time. An Al/Nb bilayer specimen was prepared by successive sputter-deposition of 300 nm niobium layer and 1200 nm aluminum layer onto silicon wafer. Regular anodic alumina matrix with modulated pore diameters was formed by sequential anodization of initial specimen in tartaric acid at 180 V, and in oxalic acid at 37 V. Further potentiodynamic reanodization of the specimen up to 400 V causes the simultaneous growth of 440 nm continuous niobium oxide layer beneath the alumina film and two types of an array of oxide nanocolumns (thick – with 100 nm width and 630 nm high and thin – with 25 nm width and 170 nm high), which are the filling of the alumina pores. The morphology of the formed anodic niobium oxide nanocolumns with modulated diameters was determined by field emission scanning electron microscopy. The formed nanostructures can be used for perspective devices of nano- and optoelectronics such as photonic crystals.

  3. Growth of anodic oxide films on oxygen-containing niobium

    Energy Technology Data Exchange (ETDEWEB)

    Habazaki, H. [Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan)]. E-mail: habazaki@eng.hokudai.ac.jp; Ogasawara, T. [Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Konno, H. [Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Shimizu, K. [University Chemical Laboratory, Keio University, Yokohama 223-8522 (Japan); Asami, K. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Saito, K. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Nagata, S. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Skeldon, P. [Corrosion and Protection Centre, School of Materials, The University of Manchester, P.O. Box 88, Manchester M60 1QD (United Kingdom); Thompson, G.E. [Corrosion and Protection Centre, School of Materials, The University of Manchester, P.O. Box 88, Manchester M60 1QD (United Kingdom)

    2005-09-20

    The present study is directed at understanding of the influence of oxygen in the metal on anodic film growth on niobium, using sputter-deposited niobium containing from about 0-52 at.% oxygen, with anodizing carried out at high efficiency in phosphoric acid electrolyte. The findings reveal amorphous anodic niobia films, with no significant effect of oxygen on the field strength, transport numbers, mobility of impurity species and capacitance. However, since niobium is partially oxidized due to presence of oxygen in the substrate, less charge is required to form the films, hence reducing the time to reach a particular film thickness and anodizing voltage. Further, the relative thickness of film material formed at the metal/film interface is increased by the incorporation of oxygen species into the films from the substrate, with an associated altered depth of incorporation of phosphorus species into the films.

  4. Surfactant-assisted growth of anodic nanoporous niobium oxide with a grained surface

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Jeong Eun [Department of Chemical Engineering, Inha University, 253 Yonghyun Dong, Nam-Gu, Incheon 402-751 (Korea, Republic of); Choi, Jinsub, E-mail: jinsub@inha.ac.k [Department of Chemical Engineering, Inha University, 253 Yonghyun Dong, Nam-Gu, Incheon 402-751 (Korea, Republic of)

    2010-07-15

    Nanoporous niobium oxide film with a maximum thickness of 520 nm was prepared by anodizing niobium in a mixture of 1 wt% HF, 1 M H{sub 3}PO{sub 4}, and a small amount of Sodium Dodecyl Sulfate (SDS) surfactant. The porosity of the anodic niobium oxide prepared without SDS is irregular with the surface of the oxide suggesting a grained surface pattern rather than an ordered porous structure. A proper amount of SDS addition can prepare a pore arrangement with stripe patterns. The pore depth and surface pattern were strongly affected by the concentration of SDS and bath temperature. We found that the addition of SDS surfactant facilitated improvement in the chemical resistance of niobium oxide, leading to the formation of pores with a longer length compared to those prepared without a SDS surfactant. This can be in part ascribed to the protection of the surface by the physical adsorption of SDS on the surface due to a charge-charge interaction and be in part attributed to the formation of Nb=O bonding on the outermost oxide layer by SDS. When anodization was carried out for 4 h, the surface dissolution of niobium oxide was observed, which means that the maximum tolerance time against chemical dissolution was less than 4 h.

  5. Preparation of self-organized porous anodic niobium oxide microcones and their surface wettability

    International Nuclear Information System (INIS)

    Oikawa, Y.; Minami, T.; Mayama, H.; Tsujii, K.; Fushimi, K.; Aoki, Y.; Skeldon, P.; Thompson, G.E.; Habazaki, H.

    2009-01-01

    Porous anodic niobium oxide with a pore size of ∼10 nm was formed at 10 V in glycerol electrolyte containing 0.6 mol dm -3 K 2 HPO 4 and 0.2 mol dm -3 K 3 PO 4 at 433 K. After prolonged anodizing for 5.4 ks, niobium oxide microcones develop on the surface. X-ray diffraction patterns of the anodized specimens revealed that the initially formed anodic oxide is amorphous, but an amorphous-to-crystalline transition occurs during anodizing. As a consequence of the preferential chemical dissolution of the initially formed amorphous oxide, due to different solubility of the amorphous and crystalline oxides, crystalline oxide microcones appear on the film surface after prolonged anodizing. The surface is superhydrophilic. After coating with fluorinated alkylsilane, the surface becomes superhydrophobic with a contact angle of 158 o for water. The surface is also oil repellent, with a contact angle as high as 140 o for salad oil.

  6. Anodic luminescence, structural, photoluminescent, and photocatalytic properties of anodic oxide films grown on niobium in phosphoric acid

    Energy Technology Data Exchange (ETDEWEB)

    Stojadinović, Stevan, E-mail: sstevan@ff.bg.ac.rs [University of Belgrade, Faculty of Physics, Studentski trg 12-16, 11000 Belgrade (Serbia); Tadić, Nenad [University of Belgrade, Faculty of Physics, Studentski trg 12-16, 11000 Belgrade (Serbia); Radić, Nenad [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoševa 12, 11000 Belgrade (Serbia); Stefanov, Plamen [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 11, 1113 Sofia (Bulgaria); Grbić, Boško [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoševa 12, 11000 Belgrade (Serbia); Vasilić, Rastko [University of Belgrade, Faculty of Physics, Studentski trg 12-16, 11000 Belgrade (Serbia)

    2015-11-15

    Graphical abstract: - Highlights: • Anodic luminescence is correlated to the existence of morphological defects in the oxide. • Spectrum under spark discharging reveals only oxygen and hydrogen lines. • Oxide films formed under spark discharging are crystallized and composed of Nb{sub 2}O{sub 5}. • Photocatalytic activity and photoluminescence of Nb{sub 2}O{sub 5} films increase with time. - Abstract: This article reports on properties of oxide films obtained by anodization of niobium in phosphoric acid before and after the dielectric breakdown. Weak anodic luminescence of barrier oxide films formed during the anodization of niobium is correlated to the existence of morphological defects in the oxide layer. Small sized sparks generated by dielectric breakdown of formed oxide film cause rapid increase of luminescence intensity. The luminescence spectrum of obtained films on niobium under spark discharging is composed of continuum radiation and spectral lines caused by electronic spark discharging transitions in oxygen and hydrogen atoms. Oxide films formed before the breakdown are amorphous, while after the breakdown oxide films are partly crystalline and mainly composed of Nb{sub 2}O{sub 5} hexagonal phase. The photocatalytic activity of obtained oxide films after the breakdown was investigated by monitoring the degradation of methyl orange. Increase of the photocatalytic activity with time is related to an increase of oxygen vacancy defects in oxide films formed during the process. Also, higher concentration of oxygen vacancy defects in oxide films results in higher photoluminescence intensity.

  7. Mechanism of formation and growth of sunflower-shaped imperfections in anodic oxide films on niobium

    Energy Technology Data Exchange (ETDEWEB)

    Nagahara, K. [Graduate School of Engineering, Hokkaido University, N13 W8 Kita-ku, Sapporo 060-8628 (Japan); Sakairi, M. [Graduate School of Engineering, Hokkaido University, N13 W8 Kita-ku, Sapporo 060-8628 (Japan); Takahashi, H. [Graduate School of Engineering, Hokkaido University, N13 W8 Kita-ku, Sapporo 060-8628 (Japan)]. E-mail: Takahasi@elechem1-mc.eng.hokudai.ac.jp; Matsumoto, K. [Cabot Supermetals K.K., Higashinagahara Works, 111 Nagayachi, Kawahigashi-machi, Kawanuma-gun, Fukushima-ken 969-3431 (Japan); Takayama, K. [Cabot Supermetals K.K., Higashinagahara Works, 111 Nagayachi, Kawahigashi-machi, Kawanuma-gun, Fukushima-ken 969-3431 (Japan); Oda, Y. [Cabot Supermetals K.K., Higashinagahara Works, 111 Nagayachi, Kawahigashi-machi, Kawanuma-gun, Fukushima-ken 969-3431 (Japan)

    2007-01-01

    Anodizing of niobium has been investigated to develop niobium solid electrolytic capacitors. Chemically polished niobium specimens were anodized in a diluted phosphoric acid solution, initially galvanostatically at i {sub a} = 4 A m{sup -2} up to E {sub a} = 100 V, and then potentiostatically at E {sub a} = 100 V for t {sub pa} = 43.2 ks. During the galvanostatic anodizing, the anode potential increased almost linearly with time, while, during potentiostatic anodizing, the anodic current decreased up to t {sub pa} = 3.6 ks, and then increased slowly before decreasing again after t {sub pa} = 30.0 ks. Images of FE-SEM and in situ AFM showed that nuclei of imperfections were formed at the ridge of cell structures before t {sub pa} = 3.6 ks. After formation, the imperfection nuclei grew, showing cracking and rolling-up of the anodic oxide film, and crystalline oxide was formed at the center of imperfections after t {sub pa} = 3.6 ks. The growth of imperfections caused increases in the anodic current between t {sub pa} = 3.6 and 30.0 ks. Long-term anodizing caused a coalescence of the imperfections, leading to decreases in the anodic current after t {sub pa} = 30.0 ks. As the imperfections grew, the dielectric dispersion of the anodic oxide films became serious, showing a bias voltage dependence of the parallel equivalent capacitance, C {sub p}, and a dielectric dissipation factor, tan {delta}. The mechanism of formation and growth of the imperfections, and the correlation between the structure and dielectric properties of anodic oxide films is discussed.

  8. X-ray spectral determination of chemical state of phosphorus and sulfur in anodic oxide films on niobium

    International Nuclear Information System (INIS)

    Bokij, L.P.; Kostikov, Yu.P.

    1989-01-01

    Chemical forms of phosphorus and sulfur in niobium oxide anodic film, obtained by electrochemical technique using niobium in H 2 SO 4 and H 3 PO 4 aqueous solutions, are determined using data on chemical shifts of X-ray emission lines. Films represent Nb 2 O 5(1-γ) (SO 4 ) 5γ and Nb 2 O 5(1-γ) (PO 4 ) 10γ/3 (γ -share of oxygen substituted by acid anion) composition oxosalts. Electrolyte role in formation of niobium anodic oxide structure and effect of phosphorus and sulfur compounds on anodic film conductivity are determined

  9. Control of morphology and surface wettability of anodic niobium oxide microcones formed in hot phosphate-glycerol electrolytes

    International Nuclear Information System (INIS)

    Yang, Shu; Habazaki, Hiroki; Fujii, Takashi; Aoki, Yoshitaka; Skeldon, Peter; Thompson, George E.

    2011-01-01

    Highlights: → Anodic niobium oxide microcones with nanofiber morphology are formed simply by anodizing. → The cone size and its tip angle are controlled by anodizing condition. → The surface shows extremely high contact angle for water after coating with a fluoroalkyl layer. - Abstract: We report the fabrication of superhydrophobic surfaces with a hierarchical morphology by self-organized anodizing process. Simply by anodizing of niobium metal in hot phosphate-glycerol electrolyte, niobium oxide microcones, consisting of highly branched oxide nanofibers, develop on the surface. The size of the microcones and their tip angles are controlled by changing the applied potential difference in anodizing and the water content in the electrolyte. Reduction of the water content increases the size of the microcones, with the nanofibers changing to nanoparticles. The size of microcones is also reduced by increasing the applied potential difference, without influencing the tip angle. The hierarchical oxide surfaces are superhydrophilic, with static contact angles close to 0 o . Coating of the anodic oxide films with a monolayer of fluoroalkyl phosphate makes the surfaces superhydrophobic with a contact angle for water as high as 175 o and a very small contact angle hysteresis of only 2 o . The present results indicate that the larger microcones with smaller tip angles show the higher contact angle for water.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Effect of electrolyte temperature on the formation of self-organized anodic niobium oxide microcones in hot phosphate-glycerol electrolyte

    Science.gov (United States)

    Yang, S.; Aoki, Y.; Habazaki, H.

    2011-07-01

    Nanoporous niobium oxide films with microcone-type surface morphology were formed by anodizing at 10 V in glycerol electrolyte containing 0.6 mol dm -3 K 2HPO 4 and 0.2 mol dm -3 K 3PO 4 in a temperature range of 428-453 K. The microcones appeared after prolonged anodizing, but the required time was largely reduced by increasing electrolyte temperature. The anodic oxide was initially amorphous at all temperatures, but crystalline oxide nucleated during anodizing. The anodic oxide microcones, which were crystalline, appeared on surface as a consequence of preferential chemical dissolution of initially formed amorphous oxide. The chemical dissolution of an initially formed amorphous layer was accelerated by increasing the electrolyte temperature, with negligible influence of the temperature on the morphology of microcones up to 448 K.

  12. Effect of electrolyte temperature on the formation of self-organized anodic niobium oxide microcones in hot phosphate-glycerol electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Yang, S.; Aoki, Y. [Division of Materials Chemistry, Faculty of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Habazaki, H., E-mail: habazaki@eng.hokudai.ac.jp [Division of Materials Chemistry, Faculty of Engineering, Hokkaido University, Sapporo 060-8628 (Japan)

    2011-07-15

    Nanoporous niobium oxide films with microcone-type surface morphology were formed by anodizing at 10 V in glycerol electrolyte containing 0.6 mol dm{sup -3} K{sub 2}HPO{sub 4} and 0.2 mol dm{sup -3} K{sub 3}PO{sub 4} in a temperature range of 428-453 K. The microcones appeared after prolonged anodizing, but the required time was largely reduced by increasing electrolyte temperature. The anodic oxide was initially amorphous at all temperatures, but crystalline oxide nucleated during anodizing. The anodic oxide microcones, which were crystalline, appeared on surface as a consequence of preferential chemical dissolution of initially formed amorphous oxide. The chemical dissolution of an initially formed amorphous layer was accelerated by increasing the electrolyte temperature, with negligible influence of the temperature on the morphology of microcones up to 448 K.

  13. Nanoporous titanium niobium oxide and titanium tantalum oxide compositions and their use in anodes of lithium ion batteries

    Science.gov (United States)

    Dai, Sheng; Guo, Bingkun; Sun, Xiao-Guang; Qiao, Zhenan

    2017-10-31

    Nanoporous metal oxide framework compositions useful as anodic materials in a lithium ion battery, the composition comprising metal oxide nanocrystals interconnected in a nanoporous framework and having interconnected channels, wherein the metal in said metal oxide comprises titanium and at least one metal selected from niobium and tantalum, e.g., TiNb.sub.2-x Ta.sub.xO.sub.y (wherein x is a value from 0 to 2, and y is a value from 7 to 10) and Ti.sub.2Nb.sub.10-vTa.sub.vO.sub.w (wherein v is a value from 0 to 2, and w is a value from 27 to 29). A novel sol gel method is also described in which sol gel reactive precursors are combined with a templating agent under sol gel reaction conditions to produce a hybrid precursor, and the precursor calcined to form the anodic composition. The invention is also directed to lithium ion batteries in which the nanoporous framework material is incorporated in an anode of the battery.

  14. Effect of current density on the anodic behaviour of zircaloy-4 and niobium: a comparative study

    International Nuclear Information System (INIS)

    Raghunath Reddy, G.; Lavanya, A.; Ch Anjaneyulu

    2004-01-01

    The kinetics of anodic oxidation of zircaloy-4 and niobium have been studied at current densities ranging from 2 to 14 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 were estimated from capacitance data. The formation rate, current efficiency and differential field were found to increase with increase in the ionic current density for both zircaloy-4 and niobium. Plots of the logarithm of formation rate vs. logarithm of the current density are fairly linear. From linear plots of logarithm of ionic current density vs. differential field, and applying the Cabrera-Mott theory, the half-jump distance and the height of the energy barrier are deduced and compared. (author)

  15. Growth of anodic films on niobium

    International Nuclear Information System (INIS)

    Gomes, M.A.B.; Bulhoes, L.O.S.

    1988-01-01

    The analysis of the response of the galvanostatic growth of anodic films on niobium metal in aqueous solutions is shown. The first spark voltage showed a dependence upon value of current density that could be explained as the incorporation of anions into the film. (M.J.C.) [pt

  16. 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.

  17. Direct Flotation of Niobium Oxide Minerals from Carbonatite Niobium Ores

    Science.gov (United States)

    Ni, Xiao

    Currently the recovery of niobium oxide minerals from carbonatite niobium ores relies on the use of non-selective cationic collectors. This leads to complicated process flowsheets involving multiple desliming and multiple reverse flotation stages, and low niobium recovery. In this research, anionic collectors that are capable of strong chemisorption on the niobium minerals were studied with the objective of directly floating the niobium oxide minerals from the carbonatite ores. In the flotation of both high purity minerals and Niobec ores, it was shown that the combination of hydroxamic acid and sodium metaphosphate was an effective reagent scheme for the direct flotation of niobium oxide from its ores. Batch flotation on the Niobec Mill Feed showed that over 95% of niobium oxide was recovered into a rougher concentrate that was less than 47% of the original feed mass. Preliminary cleaning tests showed that the reagent scheme could also be used to upgrade the rougher concentrate, although the depression of iron oxide minerals required further study. X-ray photoelectron spectroscopic (XPS) measurement results confirm that OHA (octyl hydroxamic acid) could chemisorb on pyrochlore surface while only physically adsorb on calcite, judging by the chemical shifts of electron binding energies in the elements in both OHA and the mineral surfaces. When hydroxamic acid was adsorbed on calcite surface, the binding energies of the N 1s electrons, at 400.3 eV, did not shift. However, after adsorption on pyrochlore, the N 1s binding energy peak split into two peaks, one at a binding energy of around 399 eV, representing chemically adsorbed OHA, the other at between 400 and 401 eV. The experimental data suggested a strong chemisorption of the OHA on pyrochlore surface in the form of a vertical head-on orientation of the OHA molecules so that the pyrochlore was strongly hydrophobized even at low OHA concentrations, followed by possibly randomly oriented physisorbed OHA molecules

  18. Kinetics and oxidation mechanisms of polycrystaline niobium

    International Nuclear Information System (INIS)

    Paschoal, J.O.A.

    1979-01-01

    The oxidation kinetics of annealed niobium was determined by thermogravimetric analysis between 450 and 800 0 C and for oxygen pressures varying from 20 to 700 mmHg. The oxidation kinetics of cold worked and/or irradiated niobium for temperatures between 500 and 700 0 C, with oxygen pressures varying from 100 to 300 mmHg. Was also determined. Using X-ray diffraction it was found that the oxide formed in the range of temperature and oxygen pressure considered in this research is γ-Nb 2 O 5 . Optical and scanning eletronic microscopy showed that for annealed niobium oxidized under 600 0 C there was formation of non-uniform oxide layers, containing cracks and pores, presenting very irregular metal/pentoxide interface. The presence of sub-oxide NbOsub(z) platelets was observed in this interface. This sub-oxide platelets where not observed in annealed oxidized niobium samples over 600 0 C; the oxide layers formed were compact. At 800 0 C and the beginning at 700 0 C the interfaces were quite regular. Through microhardness measurements for the metal near the metal/pentoxide interface, the formation of oxygen solid solution was found and the oxygen diffusion coefficient was calculated. The results showed that at 600 0 C the oxygen diffusion coefficient in cold worked niobium is three times larger than the value obtained for annealed niobium. The results suggest that the reaction between annealed niobium and oxygen undaer 600 0 C is controlled by reaction in interface where the oxide layers are not compacted, parcially due to Nb sub(z) platelets formation.(Author) [pt

  19. Spectrographic determination of impurities in high-purity tantalum oxide and niobium oxide

    International Nuclear Information System (INIS)

    Anderson, S.T.G.; Russell, G.M.

    1990-01-01

    The development of spectrographic methods by direct current arc excitation and carrier distillation for the determination of impurities in tantalum and niobium oxides are described. Iron, silicon, aluminium, titanium, calcium, silver, tin, magnesium, and manganese can be determined in tantalum oxide and niobium oxide in concentrations ranging from 3 to 300 p.p.m. Niobium can be determined in tantalum oxide in concentrations ranging from 10 to 300 p.p.m. Tantalum cannot be determined in niobium oxide, and tungsten cannot be determined in either matrix as a result of the absence of sensitive lines in the spectra of these elements. Relative standard deviations of analyte element concentrations are in the region of 0,18 for tantalum oxide samples, and 0,13 for niobium oxide samples. A detailed laboratory method is included. 4 figs., 4 tabs., 3 refs

  20. Free energy of hydration of niobium oxide

    International Nuclear Information System (INIS)

    Plodinec, M.J.

    1996-01-01

    Some of the glasses being formulated by SRTC researchers contain niobium oxide. In this report, the free energy of hydration of the oxide is calculated from the free energies of formation of the oxide, the hydroxide, and water. This value can be used in calculations of the free energy of hydration of glasses containing niobium

  1. Anodization-based process for the fabrication of all niobium nitride Josephson junction structures

    Directory of Open Access Journals (Sweden)

    Massimiliano Lucci

    2017-03-01

    Full Text Available We studied the growth and oxidation of niobium nitride (NbN films that we used to fabricate superconductive tunnel junctions. The thin films were deposited by dc reactive magnetron sputtering using a mixture of argon and nitrogen. The process parameters were optimized by monitoring the plasma with an optical spectroscopy technique. This technique allowed us to obtain NbN as well as good quality AlN films and both were used to obtain NbN/AlN/NbN trilayers. Lift-off lithography and selective anodization of the NbN films were used, respectively, to define the main trilayer geometry and/or to separate electrically, different areas of the trilayers. The anodized films were characterized by using Auger spectroscopy to analyze compounds formed on the surface and by means of a nano-indenter in order to investigate its mechanical and adhesion properties. The transport properties of NbN/AlN/NbN Josephson junctions obtained as a result of the above described fabrication process were measured in liquid helium at 4.2 K.

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

    International Nuclear Information System (INIS)

    Helali, S.; Abdelghani, A.; Hafaiedh, I.; Martelet, C.; Prodromidis, M.I.; Albanis, T.; Jaffrezic-Renault, N.

    2008-01-01

    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 2 SO 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

  3. Structural phase transitions in niobium oxide nanocrystals

    Science.gov (United States)

    Yuvakkumar, R.; Hong, Sun Ig

    2015-09-01

    Niobium oxide nanocrystals were successfully synthesized employing the green synthesis method. Phase formation, microstructure and compositional properties of 1, 4 and 7 days incubation treated samples after calcinations at 450 °C were examined using X-ray diffraction, Raman, photoluminescence (PL), infrared, X-ray photoelectron spectra and transmission electron microscopic characterizations. It was observed that phase formation of Nb2O5 nanocrystals was dependent upon the incubation period required to form stable metal oxides. The characteristic results clearly revealed that with increasing incubation and aging, the transformation of cubic, orthorhombic and monoclinic phases were observed. The uniform heating at room temperature (32 °C) and the ligation of niobium atoms due to higher phenolic constituents of utilized rambutan during aging processing plays a vital role in structural phase transitions in niobium oxide nanocrystals. The defects over a period of incubation and the intensities of the PL spectra changing over a period of aging were related to the amount of the defects induced by the phase transition.

  4. 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

  5. Method of removing niobium from uranium-niobium alloy

    International Nuclear Information System (INIS)

    Pollock, E.N.; Schlier, D.S.; Shinopulos, G.

    1992-01-01

    This patent describes a method of removing niobium from a uranium-niobium alloy. It comprises dissolving the uranium-niobium alloy metal pieces in a first aqueous solution containing an acid selected from the group consisting of hydrochloric acid and sulfuric acid and fluoboric acid as a catalyst to provide a second aqueous solution, which includes uranium (U +4 ), acid radical ions, the acids insolubles including uranium oxides and niobium oxides; adding nitric acid to the insolubles to oxidize the niobium oxides to yield niobic acid and to complete the solubilization of any residual uranium; and separating the niobic acid from the nitric acid and solubilized uranium

  6. 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.

  7. Mesostructured niobium-doped titanium oxide-carbon (Nb-TiO2-C) composite as an anode for high-performance lithium-ion batteries

    Science.gov (United States)

    Hwang, Keebum; Sohn, Hiesang; Yoon, Songhun

    2018-02-01

    Mesostructured niobium (Nb)-doped TiO2-carbon (Nb-TiO2-C) composites are synthesized by a hydrothermal process for application as anode materials in Li-ion batteries. The composites have a hierarchical porous structure with the Nb-TiO2 nanoparticles homogenously distributed throughout the porous carbon matrix. The Nb content is controlled (0-10 wt%) to investigate its effect on the physico-chemical properties and electrochemical performance of the composite. While the crystalline/surface structure varied with the addition of Nb (d-spacing of TiO2: 0.34-0.36 nm), the morphology of the composite remained unaffected. The electrochemical performance (cycle stability and rate capability) of the Nb-TiO2-C composite anode with 1 wt% Nb doping improved significantly. First, a full cut-off potential (0-2.5 V vs. Li/Li+) of Nb-doped composite anode (1 wt%) provides a higher energy utilization than that of the un-doped TiO2-C anode. Second, Nb-TiO2-C composite anode (1 wt%) exhibits an excellent long-term cycle stability (100% capacity retention, 297 mAh/g at 0.5 C after 100 cycles and 221 mAh/g at 2 C after 500 cycles) and improved rate-capability (192 mAh/g at 5 C), respectively (1 C: 150 mA/g). The superior electrochemical performance of Nb-TiO2-C (1 wt%) could be attributed to the synergistic effect of improved electronic conductivity induced by optimal Nb doping (1 wt%) and lithium-ion penetration (high diffusion kinetics) through unique pore structures.

  8. Study on thermo-oxide layers of uranium-niobium alloy

    International Nuclear Information System (INIS)

    Luo Lizhu; Yang Jiangrong; Zhou Ping

    2010-01-01

    Surface oxides structure of uranium-niobium alloys which were annealed under different temperatures (room temperature, 100, 200, 300 degree C, respectively)in air were studied by X-ray photoelectron spectroscopy (XPS) analysis and depth profile. Thickness of thermo-oxide layers enhance with the increasing oxide temperature, and obvious changes to oxides structure are observed. Under different delt temperatures, Nb 2 O 5 are detected on the initial surface of U-Nb alloys, and a layer of NbO mixed with some NbO x (0 2 O 5 and Nb metal. Dealing samples in air from room temperature to 200 degree C, non-stoichiometric UO 2+x (UO 2 + interstitial oxygen, P-type semiconductor) are found on initial surface of U-Nb alloys, which has 0.7 eV shift to lower binding energy of U 4f 7/2 characteristics comparing to that of UO 2 . Under room temperature, UO 2 are commonly detected in the oxides layer, while under temperature of 100 and 200 degree C, some P-type UO 2+x are found in the oxide layers,which has a satellite at binding energy of 396.6 eV. When annealing at 300 degree C, higher valence oxides, such as U 3 O 8 or UO x (2 5/2 and U 4f 7/2 peaks are 392.2 and 381.8 eV, respectively. UO 2 mixed uranium metal are the main compositions in the oxide layers. From the results, influence of temperature to oxidation of uranium is more visible than to niobium in uranium-niobium alloys. (authors)

  9. 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

  10. The oxidative coupling of methane and the oxidative dehydrogenation of ethane over a niobium promoted lithium doped magnesium oxide catalyst

    NARCIS (Netherlands)

    Swaan, H.M.; Swaan, H.M.; Li, X.; Seshan, Kulathuiyer; van Ommen, J.G.; Ross, J.R.H.; Ross, J.R.H.

    1993-01-01

    The promoting effect of niobium in a Li/MgO catalyst for the oxidative coupling of methane (OCM) and for the oxidative dehydrogenation of ethane (ODHE) has been studied in some detail. It has been found that a Li/Nb/MgO catalyst with 16 wt % niobium showed the highest activity for the C2 production

  11. Niobium and hafnium grown on porous membranes

    International Nuclear Information System (INIS)

    Morant, C.; Marquez, F.; Campo, T.; Sanz, J.M.; Elizalde, E.

    2010-01-01

    In this work we report on a method for fabricating highly ordered nanostructures of niobium and hafnium metals by physical vapour deposition using two different templates: anodized aluminum oxide membranes (AAO) and zirconium onto AAO membranes (Zr/AAO). The growth mechanism of these metal nanostructures is clearly different depending on the material used as a template. A different morphology was obtained by using AAO or Zr/AAO templates: when the metal is deposited onto AAO membranes, nanospheres with ordered hexagonal regularity are obtained; however, when the metal is deposited onto a Zr/AAO template, highly ordered nanocones are formed. The experimental approach described in this work is simple and suitable for synthesizing nanospheres or nanoholes of niobium and hafnium metals in a highly ordered structure.

  12. Electrochemical Thinning for Anodic Aluminum Oxide and Anodic Titanium Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Lee, In Hae; Jo, Yun Kyoung; Kim, Yong Tae; Tak, Yong Sug; Choi, Jin Sub [Inha University, Incheon (Korea, Republic of)

    2012-05-15

    For given electrolytes, different behaviors of anodic aluminum oxide (AAO) and anodic titanium oxide (ATO) during electrochemical thinning are explained by ionic and electronic current modes. Branched structures are unavoidably created in AAO since the switch of ionic to electronic current is slow, whereas the barrier oxide in ATO is thinned without formation of the branched structures. In addition, pore opening can be possible in ATO if chemical etching is performed after the thinning process. The thinning was optimized for complete pore opening in ATO and potential-current behavior is interpreted in terms of ionic current-electronic current switching.

  13. Study of niobium corrosion in alkaline medium

    International Nuclear Information System (INIS)

    Almeida, S.H. de.

    1987-01-01

    A comparative study of niobium electrochemical behaviour in NaOH and KOH solution, with concentrations between 0,5 and 6,1M is presented. The studies were done through electrochemicals assays, consisting in the corrosion potential and anodic and cathodic polarization curves, complemented by loss of mass experiments. The niobium anodic behaviour in alkaline medium is characterized by passivation occurrence, with a stable film formation. The Na oH solution in alkaline medium are more corrosible to niobium than the KOH solution. The loss of mass assays showed that the corrosion velocit is more dependente of hydroxide concentration in KOH medium than the NaOH medium. (C.G.C.) [pt

  14. Formation and oxidation resistance of NbSi2 coatings on niobium by pack cementation

    International Nuclear Information System (INIS)

    Li Ming; Song Lixin; Le Jun; Zhang Xiaowei; Pei Baogen; Hu Xingfang

    2005-01-01

    NbSi 2 coatings were formed on niobium by halide-activated pack cementation process. The as-coated niobium samples were oxidized in air up to 1723 K by thermogravimetry method. The surface and cross-sectional morphology, phase composition and element distribution of the NbSi 2 coatings before and after oxidation were characterized by SEM, XRD and EPMA. The results show that the as-formed coatings consist of single phase of hexagonal NbSi 2 and the oxidation resistance of pure niobium can be greatly improved by pack siliconizing. (orig.)

  15. Niobium–niobium oxide multilayered coatings for corrosion protection of proton-irradiated liquid water targets for ["1"8F] production

    International Nuclear Information System (INIS)

    Skliarova, Hanna; Renzelli, Marco; Azzolini, Oscar; Felicis, Daniele de; Bemporad, Edoardo; Johnson, Richard R.; Palmieri, Vincenzo

    2015-01-01

    Chemically inert coatings on Havar"® entrance foils of the targets for ["1"8F] production via proton irradiation of enriched water at pressurized conditions are needed to decrease the amount of ionic contaminants released from Havar"®. During current investigation, magnetron sputtered niobium and niobium oxide were chosen as the candidates for protective coatings because of their superior chemical resistance. Aluminated quartz substrates allowed us to verify the protection efficiency of the desirable coatings as diffusion barriers. Two modeling corrosion tests based on the extreme susceptibility of aluminum to liquid gallium and acid corrosion were applied. As far as niobium coatings obtained by magnetron sputtering are columnar, the grain boundaries provide a fast diffusion path for active species of corrosive media to penetrate and to corrode the substrate. Amorphous niobium oxide films obtained by reactive magnetron sputtering showed superior barrier properties according to the corrosion tests performed. In order to prevent degrading of brittle niobium oxide at high pressures, multilayers combining high ductility of niobium with superior diffusion barrier efficiency of niobium oxide were proposed. The intercalation of niobium oxide interlayers was proved to interrupt the columnar grain growth of niobium during sputtering, resulting in improved diffusion barrier efficiency of obtained multilayers. The thin layer multilayer coating architecture with 70 nm bi-layer thickness was found preferential because of higher thermal stability. - Highlights: • Diffusion barrier efficiency of niobium, niobium oxide and their multilayers was studied. • The intercalation of niobium oxide layers interrupted the columnar grain growth of niobium. • The bilayer architectures influenced the stability of the multilayer coatings. • The thin layer multilayer coating with 70 nm double-layer was found superior.

  16. Niobium–niobium oxide multilayered coatings for corrosion protection of proton-irradiated liquid water targets for [{sup 18}F] production

    Energy Technology Data Exchange (ETDEWEB)

    Skliarova, Hanna, E-mail: Hanna.Skliarova@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell' Università, 2, 35020 Legnaro, Padua (Italy); University of Ferrara, Ferrara (Italy); Renzelli, Marco, E-mail: marco.renzelli@uniroma3.it [University of Rome “Roma TRE”, Via della Vasca Navale, 79, 00146 Rome (Italy); Azzolini, Oscar, E-mail: Oscar.Azzolini@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell' Università, 2, 35020 Legnaro, Padua (Italy); Felicis, Daniele de, E-mail: daniele.defelicis@uniroma3.it [University of Rome “Roma TRE”, Via della Vasca Navale, 79, 00146 Rome (Italy); Bemporad, Edoardo, E-mail: edoardo.bemporad@uniroma3.it [University of Rome “Roma TRE”, Via della Vasca Navale, 79, 00146 Rome (Italy); Johnson, Richard R., E-mail: richard.johnson@teambest.com [BEST Cyclotron Systems Inc., 8765 Ash Street Unit 7, Vancouver BC V6P 6T3 (Canada); Palmieri, Vincenzo, E-mail: Vincenzo.Palmieri@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell' Università, 2, 35020 Legnaro, Padua (Italy); University of Padua, Padua (Italy)

    2015-09-30

    Chemically inert coatings on Havar{sup ®} entrance foils of the targets for [{sup 18}F] production via proton irradiation of enriched water at pressurized conditions are needed to decrease the amount of ionic contaminants released from Havar{sup ®}. During current investigation, magnetron sputtered niobium and niobium oxide were chosen as the candidates for protective coatings because of their superior chemical resistance. Aluminated quartz substrates allowed us to verify the protection efficiency of the desirable coatings as diffusion barriers. Two modeling corrosion tests based on the extreme susceptibility of aluminum to liquid gallium and acid corrosion were applied. As far as niobium coatings obtained by magnetron sputtering are columnar, the grain boundaries provide a fast diffusion path for active species of corrosive media to penetrate and to corrode the substrate. Amorphous niobium oxide films obtained by reactive magnetron sputtering showed superior barrier properties according to the corrosion tests performed. In order to prevent degrading of brittle niobium oxide at high pressures, multilayers combining high ductility of niobium with superior diffusion barrier efficiency of niobium oxide were proposed. The intercalation of niobium oxide interlayers was proved to interrupt the columnar grain growth of niobium during sputtering, resulting in improved diffusion barrier efficiency of obtained multilayers. The thin layer multilayer coating architecture with 70 nm bi-layer thickness was found preferential because of higher thermal stability. - Highlights: • Diffusion barrier efficiency of niobium, niobium oxide and their multilayers was studied. • The intercalation of niobium oxide layers interrupted the columnar grain growth of niobium. • The bilayer architectures influenced the stability of the multilayer coatings. • The thin layer multilayer coating with 70 nm double-layer was found superior.

  17. Catalysts Promoted with Niobium Oxide for Air Pollution Abatement

    Directory of Open Access Journals (Sweden)

    Wendi Xiang

    2017-05-01

    Full Text Available Pt-containing catalysts are currently used commercially to catalyze the conversion of carbon monoxide (CO and hydrocarbon (HC pollutants from stationary chemical and petroleum plants. It is well known that Pt-containing catalysts are expensive and have limited availability. The goal of this research is to find alternative and less expensive catalysts to replace Pt for these applications. This study found that niobium oxide (Nb2O5, as a carrier or support for certain transition metal oxides, promotes oxidation activity while maintaining stability, making them candidates as alternatives to Pt. The present work reports that the orthorhombic structure of niobium oxide (formed at 800 °C in air promotes Co3O4 toward the oxidation of both CO and propane, which are common pollutants in volatile organic compound (VOC applications. This was a surprising result since this structure of Nb2O5 has a very low surface area (about 2 m2/g relative to the more traditional Al2O3 support, with a surface area of 150 m2/g. The results reported demonstrate that 1% Co3O4/Nb2O5 has comparable fresh and aged catalytic activity to 1% Pt/γ-Al2O3 and 1% Pt/Nb2O5. Furthermore, 6% Co3O4/Nb2O5 outperforms 1% Pt/Al2O3 in both catalytic activity and thermal stability. These results suggest a strong interaction between niobium oxide and the active component—cobalt oxide—likely by inducing an oxygen defect structure with oxygen vacancies leading to enhanced activity toward the oxidation of CO and propane.

  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. Dislocations and related defects in niobium oxide structures

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, J S; Hutchinson, J L; Lincoln, F J [Oxford Univ. (UK). Inorganic Chemistry Lab.

    1977-01-07

    Lattice images of the niobium oxides, structures based on the linkage of octahedral groups in continuous networks, occasionally contain features recognizable as dislocations. Since lattice imaging enables the microstructure to be resolved in greater detail, at the level of local structural organization, it is possible to determine the configuration, and also to infer the chemical composition, of dislocated areas. By treating the niobium oxide 'block' structures as superstructures of the ReO/sub 3/ (DO/sub 9/) type, the topology of dislocations can be expressed by relations between the insertion (or deletion) of one or more half-planes of cations, or of oxygen atoms only, changes in the number of crystallographic shear plane interfaces between blocks or columns, changes in (idealized) dimensions and any requisite distortion in the third dimension. Mapping the structure around a dislocation, from the lattice image, is directly equivalent to plotting the Burgers' circuit. In this way, the precise nature of a dislocating perturbation and its implications for the local chemical composition of the crystal can be directly identified. The method is exemplified by analysis of dislocations and of related extended defects of several types, associated with twinning phenomena, semicoherent intergrowth between different ReO/sub 3/-type superstructures and arrays building up a low angle boundary. The essential features of the analysis are not restricted to structures of the niobium oxide type, but can be extended to other types of polyhedron networks.

  20. Niobium electrodeposition from molten fluorides

    International Nuclear Information System (INIS)

    Sartori, A.F.

    1987-01-01

    Niobium electrodeposition from molten alkali fluorides has been studied aiming the application of this technic to the processes of electrorefining and galvanotechnic of this metal. The effects of current density, temperature, niobium concentration in the bath, electrolysis time, substrate nature, ratio between anodic and cathodic areas, electrodes separation and the purity of anodes were investigated in relation to the cathodic current efficiency, electrorefining, electroplating and properties of the deposit and the electrolytic solution. The work also gives the results of the conctruction and operation of a pilot plant for refractory metals electrodeposition and shows the electrorefining and electroplating compared to those obtained at the laboratory scale. (author) [pt

  1. Anodic oxidation of benzoquinone using diamond anode.

    Science.gov (United States)

    Panizza, Marco

    2014-01-01

    The anodic degradation of 1,4-benzoquinone (BQ), one of the most toxic xenobiotic, was investigated by electrochemical oxidation at boron-doped diamond anode. The electrolyses have been performed in a single-compartment flow cell in galvanostatic conditions. The influence of applied current (0.5-2 A), BQ concentration (1-2 g dm(-3)), temperature (20-45 °C) and flow rate (100-300 dm(3) h(-1)) has been studied. BQ decay kinetic, the evolution of its oxidation intermediates and the mineralization of the aqueous solutions were monitored during the electrolysis by high-performance liquid chromatograph (HPLC) and chemical oxygen demand (COD) measurements. The results obtained show that the use of diamond anode leads to total mineralization of BQ in any experimental conditions due to the production of oxidant hydroxyl radicals electrogenerated from water discharge. The decay kinetics of BQ removal follows a pseudo-first-order reaction, and the rate constant increases with rising current density. The COD removal rate was favoured by increasing of applied current, recirculating flow rate and it is almost unaffected by solution temperature.

  2. Niobium, catalyst repair kit

    International Nuclear Information System (INIS)

    Tanabe, K.

    1991-01-01

    This paper reports that niobium oxides, when small amounts are added to known catalysts, enhance catalytic activity and selectivity and prolong catalyst life. Moreover, niobium oxides exhibit a pronounced effect as supports of metal or metal oxide catalysts. Recently we found that the surface acidity of hydrated niobium pentoxide, niobic acid (Nb 2 O 5 · nH 2 O), corresponds to the acidity of 70% sulfuric acid and exhibits high catalytic activity, selectivity, and stability for acid-catalyzed reactions in which water molecules participate. Although there are few differences in electronegativity and ionic radius between niobium and its neighbors in the periodic table, it is interesting that the promoter effect, support effect, and acidic nature of niobium compounds are quite different from those of compounds of the surrounding elements. Here we review what's known of niobium compounds from the viewpoint of their pronounced catalytic behavior

  3. Thermodynamic analysis of reduction reactions of niobium oxides

    International Nuclear Information System (INIS)

    Takano, C.

    1981-01-01

    Reduction processes of niobium oxides by hydrogen, carbon and aluminium are analysed thermodinamically. It is shown that reduction by hydrogen is not technically feasible. High purity of raw materials is required. In the carbothermic process impurities which react to form high stability carbides should be avoided. (Author) [pt

  4. Vitreous-enamel protective coatings for niobium and niobium alloys

    International Nuclear Information System (INIS)

    Kobyakov, V.P.; Sedmale, G.P.; Tsimdin', R.A.; Sedmalis, U.Ya.; Tsetskhladze, D.L.; Gosudarstvennyj Komitet po Ispol'zovaniyu Atomnoj Ehnergii SSSR, Sukhumi. Fiziko-Tekhnicheskij Inst.)

    1988-01-01

    Vitreous-enanel coatings to protect niobium and niobium alloys, used in oxidizing media at temperatures up to 1000degC, from embrittlement are developed on the basis of Al 2 O 3 -SiO 2 -P 2 O 5 -Ba vetrificating system. By means of microhardness measurement and IR-spectroscopy it is found, that at coating formation the intermediate ∼20 mkm width zone which prevents oxygen penetration in niobium is formed. Test of niobium pieces with ERS-1000 vitreous-enamel coating have shown, that coating provides niobium reliable protection in the air at 800degC and atmospheric pressure

  5. 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.

  6. Multi-component titanium–copper–cobalt- and niobium nanostructured oxides as catalysts for ethyl acetate oxidation

    Czech Academy of Sciences Publication Activity Database

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

    2015-01-01

    Roč. 116, č. 2 (2015), s. 397-408 ISSN 1878-5190 Institutional support: RVO:61388980 Keywords : Copper and cobalt oxides * Effect of support * Ethyl acetate combustion * Multicomponent oxides * Titania doped with niobium Subject RIV: CA - Inorganic Chemistry Impact factor: 1.265, year: 2015

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

    International Nuclear Information System (INIS)

    Dabirian, Ali; Kuzminykh, Yury; Wagner, Estelle; Benvenuti, Giacomo; Rushworth, Simon; Hoffmann, Patrik

    2014-01-01

    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 2 (OEt) 10 does not fulfil this requirement since it partially dissociates upon heating. Dimethylamino functionalization of an ethoxy ligand of Nb(OEt) 5 acts as an octahedral field completing entity and leads to Nb(OEt) 4 (dmae). We show that Nb(OEt) 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 −1 to values larger than 400 nm·h −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) 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) 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 atomic layer deposition (ALD) process

  8. Electrochemical oxidation of biological pretreated and membrane separated landfill leachate concentrates on boron doped diamond anode

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Bo, E-mail: 357436235@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Yu, Zhiming, E-mail: zhiming@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Wei, Qiuping, E-mail: qiupwei@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Long, HangYu, E-mail: 55686385@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Xie, Youneng, E-mail: 1187272844@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Wang, Yijia, E-mail: 503630433@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)

    2016-07-30

    Highlights: • High quality boron-doped diamond film electrodes were synthesized on Nb substrates. • Electrochemical oxidation on boron-doped diamond anode is an effective method for treating landfill leachate concentrates. • Optimal operating conditions for electrochemical oxidation of landfill leachate concentrates is determined. • 87.5% COD removal and 74.06% NH{sub 3}−N removal were achieved after 6 h treatment. - Abstract: In the present study, the high quality boron-doped diamond (BDD) electrodes with excellent electrochemical properties were deposited on niobium (Nb) substrates by hot filament chemical vapor deposition (HFCVD) method. The electrochemical oxidation of landfill leachate concentrates from disc tube reverse osmosis (DTRO) process over a BDD anode was investigated. The effects of varying operating parameters, such as current density, initial pH, flow velocity and cathode material on degradation efficiency were also evaluated following changes in chemical oxygen demand (COD) and ammonium nitrogen (NH{sub 3}−N). The instantaneous current efficiency (ICE) was used to appraise different operating conditions. As a result, the best conditions obtained were as follows, current density 50 mA cm{sup −2}, pH 5.16, flow velocity 6 L h{sup −1}. Under these conditions, 87.5% COD and 74.06% NH{sub 3}−N removal were achieved after 6 h treatment, with specific energy consumption of 223.2 kWh m{sup −3}. In short, these results indicated that the electrochemical oxidation with BDD/Nb anode is an effective method for the treatment of landfill leachate concentrates.

  9. Niobium nitride Josephson tunnel junctions with magnesium oxide barriers

    International Nuclear Information System (INIS)

    Shoji, A.; Aoyagi, M.; Kosaka, S.; Shinoki, F.; Hayakawa, H.

    1985-01-01

    Niobium nitride-niobium nitride Josephson tunnel junctions have been fabricated using amorphous magnesium oxide (a-MgO) films as barriers. These junctions have excellent tunneling characteristics. For example, a large gap voltage (V/sub g/ = 5.1 mV), a large product of the maximum critical current and the normal tunneling resistance (I/sub c/R/sub n/ = 3.25 mV), and a small subgap leakage current (V/sub m/ = 45 mV, measured at 3 mV) have been obtained for a NbN/a-MgO/NbN junction. The critical current of this junction remains finite up to 14.5 K

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

    International Nuclear Information System (INIS)

    Lee, W; Nielsch, K; Goesele, U

    2007-01-01

    The self-ordering behavior of anodic aluminum oxide (AAO) has been investigated for anodization of aluminum in malonic acid (H 4 C 3 O 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 ∼100 mA cm -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 int ) for a given anodization potential (U) during malonic acid anodization

  11. Color change mechanism of niobium oxide thin film with incidental light angle and applied voltage

    Energy Technology Data Exchange (ETDEWEB)

    Komatsu, Isao [Course of Information Science and Technology, Graduate School of Science and Technology, Tokai University (Japan); Aoki, Hayata [Course of Electro Photo Optics, Graduate School of Engineering, Tokai University (Japan); Ebisawa, Mizue [Tokyo Metropolitan Industrial Technology Research Institute (Japan); Kuroda, Akihiro [Department of Optical and Imaging Science & Technology, Faculty of Engineering, Tokai University (Japan); Kuroda Consulting Incorporated (Japan); Kuroda, Koichi [Kuroda Consulting Incorporated (Japan); Maeda, Shuichi [Course of Information Science and Technology, Graduate School of Science and Technology, Tokai University (Japan); Course of Electro Photo Optics, Graduate School of Engineering, Tokai University (Japan); Department of Optical and Imaging Science & Technology, Faculty of Engineering, Tokai University (Japan)

    2016-03-31

    Niobium oxide thin layers made by the anodization process showed coloration owing to thin film interference. The reflection spectra depended on both the applied voltage and incident light angle. Large color differences were observed at incident light angles between 5° and 70°, when the applied voltage was over 60 V. In this study, we explored the cause of these results using ellipsometry and goniophotometry to understand the transition of optical constants and the reflection spectra with applied voltage. Finally, we concluded that the coloration of the reflection spectra, which included only a first-order interference peak, exhibits a smaller change because the first order interference peak has a wider half value width than higher order interference peaks. - Highlights: • We investigated color change of Nb{sub 2}O{sub 5} oxide thin layers with incidental light angle. • The reflection spectra shift to lower wavelength region with increasing incident light angle. • The reflection spectra shift to higher wavelength region with increasing applied voltage. • First-order interference has wider half value width, and exhibits small color change.

  12. Spectroellipsometric detection of silicon substrate damage caused by radiofrequency sputtering of niobium oxide

    Science.gov (United States)

    Lohner, Tivadar; Serényi, Miklós; Szilágyi, Edit; Zolnai, Zsolt; Czigány, Zsolt; Khánh, Nguyen Quoc; Petrik, Péter; Fried, Miklós

    2017-11-01

    Substrate surface damage induced by deposition of metal atoms by radiofrequency (rf) sputtering or ion beam sputtering onto single-crystalline silicon (c-Si) surface has been characterized earlier by electrical measurements. The question arises whether it is possible to characterize surface damage using spectroscopic ellipsometry (SE). In our experiments niobium oxide layers were deposited by rf sputtering on c-Si substrates in gas mixture of oxygen and argon. Multiple angle of incidence spectroscopic ellipsometry measurements were performed, a four-layer optical model (surface roughness layer, niobium oxide layer, native silicon oxide layer and ion implantation-amorphized silicon [i-a-Si] layer on a c-Si substrate) was created in order to evaluate the spectra. The evaluations yielded thicknesses of several nm for the i-a-Si layer. Better agreement could be achieved between the measured and the generated spectra by inserting a mixed layer (with components of c-Si and i-a-Si applying the effective medium approximation) between the silicon oxide layer and the c-Si substrate. High depth resolution Rutherford backscattering (RBS) measurements were performed to investigate the interface disorder between the deposited niobium oxide layer and the c-Si substrate. Atomic resolution cross-sectional transmission electron microscopy investigation was applied to visualize the details of the damaged subsurface region of the substrate.

  13. ORDERED POROUS ANODIC ALUMINUM OXIDE FILMS MADE BY TWO-STEP ANODIZATION

    OpenAIRE

    HANSONG XUE; HUAJI LI; YU YI; HUIFANG HU

    2007-01-01

    Porous Anodic Aluminum Oxide (AAO) films were prepared by two-step anodizing in sulfuric and oxalic acid solutions and observed by transmission electron microscope (TEM) and X-ray diffraction. The results show that the form of AAO film is affected by the varieties and concentrations of electrolyte, anodizing voltage, and the anodizing time; the formation and evolution processes of the AAO film are relative with the anodizing voltage severely, and the appropriate voltage is helpful to the orde...

  14. Chemical transport of niobium(V) oxide and of lithium niobate with sulphur

    International Nuclear Information System (INIS)

    Schaefer, H.

    1988-01-01

    Niobium(V) oxide is transported by means of sulphur (calculated for 10 bar at 1223 K) from 1273 → 1173 K. The same applies for lithium niobate. Similar experiments of lithium oxide lead to turbidity of the quartz ampoule. (author)

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

    International Nuclear Information System (INIS)

    Kraft, Alexander; Stadelmann, Manuela; Blaschke, Manfred

    2003-01-01

    Boron-doped diamond anodes allow to directly produce OH· 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

  16. Synthesis and characterization of new oxides and oxynitrides of niobium; Synthese und Charakterisierung neuer Oxide und Oxidnitride des Niobs

    Energy Technology Data Exchange (ETDEWEB)

    Orthmann, Steven

    2017-11-02

    By different synthesis routes the first oxide nitrides in the series scandium-niobium-oxygen-nitrogen could be synthesized and characterized. ScNb{sub 4}O{sub 7}N{sub 3}, which crystallizes in the rutile-type structure, exhibit a band gap of 2.62 eV after a short oxidation. Furthermore anion-deficit NbSc{sub 2}(O,N,□){sub 6} with fluorite-type structure could be synthesized. UV-Vis measurements point to a band gap of 3.36 eV after a short oxidation of the product. In the series zirconium-niobium-oxygen-nitrogen new oxides and oxide nitrides could be synthesized. By replacing zirconium with hafnium isotopical compounds with comparable composition could be obtained. The crystal structure of these new compounds is discussed respecting magnetism and the results of electron microscopy and neutron diffraction. By partially substitution of niobium with magnesium or zinc three additional oxide nitrides with the compositions Mg{sub 2}Nb{sub 4}O{sub 2}N{sub 5}, Zn{sub 2}NbO{sub 0,3}N{sub 2,8}, and ZnNb{sub 3}O{sub 0,1}N{sub 4,5}, showing a tetragonal Nb{sub 4}N{sub 5}-type structure, could be synthesized.

