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Sample records for anodic polarization behavior

  1. Anodic polarization behavior of pure copper in carbonate solutions

    International Nuclear Information System (INIS)

    Kawasaki, Manabu; Taniguchi, Naoki; Naitou, Morimasa

    2008-03-01

    Copper is one of the candidate materials for overpacks. The redox condition at the early stage of the post closure will be oxidizing. In order to understand the influence of environmental factors on the corrosion behavior of copper in such oxidizing environment, anodic polarization tests were performed in carbonate aqueous solution with varying the concentration of representative chemical species in groundwater. As the results of potentiodynamic and potentiostatic tests, anodic polarization behavior of pure copper was summarized as follows; Carbonate ion and bicarbonate ion promoted the passivation of pure copper, and suppressed the initiation of film breakdown. Chloride ion promoted both the active dissolution and initiation of film breakdown of pure copper. The influence of sulfate ion and pH was small, but the action of sulfate ion to the pure copper was similar to that of chloride ion, and the increase of pH was likely to promote the passivation and suppress the initiation of film breakdown. The film breakdown potential, Eb, was represented as a function of the ratio of aggressive ion and inhibiting ion such as [Cl - ]/[HCO 3 - ], [SO 4 2- ]/[HCO 3 - ]. When the ratio exceeds a certain value, the anodic polarization curve becomes active dissolution type so that no macroscopic film breakdown can not be occurred. The lower limit of Eb in passive type region was estimated to be about -200 mV vs. SCE. As the results of potentio static tests, the corrosion form near the Eb was uniform dissolution over the surface, but pitting corrosion and non-uniform corrosion occurred according to the condition of the test solution. Neither pitting corrosion nor non-uniform corrosion occurred at the potential below Eb in every test cases. (author)

  2. Anodic polarization behavior and film breakdown potential of pure copper in the simulated geological environment containing carbonate

    International Nuclear Information System (INIS)

    Kawasaki, Manabu; Taniguchi, Naoki; Naito, Morimasa

    2009-01-01

    In order to clarify the influence of environmental factors on the corrosion behavior of copper overpacks in oxidizing environment, potentiodynamic and potentiostatic anodic polarization tests were performed in carbonate aqueous solutions at 80degC. As the results, the passivation was promoted and film breakdown was suppressed in higher carbonate concentrations, in lower chloride ion concentrations, and in higher pH conditions. The sulfate ion tended to promote the film breakdown of copper. The effects of the composition of the test solutions on the anodic polarization curve of copper in bentonite/sand mixture were quite smaller than those in simple aqueous solution. By comparison with previous data for lower temperature condition, it was clarified that passivation of copper was promoted in higher temperature condition, but breakdown potential, Eb was independent of temperature. The Eb, was expressed as a function of the ratio of aggressive ion and inhibiting ion such as [Cl - ]/[HCO 3 - ] and [SO 4 2- ]/[HCO 3 - ], and it was confirmed that the Eb was lowered with increasing the ratio. When the ratio exceeds a certain value, the Eb was no longer able to be determined since the anodic polarization curve becomes active dissolution type. The lower limit of Eb in passive type region was estimated to be about -200 mV vs. SCE. The results of potentiostatic tests showed that pitting corrosion or non-uniform corrosion was observed at the potentials over Eb or second current peak potentials in anodic polarization curve. (author)

  3. Tungsten behaviour under anodic polarization

    International Nuclear Information System (INIS)

    Vas'ko, A.T.; Patsyuk, F.N.

    1980-01-01

    Electrochemical investigations have been carried out to identify the state of elements of the tungsten galvanic coating. Active zones on anode polarization curves in the hydrogen region of galvanic tungsten are established. The difference in the behaviour of monocrystal and galvanic tungsten electrodes is shown to be connected with the oxidation of hydrogen in the galvanic sediment

  4. Anodic behavior of Al-Zn-In sacrificial anodes at different concentration of zinc and indium

    Energy Technology Data Exchange (ETDEWEB)

    Keyvani, Ahmad [Shahrekord Univ. (Iran, Islamic Republic of). Dept. of Materials Engineering; Tehran Univ. (Iran, Islamic Republic of). School of Metallurgy and Materials; Saremi, Mohsen [Tehran Univ. (Iran, Islamic Republic of). School of Metallurgy and Materials; Saeri, Mohammad Reza [Shahrekord Univ. (Iran, Islamic Republic of). Dept. of Materials Engineering

    2012-12-15

    Al-Zn-In anodes show better performance due to the beneficial effects of Zn and In on prevention of aluminum passivity and producing a homogeneous structure for uniform corrosion of the anodes. However, there are different views about the optimum concentration of each element in the anode. In this study, the anodic behavior of Al-Zn-In alloy with different concentrations of zinc from 1 to 6wt.% and indium from 0.01 to 0.05wt.% are studied. The NACE efficiency test and polarization are used in 3wt.% NaCl solution for corrosion characterization. The results showed that zinc and indium change the anode potential to more active potentials and improve the microstructure uniformity of anodes. The latter leads to more uniform corrosion. Optimum concentrations of zinc (5wt.%) and indium (0.02wt.%) were found in this respect. (orig.)

  5. DMFC anode polarization: Experimental analysis and model validation

    Energy Technology Data Exchange (ETDEWEB)

    Casalegno, A.; Marchesi, R. [Dipartimento di Energetica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2008-01-03

    Anode two-phase flow has an important influence on DMFC performance and methanol crossover. In order to elucidate two-phase flow influence on anode performance, in this work, anode polarization is investigated combining experimental and modelling approach. A systematic experimental analysis of operating conditions influence on anode polarization is presented. Hysteresis due to operating condition is observed; experimental results suggest that it arises from methanol accumulation and has to be considered in evaluating DMFC performances and measurements reproducibility. A model of DMFC anode polarization is presented and utilised as tool to investigate anode two-phase flow. The proposed analysis permits one to produce a confident interpretation of the main involved phenomena. In particular, it confirms that methanol electro-oxidation kinetics is weakly dependent on methanol concentration and that methanol transport in gas phase produces an important contribution in anode feeding. Moreover, it emphasises the possibility to optimise anode flow rate in order to improve DMFC performance and reduce methanol crossover. (author)

  6. Polarization Induced Deterioration of Reinforced Concrete with CFRP Anode.

    Science.gov (United States)

    Zhu, Ji-Hua; Wei, Liangliang; Zhu, Miaochang; Sun, Hongfang; Tang, Luping; Xing, Feng

    2015-07-15

    This paper investigates the deterioration of reinforced concrete with carbon fiber reinforced polymer (CFRP) anode after polarization. The steel in the concrete was first subjected to accelerated corrosion to various extents. Then, a polarization test was performed with the external attached CFRP as the anode and the steel reinforcement as the cathode. Carbon fiber reinforced mortar and conductive carbon paste as contact materials were used to adhere the CFRP anode to the concrete. Two current densities of 1244 and 2488 mA/m², corresponding to the steel reinforcements were applied for 25 days. Electrochemical parameters were monitored during the test period. The deterioration mechanism that occurred at the CFRP/contact material interface was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The increase of feeding voltage and the failure of bonding was observed during polarization process, which might have resulted from the deterioration of the interface between the contact material and CFRP. The formation and accumulation of NaCl crystals at the contact material/CFRP interface were inferred to be the main causes of the failure at the interface.

  7. Effect of friction on anodic polarization properties of metallic biomaterials.

    Science.gov (United States)

    Okazaki, Yoshimitsu

    2002-05-01

    The effect of friction on the anodic polarization properties of metallic biomaterials in a physiological saline solution was investigated. The current density during friction becomes higher than during the static condition. The fluctuation range of the current density caused by the destruction and formation of passive film was observed. For SUS316L stainless steel and Co-Cr-Mo casting alloy, the fluctuation range was observed in the passivity zone. Otherwise, for Ti alloys, the fluctuation range was observed in both the activity and passivity zones. The decrease of the corrosion potential for Ti alloys due to friction was much larger than that of SUS316L stainless steel and Co-Cr-Mo casting alloy. From this result, it was considered that in a the frictional environment, the stressing zone turned anodic and its periphery cathodic, and corrosion tended to progress more than in the static environment. The effect of wear on the anodic polarization curves also changed depending on the frictional load, potential zone and the pH of the solution. A rapid increase in current density due to corrosion starting from the frictional area was found in the Ti-6Al-4V and Ti-15Mo-5Zr-3Al alloys containing Al. However, for the new Ti-15Zr-4Nb-4Ta alloy, this rapid increase was not seen in the high-potential region. The effect of the lateral reciprocal speed was also negligible for the new Ti alloy. It was found that the new Ti-15Zr-4Nb-4Ta alloy exhibited excellent corrosion resistance under friction.

  8. Electrocnecical behaviour of zirconium during its anodic polarization in nitrate solutions

    International Nuclear Information System (INIS)

    Stabrovskij, A.I.; Karasev, A.F.

    1983-01-01

    Electrochemical behaviour of zirconium during its anodic polarization in nitrate solutions is investigated in detail to find the method of its complete dissolution. A study has been made of the influence of varioUs factors: current density electric potential, composition and temperature of the solution, anodic polarization duration on the Zr anodic polarization in nitric acid, on the maximum permissible current density and on the zirconium yield to the solution. The zirconium polarization decreases with an acid concentration and temperature increase and increases with the current density. Iron nitrate additions to nitric acid decrease, while ammonium fluoride additions increase zirconium yield into the solution

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

    Science.gov (United States)

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

    2014-12-01

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

  10. Magnesium sacrificial anode behavior at elevated temperature

    International Nuclear Information System (INIS)

    Othman, Mohsen Othman

    2006-01-01

    Magnesium sacrificial anode coupled to mild steel was tasted in sodium chloride and tap water environments at elevated temperatures. The anode failed to protect the mild steel specimens in tap water environment at all temperatures specified. This was partly due to low conductivity of this medium. The temperature factor did not help to activate the anode in this medium. In sodium chloride environment the anode demonstrated good protection for steel cathodes. The weight loss was high for magnesium in sodium chloride environment particularly beyond 60 degree centigrade. In tap water environment the weight loss was negligible for the anode. It also suffered localized shallow pitting corrosion. Magnesium anode cannot be utilized where high temperature is involved particularly in high conductivity mediums. Protection of structures containing high resistivity waters is not feasible using sacrificial anode system. (author)

  11. Anodic behavior of nickel alloys in media containing bicarbonate ions

    International Nuclear Information System (INIS)

    Zadorozne, N.S; Carranza, R. M.; Giordano, C.M.

    2011-01-01

    Alloy 22 has been designed to resist corrosion in oxidizing and reducing conditions. Thanks to these properties it is considered a possible candidate for the fabrication of containers of high-level radioactive waste. Since the containers provide services in natural environments characterized by multi-ionic solutions, it is estimated they could suffer three types of deterioration: general corrosion, localized corrosion (specifically crevice corrosion) and stress corrosion cracking (SCC). It has been confirmed that the presence of bicarbonate and chloride ions is required in order to produce cracking. It has also been determined that the susceptibility to SCC could be related to the occurrence of an anodic peak in the polarization curves in these media potentials below trans-passivity. The aim of this work is to study the anodic behavior of Alloy 22 in different media containing bicarbonate and chloride ions in various concentrations and temperatures and compare the results with other alloys containing nickel, and relate them to the susceptibility to stress corrosion cracking in a future job. Polarization curves were made on alloy 22 (Ni-Cr-Mo), 600 (Ni- Cr-Fe), 800h (Ni-Fe- Cr) and 201 (Ni commercially pure) in the following environments: 1.148 mol/L NaHCO 3 , 1.148 mol/L NaHCO 3 + 1 mol/L NaCl, 1.148 mol/L NaHCO 3 + 0.1 mol/L NaCl. The tests were performed at the following temperatures: 90°C, 75°C, 60°C and 25°C. It was found that alloy 22 has a current peak in the anodic domain at potentials below trans-passivity between 200 and 300 m VECS, when the test temperature was 90°C. The potential, at which this peak occurred, increased with decreasing temperature. Also there was a variation of the peak with the composition of the solution. When bicarbonate ions were added to a solution containing chloride ions, the peak potential shifted to higher current densities, depending on the concentration of added chloride ions. It was found that diminishing the content of

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

    International Nuclear Information System (INIS)

    Lee, W; Nielsch, K; Goesele, U

    2007-01-01

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

  13. Anodic polarization of carbon graphite electrodes in chloride fluoride melts zirconium containing

    International Nuclear Information System (INIS)

    Lyapustin, A.A.; Kanashin, Yu.P.; Nichkov, I.F.; Smyshlyaev, V.Yu.

    1985-01-01

    Polarization of carbon graphite anodes in zircorium containing chloride fluoride melts of the KCl-K 2 ZrF 6 -KF composition at molar ratios [F]:[Zr] being equal to 6, 12, 18, 24, 30 has been studied. K 2 ZrF 6 concentration constitutes 25; 18.9; 15.2; 12.7; 11.8% (by mass), correspondingly. Vitreous carbon (VC-2500), high purity graphite and graphite EhG-0 have been used as anodic materials. Anodic polarization curves have been obtained under electrotype steady-state conditions at 973, 1023, 1073 K. Influence of concentration of fluorine ions in melt on polarization of carbon graphite anodes is shown. Content growth of fluorine ions in melt leads to shift of steady-state anode potentials to their negative values regardless a graphite mark. The most con siderable potential shift on 0.5 V takes plase at molar ratio [F]:[Zr] increasing from 6 to 12. Temperature increase, as measurements showed, doesn't influence greatly on polarization curve shape

  14. The anodizing behavior of aluminum in malonic acid solution and morphology of the anodic films

    Science.gov (United States)

    Ren, Jianjun; Zuo, Yu

    2012-11-01

    The anodizing behavior of aluminum in malonic acid solution and morphology of the anodic films were studied. The voltage-time response for galvanostatic anodization of aluminum in malonic acid solution exhibits a conventional three-stage feature but the formation voltage is much higher. With the increase of electrolyte concentration, the electrolyte viscosity increases simultaneously and the high viscosity decreases the film growth rate. With the concentration increase of the malonic acid electrolyte, the critical current density that initiates local "burning" on the sample surface decreases. For malonic acid anodization, the field-assisted dissolution on the oxide surface is relatively weak and the nucleation of pores is more difficult, which results in greater barrier layer thickness and larger cell dimension. The embryo of the porous structure of anodic film has been created within the linear region of the first transient stage, and the definite porous structure has been established before the end of the first transient stage. The self-ordering behavior of the porous film is influenced by the electrolyte concentration, film thickness and the applied current density. Great current density not only improves the cell arrangement order but also brings about larger cell dimension.

  15. Polarization behavior of new and used lead alloys in acid sulfate solutions

    Energy Technology Data Exchange (ETDEWEB)

    Yu, P.; O' Keefe, T.J. [Univ. of Missouri-Rolla, Materials Research Center and Dept. of Metallurgical Engineering, Rolla, Missouri (United States)

    2001-07-01

    Polarization and Electrochemical impedance were used to study various lead alloys commercially used to electrowin zinc and copper from acidic sulfate solutions. Anode specimens that had been in service at several electrowinning operations were tested and their electrochemical performance was compared to that obtained from new anode samples. Tests were conducted in sulfuric acid. Cyclic voltammetry was used in a potential range in which both Pb{sup +2} and Pb{sup +4} formed stable phases. Selected polarization tests were also made to study a number of variables, including changes in the concentration of cobalt and manganese in the electrolyte. Results showed that the phases formed on the surface of the anode were critical in defining the electrochemical behavior of the anodes. In particular, certain active phases, which were depolarizing were identified on some of the used anodes. It was possible to duplicate some of these phases in the laboratory. (author)

  16. Anodic behavior of stainless-steel substrate in organic electrolyte solutions containing different lithium salts

    International Nuclear Information System (INIS)

    Furukawa, Kazuki; Yoshimoto, Nobuko; Egashira, Minato; Morita, Masayuki

    2014-01-01

    Highlights: • We investigated anodic behavior of stainless-steel in organic electrolytes for advanced capacitor. • Anion of the electrolyte affected the anodic stability of the alloy. • Anodic passivation occurs in LiPF 6 solution but pitting or active dissolution proceeds in other electrolyte solutions. • Fluoride source in the solution contributes to forming a stable surface layer on the stainless steel. - Abstract: The anodic behavior of austenitic stainless-steel, SUS304, as a current collector of positive electrode in lithium-ion battery/capacitor has been investigated in organic electrolyte solutions based on a mixed alkyl carbonate solvent with different lithium salts. Stable passivation characteristics were observed for the stainless-steel in the LiPF 6 solution, but pitting corrosion or active dissolution proceeded in the solutions containing other anions, BF 4 - , (CF 3 SO 2 ) 2 N - (TFSA - ) and ClO 4 - . The mass ratios of the dissolved metal species in the solutions of LiTFSA and LiClO 4 were equivalent to that of the alloy composition, which suggests that no preferential dissolution occurs during the anodic polarization in these electrolyte solutions. An HF component formed by decomposition of PF 6 - with the contaminate water will act as an F - source for the formation of a surface fluoride layer, that will contribute to the anodic stability of SUS304 in the LiPF 6 solution. The anodic corrosion in the LiTFSA solution was suppressed in part by mixing the PF 6 salt or adding HF in the electrolyte

  17. Corrosion rate of construction materials in hot phosphoric acid with the contribution of anodic polarization

    DEFF Research Database (Denmark)

    Kouril, M.; Christensen, Erik; Eriksen, S.

    2011-01-01

    The paper is focused on selection of a proper material for construction elements of water electrolysers, which make use of a 85% phosphoric acid as an electrolyte at temperature of 150 8C and which might be loaded with anodic polarization up to 2.5 V versus a saturated Ag/AgCl electrode (SSCE...

  18. Anodic behavior of alloy 22 in bicarbonate containing media: Effect of alloying

    International Nuclear Information System (INIS)

    Zadorozne, N S; Giordano, C M; Rebak, R B; Ares, A E; Carranza, R M

    2012-01-01

    Alloy 22 is one of the candidates for the manufacture of high level nuclear waste containers. These containers provide services in natural environments characterized by multi-ionic solutions.It is estimated they could suffer three types of deterioration: general corrosion, localized corrosion (specifically crevice corrosion) and stress corrosion cracking (SCC). It has been confirmed that the presence of bicarbonate and chloride ions is necessary to produce cracking, . It has also been determined that the susceptibility to SCC could be related to the occurrence of an anodic peak in the polarization curves in these media at potentials below transpassivity. The aim of this work is to study the effect of alloying elements on the anodic behavior of Alloy 22 in media containing bicarbonate and chloride ions at different concentrations and temperatures. Polarization curves were made on alloy 22 (Ni-22% Cr-13% Mo), Ni-Mo (Ni-28, 5% Mo) and Ni-Cr (Ni-20% Cr) in the following solutions: 1 mol/L NaCl at 90 o C, and 1.148 mol/L NaHCO 3 ; 1.148 mol/L NaHCO 3 + 1 mol/L NaCl; 1.148 mol/L NaHCO 3 + 0.1 mol/L NaCl, at 90 o C, 75 o C, 60 o C and 25 o C. It was found that alloy 22 has a anodic current density peak at potentials below transpassivity, only in the presence of bicarbonate ions. Curves performed in 1 mol/L NaCl did not show any anodic peak, in any of the tested alloys. The curves made on alloys Ni-Mo and Ni-Cr in the presence of bicarbonate ions, allowed to determine that Cr, is responsible for the appearance of the anodic peak in alloy 22. The curves of alloy Ni-Mo showed no anodic peak in the studied conditions. The potential at which the anodic peak appears in alloy 22 and Ni-Cr alloy, increases with decreasing temperature. The anodic peak was also affected by solution composition. When chloride ion is added to bicarbonate solutions, the anodic peak is shifted to higher potential and current densities, depending on the concentration of added chloride ions (author)

  19. Polarization behavior of lithium electrode in polymetric solid electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, Yoshiharu (Dept. of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Yamaguchi Univ., Ube (Japan)); Morita, Masayuki (Dept. of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Yamaguchi Univ., Ube (Japan)); Tsutsumi, Hiromori (Dept. of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Yamaguchi Univ., Ube (Japan))

    1993-04-15

    Complexes of novel polymer matrices and lithium salts have been prepared as polymeric solid electrolytes for lithium batteries. Poly(ethylene oxide)-grafted poly(methylmethacrylate) (PEO-PMMA) and poly(methylsiloxane) (PMS) were used as the matrices. The conductance behavior of the complexes and the basic polarization characteristics of the lithium electrode in the polymeric electrolytes were studied. As high conductivities as 10[sup -3] S cm[sup -1] were obtained at room temperature for the PMMA-based electrolytes containing some liquid plasticizer. Limiting current densities of 3 to 5 mA cm[sup -2] were observed for the anodic and cathodic polarization of the lithium electrode. The transport number of Li[sup +] was approximately unity in 'single-ion type' PMS-based electrolyte, in which the polarization curve of the lithium electrode showed no current hysteresis. (orig.)

  20. Corrosion behaviour of nickel during anodic polarization in chloride solution

    International Nuclear Information System (INIS)

    Memon, S.A.; Isani, A.A.; Memon, A.N.

    1998-01-01

    This research presents the effect of oxygen and nitrogen on the corrosion behaviour of nickel in the chloride solution, at the steady state polarized and unpolarized potentials. The additives were selected from those, which are used for bright nickel plating. It was observed that the agitation of electrolyte in a particular pH-(Cl)' range increase the potentials in comparison of the potentials to the un-agitated electrolytes. (author)

  1. Description of SOFC anode behavior by a mathematical modelling procedure

    International Nuclear Information System (INIS)

    Ielo, I.; Maggio, G.; Antonucci, V.; Giordano, N.

    1993-01-01

    One of the principal objectives in the development of SOFC is the identification of a stable Ni-cermet anode material with low polarization at high current density. In this respect, a mathematical approach, based on theoretical considerations, has been made in order to identify the optimal combination of geometrical and morphological characteristics of the system. The two limiting cases of diffusion-controlled and kinetic-controlled mechanisms are taken into account. Results in terms of limiting current have been treated by substituting into the related equations morphological parameters (surface area and pore size distribution of the support, metal content and surface area, electrode film thickness). Results are compared to existing experimental data and the influence of various parameters on the overall anode performance is evaluated. 2 tabs., 24 refs

  2. Effect of calcium on the electrochemical behavior of lithium anode in LiOH aqueous solution used for lithium–water battery

    International Nuclear Information System (INIS)

    Zhang Ziyan; Chen Kanghua; Ni Erfu

    2012-01-01

    The effect of minor addition of calcium to lithium anode on the electrochemical behavior of lithium anode in 4 M LiOH at 30 °C temperature is investigated by hydrogen collection, polarization curves and electrochemical impedance spectroscopy. The results show that the hydrogen evolution rate is marginally reduced with increasing calcium content. Addition of calcium to lithium mainly inhibits the anodic process. Minor addition of calcium to lithium slightly reduced the discharge current of lithium anode. Minor addition of calcium to lithium anode marginally enhances the hydrogen inhibition of lithium by the formation of calcium hydride combined with LiOH and LiOH·H 2 O formed on the anode surface.

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

    Science.gov (United States)

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

    2013-11-01

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

  4. Electrocoagulation of whey acids: anode and cathode materials, electroactive area and polarization curves

    Directory of Open Access Journals (Sweden)

    Francisco Prieto Garcia

    2017-06-01

    Full Text Available Anode (Al and Fe and cathode (graphite and Ti/RuO2 materials have been tested for electrocoagulation (EC and purification of the acid whey. The electroactive areas (EA of electrodes were calculated by the double layer capacitance method. Experiments were performed by cyclic voltammetry, chronoamperometry and polarization experiments. Among cathodic materials, the Ti/RuO2 electrode showed higher EA (2167 cm2 than graphite (1560 cm2. The Fe anode was found more stable than Al with greater charge transfer carried out in less time. Correlation of these results with those obtained during preliminary tests confirmed high removals (79 % in 8 h. For the Al electrode, 24 h were required to achieve efficiency of 49 %.

  5. Polarization characteristics of RTO anodes in the conditions of sodium chlorate preparation

    International Nuclear Information System (INIS)

    Ehberil', V.I.; Fedotova, N.S.; Novikov, E.A.

    1997-01-01

    By the method of polarization curves plotting in galvanostatic conditions in chloride-chlorate solutions of different compositions at different pH and temperatures it is shown that critical potential for oxide ruthenium-titanium anodes at current density less than 0.7 A/cm 2 is reached in solutions with NaCl concentration 50 g/l and low. The mechanism of potential transition to supercritical range is considered on the basis of ruthenium-water system analysis. (author)

  6. Anodic behavior of Mg in acidic AlCl3–1-ethyl-3-methyl-imidazolium chloride ionic liquid

    International Nuclear Information System (INIS)

    Xu, Bajin; Qu, Rui; Ling, Guoping

    2014-01-01

    Highlights: • A viscous layer formed at Mg/ionic liquid interface after the dissolution of Mg. • As direct evidence, photo of viscous layer at the interface was presented. • Viscous layer was resulted from accumulation of dissolved Mg(II) at interface. • Formation of viscous layer resulted in a homogenous etched Mg surface. • Dissolution model of Mg and formation mechanism of viscous layer was discussed. - Abstract: In this paper, anodic behavior of Mg in acidic AlCl 3 –1-ethyl-3-methyl-imidazolium chloride (AlCl 3 –EMIC) ionic liquid was investigated by conducting linear sweep voltammetry, chronoamperometry and chonopotentiometry. The viscosity of Mg dissolved ionic liquid and the surface morphologies of Mg were characterized using an Ostwald viscometer and a scanning electron microscopy, respectively. The results showed that the oxide film on the surface of Mg had great effects on the anodic behavior. The dissolution of Mg under anodic polarization occurred after the breakdown of oxide film. A viscous layer was observed forming at the interface of Mg/ionic liquid during the dissolution process. The formation of viscous layer was attributed to the accumulation of Mg dissolved AlCl 3 –EMIC ionic liquid at the interface, which was of high viscosity. With a viscous layer formed in the anodic process, the etched surface of Mg anode was homogeneous and flat without any etching pits. Otherwise, the Mg showed a morphology of pitting on the surface

  7. Zinc sacrificial anode behavior at elevated temperatures in sodium chloride and tap water environments

    International Nuclear Information System (INIS)

    Othman, Othman Mohsen

    2005-01-01

    Zinc sacrificial anode coupled to mild steel was tested in sodium chloride and tap water environments at elevated temperatures. The anode failed to protect the mild steel specimens in tap water environment at all temperatures specified for this study. This was partly due to the high resistivity of the medium. The temperature factor did not help to activate the anode in water tap medium. In sodium chloride environment the anode demonstrated good protection for steel cathodes. In tap water environment the anode weight loss was negligible. The zinc anode suffered intergranular corrosion in sodium chloride environment and this was noticed starting at 40 degree centigrade. In tap water environment the zinc anode demonstrated interesting behavior beyond 60 degree centigrade, that could be attributed to the phenomenon of reversal of potential at elevated temperatures. It also showed shallow pitting spots in tap water environment without any sign of intergranular corrosion. Zinc anodes would suffer intergranular corrosion at high temperatures. (author)

  8. Corrosion rate of construction materials in hot phosphoric acid with the contribution of anodic polarization

    Energy Technology Data Exchange (ETDEWEB)

    Kouril, M. [Institute of Chemical Technology, Technicka 5, 166 28 Prague (Czech Republic); Christensen, E. [Technical University of Denmark, Kemitorvet, 2800 Kgs. Lyngby (Denmark); Eriksen, S.; Gillesberg, B. [Tantaline A/S, Nordborgvej 81, 6430 Nordborg (Denmark)

    2012-04-15

    The paper is focused on selection of a proper material for construction elements of water electrolysers, which make use of a 85% phosphoric acid as an electrolyte at temperature of 150 C and which might be loaded with anodic polarization up to 2.5 V versus a saturated Ag/AgCl electrode (SSCE). Several grades of stainless steels were tested as well as tantalum, niobium, titanium, nickel alloys and silicon carbide. The corrosion rate was evaluated by means of mass loss at free corrosion potential as well as under various levels of polarization. The only corrosion resistant material in 85% phosphoric acid at 150 C and at polarization of 2.5 V/SSCE is tantalum. In that case, even a gentle cathodic polarization is harmful in such an acidic environment. Hydrogen reduction leads to tantalum hydride formation, to loss of mechanical properties and to complete disintegration of the metal. Contrary to tantalum, titanium is free of any corrosion resistance in hot phosphoric acid. Its corrosion rate ranges from tens of millimetres to metres per year depending on temperature of the acid. Alloy bonded tantalum coating was recognized as an effective corrosion protection for both titanium and stainless steel. Its serviceability might be limited by slow dissolution of tantalum that is in order of units of mm/year. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

    Science.gov (United States)

    Fattah-Alhosseini, Arash; Khan, Hamid Yazdani

    2017-06-01

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

  10. Anodic galvanostatic polarization of AA2024-T3 aircraft alloy in conventional mineral acids

    Energy Technology Data Exchange (ETDEWEB)

    Kozhukharov, S., E-mail: stephko1980@abv.bg [Department of Chemical Sciences, University of Chemical Technology and Metallurgy, 8 “Kliment Okhridski” Blvd, 1756, Sofia (Bulgaria); Girginov, Ch. [Department of Chemical Sciences, University of Chemical Technology and Metallurgy, 8 “Kliment Okhridski” Blvd, 1756, Sofia (Bulgaria); Avramova, I. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Science, 11 “Georgi Bonchev” Str., 1113, Sofia (Bulgaria); Machkova, M. [Department of Chemical Sciences, University of Chemical Technology and Metallurgy, 8 “Kliment Okhridski” Blvd, 1756, Sofia (Bulgaria)

    2016-09-01

    The present study is devoted to the determination of the impact of the anodization of AA2024-T3 alloys in HCl, HNO{sub 3}, H{sub 2}SO{sub 4} or H{sub 3}PO{sub 4} on the samples’ surface morphology and properties. Subsequent systematic assessments were performed by Scanning Electron Microscopy (SEM), Energy Dispersion X-Ray Spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS). These observations were combined with Linear Voltammetry (LVA) and Electrochemical Impedance Spectroscopy (EIS) after 48 and 168 h of exposure to a 3.5% NaCl model corrosive medium. The main result is, that completely different effects were observed in accordance to the acid used. It was established that the monoprotonic acids have a deep destructive effect due to dissolution of the alloy components, whereas the polyprotonic ones possess either indistinguishable influence, or surface film formation. - Highlights: • AA2024 was polarized anodically in 15%{sub wt} acid solutions at 15 mA cm{sup −2} for 2 h. • Four mineral acids were selected for investigation: HCl, HNO{sub 3}, H{sub 2}SO{sub 4} and H{sub 3}PO{sub 4}. • SEM, EDX and XPS were applied for morphological description. • Electrochemical characterizations were performed by EIS and linear voltammetry. • The acid used predetermines completely different interaction with the AA2024 alloy.

  11. Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2004-01-01

    1.1 This test method covers an experimental procedure for checking experimental technique and instrumentation. If followed, this test method will provide repeatable potentiostatic and potentiodynamic anodic polarization measurements that will reproduce data determined by others at other times and in other laboratories provided all laboratories are testing reference samples from the same lot of Type 430 stainless steel. 1.2 Values stated in SI units are to be regarded as the standard. Inch-pound units given in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  12. Anodic Behavior of Alloy 22 in Calcium Chloride and in Calcium Chloride Plus Calcium Nitrate Brines

    International Nuclear Information System (INIS)

    Evans, K.J.; Day, S.D.; Ilevbare, G.O.; Whalen, M.T.; King, K.J.; Hust, G.A.; Wong, L.L.; Estill, J.C.; Rebak, R.B.

    2003-01-01

    Alloy 22 (UNS N60622) is a nickel-based alloy, which is extensively used in aggressive industrial applications, especially due to its resistance to localized corrosion and stress corrosion cracking in high chloride environments. The purpose of this work was to characterize the anodic behavior of Alloy 22 in concentrated calcium chloride (CaCl 2 ) brines and to evaluate the inhibitive effect of nitrate, especially to localized corrosion. Standard electrochemical tests such as polarization resistance and cyclic polarization were used. Results show that the corrosion potential of Alloy 22 was approximately -360 mV in the silver-silver chloride (SSC) scale and independent of the tested temperature. Cyclic polarization tests showed that Alloy 22 was mainly susceptible to localized attack in 5 M CaCl 2 at 75 C and higher temperatures. The addition of nitrate in a molar ratio of chloride to nitrate equal to 10 increased the onset of localized corrosion to approximately 105 C. The addition of nitrate to the solution also decreased the uniform corrosion rate and the passive current of the alloy

  13. Effect of anode polarization on biofilm formation and electron transfer in Shewanella oneidensis/graphite felt microbial fuel cells.

    Science.gov (United States)

    Pinto, David; Coradin, Thibaud; Laberty-Robert, Christel

    2018-04-01

    In microbial fuel cells, electricity generation is assumed by bacterial degradation of low-grade organics generating electrons that are transferred to an electrode. The nature and efficiency of the electron transfer from the bacteria to the electrodes are determined by several chemical, physical and biological parameters. Specifically, the application of a specific potential at the bioanode has been shown to stimulate the formation of an electro-active biofilm, but the underlying mechanisms remain poorly understood. In this study, we have investigated the effect of an applied potential on the formation and electroactivity of biofilms established by Shewanella oneidensis bacteria on graphite felt electrodes in single- and double-chamber reactor configurations in oxic conditions. Using amperometry, cyclic voltammetry, and OCP/Power/Polarization curves techniques, we showed that a potential ranging between -0.3V and +0.5V (vs. Ag/AgCl/KCl sat.) and its converse application to a couple of electrodes leads to different electrochemical behaviors, anodic currents and biofilm architectures. For example, when the bacteria were confined in the anodic compartment of a double-chamber cell, a negative applied potential (-0.3V) at the bioanode favors a mediated electron transfer correlated with the progressive formation of a biofilm that fills the felt porosity and bridges the graphite fibers. In contrast, a positive applied potential (+0.3V) at the bioanode stimulates a direct electron transfer resulting in the fast-bacterial colonization of the fibers only. These results provide significant insight for the understanding of the complex bacteria-electrode interactions in microbial fuel cells. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Transformation of atmospheric components near a spark discharge at the anode polarization of a metallic electrode hanging over a solution

    Science.gov (United States)

    Orlov, A. M.; Yavtushenko, I. O.; Bodnarskii, D. S.

    2013-03-01

    The variation of the pressure of a gas phase activated by spark discharges between an aqueous electrolyte solution (liquid cathode) and a metallic electrode (anode) hanging over the solution is studied. A mathematical model of the proceeding reaction kinetics is constructed, and the variation of the partial pressures of all initial and produced components in the gas phase is calculated. Both the Faraday and non-Faraday mechanisms of gas component production from water are confirmed. It is found that a large overhanging drop responsible for additional supply of simultaneously produced H2 and O2 molecules forms rapidly at the end face of the anodically polarized electrode.

  15. Understanding improved osteoblast behavior on select nanoporous anodic alumina

    Science.gov (United States)

    Ni, Siyu; Li, Changyan; Ni, Shirong; Chen, Ting; Webster, Thomas J

    2014-01-01

    The aim of this study was to prepare different sized porous anodic alumina (PAA) and examine preosteoblast (MC3T3-E1) attachment and proliferation on such nanoporous surfaces. In this study, PAA with tunable pore sizes (25 nm, 50 nm, and 75 nm) were fabricated by a two-step anodizing procedure in oxalic acid. The surface morphology and elemental composition of PAA were characterized by field emission scanning electron microscopy and X-ray photoelectron spectroscopy analysis. The nanopore arrays on all of the PAA samples were highly regular. X-ray photoelectron spectroscopy analysis suggested that the chemistry of PAA and flat aluminum surfaces were similar. However, contact angles were significantly greater on all of the PAA compared to flat aluminum substrates, which consequently altered protein adsorption profiles. The attachment and proliferation of preosteoblasts were determined for up to 7 days in culture using field emission scanning electron microscopy and a Cell Counting Kit-8. Results showed that nanoporous surfaces did not enhance initial preosteoblast attachment, whereas preosteoblast proliferation dramatically increased when the PAA pore size was either 50 nm or 75 nm compared to all other samples (Paluminum by modifying surface nano-roughness alone (and not changing chemistry) through an anodization process to improve osteoblast density, and, thus, should be further studied as a bioactive interface for orthopedic applications. PMID:25045263

  16. Understanding improved osteoblast behavior on select nanoporous anodic alumina

    Directory of Open Access Journals (Sweden)

    Ni S

    2014-07-01

    Full Text Available Siyu Ni,1 Changyan Li,1 Shirong Ni,2 Ting Chen,1 Thomas J Webster3,4 1College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, People’s Republic of China; 2Department of Pathophysiology, Wenzhou Medical University, Wenzhou, People’s Republic of China; 3Department of Chemical Engineering, College of Engineering, Northeastern University, Boston, MA, USA; 4Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia Abstract: The aim of this study was to prepare different sized porous anodic alumina (PAA and examine preosteoblast (MC3T3-E1 attachment and proliferation on such nanoporous surfaces. In this study, PAA with tunable pore sizes (25 nm, 50 nm, and 75 nm were fabricated by a two-step anodizing procedure in oxalic acid. The surface morphology and elemental composition of PAA were characterized by field emission scanning electron microscopy and X-ray photoelectron spectroscopy analysis. The nanopore arrays on all of the PAA samples were highly regular. X-ray photoelectron spectroscopy analysis suggested that the chemistry of PAA and flat aluminum surfaces were similar. However, contact angles were significantly greater on all of the PAA compared to flat aluminum substrates, which consequently altered protein adsorption profiles. The attachment and proliferation of preosteoblasts were determined for up to 7 days in culture using field emission scanning electron microscopy and a Cell Counting Kit-8. Results showed that nanoporous surfaces did not enhance initial preosteoblast attachment, whereas preosteoblast proliferation dramatically increased when the PAA pore size was either 50 nm or 75 nm compared to all other samples (P<0.05. Thus, this study showed that one can alter surface energy of aluminum by modifying surface nano-roughness alone (and not changing chemistry through an anodization process to improve osteoblast density, and, thus, should be

  17. Difference in Thermal Degradation Behavior of ZrO2 and HfO2 Anodized Capacitors

    Science.gov (United States)

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

    2004-09-01

    Microcrystalline ZrO2 and HfO2 thin film capacitors were prepared by anodizing sputter-deposited Zr and Hf films. The thermal degradation behavior of both anodized capacitors was clarified by the measurement of their capacitance properties and Auger depth profiles before and after heat treatment in air. As a result, it is confirmed that the heat-resistance property of the HfO2 anodized capacitor is superior to that of the ZrO2 capacitor. In addition, it is revealed that the thermal degradation of the ZrO2 anodized capacitor is caused by the diffusion of Zr atoms from the underlying layer into the ZrO2 anodized layer, while that of the HfO2 anodized capacitor is caused by the diffusion of oxygen atoms from the anodized layer into the underlying Hf layer.

  18. Behavior of CuP and OFHC Cu anodes under electrodeposition conditions

    Energy Technology Data Exchange (ETDEWEB)

    Frankel, G.S.; Schrott, A.G.; Horkans, J.; Andricacos, P.C. (International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center); Isaacs, H.S. (Brookhaven National Lab., Upton, NY (United States))

    1992-01-01

    Films formed on CuP (with 0.05 wt % P) and OFHC Cu anodes in electroplating solutions were studied by X-ray Photoelectron Spectroscopy, X-ray Absorption Spectroscopy, electrochemical methods, and a newly developed gravimetric technique. The black film formed on CuP in Cl-containing solutions was found to resemble a porous sponge composed of CuCl but laden/with concentrated CuSO{sub 4} solution. The difference between the buoyancy-corrected measured mass change and the charge-equivalent mass change was found to have two components: a reversible part that comes and goes as the current is turned on and off, and an irreversible part that remains on the surface and increase in mass with time. The irreversible part results from the anodic film, which increases linearly with charge density but independent of current density. The reversible part of the mass change arises from the weight of the diffusion layer. In contrast to CuP, OFHC Cu releases much more Cu{sup +1} during anodic polarization and forms a poorly-adherent anodic film that is considerably heavier than the black film for a given charge density.

  19. Behavior of CuP and OFHC Cu anodes under electrodeposition conditions

    Energy Technology Data Exchange (ETDEWEB)

    Frankel, G.S.; Schrott, A.G.; Horkans, J.; Andricacos, P.C. [International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center; Isaacs, H.S. [Brookhaven National Lab., Upton, NY (United States)

    1992-08-01

    Films formed on CuP (with 0.05 wt % P) and OFHC Cu anodes in electroplating solutions were studied by X-ray Photoelectron Spectroscopy, X-ray Absorption Spectroscopy, electrochemical methods, and a newly developed gravimetric technique. The black film formed on CuP in Cl-containing solutions was found to resemble a porous sponge composed of CuCl but laden/with concentrated CuSO{sub 4} solution. The difference between the buoyancy-corrected measured mass change and the charge-equivalent mass change was found to have two components: a reversible part that comes and goes as the current is turned on and off, and an irreversible part that remains on the surface and increase in mass with time. The irreversible part results from the anodic film, which increases linearly with charge density but independent of current density. The reversible part of the mass change arises from the weight of the diffusion layer. In contrast to CuP, OFHC Cu releases much more Cu{sup +1} during anodic polarization and forms a poorly-adherent anodic film that is considerably heavier than the black film for a given charge density.

  20. Synthesis of calcium-phosphorous doped TiO2 nanotubes by anodization and reverse polarization: A promising strategy for an efficient biofunctional implant surface

    International Nuclear Information System (INIS)

    Alves, Sofia A.; Patel, Sweetu B.; Sukotjo, Cortino; Mathew, Mathew T.; Filho, Paulo N.; Celis, Jean-Pierre

    2017-01-01

    Highlights: • A new surface modification methodology for bio-functionalization of TiO2 NTs is addressed • Bone-like structured TiO2 nanotubular surfaces containing Ca and P were synthesized. • Ca/P-doped TiO2 NTs enhanced adhesion and proliferation of osteoblastic-like cells. • The bio-functionalization granted improved bio-electrochemical stability to TiO2 NTs. - Abstract: The modification of surface features such as nano-morphology/topography and chemistry have been employed in the attempt to design titanium oxide surfaces able to overcome the current dental implants failures. The main goal of this study is the synthesis of bone-like structured titanium dioxide (TiO 2 ) nanotubes enriched with Calcium (Ca) and Phosphorous (P) able to enhance osteoblastic cell functions and, simultaneously, display an improved corrosion behavior. To achieve the main goal, TiO 2 nanotubes were synthetized and doped with Ca and P by means of a novel methodology which relied, firstly, on the synthesis of TiO 2 nanotubes by anodization of titanium in an organic electrolyte followed by reverse polarization and/or anodization, in an aqueous electrolyte. Results show that hydrophilic bone-like structured TiO 2 nanotubes were successfully synthesized presenting a highly ordered nano-morphology characterized by non-uniform diameters. The chemical analysis of such nanotubes confirmed the presence of CaCO 3 , Ca 3 (PO 4 ) 2 , CaHPO 4 and CaO compounds. The nanotube surfaces submitted to reverse polarization, presented an improved cell adhesion and proliferation compared to smooth titanium. Furthermore, these surfaces displayed a significantly lower passive current in artificial saliva, and so, potential to minimize their bio-degradation through corrosion processes. This study addresses a very simple and promising multidisciplinary approach bringing new insights for the development of novel methodologies to improve the outcome of osseointegrated implants.

  1. Corrosion and Discharge Behaviors of Mg-Al-Zn and Mg-Al-Zn-In Alloys as Anode Materials

    Directory of Open Access Journals (Sweden)

    Jiarun Li

    2016-03-01

    Full Text Available The Mg-6%Al-3%Zn and Mg-6%Al-3%Zn-(1%, 1.5%, 2%In alloys were prepared by melting and casting. Their microstructures were investigated via metallographic and energy-dispersive X-ray spectroscopy (EDS analysis. Moreover, hydrogen evolution and electrochemical tests were carried out in 3.5 wt% NaCl solution aiming at identifying their corrosion mechanisms and discharge behaviors. The results suggested that indium exerts an improvement on both the corrosion rate and the discharge activity of Mg-Al-Zn alloy via the effects of grain refining, β-Mg17Al12 precipitation, dissolving-reprecipitation, and self-peeling. The Mg-6%Al-3%Zn-1.5%In alloy with the highest corrosion rate at free corrosion potential did not perform desirable discharge activity indicating that the barrier effect caused by the β-Mg17Al12 phase would have been enhanced under the conditions of anodic polarization. The Mg-6%Al-3%Zn-1.0%In alloy with a relative low corrosion rate and a high discharge activity is a promising anode material for both cathodic protection and chemical power source applications.

  2. Aluminum anode for aluminum-air battery - Part II: Influence of In addition on the electrochemical characteristics of Al-Zn alloy in alkaline solution

    Science.gov (United States)

    Park, In-Jun; Choi, Seok-Ryul; Kim, Jung-Gu

    2017-07-01

    Effects of Zn and In additions on the aluminum anode for Al-air battery in alkaline solution are examined by the self-corrosion rate, cell voltage, current-voltage characteristics, anodic polarization, discharge performance and AC impedance measurements. The passivation behavior of Zn-added anode during anodic polarization decreases the discharge performance of Al-air battery. The addition of In to Al-Zn anode reduces the formation of Zn passivation film by repeated adsorption and desorption behavior of In ion onto anode surface. The attenuated Zn passive layer by In ion attack leads to the improvement of discharge performance of Al-air battery.

  3. Anodic behavior of uranium in AlCl3-1-ethyl-3-methyl-imidazolium chloride ionic liquid

    Science.gov (United States)

    Jiang, Yidong; Luo, Lizhu; Wang, Shaofei; Bin, Ren; Zhang, Guikai; Wang, Xiaolin

    2018-01-01

    The oxidation state of metals unambiguously affects its anodic behavior in ionic liquid. We systematically investigated the anodic behavior of uranium with different surface oxidation states by electrochemical measurements, spectroscopic methods and surface analysis techniques. In the anodic process, metal uranium can be oxidized to U3+. The corresponding products accumulated on the metal/ILs interface will form a viscous layer. The anodic behavior of uranium is also strongly dependent upon the surface oxide states including thickness and homogeneity of the oxide film. With an increase in the thickness of oxide film, it will be breached at potentials in excess of a critical value. A uniform oxide on uranium surface can be breached evenly, and then the underlying metal starts to dissolve forming a viscous layer which can facilitate uniformly stripping of oxide, thus giving an oxide-free surface. Otherwise, a nonuniform oxide can result in a severe pitted surface with residue oxygen.

  4. Synthesis of calcium-phosphorous doped TiO{sub 2} nanotubes by anodization and reverse polarization: A promising strategy for an efficient biofunctional implant surface

    Energy Technology Data Exchange (ETDEWEB)

    Alves, Sofia A., E-mail: sofiafonso@msn.com [CMEMS – Center of MicroElectroMechanical Systems, Department of Mechanical Engineering, University of Minho, 4800-058 Guimarães (Portugal); IBTN/US – American Branch of the Institute of Biomaterials, Tribocorrosion and Nanomedicine, UIC College of Dentistry, 60612 Chicago, IL (United States); Patel, Sweetu B. [IBTN/US – American Branch of the Institute of Biomaterials, Tribocorrosion and Nanomedicine, UIC College of Dentistry, 60612 Chicago, IL (United States); Department of Mechanical Engineering, Michigan Technological University, 49931 Houghton, MI (United States); Sukotjo, Cortino [IBTN/US – American Branch of the Institute of Biomaterials, Tribocorrosion and Nanomedicine, UIC College of Dentistry, 60612 Chicago, IL (United States); Departmenmt of Restorative Dentistry, University of Illinois at Chicago, 60612 Chicago, IL (United States); Mathew, Mathew T. [IBTN/US – American Branch of the Institute of Biomaterials, Tribocorrosion and Nanomedicine, UIC College of Dentistry, 60612 Chicago, IL (United States); Department of Orthopedic Surgery, Rush University Medical Center, 60612 Chicago, IL (United States); Department of Biomedical Science, UIC School of Medicine at Rockford, 61107 Rockford, IL (United States); Filho, Paulo N. [IBTN/Br – Brazilian Branch of the Institute of Biomaterials, Tribocorrosion and Nanomedicine, UNESP – Universidade Estadual Paulista, Faculdade de Ciências, 17033-360 Bauru, São Paulo (Brazil); Faculdade de Ciências, Departamento de Física, UNESP - Universidade Estadual Paulista, 17033-360 Bauru, São Paulo (Brazil); Celis, Jean-Pierre [Department of Materials Engineering, KU Leuven, 3001 Leuven (Belgium); and others

    2017-03-31

    Highlights: • A new surface modification methodology for bio-functionalization of TiO2 NTs is addressed • Bone-like structured TiO2 nanotubular surfaces containing Ca and P were synthesized. • Ca/P-doped TiO2 NTs enhanced adhesion and proliferation of osteoblastic-like cells. • The bio-functionalization granted improved bio-electrochemical stability to TiO2 NTs. - Abstract: The modification of surface features such as nano-morphology/topography and chemistry have been employed in the attempt to design titanium oxide surfaces able to overcome the current dental implants failures. The main goal of this study is the synthesis of bone-like structured titanium dioxide (TiO{sub 2}) nanotubes enriched with Calcium (Ca) and Phosphorous (P) able to enhance osteoblastic cell functions and, simultaneously, display an improved corrosion behavior. To achieve the main goal, TiO{sub 2} nanotubes were synthetized and doped with Ca and P by means of a novel methodology which relied, firstly, on the synthesis of TiO{sub 2} nanotubes by anodization of titanium in an organic electrolyte followed by reverse polarization and/or anodization, in an aqueous electrolyte. Results show that hydrophilic bone-like structured TiO{sub 2} nanotubes were successfully synthesized presenting a highly ordered nano-morphology characterized by non-uniform diameters. The chemical analysis of such nanotubes confirmed the presence of CaCO{sub 3}, Ca{sub 3}(PO{sub 4}){sub 2}, CaHPO{sub 4} and CaO compounds. The nanotube surfaces submitted to reverse polarization, presented an improved cell adhesion and proliferation compared to smooth titanium. Furthermore, these surfaces displayed a significantly lower passive current in artificial saliva, and so, potential to minimize their bio-degradation through corrosion processes. This study addresses a very simple and promising multidisciplinary approach bringing new insights for the development of novel methodologies to improve the outcome of osseointegrated

  5. Electrochemical behavior of anodized AA6063-T6 alloys affected by matrix structures

    International Nuclear Information System (INIS)

    Huang, Yung-Sen; Shih, Teng-Shih; Wu, Chen-En

    2013-01-01

    Highlights: ► Deformation after solution treatment introduced Al matrix to have deformation bands and few Si particles. ► Dislocations remained in the matrix lift up field potential and produce AlOOH oxide in the AAO film. ► The silicon-containing particles were found to trap in the AAO film. ► The silicon particles and the Al(OOH) oxide is significantly to influence the electrochemical behavior of AAO films. - Abstract: AA 6063 alloys were cold-rolled (CR) either before or after solution treatment (S) and then different samples were artificially aged (T6) to obtain different samples (CRST6 and SCRT6). The highest dislocation density was observed in the SCRT6 sample which also showed the lowest particle count among the three samples; ST6, CRST6 and SCRT6. Subsequently, all samples were anodized in a 15 wt% sulfuric acid solution for different time spans to obtain anodic aluminum oxide (AAO) films. The anodized samples were further analyzed with X-ray Photoelectron Spectroscopy (XPS) analysis. We determined that the constituent phases in the AAO film were composed of hydrated amorphous alumina, hydrated oxide (Al(OH) 3 ) and oxyhydroxide (AlOOH) phases together with some silicon-containing particles trapped in the films on all samples. In the electrochemical test, the silicon-containing particles and hydrated Al(OH) 3 oxide that existed at the electrolyte/film (e/f) interface were found to inversely influence the corrosion resistance of the anodized samples.

  6. Anodic characteristics and stress corrosion cracking behavior of nickel rich alloys in bicarbonate and buffer solutions

    International Nuclear Information System (INIS)

    Zadorozne, Natalia S.; Giordano, Mabel C.; Ares, Alicia E.; Carranza, Ricardo M.; Rebak, Raul B.

    2016-01-01

    Highlights: • We investigate which element in alloy C-22 may be responsible for the cracking susceptibility of the high nickel alloy. • Six nickel based alloys with different amount of Cr and Mo were selected for the electrochemical tests and response to SSRT. • Polarization tests showed that an anodic peak appear in the passive region in Cr containing alloys. • Cracking of Ni alloys in carbonate solutions seem to be a consequence of the instability of the passivating chromium oxide. • Alloys containing both Cr and Mo have the highest susceptibility. - Abstract: The aim of this work is to investigate which alloying element in C-22 is responsible for the cracking susceptibility of the alloy in bicarbonate and two buffer solutions (tungstate and borate). Six nickel based alloys, with different amount of chromium (Cr) and molybdenum (Mo) were tested using electrochemical methods and slow strain rate tests (SSRT) at 90 °C. All Cr containing alloys had transgranular cracking at high anodic potential; however, C-22 containing high Cr and high Mo was the most susceptible alloy to cracking. Bicarbonate was the most aggressive of three tested environments of similar pH.

  7. Polarization and EIS studies to evaluate the effect of aluminum concentration on the corrosion behavior of SAC105 solder alloy

    Directory of Open Access Journals (Sweden)

    Liyana N. K.

    2018-03-01

    Full Text Available This paper presents an investigation on corrosion behavior of Sn-1.0Ag-0.5Cu-XAl (X = 0, 0.1, 0.5, 1.0 by means of polarization and electrochemical impedance spectroscopy (EIS measurements in 3.5 wt.% NaCl solution. The results show that addition of aluminum into SAC105 shifts the corrosion current density and passivation current density towards more positive values. It is also found that with an increase in aluminum concentration in SAC105 solder alloy, the corrosion current density increases and polarization resistance decreases. This suggests that SAC105 with the highest concentration of Al has the lowest corrosion resistance. In this case, the corrosion behavior seems to be attributed to anodic dissolution of aluminum and Sn-matrix.

  8. Incoloy 800 anodic behavior in sulfate and chloride solutions at high temperature

    International Nuclear Information System (INIS)

    Lafont, C.; Alvarez, M.G.

    1992-01-01

    The anodic behavior and pitting corrosion resistance of Incoloy 800 in concentrated aqueous chloride and sulphate solutions has been studied by means of electrochemical techniques. The effect of different environmental variables, such as temperature (in the 100 0 C to 280 0 C range) and sulphate ion concentration (0.02 M to 2 M), was evaluated. In another set of experiments, the influence of sulphate ions additions on the pitting resistance and pitting morphology of Incoloy 800 in chloride solutions at high temperature was also examined. (author)

  9. Deriving the polarization behavior of many-layer mirror coatings

    Science.gov (United States)

    White, Amanda J.; Harrington, David M.; Sueoka, Stacey R.

    2018-06-01

    End-to-end models of astronomical instrument performance are becoming commonplace to demonstrate feasibility and guarantee performance at large observatories. Astronomical techniques like adaptive optics and high contrast imaging have made great strides towards making detailed performance predictions, however, for polarimetric techniques, fundamental tools for predicting performance do not exist. One big missing piece is predicting the wavelength and field of view dependence of a many-mirror articulated optical system particularly with complex protected metal coatings. Predicting polarization performance of instruments requires combining metrology of mirror coatings, tools to create mirror coating models, and optical modeling software for polarized beam propagation. The inability to predict instrument induced polarization or to define polarization performance expectations has far reaching implications for up and coming major observatories, such as the Daniel K. Inouye Solar Telescope (DKIST), that aim to take polarization measurements at unprecedented sensitivity and resolution.Here we present a method for modelling the wavelength dependent refractive index of an optic using Berreman calculus - a mathematical formalism that describes how an electromagnetic field propagates through a birefringent medium. From Berreman calculus, we can better predict the Mueller matrix, diattenuation, and retardance of an arbitrary thicknesses of amorphous many-layer coatings as well as stacks of birefringent crystals from laboratory measurements. This will allow for the wavelength dependent refractive index to be accurately determined and the polarization behavior to be derived for a given optic.

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

    Science.gov (United States)

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

    2015-02-01

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

  11. Self-injection locking of the DFB laser through an external ring fiber cavity: Polarization behavior

    Directory of Open Access Journals (Sweden)

    J.L. Bueno Escobedo

    Full Text Available We study stability of self-injection locking realized with DFB laser coupled with an external fiber optic ring cavity. Polarization behavior of the radiation circulating in the feedback loop is reported. Two regimes of mode hopping have been observed; one of them is accompanied by polarization bistability involving two orthogonal polarization states. Keywords: Self-injection locking, Polarization, Optical fiber

  12. Corrosion Behavior of Surface-Treated Implant Ti-6Al-4V by Electrochemical Polarization and Impedance Studies

    Science.gov (United States)

    Paul, Subir; Yadav, Kasturi

    2011-04-01

    Implant materials for orthopedic and heart surgical services demand a better corrosion resistance material than the presently used titanium alloys, where protective oxide layer breaks down on a prolonged stay in aqueous physiological human body, giving rise to localized corrosion of pitting, crevice, and fretting corrosion. A few surface treatments on Ti alloy, in the form of anodization, passivation, and thermal oxidation, followed by soaking in Hank solution have been found to be very effective in bringing down the corrosion rate as well as producing high corrosion resistance surface film as reflected from electrochemical polarization, cyclic polarization, and Electrochemical Impedance Spectroscopy (EIS) studies. The XRD study revealed the presence of various types of oxides along with anatase and rutile on the surface, giving rise to high corrosion resistance film. While surface treatment of passivation and thermal oxidation could reduce the corrosion rate by 1/5th, anodization in 0.3 M phosphoric acid at 16 V versus stainless steel cathode drastically brought down the corrosion rate by less than ten times. The mechanism of corrosion behavior and formation of different surface films is better understood from the determination of EIS parameters derived from the best-fit equivalent circuit.

  13. Effects Of Anodic Protection On SCC Behavior Of X80 Pipeline Steel In High-pH Carbonate-Bicarbonate Solution

    Directory of Open Access Journals (Sweden)

    Zhao W.

    2015-06-01

    Full Text Available The potentiodynamic polarization test and slow strain rate tensile tests of X80 pipeline steel were performed in 0.5M Na2CO3-1M NaHCO3 solution to study the electrochemical and stress corrosion cracking properties. The results of potentiodynamic polarization test show that there is an obvious stable passive region, about from 0v to 0.8V (SCE, indicating that anodic protection is feasible. The results of slow strain rate tensile tests show that the stress corrosion cracking sensibility is high and cathodic protection effect is restricted due to the hydrogen permeation. However, the elongation, yielding strength and tensile strength all increase with anodic protection. The higher anodic protection potential in the stable passive region is benefit to improve tensile strength and yielding strength. However, the higher elongation is obtained at 0.5V (SCE anodic protection potential.

  14. Effect of Pore Thickness and the State of Polarization on the Optical Properties of Hexagonal Nanoarray of Au/Nanoporous Anodic Alumina Membrane

    Directory of Open Access Journals (Sweden)

    Mohamed Shaban

    2015-01-01

    Full Text Available Hexagonal nanoarrays of Au particles were deposited on nanoporous anodic alumina membrane (NAAM utilizing r.f. magnetron sputtering. The thickness of the NAAMs is adjusted by changing the second anodization time from 5 min to 20 min. The surface morphology, composition, and optical properties are characterized by using SEM, EDX, and spectrophotometer, respectively. The effects of the NAAM thickness and state of polarization on the morphological changes and on the optical properties of the fabricated nanoarrays were addressed. According to the measured optical spectra, the rate of decrease of NAAMs refractive index was found to be 3.825 × 10−4 nm−1. Using the modified Kubelka-Munk radiative transfer model, the energy gap of NAAMs was calculated from diffused reflectance and was decreased from 1.682 to 1.376 as the anodization time increased from 5 to 20 min. Also, the saturation of interference fringes is substantially enhanced, and field enhancement can be achieved due to the excitation and constructive interference of surface plasmon waves by coating NAAMs with the hexagonal nanoarrays of Au. Based on the advantages of the fabrication approach and the enhanced and controlled properties, this new generation of samples can be used as promising building blocks for nanophotonic and nanoelectronics devices.

  15. An open circuit voltage equation enabling separation of cathode and anode polarization resistances of ceria electrolyte based solid oxide fuel cells

    Science.gov (United States)

    Zhang, Yanxiang; Chen, Yu; Yan, Mufu

    2017-07-01

    The open circuit voltage (OCV) of solid oxide fuel cells is generally overestimated by the Nernst equation and the Wagner equation, due to the polarization losses at electrodes. Considering both the electronic conduction of electrolyte and the electrode polarization losses, we express the OCV as an implicit function of the characteristic oxygen pressure of electrolyte (p* [atm], at which the electronic and ionic conductivities are the same), and the relative polarization resistance of electrodes (rc = Rc/Ri and ra = Ra/Ri, where Ri/c/a [Ωcm2] denotes the ionic resistance of electrolyte, and the polarization resistances of cathode and anode, respectively). This equation approaches to the Wagner equation when the electrodes are highly active (rc and ra → 0), and approaches to the Nernst equation when the electrolyte is a purely ionic conductor (p* → 0). For the fuel cells whose OCV is well below the prediction of the Wagner equation, for example with thin doped ceria electrolyte, it is demonstrated that the combination of OCV and impedance spectroscopy measurements allows the determination of p*, Rc and Ra. This equation can serve as a simple yet powerful tool to study the internal losses in the cell under open circuit condition.

  16. The aluminum anode in deep ocean environments

    International Nuclear Information System (INIS)

    Schreiber, C.F.

