Science.gov

Sample records for layered cobalt oxide

  1. Growth of iron cobalt oxides by atomic layer deposition.

    PubMed

    Lie, Martin; Barnholt Klepper, Karina; Nilsen, Ola; Fjellvåg, Helmer; Kjekshus, Arne

    2008-01-14

    Thin films of iron cobalt oxides with spinel-type structure are made by the atomic layer deposition (ALD) technique using Fe(thd)3 (Hthd = 2,2,6,6-tetramethylheptane-3,5-dione), Co(thd)2, and ozone as precursors. Pulse parameters for ALD-type growth are established and such growth can be achieved at deposition temperatures between 185 and 310 degrees C. Films have been deposited on amorphous soda-lime glass and single-crystalline substrates of Si(100), MgO(100), and alpha-Al2O3(001) which all provide crystalline films, but with various orientations and crystallite sizes. Application of an external magnetic field during the film growth does not influence film growth characteristics (growth rate, crystallinity, topography etc.). Magnetization data are reported for phase-pure films of spinel-type structure with composition Fe2CoO4.

  2. Direct evidence for charge stripes in a layered cobalt oxide

    PubMed Central

    Babkevich, P.; Freeman, P. G.; Enderle, M.; Prabhakaran, D.; Boothroyd, A. T.

    2016-01-01

    Recent experiments indicate that static stripe-like charge order is generic to the hole-doped copper oxide superconductors and competes with superconductivity. Here we show that a similar type of charge order is present in La5/3Sr1/3CoO4, an insulating analogue of the copper oxide superconductors containing cobalt in place of copper. The stripe phase we have detected is accompanied by short-range, quasi-one-dimensional, antiferromagnetic order, and provides a natural explanation for the distinctive hourglass shape of the magnetic spectrum previously observed in neutron-scattering measurements of La2−xSrxCoO4 and many hole-doped copper oxide superconductors. The results establish a solid empirical basis for theories of the hourglass spectrum built on short-range, quasi-static, stripe correlations. PMID:27212023

  3. Partially oxidized atomic cobalt layers for carbon dioxide electroreduction to liquid fuel.

    PubMed

    Gao, Shan; Lin, Yue; Jiao, Xingchen; Sun, Yongfu; Luo, Qiquan; Zhang, Wenhua; Li, Dianqi; Yang, Jinlong; Xie, Yi

    2016-01-01

    Electroreduction of CO2 into useful fuels, especially if driven by renewable energy, represents a potentially 'clean' strategy for replacing fossil feedstocks and dealing with increasing CO2 emissions and their adverse effects on climate. The critical bottleneck lies in activating CO2 into the CO2(•-) radical anion or other intermediates that can be converted further, as the activation usually requires impractically high overpotentials. Recently, electrocatalysts based on oxide-derived metal nanostructures have been shown to enable CO2 reduction at low overpotentials. However, it remains unclear how the electrocatalytic activity of these metals is influenced by their native oxides, mainly because microstructural features such as interfaces and defects influence CO2 reduction activity yet are difficult to control. To evaluate the role of the two different catalytic sites, here we fabricate two kinds of four-atom-thick layers: pure cobalt metal, and co-existing domains of cobalt metal and cobalt oxide. Cobalt mainly produces formate (HCOO(-)) during CO2 electroreduction; we find that surface cobalt atoms of the atomically thin layers have higher intrinsic activity and selectivity towards formate production, at lower overpotentials, than do surface cobalt atoms on bulk samples. Partial oxidation of the atomic layers further increases their intrinsic activity, allowing us to realize stable current densities of about 10 milliamperes per square centimetre over 40 hours, with approximately 90 per cent formate selectivity at an overpotential of only 0.24 volts, which outperforms previously reported metal or metal oxide electrodes evaluated under comparable conditions. The correct morphology and oxidation state can thus transform a material from one considered nearly non-catalytic for the CO2 electroreduction reaction into an active catalyst. These findings point to new opportunities for manipulating and improving the CO2 electroreduction properties of metal systems

  4. Partially oxidized atomic cobalt layers for carbon dioxide electroreduction to liquid fuel

    NASA Astrophysics Data System (ADS)

    Gao, Shan; Lin, Yue; Jiao, Xingchen; Sun, Yongfu; Luo, Qiquan; Zhang, Wenhua; Li, Dianqi; Yang, Jinlong; Xie, Yi

    2016-01-01

    Electroreduction of CO2 into useful fuels, especially if driven by renewable energy, represents a potentially ‘clean’ strategy for replacing fossil feedstocks and dealing with increasing CO2 emissions and their adverse effects on climate. The critical bottleneck lies in activating CO2 into the CO2•- radical anion or other intermediates that can be converted further, as the activation usually requires impractically high overpotentials. Recently, electrocatalysts based on oxide-derived metal nanostructures have been shown to enable CO2 reduction at low overpotentials. However, it remains unclear how the electrocatalytic activity of these metals is influenced by their native oxides, mainly because microstructural features such as interfaces and defects influence CO2 reduction activity yet are difficult to control. To evaluate the role of the two different catalytic sites, here we fabricate two kinds of four-atom-thick layers: pure cobalt metal, and co-existing domains of cobalt metal and cobalt oxide. Cobalt mainly produces formate (HCOO-) during CO2 electroreduction; we find that surface cobalt atoms of the atomically thin layers have higher intrinsic activity and selectivity towards formate production, at lower overpotentials, than do surface cobalt atoms on bulk samples. Partial oxidation of the atomic layers further increases their intrinsic activity, allowing us to realize stable current densities of about 10 milliamperes per square centimetre over 40 hours, with approximately 90 per cent formate selectivity at an overpotential of only 0.24 volts, which outperforms previously reported metal or metal oxide electrodes evaluated under comparable conditions. The correct morphology and oxidation state can thus transform a material from one considered nearly non-catalytic for the CO2 electroreduction reaction into an active catalyst. These findings point to new opportunities for manipulating and improving the CO2 electroreduction properties of metal systems

  5. Partially oxidized atomic cobalt layers for carbon dioxide electroreduction to liquid fuel.

    PubMed

    Gao, Shan; Lin, Yue; Jiao, Xingchen; Sun, Yongfu; Luo, Qiquan; Zhang, Wenhua; Li, Dianqi; Yang, Jinlong; Xie, Yi

    2016-01-01

    Electroreduction of CO2 into useful fuels, especially if driven by renewable energy, represents a potentially 'clean' strategy for replacing fossil feedstocks and dealing with increasing CO2 emissions and their adverse effects on climate. The critical bottleneck lies in activating CO2 into the CO2(•-) radical anion or other intermediates that can be converted further, as the activation usually requires impractically high overpotentials. Recently, electrocatalysts based on oxide-derived metal nanostructures have been shown to enable CO2 reduction at low overpotentials. However, it remains unclear how the electrocatalytic activity of these metals is influenced by their native oxides, mainly because microstructural features such as interfaces and defects influence CO2 reduction activity yet are difficult to control. To evaluate the role of the two different catalytic sites, here we fabricate two kinds of four-atom-thick layers: pure cobalt metal, and co-existing domains of cobalt metal and cobalt oxide. Cobalt mainly produces formate (HCOO(-)) during CO2 electroreduction; we find that surface cobalt atoms of the atomically thin layers have higher intrinsic activity and selectivity towards formate production, at lower overpotentials, than do surface cobalt atoms on bulk samples. Partial oxidation of the atomic layers further increases their intrinsic activity, allowing us to realize stable current densities of about 10 milliamperes per square centimetre over 40 hours, with approximately 90 per cent formate selectivity at an overpotential of only 0.24 volts, which outperforms previously reported metal or metal oxide electrodes evaluated under comparable conditions. The correct morphology and oxidation state can thus transform a material from one considered nearly non-catalytic for the CO2 electroreduction reaction into an active catalyst. These findings point to new opportunities for manipulating and improving the CO2 electroreduction properties of metal systems

  6. Microstructures and Thermoelectric Properties of Sintered Misfit-Layered Cobalt Oxide

    NASA Astrophysics Data System (ADS)

    Morimura, Takao; Yamaguchi, Takahiro; Kojima, Takuya; Matsuya, Noriki; Kondo, Shin-ichiro; Nakashima, Hiromichi

    2014-06-01

    Misfit-layered cobalt oxide Ca3Co4O9 is considered to be a prospective material for thermoelectric conversion. The thermoelectric properties are anisotropic owing to its anisotropic crystal structure. The crystal has preferred thermoelectric properties along the a- b plane. Therefore, the thermoelectric properties are improved and controlled by the degree of orientation of the sintered sample. In the present work, Sr-doped misfit cobalt oxide Ca2.7Sr0.3Co4O9 was prepared by solid-phase reaction, followed by uniaxial compression molding and sintering at 1173 K. The Seebeck coefficient α, electrical resistivity ρ, and dimensionless figure of merit ZT were measured as a function of the compression pressure applied in the uniaxial molding. α, ρ, and ZT as functions of the degree of orientation and the relative density are experimentally clarified and explained by calculations using the compound model.

  7. New misfit-layered cobalt oxide (CaOH){sub 1.14}CoO{sub 2}

    SciTech Connect

    Shizuya, Mitsuyuki; Isobe, Masaaki Baba, Yuji; Nagai, Takuro; Osada, Minoru; Kosuda, Kosuke; Takenouchi, Satoshi; Matsui, Yoshio; Takayama-Muromachi, Eiji

    2007-01-15

    We synthesized a new cobalt oxide (CaOH){sub 1.14}CoO{sub 2} by utilizing a high-pressure technique. X-ray and electron diffraction studies revealed that the compound has a layered structure that consists of CdI{sub 2}-type CoO{sub 2} layers and rock-salt-type double CaOH atomic layers. The two subcells have incommensurate periodicity along the a-axis, resulting in a misfit-layered structure. From resistivity and Seebeck coefficient measurements, we have shown that the two-dimensional (2-D) variable-range hopping (VRH) regime with hole conduction is dominant at low temperature for this compound. As temperature increases, the conduction mechanism undergoes crossover from the 2-D VRH regime to a thermal activation-energy-type regime. - Graphical abstract: Crystal-structure model of the misfit-layered cobalt oxide (CaOH){sub 1.14}CoO{sub 2}. The rectangles indicate unit cells of the two subsystems. The open circles and squares represent the cobalt atoms situated at different positions along the projected coordinate.

  8. Thermoelectric misfit-layered cobalt oxides with interlayers of hydroxide and peroxide species

    SciTech Connect

    Chou, Ta-Lei; Lybeck, Jenni; Chan, Ting-Shan; Hsu, Ying-Ya; Tewari, Girish C.; Rautama, Eeva-Leena; Yamauchi, Hisao; Karppinen, Maarit

    2013-12-15

    Among the thermoelectric misfit-layered cobalt oxides, [M{sub m}A{sub 2}O{sub m+2}]{sub q}CoO{sub 2}, the parent m=0 phases exhibit divergent chemical features but are less understood than the more common m>0 members of the series. Here we synthesize Sr-for-Ca substituted [(Ca{sub 1−x}Sr{sub x}){sub z}(O,OH){sub 2}]{sub q}CoO{sub 2} zero phases up to x=0.2 through low-temperature hydrothermal conversion of precursor powders of the m=1 misfit system, [Co(Ca{sub 1−x}Sr{sub x}){sub 2}O{sub 3}]{sub q}CoO{sub 2}. In the zero-phase [(Ca{sub 1−x}Sr{sub x}){sub z}(O,OH){sub 2}]{sub q}CoO{sub 2} system, as the Sr content x increases the lattice expands anisotropically along the c axis such that the ab-plane dimension and the misfit parameter q remain essentially constant. X-ray absorption spectroscopy data suggest the presence of peroxide-type oxygen species in the (Ca{sub 1−x}Sr{sub x}){sub z}(O,OH){sub 2} rock-salt block and together with infrared spectroscopy, thermogravimetric and low-temperature resistivity and thermopower measurements evidence that the isovalent Sr-for-Ca substitution controls the balance between the peroxide and hydroxide species in the (Ca{sub 1−x}Sr{sub x}){sub z}(O,OH){sub 2} block but leaves the valence of Co essentially intact in the CoO{sub 2} block. The higher electrical conductivity of the Sr-substituted phases is explained as a consequence of increased carrier mobility. - Graphical abstract: Among the thermoelectric misfit-layered cobalt oxides, [M{sub m}A{sub 2}O{sub m+2}]{sub q}CoO{sub 2}, the parent zero (m=0) phases exhibit divergent chemical features. For [(Ca{sub 1−x}Sr{sub x}){sub z}(O,OH){sub 2}]{sub q}CoO{sub 2}, X-ray absorption spectroscopy data suggest the presence of peroxide-type oxygen species in the (Ca{sub 1−x}Sr{sub x}){sub z}(O,OH){sub 2} rock-salt block and together with thermogravimetric and low-temperature transport-property measurements evidence that the isovalent Sr-for-Ca substitution controls the

  9. Thermoelectric misfit-layered cobalt oxides with interlayers of hydroxide and peroxide species

    NASA Astrophysics Data System (ADS)

    Chou, Ta-Lei; Lybeck, Jenni; Chan, Ting-Shan; Hsu, Ying-Ya; Tewari, Girish C.; Rautama, Eeva-Leena; Yamauchi, Hisao; Karppinen, Maarit

    2013-12-01

    Among the thermoelectric misfit-layered cobalt oxides, [MmA2Om+2]qCoO2, the parent m=0 phases exhibit divergent chemical features but are less understood than the more common m>0 members of the series. Here we synthesize Sr-for-Ca substituted [(Ca1-xSrx)z(O,OH)2]qCoO2 zero phases up to x=0.2 through low-temperature hydrothermal conversion of precursor powders of the m=1 misfit system, [Co(Ca1-xSrx)2O3]qCoO2. In the zero-phase [(Ca1-xSrx)z(O,OH)2]qCoO2 system, as the Sr content x increases the lattice expands anisotropically along the c axis such that the ab-plane dimension and the misfit parameter q remain essentially constant. X-ray absorption spectroscopy data suggest the presence of peroxide-type oxygen species in the (Ca1-xSrx)z(O,OH)2 rock-salt block and together with infrared spectroscopy, thermogravimetric and low-temperature resistivity and thermopower measurements evidence that the isovalent Sr-for-Ca substitution controls the balance between the peroxide and hydroxide species in the (Ca1-xSrx)z(O,OH)2 block but leaves the valence of Co essentially intact in the CoO2 block. The higher electrical conductivity of the Sr-substituted phases is explained as a consequence of increased carrier mobility.

  10. Preparation and electrochemical performances of nanoporous/cracked cobalt oxide layer for supercapacitors

    NASA Astrophysics Data System (ADS)

    Gobal, Fereydoon; Faraji, Masoud

    2014-12-01

    Nanoporous/cracked structures of cobalt oxide (Co3O4) electrodes were successfully fabricated by electroplating of zinc-cobalt onto previously formed TiO2 nanotubes by anodizing of titanium, leaching of zinc in a concentrated alkaline solution and followed by drying and annealing at 400 °C. The structure and morphology of the obtained Co3O4 electrodes were characterized by X-ray diffraction, EDX analysis and scanning electron microscopy. The results showed that the obtained Co3O4 electrodes were composed of the nanoporous/cracked structures with an average pore size of about 100 nm. The electrochemical capacitive behaviors of the nanoporous Co3O4 electrodes were investigated by cyclic voltammetry, galvanostatic charge-discharge studies and electrochemical impedance spectroscopy in 1 M NaOH solution. The electrochemical data demonstrated that the electrodes display good capacitive behavior with a specific capacitance of 430 F g-1 at a current density of 1.0 A g-1 and specific capacitance retention of ca. 80 % after 10 days of being used in electrochemical experiments, indicating to be promising electroactive materials for supercapacitors. Furthermore, in comparison with electrodes prepared by simple cathodic deposition of cobalt onto TiO2 nanotubes(without dealloying procedure), the impedance studies showed improved performances likely due to nanoporous/cracked structures of electrodes fabricated by dealloying of zinc, which provide fast ion and electron transfer routes and large reaction surface area with the ensued fast reaction kinetics.

  11. Evidence of a reduction reaction of oxidized iron/cobalt by boron atoms diffused toward naturally oxidized surface of CoFeB layer during annealing

    SciTech Connect

    Sato, Soshi Honjo, Hiroaki; Niwa, Masaaki; Ikeda, Shoji; Ohno, Hideo; Endoh, Tetsuo

    2015-04-06

    We have investigated the redox reaction on the surface of Ta/CoFeB/MgO/CoFeB magnetic tunnel junction stack samples after annealing at 300, 350, and 400 °C for 1 h using angle-resolved X-ray photoelectron spectroscopy for precise analysis of the chemical bonding states. At a capping tantalum layer thickness of 1 nm, both the capping tantalum layer and the surface of the underneath CoFeB layer in the as-deposited stack sample were naturally oxidized. By comparison of the Co 2p and Fe 2p spectra among the as-deposited and annealed samples, reduction of the naturally oxidized cobalt and iron atoms occurred on the surface of the CoFeB layer. The reduction reaction was more significant at higher annealing temperature. Oxidized cobalt and iron were reduced by boron atoms that diffused toward the surface of the top CoFeB layer. A single CoFeB layer was prepared on SiO{sub 2}, and a confirmatory evidence of the redox reaction with boron diffusion was obtained by angle-resolved X-ray photoelectron spectroscopy analysis of the naturally oxidized surface of the CoFeB single layer after annealing. The redox reaction is theoretically reasonable based on the Ellingham diagram.

  12. Cobalt Ferrite Bearing Nitrogen-Doped Reduced Graphene Oxide Layers Spatially Separated with Microporous Carbon as Efficient Oxygen Reduction Electrocatalyst.

    PubMed

    Kashyap, Varchaswal; Singh, Santosh K; Kurungot, Sreekumar

    2016-08-17

    The present work discloses how high-quality dispersion of fine particles of cobalt ferrite (CF) could be attained on nitrogen-doped reduced graphene oxide (CF/N-rGO) and how this material in association with a microporous carbon phase could deliver significantly enhanced activity toward electrochemical oxygen reduction reaction (ORR). Our study indicates that the microporous carbon phase plays a critical role in spatially separating the layers of CF/N-rGO and in creating a favorable atmosphere to ensure the seamless distribution of the reactants to the active sites located on CF/N-rGO. In terms of the ORR current density, the heat-treated hybrid catalyst at 150 °C (CF/N-rGO-150) is found to be clearly outperforming (7.4 ± 0.5 mA/cm(2)) the state-of-the-art 20 wt % Pt-supported carbon catalyst (PtC) (5.4 ± 0.5 mA/cm(2)). The mass activity and stability of CF-N-rGO-150 are distinctly superior to PtC even after 5000 electrochemical cycles. As a realistic system level exploration of the catalyst, testing of a primary zinc-air battery could be demonstrated using CF/N-rGO-150 as the cathode catalyst. The battery is giving a galvanostatic discharge time of 15 h at a discharge current density of 20 mA/cm(2) and a specific capacity of ∼630 mAh g(-1) in 6 M KOH by using a Zn foil as the anode. Distinctly, the battery performance of this system is found to be superior to that of PtC in less concentrated KOH solution as the electrolyte. PMID:27464229

  13. Cobalt Ferrite Bearing Nitrogen-Doped Reduced Graphene Oxide Layers Spatially Separated with Microporous Carbon as Efficient Oxygen Reduction Electrocatalyst.

    PubMed

    Kashyap, Varchaswal; Singh, Santosh K; Kurungot, Sreekumar

    2016-08-17

    The present work discloses how high-quality dispersion of fine particles of cobalt ferrite (CF) could be attained on nitrogen-doped reduced graphene oxide (CF/N-rGO) and how this material in association with a microporous carbon phase could deliver significantly enhanced activity toward electrochemical oxygen reduction reaction (ORR). Our study indicates that the microporous carbon phase plays a critical role in spatially separating the layers of CF/N-rGO and in creating a favorable atmosphere to ensure the seamless distribution of the reactants to the active sites located on CF/N-rGO. In terms of the ORR current density, the heat-treated hybrid catalyst at 150 °C (CF/N-rGO-150) is found to be clearly outperforming (7.4 ± 0.5 mA/cm(2)) the state-of-the-art 20 wt % Pt-supported carbon catalyst (PtC) (5.4 ± 0.5 mA/cm(2)). The mass activity and stability of CF-N-rGO-150 are distinctly superior to PtC even after 5000 electrochemical cycles. As a realistic system level exploration of the catalyst, testing of a primary zinc-air battery could be demonstrated using CF/N-rGO-150 as the cathode catalyst. The battery is giving a galvanostatic discharge time of 15 h at a discharge current density of 20 mA/cm(2) and a specific capacity of ∼630 mAh g(-1) in 6 M KOH by using a Zn foil as the anode. Distinctly, the battery performance of this system is found to be superior to that of PtC in less concentrated KOH solution as the electrolyte.

  14. Cobalt-free nickel rich layered oxide cathodes for lithium-ion batteries.

    PubMed

    Sun, Yang-Kook; Lee, Dong-Ju; Lee, Yun Jung; Chen, Zonghai; Myung, Seung-Taek

    2013-11-13

    We propose a feasibility of Co-free Ni-rich Li(Ni(1-x)Mn(x))O2 layer compound. Li(Ni(1-x)Mn(x))O2 (0.1 ≤ x ≤ 0.5) have been synthesized by a coprecipitation method. Rietveld refinement of X-ray diffraction and microscopic studies reveal dense and spherical secondary particles of highly crystalline phase with low cation mixing over the whole compositions, implying successful optimization of synthetic conditions. Electrochemical test results indicated that the Co-free materials delivered high capacity with excellent capacity retention and reasonable rate capability. In particular, Li(Ni0.9Mn0.1)O2, which possesses the lowest cation mixing in the Li layers among samples, exhibited exceptionally high rate capacity (approximately 149 mAh g(-1) at 10 C rate) at 25 °C and high discharge capacity upon cycling under a severe condition, in the voltage range of 2.7-4.5 V at 55 °C. The cation mixing in Li(Ni0.9Mn0.1)O2 increased slightly even after the extensive cycling at the elevated temperature, which is ascribed to the structural integrity induced from the optimized synthetic condition using the coprecipitation. PMID:24127791

  15. Layer by Layer Ex-Situ Deposited Cobalt-Manganese Oxide as Composite Electrode Material for Electrochemical Capacitor

    PubMed Central

    Rusi; Chan, P. Y.; Majid, S. R.

    2015-01-01

    The composite metal oxide electrode films were fabricated using ex situ electrodeposition method with further heating treatment at 300°C. The obtained composite metal oxide film had a spherical structure with mass loading from 0.13 to 0.21 mg cm-2. The structure and elements of the composite was investigated using X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The electrochemical performance of different composite metal oxides was studied by cyclic voltammetry (CV) and galvanostatic charge-discharge (CD). As an active electrode material for a supercapacitor, the Co-Mn composite electrode exhibits a specific capacitance of 285 Fg-1 at current density of 1.85 Ag-1 in 0.5M Na2SO4 electrolyte. The best composite electrode, Co-Mn electrode was then further studied in various electrolytes (i.e., 0.5M KOH and 0.5M KOH/0.04M K3Fe(CN) 6 electrolytes). The pseudocapacitive nature of the material of Co-Mn lead to a high specific capacitance of 2.2 x 103 Fg-1 and an energy density of 309 Whkg-1 in a 0.5MKOH/0.04MK3Fe(CN) 6 electrolyte at a current density of 10 Ag-1. The specific capacitance retention obtained 67% of its initial value after 750 cycles. The results indicate that the ex situ deposited composite metal oxide nanoparticles have promising potential in future practical applications. PMID:26158447

  16. Oxidation of low cobalt alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.

    1982-01-01

    Four high temperature alloys: U-700, Mar M-247, Waspaloy and PM/HIP U-700 were modified with various cobalt levels ranging from 0 percent to their nominal commercial levels. The alloys were then tested in cyclic oxidation in static air at temperatures ranging from 1000 to 1150 C at times from 500 to 100 1 hour cycles. Specific weight change with time and X-ray diffraction analyses of the oxidized samples were used to evaluate the alloys. The alloys tend to be either Al2O3/aluminate spinel or Cr2O3/chromite spinel formers depending on the Cr/Al ratio in the alloy. Waspaloy with a ratio of 15:1 is a strong Cr2O3 former while this U-700 with a ratio of 3.33:1 tends to form mostly Cr2O3 while Mar M-247 with a ratio of 1.53:1 is a strong Al2O3 former. The best cyclic oxidation resistance is associated with the Al2O3 formers. The cobalt levels appear to have little effect on the oxidation resistance of the Al2O3/aluminate spinel formers while any tendency to form Cr2O3 is accelerated with increased cobalt levels and leads to increased oxidation attack.

  17. X-ray absorption spectroscopy study of parent misfit-layered cobalt oxide [Sr₂O₂]q}CoO₂

    SciTech Connect

    Chou, Ta-Lei; Chan, Ting-Shan; Chen, Jin-Ming; Yamauchi, Hisao; Karppinen, Maarit

    2013-06-01

    Here we present a comprehensive X-ray absorption spectroscopy study carried out at Co-L₂,₃, Co-K, O-K and Sr-K edges for the parent misfit-layered cobalt oxide phase [Sr₂O₂]₀.₅₂CoO₂; comparison is made to another misfit-layered oxide [CoCa₂O₃]₀.₆₂CoO₂ and the perovskite oxide LaCoO₃. A high-quality sample of [Sr₂O₂]₀.₅₂CoO₂ was obtained through ultra-high-pressure synthesis using Sr₃Co₂O₆ and Sr(OH)₂∙8H₂O as starting materials. Different dosages of KClO₃ were mixed with the raw materials as an oxygen source and tested, but it was found that the window for the redox control of [Sr₂O₂]₀.₅₂CoO₂ is rather narrow. From Co-K and Co-L₂,₃ spectra a mixed III/IV valence state is revealed for cobalt in [Sr₂O₂]₀.₅₂}CoO₂, but the average valence value is a little lower than in [CoCa₂O₃]₀.₆₂CoO₂. Then, Sr-K spectrum indicates that the [Sr₂O₂] double-layer block in [Sr₂O₂]₀.₅₂CoO₂ clearly deviates from the cubic SrO rock-salt structure, suggesting a more complicated coordination environment for strontium. This together with a somewhat low Co-valence value and the fact that the phase formation of [Sr₂O₂]₀.₅₂CoO₂ required the presence of Sr(OH)₂∙8H₂O in the high-pressure synthesis suggest that the [Sr₂O₂] block contains ---OH groups, i.e. [Sr₂(O,OH)₂]₀.₅₂CoO₂. - Graphical abstract: [Sr₂O₂]₀.₅₂CoO₂ obtained through high-pressure synthesis is a parent of misfit-layered cobalt oxides, such as [CoCa₂O₃]₀.₆₂CoO₂ or [MmA₂O2+m]qCoO₂ in general. Our comprehensive X-ray absorption spectroscopy study shows that both [Sr₂O₂]₀.₅₂CoO₂ and [CoCa₂O₃]₀.₆₂CoO₂ possess mixed III/IV valence cobalt, but the average Co-valence is a little lower in the former. This is tentatively believed to be due to OH--- groups replacing part of O²⁻ ions in the [Sr

  18. Insight of an easy topochemical oxidative reaction in obtaining high performance electrochemical capacitor based on CoIICoIII monometallic cobalt Layered Double Hydroxide

    NASA Astrophysics Data System (ADS)

    Vialat, Pierre; Rabu, Pierre; Mousty, Christine; Leroux, Fabrice

    2015-10-01

    A series of monometallic Layered Double Hydroxides (LDH) using electroactive cation, i.e. divalent or trivalent cobalt, was prepared by Topochemical Oxidation Reaction (TOR) under O2 atmosphere at 40 °C from pristine β-Co(OH)2 platelets. The oxidation state of the ill-defined layered materials was evaluated by coupling thermal measurements and chemical titration (iodometry). Their characterization by ancillary techniques was completed by the study of their magnetic behavior. The obtained magnetic moments suggest the presence of structural local deformation around the CoII ions, unhomogeneous charge distribution yielding to clustering effects cannot be discarded. Their pseudo-faradic properties as supercapacitor in KOH solution was thoroughly investigated by using Cyclic Voltammetry (CV), Galvanostatic Cycling with Potential Limitation (GCPL) and Electrochemical Impedance Spectroscopy (EIS) techniques. As a function of the oxygen treatment, the relative amount of CoII/CoIII was found to range into 5.3 and 13.3, which is unusually high when compared to classical LDH charge distribution. Pseudocapacitance as high as 1540 F g-1 was obtained underlining a high percentage of CoII, ≈40%, involved in electrochemical process. This high percentage is tentatively explained by an extended outer-active electrochemical surface which demonstrates that TOR is a quick and easy process to get a high pseudocapacitive performance.

  19. Metal-Organic Framework Thin Films as Platforms for Atomic Layer Deposition of Cobalt Ions To Enable Electrocatalytic Water Oxidation.

    PubMed

    Kung, Chung-Wei; Mondloch, Joseph E; Wang, Timothy C; Bury, Wojciech; Hoffeditz, William; Klahr, Benjamin M; Klet, Rachel C; Pellin, Michael J; Farha, Omar K; Hupp, Joseph T

    2015-12-30

    Thin films of the metal-organic framework (MOF) NU-1000 were grown on conducting glass substrates. The films uniformly cover the conducting glass substrates and are composed of free-standing sub-micrometer rods. Subsequently, atomic layer deposition (ALD) was utilized to deposit Co(2+) ions throughout the entire MOF film via self-limiting surface-mediated reaction chemistry. The Co ions bind at aqua and hydroxo sites lining the channels of NU-1000, resulting in three-dimensional arrays of separated Co ions in the MOF thin film. The Co-modified MOF thin films demonstrate promising electrocatalytic activity for water oxidation.

  20. Metal-Organic Framework Thin Films as Platforms for Atomic Layer Deposition of Cobalt Ions To Enable Electrocatalytic Water Oxidation.

    PubMed

    Kung, Chung-Wei; Mondloch, Joseph E; Wang, Timothy C; Bury, Wojciech; Hoffeditz, William; Klahr, Benjamin M; Klet, Rachel C; Pellin, Michael J; Farha, Omar K; Hupp, Joseph T

    2015-12-30

    Thin films of the metal-organic framework (MOF) NU-1000 were grown on conducting glass substrates. The films uniformly cover the conducting glass substrates and are composed of free-standing sub-micrometer rods. Subsequently, atomic layer deposition (ALD) was utilized to deposit Co(2+) ions throughout the entire MOF film via self-limiting surface-mediated reaction chemistry. The Co ions bind at aqua and hydroxo sites lining the channels of NU-1000, resulting in three-dimensional arrays of separated Co ions in the MOF thin film. The Co-modified MOF thin films demonstrate promising electrocatalytic activity for water oxidation. PMID:26636174

  1. Effects of cobalt addition on the catalytic activity of the Ni-YSZ anode functional layer and the electrochemical performance of solid oxide fuel cells.

    PubMed

    Guo, Ting; Dong, Xiaolei; Shirolkar, Mandar M; Song, Xiao; Wang, Meng; Zhang, Lei; Li, Ming; Wang, Haiqian

    2014-09-24

    The effects of cobalt (Co) addition in the Ni-YSZ anode functional layer (AFL) on the structure and electrochemical performance of solid oxide fuel cells (SOFCs) are investigated. X-ray diffraction (XRD) analyses confirmed that the active metallic phase is a Ni(1-x)Co(x) alloy under the operation conditions of the SOFC. Scanning electron microscopy (SEM) observations indicate that the grain size of Ni(1-x)Co(x) increases with increasing Co content. Thermogravimetric analyses on the reduction of the Ni(1-x)Co(x)O-YSZ powders show that there are two processes: the chemical-reaction-controlled process and the diffusion-controlled process. It is found that the reduction peak corresponding to the chemical-reaction-controlled process in the DTG curves moves toward lower temperatures with increasing Co content, suggesting that the catalytic activity of Ni(1-x)Co(x) is enhanced by the doping of Co. It is observed that the SOFC shows the best performance at x = 0.03, and the corresponding maximum power densities are 445, 651, and 815 mW cm(-2) at 700, 750, and 800 °C, respectively. The dependence of the SOFC performance on the Co content can be attributed to the competing results between the decreased three-phase-boundary length in the AFL and the enhanced catalytic activity of the Ni(1-x)Co(x) phase with increasing Co content.

  2. Negative magnetoresistance in (Bi,Pb){sub 2}Sr{sub 3}Co{sub 2}O{sub 9} layered cobalt oxides

    SciTech Connect

    Tsukada, I.; Yamamoto, T.; Takagi, M.; Tsubone, T.; Uchinokura, K.

    1998-12-31

    Transport and magnetic properties of layered cobalt oxide (BiPb){sub 2}Sr{sub 3}Co{sub 2}O{sub 9} are investigated in detail under magnetic field up to 8 T. Parent compound, Bi{sub 2}Sr{sub 3}Co{sub 2}O{sub 9}, is a typical band insulator with Co ions being in a low-spin 3+ state because of the well-separated d{epsilon} and d{gamma} levels possibly due to a strong crystal field. The authors have tried to introduce holes mainly by Pb substitution for Bi. The hole-doped sample shows metallic behavior in a resistivity measurement between 300 and 30 K. Below 30 K, however, the resistivity increases. Under the magnetic field the resistivity is strongly suppressed in this region. The authors observed more than 30% resistivity drop at 2 K under H = 8 T, which is comparable to insulating (La,Sr)CoO{sub 3} system. They discuss the mechanism of hole doping and the origin of negative magnetoresistance with transport and magnetic properties, and point out that the conventional double-exchange mechanism cannot be applied to this system. This means that some new mechanism is necessary to explain this phenomenon.

  3. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  4. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  5. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  6. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  7. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  8. [Lead adsorption and arsenite oxidation by cobalt doped birnessite].

    PubMed

    Yin, Hui; Feng, Xiong-Han; Qiu, Guo-Hong; Tan, Wen-Feng; Liu, Fan

    2011-07-01

    In order to study the effects of transition metal ions on the physic-chemical properties of manganese dioxides as environmental friendly materials, three-dimensional nano-microsphere cobalt-doped birnessite was synthesized by reduction of potassium permanganate by mixtures of concentrated hydrochloride and cobalt (II) chloride. Powder X-ray diffraction, chemical analysis, N2 physical adsorption, field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectra (XPS) were used to characterize the crystal structure, chemical composition and micro-morphologies of products. In the range of molar ratios from 0.05 to 0.20, birnessite was fabricated exclusively. It was observed that cobalt incorporated into the layers of birnessite and had little effect on the crystal structure and micromorpholgy, but crystallinity decreased after cobalt doping. Both chemical analysis and XPS results showed that manganese average oxidation state decreased after cobalt doping, and the percentage of Mn3+ increased. Co(III) OOH existed mainly in the structure. With the increase of cobalt, hydroxide oxygen percentage in molar increased from 12.79% for undoped birnessite to 13.05%, 17.69% and 17.79% for doped samples respectively. Adsorption capacity for lead and oxidation of arsenite of birnessite were enhanced by cobalt doping. The maximum capacity of Pb2+ adsorption increased in the order HB (2 538 mmol/kg) < CoB5 (2798 mmol/kg) < CoB10 (2932 mmol/kg) < CoB20 (3 146 mmol/kg). Oxidation percentage of arsenite in simulated waste water by undoped birnessite was 76.5%, those of doped ones increased by 2.0%, 12.8% and 18.9% respectively. Partial of Co3+ substitution for Mn4+ results in the increase of negative charge of the layer and the content of hydroxyl group, which could account for the improved adsorption capacity of Pb2+. After substitution of manganese by cobalt, oxidation capacity of arsenite by birnessite increases likely due to the higher standard redox potential of

  9. Cobalt based layered perovskites as cathode material for intermediate temperature Solid Oxide Fuel Cells: A brief review

    NASA Astrophysics Data System (ADS)

    Pelosato, Renato; Cordaro, Giulio; Stucchi, Davide; Cristiani, Cinzia; Dotelli, Giovanni

    2015-12-01

    Nowadays, the cathode is the most studied component in Intermediate Temperature-Solid Oxide Fuel Cells (IT-SOFCs). Decreasing SOFCs operating temperature implies slow oxygen reduction kinetics and large polarization losses. Double perovskites with general formula REBaCo2O5+δ are promising mixed ionic-electronic conductors, offering a remarkable enhancement of the oxygen diffusivity and surface exchange respect to disordered perovskites. In this review, more than 250 compositions investigated in the literature were analyzed. The evaluation was performed in terms of electrical conductivity, Area Specific Resistance (ASR), chemical compatibility with electrolytes and Thermal Expansion Coefficient (TEC). The most promising materials have been identified as those bearing the mid-sized rare earths (Pr, Nd, Sm, Gd). Doping strategies have been analyzed: Sr doping on A site promotes higher electrical conductivity, but worsen ASR and TECs; B-site doping (Fe, Ni, Mn) helps lowering TECs, but is detrimental for the electrochemical properties. A promising boost of the electrochemical activity is obtained by simply introducing a slight Ba under-stoichiometry. Still, the high sensitivity of the electrochemical properties against slight changes in the stoichiometry hamper a conclusive comparison of all the investigated compounds. Opportunities for an improvement of double perovskite cathodes performance is tentatively foreseen in combining together the diverse effective doping strategies.

  10. Triethylborate as an electrolyte additive for high voltage layered lithium nickel cobalt manganese oxide cathode of lithium ion battery

    NASA Astrophysics Data System (ADS)

    Wang, Zaisheng; Xing, Lidan; Li, JianHui; Xu, Mengqing; Li, Weishan

    2016-03-01

    Triethylborate (TEB) is used as an electrolyte additive to improve the electrochemical performances of LiNi1/3Co1/3Mn1/3O2 (LNCM) upon cycling at 4.5 V vs. Li/Li+. Charge/discharge tests demonstrate that the cyclic stability of LNCM at room and elevated temperature can be improved effectively by TEB. With addition of 10 wt. % TEB into STD electrolyte (1.0 M LiPF6/EC:EMC:DEC), LNCM achieves a capacity retention of 99.8% after 150 cycles and 94.7% after 120 cycles at room and elevated temperature, respectively, comparing to that of 68.9% and 68.8% of STD electrolyte. In addition, 10 wt. % TEB also improves the rate capability of LNCM at room temperature. Physical and electrochemical characterizations from XRD, SEM, TEM, XPS, ICP-MS, LSV, CA, and EIS reveal that the preferential oxidative reaction of TEB generates a thin, uniform and low interfacial resistance film on the LNCM surface. This film not only suppresses the subsequent decomposition of STD electrolyte, but also prevents the dissolution of transition metal ions from LNCM, resulting in improved cyclic stability and rate capability of LNCM.

  11. Synthesis of three-dimensional reduced graphene oxide layer supported cobalt nanocrystals and their high catalytic activity in F-T CO2 hydrogenation.

    PubMed

    He, Fei; Niu, Na; Qu, Fengyu; Wei, Shuquan; Chen, Yujin; Gai, Shili; Gao, Peng; Wang, Yan; Yang, Piaoping

    2013-09-21

    The reduced graphene oxide (rGO) supported cobalt nanocrystals have been synthesized through an in situ crystal growth method using Co(acac)2 under solvothermal conditions by using DMF as the solvent. By carefully controlling the reaction temperature, the phase transition of the cobalt nanocrystals from the cubic phase to the hexagonal phase has been achieved. Moreover, the microscopic structure and morphology as well as the reduction process of the composite have been investigated in detail. It is found that oxygen-containing functional groups on the graphene oxide (GO) can greatly influence the formation process of the Co nanocrystals by binding the Co(2+) cations dissociated from the Co(acac)2 in the initial reaction solution at 220 °C, leading to the 3D reticular structure of the composite. Furthermore, this is the first attempt to use a Co/rGO composite as the catalyst in the F-T CO2 hydrogenation process. The catalysis testing results reveal that the as-synthesized 3D structured composite exhibits ideal catalytic activity and good stability, which may greatly extend the scope of applications for this kind of graphene-based metal hybrid material. PMID:23892431

  12. In situ formation of cobalt oxide nanocubanes as efficient oxygen evolution catalysts.

    PubMed

    Hutchings, Gregory S; Zhang, Yan; Li, Jian; Yonemoto, Bryan T; Zhou, Xinggui; Zhu, Kake; Jiao, Feng

    2015-04-01

    Oxygen evolution from water poses a significant challenge in solar fuel production because it requires an efficient catalyst to bridge the one-electron photon capture process with the four-electron oxygen evolution reaction (OER). Here, a new strategy was developed to synthesize nonsupported ultrasmall cobalt oxide nanocubanes through an in situ phase transformation mechanism using a layered Co(OH)(OCH3) precursor. Under sonication, the precursor was exfoliated and transformed into cobalt oxide nanocubanes in the presence of NaHCO3-Na2SiF6 buffer solution. The resulting cobalt catalyst with an average particle size less than 2 nm exhibited a turnover frequency of 0.023 per second per cobalt in photocatalytic water oxidation. X-ray absorption results suggested a unique nanocubane structure, where 13 cobalt atoms fully coordinated with oxygen in an octahedral arrangement to form 8 Co4O4 cubanes, which may be responsible for the exceptionally high OER activity.

  13. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Cobalt lithium manganese nickel oxide... Specific Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and... nickel oxide (PMN P-04-269; CAS No. 182442-95-1) is subject to reporting under this section for...

  14. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Cobalt lithium manganese nickel oxide... Specific Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and... nickel oxide (PMN P-04-269; CAS No. 182442-95-1) is subject to reporting under this section for...

  15. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Cobalt lithium manganese nickel oxide... Specific Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and... nickel oxide (PMN P-04-269; CAS No. 182442-95-1) is subject to reporting under this section for...

  16. Electrodeposited cobalt sulfide hole collecting layer for polymer solar cells

    SciTech Connect

    Zampetti, Andrea; De Rossi, Francesca; Brunetti, Francesca; Reale, Andrea; Di Carlo, Aldo; Brown, Thomas M.

    2014-08-11

    In polymer solar cells based on the blend of regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester, the hole collecting layer has to be endowed with its ionization potential close to or greater than that of P3HT (∼5 eV). Conductive polymer blends such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and metal oxides such as vanadium pentoxide (V{sub 2}O{sub 5}) and molybdenum trioxide (MoO{sub 3}) satisfy this requirement and have been the most common materials used so far in bulk heterojunction structures. We report here cobalt sulfide (CoS) to be a promising hole collecting material deposited by convenient and room temperature electrodeposition. By simply tuning the CoS electrodeposition parameters, power conversion efficiencies similar (within 15%) to a reference structure with PEDOT:PSS were obtained.

  17. Cobalt-based nanocatalysts for green oxidation and hydrogenation processes.

    PubMed

    Jagadeesh, Rajenahally V; Stemmler, Tobias; Surkus, Annette-Enrica; Bauer, Matthias; Pohl, Marga-Martina; Radnik, Jörg; Junge, Kathrin; Junge, Henrik; Brückner, Angelika; Beller, Matthias

    2015-06-01

    This protocol describes the preparation of cobalt-based nanocatalysts and their applications in environmentally benign redox processes for fine chemical synthesis. The catalytically active material consists of nanoscale Co3O4 particles surrounded by nitrogen-doped graphene layers (NGrs), which have been prepared by pyrolysis of phenanthroline-ligated cobalt acetate on carbon. The resulting materials have been found to be excellent catalysts for the activation of both molecular oxygen and hydrogen; in all tested reactions, water was the only by-product. By applying these catalysts, green oxidations of alcohols and hydrogenation of nitroarenes for the synthesis of nitriles, esters and amines are demonstrated. The overall time required for catalyst preparation and for redox reactions is 35 h and 10-30 h, respectively.

  18. Nitrogen oxides storage catalysts containing cobalt

    DOEpatents

    Lauterbach, Jochen; Snively, Christopher M.; Vijay, Rohit; Hendershot, Reed; Feist, Ben

    2010-10-12

    Nitrogen oxides (NO.sub.x) storage catalysts comprising cobalt and barium with a lean NO.sub.x storage ratio of 1.3 or greater. The NO.sub.x storage catalysts can be used to reduce NO.sub.x emissions from diesel or gas combustion engines by contacting the catalysts with the exhaust gas from the engines. The NO.sub.x storage catalysts can be one of the active components of a catalytic converter, which is used to treat exhaust gas from such engines.

  19. Preliminary study of a solar selective coating system using black cobalt oxide for high temperature solar collectors

    NASA Technical Reports Server (NTRS)

    Mcdonald, G.

    1980-01-01

    Black cobalt oxide coatings (high solar absorptance layer) were deposited on thin layers of silver or gold (low emittance layer) which had been previously deposited on oxidized (diffusion barrier layer) stainless steel substrates. The reflectance properties of these coatings were measured at various thicknesses of cobalt for integrated values of the solar and infrared spectrum. The values of absorptance and emittance were calculated from the measured reflectance values, before and after exposure in air at 650 C for approximately 1000 hours. Absorptance and emittance were interdependent functions of the weight of cobalt oxide. Also, these cobalt oxide/noble metal/oxide diffusion barrier coatings have absorptances greater than 0.90 and emittances of approximately 0.20 even after about 1000 hours at 650 C.

  20. When Layered Nickel-Cobalt Silicate Hydroxide Nanosheets Meet Carbon Nanotubes: A Synergetic Coaxial Nanocable Structure for Enhanced Electrocatalytic Water Oxidation.

    PubMed

    Qiu, Ce; Jiang, Jing; Ai, Lunhong

    2016-01-13

    Developing robust earth-abundant electrocatalysts for oxygen evolution reaction (OER) is an ongoing scientific challenge, which is coupled with a number of important electrochemical processes and many key renewable energy systems, such as water splitting, rechargeable metal-air batteries, and regenerative fuel cells. Here, we proposed a rational design and fabrication of the synergetic coaxial nanocable structures by intimate growth of the layered nickel-cobalt silicate hydroxide nanosheets on the outer surfaces of multiwalled carbon nanotubes (MWCNTs@NCS) and demonstrated their high efficiency in electrocatalytic OER from water splitting. The electrocatalytic activities of the MWCNTs@NCS were found to be significantly higher than that of bare NCS and pristine MWCNTs, synergetically determining by such the constituted individual components. Among them, the MWCNTs@NCS-2 exhibited best electrocatalytic OER performance, showing a small OER onset potential, large anodic current and long-term durability, which was favorably comparable to the previously reported NiCo-based OER electrocatalysts in alkaline electrolytes. To the best of our knowledge, this was a first example on the earth-abundant metal silicate hydroxides utilized in electrochemical water splitting. PMID:26671308

  1. Preliminary study of a solar selective coating system using black cobalt oxide for high temperature solar collectors

    NASA Technical Reports Server (NTRS)

    Mcdonald, G.

    1980-01-01

    Black cobalt oxide coatings were deposited on thin layers of silver or gold which had been deposited on oxidized stainless steel substrates. The reflectance properties of these coatings were measured at various thicknesses of cobalt oxide for integrated values of the solar and infrared spectrum. The values of absorptance and emittance were calculated from the measured reflectance values before and after exposure in air at 650 C for 1000 hours. Also, these cobalt oxide/noble metal/oxide diffusion barrier coatings have absorptances greater than 0.90 and emittances of approximately 0.20 even after about 1000 hours at 650 C.

  2. Cobalt oxide silica membranes for desalination.

    PubMed

    Lin, Chun Xiang C; Ding, Li Ping; Smart, Simon; da Costa, João C Diniz

    2012-02-15

    This work shows for the first time the potential of cobalt oxide silica (CoO(x)Si) membranes for desalination of brackish (1 wt.% NaCl), seawater (3.5 wt.% NaCl) and brine (7.5-15 wt.% NaCl) concentrations at feed temperatures between 25 and 75 °C. CoO(x)Si xerogels were synthesised via a sol-gel method including TEOS, cobalt nitrate hydrate and peroxide. Initial hydrothermal exposure (<2 days) of xerogels prepared with various pH (3-6) resulted in densification of the xerogel via condensation reactions within the silica matrix, with the xerogel synthesised at pH 5 the most resistant. Subsequent exposure was not found to significantly alter the pore structure of the xerogels, suggesting they were hydrostable and that the pore sizes remained at molecular sieving dimensions. Membranes were then synthesised using identical sol-gel conditions to the xerogel samples and testing showed that elevated feed temperatures resulted in increased water fluxes, whilst increasing the saline feed concentration resulted in decreased water fluxes. The maximum flux observed was 1.8 kg m(-2) h(-1) at 75 °C for a 1 wt.% NaCl feed concentration. The salt rejection was consistently in excess of 99%, independent of either the testing temperature or salt feed concentration.

  3. Electrosynthesis of highly transparent cobalt oxide water oxidation catalyst films from cobalt aminopolycarboxylate complexes.

    PubMed

    Bonke, Shannon A; Wiechen, Mathias; Hocking, Rosalie K; Fang, Xi-Ya; Lupton, David W; MacFarlane, Douglas R; Spiccia, Leone

    2015-04-24

    Efficient catalysis of water oxidation represents one of the major challenges en route to efficient sunlight-driven water splitting. Cobalt oxides (CoOx ) have been widely investigated as water oxidation catalysts, although the incorporation of these materials into photoelectrochemical devices has been hindered by a lack of transparency. Herein, the electrosynthesis of transparent CoOx catalyst films is described by utilizing cobalt(II) aminopolycarboxylate complexes as precursors to the oxide. These complexes allow control over the deposition rate and morphology to enable the production of thin, catalytic CoOx films on a conductive substrate, which can be exploited in integrated photoelectrochemical devices. Notably, under a bias of 1.0 V (vs. Ag/AgCl), the film deposited from [Co(NTA)(OH2 )2 ](-) (NTA=nitrilotriacetate) decreased the transmission by only 10 % at λ=500 nm, but still generated >80 % of the water oxidation current produced by a [Co(OH2 )6 ](2+) -derived oxide film whose transmission was only 40 % at λ=500 nm.

  4. Electrosynthesis of highly transparent cobalt oxide water oxidation catalyst films from cobalt aminopolycarboxylate complexes.

    PubMed

    Bonke, Shannon A; Wiechen, Mathias; Hocking, Rosalie K; Fang, Xi-Ya; Lupton, David W; MacFarlane, Douglas R; Spiccia, Leone

    2015-04-24

    Efficient catalysis of water oxidation represents one of the major challenges en route to efficient sunlight-driven water splitting. Cobalt oxides (CoOx ) have been widely investigated as water oxidation catalysts, although the incorporation of these materials into photoelectrochemical devices has been hindered by a lack of transparency. Herein, the electrosynthesis of transparent CoOx catalyst films is described by utilizing cobalt(II) aminopolycarboxylate complexes as precursors to the oxide. These complexes allow control over the deposition rate and morphology to enable the production of thin, catalytic CoOx films on a conductive substrate, which can be exploited in integrated photoelectrochemical devices. Notably, under a bias of 1.0 V (vs. Ag/AgCl), the film deposited from [Co(NTA)(OH2 )2 ](-) (NTA=nitrilotriacetate) decreased the transmission by only 10 % at λ=500 nm, but still generated >80 % of the water oxidation current produced by a [Co(OH2 )6 ](2+) -derived oxide film whose transmission was only 40 % at λ=500 nm. PMID:25826458

  5. Selective Area Band Engineering of Graphene using Cobalt-Mediated Oxidation.

    PubMed

    Bazylewski, Paul F; Nguyen, Van Luan; Bauer, Robert P C; Hunt, Adrian H; McDermott, Eamon J G; Leedahl, Brett D; Kukharenko, Andrey I; Cholakh, Seif O; Kurmaev, Ernst Z; Blaha, Peter; Moewes, Alexander; Lee, Young Hee; Chang, Gap Soo

    2015-01-01

    This study reports a scalable and economical method to open a band gap in single layer graphene by deposition of cobalt metal on its surface using physical vapor deposition in high vacuum. At low cobalt thickness, clusters form at impurity sites on the graphene without etching or damaging the graphene. When exposed to oxygen at room temperature, oxygen functional groups form in proportion to the cobalt thickness that modify the graphene band structure. Cobalt/Graphene resulting from this treatment can support a band gap of 0.30 eV, while remaining largely undamaged to preserve its structural and electrical properties. A mechanism of cobalt-mediated band opening is proposed as a two-step process starting with charge transfer from metal to graphene, followed by formation of oxides where cobalt has been deposited. Contributions from the formation of both CoO and oxygen functional groups on graphene affect the electronic structure to open a band gap. This study demonstrates that cobalt-mediated oxidation is a viable method to introduce a band gap into graphene at room temperature that could be applicable in electronics applications. PMID:26486966

  6. Selective Area Band Engineering of Graphene using Cobalt-Mediated Oxidation

    PubMed Central

    Bazylewski, Paul F.; Nguyen, Van Luan; Bauer, Robert P.C.; Hunt, Adrian H.; McDermott, Eamon J. G.; Leedahl, Brett D.; Kukharenko, Andrey I.; Cholakh, Seif O.; Kurmaev, Ernst Z.; Blaha, Peter; Moewes, Alexander; Lee, Young Hee; Chang, Gap Soo

    2015-01-01

    This study reports a scalable and economical method to open a band gap in single layer graphene by deposition of cobalt metal on its surface using physical vapor deposition in high vacuum. At low cobalt thickness, clusters form at impurity sites on the graphene without etching or damaging the graphene. When exposed to oxygen at room temperature, oxygen functional groups form in proportion to the cobalt thickness that modify the graphene band structure. Cobalt/Graphene resulting from this treatment can support a band gap of 0.30 eV, while remaining largely undamaged to preserve its structural and electrical properties. A mechanism of cobalt-mediated band opening is proposed as a two-step process starting with charge transfer from metal to graphene, followed by formation of oxides where cobalt has been deposited. Contributions from the formation of both CoO and oxygen functional groups on graphene affect the electronic structure to open a band gap. This study demonstrates that cobalt-mediated oxidation is a viable method to introduce a band gap into graphene at room temperature that could be applicable in electronics applications. PMID:26486966

  7. Selective Area Band Engineering of Graphene using Cobalt-Mediated Oxidation.

    PubMed

    Bazylewski, Paul F; Nguyen, Van Luan; Bauer, Robert P C; Hunt, Adrian H; McDermott, Eamon J G; Leedahl, Brett D; Kukharenko, Andrey I; Cholakh, Seif O; Kurmaev, Ernst Z; Blaha, Peter; Moewes, Alexander; Lee, Young Hee; Chang, Gap Soo

    2015-10-21

    This study reports a scalable and economical method to open a band gap in single layer graphene by deposition of cobalt metal on its surface using physical vapor deposition in high vacuum. At low cobalt thickness, clusters form at impurity sites on the graphene without etching or damaging the graphene. When exposed to oxygen at room temperature, oxygen functional groups form in proportion to the cobalt thickness that modify the graphene band structure. Cobalt/Graphene resulting from this treatment can support a band gap of 0.30 eV, while remaining largely undamaged to preserve its structural and electrical properties. A mechanism of cobalt-mediated band opening is proposed as a two-step process starting with charge transfer from metal to graphene, followed by formation of oxides where cobalt has been deposited. Contributions from the formation of both CoO and oxygen functional groups on graphene affect the electronic structure to open a band gap. This study demonstrates that cobalt-mediated oxidation is a viable method to introduce a band gap into graphene at room temperature that could be applicable in electronics applications.

  8. Selective Area Band Engineering of Graphene using Cobalt-Mediated Oxidation

    NASA Astrophysics Data System (ADS)

    Bazylewski, Paul F.; Nguyen, Van Luan; Bauer, Robert P. C.; Hunt, Adrian H.; McDermott, Eamon J. G.; Leedahl, Brett D.; Kukharenko, Andrey I.; Cholakh, Seif O.; Kurmaev, Ernst Z.; Blaha, Peter; Moewes, Alexander; Lee, Young Hee; Chang, Gap Soo

    2015-10-01

    This study reports a scalable and economical method to open a band gap in single layer graphene by deposition of cobalt metal on its surface using physical vapor deposition in high vacuum. At low cobalt thickness, clusters form at impurity sites on the graphene without etching or damaging the graphene. When exposed to oxygen at room temperature, oxygen functional groups form in proportion to the cobalt thickness that modify the graphene band structure. Cobalt/Graphene resulting from this treatment can support a band gap of 0.30 eV, while remaining largely undamaged to preserve its structural and electrical properties. A mechanism of cobalt-mediated band opening is proposed as a two-step process starting with charge transfer from metal to graphene, followed by formation of oxides where cobalt has been deposited. Contributions from the formation of both CoO and oxygen functional groups on graphene affect the electronic structure to open a band gap. This study demonstrates that cobalt-mediated oxidation is a viable method to introduce a band gap into graphene at room temperature that could be applicable in electronics applications.

  9. Cobalt Oxide Hollow Nanoparticles Derived by Bio-Templating

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Woo; Choi, Sang H.; Lillehei, Peter T.; Chu, Sang-Hyon; King, Glen C.; Watt, Gerald D.

    2005-01-01

    We present here the first fabrication of hollow cobalt oxide nanoparticles produced by a protein-regulated site-specific reconstitution process in aqueous solution and describe the metal growth mechanism in the ferritin interior.

  10. Annealing effects on microstrain of cobalt oxide nanoparticles

    SciTech Connect

    Deotale, Anjali Jain Nandedkar, R. V.; Sinha, A. K.; Singh, M. N.; Upadhyay, Anuj

    2014-04-24

    Cobalt oxide nanoparticles in different phases have been synthesized using ash supported method. The effect of isochronal annealing on micro-strain of cobalt oxide nanoparticles has been studied. The lattice strain contribution to the x-ray diffraction line broadening in the nanoparticles was analyzed using Williamson Hall (W-H) plot. It is observed that micro-strain was released at higher annealing temperature.

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

    NASA Astrophysics Data System (ADS)

    Harthøj, Anders; Holt, Tobias; Møller, Per

    2015-05-01

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

  12. Ca-for-Sr substitution in the thermoelectric [(Sr,Ca){sub 2}(O,OH){sub 2}]{sub q}[CoO{sub 2}] misfit-layered cobalt-oxide system

    SciTech Connect

    Yamauchi, Hisao; Karvonen, Lassi; Egashira, Takayuki; Tanaka, Yoshiaki; Karppinen, Maarit

    2011-01-15

    Calcium-for-strontium substituted samples of the misfit-layered cobalt-oxide system, [(Sr{sub 1-x}Ca{sub x}){sub 2}(O,OH){sub 2}]{sub q}[CoO{sub 2}], were successfully synthesized up to x=0.2 with a sample-encapsulation technique originally developed for the x=0 end phase. While the x=0 sample has a commensurate match between the two layer blocks (i.e. q=0.5), isovalent Ca-for-Sr substitution induces lattice misfit (i.e. q>0.5). At the same time the Seebeck coefficient gets increased, but the increase in resistivity results in suppressing the thermoelectric power factor. The magnetic anomaly in the x=0 sample gets released upon the Ca substitution for the x=0.2 sample to exhibit an almost Curie-Weiss behavior. It is concluded that with increasing x in [(Sr{sub 1-x}Ca{sub x}){sub 2}(O,OH){sub 2}]{sub q}[CoO{sub 2}] the properties smoothly evolve towards those previously reported for the x=1.0 end member, [Ca{sub 1.7}O{sub 2.1}H{sub 2.4}]{sub 0.58}[CoO{sub 2}]. -- Graphical abstract: In the misfit-layered [(Sr{sub 1-x}Ca{sub x}){sub 2}(O,OH){sub 2}]{sub q}[CoO{sub 2}] (0.0{<=}x{<=}0.2) system the x=0 phase has a commensurate match between the two layer blocks (i.e. q=0.5), while isovalent Ca-for-Sr substitution induces lattice misfit (i.e. q>0.5). At the same time Seebeck coefficient gets increased. Simultaneous increase in resistivity however outweighs this benefit, and accordingly the thermoelectric power factor is decreased. Display Omitted

  13. Coordination tuning of cobalt phosphates towards efficient water oxidation catalyst

    PubMed Central

    Kim, Hyunah; Park, Jimin; Park, Inchul; Jin, Kyoungsuk; Jerng, Sung Eun; Kim, Sun Hee; Nam, Ki Tae; Kang, Kisuk

    2015-01-01

    The development of efficient and stable water oxidation catalysts is necessary for the realization of practically viable water-splitting systems. Although extensive studies have focused on the metal-oxide catalysts, the effect of metal coordination on the catalytic ability remains still elusive. Here we select four cobalt-based phosphate catalysts with various cobalt- and phosphate-group coordination as a platform to better understand the catalytic activity of cobalt-based materials. Although they exhibit various catalytic activities and stabilities during water oxidation, Na2CoP2O7 with distorted cobalt tetrahedral geometry shows high activity comparable to that of amorphous cobalt phosphate under neutral conditions, along with high structural stability. First-principles calculations suggest that the surface reorganization by the pyrophosphate ligand induces a highly distorted tetrahedral geometry, where water molecules can favourably bind, resulting in a low overpotential (∼0.42 eV). Our findings emphasize the importance of local cobalt coordination in the catalysis and suggest the possible effect of polyanions on the water oxidation chemistry. PMID:26365091

  14. Coordination tuning of cobalt phosphates towards efficient water oxidation catalyst

    NASA Astrophysics Data System (ADS)

    Kim, Hyunah; Park, Jimin; Park, Inchul; Jin, Kyoungsuk; Jerng, Sung Eun; Kim, Sun Hee; Nam, Ki Tae; Kang, Kisuk

    2015-09-01

    The development of efficient and stable water oxidation catalysts is necessary for the realization of practically viable water-splitting systems. Although extensive studies have focused on the metal-oxide catalysts, the effect of metal coordination on the catalytic ability remains still elusive. Here we select four cobalt-based phosphate catalysts with various cobalt- and phosphate-group coordination as a platform to better understand the catalytic activity of cobalt-based materials. Although they exhibit various catalytic activities and stabilities during water oxidation, Na2CoP2O7 with distorted cobalt tetrahedral geometry shows high activity comparable to that of amorphous cobalt phosphate under neutral conditions, along with high structural stability. First-principles calculations suggest that the surface reorganization by the pyrophosphate ligand induces a highly distorted tetrahedral geometry, where water molecules can favourably bind, resulting in a low overpotential (~0.42 eV). Our findings emphasize the importance of local cobalt coordination in the catalysis and suggest the possible effect of polyanions on the water oxidation chemistry.

  15. Coordination tuning of cobalt phosphates towards efficient water oxidation catalyst.

    PubMed

    Kim, Hyunah; Park, Jimin; Park, Inchul; Jin, Kyoungsuk; Jerng, Sung Eun; Kim, Sun Hee; Nam, Ki Tae; Kang, Kisuk

    2015-01-01

    The development of efficient and stable water oxidation catalysts is necessary for the realization of practically viable water-splitting systems. Although extensive studies have focused on the metal-oxide catalysts, the effect of metal coordination on the catalytic ability remains still elusive. Here we select four cobalt-based phosphate catalysts with various cobalt- and phosphate-group coordination as a platform to better understand the catalytic activity of cobalt-based materials. Although they exhibit various catalytic activities and stabilities during water oxidation, Na2CoP2O7 with distorted cobalt tetrahedral geometry shows high activity comparable to that of amorphous cobalt phosphate under neutral conditions, along with high structural stability. First-principles calculations suggest that the surface reorganization by the pyrophosphate ligand induces a highly distorted tetrahedral geometry, where water molecules can favourably bind, resulting in a low overpotential (∼0.42 eV). Our findings emphasize the importance of local cobalt coordination in the catalysis and suggest the possible effect of polyanions on the water oxidation chemistry. PMID:26365091

  16. High-performance hybrid oxide catalyst of manganese and cobalt for low-pressure methanol synthesis

    NASA Astrophysics Data System (ADS)

    Li, Cheng-Shiuan; Melaet, Gérôme; Ralston, Walter T.; An, Kwangjin; Brooks, Christopher; Ye, Yifan; Liu, Yi-Sheng; Zhu, Junfa; Guo, Jinghua; Alayoglu, Selim; Somorjai, Gabor A.

    2015-03-01

    Carbon dioxide capture and use as a carbon feedstock presents both environmental and industrial benefits. Here we report the discovery of a hybrid oxide catalyst comprising manganese oxide nanoparticles supported on mesoporous spinel cobalt oxide, which catalyses the conversion of carbon dioxide to methanol at high yields. In addition, carbon-carbon bond formation is observed through the production of ethylene. We document the existence of an active interface between cobalt oxide surface layers and manganese oxide nanoparticles by using X-ray absorption spectroscopy and electron energy-loss spectroscopy in the scanning transmission electron microscopy mode. Through control experiments, we find that the catalyst’s chemical nature and architecture are the key factors in enabling the enhanced methanol synthesis and ethylene production. To demonstrate the industrial applicability, the catalyst is also run under high conversion regimes, showing its potential as a substitute for current methanol synthesis technologies.

  17. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for...

  18. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for...

  19. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for...

  20. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for...

  1. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for...

  2. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  3. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  4. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  5. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  6. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  7. 40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Cobalt iron manganese oxide... Significant New Uses for Specific Chemical Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid... substance identified generically as cobalt iron manganese oxide, carboxylic acid-modified (PMN P-12-35)...

  8. 40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Cobalt iron manganese oxide... Significant New Uses for Specific Chemical Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid... substance identified generically as cobalt iron manganese oxide, carboxylic acid-modified (PMN P-12-35)...

  9. Synthesis of cobalt oxide nanoparticles via homogeneous precipitation using different synthetic conditions.

    PubMed

    Kishore, P N R; Jeevanandam, P

    2013-04-01

    Cobalt oxide nanoparticles have been prepared via homogeneous precipitation using different synthetic conditions. The effect of using cobalt salts with different anions (nitrate, acetate, chloride and sulphate) and concentrations on the final products has been investigated. The precursors to the cobalt oxide nanoparticles, obtained by the homogeneous precipitation, were found to be alpha-cobalt hydroxides with different stoichiometries. Pink and blue coloured alpha-cobalt hydroxides were obtained depending on the anion and concentration of the cobalt salt used. Co3O4 nanoparticles were obtained by thermal decomposition of the cobalt hydroxides in air at 350 degrees C. The precursors and the cobalt oxide nanoparticles were characterized by a variety of analytical techniques and magnetic properties of the different cobalt oxide nanoparticles have also been investigated.

  10. Fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing

    DOEpatents

    Bates, John B.

    2003-04-29

    Systems and methods are described for fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing. A method of forming a lithium cobalt oxide film includes depositing a film of lithium cobalt oxide on a substrate; rapidly heating the film of lithium cobalt oxide to a target temperature; and maintaining the film of lithium cobalt oxide at the target temperature for a target annealing time of at most, approximately 60 minutes. The systems and methods provide advantages because they require less time to implement and are, therefore less costly than previous techniques.

  11. Fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing

    DOEpatents

    Bates, John B.

    2002-01-01

    Systems and methods are described for fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing. A method of forming a lithium cobalt oxide film includes depositing a film of lithium cobalt oxide on a substrate; rapidly heating the film of lithium cobalt oxide to a target temperature; and maintaining the film of lithium cobalt oxide at the target temperature for a target annealing time of at most, approximately 60 minutes. The systems and methods provide advantages because they require less time to implement and are, therefore less costly than previous techniques.

  12. Fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing

    DOEpatents

    Bates, John B.

    2003-05-13

    Systems and methods are described for fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing. A method of forming a lithium cobalt oxide film includes depositing a film of lithium cobalt oxide on a substrate; rapidly heating the film of lithium cobalt oxide to a target temperature; and maintaining the film of lithium cobalt oxide at the target temperature for a target annealing time of at most, approximately 60 minutes. The systems and methods provide advantages because they require less time to implement and are, therefore less costly than previous techniques.

  13. Cobalt on rhenium(0001) an example of thermally activated layer intermixing and surface alloying

    NASA Astrophysics Data System (ADS)

    Parschau, M.; Christmann, K.

    1999-03-01

    The growth and morphology of cobalt thin films deposited onto a Re(0001) surface at 300, 400 and 550 K were followed in the coverage range 0 ML< Θ<6 ML by combined low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The interaction phenomena are complex and depend strongly on temperature. At 300 K, cobalt nucleates homogeneously on terraces and heterogeneously at steps forming dendritic islands. Larger cobalt coverages lead to incomplete layer growth. Interdiffusion and alloying play a minor role only at 300 K, but become dominant for T>400 K in that different (2×2) phases form within the first Re-Co bilayer, one within the rhenium substrate surface, the others within the cobalt islands. The (2×2) phases can be associated with Re/Co surface alloys of different stoichiometry, depending on cobalt coverage. As the cobalt coverages exceed two monolayers (ML), genuine but incomplete cobalt layers grow. Within the third and fourth cobalt layer, periodic triangular features with a lattice constant of ~28 Å appear in STM, followed by a Moiré pattern for Θ>4 ML. Both structures produce an incomplete (10×10) LEED pattern. After growth of the fifth or sixth layer the lattice misfit is overcome, and cobalt essentially grows layer-by-layer in a pseudo Frank-van der Merwe mechanism, the details being strongly temperature-dependent.

  14. Cobalt.

    PubMed

    Fowler, Joseph F

    2016-01-01

    Cobalt has been a recognized allergen capable of causing contact dermatitis for decades. Why, therefore, has it been named 2016 "Allergen of the Year"? Simply put, new information has come to light in the last few years regarding potential sources of exposure to this metallic substance. In addition to reviewing some background on our previous understanding of cobalt exposures, this article will highlight the recently recognized need to consider leather as a major site of cobalt and the visual cues suggesting the presence of cobalt in jewelry. In addition, a chemical spot test for cobalt now allows us to better identify its presence in suspect materials.

  15. 40 CFR 721.10600 - Calcium cobalt lead strontium titanium tungsten oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Calcium cobalt lead strontium titanium... Specific Chemical Substances § 721.10600 Calcium cobalt lead strontium titanium tungsten oxide. (a... calcium cobalt lead strontium titanium tungsten oxide (PMN P-11-272; CAS No. 1262279-30-0) is subject...

  16. 40 CFR 721.10600 - Calcium cobalt lead strontium titanium tungsten oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Calcium cobalt lead strontium titanium... Specific Chemical Substances § 721.10600 Calcium cobalt lead strontium titanium tungsten oxide. (a... calcium cobalt lead strontium titanium tungsten oxide (PMN P-11-272; CAS No. 1262279-30-0) is subject...

  17. 40 CFR 721.10599 - Calcium cobalt lead titanium tungsten oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Calcium cobalt lead titanium tungsten... Specific Chemical Substances § 721.10599 Calcium cobalt lead titanium tungsten oxide. (a) Chemical... cobalt lead titanium tungsten oxide (PMN P-11-271; CAS No. 1262279-31-1) is subject to reporting...

  18. 40 CFR 721.10599 - Calcium cobalt lead titanium tungsten oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Calcium cobalt lead titanium tungsten... Specific Chemical Substances § 721.10599 Calcium cobalt lead titanium tungsten oxide. (a) Chemical... cobalt lead titanium tungsten oxide (PMN P-11-271; CAS No. 1262279-31-1) is subject to reporting...

  19. Degradation of atrazine by cobalt-mediated activation of peroxymonosulfate: Different cobalt counteranions in homogenous process and cobalt oxide catalysts in photolytic heterogeneous process.

    PubMed

    Chan, K H; Chu, W

    2009-05-01

    The degradation of atrazine (ATZ) by cobalt-mediated activation of peroxymonosulfate (PMS) has been studied in this work. For the homogenous process, different cobalt counteranions: cobalt(II) nitrate Co(NO(3))(2), cobalt(II) sulfate CoSO(4), cobalt(II) chloride CoCl(2), and cobalt(II) acetate Co(CH(3)COO)(2), have been examined. The inhibitory effect was observed in the process initiated by CoCl(2). For the pH test, wide range of pH level (2-10) has been investigated. It was found that the higher rates were obtained in the normal pH levels. At extreme pH levels, the process was impeded by inactivation of PMS at acidic pH and prohibited by precipitation at basic pH. On the other hand, the recycling capability of cobalt oxide and the oxidative potential of cobalt-immobilized titanium dioxide Co-TiO(2) catalyst were analyzed in the heterogeneous process. It was found that the higher the cobalt content in the catalyst, the better the removal performance was resulted. At last, the Co-TiO(2) catalyst synthesized in this work was found to be very effective in transforming ATZ as well as its intermediate in the presence of UV-vis irradiation.

  20. Determination of the magnetic contribution to the heat capacity of cobalt oxide nanoparticles and the thermodynamic properties of the hydration layers.

    PubMed

    Spencer, E C; Ross, N L; Parker, S F; Woodfield, B F; Boerio-Goates, J; Smith, S J; Olsen, R E; Kolesnikov, A I; Navrotsky, A; Ma, C

    2011-05-25

    We present low temperature (11 K) inelastic neutron scattering (INS) data on four hydrated nanoparticle systems: 10 nm CoO·0.10H(2)O (1), 16 nm Co(3)O(4)·0.40H(2)O (2), 25 nm Co(3)O(4)·0.30H(2)O (3) and 40 nm Co(3)O(4)·0.026H(2)O (4). The vibrational densities of states were obtained for all samples and from these the isochoric heat capacity and vibrational energy for the hydration layers confined to the surfaces of these nanoparticle systems have been elucidated. The results show that water on the surface of CoO nanoparticles is more tightly bound than water confined to the surface of Co(3)O(4), and this is reflected in the reduced heat capacity and vibrational entropy for water on CoO relative to water on Co(3)O(4) nanoparticles. This supports the trend, seen previously, for water to be more tightly bound in materials with higher surface energies. The INS spectra for the antiferromagnetic Co(3)O(4) particles (2-4) also show sharp and intense magnetic excitation peaks at 5 meV, and from this the magnetic contribution to the heat capacity of Co(3)O(4) nanoparticles has been calculated; this represents the first example of use of INS data for determining the magnetic contribution to the heat capacity of any magnetic nanoparticle system.

  1. Determination of the magnetic contribution to the heat capacity of cobalt oxide nanoparticles and the thermodynamic properties of the hydration layers

    SciTech Connect

    Spencer, Elinor; Ross, Dr. Nancy; Parker, Stewart F.; Woodfield, Brian; Boerio-Goates, Juliana; Smith, S. J.; Olsen, R. E.; Kolesnikov, Alexander I; Navrotsky, Alexandra; Ma, C

    2011-01-01

    We present low temperature (11 K) inelastic neutron scattering (INS) data on four hydrated nanoparticle systems: 10 nm CoO 0.10H2O (1), 16 nmCo3O4 0.40H2O (2), 25 nm Co3O4 0.30H2O (3) and 40 nmCo3O4 0.026H2O (4). The vibrational densities of states were obtained for all samples and from these the isochoric heat capacity and vibrational energy for the hydration layers confined to the surfaces of these nanoparticle systems have been elucidated. The results show that water on the surface of CoO nanoparticles is more tightly bound than water confined to the surface of Co3O4, and this is reflected in the reduced heat capacity and vibrational entropy for water on CoO relative to water on Co3O4 nanoparticles. This supports the trend, seen previously, for water to be more tightly bound in materials with higher surface energies. The INS spectra for the antiferromagnetic Co3O4 particles (2 4) also show sharp and intense magnetic excitation peaks at 5 meV, and from this the magnetic contribution to the heat capacity of Co3O4 nanoparticles has been calculated; this represents the first example of use of INS data for determining the magnetic contribution to the heat capacity of any magnetic nanoparticle system.