  17. Study of niobium oxidation by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Durand, C.

    1985-01-01

    The chemical composition of thin oxide layers, grown on clean niobium, in low oxygen pressure, was studied by a surface analysis method: X-ray Photoelectron Spectroscopy. The purpose of this study was to find the best conditions for the building of Nb/Nb oxide/Pb Josephson junctions, and particularly to minimise the interface thickness during the formation of the insulator film (Nb 2 O 5 ) on the metal (Nb). This interface is essentially formed by the monoxide (NbO) and dioxide (NbO 2 ). Nb 3d XPS core level peak positions and area ratios (obtained by the signal decomposition) of the components of the total peak, were used to determine the presence of the different oxidation states II, IV and V, their relative abundance, oxide thicknesses and their depth distribution. All this information was extracted by a special numerical procedure [fr

  18. Coulometric titration of niobium in 1F sulfuric acid

    International Nuclear Information System (INIS)

    Pannu, S.S.

    1975-01-01

    A coulometric titration at constant current has been devised for Nb in 1F sulfuric acid. The titration was based on the oxidation of Nb(III) to Nb(V) by Fe(III) electrogenerated at a graphite anode. Both potentiometric and amperometric end points were used. The Nb(V) was prior reduced at a mercury cathode by exhaustive electrolysis at a current density of 15 ma/mc 2 for at least 10 hr. Ta,V,Ti and a working platinum anode interfered, but the separation of the potentials of Nb(V)/Nb(III) and Ti(IV)/Ti(III) permitted the titration of first Nb and then Ti. The average error for the titration of 0.30 to 13.00 mg of niobium in 100 ml of 1F sulfuric acid was + 0.57%. (author)

  19. 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.

  20. Localized and collectivized behaviour of d-electrons in complicated titanium, vanadium and niobium oxides

    International Nuclear Information System (INIS)

    Bazuev, G.V.; Shvejkin, G.P.

    1980-01-01

    On the basis of investigation of electric and magnetic properties of oxide compounds of transition metals made are the conclusions on the degree of localization and delocalization of d-electrons in them. Generalized are the investigation results of complicated titanium, vanadium, niobium oxide compounds in low degrees of oxidation with rare earth and alkaline earth elements belonging to the two structural types: perovskite and pyrochlore. Presented are the results of investigations of perovskite-like solid solutions and of variable-content phases containing cations of transition metals in two different oxidation degrees: oxide niobium bronzes of two-valent europium and titanium bronzes of rare-earth elements, as well as Lnsub(1-x)Msub(x)Vsub(1-x)sup(3+)Vsub(x)sup(4+)Osub(3), where M is an alkaline earth element

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

    OpenAIRE

    Gerrard Eddy Jai Poinern; Derek Fawcett; Nurshahidah Ali

    2011-01-01

    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 ...

  2. Oxidation behavior of niobium aluminide intermetallics protected by aluminide and silicide diffusion coatings

    International Nuclear Information System (INIS)

    Li, Y.; Soboyejo, W.; Rapp, R.A.

    1999-01-01

    The isothermal and cyclic oxidation behavior of a new class of damage-tolerant niobium aluminide (Nb 3 Al-xTi-yCr) intermetallics is studied between 650 C and 850 C. Protective diffusion coatings were deposited by pack cementation to achieve the siliciding or aluminizing of substrates with or without intervening Mo or Ni layers, respectively. The compositions and microstructures of the resulting coatings and oxidized surfaces were characterized. The isothermal and cyclic oxidation kinetics indicate that uncoated Nb-40Ti-15Al-based intermetallics may be used up to ∼750 C. Alloying with Cr improves the isothermal oxidation resistance between 650 C and 850 C. The most significant improvement in oxidation resistance is achieved by the aluminization of electroplated Ni interlayers. The results suggest that the high-temperature limit of niobium aluminide-based alloys may be increased to 800 C to 850 C by aluminide-based diffusion coatings on ductile Ni interlayers. Indentation fracture experiments also indicate that the ductile nickel interlayers are resistant to crack propagation in multilayered aluminide-based coatings

  3. Effect of post annealing treatment on electrochromic properties of spray deposited niobium oxide thin films

    International Nuclear Information System (INIS)

    Mujawar, S.H.; Inamdar, A.I.; Betty, C.A.; Ganesan, V.; Patil, P.S.

    2007-01-01

    Niobium oxide thin films were deposited on the glass and fluorine doped tin oxide (FTO) coated glass substrates using simple and inexpensive spray pyrolysis technique. During deposition of the films various process parameters like nozzle to substrate distance, spray rate, concentration of sprayed solution were optimized to obtain well adherent and transparent films. The films prepared were further annealed and effect of post annealing on the structural, morphological, optical and electrochromic properties was studied. Structural and morphological characterizations of the films were carried out using scanning electron microscopy, atomic force microscopy and X-ray diffraction techniques. Electrochemical properties of the niobium oxide thin films were studied by using cyclic-voltammetry, chronoamperometry and chronocoulometry

  4. 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.

  5. 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

  6. Anodic oxidation of InP in pure water

    International Nuclear Information System (INIS)

    Robach, Y.; Joseph, J.; Bergignat, E.; Hollinger, G.

    1989-01-01

    It is shown that thin InP native oxide films can be grown by anodization of InP in pure water. An interfacial phosphorus-rich In(PO 3 ) 3 -like condensed phosphate is obtained this way. This condensed phosphate has good passivating properties and can be used in electronic device technology. The chemical composition of these native oxides was found similar to that of an anodic oxide grown in an anodization in glycol and water (AGW) electrolyte. From the similarity between the two depth profiles observed in pure water and AGW electrolyte, they can conclude that dissolution phenomena do not seem to play a major role. The oxide growth seems to be controlled by the drift of ionic species under the electric field

  7. Surface Characterization of Impurities in Superconducting Niobium for Radio Frequency (RF) Cavities used in Particle Accelerators

    Science.gov (United States)

    Maheshwari, Prateek

    absorption/desorption of hydrogen and that hydrogen does not diffuse in the oxide. Subsequent ion implantation of hydrogen in an anodized niobium sample thus provided a quantification factor of hydrogen in niobium oxide, which was used to obtain an estimate of the hydrogen concentration in niobium. This estimate was found to be 40% atomic H in a non heat treated niobium sample. Such high levels of hydrogen observed in Nb before heat treatment ensures that is the main contributor to cavity degradation. TEM analysis was performed to study the effect of heat treatment on the surface oxide thickness of niobium. Results showed a continuous oxide layer with a sharp metal-oxide interface. No significant changes in the oxide thickness were seen after heat treatment. Time of Flight (TOF)-SIMS imaging was used to characterize the grain boundaries of large grain niobium bicrystals, since it was believed that impurity segregation at the grain boundaries of Nb might deteriorate cavity performance. Images showed segregation of carbon at the grain boundaries after 800°C heat treatment of the samples, while no segregation of hydrogen and oxygen were seen for both non heat treated and heat treated samples. An important aspect of this study was the record-performance improvement of the 1400°C heat treated cavity, which showed a 200% increase in the cavity efficiency. SIMS analysis of the surface of this sample showed high levels of titanium, down to 1im depth, and it is speculated that this Ti might be responsible for high performance of the cavity by affecting the distribution of impurities within the penetration depth.

  8. On the anodic aluminium oxide refractive index of nanoporous templates

    International Nuclear Information System (INIS)

    Hierro-Rodriguez, A; Rocha-Rodrigues, P; Araujo, J P; Valdés-Bango, F; Alameda, J M; Teixeira, J M; Jorge, P A S; Santos, J L; Guerreiro, A

    2015-01-01

    In the present study, we have determined the intrinsic refractive index of anodic aluminium oxide, which is originated by the formation of nanoporous alumina templates. Different templates have been fabricated by the conventional two-step anodization procedure in oxalic acid. Their porosities were modified by chemical wet etching allowing the tuning of their effective refractive indexes (air-filled nanopores  +  anodic aluminium oxide). By standard spectroscopic light transmission measurements, the effective refractive index for each different template was extracted in the VIS–NIR region. The determination of the intrinsic anodic aluminium oxide refractive index was performed by using the Maxwell–Garnett homogenization theory. The results are coincident for all the fabricated samples. The obtained refractive index (∼1.55) is quite lower (∼22%) than the commonly used Al 2 O 3 handbook value (∼1.75), showing that the amorphous nature of the anodic oxide structure strongly conditions its optical properties. This difference is critical for the correct design and modeling of optical plasmonic metamaterials based on anodic aluminium oxide nanoporous templates. (paper)

  9. The oxidation kinetics for sublimates formed during niobium electron-beam remelting

    International Nuclear Information System (INIS)

    Chumarev, V.M.; Gulyaeva, R.I.; Mar'evich, V.P.; Upolovnikova, A.G.; Udoeva, L.Yu.

    2003-01-01

    The oxidation of sublimates of Nb-Al electron beam remelting is investigated under conditions of isothermal and continuous heating in the air. It is stated that basic oxidation products are niobium and aluminium oxides, as well as aluminium niobates of variable composition of Al 2 O 3 · mNb 2 O 5 . The more aluminium enriched sublimates possess an increased resistance to oxidation. Formed in sublimates NbAl 3 intermetallic compound features the highest heat resistance. Oxidation parameters are determined by the method of nonisothermic kinetics. It is noted that the running processes exhibit a multistage nature and are limited by internal diffusion [ru

  10. Conducting metal oxide and metal nitride nanoparticles

    Science.gov (United States)

    DiSalvo, Jr., Francis J.; Subban, Chinmayee V.

    2017-12-26

    Conducting metal oxide and nitride nanoparticles that can be used in fuel cell applications. The metal oxide nanoparticles are comprised of for example, titanium, niobium, tantalum, tungsten and combinations thereof. The metal nitride nanoparticles are comprised of, for example, titanium, niobium, tantalum, tungsten, zirconium, and combinations thereof. The nanoparticles can be sintered to provide conducting porous agglomerates of the nanoparticles which can be used as a catalyst support in fuel cell applications. Further, platinum nanoparticles, for example, can be deposited on the agglomerates to provide a material that can be used as both an anode and a cathode catalyst support in a fuel cell.

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

    Science.gov (United States)

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

    2015-07-14

    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).

  12. Effect of hydrogen on stresses in anodic oxide film on titanium

    International Nuclear Information System (INIS)

    Kim, Joong-Do; Pyun, Su-Il; Seo, Masahiro

    2003-01-01

    Stresses in anodic oxide film on titanium thin film/glass electrode in pH 8.4 borate solution were investigated by a bending beam method. The increases in compressive stress observed with cathodic potential sweeps after formation of anodic oxide film were attributed to the volume expansion due to the compositional change of anodic oxide film from TiO 2 to TiO 2-x (OH) x . The instantaneous responses of changes in stress, Δσ, in the anodic oxide film to potential steps demonstrated the reversible characteristic of the TiO 2-x (OH) x formation reaction. In contrast, the transient feature of Δσ for the titanium without anodic oxide film represented the irreversible formation of TiH x at the metal/oxide interphase. The large difference in stress between with and without the oxide film, has suggested that most of stresses generated during the hydrogen absorption/desorption reside in the anodic oxide film. A linear relationship between changes in stress, Δ(Δσ) des , and electric charge, ΔQ des , during hydrogen desorption was found from the current and stress transients, manifesting that the stress changes were crucially determined by the amount of hydrogen desorbed from the oxide film. The increasing tendency of -Δ(Δσ) des with increasing number of potential steps and film formation potential were discussed in connection with the increase in desorption amount of hydrogen in the oxide film with increasing absorption/desorption cycles and oxide film thickness

  13. Formation of oxide layers on aluminum, niobium, and tantalum in molten alkali metal carbonates

    Science.gov (United States)

    Nikitina, E. V.; Kazakovtseva, N. A.

    2013-08-01

    The electrochemical synthesis of niobium, tantalum, and aluminum oxide nanolayers is studied in the melt of lithium, sodium, and potassium carbonates with various additives to a salt phase in an oxidizing atmosphere at a temperature of 773 and 873 K. A scheme is proposed for high-temperature anion local activation of the process.

  14. Spectrographic determination of niobium in uranium - niobium alloys

    International Nuclear Information System (INIS)

    Charbel, M.Y.; Lordello, A.R.

    1984-01-01

    A method for the spectrographic determination of niobium in uranium-niobium alloys in the concentration range 1-10% has been developed. The metallic sample is converted to oxide by calcination in a muffle furnace at 800 0 C for two hours. The standards are prepared synthetically by dry-mixing. One part of the sample or standard is added to nineteen parts of graphite powder and the mixture is excited in a DC arc. Hafnium has been used as internal standard. The precision of the method is + - 4.8%. (Author) [pt

  15. High performance fuel electrode for a solid oxide electrochemical cell

    DEFF Research Database (Denmark)

    2013-01-01

    perovskite oxides selected from the group consisting of niobium-doped strontium titanate, vanadium-doped strontium titanate, tantalum-doped strontium titanate and mixtures thereof, thereby obtaining a porous anode backbone, (b) sintering the coated electrolyte at a high temperature, such as 1200 DEG C...

  16. 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

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

    Directory of Open Access Journals (Sweden)

    G. Ciovati

    2007-06-01

    Full Text Available 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 Q_{0}(B_{p} as the peak surface magnetic field (B_{p} 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 and 2.0 K on a single-cell cavity made of high-purity large (with area of the order of few cm^{2} 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 reappear 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 and secondary ion mass spectroscopy. 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 postpurification treatment at 1250°C. A statistic of the position of the “hot spots” on the

  18. Some organoperoxo complexes of antimony, niobium and tantalum and their oxidation properties

    International Nuclear Information System (INIS)

    Tarafder, M.T.H.

    1999-05-01

    Several novel organoperoxo complexes of Nb(V), Ta(V) and Sb(V) have been synthesized and characterized. The complexes have the compositions [M(O 2 ) 2 L Cl] and [M(O 2 ) 2 L'] [L = monodentate and bidentate, neutral ligand; L' = bidentate, uninegative ligand]. These complexes are very reactive to both organic and inorganic substrates. Niobium and tantalum complexes were found to oxidize phosphines and arsines to their oxides. These also oxidize olefins to epoxides under stoichiometric conditions while under catalytic conditions, ring opening of the epoxides occur producing α-hydroxyketone when the substrate is trans-stilbene. The antimony complexes are decidedly inert towards oxidation. (author)

  19. Removal of organic contaminants from secondary effluent by anodic oxidation with a boron-doped diamond anode as tertiary treatment

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Segura, Sergi, E-mail: sergigarcia@ub.edu [Advanced Water Management Centre, The University of Queensland, Level 4, Gehrmann Bld. (60), St Lucia, QLD 072 (Australia); Laboratori d’Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona (Spain); Keller, Jürg [Advanced Water Management Centre, The University of Queensland, Level 4, Gehrmann Bld. (60), St Lucia, QLD 072 (Australia); Brillas, Enric [Laboratori d’Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona (Spain); Radjenovic, Jelena, E-mail: j.radjenovic@awmc.uq.edu.au [Advanced Water Management Centre, The University of Queensland, Level 4, Gehrmann Bld. (60), St Lucia, QLD 072 (Australia)

    2015-02-11

    Graphical abstract: - Highlights: • Mineralization of secondary effluent by anodic oxidation with BDD anode. • Complete removal of 29 pharmaceuticals and pesticides at trace level concentrations. • Organochlorine and organobromine byproducts were formed at low μM concentrations. • Chlorine species evolution assessed to evaluate the anodic oxidation applicability. - Abstract: Electrochemical advanced oxidation processes (EAOPs) have been widely investigated as promising technologies to remove trace organic contaminants from water, but have rarely been used for the treatment of real waste streams. Anodic oxidation with a boron-doped diamond (BDD) anode was applied for the treatment of secondary effluent from a municipal sewage treatment plant containing 29 target pharmaceuticals and pesticides. The effectiveness of the treatment was assessed from the contaminants decay, dissolved organic carbon and chemical oxygen demand removal. The effect of applied current and pH was evaluated. Almost complete mineralization of effluent organic matter and trace contaminants can be obtained by this EAOP primarily due to the action of hydroxyl radicals formed at the BDD surface. The oxidation of Cl{sup −} ions present in the wastewater at the BDD anode gave rise to active chlorine species (Cl{sub 2}/HClO/ClO{sup −}), which are competitive oxidizing agents yielding chloramines and organohalogen byproducts, quantified as adsorbable organic halogen. However, further anodic oxidation of HClO/ClO{sup −} species led to the production of ClO{sub 3}{sup −} and ClO{sub 4}{sup −} ions. The formation of these species hampers the application as a single-stage tertiary treatment, but posterior cathodic reduction of chlorate and perchlorate species may reduce the risks associated to their presence in the environment.

  20. Chemical interaction in resistors based on lead ruthenite with additions of niobium(5) oxide compounds

    International Nuclear Information System (INIS)

    Lozinskij, N.S.; Shevtsova, N.A.; Gruba, A.I.; Volkov, V.I.

    1986-01-01

    The method of X-ray phase analysis was used to study chemical interaction in isothermal cross-section of Pb 2 RU 2 O 6 -Nb 2 O 5 , Rbsub(2)Rusub(2)Osub(6)-NbWOsub(5.5) and Rb 2 Ru 2 O 6 -Pb 2 Nb 2 O 7 systems at 850 deg C as well as in models of real ruthenium resistors. Chemical interaction is stated to take place in systems with niobium (5) oxide and NbWOsub(5.5). Niobium (5) and tungsten (6) displace ruthenium (4) from its compounds with formation of their lead salts. Similar chemical interactions between current-carrying phase of the resistor and modifiers representing niobium-containing take place in models of components of the studied systems take place in models of resistors

  1. Fabrication of Well-Ordered, Anodic Aluminum Oxide Membrane Using Hybrid Anodization.

    Science.gov (United States)

    Kim, Jungyoon; Ganorkar, Shraddha; Choi, Jinnil; Kim, Young-Hwan; Kim, Seong-II

    2017-01-01

    Anodic Aluminum Oxide (AAO) is one of the most favorable candidates for fabrication of nano-meshed membrane for various applications due to its controllable pore size and self-ordered structure. The mechanism of AAO membrane is a simple and has been studied by many research groups, however the actual fabrication of membrane has several difficulties owing to its sensitivity of ordering, long anodizing time and unclearness of the pore. In this work, we have demonstrated enhanced process of fabrication symmetric AAO membrane by using “hybrid anodizing” (Hyb-A) method which include mild anodization (MA) followed by hard anodization (HA). This Hyb-A process can give highly ordered membrane with more vivid pore than two-step anodizing process. HA was implemented on the Al plate which has been already textured by MA for more ordered structure and HA plays a key role for formation of more obvious pore in Hyb-A. Our experimental results indicate that Hyb-A with proper process sequence would be one of the fast and useful fabrication methods for the AAO membrane.

  2. 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.

  3. Process for the production of a tantalum and niobium bearing concentrate from a tantalum and niobium bearing ferro-alloy

    International Nuclear Information System (INIS)

    Deweck, J.; Van, H.

    1980-01-01

    In a process for the production of a tantalum and niobium bearing concentrate from a tantalum and niobium bearing ferro-alloy containing tantalum and niobium as carbide, by treating the ferro-alloy in molten state with a controlled amount of an oxidizing agent in order to slag at least most of the tantalum and at least part of the niobium and by separting the so obtained slag phase from the metal phase, the improvement which comprises using air, oxygen enriched air or oxygen as oxidizing agent and adjusting the iron content to the ferro-alloy by adding at least 70% by weight of iron prior to the step of forming the slag so that at least most of the tantalum carbide is dissolved in the molten ferro-alloy

  4. In-Situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes

    Science.gov (United States)

    2010-12-28

    DATES COVERED (From - To) 1/29/10-9/30/10 4. TITLE AND SUBTITLE In situ optical studies of oxidation/reduction kinetics on SOFC cermet anodes 5a...0572 In-situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes Department of Chemistry and Biochemistry Montana State University...of Research In-situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes Principal Investigator Robert Walker Organization

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

    Science.gov (United States)

    Poinern, Gerrard Eddy Jai; Ali, Nurshahidah; Fawcett, Derek

    2011-01-01

    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. PMID:28880002

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

    Science.gov (United States)

    Poinern, Gerrard Eddy Jai; Ali, Nurshahidah; Fawcett, Derek

    2011-02-25

    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.

  7. 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.

  8. Superficial oxidation in mono and polycrystalline niobium films for Josephson joints

    International Nuclear Information System (INIS)

    Celaschi, S.; Geballi, T.H.

    1984-01-01

    Niobium thin films (Nb) with multigranular and monocrystalline structure with 3000 A of thickness was put in different temperatures on sapphire monocrystalline substrate by high vaccum evaporation technique (10 -8 Torr). The evaporation process and some of structural properties of the films are described. The oxidation process is studied through the characteristics of the current curves x voltage measured in low temperature (4.2 K). (E.G.) [pt

  9. Anodic oxidation of commercially pure titanium for purification of polluted water

    Science.gov (United States)

    Benkafada, Faouzia; Kerdoud, Djahida; Bouchoucha, Ali

    2018-05-01

    Anodisation of pure titanium has been carried out in sulphuric acid solution at potentials ranging from 40 V to 5 days. We studied the parameters influencing the anodic deposition such as acid concentration and anodic periods. Anodic oxides thin films were characterized by X-ray diffraction, cyclic polarization and electrochemical impedance spectroscopy. The I-V curves and electrochemical impedance measurements were carried out in 0.1 N NaOH solution. The results indicated that although the thin films obtained by anodic oxidation are nonstoichiometric, they have an electric behaviour like n-type semiconducting material.

  10. Cleavage of olefinic double bonds by mediated anodic oxidation

    International Nuclear Information System (INIS)

    Baeumer, U.-St.; Schaefer, H.J.

    2003-01-01

    Seven alkenes, e.g. 1-decene, methyl oleate, cyclododecene, norbornene, are cleaved by indirect anodic oxidation with IO 4 - /RuCl 3 as mediator to carboxylic acids. The best performance was achieved with two alternative ex cell-methods. Periodate is regenerated from iodate in a divided cell at a PbO 2 /Ti-anode. In the chemical reactor alkene and the produced carboxylic acid are immobilized in a chromatography column on Chromosorb W and oxidized with IO 4 - /RuO 4 in CH 3 CN/water. In the alternative version the alkene is oxidized in an emulsion generated by sonication and the organic phase is retained in the reactor by a separator. Acids and diacids are obtained in 61-91% chemical yield and good current yields. The amount of consumed periodate can be reduced to less than 5% of the amount needed for the chemical oxidation. The mediated anodic cleavage of alkenes is altogether an interesting alternative to ozonolysis

  11. 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.

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

    International Nuclear Information System (INIS)

    Kukkola, Jarmo; Rautio, Aatto; Sala, Giovanni; Pino, Flavio; Toth, Geza; Leino, Anne-Riikka; Maeklin, Jani; Jantunen, Heli; Uusimaeki, Antti; Kordas, Krisztian; 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.

  13. 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.

  14. 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...

  15. Catalytic properties of niobium compounds

    International Nuclear Information System (INIS)

    Tanabe, K.; Iizuka, T.

    1983-04-01

    The catalytic activity and selectivity of niobium compounds including oxides, salts, organometallic compounds and others are outlined. The application of these compounds as catalysts to diversified reactions is reported. The nature and action of niobium catalysts are characteristic and sometimes anomalous, suggesting the necessity of basic research and the potential use as catalysts for important processes in the chemical industry. (Author) [pt

  16. The anodization synthesis of copper oxide nanosheet arrays and their photoelectrochemical properties

    Energy Technology Data Exchange (ETDEWEB)

    Shu, Xia [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Zheng, Hongmei [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Key Laboratory of Advanced Functional Materials and Devices of Anhui Province, Hefei 230009 (China); Xu, Guangqing, E-mail: gqxu1979@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Key Laboratory of Advanced Functional Materials and Devices of Anhui Province, Hefei 230009 (China); Zhao, Jiebo [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Cui, Lihua [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); School of Materials Science and Engineering, Beifang University of Nationalities, Yinchuan 750021 (China); Cui, Jiewu; Qin, Yongqiang; Wang, Yan [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Zhang, Yong [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Key Laboratory of Advanced Functional Materials and Devices of Anhui Province, Hefei 230009 (China); Wu, Yucheng, E-mail: ycwu@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Key Laboratory of Advanced Functional Materials and Devices of Anhui Province, Hefei 230009 (China)

    2017-08-01

    Graphical abstract: Current-time and potential-time curves of the copper foil anodization process, CV of copper substrate in anodization solution and SEM morphologies of anodization products on Cu substrates obtained at different time. - Highlights: • Copper oxides nanosheet arrays were achieved via anodization method. • The growth mechanisms of the copper anodization process were studied. • Photoelectrochemical performances of copper oxides NSAs were studied. - Abstract: We studied the growth of copper oxide nanosheet arrays on copper foil via a simple anodization method. The structures, morphologies, and elemental compositions of the specimens were characterized with an X-ray diffractometer, scanning electron microscope, high resolution transmission electron microscope, and X-ray photoelectron spectrometer. The copper oxide (Cu{sub 2}O and CuO) nanosheet arrays were comprised of 30-nm-thick nanosheets that stand vertically on the Cu substrate. The anodizing parameters, such as the current density, temperature, and polyethylene glycol concentration, were optimized to obtain the regular nanosheet arrays. The optical absorption properties of the anodized products were evaluated using a diffuse reflectance spectrometer, and broad and strong optical absorption bands arising from the UV to visible region were observed. The photoelectrochemical performance of the nanosheet arrays was measured with chronoamperometry and cyclic voltammetry on an electrochemical workstation equipped with a Xe lamp (wavelength >400 nm). A negative photocurrent was obtained due to the p-type semiconductor of the copper oxides. The copper oxide nanosheet arrays achieve the highest photocurrent of 0.4 mA/cm{sup 2} at the current density of 1.0 A/dm{sup 2}, temperature of 70 °C, and polyethylene glycol concentration of 0.5 g/L.

  17. Niobium based coatings for dental implants

    International Nuclear Information System (INIS)

    Ramirez, G.; Rodil, S.E.; Arzate, H.; Muhl, S.; Olaya, J.J.

    2011-01-01

    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 2 O 5 (a-Nb 2 O 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.

  18. Molecular beam epitaxy growth of niobium oxides by solid/liquid state oxygen source and lithium assisted metal-halide chemistry

    Science.gov (United States)

    Tellekamp, M. Brooks; Greenlee, Jordan D.; Shank, Joshua C.; Doolittle, W. Alan

    2015-09-01

    In order to consistently grow high quality niobium oxides and lithium niobium oxides, a novel solid/liquid state oxygen source, LiClO4, has been implemented in a molecular beam epitaxy (MBE) system. LiClO4 is shown to decompose into both molecular and atomic oxygen upon heating. This allows oxidation rates similar to that of molecular oxygen but at a reduced overall beam flux, quantified by in situ Auger analysis. LiClO4 operation is decomposition limited to less than 400 °C, and other material limitations are identified. The design of a custom near-ambient NbCl5 effusion cell is presented, which improves both short and long term stability. Films of Nb oxidation state +2, +3, and +5 are grown using these new tools, including the multi-functional sub-oxide LiNbO2.

  19. 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.

  20. Low temperature oxidation of niobium alloy with silicon-aluminium coating

    International Nuclear Information System (INIS)

    Lazarev, Eh.M.; Sapozhnikova, L.V.; Shabanova, M.E.; Pod'yachev, V.N.; Kornilova, Z.I.

    1987-01-01

    Using the gravimetry methods heat resistance of niobium-titanium-aluminium alloy in the air and at 700 deg C in the initial state and when it is protected by silicide-aluminium coatings (with variable content of aluminium) is investigated. Using X-ray diffraction and micro X-ray diffraction analyses, mechanisms of the alloy oxidation and the coating protective effect are studied. The role of aluminium in the formation of coatings is analyzed and according to bend tests the plasticity of the coatings is evaluated

  1. Pilot demonstration of cerium oxide coated anodes

    Energy Technology Data Exchange (ETDEWEB)

    Gregg, J.S.; Frederick, M.S.; Shingler, M.J.; Alcorn, T.R.

    1992-10-01

    Cu cermet anodes were tested for 213 to 614 hours with an in-situ deposited CEROX coating in a pilot cell operated by Reynolds Manufacturing Technology Laboratory. At high bath ratio ([approximately]1.5) and low current density (0.5 A/cm[sup 2]), a [ge]1 mm thick dense CEROX coating was deposited on the anodes. At lower bath ratios and higher current density, the CEROX coating was thinner and less dense, but no change in corrosion rate was noted. Regions of low current density on the anodes and sides adjacent to the carbon anode sometimes had thin or absent CEROX coatings. Problems with cracking and oxidation of the cermet substrates led to higher corrosion rates in a pilot cell than would be anticipated from lab scale results.

  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. Controlling the anodizing conditions in preparation of an nanoporous anodic aluminium oxide template

    Science.gov (United States)

    Nazemi, Azadeh; Abolfazl, Seyed; Sadjadi, Seyed

    2014-12-01

    Porous anodic aluminium oxide (AAO) template is commonly used in the synthesis of one-dimensional nanostructures, such as nanowires and nanorods, due to its simple fabrication process. Controlling the anodizing conditions is important because of their direct influence on the size of AAO template pores; it affects the size of nanostructures that are fabricated in AAO template. In present study, several alumina templates were fabricated by a two-step electrochemical anodization in different conditions, such as the time of first process, its voltage, and electrolyte concentration. The effect of these factors on pore diameters of AAO templates was investigated using scanning electron microscopy (SEM).

  4. Lithium alloys and metal oxides as high-capacity anode materials for lithium-ion batteries

    International Nuclear Information System (INIS)

    Liang, Chu; Gao, Mingxia; Pan, Hongge; Liu, Yongfeng; Yan, Mi

    2013-01-01

    Highlights: •Progress in lithium alloys and metal oxides as anode materials for lithium-ion batteries is reviewed. •Electrochemical characteristics and lithium storage mechanisms of lithium alloys and metal oxides are summarized. •Strategies for improving electrochemical lithium storage properties of lithium alloys and metal oxides are discussed. •Challenges in developing lithium alloys and metal oxides as commercial anodes for lithium-ion batteries are pointed out. -- Abstract: Lithium alloys and metal oxides have been widely recognized as the next-generation anode materials for lithium-ion batteries with high energy density and high power density. A variety of lithium alloys and metal oxides have been explored as alternatives to the commercial carbonaceous anodes. The electrochemical characteristics of silicon, tin, tin oxide, iron oxides, cobalt oxides, copper oxides, and so on are systematically summarized. In this review, it is not the scope to retrace the overall studies, but rather to highlight the electrochemical performances, the lithium storage mechanism and the strategies in improving the electrochemical properties of lithium alloys and metal oxides. The challenges and new directions in developing lithium alloys and metal oxides as commercial anodes for the next-generation lithium-ion batteries are also discussed

  5. Reaction kinetics of oxygen on single-phase alloys, oxidation of nickel and niobium alloys

    International Nuclear Information System (INIS)

    Lalauze, Rene

    1973-01-01

    This research thesis first addresses the reaction kinetics of oxygen on alloys. It presents some generalities on heterogeneous reactions (conventional theory, theory of jumps), discusses the core reaction (with the influence of pressure), discusses the influence of metal self-diffusion on metal oxidation kinetics (equilibrium conditions at the interface, hybrid diffusion regime), reports the application of the hybrid diffusion model to the study of selective oxidation of alloys (Wagner model, hybrid diffusion model) and the study of the oxidation kinetics of an alloy forming a solid solution of two oxides. The second part reports the investigation of the oxidation of single phase nickel and niobium alloys (phase α, β and γ)

  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. 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.

  8. Anodic ammonia oxidation to nitrogen gas catalyzed by mixed biofilms in bioelectrochemical systems

    International Nuclear Information System (INIS)

    Zhan, Guoqiang; Zhang, Lixia; Tao, Yong; Wang, Yujian; Zhu, Xiaoyu; Li, Daping

    2014-01-01

    In this paper we report ammonia oxidation to nitrogen gas using microbes as biocatalyst on the anode, with polarized electrode (+600 mV vs. Ag/AgCl) as electron acceptor. In batch experiments, the maximal rate of ammonia-N oxidation by the mixed culture was ∼ 60 mg L −1 d −1 , and nitrogen gas was the main products in anode compartment. Cyclic voltammetry for testing the electroactivity of the anodic biofilms revealed that an oxidation peak appeared at +600 mV (vs. Ag/AgCl), whereas the electrode without biofilms didn’t appear oxidation peak, indicating that the bioanode had good electroactivities for ammonia oxidation. Microbial community analysis of 16S rRNA genes based on high throughput sequencing indicated that the combination of the dominant genera of Nitrosomonas, Comamonas and Paracocus could be important for the electron transfer from ammonia oxidation to anode

  9. Study of ionic movements during anodic oxidation of nitrogen-implanted aluminium

    International Nuclear Information System (INIS)

    Terwagne, G.; Lucas, S.; Bodart, F.; Sorensen, G.; Jensen, H.

    1990-01-01

    In recent years there has been a considerable interest in synthesizing aluminium nitrides by ion implantation in order to modify the tribological properties of aluminium. The growth of an oxide layer by anodic process on these synthesized aluminium nitrides gives an interesting oxide-on-semiconductor material with surprising dynamic and decorative properties. During the anodic oxidation, ionic movements are involved in the near-surface region of the aluminium material; these ionic movements have been studied by Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA) on thin aluminium foils (7000 A) preimplanted with nitrogen and post-oxidized in an ammonium pentaborate solution. The growth of the oxide layer is reduced when the aluminium is preimplanted with nitrogen: the speed of oxidation depends on the implantation conditions (energy and fluence). Moreover, the aluminium nitride can be dissolved when all metallic aluminium staying between the surface and the AlN are consumed by the anodic process. (orig.)

  10. In-situ electrochemical doping of nanoporous anodic aluminum oxide with indigo carmine organic dye

    International Nuclear Information System (INIS)

    Stępniowski, Wojciech J.; Norek, Małgorzata; Budner, Bogusław; Michalska-Domańska, Marta; Nowak-Stępniowska, Agata; Bombalska, Aneta; Kaliszewski, Miron; Mostek, Anna; Thorat, Sanjay; Salerno, Marco; Giersig, Michael; Bojar, Zbigniew

    2016-01-01

    Nanoporous anodic aluminum oxide was formed in sulfuric acid with addition of indigo carmine. During anodizing, the organic dye was incorporated into the porous oxide walls. X-ray photoelectron spectroscopy revealed the presence of nitrogen and sulfur in the anodic aluminum oxide. Two types of incorporated sulfur were found: belonging to the sulfate anions SO_4"2"− of the electrolyte and belonging to the C-SO_3"− side groups of the indigo carmine. Raman spectroscopy confirmed the incorporation and showed that the inorganic–organic hybrid material inherited optical properties from the indigo carmine. Typical modes from pyrrolidone rings, unique for indigo carmine in the investigated system (650 and 1585 cm"−"1), were found to be the strongest for the greatest anodizing voltages used. Despite the indigo carmine incorporation, the morphology of the oxide is still nanoporous and its geometry is still tuned by the voltage applied during aluminum anodization. This work presents an inexpensive and facile approach to doping an inorganic oxide material with organic compounds. - Highlights: • Nanoporous anodic alumina was formed in electrolyte with indigo carmine. • XPS confirmed the presence of N and S in anodic alumina. • Raman spectroscopy revealed indigo carmine bands in anodic alumina. • The higher the voltage, the more indigo carmine was incorporated.

  11. Effect of sealing on the morphology of anodized aluminum oxide

    International Nuclear Information System (INIS)

    Hu, Naiping; Dong, Xuecheng; He, Xueying; Browning, James F.; Schaefer, Dale W.

    2015-01-01

    Highlights: • We explored structural change of anodizing aluminum oxide induced by sealing. • All sealing methods decrease pore size as shown by X-ray/neutron scattering. • Cold sealing and hot water sealing do not alter the aluminum oxide framework. • Hot nickel acetate sealing both fills the pores and deposits on air oxide interface. • Samples with hot nickel acetate sealing outperform other sealing methods. - Abstract: Ultra-small angle X-ray scattering (USAXS), small-angle neutron scattering (SANS), X-ray reflectometry (XRR) and neutron reflectometry (NR) were used to probe structure evolution induced by sealing of anodized aluminum. While cold nickel acetate sealing and hot-water sealing decrease pore size, these methods do not alter the cylindrical porous framework of the anodic aluminum oxide layer. Hot nickel acetate both fills the pores and deposits on the air surface (air–oxide interface), leading to low porosity and small mean pore radius (39 Å). Electrochemical impedance spectroscopy and direct current polarization show that samples sealed by hot nickel acetate outperform samples sealed by other sealing methods

  12. 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.

  13. Improvement of biological properties of titanium by anodic oxidation and ultraviolet irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Baoe [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Li, Ying [Stomatological Hospital, Tianjin Medical University, Tianjin 300070 (China); Li, Jun [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Fu, Xiaolong; Li, Changyi [Stomatological Hospital, Tianjin Medical University, Tianjin 300070 (China); Wang, Hongshui [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Liu, Shimin [Business School, Tianjin University of Commerce, Tianjin 300134 (China); Guo, Litong [China University of Mining and Technology, Xuzhou 221116 (China); Xin, Shigang [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Liang, Chunyong, E-mail: liangchunyong@126.com [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Li, Haipeng, E-mail: lhpcx@163.com [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China)

    2014-07-01

    Anodic oxidation was applied to produce a homogeneous and uniform array of nanotubes of about 70 nm on the titanium (Ti) surface, and then, the nanotubes were irradiated by ultraviolet. The bioactivity of the Ti surface was evaluated by simulated body fluid soaking test. The biocompatibility was investigated by in vitro cell culture test. The results showed that bone-like apatite was formed on the anodic oxidized and UV irradiated Ti surface, but not on the as-polished Ti surface after immersion in simulated body fluid for two weeks. Cells cultured on the anodic oxidized Ti surface showed enhanced cell adhesion and proliferation, also presented an up-regulated gene expression of osteogenic markers OPG, compared to those cultured on the as-polished Ti surface. After UV irradiation, the cell behaviors were further improved, indicating better biocompatibility of Ti surface. Based on these results, it can be concluded that anodic oxidation improved the biological properties (bioactivity and biocompatibility) of Ti surface, while UV irradiation improved the biocompatibility to a better extent. The improved biological properties were attributed to the nanostructures as well as the enhanced hydrophilicity. Therefore, anodic oxidation combined with UV irradiation can be used to enhance the biological properties of Ti-based implants.

  14. Halogen effect for improving high temperature oxidation resistance of Ti-50Al by anodization

    Science.gov (United States)

    Mo, Min-Hua; Wu, Lian-Kui; Cao, Hua-Zhen; Lin, Jun-Pin; Zheng, Guo-Qu

    2017-06-01

    The high temperature oxidation resistance of Ti-50Al was significantly improved via halogen effect which was achieved by anodizing in an ethylene glycol solution containing with fluorine ion. The anodized Ti-50Al with holes and micro-cracks could be self-repaired during oxidation at 1000 °C. The thickness of the oxide scale increases with the prolonging of oxidation time. On the basis of halogen effect for improving the high temperature oxidation resistance of Ti-50Al by anodization, only fluorine addition into the electrolyte can effectively improve the high temperature oxidation resistance of Ti-50Al.

  15. In-situ electrochemical doping of nanoporous anodic aluminum oxide with indigo carmine organic dye

    Energy Technology Data Exchange (ETDEWEB)

    Stępniowski, Wojciech J., E-mail: wojciech.stepniowski@wat.edu.pl [Department of Advanced Materials and Technology, Faculty of Advanced Technology and Chemistry, Military University of Technology, 2 Kaliskiego Str., 00-908 Warszawa (Poland); Norek, Małgorzata [Department of Advanced Materials and Technology, Faculty of Advanced Technology and Chemistry, Military University of Technology, 2 Kaliskiego Str., 00-908 Warszawa (Poland); Budner, Bogusław [Institute of Optoelectronics, Military University of Technology, 2 Kaliskiego Str., 00-908 Warszawa (Poland); Michalska-Domańska, Marta [Department of Advanced Materials and Technology, Faculty of Advanced Technology and Chemistry, Military University of Technology, 2 Kaliskiego Str., 00-908 Warszawa (Poland); Institute of Optoelectronics, Military University of Technology, 2 Kaliskiego Str., 00-908 Warszawa (Poland); Nowak-Stępniowska, Agata; Bombalska, Aneta; Kaliszewski, Miron [Institute of Optoelectronics, Military University of Technology, 2 Kaliskiego Str., 00-908 Warszawa (Poland); Mostek, Anna [Department of Advanced Materials and Technology, Faculty of Advanced Technology and Chemistry, Military University of Technology, 2 Kaliskiego Str., 00-908 Warszawa (Poland); Thorat, Sanjay; Salerno, Marco [Department of Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, Genova I-16163 (Italy); Giersig, Michael [Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany); Bojar, Zbigniew [Department of Advanced Materials and Technology, Faculty of Advanced Technology and Chemistry, Military University of Technology, 2 Kaliskiego Str., 00-908 Warszawa (Poland)

    2016-01-01

    Nanoporous anodic aluminum oxide was formed in sulfuric acid with addition of indigo carmine. During anodizing, the organic dye was incorporated into the porous oxide walls. X-ray photoelectron spectroscopy revealed the presence of nitrogen and sulfur in the anodic aluminum oxide. Two types of incorporated sulfur were found: belonging to the sulfate anions SO{sub 4}{sup 2−} of the electrolyte and belonging to the C-SO{sub 3}{sup −} side groups of the indigo carmine. Raman spectroscopy confirmed the incorporation and showed that the inorganic–organic hybrid material inherited optical properties from the indigo carmine. Typical modes from pyrrolidone rings, unique for indigo carmine in the investigated system (650 and 1585 cm{sup −1}), were found to be the strongest for the greatest anodizing voltages used. Despite the indigo carmine incorporation, the morphology of the oxide is still nanoporous and its geometry is still tuned by the voltage applied during aluminum anodization. This work presents an inexpensive and facile approach to doping an inorganic oxide material with organic compounds. - Highlights: • Nanoporous anodic alumina was formed in electrolyte with indigo carmine. • XPS confirmed the presence of N and S in anodic alumina. • Raman spectroscopy revealed indigo carmine bands in anodic alumina. • The higher the voltage, the more indigo carmine was incorporated.

  16. Anodic oxidation of Ta/Fe alloys

    International Nuclear Information System (INIS)

    Mato, S.; Alcala, G.; Thompson, G.E.; Skeldon, P.; Shimizu, K.; Habazaki, H.; Quance, T.; Graham, M.J.; Masheder, D.

    2003-01-01

    The behaviour of iron during anodizing of sputter-deposited Ta/Fe alloys in ammonium pentaborate electrolyte has been examined by transmission electron microscopy, Rutherford backscattering spectroscopy, glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy. Anodic films on Ta/1.5 at.% Fe, Ta/3 at.% Fe and Ta/7 at.% Fe alloys are amorphous and featureless and develop at high current efficiency with respective formation ratios of 1.67, 1.60 and 1.55 nm V -1 . Anodic oxidation of the alloys proceeds without significant enrichment of iron in the alloy in the vicinity of the alloy/film interface and without oxygen generation during film growth, unlike the behaviour of Al/Fe alloys containing similar concentrations of iron. The higher migration rate of iron species relative to that of tantalum ions leads to the formation of an outer iron-rich layer at the film surface

  17. 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.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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.

  19. 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.

  20. Luminescence properties of oxide films formed by anodization of aluminum in 12-tungstophosphoric acid

    International Nuclear Information System (INIS)

    Stojadinovic, S.; Vasilic, R.; Petkovic, M.; Nedic, Z.; Kasalica, B.; Belca, I.; Zekovic, Lj.

    2010-01-01

    In this paper, we have investigated luminescence properties of oxide films formed by anodization of aluminum in 12-tungstophosphoric acid. For the first time we have measured weak luminescence during anodization of aluminum in this electrolyte (so-called galvanoluminescence GL) and showed that there are wide GL bands in the visible region of the spectrum and observed two dominant spectral peaks. The first one is at about 425 nm, and the second one shifts with anodization voltage. As the anodization voltage approaches the breakdown voltage, a large number of sparks appear superimposed on the anodic GL. Several intensive band peaks were observed under breakdown caused by electron transitions in W, P, Al, O, H atoms. Furthermore, photoluminescence (PL) of anodic oxide films and anodic-spark formed oxide coatings were performed. In both cases wide PL bands in the range from 320 nm to 600 nm were observed.

  1. 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.

  2. Electrodeposition of some metals and niobium superconducting alloys from molten fluorides

    International Nuclear Information System (INIS)

    Cohen, U.

    1978-01-01

    The major goal of this thesis was to study the feasibility of electrodeposition from molten fluorides of the pure elements niobium, aluminium, tin, germanium and silicon, and the niboium superconducting intermetallic compounds with these elements, and to prepare and study films of these materials in the form of coherent and uniform coatings. Decomposition potential measurements with a gold anode were carried out on the alkali fluoride solvent and the fluoride salt solutions of niobium, aluminum, tin, and germanium to provide important initial thermodynamic data. Attempts to codeposit niobium and aluminum invariably failed, niobium being the exclusive deposit in all cases. Codeposition of niobium--tin alloys was demonstrated. Of the four intermetallic compounds of the niobium--germanium system, three were obtained as single-phase coatings. The superconducting compound (A15 phase) was not successfully electrodeposited in a single-phase form. It was obtained, however, in phase-mixture coatings. Application of alternating square wave pulses produced substantial changes in the morphology of niobium deposits. Silicon electrocrystallization epitaxy (ECE) was demonstrated for the first time. Uniform, coherent, and well adherent coatings of polycrystalline Si with a grain diameter of up to 40 to 50 μm were plated onto nonalloying metal substrates, such as silver and tungsten.These processes offer some attractive features for both integrated circuit technology and silicon solar cell fabrication. Aluminum, tin, and germanium were also electrodeposited from molten fluorides

  3. 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)

  4. Synthesis, Characterization, and Optimization of Novel Solid Oxide Fuel Cell Anodes

    Science.gov (United States)

    Miller, Elizabeth C.

    This dissertation presents research on the development of novel materials and fabrication procedures for solid oxide fuel cell (SOFC) anodes. The work discussed here is divided into three main categories: all-oxide anodes, catalyst exsolution oxide anodes, and Ni-infiltrated anodes. The all-oxide and catalyst exsolution anodes presented here are further classi?ed as Ni-free anodes operating at the standard 700-800°C SOFC temperature while the Ni-infiltrated anodes operate at intermediate temperatures (≤650°C). Compared with the current state-of-the-art Ni-based cermets, all-oxide, Ni-free SOFC anodes offer fewer coking issues in carbon-containing fuels, reduced degradation due to fuel contaminants, and improved stability during redox cycling. However, electrochemical performance has proven inferior to Ni-based anodes. The perovskite oxide Fe-substituted strontium titanate (STF) has shown potential as an anode material both as a single phase electrode and when combined with Gd-doped ceria (GDC) in a composite electrode. In this work, STF is synthesized using a modified Pechini processes with the aim of reducing STF particle size and increasing the electrochemically active area in the anode. The Pechini method produced particles ? 750 nm in diameter, which is signi°Cantly smaller than the typically micron-sized solid state reaction powder. In the first iteration of anode fabrication with the Pechini powder, issues with over-sintering of the small STF particles limited gas di?usion in the anode. However, after modifying the anode firing temperature, the Pechini cells produced power density comparable to solid state reaction based cells from previous work by Cho et al. Catalyst exsolution anodes, in which metal cations exsolve out of the lattice under reducing conditions and form nanoparticles on the oxide surface, are another Ni-free option for standard operating temperature SOFCs. Little information is known about the onset of nanoparticle formation, which

  5. 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......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 lamination will be described. Flexural strength of the reduced cermets measured using three-point bending configuration is 468±37MPa. The graded anode supports are characterized by scanning electron microscope observations, mercury porosimetry intrusion, and resistivity measurements, showing an adequate...... of tapes at room temperature without using plasticizers. This is made by the combination of two different binders with varying Tg (glass transition temperature) which resulted in plastic deformation at room temperature. Those results indicate that the proposed process is a cost-effective method...

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

    International Nuclear Information System (INIS)

    Gianluigi Ciovati; Peter Kneisel; Alex Gurevich

    2008-01-01

    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 thermomagnetic instability governing the Q-drop and the baking effect.

  7. 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.

  8. cw argon laser annealing of anodic oxide on GaAs

    International Nuclear Information System (INIS)

    Chakravarti, S.N.; Das, P.; Webster, R.T.; Bhat, K.N.

    1981-01-01

    Anodic oxide films (850 +- 50 A thick) grown on n + (100) bulk GaAs were subjected to selective area annealing using a cw argon laser operating at an output power of 1.2 W. Capacitance-voltage (C-V) measurements performed on Al-anodic oxide-GaAs MOS capacitor structures show that laser-annealed capacitor dots have greatly reduced field-induced hysteresis effects in their capacitance-voltage characteristics compared to the unannealed ones. The oxide leakage current also shows a significant improvement: the leakage current magnitude of MOS capacitors in laser-annealed oxide island is over four orders of magnitude less than the oxide region which was not exposed to the laser radiation. Dielectric breakdown measurement indicates that laser-annealed capacitors have considerably higher breakdown voltages, about a factor of 2 higher than the unannealed capacitors

  9. Friction behaviour of anodic oxide film on aluminum impregnated with molybdenum sulfide compounds

    Energy Technology Data Exchange (ETDEWEB)

    Maejima, M.; Saruwatari, K. [Fujikura Ltd., Tokyo (Japan); Takaya, M. [Faculty of Engineering, Chiba Institute of Technology 17-1, Tsudanuma 2-Chome, 275-0016, Narasino-shi Chiba (Japan)

    2000-10-23

    In order to improve the lubricity and wear resistance of aluminum anodic oxide films, it is necessary to ensure the film layers are dense to prevent cracking, and to harden the films as well as reduce the shear stress of the film surfaces. From this view point, lubricious, hard anodic oxide films have been studied in the past, but fully satisfactory results have yet to be realized. In this paper, we report on our study of the re-anodizing of anodic oxide film in an aqueous solution of (NH)MoS. Molybdenum sulfide and compounds filled the 20-nm diameter pores of the film, creating internal stress which compressed the film, suppressing the occurrence of cracks and reducing the friction coefficient. (orig.)

  10. Niobium and tantalum

    Science.gov (United States)

    Schulz, Klaus J.; Piatak, Nadine M.; Papp, John F.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    Niobium and tantalum are transition metals that are almost always found together in nature because they have very similar physical and chemical properties. Their properties of hardness, conductivity, and resistance to corrosion largely determine their primary uses today. The leading use of niobium (about 75 percent) is in the production of high-strength steel alloys used in pipelines, transportation infrastructure, and structural applications. Electronic capacitors are the leading use of tantalum for high-end applications, including cell phones, computer hard drives, and such implantable medical devices as pacemakers. Niobium and tantalum are considered critical and strategic metals based on the potential risks to their supply (because current production is restricted to only a few countries) and the significant effects that a restriction in supply would have on the defense, energy, high-tech industrial, and medical sectors.The average abundance of niobium and tantalum in bulk continental crust is relatively low—8.0 parts per million (ppm) niobium and 0.7 ppm tantalum. Their chemical characteristics, such as small ionic size and high electronic field strength, significantly reduce the potential for these elements to substitute for more common elements in rock-forming minerals and make niobium and tantalum essentially immobile in most aqueous solutions. Niobium and tantalum do not occur naturally as pure metals but are concentrated in a variety of relatively rare oxide and hydroxide minerals, as well as in a few rare silicate minerals. Niobium is primarily derived from the complex oxide minerals of the pyrochlore group ((Na,Ca,Ce)2(Nb,Ti,Ta)2(O,OH,F)7), which are found in some alkaline granite-syenite complexes (that is, igneous rocks containing sodium- or potassium-rich minerals and little or no quartz) and carbonatites (that is, igneous rocks that are more than 50 percent composed of primary carbonate minerals, by volume). Tantalum is derived mostly from the

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

    International Nuclear Information System (INIS)

    Asoh, Hidetaka; Uchibori, Kota; Ono, Sachiko

    2009-01-01

    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.

