WorldWideScience

Sample records for surface tungsten oxide

  1. Covalent attachment of diamondoid phosphonic acid dichlorides to tungsten oxide surfaces.

    Science.gov (United States)

    Li, Fei Hua; Fabbri, Jason D; Yurchenko, Raisa I; Mileshkin, Alexander N; Hohman, J Nathan; Yan, Hao; Yuan, Hongyuan; Tran, Ich C; Willey, Trevor M; Bagge-Hansen, Michael; Dahl, Jeremy E P; Carlson, Robert M K; Fokin, Andrey A; Schreiner, Peter R; Shen, Zhi-Xun; Melosh, Nicolas A

    2013-08-06

    Diamondoids (nanometer-sized diamond-like hydrocarbons) are a novel class of carbon nanomaterials that exhibit negative electron affinity (NEA) and strong electron-phonon scattering. Surface-bound diamondoid monolayers exhibit monochromatic photoemission, a unique property that makes them ideal electron sources for electron-beam lithography and high-resolution electron microscopy. However, these applications are limited by the stability of the chemical bonding of diamondoids on surfaces. Here we demonstrate the stable covalent attachment of diamantane phosphonic dichloride on tungsten/tungsten oxide surfaces. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) spectroscopy revealed that diamondoid-functionalized tungsten oxide films were stable up to 300-350 °C, a substantial improvement over conventional diamondoid thiolate monolayers on gold, which dissociate at 100-200 °C. Extreme ultraviolet (EUV) light stimulated photoemission from these diamondoid phosphonate monolayers exhibited a characteristic monochromatic NEA peak with 0.2 eV full width at half-maximum (fwhm) at room temperature, showing that the unique monochromatization property of diamondoids remained intact after attachment. Our results demonstrate that phosphonic dichloride functionality is a promising approach for forming stable diamondoid monolayers for elevated temperature and high-current applications such as electron emission and coatings in micro/nano electromechanical systems (MEMS/NEMS).

  2. Tungsten Incorporation into Gallium Oxide: Crystal Structure, Surface and Interface Chemistry, Thermal Stability and Interdiffusion

    Energy Technology Data Exchange (ETDEWEB)

    Rubio, E. J.; Mates, T. E.; Manandhar, S.; Nandasiri, M.; Shutthanandan, V.; Ramana, C. V.

    2016-12-01

    Tungsten (W) incorporated gallium oxide (Ga2O3) (GWO) thin films were deposited by radio-frequency magnetron co-sputtering of W-metal and Ga2O3-ceramic targets. Films were produced by varying sputtering power applied to the W-target in order to achieve variable W-content (0-12 at%) into Ga2O3 while substrate temperature was kept constant at 500 °C. Chemical composition, chemical valence states, microstructure and crystal structure of as-deposited and annealed GWO films were evaluated as a function of W-content. The structural and chemical analyses indicate that the samples deposited without any W-incorporation are stoichiometric, nanocrystalline Ga2O3 films, which crystallize in β-phase monoclinic structure. While GWO films also crystallize in monoclinic β-Ga2O3 phase, W-incorporation induces surface amorphization as revealed by structural studies. The chemical valence state of Ga ions probed by X-ray photoelectron spectroscopic (XPS) analyses is characterized by the highest oxidation state i.e., Ga3+. No changes in Ga chemical state are noted for variable W-incorporation in the range of 0-12 at%. Rutherford backscattering spectrometry (RBS) analyses indicate the uniform distribution of W-content in the GWO films. However, XPS analyses indicate the formation of mixed valence states for W ions, which may be responsible for surface amorphization in GWO films. GWO films were stable up to 900 oC, at which point thermally induced secondary phase (W-oxide) formation was observed. A transition to mesoporous structure coupled with W interdiffusion occurs due to thermal annealing as derived from the chemical analyses at the GWO films’ surface as well as depth-profiling towards the GWO-Si interface. A model has been formulated to account for the mechanism of W-incorporation, thermal stability and interdiffusion via pore formation in GWO films.

  3. Visible light photoinactivation of bacteria by tungsten oxide nanostructures formed on a tungsten foil

    Energy Technology Data Exchange (ETDEWEB)

    Ghasempour, Fariba [Plasma Physics Research Centre, Science and Research Branch, Islamic Azad University, P.O. Box 147789-3855, Tehran (Iran, Islamic Republic of); Azimirad, Rouhollah [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Amini, Abbas [School of Computing, Engineering and Mathematics, University of Western Sydney, Kingswood, NSW 2751 (Australia); Akhavan, Omid, E-mail: oakhavan@sharif.edu [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran (Iran, Islamic Republic of)

    2015-05-30

    Highlights: • Synthesis of tungsten oxide nano/micro-structures on W foils using KOH as a catalyst. • Strong antibacterial activity of tungsten oxide nanorods under visible light irradiation. • Decrease in photoinactivation of bacteria on tungsten oxide nano/micro-rods doped by potassium. - Abstract: Antibacterial activity of tungsten oxide nanorods/microrods were studied against Escherichia coli bacteria under visible light irradiation and in dark. A two-step annealing process at temperatures up to 390 °C and 400–800 °C was applied to synthesize the tungsten oxide nanorods/microrods on tungsten foils using KOH as a catalyst. Annealing the foils at 400 °C in the presence of catalyst resulted in formation of tungsten oxide nanorods (with diameters of 50–90 nm and crystalline phase of WO{sub 3}) on surface of tungsten foils. By increasing the annealing temperature up to 800 °C, tungsten oxide microrods with K{sub 2}W{sub 6}O{sub 19} crystalline phase were formed on the foils. The WO{sub 3} nanorods showed a strong antibacterial property under visible light irradiation, corresponding to >92% bacterial inactivation within 24 h irradiation at room temperature, while the K{sub 2}W{sub 6}O{sub 19} microrods formed at 800 °C could inactivate only ∼45% of the bacteria at the same conditions.

  4. Preparation of tungsten oxide

    Science.gov (United States)

    Bulian, Christopher J.; Dye, Robert C.; Son, Steven F.; Jorgensen, Betty S.; Perry, W. Lee

    2009-09-22

    Tungsten trioxide hydrate (WO.sub.3.H.sub.2O) was prepared from a precursor solution of ammonium paratungstate in concentrated aqueous hydrochloric acid. The precursor solution was rapidly added to water, resulting in the crash precipitation of a yellow white powder identified as WO.sub.3.H.sub.2O nanosized platelets by x-ray diffraction and scanning electron microscopy. Annealing of the powder at 200.degree. C. provided cubic phase WO.sub.3 nanopowder, and at 400.degree. C. provided WO.sub.3 nanopowder as a mixture of monoclinic and orthorhombic phases.

  5. Visible light photoinactivation of bacteria by tungsten oxide nanostructures formed on a tungsten foil

    Science.gov (United States)

    Ghasempour, Fariba; Azimirad, Rouhollah; Amini, Abbas; Akhavan, Omid

    2015-05-01

    Antibacterial activity of tungsten oxide nanorods/microrods were studied against Escherichia coli bacteria under visible light irradiation and in dark. A two-step annealing process at temperatures up to 390 °C and 400-800 °C was applied to synthesize the tungsten oxide nanorods/microrods on tungsten foils using KOH as a catalyst. Annealing the foils at 400 °C in the presence of catalyst resulted in formation of tungsten oxide nanorods (with diameters of 50-90 nm and crystalline phase of WO3) on surface of tungsten foils. By increasing the annealing temperature up to 800 °C, tungsten oxide microrods with K2W6O19 crystalline phase were formed on the foils. The WO3 nanorods showed a strong antibacterial property under visible light irradiation, corresponding to >92% bacterial inactivation within 24 h irradiation at room temperature, while the K2W6O19 microrods formed at 800 °C could inactivate only ∼45% of the bacteria at the same conditions.

  6. Ambient Pressure Synthesis of Nanostructured Tungsten Oxide Crystalline Films

    Directory of Open Access Journals (Sweden)

    H. X. Zhang

    2008-01-01

    Full Text Available We report the results of the ambient pressure synthesis of tungsten oxide nanowires and nanoparticles on AlN substrates using the hot filament CVD techniques. The morphologic surface, crystallographic structures, chemical compositions, and bond structures of the obtained samples have been investigated using scanning electron microscopy (SEM, X-ray diffraction (XRD, energy dispersive X-ray spectroscopy (EDX, and Raman scattering, respectively. Different morphologies were observed for different substrate temperatures, but otherwise identical growth conditions. The experimental measurements reveal the evolutions of the crystalline states and bond structures following the substrate temperatures. Besides, different substrate materials also affected the tungsten oxide nanostructures. Bundles of wire-type tungsten oxide nanowires with a length of up to 5 mm were obtained on Al2O3 substrate. Furthermore, the sensitive properties of the super long nanowires to the gas and different temperature were investigated. The dependence of the sensitivity of tungsten oxide nanowires to the methane as a function of the time was obtained. The sensitive properties of the tungsten oxide nanowires have almost linear relationship with the temperature.

  7. Structural and electrical properties in tungsten/tungsten oxide multilayers

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    Cacucci, Arnaud [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Avenue Alain Savary, BP47870, F-21078 DIJON Cedex (France); Potin, Valérie, E-mail: valerie.potin@u-bourgogne.fr [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Avenue Alain Savary, BP47870, F-21078 DIJON Cedex (France); Imhoff, Luc [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Avenue Alain Savary, BP47870, F-21078 DIJON Cedex (France); Martin, Nicolas [Institut FEMTO-ST, UMR 6174 CNRS, Université de Franche-Comté, ENSMM, UTBM, 32 Avenue de l' observatoire, F-25044, BESANCON Cedex (France)

    2014-02-28

    Tungsten and tungsten oxide periodic nanometric multilayers have been deposited by DC reactive sputtering using the reactive gas pulsing process. Different pulsing periods have been used for each deposition to produce metal-oxide periodic alternations ranging from 3.3 to 71.5 nm. The morphology, crystallinity and chemical composition of these films have been investigated by transmission electron microscopy and energy-dispersive X-ray spectroscopy techniques. The produced multilayers exhibited an amorphous structure and the composition stability of WO{sub 3} sub-layers has been pointed out. Moreover, electrical properties have also been studied by the van der Pauw technique. It revealed a clear stability of resistivity versus temperature for almost all samples and an influence of the multilayered structure on the resistivity behavior. - Highlights: • W/WO{sub 3} multilayers with nanometric periods are produced by gas pulsing. • Multilayers are mainly amorphous and the oxide sub-layers composed of WO{sub 3}. • Crystallized inclusions of β-W and β-W{sub 3}O phases in metallic sub-layers • Metallic-like behavior with low temperature coefficient of resistance.

  8. 40 CFR 721.10168 - Cesium tungsten oxide.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Cesium tungsten oxide. 721.10168... Substances § 721.10168 Cesium tungsten oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cesium tungsten oxide (PMN P-08-275; CAS No....

  9. Seed growth of tungsten diselenide nanotubes from tungsten oxides.

    Science.gov (United States)

    Kim, Hyun; Yun, Seok Joon; Park, Jin Cheol; Park, Min Ho; Park, Ji-Hoon; Kim, Ki Kang; Lee, Young Hee

    2015-05-13

    We report growth of tungsten diselenide (WSe2) nanotubes by chemical vapor deposition with a two-zone furnace. WO3 nanowires were first grown by annealing tungsten thin films under argon ambient. WSe2 nanotubes were then grown at the tips of WO3 nanowires through selenization via two steps: (i) formation of tubular WSe2 structures on the outside of WO3 nanowires, resulting in core (WO3)-shell (WSe2) and (ii) growth of WSe2 nanotubes at the tips of WO3 nanowires. The observed seed growth is markedly different from existing substitutional growth of WSe2 nanotubes, where oxygen atoms are replaced by selenium atoms in WO3 nanowires to form WSe2 nanotubes. Another advantage of our growth is that WSe2 film was grown by simply supplying hydrogen gas, where the native oxides were reduced to thin film instead of forming oxide nanowires. Our findings will contribute to engineer other transition metal dichacogenide growth such as MoS2, WS2, and MoSe2.

  10. Microstructural characterization and field emission properties of tungsten oxide and titanium-oxide-doped tungsten oxide nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Su, Chia-Hsiang [Department of Mechanical Engineering, Southern Taiwan University of Science and Technology, Tainan, Taiwan (China); Su, Cherng-Yuh, E-mail: cysu@ntut.edu.tw [Department of Mechanical Engineering, National Taipei University of Technology, Taipei, Taiwan (China); Lin, Yan-Fu [Department of Mechanical Engineering, National Taipei University of Technology, Taipei, Taiwan (China)

    2015-03-01

    Tungsten oxide and titanium-oxide-doped tungsten oxide nanowires were synthesized by using the DC magnetron sputtering and infrared furnace annealing processes. Scanning election microscopy (SEM) and transmission electron microscopy (TEM) were utilized to evaluate the topography and sizes. X-ray diffraction (XRD), grazing incidence X-ray diffraction (GI-XRD), and high-resolution transmission electron microscopy (HRTEM) were used to analyze the composition and structure. From the results of HRTEM, it was discovered that the prepared nanowires have a monoclinic single-crystal phase of W{sub 18}O{sub 49} with lattice growth along the (010) lattice plane, and the lattice spacing is 0.378 nm, which agrees with XRD and GI-XRD results. The prepared tungsten oxide and titanium-oxide-doped tungsten oxide nanowires have turn-on voltage of 3.06 V/μm and 1.46 V/μm respectively. They also possess superior field enhancement factors of 5103 and 10667 respectively. Their behavior thus follows the Fowler-Nordheim expression for tunneling. - Highlights: • A simple method to prepare tungsten oxide nanowires by annealing tungsten film. • High aspect ratio of the 1D titanium-oxide-doped tungsten oxide nanowires. • High field enhancement factor of titanium-oxide-doped tungsten oxide nanowires.

  11. Activation of tungsten oxide catalyst on SiO sub 2 surface by low-temperature plasma

    Energy Technology Data Exchange (ETDEWEB)

    Blecha, J.; Dudas, J.; Lodes, A.; Derco, J. (Slovak Technical Univ., Bratislava (Czechoslovakia))

    1989-03-01

    The disproportionation of alkenes, in particular propene, promotes an improvement in the balance of crude oil processing and is one of the possibilities of gaining a new raw-material source for petrochemical syntheses. The disproportionation processes comprising conversion of alkenes into the two qualitatively new ones proceed only in the presence of the catalysts. As the catalyst, tungsten oxide which is applicable on the silica gel carrier may be used. It was a practical effort which led the authors to study the plasma interaction with the WO{sub 3}/SiO{sub 3} catalyst to accelerate and achieve the more effective preparation of the catalyst needed for heterogeneous catalysis of propene, and thus to positively influence the catalyst quality. On the basis of investigation carried out on the catalyst's activity, selectivity, and lifetime - in relation to propene disproportionation - it may be stated that: the equilibrium degree of conversion is attainable with lower W/F values (W = mass of catalysts, F = feed rate); the composition of disproportionation products is shifted more to the ethylene formation; the lifetime of the catalyst remains unchanged; and for both dimerization and cracking no active centers are formed.

  12. Silicon and tungsten oxide nanostructures for water splitting

    Science.gov (United States)

    Reyes Gil, Karla R.; Spurgeon, Joshua M.; Lewis, Nathan S.

    2009-08-01

    Inorganic semiconductors are promising materials for driving photoelectrochemical water-splitting reactions. However, there is not a single semiconductor material that can sustain the unassisted splitting of water into H2 and O2. Instead, we are developing a three part cell design where individual catalysts for water reduction and oxidation will be attached to the ends of a membrane. The job of splitting water is therefore divided into separate reduction and oxidation reactions, and each catalyst can be optimized independently for a single reaction. Silicon might be suitable to drive the water reduction. Inexpensive highly ordered Si wire arrays were grown on a single crystal wafer and transferred into a transparent, flexible polymer matrix. In this array, light would be absorbed along the longer axial dimension while the resulting electrons or holes would be collected along the much shorter radial dimension in a massively parallel array resembling carpet fibers on a microscale, hence the term "solar carpet". Tungsten oxide is a good candidate to drive the water oxidation. Self-organized porous tungsten oxide was successfully synthesized on the tungsten foil by anodization. This sponge-like structure absorbs light efficiently due to its high surface area; hence we called it "solar sponge".

  13. Synthesis and electrical characterization of tungsten oxide nanowires

    Institute of Scientific and Technical Information of China (English)

    Huang Rui; Zhu Jing; Yu Rong

    2009-01-01

    Tungsten oxide nanowires of diameters ranging from 7 to 200 nm are prepared on a tungsten rod substrate by using the chemical vapour deposition (CVD) method with vapour-solid (VS) mechanism. Tin powders are used to control oxygen concentration in the furnace, thereby assisting the growth of the tungsten oxide nanowires. The grown tungsten oxide nanowires are determined to be of crystalline W18O49. Ⅰ-Ⅴ curves are measured by an in situ transmission electron microscope (TEM) to investigate the electrical properties of the nanowires. All of the Ⅰ-Ⅴ curves observed are symmetric, which reveals that the tungsten oxide nanowires are semiconducting. Quantitative analyses of the experimental I V curves by using a metal-semiconductor-metal (MSM) model give some intrinsic parameters of the tungsten oxide nanowires, such as the carrier concentration, the carrier mobility and the conductivity.

  14. Space-confined preparation of high surface area tungsten oxide and tungsten nitride inside the pores of mesoporous silica SBA-15

    DEFF Research Database (Denmark)

    Meyer, Simon; Beyer, Hans; Köhler, Klaus

    2015-01-01

    For the direct preparation of high surface area nitride materials, a lack of suitable precursors exists. Indirect preparation by gas phase nitridation (e.g. by ammonia) requires high temperatures and often results in sintering. The present work demonstrates that the space-confined preparation of ...

  15. Nanostructured Tungsten Oxide Composite for High-Performance Gas Sensors

    Directory of Open Access Journals (Sweden)

    Siyuan Feng Chen

    2015-10-01

    Full Text Available We report the results of composite tungsten oxide nanowires-based gas sensors. The morphologic surface, crystallographic structures, and chemical compositions of the obtained nanowires have been investigated using scanning electron microscopy (SEM, X-ray diffraction (XRD, and Raman scattering, respectively. The experimental measurements reveal that each wire consists of crystalline nanoparticles with an average diameter of less than 250 nm. By using the synthesized nanowires, highly sensitive prototypic gas sensors have been designed and fabricated. The dependence of the sensitivity of tungsten oxide nanowires to the methane and hydrogen gases as a function of time has been obtained. Various sensing parameters such as sensitivity, response time, stability, and repeatability were investigated in order to reveal the sensing ability.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-04-15

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

  17. Porous tungsten oxide nanoflakes for highly alcohol sensitive performance.

    Science.gov (United States)

    Xiao, J; Liu, P; Liang, Y; Li, H B; Yang, G W

    2012-11-21

    Porous tungsten oxide (WO(3)) nanoflakes have been synthesized by a simple and green approach in an ambient environment. As a precursor solution a polycrystalline hydrated tungstite (H(2)WO(4)·H(2)O) nanoparticles colloid was first prepared by pulsed-laser ablation of a tungsten target in water. The H(2)WO(4)·H(2)O nanoflakes were produced by 72 h aging treatment at room temperature. Finally, porous WO(3) nanoflakes were synthesized by annealing at 800 °C for 4 h. Considering the large surface-to-volume ratio of porous nanoflakes, a porous WO(3) nanoflake gas sensor was fabricated, which exhibits an excellent sensor response performance to alcohol concentrations in the range of 20 to 600 ppm under low working temperature. This high response was attributed to the highly crystalline and porous flake-like morphology, which leads to effective adsorption and desorption, and provides more active sites for the gas molecules' reaction. These findings showed that the porous tungsten oxide nanoflake has great potential in gas-sensing performance.

  18. Aerosol-assisted chemical vapor deposition of tungsten oxide films and nanorods from oxo tungsten(VI) fluoroalkoxide precursors.

    Science.gov (United States)

    Kim, Hankook; Bonsu, Richard O; O'Donohue, Christopher; Korotkov, Roman Y; McElwee-White, Lisa; Anderson, Timothy J

    2015-02-04

    Aerosol-assisted chemical vapor deposition (AACVD) of WOx was demonstrated using the oxo tungsten(VI) fluoroalkoxide single-source precursors, WO[OCCH3(CF3)2]4 and WO[OC(CH3)2CF3]4. Substoichiometric amorphous tungsten oxide thin films were grown on indium tin oxide (ITO) substrates in nitrogen at low deposition temperature (100-250 °C). At growth temperatures above 300 °C, the W18O49 monoclinic crystalline phase was observed. The surface morphology and roughness, visible light transmittance, electrical conductivity, and work function of the tungsten oxide materials are reported. The solvent and carrier gas minimally affected surface morphology and composition at low deposition temperature; however, material crystallinity varied with solvent choice at higher temperatures. The work function of the tungsten oxide thin films grown between 150 and 250 °C was determined to be in the range 5.0 to 5.7 eV, according to ultraviolet photoelectron spectroscopy (UPS).

  19. Epitaxial growth of tungsten nanoparticles on alumina and spinel surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Suarez, T; Lopez-Esteban, S; Pecharroman, C; Esteban-Cubillo, A; Moya, J S [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), C/ Sor Juana Ines de la Cruz 3, 28049, Cantoblanco, Madrid (Spain); Diaz, L A; Torrecillas, R [Nanomaterials and Nanotechnology Research Center (CINN), Consejo Superior de Investigaciones CientIficas (CSIC), C/ Francisco Pintado Fe 26, 33011, Oviedo, Asturias (Spain); Gremillard, L [Universite de Lyon, INSA-Lyon, MATEIS, UMR CNRS 5510, 20 avenue Albert Einstein, Villeurbanne F-69621 (France)], E-mail: jsmoya@icmm.csic.es

    2008-05-28

    Isolated tungsten nanoparticles ({alpha}-W and {beta}-W phase) were synthesized and epitaxially grown on alumina and spinel particle surfaces with an average tungsten size of {<=}20 nm for a low tungsten content (of {<=}1.5 vol%). Using tungsten (VI) ethoxide alcoholic solutions, tungsten trioxide hydrated precursors were attached to a ceramic grains surface as a nanoparticle coating. High-resolution transmission electron microscopy (HRTEM) micrographs showed epitaxial interfaces between alumina, spinel and metallic tungsten. This epitaxial growth is assumed to be due to the effect of water vapour on the sublimation of ortho-tungstic acid during the reduction process in a hydrogen atmosphere. The planes involved in the epitaxy were found to be (22-bar 0){sub Al2O3} parallel (121){sub W} and (311){sub MgAl2O4} parallel (110){sub W}.

  20. Preparation and catalytic properties of tungsten oxides with different morphologies

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    Bi Yunfei, E-mail: beiyf2003@yahoo.com.cn [Research Institute of Petroleum Processing, SINOPEC, 18 Xue Yuan Road, 100083 Beijing (China); Li Dadong; Nie Hong [Research Institute of Petroleum Processing, SINOPEC, 18 Xue Yuan Road, 100083 Beijing (China)

    2010-09-01

    Tungsten oxides with different morphologies including platelet-like sheets, nanobelts, and nanoparticles have been successfully prepared by changing the ions in the synthetic solution. Transmission electron microscopy, X-ray diffraction, Fourier-transform infrared analysis and N{sub 2} adsorption were employed to reveal the morphological evolution, and results show that the morphological evolution can be attributed to the alteration of coordination environment of tungstenic cations contained in the synthetic solution. Furthermore, these products have been applied into hydrodesulfurization measurement to investigate the relationship between the morphologies of tungsten oxides and their catalytic properties. It is concluded that the catalysts originating from nanobelt-like tungsten oxides have highest catalytic activity and excellent selectivity due to their scrolled character and strong metallic edges.

  1. Tungsten Oxides for Photocatalysis, Electrochemistry, and Phototherapy.

    Science.gov (United States)

    Huang, Zhen-Feng; Song, Jiajia; Pan, Lun; Zhang, Xiangwen; Wang, Li; Zou, Ji-Jun

    2015-09-23

    The conversion, storage, and utilization of renewable energy have all become more important than ever before as a response to ever-growing energy and environment concerns. The performance of energy-related technologies strongly relies on the structure and property of the material used. The earth-abundant family of tungsten oxides (WOx ≤3 ) receives considerable attention in photocatalysis, electrochemistry, and phototherapy due to their highly tunable structures and unique physicochemical properties. Great breakthroughs have been made in enhancing the optical absorption, charge separation, redox capability, and electrical conductivity of WOx ≤3 through control of the composition, crystal structure, morphology, and construction of composite structures with other materials, which significantly promotes the efficiency of processes and devices based on this material. Herein, the properties and synthesis of WOx ≤3 family are reviewed, and then their energy-related applications are highlighted, including solar-light-driven water splitting, CO2 reduction, and pollutant removal, electrochromism, supercapacitors, lithium batteries, solar and fuel cells, non-volatile memory devices, gas sensors, and cancer therapy, from the aspect of function-oriented structure design and control.

  2. Catalytic conversions of alcohols--7. Alkene selectivity of tungsten oxides

    Energy Technology Data Exchange (ETDEWEB)

    Davis, B.H.

    1978-11-01

    The reactions of C/sub 5/-C/sub 8/ alcohols, including 2- and 3-pentanol, trans-2-methylcyclohexanol, and 2-octanol, with and without alkene additions to the feed, were studied at 1 atm over hydrogen-treated and oxygen-treated tungsten oxides. The oxygen-treated catalysts yielded high cis-2/trans-2-alkene ratios from 2-alcohols; the hydrogen-pretreated catalysts yielded larger trans-2-alkene amounts from 2-alcohols. With oxygen-treated catalysts, the amount of trans-2-alkene increased slightly with increasing temperature, and the 1-alkene yield increased slightly with increasing chain length of the 2-alcohol. No cis-trans isomerization was observed with 2-methylcyclohexanol. Surface reactions and intermediates are briefly discussed.

  3. Material and gas-sensing properties of tungsten oxide nanorod thin-films.

    Science.gov (United States)

    Kim, Yong Shin; Lee, Kwangyeol

    2009-04-01

    Tungsten oxide thin-films were deposited simply by drop-casting a solution containing single-crystalline and monodispersed W18O49 nanorods prepared by a large-scale colloidal synthesis route. They were verified to be highly porous, nonstoichiometric, and monoclinic crystal structure only with little carbon impurities. These material properties heavily reflect relevant nanostructural characteristics of the nanorods acting as a basic building block. It could be comprehended by the observed structure of randomly arranged tungsten oxide agglomerates formed by favorable parallel alignment of individual nanorod units. Tungsten oxide nanorod sensors exhibit sensitive detection capability even at room temperature to various reducing volatile organic compounds (VOCs). This anomalous performance seems to result from unique nanostructural features of the thin-films, allowing a high surface-to-volume ratio and a considerable amount of active sensing sites due to the highly anisotropic, nonstoichiometric structure of W18O49 nanorods.

  4. Toxicologic evaluation of tungsten: 28-day inhalation study of tungsten blue oxide in rats.

    Science.gov (United States)

    Rajendran, Narayanan; Hu, Shu-Chieh; Sullivan, Dennis; Muzzio, Miguel; Detrisac, Carol J; Venezia, Carmen

    2012-12-01

    The toxicity and toxicokinetics of tungsten blue oxide (TBO) were examined. TBO is an intermediate in the production of tungsten powder, and has shown the potential to cause cellular damage in in vitro studies. However, in vivo evidence seems to indicate a lack of adverse effects. The present study was undertaken to address the dearth of longer-term inhalation toxicity studies of tungsten oxides by investigating the biological responses induced by TBO when administered via nose-only inhalation to rats at levels of 0.08, 0.325, and 0.65 mg TBO/L of air for 6 h/day for 28 consecutive days, followed by a 14-day recovery period. Inhaled TBO was absorbed systemically and blood levels of tungsten increased as inhaled concentration increased. Among the tissues analyzed for tungsten levels, lung, femur and kidney showed increased levels, with lung at least an order of magnitude greater than kidney or femur. By exposure day 14, tungsten concentration in tissues had reached steady-state. Increased lung weight was noted for both terminal and recovery animals and was attributed to deposition of TBO in the lungs, inducing a macrophage influx. Microscopic evaluation of tissues revealed a dose-related increase in alveolar pigmented macrophages, alveolar foreign material and individual alveolar foamy macrophages in lung. After a recovery period there was a slight reduction in the incidence and severity of histopathological findings. Based on the absence of other adverse effects, the increased lung weights and the microscopic findings were interpreted as nonadverse response to exposure and were not considered a specific reaction to TBO.

  5. Surface tungsten reduction during thermal decomposition of ammonium paratungstate tetrahydrate in oxidising atmosphere: A paradox?

    Energy Technology Data Exchange (ETDEWEB)

    Fait, Martin J.G., E-mail: martin.fait@catalysis.de [Leibniz-Institut für Katalyse e.V., Albert-Einstein-Strasse 29a, 18059 Rostock (Germany); Radnik, Jörg [Leibniz-Institut für Katalyse e.V., Albert-Einstein-Strasse 29a, 18059 Rostock (Germany); Lunk, Hans-Joachim [2858 Lake RD, Towanda, PA 18848 (United States)

    2016-06-10

    Highlights: • Detection of reduced tungsten ions at the solid’s surface in oxidising atmosphere. • Detection of gaseous ammonia liberated as oxidising agent. • Detection of ammonia’s oxidation products. • Quantification of the ammonia/tungsten redox process. - Abstract: The interaction of ammonia, liberated during thermal decomposition of ammonium paratungstate tetrahydrate in oxidising atmosphere, with tungsten has been studied employing a conventional microbalance combined with MS (Setaram’s instrument Sensys). Applying XPS a partial reduction of tungsten at the surface with the minimal tungsten oxidation number of +5.3 for a sample generated at 293 °C was detected. The balancing oxidation of ammonia to nitrogen/nitrogen oxides has been proven by MS. An amount of 0.049 mol e{sup −} per mol W was transferred which resulted in an ammonia conversion degree from 2.1 mol% (NO{sub 2} formation) to 3.0 mol% (N{sub 2} formation).

  6. Hexagonal tungsten oxide nanoflowers as enzymatic mimetics and electrocatalysts

    Science.gov (United States)

    Park, Chan Yeong; Seo, Ji Min; Jo, Hongil; Park, Juhyun; Ok, Kang Min; Park, Tae Jung

    2017-01-01

    Tungsten oxide (WOx) has been widely studied for versatile applications based on its photocatalytic, intrinsic catalytic, and electrocatalytic properties. Among the several nanostructures, we focused on the flower-like structures to increase the catalytic efficiency on the interface with both increased substrate interaction capacities due to their large surface area and efficient electron transportation. Therefore, improved WOx nanoflowers (WONFs) with large surface areas were developed through a simple hydrothermal method using sodium tungstate and hydrogen chloride solution at low temperature, without any additional surfactant, capping agent, or reducing agent. Structural determination and electrochemical analyses revealed that the WONFs have hexagonal Na0.17WO3.085·0.17H2O structure and exhibit peroxidase-like activity, turning from colorless to blue by catalyzing the oxidation of a peroxidase substrate, such as 3,3′,5,5′-tetramethylbenzidine, in the presence of H2O2. Additionally, a WONF-modified glassy carbon electrode was adopted to monitor the electrocatalytic reduction of H2O2. To verify the catalytic efficiency enhancement by the unique shape and structure of the WONFs, they were compared with calcinated WONFs, cesium WOx nanoparticles, and other peroxidase-like nanomaterials. The results indicated that the WONFs showed a low Michaelis-Menten constant (km), high maximal reaction velocity (vmax), and large surface area. PMID:28128306

  7. Hexagonal tungsten oxide nanoflowers as enzymatic mimetics and electrocatalysts

    Science.gov (United States)

    Park, Chan Yeong; Seo, Ji Min; Jo, Hongil; Park, Juhyun; Ok, Kang Min; Park, Tae Jung

    2017-01-01

    Tungsten oxide (WOx) has been widely studied for versatile applications based on its photocatalytic, intrinsic catalytic, and electrocatalytic properties. Among the several nanostructures, we focused on the flower-like structures to increase the catalytic efficiency on the interface with both increased substrate interaction capacities due to their large surface area and efficient electron transportation. Therefore, improved WOx nanoflowers (WONFs) with large surface areas were developed through a simple hydrothermal method using sodium tungstate and hydrogen chloride solution at low temperature, without any additional surfactant, capping agent, or reducing agent. Structural determination and electrochemical analyses revealed that the WONFs have hexagonal Na0.17WO3.085·0.17H2O structure and exhibit peroxidase-like activity, turning from colorless to blue by catalyzing the oxidation of a peroxidase substrate, such as 3,3‧,5,5‧-tetramethylbenzidine, in the presence of H2O2. Additionally, a WONF-modified glassy carbon electrode was adopted to monitor the electrocatalytic reduction of H2O2. To verify the catalytic efficiency enhancement by the unique shape and structure of the WONFs, they were compared with calcinated WONFs, cesium WOx nanoparticles, and other peroxidase-like nanomaterials. The results indicated that the WONFs showed a low Michaelis-Menten constant (km), high maximal reaction velocity (vmax), and large surface area.

  8. Engineered Surface Properties of Porous Tungsten from Cryogenic Machining

    Science.gov (United States)

    Schoop, Julius Malte

    Porous tungsten is used to manufacture dispenser cathodes due to it refractory properties. Surface porosity is critical to functional performance of dispenser cathodes because it allows for an impregnated ceramic compound to migrate to the emitting surface, lowering its work function. Likewise, surface roughness is important because it is necessary to ensure uniform wetting of the molten impregnate during high temperature service. Current industry practice to achieve surface roughness and surface porosity requirements involves the use of a plastic infiltrant during machining. After machining, the infiltrant is baked and the cathode pellet is impregnated. In this context, cryogenic machining is investigated as a substitutionary process for the current plastic infiltration process. Along with significant reductions in cycle time and resource use, surface quality of cryogenically machined un-infiltrated (as-sintered) porous tungsten has been shown to significantly outperform dry machining. The present study is focused on examining the relationship between machining parameters and cooling condition on the as-machined surface integrity of porous tungsten. The effects of cryogenic pre-cooling, rake angle, cutting speed, depth of cut and feed are all taken into consideration with respect to machining-induced surface morphology. Cermet and Polycrystalline diamond (PCD) cutting tools are used to develop high performance cryogenic machining of porous tungsten. Dry and pre-heated machining were investigated as a means to allow for ductile mode machining, yet severe tool-wear and undesirable smearing limited the feasibility of these approaches. By using modified PCD cutting tools, high speed machining of porous tungsten at cutting speeds up to 400 m/min is achieved for the first time. Beyond a critical speed, brittle fracture and built-up edge are eliminated as the result of a brittle to ductile transition. A model of critical chip thickness ( hc ) effects based on cutting

  9. Hydrofluoric–nitric–sulphuric-acid surface treatment of tungsten for carbon fibre-reinforced composite hybrids in space applications

    Energy Technology Data Exchange (ETDEWEB)

    Kanerva, M., E-mail: Mikko.Kanerva@aalto.fi [Aalto University, School of Engineering, Department of Applied Mechanics, P.O.B. 14300, FI-00076 Aalto (Finland); Johansson, L.-S.; Campbell, J.M. [Aalto University, School of Chemical Technology, Department of Forest Products Technology, P.O.B. 16300, FI-00076 Aalto (Finland); Revitzer, H. [Aalto University, School of Chemical Technology, Department of Chemistry, P.O.B. 16300, FI-00076 Aalto (Finland); Sarlin, E. [Tampere University of Technology, Department of Materials Science, P.O.B. 589, FI-33101 Tampere (Finland); Brander, T.; Saarela, O. [Aalto University, School of Engineering, Department of Applied Mechanics, P.O.B. 14300, FI-00076 Aalto (Finland)

    2015-02-15

    Highlights: • XPS and AFM analysis of the effect of hydrofluoric–nitric–sulphuric-acid on tungsten. • Dreiling's model established 54.4% thinning of WO{sub 3} due to 67 s treatment. • Strain energy release rate increased ≈8.4 J/m{sup 2} at the interface. • Failure loci analysis expressed the oxide and carbon fibre surfaces as weak points. - Abstract: Hybrid material systems, such as combinations of tungsten foils and carbon fibre-reinforced plastic (CFRP), are replacing metal alloy concepts in spacecraft enclosures. However, a good adhesion between the tungsten oxide scale and the epoxy resin used is required. Here, the effects of a hydrofluoric–nitric–sulphuric-acid (HFNS) treatment on tungsten oxides and subsequent adhesion to CFRP are analysed using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and fracture testing. The work shows that HFNS treatment results in decreased oxygen content, over 50% thinner tungsten trioxide (WO{sub 3}) layer and increased nano-roughness on thin tungsten foils. Fracture testing established a 39% increase in the average critical strain for tungsten–CFRP specimens after HFNS treatment was carried out on tungsten. The effect of the oxide scale modification regarding the critical strain energy release rate was ΔG{sub c}≈ 8.4 J/m{sup 2}.

  10. Effects of laser ablation on cemented tungsten carbide surface quality

    Energy Technology Data Exchange (ETDEWEB)

    Tan, J.L.; Butler, D.L.; Sim, L.M.; Jarfors, A.E.W. [Singapore Institute of Manufacturing Technology, Singapore (Singapore)

    2010-11-15

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable. (orig.)

  11. Effects of laser ablation on cemented tungsten carbide surface quality

    Science.gov (United States)

    Tan, J. L.; Butler, D. L.; Sim, L. M.; Jarfors, A. E. W.

    2010-11-01

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable.

  12. Metallic Tungsten Nanostructures and Highly Nanostructured Thin Films by Deposition of Tungsten Oxide and Subsequent Reduction in a Single Hot-Wire CVD Process

    NARCIS (Netherlands)

    Harks, P.P.R.M.L.; Houweling, Z.S.; de Jong, M.M.; Kuang, Y; Geus, J.W.; Schropp, R.E.I.

    2012-01-01

    The synthesis of metallic tungsten nanostructures and highly nanostructured thin films is presented. Crystalline tungsten oxide nanostructures are deposited on glassy carbon substrates kept at 700 100 8C by oxidizing resistively heated tungsten filaments in an air flow under subatmospheric pressures

  13. Electrochromic behavior in CVD grown tungsten oxide films

    Science.gov (United States)

    Gogova, D.; Iossifova, A.; Ivanova, T.; Dimitrova, Zl; Gesheva, K.

    1999-03-01

    Solid state electrochemical devices (ECDs) for smart windows, large area displays and automobile rearview mirrors are of considerable technological and commercial interest. In this paper, we studied the electrochromic properties of amorphous and polycrystalline CVD carbonyl tungsten oxide films and the possibility for sol-gel thin TiO 2 film to play the role of passive electrode in an electrochromic window with solid polymer electrolyte.

  14. Electrochromic behavior in CVD grown tungsten oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Gogova, D.; Iossifova, A.; Ivanova, T.; Gesheva, K.; Dimitrova, Z. [Central Laboratory for Solar Energy and New Energy Sources at Bulgarian Academy of Science, 72 Tzarigradsko shossee Blvd., Sofia (Bulgaria)

    1999-03-15

    Solid state electrochemical devices (ECDs) for smart windows, large area displays and automobile rearview mirrors are of considerable technological and commercial interest. In this paper, we studied the electrochromic properties of amorphous and polycrystalline CVD carbonyl tungsten oxide films and the possibility for sol-gel thinTiO{sub 2} film to play the role of passive electrode in an electrochromic window with solid polymer electrolyte

  15. Helium effects on tungsten surface morphology and deuterium retention

    NARCIS (Netherlands)

    Ueda, Y.; H. Y. Peng,; H. T. Lee,; N. Ohno,; S. Kajita,; Yoshida, N.; Doerner, R.; De Temmerman, G.; V. Alimov,; G. Wright,

    2013-01-01

    Recent experimental results on tungsten surface morphology, especially nano-structure (fuzz), induced by helium plasma exposure at temperatures between 1000 K and 2000 K are reviewed. This structure was firstly reported in 2006. In this review, most of experimental results reported

  16. pH-controllable synthesis of unique nanostructured tungsten oxide aerogel and its sensitive glucose biosensor.

    Science.gov (United States)

    Sun, Qiang-Qiang; Xu, Maowen; Bao, Shu-Juan; Li, Chang Ming

    2015-03-20

    This work presents a controllable synthesis of nanowire-networked tungsten oxide aerogels, which was performed by varying the pH in a polyethyleneimine (PEI)-assisted hydrothermal process. An enzyme-tungsten oxide aerogel co-modified electrode shows high activity and selectivity toward glucose oxidation, thus holding great promise for applications in bioelectronics.

  17. Helium segregation on surfaces of plasma-exposed tungsten.

    Science.gov (United States)

    Maroudas, Dimitrios; Blondel, Sophie; Hu, Lin; Hammond, Karl D; Wirth, Brian D

    2016-02-17

    We report a hierarchical multi-scale modeling study of implanted helium segregation on surfaces of tungsten, considered as a plasma facing component in nuclear fusion reactors. We employ a hierarchy of atomic-scale simulations based on a reliable interatomic interaction potential, including molecular-statics simulations to understand the origin of helium surface segregation, targeted molecular-dynamics (MD) simulations of near-surface cluster reactions, and large-scale MD simulations of implanted helium evolution in plasma-exposed tungsten. We find that small, mobile He n (1⩽  n  ⩽  7) clusters in the near-surface region are attracted to the surface due to an elastic interaction force that provides the thermodynamic driving force for surface segregation. This elastic interaction force induces drift fluxes of these mobile He n clusters, which increase substantially as the migrating clusters approach the surface, facilitating helium segregation on the surface. Moreover, the clusters' drift toward the surface enables cluster reactions, most importantly trap mutation, in the near-surface region at rates much higher than in the bulk material. These near-surface cluster dynamics have significant effects on the surface morphology, near-surface defect structures, and the amount of helium retained in the material upon plasma exposure. We integrate the findings of such atomic-scale simulations into a properly parameterized and validated spatially dependent, continuum-scale reaction-diffusion cluster dynamics model, capable of predicting implanted helium evolution, surface segregation, and its near-surface effects in tungsten. This cluster-dynamics model sets the stage for development of fully atomistically informed coarse-grained models for computationally efficient simulation predictions of helium surface segregation, as well as helium retention and surface morphological evolution, toward optimal design of plasma facing components.

  18. Blistering on tungsten surface exposed to high flux deuterium plasma

    NARCIS (Netherlands)

    Xu, H.Y.; Liu, W.; Luo, G. N.; Yuan, Y.; Jia, Y. Z.; Fu, B. Q.; De Temmerman, G.

    2016-01-01

    The blistering behaviour of tungsten surfaces exposed to very high fluxes (1–2 × 1024/m2/s) of low energy (38 eV) deuterium plasmas was investigated as a function of ion fluence (0.2–7 × 1026 D/m2) and surface temperature (423–873 K). Blisters were observed under all conditions, especially up to

  19. Direct Growth of Crystalline Tungsten Oxide Nanorod Arrays by a Hydrothermal Process and Their Electrochromic Properties

    Science.gov (United States)

    Lu, Chih-Hao; Hon, Min Hsiung; Leu, Ing-Chi

    2016-12-01

    Transparent crystalline tungsten oxide nanorod arrays for use as an electrochromic layer have been directly prepared on fluorine-doped tin oxide-coated glass via a facile tungsten film-assisted hydrothermal process using aqueous tungsten hexachloride solution. X-ray diffraction analysis and field-emission scanning electron microscopy were used to characterize the phase and morphology of the grown nanostructures. Arrays of tungsten oxide nanorods with diameter of ˜22 nm and length of ˜240 nm were obtained at 200°C after 8 h of hydrothermal reaction. We propose a growth mechanism for the deposition of the monoclinic tungsten oxide phase in the hydrothermal environment. The tungsten film was first oxidized to tungsten oxide to provide seed sites for crystal growth and address the poor connection between the growing tungsten oxide and substrate. Aligned tungsten oxide nanorod arrays can be grown by a W thin film-assisted heterogeneous nucleation process with NaCl as a structure-directing agent. The fabricated electrochromic device demonstrated optical modulation (coloration/bleaching) at 632.8 nm of ˜41.2% after applying a low voltage of 0.1 V for 10 s, indicating the potential of such nanorod array films for use in energy-saving smart windows.

  20. Direct Growth of Crystalline Tungsten Oxide Nanorod Arrays by a Hydrothermal Process and Their Electrochromic Properties

    Science.gov (United States)

    Lu, Chih-Hao; Hon, Min Hsiung; Leu, Ing-Chi

    2017-04-01

    Transparent crystalline tungsten oxide nanorod arrays for use as an electrochromic layer have been directly prepared on fluorine-doped tin oxide-coated glass via a facile tungsten film-assisted hydrothermal process using aqueous tungsten hexachloride solution. X-ray diffraction analysis and field-emission scanning electron microscopy were used to characterize the phase and morphology of the grown nanostructures. Arrays of tungsten oxide nanorods with diameter of ˜22 nm and length of ˜240 nm were obtained at 200°C after 8 h of hydrothermal reaction. We propose a growth mechanism for the deposition of the monoclinic tungsten oxide phase in the hydrothermal environment. The tungsten film was first oxidized to tungsten oxide to provide seed sites for crystal growth and address the poor connection between the growing tungsten oxide and substrate. Aligned tungsten oxide nanorod arrays can be grown by a W thin film-assisted heterogeneous nucleation process with NaCl as a structure-directing agent. The fabricated electrochromic device demonstrated optical modulation (coloration/bleaching) at 632.8 nm of ˜41.2% after applying a low voltage of 0.1 V for 10 s, indicating the potential of such nanorod array films for use in energy-saving smart windows.

  1. Investigations on bactericidal properties of molybdenum-tungsten oxides combinatorial thin film material libraries.

    Science.gov (United States)

    Mardare, Cezarina Cela; Hassel, Achim Walter

    2014-11-10

    A combinatorial thin film material library from the molybdenum-tungsten refractory metals oxides system was prepared by thermal coevaporation, and its structural and morphological properties were investigated after a multiple step heat treatment. A mixture of crystalline and amorphous oxides and suboxides was obtained, as well as surface structuring caused by the enrichment of molybdenum oxides in large grains. It was found that the oxide phases and the surface morphology change as a function of the compositional gradient. Tests of the library antimicrobial activity against E. coli were performed and the antimicrobial activity was proven in some defined compositional ranges. A mechanism for explaining the observed activity is proposed, involving a collective contribution from (i) increased local acidity due to the enrichment in large grains of molybdenum oxides with different stoichiometry and (ii) the release of free radicals from the W18O49 phase under visible light.

  2. Solid state tungsten oxide hydrate/tin oxide hydrate electrochromic device prepared by electrochemical reactions

    Science.gov (United States)

    Nishiyama, Kentaro; Matsuo, Ryo; Sasano, Junji; Yokoyama, Seiji; Izaki, Masanobu

    2017-03-01

    The solid state electrochromic device composed of tungsten oxide hydrate (WO3(H2O)0.33) and tin oxide hydrate (Sn(O,OH)) has been constructed by anodic deposition of WO3(H2O)0.33 and Sn(O,OH) layers and showed the color change from clear to blue by applying voltage through an Au electrode.

  3. Laminated electrochromic windows based on nickel oxide, tungsten oxide, and gel electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Passerini, S.; Scrosati, B.; Hermann, V. (Univ. di Roma (Italy). Dipt. di Chimica); Holmblad, C.; Bartlett, T. (Medtronic Promeon, Minneapolis, MN (United States))

    1994-04-01

    The characteristic and the performance of solid-state, laminated electrochromic windows using tungsten oxide as the principal electrochromic electrode and nonstoichiometric nickel oxide as the counterelectrode separated by selected gel electrolytes, are presented and discussed. These advanced-design, electro-optical devices show a very promising behavior in terms of light modulation and cyclability.

  4. Photo-Oxidation of Water Using Nanocrystalline Tungsten Oxide under Visible Light

    Directory of Open Access Journals (Sweden)

    J. W. J. Hamilton

    2008-01-01

    Full Text Available The photoelectrolysis of water to yield hydrogen and oxygen using visible light has enormous potential for solar energy harvesting if suitable photoelectrode materials can be developed. Few of the materials with a band gap suitable for visible light activation have the necessary band-edge potentials or photochemical stability to be suitable candidates. Tungsten oxide (bg 2.8 eV is a good candidate with absorption up to ≈440 nm and known photochemical stability. Thin films of tungsten oxide were prepared using an electrolytic route from peroxo-tungsten precursors. The tungsten oxide thin films were characterised by FESEM, Auger electron spectroscopy, and photoelectrochemical methods. The magnitude of the photocurrent response of the films under solar simulated irradiation showed a dependence on precursor used in the film preparation, with a comparatively lower response for samples containing impurities. The photocurrent response spectrum of the tungsten oxide films was more favourable than that recorded for titanium dioxide (TiO2 thin films. The WO3 photocurrent response was of equivalent magnitude but shifted into the visible region of the spectrum, as compared to that of the TiO2.

  5. Electrochromic study on amorphous tungsten oxide films by sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chuan, E-mail: cli10@yahoo.com [Department of Biomedical Engineering, National Yang Ming University, Taipei 11221, Taiwan (China); Department of Mechanical Engineering, National Central University, Jhongli, Taoyuan 32001, Taiwan (China); Hsieh, J.H. [Department of Materials Engineering, Ming Chi University of Technology, Taishan, Taipei 24301, Taiwan (China); Hung, Ming-Tsung [Department of Mechanical Engineering, National Central University, Jhongli, Taoyuan 32001, Taiwan (China); Huang, B.Q. [Department of Biomedical Engineering, National Yang Ming University, Taipei 11221, Taiwan (China)

    2015-07-31

    Tungsten oxide films under different oxygen flow rates are deposited by DC sputtering. The voltage change at target and analyses for the deposited films by X-ray diffraction, scanning electronic microscope, X-ray photoelectron spectroscopy and ultraviolet–visible-near infrared spectroscopy consistently indicate that low oxygen flow rate (5 sccm) only creates metal-rich tungsten oxide films, while higher oxygen flow rate (10–20 sccm) assures the deposition of amorphous WO{sub 3} films. To explore the electrochromic function of deposited WO{sub 3} films, we use electrochemical tests to perform the insertion of lithium ions and electrons into films. The WO{sub 3} films switch between color and bleach states effectively by both potentiostat and cyclic voltammetry. Quantitative evaluation on electrochemical tests indicates that WO{sub 3} film with composition close to its stoichiometry is an optimal choice for electrochromic function. - Highlights: • Amorphous WO{sub 3} films are deposited by DC sputtering under different O{sub 2} flow rates. • Higher oxygen flow rate (> 10 sccm) assures the deposition of amorphous WO{sub 3} films. • Both potentiostat and cyclic voltammetry make WO{sub 3} films switch its color. • An optimal electrochromic WO{sub 3} is to make films close to its stoichiometry.

  6. Recycling high density tungsten alloy powder by oxidization-reduction process

    Institute of Scientific and Technical Information of China (English)

    张兆森; 陈立宝; 贺跃辉; 黄伯云

    2002-01-01

    The processes of directly recycling high density tungsten alloy by oxidation-reduction technique were investigated. The particle size of recycled powder is fine, and the shape of powder particle is regular when the final reduction temperature is 850℃, in which the average size of the tungsten alloy particles reduced is about 1.5μm. The average size of the alloy particles increase to 6μm and 9μm when increasing the reduction temperature to 900℃ and 950℃, respectively. However, if the reduction temperature is higher than 900℃, the surface feature of powder is complicated. Increasing reduction temperature from 900℃ to 950℃, the content of oxygen of recycled powder decreases from 0.2314% to 0.1700%, and powder particles grow slightly. It has been also found that the chemical composition of the recycled alloy powder is the same as the initial powder.

  7. Structural, electrochemical and optical comparisons of tungsten oxide coatings derived from tungsten powder-based sols

    Energy Technology Data Exchange (ETDEWEB)

    Isik, Dilek, E-mail: e145342@metu.edu.t [Department of Metallurgical and Materials Engineering, METU, 06531 Ankara (Turkey); Ak, Metin, E-mail: metinak@pamukkale.edu.t [Department of Chemistry, Pamukkale University, 20017 Denizli (Turkey); Durucan, Caner, E-mail: cdurucan@metu.edu.t [Department of Metallurgical and Materials Engineering, METU, 06531 Ankara (Turkey)

    2009-11-02

    Tungsten trioxide (WO{sub 3}) electrochromic coatings have been formed on indium tin oxide-coated glass substrates by aqueous routes. Coating sols are obtained by dissolving tungsten powder in acetylated (APTA) or plain peroxotungstic acid (PTA) solutions. The structural evolution and electrochromic performance of the coatings as a function of calcination temperature (250 {sup o}C and 400 {sup o}C) have been reported. Differential scanning calorimetry and X-ray diffraction have shown that amorphous WO{sub 3} films are formed after calcination at 250 {sup o}C for both processing routes; however, the coatings that calcined at 400 {sup o}C were crystalline in both cases. The calcination temperature-dependent crystallinity of the coatings results in differences in optical properties of the coatings. Higher coloration efficiencies can be achieved with amorphous coatings than could be seen in the crystalline coatings. The transmittance values (at 800 nm) in the colored state are 35% and 56% for 250 {sup o}C and 400 {sup o}C-calcined coatings, respectively. The electrochemical properties are more significantly influenced by the method of sol preparation. The ion storage capacities designating the electrochemical properties are found in the range of 1.62-2.74 x 10{sup -3} (mC cm{sup -2}) for APTA coatings; and 0.35-1.62 x 10{sup -3} (mC cm{sup -2}) for PTA coatings. As a result, a correlation between the microstructure and the electrochromic performance has been established.

  8. The hydrothermal synthesis of tetragonal tungsten bronze-based catalysts for the selective oxidation of hydrocarbons.

    Science.gov (United States)

    Botella, Pablo; Solsona, Benjamín; García-González, Ester; González-Calbet, José M; López Nieto, José M

    2007-12-21

    Mixed metal oxides with tetragonal tungsten bronze (TTB) structure, showing high activity and selectivity for the gas phase partial oxidation of olefins, have been prepared by hydrothermal synthesis from Keggin-type heteropolyacids.

  9. Indication of worn WC/C surface locations of a dry-running twin-screw rotor by the oxygen incorporation in tungsten-related Raman modes

    Science.gov (United States)

    Debus, J.; Schindler, J. J.; Waldkirch, P.; Goeke, S.; Brümmer, A.; Biermann, D.; Bayer, M.

    2016-10-01

    By comparing the worn and untouched locations of a tungsten-carbide/carbon surface of a dry-running twin-screw rotor, we demonstrate that tungsten-oxide Raman modes become observable only at worn locations and the integral intensity of the Raman line at 680 cm-1, which is related to the incipient oxidation of the tungsten-carbide stretching mode, is enhanced. Its frequency and width moreover change significantly, thus indicating the mechanical distortion of the bonding that has been occurred during the wearing process. The shape of the tungsten-oxide Raman lines, resembling the Voigt function, hints at a surface morphology that is a characteristic for an amorphous solid environment. Our Raman scattering results may be exploited to characterize the degree of wear of coated surfaces and to identify signatures of a tribological layer.

  10. Synthesis, structural and mechanical characterization of sputtered tungsten oxide coatings

    Energy Technology Data Exchange (ETDEWEB)

    Parreira, N.M.G. [ICEMS-Grupo de Materiais e Engenharia de Superficies, Faculdade de Ciencias e Tecnologia da Universidade de Coimbra-Polo II, 3030-201 Coimbra (Portugal)]. E-mail: nuno.parreira@dem.uc.pt; Carvalho, N.J.M. [ICEMS-Grupo de Materiais e Engenharia de Superficies, Faculdade de Ciencias e Tecnologia da Universidade de Coimbra-Polo II, 3030-201 Coimbra (Portugal)]. E-mail: nuno.carvalho@dem.uc.pt; Cavaleiro, A. [ICEMS-Grupo de Materiais e Engenharia de Superficies, Faculdade de Ciencias e Tecnologia da Universidade de Coimbra-Polo II, 3030-201 Coimbra (Portugal)]. E-mail: albano.cavaleiro@dem.uc.pt

    2006-07-03

    Tungsten oxide coatings were deposited without substrate bias by DC reactive magnetron sputtering of a tungsten target using oxygen as reactive gas. By tuning the partial pressure of oxygen (p {sub O{sub 2}}/p {sub Ar}) between 0 and 4, the oxygen content of the films was changed from 0 to 75 at.%. The structure of the films (investigated by X-ray diffraction) depends on their oxygen content. For low oxygen contents, the {alpha}-W and {beta}-W{sub 3}O phases were observed (< 30 at.%), and with the increase of oxygen content (30 at.% < O < 67 at.%) the structure became amorphous. A transition region was obtained for oxygen content between 67 at.% and 75 at.%, and when O > 75 at.%, a nanocrystalline (WO{sub 3}) structure was reached. The hardness and Young's modulus were evaluated by depth sensing indentation. The decrease in hardness followed the four different ranges of chemical compositions accordingly, from {approx} 23 GPa for pure W down to {approx} 7 GPa for WO{sub 3} films. A similar behaviour was observed for the Young's modulus, which ranged from 450 GPa to 150 GPa. The cohesion/adhesion of the films were investigated using a scratch-test apparatus. These coatings displayed a low adhesion (critical load, L {sub c} < 15 N) to the steel substrate because the depositions were carried out intentionally without an adhesion interfacial layer.

  11. Microwave synthesis of ultrafine and nanosized powders of tungsten oxide and carbide

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaenko, Irina; Kedin, Nikolay; Shveikin, Gennadii; Polyakov, Evgenii [Russian Academy of Sciences, Ekaterinburg (Russian Federation). Inst. of Solid State Chemistry

    2014-03-15

    A new method of synthesis of nanosized and ultrafine tungsten oxide and carbide powders is offered, which combines carbon carrier supported classical liquid-phase precipitation and low-temperature microwave treatment. The full range of intermediate substances obtained during thermolysis, reduction and carburization of precursors to final products is presented. It is shown that cooling of ammonium tungstate solution to 4 C and the use of carbon carrier at the precipitation stage can increase the specific surface area from 20 to 100 m{sup 2} g{sup -1}. (orig.)

  12. Mesoporous carbon nitride-tungsten oxide composites for enhanced photocatalytic hydrogen evolution.

    Science.gov (United States)

    Kailasam, Kamalakannan; Fischer, Anna; Zhang, Guigang; Zhang, Jinshui; Schwarze, Michael; Schröder, Marc; Wang, Xinchen; Schomäcker, Reinhard; Thomas, Arne

    2015-04-24

    Composites of mesoporous polymeric carbon nitride and tungsten(VI) oxide show very high photocatalytic activity for the evolution of hydrogen from water under visible light and in the presence of sacrificial electron donors. Already addition of very small amounts of WO3 yields up to a twofold increase in the efficiency when compared to bulk carbon nitrides and their composites and more notably even to the best reported mesoporous carbon nitride-based photocatalytic materials. The higher activity can be attributed to the high surface area and synergetic effect of the carbon nitrides and the WO3 resulting in improved charge separation through a photocatalytic solid-state Z-scheme mechanism.

  13. Nuclear thermionic converter. [tungsten-thorium oxide rods

    Science.gov (United States)

    Phillips, W. M.; Mondt, J. F. (Inventor)

    1977-01-01

    Efficient nuclear reactor thermionic converter units are described which can be constructed at low cost and assembled in a reactor which requires a minimum of fuel. Each converter unit utilizes an emitter rod with a fluted exterior, several fuel passages located in the bulges that are formed in the rod between the flutes, and a collector receiving passage formed through the center of the rod. An array of rods is closely packed in an interfitting arrangement, with the bulges of the rods received in the recesses formed between the bulges of other rods, thereby closely packing the nuclear fuel. The rods are constructed of a mixture of tungsten and thorium oxide to provide high power output, high efficiency, high strength, and good machinability.

  14. Growth Process Conditions of Tungsten Oxide Thin Films Using Hot-Wire Chemical Vapor Deposition

    NARCIS (Netherlands)

    Houweling, Z.S.; Geus, J.W.; de Jong, M.; Harks, P.P.R.M.L.; van der Werf, C.H.M.; Schropp, R.E.I.

    2011-01-01

    We report the growth conditions of nanostructured tungsten oxide (WO3−x) thin films using hot-wire chemical vapor deposition (HWCVD). Two tungsten filaments were resistively heated to various temperatures and exposed to an air flow at various subatmospheric pressures. The oxygen partial pressure was

  15. Femtosecond laser fabrication of microspike-arrays on tungsten surface

    Energy Technology Data Exchange (ETDEWEB)

    Sano, Tomokazu [Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 (Japan)]. E-mail: sano@mapse.eng.osaka-u.ac.jp; Yanai, Masato [Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 (Japan); Ohmura, Etsuji [Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 (Japan); Nomura, Yasumitsu [Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 (Japan); Miyamoto, Isamu [Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 (Japan); Hirose, Akio [Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 (Japan); Kobayashi, Kojiro F. [Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 (Japan)

    2005-07-15

    Microspike-arrays were fabricated by irradiating a femtosecond laser on a tungsten surface through a mask opening in air. The natural logarithms of the calculated intensity distributions diffracted at the edge of the mask opening were qualitatively consistent with the experimental results of the shape and arrays of microspikes fabricated. The shape and the array of microspikes depend on the intensity distribution diffracted at the edge of the mask opening. This microspike-array has the potential to be used as a source of micro emitter tips.

  16. Tungsten oxide-Au nanosized film composites for glucose oxidation and sensing in neutral medium.

    Science.gov (United States)

    Gougis, Maxime; Ma, Dongling; Mohamedi, Mohamed

    2015-01-01

    In this work, we report for the first time the use of tungsten oxide (WOx) as catalyst support for Au toward the direct electrooxidation of glucose. The nanostructured WOx/Au electrodes were synthesized by means of laser-ablation technique. Both micro-Raman spectroscopy and transmission electron microscopy showed that the produced WOx thin film is amorphous and made of ultrafine particles of subnanometer size. X-ray diffraction and X-ray photoelectron spectroscopy revealed that only metallic Au was present at the surface of the WOx/Au composite, suggesting that the WOx support did not alter the electronic structure of Au. The direct electrocatalytic oxidation of glucose in neutral medium such as phosphate buffered saline (pH 7.2) solution has been investigated with cyclic voltammetry, chronoamperometry, and square-wave voltammetry. Sensitivity as high as 65.7 μA cm(-2) mM(-1) up to 10 mM of glucose and a low detection limit of 10 μM were obtained with square-wave voltammetry. This interesting analytical performance makes the laser-fabricated WOx/Au electrode potentially promising for implantable glucose fuel cells and biomedical analysis as the evaluation of glucose concentration in biological fluids. Finally, owing to its unique capabilities proven in this work, it is anticipated that the laser-ablation technique will develop as a fabrication tool for chip miniature-sized sensors in the near future.

  17. Studies on argon collisions with smooth and rough tungsten surfaces.

    Science.gov (United States)

    Ozhgibesov, M S; Leu, T S; Cheng, C H; Utkin, A V

    2013-09-01

    The aim of this work is to investigate argon scattering behaviors on the smooth and rough tungsten surfaces. Current work deals with numerical simulation of nanoscale heat transfer process accompanying with rarefied gas-solid substrate interactions using molecular dynamics (MD) method. Taking into account that this method is very time consuming, MD simulation using CUDA capable Graphic Cards is implemented. The results found that imperfection of the surface significantly influences on gas atom's momentum change upon collision. However, the energy exchange rate remains unchanged regardless to the surface roughness. This finding is in contrast with the results in extant literatures. We believed the results found in this paper are important for both numerical and theoretical analyses of rarefied gas flow in micro- and nano-systems where the choice of boundary conditions significantly influences flow.

  18. Surface Modification of Mild Steel Using Tungsten Inert Gas Torch Surface Cladding

    Directory of Open Access Journals (Sweden)

    S. Dyuti

    2010-01-01

    Full Text Available Problem statement: There is an increasing demand for claddings which possess an optimized combination of different functional properties such as high hardness, high resistance to wear and oxidation. In this respect, hard TiAlN cladding has gained much attention. These claddings can be suitable replacements for the conventional ceramic coatings applied in many components of chemical plants and automotive industries to protect against high temperature oxidation and wear. Approach: In this study the possibility of the formation of intermetallic and nitride claddings on plain carbon steel surfaces by in situ melting of preplaced titanium and aluminum powder mixture under Tungsten Inert Gas (TIG torch had been investigated. Results: Addition of 1.3 and 1.8 mg mm-2 Ti and Al powder and melting at energy inputs between 540-675 J mm-1 in nitrogen environment successfully created more than 1 mm thick clad layer consisting of a mixture of titanium-aluminum nitrides and aluminides. All resolidified melt layers produced dendrite microstructures; the dendrite concentration is more near the surface area compared to the deeper melt depth. A maximum surface hardness of around 900 Hv was developed in most of the tracks and this hardness corresponds to high concentration of dendrites within the modified layer. Oxidation at 600°C for 72 h, of the clad steel gave weight gains of 0.13 mg mm-2, compared to 0.37 mg mm-2 for the substrate. Conclusion: The results showed that clad steel gave better mechanical and oxidation properties compared to plain carbon steel substrate.

  19. Tantalum-Tungsten Oxide Thermite Composite Prepared by Sol-Gel Synthesis and Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes, O; Kuntz, J; Gash, A; Munir, Z

    2009-02-13

    Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition tested and results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The sol-gel derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO{sub 3}) energetic composite was consolidated to a density of 9.17 g.cm{sup -3} or 93% relative density. In addition those parts were consolidated without significant pre-reaction of the constituents, thus the sample retained its stored chemical energy.

  20. Synthesis, Consolidation and Characterization of Sol-gel Derived Tantalum-Tungsten Oxide Thermite Composites

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes, O [Univ. of California, Davis, CA (United States)

    2010-06-01

    Energetic composite powders consisting of sol-gel (SG) derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition-tested and results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the SG derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The SG derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO3) energetic composite was consolidated to a density of 9.17 g·cm-3 or 93% relative density. In addition, those samples were consolidated without significant pre-reaction of the constituents, thus retaining their stored chemical energy.

  1. Annealing induced structural evolution and electrochromic properties of nanostructured tungsten oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Ching-Lin [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Lin, Chung-Kwei [School of Dental Technology, Taipei Medical University, Taipei City 110, Taiwan, ROC (China); Wang, Chun-Kai [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Wang, Sheng-Chang [Department of Mechanical Engineering, Southern Taiwan University, Tainan 710, Taiwan, ROC (China); Huang, Jow-Lay, E-mail: JLH888@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan, ROC (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 701, Taiwan, ROC (China)

    2013-12-31

    The effect of microstructure on the optical and electrochemical properties of nanostructured tungsten oxide films was evaluated as a function of annealing temperature. The films using block copolymer as the template were prepared from peroxotungstic acid (PTA) by spin-coating onto the substrate and post-annealed at 250–400 °C to form tungsten oxide films with nanostructure. The microstructure of the films was measured by X-ray diffraction and surface electron microscopy. The films annealed at temperatures below 300 °C are characterized by amorphous or nanocrystalline structures with a pore size of less than 10 nm. The evaluated annealing temperature caused a triclinic crystalline structure and microcracks. Cyclic voltammetry measurements were performed in a LiClO{sub 4}-propylene carbonate electrolyte. The results showed that the ion inserted capacity were maximized for films annealed at 300 °C and decreased with the increasing of annealing temperature. The electrochromic properties of the nanostructured tungsten oxide films were evaluated simultaneously by potentiostat and UV–vis spectroscopy. The films annealed at 300 °C exhibit high transmission modulation (∆T ∼ 40%) at λ = 633 nm and good kinetic properties. As a result, the correlation between the microstructure and kinetic properties was established, and the electrochromic properties have been demonstrated. - Highlights: • Surfactant-assisted WO{sub 3} films have been prepared by sol–gel method. • Nanostructure of porous WO{sub 3} film is retained after crystallization. • Kinetic properties of WO{sub 3} can be improved by nanostructure and crystallinity.

  2. Efficient emission of positronium atoms from an Na-coated polycrystalline tungsten surface

    Science.gov (United States)

    Terabe, H.; Iida, S.; Wada, K.; Hyodo, T.; Yagishita, A.; Nagashima, Y.

    2013-06-01

    Time-of-flight spectra for the ortho-positronium emitted from clean and Na-coated tungsten surfaces have been measured using the pulsed slow positron beam at KEK-IMSS slow positron facility. Emission efficiency of positronium from the Na-coated sample was found to be several times greater than that from uncoated tungsten surfaces.

  3. Structure Characterization of Semiconducting Tin and Tungsten Mixed Oxides

    Science.gov (United States)

    Solis, J. L.; Frantti, J.; Lantto, V.; Häggström, L.; Wikner, M.

    Mixed-oxide powders of tin and tungsten were made by heating various mixtures of SnO and WO3 powders, corresponding to the nominal formula SnxWO3+x with x between 0.5 and 2.0, in an argon atmosphere at 600°C for 15 hours. The α-SnWO4 phase was the result of heating of an equi-molar mixture of SnO and WO3 powders. In addition to 119Sn Mössbauer experiments, X-ray diffraction and Raman spectroscopy were used to study the phase structures of the mixed-oxide powders. Mössbauer spectra from all samples show a small peak at ∽0mm/s from phase(s) like rutile SnO2, and a larger peak doublet centred at ∽3.4mm/s from the α-SnWO4 phase, where tin is in the form Sn4+ and Sn2+, respectively. Another peak doublet centred at ∽3.0mm/s was needed to obtain reasonable fits for samples with x≥1.3. This doublet originates from an undocumented phase where tin is also in the divalent form Sn2+. 119Sn Mössbauer spectroscopy made it possible to reveal the relative amounts of the two valence states of tin in the mixed-oxide structures. Raman spectroscopy as the other probe for ``local'' structures was insensitive to reveal the changes in the phase structures between different mixed-oxide samples up to x=1.72, but an extra peak at ∽890cm-1 in the Raman spectrum from the sample with x=2.0 indicates also the presence of the undocumented phase.

  4. Combined flame and solution synthesis of nanoscale tungsten-oxide and zinc/tin-oxide heterostructures.

    Science.gov (United States)

    Dong, Zhizhong; Huo, Di; Kear, Bernard H; Tse, Stephen D

    2015-12-28

    Heterostructures of tungsten-oxide nanowires decorated with zinc/tin-oxide nanostructures are synthesized via a combined flame and solution synthesis approach. Vertically well-aligned tungsten-oxide nanowires are grown on a tungsten substrate by a flame synthesis method. Here, tetragonal WO(2.9) nanowires (diameters of 20-50 nm, lengths >10 μm, and coverage density of 10(9)-10(10) cm(-2)) are produced by the vapor-solid mechanism at 1720 K. Various kinds of Zn/Sn-oxide nanostructures are grown or deposited on the WO(2.9) nanowires by adjusting the Sn(2+) : Zn(2+) molar ratio in an aqueous ethylenediamine solution at 65 °C. With WO(2.9) nanowires serving as the base structures, sequential growth or deposition on them of hexagonal ZnO nanoplates, Zn(2)SnO(4) nanocubes, and SnO(2) nanoparticles are attained for Sn(2+) : Zn(2+) ratios of 0 : 1, 1 : 10, and 10 : 1, respectively, along with different saturation conditions. High-resolution transmission electron microscopy of the interfaces at the nanoheterojunctions shows abrupt interfaces for ZnO/WO(2.9) and Zn(2)SnO(4)/WO(2.9), despite lattice mismatches of >20%.

  5. A Room Temperature Nitric Oxide Gas Sensor Based on a Copper-Ion-Doped Polyaniline/Tungsten Oxide Nanocomposite

    Science.gov (United States)

    Wang, Shih-Han; Shen, Chi-Yen; Su, Jian-Ming; Chang, Shiang-Wen

    2015-01-01

    The parts-per-billion-level nitric oxide (NO) gas sensing capability of a copper-ion-doped polyaniline/tungsten oxide nanocomposite (Cu2+/PANI/WO3) film coated on a Rayleigh surface acoustic wave device was investigated. The sensor developed in this study was sensitive to NO gas at room temperature in dry nitrogen. The surface morphology, dopant distribution, and electric properties were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy mapping, and Hall effect measurements, respectively. The Cu2+/PANI/WO3 film exhibited high NO gas sensitivity and selectivity as well as long-term stability. At 1 ppb of NO, a signal with a frequency shift of 4.3 ppm and a signal-to-noise ratio of 17 was observed. The sensor exhibited distinct selectivity toward NO gas with no substantial response to O2, NH3 and CO2 gases. PMID:25811223

  6. A Room Temperature Nitric Oxide Gas Sensor Based on a Copper-Ion-Doped Polyaniline/Tungsten Oxide Nanocomposite

    Directory of Open Access Journals (Sweden)

    Shih-Han Wang

    2015-03-01

    Full Text Available The parts-per-billion-level nitric oxide (NO gas sensing capability of a copper-ion-doped polyaniline/tungsten oxide nanocomposite (Cu2+/PANI/WO3 film coated on a Rayleigh surface acoustic wave device was investigated. The sensor developed in this study was sensitive to NO gas at room temperature in dry nitrogen. The surface morphology, dopant distribution, and electric properties were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy mapping, and Hall effect measurements, respectively. The Cu2+/PANI/WO3 film exhibited high NO gas sensitivity and selectivity as well as long-term stability. At 1 ppb of NO, a signal with a frequency shift of 4.3 ppm and a signal-to-noise ratio of 17 was observed. The sensor exhibited distinct selectivity toward NO gas with no substantial response to O2, NH3 and CO2 gases.