  2. Formation of bile pigments by coupled oxidation of cobalt-substituted haemoglobin and myoglobin.

    PubMed Central

    Vernon, D I; Brown, S B

    1984-01-01

    Treatment of cobalt-substituted haemoglobin and myoglobin with ascorbate and molecular O2 (coupled oxidation) resulted in biliverdin formation from the cobalt(II) derivatives but not from the cobalt(III) derivatives. This was apparently due to the inability of ascorbate to reduce cobalt(III) haemoproteins. Isomer analysis of the biliverdins produced from coupled oxidation of cobalt(II) oxyhaemoglobin suggested that the orientation of the cobalt protoporphyrin IX in the haem pocket differed slightly from that of the haem in native haemoglobin. PMID:6497839

  3. Water-induced Formation of Cobalt Oxides Over Supported Cobalt/Ceria-Zirconia Catalysts under Ethanol-Steam Conditions

    SciTech Connect

    Lin, Sean S.-Y.; Kim, Do Heui; Engelhard, Mark H.; Ha, Su Y.

    2010-07-28

    The formation of water-induced cobalt oxides by re-oxidizing the metallic cobalt in the pre-reduced 10% Co/CeO2-ZrO2 catalyst was verified by in-situ TPR and in-situ XPS studies under various ethanol-steam conditions. The formation and transformation of water-induced cobalt oxide species were affected by the pre-reduction conditions used for the catalysts and the feed stream composition used in the reaction. This result suggests that the surface composition of the cobalt species in 10% Co-CZ catalyst, initially governed by the catalyst pre-treatment, was changed toward an equilibrium state that governed by the feed stream composition as the reaction proceeds. In addition, the reducibility of the ceria sites may play a significant role in the redox process involved both cobalt and ceria sites under ethanol-steam environment. Finally, the effect of the water-induced cobalt oxides on the catalytic performance, in particular for the carbon-carbon bond cleavage of ethanol, is negligible. However, these water-induced oxides may show importance for the subsequent reaction steps that determine the product selectivity during ethanol steam reforming, as their coexistence with the metallic cobalt species was revealed by the in-situ study under ethanol-steam conditions.

  4. Polymer - supported cobalt (II) catalysts for the oxidation of alkenes.

    PubMed

    Błaz, Edyta; Pielichowski, Jan

    2006-01-31

    Polymer-supported heterogeneous catalysts in a form of complexes of 8-hydroxy- quinoline with cobalt acetate were synthesized. Conjugated polymers - polyaniline (PANI), poly-o-toluidine (POT), poly-o-anisidine (POA) - were used as supports. Oxidation reactions of aliphatic and aromatic hydrocarbons were carried out in the presence of molecular oxygen at atmospheric pressure and epoxides or ketones were obtained as the main products with high selectivity.

  5. In situ oxidation of carbon-encapsulated cobalt nanocapsules creates highly active cobalt oxide catalysts for hydrocarbon combustion

    PubMed Central

    Wang, Han; Chen, Chunlin; Zhang, Yexin; Peng, Lixia; Ma, Song; Yang, Teng; Guo, Huaihong; Zhang, Zhidong; Su, Dang Sheng; Zhang, Jian

    2015-01-01

    Combustion catalysts have been extensively explored to reduce the emission of hydrocarbons that are capable of triggering photochemical smog and greenhouse effect. Palladium as the most active material is widely applied in exhaust catalytic converter and combustion units, but its high capital cost stimulates the tremendous research on non-noble metal candidates. Here we fabricate highly defective cobalt oxide nanocrystals via a controllable oxidation of carbon-encapsulated cobalt nanoparticles. Strain gradients induced in the nanoconfined carbon shell result in the formation of a large number of active sites featuring a considerable catalytic activity for the combustion of a variety of hydrocarbons (methane, propane and substituted benzenes). For methane combustion, the catalyst displays a unique activity being comparable or even superior to the palladium ones. PMID:26074206

  6. In situ oxidation of carbon-encapsulated cobalt nanocapsules creates highly active cobalt oxide catalysts for hydrocarbon combustion.

    PubMed

    Wang, Han; Chen, Chunlin; Zhang, Yexin; Peng, Lixia; Ma, Song; Yang, Teng; Guo, Huaihong; Zhang, Zhidong; Su, Dang Sheng; Zhang, Jian

    2015-01-01

    Combustion catalysts have been extensively explored to reduce the emission of hydrocarbons that are capable of triggering photochemical smog and greenhouse effect. Palladium as the most active material is widely applied in exhaust catalytic converter and combustion units, but its high capital cost stimulates the tremendous research on non-noble metal candidates. Here we fabricate highly defective cobalt oxide nanocrystals via a controllable oxidation of carbon-encapsulated cobalt nanoparticles. Strain gradients induced in the nanoconfined carbon shell result in the formation of a large number of active sites featuring a considerable catalytic activity for the combustion of a variety of hydrocarbons (methane, propane and substituted benzenes). For methane combustion, the catalyst displays a unique activity being comparable or even superior to the palladium ones.

  7. In situ oxidation of carbon-encapsulated cobalt nanocapsules creates highly active cobalt oxide catalysts for hydrocarbon combustion

    NASA Astrophysics Data System (ADS)

    Wang, Han; Chen, Chunlin; Zhang, Yexin; Peng, Lixia; Ma, Song; Yang, Teng; Guo, Huaihong; Zhang, Zhidong; Su, Dang Sheng; Zhang, Jian

    2015-06-01

    Combustion catalysts have been extensively explored to reduce the emission of hydrocarbons that are capable of triggering photochemical smog and greenhouse effect. Palladium as the most active material is widely applied in exhaust catalytic converter and combustion units, but its high capital cost stimulates the tremendous research on non-noble metal candidates. Here we fabricate highly defective cobalt oxide nanocrystals via a controllable oxidation of carbon-encapsulated cobalt nanoparticles. Strain gradients induced in the nanoconfined carbon shell result in the formation of a large number of active sites featuring a considerable catalytic activity for the combustion of a variety of hydrocarbons (methane, propane and substituted benzenes). For methane combustion, the catalyst displays a unique activity being comparable or even superior to the palladium ones.

  8. In situ oxidation of carbon-encapsulated cobalt nanocapsules creates highly active cobalt oxide catalysts for hydrocarbon combustion.

    PubMed

    Wang, Han; Chen, Chunlin; Zhang, Yexin; Peng, Lixia; Ma, Song; Yang, Teng; Guo, Huaihong; Zhang, Zhidong; Su, Dang Sheng; Zhang, Jian

    2015-01-01

    Combustion catalysts have been extensively explored to reduce the emission of hydrocarbons that are capable of triggering photochemical smog and greenhouse effect. Palladium as the most active material is widely applied in exhaust catalytic converter and combustion units, but its high capital cost stimulates the tremendous research on non-noble metal candidates. Here we fabricate highly defective cobalt oxide nanocrystals via a controllable oxidation of carbon-encapsulated cobalt nanoparticles. Strain gradients induced in the nanoconfined carbon shell result in the formation of a large number of active sites featuring a considerable catalytic activity for the combustion of a variety of hydrocarbons (methane, propane and substituted benzenes). For methane combustion, the catalyst displays a unique activity being comparable or even superior to the palladium ones. PMID:26074206

  9. Pro-oxidative interactions of cobalt with human neutrophils.

    PubMed

    Ramafi, Grace J; Theron, Annette J; Anderson, Ronald

    2004-08-01

    The primary objectives of this study were to investigate the effects of cobalt(II) chloride (Co, 1.5-25 microM) on the reactivity of hydrogen peroxide (H2O2, 100 microM) or oxidants generated by activated human neutrophils. The prooxidative interactions of Co with H2O2 or cells were measured by luminol-enhanced chemiluminescence (LECL), and according to the extent of oxidative inactivation of added alpha-1-proteinase inhibitor (API). Cobalt dramatically potentiated the oxidation of luminol and API by both H2O2 and neutrophils activated with phorbol 12-myristate 13-acetate (5 ng/ml), without affecting the assembly of NADPH oxidase or the magnitude of oxygen consumption by the cells. Using 5,5-dimethyl-pyrolline 1-oxide-based electron spin resonance spectroscopy we were unable to detect hydroxyl radical formation by Co in the presence of either H2O2 or activated neutrophils, while the corresponding LECL responses were unaffected by the hydroxyl radical scavengers benzoate and mannitol (50 mM). These observations indicate that Co potentiates the reactivity of neutrophil-derived oxidants, primarily H2O2, which if operative in vivo during exposure to the heavy metal may pose the risk of oxidant- and protease-mediated tissue injury.

  10. Buried oxide layer in silicon

    DOEpatents

    Sadana, Devendra Kumar; Holland, Orin Wayne

    2001-01-01

    A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

  11. 76 FR 47996 - Cobalt Lithium Manganese Nickel Oxide; Significant New Use Rule

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-08

    ... AGENCY 40 CFR Parts 9 and 721 RIN 2070-AB27 Cobalt Lithium Manganese Nickel Oxide; Significant New Use... chemical substance identified as cobalt lithium manganese nickel oxide (CAS No. 182442-95-1), which was the... nickel oxide (PMN P-04-269; CAS No. 182442-95-1). This action requires persons who intend to...

  12. Water oxidation by amorphous cobalt-based oxides: volume activity and proton transfer to electrolyte bases.

    PubMed

    Klingan, Katharina; Ringleb, Franziska; Zaharieva, Ivelina; Heidkamp, Jonathan; Chernev, Petko; Gonzalez-Flores, Diego; Risch, Marcel; Fischer, Anna; Dau, Holger

    2014-05-01

    Water oxidation in the neutral pH regime catalyzed by amorphous transition-metal oxides is of high interest in energy science. Crucial determinants of electrocatalytic activity were investigated for a cobalt-based oxide film electrodeposited at various thicknesses on inert electrodes. For water oxidation at low current densities, the turnover frequency (TOF) per cobalt ion of the bulk material stayed fully constant for variation of the thickness of the oxide film by a factor of 100 (from about 15 nm to 1.5 μm). Thickness variation changed neither the nanostructure of the outer film surface nor the atomic structure of the oxide catalyst significantly. These findings imply catalytic activity of the bulk hydrated oxide material. Nonclassical dependence on pH was observed. For buffered electrolytes with pKa values of the buffer base ranging from 4.7 (acetate) to 10.3 (hydrogen carbonate), the catalytic activity reflected the protonation state of the buffer base in the electrolyte solution directly and not the intrinsic catalytic properties of the oxide itself. It is proposed that catalysis of water oxidation occurs within the bulk hydrated oxide film at the margins of cobalt oxide fragments of molecular dimensions. At high current densities, the availability of a proton-accepting base at the catalyst-electrolyte interface controls the rate of water oxidation. The reported findings may be of general relevance for water oxidation catalyzed at moderate pH by amorphous transition-metal oxides.

  13. Catalysis on cobalt oxide-based nanocatalysts

    NASA Astrophysics Data System (ADS)

    Zhang, Shiran

    Heterogeneous catalysis, being the focus of attention in the realm of catalysis, plays a vital role in modern chemical and energy industries. A prototype of heterogeneous catalyst consists of metal nanoparticles dispersed and supported on a substrate. Transition metal oxide is one of the key components of heterogeneous catalyst and is frequently used as catalyst support for noble metal nanoparticle catalysts due to low cost. As a result of the high cost of noble metal elements, it is particularly favorable to design and develop transition metal oxide-based nanocatalysts mainly made of earthabundant elements with no or less noble metal with comparable or better catalytic performance than noble metal-based nanocatalysts in a catalytic reaction. In some cases, surface chemistry and structure of nanocatalysts are not invariable during catalysis. They evolve in terms of surface restructuring or phase change, which contributes to the complexity of catalyst surface under different catalytic conditions. Transition metal oxides, especially reducible transition metal oxides, have multiple cationic valence states and crystallographic structures. New catalytic active phases or sites could be formed upon surface restructuring under certain catalytic conditions while they may not be preserved if exposed to ambient conditions. Thus, it is essential to characterize catalyst surface under reaction conditions so that chemistry and structure of catalyst surface could be correlated with the corresponding catalytic performance. It also suggests a new route to design nanocatalysts through restructuring catalyst precursor under certain catalytic conditions tracked with in-situ analytical techniques. Catalysis occurs on catalyst surface. For noble metal nanoparticle catalysts, only atoms exposed on surface participate in catalytic processes, while atoms in bulk do not. In order to make full use of noble metal atoms, it is crucial to maximize the dispersion. A configuration of noble metal

  14. Temperature-programmed sulfiding of precursor cobalt oxide genesis of highly active sites on sulfided cobalt catalyst for hydrogenation and isomerization

    SciTech Connect

    Inamura, Kazuhiro; Takyu, Toshiyuki ); Okamoto, Yasuaki; Nagata, Kozo; Imanaka, Toshinobu )

    1992-02-01

    It was found that the method of sulfidation of cobalt oxide strongly affects the catalytic activities and selectivities of the resultant cobalt sulfide catalyst, as well as the calcination temperature of the cobalt oxide. When cobalt oxide was sulfided at 673 K by a temperature-programmed sulfiding method (a heating rate of 6 K/min), catalytic activities for the hydrogenation of butadiene and the isomerization of 1-butene were considerably enhanced compared with those for cobalt sulfide prepared by isothermal sulfidation at 673 K. Results of temperature-programmed sulfiding (TPS), temperature-programmed reduction (TPR), and X-ray diffraction (XRD) suggest that the catalysts showing high catalytic activities after sulfidation are partially sulfided at 673 K and consist of the unsulfided cobalt core phases (CoO or metallic Co). The sulfidation property of precursor cobalt oxides has been studied using TPS, simulating the sulfidation process of the cobalt sulfide catalysts. Two distinctly different kinds of sulfidation process are estimated by TPS measurements of the cobalt oxides. The calcination temperature of the precursor cobalt oxides strongly affects the sulfidation paths. They are differentiated in terms of the presence of a metallic Co intermediate. The relationship of the mechanism of sulfidation of the cobalt oxides to the generation of highly active sites is discussed.

  15. Nanotubes from Oxide-Based Misfit Family: The Case of Calcium Cobalt Oxide.

    PubMed

    Panchakarla, Leela S; Lajaunie, Luc; Ramasubramaniam, Ashwin; Arenal, Raul; Tenne, Reshef

    2016-06-28

    Misfit layered compounds (MLCs) have generated significant interest in recent years as potential thermoelectric materials. MLC nanotubes could reveal behavior that is entirely different from the bulk material. Recently, new chemical strategies were exploited for the synthesis of nanotubular forms of chalcogenide-based MLCs, which are promising candidates for thermoelectric materials. However, analogous synthesis of oxide-based MLC nanotubes has not been demonstrated until now. Here, we report a chemical strategy for synthesis of cobalt-oxide-based misfit nanotubes. A combination of high-resolution (scanning) transmission electron microscopy (including image simulations), spatially resolved electron energy-loss spectroscopy, electron diffraction, and density functional theory (DFT) calculations is used to discover the formation of a phase within these nanotubes that differs significantly from bulk calcium cobaltite MLCs. Furthermore, DFT calculations show that this phase is semiconducting with a band gap in excess of 1 eV, unlike bulk calcium cobaltite MLCs, which are known to be metallic. Through systematic experiments, we propose a formation mechanism for these nanotubes that could also apply more generally to realizing other oxide-based MLC nanotubes. PMID:27215812

  16. Applications of x ray absorption fine structure to the in situ study of the effect of cobalt in nickel hydrous oxide electrodes for fuel cells and rechargeable batteries

    NASA Technical Reports Server (NTRS)

    Kim, Sunghyun; Tryk, Donald A.; Scherson, Daniel A.; Antonio, Mark R.

    1993-01-01

    Electronic and structural aspects of composite nickel-cobalt hydrous oxides have been examined in alkaline solutions using in situ X-ray absorption fine structure (XAFS). The results obtained have indicated that cobalt in this material is present as cobaltic ions regardless of the oxidation state of nickel in the lattice. Furthermore, careful analysis of the Co K-edge Extended X-ray absorption fine structure data reveals that the co-electrodeposition procedure generates a single phase, mixed metal hydrous oxide, in which cobaltic ions occupy nickel sites in the NiO2 sheet-like layers and not two intermixed phases each consisting of a single metal hydrous oxide.

  17. Unusual dielectric response in cobalt doped reduced graphene oxide

    SciTech Connect

    Akhtar, Abu Jahid; Gupta, Abhisek; Kumar Shaw, Bikash; Saha, Shyamal K.

    2013-12-09

    Intensive research on cobalt doped reduced graphene oxide (Co-RGO) to investigate the modification in graphene magnetism and spin polarization due to presence of transition metal atom has been carried out, however, its dielectric spectroscopy, particularly, how capacitance changes with impurity levels in graphene is relatively unexplored. In the present work, dielectric spectroscopy along with magneto-dielectric effect are investigated in Co-RGO. Contrary to other materials, here permittivity increases abruptly with frequency in the low frequency region and continues to increase till 10{sup 7} Hz. This unusual behavior is explained on the basis of trap induced capacitance created due to impurity levels.

  18. Physical and electrochemical study of cobalt oxide nano- and microparticles

    SciTech Connect

    Alburquenque, D.; Vargas, E.; Denardin, J.C.; Escrig, J.; Marco, J.F.; Gautier, J.L.

    2014-07-01

    Cobalt oxide nanocrystals of size 17–21 nm were synthesized by a simple reaction between cobalt acetate (II) and dodecylamine. On the other hand, micrometric Co{sub 3}O{sub 4} was prepared using the ceramic method. The structural examination of these materials was performed using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM and HRTEM). XRD studies showed that the oxides were pure, well-crystallized, spinel cubic phases with a-cell parameter of 0.8049 nm and 0.8069 nm for the nano and micro-oxide, respectively. The average particle size was 19 nm (nano-oxide) and 1250 μm (micro-oxide). Morphological studies carried out by SEM and TEM analyses have shown the presence of octahedral particles in both cases. Bulk and surface properties investigated by X-ray photoelectron spectroscopy (XPS), point zero charge (pzc), FTIR and cyclic voltammetry indicated that there were no significant differences in the composition on both materials. The magnetic behavior of the samples was determined using a vibrating sample magnetometer. The compounds showed paramagnetic character and no coercivity and remanence in all cases. Galvanostatic measurements of electrodes formed with nanocrystals showed better performance than those built with micrometric particles. - Highlights: • Spinel Co{sub 3}O{sub 4} nanoparticles and microparticles with same structure but with different cell parameters, particle size and surface area were synthesized. • Oxide nanoparticles showed better electrochemical behavior than micrometric ones due to area effect.

  19. Chitosan-modified cobalt oxide nanoparticles stimulate TNF-α-mediated apoptosis in human leukemic cells.

    PubMed

    Chattopadhyay, Sourav; Dash, Sandeep Kumar; Kar Mahapatra, Santanu; Tripathy, Satyajit; Ghosh, Totan; Das, Balaram; Das, Debasis; Pramanik, Panchanan; Roy, Somenath

    2014-03-01

    The objective of this study was to develop chitosan-based delivery of cobalt oxide nanoparticles to human leukemic cells and investigate their specific induction of apoptosis. The physicochemical properties of the chitosan-coated cobalt oxide nanoparticles were characterized using transmission electron microscopy, dynamic light scattering, X-ray diffraction, and Fourier transform infrared spectroscopy. The solubility of chitosan-coated cobalt oxide nanoparticles was higher at acidic pH, which helps to release more cobalt ions into the medium. Chitosan-coated cobalt oxide nanoparticles showed good compatibility with normal cells. However, our results showed that exposure of leukemic cells (Jurkat cells) to chitosan-coated cobalt oxide nanoparticles caused an increase in reactive oxygen species generation that was abolished by pretreatment of cells with the reactive oxygen species scavenger N-acetyl-L-cysteine. The apoptosis of Jurkat cells was confirmed by flow-cytometric analysis. Induction of TNF-α secretion was observed from stimulation of Jurkat cells with chitosan-coated cobalt oxide nanoparticles. We also tested the role of TNF-α in the induction of Jurkat cell death in the presence of TNF-α and caspase inhibitors. Treatment of leukemic cells with a blocker had a greater effect on cancer cell viability. From our findings, oxidative stress and caspase activation are involved in cancer cell death induced by chitosan-coated cobalt oxide nanoparticles.

  20. Topochemical synthesis of cobalt oxide-based porous nanostructures for high-performance lithium-ion batteries.

    PubMed

    Li, Cheng Chao; Yin, Xiao Ming; Li, Qiu Hong; Chen, Li Bao; Wang, Tai Hong

    2011-02-01

    Two kinds of topochemical conversion routes from cobalt hydroxide precursors to cobalt oxide-based porous nanostructures are presented: pyrolysis in air and hydrothermal treatment by the Kirkendall diffusion effect. These cobalt hydroxide precursors were synthesized by a simple hydrothermal approach with sodium acetate as mineralizer at 200 °C. Detailed proof indicates that the process of cobalt hydroxide precursor growth is dominated by a nucleation, dissolution, renucleation, growth, and exfoliation mechanism. By the topochemical conversion processes several Co(3)O(4) nanostructures, such as cobalt oxide-coated cobalt hydroxide carbonate nanowires, cobalt oxide nanotubes, hollow cobalt oxide spheres, and porous cobalt oxide nanowires, have been synthesized. The obtained Co(3)O(4) nanostructures have also been evaluated as the anode materials in lithium-ion batteries. It was found that the as-prepared Co(3)O(4) nanostructures exhibited high reversible capacity and good cycle performance due to their porous structure and small size.

  1. The Structure and Properties of Plasma Sprayed Iron Oxide Doped Manganese Cobalt Oxide Spinel Coatings for SOFC Metallic Interconnectors

    NASA Astrophysics Data System (ADS)

    Puranen, Jouni; Lagerbom, Juha; Hyvärinen, Leo; Kylmälahti, Mikko; Himanen, Olli; Pihlatie, Mikko; Kiviaho, Jari; Vuoristo, Petri

    2011-01-01

    Manganese cobalt oxide spinel doped with Fe2O3 was studied as a protective coating on ferritic stainless steel interconnects. Chromium alloying causes problems at high operation temperatures in such oxidizing conditions where chromium compounds evaporate and poison the cathode active area, causing the degradation of the solid oxide fuel cell. In order to prevent chromium evaporation, these interconnectors need a protective coating to block the chromium evaporation and to maintain an adequate electrical conductivity. Thermal spraying is regarded as a promising way to produce dense and protective layers. In the present work, the ceramic Mn-Co-Fe oxide spinel coatings were produced by using the atmospheric plasma spray process. Coatings with low thickness and low amount of porosity were produced by optimizing deposition conditions. The original spinel structure decomposed because of the fast transformation of solid-liquid-solid states but was partially restored by using post-annealing treatment.

  2. Nitrous oxide activation by a cobalt(ii) complex for aldehyde oxidation under mild conditions.

    PubMed

    Corona, Teresa; Company, Anna

    2016-10-01

    Nitrous oxide (N2O) is a waste gas produced in many industrial processes with an important environmental impact. Thus, its application as an oxidant is highly desirable because it produces innocuous N2 as a by-product. In this work we report a new cobalt(ii) complex that reacts with N2O under mild conditions and the catalytic application of this system to carry out the oxidation of aldehydes. PMID:27445004

  3. Nitrous oxide activation by a cobalt(ii) complex for aldehyde oxidation under mild conditions.

    PubMed

    Corona, Teresa; Company, Anna

    2016-10-01

    Nitrous oxide (N2O) is a waste gas produced in many industrial processes with an important environmental impact. Thus, its application as an oxidant is highly desirable because it produces innocuous N2 as a by-product. In this work we report a new cobalt(ii) complex that reacts with N2O under mild conditions and the catalytic application of this system to carry out the oxidation of aldehydes.

  4. Nano-Web Cobalt Modified Silica Nanoparticles Catalysts for Water Oxidation and MB Oxidative Degradation.

    PubMed

    Wang, Li; Chen, Qiuyun; Li, Chenghao; Fang, Fang

    2016-05-01

    Dioxygen generating materials, using water as oxygen source, can be used as catalysts in hypoxic environments. Cobalt(II) modified silica (SiO2@NPCo) nanoparticles were synthesized through coordination of cobalt(II) ions with nitrogen atoms from 2-acetylpyridine modified silica (SiO2@NP). The SiO2@NPCo nanoparticles further reacted with 1,3,5-benzenetricarboxylic acids, forming porous nano-web nanoparticles (SiO2@NPCoCOOH). The synthesized SiO2@NPCoCOOH nanoparticles were demonstrated as better white LED light driven photochemical catalysts for oxidation of water than individual nanoparticles (SiO2@NPCo). Moreover, the SiO2@NPCoCOOH/water system could decrease the content of methylene blue (MB) in solution and therefore, the nanoweb cobalt(II) modified silica nanoparticles can be environmentally friendly catalysts for oxidative degradation of MB, using water as the oxygen source. PMID:27483932

  5. Nano-Web Cobalt Modified Silica Nanoparticles Catalysts for Water Oxidation and MB Oxidative Degradation.

    PubMed

    Wang, Li; Chen, Qiuyun; Li, Chenghao; Fang, Fang

    2016-05-01

    Dioxygen generating materials, using water as oxygen source, can be used as catalysts in hypoxic environments. Cobalt(II) modified silica (SiO2@NPCo) nanoparticles were synthesized through coordination of cobalt(II) ions with nitrogen atoms from 2-acetylpyridine modified silica (SiO2@NP). The SiO2@NPCo nanoparticles further reacted with 1,3,5-benzenetricarboxylic acids, forming porous nano-web nanoparticles (SiO2@NPCoCOOH). The synthesized SiO2@NPCoCOOH nanoparticles were demonstrated as better white LED light driven photochemical catalysts for oxidation of water than individual nanoparticles (SiO2@NPCo). Moreover, the SiO2@NPCoCOOH/water system could decrease the content of methylene blue (MB) in solution and therefore, the nanoweb cobalt(II) modified silica nanoparticles can be environmentally friendly catalysts for oxidative degradation of MB, using water as the oxygen source.

  6. Unification of catalytic water oxidation and oxygen reduction reactions: amorphous beat crystalline cobalt iron oxides.

    PubMed

    Indra, Arindam; Menezes, Prashanth W; Sahraie, Nastaran Ranjbar; Bergmann, Arno; Das, Chittaranjan; Tallarida, Massimo; Schmeißer, Dieter; Strasser, Peter; Driess, Matthias

    2014-12-17

    Catalytic water splitting to hydrogen and oxygen is considered as one of the convenient routes for the sustainable energy conversion. Bifunctional catalysts for the electrocatalytic oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are pivotal for the energy conversion and storage, and alternatively, the photochemical water oxidation in biomimetic fashion is also considered as the most useful way to convert solar energy into chemical energy. Here we present a facile solvothermal route to control the synthesis of amorphous and crystalline cobalt iron oxides by controlling the crystallinity of the materials with changing solvent and reaction time and further utilize these materials as multifunctional catalysts for the unification of photochemical and electrochemical water oxidation as well as for the oxygen reduction reaction. Notably, the amorphous cobalt iron oxide produces superior catalytic activity over the crystalline one under photochemical and electrochemical water oxidation and oxygen reduction conditions.

  7. Porous nickel MCFC cathode coated by potentiostatically deposited cobalt oxide. I. A structural and morphological study

    NASA Astrophysics Data System (ADS)

    Escudero, M. J.; Rodrigo, T.; Mendoza, L.; Cassir, M.; Daza, L.

    Porous nickel cathode was protected by potentiostatically deposited cobalt at different experimental conditions: oxidation potential and electrolysis duration. The deposition growth increased with the oxidation potential yielding a more developed granular structure with smaller grains. Thin layers of Co 3O 4 were identified by X-ray diffraction (XRD) and Raman spectroscopy. CoOOH was detected by X-ray photoelectron spectroscopy (XPS) before annealing treatment and Co 3O 4 after heating the sample at 500 °C during 4 h in air. After this treatment, some morphological changes were observed on the coated samples due to grain compaction and oxidation of the nickel substrate. The porosity of the coated samples was relatively close to that of the sole porous nickel. These coatings exhibited an appropriate dual-pore structure with macro and micro pores, a basic MCFC requirement.

  8. Epitaxial cobalt oxide films on Ir(100)-the importance of crystallographic analyses.

    PubMed

    Heinz, K; Hammer, L

    2013-05-01

    Epitaxial cobalt oxide films on Ir(100) exhibit a rich scenario of different structural phases which are reviewed in this paper. The great majority of phases could be, as a rare case, crystallographically described by the joint application of atomically resolved STM and quantitative LEED, whereby structural surprises were more the rule than the exception. So, the oxide grows in the polar (111) orientation for both the Co3O4 and CoO stoichiometry on the bare Ir substrate in spite of the latter's square symmetry. Moreover, the film orientation can be tuned to non-polar (100) growth when one or several pseudomorphic Co layers are introduced as an interface between oxide and Ir substrate. By using the nanostructured Ir(100)-(5 × 1)-H phase as a template a nanostructured Co film can be formed whose oxidation leads to a nanostructured oxide. The nominally polar films circumvent the polarity problem by appropriate surface terminations. That of CoO(111) is, again as a surprise, realized by a switch from rocksalt-type to wurtzite-type stacking near the surface, by which the latter becomes metallic. The stepwise oxidation of a pseudomorphic Co layer on the bare Ir substrate leads to the sequential formation of rocksalt-type tetrahedral Co-O building blocks (with intermediate BN-type blocks) whereby the Co species more and more assume positions determined by the inner-oxidic binding.

  9. Structural, morphological, and electrical characteristics of the electrodeposited cobalt oxide electrode for supercapacitor applications

    SciTech Connect

    Kandalkar, Sunil G.; Lee, Hae-Min; Chae, Heeyeop; Kim, Chang-Koo

    2011-01-15

    Cobalt oxide (Co{sub 3}O{sub 4}) thin films were prepared through electrodeposition on copper substrates using an ammonia-complexed cobalt chloride solution. The structural and morphological properties of the film were studied using an X-ray diffractometer and scanning electron microscopy, and the results showed that the electrodeposited cobalt oxide film had a nanocrystalline and porous structure. The electrochemical behavior of the electrodeposited cobalt oxide electrode was evaluated in a KOH solution using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests. The electrodeposited cobalt oxide electrode exhibited a specific capacitance of 235 F/g at a scan rate of 20 mV/s. The specific energy and the specific power of the electrode were 4.0 Wh/kg and 1.33 kW/kg, respectively.

  10. Influence of precursors chemistry on ALD growth of cobalt-molybdenum oxide films.

    PubMed

    Diskus, Madeleine; Balasundaram, Murugan; Nilsen, Ola; Fjellvåg, Helmer

    2012-02-28

    Cobalt molybdenum compounds are important catalytic materials in many processes, e.g. in splitting of ammonia to form CO free hydrogen fuel. We here report on deposition of such cobalt molybdenum oxides by atomic layer deposition (ALD) using different types of metal precursors CoCp(2) (Cp = cyclopentadienyl), Co(thd)(2) (Hthd = 2,2,6,6-tetramethylheptan-3,5-dione), Mo(CO)(6) and oxygen precursors O(3), H(2)O, and (O(3) + H(2)O). The growth dynamics have been investigated using quartz crystal microbalance (QCM) methods. It is evident that mixing of the different precursor chemistries affect the growth patterns. When water is introduced to the reactions, a surface controlled mechanism takes place which guides the deposited stoichiometry towards the CoMoO(4) phase over a wide range of cobalt rich pulsed compositions. This is a rare example of how surface chemistry can control stoichiometry of depositions in ALD. The deposited films have been investigated by X-ray diffraction, Raman spectroscopy and atomic force microscopy. The catalytic activity of selected films have been characterized by temperature programmed ammonia decomposition, proving the films to be catalytically active and lowering the decomposition temperature by some 200 °C.

  11. Cobalt-promoted Iron Oxide Nanoparticles for the Selective Oxidative Dehydrogenation of Cyclohexane

    NASA Astrophysics Data System (ADS)

    Rutter, Matthew

    Recent work has shown that both cobalt and iron oxide nanoparticles are active for the oxidative dehydrogenation (ODH) of cyclohexane to benzene, the former more active than the latter. Further study has shown that the addition of gold species as a minority component into iron oxide nanocrystals increases the selectivity of the reaction to benzene. Since a primary motivation for this work is the addition of catalysts in jet fuels to facilitate the dehydrogenation and cracking reactions preceding their combustion, a low-cost, sacrificial catalyst is sought after. In this application, catalyst nanoparticles suspended in the fuel stream will dehydrogenate cyclic alkanes (cyclohexane) to their aromatic counterparts (benzene). Alkenes and aromatics have a much higher rate of combustion, which decreases the amount of uncombusted fuel in the exhaust, thereby increasing performance. As these catalysts are not recyclable, there is significant impetus to substitute cheaper base metals for expensive noble metals. In this work, iron oxide nanoparticles are doped with varying levels of cobalt to examine the effect of cobalt content and oxidation state on the selectivity and activity of the iron oxide for the oxidative dehydrogenation of cyclohexane, used as a model cyclic alkane in jet fuel. We have shown previously that small (˜5nm) cobalt oxide nanoparticles favor the production of benzene over the partial dehydrogenation products cyclohexene and cyclohexadiene, or the complete oxidation product carbon dioxide. It is the aim of this work to examine the surface of these cobalt-iron oxide nanoparticles to determine the conditions most favorable for this selective oxidative dehydrogenation. Cobalt-doped iron nanoparticles were prepared by a surfactant-free hydrothermal co-precipitation technique that enabled a high degree of composition control and size control. These samples were characterized via Transmission Electron Microscopy (TEM), powder X-Ray Diffraction (XRD), X

  12. Impedance spectroscopy of the oxide films formed during high temperature oxidation of a cobalt-plated ferritic alloy

    NASA Astrophysics Data System (ADS)

    Velraj, S.; Zhu, J. H.; Painter, A. S.; Du, S. W.; Li, Y. T.

    2014-02-01

    Impedance spectroscopy was used to evaluate the oxide films formed on cobalt-coated Crofer 22 APU ferritic stainless steel after thermal oxidation at 800 °C in air for different times (i.e. 2, 50, 100 and 500 h). Impedance spectra of the oxide films exhibited two or three semicircles depending on the oxidation time, which correspond to the presence of two or three individual oxide layers. Coupled with scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD), the individual oxide layer corresponding to each semicircle was determined unambiguously. Impedance spectrum analysis of the oxide films formed on the sample after thermal exposure at 800 °C in air for 2 h led to the identification of the low-frequency and high-frequency semicircles as being from Cr2O3 and Co3O4, respectively. SEM/EDS and XRD analysis of the 500-h sample clearly revealed the presence of three oxide layers, analyzed to be Co3-xCrxO4, CoCr2O4, and Cr2O3. Although the SEM images of the 50-h and 100-h samples did not clearly show the CoCr2O4 layer, impedance plots implied their presence. The oxide scales were assigned to their respective semicircles and the electrical properties of Co3-xCrxO4, CoCr2O4 and Cr2O3 were determined from the impedance data.

  13. Humidity Sensing Using Gelatin and Cobalt Chloride Coating on Indium Tin Oxide-Coated Long-Period Grating

    NASA Astrophysics Data System (ADS)

    Nidhi; Kaler, R. S.; Kapur, Pawan

    2014-01-01

    In this article, humidity sensing using gelatin and cobalt chloride on indium tin oxide coated long-period gratings was proposed and demonstrated. First, a thin overlay of indium tin oxide was deposited on a long-period grating by using a simple dip coating methodology. Similarly, a combination of gelatin and cobalt chloride was deposited onto the indium tin oxide layer. A field emission scanning electron microscope provided detailed evidence of the attachment of amalgamation on long-period gratings. The designed sensor showed a significant shift in the resonance wavelength when the relative humidity varied from 40% to 95%, with a sensitivity of 0.12 nm/% relative humidity and an accuracy of 98.45%.

  14. Magnetic and microwave absorption properties of self-assemblies composed of core-shell cobalt-cobalt oxide nanocrystals.

    PubMed

    Wang, Zhongzhu; Bi, Hong; Wang, Peihong; Wang, Min; Liu, Zhiwei; Shen, Lei; Liu, Xiansong

    2015-02-01

    Core-shell structure cobalt-cobalt oxide nanocomposites were directly synthesized via annealing Co nanocrystals in air at 300 °C. Their microstructure and magnetic properties were characterized by XRD, TEM, XPS and VSM, respectively. The microwave absorbing properties of the nanocomposite powders by dispersing them in wax were investigated in the 2-18 GHz frequency range. The sample that was annealed for 1 h exhibits the maximum reflection loss of -30.5 dB and a bandwidth of less than -10 dB covering the 12.6-17.3 GHz range with the coating thickness of only 1.7 mm. At the same thickness, the sample annealed for 3 h exhibits the maximum reflection loss of -24 dB and a bandwidth that almost covers the whole X-band (8-11.5 GHz). With increase in the insulating cobalt oxide shell, the enhanced permeability could contribute to the decrease of eddy current loss, and the permittivity could be easily adjusted; thus, the microwave absorption properties of the cobalt oxide nanocrystals could be easily adjusted. PMID:25559407

  15. Incommensurate spin correlations in highly oxidized cobaltates La2−xSrxCoO4

    PubMed Central

    Li, Z. W.; Drees, Y.; Kuo, C. Y.; Guo, H.; Ricci, A.; Lamago, D.; Sobolev, O.; Rütt, U.; Gutowski, O.; Pi, T. W.; Piovano, A.; Schmidt, W.; Mogare, K.; Hu, Z.; Tjeng, L. H.; Komarek, A. C.

    2016-01-01

    We observe quasi-static incommensurate magnetic peaks in neutron scattering experiments on layered cobalt oxides La2−xSrxCoO4 with high Co oxidation states that have been reported to be paramagnetic. This enables us to measure the magnetic excitations in this highly hole-doped incommensurate regime and compare our results with those found in the low-doped incommensurate regime that exhibit hourglass magnetic spectra. The hourglass shape of magnetic excitations completely disappears given a high Sr doping. Moreover, broad low-energy excitations are found, which are not centered at the incommensurate magnetic peak positions but around the quarter-integer values that are typically exhibited by excitations in the checkerboard charge ordered phase. Our findings suggest that the strong inter-site exchange interactions in the undoped islands are critical for the emergence of hourglass spectra in the incommensurate magnetic phases of La2−xSrxCoO4. PMID:27117928

  16. High quality thin films of thermoelectric misfit cobalt oxides prepared by a chemical solution method.

    PubMed

    Rivas-Murias, Beatriz; Manuel Vila-Fungueiriño, José; Rivadulla, Francisco

    2015-07-08

    Misfit cobaltates ([Bi/Ba/Sr/Ca/CoO]n(RS)[CoO2]q) constitute the most promising family of thermoelectric oxides for high temperature energy harvesting. However, their complex structure and chemical composition makes extremely challenging their deposition by high-vacuum physical techniques. Therefore, many of them have not been prepared as thin films until now. Here we report the synthesis of high-quality epitaxial thin films of the most representative members of this family of compounds by a water-based chemical solution deposition method. The films show an exceptional crystalline quality, with an electrical conductivity and thermopower comparable to single crystals. These properties are linked to the epitaxial matching of the rock-salt layers of the structure to the substrate, producing clean interfaces free of amorphous phases. This is an important step forward for the integration of these materials with complementary n-type thermoelectric oxides in multilayer nanostructures.

  17. High quality thin films of thermoelectric misfit cobalt oxides prepared by a chemical solution method

    PubMed Central

    Rivas-Murias, Beatriz; Manuel Vila-Fungueiriño, José; Rivadulla, Francisco

    2015-01-01

    Misfit cobaltates ([Bi/Ba/Sr/Ca/CoO]nRS[CoO2]q) constitute the most promising family of thermoelectric oxides for high temperature energy harvesting. However, their complex structure and chemical composition makes extremely challenging their deposition by high-vacuum physical techniques. Therefore, many of them have not been prepared as thin films until now. Here we report the synthesis of high-quality epitaxial thin films of the most representative members of this family of compounds by a water-based chemical solution deposition method. The films show an exceptional crystalline quality, with an electrical conductivity and thermopower comparable to single crystals. These properties are linked to the epitaxial matching of the rock-salt layers of the structure to the substrate, producing clean interfaces free of amorphous phases. This is an important step forward for the integration of these materials with complementary n-type thermoelectric oxides in multilayer nanostructures. PMID:26153533

  18. Cobalt Oxide Nanoflowers for Electrochemical Determination of Glucose

    NASA Astrophysics Data System (ADS)

    Balouch, Quratulain; Ibupoto, Zafar Hussain; Khaskheli, Ghulam Qadir; Soomro, Razium Ali; Sirajuddin; Samoon, Muhammad Kashif; Deewani, Vinod Kumar

    2015-10-01

    This study reports a simple, economic, and efficient approach for synthesis of cobalt oxide (Co3O4) nanostructures by a low-temperature aqueous chemical growth method. The synthesized Co3O4 nanostructures were characterized by various techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, and scanning electron microscopy. The synthesized nanostructures exhibited flower-shaped morphology with thickness of each pellet in the range of 200 to 300 nm. The synthesized Co3O4 nanostructures with excellent structural features exhibited high electrocatalytic activity towards the oxidation of glucose in alkaline solution. This enabled development of a highly sensitive (1618.71 µA mM-1 cm-2), stable and reproducible non-enzymatic glucose sensor. The developed sensor demonstrated high anti-interference capability against common interferents such as dopamine, ascorbic acid and uric acid. Furthermore, the applicability of the developed sensor for the determination of glucose from human blood serum provides an alternative approach for the routine glucose analysis.

  19. Synthesis of Cobalt Oxides Thin Films Fractal Structures by Laser Chemical Vapor Deposition

    PubMed Central

    Haniam, P.; Kunsombat, C.; Chiangga, S.; Songsasen, A.

    2014-01-01

    Thin films of cobalt oxides (CoO and Co3O4) fractal structures have been synthesized by using laser chemical vapor deposition at room temperature and atmospheric pressure. Various factors which affect the density and crystallization of cobalt oxides fractal shapes have been examined. We show that the fractal structures can be described by diffusion-limited aggregation model and discuss a new possibility to control the fractal structures. PMID:24672354

  20. Synthesis of cobalt oxides thin films fractal structures by laser chemical vapor deposition.

    PubMed

    Haniam, P; Kunsombat, C; Chiangga, S; Songsasen, A

    2014-01-01

    Thin films of cobalt oxides (CoO and Co3O4) fractal structures have been synthesized by using laser chemical vapor deposition at room temperature and atmospheric pressure. Various factors which affect the density and crystallization of cobalt oxides fractal shapes have been examined. We show that the fractal structures can be described by diffusion-limited aggregation model and discuss a new possibility to control the fractal structures. PMID:24672354

  1. Supported, Alkali-Promoted Cobalt Oxide Catalysts for NOx Removal from Coal Combustion Flue Gases

    SciTech Connect

    Morris D. Argyle

    2005-12-31

    A series of cobalt oxide catalysts supported on alumina ({gamma}-Al{sub 2}O{sub 3}) were synthesized with varying contents of cobalt and of added alkali metals, including lithium, sodium, potassium, rubidium, and cesium. Unsupported cobalt oxide catalysts and several cobalt oxide catalysts supported ceria (CeO{sub 2}) with varying contents of cobalt with added potassium were also prepared. The catalysts were characterized with UV-visible spectroscopy and were examined for NO{sub x} decomposition activity. The CoO{sub x}/Al{sub 2}O{sub 3} catalysts and particularly the CoO{sub x}/CeO{sub 2} catalysts show N{sub 2}O decomposition activity, but none of the catalysts (unsupported Co{sub 3}O{sub 4} or those supported on ceria or alumina) displayed significant, sustained NO decomposition activity. For the Al{sub 2}O{sub 3}-supported catalysts, N{sub 2}O decomposition activity was observed over a range of reaction temperatures beginning about 723 K, but significant (>50%) conversions of N{sub 2}O were observed only for reaction temperatures >900 K, which are too high for practical commercial use. However, the CeO{sub 2}-supported catalysts display N{sub 2}O decomposition rates similar to the Al{sub 2}O{sub 3}-supported catalysts at much lower reaction temperatures, with activity beginning at {approx}573 K. Conversions of >90% were achieved at 773 K for the best catalysts. Catalytic rates per cobalt atom increased with decreasing cobalt content, which corresponds to increasing edge energies obtained from the UV-visible spectra. The decrease in edge energies suggests that the size and dimensionality of the cobalt oxide surface domains increase with increasing cobalt oxide content. The rate data normalized per mass of catalyst that shows the activity of the CeO{sub 2}-supported catalysts increases with increasing cobalt oxide content. The combination of these data suggest that supported cobalt oxide species similar to bulk Co{sub 3}O{sub 4} are inherently more active than

  2. Modification of Wide-Band-Gap Oxide Semiconductors with Cobalt Hydroxide Nanoclusters for Visible-Light Water Oxidation.

    PubMed

    Maeda, Kazuhiko; Ishimaki, Koki; Tokunaga, Yuki; Lu, Daling; Eguchi, Miharu

    2016-07-11

    Cobalt-based compounds, such as cobalt(II) hydroxide, are known to be good catalysts for water oxidation. Herein, we report that such cobalt species can also activate wide-band-gap semiconductors towards visible-light water oxidation. Rutile TiO2 powder, a well-known wide-band-gap semiconductor, was capable of harvesting visible light with wavelengths of up to 850 nm, and thus catalyzed water oxidation to produce molecular oxygen, when decorated with cobalt(II) hydroxide nanoclusters. To the best of our knowledge, this system constitutes the first example that a particulate photocatalytic material that is capable of water oxidation upon excitation by visible light can also operate at such long wavelengths, even when it is based on earth-abundant elements only. PMID:27225394

  3. Electrochemical Water Oxidation of Ultrathin Cobalt Oxide-Based Catalyst Supported onto Aligned ZnO Nanorods.

    PubMed

    Koteeswara Reddy, Nandanapalli; Winkler, Stefanie; Koch, Norbert; Pinna, Nicola

    2016-02-10

    A stable and durable electrochemical water oxidation catalyst based on CoO functionalized ZnO nanorods (NRs) is introduced. ZnO NRs were grown on fluorine-doped tin oxide (FTO) by using a low-temperature chemical solution method and were functionalized with cobalt oxide by electrochemical deposition. The electrochemical water oxidation performance of cobalt oxide functionalized ZnO NRs was studied under alkaline (pH = 10) conditions. From these studies, it is noticed that cobalt oxide functionalized ZnO NRs show electrocatalytic activity toward water oxidation with current density on the order of several mA cm(-2). Further, 30 s CoO deposited ZnO nanorods exhibited excellent galvanostatic stability at a current density of 1 mA cm(-2) and potentiostatic stability at 1.25 V vs Ag/AgCl over an electrolysis period of 1 h. PMID:26784675

  4. Tailoring the oxidation state of cobalt through halide functionality in sol-gel silica

    PubMed Central

    Olguin, Gianni; Yacou, Christelle; Smart, Simon; Diniz da Costa, João C.

    2013-01-01

    The functionality or oxidation state of cobalt within a silica matrix can be tailored through the use of cationic surfactants and their halide counter ions during the sol-gel synthesis. Simply by adding surfactant we could significantly increase the amount of cobalt existing as Co3O4 within the silica from 44% to 77%, without varying the cobalt precursor concentration. However, once the surfactant to cobalt ratio exceeded 1, further addition resulted in an inhibitory mechanism whereby the altered pyrolysis of the surfactant decreased Co3O4 production. These findings have significant implications for the production of cobalt/silica composites where maximizing the functional Co3O4 phase remains the goal for a broad range of catalytic, sensing and materials applications. PMID:24022785

  5. Marine cobalt resources

    USGS Publications Warehouse

    Manheim, F. T.

    1986-01-01

    Ferromanganese oxides in the open oceans are more enriched in cobalt than any other widely distributed sediments or rocks. Concentrations of cobalt exceed 1 percent in ferromanganese crusts on seamounts, ocean ridges, and other raised areas of the ocean. The cobalt-rich crusts may be the slowest growing of any earth material, accumulating one molecular layer every 1 to 3 months. Attention has been drawn to crusts as potential resources because they contain cobalt, manganese, and platinum, three of the four priority strategic metals for the United States. Moreover, unlike abyssal nodules, whose recovery is complicated by their dominant location in international waters, some of the most cobalt-rich crusts occur within the exclusive economic zone of the United States and other nations. Environmental impact statements for crust exploitation are under current development by the Department of the Interior.

  6. Microanalysis of an oxidized cobalt oxide: Zirconia eutectic

    SciTech Connect

    Bentley, J.; McKernan, S.; Carter, C.B.; Revcolevschi, A.

    1993-12-31

    The compositions of CoO, Co{sub 3}O{sub 4}, and Ca-stabilized cubic ZrO{sub 2} in an oxidized directionally solidified CoO-ZrO{sub 2} eutectic were determined by PEELS and EDS. An oxygen gradient exists across the Co{sub 3}O{sub 4} with highest levels near the ZrO{sub 2} interface. Oxygen ELNES for CoO and Co{sub 3}O{sub 4} are quite different; published oxygen ELNES have been incorrectly attributed to CoO. Normalized Co-L{sub 23} white line intensity (WLI) ratios for CoO and Co{sub 3}O{sub 4} are similar (0.53 {plus_minus} 0.02) but L{sub 3}/L{sub 2} WLI ratios are 3.88 and 2.58, respectively. ELCE data suggest Co{sub 3}O{sub 4} has the inverse spinel structure.

  7. Kinetic phase evolution of spinel cobalt oxide during lithiation

    DOE PAGESBeta

    Li, Jing; He, Kai; Meng, Qingping; Li, Xin; Zhu, Yizhou; Hwang, Sooyeon; Sun, Ke; Gan, Hong; Zhu, Yimei; Mo, Yifei; et al

    2016-09-15

    Spinel cobalt oxide has been proposed to undergo a multiple-step reaction during the electrochemical lithiation process. Understanding the kinetics of the lithiation process in this compound is crucial to optimize its performance and cyclability. In this work, we have utilized a low-angle annular dark-field scanning transmission electron microscopy method to visualize the dynamic reaction process in real time and study the reaction kinetics at different rates. We show that the particles undergo a two-step reaction at the single-particle level, which includes an initial intercalation reaction followed by a conversion reaction. At low rates, the conversion reaction starts after the intercalationmore » reaction has fully finished, consistent with the prediction of density functional theoretical calculations. At high rates, the intercalation reaction is overwhelmed by the subsequently nucleated conversion reaction, and the reaction speeds of both the intercalation and conversion reactions are increased. Phase-field simulations show the crucial role of surface diffusion rates of lithium ions in controlling this process. Furthermore, this work provides microscopic insights into the reaction dynamics in non-equilibrium conditions and highlights the effect of lithium diffusion rates on the overall reaction homogeneity as well as the performance.« less

  8. High pressure μSR study on cobalt oxide spinel

    NASA Astrophysics Data System (ADS)

    Ikedo, Yutaka; Sugiyama, Jun; Nozaki, Hiroshi; Mukai, Kazuhiko; Itahara, Hiroshi; Russo, Peter L.; Andreica, Daniel; Amato, Alex

    2009-04-01

    The magnetic nature of the cobalt oxide spinel Co 3O 4 has been studied under hydrostatic pressure up to 1.34 GPa by means of zero field (ZF) and weak transverse field (wTF) μ+SR techniques using a polycrystalline sample. At ambient pressure, Co 3O 4 enters into an antiferromagnetic (AF) phase below 30 K, as evidenced by two distinct spontaneous muon-spin precessions in its ZF spectrum. wTF measurements show that AF transition temperature (TN) clearly increases with increasing pressure. Since only the Co ions at the tetrahedral site (A site) in the spinel lattice are magnetic, this indicates that the AF interaction between the Co ions at A site is enhanced by applying pressure through the decrease in the distance between the adjacent A-site ions. On the other hand, ZF measurements show that the frequency of spontaneous muon-spin precession is almost independent of pressure. This could suggest that the AF structure is not altered by pressure at least up to 1.34 GPa.

  9. Effects of Cobalt on Manganese Oxidation by Pseudomonas putida MnB1

    NASA Astrophysics Data System (ADS)

    Pena, J.; Bargar, J.; Sposito, G.

    2005-12-01

    The oxidation of Mn(II) in the environment is thought to occur predominantly through biologically mediated pathways. During the stationary phase of growth, the well-characterized freshwater and soil bacterium Pseudomonas putida MnB1 oxidizes soluble Mn(II) to a poorly crystalline layer type Mn(IV) oxide. These Mn oxide particles (2 - 5 nm thickness) are deposited in a matrix of extracellular polymeric substances (EPS) surrounding the cell, creating a multi-component system distinct from commonly studied synthetic Mn oxides. Accurate characterization of the reactivity of these biomineral assemblages is essential to understanding trace metal biogeochemistry in natural waters and sediments. Moreover, these biogenic oxides may potentially be used for the remediation of surface and ground waters impacted by mining, industrial pollution, and other anthropogenic activities. In this study, we consider the interactions between Co, P. putida MnB1, and its biogenic Mn oxide. Cobalt is a redox-active transition metal which exists in the environment as Co(II) and Co(III). While Co is not generally found in the environment at toxic concentrations, it may be released as a byproduct of mining activities (e.g. levels of up to 20 μM are found in Pinal Creek, AZ, a stream affected by copper mining). In addition, the radionuclide 60Co, formed by neutron activation in nuclear reactors, is of concern at Department of Energy sites, such as that at Hanford, and has several industrial applications, including radiotherapy. We address the following questions: Do high levels of Co inhibit enzymatic processes such as Mn(II) oxidation? Can the multicopper oxidase enzyme involved in Mn(II) oxidation facilitate Co(II) oxidation? Lastly, does the organic matter surrounding the oxides affect Co or Mn oxide reactivity? These issues were approached via wet chemical analysis, synchrotron radiation X-ray diffraction (SR-XRD), and extended X-ray absorption fine structure (EXAFS) spectroscopy. In the

  10. Spinel-type lithium cobalt oxide as a bifunctional electrocatalyst for the oxygen evolution and oxygen reduction reactions.

    PubMed

    Maiyalagan, Thandavarayan; Jarvis, Karalee A; Therese, Soosairaj; Ferreira, Paulo J; Manthiram, Arumugam

    2014-05-27

    Development of efficient, affordable electrocatalysts for the oxygen evolution reaction and the oxygen reduction reaction is critical for rechargeable metal-air batteries. Here we present lithium cobalt oxide, synthesized at 400 °C (designated as LT-LiCoO2) that adopts a lithiated spinel structure, as an inexpensive, efficient electrocatalyst for the oxygen evolution reaction. The catalytic activity of LT-LiCoO2 is higher than that of both spinel cobalt oxide and layered lithium cobalt oxide synthesized at 800 °C (designated as HT-LiCoO2) for the oxygen evolution reaction. Although LT-LiCoO2 exhibits poor activity for the oxygen reduction reaction, the chemically delithiated LT-Li1-xCoO2 samples exhibit a combination of high oxygen reduction reaction and oxygen evolution reaction activities, making the spinel-type LT-Li0,5CoO2 a potential bifunctional electrocatalyst for rechargeable metal-air batteries. The high activities of these delithiated compositions are attributed to the Co4O4 cubane subunits and a pinning of the Co(3+/4+):3d energy with the top of the O(2-):2p band.

  11. An hydrothermal experimental study of the cobalt-cobalt oxide redox buffer

    USGS Publications Warehouse

    Lemke, K.H.; Rosenbauer, R.J.; Bischoff, J.L.; Bird, D.K.

    2008-01-01

    Equilibrium aqueous hydrogen concentration and corresponding energies of reaction, ??Grxno(T, P), for the reaction Co(s) + H2O(l) = CoO(s) + H2(aq) have been determined at temperatures between 256 and 355 ??C and at 400 bar. Steady-state concentrations of hydrogen were approached in experiments under conditions of both H2 excess and deficiency containing the solids Co, CoO and liquid water. All experiments were carried out in flexible gold and titanium reactors with the capability of on-line fluid sampling. Measured equilibrium molal concentrations of H2(aq) at 256, 274, 300, 324 and 355 ??C are 0.81(?? 0.01) ?? 10- 3 1.11(?? 0.01) ?? 10- 3, 1.92(?? 0.01) ?? 10- 3, 3.71(?? 0.06) ?? 10- 3, 7.54(?? 0.12) ?? 10- 3, respectively, and corresponding values of ??Grxno(T, P) in units kJ ?? mol- 1 are 31.4(?? 0.1), 31.0(?? 0.1), 29.8(?? 0.1), 27.7(?? 0.5) and 25.5(?? 0.9), respectively. Using published heat capacity data for Co(s) and CoO(s) and - 79.6 J ?? mol- 1 ?? K- 1 for the entropy of formation of CoO we calculated for this study a value for ??GCoO,Tr,Pro = - 214.5(?? 0.9) kJ ?? mol- 1 and ??HCoO,Tr,Pro = - 238.3(?? 0.9) kJ ?? mol- 1 at 25 ??C and 1 bar. The value of ??HCoO,Tr,Pro determined in this study compares well with the reported calorimetric value of - 238.9(?? 1.2) kJ ?? mol- 1 [Boyle, B.J., King, E.G., Conway, K.C., 1954. Heats of formation of nickel and cobalt oxides (NiO and CoO) by combustion calorimetry. Journal of the American Chemical Society, 76, 3835-3837]. ?? 2008 Elsevier B.V. All rights reserved.

  12. Cobalt oxide nanoparticles can enter inside the cells by crossing plasma membranes

    PubMed Central

    Bossi, Elena; Zanella, Daniele; Gornati, Rosalba; Bernardini, Giovanni

    2016-01-01

    The ability of nanoparticles (NPs) to be promptly uptaken by the cells makes them both dangerous and useful to human health. It was recently postulated that some NPs might cross the plasma membrane also by a non-endocytotic pathway gaining access to the cytoplasm. To this aim, after having filled mature Xenopus oocytes with Calcein, whose fluorescence is strongly quenched by divalent metal ions, we have exposed them to different cobalt NPs quantifying quenching as evidence of the increase of the concentration of Co2+ released by the NPs that entered into the cytoplasm. We demonstrated that cobalt oxide NPs, but not cobalt nor cobalt oxide NPs that were surrounded by a protein corona, can indeed cross plasma membranes. PMID:26924527

  13. Electrochemical sensing chemical oxygen demand based on the catalytic activity of cobalt oxide film.

    PubMed

    Wang, Jinqi; Wu, Can; Wu, Kangbing; Cheng, Qin; Zhou, Yikai

    2012-07-29

    Cobalt oxide sensing film was in situ prepared on glassy carbon electrode surface via constant potential oxidation. Controlling at 0.8 V in NaOH solution, the high-valence cobalt catalytically oxidized the reduced compounds, decreasing its surface amount and current signal. The current decline was used as the response signal of chemical oxygen demand (COD) because COD represents the summation of reduced compounds in water. The surface morphology and electrocatalytic activity of cobalt oxide were readily tuned by variation of deposition potential, time, medium and Co(2+) concentration. As confirmed from the atomic force microscopy measurements, the cobalt oxide film, that prepared at 1.3 V for 40 s in pH 4.6 acetate buffer containing 10 mM Co(NO(3))(2), possesses large surface roughness and numerous three-dimensional structures. Electrochemical tests indicated that the prepared cobalt oxide exhibited high electrocatalytic activity to the reduced compounds, accompanied with strong COD signal enhancement. As a result, a novel electrochemical sensor with high sensitivity, rapid response and operational simplicity was developed for COD. The detection limit was as low as 1.1 mg L(-1). The analytical application was studied using a large number of lake water samples, and the accuracy was tested by standard method.

  14. Two dimensionality in quasi-one-dimensional cobalt oxides

    NASA Astrophysics Data System (ADS)

    Sugiyama, J.; Nozaki, H.; Brewer, J. H.; Ansaldo, E. J.; Morris, G. D.; Takami, T.; Ikuta, H.; Mizutani, U.

    2006-03-01

    Magnetism of quasi-one-dimensional (1D) cobalt oxides ACoO ( A=Ca, Sr and Ba, n=1-5 and ∞) was investigated by μ+SR using polycrystalline samples, at temperatures from 300 K down to 1.8 K. The wTF- μ+SR experiments showed the existence of a magnetic transition in all six samples investigated. The onset temperature of the transition (Tcon) was found to decrease with n; that is, 100±25, 90±10, 85±10, 65±10 50±10, and 15±1 K for n=1-5, and ∞, respectively. In particular, for the samples with n=2-5, Tcon was detected only by the present μ+SR measurements. A muon spin oscillation was clearly observed in both Ca 3Co 2O 6(n=1) and BaCoO 3(n=∞), whereas only a fast relaxation is apparent even at 1.8 K in the other four samples ( n=2-5). Taking together with the fact that the paramagnetic Curie temperature ranges from -150 to -200 K for the compound with n=2 and 3, the μ+SR result indicates that a two-dimensional (2D) short-range antiferromagnetic (AF) order, which has been thought to be unlikely to exist at high T due to a relatively strong 1D F interaction, appears below Tcon for all compounds with n=1-5; but quasi-static long-range AF order formed only in Ca 3Co 2O 6, below 25 K. For BaCoO 3(n=∞), as T decreased from 300 K, 1D F order appeared below 53 K, and a sharp 2D AF transition occurred at 15 K.

  15. Atomic-Scale Study Of Complex Cobalt Oxide Using Scanning Transmission Electron Microscope

    NASA Astrophysics Data System (ADS)

    Gulec, Ahmet

    Cobalt oxides offer a rich ?eld for the formation of novel phases, including superconductors and exotic magnetic phases, involving a mixed valence state for cobalt and/or the presence of oxygen vacancies. Having spin states, such as, low spin (LS), high spin (HS), and intermediate spin (IS), cobalt oxides differ from other 3d metal oxides The presence of such spin states make the physics of the cobalt oxides so complicated that it has not yet been completely understood. In order to improve our understanding of the various phase transitions observed in Cobalt oxides and to comprehend the relationship between crystal and electronic structure, both high energy resolution and high spatial resolution are essential. Fortunately, transmission electron microscopy (TEM) is a technique which is capable of ful?lling both of these requirements. In this thesis, I have utilized unique techniques in a scanning transmission electron microscope (STEM) to analyze the atomic-scale structure-property relationship, both at room temperature and through insitu cooling to liquid nitrogen (LN2) temperature. In particular, by using correlated Z-contrast imaging, electron energy loss spectrum (EELS) and electron energy loss magnetic circular dichroism (EMCD), the structure, composition, bonding and magnetic behavior are characterized directly on the atomic scale.

  16. Thermal-fatigue and oxidation resistance of cobalt-modified Udimet 700 alloy

    NASA Technical Reports Server (NTRS)

    Bizon, P. T.; Barrow, B. J.

    1986-01-01

    Comparative thermal-fatigue and oxidation resistances of cobalt-modified wrought Udimet 700 alloy (obtained by reducing the cobalt level by direct substitution of nickel) were determined from fluidized-bed tests. Bed temperatures were 1010 and 288 C (1850 and 550 C) for the first 5500 symmetrical 6-min cycles. From cycle 5501 to the 14000-cycle limit of testing, the heating bed temperature was increased to 1050 C (1922 F). Cobalt levels between 0 and 17 wt% were studied in both the bare and NiCrAlY overlay coated conditions. A cobalt level of about 8 wt% gave the best thermal-fatigue life. The conventional alloy specification is for 18.5% cobalt, and hence, a factor of 2 in savings of cobalt could be achieved by using the modified alloy. After 13500 cycles, all bare cobalt-modified alloys lost 10 to 13 percent of their initial weight. Application of the NiCrAlY overlay coating resulted in weight losses of 1/20 to 1/100 of that of the corresponding bare alloy.

  17. Thermal NF3 fluorination/oxidation of cobalt, yttrium, zirconium, and selected lanthanide oxides

    SciTech Connect

    Scheele, Randall D.; McNamara, Bruce K.; Casella, Andrew M.; Kozelisky, Anne E.; Neiner, Doinita

    2013-02-01

    This paper presents results of our continuing investigation on the use of nitrogen trifluoride as a fluorination or fluorination/oxidation agent for separating valuable constituents from used nuclear fuels by exploiting the different volatilities of the constituent fission product and actinide fluorides. This article focuses on fission products that do not have volatile fluorides or oxyfluorides at expected operations temperatures. Our thermodynamic calculations show that nitrogen trifluoride has the potential to completely fluorinate fission product oxides to their fluorides. Simultaneous thermogravimetric and differential thermal analyses show that the oxides of cobalt, zirconium, and the lanthanides are fluorinated but do not form volatile fluorides when treated with nitrogen trifluoride at temperatures up to 550°C. Our studies of gadolinium-doped commercial nuclear fuel indicate that nitrogen trifluoride can extract uranium from the non-volatile gadolinium.

  18. Cobalt Oxide Nanosheet and CNT Micro Carbon Monoxide Sensor Integrated with Readout Circuit on Chip

    PubMed Central

    Dai, Ching-Liang; Chen, Yen-Chi; Wu, Chyan-Chyi; Kuo, Chin-Fu

    2010-01-01

    The study presents a micro carbon monoxide (CO) sensor integrated with a readout circuit-on-a-chip manufactured by the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and a post-process. The sensing film of the sensor is a composite cobalt oxide nanosheet and carbon nanotube (CoOOH/CNT) film that is prepared by a precipitation-oxidation method. The structure of the CO sensor is composed of a polysilicon resistor and a sensing film. The sensor, which is of a resistive type, changes its resistance when the sensing film adsorbs or desorbs CO gas. The readout circuit is used to convert the sensor resistance into the voltage output. The post-processing of the sensor includes etching the sacrificial layers and coating the sensing film. The advantages of the sensor include room temperature operation, short response/recovery times and easy post-processing. Experimental results show that the sensitivity of the CO sensor is about 0.19 mV/ppm, and the response and recovery times are 23 s and 34 s for 200 ppm CO, respectively. PMID:22294897

  19. Facile preparation of highly-dispersed cobalt-silicon mixed oxide nanosphere and its catalytic application in cyclohexane selective oxidation

    PubMed Central

    2011-01-01

    Highly dispersed cobalt-silicon mixed oxide [Co-SiO2] nanosphere was successfully prepared with a modified reverse-phase microemulsion method. This material was characterized in detail by X-ray diffraction, transmission electron microscopy, Fourier transform infrared, ultraviolet-visible diffuse reflectance spectra, X-ray absorption spectroscopy near-edge structure, and N2 adsorption-desorption measurements. High valence state cobalt could be easily obtained without calcination, which is fascinating for the catalytic application for its strong oxidation ability. In the selective oxidation of cyclohexane, Co-SiO2 acted as an efficient catalyst, and good activity could be obtained under mild conditions. PMID:22067075

  20. Three-dimensional cobalt oxide microstructures with brush-like morphology via surfactant-dependent assembly.

    PubMed

    Dam, Duc Tai; Lee, Jong-Min

    2014-12-10

    In this study, three-dimensional cobalt oxide microstructures were developed. Cobalt oxide microdumbbells and microspheres, assembled by nanowires and primary particles, were successfully synthesized by a multistep hydrothermal method. Of all of the structures, the cobalt oxide microdumbbell electrode possesses the largest surface area of 70.8 m(2) g(-1) and the highest specific capacitance of 407.5 F g(-1). The as-prepared electrode also demonstrates excellent electrochemical stability and retains 97.5% of the initial capacitance after 2000 charge-discharge cycles. This performance is attributed to the desirable morphology, uniform microarchitecture stability, and high surface area. The results show that the as-fabricated Co3O4 is a promising electrode material for supercapacitor applications. PMID:25415605

  1. Atomically Precise Growth of Catalytically Active Cobalt Sulfide on Flat Surfaces and within a Metal-Organic Framework via Atomic Layer Deposition.

    PubMed

    Peters, Aaron W; Li, Zhanyong; Farha, Omar K; Hupp, Joseph T

    2015-08-25

    Atomic layer deposition (ALD) has been employed as a new synthetic route to thin films of cobalt sulfide on silicon and fluorine-doped tin oxide platforms. The self-limiting nature of the stepwise synthesis is established through growth rate studies at different pulse times and temperatures. Additionally, characterization of the materials by X-ray diffraction and X-ray photoelectron spectroscopy indicates that the crystalline phase of these films has the composition Co9S8. The nodes of the metal-organic framework (MOF) NU-1000 were then selectively functionalized with cobalt sulfide via ALD in MOFs (AIM). Spectroscopic techniques confirm uniform deposition of cobalt sulfide throughout the crystallites, with no loss in crystallinity or porosity. The resulting material, CoS-AIM, is catalytically active for selective hydrogenation of m-nitrophenol to m-aminophenol, and outperforms the analogous oxide AIM material (CoO-AIM) as well as an amorphous CoSx reference material. These results reveal AIM to be an effective method of incorporating high surface area and catalytically active cobalt sulfide in metal-organic frameworks.

  2. Atomically Precise Growth of Catalytically Active Cobalt Sulfide on Flat Surfaces and within a Metal-Organic Framework via Atomic Layer Deposition.

    PubMed

    Peters, Aaron W; Li, Zhanyong; Farha, Omar K; Hupp, Joseph T

    2015-08-25

    Atomic layer deposition (ALD) has been employed as a new synthetic route to thin films of cobalt sulfide on silicon and fluorine-doped tin oxide platforms. The self-limiting nature of the stepwise synthesis is established through growth rate studies at different pulse times and temperatures. Additionally, characterization of the materials by X-ray diffraction and X-ray photoelectron spectroscopy indicates that the crystalline phase of these films has the composition Co9S8. The nodes of the metal-organic framework (MOF) NU-1000 were then selectively functionalized with cobalt sulfide via ALD in MOFs (AIM). Spectroscopic techniques confirm uniform deposition of cobalt sulfide throughout the crystallites, with no loss in crystallinity or porosity. The resulting material, CoS-AIM, is catalytically active for selective hydrogenation of m-nitrophenol to m-aminophenol, and outperforms the analogous oxide AIM material (CoO-AIM) as well as an amorphous CoSx reference material. These results reveal AIM to be an effective method of incorporating high surface area and catalytically active cobalt sulfide in metal-organic frameworks. PMID:26241521

  3. Ferroelectric control of magnetic domains in ultra-thin cobalt layers

    SciTech Connect

    Huang, Z.; Stolichnov, I.; Setter, N.; Bernand-Mantel, A.; Borrel, J.; Pizzini, S.; Ranno, L.; Herrera Diez, L.; Auffret, S.; Gaudin, G.; Boulle, O.

    2013-11-25

    Non-volatile ferroelectric control of magnetic domains has been demonstrated in ultra-thin cobalt layers at room temperature. The sensitivity of magnetic anisotropy energy to the electronic structure in a few atomic layers adjacent to the interface allows for ferroelectric control of coercivity and magnetic domain dynamics. These effects have been monitored and quantified using magneto-optical Kerr effect. In particular, the regimes, where the ferroelectric domains enhance/inhibit the magnetic domain nucleation or increase/reduce domain wall velocity, have been explored. Thus, non-destructive and reversible ferroelectric domain writing provides a tool to define the magnetic domain paths, create nucleation sites, or control domain movement.

  4. Magnetic properties of cobalt single layer added on graphene: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Afshar, M.; Doosti, H.

    2015-01-01

    In this paper, we have demonstrated magnetic ordering of single cobalt layer added on graphene using relativistic density functional theory at the level of generalized gradient approximation. We have shown that the single Co layer added on graphene show ferromagnetic ordering with perpendicular alignment to the graphene sheet. In the presence of spin-orbit coupling, a spin-polarization degree of about 92% was found for this quasi-two-dimensional magnetic system where it is shown a nearly half-metallic feature.

  5. Water Oxidation and Oxygen Monitoring by Cobalt-Modified Fluorine-Doped Tin Oxide Electrodes

    SciTech Connect

    Kent, CA; Concepcion, JJ; Dares, CJ; Torelli, DA; Rieth, AJ; Miller, AS; Hoertz, PG; Meyer, TJ

    2013-06-12

    Electrocatalytic water oxidation occurs at fluoride-doped tin oxide (FTO) electrodes that have been surface-modified by addition of Co(II). On the basis of X-ray photoelectron spectroscopy and transmission electron microscopy measurements, the active surface site appears to be a single site or small-molecule assembly bound as Co(II), with no evidence for cobalt oxide film or cluster formation. On the basis of cyclic voltammetry measurements, surface-bound Co(II) undergoes a pH-dependent 1e(-)/1H(+) oxidation to Co(III), which is followed by pH-dependent catalytic water oxidation. O-2 reduction at FTO occurs at -0.33 V vs NHE, allowing for in situ detection of oxygen as it is formed by water oxidation on the surface. Controlled-potential electrolysis at 1.61 V vs NHE at pH 7.2 resulted in sustained water oxidation catalysis at a current density of 0.16 mA/cm(2) with 29 000 turnovers per site over an electrolysis period of 2 h. The turnover frequency for oxygen production per Co site was 4 s(-1) at an overpotential of 800 mV at pH 7.2. Initial experiments with Co(II) on a mesoporous, high-surface-area nanoFTO electrode increased the current density by a factor of similar to 5

  6. Photo-catalytic Degradation and Sorption of Radio-cobalt from EDTA-Co Complexes Using Manganese Oxide Materials - 12220

    SciTech Connect

    Koivula, Risto; Harjula, Risto; Tusa, Esko

    2012-07-01

    The synthesised cryptomelane-type α-MnO{sub 2} was tested for its Co-57 uptake properties in UV-photo-reactor filled with 10 μM Co-EDTA solution with a background of 10 mM NaNO{sub 3}. High cobalt uptake of 96% was observed after 1 hour of UV irradiation. As for comparison, a well-known TiO{sub 2} (Degussa P25) was tested as reference material that showed about 92% cobalt uptake after six hours of irradiation in identical experiment conditions. It was also noted that the cobalt uptake on cryptomelane with out UV irradiation was modest, only about 10%. Decreasing the pH of the Co-EDTA solution had severe effects on the cobalt uptake mainly due to the rather high point of zero charge of the MnO{sub 2} surface (pzc at pH ∼4.5). Modifying the synthesis procedure we were able to produce a material that functioned well even in solution of pH 3 giving cobalt uptake of almost 99%. The known properties, catalytic and ion exchange, of manganese oxides were simultaneously used for the separation of EDTA complexed Co-57. Tunnel structured cryptomelane -type showed very fast and efficient Co uptake properties outperforming the well known and widely used Degussa P25 TiO{sub 2} in both counts. The layered structured manganese oxide, birnessite, reached also as high Co removal level as the reference material Degussa did but the reaction rate was considerably faster. Since the decontamination solutions are typically slightly acidic and the point of zero charge of the manganese oxides are rather high > pH 4.5 the material had to be modified. This modified material had tolerance to acidic solutions and it's Co uptake performance remained high in the solutions of lower pH (pH 3). Increasing the ion concentration of test solutions, background concentration, didn't affect the final Co uptake level; however, some changes in the uptake kinetics could be seen. The increase in EDTA/MoMO ratio was clearly reflected in the Co uptake curves. The obtained results of manganese oxide were

  7. High power density aqueous hybrid supercapacitor combining activated carbon and highly conductive spinel cobalt oxide

    NASA Astrophysics Data System (ADS)

    Godillot, G.; Taberna, P.-L.; Daffos, B.; Simon, P.; Delmas, C.; Guerlou-Demourgues, L.