    1989-01-01

    Results of field and mini-plant studies are presented for A1 + 0.045% Hg + 0.1% Si + 0.45% Zn* and A1 + 0.015% In + 0.1% Si + 3% Zn** anodes in varying depths of natural seawater. Current capacity and potential information are presented. In addition to information on anode current capacity and potential, polarization curves were obtained on both aluminum alloys using potentiostatic techniques at a simulated ocean depth of 1090 ft. (332 m). These data were compared with similarly run experiments at ocean surface pressures. As a basis of comparison, zinc anodes (U.S. Mil-A-18001H) were included as a companion alloy. Information gained on zinc is sufficient to accurately represent the behavior of this alloy. Results conclude that conditions of high pressure (and low temperature) associated with the alloys under test did not alter their galvanic behavior from that noted at the ocean surface

  17. Polarization-coupled tunable resistive behavior in oxide ferroelectric heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Gruverman, Alexei [Univ. of Nebraska, Lincoln, NE (United States); Tsymbal, Evgeny Y. [Univ. of Nebraska, Lincoln, NE (United States); Eom, Chang-Beom [Univ. of Wisconsin, Madison, WI (United States)

    2017-05-03

    This research focuses on investigation of the physical mechanism of the electrically and mechanically tunable resistive behavior in oxide ferroelectric heterostructures with engineered interfaces realized via a strong coupling of ferroelectric polarization with tunneling electroresistance and metal-insulator (M-I) transitions. This report describes observation of electrically conductive domain walls in semiconducting ferroelectrics, voltage-free control of resistive switching and demonstration of a new mechanism of electrical control of 2D electron gas (2DEG) at oxide interfaces. The research goals are achieved by creating strong synergy between cutting-edge fabrication of epitaxial single-crystalline complex oxides, nanoscale electrical characterization by scanning probe microscopy and theoretical modeling of the observed phenomena. The concept of the ferroelectric devices with electrically and mechanically tunable nonvolatile resistance represents a new paradigm shift in realization of the next-generation of non-volatile memory devices and low-power logic switches.

  18. Using tri-axial accelerometers to identify wild polar bear behaviors

    Science.gov (United States)

    Pagano, Anthony M.; Rode, Karyn D.; Cutting, A.; Owen, M.A.; Jensen, S.; Ware, J.V.; Robbins, C.T.; Durner, George M.; Atwood, Todd C.; Obbard, M.E.; Middel, K.R.; Thiemann, G.W.; Williams, T.M.

    2017-01-01

    Tri-axial accelerometers have been used to remotely identify the behaviors of a wide range of taxa. Assigning behaviors to accelerometer data often involves the use of captive animals or surrogate species, as their accelerometer signatures are generally assumed to be similar to those of their wild counterparts. However, this has rarely been tested. Validated accelerometer data are needed for polar bears Ursus maritimus to understand how habitat conditions may influence behavior and energy demands. We used accelerometer and water conductivity data to remotely distinguish 10 polar bear behaviors. We calibrated accelerometer and conductivity data collected from collars with behaviors observed from video-recorded captive polar bears and brown bears U. arctos, and with video from camera collars deployed on free-ranging polar bears on sea ice and on land. We used random forest models to predict behaviors and found strong ability to discriminate the most common wild polar bear behaviors using a combination of accelerometer and conductivity sensor data from captive or wild polar bears. In contrast, models using data from captive brown bears failed to reliably distinguish most active behaviors in wild polar bears. Our ability to discriminate behavior was greatest when species- and habitat-specific data from wild individuals were used to train models. Data from captive individuals may be suitable for calibrating accelerometers, but may provide reduced ability to discriminate some behaviors. The accelerometer calibrations developed here provide a method to quantify polar bear behaviors to evaluate the impacts of declines in Arctic sea ice.

  19. Electrochemical behavior of uranyl in anhydrous polar organic media

    Energy Technology Data Exchange (ETDEWEB)

    Burn, Adam G.; Nash, Kenneth L. [Washington State Univ., Pullmann, WA (United States). Dept. of Chemistry

    2017-09-01

    Weak complexes between pentavalent and hexavalent actinyl cations have been reported to exist in acidic, non-complexing high ionic strength aqueous media. Such ''cation-cation complexes'' were first identified in the context of actinide-actinide redox reactions in acidic aqueous media relevant to solvent extraction-based separation systems, hence their characterization is of potential interest for advanced nuclear fuel reprocessing. This chemistry could be relevant to efforts to develop advanced actinide separations based on the upper oxidation states of americium, which are of current interest. In the present study, the chemical behavior of pentavalent uranyl was examined in non-aqueous, aprotic polar organic solvents (propylene carbonate and acetonitrile) to determine whether UO{sub 2}{sup +} cations generated at the reducing working electrode surface would interact with the UO{sub 2}{sup 2+} cations in the bulk phase to form cation-cation complexes in such media. In magnesium perchlorate media, the electrolyte adsorbed onto the working electrode surface and interfered with the uranyl reduction/diffusion process through an ECE (electron transfer/chemical reaction/electron transfer) mechanism. In parallel studies of uranyl redox behavior in tetrabutylammonium hexafluorophosphate solutions, an EC (electron transfer/chemical reaction) mechanism was observed in the cyclic voltammograms. Ultimately, no conclusive electrochemical evidence demonstrated uranyl cation-cation interactions in the non-aqueous, aprotic polar organic solvent solutions, though the results reported do not completely rule out the presence of UO{sub 2}{sup +}.UO{sub 2}{sup 2+} complexes.

  20. Effect of Slotted Anode on Gas Bubble Behaviors in Aluminum Reduction Cell

    Science.gov (United States)

    Sun, Meijia; Li, Baokuan; Li, Linmin; Wang, Qiang; Peng, Jianping; Wang, Yaowu; Cheung, Sherman C. P.

    2017-12-01

    In the aluminum reduction cells, gas bubbles are generated at the bottom of the anode which eventually reduces the effective current contact area and the system efficiency. To encourage the removal of gas bubbles, slotted anode has been proposed and increasingly adopted by some industrial aluminum reduction cells. Nonetheless, the exact gas bubble removal mechanisms are yet to be fully understood. A three-dimensional (3D) transient, multiphase flow mathematical model coupled with magnetohydrodynamics has been developed to investigate the effect of slotted anode on the gas bubble movement. The Eulerian volume of fluid approach is applied to track the electrolyte (bath)-molten aluminum (metal) interface. Meanwhile, the Lagrangian discrete particle model is employed to handle the dynamics of gas bubbles with considerations of the buoyancy force, drag force, virtual mass force, and pressure gradient force. The gas bubble coalescence process is also taken into account based on the O'Rourke's algorithm. The two-way coupling between discrete bubbles and fluids is achieved by the inter-phase momentum exchange. Numerical predictions are validated against the anode current variation in an industrial test. Comparing the results using slotted anode with the traditional one, the time-averaged gas bubble removal rate increases from 36 to 63 pct; confirming that the slotted anode provides more escaping ways and shortens the trajectories for gas bubbles. Furthermore, the slotted anode also reduces gas bubble's residence time and the probability of coalescence. Moreover, the bubble layer thickness in aluminum cell with slotted anode is reduced about 3.5 mm (17.4 pct), so the resistance can be cut down for the sake of energy saving and the metal surface fluctuation amplitude is significantly reduced for the stable operation due to the slighter perturbation with smaller bubbles.

  1. Interfacial behavior of polar, weakly polar, and nonpolar compounds bound to activated carbons.

    Science.gov (United States)

    Gun'ko, V M; Turov, V V; Zarko, V I; Goncharuk, O V; Nychiporuk, Yu M; Kozynchenko, O P; Skubiszewska-Zięba, J; Leboda, R; Charmas, B; Balakin, D Yu; Ptushinskii, Yu G

    2013-08-15

    Detailed analysis of the interfacial behavior of water and weakly polar or nonpolar organics adsorbed alone or co-adsorbed onto activated carbons (AC) at different temperatures is a complex problem important for practical applications of adsorbents. Interaction of water, 1-decanol, and n-decane with AC possessing highly developed porosity (pore volume Vp≈1.4-2.3 cm(3)/g, specific surface area S(BET)≈1500-3500 m(2)/g) was studied over a broad temperature range using differential scanning calorimetry (DSC), thermoporometry, (1)H NMR spectroscopy, cryoporometry, and temperature-programmed desorption with mass-spectrometry control methods. Comparison of the pore size distributions (PSD) calculated using the DSC thermoporometry, NMR cryoporometry, and nitrogen adsorption isotherms allows us to determine localization of adsorbates in different pores, as well as changes in the PSD of AC due to freezing of adsorbates in pores. Theoretical calculations (using ab initio HF/6-31G(d,p), DFT B3LYP/6-31G(d,p), and PM7 methods) explain certain aspects of the interfacial behavior of water, decane, and decanol adsorbed onto AC that appear in the experimental data. Obtained results show strong temperature dependence (above and below the freezing point, Tf, of bulk liquids) of the interfacial behavior of adsorbates on the textural characteristics and hydrophilic/hydrophobic properties of AC and the adsorbate amounts that affect the distributions of adsorbates unfrozen at T

  2. Process and electrolyte for applying barrier layer anodic coatings

    International Nuclear Information System (INIS)

    Dosch, R.G.; Prevender, T.S.

    1975-01-01

    Various metals may be anodized, and preferably barrier anodized, by anodizing the metal in an electrolyte comprising quaternary ammonium compound having a complex metal anion in a solvent containing water and a polar, water soluble organic material. (U.S.)

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

    Energy Technology Data Exchange (ETDEWEB)

    Hartig, K J; Getoff, N

    1983-07-01

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

  4. Formation of titanium diboride coatings during the anodic polarization of titanium in a chloride melt with a low boron oxide content

    Science.gov (United States)

    Elshina, L. A.; Malkov, V. B.; Molchanova, N. G.

    2015-02-01

    The corrosion-electrochemical behavior of titanium in a molten eutectic mixture of cesium and sodium chlorides containing up to 1 wt % boron oxide is studied in the temperature range 810-870 K in an argon atmosphere. The potential, the current, and the rate of titanium corrosion are determined. The optimum conditions of forming a dense continuous titanium diboride coating on titanium with high adhesion to the metallic base are found for the anodic activation of titanium in the molten electrolyte under study.

  5. Study of the electrochemical behavior at low temperatures of green anodes for Lithium ion batteries prepared with anatase TiO2 and water soluble sodium carboxymethyl cellulose binder

    International Nuclear Information System (INIS)

    Mancini, M.; Nobili, F.; Tossici, R.; Marassi, R.

    2012-01-01

    Highlights: ► Water soluble CMC and PVDF binders are used to prepare anatase TiO 2 electrodes. ► The electrochemical behavior of the different electrodes is studied between 20 and −30 °C. ► CMC/TiO 2 anodes show lower ICL, lower polarization and higher low-temperature capacity at high rates than PVDF/TiO 2 anodes. ► Electrochemical Impedance Spectroscopy results show better kinetics for CMC/TiO 2 electrodes. - Abstract: The electrochemical behavior at low temperatures of anatase TiO 2 electrodes for Lithium ion batteries have been evaluated by galvanostatic cycles in the temperature range 20 to −30 °C. Two different manufacturing processes have been used to prepare anatase anodes containing water soluble sodium carboxymethyl cellulose (CMC) or poly(vinilydene fluoride) (PVDF) as binder. The low temperature performances at different charge/discharge rates of TiO 2 /CMC and TiO 2 /PVDF electrodes are compared and discussed in terms of irreversible capacity loss (ICL) at the first cycle, capacity retention and reversible capacity. The kinetics of the electrodes containing CMC or PVDF is evaluated by Electrochemical Impedance Spectroscopy.

  6. Behavior of tight-junction, adherens-junction and cell polarity proteins during HNF-4α-induced epithelial polarization

    International Nuclear Information System (INIS)

    Satohisa, Seiro; Chiba, Hideki; Osanai, Makoto; Ohno, Shigeo; Kojima, Takashi; Saito, Tsuyoshi; Sawada, Norimasa

    2005-01-01

    We previously reported that expression of tight-junction molecules occludin, claudin-6 and claudin-7, as well as establishment of epithelial polarity, was triggered in mouse F9 cells expressing hepatocyte nuclear factor (HNF)-4α [H. Chiba, T. Gotoh, T. Kojima, S. Satohisa, K. Kikuchi, M. Osanai, N. Sawada. Hepatocyte nuclear factor (HNF)-4α triggers formation of functional tight junctions and establishment of polarized epithelial morphology in F9 embryonal carcinoma cells, Exp. Cell Res. 286 (2003) 288-297]. Using these cells, we examined in the present study behavior of tight-junction, adherens-junction and cell polarity proteins and elucidated the molecular mechanism behind HNF-4α-initiated junction formation and epithelial polarization. We herein show that not only ZO-1 and ZO-2, but also ZO-3, junctional adhesion molecule (JAM)-B, JAM-C and cell polarity proteins PAR-3, PAR-6 and atypical protein kinase C (aPKC) accumulate at primordial adherens junctions in undifferentiated F9 cells. In contrast, CRB3, Pals1 and PATJ appeared to exhibit distinct subcellular localization in immature cells. Induced expression of HNF-4α led to translocation of these tight-junction and cell polarity proteins to beltlike tight junctions, where occludin, claudin-6 and claudin-7 were assembled, in differentiated cells. Interestingly, PAR-6, aPKC, CRB3 and Pals1, but not PAR-3 or PATJ, were also concentrated on the apical membranes in differentiated cells. These findings indicate that HNF-4α provokes not only expression of tight-junction adhesion molecules, but also modulation of subcellular distribution of junction and cell polarity proteins, resulting in junction formation and epithelial polarization

  7. Investigations of the polarization behavior of quantum cascade lasers by Stokes parameters.

    Science.gov (United States)

    Janassek, Patrick; Hartmann, Sébastien; Molitor, Andreas; Michel, Florian; Elsäßer, Wolfgang

    2016-01-15

    We experimentally investigate the full polarization behavior of mid-infrared emitting quantum cascade lasers (QCLs) in terms of measuring the complete Stokes parameters, instead of only projecting them on a linear polarization basis. We demonstrate that besides the pre-dominant linear TM polarization of the emitted light as governed by the selection rules of the intersubband transition, small non-TM contributions, e.g., circularly polarized light, are present reflecting the birefringent behavior of the semiconductor quantum well waveguide. Surprisingly unique is the persistence of these polarization properties well below laser threshold. These investigations give further insight into understanding, manipulating, and exploiting the polarization properties of QCLs, both from a laser point of view and with respect toward applications.

  8. Effects of entropy changes in anodes and cathodes on the thermal behavior of lithium ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Williford, Ralph E.; Viswanathan, Vilayanur V.; Zhang, Ji-Guang [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States)

    2009-04-01

    The entropy changes ({delta}S) in various cathode and anode materials, as well as complete Li-ion batteries, were measured using an electrochemical thermodynamic measurement system (ETMS). A thermal model based on the fundamental properties of individual electrodes was used to obtain transient and equilibrium temperature distributions of Li-ion batteries. The results from theoretical simulations were compared with results obtained in experimental measurements. We found that the detailed shape of the entropy curves strongly depends on the manufacturer of the materials even for the same nominal compositions. LiCoO{sub 2} has a much larger entropy change than LiNi{sub x}Co{sub y}Mn{sub z}O{sub 2}. This means that LiNi{sub x}Co{sub y}Mn{sub z}O{sub 2} is much more thermodynamically stable than LiCoO{sub 2}. The temperatures around the positive terminal of a prismatic battery are consistently higher than those at the negative terminal, due to differences in the thermal conductivities of the different terminal connectors. When all other simulation parameters are the same, simulations that use a battery-averaged entropy tend to overestimate the predicted temperatures when compared with simulations that use individual entropies for the anode and the cathode, due to computational averaging. (author)

  9. Fabrication of Anodic Porous Alumina by Squaric Acid Anodizing

    OpenAIRE

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

    2014-01-01

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

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

    OpenAIRE

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

    2017-01-01

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

  11. Anode behaviors of aluminum antimony synthesized by mechanical alloying for lithium secondary battery

    International Nuclear Information System (INIS)

    Honda, H.; Sakaguchi, H.; Fukuda, Y.; Esaka, T.

    2003-01-01

    AlSb was synthesized as an anode active material for lithium secondary battery using mechanical alloying (MA). Electrochemical performance was examined on the electrodes of AlSb synthesized with different MA time. The first charge (lithium-insertion) capacity of the AlSb electrodes decreased with increasing the MA time. The discharge capacity on repeating charge-discharge cycle, however, did not show the same dependence. The electrode, consisting of the 20 h MA sample exhibited the longest charge-discharge life cycle, suggesting that there is the optimum degree of internal energy derived from the strain and/or the amorphization due to mechanical alloying. These results were evaluated using ex situ X-ray diffraction and differential scanning calorimetry

  12. Electrochemical polarization behavior of sensitized SUS 304 stainless steel in high temperature water

    Energy Technology Data Exchange (ETDEWEB)

    Kushiya, K [Tohoku Univ., Sendai (Japan); Sugimoto, K; Ejima, T

    1978-11-01

    Anodic polarization curves for a solution-treated or sensitized SUS 304 stainless steel and solution-treated Fe-Ni-Cr ternary alloys containing 10%Ni and 6 to 14%Cr have been measured in deaerated 0.5 mol/l Na/sub 2/SO/sub 4/ solutions of pH 2.0 to 5.9 at 298, 523 and 553 K. Corrosion potentials for U-bend SCC test specimens of sensitized SUS 304 stainless steel have also been monitored for a long time in the same solutions as those used for the polarization measurements except that they were aerated. It was found that the differences in the current densities in the passive state, i sub(pass), between the solution treated steel and the sensitized one and also between the ternary alloy with higher Cr content and the one with lower Cr content become large with increasing temperature and decreasing pH. This means that the difference in the values of i sub(pass) between grain bodies and Cr-depleted zones along grain boundaries of sensitized steel becomes larger and susceptibility to intergranular corrosion of the sensitized steel in the passivation region becomes higher with increasing temperature and decreasing pH. Since corrosion potentials for the U-bend SCC test specimens in air-satulated solutions lie in the passive region of anodic polarization curves for the sensitized steel in deaerated solutions, the intergranular stress-corrosion cracking of the sensitized steel in high temperature water with dissolved oxygen is considered to be caused by the preferential corrosion in the Cr-depleted zone.

  13. Individual effects of seasonal changes, visitor density, and concurrent bear behavior on stereotypical behaviors in captive polar bears (Ursus maritimus).

    Science.gov (United States)

    Kelly, Krista R; Harrison, Michelle L; Size, Daniele D; MacDonald, Suzanne E

    2015-01-01

    Stereotypical behaviors in captive polar bears (Ursus maritimus) can be detrimental to their welfare. These behaviors can be reduced through enrichment programs but are often not completely eliminated, so identifying potential triggers is important. The present study investigated the influences of seasonal changes, visitor density, and concurrent bear activity on stereotypical behaviors exhibited by 3 captive polar bears at the Toronto Zoo. All bears exhibited these behaviors; however, individual differences were found in duration and form. The male exhibited less stereotypical behavior during spring, and the females exhibited less stereotypical behavior during winter. An increase in visitor density was associated with more stereotypical behavior in 1 female but less stereotypical behavior in the other 2 bears. All bears engaged in more stereotypical behaviors when the other bears were inactive, and 1 female engaged in more stereotypical behaviors when the other bears were out of sight. Further, when conspecifics were active, all bears engaged in less stereotypical behaviors. Given the variability among individual bears, future enrichment programs must be tailored to the needs of individuals to maximize efficacy.

  14. Understanding the nanoscale redox-behavior of iron-anodes for rechargeable iron-air batteries

    Energy Technology Data Exchange (ETDEWEB)

    Weinrich, Henning [Forschungszentrum Julich (Germany). Inst. for Energy and Climate Research-Fundamental Electrochemistry (IEK-9); RWTH Aachen Univ., Aachen (Germany). Inst. of Physical Chemistry; Come, Jérémy [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Tempel, Hermann [Forschungszentrum Julich (Germany). Inst. for Energy and Climate Research-Fundamental Electrochemistry (IEK-9); Kungl, Hans [Forschungszentrum Julich (Germany). Inst. for Energy and Climate Research-Fundamental Electrochemistry (IEK-9); Eichel, Rüdiger-A. [Forschungszentrum Julich (Germany). Inst. for Energy and Climate Research-Fundamental Electrochemistry (IEK-9); Balke, Nina [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS)

    2017-10-10

    Iron-air cells provide a promising and resource-efficient alternative battery concept with superior area specific power density characteristics compared to state-of-the-art Li-air batteries and potentially superior energy density characteristics compared to present Li-ion batteries. Understanding charge-transfer reactions at the anode-electrolyte interface is the key to develop high-performance cells. By employing in-situ electrochemical atomic force microscopy (in-situ EC-AFM), in-depth insight into the electrochemically induced surface reaction processes on iron in concentrated alkaline electrolyte is obtained. The results highlight the formation and growth of the redox-layer on iron over the course of several oxidation/reduction cycles. By this means, a direct correlation between topography changes and the corresponding electrochemical reactions at the nanoscale could unambiguously be established. Here in this paper, the twofold character of the nanoparticulate redox-layer in terms of its passivating character and its contribution to the electrochemical reactions is elucidated. Furthermore, the evolution of single nanoparticles on the iron electrode surface is evaluated in unprecedented and artifact-free detail. Based on the dedicated topography analysis, a detailed structural model for the evolution of the redox-layer which is likewise elementary for corrosion science and battery research is derived.

  15. Investigation of the Effects of Solution Temperature on the Corrosion Behavior of Austenitic Low-Nickel Stainless Steels in Citric Acid using Impedance and Polarization Measurements

    Directory of Open Access Journals (Sweden)

    Mulimbayan Francis M.

    2015-01-01

    Full Text Available Stainless steels may be classified according to alloy microstructure – ferritic, austenitic, martensitic, duplex, and precipitation hardening grades. Among these, austenitic grade has the largest contribution to market due to the alloy’s numerous industrial and domestic applications. In this study, the corrosion behavior of low-Nickel stainless steel in citric acid was investigated using potentiodynamic polarization techniques and Electrochemical Impedance Spectroscopy (EIS. The corrosion current density which is directly related to corrosion rate was extracted from the generated anodic polarization curve. Increasing the temperature of the citric acid resulted to increased corrosion current densities indicating higher corrosion rates at initial corrosion condition. EIS was performed to generate Nyquist plots whose shape and size depicts the corrosion mechanism and corrosion resistance of the alloy in citric acid, respectively. All the generated Nyquist plots have depressed semi-circle shapes implying that corrosion process takes place with charge-transfer as the rate-determining step. Based from the extracted values of polarization resistance (Rp, the temperature of the solution has negative correlation with the corrosion resistance of the studied alloy.

  16. The influence of Ti and Sr alloying elements on electrochemical properties of aluminum sacrificial anodes

    Energy Technology Data Exchange (ETDEWEB)

    Saremi, M.; Sina, H.; Keyvani, A.; Emamy, M. [Metallurgy and Materials Department, University of Tehran, P.O. Box 11365/4563, Tehran (Iran)

    2004-07-01

    Aluminum sacrificial anodes are widely used in cathodic protection of alloys in seawater. The interesting properties due to low specific weight, low electrode potential and high current capacity are often hindered by the presence of a passive oxide film which causes several difficulties in their practical application. In this investigation, the electrochemical behavior of Al- 5Zn-0.02In sacrificial anode is studied in 3 wt. % sodium chloride solution. The experiments focused on the influence of Ti and Sr as alloying elements on electrochemical behavior of aluminum sacrificial anode. Ti and Sr are used in different concentrations from 0.03 to 0.1 wt.% 0.01 to 0.05 wt.%, respectively. NACE efficiency and polarization tests are used in this case. It is shown that by using 0.03 wt.% Ti and 0.01 wt.% Sr as the alloying elements to investigate the anodic behavior of the anodes, homogeneous microstructures are obtained which results in improvement of electrochemical properties of aluminum sacrificial anode such as current capacity and anode efficiency. (authors)

  17. Oxidation behavior of a Ni-Fe support in SOFC anode atmosphere

    DEFF Research Database (Denmark)

    Xu, Na; Chen, Ming; Han, Minfang

    2018-01-01

    In this work, we investigated the long-term oxidation behavior of a Ni-Fe (1:1 weight ratio) support for solid oxide fuel cell (SOFC) applications. Ni-Fe supports were obtained through tape casting, high temperature sintering and pre-reducing in 97% H2/N2 (9/91)-3% H2O at 750 and 1000 °C, respect...... annealed in the two atmospheres maintained sufficiently high conductivity. The results from the current work demonstrate that the porous Ni-Fe support can be well employed in SOFCs, especially metal-supported SOFCs....

  18. Semiconducting behavior of the anodically passive films formed on AZ31B alloy

    Directory of Open Access Journals (Sweden)

    A. Fattah-alhosseini

    2014-12-01

    Full Text Available This work includes determination of the semiconductor character and estimation of the dopant levels in the passive film formed on AZ31B alloy in 0.01 M NaOH, as well as the estimation of the passive film thickness as a function of the film formation potential. Mott–Schottky analysis revealed that the passive films displayed n-type semiconductive characteristics, where the oxygen vacancies and interstitials preponderated. Based on the Mott–Schottky analysis, it was shown that the calculated donor density increases linearly with increasing the formation potential. Also, the electrochemical impedance spectroscopy (EIS results indicated that the thickness of the passive film was decreased linearly with increasing the formation potential. The results showed that decreasing the formation potential offer better conditions for forming the passive films with higher protection behavior, due to the growth of a much thicker and less defective films.

  19. Electrochemical behavior of thin anodic oxide films on Zircaloy-4: Role of the mobile defects

    International Nuclear Information System (INIS)

    Salot, R.; Lefebvre-Joud, F.; Baroux, B.

    1996-01-01

    The first stages of the electrochemical oxidation of Zircaloy-4 are investigated using simple electrochemical tests and modeling the passive film modifications occurring as a result of contact with the electrolyte. Variations in electrode potential (open-circuit conditions) or current density (potentiodynamic scans) can be simply explained by a high field (F ∼ 10 6 V/cm) assisted passive film growth. Under open-circuit conditions, this field does not vary with exposure time (in the 2 h to 48 h range). The minimum electric field for the onset of high-field behavior is also evaluated and found smaller than the theoretical value which can be explained by a variation in the concentration of mobile defects throughout the film. Measurements of the electrode potential decay after a potentiodynamic scan confirm this model, allowing interpretation of the film modification as a combination of two separate phenomena: film growth under a high electric field and point defect annihilation

  20. Comparison of the Degradation of the Polarization Resistance of Symmetrical LSM-YSZ Cells, with Anode Supported Ni-YSZ/YSZ/LSM-YSZ SOFCs

    DEFF Research Database (Denmark)

    Torres da Silva, Iris Maura; Nielsen, Jimmi; Hjelm, Johan

    2009-01-01

    Impedance spectra of a symmetrical cell with SOFC cathodes (LSM-YSZ/YSZ/LSM-YSZ) and an anode supported planar SOFC (Ni-YSZ/YSZ/LSM-YSZ) were collected at OCV at 650{degree sign}C in air (cathode) and humidified (4%) hydrogen (anode), over 155 hours. The impedance was affected by degradation over...... time in the same frequency range for both cells (~10 Hz), possibly indicating that the same physical process was affected in both types of cell. However, deconvolution of the impedance data was not straightforward. When n-values of the constant phase elements in the otherwise identical equivalent...

  1. Experimental and analytical analysis of polarization and water transport behaviors of hydrogen alkaline membrane fuel cell

    Science.gov (United States)

    Huo, Sen; Zhou, Jiaxun; Wang, Tianyou; Chen, Rui; Jiao, Kui

    2018-04-01

    Experimental test and analytical modeling are conducted to investigate the operating behavior of an alkaline electrolyte membrane (AEM) fuel cell fed by H2/air (or O2) and explore the effect of various operating pressures on the water transfer mechanism. According to the experimental test, the cell performance is greatly improved through increasing the operating pressure gradient from anode to cathode which leads to significant liquid water permeation through the membrane. The high frequency resistance of the A901 alkaline membrane is observed to be relatively stable as the operating pressure varies based on the electrochemical impedance spectroscopy (EIS) method. Correspondingly, based on the modeling prediction, the averaged water content in the membrane electrode assembly (MEA) does not change too much which leads to the weak variation of membrane ohmic resistance. This reveals that the performance enhancement should give the credit to better electro-chemical reaction kinetics for both the anode and cathode, also prone by the EIS results. The reversion of water back diffusion direction across the membrane is also observed through analytical solution.

  2. Anodic oxidation

    CERN Document Server

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

    2013-01-01

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

  3. The dynamic behavior of pressure during purge process in the anode of a PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Gou, Jun; Pei, Pucheng; Wang, Ying [State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084 (China)

    2006-11-22

    A one-dimensional mathematic computational fluid dynamics model of a proton exchange membrane (PEM) fuel cell is presented in this paper to simulate the transient behavior of hydrogen pressure in the flow field during a typical dynamic process-the purge process. This model accounts for the mechanism of pressure wave transmission in the channels by employing the characteristic line method. A unique parameter-pressure swing, which represents the top value of pressure variation at certain point in the channel during the purge process, is brought up and studied as well as the pressure drop. The pressure distribution along the channel and the pressure drop during the purge process for different operating pressures, lengths of purge time, stoichiometric ratios and current densities are studied. The results indicate that the distributed pressure, pressure drop and pressure swing all increase with the increment of operating pressure. With a high operating pressure a second-falling stage can be seen in the pressure drop profile while with a relatively low operating pressure, a homogeneous distribution of pressure swing can be attained. A long purge time will provide enough time to show the whole part of the pressure drop curve, while only a part of the curve can be attained if a short purge time is adopted, but a relatively uniform distribution of pressure swing will show up at the moment. Compared with the condition of stoichiometric ratio 1, the pressure drop curve decreases more sharply after the top value and the pressure swing displays a more uniform distribution when the ratio is set beyond 1. Different current densities have no apparent influence on the pressure drop and the pressure swing during this transient process. All the distribution rules of related parameters deducted from this study will be helpful for optimizing the purging strategies on vehicles. (author)

  4. Polarization Behavior of Squeeze Cast Al2O3 Fiber Reinforced Aluminum Matrix Composites

    International Nuclear Information System (INIS)

    Ham, S. H.; Kang, Y. C.; Cho, K. M.; Park, I. M.

    1992-01-01

    Electrochemical polarization behavior of squeeze cast Al 2 O 3 short fiber reinforced Al alloy matrix composites was investigated for the basic understanding of the corrosion properties of the composites. The composites were fabricated with variations of fiber volume fraction and matrix alloys. It was found that the reinforced composites are more susceptible to corrosion attack than the unreinforced matrix alloys in general. Corrosion resistance shows decreasing tendency with increasing Al 2 O 3 fiber volume fraction in AC8A matrix. Effect of the matrix alloys revealed that the AC8A Al matrix composite is less susceptible to corrosion attack than the 2024 and 7075 Al matrix composites. Effect of plastic deformation on electrochemical polarization behavior of the squeeze cast Al/Al 2 O 3 composites was examined after extrusion of AC8A-10v/o Al 2 O 3 . Result shows that corrosion resistance is deteriorated after plastic deformation

  5. Differential behavioral and physiological effects of anodal transcranial direct current stimulation in healthy adults of younger and older age

    Science.gov (United States)

    Heise, Kirstin-Friederike; Niehoff, Martina; Feldheim, J.-F.; Liuzzi, Gianpiero; Gerloff, Christian; Hummel, Friedhelm C.

    2014-01-01

    Changes in γ-aminobutyric acid (GABA) mediated synaptic transmission have been associated with age-related motor and cognitive functional decline. Since anodal transcranial direct current stimulation (atDCS) has been suggested to target cortical GABAergic inhibitory interneurons, its potential for the treatment of deficient inhibitory activity and functional decline is being increasingly discussed. Therefore, after-effects of a single session of atDCS on resting-state and event-related short-interval intracortical inhibition (SICI) as evaluated with double-pulse TMS and dexterous manual performance were examined using a sham-controlled cross-over design in a sample of older and younger participants. The atDCS effect on resting-state inhibition differed in direction, magnitude, and timing, i.e., late relative release of inhibition in the younger and early relative increase in inhibition in the older. More pronounced release of event-related inhibition after atDCS was exclusively seen in the older. Event-related modulation of inhibition prior to stimulation predicted the magnitude of atDCS-induced effects on resting-state inhibition. Specifically, older participants with high modulatory capacity showed a disinhibitory effect comparable to the younger. Beneficial effects on behavior were mainly seen in the older and in tasks requiring higher dexterity, no clear association with physiological changes was found. Differential effects of atDCS on SICI, discussed to reflect GABAergic inhibition at the level of the primary motor cortex, might be distinct in older and younger participants depending on the functional integrity of the underlying neural network. Older participants with preserved modulatory capacity, i.e., a physiologically “young” motor network, were more likely to show a disinhibitory effect of atDCS. These results favor individually tailored application of tDCS with respect to specific target groups. PMID:25071555

  6. Effect of Nitrite Inhibitor on the Macrocell Corrosion Behavior of Reinforcing Steel

    Directory of Open Access Journals (Sweden)

    Zhonglu Cao

    2015-01-01

    Full Text Available The effect of nitrite ions on the macrocell corrosion behavior of reinforcing steel embedded in cement mortar was investigated by comparing and analyzing the macrocell corrosion current, macrocell polarization ratios, and slopes of anodic and cathodic steels. Based on the experimental results, the relationship between macrocell potential difference and macrocell current density was analyzed, and the mechanism of macrocell corrosion affected by nitrite ions was proposed. The results indicated that nitrite ions had significant impact on the macrocell polarization ratios of cathode and anode. The presence of nitrite could reduce the macrocell current by decreasing the macrocell potential difference and increasing the macrocell polarization resistance of the anode.

  7. Behavior of Lithium Metal Anodes under Various Capacity Utilization and High Current Density in Lithium Metal Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Shuhong; Zheng, Jianming; Li, Qiuyan; Li, Xing; Engelhard, Mark H.; Cao, Ruiguo; Zhang, Ji-Guang; Xu, Wu

    2018-01-01

    Lithium (Li) metal batteries (LMBs) are regarded as the most promising power sources for electric vehicles. Besides the Li dendrite growth and low Li Coulombic efficiency, how to well match Li metal anode with a high loading (normally over 3.0 mAh cm-2) cathode is another key challenge to achieve the real high energy density battery. In this work, we systematically investigate the effects of the Li metal capacity usage in each cycle, manipulated by varying the cathode areal loading, on the stability of Li metal anode and the cycling performance of LMBs using the LiNi1/3Mn1/3Co1/3O2 (NMC) cathode and an additive-containing dual-salt/carbonate-solvent electrolyte. It is demonstrated that the Li||NMC cells show decent long-term cycling performance even with NMC areal capacity loading up to ca. 4.0 mAh cm-2 and at a charge current density of 1.0 mA cm-2. The increase of the Li capacity usage in each cycle causes variation in the components of the solid electrolyte interphase (SEI) layer on Li metal anode and generates more ionic conductive species from this electrolyte. Further study reveals for the first time that the degradation of Li metal anode and the thickness of SEI layer on Li anode show linear relationship with the areal capacity of NMC cathode. Meanwhile, the expansion rate of consumed Li and the ratio of SEI thickness to NMC areal loading are kept almost the same value with increasing cathode loading, respectively. These fundamental findings provide new perspectives on the rational evaluation of Li metal anode stability for the development of rechargeable LMBs.

  8. Length-dependent corrosion behavior, Ni2+ release, cytocompatibility, and antibacterial ability of Ni-Ti-O nanopores anodically grown on biomedical NiTi alloy.

    Science.gov (United States)

    Hang, Ruiqiang; Liu, Yanlian; Bai, Long; Zhang, Xiangyu; Huang, Xiaobo; Jia, Husheng; Tang, Bin

    2018-08-01

    In the present work, nickel-titanium-oxygen nanopores with different length (0.55-114 μm) were anodically grown on nearly equiatomic nickel-titanium (NiTi) alloy. Length-dependent corrosion behavior, nickel ion (Ni 2+ ) release, cytocompatibility, and antibacterial ability were investigated by electrochemical, analytical chemistry, and biological methods. The results show constructing nanoporous structure on the NiTi alloy improve its corrosion resistance. However, the anodized samples release more Ni 2+ than that of the bare NiTi alloy, suggesting chemical dissolution of the nanopores rather than electrochemical corrosion governs the Ni 2+ release. In addition, the Ni 2+ release amount increases with nanopore length. The anodized samples show good cytocompatibility when the nanopore length is covers the one (1-11 μm) that the nanopores showing favorable antibacterial ability. Consequently, the nanopores with length in the range of 1-11 μm are promising as coatings of biomedical NiTi alloy for anti-infection, drug delivery, and other desirable applications. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. Behavior of Lithium Metal Anodes under Various Capacity Utilization and High Current Density in Lithium Metal Batteries

    International Nuclear Information System (INIS)

    Jiao, Shuhong; University of Science and Technology of China, Hefei; Zheng, Jianming; Li, Qiuyan; Li, Xing

    2017-01-01

    We report that lithium (Li) metal batteries (LMBs) have recently attracted extensive interest in the energy-storage field after silence from the public view for several decades. However, many challenges still need to be overcome before their practical application, especially those that are related to the interfacial instability of Li metal anodes. Here, we reveal for the first time that the thickness of the degradation layer on the metallic Li anode surface shows a linear relationship with Li areal capacity utilization up to 4.0 mAh cm -2 in a practical LMB system. The increase in Li capacity utilization in each cycle causes variations in the morphology and composition of the degradation layer on the Li anode. Under high Li capacity utilization, the current density for charge (i.e., Li deposition) is identified to be a key factor controlling the corrosion of the Li metal anode. Lastly, these fundamental findings provide new perspectives for the development of rechargeable LMBs.

  10. Investigation of the atmospheric behavior of dicarboxylic acids and other polar organic aerosol constituents

    International Nuclear Information System (INIS)

    Limbeck, A.

    2001-05-01

    The objective of the present work was to improve the present knowledge about the atmospheric behavior of polar organic aerosol constituents with special respect to dicarboxylic acids. To enable the simultaneous determination of polar organic compounds in atmospheric samples like aerosol or precipitation samples (atmospheric hydrometeors) a new GCMS method was developed. Almost all classes of oxygenated organic compounds like mono- and dicarboxylic acids, aldehydes, alcohols or polar aromatic compounds like phthalates could be determined with only one sample preparation scheme. The separation into two classes of organic compounds with different polarity was performed using solid phase extraction. After a sample pre-treatment of the derived fractions, including esterification of the acids and extraction with cyclohexane, the samples were analyzed with a GCMS system. The new method was applied for the analysis of simultaneously collected interstitial aerosol and cloud water samples from a continental background site in Central Europe (Sonnblick Observatory, located at 3106-m elevation in the Austrian Alps). In all samples a large variety of mono- and dicarboxylic acids were identified and quantified, together with some aldehydes, alcohols and aromatic compounds. Using the obtained data set, for the first time in-cloud scavenging efficiencies for dicarboxylic acids, monocarboxylic acids, and other polar organic compounds were calculated. The results were compared to sulfate, which exhibited an average scavenging efficiency of 0.94. In the last part of the present work the results from laboratory and field investigations conducted with the intention to yield an improved sampling technique for the correction of the positive sampling artifact (adsorption of gas phase organics onto the filter substrate) were presented. (author)

  11. Impact of optical feedback on current-induced polarization behavior of 1550 nm vertical-cavity surface-emitting lasers.

    Science.gov (United States)

    Deng, Tao; Wu, Zheng-Mao; Xie, Yi-Yuan; Wu, Jia-Gui; Tang, Xi; Fan, Li; Panajotov, Krassimir; Xia, Guang-Qiong

    2013-06-01

    Polarization switching (PS) between two orthogonal linearly polarized fundamental modes is experimentally observed in commercial free-running 1550 nm vertical-cavity surface-emitting lasers (VCSELs) (Raycan). The characteristics of this PS are strongly modified after introducing a polarization-preserved (PP) or polarization-orthogonal (PO) optical feedback. Under the case that the external cavity is approximately 30 cm, the PP optical feedback results in the PS point shifting toward a lower injection current, and the region within which the two polarization modes coexist is enlarged with the increase of the PP feedback strength. Under too-strong PP feedback levels, the PS disappears. The impact of PO optical feedback on VCSEL polarization behavior is quite similar to that of PP optical feedback, but larger feedback strength is needed to obtain similar results.

  12. Anodic dissolution and corrosion of alloy Cu30Ni in chloride solutions

    International Nuclear Information System (INIS)

    Zolotarev, E.I.

    1989-01-01

    The anodic and corrosion behavior of alloy Cu30Ni is studied in a solution of 3 N NaCl + 0.01 N HCl by a radiometric method using gamma isotopes of 58 Co (as a marker for Ni) and 64 Cu in combination with electrochemical measurements. It was established that under stationary conditions there was uniform dissolution of the alloy both during free corrosion and anodic polarization. The authors obtained partial anodic dissolution curves for the components of the alloy. It was shown that the dissolution kinetics differed from the mechanisms controlling dissolution of the corresponding pure metals. During corrosion of the alloy in an oxygen atmosphere a back precipitation of copper on the surface of the alloy was not observed. The characteristics observed in the corrosion-electrochemical behavior of the alloy in concentrated chloride solutions can be explained by the presence of Ni on the surface of the dissolving alloy

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

    Science.gov (United States)

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

    2014-12-01

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

  14. Effect of electrostatic interaction on thermochemical behavior of 12-crown-4 ether in various polar solvents

    International Nuclear Information System (INIS)

    Barannikov, Vladimir P.; Guseynov, Sabir S.; Vyugin, Anatoliy I.

    2010-01-01

    The enthalpies of solution of 12-crown-4 ether have been measured in chloroform, ethyl acetate, acetone, pyridine, acetonitrile and methanol at 298.15 K. The values of enthalpy of solvation and solute-solvent interaction were determined from the obtained results and similar literature data for 12-crown-4 in solvents of various polarities. It was shown that the certain correlation is observed between the enthalpy of solute-solvent interaction and the squared dipole moment of the solvent molecules for solutions in tetrachlormethane, ethyl acetate, pyridine, acetonitrile, DMF, DMSO and propylene carbonate. This means that the electrostatic interaction of 12-crown-4 with polar solvent molecules contributes significantly to the exothermic effect of solvation. The understated negative value was found for the enthalpy of interaction of 12-crown-4 with acetone that can be connected with domination of low polar conformer of the crown ether in acetone medium. The most negative values of enthalpy of solvation are observed for solutions in chloroform and water because of hydrogen bonding between O-atoms of crown ether and molecules of the indicated solvents. This effect is not observed for methanol. The negative coefficient of pairwise solute-solute interaction in methanol indicates that the effects of solvophobic solute-solute interaction and H-bonding of the ether molecule with chain associates of methanol are not evinced in the thermochemical behavior of 12-crown-4.

  15. Effects of anodal transcranial direct current stimulation (tDCS) on behavioral and spatial memory during the early stage of traumatic brain injury in the rats.

    Science.gov (United States)

    Yoon, Kyung Jae; Lee, Yong-Taek; Chae, Seoung Wan; Park, Chae Ri; Kim, Dae Yul

    2016-03-15

    Transcranial direct current stimulation (tDCS) is a noninvasive technique to modulate the neural membrane potential. Its effects in the early stage of traumatic brain injury (TBI) have rarely been investigated. This study assessed the effects of anodal tDCS on behavioral and spatial memory in a rat model of traumatic brain injury. Thirty six rats underwent lateral fluid percussion and were then randomly assigned to one of three groups: control (n=12), five-day tDCS over peri-lesional cortex at one (1W, n=12), or two (2W, n=12) weeks post-injury. The Barnes maze (BM) and Rotarod (RR) tests were evaluated in a blind manner on day 1, week 3 and week 5 post-injury. After three weeks, both the 1W and 2W groups showed significant improvements in the BM ratio (PtDCS ameliorated behavioral and spatial memory function in the early phase after TBI when it is delivered two weeks post-injury. Earlier stimulation (one week post-injury) improves spatial memory only. However, the beneficial effects did not persist after cessation of the anodal stimulation. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Potentiodynamic polarization study of the corrosion behavior of palladium-silver dental alloys.

    Science.gov (United States)

    Sun, Desheng; Brantley, William A; Frankel, Gerald S; Heshmati, Reza H; Johnston, William M

    2018-04-01

    Although palladium-silver alloys have been marketed for over 3 decades for metal-ceramic restorations, understanding of the corrosion behavior of current alloys is incomplete; this understanding is critical for evaluating biocompatibility and clinical performance. The purpose of this in vitro study was to characterize the corrosion behavior of 3 representative Pd-Ag alloys in simulated body fluid and oral environments and to compare them with a high-noble Au-Pd alloy. The study obtained values of important electrochemical corrosion parameters, with clinical relevance, for the rational selection of casting alloys. The room temperature in vitro corrosion characteristics of the 3 Pd-Ag alloys and the high-noble Au-Pd alloy were evaluated in 0.9% NaCl, 0.09% NaCl, and Fusayama solutions. After simulated porcelain firing heat treatment, 5 specimens of each alloy were immersed in the electrolytes for 24 hours. For each specimen, the open-circuit potential (OCP) was first recorded, and linear polarization was then performed from -20 mV to +20 mV (versus OCP) at a rate of 0.125 mV/s. Cyclic polarization was subsequently performed on 3 specimens of each alloy from -300 mV to +1000 mV and back to -300 mV (versus OCP) at a scanning rate of 1 mV/s. The differences in OCP and corrosion resistance parameters (zero-current potential and polarization resistance) among alloys and electrolyte combinations were compared with the 2-factor ANOVA (maximum-likelihood method) with post hoc Tukey adjustments (α=.05). The 24-hour OCPs and polarization resistance values of the 3 Pd-Ag alloys and the Au-Pd alloy were not significantly different (P=.233 and P=.211, respectively) for the same electrolyte, but significant differences were found for corrosion test results in different electrolytes (Palloy and electrolyte (P=.249 and P=.713, respectively). The 3 Pd-Ag silver alloys appeared to be resistant to chloride ion corrosion, and passivation and de-alloying were identified for these

  17. Enhanced tribological behavior of anodic films containing SiC and PTFE nanoparticles on Ti6Al4V alloy

    International Nuclear Information System (INIS)

    Li, Songmei; Zhu, Mengqi; Liu, Jianhua; Yu, Mei; Wu, Liang; Zhang, Jindan; Liang, Hongxing

    2014-01-01

    Highlights: • An environmental friendly sodium tartrate (C 4 O 6 H 4 Na 2 ) electrolyte is used. • SiC and PTFE nanoparticles reduce friction coefficient of composite films. • SiC and PTFE nanoparticles demonstrate a favorable synergistic effect on improving tribological properties of composite films. • Lubricating mechanisms of SiC and PTFE nanoparticles are discussed. - Abstract: Anodic films containing SiC and polytetrafluoroethylene (PTFE) nanoparticles were successfully fabricated on Ti6Al4V alloy by using anodic oxidation method in an environmental friendly electrolyte. The morphology, structure and composition of the films were studied with the scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results showed that the film contained a layered structure and have a surface full of petaloid bulges, which was totally different from the common anodic oxide film of the porous kind. The tribological properties of the films were investigated with dry friction tests in terms of the friction coefficient, wear rate and the morphology of worn surfaces. The results indicated that the SiC/PTFE composite film exhibited much better anti-wear and anti-friction performances than that of the SiC composite film, the PTFE composite film and the ordinary film without nanoparticles. The SiC/PTFE composite film has friction coefficient of 0.1 and wear rate of 20.133 mg/m, which was decreased respectively by 80% and 44.5% compared with that of the ordinary film. The lubricating mechanisms of the composite film containing SiC and PTFE nanoparticles were discussed. PTFE nanoparticles could lead to the formation of lubricating layer while SiC nanoparticles inside the lubricating layer turned sliding friction to rolling friction

  18. Impact of anode substrates on electrodeposited zinc over cycling in zinc-anode rechargeable alkaline batteries

    International Nuclear Information System (INIS)

    Wei, Xia; Desai, Divyaraj; Yadav, Gautam G.; Turney, Damon E.; Couzis, Alexander; Banerjee, Sanjoy

    2016-01-01

    Electrochemical behavior of Ag, Bi, Cu, Fe, Ni and Sn substrates on zinc deposition was evaluated over battery cycling by cyclic voltammetry and electrochemical impedance spectroscopy. The effect of Bi, Cu, Ni, and Sn substrates on zinc electrodeposition during battery cycling was investigated using scanning electron microscopy and X-ray diffraction. The corrosion behavior of each metal in 9 M KOH and the corrosion rates of zinc plated on each substrate were analyzed by Tafel extrapolation method from the potentiodynamic polarization curves and electrochemical impedance spectroscopy. Although the charge-transfer resistance (R_c_t) of zinc electrodeposition is lowest on Sn, Sn eventually corrodes on cycling in alkaline media. Use of Ni as a substrate causes zinc to deteriorate on account of rapid hydrogen evolution. Bi and Cu substrates are more suitable for use as current collectors in zinc-anode alkaline rechargeable batteries because of their low corrosion rate and compact zinc deposition over battery cycling.

  19. DFT study of the polarization behaviors of various distorted barium titanate crystals: The role of atomic displacements

    Science.gov (United States)

    Mirseraji, Mojtaba; Shahraki, Mehran Gholipour

    2018-06-01

    A Local Density Approximation (LDA) was employed to investigate the influence of applied strains on valence charge distributions, atomic displacements, Tisbnd O (3) bond distances and the total polarizations in barium titanate (BaTiO3). Four types of various strains were imposed on perfect tetragonal BaTiO3 along the a, c, ab and abc axial directions. Electromechanical properties of BaTiO3 were evaluated in LDA framework and a good agreement with previous results was achieved. The results show that, in the cases of a, ab strains, the values of polarization are almost constant in negative strains and increased by gradual increasing of the positive strains after a sudden enhancement at about +0.1% strain. In the case of c-strain, axial oxygen and Ti atoms underwent the highest displacements and the polarization linearly increased by applied strain. The case of abc-strain, represent the both types of features. In negative abc-strain show a similar polarization behavior like c-strain case and in positive region, polarization behavior is the same as a- and ab-strain cases. In the abc-strains of -0.3% and +0.1%, an abrupt jump in total polarization curve and a small change, are observed due to abnormal atomic displacements. In the most cases a direct relation between polarization and Tisbnd O (3) bond distance was also beheld. Finally, the effects of valence charge distributions on the atomic displacements and total polarizations are studied. It is found that there is a direct relation between polarization and Valence Charge Asymmetry of 3d -orbitals.

  20. Polarization-dependent asymmetric hysteresis behavior in ZnCrO layers

    International Nuclear Information System (INIS)

    Lee, Youngmin; Kim, Deukyoung; Lee, Sejoon; Fu, Dejun

    2012-01-01

    A ZnCrO layer grown on a Pt (111)/Al 2 O 3 (0001) substrate exhibits a lattice displacement induced ferroelectric behavior due to a modulation in the lattice translation symmetry. The top-to-bottom Pt/ZnCrO/Pt structure shows asymmetric hysteresis loops in positive and negative voltage bias regions. This is attributed to a change in the Schottky emission rate due to the nonlinear polarization of the ZnCrO barrier. The characteristics of the hysteresis loops depend on the film textures of ZnCrO, which vary with the oxygen partial pressure during the growth stage of the ZnCrO layers. The results suggest that ZnCrO has efficacy characteristics for applications in the non-volatile resistive-switching systems.

  1. Polarization-dependent asymmetric hysteresis behavior in ZnCrO layers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Youngmin; Kim, Deukyoung; Lee, Sejoon [Dongguk University, Seoul (Korea, Republic of); Fu, Dejun [Wuhan University, Wuhan (China)

    2012-06-15

    A ZnCrO layer grown on a Pt (111)/Al{sub 2}O{sub 3} (0001) substrate exhibits a lattice displacement induced ferroelectric behavior due to a modulation in the lattice translation symmetry. The top-to-bottom Pt/ZnCrO/Pt structure shows asymmetric hysteresis loops in positive and negative voltage bias regions. This is attributed to a change in the Schottky emission rate due to the nonlinear polarization of the ZnCrO barrier. The characteristics of the hysteresis loops depend on the film textures of ZnCrO, which vary with the oxygen partial pressure during the growth stage of the ZnCrO layers. The results suggest that ZnCrO has efficacy characteristics for applications in the non-volatile resistive-switching systems.

  2. Factors Affecting Dissolution Resistance of AC Anodizing Al in Sodium Carbonate Solution

    International Nuclear Information System (INIS)

    Abou-Krisha, M.

    2001-01-01

    Studies were performed to determine the effect of different factors on the properties and so the dissolution resistance of the anodic film of Al. Conductance and thermometric measurements were applied to evaluate the dissolution rate. The effect of applied AC voltage concentration of sodium carbonate solution, the anodization time and the temperature of sodium carbonate solutions show a parallel increase in the dissolution resistance of studied Al in hydrochloride acid. The results show that films formed by sodium carbonate solution were of porous type and have pronounced high resistance. Scanning electron microscope and x-ray diffraction further examined the films. The anodic and cathodic behavior and the effect of the scanning rate on the polarization of Al in sodium carbonate solution were studied. The regression analysis was applied to all results. (Author)

  3. Thermal behavior and ice-table depth within the north polar erg of Mars

    Science.gov (United States)

    Putzig, Nathaniel E.; Mellon, Michael T.; Herkenhoff, Kenneth E.; Phillips, Roger J.; Davis, Brian J.; Ewer, Kenneth J.; Bowers, Lauren M.

    2014-02-01

    We fully resolve a long-standing thermal discrepancy concerning the north polar erg of Mars. Several recent studies have shown that the erg's thermal properties are consistent with normal basaltic sand overlying shallow ground ice or ice-cemented sand. Our findings bolster that conclusion by thoroughly characterizing the thermal behavior of the erg, demonstrating that other likely forms of physical heterogeneity play only a minor role, and obviating the need to invoke exotic materials. Thermal inertia as calculated from orbital temperature observations of the dunes has previously been found to be more consistent with dust-sized materials than with sand. Since theory and laboratory data show that dunes will only form out of sand-sized particles, exotic sand-sized agglomerations of dust have been invoked to explain the low values of thermal inertia. However, the polar dunes exhibit the same darker appearance and color as that of dunes found elsewhere on the planet that have thermal inertia consistent with normal sand-sized basaltic grains, whereas Martian dust deposits are generally lighter and redder. The alternative explanation for the discrepancy as a thermal effect of a shallow ice table is supported by our analysis of observations from the Mars Global Surveyor Thermal Emission Spectrometer and the Mars Odyssey Thermal Emission Imaging System and by forward modeling of physical heterogeneity. In addition, our results exclude a uniform composition of dark dust-sized materials, and they show that the thermal effects of the dune slopes and bright interdune materials evident in high-resolution images cannot account for the erg's thermal behavior.

  4. Thermal behavior and ice-table depth within the north polar erg of Mars

    Science.gov (United States)

    Putzig, Nathaniel E.; Mellon, Michael T.; Herkenhoff, Kenneth E.; Phillips, Roger J.; Davis, Brian J.; Ewer, Kenneth J.; Bowers, Lauren M.

    2014-01-01

    We fully resolve a long-standing thermal discrepancy concerning the north polar erg of Mars. Several recent studies have shown that the erg’s thermal properties are consistent with normal basaltic sand overlying shallow ground ice or ice-cemented sand. Our findings bolster that conclusion by thoroughly characterizing the thermal behavior of the erg, demonstrating that other likely forms of physical heterogeneity play only a minor role, and obviating the need to invoke exotic materials. Thermal inertia as calculated from orbital temperature observations of the dunes has previously been found to be more consistent with dust-sized materials than with sand. Since theory and laboratory data show that dunes will only form out of sand-sized particles, exotic sand-sized agglomerations of dust have been invoked to explain the low values of thermal inertia. However, the polar dunes exhibit the same darker appearance and color as that of dunes found elsewhere on the planet that have thermal inertia consistent with normal sand-sized basaltic grains, whereas Martian dust deposits are generally lighter and redder. The alternative explanation for the discrepancy as a thermal effect of a shallow ice table is supported by our analysis of observations from the Mars Global Surveyor Thermal Emission Spectrometer and the Mars Odyssey Thermal Emission Imaging System and by forward modeling of physical heterogeneity. In addition, our results exclude a uniform composition of dark dust-sized materials, and they show that the thermal effects of the dune slopes and bright interdune materials evident in high-resolution images cannot account for the erg’s thermal behavior.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-05-15

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

  6. Effect of small addition of aluminum on electrochemical corrosion behavior of magnesium-calcium sacrificial anode in underground environment

    International Nuclear Information System (INIS)

    Rizam, S.S.; Sasirehka, G.; Firdaus, A.M.H.; Mahdi, C.I.; Nazree, D.M.; Abdul Razak Daud; Azrem, A.A.

    2009-01-01

    The effect of small addition of Al on the electrochemical performances was investigated by open circuit potential and Tafel Extrapolation method. The results show that open circuit potential reveals as-cast Mg containing Ca alloys with minor content of Al maintained highly negative potential with the range of -1.68 to -1.63 V SCE in comparison to both pure Mg (-1.60V SCE ) and commercial high potential Mg content. Corrosion rate for the as-cast samples remains higher (30-17 mpy) than pure Mg (3 mpy) and commercial high potential Mg anode (14 mpy). The increasing small content of Al results in the reduction of corrosion rate significantly. Therefore, it proves that the performance of Mg containing Ca alloy is strongly influenced by the concentration of Al. (author)

  7. Li and Na storage behavior of bowl-like hollow Co3O4 microspheres as an anode material for lithium-ion and sodium-ion batteries

    International Nuclear Information System (INIS)

    Wen, Jian-Wu; Zhang, Da-Wei; Zang, Yong; Sun, Xin; Cheng, Bin; Ding, Chu-Xiong; Yu, Yan; Chen, Chun-Hua

    2014-01-01

    Highlights: • A unique bowl-like hollow spherical Co 3 O 4 structure is prepared through a simple, low-cost and mass-yield method. • Such a bowl-like hollow Co 3 O 4 microsphere demonstrates extraordinary rate and cycling performance for Li-storage. • The sodium-storage behavior of Co 3 O 4 is investigated for the first time. - Abstract: Bowl-like hollow Co 3 O 4 microspheres are prepared via a simple and low-cost route by thermally treating Co-containing resorcinol-formaldehyde composites gel in air. Scanning electron microscopy, transmission electron microscope and N 2 adsorption-desorption measurements demonstrate that these bowl-like hollow Co 3 O 4 microspheres are composed of hollow inner cavities and outer shell walls (70 nm thickness), on which a considerable amount of mesopores centered around 5-17 nm size are distributed. When employed as the anode material for lithium-ion batteries, these bowl-like hollow Co 3 O 4 microspheres exhibit extraordinary cycling performance (111% retention after 50 cycles owing to capacity rise), fairly high rate capacity (650 mAh g −1 at 5 C) and enhanced lithium storage capacity. Meanwhile, the Na-storage behavior of Co 3 O 4 as an anode material of Na-ion batteries is initially investigated based on such a hollow structure and it exhibits similar feature of discharge/charge profiles and a high initial discharge capacity but relatively moderate capacity retention compared with the Li-storage performance

  8. Differences in the electrochemical behavior of ruthenium and iridium oxide in electrocatalytic coatings of activated titanium anodes prepared by the sol–gel procedure

    Directory of Open Access Journals (Sweden)

    VLADIMIR V. PANIĆ

    2010-10-01

    Full Text Available The electrochemical characteristics of Ti0.6Ir0.4O2/Ti and Ti0.6Ru0.4O2/Ti anodes prepared by the sol–gel procedure from the corresponding oxide sols, obtained by force hydrolysis of the corresponding metal chlorides, were compared. The voltammetric properties in H2SO4 solution indicate that Ti0.6Ir0.4O2/Ti has more pronounced pseudocapacitive characteristics, caused by proton-assisted, solid state surface redox transitions of the oxide. At potentials negative to 0.0 VSCE, this electrode is of poor conductivity and activity, while the voltammetric behavior of the Ti0.6Ru0.4O2/Ti electrode is governed by proton injection/ejection into the oxide structure. The Ti0.6Ir0.4O2/Ti electrode had a higher electrocatalytical activity for oxygen evolution, while the investigated anodes were of similar activity for chlorine evolution. The potential dependence of the impedance characteristics showed that the Ti0.6Ru0.4O2/Ti electrode behaved like a capacitor over a wider potential range than the Ti0.6Ir0.4O2/Ti electrode, with fully-developed pseudocapacitive properties at potentials positive to 0.60 VSCE. However, the impedance characteristics of the Ti0.6Ir0.4O2/Ti electrode changed with increasing potential from resistor-like to capacitor-like behavior.

  9. Anodizing of aluminum with improved corrosion properties

    International Nuclear Information System (INIS)

    John, P.; Khan, I.U.

    2010-01-01

    Anodizing of aluminum was studied in sulphuric/oxalic/boric acid electroiyte system. The corrosion resistance of the anodic oxide coating of aluminum was determined by potentiodynamic polarization test and scanning electron microscope (SEM) was used to investigate the surface morphology before and after corrosion test. It was found that the oxide coating obtained by this method showed better corrosion resistance with no significant difference in surface morphology. (author)

  10. The enhanced spin-polarized transport behaviors through cobalt benzene-porphyrin-benzene molecular junctions: the effect of functional groups

    Science.gov (United States)

    Cheng, Jue-Fei; Zhou, Liping; Wen, Zhongqian; Yan, Qiang; Han, Qin; Gao, Lei

    2017-05-01

    The modification effects of the groups amino (NH2) and nitro (NO2) on the spin polarized transport properties of the cobalt benzene-porphyrin-benzene (Co-BPB) molecule coupled to gold (Au) nanowire electrodes are investigated by the nonequilibrium Green’s function method combined with the density functional theory. The calculation results show that functional groups can lead to the significant spin-filter effect, enhanced low-bias negative differential resistance (NDR) behavior and novel reverse rectifying effect in Co-BPB molecular junction. The locations and types of functional groups have distinct influences on spin-polarized transport performances. The configuration with NH2 group substituting H atom in central porphyrin ring has larger spin-down current compared to that with NO2 substitution. And Co-BPB molecule junction with NH2 group substituting H atom in side benzene ring shows reverse rectifying effect. Detailed analyses confirm that NH2 and NO2 group substitution change the spin-polarized transferred charge, which makes the highest occupied molecular orbitals (HOMO) of spin-down channel of Co-BPB closer to the Fermi level. And the shift of HOMO strengthens the spin-polarized coupling between the molecular orbitals and the electrodes, leading to the enhanced spin-polarized behavior. Our findings might be useful in the design of multi-functional molecular devices in the future.

