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Sample records for h7546b anode current

  1. MAPMT H7546B anode current response study for ILC SiD muon system prototype

    SciTech Connect

    Dyshkant, A.; Blazey, G.; Francis, K.; Hedin, D.; Zutshi, V.; Fisk, H.; Milstene, C.; Abrams, R.; /Indiana U.

    2007-10-01

    The proposed Silicon Detector (SiD) concept for the ILC has barrel and end cap muon systems. An SiD scintillator based muon system prototype has 256 strips and was constructed from extruded strips, WLS fibers, clear fibers, and multianode photo multiplier tubes (MAPMT) Hamamatsu H7546B. Six MAPMTs were used. As a first step to understand strip output, the response of every anode to a given brightness of light and applied voltage must be measured. For the test, a custom made light source was used. Each MAPMT output was measured independently. The anode currents were measured at constant (green) input light brightness and the same photocathode to anode voltage (800V). The anode currents have a wide spread; for all tubes the maximum value is 5.23 times larger than the minimum value. The MAPMT cross talk was measured for one of the central inputs. The maximum cross talk value is about 4.9%. The average cross talk for the nearest four neighboring channels is 3.9%, for the farthest four is 1%. To assure the reproducibility and repeatability of the measurements, the double reference method was used.

  2. Anode current density distribution in a cusped field thruster

    SciTech Connect

    Wu, Huan Liu, Hui Meng, Yingchao; Zhang, Junyou; Yang, Siyu; Hu, Peng; Chen, Pengbo; Yu, Daren

    2015-12-15

    The cusped field thruster is a new electric propulsion device that is expected to have a non-uniform radial current density at the anode. To further study the anode current density distribution, a multi-annulus anode is designed to directly measure the anode current density for the first time. The anode current density decreases sharply at larger radii; the magnitude of collected current density at the center is far higher compared with the outer annuli. The anode current density non-uniformity does not demonstrate a significant change with varying working conditions.

  3. Testing and Characterization of Anode Current in Aluminum Reduction Cells

    NASA Astrophysics Data System (ADS)

    Wang, Yongliang; Tie, Jun; Sun, Shuchen; Tu, Ganfeng; Zhang, Zhifang; Zhao, Rentao

    2016-06-01

    Anode current is an important parameter in the aluminum reduction process, but to test the anode current accurately is difficult at present. This study tested the individual anode current using the fiber-optic current sensor. The testing results show that this method can effectively avoid the interference of the electromagnetic field, and the current is measured with high precision which error is less than 1 pct. In the paper, the test currents under different cell conditions, including anode changing, metal tapping, abnormal current, and anode effect, are investigated using the method of time-domain and frequency-domain analysis, and the simulation method is also combined to investigate the cell conditions. The results prove that different cell conditions will show different anode current characteristics, and the individual current can monitor the cell conditions, especially the localized cell conditions. Some abnormal cell conditions can be found through anode current rather than cell voltage. The anode current can also be used for early detection of anode effect.

  4. Current collection by high voltage anodes in near ionospheric conditions

    NASA Technical Reports Server (NTRS)

    Antoniades, John A.; Greaves, Rod G.; Boyd, D. A.; Ellis, R.

    1990-01-01

    The authors experimentally identified three distinct regimes with large differences in current collection in the presence of neutrals and weak magnetic fields. In magnetic field/anode voltage space the three regions are separated by very sharp transition boundaries. The authors performed a series of laboratory experiments to study the dependence of the region boundaries on several parameters, such as the ambient neutral density, plasma density, magnetic field strength, applied anode voltage, voltage pulsewidth, chamber material, chamber size and anode radius. The three observed regimes are: classical magnetic field limited collection; stable medium current toroidal discharge; and large scale, high current space glow discharge. There is as much as several orders of magnitude of difference in the amount of collected current upon any boundary crossing, particularly if one enters the space glow regime. They measured some of the properties of the plasma generated by the breakdown that is present in regimes II and III in the vicinity of the anode including the sheath modified electrostatic potential, I-V characteristics at high voltage as well as the local plasma density.

  5. Influence of cathodic and anodic currents on cavitation erosion

    SciTech Connect

    Auret, J.G.; Damm, O.F.R.A.; Wright, G.J. . Div. of Materials Science and Technology); Robinson, F.P.A. . Dept. of Metallurgy and Materials Engineering)

    1993-11-01

    A vibratory-type cavitation test rig was constructed to study the effect of polarizing currents applied to a cavitating body. The generation of gas by electrolysis reduced mechanical damage suffered by a cavitating body because of bubble collapse cushioning. However, the net effect on overall damage depended on several factors, including the intensity of mechanical attack, corrosion rate, and surface geometrical effects. A cathodic current was shown to always decrease the total volume loss rate, but the volume loss rate sometimes was increased and sometimes was reduced in the anodic current range.

  6. Different Current Intensities of Anodal Transcranial Direct Current Stimulation Do Not Differentially Modulate Motor Cortex Plasticity

    PubMed Central

    Kidgell, Dawson J.; Daly, Robin M.; Young, Kayleigh; Lum, Jarrod; Tooley, Gregory; Jaberzadeh, Shapour; Zoghi, Maryam; Pearce, Alan J.

    2013-01-01

    Transcranial direct current stimulation (tDCS) is a noninvasive technique that modulates the excitability of neurons within the motor cortex (M1). Although the aftereffects of anodal tDCS on modulating cortical excitability have been described, there is limited data describing the outcomes of different tDCS intensities on intracortical circuits. To further elucidate the mechanisms underlying the aftereffects of M1 excitability following anodal tDCS, we used transcranial magnetic stimulation (TMS) to examine the effect of different intensities on cortical excitability and short-interval intracortical inhibition (SICI). Using a randomized, counterbalanced, crossover design, with a one-week wash-out period, 14 participants (6 females and 8 males, 22–45 years) were exposed to 10 minutes of anodal tDCS at 0.8, 1.0, and 1.2 mA. TMS was used to measure M1 excitability and SICI of the contralateral wrist extensor muscle at baseline, immediately after and 15 and 30 minutes following cessation of anodal tDCS. Cortical excitability increased, whilst SICI was reduced at all time points following anodal tDCS. Interestingly, there were no differences between the three intensities of anodal tDCS on modulating cortical excitability or SICI. These results suggest that the aftereffect of anodal tDCS on facilitating cortical excitability is due to the modulation of synaptic mechanisms associated with long-term potentiation and is not influenced by different tDCS intensities. PMID:23577272

  7. Thermal investigation of an electrical high-current arc with porous gas-cooled anode

    NASA Technical Reports Server (NTRS)

    Eckert, E. R. G.; Schoeck, P. A.; Winter, E. R. F.

    1984-01-01

    The following guantities were measured on a high-intensity electric arc with tungsten cathode and transpiration-cooled graphite anode burning in argon: electric current and voltage, cooling gas flow rate (argon), surface temperature of the anode and of the anode holder, and temperature profile in three cross-sections of the arc are column. The last mentioned values were obtained from spectroscopic photographs. From the measured quantities, the following values were calculated: the heat flux into the anode surface, the heat loss of the anode by radiation and conduction, and the heat which was regeneratively transported by the cooling gas back into the arc space. Heat balances for the anode were also obtained. The anode losses (which are approximately 80% of the total arc power for free burning arcs) were reduced by transpiration cooling to 20%. The physical processes of the energy transfer from the arc to the anode are discussed qualitatively.

  8. Modeling of the anode surface deformation in high-current vacuum arcs with AMF contacts

    NASA Astrophysics Data System (ADS)

    Huang, Xiaolong; Wang, Lijun; Deng, Jie; Jia, Shenli; Qin, Kang; Shi, Zongqian

    2016-02-01

    A high-current vacuum arc subjected to an axial magnetic field is maintained in a diffuse status. With an increase in arc current, the energy carried by the arc column to the anode becomes larger and finally leads to the anode temperature exceeding the melting point of the anode material. When the anode melting pool is formed, and the rotational plasma of the arc column delivers its momentum to the melting pool, the anode melting pool starts to rotate and also flow outwards along the radial direction, which has been photographed by some researchers using high-speed cameras. In this paper, the anode temperature and melting status is calculated using the melting and solidification model. The swirl flow of the anode melting pool and deformation of the anode is calculated using the magneto-hydrodynamic (MHD) model with the volume of fraction (VOF) method. All the models are transient 2D axial-rotational symmetric models. The influence of the impaction force of the arc plasma, electromagnetic force, viscosity force, and surface tension of the liquid metal are all considered in the model. The heat flux density injected into the anode and the arc pressure are obtained from the 3D numerical simulation of the high-current vacuum arc using the MHD model, which gives more realistic parameters for the anode simulation. Simulation results show that the depth of the anode melting pool increases with an increase in the arc current. Some droplets sputter out from the anode surface, which is caused by the inertial centrifugal force of the rotational melting pool and strong plasma pressure. Compared with the previous anode melting model without consideration of anode deformation, when the deformation and swirl flow of the anode melting pool are considered, the anode temperature is relatively lower, and just a little more than the melting point of Cu. This is because of liquid droplets sputtering out of the anode surface taking much of the energy away from the anode surface. The

  9. Effect of an axial magnetic field and arc current on the anode current density in diffuse vacuum arcs

    NASA Astrophysics Data System (ADS)

    Ma, Hui; Geng, Yingsan; Liu, Zhiyuan; Wang, Jianhua; Wang, Zhenxing; Zhang, Zaiqin

    2016-09-01

    The objective of this paper is to measure the effect of an axial magnetic field (AMF) BAMF and arc current on the anode current density in diffuse vacuum arcs. The experimental geometry included a split anode and a butt-type cathode, both with a diameter of 60 mm. The anode surface was divided into a central area and three symmetrically disposed peripheral annular areas. The central area of the split anode had a diameter of 20 mm. The contact material was CuCr25 (25% Cr). The arc current IARC ranged from 4 to 14 kA (rms) at 50 Hz. The opening velocity was 2.4 m/s. The currents of the four areas on the anode contact were measured using four Rogowski coils situated outside the vacuum chamber. An external uniform AMF BAMF ranging from 0 to 110 mT was applied during the experiment. The observed arc modes were recorded by a high-speed charge-coupled device video camera. The experimental results quantitatively reveal that the current density distribution on the anode surface in the diffuse arc mode was not uniform but concentrated in the central area. The current density in the central anode area at the current peak JPeakArea I decreased with increasing BAMF following a power law. For BAMF of 0-110 mT and IARC of 4-14 kA, JPeakArea I = (2.2 IARC + 0.069 IARC2) BAMF-0.22, where JPeakArea I is in A/mm2, BAMF is in mT, and IARC is in kA. Moreover, the current distribution was uneven in the three peripheral areas.

  10. Potential threshold of anode materials for foldable lithium-ion batteries featuring carbon nanotube current collectors

    NASA Astrophysics Data System (ADS)

    Wang, Qing Hui; Zhong, Sheng Wen; Hu, Jing Wei; Liu, Ting; Zhu, Xian Yan; Chen, Jing; Hong, Yin Yan; Wu, Zi Ping

    2016-04-01

    Flexible carbon nanotube macro-films (CMFs) are perfect current collectors for preparing foldable lithium-ion batteries (LIBs). However, selecting appropriate anodes for electrode is difficult because of the different potentials (vs. Li/Li+) of carbon nanotubes and traditional metallic current collector. This study demonstrated an additional reaction at potential below 0.9 V (vs. Li/Li+) caused by CMF, And Li+ will be constrained, which decreased capacity of anode/CMF electrode. Conversely, results changed when the anode potential exceeded 0.9 V (vs. Li/Li+) because Li+ passed the potential threshold, and the CMF retained its electrochemical inactivity. Consequently, the CMF-based foldable LIBs performed well. The potential threshold mechanism of anode is expected to provide new impetus to both academia and industry for exploring flexible or foldable LIBs.

  11. Gyrotron Output Power Stabilization by PID Feedback Control of Heater Current and Anode Voltage

    NASA Astrophysics Data System (ADS)

    Khutoryan, E. M.; Idehara, T.; Kuleshov, A. N.; Ueda, K.

    2014-12-01

    To provide stable output power of a gyrotron during long operation time the power stabilization was achieved by two schemes with PID feedback control of heater current and anode voltage. It was based on the dependence of the output power on both the anode voltage and the beam current and also on the dependence of the beam current on the gun heater current. Both schemes provided decrease of the power standard deviation to 0.3-0.5%. The comparison between parameters of both schemes is discussed in the paper.

  12. Effect of current connection to the anode nozzle on plasma torch efficiency

    SciTech Connect

    Collares, M.P.; Pfender, E.

    1997-10-01

    Experiments have been performed to demonstrate the influence of the location of the electric power connection to the anode nozzle on the efficiency of dc plasma torches. The dc plasma torch used in these experiments offers the flexibility to work with different anode geometries and the possibility of connecting the electrical power to the anode at two different locations. For each set of experiments, the controllable parameters such as total gas flow rate, gas composition, and electric current were kept constant, changing only the location of the electrical connection to the anode nozzle. The efficiency of the torch, derived from a conventional energy balance, shows a significant change as the location of the electrical connection to the anode nozzle is changed. The measured mean voltage as well as the amplitude of the voltage fluctuations were also affected by the location of the electrical connection to the anode nozzle. An explanation for the arc behavior is given, based on an analysis of the forces acting on the anode arc column and their influence on the variation of the arc column length. Experimental data are in good agreement with analytical predictions.

  13. Parasitic Currents Caused by Different Ionic and Electronic Conductivities in Fuel Cell Anodes.

    PubMed

    Schalenbach, Maximilian; Zillgitt, Marcel; Maier, Wiebke; Stolten, Detlef

    2015-07-29

    The electrodes in fuel cells simultaneously realize electric and ionic conductivity. In the case of acidic polymer electrolytes, the electrodes are typically made of composites of carbon-supported catalyst and Nafion polymer electrolyte binder. In this study, the interaction of the proton conduction, the electron conduction, and the electrochemical hydrogen conversion in such composite electrode materials was examined. Exposed to a hydrogen atmosphere, these composites displayed up to 10-fold smaller resistivities for the proton conduction than that of Nafion membranes. This effect was ascribed to the simultaneously occurring electrochemical hydrogen oxidation and evolution inside the composite samples, which are driven by different proton and electron resistivities. The parasitic electrochemical currents resulting were postulated to occur in the anode of fuel cells with polymer, solid oxide, or liquid alkaline electrolytes, when the ohmic drop of the ion conduction in the anode is higher with the anodic kinetic overvoltage (as illustrated in the graphical abstract). In this case, the parasitic electrochemical currents increase the anodic kinetic overpotential and the ohmic drop in the anode. Thinner fuel cell anodes with smaller ohmic drops for the ion conduction may reduce the parasitic electrochemical currents.

  14. Anode-pore tortuosity in solid oxide fuel cells found from gas and current flow rates

    NASA Astrophysics Data System (ADS)

    Schmidt, V. Hugo; Tsai, Chih-Long

    The effect of solid oxide fuel cell (SOFC) anode thickness, porosity, pore size, and pore tortuosity on fuel and exhaust gas flow is calculated. Also determined is the concentration of these gases and of diluent gases as a function of position across the anode. The calculation is based on the dusty-gas model which includes a Knudsen (molecule-wall) collision term in the Stefan-Maxwell equation which is based on unlike-molecule collisions. Commonly made approximations are avoided in order to obtain more exact results. One such approximation is the assumption of uniform total gas pressure across the anode. Another such approximation is the assumption of zero fuel gas concentration at the anode-electrolyte interface under the anode saturation condition for which the SOFC output voltage goes to zero. Elimination of this approximation requires use of a model we developed (published elsewhere) for terminal voltage V as a function of electrolyte current density i. Key formulae from this model are presented. The formulae developed herein for gas flow and tortuosity are applied to the results of a series of careful experiments performed by another group, who used binary and ternary gas mixtures on the anode side of an SOFC. Our values for tortuosity are in a physically reasonable low range, from 1.7 to 3.3. They are in fair agreement with those obtained by the other group, once a difference in nomenclature is taken into account. This difference consists in their definition of tortuosity being what some call tortuosity factor, which is the square of what we and some others call tortuosity. The results emphasize the need for careful design of anode pore structures, especially in anode-supported SOFCs which require thicker anodes.

  15. A Patterned 3D Silicon Anode Fabricated by Electrodeposition on a Virus-Structured Current Collector

    SciTech Connect

    Chen, X L; Gerasopoulos, K; Guo, J C; Brown, A; Wang, Chunsheng; Ghodssi, Reza; Culver, J N

    2010-11-09

    Electrochemical methods were developed for the deposition of nanosilicon onto a 3D virus-structured nickel current collector. This nickel current collector is composed of self-assembled nanowire-like rods of genetically modified tobacco mosaic virus (TMV1cys), chemically coated in nickel to create a complex high surface area conductive substrate. The electrochemically depo­sited 3D silicon anodes demonstrate outstanding rate performance, cycling stability, and rate capability. Electrodeposition thus provides a unique means of fabricating silicon anode materials on complex substrates at low cost.

  16. Polarographic study of hydrogen peroxide anodic current and its application to antioxidant activity determination.

    PubMed

    Sužnjević, Desanka Ž; Pastor, Ferenc T; Gorjanović, Stanislava Ž

    2011-09-15

    Behavior of hydrogen peroxide in alkaline medium has been studied by direct current (DC) polarography with dropping mercury electrode (DME) aiming to apply it in antioxidant (AO) activity determination. Development of a peroxide anodic current having form of a peak, instead of common polarographic wave, has been investigated. As a base for this investigation the interaction of H(2)O(2) with anodically dissolved mercury was followed. Formation of mercury complex [Hg(O(2)H)(OH)] has been confirmed. The relevant experimental conditions, such as temperature, concentration and pH dependence, as well as time stability of hydrogen peroxide anodic current, have been assessed. Development of an AO assay based on decrease of anodic current of hydrogen peroxide in the presence of antioxidants (AOs) has been described. Under optimized working conditions, a series of benzoic acids along with corresponding cinnamate analogues have been tested for hydrogen peroxide scavenging activity. In addition, the assay versatility has been confirmed on various complex samples.

  17. Current-less anodization of intrinsic silicon powder grains: Formation of fluorescent Si nanoparticles

    NASA Astrophysics Data System (ADS)

    Nielsen, D.; Abuhassan, L.; Alchihabi, M.; Al-Muhanna, A.; Host, Jon; Nayfeh, M. H.

    2007-06-01

    We examine current-less anodization of Si powder grains which are dispersed in a liquid. The grains are prepared red luminescent using a platinum catalyst from a chloroplatinic acid precursor. We also use the procedure to form dispersions of fluorescent Si nanoparticles in the size range of 3-6 nm across by subsequent sonication of the grains. The results are discussed in terms of the calculated thickness of the depletion layer in the grains due to a light metal doping and compared with recent results for the anodization of wirelike geometry.

  18. Electronic currents and the formation of nanopores in porous anodic alumina

    NASA Astrophysics Data System (ADS)

    Zhu, Xu-Fei; Song, Ye; Liu, Lin; Wang, Chen-Yu; Zheng, Jie; Jia, Hong-Bing; Wang, Xin-Long

    2009-11-01

    The formation processes of barrier anodic alumina (BAA) and porous anodic alumina (PAA) are discussed in detail. The anodizing current JT within the oxide includes ionic current jion and electronic current je during the anodizing process. The jion is used to form an oxide and the je is used to give rise to oxygen gas or sparking. The je results from the impurity centers within the oxide. For a given electrolyte, the je is dependent on the impurity centers and independent of the JT. The formation of nanopores can be ascribed to the oxygen evolution within the oxide. Oxygen gas will begin to be released at the critical thickness dc. The manner of the development of PAA is in accordance with that of BAA. The differences between PAA and BAA are the magnitude of je or the continuity of oxygen evolution. There are two competitive reactions, i.e. oxide growth (\\mathrm {2Al^{3+}+3O^{2-}} \\to \\mathrm {Al_{2}O_{3}} ) and oxygen evolution (\\mathrm {2O^{2-}} \\to \\mathrm {O_{2}} {\\uparrow } +4\\rme ). The former keeps the wall of the channel lengthened, the latter keeps the channel open. By controlling the release rate of oxygen gas under different pressures, the shape of the channels can be adjusted. The present results may open up some opportunities for fabricating special templates.

  19. Incorporation of Ca and P on anodized titanium surface: Effect of high current density.

    PubMed

    Laurindo, Carlos A H; Torres, Ricardo D; Mali, Sachin A; Gilbert, Jeremy L; Soares, Paulo

    2014-04-01

    This study systematically evaluated the surface and corrosion characteristics of commercially pure titanium (grade 2) modified by plasma electrolytic oxidation (PEO) with high current density. The anodization process was carried out galvanostatically (constant current density) using a solution containing calcium glycerophosphate (0.02mol/L) and calcium acetate (0.15mol/L). The current densities applied were 400, 700, 1000 and 1200mA/cm(2) for a period of 15s. Composition, crystalline structure, morphology, roughness, wettability and "in-vitro" bioactivity test in SBF of the anodized layer were evaluated by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, profilometry and contact angle measurements. Corrosion properties were evaluated by open circuit potential, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results show that the TiO2 oxide layers present an increase of thickness, porosity, roughness, wettability, Ca/P ratio, and bioactivity, with the applied current density up to 1000mA/cm(2). Corrosion resistance also increases with applied current density. It is observed that for 1200mA/cm(2), there is a degradation of the oxide layer. In general, the results suggest that the anodized TiO2 layer with better properties is formed with an applied current of 1000mA/cm(2).