    2016-11-01

    The remarkable electrochemical behavior of complete activated carbon/cobalt oxide cells is reported in the present work. Among the various weight ratios between the positive and negative electrodes evaluated, the best features are obtained with an overcapacitive cobalt oxide electrode. The energy densities obtained by this system (20 Wh kg-1 for a power density of 209 W kg-1) are twice higher than those measured for a activated carbon/activated carbon symmetric cell, in the same operating conditions. With discharge capacities around 62 F g-1, this system is among the best ones reported in the literature for this category.

  8. Catalytic Decomposition of N2O at Low Temperature by Reduced Cobalt Oxides.

    PubMed

    Eom, Won-Hyun; Ayoub, Muhammad; Yoo, Kyung-Seun

    2016-05-01

    Various forms of cobalt oxide (Co3O4 and C0203) were subsequently prepared and tested for decomposition of N2O at low temperature in a fix bed differential reactor at steady state conditions. These different types of oxides were prepared by precipitation method (PM) and by calcination of commercially available CoCO3. Commercially available cobalt oxides C03O4 and C02O3 were also tested for N2O decomposition at different temperatures. All types of prepared and commercially available cobalt oxide were found inactive for N2O decomposition in the presence of oxygen at temperature less than 300 degrees C. Similar unsatisfactory results were found at low temperature N2O decomposition after impregnation of alkali metal (10% Na) and alkaline earth metal (10% Ba) over Co3O4. These catalysts were then reduced under reduction media (H2 gas). It was found that after reduction cobalt oxide catalysts became active for N2O decomposition for short time in the presence of oxygen at low temperature. The reduced form of Co3O4 catalyst showed enormous efficiency i.e., 98% at temperature (300 degrees C) under the same conditions. From results it seems that Co3O4 itself is not active for N2O decomposition but its reduced form is highly active for this reaction due to oxidation state change of C03O4 during reduction process. PMID:27483805

  9. Catalytic Decomposition of N2O at Low Temperature by Reduced Cobalt Oxides.

    PubMed

    Eom, Won-Hyun; Ayoub, Muhammad; Yoo, Kyung-Seun

    2016-05-01

    Various forms of cobalt oxide (Co3O4 and C0203) were subsequently prepared and tested for decomposition of N2O at low temperature in a fix bed differential reactor at steady state conditions. These different types of oxides were prepared by precipitation method (PM) and by calcination of commercially available CoCO3. Commercially available cobalt oxides C03O4 and C02O3 were also tested for N2O decomposition at different temperatures. All types of prepared and commercially available cobalt oxide were found inactive for N2O decomposition in the presence of oxygen at temperature less than 300 degrees C. Similar unsatisfactory results were found at low temperature N2O decomposition after impregnation of alkali metal (10% Na) and alkaline earth metal (10% Ba) over Co3O4. These catalysts were then reduced under reduction media (H2 gas). It was found that after reduction cobalt oxide catalysts became active for N2O decomposition for short time in the presence of oxygen at low temperature. The reduced form of Co3O4 catalyst showed enormous efficiency i.e., 98% at temperature (300 degrees C) under the same conditions. From results it seems that Co3O4 itself is not active for N2O decomposition but its reduced form is highly active for this reaction due to oxidation state change of C03O4 during reduction process.

  10. Electrodeposited reduced-graphene oxide/cobalt oxide electrodes for charge storage applications

    NASA Astrophysics Data System (ADS)

    García-Gómez, A.; Eugénio, S.; Duarte, R. G.; Silva, T. M.; Carmezim, M. J.; Montemor, M. F.

    2016-09-01

    In the present work, electrochemically reduced-graphene oxide/cobalt oxide composites for charge storage electrodes were prepared by a one-step pulsed electrodeposition route on stainless steel current collectors and after that submitted to a thermal treatment at 200 °C. A detailed physico-chemical characterization was performed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Raman spectroscopy. The electrochemical response of the composite electrodes was studied by cyclic voltammetry and charge-discharge curves and related to the morphological and phase composition changes induced by the thermal treatment. The results revealed that the composites were promising materials for charge storage electrodes for application in redox supercapacitors, attaining specific capacitances around 430 F g-1 at 1 A g-1 and presenting long-term cycling stability.

  11. Catalytic Aerobic Dehydrogenation of Nitrogen Heterocycles Using Heterogeneous Cobalt Oxide Supported on Nitrogen-Doped Carbon.

    PubMed

    Iosub, Andrei V; Stahl, Shannon S

    2015-09-18

    Dehydrogenation of (partially) saturated heterocycles provides an important route to heteroaromatic compounds. A heterogeneous cobalt oxide catalyst, previously employed for aerobic oxidation of alcohols and amines, is shown to be effective for aerobic dehydrogenation of various 1,2,3,4-tetrahydroquinolines to the corresponding quinolines. The reactions proceed in good yields under mild conditions. Other N-heterocycles are also successfully oxidized to their aromatic counterparts.

  12. A Bioinspired Molecular Polyoxometalate Catalyst with Two Cobalt(II) Oxide Cores for Photocatalytic Water Oxidation.

    PubMed

    Wei, Jie; Feng, Yingying; Zhou, Panpan; Liu, Yan; Xu, Jingyin; Xiang, Rui; Ding, Yong; Zhao, Chongchao; Fan, Linyuan; Hu, Changwen

    2015-08-24

    To overcome the bottleneck of water splitting, the exploration of efficient, selective, and stable water oxidation catalysts (WOCs) is crucial. We report an all-inorganic, oxidatively and hydrolytically stable WOC based on a polyoxometalate [(A-α-SiW9 O34)2Co8(OH)6(H2O)2(CO3)3](16-) (Co8 POM). As a cobalt(II)-based cubane water oxidation catalyst, Co8POM embeds double Co(II)4O3 cores. The self-assembled catalyst is similar to the oxygen evolving complex (OEC) of photosystem II (PS II). Using [Ru(bpy)3](2+) as a photosensitizer and persulfate as a sacrificial electron acceptor, Co8POM exhibits excellent water oxidation activity with a turnover number (TON) of 1436, currently the highest among bioinspired catalysts with a cubical core, and a high initial turnover frequency (TOF). Investigation by several spectroscopy, spectrometry, and other techniques confirm that Co8POM is a stable and efficient catalyst for visible light-driven water oxidation. The results offer a useful insight into the design of water oxidation catalysts.

  13. Marine cobalt resources.

    PubMed

    Manheim, F T

    1986-05-01

    Ferromanganese oxides in the open oceans are more enriched in cobalt than any other widely distributed sediments or rocks. Concentrations of cobalt exceed 1 percent in ferromanganese crusts on seamounts, ocean ridges, and other raised areas of the ocean. The cobaltrich crusts may be the slowest growing of any earth material, accumulating one molecular layer every 1 to 3 months. Attention has been drawn to crusts as potential resources because they contain cobalt, manganese, and platinum, three of the four priority strategic metals for the United States. Moreover, unlike abyssal nodules, whose recovery is complicated by their dominant location in international waters, some of the most cobalt-rich crusts occur within the exclusive economic zone of the United States and other nations. Environmental impact statements for crust exploitation are under current development by the Department of the Interior. PMID:17781410

  14. Marine cobalt resources.

    PubMed

    Manheim, F T

    1986-05-01

    Ferromanganese oxides in the open oceans are more enriched in cobalt than any other widely distributed sediments or rocks. Concentrations of cobalt exceed 1 percent in ferromanganese crusts on seamounts, ocean ridges, and other raised areas of the ocean. The cobaltrich crusts may be the slowest growing of any earth material, accumulating one molecular layer every 1 to 3 months. Attention has been drawn to crusts as potential resources because they contain cobalt, manganese, and platinum, three of the four priority strategic metals for the United States. Moreover, unlike abyssal nodules, whose recovery is complicated by their dominant location in international waters, some of the most cobalt-rich crusts occur within the exclusive economic zone of the United States and other nations. Environmental impact statements for crust exploitation are under current development by the Department of the Interior.

  15. Hierarchical cobalt-based hydroxide microspheres for water oxidation.

    PubMed

    Zhang, Ye; Cui, Bai; Derr, Olivia; Yao, Zhibo; Qin, Zhaotong; Deng, Xiangyun; Li, Jianbao; Lin, Hong

    2014-03-21

    3D hierarchical cobalt hydroxide carbonate hydrate (Co(CO3)0.5(OH)·0.11H2O) has been synthesized featuring a hollow urchin-like structure by a one-step hydrothermal method at modest temperature on FTO glass substrates. The functionalities of precursor surfactants were isolated and analyzed. A plausible formation mechanism of the spherical urchin-like microclusters has been furnished through time-dependent investigations. Introduction of other transitional metal doping (Cu, Ni) would give rise to a substantial morphological change associated with a surface area drop. The directly grown cobalt-based hydroxide composite electrodes were found to be capable of catalyzing oxygen evolution reaction (OER) under both neutral pH and alkaline conditions. The favorable 3D dendritic morphology and porous structure provide large surface areas and possible defect sites that are likely responsible for their robust electrochemical activity.

  16. Effect of Co/Ni ratios in cobalt nickel mixed oxide catalysts on methane combustion

    SciTech Connect

    Lim, Tae Hwan; Cho, Sung June; Yang, Hee Sung; Engelhard, Mark H.; Kim, Do Heui

    2015-07-31

    A series of cobalt nickel mixed oxide catalysts with the varying ratios of Co to Ni, prepared by co-precipitation method, were applied to methane combustion. Among the various ratios, cobalt nickel mixed oxides having the ratios of Co to Ni of (50:50) and (67:33) demonstrate the highest activity for methane combustion. Structural analysis obtained from X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) evidently demonstrates that CoNi (50:50) and (67:33) samples consist of NiCo2O4and NiO phase and, more importantly, NiCo2O4spinel structure is largely distorted, which is attributed to the insertion of Ni2+ions into octahedral sites in Co3O4spinel structure. Such structural dis-order results in the enhanced portion of surface oxygen species, thus leading to the improved reducibility of the catalysts in the low temperature region as evidenced by temperature programmed reduction by hydrogen (H2TPR) and X-ray photoelectron spectroscopy (XPS) O 1s results. They prove that structural disorder in cobalt nickel mixed oxides enhances the catalytic performance for methane combustion. Thus, it is concluded that a strong relationship between structural property and activity in cobalt nickel mixed oxide for methane combustion exists and, more importantly, distorted NiCo2O4spinel structure is found to be an active site for methane combustion.

  17. Cobalt carbonate/ and cobalt oxide/graphene aerogel composite anodes for high performance Li-ion batteries.

    PubMed

    Garakani, Mohammad Akbari; Abouali, Sara; Zhang, Biao; Takagi, Curtis Alton; Xu, Zheng-Long; Huang, Jian-qiu; Huang, Jiaqiang; Kim, Jang-Kyo

    2014-11-12

    Nanocomposites consisting of ultrafine, cobalt carbonate nanoneedles and 3D porous graphene aerogel (CoCO3/GA) are in situ synthesized based on a one-step hydrothermal route followed by freeze-drying. A further heat treatment produces cobalt oxide nanoparticles embedded in the conductive GA matrix (Co(3)O(4)/GA). Both the composite anodes deliver excellent specific capacities depending on current density employed: the CoCO(3)/GA anode outperforms the Co(3)O(4)/GA anode at low current densities, and vice versa at current densities higher than 500 mA g(-1). Their electrochemical performances are considered among the best of similar composite anodes consisting of CoCO(3) or Co(3)O(4) active particles embedded in a graphene substrate. The stable multistep electrochemical reactions of the carbonate compound with a unique nanoneedle structure contribute to the excellent cyclic stability of the CoCO(3)/GA electrode, whereas the highly conductive networks along with low charge transfer resistance are responsible for the high rate performance of the Co(3)O(4)/GA electrode.

  18. Cobalt(II) Oxidation by the Marine Manganese(II)-Oxidizing Bacillus sp. Strain SG-1

    PubMed Central

    Lee, Yoon; Tebo, Bradley M.

    1994-01-01

    The geochemical cycling of cobalt (Co) has often been considered to be controlled by the scavenging and oxidation of Co(II) on the surface of manganese [Mn(III,IV)] oxides or manganates. Because Mn(II) oxidation in the environment is often catalyzed by bacteria, we have investigated the ability of Mn(II)-oxidizing bacteria to bind and oxidize Co(II) in the absence of Mn(II) to determine whether some Mn(II)-oxidizing bacteria also oxidize Co(II) independently of Mn oxidation. We used the marine Bacillus sp. strain SG-1, which produces mature spores that oxidize Mn(II), apparently due to a protein in their spore coats (R.A. Rosson and K. H. Nealson, J. Bacteriol. 151:1027-1034, 1982; J. P. M. de Vrind et al., Appl. Environ. Microbiol. 52:1096-1100, 1986). A method to measure Co(II) oxidation using radioactive 57Co as a tracer and treatments with nonradioactive (cold) Co(II) and ascorbate to discriminate bound Co from oxidized Co was developed. SG-1 spores were found to oxidize Co(II) over a wide range of pH, temperature, and Co(II) concentration. Leucoberbelin blue, a reagent that reacts with Mn(III,IV) oxides forming a blue color, was found to also react with Co(III) oxides and was used to verify the presence of oxidized Co in the absence of added Mn(II). Co(II) oxidation occurred optimally around pH 8 and between 55 and 65°C. SG-1 spores oxidized Co(II) at all Co(II) concentrations tested from the trace levels found in seawater to 100 mM. Co(II) oxidation was found to follow Michaelis-Menten kinetics. An Eadie-Hofstee plot of the data suggests that SG-1 spores have two oxidation systems, a high-affinity-low-rate system (Km, 3.3 × 10-8 M; Vmax, 1.7 × 10-15 M · spore-1 · h-1) and a low-affinity-high-rate system (Km, 5.2 × 10-6 M; Vmax, 8.9 × 10-15 M · spore-1 · h-1). SG-1 spores did not oxidize Co(II) in the absence of oxygen, also indicating that oxidation was not due to abiological Co(II) oxidation on the surface of preformed Mn(III,IV) oxides. These

  19. Adsorption of cobalt ferrite nanoparticles within layer-by-layer films: a kinetic study carried out using quartz crystal microbalance.

    PubMed

    Alcantara, Gustavo B; Paterno, Leonardo G; Afonso, André S; Faria, Ronaldo C; Pereira-da-Silva, Marcelo A; Morais, Paulo C; Soler, Maria A G

    2011-12-28

    The paper reports on the successful use of the quartz crystal microbalance technique to assess accurate kinetics and equilibrium parameters regarding the investigation of in situ adsorption of nanosized cobalt ferrite particles (CoFe(2)O(4)--10.5 nm-diameter) onto two different surfaces. Firstly, a single layer of nanoparticles was deposited onto the surface provided by the gold-coated quartz resonator functionalized with sodium 3-mercapto propanesulfonate (3-MPS). Secondly, the layer-by-layer (LbL) technique was used to build multilayers in which the CoFe(2)O(4) nanoparticle-based layer alternates with the sodium sulfonated polystyrene (PSS) layer. The adsorption experiments were conducted by modulating the number of adsorbed CoFe(2)O(4)/PSS bilayers (n) and/or by changing the CoFe(2)O(4) nanoparticle concentration while suspended as a stable colloidal dispersion. Adsorption of CoFe(2)O(4) nanoparticles onto the 3-MPS-functionalized surface follows perfectly a first order kinetic process in a wide range (two orders of magnitude) of nanoparticle concentrations. These data were used to assess the equilibrium constant and the adsorption free energy. Alternatively, the Langmuir adsorption constant was obtained while analyzing the isotherm data at the equilibrium. Adsorption of CoFe(2)O(4) nanoparticles while growing multilayers of CoFe(2)O(4)/PSS was conducted using colloidal suspensions with CoFe(2)O(4) concentration in the range of 10(-8) to 10(-6) (moles of cobalt ferrite per litre) and for different numbers of cycles n = 1, 3, 5, and 10. We found the adsorption of CoFe(2)O(4) nanoparticles within the CoFe(2)O(4)/PSS bilayers perfectly following a first order kinetic process, with the characteristic rate constant growing with the increase of CoFe(2)O(4) nanoparticle concentration and decreasing with the rise of the number of LbL cycles (n). Additionally, atomic force microscopy was employed for assessing the LbL film roughness and thickness. We found the film

  20. Atomic layer deposition of cobalt carbide films and their magnetic properties using propanol as a reducing agent

    NASA Astrophysics Data System (ADS)

    Sarr, Mouhamadou; Bahlawane, Naoufal; Arl, Didier; Dossot, Manuel; McRae, Edward; Lenoble, Damien

    2016-08-01

    The investigation of highly conformal thin films using Atomic Layer Deposition (ALD) is driven by a variety of applications in modern technologies. In particular, the emergence of 3D memory device architectures requires conformal materials with tuneable magnetic properties. Here, nanocomposites of carbon, cobalt and cobalt carbide are deposited by ALD using cobalt acetylacetonate with propanol as a reducing agent. Films were grown by varying the ALD deposition parameters including deposition temperature and propanol exposure time. The morphology, the chemical composition and the crystalline structure of the cobalt carbide film were investigated. Vibrating Sample Magnetometer (VSM) measurements revealed magnetic hysteresis loops with a coercivity reaching 500 Oe and a maximal saturation magnetization of 0.9 T with a grain size less than 15 nm. Magnetic properties are shown to be tuneable by adjusting the deposition parameters that significantly affect the microstructure and the composition of the deposited films.

  1. Platinum-induced structural collapse in layered oxide polycrystalline films

    SciTech Connect

    Wang, Jianlin; Liu, Changhui; Huang, Haoliang; Fu, Zhengping; Peng, Ranran E-mail: yllu@ustc.edu.cn; Zhai, Xiaofang; Lu, Yalin E-mail: yllu@ustc.edu.cn

    2015-03-30

    Effect of a platinum bottom electrode on the SrBi{sub 5}Fe{sub 1−x}Co{sub x}Ti{sub 4}O{sub 18} layered oxide polycrystalline films was systematically studied. The doped cobalt ions react with the platinum to form a secondary phase of PtCoO{sub 2}, which has a typical Delafossite structure with a weak antiferromagnetism and an exceptionally high in-plane electrical conductivity. Formation of PtCoO{sub 2} at the interface partially consumes the cobalt dopant and leads to the structural collapsing from 5 to 4 layers, which was confirmed by X-ray diffraction and high resolution transmission electron microscopy measurements. Considering the weak magnetic contribution from PtCoO{sub 2}, the observed ferromagnetism should be intrinsic of the Aurivillius compounds. Ferroelectric properties were also indicated by the piezoresponse force microscopy. In this work, the platinum induced secondary phase at the interface was observed, which has a strong impact on Aurivillius structural configuration and thus the ferromagnetic and ferroelectric properties.

  2. Phase equilibria in the iron oxide-cobalt oxide-phosphorus oxide system

    NASA Technical Reports Server (NTRS)

    De Guire, Mark R.; Prasanna, T. R. S.; Kalonji, Gretchen; O'Handley, Robert C.

    1987-01-01

    Two novel ternary compounds are noted in the present study of 1000 C solid-state equilibria in the Fe-Co-P-O system's Fe2O3-FePO4-Co3(Po4)2-CoO region: CoFe(PO4)O, which undergoes incongruent melting at 1130 C, and Co3Fe4(PO4)6, whose incongruent melting occurs at 1080 C. The liquidus behavior-related consequences of rapidly solidified cobalt ferrite formation from cobalt ferrite-phosphate melts are discussed with a view to spinel formation. It is suggested that quenching from within the spinel-plus-liquid region may furnish an alternative to quenching a homogeneous melt.

  3. Stability of phosphonic self assembled monolayers (SAMs) on cobalt chromium (Co-Cr) alloy under oxidative conditions

    NASA Astrophysics Data System (ADS)

    Bhure, Rahul; Abdel-Fattah, Tarek M.; Bonner, Carl; Hall, Felicia; Mahapatro, Anil

    2011-04-01

    Cobalt chromium (Co-Cr) alloys have been widely used in the biomedical arena for cardiovascular, orthopedic and dental applications. Surface modification of the alloy allows us to tailor the interfacial properties to address critical challenges of Co-Cr alloy in medical applications. Self assembled monolayers (SAMs) of Octadecylphosphonic acid (ODPA) have been used to form thin films on the oxide layer of the Co-Cr alloy surface by solution deposition technique. The SAMs formed were investigated for their stability to oxidative conditions of ambient laboratory environment over periods of 1, 3, 7 and 14 days. The samples were then characterized for their stability using X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and contact angle measurements. Detailed high energy XPS elemental scans confirmed the presence of the phosphonic monolayer after oxidative exposure which suggested that the SAMs were firmly attached to the oxide layer of Co-Cr alloy. AFM images gave topographical data of the surface and showed islands of SAMs on Co-Cr alloy surface, before and after SAM formation and also over the duration of the oxidative exposure. Contact angle measurements confirmed the hydrophobicity of the surface over 14 days. Thus the SAMs were found to be stable for the duration of the study. These SAMs could be subsequently tailored by modifying the terminal functional groups and could be used for various potential biomedical applications such as drug delivery, biocompatibility and tissue integration.

  4. Effect of current stress during thermal CVD of multilayer graphene on cobalt catalytic layer

    NASA Astrophysics Data System (ADS)

    Ueno, Kazuyoshi; Ichikawa, Hiroyasu; Uchida, Takaki

    2016-04-01

    To improve the crystallinity of multilayer graphene (MLG) by CVD at a low temperature, the effect of current stress during thermal CVD on a cobalt (Co) catalytic layer was investigated. The crystallinity of MLG obtained by CVD with current was higher than that without current at the same temperature. This indicates that current has effects besides the Joule heating effect. The current effects on the Co catalytic layer and the MLG growth reaction were investigated, and it was found that current had small effects on the grain size and crystal structure of the Co catalyst and large effects on the MLG growth reaction such as large grain growth and a low activation energy of 0.49 eV, which is close to the value reported for carbon surface diffusion on Co. It is considered that the enhancement of MLG growth reaction by current leads to the improved crystallinity of MLG at a relatively low temperature.

  5. Cobalt (hydro)oxide electrodes under electrochemical conditions: a first principle study

    NASA Astrophysics Data System (ADS)

    Chen, Jia; Selloni, Annabella

    2013-03-01

    There is currently much interest in photoelectrochemical water splitting as a promising pathway towards sustainable energy production. A major issue of such photoelectrochemical devices is the limited efficiency of the anode, where the oxygen evolution reaction (OER) takes place. Cobalt (hydro)oxides, particularly Co3O4 and Co(OH)2, have emerged as promising candidates for use as OER anode materials. Interestingly, recent in-situ Raman spectroscopy studies have shown that Co3O4 electrodes undergo progressive oxidation and transform into oxyhydroxide, CoO(OH), under electrochemical working conditions. (Journal of the American Chemical Society 133, 5587 (2011))Using first principle electronic structure calculations, we provide insight into these findings by presenting results on the structural, thermodynamic, and electronic properties of cobalt oxide, hydroxide and oxydroxide CoO(OH), and on their relative stabilities when in contact with water under external voltage.

  6. Kagóme Cobalt(II)-Organic Layers as Robust Scaffolds for Highly Efficient Photocatalytic Oxygen Evolution.

    PubMed

    Xu, Jiaheng; Wang, Zhi; Yu, Wenguang; Sun, Di; Zhang, Qing; Tung, Chen-Ho; Wang, Wenguang

    2016-05-23

    Two Kagóme cobalt(II)-organic layers of [Co3 (μ3 -OH)2 (bdc)2 ]n (1) and [Co3 (μ3 -OH)2 (chdc)2 ]n (2) (bdc=o-benzenedicarboxylate and chdc=1,2-cyclohexanedicarboxylate) that bear bridging OH(-) ligands were explored as water oxidation catalysts (WOCs) for photocatalytic O2 production. The activities of 1 and 2 towards H2 O oxidation were assessed by monitoring the in situ O2 concentration versus time in the reaction medium by utilizing a Clark-type oxygen electrode under photochemical conditions. The oxygen evolution rate (RO2 ) was 24.3 μmol s(-1)  g(-1) for 1 and 48.8 μmol s(-1)  g(-1) for 2 at pH 8.0. Photocatalytic reaction studies show that 1 and 2 exhibit enhanced activities toward the oxidation of water compared to commercial nanosized Co3 O4 . In scaled-up photoreactions, the pH value of the reaction medium decreased from 8.0 to around 7.0 after 20 min and the O2 production ceased. Based on the amounts of the sacrificial oxidant (K2 S2 O8 ) used, the yield of O2 produced is 49.6 % for 2 and 29.8 % for 1. However, the catalyst can be recycled without a significant loss of catalytic activity. Spectroscopic studies suggest that the structure and composition of recycled 1 and 2 are maintained. In isotope-labeling H2 (18) O (97 % enriched) experiments, the distribution of (16) O(16) O/(16) O(18) O/(18) O(18) O detected was 0:7.55:92.45, which is comparable to the theoretical values of 0.09:5.82:94.09. This work not only provides new catalysts that resemble ligand-protected cobalt oxide materials but also establishes the significance of the existence of OH(-) (or H2 O) binding sites at the metal center in WOCs.

  7. Kagóme Cobalt(II)-Organic Layers as Robust Scaffolds for Highly Efficient Photocatalytic Oxygen Evolution.

    PubMed

    Xu, Jiaheng; Wang, Zhi; Yu, Wenguang; Sun, Di; Zhang, Qing; Tung, Chen-Ho; Wang, Wenguang

    2016-05-23

    Two Kagóme cobalt(II)-organic layers of [Co3 (μ3 -OH)2 (bdc)2 ]n (1) and [Co3 (μ3 -OH)2 (chdc)2 ]n (2) (bdc=o-benzenedicarboxylate and chdc=1,2-cyclohexanedicarboxylate) that bear bridging OH(-) ligands were explored as water oxidation catalysts (WOCs) for photocatalytic O2 production. The activities of 1 and 2 towards H2 O oxidation were assessed by monitoring the in situ O2 concentration versus time in the reaction medium by utilizing a Clark-type oxygen electrode under photochemical conditions. The oxygen evolution rate (RO2 ) was 24.3 μmol s(-1)  g(-1) for 1 and 48.8 μmol s(-1)  g(-1) for 2 at pH 8.0. Photocatalytic reaction studies show that 1 and 2 exhibit enhanced activities toward the oxidation of water compared to commercial nanosized Co3 O4 . In scaled-up photoreactions, the pH value of the reaction medium decreased from 8.0 to around 7.0 after 20 min and the O2 production ceased. Based on the amounts of the sacrificial oxidant (K2 S2 O8 ) used, the yield of O2 produced is 49.6 % for 2 and 29.8 % for 1. However, the catalyst can be recycled without a significant loss of catalytic activity. Spectroscopic studies suggest that the structure and composition of recycled 1 and 2 are maintained. In isotope-labeling H2 (18) O (97 % enriched) experiments, the distribution of (16) O(16) O/(16) O(18) O/(18) O(18) O detected was 0:7.55:92.45, which is comparable to the theoretical values of 0.09:5.82:94.09. This work not only provides new catalysts that resemble ligand-protected cobalt oxide materials but also establishes the significance of the existence of OH(-) (or H2 O) binding sites at the metal center in WOCs. PMID:27098180

  8. Some new aspects of low-temperature lithium cobalt oxides prepared through citric acid precursor route

    SciTech Connect

    Adhikary, K.; Takahashi, Masao; Kikkawa, Shinichi

    1998-12-01

    Low-temperature (LT) lithium cobalt oxides were prepared at 300 C by the solid-state reaction between Li{sub 2}CO{sub 3} and Co{sub 3}O{sub 4}, having various starting compositions Li{sub 1+x}CoO{sub 2} with x = {minus}0.2, 0.0, 0.2, and 0.4. A finely mixed precursor of the reacting compounds was obtained in molten citric acid. The morphology observed by scanning electron microscopy (SEM) showed the homogeneous observed by scanning electron microscopy (SEM) showed the homogeneous and fluffy nature of the specimens, with a BET specific surface as high as 19 m{sup 2}g{sup {minus}1}. The cubic crystal lattice was found to decrease from a = 7.990 to 7.984 {angstrom} against Li/Co = 0.62 to 0.90 in molar ratio of the water-leached products. The resistivity and open circuit voltage (OCV) against lithium metal were found to be sensitive to the initial lithium content of the samples. Chemical titration showed that all of the samples contained an appreciable amount of Co{sup 2+} in addition to trivalent cobalt. XANES spectra supported the presence of tetrahedrally coordinated divalent cobalt. A model is proposed in which oxidation of divalent cobalt explains the electrochemical charge-discharge irreversibility in the initial cycle.

  9. Electrocatalytic Properties of Nanocrystalline Calcium-Doped Lanthanum Cobalt Oxide for Bifunctional Oxygen Electrodes

    SciTech Connect

    Malkhandi, S; Yang, B; Manohar, AK; Manivannan, A; Prakash, GKS; Narayanan, SR

    2012-04-19

    Calcium-doped lanthanum cobalt oxide is a promising electrocatalyst for oxygen evolution and oxygen reduction in rechargeable metal air batteries and water electrolyzers operating with alkaline electrolyte. Nanocrystalline perovskite of composition La0.6Ca0.4CoO3 with a unique cellular internal structure was prepared at 350 degrees C and then annealed in air at progressively higher temperatures in the range of 600-750 degrees C. The samples were characterized by electrochemical techniques and X-ray photoelectron spectroscopy. The area-specific electrocatalytic activity for oxygen evolution/oxygen reduction, the oxidation state of cobalt, and the crystallite size increased with annealing temperature, while the Tafel slope remained constant. These trends provide new insights into the role of the cobalt center in oxygen evolution and oxygen reduction, and how preparation conditions can be altered to tune the activity of the cobalt center for electrocatalysis. We expect these findings to guide the design of electrocatalysts for bifunctional oxygen electrodes, in general.

  10. Cobalt-phosphate-assisted photoelectrochemical water oxidation by arrays of molybdenum-doped zinc oxide nanorods.

    PubMed

    Lin, Yan-Gu; Hsu, Yu-Kuei; Chen, Ying-Chu; Lee, Bing-Wei; Hwang, Jih-Shang; Chen, Li-Chyong; Chen, Kuei-Hsien

    2014-09-01

    We report the first demonstration of cobalt phosphate (Co-Pi)-assisted molybdenum-doped zinc oxide nanorods (Zn(1-x)Mo(x)O NRs) as visible-light-sensitive photofunctional electrodes to fundamentally improve the performance of ZnO NRs for photoelectrochemical (PEC) water splitting. A maximum photoconversion efficiency as high as 1.05% was achieved, at a photocurrent density of 1.4 mA cm(-2). More importantly, in addition to achieve the maximum incident photon to current conversion efficiency (IPCE) value of 86%, it could be noted that the IPCE of Zn(1-x)Mo(x)O photoanodes under monochromatic illumination (450 nm) is up to 12%. Our PEC performances are comparable to those of many oxide-based photoanodes in recent reports. The improvement in photoactivity of PEC water splitting may be attributed to the enhanced visible-light absorption, increased charge-carrier densities, and improved interfacial charge-transfer kinetics due to the combined effect of molybdenum incorporation and Co-Pi modification, contributing to photocatalysis. The new design of constructing highly photoactive Co-Pi-assisted Zn(1-x)Mo(x)O photoanodes enriches knowledge on doping and advances the development of high-efficiency photoelectrodes in the solar-hydrogen field.

  11. Facile synthesis of cobalt oxide/reduced graphene oxide composites for electrochemical capacitor and sensor applications

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi Toan; Nguyen, Van Hoa; Deivasigamani, Ranjith Kumar; Kharismadewi, Dian; Iwai, Yoshio; Shim, Jae-Jin

    2016-03-01

    Reduced graphene oxide sheets decorated with cobalt oxide nanoparticles (Co3O4/rGO) were produced using a hydrothermal method without surfactants. Both the reduction of GO and the formation of Co3O4 nanoparticles occurred simultaneously under this condition. At the same current density of 0.5 A g-1, the Co3O4/rGO nanocomposites exhibited much a higher specific capacitance (545 F g-1) than that of bare Co3O4 (100 F g-1). On the other hand, for the detection of H2O2, the peak current of Co3O4/rGO was 4 times higher than that of Co3O4. Moreover, the resulting composite displayed a low detection limit of 0.62 μM and a high sensitivity of 28,500 μA mM-1cm-2 for the H2O2 sensor. These results suggest that the Co3O4/rGO nanocomposite is a promising material for both supercapacitor and non-enzymatic H2O2 sensor applications.

  12. Superconductive articles including cerium oxide layer

    DOEpatents

    Wu, Xin D.; Muenchausen, Ross E.

    1993-01-01

    A ceramic superconductor comprising a metal oxide substrate, a ceramic high temperature superconductive material, and a intermediate layer of a material having a cubic crystal structure, said layer situated between the substrate and the superconductive material is provided, and a structure for supporting a ceramic superconducting material is provided, said structure comprising a metal oxide substrate, and a layer situated over the surface of the substrate to substantially inhibit interdiffusion between the substrate and a ceramic superconducting material deposited upon said structure.

  13. Controllable Cobalt Oxide/Au Hierarchically Nanostructured Electrode for Nonenzymatic Glucose Sensing.

    PubMed

    Su, Yingying; Luo, Binbin; Zhang, Jin Zhong

    2016-02-01

    By electrodeposition and galvanic replacement reaction, we developed a facile, time-saving, cost-effective, and environmentally friendly, two-step synthesis route to obtain a controllable cobalt oxide/Au hierarchically nanostructured electrode for glucose sensing. The nanomaterials were characterized by transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, energy-dispersive spectrometry, and X-ray photoelectron spectroscopy, meanwhile, the sensing performance was investigated by cyclic voltammetry and amperometric response. The results revealed that this novel electrode exhibited excellent electrocatalytic performance toward glucose oxidation, with a wide double-linear range from 0.2 μM to 20 mM and a low detection limit of 0.1 μM based on a signal-to-noise ratio of 3, which was mainly attributed to the ability of loading a small amount of Au with good electron conductivity on the surface of cobalt oxide nanosheets with large active surface area and synergistic electrocatalytic activity of Au and cobalt oxide toward glucose electrooxidation. This facile, sensitive, and selective glucose sensor is also proven to be suitable for the detection of glucose in human serum.

  14. Controllable Cobalt Oxide/Au Hierarchically Nanostructured Electrode for Nonenzymatic Glucose Sensing.

    PubMed

    Su, Yingying; Luo, Binbin; Zhang, Jin Zhong

    2016-02-01

    By electrodeposition and galvanic replacement reaction, we developed a facile, time-saving, cost-effective, and environmentally friendly, two-step synthesis route to obtain a controllable cobalt oxide/Au hierarchically nanostructured electrode for glucose sensing. The nanomaterials were characterized by transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, energy-dispersive spectrometry, and X-ray photoelectron spectroscopy, meanwhile, the sensing performance was investigated by cyclic voltammetry and amperometric response. The results revealed that this novel electrode exhibited excellent electrocatalytic performance toward glucose oxidation, with a wide double-linear range from 0.2 μM to 20 mM and a low detection limit of 0.1 μM based on a signal-to-noise ratio of 3, which was mainly attributed to the ability of loading a small amount of Au with good electron conductivity on the surface of cobalt oxide nanosheets with large active surface area and synergistic electrocatalytic activity of Au and cobalt oxide toward glucose electrooxidation. This facile, sensitive, and selective glucose sensor is also proven to be suitable for the detection of glucose in human serum. PMID:26745577

  15. Nanoporous gold supported cobalt oxide microelectrodes as high-performance electrochemical biosensors.

    PubMed

    Lang, Xing-You; Fu, Hong-Ying; Hou, Chao; Han, Gao-Feng; Yang, Ping; Liu, Yong-Bing; Jiang, Qing

    2013-01-01

    Tremendous demands for electrochemical biosensors with high sensitivity and reliability, fast response and excellent selectivity have stimulated intensive research on developing versatile materials with ultrahigh electrocatalytic activity. Here we report flexible and self-supported microelectrodes with a seamless solid/nanoporous gold/cobalt oxide hybrid structure for electrochemical nonenzymatic glucose biosensors. As a result of synergistic electrocatalytic activity of the gold skeleton and cobalt oxide nanoparticles towards glucose oxidation, amperometric glucose biosensors based on the hybrid microelectrodes exhibit multi-linear detection ranges with ultrahigh sensitivities at a low potential of 0.26 V (versus Ag/AgCl). The sensitivity up to 12.5 mA mM⁻¹ cm⁻² with a short response time of less than 1 s gives rise to ultralow detection limit of 5 nM. The outstanding performance originates from a novel nanoarchitecture in which the cobalt oxide nanoparticles are incorporated into pore channels of the seamless solid/nanoporous Au microwires, providing excellent electronic/ionic conductivity and mass transport for the enhanced electrocatalysis.

  16. Cobalt pivalate complex as a catalyst for liquid phase oxidation of n-hexane

    NASA Astrophysics Data System (ADS)

    Moskovskaya, I. F.; Maerle, A. A.; Shvydkiy, N. V.; Romanovsky, B. V.; Ivanova, I. I.

    2015-09-01

    Catalytic properties of cobalt(II) pivalate complex as both individual and supported on mesoporous molecular sieves Si-KIT-6, Al-KIT-6, and Ce-KIT-6 were investigated in liquid-phase oxidation of n-hexane with molecular oxygen. This complex was shown to be an active and selective catalyst for the oxidation of n-C6H14 into C1-C4 carboxylic acids. The activity of Co(II) pivalate remains practically unchanged on heterogenizing the complex on molecular sieve supports. At the same time, its selectivity and resistance towards an oxidative degradation are slightly increased.

  17. Controllable fabrication and magnetic properties of double-shell cobalt oxides hollow particles

    PubMed Central

    Zhang, Dan; Zhu, Jianyu; Zhang, Ning; Liu, Tao; Chen, Limiao; Liu, Xiaohe; Ma, Renzhi; Zhang, Haitao; Qiu, Guanzhou

    2015-01-01

    Double-shell cobalt monoxide (CoO) hollow particles were successfully synthesized by a facile and effective one-pot solution-based synthetic route. The inner architecture and outer structure of the double-shell CoO hollow particles could be readily created through controlling experimental parameters. A possible formation mechanism was proposed based on the experimental results. The current synthetic strategy has good prospects for the future production of other transition-metal oxides particles with hollow interior. Furthermore, double-shell cobalt oxide (Co3O4) hollow particles could also be obtained through calcinating corresponding CoO hollow particles. The magnetic measurements revealed double-shell CoO and Co3O4 hollow particles exhibit ferromagnetic and antiferromagnetic behaviour, respectively. PMID:25736824

  18. Adsorption of microbial esterases on Bacillus subtilis-templated cobalt oxide nanoparticles.

    PubMed

    Jang, Eunjin; Ryu, Bum Han; Shim, Hyun-Woo; Ju, Hansol; Kim, Dong-Wan; Kim, T Doohun

    2014-04-01

    Due to low diffusion rates and large surface areas, nanomaterials have received great interest as supporting materials for enzyme immobilization. Here, the preparation of a cobalt oxide nanoparticle using Bacillus subtilis as a biological template and use of the nanostructure for microbial esterase immobilization is described. Morphological features and size distributions were investigated using electron microscopy (EM) and dynamic light scattering (DLS). Catalytic properties of enzyme-coated nanostructures were investigated using 4-methylumbelliferyl acetate and p-nitrophenyl (PNP) acetate as model substrates. Enzyme-coated nanostructures were observed to retain ∼85% of the initial activity after 15 successive reaction cycles, and enzyme immobilization processes could be repeated four times without a loss of immobilization potential. The present work demonstrates that B. subtilis-templated cobalt oxide nanoparticles have the potential to be used as biocompatible immobilization materials, and are promising candidates for the preparation of effective nanobiocatalysts.

  19. Synthesis of cobalt stearate as oxidant additive for oxo-biodegradable polyethylene

    NASA Astrophysics Data System (ADS)

    Asriza, Ristika O.; Arcana, I. Made

    2015-09-01

    Cobalt stearate is an oxidant additives that can initiate a process of degradation in high density polyethylene (HDPE). To determine the effect of cobalt stearate in HDPE, oxo-biodegradable polyethylene film was given an irradiation with UV light or heating at various temperature. After given a heating, the FTIR spectra showed a new absorption peak at wave number 1712 cm-1 indicating the presence of carbonyl groups in polymers, whereas after irradiation with UV light is not visible the presence of this absorption peak. The increase concentration of cobalt stearate added in HDPE and the higher heating temperature, the intensity of the absorption peak of the carbonyl group increased. The increasing intensity of the carbonyl group absorption is caused the presence of damage in the film surface after heating, and this result is supported by analysis the surface properties of the film with using SEM. Biodegradation tests were performed on oxo-biodegradable polyethylene film which has been given heating or UV light with using activated sludge under optimal conditions the growth of microorganisms. After biodegradation, the maximum weight decreased by 23% in the oxo-biodegradable polyethylene film with a cobalt stearate concentration of 0.2% and after heating at a temperature of 75 °C for 10 days, and only 0.69% in the same film after irradiation UV light for 10 days. Based on the results above, cobalt stearate additive is more effective to initiate the oxidative degradation of HDPE when it is initiated by heating compared to irradiation with UV light.

  20. Calcium- and Cobalt-doped Yttrium Chromites as an Interconnect Material for Solid Oxide Fuel Cells

    SciTech Connect

    Yoon, Kyung J.; Cramer, Carolyn N.; Thomsen, Edwin C.; Coyle, Christopher A.; Coffey, Greg W.; Marina, Olga A.

    2010-04-23

    The structural, thermal and electrical characteristics of calcium- and cobalt-doped yttrium chromites were studied for a potential use as the interconnect material in high temperature solid oxide fuel cells (SOFCs) as well as other high temperature electrochemical and thermoelectric devices. The Y0.8Ca0.2Cr1-xCoxO3±δ (x=0, 0.1, 0.2, 0.3) compositions had single phase orthorhombic perovskite structures in the wide range of oxygen pressures. Sintering behavior was remarkably enhanced upon cobalt doping and densities 95% and 97% of theoretical density were obtained after sintering at 1300oC in air, when x was 0.2 and 0.3, respectively. The electrical conductivity in both oxidizing and reducing atmospheres was significantly improved with cobalt content, and values of 49 and 10 S/cm at 850oC and 55 and 14 S/cm at 950oC in air and forming gas, respectively, were reported for x=0.2. The conductivity increase was attributed to the charge carrier density increase upon cobalt substitution for chromium confirmed with Seebeck measurements. The thermal expansion coefficient (TEC) was increased with cobalt content and closely matched to that of an 8 mol% yttria-stabilized zirconia (YSZ) electrolyte for 0.1 ≤ x ≤ 0.2. The chemical compatibility between Y0.8Ca0.2Cr1-xCoxO3±δ and YSZ was evaluated firing the two at 1400oC and no reaction products were found if x value was kept lower than 0.2.

  1. Synthesis of cobalt stearate as oxidant additive for oxo-biodegradable polyethylene

    SciTech Connect

    Asriza, Ristika O.; Arcana, I Made

    2015-09-30

    Cobalt stearate is an oxidant additives that can initiate a process of degradation in high density polyethylene (HDPE). To determine the effect of cobalt stearate in HDPE, oxo-biodegradable polyethylene film was given an irradiation with UV light or heating at various temperature. After given a heating, the FTIR spectra showed a new absorption peak at wave number 1712 cm{sup −1} indicating the presence of carbonyl groups in polymers, whereas after irradiation with UV light is not visible the presence of this absorption peak. The increase concentration of cobalt stearate added in HDPE and the higher heating temperature, the intensity of the absorption peak of the carbonyl group increased. The increasing intensity of the carbonyl group absorption is caused the presence of damage in the film surface after heating, and this result is supported by analysis the surface properties of the film with using SEM. Biodegradation tests were performed on oxo-biodegradable polyethylene film which has been given heating or UV light with using activated sludge under optimal conditions the growth of microorganisms. After biodegradation, the maximum weight decreased by 23% in the oxo-biodegradable polyethylene film with a cobalt stearate concentration of 0.2% and after heating at a temperature of 75 °C for 10 days, and only 0.69% in the same film after irradiation UV light for 10 days. Based on the results above, cobalt stearate additive is more effective to initiate the oxidative degradation of HDPE when it is initiated by heating compared to irradiation with UV light.

  2. Oxidation behavior of nanostructured cobalt nickel chromium aluminum yttrium and nickel cobalt chromium aluminum yttrium sprayed by HVOF

    NASA Astrophysics Data System (ADS)

    Mercier, Dominic

    In recent years, much development has been made in the world of nanotechnologies. Hence, nanomaterials, which possess unique characteristics and excellent mechanical properties, are now being used in innovative and advanced applications. Despite the incredible potential of nanomaterials, their use is still at an embryonic stage as a result of the difficulty to mass-produce them. Among the potentially viable application remains the fabrication of nanostructured powders to produce high temperature oxidation resistance coatings. Nanostructured coatings were obtained by thermally spraying cryomilled CoNiCrAlY and NiCoCrAlY feedstock using the HVOF technique. It was found that the milling process used to prepare the powder significantly altered the microstructure of the alloy. In addition to achieving grain size refinement, significant aluminum segregation at grain boundaries was observed. Upon oxidation experiments up to 96 hours in static air at 1000°C an oxide scale composed of an adherent and dense alpha-Al2O3 inner layer with a top layer of fast growing oxides such as NiO, Cr2O3, CoAl2O4 and NiAl2O4 evolved from the coatings. It was found that the formation of a two-layer scale could be prevented through surface grinding prior to oxidation. Moreover, the comparison of the oxidation results of the powders and those of the coatings revealed that the spraying process has a considerable influence on the oxidation behavior of MCrAlYs attributable to the formation of oxide seeds during the spraying process.

  3. Synthesis of cobalt-containing mesoporous catalysts using the ultrasonic-assisted "pH-adjusting" method: Importance of cobalt species in styrene oxidation

    NASA Astrophysics Data System (ADS)

    Li, Baitao; Zhu, Yanrun; Jin, Xiaojing

    2015-01-01

    Cobalt-containing SBA-15 and MCM-41 (Co-SBA-15 and Co-MCM-41) mesoporous catalysts were prepared via ultrasonic-assisted "pH-adjusting" technique in this study. Their physiochemical structures were comprehensively characterized and correlated with catalytic activity in oxidation of styrene. The nature of cobalt species depended on the type of mesoporous silica as well as pH values. The different catalytic performance between Co-SBA-15 and Co-MCM-41 catalysts originated from cobalt species. Cobalt species were homogenously incorporated into the siliceous framework of Co-SBA-15 in single-site Co(II) state, while Co3O4 particles were loaded on Co-MCM-41 catalysts. The styrene oxidation tests showed that the single-site Co(II) state was more beneficial to the catalytic oxidation of styrene. The higher styrene conversion and benzaldehyde selectivity over Co-SBA-15 catalysts were mainly attributed to single-site Co(II) state incorporated into the framework of SBA-15. The highest conversion of styrene (34.7%) with benzaldehyde selectivity of 88.2% was obtained over Co-SBA-15 catalyst prepared at pH of 7.5, at the mole ratio of 1:1 (styrene to H2O2) at 70 °C.

  4. Structural and optical properties of cobalt slanted nanopillars conformally coated with few-layer graphene

    SciTech Connect

    Wilson, Peter M.; Lipatov, Alexey; Schmidt, Daniel; Schubert, Eva; Schubert, Mathias; Hofmann, Tino E-mail: thofmann@engr.unl.edu; Sinitskii, Alexander E-mail: thofmann@engr.unl.edu

    2015-06-08

    Optical characterization of anisotropic multicomponent nanostructures is generally not a trivial task, since the relation between a material's structural properties and its permittivity tensor is nonlinear. In this regard, an array of slanted cobalt nanopillars that are conformally coated with few-layer graphene is a particularly challenging object for optical characterization, as it has a complex anisotropic geometry and comprises several materials with different topologies and filling fractions. Normally, a detailed characterization of such complex nanostructures would require a combination of several microscopic and spectroscopic techniques. In this letter, we demonstrate that the important structural parameters of these graphene-coated sculptured thin films can be determined using a fast and simple generalized spectroscopic ellipsometry test combined with an anisotropic Bruggeman effective medium approximation. The graphene coverage as well as structural parameters of nanostructured thin films agree excellently with electron microscopy and Raman spectroscopy observations. The demonstrated optical approach may also be applied to the characterization of other nanostructured materials.

  5. Layer Control of WSe2 via Selective Surface Layer Oxidation.

    PubMed

    Li, Zhen; Yang, Sisi; Dhall, Rohan; Kosmowska, Ewa; Shi, Haotian; Chatzakis, Ioannis; Cronin, Stephen B

    2016-07-26

    We report Raman and photoluminescence spectra of mono- and few-layer WSe2 and MoSe2 taken before and after exposure to a remote oxygen plasma. For bilayer and trilayer WSe2, we observe an increase in the photoluminescence intensity and a blue shift of the photoluminescence peak positions after oxygen plasma treatment. The photoluminescence spectra of trilayer WSe2 exhibit features of a bilayer after oxygen plasma treatment. Bilayer WSe2 exhibits features of a monolayer, and the photoluminescence of monolayer WSe2 is completely absent after the oxygen plasma treatment. These changes are observed consistently in more than 20 flakes. The mechanism of the changes observed in the photoluminescence spectra of WSe2 is due to the selective oxidation of the topmost layer. As a result, N-layer WSe2 is reduced to N-1 layers. Raman spectra and AFM images taken from the WSe2 flakes before and after the oxygen treatment corroborate these findings. Because of the low kinetic energy of the oxygen radicals in the remote oxygen plasma, the oxidation is self-limiting. By varying the process duration from 1 to 10 min, we confirmed that the oxidation will only affect the topmost layer of the WSe2 flakes. X-ray photoelectron spectroscopy shows that the surface layer WOx of the sample can be removed by a quick dip in KOH solution. Therefore, this technique provides a promising way of controlling the thickness of WSe2 layer by layer. PMID:27391161

  6. Tuning of magnetic parameters in cobalt-polystyrene nanocomposites by reduction cycling

    SciTech Connect

    Nair, Swapna S.; Sunny, Vijutha; Anantharaman, M.R.

    2011-10-15

    Graphical abstract: Cobalt nanoparticles were prepared by a reduction process inside polymer pores. A porous polymer network (polystyrene) was chosen as the template for the synthesis of elementary cobalt as high surface area cobalt nanoparticles are prone to oxidation. The preliminary studies reveal that the cobalt is first formed with an oxide protective layer outside and upon repeating the reduction cycles, inner pores of the polymers are opened which enhanced the yield of metallic cobalt. These high surface area cobalt nanoparticles embedded in a polymer are ideal for the synthesis of carbon nanotubes as cobalt can act as a catalyst for the nanotube synthesis. The concentration of cobalt can be tuned in this technique by repeating the cycling process. Highlights: {yields} Elementary cobalt nanoparticles were synthesized inside polystyrene by a novel process. {yields} The self protection is achieved by the auto-shelling with the metal oxide. {yields} The magnetisation and coercivity could be tuned by repeating the cycles. {yields} Tuning of magnetic properties (both coercivity and magnetisation) could be achieved by the repetition of reduction cycles. {yields} Synthesized nanocomposite can act as a catalyst for carbon nanotube synthesis. -- Abstract: Cobalt nanoparticles were prepared by a reduction process inside polymer pores using CoSO{sub 4}.7H{sub 2}O and NaBH{sub 4}. A porous polymer network (sulphonated polystyrene) was chosen, as the template for the synthesis of elementary cobalt as high surface area cobalt nanoparticles are prone to oxidation. The preliminary studies reveal that the cobalt is first formed with an oxide protective layer outside and upon repeating the reduction cycles, inner pores of the polymers are opened which enhanced the yield of metallic cobalt. These high surface area cobalt nanoparticles embedded in a polymer are ideal for the synthesis of carbon nanotubes as cobalt can act as a catalyst for the nanotube synthesis. The

  7. High energy and power density asymmetric supercapacitors using electrospun cobalt oxide nanowire anode

    NASA Astrophysics Data System (ADS)

    Vidyadharan, Baiju; Aziz, Radhiyah Abd; Misnon, Izan Izwan; Anil Kumar, Gopinathan M.; Ismail, Jamil; Yusoff, Mashitah M.; Jose, Rajan

    2014-12-01

    Electrochemical materials are under rigorous search for building advanced energy storage devices. Herein, supercapacitive properties of highly crystalline and ultrathin cobalt oxide (Co3O4) nanowires (diameter ∼30-60 nm) synthesized using an aqueous polymeric solution based electrospinning process are reported. These nanowire electrodes show a specific capacitance (CS) of ∼1110 F g-1 in 6 M KOH at a current density of 1 A g-1 with coulombic efficiency ∼100%. Asymmetric supercapacitors (ASCs) (CS ∼175 F g-1 at 2 A g-1 galvanostatic cycling) are fabricated using the Co3O4 as anode and commercial activated carbon (AC) as cathode and compared their performance with symmetric electrochemical double layer capacitors (EDLCs) fabricated using AC (CS ∼31 F g-1 at 2 A g-1 galvanostatic cycling). The Co3O4//AC ASCs deliver specific energy densities (ES) of 47.6, 35.4, 20 and 8 Wh kg-1 at specific power densities (PS) 1392, 3500, 7000 and 7400 W kg-1, respectively. The performance of ASCs is much superior to the control EDLCs, which deliver ES of 9.2, 8.9, 8.4 and 6.8 Wh kg-1 at PS 358, 695, 1400 and 3500 W kg-1, respectively. The ASCs show nearly six times higher energy density (∼47.6 Wh kg-1) than EDLC (8.4 Wh kg-1) without compromising its power density (∼1400 W kg-1) at similar galvanostatic cycling conditions (2 A g-1).

  8. Ten-Year Comparison of Oxidized Zirconium and Cobalt-Chromium Femoral Components in Total Knee Arthroplasty

    PubMed Central

    Roe, Justin; Vioreanu, Mihai; Salmon, Lucy; Waller, Alison; Pinczewski, Leo

    2016-01-01

    Objective: The purpose of this study was to determine if oxidized zirconium femoral components had better outcomes than cobalt-chromium in vivo at medium and long term and if the use of oxidized zirconium components had clinical adverse effects. Methods: Forty consecutive patients (eighty knees) underwent simultaneous bilateral cruciate-retaining total knee arthroplasty for primary osteoarthritis from January 2002 to December 2003. For each patient, the knees were randomized to receive the oxidized zirconium femoral component, with the contralateral knee receiving the cobalt-chromium component. Outcome measures included the Western Ontario and McMaster Universities Osteoarthritis Index, Knee Injury and Osteoarthritis Outcome Score, Knee Society score, and British Orthopaedic Association patient satisfaction scale. Radiographic outcomes include the Knee Society total knee arthroplasty roentgenographic evaluation and scoring system and measurement of radiographic wear. Patients and assessors were blinded to the treatment groups and results. Results: There were no significant differences in clinical, subjective, and radiographic outcomes between the two implants at ten years postoperatively. Ten years following surgery, 36% of the patients preferred the cobalt-chromium knee compared with 11% who preferred the oxidized zirconium knee (p = 0.02) and 53% had no preference. Conclusions: Ten-year outcomes after total knee arthroplasty with oxidized zirconium and cobalt-chromium femoral components showed no significant differences in clinical, subjective, and radiographic outcomes. Patients had no preference or preferred the cobalt chromium prosthesis to the oxidized zirconium prosthesis. There were no adverse effects associated with the use of oxidized zirconium femoral implants.

  9. Mechanistic Investigations of Water Oxidation by a Molecular Cobalt Oxide Analogue: Evidence for a Highly Oxidized Intermediate and Exclusive Terminal Oxo Participation.

    PubMed

    Nguyen, Andy I; Ziegler, Micah S; Oña-Burgos, Pascual; Sturzbecher-Hohne, Manuel; Kim, Wooyul; Bellone, Donatela E; Tilley, T Don

    2015-10-14

    Artificial photosynthesis (AP) promises to replace society's dependence on fossil energy resources via conversion of sunlight into sustainable, carbon-neutral fuels. However, large-scale AP implementation remains impeded by a dearth of cheap, efficient catalysts for the oxygen evolution reaction (OER). Cobalt oxide materials can catalyze the OER and are potentially scalable due to the abundance of cobalt in the Earth's crust; unfortunately, the activity of these materials is insufficient for practical AP implementation. Attempts to improve cobalt oxide's activity have been stymied by limited mechanistic understanding that stems from the inherent difficulty of characterizing structure and reactivity at surfaces of heterogeneous materials. While previous studies on cobalt oxide revealed the intermediacy of the unusual Co(IV) oxidation state, much remains unknown, including whether bridging or terminal oxo ligands form O2 and what the relevant oxidation states are. We have addressed these issues by employing a homogeneous model for cobalt oxide, the [Co(III)4] cubane (Co4O4(OAc)4py4, py = pyridine, OAc = acetate), that can be oxidized to the [Co(IV)Co(III)3] state. Upon addition of 1 equiv of sodium hydroxide, the [Co(III)4] cubane is regenerated with stoichiometric formation of O2. Oxygen isotopic labeling experiments demonstrate that the cubane core remains intact during this stoichiometric OER, implying that terminal oxo ligands are responsible for forming O2. The OER is also examined with stopped-flow UV-visible spectroscopy, and its kinetic behavior is modeled, to surprisingly reveal that O2 formation requires disproportionation of the [Co(IV)Co(III)3] state to generate an even higher oxidation state, formally [Co(V)Co(III)3] or [Co(IV)2Co(III)2]. The mechanistic understanding provided by these results should accelerate the development of OER catalysts leading to increasingly efficient AP systems.

  10. Photocatalytic water oxidation by molecular assemblies based on cobalt catalysts.

    PubMed

    Zhou, Xu; Li, Fei; Li, Hua; Zhang, Biaobiao; Yu, Fengshou; Sun, Licheng

    2014-09-01

    Chromophore-catalyst molecular assemblies towards visible light-driven water oxidation were synthesized by covalent integration of a light-harvesting complex [Ru(bpy)3](2+) (bpy=2,2'-bipyridine) and a Co4O4 cubane water oxidation catalyst. The two components were assembled either in linear or macrocyclic configurations. In the presence of the sacrificial reagent, the Ru-Co metallocycle exhibits remarkable photocatalytic activity for oxygen evolution, which is one order of magnitude higher than that of a multicomponent system and exceeds that of a linear assembly by a factor of five, offering access to highly active photocatalyst through molecular design. PMID:25111070

  11. Intra- and interparticle magnetism of cobalt-doped iron-oxide nanoparticles encapsulated in a synthetic ferritin cage

    NASA Astrophysics Data System (ADS)

    Skoropata, E.; Desautels, R. D.; Falvo, E.; Ceci, P.; Kasyutich, O.; Freeland, J. W.; van Lierop, J.

    2014-11-01

    We present an in-depth examination of the composition and magnetism of cobalt (Co2 +)-doped iron-oxide nanoparticles encapsulated in Pyrococcus furiosus ferritin shells. We show that the Co2 + dopant ions were incorporated into the γ -Fe2O3/Fe3O4 core, with small paramagnetic-like clusters likely residing on the surface of the nanoparticle that were observed for all cobalt-doped samples. In addition, element-specific characterization using Mössbauer spectroscopy and polarized x-ray absorption indicated that Co2 + was incorporated exclusively into the octahedral B sites of the spinel-oxide nanoparticle. Comparable superparamagnetic blocking temperatures, coercivities, and effective anisotropies were obtained for 7%, 10%, and 12% cobalt-doped nanoparticles, and were only slightly reduced for 3% cobalt, indicating a strong effect of cobalt incorporation, with a lesser effect of cobalt content. Due to the regular particle size and separation that result from the use of the ferritin cage, a comparison of the effects of interparticle interactions on the disordered assembly of nanoparticles was also obtained that indicated significantly different behaviors between undoped and cobalt-doped nanoparticles.

  12. Elucidating the domain structure of the cobalt oxide water splitting catalyst by X-ray pair distribution function analysis.

    PubMed

    Du, Pingwu; Kokhan, Oleksandr; Chapman, Karena W; Chupas, Peter J; Tiede, David M

    2012-07-11

    Pair distribution function (PDF) analysis was applied for structural characterization of the cobalt oxide water-splitting catalyst films using high energy X-ray scattering. The catalyst was found to be composed of domains consistent with a cobalt dioxide lattice sheet structure, possibly containing a Co(4)O(4) cubane-type "defect". The analysis identifies the film to consist of domains composed of 13-14 cobalt atoms with distorted coordination geometries that can be modeled by alteration in terminal oxygen atom positions at the domain edge. Phosphate is seen as a disordered component in the films. This work establishes an approach that can be applied to study the structure of in situ cobalt oxide water-splitting film under functional catalytic conditions.

  13. Supported cobalt oxide on graphene oxide: highly efficient catalysts for the removal of Orange II from water.

    PubMed

    Shi, Penghui; Su, Ruijing; Zhu, Shaobo; Zhu, Mincong; Li, Dengxin; Xu, Shihong

    2012-08-30

    The current paper investigated the removal of the azo dye Orange II from water using advanced oxidation processes based on sulfate radicals. The cobalt oxide catalyst immobilized on graphene oxide (GO) can activate peroxymonosulfate (PMS) for the degradation of Orange II in water. The Co(3)O(4)/GO catalyst system was characterized via X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and X-ray spectroscopy. Results showed that Co(3)O(4) was distributed on GO. The Co(3)O(4)/GO catalyst system exhibited high activity in Orange II oxidation when the Co(3)O(4)/GO catalyst has an optimum Co(3)O(4) loading. In addition, 100% decomposition could be achieved within 6 min with 0.2mM Orange II, 0.1 g L(-1) catalyst, and 2mM PMS. Meanwhile, inductively coupled plasma analysis revealed that the leach of cobalt ions was low. The catalyst also exhibited stable performance after several rounds of regeneration. Several operational parameters, such as catalyst amount, oxidant amount, pH, temperature, and oxidation rate, affected the degradation of Orange II. PMID:22738772

  14. Electrochemically tunable thermal conductivity of lithium cobalt oxide.

    PubMed

    Cho, Jiung; Losego, Mark D; Zhang, Hui Gang; Kim, Honggyu; Zuo, Jianmin; Petrov, Ivan; Cahill, David G; Braun, Paul V

    2014-06-03

    Using time-domain thermoreflectance, the thermal conductivity and elastic properties of a sputter deposited LiCoO2 film, a common lithium-ion cathode material, are measured as a function of the degree of lithiation. Here we report that via in situ measurements during cycling, the thermal conductivity of a LiCoO2 cathode reversibly decreases from ~5.4 to 3.7 W m(-1) K(-1), and its elastic modulus decreases from 325 to 225 GPa, as it is delithiated from Li1.0CoO2 to Li0.6CoO2. The dependence of the thermal conductivity on lithiation appears correlated with the lithiation-dependent phase behaviour. The oxidation-state-dependent thermal conductivity of electrolytically active transition metal oxides provides opportunities for dynamic control of thermal conductivity and is important to understand for thermal management in electrochemical energy storage devices.

  15. Microbially mediated cobalt oxidation in seawater revealed by radiotracer experiments

    SciTech Connect

    Lee, B.G.; Fisher, N.S. )

    1993-12-01

    The influence of microbial activity on Co and Mn oxidation in decomposing diatom cultures was determined with radiotracer techniques. Adding a consortium of microorganisms collected from coastal seawater (0.2-3-[mu]m size fraction) to the cultures increased particulate Co formation rates at 18[degrees]C by an order of magnitude (to 3.8% d[sup [minus]1]) and particulate Mn formation rates 3-fold (to 7.9% d[sup [minus

  16. Cobalt vanadium oxide thin nanoplates: primary electrochemical capacitor application.

    PubMed

    Zhang, Youjuan; Liu, Yuanying; Chen, Jing; Guo, Qifei; Wang, Ting; Pang, Huan

    2014-01-01

    Co3V2O8 thin nanoplates are firstly described as a kind of electrode material for supercapacitors. More importantly, from electrochemical measurements, the obtained Co3V2O8 nanoplate electrode shows a good specific capacitance (0.5 A g(-1), 739 F g(-1)) and cycling stability (704 F g(-1) retained after 2000 cycles). This study essentially offers a new kind of metal vanadium oxides as electrochemical active material for the development of supercapacitors. PMID:25023373

  17. Cobalt vanadium oxide thin nanoplates: primary electrochemical capacitor application

    NASA Astrophysics Data System (ADS)

    Zhang, Youjuan; Liu, Yuanying; Chen, Jing; Guo, Qifei; Wang, Ting; Pang, Huan

    2014-07-01

    Co3V2O8 thin nanoplates are firstly described as a kind of electrode material for supercapacitors. More importantly, from electrochemical measurements, the obtained Co3V2O8 nanoplate electrode shows a good specific capacitance (0.5 A g-1, 739 F g-1) and cycling stability (704 F g-1 retained after 2000 cycles). This study essentially offers a new kind of metal vanadium oxides as electrochemical active material for the development of supercapacitors.

  18. [Preparation of cobalt oxide mesoporous metallic oxide-clay composites and their catalytic performance in the oxidation of benzene].

    PubMed

    Mu, Zhen; Ma, Chun-Yan; Cheng, Jie; Li, Jin-Jun

    2014-10-01

    Laponite clays composited with alumina, ceria and zirconia etc. were prepared using polyoxocations or simple metal ions as precursors, and then cobalt oxide was loaded onto them to obtain the catalysts. The results showed that compared with laponite clays, the as-prepared laponite had wide range of pore size distribution and increased pore volume. The pore volumes of laponite clays composited with alumina and ceria were more than 0.75 cm3 · g(-1). N2 isotherm type was maintained after Co3O4 loading, however, the N2 adsorption decreased with the increase of Co3 O4 loading, indicating the decrease of pore volume, which was caused by the blockage of metallic oxide/clay composites support. Furthermore, dispersion and catalytic performance of the catalysts were significantly influenced by the composited metallic elements. It was shown that according to the diffraction peak half-width of 311 crystal facet and scherrer equation, when the Co loading was 21.3% at laponite clays composited with Fe, Zr, Ce, Al, the average sizes of Co3O4 were 17.2, 16.0, 16.5 and 18.0 nm, respectively. Alumina composited clay with 21.3% Co loading showed high catalytic activity, the complete conversion temperature of benzene was 350°C. Among metallic oxide/laponite composites, the ZrO composited laponite with 21.3% Co loading exhibited the best catalytic performance, which could completely convert benzene at 310°C.

  19. Template-free hydrothermal derived cobalt oxide nanopowders: Synthesis, characterization, and removal of organic dyes

    SciTech Connect

    Nassar, Mostafa Y.; Ahmed, Ibrahim S.

    2012-09-15

    Graphical abstract: XRD patterns of the products obtained by hydrothermal treatment at 160 °C for 24 h, and at different [Co{sup 2+}]/[CO{sub 3}{sup 2−}] ratios: (a) 1:6, (b) 1:3, (c) 1:1.5, (d) 1:1, (e) 1:0.5. Highlights: ► Spinel cobalt oxide nanoparticles with different morphologies were prepared by hydrothermal approach. ► The optical characteristics of the as-prepared cobalt oxide revealed the presence of two band gaps. ► Adsorption of methylene blue dye on Co{sub 3}O{sub 4} was investigated and the percent uptake was found to be >99% in 24 h. -- Abstract: Pure spinel cobalt oxide nanoparticles were prepared through hydrothermal approach using different counter ions. First, the pure and uniform cobalt carbonate (with particle size of 21.8–29.8 nm) were prepared in high yield (94%) in an autoclave in absence unfriendly organic surfactants or solvents by adjusting different experimental parameters such as: pH, reaction time, temperature, counter ions, and (Co{sup 2+}:CO{sub 3}{sup 2−}) molar ratios. Thence, the spinel Co{sub 3}O{sub 4} (with mean particle size of 30.5–47.35 nm) was produced by thermal decomposition of cobalt carbonate in air at 500 °C for 3 h. The products were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscope (TEM), scanning electron microscope (SEM), and thermal analysis (TA). Also, the optical characteristics of the as-prepared Co{sub 3}O{sub 4} nanoparticles revealed the presence of two band gaps (1.45–1.47, and 1.83–1.93 eV). Additionally, adsorption of methylene blue dye on Co{sub 3}O{sub 4} nanoparticles was investigated and the uptake% was found to be >99% in 24 h.

  20. Sol-gel derived mesoporous cobalt silica catalyst: Synthesis, characterization and its activity in the oxidation of phenol

    NASA Astrophysics Data System (ADS)

    Andas, Jeyashelly; Adam, Farook; Rahman, Ismail Ab.

    2014-10-01

    Highly mesoporous cobalt silica rice husk catalysts with (5-15 wt.%) Co2+ loading were prepared via a simple sol-gel technique at room temperature. The successful insertion of cobalt ions into silica matrix was evidenced from FT-IR, NMR, XPS and AAS analyses. Preservation of the mesoporosity nature of silica upon incorporating Co2+ was confirmed from the N2-sorption studies. The topography and morphology viewed by TEM analysis differs as the cobalt concentration varies from 5 to 15 wt.%. Parallel pore channels and spherical nanoparticles of 9.44 nm were achieved for cobalt silica catalysts with 10 and 15 wt.% respectively. Cobalt catalysts were active in the liquid-phase oxidation of phenol with H2O2 as an oxygen source. The performances of the catalysts were greatly influenced by various parameters such as reaction temperature, catalyst amount, molar ratio of substrate to oxidant, nature of solvent, metal loading and homogeneous precursor salt. Water served as the best reaction medium for this oxidation system. The regeneration studies confirmed cobalt catalyst could be reused for five cycles without experiencing large loss in the conversion. Both leaching and reusability studies testified that the catalysts were truly heterogeneous.

  1. Toxicity of cobalt oxide nanoparticles to normal cells; an in vitro and in vivo study.

    PubMed

    Chattopadhyay, Sourav; Dash, Sandeep Kumar; Tripathy, Satyajit; Das, Balaram; Mandal, Debasis; Pramanik, Panchanan; Roy, Somenath

    2015-01-25

    The aim of this study was to find out the intracellular signaling transduction pathways involved in cobalt oxide nanoparticles (CoO NPs) mediated oxidative stress in vitro and in vivo system. Cobalt oxide nanoparticles released excess Co++ ions which could activated the NADPH oxidase and helps in generating the reactive oxygen species (ROS). Our results showed that CoO NPs elicited a significant (p<0.05) amount of ROS in lymphocytes. In vitro pretreatment with N-acetylene cystine had a protective role on lymphocytes death induced by CoO NPs. In vitro and in vivo results showed the elevated level of TNF-α after CoO NPs treatment. This TNF-α phosphorylated the p38 mitogen-activated protein kinase followed by activation of caspase 8 and caspase 3 which could induce cell death. This study showed that CoO NPs induced oxidative stress and activated the signaling pathway of TNF-α-caspase-8-p38-caspase-3 to primary immune cells. This study suggested that bare CoO NPs are a toxic for primary human immune cells that deals directly with human health. Surface modification or surface functionalization may open the gateway for further use of CoO NPs in different industrial use or in biomedical sciences.

  2. Cobalt vanadium oxide thin nanoplates: primary electrochemical capacitor application

    PubMed Central

    Zhang, Youjuan; Liu, Yuanying; Chen, Jing; Guo, Qifei; Wang, Ting; Pang, Huan

    2014-01-01

    Co3V2O8 thin nanoplates are firstly described as a kind of electrode material for supercapacitors. More importantly, from electrochemical measurements, the obtained Co3V2O8 nanoplate electrode shows a good specific capacitance (0.5 A g−1, 739 F g−1) and cycling stability (704 F g−1 retained after 2000 cycles). This study essentially offers a new kind of metal vanadium oxides as electrochemical active material for the development of supercapacitors. PMID:25023373

  3. Ascorbic Acid Assisted Synthesis of Cobalt Oxide Nanostructures, Their Electrochemical Sensing Application for the Sensitive Determination of Hydrazine

    NASA Astrophysics Data System (ADS)

    Tahira, Aneela; Nafady, Ayman; Baloach, Quarratulain; Sirajuddin; Sherazi, Syed Tufail Hussain; Shaikh, Tayyaba; Arain, Munazza; Willander, Magnus; Ibupoto, Zafar Hussain

    2016-07-01

    This study describes, the synthesis of cobalt oxide nanostructures using ascorbic acid as a growth directing agent by the hydrothermal method. Ascorbic acid is used for the first time for the synthesis of cobalt oxide nanostructures and a unique morphology is prepared in the present study. The cobalt oxide nanostructures were characterized by scanning electron microcopy, x-ray diffraction, and x-ray photoelectron spectroscopy techniques. These analytical techniques demonstrated well defined morphology, good crystalline quality, and high purity of as prepared cobalt oxide nanostructures. The glassy carbon electrode was modified with cobalt oxide nanostructures for the development of a sensitive and selective electrochemical hydrazine sensor. The developed hydrazine sensor exhibits a linear range of 2-24 μM. The sensitivity and limit of detection of presented hydrazine sensors are 12,734 μA/mM/cm2 and 0.1 μM respectively. The developed hydrazine sensor is highly selective, stable, and reproducible. The proposed sensor is successfully applied for the detection of hydrazine from different water samples. The present study provides the development of an alternative tool for the reliable monitoring of hydrazine from environmental and biological samples.

  4. Selective synthesis of pure cobalt disulfide on reduced graphene oxide sheets and its high electrocatalytic activity for hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Ahn, Seongjoon; Yang, Jieun; Lim, Hyunseob; Shin, Hyeon Suk

    2016-01-01

    We synthesized single-phase CoS2 on a large scale by adding graphene oxide of sufficient quantity via the hydrothermal method using cobalt acetate and thioacetamide as precursors; this produced the hybrid of CoS2 with reduced graphene oxide which exhibited high electrocatalytic activity in the hydrogen evolution reaction.

  5. Influence of Cr doping on the stability and structure of small cobalt oxide clusters

    SciTech Connect

    Tung, Nguyen Thanh; Lievens, Peter; Janssens, Ewald; Tam, Nguyen Minh; Nguyen, Minh Tho

    2014-07-28

    The stability of mass-selected pure cobalt oxide and chromium doped cobalt oxide cluster cations, Co{sub n}O{sub m}{sup +} and Co{sub n−1}CrO{sub m}{sup +} (n = 2, 3; m = 2–6 and n = 4; m = 3–8), has been investigated using photodissociation mass spectrometry. Oxygen-rich Co{sub n}O{sub m}{sup +} clusters (m ⩾ n + 1 for n = 2, 4 and m ⩾ n + 2 for n = 3) prefer to photodissociate via the loss of an oxygen molecule, whereas oxygen poorer clusters favor the evaporation of oxygen atoms. Substituting a single Co atom by a single Cr atom alters the dissociation behavior. All investigated Co{sub n−1}CrO{sub m}{sup +} clusters, except CoCrO{sub 2}{sup +} and CoCrO{sub 3}{sup +}, prefer to decay by eliminating a neutral oxygen molecule. Co{sub 2}O{sub 2}{sup +}, Co{sub 4}O{sub 3}{sup +}, Co{sub 4}O{sub 4}{sup +}, and CoCrO{sub 2}{sup +} are found to be relatively difficult to dissociate and appear as fragmentation product of several larger clusters, suggesting that they are particularly stable. The geometric structures of pure and Cr doped cobalt oxide species are studied using density functional theory calculations. Dissociation energies for different evaporation channels are calculated and compared with the experimental observations. The influence of the dopant atom on the structure and the stability of the clusters is discussed.