  7. A room temperature nitric oxide gas sensor based on a copper-ion-doped polyaniline/tungsten oxide nanocomposite.

    Science.gov (United States)

    Wang, Shih-Han; Shen, Chi-Yen; Su, Jian-Ming; Chang, Shiang-Wen

    2015-03-24

    The parts-per-billion-level nitric oxide (NO) gas sensing capability of a copper-ion-doped polyaniline/tungsten oxide nanocomposite (Cu(2+)/PANI/WO3) film coated on a Rayleigh surface acoustic wave device was investigated. The sensor developed in this study was sensitive to NO gas at room temperature in dry nitrogen. The surface morphology, dopant distribution, and electric properties were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy mapping, and Hall effect measurements, respectively. The Cu(2+)/PANI/WO3 film exhibited high NO gas sensitivity and selectivity as well as long-term stability. At 1 ppb of NO, a signal with a frequency shift of 4.3 ppm and a signal-to-noise ratio of 17 was observed. The sensor exhibited distinct selectivity toward NO gas with no substantial response to O2, NH3 and CO2 gases.

  8. Blistering on tungsten surface exposed to high flux deuterium plasma

    Energy Technology Data Exchange (ETDEWEB)

    Xu, H.Y., E-mail: donaxu@163.com [Center of Interface Dynamics for Sustainability, Institute of Materials, CAEP, Chengdu 610200 (China); Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Liu, W., E-mail: liuw@mail.tsinghua.edu.cn [Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Luo, G.N. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Yuan, Y. [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Jia, Y.Z.; Fu, B.Q. [Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); De Temmerman, G. [FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Trilateral Euregio Cluster, Edisonbaan 14, 3439 MN Nieuwegein (Netherlands); ITER Organization, Route de Vinon-sur-Verdon CS 90046-13067, St Paul Lez Durance Cedex (France)

    2016-04-01

    The blistering behaviour of tungsten surfaces exposed to very high fluxes (1–2 × 10{sup 24}/m{sup 2}/s) of low energy (38 eV) deuterium plasmas was investigated as a function of ion fluence (0.2–7 × 10{sup 26} D/m{sup 2}) and surface temperature (423–873 K). Blisters were observed under all conditions, especially up to temperatures of 873 K. The blister parameters are evaluated with blister size, blister density and surface coverage. The blister size always peaked at less than 0.5 μm and no blister larger than 10 μm is observed even at high fluence. The blister densities are found in high magnitude of 10{sup 6} blisters/m{sup 2}, with the surface coverages lower than 2%. The formation of cracks in the sub-surface region was observed by cross-section imaging. Changes in blister size and shape with fluence and temperature suggest processes of predominantly nucleation and subsequent growth of blisters. The smaller blister size is considered to be caused by a combination of flux-related effects such as enhanced defect formation in the near surface region, reduced deuterium diffusivity and relatively short exposure times.

  9. Blistering on tungsten surface exposed to high flux deuterium plasma

    Science.gov (United States)

    Xu, H. Y.; Liu, W.; Luo, G. N.; Yuan, Y.; Jia, Y. Z.; Fu, B. Q.; De Temmerman, G.

    2016-04-01

    The blistering behaviour of tungsten surfaces exposed to very high fluxes (1-2 × 1024/m2/s) of low energy (38 eV) deuterium plasmas was investigated as a function of ion fluence (0.2-7 × 1026 D/m2) and surface temperature (423-873 K). Blisters were observed under all conditions, especially up to temperatures of 873 K. The blister parameters are evaluated with blister size, blister density and surface coverage. The blister size always peaked at less than 0.5 μm and no blister larger than 10 μm is observed even at high fluence. The blister densities are found in high magnitude of 106 blisters/m2, with the surface coverages lower than 2%. The formation of cracks in the sub-surface region was observed by cross-section imaging. Changes in blister size and shape with fluence and temperature suggest processes of predominantly nucleation and subsequent growth of blisters. The smaller blister size is considered to be caused by a combination of flux-related effects such as enhanced defect formation in the near surface region, reduced deuterium diffusivity and relatively short exposure times.

  10. Coating of tips for electrochemical scanning tunneling microscopy by means of silicon, magnesium, and tungsten oxides.

    Science.gov (United States)

    Salerno, Marco

    2010-09-01

    Different combinations of metal tips and oxide coatings have been tested for possible operation in electrochemical scanning tunneling microscopy. Silicon and magnesium oxides have been thermally evaporated onto gold and platinum-iridium tips, respectively. Two different thickness values have been explored for both materials, namely, 40 and 120 nm for silicon oxide and 20 and 60 nm for magnesium oxide. Alternatively, tungsten oxide has been grown on tungsten tips via electrochemical anodization. In the latter case, to seek optimal results we have varied the pH of the anodizing electrolyte between one and four. The oxide coated tips have been first inspected by means of scanning electron microscopy equipped with microanalysis to determine the morphological results of the coating. Second, the coated tips have been electrically characterized ex situ for stability in time by means of cyclic voltammetry in 1 M aqueous KCl supporting electrolyte, both bare and supplemented with K(3)[Fe(CN)(6)] complex at 10 mM concentration in milliQ water as an analyte. Only the tungsten oxide coated tungsten tips have shown stable electrical behavior in the electrolyte. For these tips, the uncoated metal area has been estimated from the electrical current levels, and they have been successfully tested by imaging a gold grating in situ, which provided stable results for several hours. The successful tungsten oxide coating obtained at pH=4 has been assigned to the WO(3) form.

  11. Activation Energy of Tantalum-Tungsten Oxide Thermite Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes, O; Kuntz, J; Gash, A; Munir, Z

    2010-02-25

    The activation energy of a high melting temperature sol-gel (SG) derived tantalum-tungsten oxide thermite composite was determined using the Kissinger isoconversion method. The SG derived powder was consolidated using the High Pressure Spark Plasma Sintering (HPSPS) technique to 300 and 400 C to produce pellets with dimensions of 5 mm diameter by 1.5 mm height. A custom built ignition setup was developed to measure ignition temperatures at high heating rates (500-2000 C {center_dot} min{sup -1}). Such heating rates were required in order to ignite the thermite composite. Unlike the 400 C samples, results show that the samples consolidated to 300 C undergo an abrupt change in temperature response prior to ignition. This change in temperature response has been attributed to the crystallization of the amorphous WO{sub 3} in the SG derived Ta-WO{sub 3} thermite composite and not to a pre-ignition reaction between the constituents. Ignition temperatures for the Ta-WO{sub 3} thermite ranged from approximately 465-670 C. The activation energy of the SG derived Ta-WO{sup 3} thermite composite consolidated to 300 and 400 C were determined to be 37.787 {+-} 1.58 kJ {center_dot} mol{sup -1} and 57.381 {+-} 2.26 kJ {center_dot} mol{sup -1}, respectively.

  12. Formation of nanoscale tungsten oxide structures and colouration characteristics

    Indian Academy of Sciences (India)

    Vijay Bhooshan Kumar; Dambarudhar Mohanta

    2011-06-01

    In this work, pH dependent evolution of tungsten oxide (WO3) nanostructures is being reported along with physical characteristics. The synthesis was carried out via an inexpensive solvothermal cum chemical reduction route, with sodium tungstate (Na2WO4) and cetyl trimethyl ammonium bromide (C19H42NBr) as main reactants. The X-ray diffraction, together with transmission electron microscopic studies have revealed formation of regular polyhedral nanocrystalline structures and fractals as one goes from higher pH (= 5.5) to lower pH (= 2) values. The average crystallite size, as calculated throughWilliamson–Hall plots, was varied within 2.8–6.8 nm for different pH samples. Fourier transform infrared spectroscopy reveals in-plane bending vibration (W–OH), observable at ∼1630 cm-1 and strong stretching (W–O–W) located at ∼814 cm-1. Raman spectroscopy has divulged WO3 Raman active optical phonon modes positioned at ∼717 and 805 cm-1. The thermochromic and photochromic properties of the nanoscale WO3 sample prepared at pH = 5.5, are also highlighted.

  13. Strontium adsorption on tantalum-doped hexagonal tungsten oxide.

    Science.gov (United States)

    Li, Xingliang; Mu, Wanjun; Xie, Xiang; Liu, Bijun; Tang, Hui; Zhou, Guanhong; Wei, Hongyuan; Jian, Yuan; Luo, Shunzhong

    2014-01-15

    Hexagonal tungsten oxide (hex-WO3) has the potential to separate (137)Cs and (90)Sr from nuclear power plant or fission (99)Mo production waste. This study aims to increase the capacity of hex-WO3 to adsorb Sr(2+). Ta-doped hex-WO3 was synthesized by the hydrothermal treatment of sodium tungstate dihydrate and tantalum chloride in concentrated HCl, in the presence of ammonium sulfate. Incorporating Ta into the WO3 framework caused the interlayer spacing to expand, and the band gap to shift to higher energy. The Sr(2+) adsorption capacity of Ta-doped hex-WO3 was significantly higher than that of hex-WO3. Sr(2+) adsorption reached equilibrium within 2h in acidic solution. Maximum Sr(2+) removal occurred at pH 4. Sr(2+) uptake by hex-WO3 was described better by the Freundlich model than by the Langmuir model. Sr(2+) adsorption on hex-WO3 was spontaneous under the studied conditions.

  14. Effects of tungsten oxide on the activity and thermal stability of a sulfate-derived titania supported platinum catalyst for propane oxidation

    Institute of Scientific and Technical Information of China (English)

    Xiaodong Wu; Zhou Zhou; Duan Weng; Bin Wang

    2012-01-01

    A Pt/WO3/TiO2 catalyst for propane oxidation was prepared by a stepwise wet impregnation method,and was aged at 800℃ for 5 hr.Compared to the sulfate-derived titania supported catalyst,the introduction of tungsten oxide as stable Brφnsted acid sites led to the formation of more metallic platinum active sites at the Pt/WO3 interface.The dissociation of surface intermediates for propane oxidation was promoted on the WO3-modified catalyst.This,as well as the inhibition effects of tungsten oxide on the sintering of anatase and the phase transformation to rutile,resulting in a high activity and thermal stability for the Pt/WO3/TiO2 catalyst.

  15. Influence of particle flux density and temperature on surface modifications of tungsten and deuterium retention

    NARCIS (Netherlands)

    Buzi, L.; De Temmerman, G.; Unterberg, B.; M. Reinhart,; Litnovsky, A.; Philipps, V.; Van Oost, G.; Möller, S.

    2014-01-01

    Systematic study of deuterium irradiation effects on tungsten was done under ITER - relevant high particle flux density, scanning a broad surface temperature range. Polycrystalline ITER - like grade tungsten samples were exposed in linear plasma devices to two different ranges of deuterium ion flux

  16. Work Function Modification of Tungsten-Doped Indium Oxides Deposited by the Co-Sputtering Method.

    Science.gov (United States)

    Oh, Gyujin; Jeon, Jia; Lee, Kyoung Su; Kim, Eun Kyu

    2016-05-01

    We have studied the work function modification of tungsten-doped indium oxides (IWOs) through the co-sputtering of indium oxide (In2O3) and indium tungsten oxide (In2O3 80 wt% + WO3 20 wt%) via a radio frequency (RF) magnetron sputtering system. By controlling the elemental deposition of IWOs, the resultant work functions varied from 4.37 eV to 4.1 eV. The IWO thin films showed excellent properties for application as transparent conducting oxide materials in the region of 0 to 2.43 at.% of tungsten versus the total metal content. The carrier concentration of n-type IWO thin films varied from 8.39 x 10(19) cm(-3) to 8.58 x 10(21) cm(-3), while the resistivity varied from 3.15 x 10(-4) Ωcm to 2.26 x 10(-3) Ωcm. The largest measured optical band gap was 3.82 eV determined at 2.43 at.% of tungsten atoms relative to the total amount of metal atoms, while the smallest optical band gap was 3.6 eV at 4.78 at.% of tungsten. IWO films containing more than 2.43 at.% of tungsten atoms relative to the total number of metal atoms revealed an average transmittance of over 80% within the visible light region.

  17. Surface roughness analysis after machining of direct laser deposited tungsten carbide

    Science.gov (United States)

    Wojciechowski, S.; Twardowski, P.; Chwalczuk, T.

    2014-03-01

    In this paper, an experimental surface roughness analysis in machining of tungsten carbide is presented. The tungsten carbide was received using direct laser deposition technology (DLD). Experiments carried out included milling of tungsten carbide samples using monolithic torus cubic boron nitride (CBN) tool and grinding with the diamond cup wheel. The effect of machining method on the generated surface topography was analysed. The 3D surface topographies were measured using optical surface profiler. The research revealed, that surface roughness generated after the machining of tungsten carbide is affected by feed per tooth (fz) value related to kinematic-geometric projection only in a minor extent. The main factor affecting machined surface roughness is the occurrence of micro grooves and protuberances on the machined surface, as well as other phenomena connected, inter alia, with the mechanism for material removal.

  18. Effects of surface orientation on lifetime of near-surface nanoscale He bubble in tungsten

    Science.gov (United States)

    Cui, Jiechao; Fu, Baoqin; Wu, Zhangwen; Hou, Qing

    2017-02-01

    In multiscale modeling of the morphological evolution of plasma facing materials in nuclear fusion reactors, the knowledge of the timescales of the involved physical processes is important. In the present study, a new method based on molecular dynamics simulations was developed to extract the lifetime of helium bubbles near tungsten surfaces. It was found that the lifetime of a helium bubble can be described by the Arrhenius equation. However, the lifetime of a helium bubble depends on the thickness of tungsten film above the helium bubble in the substrate and the bubble size. The influence of surface orientations on the lifetime of helium bubbles was also observed, and the performance of helium bubbles on the (1 1 1) surface is very different from on the (0 0 1) and (0 1 1) surfaces. The role of the helium bubble lifetime in other simulation techniques, such as in kinetic Monte Carlo methods and rate theory, is discussed.

  19. Effects of surface orientation on lifetime of near-surface nanoscale He bubble in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Jiechao; Fu, Baoqin; Wu, Zhangwen; Hou, Qing, E-mail: qhou@scu.edu.cn

    2017-02-15

    In multiscale modeling of the morphological evolution of plasma facing materials in nuclear fusion reactors, the knowledge of the timescales of the involved physical processes is important. In the present study, a new method based on molecular dynamics simulations was developed to extract the lifetime of helium bubbles near tungsten surfaces. It was found that the lifetime of a helium bubble can be described by the Arrhenius equation. However, the lifetime of a helium bubble depends on the thickness of tungsten film above the helium bubble in the substrate and the bubble size. The influence of surface orientations on the lifetime of helium bubbles was also observed, and the performance of helium bubbles on the (1 1 1) surface is very different from on the (0 0 1) and (0 1 1) surfaces. The role of the helium bubble lifetime in other simulation techniques, such as in kinetic Monte Carlo methods and rate theory, is discussed.

  20. UNS S31603 Stainless Steel Tungsten Inert Gas Welds Made with Microparticle and Nanoparticle Oxides

    Directory of Open Access Journals (Sweden)

    Kuang-Hung Tseng

    2014-06-01

    Full Text Available The purpose of this study was to investigate the difference between tungsten inert gas (TIG welding of austenitic stainless steel assisted by microparticle oxides and that assisted by nanoparticle oxides. SiO2 and Al2O3 were used to investigate the effects of the thermal stability and the particle size of the activated compounds on the surface appearance, geometric shape, angular distortion, delta ferrite content and Vickers hardness of the UNS S31603 stainless steel TIG weld. The results show that the use of SiO2 leads to a satisfactory surface appearance compared to that of the TIG weld made with Al2O3. The surface appearance of the TIG weld made with nanoparticle oxide has less flux slag compared with the one made with microparticle oxide of the same type. Compared with microparticle SiO2, the TIG welding with nanoparticle SiO2 has the potential benefits of high joint penetration and less angular distortion in the resulting weldment. The TIG welding with nanoparticle Al2O3 does not result in a significant increase in the penetration or reduction of distortion. The TIG welding with microparticle or nanoparticle SiO2 uses a heat source with higher power density, resulting in a higher ferrite content and hardness of the stainless steel weld metal. In contrast, microparticle or nanoparticle Al2O3 results in no significant difference in metallurgical properties compared to that of the C-TIG weld metal. Compared with oxide particle size, the thermal stability of the oxide plays a significant role in enhancing the joint penetration capability of the weld, for the UNS S31603 stainless steel TIG welds made with activated oxides.

  1. Propene metathesis over silica-supported tungsten oxide catalyst-catalyst induction mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Basrur, A.G.; Patwardhan, S.R.; Vyas, S.N. (Indian Inst. of Tech., Bombay (India))

    1991-01-01

    The propene metathesis reaction was studied from the point of view of elucidating the mechanism of catalyst induction and establishing conditions for maximum activity. Instrumental techniques such as ESR, IR, and TPD were used to study the various aspects. During catalyst induction, trace quantities of acetone and acetaldehyde were detected in the product stream, indicating that lattice oxygen from tungsten oxide might be responsible for these products. Induction appeared to proceed via two steps since pretreatment of the catalyst with nitrogen and hydrogen yielded a decreased amount of acetone in the latter case whereas acetaldehyde remained unaffected. ESR studies indicated some interaction between tungsten oxide and silica at the catalyst preparatory stage as well as stabilization of reduced tungsten species on the catalyst after its use and regeneration. Catalyst activity appeared to depend on conditions of pretreatment. Change in nitrogen pretreatment temperature from 500 to 600{sup o}C resulted in transition from strong to negligible external mass transfer behavior of the catalyst. TPD studies in this context showed possible loss of lattice oxygen from tungsten oxide under the above-mentioned conditions of catalyst pretreatment. ESR studies indicated the reduction of WO{sub 3} to a nonstoichiometric oxidation state. Hence catalytic activity appears to be related to the nonstoichiometric state of tungsten oxide, which may be WO{sub 2.9} (as deduced from the blue-violet color of the used catalyst).

  2. Estimation of the composition parameter of electrochemically colored amorphous hydrogen tungsten oxide films

    Science.gov (United States)

    Kaneko, Hiroko; Miyake, Kiyoshi

    1989-07-01

    The electrical and optical steady state observed in electrochemical coloration has been studied using asymmetric cells consisting of evaporated amorphous tungsten oxide films with 350-6000 Å thickness. The counter electrode used is indium wire, steel wire, or antimony-tin oxide film, and the electrolyte is a 1-N H2SO4 aqueous solution containing 10 vol % glycerol. The current and optical transmittance of the cells decrease with increasing time during coloration, and simultaneously reach a steady state. The optical density (λ=0.5 μm) in the steady state is proportional to the thickness of the tungsten oxide film, and the absorption coefficient at λ=0.5 μm of the colored oxide film in the state is approximately 9.0×104 cm-1. The effective charges which contribute to the coloration of films calculated from the charge injected until the electro-optical steady state were found to be 1.03-1.20×103 C/cm3. Assuming that the evaporated tungsten oxide films used have a distorted ReO3 structure, and that a hydrogen tungsten bronze HxWO3 is formed by coloration, the composition parameter x calculated from the average value of the effective charge, is 0.36, which is comparable with that of hydrogen tungsten bronze H0.33WO3 obtained for the colored crystalline WO3 films.

  3. Electrospun tungsten oxide NPs/PVA nanofibers: A study on the morphology and Kramers-Kronig analysis of infrared reflectance spectra

    Science.gov (United States)

    Chenari, Hossein Mahmoudi; Kangarlou, Haleh

    2016-10-01

    The major objective of this work is focused on the preparation and characterization of poly (vinyl alcohol) (PVA) embedding tungsten oxide nanoparticles based on electrospinning technique. A surfactant (CTAB) was introduced to incorporate tungsten oxide nanoparticles into the PVA nanofibers homogeneously. To prepare a viscous solution of PVA nanofiber containing tungsten oxide nanoparticles, the distance between the tip of the needle and the surface of the foil was chosen as 10 and 15 cm. The tungsten oxide NPs/PVA composite nanofibers have been characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and reflectance spectrum in the wave length range of 200-1200 nm. Fiber diameters decrease with increasing of tip-to-collector distance from 10 to 15 cm. The average diameters were estimated about 165±30 nm and 145±30 nm from scanning electron microscopy at 10 and 15 cm, respectively. The optical properties of the electrospun nanofibers were examined by the Kramers-Kronig model. The optical results show that tungsten oxide nanopowder show almost five times higher conductivity, lower absorbance and zero band gap energy.

  4. Hydrofluoric-nitric-sulphuric-acid surface treatment of tungsten for carbon fibre-reinforced composite hybrids in space applications

    Science.gov (United States)

    Kanerva, M.; Johansson, L.-S.; Campbell, J. M.; Revitzer, H.; Sarlin, E.; Brander, T.; Saarela, O.

    2015-02-01

    Hybrid material systems, such as combinations of tungsten foils and carbon fibre-reinforced plastic (CFRP), are replacing metal alloy concepts in spacecraft enclosures. However, a good adhesion between the tungsten oxide scale and the epoxy resin used is required. Here, the effects of a hydrofluoric-nitric-sulphuric-acid (HFNS) treatment on tungsten oxides and subsequent adhesion to CFRP are analysed using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and fracture testing. The work shows that HFNS treatment results in decreased oxygen content, over 50% thinner tungsten trioxide (WO3) layer and increased nano-roughness on thin tungsten foils. Fracture testing established a 39% increase in the average critical strain for tungsten-CFRP specimens after HFNS treatment was carried out on tungsten. The effect of the oxide scale modification regarding the critical strain energy release rate was ΔGc≈ 8.4 J/m2.

  5. Preparation of self-organized porous tungsten oxide using HFCVD technique

    Energy Technology Data Exchange (ETDEWEB)

    Chavez, Fernando [Departamento de Fisicoquimica de Materiales, ICUAP, Benemerita Universidad Autonoma de Puebla, Puebla, 72000 (Mexico); Felipe, Carlos, E-mail: cfelipe98@gmail.com [Departamento de Fisicoquimica de Materiales, ICUAP, Benemerita Universidad Autonoma de Puebla, Puebla, 72000 (Mexico); Departamento de Biociencias e Ingenieria, CIIEMAD, Instituto Politecnico Nacional, Mexico D.F., 07340 (Mexico); Lima, Enrique [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Mexico D.F., 04510 (Mexico); Lara, Victor [Departamento de Quimica, Universidad Autonoma Metropolitana, Iztapalapa, Mexico D.F., 09340 (Mexico); Angeles-Chavez, Carlos [Programa de Ingenieria Molecular, Instituto Mexicano del Petroleo, Mexico D.F., 07730 (Mexico); Hernandez, Miguel A. [Departamento de Investigacion en Zeolitas, ICUAP, Benemerita Universidad Autonoma de Puebla, Puebla, 72000 (Mexico)

    2010-03-15

    Hot filament chemical vapour deposition (HFCVD) technique was applied to deposit a porous tungsten oxide film on glass wafers. The tungsten filament was used as a source in a vacuum atmosphere. The porous film was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray thermodiffraction, nitrogen sorption and small-angle X-ray scattering. From these characterization techniques it was found that porous film presents a clusters-like morphology of WO{sub 3-x} particles. The particles are arranged on substrate in a way that free spaces are originated, as a 3D network of pores. By increasing temperature, the BET specific surface area of the porous film changes from 38.67 to 34.5 m{sup 2} g{sup -1} most likely due to the particles have a tendency to stick together to form aggregates, particularly at high temperature. A fractal geometry approach permits to elucidate the interconnection between the particles and a simple model of the porous structure is proposed.

  6. Optical properties of tungsten oxide thin films by non-reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Acosta, M., E-mail: milenis@yahoo.co [Laboratorio de Ciencia de Materiales, Facultad de Ingenieria, Universidad Autonoma de Yucatan, Avenida Industrias No Contaminantes S/N, A.P. 150, Cordemex, Merida (Mexico); Gonzalez, D.; Riech, I. [Laboratorio de Ciencia de Materiales, Facultad de Ingenieria, Universidad Autonoma de Yucatan, Avenida Industrias No Contaminantes S/N, A.P. 150, Cordemex, Merida (Mexico)

    2009-07-31

    Tungsten oxide thin films were grown on glass substrates by RF sputtering at room temperature using a tungsten trioxide target for several values of the argon pressure (P{sub Ar}). The structural and morphological properties of these films were studied using X-ray diffraction and atomic force microscopy. The as-deposited films were amorphous irrespective of the argon pressure, and crystallized in a mixture of hexagonal and monoclinic phases after annealing at a temperature of 350 {sup o}C in air. Surface-roughness increased by an order of magnitude (from 1 nm to 20 nm) after thermal treatment. The argon pressure, however, had a strong influence on the optical properties of the films. Three different regions are clearly identified: deep blue films for P{sub Ar} {<=} 2.67 Pa with low transmittance values, light blue films for 2.67 Pa < P{sub Ar} < 6 Pa with intermediate transmittance values and transparent films for P{sub Ar} {>=} 6 Pa with high transmittance values. We suggest that the observed changes in optical properties are due to an increasing number of oxygen vacancies as the growth argon pressure decreases.

  7. Surface modification of tungsten and tungsten-tantalum alloys exposed to high-flux deuterium plasma and its impact on deuterium retention

    NARCIS (Netherlands)

    Zayachuk, Y.; Hoen, M. H. J. 't; van Emmichoven, P. A. Zeijlma; Terentyev, D.; Uytdenhouwen, I.; Van Oost, G.

    2013-01-01

    Samples of tungsten and tungsten-tantalum alloy (with 5 mass per cent of Ta) were exposed to high-flux deuterium plasma at different fluences. The surface modification was studied with scanning electron microscopy, and deuterium retention was measured by thermal desorption spectroscopy (TDS). In the

  8. Inkjet printing of sol-gel synthesized hydrated tungsten oxide nanoparticles for flexible electrochromic devices.

    Science.gov (United States)

    Costa, Cláudia; Pinheiro, Carlos; Henriques, Inês; Laia, César A T

    2012-03-01

    Tungsten oxide nanoparticles were synthesized via a sol-gel route using metallic tungsten as precursor, and were printed on a flexible electrode using inkjet printing in order to build solid-state electrochromic cells. Several spectroscopic techniques were used to characterize and compare tungsten oxide particles obtained from different origins. FTIR, Raman and X-ray diffraction spectroscopic measurements showed that the sol-gel synthesis described here produces nanoparticles mainly in an amorphous state with hexagonal crystalline domains and allowed the analysis of the hydration extent of those nanoparticles. The size was measured combining dynamic light scattering, sedimentation, and microscopic techniques (AFM), showing a consistent size of about 200 nm. The tungsten oxide nanoparticles were used to produce an ink formulation for application in inkjet printing. Solid-state electrochromic devices were assembled at room temperature, without sintering the tungsten oxide printed films, showing excellent contrast between on/off states. Electrochemical characterization of those films is described using cyclic voltammetry. The devices were then tested through spectroelectrochemistry by Visible/NIR absorption spectroscopy (400-2200 nm range), showing a dual spectroscopic response depending on the applied voltage. This phenomenon is attributed to the presence of two different crystalline states in accordance with results obtained from the spectroscopic characterization of the nanoparticles. The electrochromic cells had a good cycling stability showing high reversibility and a cyclability up to more than 50,000 cycles with a degradation of 25%. © 2012 American Chemical Society

  9. Polaron transitions in charge intercalated amorphous tungsten oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Saenger, M.F.; Hofmann, T.; Schubert, M. [Department of Electrical Engineering, and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln (United States); Hoeing, T. [Flabeg GmbH and Co. KG, Furth im Wald (Germany)

    2008-04-15

    We present a parametric dielectric function model in dependence of the intercalated charge per tungsten ion ratio x, which excellently describes the ellipsometric experimental data, and allows the identification of two polaron modes corresponding to transitions between W{sup 4+} and W{sup 5+} and between W{sup 5+} and W{sup 6+} tungsten ion sites. A competitive relation between the two polaron transitions is found. An empirical relation for the amplitude of the polaron transitions is found useful to provide a good description of the polaron transition dependence on x. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Tungsten oxide-Au nanosized film composites for glucose oxidation and sensing in neutral medium

    Directory of Open Access Journals (Sweden)

    Gougis M

    2015-04-01

    Full Text Available Maxime Gougis, Dongling Ma, Mohamed Mohamedi INRS-Énergie, Matériaux et Télécommunications, Varennes, Québec, Canada Abstract: In this work, we report for the first time the use of tungsten oxide (WOx as catalyst support for Au toward the direct electrooxidation of glucose. The nanostructured WOx/Au electrodes were synthesized by means of laser-ablation technique. Both micro-Raman spectroscopy and transmission electron microscopy showed that the produced WOx thin film is amorphous and made of ultrafine particles of subnanometer size. X-ray diffraction and X-ray photoelectron spectroscopy revealed that only metallic Au was present at the surface of the WOx/Au composite, suggesting that the WOx support did not alter the electronic structure of Au. The direct electrocatalytic oxidation of glucose in neutral medium such as phosphate buffered saline (pH 7.2 solution has been investigated with cyclic voltammetry, chronoamperometry, and square-wave voltammetry. Sensitivity as high as 65.7 µA cm-2 mM-1 up to 10 mM of glucose and a low detection limit of 10 µM were obtained with square-wave voltammetry. This interesting analytical performance makes the laser-fabricated WOx/Au electrode potentially promising for implantable glucose fuel cells and biomedical analysis as the evaluation of glucose concentration in biological fluids. Finally, owing to its unique capabilities proven in this work, it is anticipated that the laser-ablation technique will develop as a fabrication tool for chip miniature-sized sensors in the near future. Keywords: Au, tungsten oxide, nanostructures, pulsed laser deposition, glucose oxidation and sensing

  11. Electrochromic performance of hybrid tungsten oxide films with multiwalled-CNT additions

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chung-Kwei, E-mail: cklin@fcu.edu.tw [Department of Materials Science and Engineering, Feng Chia University, Taichung, Taiwan (China); Tseng, Sheng-Chung; Cheng, Chin-Hua; Chen, Chin-Yi [Department of Materials Science and Engineering, Feng Chia University, Taichung, Taiwan (China); Chen, Chien-Chon [Department of Energy and Resources, National United University, Miaoli, Taiwan (China)

    2011-12-30

    In this study, tungsten oxide films were prepared by sol-gel technique. Various amounts of multiwalled carbon nanotubes (MWCNTs) were added during sol-gel process to obtain hybrid WO{sub 3}/MWCNT films. The original and hybrid films were characterized by thermogravimetric analysis, X-ray diffraction analysis, and scanning electron microscopy analysis, whereas the electrochromic performance was evaluated by measuring changes in the optical transmittance caused by potentiostatic charge-discharge intercalation. The influence on the structure and properties of tungsten oxide film due to MWCNT addition was also investigated. The results showed that all of the films were amorphous and exhibited porous microstructure. The electrochromic performance of pristine WO{sub 3} film was improved by adding MWCNTs that served as a template for the growth of WO{sub 3} and resulted in more porous microstructure. The hybrid tungsten oxide films with 0.1 wt.% MWCNT addition exhibited the best electrochromic performance.

  12. Novel Approach: Tungsten Oxide Nanoparticle as a Catalyst for Malonic Acid Ester Synthesis via Ozonolysis

    Directory of Open Access Journals (Sweden)

    Bilal A. Wasmi

    2014-01-01

    Full Text Available Malonic acid ester was synthesized via the one-step ozonolysis of palm olein. Malonic acid ester was spectroscopically characterized using gas chromatography mass spectroscopy (GC-MS. Tungsten oxide nanoparticles were used as the catalyst, which was characterized via X-ray powder diffraction (XRD and field emission scanning electron microscopy (FE-SEM. Tungsten oxide provided several advantages as a catalyst for the esterification malonic acid such as simple operation for a precise ozonation method, an excellent yield of approximately 10%, short reaction times of 2 h, and reusability due to its recyclability.

  13. Tungsten oxide thin films obtained by anodisation in low electrolyte concentration

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Nadja B.D. da [Centro de Ciências Químicas, Farmacêuticas e de Alimentos, Universidade Federal de Pelotas, Campus Capão do Leão, s/n, Pelotas, RS (Brazil); Pazinato, Julia C.O. [Instituto de Química, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500 Porto Alegre, RS (Brazil); Sombrio, Guilherme; Pereira, Marcelo B.; Boudinov, Henri [Instituto de Física, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500 Porto Alegre, RS (Brazil); Gündel, André; Moreira, Eduardo C. [Universidade Federal do Pampa, Travessa 45, 1650 Bagé, RS (Brazil); Garcia, Irene T.S., E-mail: irene.garcia@ufrgs.br [Instituto de Química, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500 Porto Alegre, RS (Brazil)

    2015-03-02

    Tungsten oxide nanostructured films were grown on tungsten substrates by anodisation under a fixed voltage and with sodium fluoride as electrolyte. The effect of the anion chloride and the influence of the modifying agent disodium hydrogen phosphate in the tungsten oxide films were also investigated. The structural characterisation of the films was performed by scanning electron microscopy, atomic force microscopy and Raman spectroscopy. The band gap was determined through diffuse reflectance spectroscopy. The thin films were photoluminescent and emitted in the range of 300 to 630 nm when irradiated at 266 nm. The synthesised films efficiently degraded of methyl orange dye in the presence of hydrogen peroxide and 250 nm radiation. The modifying agent was responsible for the improvement of the photocatalytic activity. Films with similar photocatalytic performance were obtained when the system sodium fluoride and disodium hydrogen phosphate were replaced by sodium chloride. The porous structure and low band gap values were responsible for the photocatalytic behaviour. - Highlights: • Tungsten oxide thin films were obtained by anodisation of tungsten in aqueous media. • The performance of the NaCl, NaF and NaF/Na{sub 2}HPO{sub 4} as electrolytes was investigated. • The relation between structure and optical behaviour has been discussed. • Films obtained with NaCl and NaF/Na{sub 2}HPO{sub 4} present similar photocatalytic activity.

  14. Photodeposition of platinum nanoparticles on well-defined Tungsten oxide: controlling oxidation state, particle size and geometrical distribution

    NARCIS (Netherlands)

    Wenderich, Kasper

    2016-01-01

    In this thesis, structure-directed photodeposition of the cocatalyst platinum (Pt) on monoclinic tungsten oxide (WO3) nanoplates is described, both considering fundamental aspects, as well as usefulness for applications in photocatalytic propane oxidation. Before such studies are described, the conc

  15. Synthesis and structural characterization of tungsten oxide particles by the glycothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Tzu Hsuan, E-mail: thchiang@nuu.edu.tw [Department of Energy Engineering, National United University, 2, Lienda, Nan-Shi Li, Miaoli, 36063, Taiwan (China); Hsu, Chia-Chun; Chen, Tso-Ming [Department of Energy Engineering, National United University, 2, Lienda, Nan-Shi Li, Miaoli, 36063, Taiwan (China); Yu, Bing-Sheng [Department of Material and Mineral Resources Engineering, National Taipei University of Technology, No 1, Sec. 3, Chung-Shiao E. Road, Taipei, 10608, Taiwan (China)

    2015-11-05

    This study investigated the glycothermal reaction, a simple method used to synthetize tungsten oxide particle through the redox potentials of ethylene glycol, which were lower than those of ammonium tungstate parapentahydrate ((NH{sub 4}){sub 10}W{sub 12}O{sub 41}·5H{sub 2}O)). The ethylene glycol has the ability to oxidize and can be oxidized into acetaldehyde that should be identified by a gas chromatography–mass spectrometry (GC–MS). The acetaldehyde subsequently formed H{sup +}; H{sup +} can react with (NH{sub 4}){sub 10}W{sub 12}O{sub 41}·5H{sub 2}O to produce tungsten oxide hydrate at 100 °C for 40 min. The particles were subjected to sintering at 400–500 °C, producing a coexisting structure of both hexagonal tungsten oxide (h-WO{sub 3}) and monoclinic tungsten oxide (m-WO{sub 3}); however, when subjected to sintering up 600 °C for 1 h, it only produced monoclinic tungsten oxide (m-WO{sub 3}), as demonstrated by X-Ray diffraction (XRD) and transmission electron microscopy (TEM). The particles have different colors, which were subjected to various sintering temperatures. The m-WO{sub 3} particle formed the smallest particle sizes, 10 ± 5 μm at 800 °C, during the sintering process. - Highlights: • The WO{sub 3} particles were synthetized by glycothermal method at 100 °C for 1 h. • The study demonstrated the use of the oxidation of ethylene glycol to prepare m-WO{sub 3}. • The WO{sub 3} particles were sintered for 1 h at 200–1000 °C, resulting in different colors. • The particles were subjected to 600 °C for 1 h produce m-WO{sub 3} structure.

  16. Atomistic simulations of tungsten surface evolution under low-energy neon implantation

    Science.gov (United States)

    Backman, Marie; Hammond, Karl D.; Sefta, Faiza; Wirth, Brian D.

    2016-04-01

    Tungsten is a candidate material for the divertor of fusion reactors, where it will be subject to a high flux of particles coming from the fusion plasma as well as a significant heat load. Under helium plasma exposure in fusion-reactor-like conditions, a nanostructured morphology is known to form on the tungsten surface in certain temperature and incident energy ranges, although the formation mechanism is not fully established. A recent experimental study (Yajima et al 2013 Plasma Sci. Technol. 15 282-6) using neon or argon exposure did not produce similar nanostructure. This article presents molecular dynamics simulations of neon implantation in tungsten aimed at investigating the surface evolution and elucidating the role of noble gas mass in fuzz formation. In contrast to helium, neon impacts can sputter both tungsten and previously implanted neon atoms. The shorter range of neon ions, along with sputtering, limit the formation of large bubbles and likely prevents nanostructure formation.

  17. Status of research on tungsten oxide-based photoelectrochemical devices at the University of Hawai'i

    Science.gov (United States)

    Gaillard, N.; Chang, Y.; Kaneshiro, J.; Deangelis, A.; Miller, E. L.

    2010-08-01

    For more than a decade, the Hawaii Natural Energy Institute has conducted research on photoelectrochemical (PEC) technologies and achieved major milestones, including the fabrication of high-performance photoactive thin film materials and the development of innovative device integrations (hybrid-photo-electrode). In this paper, we focus our discussion on tungsten oxide-based materials, one of our two principal topics of research in this field. After a description of pure WO3 physical, chemical and energetic properties we present our latest results on tungsten oxide PEC properties improvement. In our general approach, each component of the PEC electrode is addressed, from the absorber (bulk) to the surface energetics (near-surface) and catalysis (surface). Recently, progresses have been made on surface treatment for catalytic purposes as well as on PEC materials integration. In the case of catalytic treatment, our studies show that reactive sputtering technique is suitable to form high quality RuO2 thin films and nanoparticles. Tests conducted on RuO2 thin films pointed out an oxygen evolution reaction potential as low as 0.2 V. When used as an anode in 2- electrode configuration, RuO2 thin films lead to a photocurrent onset potential reduction as low as 500 mV for p-type PEC materials (CGSe2 and a-SiC, so far tested) when compared to platinum. In the case of RuO2 nanoparticles, a photocurrent density increase of approx. 20% was observed on treated tungsten oxide films. Finally, we present a new integration scheme to increase photocurrent density using highly textured substrates (HTS). In our approach, HTS were obtained by anisotropic etching of [100] silicon substrates in KOH solution. Initial results indicated a very good coverage of WO3 onto the silicon pyramids and a photocurrent doubling is observed when compared to WO3 deposited on flat silicon substrates.

  18. High Purity Tungsten Spherical Particle Preparation From WC-Co Spent Hard Scrap

    Directory of Open Access Journals (Sweden)

    Han Chulwoong

    2015-06-01

    Full Text Available Tungsten carbide-cobalt hard metal scrap was recycled to obtain high purity spherical tungsten powder by a combined hydrometallurgy and physical metallurgy pathway. Selective leaching of tungsten element from hard metal scrap occurs at solid / liquid interface and therefore enlargement of effective surface area is advantageous. Linear oxidation behavior of Tungsten carbide-cobalt and the oxidized scrap is friable to be pulverized by milling process. In this regard, isothermally oxidized Tungsten carbide-cobalt hard metal scrap was mechanically broken into particles and then tungsten trioxide particle was recovered by hydrometallurgical method. Recovered tungsten trioxide was reduced to tungsten particle in a hydrogen environment. After that, tungsten particle was melted and solidified to make a spherical one by RF (Ratio Frequency thermal plasma process. Well spherical tungsten micro-particle was successfully obtained from spent scrap. In addition to the morphological change, thermal plasma process showed an advantage for the purification of feedstock particle.

  19. Lysozyme-mediated biomineralization of titanium-tungsten oxide hybrid nanoparticles with high photocatalytic activity.

    Science.gov (United States)

    Kim, Jung Kyu; Jang, Ji-ryang; Choi, Noori; Hong, Dahyun; Nam, Chang-Hoon; Yoo, Pil J; Park, Jong Hyeok; Choe, Woo-Seok

    2014-10-21

    Titanium-tungsten oxide composites with greatly enhanced photocatalytic activity were synthesized by lysozyme-mediated biomineralization. It was shown for the first time that simple control of the onset of biomineralization could enable fine tuning of the composition and crystallinity of the composites to determine their photocatalytic performance.

  20. Volume and surface photoemission from tungsten. II. Experiment

    DEFF Research Database (Denmark)

    Feuerbacher, B.; Egede Christensen, N.

    1974-01-01

    Energy-distribution spectra of photoelectrons emitted normal to three single-crystal faces of tungsten have been measured for photon energies between 7.7 and 21.2 eV. The results are interpreted in terms of one-dimensional electronic properties along the symmetry lines in k space that correspond...

  1. Specular reflection based sensing surface deformation of gas tungsten arc weld pool

    Institute of Scientific and Technical Information of China (English)

    Zhang Shiliang; Gao Jinqiang; Wu Chuansong; Zhang Yuming

    2007-01-01

    A sensing system is developed to measure the weld pool boundary and pool surface deformation in gas tungsten arc welding. LaserStrobe technique is used to eliminate the strong arc light interference, and specular reflection from the pool surface is sensed to describe the relation between the deformed stripes and pool surface depression. Clear images of both the pool boundary and the deformed stripes edges are obtained during gas tungsten arc welding process, which lays foundation for real-time monitoring the pool surface depression and weld penetration.

  2. Correlations between structure, composition and electrical properties of tungsten/tungsten oxide periodic multilayers sputter deposited by gas pulsing

    Science.gov (United States)

    Potin, Valérie; Cacucci, Arnaud; Martin, Nicolas

    2017-01-01

    W/WOx multilayered thin films have been deposited by DC reactive sputtering using the reactive gas pulsing process. It is implemented to produce regular alternations of metal-oxide compounds at the nanometric scale. Structure and growth have been investigated by high resolution transmission electron microscopy, scanning transmission electron microscopy, X-ray energy dispersive spectroscopy and electron energy loss spectroscopy. Regularity of tungsten-based alternations, quality of interfaces as well as oxygen presence through the multilayered structure have been determined and linked to the growth conditions. Chemical information was obtained from the energy dispersive X-ray spectroscopy and low-loss electron energy loss spectroscopy. As they can be related to the chemical composition of the periodic layers, the position and the broadening of the bulk plasmon peak were studied. For the smallest periods (structural and chemical parameters and electrical properties in periodic multilayers.

  3. LEED STUDY OF NAXWO3 TUNGSTEN BRONZE - STRUCTURAL RELAXATION OF A PEROVSKITE SURFACE

    NARCIS (Netherlands)

    PEACOR, SD; HIBMA, T

    1993-01-01

    We have performed a low energy electron diffraction study of the sodium tungsten bronze, NaxWO3, x = 0.8, surface. Temperature dependent changes of both polished and cleaved surfaces indicate structural phase transitions of the surface structure, and reflect the general trend in structural phase tra

  4. Deuterium retention and surface modifications of nanocrystalline tungsten films exposed to high-flux plasma

    Energy Technology Data Exchange (ETDEWEB)

    Hoen, M.H.J. ' t [FOM Institute DIFFER (Dutch Institute for Fundamental Energy Research), Association EURATOM-FOM, Partner in the Trilateral Euregio Cluster, 3439 MN Nieuwegein (Netherlands); Dellasega, D.; Pezzoli, A.; Passoni, M. [Politecnico di Milano, EURATOM-ENEA-CNR Association, Milano (Italy); Kleyn, A.W., E-mail: A.W.Kleijn@uva.nl [FOM Institute DIFFER (Dutch Institute for Fundamental Energy Research), Association EURATOM-FOM, Partner in the Trilateral Euregio Cluster, 3439 MN Nieuwegein (Netherlands); University of Amsterdam, Science Park 904, NL-1098 XH Amsterdam (Netherlands); Center of Interface Dynamics for Sustainability, CDCST, CAEP, Chengdu, Sichuan 610207 (China); Zeijlmans van Emmichoven, P.A. [FOM Institute DIFFER (Dutch Institute for Fundamental Energy Research), Association EURATOM-FOM, Partner in the Trilateral Euregio Cluster, 3439 MN Nieuwegein (Netherlands)

    2015-08-15

    Highlights: • The films withstand the intense plasma exposure maintaining overall integrity. • An increase of deuterium retention was observed with decreasing tungsten density. • Formation of micrometer-sized blisters as well as structures on the nanometer scale depending on the layer type. - Abstract: Deuterium retention studies are presented for nanostructured tungsten films exposed to high-flux deuterium plasmas. Thin tungsten films of ∼1 μm thickness were deposited with pulsed laser deposition (PLD) on bulk tungsten. Surface modifications were studied with scanning electron microscopy and deuterium retention with thermal desorption spectroscopy. Three types of PLD films with different densities and crystallinity were studied after exposure to deuterium plasmas. The surface temperature ranged from about 460 K at the periphery to about 520 K in the centre of the targets. The films withstand the intense plasma exposure well and maintain their overall integrity. An increase of deuterium retention is observed with decreasing tungsten density and crystallite size. We found that the filling of these thin films with deuterium is significantly faster than for pre-damaged polycrystalline tungsten. We observed formation of micrometer-sized blisters as well as structures on the nanometer scale, both depending on the layer type.

  5. Application of diffusion barriers to the refractory fibers of tungsten, columbium, carbon and aluminum oxide

    Science.gov (United States)

    Douglas, F. C.; Paradis, E. L.; Veltri, R. D.

    1973-01-01

    A radio frequency powered ion-plating system was used to plate protective layers of refractory oxides and carbide onto high strength fiber substrates. Subsequent overplating of these combinations with nickel and titanium was made to determine the effectiveness of such barrier layers in preventing diffusion of the overcoat metal into the fibers with consequent loss of fiber strength. Four substrates, five coatings, and two metal matrix materials were employed for a total of forty material combinations. The substrates were tungsten, niobium, NASA-Hough carbon, and Tyco sapphire. The diffusion-barrier coatings were aluminum oxide, yttrium oxide, titanium carbide, tungsten carbide with 14% cobalt addition, and zirconium carbide. The metal matrix materials were IN 600 nickel and Ti 6/4 titanium. Adhesion of the coatings to all substrates was good except for the NASA-Hough carbon, where flaking off of the oxide coatings in particular was observed.

  6. Conical tungsten stamps for the replication of pore arrays in anodic aluminium oxide films.

    Science.gov (United States)

    LeClere, D J; Thompson, G E; Derby, B

    2009-06-17

    A tungsten master stamp has been generated by applying a novel procedure that includes two-step anodizing, followed by sequential anodizing and pore widening to develop nominally funnelled pores. These conical-shaped pores were filled with tungsten by sputter coating to manufacture a master stamp. Under a pressure of 65 MPa, the master stamp successfully embossed the surface of annealed and electropolished aluminium. The embossed surface was then used to control the position of pores created by anodizing under the conditions used to produce the original pore array.

  7. Tungsten(VI) Oxide Flake-Wall Film Electrodes for Photoelectrochemical Oxygen Evolution from Water

    OpenAIRE

    Amano, Fumiaki; Li, Ding; Ohtani, Bunsho

    2010-01-01

    A vertically arrayed flake film, "flake-wall film", of monoclinic tungsten(VI) oxide (WO3) was prepared on a transparent conductive glass. The WO3 flake-wall film exhibited superior performance for photoelectrochemical water oxidation under visible-light irradiation compared to that of a film consisting of horizontally laminated WO3 flakes. The small difference between photocurrent densities under front-side irradiation and back-side irradiation indicates the excellent electron transport prop...

  8. Thermal annealing and exposure to divertor-like deuterium plasma of tailored tungsten oxide coatings

    Energy Technology Data Exchange (ETDEWEB)

    Pezzoli, A., E-mail: andrea.pezzoli@polimi.it [Dipartimento di Energia and NEMAS, Center for NanoEngineered Materials and Surfaces, Politecnico di Milano, Milano (Italy); Dellasega, D. [Dipartimento di Energia and NEMAS, Center for NanoEngineered Materials and Surfaces, Politecnico di Milano, Milano (Italy); Istituto di Fisica del Plasma, CNR, EURATOM-ENEA-CNR Association, Milano (Italy); Russo, V. [Dipartimento di Energia and NEMAS, Center for NanoEngineered Materials and Surfaces, Politecnico di Milano, Milano (Italy); Gallo, A. [Dipartimento di Energia and NEMAS, Center for NanoEngineered Materials and Surfaces, Politecnico di Milano, Milano (Italy); FOM Institute DIFFER – Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Partner in the Trilateral Euregio Cluster, Nieuwegein (Netherlands); Zeijlmans van Emmichoven, P.A. [FOM Institute DIFFER – Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Partner in the Trilateral Euregio Cluster, Nieuwegein (Netherlands); Passoni, M. [Dipartimento di Energia and NEMAS, Center for NanoEngineered Materials and Surfaces, Politecnico di Milano, Milano (Italy); Istituto di Fisica del Plasma, CNR, EURATOM-ENEA-CNR Association, Milano (Italy)

    2015-08-15

    In this work we produced tungsten (W) and W oxide (WO{sub x}) films by pulsed laser deposition (PLD) with the aim of the addressing modifications of structure and morphology that occur after annealing treatments and high-flux deuterium plasma. Thanks to the high flexibility of PLD we produced nanostructured W containing non-bounded oxygen, different types of WO{sub x} and multilayered films. W coatings are dense, non-porous and exhibit a nanocrystalline structure, resembling the coatings used as first wall in tokamaks. The oxide films are nearly stoichiometric amorphous WO{sub x} (x = 3) with different morphology from compact to porous. Depending on annealing temperature, nucleation of different crystalline phases (e.g. WO{sub 3}, W{sub 18}O{sub 49}) occurs. Exposure of films to high-flux (∼10{sup 24} m{sup −2} s{sup −1}) deuterium plasmas in Magnum-PSI at different surface temperatures (T{sub max} = 580 K) determines material modifications at the nanoscale (e.g. nanometric defects) but no delamination. In addition preliminary deuterium retention results are reported.

  9. In situ observation of surface morphology evolution in tungsten under focused Ga{sup +} ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ran Guang, E-mail: gran@umich.edu [School of Energy Research, Xiamen University, Xiamen, Fujian 361005 (China); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Liu Xiang; Wu Jihong [Southwestern Institute of Physics, Chengdu, Sichuan 610041 (China); Li Ning [School of Energy Research, Xiamen University, Xiamen, Fujian 361005 (China); Zu Xiaotao [Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Wang Lumin, E-mail: lmwang@umich.edu [School of Energy Research, Xiamen University, Xiamen, Fujian 361005 (China); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)

    2012-05-15

    The effects of energetic Ga ion bombardment on the surface morphology of mechanically polished polycrystalline tungsten are investigated by focused Ga{sup +} ion beam irradiation with in situ scanning electron microscopy, as well as ex situ atomic force microscopy. The amount of removed material from the tungsten surface increased with increasing of incident ion angle, and also increased with ion energy from 5 to 30 keV while keeping all other bombardment parameters constant. The nanoneedle-shaped morphology formed by self-assembly in the surface of tungsten under off-normal angle bombardment, the larger the incident angle, the easier for the needle formation. In contrast, only a net-like microstructure formed under normal incident angle. Moreover, more Ga{sup +} ion fluence was needed to form pores at normal incident angle comparing to that under 52 Degree-Sign incident angle.

  10. Studies on growth and characterization of heterogeneous tungsten oxide nanostructures for photoelectrochemical and gas sensing applications

    Science.gov (United States)

    Senthilkumar, R.; Mahalingam, T.; Ravi, G.

    2016-01-01

    Tungsten oxide nanostructures were developed on indium tin oxide coated glass substrates by modified thermal evaporation process without using catalyst and vacuum. Depending on the substrate temperature and vapor concentration, different nanostructures like rod, sheet and pyramid were formed. Morphology, phase structure and crystallinity of the nanostructure films were characterized by Scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy and HR-TEM. The samples were investigated under dark current and photocurrent and in H2SO4 aqueous solution as a function of applied potential. The saturated photocurrent density of tungsten oxide was found to be ≈14.4 μA cm-2. The films were also investigated as resistive gas sensor for ethanol gases (10-50 ppm) at room temperature. The response and recovery time were also determined.

  11. Combined flame and electrodeposition synthesis of energetic coaxial tungsten-oxide/aluminum nanowire arrays.

    Science.gov (United States)

    Dong, Zhizhong; Al-Sharab, Jafar F; Kear, Bernard H; Tse, Stephen D

    2013-09-11

    A nanostructured thermite composite comprising an array of tungsten-oxide (WO2.9) nanowires (diameters of 20-50 nm and lengths of >10 μm) coated with single-crystal aluminum (thickness of ~16 nm) has been fabricated. The method involves combined flame synthesis of tungsten-oxide nanowires and ionic-liquid electrodeposition of aluminum. The geometry not only presents an avenue to tailor heat-release characteristics due to anisotropic arrangement of fuel and oxidizer but also eliminates or minimizes the presence of an interfacial Al2O3 passivation layer. Upon ignition, the energetic nanocomposite exhibits strong exothermicity, thereby being useful for fundamental study of aluminothermic reactions as well as enhancing combustion characteristics.

  12. Helium concentration in tungsten nano-tendril surface morphology using Elastic Recoil Detection

    NARCIS (Netherlands)

    Woller, K.B.; Whyte, D. G.; Wright, G. M.; Doerner, R. P.; De Temmerman, G.

    2013-01-01

    Helium (He) concentrations in tungsten nano-tendrils (W fuzz) have been measured for the first time using Elastic Recoil Detection (ERD). Fuzzy and non-fuzzy W surfaces were analyzed in order to illuminate the role of He in the transition in surface morphologies. Samples grown in the PISCES-A and PI

  13. Surface morphology and deuterium retention in tungsten exposed to high flux D plasma at high temperatures

    NARCIS (Netherlands)

    Jia, Y. Z.; De Temmerman, G.; Luo, G. N.; Xu, H.Y.; Li, C.; Fu, B. Q.; Liu, W.

    2015-01-01

    Surface modifications and deuterium retention induced in tungsten by high fluxes (1024 m−2 s−1) low energy (38 eV) deuterium ions were studied as a function of surface temperature. Blister formation was studied by scanning electron microscopy and electron backscatter diffraction, while deuterium ret

  14. Surface morphology and deuterium retention of tungsten after low- and high-flux deuterium plasma exposure

    NARCIS (Netherlands)

    Hoen, M. H. J. 't; Balden, M.; Manhard, A.; Mayer, M.; Elgeti, S.; Kleyn, A. W.; van Emmichoven, P. A. Zeijlma

    2014-01-01

    The surface morphology and deuterium retention were investigated of polycrystalline tungsten targets that were exposed to deuterium plasmas at widely varying conditions. By changing only one parameter at a time, the isolated effects of flux, time and pre-damaging on surface modifications and deuteri

  15. Elastic–plastic adhesive impacts of tungsten dust with metal surfaces in plasma environments

    Energy Technology Data Exchange (ETDEWEB)

    Ratynskaia, S., E-mail: svetlana.ratynskaia@ee.kth.se [KTH Royal Institute of Technology, Association EUROfusion-VR, Stockholm (Sweden); Tolias, P. [KTH Royal Institute of Technology, Association EUROfusion-VR, Stockholm (Sweden); Shalpegin, A. [Université de Lorraine, Institut Jean Lamour, Vandoeuvre-lès-Nancy (France); Vignitchouk, L. [KTH Royal Institute of Technology, Association EUROfusion-VR, Stockholm (Sweden); De Angeli, M. [Istituto di Fisica del Plasma – Consiglio Nazionale delle Ricerche, Milan (Italy); Bykov, I. [KTH Royal Institute of Technology, Association EUROfusion-VR, Stockholm (Sweden); Bystrov, K.; Bardin, S. [FOM Institute DIFFER, Dutch Institute For Fundamental Energy Research, Edisonbaan 14, 3439MN Nieuwegein (Netherlands); Brochard, F. [Université de Lorraine, Institut Jean Lamour, Vandoeuvre-lès-Nancy (France); Ripamonti, D. [Istituto per l’Energetica e le Interfasi – Consiglio Nazionale delle Ricerche, Milan (Italy); Harder, N. den; De Temmerman, G. [FOM Institute DIFFER, Dutch Institute For Fundamental Energy Research, Edisonbaan 14, 3439MN Nieuwegein (Netherlands)

    2015-08-15

    Dust-surface collisions impose size selectivity on the ability of dust grains to migrate in scrape-off layer and divertor plasmas and to adhere to plasma-facing components. Here, we report first experimental evidence of dust impact phenomena in plasma environments concerning low-speed collisions of tungsten dust with tungsten surfaces: re-bouncing, adhesion, sliding and rolling. The results comply with the predictions of the model of elastic-perfectly plastic adhesive spheres employed in the dust dynamics code MIGRAINe for sub- to several meters per second impacts of micrometer-range metal dust.

  16. Relating n-pentane isomerization activity to the tungsten surface density of WO(x)/ZrO2.

    Science.gov (United States)

    Soultanidis, Nikolaos; Zhou, Wu; Psarras, Antonis C; Gonzalez, Alejandro J; Iliopoulou, Eleni F; Kiely, Christopher J; Wachs, Israel E; Wong, Michael S

    2010-09-29

    Zirconia-supported tungsten oxide (WO(x)/ZrO(2)) is considered an important supported metal oxide model acid catalyst, for which structure-property relationships have been studied for numerous acid-catalyzed reactions. The catalytic activity for xylene isomerization, alcohol dehydration, and aromatic acylation follows a volcano-shape dependence on tungsten surface density. However, WO(x)/ZrO(2) has not been studied for more acid-demanding reactions, like n-pentane isomerization, with regard to surface density dependence. In this work, WO(x)/ZrO(2) was synthesized using commercially available amorphous ZrO(x)(OH)(4-2x) and model crystalline ZrO(2) as support precursors. They were analyzed for n-pentane isomerization activity and selectivity as a function of tungsten surface density, catalyst support type, and calcination temperature. Amorphous ZrO(x)(OH)(4-2x) led to WO(x)/ZrO(2) (WZrOH) that exhibited maximum isomerization activity at ∼5.2 W·nm(-2), and the crystalline ZrO(2) led to a material (WZrO(2)) nearly inactive at all surface densities. Increasing the calcination temperature from 773 to 973 K increased the formation of 0.8-1 nm Zr-WO(x) clusters detected through direct imaging on an aberration-corrected high-resolution scanning transmission electron microscope (STEM). Calcination temperature further increased catalytic activity by at least two times. Brønsted acidity was not affected but Lewis acidity decreased in number, as quantified via pyridine adsorption infrared spectroscopy. WO(x)/ZrO(2) exhibited isomerization activity that peaked within the first 2 h time-on-stream, which may be due to Zr-WO(x) clusters undergoing an activation process.

  17. The formation of tungsten doped Al{sub 2}O{sub 3}/ZnO coatings on aluminum by plasma electrolytic oxidation and their application in photocatalysis

    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); Vasilić, Rastko [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); Tadić, Nenad [University of Belgrade, Faculty of Physics, Studentski trg 12-16, 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)

    2016-07-30

    Highlights: • Tungsten doped Al{sub 2}O{sub 3}/ZnO coatings are formed by plasma electrolytic oxidation (PEO). • Coatings are mainly composed of alpha alumina, ZnO and metallic tungsten. • Photocatalytic activity of doped Al{sub 2}O{sub 3}/ZnO coatings is higher than of undoped ones. • The increase of photoluminescence corresponds to decrease of photocatalytic activity. • Tungsten acts as a charge trap to reduce the recombination rate of electron/hole pairs. - Abstract: Tungsten doped Al{sub 2}O{sub 3}/ZnO coatings are formed by plasma electrolytic oxidation of aluminum substrate in supporting electrolyte (0.1 M boric acid + 0.05 M borax + 2 g/L ZnO) with addition of different concentrations of Na{sub 2}WO{sub 4}·2H{sub 2}O. The morphology, crystal structure, chemical composition, and light absorption characteristics of formed surface coatings are investigated. The X-ray diffraction and X-ray photoelectron spectroscopy results indicate that formed surface coatings consist of alpha and gamma phase of Al{sub 2}O{sub 3}, ZnO, metallic tungsten and WO{sub 3}. Obtained results showed that incorporated tungsten does not have any influence on the absorption spectra of Al{sub 2}O{sub 3}/ZnO coatings, which showed invariable band edge at about 385 nm. The photocatalytic activity of undoped and tungsten doped Al{sub 2}O{sub 3}/ZnO coatings is estimated by the photodegradation of methyl orange. The photocatalytic activity of tungsten doped Al{sub 2}O{sub 3}/ZnO coatings is higher thanof undoped Al{sub 2}O{sub 3}/ZnO coatings; the best photocatalytic activity is ascribed to coatings formed in supporting electrolyte with addition of 0.3 g/L Na{sub 2}WO{sub 4}·2H{sub 2}O. Tungsten in Al{sub 2}O{sub 3}/ZnO coatings acts as a charge trap, thus reducing the recombination rate of photogenerated electron-hole pairs. The results of PL measurements are in agreement with photocatalytic activity. Declining PL intensity corresponds to increasing photocatalytic activity of the

  18. Observations of orientation dependence of surface morphology in tungsten implanted by low energy and high flux D plasma

    NARCIS (Netherlands)

    Xu, H.Y.; Zhang, Y. B.; Yuan, Y.; Fu, B. Q.; Godfrey, A.; De Temmerman, G.; Liu, W.; Huang, X.

    2013-01-01

    Surface modification by formation of blistering and nanostructures with pronounced orientation dependence has been observed on surfaces of rolled tungsten and recrystallized tungsten after exposure to a low energy (38 eV) deuterium (D) plasma with a high flux of 1024 m-2 s -1. The correlation betwee

  19. Effect of neon plasma pre-irradiation on surface morphology and deuterium retention of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, L., E-mail: L.Cheng@buaa.edu.cn [School of Physics & Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); De Temmerman, G.; Zeijlmans van Emmichoven, P.A. [FOM Institute DIFFER, Dutch Institute For Fundamental Energy Research, Association EURATOM-FOM, Trilateral Euregion Cluster, Nieuwegein (Netherlands); Ji, G. [Unité Matériaux et Transformations, UMR CNRS 8207, Université Lille 1, 59655 Villeneuve d’Ascq (France); Zhou, H.B. [School of Physics & Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Wang, B. [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Yuan, Y., E-mail: yueyuan@buaa.edu.cn [School of Physics & Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Zhang, Y. [School of Physics & Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Lu, G.H., E-mail: LGH@buaa.edu.cn [School of Physics & Nuclear Energy Engineering, Beihang University, Beijing 100191 (China)

    2015-08-15

    Neon and deuterium plasma irradiation of polycrystalline tungsten targets have been performed at high fluxes of ∼10{sup 24} ions m{sup −2} s{sup −1} to study the interaction of neon with tungsten and the influence of neon on deuterium retention. Tungsten exposure to neon plasma leads to the formation of wavy nanostructures on the surface. Subsequent exposure to high-flux deuterium plasma leads to blister formation of micrometer size on top of the wavy structures. The total deuterium retention is decreased by neon pre-irradiation for all surface temperatures used in the present experiments. It is suggested that a barrier of trapped Ne is formed that interrupts the D transport and reduces D retention.

  20. Synergistic tungsten oxide/organic framework hybrid nanofibers for electrochromic device application

    Science.gov (United States)

    Dulgerbaki, Cigdem; Komur, Ali Ihsan; Nohut Maslakci, Neslihan; Kuralay, Filiz; Uygun Oksuz, Aysegul

    2017-08-01

    We report the first successful applications of tungsten oxide/conducting polymer hybrid nanofiber assemblies in electrochromic devices. Poly(3,4-ethylenedioxythiophene)/tungsten oxide (PEDOT/WO3) and polypyrrole/tungsten oxide (PPy/WO3) composites were prepared by an in situ chemical oxidative polymerization of monomers in different ionic liquids; 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (BMIMTFSI) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (BMPTFSI). Electrospinning process was used to form hybrid nanofibers from chemically synthesized nanostructures. The electrospun hybrid samples were compared from both morphological and electrochemical perspectives. Importantly, deposition of nanofibers from chemically synthesized hybrids can be achieved homogenously, on nanoscale dimensions. The morphologies of these assemblies were evaluated by SEM, whereas their electroactivity was characterized by cyclic voltammetry. Electrochromic devices made from hybrid nanofiber electrodes exhibited highest chromatic contrast of 37.66% for PEDOT/WO3/BMIMPF6, 40.42% for PPy/WO3/BMIMBF4 and show a strong electrochromic color change from transparent to light brown. Furthermore, the nanofiber devices exhibit outstanding stability when color switching proceeds, which may ensure a versatile platform for color displays, rear-view mirrors and smart windows.

  1. Effects of distance between tungsten wire and glass substrate on particle size and photochromic characteristic of tungsten oxide prepared by electric current heating method

    Energy Technology Data Exchange (ETDEWEB)

    Hagizawa, T; Honma, T; Kuroki, Y; Okamoto, T; Takata, M, E-mail: takata@vos.nagaokaut.ac.jp [Department of Electrical Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188 (Japan)

    2011-10-29

    Tungsten oxide films consisting of particles were prepared on the substrates placed at various distances from the tungsten wires heated by electric current. The shapes of the particles were sphere in an area on the substrate just above the wire while octahedral shape was found in other area. For the spherical particles, with increasing the distance, the mean particle diameter increased, reached its maximum value and gradually decreased. The particles in each area showed the photochromism especially in near-infrared region. The spherical particles with the smallest size exhibited a significant photochromic effect which could be controlled by changing the distance between the wire and the substrate.

  2. CHEMILUMINESCENCE ON OXIDE SURFACE

    OpenAIRE

    L. I. IVANKIV; O. V. DZYUPYN; O.A. Balitskii

    2008-01-01

    This paper describes the oxygen adsorption properties on magnesium oxide surface. The results are compared with theoretical adsorption kinetics. Temperature and time dependences of adsorption mechanisms and chemiluminescence are discussed.

  3. Gas-phase photofragmentation of tris(methyl vinyl ketone) tungsten(0) and the relationship to laser-assisted CVD of tungsten oxide thin films.

    Science.gov (United States)

    Bitner, Theodore W; Zink, Jeffrey I

    2002-02-25

    The gas-phase laser-induced photofragmentation of tris(methyl vinyl ketone) tungsten(0) is studied, and the photoproducts are identified by time-of-flight mass spectroscopy. The initially populated excited electronic state of the complex is attributed to metal-to-ligand charge transfer by analysis of the electronic and preresonance Raman spectra. The major metal-containing photofragmentation products are W(+) and WO(+); smaller amounts of WC(+) and W(C(2)H(2))(+) are also observed. Intramolecular ligand coupling occurs, and dimeric products and their fragments are identified. Reaction pathways that explain the observed products are proposed. Thin films on silicon substrates are produced by laser-assisted chemical vapor deposition. The films consist of polycrystalline tungsten oxide with less than 10% tungsten carbide and are characterized by X-ray diffraction, SEM, and Auger electron spectroscopy. Relationships between the composition of the gas-phase photofragments and that of the solid films are discussed.

  4. Tailoring nanoscale properties of tungsten oxide for inkjet printed electrochromic devices

    Science.gov (United States)

    Wojcik, Pawel Jerzy; Santos, Lidia; Pereira, Luis; Martins, Rodrigo; Fortunato, Elvira

    2015-01-01

    This paper focuses on the engineering procedures governing the synthesis of tungsten oxide nanocrystals and the formulation of printable dispersions for electrochromic applications. By that means, we aim to stress the relevancy of a proper design strategy that results in improved physicochemical properties of nanoparticle loaded inks. In the present study inkjet printable nanostructured tungsten oxide particles were successfully synthesized via hydrothermal processes using pure or acidified aqueous sol-gel precursors. Based on the proposed scheme, the structure and morphology of the nanoparticles were tailored to ensure the desired printability and electrochromic performance. The developed nanomaterials with specified structures effectively improved the electrochemical response of printed films, resulting in 2.5 times higher optical modulation and 2 times faster coloration time when compared with pure amorphous films.This paper focuses on the engineering procedures governing the synthesis of tungsten oxide nanocrystals and the formulation of printable dispersions for electrochromic applications. By that means, we aim to stress the relevancy of a proper design strategy that results in improved physicochemical properties of nanoparticle loaded inks. In the present study inkjet printable nanostructured tungsten oxide particles were successfully synthesized via hydrothermal processes using pure or acidified aqueous sol-gel precursors. Based on the proposed scheme, the structure and morphology of the nanoparticles were tailored to ensure the desired printability and electrochromic performance. The developed nanomaterials with specified structures effectively improved the electrochemical response of printed films, resulting in 2.5 times higher optical modulation and 2 times faster coloration time when compared with pure amorphous films. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05765a

  5. Effects of oxygen partial pressure and annealing temperature on the formation of sputtered tungsten oxide films

    OpenAIRE

    2002-01-01

    Thin films of tungsten oxide were deposited on silicon substrates using reactive radio frequency sputtering. The structure of the films strongly depends on the conditions of deposition and post-treatment. Important issues are the influences of oxygen pressure during deposition and annealing temperature on the morphology. Atomic force microscopy and scanning electron microscopy revealed that films were formed by grains. The sample deposited with an Ar:O(2) partial pressure ratio of 1: 1 showed...

  6. Modelling of Magnetron Sputtering of Tungsten Oxide with Reactive Gas Pulsing

    OpenAIRE

    2007-01-01

    Reactive sputtering is one of the most commonly employed processes for the deposition of thin films. However, the range of applications is limited by inherent instabilities, which necessitates the use of a complex feedback control of reactive gas (RG) partial pressure. Recently pulsing of the RG has been suggested as a possible alternative. In this report, the concept of periodically switching the RG flow between two different values is applied to the deposition of tungsten oxide. The trends ...

  7. The Beer-Lambert law for electrochromic tungsten oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Scarminio, J.; Urbano, A. [Universidade Estadual de Londrina (Brazil). Dept. de Fisica; Gardes, B. [Universidade Estadual de Londrina, Dept. de Quimica, Lab. FILMAT, 86.051-970, Londrina (Brazil)

    1999-10-15

    Electrochemical intercalation of Li{sup +} ions into amorphous and polycrystalline tungsten oxide films were performed by cyclic voltammetry and chronopotentiometry techniques. From transmittance measurements at 632 nm, it was observed that the optical absorption intensities were proportional to the intercalated charge. The Beer-Lambert law is suggested to explain these results for which the intercalated electrons answer as absorptive species. The highest optical absorption coefficients or electrochromic efficiencies were obtained for the amorphous films. (orig.)