  12. 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.

  13. Study for preparation of nanoporous titania on titanium by anodic oxidation

    International Nuclear Information System (INIS)

    Passos, Alessandra Pires

    2014-01-01

    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 3 PO 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 2 . The results obtained in this study showed no

  14. 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.

  15. Effect of passivation with CO on the electrochemical corrosion behavior of uranium-niobium alloy

    International Nuclear Information System (INIS)

    Fu Xiaoguo; Dai Lianxin; Zou Juesheng; Bai Chaomao; Wang Xiaolin

    2000-01-01

    Electrochemical studies are performed to investigate the corrosion resistance of uranium-niobium alloy before and after passivated with carbon monoxide. Using X-ray photoelectron spectroscopy (XPS), the surface composition of specimen passivated with carbon monoxide is determined. The corrosion resistance of uranium-niobium alloy is well improved because the passive layer (UC/UC x O y + Nb 2 O 5 + UO 2 ) on surface serves as passive film and increases the anodic impedance after the specimen is passivated with carbon monoxide

  16. The cooperative electrochemical oxidation of chlorophenols in anode-cathode compartments

    International Nuclear Information System (INIS)

    Wang Hui; Wang Jianlong

    2008-01-01

    By using a self-made carbon/polytetrafluoroethylene (C/PTFE) O 2 -fed as the cathode and Ti/IrO 2 /RuO 2 as the anode, the degradation of three organic compounds (phenol, 4-chlorophenol, and 2,4-dichlorophenol) was investigated in the diaphragm (with terylene as diaphragm material) electrolysis device by electrochemical oxidation process. The result indicated that the concentration of hydrogen peroxide (H 2 O 2 ) was 8.3 mg/L, and hydroxyl radical (HO·) was determined in the cathodic compartment by electron spin resonance spectrum (ESR). The removal efficiency for organic compounds reached about 90% after 120 min, conforming to the sequence of phenol, 4-chlorophenol, and 2,4-dichlorophenol. And the dechlorination degree of 4-chlorophenol exceeded 90% after 80 min. For H 2 O 2 , HO· existed in the catholyte and reduction dechlorination at the cathode, the mineralization of organics in the cathodic compartment was better than that in the anodic compartment. The degradation of organics was supposed to be cooperative oxidation by direct or indirect electrochemical oxidation at the anode and H 2 O 2 , HO· produced by oxygen reduction at the cathode. High-performance liquid chromatography (HPLC) allowed identifying phenol as the dechlorination product of 4-chlorophenol in the cathodic compartment, and hydroquinone, 4-chlorocatechol, benzoquinone, maleic, fumaric, oxalic, and formic acids as the main oxidation intermediates in the cathodic and anodic compartments. A reaction scheme involving all these intermediates was proposed

  17. A Highly Controllable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membranes

    Science.gov (United States)

    Lin, Yuanjing; Lin, Qingfeng; Liu, Xue; Gao, Yuan; He, Jin; Wang, Wenli; Fan, Zhiyong

    2015-12-01

    Due to the broad applications of porous alumina nanostructures, research on fabrication of anodized aluminum oxide (AAO) with nanoporous structure has triggered enormous attention. While fabrication of highly ordered nanoporous AAO with tunable geometric features has been widely reported, it is known that its growth rate can be easily affected by the fluctuation of process conditions such as acid concentration and temperature during electrochemical anodization process. To fabricate AAO with various geometric parameters, particularly, to realize precise control over pore depth for scientific research and commercial applications, a controllable fabrication process is essential. In this work, we revealed a linear correlation between the integrated electric charge flow throughout the circuit in the stable anodization process and the growth thickness of AAO membranes. With this understanding, we developed a facile approach to precisely control the growth process of the membranes. It was found that this approach is applicable in a large voltage range, and it may be extended to anodization of other metal materials such as Ti as well.

  18. Evaluation of Niobium as Candidate Electrode Material for DC High Voltage Photoelectron Guns

    Science.gov (United States)

    BastaniNejad, M.; Mohamed, Abdullah; Elmustafa, A. A.; Adderley, P.; Clark, J.; Covert, S.; Hansknecht, J.; Hernandez-Garcia, C.; Poelker, M.; Mammei, R.; hide

    2012-01-01

    The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror-like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain, and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (< 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18:7 MV/m.

  19. Application of infiltrated LSCM-GDC oxide anode in direct carbon/coal fuel cells.

    Science.gov (United States)

    Yue, Xiangling; Arenillas, Ana; Irvine, John T S

    2016-08-15

    Hybrid direct carbon/coal fuel cells (HDCFCs) utilise an anode based upon a molten carbonate salt with an oxide conducting solid electrolyte for direct carbon/coal conversion. They can be fuelled by a wide range of carbon sources, and offer higher potential chemical to electrical energy conversion efficiency and have the potential to decrease CO2 emissions compared to coal-fired power plants. In this study, the application of (La, Sr)(Cr, Mn)O3 (LSCM) and (Gd, Ce)O2 (GDC) oxide anodes was explored in a HDCFC system running with two different carbon fuels, an organic xerogel and a raw bituminous coal. The electrochemical performance of the HDCFC based on a 1-2 mm thick 8 mol% yttria stabilised zirconia (YSZ) electrolyte and the GDC-LSCM anode fabricated by wet impregnation procedures was characterized and discussed. The infiltrated oxide anode showed a significantly higher performance than the conventional Ni-YSZ anode, without suffering from impurity formation under HDCFC operation conditions. Total polarisation resistance (Rp) reached 0.8-0.9 Ω cm(2) from DCFC with an oxide anode on xerogel and bituminous coal at 750 °C, with open circuit voltage (OCV) values in the range 1.1-1.2 V on both carbon forms. These indicated the potential application of LSCM-GDC oxide anode in HDCFCs. The chemical compatibility of LSCM/GDC with carbon/carbonate investigation revealed the emergence of an A2BO4 type oxide in place of an ABO3 perovskite structure in the LSCM in a reducing environment, due to Li attack as a result of intimate contact between the LSCM and Li2CO3, with GDC being stable under identical conditions. Such reaction between LSCM and Li2CO3 was not observed on a LSCM-YSZ pellet treated with Li-K carbonate in 5% H2/Ar at 700 °C, nor on a GDC-LSCM anode after HDCFC operation. The HDCFC durability tests of GDC-LSCM oxide on a xerogel and on raw bituminous coal were performed under potentiostatic operation at 0.7 V at 750 °C. The degradation mechanisms were

  20. Ultra-High Density Single Nanometer-Scale Anodic Alumina Nanofibers Fabricated by Pyrophosphoric Acid Anodizing

    Science.gov (United States)

    Kikuchi, Tatsuya; Nishinaga, Osamu; Nakajima, Daiki; Kawashima, Jun; Natsui, Shungo; Sakaguchi, Norihito; Suzuki, Ryosuke O.

    2014-12-01

    Anodic oxide fabricated by anodizing has been widely used for nanostructural engineering, but the nanomorphology is limited to only two oxides: anodic barrier and porous oxides. Therefore, the discovery of an additional anodic oxide with a unique nanofeature would expand the applicability of anodizing. Here we demonstrate the fabrication of a third-generation anodic oxide, specifically, anodic alumina nanofibers, by anodizing in a new electrolyte, pyrophosphoric acid. Ultra-high density single nanometer-scale anodic alumina nanofibers (1010 nanofibers/cm2) consisting of an amorphous, pure aluminum oxide were successfully fabricated via pyrophosphoric acid anodizing. The nanomorphologies of the anodic nanofibers can be controlled by the electrochemical conditions. Anodic tungsten oxide nanofibers can also be fabricated by pyrophosphoric acid anodizing. The aluminum surface covered by the anodic alumina nanofibers exhibited ultra-fast superhydrophilic behavior, with a contact angle of less than 1°, within 1 second. Such ultra-narrow nanofibers can be used for various nanoapplications including catalysts, wettability control, and electronic devices.

  1. Interaction of Cr-Ti-Si coating on VN-3 niobium alloy with air environment

    International Nuclear Information System (INIS)

    Lazarev, Eh.M.; Kozlov, A.T.; Monakhova, L.A.

    1985-01-01

    Investigation of heat-resistance, microstructure and phase composition of Cr-Ti-Si coating on VN-3 niobium alloy with air oxidation in the temperature interval of 1200-1600 deg C is conducted. Thermogravimetry, metallography, X-ray diffraction and microprobe analysis methods are used. It is ascertained that the coating is a dense niobium disilicide layer, luriched on the surface with chromium and titanium disilicides and separated and from the protected alloy by a narrow zone of the lowest niobium silicide Nb 5 Si 3 . The coating protective junctions are provided by a selective chromium and titanium disilicides oxidation as well as niobium disilicide oxidation at the temperature of 1600 deg C, and by the rates of niobium and silicon diffusion through Nb 5 SI 3 and NbSi 2 and oxygen diffusion through the amorphous SiO 2

  2. Structural and optical characterization of porous anodic aluminum oxide

    International Nuclear Information System (INIS)

    Galca, Aurelian C.; Kooij, E. Stefan; Wormeester, Herbert; Salm, Cora; Leca, Victor; Rector, Jan H.; Poelsema, Bene

    2003-01-01

    Spectroscopic ellipsometry and scanning electron microscopy (SEM) experiments are employed to characterize porous aluminum oxide obtained by anodization of thin aluminum films. Rutherford backscattering spectra and x-ray diffraction experiments provide information on the composition and the structure of the samples. Results on our thin film samples with a well-defined geometry show that anodization of aluminum is reproducible and results in a porous aluminum oxide network with randomly distributed, but perfectly aligned cylindrical pores perpendicular to the substrate. The ellipsometry spectra are analyzed using an anisotropic optical model, partly based on the original work by Bruggeman. The model adequately describes the optical response of the anodized film in terms of three physically relevant parameters: the film thickness, the cylinder fraction, and the nanoporosity of the aluminum oxide matrix. Values of the first two quantities, obtained from fitting the spectra, are in perfect agreement with SEM results, when the nanoporosity of the aluminum oxide matrix is taken into account. The validity of our optical model was verified over a large range of cylinder fractions, by widening of the pores through chemical etching in phosphoric acid. While the cylinder fraction increases significantly with etch time and etchant concentration, the nanoporosity remains almost unchanged. Additionally, based on a simple model considering a linear etch rate, the concentration dependence of the etch rate was determined

  3. Characterization and sintering of niobium-ATR alumina

    International Nuclear Information System (INIS)

    Sibuya, N.H.; Iwasaki, H.; Suzuki, C.K.; Pinatti, D.G.

    1987-01-01

    In the niobium aluminothermy a slag is produced, composed mostly of alumina and other compounds such as niobium oxide and silica. The phase composition of this ATR alumina was characterized by X-ray powder diffractometry, and afterwards this alumina was subjected to leaching processes. It was noticed that the original content of 70% α-alumina in slag rose to 95% after the calcination. ATR alumina (leached and calcined, and without any treatment) was used to make pressed bodies which were fired in air at 1200 to 1400 0 C for 1 to 10,5 hours; and in vacuum at 1550 to 1800$0C for 2 hours. Characterization was done by density measurements, X-ray diffractometry and ultrasonic analysis. Ultrasonic analysis of some vacuum fired bodies showed londitudinal velocities close to the value found in literature. Correlation of several techniques measurements disclosed the niobium oxide interference in sintering. (Author) [pt

  4. 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....

  5. 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

    -containing intermetallic particles incorporated into the anodic oxide films on industrially pure aluminium (AA1050, 99.5 per cent) has been investigated. AA1050 aluminium was anodized in a 100?ml/l sulphuric acid bath with an applied voltage of 14?V at 20°C ±2°C for 10 or 120?min. The anodic film subsequently was analyzed......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......-shaped particles were embedded in the anodic oxide film as a thin strip structure and located near the top surface of the film, whereas the round-shaped particles were trapped in the film with a spherical structure, but partially dissolved and were located throughout the thickness of the anodic film. The Fe...

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

    International Nuclear Information System (INIS)

    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/dm 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.

  7. Mechanism of anodic oxidation of molybdenum and tungsten in nitrate-nitrite melts

    International Nuclear Information System (INIS)

    Yurkinskij, V.P.; Firsova, E.G.; Morachevskij, A.G.

    1987-01-01

    The mechanism of anode oxidation of tungsten and molybdenum in NaNO 3 -KNO 3 (50 mass %) nitrate-nitrite melts with NaNO 2 -KNO 2 (0.5-50 mass %) addition and in NaNO 2 -KNO 2 (35 mole %) nitrite melt in the 516-580 K temperature range is studied. It is supposed that the process of anode dissloving of the mentioned metals in nitrite melt and nitrate-nitrite mixtures is two-electron. Formation of oxide passivating film is possible under electrolysis on the anode surface, the film is then dissolved in nitrate-nitrite melt with formation of molybdates or tungstates

  8. The thermomechanical stability of micro-solid oxide fuel cells fabricated on anodized aluminum oxide membranes

    Science.gov (United States)

    Kwon, Chang-Woo; Lee, Jae-Il; Kim, Ki-Bum; Lee, Hae-Weon; Lee, Jong-Ho; Son, Ji-Won

    2012-07-01

    The thermomechanical stability of micro-solid oxide fuel cells (micro-SOFCs) fabricated on an anodized aluminum oxide (AAO) membrane template is investigated. The full structure consists of the following layers: AAO membrane (600 nm)/Pt anode/YSZ electrolyte (900 nm)/porous Pt cathode. The utilization of a 600-nm-thick AAO membrane significantly improves the thermomechanical stability due to its well-known honeycomb-shaped nanopore structure. Moreover, the Pt anode layer deposited in between the AAO membrane and the YSZ electrolyte preserves its integrity in terms of maintaining the triple-phase boundary (TPB) and electrical conductivity during high-temperature operation. Both of these results guarantee thermomechanical stability of the micro-SOFC and extend the cell lifetime, which is one of the most critical issues in the fabrication of freestanding membrane-type micro-SOFCs.

  9. Optoelectronic properties of valence-state-controlled amorphous niobium oxide

    Science.gov (United States)

    Onozato, Takaki; Katase, Takayoshi; Yamamoto, Akira; Katayama, Shota; Matsushima, Koichi; Itagaki, Naho; Yoshida, Hisao; Ohta, Hiromichi

    2016-06-01

    In order to understand the optoelectronic properties of amorphous niobium oxide (a-NbO x ), we have investigated the valence states, local structures, electrical resistivity, and optical absorption of a-NbO x thin films with various oxygen contents. It was found that the valence states of Nb ion in a-NbO x films can be controlled from 5+  to 4+  by reducing oxygen pressure during film deposition at room temperature, together with changing the oxide-ion arrangement around Nb ion from Nb2O5-like to NbO2-like local structure. As a result, a four orders of magnitude reduction in the electrical resistivity of a-NbO x films was observed with decreasing oxygen content, due to the carrier generation caused by the appearance and increase of an oxygen-vacancy-related subgap state working as an electron donor. The tunable optoelectronic properties of a-NbO x films by valence-state-control with oxygen-vacancy formation will be useful for potential flexible optoelectronic device applications.

  10. Nano-porous anodic aluminium oxide membranes with 6-19 nm pore diameters formed by a low-potential anodizing process

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Fan; Liu Xiaohua; Pan Caofeng; Zhu Jing [Beijing National Center for Electron Microscopy, Tsinghua University, Beijing 100084 (China); Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2007-08-29

    Self-organized nano-porous anodic aluminium oxide (AAO) membranes with small pore diameters were obtained by applying a low anodizing potential in sulfuric acid solutions. The pore diameters of the as-prepared AAO membranes were in the range of about 6-19 nm and the interpore distances were about 20-58 nm. Low potentials (6-18 V) were applied in anodizing processes to make such small pores. A linear relationship between the anodizing potential (U{sub a}) and the interpore distance (D{sub int}) was also revealed. By carefully monitoring the current density's evolution as a function of time with different U{sub a} (2-18 V) during the anodizing processes, a new formula is proposed to simulate the self-ordering anodizing process.

  11. 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.

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

    KAUST Repository

    Li, Cheng Chao; Dou, Jian; Chen, Luwei; Lin, Jianyi; Zeng, Hua Chun

    2012-01-01

    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.

  13. 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.

  14. 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.

  15. Selection of a Commercial Anode Oxide Coating for Electro-oxidation of Cyanide

    Directory of Open Access Journals (Sweden)

    Lanza Marcos Roberto V.

    2002-01-01

    Full Text Available This paper presents a study of the performance of two commercial dimensionally stable anode (DSA® oxide coatings in the electrochemical process for cyanide oxidation. The coatings studied were 70TiO2/30RuO2 and 55Ta2O5/45IrO2, on Ti substrate. The efficiency of both materials in the electro-oxidation of free cyanide was compared using linear voltammetry and electrolysis at constant potential. The 70TiO2/30RuO2 electrode shows a better performance in the electro-oxidation of free cyanide.

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

    Science.gov (United States)

    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.

  17. Thermal diffusivity of alumina-zirconia sintered with niobium additions

    International Nuclear Information System (INIS)

    Santos, W.N. dos; Paulin Filho, P.I.; Taylor, R.

    1994-01-01

    The effect of niobium oxide addition on the alumina-zirconia thermal diffusivity was investigated from 100 0 C to 1000 0 C by the laser flash method. It was observed that 4 to 6% addition of niobium oxide increases the thermal diffusivity when samples were sintered at 1450 0 C. This effect was due to elimination of porosity by formation of liquid please above 1420 0 C in the Al 2 O 3 - Nb 2 O 5 system. (author). 7 refs., 3 figs

  18. Corrosion of niobium and niobium alloys

    International Nuclear Information System (INIS)

    Yau, T.L.; Webster, R.T.

    1987-01-01

    Niobium and niobium alloys are used in several corrosion-resistant applications, principally rocket and jet engines, nuclear reactors, sodium vapor highway lighting, and chemical-processing equipment. Niobium has many of the same properties of tantalum, its sister metal, but has one half the density of tantalum (see the article ''Corrosion of Tantalum'' in this Volume). A common property of niobium and tantalum is the interaction with the reactive elements hydrogen, oxygen, nitrogen, and carbon at temperatures above 300 0 C (570 0 F). These reactions will cause severe embrittlement. Consequently, at elevated temperatures, the metal must be protectively coated or used in vacuum or inert atmospheres. Niobium resists a wide variety of corrosive environments, including concentrated mineral acids, organic acids, liquid metals (particularly sodium and lithium), metal vapors, and molten salts

  19. Diffusion of oxygen in niobium during bake-out

    CERN Document Server

    Calatroni, Sergio; Ruzinov, V

    2001-01-01

    Bake-outs at temperatures between 100 C and 150 C for a duration up to two days have become customary for optimising the performance of bulk niobium cavities. This treatment results in the diffusion of oxygen, originating from the surface oxide, into the niobium. The theoretical oxygen profile has been simulated using the diffusion equations, and compared with some experimental results.

  20. Diffusion of oxygen in niobium during bake-out

    International Nuclear Information System (INIS)

    Benvenuti, C.; Calatroni, S.; Ruzinov, V.

    2003-01-01

    Bake-outs at temperatures between 100 degC and 150 degC for duration up to two days have become customary for optimising the performance of bulk niobium cavities. This treatment results in the diffusion of oxygen, originating from the surface oxide, into the niobium. The theoretical oxygen profile has been simulated using the diffusion equations, and compared with some experimental results. (author)

  1. 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...

  2. Electrochemical Energy Storage Applications of CVD Grown Niobium Oxide Thin Films.

    Science.gov (United States)

    Fiz, Raquel; Appel, Linus; Gutiérrez-Pardo, Antonio; Ramírez-Rico, Joaquín; Mathur, Sanjay

    2016-08-24

    We report here on the controlled synthesis, characterization, and electrochemical properties of different polymorphs of niobium pentoxide grown by CVD of new single-source precursors. Nb2O5 films deposited at different temperatures showed systematic phase evolution from low-temperature tetragonal (TT-Nb2O5, T-Nb2O5) to high temperature monoclinic modifications (H-Nb2O5). Optimization of the precursor flux and substrate temperature enabled phase-selective growth of Nb2O5 nanorods and films on conductive mesoporous biomorphic carbon matrices (BioC). Nb2O5 thin films deposited on monolithic BioC scaffolds produced composite materials integrating the high surface area and conductivity of the carbonaceous matrix with the intrinsically high capacitance of nanostructured niobium oxide. Heterojunctions in Nb2O5/BioC composites were found to be beneficial in electrochemical capacitance. Electrochemical characterization of Nb2O5/BioC composites showed that small amounts of Nb2O5 (as low as 5%) in conjunction with BioCarbon resulted in a 7-fold increase in the electrode capacitance, from 15 to 104 F g(-1), while imparting good cycling stability, making these materials ideally suited for electrochemical energy storage applications.

  3. Effects of anodizing conditions and annealing temperature on the morphology and crystalline structure of anodic oxide layers grown on iron

    Science.gov (United States)

    Pawlik, Anna; Hnida, Katarzyna; Socha, Robert P.; Wiercigroch, Ewelina; Małek, Kamilla; Sulka, Grzegorz D.

    2017-12-01

    Anodic iron oxide layers were formed by anodization of the iron foil in an ethylene glycol-based electrolyte containing 0.2 M NH4F and 0.5 M H2O at 40 V for 1 h. The anodizing conditions such as electrolyte composition and applied potential were optimized. In order to examine the influence of electrolyte stirring and applied magnetic field, the anodic samples were prepared under the dynamic and static conditions in the presence or absence of magnetic field. It was shown that ordered iron oxide nanopore arrays could be obtained at lower anodizing temperatures (10 and 20 °C) at the static conditions without the magnetic field or at the dynamic conditions with the applied magnetic field. Since the as-prepared anodic layers are amorphous in nature, the samples were annealed in air at different temperatures (200-500 °C) for a fixed duration of time (1 h). The morphology and crystal phases developed after anodization and subsequent annealing were characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The results proved that the annealing process transforms the amorphous layer into magnetite and hematite phases. In addition, the heat treatment results in a substantial decrease in the fluorine content and increase in the oxygen content.

  4. Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns

    Directory of Open Access Journals (Sweden)

    M. BastaniNejad

    2012-08-01

    Full Text Available The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirrorlike finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain, and two fine-grain that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field emission from electrodes (stainless steel and/or niobium could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (<10  pA at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18.7  MV/m.

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

    Science.gov (United States)

    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. 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.

  7. Multi-metallic anodes for solid oxide fuel cell applications

    International Nuclear Information System (INIS)

    Restivo, T.A. Guisard; Mello-Castanho, S.R.H.; Leite, D. Will

    2009-01-01

    A new method for direct preparation of materials for solid oxide fuel cell anode - Ni- YSZ cermets - based on mechanical alloying (MA) of the original powders is developed, allowing to admix homogeneously any component. Additive metals are selected from thermodynamic criteria, leading to compacts consolidation through sintering by activated surface (SAS). The combined process MA-SSA can reduce the sintering temperature by 300 deg C, yielding porous anodes. Densification mechanisms are discussed from quasi-isothermal sintering kinetics results. Doping with Ag, W, Cu, Mo, Nb, Ta, in descending order, promotes the densification of pellets through liquid phase sintering and evaporation of metals and oxides, which allow reducing the sintering temperature. Powders and pellets characterization by electronic microscopy and X-ray diffraction completes the result analyses. (author)

  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. Change in high field Q-slope by baking and anodizing

    Energy Technology Data Exchange (ETDEWEB)

    Eremeev, G. [LEPP, Cornell University, Ithaca, NY 14853 (United States); Padamsee, H. [LEPP, Cornell University, Ithaca, NY 14853 (United States)

    2006-07-15

    Low temperature RF performance of two niobium cavities that underwent different chemical treatments was measured after they were heat treated at 100 deg, C for 48 h. After heat treatment cavities were anodized in ammonia hydroxide solution for sequentially increasing voltage until baking effect was gone. The thickness of niobium finally consumed is estimated to be 20 nm. The results are discussed in view of one of the current models for the baking effect on the high field Q-slope.

  10. Structural transformation of nickel hydroxide films during anodic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Crocker, Robert W. [Univ. of California, Berkeley, CA (United States); Muller, Rolf H. [Univ. of California, Berkeley, CA (United States)

    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 - 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.

  11. 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.

  12. Structural-morphological variations in pseudo-barrier films of anode aluminium oxide under irradiation with high-energy particles

    International Nuclear Information System (INIS)

    Chernykh, M.A.; Belov, V.T.

    1988-01-01

    Comparative study of structural-morphological variations under electron beam effect in pseudo-barrier films of anode aluminium oxide, obtained in seven different solutions and proton or X-rays pre-irradiated to determine structure peculiarities of anode aluminium oxides, is presented. Such study is a matter of interest from the solid-phase transformation theory point of view and for anode aluminium films application under radiation. Stability increase of pseudo-barrier films of anode aluminium oxide to the effect of UEhMV-100 K microscope electron beam at standard modes of operation (75 kV) due to proton or X-rays irradiation is found. Difference in structural-monorphological variations obtained in different solutions of anode aluminium films under high-energy particles irradiation is determined. Strucural-phase microinhomogeneity of amorphous pseudo-barrier films of anode aluminium oxide and its influence on solid-phase transformations character under electron bean of maximal intensity are detected

  13. Niobium technological alternatives

    International Nuclear Information System (INIS)

    Pinatti, D.G.; Dainesi, C.R.

    1981-01-01

    The process-product matrix of Niobium is presented, through which the technological alternatives for Niobium are identified. It is shown that the three axes of Niobium application, steels, superalloys and metallic Niobium have a tendency to be economical by equivalent. The critical points where technological development of Niobium is needed are analyzed and results are presented on the following products: Nb 2 O 5 by volatilization, metalic Niobium, Niobium powder, bars and sheets, NbTi alloy, corrosion resistent Niobium alloys and superconductor cable and wires. (Author) [pt

  14. Analysis of the kinetics of methanol oxidation in a porous Pt-Ru anode

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yan-Ping; Xing, Lei [Chemical Engineering Department, Taiyuan University of Technology, Shanxi 030024 (China); Scott, Keith [School of Chemical Engineering and Advanced Materials, Merz Court, University of Newcastle, Newcastle upon Tyne NE1 7RU (United Kingdom)

    2010-01-01

    A kinetic model of a porous Pt-Ru anode for methanol oxidation is presented. It was based on the dual-site mechanism for methanol oxidation and used to predict anode performance and the influence of species adsorption on the overall oxidation (macro-) kinetics. The performance of the porous Pt-Ru anode depended on the parameters of the intrinsic chemical kinetics of methanol oxidation and physical parameters such as electrode thickness, surface area, effective diffusion and charge transfer coefficients and concentration of methanol and temperature. The model was solved by using the finite difference method with a subroutine for solving a set of nonlinear algebraic equations in each step. Surface coverage ratio distributions of adsorbed species, effectiveness of the porous electrode and macro-polarisation curves were obtained. The simulated polarisation curves were compared to experimental polarisation data for methanol oxidation on Pt-Ru porous anodes at different temperatures and methanol concentrations. The intrinsic kinetic parameters were regressed from the corresponding experimental data. The predicted polarisation curves calculated by the model, were consistent with experimental polarisation data at lower current densities. The departure of experimental data from the predicted polarisation curves at high concentration and high apparent current densities was believed to be due to two-phase flow in the electrode. (author)

  15. 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.

  16. Electrocatalysis of anodic oxidation of ethanol

    Science.gov (United States)

    Tarasevich, M. R.; Korchagin, O. V.; Kuzov, A. V.

    2013-11-01

    The results of fundamental and applied studies in the field of electrocatalysis of anodic oxidation of ethanol in fuel cells are considered. Features of the mechanism of ethanol electrooxidation are discussed as well as the structure and electrochemical properties of the most widely used catalysts of this process. The prospects of further studies of direct ethanol fuel cells with alkaline and acidic electrolytes are outlined. The bibliography includes 166 references.

  17. Electrocatalysis of anodic oxidation of ethanol

    International Nuclear Information System (INIS)

    Tarasevich, M R; Korchagin, O V; Kuzov, A V

    2013-01-01

    The results of fundamental and applied studies in the field of electrocatalysis of anodic oxidation of ethanol in fuel cells are considered. Features of the mechanism of ethanol electrooxidation are discussed as well as the structure and electrochemical properties of the most widely used catalysts of this process. The prospects of further studies of direct ethanol fuel cells with alkaline and acidic electrolytes are outlined. The bibliography includes 166 references

  18. 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.

  19. 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.

  20. Josephson tunnel junctions in niobium films

    International Nuclear Information System (INIS)

    Wiik, Tapio.

    1976-12-01

    A method of fabricating stable Josephson tunnel junctions with reproducible characteristics is described. The junctions have a sandwich structure consisting of a vacuum evaporated niobium film, a niobium oxide layer produced by the glow discharge method and a lead film deposited by vacuum evaporation. Difficulties in producing thin-film Josephson junctions are discussed. Experimental results suggest that the lower critical field of the niobium film is the most essential parameter when evaluating the quality of these junctions. The dependence of the lower critical field on the film thickness and on the Ginzburg-Landau parameter of the film is studied analytically. Comparison with the properties of the evaporated films and with the previous calculations for bulk specimens shows that the presented model is applicable for most of the prepared samples. (author)

  1. 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.

  2. THE USE OF /cap beta/-SPECTROSCOPY FOR THE STUDY OF ANODIC OXIDATION

    Energy Technology Data Exchange (ETDEWEB)

    Pringle, J. P.S.; Davies, J. A.

    1964-04-15

    Anodic oxidation of metal foils can be studied by injectin Xe/sup 125/ atoms into the foils, measuring the beta spectrum, anodi-zing the foils, and measuring the beta spectrum again Calibration of the method was achieved by injecting Xe/sup 125/ into Al and W foils. The method was applied to the anodization of W, Nb, Ta, and Al, and the reasons for the discrepancies are discussed. (D.L.C.)

  3. Pore-scale investigation of mass transport and electrochemistry in a solid oxide fuel cell anode

    Energy Technology Data Exchange (ETDEWEB)

    Grew, Kyle N.; Joshi, Abhijit S.; Peracchio, Aldo A.; Chiu, Wilson K.S. [Department of Mechanical Engineering, University of Connecticut, 191 Auditorium Road, Storrs, CT 06269-3139 (United States)

    2010-04-15

    The development and validation of a model for the study of pore-scale transport phenomena and electrochemistry in a Solid Oxide Fuel Cell (SOFC) anode are presented in this work. This model couples mass transport processes with a detailed reaction mechanism, which is used to model the electrochemical oxidation kinetics. Detailed electrochemical oxidation reaction kinetics, which is known to occur in the vicinity of the three-phase boundary (TPB) interfaces, is discretely considered in this work. The TPB regions connect percolating regions of electronic and ionic conducting phases of the anode, nickel (Ni) and yttria-stabilized zirconia (YSZ), respectively; with porous regions supporting mass transport of the fuel and product. A two-dimensional (2D), multi-species lattice Boltzmann method (LBM) is used to describe the diffusion process in complex pore structures that are representative of the SOFC anode. This diffusion model is discretely coupled to a kinetic electrochemical oxidation mechanism using localized flux boundary conditions. The details of the oxidation kinetics are prescribed as a function of applied activation overpotential and the localized hydrogen and water mole fractions. This development effort is aimed at understanding the effects of the anode microstructure within TPB regions. This work describes the methods used so that future studies can consider the details of SOFC anode microstructure. (author)

  4. 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

  5. Effect of niobium addition in support catalysts applied in satellite propulsion

    Energy Technology Data Exchange (ETDEWEB)

    Soares, M.S., E-mail: marciosteinmetz@hotmail.com.br [Space Research National Institute, Combustion & Propulsion Associated Laboratory (Brazil); University of São Paulo, Lorena Engineering School, Materials Engineering Dept. (Brazil); Barbosa, R.D. [Space Research National Institute, Combustion & Propulsion Associated Laboratory (Brazil); University of São Paulo, Lorena Engineering School, Chemical Engineering Dept. (Brazil); Cruz, G.M. da; Rodrigues, J.A.J. [Space Research National Institute, Combustion & Propulsion Associated Laboratory (Brazil); Ribeiro, S. [University of São Paulo, Lorena Engineering School, Materials Engineering Dept. (Brazil)

    2017-03-01

    Catalysts composed of iridium as the active phase dispersed in aluminum oxide (Ir/Al{sub 2}O{sub 3}) are used in propulsion systems that employ hydrazine as monopropellant in the control of satellite orbit and attitude. The aluminum oxide (Al{sub 2}O{sub 3}) utilized as support must present high values of specific surface area, pore volume, and crush strength. The niobium effect was evaluated in this work, in its oxide form (Nb{sub 2}O{sub 5}), by 3 different methods: with the employment of a NbCl{sub 5} precursor solution, by wet impregnation and dry impregnation of an alumina obtained from a mixture of gibbsite and boehmite and by physical mixing of gibbsite and hydrated niobium oxide, both autoclaved separately. Aluminum oxides were prepared in both cases containing Nb{sub 2}O{sub 5} contents of 10, 20, and 30% w/w. The acid impregnating NbCl{sub 5} solution in the wet impregnation method caused a strong attack to the Al{sub 2}O{sub 3} support, altering and compromising its initial structure and morphology. This process did not occur in the supports prepared by dry impregnation. However, results indicated that the use of this methodology with Nb{sub 2}O{sub 5} contents of 20% and 30%, caused an extensive coverage of the support by Nb{sub 2}O{sub 5}, modifying the nature and amount of alumina sites responsible for anchorage of the iridium precursor. In the case of supports prepared through physical mixture (Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3}) from aluminum hydroxide and niobium acid precursor compounds, with both being previously autoclaved separately, the 20% and 30% Nb{sub 2}O{sub 5} contents presented the most promising properties, since the binder effect caused by amorphous Nb{sub 2}O{sub 5} increased the crush strength of the support, without compromising the aluminum oxide morphology and texture. Despite of existence of stronger acid sites due to the addition of niobium oxide to aluminum oxide, no increase in the acidity of the materials was observed due

  6. 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.

  7. Dielectric breakdown and healing of anodic oxide films on aluminium under single pulse anodizing

    International Nuclear Information System (INIS)

    Sah, Santosh Prasad; Tatsuno, Yasuhiro; Aoki, Yoshitaka; Habazaki, Hiroki

    2011-01-01

    Research highlights: → We examined dielectric breakdown of anodic alumina by single pulse anodizing. → Current transients and morphology of discharge channels are dependent upon electrolyte and voltage. → There is a good correlation between current transient and morphology of discharge channel. → Healing of open discharge pores occurs in alkaline silicate, but not in pentaborate electrolyte. - Abstract: Single pulse anodizing of aluminium micro-electrode has been employed to study the behaviour of dielectric breakdown and subsequent oxide formation on aluminium in alkaline silicate and pentaborate electrolytes. Current transients during applying pulse voltage have been measured, and surface has been observed by scanning electron microscopy. Two types of current transients are observed, depending on the electrolyte and applied voltage. There is a good correlation between the current transient behaviour and the shape of discharge channels. In alkaline silicate electrolyte, circular open pores are healed by increasing the pulse width, but such healing is not obvious in pentaborate electrolyte.

  8. Proposal of a new biokinetic model for niobium

    International Nuclear Information System (INIS)

    Oliveira, Roges

    2006-01-01

    There are two niobium isotopes generated in nuclear power plants: 95 Nb and 94 Nb. Workers and members of the public are subjects to intake these radionuclides in accident situation. For dose calculation purpose, it is very important to develop a model that describes in a more realistic way the kinetics of niobium inside of the human body. Presently the model adopted by ICRP (ICRP, 1989) is based on animal studies and describes the behavior of niobium in human being in a simple manner. The new model proposal describes the kinetics of the niobium from the intake into the blood until the excretion, doing this in a more realistic form and considering not only data from animals but data from human beings as well. For this objective, a workers group of a niobium extraction and processing industry exposed to stable niobium (93 Nb) in oxide insoluble form with associated uranium, was monitored for uranium and niobium determination in urinary and fecal excretion, by mass spectrometry. Based in the ratios of the niobium concentration in urinary and faecal excretion of this workers and animal data study, a new biokinetic model for niobium was proposed, with the followings modifications relative to ICRP model: a new compartment that represents muscular tissue; the fractions which are deposited into the compartment are modified; a third component in the retention equation of the bone tissue; introduction of recirculation between organs and blood. The new model was applied for a case of accidental intake and described adequately the experimental data

  9. Thermal imaging of solid oxide fuel cell anode processes

    Energy Technology Data Exchange (ETDEWEB)

    Pomfret, Michael B.; Kidwell, David A.; Owrutsky, Jeffrey C. [Chemistry Division, U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Steinhurst, Daniel A. [Nova Research Inc., Alexandria, VA 22308 (United States)

    2010-01-01

    A Si-charge-coupled device (CCD), camera-based, near-infrared imaging system is demonstrated on Ni/yttria-stabilized zirconia (YSZ) fragments and the anodes of working solid oxide fuel cells (SOFCs). NiO reduction to Ni by H{sub 2} and carbon deposition lead to the fragment cooling by 5 {+-} 2 C and 16 {+-} 1 C, respectively. When air is flowed over the fragments, the temperature rises 24 {+-} 1 C as carbon and Ni are oxidized. In an operational SOFC, the decrease in temperature with carbon deposition is only 4.0 {+-} 0.1 C as the process is moderated by the presence of oxides and water. Electrochemical oxidation of carbon deposits results in a {delta}T of +2.2 {+-} 0.2 C, demonstrating that electrochemical oxidation is less vigorous than atmospheric oxidation. While the high temperatures of SOFCs are challenging in many respects, they facilitate thermal imaging because their emission overlaps the spectral response of inexpensive Si-CCD cameras. Using Si-CCD cameras has advantages in terms of cost, resolution, and convenience compared to mid-infrared thermal cameras. High spatial ({proportional_to}0.1 mm) and temperature ({proportional_to}0.1 C) resolutions are achieved in this system. This approach provides a convenient and effective analytical technique for investigating the effects of anode chemistry in operating SOFCs. (author)

  10. Thermal imaging of solid oxide fuel cell anode processes

    Science.gov (United States)

    Pomfret, Michael B.; Steinhurst, Daniel A.; Kidwell, David A.; Owrutsky, Jeffrey C.

    A Si-charge-coupled device (CCD), camera-based, near-infrared imaging system is demonstrated on Ni/yttria-stabilized zirconia (YSZ) fragments and the anodes of working solid oxide fuel cells (SOFCs). NiO reduction to Ni by H 2 and carbon deposition lead to the fragment cooling by 5 ± 2 °C and 16 ± 1 °C, respectively. When air is flowed over the fragments, the temperature rises 24 ± 1 °C as carbon and Ni are oxidized. In an operational SOFC, the decrease in temperature with carbon deposition is only 4.0 ± 0.1 °C as the process is moderated by the presence of oxides and water. Electrochemical oxidation of carbon deposits results in a Δ T of +2.2 ± 0.2 °C, demonstrating that electrochemical oxidation is less vigorous than atmospheric oxidation. While the high temperatures of SOFCs are challenging in many respects, they facilitate thermal imaging because their emission overlaps the spectral response of inexpensive Si-CCD cameras. Using Si-CCD cameras has advantages in terms of cost, resolution, and convenience compared to mid-infrared thermal cameras. High spatial (∼0.1 mm) and temperature (∼0.1 °C) resolutions are achieved in this system. This approach provides a convenient and effective analytical technique for investigating the effects of anode chemistry in operating SOFCs.

  11. 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 LiC 6 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.

  12. Fabrication of Anodic Porous Alumina by Squaric Acid Anodizing

    OpenAIRE

    Kikuchi, Tatsuya; Yamamoto, Tsuyoshi; Natsui, Shungo; Suzuki, Ryosuke O.

    2014-01-01

    The growth behavior of anodic porous alumina formed via anodizing in a new electrolyte, squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione), is reported for the first time. A high-purity aluminum foil was anodized in a 0.1 M squaric acid solution at 293 K and a constant applied potential of 100-150 V. Anodic oxides grew on the aluminum foil at applied potentials of 100-120 V, but a burned oxide film was formed at higher voltage. Anodic porous alumina with a cell size of approximately 200-400...

  13. Structural and morphological changes in pseudobarrier films of anodic aluminum oxide caused by irradiation with high-energy particles

    International Nuclear Information System (INIS)

    Chernykh, M.A.; Belov, V.T.

    1988-01-01

    We have studied the structural and morphological changes, occurring under the electron beam in pseudobarrier films of anodic aluminum oxide, prepared in seven different solutions and irradiated beforehand by protons of x-rays, with the aim of elucidating the structure of anodic aluminum oxides. An increased stability of the pseudobarrier films of anodic aluminum oxide has been observed towards the action of the electron beam of an UEMV-100K microscope at standard working regimes (75 keV) as a result of irradiation with protons or x-rays. A difference has been found to exist between structural and morphological changes of anodic aluminum oxide films, prepared in different solutions, when irradiated with high-energy particles. A structural and phase inhomogeneity of amorphous pseudobarrier films of anodic aluminum oxide has been detected and its influence on the character of solid-phase transformations under the maximum-intensity electron beam

  14. Electronic properties of electrolyte/anodic alumina junction during porous anodizing

    Energy Technology Data Exchange (ETDEWEB)

    Vrublevsky, I. [Department of Microelectronics, Belarusian State University of Informatics and Radioelectronics, 6 Brovka Street, Minsk 220013 (Belarus)]. E-mail: nil-4-2@bsuir.edu.by; Jagminas, A. [Institute of Chemistry, A. Gostauto 9, LT-01108 Vilnius (Lithuania); Schreckenbach, J. [Institut fuer Chemie, Technische Universitaet Chemnitz, Chemnitz D-09107 (Germany); InnoMat GmbH, Chemnitz (Germany); Goedel, Werner A. [Institut fuer Chemie, Technische Universitaet Chemnitz, Chemnitz D-09107 (Germany)

    2007-03-15

    The growth of porous oxide films on aluminum (99.99% purity), formed in 4% phosphoric acid was studied as a function of the anodizing voltage (23-53 V) using a re-anodizing technique and transmission electron microscopy (TEM) study. The chemical dissolution behavior of freshly anodized and annealed at 200 deg. C porous alumina films was studied. The obtained results indicate that porous alumina has n-type semiconductive behavior during anodizing in 4% phosphoric acid. During anodising, up to 39 V in the barrier layer of porous films, one obtains an accumulation layer (the thickness does not exceed 1 nm) where the excess electrons have been injected into the solid producing a downward bending of the conductive and valence band towards the interface. The charge on the surface of anodic oxide is negative and decreases with growing anodizing voltage. At the anodizing voltage of about 39 V, the charge on the surface of anodic oxide equals to zero. Above 39 V, anodic alumina/electrolyte junction injects protons from the electrolyte. These immobile positive charges in the surface layer of oxide together with an ionic layer of hydroxyl ions concentrated near the interface create a field, which produces an upward bending of the bands.

  15. Technological challenges in extractive metallurgy and refining of niobium, tantalum and preparation of their alloys

    International Nuclear Information System (INIS)

    Mirji, K.V.; Sheela; Saibaba, N.

    2016-01-01

    Manufacturing of refractory and reactive metals, their alloys and fabricated products has been always difficult due to their high affinity with atmospheric gases, stringent specifications and exhaustive quality requirements. In the field of development of these materials, Nuclear Fuel Complex (NFC), Hyderabad has been at the fore front in accepting the challenges for the advancement of technological growth. Extensive developments have been carried out during the last few decades in the field of niobium, tantalum, zirconium etc in the form of pure metal, their compounds and alloys. Over the period of time, efforts have been made for developing sophisticated facilities along with trained man power for manufacturing of critical items for which technical knowhow is not available either with private industries or any other organizations in the country. In the field of reactive metals, though general theory is well established, production is intriguing and requires expert handling on the field. At NFC, efforts were put towards industrial adoptability of the useful knowledge gained from lab scale to reliable production scale. Comprehensive study was conducted to systematically study the effects of various process parameters starting from ore to the metals and their alloys, equipment were modified for ease of operation with stress on recycling/reusing of the waste and handling of effluents. However scale of operation and therefore cost of production has been matter of concern in the field of tantalum and niobium. Electron beam refining is used for production of highly pure reactive and refractory metals like tantalum, niobium, zirconium etc. and their alloys under high vacuum. Special Materials Plant (SMP) at Nuclear Fuel Complex, Hyderabad has developed processes for production of niobium oxide, tantalum oxide, tantalum metal powder, tantalum anodes/capacitors, potassium tantalum fluoride, Nb thermit, Nb metal granules, RRR grade niobium, Nb base alloys such as Zr

  16. Experimental and Theoretical Studies on Corrosion Inhibition of Niobium and Tantalum Surfaces by Carboxylated Graphene Oxide

    Directory of Open Access Journals (Sweden)

    Valbonë Mehmeti

    2018-05-01

    Full Text Available The corrosion of two different metals, niobium and tantalum, in aqueous sulfuric acid solution has been studied in the presence and absence of carboxylated graphene oxide. Potentiodynamic measurements indicate that this nanomaterial inhibits corrosion due to its adsorption on the metal surfaces. The adsorbed layer of carboxylated graphene hinders two electrochemical reactions: the oxidation of the metal and the transport of metal ions from the metal to the solution but also hydrogen evolution reaction by acting as a protective barrier. The adsorption behavior at the molecular level of the carboxylated graphene oxide with respect to Nb, NbO, Ta, and TaO (111 surfaces is also investigated using Molecular Dynamic and Monte Carlo calculations.

  17. 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).

  18. Tantalum(V) impurity extraction by octanol from niobium(V) fluoride solutions

    International Nuclear Information System (INIS)

    Majorov, V.G.; Nikolaev, A.I.; Kopkov, V.K.

    2002-01-01

    The conditions of the niobium and tantalum extraction separation by octanol in the fluoride solutions, depending on the metals and free hydrofluoric acid concentration as well as on the organic and water phases voluminous relation, are studied for the purpose of developing the technology of niobium deep purification from the tantalum impurities. The technological scheme of the niobium solutions(V) extraction purification from the tantalum impurities(V), which provides for obtaining the niobium oxide(V), containing less than 0.005 mass % Ta 2 O 5 , is proposed on the basis of the established optimal separation conditions. The possibility of using the developed technology by the pyrochlore reprocessing is indicated [ru

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

    International Nuclear Information System (INIS)

    Huang, Jianming; Liu, Weifeng; Lv, Yong; Yao, Lianzeng

    2010-01-01

    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 3 PO 4 and 0.15 M H 2 CrO 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 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 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

  20. 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.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    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. (paper)

  2. 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.

  3. XPS characterization of the anodic oxide film formed on uranium metal in sodium hydroxide solution

    International Nuclear Information System (INIS)

    Fu Xiaoguo; Wang Xiaolin; Guo Huanjun; Wang Qingfu; Zhao Zhengping; Zhong Yongqiang

    2002-01-01

    X-ray photoelectron spectroscopy (XPS) is used to examine the anodic oxide film formed on uranium metal in 0.8 mol/L NaOH solution. The U4f 7/2 fitting spectra suggests that the anodic oxide film is composed of uranium trioxide and a small amount of UO 2+x . Under UHV condition, the U4f peak shifts to the lower binding energy, while a gradual increase in the intensity of U5f peak and the broad of U4f peak are also observed. All of these changes are due to reduction of uranium trioxide in the anodic oxide film. XPS quantitative analysis confirms the occurrence of reduction reaction

  4. Effect of Different Binders on the Electrochemical Performance of Metal Oxide Anode for Lithium-Ion Batteries

    Science.gov (United States)

    Wang, Rui; Feng, Lili; Yang, Wenrong; Zhang, Yinyin; Zhang, Yanli; Bai, Wei; Liu, Bo; Zhang, Wei; Chuan, Yongming; Zheng, Ziguang; Guan, Hongjin

    2017-10-01

    When testing the electrochemical performance of metal oxide anode for lithium-ion batteries (LIBs), binder played important role on the electrochemical performance. Which binder was more suitable for preparing transition metal oxides anodes of LIBs has not been systematically researched. Herein, five different binders such as polyvinylidene fluoride (PVDF) HSV900, PVDF 301F, PVDF Solvay5130, the mixture of styrene butadiene rubber and sodium carboxymethyl cellulose (SBR+CMC), and polyacrylonitrile (LA133) were studied to make anode electrodes (compared to the full battery). The electrochemical tests show that using SBR+CMC and LA133 binder which use water as solution were significantly better than PVDF. The SBR+CMC binder remarkably improve the bonding capacity, cycle stability, and rate performance of battery anode, and the capacity retention was about 87% after 50th cycle relative to the second cycle. SBR+CMC binder was more suitable for making transition metal oxides anodes of LIBs.

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

    International Nuclear Information System (INIS)

    Souza, Kellie Provazi de

    2006-01-01

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

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

    Science.gov (United States)

    2012-01-01

    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. PMID:23272786

  7. Hydrogen Oxidation Reaction at the Ni/YSZ Anode of Solid Oxide Fuel Cells from First Principles

    Science.gov (United States)

    Cucinotta, Clotilde S.; Bernasconi, Marco; Parrinello, Michele

    2011-11-01

    By means of ab initio simulations we here provide a comprehensive scenario for hydrogen oxidation reactions at the Ni/zirconia anode of solid oxide fuel cells. The simulations have also revealed that in the presence of water chemisorbed at the oxide surface, the active region for H oxidation actually extends beyond the metal/zirconia interface unraveling the role of water partial pressure in the decrease of the polarization resistance observed experimentally.

  8. Leakage Current Degradation Due to Ion Drift and Diffusion in Tantalum and Niobium Oxide Capacitors

    Directory of Open Access Journals (Sweden)

    Kuparowitz Martin

    2017-06-01

    Full Text Available High temperature and high electric field applications in tantalum and niobium capacitors are limited by the mechanism of ion migration and field crystallization in a tantalum or niobium pentoxide insulating layer. The study of leakage current (DCL variation in time as a result of increasing temperature and electric field might provide information about the physical mechanism of degradation. The experiments were performed on tantalum and niobium oxide capacitors at temperatures of about 125°C and applied voltages ranging up to rated voltages of 35 V and 16 V for tantalum and niobium oxide capacitors, respectively. Homogeneous distribution of oxygen vacancies acting as positive ions within the pentoxide layer was assumed before the experiments. DCL vs. time characteristics at a fixed temperature have several phases. At the beginning of ageing the DCL increases exponentially with time. In this period ions in the insulating layer are being moved in the electric field by drift only. Due to that the concentration of ions near the cathode increases producing a positively charged region near the cathode. The electric field near the cathode increases and the potential barrier between the cathode and insulating layer decreases which results in increasing DCL. However, redistribution of positive ions in the insulator layer leads to creation of a ion concentration gradient which results in a gradual increase of the ion diffusion current in the direction opposite to the ion drift current component. The equilibrium between the two for a given temperature and electric field results in saturation of the leakage current value. DCL vs. time characteristics are described by the exponential stretched law. We found that during the initial part of ageing an exponent n = 1 applies. That corresponds to the ion drift motion only. After long-time application of the electric field at a high temperature the DCL vs. time characteristics are described by the exponential

  9. 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.

  10. Anodic Aluminum Oxide Templates for Nano wires Array Fabrication

    International Nuclear Information System (INIS)

    Nur Ubaidah Saidin; Kok, K.Y.; Ng, I.K.

    2011-01-01

    This paper reports on the process developed to fabricate anodic aluminium oxide (AAO) templates suitable for the fabrication of nano wire arrays. Anodization process has been used to fabricate the AAO templates with pore diameters ranging from 15 nm to 30 nm. Electrodeposition of parallel arrays of high aspect ratio nickel nano wires were demonstrated using these fabricated AAO templates. The nano wires produced were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the orientations of the electrodeposited nickel nano wires were governed by the deposition current and electrolyte conditions. (author)

  11. 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. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Development of Carbon and Sulphur Tolerant Anodes of Solid Oxide Fuel Cells

    Science.gov (United States)

    2010-01-14

    Thus, in this Chapter we report a detail study of the electrode behavior of pure Ni/GDC and Ni/YSZ cermet anodes in weakly humidified H2 fuel...impedance behavior for the oxidation reaction in hydrogen, methane and ethanol over a pure and Pd-impregnated Ni/GDC anode of SOFC were also studied ...surfaces [1]. So Ni/YSZ based cermet anodes have a very low tolerance to fuels containing H2S even at a very low level (ppm) [2]. Thus, the development of

  13. Fabrication of free standing anodic titanium oxide membranes with clean surface using recycling process.

    Science.gov (United States)

    Meng, Xianhui; Lee, Tae-Young; Chen, Huiyu; Shin, Dong-Wook; Kwon, Kee-Won; Kwon, Sang Jik; Yoo, Ji-Beom

    2010-07-01

    Large area of self-organized, free standing anodic titanium oxide (ATO) nanotube membranes with clean surfaces were facilely prepared to desired lengths via electrochemical anodization of highly pure Ti sheets in an ethylene glycol electrolyte, with a small amount of NH4F and H2O at 50 V, followed by self-detachment of the ATO membrane from the Ti substrate using recycling processes. In the first anodization step, the nanowire oxide layer existed over the well-arranged ATO nanotube. After sufficiently rinsing with water, the whole ATO layer was removed from the Ti sheet by high pressure N2 gas, and a well-patterned dimple layer with a thickness of about 30 nm existed on the Ti substrate. By using these naturally formed nano-scale pits as templates, in the second and third anodization process, highly ordered, vertically aligned, and free standing ATO membranes with the anodic aluminum oxide (AAO)-like clean surface were obtained. The inter-pore distance and diameter was 154 +/- 2 nm and 91+/- 2 nm, the tube arrays lengths for 25 and 46 hours were 44 and 70 microm, respectively. The present study demonstrates a simple approach to producing high quality, length controllable, large area TiO2 membrane.