  11. Effect of pulse current parameters on the mechanical and corrosion properties of anodized nanoporous aluminum coatings

    International Nuclear Information System (INIS)

    Mohammadi, Iman; Ahmadi, Shahab; Afshar, Abdollah

    2016-01-01

    In this study, the effects of pulse current parameters on corrosion resistance and mechanical properties of anodized coatings were evaluated. Hardness measurements, polarization and electrochemical impedance spectroscopy tests were employed to investigate the mechanical properties and corrosion behavior of these coatings. Also, field emission scanning electron microscopy (FE-SEM) was used to analyze the surface morphology and microstructure of the coatings. It was found that the properties of anodized coatings were dependent on various parameters, among which, time, temperature and pulse current parameters (current density limit, frequency and duty cycle) were optimized. Analysis of Variance (ANOVA) was conducted in order to optimize the results of designed experiments for predicting the hardness of anodic Al_2O_3 coatings. Experimental results showed that the temperature and the interaction of quadratic behavior of minimum current density with frequency and duty cycle were the most important factors influencing the hardness of these coatings. It was indicated that the highest hardness value of 642 HV was attained at the maximum and minimum current densities of 4.4, 1.27 A/dm"2, respectively, a frequency of 82 Hz, procedure time of 27.2 min, duty cycle of 80.2% and the bath temperature of 13.5 °C. In addition, the FE-SEM micrographs showed that the highest density is obtained through the mentioned optimum conditions. Moreover, the electrochemical tests revealed that the highest polarization resistance obtained at optimum conditions was more than 20 times greater than the other samples. - Highlights: • Electrolyte temperature undesirably influences the hardness of anodized coatings. • Maximum hardness of coatings was evaluated by optimization of effective parameters. • The diameter of alumina nanotube considerably affects hardness of anodized coating. • R_P of the sample formed at optimum condition was at least 20 times more than others. • Porosity is the

  12. Effect of pulse current parameters on the mechanical and corrosion properties of anodized nanoporous aluminum coatings

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadi, Iman, E-mail: imanmohammadi68@gmail.com; Ahmadi, Shahab; Afshar, Abdollah

    2016-11-01

    In this study, the effects of pulse current parameters on corrosion resistance and mechanical properties of anodized coatings were evaluated. Hardness measurements, polarization and electrochemical impedance spectroscopy tests were employed to investigate the mechanical properties and corrosion behavior of these coatings. Also, field emission scanning electron microscopy (FE-SEM) was used to analyze the surface morphology and microstructure of the coatings. It was found that the properties of anodized coatings were dependent on various parameters, among which, time, temperature and pulse current parameters (current density limit, frequency and duty cycle) were optimized. Analysis of Variance (ANOVA) was conducted in order to optimize the results of designed experiments for predicting the hardness of anodic Al{sub 2}O{sub 3} coatings. Experimental results showed that the temperature and the interaction of quadratic behavior of minimum current density with frequency and duty cycle were the most important factors influencing the hardness of these coatings. It was indicated that the highest hardness value of 642 HV was attained at the maximum and minimum current densities of 4.4, 1.27 A/dm{sup 2}, respectively, a frequency of 82 Hz, procedure time of 27.2 min, duty cycle of 80.2% and the bath temperature of 13.5 °C. In addition, the FE-SEM micrographs showed that the highest density is obtained through the mentioned optimum conditions. Moreover, the electrochemical tests revealed that the highest polarization resistance obtained at optimum conditions was more than 20 times greater than the other samples. - Highlights: • Electrolyte temperature undesirably influences the hardness of anodized coatings. • Maximum hardness of coatings was evaluated by optimization of effective parameters. • The diameter of alumina nanotube considerably affects hardness of anodized coating. • R{sub P} of the sample formed at optimum condition was at least 20 times more than others

  13. Polarization fluctuation behavior of lanthanum substituted Bi{sub 4}Ti{sub 3}O{sub 12} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Ni; Xiang, Ping-Hua, E-mail: phxiang@ee.ecnu.edu.cn; Zhang, Yuan-Yuan; Wu, Xing; Tang, Xiao-Dong; Yang, Ping-Xiong; Duan, Chun-Gang; Chu, Jun-Hao [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China)

    2015-09-14

    Polarization fluctuation behavior of lanthanum substituted Bi{sub 4}Ti{sub 3}O{sub 12} (Bi{sub 4−x}La{sub x}Ti{sub 3}O{sub 12}, BLT) ferroelectric thin films has been examined. Remnant polarization exhibits an initial increase (P{sub up}, 1–10{sup 6} cycles) and a subsequent decrease (P{sub down}, 10{sup 6}–10{sup 9} cycles) with switching cycles, whereas the dielectric constant exhibits a continuous decrease. By careful investigations on the effect of switching frequency and annealing atmosphere on the polarization fluctuation characteristics, we propose that this polarization fluctuation characteristic of BLT films is attributed to the competition between domain pinning and passive layer growing effect, due to the redistribution of oxygen vacancy related defect under external applied field. P{sub up} behavior is dominated by the unpinning of pinned domain, while P{sub down} behavior is dominated by the reduction of applied field on BLT bulk layer, due to the growing of the passive layer between BLT and Pt electrode. By assuming the dielectric constant and initial thickness of passive layer, the passive layer was estimated to be about 2–5 times thicker than the initial state after 10{sup 9} cycling.

  14. Vacuum arc anode phenomena

    International Nuclear Information System (INIS)

    Miller, H.C.

    1976-01-01

    A brief review of anode phenomena in vacuum arcs is presented. Discussed in succession are: the transition of the arc into the anode spot mode; the temperature of the anode before, during and after the anode spot forms; and anode ions. Characteristically the anode spot has a temperature of the order of the atmospheric boiling point of the anode material and is a copious source of vapor and energetic ions. The dominant mechanism controlling the transition of the vacuum arc into the anode spot mode appears to depend upon the electrode geometry, the electrode material, and the current waveform of the particular vacuum arc being considered. Either magnetic constriction in the gap plasma or gross anode melting can trigger the transition; indeed, a combination of the two is a common cause of anode spot formation

  15. Research on high-temperature compression and creep behavior of porous Cu–Ni–Cr alloy for molten carbonate fuel cell anodes

    Directory of Open Access Journals (Sweden)

    Li W.

    2015-06-01

    Full Text Available The effect of porosity on high temperature compression and creep behavior of porous Cu alloy for the new molten carbonate fuel cell anodes was examined. Optical microscopy and scanning electron microscopy were used to investigate and analyze the details of the microstructure and surface deformation. Compression creep tests were utilized to evaluate the mechanical properties of the alloy at 650 °C. The compression strength, elastic modulus, and yield stress all increased with the decrease in porosity. Under the same creep stress, the materials with higher porosity exhibited inferior creep resistance and higher steadystate creep rate. The creep behavior has been classified in terms of two stages. The first stage relates to grain rearrangement which results from the destruction of large pores by the applied load. In the second stage, small pores are collapsed by a subsequent sintering process under the load. The main deformation mechanism consists in that several deformation bands generate sequentially under the perpendicular loading, and in these deformation bands the pores are deformed by flattering and collapsing sequentially. On the other hand, the shape of a pore has a severe influence on the creep resistance of the material, i.e. every increase of pore size corresponds to a decrease in creep resistance.

  16. Self-ordered Porous Alumina Fabricated via Phosphonic Acid Anodizing

    OpenAIRE

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

    2016-01-01

    Self-ordered periodic porous alumina with an undiscovered cell diameter was fabricated via electrochemical anodizing in a new electrolyte, phosphonic acid (H3PO3). High-purity aluminum plates were anodized in phosphonic acid solution under various operating conditions of voltage, temperature, concentration, and anodizing time. Phosphonic acid anodizing at 150-180 V caused the self-ordering behavior of porous alumina, and an ideal honeycomb nanostructure measuring 370-440 nm in cell diameter w...

  17. Synthesis and characterization of titania nanotubes by anodizing of titanium in fluoride containing electrolytes

    Science.gov (United States)

    Ahmad, Akhlaq; Haq, Ehsan Ul; Akhtar, Waseem; Arshad, Muhammad; Ahmad, Zubair

    2017-11-01

    Titania nanotubular structure was prepared by anodizing titanium metal in the fluoride containing electrolytes and studied for hydrogen reduction using photo electrochemical cell. Potentiodynamic scan was performed before actual anodizing to optimize the anodizing conditions. The morphology of the TiO2 nanotubes was investigated by SEM and the presence of TiO2 nanotubes was confirmed. Raman spectroscopy was done to confirm the different phases present. Hydrogen generation capability was revealed by electrochemical testing in three-electrode system in dark and in visible light at 200 W power using Gamry Potentiostat. The corrosion potential of TiO2 nanotubes produced was found to be more active side in potassium hydroxide solution under visible light than in the dark condition. Cathodic polarization behavior of specimens in the presence of light showed more activity towards hydrogen generation than in dark condition. In comparison, the hydrogen generation capability of specimen anodized in 2H15 electrolyte was higher than specimens anodized in other electrolytes. Electrochemical impedance spectroscopy was used to study the charge transfer resistance of the nanotubes produced. The results showed that TiO2 nanotubular structure is a promising material for photoelectrochemical cell. Low-charge transfer resistance also depicts that it can be efficiently used to harvest solar energy.

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

    Directory of Open Access Journals (Sweden)

    CHEN Gao-hong

    2017-07-01

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

  19. Yeast G-proteins mediate directional sensing and polarization behaviors in response to changes in pheromone gradient direction

    Science.gov (United States)

    Moore, Travis I.; Tanaka, Hiromasa; Kim, Hyung Joon; Jeon, Noo Li; Yi, Tau-Mu

    2013-01-01

    Yeast cells polarize by projecting up mating pheromone gradients, a classic cell polarity behavior. However, these chemical gradients may shift direction. We examine how yeast cells sense and respond to a 180o switch in the direction of microfluidically generated pheromone gradients. We identify two behaviors: at low concentrations of α-factor, the initial projection grows by bending, whereas at high concentrations, cells form a second projection toward the new source. Mutations that increase heterotrimeric G-protein activity expand the bending-growth morphology to high concentrations; mutations that increase Cdc42 activity result in second projections at low concentrations. Gradient-sensing projection bending requires interaction between Gβγ and Cdc24, whereas gradient-nonsensing projection extension is stimulated by Bem1 and hyperactivated Cdc42. Of interest, a mutation in Gα affects both bending and extension. Finally, we find a genetic perturbation that exhibits both behaviors. Overexpression of the formin Bni1, a component of the polarisome, makes both bending-growth projections and second projections at low and high α-factor concentrations, suggesting a role for Bni1 downstream of the heterotrimeric G-protein and Cdc42 during gradient sensing and response. Thus we demonstrate that G-proteins modulate in a ligand-dependent manner two fundamental cell-polarity behaviors in response to gradient directional change. PMID:23242998

  20. Implications of rapid environmental change for polar bear behavior and sociality

    Science.gov (United States)

    Atwood, Todd C.

    2017-01-01

    Historically, the Arctic sea ice has functioned as a structural barrier that has limited the nature and extent of interactions between humans and polar bears (Ursus maritimus). However, declining sea ice extent, brought about by global climate change, is increasing the potential for human-polar bear interactions. Loss of sea ice habitat is driving changes to both human and polar bear behavior—it is facilitating increases in human activities (e.g., offshore oil and gas exploration and extraction, trans-Arctic shipping, recreation), while also causing the displacement of bears from preferred foraging habitat (i.e., sea ice over biologically productive shallow) to land in some portions of their range. The end result of these changes is that polar bears are spending greater amounts of time in close proximity to people. Coexistence between humans and polar bears will require imposing mechanisms to manage further development, as well as mitigation strategies that reduce the burden to local communities.

  1. The effect of zinc on the aluminum anode of the aluminum-air battery

    Science.gov (United States)

    Tang, Yougen; Lu, Lingbin; Roesky, Herbert W.; Wang, Laiwen; Huang, Baiyun

    Aluminum is an ideal material for batteries, due to its excellent electrochemical performance. Herein, the effect of zinc on the aluminum anode of the aluminum-air battery, as an additive for aluminum alloy and electrolytes, has been studied. The results show that zinc can decrease the anodic polarization, restrain the hydrogen evolution and increase the anodic utilization rate.

  2. Electrochemical energy storage behavior of Sn/SnO2 double phase nanocomposite anodes produced on the multiwalled carbon nanotube buckypapers for lithium-ion batteries

    Science.gov (United States)

    Alaf, Mirac; Akbulut, Hatem

    2014-02-01

    Recent development of electrode materials for Li-ion batteries is driven mainly by hybrid nanocomposite structures consisting of Li storage compounds and CNTs. In this study, tin/tinoxide (Sn/SnO2) films and tin/tinoxide/multi walled carbon nanotube (Sn/SnO2/MWCNT) nanocomposites are produced by a two steps process; thermal evaporation and subsequent plasma oxidation as anode materials for Li-ion batteries. The physical, structural, and electrochemical behaviors of the nanocomposite electrodes containing MWCNTs are discussed. The ratio between metallic tin (Sn) and tinoxide (SnO2) is controlled with plasma oxidation time and effects of the ratio are investigated on the structural and electrochemical properties. The greatly enhanced electrochemical performance is mainly due to the morphological stability and reduced diffusion resistance, which are induced by MWCNT core and deposited Sn/SnO2 double phase shell. The outstanding long-term cycling stability is a result of the two layers Sn and SnO2 phases on MWCNTs. The nanoscale Sn/SnO2/MWCNT network provides good electrical conductivity, and the creation of open spaces that buffer a large volume change during the Li-alloying/de-alloying reaction.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-03-15

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

  4. Pt -based anode catalysts for direct ethanol fuel cells

    International Nuclear Information System (INIS)

    Hoyos, Bibian; Sanchez, Carlos; Gonzalez, Javier

    2007-01-01

    In this work it is studied the electro-catalytic behavior of pure platinum and platinum-based alloys with Ru, Sn, Ir, and Os supported on carbon to the ethanol electro-oxidation in aims to develop anodic catalysts for direct ethanol fuel cells, additionally, porous electrodes and membrane electrode assemblies were built for proton exchange membrane fuel cells in which the electrodes were tested. Catalysts characterization was made by cyclic voltammetry whereas the fuel cells behavior tests were made by current-potential polarization curves. in general, all alloys show a lower on-set reaction potential and a higher catalytic activity than pure platinum. However, in the high over potential zone, pure platinum has higher catalytic activity than the alloys. In agreement with these results, the alloys studied here could be useful in fuel cells operating on moderated and low current

  5. A STUDY OF BROADBAND FARADAY ROTATION AND POLARIZATION BEHAVIOR OVER 1.3–10 GHz IN 36 DISCRETE RADIO SOURCES

    International Nuclear Information System (INIS)

    Anderson, C. S.; Gaensler, B. M.; Feain, I. J.

    2016-01-01

    We present a broadband polarization analysis of 36 discrete polarized radio sources over a very broad, densely sampled frequency band. Our sample was selected on the basis of polarization behavior apparent in narrowband archival data at 1.4 GHz: half the sample shows complicated frequency-dependent polarization behavior (i.e., Faraday complexity) at these frequencies, while half shows comparatively simple behavior (i.e., they appear Faraday simple ). We re-observed the sample using the Australia Telescope Compact Array in full polarization, with 6 GHz of densely sampled frequency coverage spanning 1.3–10 GHz. We have devised a general polarization modeling technique that allows us to identify multiple polarized emission components in a source, and to characterize their properties. We detect Faraday complex behavior in almost every source in our sample. Several sources exhibit particularly remarkable polarization behavior. By comparing our new and archival data, we have identified temporal variability in the broadband integrated polarization spectra of some sources. In a number of cases, the characteristics of the polarized emission components, including the range of Faraday depths over which they emit, their temporal variability, spectral index, and the linear extent of the source, allow us to argue that the spectropolarimetric data encode information about the magneto-ionic environment of active galactic nuclei themselves. Furthermore, the data place direct constraints on the geometry and magneto-ionic structure of this material. We discuss the consequences of restricted frequency bands on the detection and interpretation of polarization structures, and the implications for upcoming spectropolarimetric surveys.

  6. Advances in aluminum anodizing

    Science.gov (United States)

    Dale, K. H.

    1969-01-01

    White anodize is applied to aluminum alloy surfaces by specific surface preparation, anodizing, pigmentation, and sealing techniques. The development techniques resulted in alloys, which are used in space vehicles, with good reflectance values and excellent corrosive resistance.

  7. Hydrogen effects in anodic grinding of WC-Co sintered alloy

    International Nuclear Information System (INIS)

    Lunarska, E.; Zaborski, St.

    2001-01-01

    The effects of anodic polarization applied in grinding of sintered WC C o alloy on properties of surface layer, quality of ground surface and efficiency of the treatment were studied. The nonmonotonical change of the surface roughness, the energy consumption and the wear of tool was stated at increasing anodic polarization. The optimum values of above parameters were achieved at application of anodic polarization at which the Co selective dissolution and hydrogen ingress into the ground metal. affecting the internal friction spectra were stated. The assistance of hydrogen induced deterioration and Co selective dissolution in the surface layer in the anodic grinding of WC-Co alloy has been discussed. (author)

  8. Effect of various de-anodizing techniques on the surface stability of non-colored and colored nanoporous AAO films in acidic solution

    Science.gov (United States)

    Awad, Ahmed M.; Shehata, Omnia S.; Heakal, Fakiha El-Taib

    2015-12-01

    Anodic aluminum oxide (AAO) is well known as an important nanostructured material, and a useful template in the fabrication of nanostructures. Nanoporous anodic alumina (PAA) with high open porosity was prepared by adopting three de-anodizing regimes following the first anodizing step and preceding the second one. The de-anodizing methods include electrolytic etching (EE) and chemical etching using either phosphoric acid (PE) or sodium hydroxide (HE) solutions. Three of the obtained AAO samples were black colored by electrodeposition of copper nanoparticles in their pores. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques were used to characterize the electrochemical performance of the two sets of the prepared samples. In general, the data obtained in aggressive aerated 0.5 M HCl solution demonstrated dissimilar behavior for the three prepared samples despite that the second anodizing step was the same for all of them. The data indicated that the resistance and thickness of the inner barrier part of nano-PAA film, are the main controlling factors determining its stability. On the other hand, coloring the film decreased its stability due to the galvanic effect. The difference in the electrochemical behavior of the three colored samples was discussed based on the difference in both the pore size and thickness of the outer porous part of PAA film as supported by SEM, TEM and cross-sectional micrographs. These results can thus contribute for better engineering applications of nanoporous AAO.

  9. Polarity dependent photoisomerization of ether substituted azodyes: Synthesis and photoswitching behavior.

    Science.gov (United States)

    Gan, Siew Mei; Pearl, Zynia Fernandes; Yuvaraj, A R; Lutfor, M R; Gurumurthy, Hegde

    2015-10-05

    Two new ether substituted azodyes were synthesized and characterized by different spectral analysis such as (1)H NMR, (13)C NMR, FTIR and UV/Vis. Synthesized compounds were used to study the photoisomerization phenomenon by using UV-Vis spectro-photometer. Interesting polarity dependent effect is observed for the first time on these materials. Trans-cis (E-Z) and cis-trans (Z-E) conversion occurred within 41 s and 445 min, respectively for both the compounds in solutions. Polarizing optical microscopy studies revealed that there is no liquid crystal phase for both the compounds. The dramatic variation in the optical property is speculated to be the polarity of the chemical species. These derivatives are useful to fabricate optical data storage devices. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Thermal behavior induced by vacuum polarization on causal horizons in comparison with the standard heat bath formalism

    Energy Technology Data Exchange (ETDEWEB)

    Schroer, Bert [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]|[Institut fuer Theoretische Physik, Berlin (Germany); E-mail schroer@cbpf.br

    2003-02-01

    Modular theory of operator algebras and the associated K MS property are used to obtain a unified description for the thermal aspects of the standard heat bath situation and those caused by quantum vacuum fluctuations from localization. An algebraic variant of light front holography reveals that the vacuum polarization on wedge horizons is compressed into the light ray direction. Their absence in the transverse direction is the prerequisite to an area (generalized Banknotes-) behavior of entropy-like measures which reveal the loss of purity due to restrictions to wedges and their horizons. Besides the well-known fact that localization-induced (generalized Hawking-) temperature is fixed by the geometric aspects, this area behavior (versus the standard volume dependence) constitutes the main difference between localization-caused and standard thermal behavior. (author)

  11. An Insoluble Titanium-Lead Anode for Sulfate Electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Ferdman, Alla

    2005-05-11

    The project is devoted to the development of novel insoluble anodes for copper electrowinning and electrolytic manganese dioxide (EMD) production. The anodes are made of titanium-lead composite material produced by techniques of powder metallurgy, compaction of titanium powder, sintering and subsequent lead infiltration. The titanium-lead anode combines beneficial electrochemical behavior of a lead anode with high mechanical properties and corrosion resistance of a titanium anode. In the titanium-lead anode, the titanium stabilizes the lead, preventing it from spalling, and the lead sheathes the titanium, protecting it from passivation. Interconnections between manufacturing process, structure, composition and properties of the titanium-lead composite material were investigated. The material containing 20-30 vol.% of lead had optimal combination of mechanical and electrochemical properties. Optimal process parameters to manufacture the anodes were identified. Prototypes having optimized composition and structure were produced for testing in operating conditions of copper electrowinning and EMD production. Bench-scale, mini-pilot scale and pilot scale tests were performed. The test anodes were of both a plate design and a flow-through cylindrical design. The cylindrical anodes were composed of cylinders containing titanium inner rods and fitting over titanium-lead bushings. The cylindrical design allows the electrolyte to flow through the anode, which enhances diffusion of the electrolyte reactants. The cylindrical anodes demonstrate higher mass transport capabilities and increased electrical efficiency compared to the plate anodes. Copper electrowinning represents the primary target market for the titanium-lead anode. A full-size cylindrical anode performance in copper electrowinning conditions was monitored over a year. The test anode to cathode voltage was stable in the 1.8 to 2.0 volt range. Copper cathode morphology was very smooth and uniform. There was no

  12. Fabrication of a novel aluminum surface covered by numerous high-aspect-ratio anodic alumina nanofibers

    OpenAIRE

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

    2015-01-01

    The formation behavior of anodic alumina nanofibers via anodizing in a concentrated pyrophosphoric acid under various conditions was investigated using electrochemical measurements and SEM/TEM observations. Pyrophosphoric acid anodizing at 293 K resulted in the formation of numerous anodic alumina nanofibers on an aluminum substrate through a thin barrier oxide and honeycomb oxide with narrow walls. However, long-term anodizing led to the chemical dissolution of the alumina nanofibers. The de...

  13. Role of Ca in Modifying Corrosion Resistance and Bioactivity of Plasma Anodized AM60 Magnesium Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Anawati, Anawati; Asoh, Hidetaka; Ono, Sachiko [Kogakuin University, Tokyo (Japan)

    2016-06-15

    The effect of alloying element Ca (0, 1, and 2 wt%) on corrosion resistance and bioactivity of the as-received and anodized surface of rolled plate AM60 alloys was investigated. A plasma electrolytic oxidation (PEO) was carried out to form anodic oxide film in 0.5 mol dm{sup -3} Na{sub 3}PO{sub 4} solution. The corrosion behavior was studied by polarization measurements while the in vitro bioactivity was tested by soaking the specimens in Simulated Body Fluid (1.5xSBF). Optical micrograph and elemental analysis of the substrate surfaces indicated that the number of intermetallic particles increased with Ca content in the alloys owing to the formation of a new phase Al2Ca. The corrosion resistance of AM60 specimens improved only slightly by alloying with 2 wt% Ca which was attributed to the reticular distribution of Al2Ca phase existed in the alloy that might became barrier for corrosion propagation across grain boundaries. Corrosion resistance of the three alloys was significantly improved by coating the substrates with anodic oxide film formed by PEO. The film mainly composed of magnesium phosphate with thickness in the range 30 - 40 μm. The heat resistant phase of Al{sub 2}Ca was believed to retard the plasma discharge during anodization and, hence, decreased the film thickness of Ca-containing alloys. The highest apatite forming ability in 1.5xSBF was observed for AM60-1Ca specimens (both substrate and anodized) that exhibited more degradation than the other two alloys as indicated by surface observation. The increase of surface roughness and the degree of supersaturation of 1.5xSBF due to dissolution of Mg ions from the substrate surface or the release of film compounds from the anodized surface are important factors to enhance deposition of Ca-P compound on the specimen surfaces.

  14. Modeling optical behavior of birefringent biological tissues for evaluation of quantitative polarized light microscopy

    NARCIS (Netherlands)

    Turnhout, van M.C.; Kranenbarg, S.; Leeuwen, van J.L.

    2009-01-01

    Quantitative polarized light microscopy (qPLM) is a popular tool for the investigation of birefringent architectures in biological tissues. Collagen, the most abundant protein in mammals, is such a birefringent material. Interpretation of results of qPLM in terms of collagen network architecture and

  15. Effect of various de-anodizing techniques on the surface stability of non-colored and colored nanoporous AAO films in acidic solution

    Energy Technology Data Exchange (ETDEWEB)

    Awad, Ahmed M. [Chemical Engineering & Pilot Plant Department, National Research Centre, Dokki, Giza (Egypt); Shehata, Omnia S. [Physical Chemistry Department, National Research Centre, Dokki, Giza (Egypt); Heakal, Fakiha El-Taib, E-mail: fakihaheakal@yahoo.com [Chemistry Department, Faculty of Science, Cairo University, Giza 12613 (Egypt)

    2015-12-30

    Highlights: • Three de-anodization methods were used during two-step fabrication of nanoporous AAO. • Electrolytic etching (EE), chemical etching with H{sub 3}PO{sub 4} (PE) or NaOH (HE) were adopted. • After the second anodizing step, HE film was the thinnest as compared to EE and HE. • Stability order of nanoporous AAO films in 0.5 M HCl solution was: PE > EE > HE. • For the colored films by electrodeposited Cu atoms, the order was: HE > EE > PE. - Abstract: Anodic aluminum oxide (AAO) is well known as an important nanostructured material, and a useful template in the fabrication of nanostructures. Nanoporous anodic alumina (PAA) with high open porosity was prepared by adopting three de-anodizing regimes following the first anodizing step and preceding the second one. The de-anodizing methods include electrolytic etching (EE) and chemical etching using either phosphoric acid (PE) or sodium hydroxide (HE) solutions. Three of the obtained AAO samples were black colored by electrodeposition of copper nanoparticles in their pores. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques were used to characterize the electrochemical performance of the two sets of the prepared samples. In general, the data obtained in aggressive aerated 0.5 M HCl solution demonstrated dissimilar behavior for the three prepared samples despite that the second anodizing step was the same for all of them. The data indicated that the resistance and thickness of the inner barrier part of nano-PAA film, are the main controlling factors determining its stability. On the other hand, coloring the film decreased its stability due to the galvanic effect. The difference in the electrochemical behavior of the three colored samples was discussed based on the difference in both the pore size and thickness of the outer porous part of PAA film as supported by SEM, TEM and cross-sectional micrographs. These results can thus contribute for better engineering

  16. Single chamber microbial fuel cell with spiral anode for dairy wastewater treatment.

    Science.gov (United States)

    Mardanpour, Mohammad Mahdi; Nasr Esfahany, Mohsen; Behzad, Tayebeh; Sedaqatvand, Ramin

    2012-01-01

    This study reports on the fabrication of a novel annular single chamber microbial fuel cell (ASCMFC) with spiral anode. The stainless steel mesh anode with graphite coating was used as anode. Dairy wastewater, containing complex organic matter, was used as substrate. ASCMFC had been operated for 450 h and results indicated a high open circuit voltage (about 810 mV) compared with previously published results. The maximum power density of 20.2 W/m(3) obtained in this study is significantly greater than the power densities reported in previous studies. Besides, a maximum coulombic efficiency of 26.87% with 91% COD removal was achieved. Good bacterial adhesion on the spiral anode is clearly shown in SEM micrographs. High power density and a successful performance in wastewater treatment in ASCMFC suggest it as a promising alternative to conventional MFCs for power generation and wastewater treatment. ASCMFC performance as a power generator was characterized based on polarization behavior and cell potentials. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Demography and behavior of polar bears summering on land in Alaska

    Science.gov (United States)

    Peacock, Lily

    2014-01-01

    Polar bears (Ursus maritimus) in the southern Beaufort Sea population (SB) are spending increased time on the coastal North Slope of Alaska between July and October (Gleason and Rode 2010). The duration spent on land by polar bears, satellite collared on the sea-ice in the spring, during the summer and fall has also increased (USGS, unpublished data; Figure 1). This change in polar bear ecology has relevance for human-bear interactions, subsistence harvest, prevalence of defense kills, and disturbance associated with existing land-based development [e.g., National Petroleum Reserve of Alaska (NPRA), Arctic National Wildlife Refuge (ANWR)], Native Alaskan communities, recreation (ANWR) and tourism (e.g., bear viewing in Kaktovik, AK). These activities have the potential to impact, in new ways, the status of the entire SB population. Concomitantly, the change in polar bear ecology will impact these human activities, and a base-line characterization of this phenomenon can better inform mitigation (e.g., industry permitting under the Endangered Species Act and Marine Mammal Protection Act). In this study we aim to characterize the demography, habitat-use, and aspects of foraging ecology and health of polar bears spending fall on land. The SB population is characterized by a divergent-sea ice ecology, where polar bears typically spend most of the year on the sea-ice, even as the pack ice retreats northward, away from the coast, to its minimal extent in September (Amstrup et al. 2008; Durner et al. 2009). From 2000 – 2005, using coastal aerial surveys, Schliebe et al. (2008) observed between 3.7 and 8% of polar bears from SB (~ 60 – 120 of 1526, Regher et al. 2006) on land during the autumn. Sighting probability was not estimated in these surveys, and therefore the numbers represent minimum numbers of bears on land. Our analysis of USGS data suggest an annual average of 15% (± 3%, SE) of polar bears satellite-tagged on the spring-time sea ice (total n = 18 of 124

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

    International Nuclear Information System (INIS)

    Nayak, Bibhuti Bhusan

    2012-01-01

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

  19. Carbonate fuel cell anodes

    Science.gov (United States)

    Donado, Rafael A.; Hrdina, Kenneth E.; Remick, Robert J.

    1993-01-01

    A molten alkali metal carbonates fuel cell porous anode of lithium ferrite and a metal or metal alloy of nickel, cobalt, nickel/iron, cobalt/iron, nickel/iron/aluminum, cobalt/iron/aluminum and mixtures thereof wherein the total iron content including ferrite and iron of the composite is about 25 to about 80 percent, based upon the total anode, provided aluminum when present is less than about 5 weight percent of the anode. A process for production of the lithium ferrite containing anode by slipcasting.

  20. Universal Approach to Estimate Perfluorocarbons Emissions During Individual High-Voltage Anode Effect for Prebaked Cell Technologies

    Science.gov (United States)

    Dion, Lukas; Gaboury, Simon; Picard, Frédéric; Kiss, Laszlo I.; Poncsak, Sandor; Morais, Nadia

    2018-04-01

    Recent investigations on aluminum electrolysis cell demonstrated limitations to the commonly used tier-3 slope methodology to estimate perfluorocarbon (PFC) emissions from high-voltage anode effects (HVAEs). These limitations are greater for smelters with a reduced HVAE frequency. A novel approach is proposed to estimate the specific emissions using a tier 2 model resulting from individual HVAE instead of estimating monthly emissions for pot lines with the slope methodology. This approach considers the nonlinear behavior of PFC emissions as a function of the polarized anode effect duration but also integrates the change in behavior attributed to cell productivity. Validation was performed by comparing the new approach and the slope methodology with measurement campaigns from different smelters. The results demonstrate a good agreement between measured and estimated emissions as well as more accurately reflect individual HVAE dynamics occurring over time. Finally, the possible impact of this approach for the aluminum industry is discussed.

  1. Assessing the high frequency behavior of non-polarizable electrodes for spectral induced polarization measurements

    Science.gov (United States)

    Abdulsamad, Feras; Florsch, Nicolas; Schmutz, Myriam; Camerlynck, Christian

    2016-12-01

    During the last decades, the usage of spectral induced polarization (SIP) measurements in hydrogeology and detecting environmental problems has been extensively increased. However, the physical mechanisms which are responsible for the induced polarization response over the usual frequency range (typically 1 mHz to 10-20 kHz) require better understanding. The phase shift observed at high frequencies is sometimes attributed to the so-called Maxwell-Wagner polarization which takes place when charges cross an interface. However, SIP measurements of tap water show a phase shift at frequencies higher than 1 kHz, where no Maxwell-Wagner polarization may occur. In this paper, we enlighten the possible origin of this phase shift and deduce its likely relationship with the types of the measuring electrodes. SIP Laboratory measurements of tap water using different types of measuring electrodes (polarizable and non-polarizable electrodes) are carried out to detect the origin of the phase shift at high frequencies and the influence of the measuring electrodes types on the observed complex resistivity. Sodium chloride is used to change the conductivity of the medium in order to quantify the solution conductivity role. The results of these measurements are clearly showing the impact of the measuring electrodes type on the measured phase spectrum while the influence on the amplitude spectrum is negligible. The phenomenon appearing on the phase spectrum at high frequency (> 1 kHz) whatever the electrode type is, the phase shows an increase compared to the theoretical response, and the discrepancy (at least in absolute value) increases with frequency, but it is less severe when medium conductivity is larger. Additionally, the frequency corner is shifted upward in frequency. The dependence of this phenomenon on the conductivity and the measuring electrodes type (electrode-electrolyte interface) seems to be due to some dielectric effects (as an electrical double layer of small

  2. A Practical Anodic and Cathodic Curve Intersection Model to Understand Multiple Corrosion Potentials of Fe-Based Glassy Alloys in OH- Contained Solutions.

    Science.gov (United States)

    Li, Y J; Wang, Y G; An, B; Xu, H; Liu, Y; Zhang, L C; Ma, H Y; Wang, W M

    2016-01-01

    A practical anodic and cathodic curve intersection model, which consisted of an apparent anodic curve and an imaginary cathodic line, was proposed to explain multiple corrosion potentials occurred in potentiodynamic polarization curves of Fe-based glassy alloys in alkaline solution. The apparent anodic curve was selected from the measured anodic curves. The imaginary cathodic line was obtained by linearly fitting the differences of anodic curves and can be moved evenly or rotated to predict the number and value of corrosion potentials.

  3. Anodized dental implant surface

    Directory of Open Access Journals (Sweden)

    Sunil Kumar Mishra

    2017-01-01

    Full Text Available Purpose: Anodized implants with moderately rough surface were introduced around 2000. Whether these implants enhanced biologic effect to improve the environment for better osseointegration was unclear. The purpose of this article was to review the literature available on anodized surface in terms of their clinical success rate and bone response in patients till now. Materials and Methods: A broad electronic search of MEDLINE and PubMed databases was performed. A focus was made on peer-reviewed dental journals. Only articles related to anodized implants were included. Both animal and human studies were included. Results: The initial search of articles resulted in 581 articles on anodized implants. The initial screening of titles and abstracts resulted in 112 full-text papers; 40 animal studies, 16 studies on cell adhesion and bacterial adhesion onto anodized surfaced implants, and 47 human studies were included. Nine studies, which do not fulfill the inclusion criteria, were excluded. Conclusions: The long-term studies on anodized surface implants do favor the surface, but in most of the studies, anodized surface is compared with that of machined surface, but not with other surfaces commercially available. Anodized surface in terms of clinical success rate in cases of compromised bone and immediately extracted sockets has shown favorable success.

  4. Anodizing Aluminum with Frills.

    Science.gov (United States)

    Doeltz, Anne E.; And Others

    1983-01-01

    "Anodizing Aluminum" (previously reported in this journal) describes a vivid/relevant laboratory experience for general chemistry students explaining the anodizing of aluminum in sulfuric acid and constrasting it to electroplating. Additions to this procedure and the experiment in which they are used are discussed. Reactions involved are…

  5. Anodized aluminum on LDEF

    Science.gov (United States)

    Golden, Johnny L.

    1993-01-01

    A compilation of reported analyses and results obtained for anodized aluminum flown on the Long Duration Exposure Facility (LDEF) was prepared. Chromic acid, sulfuric acid, and dyed sulfuric acid anodized surfaces were exposed to the space environment. The vast majority of the anodized surface on LDEF was chromic acid anodize because of its selection as a thermal control coating for use on the spacecraft primary structure, trays, tray clamps, and space end thermal covers. Reports indicate that the chromic acid anodize was stable in solar absorptance and thermal emittance, but that contamination effects caused increases in absorptance on surfaces exposed to low atomic oxygen fluences. There were some discrepancies, however, in that some chromic acid anodized specimens exhibited significant increases in absorptance. Sulfuric acid anodized surfaces also appeared stable, although very little surface area was available for evaluation. One type of dyed sulfuric acid anodize was assessed as an optical baffle coating and was observed to have improved infrared absorptance characteristics with exposure on LDEF.

  6. Anodized titanium and stainless steel in contact with CFRP: an electrochemical approach considering galvanic corrosion.

    Science.gov (United States)

    Mueller, Yves; Tognini, Roger; Mayer, Joerg; Virtanen, Sannakaisa

    2007-09-15

    The combination of different materials in an implant gives the opportunity to better fulfill the requirements that are needed to improve the healing process. However, using different materials increases the risk of galvanic coupling corrosion. In this study, coupling effects of gold-anodized titanium, stainless steel for biomedical applications, carbon fiber reinforced polyetheretherketone (CFRP), and CFRP containing tantalum fibers are investigated electrochemically and by long-term immersion experiments in simulated body fluid (SBF). Potentiodynamic polarization experiments (i/E curves) and electrochemical impedance spectroscopy (EIS) of the separated materials showed a passive behavior of the metallic samples. Anodized titanium showed no corrosion attacks, whereas stainless steel is highly susceptibility for localized corrosion. On the other side, an active dissolution behavior of both of the CFRPs in the given environment could be determined, leading to delaminating of the carbon fibers from the matrix. Long-term immersion experiments were carried out using a set-up especially developed to simulate coupling conditions of a point contact fixator system (PC-Fix) in a biological environment. Electrochemical data were acquired in situ during the whole immersion time. The results of the immersion experiments correlate with the findings of the electrochemical investigation. Localized corrosion attacks were found on stainless steel, whereas anodized titanium showed no corrosion attacks. No significant differences between the two CFRP types could be found. Galvanic coupling corrosion in combination with crevice conditions and possible corrosion mechanisms are discussed. Copyright 2007 Wiley Periodicals, Inc.

  7. Composite anode for lithium ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    de Guzman, Rhet C.; Ng, K.Y. Simon; Salley, Steven O.

    2018-03-06

    A composite anode for a lithium-ion battery is manufactured from silicon nanoparticles having diameters mostly under 10 nm; providing an oxide layer on the silicon nanoparticles; dispersing the silicon nanoparticles in a polar liquid; providing a graphene oxide suspension; mixing the polar liquid containing the dispersed silicone nanoparticles with the graphene oxide suspension to obtain a composite mixture; probe-sonicating the mixture for a predetermined time; filtering the composite mixture to obtain a solid composite; drying the composite; and reducing the composite to obtain graphene and silicon.

  8. Polarization dependent behavior of CdS around the first and second LO-phonon modes

    International Nuclear Information System (INIS)

    Frausto-Reyes, C.; Molina-Contreras, J.R.; Lopez-Alvarez, Y.F.; Medel-Ruiz, C.I.; Perez Ladron de Guevara, H.; Ortiz-Morales, M.

    2010-01-01

    The present work report studies on resonant Raman experimental line shape for CdS around the first and second LO-phonon modes. The application of our method to the study of LO-phonon modes of CdS suggests that the scattered intensity is dominated by the surface and dependent on polarization. Results showed that the Raman spectra for CdS, roughly fall into three groups: a broad line-wing with apparent maxima around 194 cm -1 in the range of 140 and 240 cm -1 which can be ascribed to overtone scattering from acoustic phonons; a band near the 1LO phonon mode which can be attributed to a combination of one-phonon scattering and peak acoustic phonon and finally, a band near the 2LO phonon mode which can be attributed to a combination of two-phonon scattering and peak acoustic phonon.

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

    DEFF Research Database (Denmark)

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

    2007-01-01

    The degradation of anode supported cells was studied over 1500 h as function of cell polarization either in air or oxygen on the cathode. Based on impedance analysis, contributions of anode and cathode to the increase of total resistance were assigned. Accordingly, the degradation rates...... of the cathode were strongly dependent on the pO(2); they were significantly smaller when testing in oxygen compared to air. Microstructural analysis of the cathode/electrolyte interface of a not-tested reference cell carried out after removal of the cathode showed sharp craters on the electrolyte surface where...

  10. Multi-q pattern classification of polarization curves

    Science.gov (United States)

    Fabbri, Ricardo; Bastos, Ivan N.; Neto, Francisco D. Moura; Lopes, Francisco J. P.; Gonçalves, Wesley N.; Bruno, Odemir M.

    2014-02-01

    Several experimental measurements are expressed in the form of one-dimensional profiles, for which there is a scarcity of methodologies able to classify the pertinence of a given result to a specific group. The polarization curves that evaluate the corrosion kinetics of electrodes in corrosive media are applications where the behavior is chiefly analyzed from profiles. Polarization curves are indeed a classic method to determine the global kinetics of metallic electrodes, but the strong nonlinearity from different metals and alloys can overlap and the discrimination becomes a challenging problem. Moreover, even finding a typical curve from replicated tests requires subjective judgment. In this paper, we used the so-called multi-q approach based on the Tsallis statistics in a classification engine to separate the multiple polarization curve profiles of two stainless steels. We collected 48 experimental polarization curves in an aqueous chloride medium of two stainless steel types, with different resistance against localized corrosion. Multi-q pattern analysis was then carried out on a wide potential range, from cathodic up to anodic regions. An excellent classification rate was obtained, at a success rate of 90%, 80%, and 83% for low (cathodic), high (anodic), and both potential ranges, respectively, using only 2% of the original profile data. These results show the potential of the proposed approach towards efficient, robust, systematic and automatic classification of highly nonlinear profile curves.

  11. Performance Factors and Sulfur Tolerance of Metal Supported Solid Oxide Fuel Cells with Nanostructured Ni:GDC Infiltrated Anodes

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Sudireddy, Bhaskar Reddy; Hagen, Anke

    2015-01-01

    at a current load of 0.25Acm-2. The results were compared with literature on the sulfur tolerance of the conventional SOFC Ni/YSZ cermet anode. The comparison in terms of absolute cell resistance increase and relative anode polarization resistance increase indicate, that the nanostructured Ni:GDC MS-SOFC based...... anode is significantly more sulfur tolerant than the conventional Ni/YSZ cermet anode. © 2015 ECS - The Electrochemical Society...

  12. Pseudocapacitive Behaviors of Li2FeTiO4/C Hybrid Porous Nanotubes for Novel Lithium-Ion Battery Anodes with Superior Performances.

    Science.gov (United States)

    Tang, Yakun; Liu, Lang; Zhao, Hongyang; Zhang, Yue; Kong, Ling Bing; Gao, Shasha; Li, Xiaohui; Wang, Lei; Jia, Dianzeng

    2018-06-20

    Hybrid nanotubes of cation disordered rock salt structured Li 2 FeTiO 4 nanoparticles embedded in porous CNTs were developed. Such unique hybrids with continuous 3D electron transportation paths and isolated small particles have been shown to be an ideal architecture that brought out enhanced electrochemical performances. Meanwhile, they exhibited improved extrinsic capacitive characteristics. In addition, we demonstrate a successful example to use cathode active material as anode for lithium-ion batteries (LIBs). More importantly, our hybrids had much superior electrochemical performances than most of the reported Li 4 Ti 5 O 12 -based nanocomposites. Therefore, it is concluded that Li 2 FeTiO 4 can be a prospective anode material for LIBs.

  13. Variables affecting the manifestation of and intensity of pacing behavior: A preliminary case study in zoo-housed polar bears.

    Science.gov (United States)

    Cless, Isabelle T; Lukas, Kristen E

    2017-09-01

    High-speed video analysis was used to quantify two aspects of gait in 10 zoo-housed polar bears. These two variables were then examined as to how they differed in the conditions of pacing versus locomoting for each bear. Percent difference calculations measured the difference between pacing and locomoting data for each bear. We inferred that the higher the percent difference between pacing and locomoting in a given subject, the more intense the pacing may be. The percent difference values were analyzed alongside caregiver survey data defining the locations, frequency, and anticipatory nature of pacing in each bear, as well as each bear's age and sex, to determine whether any variables were correlated. The frequency and intensity of pacing behavior were not correlated. However, location of pacing was significantly correlated both with the subjects' age and whether or not the subject was classified as an anticipatory pacer. Bears appeared to select specific spots within their exhibits to pace, and the location therefore seemed tied to underlying motivation for the behavior. Additionally, bears that were classified in the survey as pacing anticipatorily displayed significantly more intense pacing behavior as quantified by gait analysis. © 2017 Wiley Periodicals, Inc.

  14. Behavior of alloying elements during anodizing of Mg-Cu and Mg-W alloys in a fluoride/glycerol electrolyte

    Czech Academy of Sciences Publication Activity Database

    Palagonia, M. S.; Němcová, A.; Kuběna, Ivo; Šmíd, Miroslav; Gao, S.; Liu, H.; Zhong, X. L.; Haigh, S. J.; Santamaria, M.; Di Quarto, F.; Habazaki, H.; Skeldon, P.; Thomson, G.

    2015-01-01

    Roč. 162, č. 9 (2015), C487-C494 ISSN 0013-4651 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : alloying element * anodizing * ion beam analysis * magnesium * TEM Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 3.014, year: 2015 http://jes.ecsdl.org/content/162/9/C487.full

  15. Corrosion fatigue behaviors of steel wires used in coalmine

    International Nuclear Information System (INIS)

    Wang, Songquan; Zhang, Dekun; Chen, Kai; Xu, Linmin; Ge, Shirong

    2014-01-01

    Highlights: • The CF life of steel wire in acid solution is the shortest. • The fatigue source zone showed dimple morphology when coupled with anode potential. • The area of dimple increases with the increase of the applied anode potential. • The strong cathode potential cannot reduce the CF life of the smooth steel wire. • The hydrogen impacted mainly on the plastic deformation of the wire surface. - Abstract: The corrosion fatigue (CF) behaviors of the mining steel wire in different solutions at different applied polarization potentials were investigated in this paper. The surfaces and fracture morphologies of the steel wire at different applied potentials were observed by scanning electron microscope (SEM). The results showed that the CF life of steel wire in acid solution is the shortest. Moreover, the strong anodic polarization potential greatly reduced the CF life of steel wire, while the strong cathode potential did not reduce the CF life. For the smooth steel wire, the hydrogen impacted mainly on the plastic deformation of the wire surface. There was obvious dimple in the fatigue source zone of the wire when coupled with anode potential, and the area of the dimple increased with the increase of the applied anode potential. Conversely, the fatigue source zone of the fracture was relatively smooth at cathode polarization potential, which indicated that the crack propagation followed the mechanism of hydrogen induced cracking

  16. Pulsed diode source of polarized ions

    International Nuclear Information System (INIS)

    Katzenstein, J.; Rostoker, N.

    1983-01-01

    The advantages of polarized nuclei for fusion reactors have recently been described. We propose a pulsed source of polarized nuclei that consists of an ion diode with a polarized anode. With magnetic resonance techniques the nuclear spins of the protons of solid NH 3 can be made about 90 to 95% polarized. This material would be used for the anode. The diode would be pulsed with a voltage of 1-200K-volts for 1-2 μ sec. Flashover of the anode produces a surface plasma from which the polarized protons would be extracted to form a beam. Depolarization could be detected by comparing reaction cross sections and/or distribution of reaction products with similar results for unpolarized beams

  17. Electrically conductive anodized aluminum coatings

    Science.gov (United States)

    Alwitt, Robert S. (Inventor); Liu, Yanming (Inventor)

    2001-01-01

    A process for producing anodized aluminum with enhanced electrical conductivity, comprising anodic oxidation of aluminum alloy substrate, electrolytic deposition of a small amount of metal into the pores of the anodized aluminum, and electrolytic anodic deposition of an electrically conductive oxide, including manganese dioxide, into the pores containing the metal deposit; and the product produced by the process.

  18. Anodic behavior of mechanically alloyed Cu–Ni–Fe and Cu–Ni–Fe–O electrodes for aluminum electrolysis in low-temperature KF-AlF3 electrolyte

    International Nuclear Information System (INIS)

    Goupil, G.; Helle, S.; Davis, B.; Guay, D.; Roué, L.

    2013-01-01

    A comparative study on the anodic behavior of Cu 65 Ni 20 Fe 15 and (Cu 65 Ni 20 Fe 15 ) 98.6 O 1.4 materials during the electrolysis of aluminum was conducted. Both materials were prepared in powder form by ball milling and subsequently consolidated to form dense pellets that were used as anodes. The electrochemical characterization was performed at 700 °C in a potassium cryolite-based electrolyte, and the composition-morphology of the oxide scales formed on both anodes were determined by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction measurements. On Cu 65 Ni 20 Fe 15 , a thick (170 μm) and porous oxide scale is formed after 15 min of electrolysis that readily dissolves (or spalls) before a denser oxide layer is formed after a longer electrolysis time (1 and 5 h). In comparison, a thin (2 μm) and dense oxide layer mainly composed of NiFe 2 O 4 is observed on a (Cu 65 Ni 20 Fe 15 ) 98.6 O 1.4 electrode after 15 min of electrolysis. The thickness of this oxide layer increases to 10 and 30 μm after 1 h and 5 h of electrolysis. However, the outward diffusion of Cu to form CuO x at the surface of the electrode is not totally hampered by the presence of NiFe 2 O 4 and a porous Cu-depleted region is formed at the oxide/alloy interface. As a result, electrolyte penetration occurs in the scale, which favors the progressive formation of an iron fluoride layer at the oxide/alloy interface

  19. Influence of boundary on the effect of double-layer polarization and the electrophoretic behavior of soft biocolloids.

    Science.gov (United States)

    Yeh, Li-Hsien; Fang, Kuo-Ying; Hsu, Jyh-Ping; Tseng, Shiojenn

    2011-12-01

    The electrophoresis of a soft particle comprising a rigid core and a charged porous membrane layer in a narrow space is modeled. This simulates, for example, the capillary electrophoresis of biocolloids such as cells and microorganisms, and biosensor types of device. We show that, in addition to the boundary effect, the effects of double-layer polarization (DLP) and the electroosmotic retardation flow can be significant, yielding interesting electrophoretic behaviors. For example, if the friction coefficient of the membrane layer and/or the boundary is large, then the DLP effect can be offset by the electroosmotic retardation flow, making the particle mobility to decrease with increasing double layer thickness, which is qualitatively consistent with many experimental observations in the literature, but has not been explained clearly in previous analyses. In addition, depending upon the thickness of double layer, the friction of the membrane layer of a particle can either retard or accelerate its movement, an interesting result which has not been reported previously. This work is the first attempt to show solid evidence for the influence of a boundary on the effect of DLP and the electrophoretic behavior of soft particles. The model proposed is verified by the experimental data in the literature. The results of numerical simulation provide valuable information for the design of bio-analytical apparatus such as nanopore-based sensing applications and for the interpretation of relevant experimental data. Copyright © 2011 Elsevier B.V. All rights reserved.

  20. Anode Support Creep

    DEFF Research Database (Denmark)

    2015-01-01

    Initial reduction temperature of an SOC is kept higher than the highest intended operation temperature of the SOC to keep the electrolyte under compression by the Anode Support at all temperatures equal to and below the maximum intended operation temperature....

  1. Anodic oxidation of benzoquinone using diamond anode.

    Science.gov (United States)

    Panizza, Marco

    2014-01-01

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

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

    NARCIS (Netherlands)

    Primdahl, Søren

    1999-01-01

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

  3. Smooth perfluorinated surfaces with different chemical and physical natures: their unusual dynamic dewetting behavior toward polar and nonpolar liquids.

    Science.gov (United States)

    Cheng, Dalton F; Masheder, Benjamin; Urata, Chihiro; Hozumi, Atsushi

    2013-09-10

    The effects of surface chemistry and the mobility of surface-tethered functional groups of various perfluorinated surfaces on their dewetting behavior toward polar (water) and nonpolar (n-hexadecane, n-dodecane, and n-decane) liquids were investigated. In this study, three types of common smooth perfluorinated surfaces, that is, a perfluoroalkylsilane (heptadecafluoro-1,1,2,2-tetrahydrooctyl-dimethylchlorosilane, FAS17) monomeric layer, an amorphous fluoropolymer film (Teflon AF 1600), and a perfluorinated polyether (PFPE)-terminated polymer brush film (Optool DSX), were prepared and their static/dynamic dewetting characteristics were compared. Although the apparent static contact angles (CAs) of these surfaces with all probe liquids were almost identical to each other, the ease of movement of liquid drops critically depended on the physical (solidlike or liquidlike) natures of the substrate surface. CA hysteresis and substrate tilt angles (TAs) of all probe liquids on the Optool DSX surface were found to be much lower than those of Teflon AF1600 and FAS17 surfaces due to its physical polymer chain mobility at room temperature and the resulting liquidlike nature. Only 6.0° of substrate incline was required to initiate movement for a small drop (5 μL) of n-decane, which was comparable to the reported substrate TA value (5.3°) for a superoleophobic surface (θ(S) > 160°, textured perfluorinated surface). Such unusual dynamic dewetting behavior of the Optool DSX surface was also markedly enhanced due to the significant increase in the chain mobility of PFPE by moderate heating (70 °C) of the surface, with substrate TA reducing to 3.0°. CA hysteresis and substrate TAs rather than static CAs were therefore determined to be of greater consequence for the estimation of the actual dynamic dewetting behavior of alkane probe liquids on these smooth perfluorinated surfaces. Their dynamic dewettability toward alkane liquids is in the order of Optool DSX > Teflon AF1600

  4. Impedance Analysis of Silicon Nanowire Lithium Ion Battery Anodes

    KAUST Repository

    Ruffo, Riccardo; Hong, Seung Sae; Chan, Candace K.; Huggins, Robert A.; Cui, Yi

    2009-01-01

    The impedance behavior of silicon nanowire electrodes has been investigated to understand the electrochemical process kinetics that influences the performance when used as a high-capacity anode in a lithium ion battery. The ac response was measured

  5. Active and inactive buffering effect on the electrochemical behavior of Sn–Ni/MWCNT composite anodes prepared by pulse electrodeposition for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Uysal, Mehmet, E-mail: mehmet_uys@yahoo.com; Cetinkaya, Tugrul; Alp, Ahmet; Akbulut, Hatem

    2015-10-05

    Highlights: • Sn–Ni/MWCNT anodes were produced by pulse electrodeposition. • The effect of MWCNT studied on electrochemical properties of composite electrodes. • A high reversible capacity, and good cyclability were achieved for Sn–Ni/MWCNT (10 g L{sup −1}). - Abstract: Cycling stability of pure tin electrodes was aimed to improve by using suitable combination of nickel and multiwalled carbon nanotubes (MWCNTs). Nanocrystalline Sn–Ni/MWCNT composite was prepared by ultrasonic-pulse electrodeposition on a copper substrate in a pyrophosphate bath containing different concentrations of multi-walled carbon nanotubes. Surface morphology of produced Sn–Ni/MWCNT composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) was conducted to understand the elemental surface composition of composites. X-ray diffraction analysis was carried out to investigate structure of Sn–Ni/MWCNT composites. The electrochemical performances of Sn–Ni/MWCNT composite electrodes have been investigated by charge/discharge tests, cyclic voltammetric experiments and the ac impedance technique. These cells discharge capacity cyclically tested by a battery tester at a constant current in voltage range between 0.02 V and 1.5 V. The concentrations of MWCNTs were shown to be a crucial factor to improve Sn–Ni/MWCNT composite anodes for cyclability and reversible capacity.

  6. First principles calculations on the influence of solute elements and chlorine adsorption on the anodic corrosion behavior of Mg (0001) surface

    Science.gov (United States)

    Luo, Zhe; Zhu, Hong; Ying, Tao; Li, Dejiang; Zeng, Xiaoqin

    2018-06-01

    The influences of solute atoms (Li, Al, Mn, Zn, Fe, Ni, Cu, Y, Zr) and Cl adsorption on the anodic corrosion performance on Mg (0001) surface have been investigated based on first-principles calculations, which might be useful for the design of corrosion-resistant Mg alloys. Work function and local electrode potential shift are chosen as descriptors since they quantify the barrier for charge transfer and anodic stability. We found that at 25% surface doping rate, Y decreased the work function of Mg, while the impact of remaining doping elements on the work function of Mg was trivial due to the small surface dipole moment change. The adsorption of Cl destabilized the Mg atoms at surface by weakening the bonding between surface Mg atoms. We find that a stronger hybridization of d orbits of alloying elements (e.g. Zr) with the orbits of Mg can greatly increase the local electrode potential,which even overbalances the negative effect introduced by Cl adsorbates and hence improves the corrosion resistance of Mg alloys.

  7. A one-dimensional model of PCP signaling: polarized cell behavior in the notochord of the ascidian Ciona.

    Science.gov (United States)

    Kourakis, Matthew J; Reeves, Wendy; Newman-Smith, Erin; Maury, Benoit; Abdul-Wajid, Sarah; Smith, William C

    2014-11-01

    Despite its importance in development and physiology the planar cell polarity (PCP) pathway remains one of the most enigmatic signaling mechanisms. The notochord of the ascidian Ciona provides a unique model for investigating the PCP pathway. Interestingly, the notochord appears to be the only embryonic structure in Ciona activating the PCP pathway. Moreover, the Ciona notochord as a single-file array of forty polarized cells is a uniquely tractable system for the study of polarization dynamics and the transmission of the PCP pathway. Here, we test models for propagation of a polarizing signal, interrogating temporal, spatial and signaling requirements. A simple cell-cell relay cascading through the entire length of the notochord is not supported; instead a more complex mechanism is revealed, with interactions influencing polarity between neighboring cells, but not distant ones. Mechanisms coordinating notochord-wide polarity remain elusive, but appear to entrain general (i.e., global) polarity even while local interactions remain important. However, this global polarizer does not appear to act as a localized, spatially-restricted determinant. Coordination of polarity along the long axis of the notochord requires the PCP pathway, a role we demonstrate is temporally distinct from this pathway's earlier role in convergent extension and intercalation. We also reveal polarity in the notochord to be dynamic: a cell's polarity state can be changed and then restored, underscoring the Ciona notochord's amenability for in vivo studies of PCP. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. Energy transfer in porous anodic alumina/rhodamine 110 nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Elhouichet, H., E-mail: habib.elhouichet@fst.rnu.tn [Laboratoire de Physico-Chimie des Materiaux Mineraux et leurs Applications, Centre National de Recherches en Sciences des Materiaux, B.P. 95, Hammam-Lif 2050 (Tunisia); Departement de Physique, Faculte des Sciences de Tunis, University of Tunis Elmanar 2092 Tunis (Tunisia); Harima, N.; Koyama, H. [Hyogo University of Teacher Education, Kato, Hyogo 673-1494 (Japan); Gaponenko, N.V. [Belarusian State University of Informatics and Radioelectronics, P. Browki St. 6, 220013 Minsk (Belarus)

    2012-09-15

    We have used porous anodic alumina (PAA) films as templates for embedding rhodamine 110 (Rh110) molecules and examined their photoluminescence (PL) properties in detail. The analysis of the polarization memory (PM) of PL strongly suggests that there is a significant energy transfer from PAA to Rh110 molecules. The effect of annealing the PAA layer on the PL properties of the nanocomposite has been studied. The results show that the energy transfer becomes more efficient in annealed PAA. - Highlights: Black-Right-Pointing-Pointer Porous anodic alumina-rhodamine 110 nanocomposites are elaborated. Black-Right-Pointing-Pointer Efficient energy transfer from the host to Rh110 molecules is evidenced from measurements of photoluminescence and degree of polarization memory spectra. Black-Right-Pointing-Pointer Thermal annealing of porous anodic alumina can improve the process of excitation transfer.

  9. Lithium batteries, anodes, and methods of anode fabrication

    KAUST Repository

    Li, Lain-Jong; Wu, Feng-Yu; Kumar, Pushpendra; Ming, Jun

    2016-01-01

    Prelithiation of a battery anode carried out using controlled lithium metal vapor deposition. Lithium metal can be avoided in the final battery. This prelithiated electrode is used as potential anode for Li- ion or high energy Li-S battery

  10. Lithium batteries, anodes, and methods of anode fabrication

    KAUST Repository

    Li, Lain-Jong

    2016-12-29

    Prelithiation of a battery anode carried out using controlled lithium metal vapor deposition. Lithium metal can be avoided in the final battery. This prelithiated electrode is used as potential anode for Li- ion or high energy Li-S battery. The prelithiation of lithium metal onto or into the anode reduces hazardous risk, is cost effective, and improves the overall capacity. The battery containing such an anode exhibits remarkably high specific capacity and a long cycle life with excellent reversibility.