  8. Induction plasma spheroidization of tungsten and molybdenum powders

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The melting, evaporation and oxidation behaviors as well as the solidification phenomena of tungsten and molybdenum in induction plasma were studied. Scanning electron microscopy was used to examine the morphology and the cross section of plasma-processed powders. X-ray diffraction was used to analyze the oxides formed on the particle surface of these two metals. The influence of spray chamber pressure on the spheroidization and oxidation phenomena was discussed. The results show that fewer Mo particles than W particles are spheroidized at the same powder feed rate under the same plasma spray condition although molybdenum has a lower melting point. A small fraction of tungsten is evaporized and condensed either on the surface of tungsten particles nearby or on the wall of spray chamber. Tungsten oxides were found in tungsten powder processed under soft vacuum condition. Extremely large grains form inside some spheroidized particles of tungsten powder.

  9. High-pressure synthesis of fully occupied tetragonal and cubic tungsten bronze oxides

    Energy Technology Data Exchange (ETDEWEB)

    Ikeuchi, Yuya; Takatsu, Hiroshi; Tassel, Cedric; Goto, Yoshihiro; Murakami, Taito; Kageyama, Hiroshi [Graduate School of Engineering, Kyoto University (Japan)

    2017-05-15

    A high-pressure reaction yielded the fully occupied tetragonal tungsten bronze K{sub 3}W{sub 5}O{sub 15} (K{sub 0.6}WO{sub 3}). The terminal phase shows an unusual transport property featuring slightly negative temperature-dependence in resistivity (dρ/dT<0) and a large Wilson ratio of R{sub W}=3.2. Such anomalous metallic behavior possibly arises from the low-dimensional electronic structure with a van Hove singularity at the Fermi level and/or from enhanced magnetic fluctuations by geometrical frustration of the tungsten sublattice. The asymmetric nature of the tetragonal tungsten bronze K{sub x}WO{sub 3}-K{sub 0.6-y}Ba{sub y}WO{sub 3} phase diagram implies that superconductivity for x≤0.45 originates from the lattice instability because of potassium deficiency. A cubic perovskite KWO{sub 3} phase was also identified as a line phase - in marked contrast to Na{sub x}WO{sub 3} and Li{sub x}WO{sub 3} with varying quantities of x (<1). This study presents a versatile method by which the solubility limit of tungsten bronze oxides can be extended. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Growth process conditions of tungsten oxide thin films using hot-wire chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Houweling, Z. Silvester, E-mail: Z.S.Houweling@uu.nl [Nanophotonics - Physics of Devices, Debye Institute for Nanomaterials Science, Utrecht University, Princetonlaan 4, 3584 CB Utrecht (Netherlands); Geus, John W. [Electron Microscopy, Utrecht University, Padualaan 8, 3584 CH Utrecht (Netherlands); Jong, Michiel de; Harks, Peter-Paul R.M.L.; Werf, Karine H.M. van der; Schropp, Ruud E.I. [Nanophotonics - Physics of Devices, Debye Institute for Nanomaterials Science, Utrecht University, Princetonlaan 4, 3584 CB Utrecht (Netherlands)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Process parameters to control hot-wire CVD of WO{sub 3-x} are categorized. Black-Right-Pointing-Pointer Growth time, oxygen partial pressure, filament and substrate temperature are varied. Black-Right-Pointing-Pointer Chemical and crystal structure, optical bandgap and morphology are determined. Black-Right-Pointing-Pointer Oxygen partial pressure determines the deposition rate up to as high as 36 {mu}m min{sup -1}. Black-Right-Pointing-Pointer Nanostructures, viz. wires, crystallites and closed crystallite films, are controllably deposited. - Abstract: We report the growth conditions of nanostructured tungsten oxide (WO{sub 3-x}) thin films using hot-wire chemical vapor deposition (HWCVD). Two tungsten filaments were resistively heated to various temperatures and exposed to an air flow at various subatmospheric pressures. The oxygen partial pressure was varied from 6.0 Multiplication-Sign 10{sup -6} to 1.0 mbar and the current through the filaments was varied from 4.0 to 9.0 A, which constitutes a filament temperature of 1390-2340 Degree-Sign C in vacuum. It is observed that the deposition rate of the films is predominantly determined by the oxygen partial pressure; it changes from about 1 to about 36,000 nm min{sup -1} in the investigated range. Regardless of the oxygen partial pressure and filament temperature used, thin films with a nanogranular morphology are obtained, provided that the depositions last for 30 min or shorter. The films consist either of amorphous or partially crystallized WO{sub 3-x} with high averaged transparencies of over 70% and an indirect optical band gap of 3.3 {+-} 0.1 eV. A prolonged deposition time entails an extended exposure of the films to thermal radiation from the filaments, which causes crystallization to monoclinic WO{sub 3} with diffraction maxima due to the (0 0 2), (2 0 0) and (0 2 0) crystallographic planes, furthermore the nanograins sinter and the films exhibit a cone

  11. Tungsten oxide thin films grown by thermal evaporation with high resistance to leaching

    Energy Technology Data Exchange (ETDEWEB)

    Correa, Diogo S. [Universidade Federal de Pelotas (UFPel), RS (Brazil). Centro de Ciencias Quimicas, Farmaceuticas e de Alimentos; Pazinato, Julia C.O.; Freitas, Mauricio A. de; Radtke, Claudio; Garcia, Irene T.S., E-mail: irene@iq.ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Instituto de Quimica; Dorneles, Lucio S. [Universidade Federal de Santa Maria (UFSM), RS (Brazil). Centro de Ciencias Naturais e Exatas

    2014-05-15

    Tungsten oxides show different stoichiometries, crystal lattices and morphologies. These characteristics are important mainly when they are used as photocatalysts. In this work tungsten oxide thin films were obtained by thermal evaporation on (100) silicon substrates covered with gold and heated at 350 and 600 °C, with different deposition times. The stoichiometry of the films, morphology, crystal structure and resistance to leaching were characterized through X-ray photoelectron spectroscopy, micro-Raman spectroscopy, scanning and transmission electron microscopy, X-ray diffractometry, Rutherford backscattering spectrometry and O{sup 16} (α,α')O{sup 16} resonant nuclear reaction. Films obtained at higher temperatures show well-defined spherical nanometric structure; they are composed of WO{sub 3.1} and the presence of hydrated tungsten oxide was also observed. The major crystal structure observed is the hexagonal. Thin films obtained through thermal evaporation present resistance to leaching in aqueous media and excellent performance as photocatalysts, evaluated through the degradation of the methyl orange dye. (author)

  12. Selective hydrodeoxygenation of cyclic vicinal diols to cyclic alcohols over tungsten oxide-palladium catalysts.

    Science.gov (United States)

    Amada, Yasushi; Ota, Nobuhiko; Tamura, Masazumi; Nakagawa, Yoshinao; Tomishige, Keiichi

    2014-08-01

    Hydrodeoxygenation of cyclic vicinal diols such as 1,4-anhydroerythritol was conducted over catalysts containing both a noble metal and a group 5-7 transition-metal oxide. The combination of Pd and WOx allowed the removal of one of the two OH groups selectively. 3-Hydroxytetrahydrofuran was obtained from 1,4-anhydroerythritol in 72 and 74% yield over WOx -Pd/C and WOx -Pd/ZrO2 , respectively. The WOx -Pd/ZrO2 catalyst was reusable without significant loss of activity if the catalyst was calcined as a method of regeneration. Characterization of WOx -Pd/C with temperature-programmed reduction, X-ray diffraction, and transmission electron microscopy/energy-dispersive X-ray spectroscopy suggested that Pd metal particles approximately 9 nm in size were formed on amorphous tungsten oxide particles. A reaction mechanism was proposed on the basis of kinetics, reaction results with tungsten oxides under an atmosphere of Ar, and density functional theory calculations. A tetravalent tungsten center (W(IV) ) was formed by reduction of WO3 with the Pd catalyst and H2 , and this center served as the reductant for partial hydrodeoxygenation.

  13. Chemical vapour deposition of tungsten oxide thin films from single-source precursors

    Science.gov (United States)

    Cross, Warren Bradley

    This thesis describes the chemical vapour deposition (CVD) of tungsten oxide thin films on glass from a wide range of single-source precursors. Chapter 1 describes previous work that has motivated this research. Chapter 2 discusses the synthesis of conventional style candidates for single-source precursors. Reactions of WOCl4 with 3-methyl salicylic acid (MesaliH2) and 3,5-di-iso-propyl salicylic acid (di-i-PrsaliH2) yielded the ditungsten complexes [WO(Mesali)(MesaliH)2(mu-O)], 1, and [WO(di-i-Prsali)(di-i-PrsaliH)2(mu-O)], 2, and the monotungsten complex [WO(di-i-Pr sali)(di-i-PrsaliH)Cl], 3. Tungsten(VI) dioxo complexes were prepared by ligand exchange reactions of [WO2(acac)2], 4, yielding [WO2(catH)2], 5, and [WO2(malt)2], 6, (catH2 = 3,5-di-tert-butyl-catechol; maltH = maltol). Chapter 3 describes thermal analyses of the complexes 1 - 6 and tungsten hexaphenoxide, and consequently their suitability for CVD. The use of [W(OPh)6] and 2 - 6 in aerosol assisted CVD is reported in Chapter 4. Brown tungsten oxide was deposited from 2 and 3 at 600 °C; blue partially-reduced WO3-x thin films were deposited from [W(OPh)6] from 300 to 500 °C, from 4 at 600 °C and 6 at 620 °C. Sintering all of the coatings in air at 550 °C afforded yellow films of stoichiometric WO3. Raman spectroscopy and glancing angle XRD showed that coatings deposited from [W(OPh)6] at 300 °C were amorphous, whereas all the other films were the monoclinic phase gamma-tungsten oxide. Taking full advantage of the aerosol vaporisation technique led to the CVD of tungsten oxide films from polyoxometalate single-source precursors, as described in Chapter 5. The isopolyanion [nBu4N]2[W6O19], 7, afforded WO3 at 410 °C; the heteropolyanions [nBu4N]4H3[PW11O39], 8, and [nBu4N]4[PNbW11O40], 9, were used to deposit doped WO3 thin films in a highly-controlled manner at 480 °C. Thus, the unprecedented use of large, charged clusters for CVD was demonstrated. Chapter 6 describes investigations of the

  14. Growth inhibition by tungsten in the sulfur-oxidizing bacterium Acidithiobacillus thiooxidans.

    Science.gov (United States)

    Negishi, Atsunori; Muraoka, Tadashi; Maeda, Terunobu; Takeuchi, Fumiaki; Kanao, Tadayoshi; Kamimura, Kazuo; Sugio, Tsuyoshi

    2005-11-01

    Growth of five strains of sulfur-oxidizing bacteria Acidithiobacillus thiooxidans, including strain NB1-3, was inhibited completely by 50 microM of sodium tungstate (Na(2)WO(4)). When the cells of NB1-3 were incubated in 0.1 M beta-alanine-SO(4)(2-) buffer (pH 3.0) with 100 microM Na(2)WO(4) for 1 h, the amount of tungsten bound to the cells was 33 microg/mg protein. Approximately 10 times more tungsten was bound to the cells at pH 3.0 than at pH 7.0. The tungsten binding to NB1-3 cells was inhibited by oxyanions such as sodium molybdenum and ammonium vanadate. The activities of enzymes involved in elemental sulfur oxidation of NB1-3 cells such as sulfur oxidase, sulfur dioxygenase, and sulfite oxidase were strongly inhibited by Na(2)WO(4). These results indicate that tungsten binds to NB1-3 cells and inhibits the sulfur oxidation enzyme system of the cells, and as a result, inhibits cell growth. When portland cement bars supplemented with 0.075% metal nickel and with 0.075% metal nickel and 0.075% calcium tungstate were exposed to the atmosphere of a sewage treatment plant containing 28 ppm of H(2)S for 2 years, the weight loss of the portland cement bar with metal nickel and calcium tungstate was much lower than the cement bar containing 0.075% metal nickel.

  15. Mechanical characterisation of tungsten-1 wt.% yttrium oxide as a function of temperature and atmosphere

    Science.gov (United States)

    Palacios, T.; Jiménez, A.; Muñóz, A.; Monge, M. A.; Ballesteros, C.; Pastor, J. Y.

    2014-11-01

    This study evaluates the mechanical behaviour of an Y2O3-dispersed tungsten (W) alloy and compares it to a pure W reference material. Both materials were processed via mechanical alloying (MA) and subsequent hot isostatic pressing (HIP). We performed non-standard three-point bending (TPB) tests in both an oxidising atmosphere and vacuum across a temperature range from 77 K, obtained via immersion in liquid nitrogen, to 1473 K to determine the mechanical strength, yield strength and fracture toughness. This research aims to evaluate how the mechanical behaviour of the alloy is affected by oxides formed within the material at high temperatures, primarily from 873 K, when the materials undergo a massive thermal degradation. The results indicate that the alloy is brittle to a high temperature (1473 K) under both atmospheres and that the mechanical properties degrade significantly above 873 K. We also used Vickers microhardness tests and the dynamic modulus by impulse excitation technique (IET) to determine the elastic modulus at room temperature. Moreover, we performed nanoindentation tests to determine the effect of size on the hardness and elastic modulus; however, no significant differences were found. Additionally, we calculated the relative density of the samples to assess the porosity of the alloy. Finally, we analysed the microstructure and fracture surfaces of the tested materials via field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). In this way, the relationship between the macroscopic mechanical properties and micromechanisms of failure could be determined based on the temperature and oxides formed.

  16. Tungsten oxide--fly ash oxide composites in adsorption and photocatalysis.

    Science.gov (United States)

    Visa, Maria; Bogatu, Cristina; Duta, Anca

    2015-05-30

    A novel composite based on tungsten oxide and fly ash was hydrothermally synthetized to be used as substrate in the advanced treatment of wastewaters with complex load resulted from the textile industry. The proposed treatment consists of one single step process combining photocatalysis and adsorption. The composite's crystalline structure was investigated by X-ray diffraction and FTIR, while atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to analyze the morphology. The adsorption capacity and photocatalytic properties of the material were tested on mono- and multi-pollutants systems containing two dyes (Bemacid Blau - BB and Bemacid Rot - BR) and one heavy metal ion-Cu(2+), and the optimized process conditions were identified. The results indicate better removal efficiencies using the novel composite material in the combined adsorption and photocatalysis, as compared to the separated processes. Dyes removal was significantly enhanced in the photocatalytic process by adding hydrogen peroxide and the mechanism was presented and discussed. The pseudo second order kinetics model best fitted the experimental data, both in the adsorption and in the combined processes. The kinetic parameters were calculated and correlated with the properties of the composite substrate.

  17. The formation of tungsten doped Al2O3/ZnO coatings on aluminum by plasma electrolytic oxidation and their application in photocatalysis

    Science.gov (United States)

    Stojadinović, Stevan; Vasilić, Rastko; Radić, Nenad; Tadić, Nenad; Stefanov, Plamen; Grbić, Boško

    2016-07-01

    Tungsten doped Al2O3/ZnO coatings are formed by plasma electrolytic oxidation of aluminum substrate in supporting electrolyte (0.1 M boric acid + 0.05 M borax + 2 g/L ZnO) with addition of different concentrations of Na2WO4·2H2O. The morphology, crystal structure, chemical composition, and light absorption characteristics of formed surface coatings are investigated. The X-ray diffraction and X-ray photoelectron spectroscopy results indicate that formed surface coatings consist of alpha and gamma phase of Al2O3, ZnO, metallic tungsten and WO3. Obtained results showed that incorporated tungsten does not have any influence on the absorption spectra of Al2O3/ZnO coatings, which showed invariable band edge at about 385 nm. The photocatalytic activity of undoped and tungsten doped Al2O3/ZnO coatings is estimated by the photodegradation of methyl orange. The photocatalytic activity of tungsten doped Al2O3/ZnO coatings is higher thanof undoped Al2O3/ZnO coatings; the best photocatalytic activity is ascribed to coatings formed in supporting electrolyte with addition of 0.3 g/L Na2WO4·2H2O. Tungsten in Al2O3/ZnO coatings acts as a charge trap, thus reducing the recombination rate of photogenerated electron-hole pairs. The results of PL measurements are in agreement with photocatalytic activity. Declining PL intensity corresponds to increasing photocatalytic activity of the coatings, indicating slower recombination of electron-hole pairs.

  18. The effect of crystal orientation on the behavior of a polycrystalline tungsten surface under focused Ga{sup +} ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Ran Guang, E-mail: gran@xmu.edu.cn [School of Energy Research, Xiamen University, Xiamen, Fujian 361005 (China); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Wu Shenghua [School of Energy Research, Xiamen University, Xiamen, Fujian 361005 (China); Liu Xiang; Wu Jihong [Southwestern Institute of Physics, Chengdu, Sichuan 610041 (China); Li, Ning [School of Energy Research, Xiamen University, Xiamen, Fujian 361005 (China); Zu Xiaotao [Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Wang Lumin, E-mail: lmwang@umich.edu [School of Energy Research, Xiamen University, Xiamen, Fujian 361005 (China); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer We in situ investigated the microstructure evolution during FIB bombardment. Black-Right-Pointing-Pointer The irradiation behaviors depended significantly on the crystal orientation. Black-Right-Pointing-Pointer Tungsten grain with (0 0 1) crystal orientation showed good irradiation resistance. - Abstract: The effect of crystal orientation on the behavior of a tungsten surface under a 30 keV focused Ga{sup +} ion beam with different bombardment angles has been investigated by in situ scanning electron microscopy and electron backscatter diffraction. Results indicate that the grains of tungsten with various orientations behave quite differently. Grains with a (0 0 1) direction parallel to the ion beam always maintain a much smoother surface morphology with less mass removal after ion bombardment, indicating a lower sputtering yield. The orientation dependence of surface sputtering of tungsten can be used to guide the fabrication of tungsten-based first wall component in a nuclear fusion reactor.

  19. Defects at oxide surfaces

    CERN Document Server

    Thornton, Geoff

    2015-01-01

    This book presents the basics and characterization of defects at oxide surfaces. It provides a state-of-the-art review of the field, containing information to the various types of surface defects, describes analytical methods to study defects, their chemical activity and the catalytic reactivity of oxides. Numerical simulations of defective structures complete the picture developed. Defects on planar surfaces form the focus of much of the book, although the investigation of powder samples also form an important part. The experimental study of planar surfaces opens the possibility of applying the large armoury of techniques that have been developed over the last half-century to study surfaces in ultra-high vacuum. This enables the acquisition of atomic level data under well-controlled conditions, providing a stringent test of theoretical methods. The latter can then be more reliably applied to systems such as nanoparticles for which accurate methods of characterization of structure and electronic properties ha...

  20. Hot-wire substoichiometric tungsten oxide films deposited in hydrogen environment with n-type conductivity

    Science.gov (United States)

    Kostis, I.; Michalas, L.; Vasilopoulou, M.; Konofaos, N.; Papaioannou, G.; Iliadis, A. A.; Kennou, S.; Giannakopoulos, K.; Papadimitropoulos, G.; Davazoglou, D.

    2012-11-01

    Substoichiometric tungsten oxide nanostructured films were synthesized by a hot-wire deposition technique in hydrogen-rich environment and characterized for their structural and electrical properties. A semiconducting behaviour was identified, allowing n-type conductivity even at room temperature which is an important result since it is well known that fully stoichiometric tungsten trioxide is nearly an insulator. Current-voltage characteristics for various temperatures were measured for tungsten oxide/Si heterostructures and analysed using proper modelling. As a result, the conduction mechanism inside the films was identified and found to be of a dual nature, with variable range hopping being dominant at near room temperatures. The saturation current was found to be thermally activated and the activation energy was calculated at 0.40 eV and the grain boundaries barrier at 150 meV. From Hall measurements it was also revealed that the dominant carriers are electrons and a carrier concentration of about 1014 cm-3 was estimated.

  1. Advanced Electrochemical Machining (ECM) for tungsten surface micro-structuring in blanket applications

    Energy Technology Data Exchange (ETDEWEB)

    Holstein, Nils, E-mail: nils.holstein@kit.edu [Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Baden-Württemberg (Germany); Krauss, Wolfgang; Konys, Jürgen [Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Baden-Württemberg (Germany); Heuer, Simon; Weber, Thomas [Research Center Jülich, Institute of Energy- and Climate Research – Plasma Physics (IEK-4), D-52425 Jülich (Germany)

    2016-11-01

    Highlights: • Electrochemical Machining is an appropriate tool for tungsten shaping. • Progress in shaping achieved by combination of ECM with advanced micro-lithography. • Application in First Wall for connection of plasma facing material to breeder blanket. • Successful development of adhesion promotors by ECM for plasma spraying interlayers. • Microstructure electrochemical manufacturing of tungsten in sizes of 100 μm achieved. - Abstract: Plasma facing components for fusion applications must have to exhibit long-term stability under extreme physical conditions, and therefore any material imperfections caused by mechanical and/or thermal stresses in the shaping processes cannot be tolerated due to a high risk of possible technical failures under fusion conditions. To avoid such defects, the method of Electrochemical Machining (ECM) enables a complete defect-free processing of removal of tungsten material during the desired shaping, also for high penetration depths. Furthermore, supported by lithographic mask pretreatment, three-dimensional distinct geometric structures can be positive-imaged via the directional galvanic dissolution applying M-ECM process into the tungsten bulk material. New required applications for tungsten components, e.g. as adhesion promotors in W-surfaces to enable sure grip and bonding of thick plasma-spraying layers for blanket components, will define the way of further miniaturization of well-established millimeter dimensioned M-ECM shaping processes to dimensions of 100 μm and furthermore down to 50 μm. Besides current M-ECM limits the article describes inevitable needs of further developments for mask resists, mask materials and the resulting ECM parameters, to reach the needed accuracy in tungsten microstructure. The achieved progress and observed correlations of processing parameters will be manifested by produced demonstrators made by the new “μM”-ECM process.

  2. Measurement of ion species produced due to bombardment of 450 eV N{sub 2}{sup +} ions with hydrocarbons-covered surface of tungsten: Formation of tungsten nitride

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S. [Atomic Physics Laboratory, Department of Physics, Institute of Science, Banaras Hindu University, Varanasi 221005 (India); Bhatt, P. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Kumar, A. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India); Singh, B.K.; Singh, B.; Prajapati, S. [Atomic Physics Laboratory, Department of Physics, Institute of Science, Banaras Hindu University, Varanasi 221005 (India); Shanker, R., E-mail: shankerorama@gmail.com [Atomic Physics Laboratory, Department of Physics, Institute of Science, Banaras Hindu University, Varanasi 221005 (India)

    2016-08-01

    A laboratory experiment has been performed to study the ions that are produced due to collisions of 450 eV N{sub 2}{sup +} ions with a hydrocarbons-covered surface of polycrystalline tungsten at room temperature. Using a TOF mass spectrometry technique, the product ions formed in these collisions have been detected, identified and analyzed. Different ion–surface reaction processes, namely, neutralization, reflection, surface induced dissociation, surface induced chemical reactions and desorption are observed and discussed. Apart from the presence of desorbed aliphatic hydrocarbon and other ions, the mass spectra obtained from the considered collisions show the formation and sputtering of tungsten nitride (WN). A layer of WN on tungsten surface is known to decrease the sputtering of bulk tungsten in fusion devices more effectively than when the tungsten is bombarded with other seeding gases (He, Ar). It is further noted that there is a negligible diffusion of N in the bulk tungsten at room temperature.

  3. Laser surface infiltration of tungsten-carbide in steel and aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Dahotre, N.B.; Mukherjee, K. (Michigan State Univ., East Lansing (USA))

    It has been demonstrated that surface modification in metals and alloys can be achieved by laser melting in conjunction with injection of particulate alloying elements in the heated zone. In our current experiments the authors have successfully implanted tungsten-carbide particles on the surface of several grades of carbon-steels as well as on the surface of a structural aluminum alloy. In both cases a significant increase in microhardness has been detected. Hardness profile from the interaction zone to the heat affected zone (HAZ) has been determined. The microstructural features of both the implanted zone and HAZ also have been determined. Effect of laser input energy, nature of tungsten-carbide particle size, size distribution and method of powder injection on the hardness profile have been investigated. Some preliminary examination of surface wear of such implanted material is also conducted. These results are discussed in detail.

  4. Estimation of the lifetime of small helium bubbles near tungsten surfaces - A methodological study

    Science.gov (United States)

    Cui, Jiechao; Wu, Zhangwen; Hou, Qing

    2016-09-01

    Under low energy and high flux/fluence irradiation of helium (He) atoms, the formation and bursting of He bubbles on tungsten (W) surfaces play important roles in the morphological evolution of component surfaces in fusion reactors. Microscopically, the bursting of He bubbles is a stochastic process, and He bubbles have statistically average lifetimes. In the present paper, a molecular dynamics-based method was developed to extract, for the first time, the lifetime of He bubbles near tungsten surfaces. It was found that He bubble bursting can be treated as an activated event. Its frequency or, equivalently, the average lifetime of bubbles follows the Arrhenius equation. For a given bubble size, the activation energy exhibits a good linear dependence with the depth, and the pre-exponential factor obeys the Meyer-Neldle rule. These results are useful for establishing a model in multi-scale simulations of the morphological evolution of component surfaces in fusion reactors.

  5. From liquid to thin film: colloidal suspensions for tungsten oxide as an electrode material for Li-ion batteries

    OpenAIRE

    2016-01-01

    Using a colloidal suspension, tungsten oxide thin films (150 nm) have been prepared via ultrasonic spray deposition using two different current collectors, namely TiN and Pt. First, the precursor chemistry was studied, revealing that the tungsten present is reduced due to the formation of chlorine gas. Due to a dehydrogenation 1,1-diethoxyethane (DEE) and hydrogen chloride (HCl) evolve from the precursor, reducing the chloride content of the precursor. The thin films were annealed at 400 and ...

  6. Surface morphology and deuterium retention in tungsten exposed to high flux D plasma at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Y.Z. [Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); De Temmerman, G. [FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Edisonbaan 14, 3439 MN Nieuwegein (Netherlands); ITER Organization, Route de Vinon-sur-Verdon-CS90046, 13067 St Paul Lez Durance Cedex (France); Luo, G.-N. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Xu, H.Y. [Science and Technology on Surface Physics and Chemistry Laboratory, Mianyang, Sichuan 621907 (China); Li, C.; Fu, B.Q. [Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Liu, W., E-mail: liuw@mail.tsinghua.edu.cn [Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2015-02-15

    Surface modifications and deuterium retention induced in tungsten by high fluxes (10{sup 24} m{sup −2} s{sup −1}) low energy (38 eV) deuterium ions were studied as a function of surface temperature. Blister formation was studied by scanning electron microscopy and electron backscatter diffraction, while deuterium retention was measured by thermal desorption spectroscopy. Blisters are observed on the surface exposed at different temperatures, ranging from 493 K to 1273 K. The blister density and D retention decrease with the increasing exposure temperature. The formation of blisters at high temperatures is attributed to the high flux of D plasma. At 943 K, with the increasing fluence, there is trend to the saturation of D retention and blister density. The defects caused by plasma exposure have an important effect on the D trapping and blistering behavior. The formation of blisters has a strong relationship with slipping system of tungsten.

  7. Escape of carbon element in surface ablation of cobalt cemented tungsten carbide with pulsed UV laser

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Dong, Jingxing; Wei, Yunrong; Liu, Jingru

    2001-03-01

    Surface ablation of cobalt cemented tungsten carbide hardmetal has been carried out in this work using a 308 nm, 30 ns XeCl excimer laser. The surface phase transformation on different pulse number of laser shots has been investigated by means of XRD and microphotography as well as AES at laser fluence of 2.5 J/cm 2. The experimental results showed that the phase structure of irradiated area has partly transformed from original WC to β-WC 1- x, then to α-W 2C and CW 3, and finally to W crystal. It is suggested that the formation of non-stoichiometric tungsten carbide should result from the escaping of carbon element due to accumulated heating of surface by pulsed laser irradiation.

  8. Recent progress in tungsten oxides based memristors and their neuromorphological applications

    Science.gov (United States)

    Qu, Bo; Younis, Adnan; Chu, Dewei

    2016-09-01

    The advance in conventional silicon based semiconductor industry is now becoming indeterminacy as it still along the road of Moore's Law and concomitant problems associated with it are the emergence of a number of practical issues such as short channel effect. In terms of memory applications, it is generally believed that transistors based memory devices will approach to their scaling limits up to 2018. Therefore, one of the most prominent challenges today in semiconductor industry is the need of a new memory technology which is able to combine the best characterises of current devices. The resistive switching memories which are regarded as "memristors" thus gain great attentions thanks to their specific nonlinear electrical properties. More importantly, their behaviour resembles with the transmission characteristic of synapse in biology. Therefore, the research of synapses biomimetic devices based on memristor will certainly bring a great research prospect in studying synapse emulation as well as building artificial neural networks. Tungsten oxides (WO x ) exhibits many essential characteristics as a great candidate for memristive devices including: accredited endurance (over 105 cycles), stoichiometric flexibility, complimentary metal-oxide-semiconductor (CMOS) process compatibility and configurable properties including non-volatile rectification, memorization and learning functions. Herein, recent progress on Tungsten oxide based materials and its associating memory devices had been reviewed. The possible implementation of this material as a bio-inspired artificial synapse is also highlighted. The penultimate section summaries the current research progress for tungsten oxide based biological synapses and end up with several proposals that have been suggested for possible future developments.

  9. Iron oxide surfaces

    Science.gov (United States)

    Parkinson, Gareth S.

    2016-03-01

    The current status of knowledge regarding the surfaces of the iron oxides, magnetite (Fe3O4), maghemite (γ-Fe2O3), haematite (α-Fe2O3), and wüstite (Fe1-xO) is reviewed. The paper starts with a summary of applications where iron oxide surfaces play a major role, including corrosion, catalysis, spintronics, magnetic nanoparticles (MNPs), biomedicine, photoelectrochemical water splitting and groundwater remediation. The bulk structure and properties are then briefly presented; each compound is based on a close-packed anion lattice, with a different distribution and oxidation state of the Fe cations in interstitial sites. The bulk defect chemistry is dominated by cation vacancies and interstitials (not oxygen vacancies) and this provides the context to understand iron oxide surfaces, which represent the front line in reduction and oxidation processes. Fe diffuses in and out from the bulk in response to the O2 chemical potential, forming sometimes complex intermediate phases at the surface. For example, α-Fe2O3 adopts Fe3O4-like surfaces in reducing conditions, and Fe3O4 adopts Fe1-xO-like structures in further reducing conditions still. It is argued that known bulk defect structures are an excellent starting point in building models for iron oxide surfaces. The atomic-scale structure of the low-index surfaces of iron oxides is the major focus of this review. Fe3O4 is the most studied iron oxide in surface science, primarily because its stability range corresponds nicely to the ultra-high vacuum environment. It is also an electrical conductor, which makes it straightforward to study with the most commonly used surface science methods such as photoemission spectroscopies (XPS, UPS) and scanning tunneling microscopy (STM). The impact of the surfaces on the measurement of bulk properties such as magnetism, the Verwey transition and the (predicted) half-metallicity is discussed. The best understood iron oxide surface at present is probably Fe3O4(100); the structure is

  10. Tungsten oxide – fly ash oxide composites in adsorption and photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Visa, Maria, E-mail: maria.visa@unitbv.ro; Bogatu, Cristina, E-mail: cristina.bogatu@unitbv.ro; Duta, Anca, E-mail: a.duta@unitbv.ro

    2015-05-30

    Highlights: • A novel fly ash – WO{sub 3} composite was synthesized via mild hydrothermal treatment. • Simultaneous dyes and copper adsorption efficiently runs on the composite. • In situ tandem systems (TiO{sub 2}–WO{sub 3}) supports the high photocatalytic activity. • The processes kinetics mainly depend on the dye’s structure and flexibility. • Thermodynamics depend on the copper–dye/copper–dye-substrate interactions. - Abstract: A novel composite based on tungsten oxide and fly ash was hydrothermally synthetized to be used as substrate in the advanced treatment of wastewaters with complex load resulted from the textile industry. The proposed treatment consists of one single step process combining photocatalysis and adsorption. The composite’s crystalline structure was investigated by X-ray diffraction and FTIR, while atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to analyze the morphology. The adsorption capacity and photocatalytic properties of the material were tested on mono- and multi-pollutants systems containing two dyes (Bemacid Blau – BB and Bemacid Rot – BR) and one heavy metal ion-Cu{sup 2+}, and the optimized process conditions were identified. The results indicate better removal efficiencies using the novel composite material in the combined adsorption and photocatalysis, as compared to the separated processes. Dyes removal was significantly enhanced in the photocatalytic process by adding hydrogen peroxide and the mechanism was presented and discussed. The pseudo second order kinetics model best fitted the experimental data, both in the adsorption and in the combined processes. The kinetic parameters were calculated and correlated with the properties of the composite substrate.

  11. Phase transformation during surface ablation of cobalt-cemented tungsten carbide with pulsed UV laser

    Energy Technology Data Exchange (ETDEWEB)

    Li, T. [Academia Sinica, Shanghai, SH (China). Shanghai Inst. of Optics and Fine Mechanics; Northwest Institute of Nuclear Technology, Xi' an (China); Lou, Q.; Dong, J.; Wei, Y. [Academia Sinica, Shanghai, SH (China). Shanghai Inst. of Optics and Fine Mechanics; Liu, J. [Northwest Institute of Nuclear Technology, Xi' an (China)

    2001-09-01

    Surface ablation of cobalt-cemented tungsten carbide hard metal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. Surface microphotography and XRD, as well as an electron probe have been used to investigate the transformation of phase and microstructure as a function of the pulse-number of laser shots at a laser fluence of 2.5 J/cm{sup 2}. The experimental results show that the microstructure of cemented tungsten carbide is transformed from the original polygonal grains of size 3 {mu}m to interlaced large, long grains with an increase in the number of laser shots up to 300, and finally to gross grains of size 10 {mu}m with clear grain boundaries after 700 shots of laser irradiation. The crystalline structure of the irradiated area is partly transformed from the original WC to {beta}WC{sub 1-x}, then to {alpha}W{sub 2}C and CW{sub 3}, and finally to W crystal. It is suggested that the undulating 'hill-valley' morphology may be the result of selective removal of cobalt binder from the surface layer of the hard metal. The formation of non-stoichiometric tungsten carbide may result from the escape of elemental carbon due to accumulated heating of the surface by pulsed laser irradiation. (orig.)

  12. Phase transformation during surface ablation of cobalt-cemented tungsten carbide with pulsed UV laser

    Science.gov (United States)

    Li, T.; Lou, Q.; Dong, J.; Wei, Y.; Liu, J.

    Surface ablation of cobalt-cemented tungsten carbide hard metal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. Surface microphotography and XRD, as well as an electron probe have been used to investigate the transformation of phase and microstructure as a function of the pulse-number of laser shots at a laser fluence of 2.5 J/cm2. The experimental results show that the microstructure of cemented tungsten carbide is transformed from the original polygonal grains of size 3 μm to interlaced large, long grains with an increase in the number of laser shots up to 300, and finally to gross grains of size 10 μm with clear grain boundaries after 700 shots of laser irradiation. The crystalline structure of the irradiated area is partly transformed from the original WC to βWC1-x, then to αW2C and CW3, and finally to W crystal. It is suggested that the undulating `hill-valley' morphology may be the result of selective removal of cobalt binder from the surface layer of the hard metal. The formation of non-stoichiometric tungsten carbide may result from the escape of elemental carbon due to accumulated heating of the surface by pulsed laser irradiation.

  13. Electrochromic Devices Based on Porous Tungsten Oxide Thin Films

    Directory of Open Access Journals (Sweden)

    Y. Djaoued

    2012-01-01

    Full Text Available Recent developments in the synthesis of transition metal oxides in the form of porous thin films have opened up opportunities in the construction of electrochromic devices with enhanced properties. In this paper, synthesis, characterization and electrochromic applications of porous WO3 thin films with different nanocrystalline phases, such as hexagonal, monoclinic, and orthorhombic, are presented. Asymmetric electrochromic devices have been constructed based on these porous WO3 thin films. XRD measurements of the intercalation/deintercalation of Li+ into/from the WO3 layer of the device as a function of applied coloration/bleaching voltages show systematic changes in the lattice parameters associated with structural phase transitions in LixWO3. Micro-Raman studies show systematic crystalline phase changes in the spectra of WO3 layers during Li+ ion intercalation and deintercalation, which agree with the XRD data. These devices exhibit interesting optical modulation (up to ~70% due to intercalation/deintercalation of Li ions into/from the WO3 layer of the devices as a function of applied coloration/bleaching voltages. The obtained optical modulation of the electrochromic devices indicates that, they are suitable for applications in electrochromic smart windows.

  14. Near infrared electrochromic variable optical attenuator based on ruthenium complex and polycrystalline tungsten oxide

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jidong; WU Xianguo; YU Hongan; YAN Donghang; WANG Zhiyuan

    2005-01-01

    A near infrared (NIR) electrochromic attenuator based on a dinuclear ruthenium complex and polycrystalline tungsten oxide was fabricated and characterized. The results show that the use of the NIR-absorbing ruthenium complex as a counter electrode material can improve the device performance. By replacing the visible electrochromic ferrocene with the NIR-absorbing ruthenium complex, the optical attenuation at 1550 nm was enhanced from 19.1 to 30.0 dB and color efficiency also increased from 29.2 to 121.2 cm2/C.

  15. Multi-Walled Carbon Nanotube-Doped Tungsten Oxide Thin Films for Hydrogen Gas Sensing

    OpenAIRE

    2010-01-01

    In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO3) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity ...

  16. Influence of surface morphology and microstructure on performance of CVD tungsten coating under fusion transient thermal loads

    Science.gov (United States)

    Lian, Youyun; Liu, Xiang; Wang, Jianbao; Feng, Fan; Lv, Yanwei; Song, Jiupeng; Chen, Jiming

    2016-12-01

    Thick tungsten coatings have been deposited by chemical vapor deposition (CVD) at a rapid growth rate. A series of tungsten coatings with different thickness and surface morphology were prepared. The surface morphology, microstructure and preferred orientation of the CVD tungsten coatings were investigated. Thermal shock analyses were performed by using an electron beam facility to study the influence of the surface morphology and the microstructure on the thermal shock resistance of the CVD tungsten coatings. Repetitive (100 pulses) ELMs-like thermal shock loads were applied at various temperatures between room temperature and 600 °C with pulse duration of 1 ms and an absorbed power density of up to 1 GW/m2. The results of the tests demonstrated that the specific surface morphology and columnar crystal structure of the CVD tungsten have significant influence on the surface cracking threshold and crack propagation of the materials. The CVD tungsten coatings with a polished surface show superior thermal shock resistance as compared with that of the as-deposited coatings with a rough surface.

  17. Synthesis of tungsten oxide (W{sub 18}O{sub 49}) nanosheets utilizing EDTA salt by microwave irradiation method

    Energy Technology Data Exchange (ETDEWEB)

    Hariharan, V.; Parthibavarman, M. [Centre for Nanoscience and Technology, Department of Physics, Periyar University, Salem 636 011, Tamilnadu (India); Sekar, C., E-mail: Sekar2025@gmail.com [Centre for Nanoscience and Technology, Department of Physics, Periyar University, Salem 636 011, Tamilnadu (India); Department of Bioelectronics and Biosensors, Alagappa University, Karaikudi 630 003, Tamilnadu (India)

    2011-04-07

    Research highlights: > We have synthesized tungsten oxide (WO{sub 3-{delta}}) nanoparticles by microwave irradiation method for the first time using EDTA as surface modulator. The variation in stoichiometric oxygen content of the annealed samples clearly indicates the role of EDTA in reaction medium. The variation in oxygen content also modified the transparency of the end product confirming the change in optical conductivity. - Abstract: We report the synthesis of crystalline W{sub 18}O{sub 49} with nanosheet like morphology by low cost microwave irradiation method without employing hydrothermal process for the first time. Initially, WO{sub 3}.H{sub 2}O was synthesized using ethylenediaminetetraacetic acid (EDTA) as surface modulator. The product was annealed at 600 {sup o}C for 6 h in ambient atmosphere in order to obtain anhydrous tungsten oxide W{sub 18}O{sub 49}. Powder X-ray diffraction results confirmed the as prepared WO{sub 3}.H{sub 2}O to be orthorhombic and W{sub 18}O{sub 49} to be monoclinic phase, respectively. Transmission electron micrographs (TEM) revealed that the W{sub 18}O{sub 49} nanosheets have the average dimensions of the order of 250 nm in length and around 150 nm in width. UV-visible diffusion reflectance spectroscopic (DRS) studies revealed the band gap energies to be 3.28 and 3.47 eV for WO{sub 3}.H{sub 2}O and W{sub 18}O{sub 49} samples, respectively. The growth mechanism of two dimensional W{sub 18}O{sub 49} nanosheets is discussed.

  18. Diode Laser Surface Alloying of Armor Steel with Tungsten Carbide

    Directory of Open Access Journals (Sweden)

    Janicki D.

    2017-06-01

    Full Text Available Metal matrix composite (MMC surface layers reinforced by WC were fabricated on armor steel ARMOX 500T plates via a laser surface alloying process. The microstructure of the layers was assessed by scanning electron microscopy and X-ray diffraction.

  19. 用于环戊烯氧化合成戊二醛反应的钨基催化剂的表征%Characterization of Tungsten-Based Catalyst Used for Selective Oxidation of cyclopentene to glutaraldehyde

    Institute of Scientific and Technical Information of China (English)

    朱志庆; 卞炜

    2008-01-01

    Tungsten-containing hexagonal mesoporous silica (W-HMS) supported tungsten oxide catalysts (WOx/W-HMS) was prepared for the selective oxidation of cyclopentene with aqueous hydrogen peroxide to glutaraldehyde. X-ray diffraction (XRD) results indicated that the crystal form of the active phase (tungsten oxide) of the WOx/W-HMS catalysts was dependent on the W loading and calcination temperature. X-ray photoelectron spec-troscopy (XPS) analysis revealed that the dispersed tungsten oxides on the surface of W-HMS support consisted of a mixture of W(V) and W(VI). It was found that a high content of amorphous W species in (5+) oxidation state resulted in the high catalytic activity. When the W loading was up to 12% (by mass) or the catalyst precursor was treated at temperature of 623 K, the catalytic activity decreased due to the presence of WO3 crystallites and the oxidation of W(V) to W(VI) on the catalyst surface. Furthermore, NH3-temperature-programmed-desorption (NH3-TPD) analysis showed that the effects of W loading and calcination temperature on the acidity of the catalysts were related to the catalytic activity. A high selectivity of 80.2% for glutaraldehyde with a complete conversion of cyclopentene was obtained over 8%WOx/W-HMS catalyst calcined at 573 K after 14 h of reaction.

  20. 自生成钨基高密度合金中间层的钨/钢真空扩散连接%Diffusion Bonding Tungsten to Steel in Vacuum with Tungsten Heavy Alloy Interlayer Formed on Tungsten Surface

    Institute of Scientific and Technical Information of China (English)

    杨宗辉; 沈以赴; 李晓泉

    2013-01-01

    tungsten matrix and tungsten heavy alloy layer. The typical cleavage fracture of tungsten matrix and the tungsten phase interface debonding fracture accompanied by MnNi-rich phase ductile fracture of tungsten heavy alloy layer are observed in the fracture surfaces.

  1. Oxidation of ZrB2 and ZrB2-SiC Ceramics With Tungsten Additions (Preprint)

    Science.gov (United States)

    2009-02-01

    Electrochemical Society . PAO Case Number: 88 ABW-2008-1143; Clearance Date: 26 Nov 2008. Paper contains color. 14. ABSTRACT The effect of tungsten...18 For submission to proceedings of the 214th meeting of the Electrochemical Society Oxidation of ZrB2 and ZrB2-SiC Ceramics with Tungsten...TaSi2 that form a protective SiO2-rich oxide scale at temperatures 1 For submission to proceedings of the 214th meeting of the Electrochemical Society above

  2. Surface response of tungsten to helium and hydrogen plasma flux as a function of temperature and incident kinetic energy

    Science.gov (United States)

    Sukumar, Harikrishnan

    Tungsten is a leading candidate material for the diverter in future nuclear fusion reactors. Previous experiments have demonstrated that surface defects and bubbles form in tungsten when ex- posed to helium and hydrogen plasmas, even at modest ion energies. In some regimes, between 1000K and 2000K, and for He energies below 100eV, "fuzz" like features form. The mechanisms leading to these surfaces comprised of nanometer sized tungsten tendrils which include visible helium bubbles are not currently known. The role of helium bubble formation in tendril morphology could very likely be the starting point of these mechanisms. Using Molecular dynamics (MD) simulations, the role of helium and hydrogen exposure in the initial formation mechanisms of tungsten "fuzz" are investigated. Molecular dynamics simulations are well suited to describe the time and length scales associated with initial formation of helium clusters that eventually grow to nano-meter sized helium bubbles. MD simulations also easily enable the modeling of a variety of surfaces such as single crystals, grain boundaries or "tendrils". While the sputtering yield of tungsten is generally low, previous observations of surface modification due to plasma exposure raise questions about the effects of surface morphology and sub-surface helium bubble populations on the sputtering behavior. Results of computational molecular dynamics are reported that investigate the influence of sub-surface helium bubble distributions on the sputtering yield of tungsten (100) and (110) surfaces induced by helium ion exposure in the range of 300 eV to 1 keV. The calculated sputtering yields are in reasonable agreement with a wide range of experimental data; but do not show any significant variation as a result of the pre-existing helium bubbles. Molecular dynamics simulations reveal a number of sub-surface mechanisms leading to nanometer- sized "fuzz" in tungsten exposed to low-energy helium plasmas. We find that during the bubble

  3. Rashba-Dirac cones at the tungsten surface: Insights from a tight-binding model and thin film subband structure

    Science.gov (United States)

    Kirczenow, George

    2016-11-01

    A tight-binding model of bcc tungsten that includes spin-orbit coupling is developed and applied to the surface states of (110) tungsten thin films. The model describes accurately the anisotropic Dirac conelike dispersion and Rashba-like spin polarization of the surface states, including the crucial effect of the relaxation of the surface atomic layer of the tungsten towards the bulk. It is shown that the surface relaxation affects the tungsten surface states because it results in increased overlaps between atomic orbitals of the surface atomic layer and nearby layers, whereas electric fields that are due to charge transfer between the tungsten and the vacuum near the surface or between the bulk and surface layers do not significantly affect the Rashba-Dirac surface states. It is found that hybridization with bulk modes has differing strengths for thin film surface states belonging to the upper and lower Rashba-Dirac cones and results in reversal of the directions of travel of spin ↑ and ↓ electrons in most of the upper Rashba-Dirac cone relative to those expected from phenomenology. It is also shown that intrasite (not intersite) matrix elements of the spin-orbit Hamiltonian are primarily responsible for the formation of the Rashba-Dirac cones and their spin polarization. This finding should be considered when modeling topological insulators, the spin Hall effect, and related phenomena.

  4. Robust superhydrophobic tungsten oxide coatings with photochromism and UV durability properties

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Ting [Hubei Collaborative Innovation Centre for Advanced Organic Chemical Materials and Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan, 430062 (China); State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000 (China); Guo, Zhiguang, E-mail: zguo@licp.cas.cn [Hubei Collaborative Innovation Centre for Advanced Organic Chemical Materials and Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan, 430062 (China); State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000 (China)

    2016-11-30

    Highlights: • Superhydrophobic tungsten oxide (TO) coatings with a water contact angle (WCA) of 155° and rolling angle of 3.5° were developed. • The superhydrophobic coatings have excellent mechanical robustness and UV durability. • The superhydrophobic TO coatings show the reversible convert of photochromism. • The coating exhibited excellent self-cleaning behavior due to its high WCA and low rolling angle. - Abstract: Robust superhydrophobic tungsten oxide (TO) coatings with a water contact angle (WCA) of 155° were developed for photochromism via a facile and substrate-independent route. Importantly, after scatch test on both a single and two orthogonal direction, the TO coating still exhibited superhydrophobic behavior, indicating excellent mechanical robustness. It is worth mentioning that the superhydrophobic TO coatings showed the reversible convert of photochromism of WO{sub 3} induced by alternating UV and visible light irradiation. Besides that, the TO coating remained superhydrophobicity after UV irradiation for 36 h, showing excellent UV durability. In addition, the coating showed good resistance to acidic droplets. Moreover, it can also be applied on other substrates, such as copper mesh, steel, paper and fiber. The coating exhibited excellent self-cleaning behavior due to its high WCA and low rolling angle. Overall, this work is a promising approach to design and produce functional superhydrophobic coatings for various substrates.

  5. A facile route to tungsten oxide nanomaterials with controlled morphology and structure

    Institute of Scientific and Technical Information of China (English)

    Hsuan-Ching Lin; Cherng-Yuh Su; Zhong-Kun Yang; Chung-Kwei Lin; Keng-Liang Ou

    2011-01-01

    Various tungsten oxide-based nanomaterials have been prepared by a modified plasma arc gas condensation technique without the use of catalysts or substrates.These products could be obtained by controlling the processing parameters during experiment.All the as-obtained samples were characterized by field emission gun scanning electron microscopy,high-resolution transmission electron microscopy,and Xray diffraction techniques.The results revealed that as-prepared tungsten oxide nanomaterials (WO3,W19O55 and W5O14 ) with different phases and morphologies could be obtained by decreasing the oxygen content in the chamber.In addition,W18O49 nanotubes and nanorod bundles were fabricated by controlling the Ar/O2 ratio under He plasma gas.W18O49/TiO2 core-shell nanoparticles were also prepared by evaporating a dual target.The experimental results showed that the present technique is unique and feasible for the fabrication of nanomaterials for use in different applications.

  6. Synergistic effect of sunlight induced photothermal conversion and H2O2 release based on hybridized tungsten oxide gel for cancer inhibition

    Science.gov (United States)

    Wang, Cong; Gao, Yibo; Gao, Xinghua; Wang, Hua; Tian, Jingxuan; Wang, Li; Zhou, Bingpu; Ye, Ziran; Wan, Jun; Wen, Weijia

    2016-01-01

    A highly efficient photochromic hydrogel was successfully fabricated via casting precursor, which is based on amorphous tungsten oxide and poly (ethylene oxide)-block-poly (propylene oxide)-block-poly (ethylene oxide). Under simulated solar illumination, the hydrogel has a rapid and controlled temperature increasing ratio as its coloration degree. Localized electrons in the amorphous tungsten oxide play a vital role in absorption over a broad range of wavelengths from 400 nm to 1100 nm, encompassing the entire visible light and infrared regions in the solar spectrum. More importantly, the material exhibits sustainable released H2O2 induced by localized electrons, which has a synergistic effect with the rapid surface temperature increase. The amount of H2O2 released by each film can be tuned by the light irradiation, and the film coloration can indicate the degree of oxidative stress. The ability of the H2O2-releasing gels in vitro study was investigated to induce apoptosis in melanoma tumor cells and NIH 3T3 fibroblasts. The in vivo experimental results indicate that these gels have a greater healing effect than the control in the early stages of tumor formation. PMID:27775086

  7. Synergistic effect of sunlight induced photothermal conversion and H2O2 release based on hybridized tungsten oxide gel for cancer inhibition

    Science.gov (United States)

    Wang, Cong; Gao, Yibo; Gao, Xinghua; Wang, Hua; Tian, Jingxuan; Wang, Li; Zhou, Bingpu; Ye, Ziran; Wan, Jun; Wen, Weijia

    2016-10-01

    A highly efficient photochromic hydrogel was successfully fabricated via casting precursor, which is based on amorphous tungsten oxide and poly (ethylene oxide)-block-poly (propylene oxide)-block-poly (ethylene oxide). Under simulated solar illumination, the hydrogel has a rapid and controlled temperature increasing ratio as its coloration degree. Localized electrons in the amorphous tungsten oxide play a vital role in absorption over a broad range of wavelengths from 400 nm to 1100 nm, encompassing the entire visible light and infrared regions in the solar spectrum. More importantly, the material exhibits sustainable released H2O2 induced by localized electrons, which has a synergistic effect with the rapid surface temperature increase. The amount of H2O2 released by each film can be tuned by the light irradiation, and the film coloration can indicate the degree of oxidative stress. The ability of the H2O2-releasing gels in vitro study was investigated to induce apoptosis in melanoma tumor cells and NIH 3T3 fibroblasts. The in vivo experimental results indicate that these gels have a greater healing effect than the control in the early stages of tumor formation.

  8. Surface damage characteristics of CFC and tungsten with repetitive ELM-like pulsed plasma irradiation

    Science.gov (United States)

    Kikuchi, Y.; Nishijima, D.; Nakatsuka, M.; Ando, K.; Higashi, T.; Ueno, Y.; Ishihara, M.; Shoda, K.; Nagata, M.; Kawai, T.; Ueda, Y.; Fukumoto, N.; Doerner, R. P.

    2011-08-01

    Surface damage of carbon fiber composite (CFC) and tungsten (W) due to repetitive ELM-like pulsed plasma irradiation has been investigated by using a magnetized coaxial plasma gun. CX2002U CFC and stress-relieved W samples were exposed to repetitive pulsed deuterium plasmas with duration of ˜0.5 ms, incident ion energy of ˜30 eV, and surface absorbed energy density of ˜0.3-0.7 MJ/m2. Bright spots on a CFC surface during pulsed plasma exposures were clearly observed with a high-speed camera, indicating a local surface heating. No melting of a W surface was observed under a single plasma pulse exposure at energy density of ˜0.7 MJ/m2, although cracks were formed. Cracking of the W surface grew with repetitive pulsed plasma exposures. Subsequently, the surface melted due to localized heat absorption.

  9. Effects of working pressure on physical properties of tungsten-oxide thin films sputtered from oxide target

    Energy Technology Data Exchange (ETDEWEB)

    Riech, I.; Acosta, M.; Pena, J. L.; Bartolo-Perez, P. [Laboratorio de Ciencia de Materiales, Facultad de Ingenieria, Universidad Autonoma de Yucatan, A. P 150. Cordemex, Merida, Yucatan 97130 (Mexico); Departamento de Fisica Aplicada, CINVESTAV-IPN Unidad Merida, A.P. 73 Cordemex, Merida, Yucatan 97130 (Mexico)

    2010-03-15

    Tungsten-oxide films were deposited on glass substrates from a metal-oxide target by nonreactive radio-frequency sputtering. The authors have studied the effect that changing Ar gas pressure has on the electrical, optical, and chemical composition in the thin films. Resistivity of WO{sub 3} changed ten orders of magnitude with working gas pressure values from 20 to 80 mTorr. Thin films deposited at 20 mTorr of Ar sputtering pressure showed lower resistivity and optical transmittance. X-ray photoelectron spectroscopy (XPS) measurements revealed similar chemical composition for all samples irrespective of Ar pressure used. However, XPS analyses of the evolution of W 4f and O 1s peaks indicated a mixture of oxides dependent on the Ar pressure used during deposition.

  10. Modified surface morphology in surface ablation of cobalt-cemented tungsten carbide with pulsed UV laser radiation

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Dong, Jingxing; Wei, Yunrong; Liu, Jingru

    2001-03-01

    Surface ablation of cobalt-cemented tungsten carbide hardmetal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. The influence of ablation rate, surface roughness, surface micromorphology as well as surface phase structure on laser conditions including laser irradiance and pulse number have been investigated. The experimental results showed that the ablation rate and surface roughness were controlled by varying the number of pulses and laser irradiance. The microstructure and crystalline structure of irradiated surface layer varied greatly with different laser conditions. After 300 shots of laser irradiation at irradiance of 125 MW/cm 2, the surface micromorphology characterizing a uniform framework pattern of "hill-valleys". With the increment of laser shots at laser irradiance of 125 MW/cm 2, the microstructure of cemented tungsten carbide transformed from original polygon grains with the size of 3 μm to interlaced large and long grains after 300 shots of laser irradiation, and finally to gross grains with the size of 10 μm with clear grain boundaries after 700 shots. The crystalline structure of irradiated area has partly transformed from original WC to β-WC 1- x, then to α-W 2C and CW 3, and finally to W crystal. At proper laser irradiance and pulse number, cobalt binder has been selectively removed from the surface layer of hardmetal. It has been demonstrated that surface ablation with pulsed UV laser should be a feasible way to selectively remove cobalt binder from surface layer of cemented tungsten carbide hardmetal.

  11. Results on the electrochromic and photocatalytic properties of vanadium doped tungsten oxide thin films prepared by reactive dc magnetron sputtering technique

    Science.gov (United States)

    Muthu Karuppasamy, K.; Subrahmanyam, A.

    2008-02-01

    In this investigation, vanadium doped tungsten oxide (V : WO3) thin films are prepared at room temperature by reactive dc magnetron sputtering employing a tungsten-vanadium 'inlay' target. In comparison with pure sputtered tungsten oxide thin films, 11% vanadium doping is observed to decrease the optical band gap, enhance the colour neutral property, decrease the coloration efficiency (from 121 to 13 cm2 C-1), increase the surface work function (4.68-4.83 eV) and significantly enhance the photocatalytic efficiency in WO3 thin films. These observations suggest that (i) vanadium creates defect levels that are responsible for optical band gap reduction, (ii) multivalent vanadium bonding with terminal oxygen in the WO3 lattice gives rise to localized covalent bonds and thus results in an increase in the work function, and (iii) a suitable work function of V : WO3 with ITO results in an enhancement of the photocatalytic activity. These results on electrochromic and photocatalytic properties of V : WO3 thin films show good promise in the low maintenance window application.

  12. Results on the electrochromic and photocatalytic properties of vanadium doped tungsten oxide thin films prepared by reactive dc magnetron sputtering technique

    Energy Technology Data Exchange (ETDEWEB)

    Karuppasamy, K Muthu; Subrahmanyam, A [Semiconductor Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India)

    2008-02-07

    In this investigation, vanadium doped tungsten oxide (V : WO{sub 3}) thin films are prepared at room temperature by reactive dc magnetron sputtering employing a tungsten-vanadium 'inlay' target. In comparison with pure sputtered tungsten oxide thin films, 11% vanadium doping is observed to decrease the optical band gap, enhance the colour neutral property, decrease the coloration efficiency (from 121 to 13 cm{sup 2} C{sup -1}), increase the surface work function (4.68-4.83 eV) and significantly enhance the photocatalytic efficiency in WO{sub 3} thin films. These observations suggest that (i) vanadium creates defect levels that are responsible for optical band gap reduction, (ii) multivalent vanadium bonding with terminal oxygen in the WO{sub 3} lattice gives rise to localized covalent bonds and thus results in an increase in the work function, and (iii) a suitable work function of V : WO{sub 3} with ITO results in an enhancement of the photocatalytic activity. These results on electrochromic and photocatalytic properties of V : WO{sub 3} thin films show good promise in the low maintenance window application.

  13. Study of the temperature dependent nitrogen retention in tungsten surfaces by XPS-analysis

    Energy Technology Data Exchange (ETDEWEB)

    Plank, Ulrike [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Fakultaet fuer Physik der Ludwig-Maximilians-Universitaet Muenchen, Schellingstrasse 4, D-80799 Muenchen (Germany); Meisl, Gerd; Hoeschen, Till [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany)

    2016-07-01

    To reduce the power load on the divertor of fusion experiments, nitrogen (N) is puffed into the plasma. As a side effect, nitrogen gets implanted into the tungsten (W) walls of the reactor and forms nitride layers. Their formation and, therefore, the N accumulation in W showed an unexpected temperature dependence in previous experiments. To study the nitrogen retention, we implanted N ions with an energy of 300 eV into W and observed the evolution of the surface composition by X-ray photoelectron spectroscopy (XPS). We find that the N content does not change when the sample is annealed up to 800 K after implantation at lower temperatures. In contrast, the N concentration decreases with increasing implantation temperature. At 800 K implantation temperature, the N saturation level is about 5 times lower compared to 300 K implantation. A possible explanation for this difference is an enhanced diffusion during ion bombardment due to changes in the structure or in the chemical state of the tungsten nitride system. Ongoing tungsten nitride erosion experiments shall help to clarify whether the strong temperature dependence is the result of enhanced diffusion or of phase changes.

  14. High-power durability of LiCoO2 thin film electrode modified with amorphous lithium tungsten oxide

    Science.gov (United States)

    Hayashi, Tetsutaro; Matsuda, Yasutaka; Kuwata, Naoaki; Kawamura, Junichi

    2017-06-01

    To investigate electrochemical performances of an amorphous lithium tungsten oxide (LWO) layer, an amorphous LWO-modified LiCoO2 (LCO) thin film electrode is fabricated by pulsed laser deposition and is exposed under a humid environment. The amorphous LWO-modified LCO exhibits high capacity retention of 80% at a rapid charge-discharge rate of 20 C. Conversely, the bare LCO exhibits capacity retention of 0% at the rates of 20 C. Electrochemical impedance spectroscopy demonstrates that the LWO-modified LCO maintains a low interfacial resistance after the cycling test compared with the bare LCO. X-ray photoemission spectroscopy (XPS), scanning transmission microscopy (STEM), and electron energy loss spectroscopy (EELS) indicate the presence of Li2CO3 on the surface of the bare LCO electrode and a thick degraded surface layer of CoO structure on the surface of LCO primary particle after electrochemical tests. XPS, STEM, and EELS indicate the presence of low amounts of Li2CO3 on the surface of the LWO-modified LCO, the LCO layer remains in a normal state, and LWO layer maintains the amorphous LWO state after the tests. Thus, the amorphous LWO protective layer contributes to suppressing the degradation of LCO and maintaining an amorphous LWO state with a lithium ion conductor, resulting in high-power durability.

  15. Tungsten Oxide Nanoplates; the Novelty in Targeting Metalloproteinase-7 Gene in Both Cervix and Colon Cancer Cells.

    Science.gov (United States)

    Yassin, Abdelrahman M; Elnouby, Mohamed; El-Deeb, Nehal M; Hafez, Elsayed E

    2016-10-01

    In this study, we synthesized tungsten oxide (WO3) nanoplates, both crystallographic phases and the morphology of the samples were determined by powder x-ray diffraction and the scanning electron microscopy, respectively. The obtained data clarified that, the all prepared WO3·H2O samples were composed of large quantity of nanoplates. The cytotoxicity patterns of nanoplates were checked on both normal and cancer mammalian cell lines. Both nanoplates cytotoxicity did not exceed the 50 % inhibitory concentration (IC50) on the all normal tested cells even by using concentrations up to 1 mg/ml. In addition, orthorhombic tungsten oxide nanoplate was more potent against both Caco2 and Hela cells by showing inhibition percentages in cellular viability 64.749 and 72.27, respectively, and with cancer selectivity index reached 3.2 and 2.6 on both colon and cervix cancer, respectively. The anticancer effects of nanoplates were translated to alteration in both pro-apoptotic and anti-apoptotic genes expressions. Tungsten oxide nanoplates down regulated the expression of B cell lymphoma 2 (Bcl-2) and metalloproteinase-7 (MMP7) genes. In addition, orthorhombic tungsten oxide nanoplates showed more potentiation in IL2 and IL8 induction (40.43 pg/ml) and upregulation of TNF-α gene expression but with lower folds than Escherichia coli lipopolysaccharide (LPS) induction.

  16. Robust superhydrophobic tungsten oxide coatings with photochromism and UV durability properties

    Science.gov (United States)

    Jiang, Ting; Guo, Zhiguang

    2016-11-01

    Robust superhydrophobic tungsten oxide (TO) coatings with a water contact angle (WCA) of 155° were developed for photochromism via a facile and substrate-independent route. Importantly, after scatch test on both a single and two orthogonal direction, the TO coating still exhibited superhydrophobic behavior, indicating excellent mechanical robustness. It is worth mentioning that the superhydrophobic TO coatings showed the reversible convert of photochromism of WO3 induced by alternating UV and visible light irradiation. Besides that, the TO coating remained superhydrophobicity after UV irradiation for 36 h, showing excellent UV durability. In addition, the coating showed good resistance to acidic droplets. Moreover, it can also be applied on other substrates, such as copper mesh, steel, paper and fiber. The coating exhibited excellent self-cleaning behavior due to its high WCA and low rolling angle. Overall, this work is a promising approach to design and produce functional superhydrophobic coatings for various substrates.

  17. Synthesis of tungsten oxide nanoparticles using a hydrothermal method at ambient pressure

    DEFF Research Database (Denmark)

    Ahmadi, Majid; Younesi, Reza; Guinel, Maxime J-F

    2014-01-01

    ) nanoparticles were synthesized using a simple and inexpensive low temperature and low pressure hydrothermal (HT) method. The precursor solution used for the HT process was prepared by adding hydrochloric acid to diluted sodium tungstate solutions (Na2WO4 center dot 2H(2)O) at temperatures below 5 degrees C...... of WO3 nanoparticles using this method is therefore a three step process: protonation of tungstate ions, crystallization of tungstite, and phase transformation to WO3. Furthermore, this process can be tailored. For example, we show that WO3 can be doped with cesium and that nanorods can also be obtained......Tungsten oxide (WO3) nanostructures receive sustained interest for a wide variety of applications, and especially for its usage as a photocatalyst. It is therefore important to find suitable methods allowing for its easy and inexpensive large scale production. Tungstite (WO3 center dot H2O...

  18. Hydrothermal synthesis of self-assembled hierarchical tungsten oxides hollow spheres and their gas sensing properties.

    Science.gov (United States)

    Li, Jinwei; Liu, Xin; Cui, Jiashan; Sun, Jianbo

    2015-05-20

    Hierarchical self-assembled hollow spheres (HS) of tungsten oxide nanosheets have been synthesized via a template-free hydrothermal method. Morphology evolution of the products is determined by the amount of H2C2O4 (oxalic acid) which serves as chelating agent. Structural features of the products were characterized by X-ray diffraction (XRD), and morphology was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, the porous structure was analyzed using the Brunauer-Emmett-Teller (BET) approach. The synthesis mechanism of the products with self-assembled hierarchical structures was proposed. The NO2 gas sensing properties of self-assembled hierarchical WO3 HS materials were investigated, the gas sensing properties of WO3 synthesized by a variety of formulations were compared, and the possible gas sensing mechanism was discussed. The obvious enhancement of the gas sensing properties was ascribed to the structure of the hierarchical HS.

  19. Tungsten Oxide and Polyaniline Composite Fabricated by Surfactant-Templated Electrodeposition and Its Use in Supercapacitors

    Directory of Open Access Journals (Sweden)

    Benxue Zou

    2014-01-01

    Full Text Available Composite nanostructures of tungsten oxide and polyaniline (PANI were fabricated on carbon electrode by electrocodeposition using sodium dodecylbenzene sulfonate (SDBS as the template. The morphology of the composite can be controlled by changing SDBS surfactant and aniline monomer concentrations in solution. With increasing concentration of aniline in surfactant solution, the morphological change from nanoparticles to nanofibers was observed. The nanostructured WO3/PANI composite exhibited enhanced capacitive charge storage with the specific capacitance of 201 F g−1 at 1.28 mA cm−2 in large potential window of -0.5~ 0.65 V versus SCE compared to the bulk composite film. The capacitance retained about 78% when the sweeping potential rate increased from 10 to 150 mV/s.

  20. Characterization of thermomechanical damage on tungsten surfaces during long-duration plasma transients

    Science.gov (United States)

    Rivera, David; Crosby, Tamer; Sheng, Andrew; Ghoniem, Nasr M.

    2014-12-01

    A new experimental facility constructed at UCLA for the simulation of high heat flux effects on plasma-facing materials is described. The High Energy Flux Test Facility (HEFTY) is equipped with a Praxair model SG-100 plasma gun, which is nominally rated at 80 kW of continuous operation, of which approximately 30 kW reaches the target due to thermal losses. The gun is used to impart high intermittent heat flux to metal samples mounted within a cylindrical chamber. The system is capable of delivering an instantaneous heat flux in the range of 30-300 MW/m2, depending on sample proximity to the gun. The duration of the plasma heat flux is in the range of 1-1000 s, making it ideal for studies of mild plasma transients of relatively long duration. Tungsten and tungsten-copper alloy metal samples are tested in these transient heat flux conditions, and the surface is characterized for damage evaluation using optical, SEM, XRD, and micro-fabrication techniques. Results from a Finite Element (FE) thermo-elastoplasticity model indicate that during the heat-up phase of a plasma transient pulse, the majority of the sample surface is under compressive stresses leading to plastic deformation of the surface. Upon sample cooling, the recovered elastic strain of cooler parts of the sample exceeds that from parts that deformed plastically, resulting in a tensile surface self-stress (residual surface stress). The intensity of the residual tensile surface stress is experimentally correlated with the onset of complex surface fracture morphology on the tungsten surface, and extending below the surface region. Micro-compression mechanical tests of W micro-pillars show that the material has significant plasticity, failing by a "barreling" mode before plasma exposure, and by normal dislocation slip and localized shear after plasma exposure. Ongoing modeling of the complex thermo-fracture process, coupled with elasto-plasticity is based on a phase field approach for distributed fracture, and

  1. Characterization of thermomechanical damage on tungsten surfaces during long-duration plasma transients

    Energy Technology Data Exchange (ETDEWEB)

    Rivera, David, E-mail: david.rivera.ucla@gmail.com; Crosby, Tamer; Sheng, Andrew; Ghoniem, Nasr M.

    2014-12-15

    A new experimental facility constructed at UCLA for the simulation of high heat flux effects on plasma-facing materials is described. The High Energy Flux Test Facility (HEFTY) is equipped with a Praxair model SG-100 plasma gun, which is nominally rated at 80 kW of continuous operation, of which approximately 30 kW reaches the target due to thermal losses. The gun is used to impart high intermittent heat flux to metal samples mounted within a cylindrical chamber. The system is capable of delivering an instantaneous heat flux in the range of 30–300 MW/m{sup 2}, depending on sample proximity to the gun. The duration of the plasma heat flux is in the range of 1–1000 s, making it ideal for studies of mild plasma transients of relatively long duration. Tungsten and tungsten-copper alloy metal samples are tested in these transient heat flux conditions, and the surface is characterized for damage evaluation using optical, SEM, XRD, and micro-fabrication techniques. Results from a Finite Element (FE) thermo-elastoplasticity model indicate that during the heat-up phase of a plasma transient pulse, the majority of the sample surface is under compressive stresses leading to plastic deformation of the surface. Upon sample cooling, the recovered elastic strain of cooler parts of the sample exceeds that from parts that deformed plastically, resulting in a tensile surface self-stress (residual surface stress). The intensity of the residual tensile surface stress is experimentally correlated with the onset of complex surface fracture morphology on the tungsten surface, and extending below the surface region. Micro-compression mechanical tests of W micro-pillars show that the material has significant plasticity, failing by a “barreling” mode before plasma exposure, and by normal dislocation slip and localized shear after plasma exposure. Ongoing modeling of the complex thermo-fracture process, coupled with elasto-plasticity is based on a phase field approach for distributed

  2. Detection and reduction of tungsten contamination in ion implantation processes

    Energy Technology Data Exchange (ETDEWEB)

    Polignano, M.L.; Galbiati, A.; Grasso, S.; Mica, I.; Barbarossa, F.; Magni, D. [STMicroelectronics, Agrate Brianza (Italy)

    2016-12-15

    In this paper, we review the results of some studies addressing the problem of tungsten contamination in implantation processes. For some tests, the implanter was contaminated by implantation of wafers with an exposed tungsten layer, resulting in critical contamination conditions. First, DLTS (deep level transient spectroscopy) measurements were calibrated to measure tungsten contamination in ion-implanted samples. DLTS measurements of tungsten-implanted samples showed that the tungsten concentration increases linearly with the dose up to a rather low dose (5 x 10{sup 10} cm{sup -2}). Tungsten deactivation was observed when the dose was further increased. Under these conditions, ToF-SIMS revealed tungsten at the wafer surface, showing that deactivation was due to surface segregation. DLTS calibration could therefore be obtained in the linear dose regime only. This calibration was used to evaluate the tungsten contamination in arsenic implantations. Ordinary operating conditions and critical contamination conditions of the equipment were compared. A moderate tungsten contamination was observed in samples implanted under ordinary operating conditions. This contamination was easily suppressed by a thin screen oxide. On the contrary, implantations in critical conditions of the equipment resulted in a relevant tungsten contamination, which could be reduced but not suppressed even by a relatively thick screen oxide (up to 150 Aa). A decontamination process consisting of high dose implantations of dummy wafers was tested for its efficiency to remove tungsten and titanium contamination. This process was found to be much more effective for titanium than for tungsten. Finally, DLTS proved to be much more sensitive that TXRF (total reflection X-ray fluorescence) in detecting tungsten contamination. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Cs8.5W15O48 and CsW2O6 : Members of a New Homologous Series of Cesium Tungsten Oxides

    NARCIS (Netherlands)

    Cava, R.J.; Roth, R.S.; Siegrist, T.; Hessen, B.; Krajewski, J.J.; Peck, Jr.