  20. Accommodating lithium into 3D current collectors with a submicron skeleton towards long-life lithium metal anodes

    PubMed Central

    Yang, Chun-Peng; Yin, Ya-Xia; Zhang, Shuai-Feng; Li, Nian-Wu; Guo, Yu-Guo

    2015-01-01

    Lithium metal is one of the most attractive anode materials for electrochemical energy storage. However, the growth of Li dendrites during electrochemical deposition, which leads to a low Coulombic efficiency and safety concerns, has long hindered the application of rechargeable Li-metal batteries. Here we show that a 3D current collector with a submicron skeleton and high electroactive surface area can significantly improve the electrochemical deposition behaviour of Li. Li anode is accommodated in the 3D structure without uncontrollable Li dendrites. With the growth of Li dendrites being effectively suppressed, the Li anode in the 3D current collector can run for 600 h without short circuit and exhibits low voltage hysteresis. The exceptional electrochemical performance of the Li-metal anode in the 3D current collector highlights the importance of rational design of current collectors and reveals a new avenue for developing Li anodes with a long lifespan. PMID:26299379

  1. Oxygen suppresses light-driven anodic current generation by a mixed phototrophic culture.

    PubMed

    Darus, Libertus; Ledezma, Pablo; Keller, Jürg; Freguia, Stefano

    2014-12-01

    This paper describes the detrimental effect of photosynthetically evolved oxygen on anodic current generation in the presence of riboflavin upon illumination of a mixed phototrophic culture enriched from a freshwater pond at +0.6 V vs standard hydrogen electrode. In the presence of riboflavin, the phototrophic biomass in the anodic compartment produced an electrical current in response to light/dark cycles (12 h/12 h) over 12 months of operation, generating a maximum current density of 17.5 mA x m(-2) during the dark phase, whereas a much lower current of approximately 2 mA x m(-2) was generated during illumination. We found that the low current generation under light exposure was caused by high rates of reoxidation of reduced riboflavin by oxygen produced during photosynthesis. Quantification of biomass by fluorescence in situ hybridization images suggested that green algae were predominant in both the anode-based biofilm (55.1%) and the anolyte suspension (87.9%) with the remaining biovolume accounted for by bacteria. Genus-level sequencing analysis revealed that bacteria were dominated by cyanobacterium Leptolyngbia (∼35%), while the prevailing algae were Dictyosphaerium, Coelastrum, and Auxenochlorella. This study offers a key comprehension of mediator sensitivity to reoxidation by dissolved oxygen for improvement of microbial solar cell performance.

  2. Short arcs at low current determination of the power lost by conduction into anode

    SciTech Connect

    Abbaoui, M.; Salihou, H.

    1995-12-31

    The mechanisms occurring at the anode of an electric arc are less important compared to that at the cathode, Many studies have been carried out to get a better understanding of anode phenomena in welding, but few of them have been reported on sham am in gases then last years. In general, for short arcs, the major problem encouraged in experiment was the instability of the arc voltage. This instability depends on the phenomena associated with the existence of the arc, the erosion, the nature and surface state of the electrode materials mainly for low currents arcs. Thus, for short arcs operating in gases at low current, experimental investigations are complicated because of their inherent instability and the metal gas interaction. Moreover, because of this instability, there are less data available. In this paper, we are concerned with low arc current (2-5A) and small electrode separation (0.4-1mm). For short arcs in gases at low-current, it is known from literature that one of the important tool is the energy balance which enables to deal with the power lost by conduction into electrodes and the current density. Calorimetric observations show that about 80% of the electrical power input is lost into both electrodes mainly by conduction. In the following analysis, a simple method of determining the power lost by conduction into different anode materials using a wall stabilised arc is presented. The experimental method consists in measuring the temperature reached in steady state at different points distributed along the electrode axis, fitting the values obtained and calculating the power supplied P{sub cd} to the anode surface facing the column.

  3. Magnetic properties of pulse-reverse electrodeposited nanocrystalline NiFe/Cu composite wires in relation to the anodic current

    NASA Astrophysics Data System (ADS)

    Seet, H. L.; Li, X. P.; Lee, K. S.; Chia, H. Y.; Zheng, H. M.; Ng, W. C.

    2007-12-01

    Ni80Fe20/Cu composite wires were developed using the pulse-reverse electrodeposition technique with the cathodic (positive) current Ic fixed at 1 mA and the anodic (negative) current IA varied from 10 to 90% of Ic. The relationship between the magnetic properties of pulse reverse electrodeposited nanocrystalline NiFe/Cu composite wires and the anodic current was investigated. The results showed that the smaller the magnitude of the anodic current, the smaller was the average nanocrystalline grain size of the deposited material and the better was the uniformity of the surface, and consequently, the better the magnetic properties.

  4. Task-Specific Facilitation of Cognition by Anodal Transcranial Direct Current Stimulation of the Prefrontal Cortex

    PubMed Central

    Pope, Paul A.; Brenton, Jonathan W.; Miall, R. Chris

    2015-01-01

    We previously speculated that depression of cerebellar excitability using cathodal transcranial direct current stimulation (tDCS) might release extra cognitive resources via the disinhibition of activity in prefrontal cortex. The objective of the present study was to investigate whether anodal tDCS over the prefrontal cortex could similarly improve performance when cognitive demands are high. Sixty-three right-handed participants in 3 separate groups performed the Paced Auditory Serial Addition Task (PASAT) and the more difficult Paced Auditory Serial Subtraction Task (PASST), before and after 20 min of anodal, cathodal, or sham stimulation over the left dorsolateral prefrontal cortex (DLPFC). Performance was assessed in terms of the accuracy, latency, and variability of correct verbal responses. All behavioral measures significantly improved for the PASST after anodal DLPFC stimulation, but not the PASAT. There were smaller practice effects after cathodal and sham stimulation. Subjective ratings of attention and mental fatigue were unchanged by tDCS over time. We conclude that anodal stimulation over the left DLPFC can selectively improve performance on a difficult cognitive task involving arithmetic processing, verbal working memory, and attention. This result might be achieved by focally improving executive functions and/or cognitive capacity when tasks are difficult, rather than by improving levels of arousal/alertness. PMID:25979089

  5. Anodal transcranial direct current stimulation over the supramarginal gyrus facilitates pitch memory.

    PubMed

    Schaal, Nora K; Williamson, Victoria J; Banissy, Michael J

    2013-11-01

    Functional neuroimaging studies have shown activation of the supramarginal gyrus during pitch memory tasks. A previous transcranial direct current stimulation study using cathodal stimulation over the left supramarginal gyrus reported a detrimental effect on short-term pitch memory performance, indicating an important role of the supramarginal gyrus in pitch memory. The current study aimed to determine whether pitch memory could be improved following anodal stimulation of the left supramarginal gyrus. The performances of non-musicians on two pitch memory tasks (pitch recognition and recall) and a visual memory control task following anodal or sham transcranial direct current stimulation were compared. The results show that, post-stimulation, the anodal group but not the control group performed significantly better on both pitch memory tasks; performance did not differ on the face memory task. These findings provide strong support for the causal involvement of the left supramarginal gyrus in the pitch memory process, and highlight the potential efficacy of transcranial direct current stimulation as a tool to improve pitch memory.

  6. Tin nanoparticle-loaded porous carbon nanofiber composite anodes for high current lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Shen, Zhen; Hu, Yi; Chen, Yanli; Zhang, Xiangwu; Wang, Kehao; Chen, Renzhong

    2015-03-01

    Metallic Sn is a promising high-capacity anode material for use in lithium-ion batteries (LIBs), but its huge volume variation during lithium ion insertion/extraction typically results in poor cycling stability. To address this, we demonstrate the fabrication of Sn nanoparticle-loaded porous carbon nanofiber (Sn-PCNF) composites via the electrospinning of Sn(II) acetate/mineral oil/polyacrylonitrile precursors in N,N-dimethylformamide solvent and their subsequent carbonization at 700 °C under an argon atmosphere. This is shown to result in an even distribution of pores on the surface of the nanofibers, allowing the Sn-PCNF composite to be used directly as an anode in lithium-ion batteries without the need to add non-active materials such as polymer binders or electrical conductors. With a discharge capacity of around 774 mA h g-1 achieved at a high current of 0.8 A g-1 over 200 cycles, this material clearly has a high rate capability and excellent cyclic stability, and thanks to its unique structure and properties, is an excellent candidate for use as an anode material in high-current rechargeable lithium-ion batteries.

  7. Free-Standing Copper Nanowire Network Current Collector for Improving Lithium Anode Performance.

    PubMed

    Lu, Lei-Lei; Ge, Jin; Yang, Jun-Nan; Chen, Si-Ming; Yao, Hong-Bin; Zhou, Fei; Yu, Shu-Hong

    2016-07-13

    Lithium metal is one of the most attractive anode materials for next-generation lithium batteries due to its high specific capacity and low electrochemical potential. However, the poor cycling performance and serious safety hazards, caused by the growth of dendritic and mossy lithium, has long hindered the application of lithium metal based batteries. Herein, we reported a rational design of free-standing Cu nanowire (CuNW) network to suppress the growth of dendritic lithium via accommodating the lithium metal in three-dimensional (3D) nanostructures. We demonstrated that as high as 7.5 mA h cm(-2) of lithium can be plated into the free-standing copper nanowire (CuNW) current collector without the growth of dendritic lithium. The lithium metal anode based on the CuNW exhibited high Coulombic efficiency (average 98.6% during 200 cycles) and outstanding rate performance owing to the suppression of lithium dendrite growth and high conductivity of CuNW network. Our results demonstrate that the rational nanostructural design of current collector could be a promising strategy to improve the performance of lithium metal anode enabling its application in next-generation lithium-metal based batteries. PMID:27253417

  8. Anodal transcranial direct current stimulation over premotor cortex facilitates observational learning of a motor sequence.

    PubMed

    Wade, Stephanie; Hammond, Geoff

    2015-06-01

    Motor skills, including complex movement sequences, can be acquired by observing a model without physical practice of the skill, a phenomenon known as observational learning. Observational learning of motor skills engages the same memory substrate as physical practice, and is thought to be mediated by the action observation network, a bilateral fronto-parietal circuit with mirror-like properties. We examined the effects of anodal transcranial direct current stimulation (tDCS) over premotor cortex, a key node of the action observation network, on observational learning of a serial response time task. Results showed that anodal tDCS during observation of the to-be-learned sequence facilitated reaction times in the subsequent behavioral test. The study provides evidence that increasing excitability of the action observation network during observation can facilitate later motor skill acquisition.

  9. High-efficiency, nickel-ceramic composite anode current collector for micro-tubular solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Tao; Wu, Zhentao; Li, K.

    2015-04-01

    High manufacturing cost and low-efficient current collection have been the two major bottlenecks that prevent micro-tubular SOFCs from large-scale application. In this work, a new nickel-based composite anode current collector has been developed for anode-supported MT-SOFC, addressing reduced cost, manufacturability and current collection efficiencies. Triple-layer hollow fibers have been successfully fabricated via a phase inversion-assisted co-extrusion process, during which a thin nickel-based inner layer was uniformly coated throughout the interior anode surface for improved adhesion with superior process economy. 10 wt.% CGO was added into the inner layer to prevent the excessive shrinkage of pure NiO, thus helping to achieve the co-sintering process. The electrochemical performance tests illustrate that samples with the thinnest anodic current collector (15% of the anode thickness) displayed the highest power density (1.07 W cm-2). The impedance analysis and theoretical calculations suggest that inserting the anodic current collector could dramatically reduce the percentage of contact loss down to 6-10 % of the total ohmic loss (compared to 70% as reported in literatures), which proves the high efficiencies of new current collector design. Moreover, the superior manufacturability and process economy suggest this composite current collector suitable for mass-scale production.

  10. Enhancement of pinch force in the lower leg by anodal transcranial direct current stimulation.

    PubMed

    Tanaka, Satoshi; Hanakawa, Takashi; Honda, Manabu; Watanabe, Katsumi

    2009-07-01

    Transcranial direct current stimulation (tDCS) is a procedure to polarize human brain. It has been reported that tDCS over the hand motor cortex transiently improves the performance of hand motor tasks. Here, we investigated whether tDCS could also improve leg motor functions. Ten healthy subjects performed pinch force (PF) and reaction time (RT) tasks using the left leg before, during and after anodal, cathodal or sham tDCS over the leg motor cortex. The anodal tDCS transiently enhanced the maximal leg PF but not RT during its application. Neither cathodal nor sham stimulation changed the performance. None of the interventions affected hand PF or RT, showing the spatial specificity of the effect of tDCS. These results indicate that motor performance of not only the hands but also the legs can be enhanced by anodal tDCS. tDCS may be applicable to the neuro-rehabilitation of patients with leg motor disability. PMID:19479243

  11. Anodic behavior of aluminum current collector in LiTFSI solutions with different solvent compositions

    NASA Astrophysics Data System (ADS)

    Morita, Masayuki; Shibata, Takuo; Yoshimoto, Nobuko; Ishikawa, Masashi

    The anodic behavior of aluminum (Al) current collector of Li-ion batteries has been investigated in organic electrolyte solutions containing lithium bis[trifluoromethylsulfonyl]imide (Li(CF 3SO 2) 2N: LiTFSI) with different compositions of solvents. The Al anode was subjected to anodic corrosion in the LiTFSI solution, but the degree of the corrosion depended on the solvent composition. The surface of Al pre-treated by mechanical polishing has suffered serious corrosion in the mixed solvent solution of ethylene carbonate (EC) and dimethyl carbonate (DMC), whereas the Al surface pre-treated by electro-polishing was relatively stable in the mixed solvent of γ-butyrolactone (GBL) and DMC. The results of electrochemical quartz crystal microbalance (EQCM) experiments showed that the mass change of the Al surface during the potential cycling in GBL + DMC was much different from that in the EC + DMC solution. Scanning electron microscope (SEM) observation proved that the corrosion pits evolved on the electro-polished Al surface after potential cycling, but GBL resulted in a smaller amount of the corrosion product on the Al surface.

  12. Silicon nitride coated silicon thin film on three dimensions current collector for lithium ion battery anode

    NASA Astrophysics Data System (ADS)

    Wu, Cheng-Yu; Chang, Chun-Chi; Duh, Jenq-Gong

    2016-09-01

    Silicon nitride coated silicon (N-Si) has been synthesized by two-step DC sputtering on Cu Micro-cone arrays (CMAs) at ambient temperature. The electrochemical properties of N-Si anodes with various thickness of nitride layer are investigated. From the potential window of 1.2 V-0.05 V, high rate charge-discharge and long cycle test have been executed to investigate the electrochemical performances of various N-Si coated Si-based lithium ion batteries anode materials. Higher specific capacity can be obtained after 200 cycles. The cycling stability is enhanced via thinner nitride layer coating as silicon nitride films are converted to Li3N with covered Si thin films. These N-Si anodes can be cycled under high rates up to 10 C due to low charge transfer resistance resulted from silicon nitride films. This indicates that the combination of silicon nitride and silicon can effectively endure high current and thus enhance the cycling stability. It is expected that N-Si is a potential candidate for batteries that can work effectively under high power.

  13. Formation and disruption of current paths of anodic porous alumina films by conducting atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Oyoshi, K.; Nigo, S.; Inoue, J.; Sakai, O.; Kitazawa, H.; Kido, G.

    2010-11-01

    Anodic porous alumina (APA) films have a honeycomb cell structure of pores and a voltage-induced bi-stable switching effect. We have applied conducting atomic force microscopy (CAFM) as a method to form and to disrupt current paths in the APA films. A bi-polar switching operation was confirmed. We have firstly observed terminals of current paths as spots or areas typically on the center of the triangle formed by three pores. In addition, though a part of the current path showed repetitive switching, most of them were not observed again at the same position after one cycle of switching operations in the present experiments. This suggests that a part of alumina structure and/or composition along the current paths is modified during the switching operations.

  14. Duty Cycling Influences Current Generation in Multi-Anode Environmental Microbial Fuel Cells

    SciTech Connect

    Gardel, EJ; Nielsen, ME; Grisdela, PT; Girguis, PR

    2012-05-01

    Improving microbial fuel cell (MFC) performance continues to be the subject of research, yet the role of operating conditions, specifically duty cycling, on MFC performance has been modestly addressed. We present a series of studies in which we use a 15-anode environmental MFC to explore how duty cycling (variations in the time an anode is connected) influences cumulative charge, current, and microbial composition. The data reveal particular switching intervals that result in the greatest time-normalized current. When disconnection times are sufficiently short, there is a striking decrease in current due to an increase in the overall electrode reaction resistance. This was observed over a number of whole cell potentials. Based on these results, we posit that replenishment of depleted electron donors within the biofilm and surrounding diffusion layer is necessary for maximum charge transfer, and that proton flux may be not limiting in the highly buffered aqueous phases that are common among environmental MFCs. Surprisingly, microbial diversity analyses found no discernible difference in gross community composition among duty cycling treatments, suggesting that duty cycling itself has little or no effect. Such duty cycling experiments are valuable in determining which factors govern performance of bioelectrochemical systems and might also be used to optimize field-deployed systems.

  15. Consumable and non-consumable thermal spray anodes for impressed current cathodic protection of reinforced concrete structures

    SciTech Connect

    Covino, B.S. Jr.; Cramer, S.D.; Bullard, Sophie J.; Holcomb, Gordon R.; Collins, Wesley K.; McGill, G.E.

    1998-01-01

    A comparison is presented of some of the differences between thermal spray Zn, a consumable anode, and catalyzed thermal spray Ti, a non-consumable anode, used for impressed current cathodic protection of reinforced concrete structures. The thermal spray process for both Ti and Zn is compared using the spray parameters, atomizing gases, spray rate, and cost. The thermal spray Ti and Zn coatings are compared in terms of physical properties, composition, and structure. Results of accelerated laboratory experiments are presented and comparisons between Ti and Zn are made on the effect of electrochemical aging on voltage requirements, bond strength, coating resistivity, water permeability, and anode-concrete interracial composition.

  16. Performance of motor imagery brain-computer interface based on anodal transcranial direct current stimulation modulation.

    PubMed

    Wei, Pengfei; He, Wei; Zhou, Yi; Wang, Liping

    2013-05-01

    Voluntarily modulating neural activity plays a key role in brain-computer interface (BCI). In general, the self-regulated neural activation patterns are used in the current BCI systems involving the repetitive trainings with feedback for an attempt to achieve a high-quality control performance. With the limitation posed by the training procedure in most BCI studies, the present work aims to investigate whether directly modulating the neural activity by using an external method could facilitate the BCI control. We designed an experimental paradigm that combines anodal transcranial direct current stimulation (tDCS) with a motor imagery (MI)-based feedback EEG BCI system. Thirty-two young and healthy human subjects were randomly assigned to the real and sham stimulation groups to evaluate the effect of tDCS-induced EEG pattern changes on BCI classification accuracy. Results showed that the anodal tDCS obviously induces sensorimotor rhythm (SMR)-related event-related desynchronization (ERD) pattern changes in the upper-mu (10-14 Hz) and beta (14-26 Hz) rhythm components. Both the online and offline BCI classification results demonstrate that the enhancing ERD patterns could conditionally improve BCI performance. This pilot study suggests that the tDCS is a promising method to help the users to develop reliable BCI control strategy in a relatively short time.

  17. Electric current generation by sulfur-reducing bacteria in microbial-anode fuel cell

    NASA Astrophysics Data System (ADS)

    Vasyliv, Oresta M.; Bilyy, Oleksandr I.; Ferensovych, Yaroslav P.; Hnatush, Svitlana O.

    2012-10-01

    Sulfur - reducing bacteria are a part of normal microflora of natural environment. Their main function is supporting of reductive stage of sulfur cycle by hydrogen sulfide production in the process of dissimilative sulfur-reduction. At the same time these bacteria completely oxidize organic compounds with CO2 and H2O formation. It was shown that they are able to generate electric current in the two chamber microbial-anode fuel cell (MAFC) by interaction between these two processes. Microbial-anode fuel cell on the basis of sulfur- and ferric iron-reducing Desulfuromonas acetoxidans bacteria has been constructed. It has been shown that the amount of electricity generation by investigated bacteria is influenced by the concentrations of carbon source (lactate) and ferric iron chloride. The maximal obtained electric current and potential difference between electrodes equaled respectively 0.28-0.29 mA and 0.19-0.2 V per 0.3 l of bacterial suspension with 0.4 g/l of initial biomass that was grown under the influence of 0.45 mM of FeCl3 and 3 g/l of sodium lactate as primal carbon source. It has also been shown that these bacteria are resistant to different concentrations of silver ions.

  18. Enhanced current and power density of micro-scale microbial fuel cells with ultramicroelectrode anodes

    NASA Astrophysics Data System (ADS)

    Ren, Hao; Rangaswami, Sriram; Lee, Hyung-Sool; Chae, Junseok

    2016-09-01

    We present a micro-scale microbial fuel cell (MFC) with an ultramicroelectrode (UME) anode, with the aim of creating a miniaturized high-current/power-density converter using carbon-neutral and renewable energy sources. Micro-scale MFCs have been studied for more than a decade, yet their current and power densities are still an order of magnitude lower than those of their macro-scale counterparts. In order to enhance the current/power densities, we engineer a concentric ring-shaped UME, with a width of 20 μm, to facilitate the diffusion of ions in the vicinity of the micro-organisms that form biofilm on the UME. The biofilm extends approximately 15 μm from the edge of the UME, suggesting the effective biofilm area increases. Measured current/power densities per the effective area and the original anode area are 7.08  ±  0.01 A m‑2 & 3.09  ±  0.04 W m‑2 and 17.7  ±  0.03 A m‑2 & 7.72  ±  0.09 W m‑2, respectively. This is substantially higher than any prior work in micro-scale MFCs, and very close, or even higher, to that of macro-scale MFCs. A Coulombic efficiency, a measure of how efficiently an MFC harvests electrons from donor substrate, of 70%, and an energy conversion efficiency of 17% are marked, highlighting the micro-scale MFC as an attractive alternative within the existing energy conversion portfolio.