  11. An electrochemical investigation on the dissolution of bilayered porous anodic alumina

    International Nuclear Information System (INIS)

    Liao, Jinfu; Ling, Zhiyuan; Li, Yi; Hu, Xing

    2015-01-01

    Highlights: • Pulse polarization was introduced to investigate the dissolution of PAA. • Electric field within the bilayers was estimated. • The formation of the barrier layer involves mainly solid-state processes. • The structure should be the determining factor in the dissolution of the bilayers. - Abstract: Anodic alumina attracts much research interest in many disciplines for its versatility. Meanwhile, some aspects regarding its growth are still not well-understood, such as the formation and properties of its bilayer structure. In this paper, along with capacitance measurement, pulse polarization is introduced to study the dissolution of bilayered porous anodic alumina (PAA). Combined with electron microscope observation, the electric field in the outer layer is estimated to be slightly higher than that in the inner layer. By comparing with (oxy-)hydroxide layers, the electric field distribution within barrier layer of PAA confirms that the bilayers are compact and are formed mainly by solid-state ionic migration. The changes of dissolution rates after annealing and application of electric pulses suggest that structure may be a determining factor for the dissolution behaviors of the bilayers.

  12. Critical behavior of the spontaneous polarization and the dielectric susceptibility close to the cubic-tetragonal transition in BaTiO3

    Directory of Open Access Journals (Sweden)

    H. Yurtseven

    2015-09-01

    Full Text Available Using Landau mean field model, the spontaneous polarization and the dielectric susceptibility are analyzed as functions of temperature and pressure close to the cubic–tetragonal (ferroelectric–paraelectric transition in BaTiO3. From the analysis of the dielectric susceptibility and the spontaneous polarization, the critical exponents are deduced in the classical and quantum limits for BaTiO3. From the critical behavior of the dielectric susceptibility, the spontaneous polarization can be described for the ferroelectric–paraelectric (cubic to tetragonal transition between 4 and 8 GPa at constant temperatures of 0 to 200 K in BaTiO3 within the Landau mean field model given here.

  13. Room Temperature Anodization of Aluminum at Low Voltage

    International Nuclear Information System (INIS)

    Kamal, A.; Abdel-Karim, R.; El-Raghy, S.; EL-Sherif, R.M.; Wheed, A.

    2013-01-01

    Membranes with nanometer-scale features have many applications, such as in optics, electronics, catalysis, selective molecule separation, filtration and purification, bio sensing, and single-molecule detection. Anodization process was conducted using 15, 20, 30 and 35% by volume phosphoric acid. Results showed that Porous Anodized Aluminum (PAA) with ideal nano pore arrays can be fabricated at room temperature by one-step anodization on high purity aluminum foil at 5 V. Morphology of the PAA was characterized by scanning electron microscopy (SEM). The electrochemical behavior of anodized aluminum was studied in 0.1 M Na 2 SO 4 solutions using electrochemical impedance spectroscopy (EIS). The highest resistance of the porous layer (R p ) was detected for the samples anodized in 20% phosphoric acid

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

    Science.gov (United States)

    Benkafada, Faouzia; Kerdoud, Djahida; Bouchoucha, Ali

    2018-05-01

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

  15. Formal behavioral evaluation of enrichment programs on a zookeeper's schedule: a case study with a polar bear (Ursus Maritimus) at the Bronx Zoo.

    Science.gov (United States)

    Canino, Wendy; Powell, David

    2010-01-01

    We conducted a brief study of the effectiveness of environmental enrichment for a polar bear at the Bronx Zoo with two objectives in mind. First we wanted to determine if a novel method of collecting data that easily fits into a zookeeper's work routine would produce usable data and if so, we wanted to evaluate the effectiveness of some new items that had been purchased for enriching the polar bear in reducing his pacing behavior. Observations were recorded for 119 days over a period of 5 months from April 2007 through August 2007. Five new items and eight previously used items were rotated and presented to the polar bear in the morning and afternoon. We recorded the bear's behavior five times per day as we passed by his exhibit during our regular work routine. Predictably, we found that the newer enrichment items were more effective at increasing play and decreasing pacing, as well as other more subtle effects on his behavior that helped us to design a better enrichment routine. More importantly, we found that this method of "multi-point scan sampling" was effective at producing ample and reliable data that could be used to analyze the bear's behavior without adding significant work to the keepers' daily routine. (c) 2009 Wiley-Liss, Inc.

  16. An evaluation of the environmental fate and behavior of munitions materiel (Tetryl and polar metabolites of TNT) in soil and plant systems. Environmental fate and behavior of tetryl

    Energy Technology Data Exchange (ETDEWEB)

    Fellows, R.J.; Harvey, S.D.; Cataldo, D.A.

    1993-09-01

    The objective of the present studies was to elucidate the environmental behavior and fate of 2,4,6trintrophenylmethylnitramine (tetryl) in the soil/plant system in three different types of soils incubated for 60 days. No tetryl was detectable after 11 days; most of the radiolabel was associated with non-extractable soil components and four transformation products appeared rapidly, of which two were identified as N-methyl-2,4,6-trintroaniline and N-methyl-aminodinitroaniline isomer. Short-term hydroponic studies indicated no significant difference in uptake rates for the three plant species employed. Kinetic studies indicated that plants have a high affinity and capacity for absorbing tetryl. Partitioning patterns indicated that the root is the major accumulation site for tetryl. Chemical fractionation and analyses of tissues showed rapid metabolism of tetryl in tissues of all species, which proceeded toward more polar metabolic products. Plant maturity studies indicated significant differences in the total relative uptake of tetryl by all three plant species based on soil type.

  17. Polarized neutrons

    International Nuclear Information System (INIS)

    Williams, W.G.

    1988-01-01

    The book on 'polarized neutrons' is intended to inform researchers in condensed matter physics and chemistry of the diversity of scientific problems that can be investigated using polarized neutron beams. The contents include chapters on:- neutron polarizers and instrumentation, polarized neutron scattering, neutron polarization analysis experiments and precessing neutron polarization. (U.K.)

  18. Contact angle studies on anodic porous alumina.

    Science.gov (United States)

    Redón, Rocío; Vázquez-Olmos, A; Mata-Zamora, M E; Ordóñez-Medrano, A; Rivera-Torres, F; Saniger, J M

    2005-07-15

    The preparation of nanostructures using porous anodic aluminum oxide (AAO) as templates involves the introduction of dissolved materials into the pores of the membranes; one way to determine which materials are preferred to fill the pores involves the measurement of the contact angles (theta) of different solvents or test liquids on the AAOs. Thus, we present measurements of contact angles of nine solvents on four different AAO sheets by tensiometric and goniometric methods. From the solvents tested, we found dimethyl sulfoxide (DMSO) and N,N(')-dimethylformamide (DMF) to interact with the AAOs, the polarity of the solvents and the surfaces being the driving force.

  19. Inert Anode Report

    Energy Technology Data Exchange (ETDEWEB)

    none,

    1999-07-01

    This ASME report provides a broad assessment of open literature and patents that exist in the area of inert anodes and their related cathode systems and cell designs, technologies that are relevant for the advanced smelting of aluminum. The report also discusses the opportunities, barriers, and issues associated with these technologies from a technical, environmental, and economic viewpoint.

  20. Superhydrophilicity of novel anodic alumina nanofibers films and their formation mechanism

    Science.gov (United States)

    Peng, Rong; Yang, Wulin; Fu, Licai; Zhu, Jiajun; Li, Deyi; Zhou, Lingping

    2017-06-01

    A novel anodic alumina nanofibers structure, which is different from the traditional porous anodic structure, has been quickly fabricated via anodizing in a new electrolyte, pyrophosphoric acid. The effects of the solution concentration and the anodizing time on the formation of the anodic alumina nanofibers were analyzed. The results show that the nanostructure of anodic alumina can change to the nanofiber oxide from the porous oxide by increasing the solution concentration. Prolonging the anodizing time is beneficial to obtain alumina nanofibers at high solution concentration. Growth behavior of the alumina nanofibers was also discussed by scanning electron microscopy observations. Owing to the unique hexagonal structure of anodic alumina as well as the preferential chemical dissolution between the porous anodic alumina and the anodic alumina nanotips, the slightly soluble anodic alumina nanotips could form novel alumina nanofibers during anodizing. The results show that the nanofibers-covered aluminum surface exhibits superhydrophilic property, with a near-zero water contact angle. Such alumina nanofibers with superhydrophilic property could be used for various potential applications.

  1. Nanomagnetic behavior of fullerene thin films in Earth magnetic field in dark and under polarization light influences.

    Science.gov (United States)

    Koruga, Djuro; Nikolić, Aleksandra; Mihajlović, Spomenko; Matija, Lidija

    2005-10-01

    In this paper magnetic fields intensity of C60 thin films of 60 nm and 100 nm thickness under the influence of polarization lights are presented. Two proton magnetometers were used for measurements. Significant change of magnetic field intensity in range from 2.5 nT to 12.3 nT is identified as a difference of dark and polarization lights of 60 nm and 100 nm thin films thickness, respectively. Specific power density of polarization light was 40 mW/cm2. Based on 200 measurement data average value of difference between magnetic intensity of C60 thin films, with 60 nm and 100 nm thickness, after influence of polarization light, were 3.9 nT and 9.9 nT respectively.

  2. Development of a model for the anodic behavior of T60 titanium in chlorinated and oxygenated aqueous media. Application to the specific conditions of hydrothermal oxidation (1 MPa

    International Nuclear Information System (INIS)

    Frayret, C.; Jaszay, Th.; Lestienne, B.; Delville, M.H.

    2003-01-01

    This work evaluates the anodic electrochemical behavior of titanium metal in hydrothermal oxidation conditions (up to 400 deg. C and 28 MPa) in chlorinated media in order to estimate the supercritical water oxidation reactors reliability for the treatment of less than 10% organic-waste waters. The titanium room temperature dissolution mechanism in chlorinated acidic medium (pH 2 oxide formation with a very limited tetravalent dissolution). In hydrothermal oxidation (pH>1), only the second branch is effective. The titanium protection is directly related to the oxide stability in high pH systems. The mechanism model is expressed in terms of 'current-potential' laws, which provide kinetic parameters using optimization calculations. The different elementary steps reaction rates were estimated as well as the evolution of the reaction intermediates coverage ratios with the potential. The quantification of each elementary step was performed to understand and/or orient the materials behavior according to different factors (pH, chloride ions contents, potentials...)

  3. Influence of fluorozirconic acid on sulfuric acid anodizing of aluminum

    OpenAIRE

    Elaish, R.; Curioni, M.; Gowers, K.; Kasuga, A.; Habazaki, H.; Hashimoto, T.; Skeldon, P.

    2017-01-01

    The effects of additions of fluorozirconic acid to sulfuric acid on the anodizing behavior of aluminum have been investigated under a constant voltage at temperatures of 0 and 20◦C. The fluoroacid increased the rate of film growth, with a dependence on the fluoroacid concentration, the electrolyte temperature and the anodizing time. Compositional analyses showed that fluorine species were present in the films. However, zirconium species were absent. The fluoroacid generally enhanced film diss...

  4. Improving pitting corrosion resistance of aluminum by anodizing process

    International Nuclear Information System (INIS)

    John, P.; Khan, I.U.

    2013-01-01

    Summary: Anodizing of aluminum was studied in sulphuric/citric/boric acid electrolyte system to improve pitting corrosion resistance. Maximum oxide film thickness was obtained using 5% sulphuric acid, 3% citric acid and 0.5% boric acid electrolyte composition. The corrosion resistance of aluminum sample was determined to find the effectiveness of oxide coating by potentiodynamic polarization test. The surface morphology of aluminum samples was investigated using scanning electron microscope (SEM) before and after corrosion test. It was found that the coated aluminum sample obtained by anodizing in sulphuric/citric/boric acid electrolyte system exhibited better pitting corrosion resistance with no significant difference in surface morphology. (author)

  5. Fabrication of porous anodic alumina using normal anodization and pulse anodization

    Science.gov (United States)

    Chin, I. K.; Yam, F. K.; Hassan, Z.

    2015-05-01

    This article reports on the fabrication of porous anodic alumina (PAA) by two-step anodizing the low purity commercial aluminum sheets at room temperature. Different variations of the second-step anodization were conducted: normal anodization (NA) with direct current potential difference; pulse anodization (PA) alternate between potential differences of 10 V and 0 V; hybrid pulse anodization (HPA) alternate between potential differences of 10 V and -2 V. The method influenced the film homogeneity of the PAA and the most homogeneous structure was obtained via PA. The morphological properties are further elucidated using measured current-transient profiles. The absent of current rise profile in PA indicates the anodization temperature and dissolution of the PAA structure were greatly reduced by alternating potential differences.

  6. Performance of a plasma opening switch in positive polarity on Gamble I using flashboard plasma sources

    International Nuclear Information System (INIS)

    Renk, T.J.

    1995-01-01

    The successful development of the Plasma Opening Switch (POS) for inductive storage applications has been largely confined to negative polarity operation. Some models of POS behavior suggest that this is because in a positive polarity coaxial configuration, the weaker magnetic field at the cathode position retards the switch opening process. This article describes experiments in which both conductor radii in the POS region were significantly reduced. Anode- and cathode-side current monitors indicate that voltages greater than open-circuit are generated at the POS position, but there is a significant amount of electron flow out of the POS, depending upon load impedance. Flow impedance analysis indicates that a relatively small gap appears in the POS plasma after switch opening. Switch performance is also compared between flashboard and carbon gun plasma sources, with the latter operated both in positive and negative polarity

  7. Liquid Silicon Pouch Anode

    Science.gov (United States)

    2017-09-06

    Number 15/696,426 Filing Date 6 September 2017 Inventor Charles J. Patrissi et al Address any questions concerning this matter to the...silicon-based anodes during cycling, lithium insertion and deinsertion. Mitigation of this problem has long been sought and will result in improved...design shown. [0032] It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been

  8. Cyclic performance tests of Sn/MWCNT composite lithium ion battery anodes at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Tocoglu, U., E-mail: utocoglu@sakarya.edu.tr; Cevher, O.; Akbulut, H. [Sakarya University, Engineering Faculty, Department of Metallurgical and Materials Engineering, Esentepe Campus 54187 (Turkey)

    2016-04-21

    In this study tin-multi walled carbon nanotube (Sn-MWCNT) lithium ion battery anodes were produced and their electrochemical galvanostatic charge/discharge tests were conducted at various (25 °C, 35 °C, 50 °C) temperatures to determine the cyclic behaviors of anode at different temperatures. Anodes were produced via vacuum filtration and DC magnetron sputtering technique. Tin was sputtered onto buckypapers to form composite structure of anodes. SEM analysis was conducted to determine morphology of buckypapers and Sn-MWCNT composite anodes. Structural and phase analyses were conducted via X-ray diffraction and Raman Spectroscopy technique. CR2016 coin cells were assembled for electrochemical tests. Cyclic voltammetry test were carried out to determine the reversibility of reactions between anodes and reference electrode between 0.01-2.0 V potential window. Galvanostatic charge/discharge tests were performed to determine cycle performance of anodes at different temperatures.

  9. Effect of samarium in corrosion and microstructure of Al-5Zn-0.5Cu as low driving voltage sacrificial anode

    Science.gov (United States)

    Pratesa, Yudha; Ferdian, Deni; Ramadhan, Fajar Yusya; Maulana, Bramuda

    2018-05-01

    Sacrificial Anode Low voltage is the latest generation of the sacrificial anode that can prevent the occurrence of Hydrogen Cracking (HIC) due to overprotection. The Al-5n-0.5Cu alloy showed the potential to be developed as the new sacrificial anode. However, the main problem is copper made Al2Cu intermetallic in grain boundary. Samarium is added to modify the shape of the intermetallic to make it finer and make the corrosion uniform. Several characterizations were conducted to analyze the effect of Samarium. Scanning electron microscope (SEM) and Energy dispersive spectroscopy was used to analyzed the microstructure of the alloy. Metallography preparation was prepared for SEM analysis. Corrosion behavior was characterized by cyclic polarization in 3.5% NaCl solution. The results show samarium can change the shape of intermetallic and refine the grains. In addition, samarium makes better pitting resistance and exhibits a tendency for uniform corrosion. It is indicated by the loop reduction (ΔEpit-prot). Current density increased as an effect of samarium addition from 6x10-5 Ampere (Al-5Zn-0.5Cu) to 2.5x10-4 Ampere (Al-5Zn-0.5Cu-0.5Sm). Steel potential protection increased after addition of samarium which is an indication the possibility of Al-Zn-Cu-Sm to be used as low voltage sacrificial anode.

  10. Experimental and theoretical studies on electropolymerization of polar amino acids on platinum electrode

    Energy Technology Data Exchange (ETDEWEB)

    Alhedabi, Taleb [Nanomedicine Lab EA4662, Bat. E, Université de Bourgogne Franche-Comté, UFR Sciences & Techniques, 16 route de Gray, 25030 Besançon Cedex (France); Department of Chemistry, College of Science, University of Thi-qar, Thi-qar (Iraq); Cattey, Hélène [Institut ICMUB - CNRS 6302, Université de Bourgogne Franche-Comté, UFR Sciences et Techniques Mirande, 9 Avenue Alain Savary, 21000 Dijon (France); Roussel, Christophe [Ecole Polytechnique Fédérale de Lausanne, Section of Chemistry and Chemical Engineering, Station 6, CH-1015 Lausanne (Switzerland); Blondeau-Patissier, Virginie [Institut FEMTO-ST, UMR CNRS 6174, Department Time-Frequency, 26, Chemin de l' épitaphe, 25030 Besançon Cedex (France); Gharbi, Tijani [Nanomedicine Lab EA4662, Bat. E, Université de Bourgogne Franche-Comté, UFR Sciences & Techniques, 16 route de Gray, 25030 Besançon Cedex (France); Herlem, Guillaume, E-mail: guillaume.herlem@univ-fcomte.fr [Nanomedicine Lab EA4662, Bat. E, Université de Bourgogne Franche-Comté, UFR Sciences & Techniques, 16 route de Gray, 25030 Besançon Cedex (France)

    2017-01-01

    The anodic oxidation of polar amino acids (L-serine, L-threonine, L-asparagine, and L-glutamine) in aqueous electrolyte on smooth platinum electrode was carried out by cyclic voltammetry coupled to electrochemical quartz crystal microbalance (EQCM). pH (zwitterion, acidic and alkaline) effects on their electrochemical behavior were examined. The maximum current values are measured for zwitterion species. In addition, the current increases with increasing of concentration and scan rate, and decreases with increasing pH. The resulting passivation was studied by spectroscopic analysis such as attenuated total reflection FT infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and mass spectroscopy (MALDI-TOF). From thin film coatings observed on the electrode surface, peptide bonds are found, and are in favor of electropolymerization of these polar amino acids into poly-L-amino acids in an irreversible way. Scanning electronic microscopy was also used to study the morphology of these electrodeposited L-amino acids. The electrodeposited poly-L-amino acids on Pt electrode were tested as bioinspired transducer for pH sensing purposes. - Highlights: • Anodic oxidation of polar amino acids with uncharged R group on platinum electrode. • Polypeptide bonds revealed by ATR-IR and XPS spectroscopies. • The film growth depends on the chemistry of the polar amino acid.

  11. High-capacity nanocarbon anodes for lithium-ion batteries

    International Nuclear Information System (INIS)

    Zhang, Haitao; Sun, Xianzhong; Zhang, Xiong; Lin, He; Wang, Kai; Ma, Yanwei

    2015-01-01

    Highlights: • The nanocarbon anodes in lithium-ion batteries deliver a high capacity of ∼1100 mA h g −1 . • The nanocarbon anodes exhibit excellent cyclic stability. • A novel structure of carbon materials, hollow carbon nanoboxes, has potential application in lithium-ion batteries. - Abstract: High energy and power density of secondary cells like lithium-ion batteries become much more important in today’s society. However, lithium-ion battery anodes based on graphite material have theoretical capacity of 372 mA h g −1 and low charging-discharging rate. Here, we report that nanocarbons including mesoporous graphene (MPG), carbon tubular nanostructures (CTN), and hollow carbon nanoboxes (HCB) are good candidate for lithium-ion battery anodes. The nanocarbon anodes have high capacity of ∼1100, ∼600, and ∼500 mA h g −1 at 0.1 A g −1 for MPG, CTN, and HCB, respectively. The capacity of 181, 141, and 139 mA h g −1 at 4 A g −1 for MPG, CTN, and HCB anodes is retained. Besides, nanocarbon anodes show high cycling stability during 1000 cycles, indicating formation of a passivating layer—solid electrolyte interphase, which support long-term cycling. Nanocarbons, constructed with graphene layers which fulfill lithiation/delithiation process, high ratio of graphite edge structure, and high surface area which facilitates capacitive behavior, deliver high capacity and improved rate-capability

  12. Behavioral and electroencephalographic evaluation of the anticonvulsive activity of Moringa oleifera leaf non-polar extracts and one metabolite in PTZ-induced seizures.

    Science.gov (United States)

    González-Trujano, María Eva; Martínez-González, Claudia Lizbeth; Flores-Carrillo, Maricela; Luna-Nophal, Sara Ibeth; Contreras-Murillo, Gerardo; Magdaleno-Madrigal, Víctor Manuel

    2018-01-15

    Moringa oleifera Lamarck is a species that has long been used in high demand in folk medicine, including for the treatment of epilepsy. Nevertheless, scientific studies demonstrating its anticonvulsant properties and the nature of the bioactive constituents are lacking. The aim of this study was to evaluate the anticonvulsant activities of the Moringa oleifera leaves in non-polar vs. polar extracts using behavioral and electroencephalographic (EEG) analyses in rodents. First, PTZ (80 mg/kg, i.p.)-induced tonic-clonic seizures were assayed via a dose-response (100, 200 and 300 mg/kg, i.p.) evaluation in mice. Then, a dosage of the extracts (100 or 300 mg/kg) and one metabolite (30 mg/kg, i.p.) was selected to evaluate its effect on PTZ (35 mg/kg, i.p.)-induced EEG paroxystic activities in rats compared to the effects of ethosuximide (reference anticonvulsant drug, 100 mg/kg, i.p.). Latent onset of the first paroxystic spike, first seizure and frequency as well as seizure severity, were determined using Racine's scale. Moringa oleifera ethanol and hexane extracts produced a delay in the seizure latency in mice and rats; this effect was improved in the presence of the hexane extract containing the active metabolite hexadecanoic acid. The anticonvulsant effects were corroborated in the spectral analysis by the potency of the EEG due to a reduction in the spike frequency and amplitude, as well as in the duration and severity of the seizures. The effects of the hexane extract resembled those observed in the reference antiepileptic drug ethosuximide. Moringa oleifera leaves possess anticonvulsant activities due to the complementary of the non-polar and polar constituents. However, the non-polar constituents appear to exert an important influence via the partial participation of fatty acids, providing evidence of the effects of this plant in epilepsy therapy. Copyright © 2017. Published by Elsevier GmbH.

  13. Process for anodizing aluminum foil

    International Nuclear Information System (INIS)

    Ball, J.A.; Scott, J.W.

    1984-01-01

    In an integrated process for the anodization of aluminum foil for electrolytic capacitors including the formation of a hydrous oxide layer on the foil prior to anodization and stabilization of the foil in alkaline borax baths during anodization, the foil is electrochemically anodized in an aqueous solution of boric acid and 2 to 50 ppm phosphate having a pH of 4.0 to 6.0. The anodization is interrupted for stabilization by passing the foil through a bath containing the borax solution having a pH of 8.5 to 9.5 and a temperature above 80 0 C. and then reanodizing the foil. The process is useful in anodizing foil to a voltage of up to 760 V

  14. Are you positive? Electric dipole polarity discrimination in the yellow stingray, Urobatis jamaicensis.

    Science.gov (United States)

    Siciliano, Avery M; Kajiura, Stephen M; Long, John H; Porter, Marianne E

    2013-10-01

    It is well established that elasmobranchs can detect dipole electric fields. However, it is unclear whether they can discriminate between the anode and cathode. To investigate this subject, we employed a behavioral assay to determine the discriminatory ability of the yellow stingray, Urobatis jamaicensis. We conditioned stingrays with food rewards to bite either the anode (n=5) or the cathode (n=6) of a direct-current dipole located on the floor of an experimental tank. All individuals successfully performed the task after 18 to 22 days. Stingrays were then tested in experimental sessions when they were rewarded only after they identified the correct pole. Stingrays successfully discriminated between the poles at a rate greater than chance, ranging among individuals from a mean of 66% to 93% correct. During experimental sessions, stingrays conditioned to distinguish the anode performed similarly to those conditioned to distinguish the cathode. We hypothesize that the ability to discriminate anode from cathode is physiologically encoded, but its utility in providing spatial information under natural conditions remains to be demonstrated. The ability to discriminate polarity may eliminate ambiguity in induction-based magnetoreception and facilitate navigation with respect to the geomagnetic field.

  15. Anode sheath in Hall thrusters

    International Nuclear Information System (INIS)

    Dorf, L.; Semenov, V.; Raitses, Y.

    2003-01-01

    A set of hydrodynamic equations is used to describe quasineutral plasma in ionization and acceleration regions of a Hall thruster. The electron distribution function and Poisson equation are invoked for description of a near-anode region. Numerical solutions suggest that steady-state operation of a Hall thruster can be achieved at different anode sheath regimes. It is shown that the anode sheath depends on the thruster operating conditions, namely the discharge voltage and the mass flow rate

  16. Superhydrophilicity of a nanofiber-covered aluminum surface fabricated via pyrophosphoric acid anodizing

    Science.gov (United States)

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

    2016-12-01

    A superhydrophilic aluminum surface covered by numerous alumina nanofibers was fabricated via pyrophosphoric acid anodizing. High-density anodic alumina nanofibers grow on the bottom of a honeycomb oxide via anodizing in concentrated pyrophosphoric acid. The water contact angle on the nanofiber-covered aluminum surface decreased with time after a 4 μL droplet was placed on the surface, and a superhydrophilic behavior with a contact angle measuring 2.2° was observed within 2 s; this contact angle is considerably lower than those observed for electropolished and porous alumina-covered aluminum surfaces. There was no dependence of the superhydrophilicity on the density of alumina nanofibers fabricated via different constant voltage anodizing conditions. The superhydrophilic property of the surface covered by anodic alumina nanofibers was maintained during an exposure test for 359 h. The quick-drying and snow-sliding behaviors of the superhydrophilic aluminum covered with anodic alumina nanofibers were demonstrated.

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

    DEFF Research Database (Denmark)

    Abdul Jabbar, Mohammed Hussain

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

  18. Fabrication of a novel aluminum surface covered by numerous high-aspect-ratio anodic alumina nanofibers

    Science.gov (United States)

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

    2015-11-01

    The formation behavior of anodic alumina nanofibers via anodizing in a concentrated pyrophosphoric acid under various conditions was investigated using electrochemical measurements and SEM/TEM observations. Pyrophosphoric acid anodizing at 293 K resulted in the formation of numerous anodic alumina nanofibers on an aluminum substrate through a thin barrier oxide and honeycomb oxide with narrow walls. However, long-term anodizing led to the chemical dissolution of the alumina nanofibers. The density of the anodic alumina nanofibers decreased as the applied voltage increased in the 10-75 V range. However, active electrochemical dissolution of the aluminum substrate occurred at a higher voltage of 90 V. Low temperature anodizing at 273 K resulted in the formation of long alumina nanofibers measuring several micrometers in length, even though a long processing time was required due to the low current density during the low temperature anodizing. In contrast, high temperature anodizing easily resulted in the formation and chemical dissolution of alumina nanofibers. The structural nanofeatures of the anodic alumina nanofibers were controlled by choosing of the appropriate electrochemical conditions, and numerous high-aspect-ratio alumina nanofibers (>100) can be successfully fabricated. The anodic alumina nanofibers consisted of a pure amorphous aluminum oxide without anions from the employed electrolyte.

  19. Sorption behavior of charged and neutral polar organic compounds on solid phase extraction materials: which functional group governs sorption?

    NARCIS (Netherlands)

    Bäuerlein, P.S.; Mansell, J.E.; ter Laak, T.L.; de Voogt, P.

    2012-01-01

    Numerous polar anthropogenic organic chemicals have been found in the aqueous environment. Solid phase extraction (SPE) has been applied for the isolation of these from aqueous matrices, employing various materials. Nevertheless, little is known about the influence of functional groups on the

  20. Environmental friendly anodizing of AZ91D magnesium alloy in alkaline borate-benzoate electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Liu Yan [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Department of Chemistry, Tianshui Normal University, Tianshui 741000 (China); Wei Zhongling [Magnesium Technology Co., Ltd., Chinese Academy of Sciences, Jiaxing 314051 (China); Yang Fuwei [Department of Chemistry, Tianshui Normal University, Tianshui 741000 (China); Zhang Zhao, E-mail: eaglezzy@zjuem.zju.edu.cn [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Key Laboratory for Light Alloy Materials Technology, Jiaxing 314051 (China)

    2011-06-02

    Highlights: > Environmental friendly PEO technology for AZ91 magnesium alloy is developed. > NaBz is used as new additive and it is low-cost and environmental friendly. > The effect of NaBz additive on the properties of the anodized film was studied. > Anodized film with excellent corrosion resistance is obtained. > The forming mechanism of anodized film in the presence of NaBz is approached. - Abstract: A kind of environmental friendly anodizing routine for AZ91D magnesium alloy, based on an alkaline borate-sodium benzoate electrolyte (NaBz) was studied. The effect of NaBz on the properties of the anodized film was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), respectively. The results showed that the anodizing process, surface morphology, thickness, phase structure and corrosion resistance of the anodized film were strongly dependent on the concentration of NaBz. In the presence of adequate NaBz, a thick, compact and smoothing anodized film with excellent corrosion resistance was produced. Moreover, the forming mechanism of the anodized film in the presence of NaBz additive was also approached, which was a suppression of arc discharge process by the adsorption of Bz{sup -} on the surface of magnesium alloy substrate.

  1. Environmental friendly anodizing of AZ91D magnesium alloy in alkaline borate-benzoate electrolyte

    International Nuclear Information System (INIS)

    Liu Yan; Wei Zhongling; Yang Fuwei; Zhang Zhao

    2011-01-01

    Highlights: → Environmental friendly PEO technology for AZ91 magnesium alloy is developed. → NaBz is used as new additive and it is low-cost and environmental friendly. → The effect of NaBz additive on the properties of the anodized film was studied. → Anodized film with excellent corrosion resistance is obtained. → The forming mechanism of anodized film in the presence of NaBz is approached. - Abstract: A kind of environmental friendly anodizing routine for AZ91D magnesium alloy, based on an alkaline borate-sodium benzoate electrolyte (NaBz) was studied. The effect of NaBz on the properties of the anodized film was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), respectively. The results showed that the anodizing process, surface morphology, thickness, phase structure and corrosion resistance of the anodized film were strongly dependent on the concentration of NaBz. In the presence of adequate NaBz, a thick, compact and smoothing anodized film with excellent corrosion resistance was produced. Moreover, the forming mechanism of the anodized film in the presence of NaBz additive was also approached, which was a suppression of arc discharge process by the adsorption of Bz - on the surface of magnesium alloy substrate.

  2. Exploring As-Cast PbCaSn-Mg Anodes for Improved Performance in Copper Electrowinning

    Science.gov (United States)

    Yuwono, Jodie A.; Clancy, Marie; Chen, Xiaobo; Birbilis, Nick

    2018-06-01

    Lead calcium tin (PbCaSn) alloys are the common anodes used in copper electrowinning (Cu EW). Given a large amount of energy consumed in Cu EW process, anodes with controlled oxygen evolution reaction (OER) kinetics and a lower OER overpotential are advantageous for reducing the energy consumption. To date, magnesium (Mg) has never been studied as an alloying element for EW anodes. As-cast PbCaSn anodes with the addition of Mg were examined herein, revealing an improved performance compared to that of the industrial standard PbCaSn anode. The alloy performances in the early stages of anode life and passivation were established from electrochemical studies which were designed to simulate industrial Cu EW process. The 24-hour polarization testing revealed that the Mg alloying depolarizes the anode potential up to 80 mV; thus, resulting in a higher Cu EW efficiency. In addition, scanning electron microscopy and X-ray photoelectron spectroscopy revealed that the alteration of the alloy microstructure and the corresponding interfacial reactions contribute to the changes of the anode electrochemical performances. The present study reveals for the first time the potency of Mg alloying in reducing the overpotential of PbCaSn anode.

  3. The Electrochemical Behavior of SnSb as an Anode for Li-ion Batteries Studied by Electrochemical Impedance Spectroscopy and Electron Microscopy

    International Nuclear Information System (INIS)

    Tesfaye, Alexander T.; Yücel, Yasemin D.; Barr, Maïssa K.S.; Santinacci, Lionel; Vacandio, Florence; Dumur, Frédéric; Maria, Sébastien; Monconduit, Laure; Djenizian, Thierry

    2017-01-01

    Highlights: •Electrochemical behavior of SnSb is investigated by EIS, SEM and TEM. •Formation of SEI and cracks occurs during cycling experiments. •The capacity fading as a result of the electrode modifications is discussed. -- Abstract: Evolution of the electrical and morphological properties of micron-sized SnSb has been investigated to understand the electrochemical behavior observed during cycling experiments. Electron microscopy techniques (scanning electron microscopy and transmission electron microscopy) and electrochemical impedance spectroscopy have been combined to evidence the electrode modifications and particularly the formation of a solid electrolyte interphase (SEI) layer. Evolution of the SEI resistance and the charge transfer resistance with the cell voltage can be explained by the electrolyte degradation and expansion/contraction of the electrode. Furthermore, we show that the SEI formation is not limited at the first discharge/charge of the battery. The continuous growth of the SEI layer up to 50 cycles associated to the electrode pulverization caused by the large volume variations are responsible for the capacity fading.

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

    International Nuclear Information System (INIS)

    Kim, Seong Jong; Okido, Masazumi

    2003-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-07-01

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

  6. Performance Factors and Sulfur Tolerance of Metal Supported Solid Oxide Fuel Cells with Nanostructured Ni:GDC Infiltrated Anodes

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Sudireddy, Bhaskar Reddy; Hagen, Anke

    2016-01-01

    galvanostatic operation at a current load of 0.25 Acm−2. The results were compared with literature on the sulfur tolerance of conventional SOFC Ni/YSZ cermet anode. The comparison in terms of absolute cell resistance increase and relative anode polarization resistance increase indicates, that the nanostructured...... Ni:GDC MS-SOFC based anode is significantly more sulfur tolerant than the conventional Ni/YSZ cermet anode. Furthermore, it was shown that the believed extension of the electrochemical three-phase-boundary reaction zone in the presence of GDC must be very limited and cannot account for the higher...

  7. Investigation of different anode materials for aluminium rechargeable batteries

    Science.gov (United States)

    Muñoz-Torrero, David; Leung, Puiki; García-Quismondo, Enrique; Ventosa, Edgar; Anderson, Marc; Palma, Jesús; Marcilla, Rebeca

    2018-01-01

    In order to shed some light into the importance of the anodic reaction in reversible aluminium batteries, we investigate here the electrodeposition of aluminium in an ionic liquid electrolyte (BMImCl-AlCl3) using different substrates. We explore the influence of the type of anodic material (aluminium, stainless steel and carbon) and its 3D geometry on the reversibility of the anodic reaction by cyclic voltammetry (CV) and galvanostatic charge-discharge. The shape of the CVs confirms that electrodeposition of aluminium was feasible in the three materials but the highest peak currents and smallest peak separation in the CV of the aluminium anode suggested that this material was the most promising. Interestingly, carbon-based substrates appeared as an interesting alternative due to the high peak currents in CV, moderate overpotentials and dual role as anode and cathode. 3D substrates such as fiber-based carbon paper and aluminium mesh showed significantly smaller overpotentials and higher efficiencies for Al reaction suggesting that the use of 3D substrates in full batteries might result in enhanced power. This is corroborated by polarization testing of full Al-batteries.

  8. Investigation of cerium salt/sulfuric acid anodizing technology for 1420 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Di Li; Yue Peng Deng; Bao Lan Guo; Guo Qiang Li [Beijing Univ. of Aeronautics and Astronautics (China). Dept. of Mater. Sci. and Eng.

    2000-07-01

    In this paper, the effect of cerium addition agent on the property of anodized coating of 1420 Al alloy has been studied by corrosion experiment (immersion test and neutral salt spray test), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and measurement of polarization curves. The result show that only pitting could be observed in all corrosion tests while intergranular corrosion and exfoliation corrosion did not appear on 1420 Al-Li alloys. When organic carboxylic acid S or the cerium (IV) salt was added into sulfuric acid anodizing electrolyte separately, there was no significant improvement in corrosion resistance of anodized film. However, in the case of adding them into sulfuric acid anodizing electrolyte together, the corrosion resistance of anodized film increased greatly owing to synergistic effect. The synergistic effect may relate to the formation of cerium-organic carboxylic acid S complex compound and its effects on film growth and film structure. (orig.)

  9. Ni-SDC cermet anode for medium-temperature solid oxide fuel cell with lanthanum gallate electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xinge; Ohara, Satoshi; Maric, R.; Mukai, Kazuo; Fukui, Takehisa [Japan Fine Ceramics Center, Nagoya (Japan); Yoshida, Hiroyuki; Nishimura, Masayoshi; Inagaki, Toru [Kansai Electr. Power Co. Inc., Hyogo (Japan); Miura, Kazuhiro [Kanden Kakou, Amagasaki (Japan)

    1999-10-01

    The polarization properties and microstructure of Ni-SDC (samaria-doped ceria) cermet anodes prepared from spray pyrolysis (SP) composite powder, and element interface diffusion between the anode and a La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}Mg{sub 0.2}O{sub 3-{delta}} (LSGM) electrolyte are investigated as a function of anode sintering temperature. The anode sintered at 1250 C displays minimum anode polarization (with anode ohmic loss), while the anode prepared at 1300 C has the best electrochemical overpotential, viz., 27 mV at 300 mA cm{sup -2} operating at 800 C. The anode ohmic loss gradually increases with increase in the sintering temperature at levels below 1300 C, and sharply increases at 1350 C. Electron micrographs show a clear grain growth at sintering temperatures higher than 1300 C. The anode microstructure appears to be optimized at 1300 C, in which nickel particles form a network with well-connected SDC particles finely distributed over the surfaces of the nickel particles. The anode sintered at 1350 C has severe grain growth and an apparent interface diffusion of nickel from the anode to the electrolyte. The nickel interface diffusion is assumed to be the main reason for the increment in ohmic loss, and the resulting loss in anode performance. The findings suggest that sintering Ni-SDC composite powder near 1250 C is the best method to prepare the anode on a LSGM electrolyte. (orig.)

  10. Ni-SDC cermet anode for medium-temperature solid oxide fuel cell with lanthanum gallate electrolyte

    Science.gov (United States)

    Zhang, Xinge; Ohara, Satoshi; Maric, Radenka; Mukai, Kazuo; Fukui, Takehisa; Yoshida, Hiroyuki; Nishimura, Masayoshi; Inagaki, Toru; Miura, Kazuhiro

    The polarization properties and microstructure of Ni-SDC (samaria-doped ceria) cermet anodes prepared from spray pyrolysis (SP) composite powder, and element interface diffusion between the anode and a La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ (LSGM) electrolyte are investigated as a function of anode sintering temperature. The anode sintered at 1250°C displays minimum anode polarization (with anode ohmic loss), while the anode prepared at 1300°C has the best electrochemical overpotential, viz., 27 mV at 300 mA cm -2 operating at 800°C. The anode ohmic loss gradually increases with increase in the sintering temperature at levels below 1300°C, and sharply increases at 1350°C. Electron micrographs show a clear grain growth at sintering temperatures higher than 1300°C. The anode microstructure appears to be optimized at 1300°C, in which nickel particles form a network with well-connected SDC particles finely distributed over the surfaces of the nickel particles. The anode sintered at 1350°C has severe grain growth and an apparent interface diffusion of nickel from the anode to the electrolyte. The nickel interface diffusion is assumed to be the main reason for the increment in ohmic loss, and the resulting loss in anode performance. The findings suggest that sintering Ni-SDC composite powder near 1250°C is the best method to prepare the anode on a LSGM electrolyte.

  11. Solvent anode for plutonium purification

    International Nuclear Information System (INIS)

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

    1986-01-01

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

  12. Stromal differences in odontogenic cysts of a common histopathogenesis but with different biological behavior: a study with picrosirius red and polarizing microscopy.

    Science.gov (United States)

    Aggarwal, P; Saxena, S

    2011-01-01

    The present study was undertaken to detect and compare the pattern of collagen fibers in odontogenic cysts and also to find out if this methodology could be used to predict the aggressive nature of odontogenic cysts by comparing with the odontogenic tumors. The collagen in the wall of 11 odontogenic keratocysts, 14 dentigerous cysts and 14 radicular cysts was studied histochemically by staining sections with picrosirius red and examining under polarizing microscope. This was compared to 10 cases of odontogenic tumors using Z test of proportion at 1% and 5%. In dentigerous cysts, odontogenic keratocysts and odontogenic tumors, the predominant color of collagen fibers birefringence was found to be orangish red, whereas in radicular cysts the collagen fiber was of green color. Similar birefringence pattern of collagen fibers between dentigerous cysts, odontogenic keratocysts and odontogenic tumors may indicate that these lesions have a common histogenesis with a broad spectrum of biological behavior and belong to the same group, i.e., are developmental in origin. Different patterns of radicular cysts suggest different biological behavior and a positive role of inflammation on polarization color of collagen fibers.

  13. Electrochemical impedance spectroscopy of nanoporous anodic alumina template

    International Nuclear Information System (INIS)

    Shahzad, K.

    2010-01-01

    Room temperature EIS characterization of nanoporous anodic alumina prepared at 40 V and 60 V has been done in 0.3 M oxalic acid solution. Rapid decrease in impedance was observed for the template prepared at 40 V. EIS study of porous anodic alumina template prepared in 0.3 M oxalic acid has been done in different electrolytes. Templates prepared in 0.3 M sulfuric acid solution were also characterized for comparison. Rapid decrease in the thickness of nonporous anodic film was observed with an increase of aggressiveness of electrolyte. Temperature based systematic study of EIS measurement has been done for porous anodic alumina template at different temperatures. Formation of micropores was observed in the nanoporous anodic alumina film formed on aluminum in 0.3 M oxalic acid solution which accelerates the dissolution rate with increase of measurement temperature. In addition to these, electropolishing behavior of pure aluminum has also been studied in different electrolytes and it was observed that electropolishing conditions prior to anodization are extremely important. (author)

  14. Iron migration from the anode surface in alumina electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Zhuravleva, Elena N.; Drozdova, Tatiana N.; Ponomareva, Svetlana V. [Siberian Federal University, Krasnoyarsk, 660041 (Russian Federation); Kirik, Sergei D., E-mail: kiriksd@yandex.ru [Siberian Federal University, Krasnoyarsk, 660041 (Russian Federation); Institute of Chemistry and Chemical Technology SB RAS, Krasnoyarsk, 660036 (Russian Federation)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer Corrosion destruction of two-component iron-based alloys in high-temperature aluminum electrolysis in the cryolite alumina melt has been studied. Black-Right-Pointing-Pointer It was found that at the first stage oxidative polarization of iron atoms on the anode surface into Fe{sup 2+} takes place. Black-Right-Pointing-Pointer Fe{sup 2+} interacts with cryolite melt producing FeF{sub 2}. Black-Right-Pointing-Pointer FeF{sub 2} gives oxides FeAl{sub 2}O{sub 4}, Fe{sub 3}O{sub 4}, Fe{sub 2}O{sub 3}. Black-Right-Pointing-Pointer The participation of oxygen in the corrosion has not been observed. - Abstract: Corrosion destruction of two-component iron-based alloys used as an anode in high-temperature alumina electrolysis in the melt of NaF/KF/AlF{sub 3} electrolyte has been considered. Ni, Si, Cu, Cr, Mn, Al, Ti in the amount of up to 10% have been tested as the dopants to an anode alloys. The composition of the corrosion products has been studied using X-ray diffraction, scanning electron microscopy and electron microprobe analysis. It has been established that the anode corrosion is induced by a surface electrochemical polarization and iron atom oxidation. Iron ions come into an exchange interaction with the fluoride components of the melted electrolyte, producing FeF{sub 2}. The last interacts with oxyfluoride species transforming into the oxide forms: FeAl{sub 2}O{sub 4}, Fe{sub 3}O{sub 4}, Fe{sub 2}O{sub 3}. Due to the low solubility, the iron oxides are accumulated in the near-electrode sheath. The only small part of iron from anode migrates to cathode that makes an production of high purity aluminum of a real task. The alloy dopants are also subjected to corrosion in accordance with electromotive series resulting corrosion tunnels on the anode surface. The oxides are final compounds which collect in the same area. The corrosion products form an anode shell which is electronic conductor at electrolysis temperature. The

  15. Mirror-finished superhydrophobic aluminum surfaces modified by anodic alumina nanofibers and self-assembled monolayers

    Science.gov (United States)

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

    2018-05-01

    We demonstrate mirror-finished superhydrophobic aluminum surfaces fabricated via the formation of anodic alumina nanofibers and subsequent modification with self-assembled monolayers (SAMs). High-density anodic alumina nanofibers were formed on the aluminum surface via anodizing in a pyrophosphoric acid solution. The alumina nanofibers became tangled and bundled by further anodizing at low temperature because of their own weight, and the aluminum surface was completely covered by the long falling nanofibers. The nanofiber-covered aluminum surface exhibited superhydrophilic behavior, with a contact angle measuring less than 10°. As the nanofiber-covered aluminum surface was modified with n-alkylphosphonic acid SAMs, the water contact angle drastically shifted to superhydrophobicity, measuring more than 150°. The contact angle increased with the applied voltage during pyrophosphoric acid anodizing, the anodizing time, and the number of carbon atoms contained in the SAM molecules modified on the alumina nanofibers. By optimizing the anodizing and SAM-modification conditions, superhydrophobic behavior could be achieved with only a brief pyrophosphoric acid anodizing period of 3 min and subsequent simple immersion in SAM solutions. The superhydrophobic aluminum surface exhibited a high reflectance, measuring approximately 99% across most of the visible spectrum, similar to that of an electropolished aluminum surface. Therefore, our mirror-finished superhydrophobic aluminum surface based on anodic alumina nanofibers and SAMs can be used as a reflective mirror in various optical applications such as concentrated solar power systems.

  16. Significant Corrosion Resistance in an Ultrafine-Grained Al6063 Alloy with a Bimodal Grain-Size Distribution through a Self-Anodic Protection Mechanism

    Directory of Open Access Journals (Sweden)

    Mahdieh Shakoori Oskooie

    2016-12-01

    Full Text Available The bimodal microstructures of Al6063 consisting of 15, 30, and 45 vol. % coarse-grained (CG bands within the ultrafine-grained (UFG matrix were synthesized via blending of high-energy mechanically milled powders with unmilled powders followed by hot powder extrusion. The corrosion behavior of the bimodal specimens was assessed by means of polarization, steady-state cyclic polarization and impedance tests, whereas their microstructural features and corrosion products were examined using optical microscopy (OM, scanning transmission electron microscopy (STEM, field emission scanning electron microscopy (FE-SEM, electron backscattered diffraction (EBSD, energy dispersive spectroscopy (EDS, and X-ray diffraction (XRD techniques. The bimodal Al6063 containing 15 vol. % CG phase exhibits the highest corrosion resistance among the bimodal microstructures and even superior electrochemical behavior compared with the plain UFG and CG materials in the 3.5% NaCl solution. The enhanced corrosion resistance is attributed to the optimum cathode to anode surface area ratio that gives rise to the formation of an effective galvanic couple between CG areas and the UFG matrix. The operational galvanic coupling leads to the domination of a “self-anodic protection system” on bimodal microstructure and consequently forms a uniform thick protective passive layer over it. In contrast, the 45 vol. % CG bimodal specimen shows the least corrosion resistance due to the catastrophic galvanic corrosion in UFG regions. The observed results for UFG Al6063 suggest that metallurgical tailoring of the grain structure in terms of bimodal microstructures leads to simultaneous enhancement in the electrochemical behavior and mechanical properties of passivable alloys that are usually inversely correlated. The mechanism of self-anodic protection for passivable metals with bimodal microstructures is discussed here for the first time.

  17. Polarization Optics in Telecommunications

    CERN Document Server

    Damask, Jay N

    2005-01-01

    The strong investments into optical telecommunications in the late 1990s resulted in a wealth of new research, techniques, component designs, and understanding of polarization effects in fiber. Polarization Optics in Telecommunications brings together recent advances in the field to create a standard, practical reference for component designers and optical fiber communication engineers. Beginning with a sound foundation in electromagnetism, the author offers a dissertation of the spin-vector formalism of polarization and the interaction of light with media. Applications discussed include optical isolators, optical circulators, fiber collimators, and a variety of applied waveplate and prism combinations. Also included in an extended discussion of polarization-mode dispersion (PMD) and polarization-dependent loss (PDL), their representation, behavior, statistical properties, and measurement. This book draws extensively from the technical and patent literature and is an up-to-date reference for researchers and c...

  18. In situ characterization of nanoscale catalysts during anodic redox processes

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Renu [National Institute of Standards and Technology; Crozier, Peter [Arizona State University; Adams, James [Arizona State University

    2013-09-19

    Controlling the structure and composition of the anode is critical to achieving high efficiency and good long-term performance. In addition to being a mixed electronic and ionic conductor, the ideal anode material should act as an efficient catalyst for oxidizing hydrogen, carbon monoxide and dry hydrocarbons without de-activating through either sintering or coking. It is also important to develop novel anode materials that can operate at lower temperatures to reduce costs and minimized materials failure associated with high temperature cycling. We proposed to synthesize and characterize novel anode cermets materials based on ceria doped with Pr and/or Gd together with either a Ni or Cu metallic components. Ceria is a good oxidation catalyst and is an ionic conductor at room temperature. Doping it with trivalent rare earths such as Pr or Gd retards sintering and makes it a mixed ion conductor (ionic and electronic). We have developed a fundamental scientific understanding of the behavior of the cermet material under reaction conditions by following the catalytic oxidation process at the atomic scale using a powerful Environmental Scanning Transmission Electron Microscope (ESTEM). The ESTEM allowed in situ monitoring of structural, chemical and morphological changes occurring at the cermet under conditions approximating that of typical fuel-cell operation. Density functional calculations were employed to determine the underlying mechanisms and reaction pathways during anode oxidation reactions. The dynamic behavior of nanoscale catalytic oxidation of hydrogen and methane were used to determine: ? Fundamental processes during anodic reactions in hydrogen and carbonaceous atmospheres ? Interfacial effects between metal particles and doped ceria ? Kinetics of redox reaction in the anode material

  19. High performance electrodes for reduced temperature solid oxide fuel cells with doped lanthanum gallate electrolyte. I. Ni-SDC cermet anode

    Science.gov (United States)

    Ohara, S.; Maric, R.; Zhang, X.; Mukai, K.; Fukui, T.; Yoshida, H.; Inagaki, T.; Miura, K.

    A Ni-samaria-doped ceria (SDC) cermet was selected as the anode material for reduced temperature (800°C) solid oxide fuel cells. The NiO-SDC composite powder, synthesized by spray pyrolysis, was employed as the starting anode powder in this study. The influence of Ni content in Ni-SDC cermets on the electrode performance was investigated in order to create the most suitable microstructures. It was found that anodic polarization was strongly influenced by the Ni content in Ni-SDC cermets. The best results were obtained for anode cermets with Ni content of around 50 vol.%; anodic polarization was about 30 mV at a current density of 300 mA/cm 2. This high performance seems to be attributable to the microstructure, in which Ni grains form a skeleton with well-connected SDC grains finely distributed over the Ni grains surfaces; such microstructure was also conducive to high stability of the anode.

  20. High performance electrodes for reduced temperature solide oxide fuel cells with doped lanthanum gallate electrolyte. Pt. 1. Ni-SDC cermet anode

    Energy Technology Data Exchange (ETDEWEB)

    Ohara, S.; Maric, R.; Zhang, X.; Mukai, K.; Fukui, T. [Japan Fine Ceramics Center, Nagoya (Japan); Yoshida, H.; Inagaki, T. [The Kansai Electroc Power Co. Inc., Hyogo (Japan); Miura, K. [Kanden Kakou Co. Ltd., Hyogo (Japan)

    2000-03-01

    A Ni-samaria-doped ceria (SDC) cermet was selected as the anode material for reduced temperature (800 C) solid oxide fuel cells. The NiO-SDC composite powder, synthesized by spray pyrolysis, was employed as the starting anode powder in this study. The influence of Ni content in Ni-SDC cermets on the electrode performance was investigated in order to create the most suitable microstructures. It was found that anodic polarization was strongly influenced by the Ni content in Ni-SDC cermets. The best results were obtained for anode cermets with Ni content of around 50 vol.%; anodic polarization was about 30 mV at a current density of 300 mA/cm{sup 2}. This high performance seems to be attributable to the microstructure, in which Ni grains form a skeleton with well-connected SDC grains finely distributed over the Ni grains surfaces; such microstructure was also conducive to high stability of the anode. (orig.)

  1. No More Polarization, Please!

    OpenAIRE

    Reinholt, Mia

    2006-01-01

    The organizational science literature on motivation has for long been polarized into two main positions; the organizational economic position focusing on extrinsic motivation and the organizational behavior position emphasizing intrinsic motivation. With the rise of the knowledge economy and the increasing levels of complexities it entails, such polarization is not fruitful in the attempt to explain motivation of organizational members. This paper claims that a more nuanced perspective on mot...

  2. Forming lead-based anodes

    Energy Technology Data Exchange (ETDEWEB)

    Ogorodnichuk, V I; Voitsekhovich, R I

    1972-01-01

    Lead-based anodes can be produced by forming a layer of lead dioxide by chemical treatment in a solution of sulfuric acid in potassium permanganate at 80 to 100/sup 0/. The solution is mixed by compressed air. (RWR)

  3. Nano structural anodes for radiation detectors

    Science.gov (United States)

    Cordaro, Joseph V.; Serkiz, Steven M.; McWhorter, Christopher S.; Sexton, Lindsay T.; Retterer, Scott T.

    2015-07-07

    Anodes for proportional radiation counters and a process of making the anodes is provided. The nano-sized anodes when present within an anode array provide: significantly higher detection efficiencies due to the inherently higher electric field, are amenable to miniaturization, have low power requirements, and exhibit a small electromagnetic field signal. The nano-sized anodes with the incorporation of neutron absorbing elements (e.g., .sup.10B) allow the use of neutron detectors that do not use .sup.3He.

  4. Electrically Conductive Anodized Aluminum Surfaces

    Science.gov (United States)

    Nguyen, Trung Hung

    2006-01-01

    Anodized aluminum components can be treated to make them sufficiently electrically conductive to suppress discharges of static electricity. The treatment was conceived as a means of preventing static electric discharges on exterior satin-anodized aluminum (SAA) surfaces of spacecraft without adversely affecting the thermal-control/optical properties of the SAA and without need to apply electrically conductive paints, which eventually peel off in the harsh environment of outer space. The treatment can also be used to impart electrical conductivity to anodized housings of computers, medical electronic instruments, telephoneexchange equipment, and other terrestrial electronic equipment vulnerable to electrostatic discharge. The electrical resistivity of a typical anodized aluminum surface layer lies between 10(exp 11) and 10(exp 13) Omega-cm. To suppress electrostatic discharge, it is necessary to reduce the electrical resistivity significantly - preferably to anodized surface becomes covered and the pores in the surface filled with a transparent, electrically conductive metal oxide nanocomposite. Filling the pores with the nanocomposite reduces the transverse electrical resistivity and, in the original intended outer-space application, the exterior covering portion of the nanocomposite would afford the requisite electrical contact with the outer-space plasma. The electrical resistivity of the nanocomposite can be tailored to a value between 10(exp 7) and 10(exp 12) Omega-cm. Unlike electrically conductive paint, the nanocomposite becomes an integral part of the anodized aluminum substrate, without need for adhesive bonding material and without risk of subsequent peeling. The electrodeposition process is compatible with commercial anodizing production lines. At present, the electronics industry uses expensive, exotic, electrostaticdischarge- suppressing finishes: examples include silver impregnated anodized, black electroless nickel, black chrome, and black copper. In

  5. Anodized Steel Electrodes for Supercapacitors.

    Science.gov (United States)

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

    2016-03-09

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

  6. Electrochemical characterization of anode passivation mechanisms in copper electrorefining

    Science.gov (United States)

    Moats, Michael Scott

    Anode passivation can decrease productivity and quality while increasing costs in modern copper electrorefineries. This investigation utilized electrochemical techniques to characterize the passivation behavior of anode samples from ten different operating companies. It is believed that this collection of anodes is the most diverse set ever to be assembled to study the effect of anode composition on passivation. Chronopotentiometry was the main electrochemical technique, employing a current density of 3820 A m-2. From statistical analysis of the passivation characteristics, increasing selenium, tellurium, silver, lead and nickel were shown to accelerate passivation. Arsenic was the only anode impurity that inhibited passivation. Oxygen was shown to accelerate passivation when increased from 500 to 1500 ppm, but further increases did not adversely affect passivation. Nine electrolyte variables were also examined. Increasing the copper, sulfuric acid or sulfate concentration of the electrolyte accelerated passivation. Arsenic in the electrolyte had no effect on passivation. Chloride and optimal concentrations of thiourea and glue delayed passivation. Linear sweep voltammetry, cyclic voltammetry, and impedance spectroscopy provided complementary information. Analysis of the electrochemical results led to the development of a unified passivation mechanism. Anode passivation results from the formation of inhibiting films. Careful examination of the potential details, especially those found in the oscillations just prior to passivation, demonstrated the importance of slimes, copper sulfate and copper oxide. Slimes confine dissolution to their pores and inhibit diffusion. This can lead to copper sulfate precipitation, which blocks more of the surface area. Copper oxide forms because of the resulting increase in potential at the interface between the copper sulfate and anode. Ultimate passivation occurs when the anode potential is high enough to stabilize the oxide film in

  7. [Corrosion resistant properties of different anodized microtopographies on titanium surfaces].

    Science.gov (United States)

    Fangjun, Huo; Li, Xie; Xingye, Tong; Yueting, Wang; Weihua, Guo; Weidong, Tian

    2015-12-01

    To investigate the corrosion resistant properties of titanium samples prepared by anodic oxidation with different surface morphologies. Pure titanium substrates were treated by anodic oxidation to obtain porous titanium films in micron, submicron, and micron-submicron scales. The surface morphologies, coating cross-sectional morphologies, crystalline structures, and surface roughness of these samples were characterized. Electrochemical technique was used to measure the corrosion potential (Ecorr), current density of corrosion (Icorr), and polarization resistance (Rp) of these samples in a simulated body fluid. Pure titanium could be modified to exhibit different surface morphologies by the anodic oxidation technique. The Tafel curve results showed that the technique can improve the corrosion resistance of pure titanium. Furthermore, the corrosion resistance varied with different surface morphologies. The submicron porous surface sample demonstrated the best corrosion resistance, with maximal Ecorr and Rp and minimal Icorr. Anodic oxidation technology can improve the corrosion resistance of pure titanium in a simulated body fluid. The submicron porous surface sample exhibited the best corrosion resistance because of its small surface area and thick barrier layer.

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

    Science.gov (United States)

    Mirfakhraei, Behzad

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

  9. Anodically-grown TiO_2 nanotubes: Effect of the crystallization on the catalytic activity toward the oxygen reduction reaction

    International Nuclear Information System (INIS)

    Sacco, Adriano; Garino, Nadia; Lamberti, Andrea; Pirri, Candido Fabrizio; Quaglio, Marzia

    2017-01-01

    Highlights: • Anodically-grown TiO_2 nanotubes as catalysts for the oxygen reduction reaction. • Amorphous NTs compared to thermal- and vapor-treated crystalline nanostructures. • The selection of the crystallization conditions leads to performance similar to Pt. - Abstract: In this work we investigated the behavior of TiO_2 nanotube (NT) arrays, grown by anodic oxidation of Ti foil, as catalysts for the oxygen reduction reaction (ORR) in alkaline water solution. In particular, as-grown amorphous NTs were compared to crystalline anatase nanostructures, obtained following two different procedures, namely thermal and vapor-induced crystallizations. The catalytic activity of these materials toward the ORR was evaluated by cyclic voltammetry measurements. ORR polarization curves, combined with the rotating disk technique, indicated a predominant four-electrons reduction path, especially for crystalline samples. The effect of the structural characteristics of the investigated materials on the catalytic activity was analyzed in details by electrochemical impedance spectroscopy. The catalytic performance of the crystalline NTs is only slightly lower with respect to the reference material for fuel cell applications, namely platinum, but is in line with other cost-effective catalysts recently proposed in the literature. However, if compared to the larger part of these low-cost catalysts, anodically-grown TiO_2 NTs are characterized by a synthesis route which is highly reproducible and easily up-scalable.

  10. Anodically-grown TiO{sub 2} nanotubes: Effect of the crystallization on the catalytic activity toward the oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Sacco, Adriano, E-mail: adriano.sacco@iit.it [Center for Sustainable Future Technologies @Polito, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Torino (Italy); Garino, Nadia [Center for Sustainable Future Technologies @Polito, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Torino (Italy); Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino (Italy); Lamberti, Andrea, E-mail: andrea.lamberti@polito.it [Center for Sustainable Future Technologies @Polito, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Torino (Italy); Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino (Italy); Pirri, Candido Fabrizio [Center for Sustainable Future Technologies @Polito, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Torino (Italy); Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino (Italy); Quaglio, Marzia [Center for Sustainable Future Technologies @Polito, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Torino (Italy)

    2017-08-01

    Highlights: • Anodically-grown TiO{sub 2} nanotubes as catalysts for the oxygen reduction reaction. • Amorphous NTs compared to thermal- and vapor-treated crystalline nanostructures. • The selection of the crystallization conditions leads to performance similar to Pt. - Abstract: In this work we investigated the behavior of TiO{sub 2} nanotube (NT) arrays, grown by anodic oxidation of Ti foil, as catalysts for the oxygen reduction reaction (ORR) in alkaline water solution. In particular, as-grown amorphous NTs were compared to crystalline anatase nanostructures, obtained following two different procedures, namely thermal and vapor-induced crystallizations. The catalytic activity of these materials toward the ORR was evaluated by cyclic voltammetry measurements. ORR polarization curves, combined with the rotating disk technique, indicated a predominant four-electrons reduction path, especially for crystalline samples. The effect of the structural characteristics of the investigated materials on the catalytic activity was analyzed in details by electrochemical impedance spectroscopy. The catalytic performance of the crystalline NTs is only slightly lower with respect to the reference material for fuel cell applications, namely platinum, but is in line with other cost-effective catalysts recently proposed in the literature. However, if compared to the larger part of these low-cost catalysts, anodically-grown TiO{sub 2} NTs are characterized by a synthesis route which is highly reproducible and easily up-scalable.