    1993-01-01

    The crystal structures of two new reduced cesium tungsten oxides are reported. Along with the previously reported compound Cs6W11O36, they represent several members of a homologous series of layer compounds between the hexagonal tungsten bronze and pyrochlore structure types. The series formula is [

  4. Influence of particle flux density and temperature on surface modifications of tungsten and deuterium retention

    Energy Technology Data Exchange (ETDEWEB)

    Buzi, Luxherta, E-mail: l.buzi@fz-juelich.de [Ghent University, Department of Applied Physics, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Edisonbaan 14, 3439 MN, PO Box 1207, 3430 BE Nieuwegein (Netherlands); Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany); Université de Lorraine, Institut Jean Lamour, CNRS UMR 7198, Bvd. des Aiguillettes, F-54506 Vandoeuvre (France); Temmerman, Greg De [FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Edisonbaan 14, 3439 MN, PO Box 1207, 3430 BE Nieuwegein (Netherlands); Unterberg, Bernhard; Reinhart, Michael; Litnovsky, Andrey; Philipps, Volker [Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany); Oost, Guido Van [Ghent University, Department of Applied Physics, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); Möller, Sören [Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany)

    2014-12-15

    Systematic study of deuterium irradiation effects on tungsten was done under ITER – relevant high particle flux density, scanning a broad surface temperature range. Polycrystalline ITER – like grade tungsten samples were exposed in linear plasma devices to two different ranges of deuterium ion flux densities (high: 3.5–7 · 10{sup 23} D{sup +}/m{sup 2} s and low: 9 · 10{sup 21} D{sup +}/m{sup 2} s). Particle fluence and ion energy, respectively 10{sup 26} D{sup +}/m{sup 2} and ∼38 eV were kept constant in all cases. The experiments were performed at three different surface temperatures 530 K, 630 K and 870 K. Experimental results concerning the deuterium retention and surface modifications of low flux exposure confirmed previous investigations. At temperatures 530 K and 630 K, deuterium retention was higher at lower flux density due to the longer exposure time (steady state plasma operation) and a consequently deeper diffusion range. At 870 K, deuterium retention was found to be higher at high flux density according to the thermal desorption spectroscopy (TDS) measurements. While blisters were completely absent at low flux density, small blisters of about 40–50 nm were formed at high flux density exposure. At the given conditions, a relation between deuterium retention and blister formation has been found which has to be considered in addition to deuterium trapping in defects populated by diffusion.

  5. Estimation of the lifetime of small helium bubbles near tungsten surfaces -- a methodological study

    CERN Document Server

    Cui, Jiechao; Hou, Qing

    2016-01-01

    Under low energy and high flux/fluence irradiation of helium (He) atoms, the formation and bursting of He bubbles on tungsten (W) surfaces play important roles in the morphological evolution of component surfaces and impurity production in fusion reactors. Microscopically, the bursting of He bubbles is a stochastic process, and He bubbles have statistically average lifetimes. In the present paper, a molecular dynamics-based method was developed to extract, for the first time, the lifetime of He bubbles near tungsten surfaces. It was found that He bubble bursting can be treated as an activated event. Its occurrence frequency or, equivalently, the average lifetime of bubbles follows the Arrhenius equation. For a given bubble size, the activation energy exhibits a good linear dependence with the depth, and the pre-exponential factor obeys the Meyer-Nedle rule. These results are useful for establishing a model in multi-scale simulations of impurity production in the fusion plasma and of the morphological evolutio...

  6. Observations of orientation dependence of surface morphology in tungsten implanted by low energy and high flux D plasma

    DEFF Research Database (Denmark)

    Xu, H.Y.; Zhang, Yubin; Yuan, Y.

    2013-01-01

    Surface modification by formation of blistering and nanostructures with pronounced orientation dependence has been observed on surfaces of rolled tungsten and recrystallized tungsten after exposure to a low energy (38 eV) deuterium (D) plasma with a high flux of 1024 m-2 s -1. The correlation...... between blisters and nanostructures with grain orientation was examined on recrystallized tungsten to exclude the influence of defects introduced during plastic deformation on the pattern of surface modification. The amount of blistering changed from the most in grains oriented close to 〈1 1 1...... near the 〈0 1 1〉 corner, and spongy structures for grains near the 〈0 0 1〉 corner. Possible reasons for the orientation dependence of both the blisters and nanostructures are discussed. © 2013 Elsevier B.V. All rights reserved....

  7. Wear behaviour of laser surface hardfaced steels with tungsten carbide powder injection

    Energy Technology Data Exchange (ETDEWEB)

    Pantelis, D. (Ecole Centrale Paris, Lab. MSS/MAT, 92 - Chatenay-Malabry (France)); Michaud, H. (IRSID-UNIEUX, Coatings Service, USINOR-SACILOR Group, 42 - Firminy (France)); Freitas, M. de (Inst. Superior Tecnico, CEMUL (INIC), Lisboa (Portugal))

    1993-05-28

    The use of a laser beam for surface alloying with carbide powder injection gives thick coatings (750-800 [mu]m) without defects such as porosity and cracks. A precise correlation between the treatment parameters and the phenomena induced during the laser-material interaction is established. Optimum treatment conditions are found and applied to laser alloying of 4140 and high speed M2 tool steels with tungsten carbide injection. The laser surface treated zones, for both steels, are strongly alloyed and present a very fine microstructure with various morphologies and very high average values of the microhardness (900 HV 50 gf and 1200 HV 50 gf) compared with those of the substrates (300 HV 50 gf and 250 HV 50 gf respectively). Friction and wear tests (using a plane-ring experimental device), revealed that the laser surface coatings on both steels present wear resistances considerably higher than that of a conventional plasma-sprayed coating. (orig.)

  8. Influence of tungsten microstructure and ion flux on deuterium plasma-induced surface modifications and deuterium retention

    NARCIS (Netherlands)

    Buzi, L.; De Temmerman, G.; Unterberg, B.; M. Reinhart,; Dittmar, T.; Matveev, D.; Linsmeier, C.; Breuer, U.; Kreter, A.; Van Oost, G.

    2015-01-01

    The influence of surface temperature, particle flux density and material microstructure on the surface morphology and deuterium retention was studied by exposing tungsten targets (20 μm and 40 μm grain size) to deuterium plasma at the same particle fluence (1026 m−2) and i

  9. Influence of near-surface blisters on deuterium transport in tungsten

    Science.gov (United States)

    Bauer, J.; Schwarz-Selinger, T.; Schmid, K.; Balden, M.; Manhard, A.; von Toussaint, U.

    2017-08-01

    The effect of near-surface blisters on deuterium transport in tungsten is studied by means of nuclear reaction analysis (NRA) and scanning electron microscopy (SEM). Gentle deuterium plasma loading of different durations and subsequent NRA depth profiling is performed in heavily pre-blistered and unblistered areas on self-damaged tungsten samples. Comparison of the deuterium depth profiles reveals a considerable reduction of the deuterium transport into the bulk due to the presence of near-surface blisters. SEM and NRA results identify the enhanced re-emission of deuterium from the sample due to open blisters as the underlying mechanism, which reduces the deuterium flux into the bulk. Based on a simple analytical hydrogen retention model, the re-emitted deuterium flux by open blisters is determined to be 80% of the implanted deuterium flux in the present conducted experiment. In addition, the deuterium flux into the bulk is reduced by 60% compared to the unblistered case. Hence the presence of blisters is not a general disadvantage in the context of retention, but can be beneficial in slowing down the build up of a certain hydrogen inventory and in reducing the permeation flux.

  10. The effect of vanadium-carbon monolayer on the adsorption of tungsten and carbon atoms on tungsten-carbide (0001 surface

    Directory of Open Access Journals (Sweden)

    Moitra A.

    2011-01-01

    Full Text Available We report a first-principles calculations to study the effect of a vanadium-carbon (VC monolayer on the adsorption process of tungsten (W and carbon (C atoms onto tungsten-carbide (WC (0001 surface. The essential configuration for the study is a supercell of hexagonal WC with a (0001 surface. When adding the VC monolayer, we employed the lowest energy configuration by examining various configurations. The total energy of the system is computed as a function of the W or C adatoms’ height from the surface. The adsorption of a W and C adatom on a clean WC (0001 surface is compared with that of a W and C adatom on a WC (0001 surface with VC monolayer. The calculations show that the adsorption energy increased for both W and C adatoms in presence of the VC monolayer. Our results provide a fundamental understanding that can explain the experimentally observed phenomena of inhibited grain growth during sintering of WC or WC-Co powders in presence of VC.

  11. Effect of neon plasma pre-irradiation on surface morphology and deuterium retention of tungsten

    NARCIS (Netherlands)

    Cheng, L.; De Temmerman, G.; van Emmichoven, P. A. Zeijlma; Ji, G.; Zhou, H. B.; Wang, B.; Yuan, Y.; Zhang, Y.; Lu, G. H.

    2015-01-01

    Neon and deuterium plasma irradiation of polycrystalline tungsten targets have been performed at high fluxes of ∼1024 ions m−2 s−1 to study the interaction of neon with tungsten and the influence of neon on deuterium retention. Tungsten exposure to neon plasma leads to the

  12. Tungsten oxide thin film exposed to low energy He plasma: Evidence for a thermal enhancement of the erosion yield

    Science.gov (United States)

    Hijazi, H.; Addab, Y.; Maan, A.; Duran, J.; Donovan, D.; Pardanaud, C.; Ibrahim, M.; Cabié, M.; Roubin, P.; Martin, C.

    2017-02-01

    Nanocrystalline tungsten oxide thin films (about 75 nm in thickness) produced by thermal oxidation of tungsten substrates were exposed to low energy He plasma (≈20 eV/He) with a flux of 2.5 × 1018 m-2 s-1 at two temperatures: room temperature and 673 K. The structure and morphology modifications which occur after this He bombardment and annealing treatments was studied using Raman spectroscopy and transmission electron microscopy. Due to the low fluence (4 × 1021 m-2) and low ion energy, we have observed only few morphology modifications after He plasma exposure at room temperature. On the contrary, at 673 K, a change in the layer color is observed associated to an important erosion. Detailed analyses before/after exposure and before/after annealing allow us to describe the He interaction with the oxide layer, its erosion and structural modification at the atomic and micrometer scale.

  13. Physical Properties of Macroporous Tungsten Oxide Thin Films and Their Impact on the Photocurrent Density

    Directory of Open Access Journals (Sweden)

    I. Riech

    2013-01-01

    Full Text Available Tungsten trioxide (WO3 films were prepared using polystyrene spheres of two different diameters as a template in order to create porous layers. X-ray diffraction data and electron microscopy images show that annealed films exhibit polycrystalline structure with monoclinic phase and pore size of approximately hundred nanometers. The optical band gap energies have been determined by photoacoustic spectroscopy as 3.17 eV, and this value was not affected by sample morphology. Low temperature photoluminescence spectra exhibit broad band in the blue region. Deconvolutions of PL spectra show that there are two transitions which intensity depends on thin film pore size. We discuss the possible origin of this emissions associated with oxygen vacancies and surface states. A comparative study of the WO3 films used as photoanodes is presented and correlated with PL results.

  14. Adsorption and Desorption of Cetyl Pyridinium Ions at a Tungsten-Coated Silicon Wafer Surface.

    Science.gov (United States)

    Free; Shah

    1998-12-01

    The use of surfactants to reduce the number of residual particles following chemical-mechanical planarization during integrated circuit manufacturing is relatively new. Recent results using cetyl pyridinium chloride and other cationic surfactant molecules show that surfactants are very effective in reducing the number density of residual polishing particles. The effectiveness of the surfactants is related to their ability to adsorb on the substrate surface. The contact angle and spectroscopic data in this study show that cetyl pyridinium ions can be readily adsorbed or desorbed from a chemical-vapor-deposited tungsten surface by controlling the concentration of other cations in solution. The mechanism for surfactant desorption is likely a competition between the cationic surfactant ions and other cations in solution. Copyright 1998 Academic Press.

  15. Characterization of Tungsten Oxide Thin Films Produced by Spark Ablation for NO2 Gas Sensing.

    Science.gov (United States)

    Isaac, Nishchay A; Valenti, Marco; Schmidt-Ott, Andreas; Biskos, George

    2016-02-17

    Tungsten oxides (WOx) thin films are currently used in electro-chromic devices, solar-cells and gas sensors as a result of their versatile and unique characteristics. In this study, we produce nanoparticulate WOx films by spark ablation and focused inertial deposition, and demonstrate their application for NO2 sensing. The primary particles in the as-deposited film samples are amorphous with sizes ranging from 10 to 15 nm. To crystallize the samples, the as-deposited films are annealed at 500 °C in air. This also caused the primary particles to grow to 30-50 nm by sintering. The morphologies and crystal structures of the resulting materials are studied using scanning and transmission electron microscopy and X-ray diffraction, whereas information on composition and oxidation states are determined by X-ray photoemission spectroscopy. The observed sensitivity of the resistance of the annealed films is ∼100 when exposed to 1 ppm of NO2 in air at 200 °C, which provides a considerable margin for employing them in gas sensors for measuring even lower concentrations. The films show a stable and repeatable response pattern. Considering the numerous advantages of spark ablation for fabricating nanoparticulate thin films, the results reported here provide a promising first step toward the production of high sensitivity and high accuracy sensors.

  16. On the energetics of cation ordering in tungsten-bronze-type oxides.

    Science.gov (United States)

    Olsen, Gerhard Henning; Selbach, Sverre Magnus; Grande, Tor

    2015-11-11

    Oxides with the tetragonal tungsten bronze (TTB) structure are well-known ferroelectrics that show a large flexibility both with respect to chemical composition and cation ordering. Two of the simplest compounds in this family are lead metaniobate (PbNb2O6 or PN) and strontium barium niobate (SrxBa1-xNb2O6 or SBN). While PN is a classical ferroelectric, SBN goes from ferroelectric to relaxor-like with increasing Sr content, with a polar direction different from that in PN. The partially occupied sublattices in both systems give the possibility for cation order-disorder phenomena, but it is not known if or how this influences the polarization and ferroelectricity. Here, we use density functional theory (DFT) calculations to investigate how cation and cation vacancy ordering influences the energetics of these compounds, by comparing both the energy differences and the barriers for transition between different cation configurations. We extend the thermodynamic model of O'Neill and Navrotsky, originally developed for cation interchange in spinels, to describe the order-disorder phenomenology in TTB oxides. The influence of order-disorder processes on the functional properties of PN and SBN is discussed.

  17. Modification of Shape Memory Polymer Foams Using Tungsten, Aluminum Oxide, and Silicon Dioxide Nanoparticles.

    Science.gov (United States)

    Hasan, S M; Thompson, R S; Emery, H; Nathan, A L; Weems, A C; Zhou, F; Monroe, M B B; Maitland, D J

    Shape memory polymer (SMP) foams were synthesized with three different nanoparticles (tungsten, silicon dioxide, and aluminum oxide) for embolization of cerebral aneurysms. Ultra-low density SMP foams have previously been utilized for aneurysm occlusion, resulting in a rapid, stable thrombus. However, the small cross section of foam struts can potentially lead to fracture and particulate generation, which would be a serious adverse event for an embolic device. The goal of this study was to improve the mechanical properties of the system by physically incorporating fillers into the SMP matrix. Thermal and mechanical characterization suggested minimal changes in thermal transition of the SMP nanocomposites and improved mechanical strength and toughness for systems with low filler content. Actuation profiles of the three polymer systems were tuned with filler type and content, resulting in faster SMP foam actuation for nanocomposites containing higher filler content. Additionally, thermal stability of the SMP nanocomposites improved with increasing filler concentration, and particulate count remained well below accepted standard limits for all systems. Extraction studies demonstrated little release of silicon dioxide and aluminum oxide from the bulk over 16 days. Tungstun release increased over the 16 day examination period, with a maximum measured concentration of approxiately 2.87 μg/mL. The SMP nanocomposites developed through this research have the potential for use in medical devices due to their tailorable mechanical properties, thermal resisitivity, and actuation profiles.

  18. China’s Tungsten Resources Supply and Demand Situation

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    <正>China’s production of tungsten products mainly includes tungsten ore concentrates and a series of intermediate tungsten products such as ferro-tungsten, tungstic acid, sodium tungstate, calcium tungstate, tungsten trioxide, tungsten blue oxide, ammonium paratungstate, ammonium metatungstate, tungsten powder etc. During the period between 1949-1997, China produced 1.85 million tons of tungsten ore concentrates, in which 873,000 tons were exported with US$3.1 billion in value.

  19. Role of Silicon Carbide in Phase-Evolution and Oxidation Behaviors of Pulse Electrodeposited Nickel-Tungsten Coating

    Science.gov (United States)

    Sribalaji, M.; Asiq Rahman, O. S.; Arun Kumar, P.; Suresh Babu, K.; Wasekar, Nitin P.; Sundararajan, G.; Keshri, Anup Kumar

    2017-01-01

    Silicon carbide (SiC) was reinforced in the pulse electrodeposited nickel-tungsten (Ni-W) coatings deposited on the steel substrate, and isothermal oxidation test was performed at 1273 K (1000 °C) for 24 hours. Addition of just 2 vol pct of SiC showed 26 pct increase in the relative oxidation resistance of Ni-W coating. The increased oxidation resistance was attributed to the phase evolution (SiO2, Cr2O3, CrSi2, Ni2SiO4, Cr7C3, Cr3C2, and Cr3Si), which suppressed the spallation of the oxide scale in Ni-W-2 vol pct SiC. The presence of Fe2O3 phase in the oxidized Ni-W coating was mainly responsible for the major multiple spallations at the interface and in the bulk, which resulted in the degradation of oxidation resistance.

  20. Laser cleaning of tungsten ribbon

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Aniruddha, E-mail: nontee65@rediffmail.com [Advanced Fuel Fabrication Facility, Bhabha Atomic Research Centre, Tarapur, Maharashtra, 401504 (India); Sonar, V.R.; Das, D.K.; Bhatt, R.B.; Behere, P.G.; Afzal, Mohd.; Kumar, Arun [Advanced Fuel Fabrication Facility, Bhabha Atomic Research Centre, Tarapur, Maharashtra, 401504 (India); Nilaya, J.P.; Biswas, D.J. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, 400085 (India)

    2014-07-01

    Removal of a thin oxide layer from a tungsten ribbon was achieved using the fundamental, second and third harmonic radiation from a Q- switched Nd-YAG laser. It was found that beyond the threshold, oxide removal was achieved at all wavelengths for a wide range of fluence values. The removal mechanism of the oxide layer was found to be critically dependent on both wavelength and fluence of the incident radiation and has been identified as ejection or sublimation. The un-cleaned and cleaned surfaces were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and atomic force microscopy (AFM). Laser cleaned tungsten ribbons were used in a thermal ionization mass spectrometer (TIMS) to determine isotopic composition of Neodymium atoms.

  1. Synthesis and Characterization of Potentiostatically Electrodeposited Tungsten Oxide Thin Films for Smart Window Application

    Science.gov (United States)

    More, A. J.; Patil, R. S.; Dalavi, D. S.; Suryawanshi, M. P.; Burungale, V. V.; Kim, J. H.; Patil, P. S.

    2017-02-01

    Tungsten oxide (WO3) thin films have been synthesized using electrodeposition in potentiostatic mode and the effect of different deposition potentials on their structural, morphological, optical, and electrochromic (EC) properties investigated. The deposition potential versus saturated calomel electrode (SCE) was varied from -0.35 V to -0.50 V in steps of -0.05 V for 20 min each. The electrodeposited WO3 thin films were characterized using x-ray diffraction analysis, micro-Raman spectroscopy, field-emission scanning electron microscopy, and ultraviolet-visible (UV-Vis) spectrophotometry, revealing amorphous nature with nanograins having average size from 40 nm to 60 nm. The EC performance of the WO3 thin films exhibited response times of 1.35 s for bleaching ( t b) and 3.1 s for coloration ( t c) with excellent reversibility of 64.36%. The highest coloration efficiency of the electrodeposited WO3 thin films was found to be 87.95 cm2/C. The electrochemical reversibility and stability of the WO3 thin films obtained in this study make them promising for use in smart window applications.

  2. Origin of ferroelectric polarization in tetragonal tungsten-bronze-type oxides

    Science.gov (United States)

    Olsen, Gerhard Henning; Aschauer, Ulrich; Spaldin, Nicola A.; Selbach, Sverre Magnus; Grande, Tor

    2016-05-01

    The origin of ferroelectric polarization in tetragonal tungsten-bronze- (TTB-) type oxide strontium barium niobate (SBN) is investigated using first-principles density functional calculations. We study in particular the relationship between the polarization and the cation and vacancy ordering on alkali-earth metal lattice sites. Lattice dynamical calculations for paraelectric structures demonstrate that all cation configurations that can be accommodated in a 1 ×1 ×2 supercell result in a single unstable polar phonon, composed primarily of relative Nb-O displacements along the polar axis, as their dominant instability. The majority of the configurations also have a second octahedral tilt-mode instability which couples weakly to the polar mode. The existence of the tilt mode is strongly dependent on the local cation ordering, consistent with the fact that it is not found experimentally. Our results suggest that ferroelectricity in the SBN system is driven by a conventional second-order Jahn-Teller mechanism caused by the d0 Nb5 + cations, and demonstrate the strong influence of the size of Sr and Ba on the lattice distortions associated with polarization and octahedral tilting. Finally, we suggest a mechanism for the relaxor behavior in Sr-rich SBN based on Sr displacement inside pentagonal channels in the TTB structure.

  3. Stability of the anodic growth porous tungsten oxide in different solutions

    Energy Technology Data Exchange (ETDEWEB)

    Chai, Y.; Yam, F. K.; Hassan, Z. [Nano-Optoelectronic Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia)

    2015-05-15

    This article presents the study of the stability of the anodic growth porous tungsten oxide (WO{sub 3}) film in different solutions. As-anodized films are relatively stable in acidic electrolytes like sulphuric acid (H{sub 2}SO{sub 4}), hydrochloric acid (HCl) but not in oxalic acid. In higher pH solution, rate of dissolution of the WO{sub 3} film is higher. Annealing at 400 °C for 2 h transform the as-grown sample from amorphous phase to the crystalline phase and this significantly improve the stability of the film in high pH solution. Photocurrent measurements reveal that there is no significant difference of the electrolyte used (0.5 M H{sub 2}SO{sub 4}, 0.33 M H{sub 3}PO{sub 4}, 0.1 M sodium sulfate (Na{sub 2}SO{sub 4})) on the photocurrent. As-annealed films exhibit good stablility for the long photoelectrochemical (PEC) measurements (1700 s) in 0.5 M H{sub 2}SO{sub 4} and 0.1 M Na{sub 2}SO{sub 4}. There is no effect on the photocurrent for the variation of the concentration of the acidic solution (H{sub 2}SO{sub 4}). However, lower photocurrent was obtained as the concentration of Na{sub 2}SO{sub 4} was increased.

  4. Photochromic Properties of Tungsten Oxide/Methylcellulose Composite Film Containing Dispersing Agents.

    Science.gov (United States)

    Yamazaki, Suzuko; Ishida, Hiroki; Shimizu, Dai; Adachi, Kenta

    2015-12-02

    Tungsten oxide-based photochromic films which changed reversibly in air between colorless- transparent in the dark and dark blue under UV irradiation were prepared by using methylcellulose as a film matrix and polyols such as ethylene glycol (EG), propylene glycol (PG), and glycerin (Gly) as dispersing agents. Influence of the dispersing agents and water in the films on the photochromic behavior was systematically studied. Under UV irradiation, absorption bands around 640 and 980 nm increased and the coloring rate was the following order: Gly > EG > PG. An increase in the amounts of dispersing agents or water accelerated the coloring rate. By increasing the water content of the film, a new absorption peak appeared at ca. 775 nm and the Raman spectra indicated a shift of W-O-W stretching vibration to lower wavenumber which was due to the formation of hydrogen bonding. All absorption spectra were fit by three Lorentz functions, whose bands were ascribed to various packing of WO6 octahedra. After the light was turned off, the formation of W(5+) was stopped and bleaching occurred by the reaction with O2 in air to recover its original transparent state. We anticipate that the biodegradable photochromic films developed in this study can be applied in recyclable display medium and especially in detachable films for glass windows whose light transmission properties are changed by sunlight, i.e., for usage as an alternative of smart windows without applying voltage.

  5. Effects of thermal treatment on the anodic growth of tungsten oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Chai, Y., E-mail: yqchai85@gmail.com; Tam, C.W.; Beh, K.P.; Yam, F.K.; Hassan, Z.

    2015-08-03

    This work reports the investigation of the effects of thermal treatment on anodic growth tungsten oxide (WO{sub 3}). The increase of the thermal treatment temperature above 400 °C significantly influences WO{sub 3} film where high porosity structure reduces to more compact film. As-grown film is amorphous, which transforms to monoclinic/orthorhombic phase upon annealing at 300–600 °C. With the reducing of porous structure, preferential growth of (002) plane shifts to (020) plane at 600 °C with more than twentyfold increase of peak's intensity compared to the film annealed at 500 °C. Films annealed at low thermal treatment show better ion intercalation and reversibility during electrochemical measurements; however, it has larger optical band gap. Photoelectrochemical measurement reveals that film annealed at 400 °C exhibits the best photocatalytic performance among the films annealed at 300–600 °C. - Highlights: • Porosity of the WO{sub 3} reduces as annealing temperature increases above 400 °C. • As-grown film is amorphous which transforms to monoclinic/orthorhombic upon annealing. • As-grown film shows better ion intercalation in electrochemical process. • Optical band gap of WO{sub 3} reduces as the annealing temperature increases. • Film annealed at 400 °C exhibits best photocatalytic performance.

  6. Molybdenum disulfide catalyzed tungsten oxide for on-chip acetone sensing

    Science.gov (United States)

    Li, Hong; Ahn, Sung Hoon; Park, Sangwook; Cai, Lili; Zhao, Jiheng; He, Jiajun; Zhou, Minjie; Park, Joonsuk; Zheng, Xiaolin

    2016-09-01

    Acetone sensing is critical for acetone leak detection and holds a great promise for the noninvasive diagnosis of diabetes. It is thus highly desirable to develop a wearable acetone sensor that has low cost, miniature size, sub-ppm detection limit, great selectivity, as well as low operating temperature. In this work, we demonstrate a cost-effective on-chip acetone sensor with excellent sensing performances at 200 °C using molybdenum disulfide (MoS2) catalyzed tungsten oxide (WO3). The WO3 based acetone sensors are first optimized via combined mesoscopic nanostructuring and silicon doping. Under the same testing conditions, our optimized mesoporous silicon doped WO3 [Si:WO3(meso)] sensor shows 2.5 times better sensitivity with ˜1000 times smaller active device area than the state-of-art WO3 based acetone sensor. Next, MoS2 is introduced to catalyze the acetone sensing reactions for Si:WO3(meso), which reduces the operating temperature by 100 °C while retaining its high sensing performances. Our miniaturized acetone sensor may serve as a wearable acetone detector for noninvasive diabetes monitoring or acetone leakage detection. Moreover, our work demonstrates that MoS2 can be a promising nonprecious catalyst for catalytic sensing applications.

  7. Multi-Walled Carbon Nanotube-Doped Tungsten Oxide Thin Films for Hydrogen Gas Sensing

    Directory of Open Access Journals (Sweden)

    Adisorn Tuantranont

    2010-08-01

    Full Text Available In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT-doped tungsten oxide (WO3 thin films by means of the powder mixing and electron beam (E-beam evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO3 hydrogen sensor prepared by the E-beam method.

  8. Multi-walled carbon nanotube-doped tungsten oxide thin films for hydrogen gas sensing.

    Science.gov (United States)

    Wongchoosuk, Chatchawal; Wisitsoraat, Anurat; Phokharatkul, Ditsayut; Tuantranont, Adisorn; Kerdcharoen, Teerakiat

    2010-01-01

    In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO(3)) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO(3) thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO(3) hydrogen sensor prepared by the E-beam method.

  9. Gas-chromism in ultrasonic spray pyrolyzed tungsten oxide thin films

    Indian Academy of Sciences (India)

    P S Patil

    2000-08-01

    A simple and inexpensive ultrasonic spray pyrolysis (USP) technique has been employed to deposit tungsten oxide (WO3) thin films by spraying 2.0 mM aqueous ammonium metatungstate solution onto the amorphous glass substrates kept at 250°C. The films were further annealed at 400°C for 4 h in air. X-ray diffraction (XRD) technique was used to determine the crystallinity and to identify the WO3 phases. It was found that the films were sub-stoichiometric, WO3–. To study gas-induced properties, a catalyzing layer of platinum (Pt) was sputtered onto it. The gas-induced electrical and optical properties of Pt/WO3/glass samples were studied and results reported. It was found that electrical resistivity decreased by a factor of 10 within 2 min and stabilized after 15 min, after H2 gas exposure. Similarly the optical transmittance of the samples attenuated from 55% to 10% within 15–20 min. The reversible changes in electrical resistivity and optical transmittance were observed when the samples were exposed to oxygen. The response times and sensitivity of the samples were estimated.

  10. Highly Efficient Near Infrared Photothermal Conversion Properties of Reduced Tungsten Oxide/Polyurethane Nanocomposites

    Directory of Open Access Journals (Sweden)

    Tolesa Fita Chala

    2017-07-01

    Full Text Available In this work, novel WO3-x/polyurethane (PU nanocomposites were prepared by ball milling followed by stirring using a planetary mixer/de-aerator. The effects of phase transformation (WO3 → WO2.8 → WO2.72 and different weight fractions of tungsten oxide on the optical performance, photothermal conversion, and thermal properties of the prepared nanocomposites were examined. It was found that the nanocomposites exhibited strong photoabsorption in the entire near-infrared (NIR region of 780–2500 nm and excellent photothermal conversion properties. This is because the particle size of WO3-x was greatly reduced by ball milling and they were well-dispersed in the polyurethane matrix. The higher concentration of oxygen vacancies in WO3-x contribute to the efficient absorption of NIR light and its conversion into thermal energy. In particular, WO2.72/PU nanocomposites showed strong NIR light absorption of ca. 92%, high photothermal conversion, and better thermal conductivity and absorptivity than other WO3/PU nanocomposites. Furthermore, when the nanocomposite with 7 wt % concentration of WO2.72 nanoparticles was irradiated with infrared light, the temperature of the nanocomposite increased rapidly and stabilized at 120 °C after 5 min. This temperature is 52 °C higher than that achieved by pure PU. These nanocomposites are suitable functional materials for solar collectors, smart coatings, and energy-saving applications.

  11. Hydrothermal Synthesis of Tungsten Oxide Micro/Nanostructures%水热法制备微纳结构氧化钨

    Institute of Scientific and Technical Information of China (English)

    高小青; 饶雪辉; 王吉德; 肖峰; 宿新泰

    2013-01-01

    Tungsten oxides inorganic semiconductor materials have received considerable attention in recent years because of their unique physico-chemical properties and widespread applications in various areas, such as electrochromic (EC) devices, gas sensors, photocatalytic systems, photoelectrochemical devices, and so on. Recently hydrothermal method has been exploited for the preparation of tungsten oxide micro/nanostructures with different sizes and shapes. Combining with our group' s work on the preparation of tungsten oxide micro/ nanomaterials, the progress of preparation of tungsten oxide micro/nanomaterials by hydrothermal method is presented. The key influencing factors, such as the choice of reagents, the reaction time and temperature, are discussed in detail. The development trends of the tungsten oxide micro/nanomaterials fabricated by hydrothermal method are also proposed.%氧化钨(Wox)无机半导体材料因其独特的物理化学性质及在气敏、光催化、电致变色、光致变色和场发射等领域的广泛应用,得到人们的普遍关注.近年来,研究者采用水热法制备出多种不同尺寸和形貌的氧化钨半导体材料.本文结合本课题组在水热法制备WOx粉体方面的最新工作,综述了近十年水热法制备微米及纳米级氧化钨粉体的研究进展,探讨了原料、辅助试剂、表面活性剂、反应时间、反应温度等条件对水热法制备氧化钨粉体材料的影响.最后,对水热法制备氧化钨粉体的发展趋势进行了展望.

  12. Tungsten coatings electro-deposited on CFC substrates from oxide molten salt

    Science.gov (United States)

    Sun, Ningbo; Zhang, Yingchun; Lang, Shaoting; Jiang, Fan; Wang, Lili

    2014-12-01

    Tungsten is considered as plasma facing material in fusion devices because of its high melting point, its good thermal conductivity, its low erosion rate and its benign neutron activation properties. On the other hand, carbon based materials like C/C fiber composites (CFC) have been used for plasma facing materials (PFMs) due to their high thermal shock resistance, light weight and high strength. Tungsten coatings on CFC substrates are used in the JET divertor in the frame of the JET ITER-like wall project, and have been prepared by plasma spray (PS) and other techniques. In this study, tungsten coatings were electro-deposited on CFC from Na2WO4-WO3 molten salt under various deposition parameters at 900 °C in air. In order to obtain tungsten coatings with excellent performance, the effects of pulse duration ratio and pulse current density on microstructures and crystal structures of tungsten coatings were investigated by X-ray diffraction (XRD, Rigaku Industrial Co., Ltd., D/MAX-RB) and a scanning electron microscope (SEM, JSM 6480LV). It is found that the pulsed duration ratio and pulse current density had a significant influence on tungsten nucleation and electro-crystallization phenomena. SEM observation revealed that intact, uniform and dense tungsten coatings formed on the CFC substrates. Both the average grain size and thickness of the coating increased with the pulsed current density. The XRD results showed that the coatings consisted of a single phase of tungsten with the body centered cubic (BCC) structure. The oxygen content of electro-deposited tungsten coatings was lower than 0.05%, and the micro-hardness was about 400 HV.

  13. Deuterium supersaturation in low-energy plasma-loaded tungsten surfaces

    Science.gov (United States)

    Gao, L.; Jacob, W.; von Toussaint, U.; Manhard, A.; Balden, M.; Schmid, K.; Schwarz-Selinger, T.

    2017-01-01

    Fundamental understanding of hydrogen-metal interactions is challenging due to a lack of knowledge on defect production and/or evolution upon hydrogen ingression, especially for metals undergoing hydrogen irradiation with ion energy below the displacement thresholds reported in literature. Here, applying a novel low-energy argon-sputter depth profiling method with significantly improved depth resolution for tungsten (W) surfaces exposed to deuterium (D) plasma at 300 K, we show the existence of a 10 nm thick D-supersaturated surface layer (DSSL) with an unexpectedly high D concentration of ~10 at.% after irradiation with ion energy of 215 eV. Electron back-scatter diffraction reveals that the W lattice within this DSSL is highly distorted, thus strongly blurring the Kikuchi pattern. We explain this strong damage by the synergistic interaction of energetic D ions and solute D atoms with the W lattice. Solute D atoms prevent the recombination of vacancies with interstitial W atoms, which are produced by collisions of energetic D ions with W lattice atoms (Frenkel pairs). This proposed damaging mechanism could also be active on other hydrogen-irradiated metal surfaces. The present work provides deep insight into hydrogen-induced lattice distortion at plasma-metal interfaces and sheds light on its modelling work.

  14. Simultaneous impact of neutron irradiation and sputtering on the surface structure of self–damaged ITER–grade tungsten

    Directory of Open Access Journals (Sweden)

    A. I. Belyaeva

    2014-07-01

    Full Text Available Simultaneous effects of neutron irradiation and long–term sputtering on the surface relief of ITER–grade tungsten were studied. The effects of neutron–induced displacement damage have been simulated by irradiation of tungsten target with W6 + ions of 20 MeV energy. Ar+ ions with energy 600 eV were used as imitation of charge exchange atoms in ITER. The surface relief was studied after each sputtering act. The singularity in the WJ–IG surface relief was ascertained experimentally at the first time, which determines the law of roughness extension under sputtering. As follows from the experimental data, the neutron irradiation has not to make a decisive additional contribution in the processes developing under impact of charge exchange atoms only.

  15. Chemical etching of Tungsten thin films for high-temperature surface acoustic wave-based sensor devices

    Energy Technology Data Exchange (ETDEWEB)

    Spindler, M., E-mail: m.spindler@ifw-dresden.de [IFW Dresden, SAWLab Saxony, P.O. Box 270116, D-01171 Dresden (Germany); Herold, S.; Acker, J. [BTU Cottbus – Senftenberg, Faculty of Sciences, P.O. Box 101548, 01968 Senftenberg (Germany); Brachmann, E.; Oswald, S.; Menzel, S.; Rane, G. [IFW Dresden, SAWLab Saxony, P.O. Box 270116, D-01171 Dresden (Germany)

    2016-08-01

    Surface acoustic wave devices are widely used as wireless sensors in different application fields. Recent developments aimed to utilize those devices as temperature sensors even in the high temperature range (T > 300 °C) and in harsh environmental conditions. Therefore, conventional materials, which are used for the substrate and for the interdigital transducer finger electrodes such as multilayers or alloys based on Al or Cu have to be exchanged by materials, which fulfill some important criteria regarding temperature related effects. Electron beam evaporation as a standard fabrication method is not well applicable for depositing high temperature stable electrode materials because of their very high melting points. Magnetron sputtering is an alternative deposition process but is also not applicable for lift-off structuring without any further improvement of the structuring process. Due to a relatively high Ar gas pressure of about 10{sup −1} Pa, the sidewalls of the photoresist line structures are also covered by the metallization, which subsequently prevents a successful lift-off process. In this study, we investigate the chemical etching of thin tungsten films as an intermediate step between magnetron sputtering deposition of thin tungsten finger electrodes and the lift-off process to remove sidewall covering for a successful patterning process of interdigital transducers. - Highlights: • We fabricated Tungsten SAW Electrodes by magnetron sputtering technology. • An etching process removes sidewall covering of photoresist, which allows lift-off. • Tungsten etching rates based on a hydrogen peroxide solutions were determined.

  16. Study of tungsten surface interaction with plasma streams at DPF-1000U

    Directory of Open Access Journals (Sweden)

    Ladygina Marina S.

    2015-06-01

    Full Text Available In this note experimental studies of tungsten (W samples irradiated by intense plasma-ion streams are reported. Measurements were performed using the modified plasma focus device DPF-1000U equipped with an axial gas-puffing system. The main diagnostic tool was a Mechelle®900 optical spectrometer. The electron density of a freely propagating plasma stream (i.e., the plasma stream observed without any target inside the vacuum chamber was estimated on the basis of the half-width of the Dβ spectral line, taking into account the linear Stark effect. For a freely propagating plasma stream the maximum electron density amounted to about 1.3 × 1017 cm−3 and was reached during the maximum plasma compression. The plasma electron density depends on the initial conditions of the experiments. It was thus important to determine first the plasma flow characteristics before attempting any target irradiation. These data were needed for comparison with plasma characteristics after an irradiation of the investigated target. In fact, spectroscopic measurements performed during interactions of plasma streams with the investigated W samples showed many WI and WII spectral lines. The surface erosion was determined from mass losses of the irradiated samples. Changes on the surfaces of the irradiated samples were also investigated with an optical microscope and some sputtering and melting zones were observed.

  17. Tungsten toxicity.

    Science.gov (United States)

    Witten, Mark L; Sheppard, Paul R; Witten, Brandon L

    2012-04-05

    There is emerging evidence that tungsten has toxic health effects. We summarize the recent tungsten toxicity research in this short review. Tungsten is widely used in many commercial and military applications because it has the second highest melting temperature of any element. Consequently, it is important to elucidate the potential health effects of tungsten.

  18. Impact of helium ion energy modulation on tungsten surface morphology and nano-tendril growth

    Science.gov (United States)

    Woller, K. B.; Whyte, D. G.; Wright, G. M.

    2017-06-01

    Time-modulated helium (He) ion energy (e.g. V Bias  =  -50  +  25·sin(2πf RF · t), f RF  =  13.56 MHz) is demonstrated to strongly affect the development of tungsten (W) surface morphology that results from He plasma irradiation in the DIONISOS linear plasma experiment. Nano-tendril bundles (NTBs), which appear as isolated ‘islands’ of nano-tendrils, can rapidly grow on an otherwise smooth W surface. This is in contrast to previously seen full-surface coverage of nano-tendril growth known as ‘fuzz’. When tall NTBs form, less than 15% of the surface contains nano-tendrils. The NTB surface coverage changes with growth conditions and the total volume of nano-tendrils in the NTBs is observed to be up to a factor of 16 larger than when fuzz is grown. This indicates that long-range W surface transport underlies nano-tendril formation. Surface temperature 870-1220 K, the DC bias potential  -30 to  -70 V, and the ion flux density 4.4  ×  1021-1.1  ×  1022 He · m-2 · s-1 are varied in the experiments. NTBs form at similar conditions as fuzz with the critical difference being the RF modulation of the ion energy bombarding the W, another indication of the importance of W surface transport. Mass loss measurements indicate net erosion with a yield of 1-8  ×  10-4 W/He when NTBs form; erosion that is not attributable to chemical or physical sputtering by He or impurities in the plasma. The erosion is correlated to the NTB growth, based on post-exposure inspection by electron microscopy indicating that NTBs are prone to loss from the surface. NTB growth is compared to the empirical growth-erosion model of fuzz, showing NTBs grow up to a factor of 100 times taller than the expected fuzz layer depth under DC bias conditions. Insights into nano-tendril growth provided by this new growth regime are discussed. Strategies to mitigate W fuzz growth may inadvertently result in rapid localized nano-tendril bundle

  19. Performance of an electrochromic window based on polyaniline, prussian blue and tungsten oxide

    Energy Technology Data Exchange (ETDEWEB)

    Jelle, Bjoern Petter; Hagen, Georg [Department of Electrochemistry, Norwegian University of Science and Technology NTNU, N-7034 Trondheim (Norway)

    1999-07-15

    In our laboratory various electrochromic windows (ECWs) have been investigated using mainly tungsten oxide (WO{sub 3}), polyaniline (PANI) and prussian blue (PB) as electrochromic materials in combination with poly(2-acrylamido-2-methyl-propane-sulphonic acid) (PAMPS) as a solid proton-conducting electrolyte. The ECWs have been characterized by AC-impedance, linear sweep voltammetry and spectroelectrochemical studies in the 290-3300 nm spectral region. The ECWs have the following general multilayered structure: Glass/ITO/EC1/IC/EC2/ITO/Glass, where ITO=indium oxide doped with tin, IC=ionic conductor, EC1 is either PANI or PANI including PB, and EC2 is WO{sub 3}. The best of these ECWs has been able to regulate up to 56% (typical 50%) of the transmission of the total solar energy in the 290-3300 nm spectral range. The combination of the two electrochromic materials PANI and PB has been shown to be mutually beneficial in such a way that the coloration of the window is enhanced by the addition of a layer of PB onto PANI, while the adhesion of PB is improved by the presence of PANI. The energy consumption of the ECW is about 0.01 Wh/m{sup 2} for one complete cycle (-1.8 V/1.2 V). The switching time for 90% colouring/bleaching is typically 10-30 s. A PANI/PB//WO{sub 3} window has been operated for about 50 days (=3700 complete cycles) without substantial loss of transmission regulation, though with an increase in switching time (10 min.). Spectra from individual layers in the ECWs have been recorded by making holes in one or two of the electrochromic layers. In this way (the hole method), it has been possible to study the transmission regulation properties for each electrochromic material separately in complete solid state windows. In addition, spectra for complete windows have been simulated by adding contributions from individual electrochromic layers

  20. Scandia doped tungsten matrix for impregnated cathode

    Institute of Scientific and Technical Information of China (English)

    WANG Jinshu; WANG Yanchun; LIU Wei; LI Hongyi; ZHOU Meiling

    2008-01-01

    As a matrix for Sc-type impregnated cathode,scandia doped tungsten with a uniform ldistribution of SC2O3 was obtained by powder metallurgy combined with the liquid-solid doping method.The microstructure and composition of the powder and the anti-ion bombardment behavior of scandium in the matrix were studied by means of SEM,EDS,XRD,and in-situ AES methods.Tungsten powder covered with scandium oxide,an ideal scandium oxide-doped tungsten powder for the preparation of Sc-type impregnated cathode,was obtained using the liquid-solid doping method.Compared with the matrix prepared with the mechanically mixed powder of tungsten and scandium oxide,SC2O3-W matrix prepared with this kind of powder had smaller grain size and uniform distribution of scandium.Sc on the surface of Sc2O3 doped tungsten mauix had good high temperature stability and good anti-ion bombardment capability.

  1. Large-area alignment of tungsten oxide nanowires over flat and patterned substrates for room-temperature gas sensing.

    Science.gov (United States)

    Cheng, Wei; Ju, Yanrui; Payamyar, Payam; Primc, Darinka; Rao, Jingyi; Willa, Christoph; Koziej, Dorota; Niederberger, Markus

    2015-01-02

    Alignment of nanowires over a large area of flat and patterned substrates is a prerequisite to use their collective properties in devices such as gas sensors. In this work, uniform single-crystalline ultrathin W18 O49 nanowires with diameters less than 2 nm and aspect ratios larger than 100 have been synthesized, and, despite their flexibility, assembled into thin films with high orientational order over a macroscopic area by the Langmuir-Blodgett technique. Alignment of the tungsten oxide nanowires was also possible on top of sensor substrates equipped with electrodes. Such sensor devices were found to exhibit outstanding sensitivity to H2 at room temperature.

  2. Combined effects of crystallography, heat treatment and surface polishing on blistering in tungsten exposed to high-flux deuterium plasma

    Science.gov (United States)

    Zayachuk, Y.; Tanyeli, I.; Van Boxel, S.; Bystrov, K.; Morgan, T. W.; Roberts, S. G.

    2016-08-01

    For tungsten exposed to low-energy hydrogen-plasmas, it has been thought that grains with surface normal are most susceptible to blistering while those with surface normal are virtually impervious to it. Here, we report results showing that non-uniformity of blister distribution depends on the state of the surface due to polishing. In electrochemically polished material blisters appear on the grains with all orientations, while in mechanically polished material blister-free areas associated with particular orientations emerge. On the other hand, blistering is shown to have a strong dependence on the level of deformation within particular grains in partially recrystallized material.

  3. INVESTIGATION OF AES AND XPS FOR THE ION BOMBARDED CARBON FILMS ON THE SURFACE OF TUNGSTEN ALLOY%离子束轰击钨合金表面碳膜的AES和XPS分析

    Institute of Scientific and Technical Information of China (English)

    李俊; 高剑; 张一云; 吴丽萍; 黄宁康; 赵纯培

    2000-01-01

    Tungsten alloy with special properties is a useful material in medical and weapon devices. Surface modification of ion technique is used to improve the surface hardness and wear resistance of tungsten alloy, where carbon films deposited with magnetron sputtering on the surface of tungsten alloy were bombarded by ion beam with different species AES and XPS analyses for these speciment show that tungsten carbide and tungsten nitride were formed due to N+ bombardment. Which is beneficial to the Surface hardness and wear resistance of tungsten alloy,but no carbide or no nitride as above with other ion species. Again,ion bombardness leads to mixing between the carbon and tungsten alloy hence improve the adhere of carbon film to the substrate.

  4. Magnetic heating properties and neutron activation of tungsten-oxide coated biocompatible FePt core-shell nanoparticles.

    Science.gov (United States)

    Seemann, K M; Luysberg, M; Révay, Z; Kudejova, P; Sanz, B; Cassinelli, N; Loidl, A; Ilicic, K; Multhoff, G; Schmid, T E

    2015-01-10

    Magnetic nanoparticles are highly desirable for biomedical research and treatment of cancer especially when combined with hyperthermia. The efficacy of nanoparticle-based therapies could be improved by generating radioactive nanoparticles with a convenient decay time and which simultaneously have the capability to be used for locally confined heating. The core-shell morphology of such novel nanoparticles presented in this work involves a polysilico-tungstate molecule of the polyoxometalate family as a precursor coating material, which transforms into an amorphous tungsten oxide coating upon annealing of the FePt core-shell nanoparticles. The content of tungsten atoms in the nanoparticle shell is neutron activated using cold neutrons at the Heinz Maier-Leibnitz (FRMII) neutron facility and thereby transformed into the radioisotope W-187. The sizeable natural abundance of 28% for the W-186 precursor isotope, a radiopharmaceutically advantageous gamma-beta ratio of γβ≈30% and a range of approximately 1mm in biological tissue for the 1.3MeV β-radiation are promising features of the nanoparticles' potential for cancer therapy. Moreover, a high temperature annealing treatment enhances the magnetic moment of nanoparticles in such a way that a magnetic heating effect of several degrees Celsius in liquid suspension - a prerequisite for hyperthermia treatment of cancer - was observed. A rise in temperature of approximately 3°C in aqueous suspension is shown for a moderate nanoparticle concentration of 0.5mg/ml after 15min in an 831kHz high-frequency alternating magnetic field of 250Gauss field strength (25mT). The biocompatibility based on a low cytotoxicity in the non-neutron-activated state in combination with the hydrophilic nature of the tungsten oxide shell makes the coated magnetic FePt nanoparticles ideal candidates for advanced radiopharmaceutical applications.

  5. The Effect of Nitrogen Surface Ligands on Propane Metathesis: Design and Characterizations of N-modified SBA15-Supported Schrock-type Tungsten Alkylidyne

    KAUST Repository

    Eid, Ahmed A.

    2014-04-01

    Catalysis, which is primarily a molecular phenomenon, is an important field of chemistry because it requires the chemical conversion of molecules into other molecules. It also has an effect on many fields, including, but not limited to, industry, environment and life Science[1]. Surface Organometallic Chemistry is an effective methodology for Catalysis as it imports the concept and mechanism of organometallic chemistry, to surface science and heterogeneous catalysis. So, it bridges the gap between homogenous and heterogeneous catalysis[1]. The aim of the present research work is to study the effect of Nitrogen surface ligands on the activity of Alkane, Propane in particular, metathesis. Our approach is based on the preparation of selectively well-defined group (VI) transition metal complexes supported onto mesoporous materials, SBA15 and bearing amido and/or imido ligands. We choose nitrogen ligands because, according to the literature, they showed in some cases better catalytic properties in homogenous catalysis in comparison with their oxygen counterparts[2]. The first section covers the modification of a highly dehydroxylated SBA15 surface using a controlled ammonia treatment. These will result in the preparation of two kind of Nitrogen surface ligands: -\\tOne with vicinal silylamine/silanol, (≡SiNH2)(≡SiOH), noted [N,O]SBA15 and, -\\tAnother\\tone\\twith\\tvicinal\\tbis-silylamine moieties (≡SiNH2)2, noted [N,N]SBA15[3]. The second section covers the reaction of Schrock type Tungsten Carbyne [W(≡C- tBu)(CH2-tBu)3] with those N-surface ligands and their characterizations by FT-IR, multiple quantum solid state NMR (1H, 13C), elemental analysis and gas phase analysis. The third section covers the generation of the active site, tungsten hydride species. Their performance toward propane metathesis reaction using the dynamic reactor technique PID compared toward previous well-known catalysts supported on silica oxide or mesoporous materials[4]. A fairly good

  6. Effect of oxygen vacancies on the electronic and optical properties of tungsten oxide from first principles calculations

    Science.gov (United States)

    Mehmood, Faisal; Pachter, Ruth; Murphy, Neil R.; Johnson, Walter E.; Ramana, Chintalapalle V.

    2016-12-01

    In this work, we investigated theoretically the role of oxygen vacancies on the electronic and optical properties of cubic, γ-monoclinic, and tetragonal phases of tungsten oxide (WO3) thin films. Following the examination of structural properties and stability of the bulk tungsten oxide polymorphs, we analyzed band structures and optical properties, applying density functional theory (DFT) and GW (Green's (G) function approximation with screened Coulomb interaction (W)) methods. Careful benchmarking of calculated band gaps demonstrated the importance of using a range-separated functional, where results for the pristine room temperature γ-monoclinic structure indicated agreement with experiment. Further, modulation of the band gap for WO3 structures with oxygen vacancies was quantified. Dielectric functions for cubic WO3, calculated at both the single-particle, essentially time-dependent DFT, as well as many-body GW-Bethe-Salpeter equation levels, indicated agreement with experimental data for pristine WO3. Interestingly, we found that introducing oxygen vacancies caused appearance of lower energy absorptions. A smaller refractive index was indicated in the defective WO3 structures. These predictions could lead to further experiments aimed at tuning the optical properties of WO3 by introducing oxygen vacancies, particularly for the lower energy spectral region.

  7. Micro-structural, electrical and spectroscopic investigations of pulsed laser ablated palladium incorporated nanostructured tungsten oxide films.

    Science.gov (United States)

    Lethy, K J; Beena, D; Pillai, V P Mahadevan; Suresh, K A

    2009-09-01

    Pure and Pd incorporated (0.5, 1 and 5 wt%) WO3 films are prepared on quartz substrates using pulsed laser ablation (PLD) technique in an oxygen ambient of 0.12 mbar, at a substrate temperature (Ts) of 873 K. Palladium incorporation effects on the microstructure, optical and electrical properties of tungsten oxide films are systematically investigated using techniques like X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), micro-Raman spectroscopy, UV-Vis absorption spectroscopy and temperature dependent electrical resistivity measurements. The micro-structural analysis by XRD and micro-Raman indicates that Pd addition can perturb the tungsten oxide lattice and suppress the grain growth. Optical band gap values of the films increases from 3.17 eV for pure WO3 to 3.29 eV for 5 wt% Pd incorporated WO3 films. All the films present high transparency in the visible spectral range. The electrical resistivity studies of the pure and Pd incorporated films done at room temperature and for the range of temperature; 170-450 K reveal that Pd addition can lower the resistivity of the WO3 thin films. Room temperature resistivity as well as activation energy of the film decreases exponentially with Pd incorporation concentration. Highly transparent, nanocrystalline and semiconducting WO3 films with low resistivity obtained by Pd incorporation can make WO3 suitable for microelectronics industry and for gas sensing applications.

  8. 黑色氧化钨的制备及其表征%Preparation and Characterization of Tungsten Black Oxides

    Institute of Scientific and Technical Information of China (English)

    黄忠良; 吴介达; 詹明军; 杨宇翔

    2000-01-01

    用肼与草酸作为添加剂制备了草酸钨酸肼复合盐,并以此作为前驱物制备黑色氧化钨.热重分析的结果表明,在500℃时热分解已经完成.应用该复合盐在氮气保护下热分解制备了黑色氧化钨.实验研究了肼与草酸添加量对产品性状的影响.确定钨酸、肼、草酸的最佳比例(物质的量比)为1.0:4.0:0.5.实验发现,热分解温度、热分解时间对产品性状有一定的影响.采用最佳比例的前驱物热分解,温度为650℃,时间为30min时,所得典型产品呈黑色.温度较高时,则产品略呈深棕色,表明此时产品主含WO2相.对黑色氧化钨中NH+4的质量分数亦进行了测定,实验表明,在所选择的条件下,氨钨青铜相可忽略不计.典型产品的粉末X射线衍射(XRD)图谱表明,产品主含W18O49相,WO2相较少.典型产品的比表面积(BET法)为12m2·g-1,团聚体粒度(d50)为3.68μm.%Hydrazinium oxalate tungstate complicated salts were prepared by using hydrazine, oxalic acid and tungstic acid as raw materials, and tungsten black oxides were prepared by using these complicated salts as precursors under the protection of purified nitrogen. The result from thermogravimetry points out that the thermal decomposition of the precursor completes at about 500 ℃. The ingredient of raw materials composing the precursor affects some properties of the product. The optimal ratio of hydrazine, oxalic acid and tungstic acid was determined to be 1.0:4.0:0.5. Temperature and time of thermal decomposition were experimentally found to affect the properties of the product too. When the precursor with the optimal.ratio is thermally decomposed at 650 ℃ and for 30 rmin, the product is typically black and called model product. The O/W index and content of ammonium ion were determined. The experimental result indicats that the O/W index is very close to that in W18O49 and the ammonium tungsten

  9. Microscopic Deformation of Tungsten Surfaces by High Energy and High Flux Helium/Hydrogen Particle Bombardment with Short Pulses

    Science.gov (United States)

    Tokitani, Masayuki; Yoshida, Naoaki; Tokunaga, Kazutoshi; Sakakita, Hajime; Kiyama, Satoru; Koguchi, Haruhisa; Hirano, Yoichi; Masuzaki, Suguru

    The neutral beam injection facility in the National Institute of Advanced Industrial Science and Technology was used to irradiate a polycrystalline tungsten specimen with high energy and high flux helium and hydrogen particles. The incidence energy and flux of the beam shot were 25 keV and 8.8 × 1022 particles/m2 s, respectively. The duration of each shot was approximately 30 ms, with 6 min intervals between each shot. Surface temperatures over 1800 K were attained. In the two cases of helium irradiation, total fluence of either 1.5 × 1022 He/m2 or 4.0 × 1022 He/m2 was selected. In the former case, large sized blisters with diameter of 500 nm were densely observed. While, the latter case, the blisters were disappeared and fine nanobranch structures appeared instead. Cross-sectional observations using a transmission electron microscope (TEM) with the focused ion beam (FIB) technique were performed. According to the TEM image, after irradiation with a beam shot of total fluence 4.0 × 1022 He/m2 , there were very dense fine helium bubbles in the tungsten of sizes 1-50 nm. As the helium bubbles grew the density of the tungsten matrix drastically decreased as a result of void swelling. These effects were not seen in hydrogen irradiation case.

  10. Improved adhesion of diamond coating on cobalt-cemented tungsten carbide hardmetal by using pulsed-UV-laser substrate surface pretreatment

    Science.gov (United States)

    Tiejun, Li; Qihong, Lou; Jingxing, Dong; Yunrong, Wei; Jun, Zhou; Jingru, Liu; Zhiming, Zhang; Fanghong, Sun

    2002-06-01

    Pulsed-UV-laser surface ablation has been applied in substrate pretreatment in order to obtain good adhesion of diamond coating grown on cobalt-cemented tungsten carbide hardmetal. The dependence of diamond coating's adhesion on different shots of pulsed-UV-laser substrate pretreatment has been studied experimentally. The results were compared with diamond coating deposited by using traditional acid-etching substrate pretreatment. It was shown that adhesion of diamond coating grown on tungsten carbide hardmetal has been greatly improved by using pulsed-UV-laser substrate pretreatment. The corresponding laser pretreatment condition for the optimal adhesion of diamond coatings was finally obtained. It has been demonstrated that pulsed-UV-laser substrate pretreatment should be a feasible and effective method for improving adhesion of diamond coating on cobalt-cemented tungsten carbide hardmetal. It is the characteristic surface morphology produced by pulsed-UV-laser surface ablation that subsequently results in this improved adhesion of diamond coating grown on tungsten carbide hardmetal. The number of laser shots being used in substrate pretreatment has a great influence to the adhesion of diamond coating deposited on tungsten carbide hardmetal. One should always apply proper number of laser shots in pulsed-UV-laser substrate pretreatment when seeking for the optimal adhesion of diamond coating on tungsten carbide hardmetal. In this work, the corresponding number of laser shots for the optimal adhesion of diamond coating has found to be 300 laser shots.

  11. Synthesis of Tungsten Oxide Nanorod, Its Application on Textile Material, and Study of Its Functional Properties

    Directory of Open Access Journals (Sweden)

    Abdul Azeem

    2016-01-01

    Full Text Available Nanomaterial and its application in textiles are emerging as vast and diverse field due to enhanced functionalized characteristics. This study emphasizes the fabrication of tungsten trioxide nanostructured rods and analyzes its electrostatic and ultraviolet resistance properties. These nanorods are synthesized by hydrothermal method. Through hydrothermal method rod like nanostructures were grown on polyester fabric as it withstands curing temperature easily. The growth mechanism of the film is investigated. Electrostatic analysis of treated polyester fabric was failed but the analysis of seeded solution revealed that it has tunable transmittance modulation under different voltages and repetitive cyclic between the clear and blue states. Ultraviolet resistance of 100% seeded polyester fabric was higher than untreated fabric with respect to increasing concentration of nanorods. Results show that although the seeded solution is perfect, the conductivity of tungsten trioxide cannot be achieved on textiles.

  12. Deposition of electrochromic tungsten oxide thin films by plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Henley, W.B.; Sacks, G.J. [Univ. of South Florida, Tampa, FL (United States). Center of Microelectronics

    1997-03-01

    Use of plasma-enhanced chemical vapor deposition (PECVD) for electrochromic WO{sub 3} film deposition is investigated. Oxygen, hydrogen, and tungsten hexafluoride were used as source gases. Reactant gas flow was investigated to determine the effect on film characteristics. High quality optical films were obtained at deposition rates on the order of 100 {angstrom}/s. Higher deposition rates were attainable but film quality and optical coherence degraded. Atomic emission spectroscopy (AES), was used to provide an in situ assessment of the plasma deposition chemistry. Through AES, it is shown that the hydrogen gas flow is essential to the deposition of the WO{sub 3} film. Oxygen gas flow and tungsten hexafluoride gas flow must be approximately equal for high quality films.

  13. Volume and surface photoemission from tungsten. I. Calculation of band structure and emission spectra

    DEFF Research Database (Denmark)

    Christensen, N. Egede; Feuerbacher, B.

    1974-01-01

    The electronic energy-band structure of tungsten has been calculated by means of the relativistic-augmented-plane-wave method. A series of mutually related potentials are constructed by varying the electronic configuration and the amount of Slater exchange included. The best band structure...

  14. Deposition and Coating Properties on CVD Tungsten

    Institute of Scientific and Technical Information of China (English)

    DU Ji-hong; LI Zheng-xiang; LIU Gao-jian; ZHOU Hui-Huang; CHUN liang

    2004-01-01

    Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.

  15. Hetero- and homogeneous three-dimensional hierarchical tungsten oxide nanostructures by hot-wire chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Houweling, Z.S., E-mail: Silvester.Houweling@asml.com [Utrecht University, Debye Institute for Nanomaterials Science, Nanophotonics—Physics of Devices, Princetonlaan 4, 3584 CB Utrecht (Netherlands); Harks, P.-P.R.M.L.; Kuang, Y.; Werf, C.H.M. van der [Utrecht University, Debye Institute for Nanomaterials Science, Nanophotonics—Physics of Devices, Princetonlaan 4, 3584 CB Utrecht (Netherlands); Geus, J.W. [Utrecht University, Inorganic Chemistry and Catalysis, Padualaan 8, 3584 CH Utrecht (Netherlands); Schropp, R.E.I. [Utrecht University, Debye Institute for Nanomaterials Science, Nanophotonics—Physics of Devices, Princetonlaan 4, 3584 CB Utrecht (Netherlands)

    2015-01-30

    We present the synthesis of three-dimensional tungsten oxide (WO{sub 3−x}) nanostructures, called nanocacti, using hot-wire chemical vapor deposition. The growth of the nanocacti is controlled through a succession of oxidation, reduction and re-oxidation processes. By using only a resistively heated W filament, a flow of ambient air and hydrogen at subatmospheric pressure, and a substrate heated to about 700 °C, branched nanostructures are deposited. We report three varieties of simple synthesis approaches to obtain hierarchical homo- and heterogeneous nanocacti. Furthermore, by using catalyst nanoparticles site-selection for the growth is demonstrated. The atomic, morphological and crystallographic compositions of the nanocacti are determined using a combination of electron microscopy techniques, energy-dispersive X-ray spectroscopy and electron diffraction. - Highlights: • Continuous upscalable hot-wire CVD of 3D hierarchical nanocacti • Controllable deposition of homo- and heterogeneous WO{sub 3−x}/WO{sub 3−y} nanocacti • Introduction of three synthesis routes comprising oxidation, reduction and re-oxidation processes • Growth of periodic arrays of hetero- and homogeneous hierarchical 3D nanocacti.

  16. Low-temperature NO2-sensing properties and morphology-controllable solvothermal synthesis of tungsten oxide nanosheets/nanorods

    Science.gov (United States)

    Wang, Zishuai; Hu, Ming; Wei, Yulong; Liu, Junfeng; Qin, Yuxiang

    2016-01-01

    Tungsten oxide (WO3) nanocrystals with various nanomorphologies were synthesized by solvothermal method using tungsten hexachloride (WCl6) as a raw material and pure ethylene glycol (EG) or water-EG as reaction solvent, and the NO2-sensing properties of the WO3 nanocrystals were studied. The morphology and crystal structure were investigated by field emission scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). The NO2 gas sensing properties of WO3 nanocrystals were investigated at different temperatures ranging from room temperature (∼25 °C) to 250 °C over NO2 concentration ranging from 0.1 to 3 ppm. The results indicate that the morphology and crystal phase of the WO3 nanocrystals depended on the water content in water-EG mixed solvent. With the increase of water content, the crystalline phase transformed from hexagonal to monoclinic. At the operating temperature below 55 °C, the sensor synthesized in EG solvent showed an abnormal p-type conductive behavior. It is found that all the sensors exhibit high sensor responses and rapid response characteristics to different concentrations of NO2, and their highest sensor responses are achieved at 100 or 50 °C.

  17. Changes in the structural and electrical properties of vacuum post-annealed tungsten- and titanium-doped indium oxide films deposited by radio frequency magnetron sputtering

    NARCIS (Netherlands)

    Yan, L.T.; Schropp, R.E.I.

    2011-01-01

    Tungsten- and titanium-doped indium oxide (IWO and ITiO) filmswere deposited at room temperature by radio frequency (RF) magnetron sputtering, and vacuum post-annealing was used to improve the electron mobility. With increasing deposition power, the as deposited films showed an increasingly crystall

  18. WO3 nano-ribbons: their phase transformation from tungstite (WO3·H2O) to tungsten oxide (WO3)

    DEFF Research Database (Denmark)

    Ahmadi, Majid; Sahoo, Satyaprakash; Younesi, Reza

    2014-01-01

    Tungsten oxide (WO3) nano-ribbons (NRs) were obtained by annealing tungstite (WO3·H2O) NRs. The latter was synthesized below room temperature using a simple, environmentally benign, and low cost aging treatment of precursors made by adding hydrochloric acid to diluted sodium tungstate solutions (Na...

  19. Investigation of Surface Alkylation Strategy in SOMC: In Situ Generation of a Silica-Supported Tungsten Methyl Catalyst for Cyclooctane Metathesis

    KAUST Repository

    Hamieh, Ali Imad Ali

    2016-07-28

    An efficient and potentially scalable method is described for the synthesis of the silica-supported complexes [(≡Si-O-)WMe5] and [(≡Si-O-)WMe2(≡CH)] obtained by in situ alkylation of the surface-grafted tungsten chloride [(≡Si-O-)WCl5] (1). [(≡Si-O-)WCl5] can be readily prepared by the reaction of commercially available and stable tungsten hexachloride WCl6 with partially dehydroxylated silica at 700 °C (SiO2-700). Further reaction with ZnMe2 at room temperature rapidly forms a mixture of surface-alkylated tungsten complexes. They were fully characterized by microanalysis, FTIR, mass balance, and solid-state NMR (1H, 13C, 1H-13C HETCOR, 1H-1H double quantum and triple quantum) and identified as [(≡Si-O-)WMe5] and another product, [(≡Si-O-)WMe2(≡CH)]. The latter might have been generated by partial decomposition of the tungsten methyl chloride compound, which is formed during the stepwise alkylation of [(≡Si-O-)WCl5]. DFT calculations were carried out to check the relative stability of the tungsten methyl chloride intermediates and the feasibility of the reaction and corroborate the experimental results. This tungsten complex and its derivative were found to be active catalysts for the metathesis of cyclooctane. © 2016 American Chemical Society.

  20. Electroreduction of Tungsten Oxide(Ⅵ) in Molten Salts with Added Metaphosphate

    Institute of Scientific and Technical Information of China (English)

    MALYSHEV Victor; GAB Angelina; POPESCU Ana-Maria; CONSTANTIN Virgil

    2013-01-01

    Tungstate ions WO42-are not electrochemically active in chloride melts.Upon introduction of PO3-ions into the melt,two waves appear in the voltammograms at potentials-0.1--0.2 V and-0.3--0.5 V vs.Pb/Pb2+ reference electrode.With a PO3-concentration ratio of 0.01<[PO3-]/[WO42-]<0.18,the potentiostatic electrolysis product of WO42-at the above mentioned potentials is metallic tungsten; a NaPO3 concentration increase for ratios [PO3-]/[WO42-]>>0.18 results in tungsten phosphide in electrolysis product.Cyclic voltammograms and dependence of half-peak potentials on electrode polarization rate indicate the irreversible character of the electrode process.Electrode process modeling allows us to state that the first wave in the voltammogram of KC1-NaC1-Na2WO4-NaPO3 system corresponds to tungsten oxychlorides discharge while the second wave appears due to the discharge of ditungstate ions.In the voltammograms of Na2WO4-NaPO3 melts,reduction wave was observed at-1.1--1.2 V potentials.Proportionality of limiting current to NaPO3 concentration,constancy ofId/v1/2 ratio,and Id/nFc constant kinetic value equal to (8.3-9.5)× 10-5 cm/s for steady-state wave indicate that electrode process rate is limited by electrochemically active particle diffusion to the electrode.Nascent ditungstate ions become electrochemically active in the overall electrode process.Charge transfer stage is reversible.

  1. Fabrication of tungsten oxide microfibers with photocatalytic activity by electrospunning from PVA/H 3PW 12O 40 gel

    Science.gov (United States)

    Sui, Chunhong; Gong, Jian; Cheng, Tiexin; Zhou, Guangdong; Dong, Shunfu

    2011-08-01

    Regarding gel poly (vinyl alcohol)/H 3PW 12O 40 as precursor, the ultra-fine fibers tungsten oxide (WO 3) was prepared by using electrospinning and calcinating techniques. Scanning electron microscope (SEM) shows that the average diameter of fibrous WO 3 were changed from 200 nm to 600 nm after calcined PVA/H 3PW 12O 40 fibers at 600 and 800 °C, respectively. X-ray diffraction (XRD) and Raman spectroscope revealed that the fibrous WO 3 was monoclinic phase, and the band-gap energies were observed by UV-vis diffuse reflectance spectra. The small size WO 3 exhibits excellent photocatalytcic activity in degradation of Rhodamine B at 365 nm wavelength.

  2. Poly-ε-caprolactone tungsten oxide nanoparticles as a contrast agent for X-ray computed tomography.

    Science.gov (United States)

    Jakhmola, Anshuman; Anton, Nicolas; Anton, Halina; Messaddeq, Nadia; Hallouard, François; Klymchenko, Andrey; Mely, Yves; Vandamme, Thierry F

    2014-03-01

    Inorganic nanomaterials based on heavy elements represent a new class of contrast agents for X-ray computed tomography (CT). Recent advances have shown that these materials are highly suited for CT imaging due to their high density and X-ray absorption capabilities. In this contribution, we demonstrated that tungsten oxide (WO3) nanoparticles coated by poly-ε-caprolactone (PCL) can be used as efficient contrast agent for CT imaging. The obtained particles were characterized by electron microscopy (TEM and SEM), and dynamic light scattering (DLS). We also validated their use for enhanced in vivo imaging, since these nanoparticles were observed to display high X-ray attenuation properties and circulation time (up to 3 h), permitting blood pool imaging.

  3. Dielectric response of tungsten modified Ba(Ti0.90Zr0.10O3 ceramics obtained by mixed oxide method

    Directory of Open Access Journals (Sweden)

    Francisco Moura

    2010-12-01

    Full Text Available The electrical response of Ba(Ti0.90Zr0.10O3 (BZT ceramics obtained by the mixed oxide method as a function of tungsten content was investigated. According to X-ray diffraction analysis the single phase BZT1W (1 wt.% W doped BZT and BZT2W (2 wt.% W doped BZT ceramics, crystallized in a perovskite structure, were obtained. It is also shown that tungsten substituted ceramics can be sintered at a reduced temperature when compared to the undoped BZT. Electron paramagnetic resonance (EPR analyses reveals that substitution of Ti4+ by W6+ causes distortion in the crystal structure changing lattice parameter. Substitution of W6+ on B-site of ABO3 perovskite BZT ceramics shifted the phase transition to lower temperatures up to a tungsten content of 2 wt.% leading to a relaxor-like behaviour.