  6. Cobalt phosphide nanowall array as an efficient 3D catalyst electrode for methanol electro-oxidation

    NASA Astrophysics Data System (ADS)

    Liu, Danni; Lu, Wenbo; Wang, Kunyang; Du, Gu; Asiri, Abdullah M.; Lu, Qun; Sun, Xuping

    2016-11-01

    In this letter, we report on the use of a cobalt phosphide nanowall array on conductive carbon cloth (CoP NA/CC) as an efficient catalyst electrode for methanol electro-oxidation under alkaline conditions. This CoP NA/CC achieves a current density of 96 mA cm–2 toward 0.5 M methanol at 0.5 V (versus a saturated calomel electrode (SCE)) in 1 M KOH. Moreover, this electrode exhibits superior stability and 93% of the initial anodic current density can be retained after 1000 cyclic voltammetry cycles when re-measured in new electrolyte.

  7. The anion-binding polyanion: a molecular cobalt vanadium oxide with anion-sensitive visual response.

    PubMed

    Seliverstov, Andrey; Forster, Johannes; Heiland, Magdalena; Unfried, Johannes; Streb, Carsten

    2014-07-25

    An anionic molecular cobalt vanadium oxide cluster, (n-Bu4N)3[Co(AcO)V4O12] and its use as anion binding site is reported. Cluster formation is controlled by an anion-dependent dynamic solution equilibrium. Reversible anion binding in solution leads to significant spectral changes, allowing the ratiometric optical detection of the anion concentration in situ, even under harsh thermal conditions (T = 90 °C). Comparative studies showed that the spectral response is dependent on the type of anion so that carboxylates, weakly coordinating anions and halides can be distinguished.

  8. Long cycle life lithium ion battery with lithium nickel cobalt manganese oxide (NCM) cathode

    NASA Astrophysics Data System (ADS)

    Liu, Shuang; Xiong, L.; He, C.

    2014-09-01

    Lithium ion batteries with lithium nickel cobalt manganese oxide (NCM) cathode were characterized by extensive cycling (>2000 cycles), discharge rate test, hybrid pulse power characterization test (HPPC), and electrochemical impedance spectroscopy (EIS). The crystal structure, morphology and particle size of cathode materials were characterized by X-ray diffraction and scanning electron microscopy (SEM). It was demonstrated that the rate performance and cycle life of battery are closely related to the cathode material composition and electrode design. With proper selection of cathode composition and electrode design, the lithium ion battery cell achieved close to 3500 cycles with 85% capacity retention at 1C current.

  9. Cobalt phosphide nanowall array as an efficient 3D catalyst electrode for methanol electro-oxidation.

    PubMed

    Liu, Danni; Lu, Wenbo; Wang, Kunyang; Du, Gu; Asiri, Abdullah M; Lu, Qun; Sun, Xuping

    2016-11-01

    In this letter, we report on the use of a cobalt phosphide nanowall array on conductive carbon cloth (CoP NA/CC) as an efficient catalyst electrode for methanol electro-oxidation under alkaline conditions. This CoP NA/CC achieves a current density of 96 mA cm(-2) toward 0.5 M methanol at 0.5 V (versus a saturated calomel electrode (SCE)) in 1 M KOH. Moreover, this electrode exhibits superior stability and 93% of the initial anodic current density can be retained after 1000 cyclic voltammetry cycles when re-measured in new electrolyte. PMID:27671347

  10. Cobalt phosphide nanowall array as an efficient 3D catalyst electrode for methanol electro-oxidation.

    PubMed

    Liu, Danni; Lu, Wenbo; Wang, Kunyang; Du, Gu; Asiri, Abdullah M; Lu, Qun; Sun, Xuping

    2016-11-01

    In this letter, we report on the use of a cobalt phosphide nanowall array on conductive carbon cloth (CoP NA/CC) as an efficient catalyst electrode for methanol electro-oxidation under alkaline conditions. This CoP NA/CC achieves a current density of 96 mA cm(-2) toward 0.5 M methanol at 0.5 V (versus a saturated calomel electrode (SCE)) in 1 M KOH. Moreover, this electrode exhibits superior stability and 93% of the initial anodic current density can be retained after 1000 cyclic voltammetry cycles when re-measured in new electrolyte.

  11. High-pressure and high-temperature equation of state of cobalt oxide: Implications for redox relations in Earth's mantle

    SciTech Connect

    Armentrout, Matthew M.; Rainey, Emma S.G.; Kavner, Abby

    2013-07-30

    The high-pressure and high-temperature equation of state of rock salt-structured cobalt oxide was measured up to 65 GPa and 2600 K using synchrotron X-ray diffraction in conjunction with the laser heated diamond-anvil cell. Fitting a Mie-Grüneisen-Debye model to the data we find best-fit parameters V0 = 77.4 (fixed) Å3, K0 = 190 (1) GPa, K' = 3.49 (4), γ0 = 1.54 (4), q = 2.87 (15), and θ0 = 517.8 K (fixed). We use this newly determined equation of state in conjunction with existing measurements of the thermoelastic parameters of cobalt metal to calculate the Gibbs free-energy difference between the cobalt oxide and cobalt metal phases as a function of pressure and temperature. A comparison of the energetics of the Co/CoO system with the Ni/NiO system predicts that below 58 GPa CoO+Ni is stable relative to NiO+Co, while above 58 GPa the reverse is true. This tipping point in energy can be mapped as a crossing point in the electrochemical potential of the two metal ions, suggesting that cobalt becomes more siderophile than nickel with increasing pressure. This result is in qualitative agreement with existing measurements of nickel and cobalt partition coefficients between mantle and core materials.

  12. Growth of oxide exchange bias layers

    DOEpatents

    Chaiken, A.; Michel, R.P.

    1998-07-21

    An oxide (NiO, CoO, NiCoO) antiferromagnetic exchange bias layer produced by ion beam sputtering of an oxide target in pure argon (Ar) sputtering gas, with no oxygen gas introduced into the system. Antiferromagnetic oxide layers are used, for example, in magnetoresistive readback heads to shift the hysteresis loops of ferromagnetic films away from the zero field axis. For example, NiO exchange bias layers have been fabricated using ion beam sputtering of an NiO target using Ar ions, with the substrate temperature at 200 C, the ion beam voltage at 1000V and the beam current at 20 mA, with a deposition rate of about 0.2 {angstrom}/sec. The resulting NiO film was amorphous. 4 figs.

  13. Growth of oxide exchange bias layers

    DOEpatents

    Chaiken, Alison; Michel, Richard P.

    1998-01-01

    An oxide (NiO, CoO, NiCoO) antiferromagnetic exchange bias layer produced by ion beam sputtering of an oxide target in pure argon (Ar) sputtering gas, with no oxygen gas introduced into the system. Antiferromagnetic oxide layers are used, for example, in magnetoresistive readback heads to shift the hysteresis loops of ferromagnetic films away from the zero field axis. For example, NiO exchange bia layers have been fabricated using ion beam sputtering of an NiO target using Ar ions, with the substrate temperature at 200.degree. C., the ion beam voltage at 1000V and the beam current at 20 mA, with a deposition rate of about 0.2 .ANG./sec. The resulting NiO film was amorphous.

  14. Synthesis of cobalt-containing mesoporous catalysts using the ultrasonic-assisted “pH-adjusting” method: Importance of cobalt species in styrene oxidation

    SciTech Connect

    Li, Baitao Zhu, Yanrun; Jin, Xiaojing

    2015-01-15

    Cobalt-containing SBA-15 and MCM-41 (Co-SBA-15 and Co-MCM-41) mesoporous catalysts were prepared via ultrasonic-assisted “pH-adjusting” technique in this study. Their physiochemical structures were comprehensively characterized and correlated with catalytic activity in oxidation of styrene. The nature of cobalt species depended on the type of mesoporous silica as well as pH values. The different catalytic performance between Co-SBA-15 and Co-MCM-41 catalysts originated from cobalt species. Cobalt species were homogenously incorporated into the siliceous framework of Co-SBA-15 in single-site Co(II) state, while Co{sub 3}O{sub 4} particles were loaded on Co-MCM-41 catalysts. The styrene oxidation tests showed that the single-site Co(II) state was more beneficial to the catalytic oxidation of styrene. The higher styrene conversion and benzaldehyde selectivity over Co-SBA-15 catalysts were mainly attributed to single-site Co(II) state incorporated into the framework of SBA-15. The highest conversion of styrene (34.7%) with benzaldehyde selectivity of 88.2% was obtained over Co-SBA-15 catalyst prepared at pH of 7.5, at the mole ratio of 1:1 (styrene to H{sub 2}O{sub 2}) at 70 °C. - Graphical abstract: Cobalt-containing mesoporous silica catalysts were developed via ultrasonic-assisted “pH-adjusting” technique. Compared with Co{sub 3}O{sub 4} in Co-MCM-41, the single-site Co(II) state in Co-SBA-15 was more efficient for the styrene oxidation. - Highlights: • Fast and cost-effective ultrasonic technique for preparing mesoporous materials. • Incorporation of Co via ultrasonic irradiation and “pH-adjusting”. • Physicochemical comparison between Co-SBA-15 and Co-MCM-41. • Correlation of styrene oxidation activity and catalyst structural property.

  15. Tailoring the energy level alignment at the Co/Alq{sub 3} interface by controlled cobalt oxidation

    SciTech Connect

    Haag, Norman; Steil, Sabine; Großmann, Nicolas; Fetzer, Roman; Cinchetti, Mirko; Aeschlimann, Martin

    2013-12-16

    We have studied the influence of oxygen exposure at the prototypical interface between cobalt and the organic semiconductor tris(8-hydroxyquinoline)aluminum (III) (Alq{sub 3}) by photoemission spectroscopy. We find that oxidation of the cobalt leads to a gradual suppression of hybrid interface states, to a progressive change in the work function and to a continuous energetic shift of the molecular orbitals towards higher binding energies. Based on these observations, we propose controlled oxidation of the ferromagnetic electrode as an easy and effective possibility to tune the performance of organic spintronics devices.

  16. Surface and redox properties of cobalt-ceria binary oxides: On the effect of Co content and pretreatment conditions

    NASA Astrophysics Data System (ADS)

    Konsolakis, Michalis; Sgourakis, Michalis; Carabineiro, Sónia A. C.

    2015-06-01

    Ceria-based transition metal catalysts have recently received considerable attention both in heterogeneous catalysis and electro-catalysis fields, due to their unique physicochemical characteristics. Their catalytic performance is greatly affected by the surface local chemistry and oxygen vacancies. The present study aims at investigating the impact of Co/Ce ratio and pretreatment conditions on the surface and redox properties of cobalt-ceria binary oxides. Co-ceria mixed oxides with different Co content (0, 20, 30, 60, 100 wt.%) were prepared by impregnation method and characterized by means of N2 adsorption at -196 °C, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The results shown the improved reducibility of Co/CeO2 mixed oxides compared to single oxides, due to a synergistic interaction between cobalt and cerium. Oxidation pretreatment results in a preferential localization of cerium species on the outer surface. In contrast, a uniform distribution of cobalt and cerium species over the entire catalyst surface is obtained by the reduction process, which facilitates the formation of oxygen vacancies though Co3+/Co2+ and Ce3+/Ce4+ redox cycles. Fundamental insights toward tuning the surface chemistry of cobalt-ceria binary oxides are provided, paving the way for real-life industrial applications.

  17. Cobalt (hydr)oxide/graphite oxide composites: importance of surface chemical heterogeneity for reactive adsorption of hydrogen sulfide.

    PubMed

    Mabayoje, Oluwaniyi; Seredych, Mykola; Bandosz, Teresa J

    2012-07-15

    Composites of cobalt (hydr)oxide and graphite oxide (GO) were obtained and evaluated as adsorbents of hydrogen sulfide at ambient conditions. The surface properties of the initial and exhausted samples were studied by FTIR, TEM, SEM/EDX, XRD, adsorption of nitrogen, potentiometric titration, and thermal analysis. The results obtained show a significant improvement in their adsorption capacities compared to parent compounds. The importance of the OH groups of cobalt (hydr)oxide/GO composites and new interface chemistry for the adsorption of hydrogen sulfide on these materials is revealed. The oxygen activation by the carbonaceous component resulted in formation of sulfites. Water enhanced the removal process. This is the result of the basic environment promoting dissociation of H(2)S and acid-base reactions. Finally, the differences in the performance of the materials with different mass ratios of GO were linked to the availability of active sites on the surface of the adsorbents, dispersion of these sites, their chemical heterogeneity, and location in the pore system.

  18. Cobalt-Schiff base complex catalyzed oxidation of para-substituted phenolics. Preparation of benzoquinones

    SciTech Connect

    Bozell, J.J.; Hames, B.R.; Dimmel, D.R.

    1995-04-21

    Para-substituted phenolics, serving as models for lignin (a renewable source of carbon), are oxidized to the corresponding benzoquinone with oxygen in the presence of catalytic amounts of Co-Schiff base complexes. The reaction products observed depend on the structure of the catalyst. The 5-coordinate catalysts (pyridine)[bis(salicylidene)ethylenediamine]cobalt[(pyr)Co(salen)]and[bis(salicylideneamino)ethylamine]cobalt [Co(n-Me salpr)] convert syringyl alcohol (3,5-dimethoxy-4-hydroxybenzyl alcohol) to 2,6-dimethoxybenzoquinone in high yield. In contrast, syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde) is unreactive toward these catalysts. However, the 4-coordinate Co(salen) converts syringaldehyde to 2,6-dimethoxybenzoiquinone in 72% isolated yield. Phenols bearing a single methoxy group on the ring are unreactive toward any catalyst in MeOH. However, vanillyl alcohol (3-methoxy-4-hydroxybenzyl alcohol) is converted to 2-methoxybenzo-quinone with Co(N-Me salpr) and oxygen in 43% yield in CH{sub 2}Cl{sub 2} and 58% yield in CH{sub 2}Cl{sub 2} in the presence of 1% CuCl{sub 2}. The success of the oxidations appears to be related to the ease of removal of the phenolic hydrogen by the Co/O{sub 2} complex. Competitive deactivation of the catalyst occurs with substrates of lower reactivity. 84 tabs.

  19. Design, fabrication and characterization of a double layer solid oxide fuel cell (DLFC)

    NASA Astrophysics Data System (ADS)

    Wang, Guangjun; Wu, Xiangying; Cai, Yixiao; Ji, Yuan; Yaqub, Azra; Zhu, Bin

    2016-11-01

    A double layer solid oxide fuel cell (DLSOFC) without using the electrolyte (layer) has been designed by integrating advantages of positive electrode material of lithium ion battery(LiNi0.8Co0.15Al0.05O2) and oxygen-permeable membranes material (trace amount cobalt incorporated terbium doped ceria, TDC + Co) based on the semiconductor physics principle. Instead of using an electrolyte layer, the depletion layer between the anode and cathode served as an electronic insulator to block the electrons but to maintain the electrolyte function for ionic transport. Thus the device with two layers can realize the function of SOFC and at the same time avoids the electronic short circuiting problem. Such novel DLFC showed good performance at low temperatures, for instance, a maximum power density of 230 mWcm-2 was achieved at 500 °C. The working principle of the new device is presented.

  20. Morphological impact on the reaction kinetics of size-selected cobalt oxide nanoparticles

    SciTech Connect

    Bartling, Stephan Meiwes-Broer, Karl-Heinz; Barke, Ingo; Pohl, Marga-Martina

    2015-09-21

    Apart from large surface areas, low activation energies are essential for efficient reactions, particularly in heterogeneous catalysis. Here, we show that not only the size of nanoparticles but also their detailed morphology can crucially affect reaction kinetics, as demonstrated for mass-selected, soft-landed, and oxidized cobalt clusters in a 6 nm to 18 nm size range. The method of reflection high-energy electron diffraction is extended to the quantitative determination of particle activation energies which is applied for repeated oxidation and reduction cycles at the same particles. We find unexpectedly small activation barriers for the reduction reaction of the largest particles studied, despite generally increasing barriers for growing sizes. We attribute these observations to the interplay of reaction-specific material transport with a size-dependent inner particle morphology.

  1. Application of Two Cobalt-Based Metal-Organic Frameworks as Oxidative Desulfurization Catalysts.

    PubMed

    Masoomi, Mohammad Yaser; Bagheri, Minoo; Morsali, Ali

    2015-12-01

    Two new porous cobalt-based metal-organic frameworks, [Co6(oba)5(OH)2(H2O)2(DMF)4]n · 5DMF (TMU-10) and [Co3(oba)3(O) (Py)0.5] n · 4DMF · Py (TMU-12) have been synthesized by solvothermal method using a nonlinear dicarboxylate ligand. Under mild reaction conditions, these compounds exhibited good catalytic activity and reusability in oxidative desulfurization (ODS) reaction of model oil which was prepared by dissolving dibenzothiophene (DBT) in n-hexane. FT-IR and Mass analysis showed that the main product of DBT oxidation is its corresponding sulfone, which was adsorbed on the surfaces of catalysts. The activation energy was obtained as 13.4 kJ/mol. PMID:26571113

  2. Porous cubes constructed by cobalt oxide nanocrystals with graphene sheet coatings for enhanced lithium storage properties.

    PubMed

    Geng, Hongbo; Guo, Yuanyuan; Ding, Xianguang; Wang, Huangwen; Zhang, Yufei; Wu, Xinglong; Jiang, Jiang; Zheng, Junwei; Yang, Yonggang; Gu, Hongwei

    2016-04-14

    In this manuscript, graphene-encapsulated porous cobalt oxide cubes (Co3O4@G) are fabricated through a facile precipitation reaction with subsequent calcination and a self-assembly process. The synthesized porous Co3O4 cubes anchored in the conductive graphene network can realize superior electrical conductivity, withstand volume variation upon prolonged cycling and shorten the diffusion path of lithium ions. When evaluated as anode materials, the Co3O4@G electrode shows excellent electrochemical properties in terms of both stable cycling performance and good rate capabilities. For example, a reversible discharge capacity of 980 mA h g(-1) is delivered after 80 cycles at a current density of 200 mA g(-1). Introducing a conductive graphene network to modify other metal oxides with poor electric conductivity and large volume excursions is of great interest in the development of lithium ion battery technologies. PMID:26997536

  3. Porous cubes constructed by cobalt oxide nanocrystals with graphene sheet coatings for enhanced lithium storage properties.

    PubMed

    Geng, Hongbo; Guo, Yuanyuan; Ding, Xianguang; Wang, Huangwen; Zhang, Yufei; Wu, Xinglong; Jiang, Jiang; Zheng, Junwei; Yang, Yonggang; Gu, Hongwei

    2016-04-14

    In this manuscript, graphene-encapsulated porous cobalt oxide cubes (Co3O4@G) are fabricated through a facile precipitation reaction with subsequent calcination and a self-assembly process. The synthesized porous Co3O4 cubes anchored in the conductive graphene network can realize superior electrical conductivity, withstand volume variation upon prolonged cycling and shorten the diffusion path of lithium ions. When evaluated as anode materials, the Co3O4@G electrode shows excellent electrochemical properties in terms of both stable cycling performance and good rate capabilities. For example, a reversible discharge capacity of 980 mA h g(-1) is delivered after 80 cycles at a current density of 200 mA g(-1). Introducing a conductive graphene network to modify other metal oxides with poor electric conductivity and large volume excursions is of great interest in the development of lithium ion battery technologies.

  4. Tailoring the properties and the reactivity of the spinel cobalt oxide.

    PubMed

    Bahlawane, Naoufal; Ngamou, Patrick Herve Tchoua; Vannier, Vincent; Kottke, Tilman; Heberle, Joachim; Kohse-Höinghaus, Katharina

    2009-10-28

    Pulsed spray evaporation chemical vapor deposition (PSE-CVD) was employed for the synthesis of cobalt-based spinel oxide thin films, Co(3-x)Fe(x)O4 with x = 0-1.56. XRD, Raman scattering and FTIR emission spectroscopy show that the normal spinel structure was retained for 0 < or = x < or = 0.65 by the selective insertion of Fe3+ in the octahedral sites. The spinel inversion was noticed above this range, whereas the insertion of Fe2+ was first indicated with x > or = 1. The room-temperature electrical resistivity of the thin films was controlled between 9 and 0.007 Omega cm by the adjustment of iron doping concentration. Furthermore an improvement of the thermal stability of the spinel was noticed upon doping by iron. The reducibility of the spinel in the presence of molecular hydrogen was efficiently adjusted by a shift of the reduction temperature by up to 110 degrees C upon the controlled insertion of iron in the octahedral sites of the spinel. The investigation of the catalytic oxidation of CO and ethanol over Co(3-x)Fe(x)O4 films with controlled structural modification enabled the confirmation of the Mars-van Krevelen mechanism for the oxidation of CO and the tight correlation between the selectivity of the conversion of ethanol to acetaldehyde and the abundance of surface basic sites. The controlled iron doping was demonstrated to be an efficient strategy to tune the reactivity and the selectivity of the cobalt-based spinel oxide. The doping-induced transition from normal to inverse spinel was observed to induce a clear discontinuity in the trend of all investigated physicochemical properties.

  5. Porous cubes constructed by cobalt oxide nanocrystals with graphene sheet coatings for enhanced lithium storage properties

    NASA Astrophysics Data System (ADS)

    Geng, Hongbo; Guo, Yuanyuan; Ding, Xianguang; Wang, Huangwen; Zhang, Yufei; Wu, Xinglong; Jiang, Jiang; Zheng, Junwei; Yang, Yonggang; Gu, Hongwei

    2016-03-01

    In this manuscript, graphene-encapsulated porous cobalt oxide cubes (Co3O4@G) are fabricated through a facile precipitation reaction with subsequent calcination and a self-assembly process. The synthesized porous Co3O4 cubes anchored in the conductive graphene network can realize superior electrical conductivity, withstand volume variation upon prolonged cycling and shorten the diffusion path of lithium ions. When evaluated as anode materials, the Co3O4@G electrode shows excellent electrochemical properties in terms of both stable cycling performance and good rate capabilities. For example, a reversible discharge capacity of 980 mA h g-1 is delivered after 80 cycles at a current density of 200 mA g-1. Introducing a conductive graphene network to modify other metal oxides with poor electric conductivity and large volume excursions is of great interest in the development of lithium ion battery technologies.In this manuscript, graphene-encapsulated porous cobalt oxide cubes (Co3O4@G) are fabricated through a facile precipitation reaction with subsequent calcination and a self-assembly process. The synthesized porous Co3O4 cubes anchored in the conductive graphene network can realize superior electrical conductivity, withstand volume variation upon prolonged cycling and shorten the diffusion path of lithium ions. When evaluated as anode materials, the Co3O4@G electrode shows excellent electrochemical properties in terms of both stable cycling performance and good rate capabilities. For example, a reversible discharge capacity of 980 mA h g-1 is delivered after 80 cycles at a current density of 200 mA g-1. Introducing a conductive graphene network to modify other metal oxides with poor electric conductivity and large volume excursions is of great interest in the development of lithium ion battery technologies. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01024e

  6. On the kinetics of the absorption of nitric oxide into ammoniacal cobalt(II) solutions.

    PubMed

    Yu, Hesheng; Tan, Zhongchao

    2014-02-18

    Experiments were conducted using a custom double-stirred tank reactor to determine the rate constants of reactions between nitric oxide (NO) and both pentaaminecobalt(II) and hexaaminecobalt(II) at temperatures of 298.2 and 303.2 K and pH levels between 8.50 and 9.87 under atmospheric pressure. The NO concentration of simulated flue gas stream ranged from 400 to 1400 ppmv. Ammoniacal cobalt(II) solutions were prepared by adding aqueous ammonia into a cobalt(II) nitrate solution in the presence of concentrated ammonium nitrate. The reaction rate constants were calculated with an enhancement factor for gas absorption associated with parallel chemical reactions. The results showed that the reaction between NO and pentaaminecobalt(II) was first order with respect to both the NO and the pentaamminecobalt(II) ion. Similarly, the reaction between NO and hexaamminecobalt(II) was first order with respect to both the NO and the hexaamminecobalt(II) ion. The forward reaction rate constants of these two reactions were 6.43 × 10(6) and 1.00 × 10(7) L · mol(-1) · s(-1) at 298.2 K, respectively, and increased to 7.57 × 10(6) and 1.12 × 10(7) L · mol(-1) · s(-1) at 303.2 K, respectively. Ammoniacal cobalt(II) solutions also have the potential to simultaneously remove CO2, SO2, and NOx from postcombustion flue gas.

  7. The effect of variations of cobalt content on the cyclic oxidation resistance of selected Ni-base superalloys

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A.

    1987-01-01

    Cobalt levels were systematically varied in the Ni-base turbine alloys U-700 (cast), U-700m (PM/HIP), Waspaloy, Mar-M-247, In-738, Nimonic-115, U-720, and SX-R-150. the cobalt levels ranged from 0 wt pct to the nominal commercial content in each alloy. the alloys were tested in cyclic oxidation in static air at 1000, 1100 and 1150 C for 500, 200, and 100 hr, respectively. An oxidation attack parameter, Ka, derived from the specific weight change versus time data was used to evaluate the oxidation behavior of the alloys along with X-ray diffraction analysis of the surface oxides. The alloys tend to form either Cr2O3/chromite spinel or Al2O3/aluminate spinel depending on the Cr/Al ratio in the alloys. Alloys with a ratio of 3.5 or higher tend to favor the Cr oxides while those under 3.0 form mostly Al oxides. In general the Al2O3/aluminate spinel forming alloys have the better oxidation resistance. Increased cobalt content lowers the scaling resistance of the higher Cr allys while a 5.0 wt pct Co content is optimum for the Al controlling alloys. The refractory metals, particularly Ta, appear beneficial to both types of oxides, perhaps due to the formation of the omnipresent trirutile Ni(Ta, Cb, Mo, W)2O6. Both scales break down as increasing amounts of NiO are formed.

  8. The effect of variations of cobalt content on the cyclic oxidation resistance of selected Ni-base superalloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.

    1986-01-01

    Cobalt levels were systematically varied in the Ni-base turbine alloys U-700 (cast), U-700m(PM/HIP), Waspaloy, Mar-M-247, In-738, Nimonic-115, U-720, and SX-R-150. The cobalt levels ranged from 0 wt % to the nominal commercial content in each alloy. The alloys were tested in cyclic oxidation in static air at 1000, 1100 and 1150 C for 500, 200 and 100 hr respectively. An oxidation attack parameter, Ka derived from the specific weight change versus time data was used to evaluate the oxidation behavior of the alloys along with X-ray diffraction analysis of the surface oxides. The alloys tend to form either Cr2O3/chromite spinel or Al2O3/aluminate spinel depending on the CR/Al ratio in the alloys. Alloys with a ratio of 3.5 or higher tend to favor the Cr oxides while those under 3.0 form mostly Al oxides. In general the Al2O3/aluminate spinel forming alloys have the better oxidation resistance. Increased cobalt content lowers the scaling resistance of the higher Cr alloys while a 5.0 wt % Co content is optimum for the Al controlling alloys. The refractory metals, particularly Ta, appear beneficial to both types of oxides perhaps due to the formation of the omni-present trirutile Ni(Ta,Cb,Mo,W)2O6. Both scales break down as increasing amounts of NiO is formed.

  9. Superconductivity and cobalt oxidation state in metastable Na{sub x}CoO{sub 2-{delta}}{center_dot}yH{sub 2}O (x{approx_equal}1/3; y{approx_equal}4x)

    SciTech Connect

    Barnes, P.W.; Avdeev, M.; Jorgensen, J.D.; Hinks, D.G.; Claus, H.; Short, S.

    2005-10-01

    We report the synthesis and superconducting properties of a metastable form of the known superconductor Na{sub x}CoO{sub 2}{center_dot}yH{sub 2}O (x{approx_equal}1/3;y{approx_equal}4x). We obtained this metastable cobaltate superconductor due to the unique way it was synthesized. Instead of using the conventional bromine-acetonitrile mixture for the Na{sup +}-deintercalation reaction, we use an aqueous bromine solution. Using this method, we oxidize the sample to a point that the sodium cobaltate becomes unstable, leading to formation of other products if not controlled. This compound has the same structure as the reported superconductor, yet it exhibits a systematic variation of the superconducting transition temperature (T{sub c}) as a function of time. Immediately after synthesis, this compound is not a superconductor, even though it contains appropriate amounts of Na{sup +} and H{sub 2}O. The samples become superconducting with low T{sub c} values after {approx}90 h. T{sub c} continually increases until it reaches a maximum value (4.5 K) after about 260 h. Then T{sub c} drops drastically, becoming nonsuperconducting approximately 100 h later. Corresponding time-dependent neutron powder diffraction data shows that the changes in superconductivity exhibited by the metastable cobaltate correspond to slow formation of oxygen vacancies in the CoO{sub 2} layers. In effect, the formation of these defects continually reduces the cobalt oxidation state causing the sample to evolve through its superconducting life cycle. Thus, the dome-shaped superconducting phase diagram is mapped as a function of cobalt oxidation state using a single sample. The width of this dome based on the formal oxidation state of cobalt is very narrow--approximately 0.1 valence units wide. Interestingly, the maximum T{sub c} in Na{sub x}CoO{sub 2}{center_dot}yH{sub 2}O occurs when the cobalt oxidation state is near +3.5. Thus, we speculate that the maximum T{sub c} occurs near the charge ordered

  10. Cobalt alleviates GA-induced programmed cell death in wheat aleurone layers via the regulation of H2O2 production and heme oxygenase-1 expression.

    PubMed

    Wu, Mingzhu; Li, Jiale; Wang, Fangquan; Li, Feng; Yang, Jun; Shen, Wenbiao

    2014-11-14

    Heme oxygenase-1 (HO-1) and hydrogen peroxide (H2O2) are key signaling molecules that are produced in response to various environmental stimuli. Here, we demonstrate that cobalt is able to delay gibberellic acid (GA)-induced programmed cell death (PCD) in wheat aleurone layers. A similar response was observed when samples were pretreated with carbon monoxide (CO) or bilirubin (BR), two end-products of HO catalysis. We further observed that increased HO-1 expression played a role in the cobalt-induced alleviation of PCD. The application of HO-1-specific inhibitor, zinc protoporphyrin-IX (ZnPPIX), substantially prevented the increases of HO-1 activity and the alleviation of PCD triggered by cobalt. The stimulation of HO-1 expression, and alleviation of PCD might be caused by the initial H2O2 production induced by cobalt. qRT-PCR and enzymatic assays revealed that cobalt-induced gene expression and the corresponding activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), three enzymes that metabolize reactive oxygen species, were consistent with the H2O2 accumulation during GA treatment. These cobalt responses were differentially blocked by co-treatment with ZnPPIX. We therefore suggest that HO-1 functions in the cobalt-triggered alleviation of PCD in wheat aleurone layers, which is also dependent on the enhancement of the activities of antioxidant enzymes.

  11. Cobalt Alleviates GA-Induced Programmed Cell Death in Wheat Aleurone Layers via the Regulation of H2O2 Production and Heme Oxygenase-1 Expression

    PubMed Central

    Wu, Mingzhu; Li, Jiale; Wang, Fangquan; Li, Feng; Yang, Jun; Shen, Wenbiao

    2014-01-01

    Heme oxygenase-1 (HO-1) and hydrogen peroxide (H2O2) are key signaling molecules that are produced in response to various environmental stimuli. Here, we demonstrate that cobalt is able to delay gibberellic acid (GA)-induced programmed cell death (PCD) in wheat aleurone layers. A similar response was observed when samples were pretreated with carbon monoxide (CO) or bilirubin (BR), two end-products of HO catalysis. We further observed that increased HO-1 expression played a role in the cobalt-induced alleviation of PCD. The application of HO-1-specific inhibitor, zinc protoporphyrin-IX (ZnPPIX), substantially prevented the increases of HO-1 activity and the alleviation of PCD triggered by cobalt. The stimulation of HO-1 expression, and alleviation of PCD might be caused by the initial H2O2 production induced by cobalt. qRT-PCR and enzymatic assays revealed that cobalt-induced gene expression and the corresponding activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), three enzymes that metabolize reactive oxygen species, were consistent with the H2O2 accumulation during GA treatment. These cobalt responses were differentially blocked by co-treatment with ZnPPIX. We therefore suggest that HO-1 functions in the cobalt-triggered alleviation of PCD in wheat aleurone layers, which is also dependent on the enhancement of the activities of antioxidant enzymes. PMID:25405743

  12. Nickel cobalt oxide nanowire-reduced graphite oxide composite material and its application for high performance supercapacitor electrode material.

    PubMed

    Wang, Xu; Yan, Chaoyi; Sumboja, Afriyanti; Lee, Pooi See

    2014-09-01

    In this paper, we report a facile synthesis method of mesoporous nickel cobalt oxide (NiCo2O4) nanowire-reduced graphite oxide (rGO) composite material by urea induced hydrolysis reaction, followed by sintering at 300 degrees C. P123 was used to stabilize the GO during synthesis, which resulted in a uniform coating of NiCo2O4 nanowire on rGO sheet. The growth mechanism of the composite material is discussed in detail. The NiCo2O4-rGO composite material showed an outstanding electrochemical performance of 873 F g(-1) at 0.5 A g(-1) and 512 F g(-1) at 40 A g(-1). This method provides a promising approach towards low cost and large scale production of supercapacitor electrode material.

  13. First-principles density functional theory study of cobalt (hydr)oxides and titanium dioxide for electrochemical oxygen evolution

    NASA Astrophysics Data System (ADS)

    Chen, Jia

    The spinel cobalt oxide Co3O4 is a magnetic semiconductor containing cobalt ions in Co2+ and Co3+ oxidation states. We have studied the electronic, magnetic and bonding properties of Co3O4 using density functional theory (DFT) at the Generalized Gradient Approximation (GGA), GGA+U, and PBE0 hybrid functional levels. (110) is a frequently exposed surface in Co3O4 nanomaterials. We employed DFT+U to study the atomic structures, energetics, magnetic and electronic properties of the two possible terminations, A and B, of this surface. These calculations predict A as the stable termination in a wide range of oxygen chemical potentials, consistent with recent experimental observations. The Co3+ ions do not have a magnetic moment in the bulk, but become magnetic at the surface, which leads to surface magnetic orderings different from the one in the bulk. Surface electronic states are present in the lower half of the bulk band gap and cause partial metallization of both surface terminations. These states are responsible for the charge compensation mechanism stabilizing both polar terminations. We also carried out DFT+U to study the interaction of water with the (110) surface of Co3O4, a widely used oxidation catalyst. Dissociative water adsorption is preferred from low coverage up to one monolayer on the A termination and up to one-half monolayer coverage on the B termination. On the latter, a mixed molecular and dissociated monolayer is more stable at full coverage. The computed structures are used to investigate the free energy changes during water oxidation on both surface terminations. Using first-principles density functional theory (DFT) calculations we determine the relative Gibbs free energies of CoO, Co(OH)2, Co 3O4, CoO(OH) and CoO2 in electrochemical environment. We find that CoO(OH) and CoO2 are the stable phases under oxidation conditions. These results, combined with surface structure studies of CoO(OH) (0001), show that a CoO2x-- (x=0~0.5) layer is present

  14. Direct atomic-scale observation of layer-by-layer oxide growth during magnesium oxidation

    SciTech Connect

    Zheng, He; Wu, Shujing; Sheng, Huaping; Liu, Chun; Liu, Yu; Cao, Fan; Zhou, Zhichao; Zhao, Dongshan E-mail: dszhao@whu.edu.cn; Wang, Jianbo E-mail: dszhao@whu.edu.cn; Zhao, Xingzhong

    2014-04-07

    The atomic-scale oxide growth dynamics are directly revealed by in situ high resolution transmission electron microscopy during the oxidation of Mg surface. The oxidation process is characterized by the layer-by-layer growth of magnesium oxide (MgO) nanocrystal via the adatom process. Consistently, the nucleated MgO crystals exhibit faceted surface morphology as enclosed by (200) lattice planes. It is believed that the relatively lower surface energies of (200) lattice planes should play important roles, governing the growth mechanism. These results facilitate the understanding of the nanoscale oxide growth mechanism that will have an important impact on the development of magnesium or magnesium alloys with improved resistance to oxidation.

  15. Thermoelectric material including conformal oxide layers and method of making the same using atomic layer deposition

    DOEpatents

    Cho, Jung Young; Ahn, Dongjoon; Salvador, James R.; Meisner, Gregory P.

    2016-06-07

    A thermoelectric material includes a substrate particle and a plurality of conformal oxide layers formed on the substrate particle. The plurality of conformal oxide layers has a total oxide layer thickness ranging from about 2 nm to about 20 nm. The thermoelectric material excludes oxide nanoparticles. A method of making the thermoelectric material is also disclosed herein.

  16. Formation of brominated disinfection by-products and bromate in cobalt catalyzed peroxymonosulfate oxidation of phenol.

    PubMed

    Liu, Kuo; Lu, Junhe; Ji, Yuefei

    2015-11-01

    Formation of halogenated disinfection by-products (DBPs) in sulfate radical [Formula: see text] based oxidation processes attracted considerable attention recently. However, the underlying reaction pathways have not been well explored. This study focused on the transformation of Br(-) in cobalt activated peroxymonosulfate (Co(2+)/PMS) oxidation process. Phenol was added as a model compound to mimic the reactivity of natural organic matter (NOM). It was revealed that Br(-) was efficiently transformed to reactive bromine species (RBS) including free bromine and bromine radicals (Br, [Formula: see text] , etc.) in Co(2+)/PMS system. [Formula: see text] played a principal role during this process. RBS thus generated resulted in the bromination of phenol and formation brominated DBPs (Br-DBPs) including bromoform and bromoacetic acids, during which brominated phenols were detected as the intermediates. Br-DBPs were further degraded by excessive [Formula: see text] and transformed to bromate ultimately. Free bromine was also formed in the absence of Co(2+), suggesting Br(-) could be oxidized by PMS per se. Free bromine was incorporated to phenol sequentially leading to Br-DBPs as well. However, Br-DBPs could not be further transformed in the absence of [Formula: see text] . This is the first study that elucidated the comprehensive transformation map of Br(-) in PMS oxidation systems, which should be taken into consideration when PMS was applied to eliminate contamination in real practice.

  17. Cobalt oxide nanosheets wrapped onto nickel foam for non-enzymatic detection of glucose

    NASA Astrophysics Data System (ADS)

    Meng, Shangjun; Wu, Meiyan; Wang, Qian; Dai, Ziyang; Si, Weili; Huang, Wei; Dong, Xiaochen

    2016-08-01

    Ultra-sensitive and highly selective detection of glucose is essential for the clinical diagnosis of diabetes. In this paper, an ultra-sensitive glucose sensor was successfully fabricated based on cobalt oxide (Co3O4) nanosheets directly grown on nickel foam through a simple hydrothermal method. Characterizations indicated that the Co3O4 nanosheets are completely and uniformly wrapped onto the surface of nickel foam to form a three-dimensional heterostructure. The resulting self-standing electrochemical electrode presents a high performance for the non-enzymatic detection of glucose, including short response time (<10 s), ultra-sensitivity (12.97 mA mM‑1 cm‑2), excellent selectivity and low detection limit (0.058 μM, S/N = 3). These results indicate that Co3O4 nanosheets wrapped onto nickel foam are a low-cost, practical, and high performance electrochemical electrode for bio sensing.

  18. Engineering surface atomic structure of single-crystal cobalt (II) oxide nanorods for superior electrocatalysis

    PubMed Central

    Ling, Tao; Yan, Dong-Yang; Jiao, Yan; Wang, Hui; Zheng, Yao; Zheng, Xueli; Mao, Jing; Du, Xi-Wen; Hu, Zhenpeng; Jaroniec, Mietek; Qiao, Shi-Zhang

    2016-01-01

    Engineering the surface structure at the atomic level can be used to precisely and effectively manipulate the reactivity and durability of catalysts. Here we report tuning of the atomic structure of one-dimensional single-crystal cobalt (II) oxide (CoO) nanorods by creating oxygen vacancies on pyramidal nanofacets. These CoO nanorods exhibit superior catalytic activity and durability towards oxygen reduction/evolution reactions. The combined experimental studies, microscopic and spectroscopic characterization, and density functional theory calculations reveal that the origins of the electrochemical activity of single-crystal CoO nanorods are in the oxygen vacancies that can be readily created on the oxygen-terminated {111} nanofacets, which favourably affect the electronic structure of CoO, assuring a rapid charge transfer and optimal adsorption energies for intermediates of oxygen reduction/evolution reactions. These results show that the surface atomic structure engineering is important for the fabrication of efficient and durable electrocatalysts. PMID:27650485

  19. Engineering surface atomic structure of single-crystal cobalt (II) oxide nanorods for superior electrocatalysis.

    PubMed

    Ling, Tao; Yan, Dong-Yang; Jiao, Yan; Wang, Hui; Zheng, Yao; Zheng, Xueli; Mao, Jing; Du, Xi-Wen; Hu, Zhenpeng; Jaroniec, Mietek; Qiao, Shi-Zhang

    2016-09-21

    Engineering the surface structure at the atomic level can be used to precisely and effectively manipulate the reactivity and durability of catalysts. Here we report tuning of the atomic structure of one-dimensional single-crystal cobalt (II) oxide (CoO) nanorods by creating oxygen vacancies on pyramidal nanofacets. These CoO nanorods exhibit superior catalytic activity and durability towards oxygen reduction/evolution reactions. The combined experimental studies, microscopic and spectroscopic characterization, and density functional theory calculations reveal that the origins of the electrochemical activity of single-crystal CoO nanorods are in the oxygen vacancies that can be readily created on the oxygen-terminated {111} nanofacets, which favourably affect the electronic structure of CoO, assuring a rapid charge transfer and optimal adsorption energies for intermediates of oxygen reduction/evolution reactions. These results show that the surface atomic structure engineering is important for the fabrication of efficient and durable electrocatalysts.

  20. Nickel-cobalt oxides/carbon nanoflakes as anode materials for lithium-ion batteries

    SciTech Connect

    NuLi, Yanna Zhang Peng; Guo Zaiping Liu Huakun; Yang Jun; Wang Jiulin

    2009-01-08

    Novel nickel-cobalt oxides/carbon nanoflakes with Ni/Co molar ratio = 1:1 and 1:2 have been synthesized by a convenient hydrothermal method followed by a simple calcination process. X-ray diffraction results showed that the composites were composed of NiO, Co{sub 3}O{sub 4}, and carbon. Scanning electron microscope measurements demonstrated that the composites were flakes less than 100 nm in thickness, and the corresponding energy dispersive spectroscopy mapping showed that the carbon was distributed homogeneously in the composites. The electrochemical results showed that the composite electrodes exhibited low initial coulombic efficiency and excellent charge-discharge cycling stability. Additionally, the effect of different Ni/Co molar ratios on the electrochemical properties of the composites was investigated, and better performance was obtained for the sample with a Ni/Co molar ratio of 1:2.

  1. Engineering surface atomic structure of single-crystal cobalt (II) oxide nanorods for superior electrocatalysis.

    PubMed

    Ling, Tao; Yan, Dong-Yang; Jiao, Yan; Wang, Hui; Zheng, Yao; Zheng, Xueli; Mao, Jing; Du, Xi-Wen; Hu, Zhenpeng; Jaroniec, Mietek; Qiao, Shi-Zhang

    2016-01-01

    Engineering the surface structure at the atomic level can be used to precisely and effectively manipulate the reactivity and durability of catalysts. Here we report tuning of the atomic structure of one-dimensional single-crystal cobalt (II) oxide (CoO) nanorods by creating oxygen vacancies on pyramidal nanofacets. These CoO nanorods exhibit superior catalytic activity and durability towards oxygen reduction/evolution reactions. The combined experimental studies, microscopic and spectroscopic characterization, and density functional theory calculations reveal that the origins of the electrochemical activity of single-crystal CoO nanorods are in the oxygen vacancies that can be readily created on the oxygen-terminated {111} nanofacets, which favourably affect the electronic structure of CoO, assuring a rapid charge transfer and optimal adsorption energies for intermediates of oxygen reduction/evolution reactions. These results show that the surface atomic structure engineering is important for the fabrication of efficient and durable electrocatalysts. PMID:27650485

  2. In Vivo Wear Performance of Cobalt-Chromium Versus Oxidized Zirconium Femoral Total Knee Replacements.

    PubMed

    Gascoyne, Trevor C; Teeter, Matthew G; Guenther, Leah E; Burnell, Colin D; Bohm, Eric R; Naudie, Douglas R

    2016-01-01

    This study examines the damage and wear on the polyethylene (PE) inserts from 52 retrieved Genesis II total knee replacements to identify differences in tribological performance between matched pairs of cobalt-chromium (CoCr) and oxidized zirconium (OxZr) femoral components. Observer damage scoring and microcomputed tomography were used to quantify PE damage and wear, respectively. No significant differences were found between CoCr and OxZr groups in terms of PE insert damage, surface penetration, or wear. No severe damage such as cracking or delamination was noted on any of the 52 PE inserts. Observer damage scoring did not correlate with penetrative or volumetric PE wear. The more costly OxZr femoral component does not demonstrate clear tribological benefit over the standard CoCr component in the short term with this total knee replacement design.

  3. Light-induced water oxidation at silicon electrodes functionalized with a cobalt oxygen-evolving catalyst.

    PubMed

    Pijpers, Joep J H; Winkler, Mark T; Surendranath, Yogesh; Buonassisi, Tonio; Nocera, Daniel G

    2011-06-21

    Integrating a silicon solar cell with a recently developed cobalt-based water-splitting catalyst (Co-Pi) yields a robust, monolithic, photo-assisted anode for the solar fuels process of water splitting to O(2) at neutral pH. Deposition of the Co-Pi catalyst on the Indium Tin Oxide (ITO)-passivated p-side of a np-Si junction enables the majority of the voltage generated by the solar cell to be utilized for driving the water-splitting reaction. Operation under neutral pH conditions fosters enhanced stability of the anode as compared to operation under alkaline conditions (pH 14) for which long-term stability is much more problematic. This demonstration of a simple, robust construct for photo-assisted water splitting is an important step towards the development of inexpensive direct solar-to-fuel energy conversion technologies.

  4. Light-induced water oxidation at silicon electrodes functionalized with a cobalt oxygen-evolving catalyst

    PubMed Central

    Pijpers, Joep J. H.; Winkler, Mark T.; Surendranath, Yogesh; Buonassisi, Tonio; Nocera, Daniel G.

    2011-01-01

    Integrating a silicon solar cell with a recently developed cobalt-based water-splitting catalyst (Co-Pi) yields a robust, monolithic, photo-assisted anode for the solar fuels process of water splitting to O2 at neutral pH. Deposition of the Co-Pi catalyst on the Indium Tin Oxide (ITO)-passivated p-side of a np-Si junction enables the majority of the voltage generated by the solar cell to be utilized for driving the water-splitting reaction. Operation under neutral pH conditions fosters enhanced stability of the anode as compared to operation under alkaline conditions (pH 14) for which long-term stability is much more problematic. This demonstration of a simple, robust construct for photo-assisted water splitting is an important step towards the development of inexpensive direct solar-to-fuel energy conversion technologies. PMID:21646536

  5. Cobalt oxide nanosheets wrapped onto nickel foam for non-enzymatic detection of glucose

    NASA Astrophysics Data System (ADS)

    Meng, Shangjun; Wu, Meiyan; Wang, Qian; Dai, Ziyang; Si, Weili; Huang, Wei; Dong, Xiaochen

    2016-08-01

    Ultra-sensitive and highly selective detection of glucose is essential for the clinical diagnosis of diabetes. In this paper, an ultra-sensitive glucose sensor was successfully fabricated based on cobalt oxide (Co3O4) nanosheets directly grown on nickel foam through a simple hydrothermal method. Characterizations indicated that the Co3O4 nanosheets are completely and uniformly wrapped onto the surface of nickel foam to form a three-dimensional heterostructure. The resulting self-standing electrochemical electrode presents a high performance for the non-enzymatic detection of glucose, including short response time (<10 s), ultra-sensitivity (12.97 mA mM-1 cm-2), excellent selectivity and low detection limit (0.058 μM, S/N = 3). These results indicate that Co3O4 nanosheets wrapped onto nickel foam are a low-cost, practical, and high performance electrochemical electrode for bio sensing.

  6. Polyethylene oxide hydration in grafted layers

    NASA Astrophysics Data System (ADS)

    Dormidontova, Elena; Wang, Zilu

    Hydration of water soluble polymers is one of the key-factors defining their conformation and properties, similar to biopolymers. Polyethylene oxide (PEO) is one of the most important biomedical-applications polymers and is known for its reverse temperature solubility due to hydrogen bonding with water. As in many practical applications PEO chains are grafted to surfaces, e.g. of nanoparticles or planar surfaces, it is important to understand PEO hydration in such grafted layers. Using atomistic molecular dynamic simulations we investigate the details of molecular conformation and hydration of PEO end-grafted to gold surfaces. We analyze polymer and water density distribution as a function of distance from the surface for different grafting densities. Based on a detailed analysis of hydrogen bonding between polymer and water in grafted PEO layers, we will discuss the extent of PEO hydration and its implication for polymer conformation, mobility and layer properties. This research is supported by NSF (DMR-1410928).

  7. Low-solubility particles and a Trojan-horse type mechanism of toxicity: the case of cobalt oxide on human lung cells

    PubMed Central

    2014-01-01

    Background The mechanisms of toxicity of metal oxide particles towards lung cells are far from being understood. In particular, the relative contribution of intracellular particulate versus solubilized fractions is rarely considered as it is very challenging to assess, especially for low-solubility particles such as cobalt oxide (Co3O4). Methods This study was possible owing to two highly sensitive, independent, analytical techniques, based on single-cell analysis, using ion beam microanalysis, and on bulk analysis of cell lysates, using mass spectrometry. Results Our study shows that cobalt oxide particles, of very low solubility in the culture medium, are readily incorporated by BEAS-2B human lung cells through endocytosis via the clathrin-dependent pathway. They are partially solubilized at low pH within lysosomes, leading to cobalt ions release. Solubilized cobalt was detected within the cytoplasm and the nucleus. As expected from these low-solubility particles, the intracellular solubilized cobalt content is small compared with the intracellular particulate cobalt content, in the parts-per-thousand range or below. However, we were able to demonstrate that this minute fraction of intracellular solubilized cobalt is responsible for the overall toxicity. Conclusions Cobalt oxide particles are readily internalized by pulmonary cells via the endo-lysosomal pathway and can lead, through a Trojan-horse mechanism, to intracellular release of toxic metal ions over long periods of time, involving specific toxicity. PMID:24669904

  8. Solar selective black cobalt: preparation, structure, and thermal stability

    SciTech Connect

    Smith, G.B.; Ignatiev, A.; Zajac, G.

    1980-08-01

    In the quest for an electroplated selective black coating stable to 500 /sup 0/C in air, black cobalts have been prepared by three techniques to yield (a) plated cobalt sulphides, (b) plated cobalt oxide-hydroxide, and (c) cobalt oxide prepared by thermal oxidation of electropolated cobalt metal. The optical properties of the various coatings are analyzed before and after exposure to air for extended periods of time at temperatures in the 300 /sup 0/--500 /sup 0/C range. The sulfide black cobalt is not acceptable as a high-temperature selective absorber due to severe thermal degradation. The plated oxide is a good selective absorber to about 400 /sup 0/C, and the thermally oxidized black to a slightly higher temperature, but degrades at 500 /sup 0/C. Structure studies via scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and x-ray photoemission spectroscopy (XPS) are reported which yield a full account of the coating chemistry before and after heating. The studies reveal that the high solar absorptance of the acceptable black cobalt coatings is due to a continuation of a porous outer layer grading into nondense oxides of cobalt; either CoO or Co/sub 3/O/sub 4/, depending on the film. Absorption is intrinsic but not due to metal particles as in black chrome. A limited amount of optical degradation occurs upon heating the oxide black cobalt in air due to oxidation of hydroxide. However, the major degradation problem is shown to be substrate oxidation in contrast to black chrome where film oxidation is the principal problem.

  9. Structural and magnetic properties of cobalt-doped iron oxide nanoparticles prepared by solution combustion method for biomedical applications

    PubMed Central

    Venkatesan, Kaliyamoorthy; Rajan Babu, Dhanakotti; Kavya Bai, Mane Prabhu; Supriya, Ravi; Vidya, Radhakrishnan; Madeswaran, Saminathan; Anandan, Pandurangan; Arivanandhan, Mukannan; Hayakawa, Yasuhiro

    2015-01-01

    Cobalt-doped iron oxide nanoparticles were prepared by solution combustion technique. The structural and magnetic properties of the prepared samples were also investigated. The average crystallite size of cobalt ferrite (CoFe2O4) magnetic nanoparticle was calculated using Scherrer equation, and it was found to be 16±5 nm. The particle size was measured by transmission electron microscope. This value was found to match with the crystallite size calculated by Scherrer equation corresponding to the prominent intensity peak (311) of X-ray diffraction. The high-resolution transmission electron microscope image shows clear lattice fringes and high crystallinity of cobalt ferrite magnetic nanoparticles. The synthesized magnetic nanoparticles exhibited the saturation magnetization value of 47 emu/g and coercivity of 947 Oe. The anti-microbial activity of cobalt ferrite nanoparticles showed better results as an anti-bacterial agent. The affinity constant was determined for the nanoparticles, and the cytotoxicity studies were conducted for the cobalt ferrite nanoparticles at different concentrations and the results are discussed. PMID:26491320

  10. Structural and magnetic properties of cobalt-doped iron oxide nanoparticles prepared by solution combustion method for biomedical applications.

    PubMed

    Venkatesan, Kaliyamoorthy; Rajan Babu, Dhanakotti; Kavya Bai, Mane Prabhu; Supriya, Ravi; Vidya, Radhakrishnan; Madeswaran, Saminathan; Anandan, Pandurangan; Arivanandhan, Mukannan; Hayakawa, Yasuhiro

    2015-01-01

    Cobalt-doped iron oxide nanoparticles were prepared by solution combustion technique. The structural and magnetic properties of the prepared samples were also investigated. The average crystallite size of cobalt ferrite (CoFe2O4) magnetic nanoparticle was calculated using Scherrer equation, and it was found to be 16±5 nm. The particle size was measured by transmission electron microscope. This value was found to match with the crystallite size calculated by Scherrer equation corresponding to the prominent intensity peak (311) of X-ray diffraction. The high-resolution transmission electron microscope image shows clear lattice fringes and high crystallinity of cobalt ferrite magnetic nanoparticles. The synthesized magnetic nanoparticles exhibited the saturation magnetization value of 47 emu/g and coercivity of 947 Oe. The anti-microbial activity of cobalt ferrite nanoparticles showed better results as an anti-bacterial agent. The affinity constant was determined for the nanoparticles, and the cytotoxicity studies were conducted for the cobalt ferrite nanoparticles at different concentrations and the results are discussed.

  11. Cobalt-Catalyzed Oxidative C-H/C-H Cross-Coupling between Two Heteroarenes.

    PubMed

    Tan, Guangying; He, Shuang; Huang, Xiaolei; Liao, Xingrong; Cheng, Yangyang; You, Jingsong

    2016-08-22

    The first example of cobalt-catalyzed oxidative C-H/C-H cross-coupling between two heteroarenes is reported, which exhibits a broad substrate scope and a high tolerance level for sensitive functional groups. When the amount of Co(OAc)2 ⋅4 H2 O is reduced from 6.0 to 0.5 mol %, an excellent yield is still obtained at an elevated temperature with a prolonged reaction time. The method can be extended to the reaction between an arene and a heteroarene. It is worth noting that the Ag2 CO3 oxidant is renewable. Preliminary mechanistic studies by radical trapping experiments, hydrogen/deuterium exchange experiments, kinetic isotope effect, electron paramagnetic resonance (EPR), and high resolution mass spectrometry (HRMS) suggest that a single electron transfer (SET) pathway is operative, which is distinctly different from the dual C-H bond activation pathway that the well-described oxidative C-H/C-H cross-coupling reactions between two heteroarenes typically undergo. PMID:27460406

  12. New insights into atrazine degradation by cobalt catalyzed peroxymonosulfate oxidation: kinetics, reaction products and transformation mechanisms.

    PubMed

    Ji, Yuefei; Dong, Changxun; Kong, Deyang; Lu, Junhe

    2015-03-21

    The widespread occurrence of atrazine in waters poses potential risk to ecosystem and human health. In this study, we investigated the underlying mechanisms and transformation pathways of atrazine degradation by cobalt catalyzed peroxymonosulfate (Co(II)/PMS). Co(II)/PMS was found to be more efficient for ATZ elimination in aqueous solution than Fe(II)/PMS process. ATZ oxidation by Co(II)/PMS followed pseudo-first-order kinetics, and the reaction rate constant (k(obs)) increased appreciably with increasing Co(II) concentration. Increasing initial PMS concentration favored the decomposition of ATZ, however, no linear relationship between k(obs) and PMS concentration was observed. Higher efficiency of ATZ oxidation was observed around neutral pH, implying the possibility of applying Co(II)/PMS process under environmental realistic conditions. Natural organic matter (NOM), chloride (Cl(-)) and bicarbonate (HCO3(-)) showed detrimental effects on ATZ degradation, particularly at higher concentrations. Eleven products were identified by applying solid phase extraction-liquid chromatography-mass spectrometry (SPE-LC/MS) techniques. Major transformation pathways of ATZ included dealkylation, dechlorination-hydroxylation, and alkyl chain oxidation. Detailed mechanisms responsible for these transformation pathways were discussed. Our results reveal that Co(II)/PMS process might be an efficient technique for remediation of groundwater contaminated by ATZ and structurally related s-triazine herbicides.

  13. Cobalt-Catalyzed Oxidative C-H/C-H Cross-Coupling between Two Heteroarenes.

    PubMed

    Tan, Guangying; He, Shuang; Huang, Xiaolei; Liao, Xingrong; Cheng, Yangyang; You, Jingsong

    2016-08-22

    The first example of cobalt-catalyzed oxidative C-H/C-H cross-coupling between two heteroarenes is reported, which exhibits a broad substrate scope and a high tolerance level for sensitive functional groups. When the amount of Co(OAc)2 ⋅4 H2 O is reduced from 6.0 to 0.5 mol %, an excellent yield is still obtained at an elevated temperature with a prolonged reaction time. The method can be extended to the reaction between an arene and a heteroarene. It is worth noting that the Ag2 CO3 oxidant is renewable. Preliminary mechanistic studies by radical trapping experiments, hydrogen/deuterium exchange experiments, kinetic isotope effect, electron paramagnetic resonance (EPR), and high resolution mass spectrometry (HRMS) suggest that a single electron transfer (SET) pathway is operative, which is distinctly different from the dual C-H bond activation pathway that the well-described oxidative C-H/C-H cross-coupling reactions between two heteroarenes typically undergo.

  14. Processes of nickel and cobalt uptake by a manganese oxide forming sediment in Pinal Creek, Globe mining district, Arizona

    USGS Publications Warehouse

    Kay, J.T.; Conklin, M.H.; Fuller, C.C.; O'Day, P. A.

    2001-01-01

    A series of column experiments was conducted using manganese oxide coated sediments collected from the hyporheic zone in Pinal Creek (AZ), a metal-contaminated stream, to study the uptake and retention of Mn, Ni, and Co. Experimental variables included the absence (abiotic) and presence (biotic) of active Mn-oxidizing bacteria, the absence and presence of dissolved Mn, and sediment manganese oxide content. Uptake of Mn under biotic conditions was between 8 and 39% higher than under abiotic conditions. Continuous uptake of Mn due to biotic oxidation was evident from extraction of column sediments. Manganese uptake is hypothesized to initially occur as adsorption, which led to subsequent surface and/or microbial oxidation. Complete breakthrough of Ni within 100 pore volumes indicated no process of continuous uptake and was modeled as an equilibrium adsorption process. Nickel uptake in the presence of dissolved Mn was 67-100% reversible. Sediment extractions suggest that Ni uptake occurred through weak and strong adsorption. Continuous uptake of cobalt increased with sediment manganese oxide content, and Co uptake was up to 75% greater under biotic than abiotic conditions. Cobalt uptake was controlled by both existing and newly formed manganese oxides. Only a small amount of Co uptake was reversible (10-25%). XANES spectral analysis indicated that most Co(II) was oxidized to Co(III) and probably incorporated structurally into manganese oxides. Although manganese oxides were the primary phase controlling uptake and retention of Mn, Ni, and Co, the mechanisms varied among the metals.

  15. Amperometric Determination of Ascorbic Acid in Pharmaceutical Formulations by a Reduced Graphene Oxide-cobalt Hexacyanoferrate Nanocomposite

    PubMed Central

    Heli, Hossein

    2015-01-01

    Investigation of the redox properties of drugs and their determination are performed by electrochemical techniques. Data obtained from electrochemical techniques are often correlated with molecular structure and pharmacological activity of drugs. In this regard, different modified electrodes were applied as sensors for quantification of different drugs. A nanocomposite of reduced graphene oxide-cobalt hexacyanoferrate was synthesized by a simple precipitation route. Scanning electron microscopy revealed that the nanocomposite comprised nanoparticles of cobalt hexacyanoferrate attached to the reduced graphene oxide nanosheets. A nanocomposite-modified carbon paste electrode was then fabricated. It represented prominent activity toward the electrocatalytic oxidation of ascorbic acid, and the kinetics of the electrooxidation process was evaluated. Finally, an amperometric method was developed for the quantification of ascorbic acid in different pharmaceutical formulations. PMID:25901152

  16. Development of new layered selenide oxides with perovskite-type oxide layers

    NASA Astrophysics Data System (ADS)

    Ushiyama, Koichi; Ogino, Hiraku; Kishio, Kohji; Shimoyama, Jun-Ichi

    2010-03-01

    Several Fe-based superconductors with perovskite-type oxide layers, such as Sr2ScFePO3 (Tc ˜ 17 K)^[1], were discovered in our previous study. These compounds are composed of alternate stacking of superconducting layers with antifluorite structure and perovskite-type blocking layers. Since both layers are flexible in terms of chemical composition, development of various new functional materials can be expected from this family. In the present study, we have attempted to synthesize new layered selenide oxides with CuSe layers and discovered more than ten compounds, such as Sr2MCu2Se2O2 (M = Mn, Co, Ni, Cu, Zn) and Sr2MCuSeO3 (M = Sc, Cr, Mn, Fe, Ga, In), thus far. These indicated that the CuSe layer can accommodate various types of blocking layers, which may lead various functions. Among them, Sr2Cu3Se2O2 has a potential as for the mother compound of superconductor, if appropriate concentration of carrier is introduced to the CuO2 layer. Crystal structure and physical properties of these newly found compounds will be reported. [1] H. Ogino et al., Supercond. Sci. Technol. 22 (2009) 075008

  17. Kinetics of Initial Layer-by-Layer Oxidation of Si(001) Surfaces

    NASA Astrophysics Data System (ADS)

    Watanabe, Heiji; Kato, Koichi; Uda, Tsuyoshi; Fujita, Ken; Ichikawa, Masakazu; Kawamura, Takaaki; Terakura, Kiyoyuki

    1998-01-01

    Layer-by-layer oxidation of Si(001) surfaces has been studied by scanning reflection electron microscopy (SREM). The oxidation kinetics of the top and second layers were independently investigated from the change in oxygen Auger peak intensity calibrated from the SREM observation. A barrierless oxidation of the first subsurface layer, as well as oxygen chemisorption onto the top layer, occurs at room temperature. The energy barrier of the second-layer oxidation was found to be 0.3 eV. The initial oxidation kinetics are discussed based on first-principles calculations.

  18. Stability of cobalt oxide infiltrated LSM/TZ8Y cathode for solid oxide fuel cells at intermediate temperatures

    NASA Astrophysics Data System (ADS)

    Chen, Xuan

    The performance of a La0.4Sr0.6MnO3/8wt% Y2O3-stabilized ZrO2 (LSM/YZ8Y) composite cathode was observed to increase by post-firing doping (infiltration) of cobalt nitrate into the pores of an LSM/TZ8Y cathode in solid oxide fuel cells. Results demonstrated that cobalt nitrate decomposed into nano-sized spinel structures of Co3O4 of sizes ranging from 40 to 60 nm. The stability of a Co3O4 infiltrated LSM/TZ8Y cathode was studied under both oxidizing and reducing environments at 700°C. This dissertation studied the coarsening effects of Co3O 4 nano-particles in the pores of LSM/TZ8Y cathodes and its chemical interaction between LSM and TZ8Y during 1000 hours of exposure to air. A scanning electron microscopy (SEM) was used to observe the microstructure. Polarization curves and electrochemical impedance spectroscopy were used to electrochemically characterize LSM/TZ8Y half cells (oxygen pump) with applied cathodic currents before and after Co3O4 infiltration. The chemical interactions of Co3O4 and an LSM/TZ8Y cathode were studied under the effects of a reducing atmosphere at various currents applied to the cathode, e.g., 500mA/cm2, 1500mA/cm2 and 3A/cm 2. The corresponding partial pressure of oxygen (P O2) at the cathode was observed and calculated from a built-in oxygen sensor which monitored applied cathodic currents. Chemical reactions were characterized through the use scanning transmission electron microscopy (STEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD) analysis.

  19. Lindqvist Polyoxoniobate Ion-Assisted Electrodeposition of Cobalt and Nickel Water Oxidation Catalysts.

    PubMed

    Liu, YuPing; Guo, Si-Xuan; Ding, Liang; Ohlin, C André; Bond, Alan M; Zhang, Jie

    2015-08-01

    A method has been developed for the efficient electrodeposition of cobalt and nickel nanostructures with the assistance of the Lindqvist ion [Nb6O19](8-). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry, and a range of electrochemical techniques have been used to characterize the morphology, composition, catalytic water oxidation activity and stability of the films in alkaline solution. SEM images show that films consisting of nanoparticles with diameters of ca. 30 to 40 nm are formed after 40-50 potential cycles of deposition. Nb and Co/Ni are detected in the films by EDX. ICP-MS results show an elemental ratio of 1:1 for Co:Nb and 1:3 for Ni:Nb, respectively. Raman spectra reveal the presence of both [Nb6O19](8-) and Co(OH)2/Ni(OH)2. The films exhibit excellent stability and efficiency for electrocatalytic water oxidation in alkaline solution. Turnover frequencies of 12.9 and 13.2 s(-1) were determined by rotating ring disk electrode voltammetry at an overpotential of 480 mV for Co and Ni films, respectively. Fourier transformed large amplitude alternating current (FTAC) voltammetry reveals an additional underlying oxidation process for Co under catalytic turnover conditions, which indicates that a Co(IV) species is involved in the efficient catalytic water oxidation reactions. FTAC voltammetric data also suggest that the Ni films undergoes a clear phase transformation upon aging in aqueous 1 M NaOH and the electrogenerated higher oxidation state Ni from β-NiOOH is the more active form of the catalyst.

  20. Lindqvist Polyoxoniobate Ion-Assisted Electrodeposition of Cobalt and Nickel Water Oxidation Catalysts.

    PubMed

    Liu, YuPing; Guo, Si-Xuan; Ding, Liang; Ohlin, C André; Bond, Alan M; Zhang, Jie

    2015-08-01

    A method has been developed for the efficient electrodeposition of cobalt and nickel nanostructures with the assistance of the Lindqvist ion [Nb6O19](8-). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry, and a range of electrochemical techniques have been used to characterize the morphology, composition, catalytic water oxidation activity and stability of the films in alkaline solution. SEM images show that films consisting of nanoparticles with diameters of ca. 30 to 40 nm are formed after 40-50 potential cycles of deposition. Nb and Co/Ni are detected in the films by EDX. ICP-MS results show an elemental ratio of 1:1 for Co:Nb and 1:3 for Ni:Nb, respectively. Raman spectra reveal the presence of both [Nb6O19](8-) and Co(OH)2/Ni(OH)2. The films exhibit excellent stability and efficiency for electrocatalytic water oxidation in alkaline solution. Turnover frequencies of 12.9 and 13.2 s(-1) were determined by rotating ring disk electrode voltammetry at an overpotential of 480 mV for Co and Ni films, respectively. Fourier transformed large amplitude alternating current (FTAC) voltammetry reveals an additional underlying oxidation process for Co under catalytic turnover conditions, which indicates that a Co(IV) species is involved in the efficient catalytic water oxidation reactions. FTAC voltammetric data also suggest that the Ni films undergoes a clear phase transformation upon aging in aqueous 1 M NaOH and the electrogenerated higher oxidation state Ni from β-NiOOH is the more active form of the catalyst. PMID:26158219

  1. Electronic structure and reactivity of cobalt oxide dimers and their hexacarbonyl complexes: a density functional study.

    PubMed

    Uzunova, Ellie L; Mikosch, Hans

    2012-03-29

    The dimers of cobalt oxide (CoO)(2) with cyclic and open bent structure are studied with the B1LYP density functional; the ordering of states is validated by the CCSD(T) method. The D(2h)-symmetry rhombic dioxide Co(2)O(2) with antiferromagnetically ordered electrons on cobalt centers is the global minimum. The cyclic peroxide Co(2)(O(2)) with side-on-bonded dioxygen in (7)B(2) ground state is separated from the global minimum by an energy gap of 3.15 eV. The dioxide is highly reactive as indicated by the high value of proton affinity and chemical reactivity indices. The four-member ring structures are more stable than those with three-member ring or chain configuration. The thermodynamic stability toward dissociation to CoO increases upon carbonylation, whereas proton affinity and reactivity with release of molecular oxygen also increase. The global minimum of Co(2)O(2)(CO)(6) corresponds to a triplet state (3)A" with oxygen atoms shifted above the molecular plane of the rhombic dioxide Co(2)O(2). The SOMO-LUMO gap in the ground-state carbonylated dioxide is wider, compared to the same gap in the bare dicobalt dioxide. The peroxo-isomer Co(2)(O(2))(CO)(6) retains the planar Co(2)(O(2)) ring and is only stable in a high-spin state (7)A". The carbonylated clusters have increased reactivity in both redox and nucleophilic reactions, as a result of the increased electron density in the Co(2)O(2)-ring area. PMID:22397598

  2. Synthesis and oxidation catalysis of [tris(oxazolinyl)borato]cobalt(II) scorpionates

    DOE PAGESBeta

    Reinig, Regina R.; Mukherjee, Debabrata; Weinstein, Zachary B.; Xie, Weiwei; Albright, Toshia; Baird, Benjamin; Gray, Tristan S.; Ellern, Arkady; Miller, Gordon J.; Winter, Arthur H.; et al

    2016-04-28

    The reaction of CoCl2·THF and thallium tris(4,4-dimethyl-2-oxazolinyl)phenylborate (TlToM) in tetrahydrofuran (THF) provides ToMCoCl (1) in 95 % yield; however, appropriate solvents and starting materials are required to favor 1 over two other readily formed side-products, (ToM)2Co (2) and {HToM}CoCl2 (3). ESR, NMR, FTIR, and UV/Vis spectroscopies were used to distinguish these cobalt(II) products and probe their electronic and structural properties. Even after the structures indicated by these methods were confirmed by X-ray crystallography, the spectroscopic identification of trace contaminants in the material was challenging. The recognition of possible contaminants in the synthesis of ToMCoCl in combination with the paramagnetic naturemore » of these complexes provided impetus for the utilization of X-ray powder diffraction to measure the purity of the ToMCoCl bulk sample. Furthermore, the X-ray powder diffraction results provide support for the bulk-phase purity of ToMCoCl in preparations that avoid 2 and 3. Thus, 1 is a precursor for new [tris(oxazolinyl)borato]cobalt chemistry, as exemplified by its reactions with KOtBu and NaOAc to give ToMCoOtBu (4) and ToMCoOAc (5), respectively. Compound 5 is a catalyst for the oxidation of cyclohexane with meta-chloroperoxybenzoic acid (mCPBA), and the rate constants and selectivity for cyclohexanol versus cyclohexanone and ϵ-caprolactone were assessed.« less

  3. High pseudocapacitive cobalt carbonate hydroxide films derived from CoAl layered double hydroxides

    NASA Astrophysics Data System (ADS)

    Lu, Zhiyi; Zhu, Wei; Lei, Xiaodong; Williams, Gareth R.; O'Hare, Dermot; Chang, Zheng; Sun, Xiaoming; Duan, Xue

    2012-05-01

    A thin nanosheet of mesoporous cobalt carbonate hydroxide (MPCCH) has been fabricated from a CoAl-LDH nanosheet following removal of the Al cations by alkali etching. The basic etched electrode exhibits enhanced specific capacitance (1075 F g-1 at 5 mA cm-2) and higher rate capability and cycling stability (92% maintained after 2000 cycles).A thin nanosheet of mesoporous cobalt carbonate hydroxide (MPCCH) has been fabricated from a CoAl-LDH nanosheet following removal of the Al cations by alkali etching. The basic etched electrode exhibits enhanced specific capacitance (1075 F g-1 at 5 mA cm-2) and higher rate capability and cycling stability (92% maintained after 2000 cycles). Electronic supplementary information (ESI) available: Detailed experimental procedure, specific capacitance calculation, EDS and FTIR results, electrochemical results of CoAl-LDH and SEM image. See DOI: 10.1039/c2nr30617d

  4. Mercury Adsorption and Oxidation over Cobalt Oxide Loaded Magnetospheres Catalyst from Fly Ash in Oxyfuel Combustion Flue Gas.

    PubMed

    Yang, Jianping; Zhao, Yongchun; Chang, Lin; Zhang, Junying; Zheng, Chuguang

    2015-07-01

    Cobalt oxide loaded magnetospheres catalyst from fly ash (Co-MF catalyst) showed good mercury removal capacity and recyclability under air combustion flue gas in our previous study. In this work, the Hg(0) removal behaviors as well as the involved reactions mechanism were investigated in oxyfuel combustion conditions. Further, the recyclability of Co-MF catalyst in oxyfuel combustion atmosphere was also evaluated. The results showed that the Hg(0) removal efficiency in oxyfuel combustion conditions was relative high compared to that in air combustion conditions. The presence of enriched CO2 (70%) in oxyfuel combustion atmosphere assisted the mercury oxidation due to the oxidation of function group of C-O formed from CO2. Under both atmospheres, the mercury removal efficiency decreased with the addition of SO2, NO, and H2O. However, the enriched CO2 in oxyfuel combustion atmosphere could somewhat weaken the inhibition of SO2, NO, and H2O. The multiple capture-regeneration cycles demonstrated that the Co-MF catalyst also present good regeneration performance in oxyfuel combustion atmosphere.

  5. Mercury Adsorption and Oxidation over Cobalt Oxide Loaded Magnetospheres Catalyst from Fly Ash in Oxyfuel Combustion Flue Gas.

    PubMed

    Yang, Jianping; Zhao, Yongchun; Chang, Lin; Zhang, Junying; Zheng, Chuguang

    2015-07-01

    Cobalt oxide loaded magnetospheres catalyst from fly ash (Co-MF catalyst) showed good mercury removal capacity and recyclability under air combustion flue gas in our previous study. In this work, the Hg(0) removal behaviors as well as the involved reactions mechanism were investigated in oxyfuel combustion conditions. Further, the recyclability of Co-MF catalyst in oxyfuel combustion atmosphere was also evaluated. The results showed that the Hg(0) removal efficiency in oxyfuel combustion conditions was relative high compared to that in air combustion conditions. The presence of enriched CO2 (70%) in oxyfuel combustion atmosphere assisted the mercury oxidation due to the oxidation of function group of C-O formed from CO2. Under both atmospheres, the mercury removal efficiency decreased with the addition of SO2, NO, and H2O. However, the enriched CO2 in oxyfuel combustion atmosphere could somewhat weaken the inhibition of SO2, NO, and H2O. The multiple capture-regeneration cycles demonstrated that the Co-MF catalyst also present good regeneration performance in oxyfuel combustion atmosphere. PMID:26024429

  6. Sensitivity of Interfibrillar and Subsarcolemmal Mitochondria to Cobalt Chloride-induced Oxidative Stress and Hydrogen Sulfide Treatment.