  14. 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.

  15. Anodic oxidation as a new practical procedure for water disinfection

    Energy Technology Data Exchange (ETDEWEB)

    Kirmaier, N; Schoeberl, M

    1980-05-01

    The anodic oxidation could be developed for practical purposes by extensive scientific investigations and engineering optimization. Its safe bactericide, virucide, fungicide and bacteriostatic effect combined with engineering advantages makes it an essential component for water processing.

  16. Fabrication of high quality ordered porous anodic aluminum oxide templates

    International Nuclear Information System (INIS)

    Liu Kai; Du Kai; Chen Jing; Zhou Lan; Zhang Lin; Fang Yu

    2010-01-01

    The preparation of porous anodic aluminum oxide (AAO) templates has been studied with oxalic acid as electrolyte. The morphology of the as-prepared templates has been characterized by field-emission scanning electron microscope (FE-SEM). The pores distributed orderly and uniformly with the diameter ranging from 40 nm to 70 nm. The experimental results indicate that electrolyte concentration, oxidation voltage, oxidation temperature and oxidation time affect the structure of AAO templates. Ordered porous AAO templates can be derived without annealing and finishing. X-ray diffraction (XRD) analysis indicates that the aluminum oxide film is mainly composed of amorphous Al 2 O 3 . (authors)

  17. 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.

  18. Research progress in formation mechanism of anodizing aluminum oxide

    Science.gov (United States)

    Lv, Yudong

    2017-12-01

    The self-ordering porous anodizing aluminum oxide (AAO) has attracted much attention because of its potential value of application. Valve metals (Al, Ti, Zr etc.) anodic studies have been conducted for more than 80 years, but the mechanism of the formation of hexagonal prismatic cell structure has so far been different. In this paper, the research results of AAO film formation mechanism are reviewed, and the growth models of several AAO films are summarized, including the field-assisted dissolution (FAD), the viscous flow model, the critical current density effect model, the bulk expansion stress model and the steady-state pore growth model and so on. It analyzed the principle of each model and its rationality. This paper will be of great help to reveal the nature of pore formation and self-ordering, and with the hope that through the study of AAO film formation mechanism, the specific effects of various oxidation parameters on AAO film morphology can be obtained.

  19. Dehydration of xylose to furfural over MCM-41-supported niobium-oxide catalysts.

    Science.gov (United States)

    García-Sancho, Cristina; Sádaba, Irantzu; Moreno-Tost, Ramón; Mérida-Robles, Josefa; Santamaría-González, José; López-Granados, Manuel; Maireles-Torres, Pedro

    2013-04-01

    A series of silica-based MCM-41-supported niobium-oxide catalysts are prepared, characterized by using XRD, N2 adsorption-desorption, X-ray photoelectron spectroscopy, Raman spectroscopy, and pyridine adsorption coupled to FTIR spectroscopy, and tested for the dehydration of D-xylose to furfural. Under the operating conditions used all materials are active in the dehydration of xylose to furfural (excluding the MCM-41 silica support). The xylose conversion increases with increasing Nb2 O5 content. At a loading of 16 wt % Nb2 O5 , 74.5 % conversion and a furfural yield of 36.5 % is achieved at 170 °C, after 180 min reaction time. Moreover, xylose conversion and furfural yield increase with the reaction time and temperature, attaining 82.8 and 46.2 %, respectively, at 190 °C and after 100 min reaction time. Notably, the presence of NaCl in the reaction medium further increases the furfural yield (59.9 % at 170 °C after 180 min reaction time). Moreover, catalyst reutilization is demonstrated by performing at least three runs with no loss of catalytic activity and without the requirement for an intermediate regeneration step. No significant niobium leaching is observed, and a relationship between the structure of the catalyst and the activity is proposed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Formation and dissolution of the anodic oxide film on zirconium in alcoholic aqueous solutions

    International Nuclear Information System (INIS)

    Mogoda, A.S.

    1995-01-01

    The dissolution behavior of the anodic oxide film formed in alcoholic aqueous solutions was studied. Results indicated the dissolution mechanism of the duplex oxide film followed a zero-order rate equation. The increase in methanol concentration in the formation medium (phosphoric acid [H 3 PO 4 ]) resulted in formation of an oxide film that incorporated little phosphate ion and that dissolved at a low rate. The dissolution rate of the oxide film decreased with increasing methanol concentration in the dissolution medium. This was attributed to the increase in the viscosity of the medium, which led to a decrease in the diffusion coefficient of the dissolution product of the zirconium oxide film. Dissolution of the anodic oxide film also was investigated as a function of the chain length of alcohols

  1. An Indium-Free Anode for Large-Area Flexible OLEDs: Defect-Free Transparent Conductive Zinc Tin Oxide

    NARCIS (Netherlands)

    Morales-Masis, M.; Dauzou, F.; Jeangros, Q.; Dabirian, A.; Lifka, H.; Gierth, R.; Ruske, M.; Moet, D.; Hessler-Wyser, A.; Ballif, C.

    2016-01-01

    Flexible large-area organic light-emitting diodes (OLEDs) require highly conductive and transparent anodes for efficient and uniform light emission. Tin-doped indium oxide (ITO) is the standard anode in industry. However, due to the scarcity of indium, alternative anodes that eliminate its use are

  2. Stability, characterization and functionality of proton conducting NiO–BaCe0.85−xNbxY0.15O3−δ cermet anodes for IT-SOFC application

    International Nuclear Information System (INIS)

    Žunić, Milan; Branković, Goran; Basoli, Francesco; Cilense, Mario; Longo, Elson; Varela, José Arana

    2014-01-01

    Highlights: • The influence niobium concentration on properties of anode substrates was investigated. • The cermet anode powders were obtained without any undesirable phases. • Porous anode substrates showed chemical stability in the CO 2 atmosphere. • Conductivity values of reduced anode samples were σ * > 50 S cm −1 . • Fuel cell tests demonstrated functionality of anode substrates. - Abstract: There are many of properties of anodes based on proton conductors, like microstructure, conductivity and chemical stability, which should be optimized. In this work we were dealing with the influence of niobium on the chemical stability, microstructural and electrical characteristics of proton conducting NiO–BaCe 0.85−x Nb x Y 0.15 O 3−δ (NiO–BCNYx) anodes. Four anode substrates NiO–BCNYx of different Nb concentration were prepared using the method of evaporation and decomposition of solutions and suspensions (EDSS). Sintered anode substrates were reduced and their microstructural and electrical properties were examined before and after reduction as a function of the amount of niobium. Chemical stability tests showed strong influence of Nb amount on the chemical stability of anodes in the CO 2 . Microstructural properties of the anode pellets before and after testing in CO 2 were investigated using X-ray diffraction analysis. Electrical properties of anode samples were examined by impedance spectroscopy measurements and the conductivity values of reduced anodes were more than 50 S cm −1 at 600 °C confirming percolation through Ni particles. Fuel cells were fabricated with aim to examine the functionality of anodes. During the fuel cell test the cell with Ni–BCNY10 anode achieved the highest performance, demonstrating a peak power density of 164 mW cm −2 at 650 °C, which confirmed the functionality of Ni–BCNY anodes

  3. Effects of Alclad Layer and Anodizing Time on Sulfuric Acid Anodizing and Film Properties of 2E12 Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    CHEN Gao-hong

    2017-07-01

    Full Text Available Alclad and unclad 2E12 aerospace aluminum alloy were treated by sulfuric acid anodic oxidation. The effects of alclad layer and anodizing time on the anodization behaviour and corrosion resistance of anodic oxide layer on 2E12 aluminum alloy were studied. Surface and cross-section morphology of anodic oxide films were observed by scanning electron microscopy. The electrochemical properties of anodic oxide films were analyzed by potentiodynamic polarization curve and electrochemical impedance spectroscopy. The results show that the protective anodic oxide layers are formed on alclad and unclad 2E12 aluminum alloy. The film thickness increases with anodizing time extending. The copper rich second phase particles lead to more cavity defects and even micro cracks on anodic oxide films of unclad 2E12 aluminum alloy. The anodic oxide films on alclad 2E12 aluminum alloy are thicker and have fewer cavity defects, resulting in better corrosion resistance. The films obtained after 30min and 45min anodic oxidation treatment exhibit lower corrosion current and higher impedance of the porous layer than other anodizing time.

  4. 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. 6.67μM As(III) in synthetic groundwater was completely oxidized to As(V) within 60min at 50mA. Direct electron transfer was mainly responsible at the current below 30mA, while hydroxyl radicals contributed increasingly with the increase in the current above 30mA. As(III) oxidation was moderately inhibited by the presence of bicarbonate (20mM), while was dramatically increased with increasing the concentration of chloride (0-10mM). 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Hydrogen traps in the oxide/alloy interface region of Zr-Nb alloys

    International Nuclear Information System (INIS)

    Khatamian, D.

    1995-03-01

    In this study the 1 H( 15 N,αγ) 12 C nuclear reaction has been used to measure hydrogen profiles of anodically oxidized Zr-Nb specimens containing various amounts of niobium. The profiles have been correlated with oxygen profiles, obtained using a Scanning Auger Microprobe (SAM), and with X-ray diffraction patterns. In addition, unoxidized Zr-2.5Nb (Zr-2.5 wt% Nb) samples were implanted with oxygen and hydrogen to study the interaction between these two species when dissolved in the alloy. All the anodically oxidized specimens, except the pure Zr and the single-phase β-Zr (Zr-20Nb) samples, displayed hydrogen peaks beneath the oxide layer. These results, in conjunction with the results from the implanted specimens, indicate that the hydrogen moves under the influence of a stress gradient to the sub-oxide region, where the metal lattice has been expanded due to superficial oxide growth. The results show that dissolved oxygen sites in Zr-2.5Nb alloy do not trap hydrogen. (author). 16 refs., 6 figs

  6. Nanocomposite anode materials for sodium-ion batteries

    Science.gov (United States)

    Manthiram, Arumugam; Kim Il, Tae; Allcorn, Eric

    2016-06-14

    The disclosure relates to an anode material for a sodium-ion battery having the general formula AO.sub.x--C or AC.sub.x--C, where A is aluminum (Al), magnesium (Mg), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zirconium (Zr), molybdenum (Mo), tungsten (W), niobium (Nb), tantalum (Ta), silicon (Si), or any combinations thereof. The anode material also contains an electrochemically active nanoparticles within the matrix. The nanoparticle may react with sodium ion (Na.sup.+) when placed in the anode of a sodium-ion battery. In more specific embodiments, the anode material may have the general formula M.sub.ySb-M'O.sub.x--C, Sb-MO.sub.x--C, M.sub.ySn-M'C.sub.x--C, or Sn-MC.sub.x--C. The disclosure also relates to rechargeable sodium-ion batteries containing these materials and methods of making these materials.

  7. Facile Fabrication of Ordered Anodized Aluminum Oxide Membranes with Controlled Pore Size by Improved Hard Anodization.

    Science.gov (United States)

    Fan, Jiangxia; Zhu, Xinxin; Wang, Kunzhou; Chen, Xiaoyuan; Wang, Xinqing; Yan, Minhao; Ren, Yong

    2018-05-01

    We have fabricated highly ordered anodized aluminum oxide (AAO) membranes with different diameter through improved hard anodization (HA) at high temperature. This process can generate thick AAO membranes (30 μm) in a short anodizing time with high growth rate 20-60 μm h-1 which is much faster than that in traditional mild two-step anodization. We enlarged the AAO pore diameter by adjusting the voltage rise rate at the same time, which has a great influence on current density and temperature. The AAO pore diameter varies from 60-110 nm to 160-190 nm. The pore diameter (Dp) of the AAO prepared by this improved process is much larger than that prepared by HA (40-60 nm) when H2C2O4 as electrolyte. It can expand potential use of the AAO membranes such as for the template-based synthesis of nanowires or nanotubes with modulated diameters and also for practical separation technology. We also has used the AAO with different diameters prepared by this improved HA to fabricate Co nanowires and γ-Fe2O3 superparamagnetic nanorods.

  8. Kinetic models of controllable pore growth of anodic aluminum oxide membrane

    Science.gov (United States)

    Huang, Yan; Zeng, Hong-yan; Zhao, Ce; Qu, Ye-qing; Zhang, Pin

    2012-06-01

    An anodized Al2O3 (AAO) membrane with apertures about 72 nm in diameter was prepared by two-step anodic oxidation. The appearance and pore arrangement of the AAO membrane were characterized by energy dispersive x-ray spectroscopy and scanning electron microscopy. It was confirmed that the pores with high pore aspect ratio were parallel, well-ordered, and uniform. The kinetics of pores growth in the AAO membrane was derived, and the kinetic models showed that pores stopped developing when the pressure ( σ) trended to equal the surface tension at the end of anodic oxidation. During pore expansion, the effects of the oxalic acid concentration and expansion time on the pore size were investigated, and the kinetic behaviors were explained with two kinetic models derived in this study. They showed that the pore size increased with extended time ( r= G· t+ G'), but decreased with increased concentration ( r = - K·ln c- K') through the derived mathematic formula. Also, the values of G, G', K, and K' were derived from our experimental data.

  9. 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.

  10. Anodic and cathodic reactions in molten calcium chloride

    International Nuclear Information System (INIS)

    Fray, D.J.

    2002-01-01

    Calcium chloride is a very interesting electrolyte in that it is available, virtually free, in high purity form as a waste product from the chemical industry. It has a very large solubility for oxide ions, far greater than many alkali halides and other divalent halides and has the same toxicity as sodium chloride and also a very high solubility in water. Intuitively, on the passage of current, it is expected that calcium would be deposited at the cathode and chlorine would evolve at the anode. However, if calcium oxide is added to the melt, it is possible to deposit calcium and evolve oxygen containing gases at the anode, making the process far less polluting than when chlorine is evolved. This process is discussed in terms of the addition of calcium to molten lead. Furthermore, these reactions can be altered dramatically depending upon the electrode materials and the other ions dissolved in the calcium chloride. As calcium is only deposited at very negative cathodic potentials, there are several interesting cathodic reactions that can occur and these include the decomposition of the carbonate ion and the ionization of oxygen, sulphur, selenium and tellurium. For example, if an oxide is used as the cathode in molten calcium chloride, the favoured reaction is shown to be the ionization of oxygen O + 2e - → O 2- rather than Ca 2+ + 2 e- → Ca. The oxygen ions dissolve in the salt leaving the metal behind, and this leads to the interesting hypothesis that metal oxides can be reduced directly to the metal purely by the use of electrons. Examples are given for the reduction of titanium dioxide, zirconium dioxide, chromium oxide and niobium oxide and by mixing oxide powders together and reducing the mixed compact, alloys and intermetallic compounds are formed. Preliminary calculations indicate that this new process should be much cheaper than conventional metallothermic reduction for these elements. (author)

  11. Investigating the structure and biocompatibility of niobium and titanium oxides as coatings for orthopedic metallic implants

    Energy Technology Data Exchange (ETDEWEB)

    Pradhan, D.; Wren, A.W.; Misture, S.T.; Mellott, N.P., E-mail: mellott@alfred.edu

    2016-01-01

    Applying sol gel based coatings to orthopedic metallic implant materials can significantly improve their properties and lifespan in vivo. For this work, niobium (Nb{sub 2}O{sub 5}) and titanium (TiO{sub 2}) oxides were prepared via solution processing in order to determine the effect of atomic arrangement (amorphous/crystalline) on bioactivity. Thermal evaluation on the synthesized materials identified an endotherm for Nb{sub 2}O{sub 5} at 75 °C with 40% weight loss below 400 °C, and minimal weight loss between 400 and 850 °C. Regarding TiO{sub 2} an endotherm was present at 92 °C with 25% weight loss below 400 °C, and 4% between 400 and 850 °C. Phase evolution was determined using High Temperature X-ray Diffraction (HT-XRD) where amorphous-Nb{sub 2}O{sub 5} (450 °C), hexagonal-Nb{sub 2}O{sub 5} (525 °C), orthorhombic-Nb{sub 2}O{sub 5} (650 °C), amorphous-TiO{sub 2} (275 °C) and tetragonal TiO{sub 2} (500 °C) structures were produced. Simulated body fluid (SBF) testing was conducted over 1, 7 and 30 days and resulted in positive chemical and morphological changes for crystalline Nb{sub 2}O{sub 5} (525 °C) and TiO{sub 2} (500 °C) after 30 days of incubation. Rod-like CaP deposits were observed on the surfaces using Scanning Electron Microscopy (FE-SEM) and Grazing Incidence-X-ray Diffraction (GI-XRD) shows that the deposits were X-ray amorphous. Cell viability was higher with the TiO{sub 2} (122%) samples when compared to the growing cell population while Nb{sub 2}O{sub 5} samples exhibited a range of viability (64–105%), partially dependent on materials atomic structure. - Highlights: • Niobium and titanium oxides were prepared to determine the effect of structure on bioactivity. • Simulated body fluid testing resulted in positive surface chemical and morphological changes. • Amorphous, rod-like CaP deposits were observed on the surfaces. • Niobium oxide exhibited a range of viability partially dependent on materials atomic structure.

  12. Influence of defects on the ordering degree of nanopores made from anodic aluminum oxide

    International Nuclear Information System (INIS)

    Yu Wenhui; Fei Guangtao; Chen Xiaomeng; Xue Fanghong; Xu Xijin

    2006-01-01

    Anodic aluminum oxide (AAO) templates with highly ordered nanoporous structure were fabricated by means of the electrochemical anodization under the constant anodic voltage and electrolyte temperature. The dependence of the ordering degree of nanopores on the point defects, dislocation configuration and grain boundary of aluminum is qualitatively analyzed. Experiment results show that the size of the ordered region of nanopores depends strongly on the point defects, dislocation cell configuration

  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......-programmed oxidation and time-of-flight secondary ion mass spectrometry. Results showed thatNi/ScYSZ/Pd-CGO was more active for catalytic dissociation of CH4 at 750°C and subsequent reactivity of deposited carbonaceous species. Sulfur deactivated most catalytic reactions except CO2 dissociation at 750°C. The presence...... 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...

  14. Characterization of Niobium Platings Obtained from NaCl-KCl Melts

    DEFF Research Database (Denmark)

    Gillesberg, Bo; Barner, Jens H. Von; Bjerrum, Niels

    1998-01-01

    -uniform in thickness. At temperatures below 550°C no niobium metal could be identified in the product.When metallic nickel was used as substrate intermetallic compounds (e.g. NbNi3) were formed in the interface between the substrate and the deposit. This resulted in poor adherence of the deposit. In the case of AISI......316 stainless steel substrates no intermetallic phases were observed. Further an excellent adhesion of the deposited niobium layer was obtained.Deposits (on nickel substrates) from NaCl-KCl melts at 750°C with oxide added (molar ratio O/Nb greater than 0.5) were thin and consisted of niobium...

  15. Surface analyses of electropolished niobium samples for superconducting radio frequency cavity

    International Nuclear Information System (INIS)

    Tyagi, P. V.; Nishiwaki, M.; Saeki, T.; Sawabe, M.; Hayano, H.; Noguchi, T.; Kato, S.

    2010-01-01

    The performance of superconducting radio frequency niobium cavities is sometimes limited by contaminations present on the cavity surface. In the recent years extensive research has been done to enhance the cavity performance by applying improved surface treatments such as mechanical grinding, electropolishing (EP), chemical polishing, tumbling, etc., followed by various rinsing methods such as ultrasonic pure water rinse, alcoholic rinse, high pressure water rinse, hydrogen per oxide rinse, etc. Although good cavity performance has been obtained lately by various post-EP cleaning methods, the detailed nature about the surface contaminants is still not fully characterized. Further efforts in this area are desired. Prior x-ray photoelectron spectroscopy (XPS) analyses of EPed niobium samples treated with fresh EP acid, demonstrated that the surfaces were covered mainly with the niobium oxide (Nb 2 O 5 ) along with carbon, in addition a small quantity of sulfur and fluorine were also found in secondary ion mass spectroscopy (SIMS) analysis. In this article, the authors present the analyses of surface contaminations for a series of EPed niobium samples located at various positions of a single cell niobium cavity followed by ultrapure water rinsing as well as our endeavor to understand the aging effect of EP acid solution in terms of contaminations presence at the inner surface of the cavity with the help of surface analytical tools such as XPS, SIMS, and scanning electron microscope at KEK.

  16. Effect of pH value and delayed-action time on catalytic activity of tartrate niobium(5) complexes

    International Nuclear Information System (INIS)

    Alekseeva, I.I.; Chernysheva, L.M.; Bobkova, M.V.; Solomonov, V.A.

    1987-01-01

    Results of thermokinetic study of catalytic activity of niobium (5) tartrate solutions in the oxidation of ascorbic acid with hydrogen peroxide are presented. Addition of tartrate-ions to a concentration of 1x10 -2 M and higher in niobium (5) diluted solution enhances the catalytic activity of Nb(5). Alkaline tartrate solutions of niobium (5) may be used as standard solutions in determination of niobium microquantities by kinetic method

  17. Investigation of anodizing parameter effect on barrier layer of anodic zirconium oxide

    International Nuclear Information System (INIS)

    Kharchenko, Eh.P.

    1979-01-01

    Effect of fluoride concentration and forming direction upon kinetics of barrier layer transformations in the process of preparation of phase anodic zirconium oxide in acid fluorine-containing solutions is considered. Suppositions are made on the mechanism of barrier layer transformation under the effect of the parameters mentioned. The thickness of the barrier layer is determined by two methods and it is shown that coefficient of the layer thickess growth at the voltage increase by 1 V is much lower than during formation of the barrier films in non-agressive electrolytes

  18. Microstructural evolution of nanograin nickel-zirconia cermet anode materials for solid oxide fuel cell applications

    International Nuclear Information System (INIS)

    Nayak, Bibhuti Bhusan

    2012-01-01

    The aim of the study is to study the structure, microstructure, porosity, thermal expansion, electrical conductivity and electrochemical behavior of the anode material thus synthesized in order to find its suitability for solid oxide fuel cell (SOFC) anode application

  19. Large-scale calculations of solid oxide fuel cell cermet anode by tight-binding quantum chemistry method

    International Nuclear Information System (INIS)

    Koyama, Michihisa; Kubo, Momoji; Miyamoto, Akira

    2005-01-01

    Improvement of anode characteristics of solid oxide fuel cells is important for the better cell performance and especially the direct use of hydrocarbons. A mixture of ceramics and metal is generally used as anode, and different combinations of ceramics and metals lead to different electrode characteristics. We performed large-scale calculations to investigate the characteristics of Ni/CeO 2 and Cu/CeO 2 anodes at the electronic level using our tight-binding quantum chemical molecular dynamics program. Charge distribution analysis clarified the electron transfer from metal to oxide in both anodes. The calculations of density of states clarified different contributions of Ni and Cu orbitals to the energy levels at around Fermi level in each cermet. Based on the obtained results, we made considerations to explain different characteristics of both cermet anodes. The effectiveness of our approach for the investigation of complex cermet system was proved

  20. Novel structure formation at the bottom surface of porous anodic alumina fabricated by single step anodization process.

    Science.gov (United States)

    Ali, Ghafar; Ahmad, Maqsood; Akhter, Javed Iqbal; Maqbool, Muhammad; Cho, Sung Oh

    2010-08-01

    A simple approach for the growth of long-range highly ordered nanoporous anodic alumina film in H(2)SO(4) electrolyte through a single step anodization without any additional pre-anodizing procedure is reported. Free-standing porous anodic alumina film of 180 microm thickness with through hole morphology was obtained. A simple and single step process was used for the detachment of alumina from aluminum substrate. The effect of anodizing conditions, such as anodizing voltage and time on the pore diameter and pore ordering is discussed. The metal/oxide and oxide/electrolyte interfaces were examined by high resolution scanning transmission electron microscope. The arrangement of pores on metal/oxide interface was well ordered with smaller diameters than that of the oxide/electrolyte interface. The inter-pore distance was larger in metal/oxide interface as compared to the oxide/electrolyte interface. The size of the ordered domain was found to depend strongly upon anodizing voltage and time. (c) 2010 Elsevier Ltd. All rights reserved.

  1. 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.

  2. Effects of Alclad Layer and Anodizing Time on Sulfuric Acid Anodizing and Film Properties of 2E12 Aluminum Alloy

    OpenAIRE

    CHEN Gao-hong; HU Yuan-sen; YU Mei; LIU Jian-hua; LI Guo-ai

    2017-01-01

    Alclad and unclad 2E12 aerospace aluminum alloy were treated by sulfuric acid anodic oxidation. The effects of alclad layer and anodizing time on the anodization behaviour and corrosion resistance of anodic oxide layer on 2E12 aluminum alloy were studied. Surface and cross-section morphology of anodic oxide films were observed by scanning electron microscopy. The electrochemical properties of anodic oxide films were analyzed by potentiodynamic polarization curve and electrochemical impedance ...

  3. 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.

  4. Self-Driven Bioelectrochemical Mineralization of Azobenzene by Coupling Cathodic Reduction with Anodic Intermediate Oxidation

    International Nuclear Information System (INIS)

    Liu, Rong-Hua; Li, Wen-Wei; Sheng, Guo-Ping; Tong, Zhong-Hua; Lam, Michael Hon-Wah; Yu, Han-Qing

    2015-01-01

    Highlights: • Azobenzene was reduced to aniline at the cathode of an acetate-fueled MFC. • Aniline was degraded at the bioanode of a single-chamber MFC. • Cathodic reduction of azobenzene was coupled with anodic oxidation of aniline. • Self-driven, complete mineralization of azobenzene in an MFC was accomplished. - Abstract: Bioelectrochemical systems have been intensively studied as a promising technology for wastewater treatment and environment remediation. Coupling of the anodic and cathodic electrochemical reactions allows an enhanced degradation of recalcitrant organics, but external power supply is usually needed to overcome the thermodynamic barrier. In this work, we report a self-driven degradation of azobenzene in a microbial fuel cell (MFC), where the cathodic reduction of azobenzene was effectively coupled with the anodic oxidation of its reduction degradation intermediate (i.e., aniline). The anodic degradation rate of aniline, as the sole carbon source, was significantly higher than that under open-circuit conditions, suggesting a considerable bioelectrochemical oxidation of aniline. Output voltages up to 8 mV were obtained in the MFC. However, a shift of cathodic electron acceptor from oxygen to azobenzene resulted in a decreased aniline degradation rate and output voltage. The present work may provide valuable implications for development of sustainable bioelectrochemical technologies for environmental remediation

  5. Syntheses of rare-earth metal oxide nanotubes by the sol-gel method assisted with porous anodic aluminum oxide templates

    International Nuclear Information System (INIS)

    Kuang Qin; Lin Zhiwei; Lian Wei; Jiang Zhiyuan; Xie Zhaoxiong; Huang Rongbin; Zheng Lansun

    2007-01-01

    In this paper, we report a versatile synthetic method of ordered rare-earth metal (RE) oxide nanotubes. RE (RE=Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) oxide nanotubes were successfully prepared from corresponding RE nitrate solution via the sol-gel method assisted with porous anodic aluminum oxide (AAO) templates. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM, and X-ray diffraction (XRD) have been employed to characterize the morphology and composition of the as-prepared nanotubes. It is found that as-prepared RE oxides evolve into bamboo-like nanotubes and entirely hollow nanotubes. A new possible formation mechanism of RE oxide nanotubes in the AAO channels is proposed. These high-quantity RE oxide nanotubes are expected to have promising applications in many areas such as luminescent materials, catalysts, magnets, etc. - Graphical abstract: A versatile synthetic method for the preparation of ordered rare-earth (RE) oxide nanotubes is reported, by which RE (RE=Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) oxide nanotubes were successfully prepared from corresponding RE nitrate solution via the sol-gel method assisted with porous anodic aluminum oxide (AAO) templates

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

    Science.gov (United States)

    Mestieri, Leticia Boldrin; Tanomaru-Filho, Mário; Gomes-Cornélio, Ana Livia; Salles, Loise Pedrosa; Bernardi, Maria Inês Basso; Guerreiro-Tanomaru, Juliane Maria

    2014-01-01

    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. 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. 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. It was concluded that the combination of PC+NbO is a potential alternative for composition of MTA.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-06-01

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

  8. Anodic oxidation of chloride ions in 1-butyl-3-methyl-limidazolium tetrafluoroborate ionic liquid

    International Nuclear Information System (INIS)

    Zhang, Qibo; Hua, Yixin; Wang, Rui

    2013-01-01

    Highlights: • The anodic oxidation of Cl − in BMIMBF 4 is electrochemically irreversible with diffusion controlled. • The oxidation of Cl − in BMIMBF 4 is more likely to form tri-chloride ion, Cl 3 − but not chlorine, Cl 2 . • The minute amount of Cl 2 detected after electrolysis forms according to the equilibrium of Cl 2 + Cl − ⇌ Cl 3 − . -- Abstract: The oxidation behavior of chloride ions on platinum electrodes was investigated in a natural ionic liquid, 1-butyl-3-methyl-limidazolium tetrafluoroborate (BMIMBF 4 ) in the presence of high concentrations of 1-butyl-3-methyl-limidazolium chloride (BMIMCl). Analysis of the electrode reaction was explored using cyclic voltammetry, and chronoamperometry with a platinum micro-disk electrode, and bulk potentiostatic electrolysis and UV–vis spectroscopy. The anodic oxidation of chloride ions on the platinum micro-disk electrode in the mixture was considered to be an irreversible process with diffusion controlled as revealed by cyclic voltammetry. The diffusion coefficient, D, and the number of electrons transferred, n, for anodic oxidation of Cl − in BMIMBF 4 derived from results of chronoamperometry revealed that the oxidation of chloride ions was more likely to form tri-chloride ion, Cl 3 − but not chlorine, Cl 2 . Bulk electrolysis and UV–vis spectroscopy further confirmed that the tri-chloride ion was the main product from the overall oxidation of the chloride ion

  9. Hollow carbon sphere/metal oxide nanocomposites anodes for lithium-ion batteries

    International Nuclear Information System (INIS)

    Wenelska, K.; Ottmann, A.; Schneider, P.; Thauer, E.; Klingeler, R.; Mijowska, E.

    2016-01-01

    HCS (Hollow carbon spheres) covered with metal oxide nanoparticles (SnO_2 and MnO_2, respectively) were successfully synthesized and investigated regarding their potential as anode materials for lithium-ion batteries. Raman spectroscopy shows a high degree of graphitization for the HCS host structure. The mesoporous nature of the nanocomposites is confirmed by Brunauer–Emmett–Teller analysis. For both metal oxides under study, the metal oxide functionalization of HCS yields a significant increase of electrochemical performance. The charge capacity of HCS/SnO_2 is 370 mA hg"−"1 after 45 cycles (266 mA hg"−"1 in HCS/MnO_2) which clearly exceeds the value of 188 mA hg"−"1 in pristine HCS. Remarkably, the data imply excellent long term cycling stability after 100 cycles in both cases. The results hence show that mesoporous HCS/metal oxide nanocomposites enable exploiting the potential of metal oxide anode materials in Lithium-ion batteries by providing a HCS host structure which is both conductive and stable enough to accommodate big volume change effects. - Highlights: • Strategy to synthesize hollow carbon spheres decorated by metal oxides nanoparticles. • High-performance of HCS/MOx storage as mesoporous hybrid material. • The results hence demonstrate high electrochemical activity of the HCS/MOx.

  10. 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.

  11. Effects of the Molybdenum Oxide/Metal Anode Interfaces on Inverted Polymer Solar Cells

    International Nuclear Information System (INIS)

    Wu Jiang; Guo Xiao-Yang; Xie Zhi-Yuan

    2012-01-01

    Inverted polymer solar cells with molybdenum oxide (MoO 3 ) as an anode buffer layer and different metals (Al or Ag) as anodes are studied. It is found that the inverted cell with a top Ag anode demonstrates enhanced charge collection and higher power conversion efficiency (PCE) compared to the cell with a top Al anode. An 18% increment of PCE is obtained by replacing Al with Ag as the top anode. Further studies show that an interfacial dipole pointing from MoO 3 to Al is formed at MoO 3 /Al interfaces due to electron transfer from Al to MoO 3 while this phenomenon cannot be observed at MoO 3 /Ag interfaces. It is speculated that the electric field at the MoO 3 /Al interface would hinder hole extraction, and hence reduce the short-circuit current

  12. Surface analyses of electropolished niobium samples for superconducting radio frequency cavity

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, P. V.; Nishiwaki, M.; Saeki, T.; Sawabe, M.; Hayano, H.; Noguchi, T.; Kato, S. [GUAS, Tsukuba, Ibaraki 305-0801 (Japan); KEK, Tsukuba, Ibaraki 305-0801 (Japan); KAKEN Inc., Hokota, Ibaraki 311-1416 (Japan); GUAS, Tsukuba, Ibaraki 305-0801 (Japan) and KEK, Tsukuba, Ibaraki 305-0801 (Japan)

    2010-07-15

    The performance of superconducting radio frequency niobium cavities is sometimes limited by contaminations present on the cavity surface. In the recent years extensive research has been done to enhance the cavity performance by applying improved surface treatments such as mechanical grinding, electropolishing (EP), chemical polishing, tumbling, etc., followed by various rinsing methods such as ultrasonic pure water rinse, alcoholic rinse, high pressure water rinse, hydrogen per oxide rinse, etc. Although good cavity performance has been obtained lately by various post-EP cleaning methods, the detailed nature about the surface contaminants is still not fully characterized. Further efforts in this area are desired. Prior x-ray photoelectron spectroscopy (XPS) analyses of EPed niobium samples treated with fresh EP acid, demonstrated that the surfaces were covered mainly with the niobium oxide (Nb{sub 2}O{sub 5}) along with carbon, in addition a small quantity of sulfur and fluorine were also found in secondary ion mass spectroscopy (SIMS) analysis. In this article, the authors present the analyses of surface contaminations for a series of EPed niobium samples located at various positions of a single cell niobium cavity followed by ultrapure water rinsing as well as our endeavor to understand the aging effect of EP acid solution in terms of contaminations presence at the inner surface of the cavity with the help of surface analytical tools such as XPS, SIMS, and scanning electron microscope at KEK.

  13. Novel iron oxide nanotube arrays as high-performance anodes for lithium ion batteries

    Science.gov (United States)

    Zhong, Yuan; Fan, Huiqing; Chang, Ling; Shao, Haibo; Wang, Jianming; Zhang, Jianqing; Cao, Chu-nan

    2015-11-01

    Nanostructured iron oxides can be promising anode materials for lithium ion batteries (LIBs). However, improvement on the rate capability and/or electrochemical cycling stability of iron oxide anode materials remains a key challenge because of their poor electrical conductivities and large volume expansion during cycling. Herein, the vertically aligned arrays of one-dimensional (1D) iron oxide nanotubes with 5.8 wt% carbon have been fabricated by a novel surfactant-free self-corrosion process and subsequent thermal treatment. The as-fabricated nanotube array electrode delivers a reversible capacity of 932 mAh g-1 after 50 charge-discharge cycles at a current of 0.6 A g-1. The electrode still shows a reversible capacity of 610 mAh g-1 even at a very high rate (8.0 A g-1), demonstrating its prominent rate capability. Furthermore, the nanotube array electrode also exhibits the excellent electrochemical cycling stability with a reversible capacity of 880 mAh g-1 after 500 cycles at a current of 4 A g-1. The nanotube array electrode with superior lithium storage performance reveals the promising potential as a high-performance anode for LIBs.

  14. Copper based anodes for bio-ethanol fueled low-temperature solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kondakindi, R.R.; Karan, K. [Queen' s Univ., Kingston, ON (Canada)

    2003-07-01

    Laboratory studies have been conducted to develop a low-temperature solid oxide fuel cell (SOFC) fueled by bio-ethanol. SOFCs are considered to be a potential source for clean and efficient electricity. The use of bio-ethanol to power the SOFC contributes even further to reducing CO{sub 2} emissions. The main barrier towards the development of the proposed SOFC is the identification of a suitable anode catalyst that prevents coking during electro-oxidation of ethanol while yielding good electrical performance. Copper was selected as the catalyst for this study. Composite anodes consisting of copper catalysts and gadolinium-doped ceria (GDC) electrolytes were prepared using screen printing of GDC and copper oxide on dense GDC electrolytes and by wet impregnation of copper nitrate in porous GDC electrolytes followed by calcination and sintering. The electrical conductivity of the prepared anodes was characterized to determine the percolation threshold. Temperature-programmed reduction and the Brunner Emmett Teller (BET) methods were used to quantify the catalyst dispersion and surface area. Electrochemical performance of the single-cell SOFC with a hydrogen-air system was used to assess the catalytic activities. Electrochemical Impedance Spectroscopy was used to probe the electrode kinetics.

  15. Different shape normal metal interlayers between niobium based SIS junctions and niobium titanium nitride leads and their influence on the electron temperature

    International Nuclear Information System (INIS)

    Selig, S; Westig, M P; Jacobs, K; Honingh, C E

    2014-01-01

    In this paper we demonstrate the reduction of heating in a niobium superconductor-insulator-superconductor (SIS) junction with aluminum-oxide tunnel barrier embedded in a niobium-titanium-nitride circuit. Nonequilibrium quasiparticles which are created due to the Andreev trap at the interface between the niobium and the niobium-titanium-nitride layers are relaxed by inserting a normal-metal conductor of gold between these two layers. In an earlier work we explained the observed relaxation of nonequilibrium quasiparticles due to the geometrically assisted cooling effect. In this paper we investigate this cooling effect in dependence of the normal-metal layer shape and size. We expect that an adapted normal-metal layer is necessary for implementation in practical terahertz SIS heterodyne mixer circuits. We observe in DC-measurements of a large number of devices a clear relation between the volume of the gold layer and the effective electron temperature in the device. Our central finding is that the shape of the gold layer does not influence the cooling provided that the volume is sufficient.

  16. Galvanic detection of sulfur dioxide in ambient air at trace levels by anodic oxidation

    NARCIS (Netherlands)

    Lindqvist, F.

    1978-01-01

    A continuous method for the measurement of SO2 in ambient air at trace levels is described. The principle of detection is based on the anodic oxidation of SO2 in a galvanic cell. A differential measuring technique with a cell with two anodes and one cathode is used; background and noise current are

  17. Voltage breakdown on niobium and copper surfaces

    International Nuclear Information System (INIS)

    Werner, G.R.; Padamsee, H.; Betzwieser, J.C.; Liu, Y.G.; Rubin, K.H.R.; Shipman, J.E.; Ying, L.T.

    2003-01-01

    Experiments have shown that voltage breakdown in superconducting niobium RF cavities is in many ways similar to voltage breakdown on niobium cathodes in DC voltage gaps; most striking are the distinctive starburst patterns and craters that mark the site of voltage breakdown in both superconducting cavities and DC vacuum gaps. Therefore, we can learn much about RF breakdown from simpler, faster DC experiments. We have direct evidence, in the form of before'' and ''after'' pictures, that breakdown events caused by high surface electric fields occur with high probability at contaminant particles on surfaces. Although the pre-breakdown behavior (field emission) seems to depend mostly on the contaminant particles present and little on the substrate, the breakdown event itself is greatly affected by the substrate-niobium, heavily oxidized niobium, electropolished copper, and diamond-machined copper cathodes lead to different kinds of breakdown events. By studying DC voltage breakdown we hope to learn more details about the processes involved in the transition from field emission to catastrophic arcing and the cratering of the surface; as well as learning how to prevent breakdown, we would like to learn how to cause breakdown, which could be important when ''processing'' cavities to reduce field emission. (author)

  18. Physicochemical and mechanical properties of zirconium oxide and niobium oxide modified Portland cement-based experimental endodontic sealers.

    Science.gov (United States)

    Viapiana, R; Flumignan, D L; Guerreiro-Tanomaru, J M; Camilleri, J; Tanomaru-Filho, M

    2014-05-01

    To evaluate the physicochemical and mechanical properties of Portland cement-based experimental sealers (ES) with different radiopacifying agents (zirconium oxide and niobium oxide micro- and nanoparticles) in comparison with the following conventional sealers: AH Plus, MTA Fillapex and Sealapex. The materials were tested for setting time, compressive strength, flow, film thickness, radiopacity, solubility, dimensional stability and formaldehyde release. Data were subjected to anova and Tukey tests (P 0.05) and lower solubility when compared with MTA Fillapex and Sealapex (P Portland cement-based experimental endodontic sealers presented physicochemical properties according to the specifications no 57 ANSI/ADA (ADA Professional Product Review, 2008) and ISO 6876 (Dentistry - Root Canal Sealing Materials, 2012, British Standards Institution, London, UK). The sealers had setting times and flow ability that was adequate for clinical use, satisfactory compressive strength and low solubility. Additional studies should be carried out with the purpose of decreasing the film thickness and to determine the ideal ratio of radiopacifying agents in Portland cement-based root canal sealers. © 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  19. 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.

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

    International Nuclear Information System (INIS)

    Sires, Ignasi; Cabot, Pere Lluis; Centellas, Francesc; Garrido, Jose Antonio; Rodriguez, Rosa Maria; Arias, Conchita; Brillas, Enric

    2006-01-01

    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 (·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 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 ·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 2 with BDD. A reaction pathway for clofibric acid degradation involving all these intermediates is proposed

  1. Cytotoxicity and Bioactivity of Calcium Silicate Cements Combined with Niobium Oxide in Different Cell Lines.

    Science.gov (United States)

    Mestieri, Leticia Boldrin; Gomes-Cornélio, Ana Lívia; Rodrigues, Elisandra Márcia; Faria, Gisele; Guerreiro-Tanomaru, Juliane Maria; Tanomaru-Filho, Mário

    2017-01-01

    The aim of this study was to evaluate the cytotoxicity and bioactivity of calcium silicate-based cements combined with niobium oxide (Nb2O5) micro and nanoparticles, comparing the response in different cell lines. This evaluation used four cell lines: two primary cultures (human dental pulp cells - hDPCs and human dental follicle cells - hDFCs) and two immortalized cultures (human osteoblast-like cells - Saos-2 and mouse periodontal ligament cells - mPDL). The tested materials were: White Portland Cement (PC), mineral trioxide aggregate (MTA), white Portland cement combined with microparticles (PC/Nb2O5µ) or nanoparticles (PC/Nb2O5n) of niobium oxide (Nb2O5). Cytotoxicity was evaluated by the methylthiazolyldiphenyl-tetrazolium bromide (MTT) and trypan blue exclusion assays and bioactivity by alkaline phosphatase (ALP) enzyme activity. Results were analyzed by ANOVA and Tukey test (a=0.05). PC/Nb2O5n presented similar or higher cell viability than PC/Nb2O5µ in all cell lines. Moreover, the materials presented similar or higher cell viability than MTA. Saos-2 exhibited high ALP activity, highlighting PC/Nb2O5µ material at 7 days of exposure. In conclusion, calcium silicate cements combined with micro and nanoparticles of Nb2O5 presented cytocompatibility and bioactivity, demonstrating the potential of Nb2O5 as an alternative radiopacifier agent for these cements. The different cell lines had similar response to cytotoxicity evaluation of calcium silicate cements. However, bioactivity was more accurately detected in human osteoblast-like cell line, Saos-2.

  2. A review of refractory materials for vapor-anode AMTEC cells

    Science.gov (United States)

    King, Jeffrey C.; El-Genk, M. S.

    2000-01-01

    Recently, refractory alloys have been considered as structural materials for vapor-anode Alkali Metal Thermal-to-Electric Conversion (AMTEC) cells, for extended (7-15 years) space missions. This paper reviewed the existing database for refractory metals and alloys of potential use as structural materials for vapor-anode sodium AMTEC cells. In addition to requiring that the vapor pressure of the material be below 10-9 torr (133 nPa) at a typical hot side temperature of 1200 K, other screening considerations were: (a) low thermal conductivity, low thermal radiation emissivity, and low linear thermal expansion coefficient; (b) low ductile-to-brittle transition temperature, high yield and rupture strengths and high strength-to-density ratio; and (c) good compatibility with the sodium AMTEC operating environment, including high corrosion resistance to sodium in both the liquid and vapor phases. Nb-1Zr (niobium-1% zirconium) alloy is recommended for the hot end structures of the cell. The niobium alloy C-103, which contains the oxygen gettering elements zirconium and hafnium as well as titanium, is recommended for the colder cell structure. This alloy is stronger and less thermally conductive than Nb-1Zr, and its use in the cell wall reduces parasitic heat losses by conduction to the condenser. The molybdenum alloy Mo-44.5Re (molybdenum-44.5% rhenium) is also recommended as a possible alternative for both structures if known problems with oxygen pick up and embrittlement of the niobium alloys proves to be intractable. .

  3. Reduction of Al2O3 in niobium--lithium systems at 10000C

    International Nuclear Information System (INIS)

    Selle, J.E.; DeVan, J.H.

    1977-07-01

    Various grades of aluminum oxide (Al 2 O 3 ) were sealed inside capsules of niobium and niobium-1% zirconium alloy which were then exposed to liquid lithium for 3000 hr at 1000 0 C. Similar unsealed capsules were exposed to a high vacuum. Reduction of the Al 2 O 3 occurred in the lithium-treated capsules, but no reaction occurred in the vacuum-treated capsules. Metallography and electron-microprobe analysis showed that reaction products in the form of compounds of niobium, aluminum, and zirconium were formed. Lithium acted as a sink for oxygen

  4. 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.

  5. Prediction of overpotential and effective thickness of Ni/YSZ anode for solid oxide fuel cell by improved species territory adsorption model

    Science.gov (United States)

    Nagasawa, Tsuyoshi; Hanamura, Katsunori

    2017-06-01

    The reliability of analytical model for hydrogen oxidation at Ni/YSZ anode in solid oxide fuel cell named as species territory adsorption model has been improved by introducing referenced thermodynamic and kinetic parameters predicted by density function theory calculations. The model can explicitly predict anode overpotential using unknown values of quantities of state for oxygen migration process in YSZ near a triple phase boundary (TPB), frequency factor for hydrogen oxidation, and effective anode thickness. The former two are determined through careful fitting process between the predicted and experimental results of Ni/YSZ cermet and Ni-patterned anodes. This makes it possible to estimate effective anode thickness, which tends to increase with temperature in six kinds of Ni/YSZ anodes in references. In addition, the comparison between the proposed model and a published numerical simulation indicates that the model can predict more precise dependence of anode overpotential on steam partial pressure than that by Butler-Volmer equation with empirical exchange current density. The introduction of present model into numerical simulation instead of Butler-Volmer equation can give more accurate prediction of anode polarization.

  6. Corrosion resistance of the substrates for the cryogenic gyroscope and electrodeposition of the superconductive niobium coatings

    Science.gov (United States)

    Dubrovskiy, A. R.; Okunev, M. A.; Makarova, O. V.; Kuznetsov, S. A.

    2017-05-01

    The interaction of different materials with the niobium containing melt was investigated. As substrate materials the ceramics, beryllium and carbopyroceram were chosen. Several spherical ceramic and beryllium samples were coated with protective molybdenum and niobium films by magnetron sputtering and PVD, respectively. After the experiment (exposition time 10 min) the exfoliation of molybdenum film from ceramic samples was observed due to interaction of the substrate with the melt. The niobium protective coatings reacted with the melt with niobium oxide formation. The beryllium samples regardless of the shape and the presence of the protective films were dissolved in the niobium containing melt due to more negative electrode potential comparing with niobium one. The carbopyroceram samples were exposed in the melt during 3 and 12 h. It was found that the carbopyroceram not corrodes in the niobium containing melt. The optimal regimes for electrodeposition of smooth uniform niobium coatings with the thickness up to 50 μm on carbopyroceram spheres were found.

  7. Influence of annealing conditions on anodic tungsten oxide layers and their photoelectrochemical activity

    International Nuclear Information System (INIS)

    Syrek, Karolina; Zych, Marta; Zaraska, Leszek; Sulka, Grzegorz D.

    2017-01-01

    Highlights: • Effect of annealing temperature on the morphology and crystalline structure of anodic WO 3 was investigated. • Photoelectrochemical properties of WO 3 layers annealed at different temperatures were studied. • Edges of conduction and valence bands were estimated for tungsten oxide layers annealed at different temperatures. • Influence of annealing time on crystalline structure, morphology and photoelectrochemical performance was studied. - Abstract: The nanoporous tungsten oxide films having an amorphous structure were prepared in an electrolyte containing fluoride ions via an anodization process. The as-synthesized anodic oxide layers can be easily converted to the monoclinic WO 3 phase upon annealing in air. The as-synthesized and annealed WO 3 layers were investigated by using X-ray diffraction, scanning electron microscopy, and photocurrent spectroscopy. The effect of annealing temperature and annealing time on the oxide morphology, crystal structure and electrochemical properties were studied. The samples were annealed in air at the temperatures ranging from 400 to 600 °C, and it was found that the original porous morphology of oxide is completely lost after annealing at 600 °C. The changes in the average crystallite sizes upon annealing were confirmed by XRD measurements. The photoelectrochemical performance of the annealed WO 3 layers were studied under pulsed UV illumination, and the highest photocurrents were observed at the incident light wavelength of 350 nm for the sample annealed at 500 °C for 2 h. The band gap energy and the positions of conduction and valence band edges were determined for all studied samples.

  8. Pilot demonstration of cerium oxide coated anodes. Final report, April 1990--October 1992

    Energy Technology Data Exchange (ETDEWEB)

    Gregg, J.S.; Frederick, M.S.; Shingler, M.J.; Alcorn, T.R.

    1992-10-01

    Cu cermet anodes were tested for 213 to 614 hours with an in-situ deposited CEROX coating in a pilot cell operated by Reynolds Manufacturing Technology Laboratory. At high bath ratio ({approximately}1.5) and low current density (0.5 A/cm{sup 2}), a {ge}1 mm thick dense CEROX coating was deposited on the anodes. At lower bath ratios and higher current density, the CEROX coating was thinner and less dense, but no change in corrosion rate was noted. Regions of low current density on the anodes and sides adjacent to the carbon anode sometimes had thin or absent CEROX coatings. Problems with cracking and oxidation of the cermet substrates led to higher corrosion rates in a pilot cell than would be anticipated from lab scale results.

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

    International Nuclear Information System (INIS)

    Sowa, Maciej; Dercz, Grzegorz; Suchanek, Katarzyna; Simka, Wojciech

    2015-01-01

    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

  10. 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.

  11. Microhardness of anodic aluminum oxide formed in an alkaline electrolyte

    Science.gov (United States)

    Kanygina, O. N.; Filyak, M. M.

    2017-04-01

    The microhardness of anodic aluminum oxide formed by anodizing of aluminum sheet in electrolyte on the basis of sodium hydroxide has been determined experimentally. The microhardness of the hard film/soft substrate system has been estimated by three approaches: indentation geometry (length of diagonals) in film surfaces, the sum of the hardnesses of the film and the surface with allowance for the indentation surface area and geometry, and with allowance for the indentation depth. It is demonstrated that the approach accounting for the indentation depth makes it possible to eliminate the influence of the substrate. It is established that the microhardness of the films formed in alkaline electrolytes is comparable with that formed in acid electrolytes.

  12. High-temperature interaction of low niobium oxides with carbon and nitrogen

    International Nuclear Information System (INIS)

    Lyubimov, V.D.; Alyamovskij, S.I.; Askarova, L.Kh.