  19. Enhanced current and power density of micro-scale microbial fuel cells with ultramicroelectrode anodes

    NASA Astrophysics Data System (ADS)

    Ren, Hao; Rangaswami, Sriram; Lee, Hyung-Sool; Chae, Junseok

    2016-09-01

    We present a micro-scale microbial fuel cell (MFC) with an ultramicroelectrode (UME) anode, with the aim of creating a miniaturized high-current/power-density converter using carbon-neutral and renewable energy sources. Micro-scale MFCs have been studied for more than a decade, yet their current and power densities are still an order of magnitude lower than those of their macro-scale counterparts. In order to enhance the current/power densities, we engineer a concentric ring-shaped UME, with a width of 20 μm, to facilitate the diffusion of ions in the vicinity of the micro-organisms that form biofilm on the UME. The biofilm extends approximately 15 μm from the edge of the UME, suggesting the effective biofilm area increases. Measured current/power densities per the effective area and the original anode area are 7.08  ±  0.01 A m-2 & 3.09  ±  0.04 W m-2 and 17.7  ±  0.03 A m-2 & 7.72  ±  0.09 W m-2, respectively. This is substantially higher than any prior work in micro-scale MFCs, and very close, or even higher, to that of macro-scale MFCs. A Coulombic efficiency, a measure of how efficiently an MFC harvests electrons from donor substrate, of 70%, and an energy conversion efficiency of 17% are marked, highlighting the micro-scale MFC as an attractive alternative within the existing energy conversion portfolio.

  20. Modeling the effects of anode secondary electron emission on transmitted current in crossed-field diodes

    NASA Astrophysics Data System (ADS)

    Gopinath, Venkatesh; Vanderberg, Bo

    1996-11-01

    Recent experimental measurements of transmitted current in a crossed-field switch by Vanderberg and Eninger ( B. H. Vanderberg and J. E. Eninger, ``Space-charge limited current cut-off in crossed fields,'' presented at IEEE ICOPS'95, Madison, Wi. ) have shown that the measured values of transmitted current are significantly smaller than the theoretically predicted limit. The experiments also showed larger decrease in transmitted current for higher magnetic fields, implying an effect due to the higher angle of incidence of incident electrons (i.e., at values of B closer to B_H). Studies by Verboncoeur and Birdsall ( J. P. Verboncoeur and C. K. Birdsall. ``Rapid current transition in a crossed-field diode,'' Phys. Plasmas 3) 3, March 1996. have shown that even small amount ( < 1%) of over injection in a crossed-field diode near cut-off led to substantial decrease in transmitted current. In our current work, we show that the same effect can be triggered by the presence of secondary electron emission from the anode. This study models the dependence of emission upon incident electron angle and energy. Since the yield of secondary electrons increases with incident angle, this model follows the experimental results as B approaches B_Hull accurately. This work was supported in part by ONR under grant FD-N00014-90-J-1198

  1. Effect of anodal high voltage pulsed current on edema formation in frog hind limbs.

    PubMed

    Fish, D R; Mendel, F C; Schultz, A M; Gottstein-Yerke, L M

    1991-10-01

    We have recently demonstrated that some forms of cathodal high voltage pulsed current (HVPC) curb posttraumatic edema formation in frog hind limbs. The purpose of this study was to determine, by assessing the capacity of anodal HVPC to curb posttraumatic edema formation, whether polarity is an important variable. Fourteen anesthetized bullfrogs were placed on large dispersive electrodes lining body slings that maintained the frogs' limbs in a dependent position throughout data collection. The frogs' feet were traumatized by impact following initial measurement of limb volumes. At the commencement of each of four 30-minute treatments, hind limbs were immersed in separate beakers and briefly stimulated until motor threshold was determined. One limb, randomly selected, received anodal HVPC at 90% of motor threshold and 120 pulses per second; the other limb served as a control. Treatments were followed by 30-minute rests. Limb volumes were measured by water displacement immediately after trauma and following each treatment and rest period. Data were expressed as changes from pretrauma volumes in milliliters per kilogram of body weight. A repeated-measures analysis of variance was used to test for treatment effect. Despite an aggressive series of treatments, virtually symmetrical bilateral edema occurred; therefore, no treatment effect was evident. This result contrasts with treatment effects previously reported for cathodal HVPC.

  2. What is the optimal anodal electrode position for inducing corticomotor excitability changes in transcranial direct current stimulation?

    PubMed

    Lee, Minji; Kim, Yun-Hee; Im, Chang-Hwan; Kim, Jung-Hoon; Park, Chang-hyun; Chang, Won Hyuk; Lee, Ahee

    2015-01-01

    Transcranial direct current stimulation (tDCS) non-invasively modulates brain function by inducing neuronal excitability. The conventional hot spot for inducing the highest current density in the hand motor area may not be the optimal site for effective stimulation. In this study, we investigated the influence of the center position of the anodal electrode on changes in motor cortical excitability. We considered three tDCS conditions in 16 healthy subjects: (i) real stimulation with the anodal electrode located at the conventional hand motor hot spot determined by motor evoked potentials (MEPs); (ii) real stimulation with the anodal electrode located at the point with the highest current density in the hand motor area as determined by electric current simulation; and (iii) sham stimulation. Motor cortical excitability as measured by MEP amplitude increased after both real stimulation conditions, but not after sham stimulation. Stimulation using the simulation-derived anodal electrode position, which was found to be posterior to the MEP hot spot for all subjects, induced higher motor cortical excitability. Individual positioning of the anodal electrode, based on the consideration of anatomical differences between subjects, appears to be important for maximizing the effects of tDCS. PMID:25450146

  3. Redox cycling performance of inert-substrate-supported tubular single cells with nickel anode current collector

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Kim, Bok-Hee; Xu, Qing; Du, Yanhai; Ahn, Byung-Guk

    2015-10-01

    An inert-substrate-supported tubular single cell, with a configuration of porous yttria-stabilized zirconia (YSZ) supporter/Ni anode current collector/Ni-Ce0.8Sm0.2O1.9 anode/YSZ/Ce0.8Sm0.2O1.9 bi-layer electrolyte/La0.6Sr0.4Co0.2Fe0.8O3-δ cathode, has been fabricated by extrusion and dip-coating techniques. Thickness of the Ni layer is modified by controlling the number of dip-coatings from one to four. Electrochemical performance and redox cycling stability of the single cell are investigated with respect to the microstructure of the Ni layer. Increasing the thickness of the Ni layer enhances the maximum power density of the cell, while it is unfavorable for the redox cycling stability. Considering the trade-off between these two aspects, an optimum dip-coating time is determined to be two. The cell shows a reasonable maximum power density of 453 mW cm-2 at 800 °C, as well as good redox cycling stability within eight redox cycles. Additionally, 10 vol.% Ce0.8Sm0.2O1.9 ceramic particle is incorporated into the Ni layer to further improve the redox cycling stability. The cell exhibits enhanced redox cycling performance after the Ce0.8Sm0.2O1.9 incorporation. Within seven redox cycles, the cell voltage loss is less than 1% at a current density of 400 mA cm-2, and it maintains 93% of its initial performance after 11 redox cycles.

  4. Delayed enhancement of multitasking performance: Effects of anodal transcranial direct current stimulation on the prefrontal cortex

    PubMed Central

    Hsu, Wan-Yu; Zanto, Theodore P.; Anguera, Joaquin A.; Lin, Yung-Yang; Gazzaley, Adam

    2015-01-01

    Background The dorsolateral prefrontal cortex (DLPFC) has been proposed to play an important role in neural processes that underlie multitasking performance. However, this claim is underexplored in terms of direct causal evidence. Objective The current study aimed to delineate the causal involvement of the DLPFC during multitasking by modulating neural activity with transcranial direct current stimulation (tDCS) prior to engagement in a demanding multitasking paradigm. Methods The study is a single-blind, crossover, sham-controlled experiment. Anodal tDCS or sham tDCS was applied over left DLPFC in forty-one healthy young adults (aged 18–35 years) immediately before they engaged in a 3-D video game designed to assess multitasking performance. Participants were separated into three subgroups: real-sham (i.e., real tDCS in the first session, followed by sham tDCS in the second session one hour later), sham-real (sham tDCS first session, real tDCS second session), and sham-sham (sham tDCS in both sessions). Results The real-sham group showed enhanced multitasking performance and decreased multitasking cost during the second session, compared to first session, suggesting delayed cognitive benefits of tDCS. Interestingly, performance benefits were observed only for multitasking and not on a single-task version of the game. No significant changes were found between the first and second sessions for either the sham-real or the sham-sham groups. Conclusions These results suggest a causal role of left prefrontal cortex in facilitating the simultaneous performance of more than one task, or multitasking. Moreover, these findings reveal that anodal tDCS may have delayed benefits that reflect an enhanced rate of learning. PMID:26073148

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

    PubMed

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

    2014-06-17

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

  6. The Homeostatic Interaction Between Anodal Transcranial Direct Current Stimulation and Motor Learning in Humans is Related to GABAA Activity

    PubMed Central

    Amadi, Ugwechi; Allman, Claire; Johansen-Berg, Heidi; Stagg, Charlotte J.

    2015-01-01

    Background The relative timing of plasticity-induction protocols is known to be crucial. For example, anodal transcranial direct current stimulation (tDCS), which increases cortical excitability and typically enhances plasticity, can impair performance if it is applied before a motor learning task. Such timing-dependent effects have been ascribed to homeostatic plasticity, but the specific synaptic site of this interaction remains unknown. Objective We wished to investigate the synaptic substrate, and in particular the role of inhibitory signaling, underpinning the behavioral effects of anodal tDCS in homeostatic interactions between anodal tDCS and motor learning. Methods We used transcranial magnetic stimulation (TMS) to investigate cortical excitability and inhibitory signaling following tDCS and motor learning. Each subject participated in four experimental sessions and data were analyzed using repeated measures ANOVAs and post-hoc t-tests as appropriate. Results As predicted, we found that anodal tDCS prior to the motor task decreased learning rates. This worsening of learning after tDCS was accompanied by a correlated increase in GABAA activity, as measured by TMS-assessed short interval intra-cortical inhibition (SICI). Conclusion This provides the first direct demonstration in humans that inhibitory synapses are the likely site for the interaction between anodal tDCS and motor learning, and further, that homeostatic plasticity at GABAA synapses has behavioral relevance in humans. PMID:26279408

  7. High-current diode with ferroelectric plasma source-assisted hollow anode

    SciTech Connect

    Vekselman, V.; Gleizer, J. Z.; Yatom, S.; Gurovich, V. Tz.; Krasik, Ya. E.

    2010-11-15

    The operation of a ferroelectric plasma source-assisted hollow anode (HA) electron source in a vacuum diode powered by an {approx}200 kV and {approx}400 ns pulsed generator was studied using time- and space-resolved laser induced fluorescence diagnostics. It was found that the plasma ion ''temperature'' in the vicinity of the HA output grid increases up to {approx}15 eV during the accelerating pulse, which is consistent with a model of the potential screening of the grid by the randomly moving ions [Phys. Plasmas 13, 073506 (2006)]. Also it was shown that the increase in the HA plasma potential up to several kilovolts because of the appearance of a noncompensated ion charge in the HA bulk plasma due to electrons fast extraction, leads to explosive emission centers being generated at the HA grid and to nonuniformity in the cross-sectional electron beam current density. Finally, the plasma prefilled mode of diode operation was studied using a simple one-dimensional model of the plasma erosion and the HA plasma electron heating by energetic ions was considered.

  8. Patient-conducted anodal transcranial direct current stimulation of the motor cortex alleviates pain in trigeminal neuralgia

    PubMed Central

    2014-01-01

    Background Transcranial direct current stimulation (tDCS) of the primary motor cortex has been shown to modulate pain and trigeminal nociceptive processing. Methods Ten patients with classical trigeminal neuralgia (TN) were stimulated daily for 20 minutes over two weeks using anodal (1 mA) or sham tDCS over the primary motor cortex (M1) in a randomized double-blind cross-over design. Primary outcome variable was pain intensity on a verbal rating scale (VRS 0–10). VRS and attack frequency were assessed for one month before, during and after tDCS. The impact on trigeminal pain processing was assessed with pain-related evoked potentials (PREP) and the nociceptive blink reflex (nBR) following electrical stimulation on both sides of the forehead before and after tDCS. Results Anodal tDCS reduced pain intensity significantly after two weeks of treatment. The attack frequency reduction was not significant. PREP showed an increased N2 latency and decreased peak-to-peak amplitude after anodal tDCS. No severe adverse events were reported. Conclusion Anodal tDCS over two weeks ameliorates intensity of pain in TN. It may become a valuable treatment option for patients unresponsive to conventional treatment. PMID:25424567

  9. 1-D nanoporous anodic alumina rugate filters by means of small current variations for real-time sensing applications

    NASA Astrophysics Data System (ADS)

    Macias, Gerard; Ferré-Borrull, Josep; Pallarès, Josep; Marsal, Lluís F.

    2014-06-01

    A rugate filter based on nanoporous anodic alumina was fabricated using an innovative sinusoidal current profile with small current variation. The resulting structure consisted of highly parallel pores with modulations of the pore diameter along the pore axis and with no branching. The effect of the period time and the pore widening post-treatment was studied. From reflectance measurements, it was seen that the position of the reflection band can be tuned by adjusting the period time and the width by pore-widening post-treatments. We tested one of the rugate filters by infiltrating the structure with EtOH and water in order to evaluate its sensing capabilities. This method allows the fabrication of complex in-depth modulated nanoporous anodic alumina structures that open up the possibility of new kinds of alumina-based optical sensing devices.

  10. 1-D nanoporous anodic alumina rugate filters by means of small current variations for real-time sensing applications.

    PubMed

    Macias, Gerard; Ferré-Borrull, Josep; Pallarès, Josep; Marsal, Lluís F

    2014-01-01

    A rugate filter based on nanoporous anodic alumina was fabricated using an innovative sinusoidal current profile with small current variation. The resulting structure consisted of highly parallel pores with modulations of the pore diameter along the pore axis and with no branching. The effect of the period time and the pore widening post-treatment was studied. From reflectance measurements, it was seen that the position of the reflection band can be tuned by adjusting the period time and the width by pore-widening post-treatments. We tested one of the rugate filters by infiltrating the structure with EtOH and water in order to evaluate its sensing capabilities. This method allows the fabrication of complex in-depth modulated nanoporous anodic alumina structures that open up the possibility of new kinds of alumina-based optical sensing devices. PMID:25024680

  11. Bundled and densified carbon nanotubes (CNT) fabrics as flexible ultra-light weight Li-ion battery anode current collectors

    NASA Astrophysics Data System (ADS)

    Yehezkel, Shani; Auinat, Mahmud; Sezin, Nina; Starosvetsky, David; Ein-Eli, Yair

    2016-04-01

    Carbon nanotubes (CNT) fabrics were studied and evaluated as anode current collectors, replacing the traditional copper foil current collector in Li-ion batteries. Glavanostatic measurements reveal high values of irreversible capacities (as high as 28%), resulted mainly from the formation of the solid electrolyte interphase (SEI) layer at the CNT fabric surface. Various pre-treatments to the CNT fabric prior to active anode material loading have shown that the lowest irreversible capacity is achieved by immersing and washing the CNT fabric with iso-propanol (IPA), which dramatically modified the fabric surface. Additionally, the use of very thin CNT fabrics (5 μm) results in a substantial irreversible capacity minimization. A combination of IPA rinse action and utilization of the thinnest CNT fabric provides the lowest irreversible capacity of 13%. The paper describes innovative and rather simple techniques towards a complete implementation of CNT fabric as an anode current collector in Li-ion batteries, instead of the relatively heavy and expensive copper foil, enabling an improvement in the gravimetric and volumetric energy densities of such advanced batteries.

  12. Preliminary Evidence That Anodal Transcranial Direct Current Stimulation Enhances Time to Task Failure of a Sustained Submaximal Contraction

    PubMed Central

    Williams, Petra S.; Hoffman, Richard L.; Clark, Brian C.

    2013-01-01

    The purpose of this study was to determine whether anodal transcranial direct current stimulation (tDCS) delivered while performing a sustained submaximal contraction would increase time to task failure (TTF) compared to sham stimulation. Healthy volunteers (n = 18) performed two fatiguing contractions at 20% of maximum strength with the elbow flexors on separate occasions. During fatigue task performance, either anodal or sham stimulation was delivered to the motor cortex for up to 20 minutes. Transcranial magnetic stimulation (TMS) was used to assess changes in cortical excitability during stimulation. There was no systematic effect of the anodal tDCS stimulation on TTF for the entire subject set (n = 18; p = 0.64). Accordingly, a posteriori subjects were divided into two tDCS-time groups: Full-Time (n = 8), where TTF occurred prior to the termination of tDCS, and Part-Time (n = 10), where TTF extended after tDCS terminated. The TTF for the Full-Time group was 31% longer with anodal tDCS compared to sham (p = 0.04), whereas TTF for the Part-Time group did not differ (p = 0.81). Therefore, the remainder of our analysis addressed the Full-Time group. With anodal tDCS, the amount of muscle fatigue was 6% greater at task failure (p = 0.05) and the amount of time the Full-Time group performed the task at an RPE between 8–10 (“very hard”) increased by 38% (p = 0.04) compared to sham. There was no difference in measures of cortical excitability between stimulation conditions (p = 0.90). That the targeted delivery of anodal tDCS during task performance both increased TTF and the amount of muscle fatigue in a subset of subjects suggests that augmenting cortical excitability with tDCS enhanced descending drive to the spinal motorpool to recruit more motor units. The results also suggest that the application of tDCS during performance of fatiguing activity has the potential to bolster the capacity to exercise under conditions

  13. Anodal transcranial direct current stimulation enhances the effects of motor imagery training in a finger tapping task.

    PubMed

    Saimpont, Arnaud; Mercier, Catherine; Malouin, Francine; Guillot, Aymeric; Collet, Christian; Doyon, Julien; Jackson, Philip L

    2016-01-01

    Motor imagery (MI) training and anodal transcranial direct current stimulation (tDCS) applied over the primary motor cortex can independently improve hand motor function. The main objective of this double-blind, sham-controlled study was to examine whether anodal tDCS over the primary motor cortex could enhance the effects of MI training on the learning of a finger tapping sequence. Thirty-six right-handed young human adults were assigned to one of three groups: (i) who performed MI training combined with anodal tDCS applied over the primary motor cortex; (ii) who performed MI training combined with sham tDCS; and (iii) who received tDCS while reading a book. The MI training consisted of mentally rehearsing an eight-item complex finger sequence for 13 min. Before (Pre-test), immediately after (Post-test 1), and at 90 min after (Post-test 2) MI training, the participants physically repeated the sequence as fast and as accurately as possible. An anova showed that the number of sequences correctly performed significantly increased between Pre-test and Post-test 1 and remained stable at Post-test 2 in the three groups (P < 0.001). Furthermore, the percentage increase in performance between Pre-test and Post-test 1 and Post-test 2 was significantly greater in the group that performed MI training combined with anodal tDCS compared with the other two groups (P < 0.05). As a potential physiological explanation, the synaptic strength within the primary motor cortex could have been reinforced by the association of MI training and tDCS compared with MI training alone and tDCS alone. PMID:26540137

  14. Pain Reduction in Myofascial Pain Syndrome by Anodal Transcranial Direct Current Stimulation Combined with Standard Treatment: A Randomized Controlled Study

    PubMed Central

    Sakrajai, Piyaraid; Janyacharoen, Taweesak; Jensen, Mark P.; Sawanyawisuth, Kittisak; Auvichayapat, Narong; Tunkamnerdthai, Orathai; Keeratitanont, Keattichai; Auvichayapat, Paradee

    2014-01-01

    Background Myofascial pain syndrome (MPS) in the shoulder is among the most prevalent pain problems in the middle-aged population worldwide. Evidence suggests that peripheral and central sensitization may play an important role in the development and maintenance of shoulder MPS. Given previous research supporting the potential efficacy of anodal transcranial direct current stimulation (tDCS) for modulating pain-related brain activity in individuals with refractory central pain, we hypothesized that anodal tDCS when applied over the primary motor cortex (M1) combined with standard treatment will be more effective for reducing pain in patients with MPS than standard treatment alone. Method Study participants were randomized to receive either (1) standard treatment with 5-consecutive days of 1 mA anodal tDCS over M1 for 20 min or (2) standard treatment plus sham tDCS. Measures of pain intensity, shoulder passive range of motion, analgesic medication use, and self-reported physical functioning were administered before treatment and again at post-treatment and 1-, 2-, 3-and 4-week follow-up. Results Thirty-one patients with MPS were enrolled. Participants assigned to the active tDCS condition reported significantly more pre- to post-treatment reductions in pain intensity that were maintained at 1-week post-treatment, and significant improvement in shoulder adduction PROM at 1-week follow-up than participants assigned to the sham tDCS condition. Conclusion 5 consecutive days of anodal tDCS over M1 combined with standard treatment appears to reduce pain intensity, and may improve PROM, faster than standard treatment alone. Further tests of the efficacy and duration of effects of tDCS in the treatment of MPS are warranted. PMID:25373724

  15. Relationship between anode material, supporting electrolyte and current density during electrochemical degradation of organic compounds in water.