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

    Science.gov (United States)

    2010-01-14

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

  12. High performance ceramic carbon electrode-based anodes for use in the Cu-Cl thermochemical cycle for hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Ranganathan, Santhanam; Easton, E. Bradley [Faculty of Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario L1H 7K4 (Canada)

    2010-02-15

    A high performance ceramic carbon electrode (CCE) was fabricated by the sol-gel method to study the CuCl electrolysis in Cu-Cl thermochemical cycle. The electrochemical behavior and stability of the CCE was investigated by polarization experiments at different concentrations of CuCl/HCl system. The CCE displayed excellent anodic performance and vastly outperformed the bare carbon fiber paper (CFP) even at high concentrations of CuCl (0.5 M) and HCl (6 M), which is explained in terms of increased active area and enhanced anion transport properties. Further enhancement of activity was achieved by coating the CCE layer onto both sides of the CFP substrate. (author)

  13. The role of anodic dissolution in the stress corrosion cracking of Al-Li-Cu alloy 2090

    International Nuclear Information System (INIS)

    Buchheit, R.G. Jr.; Wall, F.D.; Stoner, G.E.; Moran, J.P.

    1991-01-01

    The short-transverse (S-T) stress corrosion cracking (SCC) behavior of Al-Li-CU alloy 2090 was studied using a static load SCC test technique. Time to failure was measured as a function of applied potential in several different environments. Rapid SCC failures ( br, T1 applied br, matrix where potentials refer to the breakaway potentials of the subgrain boundary T 1 (Al 2 CuLi) phase and the α-Al matrix phase. E br values were measured using potentiodynamic polarization of bulk materials intended to simulate the individual phases found in the subgrain boundary region. Results strongly suggest an anodic dissolution based SCC mechanism for this alloy where selective dissolution of T 1 on the subgrain boundary is a critical step. The unusual pre-exposure embrittlement phenomenon demonstrated by Al- Li alloys is also shown to be consistent with these simple SCC criteria. 21 refs., 9 figs., 6 tabs

  14. Resistive switching in microscale anodic titanium dioxide-based memristors

    Science.gov (United States)

    Aglieri, V.; Zaffora, A.; Lullo, G.; Santamaria, M.; Di Franco, F.; Lo Cicero, U.; Mosca, M.; Macaluso, R.

    2018-01-01

    The potentiality of anodic TiO2 as an oxide material for the realization of resistive switching memory cells has been explored in this paper. Cu/anodic-TiO2/Ti memristors of different sizes, ranging from 1 × 1 μm2 to 10 × 10 μm2 have been fabricated and characterized. The oxide films were grown by anodizing Ti films, using three different process conditions. Measured IV curves have shown similar asymmetric bipolar hysteresis behaviors in all the tested devices, with a gradual switching from the high resistance state to the low resistance state and vice versa, and a ROFF/RON ratio of 80 for the thickest oxide film devices.

  15. Carbon Anode Materials

    Science.gov (United States)

    Ogumi, Zempachi; Wang, Hongyu

    Accompanying the impressive progress of human society, energy storage technologies become evermore urgent. Among the broad categories of energy sources, batteries or cells are the devices that successfully convert chemical energy into electrical energy. Lithium-based batteries stand out in the big family of batteries mainly because of their high-energy density, which comes from the fact that lithium is the most electropositive as well as the lightest metal. However, lithium dendrite growth after repeated charge-discharge cycles easily will lead to short-circuit of the cells and an explosion hazard. Substituting lithium metal for alloys with aluminum, silicon, zinc, and so forth could solve the dendrite growth problem.1 Nevertheless, the lithium storage capacity of alloys drops down quickly after merely several charge-discharge cycles because the big volume change causes great stress in alloy crystal lattice, and thus gives rise to cracking and crumbling of the alloy particles. Alternatively, Sony Corporation succeeded in discovering the highly reversible, low-voltage anode, carbonaceous material and commercialized the C/LiCoO2 rocking chair cells in the early 1990s.2 Figure 3.1 schematically shows the charge-discharge process for reversible lithium storage in carbon. By the application of a lithiated carbon in place of a lithium metal electrode, any lithium metal plating process and the conditions for the growth of irregular dendritic lithium could be considerably eliminated, which shows promise for reducing the chances of shorting and overheating of the batteries. This kind of lithium-ion battery, which possessed a working voltage as high as 3.6 V and gravimetric energy densities between 120 and 150 Wh/kg, rapidly found applications in high-performance portable electronic devices. Thus the research on reversible lithium storage in carbonaceous materials became very popular in the battery community worldwide.

  16. Polarization developments

    International Nuclear Information System (INIS)

    Prescott, C.Y.

    1993-07-01

    Recent developments in laser-driven photoemission sources of polarized electrons have made prospects for highly polarized electron beams in a future linear collider very promising. This talk discusses the experiences with the SLC polarized electron source, the recent progress with research into gallium arsenide and strained gallium arsenide as a photocathode material, and the suitability of these cathode materials for a future linear collider based on the parameters of the several linear collider designs that exist

  17. The kinetics of anodic dissolution of rhenium in aqueous electrolyte solutions

    International Nuclear Information System (INIS)

    Atanasyants, A.G.; Kornienko, V.A.

    1986-01-01

    The kinetics of anodic rhenium dissolution was investigated by means of potentiodynamic and potentiostatic polarization curves recorded at temperature from 293 to 333 K in different media (NaOH, KOH, NaCl, NaBr, HCl, H 2 SO 4 ) using the rotating disc technique. It is shown that the kinetics of anodic rhenium dissolution and effective activation energy depend not only on the composition and pH value of the solutions but also on the structure of the dissolving rhenium surface. The investigation of the anodic behaviour of the rhenium monocrystal revealed the existence of anisotropy of the monocrystal electrochemical properties. The experimental results point to an important role of adsorption processes in anodic rhenium dissolution. Rhenium dissolution proceeds with formation of intermediate surface adsorption complexes between the metal and the components of the solution

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  19. Effect of gate voltage polarity on the ionic liquid gating behavior of NdNiO3/NdGaO3 heterostructures

    Directory of Open Access Journals (Sweden)

    Yongqi Dong

    2017-05-01

    Full Text Available The effect of gate voltage polarity on the behavior of NdNiO3 epitaxial thin films during ionic liquid gating is studied using in situ synchrotron X-ray techniques. We show that while negative biases have no discernible effect on the structure or composition of the films, large positive gate voltages result in the injection of a large concentration of oxygen vacancies (∼3% and pronounced lattice expansion (0.17% in addition to a 1000-fold increase in sheet resistance at room temperature. Despite the creation of large defect densities, the heterostructures exhibit a largely reversible switching behavior when sufficient time is provided for the vacancies to migrate in and out of the thin film surface. The results confirm that electrostatic gating takes place at negative gate voltages for p-type complex oxides while positive voltages favor the electrochemical reduction of Ni3+. Switching between positive and negative gate voltages therefore involves a combination of electronic and ionic doping processes that may be utilized in future electrochemical transistors.

  20. Effect of heat treatment on anodic activation of aluminium by trace element indium

    Energy Technology Data Exchange (ETDEWEB)

    Graver, Brit [Department of Materials Science and Engineering, Norwegian University of Science and Technology, N-7491 Trondheim (Norway); Helvoort, Antonius T.J. van [Department of Physics, Norwegian University of Science and Technology, N-7491 Trondheim (Norway); Nisancioglu, Kemal, E-mail: kemal.nisancioglu@material.ntnu.n [Department of Materials Science and Engineering, Norwegian University of Science and Technology, N-7491 Trondheim (Norway)

    2010-11-15

    Research highlights: {yields} Indium segregation activates AlIn alloy surface anodically in chloride solution. {yields} Enrichment of In on Al surface can occur thermally by heat treatment at 300 {sup o}C. {yields} Increasing temperature homogenises indium in aluminium reducing anodic activation. {yields} Indium can activate AlIn surface by segregating through dealloying of aluminium. {yields} Anodic activation is caused by AlIn amalgam formation at aluminium surface. - Abstract: The presence of trace elements in Group IIIA-VA is known to activate aluminium anodically in chloride environment. The purpose of this paper is to investigate the surface segregation of trace element In by heat treatment and resulting surface activation. Model binary AlIn alloys, containing 20 and 1000 ppm by weight of In, were characterized after heat treatment at various temperatures by use of glow discharge optical emission spectroscopy, electron microscopy and electrochemical polarization. Heat treatment for 1 h at 300 {sup o}C gave significant segregation of discrete In particles (thermal segregation), which activated the surface. Indium in solid solution with aluminium, obtained by 1 h heat treatment at 600 {sup o}C, also activated by surface segregation of In on alloy containing 1000 ppm In, resulting from the selective dissolution of the aluminium component during anodic oxidation (anodic segregation). The effect of anodic segregation was reduced by decreasing indium concentration in solid solution; it had negligible effect at the 20 ppm level. The segregated particles were thought to form a liquid phase alloy with aluminium during anodic polarization, which in turn, together with the chloride in the solution destabilized the oxide.

  1. The function of microporous layers and the interaction between the anode and cathode in DMFCs

    DEFF Research Database (Denmark)

    Zhang, H. F.; Wang, SY; Pei, PC

    2008-01-01

    A combined effect of microporous layers (MPLs) on direct methanol fuel cells (DMFCs) is investigated. From the distribution of the outstanding carbon loading combinations of the cathode MPL and anode MPL as well as the evolutions of polarization curves, a combined effect in which the contributions...

  2. Neutron polarization

    International Nuclear Information System (INIS)

    Firk, F.W.K.

    1976-01-01

    Some recent experiments involving polarized neutrons are discussed; they demonstrate how polarization studies provide information on fundamental aspects of nuclear structure that cannot be obtained from more traditional neutron studies. Until recently, neutron polarization studies tended to be limited either to very low energies or to restricted regions at higher energies, determined by the kinematics of favorable (p, vector n) and (d, vector n) reactions. With the advent of high intensity pulsed electron and proton accelerators and of beams of vector polarized deuterons, this is no longer the case. One has entered an era in which neutron polarization experiments are now being carried out, in a routine way, throughout the entire range from thermal energies to tens-of-MeV. The significance of neutron polarization studies is illustrated in discussions of a wide variety of experiments that include the measurement of T-invariance in the β-decay of polarized neutrons, a search for the effects of meson exchange currents in the photo-disintegration of the deuteron, the determination of quantum numbers of states in the fission of aligned 235 U and 237 Np induced by polarized neutrons, and the double- and triple-scattering of fast neutrons by light nuclei

  3. Polarization holography

    DEFF Research Database (Denmark)

    Nikolova, L.; Ramanujam, P.S.

    Current research into holography is concerned with applications in optically storing, retrieving, and processing information. Polarization holography has many unique properties compared to conventional holography. It gives results in high efficiency, achromaticity, and special polarization...... properties. This books reviews the research carried out in this field over the last 15 years. The authors provide basic concepts in polarization and the propagation of light through anisotropic materials, before presenting a sound theoretical basis for polarization holography. The fabrication...... and characterization of azobenzene based materials, which remain the most efficient for the purpose, is described in detail. This is followed by a description of other materials that are used in polarization holography. An in-depth description of various applications, including display holography and optical storage...

  4. Anodic selective functionalization of cyclic amine derivatives

    OpenAIRE

    Onomura, Osamu

    2012-01-01

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

  5. Synthesis and characterization of cathode, anode and electrolyte materials for rechargeable lithium batteries

    Science.gov (United States)

    Yang, Shoufeng

    Two new classes of cathode materials were studied: iron phosphate/sulfate materials and layered manganese oxides, both of which are low cost and had shown some potential. The first class of materials have poor conductivity and cyclability. I studied a number of methods for increasing the conductivity, and determined that grinding the material with carbon black was as effective as special in-situ coatings. The optimum carbon loading was determined to be between 6 and 15 wt%. Too much carbon reduces the volumetric energy density, whereas too little significantly increased cell polarization (reduced the rate of reaction). The kinetic and thermodynamic stability of LiFePO 4 was also studied and it was determined that over discharge protection will be needed as irreversible Li3PO4 can be formed at low potentials. A novel hydrothermal synthesis method was developed, but the significant level of Fe on the Li site reduces the reaction rate too much. In the case of the layered manganese oxide, cation substitution with Co and Ni is found to be effective in avoiding Jahn-Teller effects and improving electrochemistry. A wide range of tin compounds have been suggested as lithium storage media for advanced anode materials, as tin can store over 4 Li per Sn atom. Lithium hexafluorophosphate, LiPF6, is presently the salt of choice for LiCoO2 batteries, but it is expensive and dissolves some manganese compounds. The lithium bis(oxolato)borate (BOB) salt was recently reported, and I made a study of its use in cells with the LiFePO4 cathode and the tin anode. During its synthesis, it became clear that LiBOB is very reactive with many solvents, and these complexes were characterized to better understand this new material. In LiBOB the lithium is five coordinated, an unstable configuration for the lithium ion so that water and many other solvents rapidly react to make a six coordination. Only in the case of ethylene carbonate was the lithium found to be four coordinated. The Li

  6. Electrolyte effects on the surface chemistry and cellular response of anodized titanium

    International Nuclear Information System (INIS)

    Ohtsu, Naofumi; Kozuka, Taro; Hirano, Mitsuhiro; Arai, Hirofumi

    2015-01-01

    Highlights: • Ti samples were anodized using various electrolytes. • Anodization decreased carbon adsorption, improving hydrophilicity. • Improved hydrophilicity led to improved cellular attachment. • Only one electrolyte showed any heteroatom incorporation into the TiO 2 layer. • Choice of electrolyte played no role on the effects of anodization. - Abstract: Anodic oxidation of titanium (Ti) material is used to enhance biocompatibility, yet the effects of various electrolytes on surface characteristics and cellular behavior have not been completely elucidated. To investigate this topic, oxide layers were produced on Ti substrates by anodizing them in aqueous electrolytes of (NH 4 ) 2 O·5B 2 O 3 , (NH 4 ) 2 SO 4 , or (NH 4 ) 3 PO 4 , after which their surface characteristics and cellular responses were examined. Overall, no surface differences between the electrolytes were visually observed. X-ray photoelectron spectroscopy (XPS) revealed that the anodized surfaces are composed of titanium dioxide (TiO 2 ), while incorporation from electrolyte was only observed for (NH 4 ) 3 PO 4 . Surface adsorption of carbon contaminants during sterilization was suppressed by anodization, leading to lower water contact angles. The attachment of MC3T3-E1 osteoblast-like cells was also improved by anodization, as evidenced by visibly enlarged pseudopods. This improved attachment performance is likely due to TiO 2 formation. Overall, electrolyte selection showed no effect on either surface chemistry or cellular response of Ti materials

  7. Anode Fall Formation in a Hall Thruster

    International Nuclear Information System (INIS)

    Dorf, Leonid A.; Raitses, Yevgeny F.; Smirnov, Artem N.; Fisch, Nathaniel J.

    2004-01-01

    As was reported in our previous work, accurate, nondisturbing near-anode measurements of the plasma density, electron temperature, and plasma potential performed with biased and emissive probes allowed the first experimental identification of both electron-repelling (negative anode fall) and electron-attracting (positive anode fall) anode sheaths in Hall thrusters. An interesting new phenomenon revealed by the probe measurements is that the anode fall changes from positive to negative upon removal of the dielectric coating, which appears on the anode surface during the course of Hall thruster operation. As reported in the present work, energy dispersion spectroscopy analysis of the chemical composition of the anode dielectric coating indicates that the coating layer consists essentially of an oxide of the anode material (stainless steel). However, it is still unclear how oxygen gets into the thruster channel. Most importantly, possible mechanisms of anode fall formation in a Hall thruster with a clean and a coated anodes are analyzed in this work; practical implication of understanding the general structure of the electron-attracting anode sheath in the case of a coated anode is also discussed

  8. Rotating anode X-ray source

    International Nuclear Information System (INIS)

    Wittry, D.B.

    1979-01-01

    A rotating anode x-ray source is described which consists of a rotary anode disc including a target ring and a chamber within the anode disc. Liquid is evaporated into the chamber from the target ring to cool the target and a method is provided of removing the latent heat of the vapor. (U.K.)

  9. Study of the alloying additives and alkaline zincate solution effects on the commercial aluminum as galvanic anode for use in alkaline batteries

    Energy Technology Data Exchange (ETDEWEB)

    Rashvand avei, M. [Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 15875-4416, Tehran (Iran, Islamic Republic of); Jafarian, M., E-mail: mjafarian@kntu.ac.ir [Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 15875-4416, Tehran (Iran, Islamic Republic of); Moghanni Bavil Olyaei, H. [Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 15875-4416, Tehran (Iran, Islamic Republic of); Gobal, F. [Department of Chemistry, Sharif University of Technology, P.O. Box 11365-8516, Tehran (Iran, Islamic Republic of); Hosseini, S.M. [Jahad Organization – Science and Technology Center, Tehran (Iran, Islamic Republic of); Mahjani, M.G. [Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 15875-4416, Tehran (Iran, Islamic Republic of)

    2013-12-16

    The corrosion behavior of different grades of commercial aluminum such as AA1040, AA5083, AA6060 and AA7075 in ZnO-containing 4 M NaOH has been determined by using open circuit potential-time measurements (OCP), galvanostatic and potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results of scanning electron microscopy (SEM) and energy dispersive analysis of X-ray (EDAX) reveal that ZnO produces the inhibition effect by the formation of a zinc-containing deposit layer on the surface of aluminum electrodes. Although the influence of zincating on the performance of aluminum alloys and considering the amount of alloying elements such as zinc, magnesium and manganese in AA7075 and AA5083 alloys is much more than AA6060 one, the AA6060 aluminum exhibits negligible corrosion rate. Alloying aluminum with other elements and modifying the composition of the electrolyte is a necessary condition for reducing the self-corrosion of the aluminum anodes, whereas the proportion of the amount of additive elements is sufficient and important condition. As AA6060 with a low amount of Zn and Mg, but the high value of the ratio of (Mg/Zn) content (>400) can serve as a good galvanic anode in the alkaline media. - Highlights: • Decreasing the corrosion rate of tested alloys in 4 M NaOH solution specially AA6060. • Lowering the extent of anodic polarization at a current density of 50 mA cm{sup −2}. • High inhibitor efficiency about 97% for AA6060.

  10. Study of the alloying additives and alkaline zincate solution effects on the commercial aluminum as galvanic anode for use in alkaline batteries

    International Nuclear Information System (INIS)

    Rashvand avei, M.; Jafarian, M.; Moghanni Bavil Olyaei, H.; Gobal, F.; Hosseini, S.M.; Mahjani, M.G.

    2013-01-01

    The corrosion behavior of different grades of commercial aluminum such as AA1040, AA5083, AA6060 and AA7075 in ZnO-containing 4 M NaOH has been determined by using open circuit potential-time measurements (OCP), galvanostatic and potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results of scanning electron microscopy (SEM) and energy dispersive analysis of X-ray (EDAX) reveal that ZnO produces the inhibition effect by the formation of a zinc-containing deposit layer on the surface of aluminum electrodes. Although the influence of zincating on the performance of aluminum alloys and considering the amount of alloying elements such as zinc, magnesium and manganese in AA7075 and AA5083 alloys is much more than AA6060 one, the AA6060 aluminum exhibits negligible corrosion rate. Alloying aluminum with other elements and modifying the composition of the electrolyte is a necessary condition for reducing the self-corrosion of the aluminum anodes, whereas the proportion of the amount of additive elements is sufficient and important condition. As AA6060 with a low amount of Zn and Mg, but the high value of the ratio of (Mg/Zn) content (>400) can serve as a good galvanic anode in the alkaline media. - Highlights: • Decreasing the corrosion rate of tested alloys in 4 M NaOH solution specially AA6060. • Lowering the extent of anodic polarization at a current density of 50 mA cm −2 . • High inhibitor efficiency about 97% for AA6060

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

    OpenAIRE

    HANSONG XUE; HUAJI LI; YU YI; HUIFANG HU

    2007-01-01

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

  12. Ellipsometry of anodic film growth

    Energy Technology Data Exchange (ETDEWEB)

    Smith, C.G.

    1978-08-01

    An automated computer interpretation of ellisometer measurements of anodic film growth was developed. Continuous mass and charge balances were used to utilize more fully the time dependence of the ellipsometer data and the current and potential measurements. A multiple-film model was used to characterize the growth of films which proceeds via a dissolution--precipitation mechanism; the model also applies to film growth by adsorption and nucleation mechanisms. The characteristic parameters for film growth describe homogeneous and heterogeneous crystallization rates, film porosities and degree of hydration, and the supersaturation of ionic species in the electrolyte. Additional descriptions which may be chosen are patchwise film formation, nonstoichiometry of the anodic film, and statistical variations in the size and orientation of secondary crystals. Theories were developed to describe the optical effects of these processes. An automatic, self-compensating ellipsometer was used to study the growth in alkaline solution of anodic films on silver, cadmium, and zinc. Mass-transport conditions included stagnant electrolyte and forced convection in a flow channel. Multiple films were needed to characterize the optical properties of these films. Anodic films grew from an electrolyte supersatuated in the solution-phase dissolution product. The degree of supersaturation depended on transport conditions and had a major effect on the structure of the film. Anodic reaction rates were limited by the transport of charge carriers through a primary surface layer. The primary layers on silver, zinc, and cadmium all appeared to be nonstoichiometric, containing excess metal. Diffusion coefficients, transference numbers, and the free energy of adsorption of zinc oxide were derived from ellipsometer measurements. 97 figures, 13 tables, 198 references.

  13. Ionic polarization

    International Nuclear Information System (INIS)

    Mahan, G.D.

    1992-01-01

    Ferroelectricity occurs in many different kinds of materials. Many of the technologically important solids, which are ferroelectric, can be classified as ionic. Any microscopic theory of ferroelectricity must contain a description of local polarization forces. We have collaborated in the development of a theory of ionic polarization which is quite successful. Its basic assumption is that the polarization is derived from the properties of the individual ions. We have applied this theory successfully to diverse subjects as linear and nonlinear optical response, phonon dispersion, and piezoelectricity. We have developed numerical methods using the local Density approximation to calculate the multipole polarizabilities of ions when subject to various fields. We have also developed methods of calculating the nonlinear hyperpolarizability, and showed that it can be used to explain light scattering experiments. This paper elaborates on this polarization theory

  14. Anode sheath transition in an anodic arc for synthesis of nanomaterials

    Science.gov (United States)

    Nemchinsky, V. A.; Raitses, Y.

    2016-06-01

    The arc discharge with ablating anode or so-called anodic arc is widely used for synthesis of nanomaterials, including carbon nanotubes and fullerens, metal nanoparticles etc. We present the model of this arc, which confirms the existence of the two different modes of the arc operation with two different anode sheath regimes, namely, with negative anode sheath and with positive anode sheath. It was previously suggested that these regimes are associated with two different anode ablating modes—low ablation mode with constant ablation rate and the enhanced ablation mode (Fetterman et al 2008 Carbon 46 1322). The transition of the arc operation from low ablation mode to high ablation mode is determined by the current density at the anode. The model can be used to self-consistently determine the distribution of the electric field, electron density and electron temperature in the near-anode region of the arc discharge. Simulations of the carbon arc predict that for low arc ablating modes, the current is driven mainly by the electron diffusion to the anode. For positive anode sheath, the anode voltage is close to the ionization potential of anode material, while for negative anode sheath, the anode voltage is an order of magnitude smaller. It is also shown that the near-anode plasma, is far from the ionization equilibrium.

  15. Anode sheath transition in an anodic arc for synthesis of nanomaterials

    International Nuclear Information System (INIS)

    Nemchinsky, V A; Raitses, Y

    2016-01-01

    The arc discharge with ablating anode or so-called anodic arc is widely used for synthesis of nanomaterials, including carbon nanotubes and fullerens, metal nanoparticles etc. We present the model of this arc, which confirms the existence of the two different modes of the arc operation with two different anode sheath regimes, namely, with negative anode sheath and with positive anode sheath. It was previously suggested that these regimes are associated with two different anode ablating modes—low ablation mode with constant ablation rate and the enhanced ablation mode (Fetterman et al 2008 Carbon 46 1322). The transition of the arc operation from low ablation mode to high ablation mode is determined by the current density at the anode. The model can be used to self-consistently determine the distribution of the electric field, electron density and electron temperature in the near-anode region of the arc discharge. Simulations of the carbon arc predict that for low arc ablating modes, the current is driven mainly by the electron diffusion to the anode. For positive anode sheath, the anode voltage is close to the ionization potential of anode material, while for negative anode sheath, the anode voltage is an order of magnitude smaller. It is also shown that the near-anode plasma, is far from the ionization equilibrium. (paper)

  16. Polarization experiments

    International Nuclear Information System (INIS)

    Halzen, F.

    1977-02-01

    In a theoretical review of polarization experiments two important points are emphasized: (a) their versatility and their relevance to a large variety of aspects of hadron physics (tests of basic symmetries; a probe of strong interaction dynamics; a tool for hadron spectroscopy); (b) the wealth of experimental data on polarization parameters in pp and np scattering in the Regge language and in the diffraction language. (author)

  17. Impedance spectroscopy for the study of anodic copper dissolution in sulfuric acid in presence of benzotriazole

    International Nuclear Information System (INIS)

    Clerc, C.; Alkire, R.C.

    1988-01-01

    The presence of an anodic surface film dramatically affects the electrochemical behavior of dissolving electrode in processes like corrosion inhibition, passivity, electropolishing or pitting. The present study was initiated to learn more about the physical properties of the surface films present at the surface of a copper electrode during anodic dissolution in 0.5 SM sulfuric acid and 40 mM benzotriazole (BTA) at 25 0 C. This study is of practical importance because this organic compound is widely used for corrosion inhibition and as etching additive. The impedance spectra measured after 10 min of polarization (with a SOLARTRAN 1250 Frequency Response Analyzer and a SOLARTRON 1286 Electrochemical Interface) were analyzed by comparison with a physical model of the electrochemical interface in which the passive electrode is covered with a barrier layer. The main assumptions are that this barrier layer is a good electronic insulator of stoichiometric composition and that charge transfer reactions and double layer charging occur at both metal-barrier layer and barrier layer-electrolyte interphases. This model also considers the change in the barrier layer thickness under the influence of the applied potential. Least squares fitting of measured impedance spectra yield physical parameters of reasonable order of magnitude to support the proposed model. As predicted it was found that the barrier layer is itself covered by an outer porous film of corrosion products and that the metallic ions transfer through the barrier layer under high field conduction. By comparing the crystallographic lattice parameters and the dielectric constants of different copper compounds, the jump distance was determined to be about 5.5 A, indicating that the barrier layer is likely to be an hydrated copper sulfate (CuSO/sub 4/ 5H/sub 2/O)

  18. The mechanism behind redox instability of anodes in high-temperature SOFCs

    DEFF Research Database (Denmark)

    Klemensø, Trine; Chung, Charissa; Larsen, Peter Halvor

    2005-01-01

    Bulk expansion of the anode upon oxidation is considered to be responsible for the lack of redox stability in high-temperature solid oxide fuel cells (SOFCs). The bulk expansion of nickel-yttria stabilized zirconia (YSZ) anode materials was measured by dilatometry as a function of sample geometry......, ceramic component, temperature, and temperature cycling. The strength of the ceramic network and the degree of Ni redistribution appeared to be key parameters of the redox behavior. A model of the redox mechanism in nickel-YSZ anodes was developed based on the dilatometry data and macro...

  19. Polarization measurement for internal polarized gaseous targets

    International Nuclear Information System (INIS)

    Ye Zhenyu; Ye Yunxiu; Lv Haijiang; Mao Yajun

    2004-01-01

    The authors present an introduction to internal polarized gaseous targets, polarization method, polarization measurement method and procedure. To get the total nuclear polarization of hydrogen atoms (including the polarization of the recombined hydrogen molecules) in the target cell, authors have measured the parameters relating to atomic polarization and polarized hydrogen atoms and molecules. The total polarization of the target during our measurement is P T =0.853 ± 0.036. (authors)

  20. An evaluation of the environmental fate and behavior of munitions materiel (tetryl and polar metabolites of TNT) in soil and plant systems. Preliminary evaluation of TNT-polar metabolites in plants

    Energy Technology Data Exchange (ETDEWEB)

    Fellows, R.J.; Harvey, S.D.; Cataldo, D.A.

    1993-09-01

    A preliminary study was conducted to elucidate the nature of the polar metabolites reported for plant tissues and xylem exudates following root accumulation of trinitrotoluene. Studies focused on the nature of the proposed conjugates of TNT-residues in xylem exudates of bush beam plants. Use of enzymatic methods failed to demonstrate that the conjugates were carbohydrate based, but acid hydrolysis indicated that the conjugates may be protein based. Of the five polar conjugates isolated from exudates, the presence of aminodinitrotoluene isomers and one unknown TNT residue was demonstrated.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  2. Newer polyanionic bio-composite anode for sodium ion batteries

    Science.gov (United States)

    Karuppiah, Saravanan; Vellingiri, Suganya; Nallathamby, Kalaiselvi

    2017-02-01

    NASICON frame work Na3V2(PO4)3 (NVP), wrapped by nitrogen and sulfur doped bio-carbon matrix derived from human hair (HHC) has been investigated for its anode behavior in SIBs. Basically, NVP is bestowed with a crystal structure of 3D open framework and a moderate theoretical capacity of 118 mAh g-1, which are the twin advantages and motivation behind the selection of this material. Prepared through a simple, scalable and facile method, the key problems associated with pristine NVP electrode material, such as inferior conductivity and severe volume change have been mitigated to a great extent through the formation of a composite containing HHC. Herein, HHC is a cheap and eco-friendly composite additive, obtained from a universal bio-waste, viz., human hair and hence NVP/HHC qualifies itself as a green composite. Interestingly, NVP/HHC-10 (in-situ) and NVP/HHC-20 (ex-situ) anodes show excellent electrochemical performance in terms of cycling stability up to 500 cycles and rate capability @ 2 A g-1, which are superior than similar category NVP anodes reported in the literature. Further, post cycling structure and morphology of NVP/HHC composite anodes evidence the appreciable stability bestowed with the select composition, which is found to get maintained upon extended cycles and even after rate capability test.

  3. Resistometric studies of anodic dissolution and passivation of chromium in weakly acid solutions

    International Nuclear Information System (INIS)

    Shlepakov, M.N.; Sukhotin, A.M.

    1984-01-01

    The method of calculating the rate of Cr anodic solution according to the change of electric resistance of chromium anodes under the effect of potentiostatic polarization, is applied. The maximum corresponding to ranges of active-passive transition is absent in weakly acid solutions with pH>3. The range of existence of active-passive transition is expanded to pH approximately 5.2. The existence of a dissolving section in Cr in the chemical mechanism is proved. Cr passivation mechanism with the formation of passivating oxide of a complex composition is suggested

  4. Sources of polarized neutrons

    International Nuclear Information System (INIS)

    Walter, L.

    1983-01-01

    Various sources of polarized neutrons are reviewed. Monoenergetic source produced with unpolarized or polarized beams, white sources of polarized neutrons, production by transmissions through polarized hydrogen targets and polarized thermal neutronsare discussed, with appropriate applications included. (U.K.)

  5. In situ study on reverse polarity effect in Cu/Sn–9Zn/Ni interconnect undergoing liquid–solid electromigration

    Energy Technology Data Exchange (ETDEWEB)

    Huang, M.L., E-mail: huang@dlut.edu.cn; Zhang, Z.J.; Zhao, N.; Yang, F.

    2015-01-15

    Highlights: • Abnormal reverse polarity effect in Cu/Sn–9Zn/Ni interconnect during L–S EM was observed. • The reverse polarity effect was resulted from directional diffusion of Zn to cathode. • Positive effective charge number is responsible for directional diffusion of Zn atom. • The effective charge number value of Zn was calculated to be +0.63 based on a model. • This effect is beneficial to EM reliability of micro-bump solder interconnect. - Abstract: Synchrotron radiation real-time imaging technology was used to in situ study the interfacial reactions in Cu/Sn–9Zn/Ni solder interconnects undergoing liquid–solid electromigration (L–S EM). The reverse polarity effect, evidenced by the continuous growth of intermetallic compound (IMC) layer at the cathode and the thinning of the IMC layer at the anode, was resulted from the abnormal directional migration of Zn atoms toward the cathode in electric field. This abnormal migration behavior was induced by the positive effective charge number (Z{sup ∗}) of Zn atoms, which was calculated to be +0.63 based on the Cu fluxes and the consumption kinetics of the anode Cu. Irrespective of the flowing direction of electrons, the consumption of Cu film was obvious while that of Ni film was limited. The dissolution of anode Cu followed a linear relationship with time while that of cathode Cu followed a parabolic relationship with time. It is more damaging with electrons flowing from the Ni to the Cu than that from the Cu to the Ni. The simulated Zn concentration distributions gave an explanation on the relationship between abnormal migration behavior of Zn atoms and the dissolution of Cu film under electron wind force. The abnormal directional migration of Zn atoms toward the cathode prevented the dissolution of cathode substrate, which is beneficial to improve the EM reliability of micro-bump solder interconnects.

  6. Reactions on carbon anodes in aluminium electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Eidet, Trygve

    1997-12-31

    The consumption of carbon anodes and energy in aluminium electrolysis is higher than what is required theoretically. This thesis studies the most important of the reactions that consume anode materials. These reactions are the electrochemical anode reaction and the airburn and carboxy reactions. The first part of the thesis deals with the kinetics and mechanism of the electrochemical anode reaction using electrochemical impedance spectroscopy. The second part deals with air and carboxy reactivity of carbon anodes and studies the effects of inorganic impurities on the reactivity of carbon anodes in the aluminium industry. Special attention is given to sulphur since its effect on the carbon gasification is not well understood. Sulphur is always present in anodes, and it is expected that the sulphur content of available anode cokes will increase in the future. It has also been suggested that sulphur poisons catalyzing impurities in the anodes. Other impurities that were investigated are iron, nickel and vanadium, which are common impurities in anodes which have been reported to catalyze carbon gasification. 88 refs., 92 figs., 24 tabs.

  7. Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

    International Nuclear Information System (INIS)

    Etchessahar, Bertrand; Bicrel, Béatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Hébert, David; Bernigaud, Virgile; Magnin, Laurent; Nicolas, Rémi; Poulet, Frédéric; Tailleur, Yaël; Caron, Michel; Cartier, Frédéric; Cartier, Stéphanie; Hourdin, Laurent; Rosol, Rodolphe; Toury, Martial; Delbos, Christophe; Garrigues, Alain; Soleilhavoup, Isabelle

    2012-01-01

    The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., “Considerations of rod-pinch diode operation in negative polarity for radiography,” in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975–978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., “Theoretical modeling and experimental characterization of a rod-pinch diode,” Phys. Plasmas 8(10), 4618–4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., “Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,” IEEE Trans. Plasma Sci. 32(5), 2004–2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., “ASTERIX, a high intensity X-ray generator,” in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567–570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., “Negative polarity rod pinch diode experiments on the ASTERIX generator,” in Conference Records–Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to achieve the most

  8. Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

    Energy Technology Data Exchange (ETDEWEB)

    Etchessahar, Bertrand; Bicrel, Beatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Hebert, David [CEA, DAM, CESTA, F-33114 Le Barp (France); Bernigaud, Virgile; Magnin, Laurent; Nicolas, Remi; Poulet, Frederic; Tailleur, Yaeel [CEA, DAM, VALDUC, F-21120 Is sur Tille (France); Caron, Michel; Cartier, Frederic; Cartier, Stephanie; Hourdin, Laurent; Rosol, Rodolphe; Toury, Martial; Delbos, Christophe; Garrigues, Alain; Soleilhavoup, Isabelle [CEA, DAM, GRAMAT, F-46500 Gramat (France); and others

    2012-09-15

    The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., 'Considerations of rod-pinch diode operation in negative polarity for radiography,' in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975-978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., 'Theoretical modeling and experimental characterization of a rod-pinch diode,' Phys. Plasmas 8(10), 4618-4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., 'Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,' IEEE Trans. Plasma Sci. 32(5), 2004-2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., 'ASTERIX, a high intensity X-ray generator,' in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567-570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., 'Negative polarity rod pinch diode experiments on the ASTERIX generator,' in Conference Records-Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to

  9. Effects of the voltage and time of anodization on modulation of the pore dimensions of AAO films for nanomaterials synthesis

    Science.gov (United States)

    Chahrour, Khaled M.; Ahmed, Naser M.; Hashim, M. R.; Elfadill, Nezar G.; Maryam, W.; Ahmad, M. A.; Bououdina, M.

    2015-12-01

    Highly-ordered and hexagonal-shaped nanoporous anodic aluminum oxide (AAO) of 1 μm thickness of Al pre-deposited onto Si substrate using two-step anodization was successfully fabricated. The growth mechanism of the porous AAO film was investigated by anodization current-time behavior for different anodizing voltages and by visualizing the microstructural procedure of the fabrication of AAO film by two-step anodization using cross-sectional and top view of FESEM imaging. Optimum conditions of the process variables such as annealing time of the as-deposited Al thin film and pore widening time of porous AAO film were experimentally determined to obtain AAO films with uniformly distributed and vertically aligned porous microstructure. Pores with diameter ranging from 50 nm to 110 nm and thicknesses between 250 nm and 1400 nm, were obtained by controlling two main influential anodization parameters: the anodizing voltage and time of the second-step anodization. X-ray diffraction analysis reveals amorphous-to-crystalline phase transformation after annealing at temperatures above 800 °C. AFM images show optimum ordering of the porous AAO film anodized under low voltage condition. AAO films may be exploited as templates with desired size distribution for the fabrication of CuO nanorod arrays. Such nanostructured materials exhibit unique properties and hold high potential for nanotechnology devices.

  10. The behavior of a type-II superconductor Nb in a magnetic field as investigated in polarized-neutron transmission experiments

    International Nuclear Information System (INIS)

    Aksenov, V.L.; Dokukin, E.B.; Kozhevnikov, S.V.; Nikitenko, Yu.V.; Petrenko, A.V.

    1995-01-01

    The type-II superconducting polycrystal Nb was investigated on the SPN-1 polarized-neutron spectrometer at the high-intensity pulsed reactor IBR-2 at Dubna. In polarized-neutron transmission experiments the magnetic-field dependence of the neutron beam polarization was measured. Experiments were performed over a wide magnetic-field range from 0 to H c2 at a temperature of 4.8 K. A quasiperiodic variation of the neutron depolarization as a function of magnetic-field strength was observed. (orig.)

  11. Polarization study

    International Nuclear Information System (INIS)

    Nurushev, S.B.

    1989-01-01

    Brief review is presented of the high energy polarization study including experimental data and the theoretical descriptions. The mostimportant proposals at the biggest accelerators and the crucial technical developments are also listed which may become a main-line of spin physics. 35 refs.; 10 figs.; 4 tabs

  12. Polar Stratigraphy

    Science.gov (United States)

    1999-01-01

    These three images were taken on three different orbits over the north polar cap in April 1999. Each shows a different part of the same ice-free trough. The left and right images are separated by a distance of more than 100 kilometers (62 miles). Note the similar layers in each image.

  13. Infrared radiation properties of anodized aluminum

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-12-31

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

  14. Enhanced corrosion resistance and biocompatibility of β-type Ti–25Nb–25Zr alloy by electrochemical anodization

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Her-Hsiung [Department of Dentistry, National Yang-Ming University, Taipei, 112 Taiwan (China); Graduate Institute of Basic Medical Science, China Medical University, Taichung, 404 Taiwan (China); Department of Biomedical Informatics, Asia University, Taichung, 413 Taiwan (China); Department of Stomatology, Taipei Veterans General Hospital, Taipei, 112 Taiwan (China); Wu, Chia-Ping; Sun, Ying-Sui; Huang, Hsun-Miao [Institute of Oral Biology, National Yang-Ming University, Taipei, 112 Taiwan (China); Lee, Tzu-Hsin, E-mail: biomaterials@hotmail.com [School of Dentistry, Chung Shan Medical University, Taichung, 402 Taiwan (China); Oral Medicine Center, Chung Shan Medical University Hospital, Taichung, 402 Taiwan (China)

    2013-12-31

    The biocompatibility of implants is largely determined by their surface characteristics. This study presents a novel method for performing electrochemical anodization on β-type Ti–25Nb–25Zr alloy with a low elastic modulus (approximately 70 GPa). This method results in a thin hybrid layer capable of enhancing the surface characteristics of the implants. We investigated the surface topography and microstructure of the resulting Ti–25Nb–25Zr alloy. The corrosion resistance was evaluated using potentiodynamic polarization curve measurements in simulated body fluid. The cytotoxicity was evaluated according to International Organization for Standardization 10993–5 specification. Cell adhesion of human bone marrow mesenchymal stem cells on the test specimens was observed using scanning electron microscopy and fluorescence microscopy. The anodization produced a thin (approximately 40 nm-thick) hybrid oxide layer with a nanoporous outer sublayer (pore size < 15 nm) and a dense inner layer. The thin hybrid oxide layer increased the corrosion resistance of the Ti–25Nb–25Zr alloy by increasing the corrosion potential and decreasing both the corrosion rate and passive current. Ti–25Nb–25Zr alloys with and without anodization treatment were non-toxic. Surface nanotopography on the anodized Ti–25Nb–25Zr alloy enhanced protein adsorption and cell adhesion. Our results demonstrate that electrochemical anodization increases the corrosion resistance and cell adhesion of β-type Ti–25Nb–25Zr alloy while providing a lower elastic modulus suitable for implant applications. - Highlights: • An electrochemical anodization was applied to β-type Ti–25Nb–25Zr alloy surface. • Anodized surface had nanoscale hybrid oxide layer. • Anodized surface increased corrosion resistance due to dense inner sublayer. • Anodized surface enhanced cell adhesion due to nanoporous outer sublayer. • Electrochemical anodization has potential as implant surface treatment.

  15. Enhanced corrosion resistance and biocompatibility of β-type Ti–25Nb–25Zr alloy by electrochemical anodization

    International Nuclear Information System (INIS)

    Huang, Her-Hsiung; Wu, Chia-Ping; Sun, Ying-Sui; Huang, Hsun-Miao; Lee, Tzu-Hsin

    2013-01-01

    The biocompatibility of implants is largely determined by their surface characteristics. This study presents a novel method for performing electrochemical anodization on β-type Ti–25Nb–25Zr alloy with a low elastic modulus (approximately 70 GPa). This method results in a thin hybrid layer capable of enhancing the surface characteristics of the implants. We investigated the surface topography and microstructure of the resulting Ti–25Nb–25Zr alloy. The corrosion resistance was evaluated using potentiodynamic polarization curve measurements in simulated body fluid. The cytotoxicity was evaluated according to International Organization for Standardization 10993–5 specification. Cell adhesion of human bone marrow mesenchymal stem cells on the test specimens was observed using scanning electron microscopy and fluorescence microscopy. The anodization produced a thin (approximately 40 nm-thick) hybrid oxide layer with a nanoporous outer sublayer (pore size < 15 nm) and a dense inner layer. The thin hybrid oxide layer increased the corrosion resistance of the Ti–25Nb–25Zr alloy by increasing the corrosion potential and decreasing both the corrosion rate and passive current. Ti–25Nb–25Zr alloys with and without anodization treatment were non-toxic. Surface nanotopography on the anodized Ti–25Nb–25Zr alloy enhanced protein adsorption and cell adhesion. Our results demonstrate that electrochemical anodization increases the corrosion resistance and cell adhesion of β-type Ti–25Nb–25Zr alloy while providing a lower elastic modulus suitable for implant applications. - Highlights: • An electrochemical anodization was applied to β-type Ti–25Nb–25Zr alloy surface. • Anodized surface had nanoscale hybrid oxide layer. • Anodized surface increased corrosion resistance due to dense inner sublayer. • Anodized surface enhanced cell adhesion due to nanoporous outer sublayer. • Electrochemical anodization has potential as implant surface treatment

  16. Improvements in the corrosion resistance and biocompatibility of biomedical Ti–6Al–7Nb alloy using an electrochemical anodization treatment

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Her-Hsiung [Department of Dentistry, National Yang-Ming University, Taipei 112, Taiwan (China); Department of Dentistry, Taipei City Hospital, Taipei 115, Taiwan (China); Department of Stomatology, Taipei Veterans General Hospital, Taipei 112, Taiwan (China); Wu, Chia-Ping; Sun, Ying-Sui [Department of Oral Biology, National Yang-Ming University, Taipei 112, Taiwan (China); Lee, Tzu-Hsin, E-mail: biomaterials@hotmail.com [School of Dentistry, Chung Shan Medical University, Taichung 402, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung 402, Taiwan (China)

    2013-01-01

    The biocompatibility of an implant material is determined by its surface characteristics. This study investigated the application of an electrochemical anodization surface treatment to improve both the corrosion resistance and biocompatibility of Ti–6Al–7Nb alloy for implant applications. The electrochemical anodization treatment produced an Al-free oxide layer with nanoscale porosity on the Ti–6Al–7Nb alloy surface. The surface topography and microstructure of Ti–6Al–7Nb alloy were analyzed. The corrosion resistance was investigated using potentiodynamic polarization curve measurements in simulated blood plasma (SBP). The adhesion and proliferation of human bone marrow mesenchymal stem cells to test specimens were evaluated using various biological analysis techniques. The results showed that the presence of a nanoporous oxide layer on the anodized Ti–6Al–7Nb alloy increased the corrosion resistance (i.e., increased the corrosion potential and decreased both the corrosion rate and the passive current) in SBP compared with the untreated Ti–6Al–7Nb alloy. Changes in the nanotopography also improved the cell adhesion and proliferation on the anodized Ti–6Al–7Nb alloy. We conclude that a fast and simple electrochemical anodization surface treatment improves the corrosion resistance and biocompatibility of Ti–6Al–7Nb alloy for biomedical implant applications. - Highlights: ► Simple/fast electrochemical anodization was applied to biomedical Ti–6Al–7Nb surface. ► Anodized surface had nano-porous topography and contained Al-free oxide layer. ► Anodized surface raised corrosion resistance in three simulated biological solutions. ► Anodized surface enhanced cell adhesion and cell proliferation. ► Electrochemical anodization has potential as biomedical implant surface treatment.

  17. Improvements in the corrosion resistance and biocompatibility of biomedical Ti–6Al–7Nb alloy using an electrochemical anodization treatment

    International Nuclear Information System (INIS)

    Huang, Her-Hsiung; Wu, Chia-Ping; Sun, Ying-Sui; Lee, Tzu-Hsin

    2013-01-01

    The biocompatibility of an implant material is determined by its surface characteristics. This study investigated the application of an electrochemical anodization surface treatment to improve both the corrosion resistance and biocompatibility of Ti–6Al–7Nb alloy for implant applications. The electrochemical anodization treatment produced an Al-free oxide layer with nanoscale porosity on the Ti–6Al–7Nb alloy surface. The surface topography and microstructure of Ti–6Al–7Nb alloy were analyzed. The corrosion resistance was investigated using potentiodynamic polarization curve measurements in simulated blood plasma (SBP). The adhesion and proliferation of human bone marrow mesenchymal stem cells to test specimens were evaluated using various biological analysis techniques. The results showed that the presence of a nanoporous oxide layer on the anodized Ti–6Al–7Nb alloy increased the corrosion resistance (i.e., increased the corrosion potential and decreased both the corrosion rate and the passive current) in SBP compared with the untreated Ti–6Al–7Nb alloy. Changes in the nanotopography also improved the cell adhesion and proliferation on the anodized Ti–6Al–7Nb alloy. We conclude that a fast and simple electrochemical anodization surface treatment improves the corrosion resistance and biocompatibility of Ti–6Al–7Nb alloy for biomedical implant applications. - Highlights: ► Simple/fast electrochemical anodization was applied to biomedical Ti–6Al–7Nb surface. ► Anodized surface had nano-porous topography and contained Al-free oxide layer. ► Anodized surface raised corrosion resistance in three simulated biological solutions. ► Anodized surface enhanced cell adhesion and cell proliferation. ► Electrochemical anodization has potential as biomedical implant surface treatment

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  19. Anode Sheath Switching in a Carbon Nanotube Arc Plasma

    International Nuclear Information System (INIS)

    Fetterman, Abe; Raitses, Yevgeny; Keidar, Michael

    2008-01-01

    The anode ablation rate is investigated as a function of anode diameter for a carbon nanotube arc plasma. It is found that anomalously high ablation occurs for small anode diameters. This result is explained by the formation of a positive anode sheath. The increased ablation rate due to this positive anode sheath could imply greater production rate for carbon nanotubes.

  20. Anodizing And Sealing Aluminum In Nonchromated Solutions

    Science.gov (United States)

    Emmons, John R.; Kallenborn, Kelli J.

    1995-01-01

    Improved process for anodizing and sealing aluminum involves use of 5 volume percent sulfuric acid in water as anodizing solution, and 1.5 to 2.0 volume percent nickel acetate in water as sealing solution. Replaces process in which sulfuric acid used at concentrations of 10 to 20 percent. Improved process yields thinner coats offering resistance to corrosion, fatigue life, and alloy-to-alloy consistency equal to or superior to those of anodized coats produced with chromated solutions.

  1. The mathematical description of the electrochemical behavior during the anodic overoxidation of conductive polymers in strong acid media A descrição matemática do comportamento eletroquímico durante o processo da sobreoxidação anódica dos polímeros condutores no meio muito ácido

    Directory of Open Access Journals (Sweden)

    Volodymyr Valentynovych Tkach

    2012-04-01

    Full Text Available The electrochemical behavior of the system with the anodic overoxidation of conducting polymers was described mathematically. The balance equation system describing it was analyzed using the linear stability theory and bifurcation analysis. The stable steady-state conditions and oscillatory instability conditions were found.O comportamento eletroquímico do sistema da sobreoxidação anôdica dos polímeros condutores foi descrito matematicamente. O conjunto das equações do balanço a descrever os processos neste sistema foi investigado usando a teoria da estabilidade linear e a análise de bifurcações. As condições do estado estacionário estável e da instabilidade oscilatória foram achadas para este sistema.

  2. Effect of anodization on the surface characteristics and electrochemical behaviour of zirconium in artificial saliva.

    Science.gov (United States)

    Romonti, Daniela E; Gomez Sanchez, Andrea V; Milošev, Ingrid; Demetrescu, Ioana; Ceré, Silvia

    2016-05-01

    The paper is focused on elaboration of ZrO2 films on pure zirconium via anodizing in phosphoric acid with and without fluoride at constant potentials of 30 V and 60 V. The structure and composition of the films were investigated using scanning electronic microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The composition of the oxides formed at both potentials can be identified as monoclinic ZrO2. In addition to Zr and O, the layers formed in phosphoric acid contain phosphorus originating from the phosphoric acid. When the phosphoric acid solution contains NaF, fluorine is also incorporated into the oxide layer. The oxides formed at a higher voltage have greater roughness than those formed at 30 V. Anodized samples exhibit smaller current densities during anodic polarization compared to the as-received zirconium covered with native oxide. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Nanostructural characterization of large-scale porous alumina fabricated via anodizing in arsenic acid solution

    Energy Technology Data Exchange (ETDEWEB)

    Akiya, Shunta; Kikuchi, Tatsuya, E-mail: kiku@eng.hokudai.ac.jp; Natsui, Shungo; Suzuki, Ryosuke O.

    2017-05-01

    Highlights: • Anodic porous alumina was formed in an arsenic acid solution. • Potential difference (voltage) anodizing at 340 V was achieved. • The porous alumina was slightly ordered under the appropriate conditions. • Pore sealing behavior was not observed in boiling distilled water. • The porous alumina exhibits a white photoluminescence emission under UV irradiation. - Abstract: Anodizing of aluminum in an arsenic acid solution is reported for the fabrication of anodic porous alumina. The highest potential difference (voltage) without oxide burning increased as the temperature and the concentration of the arsenic acid solution decreased, and a high anodizing potential difference of 340 V was achieved. An ordered porous alumina with several tens of cells was formed in 0.1–0.5 M arsenic acid solutions at 310–340 V for 20 h. However, the regularity of the porous alumina was not improved via anodizing for 72 h. No pore sealing behavior of the porous alumina was observed upon immersion in boiling distilled water, and it may be due to the formation of an insoluble complex on the oxide surface. The porous alumina consisted of two different layers: a hexagonal alumina layer that contained arsenic from the electrolyte and a pure alumina honeycomb skeleton. The porous alumina exhibited a white photoluminescence emission at approximately 515 nm under UV irradiation at 254 nm.

  4. Development and testing of immersed-Bz diodes with cryogenic anodes

    International Nuclear Information System (INIS)

    Bruner, Nichelle Lee; Cordova, Steve Ray; Oliver, Bryan Velten; Portillo, Salvador; Cooper, Graham; Puetz, Elizabeth A.; Johnston, Mark D.; Hahn, Kelly Denise; McLean, John; Molina, Isidro; Droemer, Darryl W.; Welch, Dale R.; Rovang, Dean Curtis; Van De Valde, David M.; Gregerson, Darryl; Maenchen, John Eric; O'Malley, John

    2005-01-01

    Sandia National Laboratories is investigating and developing high-dose, high-brightness flash radiographic sources. The immersed-B z diode employs large-bore, high-field solenoid magnets to help guide and confine an intense electron beam from a needle-like cathode 'immersed' in the axial field of the magnet. The electron beam is focused onto a high-atomic-number target/anode to generate an intense source of bremsstrahlung X-rays. Historically, these diodes have been unable to achieve high dose (> 500 rad (at) m) from a small spot (< 3 mm diameter). It is believed that this limitation is due in part to undesirable effects associated with the interaction of the electron beam with plasmas formed at either the anode or the cathode. Previous research concentrated on characterizing the behavior of diodes, which used untreated, room temperature (RT) anodes. Research is now focused on improving the diode performance by modifying the diode behavior by using cryogenic anodes that are coated in-situ with frozen gases. The objective of these cryogenically treated anodes is to control and limit the ion species of the anode plasma formed and hence the species of the counter-streaming ions that can interact with the electron beam. Recent progress in the development, testing and fielding of the cryogenically cooled immersed diodes at Sandia is described.

  5. Electrochemical noise evaluation of anodized aluminum. Comparative study against corrosion behaviour in the atmosphere

    International Nuclear Information System (INIS)

    Betancourt, N.; Corvo, F.; Mendoza, A.; Simancas, J.; Morcillo, M.; Gonzalez, J. A.; Fragata, F.; Pena, J. J.; Sanchez de Villalaz, M.; Flores, S.; Almeida, E.; Rivero, S.; Rincon, O. T. de.

    2003-01-01

    The present work reports the evaluation of aluminum and anodized aluminum by electrochemical noise, as a part of the PATINE/CYTED project of the working group NS5. A visual examination is also made. The samples were exposed at several Ibero-American atmospheres up to 2 years of exposure. Different thickness of anodized aluminum were evaluated. The electrochemical potential noise of the 5 μm unexposed sample (pattern) showed a different behaviour to that showed by the other anodized specimens. This could be due to a slower sealed of the samples of higher thickness. The same behavior was observed on the samples exposed at the rural station. el Pardo. According to the visual examination, the samples of bare aluminum and those of anodized 5 μm thickness were the most affected by pitting corrosion in the highly polluted atmospheres. A good correlation between corrosion behaviour determined by visual examination and EN was obtained. (Author) 4 refs

  6. EIS and potentiodynamic polarization studies on immiscible monotectic Al–In alloys

    International Nuclear Information System (INIS)

    Osório, Wislei R.; Freitas, Emmanuelle S.; Garcia, Amauri

    2013-01-01

    Highlights: • The Al–In alloy microstructure is characterized by In droplets spread in an Al matrix. • The scale of phases forming the microstructure affect the electrochemical behavior. • Larger interphase spacing/droplet diameter is related to higher corrosion resistance. • The deleterious effect in corrosion resistance is due to strains and galvanic cells. -- Abstract: The electrochemical behavior of monotectic Al–In alloys is experimentally investigated. Electrochemical impedance spectroscopy (EIS), potentiodynamic anodic polarization techniques and an equivalent circuit analysis were used to evaluate the corrosion response in a stagnant and naturally aerated 0.5 M NaCl solution at 25 °C. It was found that a better galvanic protection can be provided for microstructures having indium droplets of larger diameters and larger interphase spacings. From five samples extracted along the length of a directionally solidified Al–In casting, that having smallest interphase spacing (λ = 18 μm) and droplet diameter (d = 0.7 μm) had its corrosion resistance significantly decreased (about 2 and 3 times in terms of the current density and polarization resistance) when compared with that of the sample having the coarsest microstructure (λ = 60 μm and d = 2.5 μm). Such behavior is attributed to both localized strains between aluminum and indium boundaries and the corrosion potential of the indium particles

  7. Anodization process produces opaque, reflective coatings on aluminum

    Science.gov (United States)

    1965-01-01

    Opaque, reflective coatings are produced on aluminum articles by an anodizing process wherein the anodizing bath contains an aqueous dispersion of finely divided insoluble inorganic compounds. These particles appear as uniformly distributed occlusions in the anodic deposit on the aluminum.

  8. Prevention of Crevice Corrosion of STS 304 Stainless Steel by a Mg-alloy Galvanic Anode

    International Nuclear Information System (INIS)

    Lim, U. J.; Yun, B. D.; Kim, J. J.

    2006-01-01

    Prevention of crevice corrosion was studied for STS 304 stainless steel using a Mg-alloy galvanic anode in solutions with various specific resistivity. The crevice corrosion and corrosion protection characteristics of the steel was investigated by the electrochemical polarization and galvanic corrosion tests. Experimental results show that the crevice corrosion of STS 304 stainless steel does not occur in solutions of high specific resistivity, but it occurs in solutions of low specific resistivity like in solutions with resistivities of 30, 60 and 115 Ω · m. With decreasing specific resistivity of the solution, the electrode potential of STS 304 stainless steel in the crevice is lowered. The potential of STS 304 stainless steel in the crevice after coupling is cathodically polarized more by decreasing specific resistivity indicating that the crevice corrosion of STS 304 stainless steel is prevented by the Mg-alloy galvanic anode

  9. Microstructural characterization and electrochemical corrosion behavior of Incoloy 800 in sulphate and chloride solutions

    International Nuclear Information System (INIS)

    Mansur, Fabio Abud; Schvartzman, Monica Maria de Abreu Mendonca; Campos, Wagner Reis da Costa; Aguiar, Antonio Eugenio de; Chaim, Marcos Souza

    2011-01-01

    Corrosion has been the major cause of tube failures in steam generators (SG) tubes in nuclear power plants. Problems have resulted from impurities in the secondary water systems which are originated from leaks of cooling water. It is important to understand the compatibility of steam generator tube materials with the environment. This study presents the microstructural characterization and electrochemical behavior of the Incoloy 800 in sodium chloride and sodium sulphate aqueous solutions at 80 degree C. Potentiodynamic anodic polarization, cyclic polarization and open circuit potential (OCP) measurements were the electrochemical techniques applied in this work. The pitting resistance of Incoloy 800 in chloride plus sulphate mixtures were also examined. Experiments performed in solutions with different concentrations of Cl- and SO 4 2- ions in solution (200 ppb, 500 ppb, 1ppm, 5 ppm, 50 ppm and 100 ppm) showed that this concentrations range had no substantial effect on the anodic behavior of the alloy. After polarization no localized corrosion was found on the samples. (author)

  10. Challenge for lowering concentration polarization in solid oxide fuel cells

    Science.gov (United States)

    Shimada, Hiroyuki; Suzuki, Toshio; Yamaguchi, Toshiaki; Sumi, Hirofumi; Hamamoto, Koichi; Fujishiro, Yoshinobu

    2016-01-01

    In the scope of electrochemical phenomena, concentration polarization at electrodes is theoretically inevitable, and lowering the concentration overpotential to improve the performance of electrochemical cells has been a continuing challenge. Electrodes with highly controlled microstructure, i.e., high porosity and uniform large pores are therefore essential to achieve high performance electrochemical cells. In this study, state-of-the-art technology for controlling the microstructure of electrodes has been developed for realizing high performance support electrodes of solid oxide fuel cells (SOFCs). The key is controlling the porosity and pore size distribution to improve gas diffusion, while maintaining the integrity of the electrolyte and the structural strength of actual sized electrode supports needed for the target application. Planar anode-supported SOFCs developed in this study realize 5 μm thick dense electrolyte (yttria-stabilized zirconia: YSZ) and the anode substrate (Ni-YSZ) of 53.6 vol.% porosity with a large median pore diameter of 0.911 μm. Electrochemical measurements reveal that the performance of the anode-supported SOFCs improves with increasing anode porosity. This Ni-YSZ anode minimizes the concentration polarization, resulting in a maximum power density of 3.09 W cm-2 at 800 °C using humidified hydrogen fuel without any electrode functional layers.