  4. Peculiarities of formation of phase composition, porous structure, and catalytic properties of tungsten oxide-based macroporous materials fabricated by sol–gel synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Papynov, Evgeniy Konstantinovich, E-mail: Papynov@mail.ru [Institute of Chemistry, Far East Branch, Russian Academy of Sciences, Prospect 100-let Vladivostoku, 159, Vladivostok 690022 (Russian Federation); Far Eastern Federal University, School of Natural Sciences, Suhanova, 8, Vladivostok 690091 (Russian Federation); Mayorov, Vitaliy Yurevich, E-mail: 024205@inbox.ru [Institute of Chemistry, Far East Branch, Russian Academy of Sciences, Prospect 100-let Vladivostoku, 159, Vladivostok 690022 (Russian Federation); Palamarchuk, Marina Sergeevna, E-mail: 02.06.1984@mail.ru [Institute of Chemistry, Far East Branch, Russian Academy of Sciences, Prospect 100-let Vladivostoku, 159, Vladivostok 690022 (Russian Federation); Avramenko, Valentin Aleksandrovich, E-mail: avramenko1@yandex.ru [Institute of Chemistry, Far East Branch, Russian Academy of Sciences, Prospect 100-let Vladivostoku, 159, Vladivostok 690022 (Russian Federation); Far Eastern Federal University, School of Natural Sciences, Suhanova, 8, Vladivostok 690091 (Russian Federation)

    2014-02-15

    The method of template sol–gel synthesis of tungsten oxide-based macroporous materials using ‘core–shell’ latex particles as colloid templates is described. The chemical composition and structural characteristics of the synthesized macroporous oxide systems have been investigated. The peculiarities of formation of material phase composition and macroporous structure under different template thermal destruction conditions have been revealed. An optimal method of a targeted synthesis of the crystalline tungsten(VI) oxide having a defect-free macroporous structure (average pore size 160 nm) and efficient catalytic properties under organic liquid phase oxidation conditions has been suggested. The prospects of the fabricated material application as catalysts of hydrothermal oxidation of radionuclide organic complexes at radioactive waste decontamination have been demonstrated. - Highlights: • Macroporous tungsten oxides were fabricated via sol–gel process. • The correlation between synthesis conditions and composition was determined. • Influence of synthesis conditions on porous structure has been explained. • The effects of template thermodestruction have been set up. • High potential of such materials for catalysis applications has been shown.

  5. Surface morphology changes and deuterium retention in Toughened, Fine-grained Recrystallized Tungsten under high-flux irradiation conditions

    Energy Technology Data Exchange (ETDEWEB)

    Oya, M., E-mail: ohya@st.eie.eng.osaka-u.ac.jp [Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Lee, H.T.; Ueda, Y. [Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Kurishita, H. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Oyaidzu, M.; Hayashi, T. [Fusion Research and Development Directorate, International Fusion Energy Research Center, Japan Atomic Energy Agency, Rokkasho-mura, Aomori 039-3212 (Japan); Yoshida, N. [Research Institute for Applied Mechanics, Kyushu University, Fukuoka (Japan); Morgan, T.W.; De Temmerman, G. [FOM Institute DIFFER Dutch Institute for Fundamental Energy Research, Nieuwegein 3439 MN (Netherlands)

    2015-08-15

    Surface morphology changes and deuterium (D) retention in Toughened, Fine-Grained Recrystallized Tungsten (TFGR W) with TaC dispersoids (W-TaC) and pure tungsten exposed to D plasmas to a fluence of 10{sup 26} D/m{sup 2} s were studied as a function of the D ion flux (10{sup 22}–10{sup 24} D/m{sup 2} s). As the flux increased from 10{sup 22} D/m{sup 2} s to 10{sup 24} D/m{sup 2} s, the numbers of blisters increased for both materials. However, smaller blisters were observed on W-TaC compared to pure W. In W-TaC, cracks beneath the surface along grain boundaries were observed, which were comparable to the blister sizes. The reason for the smaller blister sizes may arise from smaller grain sizes of W-TaC. In addition, reduction of the D retention in W-TaC was observed for higher flux exposures. D depth profiles indicate this reduction arises due to decrease in trapping in the bulk.

  6. Prediction of Weld Quality of A Tungsten Inertr Gas Welded Mild Steel Pipe Joint Using Response Surface Methodology (Rsm

    Directory of Open Access Journals (Sweden)

    I.U. Abhulimen

    2014-08-01

    Full Text Available The weld quality of tungsten inert gas (TIG welded joint has been investigated to identify the most economical weld parameters that will bring about optimum properties. Response surface methodology has been used in the optimization of the tungsten inert gas weld of mild steel pipes. Response surface methodology, based on the central composite face centered design was generated for the purpose of optimization of the weld quality.All the process parameters have desirability of 1. Tensile strength response for this solution have a desirability of 0.910595 and the yield strength of 0.59. Result showed that minimizing current and voltage an average tensile strength of 535.452MPa and yield strength of up to 408.74MPa can be achieved, while keeping gas flow rate and electrode diameter within the range of test. It was also deduced that tensile elongation of the TIG weld is not influenced by the process parameters selected for the purpose of this study.

  7. Nature of active centers and mechanism of olefin metathesis on applied oxide catalysts of molybdenum, tungsten and rhenium

    Energy Technology Data Exchange (ETDEWEB)

    Kadushin, A.A. (USSR Academy of Sciences); Aliyev, R.K.; Krylov, O.V.; Andreyev, A.A.; Yedreva-Kardzhiyeva, R.M.; Shopov, D.M.

    1982-03-01

    The authors undertook a systematic study of the effects of the carrier, activation conditions and the reaction itself on the formation and structure of active centers. Spectral characteristics of the systems studied were compared by infrared, ultraviolet, X-ray-electron and electron absorption spectroscopy, and X-ray-phase and chromatographic analyses. Catalytic activity in a metathesis reaction of propylene and butene-1 was tested in a quartz flow reactor at atmospheric pressure in a temperature range of 25-600/sup 0/C, with contact time of 3-50 seconds. The deposited oxide catalysts of the title minerals are discussed in terms of preparing the catalysts, studying their activity, and observing optical spectra. Tungsten ions were found to reduce at higher temperatures than molbydenum ions. Olefin treatment brought reduction of rhenium to lower oxidation levels. The low activities of Re/sub 2/O/sub 7//MgO at low temperatures is related to difficult electron transfer. The studies indicated the presence of a mobile center in the metathesis of olefins for oxide catalysis of all 3 title minerals, which is dependent on the chemical nature of the carrier and its crystalline structure.

  8. L-Edge Xanes Measurements of the Oxidation State of Tungsten in Iron Bearing and Iron Free Silicate Glasses

    Science.gov (United States)

    Danielson, L. R.; Righter, K.; Sutton, S.; Newville, M.

    2008-01-01

    Tungsten is important in constraining core formation of the Earth because this element is a moderately siderophile element (depleted 10 relative to chondrites) and, as a member of the Hf-W isotopic system, it is useful in constraining the timing of core formation. A number of previous experimental studies have been carried out to determine the silicate solubility and metal-silicate partitioning behavior of W, including its concomitant oxidation state. However, results of previous studies are inconsistent on whether W occurs as W(4+) or W(6+). It is assumed that W(4+) is the cation valence relevant to core formation. Given the sensitivity to silicate composition of high valence cations, knowledge of the oxidation state of W over a wide range of fO2 is critical to understanding the oxidation state of the mantle and core formation processes. This study seeks to measure the W valence and change in valence state over the range of fO2 most relevant to core formation, around IW-2.

  9. Tungsten carbide modified high surface area carbon as fuel cell catalyst support

    Science.gov (United States)

    Shao, Minhua; Merzougui, Belabbes; Shoemaker, Krista; Stolar, Laura; Protsailo, Lesia; Mellinger, Zachary J.; Hsu, Irene J.; Chen, Jingguang G.

    Phase pure WC nanoparticles were synthesized on high surface area carbon black (800 m 2 g -1) by a temperature programmed reaction (TPR) method. The particle size of WC can be controlled under 30 nm with a relatively high coverage on the carbon surface. The electrochemical testing results demonstrated that the corrosion resistance of carbon black was improved by 2-fold with a surface modification by phase pure WC particles. However, the WC itself showed some dissolution under potential cycling. Based on the X-ray diffraction (XRD) and inductively coupled plasma (ICP) analysis, most of the WC on the surface was lost or transformed to oxides after 5000 potential cycles in the potential range of 0.65-1.2 V. The Pt catalyst supported on WC/C showed a slightly better ORR activity than that of Pt/C, with the Pt activity loss rate for Pt/WC/C being slightly slower compared to that of Pt/C. The performance and decay rate of Pt/WC/C were also evaluated in a fuel cell.

  10. Superficial roughness on composite surface, composite enamel and composite dentin junctions after different finishing and polishing procedures. Part I: roughness after treatments with tungsten carbide vs diamond burs.

    Science.gov (United States)

    Ferraris, Federico; Conti, Alessandro

    2014-01-01

    The aim of this study is to investigate different instruments for finishing composite restorations, as well as examining different surfaces and interfaces of the same restoration. The null hypothesis is represented by the fact that there are no significant differences on roughness of composite restorations finishing between tungsten carbide and diamond burs, furthermore the null hypothesis is that there are no significant differences on roughness between finishing on composite surfaces (C), compositeenamel (CE) and composite-dentin (CD) interfaces. The study was performed on 28 teeth, and class V cavities were prepared on the extracted teeth. Restorations were done in Filtek XTE nanofilled composite (3M Espe) in a standardized method, to then be finished. A comparison was made in the phase 1 between tungsten carbide burs (16 blades), diamond burs (46 μm), with a similar shape by the same manufacturer (Komet). Each surface received 5 bur applications. Consequently, an analysis with a profilometer was performed. Phase 2 involved further confrontation of ulterior finishing with ultrafine tungsten carbide burs (30 blades) and with extra and ultrafine diamond burs (25 and 8 μm) (the same shape as previously mentioned). A second analysis was then performed with a profilometer. All measurements were taken on C surfaces, CE and CD interfaces. Statistical analyses were carried out with c2 test (a = 0.05). The finishing procedures with fine grit or toothing burs gave a better smoothness with tungsten carbide burs compared to diamond burs. While with the ultrafine grit no significant differences were noted between tungsten carbide and diamond burs on the CE and CD interfaces, the diamond bur left less superficial roughness on the C surfaces. With regards to the superficial roughness of the different areas of restoration, it can be concluded that: minor roughness was detected on C surfaces, while the CD interface had the most superficial roughness, regardless of whether the

  11. Electro-optical evaluation of tungsten oxide and vanadium pentoxide thin films for modeling an electrochromic device

    Directory of Open Access Journals (Sweden)

    H Najafi Ashtiani

    2015-01-01

    Full Text Available In this study, tungsten oxide and vanadium oxide electrochromic thin films were placed in vacuum and in a thickness of 200 nm on a transparent conductive substrate of SnO2:F using the physical method of thermal evaporation. Then they were studied for the optical characteristics in the wavelength range from 400 to 700 nm and for their electrical potentials in the range form +1.5 to -1.5 volts. The films were post heated in order to assess changes in energy gap with temperature, at temperatures120 , 300 and 500°C. Refractive and extinction coefficients and the transition type of films in the visible light range and in the thickness of 200 nm were determined and measured. X-ray diffraction pattern and SEM images and cyclic Voltammetry of layers were also studied. The results of this study due to the deposition of layers, the layer thickness selected, the type of substrate, the range of annealing temperatures and selected electrolyte were in full compliance with the works of other researchers [1,2,3]. Therefore, these layers with features such as crystal structure, refractive and even extinction coefficients in the range of visible light, the appropriate response of chromic switch in the replication potential, good adhesion to the substrate, and the high amount of optical transmition and so on, prove useful to be used in an electrochromic device

  12. A Facile One-Step Solvothermal Synthesis and Electrical Properties of Reduced Graphene Oxide/Rod-Shaped Potassium Tungsten Bronze Nanocomposite.

    Science.gov (United States)

    Liu, Bin; Yin, Shu; Wang, Yuhua; Guo, Chongshen; Wu, Xiaoyong; Dong, Qiang; Kobayashi, Makoto; Kakihana, Masato; Sato, Tsugio

    2015-09-01

    Reduced graphene oxide (rGO)/rod-shaped potassium tungsten bronze nanocomposites with the different ratio were successfully synthesized by solvothermal reaction and followed by the reduction in H2(5 vol.%)/N2 atmosphere at 550 degrees C. The coupled samples showed excellent shielding ability of NIR light as well as certain visible lights transparency. The synergistic effects could be observed in the composites, i.e., when 15 wt% and 20 wt% of rGO which was fabricated by chemical reduction of graphene oxide, were composed into K(x)WO3, the composite showed the higher electrical conductivity than those of rGO and potassium tungsten bronze.

  13. Crystal orientation effects on implantation of low-energy hydrogen, helium and hydrogen/helium mixtures in plasma-facing tungsten surfaces

    Science.gov (United States)

    Linn, Brian C.

    The development of plasma-facing materials (PFM) is one of the major challenges in. realizing fusion reactors. Materials deployed in PFMs must be capable of withstanding the high-flux of low-energy hydrogen and helium ions omitted from the plasma. while not hindering the plasma. Tungsten is considered a promising candidate material due to desirable material properties including its high melting temperature, good thermal conductivity and relatively low physical and chemical sputtering yields. This thesis uses molecular dynamic simulations to investigate helium and hydrogen bombardment of tungsten and the underlying physical effects (e.g. sputtering, erosion, blistering). Non-cumulative and cumulative bombardment simulations of helium, hydrogen, and hydrogen/helium bombardment of tungsten were modeled using the molecular dynamics code LAMMPS. Two orientations of monocrystalline bcc tungsten surfaces were considered, (001) and (111). Simulations were performed for temperatures ranging from 600K up to 1500K and helium / hydrogen incident energies of 20eV to 100eV . The results of these simulations showed the effect of temperature and incident particle energy on retention rates and implantation/deposition profiles in tungsten.

  14. Surface modifications on toughened, fine-grained, recrystallized tungsten with repetitive ELM-like pulsed plasma irradiation

    Science.gov (United States)

    Kikuchi, Y.; Sakuma, I.; Kitagawa, Y.; Asai, Y.; Onishi, K.; Fukumoto, N.; Nagata, M.; Ueda, Y.; Kurishita, H.

    2015-08-01

    Surface modifications of toughened, fine-grained, recrystallized tungsten (TFGR W) materials with 1.1 wt.% TiC and 3.3 wt.% TaC dispersoids due to repetitive ELM-like pulsed (∼0.15 ms) helium plasma irradiation have been investigated by using a magnetized coaxial plasma gun. No surface cracking at the center part of the TFGR W samples exposed to 20 plasma pulses of ∼0.3 MJ m-2 was observed. The suppression of surface crack formation due to the increase of the grain boundary strength by addition of TiC and TaC dispersoids was confirmed in comparison with a pure W material. On the other hand, surface cracks and small pits appeared at the edge part of the TFGR W sample after the pulsed plasma irradiation. Erosion of the TiC and TaC dispersoids due to the pulsed plasma irradiation could cause the small pits on the surface, resulting in the surface crack formation.

  15. Surface cracking and melting of different tungsten grades under transient heat and particle loads in a magnetized coaxial plasma gun

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, Y., E-mail: ykikuchi@eng.u-hyogo.ac.jp [Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280 (Japan); Sakuma, I.; Iwamoto, D.; Kitagawa, Y.; Fukumoto, N.; Nagata, M. [Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280 (Japan); Ueda, Y. [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)

    2013-07-15

    Surface damage of pure tungsten (W), W alloys with 2 wt.% tantalum (W–Ta) and vacuum plasma spray (VPS) W coating on a reduced activation material of ferritic steel (F82H) due to repetitive ELM-like pulsed (∼0.3 ms) deuterium plasma irradiation has been investigated by using a magnetized coaxial plasma gun. Surface cracks appeared on a pure W sample exposed to 10 plasma pulses of ∼0.3 MJ m{sup −2}, while a W–Ta sample did not show surface cracks with similar pulsed plasma irradiation. The energy density threshold for surface cracking was significantly increased by the existence of the alloying element of tantalum. No surface morphology change of a VPS W coated F82H sample was observed under 10 plasma pulses of ∼0.3 MJ m{sup −2}, although surface melting and cracks in the resolidification layer occurred at higher energy density of ∼0.9 MJ m{sup −2}. There was no indication of exfoliation of the W coating from the substrate of F82H after the pulsed plasma exposures.

  16. Surface cracking and melting of different tungsten grades under transient heat and particle loads in a magnetized coaxial plasma gun

    Science.gov (United States)

    Kikuchi, Y.; Sakuma, I.; Iwamoto, D.; Kitagawa, Y.; Fukumoto, N.; Nagata, M.; Ueda, Y.

    2013-07-01

    Surface damage of pure tungsten (W), W alloys with 2 wt.% tantalum (W-Ta) and vacuum plasma spray (VPS) W coating on a reduced activation material of ferritic steel (F82H) due to repetitive ELM-like pulsed (˜0.3 ms) deuterium plasma irradiation has been investigated by using a magnetized coaxial plasma gun. Surface cracks appeared on a pure W sample exposed to 10 plasma pulses of ˜0.3 MJ m-2, while a W-Ta sample did not show surface cracks with similar pulsed plasma irradiation. The energy density threshold for surface cracking was significantly increased by the existence of the alloying element of tantalum. No surface morphology change of a VPS W coated F82H sample was observed under 10 plasma pulses of ˜0.3 MJ m-2, although surface melting and cracks in the resolidification layer occurred at higher energy density of ˜0.9 MJ m-2. There was no indication of exfoliation of the W coating from the substrate of F82H after the pulsed plasma exposures.

  17. Surface modifications on toughened, fine-grained, recrystallized tungsten with repetitive ELM-like pulsed plasma irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, Y., E-mail: ykikuchi@eng.u-hyogo.ac.jp [Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, 671-2280 Hyogo (Japan); Sakuma, I.; Kitagawa, Y.; Asai, Y.; Onishi, K.; Fukumoto, N.; Nagata, M. [Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, 671-2280 Hyogo (Japan); Ueda, Y. [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Kurishita, H. [Institute for Materials Research, Tohoku University, Ibaraki 311-1313 (Japan)

    2015-08-15

    Surface modifications of toughened, fine-grained, recrystallized tungsten (TFGR W) materials with 1.1 wt.% TiC and 3.3 wt.% TaC dispersoids due to repetitive ELM-like pulsed (∼0.15 ms) helium plasma irradiation have been investigated by using a magnetized coaxial plasma gun. No surface cracking at the center part of the TFGR W samples exposed to 20 plasma pulses of ∼0.3 MJ m{sup −2} was observed. The suppression of surface crack formation due to the increase of the grain boundary strength by addition of TiC and TaC dispersoids was confirmed in comparison with a pure W material. On the other hand, surface cracks and small pits appeared at the edge part of the TFGR W sample after the pulsed plasma irradiation. Erosion of the TiC and TaC dispersoids due to the pulsed plasma irradiation could cause the small pits on the surface, resulting in the surface crack formation.

  18. Template-Free Mesoporous Electrochromic Films on Flexible Substrates from Tungsten Oxide Nanorods.

    Science.gov (United States)

    Heo, Sungyeon; Kim, Jongwook; Ong, Gary K; Milliron, Delia J

    2017-09-13

    Low-temperature processed mesoporous nanocrystal thin films are platforms for fabricating functional composite thin films on flexible substrates. Using a random arrangement of anisotropic nanocrystals can be a facile solution to generate pores without templates. However, the tendency for anisotropic particles to spontaneously assemble into a compact structure must be overcome. Here, we present a method to achieve random networking of nanorods during solution phase deposition by switching their ligand-stabilized colloidal nature into a charge-stabilized nature by a ligand-stripping chemistry. Ligand-stripped tungsten suboxide (WO2.72) nanorods result in uniform mesoporous thin films owing to repulsive electrostatic forces preventing nanorods from densely packing. Porosity and pore size distribution of thin films are controlled by changing the aspect ratio of the nanorods. This template-free mesoporous structure, achieved without annealing, provides a framework for introducing guest components, therefore enabling our fabrication of inorganic nanocomposite electrochromic films on flexible substrates. Following infilling of niobium polyoxometalate clusters into pores and successive chemical condensation, a WOx-NbOx composite film is produced that selectively controls visible and near-infrared light transmittance without any annealing required. The composite shows rapid switching kinetics and can be stably cycled between optical states over 2000 times. This simple strategy of using anisotropic nanocrystals gives insight into mesoporous thin film fabrication with broader applications for flexible devices.

  19. Crystal Structure and Catalytic Behavior in Olefin Epoxidation of a One-Dimensional Tungsten Oxide/Bipyridine Hybrid.

    Science.gov (United States)

    Amarante, Tatiana R; Antunes, Margarida M; Valente, Anabela A; Paz, Filipe A Almeida; Pillinger, Martyn; Gonçalves, Isabel S

    2015-10-19

    The tungsten oxide/2,2'-bipyridine hybrid material [WO3(2,2'-bpy)]·nH2O (n = 1-2) (1) has been prepared in near quantitative yield by the reaction of H2WO4, 2,2'-bpy, and H2O in the mole ratio of ca. 1:2:700 at 160 °C for 98 h in a rotating Teflon-lined digestion bomb. The solid-state structure of 1 was solved and refined through Rietveld analysis of high-resolution synchrotron X-ray diffraction data collected for the microcrystalline powder. The material, crystallizing in the orthorhombic space group Iba2, is composed of a one-dimensional organic-inorganic hybrid polymer, ∞(1)[WO3(2,2'-bpy)], topologically identical to that found in the previously reported anhydrous phases [MO3(2,2'-bpy)] (M = Mo, W). While in the latter the N,N'-chelated 2,2'-bpy ligands of adjacent corner-shared {MO4N2} octahedra are positioned on the same side of the 1D chain, in 1 the 2,2'-bpy ligands alternate above and below the chain. The catalytic behavior of compound 1 for the epoxidation of cis-cyclooctene was compared with that for several other tungsten- or molybdenum-based (pre)catalysts, including the hybrid polymer [MoO3(2,2'-bpy)]. While the latter exhibits superior performance when tert-butyl hydroperoxide (TBHP) is used as the oxidant, compound 1 is superior when aqueous hydrogen peroxide is used, allowing near-quantitative conversion of the olefin to the epoxide. With H2O2, compounds 1 and [MoO3(2,2'-bpy)] act as sources of soluble active species, namely, the oxodiperoxo complex [MO(O2)2(2,2'-bpy)], which is formed in situ. Compounds 1 and [WO(O2)2(2,2'-bpy)] (2) were further tested in the epoxidation of cyclododecene, trans-2-octene, 1-octene, (R)-limonene, and styrene. The structure of 2 was determined by single-crystal X-ray diffraction and found to be isotypical with the molybdenum analogue.

  20. Enhanced efficiency of polymer solar cells by structure-differentiated silver nano-dopants in solution-processed tungsten oxide layer

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Wenfei [Institute of Hybrid Materials, The Growing Base for State Key Laboratory, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Tang, Jianguo, E-mail: jianguotangde@hotmail.com [Institute of Hybrid Materials, The Growing Base for State Key Laboratory, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Wang, Die [Institute of Hybrid Materials, The Growing Base for State Key Laboratory, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Yang, Renqiang, E-mail: yangrq@qibebt.ac.cn [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Chen, Weichao; Bao, Xichang [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Wang, Yao; Jiao, Jiqing; Wang, Yanxin; Huang, Zhen; Huang, Linjun; Liu, Jixian; Wang, Wei [Institute of Hybrid Materials, The Growing Base for State Key Laboratory, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Wu, Pinghui [State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, Hangzhou 310027 (China); Belfiore, Laurence A., E-mail: belfiore@engr.colostate.edu [Institute of Hybrid Materials, The Growing Base for State Key Laboratory, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO 80523 (United States)

    2016-04-15

    Graphical abstract: - Highlights: • Incorporating different structures of Ag NPs in solution-processed WO{sub 3} layer. • The LSPR effect of metallic nanoparticles is represented by FDTD method. • Enhanced PCE are greatly increased by the LSPR effect of SiAgP and nAgPl. • Naked Ag nanoparticles decreased the PCE of PSCs due to the interface excitons quenching. • Avoiding interface excitons quenching is greatly needed for utilizing metallic NPS in PSCs. - Abstract: In this article, we creatively incorporate naked Ag nanoparticles (nAgp), SiO{sub 2}-covered Ag nanoparticles (SiAgp), and naked Ag nanoplates (nAgPl) into solution-processed tungsten oxide (WO{sub 3}) hole transport layer in polymer solar cells (PSCs) to increase the light absorption through localized surface plasmon resonance (LSPR) effect. With optimized doping concentrations, nAgp decreases power conversion efficiency (PCE), however, SiAgp increases PCE by 13.2% and nAgPl increases PCE by 19.7%. In detail, the great PCEs discrepancies are mainly caused by the discrepancies of short circuit currents (J{sub sc}). The experiments results indicate that the naked surface of nAgp causes the exciton-quenching to decrease the J{sub sc} of PSCs. Whereas the capsulation of SiO{sub 2} at the surface of nAgp and the embedment of nAgPl in WO{sub 3} layer can prevent the exciton-quenching and help to use LSPR effect of Ag nano-dopants to enhance the J{sub sc} of PSCs.

  1. Oxide driven strength evolution of silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Grutzik, Scott J.; Zehnder, Alan T., E-mail: atz2@cornell.edu [Field of Theoretical and Applied Mechanics, Cornell University, Ithaca, New York 14853 (United States); Milosevic, Erik [Department of Nanoengineering, SUNY Polytechnic University, Albany, New York 12203 (United States); Boyce, Brad L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-0889 (United States)

    2015-11-21

    Previous experiments have shown a link between oxidation and strength changes in single crystal silicon nanostructures but provided no clues as to the mechanisms leading to this relationship. Using atomic force microscope-based fracture strength experiments, molecular dynamics modeling, and measurement of oxide development with angle resolved x-ray spectroscopy we study the evolution of strength of silicon (111) surfaces as they oxidize and with fully developed oxide layers. We find that strength drops with partial oxidation but recovers when a fully developed oxide is formed and that surfaces intentionally oxidized from the start maintain their high initial strengths. MD simulations show that strength decreases with the height of atomic layer steps on the surface. These results are corroborated by a completely separate line of testing using micro-scale, polysilicon devices, and the slack chain method in which strength recovers over a long period of exposure to the atmosphere. Combining our results with insights from prior experiments we conclude that previously described strength decrease is a result of oxidation induced roughening of an initially flat silicon (1 1 1) surface and that this effect is transient, a result consistent with the observation that surfaces flatten upon full oxidation.

  2. Giant hollow heterometallic polyoxoniobates with sodalite-type lanthanide-tungsten-oxide cages: discrete nanoclusters and extended frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Lu; Li, Xin-Xiong; Qi, Yan-Jie; Niu, Ping-Ping; Zheng, Shou-Tian [State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fujian (China)

    2016-10-24

    The first series of niobium-tungsten-lanthanide (Nb-W-Ln) heterometallic polyoxometalates {Ln_1_2W_1_2O_3_6(H_2O)_2_4(Nb_6O_1_9)_1_2} (Ln=Y, La, Sm, Eu, Yb) have been obtained, which are comprised of giant cluster-in-cluster-like ({Ln_1_2W_1_2}-in-{Nb_7_2}) structures built from 12 hexaniobate {Nb_6O_1_9} clusters gathered together by a rare 24-nuclearity sodalite-type heterometal-oxide cage {Ln_1_2W_1_2O_3_6(H_2O)_2_4}. The Nb-W-Ln clusters present the largest multi-metal polyoxoniobates and a series of rare high-nuclearity 4d-5d-4f multicomponent clusters. Furthermore, the giant Nb-W-Ln clusters may be isolated as discrete inorganic alkali salts and can be used as building blocks to form high-dimensional inorganic-organic hybrid frameworks. (copyright 2016 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. A novel composite electrode based on tungsten oxide nanoparticles and carbon nanotubes for the electrochemical determination of paracetamol.

    Science.gov (United States)

    Baytak, Aysegul Kutluay; Duzmen, Sehriban; Teker, Tugce; Aslanoglu, Mehmet

    2015-12-01

    An electrochemical sensor was prepared by the modification of a glassy carbon electrode (GCE) with a composite of nanoparticles of tungsten oxide (WO3) and carbon nanotubes (CNTs) for the quantification of paracetamol (PR). Energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) were performed for the characterization of the nanocomposite layer. Compared with a bare GCE and a GCE modified with CNTs, the proposed electrode (WO3NPs/CNTs/GCE) exhibited a well-defined redox couple for PR and a marked enhancement of the current response. The experimental results also showed that ascorbic acid (AA) did not interfere with the selective determination of PR. The proposed electrode was used for the determination of PR in 0.1M phosphate buffer solution (PBS) at pH7.0 using square wave voltammetry (SWV). The peak current increased linearly with the concentration of PR in the range of 1.0×10(-9)-2.0×10(-7)M. The detection limit (LOD) was 5.54×10(-11)M (based on 3Sb/m). The proposed voltammetric sensor provided long-time stability, improved voltammetric behavior and good reproducibility for PR. The selective, accurate and precise determination of PR makes the proposed electrode of great interest for monitoring its therapeutic use.

  4. Influence of carbon and metal oxide nanomaterials on aqueous concentrations of the munition constituents cyclotrimethylenetrinitramine (RDX) and tungsten.

    Science.gov (United States)

    Brame, Jonathon A; Kennedy, Alan J; Lounds, Christopher D; Bednar, Anthony J; Alvarez, Pedro J J; Scott, Andrea M; Stanley, Jacob K

    2014-05-01

    There is an increasing likelihood of interactions between nanomaterials and munitions constituents in the environment resulting from the use of nanomaterials as additives to energetic formulations and potential contact in waste streams from production facilities and runoff from training ranges. The purpose of the present research was to determine the ability of nano-aluminum oxide (Al(2)O(3)) and multiwalled carbon nanotubes (MWCNTs) to adsorb the munitions constituents cyclotrimethylenetrinitramine (RDX) and tungsten (W) from aqueous solution as a first step in determining the long-term exposure, transport, and bioavailability implications of such interactions. The results indicate significant adsorption of RDX by MWCNTs and of W by nano-Al(2)O(3) (but not between W and MWCNT or RDX and nano-Al(2)O(3)). Kinetic sorption and desorption investigations indicated that the most sorption occurs nearly instantaneously (<5 min), with a relatively slower, secondary binding leading to statistically significant but relatively smaller increases in adsorption over 30 d. The RDX sorption that occurred during the initial interaction was irreversible, with long-term, reversible sorption likely the result of a secondary interaction; as interaction time increased, however, the portion of W irreversibly sorbed onto nano-Al(2)O(3) also increased. The present study shows that strong interactions between some munitions constituents and nanomaterials following environmental release are likely. Time-dependent binding has implications for the bioavailability, migration, transport, and fate of munitions constituents in the environment.

  5. Study of deuterium retention on lithiated tungsten exposed to high-flux deuterium plasma using laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Cong; Wu, Xingwei; Zhang, Chenfei [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Chinese Ministry of Education, School of Physics and Optical Electronic Technology, Dalian University of Technology, Dalian 116024 (China); Ding, Hongbin, E-mail: hding@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Chinese Ministry of Education, School of Physics and Optical Electronic Technology, Dalian University of Technology, Dalian 116024 (China); De Temmerman, G., E-mail: G.C.DeTemmerman@differ.nl [FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Trilateral Euregio Cluster, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands); Meiden, H.J. van der [FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Trilateral Euregio Cluster, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands)

    2014-10-15

    Highlights: • Deuterium retention effects on both pure tungsten and lithiated tungsten have been investigated in the linear plasma simulator Magnum-PSI by an in-situ laser-induced breakdown spectroscopy. • The lithiation can inhibit the blistering on tungsten surface. • The re-deposition of lithium results in the formation of chemical state of Li{sub 2}CO{sub 3} and tungsten oxides on a fresh surface of tungsten. - Abstract: Tungsten is under consideration for use as a plasma-facing material in the divertor region of ITER. Lithiation can significantly improve plasma performance in long-pulse tokamaks like EAST. The investigation of lithiated tungsten is important for understanding the lithium conditioning effects for EAST, where tungsten will be used as a plasma-facing material. In this paper, a few important issues of lithiated tungsten interacting with high-flux deuterium plasma have been studied, such as the effect of lithiation on deuterium retention, the profile of elemental distribution, and the chemical state of lithiated tungsten. Deuterium retention inside both pure and lithiated tungsten has been investigated for the first time in the linear plasma simulator Magnum-PSI by in-situ laser induced breakdown spectroscopy (LIBS). The results indicate that, after deuterium plasma exposure, deuterium retention could be saturated in the lithiation layer, and the lithium in the lithiated layer is chemically bound with deuterium. Moreover, the lithiation can inhibit the blistering on the tungsten surface. These results can be valuable for the application of LIBS as a diagnostic technique for plasma-facing components of tokamaks.

  6. Silica-templated synthesis of ordered mesoporous tungsten carbide/graphitic carbon composites with nanocrystalline walls and high surface areas via a temperature-programmed carburization route.

    Science.gov (United States)

    Wu, Zhangxiong; Yang, Yunxia; Gu, Dong; Li, Qiang; Feng, Dan; Chen, Zhenxia; Tu, Bo; Webley, Paul A; Zhao, Dongyuan

    2009-12-01

    Ordered mesostructured tungsten carbide and graphitic carbon composites (WC/C) with nanocrystalline walls are fabricated for the first time by a temperature-programmed carburization approach with phosphotungstic acid (PTA) as a precursor and mesoporous silica materials as hard templates. The mesostructure, crystal phase, and amount of deposited graphitic carbon can be conveniently tuned by controlling the silica template (SBA-15 or KIT-6), carburizing temperature (700-1000 degrees C), the PTA-loading amount, and the carburizing atmosphere (CH(4) or a CH(4)/H(2) mixture). A high level of deposited carbon is favorable for connecting and stabilizing the WC nanocrystallites to achieve high mesostructural regularity, as well as promoting the carburization reaction. Meanwhile, large pore sizes and high mesoporosity of the silica templates can promote WC-phase formation. These novel, ordered, mesoporous WC/C nanocomposites with high surface areas (74-169 m(2) g(-1)), large pore volumes (0.14-0.17 cm(3) g(-1)), narrow pore-size distributions (centered at about 3 nm), and very good oxidation resistance (up to 750 degrees C) have potential applications in fuel-cell catalysts and nanodevices.

  7. Electronic band structure and Fermi surfaces of the quasi-two-dimensional monophosphate tungsten bronze, P4W12O44

    Science.gov (United States)

    Paul, S.; Ghosh, A.; Sato, T.; Sarma, D. D.; Takahashi, T.; Wang, E.; Greenblatt, M.; Raj, S.

    2014-02-01

    The electronic structure of quasi-two-dimensional monophosphate tungsten bronze, P4W12O44, has been investigated by high-resolution angle-resolved photoemission spectroscopy and density functional theoretical calculations. Experimental electron-like bands around \\Gamma point and Fermi surfaces have similar shapes as predicted by calculations. Fermi surface mapping at different temperatures shows a depletion of density of states at low temperature in certain flat portions of the Fermi surfaces. These flat portions of the Fermi surfaces satisfy the partial nesting condition with incommensurate nesting vectors q_1 and q_2 , which leads to the formation of charge density waves in this phosphate tungsten bronzes. The setting up of charge density wave in these bronzes can well explain the anomaly observed in its transport properties.

  8. Surface modification to prevent oxide scale spallation

    Science.gov (United States)

    Stephens, Elizabeth V; Sun, Xin; Liu, Wenning; Stevenson, Jeffry W; Surdoval, Wayne; Khaleel, Mohammad A

    2013-07-16

    A surface modification to prevent oxide scale spallation is disclosed. The surface modification includes a ferritic stainless steel substrate having a modified surface. A cross-section of the modified surface exhibits a periodic morphology. The periodic morphology does not exceed a critical buckling length, which is equivalent to the length of a wave attribute observed in the cross section periodic morphology. The modified surface can be created using at least one of the following processes: shot peening, surface blasting and surface grinding. A coating can be applied to the modified surface.

  9. Surface cracking of tungsten-vanadium alloys under transient heat loads

    Directory of Open Access Journals (Sweden)

    Kameel Arshad

    2015-07-01

    Full Text Available To evaluate high heat load performance of tungsten-vanadium (W-V alloys as a potential candidate for plasma facing materials of fusion devices, the target materials with three different V concentrations (1, 5 and 10 wt% are exposed to thermal shock loading. The alloys are fabricated by cold isostatic pressing and subsequently sintered in a vacuum furnace. Thereafter, they are exposed to different high heat flux densities ranging from 340 to 675 MW/m2 for single shot of 5 ms duration in an intense electron beam test facility. The alloys with lowest V concentration (1 wt% are highly damaged in form of seriously cracking. The ones with intermediate V content (5 wt% has shown comparatively better performance than both highest and lowest V contents alloys. The results indicate that improved mechanical properties and reduced thermal conductivity due to V addition comprehensively affect the cracking behavior of W-V alloy under transient thermal shock.

  10. Analysis of effect of temperature gradients on surface-tension phenomena in gas-tungsten-arc welds

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H.A.; Chien, P.S.J.

    1982-10-01

    Fluid motion directed by surface tension is considered as a contributor to heat penetration in a weld pool. The potential phenomena at the gas-liquid interface were analyzed, and the dependence of surface motion on temperature in the gas-tungsten-arc (GTA) welding process was examined. An existing heat-transfer model was used and was able to predict weld size to +- 50% of the actual value. A momentum-transfer equation was derived by considering the contribution of Lorentz force. The momentum boundary condition was developed and was able to predict the Marangoni effect. The magnitude of surface-tension-driven force is comparable to the gravitational force on one gram. An empirical approach was proposed to couple heat-transfer and momentum-transfer phenomena. A dimensional analysis identified the pertinent dimensionless groups as Reynolds, Weber, Froude, Peclet, and Power numbers and a dimensionless velocity. A simplified form of the correction was developed by combining dimensionless groups to yield a correlation with the Bond, Prandtl, and modified power numbers. Future experimental work was proposed to test the functionality of the dimensionless groups.

  11. Influence of tungsten microstructure and ion flux on deuterium plasma-induced surface modifications and deuterium retention

    Energy Technology Data Exchange (ETDEWEB)

    Buzi, L., E-mail: l.buzi@fz-juelich.de [Forschungszentrum Jülich GmbH, Institut für Energie – und Klimaforschung - Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich (Germany); FOM Institute DIFFER – Dutch Institute for Fundamental Energy Research, Partner in the Trilateral Euregio Cluster (Netherlands); Gent University, Sint-Pietersnieuwstraat 41, B-9000 Gent (Belgium); Université de Lorraine, Institut Jean Lamour, CNRS UMR 7198, Bvd. des Aiguillettes, F-54506 Vandoeuvre (France); De Temmerman, G. [FOM Institute DIFFER – Dutch Institute for Fundamental Energy Research, Partner in the Trilateral Euregio Cluster (Netherlands); Unterberg, B.; Reinhart, M.; Dittmar, T.; Matveev, D.; Linsmeier, Ch. [Forschungszentrum Jülich GmbH, Institut für Energie – und Klimaforschung - Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich (Germany); Breuer, U. [Central Institute of Engineering, Electronics and Analytics, ZEA-3 Analytics, Research Centre Jülich GmbH, 52425 Jülich (Germany); Kreter, A. [Forschungszentrum Jülich GmbH, Institut für Energie – und Klimaforschung - Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich (Germany); Van Oost, G. [Gent University, Sint-Pietersnieuwstraat 41, B-9000 Gent (Belgium)

    2015-08-15

    The influence of surface temperature, particle flux density and material microstructure on the surface morphology and deuterium retention was studied by exposing tungsten targets (20 μm and 40 μm grain size) to deuterium plasma at the same particle fluence (10{sup 26} m{sup −2}) and incident ion energy (40 eV) to two different ion fluxes (low flux: 10{sup 22} m{sup −2} s{sup −1}, high flux: 10{sup 24} m{sup −2} s{sup −1}). The maximum of deuterium retention was observed at ∼630 K for low flux density and at ∼870 K for high flux density, as indicated from the thermal desorption spectroscopy data (TDS). Scanning electron microscopy observations revealed the presence of blisters with a diameter of up to 1 μm which were formed at high flux density and high temperature (1170 K) contrasting with previously reported surface modification results at such exposure conditions.

  12. Deuterium retention and morphological modifications of the surface in five grades of tungsten after deuterium plasma exposure

    Energy Technology Data Exchange (ETDEWEB)

    Balden, M., E-mail: Martin.Balden@ipp.mpg.de; Manhard, A.; Elgeti, S.

    2014-09-15

    Highlights: • D retention for used W grades varies by more than one order of magnitude. • Hydrogen loading-induced damaging manifests in surface modifications and retention. • Effects of plasma flux on retention and surface modifications are discussed. • Higher fluxes produce more severe hydrogen loading-induced damaging. - Abstract: Five tungsten (W) grades were simultaneously exposed to deuterium (D) plasma with 10{sup 20} D/(m{sup 2} s) of 38 eV/D up to 10{sup 26} D/m{sup 2} at 500 K specimen temperature. The D inventories and their depth profiles within the topmost 12 μm were determined by nuclear reaction analysis (D({sup 3}He, p)α). Morphological modifications at and below the surface were analysed by confocal laser scanning microscopy and scanning electron microscopy assisted by focused ion beam cross-sectioning. The observed variation of the D inventory by more than one order of magnitude (0.5–15 × 10{sup 20} D/m{sup 2}) is attributed only to the different properties of each W grade. Spherical blisters and stepped flat-topped extrusions are observed depending on the W grade. These modifications are interpreted as an indication for hydrogen loading-induced damaging. The exposure conditions and W grades were chosen to allow a comparison between published data sets.

  13. Analysis of effect of temperature gradients on surface-tension phenomena in gas-tungsten-arc welds

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H.A.; Chien, P.S.J.

    1982-10-01

    Fluid motion directed by surface tension is considered as a contributor to heat penetration in a weld pool. The potential phenomena at the gas-liquid interface were analyzed, and the dependence of surface motion on temperature in the gas-tungsten-arc (GTA) welding process was examined. An existing heat-transfer model was used and was able to predict weld size to +- 50% of the actual value. A momentum-transfer equation was derived by considering the contribution of Lorentz force. The momentum boundary condition was developed and was able to predict the Marangoni effect. The magnitude of surface-tension-driven force is comparable to the gravitational force on one gram. An empirical approach was proposed to couple heat-transfer and momentum-transfer phenomena. A dimensional analysis identified the pertinent dimensionless groups as Reynolds, Weber, Froude, Peclet, and Power numbers and a dimensionless velocity. A simplified form of the correction was developed by combining dimensionless groups to yield a correlation with the Bond, Prandtl, and modified power numbers. Future experimental work was proposed to test the functionality of the dimensionless groups.

  14. In situ diagnosis of pulsed UV laser surface ablation of tungsten carbide hardmetal by using laser-induced optical emission spectroscopy

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

    2001-12-01

    Surface ablation of cobalt cemented tungsten carbide hardmetal with pulsed UV laser has been in situ diagnosed by using the technique of laser-induced optical emission spectroscopy. The dependence of emission intensity of cobalt lines on number of laser shots was investigated at laser fluence of 2.5 J/cm 2. As a comparison, the reliance of emission intensity of cobalt lines as a function of laser pulse number by using pure cobalt as ablation sample was also studied at the same laser condition. It was found that for surface ablation of tungsten carbide hardmetal at laser fluence of 2.5 J/cm 2, the intensities of cobalt lines fell off dramatically in the first 300 consecutive laser shots and then slowed down to a low stable level with even more shots. For surface ablation of pure cobalt at the same laser condition, the intensities of cobalt lines remained constant more or less even after 500 laser shots and then reduced very slowly with even more shots. It was concluded that selective evaporation of cobalt at this laser fluence should be responsible for the dramatic fall-off of cobalt lines with laser shots accumulation for surface ablation of tungsten carbide hardmetal. In contrast, for surface ablation of pure cobalt, the slow reduction of cobalt lines with pulse number accumulation should be due to the formation of laser-induced crater effect.

  15. Surface wrinkling on polydimethylsiloxane microspheres via wet surface chemical oxidation.

    Science.gov (United States)

    Yin, Jian; Han, Xue; Cao, Yanping; Lu, Conghua

    2014-07-16

    Here we introduce a simple low-cost yet robust method to realize spontaneously wrinkled morphologies on spherical surfaces. It is based on surface chemical oxidation of aqueous-phase-synthesized polydimethylsiloxane (PDMS) microspheres in the mixed H2SO4/HNO3/H2O solution. Consequently, curvature and overstress-sensitive wrinkles including dimples and labyrinth patterns are successfully induced on the resulting oxidized PDMS microspheres. A power-law dependence of the wrinkling wavelength on the microsphere radius exists. The effects of experimental parameters on these tunable spherical wrinkles have been systematically investigated, when the microspheres are pre-deposited on a substrate. These parameters include the radius and modulus of microspheres, the mixed acid solution composition, the oxidation duration, and the water washing post-treatment. Meanwhile, the complicated chemical oxidation process has also been well studied by in-situ optical observation via the microsphere system, which represents an intractable issue in a planar system. Furthermore, we realize surface wrinkled topographies on the whole microspheres at a large scale, when microspheres are directly dispersed in the mixed acid solution for surface oxidation. These results indicate that the introduced wet surface chemical oxidation has the great potential to apply to other complicated curved surfaces for large-scale generation of well-defined wrinkling patterns, which endow the solids with desired physical properties.

  16. The synthesis of tungsten trioxide gel by dissolution of tungsten in hydrogen peroxide and its transformations during the heat treatment in oxidation and reduction atmospheres

    Directory of Open Access Journals (Sweden)

    Georgijević Radovan

    2011-01-01

    Full Text Available The structure and the thermal behavior of WO3 samples in air and in reduction atmosphere were studied. The sample I was prepared by the dissolution of fine metallic tungsten powder in hydrogen peroxide followed by solvent evaporation in the air at 60°C. Sample II was obtained by draining a part of the sample I at 60°C and then heating it up to 430°C. By the means of X-ray diffractometry, scanning electron microscopy and thermal analysis it was evidenced that the sample I was the amorphous hydrated gel, with the WO3•1.5H2O composition, while the second one was the anhidrous monoclinic WO3 with the mean particle size of 100 nm. Additionally, using the thermogravimetric and the differential thermal analysis simultaneously in the reduction atmosphere, both samples types were examined. After reduction the distribution of the metal particles number in respect to the diameters of the anhidrous sample was examined using the electron microscopy.

  17. Hydrothermal Synthesis and Photochromism Property of Superfine Powders of Metastable Tungsten Oxide%介稳态氧化钨超微粉体的水热合成与光致变色性质研究

    Institute of Scientific and Technical Information of China (English)

    徐英明; 霍丽华; 赵辉; 高山; 赵经贵

    2005-01-01

    Under hydrothermal conditions, the superfine powders of cubic pyrochlore-type of tungsten oxide and hexagonal tungsten bronze were obtained by using Na2WO4·2H2O as the starting material. The products were characterized by XRD, TG, IR, UV and EPMA, respectively. The effects of the pH value, the acid concentration, reaction temperature and time on the structure and particle size of products were investigated in detail. The conditions for the preparation of superfine powders of tungsten oxide were optimized. The pH 2.5~4.5 of the reaction system led to the formation of a pyroehlore phase and pH 0.5~2.0 gave the hexagonal tungsten bronze structure. The photochromism property of the hexagonal tungsten bronze was studied. The results show that pyroehlore and bronze phases are decomposed at 300℃ and 450℃, respectively. With the increasing of temperature, the structure of the two oxides changes. The pyrochlore-type powder changes completely into trielinic Na2W4O13 around 500℃, while the bronze phase into a mixture of Na2W6O19 and trielinie WO3 at 550℃. The powder of the hexagonal tungsten bronze showed better photochromism property。

  18. Deuterium trapping and surface modification of polycrystalline tungsten exposed to a high-flux plasma at high fluences

    Science.gov (United States)

    Zibrov, M.; Balden, M.; Morgan, T. W.; Mayer, M.

    2017-04-01

    Deuterium (D) retention and surface modifications of hot-rolled polycrystalline tungsten (W) exposed to a low-energy (~40 eV D‑1), high-flux (2–5  ×  1023 D m‑2 s‑1) D plasma at temperatures of ~380 K and ~1140 K to fluences up to 1.2  ×  1028 D m‑2 have been examined by using nuclear reaction analysis, thermal desorption spectroscopy, and scanning electron microscopy. The samples exposed at ~380 K exhibited various types of surface modifications: dome-shaped blister-like structures, stepped flat-topped protrusions, and various types of nanostructures. It was observed that a large fraction of the surface was covered with blisters and protrusions, but their average size and the number density showed almost no fluence dependence. The D depth distributions and total D inventories also barely changed with increasing fluence at ~380 K. A substantial amount of D was retained in the subsurface region, and thickness correlated with the depth where the cavities of blisters and protrusions were located. It is therefore suggested that defects appearing during creation of blisters and protrusions govern the D trapping in the investigated fluence range. In addition, a large number of small cracks was observed on the exposed surfaces, which can serve as fast D release channels towards the surface, resulting in a reduction of the effective D influx into the W bulk. On the samples exposed at ~1140 K no blisters and protrusions were found. However, wave-like and faceted terrace-like structures were formed instead. The concentrations of trapped D were very low (<10‑5 at. fr.) after the exposure at ~1140 K.

  19. Solution-processed hybrid light emitting and photovoltaic devices comprising zinc oxide nanorod arrays and tungsten trioxide layers

    Directory of Open Access Journals (Sweden)

    Wei-Chi Chen

    2017-04-01

    Full Text Available The goal of this research is to prepare inverted optoelectronic devices with improved performance by combining zinc oxide (ZnO nanorod arrays and tungsten trioxide (WO3 layer. ZnO seed layers with thickness of 52 nm were established, followed by growth of ZnO nanorods with length of 300 nm vertical to the ITO substrates in the precursor bath. The ZnO nanorod arrays possess high transmittance up to 92% in the visible range. Inverted light-emitting devices with the configuration of ITO/ZnO nanorods/ionic PF/MEH-PPV/PEDOT:PSS/Au were constructed. The best device achieved a max brightness and current efficiency of 10,620 cd/m2 and 0.25 cd/A at 10 V, respectively, revealing much higher brightness compared with conventional devices using Ca/Al as cathode, or inverted devices based on ZnO thin film. By inserting a WO3 thin layer between PEDOT:PSS and Au electrode, the max brightness and current efficiency were further improved to 21,881 cd/m2 and 0.43 cd/A, respectively. Inverted polymer solar cells were also fabricated with the configuration of ITO/ZnO nanorods/ionic PF/P3HT:PC61BM/PEDOT/WO3/Au. The best device parameters, including the open-circuit voltage, short-circuit current density, fill factor, and power conversion efficiency, reached 0.54 V, 14.87 mA/cm2, 41%, and 3.31%, respectively

  20. A novel composite electrode based on tungsten oxide nanoparticles and carbon nanotubes for the electrochemical determination of paracetamol

    Energy Technology Data Exchange (ETDEWEB)

    Baytak, Aysegul Kutluay; Duzmen, Sehriban; Teker, Tugce; Aslanoglu, Mehmet, E-mail: maslanoglu@harran.edu.tr

    2015-12-01

    An electrochemical sensor was prepared by the modification of a glassy carbon electrode (GCE) with a composite of nanoparticles of tungsten oxide (WO{sub 3}) and carbon nanotubes (CNTs) for the quantification of paracetamol (PR). Energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) were performed for the characterization of the nanocomposite layer. Compared with a bare GCE and a GCE modified with CNTs, the proposed electrode (WO{sub 3}NPs/CNTs/GCE) exhibited a well-defined redox couple for PR and a marked enhancement of the current response. The experimental results also showed that ascorbic acid (AA) did not interfere with the selective determination of PR. The proposed electrode was used for the determination of PR in 0.1 M phosphate buffer solution (PBS) at pH 7.0 using square wave voltammetry (SWV). The peak current increased linearly with the concentration of PR in the range of 1.0 × 10{sup −9}–2.0 × 10{sup −7} M. The detection limit (LOD) was 5.54 × 10{sup −11} M (based on 3 S{sub b}/m). The proposed voltammetric sensor provided long-time stability, improved voltammetric behavior and good reproducibility for PR. The selective, accurate and precise determination of PR makes the proposed electrode of great interest for monitoring its therapeutic use. - Highlights: • A voltammetric nanosensor was prepared using nanoparticles of WO{sub 3} and CNTs. • A selective quantification of paracetamol was carried out in the presence of AA. • A linear plot was obtained for current responses versus concentrations over the range from 1.0 × 10{sup −9} to 2.0 × 10{sup −7} M. • A detection limit of 554 pM was obtained for paracetamol using the proposed nanosensor. • An accurate quantification makes the proposed nanosensor of great interest for public health.

  1. CO oxidation on PdO surfaces

    DEFF Research Database (Denmark)

    Hirvi, Janne T.; Kinnunen, Toni-Jani J.; Suvanto, Mika;

    2010-01-01

    , the reaction with the site blocking molecular oxygen is slightly more favorable, enabling also possible formation of carbonate surface species at low temperatures. The extreme activity of strongly bonded surface oxygen atoms is more greatly emphasized on the PdO(100)–O surface. The direct reaction without...... adsorption, following the Eley–Rideal mechanism and taking advantage of the reaction tunnel provided by the adjacent palladium atom, has an activation energy of only 0.24 eV. The reaction mechanism and activation energy for the palladium activated CO oxidation on the most stable PdO(100)–O surface......Density functional calculations were performed in order to investigate CO oxidation on two of the most stable bulk PdO surfaces. The most stable PdO(100) surface, with oxygen excess, is inert against CO adsorption, whereas strong adsorption on the stoichiometric PdO(101) surface leads to favorable...

  2. Surface protected lithium-metal-oxide electrodes

    Science.gov (United States)

    Thackeray, Michael M.; Kang, Sun-Ho

    2016-04-05

    A lithium-metal-oxide positive electrode having a layered or spinel structure for a non-aqueous lithium electrochemical cell and battery is disclosed comprising electrode particles that are protected at the surface from undesirable effects, such as electrolyte oxidation, oxygen loss or dissolution by one or more lithium-metal-polyanionic compounds, such as a lithium-metal-phosphate or a lithium-metal-silicate material that can act as a solid electrolyte at or above the operating potential of the lithium-metal-oxide electrode. The surface protection significantly enhances the surface stability, rate capability and cycling stability of the lithium-metal-oxide electrodes, particularly when charged to high potentials.

  3. Nanostructured tungsten trioxide thin films synthesized for photoelectrocatalytic water oxidation: a review.

    Science.gov (United States)

    Zhu, Tao; Chong, Meng Nan; Chan, Eng Seng

    2014-11-01

    The recent developments of nanostructured WO3 thin films synthesized through the electrochemical route of electrochemical anodization and cathodic electrodeposition for the application in photoelectrochemical (PEC) water splitting are reviewed. The key fundamental reaction mechanisms of electrochemical anodization and cathodic electrodeposition methods for synthesizing nanostructured WO3 thin films are explained. In addition, the effects of metal oxide precursors, electrode substrates, applied potentials and current densities, and annealing temperatures on size, composition, and thickness of the electrochemically synthesized nanostructured WO3 thin films are elucidated in detail. Finally, a summary is given for the general evaluation practices used to calculate the energy conversion efficiency of nanostructured WO3 thin films and a recommendation is provided to standardize the presentation of research results in the field to allow for easy comparison of reported PEC efficiencies in the near future. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Kinetics of Coloration in Photochromic Tungsten(VI) Oxide/Silicon Oxycarbide/Silica Hybrid Xerogel: Insight into Cation Self-diffusion Mechanisms.

    Science.gov (United States)

    Adachi, Kenta; Tokushige, Masataka; Omata, Kaoru; Yamazaki, Suzuko; Iwadate, Yoshiaki

    2016-06-08

    Silicon oxycarbide/silica composites with well-dispersed tungsten(VI) oxide (WO3) nanoparticles were obtained as transparent hybrid xerogels via an acid-catalyzed sol-gel process (hydrolysis/condensation polymerization) of 3-(triethoxysilyl)propyl methacrylate (TESPMA) and tetraethoxysilane (TEOS). The self-diffusion mechanism of alkali-metal cations and the kinetics of the photochromic coloration process in the WO3/TESPMA/TEOS hybrid xerogel systems have been systematically investigated. Under continuous UV illumination, a gradual color change (colorless → blue) corresponding to the reduction of W(6+) into W(5+) states in WO3 nanoparticles can be confirmed from the WO3/TESPMA/TEOS hybrid xerogels containing alkali-metal sulfates, although no coloration of the hybrid xerogel without alkali-metal sulfate was observed. The coloration behavior depended exclusively on a variety of alkali-metal cations present in the hybrid xerogel system. Furthermore, a detailed analysis of the self-diffusion mechanism confirmed that the alkali-metal cations electrostatically interact with a layer of unreacted silanol groups on the TESPMA/TEOS matrix surface, and subsequently pass through the interconnected pore network of the hybrid xerogel. More interestingly, in the context of an Arrhenius analysis, we found a good coincidence between the activation energies for alkali-metal cation self-diffusion and UV-induced coloration in the WO3/TESPMA/TEOS hybrid xerogel system containing the corresponding alkali-metal sulfate. It is experimentally obvious that the photochromic properties are dominated by the diffusion process of alkali-metal cations in the WO3/TESPMA/TEOS hybrid xerogel system. Such hybrid materials with cation-controlled photochromic properties will show promising prospects in applications demanding energy-efficient "smart windows" and "smart glasses".

  5. Hydrophobic monolayered nanoflakes of tungsten oxide: coupled exfoliation and fracture in a nonpolar organic medium.

    Science.gov (United States)

    Honda, Masashi; Oaki, Yuya; Imai, Hiroaki

    2015-06-21

    Coupled exfoliation and fracture induced formation of hydrophobic monolayered nanoflakes in a nonpolar organic medium. The hydrophobic monolayered nanoflakes 5-20 nm in lateral size consisted of a tungstate layer with surface modification by stearylammonium ions (C18H37NH3)0.397 H0.603Cs3W11O35·xH2O (x < 0.625).

  6. First-principles investigation of helium dissolution and clustering at a tungsten (1 1 0) surface

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jinlong; Zhang, Ying, E-mail: zhyi@buaa.edu.cn; Zhou, Hong-Bo; Jin, Shuo; Lu, Guang-Hong, E-mail: lgh@buaa.edu.cn

    2015-06-15

    Using a first-principles method, we have investigated dissolution, self-trapping and clustering of He at a W(1 1 0) surface. We found that the He atom is not energetically favorable at both the surface and the subsurface, but it becomes stable under the second atomic layer from the surface. The He is easier to be self-trapped to form an He cluster at the near surface in comparison with the bulk due to the larger self-trapping range and the stronger binding energy. With the formation of such He cluster, the vacancy and thus the He-vacancy complex are able to form at the near surface. The results will provide a useful reference for understanding formation of the He bubble at the W surface.

  7. Alloying the X40CrMoV5-1 steel surface layer with tungsten carbide by the use of a high power diode laser

    Energy Technology Data Exchange (ETDEWEB)

    Dobrzanski, L.A. [Institute of Engineering Materials and Biomaterials, Silesian University of Technology, 44-100 Gliwice, Konarskiego St. 18A (Poland); Bonek, M. [Institute of Engineering Materials and Biomaterials, Silesian University of Technology, 44-100 Gliwice, Konarskiego St. 18A (Poland)]. E-mail: mb@zmn.mt.polsl.gliwice.pl; Hajduczek, E. [Institute of Engineering Materials and Biomaterials, Silesian University of Technology, 44-100 Gliwice, Konarskiego St. 18A (Poland); Klimpel, A. [Welding Department, Silesian University of Technology, 44-100 Gliwice, Konarskiego St. 18A (Poland)

    2005-07-15

    The paper presents the effect of alloying with tungsten carbide on properties of the X40CrMoV5-1 steel surface layer, using the high power diode laser (HPDL). Selection of laser operating conditions is discussed, as well as thickness of the alloying layer, and their influence on structure and chemical composition of the steel. Analysis of the influence of the process conditions on the thicknesses of the alloyed layer and heat-affected zone is presented.

  8. Alloying the X40CrMoV5-1 steel surface layer with tungsten carbide by the use of a high power diode laser

    Science.gov (United States)

    Dobrzański, L. A.; Bonek, M.; Hajduczek, E.; Klimpel, A.

    2005-07-01

    The paper presents the effect of alloying with tungsten carbide on properties of the X40CrMoV5-1 steel surface layer, using the high power diode laser (HPDL). Selection of laser operating conditions is discussed, as well as thickness of the alloying layer, and their influence on structure and chemical composition of the steel. Analysis of the influence of the process conditions on the thicknesses of the alloyed layer and heat-affected zone is presented.

  9. Tungsten chemical vapor deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Hirano, Kiichi; Takeda, Nobuo.

    1993-07-13

    A tungsten chemical vapor deposition method is described, comprising: a first step of selectively growing a first thin tungsten film of a predetermined thickness in a desired region on the surface of a silicon substrate by reduction of a WF[sub 6] gas introduced into an atmosphere of a predetermined temperature containing said silicon substrate; and a second step of selectively growing a second tungsten film of a predetermined thickness on said first thin tungsten film by reduction of said WF[sub 6] with a silane gas further introduced into said atmosphere, wherein the surface state of said substrate is monitored by a pyrometer and the switching from said first step to said second step is performed when the emissivity of infrared light from the substrate surfaces reaches a predetermined value.

  10. Predicting a quaternary tungsten oxide for sustainable photovoltaic application by density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Sarker, Pranab; Huda, Muhammad N., E-mail: huda@uta.edu [Department of Physics, University of Texas at Arlington, Arlington, Texas 76019 (United States); Al-Jassim, Mowafak M. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

    2015-12-07

    A quaternary oxide, CuSnW{sub 2}O{sub 8} (CTTO), has been predicted by density functional theory (DFT) to be a suitable material for sustainable photovoltaic applications. CTTO possesses band gaps of 1.25 eV (indirect) and 1.37 eV (direct), which were evaluated using the hybrid functional (HSE06) as a post-DFT method. The hole mobility of CTTO was higher than that of silicon. Further, optical absorption calculations demonstrate that CTTO is a better absorber of sunlight than Cu{sub 2}ZnSnS{sub 4} and CuIn{sub x}Ga{sub 1−x}Se{sub 2} (x = 0.5). In addition, CTTO exhibits rigorous thermodynamic stability comparable to WO{sub 3}, as investigated by different thermodynamic approaches such as bonding cohesion, fragmentation tendency, and chemical potential analysis. Chemical potential analysis further revealed that CTTO can be synthesized at flexible experimental growth conditions, although the co-existence of at least one secondary phase is likely. Finally, like other Cu-based compounds, the formation of Cu vacancies is highly probable, even at Cu-rich growth condition, which could introduce p-type activity in CTTO.

  11. Occupational Exposure to Cobalt and Tungsten in the Swedish Hard Metal Industry: Air Concentrations of Particle Mass, Number, and Surface Area

    Science.gov (United States)

    Bryngelsson, Ing-Liss; Pettersson, Carin; Husby, Bente; Arvidsson, Helena; Westberg, Håkan

    2016-01-01

    Exposure to cobalt in the hard metal industry entails severe adverse health effects, including lung cancer and hard metal fibrosis. The main aim of this study was to determine exposure air concentration levels of cobalt and tungsten for risk assessment and dose–response analysis in our medical investigations in a Swedish hard metal plant. We also present mass-based, particle surface area, and particle number air concentrations from stationary sampling and investigate the possibility of using these data as proxies for exposure measures in our study. Personal exposure full-shift measurements were performed for inhalable and total dust, cobalt, and tungsten, including personal real-time continuous monitoring of dust. Stationary measurements of inhalable and total dust, PM2.5, and PM10 was also performed and cobalt and tungsten levels were determined, as were air concentration of particle number and particle surface area of fine particles. The personal exposure levels of inhalable dust were consistently low (AM 0.15mg m−3, range industrial settings. Regression analysis implied the use of stationary determined mass-based and particle surface area aerosol concentration as proxies for various exposure measures in our study. PMID:27143598

  12. Environmental remediation and superhydrophilicity of ultrafine antibacterial tungsten oxide-based nanofibers under visible light source

    Energy Technology Data Exchange (ETDEWEB)

    Srisitthiratkul, Chutima; Yaipimai, Wittaya [Nano Functional Textile Laboratory, National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), 111 Thailand Science Park, Phahonyothin Rd., Klong 1, Klong Luang, Pathumthani 12120 (Thailand); Intasanta, Varol, E-mail: varol@nanotec.or.th [Nano Functional Textile Laboratory, National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), 111 Thailand Science Park, Phahonyothin Rd., Klong 1, Klong Luang, Pathumthani 12120 (Thailand)

    2012-10-15

    Graphical abstract: Nanosilver-decorated WO{sub 3} photocatalytic nanofibers are antibacterial and superhydrophilic under a visible light source. Highlights: Black-Right-Pointing-Pointer Deposition of nanosilver onto electrospun WO{sub 3} nanofibers' surface was done exploiting visible or UV light driven photoreduction of silver ion. Black-Right-Pointing-Pointer Nanofibers showed antibacterial characteristics. Black-Right-Pointing-Pointer Nanofibers degraded a model toxin effectively. Black-Right-Pointing-Pointer Nanofibers showed superhydrophilicity under a visible light source. - Abstract: Fabrication of nanosilver-decorated WO{sub 3} nanofibers was successfully performed. First, deposition of nanosilver onto electrospun WO{sub 3} nanofibers' surface was done via photoreduction of silver ion under visible or UV light. The resulting hybrid nanofibers not only revealed antibacterial characteristics but also maintained their photocatalytic performance towards methylene blue decomposition. Unexpectedly, the nanofibrous layers prepared from these nanofibers showed superhydrophilicity under a visible light source. The nanofibers might be advantageous in environmental and hygienic nanofiltration under natural light sources, where the self-cleaning characteristics could be valuable in maintenance processes.

  13. Electrocatalytic Activity of Tungsten Trioxide Micro-spheres, Tungsten Carbide Microspheres and Multi-walled Carbon Nanotube-tungsten Carbide Composites

    Institute of Scientific and Technical Information of China (English)

    LU Hongzhi; YAN Taining

    2009-01-01

    Tungsten trioxide micropheres were prepared by spray pyrolysis, and tungsten carbidemicrospheres were produced by spray pyrolysis-low temperature reduction and carbonization technology.Multi-walled carbon nanotube-tungsten carbide composites were prepared by the continuous reductionand carbonization process using multi-walled carbon nanotubes (MWCNTs) and WO_3 precursor by mo-lecular level mixing and calcination. The morphology and structure of the samples were characterized byscanning electron microscope and transmission electron microscope. Furthermore, the crystal phase was identified by X-ray diffraction. The electrocatalytic activity of the sample was analyzed by means of me-thanol oxidation. Tungsten carbide microspheres were catalytic active for methanol oxidation reaction.Nevertheless tungsten trioxide microspheres and multi-walled carbon nanotube-tungsten carbide compos-ites were not catalytic active for methanol oxidation reaction. These results indicate that tungsten carbide micropheres are promising catalyst for methanol oxidation.

  14. Increased monolayer domain size and patterned growth of tungsten disulfide through controlling surface energy of substrates

    Science.gov (United States)

    Godin, Kyle; Kang, Kyungnam; Fu, Shichen; Yang, Eui-Hyeok

    2016-08-01

    We report a surface energy-controlled low-pressure chemical vapor deposition growth of WS2 monolayers on SiO2 using pre-growth oxygen plasma treatment of substrates, facilitating increased monolayer surface coverage and patterned growth without lithography. Oxygen plasma treatment of the substrate caused an increase in the average domain size of WS2 monolayers by 78%  ±  2% while having a slight reduction in nucleation density, which translates to increased monolayer surface coverage. This substrate effect on growth was exploited to grow patterned WS2 monolayers by patterned plasma treatment on patterned substrates and by patterned source material with resolutions less than 10 µm. Contact angle-based surface energy measurements revealed a dramatic increase in polar surface energy. A growth model was proposed with lowered activation energies for growth and increased surface diffusion length consistent with the range of results observed. WS2 samples grown with and without oxygen plasma were similar high quality monolayers verified through transmission electron microscopy, selected area electron diffraction, atomic force microscopy, Raman, and photoluminescence measurements. This technique enables the production of large-grain size, patterned WS2 without a post-growth lithography process, thereby providing clean surfaces for device applications.

  15. Characterization of a Cobalt-Tungsten Interconnect

    DEFF Research Database (Denmark)

    Harthøj, Anders; Holt, Tobias; Caspersen, Michael

    2012-01-01

    A ferritic steel interconnect for a solid oxide fuel cell must be coated in order to prevent chromium evaporation from the steel substrate. The Technical University of Denmark and Topsoe Fuel Cell have developed an interconnect coating based on a cobalt-tungsten alloy. The purpose of the coating...... is to act both as a diffusion barrier for chromium and provide better protection against high temperature oxidation than a pure cobalt coating. This work presents a characterization of a cobalt-tungsten alloy coating electrodeposited on the ferritic steel Crofer 22 H which subsequently was oxidized in air...... of oxidation time. The coating had completely oxidized during the 300 h oxidation time. GDOES measurements showed that the tungsten was located in an inner zone in the coating/substrate interface. The outer layer of the coating did not contain any tungsten after oxidation but consisted mainly of cobalt...

  16. Surface studies of gas sensing metal oxides.

    Science.gov (United States)

    Batzill, Matthias; Diebold, Ulrike

    2007-05-21

    The relation of surface science studies of single crystal metal oxides to gas sensing applications is reviewed. Most metal oxide gas sensors are used to detect oxidizing or reducing gases and therefore this article focuses on surface reduction processes and the interaction of oxygen with these surfaces. The systems that are discussed are: (i) the oxygen vacancy formation on the surface of the ion conductor CeO(2)(111); (ii) interaction of oxygen with TiO(2) (both adsorption processes and the incorporation of oxygen into the TiO(2)(110) lattice are discussed); (iii) the varying surface composition of SnO(2)(101) and its consequence for the adsorption of water; and (iv) Cu modified ZnO(0001)-Zn surfaces and its interaction with oxygen. These examples are chosen to give a comprehensive overview of surface science studies of different kinds of gas sensing materials and to illustrate the potential that surface science studies have to give fundamental insight into gas sensing phenomena.

  17. Gas-tungsten arc welding of aluminum alloys

    Science.gov (United States)

    Frye, Lowell D.

    1984-01-01

    A gas-tungsten arc welding method for joining together structures formed of aluminum alloy with these structures disposed contiguously to a heat-damagable substrate of a metal dissimilar to the aluminum alloy. The method of the present invention is practiced by diamond machining the fay surfaces of the aluminum alloy structures to provide a mirror finish thereon having a surface roughness in the order of about one microinch. The fay surfaces are aligned and heated sufficiently by the tungsten electrode to fuse the aluminum alloy contiguous to the fay surfaces to effect the weld joint. The heat input used to provide an oxide-free weld is significantly less than that required if the fay surfaces were prepared by using conventional chemical and mechanical practices.

  18. Atomically flat single terminated oxide substrate surfaces

    Science.gov (United States)

    Biswas, Abhijit; Yang, Chan-Ho; Ramesh, Ramamoorthy; Jeong, Yoon H.

    2017-05-01

    Scientific interest in atomically controlled layer-by-layer fabrication of transition metal oxide thin films and heterostructures has increased intensely in recent decades for basic physics reasons as well as for technological applications. This trend has to do, in part, with the coming post-Moore era, and functional oxide electronics could be regarded as a viable alternative for the current semiconductor electronics. Furthermore, the interface of transition metal oxides is exposing many new emergent phenomena and is increasingly becoming a playground for testing new ideas in condensed matter physics. To achieve high quality epitaxial thin films and heterostructures of transition metal oxides with atomically controlled interfaces, one critical requirement is the use of atomically flat single terminated oxide substrates since the atomic arrangements and the reaction chemistry of the topmost surface layer of substrates determine the growth and consequent properties of the overlying films. Achieving the atomically flat and chemically single terminated surface state of commercially available substrates, however, requires judicious efforts because the surface of as-received substrates is of chemically mixed nature and also often polar. In this review, we summarize the surface treatment procedures to accomplish atomically flat surfaces with single terminating layer for various metal oxide substrates. We particularly focus on the substrates with lattice constant ranging from 4.00 Å to 3.70 Å, as the lattice constant of most perovskite materials falls into this range. For materials outside the range, one can utilize the substrates to induce compressive or tensile strain on the films and explore new states not available in bulk. The substrates covered in this review, which have been chosen with commercial availability and, most importantly, experimental practicality as a criterion, are KTaO3, REScO3 (RE = Rare-earth elements), SrTiO3, La0.18Sr0.82Al0.59Ta0.41O3 (LSAT), Nd

  19. Cyclic Nanostructures of Tungsten Oxide (WO3) n   (n = 2-6) as NO x Gas Sensor: A Theoretical Study.

    Science.gov (United States)

    Izadyar, Mohammad; Jamsaz, Azam

    2014-01-01

    Today's WO3-based gas sensors have received a lot of attention, because of important role as a sensitive layer for detection of the small quantities of  NO x . In this research, a theoretical study has been done on the sensing properties of different cyclic nanoclusters of (WO3) n   (n = 2-6) for NO x   (x = 1,2) gases. Based on the calculated adsorption energies by B3LYP and X3LYP functionals, from the different orientations of  NO x molecule on the tungsten oxide clusters, O-N⋯W was preferred. Different sizes of the mentioned clusters have been analyzed and W2O6 cluster was chosen as the best candidate for NO x detection from the energy viewpoint. Using the concepts of the chemical hardness and electronic charge transfer, some correlations between the energy of adsorption and interaction energy have been established. These analyses confirmed that the adsorption energy will be boosted with charge transfer enhancement. However, the chemical hardness relationship is reversed. Finally, obtained results from the natural bond orbital and electronic density of states analysis confirmed the electronic charge transfer from the adsorbates to WO3 clusters and Fermi level shifting after adsorption, respectively. The last parameter confirms that the cyclic clusters of tungsten oxide can be used as NO x gas sensors.