    PubMed

    Guzmán-Duque, Fernando L; Palma-Goyes, Ricardo E; González, Ignacio; Peñuela, Gustavo; Torres-Palma, Ricardo A

    2014-08-15

    Taking crystal violet (CV) dye as pollutant model, the electrode, electrolyte and current density (i) relationship for electro-degrading organic molecules is discussed. Boron-doped diamond (BDD) or Iridium dioxide (IrO2) used as anode materials were tested with Na2SO4 or NaCl as electrolytes. CV degradation and generated oxidants showed that degradation pathways and efficiency are strongly linked to the current density-electrode-electrolyte interaction. With BDD, the degradation pathway depends on i: If icurrent density (i(lim)), CV is mainly degraded by OH radicals, whereas if i>i(lim), generated oxidants play a major role in the CV elimination. When IrO2 was used, CV removal was not dependent on i, but on the electrolyte. Pollutant degradation in Na2SO4 on IrO2 seems to occur via IrO3; however, in the presence of NaCl, degradation was dependent on the chlorinated oxidative species generated. In terms of efficiency, the Na2SO4 electrolyte showed better results than NaCl when BDD anodes were employed. On the contrary, NaCl was superior when combined with IrO2. Thus, the IrO2/Cl(-) and BDD/SO4(2-) systems were better at removing the pollutant, being the former the most effective. On the other hand, pollutant degradation with the BDD/SO4(2-) and IrO2/Cl(-) systems is favored at low and high current densities, respectively.

  16. Relationship between anode material, supporting electrolyte and current density during electrochemical degradation of organic compounds in water.

    PubMed

    Guzmán-Duque, Fernando L; Palma-Goyes, Ricardo E; González, Ignacio; Peñuela, Gustavo; Torres-Palma, Ricardo A

    2014-08-15

    Taking crystal violet (CV) dye as pollutant model, the electrode, electrolyte and current density (i) relationship for electro-degrading organic molecules is discussed. Boron-doped diamond (BDD) or Iridium dioxide (IrO2) used as anode materials were tested with Na2SO4 or NaCl as electrolytes. CV degradation and generated oxidants showed that degradation pathways and efficiency are strongly linked to the current density-electrode-electrolyte interaction. With BDD, the degradation pathway depends on i: If icurrent density (i(lim)), CV is mainly degraded by OH radicals, whereas if i>i(lim), generated oxidants play a major role in the CV elimination. When IrO2 was used, CV removal was not dependent on i, but on the electrolyte. Pollutant degradation in Na2SO4 on IrO2 seems to occur via IrO3; however, in the presence of NaCl, degradation was dependent on the chlorinated oxidative species generated. In terms of efficiency, the Na2SO4 electrolyte showed better results than NaCl when BDD anodes were employed. On the contrary, NaCl was superior when combined with IrO2. Thus, the IrO2/Cl(-) and BDD/SO4(2-) systems were better at removing the pollutant, being the former the most effective. On the other hand, pollutant degradation with the BDD/SO4(2-) and IrO2/Cl(-) systems is favored at low and high current densities, respectively. PMID:24981674

  17. Anodal transcranial direct current stimulation boosts synaptic plasticity and memory in mice via epigenetic regulation of Bdnf expression

    PubMed Central

    Podda, Maria Vittoria; Cocco, Sara; Mastrodonato, Alessia; Fusco, Salvatore; Leone, Lucia; Barbati, Saviana Antonella; Colussi, Claudia; Ripoli, Cristian; Grassi, Claudio

    2016-01-01

    The effects of transcranial direct current stimulation (tDCS) on brain functions and the underlying molecular mechanisms are yet largely unknown. Here we report that mice subjected to 20-min anodal tDCS exhibited one-week lasting increases in hippocampal LTP, learning and memory. These effects were associated with enhanced: i) acetylation of brain-derived neurotrophic factor (Bdnf) promoter I; ii) expression of Bdnf exons I and IX; iii) Bdnf protein levels. The hippocampi of stimulated mice also exhibited enhanced CREB phosphorylation, pCREB binding to Bdnf promoter I and recruitment of CBP on the same regulatory sequence. Inhibition of acetylation and blockade of TrkB receptors hindered tDCS effects at molecular, electrophysiological and behavioral levels. Collectively, our findings suggest that anodal tDCS increases hippocampal LTP and memory via chromatin remodeling of Bdnf regulatory sequences leading to increased expression of this gene, and support the therapeutic potential of tDCS for brain diseases associated with impaired neuroplasticity. PMID:26908001

  18. No Effect of Anodal Transcranial Direct Current Stimulation Over the Motor Cortex on Response-Related ERPs during a Conflict Task.

    PubMed

    Conley, Alexander C; Fulham, W R; Marquez, Jodie L; Parsons, Mark W; Karayanidis, Frini

    2016-01-01

    Anodal transcranial direct current stimulation (tDCS) over the motor cortex is considered a potential treatment for motor rehabilitation following stroke and other neurological pathologies. However, both the context under which this stimulation is effective and the underlying mechanisms remain to be determined. In this study, we examined the mechanisms by which anodal tDCS may affect motor performance by recording event-related potentials (ERPs) during a cued go/nogo task after anodal tDCS over dominant primary motor cortex (M1) in young adults (Experiment 1) and both dominant and non-dominant M1 in older adults (Experiment 2). In both experiments, anodal tDCS had no effect on either response time (RT) or response-related ERPs, including the cue-locked contingent negative variation (CNV) and both target-locked and response-locked lateralized readiness potentials (LRP). Bayesian model selection analyses showed that, for all measures, the null effects model was stronger than a model including anodal tDCS vs. sham. We conclude that anodal tDCS has no effect on RT or response-related ERPs during a cued go/nogo task in either young or older adults. PMID:27547180

  19. No Effect of Anodal Transcranial Direct Current Stimulation Over the Motor Cortex on Response-Related ERPs during a Conflict Task

    PubMed Central

    Conley, Alexander C.; Fulham, W. R.; Marquez, Jodie L.; Parsons, Mark W.; Karayanidis, Frini

    2016-01-01

    Anodal transcranial direct current stimulation (tDCS) over the motor cortex is considered a potential treatment for motor rehabilitation following stroke and other neurological pathologies. However, both the context under which this stimulation is effective and the underlying mechanisms remain to be determined. In this study, we examined the mechanisms by which anodal tDCS may affect motor performance by recording event-related potentials (ERPs) during a cued go/nogo task after anodal tDCS over dominant primary motor cortex (M1) in young adults (Experiment 1) and both dominant and non-dominant M1 in older adults (Experiment 2). In both experiments, anodal tDCS had no effect on either response time (RT) or response-related ERPs, including the cue-locked contingent negative variation (CNV) and both target-locked and response-locked lateralized readiness potentials (LRP). Bayesian model selection analyses showed that, for all measures, the null effects model was stronger than a model including anodal tDCS vs. sham. We conclude that anodal tDCS has no effect on RT or response-related ERPs during a cued go/nogo task in either young or older adults. PMID:27547180

  20. Characterization of plasma ion source utilizing anode spot with positively biased electrode for stable and high-current ion beam extraction

    SciTech Connect

    Park, Yeong-Shin; Lee, Yuna; Chung, Kyoung-Jae; Hwang, Y. S.

    2011-12-15

    The operating conditions of a rf plasma ion source utilizing a positively biased electrode have been investigated to develop a stably operating, high-current ion source. Ion beam characteristics such as currents and energies are measured and compared with bias currents by varying the bias voltages on the electrode immersed in the ambient rf plasma. Current-voltage curves of the bias electrode and photographs confirm that a small and dense plasma, so-called anode spot, is formed near an extraction aperture and plays a key role to enhance the performance of the plasma ion source. The ion beam currents from the anode spot are observed to be maximized at the optimum bias voltage near the knee of the characteristic current-voltage curve of the anode spot. Increased potential barrier to obstruct beam extraction is the reason for the reduction of the ion beam current in spite of the increased bias current indicating the density of the anode spot. The optimum bias voltage is measured to be lower at higher operating pressure, which is favorable for stable operation without severe sputtering damage on the electrode. The ion beam current can be further enhanced by increasing the power for the ambient plasma without increasing the bias voltage. In the same manner, noble gases with higher atomic number as a feedstock gas are preferable for extracting higher beam current more stably. Therefore, performance of the plasma ion source with a positively biased electrode can be enhanced by controlling the operating conditions of the anode spot in various manners.

  1. Transcranial direct current stimulation facilitates cognitive multi-task performance differentially depending on anode location and subtask

    PubMed Central

    Scheldrup, Melissa; Greenwood, Pamela M.; McKendrick, Ryan; Strohl, Jon; Bikson, Marom; Alam, Mahtab; McKinley, R. Andy; Parasuraman, Raja

    2014-01-01

    There is a need to facilitate acquisition of real world cognitive multi-tasks that require long periods of training (e.g., air traffic control, intelligence analysis, medicine). Non-invasive brain stimulation—specifically transcranial Direct Current Stimulation (tDCS)—has promise as a method to speed multi-task training. We hypothesized that during acquisition of the complex multi-task Space Fortress, subtasks that require focused attention on ship control would benefit from tDCS aimed at the dorsal attention network while subtasks that require redirection of attention would benefit from tDCS aimed at the right hemisphere ventral attention network. We compared effects of 30 min prefrontal and parietal stimulation to right and left hemispheres on subtask performance during the first 45 min of training. The strongest effects both overall and for ship flying (control and velocity subtasks) were seen with a right parietal (C4, reference to left shoulder) montage, shown by modeling to induce an electric field that includes nodes in both dorsal and ventral attention networks. This is consistent with the re-orienting hypothesis that the ventral attention network is activated along with the dorsal attention network if a new, task-relevant event occurs while visuospatial attention is focused (Corbetta et al., 2008). No effects were seen with anodes over sites that stimulated only dorsal (C3) or only ventral (F10) attention networks. The speed subtask (update memory for symbols) benefited from an F9 anode over left prefrontal cortex. These results argue for development of tDCS as a training aid in real world settings where multi-tasking is critical. PMID:25249958

  2. The effect of ion current density amplification in a diode with passive anode in magnetic self-isolation mode

    SciTech Connect

    Pushkarev, Alexander I.; Isakova, Yulia I.; Vakhrushev, Dmitry V.

    2010-12-15

    The results of a study on gigawatt power pulsed ion beam parameters are presented here. The pulsed ion beam is formed by a diode with an explosive-emission potential electrode, in magnetic self-isolation mode [A. I. Pushkarev, J. I. Isakova, M. S. Saltimakov et al., Phys. Plasmas 17, 013104 (2010)]. The ion current density is 20-40 A/cm{sup 2}, the energy of the ions is 200-250 keV, and the beam composition is of protons and carbon ions. Experiments have been performed on the TEMP-4M accelerator, set in double-pulse formation mode. To measure the beam parameters, we used a time-of-flight diagnosis. It is shown that the carbon ion current density, formed in a planar diode with graphite potential electrode, is five to seven times higher than the values calculated from the Child-Langmuir ratio. A model of ion current density amplification in a diode with magnetic self-isolation is proposed. The motion of electrons in the anode-cathode gap is simulated using the program CST PARTICLE STUDIO.

  3. Ring laser gyroscope anode

    SciTech Connect

    Ljung, B.H.

    1981-03-17

    An anode for a ring laser gyroscope which provides improved current stability in the glow discharge path is disclosed. The anode of this invention permits operation at lower currents thereby allowing a reduction of heat dissipation in the ring laser gyroscope. The anode of one embodiment of this invention is characterized by a thumbtack appearance with a spherical end where the normal sharp end of the thumbtack would be located. The stem of the anode extends from the outside of the gyroscope structure to the interior of the structure such that the spherical end is substantially adjacent to the laser beam.

  4. A glucose anode for enzymatic fuel cells optimized for current production under physiological conditions using a design of experiment approach.

    PubMed

    Kumar, Rakesh; Leech, Dónal

    2015-12-01

    This study reports a design of experiment methodology to investigate and improve the performance of glucose oxidizing enzyme electrodes. Enzyme electrodes were constructed by co-immobilization of amine-containing osmium redox complexes, multiwalled carbon nanotubes and glucose oxidase in a carboxymethyldextran matrix at graphite electrode surfaces to provide a 3-dimensional matrix for electrocatalytic oxidation of glucose. Optimization of the amount of the enzyme electrode components to produce the highest current density under pseudo-physiological conditions of 5 mM glucose in saline buffer at 37 °C was performed using response surface methodology. A statistical analysis showed that the proposed model had a good fit with the experimental results. From the validated model, the addition of multiwalled carbon nanotubes and carboxymethyldextran components was identified as major contributing factors to the improved performance. Based on the optimized amount of components, enzyme electrodes display current densities of 1.2±0.1 mA cm(-2) and 5.2±0.2 mA cm(-2) at 0.2 V vs. Ag/AgCl in buffer containing 5 mM and 100 mM glucose, respectively, largely consistent with the predicted values. This demonstrates that use of a design of experiment approach can be applied effectively and efficiently to improve the performance of enzyme electrodes as anodes for biofuel cell device development. PMID:26116416

  5. A glucose anode for enzymatic fuel cells optimized for current production under physiological conditions using a design of experiment approach.

    PubMed

    Kumar, Rakesh; Leech, Dónal

    2015-12-01

    This study reports a design of experiment methodology to investigate and improve the performance of glucose oxidizing enzyme electrodes. Enzyme electrodes were constructed by co-immobilization of amine-containing osmium redox complexes, multiwalled carbon nanotubes and glucose oxidase in a carboxymethyldextran matrix at graphite electrode surfaces to provide a 3-dimensional matrix for electrocatalytic oxidation of glucose. Optimization of the amount of the enzyme electrode components to produce the highest current density under pseudo-physiological conditions of 5 mM glucose in saline buffer at 37 °C was performed using response surface methodology. A statistical analysis showed that the proposed model had a good fit with the experimental results. From the validated model, the addition of multiwalled carbon nanotubes and carboxymethyldextran components was identified as major contributing factors to the improved performance. Based on the optimized amount of components, enzyme electrodes display current densities of 1.2±0.1 mA cm(-2) and 5.2±0.2 mA cm(-2) at 0.2 V vs. Ag/AgCl in buffer containing 5 mM and 100 mM glucose, respectively, largely consistent with the predicted values. This demonstrates that use of a design of experiment approach can be applied effectively and efficiently to improve the performance of enzyme electrodes as anodes for biofuel cell device development.

  6. Current perpendicular to plane giant magnetoresistance of multilayered nanowires electrodeposited in anodic aluminum oxide membranes

    NASA Astrophysics Data System (ADS)

    Evans, P. R.; Yi, G.; Schwarzacher, W.

    2000-01-01

    Co-Ni-Cu/Cu multilayered nanowires were prepared by electrodeposition using nanoporous aluminum oxide membranes rather than the more usual track-etched polycarbonate membranes as templates. Very large values of the current perpendicular to plane giant magnetoresistance (CPP-GMR) were recorded: 55% at room temperature and 115% at 77 K. The use of aluminum oxide membranes also made possible a study of the effects of annealing on the CPP-GMR.

  7. PIG Ion Source with Permanent Magnets: Model Based Anode Current Return Circuit

    NASA Astrophysics Data System (ADS)

    Babapour Ghadikolaee, Mohammad Reza

    2012-12-01

    Ion sources are widely used in fusion technologies. A new high voltage pulsed power supply for use in penning ion gauge ion sources is proposed in this paper. To use discharge current, a diode-capacitor bank is included. The power supply is composed of 3 stages. A fast switching transistor is used as a single switch which is trigged by a pulse generator. A transformer is used to level up the voltage up to 2 kV without power loss. It is also used to isolate input and high voltage output. Also; the proposed high voltage power supply implementation uses a diode-capacitor bank whose capacitors are charged during plasma discharge. This system structure gives compactness and easiness to implement the total system which in combination with inexpensive commercially available components, makes the unit versatile and inexpensive.

  8. Neuromodulation of conditioned placebo/nocebo in heat pain: anodal vs cathodal transcranial direct current stimulation to the right dorsolateral prefrontal cortex.

    PubMed

    Egorova, Natalia; Yu, Rongjun; Kaur, Navneet; Vangel, Mark; Gollub, Randy L; Dougherty, Darin D; Kong, Jian; Camprodon, Joan A

    2015-07-01

    Placebo and nocebo play an important role in clinical practice and medical research. Modulating placebo/nocebo responses using noninvasive brain stimulation methods, such as transcranial direct current stimulation (tDCS), has the potential to harness these effects to therapeutic benefit in a clinical setting. In this study, we assessed the effect of anodal and cathodal tDCS over the right dorsolateral prefrontal cortex (rDLPFC) on conditioned placebo/nocebo cue response to heat pain. Two matched groups of healthy volunteers were subjected to an identical session of conditioning, during which low and high cues (abstract images) were associated with low and high pain levels, respectively. Twenty-minute 2-mA tDCS (either anodal or cathodal) over the rDLPFC was applied. The influence of tDCS current polarity (anodal vs cathodal) on placebo and nocebo was assessed, using subjects' pain ratings in response to identical pain preceded by the conditioned high or low cues. The duration of cue presentation varied to allow either fully conscious or subliminal processing. Significant placebo and nocebo effects in the anodal but not the cathodal group were elicited with the conditioning paradigm. This study provides evidence of a possibility to modulate the conditioned placebo and nocebo effect by changing the excitability of the rDLPFC using tDCS. PMID:25806605

  9. Neuromodulation of conditioned placebo/nocebo in heat pain: anodal vs cathodal transcranial direct current stimulation to the right dorsolateral prefrontal cortex.

    PubMed

    Egorova, Natalia; Yu, Rongjun; Kaur, Navneet; Vangel, Mark; Gollub, Randy L; Dougherty, Darin D; Kong, Jian; Camprodon, Joan A

    2015-07-01

    Placebo and nocebo play an important role in clinical practice and medical research. Modulating placebo/nocebo responses using noninvasive brain stimulation methods, such as transcranial direct current stimulation (tDCS), has the potential to harness these effects to therapeutic benefit in a clinical setting. In this study, we assessed the effect of anodal and cathodal tDCS over the right dorsolateral prefrontal cortex (rDLPFC) on conditioned placebo/nocebo cue response to heat pain. Two matched groups of healthy volunteers were subjected to an identical session of conditioning, during which low and high cues (abstract images) were associated with low and high pain levels, respectively. Twenty-minute 2-mA tDCS (either anodal or cathodal) over the rDLPFC was applied. The influence of tDCS current polarity (anodal vs cathodal) on placebo and nocebo was assessed, using subjects' pain ratings in response to identical pain preceded by the conditioned high or low cues. The duration of cue presentation varied to allow either fully conscious or subliminal processing. Significant placebo and nocebo effects in the anodal but not the cathodal group were elicited with the conditioning paradigm. This study provides evidence of a possibility to modulate the conditioned placebo and nocebo effect by changing the excitability of the rDLPFC using tDCS.

  10. Characterization of Electrical Current-Generation Capabilities from Thermophilic Bacterium Thermoanaerobacter pseudethanolicus Using Xylose, Glucose, Cellobiose, or Acetate with Fixed Anode Potentials.

    PubMed

    Lusk, Bradley G; Khan, Qaiser Farid; Parameswaran, Prathap; Hameed, Abdul; Ali, Naeem; Rittmann, Bruce E; Torres, Cesar I

    2015-12-15

    Thermoanaerobacter pseudethanolicus 39E (ATCC 33223), a thermophilic, Fe(III)-reducing, and fermentative bacterium, was evaluated for its ability to produce current from four electron donors-xylose, glucose, cellobiose, and acetate-with a fixed anode potential (+ 0.042 V vs SHE) in a microbial electrochemical cell (MXC). Under thermophilic conditions (60 °C), T. pseudethanolicus produced high current densities from xylose (5.8 ± 2.4 A m(-2)), glucose (4.3 ± 1.9 A m(-2)), and cellobiose (5.2 ± 1.6 A m(-2)). It produced insignificant current when grown with acetate, but consumed the acetate produced from sugar fermentation to produce electrical current. Low-scan cyclic voltammetry (LSCV) revealed a sigmoidal response with a midpoint potential of -0.17 V vs SHE. Coulombic efficiency (CE) varied by electron donor, with xylose at 34.8% ± 0.7%, glucose at 65.3% ± 1.0%, and cellobiose at 27.7% ± 1.5%. Anode respiration was sustained over a pH range of 5.4-8.3, with higher current densities observed at higher pH values. Scanning electron microscopy showed a well-developed biofilm of T. pseudethanolicus on the anode, and confocal laser scanning microscopy demonstrated a maximum biofilm thickness (Lf) greater than ~150 μm for the glucose-fed biofilm.

  11. Degradation of tetracycline at a boron-doped diamond anode: influence of initial pH, applied current intensity and electrolyte.