  11. The Polarized Electron Source at ELSA

    International Nuclear Information System (INIS)

    Drachenfels, Wolther von; Frommberger, Frank; Gowin, Michael; Hillert, Wolfgang; Hoffmann, Markus; Neff, Bernhold

    2003-01-01

    At the electron stretcher accelerator ELSA in Bonn a pulsed 50 kV inverted gun of polarized electrons has been in operation since February 2000. A strained-layer superlattice crystal is used to deliver a beam with a polarization of about 80 %. A flashlamp-pumped Ti-Sapphire laser with a pulse repetition rate of 50 Hz serves as source of light. The gun is operated in space charge limitation. The current can be chosen by varying the distance between cathode and anode. With 1 μs pulses of 100 mA the source was particularly used together with a polarized target for a GDH sum rule experiment. The high photocathode lifetime allows continuous operation at 100 mA typically for periods of about two weeks without maintenance. So far no change of the crystal was necessary

  12. CO tolerance of PdPt/C and PdPtRu/C anodes for PEMFC

    International Nuclear Information System (INIS)

    Garcia, Amanda C.; Paganin, Valdecir A.; Ticianelli, Edson A.

    2008-01-01

    The performance of H 2 /O 2 proton exchange membrane fuel cells (PEMFCs) fed with CO-contaminated hydrogen was investigated for anodes with PdPt/C and PdPtRu/C electrocatalysts. The physicochemical properties of the catalysts were characterized by energy dispersive X-ray (EDX) analyses, X-ray diffraction (XRD) and 'in situ' X-ray absorption near edge structure (XANES). Experiments were conducted in electrochemical half and single cells by cyclic voltammetry (CV) and I-V polarization measurements, while DEMS was employed to verify the formation of CO 2 at the PEMFC anode outlet. A quite high performance was achieved for the PEMFC fed with H 2 + 100 ppm CO with the PdPt/C and PdPtRu/C anodes containing 0.4 mg metal cm -2 , with the cell presenting potential losses below 200 mV at 1 A cm -2 , with respect to the system fed with pure H 2 . For the PdPt/C catalysts no CO 2 formation was seen at the PEMFC anode outlet, indicating that the CO tolerance is improved due to the existence of more free surface sites for H 2 electrooxidation, probably due to a lower Pd-CO interaction compared to pure Pd or Pt. For PdPtRu/C the CO tolerance may also have a contribution from the bifunctional mechanism, as shown by the presence of CO 2 in the PEMFC anode outlet

  13. Photo-electrochemical and impedance investigation of passive layers grown anodically on titanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, N.T.C. [Departamento de Quimica, Universidade Federal de Sao Carlos, CP 676, 13560-970 Sao Carlos, SP (Brazil); Biaggio, S.R. [Departamento de Quimica, Universidade Federal de Sao Carlos, CP 676, 13560-970 Sao Carlos, SP (Brazil); Piazza, S. [Dipartimento di Ingegneria Chimica dei Processi e dei Materiali, Universita di Palermo, Viale delle Scienze, 90128 Palermo (Italy)]. E-mail: piazza@dicpm.unipa.it; Sunseri, C. [Dipartimento di Ingegneria Chimica dei Processi e dei Materiali, Universita di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Di Quarto, F. [Dipartimento di Ingegneria Chimica dei Processi e dei Materiali, Universita di Palermo, Viale delle Scienze, 90128 Palermo (Italy)

    2004-10-15

    The anodic behaviour of two titanium cast alloys, obtained by fusion in a voltaic arc under argon atmosphere, was analyzed in aerated aqueous solutions having different pH values. In all solutions the alloys, having nominal compositions Ti-50Zr at.% and Ti-13Zr-13Nb wt.%, displayed a valve-metal behaviour, owing to the formation of barrier-type oxide films. Passive films, grown potentiodynamically up to about 9 V, were investigated by photocurrent spectroscopy (PCS) and electrochemical impedance spectroscopy (EIS). These passive layers show photoactivity under anodic polarizations, with optical gaps close to 3.55 and 3.25 eV for the binary and the ternary alloy, respectively, independent of the anodizing electrolyte. Films grown on the binary alloy present insulating behaviour and anodic impedance spectra with one time constant; this was interpreted in terms of a single-layer mixed Ti-Zr oxide enriched in Ti with respect to the alloy composition. Also for the ternary alloy the results are consistent with the formation, upon anodization, of Ti-Nb-Zr mixed oxide films, but they display n-type semiconducting behaviour, owing to their poor content of ZrO{sub 2} groups.

  14. Application of in situ digital holography to the study of the effect of a magnetic field on the anodic dissolution of iron in thichloroacetic acid

    Directory of Open Access Journals (Sweden)

    XUEGENG YANG

    2006-01-01

    Full Text Available The effect of a magnetic field on the anodic dissolution of iron in 1.0 mol dm-3 trichloroacetic acid solution was studied by the potentiodynamic polarization method and in situ digital holography. It was found that the magnetohydrodynamic force increased the mass transport, which resulted in a faster anodic dissolution of iron. The effect of the magnetic field was analyzed by holograms and is discussed in terms of the magnetohydrodynamic force.

  15. Ultraviolet-light-induced multi-physics behaviors of 0–3 polarized transparent PLZT plates: II. Finite element analysis and validation

    International Nuclear Information System (INIS)

    Luo, Quantian; Tong, Liyong

    2011-01-01

    This paper presents a novel finite element formulation for 0–3 polarized PbLaZrTi (PLZT) plates and a comparison of the predicted and measured bending displacements. The coupled multi-physics fields and Hamilton's principle for piezoelectric (PZT) materials are first extended to PLZT ceramics by including the anomalous photovoltaic and photo-thermal effects. The photo-induced non-uniform electrical field and mechanical strains across the thickness are modeled in the present finite element formulation for 0–3 polarized PLZT plates, and the associated actuator and sensor equations are derived. The transverse displacements of a 0–3 polarized PLZT plate are predicted using the present finite element formulation and compared with the measured data given in part I. A reasonably good correlation is noted for the transverse displacements at the ten measurement points

  16. Anodic solution of alkali earth alloys in potassium chloride-sodium chloride melts

    International Nuclear Information System (INIS)

    Volkovich, A.V.

    1997-01-01

    Generalized results of studying the process of anodic dissolution of alkaline-earth metal alloys with zinc, aluminium and copper in the melts of KCl-NaCl equimolar mixture containing alkaline-earth metal chlorides, are presented. It is shown that during dissolution of both pure liquid metals and their alloys there is no electrode polarization in the range of the current densities lower or comparable in their values to corrosion current

  17. Experimental Studies of the Effects of Anode Composition and Process Parameters on Anode Slime Adhesion and Cathode Copper Purity by Performing Copper Electrorefining in a Pilot-Scale Cell

    Science.gov (United States)

    Zeng, Weizhi; Wang, Shijie; Free, Michael L.

    2016-10-01

    Copper electrorefining tests were conducted in a pilot-scale cell under commercial tankhouse environment to study the effects of anode compositions, current density, cathode blank width, and flow rate on anode slime behavior and cathode copper purity. Three different types of anodes (high, mid, and low impurity levels) were used in the tests and were analyzed under SEM/EDS. The harvested copper cathodes were weighed and analyzed for impurities concentrations using DC Arc. The adhered slimes and released slimes were collected, weighed, and analyzed for compositions using ICP. It was shown that the lead-to-arsenic ratio in the anodes affects the sintering and coalescence of slime particles. High current density condition can improve anode slime adhesion and cathode purity by intensifying slime particles' coalescence and dissolving part of the particles. Wide cathode blanks can raise the anodic current densities significantly and result in massive release of large slime particle aggregates, which are not likely to contaminate the cathode copper. Low flow rate can cause anode passivation and increase local temperatures in front of the anode, which leads to very intense sintering and coalescence of slime particles. The results and analyses of the tests present potential solutions for industrial copper electrorefining process.

  18. An evaluation of the environmental fate and behavior of munitions materiel (tetryl and polar metabolites of TNT) in soil and plant systems

    International Nuclear Information System (INIS)

    Fellows, R.J.; Harvey, S.D.; Cataldo, D.A.

    1993-09-01

    A preliminary study was conducted to elucidate the nature of the polar metabolites reported for plant tissues and xylem exudates following root accumulation of trinitrotoluene. Studies focused on the nature of the proposed conjugates of TNT-residues in xylem exudates of bush beam plants. Use of enzymatic methods failed to demonstrate that the conjugates were carbohydrate based, but acid hydrolysis indicated that the conjugates may be protein based. Of the five polar conjugates isolated from exudates, the presence of aminodinitrotoluene isomers and one unknown TNT residue was demonstrated

  19. Anodic behaviour of the stainless steel AISI 430 in aqueous solutions of chloride and sulphate ions

    International Nuclear Information System (INIS)

    Sebrao, M.Z.

    1982-01-01

    The kinetics of the dissolution of stainless steel AISI 430 in the presence of chloride and sulphate ions has been studied in terms of the ion concentration, the pH variation, and the velocity of the working electrode. The experimental method utilized was the potentiostatic anodic polarization, and the reactants used were NaCl and Na 2 SO 4 at room temperature. Atomic Absorption spectrophotometry and Auger Electrons spectroscopy (AES) analyses were made in order to support the interpretation of results obtained by means of the potentiostatic polarization method. (author)

  20. Polar Polygons

    Science.gov (United States)

    2005-01-01

    18 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark-outlined polygons on a frost-covered surface in the south polar region of Mars. In summer, this surface would not be bright and the polygons would not have dark outlines--these are a product of the presence of seasonal frost. Location near: 77.2oS, 204.8oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  1. Intermittent contact of fluidized anode particles containing exoelectrogenic biofilms for continuous power generation in microbial fuel cells

    KAUST Repository

    Liu, Jia

    2014-09-01

    Current generation in a microbial fuel cell can be limited by the amount of anode surface area available for biofilm formation, and slow substrate degradation kinetics. Increasing the anode surface area can increase the amount of biofilm, but performance will improve only if the anode material is located near the cathode to minimize solution internal resistance. Here we demonstrate that biofilms do not have to be in constant contact with the anode to produce current in an MFC. Granular activated carbon particles enriched with exoelectrogenic biofilm are fluidized (by stirring) in the anode chamber of the MFC, resulting in only intermittent contact between the particles and the anode current collector. The maximum power density generated is 951 ± 10 mW m-2, compared to 813 ± 2 mW m-2 for the control without stirring (packed bed), and 525 ± 1 mW m-2 in the absence of GAC particles and without stirring. GAC-biofilm particles demonstrate capacitor-like behavior, but achieve nearly constant discharge conditions due to the large number of particles that contact the current collector. These results provide proof of concept for the development of flowable electrode reactors, where anode biofilms can be electrically charged in a separate storage tank and then rapidly discharged in compact anode chambers. © 2014 Elsevier B.V. All rights reserved.

  2. Intermittent contact of fluidized anode particles containing exoelectrogenic biofilms for continuous power generation in microbial fuel cells

    KAUST Repository

    Liu, Jia; Zhang, Fang; He, Weihua; Zhang, Xiaoyuan; Feng, Yujie; Logan, Bruce E.

    2014-01-01

    Current generation in a microbial fuel cell can be limited by the amount of anode surface area available for biofilm formation, and slow substrate degradation kinetics. Increasing the anode surface area can increase the amount of biofilm, but performance will improve only if the anode material is located near the cathode to minimize solution internal resistance. Here we demonstrate that biofilms do not have to be in constant contact with the anode to produce current in an MFC. Granular activated carbon particles enriched with exoelectrogenic biofilm are fluidized (by stirring) in the anode chamber of the MFC, resulting in only intermittent contact between the particles and the anode current collector. The maximum power density generated is 951 ± 10 mW m-2, compared to 813 ± 2 mW m-2 for the control without stirring (packed bed), and 525 ± 1 mW m-2 in the absence of GAC particles and without stirring. GAC-biofilm particles demonstrate capacitor-like behavior, but achieve nearly constant discharge conditions due to the large number of particles that contact the current collector. These results provide proof of concept for the development of flowable electrode reactors, where anode biofilms can be electrically charged in a separate storage tank and then rapidly discharged in compact anode chambers. © 2014 Elsevier B.V. All rights reserved.

  3. Performance study of the gamma-ray bursts polarimeter POLAR

    Science.gov (United States)

    Sun, J. C.; Wu, B. B.; Bao, T. W.; Batsch, T.; Bernasconi, T.; Britvitch, I.; Cadoux, F.; Cernuda, I.; Chai, J. Y.; Dong, Y. W.; Gauvin, N.; Hajdas, W.; He, J. J.; Kole, M.; Kong, M. N.; Kong, S. W.; Lechanoine-Leluc, C.; Li, Lu; Liu, J. T.; Liu, X.; Marcinkowski, R.; Orsi, S.; Pohl, M.; Produit, N.; Rapin, D.; Rutczynska, A.; Rybka, D.; Shi, H. L.; Song, L. M.; Szabelski, J.; Wang, R. J.; Wen, X.; Xiao, H. L.; Xiong, S. L.; Xu, H. H.; Xu, M.; Zhang, L.; Zhang, L. Y.; Zhang, S. N.; Zhang, X. F.; Zhang, Y. J.; Zwolinska, A.

    2016-07-01

    The Gamma-ray Burst Polarimeter-POLAR is a highly sensitive detector which is dedicated to the measurement of GRB's polarization with a large effective detection area and a large field of view (FOV). The optimized performance of POLAR will contribute to the capture and measurement of the transient sources like GRBs and Solar Flares. The detection energy range of POLAR is 50 keV 500 keV, and mainly dominated by the Compton scattering effect. POLAR consists of 25 detector modular units (DMUs), and each DMU is composed of low Z material Plastic Scintillators (PS), multi-anode photomultipliers (MAPMT) and multi-channel ASIC Front-end Electronics (FEE). POLAR experiment is an international collaboration project involving China, Switzerland and Poland, and is expected to be launched in September in 2016 onboard the Chinese space laboratory "Tiangong-2 (TG-2)". With the efforts from the collaborations, POLAR has experienced the Demonstration Model (DM) phase, Engineering and Qualification Model (EQM) phase, Qualification Model (QM) phase, and now a full Flight Model (FM) of POLAR has been constructed. The FM of POLAR has passed the environmental acceptance tests (thermal cycling, vibration, shock and thermal vacuum tests) and experienced the calibration tests with both radioactive sources and 100% polarized Gamma-Ray beam at ESRF after its construction. The design of POLAR, Monte-Carlo simulation analysis, as well as the performance test results will all be introduced in this paper.

  4. Discharge modes at the anode of a vacuum arc

    International Nuclear Information System (INIS)

    Miller, H.C.

    1982-01-01

    The two most common anode modes in a vacuum arc are the low current mode, where the anode is basically inert; and the high current mode with a fully developed anode spot. This anode spot is very bright, has a temperature near the boiling point of the anode material, and is a copious source of vapor and energetic ions. However, other anode modes can exist. A low current vacuum arc with electrodes of readily sputterable material will emit a flux of sputtered atoms from the anode. An intermediate currents an anode footpoint can form. This footpoint is luminous, but much cooler than a true anode spot. Finally, a high current mode can exist where several small anode spots are present instead of a single large anode spot

  5. Porous anodic film formation on an Al-3.5 wt% Cu alloy

    Energy Technology Data Exchange (ETDEWEB)

    Paez, M.A.; Bustos, O.; Thompson, G.E.; Skeldon, P.; Shimizu, K.; Wood, G.C.

    2000-03-01

    Anodic film growth has been undertaken on an electropolished Al-3.5 wt % Cu alloy to determine the influence of copper in solid solution on the anodizing behavior. At the commencement of anodizing of the electropolished alloy, in the presence of interfacial enrichment of copper, Al{sup 3+} and Cu{sup 2+} ions egress and O{sup 2{minus}} ion ingress proceed; film growth occurs at the alloy/film interface though O{sup 2{minus}} ion ingress, with outwardly mobile Al{sup 3+} and Cu{sup 2+} ions ejected at the film/electrolyte interface, and field-assisted dissolution proceeding at the bases of pores. Oxidation of copper, in the presence of the enriched layer, is also associated with O{sub 2} gas generation, leading to development of oxygen-filled voids. As a result of significant pressures in the voids, film rupture proceeds, with electrolyte access to the alloy, dissolution of the enriched interfacial layer and re-anodizing. The consequence of such processes in the development of anodic films of increased porosity and reduced efficiency of film formation compared with anodizing of superpure aluminum under similar conditions.

  6. Strategic Polarization.

    Science.gov (United States)

    Kalai, Adam; Kalai, Ehud

    2001-08-01

    In joint decision making, similarly minded people may take opposite positions. Consider the example of a marriage in which one spouse gives generously to charity while the other donates nothing. Such "polarization" may misrepresent what is, in actuality, a small discrepancy in preferences. It may be that the donating spouse would like to see 10% of their combined income go to charity each year, while the apparently frugal spouse would like to see 8% donated. A simple game-theoretic analysis suggests that the spouses will end up donating 10% and 0%, respectively. By generalizing this argument to a larger class of games, we provide strategic justification for polarization in many situations such as debates, shared living accommodations, and disciplining children. In some of these examples, an arbitrarily small disagreement in preferences leads to an arbitrarily large loss in utility for all participants. Such small disagreements may also destabilize what, from game-theoretic point of view, is a very stable equilibrium. Copyright 2001 Academic Press.

  7. Dissolution of anodic zirconium dioxide films in aqueous media

    International Nuclear Information System (INIS)

    Merati, A.; Cox, B.

    1999-01-01

    Zirconium with a low thermal neutron cross section, good corrosion resistance in high-temperature water, and high thermal conductivity is an ideal material for nuclear reactors. Its good resistance to water and steam at reactor temperatures is of the greatest interest to nuclear fuel designers. Dissolution of zirconium dioxide (ZrO 2 ) films in aggressive media was investigated. The extent of uniform and localized dissolution was measured by ultraviolet-visible (UV-VIS) spectrometry and an alternating current (AC) impedance test, respectively. Scanning electron microscopy (SEM) showed the extent of dissolution of ZrO 2 was a function only of the fluoride ion content and pH of the medium. Cathodic polarization was used to identify the preferred sites for localized dissolution of the oxide film. In 0.1 M potassium bifluoride (KHF 2 ), both uniform thinning and local breakdown of the oxide were observed. Within the limits of the investigating techniques, no evidence of dissolution was observed in the other solutions tested: 0.5 M sulfuric acid (H 2 SO 4 ). 1.0 M nitric acid (HNO 3 ), 5 M hydrochloric acid (HCl), or 0.1 M potassium fluoride (KF). In areas around iron-containing particles, fine cracks in the anodic oxide at prior metal grain boundaries and arrays of cracks in the oxide associated with residual scratches from the initial specimen preparation were the preferred spots for localized dissolution of the oxide film. Iron precipitates immediately below the surface of the oxide layer increased the local electrical conductivity. Enrichment of iron in the oxide matrix around these precipitates during the anodization process appeared to cause prospective spots, acting as anodic sites for pH formation

  8. Perovskites synthesis to SOFC anodes

    International Nuclear Information System (INIS)

    Wendler, L.P.; Chinelatto, A.L.; Chinelatto, A.S.A.; Ramos, K.

    2012-01-01

    Perovskite structure materials containing lanthanum have been widely applied as solid oxide fuel cells (SOFCs) electrodes, due to its electrical properties. Was investigated the obtain of the perovskite structure LaCr 0,5 Ni 0,5 O 3 , by Pechini method, and its suitability as SOFC anode. The choice of this composition was based on the stability provided by chromium and the catalytic properties of nickel. After preparing the resins, the samples were calcined at 300 deg C, 600 deg C, 700 deg C and 850 deg C. The resulting powders were characterized by X-ray diffraction to determine the existing phases. Furthermore, were performed other analysis, like X-ray fluorescence, He pycnometry, specific surface area by BET isotherm and scanning electronic microscopy (author)

  9. PEO of pre-anodized Al-Si alloys: Corrosion properties and influence of sealings

    Science.gov (United States)

    Mohedano, M.; Matykina, E.; Arrabal, R.; Mingo, B.; Pardo, A.

    2015-08-01

    Voltage-controlled PEO coatings were developed on A356 aluminum alloys (gravity-cast and rheocast) with a pre-anodized layer. The influence of the alloy manufacturing process and the effect of Si-rich phase on the structure and composition of the oxide layers were evaluated using SEM, EDS and XRD. The pre-anodized oxide layer preserves the microstructure of the substrate due to the presence of secondary phases that have a different behavior relative to the matrix during anodizing. PEO coatings consisted of a mixture of α-Al2O3, γ-Al2O3 and mullite. The corrosion behavior and the effectiveness of different sealing techniques based on salts of nickel, cobalt, cerium and phosphonic acid were also studied. Post-treatments improved the hydrophobic properties of the coatings and showed a beneficial effect, significantly increasing the coating impedance and thereby reducing the susceptibility to corrosion.

  10. Anode plasma and focusing reb diodes

    International Nuclear Information System (INIS)

    Goldstein, S.A.; Swain, D.W.; Hadley, G.R.; Mix, L.P.

    1975-01-01

    The use of electrical, optical, x-ray, and particle diagnostics to characterize the production of anode plasma and to monitor its influence on beam generation and focusing is reviewed. Studies using the Nereus accelerator show that after cathode turn-on, deposition of several kJ/gm on the anode is necessary before ions from hydrocarbons, adsorbed gases, and heavier metallic species are detected. The actual time at which ions are liberated depends on several factors, one of which is the specific heat of the anode substrate. Once formed, anode ions cross the A-K gap (with an energy equal to the diode voltage) and interact with the cathode to produce an axially peaked beam profile, a ''pinch'' which does not follow the critical current criterion. Experiments with externally generated anode plasma show that this type of pinch can be attracted to localized areas on the anode. Preliminary observations on Hydra indicate the anode plasma composition is similar to that on Nereus. The effect of this plasma on pinch dynamics currently is under investigation

  11. Anode baking process optimization through computer modelling

    Energy Technology Data Exchange (ETDEWEB)

    Wilburn, D.; Lancaster, D.; Crowell, B. [Noranda Aluminum, New Madrid, MO (United States); Ouellet, R.; Jiao, Q. [Noranda Technology Centre, Pointe Claire, PQ (Canada)

    1998-12-31

    Carbon anodes used in aluminum electrolysis are produced in vertical or horizontal type anode baking furnaces. The carbon blocks are formed from petroleum coke aggregate mixed with a coal tar pitch binder. Before the carbon block can be used in a reduction cell it must be heated to pyrolysis. The baking process represents a large portion of the aluminum production cost, and also has a significant effect on anode quality. To ensure that the baking of the anode is complete, it must be heated to about 1100 degrees C. To improve the understanding of the anode baking process and to improve its efficiency, a menu-driven heat, mass and fluid flow simulation tool, called NABSIM (Noranda Anode Baking SIMulation), was developed and calibrated in 1993 and 1994. It has been used since then to evaluate and screen firing practices, and to determine which firing procedure will produce the optimum heat-up rate, final temperature, and soak time, without allowing unburned tar to escape. NABSIM is used as a furnace simulation tool on a daily basis by Noranda plant process engineers and much effort is expended in improving its utility by creating new versions, and the addition of new modules. In the immediate future, efforts will be directed towards optimizing the anode baking process to improve temperature uniformity from pit to pit. 3 refs., 4 figs.

  12. Study of the Polarization Behavior of Ce0.9Gd0.1O2-δ Single Crystals below 350°C to Room Temperature

    DEFF Research Database (Denmark)

    Neuhaus, K.; Bernemann, M.; Hansen, Karin Vels

    2016-01-01

    was investigated by mapping the introduced defect gradient and its decay with time using Kelvin probe force microscopy. The generated surface potential gradients were found to have a diameter of up to 1 μm, which is explained by the local ionization of defect associates by the applied high electric field......Single crystalline ceria samples with the composition Ce0.9Gd0.1O2-δ were pre-polarized with ±5 V for up to 300 s using a Pt coated AFM tip as working electrode. The direct contact zone had a diameter of potential of the samples....... Measurements were performed at room temperature and 50°C. The polarization behavior of the Ce0.9Gd0.1O2-δ single crystals was compared to cyclovoltammetry and polarization-relaxation experiments at T ≤ 350°C and in dry air or nitrogen which were performed using a specially suited AFM (Controlled Atmosphere...

  13. Polarized secondary radioactive beams

    International Nuclear Information System (INIS)

    Zaika, N.I.

    1992-01-01

    Three methods of polarized radioactive nuclei beam production: a) a method nuclear interaction of the non-polarized or polarized charged projectiles with target nuclei; b) a method of polarization of stopped reaction radioactive products in a special polarized ion source with than following acceleration; c) a polarization of radioactive nuclei circulating in a storage ring are considered. Possible life times of the radioactive ions for these methods are determined. General schemes of the polarization method realizations and depolarization problems are discussed

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

    Science.gov (United States)

    Nagasawa, Tsuyoshi; Hanamura, Katsunori

    2017-06-01

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

  15. Polar crane

    International Nuclear Information System (INIS)

    Makosinski, S.

    1981-01-01

    In many applications polar cranes have to be repeatedly positioned with high accuracy. A guidance system is disclosed which has two pairs of guides. Each guide consists of two rollers carried by a sheave rotatable mounted on the crane bridge, the rollers being locatable one on each side of a guideway, e.g. the circular track on which the bridge runs. The pairs of guides are interconnected by respective rope loops which pass around and are locked to the respective pairs of sheaves in such a manner that movement of one guide results in equal movement of the other guide in a sense to maintain the repeatability of positioning of the centre of the bridge. A hydraulically-linked guide system is also described. (author)

  16. Battery designs with high capacity anode materials and cathode materials

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-10-03

    Improved high energy capacity designs for lithium ion batteries are described that take advantage of the properties of high specific capacity anode active compositions and high specific capacity cathode active compositions. In particular, specific electrode designs provide for achieving very high energy densities. Furthermore, the complex behavior of the active materials is used advantageously in a radical electrode balancing design that significantly reduced wasted electrode capacity in either electrode when cycling under realistic conditions of moderate to high discharge rates and/or over a reduced depth of discharge.

  17. Investigation of fatigue behavior of Pb(Zr0.45Ti0.55)O3 thin films under asymmetric polarization switching

    Science.gov (United States)

    Zhu, Hui; Chen, Yueyuan; Chu, Daping; Feng, Shiwei; Zhang, Yingqiao; Wang, Pengfei

    2016-09-01

    The fatigue of lead zirconate titanate (PZT) thin films was measured under repetitive switching using asymmetric square waves. The remnant polarization and coercive voltage were found to present regular changes in the initial 10 s, independent of the asymmetry or frequency of switching waves. We attributed the change to the relaxation of stress in the film and identified a coercive voltage V 0 of 0.6 V for the stress-free film. By comparing the coercive voltage and V 0, we found that a built-in electric field was induced by asymmetric switching, where the direction and magnitude were dependent on the degree of waveform asymmetry. Furthermore, the fatigue speed was suggested to be closely related to the generation rate of oxygen vacancies. It was confirmed by our result that a faster decay of remnant polarization can be obtained by applying square waves with a higher degree of asymmetry or symmetry of square waves with a lower frequency.

  18. Anodization of Aluminium using a fast two-step process

    Indian Academy of Sciences (India)

    283.6 eV. Keywords. Anodization; phosphoric acid; anodization time; anodized aluminium oxide; aluminium. ... of anodization.5–7 The AAO layer has a large band gap, good ..... transmittance increases as the anodised membrane is heated to ...

  19. PEO of pre-anodized Al–Si alloys: Corrosion properties and influence of sealings

    Energy Technology Data Exchange (ETDEWEB)

    Mohedano, M., E-mail: marta.mohedano@hzg.de [Helmholtz Zentrum Geesthacht, Magnesium Innovation Centre, Institute of Materials Research, Max-Planck-Str. 1, D-21502 Geesthacht (Germany); Matykina, E.; Arrabal, R.; Mingo, B.; Pardo, A. [Departamento de Ciencia de Materiales, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid (Spain)

    2015-08-15

    Highlights: • A356 gravity-cast and rheocast pre-anodized aluminium alloys were coated by PEO. • Different sealing techniques were applied after the coating process. • Iron-rich constituents of the substrate occlude the continuity of the porous anodic film. • PEO coatings consisted of a mixture of α-Al{sub 2}O{sub 3}, γ-Al{sub 2}O{sub 3} and mullite. • Post-treatments improved both hydrophobic and corrosion properties. - Abstract: Voltage-controlled PEO coatings were developed on A356 aluminum alloys (gravity-cast and rheocast) with a pre-anodized layer. The influence of the alloy manufacturing process and the effect of Si-rich phase on the structure and composition of the oxide layers were evaluated using SEM, EDS and XRD. The pre-anodized oxide layer preserves the microstructure of the substrate due to the presence of secondary phases that have a different behavior relative to the matrix during anodizing. PEO coatings consisted of a mixture of α-Al{sub 2}O{sub 3}, γ-Al{sub 2}O{sub 3} and mullite. The corrosion behavior and the effectiveness of different sealing techniques based on salts of nickel, cobalt, cerium and phosphonic acid were also studied. Post-treatments improved the hydrophobic properties of the coatings and showed a beneficial effect, significantly increasing the coating impedance and thereby reducing the susceptibility to corrosion.

  20. Electrochemically exfoliated graphene anodes with enhanced biocurrent production in single-chamber air-breathing microbial fuel cells.

    Science.gov (United States)

    Najafabadi, Amin Taheri; Ng, Norvin; Gyenge, Előd

    2016-07-15

    Microbial fuel cells (MFCs) present promising options for environmentally sustainable power generation especially in conjunction with waste water treatment. However, major challenges remain including low power density, difficult scale-up, and durability of the cell components. This study reports enhanced biocurrent production in a membrane-free MFC, using graphene microsheets (GNs) as anode and MnOx catalyzed air cathode. The GNs are produced by ionic liquid assisted simultaneous anodic and cathodic electrochemical exfoliation of iso-molded graphite electrodes. The GNs produced by anodic exfoliation increase the MFC peak power density by over 300% compared to plain carbon cloth (i.e., 2.85Wm(-2) vs 0.66Wm(-2), respectively), and by 90% compared to conventional carbon black (i.e., Vulcan XC-72) anode. These results exceed previously reported power densities for graphene-containing MFC anodes. The fuel cell polarization results are corroborated by electrochemical impedance spectroscopy indicating three times lower charge transfer resistance for the GN anode. Material characterizations suggest that the best performing GN samples were of relatively smaller size (~500nm), with higher levels of ionic liquid induced surface functionalization during the electrochemical exfoliation process. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Performance Factors and Sulfur Tolerance of Metal Supported Solid Oxide Fuel Cells with Nanostructured Ni:GDC Infiltrated Anodes

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Persson, Åsa Helen; Sudireddy, Bhaskar Reddy

    2015-01-01

    poisoning. The ceria can be incorporated as a Ni:GDC cermet anode, but also via infiltration of ceria and doped ceria into the conventional Ni:YSZ cermet anode. Both approaches have been reported to improve the tolerance towards sulfur poisoning [1-3]. In the present study we report the performance...... concentrations of 2, 5 and 10 ppm in hydrogen fuel, during galvanostatic operation at a current load of 0.25 Acm-2. The results are illustrated and compared with the conventional SOFC Ni:YSZ cermet anode in figure 1, where the relative increase in anode polarization resistance as a function of Ni sulfur coverage...... is shown. The comparison indicate the MS-SOFC anode of the present study to be more tolerant towards sulfur poisoning than the conventional Ni:YSZ cermet anode. [1] K. Sasaki et al., J. Electrochem. Soc., 153, A2023–A2029 (2006). [2] L. Zhang et al., International Journal of Hydrogen Energy, 35, 12359...

  2. Selective formation of porous layer on n-type InP by anodic etching combined with scratching

    International Nuclear Information System (INIS)

    Seo, Masahiro; Yamaya, Tadafumi

    2005-01-01

    The selective formation of porous layer on n-type InP (001) surface was investigated by using scratching with a diamond scriber followed by anodic etching in deaerated 0.5M HCl. Since the InP specimen was highly doped, the anodic etching proceeded in the dark. The potentiodynamic polarization showed the anodic current shoulder in the potential region between 0.8 and 1.3V (SHE) for the scratched area in addition to the anodic current peak at 1.7V (SHE) for the intact area. The selective formation of porous layer on the scratched are was brought by the anodic etching at a constant potential between 1.0 and 1.2V (SHE) for a certain time. The nucleation and growth of etch pits on intact area, however, took place when the time passed the critical value. The cross section of porous layer on the scratched area perpendicular to the [1-bar 10] or [110] scratching direction had a V-shape, while the cross section of porous layer on the scratched area parallel to the [1-bar 10] or [110] scratching direction had a band structure with stripes oriented to the [1-bar 11] or [11-bar 1] direction. Moreover, nano-scratching at a constant normal force in the micro-Newton range followed by anodic etching showed the possibility for selective formation of porous wire with a nano-meter width

  3. Selective formation of porous layer on n-type InP by anodic etching combined with scratching

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Masahiro [Graduate School of Engineering, Hokkaido University, Kita-13 Jo, Nishi-8 Chome, Kita-ku, Sapporo 060-8628 (Japan)]. E-mail: seo@elechem1-mc.eng.hokudai.ac.jp; Yamaya, Tadafumi [Graduate School of Engineering, Hokkaido University, Kita-13 Jo, Nishi-8 Chome, Kita-ku, Sapporo 060-8628 (Japan)

    2005-11-10

    The selective formation of porous layer on n-type InP (001) surface was investigated by using scratching with a diamond scriber followed by anodic etching in deaerated 0.5M HCl. Since the InP specimen was highly doped, the anodic etching proceeded in the dark. The potentiodynamic polarization showed the anodic current shoulder in the potential region between 0.8 and 1.3V (SHE) for the scratched area in addition to the anodic current peak at 1.7V (SHE) for the intact area. The selective formation of porous layer on the scratched are was brought by the anodic etching at a constant potential between 1.0 and 1.2V (SHE) for a certain time. The nucleation and growth of etch pits on intact area, however, took place when the time passed the critical value. The cross section of porous layer on the scratched area perpendicular to the [1-bar 10] or [110] scratching direction had a V-shape, while the cross section of porous layer on the scratched area parallel to the [1-bar 10] or [110] scratching direction had a band structure with stripes oriented to the [1-bar 11] or [11-bar 1] direction. Moreover, nano-scratching at a constant normal force in the micro-Newton range followed by anodic etching showed the possibility for selective formation of porous wire with a nano-meter width.

  4. Analyzing the propagation behavior of coherence and polarization degrees of a phase-locked partially coherent radial flat-topped array laser beam in underwater turbulence.

    Science.gov (United States)

    Kashani, Fatemeh Dabbagh; Yousefi, Masoud

    2016-08-10

    In this research, based on an analytical expression for cross-spectral density (CSD) matrix elements, coherence and polarization properties of phase-locked partially coherent flat-topped (PCFT) radial array laser beams propagating through weak oceanic turbulence are analyzed. Spectral degrees of coherence and polarization are analytically calculated using CSD matrix elements. Also, the effective width of spatial degree of coherence (EWSDC) is calculated numerically. The simulation is done by considering the effects of source parameters (such as radius of the array setup's circle, effective width of the spectral degree of coherence, and wavelength) and turbulent ocean factors (such as the rate of dissipation of the turbulent kinetic energy per unit mass of fluid and relative strength of temperature and salinity fluctuations, Kolmogorov micro-scale, and rate of dissipation of the mean squared temperature) in detail. Results indicate that any change in the amount of turbulence factors that increase the turbulence power reduces the EWSDC significantly and causes the reduction in the degree of polarization, and occurs at shorter propagation distances but with smaller magnitudes. In addition, being valid for all conditions, the degradation rate of the EWSDC of Gaussian array beams are more in comparison with the PCFT ones. The simulation and calculation results are shown by graphs.

  5. Electrochemical corrosion behaviors of the X90 linepipe steel in NS4 solution

    Directory of Open Access Journals (Sweden)

    Jinheng Luo

    2016-10-01

    Full Text Available Oil and gas line pipes are laid underground and run through different areas in the laying process, so they will be subjected to different degrees of corrosion and even crack, leading to enormous casualties and economic losses. In order to guarantee the safe operation of line pipes, therefore, it is significant to investigate the electrochemical corrosion behaviors of pipe steel in a simulated soil environment. In this paper, the electrochemical corrosion behaviors of the base metals and welding materials of API 5L X90 steel longitudinally submerged arc welding pipes in near-neutral simulated soil solution (NS4 were studied by means of the electrochemical impedance spectroscopy (EIS and the potentiodynamic polarization testing technology. It is shown that the typical characteristic of anodic dissolution is presented but with no passivation phenomenon when X90 linepipe steel is put in NS4 solution. The base material is thermodynamically more stable than the seam weld material. The base material and seam weld samples were polarized under −850 mV polarization potential for different durations. It is demonstrated that with the proceeding of polarization, the polarization resistance and the corrosion resistance increase while the corrosion current density decreases. And the corrosion resistance of base material is better than that of seam weld material.

  6. Behaviorism

    Science.gov (United States)

    Moore, J.

    2011-01-01

    Early forms of psychology assumed that mental life was the appropriate subject matter for psychology, and introspection was an appropriate method to engage that subject matter. In 1913, John B. Watson proposed an alternative: classical S-R behaviorism. According to Watson, behavior was a subject matter in its own right, to be studied by the…

  7. Effect of microstructure on corrosion behavior of Ag-30Cu-27Sn alloy in vitro media

    International Nuclear Information System (INIS)

    Salehisaki, Mehdi; Aryana, Maryam

    2014-01-01

    Highlights: • High cooling rates decrease the number of Ag intermetallic particles in Cu-rich phase. • Increasing cooling rate improves corrosion behavior of Ag-30Cu-27Sn dental alloy. • Cathode/anode ratio in Cu-rich phases determines the corrosion behavior of alloy. - Abstract: In the present work, three simple heat treatment cycles were used to study the effects of microstructure on electrochemical corrosion behavior of Ag-30Cu-27Sn dental alloy. The electrochemical impedance spectroscopy (EIS) measurements and potentiodynamic polarization tests were carried out to investigate the corrosion behavior of as-cast and heat treated samples in synthetic saliva solution. The presence of intermetallic compounds were studied by X-ray diffraction method (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray detector (EDAX). The microstructural observations and electrochemical corrosion results revealed that, increasing the cooling rate improves the corrosion behavior of under investigation samples. Improvement of the corrosion behavior is attributed to reducing the area of fine distributed Ag 3 Sn islands in the Cu-rich matrix which decrease the cathode/anode ratio of microgalvanic cells

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

    OpenAIRE

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

    2015-01-01

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

  9. Effect of Anode Dielectric Coating on Hall Thruster Operation

    International Nuclear Information System (INIS)

    Dorf, L.; Raitses, Y.; Fisch, N.J.; Semenov, V.

    2003-01-01

    An interesting phenomenon observed in the near-anode region of a Hall thruster is that the anode fall changes from positive to negative upon removal of the dielectric coating, which is produced on the anode surface during the normal course of Hall thruster operation. The anode fall might affect the thruster lifetime and acceleration efficiency. The effect of the anode coating on the anode fall is studied experimentally using both biased and emissive probes. Measurements of discharge current oscillations indicate that thruster operation is more stable with the coated anode

  10. Electrical and Mechanical Performance of Carbon Fiber-Reinforced Polymer Used as the Impressed Current Anode Material

    Directory of Open Access Journals (Sweden)

    Ji-Hua Zhu

    2014-07-01

    Full Text Available An investigation was performed by using carbon fiber-reinforced polymer (CFRP as the anode material in the impressed current cathodic protection (ICCP system of steel reinforced concrete structures. The service life and performance of CFRP were investigated in simulated ICCP systems with various configurations. Constant current densities were maintained during the tests. No significant degradation in electrical and mechanical properties was found for CFRP subjected to anodic polarization with the selected applied current densities. The service life of the CFRP-based ICCP system was discussed based on the practical reinforced concrete structure layout.

  11. Electrical and Mechanical Performance of Carbon Fiber-Reinforced Polymer Used as the Impressed Current Anode Material.

    Science.gov (United States)

    Zhu, Ji-Hua; Zhu, Miaochang; Han, Ningxu; Liu, Wei; Xing, Feng

    2014-07-24

    An investigation was performed by using carbon fiber-reinforced polymer (CFRP) as the anode material in the impressed current cathodic protection (ICCP) system of steel reinforced concrete structures. The service life and performance of CFRP were investigated in simulated ICCP systems with various configurations. Constant current densities were maintained during the tests. No significant degradation in electrical and mechanical properties was found for CFRP subjected to anodic polarization with the selected applied current densities. The service life of the CFRP-based ICCP system was discussed based on the practical reinforced concrete structure layout.

  12. Low voltage aluminium anodes. Optimization of the insert-anode bond

    Energy Technology Data Exchange (ETDEWEB)

    Le Guyader, Herve; Debout, Valerie; Grolleau, Anne-Marie [DCN Cherbourg, Departement 2EI, Place Bruat, BP 440, 50104 Cherbourg-Octeville (France); Pautasso, Jean-Pierre [DGA/CTA 16 bis, avenue Prieur de la Cote D' Or, 94 114 Arcueil Cedex (France)

    2004-07-01

    Zinc or Al/Zn/In sacrificial anodes are widely used to protect submerged marine structures from corrosion. Their Open Circuit Potential range from - 1 V vs. Ag/AgCl for Zn anodes to -1.1 V vs. Ag/AgCl for Al/Zn/In. These potentials are sufficiently electronegative as to reduce the threshold for stress corrosion cracking and/or hydrogen embrittlement, KISCC, especially in the presence of high strength alloys. In the 90's, an extensive research programme was initiated by DGA/DCN to implement a new low voltage material. Laboratory and full scale marine tests performed on industrial castings, as previously reported, led to the development of a new patented Al- 0.1%Ga alloy having a working potential of - 0.80 to - 0.83 V vs. Ag/AgCl. This alloy was also evaluated at full scale at the Naval Research Laboratory anode qualification site in Key West, Fl, and gave satisfactory results. Around 500 cylindrical AlGa anodes were then installed on a submerged marine structure replacing the classical zinc anode. A first inspection, carried out after a few months of service, showed that some of the anodes had not operated as expected, which led to further investigations. The examinations performed indicated that the problem was due to a bad metallurgical compatibility between the insert and the sacrificial materials inducing a poor bond between the anode and the plain rod insert. Progressive loss of contact between the anode and the structure to be protected was then induced by penetration of sea water and corrosion at the anode-insert interface. This phenomenon was aggravated by seawater pressure. Additional studies were therefore launched with two aims: (1) find temporary remedies for the anodes already installed on the structure; (2) correct the anode original design and/or manufacturing process to achieve the maximum performance on new anodes lots. This paper describes the various solutions investigated to improve the insert-anode bond: design of the anode, rugosity and

  13. EFFECT OF PHOSPHORIC ACID CONCENTRATION AND ANODIZING TIME ON THE PROPERTIES OF ANODIC FILMS ON TITANIUM

    Directory of Open Access Journals (Sweden)

    DIMAS L. TORRES

    2015-07-01

    Full Text Available In this study, it was investigated the influence of electrolyte concentration and anodizing time on the electrochemical behaviour and morphology of anodic films formed on commercially pure Ti. Electrochemical methods and surface analyses were used to characterize the films. It was found that the electrolyte concentration and anodizing time affect the growth and protective characteristics of films in a physiologic medium. It was possible to observe their non-uniformity on Ti substrates under the tested conditions. In potentiodynamic profiles, it was observed that passivation current values are affected by an anodizing time increase. Variations in impedance spectra were associated with an increase of defects within the film.

  14. Structural Engineering of Nanoporous Anodic Alumina Photonic Crystals by Sawtooth-like Pulse Anodization.

    Science.gov (United States)

    Law, Cheryl Suwen; Santos, Abel; Nemati, Mahdieh; Losic, Dusan

    2016-06-01

    This study presents a sawtooth-like pulse anodization approach aiming to create a new type of photonic crystal structure based on nanoporous anodic alumina. This nanofabrication approach enables the engineering of the effective medium of nanoporous anodic alumina in a sawtooth-like manner with precision. The manipulation of various anodization parameters such as anodization period, anodization amplitude, number of anodization pulses, ramp ratio and pore widening time allows a precise control and fine-tuning of the optical properties (i.e., characteristic transmission peaks and interferometric colors) exhibited by nanoporous anodic alumina photonic crystals (NAA-PCs). The effect of these anodization parameters on the photonic properties of NAA-PCs is systematically evaluated for the establishment of a fabrication methodology toward NAA-PCs with tunable optical properties. The effective medium of the resulting NAA-PCs is demonstrated to be optimal for the development of optical sensing platforms in combination with reflectometric interference spectroscopy (RIfS). This application is demonstrated by monitoring in real-time the formation of monolayers of thiol molecules (11-mercaptoundecanoic acid) on the surface of gold-coated NAA-PCs. The obtained results reveal that the adsorption mechanism between thiol molecules and gold-coated NAA-PCs follows a Langmuir isotherm model, indicating a monolayer sorption mechanism.

  15. Masking of aluminum surface against anodizing

    Science.gov (United States)

    Crawford, G. B.; Thompson, R. E.

    1969-01-01

    Masking material and a thickening agent preserve limited unanodized areas when aluminum surfaces are anodized with chromic acid. For protection of large areas it combines well with a certain self-adhesive plastic tape.

  16. Electrometallurgy of copper refinery anode slimes

    Science.gov (United States)

    Scott, J. D.

    1990-08-01

    High-selenium copper refinery anode slimes form two separate and dynamically evolving series of compounds with increasing electrolysis time. In one, silver is progressively added to non-stoichiometric copper selenides, both those originally present in the anode and those formed subsequently in the slime layer, and in the other, silver-poor copper selenides undergo a dis-continuous crystallographic sequence of anodic-oxidative transformations. The silver-to-selenium molar ratio in the as-cast anode and the current density of electrorefining can be used to construct predominance diagrams for both series and, thus, to predict the final bulk “mineralogy” of the slimes. Although totally incorrect in detail, these bulk data are sufficiently accurate to provide explanations for several processing problems which have been experienced by Kidd Creek Division, Falconbridge Ltd., in its commercial tankhouse. They form the basis for a computer model which predicts final cathode quality from chemical analyses of smelter feed.

  17. Pilot demonstration of cerium oxide coated anodes

    Energy Technology Data Exchange (ETDEWEB)

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

    1992-10-01

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

  18. Lithium Ion Battery Anode Aging Mechanisms

    Science.gov (United States)

    Agubra, Victor; Fergus, Jeffrey

    2013-01-01

    Degradation mechanisms such as lithium plating, growth of the passivated surface film layer on the electrodes and loss of both recyclable lithium ions and electrode material adversely affect the longevity of the lithium ion battery. The anode electrode is very vulnerable to these degradation mechanisms. In this paper, the most common aging mechanisms occurring at the anode during the operation of the lithium battery, as well as some approaches for minimizing the degradation are reviewed. PMID:28809211

  19. Anodic growth of titanium dioxide nanostructures

    DEFF Research Database (Denmark)

    2010-01-01

    Disclosed is a method of producing nanostructures of titanium dioxide (TiO 2 ) by anodisation of titanium (Ti) in an electrochemical cell, comprising the steps of: immersing a non-conducting substrate coated with a layer of titanium, defined as the anode, in an electrolyte solution...... an electrical contact to the layer of titanium on the anode, where the electrical contact is made in the electrolyte solution...

  20. Electrochemical behavior of rare earth metals and their nitrides

    International Nuclear Information System (INIS)

    Ito, Yasuhiko; Goto, Takuya

    2004-01-01

    Pyrometallurgical recycle process using molten salts is considered to be a high potential in pyro-reprocess technologies for spent nitride fuels, and it is important to understand chemical and electro-chemical behavior of nitrides and metals in molten salts. In this study, cadmium nitrates deposited on the anode Cd plate in motlen salt (LiCl-KCl) with addition of Li 3 N are examined. The cadmium nitrates deposited have various compositions corresponding to polarization potentials and then, the relationship between the deposition potential of nitride Cd and their composition is cleared. Their standard chemical potential of CdN is estimated from electrochemical measurement. And then, potential-pH 3- diagram is drawn by voltametry examination of nitride resolution behavior with using thermochemical data of nitrides. (A. Hishinuma)

  1. 3D Microstructure Effects in Ni-YSZ Anodes: Influence of TPB Lengths on the Electrochemical Performance

    Directory of Open Access Journals (Sweden)

    Omar M. Pecho

    2015-10-01

    Full Text Available 3D microstructure-performance relationships in Ni-YSZ anodes for electrolyte-supported cells are investigated in terms of the correlation between the triple phase boundary (TPB length and polarization resistance (Rpol. Three different Ni-YSZ anodes of varying microstructure are subjected to eight reduction-oxidation (redox cycles at 950 °C. In general the TPB lengths correlate with anode performance. However, the quantitative results also show that there is no simplistic relationship between TPB and Rpol. The degradation mechanism strongly depends on the initial microstructure. Finer microstructures exhibit lower degradation rates of TPB and Rpol. In fine microstructures, TPB loss is found to be due to Ni coarsening, while in coarse microstructures reduction of active TPB results mainly from loss of YSZ percolation. The latter is attributed to weak bottlenecks associated with lower sintering activity of the coarse YSZ. The coarse anode suffers from complete loss of YSZ connectivity and associated drop of TPBactive by 93%. Surprisingly, this severe microstructure degradation did not lead to electrochemical failure. Mechanistic scenarios are discussed for different anode microstructures. These scenarios are based on a model for coupled charge transfer and transport, which allows using TPB and effective properties as input. The mechanistic scenarios describe the microstructure influence on current distributions, which explains the observed complex relationship between TPB lengths and anode performances. The observed loss of YSZ percolation in the coarse anode is not detrimental because the electrochemical activity is concentrated in a narrow active layer. The anode performance can be predicted reliably if the volume-averaged properties (TPBactive, effective ionic conductivity are corrected for the so-called short-range effect, which is particularly important in cases with a narrow active layer.

  2. 3D Microstructure Effects in Ni-YSZ Anodes: Influence of TPB Lengths on the Electrochemical Performance.

    Science.gov (United States)

    Pecho, Omar M; Mai, Andreas; Münch, Beat; Hocker, Thomas; Flatt, Robert J; Holzer, Lorenz

    2015-10-21

    3D microstructure-performance relationships in Ni-YSZ anodes for electrolyte-supported cells are investigated in terms of the correlation between the triple phase boundary (TPB) length and polarization resistance ( R pol ). Three different Ni-YSZ anodes of varying microstructure are subjected to eight reduction-oxidation (redox) cycles at 950 °C. In general the TPB lengths correlate with anode performance . However, the quantitative results also show that there is no simplistic relationship between TPB and R pol . The degradation mechanism strongly depends on the initial microstructure. Finer microstructures exhibit lower degradation rates of TPB and R pol . In fine microstructures, TPB loss is found to be due to Ni coarsening, while in coarse microstructures reduction of active TPB results mainly from loss of YSZ percolation. The latter is attributed to weak bottlenecks associated with lower sintering activity of the coarse YSZ. The coarse anode suffers from complete loss of YSZ connectivity and associated drop of TPB active by 93%. Surprisingly, this severe microstructure degradation did not lead to electrochemical failure. Mechanistic scenarios are discussed for different anode microstructures. These scenarios are based on a model for coupled charge transfer and transport, which allows using TPB and effective properties as input. The mechanistic scenarios describe the microstructure influence on current distributions, which explains the observed complex relationship between TPB lengths and anode performances. The observed loss of YSZ percolation in the coarse anode is not detrimental because the electrochemical activity is concentrated in a narrow active layer. The anode performance can be predicted reliably if the volume-averaged properties (TPB active , effective ionic conductivity) are corrected for the so-called short-range effect, which is particularly important in cases with a narrow active layer.

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

    Science.gov (United States)

    Miller, Elizabeth C.

    (SLT) anode supports, thin La1--xSr x Ga0.8Mg0.2O3 (x = 0.1, 0.2) dense electrolytes, and porous LSGM anode functional layers. The SLT support and the LSGM functional layer are infiltrated with nanoscale Ni, creating extensive electrochemically active triple phase boundary area. The scope of the work presented here encompasses every step of cell development including powder synthesis, optimization of firing conditions, and long-term stability testing. Using an optimized fabrication process, cells with power density > 1.2 W cm-2 were fabricated. Dry pressing and colloidal de-position were used to make the first generation of these cells, and once suitable times and temperatures were determined, the process was shifted to tape casting to make larger batches of uniform cells. After obtaining initial results of low anode polarization resistance and high power density, the long-term stability of the Ni-infiltrated anodes was examined. A coarsening model was developed using the data from accelerated degradation tests to predict cell performance over a typical device lifetime. This thesis encompasses a broad range of novel SOFC anode materials, each of which has its own strengths and weaknesses. Presenting several possible avenues for SOFC development provides a complete picture of the ?eld and its current focuses. The wide scope of this work offers multiple solutions for the SOFC community and demonstrates that SOFCs are a strong candidate for meeting the United States' need for energy conversion and storage.

  4. Multi-anode deep well radiation detector

    International Nuclear Information System (INIS)

    Rogers, A.H.; Sullivan, K.J.; Mansfield, G.R.

    1984-01-01

    An inner cylindrical cathode and outer cylindrical cathode are concentrically positioned about a vertical center axis. Vertical anode electrodes extend parallel to the center axis and are symmetrically arranged around the inter-cylinder space between the cathodes. The ends of the anode wires are supported by a pair of insulator rings and mounted near the top and bottom of the cathode cylinders. A collection voltage applied to each anode wire for establishing an inward radial E field to the inner cathode cylinder and an outward radial E field to the outer cathode cylinder. The anode-cathode assembly is mounted within a housing containing a conversion gas. A radioactive sample is inserted into the inner cathode which functions as a tubular, deep well radiation window between the sample environment and the conversion gas environment. A portion of the gamma radiations passing through the inter-cylinder region interact with the conversion gas to produce free electrons which are accelerated by the E fields and collected on the anode wires. The extremely small diameter of the anode wires intensifies the electric fields proximate each wire causing avalanche multiplication of the free electrons resulting in a detectable charge pulse. (author)

  5. Nuclear polarization and neutrons

    International Nuclear Information System (INIS)

    Glaettli, H.

    1985-01-01

    Different possibilities for the use of polarized nuclei in thermal neutron scattering on condensed matter are reviewed. Highly polarized nuclei are the starting point for studying dipolar magnetic order. Systematic measurement of spin-dependent scattering lengths is possible on samples with polarized nuclei. Highly polarized hydrogen should help to unravel complicated structures in chemistry and biology. The use of polarized proton targets as an energy-independent neutron polarizer in the thermal and epithermal region should be considered afresh. (author)

  6. An Auger electron spectroscopy study on the anodization process of high-quality thin-film capacitors made of hafnium

    International Nuclear Information System (INIS)

    Noya, Atsushi; Sasaki, Katsutaka; Umezawa, Toshiji

    1989-01-01

    Formation process of the anodic oxide film of hafnium for use as a thin-film capacitor has been examined by the current-voltage characteristics of the anodization and the in-depth analysis of formed oxide using Auger electron spectroscopy. It is found that the oxide growth obeys three different rate laws such as the linear rate law at first and next the parabolic rate law during the constant current anodization, and then the reciprocal logarithmic rate law during the constant voltage anodization following after the constant current process. From the Auger electron spectroscopy analysis, it is found that the shape of the compositional depth profile of the grown oxide film varies associating with the rate law of oxidation obeyed. The variation of depth profile correlating with the rate law is discussed with respect to each elementary process such as the transport and/or the reaction of chemical species interpreted from the over-all behavior of anodization process. It is revealed that the stoichiometric film having an interface with sharp transition, which is favorable for obtaining excellent electrical properties of the capacitor, can be obtained under the condition that the phase-boundary reaction is the rate-determining step of the anodization. The constant voltage anodization process also satisfies such circumstances and therefore can be favorable method for preparing highquality thin-film capacitors. (author)

  7. Analysis of carbon fiber brush loading in anodes on startup and performance of microbial fuel cells

    KAUST Repository

    Hutchinson, Adam J.

    2011-11-01

    Flat carbon anodes placed near a cathode in a microbial fuel cell (MFC) are adversely affected by oxygen crossover, but graphite fiber brush anodes placed near the cathode produce high power densities. The impact of the brush size and electrode spacing was examined by varying the distance of the brush end from the cathode and solution conductivity in multiple MFCs. The startup time was increased from 8 ± 1 days with full brushes (all buffer concentrations) to 13 days (50 mM), 14 days (25 mM) and 21 days (8 mM) when 75% of the brush anode was removed. When MFCs were all first acclimated with a full brush, up to 65% of the brush material could be removed without appreciably altering maximum power. Electrochemical impedance spectroscopy (EIS) showed that the main source of internal resistance (IR) was diffusion resistance, which together with solution resistance reached 100 Ω. The IR using EIS compared well with that obtained using the polarization data slope method, indicating no major components of IR were missed. These results show that using full brush anodes avoids adverse effects of oxygen crossover during startup, although brushes are much larger than needed to sustain high power. © 2011 Elsevier B.V.

  8. Controlling the occurrence of power overshoot by adapting microbial fuel cells to high anode potentials

    KAUST Repository

    Zhu, Xiuping

    2013-04-01

    Power density curves for microbial fuel cells (MFCs) often show power overshoot, resulting in inaccurate estimation of MFC performance at high current densities. The reasons for power overshoot are not well understood, but biofilm acclimation and development are known factors. In order to better explore the reasons for power overshoot, exoelectrogenic biofilms were developed at four different anode potentials (-0.46 V, -0.24 V, 0 V, and 0.50 V vs. Ag/AgCl), and then the properties of the biofilms were examined using polarization tests and cyclic voltammetry (CV). The maximum power density of the MFCs was 1200±100 mW/m2. Power overshoot was observed in MFCs incubated at -0.46 V, but not those acclimated atmore positive potentials, indicating that bacterial activitywas significantly influenced by the anode acclimation potential. CV results further indicated that power overshoot of MFCs incubated at the lowest anode potential was associatedwith a decreasing electroactivity of the anodic biofilm in the high potential region,which resulted from a lack of sufficient electron transfer components to shuttle electrons at rates needed for these more positive potentials. © 2012 Elsevier B.V.

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

    Science.gov (United States)

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

    2015-10-13

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

  10. Hierarchically ordered self-lubricating superhydrophobic anodized aluminum surfaces with enhanced corrosion resistance.

    Science.gov (United States)

    Vengatesh, Panneerselvam; Kulandainathan, Manickam Anbu

    2015-01-28

    Herein, we report a facile method for the fabrication of self-lubricating superhydrophobic hierarchical anodic aluminum oxide (AAO) surfaces with improved corrosion protection, which is greatly anticipated to have a high impact in catalysis, aerospace, and the shipping industries. This method involves chemical grafting of as-formed AAO using low surface free energy molecules like long chain saturated fatty acids, perfluorinated fatty acid (perfluorooctadecanoic acid, PFODA), and perfluorosulfonicacid-polytetrafluoroethylene copolymer. The pre and post treatment processes in the anodization of aluminum (Al) play a vital role in the grafting of fatty acids. Wettability and surface free energy were analyzed using a contact angle meter and achieved 161.5° for PFODA grafted anodized aluminum (PFODA-Al). This study was also aimed at evaluating the surface for corrosion resistance by Tafel polarization and self-lubricating properties by tribological studies using a pin-on-disc tribometer. The collective results showed that chemically grafted AAO nanostructures exhibit high corrosion resistance toward seawater and low frictional coefficient due to low surface energy and self-lubricating property of fatty acids covalently linked to anodized Al surfaces.

  11. Analysis of carbon fiber brush loading in anodes on startup and performance of microbial fuel cells

    KAUST Repository

    Hutchinson, Adam J.; Tokash, Justin C.; Logan, Bruce E.

    2011-01-01

    Flat carbon anodes placed near a cathode in a microbial fuel cell (MFC) are adversely affected by oxygen crossover, but graphite fiber brush anodes placed near the cathode produce high power densities. The impact of the brush size and electrode spacing was examined by varying the distance of the brush end from the cathode and solution conductivity in multiple MFCs. The startup time was increased from 8 ± 1 days with full brushes (all buffer concentrations) to 13 days (50 mM), 14 days (25 mM) and 21 days (8 mM) when 75% of the brush anode was removed. When MFCs were all first acclimated with a full brush, up to 65% of the brush material could be removed without appreciably altering maximum power. Electrochemical impedance spectroscopy (EIS) showed that the main source of internal resistance (IR) was diffusion resistance, which together with solution resistance reached 100 Ω. The IR using EIS compared well with that obtained using the polarization data slope method, indicating no major components of IR were missed. These results show that using full brush anodes avoids adverse effects of oxygen crossover during startup, although brushes are much larger than needed to sustain high power. © 2011 Elsevier B.V.

  12. Anodized aluminum on LDEF: A current status of measurements on chromic acid anodized aluminum

    International Nuclear Information System (INIS)

    Golden, J.L.

    1992-01-01

    Chromic acid anodize was used as the exterior coating for aluminum surfaces on LDEF to provide passive thermal control. Chromic acid anodized aluminum was also used as test specimens in thermal control coatings experiments. The following is a compilation and analysis of the data obtained thus far

  13. Anodized aluminum on LDEF: A current status of measurements on chromic acid anodized aluminum

    Science.gov (United States)

    Golden, Johnny L.

    1992-01-01

    Chromic acid anodize was used as the exterior coating for aluminum surfaces on LDEF to provide passive thermal control. Chromic acid anodized aluminum was also used as test specimens in thermal control coatings experiments. The following is a compilation and analysis of the data obtained thus far.

  14. Anode pattern formation in atmospheric pressure air glow discharges with water anode

    NARCIS (Netherlands)

    Verreycken, T.; Bruggeman, P.J.; Leys, C.

    2009-01-01

    Pattern formation in the anode layer at a water electrode in atmospheric pressure glow discharges in air is studied. With increasing current a sequence of different anode spot structures occurs from a constricted homogeneous spot in the case of small currents to a pattern consisting of small

  15. Neutron polarization in polarized 3He targets

    International Nuclear Information System (INIS)

    Friar, J.L.; Gibson, B.F.; Payne, G.L.; Bernstein, A.M.; Chupp, T.E.