  20. The co-adsorption of copper and oxygen on a tungsten 100 plane-type surface

    Science.gov (United States)

    Bauer, E.; Poppa, H.; Davis, P. R.; Viswanath, Y.

    1978-01-01

    The coadsorption of Cu on O2 and a W 100 plane-type surface is studied by Auger electron spectroscopy, thermal desorption, low energy electron diffraction and by work function change measurements. It is shown that the presence of Cu on the surface initially decreases the sticking coefficient of O2. For longer oxygen exposures and for higher adsorption temperatures, the coverage of preadsorbed oxygen reaches values larger than those on the clean surface for the same O2 exposure. Except at the highest values and temperatures of the coverage of preadsorbed oxygen, the sticking coefficient for copper is unity and is independent of the oxygen coverage in the range studied. Coadsorption at room temperatures does not produce any long range order while coadsorption at elevated temperature leads to ordered structures. The saturation coverage of the two dimensional coadsorbate at 800 K is given by a relation. The work function is a complicated function of the coverage of preadsorbed oxygen and the coverage of preadsorbed Cu and is determined predominantly by the temperature at which oxygen is adsorbed. At high temperatures the sequence of adsorption has no influence, in contrast to the room temperature behavior.

  1. Surface modification of cobalt-chromium-tungsten-nickel alloy using octadecyltrichlorosilanes

    Energy Technology Data Exchange (ETDEWEB)

    Mani, Gopinath [Department of Biomedical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States); Feldman, Marc D. [Department of Biomedical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States); Division of Cardiology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229 (United States); The Department of Veteran Affairs South Texas Health Care System, 7400 Merton Minter Blvd., San Antonio, TX 78229 (United States); Oh, Sunho [Department of Biomedical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States); Agrawal, C. Mauli [Department of Biomedical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States)], E-mail: Mauli.Agrawal@utsa.edu

    2009-03-15

    Cobalt-chromium (Co-Cr) alloys have been extensively used for medical implants because of their excellent mechanical properties, corrosion resistance, and biocompatibility. This first time study reports the formation and stability of self-assembled monolayers (SAMs) on a Co-Cr-W-Ni alloy. SAMs of octadecyltrichlorosilanes (OTS) were coated on sputtered Co-Cr-W-Ni alloy thin film and bulk Co-Cr-W-Ni alloy. OTS SAM coated alloy specimens were characterized using contact angle goniometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Contact angle analysis and FTIR suggested that ordered monolayers were coated on both sputtered and bulk alloy. XPS suggested the selective dissolution of cobalt from the alloy during the formation of OTS SAM. The bonding between the alloy and the OTS SAM was mainly attributed to Si-O-Cr and Si-O-W covalent bonds and a smaller contribution from Si-O-Co bonds. AFM images showed the distribution of islands of monolayers coated on the alloy. The height of monolayers in majority of the islands was closer to the theoretical length of fully extended OTS molecules oriented perpendicular to the surface. The stability of OTS SAM was investigated in tris-buffered saline at 37 {sup o}C for up to 7 days. Contact angle, FTIR, and XPS collectively confirmed that the monolayers remain ordered and bound to the alloy surface under this condition. This study shows that Co-Cr alloys can be surface modified using SAMs for potential biomedical applications.

  2. A chemical approach to understanding oxide surfaces

    Science.gov (United States)

    Enterkin, James A.; Becerra-Toledo, Andres E.; Poeppelmeier, Kenneth R.; Marks, Laurence D.

    2012-02-01

    Chemical bonding has often been ignored in favor of physics based energetic considerations in attempts to understand the structure, stability, and reactivity of oxide surfaces. Herein, we analyze the chemical bonding in published structures of the SrTiO3, MgO, and NiO surfaces using bond valence sum (BVS) analysis. These simple chemical bonding theories compare favorably with far more complex quantum mechanical calculations in assessing surface structure stability. Further, the coordination and bonding of surface structures explains the observed stability in a readily comprehensible manner. Finally, we demonstrate how simple chemical bonding models accurately predict the adsorption of foreign species onto surfaces, and how such models can be used to predict changes in surface structures.

  3. Geometric and electronic structure of dysprosium thin films on tungsten surfaces Structural and magnetic properties

    CERN Document Server

    Moslemzadeh, N

    2001-01-01

    The rare earth thin films are frequently the focus of investigators due to their unusual structural and magnetic properties. Despite the potential interest of Dy/W systems to the surface/rare earth community, they have been little studied. This study is the first try of growing Dy on W(100) and W(112) and W(110) in which almost a complete set of information about film morphology and electronic structure of the surface and interface have been achieved. A set of different experiments have been done for this purpose including LEED, XPS, UPS (with synchrotron radiation) and STM. The growth modes of Dy on different W substrates (W(100), W(112) and W(110)) at RT and at elevated temperatures have been determined by XPS of Dy 3d sub 3 sub / sub 2 and W 4f intensities. Crystallographic ordering and the epitaxial relationship between adsorbate Dy and different W substrates have been studied with LEED and the effect of annealing temperature on the resultant superstructures was investigated. As a complementary study to t...

  4. In vivo corrosion, tumor outcome, and microarray gene expression for two types of muscle-implanted tungsten alloys.

    Science.gov (United States)

    Schuster, B E; Roszell, L E; Murr, L E; Ramirez, D A; Demaree, J D; Klotz, B R; Rosencrance, A B; Dennis, W E; Bao, W; Perkins, E J; Dillman, J F; Bannon, D I

    2012-11-15

    Tungsten alloys are composed of tungsten microparticles embedded in a solid matrix of transition metals such as nickel, cobalt, or iron. To understand the toxicology of these alloys, male F344 rats were intramuscularly implanted with pellets of tungsten/nickel/cobalt, tungsten/nickel/iron, or pure tungsten, with tantalum pellets as a negative control. Between 6 and 12 months, aggressive rhabdomyosarcomas formed around tungsten/nickel/cobalt pellets, while those of tungsten/nickel/iron or pure tungsten did not cause cancers. Electron microscopy showed a progressive corrosion of the matrix phase of tungsten/nickel/cobalt pellets over 6 months, accompanied by high urinary concentrations of nickel and cobalt. In contrast, non-carcinogenic tungsten/nickel/iron pellets were minimally corroded and urinary metals were low; these pellets having developed a surface oxide layer in vivo that may have restricted the mobilization of carcinogenic nickel. Microarray analysis of tumors revealed large changes in gene expression compared with normal muscle, with biological processes involving the cell cycle significantly up-regulated and those involved with muscle development and differentiation significantly down-regulated. Top KEGG pathways disrupted were adherens junction, p53 signaling, and the cell cycle. Chromosomal enrichment analysis of genes showed a highly significant impact at cytoband 7q22 (chromosome 7) which included mouse double minute (MDM2) and cyclin-dependant kinase (CDK4) as well as other genes associated with human sarcomas. In conclusion, the tumorigenic potential of implanted tungsten alloys is related to mobilization of carcinogenic metals nickel and cobalt from corroding pellets, while gene expression changes in the consequent tumors are similar to radiation induced animal sarcomas as well as sporadic human sarcomas.

  5. Surface morphology, composition and thermal behavior of tungsten-containing anodic spark coatings on aluminium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Lukiyanchuk, I.V.; Rudnev, V.S.; Kuryavyi, V.G.; Boguta, D.L.; Bulanova, S.B.; Gordienko, P.S

    2004-01-01

    Anodic spark coatings on aluminium alloy were prepared in aqueous electrolytes with sodium tungstate. The influence of boric acid addition in the electrolyte on the surface morphology, elemental and phase composition of the coatings was investigated. In both cases the coatings contained O, Al and W. The coatings obtained in electrolyte with boric acid and sodium tungstate contain also B at approximately 1 at.%. Scanning electron microscopy indicated that the coatings had three layers: the grey underlayer of anodic alumina, the second black layer of crystalline or amorphous aluminium tungstate agglomerated into fibers and the outer green layer of WO{sub 3}. It was proposed that isopoly- and heteropolyanions in the electrolyte used take part in the coating growth.

  6. Electrolysis of water on (oxidized) metal surfaces

    DEFF Research Database (Denmark)

    Rossmeisl, Jan; Logadottir, Ashildur; Nørskov, Jens Kehlet

    2005-01-01

    directly from the electronic structure calculations. We consider electrodes of Pt(111) and Au(111) in detail and then discuss trends for a series of different metals. We show that the difficult step in the water splitting process is the formation of superoxy-type (OOH) species on the surface...... by the splitting of a water molecule on top an adsorbed oxygen atom. One conclusion is that this is only possible on metal surfaces that are (partly) oxidized. We show that the binding energies of the different intermediates are linearly correlated for a number of metals. In a simple analysis, where the linear...... relations are assumed to be obeyed exactly, this leads to a universal relationship between the catalytic rate and the oxygen binding energy. Finally, we conclude that for systems obeying these relations, there is a limit to how good a water splitting catalyst an oxidized metal surface can become. (c) 2005...

  7. The Newly Released Export Quota for Tungsten Products

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    <正>China’s Ministry of Commerce recently announced the second lot of export quota for tungsten products in 2005. Based on the new quota, the second lot for Ammonium Paratung-state (APT) and Ammonium Metatungstate (AMT) will be 1,232 tons. The second lot for tungsten trioxide and blue tungsten oxide will be 1,480 tons and the second lot for tungsten powder and its products will be 428 tons.

  8. In vivo corrosion, tumor outcome, and microarray gene expression for two types of muscle-implanted tungsten alloys

    Energy Technology Data Exchange (ETDEWEB)

    Schuster, B.E. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States); Roszell, L.E. [U.S. Army Institute of Public Health, 5158 Blackhawk Road, Aberdeen Proving Ground, MD 21010‐5403 (United States); Murr, L.E.; Ramirez, D.A. [Department of Metallurgical and Materials Engineering, University of Texas, El Paso, TX 79968 (United States); Demaree, J.D. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States); Klotz, B.R. [Dynamic Science Inc., Aberdeen Proving Ground, MD 21005‐5609 (United States); Rosencrance, A.B.; Dennis, W.E. [U.S. Army Center for Environmental Health Research, Department of Chemistry, Ft. Detrick, MD 21702‐5010 (United States); Bao, W. [SAS Institute, Inc. SAS Campus Drive, Cary, NC 27513 (United States); Perkins, E.J. [U.S. Army Engineer Research and Development Center, 3909 Hall Ferry Road, Vicksburg MS 39180 (United States); Dillman, J.F. [U.S. Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground, MD 21010‐5400 (United States); Bannon, D.I., E-mail: desmond.bannon@us.army.mil [U.S. Army Institute of Public Health, 5158 Blackhawk Road, Aberdeen Proving Ground, MD 21010‐5403 (United States)

    2012-11-15

    Tungsten alloys are composed of tungsten microparticles embedded in a solid matrix of transition metals such as nickel, cobalt, or iron. To understand the toxicology of these alloys, male F344 rats were intramuscularly implanted with pellets of tungsten/nickel/cobalt, tungsten/nickel/iron, or pure tungsten, with tantalum pellets as a negative control. Between 6 and 12 months, aggressive rhabdomyosarcomas formed around tungsten/nickel/cobalt pellets, while those of tungsten/nickel/iron or pure tungsten did not cause cancers. Electron microscopy showed a progressive corrosion of the matrix phase of tungsten/nickel/cobalt pellets over 6 months, accompanied by high urinary concentrations of nickel and cobalt. In contrast, non-carcinogenic tungsten/nickel/iron pellets were minimally corroded and urinary metals were low; these pellets having developed a surface oxide layer in vivo that may have restricted the mobilization of carcinogenic nickel. Microarray analysis of tumors revealed large changes in gene expression compared with normal muscle, with biological processes involving the cell cycle significantly up‐regulated and those involved with muscle development and differentiation significantly down‐regulated. Top KEGG pathways disrupted were adherens junction, p53 signaling, and the cell cycle. Chromosomal enrichment analysis of genes showed a highly significant impact at cytoband 7q22 (chromosome 7) which included mouse double minute (MDM2) and cyclin‐dependant kinase (CDK4) as well as other genes associated with human sarcomas. In conclusion, the tumorigenic potential of implanted tungsten alloys is related to mobilization of carcinogenic metals nickel and cobalt from corroding pellets, while gene expression changes in the consequent tumors are similar to radiation induced animal sarcomas as well as sporadic human sarcomas. -- Highlights: ► Tungsten/nickel/cobalt, tungsten/nickel/iron, and pure tungsten were studied. ► Male Fischer rats implanted with

  9. Surface and bulk aspects of mixed oxide catalytic nanoparticles: oxidation and dehydration of CH(3)OH by polyoxometallates.

    Science.gov (United States)

    Nakka, Lingaiah; Molinari, Julie E; Wachs, Israel E

    2009-10-28

    The molecular structures and surface chemistry of mixed metal oxide heteropolyoxo vanadium tungstate (H(3+x)PW(12-x)V(x)O(40) with x = 0, 1, 2, and 3) Keggin nanoparticles (NPs), where vanadium is incorporated into the primary Keggin structure, and supported VO(x) on tungstophosphoric acid (TPA, H(3)PW(12)O(40)), where vanadium is present on the surface of the Keggin unit, were investigated with solid-state magic angle spinning (51)V NMR, FT-IR, in situ Raman, in situ UV-vis, CH(3)OH temperature-programmed surface reaction (TPSR), and steady-state methanol oxidation. The incorporated VO(x) unit possesses one terminal V horizontal lineO bond, four bridging V-O-W/V bonds, and one long V-O-P bond in the primary Keggin structure, and the supported VO(x) unit possesses a similar coordination in the secondary structure under ambient conditions. The specific redox reaction rate for VO(x) in the Keggin primary structure is comparable to that of bulk V(2)O(5) and the more active supported vanadium oxide catalysts. The specific acidic reaction rate for the WO(x) in the TPA Keggin, however, is orders of magnitude greater than found for bulk WO(3), supported tungsten oxide catalysts, and even the highly acidic WO(3)-ZrO(2) catalyst synthesized by coprecipitation of ammonium metatungstate and ZrO(OH)(2). From CH(3)OH-TPSR and in situ Raman spectroscopy it was found that incorporation of vanadium oxide into the primary Keggin structure is also accompanied by the formation of surface VO(x) species at secondary sites on the Keggin outer surface. Both CH(3)OH-TPSR and steady-state methanol oxidation studies demonstrated that the surface VO(x) species on the Keggin outer surface are significantly less active than the VO(x) species incorporated into the primary Keggin structure. The presence of the less active surface VO(x) sites in the Keggins, thus, decreases the specific reaction rates for both methanol oxidation and methanol dehydration. During methanol oxidation/dehydration (O(2

  10. Laser-induced breakdown spectroscopy for on-line control of selective removal of cobalt binder from tungsten carbide hardmetal by pulsed UV laser surface ablation

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

    2001-09-01

    Laser-induced breakdown spectroscopy (LIBS) was successfully used in on-line control of selective removal of cobalt from tungsten carbide hardmetal by pulsed UV laser surface ablation. The dependence of LIBS on number of laser shots was investigated at different laser fluences. The optimal laser fluence of 2.5 J/cm 2 suited for selective removal of cobalt from surface layer of hardmetal was confirmed. The result sample was also subject to different post-examinations to evaluate the feasibility of the application of LIBS in this laser ablation process. It was demonstrated that, monitoring of the emission intensity of cobalt lines could be used as a control parameter for selective removal of cobalt from surface layer of hardmetal by pulsed UV laser. The on-line implementation of the spectroscopic technique LIBS to the surface-ablation process provided important information about the optimal-ablation parameters.

  11. Preparation and electrocatalytic properties of tungsten carbide electrocatalysts

    Institute of Scientific and Technical Information of China (English)

    马淳安; 张文魁; 成旦红; 周邦新

    2002-01-01

    The tungsten carbide(WC) electrocatalysts with definite phase components and high specific surface area were prepared by gas-solid reduction method. The crystal structure, phase components and electrochemical properties of the as-prepared materials were characterized by XRD, BET(Brunauer Emmett and Teller Procedure) and electrochemical test techniques. It is shown that the tungsten carbide catalysts with definite phase components can be obtained by controlling the carburizing conditions including temperature, gas flowing rate and duration time. The electrocatalysts with the major phase of W2C show higher electrocatalytic activity for the hydrogen evolution reaction. The electrocatalysts with the major phase of WC are suitable to be used as the anodic electrocatalyst for hydrogen anodic oxidation, which exhibit higher hydrogen anodic oxidation electrocatalytic properties in HCl solutions.

  12. Tungsten(VI) Carbyne/Bis(carbene) Tautomerization Enabled by N-Donor SBA15 Surface Ligands: A Solid-State NMR and DFT Study

    KAUST Repository

    Bendjeriou-Sedjerari, Anissa

    2016-08-11

    Designing supported well-defined bis(carbene) complexes remains a key challenge in heterogeneous catalysis. The reaction of W(CtBu)(CH(2)tBu)(3) with amine-modified mesoporous SBA15 silica, which has vicinal silanol/silylamine pairs [(SiOH)(SiNH2)], leads to [(SiNH2-)(SiO-)W(CHtBu)(CH(2)tBu)(2)] and [(SiNH2-)(SiO-)W(=CHtBu)(2)(CH(2)tBu). Variable temperature, H-1-H-1 2D double-quantum, H-1-C-13 HETCOR, and HETCOR with spin diffusion solid-state NMR spectroscopy demonstrate tautomerization between the alkyl alkylidyne and the bis(alkylidene) on the SBA15 surface. Such equilibrium is possible through the coordination of W to the surface [(Si-OH)(Si-NH2)] groups, which act as a [N,O] pincer ligand. DFT calculations provide a rationalization for the surface-complex tautomerization and support the experimental results. This direct observation of such a process shows the strong similarity between molecular mechanisms in homogeneous and heterogeneous catalysis. In propane metathesis (at 150 degrees C), the tungsten bis(carbene) tautomer is favorable, with a turnover number (TON) of 262. It is the highest TON among all the tungsten alkyl-supported catalysts.

  13. Surface Chemistry and Spectroscopy of Chromium in Inorganic Oxides

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Wachs, I.E.; Schoonheydt, R.A.

    1996-01-01

    Focuses on the surface chemistry and spectroscopy of chromium in inorganic oxides. Characterization of the molecular structures of chromium; Mechanics of hydrogenation-dehydrogenation reactions; Mobility and reactivity on oxidic surfaces.

  14. Fabrication of tungsten oxide microfibers with photocatalytic activity by electrospunning from PVA/H{sub 3}PW{sub 12}O{sub 40} gel

    Energy Technology Data Exchange (ETDEWEB)

    Sui Chunhong [College of Chemistry, Jilin University, Changchun 130023 (China); Department of Chemistry, Jilin Medical College, Jilin, 132013 (China); Gong Jian [Key Laboratory of Polyoxometalates Science of Ministry of Education, Northeast Normal University, Changchun 130024 (China); Cheng Tiexin [College of Chemistry, Jilin University, Changchun 130023 (China); Zhou Guangdong, E-mail: zhougd@jlu.edu.cn [College of Chemistry, Jilin University, Changchun 130023 (China); Dong Shunfu [Department of Chemistry, Jilin Medical College, Jilin, 132013 (China)

    2011-08-01

    Regarding gel poly (vinyl alcohol)/H{sub 3}PW{sub 12}O{sub 40} as precursor, the ultra-fine fibers tungsten oxide (WO{sub 3}) was prepared by using electrospinning and calcinating techniques. Scanning electron microscope (SEM) shows that the average diameter of fibrous WO{sub 3} were changed from 200 nm to 600 nm after calcined PVA/H{sub 3}PW{sub 12}O{sub 40} fibers at 600 and 800 {sup o}C, respectively. X-ray diffraction (XRD) and Raman spectroscope revealed that the fibrous WO{sub 3} was monoclinic phase, and the band-gap energies were observed by UV-vis diffuse reflectance spectra. The small size WO{sub 3} exhibits excellent photocatalytcic activity in degradation of Rhodamine B at 365 nm wavelength.

  15. Noble-metal-free tungsten oxide/carbon (WOx/C) hybrid manowires for highly efficient hydrogen evolution.

    Science.gov (United States)

    Liu, Changhai; Qiu, Yangyang; Xia, Yujian; Wang, Fang; Liu, Xiaocun; Sun, Xuhui; Liang, Qian; Chen, Zhidong

    2017-08-14

    Developing active, stable, and low-cost electrocatalysts to generate hydrogen is a great challenge in the fields of chemistry and energy. Nonprecious metal catalysts comprised of inexpensive and earth-abundant transition metals are regarded as a promising substitute for noble metal catalysts used in hydrogen evolution reaction (HER), but are still practically unfeasible mainly due to unsatisfactory activity and durability. Here we report a facile two-step preparation method for WOx nanowires with high concentration of oxygen vacancies (OVs) via calcination of W-polydopamine compound precursors. The resulting hybrid material possesses a uniform and ultralong 1D nanowires structure and a rough and raised surface, which can effectively improve the specific surface area. The products exhibit excellent performance for H2 generation: the required overpotentials for 1 and 10 mA cm(-2) are 18 and 108 mV, the Tafel slope is 46 mV/decade, and the electrochemically active surface area is estimated to be ∼77.0 m(2) g(-1). After 1000 cycles, the catalyst works well without significant current density drop. Our experimental results verified metallic transition metal oxides as superior non-Pt electrocatalysts for practical hydrogen evolution reactions.

  16. Perfluorodiethoxymethane on nickel and nickel oxide surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Jacobson, Joyce [Iowa State Univ., Ames, IA (United States)

    1994-03-03

    The interaction of perfluorodiethoxymethane with a nickel single crystal, Ni(100); a nickel crystal with chemisorbed oxygen, Ni(100)-c(2x2)O; and a nickel crystal with nickel oxide crystallites, NiO(100) is investigated in an ultra high vacuum environment using thermal desorption spectroscopy and high resolution electron energy loss spectroscopy. Nickel, a component of hard disk drives and stainless steel, is used to represent metal surfaces in these "real" systems. Perfluorodiethoxymethane is used in this study as a model compound of industrial perfluoropolyether lubricants. These lubricants are known for their exceptional stability, except in the presence of metals. Perfluorodiethoxymethane contains the acetal group (-OCF2O-), believed to be particularly vulnerable to attack in the presence of Lewis acids. Since the surfaces studied show increasing Lewis acidity at the nickel atom sites, one might expect to see increasing decomposition of perfluorodiethoxymethane due to acidic attack of the acetal group. No decomposition of perfluorodiethoxymethane is observed on the clean Ni(100) surface, while more research is needed to determine whether a small decomposition pathway is observed on the oxygenated surfaces, or whether sample impurities are interfering with results. The strength of the bonding of perfluorodiethoxymethane to the surface is found to increase as the nickel atoms sites become more acidic in moving from Ni(100) to Ni (100)-c(2x2)O to NiO (100).

  17. Photocatalytic Degradation of Methylene Blue by Tungsten Oxide and Reaction Order Discussion%三氧化钨光催化体系降解亚甲基蓝及反应级数的探讨

    Institute of Scientific and Technical Information of China (English)

    高红; 王学同

    2014-01-01

    三氧化钨是一种半导体光催化剂,可用于降解水中污染物。在用三氧化钨作为光催化剂处理亚甲基蓝模拟废水的反应中,通过单因素和正交实验,确定最佳处理条件为三氧化钨用量50mg、反应时间40min、H2O2用量4mL。并通过动力学研究,确定在不同三氧化钨光催化反应体系中的降解反应级数。%Tungsten trioxide was a semiconductor photocatalyst which could be used for degradation of pollutants in water. In the treatment of methylene blue simulation wastewater, tungsten oxide was applied as a photocatalyst, and through the single factor and orthogonal experiments, the optimal processing conditions were obtained:tungsten trioxide content 50mg, reaction time 40min, the dosage of H2O2 4mL. By the kinetics study, the degradation reaction order was determined in different tungsten oxide photocatalysis reaction system.

  18. Electroanalytical determination of tungsten and molybdenum in proteins.

    Science.gov (United States)

    Hagedoorn, P L; van't Slot, P; van Leeuwen, H P; Hagen, W R

    2001-10-01

    Recent crystal structure determinations accelerated the progress in the biochemistry of tungsten-containing enzymes. In order to characterize these enzymes, a sensitive determination of this metal in protein-containing samples is necessary. An electroanalytical tungsten determination has successfully been adapted to determine the tungsten and molybdenum content in enzymes. The tungsten and molybdenum content can be measured simultaneously from 1 to 10 microg of purified protein with little or no sample handling. More crude protein samples require precipitation of interfering surface active material with 10% perchloric acid. This method affords the isolation of novel molybdenum- and tungsten-containing proteins via molybdenum and tungsten monitoring of column fractions, without using radioactive isotopes. A screening of soluble proteins from Pyrococcus furiosus for tungsten, using anion-exchange column chromatography to separate the proteins, has been performed. The three known tungsten-containing enzymes from P. furiosus were recovered with this screening.

  19. Radiolysis of water with aluminum oxide surfaces

    Science.gov (United States)

    Reiff, Sarah C.; LaVerne, Jay A.

    2017-02-01

    Aluminum oxide, Al2O3, nanoparticles with water were irradiated with γ-rays and 5 MeV He ions followed by the determination of the production of molecular hydrogen, H2, and characterization of changes in the particle surface. Surface analysis techniques included: diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), nitrogen absorption with the Brunauer - Emmett - Teller (BET) methodology for surface area determination, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Production of H2 by γ-ray radiolysis was determined for samples with adsorbed water and for Al2O3 - water slurries. For Al2O3 samples with adsorbed water, the radiation chemical yield of H2 was measured as 80±20 molecules/100 eV (1 molecule/100 eV=1.04×10-7 mol/J). The yield of H2 was observed to decrease as the amount of water present in the Al2O3 - water slurries increased. Surface studies indicated that the α-phase Al2O3 samples changed phase following irradiation by He ions, and that the oxyhydroxide layer, present on the pristine sample, is removed by γ-ray and He ion irradiation.

  20. Synthesis of the cactus-like silicon nanowires/tungsten oxide nanowires composite for room-temperature NO{sub 2} gas sensor

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Weiyi, E-mail: zhangweiyi@tju.edu.cn [School of Electronic Information Engineering, Tianjin University, Tianjin, 300072 (China); Hu, Ming [School of Electronic Information Engineering, Tianjin University, Tianjin, 300072 (China); Key Laboratory for Advanced Ceramics and Machining Technology, Ministry of Education, School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Liu, Xing; Wei, Yulong; Li, Na [School of Electronic Information Engineering, Tianjin University, Tianjin, 300072 (China); Qin, Yuxiang, E-mail: qinyuxiang@tju.edu.cn [School of Electronic Information Engineering, Tianjin University, Tianjin, 300072 (China); Key Laboratory for Advanced Ceramics and Machining Technology, Ministry of Education, School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China)

    2016-09-15

    In the present work, the tungsten oxide (WO{sub 3}) nanowires functionalized silicon nanowires (SiNWs) with cactus-like structure has been successfully synthesized for room-temperature NO{sub 2} detection. The novel nanocomposite was fabricated by metal-assisted chemical etching (MACE) and thermal annealing of tungsten film. The WO{sub 3} nanowires were evenly distributed from the upper to the lower part of the SiNWs, indicating excellent uniformity which is conducive to adsorption and desorption of gas molecules. The gas-sensing properties have been examined by measuring the resistance change towards 0.25–5 ppm NO{sub 2} gas. At room temperature, which is the optimum working temperature, the SiNWs/WO{sub 3} nanowires composite showed two-times higher NO{sub 2} response than that of the bare SiNWs at 2 ppm NO{sub 2}. On the contrary, the responses of composite sensors to high concentrations of other reducing gases were very low, indicating excellent selectivity. Simultaneously, the composite sensors exhibited good sensing repeatability and stability. The enhancement in gas sensing properties may be attributed to the change in width of the space charge region, which is similar to the behavior of p-n junctions under forward bias, in the high-density p-n heterojunction structure formed between SiNWs and WO{sub 3} nanowires. - Highlights: • SiNWs/WO{sub 3} nanowires composite with cactus-like structure is synthesized. • The morphology of WO{sub 3} nanowires depends on the thermal annealing temperature. • The nanocomposite sensor exhibit better gas response than that of bare SiNWs. • The gas sensing mechanism is discussed using p-n heterojunction theory.

  1. Non-conventional halide oxidation pathways : oxidation by imidazole triplet and surface specific oxidation by ozone

    Science.gov (United States)

    Ammann, Markus; Corral-Arroyo, Pablo; Aellig, Raphael; Orlando, Fabrizio; Lee, Ming-Tao; Artiglia, Luca

    2016-04-01

    Oxidation of halide ions (chloride, bromide, iodide) are the starting point of halogen release mechanisms out of sea water, marine aerosol or other halide containing continental aerosols. Slow oxidation of chloride and bromide by ozone in the bulk aqueous phase is of limited relevance. Faster surface specific oxidation has been suggested based on heterogeneous kinetics experiments. We provide first insight into very efficient bromide oxidation by ozone at the aqueous solution - air interface by surface sensitive X-ray photoelectron spectroscopy indicating significant build-up of an oxidized intermediate at the surface within millisecond time scales. The second source of oxidants in the condensed we have considered is the absorption of light by triplet forming photosensitizers at wavelengths longer than needed for direct photolysis and radical formation. We have performed coated wall flow tube experiments with mixtures of citric acid (CA) and imidazole-2-carboxaldehyde (IC) to represent secondary organic material rich marine aerosol. The halide ions bromide and iodide have been observed to act as efficient electron donors leading to their oxidation, HO2 formation and finally release of molecular halogen compounds. The photosensitization of imidazole-2-carboxaldehyde (IC) involves a well-known mechanism where the triplet excited state of IC is reduced by citric acid to a reduced ketyl radical that reacts with halide ions. A competition kinetics approach has been used to evaluate the rate limiting steps and to assess the significance of this source of halogens to the gas phase.

  2. TUNGSTEN BASE ALLOYS

    Science.gov (United States)

    Schell, D.H.; Sheinberg, H.

    1959-12-15

    A high-density quaternary tungsten-base alloy having high mechanical strength and good machinability composed of about 2 wt.% Ni, 3 wt.% Cu, 5 wt.% Pb, and 90wt.% W is described. This alloy can be formed by the powder metallurgy technique of hot pressing in a graphite die without causing a reaction between charge and the die and without formation of a carbide case on the final compact, thereby enabling re-use of the graphite die. The alloy is formable at hot- pressing temperatures of from about 1200 to about 1350 deg C. In addition, there is little component shrinkage, thereby eliminating the necessity of subsequent extensive surface machining.

  3. The oxidation and surface speciation of indium and indium oxides exposed to atmospheric oxidants

    Science.gov (United States)

    Detweiler, Zachary M.; Wulfsberg, Steven M.; Frith, Matthew G.; Bocarsly, Andrew B.; Bernasek, Steven L.

    2016-06-01

    Metallic indium and its oxides are useful in electronics applications, in transparent conducting electrodes, as well as in electrocatalytic applications. In order to understand more fully the speciation of the indium and oxygen composition of the indium surface exposed to atmospheric oxidants, XPS, HREELS, and TPD were used to study the indium surface exposed to water, oxygen, and carbon dioxide. Clean In and authentic samples of In2O3 and In(OH)3 were examined with XPS to provide standard spectra. Indium was exposed to O2 and H2O, and the ratio of O2 - to OH- in the O1s XPS region was used to monitor oxidation and speciation of the surface. HREELS and TPD indicate that water dissociates on the indium surface even at low temperature, and that In2O3 forms at higher temperatures. Initially, OH- is the major species at the surface. Pure In2O3 is also OH- terminated following water exposure. Ambient pressure XPS studies of water exposure to these surfaces suggest that high water pressures tend to passivate the surface, inhibiting extensive oxide formation.

  4. Low-Temperature Preparation of Tungsten Oxide Anode Buffer Layer via Ultrasonic Spray Pyrolysis Method for Large-Area Organic Solar Cells.

    Science.gov (United States)

    Ji, Ran; Zheng, Ding; Zhou, Chang; Cheng, Jiang; Yu, Junsheng; Li, Lu

    2017-07-18

    Tungsten oxide (WO₃) is prepared by a low-temperature ultrasonic spray pyrolysis method in air atmosphere, and it is used as an anode buffer layer (ABL) for organic solar cells (OSCs). The properties of the WO₃ transition metal oxide material as well as the mechanism of ultrasonic spray pyrolysis processes are investigated. The results show that the ultrasonic spray pyrolysized WO₃ ABL exhibits low roughness, matched energy level, and high conductivity, which results in high charge transport efficiency and suppressive recombination in OSCs. As a result, compared to the OSCs based on vacuum thermal evaporated WO₃, a higher power conversion efficiency of 3.63% is reached with low-temperature ultrasonic spray pyrolysized WO₃ ABL. Furthermore, the mostly spray-coated OSCs with large area was fabricated, which has a power conversion efficiency of ~1%. This work significantly enhances our understanding of the preparation and application of low temperature-processed WO₃, and highlights the potential of large area, all spray coated OSCs for sustainable commercial fabrication.

  5. Low-Temperature Preparation of Tungsten Oxide Anode Buffer Layer via Ultrasonic Spray Pyrolysis Method for Large-Area Organic Solar Cells

    Directory of Open Access Journals (Sweden)

    Ran Ji

    2017-07-01

    Full Text Available Tungsten oxide (WO3 is prepared by a low-temperature ultrasonic spray pyrolysis method in air atmosphere, and it is used as an anode buffer layer (ABL for organic solar cells (OSCs. The properties of the WO3 transition metal oxide material as well as the mechanism of ultrasonic spray pyrolysis processes are investigated. The results show that the ultrasonic spray pyrolysized WO3 ABL exhibits low roughness, matched energy level, and high conductivity, which results in high charge transport efficiency and suppressive recombination in OSCs. As a result, compared to the OSCs based on vacuum thermal evaporated WO3, a higher power conversion efficiency of 3.63% is reached with low-temperature ultrasonic spray pyrolysized WO3 ABL. Furthermore, the mostly spray-coated OSCs with large area was fabricated, which has a power conversion efficiency of ~1%. This work significantly enhances our understanding of the preparation and application of low temperature-processed WO3, and highlights the potential of large area, all spray coated OSCs for sustainable commercial fabrication.

  6. Tungsten carbide nanoparticles as efficient cocatalysts for photocatalytic overall water splitting

    KAUST Repository

    Garcia Esparza, Angel T.

    2012-12-17

    Tungsten carbide exhibits platinum-like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C3N 4 (mpg-C3N4) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W 2C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H2 and O2 in a stoichiometric ratio from H 2O decomposition when supported on a Na-doped SrTiO3 photocatalyst. Herein, we present tungsten carbide (on a small scale) as a promising and durable catalyst substitute for platinum and other scarce noble-metal catalysts in catalytic reaction systems used for renewable energy generation. Platinum replacement: The phase-controlled synthesis of tungsten carbide nanoparticles from the nanoconfinement of a mesoporous graphite C 3N4 (mpg-C3N4) reactive template is shown. The nanomaterials catalyze hydrogen evolution/oxidation reactions, but are inactive in the oxygen reduction reaction. Tungsten carbide is an effective cocatalyst for photocatalytic overall water splitting (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Selective catalytic reduction of NOx with NH3 over iron-cerium-tungsten mixed oxide catalyst prepared by different methods

    Science.gov (United States)

    Xiong, Zhi-bo; Liu, Jing; Zhou, Fei; Liu, Dun-yu; Lu, Wei; Jin, Jing; Ding, Shi-fa

    2017-06-01

    A series of magnetic Fe0.85Ce0.10W0.05Oz catalysts were synthesized by three different methods(Co-precipitation(Fe0.85Ce0.10W0.05Oz-CP), Hydrothermal treatment assistant critic acid sol-gel method(Fe0.85Ce0.10W0.05Oz-HT) and Microwave irradiation assistant critic acid sol-gel method(Fe0.85Ce0.10W0.05Oz-MW)), and the catalytic activity was evaluated for selective catalytic reduction of NO with NH3. The catalyst was characterized by XRD, N2 adsorption-desorption, XPS, H2-TPR and NH3-TPD. Among the tested catalysts, Fe0.85Ce0.10W0.05Oz-MW shows the highest NOx conversion over per gram in unit time with NOx conversion of 60.8% at 350 °C under a high gas hourly space velocity of 1,200,000 ml/(g h). Different from Fe0.85Ce0.10W0.05Oz-CP catalyst, there exists a large of iron oxide crystallite(γ-Fe2O3 and α-Fe2O3) scattered in Fe0.85Ce0.10W0.05Oz catalysts prepared through hydrothermal treatment or microwave irradiation assistant critic acid sol-gel method, and higher iron atomic concentration on their surface. And Fe0.85Ce0.10W0.05Oz-MW shows higher surface absorbed oxygen concentration and better dispersion compared with Fe0.85Ce0.10W0.05Oz-HT catalyst. These features were favorable for the high catalytic performance of NO reduction with NH3 over Fe0.85Ce0.10W0.05Oz-MW catalyst.

  8. Fabrication of a tantalum-clad tungsten target for LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, A.T., E-mail: atnelson@lanl.gov [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); O' Toole, J.A.; Valicenti, R.A. [Accelerator Operations and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Maloy, S.A. [Civilian Nuclear Program Office, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2012-12-15

    Development of a solid state bonding technique suitable to clad tungsten targets with tantalum was completed to improve operation of the Los Alamos Neutron Science Centers spallation target. Significant deterioration of conventional bare tungsten targets has historically resulted in transfer of tungsten into the cooling system through corrosion resulting in increased radioactivity outside the target and reduction of delivered neutron flux. The fabrication method chosen to join the tantalum cladding to the tungsten was hot isostatic pressing (HIP) given the geometry constraints of a cylindrical assembly and previous success demonstrated at KENS. Nominal HIP parameters of 1500 Degree-Sign C, 200 MPa, and 3 h were selected based upon previous work. Development of the process included significant surface engineering controls and characterization given tantalums propensity for oxide and carbide formation at high temperatures. In addition to rigorous acid cleaning implemented at each step of the fabrication process, a three layer tantalum foil gettering system was devised such that any free oxygen and carbon impurities contained in the argon gas within the HIP vessel was mitigated to the extent possible before coming into contact with the tantalum cladding. The result of the numerous controls and refined techniques was negligible coarsening of the native Ta{sub 2}O{sub 5} surface oxide, no measureable oxygen diffusion into the tantalum bulk, and no detectable carburization despite use of argon containing up to 5 ppm oxygen and up to 40 ppm total CO, CO{sub 2}, or organic contaminants. Post bond characterization of the interface revealed continuous bonding with a few microns of species interdiffusion.

  9. Fabrication of a tantalum-clad tungsten target for LANSCE

    Science.gov (United States)

    Nelson, A. T.; O'Toole, J. A.; Valicenti, R. A.; Maloy, S. A.

    2012-12-01

    Development of a solid state bonding technique suitable to clad tungsten targets with tantalum was completed to improve operation of the Los Alamos Neutron Science Centers spallation target. Significant deterioration of conventional bare tungsten targets has historically resulted in transfer of tungsten into the cooling system through corrosion resulting in increased radioactivity outside the target and reduction of delivered neutron flux. The fabrication method chosen to join the tantalum cladding to the tungsten was hot isostatic pressing (HIP) given the geometry constraints of a cylindrical assembly and previous success demonstrated at KENS. Nominal HIP parameters of 1500 °C, 200 MPa, and 3 h were selected based upon previous work. Development of the process included significant surface engineering controls and characterization given tantalums propensity for oxide and carbide formation at high temperatures. In addition to rigorous acid cleaning implemented at each step of the fabrication process, a three layer tantalum foil gettering system was devised such that any free oxygen and carbon impurities contained in the argon gas within the HIP vessel was mitigated to the extent possible before coming into contact with the tantalum cladding. The result of the numerous controls and refined techniques was negligible coarsening of the native Ta2O5 surface oxide, no measureable oxygen diffusion into the tantalum bulk, and no detectable carburization despite use of argon containing up to 5 ppm oxygen and up to 40 ppm total CO, CO2, or organic contaminants. Post bond characterization of the interface revealed continuous bonding with a few microns of species interdiffusion.

  10. Oxidation of nickel surfaces by low energy ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Saric, Iva [Faculty of Civil Engineering, University of Rijeka (Croatia); Center for Micro and Nano Sciences and Technologies, University of Rijeka (Croatia); Peter, Robert; Kavre, Ivna; Badovinac, Ivana Jelovica; Petravic, Mladen [Center for Micro and Nano Sciences and Technologies, University of Rijeka (Croatia); Department of Physics, University of Rijeka (Croatia)

    2016-03-15

    We have studied formation of oxides on Ni surfaces by low energy oxygen bombardment using X-ray photoemission spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). Different oxidation states of Ni ions have been identified in XPS spectra measured around Ni 2p and O 1s core-levels. We have compared our results with thermal oxidation of Ni and shown that ion bombardment is more efficient in creating thin oxide films on Ni surfaces. The dominant Ni-oxide in both oxidation processes is NiO (Ni{sup 2+} oxidation state), while some Ni{sub 2}O{sub 3} contributions (Ni{sup 3+} oxidation state) are still present in all oxidised samples. The oxide thickness of bombarded Ni samples, as determined by SIMS, was shown to be related to the penetration depth of oxygen ions in Ni.

  11. Tungsten Alloy Outgassing Measurements

    CERN Document Server

    Rutherfoord, John P; Shaver, L

    1999-01-01

    Tungsten alloys have not seen extensive use in liquid argon calorimeters so far. Because the manufacturing process for tungsten is different from the more common metals used in liquid argon there is concern that tungsten could poison the argon thereby creating difficulties for precision calorimetry. In this paper we report measurements of outgassing from the tungsten alloy slugs proposed for use in the ATLAS FCal module and estimate limits on potential poisoning with reasonable assumptions. This estimate gives an upper limit poisoning rate of tungsten slugs.

  12. Ab initio study of proton dynamics on perovskite oxide surfaces

    Directory of Open Access Journals (Sweden)

    Fuyuki Shimojo

    2007-01-01

    Full Text Available First-principles studies of the proton dynamics in perovskite oxides and the water adsorption on various oxide surfaces are briefly reviewed. Recent progress in the study of the microscopic mechanism of the proton absorption from perovskite oxide surfaces is also presented. It is shown that dopant ions on the surface and oxygen vacancies in the inside just below the surface play an important role for the proton absorption, while oxygen vacancies on the surface are influential for the dissociative adsorption of water molecules.

  13. Extraction Factor Of Tungsten Sources From Tungsten Scraps By Zinc Decomposition Process

    Directory of Open Access Journals (Sweden)

    Pee J.-H.

    2015-06-01

    Full Text Available Decomposition promoting factors and extraction process of tungsten carbide and tungstic acid powders in the zinc decomposition process of tungsten scraps which are composed mostly of tungsten carbide and cobalt were evaluated. Zinc volatility was suppressed by the enclosed graphite crucible and zinc volatilization pressure was produced in the reaction graphite crucible inside an electric furnace for ZDP (Zinc Decomposition Process. Decomposition reaction was done for 2hours at 650°, which 100% decomposed the tungsten scraps that were over 30 mm thick. Decomposed scraps were pulverized under 75μm and were composed of tungsten carbide and cobalt identified by the XRD (X-ray Diffraction. To produce the WC(Tungsten Carbide powder directly from decomposed scraps, pulverized powders were reacted with hydrochloric acid to remove the cobalt binder. Also to produce the tungstic acid, pulverized powders were reacted with aqua regia to remove the cobalt binder and oxidize the tungsten carbide. Tungsten carbide and tungstic acid powders were identified by XRD and chemical composition analysis.

  14. ITER tungsten divertor design development and qualification program

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, T., E-mail: takeshi.hirai@iter.org [ITER Organization, Route de Vinon sur Verdon, F-13115 Saint Paul lez Durance (France); Escourbiac, F.; Carpentier-Chouchana, S.; Fedosov, A.; Ferrand, L.; Jokinen, T.; Komarov, V.; Kukushkin, A.; Merola, M.; Mitteau, R.; Pitts, R.A.; Shu, W.; Sugihara, M. [ITER Organization, Route de Vinon sur Verdon, F-13115 Saint Paul lez Durance (France); Riccardi, B. [F4E, c/ Josep Pla, n.2, Torres Diagonal Litoral, Edificio B3, E-08019 Barcelona (Spain); Suzuki, S. [JAEA, Fusion Research and Development Directorate JAEA, 801-1 Mukouyama, Naka, Ibaragi 311-0193 (Japan); Villari, R. [Associazione EURATOM-ENEA sulla Fusione, Via Enrico Fermi 45, I-00044 Frascati, Rome (Italy)

    2013-10-15

    Highlights: • Detailed design development plan for the ITER tungsten divertor. • Latest status of the ITER tungsten divertor design. • Brief overview of qualification program for the ITER tungsten divertor and status of R and D activity. -- Abstract: In November 2011, the ITER Council has endorsed the recommendation that a period of up to 2 years be set to develop a full-tungsten divertor design and accelerate technology qualification in view of a possible decision to start operation with a divertor having a full-tungsten plasma-facing surface. To ensure a solid foundation for such a decision, a full tungsten divertor design, together with a demonstration of the necessary high performance tungsten monoblock technology should be completed within the required timescale. The status of both the design and technology R and D activity is summarized in this paper.

  15. A Study of Scandia Doped Tungsten Nano-Powders

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Scandia and rhenium doped tungsten powders were prepared by solid-liquid doping combined with two-step reduction method. The particle size of doped tungsten and distribution of scandia and rhenium were studied by SEM, EDS, XRD and granularity analysis. Experimental results showed that scandia distributed evenly on the surface of tungsten particles. Addition of scandia and rhenium decreased the particle size of doped tungsten, and the more the content of scandia and rhenium, the smaller the doped tungsten particles. Tungsten powders doped with 3% Sc2O3 and 3% Re (mass fraction) had an average size of about 80 nm in diameter. The mechanism of the decrease in the tungsten particle size was discussed.

  16. Engineering Polarons at a Metal Oxide Surface

    Science.gov (United States)

    Yim, C. M.; Watkins, M. B.; Wolf, M. J.; Pang, C. L.; Hermansson, K.; Thornton, G.

    2016-09-01

    Polarons in metal oxides are important in processes such as catalysis, high temperature superconductivity, and dielectric breakdown in nanoscale electronics. Here, we study the behavior of electron small polarons associated with oxygen vacancies at rutile TiO2(110 ) , using a combination of low temperature scanning tunneling microscopy (STM), density functional theory, and classical molecular dynamics calculations. We find that the electrons are symmetrically distributed around isolated vacancies at 78 K, but as the temperature is reduced, their distributions become increasingly asymmetric, confirming their polaronic nature. By manipulating isolated vacancies with the STM tip, we show that particular configurations of polarons are preferred for given locations of the vacancies, which we ascribe to small residual electric fields in the surface. We also form a series of vacancy complexes and manipulate the Ti ions surrounding them, both of which change the associated electronic distributions. Thus, we demonstrate that the configurations of polarons can be engineered, paving the way for the construction of conductive pathways relevant to resistive switching devices.

  17. Surface oxidation of cobalt nanoparticles studied by Mossbauer spectroscopy

    DEFF Research Database (Denmark)

    Bødker, Franz; Mørup, Steen; Charles, S.W.

    1999-01-01

    The surface oxide formed on cobalt nanoparticles has been studied by Mossbauer emission spectroscopy. Exposure of the cobalt particles to oxygen at room temperature was found to result in the formation of a relatively well-ordered surface oxide with Mossbauer parameters similar to those of CoO....

  18. Enhancing the photoelectrochemical water splitting characteristics of titanium and tungsten oxide based materials via doping and sensitization

    Science.gov (United States)

    Gakhar, Ruchi

    To better utilize solar energy for clean energy production, efforts are needed to overcome the natural diurnal variation and the diffuse nature of sunlight. Photoelectrochemical (PEC) hydrogen generation by water splitting is a promising approach to harvest solar energy. Hydrogen gas is a clean and high energy capacity fuel. However, the solar-to-hydrogen conversion efficiency is determined mainly by the properties of the materials employed as photoanodes. Improving the power-conversion efficiency of PEC water splitting requires the design of inexpensive and efficient photoanodes that have strong visible light absorption, fast charge separation, and lower charge recombination rate. In the present study, PEC characteristics of various semiconducting photoelectrodes such as TiO2, WO3 and CuWO4 were investigated. Due to the inherent wide gap, such metal oxides absorb only ultraviolet radiation. Since ultraviolet radiation only composes of 4% of the sun's spectrum, the wide band gap results in lower charge collection and efficiency. Thusto improve optical absorption and charge separation, it is necessary to modify the band gap with low band gap materials.The two approaches followed for modification of band gap are doping and sensitization. Here, TiO2 and WO3 based photoanodes were sensitized with ternary quatum dots, while doping was the primary method utilized to investigate the modification of the band gap of CuWO4. The first part of this dissertation reports the synthesis of ternary quantum dot - sensitized titania nanotube array photoelectrodes. Ternary quantum dots with varying band gaps and composition (MnCdSe, ZnCdSe and CdSSe) were tethered to the surface of TiO2 nanotubes using succcessive ionic layer adsorption and reaction (SILAR) technique. The stoichiometry of ternary quantum dots was estimated to beMn0.095Cd0.95Se, Zn0.16Cd0.84Se and CdS0.54Se0.46. The effect of varying number of sensitization cycles and annealing temperature on optical and

  19. Process for the recovery of tungsten in a pure form from tungsten-containing materials

    Energy Technology Data Exchange (ETDEWEB)

    Fruchter, M.; Moscovici, A.

    1986-12-16

    A process is described for the recovery of tungsten from tungsten-containing materials which comprises the steps of (i) admixing the tungsten-containing material with a melt at a temperature of between 680/sup 0/C and 750/sup 0/C. The melt consists of a salt selected from the group consisting of sodium nitrate, sodium nitrite and mixtures thereof in a substantially stoichiometrical amount to the tungsten constituent of the tungsten-containing material. This is done to disintegrate the tungsten-containing material and to form sodium tungstate, cooling the melt, and leaching the cooled melt with water to obtain an aqueous solution of sodium tungstate; (ii) admixing a solution of calcium chloride with the aqueous solution of sodium tungstate at a temperature of between 40/sup 0/C and 95/sup 0/C to form a calcium tungstate precipitate and separating the calcium tungstate; (iii) admixing the calcium tungstate with a preheated concentrated hydrochloric acid solution to form a tungstic acid precipitate and a CaCl/sub 2/ solution having a concentration of between 80 g/l and 180 g/l free HCl and separating the tungstic acid precipitate and obtaining tungstic acid which is substantially free of calcium ions, and (iv) calcining the tungstic acid to convert it to tungstic oxide and reducing the tungstic oxide to form metallic tungsten.

  20. Developing a Thermal- and Coking-Resistant Cobalt-Tungsten Bimetallic Anode Catalyst for Solid Oxide Fuel Cells

    NARCIS (Netherlands)

    Yan, N.; Pandey, J.; Zeng, Y.; Amirkhiz, B.S.; Hua, B.; Geels, N.J.; Luo, J.L.; Rothenberg, G.

    2016-01-01

    We report the development of a novel Co–W bimetallic anode catalyst for solid oxide fuel cells (SOFCs) via a facile infiltration-annealing process. Using various microscopic and spectroscopic measurements, we find that the formed intermetallic nanoparticles are highly thermally stable up to 900 °C

  1. Relationship Between Iron Oxides and Surface Charge Characteristics in Soils

    Institute of Scientific and Technical Information of China (English)

    SHAOZONG-CHEN; WANGWEI-JUN

    1991-01-01

    The relationship between iron oxides and surface charge characteristics in variable charge soils (latosol and red earth) was studied in following three ways.(1)Remove free iron oxides (Fed) and amorphous iron oxides (Feo) from the soils with sodium dithionite and acid ammonium oxalate solution respectively.(2) Add 2% glucose (on the basis of air-dry soil weight) to soils and incubate under submerged condition to activate iron oxides,and then the mixtures are dehydrated and air-dried to age iron oxides.(3) Precipitate various crystalline forms of iron oxides onto kaolinite.The results showed that free iron oxides (Fed) were the chief carrier of variable positive charges.Of which crystalline iron oxides (Fed-Feo) presented mainly as discrete particles in the soils and could only play a role of the carrier of positive charges,and did little influence on negative charges.Whereas the amorphous iron oxides (Feo),which presented mainly fas a coating with a large specific surface area,not only had positive charges,but also blocked the negative charge sites in soils.Submerged incubation activated iron oxides in the soils,and increased the amount of amorphous iron oxides and the degree of activation of iron oxide,which resulted in the increase of positive and negative charges of soils.Dehydration and air-dry aged iron oxides in soils and decreased the amount of amorphous iron oxides and the degree of activation of iron oxide,and also led to the decrease of positive and negative charges.Both the submerged incubation and the dehydration and air-dry had no significant influence on net charges.Precipitation of iron oxides onto kaolinite markedly increased positive charges and decreased negative charges.Amorphous iron oxide having a larger surface area contributed more positive charge sites and blocked more negative charge sites in kaolinite than crystalline goethite.

  2. Surface chemistry of rare-earth oxide surfaces at ambient conditions: reactions with water and hydrocarbons

    National Research Council Canada - National Science Library

    Elçin Külah; Laurent Marot; Roland Steiner; Andriy Romanyuk; Thomas A Jung; Aneliia Wäckerlin; Ernst Meyer

    2017-01-01

    .... Here we first address physical properties of the RE oxide, nitride and fluoride surfaces modified by exposure to ambient air and then we report a room temperature reaction between PAH and RE oxide...

  3. Influence of ambient gases on the dc saturated breakdown field of molybdenum, tungsten, and copper during intense breakdown conditioning

    CERN Document Server

    Ramsvik, T; Reginelli, A; Taborelli, M

    2007-01-01

    A comprehensive investigation of the effect of Ar, H2, air, and CO on the saturated breakdown field (Esat) of molybdenum, tungsten, and copper has been performed at intensive breakdown conditioning. A significant decrease in Esat is observed for molybdenum and tungsten when exposed to air. Specifically, at air pressures of ∼10-5   mbar, the decrease in Esat is found to be up to 50% and ∼30% compared to UHV conditions for molybdenum and tungsten, respectively. In addition, a ∼30% decrease is found when molybdenum is conditioned with a ∼10-5   mbar CO pressure. Surface analysis measurements and breakdown conditioning in O2 ambience imply that the origin of the decrease in Esat is closely linked to oxide formation on the electrode surfaces. Ex situ heat treatment of molybdenum is shown to improve the breakdown characteristics drastically.

  4. Effect of ingested tungsten oxide (WOx) nanofibers on digestive gland tissue of Porcellio scaber (Isopoda, Crustacea): fourier transform infrared (FTIR) imaging.

    Science.gov (United States)

    Novak, Sara; Drobne, Damjana; Vaccari, Lisa; Kiskinova, Maya; Ferraris, Paolo; Birarda, Giovanni; Remškar, Maja; Hočevar, Matej

    2013-10-01

    Tungsten nanofibers are recognized as biologically potent. We study deviations in molecular composition between normal and digestive gland tissue of WOx nanofibers (nano-WOx) fed invertebrate Porcellio scaber (Iosopda, Crustacea) and revealed mechanisms of nano-WOx effect in vivo. Fourier Transform Infrared (FTIR) imaging performed on digestive gland epithelium was supplemented by toxicity and cytotoxicity analyses as well as scanning electron microscopy (SEM) of the surface of the epithelium. The difference in the spectra of the Nano-WOx treated and control cells showed up in the central region of the cells and were related to lipid peroxidation, and structural changes of nucleic acids. The conventional toxicity parameters failed to show toxic effects of nano-WOx, whereas the cytotoxicity biomarkers and SEM investigation of digestive gland epithelium indicated sporadic effects of nanofibers. Since toxicological and cytological measurements did not highlight severe effects, the biochemical alterations evidenced by FTIR imaging have been explained as the result of cell protection (acclimation) mechanisms to unfavorable conditions and indication of a nonhomeostatic state, which can lead to toxic effects.

  5. Understanding the surface and structural characteristics of tungsten oxide supported on tin oxide catalysts for the conversion of glycerol

    Indian Academy of Sciences (India)

    M Srinivas; G Raveendra; G Parameswaram; P S Sai Prasad; S Loridant; N Lingaiah

    2015-05-01

    Catalysts with varying WO3 content on SnO2 were prepared and characterized by X-ray diffraction, in situ Raman spectroscopy, X-ray photoelectron spectroscopy and temperature programmed desorption of NH3. In situ Raman analysis reveals the presence isolated monomers and polymeric species of WO3. These catalysts were evaluated for the conversion of glycerol into value added chemicals. Etherification of glycerol with tertiary butanol and preparation of glycerol carbonate from glycerol and urea are studied over these catalysts. The catalytic activity results suggest that the glycerol conversion and selectivity depends on the morphology of WO3 which in turn is related to its content in the catalyst. The catalysts with 5 wt.% of WO3 on SnO2 resulted in high dispersion with larger number of strong acidic sites. The selectivity in the glycerol etherification is related to the nature of the catalyst and reaction time. These catalysts also exhibited high activity for synthesis of glycerol carbonate. The effect of various reaction parameters was studied to optimize the reaction conditions. The catalysts also exhibited consistent activity upon reuse.

  6. Ellipsometrically determined optical properties of nickel-containing tungsten oxide thin films: Nanostructure inferred from effective medium theory

    OpenAIRE

    Valyukh, I.; Green, S.V.; Granqvist, C. G.; Gunnarsson, K.; Arwin, H.; Niklasson, G. A.

    2012-01-01

    Films of NixW1-x oxide with 0.05 andlt;= x andlt;= 0.53 were produced by reactive dc magnetron co-sputtering onto Si. Such films have documented electrochromism. Spectroscopic ellipsometry was used to extract accurate data on the dielectric function in the photon range 0.062 to 5.62 eV. The results for 0.62 to 5.62 eV were compared with computations from the Bruggeman effective medium theory applied to two nanostructural models: one representing a random mixture of structural entities charact...

  7. Electrochromic and electrochemical capacitive properties of tungsten oxide and its polyaniline nanocomposite films obtained by chemical bath deposition method

    CSIR Research Space (South Africa)

    Nwanya, AC

    2014-05-01

    Full Text Available Kenneth I. Ozoemena Fabian I. EzemaISE student member.ISE member. PII: S0013...-mail address: fiezema@yahoo.com 1 ISE student member 2 ISE member Page 2 of 31 Ac ce pte d M an us cri pt 2 Polyanine and its nanocomposite WO3/PANI films were deposited on Fluorine doped tin oxide (FTO) glass slides by simple Chemical Bath Deposition Method...

  8. Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

    Directory of Open Access Journals (Sweden)

    He Quanguo

    2008-01-01

    Full Text Available Abstract Surface functionalized magnetic iron oxide nanoparticles (NPs are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed.

  9. Volcano Relations for Oxidation of Hydrogen Halides over Rutile Oxide Surfaces

    DEFF Research Database (Denmark)

    Toftelund, Anja; Man, Isabela C.; Hansen, Heine A.

    2012-01-01

    We investigate the heterogeneously catalysed oxidation of HX (X=Cl, Br and I) on the RuO2 (110) surface with DFT. We also solve a micro-kinetic model of HX oxidation and compare oxidation activity at different coverages. We further establish linear energy relations for the reaction intermediates ...

  10. One-step inkjet printing of tungsten oxide-poly(3,4-ethylenedioxythiophene):polystyrene sulphonate hybrid film and its applications in electrochromic devices

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Thi-Thuy-Nga, E-mail: thuysnga@gmail.com; Chan, Chih-Yu; He, Ju-Liang

    2016-03-31

    Hybrid film comprised tungsten oxide and poly (3,4-ethylenedioxythiophene):polystyrene sulphonate (WO{sub 3}–PEDOT:PSS) was developed by applying one-step inkjet printing from an office inkjet printer. The WO{sub 3} nanoparticles were synthesized from commercial crystalline WO{sub 3} powder through a wet ball-milling process, which is a simple, environmentally friendly, and cost-effective method of using water as a green solvent and low-energy milling. The WO{sub 3}–PEDOT:PSS inkjet ink was prepared by dispersing the as-milled WO{sub 3} and PEDOT:PSS in n-propanol and deionized water. The inkjet-printed WO{sub 3}–PEDOT:PSS thin films show marked improvements of cathodic electrochromism over WO{sub 3} films: the transmittance change of 20% at 550 nm (visible region) and 35% at 900 nm (infrared region) along with the response time of 5.67/0.30 s in their colored/bleached state, and the electrochromic coloration efficiency of 27.86 cm{sup 2}/C at 550 nm and 69.64 cm{sup 2}/C at 900 nm. - Highlights: • WO{sub 3} nanoparticles were synthesized by milling commercial crystalline WO{sub 3}. • Wet ball-milling was carried out by using water as a green solvent and low energy. • WO{sub 3}–PEDOT:PSS hybrid ink was simply prepared by adding n-propanol and DI water. • WO{sub 3}–PEDOT:PSS hybrid films were inkjet-printed via an office inkjet printer. • WO{sub 3}–PEDOT:PSS films show better electrochromic performances than WO{sub 3} films.

  11. Ultrasensitive electrochemical sensing platform for microRNA based on tungsten oxide-graphene composites coupling with catalyzed hairpin assembly target recycling and enzyme signal amplification.

    Science.gov (United States)

    Shuai, Hong-Lei; Huang, Ke-Jing; Xing, Ling-Li; Chen, Ying-Xu

    2016-12-15

    An ultrasensitive electrochemical biosensor for microRNA (miRNA) is developed based on tungsten oxide-graphene composites coupling with catalyzed hairpin assembly target recycling and enzyme signal amplification. WO3-Gr is prepared by a simple hydrothermal method and then coupled with gold nanoparticles to act as a sensing platform. The thiol-terminated capture probe H1 is immobilized on electrode through Au-S interaction. In the presence of target miRNA, H1 opens its hairpin structure by hybridization with target miRNA. This hybridization can be displaced from the structure by another stable biotinylated hairpin DNA (H2), and target miRNA is released back to the sample solution for next cycle. Thus, a large amount of H1-H2 duplex is produced after the cyclic process. At this point, a lot of signal indicators streptavidin-conjugated alkaline phosphatase (SA-ALP) are immobilized on the electrode by the specific binding of avidin-biotin. Then, thousands of ascorbic acid, which is the enzymatic product of ALP, induces the electrochemical-chemical-chemical redox cycling to produce a strongly electrochemical response in the presence of ferrocene methanol and tris (2-carboxyethyl) phosphine. Under the optimal experimental conditions, the established biosensor can detect target miRNA down to 0.05fM (S/N=3) with a linear range from 0.1fM to 100pM, and discriminate target miRNA from mismatched miRNA with a high selectivity.

  12. Oxidation and photo-oxidation of water on TiO2 surface

    DEFF Research Database (Denmark)

    Valdes, A.; Qu, Z.W.; Kroes, G.J.

    2008-01-01

    The oxidation and photo-oxidation of water on the rutile TiO2(110) surface is investigated using density functional theory (DFT) calculations. We investigate the relative stability of different surface terminations of TiO2 interacting with H2O and analyze the overpotential needed...

  13. Interactions of graphene oxide nanomaterials with natural organic matter and metal oxide surfaces.

    Science.gov (United States)

    Chowdhury, Indranil; Duch, Matthew C; Mansukhani, Nikhita D; Hersam, Mark C; Bouchard, Dermont

    2014-08-19

    Interactions of graphene oxide (GO) nanomaterials with natural organic matter (NOM) and metal oxide surfaces were investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Three different types of NOM were studied: Suwannee River humic and fulvic acids (SRHA and SRFA) and alginate. Aluminum oxide surface was used as a model metal oxide surface. Deposition trends show that GO has the highest attachment on alginate, followed by SRFA, SRHA, and aluminum oxide surfaces, and that GO displayed higher interactions with all investigated surfaces than with silica. Deposition and release behavior of GO on aluminum oxide surface is very similar to positively charged poly-L-lysine-coated surface. Higher interactions of GO with NOM-coated surfaces are attributed to the hydroxyl, epoxy, and carboxyl functional groups of GO; higher deposition on alginate-coated surfaces is attributed to the rougher surface created by the extended conformation of the larger alginate macromolecules. Both ionic strength (IS) and ion valence (Na(+) vs Ca(2+)) had notable impact on interactions of GO with different environmental surfaces. Due to charge screening, increased IS resulted in greater deposition for NOM-coated surfaces. Release behavior of deposited GO varied significantly between different environmental surfaces. All surfaces showed significant release of deposited GO upon introduction of low IS water, indicating that deposition of GO on these surfaces is reversible. Release of GO from NOM-coated surfaces decreased with IS due to charge screening. Release rates of deposited GO from alginate-coated surface were significantly lower than from SRHA and SRFA-coated surfaces due to trapping of GO within the rough surface of the alginate layer.

  14. Efficient oxidative hydrogen peroxide production and accumulation in photoelectrochemical water splitting using a tungsten trioxide/bismuth vanadate photoanode.

    Science.gov (United States)

    Fuku, Kojiro; Sayama, Kazuhiro

    2016-04-07

    An aqueous solution of hydrogen carbonate (HCO3(-)) facilitated oxidative hydrogen peroxide (H2O2) production from water on a WO3/BiVO4 photoanode with the simultaneous production of hydrogen (H2) on a Pt cathode even at an applied voltage far lower than the theoretical electrolysis voltage (+1.77 V vs. RHE) under simulated solar light. The unprecedentedly efficient simultaneous production and accumulation of H2O2 and H2 was achieved in 2.0 M KHCO3 at low temperature, and the maximum selectivity, accumulated concentration and turnover number (TON) of H2O2 generated reached ca. 54%, more than 2 mM and 108, respectively.

  15. Impact of graphene and single-layer BN insertion on bipolar resistive switching characteristics in tungsten oxide resistive memory

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jongmin; Kim, Duhwan; Jo, Yongcheol; Han, Jaeseok; Woo, Hyeonseok [Division of Physics and Semiconductor Science, Dongguk University, Seoul 100-715 (Korea, Republic of); Kim, Hyungsang, E-mail: hskim@dongguk.edu [Division of Physics and Semiconductor Science, Dongguk University, Seoul 100-715 (Korea, Republic of); Kim, K.K., E-mail: kkkim@dongguk.edu [Department of Energy and Materials Engineering, Dongguk University, Seoul 100-715 (Korea, Republic of); Hong, J.P. [Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Im, Hyunsik, E-mail: hyunsik7@dongguk.edu [Division of Physics and Semiconductor Science, Dongguk University, Seoul 100-715 (Korea, Republic of)

    2015-08-31

    The role of the atomic interface in the resistive switching in Al–WO{sub 3}–Al devices is investigated by inserting metallic graphene or insulating hexagonal BN sheet between the top Al electrode and WO{sub 3} film. Clear reversible bipolar-type resistive switching phenomena were observed, regardless of the interface modification. However, endurance and retention properties were affected by the nature of the interface. While the device containing the graphene interface showed significantly improved performance, another device containing the hexagonal BN sheet showed degraded performance. These experimental findings suggest that atomic configuration of the electrode/oxide interface plays a key role in determining the resistive switching characteristics. - Highlights: • We fabricated WO{sub 3}-based non-volatile memories. • Effects of interface on memory performance were studied using graphene and BN. • The graphene-inserted device showed significantly improved performance.

  16. Advanced smart tungsten alloys for a future fusion power plant

    Science.gov (United States)

    Litnovsky, A.; Wegener, T.; Klein, F.; Linsmeier, Ch; Rasinski, M.; Kreter, A.; Tan, X.; Schmitz, J.; Mao, Y.; Coenen, J. W.; Bram, M.; Gonzalez-Julian, J.

    2017-06-01

    The severe particle, radiation and neutron environment in a future fusion power plant requires the development of advanced plasma-facing materials. At the same time, the highest level of safety needs to be ensured. The so-called loss-of-coolant accident combined with air ingress in the vacuum vessel represents a severe safety challenge. In the absence of a coolant the temperature of the tungsten first wall may reach 1200 °C. At such a temperature, the neutron-activated radioactive tungsten forms volatile oxide which can be mobilized into atmosphere. Smart tungsten alloys are being developed to address this safety issue. Smart alloys should combine an acceptable plasma performance with the suppressed oxidation during an accident. New thin film tungsten-chromium-yttrium smart alloys feature an impressive 105 fold suppression of oxidation compared to that of pure tungsten at temperatures of up to 1000 °C. Oxidation behavior at temperatures up to 1200 °C, and reactivity of alloys in humid atmosphere along with a manufacturing of reactor-relevant bulk samples, impose an additional challenge in smart alloy development. First exposures of smart alloys in steady-state deuterium plasma were made. Smart tungsten-chroimium-titanium alloys demonstrated a sputtering resistance which is similar to that of pure tungsten. Expected preferential sputtering of alloying elements by plasma ions was confirmed experimentally. The subsequent isothermal oxidation of exposed samples did not reveal any influence of plasma exposure on the passivation of alloys.

  17. Boron carbide coating deposition on tungsten and testing of tungsten layers and coating under intense plasma load

    Energy Technology Data Exchange (ETDEWEB)

    Airapetov, A. A.; Begrambekov, L. B., E-mail: lbb@plasma.mephi.ru [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation); Buzhinskiy, O. I. [State Research Center Troitsk Institute for Innovation and Fusion Research (TRINITI) (Russian Federation); Grunin, A. V.; Gordeev, A. A.; Zakharov, A. M.; Kalachev, A. M.; Sadovskiy, Ya. A.; Shigin, P. A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation)

    2015-12-15

    A device intended for boron carbide coating deposition and material testing under high heat loads is presented. A boron carbide coating 5 μm thick was deposited on the tungsten substrate. These samples were subjected to thermocycling loads in the temperature range of 400–1500°C. Tungsten layers deposited on tungsten substrates were tested in similar conditions. Results of the surface analysis are presented.

  18. Boron carbide coating deposition on tungsten and testing of tungsten layers and coating under intense plasma load

    Science.gov (United States)

    Airapetov, A. A.; Begrambekov, L. B.; Buzhinskiy, O. I.; Grunin, A. V.; Gordeev, A. A.; Zakharov, A. M.; Kalachev, A. M.; Sadovskiy, Ya. A.; Shigin, P. A.

    2015-12-01

    A device intended for boron carbide coating deposition and material testing under high heat loads is presented. A boron carbide coating 5 μm thick was deposited on the tungsten substrate. These samples were subjected to thermocycling loads in the temperature range of 400-1500°C. Tungsten layers deposited on tungsten substrates were tested in similar conditions. Results of the surface analysis are presented.

  19. Thermal instability of GaSb surface oxide

    Science.gov (United States)

    Tsunoda, K.; Matsukura, Y.; Suzuki, R.; Aoki, M.

    2016-05-01

    In the development of InAs/GaSb Type-II superlattice (T2SL) infrared photodetectors, the surface leakage current at the mesa sidewall must be suppressed. To achieve this requirement, both the surface treatment and the passivation layer are key technologies. As a starting point to design these processes, we investigated the GaSb oxide in terms of its growth and thermal stability. We found that the formation of GaSb oxide was very different from those of GaAs. Both Ga and Sb are oxidized at the surface of GaSb. In contrast, only Ga is oxidized and As is barely oxidized in the case of GaAs. Interestingly, the GaSb oxide can be formed even in DI water, which results in a very thick oxide film over 40 nm after 120 minutes. To examine the thermal stability, the GaSb native oxide was annealed in a vacuum and analyzed by XPS and Raman spectroscopy. These analyses suggest that SbOx in the GaSb native oxide will be reduced to metallic Sb above 300°C. To directly evaluate the effect of oxide instability on the device performance, a T2SL p-i-n photodetector was fabricated that has a cutoff wavelength of about 4 μm at 80 K. As a result, the surface leakage component was increased by the post annealing at 325°C. On the basis of these results, it is possible to speculate that a part of GaSb oxide on the sidewall surface will be reduced to metallic Sb, which acts as an origin of additional leakage current path.