    PubMed

    Brinzila, C I; Monteiro, N; Pacheco, M J; Ciríaco, L; Siminiceanu, I; Lopes, A

    2014-01-01

    The anodic oxidation of tetracycline was performed in an up-flow reactor, operating in batch mode with recirculation, using as anode a boron-doped diamond electrode. The influence on the degradation rate of solution initial pH (2 to 12), applied current intensity (25 to 300 A m(-2)) and type of electrolyte (sodium sulphate or sodium chloride) were investigated. For the assays run at equal current density, with sodium sulphate as electrolyte, the solution's initial pH of 2 presented the highest absorbance and chemical oxygen demand removals. Regarding the influence of current density, for equal charge passed, the organic load removal rate decreased with the increase in applied current. When sodium sulphate was used as an electrolyte, high-performance liquid chromatography (HPLC) results have shown an almost complete removal of tetracycline after a 2-h assay. HPLC results have also shown the presence of oxamic acid as one of the intermediates of tetracycline anodic oxidation. The complete removal of tetracycline was much faster in the presence of chloride ions that promoted the complete degradation of this antibiotic in 30 min. However, in the presence of chloride ions, the tetracycline mineralization is slower, as observed by the lower organic carbon removal rate when compared to that of the tetracycline degradation in the presence of sulphate.

  12. Degradation of tetracycline at a boron-doped diamond anode: influence of initial pH, applied current intensity and electrolyte.

    PubMed

    Brinzila, C I; Monteiro, N; Pacheco, M J; Ciríaco, L; Siminiceanu, I; Lopes, A

    2014-01-01

    The anodic oxidation of tetracycline was performed in an up-flow reactor, operating in batch mode with recirculation, using as anode a boron-doped diamond electrode. The influence on the degradation rate of solution initial pH (2 to 12), applied current intensity (25 to 300 A m(-2)) and type of electrolyte (sodium sulphate or sodium chloride) were investigated. For the assays run at equal current density, with sodium sulphate as electrolyte, the solution's initial pH of 2 presented the highest absorbance and chemical oxygen demand removals. Regarding the influence of current density, for equal charge passed, the organic load removal rate decreased with the increase in applied current. When sodium sulphate was used as an electrolyte, high-performance liquid chromatography (HPLC) results have shown an almost complete removal of tetracycline after a 2-h assay. HPLC results have also shown the presence of oxamic acid as one of the intermediates of tetracycline anodic oxidation. The complete removal of tetracycline was much faster in the presence of chloride ions that promoted the complete degradation of this antibiotic in 30 min. However, in the presence of chloride ions, the tetracycline mineralization is slower, as observed by the lower organic carbon removal rate when compared to that of the tetracycline degradation in the presence of sulphate. PMID:24664638

  13. A new, high current output, galvanic (sacrificial) anode, electrochemical rehabilitation system for reinforced and prestressed concrete structures

    SciTech Connect

    Clear, K.C.

    1999-07-01

    This paper summarizes 1995 through 1998 laboratory, outdoor exposure facility, and field data on the subject concrete rehab system. The system shows promise as a means of providing cathodic protection to the reinforcing, as a chloride removal process, as a re-alkalization process, and/or as a lithium injection procedure to minimize alkali-aggregate reactions in the concrete. Unique characteristics of the system include: (1) Surrounding each galvanic anode with a highly corrosive liquid which maintains it (the anode) at peak output voltage throughout its life; and (2) Placing an ionic transfer layer between the anode and the concrete surface that is high volume, low resistivity and deliquescent (i.e. pulls water vapor out of the air at relative humidities of 35% or higher). The ionic transfer layer typically consists of sponge, felt or sand loaded with calcium chloride (and/or other chemicals such as sodium hydroxide, potassium acetate, and lithium-salts). In some cases it also contains a wetting agent and is encapsulated (fully or partially) in vapor permeable, but water impermeable materials. The ionic transfer layer will not freeze at temperatures as low as {minus}20 C ({minus}5 F), and provides sufficient space for all anode corrosion products, thus preventing undesirable stresses on the concrete, the anode assembly and any cosmetic covering.

  14. Controlling the Emotional Bias: Performance, Late Positive Potentials, and the Effect of Anodal Transcranial Direct Current Stimulation (tDCS)

    PubMed Central

    Faehling, Florian; Plewnia, Christian

    2016-01-01

    Cognitive control of emotional processing is essential for adaptive human behavior. Biased attention toward emotionally salient information is critically linked with affective disorders and is discussed as a promising treatment target. Anodal (activity enhancing) transcranial direct current stimulation (tDCS) has been shown to increase healthy and impaired cognitive control over emotional distraction and is therefore widely used for the investigation and experimental treatment of this disorder. In this study, event-related potential (ERP) were recorded parallel to tDCS to track its online effects. Healthy volunteers (n = 87) performed a delayed working memory paradigm with emotional salient and neutral distractors during stimulation with different intensities (sham, 0.5, 1, 1.5 mA). Measuring the late positive potential (LPP), an ERP that indexes attention allocation, we found that a valence-specific increase of the early portion of the LPP (eLPP, 250–500 ms) was associated with less emotional distraction in the sham group. Of note, stimulation with tDCS exerted an intensity related effect on this correlation. The later part of the LPP (lLPP, 500–1000 ms) was found to be correlated with reaction time, regardless of valence. General effect of tDCS on LPPs and task performance were not observed. These findings demonstrate that ERP recordings parallel to tDCS are feasible to investigate the neuronal underpinnings of stimulation effects on executive functions. Furthermore, they support the notion that the LPP induced by a distractive stimulus during a working memory task mirrors the additional allocation of neuronal resources with a specific sensitivity of the early LPP for highly arousing negative stimuli. Finally, together with the variable magnitude and direction of the emotional bias, the lack of systematic modulations of LPPs and behavior by tDCS further underlines the important influence of the individual brain activity patterns on stimulation effects both on

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

    NASA Astrophysics Data System (ADS)

    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.

  16. One-minute deposition of micrometre-thick porous Si-Cu anodes with compositional gradients on Cu current collectors for lithium secondary batteries

    NASA Astrophysics Data System (ADS)

    Lee, Jungho; Hasegawa, Kei; Momma, Toshiyuki; Osaka, Tetsuya; Noda, Suguru

    2015-07-01

    We report micrometre-thick porous Si-Cu anodes that are rapidly co-deposited on Cu current collectors in 1 min. This rapid deposition is realized by heating Si and Cu powders to ∼2000 °C and elevating their vapour pressures, while the porous and amorphous anode structure is realized by keeping the substrates at 100 °C. The films spontaneously form a 2-4.5-μm-thick composition gradient that changes from a Cu-rich region at the bottom to a Si-rich region at the top of the film, because of the higher vapour pressure for Cu than Si. A small addition of 5 wt% Cu to the Si source enhances the cycle performance of the film remarkably in a half-cell test, yielding a gravimetric capacity of 1250 mAh gfilm-1, a volumetric capacity of 1956 mAh cmfilm-3, and an areal capacity of 0.96 mAh cmanode-2 at the 100th cycle. However, excess addition of Cu causes partial Si crystallization in the films, which results in poorer cycle performance. While further improvement is needed, this rapid vapour deposition method yields Si-Cu films with compositional gradients on Cu current collectors in 1 min using inexpensive and safe Si and Cu powder sources, and is attractive for practical Si-based anode fabrication.

  17. Comparison of the anodic behavior of aluminum current collectors in imide-based ionic liquids and consequences on the stability of high voltage supercapacitors

    NASA Astrophysics Data System (ADS)

    Kühnel, Ruben-Simon; Balducci, Andrea

    2014-03-01

    In this work, the influence of two common ionic liquid (IL) anions on the anodic stability of Al current collectors was studied. Namely, the Al corrosion/passivation process in N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) is compared to the one in N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14FSI). It is shown, that Al slowly corrodes in PYR14FSI, while it is much better passivated in PYR14TFSI, although the ionic liquids were prepared in the same way. Float tests were carried out to illustrate the consequences of these different anodic stabilities of Al on the cycling stability of supercapacitors. Interestingly, when the chloride content of PYR14FSI was <1 ppm, Al electrodes were also pretty stable in this IL, and a similar cycling stability during float tests than for PYR14TFSI could be obtained.

  18. Thin film buried anode battery

    DOEpatents

    Lee, Se-Hee; Tracy, C. Edwin; Liu, Ping

    2009-12-15

    A reverse configuration, lithium thin film battery (300) having a buried lithium anode layer (305) and process for making the same. The present invention is formed from a precursor composite structure (200) made by depositing electrolyte layer (204) onto substrate (201), followed by sequential depositions of cathode layer (203) and current collector (202) on the electrolyte layer. The precursor is subjected to an activation step, wherein a buried lithium anode layer (305) is formed via electroplating a lithium anode layer at the interface of substrate (201) and electrolyte film (204). The electroplating is accomplished by applying a current between anode current collector (201) and cathode current collector (202).

  19. Predicting Modulation in Corticomotor Excitability and in Transcallosal Inhibition in Response to Anodal Transcranial Direct Current Stimulation

    PubMed Central

    Davidson, Travis W.; Bolic, Miodrag; Tremblay, François

    2016-01-01

    Introduction: Responses to neuromodulatory protocols based either on transcranial direct current stimulation (tDCS) or transcranial magnetic stimulation (TMS) are known to be highly variable between individuals. In this study, we examined whether variability of responses to anodal tDCS (a-tDCS) could be predicted from individual differences in the ability to recruit early or late indirect waves (I-waves), as reflected in latency differences of motor evoked potentials (MEPs) evoked by TMS of different coil orientation. Methods: Participants (n = 20) first underwent TMS to measure latency of MEPs elicited at different coil orientations (i.e., PA, posterior-anterior; AP, anterior-posterior; LM, latero-medial). Then, participants underwent a-tDCS (20 min @ 2 mA) targeting the primary motor cortex of the contralateral preferred hand (right, n = 18). Individual responses to a-tDCS were determined by monitoring changes in MEP amplitude at rest and in the duration of the contralateral silent period (cSP) and ipsilateral silent period (iSP) during contraction; the latter providing an index of the latency and duration of transcallosal inhibition (LTI and DTI). Results: Consistent with previous reports, individual responses to a-tDCS were highly variable when expressed in terms of changes in MEP amplitude or in cSP duration with ~50% of the participants showing either little or no modulation. In contrast, individual variations in measures of transcallosal inhibition were less variable, allowing detection of significant after-effects. The reduced LTI and prolonged DTI observed post-tDCS were indicative of an enhanced excitability of the transcallosal pathway in the stimulated hemisphere. In terms of predictions, AP-LM latency differences proved to be good predictors of responses to a-tDCS when considering MEP modulation. Conclusion: The present results corroborate the predictive value of latency differences derived from TMS to determine who is likely to express

  20. Rational design of high-rate lithium zinc titanate anode electrode by modifying Cu current collector with graphene and Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Xinxi; Wang, Lijuan; Li, Chengfei; Chen, Baokuan; Zhao, Qiang; Zhang, Guoqing

    2016-03-01

    Lithium zinc titanate (Li2ZnTi3O8) is a desirable anode material for lithium ion batteries (LIBs) due to its low cost, non-toxicity and high safety. However, the low electronic conductivity and not perfect rate capability hinder the commercial application of Li2ZnTi3O8. Here, a facile and effective strategy is developed to fabricate the Li2ZnTi3O8 electrode using the Cu foil with grown graphene and deposited Au nanoparticles as the current collector. The graphene and Au nanoparticles greatly enhance the electrical conductivity of the current collector. The structured Cu current collector has rough interface which can strengthen the adhesion between the Li2ZnTi3O8 active material layer and the current collector, providing an excellent electron transport network and reducing the internal resistance of LIBs. The Li2ZnTi3O8 material supported on the unique structured Cu current collector demonstrates outstanding Li+ storage properties with the reversible capacity of 172.2 mAh g-1 after 100 cycles at high current density of 4 A g-1. Even at 6 A g-1, 148.4 mAh g-1 can be delivered. The improved rate capability of the structured Li2ZnTi3O8 electrode makes it a promising anode candidate for high performance LIBs.

  1. Generation of High Current Densities by Pure Cultures of Anode-Respiring Geoalkalibacter spp. under Alkaline and Saline Conditions in Microbial Electrochemical Cells

    PubMed Central

    Badalamenti, Jonathan P.; Krajmalnik-Brown, Rosa; Torres, César I.

    2013-01-01

    ABSTRACT Anode-respiring bacteria (ARB) generate electric current in microbial electrochemical cells (MXCs) by channeling electrons from the oxidation of organic substrates to an electrode. Production of high current densities by monocultures in MXCs has resulted almost exclusively from the activity of Geobacter sulfurreducens, a neutrophilic freshwater Fe(III)-reducing bacterium and the highest-current-producing member documented for the Geobacteraceae family of the Deltaproteobacteria. Here we report high current densities generated by haloalkaliphilic Geoalkalibacter spp., thus broadening the capability for high anode respiration rates by including other genera within the Geobacteraceae. In this study, acetate-fed pure cultures of two related Geoalkalibacter spp. produced current densities of 5.0 to 8.3 and 2.4 to 3.3 A m−2 under alkaline (pH 9.3) and saline (1.7% NaCl) conditions, respectively. Chronoamperometric studies of halophilic Glk. subterraneus DSM 23483 and alkaliphilic Glk. ferrihydriticus DSM 17813 suggested that cells performed long-range electron transfer through electrode-attached biofilms and not through soluble electron shuttles. Glk. ferrihydriticus also oxidized ethanol directly to produce current, with maximum current densities of 5.7 to 7.1 A m−2 and coulombic efficiencies of 84 to 95%. Cyclic voltammetry (CV) elicited a sigmoidal response with characteristic onset, midpoint, and saturation potentials, while CV performed in the absence of an electron donor suggested the involvement of redox molecules in the biofilm that were limited by diffusion. These results matched those previously reported for actively respiring Gb. sulfurreducens biofilms producing similar current densities (~5 to 9 A m−2). PMID:23631915

  2. Development of Point of Care Testing Device for Neurovascular Coupling From Simultaneous Recording of EEG and NIRS During Anodal Transcranial Direct Current Stimulation

    PubMed Central

    Jindal, Utkarsh; Sood, Mehak; Dutta, Anirban; Chowdhury, Shubhajit Roy

    2015-01-01

    This paper presents a point of care testing device for neurovascular coupling (NVC) from simultaneous recording of electroencephalogram (EEG) and near infrared spectroscopy (NIRS) during anodal transcranial direct current stimulation (tDCS). Here, anodal tDCS modulated cortical neural activity leading to hemodynamic response can be used to identify the impaired cerebral microvessels functionality. The impairments in the cerebral microvessels functionality may lead to impairments in the cerebrovascular reactivity (CVR), where severely reduced CVR predicts the chances of transient ischemic attack and ipsilateral stroke. The neural and hemodynamic responses to anodal tDCS were studied through joint imaging with EEG and NIRS, where NIRS provided optical measurement of changes in tissue oxy-(\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$HbO2)$ \\end{document} and deoxy-(\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$Hb$ \\end{document}) hemoglobin concentration and EEG captured alterations in the underlying neuronal current generators. Then, a cross-correlation method for the assessment of NVC underlying the site of anodal tDCS is presented. The feasibility studies on healthy subjects and stroke survivors showed detectable changes in the EEG and the NIRS responses to a 0.526 A/\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$\\mathrm{m}^{2}$ \\end{document} of anodal tDCS. The NIRS system

  3. Optimum structural properties for an anode current collector used in a polymer electrolyte membrane water electrolyzer operated at the boiling point of water

    NASA Astrophysics Data System (ADS)

    Li, Hua; Fujigaya, Tsuyohiko; Nakajima, Hironori; Inada, Akiko; Ito, Kohei

    2016-11-01

    This study attempts to optimize the properties of the anode current collector of a polymer electrolyte membrane water electrolyzer at high temperatures, particularly at the boiling point of water. Different titanium meshes (4 commercial ones and 4 modified ones) with various properties are experimentally examined by operating a cell with each mesh under different conditions. The average pore diameter, thickness, and contact angle of the anode current collector are controlled in the ranges of 10-35 μm, 0.2-0.3 mm, and 0-120°, respectively. These results showed that increasing the temperature from the conventional temperature of 80 °C to the boiling point could reduce both the open circuit voltage and the overvoltages to a large extent without notable dehydration of the membrane. These results also showed that decreasing the contact angle and the thickness suppresses the electrolysis overvoltage largely by decreasing the concentration overvoltage. The effect of the average pore diameter was not evident until the temperature reached the boiling point. Using operating conditions of 100 °C and 2 A/cm2, the electrolysis voltage is minimized to 1.69 V with a hydrophilic titanium mesh with an average pore diameter of 21 μm and a thickness of 0.2 mm.

  4. Anodic films

    SciTech Connect

    Muller, R.H.

    1983-08-01

    Surface layers are formed on many metals by anodic reaction. Such layers include the products of charge and discharge in many storage batteries, dielectric films used in electronic and optical circuits and display devices, layers responsible for passivity and corrosion protection, and films generated in metal shaping and finishing operations such as anodization, coloring, electropolishing, electrochemical machining and deburring. Anodic films are formed by solid-solid transformations or by dissolution-precipitation processes. Film properties and mechanisms of formation can be determined in situ by a number of optical techniques which have recently become available.

  5. Use of functional near-infrared spectroscopy to evaluate the effects of anodal transcranial direct current stimulation on brain connectivity in motor-related cortex

    NASA Astrophysics Data System (ADS)

    Yan, Jiaqing; Wei, Yun; Wang, Yinghua; Xu, Gang; Li, Zheng; Li, Xiaoli

    2015-04-01

    Transcranial direct current stimulation (tDCS) is a noninvasive, safe and convenient neuro-modulatory technique in neurological rehabilitation, treatment, and other aspects of brain disorders. However, evaluating the effects of tDCS is still difficult. We aimed to evaluate the effects of tDCS using hemodynamic changes using functional near-infrared spectroscopy (fNIRS). Five healthy participants were employed and anodal tDCS was applied to the left motor-related cortex, with cathodes positioned on the right dorsolateral supraorbital area. fNIRS data were collected from the right motor-related area at the same time. Functional connectivity (FC) between intracortical regions was calculated between fNIRS channels using a minimum variance distortion-less response magnitude squared coherence (MVDR-MSC) method. The levels of Oxy-HbO change and the FC between channels during the prestimulation, stimulation, and poststimulation stages were compared. Results showed no significant level difference, but the FC measured by MVDR-MSC significantly decreased during tDCS compared with pre-tDCS and post-tDCS, although the FC difference between pre-tDCS and post-tDCS was not significant. We conclude that coherence calculated from resting state fNIRS may be a useful tool for evaluating the effects of anodal tDCS and optimizing parameters for tDCS application.

  6. Anode power deposition in quasi-steady MPD arcs. [accelerator anode heat flux measurement

    NASA Technical Reports Server (NTRS)

    Saber, A. J.; Jahn, R. G.

    1973-01-01

    The power deposited in the anode of a quasi-steady MPD accelerator has been measured directly by thermocouples attached to the inside surface of a shell anode which provide a local measurement of anode heat flux. The results over a range of arc currents from 5.5 to 44 kiloamperes and argon mass flows from 1 g/sec to 48 g/sec show that the fraction of the total input power deposited in the anode decreases drastically from 50% at an arc power of 200 kW to 10% at 20 MW, and that anode power is not uniformly deposited in the anode. A theoretical model of the anode heat transfer, including effects of anode work function, electron thermal energy, and anode sheath, can be brought into reasonable agreement with the measurements, provided the effective range of the conduction electrons from within the discharge plasma to the anode surface is properly acknowledged.

  7. Anodic oxidation of benzoquinone using diamond anode.

    PubMed

    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. PMID:24710725

  8. Sulfur tolerant anode materials

    SciTech Connect

    Not Available

    1988-05-01

    The goal of this program is the development of a molten carbonate fuel cell (MCFC) anode which is more tolerant of sulfur contaminants in the fuel than the current state-of-the-art nickel-based anode structures. This program addresses two different but related aspects of the sulfur contamination problem. The primary aspect is concerned with the development of a sulfur tolerant electrocatalyst for the fuel oxidation reaction. A secondary issue is the development of a sulfur tolerant water-gas-shift reaction catalyst and an investigation of potential steam reforming catalysts which also have some sulfur tolerant capabilities. These two aspects are being addressed as two separate tasks.

  9. Sulfur tolerant anode materials

    SciTech Connect

    Not Available

    1988-02-01

    The goal of this program is the development of a molten carbonate fuel cell (MCFC) anode which is more tolerant of sulfur contaminants in the fuel than the current state-of-the-art nickel-based anode structures. This program addresses two different but related aspects of the sulfur contamination problem. The primary aspect is concerned with the development of a sulfur tolerant electrocatalyst for the fuel oxidation reaction. A secondary issue is the development of a sulfur tolerant water-gas-shift reaction catalyst and an investigation of potential steam reforming catalysts which also have some sulfur tolerant capabilities. These two aspects are being addressed as two separate tasks.

  10. Sulfur tolerant anode materials

    SciTech Connect

    Not Available

    1987-02-01

    The goal of this program is the development of a molten carbonate fuel cell (MCFC) anode which is more tolerant of sulfur contaminants in the fuel than the current state-of-the-art nickel-based anode structures. This program addresses two different but related aspects of the sulfur contamination problem. The primary aspect is concerned with the development of a sulfur tolerant electrocatalyst for the fuel oxidation reaction. A secondary issue is the development of a sulfur tolerant water-gas-shift reaction catalyst and an investigation of potential steam reforming catalysts which also have some sulfur tolerant capabilities. These two aspects are being addressed as two separate tasks.