    1980-01-01

    Presented are the results of investigation on the process of high-temperature interaction (1200-1300 deg C) of NbO 2 and NbO with carbon (in the helium medium) and nitrogen. The reaction between NbO 2 and carbon is successfully realized at 1300 deg C and involves two stages, viz. reduction of oxide by the mechanism of direct reduction and subsequent insertion of metalloid into the oxygen vacancies formed. As a result, on the base of the initial oxide a cubic phase is formed, its final composition at 1300 deg C corresponding to the formula NbCsub(0.74)Osub(0.28). Neither NbO monoxide, nor metal is detected in the reaction products under these conditions. Interaction of NbO 2 with carbon and nitrogen proceeds in the similar way. In this case, the oxygen vacancies formed are occupied by the atoms of the two metalloids the end-product of the reaction at 1300 deg C being oxycarbonitride NbCsub(0.30)Nsub(0.66)Osub(0.66). Intermediate products of the reaction between NbO and metalloids involve oxycarbide, oxynitride, or oxycarbonitride and dioxide of niobium, while the end products contain only a cubic phase [ru

  13. 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.

  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. Niobium in steels and alloys

    International Nuclear Information System (INIS)

    Lyakishev, N.P.; Tulin, N.A.; Pliner, Y.L.

    1984-01-01

    Data are presented on the reserves and processing of niobium raw materials followed by brief review of the current status and long-range trends in the commercial usage of niobium and its compounds. A survey is made of the physical properties of niobium and its chemical reactions with elements of direct concern in the manufacture of ferroalloys, quality steels and other products. Niobium minerals and ores, along with common ore processing practices are described briefly. Attention is paid to Brazilian niobium ores, and to the Araxa deposit specifically. Some emphasis has been given to methods of processing lean niobium ores not easily amenable to simple concentration. A systematic review is presented of the techniques used in the production of niobium ferroalloys. (E.G.) [pt

  16. Optical constants of anodic aluminum oxide films formed in oxalic acid solution

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jian [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Wang Chengwei [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)], E-mail: cwwang@nwnu.edu.cn; Li Yan [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Liu Weimin [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2008-09-01

    The anodic aluminum oxide (AAO) films with highly ordered nanopore arrays were prepared in oxalic acid solution under different anodizing voltage and time, its surface and cross section appearances were characterized by using field emission scanning electron microscopy, the transmission spectra with the interference fringes were measured at normal incidence over the wavelength range 200 to 2500 nm. Then the modified Swanepoel method was used for the determination of the optical constants and thickness of the free standing AAO films. The results indicate that the refractive index increases with the increase of anodizing voltage and the decrease of anodizing time, which is mainly due to the content of Al{sub 2}O{sub 3} with octahedron increases in the AAO films. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple-DiDomenico model, and the energy dependence of the absorption coefficient can be described using the direct transition model proposed by Tauc. Likewise, the optical energy gap E{sub g} is derived from Tauc's extrapolation, and E{sub g} increases from 4.178 to 4.256 eV with the anodizing voltage, but is weakly dependent on anodizing time. All the results are self-consistent in the paper.

  17. Destination of organic pollutants during electrochemical oxidation of biologically-pretreated dye wastewater using boron-doped diamond anode

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiuping [Department of Environmental Engineering, Peking University, the Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing100871 (China); Ni, Jinren, E-mail: nijinren@iee.pku.edu.cn [Department of Environmental Engineering, Peking University, the Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing100871 (China); Wei, Junjun; Xing, Xuan; Li, Hongna [Department of Environmental Engineering, Peking University, the Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing100871 (China)

    2011-05-15

    Electrochemical oxidation of biologically-pretreated dye wastewater was performed in a boron-doped diamond (BDD) anode system. After electrolysis of 12 h, the COD was decreased from 532 to 99 mg L{sup -1} (<100 mg L{sup -1}, the National Discharge Standard of China). More importantly, the destination of organic pollutants during electrochemical oxidation process was carefully investigated by molecular weight distribution measurement, resin fractionation, ultraviolet-visible spectroscopy, HPLC and GC-MS analysis, and toxicity test. As results, most organic pollutants were completely removed by electrochemical oxidation and the rest was primarily degraded to simpler compounds (e.g., carboxylic acids and short-chain alkanes) with less toxicity, which demonstrated that electrochemical oxidation of biologically-pretreated dye wastewater with BDD anode was very effective and safe. Especially, the performance of BDD anode system in degradation of large molecular organics such as humic substances makes it very promising in practical applications as an advanced treatment of biologically-pretreated wastewaters.

  18. Destination of organic pollutants during electrochemical oxidation of biologically-pretreated dye wastewater using boron-doped diamond anode.

    Science.gov (United States)

    Zhu, Xiuping; Ni, Jinren; Wei, Junjun; Xing, Xuan; Li, Hongna

    2011-05-15

    Electrochemical oxidation of biologically-pretreated dye wastewater was performed in a boron-doped diamond (BDD) anode system. After electrolysis of 12h, the COD was decreased from 532 to 99 mg L(-1) (destination of organic pollutants during electrochemical oxidation process was carefully investigated by molecular weight distribution measurement, resin fractionation, ultraviolet-visible spectroscopy, HPLC and GC-MS analysis, and toxicity test. As results, most organic pollutants were completely removed by electrochemical oxidation and the rest was primarily degraded to simpler compounds (e.g., carboxylic acids and short-chain alkanes) with less toxicity, which demonstrated that electrochemical oxidation of biologically-pretreated dye wastewater with BDD anode was very effective and safe. Especially, the performance of BDD anode system in degradation of large molecular organics such as humic substances makes it very promising in practical applications as an advanced treatment of biologically-pretreated wastewaters. Copyright © 2011 Elsevier B.V. All rights reserved.

  19. Destination of organic pollutants during electrochemical oxidation of biologically-pretreated dye wastewater using boron-doped diamond anode

    International Nuclear Information System (INIS)

    Zhu, Xiuping; Ni, Jinren; Wei, Junjun; Xing, Xuan; Li, Hongna

    2011-01-01

    Electrochemical oxidation of biologically-pretreated dye wastewater was performed in a boron-doped diamond (BDD) anode system. After electrolysis of 12 h, the COD was decreased from 532 to 99 mg L -1 ( -1 , the National Discharge Standard of China). More importantly, the destination of organic pollutants during electrochemical oxidation process was carefully investigated by molecular weight distribution measurement, resin fractionation, ultraviolet-visible spectroscopy, HPLC and GC-MS analysis, and toxicity test. As results, most organic pollutants were completely removed by electrochemical oxidation and the rest was primarily degraded to simpler compounds (e.g., carboxylic acids and short-chain alkanes) with less toxicity, which demonstrated that electrochemical oxidation of biologically-pretreated dye wastewater with BDD anode was very effective and safe. Especially, the performance of BDD anode system in degradation of large molecular organics such as humic substances makes it very promising in practical applications as an advanced treatment of biologically-pretreated wastewaters.

  20. 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

    2017-06-01

    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.

  1. Interaction of Human Osteoblast-Like Saos-2 and MG-63 Cells with Thermally Oxidized Surfaces of a Titanium-Niobium Alloy

    Czech Academy of Sciences Publication Activity Database

    Vandrovcová, Marta; Jirka, Ivan; Novotná, Katarína; Lisá, Věra; Frank, Otakar; Kolská, Z.; Starý, V.; Bačáková, Lucie

    2014-01-01

    Roč. 9, č. 6 (2014), e100475 E-ISSN 1932-6203 R&D Projects: GA ČR(CZ) GAP108/10/1858; GA ČR(CZ) GAP107/12/1025; GA MPO FR-TI3/088 Institutional support: RVO:67985823 ; RVO:61388955 Keywords : thermally oxidized surface * titanium-niobium * TiO2 * osteoblast * macrophage Subject RIV: EI - Biotechnology ; Bionics Impact factor: 3.234, year: 2014

  2. Electrochemical and morphological analyses on the titanium surface modified by shot blasting and anodic oxidation processes

    Energy Technology Data Exchange (ETDEWEB)

    Szesz, Eduardo M., E-mail: eszesz@neoortho.com.br [Neoortho Research Institute, Rua Ângelo Domingos Durigan, 607-Cascatinha, CEP 82025-100 Curitiba, PR (Brazil); Pereira, Bruno L., E-mail: brnl7@hotmail.com [Physics Department, Universidade Federal do Paraná, 81531-980 Curitiba, PR (Brazil); Kuromoto, Neide K., E-mail: kuromoto@fisica.ufpr.br [Physics Department, Universidade Federal do Paraná, 81531-980 Curitiba, PR (Brazil); Marino, Claudia E.B., E-mail: claudiamarino@yahoo.com [Mechanical Engineering Department, Universidade Federal do Paraná, 81531-980 Curitiba, PR (Brazil); Souza, Gelson B. de, E-mail: gelsonbs@uepg.br [Physics Department, Universidade Estadual de Ponta Grossa, 84051-510 Ponta Grossa, PR (Brazil); Soares, Paulo, E-mail: pa.soares@pucpr.br [Mechanical Engineering Department, Pontifícia Universidade Católica do Paraná, 80215-901 Curitiba, PR (Brazil)

    2013-01-01

    In recent years, many surface modification processes have been developed in order to induce the osseointegration on titanium surface and thus to improve the implants' biocompatibility. In this work, Ti surface has been modified by shot blasting followed by anodic oxidation process in order to associate the good surface characteristics of both processes to obtain a rough and porous surface able to promote the titanium surface bioactivity. Commercially pure titanium (grade 2) plates were used on the surface treatments that were as follows: Shot blasting (SB) performed using alumina (Al{sub 2}O{sub 3}) particles, and anodic oxidation (AO) using NaOH electrolyte. The morphology, structural changes and the open-circuit potentials (OCP) of the surfaces were analyzed. It can be observed that an increase on the roughness of the blasted surface and a rough and porous surface happens after the AO process. The anodic film produced is thin and followed the blasted surface topography. It can be observed that there are small pores with regular shape covering the entire surface. X-ray diffraction results showed the presence of the anatase and rutile phases on the blasted and anodized surface after heat treatment at 600 °C/1 h. Concerning electrochemical measurements, when the different samples were submitted to open-circuit conditions in a physiological electrolyte, the protective effect increases with the oxidation process due to the oxide layer. When the surface was blasted, the OCP was more negative when compared with the Ti surface without surface treatments. - Highlights: ► A combination of shot blasting and anodic oxidation surface treatments is proposed. ► Both processes produced an increase in roughness compared to the polished surface. ► The combination of processes produced a rough and porous surface. ► Open circuit results show that the protective effect increases with oxidation process. ► The combination of processes presents the better results in this

  3. Anodization of Zr-Nb-Cu alloy in mandelic acid - effect of solvent and anionic impurities

    International Nuclear Information System (INIS)

    Lavanya, A.; Raghunath Reddy, G.; Ch Anjaneyulu

    2004-01-01

    Anodization of zirconium-niobium-copper (ZNC) alloy in 0.1 M mandelic acid has been carried out. The effect of solvent (ethylene glycol) and added anionic impurities (sulphates, phosphates and carbonates) showed better kinetic results (formation rate, current efficiency and differential field of formation). (author)

  4. Niobium-base superalloys via powder metallurgy technology

    International Nuclear Information System (INIS)

    Loria, E.A.

    1987-01-01

    This paper provides some insight into an area that has been neglected, namely the possibility of developing high-strength, niobium-base alloys by improved oxidation resistance via the consolidation of rapidly solidified powders. Powder metallurgy (P/M) is an attractive processing technique because of its flexibility and versatility, and it may provide the alloys with properties and workability not obtainable via metal casting. A critical review of both U.S. and Russian literature is presented along with suggestions on the most promising compositions and processing techniques available to meet these competing goals. Previous work on many niobium alloys reveals that long term properties are retained well above those obtained on nickel-base superalloys. Cast and wrought alloys extend specific strength beyond 1200 0 C (2200 0 F), but lack oxidation resistance. Remarkable oxidation resistance is obtained, however, on miniature castings of certain ternary alloys which are too brittle for any processing. A better understanding of the oxidation mechanism is necessary before the proper P/M (RST) approach is taken on compositions which could provide compatibility between the two competing goals through grain refinement and a homogeneous distribution of the contributory phases. Finally, ways to up-scale production of Nb powder are discussed, including thermodynamic feasibility for the direct reduction of NbCl/sub 5/ in a 1.5 MW plasma reactor

  5. Catalytic applications of niobium compounds

    International Nuclear Information System (INIS)

    Wright, C.J.; England, W.A.

    1984-01-01

    This article examines the potential uses of niobium, and its compounds, as catalysts in chemical processing. The word potential is deliberately chosen because in 1978 none of the world's twenty-five major catalysts (1) contained niobium. On the other hand, catalysts containing molybdenum and vanadium, neighbors of niobium in the periodic table, realized over 80 x 10 6 of sales in that same year. At the same time many of the patents for niobium catalysts cover applications in which niobium improves the activity of, or substitutes for, molybdenum based compounds. With favorable cost differentials and improvements in understanding, niobium may be able to replace molybdenum in some its traditional uses

  6. A process for electrodeposition of layers of niobium, vanadium, molybdenum or tungsten, or of their alloys

    International Nuclear Information System (INIS)

    Diepers, H.; Schmidt, O.

    1977-01-01

    An improvement is proposed for the process for electrodeposition of layers of niobium, vanadium, molybdenum or tungsten or of their alloys from molten-salt electrolytes (fluorid melts) which is to increase the quality of layers in order to obtain regular thickness and smooth surfaces. According to the invention, a pre-separation is executed on an auxiliary cathode before the (preheated) cathode is immersed. The cathode is only charged for separation after the adjustment of a constant anode potential. It is an advantage that the auxiliary cathode is mechanically and electrically connected with the cathode. As an electrolyte, a mixture of niobium fluorides and a eustetic mixture of potassium fluorides, sodium fluorides and lithium fluorides are particularly suitable for the electrodeposition of miobium. (UWI) [de

  7. Optical scattering characteristic of annealed niobium oxide films

    International Nuclear Information System (INIS)

    Lai Fachun; Li Ming; Wang Haiqian; Hu Hailong; Wang Xiaoping; Hou, J.G.; Song Yizhou; Jiang Yousong

    2005-01-01

    Niobium oxide (Nb 2 O 5 ) films with thicknesses ranging from 200 to 1600 nm were deposited on fused silica at room temperature by low frequency reactive magnetron sputtering system. In order to study the optical losses resulting from the microstructures, the films with 500 nm thickness were annealed at temperatures between 600 and 1100 deg. C, and films with thicknesses from 200 to 1600 nm were annealed at 800 deg. C. Scanning electron microscopy and atomic force microscopy images show that the root mean square of surface roughness, the grain size, voids, microcracks, and grain boundaries increase with increasing both the annealing temperature and the thickness. Correspondingly, the optical transmittance and reflectance decrease, and the optical loss increases. The mechanisms of the optical losses are discussed. The results suggest that defects in the volume and the surface roughness should be the major source for the optical losses of the annealed films by causing pronounced scattering. For samples with a determined thickness, there is a critical annealing temperature, above which the surface scattering contributes to the major optical losses. In the experimental scope, for the films annealed at temperatures below 900 deg. C, the major optical losses resulted from volume scattering. However, surface roughness was the major source for the optical losses when the 500-nm films were annealed at temperatures above 900 deg. C

  8. Effect of anode firing on the performance of lanthanum and nickel co-doped SrTiO3 (La0.2Sr0.8Ti0.9Ni0.1O3-δ) anode of solid oxide fuel cell

    Science.gov (United States)

    Park, Byung Hyun; Choi, Gyeong Man

    2015-10-01

    Perovskite oxides have potential for use as alternative anode materials in solid oxide fuel cells (SOFCs) due to stability in anode atmosphere; donor-doped SrTiO3 (e.g., La0.2Sr0.8TiO3-δ) is a good candidate for this purpose. Electro-catalytic nanoparticles can be produced in oxide anodes by the ex-solution method, e.g., by incorporating Ni into a perovskite oxide in air, then reducing the oxide in H2 atmosphere. In this study, we varied the temperature (1100, 1250 °C) and atmosphere (air, H2) of La0.2Sr0.8Ti0.9Ni0.1O3-δ (LSTN) anode firing to control the degree of Ni ex-solution and microstructure. LSTN fired at 1250 °C in H2 showed the best anodic performance for scandia-stabilized zirconia (ScSZ) electrolyte-supported cells in H2 and CH4 fuels due to the favorable microstructure and Ni ex-solution.

  9. Recent progress in large grain/single crystal high RRR niobium

    International Nuclear Information System (INIS)

    Ganapati Rao Myneni; Peter Kneisel; Tadeu Carneiro; S.R. Agnew; F. Stevie

    2005-01-01

    High RRR bulk niobium Superconducting Radio Frequency (SRF) cavity technology is chosen for the International Linear Collider (ILC). The SRF community was convinced until now that fine grain polycrystalline RRR niobium sheets obtained via forging and cross rolling are essential for forming the SRF Cavities. However, it was recently discovered under a joint Reference Metals Company, Inc., - JLAB CRADA that large grain/single crystal RRR niobium sliced directly from ingots is highly ductile reaching 100 percent elongation. This discovery led to the successful fabrication of several SRF single and/or multi cell structures, formed with sliced RRR discs from the ingots, operating at 2.3, 1.5 and 1.3 GHz. This new exciting development is expected to offer high performance accelerator structures not only at reduced costs but also with simpler fabrication and processing conditions. As a result there is a renewed interest in the evaluation and understanding of the large grain and single crystal niobium with respect to their mechanical and physical properties as well as the oxidation behavior and the influence of impurities such as hydrogen and Ta. In this paper the results of many collaborative studies on large grain and single crystal high RRR niobium between JLAB, Universities and Industry are presented

  10. Anodic oxidation of anthraquinone dye Alizarin Red S at Ti/BDD electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Sun Jianrui; Lu Haiyan [College of Chemistry, Jilin University, Changchun 130012 (China); Du Lili [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Lin Haibo, E-mail: lhb910@jlu.edu.cn [College of Chemistry, Jilin University, Changchun 130012 (China); State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130012 (China); Li Hongdong, E-mail: hdli@jlu.edu.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China)

    2011-05-15

    The boron-doped diamond (BDD) thin-film electrode with high quality using industrially titanium plate (Ti/BDD) as substrate has been prepared and firstly used in the oxidation of anthraquinone dye Alizarin Red S (ARS) in wastewaters. The Ti/BDD electrodes are shown to have high concentration of sp{sup 3}-bonded carbon and wide electrochemical window. The results of the cyclic voltammetries show that BDD has unique properties such as high anodic stability and the production of active intermediates at the high potential. The oxidation regions of ARS and water are significantly separated at the Ti/BDD electrode, and the peak current increases linearly with increasing ARS concentration. The bulk electrolysis shows that removal of chemical oxygen demand (COD) and color can be completely reached and the electrooxidation of ARS behaves as a mass-transfer-controlled process at the Ti/BDD electrode. It is demonstrated that the performances of the Ti/BDD electrode for anodic oxidation ARS have been significantly improved with respect to the traditional electrodes.

  11. Comparative use of anodic oxidation, electro-Fenton and photoelectro-Fenton with Pt or boron-doped diamond anode to decolorize and mineralize Malachite Green oxalate dye

    International Nuclear Information System (INIS)

    El-Ghenymy, Abdellatif; Centellas, Francesc; Rodríguez, Rosa María; Cabot, Pere Lluís; Garrido, José Antonio; Sirés, Ignasi; Brillas, Enric

    2015-01-01

    Highlights: • Degradation of Malachite Green oxalate solutions at pH 3.0 by AO, AO-H 2 O 2 , EF and PEF. • A Pt anode leads to slower decolorization and mineralization than BDD. • Up to 97% mineralization by the most powerful PEF process with BDD at 100 mA cm −2 . • Study of the evolution of seven final short-chain aliphatic carboxylic acids. • Conversion of the initial N atoms of the dye mainly into NH 4 + , along with small amounts of NO 3 − . - Abstract: The degradation of 100 cm 3 of 177 mg dm −3 of the triphenylmethane dye Malachite Green oxalate at pH 3.0 was studied by anodic oxidation with stainless steel cathode (AO-SS), AO with air-diffusion cathode (AO-H 2 O 2 ), electro-Fenton (EF) and photoelectro-Fenton (PEF) with UVA light. The main oxidizing species were hydroxyl radicals formed from either water oxidation at the anode surface or in the bulk between added Fe 2+ and H 2 O 2 generated at the air-diffusion cathode. The use of a Pt anode led to slower decolorization and mineralization than BDD in all treatments because of the higher oxidation power of the latter. The decolorization was much faster for EF and PEF compared to AO-SS and AO-H 2 O 2 due to the contribution of hydroxyl radicals in the bulk. PEF allowed the quickest color removal by the rapid Fe 2+ regeneration from the photolysis of Fe(III) complexes with oxalate. The most powerful process was PEF with BDD, which yielded total decolorization in 6 min and 97% mineralization at 240 min operating at 100 mA cm −2 , thanks to hydroxyl radicals formed at the anode surface and in the bulk along with the photolytic action of UVA radiation. The evolution of final carboxylic acids like maleic, fumaric, succinic, acetic, oxalic, formic and oxamic was followed by ion-exclusion HPLC. All these acids and their Fe(III) complexes were removed more slowly with Pt anode. The initial N atoms of the dye were pre-eminently accumulated as NH 4 + ion, along with small amounts of NO 3 − ion.

  12. Influence of anode material on the electrochemical oxidation of 2-naphthol Part 1. Cyclic voltammetry and potential step experiments

    International Nuclear Information System (INIS)

    Panizza, M.; Cerisola, G.

    2003-01-01

    The anodic oxidation of 2-naphthol has been studied by cyclic voltammetry and chronoamperometry, using a range of electrode materials such as Ti-Ru-Sn ternary oxide, lead dioxide and boron-doped diamond (BDD) anodes. The results show that polymeric films, which cause electrode fouling, are formed during oxidation in the potential region of supporting electrolyte stability. IR spectroscopy verified the formation of this organic film. While the Ti-Ru-Sn ternary oxide surface cannot be reactivated, PbO 2 and BDD can be restored to their initial activity by simple anodic treatment in the potential region of electrolyte decomposition. In fact, during the polarization in this region, complex oxidation reactions leading to the complete incineration of polymeric materials can take place on these electrodes due to electrogenerated hydroxyl radicals. Moreover, it was found that BDD deactivation was less pronounced and its reactivation was faster than that of the other electrodes

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

    KAUST Repository

    Ghosh, Subhash Chandra; Li, Cheng Chao; Zeng, Hua Chun; Ngiam, Joyce S Y; Seayad, Abdul M.; Chen, Anqi

    2014-01-01

    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.

  14. 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.

  15. In situ electrochemical creation of cobalt oxide nanosheets with favorable performance as a high tap density anode material for lithium-ion batteries

    International Nuclear Information System (INIS)

    Lin, Qian; Sha, Yujing; Zhao, Bote; Chen, Yubo; Tadé, Moses O.; Shao, Zongping

    2015-01-01

    Highlights: • Cobalt oxide nanosheets in situ electrochemical generated from commercial LiCoO_2. • TEM indicates creation of cobalt oxide nanosheets from coarse layered LiCoO_2_. • Coarse-type LiCoO_2 with high tap density shows promising anode performance. • Optimizing weight ratio of LiCoO_2 in electrode, a high capacity was achieved. - Abstract: Cobalt oxides are attractive alternative anode materials for next-generation lithium-ion batteries (LIBs). To improve the performance of conversion-type anode materials such as cobalt oxides, well dispersed and nanosized particulate morphology is typically required. In this study, we describe the in situ electrochemical generation of cobalt oxide nanosheets from commercial micrometer-sized LiCoO_2 oxide as an anode material for LIBs. The electrode material as prepared was analyzed by XRD, FE-SEM and TEM. The electrochemical properties were investigated by cyclic voltammetry and by a constant current galvanostatic discharge–charge test. The material shows a high tap density and promising anode performance in terms of capacity, rate performance and cycling stability. A capacity of 560 mA h g"−"1 is still achieved at a current density of 1000 mA g"−"1 by increasing the amount of additives in the electrode to 40 wt%. This paper provides a new technique for developing a high-performance conversion-type anode for LIBs.

  16. Electrochemical destruction of chlorophenoxy herbicides by anodic oxidation and electro-Fenton using a boron-doped diamond electrode

    International Nuclear Information System (INIS)

    Brillas, Enric; Boye, Birame; Sires, Ignasi; Garrido, Jose Antonio; Rodriguez, Rosa Maria; Arias, Conchita; Cabot, Pere-Lluis; Comninellis, Christos

    2004-01-01

    The degradation of herbicides 4-chlorophenoxyacetic acid (4-CPA), 4-chloro-2-methylphenoxyacetic acid (MCPA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in aqueous medium of pH 3.0 has been comparatively studied by anodic oxidation and electro-Fenton using a boron-doped diamond (BDD) anode. All solutions are totally mineralized by electro-Fenton, even at low current, being the process more efficient with 1 mM Fe 2+ as catalyst. This is due to the production of large amounts of oxidant hydroxyl radical (OH·) on the BDD surface by water oxidation and from Fenton's reaction between added Fe 2+ and H 2 O 2 electrogenerated at the O 2 -diffusion cathode. The herbicide solutions are also completely depolluted by anodic oxidation. Although a quicker degradation is found at the first stages of electro-Fenton, similar times are required for achieving overall mineralization in both methods. The decay kinetics of all herbicides always follows a pseudo first-order reaction. Reversed-phase chromatography allows detecting 4-chlorophenol, 4-chloro-o-cresol, 2,4-dichlorophenol and 2,4,5-trichlorophenol as primary aromatic intermediates of 4-CPA, MCPA, 2,4-D and 2,4,5-T, respectively. Dechlorination of these products gives Cl - , which is slowly oxidized on BDD. Ion-exclusion chromatography reveals the presence of persistent oxalic acid in electro-Fenton by formation of Fe 3+ -oxalato complexes, which are slowly destroyed by OH· adsorbed on BDD. In anodic oxidation, oxalic acid is mineralized practically at the same rate as generated

  17. Platinum Monolayer Electrocatalysts for Anodic Oxidation of Alcohols.

    Science.gov (United States)

    Li, Meng; Liu, Ping; Adzic, Radoslav R

    2012-12-06

    The slow, incomplete oxidation of methanol and ethanol on platinum-based anodes as well as the high price and limited reserves of Pt has hampered the practical application of direct alcohol fuel cells. We describe the electrocatalysts consisting of one Pt monolayer (one atom thick layer) placed on extended or nanoparticle surfaces having the activity and selectivity for the oxidation of alcohol molecules that can be controlled with platinum-support interaction. The suitably expanded Pt monolayer (i.e., Pt/Au(111)) exhibits a factor of 7 activity increase in catalyzing methanol electrooxidation relative to Pt(111). Sizable enhancement is also observed for ethanol electrooxidation. Furthermore, a correlation between substrate-induced lateral strain in a Pt monolayer and its activity/selectivity is established and rationalized by experimental and theoretical studies. The knowledge we gained with single-crystal model catalysts was successfully applied in designing real nanocatalysts. These findings for alcohols are likely to be applicable for the oxidation of other classes of organic molecules.

  18. Kinetics of Carbon Monoxide Electro-Oxidation in Solid-Oxide Fuel Cells from Ni-YSZ Patterned-Anode Measurements

    KAUST Repository

    Hanna, J.; Lee, W. Y.; Ghoniem, A. F.

    2013-01-01

    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.

  19. 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.

  20. Improvement of transistor characteristics and stability for solution-processed ultra-thin high-valence niobium doped zinc-tin oxide thin film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Jeng, Jiann-Shing, E-mail: jsjeng@mail.nutn.edu.tw

    2016-08-15

    Nb-doped Zinc tin oxide (NZTO) channel materials have been prepared by solution process in combination with the spin-coating method. All NZTO thin film transistors (TFTs) are n-type enhancement-mode devices, either without or with Nb additives. High-valence niobium ion (ionic charge = +5) has a larger ionic potential and similar ionic radius to Zn{sup 2+} and Sn{sup 4+} ions. As compared with the pure ZTO device, introducing Nb{sup 5+} ions into the ZTO channel layers can improve the electrical properties and bias stability of TFTs because of the reduction of the oxygen vacancies. This study discusses the connection among the material properties of the NZTO films and the electrical performance and bias stability of NZTO TFTs and how they are influenced by the Nb/(Nb + Sn) molar ratios of NZTO films. - Highlights: • Ultra-thin high-valence niobium doped zinc-tin oxide (NZTO) thin films are prepared using a solution process. • Nb dopants in ZTO films reduce the oxygen vacancy and subgap adsorption of the ZTO films. • The Nb-doping concentration of the NZTO channel layer has a strong influence on the TFT performance.

  1. Determination of impurities in uranium--niobium (7.5%)--zirconium (2.5%) alloy

    Energy Technology Data Exchange (ETDEWEB)

    Arragon, Y

    1973-10-01

    The determination of 11 impurities in uranium--niobium-- zirconium alloys was studied. Elements of which the alloy is composed are considered and information is given on the determination of niobium by niobic acid precipitation. Selective elimination of the three components is discussed. Two liquid-liquid extractions are used. The nioblum is separated by methylisobutylketone in a hydrochloric --hydrofluoric medium and the zirconium and uranium by tributyl phosphate in a nitric medium. The determination of trace elements using electrochemical methods is discussed. Anodic re-dissolution polarography or square wave polarography enabled six elements (cadmium, copper, lead, zinc, bismuth, and thallium) to be determined in a carbonate medium together with aluminium in tetraethylammonium perchlorate, molybdenum in nitric acid, ammonium nitrate, and tungsten in hydrochloric acid with added double sodium and potassium tartrate. Fluorine was determined using ionometric techniques with a specific electrode and carbon was titrated by conductometry after combustion of the sample in an oxygen current. (auth)

  2. Nanoporous niobium nitride (Nb2N) with enhanced electrocatalytic performance for hydrogen evolution

    Science.gov (United States)

    Li, Yan; Zhang, Jianli; Qian, Xingyue; Zhang, Yue; Wang, Yining; Hu, Rudan; Yao, Chao; Zhu, Junwu

    2018-01-01

    The transition metal nitrides (TMNs) with nanoporous structure have shown great promise as potential electrocatalysts for the hydrogen evolution reaction (HER). Herein, self-organized nanoporous Nb2N was first successfully synthesized through the anodization of niobium in mixed oxalic acid/HF electrolyte, followed by a simple annealing treatment in the ammonia atmosphere. Due to the highly ordered nanoporous structure with abundant active sites and the enhanced electrical conductivity, the Nb2N exhibits a high catalytic current (326.3 mA cm-2) and low onset potential (96.3 mV), which is almost 3.9 times and 4.2 times better than that of Nb2O5, respectively. Meanwhile, the Nb2N also presents low Tafel slope (92 mV dec-1), and excellent cycling durability. More importantly, this study will provide more opportunities for designing and fabricating niobium compounds as an innovative HER catalysts.

  3. 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.

  4. Solid oxide fuel cell bi-layer anode with gadolinia-doped ceria for utilization of solid carbon fuel

    Energy Technology Data Exchange (ETDEWEB)

    Kellogg, Isaiah D. [Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, 290A Toomey Hall, 400 West 13th Street, Rolla, MO 65409 (United States); Department of Materials Science and Engineering, Missouri University of Science and Technology, 223 McNutt Hall, 1400 N. Bishop, Rolla, MO 65409 (United States); Koylu, Umit O. [Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, 290A Toomey Hall, 400 West 13th Street, Rolla, MO 65409 (United States); Dogan, Fatih [Department of Materials Science and Engineering, Missouri University of Science and Technology, 223 McNutt Hall, 1400 N. Bishop, Rolla, MO 65409 (United States)

    2010-11-01

    Pyrolytic carbon was used as fuel in a solid oxide fuel cell (SOFC) with a yttria-stabilized zirconia (YSZ) electrolyte and a bi-layer anode composed of nickel oxide gadolinia-doped ceria (NiO-GDC) and NiO-YSZ. The common problems of bulk shrinkage and emergent porosity in the YSZ layer adjacent to the GDC/YSZ interface were avoided by using an interlayer of porous NiO-YSZ as a buffer anode layer between the electrolyte and the NiO-GDC primary anode. Cells were fabricated from commercially available component powders so that unconventional production methods suggested in the literature were avoided, that is, the necessity of glycine-nitrate combustion synthesis, specialty multicomponent oxide powders, sputtering, or chemical vapor deposition. The easily-fabricated cell was successfully utilized with hydrogen and propane fuels as well as carbon deposited on the anode during the cyclic operation with the propane. A cell of similar construction could be used in the exhaust stream of a diesel engine to capture and utilize soot for secondary power generation and decreased particulate pollution without the need for filter regeneration. (author)

  5. Steady-state oxygen-solubility in niobium

    International Nuclear Information System (INIS)

    Schulze, K.; Jehn, H.

    1977-01-01

    During annealing of niobium in oxygen in certain temperature and pressure ranges steady states are established between the absorption of molecular oxygen and the evaporation of volatile oxides. The oxygen concentration in the niobium-oxygen α-solid solution is a function of oxygen pressure and temperature and has been redetermined in the ranges 10 -5 - 10 -2 Pa O 2 and 2,070 - 2,470 K. It follows differing from former results the equation csub(o) = 9.1 x 10 -6 x sub(po2) x exp (502000/RT) with csub(o) in at.-ppm, sub(po2) in Pa, T in K, R = 8.31 J x mol -1 x K -1 . The existence of steady states is limited to a temperature range from 1870 to 2470 K and to oxygen concentrations below the solubility limit given by solidus and solvus lines in the T-c diagram. In the experiments high-purity niobium wires with a specific electrical ratio rho (273 K)/rho(4.2 K) > 5,000 have been gassed under isothermal-isobaric conditions until the steady state has been reached. The oxygen concentration has been determined analytically by vacuum fusion extraction with platinum-flux technique as well as by electrical residual resistivity measurements at 4.2 K. (orig.) [de

  6. Influence of anode material on the electrochemical oxidation of 2-naphthol Part 1. Cyclic voltammetry and potential step experiments

    Energy Technology Data Exchange (ETDEWEB)

    Panizza, M.; Cerisola, G

    2003-10-15

    The anodic oxidation of 2-naphthol has been studied by cyclic voltammetry and chronoamperometry, using a range of electrode materials such as Ti-Ru-Sn ternary oxide, lead dioxide and boron-doped diamond (BDD) anodes. The results show that polymeric films, which cause electrode fouling, are formed during oxidation in the potential region of supporting electrolyte stability. IR spectroscopy verified the formation of this organic film. While the Ti-Ru-Sn ternary oxide surface cannot be reactivated, PbO{sub 2} and BDD can be restored to their initial activity by simple anodic treatment in the potential region of electrolyte decomposition. In fact, during the polarization in this region, complex oxidation reactions leading to the complete incineration of polymeric materials can take place on these electrodes due to electrogenerated hydroxyl radicals. Moreover, it was found that BDD deactivation was less pronounced and its reactivation was faster than that of the other electrodes.

  7. Engineering of the energetic structure of the anode of organic photovoltaic devices utilizing hot-wire deposited transition metal oxide layers

    Energy Technology Data Exchange (ETDEWEB)

    Vasilopoulou, M., E-mail: mariva@imel.demokritos.gr [Institute of Nanoscience and Nanotechnology, Department of Microelectronics, National Center for Scientific Research Demokritos, POB 60228, 15310 Agia Paraskevi, Attiki (Greece); Stathopoulos, N.A.; Savaidis, S.A. [Department of Electronics, Technological and Educational Institute (TEI) of Piraeus, Petrou Ralli & Thivon, 12244 Aegaleo (Greece); Kostis, I. [Institute of Nanoscience and Nanotechnology, Department of Microelectronics, National Center for Scientific Research Demokritos, POB 60228, 15310 Agia Paraskevi, Attiki (Greece); Department of Electronics, Technological and Educational Institute (TEI) of Piraeus, Petrou Ralli & Thivon, 12244 Aegaleo (Greece); Papadimitropoulos, G. [Institute of Nanoscience and Nanotechnology, Department of Microelectronics, National Center for Scientific Research Demokritos, POB 60228, 15310 Agia Paraskevi, Attiki (Greece); Davazoglou, D., E-mail: d.davazoglou@imel.demokritos.gr [Institute of Nanoscience and Nanotechnology, Department of Microelectronics, National Center for Scientific Research Demokritos, POB 60228, 15310 Agia Paraskevi, Attiki (Greece)

    2015-09-30

    Graphical abstract: In this work we perform successful engineering of the anode of organic photovoltaics based on poly(3-hexylthiophene):[6,6]-phenyl butyric acid methyl ester blends by using metal oxide transport layers exhibiting shallow gap states which act as a barrier-free path for hole transport toward the anode. - Highlights: • Interface engineering of the anode. • Organic photovoltaics (OPVs). • Shallow gap states. • Barrier-free hole transport. • Design rules for interface engineering in OPVs. - Abstract: In this work we use hydrogen deposited molybdenum and tungsten oxides (chemically described as H:MO{sub x}x ≤ 3 where M = Mo or W) to control the energetics at the anode of bulk heterojunction (BHJ) organic photovoltaics (OPVs) based on poly(3-hexylthiophene):[6,6]-phenyl butyric acid methyl ester (P3HT:PC{sub 71}BM) blends. Significantly improved current densities and open circuit voltages were achieved as a result of improved hole transport from the P3HT highest occupied molecular orbital (HOMO) toward indium tin oxide (ITO) anode. This was attributed to the formation of shallow gap states in these oxides which are located just below the Fermi level and above the polymer HOMO and thus may act as a barrier-free path for the extraction of holes. Consequently, these states can be used for controlling the energetic structure of the anode of OPVs. By using ultraviolet photoelectron spectroscopy it was found that dependent on the deposition conditions these gap states and work function of the metal oxides may be tailored to contribute to the precise alignment of the HOMO of the organic semiconductor (OSC) with the Fermi level of the anode electrode resulting in further enhancement of the device performance.

  8. Structural evolution in nanoporous anodic aluminium oxide

    International Nuclear Information System (INIS)

    Rocca, Emmanuel; Vantelon, Delphine; Reguer, Solenn; Mirambet, François

    2012-01-01

    Nanoporous and self-organized layers of aluminium alloys are used in many applications as membranes, templates for nanometric objects or corrosion protection for aluminium alloys. The use of this nanometric structure widely remains empirical, especially in the case of very small pores ( 4 into AlO 6 cluster and a partial release of sulphate ions are an important chemical transformation of the amorphous structure. This structural transformation defines the chemistry (pH and surface charge) inside the nanopores, the ageing behaviour and the possible incorporation or diffusion of chemical species in the nanostructure. Highlights: ► Investigations of local chemical environment of aluminium atoms in anodic aluminium oxide. ► The oxide structure is constituted by 2/3 of aluminium in tetrahedral coordination 1/3 in octahedral coordination. ► In contact with water, AlO 4 clusters are transformed into AlO 6 cluster and the aluminium sulphate bonds are hydrolysed. ► These transformations induce a pH decrease inside the nanostructure.

  9. 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.

  10. Flexible anodized aluminum oxide membranes with customizable back contact materials.

    Science.gov (United States)

    Nadimpally, B; Jarro, C A; Mangu, R; Rajaputra, S; Singh, V P

    2016-12-16

    Anodized aluminum oxide (AAO) membranes were fabricated using flexible substrate/carrier material. This method facilitates the use of AAO templates with many different materials as substrates that are otherwise incompatible with most anodization techniques. Thin titanium (Ti) and tungsten (W) layers were employed as interlayer materials. Titanium enhances adhesion. Tungsten not only helps eliminate the barrier layer but also plays a critical role in enabling the use of flexible substrates. The resulting flexible templates provide new, exciting opportunities in photovoltaic and other device applications. CuInSe 2 nanowires were electrochemically deposited into porous AAO templates with molybdenum (Mo) as the back contact material. The feasibility of using any material to form a contact with semiconductor nanowires has been demonstrated for the first time enabling new avenues in photovoltaic applications.

  11. Flexible anodized aluminum oxide membranes with customizable back contact materials

    Science.gov (United States)

    Nadimpally, B.; Jarro, C. A.; Mangu, R.; Rajaputra, S.; Singh, V. P.

    2016-12-01

    Anodized aluminum oxide (AAO) membranes were fabricated using flexible substrate/carrier material. This method facilitates the use of AAO templates with many different materials as substrates that are otherwise incompatible with most anodization techniques. Thin titanium (Ti) and tungsten (W) layers were employed as interlayer materials. Titanium enhances adhesion. Tungsten not only helps eliminate the barrier layer but also plays a critical role in enabling the use of flexible substrates. The resulting flexible templates provide new, exciting opportunities in photovoltaic and other device applications. CuInSe2 nanowires were electrochemically deposited into porous AAO templates with molybdenum (Mo) as the back contact material. The feasibility of using any material to form a contact with semiconductor nanowires has been demonstrated for the first time enabling new avenues in photovoltaic applications.

  12. The electrochemical properties and mechanism of formation of anodic oxide films on Mg-Al alloys

    International Nuclear Information System (INIS)

    Kim, Seong Jong; Okido, Masazumi

    2003-01-01

    The electronchemical properties and the mechanism of formation of anodic oxide films on Mg alloys containing 0-15 mass% Al, when anodized in NaOH solution, were investigated by focusing on the effects of anodizing potential, Al content, and anodizing time. The intensity ratio of Mg(OH) 2 in the XRD analysis decreased with increasing applied potential, while that of MgO increased. Mg(OH) 2 was barely detected at 80 V, while MgO was readily detected. The anti-corrosion properties of anodized specimens at each constant potential were better than those of non-anodized specimens. The specimen anodized at an applied potential of 3 V had the best anti-corrosion property. The intensity ratio of the β phase increased with aluminum content in Mg-Al alloys. During anodizing, the active dissolution reaction occurred preferentially in β phase until about 4 min, and then the current density increased gradually until 7 min. The dissolution reaction progressed in α phase, which had a lower Al content. In the anodic polarization test in 0.017 mol·dm -3 NaCl and 0.1 mol·dm -3 Na 2 SO 4 at 298 K, the current density of Mg-15 mass% Al alloy anodized for 10 min increased, since the anodic film that forms on the α phase is a non-compacted film. The anodic film on the α phase at 30 min was a compact film as compared with that at 10 min

  13. 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.

  14. 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.

  15. Hardening of niobium alloys at precrystallization annealing

    International Nuclear Information System (INIS)

    Vasil'eva, E.V.; Pustovalov, V.A.

    1989-01-01

    Niobium base alloys were investigated. It is shown that precrystallization annealing of niobium-molybdenum, niobium-vanadium and niobium-zirconium alloys elevates much more sufficiently their resistance to microplastic strains, than to macroplastic strains. Hardening effect differs sufficiently for different alloys. The maximal hardening is observed for niobium-vanadium alloys, the minimal one - for niobium-zirconium alloys

  16. Determination of Ti, Cr, Cu and Ta in niobium oxide by X-ray fluorescence method

    International Nuclear Information System (INIS)

    Dixit, R.M.; Deshpande, S.S.

    1986-01-01

    An x-ray fluorescence method for the determination of Ti, Cr, Cu and Ta in niobium oxide has been developed. Samples/standards in powder form are mixed with boric acid in the proportion of 1:1 (400 mg. each). Double layer pellets are prepared by pressing this mixture over a primary boric acid pellet. Philips PW-1220, a semiautomatic x-ray spectrometer with tungsten target x-ray tube for excitation and LiF (200) crystal for dispersion have been used. The determination range is from 0.005 to 0.1per cent for Ti and Cr, 0.01 to 0.1per cent for Cu and 0.05 to 1per cent for Ta. (author)

  17. Synergism between anodic oxidation with diamond anodes and heterogeneous catalytic photolysis for the treatment of pharmaceutical pollutants

    Directory of Open Access Journals (Sweden)

    Juan M. Peralta-Hernández

    2016-03-01

    Full Text Available The mineralization of diclofenac and acetaminophen has been studied by single anodic oxidation with boron-doped diamond (AO-BDD using an undivided electrolysis cell, by single heterogeneous catalytic photolysis with titanium dioxide (HCP-TiO2 and by the combination of both advanced oxidation processes. The results show that mineralization can be obtained with either single technology. The type of functional groups of the pollutant does not influence the results of the single AO-BDD process, but it has a significant influence on the results obtained with HCP-TiO2. A clear synergistic effect appears when both processes are combined showing improvements in the oxidation rate of more than 50% for diclofenac and nearly 200% for acetaminophen at the highest current exerted. Results obtained are explained in terms of the production of oxidants on the surface of BDD (primarily peroxodisulfate and the later homogeneous catalytic light decomposition of these oxidants in the bulk. This mechanism is consistent with the larger improvement observed at higher current densities, for which the production of oxidants is promoted.

  18. Anodic electrochemical treatment of amorphous alloys

    International Nuclear Information System (INIS)

    Isaev, N.I.; Yakovlev, V.B.; Osipov, Eh.K.; Isaev, A.V.; Trofimova, E.A.; Vasil'ev, V.Yu.

    1983-01-01

    The aim of the investigation is to reveal peculiarities of the process of anodic oxidation and properties of anode oxide films, formed on the surface of amorphous alloys. Amorphous alloys on the base of rectifying metals of Zr-Ni, Zr-Cu-Ni, Zr-Al-Ni, Zr-Cu-Sn, Zr-Al, Zr-Mo systems are studied. Electrolytes which do not dissolve or weakly dissolve oxide film, such as boric acid electrolyte (40-45 g/l H 3 BO 3 and 18 cm 3 /l of the 25% aqueous NH 4 OH solution) and 20% H 2 SO 4 solution, are used for oxidation. Results of investigations, carried out on amorphous alloys, contaning noticeable quantities of non-rectifying components - Cu, Ni, Sn, Fe, Mo etc - have shown that non-rectifying components harden a process of anodic oxidation and decrease the current efficiency. Amorphous alloys, containing only rectifying components are oxidated in anodic way, the regularities of film growth being similar to those obtained for crystalline materials

  19. 10-fold enhancement in light-driven water splitting using niobium oxynitride microcone array films

    KAUST Repository

    Shaheen, Basamat

    2016-03-26

    We demonstrate, for the first time, the synthesis of highly ordered niobium oxynitride microcones as an attractive class of materials for visible-light-driven water splitting. As revealed by the ultraviolet photoelectron spectroscopy (UPS), photoelectrochemical and transient photocurrent measurements, the microcones showed enhanced performance (~1000% compared to mesoporous niobium oxide) as photoanodes for water splitting with remarkable stability and visible light activity. © 2016 Elsevier B.V. All rights reserved.

  20. 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.

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

    International Nuclear Information System (INIS)

    Sulka, Grzegorz D.; Brzozka, Agnieszka; Liu, Lifeng

    2011-01-01

    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.

  2. Anomalous diffusion in niobium. Study of solute diffusion mechanism of iron in niobium

    International Nuclear Information System (INIS)

    Ablitzer, D.

    1977-01-01

    In order to explain anomalously high diffusion velocities observed for iron diffusion in niobium, the following parameters were measured: isotope effect, b factor (which expresses the effect of iron on niobium self-diffusion), self-diffusion coefficient of niobium, solute diffusion coefficient of iron in niobium. The results obtained show that neither pure vacancy models, nor diffusion in the lattice defects (dislocations, sub-boundaries, grain boundaries), nor pure interstitialy mechanisms, nor simple or cyclic exchange mechanisms agree with experiments. A mechanism is proposed which considers an equilibrium between substitution iron atoms and interstitial iron atoms. The diffusion of iron then occurs through interstitial vancancy pairs [fr

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

    OpenAIRE

    Hsueh , Cheng-Chih; Wang , Gou-Jen; Hsu , Shan-Hui; Hung , Huey-Shan

    2008-01-01

    Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/16838); International audience; 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...

  4. 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

  5. The electrochemical properties and mechanism of formation of anodic oxide films on Mg-Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seong Jong; Okido, Masazumi [Nagoya Univ., Nagoya (Japan)

    2003-07-01

    The electronchemical properties and the mechanism of formation of anodic oxide films on Mg alloys containing 0-15 mass% Al, when anodized in NaOH solution, were investigated by focusing on the effects of anodizing potential, Al content, and anodizing time. The intensity ratio of Mg(OH){sub 2} in the XRD analysis decreased with increasing applied potential, while that of MgO increased. Mg(OH){sub 2} was barely detected at 80 V, while MgO was readily detected. The anti-corrosion properties of anodized specimens at each constant potential were better than those of non-anodized specimens. The specimen anodized at an applied potential of 3 V had the best anti-corrosion property. The intensity ratio of the {beta} phase increased with aluminum content in Mg-Al alloys. During anodizing, the active dissolution reaction occurred preferentially in {beta} phase until about 4 min, and then the current density increased gradually until 7 min. The dissolution reaction progressed in {alpha} phase, which had a lower Al content. In the anodic polarization test in 0.017 mol{center_dot}dm{sup -3} NaCl and 0.1 mol{center_dot}dm{sup -3} Na{sub 2}SO{sub 4} at 298 K, the current density of Mg-15 mass% Al alloy anodized for 10 min increased, since the anodic film that forms on the {alpha} phase is a non-compacted film. The anodic film on the {alpha} phase at 30 min was a compact film as compared with that at 10 min.

  6. 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.

  7. Study of the role of the interface between niobium films and copper RF resonators

    CERN Document Server

    Benvenuti, Cristoforo; Campisi, I E; Darriulat, Pierre; Peck, M A; Russo, R

    1997-01-01

    Niobium-coated copper resonators are usually produced with an oxide interface between the film and the substrate. This oxide has two sources: the passivation layer inevitably formed on the surface of the cavity after chemical preparation before coating, and the niobium oxide which builds up on the surface of the cathode when it is exposed to air, and is transferred to the cavity surface during coa ting. The oxide layer may influence both the purity and the structural properties of the film, and in turn its RF behaviour. To study its effect, some cavities have been coated with a special two-cath ode sputtering system, allowing for a complete removal of both oxide layers by sputter-etching. For comparison, a few cavities have also been produced with the same coating system without sputter-etch ing, or with a controlled oxidation of the copper surface of the cavity after sputter-etching. Two cavities have also been produced without oxide interface using Kr and Ne as sputter gas instead of Ar .

  8. Characteristics of Sr0.92Y0.08Ti1-yNiyO3-δ anode and Ni-infiltrated Sr0.92Y0.08TiO3-δ anode using CH4 fuel in solid oxide fuel cells

    Science.gov (United States)

    Park, Eun Kyoung; Lee, Soonil; Yun, Jeong Woo

    2018-01-01

    Strontium titanium oxide co-doped with yttrium and nickel (SrxY1-xTiyNi1-yO3-δ; hereafter, SYTN), was investigated as an alternative anode material for solid oxide fuel cells. To improve the ionic conductivity of the Sr0.92Y0.08TiO3-δ (SYT) anode, Ni2+ was substituted into the B-site (initially occupied by Ti4+), thereby forming oxygen vacancies. To analyze the effects of Ni-doping in the SYT anode, the electrochemical properties of the SYTN anode were compared with those of the Ni-infiltrated SYT(Ni@SYT) using H2 and CH4 as fuels. The electrochemical reactions at the SYTN anode in the presence of both H2 and CH4 were limited by relatively slow reactions, such as non-charged processes including oxygen surface exchange and solid surface diffusion. The high electrical conductivity and excellent catalytic activity of the Ni nanoparticles in the Ni@SYT anode led to improved cell performance. CH4 decomposition at the Ni@SYT anode occurred via thermal pyrolysis of CH4 rather than by steam methane reforming, resulting in carbon deposition. In comparison, the poor inherent catalytic activity for CH4 oxidation exhibited by the SYTN anode minimized carbon deposition on the anode surface.

  9. Apatite Formation and Biocompatibility of a Low Young’s Modulus Ti-Nb-Sn Alloy Treated with Anodic Oxidation and Hot Water

    Science.gov (United States)

    Tanaka, Hidetatsu; Mori, Yu; Noro, Atsushi; Kogure, Atsushi; Kamimura, Masayuki; Yamada, Norikazu; Hanada, Shuji; Masahashi, Naoya; Itoi, Eiji

    2016-01-01

    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. PMID:26914329

  10. Anodic selective functionalization of cyclic amine derivatives

    OpenAIRE

    Onomura, Osamu

    2012-01-01

    Anodic reactions are desirable methods from the viewpoint of Green Chemistry, since no toxic oxidants are necessary for the oxidation of organic molecules. This review introduces usefulness of anodic oxidation and successive reaction for selective functionalization of cyclic amine derivatives.

  11. Biomimetic novel nanoporous niobium oxide coating for orthopaedic applications

    Science.gov (United States)

    Pauline, S. Anne; Rajendran, N.