    PubMed

    Ayswarya, A; Kurian, G A

    2016-01-01

    Oxidative stress plays a significant role not only in cardiovascular disease but also in non-communicable diseases, where it plays a significant role the mortality rate. Hydrogen sulfide, the biological gaseous signaling molecule that preserves mitochondria in its mode of action, is an effective cardioprotective drug. However, cardiac mitochondria comprise of two distinct populations, namely interfibrillar and subsarcolemmal mitochondria, which respond distinctly in cardiovascular disease. This study was designed to determine the direct impact of cobalt chloride-induced oxidative stress in isolated mitochondrial subpopulations with an intention to examine the efficacy of hydrogen sulfide in preserving interfibrillar and subsarcolemmal mitochondria functional activities when they were incubated as pretreated, co-treated and post-treated agent. Mitochondrial subpopulations were isolated from the heart of male Wistar rats and subjected to cobalt chloride treatment (500 μM) for 20 min, followed by incubation with 10 μM sodium hydrosulfide in three different ways (Pre, Co, and Post-cobalt chloride treatment). Mitochondrial oxidative stress was measured by the concentration of thiobarbituric acid reactive species, reduced glutathione and the activities of enzymes like superoxide dismutase, catalase and glutathione peroxidase. Mitochondrial membrane potential, swelling behavior and enzyme activities were measured to assess its function. The increased level of lipid peroxidation and the decreased level of reduced glutathione in cobalt chloride-induced group confirm the induction of oxidative stress and were more predominant in the subsarcolemmal mitochondria. Hydrogen sulfide treatment to interfibrillar and subsarcolemmal mitochondria preserved their functional activities, but the effect was prominent only with co-treated group. In conclusion, the present study demonstrated that subsarcolemmal mitochondria are more prone to oxidative stress and the co-treatment of the

  7. Sensitivity of Interfibrillar and Subsarcolemmal Mitochondria to Cobalt Chloride-induced Oxidative Stress and Hydrogen Sulfide Treatment

    PubMed Central

    Ayswarya, A.; Kurian, G. A.

    2016-01-01

    Oxidative stress plays a significant role not only in cardiovascular disease but also in non-communicable diseases, where it plays a significant role the mortality rate. Hydrogen sulfide, the biological gaseous signaling molecule that preserves mitochondria in its mode of action, is an effective cardioprotective drug. However, cardiac mitochondria comprise of two distinct populations, namely interfibrillar and subsarcolemmal mitochondria, which respond distinctly in cardiovascular disease. This study was designed to determine the direct impact of cobalt chloride-induced oxidative stress in isolated mitochondrial subpopulations with an intention to examine the efficacy of hydrogen sulfide in preserving interfibrillar and subsarcolemmal mitochondria functional activities when they were incubated as pretreated, co-treated and post-treated agent. Mitochondrial subpopulations were isolated from the heart of male Wistar rats and subjected to cobalt chloride treatment (500 μM) for 20 min, followed by incubation with 10 μM sodium hydrosulfide in three different ways (Pre, Co, and Post-cobalt chloride treatment). Mitochondrial oxidative stress was measured by the concentration of thiobarbituric acid reactive species, reduced glutathione and the activities of enzymes like superoxide dismutase, catalase and glutathione peroxidase. Mitochondrial membrane potential, swelling behavior and enzyme activities were measured to assess its function. The increased level of lipid peroxidation and the decreased level of reduced glutathione in cobalt chloride-induced group confirm the induction of oxidative stress and were more predominant in the subsarcolemmal mitochondria. Hydrogen sulfide treatment to interfibrillar and subsarcolemmal mitochondria preserved their functional activities, but the effect was prominent only with co-treated group. In conclusion, the present study demonstrated that subsarcolemmal mitochondria are more prone to oxidative stress and the co-treatment of the

  8. Sensitivity of Interfibrillar and Subsarcolemmal Mitochondria to Cobalt Chloride-induced Oxidative Stress and Hydrogen Sulfide Treatment.

    PubMed

    Ayswarya, A; Kurian, G A

    2016-01-01

    Oxidative stress plays a significant role not only in cardiovascular disease but also in non-communicable diseases, where it plays a significant role the mortality rate. Hydrogen sulfide, the biological gaseous signaling molecule that preserves mitochondria in its mode of action, is an effective cardioprotective drug. However, cardiac mitochondria comprise of two distinct populations, namely interfibrillar and subsarcolemmal mitochondria, which respond distinctly in cardiovascular disease. This study was designed to determine the direct impact of cobalt chloride-induced oxidative stress in isolated mitochondrial subpopulations with an intention to examine the efficacy of hydrogen sulfide in preserving interfibrillar and subsarcolemmal mitochondria functional activities when they were incubated as pretreated, co-treated and post-treated agent. Mitochondrial subpopulations were isolated from the heart of male Wistar rats and subjected to cobalt chloride treatment (500 μM) for 20 min, followed by incubation with 10 μM sodium hydrosulfide in three different ways (Pre, Co, and Post-cobalt chloride treatment). Mitochondrial oxidative stress was measured by the concentration of thiobarbituric acid reactive species, reduced glutathione and the activities of enzymes like superoxide dismutase, catalase and glutathione peroxidase. Mitochondrial membrane potential, swelling behavior and enzyme activities were measured to assess its function. The increased level of lipid peroxidation and the decreased level of reduced glutathione in cobalt chloride-induced group confirm the induction of oxidative stress and were more predominant in the subsarcolemmal mitochondria. Hydrogen sulfide treatment to interfibrillar and subsarcolemmal mitochondria preserved their functional activities, but the effect was prominent only with co-treated group. In conclusion, the present study demonstrated that subsarcolemmal mitochondria are more prone to oxidative stress and the co-treatment of the

  9. The effect of zinc addition on the oxidation state of cobalt in Co/ZrO2 catalysts.

    PubMed

    Lebarbier, Vanessa M; Karim, Ayman M; Engelhard, Mark H; Wu, Yu; Xu, Bo-Qing; Petersen, Eric J; Datye, Abhaya K; Wang, Yong

    2011-11-18

    The effect of zinc promotion on the oxidation state of cobalt in Co/ZrO(2) catalysts was investigated and correlated with the activity and selectivity for ethanol steam reforming (ESR). Catalysts were synthesized by applying incipient wetness impregnation and characterized by using Brunauer-Emmett-Teller (BET), temperature-programmed reduction (TPR) measurements, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Higher ethanol conversion and lower CH(4) selectivity are observed for the Co/ZrO(2) catalyst promoted with Zn as compared to the Co/ZrO(2) catalyst alone. Addition of Zn inhibits the oxidation of metallic cobalt (Co(0) ) particles and results in a higher ratio of Co(0) /Co(2+) in the Zn-promoted Co/ZrO(2) catalyst. These results suggest that metallic cobalt (Co(0) ) is more active than Co(2+) in the ethanol conversion through dehydrogenation and that Co(2+) may play a role in the CH(4) formation. TPR measurements, on the other hand, reveal that Zn addition inhibits the reduction of Co(2+) and Co(3+) , which would lead to the false conclusion that oxidized Co is required to reduce the CH(4) formation. Therefore, TPR measurements may not be appropriate to correlate the degree of metal reducibility (in this case Co(0)) with the catalyst activity for reactions, such as ESR, where oxidizing conditions exist. PMID:21919212

  10. Magnetic properties of nickel and cobalt catalysts supported on nanoporous oxides.

    PubMed

    Gómez-Polo, C; Gil, A; Korili, S A; Pérez-Landazabal, J I; Recarte, V; Trujillano, R; Vicente, M A

    2008-06-01

    The aim of this work is to use magnetic measurements as a research tool in the study of possible metal-support interactions in nickel and cobalt nanoporous catalysts. Several physicochemical techniques, namely nitrogen adsorption, X-ray diffraction, temperature-programmed reduction and chemical analysis, were used to analyze the role of the preparation method and the nature of the support on the existence of such metal-support interactions and to relate them with the magnetic response of these nanoporous systems. The catalysts were prepared by incipient wetness impregnation and precipitation-deposition with two commercial oxides, gamma-Al2O3 and SiO2, as supports. The magnetic behavior of the catalysts is drastically affected by the existence of interactions between the metal and the support during the preparation procedure. The samples with weak metal-support interactions have characteristic magnetic behavior of antiferromagnetic metal oxide nanoparticles, while the ones having strong interactions display spin-glass like behavior.

  11. Graphene-Encapsulated Nanosheet-Assembled Zinc-Nickel-Cobalt Oxide Microspheres for Enhanced Lithium Storage.

    PubMed

    Zhang, Qiaobao; Chen, Huixin; Han, Xiang; Cai, Junjie; Yang, Yong; Liu, Meilin; Zhang, Kaili

    2016-01-01

    The appropriate combination of hierarchical transition-metal oxide (TMO) micro-/nanostructures constructed from porous nanobuilding blocks with graphene sheets (GNS) in a core/shell geometry is highly desirable for high-performance lithium-ion batteries (LIBs). A facile and scalable process for the fabrication of 3D hierarchical porous zinc-nickel-cobalt oxide (ZNCO) microspheres constructed from porous ultrathin nanosheets encapsulated by GNS to form a core/shell geometry is reported for improved electrochemical performance of the TMOs as an anode in LIBs. By virtue of their intriguing structural features, the produced ZNCO/GNS core/shell hybrids exhibit an outstanding reversible capacity of 1015 mA h g(-1) at 0.1 C after 50 cycles. Even at a high rate of 1 C, a stable capacity as high as 420 mA h g(-1) could be maintained after 900 cycles, which suggested their great potential as efficient electrodes for high-performance LIBs.

  12. Graphene-Encapsulated Nanosheet-Assembled Zinc-Nickel-Cobalt Oxide Microspheres for Enhanced Lithium Storage.

    PubMed

    Zhang, Qiaobao; Chen, Huixin; Han, Xiang; Cai, Junjie; Yang, Yong; Liu, Meilin; Zhang, Kaili

    2016-01-01

    The appropriate combination of hierarchical transition-metal oxide (TMO) micro-/nanostructures constructed from porous nanobuilding blocks with graphene sheets (GNS) in a core/shell geometry is highly desirable for high-performance lithium-ion batteries (LIBs). A facile and scalable process for the fabrication of 3D hierarchical porous zinc-nickel-cobalt oxide (ZNCO) microspheres constructed from porous ultrathin nanosheets encapsulated by GNS to form a core/shell geometry is reported for improved electrochemical performance of the TMOs as an anode in LIBs. By virtue of their intriguing structural features, the produced ZNCO/GNS core/shell hybrids exhibit an outstanding reversible capacity of 1015 mA h g(-1) at 0.1 C after 50 cycles. Even at a high rate of 1 C, a stable capacity as high as 420 mA h g(-1) could be maintained after 900 cycles, which suggested their great potential as efficient electrodes for high-performance LIBs. PMID:26676945

  13. Oxidation of formic acid on platinum surfaces decorated with cobalt(III) macrocyclic complexes

    NASA Astrophysics Data System (ADS)

    Stevanović, S.; Babić-Samardžija, K.; Sovilj, S. P.; Tripković, A.; Jovanović, V. M.

    2009-09-01

    Platinum electrode decorated with three different mixed-ligand cobalt(III) complexes of the general formula [Co(Rdtc)cyclam](ClO4)2 [cyclam = 1,4,8,11-tetraazacyclotetradecane, Rdtc- = morpholine-(Morphdtc), piperidine-(Pipdtc), and 4-methylpiperidine-(4-Mepipdtc) dithiocarbamates, respectively] was used to study oxidation of formic acid in acidic solution. The complexes were adsorbed on differently prepared Pt surfaces, at open circuit potential. The preliminary results show increased catalytic activity of Pt for formic acid oxidation with complex ion adsorbed on the polycrystalline surfaces. The increase in catalytic activity depends on the structure of the complex applied and follows the order of metal-coordinated bidentate ligand as Morphdtc > Pipdtc > 4-Mepipdtc. Based on IR and NMR data, the main characteristics of the Rdtc ligands do not vary dramatically, but high symmetry of the corresponding complexes decreases in the same order. Accordingly, the complexes are distinctively more mobile, causing chemical interactions to occur on the surface with appreciable speed and enhanced selectivity. The effect of the complexes on catalytic activity presumably depends on structural changes on Pt surfaces caused by their adsorption.

  14. Synthesis of lithium cobalt oxide by single-step soft hydrothermal method

    SciTech Connect

    Kumar Bokinala, Kiran; Pollet, M.; Artemenko, A.; Miclau, M.; Grozescu, I

    2013-02-15

    Lithium cobalt double oxide LiCoO{sub 2} was synthesized at 220 Degree-Sign C by soft hydrothermal method using Co(OH){sub 2} and LiOH as precursors, LiOH/NaOH as mineralizers and H{sub 2}O{sub 2} as oxidant. The soft hydrothermal synthesis method offers the dual advantage of a much lower synthesis time and a higher purity in comparison with other synthesis methods. The compound was identified by X-ray diffraction and its purity was checked by magnetic and electron magnetic resonance measurements. The grain morphology was studied by Scanning Electron Microscopy and an exponential growth of particle size with synthesis time was observed. - Graphical abstract: Concave cuboctohedrons obtained after 60 h reaction time. Highlights: Black-Right-Pointing-Pointer An optimized soft hydrothermal method for a fast synthesis of high purity LiCoO{sub 2} compound is reported. Black-Right-Pointing-Pointer Both lamellar and cuboctahedral particles could be stabilized. Black-Right-Pointing-Pointer Secondary phases content is lower than 0.1%. Black-Right-Pointing-Pointer Close to surface defects were evidenced using EMR.

  15. Magnetic properties of nickel and cobalt catalysts supported on nanoporous oxides.

    PubMed

    Gómez-Polo, C; Gil, A; Korili, S A; Pérez-Landazabal, J I; Recarte, V; Trujillano, R; Vicente, M A

    2008-06-01

    The aim of this work is to use magnetic measurements as a research tool in the study of possible metal-support interactions in nickel and cobalt nanoporous catalysts. Several physicochemical techniques, namely nitrogen adsorption, X-ray diffraction, temperature-programmed reduction and chemical analysis, were used to analyze the role of the preparation method and the nature of the support on the existence of such metal-support interactions and to relate them with the magnetic response of these nanoporous systems. The catalysts were prepared by incipient wetness impregnation and precipitation-deposition with two commercial oxides, gamma-Al2O3 and SiO2, as supports. The magnetic behavior of the catalysts is drastically affected by the existence of interactions between the metal and the support during the preparation procedure. The samples with weak metal-support interactions have characteristic magnetic behavior of antiferromagnetic metal oxide nanoparticles, while the ones having strong interactions display spin-glass like behavior. PMID:18681026

  16. Cosine (Cobalt Silicide Growth Through Nitrogen-Induced Epitaxy) Process For Epitaxial Cobalt Silicide Formation For High Performance Sha

    SciTech Connect

    Lim, Chong Wee; Shin, Chan Soo; Gall, Daniel; Petrov, Ivan Georgiev; Greene, Joseph E.

    2004-09-28

    A method for forming an epitaxial cobalt silicide layer on a MOS device includes sputter depositing cobalt in an ambient to form a first layer of cobalt suicide on a gate and source/drain regions of the MOS device. Subsequently, cobalt is sputter deposited again in an ambient of argon to increase the thickness of the cobalt silicide layer to a second thickness.

  17. Method of forming buried oxide layers in silicon

    DOEpatents

    Sadana, Devendra Kumar; Holland, Orin Wayne

    2000-01-01

    A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

  18. Graphene oxide monolayers as atomically thin seeding layers for atomic layer deposition of metal oxides

    NASA Astrophysics Data System (ADS)

    Nourbakhsh, Amirhasan; Adelmann, Christoph; Song, Yi; Lee, Chang Seung; Asselberghs, Inge; Huyghebaert, Cedric; Brizzi, Simone; Tallarida, Massimo; Schmeißer, Dieter; van Elshocht, Sven; Heyns, Marc; Kong, Jing; Palacios, Tomás; de Gendt, Stefan

    2015-06-01

    Graphene oxide (GO) was explored as an atomically-thin transferable seed layer for the atomic layer deposition (ALD) of dielectric materials on any substrate of choice. This approach does not require specific chemical groups on the target surface to initiate ALD. This establishes GO as a unique interface which enables the growth of dielectric materials on a wide range of substrate materials and opens up numerous prospects for applications. In this work, a mild oxygen plasma treatment was used to oxidize graphene monolayers with well-controlled and tunable density of epoxide functional groups. This was confirmed by synchrotron-radiation photoelectron spectroscopy. In addition, density functional theory calculations were carried out on representative epoxidized graphene monolayer models to correlate the capacitive properties of GO with its electronic structure. Capacitance-voltage measurements showed that the capacitive behavior of Al2O3/GO depends on the oxidation level of GO. Finally, GO was successfully used as an ALD seed layer for the deposition of Al2O3 on chemically inert single layer graphene, resulting in high performance top-gated field-effect transistors.Graphene oxide (GO) was explored as an atomically-thin transferable seed layer for the atomic layer deposition (ALD) of dielectric materials on any substrate of choice. This approach does not require specific chemical groups on the target surface to initiate ALD. This establishes GO as a unique interface which enables the growth of dielectric materials on a wide range of substrate materials and opens up numerous prospects for applications. In this work, a mild oxygen plasma treatment was used to oxidize graphene monolayers with well-controlled and tunable density of epoxide functional groups. This was confirmed by synchrotron-radiation photoelectron spectroscopy. In addition, density functional theory calculations were carried out on representative epoxidized graphene monolayer models to correlate the

  19. A novel and easy chemical-clock synthesis of nanocrystalline iron-cobalt bearing layered double hydroxides.

    PubMed

    Hadi, Jebril; Grangeon, Sylvain; Warmont, Fabienne; Seron, Alain; Greneche, Jean-Marc

    2014-11-15

    A novel synthesis of cobalt-iron layered double hydroxide (LDH) with interlayer chlorides was investigated. The method consists in mixing concentrated solutions of hexaamminecobalt(III) trichloride with ferrous chloride at room temperature and in anoxic conditions. Four initial Fe/Co atomic ratios have been tried out (0.12, 0.6, 1.2 and 1.8). Neither heating nor addition of alkali was employed for adjusting the pH and precipitating the metal hydroxides. Still, each mixture led to the spontaneous precipitation of a LDH-rich solid having a crystal-chemistry that depended on the initial solution Fe/Co. These LDHs phases were carefully characterized by mean of X-ray diffraction, (57)Fe Mössbauer spectrometry, transmission electron microscopy and chemical analysis (total dissolution and phenanthroline method). Solution Eh and pH were also monitored during the synthesis. Increasing initial Fe/Co ratio impacted the dynamic of the observed stepwise reaction and the composition of the resulting product. Once the two solutions are mixed, a spontaneous and abrupt color change occurs after an induction time which depends on the starting Fe/Co ratio. This makes the overall process acting as a chemical clock. This spontaneous generation of CoFe-LDH arises from the interplay between redox chemistries of iron and cobalt-ammonium complexes. PMID:25173991

  20. A novel and easy chemical-clock synthesis of nanocrystalline iron-cobalt bearing layered double hydroxides.

    PubMed

    Hadi, Jebril; Grangeon, Sylvain; Warmont, Fabienne; Seron, Alain; Greneche, Jean-Marc

    2014-11-15

    A novel synthesis of cobalt-iron layered double hydroxide (LDH) with interlayer chlorides was investigated. The method consists in mixing concentrated solutions of hexaamminecobalt(III) trichloride with ferrous chloride at room temperature and in anoxic conditions. Four initial Fe/Co atomic ratios have been tried out (0.12, 0.6, 1.2 and 1.8). Neither heating nor addition of alkali was employed for adjusting the pH and precipitating the metal hydroxides. Still, each mixture led to the spontaneous precipitation of a LDH-rich solid having a crystal-chemistry that depended on the initial solution Fe/Co. These LDHs phases were carefully characterized by mean of X-ray diffraction, (57)Fe Mössbauer spectrometry, transmission electron microscopy and chemical analysis (total dissolution and phenanthroline method). Solution Eh and pH were also monitored during the synthesis. Increasing initial Fe/Co ratio impacted the dynamic of the observed stepwise reaction and the composition of the resulting product. Once the two solutions are mixed, a spontaneous and abrupt color change occurs after an induction time which depends on the starting Fe/Co ratio. This makes the overall process acting as a chemical clock. This spontaneous generation of CoFe-LDH arises from the interplay between redox chemistries of iron and cobalt-ammonium complexes.

  1. Metallic phases of cobalt-based catalysts in ethanol steam reforming: The effect of cerium oxide

    SciTech Connect

    Lin, Sean S.-Y.; Kim, Do Heui; Ha, Su Y.

    2009-02-28

    The catalytic activity of cobalt in the production of hydrogen via ethanol steam reforming has been investigated in its relation to the crystalline structure of metallic cobalt. At a reaction temperature of 350 8C, the specific hydrogen production rates show that hexagonal close-packed (hcp) cobalt possesses higher activity than face-centered cubic (fcc) cobalt. However, at typical reaction temperatures (400– 500 8C) for ethanol steam reforming, hcp cobalt is transformed to less active fcc cobalt, as confirmed by in situ X-ray diffractometry (XRD). The addition of CeO2 promoter (10 wt.%) stabilizes the hcp cobalt structure at reforming temperatures up to 600 8C. Moreover, during the pre-reduction process, CeO2 promoter prevents sintering during the transformation of Co3O4 to hcp cobalt. Both reforming experiments and in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that the surface reactions were modified by CeO2 promoter on 10% Ce–Co (hcp) to give a lower CO selectivity and a higher H2 yield as compared with the unpromoted hcp Co.

  2. Ultrathin cobalt-alloyed barrier layers for copper metallization by a new seeding and electroless-deposition process

    NASA Astrophysics Data System (ADS)

    Chen, Sung-Te; Liu, Yuan-Yu; Chen, Giin-Shan

    2015-11-01

    Pioneering activation-seeding processes grow catalytic particles with sizes exceeding 10 nm due to agglomeration, and thus are unable to act as a template for electroless deposition of a barrier layer with a thickness of 10 nm or less, which is desperately needed for the incoming ULSI copper interconnecting technology. In this work, the capacity of a seeding process to grow a continuous Co-P barrier layer of 8-nm thickness on thermally oxidized SiO2 layers using electroless deposition will be demonstrated. The Co-P barrier layer works effectively in retarding (a) Cu agglomeration and (b) Cu diffusion into the dielectric layer subjected to thermal annealing. Evidently, thermal stability of the Cu film on SiO2 is markedly strengthened by interposing the 8-nm-thick barrier layer. The mechanism of the interposed barrier layer in enhancing thermal stability of the metallization layer is currently under investigation.

  3. Fabrication of lanthanum strontium cobalt ferrite (LSCF) cathodes for high performance solid oxide fuel cells using a low price commercial inkjet printer

    NASA Astrophysics Data System (ADS)

    Han, Gwon Deok; Neoh, Ke Chean; Bae, Kiho; Choi, Hyung Jong; Park, Suk Won; Son, Ji-Won; Shim, Joon Hyung

    2016-02-01

    In this study, we investigate a method to fabricate high quality lanthanum strontium cobalt ferrite (LSCF) cathodes for solid oxide fuel cells (SOFCs) using a commercial low price inkjet printer. The ink source is synthesized by dissolving the LSCF nanopowder in a water-based solvent with a proper amount of surfactants. Microstructures of the LSCF layer, including porosity and thickness per printing scan cycle, are adjusted by grayscale in the printing image. It is successfully demonstrated that anode-supported SOFCs with optimally printed LSCF cathodes can produce decent power output, i.e., a maximum peak power density of 377 mW cm-2 at 600 °C, in our experiment. We expect that this approach can support the quick and easy prototyping and evaluating of a variety of cathode materials in SOFC research.

  4. Cobalt iron-oxide nanoparticle modified poly(methyl methacrylate) nanodielectrics. Dielectric and electrical insulation properties

    NASA Astrophysics Data System (ADS)

    Tuncer, Enis; Rondinone, Adam J.; Woodward, Jonathan; Sauers, Isidor; James, D. Randy; Ellis, Alvin R.

    2009-03-01

    In this paper, we report the dielectric properties of composite systems (nanodielectrics) made of small amounts of mono dispersed magnetic nanoparticles embedded in a polymer matrix. It is observed from the transmission electron microscope images that the matrix polymeric material is confined in approximately 100 nm size cages between particle clusters. The particle clusters are composed of separated spherical particles which comprise unconnected networks in the matrix. The dielectric relaxation and breakdown characteristics of the matrix polymeric material are altered with the addition of nanometer size cobalt iron-oxide particles. The dielectric breakdown measurements performed at 77 K showed that these nanodielectrics are potentially useful as an electrical insulation material for cryogenic high voltage applications. Finally, structural and dielectric properties of nanocomposite dielectrics are discussed to present plausible reasons for the observed low effective dielectric permittivity values in the present and similar nanodielectric systems. It is concluded that polymeric nanoparticle composites would have low dielectric permittivity regardless of the permittivity of nanoparticles are when the particles are coordinated with a low dielectric permittivity surfactant.

  5. In vitro evaluation of anticancer and antibacterial activities of cobalt oxide nanoparticles.

    PubMed

    Khan, Shahanavaj; Ansari, Anees A; Khan, Abdul Arif; Ahmad, Rehan; Al-Obaid, Omar; Al-Kattan, Wael

    2015-12-01

    Cobalt oxide nanoparticles (Co3O4-NPs) were synthesized using simple urea-based thermal decomposition method. Phase purity and particle size of as-synthesized nanoparticles were characterized through X-ray diffraction pattern (XRD) and transmission electron microscopy. Through XRD morphology of the Co3O4-NPs was found to be variable in size with range of 36 nm. In our present study, we explored the potential cytotoxic and antibacterial effects of Co3O4-NPs in human colorectal types of cancerous cells (HT29 and SW620) and also nine Gram-positive and Gram-negative bacteria. Co3O4-NPs showed promising anticancer activity against HT29 and SW620 cells with IC50 value of 2.26 and 394.5 μg/mL, respectively. However, no significant effect of Co3O4-NPs was observed against bacterial strains. Furthermore, a detailed study has been carried out to investigate the possible mechanism of cell death in HT29 cancer cell line through the analysis of expression level of anti-apoptotic Bcl2 and BclxL markers. Western blot analysis results suggested significant role of Co3O4-NPs exposure in cell death due to apoptosis.

  6. Analysis of geometric and electrochemical characteristics of lithium cobalt oxide electrode with different packing densities

    NASA Astrophysics Data System (ADS)

    Lim, Cheolwoong; Yan, Bo; Kang, Huixiao; Song, Zhibin; Lee, Wen Chao; De Andrade, Vincent; De Carlo, Francesco; Yin, Leilei; Kim, Youngsik; Zhu, Likun

    2016-10-01

    To investigate geometric and electrochemical characteristics of Li ion battery electrode with different packing densities, lithium cobalt oxide (LiCoO2) cathode electrodes were fabricated from a 94:3:3 (wt%) mixture of LiCoO2, polymeric binder, and super-P carbon black and calendered to different densities. A synchrotron X-ray nano-computed tomography system with a spatial resolution of 58.2 nm at the Advanced Photon Source of the Argonne National Laboratory was employed to obtain three dimensional morphology data of the electrodes. The morphology data were quantitatively analyzed to characterize their geometric properties, such as porosity, tortuosity, specific surface area, and pore size distribution. The geometric and electrochemical analysis reveal that high packing density electrodes have smaller average pore size and narrower pore size distribution, which improves the electrical contact between carbon-binder matrix and LiCoO2 particles. The better contact improves the capacity and rate capability by reducing the possibility of electrically isolated LiCoO2 particles and increasing the electrochemically active area. The results show that increase of packing density results in higher tortuosity, but electrochemically active area is more crucial to cell performance than tortuosity at up to 3.6 g/cm3 packing density and 4 C rate.

  7. Nitrite Oxidation with Copper-Cobalt Nanoparticles on Carbon Nanotubes Doped Conducting Polymer PEDOT Composite.

    PubMed

    Wang, Junjie; Xu, Guiyun; Wang, Wei; Xu, Shenghao; Luo, Xiliang

    2015-09-01

    Copper-cobalt bimetal nanoparticles (Cu-Co) have been electrochemically prepared on glassy carbon electrodes (GCEs), which were electrodeposited with conducting polymer nanocomposites of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with carbon nanotubes (CNTs). Owing to their good conductivity, high mechanical strength, and large surface area, the PEDOT/CNTs composites offered excellent substrates for the electrochemical deposition of Cu-Co nanoparticles. As a result of their nanostructure and the synergic effect between Cu and Co, the Cu-Co/PEDOT/CNTs composites exhibited significantly enhanced catalytic activity towards the electrochemical oxidation of nitrite. Under optimized conditions, the nanocomposite-modified electrodes had a fast response time within 2 s and a linear range from 0.5 to 430 μm for the detection of nitrite, with a detection limit of 60 nm. Moreover, the Cu-Co/PEDOT/CNTs composites were highly stable, and the prepared nitrite sensors could retain more than 96 % of their initial response after 30 days.

  8. Reduced Graphene Oxide Functionalized with Cobalt Ferrite Nanocomposites for Enhanced Efficient and Lightweight Electromagnetic Wave Absorption.

    PubMed

    Ding, Yi; Liao, Qingliang; Liu, Shuo; Guo, Huijing; Sun, Yihui; Zhang, Guangjie; Zhang, Yue

    2016-01-01

    In this paper, reduced graphene oxide functionalized with cobalt ferrite nanocomposites (CoFe@rGO) as a novel type of electromagnetic wave (EW) absorbing materials was successfully prepared by a three-step chemical method including hydrothermal synthesis, annealing process and mixing with paraffin. The effect of the sample thickness and the amount of paraffin on the EW absorption properties of the composites was studied, revealing that the absorption peaks shifted toward the low frequency regions with the increasing thickness while other conditions had little or no effect. It is found that the CoFe@rGO enhanced both dielectric losses and magnetic losses and had the best EW absorption properties and the wide wavelength coverage of the hole Ku-Band when adding only 5wt% composites to paraffin. Therefore, CoFe@rGO could be used as an efficient and lightweight EW absorber. Compared with the research into traditional absorbing materials, this figures of merit are typically of the same order of magnitude, but given the lightweight nature of the material and the high level of compatibility with mass production standards, making use of CoFe@rGO as an electromagnetic absorber material shows great potential for real product applications. PMID:27587001

  9. Investigations of nanocomposite magnetic materials based on the oxides of iron, nickel, cobalt and silicon dioxide

    NASA Astrophysics Data System (ADS)

    Gracheva, Irina E.; Olchowik, Grazyna; Gareev, Kamil G.; Moshnikov, Vyatcheslav A.; Kuznetsov, Vladimir V.; Olchowik, Jan M.

    2013-05-01

    This paper is concerned with the study of magnetic nanocomposites containing silicon, iron, nickel, and cobalt oxides. These materials were produced in the form of thin films based on Fe-Si-O, Ni-Co-Si-O and Fe-Ni-Co-Si-O systems and powders based on Fe-Si-O, Ni-Si-O, Co-Si-O and Fe-Ni-Co-Si-O systems using sol-gel technology, through centrifugation, and deposition of ammonia solution. The morphology and magnetic properties of materials in the form of thin films were studied by using the atomic force microscopy. The phase composition, specific surface area and magnetic properties of materials in the form of powders were studied by using the X-ray phase analysis, thermal desorption, vibrational magnetometry and immittance measurements. The dependencies of the main parameters were derived for the magnetic materials from their structure and manufacturing conditions. Ways to optimise the technological processes were proposed, aimed at reducing the size of the magnetic particles in an amorphous lattice.

  10. Reduced Graphene Oxide Functionalized with Cobalt Ferrite Nanocomposites for Enhanced Efficient and Lightweight Electromagnetic Wave Absorption

    NASA Astrophysics Data System (ADS)

    Ding, Yi; Liao, Qingliang; Liu, Shuo; Guo, Huijing; Sun, Yihui; Zhang, Guangjie; Zhang, Yue

    2016-09-01

    In this paper, reduced graphene oxide functionalized with cobalt ferrite nanocomposites (CoFe@rGO) as a novel type of electromagnetic wave (EW) absorbing materials was successfully prepared by a three-step chemical method including hydrothermal synthesis, annealing process and mixing with paraffin. The effect of the sample thickness and the amount of paraffin on the EW absorption properties of the composites was studied, revealing that the absorption peaks shifted toward the low frequency regions with the increasing thickness while other conditions had little or no effect. It is found that the CoFe@rGO enhanced both dielectric losses and magnetic losses and had the best EW absorption properties and the wide wavelength coverage of the hole Ku-Band when adding only 5wt% composites to paraffin. Therefore, CoFe@rGO could be used as an efficient and lightweight EW absorber. Compared with the research into traditional absorbing materials, this figures of merit are typically of the same order of magnitude, but given the lightweight nature of the material and the high level of compatibility with mass production standards, making use of CoFe@rGO as an electromagnetic absorber material shows great potential for real product applications.

  11. Reduced Graphene Oxide Functionalized with Cobalt Ferrite Nanocomposites for Enhanced Efficient and Lightweight Electromagnetic Wave Absorption

    PubMed Central

    Ding, Yi; Liao, Qingliang; Liu, Shuo; Guo, Huijing; Sun, Yihui; Zhang, Guangjie; Zhang, Yue

    2016-01-01

    In this paper, reduced graphene oxide functionalized with cobalt ferrite nanocomposites (CoFe@rGO) as a novel type of electromagnetic wave (EW) absorbing materials was successfully prepared by a three-step chemical method including hydrothermal synthesis, annealing process and mixing with paraffin. The effect of the sample thickness and the amount of paraffin on the EW absorption properties of the composites was studied, revealing that the absorption peaks shifted toward the low frequency regions with the increasing thickness while other conditions had little or no effect. It is found that the CoFe@rGO enhanced both dielectric losses and magnetic losses and had the best EW absorption properties and the wide wavelength coverage of the hole Ku-Band when adding only 5wt% composites to paraffin. Therefore, CoFe@rGO could be used as an efficient and lightweight EW absorber. Compared with the research into traditional absorbing materials, this figures of merit are typically of the same order of magnitude, but given the lightweight nature of the material and the high level of compatibility with mass production standards, making use of CoFe@rGO as an electromagnetic absorber material shows great potential for real product applications. PMID:27587001

  12. Graphene oxide monolayers as atomically thin seeding layers for atomic layer deposition of metal oxides.

    PubMed

    Nourbakhsh, Amirhasan; Adelmann, Christoph; Song, Yi; Lee, Chang Seung; Asselberghs, Inge; Huyghebaert, Cedric; Brizzi, Simone; Tallarida, Massimo; Schmeisser, Dieter; Van Elshocht, Sven; Heyns, Marc; Kong, Jing; Palacios, Tomás; De Gendt, Stefan

    2015-06-28

    Graphene oxide (GO) was explored as an atomically-thin transferable seed layer for the atomic layer deposition (ALD) of dielectric materials on any substrate of choice. This approach does not require specific chemical groups on the target surface to initiate ALD. This establishes GO as a unique interface which enables the growth of dielectric materials on a wide range of substrate materials and opens up numerous prospects for applications. In this work, a mild oxygen plasma treatment was used to oxidize graphene monolayers with well-controlled and tunable density of epoxide functional groups. This was confirmed by synchrotron-radiation photoelectron spectroscopy. In addition, density functional theory calculations were carried out on representative epoxidized graphene monolayer models to correlate the capacitive properties of GO with its electronic structure. Capacitance-voltage measurements showed that the capacitive behavior of Al2O3/GO depends on the oxidation level of GO. Finally, GO was successfully used as an ALD seed layer for the deposition of Al2O3 on chemically inert single layer graphene, resulting in high performance top-gated field-effect transistors.

  13. An in-situ gas chromatography investigation into the suppression of oxygen gas evolution by coated amorphous cobalt-phosphate nanoparticles on oxide electrode

    PubMed Central

    Gim, Jihyeon; Song, Jinju; Kim, Sungjin; Jo, Jeonggeun; Kim, Seokhun; Yoon, Jaegu; Kim, Donghan; Hong, Suk-Gi; Park, Jin-Hwan; Mathew, Vinod; Han, Junhee; Song, Sun-Ju; Kim, Jaekook

    2016-01-01

    The real time detection of quantitative oxygen release from the cathode is performed by in-situ Gas Chromatography as a tool to not only determine the amount of oxygen release from a lithium-ion cell but also to address the safety concerns. This in-situ gas chromatography technique monitoring the gas evolution during electrochemical reaction presents opportunities to clearly understand the effect of surface modification and predict on the cathode stability. The oxide cathode, 0.5Li2MnO3∙0.5LiNi0.4Co0.2Mn0.4O2, surface modified by amorphous cobalt-phosphate nanoparticles (a-CoPO4) is prepared by a simple co-precipitation reaction followed by a mild heat treatment. The presence of a 40 nm thick a-CoPO4 coating layer wrapping the oxide powders is confirmed by electron microscopy. The electrochemical measurements reveal that the a-CoPO4 coated overlithiated layered oxide cathode shows better performances than the pristine counterpart. The enhanced performance of the surface modified oxide is attributed to the uniformly coated Co-P-O layer facilitating the suppression of O2 evolution and offering potential lithium host sites. Further, the formation of a stable SEI layer protecting electrolyte decomposition also contributes to enhanced stabilities with lesser voltage decay. The in-situ gas chromatography technique to study electrode safety offers opportunities to investigate the safety issues of a variety of nanostructured electrodes. PMID:27001370

  14. Mid-term survivorship and clinical outcomes of cobalt-chrome and oxidized zirconium on highly crosslinked polyethylene

    PubMed Central

    Petis, Stephen M.; Vasarhelyi, Edward M.; Lanting, Brent A.; Howard, James L.; Naudie, Douglas D.R.; Somerville, Lyndsay E.; McCalden, Richard W.

    2016-01-01

    Background The choice of bearing articulation for total hip arthroplasty in younger patients is amenable to debate. We compared mid-term patient-reported outcomes and survivorship across 2 different bearing articulations in a young patient cohort. Methods We reviewed patients with cobalt-chrome or oxidized zirconium on highly crosslinked polyethylene who were followed prospectively between 2004 and 2012. Kaplan–Meier analysis was used to determine predicted cumulative survivorship at 5 years with all-cause and aseptic revisions as the outcome. We compared patient-reported outcomes, including the Harris hip score (HHS), Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and Short-form 12 (SF-12) scores. Results A total of 622 patients were followed during the study period. Mean follow-up was 8.2 (range 2.0–10.6) years for cobalt-chrome and 7.8 (range 2.1–10.7) years for oxidized zirconium. Mean age was 54.9 ± 10.6 years for cobalt-chrome and 54.8 ± 10.7 years for oxidized zirconium. Implant survivorship was 96.0% (95% confidence interval [CI] 94.9%–97.1%) for cobalt-chrome and 98.7% (95% CI 98.0%–99.4%) for oxidized zirconium on highly crosslinked polyethylene for all-cause revisions, and 97.2% (95% CI 96.2%–98.2%) for cobalt-chrome and 99.0% (95% CI 98.4%–99.6%) for oxidized zirconium for aseptic revisions. An age-, sex- and diagnosis-matched comparison of the HHS, WOMAC and SF-12 scores demonstrated no significant changes in clinical outcomes across the groups. Conclusion Both bearing surface couples demonstrated excellent mid-term survivorship and outcomes in young patient cohorts. Future analyses on wear and costs are warranted to elicit differences between the groups at long-term follow-up. PMID:26812409

  15. Cobalt Oxide Nanoparticles: Behavior towards Intact and Impaired Human Skin and Keratinocytes Toxicity

    PubMed Central

    Mauro, Marcella; Crosera, Matteo; Pelin, Marco; Florio, Chiara; Bellomo, Francesca; Adami, Gianpiero; Apostoli, Piero; De Palma, Giuseppe; Bovenzi, Massimo; Campanini, Marco; Larese Filon, Francesca

    2015-01-01

    Skin absorption and toxicity on keratinocytes of cobalt oxide nanoparticles (Co3O4NPs) have been investigated. Co3O4NPs are commonly used in industrial products and biomedicine. There is evidence that these nanoparticles can cause membrane damage and genotoxicity in vitro, but no data are available on their skin absorption and cytotoxicity on keratinocytes. Two independent 24 h in vitro experiments were performed using Franz diffusion cells, using intact (experiment 1) and needle-abraded human skin (experiment 2). Co3O4NPs at a concentration of 1000 mg/L in physiological solution were used as donor phase. Cobalt content was evaluated by Inductively Coupled–Mass Spectroscopy. Co permeation through the skin was demonstrated after 24 h only when damaged skin protocol was used (57 ± 38 ng·cm−2), while no significant differences were shown between blank cells (0.92 ± 0.03 ng cm−2) and those with intact skin (1.08 ± 0.20 ng·cm−2). To further investigate Co3O4NPs toxicity, human-derived HaCaT keratinocytes were exposed to Co3O4NPs and cytotoxicity evaluated by MTT, Alamarblue® and propidium iodide (PI) uptake assays. The results indicate that a long exposure time (i.e., seven days) was necessary to induce a concentration-dependent cell viability reduction (EC50 values: 1.3 × 10−4 M, 95% CL = 0.8–1.9 × 10−4 M, MTT essay; 3.7 × 10−5 M, 95% CI = 2.2–6.1 × 10−5 M, AlamarBlue® assay) that seems to be associated to necrotic events (EC50 value: 1.3 × 10−4 M, 95% CL = 0.9–1.9 × 10−4 M, PI assay). This study demonstrated that Co3O4NPs can penetrate only damaged skin and is cytotoxic for HaCat cells after long term exposure. PMID:26193294

  16. Cobalt Oxide Nanoparticles: Behavior towards Intact and Impaired Human Skin and Keratinocytes Toxicity.

    PubMed

    Mauro, Marcella; Crosera, Matteo; Pelin, Marco; Florio, Chiara; Bellomo, Francesca; Adami, Gianpiero; Apostoli, Piero; De Palma, Giuseppe; Bovenzi, Massimo; Campanini, Marco; Filon, Francesca Larese

    2015-07-17

    Skin absorption and toxicity on keratinocytes of cobalt oxide nanoparticles (Co3O4NPs) have been investigated. Co3O4NPs are commonly used in industrial products and biomedicine. There is evidence that these nanoparticles can cause membrane damage and genotoxicity in vitro, but no data are available on their skin absorption and cytotoxicity on keratinocytes. Two independent 24 h in vitro experiments were performed using Franz diffusion cells, using intact (experiment 1) and needle-abraded human skin (experiment 2). Co3O4NPs at a concentration of 1000 mg/L in physiological solution were used as donor phase. Cobalt content was evaluated by Inductively Coupled-Mass Spectroscopy. Co permeation through the skin was demonstrated after 24 h only when damaged skin protocol was used (57 ± 38 ng·cm⁻²), while no significant differences were shown between blank cells (0.92 ± 0.03 ng cm⁻²) and those with intact skin (1.08 ± 0.20 ng·cm⁻²). To further investigate Co3O4NPs toxicity, human-derived HaCaT keratinocytes were exposed to Co3O4NPs and cytotoxicity evaluated by MTT, Alamarblue and propidium iodide (PI) uptake assays. The results indicate that a long exposure time (i.e., seven days) was necessary to induce a concentration-dependent cell viability reduction (EC50 values: 1.3 × 10-4 M, 95% CL = 0.8-1.9 × 10⁻⁴ M, MTT essay; 3.7 × 10⁻⁵ M, 95% CI = 2.2-6.1 × 10⁻⁵ M, AlamarBlue assay) that seems to be associated to necrotic events (EC50 value: 1.3 × 10⁻⁴ M, 95% CL = 0.9-1.9 × 10⁻⁴ M, PI assay). This study demonstrated that Co3O4NPs can penetrate only damaged skin and is cytotoxic for HaCat cells after long term exposure.

  17. Morphology of thermal oxide layers on GaAs

    NASA Astrophysics Data System (ADS)

    Beserman, R.; Schwarz, S. A.; Hwang, D. M.; Chen, C. Y.

    1991-08-01

    The oxidation process of pure GaAs has been studied with use of several complementary experimental techniques: Raman scattering, electrical conductivity, transmission electron microscopy, and secondary-ion mass spectrometry. The morphology of the oxide layer and the oxide-GaAs interface evolve as a function of oxidation time. A high density of well-oriented As microcrystallites penetrates into the substrate, forming a conductive interfacial layer in the early stages of the oxidation process. After longer oxidation times, when the Raman As intensity and the interfacial conductivity are reduced, As is distributed into the oxide layer, forming crystallites that are no longer well oriented. Simultaneously, the crystalline gallium oxide breaks up to into microcrystallites that could provide channels for the outdiffusion of As. From the experimental evidence, we deduce that the interfacial density of crystalline As is reduced for long oxidation times.

  18. Effect of wollastonite ceramics and bioactive glass on the formation of a bonelike apatite layer on a cobalt base alloy.

    PubMed

    Cortés, D A; Medina, A; Escobedo, J C; Escobedo, S; López, M A

    2004-08-01

    A biomimetic method was used to promote a bioactive surface on a cobalt base alloy (ASTM F-75). The metallic substrates were alkali treated and some of the samples were subsequently heat treated. The treated samples were immersed in simulated body fluid (SBF) on granular particles of either bioactive glass or wollastonite. For comparative purposes, no bioactive system was used in some tests. Three different methods were used for the immersion of the samples in SBF: 1) 21 days in SBF, 2) 21 days in 1.5 SBF, and 3) 7 days in SBF followed by 14 days in 1.5 SBF (re-immersion method). A bonelike apatite layer was formed on all the samples placed on wollastonite and bioactive glass particles. The morphology of the apatite layer formed by using the re-immersion method and wollastonite closely resembled the existing bioactive systems. No apatite layer was observed on the samples treated without bioactive material and soaked for 21 days in SBF or 1.5 SBF, apart from the substrates treated by using the re-immersion method. The heat treatment delayed the apatite formation in all the cases studied.

  19. An acetate bound cobalt oxide catalyst for water oxidation: role of monovalent anions and cations in lowering overpotential.

    PubMed

    Dey, Subal; Mondal, Biswajit; Dey, Abhishek

    2014-06-28

    A homogeneous solution of Co(II) in acetate buffer at pH 7 is found to be an efficient water oxidation catalyst (WOC) showing significantly greater current density than Co(II) in phosphate buffer (Co-Pi) under identical conditions owing to the higher solubility of the former. When electrodeposited on ITO/FTO electrodes it forms acetate bound cobalt(II)-oxide materials (Co-Ac-WOC) showing a catalytic current density of 0.1 mA cm(-2) at 830 mV and 1 mA cm(-2) at 1 V in a pH 7 buffer solution. The morphology of Co-Ac-WOC and its evolution with time and deposition potential is investigated with AFM, HR-TEM and SEM. The chemical composition of Co-Ac-WOC is investigated using XPS, EDX, ATR-FTIR and combustion analysis which indicate that this material has a CoO core with chloride and acetate anions bound to the Co center. Sodium is found to be integrated in the Co-Ac-WOC. The presence of the sodium and chloride ions lowers the onset potential for the oxygen evolution reaction (OER) by 240 mV relative to the classic Co-Pi at pH 7. The lower onset potential and higher OER current lowers the exchange current density to 10(-6.7) A cm(-2) in Co-Ac-WOC relative to 10(-8)-10(-10) A cm(-2) in Co-Pi and its derivatives.

  20. One-dimensional manganese-cobalt oxide nanofibres as bi-functional cathode catalysts for rechargeable metal-air batteries

    NASA Astrophysics Data System (ADS)

    Jung, Kyu-Nam; Hwang, Soo Min; Park, Min-Sik; Kim, Ki Jae; Kim, Jae-Geun; Dou, Shi Xue; Kim, Jung Ho; Lee, Jong-Won

    2015-01-01

    Rechargeable metal-air batteries are considered a promising energy storage solution owing to their high theoretical energy density. The major obstacles to realising this technology include the slow kinetics of oxygen reduction and evolution on the cathode (air electrode) upon battery discharging and charging, respectively. Here, we report non-precious metal oxide catalysts based on spinel-type manganese-cobalt oxide nanofibres fabricated by an electrospinning technique. The spinel oxide nanofibres exhibit high catalytic activity towards both oxygen reduction and evolution in an alkaline electrolyte. When incorporated as cathode catalysts in Zn-air batteries, the fibrous spinel oxides considerably reduce the discharge-charge voltage gaps (improve the round-trip efficiency) in comparison to the catalyst-free cathode. Moreover, the nanofibre catalysts remain stable over the course of repeated discharge-charge cycling; however, carbon corrosion in the catalyst/carbon composite cathode degrades the cycling performance of the batteries.

  1. One-dimensional manganese-cobalt oxide nanofibres as bi-functional cathode catalysts for rechargeable metal-air batteries.

    PubMed

    Jung, Kyu-Nam; Hwang, Soo Min; Park, Min-Sik; Kim, Ki Jae; Kim, Jae-Geun; Dou, Shi Xue; Kim, Jung Ho; Lee, Jong-Won

    2015-01-07

    Rechargeable metal-air batteries are considered a promising energy storage solution owing to their high theoretical energy density. The major obstacles to realising this technology include the slow kinetics of oxygen reduction and evolution on the cathode (air electrode) upon battery discharging and charging, respectively. Here, we report non-precious metal oxide catalysts based on spinel-type manganese-cobalt oxide nanofibres fabricated by an electrospinning technique. The spinel oxide nanofibres exhibit high catalytic activity towards both oxygen reduction and evolution in an alkaline electrolyte. When incorporated as cathode catalysts in Zn-air batteries, the fibrous spinel oxides considerably reduce the discharge-charge voltage gaps (improve the round-trip efficiency) in comparison to the catalyst-free cathode. Moreover, the nanofibre catalysts remain stable over the course of repeated discharge-charge cycling; however, carbon corrosion in the catalyst/carbon composite cathode degrades the cycling performance of the batteries.

  2. One-dimensional manganese-cobalt oxide nanofibres as bi-functional cathode catalysts for rechargeable metal-air batteries.

    PubMed

    Jung, Kyu-Nam; Hwang, Soo Min; Park, Min-Sik; Kim, Ki Jae; Kim, Jae-Geun; Dou, Shi Xue; Kim, Jung Ho; Lee, Jong-Won

    2015-01-01

    Rechargeable metal-air batteries are considered a promising energy storage solution owing to their high theoretical energy density. The major obstacles to realising this technology include the slow kinetics of oxygen reduction and evolution on the cathode (air electrode) upon battery discharging and charging, respectively. Here, we report non-precious metal oxide catalysts based on spinel-type manganese-cobalt oxide nanofibres fabricated by an electrospinning technique. The spinel oxide nanofibres exhibit high catalytic activity towards both oxygen reduction and evolution in an alkaline electrolyte. When incorporated as cathode catalysts in Zn-air batteries, the fibrous spinel oxides considerably reduce the discharge-charge voltage gaps (improve the round-trip efficiency) in comparison to the catalyst-free cathode. Moreover, the nanofibre catalysts remain stable over the course of repeated discharge-charge cycling; however, carbon corrosion in the catalyst/carbon composite cathode degrades the cycling performance of the batteries. PMID:25563733

  3. One-dimensional manganese-cobalt oxide nanofibres as bi-functional cathode catalysts for rechargeable metal-air batteries

    PubMed Central

    Jung, Kyu-Nam; Hwang, Soo Min; Park, Min-Sik; Kim, Ki Jae; Kim, Jae-Geun; Dou, Shi Xue; Kim, Jung Ho; Lee, Jong-Won

    2015-01-01

    Rechargeable metal-air batteries are considered a promising energy storage solution owing to their high theoretical energy density. The major obstacles to realising this technology include the slow kinetics of oxygen reduction and evolution on the cathode (air electrode) upon battery discharging and charging, respectively. Here, we report non-precious metal oxide catalysts based on spinel-type manganese-cobalt oxide nanofibres fabricated by an electrospinning technique. The spinel oxide nanofibres exhibit high catalytic activity towards both oxygen reduction and evolution in an alkaline electrolyte. When incorporated as cathode catalysts in Zn-air batteries, the fibrous spinel oxides considerably reduce the discharge-charge voltage gaps (improve the round-trip efficiency) in comparison to the catalyst-free cathode. Moreover, the nanofibre catalysts remain stable over the course of repeated discharge-charge cycling; however, carbon corrosion in the catalyst/carbon composite cathode degrades the cycling performance of the batteries. PMID:25563733

  4. The chemistry of nitrogen oxides on small size-selected cobalt clusters, Co{sub n}{sup +}

    SciTech Connect

    Anderson, Marie L.; Lacz, Agnieszka; Drewello, Thomas; Derrick, Peter J.; Woodruff, D. Phil; Mackenzie, Stuart R.

    2009-02-14

    Fourier transform ion cyclotron resonance mass spectrometry has been employed to study the reactions of gas-phase cationic cobalt clusters, Co{sub n}{sup +} (n=4-30), with nitric oxide, NO, and nitrous oxide, N{sub 2}O, under single collision conditions. Isolation of the initial cluster permits detailed investigation of fragmentation channels which characterize the reactions of all but the largest clusters studied. In reaction with N{sub 2}O, most clusters generate the monoxides Co{sub n}O{sup +} without fragmentation, cobalt atom loss accompanying only subsequent reactions. By contrast, chemisorption of even a single NO molecule is accompanied by fragmentation of the cluster. The measured rate coefficients for the Co{sub n}{sup +}+N{sub 2}O reaction as a function of cluster size are significantly smaller than those calculated using the surface charge capture model, while for NO the rates are comparable. The reactions have been studied under high coverage conditions by storing clusters for extended periods to permit multiple reactions to occur. This leads to interesting chemistry on the surface of the cluster resulting in the formation of stable oxide clusters and/or the decomposition of nitric oxide on the cluster with the resulting loss of molecular nitrogen.

  5. Two- and three-dimensional magnetic order in the layered cobalt oxychloride Sr2CoO3Cl

    NASA Astrophysics Data System (ADS)

    Knee, Christopher S.; Price, Daniel J.; Lees, Martin R.; Weller, Mark T.

    2003-11-01

    The temperature dependence of the nuclear and magnetic structure of the cobalt oxychloride Sr2CoO3Cl has been studied using neutron powder diffraction. The material crystallizes with a structure related to K2NiF4 and contains two-dimensional (2D) layers of CoO5 square pyramids that are segregated along z by alternate rocksalt SrCl and SrO blocks. The development of magnetic Bragg scattering indicates that the compound orders antiferromagnetically with a TN=330(5) K. The phase adopts a collinear magnetic structure related to the nuclear cell by the propagation vector k=(1/2, 1/2, 0) with the cobalt spins aligned along the a axis of the magnetic cell. The ordered moment μ=2.82(3)μB, refined at 3 K, is consistent with a high-spin (t42ge2g) electron configuration for the Co(III) ions. The onset of long-range magnetic order is characterized by a three-dimensional transition and is accompanied by anomalous behavior in the Co environment with distinct magnetostriction effects observed in the interlayer Co to Co exchange pathways. The transition is preceded by diffuse magnetic scattering arising from short-range in-plane correlations, with significant diffuse intensity observed up to the maximum temperature studied of 378 K. Magnetic susceptibility measurements indicate that the onset of significant 2D interactions occurs at T≈500 K. The diffuse intensity can be fitted using the Warren function to give a maximum in the 2D correlation length ξ of 40(4) Å just above TN. Below TN diffuse scattering coexists with magnetic Bragg scattering, indicating that the transition to long-range order is hindered most probably due to the presence of stacking disorder between the antiferromagnetic sheets.

  6. Substrate dependent self-organization of mesoporous cobalt oxide nanowires with remarkable pseudocapacitance.

    PubMed

    Rakhi, R B; Chen, Wei; Cha, Dongkyu; Alshareef, H N

    2012-05-01

    A scheme of current collector dependent self-organization of mesoporous cobalt oxide nanowires has been used to create unique supercapacitor electrodes, with each nanowire making direct contact with the current collector. The fabricated electrodes offer the desired properties of macroporosity to allow facile electrolyte flow, thereby reducing device resistance and nanoporosity with large surface area to allow faster reaction kinetics. Co(3)O(4) nanowires grown on carbon fiber paper collectors self-organize into a brush-like morphology with the nanowires completely surrounding the carbon microfiber cores. In comparison, Co(3)O(4) nanowires grown on planar graphitized carbon paper collectors self-organize into a flower-like morphology. In three electrode configuration, brush-like and flower-like morphologies exhibited specific capacitance values of 1525 and 1199 F/g, respectively, at a constant current density of 1 A/g. In two electrode configuration, the brush-like nanowire morphology resulted in a superior supercapacitor performance with high specific capacitances of 911 F/g at 0.25 A/g and 784 F/g at 40 A/g. In comparison, the flower-like morphology exhibited lower specific capacitance values of 620 F/g at 0.25 A/g and 423 F/g at 40 A/g. The Co(3)O(4) nanowires with brush-like morphology exhibited high values of specific power (71 kW/kg) and specific energy (81 Wh/kg). Maximum energy and power densities calculated for Co(3)O(4) nanowires with flower-like morphology were 55 Wh/kg and 37 kW/kg respectively. Both electrode designs exhibited excellent cycling stability by retaining ∼91-94% of their maximum capacitance after 5000 cycles of continuous charge-discharge. PMID:22494065

  7. Cycling-Induced Changes in the Entropy Profiles of Lithium Cobalt Oxide Electrodes

    SciTech Connect

    Hudak, N. S.; Davis, L. E.; Nagasubramanian, G.

    2014-12-09

    Entropy profiles of lithium cobalt oxide (LiCoO2) electrodes were measured at various stages in the cycle life to examine performance degradation and cycling-induced changes, or lack thereof, in thermodynamics. LiCoO2 electrodes were cycled at C/2 rate in half-cells (vs. lithium anodes) up to 20 cycles or C/5 rate in full cells (vs. MCMB anodes) up to 500 cycles. The electrodes were then subjected to entropy measurements (∂E/∂T, where E is open-circuit potential and T is temperature) in half-cells at regular intervals over the approximate range 0.5 ≤ x ≤ 1 in LixCoO2. Despite significant losses in capacity upon cycling, neither cycling rate resulted in any change to the overall shape of the entropy profile relative to an uncycled electrode, indicating retention of the basic LiCoO2 structure, lithium insertion mechanism, and thermodynamics. This confirms that cycling-induced performance degradation in LiCoO2 electrodes is primarily caused by kinetic barriers that increase with cycling. In the case of electrodes cycled at C/5, there was a subtle, quantitative, and gradual change in the entropy profile in the narrow potential range of the hexagonal-to-monoclinic phase transition. The observed change is indicative of a decrease in the intralayer lithium ordering that occurs at these potentials, and it demonstrates that a cyclinginduced structural disorder accompanies the kinetic degradation mechanisms.

  8. Cycling-Induced Changes in the Entropy Profiles of Lithium Cobalt Oxide Electrodes

    DOE PAGESBeta

    Hudak, N. S.; Davis, L. E.; Nagasubramanian, G.

    2014-12-09

    Entropy profiles of lithium cobalt oxide (LiCoO2) electrodes were measured at various stages in the cycle life to examine performance degradation and cycling-induced changes, or lack thereof, in thermodynamics. LiCoO2 electrodes were cycled at C/2 rate in half-cells (vs. lithium anodes) up to 20 cycles or C/5 rate in full cells (vs. MCMB anodes) up to 500 cycles. The electrodes were then subjected to entropy measurements (∂E/∂T, where E is open-circuit potential and T is temperature) in half-cells at regular intervals over the approximate range 0.5 ≤ x ≤ 1 in LixCoO2. Despite significant losses in capacity upon cycling, neithermore » cycling rate resulted in any change to the overall shape of the entropy profile relative to an uncycled electrode, indicating retention of the basic LiCoO2 structure, lithium insertion mechanism, and thermodynamics. This confirms that cycling-induced performance degradation in LiCoO2 electrodes is primarily caused by kinetic barriers that increase with cycling. In the case of electrodes cycled at C/5, there was a subtle, quantitative, and gradual change in the entropy profile in the narrow potential range of the hexagonal-to-monoclinic phase transition. The observed change is indicative of a decrease in the intralayer lithium ordering that occurs at these potentials, and it demonstrates that a cyclinginduced structural disorder accompanies the kinetic degradation mechanisms.« less

  9. Thermal properties of rare earth cobalt oxides and of La1- x Gd x CoO3 solid solutions

    NASA Astrophysics Data System (ADS)

    Orlov, Yu. S.; Dudnikov, V. A.; Gorev, M. V.; Vereshchagin, S. N.; Solov'ev, L. A.; Ovchinnikov, S. G.

    2016-05-01

    Powder X-ray diffraction data for the crystal structure, phase composition, and molar specific heat for La1‒ x Gd x CoO3 cobaltites in the temperature range of 300-1000 K have been analyzed. The behavior of the volume thermal expansion coefficient in cobaltites with isovalent doping in the temperature range of 100-1000 K is studied. It is found that the β( T) curve exhibits two peaks at some doping levels. The rate of the change in the occupation number for the high-spin state of cobalt ions is calculated for the compounds under study taking into account the spin-orbit interaction. With the Birch-Murnaghan equation of state, it is demonstrated that the low-temperature peak in the thermal expansion shifts with the growth of the pressure toward higher temperatures and at pressure P ˜ 7 GPa coincides with the second peak. The similarity in the behavior of the thermal expansion coefficient in the La1- x Gd x CoO3 compounds with the isovalent substitution and the undoped LnCoO3 compound (Ln is a lanthanide) is considered. For the whole series of rare earth cobalt oxides, the nature of two specific features in the temperature dependence of the specific heat and thermal expansion is revealed and their relation to the occupation number for the high-spin state of cobalt ions and to the insulator-metal transition is established.

  10. Solder for oxide layer-building metals and alloys

    DOEpatents

    Kronberg, James W.

    1992-01-01

    A low temperature solder and method for soldering an oxide layer-building metal such as aluminum, titanium, tantalum or stainless steel. The comosition comprises tin and zinc; germanium as a wetting agent; preferably small amounts of copper and antimony; and a grit, such as silicon carbide. The grit abrades any oxide layer formed on the surface of the metal as the germanium penetrates beneath and loosens the oxide layer to provide good metal-to-metal contact. The germanium comprises less than aproximatley 10% by weight of the solder composition so that it provides sufficient wetting action but does not result in a melting temperature above approximately 300.degree. C. The method comprises the steps rubbing the solder against the metal surface so the grit in the solder abrades the surface while heating the surface until the solder begins to melt and the germanium penetrates the oxide layer, then brushing aside any oxide layer loosened by the solder.

  11. Solder for oxide layer-building metals and alloys

    DOEpatents

    Kronberg, J.W.

    1992-09-15

    A low temperature solder and method for soldering an oxide layer-building metal such as aluminum, titanium, tantalum or stainless steel is disclosed. The composition comprises tin and zinc; germanium as a wetting agent; preferably small amounts of copper and antimony; and a grit, such as silicon carbide. The grit abrades any oxide layer formed on the surface of the metal as the germanium penetrates beneath and loosens the oxide layer to provide good metal-to-metal contact. The germanium comprises less than approximately 10% by weight of the solder composition so that it provides sufficient wetting action but does not result in a melting temperature above approximately 300 C. The method comprises the steps rubbing the solder against the metal surface so the grit in the solder abrades the surface while heating the surface until the solder begins to melt and the germanium penetrates the oxide layer, then brushing aside any oxide layer loosened by the solder.

  12. Electrostatic doping as a source for robust ferromagnetism at the interface between antiferromagnetic cobalt oxides

    PubMed Central

    Li, Zi-An; Fontaíña-Troitiño, N.; Kovács, A.; Liébana-Viñas, S.; Spasova, M.; Dunin-Borkowski, R. E.; Müller, M.; Doennig, D.; Pentcheva, R.; Farle, M.; Salgueiriño, V.

    2015-01-01

    Polar oxide interfaces are an important focus of research due to their novel functionality which is not available in the bulk constituents. So far, research has focused mainly on heterointerfaces derived from the perovskite structure. It is important to extend our understanding of electronic reconstruction phenomena to a broader class of materials and structure types. Here we report from high-resolution transmission electron microscopy and quantitative magnetometry a robust – above room temperature (Curie temperature TC ≫ 300 K) – environmentally stable- ferromagnetically coupled interface layer between the antiferromagnetic rocksalt CoO core and a 2–4 nm thick antiferromagnetic spinel Co3O4 surface layer in octahedron-shaped nanocrystals. Density functional theory calculations with an on-site Coulomb repulsion parameter identify the origin of the experimentally observed ferromagnetic phase as a charge transfer process (partial reduction) of Co3+ to Co2+ at the CoO/Co3O4 interface, with Co2+ being in the low spin state, unlike the high spin state of its counterpart in CoO. This finding may serve as a guideline for designing new functional nanomagnets based on oxidation resistant antiferromagnetic transition metal oxides. PMID:25613569

  13. Electrostatic doping as a source for robust ferromagnetism at the interface between antiferromagnetic cobalt oxides

    NASA Astrophysics Data System (ADS)

    Li, Zi-An; Fontaíña-Troitiño, N.; Kovács, A.; Liébana-Viñas, S.; Spasova, M.; Dunin-Borkowski, R. E.; Müller, M.; Doennig, D.; Pentcheva, R.; Farle, M.; Salgueiriño, V.

    2015-01-01

    Polar oxide interfaces are an important focus of research due to their novel functionality which is not available in the bulk constituents. So far, research has focused mainly on heterointerfaces derived from the perovskite structure. It is important to extend our understanding of electronic reconstruction phenomena to a broader class of materials and structure types. Here we report from high-resolution transmission electron microscopy and quantitative magnetometry a robust - above room temperature (Curie temperature TC >> 300 K) - environmentally stable- ferromagnetically coupled interface layer between the antiferromagnetic rocksalt CoO core and a 2-4 nm thick antiferromagnetic spinel Co3O4 surface layer in octahedron-shaped nanocrystals. Density functional theory calculations with an on-site Coulomb repulsion parameter identify the origin of the experimentally observed ferromagnetic phase as a charge transfer process (partial reduction) of Co3+ to Co2+ at the CoO/Co3O4 interface, with Co2+ being in the low spin state, unlike the high spin state of its counterpart in CoO. This finding may serve as a guideline for designing new functional nanomagnets based on oxidation resistant antiferromagnetic transition metal oxides.

  14. The Influence of Fe Substitution in Lanthanum Calcium Cobalt Oxide on the Oxygen Evolution Reaction in Alkaline Media

    DOE PAGESBeta

    Abreu-Sepulveda, Maria A.; Dhital, Chetan; Huq, Ashfia; Li, Ling; Bridges, Craig A.; Paranthaman, M. Parans; Narayanan, S. R.; Quesnel, David J.; Tryk, Donald A.; Manivannan, A.

    2016-07-30

    The effect due to systematic substitution of cobalt by iron in La0.6Ca0.4Co1-xFexO3 towards the oxygen evolution reaction(OER) in alkaline media has been investigated. We synthesized these compounds by a facile glycine-nitrate synthesis and the phase formation was confirmed by X-ray diffraction and Neutron Diffraction elemental analysis. The apparent OER activity was evaluated by quasi steady state current measurements in alkaline media using a traditional three-electrode cell. X-ray photoelectron spectroscopy shows iron substitution causes an increase in the surface concentration of various cobalt oxidation states. Tafel slope in the vicinity of 60 mV/decade and electrochemical reaction order towards OH- near unitymore » were achieved for the unsubstituted La0.6Ca0.4CoO3. Moreover, a decrease in the Tafel slope to 49 mV/decade was observed when iron is substituted in high amounts in the perovskite structure. The area specific current density showed dependence on the Fe fraction, however the relationship of specific current density with Fe fraction is not linear. High Fe substitutions, La0.6Ca0.4Co0.2Fe0.8O3 and La0.6Ca0.4Co0.1Fe0.9O3 showed higher area specific activity towards OER than La0.6Ca0.4CoO3 or La0.6Ca0.4FeO3. Finally, we believe iron inclusion in the cobalt sites of the perovskite helps decrease the electron transfer barrier and facilitates the formation of cobalt-hydroxide at the surface. Possible OER mechanisms based on the observed kinetic parameters will be discussed.« less

  15. Role of Amphiphilic Block Copolymer Composition on Pore Characteristics of Micelle-Templated Mesoporous Cobalt Oxide Films.

    PubMed

    Wang, Siyang; Tangvijitsakul, Pattarasai; Qiang, Zhe; Bhaway, Sarang M; Lin, Kehua; Cavicchi, Kevin A; Soucek, Mark D; Vogt, Bryan D

    2016-04-26

    Block copolymer templating is a versatile approach for the generation of well-defined porosity in a wide variety of framework chemistries. Here, we systematically investigate how the composition of a poly(methoxy poly[ethylene glycol] methacrylate)-block-poly(butyl acrylate) (PMPEG-PBA) template impacts the pore characteristics of mesoporous cobalt oxide films. Three templates with a constant PMPEG segment length and different hydrophilic block volume fractions of 17%, 51%, and 68% for the PMPEG-PBA are cooperatively assembled with cobalt nitrate hexahydrate and citric acid. Irrespective of template composition, a spherical nanostructure is templated and elliptical mesostructures are obtained on calcination due to uniaxial contraction of the film. The average pore size increases from 11.4 ± 2.8 to 48.5 ± 4.3 nm as the length of the PBA segment increases as determined from AFM. For all three templates examined, a maximum in porosity (∼35% in all cases) and surface area is obtained when the precursor solids contain 35-45 wt % PMPEG-PBA. This invariance suggests that the total polymer content drives the structure through interfacial assembly. The composition for maximizing porosity and surface area with the micelle-templating approach results from a general decrease in porosity with increasing cobalt nitrate hexahydrate content and the increasing mechanical integrity of the framework to resist collapse during template removal/crystallization as the cobalt nitrate hexahydrate content increases. Unlike typical evaporation induced self-assembly with sol-gel chemistry, the hydrophilic/hydrophobic composition of the block copolymer template is not a critical component to the mesostructure developed with micelle-templating using metal nitrate-citric acid as the precursor. PMID:27040316

  16. Comparative cytotoxicity and genotoxicity of cobalt (II, III) oxide, iron (III) oxide, silicon dioxide, and aluminum oxide nanoparticles on human lymphocytes in vitro.

    PubMed

    Rajiv, S; Jerobin, J; Saranya, V; Nainawat, M; Sharma, A; Makwana, P; Gayathri, C; Bharath, L; Singh, M; Kumar, M; Mukherjee, A; Chandrasekaran, N

    2016-02-01

    Despite the extensive use of nanoparticles (NPs) in various fields, adequate knowledge of human health risk and potential toxicity is still lacking. The human lymphocytes play a major role in the immune system, and it can alter the antioxidant level when exposed to NPs. Identification of the hazardous NPs was done using in vitro toxicity tests and this study mainly focuses on the comparative in vitro cytotoxicity and genotoxicity of four different NPs including cobalt (II, III) oxide (Co3O4), iron (III) oxide (Fe2O3), silicon dioxide (SiO2), and aluminum oxide (Al2O3) on human lymphocytes. The Co3O4 NPs showed decrease in cellular viability and increase in cell membrane damage followed by Fe2O3, SiO2, and Al2O3 NPs in a dose-dependent manner after 24 h of exposure to human lymphocytes. The oxidative stress was evidenced in human lymphocytes by the induction of reactive oxygen species, lipid peroxidation, and depletion of catalase, reduced glutathione, and superoxide dismutase. The Al2O3 NPs showed the least DNA damage when compared with all the other NPs. Chromosomal aberration was observed at 100 µg/ml when exposed to Co3O4 NPs and Fe2O3 NPs. The alteration in the level of antioxidant caused DNA damage and chromosomal aberration in human lymphocytes.

  17. Improve oxidation resistance at high temperature by nanocrystalline surface layer

    PubMed Central

    Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

    2015-01-01

    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. PMID:26269034

  18. Electronic properties of strongly correlated layered oxides

    NASA Astrophysics Data System (ADS)

    Lee, Wei-Cheng

    The two-dimensional electronic systems (2DESs) have kept surprising physicists for the last few decades. Examples include the integer and fractional quantum Hall effects, cuprate superconductivity, and graphene. This thesis is intended to develop suitable theoretical tools which can be generalized to study new types of 2DESs with strong correlation feature. The first part of this thesis describes the investigation of heterostructures made by Mott insulators. This work is mostly motivated by the significant improvement of techniques for layer-by-layer growth of transition metal oxides in the last few years. We construct a toy model based on generalized Hubbard model complemented with long-ranged Coulomb interaction, and we study it by Hartree-Fock theory, dynamical mean-field theory, and Thomas-Fermi theory. We argue that interesting 2D strongly correlated electronic systems can be created in such heterostructures under several conditions. Since these 2D systems are formed entirely due to the gap generated by electron-electron interaction, they are not addiabatically connected to a noninteracting electron states. This feature makes these 2D systems distinguish from the ones created in semiconductor heterostructures, and they may be potential systems having non-Fermi liquid behaviors. The second part of this thesis is devoted to the study of collective excitations in high-temperature superconductors. One important achievement in this work is to develop a time-dependent mean-field theory for t -- U -- J -- V model, an effective low energy model for cuprates. The time-dependent mean-field theory is proven to be identical to the generalized random-phase approximation (GRPA) which includes both the bubble and ladder diagrams. We propose that the famous 41 meV magnetic resonance mode observed in the inelastic neutron scattering measurements is a collective mode arising from a conjugation relation, which has been overlooked in previous work, between the antiferromagnetic

  19. Solar absorptance of copper-cobalt oxide thin film coatings with nano-size, grain-like morphology: Optimization and synchrotron radiation XPS studies

    NASA Astrophysics Data System (ADS)

    Amri, Amun; Duan, XiaoFei; Yin, Chun-Yang; Jiang, Zhong-Tao; Rahman, M. Mahbubur; Pryor, Trevor

    2013-06-01

    Copper-cobalt oxides thin films had been successfully coated on reflective aluminium substrates via a facile sol-gel dip-coating method for solar absorptance study. The optimum absorptance in the range of solar radiation is needed for further optimum design of this material for selective solar absorber application. Field emission scanning electron microscopy was used to characterize the surface morphology of the coating whereby nano-size, grain-like morphology was observed. Synchrotron radiation X-ray photoelectron spectroscopy was employed to analyze the electronic structure of the coated surface showing that the (i) oxygen consisted of lattice, surface and subsurface oxygen, (ii) copper consisted of octahedral and tetrahedral Cu+, as well as octahedral and paramagnetic Cu2+ oxidation states, and (iii) cobalt consisted of tetrahedral and paramagnetic Co(II), octahedral Co(III) as well as mixed Co(II,III) oxidation states. In order to optimize the solar absorptance of the coatings, relevant parameters such as concentrations of cobalt and copper, copper/cobalt concentration ratios and dip-speed were investigated. The optimal coating with α = 83.4% was produced using 0.25 M copper acetate and 0.25 M cobalt chloride (Cu/Co ratio = 1) with dip-speed 120 mm/min (four cycles). The operational simplicity of the dip-coating system indicated that it could be extended for coating of other mixed metal oxides as well.