  11. Functional improvement and neuroplastic effects of anodal transcranial direct current stimulation (tDCS) delivered 1 day vs. 1 week after cerebral ischemia in rats.

    PubMed

    Yoon, Kyung Jae; Oh, Byung-Mo; Kim, Dae-Yul

    2012-05-01

    Transcranial direct current stimulation (tDCS) is an emerging tool for improving recovery from stroke. However, there has been no trial to determine whether it has a therapeutic benefit in the early stage of cerebral ischemia, and there is no consensus on the optimal time window of stimulation. Here, we described the effects of anodal tDCS in early cerebral ischemia, assessing functional improvements and changes in neuronal plasticity, and identifying the optimal time window for delivering tDCS to maximize functional gains. Thirty rats were randomly assigned to three groups: sham (n=10); early tDCS (ET), receiving tDCS 1day after ischemia for 5 days (n=10), and late tDCS (LT), receiving tDCS 1 week after ischemia for 5 days (n=10). Both ET and LT groups showed improved Barnes maze performance and motor behavioral index scores. However, only the LT group exhibited improvement in beam balance test. Immunohistochemical stainings showed that the ET group reinforced notable MAP-2 expression and the LT group enhanced mainly the level of GAP-43 in both peri-lesional and contralesional cortex. These immunohistochemical results had significant correlation with behavioral and cognitive functions. However, brain MRI and (1)H MRS showed no significant differences among the three groups in ischemic volume and metabolic alteration. These results suggest that anodal tDCS has the potential to modulate neural plasticity around the ischemic penumbra and even in the contralesional area without aggravating infarction volume and metabolic alteration. The degree of functional improvement was slightly greater when tDCS was applied 1 week rather than 1 day after ischemic injury.

  12. Anode film formation and control

    DOEpatents

    Koski, O.; Marschman, S.C.

    1990-05-01

    A protective film is created about the anode within a cryolite-based electrolyte during electrolytic production of aluminum from alumina. The film functions to minimize corrosion of the anode by the cryolitic electrolyte and thereby extend the life of the anode. Various operating parameters of the electrolytic process are controlled to maintain the protective film about the anode in a protective state throughout the electrolytic reduction of alumina. Such parameters include electrolyte temperature, electrolyte ratio, current density, and Al[sub 2]O[sub 3] concentration. An apparatus is also disclosed to enable identification of the onset of anode corrosion due to disruption of the film to provide real time information regarding the state of the film. 3 figs.

  13. Anode film formation and control

    DOEpatents

    Koski, Oscar; Marschman, Steven C.

    1990-01-01

    A protective film is created about the anode within a cryolite-based electrolyte during electrolytic production of aluminum from alumina. The film function to minimize corrosion of the anode by the cryolitic electrolyte and thereby extend the life of the anode. Various operating parameters of the electrolytic process are controlled to maintain the protective film about the anode in a protective state throughout the electrolytic reduction of alumina. Such parameters include electrolyte temperature, electrolyte ratio, current density, and Al.sub.2 O.sub.3 concentration. An apparatus is also disclosed to enable identification of the onset of anode corrosion due to disruption of the film to provide real time information regarding the state of the film.

  14. Mussel-inspired Polydopamine-treated Copper Foil as a Current Collector for High-performance Silicon Anodes

    PubMed Central

    Cho, Inseong; Gong, Seokhyeon; Song, Danoh; Lee, Young-Gi; Ryou, Myung-Hyun; Lee, Yong Min

    2016-01-01

    A new Cu current collector was prepared by introducing a mussel-inspired polydopamine coating onto a Cu foil surface to improve the electrochemical performance of a Si electrode. The polydopamine coating covalently bonded the polymeric binder (with hydroxyl functional groups) via a condensation reaction. The coating improved the adhesion strength between the Si composite electrode and the Cu current collector (245.5 N m−1, 297.5 N m−1, and 353.2 N m−1 for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively). We demonstrate that the detachment between the Si composite electrode and the current collector plays an important role in determining the electrochemical performance of the Si electrode. The cycle life and rate capability of the Si electrode improved when the polydopamine surface-treated Cu current collector was used (963.9 mAh g−1, 1361.1 mAh g−1, and 1590.0 mAh g−1 for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively, at C/2 after 500 cycles). PMID:27530802

  15. Syntrophic interactions between H2-scavenging and anode-respiring bacteria can improve current density in microbial electrochemical cells

    EPA Science Inventory

    High current density of 10.0-14.6 A/m2 and COD removal up to 96% were obtained in a microbial electrochemical cell (MEC) fed with digestate at hydraulic retention time (HRT) of 4d and 8d. Volatile fatty acids became undetectable in MEC effluent (HRT 8d), except for trivial acetat...

  16. Mussel-inspired Polydopamine-treated Copper Foil as a Current Collector for High-performance Silicon Anodes

    NASA Astrophysics Data System (ADS)

    Cho, Inseong; Gong, Seokhyeon; Song, Danoh; Lee, Young-Gi; Ryou, Myung-Hyun; Lee, Yong Min

    2016-08-01

    A new Cu current collector was prepared by introducing a mussel-inspired polydopamine coating onto a Cu foil surface to improve the electrochemical performance of a Si electrode. The polydopamine coating covalently bonded the polymeric binder (with hydroxyl functional groups) via a condensation reaction. The coating improved the adhesion strength between the Si composite electrode and the Cu current collector (245.5 N m‑1, 297.5 N m‑1, and 353.2 N m‑1 for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively). We demonstrate that the detachment between the Si composite electrode and the current collector plays an important role in determining the electrochemical performance of the Si electrode. The cycle life and rate capability of the Si electrode improved when the polydopamine surface-treated Cu current collector was used (963.9 mAh g‑1, 1361.1 mAh g‑1, and 1590.0 mAh g‑1 for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively, at C/2 after 500 cycles).

  17. Mussel-inspired Polydopamine-treated Copper Foil as a Current Collector for High-performance Silicon Anodes.

    PubMed

    Cho, Inseong; Gong, Seokhyeon; Song, Danoh; Lee, Young-Gi; Ryou, Myung-Hyun; Lee, Yong Min

    2016-01-01

    A new Cu current collector was prepared by introducing a mussel-inspired polydopamine coating onto a Cu foil surface to improve the electrochemical performance of a Si electrode. The polydopamine coating covalently bonded the polymeric binder (with hydroxyl functional groups) via a condensation reaction. The coating improved the adhesion strength between the Si composite electrode and the Cu current collector (245.5 N m(-1), 297.5 N m(-1), and 353.2 N m(-1) for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively). We demonstrate that the detachment between the Si composite electrode and the current collector plays an important role in determining the electrochemical performance of the Si electrode. The cycle life and rate capability of the Si electrode improved when the polydopamine surface-treated Cu current collector was used (963.9 mAh g(-1), 1361.1 mAh g(-1), and 1590.0 mAh g(-1) for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively, at C/2 after 500 cycles).

  18. Mussel-inspired Polydopamine-treated Copper Foil as a Current Collector for High-performance Silicon Anodes.

    PubMed

    Cho, Inseong; Gong, Seokhyeon; Song, Danoh; Lee, Young-Gi; Ryou, Myung-Hyun; Lee, Yong Min

    2016-01-01

    A new Cu current collector was prepared by introducing a mussel-inspired polydopamine coating onto a Cu foil surface to improve the electrochemical performance of a Si electrode. The polydopamine coating covalently bonded the polymeric binder (with hydroxyl functional groups) via a condensation reaction. The coating improved the adhesion strength between the Si composite electrode and the Cu current collector (245.5 N m(-1), 297.5 N m(-1), and 353.2 N m(-1) for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively). We demonstrate that the detachment between the Si composite electrode and the current collector plays an important role in determining the electrochemical performance of the Si electrode. The cycle life and rate capability of the Si electrode improved when the polydopamine surface-treated Cu current collector was used (963.9 mAh g(-1), 1361.1 mAh g(-1), and 1590.0 mAh g(-1) for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively, at C/2 after 500 cycles). PMID:27530802

  19. Anode power deposition in magnetoplasmadynamic thrusters

    NASA Technical Reports Server (NTRS)

    Gallimore, A. D.; Kelly, A. J.; Jahn, R. G.

    1993-01-01

    Results of anode heat-flux and anode fail measurements from a multimegawatt self-field quasi-steady magnetoplasmadynamic (MPD) thruster are presented. Measurements were obtained with argon and helium propellants for a variety of currents and mass flow rates. Anode heat flux was directly measured with thermocouples attached to the inner surface of a hollowed section. Anode falls were determined both from floating probes and through heat flux measurements. Comparison of data acquired through either method shows excellent agreement. Anode falls varied between 4-50 V with anode power fractions reaching 70 percent with helium at 150 kW, and 50 percent with argon at 1.9 MW. The anode fall was found to correlate well with electron Hall parameters calculated from triple Langmuir and magnetic probe data collected near the anode. Two possible explanations for this result are proposed: (1) the establishment of large electric fields at the anode to maintain current conduction across the strong magnetic fields; and (2) anomalous resistivity resulting from the onset of microturbulence in the plasma. To investigate the latter hypothesis, electric field, magnetic field, and current density profiles measured in the vicinity of the anode were incorporated into Ohm's law to estimate the electrical conductivity. Results of this analysis show a substantial deviation of the measured conductivity from that calculated with classical formulas. These results imply that anomalous effects are present in the plasma near the anode.

  20. Effects of atmospheric air plasma treatment of graphite and carbon felt electrodes on the anodic current from Shewanella attached cells.

    PubMed

    Epifanio, Monica; Inguva, Saikumar; Kitching, Michael; Mosnier, Jean-Paul; Marsili, Enrico

    2015-12-01

    The attachment of electrochemically active microorganisms (EAM) on an electrode is determined by both the chemistry and topography of the electrode surface. Pre-treatment of the electrode surface by atmospheric air plasma introduces hydrophilic functional groups, thereby increasing cell attachment and electroactivity in short-term experiments. In this study, we use graphite and carbon felt electrodes to grow the model EAM Shewanella loihica PV-4 at oxidative potential (0.2 V vs. Ag/AgCl). Cell attachment and electroactivity are measured through electrodynamic methods. Atmospheric air plasma pre-treatment increases cell attachment and current output at graphite electrodes by 25%, while it improves the electroactivity of the carbon felt electrodes by 450%. Air plasma pre-treatment decreased the coulombic efficiency on both carbon felt and graphite electrodes by 60% and 80%, respectively. Microbially produced flavins adsorb preferentially at the graphite electrode, and air plasma pre-treatment results in lower flavin adsorption at both graphite and carbon felt electrodes. Results show that air plasma pre-treatment is a feasible option to increase current output in bioelectrochemical systems.

  1. Self-ordered nanopore arrays through hard anodization assisted by anode temperature ramp

    NASA Astrophysics Data System (ADS)

    Mohammadniaei, M.; Maleki, K.; Kashi, M. Almasi; Ramezani, A.; Mayamei, Y.

    2016-10-01

    In the present work, hard anodization assisted by anode temperature ramp was employed to fabricate self-ordered nanoporous alumina in the wide range of interpore distances (259-405 nm) in pure oxalic acid and mixture of oxalic and phosphoric acid solutions. Anode temperature ramp technique was employed to adjust the anodization current density to optimize the self-ordering of the nanopore arrays in the interpore range in which no ordered self-assembled hard anodized anodic aluminum oxide has reported. It is found that the certain ratios of oxalic and phosphoric acid solutions in this anodization technique increased self-ordering of the nanopores especially for anodization voltages over the 170 V by increasing alumina's viscous flow which could lead to decrease the overall current density of anodization, yet leveled up by anode temperature ramp. However, below 150 V anodization voltage, the ratio of interpore distance to the anodization voltage of the both anodization techniques was the same (~2 nm/V), while above this voltage, it increased to about 2.2 nm/V.

  2. The anodic passivation of lithium

    SciTech Connect

    James, S.D.

    1983-10-01

    The anodic passivation of Li has been characterized at room temperature in a variety of electrolytes (propylene carbonate, thionyl chloride, sulfur dioxide), as a function of convection and current density and in the presence of water and other impurities. In thionyl chloride the effect of salt concentration (0.5-4.5M, LiA1C1/sub 4/) and acidity (0.5-3M, A1C1/sub 3/) has been studied. The evidence accumulated suggests that anodic passivation is caused by anodic enrichment and eventual precipitation of electrolyte salt in superficial anolyte.

  3. Electrochemical impedance analysis of electrodeposited Si-O-C composite thick film on Cu microcones-arrayed current collector for lithium ion battery anode

    NASA Astrophysics Data System (ADS)

    Hang, Tao; Mukoyama, Daikichi; Nara, Hiroki; Yokoshima, Tokihiko; Momma, Toshiyuki; Li, Ming; Osaka, Tetsuya

    2014-06-01

    The impedance behaviors of Si-O-C composite film electrodeposited on Cu microcones-arrayed current collector have been investigated to understand the electrochemical process kinetics that influences the cycling performance when used as a highly-durable anode in a lithium battery. The impedance was measured by using impedance spectroscopy in equilibrium conditions at various depths of discharge and during several hundred charge-discharge cycles. The measured impedance was interpreted with an equivalent circuit composed of solid electrolyte interphase (SEI) film, charge transfer and solid state diffusion. The impedance analysis shows that the change of charge transfer resistance is the main contribution to the total resistance change during discharge, but an abrupt augmentation of diffusive resistance at high depth of discharge is also observed which cannot be explained very well by the presented model. The impedance evolution of this electrode during charge-discharge cycles suggests that the slow growth of the SEI film as well as the increase of the electrode density are responsible for the capacity fading after long term cycling.

  4. The effect of anodal transcranial direct current stimulation on motor sequence learning in healthy individuals: A systematic review and meta-analysis.

    PubMed

    Hashemirad, Fahimeh; Zoghi, Maryam; Fitzgerald, Paul B; Jaberzadeh, Shapour

    2016-02-01

    A large number of studies have indicated the effect of anodal transcranial direct current stimulation (a-tDCS) on the primary motor cortex (M1) during motor skill training. The effects of a-tDCS on different stages of motor sequence learning are not yet completely understood. The purpose of this meta-analysis was to determine the effects of single and multiple sessions of a-tDCS on two different tasks: the sequential finger tapping task/serial reaction time task (SEQTAP/SRTT) and the sequential visual isometric pinch task (SVIPT). We searched electronic databases for M1 a-tDCS studies. Thirteen studies met the inclusion criteria. The results indicate that application of multiple sessions of a-tDCS, compared to single session a-tDCS induced a significant improvement in skill in both SEQTAP/SRTT and SVIPT. Retention after a single day and multiple days of a-tDCS was statistically significant for the SEQTAP/SRTT task but not for SVIPT. Therefore, our findings suggest that application of M1 a-tDCS across the three or five consecutive days can be helpful to improve motor sequence learning.

  5. Anodes for cathodic protection of reinforced concrete

    SciTech Connect

    S.J. Bullard; B.S. Covino, Jr.; S.D. Cramer; G.R. Holcomb; J.H. Russell

    2000-03-01

    Consumable anodes were evaluated in the laboratory for use in cathodic protection systems for steel reinforced concrete bridges in coastal environments and in areas where de-icing salts are employed. The anode materials include Zn-hydrogel and thermal-sprayed Zn, Zn-15Al, and Al-12Zn-0.2In. These anodes were evaluated for service in both galvanic (GCP) and impressed current (ICCP) cathodic protection systems. ICCP anodes were electrochemically aged at a factor of 15 times greater than used by the Oregon Department of Transportation in typical coastal ICCP systems (2.2 mA/m{sup 2} based on anode area). Increasing moisture at the anode-concrete interface reduced the operating voltage of all the anodes. The pH at the anode-concrete interface fell to 7 to 8.5 with electrochemical age. Bond strength between the anodes and concrete decreased with electrochemical aging. Interfacial chemistry was the critical link between long-term anode performance and electrochemical age. Zn-hydrogel and the rmal-sprayed Zn and Al-12Zn-0.2In GCP anodes appear to supply adequate protection current to rebar in the Cape Perpetua Viaduct.

  6. Anode power in quasisteady magnetoplasmadynamic accelerators

    NASA Technical Reports Server (NTRS)

    Saber, A. J.; Jahn, R. G.

    1978-01-01

    Anode heat flux in a quasi-steady MPD accelerator has been measured directly and locally by thermocouples attached to the inside surface of a shell anode. These measurements show that over a range of arc current from 5.5 to 44 kA, and argon mass flow from 1 to 48 g/s, the fraction of the total arc power deposited in the anode decreases from 50% at 200 kW to 10% at 20 MW. A theoretical model of the anode heat transfer asserts that energy exchange between electrons and heavy particles in the plasma near the anode occurs over distances greater than the anode sheath thickness, and hence the usual anode fall voltage, electron temperature, and work function contributions to the anode heat flux are supplemented by a contribution from the interelectrode potential. Calculations of anode heat flux using the measured current density, plasma potential, and electron temperature in the plasma adjacent to the anode agree with the direct measurements and indicate that the decrease in anode power fraction at higher arc powers can be attributed to the smaller mean free paths in the interelectrode plasma.

  7. ANODIC TREATMENT OF URANIUM

    DOEpatents

    Kolodney, M.

    1959-02-01

    A method is presented for effecting eloctrolytic dissolution of a metallic uranium article at a uniform rate. The uranium is made the anode in an aqueous phosphoric acid solution containing nitrate ions furnished by either ammonium nitrate, lithium nitrate, sodium nitrate, or potassium nitrate. A stainless steel cathode is employed and electrolysls carried out at a current density of about 0.1 to 1 ampere per square inch.

  8. Anode power deposition in applied-field MPD thrusters

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.; Soulas, George C.

    1992-01-01

    Anode power deposition is the principal performance limiter of magnetoplasmadynamic (MPD) thrusters. Current thrusters lose between 50 and 70 percent of the input power to the anode. In this work, anode power deposition was studied for three cylindrical applied magnetic field thrusters for a range of argon propellant flow rates, discharge currents, and applied-field strengths. Between 60 and 95 percent of the anode power depositions resulted from electron current conduction into the anode, with cathode radiation depositing between 5 and 35 percent of the anode power, and convective heat transfer from the hot plasma accounting for less than 5 percent. While the fractional anode power loss decreased with increasing applied-field strength and anode size, the magnitude of the anode power increased. The rise in anode power resulted from a linear rise in the anode fall voltage with applied-field strength and anode radius. The anode fall voltage also rose with decreasing propellant flow rate. The trends indicate that the anode fall region is magnetized, and suggest techniques for reducing the anode power loss in MPD thrusters.

  9. Anode power deposition in applied-field MPD thrusters

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.; Soulas, George C.

    1992-01-01

    Anode power deposition is the principle performance limiter of magnetoplasmadynamic (MPD) thrusters. Current thrusters lose between 50 and 70 percent of the input power to the anode. In this work, anode power deposition was studied for three cylindrical applied magnetic field thrusters for a range of argon propellant flow rates, discharge currents, and applied-field strengths. Between 60 and 95 percent of the anode power deposition resulted from electron current conduction into the anode, with cathode radiation depositing between 5 and 35 percent of the anode power, and convective heat transfer from the hot plasma accounting for less than 5 percent. While the fractional anode power loss decreased with increasing applied-field strength and anode size, the magnitude of the anode power increased. The rise in anode power resulted from a linear rise in the anode fall voltage with applied-field strength and anode radius. The anode fall voltage also rose with decreasing propellant flow rate. The trends indicate that the anode fall region is magnetized, and suggest techniques for reducing the anode power loss in MPD thrusters.

  10. A review of anode phenomena in vacuum arces

    NASA Astrophysics Data System (ADS)

    Miller, H. Craig

    1988-09-01

    This report discusses arc modes at the anode, experimental results pertinent to anode phenomena, and theoretical explanations of anode phenomena. The dominant mechanism controlling the formation of an anode spot appears to depend upon the electrode geometry, the electrode material, and the current waveforms of the particular vacuum arc being considered. In specific experimental conditions, either magnetic constriction in the gap plasma or gross anode melting or local anode evaporation can trigger the transition. However, the most probable explanation of anode spot formation is a combination theory, which considers magnetic constriction in the plasma together with the fluxes of material from the anode and cathode as well as the thermal, electrical, and geometric effects of the anode in analyzing the behavior of the anode and the nearby plasma.

  11. A review of anode phenomena in vacuum arces

    SciTech Connect

    Miller, H.C.

    1988-09-01

    This report discusses arc modes at the anode, experimental results pertinent to anode phenomena, and theoretical explanations of anode phenomena. The dominant mechanism controlling the formation of an anode spot appears to depend upon the electrode geometry, the electrode material, and the current waveforms of the particular vacuum arc being considered. In specific experimental conditions, either magnetic constriction in the gap plasma or gross anode melting or local anode evaporation can trigger the transition. However, the most probable explanation of anode spot formation is a combination theory, which considers magnetic constriction in the plasma together with the fluxes of material from the anode and cathode as well as the thermal, electrical, and geometric effects of the anode in analyzing the behavior of the anode and the nearby plasma. 88 refs., 6 figs., 8 tabs.

  12. Employing a Flexible and Low-Cost Polypyrrole Nanotube Membrane as an Anode to Enhance Current Generation in Microbial Fuel Cells.