    1990-01-01

    Simple formulas for the neutron and proton polarizations in polarized 3 He targets are derived assuming (1) quasielastic final states; (2) no final-state interactions; (3) no meson-exchange currents; (4) large momentum transfers; (5) factorizability of 3 He SU(4) response-function components. Numerical results from a wide variety of bound-state solutions of the Faddeev equations are presented. It is found that this simple model predicts the polarization of neutrons in a fully polarized 3 He target to be 87%, while protons should have a slight residual polarization of -2.7%. Numerical studies show that this model works very well for quasielastic electron scattering

  16. The impact of steam and current density on carbon formation from biomass gasification tar on Ni/YSZ, and Ni/CGO solid oxide fuel cell anodes

    Science.gov (United States)

    Mermelstein, Joshua; Millan, Marcos; Brandon, Nigel

    The combination of solid oxide fuel cells (SOFCs) and biomass gasification has the potential to become an attractive technology for the production of clean renewable energy. However the impact of tars, formed during biomass gasification, on the performance and durability of SOFC anodes has not been well established experimentally. This paper reports an experimental study on the mitigation of carbon formation arising from the exposure of the commonly used Ni/YSZ (yttria stabilized zirconia) and Ni/CGO (gadolinium-doped ceria) SOFC anodes to biomass gasification tars. Carbon formation and cell degradation was reduced through means of steam reforming of the tar over the nickel anode, and partial oxidation of benzene model tar via the transport of oxygen ions to the anode while operating the fuel cell under load. Thermodynamic calculations suggest that a threshold current density of 365 mA cm -2 was required to suppress carbon formation in dry conditions, which was consistent with the results of experiments conducted in this study. The importance of both anode microstructure and composition towards carbon deposition was seen in the comparison of Ni/YSZ and Ni/CGO anodes exposed to the biomass gasification tar. Under steam concentrations greater than the thermodynamic threshold for carbon deposition, Ni/YSZ anodes still exhibited cell degradation, as shown by increased polarization resistances, and carbon formation was seen using SEM imaging. Ni/CGO anodes were found to be more resilient to carbon formation than Ni/YSZ anodes, and displayed increased performance after each subsequent exposure to tar, likely due to continued reforming of condensed tar on the anode.

  17. Sulfur poisoning of Ni/Gadolinium-doped ceria anodes: A long-term study outlining stable solid oxide fuel cell operation

    Science.gov (United States)

    Riegraf, Matthias; Zekri, Atef; Knipper, Martin; Costa, Rémi; Schiller, Günter; Friedrich, K. Andreas

    2018-03-01

    This work presents an analysis of the long-term behavior of nickel/gadolinium-doped ceria (CGO) anode-based solid oxide fuel cells (SOFC) under sulfur poisoning conditions. A parameter study of sulfur-induced irreversible long-term degradation of commercial, high-performance single cells was carried out at 900 °C for different H2/N2/H2S fuel gas atmospheres, current densities and Ni/CGO anodes. The poisoning periods of the cells varied from 200 to 1500 h. The possibility of stable long-term Ni/CGO anode operation under sulfur exposure is established and the critical operating regime is outlined. Depending on the operating conditions, two degradation phenomena can be observed. Small degradation of the ohmic resistance was witnessed for sulfur exposure times of approximately 1000 h. Moreover, degradation of the anode charge transfer resistance was observed to be triggered by the combination of a small anodic potential step and high sulfur coverage on Ni. The microstructural evolution of altered Ni/CGO anodes was examined post-mortem by means of SEM and FIB/SEM, and is correlated to the anode performance degradation under critical operating conditions, establishing Ni depletion, porosity increase and a tripe phase boundary density decrease in the anode functional layer. It is shown that short-term sulfur poisoning behavior can be used to assess long-term stability.

  18. Modification of diode characteristics by electron back-scatter from high-atomic-number anodes

    International Nuclear Information System (INIS)

    Mosher, D.; Cooperstein, G.; Rose, D.V.; Swanekamp, S.B.

    1996-01-01

    In high-power vacuum diodes with high-atomic-number anodes, back-scattered electrons alter the vacuum space charge and resulting electron and ion currents. Electron multiple back-scattering was studied through equilibrium solutions of the Poisson equation for 1-dimensional, bipolar diodes in order to predict their early-time behavior. Before ion turn-on, back-scattered electrons from high-Z anodes suppress the diode current by about 10%. After ion turn-on in the same diodes, electron back-scatter leads to substantial enhancements of both the electron and ion currents above the Child-Langmuir values. Current enhancements with ion flow from low-Z anodes are small. (author). 5 figs., 7 refs

  19. Morphological evolution of porous nanostructures grown from a single isolated anodic alumina nanochannel

    Science.gov (United States)

    Chen, Shih-Yung; Chang, Hsuan-Hao; Lai, Ming-Yu; Liu, Chih-Yi; Wang, Yuh-Lin

    2011-09-01

    Porous anodic aluminum oxide (AAO) membranes have been widely used as templates for growing nanomaterials because of their ordered nanochannel arrays with high aspect ratio and uniform pore diameter. However, the intrinsic growth behavior of an individual AAO nanochannel has never been carefully studied for the lack of a means to fabricate a single isolated anodic alumina nanochannel (SIAAN). In this study, we develop a lithographic method for fabricating a SIAAN, which grows into a porous hemispherical structure with its pores exhibiting fascinating morphological evolution during anodization. We also discover that the mechanical stress affects the growth rate and pore morphology of AAO porous structures. This study helps reveal the growth mechanism of arrayed AAO nanochannels grown on a flat aluminum surface and provides insights to help pave the way to altering the geometry of nanochannels on AAO templates for the fabrication of advanced nanocomposite materials.

  20. Morphological evolution of porous nanostructures grown from a single isolated anodic alumina nanochannel

    International Nuclear Information System (INIS)

    Chen, Shih-Yung; Wang, Yuh-Lin; Chang, Hsuan-Hao; Lai, Ming-Yu; Liu, Chih-Yi

    2011-01-01

    Porous anodic aluminum oxide (AAO) membranes have been widely used as templates for growing nanomaterials because of their ordered nanochannel arrays with high aspect ratio and uniform pore diameter. However, the intrinsic growth behavior of an individual AAO nanochannel has never been carefully studied for the lack of a means to fabricate a single isolated anodic alumina nanochannel (SIAAN). In this study, we develop a lithographic method for fabricating a SIAAN, which grows into a porous hemispherical structure with its pores exhibiting fascinating morphological evolution during anodization. We also discover that the mechanical stress affects the growth rate and pore morphology of AAO porous structures. This study helps reveal the growth mechanism of arrayed AAO nanochannels grown on a flat aluminum surface and provides insights to help pave the way to altering the geometry of nanochannels on AAO templates for the fabrication of advanced nanocomposite materials.

  1. Modification of diode characteristics by electron back-scatter from high-atomic-number anodes

    Energy Technology Data Exchange (ETDEWEB)

    Mosher, D; Cooperstein, G [Naval Research Laboratory, Washington, DC (United States); Rose, D V; Swanekamp, S B [JAYCOR, Vienna, VA (United States)

    1997-12-31

    In high-power vacuum diodes with high-atomic-number anodes, back-scattered electrons alter the vacuum space charge and resulting electron and ion currents. Electron multiple back-scattering was studied through equilibrium solutions of the Poisson equation for 1-dimensional, bipolar diodes in order to predict their early-time behavior. Before ion turn-on, back-scattered electrons from high-Z anodes suppress the diode current by about 10%. After ion turn-on in the same diodes, electron back-scatter leads to substantial enhancements of both the electron and ion currents above the Child-Langmuir values. Current enhancements with ion flow from low-Z anodes are small. (author). 5 figs., 7 refs.

  2. New High-Energy Nanofiber Anode Materials

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiangwu [North Carolina State Univ., Raleigh, NC (United States); Fedkiw, Peter [North Carolina State Univ., Raleigh, NC (United States); Khan, Saad [North Carolina State Univ., Raleigh, NC (United States); Huang, Alex [North Carolina State Univ., Raleigh, NC (United States); Fan, Jiang [North Carolina State Univ., Raleigh, NC (United States)

    2013-11-15

    The overall goal of the proposed work was to use electrospinning technology to integrate dissimilar materials (lithium alloy and carbon) into novel composite nanofiber anodes, which simultaneously had high energy density, reduced cost, and improved abuse tolerance. The nanofiber structure allowed the anodes to withstand repeated cycles of expansion and contraction. These composite nanofibers were electrospun into nonwoven fabrics with thickness of 50 μm or more, and then directly used as anodes in a lithium-ion battery. This eliminated the presence of non-active materials (e.g., conducting carbon black and polymer binder) and resulted in high energy and power densities. The nonwoven anode structure also provided a large electrode-electrolyte interface and, hence, high rate capacity and good lowtemperature performance capability. Following are detailed objectives for three proposed project periods. During the first six months: Obtain anodes capable of initial specific capacities of 650 mAh/g and achieve ~50 full charge/discharge cycles in small laboratory scale cells (50 to 100 mAh) at the 1C rate with less than 20 percent capacity fade; In the middle of project period: Assemble, cycle, and evaluate 18650 cells using proposed anode materials, and demonstrate practical and useful cycle life (750 cycles of ~70% state of charge swing with less than 20% capacity fade) in 18650 cells with at least twice improvement in the specific capacity than that of conventional graphite electrodes; At the end of project period: Deliver 18650 cells containing proposed anode materials, and achieve specific capacities greater than 1200 mAh/g and cycle life longer than 5000 cycles of ~70% state of charge swing with less than 20% capacity fade.

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

    Energy Technology Data Exchange (ETDEWEB)

    Panizza, M.; Cerisola, G

    2003-10-15

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

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

    International Nuclear Information System (INIS)

    Panizza, M.; Cerisola, G.

    2003-01-01

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

  5. Performance of Mg-14Li-1Al-0.1Ce as anode for Mg-air battery

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yibin; Li, Deyu [School of Chemical Engineering and Technology, Harbin Institute of Technology, West Street No. 92, Harbin 150001 (China); Li, Ning [School of Chemical Engineering and Technology, Harbin Institute of Technology, West Street No. 92, Harbin 150001 (China); Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Zhang, Milin; Huang, Xiaomei [Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)

    2011-02-15

    In this research, a new Mg-air battery based on Mg-14Li-1Al-0.1Ce was prepared and the battery performance was investigated by constant current discharge test. The corrosion behavior of Mg, AZ31 and Mg-Li-Al-Ce were studied by self-corrosion rate measurement and potentiodynamic polarization measurement. The characteristics of Mg-Li-Al-Ce after discharge were investigated by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that Mg-Li-Al-Ce is more active than Mg and AZ31. The self-corrosion rate is found to be in the order: Mg-Li-Al-Ce < Mg < AZ31. It has been observed that the Mg-air battery based on Mg-Li-Al-Ce offers higher operating voltage, anodic efficiency and capacity than those with Mg and AZ31. SEM and EIS results show that the discharge product of Mg-Li-Al-Ce is loosely adhered to the alloy surface, and thus Mg-Li-Al-Ce could keep high discharge activity during discharge. (author)

  6. Structural study of anodic films formed on aluminum in nitric acid electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Yakovleva, N.M.; Anicai, L.; Yakovlev, A.N.; Dima, L.; Khanina, E.Ya.; Buda, M.; Chupakhina, E.A

    2002-09-02

    The paper presents the results of investigations of porous Al anodic films formed in HNO{sub 3} electrolytes carried out by means of electrochemical techniques and X-ray diffraction as well as scanning electron microscopy (SEM). It was assumed that both electrochemical formation of a porous oxide and anodic dissolution of metal take place at Al/oxide interface at the same time. The analysis of short-range order (SRO) parameters for relatively high current density, 1x10{sup 3} A/m{sup 2}, and anodizing time, 10 min, leads to the conclusion that films mainly consist of amorphous alumina with {gamma}'-Al{sub 2}O{sub 3}-like SRO and a small amount ({approx}10%) of amorphous aluminum oxyhydroxide. SEM investigation of the films revealed strong dependence of the surface relief on different applied forming conditions. This marked change in the surface relief is discussed taking into account the relatively complex behavior of Al during anodization in HNO{sub 3} electrolytes, that involves both electrochemical growth and dissolution processes of anodic film associated with an electrochemical dissolution of aluminum substrate.

  7. Structural study of anodic films formed on aluminum in nitric acid electrolyte

    International Nuclear Information System (INIS)

    Yakovleva, N.M.; Anicai, L.; Yakovlev, A.N.; Dima, L.; Khanina, E.Ya.; Buda, M.; Chupakhina, E.A.

    2002-01-01

    The paper presents the results of investigations of porous Al anodic films formed in HNO 3 electrolytes carried out by means of electrochemical techniques and X-ray diffraction as well as scanning electron microscopy (SEM). It was assumed that both electrochemical formation of a porous oxide and anodic dissolution of metal take place at Al/oxide interface at the same time. The analysis of short-range order (SRO) parameters for relatively high current density, 1x10 3 A/m 2 , and anodizing time, 10 min, leads to the conclusion that films mainly consist of amorphous alumina with γ'-Al 2 O 3 -like SRO and a small amount (∼10%) of amorphous aluminum oxyhydroxide. SEM investigation of the films revealed strong dependence of the surface relief on different applied forming conditions. This marked change in the surface relief is discussed taking into account the relatively complex behavior of Al during anodization in HNO 3 electrolytes, that involves both electrochemical growth and dissolution processes of anodic film associated with an electrochemical dissolution of aluminum substrate

  8. Porous aluminum room temperature anodizing process in a fluorinated-oxalic acid solution

    Science.gov (United States)

    Dhahri, S.; Fazio, E.; Barreca, F.; Neri, F.; Ezzaouia, H.

    2016-08-01

    Anodizing of aluminum is used for producing porous insulating films suitable for different applications in electronics and microelectronics. Porous-type aluminum films are most simply realized by galvanostatic anodizing in aqueous acidic solutions. The improvement in application of anodizing technique is associated with a substantial reduction of the anodizing voltage at appropriate current densities as well as to the possibility to carry out the synthesis process at room temperature in order to obtain a self-planarizing dielectric material incorporated in array of super-narrow metal lines. In this work, the anodizing of aluminum to obtain porous oxide was carried out, at room temperature, on three different substrates (glass, stainless steel and aluminum), using an oxalic acid-based electrolyte with the addition of a relatively low amount of 0.4 % of HF. Different surface morphologies, from nearly spherical to larger porous nanostructures with smooth edges, were observed by means of scanning electron microscopy. These evidences are explained by considering the formation, transport and adsorption of the fluorine species which react with the Al3+ ions. The behavior is also influenced by the nature of the original substrate.

  9. Dendrite-Free Sodium-Metal Anodes for High-Energy Sodium-Metal Batteries.

    Science.gov (United States)

    Sun, Bing; Li, Peng; Zhang, Jinqiang; Wang, Dan; Munroe, Paul; Wang, Chengyin; Notten, Peter H L; Wang, Guoxiu

    2018-05-31

    Sodium (Na) metal is one of the most promising electrode materials for next-generation low-cost rechargeable batteries. However, the challenges caused by dendrite growth on Na metal anodes restrict practical applications of rechargeable Na metal batteries. Herein, a nitrogen and sulfur co-doped carbon nanotube (NSCNT) paper is used as the interlayer to control Na nucleation behavior and suppress the Na dendrite growth. The N- and S-containing functional groups on the carbon nanotubes induce the NSCNTs to be highly "sodiophilic," which can guide the initial Na nucleation and direct Na to distribute uniformly on the NSCNT paper. As a result, the Na-metal-based anode (Na/NSCNT anode) exhibits a dendrite-free morphology during repeated Na plating and striping and excellent cycling stability. As a proof of concept, it is also demonstrated that the electrochemical performance of sodium-oxygen (Na-O 2 ) batteries using the Na/NSCNT anodes show significantly improved cycling performances compared with Na-O 2 batteries with bare Na metal anodes. This work opens a new avenue for the development of next-generation high-energy-density sodium-metal batteries. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-03

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

  12. Anodizing color coded anodized Ti6Al4V medical devices for increasing bone cell functions

    Directory of Open Access Journals (Sweden)

    Webster TJ

    2013-01-01

    Full Text Available Alexandra P Ross, Thomas J WebsterSchool of Engineering and Department of Orthopedics, Brown University, Providence, RI, USAAbstract: Current titanium-based implants are often anodized in sulfuric acid (H2SO4 for color coding purposes. However, a crucial parameter in selecting the material for an orthopedic implant is the degree to which it will integrate into the surrounding bone. Loosening at the bone–implant interface can cause catastrophic failure when motion occurs between the implant and the surrounding bone. Recently, a different anodization process using hydrofluoric acid has been shown to increase bone growth on commercially pure titanium and titanium alloys through the creation of nanotubes. The objective of this study was to compare, for the first time, the influence of anodizing a titanium alloy medical device in sulfuric acid for color coding purposes, as is done in the orthopedic implant industry, followed by anodizing the device in hydrofluoric acid to implement nanotubes. Specifically, Ti6Al4V model implant samples were anodized first with sulfuric acid to create color-coding features, and then with hydrofluoric acid to implement surface features to enhance osteoblast functions. The material surfaces were characterized by visual inspection, scanning electron microscopy, contact angle measurements, and energy dispersive spectroscopy. Human osteoblasts were seeded onto the samples for a series of time points and were measured for adhesion and proliferation. After 1 and 2 weeks, the levels of alkaline phosphatase activity and calcium deposition were measured to assess the long-term differentiation of osteoblasts into the calcium depositing cells. The results showed that anodizing in hydrofluoric acid after anodizing in sulfuric acid partially retains color coding and creates unique surface features to increase osteoblast adhesion, proliferation, alkaline phosphatase activity, and calcium deposition. In this manner, this study

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  14. Effect of Sn4+ Additives on the Microstructure and Corrosion Resistance of Anodic Coating Formed on AZ31 Magnesium Alloy in Alkaline Solution

    Science.gov (United States)

    Salman, S. A.; Kuroda, K.; Saito, N.; Okido, M.

    Magnesium is the lightest structural metal with high specific strength and good mechanical properties. However, poor corrosion resistance limits its widespread use in many applications. Magnesium is usually treated with Chromate conversion coatings. However, due to changing environmental regulations and pollution prevention requirements, a significant push exists to find new, alternative for poisonous Cr6+. Therefore, we aim to improve corrosion resistance of anodic coatings on AZ31 alloys using low cost non-chromate electrolyte. Anodizing was carried out in alkaline solutions with tin additives. The effect of tin additives on the coating film was characterized by SEM and XRD. The corrosion resistance was evaluated using anodic and cathodic polarizations and electrochemical impedance spectroscopy (EIS). Corrosion resistance property was improved with tin additives and the best anti-corrosion property was obtained with addition of 0.03 M Na2SnO3.3H2O to anodizing solution.

  15. Vacuum arc anode plasma. I. Spectroscopic investigation

    International Nuclear Information System (INIS)

    Bacon, F.M.

    1975-01-01

    A spectroscopic investigation was made of the anode plasma of a pulsed vacuum arc with an aluminum anode and a molybdenum cathode. The arc was triggered by a third trigger electrode and was driven by a 150-A 10-μs current pulse. The average current density at the anode was sufficiently high that anode spots were formed; these spots are believed to be the source of the aluminum in the plasma investigated in this experiment. By simultaneously measuring spectral emission lines of Al I, Al II, and Al III, the plasma electron temperature was shown to decrease sequentially through the norm temperatures of Al III, Al II, and Al I as the arc was extinguished. The Boltzmann distribution temperature T/subD/ of four Al III excited levels was shown to be kT/subD//e=2.0plus-or-minus0.5 V, and the peak Al III 4D excited state density was shown to be about 5times10 17 m -3 . These data suggest a non-local-thermodynamic-equilibrium (non-LTE) model of the anode plasma when compared with the Al 3+ production in the plasma. The plasma was theoretically shown to be optically thin to the observed Al III spectral lines

  16. Assessment of the cathode contribution to the degradation of anode-supported solid oxide fuel cells

    DEFF Research Database (Denmark)

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

    2008-01-01

    The degradation of anode-supported cells was studied over 1500 h as a function of cell polarization either in air or oxygen on the cathode side. Based on impedance analysis, contributions of the anode and cathode to the increase of total resistance were assigned. Accordingly, the degradation rates...... of the cathode were strongly dependent on the pO(2). Microstructural analysis of the cathode/electrolyte interface carried out after removal of the cathode showed craters on the electrolyte surface where the lanthanum strontium manganite (LSM) particles had been located. The changes of shape and size...... of these craters observed after testing correlated with the cell voltage degradation rates. The results can be interpreted in terms of element redistribution at the cathode/electrolyte interface and formation of foreign phases giving rise to a weakening of local contact points of the LSM cathode and yttria...

  17. Improving the Performance of SOFC Anodes by Decorating Perovskite with Ni Nanoparticles

    KAUST Repository

    Boulfrad, S.; Cassidy, M.; Traversa, Enrico; Irvine, J. T. S.

    2013-01-01

    In this work (La0.75Sr0.25)0.97Cr0.5Mn0.5O3 (LSCM) perovskite powders were pre-coated with 5 wt% nickel and mixed with different amounts of CGO for testing as anode materials under 3% wet H2. By using scanning transmission electron microscopy (STEM) with X-ray energy dispersive spectroscopy (EDS), we demonstrated that Ni forms a solid solution in the perovkite phase under oxidizing atmosphere and exsolves in form of nanoparticles under reducing atmospheres. The presence of the catalyst nanoparticles led to a decrease in the anodic activation energy by half and thus the polarization resistance was dropped by 60% at 800¢ªC. The effect of CGO amount will be also discussed.

  18. Promising Ni-Fe-LSGMC anode compatible with lanthanum gallate electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Wang Shizhong [Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 (United States)], E-mail: shizwang@sohu.com; He, Qiong [Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Liu Meilin [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 (United States)], E-mail: meilin.liu@mse.gatech.edu

    2009-06-01

    A number of composite materials in the Ni-Fe-LSGMC family have been studied as potential anodes for solid oxide fuel cells (SOFCs) based on strontium, magnesium, and cobalt doped lanthanum gallate electrolyte (LSGMC). The results show that Ni reacts with LSGMC especially under reducing conditions at high temperatures, resulting in high contact resistance, large electrode polarization, and poor performance. The reaction between Ni and LSGMC depends strongly on the composition and pre-sintering temperature of LSGMC, the concentration of iron in the electrode, and the processing and operating temperatures. Under proper conditions, Ni-Fe-LSGMC5 could be a promising high-performance anode with good compatibility with LSGMC5 electrolyte.

  19. Promising Ni-Fe-LSGMC anode compatible with lanthanum gallate electrolyte

    International Nuclear Information System (INIS)

    Wang Shizhong; He, Qiong; Liu Meilin

    2009-01-01

    A number of composite materials in the Ni-Fe-LSGMC family have been studied as potential anodes for solid oxide fuel cells (SOFCs) based on strontium, magnesium, and cobalt doped lanthanum gallate electrolyte (LSGMC). The results show that Ni reacts with LSGMC especially under reducing conditions at high temperatures, resulting in high contact resistance, large electrode polarization, and poor performance. The reaction between Ni and LSGMC depends strongly on the composition and pre-sintering temperature of LSGMC, the concentration of iron in the electrode, and the processing and operating temperatures. Under proper conditions, Ni-Fe-LSGMC5 could be a promising high-performance anode with good compatibility with LSGMC5 electrolyte.

  20. Improving the Performance of SOFC Anodes by Decorating Perovskite with Ni Nanoparticles

    KAUST Repository

    Boulfrad, S.

    2013-10-07

    In this work (La0.75Sr0.25)0.97Cr0.5Mn0.5O3 (LSCM) perovskite powders were pre-coated with 5 wt% nickel and mixed with different amounts of CGO for testing as anode materials under 3% wet H2. By using scanning transmission electron microscopy (STEM) with X-ray energy dispersive spectroscopy (EDS), we demonstrated that Ni forms a solid solution in the perovkite phase under oxidizing atmosphere and exsolves in form of nanoparticles under reducing atmospheres. The presence of the catalyst nanoparticles led to a decrease in the anodic activation energy by half and thus the polarization resistance was dropped by 60% at 800¢ªC. The effect of CGO amount will be also discussed.

  1. Fabrication and characterization of anode-supported micro-tubular solide oxide fuel cell by phase inversion method

    Science.gov (United States)

    Ren, Cong

    performance was attributed to the phase purity of the anode fabricated by different polymer binders. Sulfur-free polymer binder PEI exhibits advantages over the commonly applied PESf and other sulfur-free polymer binder candidates. To eliminate the skin layer formed close to the inner side of the tubular sample when using the phase inversion method. Polyethersulfone (PESf)-polyethylenimine (PEI) blend was employed as the polymer binder to fabricate the micro-tubular solid oxide fuel cells (MT-SOFCs). The potential impurity introduced in the anode support by the polymer binder was examined by XPS and the resulting novel microstructure was analyzed based on the backscattered electron (BSE) images. Cells fabricated with blend polymer binder showed significantly enhanced power output compared with those cells only fabricated with PEI or PESf. The improved cell performance demonstrated that using blend polymer as binder is a promising and versatile approach for MT-SOFC fabrication via phase inversion method. Finally, to investigate the effect of the anode microstructure on the total cell performance, two types of anode support with different microstructure were prepared via the phase inversion method at different temperature. Cells fabricated based on these two anode supports were tested at 750 °C with hydrogen or hydrogen mixture with fuel gas. The measured current density-voltage (I-V) curves were fitted by a polarization model, and several parameters were archived through the modeling process. The influence of the anode support on the total cell performance was discussed based on the calculated result.

  2. Polarized electron sources

    International Nuclear Information System (INIS)

    Prepost, R.

    1994-01-01

    The fundamentals of polarized electron sources are described with particular application to the Stanford Linear Accelerator Center. The SLAC polarized electron source is based on the principle of polarized photoemission from Gallium Arsenide. Recent developments using epitaxially grown, strained Gallium Arsenide cathodes have made it possible to obtain electron polarization significantly in excess of the conventional 50% polarization limit. The basic principles for Gallium and Arsenide polarized photoemitters are reviewed, and the extension of the basic technique to strained cathode structures is described. Results from laboratory measurements of strained photocathodes as well as operational results from the SLAC polarized source are presented

  3. Polarized electron sources

    Energy Technology Data Exchange (ETDEWEB)

    Prepost, R. [Univ. of Wisconsin, Madison, WI (United States)

    1994-12-01

    The fundamentals of polarized electron sources are described with particular application to the Stanford Linear Accelerator Center. The SLAC polarized electron source is based on the principle of polarized photoemission from Gallium Arsenide. Recent developments using epitaxially grown, strained Gallium Arsenide cathodes have made it possible to obtain electron polarization significantly in excess of the conventional 50% polarization limit. The basic principles for Gallium and Arsenide polarized photoemitters are reviewed, and the extension of the basic technique to strained cathode structures is described. Results from laboratory measurements of strained photocathodes as well as operational results from the SLAC polarized source are presented.

  4. Structural transformation of nickel hydroxide films during anodic oxidation

    Energy Technology Data Exchange (ETDEWEB)

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

    1992-05-01

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

  5. Structural transformation of nickel hydroxide films during anodic oxidation

    Energy Technology Data Exchange (ETDEWEB)

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

    1992-05-01

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

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

    Science.gov (United States)

    Li, Wenyuan

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

  7. Polarized tagged photons

    International Nuclear Information System (INIS)

    Maximon, L.C.; Ganz, Eric; Aniel, Thierry; Miniac, Arlette de.

    1982-03-01

    We consider in detail the differential cross section for polarized bremsstrahlung for angles and energies in the range of interest for a tagging system and derive a high energy, small angle approximation for this cross section. We use these approximations to determine the maxima and minima of the cross sections for these two polarization states, dσperpendicular and dσparallel, and to evaluate these cross sections at the extrema. It is shown that both dσperpendicular and dσparallel have a very sharp dip in the region of small momentum transfers. However, their behavior in the region of the dip, as a function of the azimuthal angle phi, is quite different over most of the photon spectrum. The cross section dσperpendicular behaves similarly to the cross section for unpolarized photons in that as phi increases, the sharp dip vanishes, the minimum fuses with the second maximum, and the cross section then has only a single maximum. In contrast, the sharp dip in the cross section dσparallel remains as phi increases. Coulomb corrections to the Born approximation are considered, and do not fill in these dips

  8. Polarized neutron spectrometer

    International Nuclear Information System (INIS)

    Abov, Yu.G.; Novitskij, V.V.; Alfimenkov, V.P.; Galinskij, E.M.; Mareev, Yu.D.; Pikel'ner, L.B.; Chernikov, A.N.; Lason', L.; Tsulaya, V.M.; Tsulaya, M.I.

    2000-01-01

    The polarized neutron spectrometer, intended for studying the interaction of polarized neutrons with nuclei and condensed media in the area of energies from thermal up to several electron-volt, is developed at the IBR-2 reactor (JINR, Dubna). Diffraction on the Co(92%)-Fe(8%) magnetized monocrystals is used for the neutron polarization and polarization analysis. The neutron polarization within the whole energy range equals ∼ 95% [ru

  9. Effect of electrolyte composition on the active-to-passive transition behavior of 2205 duplex stainless steel in H2SO4/HCl solutions

    International Nuclear Information System (INIS)

    Lo, I-H.; Fu Yan; Lin, C.-J.; Tsai, W.-T.

    2006-01-01

    Selective dissolution could occur in duplex stainless steels (DSSs) due to the difference in chemical composition between the two constituent phases. In this study, the effect of H 2 SO 4 /HCl composition on the selective dissolution behavior was investigated. The results indicated that there were two distinct peaks appeared in the active-to-passive transition region in the polarization curve. The peak appeared at a lower potential region was associated with the preferential dissolution of ferrite phase while that for austenite at a higher potential. In the concentration ranges of 0.25-2 M of H 2 SO 4 and 0.25-2 M of HCl, the magnitude of the peak anodic current density and the resolution between these two peaks greatly depended on the composition of H 2 SO 4 /HCl. However, the anodic peaks corresponding to the respective dissolutions of ferrite and austenite became less distinguishable when the concentrations of HCl exceeded 1.2 M. Image analysis using scanning electron microscopy (SEM) was performed to confirm the selective dissolution of each constituent phase after potentiostatic polarization at the respective anodic peak potential

  10. Infrared radiative properties of anodized aluminium

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, V.C.; Sharma, A.

    1983-10-01

    Measurements of anodic film thicknesses and their total hemispherical thermal emittance for various current densities (0.55-3.85 ampere/dm/sup 2/), anodizing times (1-20 min), and oxalic acid concentrations (1-6 wt.%) show a linear relationship between the film thickness and the total hemispherical thermal emittance (epsilon). Changes in oxalic acid concentration (2-4 wt.%) have no significant effect on the film growth-rate and the rate at which epsilon increases with increasing anodizing time. Measurements of epsilon for wavelengths from 3 to 30 ..mu..m show that the film growth-rate has a marked effect on the I.R. radiative properties of aluminum.

  11. Anodic oxidation of Ta/Fe alloys

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  12. Behavior of copper in acidic sulfate solution: Comparison with acidic chloride

    Energy Technology Data Exchange (ETDEWEB)

    Tromans, D.; Silva, J.C. [Univ. of British Columbia, Vancouver, British Columbia (Canada). Dept. of Metals and Materials Engineering

    1997-03-01

    The anodic polarization behavior of copper in a 0.1 M sulfuric acid (H{sub 2}SO{sub 4}) + 1 M sodium sulfate (Na{sub 2}SO{sub 4}) solution (pH = 2.0) was studied at room temperature under quiescent and stirred conditions. The behavior was compared with aqueous equilibria via construction of a potential-vs-pH (E-pH) diagram for the copper-sulfate-water (Cu-SO{sub 4}{sup 2}-H{sub 2}O) system. Interpretation of the behavior was aided by comparison with aqueous equilibria and polarization studies of copper in a 0.2 M hydrochloric acid (HCl) + 1 M sodium chloride (NaCl) solution(pH = 0.8). The initial anodic dissolution region in the acidic sulfate solution exhibited Tafel behavior with a slope consistent with formation of cupric ions (Cu{sup 2+}) whose rate of formation was charge-transfer controlled. At higher potentials, limiting current density (i{sub L}) behavior was observed under E-pH conditions that were consistent with formation of a film of copper sulfate pentahydrate (CuSO{sub 4} {degree} 5H{sub 2}O). Comparison of experimental i{sub L} values with those predicted by mass transport-controlled processes, using estimates of the diffusion layer thickness obtained from the mass transfer-influenced region of apparent Tafel behavior in the acidic chloride solution, were in sufficient agreement to indicate i{sub L} was controlled by the rate of dissolution of the CuSO{sub 4} {degree} 5H{sub 2}O film via transport of Cu{sup 2+} from the film-electrolyte interface into the bulk solution.

  13. Electron Cyclotron Waves Polarization in the TJII Stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Cappa, A.; Martinez-Fernandez, J.; Wagner, D.

    2013-05-01

    This report describes the theoretical calculations related with the electron cyclotron (EC) waves polarization control in the TJII stellarator. Two main aspects will be distinguished: the determination of the vacuum polarization that the wave must exhibit if a given propagation mode in a cold plasma is desired and the calculation of the behavior of the grooved polarizers and other transmission systems used to launch the vacuum wave with the required polarization. (Author) 13 refs.

  14. Air plasma spray processing and electrochemical characterization of Cu-SDC coatings for use in solid oxide fuel cell anodes

    Energy Technology Data Exchange (ETDEWEB)

    Benoved, Nir [Department of Mechanical Engineering, The University of British Columbia, 2054-6250 Applied Sciences Lane, Vancouver, British Columbia (Canada); Kesler, O. [Department of Mechanical and Industrial Engineering, University of Toronto, 5 King' s College Road, Toronto, Ontario (Canada)

    2009-09-05

    Air plasma spraying has been used to produce porous composite anodes based on Ce{sub 0.8}Sm{sub 0.2}O{sub 1.9} (SDC) and Cu for use in solid oxide fuel cells (SOFCs). Preliminarily, a range of plasma conditions has been examined for the production of composite coatings from pre-mixed SDC and CuO powders. Plasma gas compositions were varied to obtain a range of plasma temperatures. After reduction in H{sub 2}, coatings were characterized for composition and microstructure using EDX and SEM. As a result of these tests, symmetrical sintered electrolyte-supported anode-anode cells were fabricated by air plasma spraying of the anodes, followed by in situ reduction of the CuO to Cu. Full cells deposited on SS430 porous substrates were then produced in one integrated process. Fine CuO and SDC powders have been used to produce homogeneously mixed anode coatings with higher surface area microstructures, resulting in area-specific polarization resistances of 4.8 {omega} cm{sup 2} in impedance tests in hydrogen at 712 C. (author)

  15. Air plasma spray processing and electrochemical characterization of Cu-SDC coatings for use in solid oxide fuel cell anodes

    Science.gov (United States)

    Benoved, Nir; Kesler, O.

    Air plasma spraying has been used to produce porous composite anodes based on Ce 0.8Sm 0.2O 1.9 (SDC) and Cu for use in solid oxide fuel cells (SOFCs). Preliminarily, a range of plasma conditions has been examined for the production of composite coatings from pre-mixed SDC and CuO powders. Plasma gas compositions were varied to obtain a range of plasma temperatures. After reduction in H 2, coatings were characterized for composition and microstructure using EDX and SEM. As a result of these tests, symmetrical sintered electrolyte-supported anode-anode cells were fabricated by air plasma spraying of the anodes, followed by in situ reduction of the CuO to Cu. Full cells deposited on SS430 porous substrates were then produced in one integrated process. Fine CuO and SDC powders have been used to produce homogeneously mixed anode coatings with higher surface area microstructures, resulting in area-specific polarization resistances of 4.8 Ω cm 2 in impedance tests in hydrogen at 712 °C.

  16. Effects of benzotriazole on anodized film formed on AZ31B magnesium alloy in environmental-friendly electrolyte

    International Nuclear Information System (INIS)

    Guo Xinghua; An Maozhong; Yang Peixia; Li Haixian; Su Caina

    2009-01-01

    An environmental-friendly electrolyte of silicate and borate, which contained an addition agent of 1H-benzotriazole (BTA) with low toxicity (LD50 of 965 mg/kg), was used to prepare an anodized film on AZ31B magnesium alloy under the constant current density of 1.5 A/dm 2 at room temperature. Effects of BTA on the properties of the anodized film were studied by scanning electron microscopy (SEM), energy dispersion spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), loss weight measurement, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), respectively. The results demonstrated that anodized growth process, surface morphology, thickness, phase structure and corrosion resistance of the anodized film were strongly dependant on the BTA concentration, which might be attributed to the formation of an BTA adsorption layer on magnesium substrate surface. When the BTA concentration was 5 g/L in the electrolyte, a compact and thick anodized film could provide excellent corrosion resistance for AZ31B magnesium alloy.

  17. Influence of 8-hydroxyquinoline on properties of anodic coatings obtained by micro arc oxidation on AZ91 magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, R.F. [Jiangxi Key Laboratory of Surface Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); School of Material Science and Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); Zhang, S.F., E-mail: zhangshufang790314@sina.com [Jiangxi Key Laboratory of Surface Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); School of Material Science and Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); Yang, N.; Yao, L.J.; He, F.X.; Zhou, Y.P.; Xu, X.; Chang, L.; Bai, S.J. [School of Material Science and Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China)

    2012-10-25

    Highlights: Black-Right-Pointing-Pointer 8-HQ can promote the coating formation and change the coating color. Black-Right-Pointing-Pointer 8-HQ can increase the coating thickness and decrease the pore size. Black-Right-Pointing-Pointer Insoluble Mg(HQ){sub 2} is formed in anodic coatings in an alkaline solution with 8-HQ. Black-Right-Pointing-Pointer 8-HQ improves the corrosion resistance of the anodized magnesium alloys. - Abstract: The influence of 8-hydroxyquinoline (8-HQ) on formation and properties of anodic coatings obtained by micro arc oxidation (MAO) on AZ91 magnesium alloys was studied by scanning electron microscope (SEM), energy dispersive spectrometry (EDS), Fourier transform infrared (FT-IR) spectroscopy and potentiodynamic polarization tests. The results demonstrate that 8-HQ can decrease the solution conductivity, take part in the coating formation and change the coating color. By developing anodic coatings with increasing thickness, insoluble Mg(HQ){sub 2} and small pore size, 8-HQ improves the corrosion resistance of the anodized magnesium alloys. The coating shows the best corrosion resistance in the solution of 10 g/L NaOH and 18 g/L Na{sub 2}SiO{sub 3} with 2 g/L 8-HQ.

  18. The effect of crystal orientation on the aluminum anodes of the aluminum-air batteries in alkaline electrolytes

    Science.gov (United States)

    Fan, Liang; Lu, Huimin; Leng, Jing; Sun, Zegao; Chen, Chunbo

    2015-12-01

    Recently, aluminum-air (Al-air) batteries have received attention from researchers as an exciting option for safe and efficient batteries. The electrochemical performance of Aluminum anode remains an active area of investigation. In this paper, the electrochemical properties of polycrystalline Al, Al (001), (110) and (111) single crystals are investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 4 M NaOH and KOH. Hydrogen corrosion rates of the Al anodes are determined by hydrogen collection. Battery performance using the anodes is tested by constant current discharge at 10 mA cm-2. This is the first report showing that the electrochemical properties of Al are closely related to the crystallographic orientation in alkaline electrolytes. The (001) crystallographic plane has good corrosion resistance but (110) is more sensitive. Al (001) single crystals display higher anode efficiency and capacity density. Controlling the crystallographic orientation of the Al anode is another way to improve the performance of Al-air batteries in alkaline electrolytes.

  19. The effect of the presence of alcohol in the dispersing phase of oxide sols on the properties of RuO2-TiO2/Ti anodes obtained by the sol–gel procedure

    Directory of Open Access Journals (Sweden)

    R. ATANASOSKI

    2000-09-01

    Full Text Available The effect of the addition of ethanol and 2-propanol to the dispersing phase of TiO2 and RuO2 sols mixture on the morphology and, consequently, on the electrochemical properties of the sol-gel obtained activated titanium anodes was investigated. The properties of the obtained anodes were compared to those obtained by the thermal decomposition of appropriate chloride salts. The morphology of the anode coatings was examined by scanning tunneling microscopy. The electrochemical behaviour was investigated by cyclic voltammetry and by polarization measurements. An accelerated stability test was used for the examination of the stability of the anodes under simultaneous oxygen and chlorine evolution reaction. A dependence of the anode stability on the type of added alcohol is indicated.

  20. Anodizing color coded anodized Ti6Al4V medical devices for increasing bone cell functions.

    Science.gov (United States)

    Ross, Alexandra P; Webster, Thomas J

    2013-01-01

    Current titanium-based implants are often anodized in sulfuric acid (H(2)SO(4)) for color coding purposes. However, a crucial parameter in selecting the material for an orthopedic implant is the degree to which it will integrate into the surrounding bone. Loosening at the bone-implant interface can cause catastrophic failure when motion occurs between the implant and the surrounding bone. Recently, a different anodization process using hydrofluoric acid has been shown to increase bone growth on commercially pure titanium and titanium alloys through the creation of nanotubes. The objective of this study was to compare, for the first time, the influence of anodizing a titanium alloy medical device in sulfuric acid for color coding purposes, as is done in the orthopedic implant industry, followed by anodizing the device in hydrofluoric acid to implement nanotubes. Specifically, Ti6Al4V model implant samples were anodized first with sulfuric acid to create color-coding features, and then with hydrofluoric acid to implement surface features to enhance osteoblast functions. The material surfaces were characterized by visual inspection, scanning electron microscopy, contact angle measurements, and energy dispersive spectroscopy. Human osteoblasts were seeded onto the samples for a series of time points and were measured for adhesion and proliferation. After 1 and 2 weeks, the levels of alkaline phosphatase activity and calcium deposition were measured to assess the long-term differentiation of osteoblasts into the calcium depositing cells. The results showed that anodizing in hydrofluoric acid after anodizing in sulfuric acid partially retains color coding and creates unique surface features to increase osteoblast adhesion, proliferation, alkaline phosphatase activity, and calcium deposition. In this manner, this study provides a viable method to anodize an already color coded, anodized titanium alloy to potentially increase bone growth for numerous implant applications.

  1. X-ray tube rotating anode

    International Nuclear Information System (INIS)

    Friedel, R.

    1979-01-01

    The anode disk of the X-ray rotating anode is blackened on the surface outside the focal spot tracks in order to improve the heat radiation. In particular the side opposite the focal spot tracks is provided with many small holes, the ratio of depth to cross-section ('pit ratio') being as large as possible: ranging from 2:1 to 10:1. They are arranged so densely that the radiating surface will nearly have the effect of a black body. (RW) [de

  2. Rotating anode X-ray tubes

    International Nuclear Information System (INIS)

    Webley, R.S.

    1981-01-01

    In a rotating anode x-ray tube it is proposed to mount the rotating anode, or means such as a shaft affixed to it, to rotate on bearings in a race the seating for which is cooled by a suitable coolant flow. A suitable bellows arrangement allows the coolant pressure to determine the contact pressure of the seating on the bearings. This allows the thermal impedance to be varied and the bearing wear to be optimised therewith as well as allowing adjustment for wear. The use of two bellows allows the seating section therebetween to move towards the other section as the rollers wear. (author)

  3. Anodic behaviours, dissolution and passivation of iron-nickel alloys in sulphuric environment. Influence of friction

    International Nuclear Information System (INIS)

    Ponthiaux, Pierre

    1990-01-01

    This research thesis reports the study of anodic dissolution and passivation of iron-nickel alloys (10, 20 and 31 pc nickel) in a sulphuric environment, with or without friction, by using anodic polarization curves. Without friction, the three alloys have a similar behaviour as pure iron. The analysis reveals different dissolution and passivation mechanisms with pure iron, and highlights the influence of nickel content on corresponding kinetics. The influence of cyclic plane-on-plane friction has been studied for the 31 pc nickel alloy which has an unsteady austenitic structure. Fretting results in some modifications of polarization curves. These modifications are analysed with respect to fretting parameters (relative speed of antagonist surfaces, contact pressure). They reveal the specific influence of the following phenomena: material strain hardening, martensitic transformation induced by strain hardening, partial destruction of adsorbates and/or of the passive film. Modifications of polarization curves give also information on the evolution of friction characteristics with respect to speed (a phenomenon of lubrication by the electrolyte occurs) [fr

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

    Science.gov (United States)

    Nazemi, Azadeh; Abolfazl, Seyed; Sadjadi, Seyed

    2014-12-01

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

  5. A new, bright and hard aluminum surface produced by anodization

    Science.gov (United States)

    Hou, Fengyan; Hu, Bo; Tay, See Leng; Wang, Yuxin; Xiong, Chao; Gao, Wei

    2017-07-01

    Anodized aluminum (Al) and Al alloys have a wide range of applications. However, certain anodized finishings have relatively low hardness, dull appearance and/or poor corrosion resistance, which limited their applications. In this research, Al was first electropolished in a phosphoric acid-based solution, then anodized in a sulfuric acid-based solution under controlled processing parameters. The anodized specimen was then sealed by two-step sealing method. A systematic study including microstructure, surface morphology, hardness and corrosion resistance of these anodized films has been conducted. Results show that the hardness of this new anodized film was increased by a factor of 10 compared with the pure Al metal. Salt spray corrosion testing also demonstrated the greatly improved corrosion resistance. Unlike the traditional hard anodized Al which presents a dull-colored surface, this newly developed anodized Al alloy possesses a very bright and shiny surface with good hardness and corrosion resistance.

  6. Characterization of electrical discharges during spark anodization of zirconium in different electrolytes

    International Nuclear Information System (INIS)

    Santos, Janaina S.; Lemos, Sherlan G.; Gonçalves, Wesley N.; Bruno, Odemir M.; Pereira, Ernesto C.

    2014-01-01

    The evolution of the electrical discharges parameters during spark anodization of metallic Zr under galvanostatic regime have been investigated by image analysis in phosphoric and oxalic acid electrolytes. The experiments were recorder using a high-speed video camera during the entire anodization with a resolution of 1.7 ms for determination of discharge lifetime and a standard resolution of 33 ms (real-time imaging) for determination of the average area and discharge population density. The discharge behavior was dependent of the current density, electrolyte composition and anodization time. During breakdown process, sparks discharges are progressively turned to micro-arcs, which can be seen by enlargement of discharge area, gradual increase of lifetime and reduction of discharge population density. A factorial design was used to estimate the effects of experimental conditions on the discharge behavior. The current density and electrolyte composition were the most important factors that affected the discharge population density. The anodization time and the electrolyte composition were the main factor that influenced the discharge area and lifetime. In comparison with the voltage vs. time curve, the results demonstrate important features of the process and the changes of the electrical discharges characteristics during the experiments

  7. Mechanical characterization and modeling for anodes and cathodes in lithium-ion batteries

    Science.gov (United States)

    Wang, Lubing; Yin, Sha; Zhang, Chao; Huan, Yong; Xu, Jun

    2018-07-01

    Mechanical properties of electrode materials have significant influence over electrochemical properties as well as mechanical integrity of lithium-ion battery cells. Here, anode and cathode in a commercially available 18650 NCA (Nickel Cobalt Aluminum Oxide)/graphite cell were comprehensively studied by tensile tests considering material anisotropy, SOC (state of charge), strain rate and electrolyte content. Results showed that the mechanical properties of both electrodes were highly dependent on strain rate and electrolyte content; however, anode was SOC dependent while cathode was not. Besides, coupled effects of strain rate and SOC of anodes were also discussed. SEM (scanning electron microscope) images of surfaces and cross-sections of electrodes showed the fracture morphology. In addition, mechanical behavior of Cu foil separated from anode with different SOC values were studied and compared. Finally, constitutive models of electrodes considering both strain rate and anisotropy effects were established. This study reveals the relationship between electrochemical dependent mechanical behavior of the electrodes. The established mechanical models of electrodes can be applied to the numerical computation of battery cells. Results are essential to predict the mechanical responses as well as the deformation of battery cell under various loading conditions, facilitating safer battery design and manufacturing.

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

    Science.gov (United States)

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

    2011-11-01

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

  9. The influence of the pyrolysis temperature on the electrochemical behavior of carbon-rich SiCN polymer-derived ceramics as anode materials in lithium-ion batteries

    Science.gov (United States)

    Reinold, Lukas Mirko; Yamada, Yuto; Graczyk-Zajac, Magdalena; Munakata, Hirokazu; Kanamura, Kiyoshi; Riedel, Ralf

    2015-05-01

    Within this study we report on the impact of the pyrolysis temperature on the structural and electrochemical properties of the poly(phenylvinylsilylcarbodiimide) derived silicon carbonitride (SiCN) ceramic. Materials pyrolysed at 800 °C and 1300 °C, SiCN 800 and SiCN 1300, are found amorphous. Raman spectroscopy measurements indicate the increase in ordering of the free carbon phase with increasing pyrolysis temperature which leads to lower capacity recovered by SiCN 1300. Significant hysteresis is found for materials pyrolysed at 800 °C during electrochemical lithium insertion/extraction. This feature is attributed to much higher hydrogen content in SiCN 800 sample. An aging of SiCN 800 reflected by a change of elemental composition upon contact to air and a strong film formation are attenuated at a higher pyrolysis temperature. Single particle microelectrode investigation on SiCN 800 and SiCN 1300 clarify different electrochemical behavior of the materials. Much lower charge transfer resistance of SiCN 1300 in comparison to SiCN 800 explains better high currents electrochemical performance. Lithium ions diffusion coefficient Dmin ranges from 3.2 10-9 cm2s-1 to 6.4 10-11 cm2s-1 and is independent on the potential.

  10. Polarized targets and beams

    International Nuclear Information System (INIS)

    Meyer, W.

    1985-01-01

    First the experimental situation of the single-pion photoproduction and the photodisintegration of the deuteron is briefly discussed. Then a description of the Bonn polarization facilities is given. The point of main effort is put on the polarized target which plays a vital role in the program. A facility for photon induced double polarization experiments at ELSA will be presented in section 4. Properties of a tensor polarized deuteron target are discussed in section 5. The development in the field of polarized targets, especially on new target materials, enables a new generation of polarized target experiments with (polarized) electrons. Some comments on the use of a polarized target in combination with electron beams will be discussed in section 6. Electron deuteron scattering from a tensor polarized deuteron target is considered and compared with other experimental possibilities. (orig./HSI)

  11. Switching on/off the chemisorption of thioctic-based self-assembled monolayers on gold by applying a moderate cathodic/anodic potential.

    Science.gov (United States)

    Sahli, Rihab; Fave, Claire; Raouafi, Noureddine; Boujlel, Khaled; Schöllhorn, Bernd; Limoges, Benoît

    2013-04-30

    An in situ and real-time electrochemical method has been devised for quantitatively monitoring the self-assembly of a ferrocene-labeled cyclic disulfide derivative (i.e., a thioctic acid derivative) on a polycrystalline gold electrode under electrode polarization. Taking advantage of the high sensitivity, specificity, accuracy, and temporal resolution of this method, we were able to demonstrate an unexpectedly facilitated formation of the redox-active SAM when the electrode was held at a moderate cathodic potential (-0.4 V vs SCE in CH3CN), affording a saturated monolayer from only micromolar solutions in less than 10 min, and a totally impeded SAM growth when the electrode was polarized at a slightly anodic potential (+0.5 V vs SCE in CH3CN). This method literally allows for switching on/off the formation of SAMs under "soft" conditions. Moreover the cyclic disulfide-based SAM was completely desorbed at this potential contrary to the facilitated deposition of a ferrocene-labeled alkanethiol. Such a strikingly contrasting behavior could be explained by an energetically favored release of the thioctic-based SAM through homolytic cleavage of the Au-S bond followed by intramolecular cyclization of the generated thiyl diradicals. Moreover, the absence of a discernible transient faradaic current response during the potential-assisted adsorption/desorption of the redox-labeled cyclic disulfide led us to conclude in a potential-dependent reversible surface reaction where no electron is released or consumed. These results provide new insights into the formation of disulfide-based SAMs on gold but also raise some fundamental questions about the intimate mechanism involved in the facilitated adsorption/desorption of SAMs under electrode polarization. Finally, the possibility to easily and selectively address the formation/removal of thioctic-based SAMs on gold by applying a moderate cathodic/anodic potential offers another degree of freedom in tailoring their properties and

  12. Corrosion behavior of carbon steel for overpack in groundwater containing bicarbonate ions

    International Nuclear Information System (INIS)

    Nishimura, Toshiyasu; Dong, Junpha

    2009-01-01

    Carbon steel is considered in Japan the candidate material for overpacks in high-level radioactive waste disposal. Effects of bicarbonate solutions on the corrosion behavior and corrosion products of carbon steel were investigated by electrochemical measurements, FT-IR and XRD analyses. The anodic polarization measurements showed that bicarbonate ions (HCO 3 - ) accelerated the anodic dissolution and the outer layer film formation of carbon steel in the case of high concentrations, on the other hand, it inhibited these processes in the case of low concentrations. The FT-IR and XRD analyses of the anodized film showed that siderite (FeCO 3 ) was formed in 0.5 to 1.0 mol/L bicarbonate solution, and Fe 2 (OH) 2 CO 3 in 0.1 to 0.2 mol/L bicarbonate solution, while Fe 6 (OH) 12 CO 3 was formed in 0.02 to 0.05 mol/L bicarbonate solutions. The stability of these corrosion products was able to be explained by using the actual potential-pH diagrams for the Fe-H 2 O-CO 2 system. (author)

  13. Cadmium plated steel caps seal anodized aluminum fittings

    Science.gov (United States)

    Padden, J.

    1971-01-01

    Cadmium prevents fracturing of hard anodic coating under torquing to system specification requirements, prevents galvanic coupling, and eliminates need for crush washers, which, though commonly used in industry, do not correct leakage problem experienced when anodized aluminum fittings and anodized aluminum cap assemblies are joined.

  14. Multilayer tape cast SOFC – Effect of anode sintering temperature

    DEFF Research Database (Denmark)

    Hauch, Anne; Birkl, Christoph; Brodersen, Karen

    2012-01-01

    Multilayer tape casting (MTC) is considered a promising, cost-efficient, up-scalable shaping process for production of planar anode supported solid oxide fuel cells (SOFC). Multilayer tape casting of the three layers comprising the half cell (anode support/active anode/electrolyte) can potentially...

  15. Variation of nanopore diameter along porous anodic alumina channels by multi-step anodization.

    Science.gov (United States)

    Lee, Kwang Hong; Lim, Xin Yuan; Wai, Kah Wing; Romanato, Filippo; Wong, Chee Cheong

    2011-02-01

    In order to form tapered nanocapillaries, we investigated a method to vary the nanopore diameter along the porous anodic alumina (PAA) channels using multi-step anodization. By anodizing the aluminum in either single acid (H3PO4) or multi-acid (H2SO4, oxalic acid and H3PO4) with increasing or decreasing voltage, the diameter of the nanopore along the PAA channel can be varied systematically corresponding to the applied voltages. The pore size along the channel can be enlarged or shrunken in the range of 20 nm to 200 nm. Structural engineering of the template along the film growth direction can be achieved by deliberately designing a suitable voltage and electrolyte together with anodization time.

  16. Recent Progress in Synthesis and Application of Low-Dimensional Silicon Based Anode Material for Lithium Ion Battery

    Directory of Open Access Journals (Sweden)

    Yuandong Sun

    2017-01-01

    Full Text Available Silicon is regarded as the next generation anode material for LIBs with its ultra-high theoretical capacity and abundance. Nevertheless, the severe capacity degradation resulting from the huge volume change and accumulative solid-electrolyte interphase (SEI formation hinders the silicon based anode material for further practical applications. Hence, a variety of methods have been applied to enhance electrochemical performances in terms of the electrochemical stability and rate performance of the silicon anodes such as designing nanostructured Si, combining with carbonaceous material, exploring multifunctional polymer binders, and developing artificial SEI layers. Silicon anodes with low-dimensional structures (0D, 1D, and 2D, compared with bulky silicon anodes, are strongly believed to have several advanced characteristics including larger surface area, fast electron transfer, and shortened lithium diffusion pathway as well as better accommodation with volume changes, which leads to improved electrochemical behaviors. In this review, recent progress of silicon anode synthesis methodologies generating low-dimensional structures for lithium ion batteries (LIBs applications is listed and discussed.

  17. Chitosan, a new and environmental benign electrode binder for use with graphite anode in lithium-ion batteries

    International Nuclear Information System (INIS)

    Chai, Lili; Qu, Qunting; Zhang, Longfei; Shen, Ming; Zhang, Li; Zheng, Honghe

    2013-01-01

    Highlights: • Chitosan is used as a new electrode binder for graphite anode. • Electrochemical properties of the chitosan-based electrode are compared with that of PVDF-based one. • Electrochemical performances of the graphite anode are improved by using chitosan binder. • Chitosan binder facilitates the formation of a thin, homogenous and stable SEI film of the electrode. -- Abstract: Chitosan was applied as the electrode binder material for a spherical graphite anode in lithium-ion batteries. Compared to using poly (vinylidene fluoride) (PVDF) binder, the graphite anode using chitosan exhibited enhanced electrochemical performances in terms of the first Columbic efficiency, rate capability and cycling behavior. With similar specific capacity, the first Columbic efficiency of the chitosan-based anode is 95.4% compared to 89.3% of the PVDF-based anode. After 200 charge–discharge cycles at 0.5C, the capacity retention of the chitosan-based electrode showed to be significantly higher than that of the PVDF-based electrode. Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) measurements were carried out to investigate the formation and evolution of the solid electrolyte interphase (SEI) formed on the graphite electrodes. The results show that a thin, homogenous and stable SEI layer is formed on the graphite electrode surface with chitosan binder compared with that using the conventional PVDF binder

  18. Characterization of the corrosion resistance of biologically active solutions: The effects of anodizing and welding

    Science.gov (United States)

    Walsh, Daniel W.

    1991-01-01

    An understanding of fabrication processes, metallurgy, electrochemistry, and microbiology is crucial to the resolution of microbiologically influenced corrosion (MIC) problems. The object of this effort was to use AC impedance spectroscopy to characterize the corrosion resistance of Type II anodized aluminum alloy 2219-T87 in sterile and biologically active media and to examine the corrosion resistance of 316L, alloy 2219-T87, and titanium alloy 6-4 in the welded and unwelded conditions. The latter materials were immersed in sterile and biologically active media and corrosion currents were measured using the polarization resistance (DC) technique.

  19. Hybrid anode for semiconductor radiation detectors

    Science.gov (United States)

    Yang, Ge; Bolotnikov, Aleksey E; Camarda, Guiseppe; Cui, Yonggang; Hossain, Anwar; Kim, Ki Hyun; James, Ralph B

    2013-11-19

    The present invention relates to a novel hybrid anode configuration for a radiation detector that effectively reduces the edge effect of surface defects on the internal electric field in compound semiconductor detectors by focusing the internal electric field of the detector and redirecting drifting carriers away from the side surfaces of the semiconductor toward the collection electrode(s).

  20. Linear sweep anodic stripping voltammetry: Determination of ...

    Indian Academy of Sciences (India)

    The aim of this work is to determine Cr(VI) in water resources by anodic stripping voltammetry using SPE-. AuNPs modified electrode .... surface area about 4 fold). 3.2 Optimization of Parameters ..... in water samples. The above system offers a.

  1. Growth of anodic films on niobium

    International Nuclear Information System (INIS)

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

    1988-01-01

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

  2. Spinal Anodes for Lithium-Ion Batteries

    CSIR Research Space (South Africa)

    Ferg, E

    1994-11-01

    Full Text Available , and layered LiCoO2. The electrochemical data demonstrated that Li+ ions will shuttle between two transition-metal host structures (anode and cathode) at a reasonably high voltage with a concomitant change in the oxidation state of the transition metal cations...

  3. Anodic electrochemical treatment of amorphous alloys

    International Nuclear Information System (INIS)

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

    1983-01-01

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

  4. Low temperature anodic bonding to silicon nitride

    DEFF Research Database (Denmark)

    Weichel, Steen; Reus, Roger De; Bouaidat, Salim

    2000-01-01

    Low-temperature anodic bonding to stoichiometric silicon nitride surfaces has been performed in the temperature range from 3508C to 4008C. It is shown that the bonding is improved considerably if the nitride surfaces are either oxidized or exposed to an oxygen plasma prior to the bonding. Both bu...

  5. Anode materials for lithium-ion batteries

    Science.gov (United States)

    Sunkara, Mahendra Kumar; Meduri, Praveen; Sumanasekera, Gamini

    2014-12-30

    An anode material for lithium-ion batteries is provided that comprises an elongated core structure capable of forming an alloy with lithium; and a plurality of nanostructures placed on a surface of the core structure, with each nanostructure being capable of forming an alloy with lithium and spaced at a predetermined distance from adjacent nanostructures.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  7. Mechanical failure of anodized aluminum under three and four-point bending tests

    International Nuclear Information System (INIS)

    Bargui, M.; Bensalah, W.; Elleuch, K.; Ayedi, H.F.

    2013-01-01

    Highlights: • We study the flexural behavior of anodic oxide layers formed on aluminum. • Three and four-point bending tests were used as techniques. • Changing the beam configuration will change the flexural response. - Abstract: In this work, three and four-point bending tests were adopted as methods for characterizing anodized aluminum beams in a sulfuric acid bath. The failure behavior of sandwich beams having aluminum oxide face sheets and aluminum core were tested. In so doing, many configurations were adopted by anodizing aluminum beams on one and both sides to investigate faces in place of tension and compression. Bending tests showed different behaviors. When the oxide was only on the top side of the beam (working in compression) a slight sudden decrease of the load was observed. This fact was absent on beams with oxide layers working in tensile. The bending behavior of sandwich beams was similar to those with oxide on top sides but with much higher loads. The mechanical failure of the oxide was mainly caused by its failure when it is placed in compression beneath the loading rollers. Finally, a morphological study of the aluminum oxide layers after bending tests was conducted by optical microscopy

  8. Effect of Multipass Friction Stir Processing on Mechanical and Corrosion Behavior of 2507 Super Duplex Stainless Steel

    Science.gov (United States)

    Mishra, M. K.; Gunasekaran, G.; Rao, A. G.; Kashyap, B. P.; Prabhu, N.