  20. DC electrical, thermal, and spectroscopic properties of various condensation polyimides containing surface cobalt oxide

    NASA Technical Reports Server (NTRS)

    Rancourt, J. D.; Boggess, R. K.; Horning, L. S.; Taylor, L. T.

    1987-01-01

    Doping polyimides with cobalt ion causes the room temperature direct current electrical resistivity to decrease relative to the polymer alone, the reduction being most pronounced for the air-side of the cobalt modified polyimides. At a constant electrical field, resistivity for the volume, air-side and glass-side modes decreases yet further with an increase in temperature as expected for semiconductors and insulators. X-ray photoelectron spectroscopy indicates the air-side of the cobalt modified polyimides is predominantly Co3O4. The bulk resistivity of the air-side and activation energy of conduction for this surface are comparable to high purity sintered Co3O4. Charging characteristics at room temperature indicate a substantial polymer matrix contribution to both the glass-side and volume mode measurements but a negligible contribution to the air-side electrical properties. Volume electrical resistivity for similar additive levels is reduced by increasing the molecular flexibility of the host polymer.

  1. Oxyanion induced variations in domain structure for amorphous cobalt oxide oxygen evolving catalysts, resolved by X-ray pair distribution function analysis.

    PubMed

    Kwon, Gihan; Kokhan, Oleksandr; Han, Ali; Chapman, Karena W; Chupas, Peter J; Du, Pingwu; Tiede, David M

    2015-12-01

    Amorphous thin film oxygen evolving catalysts, OECs, of first-row transition metals show promise to serve as self-assembling photoanode materials in solar-driven, photoelectrochemical `artificial leaf' devices. This report demonstrates the ability to use high-energy X-ray scattering and atomic pair distribution function analysis, PDF, to resolve structure in amorphous metal oxide catalyst films. The analysis is applied here to resolve domain structure differences induced by oxyanion substitution during the electrochemical assembly of amorphous cobalt oxide catalyst films, Co-OEC. PDF patterns for Co-OEC films formed using phosphate, Pi, methylphosphate, MPi, and borate, Bi, electrolyte buffers show that the resulting domains vary in size following the sequence Pi < MPi < Bi. The increases in domain size for CoMPi and CoBi were found to be correlated with increases in the contributions from bilayer and trilayer stacked domains having structures intermediate between those of the LiCoOO and CoO(OH) mineral forms. The lattice structures and offset stacking of adjacent layers in the partially stacked CoMPi and CoBi domains were best matched to those in the LiCoOO layered structure. The results demonstrate the ability of PDF analysis to elucidate features of domain size, structure, defect content and mesoscale organization for amorphous metal oxide catalysts that are not readily accessed by other X-ray techniques. PDF structure analysis is shown to provide a way to characterize domain structures in different forms of amorphous oxide catalysts, and hence provide an opportunity to investigate correlations between domain structure and catalytic activity.

  2. Oxyanion induced variations in domain structure for amorphous cobalt oxide oxygen evolving catalysts, resolved by X-ray pair distribution function analysis

    PubMed Central

    Kwon, Gihan; Kokhan, Oleksandr; Han, Ali; Chapman, Karena W.; Chupas, Peter J.; Du, Pingwu; Tiede, David M.

    2015-01-01

    Amorphous thin film oxygen evolving catalysts, OECs, of first-row transition metals show promise to serve as self-assembling photoanode materials in solar-driven, photoelectrochemical ‘artificial leaf’ devices. This report demonstrates the ability to use high-energy X-ray scattering and atomic pair distribution function analysis, PDF, to resolve structure in amorphous metal oxide catalyst films. The analysis is applied here to resolve domain structure differences induced by oxyanion substitution during the electrochemical assembly of amorphous cobalt oxide catalyst films, Co-OEC. PDF patterns for Co-OEC films formed using phosphate, Pi, methylphosphate, MPi, and borate, Bi, electrolyte buffers show that the resulting domains vary in size following the sequence Pi < MPi < Bi. The increases in domain size for CoMPi and CoBi were found to be correlated with increases in the contributions from bilayer and trilayer stacked domains having structures intermediate between those of the LiCoOO and CoO(OH) mineral forms. The lattice structures and offset stacking of adjacent layers in the partially stacked CoMPi and CoBi domains were best matched to those in the LiCoOO layered structure. The results demonstrate the ability of PDF analysis to elucidate features of domain size, structure, defect content and mesoscale organization for amorphous metal oxide catalysts that are not readily accessed by other X-ray techniques. PDF structure analysis is shown to provide a way to characterize domain structures in different forms of amorphous oxide catalysts, and hence provide an opportunity to investigate correlations between domain structure and catalytic activity. PMID:26634728

  3. Oxyanion Induced Variations in Domain Structure for Amorphous Cobalt Oxide Oxygen Evolving Catalysts, Resolved by X-ray Pair Distribution Function Analysis

    SciTech Connect

    Kwon, Gihan; Kokhan, Oleksandr; Han, Ali; Chapman, Karena W.; Chupas, Peter J.; Du, Pingwu; Tiede, David M.

    2015-12-01

    Amorphous thin film oxygen evolving catalysts, OECs, of first-row transition metals show promise to serve as self-assembling photoanode materials in solar-driven, photoelectrochemical `artificial leaf' devices. This report demonstrates the ability to use high-energy X-ray scattering and atomic pair distribution function analysis, PDF, to resolve structure in amorphous metal oxide catalyst films. The analysis is applied here to resolve domain structure differences induced by oxyanion substitution during the electrochemical assembly of amorphous cobalt oxide catalyst films, Co-OEC. PDF patterns for Co-OEC films formed using phosphate, Pi, methylphosphate, MPi, and borate, Bi, electrolyte buffers show that the resulting domains vary in size following the sequence Pi < MPi < Bi. The increases in domain size for CoMPi and CoBi were found to be correlated with increases in the contributions from bilayer and trilayer stacked domains having structures intermediate between those of the LiCoOO and CoO(OH) mineral forms. The lattice structures and offset stacking of adjacent layers in the partially stacked CoMPi and CoBi domains were best matched to those in the LiCoOO layered structure. The results demonstrate the ability of PDF analysis to elucidate features of domain size, structure, defect content and mesoscale organization for amorphous metal oxide catalysts that are not readily accessed by other X-ray techniques. Finally, PDF structure analysis is shown to provide a way to characterize domain structures in different forms of amorphous oxide catalysts, and hence provide an opportunity to investigate correlations between domain structure and catalytic activity.

  4. Oxyanion Induced Variations in Domain Structure for Amorphous Cobalt Oxide Oxygen Evolving Catalysts, Resolved by X-ray Pair Distribution Function Analysis

    DOE PAGESBeta

    Kwon, Gihan; Kokhan, Oleksandr; Han, Ali; Chapman, Karena W.; Chupas, Peter J.; Du, Pingwu; Tiede, David M.

    2015-12-01

    Amorphous thin film oxygen evolving catalysts, OECs, of first-row transition metals show promise to serve as self-assembling photoanode materials in solar-driven, photoelectrochemical `artificial leaf' devices. This report demonstrates the ability to use high-energy X-ray scattering and atomic pair distribution function analysis, PDF, to resolve structure in amorphous metal oxide catalyst films. The analysis is applied here to resolve domain structure differences induced by oxyanion substitution during the electrochemical assembly of amorphous cobalt oxide catalyst films, Co-OEC. PDF patterns for Co-OEC films formed using phosphate, Pi, methylphosphate, MPi, and borate, Bi, electrolyte buffers show that the resulting domains vary in sizemore » following the sequence Pi < MPi < Bi. The increases in domain size for CoMPi and CoBi were found to be correlated with increases in the contributions from bilayer and trilayer stacked domains having structures intermediate between those of the LiCoOO and CoO(OH) mineral forms. The lattice structures and offset stacking of adjacent layers in the partially stacked CoMPi and CoBi domains were best matched to those in the LiCoOO layered structure. The results demonstrate the ability of PDF analysis to elucidate features of domain size, structure, defect content and mesoscale organization for amorphous metal oxide catalysts that are not readily accessed by other X-ray techniques. Finally, PDF structure analysis is shown to provide a way to characterize domain structures in different forms of amorphous oxide catalysts, and hence provide an opportunity to investigate correlations between domain structure and catalytic activity.« less

  5. Suppression of irreversible capacity loss in Li-rich layered oxide by fluorine doping

    NASA Astrophysics Data System (ADS)

    Song, Jay Hyok; Kapylou, Andrei; Choi, Hee Sung; Yu, Byong Yong; Matulevich, Evegeniya; Kang, Sun Ho

    2016-05-01

    Li[Li1/6Ni1/6Co1/6Mn1/2]O2-xFx (x = 0.00 to 0.07) materials were synthesized with low temperature heat treatment (700 °C) and their electrochemical performances were evaluated. With the addition of fluorine, the reversible capacity significantly increased as the irreversibility was suppressed during the first cycle. The reduction of irreversibility was mainly attributed to the enhanced first cycle efficiency of Li2MnO3-like component after the fluorine addition. By combining results of the X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), In-situ X-ray absorption spectroscopy (XAS) analyses, and first principle calculations, it was proposed that the presence of fluorine facilitated the reduction of cobalt and manganese ions in Li-rich layered oxide, and that the reduced transition metal (TM) ions suppressed structural changes.

  6. Oxide film on metal substrate reduced to form metal-oxide-metal layer structure

    NASA Technical Reports Server (NTRS)

    Youngdahl, C. A.

    1967-01-01

    Electrically conductive layer of zirconium on a zirconium-oxide film residing on a zirconium substrate is formed by reducing the oxide in a sodium-calcium solution. The reduced metal remains on the oxide surface as an adherent layer and seems to form a barrier that inhibits further reaction.

  7. Heterogenite vs asbolane: a mineralogical study of cobalt oxides from the DRC (Democratic Republic of the Congo)

    NASA Astrophysics Data System (ADS)

    Burlet, Christian; Vanbrabant, Yves; Decree, Sophie

    2014-05-01

    The largest cobalt ore reserves are located in DRC, the Democratic Republic of Congo. Most of cobalt is observed as black cobaltic oxide minerals: heterogenite [HCoO2] and asbolane [(Ni,Co)2-xMn(O,OH)4.nH2O] which are hardly differentiable since they exhibit similar macroscopic habit and textures. These minerals are frequently observed in similar environment (oxidized horizon of ore deposits) and they are commonly poorly-crystallized limiting their study with XRD. Their chemical composition is also not very well-constrained since they exhibit significant chemical substitutions with cations as Cu, Co, Ni, Mn. Our observations on a set of heterogenite and asbolane samples from DRC combined with samples from other localities shows that each phase, even under an amorphous form, can be readily distinguished by Raman microspectrometry. This technique is therefore attractive during ore deposit characterization campaigns or during the follow-up extraction operations where it is important to distinguish the main constituting Co-phase(s). The main advantage of this technique is its speed since no sample preparation is required during the collection Raman spectra that usually last few tens of seconds. The method provides information at a μm-scale and several points are thus required to fully characterize ore batches composed of different mineralogical phases. Our petrographical observations show also that asbolane and heterogenite mineralogical phases can coexist at a μm-scale as two distinct phases into 'heterogenite' ore. The distinction between heterogenite and asbolane from our sample set can also be conducted on a chemical base showing that heterogenite represents the richer Co-phase with variable Cu concentrations. By contrast, only Mn traces are usually observed in heterogenite minerals from DRC except in few samples, but always in lower concentration than in asbolane. The latter shows variable Mn/(Mn+Co) ratio between 0.85 and 0.3 and the decrease of this value is

  8. Structure and valency of a cobalt-phosphate water oxidation catalyst determined by in situ X-ray spectroscopy.

    PubMed

    Kanan, Matthew W; Yano, Junko; Surendranath, Yogesh; Dincă, Mircea; Yachandra, Vittal K; Nocera, Daniel G

    2010-10-01

    A water oxidation catalyst generated via electrodeposition from aqueous solutions containing phosphate and Co(2+) (Co-Pi) has been studied by in situ X-ray absorption spectroscopy. Spectra were obtained for Co-Pi films of two different thicknesses at an applied potential supporting water oxidation catalysis and at open circuit. Extended X-ray absorption fine structure (EXAFS) spectra indicate the presence of bis-oxo/hydroxo-bridged Co subunits incorporated into higher nuclearity clusters in Co-Pi. The average cluster nuclearity is greater in a relatively thick film (∼40-50 nmol Co ions/cm(2)) deposited at 1.25 V vs NHE than in an extremely thin film (∼3 nmol Co ions/cm(2)) deposited at 1.1 V. X-ray absorption near edge structure (XANES) spectra and electrochemical data support a Co valency greater than 3 for both Co-Pi samples when catalyzing water oxidation at 1.25 V. Upon switching to open circuit, Co-Pi undergoes a continuous reduction due to residual water oxidation catalysis, as indicated by the negative shift of the edge energy. The rate of reduction depends on the average cluster size. On the basis of structural parameters extracted from fits to the EXAFS data of Co-Pi with two different thicknesses and comparisons with EXAFS spectra of Co oxide compounds, a model is proposed wherein the Co oxo/hydroxo clusters of Co-Pi are composed of edge-sharing CoO(6) octahedra, the structural motif found in cobaltates. Whereas cobaltates contain extended planes of CoO(6) octahedra, the Co-Pi clusters are of molecular dimensions.

  9. Graphene-Inorganic Hybrids with Cobalt Oxide Polymorphs for Electrochemical Energy Systems and Electrocatalysis: Synthesis, Processing and Properties

    NASA Astrophysics Data System (ADS)

    Gupta, Sanju; Carrizosa, Sara B.

    2015-11-01

    We report on the synthesis and physical property characterization of graphene-inorganic `hybrid' nanomaterials coupled with nano-/microscale transition metal oxide polymorphs namely, cobalt oxides, i.e. CoO [Co(II)] and Co3O4 [Co(II, III)]), for alternative energy storage and conversion devices. Their demand is owed to higher specific capacitance, wide operational potential window, stability through charge-discharge cycling, environmentally benignity, easily processability, reproducibility and manufacturability. To accomplish this, we strategically designed these hybrids by direct anchoring or physisorption of CoO and CO3O4 on two different variants of graphene: graphene oxide which is semiconducting, and its reduced form showing conducting behavior via mixing dispersions of the constituents under mild ultrasonication and drop-cast (or spray-cast) resulting in different combinations. This facile approach affords strong chemical/physical attachment and is expected to have coupling between the pseudocapacitive transition metal oxides and supercapacitive graphene showing enhanced surface activity/reactivity and reasonable areal density of tailored interfaces. We used a range of complementary tools to establish microscopic structure-property-function correlations including scanning electron microscopy combined with energy dispersive x-ray spectroscopy, atomic force microscopy, x-ray diffraction, transmission electron microscopy in conjunction with selected-area electron diffraction, and resonance Raman spectroscopy combined with elemental Raman mapping. They reveal surface morphology, local (lattice dynamical) and average structure and surface charge transfer/doping due to physically (or chemically) adsorbed cobalt oxide and highlight the surface structure and interfaces. This lays the groundwork to further investigate the electrochemical properties as high-performance supercapacitor cathodes, rechargeable secondary battery anodes and electrocatalytical platforms.

  10. Electronic structure description of a [Co(III)3Co(IV)O4] cluster: a model for the paramagnetic intermediate in cobalt-catalyzed water oxidation.

    PubMed

    McAlpin, J Gregory; Stich, Troy A; Ohlin, C André; Surendranath, Yogesh; Nocera, Daniel G; Casey, William H; Britt, R David

    2011-10-01

    Multifrequency electron paramagnetic resonace (EPR) spectroscopy and electronic structure calculations were performed on [Co(4)O(4)(C(5)H(5)N)(4)(CH(3)CO(2))(4)](+) (1(+)), a cobalt tetramer with total electron spin S = 1/2 and formal cobalt oxidation states III, III, III, and IV. The cuboidal arrangement of its cobalt and oxygen atoms is similar to that of proposed structures for the molecular cobaltate clusters of the cobalt-phosphate (Co-Pi) water-oxidizing catalyst. The Davies electron-nuclear double resonance (ENDOR) spectrum is well-modeled using a single class of hyperfine-coupled (59)Co nuclei with a modestly strong interaction (principal elements of the hyperfine tensor are equal to [-20(±2), 77(±1), -5(±15)] MHz). Mims (1)H ENDOR spectra of 1(+) with selectively deuterated pyridine ligands confirm that the amount of unpaired spin on the cobalt-bonding partner is significantly reduced from unity. Multifrequency (14)N ESEEM spectra (acquired at 9.5 and 34.0 GHz) indicate that four nearly equivalent nitrogen nuclei are coupled to the electron spin. Cumulatively, our EPR spectroscopic findings indicate that the unpaired spin is delocalized almost equally across the eight core atoms, a finding corroborated by results from DFT calculations. Each octahedrally coordinated cobalt ion is forced into a low-spin electron configuration by the anionic oxo and carboxylato ligands, and a fractional electron hole is localized on each metal center in a Co 3d(xz,yz)-based molecular orbital for this essentially [Co(+3.125)(4)O(4)] system. Comparing the EPR spectrum of 1(+) with that of the catalyst film allows us to draw conclusions about the electronic structure of this water-oxidation catalyst.

  11. Regenerable cobalt oxide loaded magnetosphere catalyst from fly ash for mercury removal in coal combustion flue gas.

    PubMed

    Yang, Jianping; Zhao, Yongchun; Zhang, Junying; Zheng, Chuguang

    2014-12-16

    To remove Hg(0) in coal combustion flue gas and eliminate secondary mercury pollution of the spent catalyst, a new regenerable magnetic catalyst based on cobalt oxide loaded magnetospheres from fly ash (Co-MF) was developed. The catalyst, with an optimal loading of 5.8% cobalt species, attained approximately 95% Hg(0) removal efficiency at 150 °C under simulated flue gas atmosphere. O2 could enhance the Hg(0) removal activity of magnetospheres catalyst via the Mars-Maessen mechanism. SO2 displayed an inhibitive effect on Hg(0) removal capacity. NO with lower concentration could promote the Hg(0) removal efficiency. However, when increasing the NO concentration to 300 ppm, a slightly inhibitive effect of NO was observed. In the presence of 10 ppm of HCl, greater than 95.5% Hg(0) removal efficiency was attained, which was attributed to the formation of active chlorine species on the surface. H2O presented a seriously inhibitive effect on Hg(0) removal efficiency. Repeated oxidation-regeneration cycles demonstrated that the spent Co-MF catalyst could be regenerated effectively via thermally treated at 400 °C for 2 h.

  12. Effect of oxidation heat treatment on the bond strength between a ceramic and cast and milled cobalt-chromium alloys.

    PubMed

    Li, Jieyin; Ye, Xiuhua; Li, Bohua; Liao, Juankun; Zhuang, Peilin; Ye, Jiantao

    2015-08-01

    There is a dearth of dental scientific literature on the effect of different oxidation heat treatments (OHTs) (as surface pretreatments) on the bonding performance of cast and milled cobalt-chromium (CoCr) alloys. The objective of this study was to evaluate the effect of different OHTs on the bond strength between a ceramic and cast and milled CoCr alloys. Cobalt-chromium metallic specimens were prepared using either a cast or a milled method. Specimens were subjected to four different OHT methods: without OHT; OHT under normal atmospheric pressure; OHT under vacuum; and OHT under vacuum followed by sandblasting. The metal-ceramic bond strength was evaluated using a three-point bending test according to ISO9693. Scanning electron microscopy and energy-dispersive spectroscopy were used to study the specimens' microstructure and elemental composition. The bond strength was not affected by the CoCr manufacturing method. Oxidation heat treatment performed under normal atmospheric pressure resulted in the highest bond strength. The concentration of oxygen on the alloy surfaces varied with the different pretreatment methods in the following order: OHT under normal atmospheric pressure > OHT under vacuum > without OHT ≈ OHT under vacuum followed by sandblasting. PMID:26104804

  13. The influence of manganese-cobalt oxide/graphene on reducing fire hazards of poly(butylene terephthalate).

    PubMed

    Wang, Dong; Zhang, Qiangjun; Zhou, Keqing; Yang, Wei; Hu, Yuan; Gong, Xinglong

    2014-08-15

    By means of direct nucleation and growth on the surface of graphene and element doping of cobalt oxide (Co3O4) nano-particles, manganese-cobalt oxide/graphene hybrids (MnCo2O4-GNS) were synthesized to reduce fire hazards of poly(butylene terephthalate) (PBT). The structure, elemental composition and morphology of the obtained hybrids were surveyed by X-ray diffraction, X-ray photoelectron spectrometer and transmission electron microscopy, respectively. Thermogravimetric analysis was applied to simulate and study the influence of MnCo2O4-GNS hybrids on thermal degradation of PBT during combustion. The fire hazards of PBT and its composites were assessed by the cone calorimeter. The cone test results had showed that peak HRR and SPR values of MnCo2O4-GNS/PBT composites were lower than that of pure PBT and Co3O4-GNS/PBT composites. Furthermore, the incorporation of MnCo2O4-GNS hybrids gave rise to apparent decrease of pyrolysis products containing aromatic compounds, carbonyl compounds, carbon monoxide and carbon dioxide, attributed to combined impact of physical barrier for graphene and cat O4 for organic volatiles and carbon monoxide. PMID:24997255

  14. Cesium and cobalt adsorption on synthetic nano manganese oxide: A two dimensional infra-red correlation spectroscopic investigation

    NASA Astrophysics Data System (ADS)

    Al Lafi, Abdul G.; Al Abdullah, Jamal

    2015-08-01

    Molecular scale information is of prime importance to understand ions coordination to mineral surfaces and consequently to aid in the design of improved ion exchange materials. This paper reports on the use of two-dimensional correlation infra-red spectroscopy (2D-COS-IR) to investigate the time dependent adsorptions of cesium and cobalt ions onto nano manganese oxide (NMO). The metal ions uptake was driven mainly by inner-sphere complex formation as demonstrated by the production of new absorption bands at 1160, 1100, 585 and 525 cm-1, which were assigned to the O-O bond vibration and the coupled vibrations of M-O and Mn-O bonds. The progressive development of the 3100 cm-1 band, which is attributed to the stretching vibration of the lattice-OH group, indicates an M+/H+ ion-exchange reaction. The new bands at 700 and 755 cm-1 in the case of cobalt ion adsorption and at 800 and 810 cm-1 in the case of cesium ion adsorption, and the splitting of other bands at 1135 and 875 cm-1 indicate the presence of different O-O bond lengths. This suggests different coordination of the two metal ions with oxygen. The infrared spectroscopy combined with 2D-COS provides a powerful tool to investigate the mechanism of interaction between heavy metals and manganese oxide.

  15. Cobalt doped antimony oxide nano-particles based chemical sensor and photo-catalyst for environmental pollutants

    NASA Astrophysics Data System (ADS)

    Jamal, Aslam; Rahman, Mohammed M.; Khan, Sher Bahadar; Faisal, Mohd.; Akhtar, Kalsoom; Rub, Malik Abdul; Asiri, Abdullah M.; Al-Youbi, Abdulrahman O.

    2012-11-01

    Cobalt doped antimony oxide nano-particles (NPs) have been synthesized by hydrothermal process and structurally characterized by utilizing X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Fourier transforms infrared spectrophotometer (FT-IR) which revealed that the synthesized cobalt antimony oxides (CoSb2O6) are well crystalline nano-particles with an average particles size of 26 ± 10 nm. UV-visible absorption spectra (˜286 nm) were used to investigate the optical properties of CoSb2O6. The chemical sensing of CoSb2O6 NPs have been primarily investigated by I-V technique, where dichloromethane is used as a model compound. The analytical performance of dichloromethane chemical sensor exhibits high sensitivity (1.2432 μA cm-2 mM-1) and a large linear dynamic range (1.0 μM-0.01 M) in short response time (10 s). The photo catalytic activity of the synthesized CoSb2O6 nano-particles was evaluated by degradation of acridine orange (AO), which degraded 58.37% in 200 min. These results indicate that CoSb2O6 nano-particles can play an excellent research impact in the environmental field.

  16. The influence of manganese-cobalt oxide/graphene on reducing fire hazards of poly(butylene terephthalate).

    PubMed

    Wang, Dong; Zhang, Qiangjun; Zhou, Keqing; Yang, Wei; Hu, Yuan; Gong, Xinglong

    2014-08-15

    By means of direct nucleation and growth on the surface of graphene and element doping of cobalt oxide (Co3O4) nano-particles, manganese-cobalt oxide/graphene hybrids (MnCo2O4-GNS) were synthesized to reduce fire hazards of poly(butylene terephthalate) (PBT). The structure, elemental composition and morphology of the obtained hybrids were surveyed by X-ray diffraction, X-ray photoelectron spectrometer and transmission electron microscopy, respectively. Thermogravimetric analysis was applied to simulate and study the influence of MnCo2O4-GNS hybrids on thermal degradation of PBT during combustion. The fire hazards of PBT and its composites were assessed by the cone calorimeter. The cone test results had showed that peak HRR and SPR values of MnCo2O4-GNS/PBT composites were lower than that of pure PBT and Co3O4-GNS/PBT composites. Furthermore, the incorporation of MnCo2O4-GNS hybrids gave rise to apparent decrease of pyrolysis products containing aromatic compounds, carbonyl compounds, carbon monoxide and carbon dioxide, attributed to combined impact of physical barrier for graphene and cat O4 for organic volatiles and carbon monoxide.

  17. Regenerable cobalt oxide loaded magnetosphere catalyst from fly ash for mercury removal in coal combustion flue gas.

    PubMed

    Yang, Jianping; Zhao, Yongchun; Zhang, Junying; Zheng, Chuguang

    2014-12-16

    To remove Hg(0) in coal combustion flue gas and eliminate secondary mercury pollution of the spent catalyst, a new regenerable magnetic catalyst based on cobalt oxide loaded magnetospheres from fly ash (Co-MF) was developed. The catalyst, with an optimal loading of 5.8% cobalt species, attained approximately 95% Hg(0) removal efficiency at 150 °C under simulated flue gas atmosphere. O2 could enhance the Hg(0) removal activity of magnetospheres catalyst via the Mars-Maessen mechanism. SO2 displayed an inhibitive effect on Hg(0) removal capacity. NO with lower concentration could promote the Hg(0) removal efficiency. However, when increasing the NO concentration to 300 ppm, a slightly inhibitive effect of NO was observed. In the presence of 10 ppm of HCl, greater than 95.5% Hg(0) removal efficiency was attained, which was attributed to the formation of active chlorine species on the surface. H2O presented a seriously inhibitive effect on Hg(0) removal efficiency. Repeated oxidation-regeneration cycles demonstrated that the spent Co-MF catalyst could be regenerated effectively via thermally treated at 400 °C for 2 h. PMID:25403026

  18. Electronic structure at transition metal phthalocyanine-transition metal oxide interfaces: Cobalt phthalocyanine on epitaxial MnO films

    SciTech Connect

    Glaser, Mathias; Peisert, Heiko Adler, Hilmar; Aygül, Umut; Ivanovic, Milutin; Chassé, Thomas; Nagel, Peter; Merz, Michael; Schuppler, Stefan

    2015-03-14

    The electronic structure of the interface between cobalt phthalocyanine (CoPc) and epitaxially grown manganese oxide (MnO) thin films is studied by means of photoemission (PES) and X-ray absorption spectroscopy (XAS). Our results reveal a flat-lying adsorption geometry of the molecules on the oxide surface which allows a maximal interaction between the π-system and the substrate. A charge transfer from MnO, in particular, to the central metal atom of CoPc is observed by both PES and XAS. The change of the shape of N-K XAS spectra at the interface points, however, to the involvement of the Pc macrocycle in the charge transfer process. As a consequence of the charge transfer, energetic shifts of MnO related core levels were observed, which are discussed in terms of a Fermi level shift in the semiconducting MnO films due to interface charge redistribution.

  19. Cobalt salophen complex supported on imidazole functionalized magnetic nanoparticles as a recoverable catalyst for oxidation of alkenes

    NASA Astrophysics Data System (ADS)

    Afshari, Mozhgan; Gorjizadeh, Maryam; Nazari, Simin; Naseh, Mohammad

    2014-08-01

    A new magnetically separable catalyst consisting of Co(II) salophen complex covalently supported on imidazole functionalized silica coated cobalt ferrite was prepared. The synthesized catalyst was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and Fourier transform infrared (FT-IR). The immobilized catalyst was shown to be an efficient heterogeneous catalyst for the oxidation of some alkenes using hydrogen peroxide (H2O2) as oxidant. The catalyst could be easily and efficiently isolated from the final product solution by magnetic decantation and be reused for 5 consecutive reactions without showing any significant activity degradation.

  20. The formation of volatile corrosion products during the mixed oxidation-chlorination of cobalt at 650 C

    NASA Technical Reports Server (NTRS)

    Jacobson, N. S.; Mcnallan, M. J.; Lee, Y. Y.

    1986-01-01

    The reaction of cobalt with 1 pct Cl2 in 1, 10, and 50 pct O2/Ar atmospheres has been studied at 650 C with thermogravimetry and mass spectrometry. The principal vapor species appear to be CoCl2 and CoCl3. In all cases, CoCl2(s) forms at the oxide/metal interface and equilibration of the volatile chlorides with Co3O4 does not occur in the early stages of the reaction. In the 1 pct Cl2 1 pct O2-Ar case, continuous volatilization occurs. In the 1 pct Cl2-10 pct O2-Ar and 1 pct CL2-50 pct O2-Ar cases, volatilization occurs only in the first few minutes of reaction. Afterwards, the reaction is predominantly oxidation.

  1. Mechanism of Layer-by-Layer Oxidation of Si(001) Surfaces by Two-Dimensional Oxide-Island Nucleation at SiO2/Si Interfaces

    NASA Astrophysics Data System (ADS)

    Watanabe, Heiji; Baba, Toshio; Ichikawa, Masakazu

    2000-04-01

    We have studied the mechanism of layer-by-layer oxidation of Si(001) surfaces. The layer-by-layer oxidation was confirmed and precisely monitored by scanning reflection electron microscopy (SREM). By combining SREM and scanning tunneling microscopy (STM) methods, we investigated the change in atomic-scale roughness at SiO2/Si(001) interfaces during the oxidation. We found that, while the oxide interface is atomically flat after the oxidation of each layer is complete, nanometer-scale oxide islands with a single atomic height are densely nucleated at the interface during the oxidation of each layer. We also observed an oscillation in the intensity of reflection high-energy electron diffraction (RHEED) spots during the top-layer oxidation. These results clearly indicate that the layer-by-layer oxidation proceeds by the nucleation of nanometer-scale oxide islands at the interfaces and by their preferential lateral island growth.

  2. Complex oxides: Creative tension in layered crystals

    NASA Astrophysics Data System (ADS)

    Gopalan, Venkatraman; Engel-Herbert, Roman

    2016-09-01

    New findings suggest that the mechanical stretching of layered crystals can transform them from a polar to a nonpolar state. This could spur the design of multifunctional materials controlled by an electric field.

  3. Electronic state of a CoO2 layer with hexagonal structure: a Kagomé lattice structure in a triangular lattice.

    PubMed

    Koshibae, W; Maekawa, S

    2003-12-19

    The electronic state in layered cobalt oxides with a hexagonal structure is examined. We find that the electronic structure reflects the nature of the Kagomé lattice hidden in the CoO2 layer which consists of stacked triangular lattices of oxygen ions and of cobalt ions. A fundamental model for the electron system is proposed, and the mechanism of the unique transport and magnetic properties of the cobalt oxides are discussed in light of the model.

  4. Manganese-Cobalt Mixed Spinel Oxides as Surface Modifiers for Stainless Steel Interconnects of Solid Oxide Fuel Cells

    SciTech Connect

    Xia, Gordon; Yang, Z Gary; Stevenson, Jeffry W.

    2006-11-06

    Ferritic stainless steels are promising candidates for interconnect applications in low- and mid-temperature solid oxide fuel cells (SOFCs). A couple of issues however remain for the particular application, including the chromium poisoning due to chromia evaporation, and long-term surface and electrical stability of the scale grown on these steels. Application of a manganese colbaltite spinel protection layer on the steels appears to be an effective approach to solve the issues. For an optimized performance, Mn{sub 1+x}Co{sub 2-x}O{sub 4} (-1 {le} x {le} 2) spinels were investigated against properties relative for protection coating applications on ferritic SOFC interconnects. Overall it appears that the spinels with x around 0.5 demonstrate a good CTE match to ceramic cell components, a relative high electrical conductivity, and a good thermal stability up to 1,250 C. This was confirmed by a long-term test on the Mn{sub 1.5}Co{sub 1.5}O{sub 4} protection layer that was thermally grown on Crofer22 APU, indicating the spinel protection layer not only significantly decreased the contact resistance between a LSF cathode and the stainless steel interconnects, but also inhibited the sub-scale growth on the stainless steels.

  5. Effect of ruthenium substitution in layered sodium cobaltate Na{sub x}CoO{sub 2}: Synthesis, structural and physical properties

    SciTech Connect

    Strobel, Pierre; Muguerra, Herve; Hebert, Sylvie; Pachoud, Elise; Colin, Claire; Julien, Marc-Henri

    2009-07-15

    Solid-state synthesis of Na{sub 0.71}Co{sub 1-x}Ru{sub x}O{sub 2} compositions shows that ruthenium can be substituted for cobalt in the hexagonal Na{sub 0.71}CoO{sub 2} phase up to x=0.5. The cell expands continuously with increasing ruthenium content. All mixed Co-Ru phases show a Curie-Weiss behaviour with no evidence of magnetic ordering down to 2 K. Unlike the parent phase Na{sub 0.71}CoO{sub 2}, ruthenium-substituted phases are all semiconducting. They exhibit high thermoelectric power, with a maximum of 165 muV/K at 300 K for x=0.3. The Curie constant C and Seebeck coefficient S show a non-monotonic evolution as a function of ruthenium content, demonstrating a remarkable interplay between magnetic properties and thermoelectricity. The presence of ruthenium has a detrimental effect on water intercalation and superconductivity in this system. Applying to Ru-substituted phases the oxidative intercalation of water known to lead to superconductivity in the Na{sub x}CoO{sub 2} system yields a 2-water layer hydrate only for x=0.1, and this phase is not superconducting down to 2 K. - Graphical Abstract: Effect of ruthenium substitution on thermoelectric power in Na{sub 0.71}Co{sub 1-x}Ru{sub x}O{sub 2} (left) and on low-temperature ac susceptibility in hydrated derivative (right).

  6. Effect of cobalt precursors on the dispersion, reduction, and CO oxidation of CoO(x)/γ-Al2O3 catalysts calcined in N2.

    PubMed

    Zhang, Lingling; Dong, Lihui; Yu, Wujiang; Liu, Lianjun; Deng, Yu; Liu, Bin; Wan, Haiqin; Gao, Fei; Sun, Keqin; Dong, Lin

    2011-03-15

    The present work tentatively investigated the effect of cobalt precursors (cobalt acetate and cobalt nitrate) on the physicochemical properties of CoO(x)/γ-Al(2)O(3) catalysts calcined in N(2). XRD, Raman, XPS, FTIR, and UV-vis DRS results suggested that CoO/γ-Al(2)O(3) was obtained from cobalt acetate precursors and CoO was dispersed on γ-Al(2)O(3) below its dispersion capacity of 1.50 mmol/(100 m(2) γ-Al(2)O(3)), whereas Co(3)O(4)/γ-Al(2)O(3) was obtained from cobalt nitrate precursors and Co(3)O(4) preferred to agglomerate above the dispersion capacity of 0.15 mmol/(100m(2) γ-Al(2)O(3)). Compared with Co(3)O(4)/γ-Al(2)O(3), CoO/γ-Al(2)O(3) catalysts were difficult to be reduced and easy to desorb oxygen species at low temperatures and presented high activities for CO oxidation as proved by H(2)-TPR, O(2)-TPD, and CO oxidation model reaction results. A surface incorporation model was proposed to explain the dispersion and reduction properties of CoO/γ-Al(2)O(3) catalysts.

  7. Effect of cobalt precursors on the dispersion, reduction, and CO oxidation of CoO(x)/γ-Al2O3 catalysts calcined in N2.

    PubMed

    Zhang, Lingling; Dong, Lihui; Yu, Wujiang; Liu, Lianjun; Deng, Yu; Liu, Bin; Wan, Haiqin; Gao, Fei; Sun, Keqin; Dong, Lin

    2011-03-15

    The present work tentatively investigated the effect of cobalt precursors (cobalt acetate and cobalt nitrate) on the physicochemical properties of CoO(x)/γ-Al(2)O(3) catalysts calcined in N(2). XRD, Raman, XPS, FTIR, and UV-vis DRS results suggested that CoO/γ-Al(2)O(3) was obtained from cobalt acetate precursors and CoO was dispersed on γ-Al(2)O(3) below its dispersion capacity of 1.50 mmol/(100 m(2) γ-Al(2)O(3)), whereas Co(3)O(4)/γ-Al(2)O(3) was obtained from cobalt nitrate precursors and Co(3)O(4) preferred to agglomerate above the dispersion capacity of 0.15 mmol/(100m(2) γ-Al(2)O(3)). Compared with Co(3)O(4)/γ-Al(2)O(3), CoO/γ-Al(2)O(3) catalysts were difficult to be reduced and easy to desorb oxygen species at low temperatures and presented high activities for CO oxidation as proved by H(2)-TPR, O(2)-TPD, and CO oxidation model reaction results. A surface incorporation model was proposed to explain the dispersion and reduction properties of CoO/γ-Al(2)O(3) catalysts. PMID:21216407

  8. Reaction of cobalt in SO2 atmospheric at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Jacobson, N. S.; Worrell, W. L.

    1983-01-01

    The reaction rate of cobalt in SO2 argon environments was measured at 650 C, 700 C, 750 C and 800 C. Product scales consist primarily of an interconnected sulfide phase in an oxide matrix. At 700 C to 800 C a thin sulfide layer adjacent to the metal is also observed. At all temperatures, the rapid diffusion of cobalt outward through the interconnected sulfide appears to be important. At 650 C, the reaction rate slows dramatically after five minutes due to a change in the distribution of these sulfides. At 700 C and 750 C the reaction is primarily diffusion controlled values of diffusivity of cobalt (CoS) calculated from this work show favorable agreement with values of diffusivity of cobalt (CoS) calculated from previous sulfidation work. At 800 C, a surface step becomes rate limiting.

  9. Reaction of cobalt in SO2 atmospheres at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Jacobson, N. S.; Worrell, W. L.

    1984-01-01

    The reaction rate of cobalt in SO2 argon environments was measured at 650 C, 700 C, 750 C and 800 C. Product scales consist primarily of an interconnected sulfide phase in an oxide matrix. At 700 C to 800 C, a thin sulfide layer adjacent to the metal is also observed. At all temperatures, the rapid diffusion of cobalt outward through the interconnected sulfide appears to be important. At 650 C, the reaction rate slows dramatically after five minutes due to a change in the distribution of these sulfides. At 700 C and 750 C, the reaction is primarily diffusion controlled; values of diffusivity of cobalt (CoS) calculated from this work show favorable agreement with values of diffusivity of cobalt (CoS) calculated from previous sulfidation work. At 800 C, a surface step becomes rate limiting. Previously announced in STAR as N83-35104

  10. Crystal structural, magnetic, and transport properties of layered cobalt oxyfluorides, Sr2CoO(3+x)F(1-x) (0 ≤ x ≤ 0.15).

    PubMed

    Tsujimoto, Yoshihiro; Sathish, Clastin I; Hong, Kun-Pyo; Oka, Kengo; Azuma, Masaki; Guo, Yanfeng; Matsushita, Yoshitaka; Yamaura, Kazunari; Takayama-Muromachi, Eiji

    2012-04-16

    The crystal structure of the layered cobalt oxyfluoride Sr(2)CoO(3)F synthesized under high-pressure and high-temperature conditions has been determined from neutron powder diffraction and synchrotron powder diffraction data collected at temperatures ranging from 320 to 3 K. This material adopts the tetragonal space group I4/mmm over the measured temperature range and the crystal structure is analogous to n = 1 Ruddlesden-Popper type layered perovskite. In contrast to related oxyhalide compounds, the present material exhibits the unique coordination environment around the Co metal center: coexistence of square pyramidal coordination around Co and anion disorder between O and F at the apical sites. Magnetic susceptibility and electrical resistivity measurements reveal that Sr(2)CoO(3)F is an antiferromagnetic insulator with the Néel temperature T(N) = 323(2) K. The magnetic structure that has been determined by neutron diffraction adopts a G-type antiferromagnetic order with the propagation vector k = (1/2 1/2 0) with an ordered cobalt moment μ = 3.18(5) μ(B) at 3 K, consistent with the high spin electron configuration for the Co(3+) ions. The antiferromagnetic and electrically insulating states remain robust even against 15%-O substation for F at the apical sites. However, applying pressure exhibits the onset of the metallic state, probably coming from change in the electronic state of square-pyramidal coordinated cobalt.

  11. Power generation using spinel manganese-cobalt oxide as a cathode catalyst for microbial fuel cell applications.

    PubMed

    Mahmoud, Mohamed; Gad-Allah, Tarek A; El-Khatib, K M; El-Gohary, Fatma

    2011-11-01

    This study focused on the use of spinel manganese-cobalt (Mn-Co) oxide, prepared by a solid state reaction, as a cathode catalyst to replace platinum in microbial fuel cells (MFCs) applications. Spinel Mn-Co oxides, with an Mn/Co atomic ratios of 0.5, 1, and 2, were prepared and examined in an air cathode MFCs which was fed with a molasses-laden synthetic wastewater and operated in batch mode. Among the three Mn-Co oxide cathodes and after 300 h of operation, the Mn-Co oxide catalyst with Mn/Co atomic ratio of 2 (MnCo-2) exhibited the highest power generation 113 mW/m2 at cell potential of 279 mV, which were lower than those for the Pt catalyst (148 mW/m2 and 325 mV, respectively). This study indicated that using spinel Mn-Co oxide to replace platinum as a cathodic catalyst enhances power generation, increases contaminant removal, and substantially reduces the cost of MFCs.

  12. Effect of cobalt doping on structural, optical and redox properties cerium oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Ansari, Anees A.; Labis, J.; Alam, M.; Ramay, Shahid M.; Ahmad, N.; Mahmood, Asif

    2016-03-01

    Cobalt-doped ceria nanoparticles were synthesized using the polyol method under co-precipitation hydrolysis. The structural, morphological, optical and redox properties were observed to investigate the influence of different concentration of cobalt ion doping on the prepared CeO2 nanomaterials in terms of X-ray diffraction, field-emission transmission electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, UV/vis absorption spectroscopy and temperature program reduction techniques. The optical band gap energy was calculated from the optical absorption spectra for doped ceria nanoparticles, which have been found to be 2.68, 2.77, and 2.82 eV for the 2, 4, and 7 mol% Co ion-doped CeO2 nanoparticles, respectively. As observed, the band gap energies increases as the doping Co ion concentrations increased, which could be due to significant increased oxygen vacancies with Co doping. The synergistic interaction between Co and CeO2 was the main factor responsible for high catalytic activity of cobalt-doped CeO2 model catalysts.

  13. Hierarchical nanostructures with unique Y-shaped interconnection networks in manganese substituted cobalt oxides: the enhancement effect on electrochemical sensing performance.

    PubMed

    Lan, Wen-Jie; Kuo, Cheng-Chi; Chen, Chun-Hu

    2013-04-14

    A general redox procedure was successfully developed for the controlled synthesis of substituted cobalt oxides with hierarchical flower-like nanostructures comprising unique Y-shaped interconnections. The substitution and nanostructures synergistically enhance the material's electrochemical activities for highly efficient sensing of H2O2.

  14. The Effect of Zn Addition on the Oxidation State of Cobalt in Co/ZrO2 Catalysts

    SciTech Connect

    Lebarbier, Vanessa MC; Karim, Ayman M.; Engelhard, Mark H.; Wu, Yu; Xu, Bo-Qing; Petersen, Eric J.; Datye, Abhaya K.; Wang, Yong

    2011-09-01

    The effect of Zn promotion on the activity and selectivity of Co/ZrO{sub 2} catalysts for ethanol steam reforming was investigated. The catalysts were synthesized by incipient wetness impregnation and characterized using BET measurements, temperature programmed reduction, X-ray diffraction, transmission electron microscopy, and X-ray electron spectroscopy. Compared to Co/ZrO{sub 2} catalyst, a higher ethanol conversion and a lower CH{sub 4} selectivity were observed for the Co/ZrO{sub 2} catalyst promoted with Zn. It was found that addition of Zn inhibits the oxidation of metallic cobalt (Co{sup 0}) particles, which results in a higher ratio of Co{sup 0}/Co{sup 2+} present in the Zn promoted Co/ZrO{sub 2} catalyst. These results suggest that metallic cobalt (Co{sup 0}) is responsible for ethanol conversion via ethanol dehydrogenation whereas Co{sup 2+} plays a role in the CH{sub 4} formation. For both catalysts, the experimental results show that CH4 is mainly produced via CO and/or CO{sub 2} methanation. TPR measurements, on the other hand, show Zn addition inhibits the reduction of Co{sup 2+} and Co{sup 3+}, which would mislead the conclusion that oxidized Co is required to reduce the CH{sub 4} formation. Therefore, TPR may not be appropriate to correlate the degree of metal reducibility (in this case Co{sup 0}) with the catalyst activity for reactions such as ethanol steam reforming where oxidizing conditions exist.

  15. Characterization of High-Velocity Solution Precursor Flame-Sprayed Manganese Cobalt Oxide Spinel Coatings for Metallic SOFC Interconnectors

    NASA Astrophysics Data System (ADS)

    Puranen, Jouni; Laakso, Jarmo; Kylmälahti, Mikko; Vuoristo, Petri

    2013-06-01

    A modified high-velocity oxy-fuel spray (HVOF) thermal spray torch equipped with liquid feeding hardware was used to spray manganese-cobalt solutions on ferritic stainless steel grade Crofer 22 APU substrates. The HVOF torch was modified in such a way that the solution could be fed axially into the combustion chamber through 250- and 300-μm-diameter liquid injector nozzles. The solution used in this study was prepared by diluting nitrates of manganese and cobalt, i.e., Mn(NO3)2·4H2O and Co(NO3)2·6H2O, respectively, in deionized water. The as-sprayed coatings were characterized by X-ray diffraction and field-emission scanning electron microscopy operating in secondary electron mode. Chemical analyses were performed on an energy dispersive spectrometer. Coatings with remarkable density could be prepared by the novel high-velocity solution precursor flame spray (HVSPFS) process. Due to finely sized droplet formation in the HVSPFS process and the use of as delivered Crofer 22 APU substrate material having very low substrate roughness ( R a < 0.5 μm), thin and homogeneous coatings, with thicknesses lower than 10 μm could be prepared. The coatings were found to have a crystalline structure equivalent to MnCo2O4 spinel with addition of Co-oxide phases. Crystallographic structure was restored back to single-phase spinel structure by heat treatment.

  16. Exploration of spin state and exchange integral of cobalt ions in stoichiometric ZnCo2O4 spinel oxides

    NASA Astrophysics Data System (ADS)

    Che, Xiangli; Li, Liping; Li, Guangshe

    2016-04-01

    This work reports on spin state and exchange integral of cobalt ions in stoichiometric ZnCo2O4 nanoparticles with varying particle size from about 24 to 105 nm. Cobalt ions in ZnCo2O4 nanoparticles are present as trivalence in mixed spin state. The effective magnetic moment is distributed in the range of 2.1 ˜ 1.31 μB at room temperature with coarsening of nanoparticles. Further, it is demonstrated that stoichiometric ZnCo2O4 undergoes a magnetic transition from paramagnetism to antiferromagnetism with decrease of temperature, showing a transition temperature of about 5 K. The standard molar entropy and enthalpy for 24 nm ZnCo2O4 are 170.6 ± 1.7 J K-1 mol-1 and 28.2 ± 0.3 kJ mol-1 at 298.15 K, respectively. Based on the heat capacity data, the exchange integral is determined to be 4.16 × 10-22 J. The results report here are really important for further understanding the magnetic and electronic properties of spinel oxides.

  17. Gate oxide damage reduction using a protective dielectric layer

    NASA Astrophysics Data System (ADS)

    Gabriel, Calvin T.; Weling, Milind G.

    1994-08-01

    Gate oxide damage from charge entering through the top surface of the gate electrode during plasma ashing, ion implantation, and LDD spacer oxide etching was measured using antenna structures. Significant charge damage to the 9.0 nm-thick gate oxide was detected for each of these processes. The damage was reduced by using a protective dielectric layer, in this case a thermally deposited TEOS oxide, over the polycide gate electrode before gate definition. The dielectric appears to block charge penetration into the antenna. Damage can be reduced further by increasing the thickness of the dielectric layer; for a sufficiently thick layer (about 150 nm), charge entering through the top surface of the antenna was effectively eliminated.

  18. Observation of oxide/Si(001)-interface during layer-by-layer oxidation by scanning reflection electron microscopy

    NASA Astrophysics Data System (ADS)

    Fujita, S.; Watanabe, H.; Maruno, S.; Ichikawa, M.; Kawamura, T.

    1997-08-01

    We have found that terrace contrast of oxidized Si(001) substrate observed with a scanning reflection electron microscopy (SREM) is reversed by progress in thermal oxidation by one atomic layer of Si. The cause for such terrace contrast reversion is that reflection electron intensity depends on Si-bond direction at oxide/Si interface. This fact was confirmed by calculations based on a multiple scattering theory. The motion of oxide/Si-bulk interface can be, thus, observed by SREM. The reversion and continuous change of the terrace contrast indicate that oxidation occurs monolayer by monolayer on Si(001) substrate.

  19. Self-limiting layer-by-layer oxidation of atomically thin WSe2.

    PubMed

    Yamamoto, Mahito; Dutta, Sudipta; Aikawa, Shinya; Nakaharai, Shu; Wakabayashi, Katsunori; Fuhrer, Michael S; Ueno, Keiji; Tsukagoshi, Kazuhito

    2015-03-11

    Growth of a uniform oxide film with a tunable thickness on two-dimensional transition metal dichalcogenides is of great importance for electronic and optoelectronic applications. Here we demonstrate homogeneous surface oxidation of atomically thin WSe2 with a self-limiting thickness from single- to trilayers. Exposure to ozone (O3) below 100 °C leads to the lateral growth of tungsten oxide selectively along selenium zigzag-edge orientations on WSe2. With further O3 exposure, the oxide regions coalesce and oxidation terminates leaving a uniform thickness oxide film on top of unoxidized WSe2. At higher temperatures, oxidation evolves in the layer-by-layer regime up to trilayers. The oxide films formed on WSe2 are nearly atomically flat. Using photoluminescence and Raman spectroscopy, we find that the underlying single-layer WSe2 is decoupled from the top oxide but hole-doped. Our findings offer a new strategy for creating atomically thin heterostructures of semiconductors and insulating oxides with potential for applications in electronic devices. PMID:25646637

  20. Self-limiting layer-by-layer oxidation of atomically thin WSe2.

    PubMed

    Yamamoto, Mahito; Dutta, Sudipta; Aikawa, Shinya; Nakaharai, Shu; Wakabayashi, Katsunori; Fuhrer, Michael S; Ueno, Keiji; Tsukagoshi, Kazuhito

    2015-03-11

    Growth of a uniform oxide film with a tunable thickness on two-dimensional transition metal dichalcogenides is of great importance for electronic and optoelectronic applications. Here we demonstrate homogeneous surface oxidation of atomically thin WSe2 with a self-limiting thickness from single- to trilayers. Exposure to ozone (O3) below 100 °C leads to the lateral growth of tungsten oxide selectively along selenium zigzag-edge orientations on WSe2. With further O3 exposure, the oxide regions coalesce and oxidation terminates leaving a uniform thickness oxide film on top of unoxidized WSe2. At higher temperatures, oxidation evolves in the layer-by-layer regime up to trilayers. The oxide films formed on WSe2 are nearly atomically flat. Using photoluminescence and Raman spectroscopy, we find that the underlying single-layer WSe2 is decoupled from the top oxide but hole-doped. Our findings offer a new strategy for creating atomically thin heterostructures of semiconductors and insulating oxides with potential for applications in electronic devices.

  1. Geometric Frustration in the Mixed Layer Pnictide Oxides

    SciTech Connect

    Enjalran, M.; Scalettar, R.T.; Kauzlarich, S.M.

    2000-06-06

    The authors present results from a Monte Carlo investigation of a simple bilayer model with geometrically frustrated interactions similar to those found in the mixed layer pnictide oxides (Sr{sub 2}Mn{sub 3}Pn{sub 2}O{sub 2}, Pn = As, Sb). The model is composed of two inequivalent square lattices with nearest-neighbor intra- and interlayer interactions. They find a ground state composed of two independent Neel ordered layers when the interlayer exchange is an order of magnitude weaker than the intralayer exchange, as suggested by experiment. Evidence for local orthogonal order between the layers is found, but it occurs in regions of parameter space which are not experimentally realized. Qualitatively similar results were observed in models with a larger number of layers. They conclude that frustration caused by nearest-neighbor interactions in the mixed layer pnictide oxides is not sufficient to explain the long-range orthogonal order that is observed experimentally.

  2. Structure, magnetism, and dissociation energy of small bimetallic cobalt-chromium oxide cluster cations: A density-functional-theory study

    NASA Astrophysics Data System (ADS)

    Pham, Hung Tan; Cuong, Ngo Tuan; Tam, Nguyen Minh; Lam, Vu Dinh; Tung, Nguyen Thanh

    2016-01-01

    We study CoxCryOm+ (x + y = 2, 3 and 1 ≤ m ≤ 4) clusters by means of density-functional-theory calculations. It is found that the clusters grow preferentially through maximizing the number of metal-oxygen bonds with a favor on Cr sites. The size- and composition-dependent magnetic behavior is discussed in relation with the local atomic magnetic moments. While doped species show an oscillatory magnetic behavior, the total magnetic moment of pure cobalt and chromium oxide clusters tends to enhance or reduce as increasing the oxygen content, respectively. The dissociation energies for different evaporation channels are also calculated to suggest the stable patterns, as fingerprints for future photofragmentation experiments.

  3. Cobalt oxide 2D nano-assemblies from infinite coordination polymer precursors mediated by a multidentate pyridyl ligand.

    PubMed

    Li, Guo-Rong; Xie, Chen-Chao; Shen, Zhu-Rui; Chang, Ze; Bu, Xian-He

    2016-05-01

    In this work, the construction of Co3O4 two dimensional (2D) nano-assemblies utilizing infinite coordination polymers (ICPs) as precursors was investigated, aiming at the morphology targeted fabrication and utilization of 2D materials. Based on the successful modulation of morphology, a rose-like Co based ICP precursor was obtained, which was further transformed into porous Co3O4 nanoflake assemblies with a well-preserved 2D morphology and a large surface area. The mechanism of the morphology modulation was illustrated by systematic investigation, which demonstrated the crucial role of a modulating agent in the formation of 2D nano-assemblies. In addition, the cobalt oxide 2D nano-assemblies are fabricated into a lithium anode combined with graphene, and the remarkable capacity and stability (900 mA h g(-1) after 50 cycles) of the resulting Co3O4/G nanocomposite indicates its potential in lithium battery applications. PMID:27064264

  4. Development and operation of gold and cobalt oxide nanoparticles containing polypropylene based enzymatic fuel cell for renewable fuels.

    PubMed

    Kilic, Muhammet Samet; Korkut, Seyda; Hazer, Baki; Erhan, Elif

    2014-11-15

    Newly synthesized gold and cobalt oxide nanoparticle embedded Polypropylene-g-Polyethylene glycol was used for a compartment-less enzymatic fuel cell. Glucose oxidase and bilirubin oxidase were selected as anodic and cathodic enzymes, respectively. Electrode fabrication and EFC operation parameters were optimized to achieve high power output. Maximum power density of 23.5 µW cm(-2) was generated at a cell voltage of +560 mV vs Ag/AgCl, in 100mM PBS pH 7.4 with the addition of 20mM of synthetic glucose solution. 20 µg of polymer amount with 185 µg of glucose oxidase and 356 µg of bilirubin oxidase was sufficient to get maximum performance. The working electrodes could harvest glucose, produced during photosynthesis reaction of Carpobrotus Acinaciformis plant, and readily found in real domestic wastewater of Zonguldak City in Turkey.

  5. Cobalt oxide 2D nano-assemblies from infinite coordination polymer precursors mediated by a multidentate pyridyl ligand.

    PubMed

    Li, Guo-Rong; Xie, Chen-Chao; Shen, Zhu-Rui; Chang, Ze; Bu, Xian-He

    2016-05-01

    In this work, the construction of Co3O4 two dimensional (2D) nano-assemblies utilizing infinite coordination polymers (ICPs) as precursors was investigated, aiming at the morphology targeted fabrication and utilization of 2D materials. Based on the successful modulation of morphology, a rose-like Co based ICP precursor was obtained, which was further transformed into porous Co3O4 nanoflake assemblies with a well-preserved 2D morphology and a large surface area. The mechanism of the morphology modulation was illustrated by systematic investigation, which demonstrated the crucial role of a modulating agent in the formation of 2D nano-assemblies. In addition, the cobalt oxide 2D nano-assemblies are fabricated into a lithium anode combined with graphene, and the remarkable capacity and stability (900 mA h g(-1) after 50 cycles) of the resulting Co3O4/G nanocomposite indicates its potential in lithium battery applications.

  6. Electron-collecting oxide layers in inverted polymer solar cells via oxidation of thermally evaporated titanium

    NASA Astrophysics Data System (ADS)

    Zampetti, A.; Salamandra, L.; Brunetti, F.; Reale, A.; Di Carlo, A.; Brown, T. M.

    2016-10-01

    A simple and intuitive deposition technique is discussed to obtain titanium oxide used as an electron collecting layer in polymer solar cells based on the thermal evaporation of pristine titanium and further thermal treatment to convert the metal in oxide. Since the degradation of indium-doped tin oxide at high temperatures is an issue, we demonstrate that the combination of glass/fluorine tin oxide and high temperatures represents a promising approach in the fabrication of inverted polymer solar cells with such a titanium oxide electron collecting layer.

  7. Synthesis and controllable oxidation of monodisperse cobalt-doped wüstite nanoparticles and their core-shell stability and exchange-bias stabilization.

    PubMed

    Chen, Chih-Jung; Chiang, Ray-Kuang; Kamali, Saeed; Wang, Sue-Lein

    2015-09-14

    Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ∼4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (H(E)), an enhanced coercivity field (H(C)), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of H(E) was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (T(N)) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy.

  8. Synthesis and controllable oxidation of monodisperse cobalt-doped wüstite nanoparticles and their core-shell stability and exchange-bias stabilization.

    PubMed

    Chen, Chih-Jung; Chiang, Ray-Kuang; Kamali, Saeed; Wang, Sue-Lein

    2015-09-14

    Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ∼4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (H(E)), an enhanced coercivity field (H(C)), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of H(E) was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (T(N)) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy. PMID:26243163

  9. Mass transfer model for two-layer TBP oxidation reactions

    SciTech Connect

    Laurinat, J.E.

    1994-09-28

    To prove that two-layer, TBP-nitric acid mixtures can be safely stored in the canyon evaporators, it must be demonstrated that a runaway reaction between TBP and nitric acid will not occur. Previous bench-scale experiments showed that, at typical evaporator temperatures, this reaction is endothermic and therefore cannot run away, due to the loss of heat from evaporation of water in the organic layer. However, the reaction would be exothermic and could run away if the small amount of water in the organic layer evaporates before the nitric acid in this layer is consumed by the reaction. Provided that there is enough water in the aqueous layer, this would occur if the organic layer is sufficiently thick so that the rate of loss of water by evaporation exceeds the rate of replenishment due to mixing with the aqueous layer. This report presents measurements of mass transfer rates for the mixing of water and butanol in two-layer, TBP-aqueous mixtures, where the top layer is primarily TBP and the bottom layer is comprised of water or aqueous salt solution. Mass transfer coefficients are derived for use in the modeling of two-layer TBP-nitric acid oxidation experiments. Three cases were investigated: (1) transfer of water into the TBP layer with sparging of both the aqueous and TBP layers, (2) transfer of water into the TBP layer with sparging of just the TBP layer, and (3) transfer of butanol into the aqueous layer with sparging of both layers. The TBP layer was comprised of 99% pure TBP (spiked with butanol for the butanol transfer experiments), and the aqueous layer was comprised of either water or an aluminum nitrate solution. The liquid layers were air sparged to simulate the mixing due to the evolution of gases generated by oxidation reactions. A plastic tube and a glass frit sparger were used to provide different size bubbles. Rates of mass transfer were measured using infrared spectrophotometers provided by SRTC/Analytical Development.

  10. Anomalies of thermal expansion and electrical resistivity of layered cobaltates YBaCo2O5 + x : The role of oxygen chain ordering

    NASA Astrophysics Data System (ADS)

    Zhdanov, K. R.; Kameneva, M. Yu.; Kozeeva, L. P.; Lavrov, A. N.

    2016-08-01

    Layered cobaltates YBaCo2O5 + x have been investigated in the oxygen concentration range 0.23 ≤ x ≤ 0.52. It has been revealed that the oxygen ordering plays the key role in the appearance of anomalies in temperature dependences of structural parameters and electron transport. It has been shown that the orthorhombic lattice distortion caused by oxygen chain ordering is a necessary "trigger" for the phase transition from the insulating state to the metallic state at T ≈ 290-295 K, after which the orthorhombic distortion is significantly more pronounced. In the boundary region of the cobaltate compositions, where the oxygen ordering has a partial or local character, there are additional low-temperature (100-240 K) structural and resistive features with a large hysteresis. The observed anomalies can be explained by a change in the spin state of the cobalt ions, which is extremely sensitive to parameters of the crystal field acting on the ions, as well as by the spin-transition-induced delocalization of electrons.

  11. Corrosion of NiTi Wires with Cracked Oxide Layer

    NASA Astrophysics Data System (ADS)

    Racek, Jan; Šittner, Petr; Heller, Luděk; Pilch, Jan; Petrenec, Martin; Sedlák, Petr

    2014-07-01

    Corrosion behavior of superelastic NiTi shape memory alloy wires with cracked TiO2 surface oxide layers was investigated by electrochemical corrosion tests (Electrochemical Impedance Spectroscopy, Open Circuit Potential, and Potentiodynamic Polarization) on wires bent into U-shapes of various bending radii. Cracks within the oxide on the surface of the bent wires were observed by FIB-SEM and TEM methods. The density and width of the surface oxide cracks dramatically increase with decreasing bending radius. The results of electrochemical experiments consistently show that corrosion properties of NiTi wires with cracked oxide layers (static load keeps the cracks opened) are inferior compared to the corrosion properties of the straight NiTi wires covered by virgin uncracked oxides. Out of the three methods employed, the Electrochemical Impedance Spectroscopy seems to be the most appropriate test for the electrochemical characterization of the cracked oxide layers, since the impedance curves (Nyquist plot) of differently bent NiTi wires can be associated with increasing state of the surface cracking and since the NiTi wires are exposed to similar conditions as the surfaces of NiTi implants in human body. On the other hand, the potentiodynamic polarization test accelerates the corrosion processes and provides clear evidence that the corrosion resistance of bent superelastic NiTi wires degrades with oxide cracking.

  12. Low Temperature Processed Complementary Metal Oxide Semiconductor (CMOS) Device by Oxidation Effect from Capping Layer

    PubMed Central

    Wang, Zhenwei; Al-Jawhari, Hala A.; Nayak, Pradipta K.; Caraveo-Frescas, J. A.; Wei, Nini; Hedhili, M. N.; Alshareef, H. N.

    2015-01-01

    In this report, both p- and n-type tin oxide thin-film transistors (TFTs) were simultaneously achieved using single-step deposition of the tin oxide channel layer. The tuning of charge carrier polarity in the tin oxide channel is achieved by selectively depositing a copper oxide capping layer on top of tin oxide, which serves as an oxygen source, providing additional oxygen to form an n-type tin dioxide phase. The oxidation process can be realized by annealing at temperature as low as 190°C in air, which is significantly lower than the temperature generally required to form tin dioxide. Based on this approach, CMOS inverters based entirely on tin oxide TFTs were fabricated. Our method provides a solution to lower the process temperature for tin dioxide phase, which facilitates the application of this transparent oxide semiconductor in emerging electronic devices field. PMID:25892711

  13. Low temperature processed complementary metal oxide semiconductor (CMOS) device by oxidation effect from capping layer.

    PubMed

    Wang, Zhenwei; Al-Jawhari, Hala A; Nayak, Pradipta K; Caraveo-Frescas, J A; Wei, Nini; Hedhili, M N; Alshareef, H N

    2015-04-20

    In this report, both p- and n-type tin oxide thin-film transistors (TFTs) were simultaneously achieved using single-step deposition of the tin oxide channel layer. The tuning of charge carrier polarity in the tin oxide channel is achieved by selectively depositing a copper oxide capping layer on top of tin oxide, which serves as an oxygen source, providing additional oxygen to form an n-type tin dioxide phase. The oxidation process can be realized by annealing at temperature as low as 190 °C in air, which is significantly lower than the temperature generally required to form tin dioxide. Based on this approach, CMOS inverters based entirely on tin oxide TFTs were fabricated. Our method provides a solution to lower the process temperature for tin dioxide phase, which facilitates the application of this transparent oxide semiconductor in emerging electronic devices field.

  14. Multishelled Nickel-Cobalt Oxide Hollow Microspheres with Optimized Compositions and Shell Porosity for High-Performance Pseudocapacitors.

    PubMed

    Li, Xiangcun; Wang, Le; Shi, Jianhang; Du, Naixu; He, Gaohong

    2016-07-13

    Nickel-cobalt oxides/hydroxides have been considered as promising electrode materials for a high-performance supercapacitor. However, their energy density and cycle stability are still very poor at high current density. Moreover, there are few reports on the fabrication of mixed transition-metal oxides with multishelled hollow structures. Here, we demonstrate a new and flexible strategy for the preparation of hollow Ni-Co-O microspheres with optimized Ni/Co ratios, controlled shell porosity, shell numbers, and shell thickness. Owing to its high effective electrode area and electron transfer number (n(3/2) A), mesoporous shells, and fast electron/ion transfer, the triple-shelled Ni-Co1.5-O electrode exhibits an ultrahigh capacitance (1884 F/g at 3A/g) and rate capability (77.7%, 3-30A/g). Moreover, the assembled sandwiched Ni-Co1.5-O//RGO@Fe3O4 asymmetric supercapacitor (ACS) retains 79.4% of its initial capacitance after 10 000 cycles and shows a high energy density of 41.5 W h kg(-1) at 505 W kg(-1). Importantly, the ACS device delivers a high energy density of 22.8 W h kg(-1) even at 7600 W kg(-1), which is superior to most of the reported asymmetric capacitors. This study has provided a facile and general approach to fabricate Ni/Co mixed transition-metal oxides for energy storage. PMID:27327877

  15. Crossed ferric oxide nanosheets supported cobalt oxide on 3-dimensional macroporous Ni foam substrate used for diesel soot elimination under self-capture contact mode

    NASA Astrophysics Data System (ADS)

    Cao, Chunmei; Li, Xingang; Zha, Yuqing; Zhang, Jing; Hu, Tiandou; Meng, Ming

    2016-03-01

    Crossed Fe2O3 nanosheets supported cobalt oxide nanoparticles on three-dimensionally macroporous nickel foam substrate (xCo/Fe-NF) was designed and successfully prepared through a facile hydrothermal and impregnation route. These catalysts showed high catalytic soot combustion activities under self-capture contact mode. The three-dimensional macroporous structures of Ni foam and the crossed Fe2O3 nanosheets constituted macroporous voids can greatly increase the contact efficiency between soot particulates and catalysts. The interaction between Co and Fe facilitated the activation of the Fe-O bond and increased the amounts of active oxygen species, thus improving the redox property of the catalysts. The 0.6Co/Fe-NF catalyst exhibited the highest turnover frequency (TOF) for soot combustion, which is in good accordance with the largest amount of active oxygen species. Based upon the catalytic performance and multiple characterization results, two reaction pathways for soot oxidation are identified, namely, the direct oxidation by the activated oxygen species via oxygen vacancies and the NOx-aided soot oxidation.Crossed Fe2O3 nanosheets supported cobalt oxide nanoparticles on three-dimensionally macroporous nickel foam substrate (xCo/Fe-NF) was designed and successfully prepared through a facile hydrothermal and impregnation route. These catalysts showed high catalytic soot combustion activities under self-capture contact mode. The three-dimensional macroporous structures of Ni foam and the crossed Fe2O3 nanosheets constituted macroporous voids can greatly increase the contact efficiency between soot particulates and catalysts. The interaction between Co and Fe facilitated the activation of the Fe-O bond and increased the amounts of active oxygen species, thus improving the redox property of the catalysts. The 0.6Co/Fe-NF catalyst exhibited the highest turnover frequency (TOF) for soot combustion, which is in good accordance with the largest amount of active oxygen

  16. Sputtered silver oxide layers for surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Büchel, D.; Mihalcea, C.; Fukaya, T.; Atoda, N.; Tominaga, J.; Kikukawa, T.; Fuji, H.

    2001-07-01

    We present results of reactively sputtered silver oxide thin films as a substrate material for surface-enhanced Raman spectroscopy (SERS). Herein, we show that deposited layers develop an increasingly strong SERS activity upon photoactivation at 488 nm. A benzoic acid/2-propanol solution was used to demonstrate that the bonding of molecules to SERS active sites at the surface can be followed by investigating temporal changes of the corresponding Raman intensities. Furthermore, the laser-induced structural changes in the silver oxide layers lead to a fluctuating SERS activity at high laser intensities which also affects the spectral features of amorphous carbon impurities.

  17. Water oxidation by electrodeposited cobalt oxides--role of anions and redox-inert cations in structure and function of the amorphous catalyst.

    PubMed

    Risch, Marcel; Klingan, Katharina; Ringleb, Franziska; Chernev, Petko; Zaharieva, Ivelina; Fischer, Anna; Dau, Holger

    2012-03-12

    For the production of nonfossil fuels, water oxidation by inexpensive cobalt-based catalysts is of high interest. Films for the electrocatalysis of water oxidation were obtained by oxidative self-assembly (electrodeposition) from aqueous solutions containing, apart from Co, either K, Li or Ca with either a phosphate, acetate or chloride anion. X-ray absorption spectroscopy (XAS) at the Co K-edge revealed clusters of edge-sharing CoO(6) octahedra in all films, but the size or structural disorder of the Co-oxido clusters differed. Whereas potassium binding is largely unspecific, CaCo(3) O(4) cubanes, which resemble the CaMn(3) O(4) cubane of the biological catalyst in oxygenic photosynthesis, may form, as suggested by XAS at the Ca K-edge. Cyclic voltammograms in a potassium phosphate buffer at pH 7 revealed that no specific combination of anions and redox-inactive cations is required for catalytic water oxidation. However, the anion type modulates not only the size (or order) of the Co-oxido clusters, but also electrodeposition rates, redox potentials, the capacity for oxidative charging, and catalytic currents. On these grounds, structure-activity relations are discussed.

  18. Geodynamic and climate controls in the formation of Mio-Pliocene world-class oxidized cobalt and manganese ores in the Katanga province, DR Congo

    NASA Astrophysics Data System (ADS)

    Decrée, Sophie; Deloule, Étienne; Ruffet, Gilles; Dewaele, Stijn; Mees, Florias; Marignac, Christian; Yans, Johan; de Putter, Thierry

    2010-10-01

    The Katanga province, Democratic Republic of Congo, hosts world-class cobalt deposits accounting for ~50% of the world reserves. They originated from sediment-hosted stratiform copper and cobalt sulfide deposits within Neoproterozoic metasedimentary rocks. Heterogenite, the main oxidized cobalt mineral, is concentrated as “cobalt caps” along the top of silicified dolomite inselbergs. The supergene cobalt enrichment process is part of a regional process of residual ore formation that also forms world-class “manganese cap” deposits in western Katanga, i.e., the “black earths” that are exploited by both industrial and artisanal mining. Here, we provide constraints on the genesis and the timing of these deposits. Ar-Ar analyses of oxidized Mn ore and in situ U-Pb SIMS measurements of heterogenite yield Mio-Pliocene ages. The Ar-Ar ages suggest a multi-phase process, starting in the Late Miocene (10-5 Ma), when the metal-rich substratum was exposed to the action of meteoric fluids, due to major regional uplift. Further oxidation took place in the Pliocene (3.7-2.3 Ma) and formed most of the observed deposits under humid conditions: Co- and Mn-caps on metal-rich substrata, and coeval Fe laterites on barren areas. These deposits formed prior to the regional shift toward more arid conditions in Central Africa. Arid conditions still prevailed during the Quaternary and resulted in erosion and valley incision, which dismantled the metal-bearing caps and led to ore accumulation in valleys and along foot slopes.

  19. Rapid photo-degradation of 2-chlorophenol under visible light irradiation using cobalt oxide-loaded TiO2/reduced graphene oxide nanocomposite from aqueous media.

    PubMed

    Sharma, Ajit; Lee, Byeong-Kyu

    2016-01-01

    The photocatalytic removal of 2-chlorophenol (2-CP) from water environment was investigated by TiO2-RGO-CoO. Cobalt oxide-loaded TiO2 (TiO2-CoO) supported with reduced graphene oxide (RGO) was synthesized using a sol-gel method and then annealed at 500 °C for 5 min. The material characteristics were analyzed by UV-Vis analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. Incorporation of cobalt oxide and RGO into the TiO2 system (TiO2-RGO-CoO) lowered the band gap energy to 2.83 eV, which greatly enhanced the visible light absorption. The TiO2-RGO-CoO photocatalyst showed complete removal of 20 mg/L 2-CP within 8 h with the addition of 0.01% H2O2 under 100 W visible light irradiation. The photo-degradation efficiency of 2-CP (10 mg/L) was 35.2, 48.9, 58.9 and 98.2% for TiO2, TiO2-RGO, TiO2-CoO and TiO2-RGO-CoO, respectively, in the presence of visible light irradiation at solution pH of 6.0. The TiO2-RGO-CoO photocatalyst retained its high removal efficiency even after five photocatalytic cycles.

  20. Atomic-layer engineering of oxide superconductors

    NASA Astrophysics Data System (ADS)

    Bollinger, A. T.; Eckstein, J. N.; Dubuis, G.; Pavuna, D.; Božović, I.

    2012-02-01

    Molecular beam epitaxy technique has enabled synthesis of atomically smooth thin films, multilayers, and superlattices of cuprates and other complex oxides. Such heterostructures show high temperature superconductivity and enable novel experiments that probe the basic physics of this phenomenon. For example, it was established that high temperature superconductivity and anti-ferromagnetic phases separate on Ångström scale, while the pseudo-gap state apparently mixes with high temperature superconductivity over an anomalously large length scale (the "Giant Proximity Effect"). We review some recent experiments on such films and superlattices, including X-ray diffraction, atomic force microscopy, angle-resolved time of flight ion scattering and recoil spectroscopy, transport measurements, highresolution transmission electron microscopy, resonant X-ray scattering, low-energy muon spin resonance, and ultrafast photo-induced reflection high energy electron diffraction. The results include an unambiguous demonstration of strong coupling of in-plane charge excitations to out-of-plane lattice vibrations, a discovery of interface high temperature superconductivity that occurs in a single CuO2 plane, evidence for local pairs, and establishing tight limits on the temperature range of superconducting fluctuations.