    2014-01-01

    Niobium oxide was synthesized by sol-gel methodology and a crystalline, nanoporous and adherent coating of Nb2O5 was deposited on 316L SS using the spin coating technique and heat treatment. The synthesis conditions were optimized to obtain a nanoporous morphology. The coating was characterized using attenuated total reflectance-Infrared spectroscopy (ATR-IR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and transmission electron microscopy (TEM) and the formation of crystalline Nb2O5 coating with nanoporous morphology was confirmed. Mechanical studies confirmed that the coating has excellent adherence to the substrate and the hardness value of the coating was excellent. Contact angle analysis showed increased hydrophilicity for the coated substrate. In vitro bioactivity test confirmed that the Nb2O5 coating with nanoporous morphology facilitated the growth of hydroxyapatite (HAp). This was further confirmed by the solution analysis test where increased uptake of calcium and phosphorous ions from simulated body fluid (SBF) was observed. Electrochemical evaluation of the coating confirmed that the crystalline coating is insulative and protective in nature and offered excellent corrosion protection to 316L SS. Thus, this study confirmed that the nanoporous crystalline Nb2O5 coating conferred bioactivity and enhanced corrosion resistance on 316L SS.

  12. Biomimetic novel nanoporous niobium oxide coating for orthopaedic applications

    Energy Technology Data Exchange (ETDEWEB)

    Pauline, S. Anne; Rajendran, N., E-mail: nrajendran@annauniv.edu

    2014-01-30

    Niobium oxide was synthesized by sol–gel methodology and a crystalline, nanoporous and adherent coating of Nb{sub 2}O{sub 5} was deposited on 316L SS using the spin coating technique and heat treatment. The synthesis conditions were optimized to obtain a nanoporous morphology. The coating was characterized using attenuated total reflectance-Infrared spectroscopy (ATR-IR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and transmission electron microscopy (TEM) and the formation of crystalline Nb{sub 2}O{sub 5} coating with nanoporous morphology was confirmed. Mechanical studies confirmed that the coating has excellent adherence to the substrate and the hardness value of the coating was excellent. Contact angle analysis showed increased hydrophilicity for the coated substrate. In vitro bioactivity test confirmed that the Nb{sub 2}O{sub 5} coating with nanoporous morphology facilitated the growth of hydroxyapatite (HAp). This was further confirmed by the solution analysis test where increased uptake of calcium and phosphorous ions from simulated body fluid (SBF) was observed. Electrochemical evaluation of the coating confirmed that the crystalline coating is insulative and protective in nature and offered excellent corrosion protection to 316L SS. Thus, this study confirmed that the nanoporous crystalline Nb{sub 2}O{sub 5} coating conferred bioactivity and enhanced corrosion resistance on 316L SS.

  13. Optimum Exploration for the Self-Ordering of Anodic Porous Alumina Formed via Selenic Acid Anodizing

    OpenAIRE

    Akiya, Shunta; Kikuchi, Tatsuya; Natsui, Shungo; Suzuki, Ryosuke O.

    2015-01-01

    Improvements of the regularity of the arrangement of anodic porous alumina formed by selenic acid anodizing were investigated under various operating conditions. The oxide burning voltage increased with the stirring rate of the selenic acid solution, and the high applied voltage without oxide burning was achieved by vigorously stirring the solution. The regularity of the porous alumina was improved as the anodizing time and surface flatness increased. Conversely, the purity of the 99.5–99.999...

  14. Nanocrystalline Mn-Mo-Ce Oxide Anode Doped Rare Earth Ce and Its Selective Electro-catalytic Performance

    Directory of Open Access Journals (Sweden)

    SHI Yan-hua

    2017-09-01

    Full Text Available The anode oxide of nanocrystalline Mn-Mo-Ce was prepared by anode electro-deposition technology, and its nanostructure and selective electro-catalytic performance were investigated using the SEM, EDS, XRD, HRTEM, electrochemical technology and oxygen evolution efficiency testing. Furthermore, the selective electro-catalytic mechanism of oxygen evolution and chlorine depression was discussed. The results show that the mesh-like nanostructure Mn-Mo-Ce oxide anode with little cerium doped is obtained, and the oxygen evolution efficiency for the anode in the seawater is 99.51%, which means a high efficiency for the selective electro-catalytic for the oxygen evolution. Due to the structural characteristics of γ-MnO2, the OH- ion is preferentially absorbed, while Cl- absorption is depressed. OH- accomplishes the oxygen evolution process during the valence transition electrocatalysis of Mn4+/Mn3+, completing the selective electro-catalysis process. Ce doping greatly increases the reaction activity, and promotes the absorption and discharge; the rising interplanar spacing between active (100 crystalline plane promotes OH- motion and the escape of newborn O2, so that the selective electro-catalytic property with high efficient oxygen evolution and chlorine depression is achieved from the nano morphology effect.

  15. Pore diameter control of anodic aluminum oxide with ordered array of nanopores

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Allen; Yang, Yong-Feng [Department of Chemical Engineering, National Tsing Hua University, Hsin-Chu, 30013 (China); Hu, Chi-Chang [Department of Chemical Engineering, National Tsing Hua University, Hsin-Chu 401 (China); Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 621 (China); Lin, Chi-Cheng [Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 621 (China)

    2008-01-01

    Highly uniform, self-ordered anodic aluminum oxide (AAO) with an ordered nanoporous array can be effectively formed from industrially pure (99.5%) aluminum sheets through an anodizing program in a mixture solution of sulfuric and oxalic acids. The influences of anodizing variables, such as applied voltage, solution temperature, oxalic acid concentration, agitation rate, and sulfuric acid concentration, on the average pore diameter of AAO were systematically investigated using fractional factorial design (FFD). The applied voltage, and sulfuric acid concentration were found to be the key factors affecting the pore diameter of AAO films in the FFD study. The pore diameter of AAO is regularly increased from ca. 50 to 150 nm when the applied voltage and the concentration of sulfuric acid are gradually increased from 53 to 80 V and from 3.5 to 8 M, respectively. Fine tuning of the pore diameter for AAO films with an ordered, nanoporous, arrayed structure from industrially pure aluminum sheets can be achieved. (author)

  16. Porous and mesh alumina formed by anodization of high purity aluminum films at low anodizing voltage

    International Nuclear Information System (INIS)

    Abd-Elnaiem, Alaa M.; Mebed, A.M.; El-Said, Waleed Ahmed; Abdel-Rahim, M.A.

    2014-01-01

    Electrochemical oxidation of high-purity aluminum (Al) films under low anodizing voltages (1–10) V has been conducted to obtain anodic aluminum oxide (AAO) with ultra-small pore size and inter-pore distance. Different structures of AAO have been obtained e.g. nanoporous and mesh structures. Highly regular pore arrays with small pore size and inter-pore distance have been formed in oxalic or sulfuric acids at different temperatures (22–50 °C). It is found that the pore diameter, inter-pore distance and the barrier layer thickness are independent of the anodizing parameters, which is very different from the rules of general AAO fabrication. The brand formation mechanism has been revealed by the scanning electron microscope study. Regular nanopores are formed under 10 V at the beginning of the anodization and then serve as a template layer dominating the formation of ultra-small nanopores. Anodization that is performed at voltages less than 5 V leads to mesh structured alumina. In addition, we have introduced a simple one-pot synthesis method to develop thin walls of oxide containing lithium (Li) ions that could be used for battery application based on anodization of Al films in a supersaturated mixture of lithium phosphate and phosphoric acid as matrix for Li-composite electrolyte. - Highlights: • We develop anodic aluminum oxide (AAO) with small pore size and inter-pore distance. • Applying low anodizing voltages onto aluminum film leads to form mesh structures. • The value of anodizing voltage (1–10 V) has no effect on pore size or inter-pore distance. • Applying anodizing voltage less than 5 V leads to mesh structured AAO. • AAO can be used as a matrix for Li-composite electrolytes

  17. Porous and mesh alumina formed by anodization of high purity aluminum films at low anodizing voltage

    Energy Technology Data Exchange (ETDEWEB)

    Abd-Elnaiem, Alaa M., E-mail: alaa.abd-elnaiem@science.au.edu.eg [KACST-Intel Consortium Center of Excellence in Nano-manufacturing Applications (CENA), Riyadh (Saudi Arabia); Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Mebed, A.M. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Department of Physics, Faculty of Science, Al-Jouf University, Sakaka 2014 (Saudi Arabia); El-Said, Waleed Ahmed [Department of Chemistry, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Abdel-Rahim, M.A. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt)

    2014-11-03

    Electrochemical oxidation of high-purity aluminum (Al) films under low anodizing voltages (1–10) V has been conducted to obtain anodic aluminum oxide (AAO) with ultra-small pore size and inter-pore distance. Different structures of AAO have been obtained e.g. nanoporous and mesh structures. Highly regular pore arrays with small pore size and inter-pore distance have been formed in oxalic or sulfuric acids at different temperatures (22–50 °C). It is found that the pore diameter, inter-pore distance and the barrier layer thickness are independent of the anodizing parameters, which is very different from the rules of general AAO fabrication. The brand formation mechanism has been revealed by the scanning electron microscope study. Regular nanopores are formed under 10 V at the beginning of the anodization and then serve as a template layer dominating the formation of ultra-small nanopores. Anodization that is performed at voltages less than 5 V leads to mesh structured alumina. In addition, we have introduced a simple one-pot synthesis method to develop thin walls of oxide containing lithium (Li) ions that could be used for battery application based on anodization of Al films in a supersaturated mixture of lithium phosphate and phosphoric acid as matrix for Li-composite electrolyte. - Highlights: • We develop anodic aluminum oxide (AAO) with small pore size and inter-pore distance. • Applying low anodizing voltages onto aluminum film leads to form mesh structures. • The value of anodizing voltage (1–10 V) has no effect on pore size or inter-pore distance. • Applying anodizing voltage less than 5 V leads to mesh structured AAO. • AAO can be used as a matrix for Li-composite electrolytes.

  18. Capacitor Property and Leakage Current Mechanism of ZrO2 Thin Dielectric Films Prepared by Anodic Oxidation

    Science.gov (United States)

    Kamijyo, Masahiro; Onozuka, Tomotake; Shinkai, Satoko; Sasaki, Katsutaka; Yamane, Misao; Abe, Yoshio

    2003-07-01

    Polycrystalline ZrO2 thin film capacitors were prepared by anodizing sputter-deposited Zr films. Electrical measurements are performed for the parallel-plate anodized capacitors with an Al-ZrO2-Zr (metal-insulator-metal) structure, and a high capacitance density (0.6 μF/cm2) and a low dielectric loss of nearly 1% are obtained for a very thin-oxide capacitor anodized at 10 V. In addition, the leakage current density of this capacitor is about 1.8 × 10-8 A/cm2 at an applied voltage of 5 V. However, the leakage current is somewhat larger than that of a low-loss HfO2 capacitor. The leakage current density (J) of ZrO2 capacitors as a function of applied electric field (E) was investigated for several capacitors with different oxide thicknesses, by plotting \\ln(J) vs E1/2 curves. As a result, it is revealed that the conduction mechanism is due to the Poole-Frenkel effect, irrespective of the oxide thickness.

  19. Thermodynamic and exergoeconomic analysis of biogas fed solid oxide fuel cell power plants emphasizing on anode and cathode recycling: A comparative study

    International Nuclear Information System (INIS)

    Mehr, A.S.; Mahmoudi, S.M.S.; Yari, M.; Chitsaz, A.

    2015-01-01

    Highlights: • Four biogas-fed solid oxide fuel cell power plants are proposed. • Performance of systems is compared with each other economically. • Efficiency of biogas fed fuel cell with anode–cathode recycling is the highest. • For current density of 6000 A/m"2 the optimum anode recycle ratio is around 0.25. • Unit product cost of biogas fed fuel cell with anode–cathode recycling is 19.07$/GJ. - Abstract: Four different configurations of natural gas and biogas fed solid oxide fuel cell are proposed and analyzed thermoeconomically, focusing on the influence of anode and/or cathode gas recycling. It is observed that the net output power is maximized at an optimum current density the value of which is lowered as the methane concentration in the biogas is decreased. Results indicate that when the current density is low, there is an optimum anode recycling ratio at which the thermal efficiency is maximized. In addition, an increase in the anode recycling ratio increases the unit product cost of the system while an increase in the cathode recycling ratio has a revers effect. For the same working conditions, the solid oxide fuel cell with anode and cathode recycling is superior to the other configurations and its thermal efficiency is calculated as 46.09% being 6.81% higher than that of the simple solid oxide fuel cell fed by natural gas. The unit product cost of the solid oxide fuel cell-anode and cathode recycling system is calculated as 19.07$/GJ which is about 35% lower than the corresponding value for the simple natural gas fed solid oxide fuel cell system.

  20. Understanding Quality Factor Degradation in Superconducting Niobium Cavities at Low Microwave Field Amplitudes

    Science.gov (United States)

    Romanenko, A.; Schuster, D. I.

    2017-12-01

    In niobium superconducting radio frequency (SRF) cavities for particle acceleration, a decrease of the quality factor at lower fields—a so-called low field Q slope or LFQS—has been a long-standing unexplained effect. By extending the high Q measurement techniques to ultralow fields, we discover two previously unknown features of the effect: (i) saturation at rf fields lower than Eacc˜0.1 MV /m ; (ii) strong degradation enhancement by growing thicker niobium pentoxide. Our findings suggest that the LFQS may be caused by the two level systems in the natural niobium oxide on the inner cavity surface, thereby identifying a new source of residual resistance and providing guidance for potential nonaccelerator low-field applications of SRF cavities.

  1. High-performance micro-solid oxide fuel cells fabricated on nanoporous anodic aluminum oxide templates

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Chang-Woo; Kim, Hyun-Mi; Kim, Ki-Bum [WCUHybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-742 (Korea, Republic of); Son, Ji-Won; Lee, Jong-Ho; Lee, Hae-Weon [High Temperature Energy Materials Center, Korea Institute of Science and Technology, 39-1, Hawolgok-dong, Seongbuk-gu, Seoul, 136-791 (Korea, Republic of)

    2011-03-22

    Micro-solid oxide fuel cells ({mu}-SOFCs) are fabricated on nanoporous anodic aluminum oxide (AAO) templates with a cell structure composed of a 600-nm-thick AAO free-standing membrane embedded on a Si substrate, sputter-deposited Pt electrodes (cathode and anode) and an yttria-stabilized zirconia (YSZ) electrolyte deposited by pulsed laser deposition (PLD). Initially, the open circuit voltages (OCVs) of the AAO-supported {mu}-SOFCs are in the range of 0.05 V to 0.78 V, which is much lower than the ideal value, depending on the average pore size of the AAO template and the thickness of the YSZ electrolyte. Transmission electron microscopy (TEM) analysis reveals the formation of pinholes in the electrolyte layer that originate from the porous nature of the underlying AAO membrane. In order to clog these pinholes, a 20-nm thick Al{sub 2}O{sub 3} layer is deposited by atomic layer deposition (ALD) on top of the 300-nm thick YSZ layer and another 600-nm thick YSZ layer is deposited after removing the top intermittent Al{sub 2}O{sub 3} layer. Fuel cell devices fabricated in this way manifest OCVs of 1.02 V, and a maximum power density of 350 mW cm{sup -2} at 500 C. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. 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

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

    International Nuclear Information System (INIS)

    Panizza, M.; Kapalka, Agnieszka; Comninellis, 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

  4. 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.

  5. A novel high performance composite anode with in situ growth of Fe-Ni alloy nanoparticles for intermediate solid oxide fuel cells

    International Nuclear Information System (INIS)

    Li, Jingcheng; Yu, Yan; Yin, Yi-Mei; Zhou, Ning; Ma, Zi-Feng

    2017-01-01

    Highlights: • A composite anode with endogenous Fe-Ni alloy nanoparticles has been prepared. • The redox reversibility of the anode has been confirmed by XRD. • The E_a of H_2 oxidation at the anode is much smaller than that at Ni-YSZ anode. • A ScSZ supported cell achieves MPD of 0.71 Wcm"−"2 and R_p of 0.16 Ω cm"2 at 800 °C. • The single cell shows stable output during 105 h testing at 800 °C 0.7 V in wet H_2". - Abstract: A redox reversible composite anode with Fe-Ni alloy nanoparticles in situ growth on SrLaFeO_4-type and LaFeO_3-type oxide substrates has been prepared for intermediate temperature solid oxide fuel cell (IT-SOFC) by reducing perovskite precursor La_0_._4Sr_0_._6Fe_0_._7_5Ni_0_._1Nb_0_._1_5O_3_-_δ (LSFNNb) in wet H_2 at 900 °C for 1 h. The anode has shown an excellent electrochemical catalytic activity for oxidation of hydrogen with much smaller E_a (25.1 ∼ 68.9 kJ mol"−"1) than the value (>160 kJ mol"−"1) at Ni-YSZ anode. A scandium stabilized zirconia (ScSZ) electrolyte supported SOFC with the anode achieves maximum power densities of 0.71, 0.52, 0.35, and 0.21 W cm"−"2 at 800, 750, 700 and 650 °C, respectively in wet H_2 (3% H_2O), and the corresponding R_p of 0.16, 0.21, 0.35, and 0.60 Ω cm"2 under OCV. Moreover, the single cell shows stable power output during ∼105 h operation at 800 °C under 0.7 V in wet H_2 after a initial degradation, indicating that R-LSFNNb is an excellent candidate as anode of IT-SOFC.

  6. 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.

  7. 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.

  8. 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.

  9. Quantitative relationship between nanotube length and anodizing current during constant current anodization

    International Nuclear Information System (INIS)

    Zhang, Yulian; Cheng, Weijie; Du, Fei; Zhang, Shaoyu; Ma, Weihua; Li, Dongdong; Song, Ye; Zhu, Xufei

    2015-01-01

    Highlights: • Ti anodization was performed by constant current rather than constant voltage. • The nanotube length was controlled by ionic current rather than dissolution current. • Electronic current can be estimated by the nanotube length and the anodizing current. • Dissolution reaction hardly contributes electric current across the barrier layer. - Abstract: The growth kinetics of anodic TiO 2 nanotubes (ATNTs) still remains unclear. ATNTs are generally fabricated under potentiostatic conditions rather than galvanostatic ones. The quantitative relationship between nanotube length and anodizing current (J total ) is difficult to determine, because the variable J total includes ionic current (J ion ) (also called oxide growth current J grow =J ion ) and electronic current (J e ), which cannot be separated from each other. One successful approach to achieve this objective is to use constant current anodization rather than constant voltage anodization, that is, through quantitative comparison between the nanotube length and the known J total during constant current anodization, we can estimate the relative magnitudes of J grow and J e . The nanotubes with lengths of 1.24, 2.23, 3.51 and 4.70 μm, were formed under constant currents (J total ) of 15, 20, 25 and 30 mA, respectively. The relationship between nanotube length (y) and anodizing current (x =J total =J grow +J e ) can be expressed by a fitting equation: y=0.23(x-10.13), from which J grow (J grow = x -10.13) and J e (∼10.13 mA) could be inferred under the present conditions. Meanwhile, the same conclusion could also be deduced from the oxide volume data. These results indicate that the nanotube growth is attributed to the oxide growth current rather than the dissolution current.

  10. Measurement of the surface charge accumulation using anodic aluminum oxide(AAO) structure in an inductively coupled plasma

    Science.gov (United States)

    Park, Ji-Hwan; Oh, Seung-Ju; Lee, Hyo-Chang; Kim, Yu-Sin; Kim, Young-Cheol; Kim, June Young; Ha, Chang-Seoung; Kwon, Soon-Ho; Lee, Jung-Joong; Chung, Chin-Wook

    2014-10-01

    As the critical dimension of the nano-device shrinks, an undesired etch profile occurs during plasma etch process. One of the reasons is the local electric field due to the surface charge accumulation. To demonstrate the surface charge accumulation, an anodic aluminum oxide (AAO) membrane which has high aspect ratio is used. The potential difference between top electrode and bottom electrode in an anodic aluminum oxide contact structure is measured during inductively coupled plasma exposure. The voltage difference is changed with external discharge conditions, such as gas pressure, input power, and gas species and the result is analyzed with the measured plasma parameters.

  11. Novel enhancement of thin-form-factor galvanic cells: Probing halogenated organic oxidizers and metal anodes

    Energy Technology Data Exchange (ETDEWEB)

    Cardenas-Valencia, Andres M.; Adornato, Lori; Short, R. Timothy; Langebrake, Larry [SRI International, Engineering and Systems Division, Marine Technology Program, 140 Seventh Avenue South, St Petersburg, FL 33701 (United States)

    2008-09-15

    The work reported herein demonstrates a novel method to improve the overall performance of thin-form-factor galvanic cells, fabricated via micro-electromechanical systems (MEMS) processes. Use of solid, low cost, cyclic-halogenated, organic catholyte materials permits water activation of cells consisting of metal anode and catalytic platinum positive electrodes. Similar cells, employing aluminum and zinc anodes, have been activated using sodium hypochlorite (NaClO) solutions, i.e. bleach, in the past. The oxidizers chosen for this study (bromo-, chloro- and iodo-succinimides, and sodium dichloroisocyanuric acid) supply the cathode's oxy-halogenated ions when in contact with water. Zinc, magnesium and aluminum anodes are utilized to fabricate galvanic cells. A comparison between these anodes, coupled with various oxidizers, is included herein. Results using aluminum anode cells show that, even though the utilization efficiency of the catholyte reagents is low (faradic efficiencies between 16 and 19%), the performance of the new water-activated cells (6 cm x 6 cm x 0.25 cm) is superior when compared to those activated with bleach. For instance, operational lives of 6 h (activation with 10% NaClO solution) increase to more than 30 h using the new approach, with a 100-ohm-load. It is also shown that specific energies of 90-110 Wh kg{sup -1} (calculated to include both reagent and packaging mass) could be obtained using the described approach with current draws between 10 and 20 mA. The specific energies obtained suggest that novel MEMS-type cells could have much broader application than low-current, bleach-activated cells. (author)

  12. 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.

  13. Structural comparison of anodic nanoporous-titania fabricated from single-step and three-step of anodization using two paralleled-electrodes anodizing cell

    Directory of Open Access Journals (Sweden)

    Mallika Thabuot

    2016-02-01

    Full Text Available Anodization of Ti sheet in the ethylene glycol electrolyte containing 0.38wt% NH4F with the addition of 1.79wt% H2O at room temperature was studied. Applied potential of 10-60 V and anodizing time of 1-3 h were conducted by single-step and three-step of anodization within the two paralleled-electrodes anodizing cell. Their structural and textural properties were investigated by X-ray diffraction (XRD and scanning electron microscopy (SEM. After annealing at 600°C in the air furnace for 3 h, TiO2-nanotubes was transformed to the higher proportion of anatase crystal phase. Also crystallization of anatase phase was enhanced as the duration of anodization as the final step increased. By using single-step of anodization, pore texture of oxide film was started to reveal at the applied potential of 30 V. Better orderly arrangement of the TiO2-nanotubes array with larger pore size was obtained with the increase of applied potential. The applied potential of 60 V was selected for the three-step of anodization with anodizing time of 1-3 h. Results showed that the well-smooth surface coverage with higher density of porous-TiO2 was achieved using prolonging time at the first and second step, however, discontinuity tube in length was produced instead of the long-vertical tube. Layer thickness of anodic oxide film depended on the anodizing time at the last step of anodization. More well arrangement of nanostructured-TiO2 was produced using three-step of anodization under 60 V with 3 h for each step.

  14. 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...... was tested at 700 deg. 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 evoltage 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 0.79Wcm-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...

  15. Solid-state electrochromic cell with anodic iridium oxide film electrodes

    International Nuclear Information System (INIS)

    Dautremont-Smith, W.C.; Beni, G.; Schiavone, L.M.; Shay, J.L.

    1979-01-01

    A new solid-state electrochromic cell has been fabricated using an anodic iridium oxide film (AIROF) display electrode. The cell has the symmetric sandwich structure AIROFvertical-barNafionvertical-barAIROF, with the Nafion solid electrolyte opacified by an in situ precipitation technique. A symmetric square-wave voltage of 1.5 V amplitude produces clearly perceivable color changes from pale to dark blue-gray in approx. =1 sec when viewed in diffuse reflection. Good open-circuit optical memory is exhibited:

  16. Photoconductivity of Germanium Nanowire Arrays Incorporated in Anodic Aluminum Oxide

    International Nuclear Information System (INIS)

    Polyakov, B; Prikulis, J; Grigorjeva, L; Millers, D; Daly, B; Holmes, J D; Erts, D

    2007-01-01

    Photoconductivity of germanium nanowire arrays of 50 and 100 nm diameter incorporated into Anodic Aluminum Oxide (AAO) membranes illuminated with visible light is investigated. Photocurrent response to excitation radiation with time constants faster than 10 -4 s were governed by absorption of incident light by nanowires, while photokinetics with time constants of the order of 10 -3 s originates from the photoluminescence of the AAO matrix. Possible applications of nanowire arrays inside AAO as photoresistors are discussed

  17. Template synthesis of indium nanowires using anodic aluminum oxide membranes.

    Science.gov (United States)

    Chen, Feng; Kitai, Adrian H

    2008-09-01

    Indium nanowires with diameters approximately 300 nm have been synthesized by a hydraulic pressure technique using anodic aluminum oxide (AAO) templates. The indium melt is injected into the AAO template and solidified to form nanostructures. The nanowires are dense, continuous and uniformly run through the entire approximately 60 microm thickness of the AAO template. X-ray diffraction (XRD) reveals that the nanowires are polycrystalline with a preferred orientation. SEM is performed to characterize the morphology of the nanowires.

  18. Effect of Processing Parameters on Pore Structure and Thickness of Anodic Aluminum Oxide (AAO) Tubular Membranes

    OpenAIRE

    Belwalkar, A.; Grasing, E.; Van Geertruyden, W.; Huang, Z.; Misiolek, W.Z.

    2008-01-01

    Nanoporous anodic aluminum oxide (AAO) tubular membranes were fabricated from aluminum alloy tubes in sulfuric and oxalic acid electrolytes using a two-step anodization process. The membranes were investigated for characteristics such as pore size, interpore distance and thickness by varying applied voltage and electrolyte concentration. Morphology of the membranes was examined using light optical and scanning electron microscopy and characterized using ImageJ software. Results showed that me...

  19. Deposition of niobium plate on niobium-titanium from molten salts

    International Nuclear Information System (INIS)

    Matychenko, Eh.S.; Shevyrev, A.A.; Stolyarova, L.A.; Sukhorzhevskaya, S.L.

    1993-01-01

    A possibility of using Nb-Ti alloys (50 and 34 mas.% of Ti) as substrates for deposition of niobium coating of chloride-fluoride and fluoride molten salts is studied. Corrosion behaviour of alloys indicates in the electrolytic bath within 970-1070 K interval, coating structure and state of coating-substrate boundary are investigated. Chloride-fluoride molten salt usefullness for making products with niobium coatings is shown

  20. Interlaboratory niobium dosimetry comparison

    International Nuclear Information System (INIS)

    Wille, P.

    1980-01-01

    For an interlaboratory comparison of neutron dosimetry using niobium the 93 sup(m)Nb activities of irradiated niobium monitors were measured. This work was performed to compare the applied techniques of dosimetry with Nb in different laboratories. The niobium monitors were irradiated in the fast breeder EBRII, USA and the BR2, Belgium. The monitors were dissolved and several samples were prepared. Their niobium contents were determined by the 94 Nb-count rates. since the original specific count rate was known. The KX radiations of the 93 sup(m)Nb of the samples and of a calibrated Nb-foil were compared. This foil was measured by PTB, Braunschweig and CBNM, Geel, which we additionally compared with the KX radiation of 88 Sr produced by a thin 88 Y source from a 88 Y-standard solution (PTB). (orig.) [de

  1. For cermet inert anode containing oxide and metal phases useful for the electrolytic production of metals

    Science.gov (United States)

    Ray, Siba P.; Liu, Xinghua; Weirauch, Douglas A.

    2002-01-01

    A cermet inert anode for the electrolytic production of metals such as aluminum is disclosed. The inert anode comprises a ceramic phase including an oxide of Ni, Fe and M, where M is at least one metal selected from Zn, Co, Al, Li, Cu, Ti, V, Cr, Zr, Nb, Ta, W, Mo, Hf and rare earths, preferably Zn and/or Co. Preferred ceramic compositions comprise Fe.sub.2 O.sub.3, NiO and ZnO or CoO. The cermet inert anode also comprises a metal phase such as Cu, Ag, Pd, Pt, Au, Rh, Ru, Ir and/or Os. A preferred metal phase comprises Cu and Ag. The cermet inert anodes may be used in electrolytic reduction cells for the production of commercial purity aluminum as well as other metals.

  2. Niobium ore OKA-1

    International Nuclear Information System (INIS)

    Steger, H.F.; Bowman, W.S.

    1981-01-01

    A 287-kg sample of a niobium ore, OKA-1, from Oka, Quebec, was prepared as a compositional reference material. OKA-1 was ground to minus 74 μm, blended in one lot, tested for homogeneity by X-ray fluorescence and chemical methods and bottled in 200-g units. In a 'free-choice' round-robin analytical program, 22 laboratories contributed results for niobium in each of two bottles of OKA-1. A statistical analysis of the data gave a recommended value of 0.37 +- 0.01% for niobium

  3. Solvent anode for plutonium purification

    International Nuclear Information System (INIS)

    Bowersox, D.F.; Fife, K.W.; Christensen, D.C.

    1986-01-01

    The purpose of this study is to develop a technique to allow complete oxidation of plutonium from the anode during plutonium electrorefining. This will eliminate the generation of a ''spent'' anode heel which requires further treatment for recovery. Our approach is to employ a solvent metal in the anode to provide a liquid anode pool throughout electrorefining. We use molten salts and metals in ceramic crucibles at 700 0 C. Our goal is to produce plutonium metal at 99.9% purity with oxidation and transfer of more than 98% of the impure plutonium feed metal from the anode into the salt and product phases. We have met these criteria in experiments on the 100 to 1000 g scale. We plan to scale our operations to 4 kg of feed plutonium and to optimize the process parameters

  4. 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.

  5. Infrared radiation properties of anodized aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Kohara, S. [Science Univ. of Tokyo, Noda, Chiba (Japan). Dept. of Materials Science and Technology; Niimi, Y. [Science Univ. of Tokyo, Noda, Chiba (Japan). Dept. of Materials Science and Technology

    1996-12-31

    The infrared radiation heating is an efficient and energy saving heating method. Ceramics have been used as an infrared radiant material, because the emissivity of metals is lower than that of ceramics. However, anodized aluminum could be used as the infrared radiant material since an aluminum oxide film is formed on the surface. In the present study, the infrared radiation properties of anodized aluminum have been investigated by determining the spectral emissivity curve. The spectral emissivity curve of anodized aluminum changed with the anodizing time. The spectral emissivity curve shifted to the higher level after anodizing for 10 min, but little changed afterwards. The infrared radiant material with high level spectral emissivity curve can be achieved by making an oxide film thicker than about 15 {mu}m on the surface of aluminum. Thus, anodized aluminum is applicable for the infrared radiation heating. (orig.)

  6. The influence of humidity on the kinetics of local anodic oxidation

    International Nuclear Information System (INIS)

    BartosIk, M; Skoda, D; Tomanec, O; Kalousek, R; Jansky, P; Zlamal, J; Spousta, J; Sikola, T

    2007-01-01

    In this paper the influence of relative humidity on fabrication of nanostructures at GaAs (100) surfaces by local anodic oxidation (LAO) is reported. The attention was paid both to the dimensions of oxide nanolines prepared at different relative humidities for tip-surface voltages of 6 - 9 V and tip speeds of 10 - 200 nm/s, and to the profiles corresponding to line trenches (etched in HCl after the nanoxidation). Contrary to the expectations the height and the half-width of oxide nanolines did not increase with relative humidity in the whole interval from 35% to 90%, but for lower relative humidities (< 50%) the lines were comparable in size to those prepared at 90%. However, this was accompanied with instabilities in the oxidation process resulting most probably from enhanced size variations of the water meniscus between the tip and the surface at these low humidities

  7. 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.

  8. Porous Anodic Aluminum Oxide with Serrated Nanochannels

    Science.gov (United States)

    Li, Dongdong; Zhao, Liang; Lu, Jia G.

    2010-03-01

    Self-assembled nanoporous anodic aluminum oxide (AAO) membrane with straight channels has long been an important tool in synthesizing highly ordered and vertically aligned quasi-1D nanostructures for various applications. Recently shape-selective nanomaterials have been achieved using AAO as a template. It is envisioned that nanowires with multi-branches will significantly increase the active functional sites for applications as sensors, catalysts, chemical cells, etc. Here AAO membranes with serrated nanochannels have been successfully fabricated via a two-step annodization method. The serrated channels with periodic intervals are aligned at an angle of ˜25^circ along the stem channels. The formation of the serrated channels is attributed to the evolution of oxygen gas bubbles and the resulted plastic deformation in oxide membrane. In order to reveal the inside channel structure, Platinum are electrodeposited into the AAO template. The as-synthesized serrated Pt nanowires demonstrate a superior electrocatalytic activity. This is attributed to the enhanced electric field strength around serrated tips as shown in the electric field simulation by COMOSL. Moreover, hierarchical serrated/straight hybrid structures can be constructed using this simple and novel self assembly technique.

  9. Synthesis of niobium nitride by pyrolysis of niobium pentachloride ammines

    International Nuclear Information System (INIS)

    Grebtsova, O.M.; Shulga, Y.M.; Troitskii, V.N.

    1986-01-01

    This paper investigates the conditions for the preparation of niobium nitride in the thermal decomposition of niobium nitride in the thermal decomposition of niobium pentachloride ammines. The synthesis of the ammines was accomplished by the reaction of powdered NbC1 5 with dry ammonia at 210 K. Thermography and x-ray diffraction, spectral, and chemical analyses were used to identify the ammonolysis products. It was established that the products of ammonolysis of NbC1 5 are a mixture of the x-ray-amorphous complex Nb (NH 2 ) /SUB 5-x/ - (NG 3 ) 3 CL 3 (x≅) and 2 moles of NH 4 C1. The steps in the thermal decomposition of this mixture were studied. The phase transition that is observed in the case of further vacuum heat treatment at 1100-1300 K is presented

  10. 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.

  11. Correlation of electrolyte-derived inclusions to crystallization in the early stage of anodic oxide film growth on titanium

    Energy Technology Data Exchange (ETDEWEB)

    Jaeggi, C., E-mail: christian.jaeggi@empa.ch [Empa, Swiss Federal Laboratories for Materials Testing and Research, Advanced Materials Processing Laboratory, Feuerwerkerstrasse 39, CH-3602 Thun (Switzerland); Parlinska-Wojtan, M., E-mail: magdalena.parlinska@empa.ch [Empa, Swiss Federal Laboratories for Materials Testing and Research, Center for Electron Microscopy, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Kern, P., E-mail: Philippe.Kern@neopac.ch [Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkerstrasse 39, CH-3602 Thun (Switzerland)

    2012-01-01

    Pure titanium has been subjected to anodization in sulfuric and phosphoric acid. For a better understanding of the oxide growth and properties of the final film, with a particular interest focused on the solution anions in the early stage of crystallization, microstructural analyses (Raman, Transmission Electron Microscopy [TEM]) of the oxide films were correlated to chemical depth profiling by glow discharge optical emission spectroscopy (GDOES). Raman spectroscopy shows that crystallization of the oxide films starts at potentials as low as 10-20 V. The onset of crystallization and the ongoing increase in crystallinity with increasing anodization potentials had already earlier been correlated to ac-impedance measurements [Jaeggi et al., Surf. Interface Anal. 38 (2006) 182]. TEM observations show a clear difference in the early phase of crystallization between oxides grown in 1 M sulfuric acid compared to 1 M phosphoric acid. Moreover, independent of electrolyte type, nano-sized pores from oxygen bubbles formation were revealed in the central part of the films. Until now, oxygen bubbles inside an anodically grown oxide have not been observed before without the presence of crystalline regions nearby. A growth model is proposed, in which the different starting locations of crystallization inside the films are correlated to the presence of the acid anions as residues in the film, as found by GDOES chemical depth-profiling.

  12. Degradation of 4,6-dinitro-o-cresol from water by anodic oxidation with a boron-doped diamond electrode

    International Nuclear Information System (INIS)

    Flox, Cristina; Garrido, Jose Antonio; Rodriguez, Rosa Maria; Centellas, Francesc; Cabot, Pere-Lluis; Arias, Conchita; Brillas, Enric

    2005-01-01

    Anodic oxidation of 4,6-dinitro-o-cresol (DNOC) has been studied in a cell of 100 ml with a boron-doped diamond anode and a graphite cathode, both of 3-cm 2 area. Solutions containing up to approximately 240 mg l -1 of compound in the pH range 2.0-12.0 have been treated at 100, 300 and 450 mA between 15 and 50 deg C. Total mineralization is always achieved due to the great amount of hydroxyl radical (·OH) produced as oxidant on the anode surface. Total organic carbon is more rapidly removed in acid medium, being the optimum pH 3.0. The degradation rate increases when temperature, current and DNOC concentration increase. However, at 100 mA depollution becomes more effective from 71 mg l -1 of initial pollutant. A pseudo first-order kinetics for DNOC decay is always found by reversed-phase chromatography, with a rate constant practically independent of pH, as expected if the same electroactive species is oxidized in all media. Ion-exclusion chromatography allowed the detection of oxalic acid as the ultimate carboxylic acid. The mineralization process leads to the complete release of NO 3 - ions from the destruction of nitroderivative intermediates. These products are oxidized simultaneously with accumulated oxalic acid up to the end of electrolyses. Comparative treatment of the same solutions with a Pt anode yields a quite poor depollution because of the generation of much lower amounts of reactive ·OH on its surface

  13. Significance of novel bioinorganic anodic aluminum oxide nanoscaffolds for promoting cellular response

    OpenAIRE

    Poinern, Gérrard Eddy Jai; Shackleton, Robert; Mamun, Shariful Islam; Fawcett, Derek

    2011-01-01

    Gérrard Eddy Jai Poinern, Robert Shackleton, Shariful Islam Mamun, Derek FawcettMurdoch Applied Nanotechnology Research Group, Department of Physics, Energy Studies and Nanotechnology, School of Engineering and Energy, Murdoch University, Murdoch, Western Australia, AustraliaAbstract: Tissue engineering is a multidisciplinary field that can directly benefit from the many advancements in nanotechnology and nanoscience. This article reviews a novel biocompatible anodic aluminum oxide...

  14. Analysis of anti-condensation mechanism on superhydrophobic anodic aluminum oxide surface

    International Nuclear Information System (INIS)

    Wu, Yanpeng; Zhang, Chaoying

    2013-01-01

    Wetting theory about superhydrophobic surfaces reveals that hydrophobicity of surfaces has great relationship with surface roughness and surface free energy. Adopt electrochemical plus fluorine silane modified method to prepare superhydrophobic surface on anodic aluminum oxide surface, which not only enhances surface roughness, but also reduces surface free energy, even the static contact angle can reach 159.2° and anti-condensation is authenticated. Based on the experimental findings, analyze the reason of anti-condensation on superhydrophobic surfaces: one is that the density of droplets formed on superhydrophobic surfaces is low and the number of droplets is little; the other is bigger static contact angle and smaller rolling angle on superhydrophobic surfaces make droplets easy to detach on smaller tilt angle. This research can solve some condensation problems of equipment using in HVAC systems, such as heat exchangers in air conditioning system, cold radiation boards, air supply outlets, and so on. Highlights: • Prepare superhydrophobic surface on anodic aluminum oxide surface. • Analyze the reason of anti-condensation on superhydrophobic surfaces. • The density of droplets formed on superhydrophobic surfaces is low. • Droplets on superhydrophobic surfaces are easy to detach. • This research can solve some problems of equipment using in HVAC systems

  15. Mechanical strenght and niobium and niobium-base alloys substructures

    International Nuclear Information System (INIS)

    Monteiro, W.A.; Andrade, A.H.P. de

    1986-01-01

    Niobium and some of its alloys have been used in several fields of technological applications such as the aerospace, chemical and nuclear industries. This is due to its excelent mechanical stringth at high temperatures and reasonable ductility at low temperatures. In this work, we review the main features of the relationship mechanical strength - substructure in niobium and its alloys, taking into account the presence of impurities, the influence of initial thermal and thermo - mechanical treatments as well as the irradiation by energetic particles. (Author) [pt

  16. Performance and properties of anodes reinforced with metal oxide nanoparticles for molten carbonate fuel cells

    Science.gov (United States)

    Accardo, Grazia; Frattini, Domenico; Yoon, Sung Pil; Ham, Hyung Chul; Nam, Suk Woo

    2017-12-01

    Development of electrode materials for molten carbonate fuel cells is a fundamental issue as a balance between mechanical and electrochemical properties is required due to the particular operating environments of these cells. As concern the anode, a viable strategy is to use nano-reinforced particles during electrodes' fabrication. Candidate nanomaterials comprise, but are not limited to, ZrO2, CeO2, TiO2, Ti, Mg, Al, etc. This work deals with the characterization and test of two different types of hard oxide nanoparticles as reinforce for NiAl-based anodes in molten carbonate fuel cells. Nano ceria and nano zirconia are compared each other and single cell test performances are presented. Compared to literature, the use of hard metal oxide nanoparticles allows good performance and promising perspectives with respect to the use a third alloying metal. However, nano zirconia performed slightly better than nano ceria as polarization and power curves are higher even if nano ceria has the highest mechanical properties. This means that the choice of nanoparticles to obtain improved anodes performance and properties is not trivial and a trade-off between relevant properties plays a key role.

  17. Surface patterned dielectrics by direct writing of anodic oxides using scanning droplet cell microscopy

    International Nuclear Information System (INIS)

    Siket, Christian M.; Mardare, Andrei Ionut; Kaltenbrunner, Martin; Bauer, Siegfried; Hassel, Achim Walter

    2013-01-01

    Highlights: • Scanning droplet cell microscopy was applied for local gate oxide writing. • Sharp lines are obtained at the highest writing speed of 1 mm min −1 . • 13.4 kC cm −3 was found as charge per volume for aluminium oxide. • High field constant of 24 nm V −1 and dielectric constant of 12 were determined for Al 2 O 3 by CV and EIS. -- Abstract: Scanning droplet cell microscopy was used for patterning of anodic oxide lines on the surface of Al thin films by direct writing. The structural modifications of the written oxide lines as a function of the writing speed were studied by analyzing the relative error of the line widths. Sharper lines were obtained for writing speeds faster than 1 mm min −1 . An increase in sharpness was observed for higher writing speeds. A theoretical model based on the Faraday law is proposed to explain the constant anodisation current measured during the writing process and yielded a charge per volume of 13.4 kC cm −3 for Al 2 O 3 . From calculated oxide film thicknesses the high field constant was found to be 24 nm V −1 . Electrochemical impedance spectroscopy revealed an increase of the electrical permittivity up to ε = 12 with the decrease of the writing speed of the oxide line. Writing of anodic oxide lines was proven to be an important step in preparing capacitors and gate dielectrics in plastic electronics

  18. Feed-forward control of a solid oxide fuel cell system with anode offgas recycle

    Science.gov (United States)

    Carré, Maxime; Brandenburger, Ralf; Friede, Wolfgang; Lapicque, François; Limbeck, Uwe; da Silva, Pedro

    2015-05-01

    In this work a combined heat and power unit (CHP unit) based on the solid oxide fuel cell (SOFC) technology is analysed. This unit has a special feature: the anode offgas is partially recycled to the anode inlet. Thus it is possible to increase the electrical efficiency and the system can be operated without external water feeding. A feed-forward control concept which allows secure operating conditions of the CHP unit as well as a maximization of its electrical efficiency is introduced and validated experimentally. The control algorithm requires a limited number of measurement values and few deterministic relations for its description.

  19. Doping profile measurements in silicon using terahertz time domain spectroscopy (THz-TDS) via electrochemical anodic oxidation

    Science.gov (United States)

    Tulsyan, Gaurav

    Doping profiles are engineered to manipulate device properties and to determine electrical performances of microelectronic devices frequently. To support engineering studies afterward, essential information is usually required from physically characterized doping profiles. Secondary Ion Mass Spectrometry (SIMS), Spreading Resistance Profiling (SRP) and Electrochemical Capacitance Voltage (ECV) profiling are standard techniques for now to map profile. SIMS yields a chemical doping profile via ion sputtering process and owns a better resolution, whereas ECV and SRP produce an electrical doping profile detecting free carriers in microelectronic devices. The major difference between electrical and chemical doping profiles is at heavily doped regions greater than 1020 atoms/cm3. At the profile region over the solubility limit, inactive dopants induce a flat plateau and detected by electrical measurements only. Destructive techniques are usually designed as stand-alone systems to study impurities. For an in-situ process control purpose, non-contact methods, such as ellipsometry and non-contact capacitance voltage (CV) techniques are current under development. In this theses work, terahertz time domain spectroscopy (THz-TDS) is utilized to achieve electrical doping profile in both destructive and non-contact manners. In recent years the Terahertz group at Rochester Institute Technology developed several techniques that use terahertz pulses to non-destructively map doping profiles. In this thesis, we study a destructive but potentially higher resolution version of the terahertz based approach to map the profile of activated dopants and augment the non-destructive approaches already developed. The basic idea of the profile mapping approach developed in this MS thesis is to anodize, and thus oxidize to silicon dioxide, thin layers (down to below 10 nm) of the wafer with the doping profile to be mapped. Since the dopants atoms and any free carriers in the silicon oxide thin

  20. A Comparative Analysis of 2-(Thiocyanomethylthio-Benzothiazole Degradation Using Electro-Fenton and Anodic Oxidation on a Boron-Doped Diamond Electrode

    Directory of Open Access Journals (Sweden)

    Armando Vázquez

    2018-01-01

    Full Text Available 2-(Thiocyanomethylthio-benzothiazole (TCMTB is used as fungicide in the paper, tannery, paint, and coatings industries, and its study is important as it is considered toxic to aquatic life. In this study, a comparison of direct anodic oxidation (AO using a boron-doped diamond electrode (BDD and electro-Fenton (EF processes for TCMTB degradation in acidic chloride and sulfate media using a FM01-LC reactor was performed. The results of the electrolysis processes studied in the FM01-LC reactor showed a higher degradation of TCMTB with the anodic oxidation process than with the electro-Fenton process, reaching 81% degradation for the former process versus 47% degradation for the latter process. This difference was attributed to the decrease in H2O2 during the EF process, due to parallel oxidation of chlorides. The degradation rate and current efficiency increased as a function of volumetric flow rate, indicating that convection promotes anodic oxidation and electro-Fenton processes. The results showed that both AO and EF processes could be useful strategies for TCMTB toxicity reduction in wastewaters.

  1. Influence of hydrogen reduction on photoelectro-chemical behavior of anodic oxidized n-TiO2 layers

    Energy Technology Data Exchange (ETDEWEB)

    Hartig, K J; Getoff, N

    1983-07-01

    The behavior of polycrystalline n-TiO2 photoanodes produced by anodic oxidation of Ti metal foils and subsequently reduced in hydrogen atmosphere at various temperatures and different times was investigated. The employed methods for their characterization were: scanning electron microscopy, X-ray diffraction, thickness determination, open-circuit voltage and capacitance/voltage studies as well as photoelectrochemical measurements. The reduction process results in an increase of oxygen deficiencies and a decrease of the amount of recombination centers and of grain-boundary energy barriers between the crystallites. All these parameters lead to a significant increase of the photoefficiency. The best photoanodes were obtained when the anodically oxidized samples were reduced under hydrogen at 800-850 C for 15 min (conversion of anatase to rutile crystal structures). 17 references.

  2. 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.

  3. Towards deriving Ni-rich cathode and oxide-based anode materials from hydroxides by sharing a facile co-precipitation method.

    Science.gov (United States)

    Qiu, Haifa; Du, Tengfei; Wu, Junfeng; Wang, Yonglong; Liu, Jian; Ye, Shihai; Liu, Sheng

    2018-05-22

    Although intensive studies have been conducted on layered transition metal oxide(TMO)-based cathode materials and metal oxide-based anode materials for Li-ion batteries, their precursors generally follow different or even complex synthesis routes. To share one route for preparing precursors of the cathode and anode materials, herein, we demonstrate a facile co-precipitation method to fabricate Ni-rich hydroxide precursors of Ni0.8Co0.1Mn0.1(OH)2. Ni-rich layered oxide of LiNi0.8Co0.1Mn0.1O2 is obtained by lithiation of the precursor in air. An NiO-based anode material is prepared by calcining the precursor or multi-walled carbon nanotubes (MWCNTs) incorporated precursors. The pre-addition of ammonia solution can simplify the co-precipitation procedures and the use of an air atmosphere can also make the heat treatment facile. LiNi0.8Co0.1Mn0.1O2 as the cathode material delivers a reversible capacity of 194 mA h g-1 at 40 mA g-1 and a notable cycling retention of 88.8% after 100 cycles at 200 mA g-1. This noticeable performance of the cathode arises from a decent particle morphology and high crystallinity of the layered oxides. As the anode material, the MWCNTs-incorporated oxides deliver a much higher reversible capacity of 811.1 mA h g-1 after 200 cycles compared to the pristine oxides without MWCNTs. The improvement on electrochemical performance can be attributed to synergistic effects from MWCNTs incorporation, including reinforced electronic conductivity, rich meso-pores and an alleviated volume effect. This facile and sharing method may offer an integrated and economical approach for commercial production of Ni-rich electrode materials for Li-ion batteries.

  4. Chemical compatibility and properties of suspension plasma-sprayed SrTiO3-based anodes for intermediate-temperature solid oxide fuel cells

    Science.gov (United States)

    Zhang, Shan-Lin; Li, Cheng-Xin; Li, Chang-Jiu

    2014-10-01

    La-doped strontium titanate (LST) is a promising, redox-stable perovskite material for direct hydrocarbon oxidation anodes in intermediate-temperature solid oxide fuel cells (IT-SOFCs). In this study, nano-sized LST and Sm-doped ceria (SDC) powders are produced by the sol-gel and glycine-nitrate processes, respectively. The chemical compatibility between LST and electrolyte materials is studied. A LST-SDC composite anode is prepared by suspension plasma spraying (SPS). The effects of annealing conditions on the phase structure, microstructure, and chemical stability of the LST-SDC composite anode are investigated. The results indicate that the suspension plasma-sprayed LST-SDC anode has the same phase structure as the original powders. LST exhibits a good chemical compatibility with SDC and Mg/Sr-doped lanthanum gallate (LSGM). The anode has a porosity of ∼40% with a finely porous structure that provides high gas permeability and a long three-phase boundary for the anode reaction. Single cells assembled with the LST-SDC anode, La0.8Sr0.2Ga0.8Mg0.2O3 electrolyte, and La0.8Sr0.2CoO3-SDC cathode show a good performance at 650-800 °C. The annealing reduces the impedances due to the enhancement in the bonding between the particles in the anode and interface of anode and LSGM electrolyte, thus improving the output performance of the cell.

  5. Technology of niobium and molybdenum refining by electron beam

    International Nuclear Information System (INIS)

    Conti, R.A.; Pinatti, D.G.; Sandim, H.R.Z.

    1988-01-01

    The uses of metals and alloys in superconductors (Nb46%Ti), aerospatial industry (Ti6Al4V), electroeletronic industry (Nb, Mo, W) and in surgical implants (Ti, Nb) are increasing nowadays. A refining process of niobium and molybdenum by electron beam technique, since the oxides reduction till the obtention of a high purity ingot is presented. (C.G.C.) [pt

  6. Properties on niobium-based Josephson tunneling elements in junction microstructures

    International Nuclear Information System (INIS)

    Albrecht, G.; Richter, J.; Weber, P.

    1982-01-01

    We describe the fabrication and electrical characteristics of niobium oxide-barrier tunnel junctions with counterelectrodes of lead/lead alloy. Primary attention is directed to the experimental conditions necessary to obtain high-quality tunnel barriers as well as studies on characterizing the atomic structure of the barrier region. In order to study the tunnel barrier homogeneity in the tunneling region the magnetic field dependence of the critical Josephson current is investigated. The I--V characteristics and dependence of the critical Josephson current on temperature are analyzed quantitatively by using a proximity effect model. Finally, we discuss experimental results on the improvement of junction quality by including traces of carbon in the rf argon plasma during the sputter cleaning of niobium base electrodes

  7. A facile and efficient approach for pore-opening detection of anodic aluminum oxide membranes

    Science.gov (United States)

    Cui, Jiewu; Wu, Yucheng; Wang, Yan; Zheng, Hongmei; Xu, Guangqing; Zhang, Xinyi

    2012-05-01

    The well aligned porous anodic aluminum oxide (AAO) membrane is fabricated by a two-step anodization method. The oxide barrier layer of AAO membrane must be removed to get through-hole membrane for synthesizing nanowires and nanotubes of metals, semiconductors and conducting polymers. Removal of the barrier layer of oxide and pore-extending is of significant importance for the preparation of AAO membrane with through-hole pore morphology and desired pore diameter. The conventional method for pore opening is that AAO membrane after removing of aluminum substrate is immersed in chemical etching solution, which is completely empirical and results in catastrophic damage for AAO membrane frequently. A very simple and efficient approach based on capillary action for detecting pore opening of AAO membrane is introduced in this paper, this method can achieve the detection for pore opening visually and control the pore diameter precisely to get desired morphology and the pore diameter of AAO membrane. Two kinds of AAO membranes with different pore shape were obtained by different pore opening methods. In addition, one-dimensional gradient gold nanowires are also fabricated by electrodeposition based on AAO membranes.