    PubMed

    Zhao, Cui-e; Wu, Jiansheng; Kjelleberg, Staffan; Loo, Joachim Say Chey; Zhang, Qichun

    2015-07-01

    The flexible and low-cost polypyrrole nanotube membrane is demonstrated as a promising anode in microbial fuel cells, which significantly enhances the extracellular electron transfer between Shewanella oneidensis MR-1 and the electrode, owing to the large active surface area and high electrical conductivity.

  13. How Does Anodal Transcranial Direct Current Stimulation of the Pain Neuromatrix Affect Brain Excitability and Pain Perception? A Randomised, Double-Blind, Sham-Control Study

    PubMed Central

    Vaseghi, Bita; Zoghi, Maryam; Jaberzadeh, Shapour

    2015-01-01

    Background Integration of information between multiple cortical regions of the pain neuromatrix is thought to underpin pain modulation. Although altered processing in the primary motor (M1) and sensory (S1) cortices is implicated in separate studies, the simultaneous changes in and the relationship between these regions are unknown yet. The primary aim was to assess the effects of anodal transcranial direct current stimulation (a-tDCS) over superficial regions of the pain neuromatrix on M1 and S1 excitability. The secondary aim was to investigate how M1 and S1 excitability changes affect sensory (STh) and pain thresholds (PTh). Methods Twelve healthy participants received 20 min a-tDCS under five different conditions including a-tDCS of M1, a-tDCS of S1, a-tDCS of DLPFC, sham a-tDCS, and no-tDCS. Excitability of dominant M1 and S1 were measured before, immediately, and 30 minutes after intervention respectively. Moreover, STh and PTh to peripheral electrical and mechanical stimulation were evaluated. All outcome measures were assessed at three time-points of measurement by a blind rater. Results A-tDCS of M1 and dorsolateral prefrontal cortex (DLPFC) significantly increased brain excitability in M1 (p < 0.05) for at least 30 min. Following application of a-tDCS over the S1, the amplitude of the N20-P25 component of SEPs increased immediately after the stimulation (p < 0.05), whilst M1 stimulation decreased it. Compared to baseline values, significant STh and PTh increase was observed after a-tDCS of all three stimulated areas. Except in M1 stimulation, there was significant PTh difference between a-tDCS and sham tDCS. Conclusion a-tDCS of M1 is the best spots to enhance brain excitability than a-tDCS of S1 and DLPFC. Surprisingly, a-tDCS of M1 and S1 has diverse effects on S1 and M1 excitability. A-tDCS of M1, S1, and DLPFC increased STh and PTh levels. Given the placebo effects of a-tDCS of M1 in pain perception, our results should be interpreted with caution

  14. Electrolytic Cell For Production Of Aluminum Employing Planar Anodes.

    DOEpatents

    Barnett, Robert J.; Mezner, Michael B.; Bradford, Donald R

    2004-10-05

    A method of producing aluminum in an electrolytic cell containing alumina dissolved in an electrolyte, the method comprising providing a molten salt electrolyte having alumina dissolved therein in an electrolytic cell. A plurality of anodes and cathodes having planar surfaces are disposed in a generally vertical orientation in the electrolyte, the anodes and cathodes arranged in alternating or interleaving relationship to provide anode planar surfaces disposed opposite cathode planar surfaces, the anode comprised of carbon. Electric current is passed through anodes and through the electrolyte to the cathodes depositing aluminum at the cathodes and forming carbon containing gas at the anodes.

  15. Mechanisms of anode power deposition in a low pressure free burning arc

    NASA Technical Reports Server (NTRS)

    Soulas, George C.; Myers, Roger M.

    1994-01-01

    Anode power deposition is a dominant power loss mechanism for arc jets and MPD thrusters. In this study, a free burning arc experiment was operated at pressures and current densities similar to those in arc jets and MPD thrusters in an attempt to identify the physics controlling this loss mechanism. Use of a free burning arc allowed for the isolation of independent variables controlling anode power deposition and provided a convenient and flexible way to cover a broad range of currents, anode surface pressures, and applied magnetic field strengths and orientations using an argon gas. Test results showed that anode power deposition decreased with increasing anode surface pressure up to 6.7 Pa (0.05 torr) and then became insensitive to pressure. Anode power increased with increasing arc current while the electron number density near the anode surface increased linearity. Anode power also increased with increasing applied magnetic field strength due to an increasing anode fall voltage. Applied magnetic field orientation had an effect only at high currents and low anode surface pressures, where anode power decreased when applied field lines intercepted the anode surface. The results demonstrated that anode power deposition was dominated by the current carrying electrons and that the anode fall voltage was the largest contributor. Furthermore, the results showed that anode power deposition can be reduced by operating at increased anode pressures, reduced arc currents, and applied magnetic field strengths and with magnetic field lines intercepting the anode.

  16. FLUORINE CELL ANODE ASSEMBLY

    DOEpatents

    Cable, R.E.; Goode, W.B. Jr.; Henderson, W.K.; Montillon, G.H.

    1962-06-26

    An improved anode assembly is deslgned for use in electrolytlc cells ln the productlon of hydrogen and fluorlne from a moIten electrolyte. The anode assembly comprises a copper post, a copper hanger supported by the post, a plurality of carbon anode members, and bolt means for clamplng half of the anode members to one slde of the hanger and for clamplng the other half of the anode members to the other slde of the hanger. The heads of the clamplng bolts are recessed withln the anode members and carbon plugs are inserted ln the recesses above the bolt heads to protect the boIts agalnst corroslon. A copper washer is provided under the head of each clamplng boIt such that the anode members can be tightly clamped to the hanger with a resultant low anode jolnt resistance. (AEC)

  17. High current-density anodic electro-dissolution in flow-injection systems for the determination of aluminium, copper and zinc in non-ferroalloys by flame atomic absorption spectrometry.

    PubMed

    Giacomozzi, C A; de Queiróz, R R; Souza, I G; Neto, J A

    1999-01-01

    An automatic procedure with a high current-density anodic electrodissolution unit (HDAE) is proposed for the determination of aluminium, copper and zinc in non-ferroalloys by flame atomic absorption spectrometry, based on the direct solid analysis. It consists of solenoid valve-based commutation in a flow-injection system for on-line sample electro-dissolution and calibration with one multi-element standard, an electrolytic cell equipped with two electrodes (a silver needle acts as cathode, and sample as anode), and an intelligent unit. The latter is assembled in a PC-compatible microcomputer for instrument control, and for data acquisition and processing. General management of the process is achieved by use of software written in Pascal. Electrolyte compositions, flow rates, commutation times, applied current and electrolysis time were investigated. A 0.5 mol l(-1) HN03 solution was elected as electrolyte and 300 A/cm(2) as the continuous current pulse.The performance of the proposed system was evaluated by analysing aluminium in Al-alloy samples, and copper/zinc in brass and bronze samples, respectively. The system handles about 50 samples per hour. Results are precise (R.S.D. < 2%) and in agreement with those obtained by ICP-AES and spectrophotometry at a 95% confidence level.

  18. Pilot demonstration of cerium oxide coated anodes

    SciTech Connect

    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.

  19. Experimental studies of anode sheath phenomena in a hall thruster.

    SciTech Connect

    Dorf, L. A.; Fisch, N. J.; Raitses, Yevgeny F.

    2004-01-01

    Both electron-repelling (negative anode fall) and electron-attracting (positive anode fall) anode sheaths in a Hall thruster were identified experimentally by performing accurate, non-disturbing near-anode measurements with biased and emissive probes. 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. Probe measurements in a Hall thruster with three different magnetic field configurations show that an anode fall at the clean anode is a function of the radial magnetic field profile inside the channel. A positive anode fall formation mechanism suggested in this work is that: (1) when the anode front surface is coated with dielectric, a discharge current closes to the anode at the surfaces that remain conductive, (2) a total thermal electron current toward the conductive area is significantly smaller than the discharge current, therefore an additional electron flux needs to be attracted toward the conductive surfaces by the electronattracting sheath that appears at these surfaces.

  20. Alternate anode materials for cathodic protection of steel reinforced concrete

    SciTech Connect

    Russell, James H.; Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Holcomb, Gordon R.; Cryer, Curtis B.

    2001-01-01

    Consumable and non-consumable anodes were evaluated in the laboratory for use in cathodic protection (CP) systems for steel reinforced concrete bridges in coastal environments and in areas where deicing salts are employed. The anode materials included Zn-hydrogel and thermal-sprayed Zn, Zn-15Al, Al-12Zn-0.2In, and cobalt-sprayed Ti. These anodes were evaluated for service in both galvanic (GCP) and impressed current (ICCP) cathodic protection systems. Impressed current CP anodes were electrochemically aged at a current density 15 times as great as that used by the Oregon Department of Transportation in typical coastal ICCP systems (2.2 mA/m2 based on anode area). Increasing moisture at the anode-concrete interface reduced the operating voltage of all the anodes. Bond strength between the anodes and concrete decreased with electrochemical aging. The Zn-15Al and Al-12Zn-0.2In anodes provided adequate protection in GCP but their life was too short in the accelerated ICCP tests. Zinc had an adequate life in ICCP tests but was inadequate as a galvanic anode. Zinc-hydrogel performed well in both tests when the hydrogel was kept moist. Titanium was an excellent anode for ICCP, but is not suitable for GCP.

  1. Alternative consumable anodes for cathodic protection of reinforced concrete bridges

    SciTech Connect

    Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Holcomb, Gordon R.; Russell, James H.; Cryer, C.B.; Laylor, H.M.

    1999-01-01

    Alternative consumable anodes were evaluated in the laboratory for use in cathodic protection systems for steel reinforced concrete bridges in coastal environments and in areas where deicing salts are employed. The anode materials included zinc hydrogel foil and thermal-sprayed Zn, Zn-15Al, and Al-12Zn-0.2In alloys. They were evaluated for service in both impressed current (ICCP) and galvanic (GCP) cathodic protection systems. ICCP anodes were electrochemically aged at current densities of five to fifteen times that used by the Oregon Department of Transportation (Oregon DOT) in typical coastal CP systems (2.2 mA/m2 based on anode area). GCP anodes were electrochemically aged at a rate defined by the steel-anode couple. Both types of anodes were exposed to 80°F, a relative humidity of 85 pct, and were periodically wetted with deionized water. The Zn anode gave the best performance in ICCP systems. The four anodes all produced sufficient current density suitable for use in GCP systems. The anodes materials, ranked in increasing order of GCP current output, were: thermal-sprayed Al-12Zn-0.2In, Zn hydrogel, thermal-sprayed Zn-15Al, and thermal-sprayed Zn.

  2. Carbonate fuel cell anodes

    DOEpatents

    Donado, R.A.; Hrdina, K.E.; Remick, R.J.

    1993-04-27

    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 is described for production of the lithium ferrite containing anode by slipcasting.

  3. Carbonate fuel cell anodes

    DOEpatents

    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.

  4. Ohmic resistance affects microbial community and electrochemical kinetics in a multi-anode microbial electrochemical cell

    NASA Astrophysics Data System (ADS)

    Dhar, Bipro Ranjan; Ryu, Hodon; Santo Domingo, Jorge W.; Lee, Hyung-Sool

    2016-11-01

    Multi-anode microbial electrochemical cells (MxCs) are considered as one of the most promising configurations for scale-up of MxCs, but understanding of anode kinetics in multiple anodes is limited in the MxCs. In this study we assessed microbial community and electrochemical kinetic parameters for biofilms on individual anodes in a multi-anode MxC to better comprehend anode fundamentals. Microbial community analysis targeting 16S rRNA Illumina sequencing showed that Geobacter genus was abundant (87%) only on the biofilm anode closest to a reference electrode (low ohmic energy loss) in which current density was the highest among three anodes. In comparison, Geobacter populations were less than 1% for biofilms on other two anodes distant from the reference electrode (high ohmic energy loss), generating small current density. Half-saturation anode potential (EKA) was the lowest at -0.251 to -0.242 V (vs. standard hydrogen electrode) for the closest biofilm anode to the reference electrode, while EKA was as high as -0.134 V for the farthest anode. Our study proves that electric potential of individual anodes changed by ohmic energy loss shifts biofilm communities on individual anodes and consequently influences electron transfer kinetics on each anode in the multi-anode MxC.

  5. Aluminum anodization in a basic ambient temperature molten salt

    SciTech Connect

    Carlin, R.T.; Osteryoung, R.A. . Dept. of Chemistry)

    1989-05-01

    The authors describe aluminum anodization studied in the basic AlCl/sub 3/:1-methyl-3-ethylimidazolium chloride (ImCl) ambient temperature molten salt (AlCl/sub 3/:ImCl molar ratio ..e..1.0). The anodization process was studied as a function of chloride anion concentration. Two different anodization processes are observed with onset potentials of approximately -1.1 and 0V. The more cathodic anodization involves formation of the tetrachloroaluminate anion and exhibits a limiting current controlled by diffusion of chloride to the electrode surface. The number of chlorides required for each Al anodized was determined to be 4.6 +- 0.4. The more anodic anodization shows no diffusion control. A value for the diffusion coefficient of chloride was obtained which is lower than previously reported; the difference involves using an n value of 1, rather than 2/3. No reduction of the tetrachloroaluminate anion was observed even at elevated temperatures.

  6. Anodized Ti3SiC2 As an Anode Material for Li-ion Microbatteries.

    PubMed

    Tesfaye, Alexander T; Mashtalir, Olha; Naguib, Michael; Barsoum, Michel W; Gogotsi, Yury; Djenizian, Thierry

    2016-07-01

    We report on the synthesis of an anode material for Li-ion batteries by anodization of a common MAX phase, Ti3SiC2, in an aqueous electrolyte containing hydrofluoric acid (HF). The anodization led to the formation of a porous film containing anatase, a small quantity of free carbon, and silica. By varying the anodization parameters, various oxide morphologies were produced. The highest areal capacity was achieved by anodization at 60 V in an aqueous electrolyte containing 0.1 v/v HF for 3 h at room temperature. After 140 cycles performed at multiple applied current densities, an areal capacity of 380 μAh·cm(-2) (200 μA·cm(-2)) has been obtained, making this new material, free of additives and binders, a promising candidate as a negative electrode for Li-ion microbatteries. PMID:27282275

  7. Anodizing Aluminum with Frills.

    ERIC Educational Resources Information Center

    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 also…

  8. Anodized aluminum on LDEF

    NASA Technical Reports Server (NTRS)

    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.

  9. Chemical enhancement of metallized zinc anode performance

    SciTech Connect

    Bennett, J.

    1998-12-31

    Galvanic current delivered to reinforced concrete by a metallized zinc anode was studied relative to the humidity of its environment and periodic direct wetting. Current decreased quickly at low humidity to values unlikely to meet accepted cathodic protection criteria, but could be easily restored by direct wetting of the anode. Thirteen chemicals were screened for their ability to enhance galvanic current. Such chemicals, when applied to the exterior surface of the anode, are easily transported by capillary action to the anode-concrete interface where they serve to maintain the interface conductive and the zinc electrochemically active. The most effective chemicals were potassium and lithium bromide, acetate, chloride and nitrate, which increased galvanic current by a factor of 2--15, depending on relative humidity and chloride contamination of the concrete. This new technique is expected to greatly expand the number of concrete structures which can be protected by simple galvanic cathodic protection, The use of lithium-based chemicals together with metallized zinc anode is also proposed for mitigation of existing problems due to ASR. In this case, lithium which prevents or inhibits expansion due to ASR can be readily injected into the concrete. A new process, electrochemical maintenance of concrete (EMC), is also proposed to benefit reinforced concrete structures suffering from chloride-induced corrosion.

  10. Modeling a short dc discharge with thermionic cathode and auxiliary anode

    SciTech Connect

    Bogdanov, E.; Demidov, V. I.; Kaganovich, I. D.; Koepke, M. E.; Kudryavtsev, A. A.

    2013-10-15

    A short dc discharge with a thermionic cathode can be used as a current and voltage stabilizer, but is subject to current oscillation. If instead of one anode two anodes are used, the current oscillations can be reduced. We have developed a kinetic model of such a discharge with two anodes, where the primary anode has a small opening for passing a fraction of the discharge current to an auxiliary anode. The model demonstrates that the current-voltage relationship of the discharge with two anodes is characterized everywhere by positive slope, i.e., positive differential resistance. Therefore, the discharge with two anodes is expected to be stable to the spontaneous oscillation in current that is induced by negative differential resistance. As a result, such a discharge can be used in an engineering application that requires stable plasma, such as a current and voltage stabilizer.

  11. Electrically conductive anodized aluminum coatings

    NASA Technical Reports Server (NTRS)

    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.

  12. Fibrous zinc anodes for high power batteries

    NASA Astrophysics Data System (ADS)

    Zhang, X. Gregory

    This paper introduces newly developed solid zinc anodes using fibrous material for high power applications in alkaline and large size zinc-air battery systems. The improved performance of the anodes in these two battery systems is demonstrated. The possibilities for control of electrode porosity and for anode/battery design using fibrous materials are discussed in light of experimental data. Because of its mechanical integrity and connectivity, the fibrous solid anode has good electrical conductivity, mechanical stability, and design flexibility for controlling mass distribution, porosity and effective surface area. Experimental data indicated that alkaline cells made of such anodes can have a larger capacity at high discharging currents than commercially available cells. It showed even greater improvement over commercial cells with a non-conventional cell design. Large capacity anodes for a zinc-air battery have also been made and have shown excellent material utilization at various discharge rates. The zinc-air battery was used to power an electric bicycle and demonstrated good results.

  13. Pack aluminization of nickel anode for molten carbonate fuel cells

    NASA Astrophysics Data System (ADS)

    Chun, H. S.; Park, G. P.; Lim, J. H.; Kim, K.; Lee, J. K.; Moon, K. H.; Youn, J. H.

    1994-04-01

    The aluminum pack cementation (pack aluminization) process on a porous nickel anode for molten carbonate fuel cells has been studied to improve anode creep resistance. The porous nickel substrates used in this study were fabricated by doctor blade equipment followed by sintering (850 C). Packs surrounding the Ni anode were made by mixing Al2O3 powder, Al powder, and NaCl as activator. The pack aluminization was performed at 700 to 850 C for 0.5-5.0 h. After pack aluminization, the principal Ni-Al intermetallic compounds detected were Ni3Al at 700 C, NiAl at 750 C and Ni3Al2 at 800 C. The aluminum content in the aluminized Ni anode was proportional to the square root of pack aluminizing time. With increasing the Al content in the anode, the creep of the anode decreased. It was nearly constant (2.0%) when the Al content was above 5.0%. Although the exchange current density (24 mA/sq cm) for the aluminized (2.5 wt.%) Ni anode was somewhat lower than that of the pure Ni anode (40 mA/sq cm), the performance of a single cell using an aluminized Ni anode was similar to that of the one with pure Ni anode.

  14. Metal assisted anodic etching of silicon.

    PubMed

    Lai, Chang Quan; Zheng, Wen; Choi, W K; Thompson, Carl V

    2015-07-01

    Metal assisted anodic etching (MAAE) of Si in HF, without H2O2, is demonstrated. Si wafers were coated with Au films, and the Au films were patterned with an array of holes. A Pt mesh was used as the cathode while the anodic contact was made through either the patterned Au film or the back side of the Si wafer. Experiments were carried out on P-type, N-type, P(+)-type and N(+)-type Si wafers and a wide range of nanostructure morphologies were observed, including solid Si nanowires, porous Si nanowires, a porous Si layer without Si nanowires, and porous Si nanowires on a thick porous Si layer. Formation of wires was the result of selective etching at the Au-Si interface. It was found that when the anodic contact was made through P-type or P(+)-type Si, regular anodic etching due to electronic hole injection leads to formation of porous silicon simultaneously with metal assisted anodic etching. When the anodic contact was made through N-type or N(+)-type Si, generation of electronic holes through processes such as impact ionization and tunnelling-assisted surface generation were required for etching. In addition, it was found that metal assisted anodic etching of Si with the anodic contact made through the patterned Au film essentially reproduces the phenomenology of metal assisted chemical etching (MACE), in which holes are generated through metal assisted reduction of H2O2 rather than current flow. These results clarify the linked roles of electrical and chemical processes that occur during electrochemical etching of Si. PMID:26059556

  15. Anode insulator for electrolytic cell

    SciTech Connect

    Robinson, D.J.

    1986-10-28

    An improved anode insulator is described for use in an electrowinning cell, including spaced anodes each supported by an anode header bar, each having the improved anode insulators disposed thereon for preventing contact with spaced cathodes that are respectively disposed between adjacent anodes, each improved anode insulator comprising: (a) first and second elongated insulating means disposed along intermediate portions of opposite faces of one of the anodes for preventing any contact between the faces of that anode and adjacent cathodes; (b) upper connecting means disposed around the top and side portions of the anode header bar supporting that anode and conforming to the shape of the header bar; and (c) lower connecting means for joining the lower end portions of the first and second elongated insulating means.

  16. Anodes - Technology review

    NASA Astrophysics Data System (ADS)

    Wallis, L.; Wills, R. G. A.

    2014-06-01

    Many electrochemical energy storage technologies utilize anodes that are specific to the chemistry of the device. Anodes must be designed for devices including primary and secondary batteries, fuel cells and capacitors. These applications include a diverse range of operational conditions, including aqueous, solid or organic media. This paper will provide a brief overview of anode technologies for medium (e.g. electric and hybrid electric vehicles) and large (e.g. integration of renewable energy generation to electrical networks) battery applications. Established and developing storage technologies will be discussed to provide an insight into how anodes (materials, manufacturing processes and modes of operation) differ between specific applications and devices. Lead-acid batteries are used as a case study to provide a practical example and guide discussion onto the question of future challenges and opportunities.