  1. Synthesis and characterization of cobalt oxide nanocomposite based on the Co3O4-zeolite Y

    NASA Astrophysics Data System (ADS)

    Davar, Fatemeh; Fereshteh, Zeinab; Shoja Razavi, Hadi; Razavi, Reza Shoja; Loghman-Estarki, Mohammad Reza

    2014-02-01

    The Co3O4 nanocomposite was synthesized by an ion-exchange of cobalt ions and Y zeolite in the presence of sodium hydroxide and calcination treatment. The products were characterized by X-ray diffraction (XRD), Raman analysis, scanning electron microscope (SEM), transmission electron microscope (TEM), BET, Energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FTIR) spectroscopy. The sizes of the migrated Co3O4 particles out of Y zeolite super cage were in the range of 29 ± 5 nm. Finally, the magnetic property of as-obtained product was investigated in a vibrating sample magnetometer (VSM). This nanocomposite showed a paramagnetic behavior at room temperature.

  2. Synthesis of nano-sized lithium cobalt oxide via a sol-gel method

    NASA Astrophysics Data System (ADS)

    Li, Guangfen; Zhang, Jing

    2012-07-01

    In this study, nano-structured LiCoO2 thin film were synthesized by coupling a sol-gel process with a spin-coating method using polyacrylic acid (PAA) as chelating agent. The optimized conditions for obtaining a better gel formulation and subsequent homogenous dense film were investigated by varying the calcination temperature, the molar mass of PAA, and the precursor's molar ratios of PAA, lithium, and cobalt ions. The gel films on the silicon substrate surfaces were deposited by multi-step spin-coating process for either increasing the density of the gel film or adjusting the quantity of PAA in the film. The gel film was calcined by an optimized two-step heating procedure in order to obtain regular nano-structured LiCoO2 materials. Both atomic force microscopy (AFM) and scanning electron microscopy (SEM) were utilized to analyze the crystalline and the morphology of the films, respectively.

  3. Investigation on cobalt-oxide nanoparticles cyto-genotoxicity and inflammatory response in two types of respiratory cells.

    PubMed

    Cavallo, Delia; Ciervo, Aureliano; Fresegna, Anna Maria; Maiello, Raffaele; Tassone, Paola; Buresti, Giuliana; Casciardi, Stefano; Iavicoli, Sergio; Ursini, Cinzia Lucia

    2015-10-01

    The increasing use of cobalt oxide (Co3 O4 ) nanoparticles (NPs) in several applications and the suggested genotoxic potential of Co-oxide highlight the importance of evaluating Co3 O4 NPs toxicity. Cyto-genotoxic and inflammatory effects induced by Co3 O4 NPs were investigated in human alveolar (A549), and bronchial (BEAS-2B) cells exposed to 1-40 µg ml(-1) . The physicochemical properties of tested NPs were analysed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Cytotoxicity was studied to analyze cell viability (WST1 test) and membrane damage (LDH assay), direct/oxidative DNA damage was assessed by the Formamido-pyrimidine glycosylase (Fpg)-modified comet assay and inflammation by interleukin (IL)-6, IL-8 and tumor necrosis factor-alpha (TNF-α) release (ELISA). In A549 cells, no cytotoxicity was found, whereas BEAS-2B cells showed a viability reduction at 40 µg ml(-1) and early membrane damage at 1, 5 and 40 µg ml-1. In A549 cells, direct and oxidative DNA damage at 20 and 40 µg ml(-1) were detected without any effects on cytokine release. In BEAS-2B cells, significant direct DNA damage at 40 µg ml(-1) and significant oxidative DNA damage with a peak at 5 µg ml(-1) , that was associated with increased TNF-α release at 1 µg ml(-1) after 2 h and increased IL-8 release at 20 µg ml(-1) after 24 h, were detected. The findings show in the transformed alveolar cells no cytotoxicity and genotoxic/oxidative effects at 20 and 40 µg ml(-1) . In normal bronchial cells, moderate cytotoxicity, direct DNA damage only at the highest concentration and significant oxidative-inflammatory effects at lower concentrations were detected. The findings confirm the genotoxic-oxidative potential of Co3 O4 NPs and show greater sensitivity of BEAS-2B cells to cytotoxic and oxidative-inflammatory effects suggesting the use of different cell lines and multiple end-points to elucidate Co3 O4 NPs toxicity.

  4. The growth of oxide and oxygen-stabilized alpha layers in steam-oxidized zircaloy

    NASA Astrophysics Data System (ADS)

    Biederman, R. R.; Ocken, H.; Sisson, R. D.

    1981-04-01

    Experimental investigations of the oxidation of Zircaloy in steam at high temperatures suggest temperature gradients exist across the oxide and oxygen-stabilized α layers even when specimens are exposed under nominally isothermal conditions. This paper presents a simple model that permits one to calculate the ratio of the thickness, of the oxide to oxygen-stabilized α layers in the presence of temperature gradients as well as under truly isothermal exposure conditions. The shape of the oxide to oxygen-stabilized α thickness ratio curve as a function of temperature was found to be in excellent agreement with oxidation kinetics data that were used to derive a scaling factor for the model. Variations in the temperature dependence of this ratio from independent measurements can be reproduced if it is assumed that temperature differences on the order of 10°C exist between the oxide layer and the oxygen-stabilized α layer. Metallographic evidence is presented that suggests the rate-controlling oxidation step occurs in the vicinity of the interface between the oxide and oxygen-stabilized a layers

  5. Dysprosium oxide and dysprosium-oxide-doped titanium oxide thin films grown by atomic layer deposition

    SciTech Connect

    Tamm, Aile Kozlova, Jekaterina; Aarik, Lauri; Aarik, Jaan; Kukli, Kaupo; Link, Joosep; Stern, Raivo

    2015-01-15

    Dysprosium oxide and dysprosium-oxide-doped titanium oxide thin films were grown by atomic layer deposition on silicon substrates. For depositing dysprosium and titanium oxides Dy(thd){sub 3}-O{sub 3} and TiCl{sub 4}-O{sub 3} were used as precursors combinations. Appropriate parameters for Dy(thd){sub 3}-O{sub 3} growth process were obtained by using a quartz crystal microbalance system. The Dy{sub 2}O{sub 3} films were deposited on planar substrates and on three-dimensional substrates with aspect ratio 1:20. The Dy/Ti ratio of Dy{sub 2}O{sub 3}-doped TiO{sub 2} films deposited on a planar silicon substrate ranged from 0.04 to 0.06. Magnetometry studies revealed that saturation of magnetization could not be observed in planar Dy{sub 2}O{sub 3} films, but it was observable in Dy{sub 2}O{sub 3} films on 3D substrates and in doped TiO{sub 2} films with a Dy/Ti atomic ratio of 0.06. The latter films exhibited saturation magnetization 10{sup −6} A cm{sup 2} and coercivity 11 kA/m at room temperature.

  6. Zinc-oxide charge trapping memory cell with ultra-thin chromium-oxide trapping layer

    SciTech Connect

    El-Atab, Nazek; Rizk, Ayman; Nayfeh, Ammar; Okyay, Ali K.

    2013-11-15

    A functional zinc-oxide based SONOS memory cell with ultra-thin chromium oxide trapping layer was fabricated. A 5 nm CrO{sub 2} layer is deposited between Atomic Layer Deposition (ALD) steps. A threshold voltage (V{sub t}) shift of 2.6V was achieved with a 10V programming voltage. Also for a 2V V{sub t} shift, the memory with CrO{sub 2} layer has a low programming voltage of 7.2V. Moreover, the deep trapping levels in CrO{sub 2} layer allows for additional scaling of the tunnel oxide due to an increase in the retention time. In addition, the structure was simulated using Physics Based TCAD. The results of the simulation fit very well with the experimental results providing an understanding of the charge trapping and tunneling physics.

  7. Cobalt ferrite nanoparticles decorated on exfoliated graphene oxide, application for amperometric determination of NADH and H2O2.

    PubMed

    Ensafi, Ali A; Alinajafi, Hossein A; Jafari-Asl, M; Rezaei, B; Ghazaei, F

    2016-03-01

    Here, cobalt ferrite nanohybrid decorated on exfoliated graphene oxide (CoFe2O4/EGO) was synthesized. The nanohybrid was characterized by different methods such as X-ray diffraction spectroscopy, scanning electron microscopy, energy dispersive X-ray diffraction microanalysis, transmission electron microscopy, FT-IR, Raman spectroscopy and electrochemical methods. The CoFe2O4/EGO nanohybrid was used to modify glassy carbon electrode (GCE). The voltammetric investigations showed that CoFe2O4/EGO nanohybrid has synergetic effect towards the electro-reduction of H2O2 and electro-oxidation of nicotinamide adenine dinucleotide (NADH). Rotating disk chronoamperometry was used for their quantitative analysis. The calibration curves were observed in the range of 0.50 to 100.0 μmol L(-1) NADH and 0.9 to 900.0 μmol L(-1) H2O2 with detections limit of 0.38 and 0.54 μmol L(-1), respectively. The repeatability, reproducibility and selectivity of the electrochemical sensor for analysis of the analytes were studied. The new electrochemical sensor was successfully applied for the determination of NADH and H2O2 in real samples with satisfactory results.

  8. Three-dimensional nanoporous gold-cobalt oxide electrode for high-performance electroreduction of hydrogen peroxide in alkaline medium

    NASA Astrophysics Data System (ADS)

    Li, Zhihao; He, Yanghua; Ke, Xi; Gan, Lin; Zhao, Jie; Cui, Guofeng; Wu, Gang

    2015-10-01

    Using a simple hydrothermal method combined with a post-annealing treatment, cobalt oxide (Co3O4) nanosheet arrays are grown on three-dimensional (3D) nanoporous gold (NPG) film supported on Ni foam substrates, in which NPG is fabricated by chemically dealloying electrodeposited Au-Sn alloy films. The morphology and structure of the Co3O4@NPG/Ni foam hybrids are characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical activity of the Co3O4@NPG/Ni foam electrode toward hydrogen peroxide electroreduction in alkaline medium is studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA). The results demonstrate that the Co3O4@NPG/Ni foam electrode possesses exceptionally high catalytic activity and excellent stability for the peroxide electroreduction, resulting mainly from the unique electrode architecture. The combined 3D hierarchical porous structures of NPG/Ni foam with the open and porous structures of Co3O4 nanosheet arrays facilitate the mass transport and charge transfer. Therefore, the metal oxides supported on 3D hierarchical porous NPG/Ni foam framework may hold great promise to be effective electrodes for electrocatalytic reduction of peroxide and other electrochemical reactions.

  9. High performance cobalt-free Cu1.4Mn1.6O4 spinel oxide as an intermediate temperature solid oxide fuel cell cathode

    NASA Astrophysics Data System (ADS)

    Zhen, Shuying; Sun, Wang; Li, Peiqian; Tang, Guangze; Rooney, David; Sun, Kening; Ma, Xinxin

    2016-05-01

    In this work Cu1.4Mn1.6O4 (CMO) spinel oxide is prepared and evaluated as a novel cobalt-free cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Single phase CMO powder with cubic structure is identified using XRD. XPS results confirm that mixed Cu+/Cu2+ and Mn3+/Mn4+ couples exist in the CMO sample, and a maximum conductivity of 78 S cm-1 is achieved at 800 °C. Meanwhile, CMO oxide shows good thermal and chemical compatibility with a 10 mol% Sc2O3 stabilized ZrO2 (ScSZ) electrolyte material. Impedance spectroscopy measurements reveals that CMO exhibits a low polarization resistance of 0.143 Ω cm2 at 800 °C. Furthermore, a Ni-ScSZ/ScSZ/CMO single cell demonstrates a maximum power density of 1076 mW cm-2 at 800 °C under H2 (3% H2O) as the fuel and ambient air as the oxidant. These results indicate that Cu1.4Mn1.6O4 is a superior and promising cathode material for IT-SOFCs.

  10. Cobalt oxide nanoparticles induced oxidative stress linked to activation of TNF-α/caspase-8/p38-MAPK signaling in human leukemia cells.

    PubMed

    Chattopadhyay, Sourav; Dash, Sandeep Kumar; Tripathy, Satyajit; Das, Balaram; Kar Mahapatra, Santanu; Pramanik, Panchanan; Roy, Somenath

    2015-06-01

    The purpose of this study was to determine the intracellular signaling transduction pathways involved in oxidative stress induced by nanoparticles in cancer cells. Activation of reactive oxygen species (ROS) has some therapeutic benefits in arresting the growth of cancer cells. Cobalt oxide nanoparticles (CoO NPs) are an interesting compound for oxidative cancer therapy. Our results showed that CoO NPs elicited a significant (P <0.05) amount of ROS in cancer cells. Co-treatment with N-aceyltine cystine (an inhibitor of ROS) had a protective role in cancer cell death induced by CoO NPs. In cultured cells, the elevated level of tumor necrosis factor-alpha (TNF-α) was noted after CoO NPs treatment. This TNF-α persuaded activation of caspase-8 followed by phosphorylation of p38 mitogen-activated protein kinase and induced cell death. This study showed that CoO NPs induced oxidative stress and activated the signaling pathway of TNF-α-Caspase-8-p38-Caspase-3 to cancer cells.

  11. Towards precise defect control in layered oxide structures by using oxide molecular beam epitaxy

    PubMed Central

    Baiutti, Federico; Christiani, Georg

    2014-01-01

    Summary In this paper we present the atomic-layer-by-layer oxide molecular beam epitaxy (ALL-oxide MBE) which has been recently installed in the Max-Planck Institute for Solid State Research and we report on its present status, providing some examples that demonstrate its successful application in the synthesis of different layered oxides, with particular reference to superconducting La2CuO4 and insulator-to-metal La2− xSrxNiO4. We briefly review the ALL-oxide MBE technique and its unique capabilities in the deposition of atomically smooth single-crystal thin films of various complex oxides, artificial compounds and heterostructures, introducing our goal of pursuing a deep investigation of such systems with particular emphasis on structural defects, with the aim of tailoring their functional properties by precise defects control. PMID:24995148

  12. Effect of added zinc on the properties of cobalt-containing ceramic pigments prepared from layered double hydroxides

    SciTech Connect

    Perez-Bernal, M.E.; Ruano-Casero, R.J.; Rives, V.

    2009-09-15

    Layered double hydroxides (LDHs) with the hydrotalcite-type structure containing Co and Al, or Zn, Co and Al in the brucite-like layers and carbonate in the interlayer have been prepared by coprecipitation. The Zn/Co molar ratio was kept to 1 in all samples, while the divalent/trivalent molar ratio was varied from 2/1 to 1/2. The samples have been characterised by element chemical analysis, powder X-ray diffraction, differential thermal and thermogravimetric analysis, temperature-programmed reduction and FT-IR spectroscopy. A single hydrotalcite-like phase is formed for samples with molar ratio 2/1, which crystallinity decreases as the Al content is increased, developing small amounts of diaspore and dawsonite and probably an additional amorphous phase. Calcination at 1200 deg. C in air led to formation of spinels; a small amount of NaAlO{sub 2} was observed in the Al-rich samples, which was removed by washing. The nature of the spinels formed (containing Co{sup II}, Co{sup III}, Al{sup III} and Zn{sup II}) strongly depends on the cations molar ratio in the starting materials and the calcination treatment, leading to a partial oxidation of Co{sup II} species to Co{sup III} ones. Colour properties (L*a*b*) of the original and calcined solids have been measured. While the original samples show a pink colour (lighter for the series containing Zn), the calcined Co,Al samples show a dark blue colour and the Zn,Co,Al ones a green colour. Changes due to the different molar ratios within a given calcined series are less evident than between samples with the same composition in different series. These calcined materials could be usable as ceramic pigments. - Abstract: Mixed oxides from layered double hydroxides (LDHs) with the hydrotalcite-type structure containing Co and Al or Zn, Co and Al in the brucite-like layers are potential candidates for ceramic pigments with tunable colour properties. Display Omitted

  13. Usage of Neural Network to Predict Aluminium Oxide Layer Thickness

    PubMed Central

    Michal, Peter; Vagaská, Alena; Gombár, Miroslav; Kmec, Ján; Spišák, Emil; Kučerka, Daniel

    2015-01-01

    This paper shows an influence of chemical composition of used electrolyte, such as amount of sulphuric acid in electrolyte, amount of aluminium cations in electrolyte and amount of oxalic acid in electrolyte, and operating parameters of process of anodic oxidation of aluminium such as the temperature of electrolyte, anodizing time, and voltage applied during anodizing process. The paper shows the influence of those parameters on the resulting thickness of aluminium oxide layer. The impact of these variables is shown by using central composite design of experiment for six factors (amount of sulphuric acid, amount of oxalic acid, amount of aluminium cations, electrolyte temperature, anodizing time, and applied voltage) and by usage of the cubic neural unit with Levenberg-Marquardt algorithm during the results evaluation. The paper also deals with current densities of 1 A·dm−2 and 3 A·dm−2 for creating aluminium oxide layer. PMID:25922850

  14. Layer structure: The oxides A 3Ti 5MO 14

    NASA Astrophysics Data System (ADS)

    Hervieu, M.; Rebbah, H.; Desgardin, G.; Raveau, B.

    1980-11-01

    Five new oxides, K 3Ti 5MO 14, Rb 3Ti 5MO 14 ( M = Ta, Nb), and Tl 3Ti 5NbO 14, have been synthesized. The structure of these oxides consists of octahedral layers similar to those observed for Na 2Ti 3O 7 and held together by monovalent ions; the sheets consist of blocks of 2 × 3 edge-sharing octahedra, which are then joined to each other by the corners of the octahedra. The relative disposition of the layers is similar to that observed for Tl 2Ti 4O 9. These oxides can be considered as the member n = 3 of a series of closely related structures with formula AnB2 nO 4 n+2 , where n indicates the number of octahedra which determines the width of the blocks of 2 × n octahedra.

  15. Deuterium accumulation in beryllium oxide layer exposed to deuterium atoms

    NASA Astrophysics Data System (ADS)

    Sharapov, V. M.; Alimov, V. Kh.; Gavrilov, L. E.

    1998-10-01

    The interaction of deuterium atoms with beryllium TIP-30 was studied at temperatures of 340, 500 and 740 K. After D atom exposure, the depth distributions of deuterium atoms and molecules in Be were measured using combined Secondary Ion Mass Spectrometry (SIMS) and Residual Gas Analysis (RGA) methods. It was shown that deuterium is mainly accumulated in the oxide layer although long tails are also observed. Deuterium is retained in two states - atomic and molecular forms. The amount of trapped deuterium in samples decreases during the sample storage in vacuum or air at room temperature. The results were explained by the chemical bonding of D atoms in BeO oxide with beryllium hydroxide formation and the trapping of deuterium molecules in bubbles which are formed at growth defects in the oxide layer.

  16. Self-Assembled Hierarchical Formation of Conjugated 3D Cobalt Oxide Nanobead-CNT-Graphene Nanostructure Using Microwaves for High-Performance Supercapacitor Electrode.

    PubMed

    Kumar, Rajesh; Singh, Rajesh Kumar; Dubey, Pawan Kumar; Singh, Dinesh Pratap; Yadav, Ram Manohar

    2015-07-15

    Here we report the electrochemical performance of a interesting three-dimensional (3D) structures comprised of zero-dimensional (0D) cobalt oxide nanobeads, one-dimensional (1D) carbon nanotubes and two-dimensional (2D) graphene, stacked hierarchically. We have synthesized 3D self-assembled hierarchical nanostructure comprised of cobalt oxide nanobeads (Co-nb), carbon nanotubes (CNTs), and graphene nanosheets (GNSs) for high-performance supercapacitor electrode application. This 3D self-assembled hierarchical nanostructure Co3O4 nanobeads-CNTs-GNSs (3D:Co-nb@CG) is grown at a large scale (gram) through simple, facile, and ultrafast microwave irradiation (MWI). In 3D:Co-nb@CG nanostructure, Co3O4 nanobeads are attached to the CNT surfaces grown on GNSs. Our ultrafast, one-step approach not only renders simultaneous growth of cobalt oxide and CNTs on graphene nanosheets but also institutes the intrinsic dispersion of carbon nanotubes and cobalt oxide within a highly conductive scaffold. The 3D:Co-nb@CG electrode shows better electrochemical performance with a maximum specific capacitance of 600 F/g at the charge/discharge current density of 0.7A/g in KOH electrolyte, which is 1.56 times higher than that of Co3O4-decorated graphene (Co-np@G) nanostructure. This electrode also shows a long cyclic life, excellent rate capability, and high specific capacitance. It also shows high stability after few cycles (550 cycles) and exhibits high capacitance retention behavior. It was observed that the supercapacitor retained 94.5% of its initial capacitance even after 5000 cycles, indicating its excellent cyclic stability. The synergistic effect of the 3D:Co-nb@CG appears to contribute to the enhanced electrochemical performances.

  17. High-rate lithium storage capability of cupric-cobaltous oxalate induced by unavoidable crystal water and functionalized graphene oxide

    NASA Astrophysics Data System (ADS)

    Feng, Fan; Kang, Wenpei; Yu, Faqi; Zhang, He; Shen, Qiang

    2015-05-01

    The combination of co-precipitation and dehydration is used to prepare hydrated and dehydrated cupric-cobaltous oxalates (Cu1/3Co2/3C2O4·xH2O, x = 1.4; Cu1/3Co2/3C2O4). Then, the hydrothermal treatment of these binary oxalates with freshly prepared graphene oxide (GO) and then dehydration are subsequently adopted to combine the hydrated or dehydrated oxalate with functionalized graphene oxide (FGO), resulting in another two targets of Cu1/3Co2/3C2O4·xH2O/FGO and Cu1/3Co2/3C2O4/FGO composites. These facilitate the comparative studies on the lithium storage capability of cupric oxalate-containing anode materials enhanced by unavoidable crystal water. As a lithium-ion battery anode, Cu1/3Co2/3C2O4·xH2O possesses a reversible capacity of 565.0 mAh g-1 at 1000 mA g-1 over 200 discharge-charge cycles, higher than that of the dehydrated counterpart (246.1 mAh g-1) but lower than those of FGO-based composites (Cu1/3Co2/3C2O4/FGO ∼ 951.2 mAh g-1; Cu1/3Co2/3C2O4·xH2O/FGO ∼ 1134.9 mAh g-1) continuously cycled at the exactly same conditions. At an ultra-high current density of 2000 or 5000 mA g-1, anode Cu1/3Co2/3C2O4·xH2O/FGO delivers a constant discharge capacity of 935.6 mAh g-1 in the 100th cycle or 388.9 mAh g-1 in the 1000th cycle, indicating a jointly positive effect of crystal water and FGO on the high-rate electrochemical performance of cupric-cobaltous oxalate for the first time.

  18. Transport properties of lead phosphate glass doped by cobalt, vanadium and chromium oxides

    NASA Astrophysics Data System (ADS)

    Roumaih, Kh.; Kaiser, M.; Elbatal, Fatma H.; Ali, I. S.

    2011-10-01

    The electrical transport properties were investigated of a glass system of basic composition 50 mol. % Pb3O4-50 mol. % P2O5 containing CoO, Cr2O3 or V2O5 dopanys. The ac conductivity and the thermoelectric power were measured as a function of temperature. Properties such as dielectric constant, loss factor tangent and electrical conductivity are reported in the frequency range 200 Hz-100 kHz and temperature range 300-450 K. The variation in electrical conductivity with temperature was found to depend on the types of transition metal ions involved. The temperature dependence of the frequency exponent, s, was analyzed using different theoretical models. The variation of the thermoelectric power with temperature indicated the presence of more than one conduction mechanism for the investigated samples. This result was confirmed with the results of the dielectric properties at different frequencies. The introduction of cobalt ions in glass formers improves the electrical properties of non-crystalline ionic conductors.

  19. Response of Lemna minor L. to short-term cobalt exposure: The effect on photosynthetic electron transport chain and induction of oxidative damage.

    PubMed

    Begović, Lidija; Mlinarić, Selma; Antunović Dunić, Jasenka; Katanić, Zorana; Lončarić, Zdenko; Lepeduš, Hrvoje; Cesar, Vera

    2016-06-01

    The effect of two concentrations of cobalt (Co(2+)) on photosynthetic activity and antioxidative response in Lemna minor L. were assessed 24, 48 and 72h after the start of the exposure. Higher concentration of cobalt (1mM) induced growth inhibition while lower concentration (0.01mM) increased photosynthetic pigments content. Analysis of chlorophyll a fluorescence transients revealed high sensitivity of photosystem II primary photochemistry to excess of Co(2+) especially at the higher concentration where decreased electron transport beyond primary quinone acceptor QA(-) and impaired function of oxygen evolving complex (OEC) was observed. Due to impairment of OEC, oxygen production was decreased at higher Co(2+) concentration. Activity of superoxide dismutase was mainly inhibited while lipid peroxidation increased, at both concentrations, indicating that cobalt-induced oxidative damage after short exposure and moreover, susceptibility of the membranes in the cell to cobalt toxicity. Results obtained in this study suggest possible application of used parameters as tools in assessment of early damage caused by metals.

  20. Study of multiphasic molybdate-based catalysts. II. Synergy effect between bismuth molybdates and mixed iron and cobalt molybdates in mild oxidation of propene

    SciTech Connect

    Millet, J.M.M.; Ponceblanc, H.; Coudurier, G.; Vedrine, J.C. ); Herrmann, J.M. )

    1993-08-01

    Results are reported concerning the synergy effect observed in the oxidation of propene to acrolein over bismuth and mixed iron and cobalt molybdates. The pure bismuth, iron, and cobalt molybdates and mixed cobalt and iron molybdates (solid solutions) have been prepared and individually tested as catalysts. Mechanical mixtures of these phases have been prepared and tested as catalysts. All the catalysts have been characterized before and after the catalytic reaction by several techniques such as ESR, XPS, EDX-STEM, TEM, XRD, and Moessbauer and UV spectroscopies. The synergy effect observed is tentatively explained as due to the deposition on the large bismuth molybdate particles of smaller mixed iron and cobalt molybdate particles with spreading of the bismuth molybdate over the latter particles. It is proposed that the Fe[sub x]Co[sub 1-x]MoO[sub 4] phase plays the role of the fast electron conducting material which enhances the electron mobility and the efficiency of the redox mechanism, the active and selective phase being the overlying bismuth molybdate compounds. 27 refs., 5 figs., 7 tabs.

  1. Response of Lemna minor L. to short-term cobalt exposure: The effect on photosynthetic electron transport chain and induction of oxidative damage.

    PubMed

    Begović, Lidija; Mlinarić, Selma; Antunović Dunić, Jasenka; Katanić, Zorana; Lončarić, Zdenko; Lepeduš, Hrvoje; Cesar, Vera

    2016-06-01

    The effect of two concentrations of cobalt (Co(2+)) on photosynthetic activity and antioxidative response in Lemna minor L. were assessed 24, 48 and 72h after the start of the exposure. Higher concentration of cobalt (1mM) induced growth inhibition while lower concentration (0.01mM) increased photosynthetic pigments content. Analysis of chlorophyll a fluorescence transients revealed high sensitivity of photosystem II primary photochemistry to excess of Co(2+) especially at the higher concentration where decreased electron transport beyond primary quinone acceptor QA(-) and impaired function of oxygen evolving complex (OEC) was observed. Due to impairment of OEC, oxygen production was decreased at higher Co(2+) concentration. Activity of superoxide dismutase was mainly inhibited while lipid peroxidation increased, at both concentrations, indicating that cobalt-induced oxidative damage after short exposure and moreover, susceptibility of the membranes in the cell to cobalt toxicity. Results obtained in this study suggest possible application of used parameters as tools in assessment of early damage caused by metals. PMID:27015565

  2. Controlled Fabrication of Nanoporous Oxide Layers on Zircaloy by Anodization

    NASA Astrophysics Data System (ADS)

    Park, Yang Jeong; Ha, Jun Mok; Ali, Ghafar; Kim, Hyun Jin; Addad, Yacine; Cho, Sung Oh

    2015-09-01

    We have presented a mechanism to explain why the resulting oxide morphology becomes a porous or a tubular nanostructure when a zircaloy is electrochemically anodized. A porous zirconium oxide nanostructure is always formed at an initial anodization stage, but the degree of interpore dissolution determines whether the final morphology is nanoporous or nanotubular. The interpore dissolution rate can be tuned by changing the anodization parameters such as anodization time and water content in an electrolyte. Consequently, porous or tubular oxide nanostructures can be selectively fabricated on a zircaloy surface by controlling the parameters. Based on this mechanism, zirconium oxide layers with completely nanoporous, completely nanotubular, and intermediate morphologies between a nanoporous and a nanotubular structure were controllably fabricated.

  3. Shape-selective sieving layers on an oxide catalyst surface.

    PubMed

    Canlas, Christian P; Lu, Junling; Ray, Natalie A; Grosso-Giordano, Nicolas A; Lee, Sungsik; Elam, Jeffrey W; Winans, Randall E; Van Duyne, Richard P; Stair, Peter C; Notestein, Justin M

    2012-12-01

    New porous materials such as zeolites, metal-organic frameworks and mesostructured oxides are of immense practical utility for gas storage, separations and heterogeneous catalysis. Their extended pore structures enable selective uptake of molecules or can modify the product selectivity (regioselectivity or enantioselectivity) of catalyst sites contained within. However, diffusion within pores can be problematic for biomass and fine chemicals, and not all catalyst classes can be readily synthesized with pores of the correct dimensions. Here, we present a novel approach that adds reactant selectivity to existing, non-porous oxide catalysts by first grafting the catalyst particles with single-molecule sacrificial templates, then partially overcoating the catalyst with a second oxide through atomic layer deposition. This technique is used to create sieving layers of Al(2)O(3) (thickness, 0.4-0.7 nm) with 'nanocavities' (<2 nm in diameter) on a TiO(2) photocatalyst. The additional layers result in selectivity (up to 9:1) towards less hindered reactants in otherwise unselective, competitive photocatalytic oxidations and transfer hydrogenations. PMID:23174984

  4. Shape-selective sieving layers on an oxide catalyst surface

    NASA Astrophysics Data System (ADS)

    Canlas, Christian P.; Lu, Junling; Ray, Natalie A.; Grosso-Giordano, Nicolas A.; Lee, Sungsik; Elam, Jeffrey W.; Winans, Randall E.; van Duyne, Richard P.; Stair, Peter C.; Notestein, Justin M.

    2012-12-01

    New porous materials such as zeolites, metal-organic frameworks and mesostructured oxides are of immense practical utility for gas storage, separations and heterogeneous catalysis. Their extended pore structures enable selective uptake of molecules or can modify the product selectivity (regioselectivity or enantioselectivity) of catalyst sites contained within. However, diffusion within pores can be problematic for biomass and fine chemicals, and not all catalyst classes can be readily synthesized with pores of the correct dimensions. Here, we present a novel approach that adds reactant selectivity to existing, non-porous oxide catalysts by first grafting the catalyst particles with single-molecule sacrificial templates, then partially overcoating the catalyst with a second oxide through atomic layer deposition. This technique is used to create sieving layers of Al2O3 (thickness, 0.4-0.7 nm) with ‘nanocavities’ (<2 nm in diameter) on a TiO2 photocatalyst. The additional layers result in selectivity (up to 9:1) towards less hindered reactants in otherwise unselective, competitive photocatalytic oxidations and transfer hydrogenations.

  5. Mesoporous composite nickel cobalt oxide/graphene oxide synthesized via a template-assistant co-precipitation route as electrode material for supercapacitors

    NASA Astrophysics Data System (ADS)

    Xu, Yanjie; Wang, Lincai; Cao, Peiqi; Cai, Chuanlin; Fu, Yanbao; Ma, Xiaohua

    2016-02-01

    A simple co-precipitation method utilizing SDS (sodium dodecyl sulfate) as template and ammonia as precipitant is successfully employed to synthesize nickel cobalt oxide/graphene oxide (NiCo2O4/GO) composite. The as-prepared composite (NCG-10) exhibits a high capacitance of 1211.25 F g-1, 687 F g-1 at the current density of 1 A g-1, 10 A g-1 and good cycling ability which renders NCG-10 as promising electrode material for supercapacitors. An asymmetric supercapacitor (ASC) (full button cell) has been constructed with NCG-10 as positive electrode and lab-made reduced graphene oxide (rGO) as negative electrode. The fabricated NCG-10//rGO with an extended stable operational voltage of 1.6 V can deliver a high specific capacitance of 144.45 F g-1 at a current density of 1 A g-1. The as-prepared NCG-10//rGO demonstrates remarkable energy density (51.36 W h kg-1 at 1 A g-1), high power density (50 kW kg-1 at 20 A g-1). The retention of capacitance is 88.6% at the current density of 8 A g-1 after 2000 cycles. The enhanced capacitive performance can be attributed to the improved specific surface area and 3D open area of NCG-10 generated by the pores and channels with the substantial function of SDS.

  6. Role of atomic layer deposited aluminum oxide as oxidation barrier for silicon based materials

    SciTech Connect

    Fiorentino, Giuseppe Morana, Bruno; Forte, Salvatore; Sarro, Pasqualina Maria

    2015-01-15

    In this paper, the authors study the protective effect against oxidation of a thin layer of atomic layer deposited (ALD) aluminum oxide (Al{sub 2}O{sub 3}). Nitrogen doped silicon carbide (poly-SiC:N) based microheaters coated with ALD Al{sub 2}O{sub 3} are used as test structure to investigate the barrier effect of the alumina layers to oxygen and water vapor at very high temperature (up to 1000 °C). Different device sets have been fabricated changing the doping levels, to evaluate possible interaction between the dopants and the alumina layer. The as-deposited alumina layer morphology has been evaluated by means of AFM analysis and compared to an annealed sample (8 h at 1000 °C) to estimate the change in the grain structure and the film density. The coated microheaters are subjected to very long oxidation time in dry and wet environment (up to 8 h at 900 and 1000 °C). By evaluating the electrical resistance variation between uncoated reference devices and the ALD coated devices, the oxide growth on the SiC is estimated. The results show that the ALD alumina coating completely prevents the oxidation of the SiC up to 900 °C in wet environment, while an oxide thickness reduction of 50% is observed at 1000 °C compared to uncoated devices.

  7. Self assembled multi-layer nanocomposite of graphene and metal oxide materials

    DOEpatents

    Liu, Jun; Aksay, Ilhan A; Choi, Daiwon; Kou, Rong; Nie, Zimin; Wang, Donghai; Yang, Zhenguo

    2015-04-28

    Nanocomposite materials having at least two layers, each layer consisting of one metal oxide bonded to at least one graphene layer were developed. The nanocomposite materials will typically have many alternating layers of metal oxides and graphene layers, bonded in a sandwich type construction and will be incorporated into an electrochemical or energy storage device.

  8. Self assembled multi-layer nanocomposite of graphene and metal oxide materials

    SciTech Connect

    Liu, Jun; Choi, Daiwon; Kou, Rong; Nie, Zimin; Wang, Donghai; Yang, Zhenguo

    2014-09-16

    Nanocomposite materials having at least two layers, each layer consisting of one metal oxide bonded to at least one graphene layer were developed. The nanocomposite materials will typically have many alternating layers of metal oxides and graphene layers, bonded in a sandwich type construction and will be incorporated into an electrochemical or energy storage device.

  9. Self assembled multi-layer nanocomposite of graphene and metal oxide materials

    SciTech Connect

    Liu, Jun; Aksay, Ilhan A; Choi, Daiwon; Kou, Rong; Nie, Zimin; Wang, Donghai; Yang, Zhenguo

    2013-10-22

    Nanocomposite materials having at least two layers, each layer consisting of one metal oxide bonded to at least one graphene layer were developed. The nanocomposite materials will typically have many alternating layers of metal oxides and graphene layers, bonded in a sandwich type construction and will be incorporated into an electrochemical or energy storage device.

  10. Magnetic Exchange Between Superconducting and Ferromagnetic Oxide Layers

    NASA Astrophysics Data System (ADS)

    Giblin, Sean; Taylor, Jon; Duffy, Jon; Dugdale, Stephen; Nakamura, T.; Santamaria, Jacobo

    2012-02-01

    The origins of high temperature superconductivity and the rich phase diagrams in complex oxides are still a matter of contention that have stimulated many novel experimental studies and observations. Recently the improvement of layer by layer growth techniques of thin films has enabled investigations of both bulk and surface properties. For most common superconductors the order parameter is thought to be antagonistic to that of the exchange mechanism in ferromagnets. Accurately grown thin fllms have enabled these competing interactions to be probed experimentally. In particular, the growth of epitaxial oxide layers, with well-characterized atomically flat interfaces, consisting of superconducting layers of YBa2Cu3O7 (YBCO) and lattice-matched ferromagnetic La2/3Ca1/3MnO3 (LCMO) has flourished. Using XMCD we demonstrate that the known superexchange between Mn and Cu across the YBCO/LCMO is modified when an apparent critical thickness of the superconducting layer is reduced. All samples show an apparent exchange below the superconducting transition but above it is dependent on the YBCO thickness. Possible origins of this behaviour will be discussed.

  11. Interface engineering in epitaxial growth of layered oxides via a conducting layer insertion

    SciTech Connect

    Yun, Yu; Meng, Dechao; Wang, Jianlin; Ma, Chao; Zhai, Xiaofang; Huang, Haoliang; Fu, Zhengping; Peng, Ranran; Brown, Gail J.; and others

    2015-07-06

    There is a long-standing challenge in the fabrication of layered oxide epitaxial films due to their thermodynamic phase-instability and the large stacking layer number. Recently, the demand for high-quality thin films is strongly pushed by their promising room-temperature multiferroic properties. Here, we find that by inserting a conducting and lattice matched LaNiO{sub 3} buffer layer, high quality m = 5 Bi{sub 6}FeCoTi{sub 3}O{sub 18} epitaxial films can be fabricated using the laser molecular beam epitaxy, in which the atomic-scale sharp interface between the film and the metallic buffer layer explains the enhanced quality. The magnetic and ferroelectric properties of the high quality Bi{sub 6}FeCoTi{sub 3}O{sub 18} films are studied. This study demonstrates that insertion of the conducting layer is a powerful method in achieving high quality layered oxide thin films, which opens the door to further understand the underline physics and to develop new devices.

  12. Synthesis and controllable oxidation of monodisperse cobalt-doped wüstite nanoparticles and their core-shell stability and exchange-bias stabilization

    NASA Astrophysics Data System (ADS)

    Chen, Chih-Jung; Chiang, Ray-Kuang; Kamali, Saeed; Wang, Sue-Lein

    2015-08-01

    Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ~4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (HE), an enhanced coercivity field (HC), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of HE was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (TN) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy.Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ~4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (HE), an enhanced coercivity field (HC), and a pronounced vertical shift, thus

  13. Interfacial bonding stabilizes rhodium and rhodium oxide nanoparticles on layered Nb oxide and Ta oxide supports.

    PubMed

    Strayer, Megan E; Binz, Jason M; Tanase, Mihaela; Shahri, Seyed Mehdi Kamali; Sharma, Renu; Rioux, Robert M; Mallouk, Thomas E

    2014-04-16

    Metal nanoparticles are commonly supported on metal oxides, but their utility as catalysts is limited by coarsening at high temperatures. Rhodium oxide and rhodium metal nanoparticles on niobate and tantalate supports are anomalously stable. To understand this, the nanoparticle-support interaction was studied by isothermal titration calorimetry (ITC), environmental transmission electron microscopy (ETEM), and synchrotron X-ray absorption and scattering techniques. Nanosheets derived from the layered oxides KCa2Nb3O10, K4Nb6O17, and RbTaO3 were compared as supports to nanosheets of Na-TSM, a synthetic fluoromica (Na0.66Mg2.68(Si3.98Al0.02)O10.02F1.96), and α-Zr(HPO4)2·H2O. High surface area SiO2 and γ-Al2O3 supports were also used for comparison in the ITC experiments. A Born-Haber cycle analysis of ITC data revealed an exothermic interaction between Rh(OH)3 nanoparticles and the layered niobate and tantalate supports, with ΔH values in the range -32 kJ·mol(-1) Rh to -37 kJ·mol(-1) Rh. In contrast, the interaction enthalpy was positive with SiO2 and γ-Al2O3 supports. The strong interfacial bonding in the former case led to "reverse" ripening of micrometer-size Rh(OH)3, which dispersed as 0.5 to 2 nm particles on the niobate and tantalate supports. In contrast, particles grown on Na-TSM and α-Zr(HPO4)2·H2O nanosheets were larger and had a broad size distribution. ETEM, X-ray absorption spectroscopy, and pair distribution function analyses were used to study the growth of supported nanoparticles under oxidizing and reducing conditions, as well as the transformation from Rh(OH)3 to Rh nanoparticles. Interfacial covalent bonding, possibly strengthened by d-electron acid/base interactions, appear to stabilize Rh(OH)3, Rh2O3, and Rh nanoparticles on niobate and tantalate supports. PMID:24654835

  14. Static and dynamic cyclic oxidation of 12 nickel-, cobalt-, and iron-base high-temperature alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Johnston, J. R.; Sanders, W. A.

    1978-01-01

    Twelve typical high-temperature nickel-, cobalt-, and iron-base alloys were tested by 1 hr cyclic exposures at 1038, 1093, and 1149 C and 0.05 hr exposures at 1093 C. The alloys were tested in both a dynamic burner rig at Mach 0.3 gas flow and in static air furnace for times up to 100 hr. The alloys were evaluated in terms of specific weight loss as a function of time, and X-ray diffraction analysis and metallographic examination of the posttest specimens. A method previously developed was used to estimate specific metal weight loss from the specific weight change of the sample. The alloys were then ranked on this basis. The burner-rig test was more severe than a comparable furnace test and resulted in an increased tendency for oxide spalling due to volatility of Cr in the protective scale and the more drastic cooling due to the air-blast quench of the samples. Increased cycle frequency also increased the tendency to spall for a given test exposure. The behavior of the alloys in both types of tests was related to their composition and their tendency to form scales. The alloys with the best overall behavior formed alpha-Al2O3 aluminate spinels.

  15. A lumped model of venting during thermal runaway in a cylindrical Lithium Cobalt Oxide lithium-ion cell

    NASA Astrophysics Data System (ADS)

    Coman, Paul T.; Rayman, Sean; White, Ralph E.

    2016-03-01

    This paper presents a mathematical model built for analyzing the intricate thermal behavior of a 18650 LCO (Lithium Cobalt Oxide) battery cell during thermal runaway when venting of the electrolyte and contents of the jelly roll (ejecta) is considered. The model consists of different ODEs (Ordinary Differential Equations) describing reaction rates and electrochemical reactions, as well as the isentropic flow equations for describing electrolyte venting. The results are validated against experimental findings from Golubkov et al. [1] [Andrey W. Golubkov, David Fuchs, Julian Wagner, Helmar Wiltsche, Christoph Stangl, Gisela Fauler, Gernot Voitice Alexander Thaler and Viktor Hacker, RSC Advances, 4:3633-3642, 2014] for two cases - with flow and without flow. The results show that if the isentropic flow equations are not included in the model, the thermal runaway is triggered prematurely at the point where venting should occur. This shows that the heat dissipation due to ejection of electrolyte and jelly roll contents has a significant contribution. When the flow equations are included, the model shows good agreement with the experiment and therefore proving the importance of including venting.

  16. Effects of cobalt on membrane ATPases, oxidant, and antioxidant values in the cerebrum and cerebellum of suckling rats.

    PubMed

    Garoui, Elmouldi; Ben Amara, Ibtissem; Driss, Dorra; Elwej, Awatef; Chaabouni, Semia Ellouze; Boudawara, Tahia; Zeghal, Najiba

    2013-09-01

    Chronic overexposure to cobalt (Co) may result in neurotoxic effects, but the mechanism of Co-induced neurotoxicity is not yet well established. Our study was conducted to determine whether Co is associated to the induction of central nervous system damage in pregnant rats and their progeny. Twelve pregnant female rats were randomly divided into 2 groups: group I served as controls and group II received Co (350 mg/L, orally). Treatments started from the 14th day of pregnancy until day 14 after delivery. Co concentration in plasma was higher in the treated groups than in the controls. Exposure to Co also increased the levels of MDA, PCO, H2O2, and AOPP, while Na(+)K(+)-ATPase and Mg(2+)-ATPase, AChE, and BuChE activities decreased in the cerebrum and cerebellum of suckling pups. A smear without ladder formation on agarose gel was also shown in the cerebrum and cerebellum, indicating random DNA degradation. A reduction in GPx, SOD, CAT, GSH, NPSH, and vitamin C values was observed. The changes were confirmed by histological results. In conclusion, these data showed that the exposure of pregnant and lactating rats to Co resulted in the development of oxidative stress and the impairment of defense systems in the cerebrum and cerebellum of their suckling pups.

  17. Honeycomb-like Porous Carbon-Cobalt Oxide Nanocomposite for High-Performance Enzymeless Glucose Sensor and Supercapacitor Applications.

    PubMed

    Madhu, Rajesh; Veeramani, Vediyappan; Chen, Shen-Ming; Manikandan, Arumugam; Lo, An-Ya; Chueh, Yu-Lun

    2015-07-29

    Herein, we report the preparation of Pongam seed shells-derived activated carbon and cobalt oxide (∼2-10 nm) nanocomposite (PSAC/Co3O4) by using a general and facile synthesis strategy. The as-synthesized PSAC/Co3O4 samples were characterized by a variety of physicochemical techniques. The PSAC/Co3O4-modified electrode is employed in two different applications such as high performance nonenzymatic glucose sensor and supercapacitor. Remarkably, the fabricated glucose sensor is exhibited an ultrahigh sensitivity of 34.2 mA mM(-1) cm(-2) with a very low detection limit (21 nM) and long-term durability. The PSAC/Co3O4 modified stainless steel electrode possesses an appreciable specific capacitance and remarkable long-term cycling stability. The obtained results suggest the as-synthesized PSAC/Co3O4 is more suitable for the nonenzymatic glucose sensor and supercapacitor applications outperforming the related carbon based modified electrodes, rendering practical industrial applications. PMID:26125456

  18. Electroanalysis of copper as a heavy metal pollutant in water using cobalt oxide modified exfoliated graphite electrode

    NASA Astrophysics Data System (ADS)

    Ndlovu, T.; Arotiba, O. A.; Sampath, S.; Krause, R. W.; Mamba, B. B.

    Copper is one of the heavy metals that have been recognized as essential for living organisms in trace amounts as a cofactor for crucial enzymes. However, excess amount of this trace element can have serious health effects. It is therefore important to monitor Cu in drinking water as it can easily be overlooked due to its biological functions. An electrochemical technique using re-compressed exfoliated graphite modified with cobalt oxide nanoparticles was evaluated as an electrochemical sensor for the detection of Cu2+ in spiked water samples. The analysis involved an accumulation step at -500 mV while stirring followed by square wave-anodic stripping voltammetry (SW-ASV). The accumulation step resulted in the reduction of Cu2+ ions in solution onto the electrode surface which were subsequently stripped off on the second step resulting in an analytical current signal. The electrodeposition time and potential were first optimised and the best conditions were used to get a detection limit of 94 μg L-1. This sensor was used for Cu analysis in real water samples using standard addition method with percentage recoveries of between 99% and 101%.

  19. Porous cobalt oxide (Co 3O 4) nanorods: Facile syntheses, optical property and application in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Xu, Rui; Wang, Jiawei; Li, Qiuyu; Sun, Guoying; Wang, Enbo; Li, Siheng; Gu, Jianmin; Ju, Mingliang

    2009-11-01

    We developed a facile synthetic route of porous cobalt oxide (Co 3O 4) nanorods via a microemulsion-based method in combination with subsequent calcination process. The porous structure was formed by controlled decomposition of the microemulsion-synthesized precursor CoC 2O 4 nanorods without destruction of the original morphology. The as-prepared Co 3O 4 nanorods, consisting of small nanoparticles with diameter of 80-150 nm, had an average diameter of 200 nm and a length of 3-5 μm. The morphology and structure of synthesized samples were characterized by transmission electron microscopy and scanning electron microscopy. The phase and composition were investigated by X-ray powder diffraction and X-ray photoelectron spectroscopy. The optical property of Co 3O 4 nanorods was investigated. Moreover, the porous Co 3O 4 nanorods exhibited high electrochemical performance when applied as cathode materials for lithium-ion batteries, which gives them good potential applications.

  20. Cobalt-Porphyrin-Platinum-Functionalized Reduced Graphene Oxide Hybrid Nanostructures: A Novel Peroxidase Mimetic System For Improved Electrochemical Immunoassay

    NASA Astrophysics Data System (ADS)

    Shu, Jian; Qiu, Zhenli; Wei, Qiaohua; Zhuang, Junyang; Tang, Dianping

    2015-10-01

    5,10,15,20-Tetraphenyl-21H,23H-porphine cobalt flat stacking on the reduced graphene oxide with platinum nanoparticles (PtNPs/CoTPP/rGO) were first synthesized and functionalized with monoclonal rabbit anti-aflatoxin B1 antibody (anti-AFB1) for highly efficient electrochemical immunoassay of aflatoxin B1 (AFB1) in this work. Transmission electron microscopy (TEM), atomic force microscope (AFM) and spectral techniques were employed to characterize the PtNPs/CoTPP/rGO hybrids. Using anti-AFB1-conjugated PtNPs/CoTPP/rGO as the signal-transduction tag, a novel non-enzymatic electrochemical immunosensing system was designed for detection of target AFB1 on the AFB1-bovine serum albumin-functionalized sensing interface. Experimental results revealed that the designed immunoassay could exhibit good electrochemical responses for target analyte and allowed the detection of AFB1 at a concentration as low as 5.0 pg mL-1 (5.0 ppt). Intra- and inter-assay coefficients of variation were below 10%. Importantly, the methodology was further validated for analyzing naturally contaminated or spiked blank peanut samples with consistent results obtained by AFB1 ELISA kit, thus providing a promising approach for quantitative monitoring of organic pollutants.

  1. Cobalt-Porphyrin-Platinum-Functionalized Reduced Graphene Oxide Hybrid Nanostructures: A Novel Peroxidase Mimetic System For Improved Electrochemical Immunoassay.

    PubMed

    Shu, Jian; Qiu, Zhenli; Wei, Qiaohua; Zhuang, Junyang; Tang, Dianping

    2015-01-01

    5,10,15,20-Tetraphenyl-21H,23H-porphine cobalt flat stacking on the reduced graphene oxide with platinum nanoparticles (PtNPs/CoTPP/rGO) were first synthesized and functionalized with monoclonal rabbit anti-aflatoxin B1 antibody (anti-AFB1) for highly efficient electrochemical immunoassay of aflatoxin B1 (AFB1) in this work. Transmission electron microscopy (TEM), atomic force microscope (AFM) and spectral techniques were employed to characterize the PtNPs/CoTPP/rGO hybrids. Using anti-AFB1-conjugated PtNPs/CoTPP/rGO as the signal-transduction tag, a novel non-enzymatic electrochemical immunosensing system was designed for detection of target AFB1 on the AFB1-bovine serum albumin-functionalized sensing interface. Experimental results revealed that the designed immunoassay could exhibit good electrochemical responses for target analyte and allowed the detection of AFB1 at a concentration as low as 5.0 pg mL(-1) (5.0 ppt). Intra- and inter-assay coefficients of variation were below 10%. Importantly, the methodology was further validated for analyzing naturally contaminated or spiked blank peanut samples with consistent results obtained by AFB1 ELISA kit, thus providing a promising approach for quantitative monitoring of organic pollutants.

  2. Cobalt-Porphyrin-Platinum-Functionalized Reduced Graphene Oxide Hybrid Nanostructures: A Novel Peroxidase Mimetic System For Improved Electrochemical Immunoassay

    PubMed Central

    Shu, Jian; Qiu, Zhenli; Wei, Qiaohua; Zhuang, Junyang; Tang, Dianping

    2015-01-01

    5,10,15,20-Tetraphenyl-21H,23H-porphine cobalt flat stacking on the reduced graphene oxide with platinum nanoparticles (PtNPs/CoTPP/rGO) were first synthesized and functionalized with monoclonal rabbit anti-aflatoxin B1 antibody (anti-AFB1) for highly efficient electrochemical immunoassay of aflatoxin B1 (AFB1) in this work. Transmission electron microscopy (TEM), atomic force microscope (AFM) and spectral techniques were employed to characterize the PtNPs/CoTPP/rGO hybrids. Using anti-AFB1-conjugated PtNPs/CoTPP/rGO as the signal-transduction tag, a novel non-enzymatic electrochemical immunosensing system was designed for detection of target AFB1 on the AFB1-bovine serum albumin-functionalized sensing interface. Experimental results revealed that the designed immunoassay could exhibit good electrochemical responses for target analyte and allowed the detection of AFB1 at a concentration as low as 5.0 pg mL−1 (5.0 ppt). Intra- and inter-assay coefficients of variation were below 10%. Importantly, the methodology was further validated for analyzing naturally contaminated or spiked blank peanut samples with consistent results obtained by AFB1 ELISA kit, thus providing a promising approach for quantitative monitoring of organic pollutants. PMID:26462136

  3. Layered manganese oxide intergrowth electrodes for rechargeable lithium batteries: Part 1-substitution with Co or Ni

    SciTech Connect

    Dolle, Mickael; Patoux, Sebastien; Doeff, Marca M.

    2004-09-08

    Lithium manganese oxides substituted with nickel or cobalt were characterized electrochemically in lithium cell configurations. The compounds studied were either single-phase layered structures with either primarily O2 or O3 stacking arrangements, or O2/O3 intergrowths, prepared from P2, P3 and P2/P3 sodium-containing precursors, respectively. The stacking arrangements are extremely sensitive to the Na/T. M. (T. M. = transition metal) ratios and the level of substitution. Phase diagrams showing the stability regions of the various arrangements for the Na-Ni-Mn-O system are presented. A possible correlation between vacancies and electrochemical performance is suggested. For high levels of substitution with Ni, fewer defects are possible for materials containing more O3 component and higher discharge capacities can be achieved, but spinel conversion upon cycling also occurs more rapidly as the O3 content increases. Intergrowths show intermediate behavior and represent a potential route towards designing stable, high capacity electrodes.

  4. Improved layered mixed transition metal oxides for Li-ion batteries

    SciTech Connect

    Doeff, Marca M.; Conry, Thomas; Wilcox, James

    2010-03-05

    Recent work in our laboratory has been directed towards development of mixed layered transition metal oxides with general composition Li[Ni, Co, M, Mn]O2 (M=Al, Ti) for Li ion battery cathodes. Compounds such as Li[Ni1/3Co1/3Mn1/3]O2 (often called NMCs) are currently being commercialized for use in consumer electronic batteries, but the high cobalt content makes them too expensive for vehicular applications such as electric vehicles (EV), plug-in hybrid electric vehicles (PHEVs), or hybrid electric vehicles (HEVs). To reduce materials costs, we have explored partial or full substitution of Co with Al, Ti, and Fe. Fe substitution generally decreases capacity and results in poorer rate and cycling behavior. Interestingly, low levels of substitution with Al or Ti improve aspects of performance with minimal impact on energy densities, for some formulations. High levels of Al substitution compromise specific capacity, however, so further improvements require that the Ni and Mn content be increased and Co correspondingly decreased. Low levels of Al or Ti substitution can then be used offset negative effects induced by the higher Ni content. The structural and electrochemical characterization of substituted NMCs is presented in this paper.

  5. Formation of Silica/Graphene Oxide Hybrid Nano Films by Layer-by-Layer Self-Assembly and Biomimetic Silicification.

    PubMed

    Yang, Sung Ho

    2015-02-01

    Silica/graphene oxide hybrid thin films were formed by layer-by-layer self-assembly and biomimetic silicification, and the thickness and structure of hybrid thin films were finely controlled at the nanometer scale, by tuning number of the layer-by-layer process. The physical properties of thin films were characterized by infrared spectroscopy, atomic force microscopy, and scanning electron microscopy. In addition, silica/graphene oxide hybrid thin films were successfully utilized for cell culture platforms.

  6. Nickel–cobalt layered double hydroxide ultrathin nanoflakes decorated on graphene sheets with a 3D nanonetwork structure as supercapacitive materials

    SciTech Connect

    Yan, Tao; Li, Ruiyi; Li, Zaijun

    2014-03-01

    Graphical abstract: The microwave heating reflux approach was developed for the fabrication of nickel–cobalt layered double hydroxide ultrathin nanoflakes decorated on graphene sheets, in which ammonia and ethanol were used as the precipitator and medium for the synthesis. The obtained composite shows a 3D flowerclusters morphology with nanonetwork structure and largely enhanced supercapacitive performance. - Highlights: • The paper reported the microwave synthesis of nickel–cobalt layered double hydroxide/graphene composite. • The novel synthesis method is rapid, green, efficient and can be well used to the mass production. • The as-synthesized composite offers a 3D flowerclusters morphology with nanonetwork structure. • The composite offers excellent supercapacitive performance. • This study provides a promising route to design and synthesis of advanced graphene-based materials with the superiorities of time-saving and cost-effective characteristics. - Abstract: The study reported a novel microwave heating reflux method for the fabrication of nickel–cobalt layered double hydroxide ultrathin nanoflakes decorated on graphene sheets (GS/NiCo-LDH). Ammonia and ethanol were employed as precipitant and reaction medium for the synthesis, respectively. The resulting GS/NiCo-LDH offers a 3D flowerclusters morphology with nanonetwork structure. Due to the greatly enhanced rate of electron transfer and mass transport, the GS/NiCo-LDH electrode exhibits excellent supercapacitive performances. The maximum specific capacitance was found to be 1980.7 F g{sup −1} at the current density of 1 A g{sup −1}. The specific capacitance can remain 1274.7 F g{sup −1} at the current density of 15 A g{sup −1} and it has an increase of about 2.9% after 1500 cycles. Moreover, the study also provides a promising approach for the design and synthesis of metallic double hydroxides/graphene hybrid materials with time-saving and cost-effective characteristics, which can be

  7. Atomic layer-deposited tunnel oxide stabilizes silicon photoanodes for water oxidation.

    PubMed

    Chen, Yi Wei; Prange, Jonathan D; Dühnen, Simon; Park, Yohan; Gunji, Marika; Chidsey, Christopher E D; McIntyre, Paul C

    2011-06-19

    A leading approach for large-scale electrochemical energy production with minimal global-warming gas emission is to use a renewable source of electricity, such as solar energy, to oxidize water, providing the abundant source of electrons needed in fuel synthesis. We report corrosion-resistant, nanocomposite anodes for the oxidation of water required to produce renewable fuels. Silicon, an earth-abundant element and an efficient photovoltaic material, is protected by atomic layer deposition (ALD) of a highly uniform, 2 nm thick layer of titanium dioxide (TiO(2)) and then coated with an optically transmitting layer of a known catalyst (3 nm iridium). Photoelectrochemical water oxidation was observed to occur below the reversible potential whereas dark electrochemical water oxidation was found to have low-to-moderate overpotentials at all pH values, resulting in an inferred photovoltage of ~550 mV. Water oxidation is sustained at these anodes for many hours in harsh pH and oxidative environments whereas comparable silicon anodes without the TiO(2) coating quickly fail. The desirable electrochemical efficiency and corrosion resistance of these anodes is made possible by the low electron-tunnelling resistance (<0.006 Ω cm(2) for p(+)-Si) and uniform thickness of atomic-layer deposited TiO(2).

  8. Improving singlet oxygen resistance during photochemical water oxidation by cobalt porphyrin catalysts.

    PubMed

    Nakazono, Takashi; Parent, Alexander R; Sakai, Ken

    2015-04-27

    Enabling the production of solar fuels on a global scale through artificial photosynthesis requires the development of water oxidation catalysts with significantly improved stability. The stability of photosystems is often reduced owing to attack by singlet oxygen, which is produced during light harvesting. Here, we report photochemical water oxidation by CoFPS, a fluorinated Co-porphyrin designed to resist attack by singlet oxygen. CoFPS exhibits significantly improved stability relative to its non-fluorinated analogue, as shown by a large increase in turnover numbers. This increased stability results from resistance of CoFPS to attack by singlet oxygen, the formation of which was monitored in situ by using 9,10-diphenylanthracene as a chemical probe. Dynamic light scattering (DLS) confirms that CoFPS remains homogeneous, proving its stability during water oxidation catalysis.

  9. Hydrometallurgical process for the recovery of high value metals from spent lithium nickel cobalt aluminum oxide based lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Joulié, M.; Laucournet, R.; Billy, E.

    2014-02-01

    A hydrometallurgical process is developed to recover valuable metals of the lithium nickel cobalt aluminum oxide (NCA) cathodes from spent lithium-ion batteries (LIBs). Effect of parameters such as type of acid (H2SO4, HNO3 and HCl), acid concentration (1-4 mol L-1), leaching time (3-18 h) and leaching temperature (25-90 °C) with a solid to liquid ratio fixed at 5% (w/v) are investigated to determine the most efficient conditions of dissolution. The preliminary results indicate that HCl provides higher leaching efficiency. In optimum conditions, a complete dissolution is performed for Li, Ni, Co and Al. In the nickel and cobalt recovery process, at first the Co(II) in the leaching liquor is selectively oxidized in Co(III) with NaClO reagent to recover Co2O3, 3H2O by a selective precipitation at pH = 3. Then, the nickel hydroxide is precipitated by a base addition at pH = 11. The recovery efficiency of cobalt and nickel are respectively 100% and 99.99%.

  10. Electrolyte-dependent electrosynthesis and activity of cobalt-based water oxidation catalysts.

    PubMed

    Surendranath, Yogesh; Dinca, Mircea; Nocera, Daniel G

    2009-02-25

    Electrolysis of Co(2+) in phosphate, methylphosphonate, and borate electrolytes effects the electrodeposition of an amorphous highly active water oxidation catalyst as a thin film on an inert anode. Electrodeposition of a catalytically competent species immediately follows oxidation of Co(2+) to Co(3+) in solution. Methylphosphonate and borate electrolytes support catalyst activity comparable to that observed for phosphate. Catalytic activity for O(2) generation in aqueous solutions containing 0.5 M NaCl is retained for catalysts grown from phosphate electrolyte.

  11. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain.

    PubMed

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

    2016-07-01

    Study of layered complex oxides emerge as one of leading topics in fundamental materials science because of the strong interplay among intrinsic charge, spin, orbital, and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials that exhibit new phenomena beyond their conventional forms. Here, we report a strain-driven self-assembly of bismuth-based supercell (SC) with a two-dimensional (2D) layered structure. With combined experimental analysis and first-principles calculations, we investigated the full SC structure and elucidated the fundamental growth mechanism achieved by the strain-enabled self-assembled atomic layer stacking. The unique SC structure exhibits room-temperature ferroelectricity, enhanced magnetic responses, and a distinct optical bandgap from the conventional double perovskite structure. This study reveals the important role of interfacial strain modulation and atomic rearrangement in self-assembling a layered singe-phase multiferroic thin film, which opens up a promising avenue in the search for and design of novel 2D layered complex oxides with enormous promise. PMID:27295399

  12. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain.

    PubMed

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

    2016-07-01

    Study of layered complex oxides emerge as one of leading topics in fundamental materials science because of the strong interplay among intrinsic charge, spin, orbital, and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials that exhibit new phenomena beyond their conventional forms. Here, we report a strain-driven self-assembly of bismuth-based supercell (SC) with a two-dimensional (2D) layered structure. With combined experimental analysis and first-principles calculations, we investigated the full SC structure and elucidated the fundamental growth mechanism achieved by the strain-enabled self-assembled atomic layer stacking. The unique SC structure exhibits room-temperature ferroelectricity, enhanced magnetic responses, and a distinct optical bandgap from the conventional double perovskite structure. This study reveals the important role of interfacial strain modulation and atomic rearrangement in self-assembling a layered singe-phase multiferroic thin film, which opens up a promising avenue in the search for and design of novel 2D layered complex oxides with enormous promise.

  13. Polytypic transformations during the thermal decomposition of cobalt hydroxide and cobalt hydroxynitrate

    SciTech Connect

    Ramesh, Thimmasandra Narayan

    2010-06-15

    The isothermal decomposition of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature leads to the formation of Co{sub 3}O{sub 4}. The phase evolution during the decomposition process was monitored using powder X-ray diffraction. The transformation of cobalt hydroxide to cobalt oxide occurs via three phase mixture while cobalt hydroxynitrate to cobalt oxide occurs through a two phase mixture. The nature of the sample and its preparation method controls the decomposition mechanism. The comparison of topotactical relationship between the precursors to the decomposed product has been reported in relation to polytypism. - Graphical abstract: Isothermal thermal decomposition studies of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature show the metastable phase formed prior to Co{sub 3}O{sub 4} phase.

  14. Quasi-one-dimensional nanostructured cobalt (Co) intercalated vanadium oxide (V{sub 2}O{sub 5}): Peroxovanadate sol gel synthesis and structural study

    SciTech Connect

    Langie da Silva, Douglas; Moreira, Eduardo Ceretta; Dias, Fábio Teixeira; Neves Vieira, Valdemar das; Brandt, Iuri Stefani; Cas Viegas, Alexandre da; Pasa, André Avelino

    2015-01-15

    Nanostructured cobalt vanadium oxide (V{sub 2}O{sub 5}) xerogels spread onto crystalline Si substrates were synthesized via peroxovanadate sol gel route. The resulting products were characterized by distinct experimental techniques. The surface morphology and the nanostructure of xerogels correlate with Co concentration. The decrease of the structural coherence length is followed by the formation of a loose network of nanopores when the concentration of intercalated species was greater than 4 at% of Co. The efficiency of the synthesis route also drops with the increase of Co concentration. The interaction between the Co(OH{sub 2}){sub 6}{sup 2+} cations and the (H{sub 2}V{sub 10}O{sub 28}){sup 4−} anions during the synthesis was suggested as a possible explanation for the incomplete condensation of the V{sub 2}O{sub 5} gel. Finally the experimental results points for the intercalation of Co between the bilayers of the V{sub 2}O{sub 5}. In this scenario two possible preferential occupation sites for the metallic atoms in the framework of the xerogel were proposed. - Graphical abstract: Quasi-one-dimensional nanostructured cobalt (Co) intercalated vanadium oxide (V{sub 2}O{sub 5}) nanoribbons synthesized by peroxovanadate sol gel route. - Highlights: • Nanostructured cobalt V{sub 2}O{sub 5} gel spread onto c{sub S}i were synthesized via peroxovanadate sol gel route. • The micro and nanostructure correlates with the cobalt content. • The efficiency of the synthesis route shows to be also dependent of Co content. • The experimental results points for the intercalation of Co between the bilayers of the V{sub 2}O{sub 5} xerogel.

  15. Double-Shelled Nanocages with Cobalt Hydroxide Inner Shell and Layered Double Hydroxides Outer Shell as High-Efficiency Polysulfide Mediator for Lithium-Sulfur Batteries.

    PubMed

    Zhang, Jintao; Hu, Han; Li, Zhen; Lou, Xiong Wen David

    2016-03-14

    Lithium-sulfur (Li-S) batteries have been considered as a promising candidate for next-generation electrochemical energy-storage technologies because of their overwhelming advantages in energy density. Suppression of the polysulfide dissolution while maintaining a high sulfur utilization is the main challenge for Li-S batteries. Here, we have designed and synthesized double-shelled nanocages with two shells of cobalt hydroxide and layered double hydroxides (CH@LDH) as a conceptually new sulfur host for Li-S batteries. Specifically, the hollow CH@LDH polyhedra with complex shell structures not only maximize the advantages of hollow nanostructures for encapsulating a high content of sulfur (75 wt %), but also provide sufficient self-functionalized surfaces for chemically bonding with polysulfides to suppress their outward dissolution. When evaluated as cathode material for Li-S batteries, the CH@LDH/S composite shows a significantly improved electrochemical performance.

  16. The cytotoxicity and genotoxicity of soluble and particulate cobalt in human lung fibroblast cells.

    PubMed

    Smith, Leah J; Holmes, Amie L; Kandpal, Sanjeev Kumar; Mason, Michael D; Zheng, Tongzhang; Wise, John Pierce

    2014-08-01

    Cobalt exposure is increasing as cobalt demand rises worldwide due to its use in enhancing rechargeable battery efficiency, super-alloys, and magnetic products. Cobalt is considered a possible human carcinogen with the lung being a primary target. However, few studies have considered cobalt-induced toxicity in human lung cells. Therefore, in this study, we sought to determine the cytotoxicity and genotoxicity of particulate and soluble cobalt in human lung cells. Cobalt oxide and cobalt chloride were used as representative particulate and soluble cobalt compounds, respectively. Exposure to both particulate and soluble cobalt induced a concentration-dependent increase in cytotoxicity, genotoxicity, and intracellular cobalt ion levels. Based on intracellular cobalt ion levels, we found that soluble cobalt was more cytotoxic than particulate cobalt while particulate and soluble cobalt induced similar levels of genotoxicity. However, soluble cobalt induced cell cycle arrest indicated by the lack of metaphases at much lower intracellular cobalt concentrations compared to cobalt oxide. Accordingly, we investigated the role of particle internalization in cobalt oxide-induced toxicity and found that particle-cell contact was necessary to induce cytotoxicity and genotoxicity after cobalt exposure. These data indicate that cobalt compounds are cytotoxic and genotoxic to human lung fibroblasts, and solubility plays a key role in cobalt-induced lung toxicity.

  17. The cytotoxicity and genotoxicity of soluble and particulate cobalt in human lung fibroblast cells.

    PubMed

    Smith, Leah J; Holmes, Amie L; Kandpal, Sanjeev Kumar; Mason, Michael D; Zheng, Tongzhang; Wise, John Pierce

    2014-08-01

    Cobalt exposure is increasing as cobalt demand rises worldwide due to its use in enhancing rechargeable battery efficiency, super-alloys, and magnetic products. Cobalt is considered a possible human carcinogen with the lung being a primary target. However, few studies have considered cobalt-induced toxicity in human lung cells. Therefore, in this study, we sought to determine the cytotoxicity and genotoxicity of particulate and soluble cobalt in human lung cells. Cobalt oxide and cobalt chloride were used as representative particulate and soluble cobalt compounds, respectively. Exposure to both particulate and soluble cobalt induced a concentration-dependent increase in cytotoxicity, genotoxicity, and intracellular cobalt ion levels. Based on intracellular cobalt ion levels, we found that soluble cobalt was more cytotoxic than particulate cobalt while particulate and soluble cobalt induced similar levels of genotoxicity. However, soluble cobalt induced cell cycle arrest indicated by the lack of metaphases at much lower intracellular cobalt concentrations compared to cobalt oxide. Accordingly, we investigated the role of particle internalization in cobalt oxide-induced toxicity and found that particle-cell contact was necessary to induce cytotoxicity and genotoxicity after cobalt exposure. These data indicate that cobalt compounds are cytotoxic and genotoxic to human lung fibroblasts, and solubility plays a key role in cobalt-induced lung toxicity. PMID:24823294

  18. Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation.

    PubMed

    Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H; Navrotsky, Alexandra

    2013-05-28

    Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn(3+)/Mn(4+) ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states.

  19. Inert anode containing oxides of nickel iron and cobalt useful for the electrolytic production of metals

    DOEpatents

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

    2002-01-01

    An inert anode for the electrolytic production of metals such as aluminum is disclosed. The inert anode includes a ceramic oxide material preferably made from NiO, Fe.sub.2 O.sub.3 and CoO. The inert anode composition may comprise the following mole fractions of NiO, Fe.sub.2 O.sub.3 and CoO: 0.15 to 0.99 NiO; 0.0001 to 0.85 Fe.sub.2 O.sub.3 ; and 0.0001 to 0.45 CoO. The inert anode may optionally include other oxides and/or at least one metal phase, such as Cu, Ag, Pd, Pt, Au, Rh, Ru, Ir and/or Os. The Ni--Fe--Co--O ceramic material exhibits very low solubility in Hall cell baths used to produce aluminum.

  20. Remote catalyzation for direct formation of graphene layers on oxides.

    PubMed

    Teng, Po-Yuan; Lu, Chun-Chieh; Akiyama-Hasegawa, Kotone; Lin, Yung-Chang; Yeh, Chao-Hui; Suenaga, Kazu; Chiu, Po-Wen

    2012-03-14

    Direct deposition of high-quality graphene layers on insulating substrates such as SiO(2) paves the way toward the development of graphene-based high-speed electronics. Here, we describe a novel growth technique that enables the direct deposition of graphene layers on SiO(2) with crystalline quality potentially comparable to graphene grown on Cu foils using chemical vapor deposition (CVD). Rather than using Cu foils as substrates, our approach uses them to provide subliming Cu atoms in the CVD process. The prime feature of the proposed technique is remote catalyzation using floating Cu and H atoms for the decomposition of hydrocarbons. This allows for the direct graphitization of carbon radicals on oxide surfaces, forming isolated low-defect graphene layers without the need for postgrowth etching or evaporation of the metal catalyst. The defect density of the resulting graphene layers can be significantly reduced by tuning growth parameters such as the gas ratios, Cu surface areas, and substrate-to-Cu distance. Under optimized conditions, graphene layers with nondiscernible Raman D peaks can be obtained when predeposited graphite flakes are used as seeds for extended growth. PMID:22332771

  1. Efficient cobalt-catalyzed oxidative conversion of lignin models to benzoquinones.

    PubMed

    Biannic, Berenger; Bozell, Joseph J

    2013-06-01

    Phenolic lignin model monomers and dimers representing the primary substructural units of lignin were successfully oxidized to benzoquinones in high yield with molecular oxygen using new Co-Schiff base catalysts bearing a bulky heterocyclic nitrogen base as a substituent. This is the first example of a catalytic system able to convert both S and G lignin model phenols in high yield, a process necessary for effective use of lignin as a chemical feedstock. PMID:23679189

  2. Electrocatalytic oxidation of salicylic acid by a cobalt hydrotalcite-like compound modified Pt electrode.

    PubMed

    Gualandi, Isacco; Scavetta, Erika; Zappoli, Sergio; Tonelli, Domenica

    2011-03-15

    In this paper a study of the electrocatalytic oxidation of salicylic acid (SA) at a Pt electrode coated with a Co/Al hydrotalcite-like compound (Co/Al HTLC coated-Pt) film is presented. The voltammetric behaviour of the modified electrode in 0.1M NaOH shows two different redox couples: Co(II)/Co(III) and Co(III)/Co(IV). The electrocatalysis occurs at the same potential of the latter couple, showing that Co(IV) centers act as the oxidant. The CV investigation demonstrates that the process is controlled both by mass and charge transfer and that the Co(IV) centers involved in the oxidation are two for each SA molecule. The estimated value of the catalytic constant is 4×10(4) M(-1) s(-1). The determination of salicylic acid was performed both by DPV and chronoamperometry. The linearity ranges and the LOD values resulted 1×10(-5) to 5×10(-4), 5×10(-7) to 1×10(-4), 6×10(-6) and 2×10(-7) M, respectively. The Co/Al HTLC electrode has been used for SA determination in BAYER Aspirina® and the obtained results are consistent with an independent HPLC analysis. PMID:21237633

  3. Preparation of Magnesium, Cobalt and Nickel Ferrite Nanoparticles from Metal Oxides using Deep Eutectic Solvents.

    PubMed

    Söldner, Anika; Zach, Julia; Iwanow, Melanie; Gärtner, Tobias; Schlosser, Marc; Pfitzner, Arno; König, Burkhard

    2016-09-01

    Natural deep eutectic solvents (DESs) dissolve simple metal oxides and are used as a reaction medium to synthesize spinel-type ferrite nanoparticles MFe2 O4 (M=Mg, Zn, Co, Ni). The best results for phase-pure spinel ferrites are obtained with the DES consisting of choline chloride (ChCl) and maleic acid. By employing DESs, the reactions proceed at much lower temperatures than usual for the respective solid-phase reactions of the metal oxides and at the same temperatures as synthesis with comparable calcination processes using metal salts. The method therefore reduces the overall required energy for the nanoparticle synthesis. Thermogravimetric analysis shows that the thermolysis process of the eutectic melts in air occurs in one major step. The phase-pure spinel-type ferrite particles are thoroughly characterized by X-ray diffraction, diffuse-reflectance UV/Vis spectroscopy, and scanning electron microscopy. The properties of the obtained nanoparticles are shown to be comparable to those obtained by other methods, illustrating the potential of natural DESs for processing metal oxides. PMID:27514793

  4. Preparation of Magnesium, Cobalt and Nickel Ferrite Nanoparticles from Metal Oxides using Deep Eutectic Solvents.

    PubMed

    Söldner, Anika; Zach, Julia; Iwanow, Melanie; Gärtner, Tobias; Schlosser, Marc; Pfitzner, Arno; König, Burkhard

    2016-09-01

    Natural deep eutectic solvents (DESs) dissolve simple metal oxides and are used as a reaction medium to synthesize spinel-type ferrite nanoparticles MFe2 O4 (M=Mg, Zn, Co, Ni). The best results for phase-pure spinel ferrites are obtained with the DES consisting of choline chloride (ChCl) and maleic acid. By employing DESs, the reactions proceed at much lower temperatures than usual for the respective solid-phase reactions of the metal oxides and at the same temperatures as synthesis with comparable calcination processes using metal salts. The method therefore reduces the overall required energy for the nanoparticle synthesis. Thermogravimetric analysis shows that the thermolysis process of the eutectic melts in air occurs in one major step. The phase-pure spinel-type ferrite particles are thoroughly characterized by X-ray diffraction, diffuse-reflectance UV/Vis spectroscopy, and scanning electron microscopy. The properties of the obtained nanoparticles are shown to be comparable to those obtained by other methods, illustrating the potential of natural DESs for processing metal oxides.