    2017-02-01

    The microstructure, mechanical properties, and corrosion behavior of 2507 super duplex stainless steel after multipass friction stir processing (FSP) were examined. A significant refinement in grain size of both ferrite and austenite was observed in stir zone resulting in improved yield and tensile strength. Electrochemical impedance spectroscopy and anodic polarization studies in 3.5 wt.% NaCl solution showed nobler corrosion characteristics with increasing number of FSP passes. This was evident from the decrease in corrosion current density, decrease in passive current density, and increase in polarization resistance. Also, the decrease in density of defects, based on Mott-Schottky analysis, further confirms the improvement in corrosion resistance of 2507 super duplex stainless steel after multipass FSP.

  9. Polarization Property Measurement of the Long Undulator Radiation Using Cr/C Multilayer Polarization Elements

    International Nuclear Information System (INIS)

    Niibe, Masahito; Mukai, Mikihito; Shoji, Yoshihiko; Kimura, Hiroaki

    2004-01-01

    A rotating analyzer ellipsometry (RAE) system was developed with Cr/C multilayers that function as polarization elements for photon energy range of 110 - 280 eV. Polarization properties of a planar undulator change axisymmetrically in off-axial manner, and the second harmonic is more remarkable for the change. By using the RAE system, the polarization property of the second harmonic radiation from the NewSUBARU long undulator at the energy of 180 eV was examined. The degree of linear polarization of the on-axis radiation was over 0.996. The spatial distribution of the polarization azimuth was measured and was in fair agreement with the theoretical calculation. A peculiar behavior of the polarization property near the radiation peak of the second harmonic was observed by changing the height of the undulator gap

  10. Scattering with polarized neutrons

    International Nuclear Information System (INIS)

    Schweizer, J.

    2007-01-01

    In the history of neutron scattering, it was shown very soon that the use of polarized neutron beams brings much more information than usual scattering with unpolarized neutrons. We shall develop here the different scattering methods that imply polarized neutrons: 1) polarized beams without polarization analysis, the flipping ratio method; 2) polarized beams with a uniaxial polarization analysis; 3) polarized beams with a spherical polarization analysis. For all these scattering methods, we shall give examples of the physical problems which can been solved by these methods, particularly in the field of magnetism: investigation of complex magnetic structures, investigation of spin or magnetization densities in metals, insulators and molecular compounds, separation of magnetic and nuclear scattering, investigation of magnetic properties of liquids and amorphous materials and even, for non magnetic material, separation between coherent and incoherent scattering. (author)

  11. Polarized Light Corridor Demonstrations.

    Science.gov (United States)

    Davies, G. R.

    1990-01-01

    Eleven demonstrations of light polarization are presented. Each includes a brief description of the apparatus and the effect demonstrated. Illustrated are strain patterns, reflection, scattering, the Faraday Effect, interference, double refraction, the polarizing microscope, and optical activity. (CW)

  12. Local deposition of polypyrrole on aluminum by anodizing, laser irradiation, and electrolytic polymerization and its application to the fabrication of micro-actuators

    Energy Technology Data Exchange (ETDEWEB)

    Akiyama, Y. [Graduate School of Engineering, Hokkaido University, N13 W8 Kita-Ku, Sapporo (Japan); Kikuchi, T. [Graduate School of Engineering, Hokkaido University, N13 W8 Kita-Ku, Sapporo (Japan)]. E-mail: kiku@elechem1-mc.eng.hokudai.ac.jp; Ueda, M. [Graduate School of Engineering, Hokkaido University, N13 W8 Kita-Ku, Sapporo (Japan); Iida, M. [Graduate School of Engineering, Hokkaido University, N13 W8 Kita-Ku, Sapporo (Japan); Sakairi, M. [Graduate School of Engineering, Hokkaido University, N13 W8 Kita-Ku, Sapporo (Japan); Takahashi, H. [Graduate School of Engineering, Hokkaido University, N13 W8 Kita-Ku, Sapporo (Japan)

    2006-06-15

    Polypyrrole was deposited at selected areas on aluminum by anodizing, laser irradiation, and electrolytic polymerization, and the application of the technique for fabricating micro-actuators was attempted. Aluminum specimens covered with porous type anodic oxide films were irradiated with a pulsed Nd-YAG laser to remove the oxide films locally, and then thin Ni layers were deposited at areas where film had been removed. Polypyrrole could be successfully deposited only on the Ni layer by anodic polarization of the specimens in pyrrole monomer solution, and a polypyrrole/Ni bilayer structure could be obtained by dissolution of the aluminum substrate and anodic oxide film in NaOH solutions. The bilayer structure was found to be inactive to doping and dedoping of ions during anodic and cathodic polarization. A three-layer structure, nitrocellulose/Ni/polypyrrole, fabricated by electrolytic polymerization after nitrocellulose coating on a Ni layer detached from the aluminum substrate, showed ion-doping and -dedoping activity, suggesting the possibility of fabricating micro-actuators in this manner.

  13. Techniques in polarization physics

    International Nuclear Information System (INIS)

    Clausnitzer, G.

    1974-01-01

    A review of the current status of the technical tools necessary to perform different kinds of polarization experiments is presented, and the absolute and relative accuracy with which data can be obtained is discussed. A description of polarized targets and sources of polarized fast neutrons is included. Applications of polarization techniques to other fields is mentioned briefly. (14 figures, 3 tables, 110 references) (U.S.)

  14. Polarization versus Temperature in Pyridinium Ionic Liquids

    DEFF Research Database (Denmark)

    Chaban, V. V.; Prezhdo, O. V.

    2014-01-01

    Electronic polarization and charge transfer effects play a crucial role in thermodynamic, structural, and transport properties of room-temperature ionic liquids (RTILs). These nonadditive interactions constitute a useful tool for tuning physical chemical behavior of RTILs. Polarization and charge...... interactions changes negligibly between 300 and 900 K, while the average dipole moment increases due to thermal fluctuations of geometries. Our results contribute to the fundamental understanding of electronic effects in the condensed phase of ionic systems and foster progress in physical chemistry...

  15. Singular behavior of the Laplace operator in polar spherical coordinates and some of its consequences for the radial wave function at the origin of coordinates

    International Nuclear Information System (INIS)

    Khelashvili, A.A.; Nadareishvili, T.P.

    2015-01-01

    Singular behavior of the Laplace operator in spherical coordinates is investigated. It is shown that in course of transition to the reduced radial wave function in the Schreodinger equation there appears additional term including the Dirac delta function, which was unnoted during the full history of physics and mathematics. The possibility of avoiding this contribution from the reduced radial equation is discussed. It is demonstrated that for this aim the necessary and sufficient condition is the requirement of the fast enough falling of the wave function at the origin. The result does not depend on character of potential - whether it is regular or singular. The various manifestations and consequences of this observation are considered as well. The cornerstone in our approach is the natural requirement that the solution of the radial equation at the same time must obey the full equation. [ru

  16. Polarized Moessbauer transitions

    International Nuclear Information System (INIS)

    Barb, D.

    1975-01-01

    Theoretical aspects of the emission, absorption and scattering of polarized gamma rays are reviewed for a general case of combined magnetic and electric hyperfine interactions; various possibilities of obtaining polarized gamma sources are described and examples are given of the applications of Moessbauer spectroscopy with polarized gamma rays in solving problems of solid state physics. (A.K.)

  17. Geographical Income Polarization

    DEFF Research Database (Denmark)

    Azhar, Hussain; Jonassen, Anders Bruun

    inter municipal income inequality. Counter factual simulations show that rising property prices to a large part explain the rise in polarization. One side-effect of polarization is tendencies towards a parallel polarization of residence location patterns, where low skilled individuals tend to live...

  18. Calculation of polarization effects

    International Nuclear Information System (INIS)

    Chao, A.W.

    1983-09-01

    Basically there are two areas of accelerator applications that involve beam polarization. One is the acceleration of a polarized beam (most likely a proton beam) in a synchrotron. Another concerns polarized beams in an electron storage ring. In both areas, numerical techniques have been very useful

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

    Directory of Open Access Journals (Sweden)

    Mallika Thabuot

    2016-02-01

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

  20. Methods for making anodes for lithium ion batteries

    Science.gov (United States)

    Xu, Wu; Canfield, Nathan L.; Zhang, Ji-Guang; Liu, Wei; Xiao, Jie; Wang, Deyu; Yang, Z. Gary

    2015-05-26

    Methods for making composite anodes, such as macroporous composite anodes, are disclosed. Embodiments of the methods may include forming a tape from a slurry including a substrate metal precursor, an anode active material, a pore-forming agent, a binder, and a solvent. A laminated structure may be prepared from the tape and sintered to produce a porous structure, such as a macroporous structure. The macroporous structure may be heated to reduce a substrate metal precursor and/or anode active material. Macroporous composite anodes formed by some embodiments of the disclosed methods comprise a porous metal and an anode active material, wherein the anode active material is both externally and internally incorporated throughout and on the surface of the macroporous structure.

  1. Spectroscopic measurements of anode plasma with cryogenic pulsed ion sources

    International Nuclear Information System (INIS)

    Yoneda, H.; Urata, T.; Ohbayashi, K.; Kim, Y.; Horioka, K.; Kasuya, K.

    1987-01-01

    In ion beam diodes, electromagnetic wave is coupled to ion beam. Ion is extracted from anode plasma, which is produced early in the power pulse. However, exact mechanism of anode plasma production, expansion and ion extraction process is unknown. In particularly, anode plasma expansion is seemed to be one of the reasons of rapid impedance collapse of the diode, which is serious problem in high power experiments. Some experimental results showed that anode plasma expansion velocity was about 5 times larger than that inferred from simple thermal velocity. Several explanations for these results were proposed; for example, electron collisionarity in anode plasma, fast neutral gas particle, diamagnetism. To solve this question, it is necessary to measure the characteristic of anode plasma with space and time resolution. The authors made spectroscopic measurements to investigate variety of electron temperature, electron density, expansion velocity of anode plasma with various ion sources

  2. Polarization Measurements in High-Energy Deuteron Photodisintegration

    International Nuclear Information System (INIS)

    Adam Sarty; Andrei Afanasev; Arunava Saha; Bogdan Wojtsekhowski; Brendan Fox; Chang, C.; Cathleen Jones; Charles Glashausser; Charles Perdrisat; Cornelis De Jager; Cornelis De Jager; Cornelis de Jager; Crovelli, D.; Daniel Simon; David Meekins; Demetrius Margaziotis; Dipangkar Dutta; Edgar Kooijman; Edward Brash; Edward Kinney; Elaine Schulte; Eugene Chudakov; Feng Xiong; Franco Garibaldi; Garth Huber; Gerfried Kumbartzki; Guido Urciuoli; Haiyan Gao; James Kelly; Javier Gomez; Jens-Ole Hansen; Jian-Ping Chen; John Calarco; John LeRose; Jordan Hovdebo; Joseph Mitchell; Juncai Gao; Kamal Benslama; Kathy McCormick; Kevin Fissum; Konrad Aniol; Krishni Wijesooriya; Louis Bimbot; Ludyvine Morand; Luminita Todor; Marat Rvachev; Mark Jones; Martin Epstein; Meihua Liang; Michael Kuss; Moskov Amarian; Nilanga Liyanage; Oleksandr Glamazdin; Olivier Gayou; Paul Ulmer; Pete Markowitz; Peter Bosted; Holt, R.; Riad Suleiman; Richard Lindgren; Rikki Roche; Robert Michaels; Roman Pomatsalyuk; Ronald Gilman; Ronald Ransome; Salvatore Frullani; Scott Dumalski; Seonho Choi; Sergey Malov; Sonja Dieterich; Steffen Strauch; Stephen Becher; Steve Churchwell; Ting Chang; Viktor Gorbenko; Vina Punjabi; Xiaodong Jiang; Zein-Eddine Meziani; Zhengwei Chai; Wang Xu

    2001-01-01

    We present measurements of the recoil proton polarization for the d(polarized y, polarized p)n reaction at thetac.m. = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization py vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(y,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime

  3. Preliminary study on the corrosion behavior of carbon steel in Horonobe groundwater environment

    International Nuclear Information System (INIS)

    Taniguchi, Naoki; Kogawa, Noritaka; Maeda, Kazuto

    2006-08-01

    It is necessary to understand the corrosion behavior of candidate overpack materials to plan the in-situ engineered barrier test at underground laboratory constructing at Horonobe and to design the overpacks suitable to Horonobe environment. The preliminary corrosion tests of carbon steel which is a candidate material for overpacks were carried out using artificial groundwater and actual groundwater sampled at Horonobe. As the results of anodic polarization experiments, the anodic polarization curves of carbon steel in buffer material were active dissolution type, and the corrosion type of carbon steel in Horonobe groundwater environment was expected to be general corrosion. The results of immersion test under air equilibrium condition showed that the degrees of corrosion localization were not exceeded the data obtained in previous studies. The trend of corrosion rates in buffer material under anaerobic condition were similar to the data obtained in previous studies. Based on the experimental results, it was confirmed that the corrosion assessment model and assumed corrosion rate in second progress report (H12 report) can be applied to the assessment for Horonobe groundwater condition. (author)

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

    Science.gov (United States)

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

    2017-12-01

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

  5. Passivation of mechanically polished, chemically etched and anodized zirconium in various aqueous solutions: Impedance measurements

    International Nuclear Information System (INIS)

    Abo-Elenien, G.M.; Abdel-Salam, O.E.

    1987-01-01

    Zirconium and its alloys are finding increasing applications especially in water-cooled nuclear reactors. Because of the fact that zirconium is electronegative (E 0 = -1.529V) its corrosion resistance in aqueous solutions is largely determined by the existence of a thin oxide film on its surface. The structure and properties of this film depend in the first place on the method of surface pre-treatment. This paper presents an experimental study of the nature of the oxide film on mechanically polished, chemically etched and anodized zirconium. Ac impedance measurements carried out in various acidic, neutral and alkaline solutions show that the film thickness depends on the method of surface pre-treatment and the type of electrolyte solution. The variation of the potential and impedance during anodization of zirconium at low current density indicates that the initial stages of polarization consist of oxide build-up at a rate dependent on the nature of the electrode surface and the electrolyte. Oxygen evolution commences at a stage where oxide thickening starts to decline. The effect of frequency on the measured impedance indicates that the surface reactivity, and hence the corrosion rate, decreases in the following order: mechanically polished > chemically etched > anodized

  6. Anodal tDCS to V1 blocks visual perceptual learning consolidation.

    Science.gov (United States)

    Peters, Megan A K; Thompson, Benjamin; Merabet, Lotfi B; Wu, Allan D; Shams, Ladan

    2013-06-01

    This study examined the effects of visual cortex transcranial direct current stimulation (tDCS) on visual processing and learning. Participants performed a contrast detection task on two consecutive days. Each session consisted of a baseline measurement followed by measurements made during active or sham stimulation. On the first day, one group received anodal stimulation to primary visual cortex (V1), while another received cathodal stimulation. Stimulation polarity was reversed for these groups on the second day. The third (control) group of subjects received sham stimulation on both days. No improvements or decrements in contrast sensitivity relative to the same-day baseline were observed during real tDCS, nor was any within-session learning trend observed. However, task performance improved significantly from Day 1 to Day 2 for the participants who received cathodal tDCS on Day 1 and for the sham group. No such improvement was found for the participants who received anodal stimulation on Day 1, indicating that anodal tDCS blocked overnight consolidation of visual learning, perhaps through engagement of inhibitory homeostatic plasticity mechanisms or alteration of the signal-to-noise ratio within stimulated cortex. These results show that applying tDCS to the visual cortex can modify consolidation of visual learning. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. Modeling of solid oxide fuel cells with particle size and porosity grading in anode electrode

    Energy Technology Data Exchange (ETDEWEB)

    Liu, L.; Flesner, R.; Kim, G.Y.; Chandra, A. [Department of Mechanical Engineering, Iowa State University, Ames, Iowa (United States)

    2012-02-15

    Solid oxide fuel cells (SOFCs) have the potential to meet the critical energy needs of our modern civilization and minimize the adverse environmental impacts from excessive energy consumption. They are highly efficient, clean, and can run on variety of fuel gases. However, little investigative focus has been put on optimal power output based on electrode microstructure. In this work, a complete electrode polarization model of SOFCs has been developed and utilized to analyze the performance of functionally graded anode with different particle size and porosity profiles. The model helps to understand the implications of varying the electrode microstructure from the polarization standpoint. The work identified conditions when grading can improve the cell performance and showed that grading is not always beneficial or necessary. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Acceleration of polarized particles

    International Nuclear Information System (INIS)

    Buon, J.

    1992-05-01

    The spin kinetics of polarized beams in circular accelerators is reviewed in the case of spin-1/2 particles (electrons and protons) with emphasis on the depolarization phenomena. The acceleration of polarized proton beams in synchrotrons is described together with the cures applied to reduce depolarization, including the use of 'Siberian Snakes'. The in-situ polarization of electrons in storage rings due to synchrotron radiation is studied as well as depolarization in presence of ring imperfections. The applications of electron polarization to accurately calibrate the rings in energy and to use polarized beams in colliding-beam experiments are reviewed. (author) 76 refs., 19 figs., 1 tab

  9. Anodal Transcranial Direct Current Stimulation Promotes Frontal Compensatory Mechanisms in Healthy Elderly Subjects.

    Science.gov (United States)

    Cespón, Jesús; Rodella, Claudia; Rossini, Paolo M; Miniussi, Carlo; Pellicciari, Maria C

    2017-01-01

    Recent studies have demonstrated that transcranial direct current stimulation (tDCS) is potentially useful to improve working memory. In the present study, young and elderly subjects performed a working memory task ( n -back task) during an electroencephalogram recording before and after receiving anodal, cathodal, and sham tDCS over the left dorsolateral prefrontal cortex (DLPFC). We investigated modulations of behavioral performance and electrophysiological correlates of working memory processes (frontal and parietal P300 event-related potentials). A strong tendency to modulated working memory performance was observed after the application of tDCS. In detail, young, but not elderly, subjects benefited from additional practice in the absence of real tDCS, as indicated by their more accurate responses after sham tDCS. The cathodal tDCS had no effect in any group of participants. Importantly, anodal tDCS improved accuracy in elderly. Moreover, increased accuracy after anodal tDCS was correlated with a larger frontal P300 amplitude. These findings suggest that, in elderly subjects, improved working memory after anodal tDCS applied over the left DLPFC may be related to the promotion of frontal compensatory mechanisms, which are related to attentional processes.

  10. Anodal Transcranial Direct Current Stimulation Promotes Frontal Compensatory Mechanisms in Healthy Elderly Subjects

    Directory of Open Access Journals (Sweden)

    Jesús Cespón

    2017-12-01

    Full Text Available Recent studies have demonstrated that transcranial direct current stimulation (tDCS is potentially useful to improve working memory. In the present study, young and elderly subjects performed a working memory task (n-back task during an electroencephalogram recording before and after receiving anodal, cathodal, and sham tDCS over the left dorsolateral prefrontal cortex (DLPFC. We investigated modulations of behavioral performance and electrophysiological correlates of working memory processes (frontal and parietal P300 event-related potentials. A strong tendency to modulated working memory performance was observed after the application of tDCS. In detail, young, but not elderly, subjects benefited from additional practice in the absence of real tDCS, as indicated by their more accurate responses after sham tDCS. The cathodal tDCS had no effect in any group of participants. Importantly, anodal tDCS improved accuracy in elderly. Moreover, increased accuracy after anodal tDCS was correlated with a larger frontal P300 amplitude. These findings suggest that, in elderly subjects, improved working memory after anodal tDCS applied over the left DLPFC may be related to the promotion of frontal compensatory mechanisms, which are related to attentional processes.

  11. Modeling for CO poisoning of a fuel cell anode

    Science.gov (United States)

    Dhar, H. P.; Kush, A. K.; Patel, D. N.; Christner, L. G.

    1986-01-01

    Poisoning losses in a half-cell in the 110-190 C temperature range have been measured in 100 wt pct H3PO4 for various mixtures of H2, CO, and CO2 gases in order to investigate the polarization loss due to poisoning by CO of a porous fuel cell Pt anode. At a fixed current density, the poisoning loss was found to vary linearly with ln of the CO/H2 concentration ratio, although deviations from linearity were noted at lower temperatures and higher current densities for high CO/H2 concentration ratios. The surface coverages of CO were also found to vary linearly with ln of the CO/H2 concentration ratio. A general adsorption relationship is derived. Standard free energies for CO adsorption were found to vary from -14.5 to -12.1 kcal/mol in the 130-190 C temperature range. The standard entropy for CO adsorption was found to be -39 cal/mol per deg K.

  12. Passivation behavior of Type 304 stainless steel in a non-aqueous alkyl carbonate solution containing LiPF6 salt

    International Nuclear Information System (INIS)

    Myung, Seung-Taek; Sasaki, Yusuke; Saito, Takamitsu; Sun, Yang-Kook; Yashiro, Hitoshi

    2009-01-01

    Passivation behavior of type 304 stainless steel in a non-aqueous alkyl carbonate solution containing LiPF 6 salt was studied using electrochemical polarization, X-ray photoelectron spectroscopy (XPS) and time of flight-secondary ion mass spectroscopy (ToF-SIMS). Cathodic polarization to 0 V vs. Li/Li + resulted in most but not complete reduction of the air-formed film from oxides to metal on the stainless steel, as confirmed by XPS. For complete elimination of the air-formed film, the surface of the stainless steel was scratched under anodic polarization conditions. At 3 V vs. Li/Li + where an anodic current peak appeared, only an indistinct layer was recognized on the newly scratched surface, according to ToF-SIMS analysis. Above 4 V vs. Li/Li + , substantial passive films were formed, which were composed of oxides and fluorides of iron and chromium. The origin of oxide was due to water contained in the non-aqueous alkyl carbonate solution, and that of fluorides were the result of the decomposition of electrolytic salt, LiPF 6 , especially at higher potential. The resultant passive films were stable in the non-aqueous alkyl carbonate solution containing LiPF 6 salt.

  13. Polarization effects. Volume 2

    Energy Technology Data Exchange (ETDEWEB)

    Courant, E.

    1981-01-01

    The use of polarized proton beams in ISABELLE is important for several general reasons: (1) With a single longitudinally polarized proton beam, effects involving parity violation can be identified and hence processes involving weak interactions can be separated from those involving strong and electromagnetic interactions. (2) Spin effects are important in the strong interactions and can be useful for testing QCD. The technique for obtaining polarized proton beams in ISABELLE appears promising, particularly in view of the present development of a polarized proton beam for the AGS. Projections for the luminosity in ISABELLE for collisions of polarized protons - one or both beams polarized with longitudinal or transverse polarization - range from 1/100 to 1 times the luminosity for unpolarized protons.

  14. The Physics of Polarization

    Science.gov (United States)

    Landi Degl'Innocenti, Egidio

    2015-10-01

    The introductory lecture that has been delivered at this Symposium is a condensed version of an extended course held by the author at the XII Canary Island Winter School from November 13 to November 21, 2000. The full series of lectures can be found in Landi Degl'Innocenti (2002). The original reference is organized in 20 Sections that are here itemized: 1. Introduction, 2. Description of polarized radiation, 3. Polarization and optical devices: Jones calculus and Muller matrices, 4. The Fresnel equations, 5. Dichroism and anomalous dispersion, 6. Polarization in everyday life, 7. Polarization due to radiating charges, 8. The linear antenna, 9. Thomson scattering, 10. Rayleigh scattering, 11. A digression on Mie scattering, 12. Bremsstrahlung radiation, 13. Cyclotron radiation, 14. Synchrotron radiation, 15. Polarization in spectral lines, 16. Density matrix and atomic polarization, 17. Radiative transfer and statistical equilibrium equations, 18. The amplification condition in polarized radiative transfer, and 19. Coupling radiative transfer and statistical equilibrium equations.

  15. Corrosion Behavior of Metal Active Gas Welded Joints of a High-Strength Steel for Automotive Application

    Science.gov (United States)

    Garcia, Mainã Portella; Mantovani, Gerson Luiz; Vasant Kumar, R.; Antunes, Renato Altobelli

    2017-10-01

    In this work, the corrosion behavior of metal active gas-welded joints of a high-strength steel with tensile yield strength of 900 MPa was investigated. The welded joints were obtained using two different heat inputs. The corrosion behavior has been studied in a 3.5 wt.% NaCl aqueous solution using electrochemical impedance spectroscopy and potentiodynamic polarization tests. Optical microscopy images, scanning electron microscopy and transmission electron microscopy with energy-dispersive x-ray revealed different microstructural features in the heat-affected zone (HAZ) and the weld metal (WM). Before and after the corrosion process, the sample was evaluated by confocal laser scanning microscopy to measure the depth difference between HAZ and WM. The results showed that the heat input did not play an important role on corrosion behavior of HSLA steel. The anodic and cathodic areas of the welded joints could be associated with depth differences. The HAZ was found to be the anodic area, while the WM was cathodic with respect to the HAZ. The corrosion behavior was related to the amount and orientation nature of carbides in the HAZ. The microstructure of the HAZ consisted of martensite and bainite, whereas acicular ferrite was observed in the weld metal.

  16. Facile synthesis of SnO2 nanocrystals anchored onto graphene nanosheets as anode materials for lithium-ion batteries.

    Science.gov (United States)

    Zhang, Yanjun; Jiang, Li; Wang, Chunru

    2015-08-21

    A SnO2/graphene nanocomposite was prepared via a facile solvothermal process using stannous octoate as a Sn source. The as-prepared SnO2/graphene nanocomposite exhibited excellent electrochemical behavior with a high reversible capacity, a long cycle life and a good rate capability when used as an anode material for lithium-ion batteries.

  17. Investigation of mechanism of anode plasma formation in ion diode with dielectric anode

    International Nuclear Information System (INIS)

    Pushkarev, A.

    2015-01-01

    The results of investigation of the anode plasma formation in a diode with a passive anode in magnetic insulation mode are presented. The experiments have been conducted using the BIPPAB-450 ion accelerator (350–400 kV, 6–8 kA, 80 ns) with a focusing conical diode with B r external magnetic field (a barrel diode). For analysis of plasma formation at the anode and the distribution of the ions beam energy density, infrared imaging diagnostics (spatial resolution of 1–2 mm) is used. For analysis of the ion beam composition, time-of-flight diagnostics (temporal resolution of 1 ns) were used. Our studies have shown that when the magnetic induction in the A-C gap is much larger than the critical value, the ion beam energy density is close to the one-dimensional Child-Langmuir limit on the entire working surface of the diode. Formation of anode plasma takes place only by the flashover of the dielectric anode surface. In this mode, the ion beam consists primarily of singly ionized carbon ions, and the delay of the start of formation of the anode plasma is 10–15 ns. By reducing the magnetic induction in the A-C gap to a value close to the critical one, the ion beam energy density is 3–6 times higher than that calculated by the one-dimensional Child-Langmuir limit, but the energy density of the ion beam is non-uniform in cross-section. In this mode, the anode plasma formation occurs due to ionization of the anode material with accelerated electrons. In this mode, also, the delay in the start of the formation of the anode plasma is much smaller and the degree of ionization of carbon ions is higher. In all modes occurred effective suppression of the electronic component of the total current, and the diode impedance was 20–30 times higher than the values calculated for the mode without magnetic insulation of the electrons. The divergence of the ion beam was 4.5°–6°

  18. Electrocatalysis of anodic oxidation of ethanol

    Science.gov (United States)

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

    2013-11-01

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

  19. Electrocatalysis of anodic oxidation of ethanol

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  20. High performance anode for advanced Li batteries

    Energy Technology Data Exchange (ETDEWEB)

    Lake, Carla [Applied Sciences, Inc., Cedarville, OH (United States)

    2015-11-02

    The overall objective of this Phase I SBIR effort was to advance the manufacturing technology for ASI’s Si-CNF high-performance anode by creating a framework for large volume production and utilization of low-cost Si-coated carbon nanofibers (Si-CNF) for the battery industry. This project explores the use of nano-structured silicon which is deposited on a nano-scale carbon filament to achieve the benefits of high cycle life and high charge capacity without the consequent fading of, or failure in the capacity resulting from stress-induced fracturing of the Si particles and de-coupling from the electrode. ASI’s patented coating process distinguishes itself from others, in that it is highly reproducible, readily scalable and results in a Si-CNF composite structure containing 25-30% silicon, with a compositionally graded interface at the Si-CNF interface that significantly improve cycling stability and enhances adhesion of silicon to the carbon fiber support. In Phase I, the team demonstrated the production of the Si-CNF anode material can successfully be transitioned from a static bench-scale reactor into a fluidized bed reactor. In addition, ASI made significant progress in the development of low cost, quick testing methods which can be performed on silicon coated CNFs as a means of quality control. To date, weight change, density, and cycling performance were the key metrics used to validate the high performance anode material. Under this effort, ASI made strides to establish a quality control protocol for the large volume production of Si-CNFs and has identified several key technical thrusts for future work. Using the results of this Phase I effort as a foundation, ASI has defined a path forward to commercialize and deliver high volume and low-cost production of SI-CNF material for anodes in Li-ion batteries.

  1. Three-dimensional polarization algebra.

    Science.gov (United States)

    R Sheppard, Colin J; Castello, Marco; Diaspro, Alberto

    2016-10-01

    If light is focused or collected with a high numerical aperture lens, as may occur in imaging and optical encryption applications, polarization should be considered in three dimensions (3D). The matrix algebra of polarization behavior in 3D is discussed. It is useful to convert between the Mueller matrix and two different Hermitian matrices, representing an optical material or system, which are in the literature. Explicit transformation matrices for converting the column vector form of these different matrices are extended to the 3D case, where they are large (81×81) but can be generated using simple rules. It is found that there is some advantage in using a generalization of the Chandrasekhar phase matrix treatment, rather than that based on Gell-Mann matrices, as the resultant matrices are of simpler form and reduce to the two-dimensional case more easily. Explicit expressions are given for 3D complex field components in terms of Chandrasekhar-Stokes parameters.

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

    Science.gov (United States)

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

    2017-01-01

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

  3. Physical-mechanical and electrical properties of aluminium anodic films

    Energy Technology Data Exchange (ETDEWEB)

    Dima, L. [Research and Design Inst. for Electr. Eng., Bucharest (Romania); Anicai, L. [Research and Design Inst. for Electr. Eng., Bucharest (Romania)

    1995-11-01

    Mechanical, thermal and electrical properties of aluminium anodic films obtained by continuously anodization of Al wires of 4.5 mm diameter and Al sheets of 40 x 0.2 mm (Al min.99.5% purity), using an electrolyte based on oxalic acid, citric acid, boric acid, isopropilic alcohol, were investigated. The thickness of Al anodic oxide layers was 5 {+-} 1{mu}, 10 {+-} 1{mu}, for Al sheet, respectively 5 {+-} 1{mu}, 10 {+-} 1{mu}, 15 {+-} 1{mu}, for Al wire. To establish the influence of anodic film formation on mechanical parameters, measurements of breaking strength and relative elongation at break for anodized and non-anodized Al conductors, were made. In order to electrically characterize the anodic films, the breakdown voltage for different curvature radii of the conductor, between 50 - 12.5 mm, were measured. The influence of the layer thickness, as well as of the cracking during its bending, was established, too. To test the thermal resistance of the insulating anodic films, the Al conductors were subjected to 1 - 5 cyclic thermal shocks at 500 C. After the experimentals were done, it was found that Al anodic films of 5 {+-} 1{mu} may assure a breakdown voltage of minimum 200 V, for coils having a curvature radius greater than 12.5 mm and operating temperatures up to 500 C. From mechanical point of view, anodic oxide film determines a relatively reinforcing of Al conductor, but it doesn`t influence its functional properties. (orig.)

  4. Chromic acid anodizing of aluminum foil

    Science.gov (United States)

    Dursch, H.

    1988-01-01

    The success of the Space Station graphite/epoxy truss structure depends on its ability to endure long-term exposure to the LEO environment, primarily the effects of atomic oxygen and the temperture cycling resulting from the 94 minute orbit. This report describes the development and evaluation of chromic acid anodized (CAA) aluminum foil as protective coatings for these composite tubes. Included are: development of solar absorptance and thermal emittance properties required of Al foil and development of CAA parameters to achieve these optical properties; developing techniques to CAA 25 ft lengths of Al foil; developing bonding processes for wrapping the Al foil to graphite/epoxy tubes; and atomic oxygen testing of the CAA Al foil. Two specifications were developed and are included in the report: Chromic Acid Anodizing of Aluminum Foil Process Specification and Bonding of Anodized Aluminum Foil to Graphite/Epoxy Tubes. Results show that CAA Al foil provides and excellent protective and thermal control coating for the Space Station truss structure.

  5. Protection of MOS capacitors during anodic bonding

    Science.gov (United States)

    Schjølberg-Henriksen, K.; Plaza, J. A.; Rafí, J. M.; Esteve, J.; Campabadal, F.; Santander, J.; Jensen, G. U.; Hanneborg, A.

    2002-07-01

    We have investigated the electrical damage by anodic bonding on CMOS-quality gate oxide and methods to prevent this damage. n-type and p-type MOS capacitors were characterized by quasi-static and high-frequency CV-curves before and after anodic bonding. Capacitors that were bonded to a Pyrex wafer with 10 μm deep cavities enclosing the capacitors exhibited increased leakage current and interface trap density after bonding. Two different methods were successful in protecting the capacitors from such damage. Our first approach was to increase the cavity depth from 10 μm to 50 μm, thus reducing the electric field across the gate oxide during bonding from approximately 2 × 105 V cm-1 to 4 × 104 V cm-1. The second protection method was to coat the inside of a 10 μm deep Pyrex glass cavity with aluminium, forming a Faraday cage that removed the electric field across the cavity during anodic bonding. Both methods resulted in capacitors with decreased interface trap density and unchanged leakage current after bonding. No change in effective oxide charge or mobile ion contamination was observed on any of the capacitors in the study.

  6. Investigation of residual anode material after electrorefining uranium in molten chloride salt

    Energy Technology Data Exchange (ETDEWEB)

    Rose, M.A., E-mail: marose@anl.gov [Department of Nuclear Engineering, Purdue University, West Lafayette, IN, 47907 (United States); Nuclear Engineering Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Williamson, M.A.; Willit, J. [Nuclear Engineering Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2015-12-15

    A buildup of material at uranium anodes during uranium electrorefining in molten chloride salts has been observed. Potentiodynamic testing has been conducted using a three electrode cell, with a uranium working electrode in both LiCl/KCl eutectic and LiCl each containing ∼5 mol% UCl{sub 3}. The anodic current response was observed at 50° intervals between 450 °C and 650 °C in the eutectic salt. These tests revealed a buildup of material at the anode in LiCl/KCl salt, which was sampled at room temperature, and analyzed using ICP-MS, XRD and SEM techniques. Examination of the analytical data, current response curves and published phase diagrams has established that as the uranium anode dissolves, the U{sup 3+} ion concentration in the diffusion layer surrounding the electrode rises precipitously to levels, which may at low temperatures exceed the solubility limit for UCl{sub 3} or in the case of the eutectic salt for K{sub 2}UCl{sub 5}. The reduction in current response observed at low temperature in eutectic salt is eliminated at 650 °C, where K{sub 2}UCl{sub 5} is absent due to its congruent melting and only simple concentration polarization effects are seen. In LiCl similar concentration effects are seen though significantly longer time at applied potential is required to effect a reduction in the current response as compared to the eutectic salt.

  7. Workshop on polarized neutron filters and polarized pulsed neutron experiments

    International Nuclear Information System (INIS)

    Itoh, Shinichi

    2004-07-01

    The workshop was held in KEK by thirty-three participants on April 26, 2004. The polarized neutron filter method was only discussed. It consists of three parts; the first part was discussed on the polarized neutron methods, the second part on the polarized neutron experiments and the third on the pulse neutron spectrometer and polarized neutron experiments. The six papers were presented such as the polarized 3 He neutron spin filter, neutron polarization by proton polarized filter, soft master and neutron scattering, polarized neutron in solid physics, polarization experiments by chopper spectroscope and neutron polarization system in superHRPD. (S.Y.)

  8. Instrumentation with polarized neutrons

    International Nuclear Information System (INIS)

    Boeni, P.; Muenzer, W.; Ostermann, A.

    2009-01-01

    Neutron scattering with polarization analysis is an indispensable tool for the investigation of novel materials exhibiting electronic, magnetic, and orbital degrees of freedom. In addition, polarized neutrons are necessary for neutron spin precession techniques that path the way to obtain extremely high resolution in space and time. Last but not least, polarized neutrons are being used for fundamental studies as well as very recently for neutron imaging. Many years ago, neutron beam lines were simply adapted for polarized beam applications by adding polarizing elements leading usually to unacceptable losses in neutron intensity. Recently, an increasing number of beam lines are designed such that an optimum use of polarized neutrons is facilitated. In addition, marked progress has been obtained in the technology of 3 He polarizers and the reflectivity of large-m supermirrors. Therefore, if properly designed, only factors of approximately 2-3 in neutron intensity are lost. It is shown that S-benders provide neutron beams with an almost wavelength independent polarization. Using twin cavities, polarized beams with a homogeneous phase space and P>0.99 can be produced without significantly sacrificing intensity. It is argued that elliptic guides, which are coated with large m polarizing supermirrors, provide the highest flux.

  9. In operando X-ray diffraction strain measurement in Ni3Sn2 - Coated inverse opal nanoscaffold anodes for Li-ion batteries

    Science.gov (United States)

    Glazer, Matthew P. B.; Wang, Junjie; Cho, Jiung; Almer, Jonathan D.; Okasinski, John S.; Braun, Paul V.; Dunand, David C.

    2017-11-01

    Volume changes associated with the (de)lithiation of a nanostructured Ni3Sn2 coated nickel inverse opal scaffold anode create mismatch stresses and strains between the Ni3Sn2 anode material and its mechanically supporting Ni scaffold. Using in operando synchrotron x-ray diffraction measurements, elastic strains in the Ni scaffold are determined during cyclic (dis)charging of the Ni3Sn2 anode. These strains are characterized using both the center position of the Ni diffraction peaks, to quantify the average strain, and the peak breadth, which describes the distribution of strain in the measured volume. Upon lithiation (half-cell discharging) or delithiation (half-cell charging), compressive strains and peak breadth linearly increase or decrease, respectively, with charge. The evolution of the average strains and peak breadths suggests that some irreversible plastic deformation and/or delamination occurs during cycling, which can result in capacity fade in the anode. The strain behavior associated with cycling of the Ni3Sn2 anode is similar to that observed in recent studies on a Ni inverse-opal supported amorphous Si anode and demonstrates that the (de)lithiation-induced deformation and damage mechanisms are likely equivalent in both anodes, even though the magnitude of mismatch strain in the Ni3Sn2 is lower due to the lower (de)lithiation-induced contraction/expansion.

  10. An in situ near-ambient pressure X-ray Photoelectron Spectroscopy study of Mn polarised anodically in a cell with solid oxide electrolyte

    International Nuclear Information System (INIS)

    Bozzini, Benedetto; Amati, Matteo; Bocchetta, Patrizia; Dal Zilio, Simone; Knop-Gericke, Axel; Vesselli, Erik; Kiskinova, Maya

    2015-01-01

    This paper reports an in situ study of the anodic behavior of a model solid oxide electrolysis cell (SOEC) by means of near-ambient pressure X-ray Photoelectron Spectroscopy (XPS) combined with near edge X-ray absorption fine structure (NEXAFS) measurements. The focus is on the anodic surface chemistry of MnO x , a model anodic material already considered in cognate SOFC-related studies, during electrochemical operation in CO 2 , CO 2 /H 2 O and H 2 O ambients. The XPS and NEXAFS results we obtained, complemented by electrochemical measurements and SEM characterisation, reveal the chemical evolution of Mn under electrochemical control. MnO is the stable chemical form at open-circuit potential (OCP), while Mn 3 O 4 forms under anodic polarisation in all the investigated gas ambients. Carbon deposits are present on the Mn electrode at OCP, but they are readily oxidised under anodic conditions. Prolonged operation of the MnO x anode leads to pitting of the Mn films, damaging of the triple-phase boundary region and also to formation of discontinuities in the Mn patch. This is accompanied by chemical transformations of the electrolyte and formation of ZrC without impact on the surface chemistry of the Mn-based anode

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

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  12. Microstructural degradation of Ni-YSZ anodes for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Thyden, K.

    2008-03-15

    Ni-YSZ cermets have been used as anode materials in SOFCs for more than 20 years. Despite this fact, the major cause of degradation within the Ni-YSZ anode, namely Ni sintering / coarsening, is still not fully understood. Even if microstructural studies of anodes in tested cells are of technological relevance, it is difficult to identify the effect from isolated parameters such as temperature, fuel gas composition and polarization. Model studies of high temperature aged Ni-YSZ cermets are generally performed in atmospheres containing relatively low concentrations of H2O. In this work, the microstructural degradation in both electrochemically longterm tested cells and high-temperature aged model materials are studied. Since Ni particle sintering / coarsening is attributed to be the major cause of anode degradation, this subject attains the primary focus. A large part of the work is focused on improving microstructural techniques and shows that the application of low acceleration voltages (<= 1 kV) in a FE-SEM makes it possible to obtain two useful types of contrast between the phases in Ni-YSZ composites. By changing between the ordinary lateral SE detector and the inlens detector, using similar microscope settings, two very different sample characteristics are probed: 1) The difference in secondary emission coefficient, delta, between the percolating and non-percolating Ni is maximized in the low-voltage range due to a high delta for the former and the suppression of delta by a positive charge for the latter. This difference yields a contrast between the two phases which is picked up by an inlens secondary electron detector. 2) The difference in backscatter coefficient, eta, between Ni and YSZ is shown to increase with decreasing voltage. The contrast is illustrated in images collected by the normal secondary detector since parts of the secondary signals are generated by backscattered electrons. High temperature aging experiments of model Ni-YSZ anode cermets show

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-10-15

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

  14. Tracer Studies of the Influence of Foreign Substances at the Surface of the Electrodes. I. Polarization Phenomena

    International Nuclear Information System (INIS)

    Llopis, J.; Gamboa, J. M.; Arizmendi, L.

    1961-01-01

    Radioactive stearic acid ( 1 4C) has been used to determine the number of molecular layers present on copper electrode surfaces and its distribution. The stability of these layers under the experimental conditions has been studied and it has been shown that its presence has no influence on the anodic and cathodic polarization. an increase of these polarizations has been observed with mixed multilayers of stearic acid and sterolamide. (Author) 13 refs

  15. Redox Stable Anodes for Solid Oxide Fuel Cells

    Directory of Open Access Journals (Sweden)

    Guoliang eXiao

    2014-06-01

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

  16. Patterned titania nanostructures produced by electrochemical anodization of titanium sheet

    Science.gov (United States)

    Dong, Junzhe; Ariyanti, Dessy; Gao, Wei; Niu, Zhenjiang; Weil, Emeline

    2017-07-01

    A two-step anodization method has been used to produce patterned arrays of TiO2 on the surface of Ti sheet. Hexagonal ripples were created on Ti substrate after removing the TiO2 layer produced by first-step anodization. The shallow concaves were served as an ideal position for the subsequent step anodization due to their low electrical resistance, resulting in novel hierarchical nanostructures with small pits inside the original ripples. The mechanism of morphology evolution during patterned anodization was studied through changing the anodizing voltages and duration time. This work provides a new idea for controlling nanostructures and thus tailoring the photocatalytic property and wettability of anodic TiO2.

  17. Multiphoton polarization Bremsstrahlung effect

    International Nuclear Information System (INIS)

    Golovinskij, P.A.

    2001-01-01

    A general approach to induced polarization effects was formulated on the basis of theory of many particles in a strong periodic field. Correlation with the perturbation theory is shown and the types of effective polarization potentials both for isolated atoms and ions, and for ions in plasma, are provided. State of art in the theory of forced polarization Bremsstrahlung effect is analyzed and some outlooks for further experimental and theoretical studies are outlined [ru

  18. Polar and low polar solvents media effect on dipole moments of some diazo Sudan dyes

    Science.gov (United States)

    Zakerhamidi, M. S.; Golghasemi Sorkhabi, Sh.; Shamkhali, A. N.

    2014-06-01

    Absorption and fluorescence spectra of three Sudan dyes (SudanIII, SudanIV and Sudan black B) were recorded in various solvents with different polarity in the range of 300-800 nm, at room temperature. The solvatochromic method was used to investigate dipole moments of these dyes in ground and excited states, in different media. The solvatochromic behavior of these substances and their solvent-solute interactions were analyzed via solvent polarity parameters. Obtained results express the effects of solvation on tautomerism and molecular configuration (geometry) of Sudan dyes in solvent media with different polarity. Furthermore, analyze of solvent-solute interactions and value of ground and excited states dipole moments suggests different forms of resonance structures for Sudan dyes in polar and low-polar solvents.

  19. Airborne Laser Polarization Sensor

    Science.gov (United States)

    Kalshoven, James, Jr.; Dabney, Philip

    1991-01-01

    Instrument measures polarization characteristics of Earth at three wavelengths. Airborne Laser Polarization Sensor (ALPS) measures optical polarization characteristics of land surface. Designed to be flown at altitudes of approximately 300 m to minimize any polarizing or depolarizing effects of intervening atmosphere and to look along nadir to minimize any effects depending on look angle. Data from measurements used in conjunction with data from ground surveys and aircraft-mounted video recorders to refine mathematical models used in interpretation of higher-altitude polarimetric measurements of reflected sunlight.

  20. Polarization of Be stars

    International Nuclear Information System (INIS)

    Johns, M.W.

    1975-01-01

    Linear polarization of starlight may be produced by electron scattering in the extended atmospheres of early type stars. Techniques are investigated for the measurement and interpretation of this polarization. Polarimetric observations were made of twelve visual double star systems in which at least one member was a B type star as a means of separating the intrinsic stellar polarization from the polarization produced in the interstellar medium. Four of the double stars contained a Be star. Evidence for intrinsic polarization was found in five systems including two of the Be systems, one double star with a short period eclipsing binary, and two systems containing only normal early type stars for which emission lines have not been previously reported. The interpretation of these observations in terms of individual stellar polarizations and their wavelength dependence is discussed. The theoretical basis for the intrinsic polarization of early type stars is explored with a model for the disk-like extended atmospheres of Be stars. Details of a polarimeter for the measurement of the linear polarization of astronomical point sources are also presented with narrow band (Δ lambda = 100A) measurements of the polarization of γ Cas from lambda 4000 to lambda 5800

  1. Polarization at SLC

    International Nuclear Information System (INIS)

    Swartz, M.L.

    1988-07-01

    The SLAC Linear Collider has been designed to readily accommodate polarized electron beams. Considerable effort has been made to implement a polarized source, a spin rotation system, and a system to monitor the beam polarization. Nearly all major components have been fabricated. At the current time, several source and polarimeter components have been installed. The installation and commissioning of the entire system will take place during available machine shutdown periods as the commissioning of SLC progresses. It is expected that a beam polarization of 45% will be achieved with no loss in luminosity. 13 refs., 15 figs

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

    OpenAIRE

    Gerrard Eddy Jai Poinern; Derek Fawcett; Nurshahidah Ali

    2011-01-01

    The anodization of aluminum is an electro-chemical process that changes the surface chemistry of the metal, via oxidation, to produce an anodic oxide layer. During this process a self organized, highly ordered array of cylindrical shaped pores can be produced with controllable pore diameters, periodicity and density distribution. This enables anodic aluminum oxide (AAO) membranes to be used as templates in a variety of nanotechnology applications without the need for expensive lithographical ...

  3. Managing focal fields of vector beams with multiple polarization singularities.

    Science.gov (United States)

    Han, Lei; Liu, Sheng; Li, Peng; Zhang, Yi; Cheng, Huachao; Gan, Xuetao; Zhao, Jianlin

    2016-11-10

    We explore the tight focusing behavior of vector beams with multiple polarization singularities, and analyze the influences of the number, position, and topological charge of the singularities on the focal fields. It is found that the ellipticity of the local polarization states at the focal plane could be determined by the spatial distribution of the polarization singularities of the vector beam. When the spatial location and topological charge of singularities have even-fold rotation symmetry, the transverse fields at the focal plane are locally linearly polarized. Otherwise, the polarization state becomes a locally hybrid one. By appropriately arranging the distribution of the polarization singularities in the vector beam, the polarization distributions of the focal fields could be altered while the intensity maintains unchanged.

  4. The corrosion protection of 2219-T87 aluminum by anodizing

    Science.gov (United States)

    Danford, M. D.

    1991-01-01

    Various types of anodizing coatings were studied for 2219-T87 aluminum. These include both type II and type III anodized coats which were water sealed and a newly developed and proprietary Magnaplate HCR (TM) coat. Results indicate that type II anodizing is not much superior to type II anodizing as far as corrosion protection for 2219-T87 aluminum is concerned. Magnaplate HCR (TM) coatings should provide superior corrosion protection over an extended period of time using a coating thickness of 51 microns (2.0 mils).

  5. Generation of high brightness ion beam from insulated anode PED

    International Nuclear Information System (INIS)

    Matsukawa, Yoshinobu

    1988-01-01

    Generation and focusing of a high density ion beam with high brightness from a organic center part of anode of a PED was reported previously. Mass, charge and energy distribution of this beam were analyzed. Three kind of anode were tried. Many highly ionized medium mass ions (up to C 4+ , O 6+ ) accelarated to several times of voltage difference between anode and cathode were observed. In the case of all insulator anode the current carried by the medium mass ions is about half of that carried by protons. (author)

  6. Controlling vortex chirality and polarity by geometry in magnetic nanodots

    OpenAIRE

    Agramunt Puig, Sebastià

    2014-01-01

    The independent control of both vortex chirality and polarity is a significant challenge in magnetic devices based on nano-sized magnetic vortex structures. By micromagnetic simulations here, we show that in soft ferromagnetic nanodots with an adequate modulated thickness, the desired combination of chirality and polarity can be achieved just by changing the direction of the in-plane applied magnetic field. Despite the complex behavior, the vortex chirality and polarity control can be summari...

  7. Quantum switching of polarization in mesoscopic ferroelectrics

    International Nuclear Information System (INIS)

    Sa de Melo, C.A.

    1996-01-01

    A single domain of a uniaxial ferroelectric grain may be thought of as a classical permanent memory. At the mesoscopic level this system may experience considerable quantum fluctuations due to tunneling between two possible memory states, thus destroying the classical permanent memory effect. To study these quantum effects the concrete example of a mesoscopic uniaxial ferroelectric grain is discussed, where the orientation of the electric polarization determines two possible memory states. The possibility of quantum switching of the polarization in mesoscopic uniaxial ferroelectric grains is thus proposed. To determine the degree of memory loss, the tunneling rate between the two polarization states is calculated at zero temperature both in the absence and in the presence of an external static electric field. In addition, a discussion of crossover temperature between thermally activated behavior and quantum tunneling behavior is presented. And finally, environmental effects (phonons, defects, and surfaces) are also considered. copyright 1996 The American Physical Society

  8. Low-density silicon thin films for lithium-ion battery anodes

    Energy Technology Data Exchange (ETDEWEB)

    Demirkan, M.T., E-mail: tmdemirkan@ualr.edu [Department of Physics and Astronomy, University of Arkansas at Little Rock, Little Rock, AR 72204 (United States); Department of Materials Science and Engineering, Gebze Technical University, Kocaeli (Turkey); Trahey, L. [Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Karabacak, T. [Department of Physics and Astronomy, University of Arkansas at Little Rock, Little Rock, AR 72204 (United States)

    2016-02-01

    Density of sputter deposited silicon (Si) thin films was changed by a simple working gas pressure control process, and its effects on the cycling performance of Si films in Li-ion batteries as anodes was investigated. Higher gas pressure results in reduced film densities due to a shadowing effect originating from lower mean free path of sputter atoms, which leads to a wider angular distribution of the incoming flux and formation of a porous film microstructure. Si thin film anodes of different densities ranging from 2.27 g/cm{sup 3} (film porosity ~ 3%) down to 1.64 g/cm{sup 3} (~ 30% porosity) were fabricated by magnetron sputtering at argon pressures varying from 0.2 Pa to 2.6 Pa, respectively. High density Si thin film anodes of 2.27 g/cm{sup 3} suffered from an unstable cycling behavior during charging/discharging depicted by a continuous reduction in specific down to ~ 830 mAh/g at the 100th cycle. Electrochemical properties of lower density films with 1.99 g/cm{sup 3} (~ 15% porosity) and 1.77 g/cm{sup 3} (~ 24% porosity) got worse resulting in only ~ 100 mAh/g capacity at 100th cycle. On the other hand, as the density of anode was further reduced down to about 1.64 g/cm{sup 3} (~ 30% porosity), cycling stability and capacity retention significantly improved resulting in specific capacity values ~ 650 mAh/g at 100th cycle with coulombic efficiencies of > 98%. Enhancement in our low density Si film anodes are believed to mainly originate from the availability of voids for volumetric expansion during lithiation and resulting compliant behavior that provides superior mechanical and electrochemical stability. - Highlights: • Low density Si thin films were studied as Li-ion battery anodes. • Low density Si films were fabricated by magnetron sputter deposition. • Density of Si films reduced down to as low as ~ 1.64 g/cm{sup 3} with a porosity of ~ 30% • Low density Si films presented superior mechanical properties during cycling.

  9. Electrolytic deposition of Sn-coated mesocarbon microbeads as anode material for lithium ion battery

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Min-Jen [Department of Materials Engineering, National Chung Hsing University, Taichung 40227, Taiwan (China); Jen-Teh Junior College of Medicine, Nursing and Management, Taiwan (China); Tsai, Du-Cheng [Department of Materials Engineering, National Chung Hsing University, Taichung 40227, Taiwan (China); Ho, Wen-Hsien [Taiwan Textile Research Institute, Taipei 23674, Taiwan (China); Li, Ching-Fei, E-mail: chingfei.li@gmail.com [Phoenix Silicon International Corporation, Hsinchu 30094, Taiwan (China); Shieu, Fuh-Sheng, E-mail: fsshieu@dragon.nchu.edu.tw [Department of Materials Engineering, National Chung Hsing University, Taichung 40227, Taiwan (China); Center of Nanoscience and Nanotechnology, National Chung Hsing University, Taichung 40227, Taiwan (China)

    2013-11-15

    Deposited of crystalline tin (Sn) coatings on mesocarbon microbead (MCMB) powder as anodes of lithium ion (Li-ion) battery was conducted in the SnSO{sub 4} solution by a cathodic electrochemical synthesis. The Sn-coated MCMB specimens were characterized by X-ray diffraction, scanning electron microscopy, and charge/discharge tests. The synthesis condition of Sn-coated MCMB was optimized by considering the agglomeration, size, and adhesion of the samples to the current collectors in the battery. The Sn-coated MCMB electrodes exhibit increased reversible capacity without sacrificing its cycling behavior, compared with bare MCMB electrodes. It is concluded that electrolysis-deposited Sn-coated MCMB electrodes may emerge as a practical and promising anode material for secondary Li-ion batteries.

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

    Science.gov (United States)

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

    2009-02-01

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

  11. Electrolytic deposition of Sn-coated mesocarbon microbeads as anode material for lithium ion battery

    International Nuclear Information System (INIS)

    Deng, Min-Jen; Tsai, Du-Cheng; Ho, Wen-Hsien; Li, Ching-Fei; Shieu, Fuh-Sheng

    2013-01-01

    Deposited of crystalline tin (Sn) coatings on mesocarbon microbead (MCMB) powder as anodes of lithium ion (Li-ion) battery was conducted in the SnSO 4 solution by a cathodic electrochemical synthesis. The Sn-coated MCMB specimens were characterized by X-ray diffraction, scanning electron microscopy, and charge/discharge tests. The synthesis condition of Sn-coated MCMB was optimized by considering the agglomeration, size, and adhesion of the samples to the current collectors in the battery. The Sn-coated MCMB electrodes exhibit increased reversible capacity without sacrificing its cycling behavior, compared with bare MCMB electrodes. It is concluded that electrolysis-deposited Sn-coated MCMB electrodes may emerge as a practical and promising anode material for secondary Li-ion batteries.

  12. Synthesis and characterization of nanocrystalline Ni-YSZ cermet anode for SOFC

    International Nuclear Information System (INIS)

    Priyatham, T.; Bauri, Ranjit

    2010-01-01

    Ni-YSZ cermet anode has been synthesized in one step using a simple and cost effective combustion synthesis process. The processed powder of NiO-YSZ is found to be nanocrystalline with crystallite sizes of 29 and 22 nm for NiO and YSZ respectively by X-ray diffraction and transmission electron microscopy analysis. X-ray diffraction analysis also shows that the precursor salts are converted to highly crystalline phases of NiO and YSZ (8 mol% Y 2 O 3 ) without any intermediate calcination step and no undesirable phases are present. Comparison with the X-ray diffraction pattern of a commercial YSZ sample shows that the process is also effective in maintaining a close compositional control. The microstructure of the sintered and reduced sample shows a well defined network of pores which is necessary for the effective functioning of the anode. The electrical conductivity as a function of temperature shows metallic behavior.

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

    International Nuclear Information System (INIS)

    Mogoda, A.S.

    1995-01-01

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

  14. Influence of the anodizing process variables on the acidic properties of anodic alumina films

    Directory of Open Access Journals (Sweden)

    D.E. Boldrini

    Full Text Available Abstract In the present work, the effect of the different variables involved in the process of aluminum anodizing on the total surface acidity of the samples obtained was studied. Aluminum foils were treated by the electro-chemical process of anodic anodizing within the following variable ranges: concentration = 1.5-2.5 M; temperature = 303-323 K; voltage = 10-20 V; time = 30-90 min. The total acidity of the samples was characterized by two different methods: acid-base titration using Hammett indicators and potentiometric titration. The results showed that anodizing time, temperature and concentration were the main variables that determined the surface acid properties of the samples, and to a lesser extent voltage. Acidity increased with increasing concentration of the electrolytic bath, whereas the rest of the variables had the opposite effect. The results obtained provide a novel tool for variable selection in order to use synthetized materials as catalytic supports, adding to previous research based on the morphology of alumina layers.

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

    Science.gov (United States)

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

    2018-05-01

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

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

    Science.gov (United States)

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

    2015-12-01

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

  17. Towards anode with low indium content as effective anode in organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Touihri, S. [Unite de Physique des Dispositifs a Semi-conducteurs, Universite El Manar Faculte des Sciences de Tunis, Campus Universitaire 2092 (Tunisia); Cattin, L.; Nguyen, D-T. [LUNAM, Universite de Nantes, Institut Jean Rouxel (IMN), UMR 6502, 2 rue de la Houssiniere, BP 92208, Nantes F-44322 (France); Morsli, M. [LUNAM, Universite de Nantes, Faculte des Sciences et des Techniques, 2 rue de la Houssiniere, BP 92208, Nantes F-44322 (France); Louarn, G. [LUNAM, Universite de Nantes, Institut Jean Rouxel (IMN), UMR 6502, 2 rue de la Houssiniere, BP 92208, Nantes F-44322 (France); Bouteville, A.; Froger, V. [Arts et Metiers Paris Tech Angers, Laboratoire Procedes-Materiaux-Instrumentation, 2, bd du Ronceray, BP 3525, 49035 Angers Cedex (France); Bernede, J.C., E-mail: jean-christian.bernede@univ-nantes.fr [LUNAM, Universite de Nantes, Moltech Anjou, CNRS, UMR 6200, FSTN, 2 Rue de la Houssiniere, BP 92208, Nantes F-44322 (France)

    2012-01-15

    In{sub 2}O{sub 3} thin films (100 nm thick) have been deposited by reactive evaporation of indium, in an oxygen partial atmosphere. Conductive ({sigma} = 3.5 Multiplication-Sign 10{sup 3} S/cm) and transparent films are obtained using the following experimental conditions: oxygen partial pressure = 1 Multiplication-Sign 10{sup -1} Pa, substrate temperature = 300 Degree-Sign C and deposition rate = 0.02 nm/s. Layers of this In{sub 2}O{sub 3} thick of 5 nm have been introduced in AZO/In{sub 2}O{sub 3} and FTO/In{sub 2}O{sub 3} multilayer anode structures. The performances of organic photovoltaic cells, based on the couple CuPc/C{sub 60}, are studied using the anode as parameter. In addition to these bilayers, other structures have been used as anode: AZO, FTO, AZO/In{sub 2}O{sub 3}/MoO{sub 3}, FTO/In{sub 2}O{sub 3}/MoO{sub 3} and FTO/MoO{sub 3}. It is shown that the use of the In{sub 2}O{sub 3} film in the bilayer structures improves significantly the cell performances. However the open circuit voltage is quite small while better efficiencies are achieved when MoO{sub 3} is present. These results are discussed in the light of surface roughness and surface work function of the different anodes.

  18. TRANSVERSELY POLARIZED Λ PRODUCTION

    International Nuclear Information System (INIS)

    BORER, D.

    2000-01-01

    Transversely polarized Λ production in hard scattering processes is discussed in terms of a leading twist T-odd fragmentation function which describes the fragmentation of an unpolarized quark into a transversely polarized Λ. We focus on the properties of this function and its relevance for the RHIC and HERMES experiments

  19. Our Polar Past

    Science.gov (United States)

    Clary, Renee; Wandersee, James

    2009-01-01

    The study of polar exploration is fascinating and offers students insights into the history, culture, and politics that affect the developing sciences at the farthest ends of Earth. Therefore, the authors think there is value in incorporating polar exploration accounts within modern science classrooms, and so they conducted research to test their…

  20. Marine polar steroids

    International Nuclear Information System (INIS)

    Stonik, Valentin A

    2001-01-01

    Structures, taxonomic distribution and biological activities of polar steroids isolated from various marine organisms over the last 8-10 years are considered. The peculiarities of steroid biogenesis in the marine biota and their possible biological functions are discussed. Syntheses of some highly active marine polar steroids are described. The bibliography includes 254 references.