  8. 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...... 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...

  9. Fabrication of porous anodic alumina films by using two-step anodization process

    International Nuclear Information System (INIS)

    Xu Zhan; Zhou Bin; Xu Xiang; Wang Xiaoli; Wu Di; Shen Jun

    2006-01-01

    This article introduces the fabrication of the porous anodic alumina films which have ordered pore arrangement by using a two-step anodization process. The films have a parallel channel structure which nanopore diameter can be 20-100 nm, and depth can reach 50 μm. The change of pore structure in the first and second anodization, moving the alumina layer, widening process was analysed. The effect of the parameters such as different electrolytes, anodization temperature and the voltage on the nanopore structure was studied. The surface and profile structure through FE-SEM (field emission scanning electron microscope), the element composition in tiny area of the anodic aluminum oxide (AAO) surface were studied. The result indicates the pore diameter of AAO which is anodized in oxalic acid solution is larger than which anodized in sulfuric acid solution. The anodization temperature and voltage can enlarge the nanopore diameter of AAO in a range. (authors)

  10. 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) con...

  11. Facile and large-scale preparation of sandwich-structured graphene-metal oxide composites as anode materials for Li-ion batteries

    International Nuclear Information System (INIS)

    Fang, Hongmei; Zhao, Li; Yue, Wenbo; Wang, Yuan; Jiang, Yang; Zhang, Yuan

    2015-01-01

    Graphene-based metal oxides are desirable as potential anode materials for lithium-ion batteries (LIBs) owing to their superior electrochemical properties. In this work, sandwich-structured graphene-metal oxide (ZnO, NiO) composites are facilely synthesized on a large scale through self-assembly of graphene oxide nanosheets and metal ammine complexes, and then thermal decomposition of the self-assembled products. ZnO or NiO nanoparticles with diameters of 5∼10 nm are immobilized between the layers of graphene nanosheets, which may provide the space for accommodating the volume change of metal oxides during cycles, and highly improve the electronic conductivity of the composites. Accordingly, these sandwich-structured composites exhibit enhanced electrochemical performances compared to metal oxide particles or stacked graphene nanosheets. This facile synthesis method is very suitable for the large-scale production of three-dimensional graphene-based composites as high-performance anodes for LIBs.

  12. Niobium interaction with chloride-carbonate melts

    International Nuclear Information System (INIS)

    Kuznetsov, S.A.; Kuznetsova, S.V.

    1996-01-01

    Niobium interaction with chloride-carbonate melt NaCl-KCl-K 2 CO 3 (5 mass %) in the temperature range of 973-1123 K has been studied. The products and niobium corrosion rate have been ascertained, depending on the temperature of melt and time of allowance. Potentials of niobium corrosion have been measured. Refs. 11, figs. 3, tabs. 2

  13. Organic photovoltaics using thin gold film as an alternative anode to indium tin oxide

    International Nuclear Information System (INIS)

    Haldar, Amrita; Yambem, Soniya D.; Liao, Kang-Shyang; Alley, Nigel J.; Dillon, Eoghan P.; Barron, Andrew R.; Curran, Seamus A.

    2011-01-01

    Indium Tin Oxide (ITO) is the most commonly used anode as a transparent electrode and more recently as an anode for organic photovoltaics (OPVs). However, there are significant drawbacks in using ITO which include high material costs, mechanical instability including brittleness and poor electrical properties which limit its use in low-cost flexible devices. We present initial results of poly(3-hexylthiophene): phenyl-C 61 -butyric acid methyl ester OPVs showing that an efficiency of 1.9% (short-circuit current 7.01 mA/cm 2 , open-circuit voltage 0.55 V, fill factor 0.49) can be attained using an ultra thin film of gold coated glass as the device anode. The initial I-V characteristics demonstrate that using high work function metals when the thin film is kept ultra thin can be used as a replacement to ITO due to their greater stability and better morphological control.

  14. 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

  15. Two-Step Cycle for Producing Multiple Anodic Aluminum Oxide (AAO) Films with Increasing Long-Range Order.

    Science.gov (United States)

    Choudhary, Eric; Szalai, Veronika

    2016-01-01

    Nanoporous anodic aluminum oxide (AAO) membranes are being used for an increasing number of applications. However, the original two-step anodization method in which the first anodization is sacrificial to pre-pattern the second is still widely used to produce them. This method provides relatively low throughput and material utilization as half of the films are discarded. An alternative scheme that relies on alternating anodization and cathodic delamination is demonstrated that allows for the fabrication of several AAO films with only one sacrificial layer thus greatly improving total aluminum to alumina yield. The thickness for which the cathodic delamination performs best to yield full, unbroken AAO sheets is around 85 μm. Additionally, an image analysis method is used to quantify the degree of long-range ordering of the unit cells in the AAO films which was found to increase with each successive iteration of the fabrication cycle.

  16. Proposal of a new biokinetic model for niobium; Proposta de um novo modelo biocinetico para o niobio

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Roges

    2006-07-01

    There are two niobium isotopes generated in nuclear power plants: 95 Nb and 94 Nb. Workers and members of the public are subjects to intake these radionuclides in accident situation. For dose calculation purpose, it is very important to develop a model that describes in a more realistic way the kinetics of niobium inside of the human body. Presently the model adopted by ICRP (ICRP, 1989) is based on animal studies and describes the behavior of niobium in human being in a simple manner. The new model proposal describes the kinetics of the niobium from the intake into the blood until the excretion, doing this in a more realistic form and considering not only data from animals but data from human beings as well. For this objective, a workers group of a niobium extraction and processing industry exposed to stable niobium (93 Nb) in oxide insoluble form with associated uranium, was monitored for uranium and niobium determination in urinary and fecal excretion, by mass spectrometry. Based in the ratios of the niobium concentration in urinary and faecal excretion of this workers and animal data study, a new biokinetic model for niobium was proposed, with the followings modifications relative to ICRP model: a new compartment that represents muscular tissue; the fractions which are deposited into the compartment are modified; a third component in the retention equation of the bone tissue; introduction of recirculation between organs and blood. The new model was applied for a case of accidental intake and described adequately the experimental data.

  17. Electrochemical oxidation of cyanide on 3D Ti-RuO2 anode using a filter-press electrolyzer.

    Science.gov (United States)

    Pérez, Tzayam; López, Rosa L; Nava, José L; Lázaro, Isabel; Velasco, Guillermo; Cruz, Roel; Rodríguez, Israel

    2017-06-01

    The novelty of this communication lies in the use of a Ti-RuO 2 anode which has not been tested for the oxidation of free cyanide in alkaline media at concentrations similar to those found in wastewater from the Merrill Crowe process (100 mg L -1 KCN and pH 11), which is typically used for the recovery of gold and silver. The anode was prepared by the Pechini method and characterized by SEM. Linear sweep voltammetries on a Ti-RuO 2 rotating disk electrode (RDE) confirmed that cyanide is oxidized at 0.45 cyanide was investigated on Ti-RuO 2 meshes fitted into a filter-press electrolyzer. Bulk electrolyzes were performed at constant potentials of 0.85 V and 0.95 V and at different mean linear flow rates ranging between 1.2 and 4.9 cm s -1 . The bulk anodic oxidation of cyanide at 0.85 V and 3.7 cm s -1 achieved a degradation of 94%, with current efficiencies of 38% and an energy consumption of 24.6 kWh m -3 . Moreover, the degradation sequence of cyanide was also examined by HPLC. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. On niobium nitrilohalogenides

    International Nuclear Information System (INIS)

    Sinitsyna, S.M.

    1977-01-01

    Niobium nitrilhalogenides of the general formula [MNH]sub(n) and [MNH 2 ]sub(n) have been synthesized and their properties investigated. The effect of the ligand nature on the properties, structure, and nature of the chemical bond in niobium nitrilhalogenides has been shown. With an increase of electron-donor properties of the ligands F 2 -800 cm -1 , NbNCl 2 -740 cm -1 , NbNBr 2 -720 cm -1 , NbNI-725 cm -1 )

  19. “Double-Sandwich-Like” CuS@reduced graphene oxide as an Anode in Lithium Ion Batteries with Enhanced Electrochemical Performance

    International Nuclear Information System (INIS)

    Ren, Yurong; Wei, Hengma; Yang, Bo; Wang, Jiawei; Ding, Jianning

    2014-01-01

    Graphical abstract: CuS@reduced graphene oxide displays excellent electrochemical behavior as an anode material for Lithium ion batteries. - Abstract: The CuS@reduced graphene oxide (CSG) was synthesized and used as an anode material in lithium ion batteries (LIBs). CuS nanoparticles were homogeneously dispersed on the surfaces of reduced graphene oxide (rGO) nanosheets via a hydrothermal method. The rGO nanosheets in the CSG hydrids can improve the electrical conductivity and structure stability of CSG. The LIB with a CSG anode displays excellent performance, with a first discharge capacity up to 851 mAh/g, a reversible capacity of 648.1 mAh/g in the initial cycle, and an enhanced cyclic performance with a discharge capacity of 710.7 mAh/g at the 100 th cycle, which corresponds to 114.3% of the theoretical value of CSG and 83.5% of the first discharge capacity accompanied by an excellent Coulombic efficiency of 99.1% at a current density of 0.2 C, which is much larger than (close to 4.5 times) that with a pure CuS anode at the 100 th cycle (159.7 mAh/g). This phenomenon can be attributed to the synergistic action of CuS nanoparticles and rGO nanosheets in the “double-sandwich-like” CSG hybrids. These results indicate that CSG is an excellent anode material and has promising prospects in lithium ion batteries applications

  20. Field emission properties of low-density carbon nanotubes prepared on anodic aluminum-oxide template

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Soo-Hwan [Samsung Advanced Institute of Technology, Suwon (Korea, Republic of); Lee, Kun-Hong [Pohang University of Science and Technology, Pohang (Korea, Republic of)

    2004-08-15

    Anodic aluminum-oxide (AAO) templates were fabricated by two-step anodizing an Al film. After the Co catalyst had been electrochemically deposited onto the bottom of the AAO template, carbon nanotubes (CNTs) were grown by using catalytic pyrolysis of C{sub 2}H{sub 2} and H{sub 2} at 650 .deg. C. Overgrowth of CNTs with low density on the AAO templates was observed. The field-emission measurements on the samples showed a turn-on field of 2.17 V/mum and a field enhancement factor of 5700. The emission pattern on a phosphor screen was quite homogeneous over the area at a relatively low electric field.

  1. Niobium in gray cast iron

    International Nuclear Information System (INIS)

    Castello Branco, C.H.; Beckert, E.A.

    1984-03-01

    The potential for utilization of niobium in gray cast iron is appraised and reviewed. Experiments described in literature indicate that niobium provides structural refinement of the eutectic cells and also promotes pearlite formation. (Author) [pt

  2. A new process of electron beam refining of niobium

    International Nuclear Information System (INIS)

    Pinatti, D.G.

    1981-01-01

    A review of thermodynamic equilibrium, the kinetic theory and experimental results of the metal-gas interaction in refractory metals is presented. N 2 , H 2 and CO absorption and desorption take place by a reversible process while O 2 takes place by a irreversible process with atom absorption and metal oxide desorption. A new technology of electron beam refining of Niobium is proposed based on four points: 1) preparation of the aluminothermic reduced electrode, 2) zone refining in the first melt, 3) kinetic theory of refining in the following melts and 4) design of a compact furnace. Experimental results in a pilot plant of 300 KW have shown complete agreement with the proposed technology yielding a productivity 2.4 times larger than the value predicted by the conventional technology of electron beam refining of Niobium. (Author) [pt

  3. Kinetics and mechanisms of interactions of nitrogen and carbon monoxide with liquid niobium

    International Nuclear Information System (INIS)

    Park, H.G.

    1990-01-01

    The kinetics and mechanisms of interactions of N 2 and CO with liquid niobium were investigated in the temperature range of 2,700 to 3,000 K in samples levitated in N 2 /Ar and CO/Ar streams. The nitrogen absorption and desorption processes were found to be second-order with respect to nitrogen concentration, indicating that the rate controlling step is either the adsorption of nitrogen molecules on the liquid surface or dissociation of absorbed nitrogen molecules into adsorbed atoms. The carbon and oxygen dissolution in liquid niobium from CO gas is an exothermic process and the solubilities of carbon and oxygen (C Ce , C Oe in at%) are related to the temperature and the partial pressure of CO. The reaction CO → [C] + [O] along with the evaporation of niobium oxide takes place during C and O dissolution, whereas C and O desorption occurs via CO evolution only

  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. HIP bonding between niobium/copper/stainless steel materials

    International Nuclear Information System (INIS)

    Inoue, Hitoshi; Fujino, Takeo; Hitomi, Nobuteru; Saito, Kenji; Yamada, Masahiro; Shibuya, Junichi; Ota, Tomoko

    2000-01-01

    We have used niobium flanges for the niobium bulk superconducting RF cavities, however, they are expensive. Stainless steel flanges instead of the niobium flanges will be used in the future large scale production of sc cavities like the KEK/JAERI joint project. For a future R and D of the vacuum sealing related to the clean horizontal assembly method or development of cavities welded a helium vessel in the KEK/JAERI joint project, a converter section of niobium material to stainless steel is required. From these requirements we need to develop the converter. We have tried a HIP bonding method between niobium materials and stainless steel or copper material. It was made clear that the technology could offer an enough bonding strength even higher than niobium tensile strength in the joined surface between niobium and stainless steel or copper. (author)

  6. Iron oxide nanotube layer fabricated with electrostatic anodization for heterogeneous Fenton like reaction

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Jun-Won; Park, Jae-Woo, E-mail: jaewoopark@hanyang.ac.kr

    2014-05-01

    Highlights: • Iron oxide nanotube was newly fabricated with potentiostatic anodization of Fe{sup 0} foil. • Cyanide was oxidized more effectively with the iron oxide nanotube and H{sub 2}O{sub 2}, resulting in fast oxidation of cyanide and cyanate. • This nanotube of Fe{sub 2}O{sub 3} on Fe{sup 0} metal can replace conventional particulate iron catalysts in Fenton-like processes. - Abstract: Iron oxide nanotubes (INT) were fabricated with potentiostatic anodization of zero valent iron foil in 1 M Na{sub 2}SO{sub 4} containing 0.5 wt% NH{sub 4}F electrolyte, holding the potential at 20, 40, and 60 V for 20 min, respectively. Field emission scanning electron microscopy and X-ray diffractometry were used to evaluate the morphology and crystalline structure of the INT film. The potential of 40 V for 20 min was observed to be optimal to produce an optimal catalytic film. Cyanide dissolved in water was degraded through the Fenton-like reaction using the INT film with hydrogen peroxide (H{sub 2}O{sub 2}). In case of INT-40 V in the presence of H{sub 2}O{sub 2} 3%, the first-order rate constant was found to be 1.7 × 10{sup −2} min{sup −1}, and 1.2 × 10{sup −2} min{sup −1} with commercial hematite powder. Degradation of cyanide was much less with only H{sub 2}O{sub 2}. Therefore, this process proposed in this work can be an excellent alternative to traditional catalysts for Fenton-like reaction.

  7. Raman spectroscopy used for structural investigations of anodically formed ZrO2

    International Nuclear Information System (INIS)

    Koneska, Zagorka; Arsova, Irena

    2003-01-01

    The structure of the oxide formed on Zr(99% + Hf) with anodic oxidation at different potentials in 1 mol/dm 3 H 3 PO 4 and 2 mol/dm 3 KOH solutions were investigated using Raman spectroscopy. Normally the anodic oxides of Zr form only crystals. Under certain circumstances, amorphous anodic ZrO 2 can be observed. Amorphous phase is observed for the anodically formed zirconium oxides in H 3 PO 4 . The oxide formed in KOH at potential of 80 V, where sparks appears on the Zr electrode showed crystalline structure. (Original)

  8. Electrocatalytic Materials and Techniques for the Anodic Oxidation of Various Organic Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Treimer, Stephen Everett [Iowa State Univ., Ames, IA (United States)

    2001-01-01

    The focus of this thesis was first to characterize and improve the applicability of Fe(III) and Bi(V) doped PbO2 film electrodes for use in anodic O-transfer reactions of toxic and waste organic compounds, e.g. phenol, aniline, benzene, and naphthalene. Further, they investigated the use of alternative solution/electrode interfacial excitation techniques to enhance the performance of these electrodes for remediation and electrosynthetic applications. Finally, they have attempted to identify a less toxic metal oxide film that may hold promise for future studies in the electrocatalysis and photoelectrocatalysis of O-transfer reactions using metal oxide film electrodes.

  9. Multiscale Interfacial Strategy to Engineer Mixed Metal-Oxide Anodes toward Enhanced Cycling Efficiency.

    Science.gov (United States)

    Ma, Yue; Tai, Cheuk-Wai; Li, Shaowen; Edström, Kristina; Wei, Bingqing

    2018-06-13

    Interconnected macro/mesoporous structures of mixed metal oxide (MMO) are developed on nickel foam as freestanding anodes for Li-ion batteries. The sustainable production is realized via a wet chemical etching process with bio-friendly chemicals. By means of divalent iron doping during an in situ recrystallization process, the as-developed MMO anodes exhibit enhanced levels of cycling efficiency. Furthermore, this atomic-scale modification coherently synergizes with the encapsulation layer across a micrometer scale. During this step, we develop a quasi-gel-state tri-copolymer, i.e., F127-resorcinol-melamine, as the N-doped carbon source to regulate the interfacial chemistry of the MMO electrodes. Electrochemical tests of the modified Fe x Ni 1- x O@NC-NiF anode in both half-cell and full-cell configurations unravel the favorable suppression of the irreversible capacity loss and satisfactory cyclability at the high rates. This study highlights a proof-of-concept modification strategy across multiple scales to govern the interfacial chemical process of the electrodes toward better reversibility.

  10. High temperature niobium alloys

    International Nuclear Information System (INIS)

    Wojcik, C.C.

    1991-01-01

    Niobium alloys are currently being used in various high temperature applications such as rocket propulsion, turbine engines and lighting systems. This paper presents an overview of the various commercial niobium alloys, including basic manufacturing processes, properties and applications. Current activities for new applications include powder metallurgy, coating development and fabrication of advanced porous structures for lithium cooled heat pipes

  11. Phenol Contaminated Water Treatment on Several Modified Dimensionally Stable Anodes.

    Science.gov (United States)

    Jayathilaka, Pavithra Bhakthi; Hapuhinna, Kushani Umanga Kumari; Bandara, Athula; Nanayakkara, Nadeeshani; Subasinghe, Nalaka Deepal

    2017-08-01

      Phenolic compounds are some of the most common hazardous organics in wastewater. Removal of these pollutants is important. Physiochemical method such as electrochemical oxidation on dimensionally stable anodes is more convenient in removing such organic pollutants. Therefore, this study focuses on development of three different anodes for phenol contaminated water treatment. The performances of steel/IrO2, steel/IrO2-Sb2O3, and Ti/IrO2-Sb2O3 anodes were tested and compared. Nearly 50, 76, and 84% of chemical oxygen demand removal efficiencies were observed for steel/IrO2, steel/IrO2-Sb2O3, and Ti/IrO2-Sb2O3 anodes, respectively. The formation of intermediates was monitored for three anodes and the Ti/IrO2-Sb2O3 anode showed the most promising results. Findings suggest that the developed anode materials can enhance phenol oxidation efficiency and that mixed metal oxide layer has major influence on the anode. Among the selected metal oxide mixtures IrO2-Sb2O3 was the most suitable under given experimental conditions.

  12. Anodized Steel Electrodes for Supercapacitors.

    Science.gov (United States)

    Sagu, Jagdeep S; Wijayantha, K G Upul; Bohm, Mallika; Bohm, Siva; Kumar Rout, Tapan

    2016-03-09

    Steel was anodized in 10 M NaOH to enhance its surface texture and internal surface area for application as an electrode in supercapacitors. A mechanism was proposed for the anodization process. Field-emission gun scanning electron microscopy (FEGSEM) studies of anodized steel revealed that it contains a highly porous sponge like structure ideal for supercapacitor electrodes. X-ray photoelectron spectroscopy (XPS) measurements showed that the surface of the anodized steel was Fe2O3, whereas X-ray diffraction (XRD) measurements indicated that the bulk remained as metallic Fe. The supercapacitor performance of the anodized steel was tested in 1 M NaOH and a capacitance of 18 mF cm(-2) was obtained. Cyclic voltammetry measurements showed that there was a large psueudocapacitive contribution which was due to oxidation of Fe to Fe(OH)2 and then further oxidation to FeOOH, and the respective reduction of these species back to metallic Fe. These redox processes were found to be remarkably reversible as the electrode showed no loss in capacitance after 10000 cycles. The results demonstrate that anodization of steel is a suitable method to produce high-surface-area electrodes for supercapacitors with excellent cycling lifetime.

  13. Behaviour of hydrogen in niobium

    International Nuclear Information System (INIS)

    Chuang, Y.C.; Tang, C.H.; Chuang, T.L.

    1982-01-01

    Polycrystalline niobium was charged electrolytically with hydrogen at room temperature. The behaviour of hydrogen in niobium has been investigated by optical microscopy, SEM, and ion microprobe analysis. It is shown that, when the hydrogen content in niobium is low, hydride tends to form at the grain boundary. As the hydrogen content is increased, precipitation of hydrides with domain structure takes place in the grain. The habit plane of the hydride formed in the vicinity of the grain boundary has been determined by Laue X-ray back reflection technique to be (130)c and (111)c. The structure of the hydride formed on the surface of niobium after 6 h hydrogen charging at room temperature (c.d. 0.2 A/cm 2 ) has been established to be identical to that of NbHsub(0.89). (orig.) [de

  14. Development and testing of anode-supported solid oxide fuel cells with slurry-coated electrolyte and cathode

    Energy Technology Data Exchange (ETDEWEB)

    Muccillo, R.; Muccillo, E.N.S.; Fonseca, F.C.; Franca, Y.V.; Porfirio, T.C. [Centro de Ciencia e Tecnologia de Materiais, Instituto de Pesquisas Energeticas e Nucleares, C.P. 11049, Pinheiros, S. Paulo, SP 05422-970 (Brazil); de Florio, D.Z. [Instituto de Quimica, UNESP, R. Prof. Francisco Degni s/n, Araraquara, SP 14801-970 (Brazil); Berton, M.A.C.; Garcia, C.M. [Instituto de Tecnologia para o Desenvolvimento, DPMA, C.P. 19067, Curitiba, PR 81531-980 (Brazil)

    2006-06-01

    A laboratory setup was designed and put into operation for the development of solid oxide fuel cells (SOFCs). The whole project consisted of the preparation of the component materials: anode, cathode and electrolyte, and the buildup of a hydrogen leaking-free sample chamber with platinum leads and current collectors for measuring the electrochemical properties of single SOFCs. Several anode-supported single SOFCs of the type (ZrO{sub 2}:Y{sub 2}O{sub 3}+NiO) thick anode/(ZrO{sub 2}:Y{sub 2}O{sub 3}) thin electrolyte/(La{sub 0.65}Sr{sub 0.35}MnO{sub 3}+ZrO{sub 2}:Y{sub 2}O{sub 3}) thin cathode have been prepared and tested at 700 and 800{sup o}C after in situ H{sub 2} anode reduction. The main results show that the slurry-coating method resulted in single-cells with good reproducibility and reasonable performance, suggesting that this method can be considered for fabrication of SOFCs. (author)

  15. Growth behavior of anodic porous alumina formed in malic acid solution

    Science.gov (United States)

    Kikuchi, Tatsuya; Yamamoto, Tsuyoshi; Suzuki, Ryosuke O.

    2013-11-01

    The growth behavior of anodic porous alumina formed on aluminum by anodizing in malic acid solutions was investigated. High-purity aluminum plates were electropolished in CH3COOH/HClO4 solutions and then anodized in 0.5 M malic acid solutions at 293 K and constant cell voltages of 200-350 V. The anodic porous alumina grew on the aluminum substrate at voltages of 200-250 V, and a black, burned oxide film was formed at higher voltages. The nanopores of the anodic oxide were only formed at grain boundaries of the aluminum substrate during the initial stage of anodizing, and then the growth region extended to the entire aluminum surface as the anodizing time increased. The anodic porous alumina with several defects was formed by anodizing in malic acid solution at 250 V, and oxide cells were approximately 300-800 nm in diameter.

  16. 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.

  17. Nb effect in the nickel oxide-catalyzed low-temperature oxidative dehydrogenation of ethane

    KAUST Repository

    Zhu, Haibo; Ould-Chikh, Samy; Anjum, Dalaver Hussain; Sun, Miao; Biausque, Gregory; Basset, Jean-Marie; Caps, Valerie

    2012-01-01

    evaporation method from nickel nitrate and ammonium niobium oxalate. These consist in NiO nanocrystallites (7-13 nm) associated, at Nb contents >3 at.%., with an amorphous thin layer (1-2 nm) of a niobium-rich mixed oxide with a structure similar

  18. Liquid-film assisted formation of alumina/niobium interfaces

    OpenAIRE

    Sugar, Joshua D.; McKeown, Joseph T.; Marks, Robert A.; Glaeser, Andreas M.

    2002-01-01

    Alumina has been joined at 1400 degrees C using niobium-based interlayers. Two different joining approaches were compared: solid-state diffusion bonding using a niobium foil as an interlayer, and liquid-film assisted bonding using a multilayer copper/niobium/copper interlayer. In both cases, a 127-(mu)m thick niobium foil was used; =1.4-(mu)m or =3-(mu)m thick copper films flanked the niobium. Room-temperature four-point bend tests showed that the introduction of a copper film had a significa...

  19. Laser-pulsed Plasma Chemistry: Laser-initiated Plasma Oxidation Of Niobium

    OpenAIRE

    Marks R.F.; Pollak R.A.; Avouris Ph.; Lin C.T.; Thefaine Y.J.

    1983-01-01

    We report the first observation of the chemical modification of a solid surface exposed to an ambient gas plasma initiated by the interaction of laser radiation with the same surface. A new technique, which we designate laser-pulsed plasma chemistry (LPPC), is proposed for activating heterogeneous chemical reactions at solid surfaces in a gaseous ambient by means of a plasma initiated by laser radiation. Results for niobium metal in one atmosphere oxygen demonstrate single-pulse, self-limitin...

  20. Studies of niobium and development of niobium resonant RF cavities for accelerator driven system

    International Nuclear Information System (INIS)

    Mondal, Jayanta

    2013-01-01

    The present approach for the fabrication of superconducting radio frequency (SRF) cavities is to roll and deep draw sheets of polycrystalline high-purity niobium. Jefferson Laboratory pioneered the use of large-grain/single-crystal Nb directly sliced from an ingot for the fabrication of single-crystal high-purity Nb SRF cavities. The large grain/single crystal niobium has several potential advantages over the polycrystalline niobium and has become a viable alternative to the standard fine grain (ASTM grain size>6 μm), high purity (RRR ≥ 250 ) niobium for the fabrication of high-performance SRF cavities for particle accelerators. The present study includes the prototype single cell low beta cavity design, fabrication, EB welding and low temperature RF test at 2K. In this study also the medium field Q-Slope has been analyzed with the help of an added non linear term in Heabel's analytical model and a linear increase of surface resistance Rs with the magnetic field

  1. Study of the surface crystallization and resistance to dissolution of niobium phosphate glasses for nuclear waste immobilization

    International Nuclear Information System (INIS)

    Vieira, Heveline

    2008-01-01

    The surface crystallization and the dissolution rate of three phosphate glass compositions containing different amounts of niobium oxide were studied. The glasses were named Nb30, Nb37, and Nb44 according to the nominal content of niobium oxide in the glass composition. The three compositions were evaluated keeping the P 2 O 5 /K 2 O ratio constant and varying the amount of Nb 2 O 5 . These glasses were produced by melting appropriate chemical compounds at 1500 deg C for 0.5 hour. The crystalline phases which were nucleated on the glass surface after heat treatment were determined by X-ray diffraction. The crystalline structures depend on the amount of niobium oxide in the glass composition. The crystal morphologies were observed by using an optical microscope, and their characteristics are specific for each kind of crystalline phase. The crystal growth rate and the surface nuclei density were determined for each glass composition, and they depend on each crystalline phase nucleated on the surface. From the differential thermal analysis curves it was determined that the Nb44 glass containing 46.5 mol por cent of niobium oxide is the most thermally stable against crystallization when compared to the Nb30 and Nb37 glasses. According to the activation energies determined for crystal growth on the surface of each glass type, the Nb44 glass can also be considered the most resistant one against crystallization. The dissolution rate for the Nb44 glass after 14 days immersed in an aqueous solution with pH equals to 7 at 90 deg C is the lowest (9.0 x 10 -7 g. cm -2 . day -1 ) when compared to the other two glass compositions. The dissolution rates in acidic and neutral solutions of all studied glasses meet the international standards for materials which can be used in the immobilization of nuclear wastes. (author)

  2. The mineralogical characterization of tellurium in copper anodes

    Science.gov (United States)

    Chen, T. T.; Dutrizac, J. E.

    1993-12-01

    A mineralogical study of a «normal» commercial copper anode and six tellurium-rich copper anodes from the CCR Refinery of the Noranda Copper Smelting and Refining Company was carried out to identify the tellurium carriers and their relative abundances. In all the anodes, the major tellurium carrier is the Cu2Se-Cu2Te phase which occurs as a constituent of complex inclusions at the copper grain boundaries. In tellurium-rich anodes, the molar tellurium content of the Cu2Se-Cu2Te phase can exceed that of selenium. Although >85 pct of the tellurium occurs as the Cu2Se-Cu2Te phase, minor amounts are present in Cu-Pb-As-Bi-Sb oxide, Cu-Bi-As oxide, and Cu-Te-As oxide phases which form part of the grain-boundary inclusions. About 1 pct of the tellurium content of silver-rich anodes occurs in various silver alloys, but gold tellurides were never detected. Surprising is the fact that 2 to 8 pct of the total tellurium content of the anodes occurs in solid solution in the copper-metal matrix, and presumably, this form of tellurium dissolves at the anode interface during electrorefining.

  3. Thermal transport properties of niobium and some niobium-based alloys from 80 to 1600 K

    Energy Technology Data Exchange (ETDEWEB)

    Moore, J P; Graves, R S; Williams, R K [Oak Ridge National Lab., TN (USA)

    1980-01-01

    The electric resistivity, rho, and Seebeck coefficient, S, of 99.8 at% niobium, and Nb-4.8 at% W, Nb-5 at% Mo, Nb-10 at% Mo, and Nb-2.4 at% Mo-2.4 at% Zr alloys were measured from 80 to 1600 K, and the thermal conductivity, lambda, of the niobium and the Nb-5 at% W alloy was measured from 80 to 1300 K. A technique is described for measuring rho and S of a specimen during radial-heat-flow measurements of lambda. The transport property results, which had uncertainties of +-0.4% for rho and +-1.4% for lambda, showed the influence of tungsten and molybdenum solutes on the transport properties of niobium and were used to obtain the electronic Lorenz function of pure niobium, which was found to approach the Sommerfeld value at high temperatures.

  4. Preparation of anodic aluminum oxide (AAO) nano-template on silicon and its application to one-dimensional copper nano-pillar array formation

    International Nuclear Information System (INIS)

    Shen, Lan; Ali, Mubarak; Gu, Zhengbin; Min, Bonggi; Kim, Dongwook; Park, Chinho

    2013-01-01

    Anodized aluminum oxide (AAO) nanotemplates were prepared using the Al/Si substrates with an aluminum layer thickness of about 300 nm. A two-step anodization process was used to prepare an ordered porous alumina nanotemplate, and the pores of various sizes and depths were constructed electrochemically through anodic oxidation. The optimum morphological structure for large area application was constructed by adjusting the applied potential, temperature, time, and electrolyte concentration. SEM investigations showed that hexagonal-close-packed alumina nano-pore arrays were nicely constructed on Si substrate, having smooth wall morphologies and well-defined diameters. It is also reported that one dimensional copper nanopillars can be fabricated using the tunable nanopore sized AAO/Si template, by controlling the copper deposition process

  5. Nickel doped indium tin oxide anode and effect on dark spot development of organic light-emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, C.M. [Southern Taiwan University, Department of Electro-Optical Engineering, 1 Nan-Tai St, Yung-Kang City, Tainan County 710, Taiwan (China)], E-mail: tedhsu@mail.stut.edu.tw; Kuo, C.S.; Hsu, W.C.; Wu, W.T. [Southern Taiwan University, Department of Electro-Optical Engineering, 1 Nan-Tai St, Yung-Kang City, Tainan County 710, Taiwan (China)

    2009-01-01

    This article demonstrated that introducing nickel (Ni) atoms into an indium tin oxide (ITO) anode could considerably decrease ITO surface roughness and eliminate the formation of dark spots of an organic light-emitting device (OLED). A dramatic drop in surface roughness from 6.52 nm of an conventional ITO to 0.46 nm of an 50 nm Ni(50 W)-doped ITO anode was observed, and this led to an improved lifetime performance of an Alq3 based OLED device attributed to reduced dark spots. Reducing thickness of Ni-doped ITO anode was found to worsen surface roughness. Meanwhile, the existence of Ni atoms showed little effect on deteriorating the light-emitting mechanism of OLED devices.

  6. Interaction at interface between superconducting yttrium ceramics and copper or niobium

    International Nuclear Information System (INIS)

    Karpov, M.I.; Korzhov, V.P.; Medved', N.V.; Myshlyaeva, M.M.

    1992-01-01

    Light metallography, scanning electron microscopy and local energy dispersion analysis have been used to study the interaction of Y-ceramics with copper and niobium. Samples in the form of wire of two types were employed, that is, consisting of ceramic core YBaCuO and Cu shell or a ceramic core YBaCuO and bimetallic Cu/Nb shell. The interaction of the ceramics with the shell metal began already at 500 deg with the formation at the interafaces Cu-YBaCuO of oxide layers containing ceramic elements, and in the ceramic core - nonsuperconducting phases. A thin Al-layer placed between the ceramics and the shell appreciably decreased the reactability of the ceramics with respect to copper and niobium

  7. Behaviour of solvent extraction of niobium in nitric acid

    International Nuclear Information System (INIS)

    Lin Cansheng; Huang Meixin; Zhang Xianzi; Zhang Chonghai

    1988-01-01

    The behaviour of solvent extraction of niobium is discussed. The expractants, includding TBP, HDBP, H 2 MBP, TBP irradiated, HDEHP, TTA and Aliquat-7402, are used. The special influence of molybdenum and zirconium on solvent extraction of niobium and the extraction behaviur of niobium with TBP irradiated are described. The effect of fluorine and uranium in aqueous phase on extraction of niobium is mentioned. It is observed that the interfacial crud has not relevance to D Nb , but niobium-95 can be absorbed on it. The species of extractable niobium, extraction mechanism, and the reason brought niobum into organic phase are discussed. Finally, the idea of increasing decontamination factor for niobium is suggested

  8. Polarography of niobium in hydrochloric acid

    International Nuclear Information System (INIS)

    Henrion, G.; Adler, F.; Andreas, B.

    1978-01-01

    Dependence between the limiting current and the concentration of niobium and hydrochloric acid has been investigated. With the decrease of niobium concentration the hydrolysis and condensation reactions proceed slower. The time dependence of condensation is shown using ethylene glycol which delays the condensation because of complexation of Nb(5). Hydroxylamine hydrochloride increases the limiting current by a kinetic effect by one order of magnitude which was observed clearly by cyclic voltammetry. Even small amounts of ethylene glycol suppress the kinetic effect. Polarographic determination of niobium in HCl as a supporting electrolyte is possible in concentration above 10 M only. Addition of ethylene glycol and hydroxylamine hydrochloride enables determination of small amounts of niobium in 4 M HCl. (author)

  9. Morphology study of niobium pentoxide

    International Nuclear Information System (INIS)

    Romero, R.P.P.; Panta, P.C.; Araujo, A.O. de; Bergmann, C.P.

    2016-01-01

    Currently, Niobium pentoxide (Nb 2 O 5 ) has been studied due to physical properties and their use in obtaining electronic ceramics, optical lenses, pH sensors, special filters for TV receivers, among other applications. This study investigated the morphology of the niobium pentoxide obtained by hydrothermal synthesis from the precursor pentachloride niobium (NbCl 5 ), where the synthesis was carried out at a temperature of 150 and 200 °C for 130 min and the product obtained was calcined at temperatures 600, 800 and 1000 °C for 60 min. The following characterizations were performed for analysis of the material, among them, X-ray diffraction (XRD) for analysis of the crystal structure, thermal gravimetric analysis (TGA) for detecting the existing functional groups and scanning electron microscopy (SEM) for morphology of material. As a result, different morphologies were obtained and consequently different niobium pentoxide properties studied. (author)

  10. Influence of desiccation procedures on the surface wettability and corrosion resistance of porous aluminium anodic oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Zheng Meng, E-mail: ZhengMeng@eng.hokudai.ac.jp [Graduate School of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-Ku, Sapporo 060-8628 (Japan); Sakairi, Masatoshi [Faculty of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-Ku, Sapporo 060-8628 (Japan); Jha, Himendra [Technische Universitaet Muenchen, Lichtenbergstrasse 4, D-85748 Garching (Germany)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Simple desiccation treatment without coating or etching produces hydrophobicity of porous anodic oxide film. Black-Right-Pointing-Pointer Treatment time can be shortened by controlling desiccation condition. Black-Right-Pointing-Pointer Surface microstructure is the key point to determine the wettability. Black-Right-Pointing-Pointer The hydrophobic surfaces show better corrosion resistance than oxide aluminium. - Abstract: A hydrophobic oxide film was formed on aluminium by anodizing followed by desiccation treatment. Films subjected to gradual heating and cooling exhibit larger water contact angles than samples exposed to fast heating and cooling at the same temperature. From SEM and Auger Electron Spectroscopic observations, the low wettability surface shows a regular porous morphology with no significant chemical composition differences due to the different treatments. The desiccation process improves the corrosion resistance, shown by immersion in NaCl. The change in morphology by the desiccation processes is considered a main reason to lower the wettability, which further affects the corrosion properties.

  11. Direct modeling of the electrochemistry in the three-phase boundary of solid oxide fuel cell anodes by density functional theory: a critical overview.

    Science.gov (United States)

    Shishkin, M; Ziegler, T

    2014-02-07

    The first principles modeling of electrochemical reactions has proven useful for the development of efficient, durable and low cost solid oxide full cells (SOFCs). In this account we focus on recent advances in modeling of structural, electronic and catalytic properties of the SOFC anodes based on density functional theory (DFT) first principle calculations. As a starting point, we highlight that the adequate analysis of cell electrochemistry generally requires modeling of chemical reactions at the metal/oxide interface rather than on individual metal or oxide surfaces. The atomic models of Ni/YSZ and Ni/CeO2 interfaces, required for DFT simulations of reactions on SOFC anodes are discussed next, together with the analysis of the electronic structure of these interfaces. Then we proceed to DFT-based findings on charge transfer mechanisms during redox reactions on these two anodes. We provide a comparison of the electronic properties of Ni/YSZ and Ni/CeO2 interfaces and present an interpretation of their different chemical performances. Subsequently we discuss the computed energy pathways of fuel oxidation mechanisms, obtained by various groups to date. We also discuss the results of DFT studies combined with microkinetic modeling as well as the results of kinetic Monte Carlo simulations. In conclusion we summarize the key findings of DFT modeling of metal/oxide interfaces to date and highlight possible directions in the future modeling of SOFC anodes.

  12. Graphene oxide-multiwalled carbon nanotubes composite as an anode for lithium ion batteries

    Directory of Open Access Journals (Sweden)

    Majchrzycki Łukasz

    2016-09-01

    Full Text Available Nowadays reduced graphene oxide (rGO is regarded as a highly interesting material which is appropriate for possible applications in electrochemistry, especially in lithium-ion batteries (LIBs. Several methods were proposed for the preparation of rGO-based electrodes, resulting in high-capacity LIBs anodes. However, the mechanism of lithium storage in rGO and related materials is still not well understood. In this work we focused on the proposed mechanism of favorable bonding sites induced by additional functionalities attached to the graphene planes. This mechanism might increase the capacity of electrodes. In order to verify this hypothesis the composite of non-reduced graphene oxide (GO with multiwalled carbon nanotubes electrodes was fabricated. Electrochemical properties of GO composite anodes were studied in comparison with similarly prepared electrodes based on rGO. This allowed us to estimate the impact of functional groups on the reversible capacity changes. As a result, it was shown that oxygen containing functional groups of GO do not create, in noticeable way, additional active sites for the electrochemical reactions of lithium storage, contrary to what has been postulated previously.

  13. Anodization of Aluminium using a fast two-step process

    Indian Academy of Sciences (India)

    283.6 eV. Keywords. Anodization; phosphoric acid; anodization time; anodized aluminium oxide; aluminium. ... of anodization.5–7 The AAO layer has a large band gap, good ..... transmittance increases as the anodised membrane is heated to ...

  14. 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.

  15. Enhanced performance of a novel anodic PdAu/VGCNF catalyst for electro-oxidation in a glycerol fuel cell.

    Science.gov (United States)

    Yahya, N; Kamarudin, S K; Karim, N A; Masdar, M S; Loh, K S

    2017-11-25

    This study presents a novel anodic PdAu/VGCNF catalyst for electro-oxidation in a glycerol fuel cell. The reaction conditions are critical issues affecting the glycerol electro-oxidation performance. This study presents the effects of catalyst loading, temperature, and electrolyte concentration. The glycerol oxidation performance of the PdAu/VGCNF catalyst on the anode side is tested via cyclic voltammetry with a 3 mm 2 active area. The morphology and physical properties of the catalyst are examined using X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. Then, optimization is carried out using the response surface method with central composite experimental design. The current density is experimentally obtained as a response variable from a set of experimental laboratory tests. The catalyst loading, temperature, and NaOH concentration are taken as independent parameters, which were evaluated previously in the screening experiments. The highest current density of 158.34 mAcm -2 is obtained under the optimal conditions of 3.0 M NaOH concentration, 60 °C temperature and 12 wt.% catalyst loading. These results prove that PdAu-VGCNF is a potential anodic catalyst for glycerol fuel cells.

  16. Thermal transport properties of niobium and some niobium base alloys from 80 to 16000K

    International Nuclear Information System (INIS)

    Moore, J.P.; Graves, R.S.; Williams, R.K.

    1980-01-01

    The electrical resistivities and absolute Seebeck coefficients of 99.8 at. % niobium with a RRR of 36, Nb-4.8 at. % W, Nb-5 at. % Mo, Nb-10 at. % Mo, and Nb-2.4 at. % Mo-2.4 at. % Zr were measured from 80 to 1600 0 K, and the thermal conductivities of the niobium and Nb-5 at. % W were measured from 80 to 1300 0 K. A technique is described for measuring the electrical resistivity and Seebeck coefficient of a specimen during radial heat flow measurements of the thermal conductivity. The transport property results, which had uncertainties of +-0.4%for electrical resistivity and +-1.4% for thermal conductivity, showed the influence of tungsten and molybdenum solutes on the transport properties of niobium and were used to obtain the electronic Lorenz function of pure niobium, which was found to approach the Sommerfeld value at high temperatures

  17. Lasing of a Solid-State Active Element Based on Anodized Aluminum Oxide Film Doped with Rhodamine 6G

    Science.gov (United States)

    Shelkovnikov, V. V.; Lyubas, G. A.; Korotaev, S. V.; Kopylova, T. N.; Tel'minov, E. N.; Gadirov, R. M.; Nikonova, E. N.; Nikonov, S. Yu.; Solodova, T. A.; Novikov, V. A.

    2017-04-01

    Spectral-luminescent and lasing characteristics of rhodamine 6G in porous aluminum oxide films anodized under various conditions are investigated. Lasing is obtained without external resonator in the longitudinal scheme under excitation by the second harmonic of Nd3+:YAG-laser radiation. The threshold pump power densities are in the range 3.5-15 MW/cm2 depending on the anodizing conditions. Wherein, the lasing line narrows down from 12 to 5 nm.

  18. Investigation of the niobium-oxygen system under low pressure and between 550 K and 2350 K: solid solution, surface overlay and reactivity

    International Nuclear Information System (INIS)

    Jupille, Jacques

    1974-09-01

    This research thesis addresses the behaviour of transition metals when interacting with oxygen, more particularly in the case of phase formation, but also adsorption and desorption which occur in the case of interaction with low pressure oxygen. It focuses on the case of niobium in solid solution. After a description of phases present in the niobium-oxygen system, and a discussion of reactivities of oxygen and water vapour, the author describes the experimental methods (apparatus and installations, samples, measured values), discusses the study of the surface-volume transfer constant of the niobium-oxygen solution, and the niobium-oxygen interaction mechanisms at high (superior to 1700 K) and low (inferior to 1000 K) temperatures: oxide desorption, oxygen reaction kinetics

  19. 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

  20. 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

  1. Effect of Solution Temperature for Al Alloy Anodizing on Cavitation Characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung-Jun [Kunsan National University, Kunsan (Korea, Republic of); Lee, Jung Hyung; Kim, Seong Jong [Mokpo National Maritime University, Haeyangdaehak-ro 91, Mokpo (Korea, Republic of)

    2015-06-15

    The commercialization of aluminum had been delayed than other metals because of its high oxygen affinity. Anodizing is a process in which oxide film is formed on the surface of a valve metal in an electrolyte solution by anodic oxidation reaction. Aluminum has thin oxide film on surface but the oxide film is inhomogeneous having a thickness only in the range of several nanometers. Anodizing process increases the thickness of the oxide film significantly. In this study, porous type oxide film was produced on the surface of aluminum in sulfuric acid as a function of electrolyte temperature, and the optimum condition were determined for anodizing film to exhibit excellent cavitation resistance in seawater environment. The result revealed that the oxide film formed at 10 ℃ represented the highest cavitation resistance, while the oxide film formed at 15 ℃ showed the lowest resistance to cavitation in spite of its high hardness.

  2. Process for anodizing aluminum foil

    International Nuclear Information System (INIS)

    Ball, J.A.; Scott, J.W.

    1984-01-01

    In an integrated process for the anodization of aluminum foil for electrolytic capacitors including the formation of a hydrous oxide layer on the foil prior to anodization and stabilization of the foil in alkaline borax baths during anodization, the foil is electrochemically anodized in an aqueous solution of boric acid and 2 to 50 ppm phosphate having a pH of 4.0 to 6.0. The anodization is interrupted for stabilization by passing the foil through a bath containing the borax solution having a pH of 8.5 to 9.5 and a temperature above 80 0 C. and then reanodizing the foil. The process is useful in anodizing foil to a voltage of up to 760 V

  3. Thermodiffusion Mo-B-Si coating on VN-3 niobium alloy

    International Nuclear Information System (INIS)

    Kozlov, A.T.; Lazarev, Eh.M.; Monakhova, L.A.; Shestova, V.F.; Romanovich, I.V.

    1985-01-01

    Protective properties of complex Mo-B-Si-coating on niobium alloy VN-3 (4.7 mass.% Mo, 1.1 mass.% Zr, 0.1 mass.% C) have been studied. It is established, that the complex Mo-B-Si-coating ensures protection from oxidation of niobium alloys in the temperature range of 800-1200 degC for 1000-1500 hr, at 1600 degC - for 10 hr. High heat resistance of Mo-B-Si - coating at 800-1200 degC is determined by the presence of amorphous film of SiOΛ2 over the layer MoSiΛ2 and barrier boride layer on the boundary with the metal protected; decrease in the coating heat resistance at 1600 degC is related to the destruction of boride layer, decomposition of MoSiΛ2 for lower cilicides and loosening of SiOΛ2 film

  4. Electron heating by photon-assisted tunneling in niobium terahertz mixers with integrated niobium titanium nitride striplines

    NARCIS (Netherlands)

    Leone, B; Gao, [No Value; Klapwijk, TM; Jackson, BD; Laauwen, WM; de Lange, G

    2001-01-01

    We describe the gap voltage depression and current-voltage (I-V) characteristics in pumped niobium superconductor-insulator-superconductor junction with niobium titanium nitride tuning stripline by introducing an electron heating power contribution resulting from the photon-assisted tunneling

  5. Analysis on porous aluminum anodic oxide film formed in Re-OA-H{sub 3}PO{sub 4} solution

    Energy Technology Data Exchange (ETDEWEB)

    Wang, H. [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai 200030 (China); Wang, H.W. [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai 200030 (China)]. E-mail: hwwang@sjtu.edu.cn

    2006-06-10

    An anodic porous film on aluminum was prepared in a mixed electrolyte of phosphoric acid and organic acid and cerium salt. The growth, morphology and chemical composition of the film were investigated. The results indicate that the growth of porous layers in this solution undergo three stages during anodizing, as in other conventional solution, while the whole growth rate is nonlinear. This electrolyte is sensitive to anodizing temperature, which affects current density in great degree. SEM indicates the surface morphology of film is strongly dependent on temperature and current density and its cross-section has two distinct oxide layers. Al, O and P are found in the film with different distribution in the two layers with EPMA. However, Ce has been detected on the outer surface with EDAX. XPS analysis on the electron binding energy of the component elements show the chemical composition of oxide film surface are Al{sub 2}O{sub 3}, Ce(OH) and some phosphates. The formation mechanics of Ce compound is also deduced.

  6. Nano sand filter with functionalized nanoparticles embedded in anodic aluminum oxide templates

    OpenAIRE

    Phuong, NguyenThi; Andisetiawan, Anugrah; Van Lam, Do; Kim, Jeong Hwan; Choi, Doo-Sun; Whang, Kyung-Hyun; Nham, Jeasun; Lee, Yun Jung; Yoo, Yeong-Eun; Yoon, Jae Sung

    2016-01-01

    Since the ancient Egyptians had used sand as filter media for water purification, its principle has been inherited through generations and it is still being used now in industries. The sand filter consists of sand literally, and the voids within the sand bed are the pores for filtration. Here we present a filtration principle using nanoparticles, so that the voids between the nanoparticles can be considered as effective pores in nanoscale dimension. Anodic aluminum oxide (AAO) membrane has be...

  7. Synthesis and electrochemical performance of ruthenium oxide-coated carbon nanofibers as anode materials for lithium secondary batteries

    Energy Technology Data Exchange (ETDEWEB)

    Hyun, Yura; Choi, Jin-Yeong [Department of Chemistry, Keimyung University (Korea, Republic of); Park, Heai-Ku [Department of Chemical Engineering, Keimyung University (Korea, Republic of); Lee, Chang-Seop, E-mail: surfkm@kmu.ac.kr [Department of Chemistry, Keimyung University (Korea, Republic of)

    2016-12-01

    Highlights: • Ruthenium oxide (RuO{sub 2}) coated carbon nanofibers (CNFs) on Ni foam were synthesized by chemical vapor deposition method and applied as anode materials of Li secondary batteries. • When RuO{sub 2}/CNFs/Ni foam was used as the anode material, initial capacity was improved from 276 mAh/g to 494 mAh/g with retention rate of 47.4% after 30 cycles. - Abstract: In this study, ruthenium oxide (RuO{sub 2}) 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 RuCl{sub 3} solution. The ruthenium oxide-coated CNFs/Ni foam was dried in a dryer at 80 °C. The morphologies, compositions, and crystal quality of RuO{sub 2}/CNFs/Ni foam were characterized by SEM, EDS, XRD, Raman spectroscopy, and XPS. The electrochemical characteristics of RuO{sub 2}/CNFs/Ni foam as anode of Li secondary batteries were investigated using three-electrode cell. The RuO{sub 2}/CNFs/Ni foam was directly employed as a working electrode without any binder, and lithium foil was used as the counter and reference electrodes. LiClO{sub 4} (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 RuO{sub 2}/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.

  8. Synthesis and electrochemical performance of ruthenium oxide-coated carbon nanofibers as anode materials for lithium secondary batteries

    International Nuclear Information System (INIS)

    Hyun, Yura; Choi, Jin-Yeong; Park, Heai-Ku; Lee, Chang-Seop

    2016-01-01

    Highlights: • Ruthenium oxide (RuO_2) coated carbon nanofibers (CNFs) on Ni foam were synthesized by chemical vapor deposition method and applied as anode materials of Li secondary batteries. • When RuO_2/CNFs/Ni foam was used as the anode material, initial capacity was improved from 276 mAh/g to 494 mAh/g with retention rate of 47.4% after 30 cycles. - Abstract: In this study, ruthenium oxide (RuO_2) 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 RuCl_3 solution. The ruthenium oxide-coated CNFs/Ni foam was dried in a dryer at 80 °C. The morphologies, compositions, and crystal quality of RuO_2/CNFs/Ni foam were characterized by SEM, EDS, XRD, Raman spectroscopy, and XPS. The electrochemical characteristics of RuO_2/CNFs/Ni foam as anode of Li secondary batteries were investigated using three-electrode cell. The RuO_2/CNFs/Ni foam was directly employed as a working electrode without any binder, and lithium foil was used as the counter and reference electrodes. LiClO_4 (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 RuO_2/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.