  5. Electrocatalytic oxidation of salicylic acid by a cobalt hydrotalcite-like compound modified Pt electrode.

    PubMed

    Gualandi, Isacco; Scavetta, Erika; Zappoli, Sergio; Tonelli, Domenica

    2011-03-15

    In this paper a study of the electrocatalytic oxidation of salicylic acid (SA) at a Pt electrode coated with a Co/Al hydrotalcite-like compound (Co/Al HTLC coated-Pt) film is presented. The voltammetric behaviour of the modified electrode in 0.1M NaOH shows two different redox couples: Co(II)/Co(III) and Co(III)/Co(IV). The electrocatalysis occurs at the same potential of the latter couple, showing that Co(IV) centers act as the oxidant. The CV investigation demonstrates that the process is controlled both by mass and charge transfer and that the Co(IV) centers involved in the oxidation are two for each SA molecule. The estimated value of the catalytic constant is 4×10(4) M(-1) s(-1). The determination of salicylic acid was performed both by DPV and chronoamperometry. The linearity ranges and the LOD values resulted 1×10(-5) to 5×10(-4), 5×10(-7) to 1×10(-4), 6×10(-6) and 2×10(-7) M, respectively. The Co/Al HTLC electrode has been used for SA determination in BAYER Aspirina® and the obtained results are consistent with an independent HPLC analysis.

  6. Cobalt hydroxide/oxide hexagonal ring-graphene hybrids through chemical etching of metal hydroxide platelets by graphene oxide: energy storage applications.

    PubMed

    Nethravathi, C; Rajamathi, Catherine R; Rajamathi, Michael; Wang, Xi; Gautam, Ujjal K; Golberg, Dmitri; Bando, Yoshio

    2014-03-25

    The reaction of β-Co(OH)2 hexagonal platelets with graphite oxide in an aqueous colloidal dispersion results in the formation of β-Co(OH)2 hexagonal rings anchored to graphene oxide layers. The interaction between the basic hydroxide layers and the acidic groups on graphene oxide induces chemical etching of the hexagonal platelets, forming β-Co(OH)2 hexagonal rings. On heating in air or N2, the hydroxide hybrid is morphotactically converted to porous Co3O4/CoO hexagonal ring-graphene hybrids. Porous NiCo2O4 hexagonal ring-graphene hybrid is also obtained through a similar process starting from β-Ni0.33Co0.67(OH)2 platelets. As electrode materials for supercapacitors or lithium-ion batteries, these materials exhibit a large capacity, high rate capability, and excellent cycling stability.

  7. Cobalt hydroxide/oxide hexagonal ring-graphene hybrids through chemical etching of metal hydroxide platelets by graphene oxide: energy storage applications.

    PubMed

    Nethravathi, C; Rajamathi, Catherine R; Rajamathi, Michael; Wang, Xi; Gautam, Ujjal K; Golberg, Dmitri; Bando, Yoshio

    2014-03-25

    The reaction of β-Co(OH)2 hexagonal platelets with graphite oxide in an aqueous colloidal dispersion results in the formation of β-Co(OH)2 hexagonal rings anchored to graphene oxide layers. The interaction between the basic hydroxide layers and the acidic groups on graphene oxide induces chemical etching of the hexagonal platelets, forming β-Co(OH)2 hexagonal rings. On heating in air or N2, the hydroxide hybrid is morphotactically converted to porous Co3O4/CoO hexagonal ring-graphene hybrids. Porous NiCo2O4 hexagonal ring-graphene hybrid is also obtained through a similar process starting from β-Ni0.33Co0.67(OH)2 platelets. As electrode materials for supercapacitors or lithium-ion batteries, these materials exhibit a large capacity, high rate capability, and excellent cycling stability. PMID:24527661

  8. Nano-sized layered Mn oxides as promising and biomimetic water oxidizing catalysts for water splitting in artificial photosynthetic systems.

    PubMed

    Najafpour, Mohammad Mahdi; Heidari, Sima; Amini, Emad; Khatamian, Masoumeh; Carpentier, Robert; Allakhverdiev, Suleyman I

    2014-04-01

    One challenge in artificial photosynthetic systems is the development of artificial model compounds to oxidize water. The water-oxidizing complex of Photosystem II which is responsible for biological water oxidation contains a cluster of four Mn ions bridged by five oxygen atoms. Layered Mn oxides as efficient, stable, low cost, environmentally friendly and easy to use, synthesize, and manufacture compounds could be considered as functional and structural models for the site. Because of the related structure of these Mn oxides and the catalytic centre of the active site of the water oxidizing complex of Photosystem II, the study of layered Mn oxides may also help to understand more about the mechanism of water oxidation by the natural site. This review provides an overview of the current status of layered Mn oxides in artificial photosynthesis and discuss the sophisticated design strategies for Mn oxides as water oxidizing catalysts.

  9. Copper cobalt spinel as a high performance cathode for intermediate temperature solid oxide fuel cells.

    PubMed

    Shao, Lin; Wang, Qi; Fan, Lishuang; Wang, Pengxiang; Zhang, Naiqing; Sun, Kening

    2016-06-30

    CuCo2O4 spinel prepared via an EDTA-citric acid process was studied as a candidate solid oxide fuel cell (SOFC) cathode material at intermediate temperatures (IT). CuCo2O4 cathodes were measured using thermal gravimetric analysis, X-ray diffraction and scanning electron microscopy. AC impedance spectroscopy and DC polarization measurements were used to study the electrode performance. The obtained value of the polarization resistances at 800 °C was 0.12 Ω cm(2) with a maximum power density of 972 mW cm(-2). PMID:27326915

  10. Copper cobalt spinel as a high performance cathode for intermediate temperature solid oxide fuel cells.

    PubMed

    Shao, Lin; Wang, Qi; Fan, Lishuang; Wang, Pengxiang; Zhang, Naiqing; Sun, Kening

    2016-06-30

    CuCo2O4 spinel prepared via an EDTA-citric acid process was studied as a candidate solid oxide fuel cell (SOFC) cathode material at intermediate temperatures (IT). CuCo2O4 cathodes were measured using thermal gravimetric analysis, X-ray diffraction and scanning electron microscopy. AC impedance spectroscopy and DC polarization measurements were used to study the electrode performance. The obtained value of the polarization resistances at 800 °C was 0.12 Ω cm(2) with a maximum power density of 972 mW cm(-2).

  11. Impact of thin metal layer on the optical and electrical properties of indium-doped-tin oxide and aluminum-doped-zinc oxide layers

    NASA Astrophysics Data System (ADS)

    Kumar, Melvin David; Park, Yun Chang; Kim, Joondong

    2015-06-01

    The distinguished transparent conductive oxide (TCO) layers like indium-doped-tin oxide (ITO) and aluminum-doped-zinc oxide (AZO) layers were prepared in different combinations with and without thin Ni metal layer. The optical and electrical properties of prepared samples were analyzed and compared with the objective to understand the role and influence of the Ni layer in each TCO combination. The highest transmittance value of 91.49% was exhibited by prepared AZO layers. Even though if the transmittance of Ni inserting TCO layers was marginally reduced than that of the ordinary TCO samples, they exhibited balanced optical properties with enhanced electrical properties. Carrier concentration of indium doped tin-oxide and aluminum doped zinc oxide (ITO/AZO) bilayer sample is increased more than double the times when the Ni layer was inserted between ITO and AZO. Thin layer of Ni in between TCO layers reduced sheet resistance and offered substantial transmittance, so that the figure of merit (FOM) value of Ni embedding TCOs was greater than that of TCOs without Ni layer. The ITO/Ni/AZO combination provided optimum results in all the electrical properties. As compared to other TCO/metal combinations, the overall performance of ITO/Ni/AZO tri-layer combination was appreciable. These results show that the optical and electrical properties of TCO layers could be enhanced by inserting a Ni layer with optimum thickness in between them.

  12. Reactive oxygen species and oxidative DNA damage mediate the cytotoxicity of tungsten-nickel-cobalt alloys in vitro

    SciTech Connect

    Harris, R.M.; Williams, T.D.; Hodges, N.J.; Waring, R.H.

    2011-01-01

    Tungsten alloys (WA) have been introduced in an attempt to find safer alternatives to depleted uranium and lead munitions. However, it is known that at least one alloy, 91% tungsten-6% nickel-3% cobalt (WNC-91-6-3), causes rhabdomyosarcomas when fragments are implanted in rat muscle. This raises concerns that shrapnel, if not surgically removable, may result in similar tumours in humans. There is therefore a clear need to develop rapid and robust in vitro methods to characterise the toxicity of different WAs in order to identify those that are most likely to be harmful to human health and to guide development of new materials in the future. In the current study we have developed a rapid visual in vitro assay to detect toxicity mediated by individual WA particles in cultured L6-C11 rat muscle cells. Using a variety of techniques (histology, comet assay, caspase-3 activity, oxidation of 2'7'-dichlorofluorescin to measure the production of reactive oxygen species and whole-genome microarrays) we show that, in agreement with the in vivo rat carcinogenicity studies, WNC-91-6-3 was the most toxic of the alloys tested. On dissolution, it produces large amounts of reactive oxygen species, causes significant amounts of DNA damage, inhibits caspase-3, triggers a severe hypoxic response and kills the cells in the immediate vicinity of the alloy particles within 24 h. By combining these in vitro data we offer a mechanistic explanation of the effect of this alloy in vivo and show that in vitro tests are a viable alternative for assessing new alloys in the future.

  13. The cytotoxicity and genotoxicity of soluble and particulate cobalt in human lung epithelial cells.

    PubMed

    Xie, Hong; Smith, Leah J; Holmes, Amie L; Zheng, Tongzhang; Pierce Wise, John

    2016-05-01

    Cobalt is a toxic metal used in various industrial applications leading to adverse lung effects by inhalation. Cobalt is considered a possible human carcinogen with the lung being a primary target. However, few studies have considered cobalt-induced toxicity in human lung cells, especially normal lung epithelial cells. Therefore, in this study, we sought to determine the cytotoxicity and genotoxicity of particulate and soluble cobalt in normal primary human lung epithelial cells. Cobalt oxide and cobalt chloride were used as representative particulate and soluble cobalt compounds, respectively. Exposure to both particulate and soluble cobalt induced a concentration-dependent increase in cytotoxicity, genotoxicity, and intracellular cobalt ion levels. Based on intracellular cobalt ion levels, we found that soluble and particulate cobalt induced similar cytotoxicity while soluble cobalt was more genotoxic than particulate cobalt. These data indicate that cobalt compounds are cytotoxic and genotoxic to human lung epithelial cells.

  14. Atomic layer deposition of ultrathin blocking layer for low-temperature solid oxide fuel cell on nanoporous substrate

    SciTech Connect

    Yu, Wonjong; Cho, Gu Young; Noh, Seungtak; Tanveer, Waqas Hassan; Cha, Suk Won; Ji, Sanghoon; An, Jihwan

    2015-01-15

    An ultrathin yttria-stabilized zirconia (YSZ) blocking layer deposited by atomic layer deposition (ALD) was utilized for improving the performance and reliability of low-temperature solid oxide fuel cells (SOFCs) supported by an anodic aluminum oxide substrate. Physical vapor-deposited YSZ and gadolinia-doped ceria (GDC) electrolyte layers were deposited by a sputtering method. The ultrathin ALD YSZ blocking layer was inserted between the YSZ and GDC sputtered layers. To investigate the effects of an inserted ultrathin ALD blocking layer, SOFCs with and without an ultrathin ALD blocking layer were electrochemically characterized. The open circuit voltage (1.14 V) of the ALD blocking-layered SOFC was visibly higher than that (1.05 V) of the other cell. Furthermore, the ALD blocking layer augmented the power density and improved the reproducibility.

  15. Exfoliation and reassembly of cobalt oxide nanosheets into a reversible lithium-ion battery cathode.

    PubMed

    Compton, Owen C; Abouimrane, Ali; An, Zhi; Palmeri, Marc J; Brinson, L Catherine; Amine, Khalil; Nguyen, SonBinh T

    2012-04-10

    An exfoliation-reassembly-activation (ERA) approach to lithium-ion battery cathode fabrication is introduced, demonstrating that inactive HCoO(2) powder can be converted into a reversible Li(1-x) H(x) CoO(2) thin-film cathode. This strategy circumvents the inherent difficulties often associated with the powder processing of the layered solids typically employed as cathode materials. The delamination of HCoO(2) via a combination of chemical and mechanical exfoliation generates a highly processable aqueous dispersion of [CoO(2) ](-) nanosheets that is critical to the ERA approach. Following vacuum-assisted self-assembly to yield a thin-film cathode and ion exchange to activate this material, the generated cathodes exhibit excellent cyclability and discharge capacities approaching that of low-temperature-prepared LiCoO(2) (~83 mAh g(-1) ), with this good electrochemical performance attributable to the high degree of order in the reassembled cathode.

  16. A computational material model of oxide layer erosion by impact

    SciTech Connect

    Veluswamy, S.; Means, K.H.

    1995-12-01

    Materials are subjected to erosion in a wide number of applications. Failure of materials due to erosion results in potential loss. To avoid such failures, proper analytical model validated by experiments is needed. Many empirical relations are available in the literature for predicting the amount of degradation during erosion. These relations have been obtained by conducting large number of experiments. But many restrictions apply in implementing them. This affects the generality of their use. Arrival of numerous new materials increases the demand for quantitative analytical models that are more generic. This paper is focused on arriving at a computational model that quantifies the effects of erosion on iron/iron-oxide system. A transient dynamic analysis is performed on a two-dimensional axisymmetric finite element model. Failure in oxide layer and the metal substrate are investigated at for different temperatures. The results show three different phases of material loss during erosion.

  17. Functionalizing Titanium Disilicide Nanonets with Cobalt Oxide and Palladium for Stable Li Oxygen Battery Operations.

    PubMed

    Yao, Xiahui; Cheng, Qingmei; Xie, Jin; Dong, Qi; Wang, Dunwei

    2015-10-01

    Li oxygen (Li-O2) batteries promise high energy densities but suffer from challenges such as poor cycling lifetime and low round-trip efficiencies. Recently, the instability of carbon cathode support has been recognized to contribute significantly to the problems faced by Li-O2 batteries. One strategy to address the challenge is to replace carbon materials with carbon-free ones. Here, we present titanium silicide nanonets (TiSi2) as such a new material platform for this purpose. Because TiSi2 exhibits no oxygen reduction reaction (ORR) or oxygen evolution reaction (OER) activities, catalysts are required to promote discharge and recharge reactions at reduced overpotentials. Pd nanoparticles grown by atomic layer deposition (ALD) were observed to provide the bifunctionalities of ORR and OER. Their adhesion to TiSi2 nanonets, however, was found to be poor, leading to drastic performance decay due to Pd detachments and aggregation. The problem was solved by adding another layer of Co3O4, also prepared by ALD. Together, the Pd/Co3O4/TiSi2 combination affords the desired functionalities and stability. Li-O2 test cells that lasted more than 126 cycles were achieved. The reversible formation and decomposition of Li2O2 was verified by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), ferrocenium back-titration, and gas-chromatography and mass spectrometry (GC-MS). Our results provide a new material platform for detailed studies of Li-O2 operations for better understanding of the chemistries involved, which is expected to help pave the way toward practical Li-O2 battery realizations.

  18. A metal-oxide-semiconductor radiation dosimeter with a thick and defect-rich oxide layer

    NASA Astrophysics Data System (ADS)

    Liu, Hongrui; Yang, Yuhao; Zhang, Jinwen

    2016-04-01

    Enhancing the density of defects in the oxide layer is the main factor in improving the sensitivity of a metal-oxide-semiconductor (MOS) radiation dosimeter. This paper reports a novel MOS dosimeter with a very thick and defect-rich oxide layer fabricated by MEMS technology. The category of defects in SiO2 and their possible effect on the radiation dose sensing was analyzed. Then, we proposed combining deep-reactive-ion etching, thermal oxidation and low pressure chemical vapor deposition to realize an oxide layer containing multiple and large interfaces which can increase defects significantly. The trench-and-beam structure of silicon was considered in detail. The fabrication process was developed for obtaining a thick and compact MEMS-made SiO2. Our devices were irradiated by γ-rays of 60Co at 2 Gy per minute for 2 h and a thermally stimulated current (TSC) method was used to determine the readout of the dosimeters. Results show that there is a peak current of about 450 nA, indicating a total TSC charge of 158 μC and sensitivity of 1.1 μC mm-3·Gy, which is 40 times the sensitivity of previous MOS dosimeters.

  19. Effects of preferred orientation and crystal size on thermoelectric properties of sodium cobalt oxide

    NASA Astrophysics Data System (ADS)

    Wu, Yin; Wang, Jun; Yaer, Xinba; Miao, Lei; Zhang, Boyu; Guo, Feng; Zhang, Shuai

    2016-11-01

    To examine the effect of crystal size and orientation effect on ZT, polycrystalline NaxCo2O4 materials were prepared by pressing layered crystals obtained in sol-gel (SG) synthesis, molten salt synthesis (MSS) with and without additional ball milling (BM) treatment and 1:1 molar ratio mixture (Mixture) of BM powder and MSS powders. We found that the orientation effect and crystal size for four samples follow Mixture < SG < BM < MSS and BM < Mixture < SG < MSS, respectively. Electrical conductivity was obviously enhanced in the highly orientated BM and MSS samples when compared with SG and Mixture. It appears that the crystal size plays a dominant role in thermal conductivity rather than Seebeck coefficient by controlling the phonon scattering at grain boundaries. Thermal conductivity for BM was significantly decreased in comparison to MSS, although both BM and MSS show comparable orientation effect. The maximum ZT value is developed to near 0.51 at 814K upon increasing the electrical resistivity and decreasing the thermal conductivity, which are mainly governed by the condition of crystal size and orientation effect.

  20. Nanostructured Cobalt Oxide Clusters in Mesoporous Silica as Efficient Oxygen-Evolving Catalysts

    SciTech Connect

    Jiao, Feng; Frei, Heinz

    2009-01-01

    The development of integrated artificial photosynthetic systems for the direct conversion of carbon dioxide and water to fuel depends on the availability of efficient and robust catalysts for the chemical transformations. Catalysts need to exhibit turnover frequency (TOF) and density (hence size) commensurate with the solar flux at ground level (1000Wm2, airmass (AM) 1.5)[1]to avoid wasting of incidentsolar photons. For example, a catalyst with a TOF of 100 s1 requires a density of one catalytic site per square nanometer. Catalysts with lower rates or taking up a larger space will require a high-surface-area, nanostructured support that affords tens to hundreds of catalytic sites per square nanometer. Furthermore, catalysts need to operate close to the thermodynamic potential of the redox reaction so that amaximum fraction of the solar photon energy is converted to chemical energy. Stability considerations favor all-inorganic oxide materials, as does avoidance of harsh reaction conditions of pH value or temperature.

  1. Hydrothermal synthesis and characterization under dynamic conditions of cobalt oxide nanoparticles supported over magnesium oxide nano-plates.

    PubMed

    Alayoglu, Selim; Rosenberg, Daniel J; Ahmed, Musahid

    2016-06-14

    A nano-catalyst comprised of oxidized Co NPs supported on MgO nano-plates was synthesized via a hydrothermal co-precipitation strategy and calcination in O2 and subsequently in H2 at 250 °C. Spectro-microscopy characterization was performed by scanning transmission electron microscopy, electron energy loss spectroscopy and scanning X-ray transmission microscopy. Surface measurements under H2 and H2 + CO atmospheres were obtained by ambient pressure X-ray photoelectron spectroscopy and in situ X-ray absorption spectroscopy in the 225-480 °C range. These measurements at the atomic and microscopic levels demonstrated that the oxidized Co nanoparticles uniformly decorated the MgO nano-plates. The surfaces are enriched with Co, and with a mixture of Co(OH)2 and CoO under H2 and H2 + CO atmospheres. Under a H2 atmosphere, the outermost surfaces were composed of (lattice) O(2-), CO3(2-) and OH(-). No inorganic carbonates were observed in the bulk. Chemisorbed CO, likely on the oxidized Co surfaces, was observed at the expense of O(2-) under 300 mTorr H2 + CO (2 : 1) at 225 °C. Gas phase CO2 was detected under 32 Torr H2 + CO (2 : 1) at 225 °C upon prolonged reaction time, and was attributed to a surface chemical reaction between O(2-) and chemisorbed CO. Furthermore, sp(3) like carbon species were detected on the otherwise carbon free surface in H2 + CO, which remained on the surface under the subsequent reaction conditions. The formation of sp(3) like hydrocarbons was ascribed to a surface catalytic reaction between the chemisorbed CO and OH(-) as the apparent hydrogen source. PMID:26979489

  2. Study of thin hafnium oxides deposited by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Ganem, J.-J.; Trimaille, I.; Vickridge, I. C.; Blin, D.; Martin, F.

    2004-06-01

    We have deposited thin films (3.5, 7.5 and 22 nm) by atomic layer deposition (ALD) using HfCl 4 and H 2O precursors at 350 °C. Growth, thermal annealing and thermal reoxidation of the thin hafnium oxide layers under controlled ultra-dry oxygen atmosphere were studied using ion beam techniques and isotopic tracing experiments. Secondary ion mass spectroscopy (SIMS) profiling shows that the composition of deposited films is homogeneous with depth and over a large area. RBS and NRA show that the films are under-stoichiometric in oxygen and contain trace chlorine contamination, more pronounced at the film-substrate interface. After oxidation for 20 min in 100 mbar O 2 enriched to 99.9% in 18O at 425 °C, nuclear resonance depth-profiling using the 151 keV 18O(p,α) 15N narrow resonance, reveals that the main process occurring is exchange between oxygen from the gas and oxygen from the film matrix. However, following a post deposition vacuum or inert gas anneal, the atomic exchange process during thermal reoxidation, in 18O 2, is significantly inhibited and limited to the superficial region. We assume a link between this effect and the crystallization of the films previously reported.

  3. The cytotoxicity and genotoxicity of soluble and particulate cobalt in human lung fibroblast cells

    SciTech Connect

    Smith, Leah J.; Holmes, Amie L.; Kandpal, Sanjeev Kumar; Mason, Michael D.; Zheng, Tongzhang; Wise, John Pierce

    2014-08-01

    Cobalt exposure is increasing as cobalt demand rises worldwide due to its use in enhancing rechargeable battery efficiency, super-alloys, and magnetic products. Cobalt is considered a possible human carcinogen with the lung being a primary target. However, few studies have considered cobalt-induced toxicity in human lung cells. Therefore, in this study, we sought to determine the cytotoxicity and genotoxicity of particulate and soluble cobalt in human lung cells. Cobalt oxide and cobalt chloride were used as representative particulate and soluble cobalt compounds, respectively. Exposure to both particulate and soluble cobalt induced a concentration-dependent increase in cytotoxicity, genotoxicity, and intracellular cobalt ion levels. Based on intracellular cobalt ion levels, we found that soluble cobalt was more cytotoxic than particulate cobalt while particulate and soluble cobalt induced similar levels of genotoxicity. However, soluble cobalt induced cell cycle arrest indicated by the lack of metaphases at much lower intracellular cobalt concentrations compared to cobalt oxide. Accordingly, we investigated the role of particle internalization in cobalt oxide-induced toxicity and found that particle-cell contact was necessary to induce cytotoxicity and genotoxicity after cobalt exposure. These data indicate that cobalt compounds are cytotoxic and genotoxic to human lung fibroblasts, and solubility plays a key role in cobalt-induced lung toxicity. - Highlights: • Particulate and soluble cobalt are cytotoxic and genotoxic to human lung cells. • Soluble cobalt induces more cytotoxicity compared to particulate cobalt. • Soluble and particulate cobalt induce similar levels of genotoxicity. • Particle-cell contact is required for particulate cobalt-induced toxicity.

  4. Ultraviolet photodetectors based on ZnO nanorods-seed layer effect and metal oxide modifying layer effect

    NASA Astrophysics Data System (ADS)

    Zhou, Hai; Fang, Guojia; Liu, Nishuang; Zhao, Xingzhong

    2011-12-01

    Pt/ZnO nanorod (NR) and Pt/modified ZnO NR Schottky barrier ultraviolet (UV) photodetectors (PDs) were prepared with different seed layers and metal oxide modifying layer materials. In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300°C, respectively. For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity ( D λ*) than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism. Also the ratio of D 254* to D 546* was calculated above 8 × 102 for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength.

  5. Atomic-layer deposited thulium oxide as a passivation layer on germanium

    SciTech Connect

    Mitrovic, I. Z. Hall, S.; Weerakkody, A. D.; Sedghi, N.; Althobaiti, M.; Hesp, D.; Dhanak, V. R.; Santoni, A.; Chalker, P. R.; Henkel, C.; Dentoni Litta, E.; Hellström, P.-E.; Östling, M.; Tan, H.; Schamm-Chardon, S.

    2015-06-07

    A comprehensive study of atomic-layer deposited thulium oxide (Tm{sub 2}O{sub 3}) on germanium has been conducted using x-ray photoelectron spectroscopy (XPS), vacuum ultra-violet variable angle spectroscopic ellipsometry, high-resolution transmission electron microscopy (HRTEM), and electron energy-loss spectroscopy. The valence band offset is found to be 3.05 ± 0.2 eV for Tm{sub 2}O{sub 3}/p-Ge from the Tm 4d centroid and Ge 3p{sub 3/2} charge-corrected XPS core-level spectra taken at different sputtering times of a single bulk thulium oxide sample. A negligible downward band bending of ∼0.12 eV is observed during progressive differential charging of Tm 4d peaks. The optical band gap is estimated from the absorption edge and found to be 5.77 eV with an apparent Urbach tail signifying band gap tailing at ∼5.3 eV. The latter has been correlated to HRTEM and electron diffraction results corroborating the polycrystalline nature of the Tm{sub 2}O{sub 3} films. The Tm{sub 2}O{sub 3}/Ge interface is found to be rather atomically abrupt with sub-nanometer thickness. In addition, the band line-up of reference GeO{sub 2}/n-Ge stacks obtained by thermal oxidation has been discussed and derived. The observed low reactivity of thulium oxide on germanium as well as the high effective barriers for holes (∼3 eV) and electrons (∼2 eV) identify Tm{sub 2}O{sub 3} as a strong contender for interfacial layer engineering in future generations of scaled high-κ gate stacks on Ge.

  6. Atomic-layer deposited thulium oxide as a passivation layer on germanium

    NASA Astrophysics Data System (ADS)

    Mitrovic, I. Z.; Hall, S.; Althobaiti, M.; Hesp, D.; Dhanak, V. R.; Santoni, A.; Weerakkody, A. D.; Sedghi, N.; Chalker, P. R.; Henkel, C.; Dentoni Litta, E.; Hellström, P.-E.; Östling, M.; Tan, H.; Schamm-Chardon, S.

    2015-06-01

    A comprehensive study of atomic-layer deposited thulium oxide (Tm2O3) on germanium has been conducted using x-ray photoelectron spectroscopy (XPS), vacuum ultra-violet variable angle spectroscopic ellipsometry, high-resolution transmission electron microscopy (HRTEM), and electron energy-loss spectroscopy. The valence band offset is found to be 3.05 ± 0.2 eV for Tm2O3/p-Ge from the Tm 4d centroid and Ge 3p3/2 charge-corrected XPS core-level spectra taken at different sputtering times of a single bulk thulium oxide sample. A negligible downward band bending of ˜0.12 eV is observed during progressive differential charging of Tm 4d peaks. The optical band gap is estimated from the absorption edge and found to be 5.77 eV with an apparent Urbach tail signifying band gap tailing at ˜5.3 eV. The latter has been correlated to HRTEM and electron diffraction results corroborating the polycrystalline nature of the Tm2O3 films. The Tm2O3/Ge interface is found to be rather atomically abrupt with sub-nanometer thickness. In addition, the band line-up of reference GeO2/n-Ge stacks obtained by thermal oxidation has been discussed and derived. The observed low reactivity of thulium oxide on germanium as well as the high effective barriers for holes (˜3 eV) and electrons (˜2 eV) identify Tm2O3 as a strong contender for interfacial layer engineering in future generations of scaled high-κ gate stacks on Ge.

  7. Iodine oxide in the global marine boundary layer

    NASA Astrophysics Data System (ADS)

    Prados-Roman, C.; Cuevas, C. A.; Hay, T.; Fernandez, R. P.; Mahajan, A. S.; Royer, S.-J.; Galí, M.; Simó, R.; Dachs, J.; Großmann, K.; Kinnison, D. E.; Lamarque, J.-F.; Saiz-Lopez, A.

    2014-08-01

    Emitted mainly by the oceans, iodine is a halogen compound important for atmospheric chemistry due to its high ozone depletion potential and effect on the oxidizing capacity of the atmosphere. Here we present a comprehensive dataset of iodine oxide (IO) measurements in the open marine boundary layer (MBL) made during the Malaspina 2010 circumnavigation. Results show IO mixing ratios ranging from 0.4 to 1 pmol mol-1 and, complemented with additional field campaigns, this dataset confirms through observations the ubiquitous presence of reactive iodine chemistry in the global marine environment. We use a global model with organic (CH3I, CH2ICl, CH2I2 and CH2IBr) and inorganic (HOI and I2) iodine ocean emissions to investigate the contribution of the different iodine source gases to the budget of IO in the global MBL. In agreement with previous estimates, our results indicate that, globally averaged, the abiotic precursors contribute about 75% to the iodine oxide budget. However, this work reveals a strong geographical pattern in the contribution of organic vs. inorganic precursors to reactive iodine in the global MBL.

  8. Atomic layer deposited aluminum oxide and Parylene C bi-layer encapsulation for biomedical implantable devices

    NASA Astrophysics Data System (ADS)

    Xie, Xianzong

    Biomedical implantable devices have been developed for both research and clinical applications, to stimulate and record physiological signals in vivo. Chronic use of biomedical devices with thin-film-based encapsulation in large scale is impeded by their lack of long-term functionality and stability. Biostable, biocompatible, conformal, and electrically insulating coatings that sustain chronic implantation are essential for chip-scale implantable electronic systems. Even though many materials have been studied to for this purpose, to date, no encapsulation method has been thoroughly characterized or qualified as a broadly applicable long-term hermetic encapsulation for biomedical implantable devices. In this work, atomic layer deposited Al2O3 and Parylene C bi-layer was investigated as encapsulation for biomedical devices. The combination of ALD Al2O3 and CVD Parylene C encapsulation extended the lifetime of coated interdigitated electrodes (IDEs) to up to 72 months (to date) with low leakage current of ~ 15 pA. The long lifetime was achieved by significantly reducing moisture permeation due to the ALD Al2O3 layer. Moreover, the bi-layer encapsulation separates the permeated moisture (mostly at the Al2O3 and Parylene interface) from the surface contaminants (mostly at the device and Al 2O3 interface), preventing the formation of localized electrolyte through condensation. Al2O3 works as an inner moisture barrier and Parylene works as an external ion barrier, preventing contact of Al2O3 with liquid water, and slowing the kinetics of alumina corrosion. Selective removal of encapsulation materials is required to expose the active sites for interacting with physiological environment. A self-aligned mask process with three steps was developed to expose active sites, composed of laser ablation, oxygen plasma etching, and BOE etching. Al2O 3 layer was found to prevent the formation of microcracks in the iridium oxide film during laser ablation. Bi-layer encapsulated

  9. A cobalt-free SrFe 0.9Sb 0.1O 3- δ cathode material for proton-conducting solid oxide fuel cells with stable BaZr 0.1Ce 0.7Y 0.1Yb 0.1O 3- δ electrolyte

    NASA Astrophysics Data System (ADS)

    Ling, Yihan; Zhang, Xiaozhen; Wang, Songlin; Zhao, Ling; Lin, Bin; Liu, Xingqin

    A cobalt-free cubic perovskite oxide SrFe 0.9Sb 0.1O 3- δ (SFSb) is investigated as a novel cathode for proton-conducting solid oxide fuel cells (H-SOFCs). XRD results show that SFSb cathode is chemically compatible with the electrolyte BaZr 0.1Ce 0.7Y 0.1Yb 0.1O 3- δ (BZCYYb) for temperatures up to 1000 °C. Thin proton-conducting BZCYYb electrolyte and NiO-BaZr 0.1Ce 0.7Y 0.1Yb 0.1O 3- δ (NiO-BZCYYb) anode functional layer are prepared over porous anode substrates composed of NiO-BZCYYb by a one-step dry-pressing/co-firing process. Laboratory-sized quad-layer cells of NiO-BZCYYb/NiO-BZCYYb/BZCYYb/SFSb are operated from 550 to 700 °C with humidified hydrogen (∼3% H 2O) as fuel and the static air as oxidant. An open-circuit potential of 0.996 V, maximum power density of 428 mW cm -2, and a low electrode polarization resistance of 0.154 Ω cm 2 are achieved at 700 °C. The experimental results indicate that the cobalt-free SFSb is a promising candidate for cathode material for H-SOFCs.

  10. Structure and properties of the CaFe{sub 2}O{sub 4}-type cobalt oxide CaCo{sub 2}O{sub 4}

    SciTech Connect

    Shizuya, Mitsuyuki; Isobe, Masaaki Takayama-Muromachi, Eiji

    2007-09-15

    The calcium cobalt oxide CaCo{sub 2}O{sub 4} was synthesized for the first time and characterized from a powder X-ray diffraction study, measuring magnetic susceptibility, specific heat, electrical resistivity, and thermoelectric power. CaCo{sub 2}O{sub 4} crystallizes in the CaFe{sub 2}O{sub 4} (calcium ferrite)-type structure, consisting of an edge- and corner-shared CoO{sub 6} octahedral network. The structure of CaCo{sub 2}O{sub 4} belongs to an orthorhombic system (space group: Pnma) with lattice parameters, a=8.789(2) A, b=2.9006(7) A and c=10.282(3) A. Curie-Weiss-like behavior in magnetic susceptibility with the nearly trivalent cobalt low-spin state (Co{sup 3+}, 3dt{sub 2g}{sup 6}, S=0), semiconductor-like temperature dependence of resistivity ({rho}=3x10{sup -1} {omega} cm at 380 K) with dominant hopping conduction at low temperature, metallic-temperature-dependent large thermoelectric power (Seebeck coefficient: S=+147 {mu}V/K at 380 K), and Schottky-type specific heat with a small Sommerfeld constant ({gamma}=4.48(7) mJ/Co mol K{sup 2}), were observed. These results suggest that the compound possesses a metallic electronic state with a small density of states at the Fermi level. The doped holes are localized at low temperatures due to disorder in the crystal. The carriers probably originate from slight off-stoichiometry of the phase. It was also found that S tends to increase even more beyond 380 K. The large S is possibly attributed to residual spin entropy and orbital degeneracy coupled with charges by strong electron correlation in the cobalt oxides. - Graphical abstract: A new calcium cobalt oxide CaCo{sub 2}O{sub 4} phase, which crystallizes in the calcium-ferrite-type structure (space group: Pnma; a=8.789(2) A, b=2.9006(7) A, and c=10.282(3) A), has been synthesized for the first time under high temperature and high pressure (1500 deg. C, 6 GPa). This compound exhibits large thermoelectric power (Seebeck coefficient: S=+147 {mu}V/K at 380 K) and

  11. Mesoporous layer-by-layer ordered nanohybrids of layered double hydroxide and layered metal oxide: highly active visible light photocatalysts with improved chemical stability.

    PubMed

    Gunjakar, Jayavant L; Kim, Tae Woo; Kim, Hyo Na; Kim, In Young; Hwang, Seong-Ju

    2011-09-28

    Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O(2) generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements and electronic structures of the component nanosheets remain intact. The obtained heterolayered nanohybrids show a strong absorption of visible light and a remarkably depressed photoluminescence signal, indicating an effective electronic coupling between the two component nanosheets. The self-assembly between 2D inorganic nanosheets leads to the formation of highly porous stacking structure, whose porosity is controllable by changing the ratio of layered titanate/Zn-Cr-LDH. The resultant heterolayered nanohybrids are fairly active for visible light-induced O(2) generation with a rate of ∼1.18 mmol h(-1) g(-1), which is higher than the O(2) production rate (∼0.67 mmol h(-1) g(-1)) by the pristine Zn-Cr-LDH material, that is, one of the most effective visible light photocatalysts for O(2) production, under the same experimental condition. This result highlights an excellent functionality of the Zn-Cr-LDH-layered titanate nanohybrids as efficient visible light active photocatalysts. Of prime interest is that the chemical stability of the Zn-Cr-LDH is significantly improved upon the hybridization, a result of the protection of the LDH lattice by highly stable titanate layer. The present findings clearly demonstrate that the layer-by-layer-ordered assembly between inorganic 2D nanosheets is quite effective not only in improving the photocatalytic activity of the component semiconductors but also in synthesizing novel porous LDH-based hybrid materials with improved chemical

  12. Time-Resolved Investigation of Cobalt Oxidation by Mn(III)-Rich δ-MnO2 Using Quick X-ray Absorption Spectroscopy.

    PubMed

    Simanova, Anna A; Peña, Jasquelin

    2015-09-15

    Manganese oxides are important environmental oxidants that control the fate of many organic and inorganic species including cobalt. We applied ex situ quick X-ray absorption spectroscopy (QXAS) to determine the time evolution of Co(II) and Co(III) surface loadings and their respective average surface speciation in Mn(III)-rich δ-MnO2 samples at pH 6.5 and loadings of 0.01-0.20 mol Co mol(-1) Mn. In this Mn oxide, which contained few unoccupied vacancies but abundant Mn(III) at edge and interlayer sites, Co(II) sorption and oxidation started at the particle edges. We found no evidence for Co(II) oxidation by interlayer Mn(III) or Mn(III, IV) adjacent to vacancy sites at <10 min. After 10 min, basal surface sites were implicated due to slow Co oxidation by interlayer Mn(III) and reactive sites formed upon removal of interlayer Mn(III), such that 50-60% of the sorbed Co was incorporated into the MnO2 sheets or adsorbed at vacancy sites by 12 h. Our findings indicate that the redox reactivity of surface sites depends on Mn valence and crystallographic location, with Mn(III) at the edges being the most effective oxidant at short reaction times and Mn(III,IV) in the MnO2 sheet contributing at longer reaction times.

  13. Zinc oxide nanoparticle suspensions and layer-by-layer coatings inhibit staphylococcal growth.

    PubMed

    McGuffie, Matthew J; Hong, Jin; Bahng, Joong Hwan; Glynos, Emmanouil; Green, Peter F; Kotov, Nicholas A; Younger, John G; VanEpps, J Scott

    2016-01-01

    Despite a decade of engineering and process improvements, bacterial infection remains the primary threat to implanted medical devices. Zinc oxide nanoparticles (ZnO-NPs) have demonstrated antimicrobial properties. Their microbial selectivity, stability, ease of production, and low cost make them attractive alternatives to silver NPs or antimicrobial peptides. Here we sought to (1) determine the relative efficacy of ZnO-NPs on planktonic growth of medically relevant pathogens; (2) establish the role of bacterial surface chemistry on ZnO-NP effectiveness; (3) evaluate NP shape as a factor in the dose-response; and (4) evaluate layer-by-layer (LBL) ZnO-NP surface coatings on biofilm growth. ZnO-NPs inhibited bacterial growth in a shape-dependent manner not previously seen or predicted. Pyramid shaped particles were the most effective and contrary to previous work, larger particles were more effective than smaller particles. Differential susceptibility of pathogens may be related to their surface hydrophobicity. LBL ZnO-NO coatings reduced staphylococcal biofilm burden by >95%. From the Clinical Editor: The use of medical implants is widespread. However, bacterial colonization remains a major concern. In this article, the authors investigated the use of zinc oxide nanoparticles (ZnO-NPs) to prevent bacterial infection. They showed in their experiments that ZnO-NPs significantly inhibited bacterial growth. This work may present a new alternative in using ZnO-NPs in medical devices. PMID:26515755

  14. Generic Nitric Oxide (NO) Generating Surface by Immobilizing Organoselenium Species via Layer-by-Layer Assembly

    PubMed Central

    Yang, Jun; Welby, Jenna L.; Meyerhoff, Mark E.

    2010-01-01

    A universal nitric oxide (NO) generating surface is assembled via Layer-by-Layer (LbL) deposition of sodium alginate (Alg) and organoselenium modified polyethyleneimine (SePEI) on quartz and polymeric substrates. The immobilized SePEI species is capable of catalytically decomposing S-nitrosothiol species (RSNO) to NO in the presence of thiol reducing agents (e.g., glutathione, cysteine, etc.). The stepwise buildup of the multilayer films is monitored by UV-Vis spectroscopy, SEM and surface contact angle measurements. X-ray photoelectron spectroscopy is used to study the stoichiometry between the polyanion and polycation, and also the presence of Se in the catalytic LbL film. A reductive annealing process is necessary to improve the stability of freshly coated multilayer films via chain rearrangement. Chemiluminescence measurements illustrate the ability of the LbL films to generate NO from S-nitrosoglutathione (GSNO) in the presence of S-glutathione (GSH). Enhanced NO fluxes can be achieved by increasing the number of catalytic (SePEI/Alg) bilayers coated on the substrates. Nitric oxide generation is observed even after prolonged contact with sheep whole blood. Preliminary applications of this LbL on silicone rubber tubings and polyurethane catheters reveal similar NO generation behavior from these biomedical grade polymeric substrates. PMID:18710268

  15. Co-exposure to nickel and cobalt chloride enhances cytotoxicity and oxidative stress in human lung epithelial cells

    SciTech Connect

    Patel, Eshan; Lynch, Christine; Ruff, Victoria; Reynolds, Mindy

    2012-02-01

    Nickel and cobalt are heavy metals found in land, water, and air that can enter the body primarily through the respiratory tract and accumulate to toxic levels. Nickel compounds are known to be carcinogenic to humans and animals, while cobalt compounds produce tumors in animals and are probably carcinogenic to humans. People working in industrial and manufacturing settings have an increased risk of exposure to these metals. The cytotoxicity of nickel and cobalt has individually been demonstrated; however, the underlying mechanisms of co-exposure to these heavy metals have not been explored. In this study, we investigated the effect of exposure of H460 human lung epithelial cells to nickel and cobalt, both alone and in combination, on cell survival, apoptotic mechanisms, and the generation of reactive oxygen species and double strand breaks. For simultaneous exposure, cells were exposed to a constant dose of 150 μM cobalt or nickel, which was found to be relatively nontoxic in single exposure experiments. We demonstrated that cells exposed simultaneously to cobalt and nickel exhibit a dose-dependent decrease in survival compared to the cells exposed to a single metal. The decrease in survival was the result of enhanced caspase 3 and 7 activation and cleavage of poly (ADP-ribose) polymerase. Co-exposure increased the production of ROS and the formation of double strand breaks. Pretreatment with N-acetyl cysteine alleviated the toxic responses. Collectively, this study demonstrates that co-exposure to cobalt and nickel is significantly more toxic than single exposure and that toxicity is related to the formation of ROS and DSB. -- Highlights: ► Decreased survival following simultaneous exposure to NiCl{sub 2} and CoCl{sub 2}. ► Enhanced caspase and PARP cleavage following co-exposure. ► Increased formation of ROS in dual exposed cells. ► N-acetyl cysteine pretreatment decreases Co and Ni toxicity. ► Co-exposure to Ni and Co enhances the formation of double

  16. Mussel-inspired approach to constructing robust cobalt-embedded N-doped carbon nanosheet toward enhanced sulphate radical-based oxidation

    PubMed Central

    Zeng, Tao; Zhang, Haiyan; He, Zhiqiao; Chen, Jianmeng; Song, Shuang

    2016-01-01

    Heterogeneous sulphate radical based advanced oxidation processes (SR-AOPs) have lately been raised as a promising candidate for water treatment. Despite the progress made, either the stability or the performance of the current catalysts is still far from satisfactory for practical applications. Herein, using polydopamine-cobalt ion complex that inspired by mussel proteins as medium, we facilely fabricate a robust SR-AOPs catalyst with cobalt nanoparticles (NPs) embedded in nitrogen-doped reduced graphene oxide matrix (NRGO@Co). The NRGO scaffold with high porosity and surface area not only stabilizes the NPs but also greatly facilitates the accessibility and adsorption of substrates to the active sites. With the synergistic effect arising from the NRGO and Co NPs, the NRGO@Co hybrid catalyst exhibits enhanced catalytic activity for activation of peroxymonosulfate (PMS) to degrade organic pollutants in water. Furthermore, taking advantage of the favorable magnetic properties, the catalyst can be easily recycled and reused for at least 4 runs with negligible loss of activity. Coupled with systematic investigation in terms of influential factors, mineralization, and radicals identification, make the catalyst hold significant potential for application in remediation of organic pollutants in water. PMID:27616643

  17. Mussel-inspired approach to constructing robust cobalt-embedded N-doped carbon nanosheet toward enhanced sulphate radical-based oxidation

    NASA Astrophysics Data System (ADS)

    Zeng, Tao; Zhang, Haiyan; He, Zhiqiao; Chen, Jianmeng; Song, Shuang

    2016-09-01

    Heterogeneous sulphate radical based advanced oxidation processes (SR-AOPs) have lately been raised as a promising candidate for water treatment. Despite the progress made, either the stability or the performance of the current catalysts is still far from satisfactory for practical applications. Herein, using polydopamine-cobalt ion complex that inspired by mussel proteins as medium, we facilely fabricate a robust SR-AOPs catalyst with cobalt nanoparticles (NPs) embedded in nitrogen-doped reduced graphene oxide matrix (NRGO@Co). The NRGO scaffold with high porosity and surface area not only stabilizes the NPs but also greatly facilitates the accessibility and adsorption of substrates to the active sites. With the synergistic effect arising from the NRGO and Co NPs, the NRGO@Co hybrid catalyst exhibits enhanced catalytic activity for activation of peroxymonosulfate (PMS) to degrade organic pollutants in water. Furthermore, taking advantage of the favorable magnetic properties, the catalyst can be easily recycled and reused for at least 4 runs with negligible loss of activity. Coupled with systematic investigation in terms of influential factors, mineralization, and radicals identification, make the catalyst hold significant potential for application in remediation of organic pollutants in water.

  18. Mussel-inspired approach to constructing robust cobalt-embedded N-doped carbon nanosheet toward enhanced sulphate radical-based oxidation.

    PubMed

    Zeng, Tao; Zhang, Haiyan; He, Zhiqiao; Chen, Jianmeng; Song, Shuang

    2016-01-01

    Heterogeneous sulphate radical based advanced oxidation processes (SR-AOPs) have lately been raised as a promising candidate for water treatment. Despite the progress made, either the stability or the performance of the current catalysts is still far from satisfactory for practical applications. Herein, using polydopamine-cobalt ion complex that inspired by mussel proteins as medium, we facilely fabricate a robust SR-AOPs catalyst with cobalt nanoparticles (NPs) embedded in nitrogen-doped reduced graphene oxide matrix (NRGO@Co). The NRGO scaffold with high porosity and surface area not only stabilizes the NPs but also greatly facilitates the accessibility and adsorption of substrates to the active sites. With the synergistic effect arising from the NRGO and Co NPs, the NRGO@Co hybrid catalyst exhibits enhanced catalytic activity for activation of peroxymonosulfate (PMS) to degrade organic pollutants in water. Furthermore, taking advantage of the favorable magnetic properties, the catalyst can be easily recycled and reused for at least 4 runs with negligible loss of activity. Coupled with systematic investigation in terms of influential factors, mineralization, and radicals identification, make the catalyst hold significant potential for application in remediation of organic pollutants in water. PMID:27616643

  19. Self-Stacked Reduced Graphene Oxide Nanosheets Coated with Cobalt-Nickel Hydroxide by One-Step Electrochemical Deposition toward Flexible Electrochromic Supercapacitors.

    PubMed

    Grote, Fabian; Yu, Zi-You; Wang, Jin-Long; Yu, Shu-Hong; Lei, Yong

    2015-09-01

    The implementation of an optical function into supercapacitors is an innovative approach to make energy storage devices smarter and to meet the requirements of smart electronics. Here, it is reported for the first time that nickel-cobalt hydroxide on reduced graphene oxide can be utilized for flexible electrochromic supercapacitors. A new and straightforward one-step electrochemical deposition process is introduced that is capable of simultaneously reducing GO and depositing amorphous Co(1-x)Ni(x)(OH)2 on the rGO. It is shown that the rGO nanosheets are homogeneously coated with metal hydroxide and are vertically stacked. No high temperature processes are used so that flexible polymer-based substrates can be coated. The synthesized self-stacked rGO-Co(1-x)Ni(x)(OH)2 nanosheet material exhibits pseudocapacitive charge storage behavior with excellent rate capability, high Columbic efficiency, and nondiffusion limited behavior. It is shown that the electrochemical behavior of the Ni(OH)2 can be modulated, by simultaneously depositing nickel and cobalt hydroxide, into broad oxidization and reduction bands. Further, the material exhibits electrochromic property and can switch between a bleached and transparent state. Literature comparison reveals that the performance characteristics of the rGO-Co(1-x)Ni(x)(OH)2 nanosheet material, in terms of gravimetric capacitance, areal capacitance, and long-term cycling stability, are among the highest reported values of supercapacitors with electrochromic property.

  20. Cobalt-ruthenium catalysts for Fischer-Tropsch synthesis

    SciTech Connect

    Iglesia, E.; Soled, S.L.; Fiato, R.A.

    1989-04-18

    A hydrocarbon synthesis process is described which comprises reacting hydrogen and carbon monoxide in the presence of a catalyst comprised of cobalt and ruthenium on titania, at reaction conditions suitable for the formation of higher hydrocarbons. The catalyst is prepared by impregnating titania with solutions of cobalt and ruthenium salts, drying the impregnated support, reducing the cobalt and ruthenium, treating the reduced metals with an oxygen containing stream at conditions sufficient to form oxides of cobalt and oxides of ruthenium and reducing the cobalt and ruthenium oxides.

  1. The role of layer structure in tin oxidation kinetics

    NASA Astrophysics Data System (ADS)

    Duhalde, S.; Arcondo, B.; Sirkin, H.

    1991-11-01

    Tin exhibits different oxidation kinetics which are composition dependent, when it forms intermetallic compounds with the chalcogenides S and Se. This phenomenon is related to the layer compounds SnS2 and SnSe2 crystalline structure. These minerals have anisotropic bonding characteristics, due to Van der Waals bonds presence between chalcogenides adjoining planes. The mentioned weak bonds allow the oxygen diffusion to the bulk, favouring the reaction with the inner tin atoms. In this work we study samples of Sn-S alloy with different thermal treatment by XRD and Mössbauer spectroscopy. Results are discussed and compared with those obtained for Sn-Se alloy in an early work [1].

  2. LiNiFe-based layered structure oxide and composite for advanced single layer fuel cells

    NASA Astrophysics Data System (ADS)

    Zhu, Bin; Fan, Liangdong; Deng, Hui; He, Yunjune; Afzal, Muhammad; Dong, Wenjing; Yaqub, Azra; Janjua, Naveed K.

    2016-06-01

    A layered structure metal oxide, LiNi0.1Fe0.90O2-δ (LNF), is explored for the advanced single layer fuel cells (SLFCs). The temperature dependent impedance profiles and concentration cells (hydrogen concentration, oxygen concentration, and H2/air atmospheres) tests prove LNF to be an intrinsically electronic conductor in air while mixed electronic and proton conductor in H2/air environment. SLFCs constructed by pure LNF materials show significant short circuiting reflected by a low device OCV and power output (175 mW cm-2 at 500 °C) due to high intrinsic electronic conduction. The power output is improved up to 640 and 760 mW cm-2, respectively at 500 and 550 °C by compositing LNF with ion conducting material, e.g., samarium doped ceria (SDC), to balance the electronic and ionic conductivity; both reached at 0.1 S cm-1 level. Such an SLFC gives super-performance and simplicity over the conventional 3-layer (anode, electrolyte and cathode) FCs, suggesting strong scientific and commercial impacts.

  3. Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

    NASA Astrophysics Data System (ADS)

    Comes, Ryan; Gu, Man; Khokhlov, Mikhail; Liu, Hongxue; Lu, Jiwei; Wolf, Stuart A.

    2013-01-01

    Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.

  4. Nanostructured cobalt oxides (Co{sub 3}O{sub 4} and CoO) and metallic Co powders synthesized by the solution combustion method

    SciTech Connect

    Toniolo, J.C.; Takimi, A.S.; Bergmann, C.P.

    2010-06-15

    The combustion synthesis technique using glycine and urea as fuels and cobalt nitrate as an oxidizer is capable of producing well-crystallized Co{sub 3}O{sub 4}, CoO, as well as metallic Co powders. An interpretation based on the thermodynamic viewpoint and the measurement of the combustion temperatures during the reactions occurring for various fuel-to-oxidant ratios was proposed for a study of the nature of combustion and its correlation with the characteristics of as-synthesized powders. The largest measured specific surface area of the powders was 36 m{sup 2}/g at a 0.14 glycine-to-nitrate ratio. The crystallites were nano-sized ranging from approximately 23 to 90 nm.

  5. A bioactive polymer grafted on titanium oxide layer obtained by electrochemical oxidation. Improvement of cell response.

    PubMed

    Hélary, Gérard; Noirclère, Flavie; Mayingi, Josselin; Bacroix, Brigitte; Migonney, Véronique

    2010-02-01

    The anchorage failure of titanium implants in human body is mainly due to biointegration problem. The proposed solution is to graft a bioactive polymer at the surface of the implant in order to improve and control the interactions with the living system. In this paper, we describe the grafting of poly sodium styrene sulfonate on titanium surface by using a silanization reaction. The key point is to increase the TiOH content at the surface of the implant which can react with methoxy silane groups of 3-methacryloxypropyltrimethoxysilane (MPS). Two procedures were used: chemical oxidation and electrochemical oxidation. The last oxidation procedure was carried out in two different electrolytes: oxalic acid and methanol. These different oxidation methods allow controlling the roughness and the depth of the oxide layer. The methacryloyl group of MPS grafted at the titanium surface by silanization reaction is copolymerized with sodium styrene sulfonate using a thermal initiator able to produce radicals by heating. Colorimetric method, ATR-FTIR, XPS techniques and contact angle measurements were applied to characterize the surfaces. MG63 osteoblastic cell response was studied on polished, oxidized and grafted titanium samples. Cell adhesion, Alkaline Phosphatase activity and calcium nodules formation were significantly enhanced on grafted titanium surfaces compared to un-modified surfaces.

  6. Layered CU-based electrode for high-dielectric constant oxide thin film-based devices

    DOEpatents

    Auciello, Orlando

    2010-05-11

    A layered device including a substrate; an adhering layer thereon. An electrical conducting layer such as copper is deposited on the adhering layer and then a barrier layer of an amorphous oxide of TiAl followed by a high dielectric layer are deposited to form one or more of an electrical device such as a capacitor or a transistor or MEMS and/or a magnetic device.

  7. Modification of surface oxide layers of titanium targets for increasing lifetime of neutron tubes

    SciTech Connect

    Zakharov, A. M. Dvoichenkova, O. A.; Evsin, A. E.

    2015-12-15

    The peculiarities of interaction of hydrogen ions with a titanium target and its surface oxide layer were studied. Two ways of modification of the surface oxide layers of titanium targets for increasing the lifetime of neutron tubes were proposed: (1) deposition of an yttrium oxide barrier layer on the target surface; (2) implementation of neutron tube work regime in which the target is irradiated with ions with energies lower than 1000 eV between high-energy ion irradiation pulses.

  8. Properties of nano-structured cuprous oxide thin films fabricated by thermal oxidation of copper layer

    NASA Astrophysics Data System (ADS)

    Gevorgyan, Vladimir; Reymers, Anna; Nersesyan, Manuk; Nitsche, Serge; Giorgio, Suzanne; Karapetyan, Artak; Marine, Wladimir

    2011-07-01

    Among the potential photovoltaic devices based on semiconductor oxides as active layer is cuprous oxide (Cu2O). Although the theoretical limit of Cu2O solar cell efficiency is 20%, the best efficiency obtained up to now is only 2%. This is due to a very limited amount of work devoted to this semiconductor and only during last few years this material has been investigated for solar cells applications. In this work we report our results of optical, structural and surface morphology investigations of Cu2O films prepared by thermal oxidation of copper layer. The effects of oxidation temperature and oxygen partial pressure on surface morphology and crystalline structure of Cu2O films were studied. Scanning electron microscope results have shown that Cu2O films have microcrystalline structure with grain size of about 5-15 μm. Analysis of fine structure shows typical lattice spacing of cubic Cu2O structure. X-ray investigations have shown that the films consist of single Cu2O phase without any interstitial phase and have a nano-grain structure. The grains have an average dimensions about (33-41) nm. Optical investigations have shown that the absorption edge of prepared films is due to a direct allowed transition. The value of the optical band gap is 2.08 eV.

  9. Iodine oxide in the global marine boundary layer

    NASA Astrophysics Data System (ADS)

    Prados-Roman, C.; Cuevas, C. A.; Hay, T.; Fernandez, R. P.; Mahajan, A. S.; Royer, S.-J.; Galí, M.; Simó, R.; Dachs, J.; Großmann, K.; Kinnison, D. E.; Lamarque, J.-F.; Saiz-Lopez, A.

    2015-01-01

    Emitted mainly by the oceans, iodine is a halogen compound important for atmospheric chemistry due to its high ozone depletion potential and effect on the oxidizing capacity of the atmosphere. Here we present a comprehensive data set of iodine oxide (IO) measurements in the open marine boundary layer (MBL) made during the Malaspina 2010 circumnavigation. Results show IO mixing ratios ranging from 0.4 to 1 pmol mol-1 (30% uncertainty) and, complemented with additional field campaigns, this data set confirms through observations the ubiquitous presence of reactive iodine chemistry in the global marine environment. We use a global model with organic (CH3I, CH2ICl, CH2I2 and CH2IBr) and inorganic (HOI and I2) iodine ocean emissions to investigate the contribution of the different iodine source gases to the budget of IO in the global MBL. In agreement with previous estimates, our results indicate that, globally averaged, the abiotic precursors contribute about 75 % to the IO budget. However, this work reveals a strong geographical pattern in the contribution of organic vs. inorganic precursors to reactive iodine in the global MBL.

  10. Spatial atomic layer deposition of zinc oxide thin films.

    PubMed

    Illiberi, A; Roozeboom, F; Poodt, P

    2012-01-01

    Zinc oxide thin films have been deposited at high growth rates (up to ~1 nm/s) by spatial atomic layer deposition technique at atmospheric pressure. Water has been used as oxidant for diethylzinc (DEZ) at deposition temperatures between 75 and 250 °C. The electrical, structural (crystallinity and morphology), and optical properties of the films have been analyzed by using Hall, four-point probe, X-ray diffraction, scanning electron microscopy, spectrophotometry, and photoluminescence, respectively. All the films have c-axis (100) preferential orientation, good crystalline quality and high transparency (∼ 85%) in the visible range. By varying the DEZ partial pressure, the electrical properties of ZnO can be controlled, ranging from heavily n-type conductive (with 4 mOhm.cm resistivity for 250 nm thickness) to insulating. Combining the high deposition rates with a precise control of functional properties (i.e., conductivity and transparency) of the films, the industrially scalable spatial ALD technique can become a disruptive manufacturing method for the ZnO-based industry.

  11. Oriented conductive oxide electrodes on SiO2/Si and glass

    DOEpatents

    Jia, Quanxi; Arendt, Paul N.

    2001-01-01

    A thin film structure is provided including a silicon substrate with a layer of silicon dioxide on a surface thereof, and a layer of cubic oxide material deposited upon the layer of silicon dioxide by ion-beam-assisted-deposition, said layer of cubic oxide material characterized as biaxially oriented. Preferably, the cubic oxide material is yttria-stabilized zirconia. Additional thin layers of biaxially oriented ruthenium oxide or lanthanum strontium cobalt oxide are deposited upon the layer of yttria-stabilized zirconia. An intermediate layer of cerium oxide is employed between the yttria-stabilized zirconia layer and the lanthanum strontium cobalt oxide layer. Also, a layer of barium strontium titanium oxide can be upon the layer of biaxially oriented ruthenium oxide or lanthanum strontium cobalt oxide. Also, a method of forming such thin film structures, including a low temperature deposition of a layer of a biaxially oriented cubic oxide material upon the silicon dioxide surface of a silicon dioxide/silicon substrate is provided.

  12. Magnetism and transport properties of layered rare-earth cobaltates Ln{sub 0.3}CoO{sub 2}

    SciTech Connect

    Knížek, K. Novák, P.; Jirák, Z.; Hejtmánek, J.; Maryško, M.; Buršík, J.

    2015-05-07

    The ab-initio (GGA+U) electronic structure calculations of layered cobaltates Ln{sub 0.3}CoO{sub 2} (Ln = La, Pr, Nd) prepared by ionic exchange from Na{sub 0.90}CoO{sub 2} precursors have been performed. The data are used for numerical modeling of Seebeck coefficient within Boltzmann transport theory using BoltzTraP program [G. K. H. Madsen and D. J. Singh, Comput. Phys. Commun. 175, 67 (2006)], as well as for determination of the crystal field split levels of rare-earth ions using a method based on a transformation of Bloch states into the basis of Wannier functions [P. Novák et al., Phys. Rev. B 87, 205139 (2013)]. An overall agreement with observed magnetism and transport properties is obtained. In particular, the high p-type thermopower is well reproduced in a broad temperature range, but instead of theoretical linear decrease down to the lowest temperatures, the real systems exhibit an anomalous change of Seebeck sign, which might be related to the change of bare metallic carriers into the polaronic ones.

  13. Ethylene Glycol Intercalated Cobalt/Nickel Layered Double Hydroxide Nanosheet Assemblies with Ultrahigh Specific Capacitance: Structural Design and Green Synthesis for Advanced Electrochemical Storage.

    PubMed

    Wang, Changhui; Zhang, Xiong; Xu, Zhongtang; Sun, Xianzhong; Ma, Yanwei

    2015-09-01

    Because of the rapid depletion of fossil fuels and severe environmental pollution, more advanced energy-storage systems need to possess dramatically improved performance and be produced on a large scale with high efficiency while maintaining low-enough costs to ensure the higher and wider requirements. A facile, energy-saving process was successfully adopted for the synthesis of ethylene glycol intercalated cobalt/nickel layered double hydroxide (EG-Co/Ni LDH) nanosheet assembly variants with higher interlayer distance and tunable transitional-metal composition. At an optimized starting Co/Ni ratio of 1, the nanosheet assemblies display a three-dimensional, spongelike network, affording a high specific surface area with advantageous mesopore structure in 2-5 nm containing large numbers of about 1.2 nm micropores for promoting electrochemical reaction. An unprecedented electrochemical performance was achieved, with a specific capacitance of 4160 F g(-1) at a discharge current density of 1 A g(-1) and of 1313 F g(-1) even at 50 A g(-1), as well as excellent cycling ability. The design and optimization of EG-Co/Ni LDH nanosheets in compositions, structures, and performances, in conjunction with the easy and relatively "green" synthetic process, will play a pivotal role in meeting the needs of large-scale manufacture and widespread application for advanced electrochemical storage. PMID:26258432

  14. Effect of La{sub 2}O{sub 3}-treatment on textural and solid-solid interactions in ferric/cobaltic oxides system

    SciTech Connect

    Fagal, Gehan A.; Badawy, Abdelrahman A.; Hassan, Neven A.; El-Shobaky, Gamil A.

    2012-10-15

    Pure and La{sub 2}O{sub 3}-containing (0.75-3.0 mol%) Fe{sub 2}O{sub 3}/Co{sub 3}O{sub 4} solids were prepared by thermal treatment of their carbonates at 500-700 Degree-Sign C. The produced solids were characterized using XRD, HRTEM, EDX and nitrogen adsorption at -196 Degree-Sign C. The results revealed that pure solids calcined at 600 and 700 Degree-Sign C consisted of nanosized CoFe{sub 2}O{sub 4} phase, while pure mixed solids calcined at 500 Degree-Sign C consisted of trace amount of CoFe{sub 2}O{sub 4} and unreacted Fe{sub 2}O{sub 3}, Co{sub 3}O{sub 4} phases. The presence of 0.75 mol% La{sub 2}O{sub 3} enhanced solid-solid interaction between Fe{sub 2}O{sub 3} and Co{sub 3}O{sub 4} at 500 Degree-Sign C yielding CoFe{sub 2}O{sub 4}. The ferrite phase existed also in all mixed oxides upon treated with La{sub 2}O{sub 3} besides LaCoO{sub 3} phase. LaCoO{sub 3} existed as a major phase in all mixed oxides treated with 3 mol% La{sub 2}O{sub 3}. La{sub 2}O{sub 3}-treatment modified the crystallite size of all phases present to an extent dependent on calcination temperature and amount of La{sub 2}O{sub 3} content. This treatment decreased effectively the S{sub BET} of all mixed solids. - Graphical Abstract: TEM photographs of pure mixed oxides calcined at 500 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Cobalt ferrite exhibit chemical stability, low electric loss and high coercivity. Black-Right-Pointing-Pointer Cobalt ferrite is used in microwave devices, computer memories and magnetic storage. Black-Right-Pointing-Pointer Solid-solid interactions in ferric/cobaltic oxides system were investigated. Black-Right-Pointing-Pointer La{sub 2}O{sub 3}-treatment modified surface compositions of the system investigated. Black-Right-Pointing-Pointer All phases present in various solids existed as nanosized solids.

  15. Nitric acid passivation of Ti6Al4V reduces thickness of surface oxide layer and increases trace element release.

    PubMed

    Callen, B W; Lowenberg, B F; Lugowski, S; Sodhi, R N; Davies, J E

    1995-03-01

    Passivation of Ti6Al4V and cpTi implants using methods based on the ASTM-F86 nitric acid protocol are used with the intention of reducing their surface reactivity, and consequently the corrosion potential, in the highly corrosive biologic milieu. The ASTM-F86 passivation protocol was originally developed for surgical implants made of stainless steel and chrome cobalt alloy. Using X-ray photoelectron spectroscopy (XPS) to examine the effect of nitric acid passivation on the surface oxide layer of mill-annealed Ti6Al4V and cpTi, we have found that such treatment actually reduced the oxide thickness on the alloy while having no significant effect on the pure metal. These results correlated with observations obtained using graphite furnace atomic absorption spectrophotometry (GFAAS) to detect trace element release from solid, mill-annealed, Ti6Al4V and cpTi into serum-containing culture medium. We detected significantly greater levels of Ti, Al, and V in the presence of passivated compared to nonpassivated Ti6Al4V. In contrast, nitric acid passivation did not influence Ti release from mill-annealed cpTi. These results, derived from two mill-annealed Ti-based metals, would indicate that re-examination of ASTM-F86-based passivation protocols with respect to Ti6Al4V should be considered in view of the widespread use of this alloy for biomedical devices. PMID:7615579

  16. Phase discrimination through oxidant selection in low-temperature atomic layer deposition of crystalline iron oxides.

    PubMed

    Riha, Shannon C; Racowski, Joy M; Lanci, Michael P; Klug, Jeffrey A; Hock, Adam S; Martinson, Alex B F

    2013-03-12

    Control over the oxidation state and crystalline phase of thin-film iron oxides was achieved by low-temperature atomic layer deposition (ALD), utilizing a novel iron precursor, bis(2,4-methylpentadienyl)iron. This low-temperature (T = 120 °C) route to conformal deposition of crystalline Fe3O4 or α-Fe2O3 thin films is determined by the choice of oxygen source selected for the second surface half-reaction. The approach employs ozone to produce fully oxidized α-Fe2O3 or a milder oxidant, H2O2, to generate the Fe(2+)/Fe(3+) spinel, Fe3O4. Both processes show self-limiting surface reactions and deposition rates of at least 0.6 Å/cycle, a significantly high growth rate at such mild conditions. We utilized this process to prepare conformal iron oxide thin films on a porous framework, for which α-Fe2O3 is active for photocatalytic water splitting.

  17. Anti-reflective conducting indium oxide layer on nanostructured substrate as a function of aspect ratio

    NASA Astrophysics Data System (ADS)

    Park, Hyun-Woo; Ji, Seungmuk; Lim, Hyuneui; Choi, Dong-won; Park, Jin-Seong; Chung, Kwun-Bum

    2016-09-01

    Antireflective conducting indium oxide layers were deposited using atomic layer deposition on a transparent nanostructured substrate grown using colloidal lithography. In order to explain the changes in the electrical resistivity and the optical transmittance of conducting indium oxide layers depending on various aspect ratios of the nanostructured substrates, we investigated the surface area and refractive index of the indium oxide layers in the film depth direction as a function of aspect ratio. The conformal indium oxide layer on a transparent nanostructured substrate with optimized geometry exhibited transmittance of 88% and resistivity of 7.32 × 10-4 Ω cm. The enhancement of electrical resistivity is strongly correlated with the surface area of the indium oxide layer depending on the aspect ratio of the nanostructured substrates. In addition, the improvement in transparency was explained by the gradual changes of the refractive index in the film depth direction according to the aspect ratio of the nanostructures.

  18. Nitrogen-doped carbon and high-content alumina containing bi-active cobalt oxides for efficient storage of lithium.

    PubMed

    Wu, Bibo; Zhang, Shilin; Yao, Feng; Huo, Ruijie; Zhang, Fazhi; Xu, Sailong

    2016-01-15

    Low-content ultrathin coating of non-active alumina (Al2O3) has been extensively utilized as one of the most effective strategies to improve electrochemical performances of electrodes for lithium-ion batteries (LIBs), however, typically by employing expensive atomic layer deposition equipment. We herein demonstrate a simple preparation of high-content and well-dispersed Al2O3 (24.33wt.%)-containing multi-component composite (CoO/Co3O4/N-C/Al2O3) by calcination of melamine/CoAl-layered double hydroxide (CoAl-LDH) mixture. The resulting composite bundles the advantages expected to improve electrochemical performances: (i) bi-active CoO/Co3O4, (ii) highly conductive N-doped carbon, and (iii) N-doped carbon and high-content non-active Al2O3 as buffering reagents, as well as (iv) good distribution of bi- and non-active components resulted from the lattice orientation and confinement effect of the LDH layers. Electrochemical evaluation shows that the composite electrode delivers a highly enhanced reversible capacity of 1078mAhg(-1) after 50cycles at 100mAg(-1), compared with the bi-active CoO/Co3O4 mixtures with and without non-active Al2O3. Transmission electron microscopy/scanning electron microscopy observations and electrochemical impedance spectra experimentally provide the information on the good distributions of multiple components and the improved conductivity underlying the enhancements, respectively. Our LDH precursor-based preparation route may be extended to design and prepare various multi-component transition metal oxides for efficient lithium storage.

  19. Atomic layer deposited gallium oxide buffer layer enables 1.2 V open-circuit voltage in cuprous oxide solar cells.

    PubMed

    Lee, Yun Seog; Chua, Danny; Brandt, Riley E; Siah, Sin Cheng; Li, Jian V; Mailoa, Jonathan P; Lee, Sang Woon; Gordon, Roy G; Buonassisi, Tonio

    2014-07-16

    The power conversion efficiency of solar cells based on copper (I) oxide (Cu2 O) is enhanced by atomic layer deposition of a thin gallium oxide (Ga2 O3 ) layer. By improving band-alignment and passivating interface defects, the device exhibits an open-circuit voltage of 1.20 V and an efficiency of 3.97%, showing potential of over 7% efficiency.

  20. Layer-by-layer assembly of functionalized reduced graphene oxide for direct electrochemistry and glucose detection.

    PubMed

    Mascagni, Daniela Branco Tavares; Miyazaki, Celina Massumi; da Cruz, Nilson Cristino; de Moraes, Marli Leite; Riul, Antonio; Ferreira, Marystela

    2016-11-01

    We report an electrochemical glucose biosensor made with layer-by-layer (LbL) films of functionalized reduced graphene oxide (rGO) and glucose oxidase (GOx). The LbL assembly using positively and negatively charged rGO multilayers represents a simple approach to develop enzymatic biosensors. The electron transport properties of graphene were combined with the specificity provided by the enzyme. rGO was obtained and functionalized using chemical methods, being positively charged with poly(diallyldimethylammonium chloride) to form GPDDA, and negatively charged with poly(styrene sulfonate) to form GPSS. Stable aqueous dispersions of GPDDA and GPSS are easily obtained, enabling the growth of LbL films on various solid supports. The use of graphene in the immobilization of GOx promoted Direct Electron Transfer, which was evaluated by Cyclic Voltammetry. Amperometric measurements indicated a detection limit of 13.4μmol·L(-1) and sensitivity of 2.47μA·cm(-2)·mmol(-1)·L for glucose with the (GPDDA/GPSS)1/(GPDDA/GOx)2 architecture, whose thickness was 19.80±0.28nm, as determined by Surface Plasmon Resonance (SPR). The sensor may be useful for clinical analysis since glucose could be detected even in the presence of typical interfering agents and in real samples of a lactose-free milk and an electrolyte solution to prevent dehydration. PMID:27524075