  20. Secondary electron emission from plasma-generated nanostructured tungsten fuzz

    Science.gov (United States)

    Patino, M.; Raitses, Y.; Wirz, R.

    2016-11-01

    Recently, several researchers [e.g., Yang et al., Sci. Rep. 5, 10959 (2015)] have shown that tungsten fuzz can grow on a hot tungsten surface under bombardment by energetic helium ions in different plasma discharges and applications, including magnetic fusion devices with plasma facing tungsten components. This work reports the direct measurements of the total effective secondary electron emission (SEE) from tungsten fuzz. Using dedicated material surface diagnostics and in-situ characterization, we find two important results: (1) SEE values for tungsten fuzz are 40%-63% lower than for smooth tungsten and (2) the SEE values for tungsten fuzz are independent of the angle of the incident electron. The reduction in SEE from tungsten fuzz is most pronounced at high incident angles, which has important implications for many plasma devices since in a negative-going sheath the potential structure leads to relatively high incident angles for the electrons at the plasma confining walls. Overall, low SEE will create a relatively higher sheath potential difference that reduces plasma electron energy loss to the confining wall. Thus, the presence or self-generation in a plasma of a low SEE surface such as tungsten fuzz can be desirable for improved performance of many plasma devices.

  1. Universality in Oxygen Evolution Electrocatalysis on Oxide Surfaces

    DEFF Research Database (Denmark)

    Man, Isabela Costinela; Su, Hai-Yan; Vallejo, Federico Calle

    2011-01-01

    Trends in electrocatalytic activity of the oxygen evolution reaction (OER) are investigated on the basis of a large database of HO* and HOO* adsorption energies on oxide surfaces. The theoretical overpotential was calculated by applying standard density functional theory in combination...... that was the same for a wide variety of oxide catalyst materials and a universal descriptor for the oxygen evolution activity, which suggests a fundamental limitation on the maximum oxygen evolution activity of planar oxide catalysts....

  2. Polar hexagonal tungsten bronze-type oxides: KNbW2O9, RbNbW2O9, and KTaW2O9.

    Science.gov (United States)

    Chang, H Y; Sivakumar, T; Ok, K M; Halasyamani, P Shiv

    2008-10-06

    The synthesis, crystal structures, second-harmonic generation (SHG), piezoelectric, pyroelectric, and ferroelectric properties of three polar noncentrosymmetric (NCS) hexagonal tungsten bronze-type oxides are reported. The materials KNbW 2O 9, RbNbW 2O 9, and KTaW 2O 9 were synthesized by standard solid-state techniques and structurally characterized by laboratory powder X-ray diffraction. The compounds are isostructural, crystallizing in the polar NCS space group Cmm2. The materials exhibit a corner-shared MO 6 (M = Nb (5+)/W (6+) or Ta (5+)/W (6+)) octahedral framework, with K (+) or Rb (+) occupying the "hexagonal" tunnels. The d (0) transition metals, Nb (5+), Ta (5+), and W (6+), are displaced from the center of their oxide octahedra attributable to second-order Jahn-Teller effects. SHG measurements using 1064 nm radiation revealed frequency-doubling efficiencies ranging from 180 to 220 x alpha-SiO 2. Converse piezoelectric measurements resulted in d 33 values ranging from 10 to 41 pm V (-1). The total pyroelectric coefficient, p, at 50 degrees C ranged from -6.5 to -34.5 muC K (-1) m (-2). The reported materials are also ferroelectric, as demonstrated by hysteresis loops (polarization vs electric field). Spontaneous polarization values, P s, ranging from 2.1 to 8.4 muC cm (-2) were measured. The magnitudes of the SHG efficiency, piezoelectric response, pyroelectric coefficient, and ferroelectric polarization are strongly dependent on the out-of-center distortion of the d (0) transition metals. Structure-property relationships are discussed and explored. Crystal data: KNbW 2O 9, orthorhombic, space group Cmm2 (No. 35), a = 21.9554(2) A, b = 12.60725(15) A, c = 3.87748(3) A, V = 1073.273(13) A (3), and Z = 6; RbNbW 2O 9, orthorhombic, space group Cmm2 (No. 35), a = 22.00985(12) A, b = 12.66916(7) A, c = 3.8989(2) A, V = 1086.182(10) A (3), and Z = 6; KTaW 2O 9, orthorhombic, space group Cmm2 (No. 35), a = 22.0025(2) A, b = 12.68532(14) A, c = 3.84456(4) A, V

  3. Functional oxide structures on a surface of metals and alloys

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ The investigations of the plasma electrolytic processes in our laboratory are aimed to the development of conditions of formation of oxide layers with determined composition, structure and functional properties on the surface of valve metals (Al, Ti) and their alloys.

  4. Surface Structure of Aerobically Oxidized Diamond Nanocrystals

    Science.gov (United States)

    2014-10-27

    a native SiO2 oxide layer (P-type; 1 Ω·cm, SQI, San Jose, CA) were washed with persulfuric acid solution prior to use. Oxidation of Diamond... Graphene . Phys. Rep.: Rev. Sect. Phys. Lett. 2009, 473, 51−87. (34) Ferrari, A. C.; Meyer, J. C.; Scardaci, V.; Casiraghi, C.; Lazzeri, M.; Mauri, F...Piscanec, S.; Jiang, D.; Novoselov, K. S.; Roth, S.; Geim, A. K. Raman Spectrum of Graphene and Graphene Layers. Phys. Rev. Lett. 2006, 97, 187401−18740

  5. Improve oxidation resistance at high temperature by nanocrystalline surface layer.

    Science.gov (United States)

    Xia, Z X; Zhang, C; Huang, X F; Liu, W B; Yang, Z G

    2015-08-13

    An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content.

  6. Tungsten Filament Fire

    Science.gov (United States)

    Ruiz, Michael J.; Perkins, James

    2016-01-01

    We safely remove the outer glass bulb from an incandescent lamp and burn up the tungsten filament after the glass is removed. This demonstration dramatically illustrates the necessity of a vacuum or inert gas for the environment surrounding the tungsten filament inside the bulb. Our approach has added historical importance since the incandescent…

  7. Surface-Controlled Metal Oxide Resistive Memory

    KAUST Repository

    Ke, Jr-Jian

    2015-10-28

    To explore the surface effect on resistive random-access memory (ReRAM), the impact of surface roughness on the characteristics of ZnO ReRAM were studied. The thickness-independent resistance and the higher switching probability of ZnO ReRAM with rough surfaces indicate the importance of surface oxygen chemisorption on the switching process. Furthermore, the improvements in switching probability, switching voltage and resistance distribution observed for ReRAM with rough surfaces can be attributed to the stable oxygen adatoms under various ambience conditions. The findings validate the surface-controlled stability and uniformity of ReRAM and can serve as the guideline for developing practical device applications.

  8. Methanol Oxidation on Model Elemental and Bimetallic Transition Metal Surfaces

    DEFF Research Database (Denmark)

    Tritsaris, G. A.; Rossmeisl, J.

    2012-01-01

    Direct methanol fuel cells are a key enabling technology for clean energy conversion. Using density functional theory calculations, we study the methanol oxidation reaction on model electrodes. We discuss trends in reactivity for a set of monometallic and bimetallic transition metal surfaces, flat...... sites on the surface and to screen for novel bimetallic surfaces of enhanced activity. We suggest platinum copper surfaces as promising anode catalysts for direct methanol fuel cells....

  9. Surface Embedded Metal Oxide Sensors (SEMOS)

    DEFF Research Database (Denmark)

    Jespersen, Jesper Lebæk; Talat Ali, Syed; Pleth Nielsen, Lars

    complex and sensors are not easily implemented in the construction. Hence sensor interface and sensor position must therefore be chosen carefully in order to make the sensors as non-intrusive as possible. Metal Oxide Sensors (MOX) for measuring H2, O2 and CO concentration in a fuel cell environment...

  10. Textbook tests with tungsten

    CERN Multimedia

    Barbara Warmbein

    2010-01-01

    CERN's linear collider detector group joins forces with CALICE in building the world's first tungsten hadronic calorimeter.   Hadronic calorimeter prototype made of tungsten for the linear collider detector being equipped with CALICE scintillators. In a hall for test beam experiments at CERN, next to the CLOUD climate experiment and an irradiation facility, sits a detector prototype that is in many ways a first. It's the first ever hadronic sandwich calorimeter (HCal) prototype made of tungsten. It's the first prototype for a detector for the Compact Linear Collider Study CLIC, developed by the linear collider detector R&D group (LCD group) at CERN. And it's the first piece of hardware that results directly from the cooperation between CLIC and ILC detector study groups. Now its makers are keen to see first particle showers in their detector. The tungsten calorimeter has just moved from a workshop at CERN, where it was assembled from finely polished tungsten squares and triangles, into the ...

  11. Preparation of tungsten carbide nanoparticles by ion implantation and electrochemical etching

    Energy Technology Data Exchange (ETDEWEB)

    Kato, S. [Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Yamaki, T., E-mail: yamaki.tetsuya@jaea.go.jp [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Yamamoto, S.; Hakoda, T. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Kawaguchi, K. [Department of Chemistry and Materials Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan); Kobayashi, T. [RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 350-0198 (Japan); Suzuki, A.; Terai, T. [Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2013-11-01

    Glassy carbon (GC) substrates were implanted with 100 keV tungsten ions at retained fluences of 4 × 10{sup 16} and 6 × 10{sup 16} ions/cm{sup 2} and surface-etched electrochemically in order to prepare tungsten-carbide (WC) nanoparticles on their topmost layers. The calculated current efficiency for the electrochemical etching was nearly the same for the two samples implanted at different fluences, suggesting the controllability of the etched depth using the consumed electric charge. The etching front reached the buried tungsten-implanted layer and increased the tungsten concentration at the surface. No oxidation of WC was observed, even under anodic potential application during electrochemical etching. The voltammogram response of the topmost nanoparticle layer was too small to be observed, probably due to the limited activity of the WC itself and the remaining low concentration. It was demonstrated that this technique could, in principle, be applied to various types of nanoparticle catalysts implanted in GC substrates.

  12. MOISTURE AND SURFACE AREA MEASUREMENTS OF PLUTONIUM-BEARING OXIDES

    Energy Technology Data Exchange (ETDEWEB)

    Crowder, M.; Duffey, J.; Livingston, R.; Scogin, J.; Kessinger, G.; Almond, P.

    2009-09-28

    To ensure safe storage, plutonium-bearing oxides are stabilized at 950 C for at least two hours in an oxidizing atmosphere. Stabilization conditions are expected to decompose organic impurities, convert metals to oxides, and result in moisture content below 0.5 wt%. During stabilization, the specific surface area is reduced, which minimizes readsorption of water onto the oxide surface. Plutonium oxides stabilized according to these criteria were sampled and analyzed to determine moisture content and surface area. In addition, samples were leached in water to identify water-soluble chloride impurity content. Results of these analyses for seven samples showed that the stabilization process produced low moisture materials (< 0.2 wt %) with low surface area ({le} 1 m{sup 2}/g). For relatively pure materials, the amount of water per unit surface area corresponded to 1.5 to 3.5 molecular layers of water. For materials with chloride content > 360 ppm, the calculated amount of water per unit surface area increased with chloride content, indicating hydration of hygroscopic salts present in the impure PuO{sub 2}-containing materials. The low moisture, low surface area materials in this study did not generate detectable hydrogen during storage of four or more years.

  13. The preparation and chemical reaction kinetics of tungsten bronze thin films and nitrobenzene with and without a catalyst

    Science.gov (United States)

    Materer, Nicholas F.; Apblett, Allen; Kadossov, Evgueni B.; Khan, Kashif Rashid; Casper, Walter; Hays, Kevin; Shams, Eman F.

    2016-06-01

    Microcrystalline tungsten bronze thin films were prepared using wet chemical techniques to reduce a tungsten oxide thin film that was prepared by thermal oxidation of a sputter deposited tungsten metal film on a quartz substrate. The crystallinity of these films was determined by X-ray diffraction and the surface was characterized by X-ray and Ultra-Violet Photoelectron spectroscopy. The total amount of hydrogen incorporated in the film was monitored using absorbance spectroscopy at 900 nm. The oxidation kinetics of the film and the hydrogenation of nitrobenzene in hexane were measured as a function of film thickness. A satisfactory fit of the resulting kinetics was obtained using a model that involves two simultaneous processes. The first one is the proton diffusion from the bulk of the film to the surface, and the second is a reaction of the surface protons with the oxidants. Finally, the dependence of the reaction rates on the presence of catalytic amounts of first row transition metals on the surface of the film was explored.

  14. Electrode potentials of tungsten in fused alkali chlorides

    Science.gov (United States)

    Ivanov, A. B.; Volkovich, V. A.; Poskryakov, D. A.; Vasin, B. D.; Griffiths, T. R.

    2016-09-01

    Anodic dissolution of tungsten was studied at 823-1173 K in the melts based on NaCl-CsCl, NaCl-KCl-CsCl and LiCl-KCl-CsCl eutectic mixtures. The process results in the formation of W(IV) ions. Prolonged contact with silica results in oxidation W(IV) ions and decreasing tungsten concentration in the electrolyte due to formation of volatile higher oxidation state chloro- and oxychloro-species. Tungsten electrode potentials were measured in NaCl-CsCl and NaCl-KCl-CsCl based melts using potentiometry.

  15. Tungsten Export Price Raised Due to Customs Tax Regulations

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    <正>Affected by the export tax rise, China’s tungsten export price rose by about 40 per cent in the first 10 months of 2006. The average price of Ammonium Paratungstate (APT) was US$23,000/MT, up by 43.5 per cent year-on-year, and that of ferro-tungsten, blue tungsten oxide as well as yellow oxide also increased by 32.4 per cent to US$24,000/MT, 27.4 per cent to US$25,000/MT and 42.6 per cent to US$26,000/MT respectively.

  16. Thermal cycling and high power density hydrogen ion beam irradiation of tungsten layers on tungsten substrate

    Science.gov (United States)

    Airapetov, A. A.; Begrambekov, L. B.; Gretskaya, I. Yu; Grunin, A. V.; Dyachenko, M. Yu; Puntakov, N. A.; Sadovskiy, Ya A.

    2016-09-01

    Tungsten layers with iron impurity were deposited on tungsten substrates modeling re-deposited layers in a fusion device. The samples were tested by thermocycling and hydrogen ion beam tests. Thermocycling revealed globule formation on the surface. The size of the globules depended on iron impurity content in the coating deposited. Pore formation was observed which in some cases lead to exfoliation of the coatings. Hydrogen ion irradiation lead to formation of blisters on the coating and finally its exfoliation.

  17. Study on Surface Depression of Ti-6Al-4V with Ultrahigh-Frequency Pulsed Gas Tungsten Arc Welding

    Science.gov (United States)

    Mingxuan, Yang; Zhou, Yang; Bojin, Qi

    2015-08-01

    Molten pool surface depression was observed with the arc welding process that was caused by arc pressure. It was supposed to have a significant effect on fluid in the molten pool that was important for the microstructure and joint properties. The impact of arc force was recognized as the reason for the surface depression during arc welding. The mathematical distribution of arc force was produced with the exponent and parabola models. Different models showed different concentrations and attenuations. The comparison between them was discussed with the simulation results. The volume of fluid method was picked up with the arc force distribution model. The surface depression was caused by the arc force. The geometry of the surface depression was discussed with liquid metal properties. The welding process was carried out with different pulsed frequencies. The results indicated the forced depression exists in molten pool and the geometry of depression was hugely due to the arc force distribution. The previous work calculated the depression in the center with force balance at one point. The other area of gas shielding was resistant by the reverse gravity from the feedback of liquid metal that was squeezed out. The article discusses the pressure effect with free deformation that allowed resistance of liquid and was easy to compare with different distributions. The curve profiles were studied with the arc force distributions, and exponent model was supposed to be more accurate to the as-weld condition.

  18. Measuring Forces between Oxide Surfaces Using the Atomic Force Microscope

    DEFF Research Database (Denmark)

    Pedersen, Henrik Guldberg; Høj, Jakob Weiland

    1996-01-01

    The interactions between colloidal particles play a major role in processing of ceramics, especially in casting processes. With the Atomic Force Microscope (AFM) it is possible to measure the inter-action force between a small oxide particle (a few micron) and a surface as function of surface sep...

  19. Measuring Forces between Oxide Surfaces Using the Atomic Force Microscope

    DEFF Research Database (Denmark)

    Pedersen, Henrik Guldberg; Høj, Jakob Weiland

    1996-01-01

    The interactions between colloidal particles play a major role in processing of ceramics, especially in casting processes. With the Atomic Force Microscope (AFM) it is possible to measure the inter-action force between a small oxide particle (a few micron) and a surface as function of surface...

  20. Structure, Bonding and Surface Chemistry of Metal Oxide Nanoclusters

    Science.gov (United States)

    2015-06-23

    Characterization of these ligand- coated oxides included laser desorption mass spectrometry, infrared, Raman and UV - visible spectroscopy ...desorption and electrospray ionization mass spectrometry, optical spectroscopy methods (IR, surface-enhanced Raman, UV - visible absorption and...clusters are studied with laser desorption and electrospray ionization mass spectrometry, optical spectroscopy methods (IR, surface-enhanced Raman, UV

  1. Electron beam induced oxidation of Al–Mg alloy surfaces

    NARCIS (Netherlands)

    Palasantzas, G.; Agterveld, D.T.L. van; Hosson, J.Th.M. De

    2002-01-01

    Electron beam currents of a few nanoamperes, currently used in nanometer scale scanning Auger/electron microscopy, induces severe oxidation of Al–Mg alloy surfaces at room temperature. Auger peak-to-peak oxygen curves for Al–Mg surfaces support the hypothesis that the electron beam creates

  2. Electron beam induced oxidation of Al–Mg alloy surfaces

    NARCIS (Netherlands)

    Palasantzas, G.; Agterveld, D.T.L. van; Hosson, J.Th.M. De

    2002-01-01

    Electron beam currents of a few nanoamperes, currently used in nanometer scale scanning Auger/electron microscopy, induces severe oxidation of Al–Mg alloy surfaces at room temperature. Auger peak-to-peak oxygen curves for Al–Mg surfaces support the hypothesis that the electron beam creates additiona

  3. Surface oxidation and water desorption of CdS

    Institute of Scientific and Technical Information of China (English)

    陈正石; 李庆霖; 金振声

    1996-01-01

    The surface oxidation and HP desorption of powder CdS were studied by means of X-ray photoetectron spectroscopy (XPS), quadrupole mass spectrometry (QMS) and in-situ FTIR. The results show that with the changes of surface composition and the elongation of store time of CdS there are four types of H2O thermally desorbed at different temperatures. It has also been found that through high-temperature air treatment for a short time the oxidized surface layer of CdS can prevent O2 and H2O in air from further attacking the inner CdS molecules.

  4. Microbial Manganese Oxidation in Saltmarsh Surface Sediments Using a Leuco Crystal Violet Manganese Oxide Detection Technique

    Science.gov (United States)

    Spratt, Henry G.; Siekmann, Ellen C.; Hodson, Robert E.

    1994-01-01

    Microbial manganese (Mn) oxide production in surface sediments of a Georgia saltmarsh was directly measured using an assay involving the oxidation of 4,4',4″-methylidynetris (N,N-dimethylaniline), leuco crystal violet (LCV), by Mn oxides to produce crystal violet. The assay exhibits high specificity for Mn oxides without interference by Mn(II) and is sufficiently sensitive to determine rates of Mn oxidation in surface sediment or saltmarsh creek water suspensions. Sample salinity affects crystal violet absorbance in the 0-25 salinity range and must be corrected for in Mn oxide determinations for estuarine samples of variable salinity. Other oxidants found to oxidize LCV slowly included Cl(I), Cr(III), I(V), Fe(III), and Mn(III), although the sensitivity of the assay for Mn(IV) oxides was found to be seven times greater than for Mn(III), and at least 100 times greater than for any of the other oxidants. Rates of abiotic Mn oxide production in sediment suspensions treated with either sodium azide or formalin, or autoclaved, were much slower than rates determined for untreated sediments. Sodium azide (7·7 mM) inhibited Mn oxide production in these sediment suspensions to rates between 5 and 10% of the rates of Mn oxidation determined for unamended suspensions. Manganese oxidation was highly temperature dependent, with maximal rates on a dry weight basis (8·9 nmol mg dwt -1 h -1), occurring at 60°C, and negligible activity at 100 and 0°C. Rates were also dependent on sample pH, with maximal rates at pH 6·7, decreasing to near 0 as the pH was lowered to approximately 3·0. For Mn(II) concentrations ranging from 9 to 91 μM, rates of Mn oxide production were independent of Mn(II) concentration, while Mn oxide production was inhibited at concentrations greater than 91 μM (e.g. by 25-40% at 450 μM). Rates of microbial Mn oxide production in surface sediment/saltmarsh creek water suspensions incubated under natural conditions of temperature, pH, and Mn

  5. Surface and Core Electronic Structure of Oxidized Silicon Nanocrystals

    Directory of Open Access Journals (Sweden)

    Noor A. Nama

    2010-01-01

    Full Text Available Ab initio restricted Hartree-Fock method within the framework of large unit cell formalism is used to simulate silicon nanocrystals between 216 and 1000 atoms (1.6–2.65 nm in diameter that include Bravais and primitive cell multiples. The investigated properties include core and oxidized surface properties. Results revealed that electronic properties converge to some limit as the size of the nanocrystal increases. Increasing the size of the core of a nanocrystal resulted in an increase of the energy gap, valence band width, and cohesive energy. The lattice constant of the core and oxidized surface parts shows a decreasing trend as the nanocrystal increases in a size that converges to 5.28 Ǻ in a good agreement with the experiment. Surface and core convergence to the same lattice constant reflects good adherence of oxide layer at the surface. The core density of states shows highly degenerate states that split at the oxygenated (001-(1×1 surface due to symmetry breaking. The nanocrystal surface shows smaller gap and higher valence and conduction bands when compared to the core part, due to oxygen surface atoms and reduced structural symmetry. The smaller surface energy gap shows that energy gap of the nanocrystal is controlled by the surface part. Unlike the core part, the surface part shows a descending energy gap that proves its obedience to quantum confinement effects. Nanocrystal geometry proved to have some influence on all electronic properties including the energy gap.

  6. Surface structure and relaxation during the oxidation of carbon monoxide on Pt Pd bimetallic surfaces

    Science.gov (United States)

    Lucas, C. A.; Markovic, N. M.; Ball, M.; Stamenkovic, V.; Climent, V.; Ross, P. N.

    2001-05-01

    The atomic structure and surface relaxation of Pd monolayer on Pt(1 1 1) has been studied by surface X-ray scattering, in an aqueous environment under electrostatic potential control, during the adsorption and oxidation of carbon monoxide. The results show that the Pd-Pt layer spacing contracts at the onset of CO oxidation before the Pd adlayer forms an oxide structure that is incommensurate with the Pt lattice. Both the oxide formation and the lattice contraction are fully reversible over many cycles of the applied electrode potential.

  7. Oxidation of silicon surface with atomic oxygen radical anions

    Institute of Scientific and Technical Information of China (English)

    Wang Lian; Song Chong-Fu; Sun Jian-Qiu; Hou Ying; Li Xiao-Guang; Li Quan-Xin

    2008-01-01

    The surface oxidation of silicon (Si) wafers by atomic oxygen radical anions (O- anions) and the preparation of metal-oxide-semiconductor (MOS) capacitors on the O--oxidized Si substrates have been examined for the first time. The O- anions are generated from a recently developed O- storage-emission material of [Ca24Al28O64]4+.4O- (C12A7-O- for short). After it has been irradiated by an O- anion beam (0.5 μA/cm2) at 300℃ for 1-10 hours, the Si wafer achieves an oxide layer with a thickness ranging from 8 to 32 nm. X-ray photoelectron spectroscopy (XPS) results reveal that the oxide layer is of a mixture of SiO2, Si2O3, and Si2O distributed in different oxidation depths. The features of the MOS capacitor of are investigated by measuring capacitance-voltage (C - V) and current-voltage (Ⅰ - Ⅴ) curves. The oxide charge density is about 6.0×1011 cm-2 derived from the C - V curves. The leakage current density is in the order of 10-6 A/cm2 below 4 MV/cm, obtained from the Ⅰ - Ⅴ curves. The Oanions formed by present method would have potential applications to the oxidation and the surface-modification of materials together with the preparation of semiconductor devices.

  8. Element 74, the Wolfram Versus Tungsten Controversy

    Energy Technology Data Exchange (ETDEWEB)

    Holden,N.E.

    2008-08-11

    Two and a quarter centuries ago, a heavy mineral ore was found which was thought to contain a new chemical element called heavy stone (or tungsten in Swedish). A few years later, the metal was separated from its oxide and the new element (Z=74) was called wolfram. Over the years since that time, both the names wolfram and tungsten were attached to this element in various countries. Sixty years ago, IUPAC chose wolfram as the official name for the element. A few years later, under pressure from the press in the USA, the alternative name tungsten was also allowed by IUPAC. Now the original, official name 'wolfram' has been deleted by IUPAC as one of the two alternate names for the element. The history of this controversy is described here.

  9. Recent applications of liquid metals featuring nanoscale surface oxides

    Science.gov (United States)

    Neumann, Taylor V.; Dickey, Michael D.

    2016-05-01

    This proceeding describes recent efforts from our group to control the shape and actuation of liquid metal. The liquid metal is an alloy of gallium and indium which is non-toxic, has negligible vapor pressure, and develops a thin, passivating surface oxide layer. The surface oxide allows the liquid metal to be patterned and shaped into structures that do not minimize interfacial energy. The surface oxide can be selectively removed by changes in pH or by applying a voltage. The surface oxide allows the liquid metal to be 3D printed to form free-standing structures. It also allows for the liquid metal to be injected into microfluidic channels and to maintain its shape within the channels. The selective removal of the oxide results in drastic changes in surface tension that can be used to control the flow behavior of the liquid metal. The metal can also wet thin, solid films of metal that accelerates droplets of the liquid along the metal traces .Here we discuss the properties and applications of liquid metal to make soft, reconfigurable electronics.

  10. Electronic Structure and Band Gap of Fullerenes on Tungsten Surfaces: Transition from a Semiconductor to a Metal Triggered by Annealing.

    Science.gov (United States)

    Monazami, Ehsan; McClimon, John B; Rondinelli, James; Reinke, Petra

    2016-12-21

    The understanding and control of molecule-metal interfaces is critical to the performance of molecular electronics and photovoltaics devices. We present a study of the interface between C60 and W, which is a carbide-forming transition metal. The complex solid-state reaction at the interface can be exploited to adjust the electronic properties of the molecule layer. Scanning tunneling microscopy/spectroscopy measurements demonstrate the progression of this reaction from wide band gap (>2.5 eV) to metallic molecular surface during annealing from 300 to 800 K. Differential conduction maps with 10(4) scanning tunneling spectra are used to quantify the transition in the density of states and the reduction of the band gap during annealing with nanometer spatial resolution. The electronic transition is spatially homogeneous, and the surface band gap can therefore be adjusted by a targeted annealing step. The modified molecules, which we call nanospheres, are quite resistant to ripening and coalescence, unlike any other metallic nanoparticle of the same size. Densely packed C60 and isolated C60 molecules show the same transition in electronic structure, which confirms that the transformation is controlled by the reaction at the C60-W interface. Density functional theory calculations are used to develop possible reaction pathways in agreement with experimentally observed electronic structure modulation. Control of the band gap by the choice of annealing temperature is a unique route to tailoring molecular-layer electronic properties.

  11. High Surface Area Tungsten Carbides: Synthesis, Characterization and Catalytic Activity towards the Hydrogen Evolution Reaction in Phosphoric Acid at Elevated Temperatures

    DEFF Research Database (Denmark)

    Tomás García, Antonio Luis; Li, Qingfeng; Jensen, Jens Oluf

    2014-01-01

    Tungsten carbide powders were synthesized as a potential electrocatalyst for the hydrogen evolution reaction in phosphoric acid at elevated temperatures. With ammonium metatungstate as the precursor, two synthetic routes with and without carbon templates were investigated. Through the intermediate...... nitride route and with carbon black as template, the obtained tungsten carbide samples had higher BET area. In 100% H3PO4 at temperatures up to 185°C, the carbide powders showed superior activity towards the hydrogen evolution reaction. A deviation was found in the correlation between the BET area...

  12. Chromatic instabilities in cesium-doped tungsten bronze nanoparticles

    Science.gov (United States)

    Adachi, Kenji; Ota, Yosuke; Tanaka, Hiroyuki; Okada, Mika; Oshimura, Nobumitsu; Tofuku, Atsushi

    2013-11-01

    Nanoparticles of alkali-doped tungsten bronzes are an excellent near-infrared shielding material, but exhibit slight chromatic instabilities typically upon applications of strong ultra-violet light or heating in humid environment, which acts detrimentally to long-life commercial applications. Origin of the chromatic instabilities in cesium-doped tungsten bronze has been investigated, and it has been found that the coloration and bleaching processes comprised electronic exchanges which accelerate or depress the polaron excitation and the localized surface plasmon resonance. Coloration on UV illumination is evidenced by electron diffraction as due to the formation of HxWO3, which is considered to take place in the surface Cs-deficient WO3 region via the double charge injection mechanism. On the other hand, bleaching on heating in air and in humid environment is shown to accompany the extraction of Cs and electrons from Cs0.33WO3 by X-ray photoelectron spectroscopy and X-ray diffraction analysis and is concluded to be an oxidation of Cs0.33WO3 on the particle surface.

  13. Chromatic instabilities in cesium-doped tungsten bronze nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Adachi, Kenji, E-mail: kenji-adachi@ni.smm.co.jp; Ota, Yosuke; Tanaka, Hiroyuki; Okada, Mika; Oshimura, Nobumitsu; Tofuku, Atsushi [Ichikawa Research Laboratories, Sumitomo Metal Mining Co., Ltd., Ichikawa 272-8588 (Japan)

    2013-11-21

    Nanoparticles of alkali-doped tungsten bronzes are an excellent near-infrared shielding material, but exhibit slight chromatic instabilities typically upon applications of strong ultra-violet light or heating in humid environment, which acts detrimentally to long-life commercial applications. Origin of the chromatic instabilities in cesium-doped tungsten bronze has been investigated, and it has been found that the coloration and bleaching processes comprised electronic exchanges which accelerate or depress the polaron excitation and the localized surface plasmon resonance. Coloration on UV illumination is evidenced by electron diffraction as due to the formation of H{sub x}WO{sub 3}, which is considered to take place in the surface Cs-deficient WO{sub 3} region via the double charge injection mechanism. On the other hand, bleaching on heating in air and in humid environment is shown to accompany the extraction of Cs and electrons from Cs{sub 0.33}WO{sub 3} by X-ray photoelectron spectroscopy and X-ray diffraction analysis and is concluded to be an oxidation of Cs{sub 0.33}WO{sub 3} on the particle surface.

  14. Surface Properties of Photo-Oxidized Bituminous Coals: Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-09-01

    Natural weathering has a detrimental effect on the hydrophobic nature of coal, which in turn can influence clean-coal recovery during flotation. Few techniques are available that can establish the quality of coal surfaces and that have a short analysis time to provide input for process control. Luminescence emissions which can be quantified with an optical microscope and photometer system, are measurably influenced by degree of weathering as well as by mild storage deterioration. In addition, it has been shown that when vitrinite is irradiated with a relatively high intensity flux of violet- or ultraviolet- light in the presence of air, photo-oxidation of the surface occurs. The combination of measuring the change in luminescence emission intensity with degree of surface oxidation provided the impetus for the current investigation. The principal aim of this research was to determine whether clear correlations could be established among surface oxygen functionality, hydrophobicity induced by photo-oxidation, and measurements of luminescence intensity and alteration. If successful, the project would result in quantitative luminescence techniques based on optical microscopy that would provide a measure of the changes in surface properties as a function of oxidation and relate them to coal cleanability. Two analytical techniques were designed to achieve these goals. Polished surfaces of vitrain bands or a narrow size fraction of powdered vitrain concentrates were photo-oxidized using violet or ultraviolet light fluxes and then changes in surface properties and chemistry were measured using a variety of near-surface analytical techniques. Results from this investigation demonstrate that quantitative luminescence intensity measurements can be performed on fracture surfaces of bituminous rank coals (vitrains) and that the data obtained do reveal significant variations depending upon the level of surface oxidation. Photo-oxidation induced by violet or ultraviolet light

  15. Large-scale synthesis of ultrathin tungsten oxide nanowire networks: an efficient catalyst for aerobic oxidation of toluene to benzaldehyde under visible light.

    Science.gov (United States)

    Bai, Hua; Yi, Wencai; Liu, Jingyao; Lv, Qing; Zhang, Qing; Ma, Qiang; Yang, Haifeng; Xi, Guangcheng

    2016-07-14

    As a very important chemical raw material, the selective formation of benzaldehyde from toluene at preparative or industrial levels requires the use of highly corrosive chlorine and high reaction temperatures, which severely corrodes equipment, pollutes the environment, and consumes a lot of energy. Herein, we report a robust and highly active catalyst for the benzaldehyde evolution reaction that is constructed by the surfactant-free growth of oxygen vacancy-rich W18O49 ultrathin nanowire networks. Under atmospheric pressure and visible-light irradiation, the new catalyst can selectively (92% selectivity) catalyze the aerobic oxidation of toluene to benzaldehyde with yields of above 95%.

  16. Facile preparation of superhydrophobic surfaces based on metal oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Xue-Mei; Cui, Jin-Feng; Sun, Han-Xue; Liang, Wei-Dong; Zhu, Zhao-Qi; An, Jin; Yang, Bao-Ping; La, Pei-Qing; Li, An, E-mail: lian2010@lut.cn

    2014-06-01

    A novel method for fabrication of superhydrophobic surfaces was developed by facile coating various metal oxide nanoparticles, including ZnO, Al{sub 2}O{sub 3} and Fe{sub 3}O{sub 4}, on various substrates followed by treatment with polydimethylsiloxane (PDMS) via chemical vapor deposition (CVD) method. Using ZnO nanoparticles as a model, the changes in the surface chemical composition and crystalline structures of the metal oxide nanoparticles by PDMS treatment were investigated by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The results show that the combination of the improved surface roughness generated from of the nanoparticles aggregation with the low surface-energy of silicon-coating originated from the thermal pyrolysis of PDMS would be responsible for the surface superhydrophobicity. By a simple dip-coating method, we show that the metal oxide nanoparticles can be easily coated onto the surfaces of various textural and dimensional substrates, including glass slide, paper, fabric or sponge, for preparation of superhydrophobic surfaces for different purpose. The present strategy may provide an inexpensive and new route to surperhydrophobic surfaces, which would be of technological significance for various practical applications especially for separation of oils or organic contaminates from water.

  17. Facile preparation of superhydrophobic surfaces based on metal oxide nanoparticles

    Science.gov (United States)

    Bao, Xue-Mei; Cui, Jin-Feng; Sun, Han-Xue; Liang, Wei-Dong; Zhu, Zhao-Qi; An, Jin; Yang, Bao-Ping; La, Pei-Qing; Li, An

    2014-06-01

    A novel method for fabrication of superhydrophobic surfaces was developed by facile coating various metal oxide nanoparticles, including ZnO, Al2O3 and Fe3O4, on various substrates followed by treatment with polydimethylsiloxane (PDMS) via chemical vapor deposition (CVD) method. Using ZnO nanoparticles as a model, the changes in the surface chemical composition and crystalline structures of the metal oxide nanoparticles by PDMS treatment were investigated by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The results show that the combination of the improved surface roughness generated from of the nanoparticles aggregation with the low surface-energy of silicon-coating originated from the thermal pyrolysis of PDMS would be responsible for the surface superhydrophobicity. By a simple dip-coating method, we show that the metal oxide nanoparticles can be easily coated onto the surfaces of various textural and dimensional substrates, including glass slide, paper, fabric or sponge, for preparation of superhydrophobic surfaces for different purpose. The present strategy may provide an inexpensive and new route to surperhydrophobic surfaces, which would be of technological significance for various practical applications especially for separation of oils or organic contaminates from water.

  18. Surface chemistry of rare-earth oxide surfaces at ambient conditions: reactions with water and hydrocarbons

    Science.gov (United States)

    Külah, Elçin; Marot, Laurent; Steiner, Roland; Romanyuk, Andriy; Jung, Thomas A.; Wäckerlin, Aneliia; Meyer, Ernst

    2017-01-01

    Rare-earth (RE) oxide surfaces are of significant importance for catalysis and were recently reported to possess intrinsic hydrophobicity. The surface chemistry of these oxides in the low temperature regime, however, remains to a large extent unexplored. The reactions occurring at RE surfaces at room temperature (RT) in real air environment, in particular, in presence of polycyclic aromatic hydrocarbons (PAHs), were not addressed until now. Discovering these reactions would shed light onto intermediate steps occurring in automotive exhaust catalysts before reaching the final high operational temperature and full conversion of organics. Here we first address physical properties of the RE oxide, nitride and fluoride surfaces modified by exposure to ambient air and then we report a room temperature reaction between PAH and RE oxide surfaces, exemplified by tetracene (C18H12) on a Gd2O3. Our study evidences a novel effect – oxidation of higher hydrocarbons at significantly lower temperatures (~300 K) than previously reported (>500 K). The evolution of the surface chemical composition of RE compounds in ambient air is investigated and correlated with the surface wetting. Our surprising results reveal the complex behavior of RE surfaces and motivate follow-up studies of reactions between PAH and catalytic surfaces at the single molecule level. PMID:28327642

  19. Surface Chemistry and Properties of Oxides as Catalyst Supports

    Energy Technology Data Exchange (ETDEWEB)

    DeBusk, Melanie Moses [ORNL; Narula, Chaitanya Kumar [ORNL; Contescu, Cristian I [ORNL

    2015-01-01

    Heterogeneous catalysis relies on metal-oxides as supports for the catalysts. Catalyst supports are an indispensable component of most heterogeneous catalysts, but the role of the support is often minimized in light of the one played by the catalytically active species it supports. The active species of supported catalysts are located on the surface of the support where their contact with liquid or gas phase reactants will be greatest. Considering that support plays a major role in distribution and stability of active species, the absorption and retention of reactive species, and in some cases in catalytic reaction, the properties and chemistry that can occur at the surface of an oxide support are important for understanding their impact on the activity of a supported catalyst. This chapter examines this rich surface chemistry and properties of oxides used as catalyst supports, and explores the influence of their interaction with the active species.

  20. Structural and surface changes of copper modified manganese oxides

    Energy Technology Data Exchange (ETDEWEB)

    Gac, Wojciech, E-mail: wojciech.gac@umcs.lublin.pl; Słowik, Grzegorz; Zawadzki, Witold

    2016-05-01

    Highlights: • Formation of MnO with regular rippled-like surface patterns. • Synthesis of copper nanorods supported on MnO nanoparticles. • Hydrogen production in steam methanol reforming over supported copper nanorods. - Abstract: The structural and surface properties of manganese and copper–manganese oxides were investigated. The oxides were prepared by the redox-precipitation method. X-ray diffraction and electron microscopy studies evidenced transformation of cryptomelane-type nanoparticles with 1-D channel structure into the large MnO crystallites with regular rippled-like surface patterns under reduction conditions. The development of Cu/CuO nanorods from strongly dispersed species was evidenced. Coper-modified manganese oxides showed good catalytic performance in methanol steam reforming reaction for hydrogen production. Low selectivity to CO was observed in the wide range of temperatures.

  1. The heterogeneous oxidation of SO2 on aerosol surface

    Institute of Scientific and Technical Information of China (English)

    高会旺; 黄美元; 徐华英

    1997-01-01

    A heterogeneous chemical model is developed by coupling aerosol, gas-phase and liquid-phase chemical model. SO2 oxidation rates on the aerosol surface are calculated and the influence of some factors is discussed. Model simulations indicate that SO2 heterogeneous oxidation rates are sensitive to the mass concentration and chemical composition of aerosols, relative humidity, initial values of SO2 and H2O2. The heterogeneous chemical model is coupled with a Eulerian deposition model. Model results show that oxidation of SO2 on the aerosol surface is found to reduce SO2 levels by 5%-33%, to increase SO2-4 concentrations by 8%-50% in the surface layer.

  2. Large-scale synthesis of ultrathin tungsten oxide nanowire networks: an efficient catalyst for aerobic oxidation of toluene to benzaldehyde under visible light

    Science.gov (United States)

    Bai, Hua; Yi, Wencai; Liu, Jingyao; Lv, Qing; Zhang, Qing; Ma, Qiang; Yang, Haifeng; Xi, Guangcheng

    2016-07-01

    As a very important chemical raw material, the selective formation of benzaldehyde from toluene at preparative or industrial levels requires the use of highly corrosive chlorine and high reaction temperatures, which severely corrodes equipment, pollutes the environment, and consumes a lot of energy. Herein, we report a robust and highly active catalyst for the benzaldehyde evolution reaction that is constructed by the surfactant-free growth of oxygen vacancy-rich W18O49 ultrathin nanowire networks. Under atmospheric pressure and visible-light irradiation, the new catalyst can selectively (92% selectivity) catalyze the aerobic oxidation of toluene to benzaldehyde with yields of above 95%.As a very important chemical raw material, the selective formation of benzaldehyde from toluene at preparative or industrial levels requires the use of highly corrosive chlorine and high reaction temperatures, which severely corrodes equipment, pollutes the environment, and consumes a lot of energy. Herein, we report a robust and highly active catalyst for the benzaldehyde evolution reaction that is constructed by the surfactant-free growth of oxygen vacancy-rich W18O49 ultrathin nanowire networks. Under atmospheric pressure and visible-light irradiation, the new catalyst can selectively (92% selectivity) catalyze the aerobic oxidation of toluene to benzaldehyde with yields of above 95%. Electronic supplementary information (ESI) available: Experimental procedure, XRD patterns, TEM and HRTEM images, energy-dispersive X-ray spectra, UV-vis spectra, X-ray photoelectron spectroscopy (XPS), and EDS. See DOI: 10.1039/c6nr02949c

  3. Process of forming catalytic surfaces for wet oxidation reactions

    Science.gov (United States)

    Jagow, R. B. (Inventor)

    1977-01-01

    A wet oxidation process was developed for oxidizing waste materials, comprising dissolved ruthenium salt in a reactant feed stream containing the waste materials. The feed stream is introduced into a reactor, and the reactor contents are then raised to an elevated temperature to effect deposition of a catalytic surface of ruthenium black on the interior walls of the reactor. The feed stream is then maintained in the reactor for a period of time sufficient to effect at least partial oxidation of the waste materials.

  4. Enhanced photothermal effect of surface oxidized silicon nanocrystals anchored to reduced graphene oxide nanosheets

    Science.gov (United States)

    Afshani, Parichehr; Moussa, Sherif; Atkinson, Garrett; Kisurin, Vitaly Y.; Samy El-Shall, M.

    2016-04-01

    We demonstrate the coupling of the photothermal effects of silicon nanocrystals and graphene oxide (GO) dispersed in water. Using laser irradiation (532 nm or 355 nm) of suspended Si nanocrystals in an aqueous solution of GO, the synthesis of surface oxidized Si-reduced GO nanocomposites (SiOx/Si-RGO) is reported. The laser reduction of GO is accompanied by surface oxidation of the Si nanocrystals resulting in the formation of the SiOx/Si-RGO nanocomposites. The SiOx/Si-RGO nanocomposites are proposed as promising materials for photothermal therapy and for the efficient conversion of solar energy into usable heat for a variety of thermal and thermomechanical applications.

  5. Formation and characterization of infrared absorbing copper oxide surfaces

    Science.gov (United States)

    Arslan, Burcu; Demirci, Gökhan; Erdoğan, Metehan; Karakaya, İshak

    2017-04-01

    Copper oxide formation has been investigated to combine the advantages of producing different size and shapes of coatings that possess good light absorbing properties. An aqueous blackening solution was investigated and optimum composition was found as 2.5 M NaOH and 0.225 M NaClO to form velvet copper oxide films. A two-step oxidation mechanism was proposed for the blackening process by carefully examining the experimental results. Formation of Cu2O was observed until the entire copper surface was covered at first. In the second step, Cu2O surface was further oxidized to CuO until the whole Cu2O surface was covered by CuO. Therefore, blackened copper surfaces consisted of Cu2O/CuO duplex oxides. Characterization of the coatings were performed in terms of microstructure, phase analysis, chemical state, infrared specular and total reflectivity by SEM, XRD, XPS, FTIR and UV-vis spectrophotometry, respectively.

  6. Structure and surface properties of supported oxides

    Energy Technology Data Exchange (ETDEWEB)

    Leyrer, J.; Vielhaber, B.; Zaki, M.I.; Zhuang Shuxian; Weitkamp, J.; Knoezinger, H.

    1985-09-15

    Supported molybdate catalysts have been prepared on Al/sub 2/O/sub 3/,TiO/sub 2/, CeO/sub 2/, ZrO/sub 2/ and SiO/sub 2/ by impregnation from aqueous solution. The isoelectric point (IEPS) of the support surfaces determines the primary adsorption interaction of the molybdate species with the surface at a given pH. Raman spectroscopy shows monolayer formation on Al/sub 2/O/sub 3/, TiO/sub 2/ and CeO/sub 2/, while high proportions of MoO/sub 3/ are detected on SiO/sub 2/ and ZrO/sub 2/. Strong support effects influence the reducibility of the supported molybdate, which decreases in the sequence Mo/TiO/sub 2/ > Mo/ > CeO/sub 2/ > Mo/Al/sub 2/O/sub 3/ > Mo/ZrO/sub 2/. The dispersion of the monolayer on TiO/sub 2/, CeO/sub 2/ and Al/sub 2/O/sub 3/ seems to be fairly stable under reduction conditions, indicating strong chemical interaction with the supports.

  7. Electron beam induced surface activation of oxide surfaces for nanofabrication

    Energy Technology Data Exchange (ETDEWEB)

    Vollnhals, Florian; Seiler, Steffen; Walz, Marie-Madeleine; Steinrueck, Hans-Peter; Marbach, Hubertus [Lehrstuhl fuer Physikalische Chemie II and Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen (Germany); Woolcot, Tom; Thornton, Geoff [London Centre for Nanotechnology and Department of Chemistry, University College London (United Kingdom)

    2012-07-01

    The controlled fabrication of structures on the nanoscale is a major challenge in science and engineering. Direct-write techniques like Electron Beam Induced Deposition (EBID) were shown to be suitable tools in this context. Recently, Electron Beam Induced Surface Activation (EBISA) has been introduced as a new focused electron beam technique. In EBISA, a surface, e.g. SiO{sub 2}, is irradiated by a focused electron beam, resulting in an activation of the exposed area. The activated area can then react and decompose precursor gases like iron pentacarbonyl, Fe(CO){sub 5}. This leads to a primary deposit, which continues to grow autocatalytically as long as Fe(CO){sub 5} is supplied, resulting in pure (> 90 % at.), crystalline iron nanostructures. We expand the use of this concept by exploring EBISA to produce metallic nanostructures on TiO{sub 2}(110) in UHV; atomistic insight into the process is obtained via Scanning Tunneling Microscopy (STM) and chemical insight via Auger Electron Spectroscopy (AES).

  8. Surface oxide formation during corona discharge treatment of AA 1050 aluminium surfaces

    DEFF Research Database (Denmark)

    Minzari, Daniel; Møller, Per; Kingshott, Peter

    2008-01-01

    Atmospheric plasmas have traditionally been used as a non-chemical etching process for polymers, but the characteristics of these plasmas could very well be exploited for metals for purposes more than surface cleaning that is presently employed. This paper focuses on how the corona discharge...... process modifies aluminium AA 1050 surface, the oxide growth and resulting corrosion properties. The corona treatment is carried out in atmospheric air. Treated surfaces are characterized using XPS, SEM/EDS, and FIB-FESEM and results suggest that an oxide layer is grown, consisting of mixture of oxide...... and hydroxide. The thickness of the oxide layer extends to 150–300 nm after prolonged treatment. Potentiodynamic polarization experiments show that the corona treatment reduces anodic reactivity of the surface significantly and a moderate reduction of the cathodic reactivity....

  9. Oxidized Zirconium Bearing Surfaces in Total Knee Arthroplasty: Lessons Learned.

    Science.gov (United States)

    Schüttler, Karl Friedrich; Efe, Turgay; Heyse, Thomas J; Haas, Steven B

    2015-10-01

    Polyethylene wear in total knee arthroplasty is a still unsolved problem resulting in osteolysis and long-term failure of knee joint replacement. To address the problem of polyethylene wear, research aimed for an optimal implant design and for an optimal combination of bearing surfaces. Oxidized zirconium was introduced to minimize surface wear and thus potentially increase long-term implant survival. This review comprises the current literature related to in vitro and in vivo studies evaluating performance of oxidized zirconium total knee arthroplasty and results from retrieval analyses.

  10. Deuterium blistering in tungsten and tungsten vanadium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Arshad, Kameel; Yuan, Yue; Cheng, Long; Wang, Jun [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Zhou, Zhang-Jian [School of Materials Science and Engineering, University of Science and Technology Beijing (USTB), Beijing 100083 (China); De Temmerman, Gregory [FOM Institute for Plasma Physics, Edisonbaan 14, 3439 MN, Nieuwegein (Netherlands); ITER Organization, Route de Vinon-sur-Verdon, CS90 046, 13067 St Paul Lez Durance Cedex (France); Lu, Guang-Hong, E-mail: lgh@buaa.edu.cn [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China)

    2016-06-15

    In order to evaluate D blistering behavior in W based plasma facing materials, rolled W and different grades of W-V targets were exposed to high flux of 1.2 × 10{sup 24} m{sup −2} s{sup −1}, low energy (38 eV) D plasma at two different surface temperatures. The blistering behavior was investigated by means of scanning electron microscopy, accompanied by electron back-scattering diffraction. Highest numbers of blisters were observed on the surface of rolled tungsten. The addition of V precursor to W suppressed D blister formation. In the case of W-V alloys, comparatively submicron V-containing materials have shown high tendency but small size blisters formation than micron V-containing samples. A high density of blisters was observed near the (111) plane on the surface of both V-containing alloys. Nano-sized blisters were also observed on V enriched surface.

  11. Tribological properties of sputtered tungsten and tungsten nitride thin films

    Institute of Scientific and Technical Information of China (English)

    Wong; K.M.; ShenY.G.; Wong; P.L.

    2001-01-01

    The surface roughness, hardness and tribological properties of tungsten (W) and tung-sten nitride (WNx) thin films prepared by dc magnetron sputtering and reactive magnetron sputter-ing in Ar-N2 gas mixtures have been studied using atomic force microscopy (AFM), nanoindenta-tion measurements and ball-on-disc wear testing. A pronounced surface roughness was observedonly for films under compressive strains. The surface was flat under tension but rough under com-pression. Similar hardness with value about 20 GPa were observed in the W and WNx (x=0.3)films. This is thought to be due to the fact the grains are restricted to a very small size in the coat-ings. The higher coefficients of friction (0.4 for W and 0.9 for WN0.3) suggest that WN0.3 is not theoptimum phase. Finally, discussions are made with tribological test results.

  12. Surface chemistry of black phosphorus under a controlled oxidative environment

    Science.gov (United States)

    Luo, Wei; Zemlyanov, Dmitry Y.; Milligan, Cory A.; Du, Yuchen; Yang, Lingming; Wu, Yanqing; Ye, Peide D.

    2016-10-01

    Black phosphorus (BP), the bulk counterpart of monolayer phosphorene, is a relatively stable phosphorus allotrope at room temperature. However, monolayer phosphorene and ultra-thin BP layers degrade in ambient atmosphere. In this paper, we report the investigation of BP oxidation and discuss the reaction mechanism based on the x-ray photoelectron spectroscopy (XPS) data. The kinetics of BP oxidation was examined under various well-controlled conditions, namely in 5% O2/Ar, 2.3% H2O/Ar, and 5% O2 and 2.3% H2O/Ar. At room temperature, the BP surface is demonstrated not to be oxidized at a high oxidation rate in 5% O2/Ar nor in 2.3% H2O/Ar, according to XPS, with the thickness of the oxidized phosphorus layer <5 Å for 5 h. On the other hand, in the O2/H2O mixture, a 30 Å thickness oxide layer was detected already after 2 h of the treatment. This result points to a synergetic effect of water and oxygen in the BP oxidation. The oxidation effect was also studied in applications to the electrical measurements of BP field-effect transistors (FETs) with or without passivation. The electrical performance of BP FETs with atomic layer deposition (ALD) dielectric passivation or h-BN passivation formed in a glove-box environment are also presented.

  13. Surface oxide growth on platinum electrode in aqueous trifluoromethanesulfonic acid

    Science.gov (United States)

    Furuya, Yoshihisa; Mashio, Tetsuya; Ohma, Atsushi; Dale, Nilesh; Oshihara, Kenzo; Jerkiewicz, Gregory

    2014-10-01

    Platinum in the form of nanoparticles is the key and most expensive component of polymer electrolyte membrane fuel cells, while trifluoromethanesulfonic acid (CF3SO3H) is the smallest fluorinated sulfonic acid. Nafion, which acts as both electrolyte and separator in fuel cells, contains -CF2SO3H groups. Consequently, research on the electrochemical behaviour of Pt in aqueous CF3SO3H solutions creates important background knowledge that can benefit fuel cell development. In this contribution, Pt electro-oxidation is studied in 0.1 M aqueous CF3SO3H as a function of the polarization potential (Ep, 1.10 ≤ Ep ≤ 1.50 V), polarization time (tp, 100 ≤ tp ≤ 104 s), and temperature (T, 278 ≤ T ≤ 333 K). The critical thicknesses (X1), which determines the applicability of oxide growth theories, is determined and related to the oxide thickness (dox). Because X1 > dox for the entire range of Ep, tp, and T values, the formation of Pt surface oxide follows the interfacial place-exchange or the metal cation escape mechanism. The mechanism of Pt electro-oxidation is revised and expanded by taking into account possible interactions of cations, anions, and water molecules with Pt. A modified kinetic equation for the interfacial place exchange is proposed. The application of the interfacial place-exchange and metal cation escape mechanisms leads to an estimation of the Ptδ+-Oδ- surface dipole (μPtO), and the potential drop (Vox) and electric field (Eox) within the oxide. The Pt-anion interactions affect the oxidation kinetics by indirectly influencing the electric field within the double layer and the surface oxide.

  14. Phase modification and surface plasmon resonance of Au/WO{sub 3} system

    Energy Technology Data Exchange (ETDEWEB)

    Bose, R. Jolly; Kavitha, V.S. [Department of Optoelectronics, University of Kerala, Kariyavattom, Thiruvananthapuram 691574, Kerala (India); Sudarsanakumar, C. [School of Pure and Applied Physics, Mahatma Gandhi University, Priyadarshini Hills, Kottayam 686560, Kerala (India); Pillai, V.P. Mahadevan, E-mail: vpmpillai9@gmail.com [Department of Optoelectronics, University of Kerala, Kariyavattom, Thiruvananthapuram 691574, Kerala (India)

    2016-08-30

    Highlights: • We have investigated the role of gold as catalyst and nucleation centers, for the crystallization and phase modification of tungsten oxide, in Au/WO{sub 3} matrix. • The phase change from triclinic WO{sub 3} to monoclinic W{sub 18}O{sub 49} is found to enhance with gold incorporation. • The surface plasmon resonance is observed in gold/tungsten oxide system with the appearance of an absorption band near the wavelength 604 nm. - Abstract: We report the action of gold as catalyst for the modification of phase from triclinic WO{sub 3} to monoclinic W{sub 18}O{sub 49} and nucleation centre for the formation of W{sub 18}O{sub 49} phase, in gold incorporated tungsten oxide films prepared by RF magnetron sputtering technique. A new band is observed near 925 cm{sup −1} in the Raman spectra of gold incorporated tungsten oxide films which is not observed in the pure tungsten oxide film. The intensity of this band enhances with gold content. A localized surface plasmon resonance (LSPR) band is observed near the wavelength 604 nm in gold incorporated tungsten oxide films. The integrated intensities of LSPR band and Raman band (∼925 cm{sup −1}) can be used for sensing the quantity of gold in the Au/WO{sub 3} matrix.

  15. Interactions of Graphene Oxide Nanomaterials with Natural Organic Matter and Metal Oxide Surfaces

    Science.gov (United States)

    Interactions of graphene oxide (GO) with silica surfaces were investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Both GO deposition and release were monitored on silica- and poly-l-lysine (PLL) coated surfaces as a function of GO concentration a...

  16. Modification of platinum surfaces by spontaneous deposition: Methanol oxidation electrocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    MacDonald, J.P.; Gualtieri, B.; Runga, N.; Teliz, E.; Zinola, C.F. [Fundamental Electrochemistry Laboratory, School of Sciences, Universidad de la Republica, Igua Street No. 4225, CP 11400, Montevideo (Uruguay)

    2008-12-15

    The presence of a second metal on platinum surfaces affects the performance of methanol oxidation. However, most of the electrocatalytic reactions are studied by using electrochemically deposited platinum alloys, but in the case of spontaneous deposition the situation is not so clear since the surface distribution, stability and morphology are usually not well documented. The formation of surface decorated samples on mono- and poly-crystalline platinum is followed by electrochemical and spectroscopic techniques and analysis of their performance towards methanol adsorption and oxidation compared with that on pure platinum. Pt/Sn and Pt/Ru are of special interest because of their well-known performance in methanol fuel cells. Methanol oxidation on Pt(111)/Ru, Pt(111)/Sn and Pt(111) shows that ruthenium is the only one able to promote the reaction since the simultaneous dissolution of tin occurs and competes with the process of interest. The in situ infrared spectroscopy is used to compare methanol oxidation on Pt(111)/Ru and Pt(111) in acid media using p-polarized light. The formation of bridge bound carbon monoxide is inhibited in the presence of ruthenium ad-species, whereas on Pt(111) the three adsorption configurations are observed. Linear sweep polarization curves and Tafel slopes (calculated from steady state potentiostatic plots) for methanol oxidation are compared on polycrystalline surfaces modified by tin or ruthenium at different coverages. There is almost no change in the Tafel slopes due to the presence of the foreign metal except for Pt/Ru, where a 0.09 V decade{sup -1} slope was calculated below 0.55 V due to hydroxyl adsorbates on ruthenium islands. The anodic stripping of methanol residues on the three surfaces indicates a lower amount of carbon monoxide-type adsorbates on Pt/Ru, and the simultaneous tin dissolution process leading to residues oxidation on Pt/Sn electrodes. (author)

  17. Synthesis of one-dimensional potassium tungsten bronze with excellent near-infrared absorption property.

    Science.gov (United States)

    Guo, Chongshen; Yin, Shu; Huang, Lijun; Sato, Tsugio

    2011-07-01

    Potassium tungsten oxide nanofibers were successfully synthesized via a facile hydrothermal reaction route in the presence of sulfate. After reduction under a reductive atmosphere of H(2)(5 vol %)/N(2), the potassium tungsten oxide transformed to potassium tungsten bronze. Because of the lack of free electrons, the potassium tungsten oxide (K(x)WO(3+x/2)) showed no NIR shielding performance; however, the potassium tungsten bronze (K(x)WO(3)) showed promising optical characteristics such as high transmittance for visible light, as well as high shielding performance for near-infrared lights, indicating its potential application as a solar filter. Meanwhile, the potassium tungsten bronze (K(x)WO(3)) showed strong absorption of near-infrared light and instantaneous conversion of photoenergy to heat.

  18. Systematic studies of the nucleation and growth of ultrananocrystalline diamond films on silicon substrates coated with a tungsten layer

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Yueh-Chieh; Jiang, Gerald [Institute of Microelectronics, No.1, University Road, Tainan 701, Taiwan (China); Tu, Chia-Hao [Institute of Nanotechnology and Microsystems Engineering, No.1, University Road, Tainan 701, Taiwan (China); Department of Materials Science and Engineering, National Cheng Kung University, No.1, University Road, Tainan 701, Taiwan (China); Chang Chi [Institute of Nanotechnology and Microsystems Engineering, No.1, University Road, Tainan 701, Taiwan (China); Liu, Chuan-pu; Ting, Jyh-Ming [Department of Materials Science and Engineering, National Cheng Kung University, No.1, University Road, Tainan 701, Taiwan (China); Lee, Hsin-Li [Industrial Technology Research Institute - South, Tainan 701, Taiwan (China); Tzeng, Yonhua [Institute of Microelectronics, No.1, University Road, Tainan 701, Taiwan (China); Advanced Optoelectronics Technology Center, No.1, University Road, Tainan 701, Taiwan (China); Auciello, Orlando [Argonne National Laboratory, Materials Science Division, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)

    2012-06-15

    We report on effects of a tungsten layer deposited on silicon surface on the effectiveness for diamond nanoparticles to be seeded for the deposition of ultrananocrystalline diamond (UNCD). Rough tungsten surface and electrostatic forces between nanodiamond seeds and the tungsten surface layer help to improve the adhesion of nanodiamond seeds on the tungsten surface. The seeding density on tungsten coated silicon thus increases. Tungsten carbide is formed by reactions of the tungsten layer with carbon containing plasma species. It provides favorable (001) crystal planes for the nucleation of (111) crystal planes by Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) in argon diluted methane plasma and further improves the density of diamond seeds/nuclei. UNCD films grown at different gas pressures on tungsten coated silicon which is pre-seeded by nanodiamond along with heteroepitaxially nucleated diamond nuclei were characterized by Raman scattering, field emission-scanning electron microscopy, and high resolution-transmission electron microscopy.

  19. Influence of mineral oil and additives on microhardness and surface chemistry of magnesium oxide (001) surface

    Science.gov (United States)

    Miyoshi, K.; Shigaki, H.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron spectroscopy analyses and hardness experiments were conducted with cleaved magnesium oxide /001/ surfaces. The magnesium oxide bulk crystals were cleaved into specimens along the /001/ surface, and indentations were made on the cleaved surface in laboratory air, in nitrogen gas, or in degassed mineral oil with and without an additive while not exposing specimen surface to any other environment. The various additives examined contained sulfur, phosphorus, chlorine, or oleic acid. The sulfur-containing additive exhibited the highest hardness and smallest dislocation patterns evidencing plastic deformation; the chlorine-containing additive exhibited the lowest hardness and largest dislocation patterns evidencing plastic deformation. Hydrocarbon and chloride (MgCl2) films formed on the magnesium oxide surface. A chloride film was responsible for the lowest measured hardness.

  20. Accumulation-layer surface plasmons in transparent conductive oxides.

    Science.gov (United States)

    Fardad, Shima; Alexander Ramos, E; Salandrino, Alessandro

    2017-05-15

    A rigorous analytical study of the eigenmodes supported by a charge accumulation layer within a transparent conductive oxide (TCO) is presented. The new class of surface plasmons termed accumulation-layer surface plasmons (ASPs) is introduced. Near resonance ASPs are tightly bound and display a vast effective index tunability that could be of great practical interest. The suppression of ASPs in the presence of epsilon-near zero regions is discussed.

  1. 二甲醚催化转化制甲苯的反应研究%Catalytic conversion of dimethyl ether to toluene over the molecular sieves modified with tungsten oxide

    Institute of Scientific and Technical Information of China (English)

    王博; 王辉; 刘广波; 李琢; 李学民; 吴晋沪

    2014-01-01

    在氧气气氛中,对氧化钨改性的不同分子筛催化剂上二甲醚( DME)转化反应进行了评价。结果表明,WO3/HZSM-5催化剂上DME可以高选择性转化为甲苯,对其反应工艺条件进行了优化,常压、290℃、DME/O2比为2:1时,二甲醚几乎完全转化,转化率为98.97%,甲苯的选择性达到39.71%。对催化剂结构和酸性进行表征,结果表明,ZSM-5分子筛的孔道结构最有利于甲苯的生成,WO3的介入调整了HZSM-5分子筛表面的酸性活性位点分布,在氧气气氛中有效地抑制了副产物的生成,使产物中甲苯的选择性提高。%The catalytic performance of various zeolites modified with tungsten oxide in the conversion of dimethyl ether ( DME ) to toluene in the presence of oxygen was investigated in a continuous flow fixed-bed reactor. The results indicated that WO3/HZSM-5 as a catalyst is highly selective in the conversion of DME to toluene;under the optimized conditions, i. e. atmospheric pressure, 290℃, and with a DME/O2 mol ratio of 2:1, the conversion of DME is 98. 97%, with the selectivity of 39. 71% to toluene. The characterization results about the catalyst structure and acidity illustrate that the porous structure of ZSM-5 is suitable for the formation of toluene from DME. The doping of WO3 adjusts the distribution of the surface acid sites and then inhibits the formation of side-products in the presence of oxygen, which is able to enhance the selectivity to toluene.

  2. Kinetics and thermodynamics of H2O dissociation and CO oxidation on the Pt/WC (0001) surface: A density functional theory study

    Science.gov (United States)

    Liang, Yuanyuan; Chen, Litao; Ma, Chun'an

    2017-02-01

    Adsorptions of H2O and CO on the Pt/WC(0001) [pseudomorphic platinum monolayer on WC(0001)] surface have been studied with periodical slab model by PW91 approach of GGA within the framework of density functional theory (DFT). The reaction pathways and mechanisms of H2O dissociation and CO oxidation are also investigated. For a comparison, similar calculation scheme are performed on the Pt (111) surface as well. The adsorption energies of H2O and CO on both concerned surfaces suggest that H2O binds preferentially on the Pt/WC (0001) surface, while CO prefers the metal surface Pt (111), agreeing well with the experimental observation that the tungsten carbides based material is less susceptible to CO poisoning than platinum. The activation energies for the stepwise H2O dehydrogenation reaction show that the progress of H2O dissociation is similar on the two surfaces; and coincidentally the oxidation of CO by surface hydroxyl is much more likely to occur than that by surface oxygen which comes up with the H2O dissociation. Although the activation barrier of H2O dissociation on the Pt/WC (0001) is similar to that on Pt (111), the key oxidant OH specials which play a key role in turning over surface carbon monoxide to carbon dioxide prefer the Pt/WC(0001) surface, and the improved CO oxidation reaction progress confirms that the Pt/WC surface is more CO-tolerant than the pure Pt. According to the electronic structure analysis we find that the increased CO tolerance is ascribed to the downshift of Pt d-band center because of the charge transfer from WC support to the coating surface.

  3. Surface functionalization of dopamine coated iron oxide nanoparticles for various surface functionalities

    Science.gov (United States)

    Sherwood, Jennifer; Xu, Yaolin; Lovas, Kira; Qin, Ying; Bao, Yuping

    2017-04-01

    We present effective conjugation of four small molecules (glutathione, cysteine, lysine, and Tris(hydroxymethyl)aminomethane) onto dopamine-coated iron oxide nanoparticles. Conjugation of these molecules could improve the surface functionality of nanoparticles for more neutral surface charge at physiological pH and potentially reduce non-specific adsorption of proteins to nanoparticles surfaces. The success of conjugation was evaluated with dynamic light scattering by measuring the surface charge changes and Fourier transform infrared spectroscopy for surface chemistry analysis. The stability of dopamine-coated nanoparticles and the ability of conjugated nanoparticles to reduce the formation of protein corona were evaluated by measuring the size and charge of the nanoparticles in biological medium. This facile conjugation method opens up possibilities for attaching various surface functionalities onto iron oxide nanoparticle surfaces for biomedical applications.

  4. Dense Pure Tungsten Fabricated by Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Dianzheng Wang

    2017-04-01

    Full Text Available Additive manufacturing using tungsten, a brittle material, is difficult because of its high melting point, thermal conductivity, and oxidation tendency. In this study, pure tungsten parts with densities of up to 18.53 g/cm3 (i.e., 96.0% of the theoretical density were fabricated by selective laser melting. In order to minimize balling effects, the raw polyhedral tungsten powders underwent a spheroidization process before laser consolidation. Compared with polyhedral powders, the spherical powders showed increased laser absorptivity and packing density, which helped in the formation of a continuous molten track and promoted densification.

  5. Covalent Attachment of 1-Alkenes to Oxidized Platinum Surfaces

    NARCIS (Netherlands)

    Alonso Carnicero, J.M.; Fabre, B.; Trilling, A.K.; Scheres, L.M.W.; Franssen, M.C.R.; Zuilhof, H.

    2015-01-01

    We report the formation of covalently bound alkyl layers onto oxidized Pt (PtOx) substrates by reaction with 1-alkenes as a novel way to bind organic molecules to metal surfaces. The organic layers were characterized by static contact angle, infrared reflection absorption spectroscopy (IRRAS), X-ray

  6. Functional oxide structures on a surface of metals and alloys

    Institute of Scientific and Technical Information of China (English)

    Rudnev; V.; S.; Yarovaya; T.; P.; Boguta; D.; L.; Lukiyanchuk; I.; V.; Tyrina; L.; M.; Morozova; V.; P.; Nedozorov; P.; M.; Vasilyeva; M.; S.; Kondrikov; N.; B.

    2005-01-01

    The investigations of the plasma electrolytic processes in our laboratory are aimed to the development of conditions of formation of oxide layers with determined composition, structure and functional properties on the surface of valve metals (Al, Ti) and their alloys.……

  7. Stability and morphology of cerium oxide surfaces in an oxidizing environment: A first-principles investigation

    Science.gov (United States)

    Fronzi, Marco; Soon, Aloysius; Delley, Bernard; Traversa, Enrico; Stampfl, Catherine

    2009-09-01

    We present density functional theory investigations of the bulk properties of cerium oxides (CeO2 and Ce2O3) and the three low index surfaces of CeO2, namely, (100), (110), and (111). For the surfaces, we consider various terminations including surface defects. Using the approach of "ab initio atomistic thermodynamics," we find that the most stable surface structure considered is the stoichiometric (111) surface under "oxygen-rich" conditions, while for a more reducing environment, the same (111) surface, but with subsurface oxygen vacancies, is found to be the most stable one, and for a highly reducing environment, the (111) Ce-terminated surface becomes energetically favored. Interestingly, this latter surface exhibits a significant reconstruction in that it becomes oxygen terminated and the upper layers resemble the Ce2O3(0001) surface. This structure could represent a precursor to the phase transition of CeO2 to Ce2O3.

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

    Institute of Scientific and Technical Information of China (English)

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

    2007-01-01

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

  9. Oxidation of clean silicon surfaces studied by four-point probe surface conductance measurements

    DEFF Research Database (Denmark)

    Petersen, Christian Leth; Grey, Francois; Aono, M.

    1997-01-01

    We have investigated how the conductance of Si(100)-(2 x 1) and Si(111)-(7 x 7) surfaces change during exposure to molecular oxygen. A monotonic decrease in conductance is seen as the (100) surfaces oxidizes. In contract to a prior study, we propose that this change is caused by a decrease in sur...

  10. MECHANICAL PROPERTIES OF WROUGHT TUNGSTEN

    Science.gov (United States)

    Mechanical properties of wrought tungsten vol. II. Creep rupture test data from 1500 to 5000 F, and tensile test data from room temperature to 5000 F at various strain rates for tungsten sheet material.

  11. First principles investigation of heterogeneous catalysis on metal oxide surfaces

    Science.gov (United States)

    Ghoussoub, Mireille

    Metal oxides possess unique electronic and structural properties that render them highly favourable for applications in heterogeneous catalysis. In this study, computational atomistic modelling based on Density Functional Theory was used to investigate the reduction of carbon dioxide over hydroxylated indium oxide nanoparticles, as well at the activation of methane over oxygen-covered bimetallic surfaces. The first study employed metadynamics-biased ab initio molecular dynamics to obtain the free energy surface of the various reaction steps at finite temperature. In the second study, the nudged elastic band method was used to probe the C-H activation mechanisms for different surface configurations. In both cases, activation energies, reaction energies, transition state structures, and charge analysis results are used to explain the underlying mechanistic pathways.

  12. Tungsten Deposition on Graphite using Plasma Enhanced Chemical Vapour Deposition.

    Science.gov (United States)

    Sharma, Uttam; Chauhan, Sachin S.; Sharma, Jayshree; Sanyasi, A. K.; Ghosh, J.; Choudhary, K. K.; Ghosh, S. K.