  9. Anodization: a promising nano-modification technique of titanium implants for orthopedic applications.

    Science.gov (United States)

    Yao, Chang; Webster, Thomas J

    2006-01-01

    Anodization is a well-established surface modification technique that produces protective oxide layers on valve metals such as titanium. Many studies have used anodization to produce micro-porous titanium oxide films on implant surfaces for orthopedic applications. An additional hydrothermal treatment has also been used in conjunction with anodization to deposit hydroxyapatite on titanium surfaces; this is in contrast to using traditional plasma spray deposition techniques. Recently, the ability to create nanometer surface structures (e.g., nano-tubular) via anodization of titanium implants in fluorine solutions have intrigued investigators to fabricate nano-scale surface features that mimic the natural bone environment. This paper will present an overview of anodization techniques used to produce micro-porous titanium oxide structures and nano-tubular oxide structures, subsequent properties of these anodized titanium surfaces, and ultimately their in vitro as well as in vivo biological responses pertinent for orthopedic applications. Lastly, this review will emphasize why anodized titanium structures that have nanometer surface features enhance bone forming cell functions.

  10. Superhydrophilicity of anodic aluminum oxide films: From 'honeycomb' to 'bird's nest'

    International Nuclear Information System (INIS)

    Ye Jiaming; Yin Qiming; Zhou Yongliang

    2009-01-01

    An electrochemical method has been used to prepare different kinds of surfaces including 'honeycomb'-like and 'bird's nest'-like surfaces on anodic aluminum oxide (AAO) films. The relationship between the morphology and wettability of the AAO films was investigated by scanning electron microscopy and the measurement of water contact angles. The results show that the 'bird's nest'-like structure is necessary for superhydrophilic property, which provide direct experimental evidences for the 3D capillary theory concerning superhydrophilicity. It is expected that this investigation will be devoted to guiding the fabrication of superhydrophilic and superhydrophobic surfaces.

  11. Recent progress in the development of anode materials for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Cowin, Peter I.; Petit, Christophe T.G.; Lan, Rong; Tao, Shanwen [Department of Chemical and Process Engineering, University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Irvine, John T.S. [School of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST (United Kingdom)

    2011-05-15

    The field of research into solid oxide fuel cell (SOFC) anode materials has been rapidly moving forward. In the four years since the last in-depth review significant advancements have been made in the reduction of the operating temperature and improvement of the performance of SOFCs. This progress report examines the developments in the field and looks to draw conclusions and inspiration from this research. A brief introduction is given to the field, followed by an overview of the principal previous materials. A detailed analysis of the developments of the last 4 years is given using a selection of the available literature, concentrating on metal-fluorite cermets and perovskite-based materials. This is followed by a consideration of alternate fuels for use in SOFCs and their associated problems and a short discussion on the effect of synthesis method on anode performance. The concluding remarks compile the significant developments in the field along with a consideration of the promise of future research. The recent progress in the development of anode materials for SOFCs based on oxygen ion conducting electrolytes is reviewed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Catalytic properties of new anode materials for solid oxide fuel cells operated under methane at intermediary temperature

    Science.gov (United States)

    Sauvet, A.-L.; Fouletier, J.

    The recent trend in solid oxide fuel cell concerns the use of natural gas as fuel. Steam reforming of methane is a well-established process for producing hydrogen directly at the anode side. In order to develop new anode materials, the catalytic activities of several oxides for the steam reforming of methane were characterized by gas chromatography. We studied the catalytic activity as a function of steam/carbon ratios r. The methane and the steam content were varied between 5 and 30% and between 1.5 and 3.5%, respectively, corresponding to r-values between 0.07 and 0.7. Catalyst (ruthenium and vanadium)-doped lanthanum chromites substituted with strontium, gadolinium-doped ceria (Ce 0.9Gd 0.1O 2) referred as to CeGdO 2, praseodymium oxide, molybdenum oxide and copper oxide were tested. The working temperature was fixed at 850°C, except for 5% ruthenium-doped La 1- xSr xCrO 3 where the temperature was varied between 700 and 850°C. Two types of behavior were observed as a function of the activity of the catalyst. The higher steam reforming efficiency was observed with 5% of ruthenium above 750°C.

  13. 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...

  14. Preparation and evaluation of a multi-component catalyst by using a co-sputtering system for anodic oxidation of ethanol

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, S.; Usui, Y.; Kimura, O. [Environmental Technology R and D Center, Ricoh Company, Ltd., 16-1 Shinei-cho, Tsuzuki-ku, Yokohama 224-0035 (Japan); Umeda, M. [Department of Chemistry, Faculty of Engineering, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka, Niigata 940-2188 (Japan); Ojima, H.; Uchida, I. [Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Aramaki-Aoba 07, Aoba-ku, Sendai 980-8579 (Japan)

    2005-12-01

    In this study, a remarkable promotion of ethanol electrooxidation by a Pt--Ru-W alloy is reported for an improvement of the anodic reaction of a direct ethanol fuel cell (DEFC). Pt-based binary and ternary electrocatalysts including Pt-Ru-W deposited onto a Au substrate were prepared by co-sputtering process. By using this process, several metals can be arranged simultaneously and uniformly. The catalysts deposited onto Au were evaluated for anodic electrode in 1moldm{sup -3} ethanol+0.5 moldm{sup -3} sulfuric acid by electrochemical measurements. The performance of Pt-Ru-W was desirable in comparison to that of binary alloys, such as Pt-W, Pt-Sn and Pt-Ru, which exhibit higher catalytic activity than single Pt metal layer electrode. Ethanol electrooxidation on Pt-Ru-W alloy showed a cathodic shift in the onset potential and a higher current density than the binary alloy electrodes. It was found that Pt-Ru-W ternary catalyst effects to not only methanol oxidation reaction but also ethanol oxidation reaction and that the current density of ethanol oxidation with Pt-Ru-W is about 2/3 to that of methanol at 0.5V versus Ag/AgCl. The onset potentials for the ethanol oxidation reaction matched well the anodic peak potentials of the background volutammograms, i.e., 0.15V versus Ag/AgCl for Pt-Ru-W and 0.35V versus Ag/AgCl for Pt-W and Pt-Ru electrodes. That is, it was postulated that the background peak current indicates the generation of oxide species like metal-OH necessary to complete the ethanol oxidation to CO{sub 2}. (author)

  15. Synthesis of aluminum oxy-hydroxide nanofibers from porous anodic alumina

    Energy Technology Data Exchange (ETDEWEB)

    Jha, Himendra; Kikuchi, Tatsuya; Sakairi, Masatoshi; Takahashi, Hideaki [Laboratory of Interface Microstructure Analysis (LIMSA), Division of Materials Science and Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan)], E-mail: himendra@eng.hokudai.ac.jp

    2008-10-01

    A novel method for the synthesis of aluminum oxy-hydroxide nanofibers from a porous anodic oxide film of aluminum is demonstrated. In the present method, the porous anodic alumina not only acts as a template, but also serves as the starting material for the synthesis. The porous anodic alumina film is hydrothermally treated for pore-sealing, which forms aluminum oxy-hydroxide inside the pores of the oxide film as well as on the surface of the film. The hydrothermally sealed porous oxide film is immersed in the sodium citrate solution, which selectively etches the porous aluminum oxide from the film, leaving the oxy-hydroxide intact. The method is simple and gives highly uniform aluminum oxy-hydroxide nanofibers. Moreover, the diameter of the nanofibers can be controlled by controlling the pore size of the porous anodic alumina film, which depends on the anodizing conditions. Nanofibers with diameters of about 38-85 nm, having uniform shape and size, were successfully synthesized using the present method.

  16. Synthesis of aluminum oxy-hydroxide nanofibers from porous anodic alumina

    International Nuclear Information System (INIS)

    Jha, Himendra; Kikuchi, Tatsuya; Sakairi, Masatoshi; Takahashi, Hideaki

    2008-01-01

    A novel method for the synthesis of aluminum oxy-hydroxide nanofibers from a porous anodic oxide film of aluminum is demonstrated. In the present method, the porous anodic alumina not only acts as a template, but also serves as the starting material for the synthesis. The porous anodic alumina film is hydrothermally treated for pore-sealing, which forms aluminum oxy-hydroxide inside the pores of the oxide film as well as on the surface of the film. The hydrothermally sealed porous oxide film is immersed in the sodium citrate solution, which selectively etches the porous aluminum oxide from the film, leaving the oxy-hydroxide intact. The method is simple and gives highly uniform aluminum oxy-hydroxide nanofibers. Moreover, the diameter of the nanofibers can be controlled by controlling the pore size of the porous anodic alumina film, which depends on the anodizing conditions. Nanofibers with diameters of about 38-85 nm, having uniform shape and size, were successfully synthesized using the present method

  17. Low Pt content Pt-Ru-Ir-Sn quaternary catalysts for anodic methanol oxidation in DMFC

    Energy Technology Data Exchange (ETDEWEB)

    Neburchilov, Vladimir; Wang, Haijiang; Zhang, Jiujun [Institute for Fuel Cell Innovation, National Research Council (Canada)

    2007-07-15

    In this communication we report our research work on low Pt content Pt-Ru-Ir-Sn quaternary catalysts for use in DMFC anodes. The carbon-supported quaternary metal alloy catalyst was synthesized according to the solution reduction method and was deposited onto a carbon fiber paper or a carbon aerogel nanofoam to form the anode for direct methanol fuel cells. The Pt loading of the electrode is 0.1 mg/cm{sup 2}. The testing results from a three-electrode electrochemical cell show that the simultaneous use of higher Ir (25-35 wt.%) and Sn (10 wt.%) content gives satisfactory stability and higher activity for methanol oxidation than the commercially available E-TEK anode (80%[0.5Pt 0.5Ru]/C on carbon cloth). Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), scanning electron microscope (SEM), and Bruner-Emmett-Teller method (BET) measurements were carried out to characterize the composition, structure, morphology, and surface area of the developed catalysts. (author)

  18. A robust NiO-Sm0.2Ce0.8O1.9 anode for direct-methane solid oxide fuel cell

    KAUST Repository

    Tian, Dong

    2015-07-02

    In order to directly use methane without a reforming process, NiO-Sm0.2Ce0.8O1.9 (NiO-SDC) nanocomposite anode are successfully synthesized via a one-pot, surfactant-assisted co-assembly approach for direct-methane solid oxide fuel cells. Both NiO with cubic phase and SDC with fluorite phase are obtained at 550 °C. Both NiO nanoparticles and SDC nanoparticles are highly monodispersed in size with nearly spherical shapes. Based on the as-synthesized NiO-SDC, two kinds of single cells with different micro/macro-porous structure are successfully fabricated. As a result, the cell performance was improved by 40%-45% with the new double-pore NiO-SDC anode relative to the cell performance with the conventional NiO-SDC anode due to a wider triple-phase-boundary (TPB) area. In addition, no significant degradation of the cell performance was observed after 60 hours, which means an increasing of long term stability. Therefore, the as-synthesized NiO-SDC nanocomposite is a promising anode for direct-methane solid oxide fuel cells.

  19. High performance electrodes for reduced temperature solid oxide fuel cells with doped lanthanum gallate electrolyte. I. Ni-SDC cermet anode

    Science.gov (United States)

    Ohara, S.; Maric, R.; Zhang, X.; Mukai, K.; Fukui, T.; Yoshida, H.; Inagaki, T.; Miura, K.

    A Ni-samaria-doped ceria (SDC) cermet was selected as the anode material for reduced temperature (800°C) solid oxide fuel cells. The NiO-SDC composite powder, synthesized by spray pyrolysis, was employed as the starting anode powder in this study. The influence of Ni content in Ni-SDC cermets on the electrode performance was investigated in order to create the most suitable microstructures. It was found that anodic polarization was strongly influenced by the Ni content in Ni-SDC cermets. The best results were obtained for anode cermets with Ni content of around 50 vol.%; anodic polarization was about 30 mV at a current density of 300 mA/cm 2. This high performance seems to be attributable to the microstructure, in which Ni grains form a skeleton with well-connected SDC grains finely distributed over the Ni grains surfaces; such microstructure was also conducive to high stability of the anode.

  20. 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).

  1. 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.

  2. Chlorination of niobium oxide in the presence of carbon monoxide

    International Nuclear Information System (INIS)

    Freitas, L.R. de

    1984-01-01

    The chlorination kinetics of niobium pentoxide in the presence of carbon monoxide between 500-800 0 C of temperature is studied. The following variable that influences on the reaction rate are analysed: gas flow, geometry and volume of the Nb 2 O 5 samples, reaction temperature and composition of the chlorinated mixture. At the same time, two other materials were studied: the CaO.Nb 2 O 5 (synthetized in laboratory) and pyrochlorine concentrates. The three materials are compared for the chlorination method used. (M.A.C.) [pt

  3. 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.

  4. Ultrahigh capacity anode material for lithium ion battery based on rod gold nanoparticles decorated reduced graphene oxide

    International Nuclear Information System (INIS)

    Atar, Necip; Eren, Tanju; Yola, Mehmet Lütfi

    2015-01-01

    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 −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 −1 . • The nanocomposite exhibited a long-term cycle stability

  5. Probing anodic oxidation kinetics and nanoscale heterogeneity within TiO2 films by Conductive Atomic Force Microscopy and combined techniques

    International Nuclear Information System (INIS)

    Diamanti, M.V.; Souier, T.; Stefancich, M.; Chiesa, M.; Pedeferri, M.P.

    2014-01-01

    Graphical abstract: - Highlights: • Nanoscale anodic titanium oxides were investigated with multidisciplinary approach. • Oxide thickness was estimated via spectrophotometry and coulometry. • C-AFM identified nanometric conductivity heterogeneities, ascribed to oxide structure. • High conductivity areas exhibited local memristive behavior. - Abstract: Anodic oxidation of titanium in acid electrolytes allows to obtain a thin, compact oxide layer with thickness, structure, color, and electrical properties that vary with process parameters imposed, among which cell voltage has a key effect. Although oxidation kinetics have been investigated in several research works, a broader vision of oxide properties–including thickness and structure–still has to be achieved, especially in the case of very thin oxide films, few tens of nanometers thick. This is vital for engineered applications of nanostructured TiO 2 films, as in the field of memristive devices, where a precise control of oxide thickness, composition and structure is required to tune its electrical response. In this work, oxide films were produced on titanium with thickness ranging from few nanometers to 200 nm. Oxide thickness was estimated by coulometry and spectrophotometry. These techniques were then combined with C-AFM, which provided a deeper understanding of oxide thickness and uniformity of the metal surface and probed the presence of crystalline nano-domains within the amorphous oxide phase affecting the overall film electrical and optical properties

  6. Gallium oxide nanorods as novel, safe and durable anode material for Li- and Na-ion batteries

    International Nuclear Information System (INIS)

    Meligrana, Giuseppina; Lueangchaichaweng, Warunee; Colò, Francesca; Destro, Matteo; Fiorilli, Sonia; Pescarmona, Paolo P.; Gerbaldi, Claudio

    2017-01-01

    Highlights: • Gallium oxide nanorods applied for the first time as anode material for Li-/Na-ion batteries. • Durable ambient temperature cycling (400 cycles) was observed in Li-based cells. • Stable reversible cycling (> 200 mAh g"−"1) was achieved for the first time in Na-based cells. - Abstract: Gallium oxide nanorods prepared by template-free synthesis are reported for the first time as safe and durable anode material for lithium- and sodium-ion batteries. The ambient temperature electrochemical response of the nanorods, tested by cyclic voltammetry and constant-current reversible cycling, is highly satisfying in terms of remarkable stability and capacity retention upon long-term operation (400 cycles), even at high current densities. The newly proposed application of gallium oxide nanorods as electrode material is notable also because this material can preserve the electrical pathway without the need of any “buffer matrix” to compensate for the expansion upon lithium or sodium reversible storage. The highly promising electrochemical performance is attributed to the high aspect ratio and high surface area that stem from the nanorod morphology and which can lead to short diffusion path and fast kinetics of both cations (Li"+ or Na"+) and electrons.

  7. Anodic Aluminum Oxide (AAO) Membranes for Cellular Devices

    Science.gov (United States)

    Ventura, Anthony P.

    Anodic Aluminum Oxide (AAO) membranes can be fabricated with a highly tunable pore structure making them a suitable candidate for cellular hybrid devices with single-molecule selectivity. The objective of this study was to characterize the cellular response of AAO membranes with varying pore sizes to serve as a proof-of-concept for an artificial material/cell synapse system. AAO membranes with pore diameters ranging from 34-117 nm were achieved via anodization at a temperature of -1°C in a 2.7% oxalic acid electrolyte. An operating window was established for this setup to create membranes with through-pore and disordered pore morphologies. C17.2 neural stem cells were seeded onto the membranes and differentiated via serum withdrawal. The data suggests a highly tunable correlation between AAO pore diameter and differentiated cell populations. Analysis of membranes before and after cell culture indicated no breakdown of the through-pore structure. Immunocytochemistry (ICC) showed that AAO membranes had increased neurite outgrowth when compared to tissue culture treated (TCT) glass, and neurite outgrowth varied with pore diameter. Additionally, lower neuronal percentages were found on AAO as compared to TCT glass; however, neuronal population was also found to vary with pore diameter. Scanning electron microscopy (SEM) and ICC images suggested the presence of a tissue-like layer with a mixed-phenotype population. AAO membranes appear to be an excellent candidate for cellular devices, but more work must be completed to understand the surface chemistry of the AAO membranes as it relates to cellular response.

  8. Carbon deposition thresholds on nickel-based solid oxide fuel cell anodes I. Fuel utilization

    Science.gov (United States)

    Kuhn, J.; Kesler, O.

    2015-03-01

    In the first of a two part publication, the effect of fuel utilization (Uf) on carbon deposition rates in solid oxide fuel cell nickel-based anodes was studied. Representative 5-component CH4 reformate compositions (CH4, H2, CO, H2O, & CO2) were selected graphically by plotting the solutions to a system of mass-balance constraint equations. The centroid of the solution space was chosen to represent a typical anode gas mixture for each nominal Uf value. Selected 5-component and 3-component gas mixtures were then delivered to anode-supported cells for 10 h, followed by determination of the resulting deposited carbon mass. The empirical carbon deposition thresholds were affected by atomic carbon (C), hydrogen (H), and oxygen (O) fractions of the delivered gas mixtures and temperature. It was also found that CH4-rich gas mixtures caused irreversible damage, whereas atomically equivalent CO-rich compositions did not. The coking threshold predicted by thermodynamic equilibrium calculations employing graphite for the solid carbon phase agreed well with empirical thresholds at 700 °C (Uf ≈ 32%); however, at 600 °C, poor agreement was observed with the empirical threshold of ∼36%. Finally, cell operating temperatures correlated well with the difference in enthalpy between the supplied anode gas mixtures and their resulting thermodynamic equilibrium gas mixtures.

  9. Polymerisation occurrence in the anodic oxidation of phosphite on a boron-doped diamond electrode

    International Nuclear Information System (INIS)

    Petrucci, Elisabetta; Montanaro, Daniele; Merli, Carlo

    2008-01-01

    The electrogeneration of polymeric phosphorus compounds during the anodic oxidation of aqueous solutions of phosphites on a boron-doped diamond electrode has been studied. Although the main oxidation product is orthophosphate, the results indicate the simultaneous generation of short-chain and cyclic compounds containing two and three phosphorus atoms whose evolution has been followed by ion chromatography. The effect on the reaction yield of several operative parameters such as current density, pH, temperature and initial phosphite concentration has been investigated. Consistently with the data presented, a new process for the generation of polymeric phosphates is obtained

  10. Session 4: The influence of elementary heterogeneous reforming chemistry within solid-oxide fuel cell anodes

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, H.; Kee, R.J. [Engineering Division, Colorado School of Mines, Golden, CO (United States); Janardhanan, V.M.; Deutschmann, O. [Karlsruhe Univ., Institute for Chemical Technology (Germany); Goodwin, D.G. [Engineering and Applied Science., California Inst. of Technology, Pasadena, CA (United States); Sullivan, N.P. [ITN Energy Systems, Littleton, CO (United States)

    2004-07-01

    In the work presented a computational model is developed that represents the coupled effects of fluid flow in fuel channels, porous media transport and chemistry in the anode, and electrochemistry associated with the membrane-electrode assembly. An important objective is to explore the role of heterogeneous chemistry within the anode. In addition to cell electrical performance the chemistry model predicts important behaviors like catalyst-fouling deposit formation (i.e., coking). The model is applied to investigate alternative fuel-cell operating conditions, including varying fuel flow rates, adding air to the fuel stream, and recirculating exhaust gases. Results include assessments of performance metrics like fuel utilization, cell efficiency, power density, and catalyst coking. The model shows that 'direct electrochemical oxidation' of hydrocarbon fuels in solid-oxide fuel cells can be explained by a process that involves reforming the fuel to H{sub 2}, with hydrogen being the only species responsible for charge exchange. The model can be applied to investigate alternative design and operating conditions, seeking to improve the overall performance. (O.M.)

  11. Surface polishing of niobium for superconducting radio frequency (SRF) cavity applications

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Liang [College of William and Mary, Williamsburg, VA (United States)

    2014-08-01

    overlapping laser tracks at proper ratio. Comparison of topography and PSD indicates that LP smooths the surface in a way similar to EP. The optimized LP parameters were applied to different types of niobium surfaces representing different stages in cavity fabrication. LP reduces the sharpness on rough surfaces effectively, while doing no harm to smooth surfaces. Secondary ion mass spectrometer (SIMS) analysis showed that LP reduces the oxide layer slightly and no contamination occurred from LP. EBSD showed no significant change on crystal structure after LP.

  12. A SRF niobium cylindrical cavity with a large silicon nitride niobium-coated membrane as one end-wall

    Science.gov (United States)

    Martinez, Luis; Castelli, Alessandro; Pate, Jacob; Thompson, Johnathon; Delmas, William; Sharping, Jay; Chiao, Raymond; Chiao Team; Sharping Team

    The development of large silicon nitride membranes and niobium film deposition techniques motivate new architectures in opto-mechanics and microwave devices that can exploit the extremely high Q's obtainable with superconducting radio frequency (SRF) niobium cavities. We present a X-band SRF cylindrical cavity-membrane system in which one end-wall of the cavity is replaced by a niobium coated centimeter-sized silicon nitride membrane. We report moderately high Q factors above 10 million. Experimental results characterizing the system and potential future applications for such schemes in microwave devices and optomechanics are discussed.

  13. Photocatalytic Activity of Nanotubular TiO2 Films Obtained by Anodic Oxidation: A Comparison in Gas and Liquid Phase

    Directory of Open Access Journals (Sweden)

    Beatriz Eugenia Sanabria Arenas

    2018-03-01

    Full Text Available The availability of immobilized nanostructured photocatalysts is of great importance in the purification of both polluted air and liquids (e.g., industrial wastewaters. Metal-supported titanium dioxide films with nanotubular morphology and good photocatalytic efficiency in both environments can be produced by anodic oxidation, which avoids release of nanoscale materials in the environment. Here we evaluate the effect of different anodizing procedures on the photocatalytic activity of TiO2 nanostructures in gas and liquid phases, in order to identify the most efficient and robust technique for the production of TiO2 layers with different morphologies and high photocatalytic activity in both phases. Rhodamine B and toluene were used as model pollutants in the two media, respectively. It was found that the role of the anodizing electrolyte is particularly crucial, as it provides substantial differences in the oxide specific surface area: nanotubular structures show remarkably different activities, especially in gas phase degradation reactions, and within nanotubular structures, those produced by organic electrolytes lead to better photocatalytic activity in both conditions tested.

  14. Electrochemical incineration of chloromethylphenoxy herbicides in acid medium by anodic oxidation with boron-doped diamond electrode

    International Nuclear Information System (INIS)

    Boye, Birame; Brillas, Enric; Marselli, Beatrice; Michaud, Pierre-Alain; Comninellis, Christos; Farnia, Giuseppe; Sandona, Giancarlo

    2006-01-01

    The electrochemical degradation of saturated solutions of herbicides 4-chloro-2-methylphenoxyacetic acid, 2-(4-chlorophenoxy)-2-methylpropionic acid and 2-(4-chloro-2-methylphenoxy)propionic acid in 1 M HClO 4 on a boron-doped diamond (BDD) thin film anode has been studied by chronoamperometry, cyclic voltammetry and bulk electrolysis. At low anodic potentials polymeric products are formed causing the fouling and deactivation of BDD. This is reactivated at high potentials when water decomposes producing hydroxyl radical as strong oxidant of organics. Electrolyses in a batch recirculation system at constant current density ≥8 mA cm -2 yielded overall decontamination of all saturated solution. The effect of current density and herbicide concentration on the degradation rate of each compound, the specific charge required for its total mineralization and instantaneous current efficiency have been investigated. Experimental results have been compared with those predicted by a theoretical model based on a fast anodic oxidation of initial herbicides, showing that at 30 mA cm -2 their degradation processes are completely controlled by mass transfer. Kinetic analysis of the change of herbicide concentration with time during electrolysis, determined by high-performance liquid chromatography, revealed that all compounds follow a pseudo first-order reaction. Aromatic intermediates and generated carboxylic acids have been identified using this technique and a general pathway for the electrochemical incineration of all herbicides on BDD is proposed

  15. Sulfur poisoning of Ni/Gadolinium-doped ceria anodes: A long-term study outlining stable solid oxide fuel cell operation

    Science.gov (United States)

    Riegraf, Matthias; Zekri, Atef; Knipper, Martin; Costa, Rémi; Schiller, Günter; Friedrich, K. Andreas

    2018-03-01

    This work presents an analysis of the long-term behavior of nickel/gadolinium-doped ceria (CGO) anode-based solid oxide fuel cells (SOFC) under sulfur poisoning conditions. A parameter study of sulfur-induced irreversible long-term degradation of commercial, high-performance single cells was carried out at 900 °C for different H2/N2/H2S fuel gas atmospheres, current densities and Ni/CGO anodes. The poisoning periods of the cells varied from 200 to 1500 h. The possibility of stable long-term Ni/CGO anode operation under sulfur exposure is established and the critical operating regime is outlined. Depending on the operating conditions, two degradation phenomena can be observed. Small degradation of the ohmic resistance was witnessed for sulfur exposure times of approximately 1000 h. Moreover, degradation of the anode charge transfer resistance was observed to be triggered by the combination of a small anodic potential step and high sulfur coverage on Ni. The microstructural evolution of altered Ni/CGO anodes was examined post-mortem by means of SEM and FIB/SEM, and is correlated to the anode performance degradation under critical operating conditions, establishing Ni depletion, porosity increase and a tripe phase boundary density decrease in the anode functional layer. It is shown that short-term sulfur poisoning behavior can be used to assess long-term stability.

  16. 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.

  17. Synthesis and performance of cerium oxide as anode materials for lithium ion batteries by a chemical precipitation method

    International Nuclear Information System (INIS)

    Liu, Haowen; Le, Qi

    2016-01-01

    In this present work, chemical precipitation method was employed for preparing cerium oxide. XRD, SEM, TEM, TGA/DTA and BET were used to investigate the structure, shape and formation mechanism, respectively. No impurities were detected. It was found that alcohol had obvious effection on the growth of the final sample. The shape of the precursor was retained after calcined at 500 °C. This result led to the possibility of an easy scale up to a commercial process. EIS and charge–discharge tests were carried out by using the as-prepared CeO_2 as an anode material for lithium ion batteries. Specially, the initial discharge specific capacity of the rhombus CeO_2 was about 529 mAh g"−"1 and stabilized reversibly at about 374 mAh g"−"1 after 50 cycles. It showed a promising usage as anode materials in lithium ion battery. - Highlights: • Chemical precipitation method was employed for the synthesis of cerium oxide. • Alcohol has obvious effection on the growth of the final sample. • The rhombus CeO_2 showed the better electrochemical properties as anode of lithium ion batteries.

  18. Synthesis and performance of cerium oxide as anode materials for lithium ion batteries by a chemical precipitation method

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Haowen, E-mail: liuhwchem@hotmail.com; Le, Qi

    2016-06-05

    In this present work, chemical precipitation method was employed for preparing cerium oxide. XRD, SEM, TEM, TGA/DTA and BET were used to investigate the structure, shape and formation mechanism, respectively. No impurities were detected. It was found that alcohol had obvious effection on the growth of the final sample. The shape of the precursor was retained after calcined at 500 °C. This result led to the possibility of an easy scale up to a commercial process. EIS and charge–discharge tests were carried out by using the as-prepared CeO{sub 2} as an anode material for lithium ion batteries. Specially, the initial discharge specific capacity of the rhombus CeO{sub 2} was about 529 mAh g{sup −1} and stabilized reversibly at about 374 mAh g{sup −1} after 50 cycles. It showed a promising usage as anode materials in lithium ion battery. - Highlights: • Chemical precipitation method was employed for the synthesis of cerium oxide. • Alcohol has obvious effection on the growth of the final sample. • The rhombus CeO{sub 2} showed the better electrochemical properties as anode of lithium ion batteries.

  19. Anodizing of aluminum with improved corrosion properties

    International Nuclear Information System (INIS)

    John, P.; Khan, I.U.

    2010-01-01

    Anodizing of aluminum was studied in sulphuric/oxalic/boric acid electroiyte system. The corrosion resistance of the anodic oxide coating of aluminum was determined by potentiodynamic polarization test and scanning electron microscope (SEM) was used to investigate the surface morphology before and after corrosion test. It was found that the oxide coating obtained by this method showed better corrosion resistance with no significant difference in surface morphology. (author)

  20. Ni/Ni-YSZ current collector/anode dual layer hollow fibers for micro-tubular solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kanawka, K.; Othman, M.H.D.; Droushiotis, N.; Wu, Z.; Kelsall, G.; Li, K. [Department of Chemical Engineering and Chemical Technology, Imperial College London, London SW7 2AZ (United Kingdom)

    2011-10-15

    A co-extrusion technique was employed to fabricate a novel dual layer NiO/NiO-YSZ hollow fiber (HF) precursor which was then co-sintered at 1,400 C and reduced at 700 C to form, respectively, a meshed porous inner Ni current collector and outer Ni-YSZ anode layers for SOFC applications. The inner thin and highly porous ''mesh-like'' pure Ni layer of approximately 50 {mu}m in thickness functions as a current collector in micro-tubular solid oxide fuel cell (SOFC), aiming at highly efficient current collection with low fuel diffusion resistance, while the thicker outer Ni-YSZ layer of 260 {mu}m acts as an anode, providing also major mechanical strength to the dual-layer HF. Achieved morphology consisted of short finger-like voids originating from the inner lumen of the HF, and a sponge-like structure filling most of the Ni-YSZ anode layer, which is considered to be suitable macrostructure for anode SOFC system. The electrical conductivity of the meshed porous inner Ni layer is measured to be 77.5 x 10{sup 5} S m{sup -1}. This result is significantly higher than previous reported results on single layer Ni-YSZ HFs, which performs not only as a catalyst for the oxidation reaction, but also as a current collector. These results highlight the advantages of this novel dual-layer HF design as a new and highly efficient way of collecting current from the lumen of micro-tubular SOFC. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Electrochemical characterization of anode passivation mechanisms in copper electrorefining

    Science.gov (United States)

    Moats, Michael Scott

    Anode passivation can decrease productivity and quality while increasing costs in modern copper electrorefineries. This investigation utilized electrochemical techniques to characterize the passivation behavior of anode samples from ten different operating companies. It is believed that this collection of anodes is the most diverse set ever to be assembled to study the effect of anode composition on passivation. Chronopotentiometry was the main electrochemical technique, employing a current density of 3820 A m-2. From statistical analysis of the passivation characteristics, increasing selenium, tellurium, silver, lead and nickel were shown to accelerate passivation. Arsenic was the only anode impurity that inhibited passivation. Oxygen was shown to accelerate passivation when increased from 500 to 1500 ppm, but further increases did not adversely affect passivation. Nine electrolyte variables were also examined. Increasing the copper, sulfuric acid or sulfate concentration of the electrolyte accelerated passivation. Arsenic in the electrolyte had no effect on passivation. Chloride and optimal concentrations of thiourea and glue delayed passivation. Linear sweep voltammetry, cyclic voltammetry, and impedance spectroscopy provided complementary information. Analysis of the electrochemical results led to the development of a unified passivation mechanism. Anode passivation results from the formation of inhibiting films. Careful examination of the potential details, especially those found in the oscillations just prior to passivation, demonstrated the importance of slimes, copper sulfate and copper oxide. Slimes confine dissolution to their pores and inhibit diffusion. This can lead to copper sulfate precipitation, which blocks more of the surface area. Copper oxide forms because of the resulting increase in potential at the interface between the copper sulfate and anode. Ultimate passivation occurs when the anode potential is high enough to stabilize the oxide film in

  2. High performance electrodes for reduced temperature solide oxide fuel cells with doped lanthanum gallate electrolyte. Pt. 1. Ni-SDC cermet anode

    Energy Technology Data Exchange (ETDEWEB)

    Ohara, S.; Maric, R.; Zhang, X.; Mukai, K.; Fukui, T. [Japan Fine Ceramics Center, Nagoya (Japan); Yoshida, H.; Inagaki, T. [The Kansai Electroc Power Co. Inc., Hyogo (Japan); Miura, K. [Kanden Kakou Co. Ltd., Hyogo (Japan)

    2000-03-01

    A Ni-samaria-doped ceria (SDC) cermet was selected as the anode material for reduced temperature (800 C) solid oxide fuel cells. The NiO-SDC composite powder, synthesized by spray pyrolysis, was employed as the starting anode powder in this study. The influence of Ni content in Ni-SDC cermets on the electrode performance was investigated in order to create the most suitable microstructures. It was found that anodic polarization was strongly influenced by the Ni content in Ni-SDC cermets. The best results were obtained for anode cermets with Ni content of around 50 vol.%; anodic polarization was about 30 mV at a current density of 300 mA/cm{sup 2}. This high performance seems to be attributable to the microstructure, in which Ni grains form a skeleton with well-connected SDC grains finely distributed over the Ni grains surfaces; such microstructure was also conducive to high stability of the anode. (orig.)

  3. Improved oxidation resistance of group VB refractory metals by Al+ ion implantation

    International Nuclear Information System (INIS)

    Hampikian, J.M.

    1996-01-01

    Aluminum ion implantation of vanadium, niobium, and tantalum improved the metals' oxidation resistances at 500 C and 735 C. Implanted vanadium oxidized only to one-third the extent of unimplanted vanadium when exposed at 500 C to air. The oxidative weight gains of implanted niobium and tantalum proved negligible when measured at 500 C and for times sufficient to fully convert the untreated metals to their pentoxides. At 735 C, implantation of vanadium only slightly retarded its oxidation, while oxidative weight gains of niobium and tantalum were reduced by factors of 3 or more. Implanted niobium exhibited weight gain in direct proportion to oxidation time squared at 735 C. Microstructural examination of the metals implanted with selected fluences of the 180 kV aluminum ions showed the following. The solubility limit of aluminum is extended by implantation, the body centered cubic (bcc) phases being retained to ∼60 at. pct Al in all three metals. The highest fluence investigated, 2.4 x 10 22 ions/m 2 , produced an ∼400-nm layer of VAl 3 beneath the surface of vanadium, and ∼300-nm layers of an amorphous phase containing ∼70 at. pct Al beneath the niobium and tantalum surfaces. All three metals, implanted to this fluence and annealed at 600 C, contained tri-aluminides, intermetallic compounds known for their oxidation resistances. Specimens implanted to this fluence were thus selected for the oxidation measurements

  4. 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.; Anthofer, Michael H.; Reich, Robert M.; D'Elia, Valerio; Basset, Jean-Marie; Herrmann, Wolfgang A.; Cokoja, Mirza; Kü hn, Fritz

    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.

  5. 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.

  6. Analysis of chemical dissolution of the barrier layer of porous oxide on aluminum thin films using a re-anodizing technique

    Energy Technology Data Exchange (ETDEWEB)

    Vrublevsky, I. [Department of Microelectronics, Belarusian State University of Informatics and Radioelectronics, 6 Brovka street, Minsk 220013 (Belarus)]. E-mail: nil-4-2@bsuir.edu.by; Parkoun, V. [Department of Microelectronics, Belarusian State University of Informatics and Radioelectronics, 6 Brovka street, Minsk 220013 (Belarus); Sokol, V. [Department of Microelectronics, Belarusian State University of Informatics and Radioelectronics, 6 Brovka street, Minsk 220013 (Belarus); Schreckenbach, J. [Institut fuer Chemie, Technische Universitaet Chemnitz, Chemnitz D-09107 (Germany)

    2005-09-30

    Chemical dissolution of the barrier layer of porous oxide formed on thin aluminum films (99.9% purity) in the 4% oxalic acid after immersion in 2 mol dm{sup -3} sulphuric acid at 50 deg. C has been studied. The barrier layer thickness before and after dissolution was calculated using a re-anodizing technique. It has been shown that above 57 V the change in the growth mechanism of porous alumina films takes place. As a result, the change in the amount of regions in the barrier oxide with different dissolution rates is observed. The barrier oxide contains two layers at 50 V: the outer layer with the highest dissolution rate and the inner layer with a low dissolution rate. Above 60 V the barrier oxide contains three layers: the outer layer with a high dissolution rate, the middle layer with the highest dissolution rate and the inner layer with a low dissolution rate. We suggest that the formation of the outer layer of barrier oxide with a high dissolution rate is linked with the injection of protons or H{sub 3}O{sup +} ions from the electrolyte into the oxide film at the anodizing voltages above 57 V.

  7. Niobium sputter deposition on quarter wave resonators

    CERN Document Server

    Viswanadham, C; Jayaprakash, D; Mishra, R L

    2003-01-01

    Niobium sputter deposition on quarter wave copper R.F resonators, have been taken up in our laboratory, An ultra high vacuum system was made for this purpose. Niobium exhibits superconducting properties at liquid Helium temperature. A uniform coating of about 1.5 mu m of niobium on the internal surfaces of the copper resonant cavities is desired. Power dissipation in the resonators can be greatly reduced by making the internal surfaces of the R.F cavity super conducting. (author)

  8. Study of Nb-oxide Nb-Pb film structures by tunnel scanning microscope

    International Nuclear Information System (INIS)

    Golyamina, E.M.; Troyanovskij, A.M.

    1986-01-01

    The surface of niobium films, which were earlier used to create niobium-niobium oxide-lead film structures on their base, was investigated, using tunnel scanning microscope. The results obtained agree well with the observed properties of these structures, containing josephson and tunnel junctions

  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. RF Characterization of Niobium Films for Superconducting Cavities

    CERN Document Server

    Aull† , S; Doebert, S; Junginger, T; Ehiasarian, AP; Knobloch, J; Terenziani, G

    2013-01-01

    The surface resistance RS of superconductors shows a complex dependence on the external parameters such as temperature, frequency or radio-frequency (RF) field. The Quadrupole Resonator modes of 400, 800 and 1200 MHz allow measurements at actual operating frequencies of superconducting cavities. Niobium films on copper substrates have several advantages over bulk niobium cavities. HIPIMS (High-power impulse magnetron sputtering) is a promising technique to increase the quality and therefore the performance of niobium films. This contribution will introduce CERNs recently developed HIPIMS coating apparatus. Moreover, first results of niobium coated copper samples will be presented, revealing the dominant loss mechanisms.

  11. Study of niobium V compounds in nitric medium

    International Nuclear Information System (INIS)

    Gue, J.-P.; Kikindai, Tivadar; CEA Centre d'Etudes Nucleaires de Fontenay-aux-Roses, 92

    1976-01-01

    Nitric solutions of niobium V were studied in the range of concentrations of 5.10 -6 M to 0,5.10 -3 M in niobium and 0,4 to 10N in nitric acid. Methods used were light scattering, electron microscopy, electrophoresis and ultracentrifugation. It is shown that niobium was in a colloidal hydroxide form. Solvent extraction studies were performed with dibutyl phosphoric acid diluted in dodecane. It appears that floculation of the sol occurs for weak organic acid concentrations. But if the concentration increases, the precipitated niobium compound is redissolved in the organic phase [fr

  12. Superhydrophilicity of novel anodic alumina nanofibers films and their formation mechanism

    Science.gov (United States)

    Peng, Rong; Yang, Wulin; Fu, Licai; Zhu, Jiajun; Li, Deyi; Zhou, Lingping

    2017-06-01

    A novel anodic alumina nanofibers structure, which is different from the traditional porous anodic structure, has been quickly fabricated via anodizing in a new electrolyte, pyrophosphoric acid. The effects of the solution concentration and the anodizing time on the formation of the anodic alumina nanofibers were analyzed. The results show that the nanostructure of anodic alumina can change to the nanofiber oxide from the porous oxide by increasing the solution concentration. Prolonging the anodizing time is beneficial to obtain alumina nanofibers at high solution concentration. Growth behavior of the alumina nanofibers was also discussed by scanning electron microscopy observations. Owing to the unique hexagonal structure of anodic alumina as well as the preferential chemical dissolution between the porous anodic alumina and the anodic alumina nanotips, the slightly soluble anodic alumina nanotips could form novel alumina nanofibers during anodizing. The results show that the nanofibers-covered aluminum surface exhibits superhydrophilic property, with a near-zero water contact angle. Such alumina nanofibers with superhydrophilic property could be used for various potential applications.

  13. Adsorption of sulfur compound utilizing rice husk ash modified with niobium

    International Nuclear Information System (INIS)

    Cavalcanti, Rodrigo M.; Pessoa Júnior, Wanison A.G.; Braga, Valdeilson S.; Barros, Ivoneide de C.L.

    2015-01-01

    Graphical abstract: - Highlights: • Adsorbents based in RHA modified with niobium were prepared by impregnation. • The impregnation modified the particle size and topology of RHA particles. • The adsorbents were applied in sulfur removal in model liquid fuels. • The larger sulfur removal (>50%) was achieved using RHA with 5 wt.% niobium oxide. • The adsorbent show great selectivity in adsorption experiments. - Abstract: Adsorbents based in rice husk ash (RHA) modified with niobium pentoxide were prepared for impregnation methods and applied in sulfur removal in liquid fuels. The solids were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, nitrogen physisorption and thermal analysis; they show that there was no qualitative change in the amorphous structure of the RHA; however, the method of impregnation could modify the particle size and topology of RHA particles. The larger sulfur removal (>50%) was achieved using RHA with 5 wt.% Nb 2 O 5 at a dosage of 10 g L −1 , after 4 h of contact with the model fuel. The kinetic study of adsorption of thiophene showed that the models of pseudo-second order and intra-particle diffusion best fit the experimental data. The adsorption experiments with the thiophenic derivatives compounds show a large selectivity of the adsorbent.

  14. Adsorption of sulfur compound utilizing rice husk ash modified with niobium

    Energy Technology Data Exchange (ETDEWEB)

    Cavalcanti, Rodrigo M.; Pessoa Júnior, Wanison A.G. [Laboratório de Catálise Química e Materiais (CATAMA), Instituto de Ciências Exatas, Universidade Federal do Amazonas (UFAM), Av. Gen. Rodrigo Otávio Jordão Ramos, 6200, 69077-000 Manaus, AM (Brazil); Braga, Valdeilson S. [Laboratório de Catálise, Centro das Ciências Exatas e das Tecnologias, Universidade Federal do Oeste da Bahia, Rua Professor José Seabra de Lemos, 316, Recanto dos Pássaros, 47808-021 Barreira, BA (Brazil); Barros, Ivoneide de C.L., E-mail: iclbarros@gmail.com [Laboratório de Catálise Química e Materiais (CATAMA), Instituto de Ciências Exatas, Universidade Federal do Amazonas (UFAM), Av. Gen. Rodrigo Otávio Jordão Ramos, 6200, 69077-000 Manaus, AM (Brazil)

    2015-11-15

    Graphical abstract: - Highlights: • Adsorbents based in RHA modified with niobium were prepared by impregnation. • The impregnation modified the particle size and topology of RHA particles. • The adsorbents were applied in sulfur removal in model liquid fuels. • The larger sulfur removal (>50%) was achieved using RHA with 5 wt.% niobium oxide. • The adsorbent show great selectivity in adsorption experiments. - Abstract: Adsorbents based in rice husk ash (RHA) modified with niobium pentoxide were prepared for impregnation methods and applied in sulfur removal in liquid fuels. The solids were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, nitrogen physisorption and thermal analysis; they show that there was no qualitative change in the amorphous structure of the RHA; however, the method of impregnation could modify the particle size and topology of RHA particles. The larger sulfur removal (>50%) was achieved using RHA with 5 wt.% Nb{sub 2}O{sub 5} at a dosage of 10 g L{sup −1}, after 4 h of contact with the model fuel. The kinetic study of adsorption of thiophene showed that the models of pseudo-second order and intra-particle diffusion best fit the experimental data. The adsorption experiments with the thiophenic derivatives compounds show a large selectivity of the adsorbent.

  15. 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.

  16. In situ observations of microstructural changes in SOFC anodes during redox cycling

    DEFF Research Database (Denmark)

    Klemensø, Trine; Appel, C. C.; Mogensen, Mogens Bjerg

    2006-01-01

    The anode-supported solid oxide fuel cell (SOFC) degrades when the anode is subjected to redox cycling. The degradation has qualitatively been related to microstructural changes in the nickel-yttria stabilized zirconia anode of the tested cells. In this work, the microstructural changes were...... observed in situ using environmental scanning electron microscopy. In the reduced state, a dynamic rounding of the nickel particles occurred. The oxide growth upon re-oxidation depended on the oxidation kinetics. During rapid oxidation, the NiO particles divided into 2-4 particles, which grew...... into the surrounding voids. For slower oxidation, an external oxide layer was seen to develop around the individual particles. (c) 2006 The Electrochemical Society....

  17. High energy density asymmetric supercapacitors with a nickel oxide nanoflake cathode and a 3D reduced graphene oxide anode.

    Science.gov (United States)

    Luan, Feng; Wang, Gongming; Ling, Yichuan; Lu, Xihong; Wang, Hanyu; Tong, Yexiang; Liu, Xiao-Xia; Li, Yat

    2013-09-07

    Here we demonstrate a high energy density asymmetric supercapacitor with nickel oxide nanoflake arrays as the cathode and reduced graphene oxide as the anode. Nickel oxide nanoflake arrays were synthesized on a flexible carbon cloth substrate using a seed-mediated hydrothermal method. The reduced graphene oxide sheets were deposited on three-dimensional (3D) nickel foam by hydrothermal treatment of nickel foam in graphene oxide solution. The nanostructured electrodes provide a large effective surface area. The asymmetric supercapacitor device operates with a voltage of 1.7 V and achieved a remarkable areal capacitance of 248 mF cm(-2) (specific capacitance of 50 F g(-1)) at a charge/discharge current density of 1 mA cm(-2) and a maximum energy density of 39.9 W h kg(-1) (based on the total mass of active materials of 5.0 mg). Furthermore, the device showed an excellent charge/discharge cycling performance in 1.0 M KOH electrolyte at a current density of 5 mA cm(-2), with a capacitance retention of 95% after 3000 cycles.

  18. High energy density asymmetric supercapacitors with a nickel oxide nanoflake cathode and a 3D reduced graphene oxide anode

    Science.gov (United States)

    Luan, Feng; Wang, Gongming; Ling, Yichuan; Lu, Xihong; Wang, Hanyu; Tong, Yexiang; Liu, Xiao-Xia; Li, Yat

    2013-08-01

    Here we demonstrate a high energy density asymmetric supercapacitor with nickel oxide nanoflake arrays as the cathode and reduced graphene oxide as the anode. Nickel oxide nanoflake arrays were synthesized on a flexible carbon cloth substrate using a seed-mediated hydrothermal method. The reduced graphene oxide sheets were deposited on three-dimensional (3D) nickel foam by hydrothermal treatment of nickel foam in graphene oxide solution. The nanostructured electrodes provide a large effective surface area. The asymmetric supercapacitor device operates with a voltage of 1.7 V and achieved a remarkable areal capacitance of 248 mF cm-2 (specific capacitance of 50 F g-1) at a charge/discharge current density of 1 mA cm-2 and a maximum energy density of 39.9 W h kg-1 (based on the total mass of active materials of 5.0 mg). Furthermore, the device showed an excellent charge/discharge cycling performance in 1.0 M KOH electrolyte at a current density of 5 mA cm-2, with a capacitance retention of 95% after 3000 cycles.

  19. A general strategy toward graphitized carbon coating on iron oxides as advanced anodes for lithium-ion batteries.

    Science.gov (United States)

    Ding, Chunyan; Zhou, Weiwei; Wang, Bin; Li, Xin; Wang, Dong; Zhang, Yong; Wen, Guangwu

    2017-08-25

    Integration of carbon materials with benign iron oxides is blazing a trail in constructing high-performance anodes for lithium-ion batteries (LIBs). In this paper, a unique general, simple, and controllable strategy is developed toward in situ uniform coating of iron oxide nanostructures with graphitized carbon (GrC) layers. The basic synthetic procedure only involves a simple dip-coating process for the loading of Ni-containing seeds and a subsequent Ni-catalyzed chemical vapor deposition (CVD) process for the growth of GrC layers. More importantly, the CVD treatment is conducted at a quite low temperature (450 °C) and with extremely facile liquid carbon sources consisting of ethylene glycol (EG) and ethanol (EA). The GrC content of the resulting hybrids can be controllably regulated by altering the amount of carbon sources. The electrochemical results reveal remarkable performance enhancements of iron oxide@GrC hybrids compared with pristine iron oxides in terms of high specific capacity, excellent rate and cycling performance. This can be attributed to the network-like GrC coating, which can improve not only the electronic conductivity but also the structural integrity of iron oxides. Moreover, the lithium storage performance of samples with different GrC contents is measured, manifesting that optimized electrochemical property can be achieved with appropriate carbon content. Additionally, the superiority of GrC coating is demonstrated by the advanced performance of iron oxide@GrC compared with its corresponding counterpart, i.e., iron oxides with amorphous carbon (AmC) coating. All these results indicate the as-proposed protocol of GrC coating may pave the way for iron oxides to be promising anodes for LIBs.

  20. The effect of foil purity on morphology of anodized nanoporous ZrO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Wierzbicka, Ewa; Syrek, Karolina [Department of Physical Chemistry & Electrochemistry, Faculty of Chemistry, Jagiellonian University in Krakow, Ingardena 3, 30-060 Krakow (Poland); Sulka, Grzegorz D., E-mail: sulka@chemia.uj.edu.pl [Department of Physical Chemistry & Electrochemistry, Faculty of Chemistry, Jagiellonian University in Krakow, Ingardena 3, 30-060 Krakow (Poland); Pisarek, Marcin; Janik-Czachor, Maria [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland)

    2016-12-01

    Highlights: • Anodization of Zr with different purities in an aqueous electrolyte was studied. • The structural parameters of formed anodic oxides were compared. • Effect of Zr foil purity on the hexagonal arrangement of pores and cells in anodic ZrO{sub 2} was investigated. • Current efficiency and rate of anodic oxide formation were estimated. - Abstract: A two-step electrochemical formation of nanoporous zirconium oxide layers on different zirconium foils (purity 99.2% and 99.8%) was investigated. Anodizations were carried out at 20 V in an electrolyte composed of 1 M (NH{sub 4}){sub 2}SO{sub 4} and 0.15 M NH{sub 4}F. It was found that the thickness of grown oxide layer, and consequently, the rate of oxide formation depend slightly on the Zr substrate purity. The pore nucleation and anodization process occur easier in the presence of higher concentration of impurities. From top view SEM images, the structural parameters of oxide layers such as pore diameter, interpore distance, pore density, wall thickness and porosity of anodic oxide layers were estimated for both types of used substrates. On the other hand, cell size, intercell distance and cell density were evaluated from the bottom side of anodic oxide layers. A special emphasis was put on the qualitative analysis of hexagonal arrangement of nanopores and cells. The nanopore and cells arrangements in formed oxides were evaluated using various approaches based on Delaunay triangulations, angular distribution functions (ADFs) and pair distribution functions (PDFs). These results were supported by calculations of percentage of defective pores and cells for both types of used Zr substrates. The use of low purity Zr for anodizing does not affect drastically the morphology of formed nanoporous zirconia and offers a promising perspective to reduce production costs and increase availability of this material.