    2016-10-01

    The tokamak concept is the frontrunner for achieving controlled thermonuclear reaction on earth, an environment friendly way to solve future energy crisis. Although much progress has been made in controlling the heated fusion plasmas (temperature ∼ 150 million degrees) in tokamaks, technological issues related to plasma wall interaction topic still need focused attention. In future, reactor grade tokamak operational scenarios, the reactor wall and target plates are expected to experience a heat load of 10 MW/m2 and even more during the unfortunate events of ELM's and disruptions. Tungsten remains a suitable choice for the wall and target plates. It can withstand high temperatures, its ductile to brittle temperature is fairly low and it has low sputtering yield and low fuel retention capabilities. However, it is difficult to machine tungsten and hence usages of tungsten coated surfaces are mostly desirable. To produce tungsten coated graphite tiles for the above-mentioned purpose, a coating reactor has been designed, developed and made operational at the SVITS, Indore. Tungsten coating on graphite has been attempted and successfully carried out by using radio frequency induced plasma enhanced chemical vapour deposition (rf -PECVD) for the first time in India. Tungsten hexa-fluoride has been used as a pre-cursor gas. Energy Dispersive X-ray spectroscopy (EDS) clearly showed the presence of tungsten coating on the graphite samples. This paper presents the details of successful operation and achievement of tungsten coating in the reactor at SVITS.

  13. Reversible Compositional Control of Oxide Surfaces by Electrochemical Potentials

    KAUST Repository

    Mutoro, Eva

    2012-01-05

    Perovskite oxides can exhibit a wide range of interesting characteristics such as being catalytically active and electronically/ionically conducting, and thus, they have been used in a number of solid-state devices such as solid oxide fuel cells (SOFCs) and sensors. As the surface compositions of perovskites can greatly influence the catalytic properties, knowing and controlling their surface compositions is crucial to enhance device performance. In this study, we demonstrate that the surface strontium (Sr) and cobalt (Co) concentrations of perovskite-based thin films can be controlled reversibly at elevated temperatures by applying small electrical potential biases. The surface compositional changes of La 0.8Sr 0.2CoO 3-δ (LSC 113), (La 0.5Sr 0.5) 2CoO 4±δ (LSC 214), and LSC 214-decorated LSC 113 films (LSC 113/214) were investigated in situ by utilizing synchrotron-based X-ray photoelectron spectroscopy (XPS), where the largest changes of surface Sr were found for the LSC 113/214 surface. These findings offer the potential of reversibly controlling the surface functionality of perovskites. © 2011 American Chemical Society.

  14. Surface State of Carbon Fibers Modified by Electrochemical Oxidation

    Institute of Scientific and Technical Information of China (English)

    Yunxia GUO; Jie LIU; Jieying LIANG

    2005-01-01

    Surface of polyacrylonitrile (PAN)-based carbon fibers was modified by electrochemical oxidation. The modification effect on carbon fibers surface was explored using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Results showed that on the modified surface of carbon fibers, the carbon contents decreased by 9.7% and the oxygen and nitrogen contents increased by 53.8% and 7.5 times, respectively. The surface roughness and the hydroxyl and carbonyl contents also increased. The surface orientation index was reduced by 1.5%which decreased tensile strength of carbon fibers by 8.1%, and the microcrystalline dimension also decreased which increased the active sites of carbon fiber surface by 78%. The physical and chemical properties of carbon fibers surface were modified through the electrochemical oxidative method, which improved the cohesiveness between the fibers and resin matrix and increased the interlaminar shear strength (ILSS) of carbon fibers reinforced epoxy composite (CFRP) over 20%.

  15. Gas-driven permeation of deuterium through tungsten and tungsten alloys

    Energy Technology Data Exchange (ETDEWEB)

    Buchenauer, Dean A., E-mail: dabuche@sandia.gov [Sandia National Laboratories, Energy Innovation Department, Livermore, CA 94550 (United States); Karnesky, Richard A. [Sandia National Laboratories, Energy Innovation Department, Livermore, CA 94550 (United States); Fang, Zhigang Zak; Ren, Chai [University of Utah, Department of Metallurgical Engineering, Salt Lake City, UT 84112 (United States); Oya, Yasuhisa [Shizuoka University, Graduate School of Science, Shizuoka (Japan); Otsuka, Teppei [Kyushu University, Department of Advanced Energy Engineering Science, Fukuoka (Japan); Yamauchi, Yuji [Hokkaido University, Third Division of Quantum Science and Engineering, Faculty of Engineering, Sapporo (Japan); Whaley, Josh A. [Sandia National Laboratories, Energy Innovation Department, Livermore, CA 94550 (United States)

    2016-11-01

    Highlights: • We have designed and performed initial studies on a high temperature gas-driven permeation cell capable of operating at temperatures up to 1150 °C and at pressures between 0.1–1 atm. • Permeation measurements on ITER grade tungsten compare well with past studies by Frauenfelder and Zahkarov in the temperature range from 500 to 1000 °C. • First permeation measurements on Ti dispersoid-strengthened ultra-fine grained tungsten show higher permeation at 500 °C, but very similar permeation with ITER tungsten at 1000 °C. Diffusion along grain boundaries may be playing a role for this type of material. - Abstract: To address the transport and trapping of hydrogen isotopes, several permeation experiments are being pursued at both Sandia National Laboratories (deuterium gas-driven permeation) and Idaho National Laboratories (tritium gas- and plasma-driven tritium permeation). These experiments are in part a collaboration between the US and Japan to study the performance of tungsten at divertor relevant temperatures (PHENIX). Here we report on the development of a high temperature (≤1150 °C) gas-driven permeation cell and initial measurements of deuterium permeation in several types of tungsten: high purity tungsten foil, ITER-grade tungsten (grains oriented through the membrane), and dispersoid-strengthened ultra-fine grain (UFG) tungsten being developed in the US. Experiments were performed at 500–1000 °C and 0.1–1.0 atm D{sub 2} pressure. Permeation through ITER-grade tungsten was similar to earlier W experiments by Frauenfelder (1968–69) and Zaharakov (1973). Data from the UFG alloy indicates marginally higher permeability (< 10×) at lower temperatures, but the permeability converges to that of the ITER tungsten at 1000 °C. The permeation cell uses only ceramic and graphite materials in the hot zone to reduce the possibility for oxidation of the sample membrane. Sealing pressure is applied externally, thereby allowing for elevation

  16. Bacterial adhesion to glass and metal-oxide surfaces.

    Science.gov (United States)

    Li, Baikun; Logan, Bruce E

    2004-07-15

    Metal oxides can increase the adhesion of negatively-charged bacteria to surfaces primarily due to their positive charge. However, the hydrophobicity of a metal-oxide surface can also increase adhesion of bacteria. In order to understand the relative contribution of charge and hydrophobicity to bacterial adhesion, we measured the adhesion of 8 strains of bacteria, under conditions of low and high-ionic strength (1 and 100 mM, respectively) to 11 different surfaces and examined adhesion as a function of charge, hydrophobicity (water contact angle) and surface energy. Inorganic surfaces included three uncoated glass surfaces and eight metal-oxide thin films prepared on the upper (non-tin-exposed) side of float glass by chemical vapor deposition. The Gram-negative bacteria differed in lengths of lipopolysaccharides on their outer surface (three Escherichia coli strains), the amounts of exopolysaccharides (two Pseudomonas aeruginosa strains), and their known relative adhesion to sand grains (two Burkholderia cepacia strains). One Gram positive bacterium was also used that had a lower adhesion to glass than these other bacteria (Bacillus subtilis). For all eight bacteria, there was a consistent increase in adhesion between with the type of inorganic surface in the order: float glass exposed to tin (coded here as Si-Sn), glass microscope slide (Si-m), uncoated air-side float glass surface (Si-a), followed by thin films of (Co(1-y-z)Fe(y)Cr(z))3O4, Ti/Fe/O, TiO2, SnO2, SnO2:F, SnO2:Sb, A1(2)O3, and Fe2O3 (the colon indicates metal doping, a slash indicates that the metal is a major component, while the dash is used to distinguish surfaces). Increasing the ionic strength from 1 to 100 mM increased adhesion by a factor of 2.0 +/- 0.6 (73% of the sample results were within the 95% CI) showing electrostatic charge was important in adhesion. However, adhesion was not significantly correlated with bacterial charge and contact angle. Adhesion (A) of the eight strains was

  17. Reactions of metal ions at surfaces of hydrous iron oxide

    Science.gov (United States)

    Hem, J.D.

    1977-01-01

    Cu, Ag and Cr concentrations in natural water may be lowered by mild chemical reduction involving ferric hydroxide-ferrous ion redox processes. V and Mo solubilities may be controlled by precipitation of ferrous vanadate or molybdate. Concentrations as low as 10-8.00 or 10-9.00 M are readily attainable for all these metals in oxygen-depleted systems that are relatively rich in Fe. Deposition of manganese oxides such as Mn3O4 can be catalyzed in oxygenated water by coupling to ferrous-ferric redox reactions. Once formed, these oxides may disproportionate, giving Mn4+ oxides. This reaction produces strongly oxidizing conditions at manganese oxide surfaces. The solubility of As is significantly influenced by ferric iron only at low pH. Spinel structures such as chromite or ferrites of Cu, Ni, and Zn, are very stable and if locally developed on ferric hydroxide surfaces could bring about solubilities much below 10-9.00 M for divalent metals near neutral pH. Solubilities calculated from thermodynamic data are shown graphically and compared with observed concentrations in some natural systems. ?? 1977.

  18. New perspectives on thermal and hyperthermal oxidation of silicon surfaces

    Science.gov (United States)

    Khalilov, Umedjon

    The growth of (ultra)thin silica (SiO2) layers on crystalline silicon (c-Si) and controlling the thickness of SiO2 is an important issue in the fabrication of microelectronics and photovoltaic devices (e.g., MOSFETs, solar cells, optical fibers etc.). Such ultrathin oxide can be grown and tuned even at low temperature (including room temperature), by hyperthermal oxidation or when performed on non-planar Si surfaces (e.g., Si nanowires or spheres). However, hyperthermal silica growth as well as small Si-NW oxidation in general and the initial stages in particular have not yet been investigated in full detail. This work is therefore devoted to controlling ultrathin silica thickness on planar and non-planar Si surfaces, which can open new perspectives in nanodevice fabrication. The simulation of hyperthermal (1-100 eV) Si oxidation demonstrate that at low impact energy (nanotechnology. Above the transition temperature such core-shell nanowires are completely converted to a-SiO2 nanowires. It can be concluded that an accurate control over the interfacial stress by choosing a suitable oxidation temperature and Si-NW diameter can lead to precise nanoscale control over the Si-core radius. All investigations were carried out by applying molecular dynamics calculations using the ReaxFF potential, allowing a accurately study of the underpinning physical and chemical processes.

  19. The role of probe oxide in local surface conductivity measurements

    Energy Technology Data Exchange (ETDEWEB)

    Barnett, C. J.; Kryvchenkova, O.; Wilson, L. S. J.; Maffeis, T. G. G.; Cobley, R. J. [Multidisciplinary Nanotechnology Centre, College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom); Kalna, K. [Electronic Systems Design Centre, College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom)

    2015-05-07

    Local probe methods can be used to measure nanoscale surface conductivity, but some techniques including nanoscale four point probe rely on at least two of the probes forming the same low resistivity non-rectifying contact to the sample. Here, the role of probe shank oxide has been examined by carrying out contact and non-contact I V measurements on GaAs when the probe oxide has been controllably reduced, both experimentally and in simulation. In contact, the barrier height is pinned but the barrier shape changes with probe shank oxide dimensions. In non-contact measurements, the oxide modifies the electrostatic interaction inducing a quantum dot that alters the tunneling behavior. For both, the contact resistance change is dependent on polarity, which violates the assumption required for four point probe to remove probe contact resistance from the measured conductivity. This has implications for all nanoscale surface probe measurements and macroscopic four point probe, both in air and vacuum, where the role of probe oxide contamination is not well understood.

  20. High Heat Load Properties of Ultra Fine Grain Tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Z.; Du, J.; Ge, C. [Lab. of Special Ceramic and P/M, University of Science and Technology, 100083 Beijing (China); Linke, J.; Pintsuk, G. [FZJ-Forschungszentrum Juelich GmbH, Association Euratom-FZJ, Institut fur Plasmaphysik, Postfach 1913, D-52425 Juelich (Germany); Song, S.X. [Research Center on Fusion Materials (RCFM), University of Science and Technology Beijing (USTB), 100083 Beijing (China)

    2007-07-01

    Full text of publication follows: Tungsten is increasingly considered as a promising candidate armour materials facing the plasma in tokamaks for medium to high heat flux components (EAST, ASDEX, ITER). Fabrication tungsten with ultra fine grain size is considered as an effective way to ameliorate some disadvantages of tungsten, such as its brittleness at room temperature. But the research data on the performance of ultra fine grain tungsten is still very limit. In this work, high heat load properties of pure ultra-fine grain tungsten have been studied. The ultra fine grain tungsten samples with average grain size of 0.2 {mu}m, 1 {mu}m and 3 {mu}m were fabricated by resistance sintering under ultra high pressure. The annealing experiments for the investigation of the material resistance against grain growth have been done by annealing samples in a vacuum furnace at different temperature holding for 2 hours respectively. It is found that recrystallization and grain growth occur at heating temperature of 1250 deg. c. The finer the initial grain sizes of tungsten, the smaller its grain growth grain. The effects of transient high thermal loads (off normal events like disruptions) on tungsten surface morphology have been performed in electron beam test facility JUDITH. The thermal loads tests have been carried out with 4 ms pulses at different power density of 0.22, 0.33, 0.44, 0.55 and 0.88 GW/m{sup 2} respectively. Horizontal cracks formed for all tungsten samples at 0.44 GW/m{sup 2}. Particle erosions occurred for tungsten with 3 {mu}m size at 0.33 GW/m{sup 2} and for tungsten with 0.2 and 1 {mu}m size at 0.55 GW/m{sup 2}. The weight loss of tungsten with 0.2, 1 and 3 {mu}m size are 2,0.1,0.6 mg respectively at 0.88 GW/m{sup 2}. The effects of a large number of very short transient repetitive thermal loads (ELM-like) on tungsten surface morphology also have been performed by using a fundamental wave of a YAG laser. It is found that tungsten with 0.2 {mu}m size has

  1. Tailoring of fuzzy nanostructures on porous tungsten skeleton by helium plasma irradiation

    Science.gov (United States)

    Kajita, Shin; Tanaka, Hirohiko; Ohno, Noriyasu

    2017-03-01

    Porous tungsten skeleton, which was fabricated by sintering of tungsten powder, was exposed to helium plasmas, and the fuzzy nanostructures were tailored on the surface. The hemispherical optical reflectance of the samples was measured at the wavelength of 633 nm. It was shown that the optical reflectance of the porous tungsten skeleton was lower than that of flat tungsten samples. The minimum reflectance was ∼0.4%, suggesting that the darkest metallic material was fabricated. The advantage of the porous tungsten skeleton with nanostructures for optical application is discussed.

  2. Formation, Removal, and Reformation of Surface Coatings on Various Metal Oxide Surfaces Inspired by Mussel Adhesives.

    Science.gov (United States)

    Kang, Taegon; Oh, Dongyeop X; Heo, Jinhwa; Lee, Han-Koo; Choy, Seunghwan; Hawker, Craig J; Hwang, Dong Soo

    2015-11-11

    Mussels survive by strongly attaching to a variety of different surfaces, primarily subsurface rocks composed of metal oxides, through the formation of coordinative interactions driven by protein-based catechol repeating units contained within their adhesive secretions. From a chemistry perspective, catechols are known to form strong and reversible complexes with metal ions or metal oxides, with the binding affinity being dependent on the nature of the metal ion. As a result, catechol binding with metal oxides is reversible and can be broken in the presence of a free metal ion with a higher stability constant. It is proposed to exploit this competitive exchange in the design of a new strategy for the formation, removal, and reformation of surface coatings and self-assembled monolayers (SAM) based on catechols as the adhesive unit. In this study, catechol-functionalized tri(ethylene oxide) (TEO) was synthesized as a removable and recoverable self-assembled monolayer (SAM) for use on oxides surfaces. Attachment and detachment of these catechol derivatives on a variety of surfaces was shown to be reversible and controllable by exploiting the high stability constant of catechol to soluble metal ions, such as Fe(III). This tunable assembly based on catechol binding to metal oxides represents a new concept for reformable coatings with applications in fields ranging from friction/wettability control to biomolecular sensing and antifouling.

  3. Optimum conditions for fabricating superhydrophobic surface on copper plates via controlled surface oxidation and dehydration processes

    Science.gov (United States)

    Zhang, Yan; Li, Wen; Ma, Fumin; Yu, Zhanlong; Ruan, Min; Ding, Yigang; Deng, Xiangyi

    2013-09-01

    The superhydrophobic surfaces on copper substrate were fabricated by direct oxidation and dehydration processes, and the reaction and modification conditions were optimized. Firstly, the oxidation conditions including the concentrations of K2S2O8 and NaOH, the oxidation time were studied. It is found that the superhydrophobicity would be better if the copper plates were oxidized in 0.06 M K2S2O8 and 3.0 M NaOH solution at 65 °C for 35 min. Then, the modification conditions including modifier concentration and modification time were investigated. The results showed that 5 wt% lauric acid and 1 h modification time were suitable modification conditions for preparing copper-based superhydrophobic surfaces. The surface fabricated under optimized conditions displayed excellent superhydrophobicity of high water contact angle of 161.1° and a low contact angle hysteresis of 2.5°. The surface microstructure and composition of the superhydrophobic surfaces were also characterized by SEM and FT-IR. It is found that the highly concentrated micro/nanostructured sheets and the low surface energy materials on the surface should be responsible for the high superhydrophobicity.

  4. Macromolecular surface design: photopatterning of functional stable nitrile oxides.

    Science.gov (United States)

    Altintas, Ozcan; Glassner, Mathias; Rodriguez-Emmenegger, Cesar; Welle, Alexander; Trouillet, Vanessa; Barner-Kowollik, Christopher

    2015-05-04

    The efficient trapping of photogenerated thioaldehydes with functional shelf-stable nitrile oxides in a 1,3-dipolar cycloaddition is a novel and versatile photochemical strategy for polymer end-group functionalization and surface modification under mild and equimolar conditions. The modular ligation in solution was followed in detail by electrospray ionization mass spectrometry (ESI-MS). X-ray photoelectron spectroscopy (XPS) was employed to analyze the functionalized surfaces, whereas time-of-flight secondary-ion mass spectrometry (ToF-SIMS) confirmed the spatial control of the surface functionalization using a micropatterned shadow mask. Polymer brushes were grown from the surface in a spatially confined regime by surface-initiated atom transfer radical polymerization (SI-ATRP) as confirmed by TOF-SIMS, XPS as well as ellipsometry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Trends in Metal Oxide Stability for Nanorods, Nanotubes, and Surfaces

    DEFF Research Database (Denmark)

    Mowbray, Duncan; Martinez, Jose Ignacio; Vallejo, Federico Calle;

    2011-01-01

    The formation energies of nanostructures play an important role in determining their properties, including their catalytic activity. For the case of 15 different rutile and 8 different perovskite metal oxides, we used density functional theory (DFT) to calculate the formation energies of (2......,2) nanorods, (3,3) nanotubes, and the (110) and (100) surfaces. These formation energies can be described semiquantitatively (mean absolute error ≈ 0.12 eV) by the fraction of metal−oxygen bonds broken and the metal d-band and p-band centers in the bulk metal oxide....

  6. Mechanical Properties of Glass Surfaces Coated with Tin Oxide

    DEFF Research Database (Denmark)

    Swindlehurst, W. E.; Cantor, B.

    1978-01-01

    of tin tetrachloride on industrial soda glass at ~800K to thicknesses of ~3×10-8 and 3×10 -7 m, commercially by the `titanising' process on industrial soda glass at ~800K to a thickness of ~3.10-9 m, and in the laboratory by radio frequency sputtering from tin oxide powder over a range of glass......The effect of tin oxide coatings on the coefficient of friction and fracture strength of glass surfaces is studied. Experiments were performed partly on commercially treated glass bottles and partly on laboratory prepared microscope slides. Coatings were applied in the laboratory by decomposition...

  7. Role of oxidation on surface conductance of the topological insulator Bi2Te2Se

    Science.gov (United States)

    Hwang, Jin Heui; Park, Joonbum; Kwon, Sangku; Kim, Jun Sung; Park, Jeong Young

    2014-12-01

    We investigated the effect of surface oxides on charge transport properties in a topological insulator (Bi2Te2Se) using conductive probe atomic force microscopy in an ultrahigh vacuum environment. Uniform distribution of the measured friction and current were observed over a single quintuple layer terrace after exposure to the ambient environment, which is an indication of uniform surface oxide coverage. An oxide-free topological insulator surface was exposed using tip-induced etching. By comparing surface conduction on a fresh surface versus a surface exposed to air, we observed a minor change in resistance when surface oxide was present. The current density varied with applied load on the oxidized surface, which implies that the topological surface states respond to tip-induced pressure even though surface oxide is present. From these results, we conclude that surface oxidation in air has a negligible effect on surface conductance in topological insulators.

  8. Tungsten oxide buffer layers fabricated in an inert sol-gel process at room-temperature for blue organic light-emitting diodes.

    Science.gov (United States)

    Höfle, Stefan; Bruns, Michael; Strässle, Stefan; Feldmann, Claus; Lemmer, Uli; Colsmann, Alexander

    2013-08-14

    WO3 deposition from tungsten ethoxide precursor solutions at room temperature is demonstrated. The W(OEt)6 precursor can be converted under inert conditions and hence avoids sample contamination with oxygen, opening a pathway to more stable devices. The stoichiometry of all WO3 layers and the optoelectronic performance of the respective SMOLEDs well match thermally evaporated WO3 and its corresponding SMOLEDs. The solution processed WO3 hole injection layers enable the fabrication of blue phosphorescent OLEDs with low onset voltage and current efficiencies of up to 14 cd A(-1) .

  9. Extraction Factor Of Tungsten Sources From Tungsten Scraps By Zinc Decomposition Process

    National Research Council Canada - National Science Library

    J.-H. Pee; G.H. Kim; H.Y. Lee; Y.J. Kim

    2015-01-01

    Decomposition promoting factors and extraction process of tungsten carbide and tungstic acid powders in the zinc decomposition process of tungsten scraps which are composed mostly of tungsten carbide...

  10. Obtaining of films of tungsten trioxide (WO3) by resistive heating of a tungsten filament

    OpenAIRE

    2008-01-01

    Thin film of tungsten oxide (WO3) has been studied extensively as an electrochromic material and has numerous applications in electrochromic devices, smart windows, gas sensors and optical windows. In order to explore the possibility of using it in electrochromic devices, thorough study the optical properties of the WO3 is an important step. The WO3 layers have been grown by hot-filament metal oxide deposition technique under atmospheric pressure and an oxygen atmosphere. By FTIR and Raman sc...

  11. Molecularly imprinted Ru complex catalysts integrated on oxide surfaces.

    Science.gov (United States)

    Muratsugu, Satoshi; Tada, Mizuki

    2013-02-19

    Selective catalysis is critical for the development of green chemical processes, and natural enzymes that possess specialized three-dimensional reaction pockets with catalytically active sites represent the most sophisticated systems for selective catalysis. A reaction space in an enzyme consists of an active metal center, functional groups for molecular recognition (such as amino acids), and a surrounding protein matrix to prepare the reaction pocket. The artificial design of such an integrated catalytic unit in a non-enzymatic system remains challenging. Molecular imprinting of a supported metal complex provides a promising approach for shape-selective catalysis. In this process, an imprinted cavity with a shape matched to a template molecule is created in a polymer matrix with a catalytically active metal site. In this Account, we review our studies on molecularly imprinted metal complex catalysts, focusing on Ru complexes, on oxide surfaces for shape-selective catalysis. Oxide surface-attached transition metal complex catalysts not only improve thermal stability and catalyst dispersion but also provide unique catalytic performance not observed in homogeneous precursors. We designed molecularly imprinted Ru complexes by using surface-attached Ru complexes with template ligands and inorganic/organic surface matrix overlayers to control the chemical environment around the active metal complex catalysts on oxide surfaces. We prepared the designed, molecularly imprinted Ru complexes on SiO(2) surfaces in a step-by-step manner and characterized them with solid-state (SS) NMR, diffuse-reflectance (DR) UV-vis, X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller isotherm (BET), X-ray fluorescence (XRF), and Ru K-edge extended X-ray absorption fine structure (EXAFS). The catalytic performances of these Ru complexes suggest that this process of molecular imprinting facilitates the artificial integration of catalytic functions at surfaces. Further advances such

  12. Sorption, desorption, and surface oxidative fate of nicotine.

    Science.gov (United States)

    Petrick, Lauren; Destaillats, Hugo; Zouev, Irena; Sabach, Sara; Dubowski, Yael

    2010-09-21

    Nicotine dynamics in an indoor environment can be greatly affected by building parameters (e.g. relative humidity (RH), air exchange rate (AER), and presence of ozone), as well as surface parameters (e.g. surface area (SA) and polarity). To better understand the indoor fate of nicotine, these parameter effects on its sorption, desorption, and oxidation rates were investigated on model indoor surfaces that included fabrics, wallboard paper, and wood materials. Nicotine sorption under dry conditions was enhanced by higher SA and higher polarity of the substrate. Interestingly, nicotine sorption to cotton and nylon was facilitated by increased RH, while sorption to polyester was hindered by it. Desorption was affected by RH, AER, and surface type. Heterogeneous nicotine-ozone reaction was investigated by Fourier transform infrared spectrometry with attenuated total reflection (FTIR-ATR), and revealed a pseudo first-order surface reaction rate of 0.035 +/- 0.015 min(-1) (at [O(3)] = 6 +/- 0.3 x 10(15) molecules cm(-3)) that was partially inhibited at high RH. Extrapolation to a lower ozone level ([O(3)] = 42 ppb) showed oxidation on the order of 10(-5) min(-1) corresponding to a half-life of 1 week. In addition, similar surface products were identified in dry and high RH using gas chromatography-mass spectrometry (GC-MS). However, FTIR analysis revealed different product spectra for these conditions, suggesting additional unidentified products and association with surface water. Knowing the indoor fate of condensed and gas phase nicotine and its oxidation products will provide a better understanding of nicotine's impact on personal exposures as well as overall indoor air quality.

  13. Ammonia modification of oxide-free Si(111) surfaces

    Science.gov (United States)

    Chopra, Tatiana Peixoto; Longo, Roberto C.; Cho, Kyeongjae; Chabal, Yves J.

    2016-08-01

    Amination of surfaces is useful in a variety of fields, ranging from device manufacturing to biological applications. Previous studies of ammonia reaction on silicon surfaces have concentrated on vapor phase rather than wet chemical processes, and mostly on clean Si surfaces. In this work, the interaction of liquid and vapor-phase ammonia is examined on three types of oxide-free surfaces - passivated by hydrogen, fluorine (1/3 monolayer) or chlorine - combining infrared absorption spectroscopy, X-ray photoelectron spectroscopy, and first-principles calculations. The resulting chemical composition highly depends on the starting surface; there is a stronger reaction on both F- and Cl-terminated than on the H-terminated Si surfaces, as evidenced by the formation of Si-NH2. Side reactions can also occur, such as solvent reaction with surfaces, formation of ammonium salt by-products (in the case of 0.2 M ammonia in dioxane solution), and nitridation of silicon (in the case of neat and gas-phase ammonia reactions for instance). Unexpectedly, there is formation of Si-H bonds on hydrogen-free Cl-terminated Si(111) surfaces in all cases, whether vapor phase of neat liquid ammonia is used. The first-principles modeling of this complex system suggests that step-edge surface defects may play a key role in enabling the reaction under certain circumstances, despite the endothermic nature for Si-H bond formation.

  14. Mechanism of glucose electrochemical oxidation on gold surface

    KAUST Repository

    Pasta, Mauro

    2010-08-01

    The complex oxidation of glucose at the surface of gold electrodes was studied in detail in different conditions of pH, buffer and halide concentration. As observed in previous studies, an oxidative current peak occurs during the cathodic sweep showing a highly linear dependence on glucose concentration, when other electrolyte conditions are unchanged. The effect of the different conditions on the intensity of this peak has stressed the limitations of the previously proposed mechanisms. A mechanism able to explain the presence of this oxidative peak was proposed. The mechanism takes into account ion-sorption and electrochemical adsorption of OH-, buffer species (K2HPO4/KH2PO4) and halides. © 2010 Elsevier Ltd. All rights reserved.

  15. Surface morphology changes and damage in hot tungsten by impact of 80 eV - 12 keV He-ions and keV-energy self-atoms

    Science.gov (United States)

    Hijazi, Hussein; Bannister, Mark E.; Krstic, Predrag S.; Parish, Chad M.; Meyer, Harry M., III; Meyer, Fred M.

    2013-10-01

    We report on measurements of interactions of 50 - 12,000 eV He ions with heated tungsten surfaces performed at the ORNL MIRF. Surface morphology changes, as well as nano-fuzz formation were investigated as function of flux and total fluence, for both virgin and pre-damaged W-targets. At low fluences, ordered surface structures are observed, with great grain-to-grain variability, together with blisters and pinholes, whose density and size increase with increasing fluence. At larger fluences, individual grain characteristics disappear, and the entire surface assumes a frothy appearance in FIB/SEM, with a multitude of near-surface bubbles with a broad range of sizes, and disordered whisker growth, while in SEM imaging the surface is indistinguishable from nano-fuzz produced on linear plasma devices. These features are evident at progressively lower fluences as the He-ion energy is increased, particularly above 1 keV, where the He beam serves not only to load the near-surface region with He to saturation, but to produce significant near-surface damage sites that can trap He. We also report on observations of the effects on surface morphology changes and nano-fuzz formation of pre-damage created by self-ion impact, and on MD simulations of near-surface damage using self-atoms. Research sponsored by the LDRD Program of ORNL, managed by UT-Battelle, LLC, for the US DOE.

  16. Oxide cathode mechanisms: Electronic and structural features of oxide cathode surfaces

    Science.gov (United States)

    Cunningham, J.; Nunan, J.

    1985-01-01

    This report describes studies made upon systems selected for their ability to model various important features of oxide cathodes and the mechanisms which enable them to function as efficient thermionic emitters at moderate temperatures. An account is given of experiments which aimed to simulate conditions upon the surfaces of polycrystalline samples of alkaline earth oxides (e.g., SrO and BaO/SrO or MgO and BaO/MgO) at various stages of their preparation in similiar fashion to that used in the thermal activation of oxide cathodes. Accounts are given of experiments which examined the interaction between the gases O2, N2O, H2 or Ch4 and appropriately preactivated surface of pure and mixed alkaline earth oxide samples. Accounts are given of experiments involving the controlled deposition in UHV conditions of zero-valent Ba ad-atoms-in amounts ranging from submonolayer to multilayer coverage - upon layers of SrO or BaO previously prepared in UHV conditions by evaporation of the corresponding metal and its subsequent oxidation. UPS spectra have been undertaken in order to examine surfaces of samples prepared by evaporation of barium metal or strontium metal and to study effects upon the UPS spectra by exposures to the gases N20, O2 and CH4.

  17. Kinetics and Mechanisms of Ciprofloxacin Oxidation on Hematite Surfaces.

    Science.gov (United States)

    Martin, Sébastien; Shchukarev, Andrey; Hanna, Khalil; Boily, Jean-François

    2015-10-20

    Adsorption of antibiotics at mineral surfaces has been extensively studied over the past 20 years, yet much remains to be learned on their interfacial properties and transformation mechanisms. In this study, interactions of Ciprofloxacin (CIP), a fluoroquinolone antibiotic with two sets of synthetic nanosized hematite particles, with relatively smooth (H10, 10-20 nm in diameter) and roughened (H80, 80-90 nm in diameter) surfaces, were studied by means of liquid chromatography (LC), mass spectrometry (MS), and spectroscopy (vibration and X-ray photoelectron). Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy provides evidence for inner-sphere bidentate complex formation of CIP at hematite surfaces in 0.01 M NaCl, irrespective of pH and particle size. ATR-FTIR spectroscopy also revealed that the sorbed mother CIP molecule decayed to other surface species over a period of at least 65 h. This was supported by the detection of three daughter products in the aqueous phase by LC/MS. The appearance of NH3(+) groups during the course of these experiments, revealed by cryogenic XPS, provides further evidence that CIP oxidation proceeds through an opening of piperazine ring via N-dealkylation. Additional in vacuo FTIR experiments under temperature-programmed desorption also showed that oxidation of sorbed byproducts were effectively degraded beyond 450 °C, a result denoting considerably strong (inter)molecular bonds of both mother and daughter products. This work also showed that rougher, possibly multidomainic particles (H80) generated slower rates of CIP decomposition but occurring through more complex schemes than at smoother particle surfaces (H10). This work thus uncovered key aspects of the binding of an important antibiotic at iron oxide surfaces, and therefore provided additional constraints to our growing understanding of the fate of emerging contaminants in the environment.

  18. Band energy control of molybdenum oxide by surface hydration

    Energy Technology Data Exchange (ETDEWEB)

    Butler, Keith T., E-mail: k.t.butler@bath.ac.uk; Walsh, Aron [Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Crespo-Otero, Rachel [School of Biological and Chemical Sciences, Queen Mary University London, Mile End Road, London E1 4NS (United Kingdom); Buckeridge, John; Scanlon, David O. [University College London, Kathleen Lonsdale Materials Chemistry, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Bovill, Edward; Lidzey, David [Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

    2015-12-07

    The application of oxide buffer layers for improved carrier extraction is ubiquitous in organic electronics. However, the performance is highly susceptible to processing conditions. Notably, the interface stability and electronic structure is extremely sensitive to the uptake of ambient water. In this study we use density functional theory calculations to asses the effects of adsorbed water on the electronic structure of MoO{sub x}, in the context of polymer-fullerene solar cells based on PCDTBT. We obtain excellent agreement with experimental values of the ionization potential for pristine MoO{sub 3} (010). We find that IP and EA values can vary by as much as 2.5 eV depending on the oxidation state of the surface and that adsorbed water can either increase or decrease the IP and EA depending on the concentration of surface water.

  19. Designing porous metallic glass compact enclosed with surface iron oxides

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jae Young; Park, Hae Jin; Hong, Sung Hwan; Kim, Jeong Tae; Kim, Young Seok; Park, Jun-Young; Lee, Naesung [Hybrid Materials Center (HMC), Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Seo, Yongho [Graphene Research Institute (GRI) & HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Park, Jin Man, E-mail: jinman_park@hotmail.com [Global Technology Center, Samsung Electronics Co., Ltd, 129 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-742 (Korea, Republic of); Kim, Ki Buem, E-mail: kbkim@sejong.ac.kr [Hybrid Materials Center (HMC), Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)

    2015-06-25

    Highlights: • Porous metallic glass compact was developed using electro-discharge sintering process. • Uniform PMGC can only be achieved when low electrical input energy was applied. • Functional iron-oxides were formed on the surface of PMGCs by hydrothermal technique. - Abstract: Porous metallic glass compact (PMGC) using electro-discharge sintering (EDS) process of gas atomized Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} metallic glass powder was developed. The formation of uniform PMGC can only be achieved when low electrical input energy was applied. Functional iron-oxides were formed on the surface of PMGCs by hydrothermal technique. This finding suggests that PMGC can be applied in the new area such as catalyst via hydrothermal technique and offer a promising guideline for using the metallic glasses as a potential functional application.

  20. SURFACE-MODIFICATION OF FINE RED IRON OXIDE PIGMENT

    Institute of Scientific and Technical Information of China (English)

    Shuilin Zheng; Qinghui Zhang

    2003-01-01

    Surface-modification of fine red iron oxide pigment was carried out in an aqueous solution of sodium polyacrylate. The sedimentation time of modified samples in water increased from 1.05 to 264.4 hours while the particle size (d50) decreased from 1.09 to 0.85 μm, and the tinting strength increased from 100 to 115. The surface-modification as well as the dispersing and stabilizing mechanisms in aqueous solution of the samples were studied by means of IR,Thermal analysis and Zeta potential. The results showed that the modifier molecules acted on the surface of the particles by chemical and physical adsorption, and after the particles were dispersed in aqueous solution, endowing the particle surface with a relatively high negative Zeta potential, thus enhancing electrostatic and steric repulsion between particles for their effective stabilization.

  1. In Situ Atomic Scale Visualization Of Surface Kinetics Driven Dynamics Of Oxide Growth On A Ni–Cr Surface

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Langli; Zou, Lianfeng; Schreiber, Daniel K.; Olszta, Matthew J.; Baer, Donald R.; Bruemmer, Stephen M.; Zhou, Guangwen; Wang, Chong M.

    2016-01-20

    We report in situ atomic-scale visualization of the dynamical three-dimensional (3D) growth of NiO during initial oxidation of Ni-10at%Cr using environmental transmission electron microscopy (ETEM). Despite the thermodynamic preference for Cr2O3 formation, cubic NiO oxides nucleated and grew epitaxially as the dominating oxide phase on the Ni-Cr (100) surface during initial oxidation. The growth of NiO islands proceeds through step-by-step adatom mechanism in 3D, which is sustained by surface diffusion of Ni and O atoms. Although the shapes of oxide islands are controlled by strain energy between oxide and alloy substrate, local surface kinetic variations can lead to the change of surface planes of oxide islands. These results demonstrate that surface diffusion dominates initial oxidation of Ni-Cr in these test conditions.

  2. Effect of Surface Treatments on Leakage of Zirconium Oxide Ceramics

    OpenAIRE

    Göknil Alkan Demetoğlu; Mustafa Zortuk

    2016-01-01

    Objective: The aim of this pilot study was to compare the effects of pretreatments on leakage of zirconia ceramics. Materials and Methods: The speciments divided into 6 groups that were subsequently treated as follows: group 1, no treatment (control); group 2, the ceramic surfaces were airborne-particle abraded with 110 μm aluminum-oxide (Al2O3) particles; group 3, after abrasion of the surfaces with 110 μm Al2O3 particles, silica coating using 30 μm (Al2O3) particles modified by silica (r...

  3. Adsorption and surface oxidation of Fe(II) on metal (hydr)oxides.

    NARCIS (Netherlands)

    Hiemstra, T.; Riemsdijk, van W.H.

    2007-01-01

    The Fe(II) adsorption by non-ferric and ferric (hydr)oxides has been analyzed with surface complexation modeling. The CD model has been used to derive the interfacial distribution of charge. The fitted CD coefficients have been linked to the mechanism of adsorption. The Fe(II) adsorption is

  4. Tungsten diffusion in olivine

    Science.gov (United States)

    Cherniak, D. J.; Van Orman, J. A.

    2014-03-01

    Diffusion of tungsten has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and olivine powders. Experiments were prepared by sealing the source material and polished olivine under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 °C. Tungsten distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0×10-8exp(-365±28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing olivine are similar, and tungsten diffusion in olivine shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in olivine indicate that Hf-W ages in olivine-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.

  5. Gas tungsten arc welder

    Science.gov (United States)

    Christiansen, D.W.; Brown, W.F.

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable axial grinder is provided in the enclosure for refurbishing the used electrode between welds.

  6. OPAL Silicon Tungsten Luminometer

    CERN Multimedia

    OPAL was one of the four experiments installed at the LEP particle accelerator from 1989 - 2000. The Silicon Tungsten Luminometer was part of OPAL's calorimeter which was used to measure the energy of particles. Most particles end their journey in calorimeters. These detectors measure the energy deposited when particles are slowed down and stopped.

  7. Effect of surface oxidation on the surface condition and deuterium permeability of a palladium membrane

    Energy Technology Data Exchange (ETDEWEB)

    Feng Wei [School of Materials Science and Engineering, Sichuan University, Chengdu, 610065 (China); Chengdu University, Chengdu, 610106 (China); Liu Ying, E-mail: liuying5536@163.com [School of Materials Science and Engineering, Sichuan University, Chengdu, 610065 (China); Lian Lixian [School of Materials Science and Engineering, Sichuan University, Chengdu, 610065 (China); Peng Lixia [National Key Laboratory for Surface Physics and Chemistry, Mianyang, 621907 (China); Li Jun [School of Materials Science and Engineering, Sichuan University, Chengdu, 610065 (China)

    2011-09-15

    Oxidation and deoxidation of a Pd membrane was conducted in a quartz tube oven in a temperature range of 23-500 deg. C. The micromorphology and chemical composition of the Pd membrane surface was characterized using scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Micropores and PdO began to form on the Pd membrane surface after oxidation at 240 deg. C for 1 h and their quantity increased gradually with increasing temperature. A rough Pd membrane surface was obtained when the temperature rose to 500 deg. C. The PdO on the Pd membrane surface was completely deoxidized once more using H{sub 2} at room temperature, but the rough surface morphology caused by oxidation remained. The deuterium permeability of the Pd membrane was tested using special equipment in the China National Key Laboratory and the results indicated that the rough Pd membrane surface had higher deuterium permeability than the original membrane. The improved deuterium permeability could be attributed to the higher Pd membrane surface area, which provided deuterium atoms with more adsorption sites and dissociation sites.

  8. Surface composition and catalytic activity of La-Fe mixed oxides for methane oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fengxiang [School of Chemistry, Beijing Institute of Technology, Liangxiang East Road, Beijing 102488 (China); Li, Zhanping [Analysis Center, Tsinghua University, Beijing 100084 (China); Ma, Hongwei [School of Chemistry, Beijing Institute of Technology, Liangxiang East Road, Beijing 102488 (China); Gao, Zhiming, E-mail: zgao@bit.edu.cn [School of Chemistry, Beijing Institute of Technology, Liangxiang East Road, Beijing 102488 (China)

    2015-10-01

    Graphical abstract: - Highlights: • The sample with La/Fe atomic ratio of 0.94 is single phase perovskite La{sub 0.94}FeO{sub 3−d}. • The excess ironic oxide exists on the surface of the perovskite crystallites. • La{sup 3+} ions are enriched on surface of the oxides even for the La{sub 0.68}Fe sample. - Abstract: Four La-Fe oxide samples with La/Fe atomic ratio y = 1.02 ∼ 0.68 (denoted as LayFe) were prepared by the citrate method. The samples had a decreased specific surface area with the La/Fe atomic ratio decreasing. XRD pattern proved that the sample La{sub 0.94}Fe is single phase perovskite La{sub 0.94}FeO{sub 3−d}. Phase composition of the samples was estimated by the Rietveld refinement method. XPS analyses indicate that La{sup 3+} ions are enriched on surface of crystallites for all the samples, and surface carbonate ions are relatively abundant on the samples La{sub 1.02}Fe and La{sub 0.94}Fe. Catalytic activity for methane oxidation per unit surface area of the samples is in the order of La{sub 0.68}Fe > La{sub 0.76}Fe > La{sub 0.94}Fe > La{sub 1.02}Fe both in the presence and in the absence of gaseous oxygen. A reason for this order would be the higher concentration of Fe{sup 3+} ion on the surface of the samples La{sub 0.68}Fe and La{sub 0.76}Fe.

  9. Low-Temperature Strengths and Ductility of Various Tungsten Sheets

    Directory of Open Access Journals (Sweden)

    Yutaka Hiraoka

    2011-01-01

    Full Text Available We used three kinds of tungsten sheets in this study. First, we examined microstructure such as grain size distribution using an optical microscope. Secondly, we carried out three-point bend tests at temperatures between about 290 and 500 K. Then, we examined fracture surface of a failed specimen using a scanning electron microscope. Lastly, by analyzing all these results, we evaluated apparent intergranular and transgranular fracture strengths and discussed strengths and ductility of tungsten. Additionally, we compared mechanical properties of tungsten with those of molybdenum.

  10. Adsorption of T4 bacteriophages on planar indium tin oxide surface via controlled surface tailoring.

    Science.gov (United States)

    Liana, Ayu Ekajayanthi; Chia, Ed Win; Marquis, Christopher P; Gunawan, Cindy; Gooding, J Justin; Amal, Rose

    2016-04-15

    The work investigates the influence of surface physicochemical properties of planar indium tin oxide (ITO) as a model substrate on T4 bacteriophage adsorption. A comparative T4 bacteriophage adsorption study shows a significant difference in bacteriophage adsorption observed on chemically modified planar ITO when compared to similarly modified particulate ITO, which infers that trends observed in virus-particle interaction studies are not necessarily transferrable to predict virus-planar surface adsorption behaviour. We also found that ITO surfaces modified with methyl groups, (resulting in increased surface roughness and hydrophobicity) remained capable of adsorbing T4 bacteriophage. The adsorption of T4 onto bare, amine and carboxylic functionalised planar ITO suggests the presence of a unique binding behaviour involving specific functional groups on planar ITO surface beyond the non-specific electrostatic interactions that dominate phage to particle interactions. The paper demonstrates the significance of physicochemical properties of surfaces on bacteriophage-surface interactions.

  11. Methane to Liquid Hydrocarbons over Tungsten-ZSM-5 and Tungsten Loaded Cu/ZSM-5 Catalysts

    Institute of Scientific and Technical Information of China (English)

    Didi Dwi Anggoro; Nor Aishah Saidina Amin

    2006-01-01

    Metal containing ZSM-5 can produce higher hydrocarbons in methane oxidation. Many researchers have studied the applicability of HZSM-5 and modify ZSM-5 for methane conversion to liquid hydrocarbons, but their research results still lead to low conversion, low selectivity and low heat resistance.The modified HZSM-5, by loading with tungsten (W), could enhance its heat resistant performance, and the high reaction temperature (800 ℃) did not lead to a loss of the W component by sublimation. The loading of HZSM-5 with tungsten and copper (Cu) resulted in an increment in the methane conversion as well as CO2 and C5+ selectivities. In contrast, CO, C2-3 and H2O selectivities were reduced. The process of converting methane to liquid hydrocarbons (C5+) was dependent on the metal surface area and the acidity of the zeolite. High methane conversion and C5+ selectivity, and low H2O selectivity are obtained over W/3.0Cu/HZSM.

  12. Inhibition of Sulfide Mineral Oxidation by Surface Coating Agents: Batch

    Science.gov (United States)

    Choi, J.; Ji, M. K.; Yun, H. S.; Park, Y. T.; Gee, E. D.; Lee, W. R.; Jeon, B.-H.

    2012-04-01

    Mining activities and mineral industries have impacted on rapid oxidation of sulfide minerals such as pyrite (FeS2) which leads to Acid Mine Drainage (AMD) formation. Some of the abandoned mines discharge polluted water without proper environmental remediation treatments, largely because of financial constraints in treating AMD. Magnitude of the problem is considerable, especially in countries with a long history of mining. As metal sulfides become oxidized during mining activities, the aqueous environment becomes acid and rich in many metals, including iron, lead, mercury, arsenic and many others. The toxic heavy metals are responsible for the environmental deterioration of stream, groundwater and soils. Several strategies to remediate AMD contaminated sites have been proposed. Among the source inhibition and prevention technologies, microencapsulation (coating) has been considered as a promising technology. The encapsulation is based on inhibition of O2 diffusion by surface coating agent and is expected to control the oxidation of pyrite for a long time. Potential of several surface coating agents for preventing oxidation of metal sulfide minerals from both Young-Dong coal mine and Il-Gwang gold mine were examined by conducting batch experiments and field tests. Powdered pyrite as a standard sulfide mineral and rock samples from two mine outcrops were mixed with six coating agents (KH2PO4, MgO and KMnO4 as chemical agents, and apatite, cement and manganite as mineral agents) and incubated with oxidizing agents (H2O2 or NaClO). Batch experiments with Young-Dong coal mine samples showed least SO42- production in presence of KMnO4 (16% sulfate production compared to no surface coating agents) or cement (4%) within 8 days. In the case of Il-Gwang mine samples, least SO42- production was observed in presence of KH2PO4 (8%) or cement (2%) within 8 days. Field-scale pilot tests at Il-Gwang site also showed that addition of KH2PO4 decreased sulfate production from 200 to

  13. Surface modification of promising cerium oxide nanoparticles for nanomedicine applications

    KAUST Repository

    Nanda, Himansu Sekhar

    2016-11-14

    Cerium oxide nanoparticles (CNPs) or nanoceria have emerged as a potential nanomedicine for the treatment of several diseases such as cancer. CNPs have a natural tendency to aggregate or agglomerate in their bare state, which leads to sedimentation in a biological environment. Since the natural biological environment is essentially aqueous, nanoparticle surface modification using suitable biocompatible hydrophilic chemical moieties is highly desirable to create effective aqueous dispersions. In this report, (6-{2-[2-(2-methoxy-ethoxy)-ethoxy]-ethoxy}-hexyl)triethoxysilane was used as a functional, biocompatible organosilane to modify the surface of CNPs to produce promising nanoparticles which open substantial therapeutic avenues. The surface modified nanoparticles were produced in situ via an ammonia-induced ethylene glycol-assisted precipitation method and were characterized using complimentary characterization techniques. The interaction between the functional moiety and the nanoparticle was studied using powerful cross polarization/magic angle sample spinning solid state nuclear magnetic resonance spectroscopy. The surface-modified nanoparticles were extremely small and demonstrated a significant improvement in aqueous dispersibility. Moreover, the existence of a strong ionic coordination between the functional moiety and the surface of the nanoparticle was realised, indicating that the surface modified nanoceria are stable and that the nanoparticles should demonstrate an enhanced circulation time in a biological environment. The surface modification approach should be promising for the production of CNPs for nanomedicine applications. © The Royal Society of Chemistry.

  14. Enhanced toughness and stable crack propagation in a novel tungsten fibre-reinforced tungsten composite produced by chemical vapour infiltration

    Science.gov (United States)

    Riesch, J.; Höschen, T.; Linsmeier, Ch; Wurster, S.; You, J.-H.

    2014-04-01

    Tungsten is a promising candidate for the plasma-facing components of a future fusion reactor, but its use is strongly restricted by its inherent brittleness. An innovative concept to overcome this problem is tungsten fibre-reinforced tungsten composite. In this paper we present the first mechanical test of such a composite material using a sample containing multiple fibres. The in situ fracture experiment was performed in a scanning electron microscope for close observation of the propagating crack. Stable crack propagation accompanied with rising load bearing capacity is observed. The fracture toughness is estimated using the test results and the surface observation.

  15. The effect of surface hydrogenation of metal oxides on the nanomorphology and the charge generation efficiency of polymer blend solar cells

    Science.gov (United States)

    Vasilopoulou, Maria

    2014-10-01

    In this work, the effect of surface hydrogenation of different metal oxides, in particular molybdenum and tungsten oxides widely used to enhance hole extraction and zinc and titanium oxides widely used to enhance electron extraction, on the nanomorphology and the charge generation efficiency of polymer blend solar cells is investigated. It was found that photoactive layers based on blends using different polymers, in particular poly(3-hexythiophene) (P3HT) and poly[(9-(1-octylnonyl)-9H-carbazole-2,7-diyl)-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT), which normally differ in both morphology and electronic structure, benefited, for both polymers, from deposition on metal oxides with high surface hydrogen content, in the sense that they exhibited improved crystallinity/order as revealed from X-ray diffraction, UV-vis absorption and elipsometric measurements. As a result, increased charge generation efficiencies and reduced recombination losses were measured in solar cells using metal oxides with highly hydrogenated surfaces at bottom electrodes and based on blends of either P3HT or PCDTBT, with a fullerene acceptor, as was verified by transient photocurrent measurements. The power conversion efficiency (PCE) of those cells reached values of 4.5% and 7.2%, respectively, an increase of about 30% compared with the cells using metal oxides with low surface hydrogen content.In this work, the effect of surface hydrogenation of different metal oxides, in particular molybdenum and tungsten oxides widely used to enhance hole extraction and zinc and titanium oxides widely used to enhance electron extraction, on the nanomorphology and the charge generation efficiency of polymer blend solar cells is investigated. It was found that photoactive layers based on blends using different polymers, in particular poly(3-hexythiophene) (P3HT) and poly[(9-(1-octylnonyl)-9H-carbazole-2,7-diyl)-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2

  16. Structure and magnetism in hexagonal tungsten bronze metal oxides AM1/3W8/3O9 (A-K, Rb, Cs; M-Cr, Fe)

    Science.gov (United States)

    Ivanov, S. A.; Sahu, J. R.; Voronkova, V. I.; Mathieu, R.; Nordblad, P.

    2015-02-01

    The structure and magnetic properties of hexagonal tungsten bronzes AM1/3W8/3O9 (A-K+, Rb+, Cs+; M- Cr3+, Fe3+) have been investigated. Pure ceramic samples were synthesized by solid-state reaction. The samples have been studied by X-ray powder diffraction in combination with magnetic measurements. The compounds crystallize in hexagonal space group P63/mcm. The substitution of magnetic ions into the WO6 octahedra yields dilute antiferromagnetic Cr3+-O2--Cr3+ (or Fe3+-O2--Fe3+) superexchange interaction causing the appearance of short-range magnetic order at low temperatures. The antiferromagnetic character of the interaction is supported by negative values of the derived Curie-Weiss temperatures, θCW. The magnitude of θCW is found to decrease with increasing ionic radius of the A cation.

  17. Surfactant-free synthesis of sub-stoichiometry tungsten oxide nanoparticles and their use as anode buffer layers in organic solar cells

    Science.gov (United States)

    Brütsch, Lennart; Czolk, Jens; Popescu, Radian; Gerthsen, Dagmar; Colsmann, Alexander; Feldmann, Claus

    2017-07-01

    A surfactant-free synthesis of small-sized tungsten trioxide is presented. Nanoparticles with an average size of 4.6 ± 1.5 nm are prepared via hot-injection techniques in ethanol. Due to the reducing properties of ethanol, a sub-stoichiometry composition WO3-x (x∼0.4) is obtained. The partial reduction of W+VI to W+V becomes visible in the bluish color of suspensions and powder samples and in optical spectroscopy (UV-Vis). The nanoparticles are further characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDXS) and infrared spectroscopy (FT-IR). Due to their small size, their high colloidal stability and the absence of surfactants, layers from the as-prepared WO3-x nanoparticles are ideally suited to form anode buffer layers in organic solar cells. Exemplary solar cells show good power conversion efficiency of 6.3%.

  18. Microarc Oxidation of Product Surfaces without Using a Bath

    Directory of Open Access Journals (Sweden)

    V. K. Shatalov

    2015-01-01

    Full Text Available While using an electrochemical method to cover the large-sized work-pieces, units, and products up to 6 м3 by protective coating, there is a certain difficulty to apply traditional anodizing techniques in a plating vat, and it is necessary to find various processing techniques.To use the existing micro-arc oxide coating (MOC methods for work-pieces of various forms and sizes in a plating vat is complicated in case it is required to provide oxide layers in separate places rather than over entire surface of a work-piece. The challenge is to treat flat surfaces in various directions, external and internal surfaces of rotation bodies, profiled surfaces, intersections, closed and through holes, pipes, as well as spline and thread openings for ensuring anti-seize properties in individual or small-scale production to meet technical requirements and operational properties of products.A design of tools to provide MOC-process of all possible surfaces of various engineering box-type products depends on many factors and can be considerably different even when processing the surfaces of the same forms. An attachment to be used is fixed directly on a large-sized design (a work-piece, a product or fastened in the special tool. The features of technological process, design shape, and arrangement of the processed surfaces define a fastening method of the attachment. Therefore it is necessary to pay much attention to a choice of the processing pattern and a design of tools.The Kaluga-branch of Bauman Moscow State Technical University is an original proposer of methods to form MOC-coatings on the separate surfaces of large-sized work-pieces using the moved and stationary electrodes to solve the above listed tasks.The following results of work will have an impact on development of the offered processing methods and their early implementation in real production:1. To provide oxide coatings on the surfaces of large-sized products or assemblies in a single or small

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

    Science.gov (United States)

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

    2007-01-24

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

  20. Deuterium implantation into tungsten at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Johannes [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Physik-Department E28, Technische Universitaet Muenchen, James-Franck-Str. 1, D-85748 Garching (Germany); Schwarz-Selinger, Thomas; Balden, Martin; Schmid, Klaus [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany)

    2016-07-01

    To study the interaction of hydrogen isotopes with tungsten many experiments are conducted in linear plasma devices, which provide high enough hydrogen fluxes to supersaturate the tungsten sample and create defects such as blister. Here an alternative approach is presented. Instead of achieving a high deuterium concentration via high flux exposure, the sample temperature is reduced and the implantation energy of deuterium into tungsten is increased. The lower temperature associated with a reduction in diffusivity as well as the deeper implantation of deuterium lead to an increase of deuterium concentration within the implantation zone. Deuterium is stepwise implanted into polycrystalline tungsten up to a fluence of 1 x 10{sup 22} D/m{sup 2} with an energy of 3.0 keV/D at a sample temperature of 134 K. The retained deuterium is measured in-situ by nuclear reaction analysis. For low fluence approximately 100 % of the implanted deuterium is retained, while for higher fluence the retention saturates. Close to the surface deuterium concentrations up to 64 % are reached. This leads to massive grain orientation dependent blistering with blister sizes between 100-1000 nm at depths between 30-150 nm. Besides the characterization of the blisters their influence on deuterium transport is studied.

  1. Nonuniform Oxidation on the Surface of Fuel Element in HTR

    Directory of Open Access Journals (Sweden)

    Peng Liu

    2016-01-01

    Full Text Available The graphite oxidation of fuel element has obtained high attention in air ingress accident analysis of high temperature gas-cooled reactor (HTR. The shape function, defined as the relationship between the maximum and the average of the oxidation, is an important factor to estimate the consequence of the accident. There are no detailed studies on the shape function currently except two experiments several decades ago. With the development of computer technology, CFD method is used in the numerical experiment about graphite oxidation in pebble bed of HTR in this paper. Structured packed beds are used in the calculation instead of random packed beds. The result shows the nonuniform distribution of oxidation on the sphere surface and the shape function in the condition of air ingress accident. Furthermore, the sensitive factors of shape function, such as temperature and Re number, are discussed in detail and the relationship between the shape function and sensitive factors is explained. According to the results in this paper, the shape function ranges from 1.05 to 4.7 under the condition of temperature varying from 600°C to 1200°C and Re varying from 16 to 1600.

  2. Hydrodynamic Analysis to Process of Hydrostatic Extrusion for Tungsten Alloy

    Institute of Scientific and Technical Information of China (English)

    Fuchi WANG; Zhaohui ZHANG; Shukui LI

    2001-01-01

    The hydrodynamic analysis to the process of the hydrostatic extrusion for tungsten alloy is carried through the hydrodynamic lubrication theory and Reynolds equation in this paper. The critical velocity equation when the hydrodynamic lubrication conditions appear between the surfaces of the work- piece and the die is obtained, and the relationship between the critical velocity and the extrusion parameters is discussed, which build the theoretical bases to the application of the hydrostatic extrusion for tungsten alloy.

  3. 铸铁表面钨极氩弧硬化%Surface hardening of cast iron by tungsten inert gas arc

    Institute of Scientific and Technical Information of China (English)

    杨莉

    2001-01-01

    The wear resistibility of gray cast iron HT200 is improved by employing inert gas tungsten arc remelting and fast solidified, the effect of current and arc moving rate on the chilling layer properties are studied.And it is compared with laser hardening. The results show that Tungsten Inert Gas Arc remelting can improve the resistance to abrasion of cast iron and it is much better and cheaper technique than others.%以HT200为试验材料,用钨极氩孤对其表面进行了局部重熔硬化,得出了相关工艺参数对重熔处理后表层性能的影响,同时与铸铁表面激光硬化进行了对比。结果表明:铸铁表面氩弧硬化是有效提高其耐磨性,发挥自身潜力,降低成本的一项新工艺。

  4. Ozone Decomposition on the Surface of Metal Oxide Catalyst

    Directory of Open Access Journals (Sweden)

    Batakliev Todor Todorov

    2014-12-01

    Full Text Available The catalytic decomposition of ozone to molecular oxygen over catalytic mixture containing manganese, copper and nickel oxides was investigated in the present work. The catalytic activity was evaluated on the basis of the decomposition coefficient which is proportional to ozone decomposition rate, and it has been already used in other studies for catalytic activity estimation. The reaction was studied in the presence of thermally modified catalytic samples operating at different temperatures and ozone flow rates. The catalyst changes were followed by kinetic methods, surface measurements, temperature programmed reduction and IR-spectroscopy. The phase composition of the metal oxide catalyst was determined by X-ray diffraction. The catalyst mixture has shown high activity in ozone decomposition at wet and dry O3/O2 gas mixtures. The mechanism of catalytic ozone degradation was suggested.

  5. Influence of corrosive solutions on microhardness and chemistry of magnesium oxide /001/ surfaces

    Science.gov (United States)

    Ishigaki, H.; Miyoshi, K.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron spectroscopy analyses and hardness experiments were conducted on cleaved magnesium oxide /001/ surfaces. The magnesium oxide bulk crystals were cleaved to specimen size along the /001/ surface, and indentations were made on the cleaved surface in corrosive solutions containing HCl, NaOH, or HNO3 and in water without exposing the specimen to any other environment. The results indicated that chloride (such as MgCl2) and sodium films are formed on the magnesium oxide surface as a result of interactions between an HCl-containing solution and a cleaved magnesium oxide surface. The chloride films soften the magnesium oxide surface. In this case microhardness is strongly influenced by the pH value of the solution. The lower the pH, the lower the microhardness. Sodium films, which are formed on the magnesium oxide surface exposed to an NaOH containing solution, do not soften the magnesium oxide surface.

  6. Degradation of tungsten under the action of a plasma jet

    Science.gov (United States)

    Voronin, A. V.; Sud'enkov, Yu. V.; Semenov, B. N.; Atroshenko, S. A.; Naumova, N. S.

    2014-07-01

    The degradation of the surface and structure of single-crystal tungsten and sintered powder tungsten during the action of a pulsed plasma jet is studied. It is shown that the degradation of a tungsten target during the action of a plasma jet with an energy flux density of 0.25-1 MJ/m2 is accompanied by surface evaporation and melting and the fracture of surface layers on scales of 150-250 μm. The results of a numerical simulation of the thermomechanical processes that occur in a tungsten target during the action of a plasma jet are presented. The degradation of tungsten during the action of a plasma jet is shown to proceed almost continuously from the action (evaporation, melting) to the times that are more than three orders of magnitude longer than the action time, which is caused by the thermomechanical processes occurring in the tungsten target. Moreover, the action of thermal stresses leads to structural and morphological changes throughout the sample volume, and these changes are accompanied by recrystallization in adiabatic shear bands.

  7. Multifunctional Indium Tin Oxide Electrode Generated by Unusual Surface Modification

    Science.gov (United States)

    Bouden, Sarra; Dahi, Antoine; Hauquier, Fanny; Randriamahazaka, Hyacinthe; Ghilane, Jalal

    2016-11-01

    The indium tin oxide (ITO) material has been widely used in various scientific fields and has been successfully implemented in several devices. Herein, the electrochemical reduction of ITO electrode in an organic electrolytic solution containing alkali metal, NaI, or redox molecule, N-(ferrocenylmethyl) imidazolium iodide, was investigated. The reduced ITO surfaces were investigated by X-ray photoelectron spectroscopy and grazing incident XRD demonstrating the presence of the electrolyte cation inside the material. Reversibility of this process after re-oxidation was evidenced by XPS. Using a redox molecule based ionic liquid as supporting electrolyte leads to fellow electrochemically the intercalation process. As a result, modified ITO containing ferrocenyl imidazolium was easily generated. This reduction process occurs at mild reducing potential around -1.8 V and causes for higher reducing potential a drastic morphological change accompanied with a decrease of the electrode conductivity at the macroscopic scale. Finally, the self-reducing power of the reduced ITO phase was used to initiate the spontaneous reduction of silver ions leading to the growth of Ag nanoparticles. As a result, transparent and multifunctional active ITO surfaces were generated bearing redox active molecules inside the material and Ag nanoparticles onto the surface.

  8. Ultralyophobic oxidized aluminum surfaces exhibiting negligible contact angle hysteresis.

    Science.gov (United States)

    Hozumi, Atsushi; McCarthy, Thomas J

    2010-02-16

    Ultralyophobic oxidized aluminum surfaces exhibiting negligible contact angle hysteresis for probe liquids were prepared by chemical vapor deposition (CVD) of bis((tridecafluoro-1,1,2,2,-tetrahydrooctyl)-dimethylsiloxy)methylsilane (CF(3)(CF(2))(5)CH(2)CH(2)Si(CH(3))(2)O)(2)SiCH(3)H, (R(F)Si(Me)(2)O)(2)SiMeH). Oxidized aluminum surfaces were prepared by photooxidation/cleaning of sputter-coated aluminum on silicon wafers (Si/Al(Al(2)(O(3)))) using oxygen plasma. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) confirmed that this facile CVD method produces a monolayer with a thickness of 1.1 nm on the Si/Al(Al(2)(O(3))) surface without a discernible change in surface morphology. After monolayer deposition, the hydrophilic Si/Al(Al(2)(O(3))) surface became both hydrophobic and oleophobic and exhibited essentially no contact angle hysteresis for water and n-hexadecane (advancing/receding contact angles (theta(A)/theta(R)) = 110 degrees/109 degrees and 52 degrees/50 degrees, respectively). Droplets move very easily on this surface and roll off of slightly tilted surfaces, independently of the contact angle (which is a practical definition of ultralyophobic). A conventional fluoroalkylsilane monolayer was also prepared from 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (CF(3)(CF(2))(7)CH(2)CH(2)Si(OCH(3))(3), R(F)Si(OMe)(3)) for comparison. The theta(A)/theta(R) values for water and n-hexadecane are 121 degrees/106 degrees and 76 degrees/71 degrees, respectively. The larger hysteresis values indicate the "pinning" of probe liquids, even though advancing contact angles are larger than those of the (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers. The (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers have excellent hydrolytic stability in water. We propose that the (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers are flexible and liquidlike and that drops in contact with these surfaces experience very low energy barriers between metastable states, leading to the

  9. Positive Biomechanical Effects of Titanium Oxide for Sandblasting Implant Surface as an Alternative to Aluminium Oxide.

    Science.gov (United States)

    Gehrke, Sergio Alexandre; Taschieri, Silvio; Del Fabbro, Massimo; Coelho, Paulo Guilherme

    2015-10-01

    The aim of this study was to evaluate the physico-chemical properties and the in vivo host response of a surface sandblasted with particles of titanium oxide (TiO2) followed by acid etching as an alternative to aluminium oxide. Thirty titanium disks manufactured in the same conditions as the implants and 24 conventional cylindrical implants were used. Half of the implants had a machined surface (Gcon) while in the other half; the surface was treated with particles of TiO2 followed by acid etching (Gexp). Surface characterization was assessed by scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDS), profilometry, and wettability. For the in vivo test, 12 implants of each group were implanted in the tibia of 6 rabbits, and were reverse torque tested after periods of 30 or 60 days after implantation. Following torque, SEM was utilized to assess residual bone-implant contact. The surface characterization by SEM showed a very homogeneous surface with uniform irregularities for Gexp and a small amount of residues of the blasting procedure, while Gcon presented a surface with minimal irregularities from the machining tools. Wettability test showed decreased contact angle for the Gcon relative to the Gexp. The Gexp removal torque at 30 and 60 days was 28.7%, and 33.2% higher relative to the Gcon, respectively. Blasting the surface with particles of TiO2 represents an adequate option for the surface treatment of dental implants, with minimal risk of contamination by the residual debris from the blasting procedure.

  10. Infrared study of lower sulfur oxides on Io's surface

    Science.gov (United States)

    Baklouti, D.; Schmitt, B.; Brissaud, O.

    2004-11-01

    Sulfur dioxide, SO2, and sulfur monoxide, SO, are the only sulfur oxides that have been firmly identified in Io's atmosphere. While SO2, according to infrared observations, is ubiquitous on Io's surface and seems to widely dominate it, SO has never been found on the surface. In fact, contrary to SO2, SO is extremely reactive and unstable. It decomposes by disproportionation forming SO2 and S2O. This latter molecule, disulfur monoxide, is much more stable than SO and, depending on temperature and pressure conditions, it can, either, directly condense on the "cold" surface, or polymerize forming polysulfuroxides, or even, thermally decompose to SO2 and sulfur. Hapke (1989, Icarus 79, 47-74) measured the spectral reflectance of S2O and its resulting polymer over the range 200-1700 nm. Using Voyager observations, he tried to show that the spectral properties of Io can be matched by combinations of SO2, S2O, polysulfuroxide and basalt, but his model was controversial and since then, no experimental data on S2O and its polymer were added to confirm or definitely reject the possibility of the presence of these molecules on Io's surface. Thus, we have undertaken series of laboratory experiments to synthesize and measure the infrared spectra of S2O and its resulting polymeric sulfuroxides, under different temperature conditions and very low pressures. The results of these experiments will be presented and compared to NIMS/Galileo data. Then, the way of formation and possible presence of these lower sulfur oxides on Io's surface will be discussed.

  11. Computer simulations for thorium doped tungsten crystals

    Energy Technology Data Exchange (ETDEWEB)

    Eberhard, Bernd

    2009-07-17

    Tungsten has the highest melting point among all metals in the periodic table of elements. Furthermore, its equilibrium vapor pressure is by far the lowest at the temperature given. Thoria, ThO{sub 2}, as a particle dopant, results in a high temperature creep resistant material. Moreover, thorium covered tungsten surfaces show a drastically reduced electronic work function. This results in a tremendous reduction of tip temperatures of cathodes in discharge lamps, and, therefore, in dramatically reduced tungsten vapor pressures. Thorium sublimates at temperatures below those of a typical operating cathode. For proper operation, a diffusional flow of thorium atoms towards the surface has to be maintained. This atomic flux responds very sensitively on the local microstructure, as grain boundaries as well as dislocation cores offer ''short circuit paths'' for thorium atoms. In this work, we address some open issues of thoriated tungsten. A molecular dynamics scheme (MD) is used to derive static as well as dynamic material properties which have their common origin in the atomistic behavior of tungsten and thorium atoms. The interatomic interactions between thorium and tungsten atoms are described within the embedded atom model (EAM). So far, in literature no W-Th interaction potentials on this basis are described. As there is no alloying system known between thorium and tungsten, we have determined material data for the fitting of these potentials using ab-initio methods. This is accomplished using the full potential augmented plane wave method (FLAPW), to get hypothetical, i.e. not occurring in nature, ''alloy'' data of W-Th. In order to circumvent the limitations of classical (NVE) MD schemes, we eventually couple our model systems to external heat baths or volume reservoirs (NVT, NPT). For the NPT ensemble, we implemented a generalization of the variable cell method in combination with the Langevin piston, which results in a

  12. The Reduction of Aqueous Metal Species on the Surfaces of Fe(II)-Containing Oxides: The Role of Surface Passivation

    Science.gov (United States)

    White, A.F.; Peterson, M.L.

    1998-01-01

    The reduction of aqueous transition metal species at the surfaces of Fe(II)- containing oxides has important ramifications in predicting the transport behavior in ground water aquifers. Experimental studies using mineral suspensions and electrodes demonstrate that structural Fe(II) heterogeneously reduces aqueous ferric, cupric, vanadate and chromate ions on magnetite and ilmenite surfaces. The rates of metal reduction on natural oxides is strongly dependent on the extent of surface passivation and redox conditions in the weathering environment. Synchrotron studies show that surface oxidation of Fe(II)-containing oxide minerals decreases their capacity for Cr(VI) reduction at hazardous waste disposal sites.

  13. TiNi shape memory alloy coated with tungsten : A novel approach for biomedical applications

    NARCIS (Netherlands)

    Li, Huafang; Zheng, Yufeng; Pei, Y. T.; de Hosson, Jeff

    2014-01-01

    This study explores the use of DC magnetron sputtering tungsten thin films for surface modification of TiNi shape memory alloy (SMA) targeting for biomedical applications. SEM, AFM and automatic contact angle meter instrument were used to determine the surface characteristics of the tungsten thin fi

  14. TiNi shape memory alloy coated with tungsten : A novel approach for biomedical applications

    NARCIS (Netherlands)

    Li, Huafang; Zheng, Yufeng; Pei, Y. T.; de Hosson, Jeff

    This study explores the use of DC magnetron sputtering tungsten thin films for surface modification of TiNi shape memory alloy (SMA) targeting for biomedical applications. SEM, AFM and automatic contact angle meter instrument were used to determine the surface characteristics of the tungsten thin

  15. Covalent attachment of 1-alkenes to oxidized platinum surfaces.

    Science.gov (United States)

    Alonso, Jose Maria; Fabre, Bruno; Trilling, Anke K; Scheres, Luc; Franssen, Maurice C R; Zuilhof, Han

    2015-03-10

    We report the formation of covalently bound alkyl layers onto oxidized Pt (PtOx) substrates by reaction with 1-alkenes as a novel way to bind organic molecules to metal surfaces. The organic layers were characterized by static contact angle, infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The grafted alkyl layers display a hydrolytic stability that is comparable to that of alkyl thiols on Au. PtOx-alkene attachment is compatible with terminal ester moieties enabling further anchoring of