  17. Mesh-on-lead anodes for copper electrowinning

    NASA Astrophysics Data System (ADS)

    Moats, Michael; Hardee, Kenneth; Brown, Carl

    2003-07-01

    ELTECH System Corporation has developed and patented a Mesh-on-Lead™ (MOL™) (Mesh-on-Lead and MOL are trademarks of ELTECH Systems Corporation) anode for primary copper electrowinning operations. Over the past five years, ELTECH has demonstrated the MOL concept with full-scale anodes at several premier commercial tankhouses. During these demonstrations MOL anodes exhibited numerous performance advantages relative to standard Pb-Ca-Sn anodes, including reduced power consumption due to lower oxygen evolution over-potential, improved cathode quality, minimized lead sludge generation, eliminated cobalt addition as a result of stabilized lead substrate, and improved current efficiency due to reduced short circuiting.

  18. Finding Platinum-Coating Gaps On Titanium Anodes

    NASA Technical Reports Server (NTRS)

    Bodemeijer, Ronnald; Flowers, Cecil E.

    1990-01-01

    Simple procedure makes gaps visible to eye. New gap-detection method consists of plating thin layer of non-silver-colored metal like copper or gold on anode. Contrast in color between plated metal and bare anode material makes gaps stand out. If anode passes inspection, copper or gold plate removable by reversal of test-plating current. Remains to be determined whether test plating and removal damages anode. New method simpler and more economical than previous attempts to identify gaps in platinum.

  19. Enhancement of anodic current attributed to oxygen evolution on α-Fe2O3 electrode by microwave oscillating electric field

    PubMed Central

    Kishimoto, Fuminao; Matsuhisa, Masayuki; Kawamura, Shinichiro; Fujii, Satoshi; Tsubaki, Shuntaro; Maitani, Masato M.; Suzuki, Eiichi; Wada, Yuji

    2016-01-01

    Various microwave effects on chemical reactions have been observed, reported and compared to those carried out under conventional heating. These effects are classified into thermal effects, which arise from the temperature rise caused by microwaves, and non-thermal effects, which are attributed to interactions between substances and the oscillating electromagnetic fields of microwaves. However, there have been no direct or intrinsic demonstrations of the non-thermal effects based on physical insights. Here we demonstrate the microwave enhancement of oxidation current of water to generate dioxygen with using an α-Fe2O3 electrode induced by pulsed microwave irradiation under constantly applied potential. The rectangular waves of current density under pulsed microwave irradiation were observed, in other words the oxidation current of water was increased instantaneously at the moment of the introduction of microwaves, and stayed stably at the plateau under continuous microwave irradiation. The microwave enhancement was observed only for the α-Fe2O3 electrode with the specific surface electronic structure evaluated by electrochemical impedance spectroscopy. This discovery provides a firm evidence of the microwave special non-thermal effect on the electron transfer reactions caused by interaction of oscillating microwaves and irradiated samples. PMID:27739529

  20. Enhancement of anodic current attributed to oxygen evolution on α-Fe2O3 electrode by microwave oscillating electric field

    NASA Astrophysics Data System (ADS)

    Kishimoto, Fuminao; Matsuhisa, Masayuki; Kawamura, Shinichiro; Fujii, Satoshi; Tsubaki, Shuntaro; Maitani, Masato M.; Suzuki, Eiichi; Wada, Yuji

    2016-10-01

    Various microwave effects on chemical reactions have been observed, reported and compared to those carried out under conventional heating. These effects are classified into thermal effects, which arise from the temperature rise caused by microwaves, and non-thermal effects, which are attributed to interactions between substances and the oscillating electromagnetic fields of microwaves. However, there have been no direct or intrinsic demonstrations of the non-thermal effects based on physical insights. Here we demonstrate the microwave enhancement of oxidation current of water to generate dioxygen with using an α-Fe2O3 electrode induced by pulsed microwave irradiation under constantly applied potential. The rectangular waves of current density under pulsed microwave irradiation were observed, in other words the oxidation current of water was increased instantaneously at the moment of the introduction of microwaves, and stayed stably at the plateau under continuous microwave irradiation. The microwave enhancement was observed only for the α-Fe2O3 electrode with the specific surface electronic structure evaluated by electrochemical impedance spectroscopy. This discovery provides a firm evidence of the microwave special non-thermal effect on the electron transfer reactions caused by interaction of oscillating microwaves and irradiated samples.

  1. Anode Interactions with Coal Gas Contaminants

    SciTech Connect

    Marina, Olga A.; Coffey, Greg W.; Coyle, Christopher A.; Nguyen, Carolyn D.; Thomsen, Edwin C.; Pederson, Larry R.

    2008-08-13

    This report describes efforts to characterize the interactions nickel anodes with phosphorus in coal gas using three different button cell configurations to emphasize particular degradation modes. Important parameters addressed included contaminant concentration, temperature, reaction time, fuel utilization, and current density. In addition, coupon tests in flow-through and flow-by arrangements were conducted to complement cell tests. The studies have involved extensive electrochemical testing using both dc and ac methods. Post-test analyses to determine the composition and extent of nickel modification are particularly important to understanding reactions that have occurred. This report also provides a thermodynamic assessment of contaminant reactions with nickel in a coal gas environment with regard to alteration phase formation. Contaminants addressed were phosphorus, arsenic, sulfur, selenium, and antimony. Phosphorus was found to interact strongly with nickel and result in extensive alteration phase formation, consistent with expectations based on thermodynamic properties. Even in button cell tests where the fuel utilization was low, phosphorus was found to be nearly completely captured by the nickel anode. For anode-supported cells, an important degradation mode involved loss of electronic percolation, the result of nickel phosphide formation, grain growth, and inducement of micro-fractures within the anode support. Even with excessive anode support conversion, electrochemical degradation rates were often very low. This is attributed to a “shadowing effect,” whereby a dense structure such as current leads prevent phosphorus from reacting with the nickel directly underneath. This effect maintains an electrical pathway to the active interface, and allows the cell to operate with minimal degradation until the anode is essentially completely consumed. In a planar stack, ribs on the interconnect plate would be expected to provide this conductive pathway in the

  2. Low cost fuel cell diffusion layer configured for optimized anode water management

    DOEpatents

    Owejan, Jon P; Nicotera, Paul D; Mench, Matthew M; Evans, Robert E

    2013-08-27

    A fuel cell comprises a cathode gas diffusion layer, a cathode catalyst layer, an anode gas diffusion layer, an anode catalyst layer and an electrolyte. The diffusion resistance of the anode gas diffusion layer when operated with anode fuel is higher than the diffusion resistance of the cathode gas diffusion layer. The anode gas diffusion layer may comprise filler particles having in-plane platelet geometries and be made of lower cost materials and manufacturing processes than currently available commercial carbon fiber substrates. The diffusion resistance difference between the anode gas diffusion layer and the cathode gas diffusion layer may allow for passive water balance control.

  3. Anodic electrosynthesis of some peroxy compounds on glassy carbon electrodes

    SciTech Connect

    Khomutov, N.E.; Zakhodyakina, N.A.; Svirida, L.V.; Nesvat, N.V.

    1987-11-10

    The authors present the results of a study of the anodic electrosynthesis of hydrogen peroxide and its derivatives on glassy carbon in solutions of sodium carbonate and sodium carbonate with sodium borate. We studied the kinetics of anodic processes on glassy carbon with the aid of polarization measurements and a method for determining the concentrations of active oxygen in the anolyte and the current efficiency. The current efficiencies with respect to active oxygen obtained on glassy carbon in the mixed solution of sodium borate and sodium carbonate are close to the current efficiencies which are observed on platinum anodes in the industrial electrosynthesis of perborates.

  4. Anode power in a quasi-steady MPD thruster. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Saber, A. J.

    1974-01-01

    Local anode heat flux in a quasi-steady MPD thruster is measured by thermocouples attached to the inside surface of a shell anode. Over a range of arc currents J from 5.5 to 44 kiloamperes and argon propellant mass flows m from 1 to 48 g/sec, with the ratio J2/m held constant, the fraction of arc power deposited in the anode is found to decrease with increasing arc power. Specifically, this anode power fraction decreases from 50% at 200 kW arc power, to 10% at 20 MW. In an effort to account for this functional behavior, the current density, plasma potential, and electron temperature in the plasma adjacent to the anode are measured with probes, and the results are used in a theoretical anode heat flux model. The model asserts that energy exchange between electrons and heavy particles in the plasma near the anode occur over distances greater than the anode sheath thickness.

  5. Focused cathode design to reduce anode heating during vircator operation

    SciTech Connect

    Lynn, Curtis F.; Dickens, James C.; Neuber, Andreas A.

    2013-10-15

    Virtual cathode oscillators, or vircators, are a type of high power microwave device which operates based on the instability of a virtual cathode, or cloud of electrons, which forms when electron current injected into the drift tube exceeds the space charge limited current within the drift tube. Anode heating by the electron beam during vircator operation ultimately limits achievable pulse lengths, repetition rates, and the duration of burst mode operation. This article discusses a novel cathode design that focuses electrons through holes in the anode, thus significantly reducing anode heating by the electrons emitted from the cathode during the first transit through the A-K gap. Reflexing electrons continue to deposit energy on the anode; however, the discussed minimization of anode heating by main beam electrons has the potential to enable higher repetition rates as well as efficiency and longer diode lifetime. A simulation study of this type of cathode design illustrates possible advantages.

  6. Interfacial chemistry of zinc anodes for reinforced concrete structures

    SciTech Connect

    Covino, B.S. Jr.; Bullard, S.J.; Cramer, S.D.; Holcomb, G.R.; McGill, G.E.; Cryer, C.B.; Stoneman, A.; Carter, R.R.

    1997-12-01

    Thermally-sprayed zinc anodes are used in both galvanic and impressed current cathodic protection systems for reinforced concrete structures. The Albany Research Center, in collaboration with the Oregon Department of Transportation, has been studying the effect of electrochemical aging on the bond strength of zinc anodes for bridge cathodic protection systems. Changes in anode bond strength and other anode properties can be explained by the chemistry of the zinc-concrete interface. The chemistry of the zinc-concrete interface in laboratory electrochemical aging studies is compared with that of several bridges with thermal-sprayed zinc anodes and which have been in service for 5 to 10 years using both galvanic and impressed current cathodic protection systems. The bridges are the Cape Creek Bridge on the Oregon coast and the East Camino Undercrossing near Placerville, CA. Also reported are interfacial chemistry results for galvanized steel rebar from the 48 year old Longbird Bridge in Bermuda.

  7. Influence of anode surface chemistry on microbial fuel cell operation.

    PubMed

    Santoro, Carlo; Babanova, Sofia; Artyushkova, Kateryna; Cornejo, Jose A; Ista, Linnea; Bretschger, Orianna; Marsili, Enrico; Atanassov, Plamen; Schuler, Andrew J

    2015-12-01

    Self-assembled monolayers (SAMs) modified gold anodes are used in single chamber microbial fuel cells for organic removal and electricity generation. Hydrophilic (N(CH3)3(+), OH, COOH) and hydrophobic (CH3) SAMs are examined for their effect on bacterial attachment, current and power output. The different substratum chemistry affects the community composition of the electrochemically active biofilm formed and thus the current and power output. Of the four SAM-modified anodes tested, N(CH3)3(+) results in the shortest start up time (15 days), highest current achieved (225 μA cm(-2)) and highest MFC power density (40 μW cm(-2)), followed by COOH (150 μA cm(-2) and 37 μW cm(-2)) and OH (83 μA cm(-2) and 27 μW cm(-2)) SAMs. Hydrophobic SAM decreases electrochemically active bacteria attachment and anode performance in comparison to hydrophilic SAMs (CH3 modified anodes 7 μA cm(-2) anodic current and 1.2 μW cm(-2) MFC's power density). A consortium of Clostridia and δ-Proteobacteria is found on all the anode surfaces, suggesting a synergistic cooperation under anodic conditions.

  8. Anode initiated surface flashover switch

    DOEpatents

    Brainard, John P.; Koss, Robert J.

    2003-04-29

    A high voltage surface flashover switch has a pair of electrodes spaced by an insulator. A high voltage is applied to an anode, which is smaller than the opposing, grounded, cathode. When a controllable source of electrons near the cathode is energized, the electrons are attracted to the anode where they reflect to the insulator and initiate anode to cathode breakdown.

  9. Inert Anode Report

    SciTech Connect

    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.

  10. Anodes for alkaline electrolysis

    DOEpatents

    Soloveichik, Grigorii Lev

    2011-02-01

    A method of making an anode for alkaline electrolysis cells includes adsorption of precursor material on a carbonaceous material, conversion of the precursor material to hydroxide form and conversion of precursor material from hydroxide form to oxy-hydroxide form within the alkaline electrolysis cell.

  11. Anodic Polarization Curves Revisited

    ERIC Educational Resources Information Center

    Liu, Yue; Drew, Michael G. B.; Liu, Ying; Liu, Lin

    2013-01-01

    An experiment published in this "Journal" has been revisited and it is found that the curve pattern of the anodic polarization curve for iron repeats itself successively when the potential scan is repeated. It is surprising that this observation has not been reported previously in the literature because it immediately brings into…

  12. Movable anode x-ray source with enhanced anode cooling

    DOEpatents

    Bird, Charles R.; Rockett, Paul D.

    1987-01-01

    An x-ray source having a cathode and a disc-shaped anode with a peripheral surface at constant radius from the anode axis opposed to the cathode. The anode has stub axle sections rotatably carried in heat conducting bearing plates which are mounted by thermoelectric coolers to bellows which normally bias the bearing plates to a retracted position spaced from opposing anode side faces. The bellows cooperate with the x-ray source mounting structure for forming closed passages for heat transport fluid. Flow of such fluid under pressure expands the bellows and brings the bearing plates into heat conducting contact with the anode side faces. A worm gear is mounted on a shaft and engages serrations in the anode periphery for rotating the anode when flow of coolant is terminated between x-ray emission events.

  13. Movable anode x-ray source with enhanced anode cooling

    DOEpatents

    Bird, C.R.; Rockett, P.D.

    1987-08-04

    An x-ray source is disclosed having a cathode and a disc-shaped anode with a peripheral surface at constant radius from the anode axis opposed to the cathode. The anode has stub axle sections rotatably carried in heat conducting bearing plates which are mounted by thermoelectric coolers to bellows which normally bias the bearing plates to a retracted position spaced from opposing anode side faces. The bellows cooperate with the x-ray source mounting structure for forming closed passages for heat transport fluid. Flow of such fluid under pressure expands the bellows and brings the bearing plates into heat conducting contact with the anode side faces. A worm gear is mounted on a shaft and engages serrations in the anode periphery for rotating the anode when flow of coolant is terminated between x-ray emission events. 5 figs.

  14. Experimental Studies of Anode Sheath Phenomena in a Hall Thruster Discharge

    SciTech Connect

    L. Dorf; Y. Raitses; N.J. Fisch

    2004-12-17

    Both electron-repelling and electron-attracting anode sheaths in a Hall thruster were characterized by measuring the plasma potential with biased and emissive probes [L. Dorf, Y. Raitses, V. Semenov, and N.J. Fisch, Appl. Phys. Let. 84 (2004) 1070]. In the present work, two-dimensional structures of the plasma potential, electron temperature, and plasma density in the near-anode region of a Hall thruster with clean and dielectrically coated anodes are identified. Possible mechanisms of anode sheath formation in a Hall thruster are analyzed. The path for current closure to the anode appears to be the determining factor in the anode sheath formation process. The main conclusion of this work is that the anode sheath formation in Hall thrusters differs essentially from that in the other gas discharge devices, like a glow discharge or a hollow anode, because the Hall thruster utilizes long electron residence times to ionize rather than high neutral pressures.

  15. Carbon paint anode for reinforced concrete bridges in coastal environments

    SciTech Connect

    Cramer, Stephen D.; Bullard, Sophie J.; Covino, Bernard S., Jr.; Holcomb, Gordon R.; Russell, James H.; Cryer, C.B.; Laylor, H.M.

    2002-01-01

    Solvent-based acrylic carbon paint anodes were installed on the north approach spans of the Yaquina Bay Bridge (Newport OR) in 1985. The anodes continue to perform satisfactorily after more than 15 years service. The anodes were inexpensive to apply and field repairs are easily made. Depolarization potentials are consistently above 100 mV with long-term current densities around 2 mA/m 2. Bond strength remains adequate, averaging 0.50 MPa (73 psi). Some deterioration of the anode-concrete interface has occurred in the form of cracks and about 4% of the bond strength measurements indicated low or no bond. Carbon anode consumption appears low. The dominant long-term anode reaction appears to be chlorine evolution, which results in limited further acidification of the anode-concrete interface. Chloride profiles were depressed compared to some other coastal bridges suggesting chloride extraction by the CP system. Further evidence of outward chloride migration was a flat chloride profile between the anode and the outer rebar.

  16. Buried anode lithium thin film battery and process for forming the same

    DOEpatents

    Lee, Se-Hee; Tracy, C. Edwin; Liu, Ping

    2004-10-19

    A reverse configuration, lithium thin film battery (300) having a buried lithium anode layer (305) and process for making the same. The present invention is formed from a precursor composite structure (200) made by depositing electrolyte layer (204) onto substrate (201), followed by sequential depositions of cathode layer (203) and current collector (202) on the electrolyte layer. The precursor is subjected to an activation step, wherein a buried lithium anode layer (305) is formed via electroplating a lithium anode layer at the interface of substrate (201) and electrolyte film (204). The electroplating is accomplished by applying a current between anode current collector (201) and cathode current collector (202).

  17. The effect of grain size on aluminum anodes for Al-air batteries in alkaline electrolytes

    NASA Astrophysics Data System (ADS)

    Fan, Liang; Lu, Huimin

    2015-06-01

    Aluminum is an ideal material for metallic fuel cells. In this research, different grain sizes of aluminum anodes are prepared by equal channel angular pressing (ECAP) at room temperature. Microstructure of the anodes is examined by electron backscatter diffraction (EBSD) in scanning electron microscope (SEM). Hydrogen corrosion rates of the Al anodes in 4 mol L-1 NaOH are determined by hydrogen collection method. The electrochemical properties of the aluminum anodes are investigated in the same electrolyte using electrochemical impedance spectroscopy (EIS) and polarization curves. Battery performance is also tested by constant current discharge at different current densities. Results confirm that the electrochemical properties of the aluminum anodes are related to grain size. Finer grain size anode restrains hydrogen evolution, improves electrochemical activity and increases anodic utilization rate. The proposed method is shown to effectively improve the performance of Al-air batteries.

  18. Does anodal transcranial direct current stimulation enhance excitability of the motor cortex and motor function in healthy individuals and subjects with stroke: a systematic review and meta-analysis.

    PubMed

    Bastani, A; Jaberzadeh, S

    2012-04-01

    The primary aim of this review is to evaluate the effects of anodal transcranial direct current stimulation (a-tDCS) on corticomotor excitability and motor function in healthy individuals and subjects with stroke. The secondary aim is to find a-tDCS optimal parameters for its maximal effects. Electronic databases were searched for studies into the effect of a-tDCS when compared to no stimulation. Studies which met the inclusion criteria were assessed and methodological quality was examined using PEDro and Downs and Black (D&B) assessment tools. Data from seven studies revealed increase in corticomotor excitability with a small but significant effect size (0.31 [0.14, 0.48], p=0.0003) in healthy subjects and data from two studies in subjects with stroke indicated significant results with moderate effect size (0.59 [0.24, 0.93], p=0.001) in favor of a-tDCS. Likewise, studies examining motor function demonstrated a small and non-significant effect (0.39 [-0.17, 0.94], p=0.17) in subjects with stroke and a large but non-significant effect (0.92 [-1.02, 2.87], p=0.35) in healthy subjects in favor of improvement in motor function. The results also indicate that efficacy of a-tDCS is dependent on current density and duration of application. A-tDCS increases corticomotor excitability in both healthy individuals and subjects with stroke. The results also show a trend in favor of motor function improvement following a-tDCS. A-tDCS is a non-invasive, cheap and easy-to-apply modality which could be used as a stand-alone technique or as an adds-on technique to enhance corticomotor excitability and the efficacy of motor training approaches. However, the small sample size of the included studies reduces the strength of the presented evidences and any conclusion in this regard should be considered cautiously.

  19. Does anodal transcranial direct current stimulation enhance excitability of the motor cortex and motor function in healthy individuals and subjects with stroke: a systematic review and meta-analysis.

    PubMed

    Bastani, A; Jaberzadeh, S

    2012-04-01

    The primary aim of this review is to evaluate the effects of anodal transcranial direct current stimulation (a-tDCS) on corticomotor excitability and motor function in healthy individuals and subjects with stroke. The secondary aim is to find a-tDCS optimal parameters for its maximal effects. Electronic databases were searched for studies into the effect of a-tDCS when compared to no stimulation. Studies which met the inclusion criteria were assessed and methodological quality was examined using PEDro and Downs and Black (D&B) assessment tools. Data from seven studies revealed increase in corticomotor excitability with a small but significant effect size (0.31 [0.14, 0.48], p=0.0003) in healthy subjects and data from two studies in subjects with stroke indicated significant results with moderate effect size (0.59 [0.24, 0.93], p=0.001) in favor of a-tDCS. Likewise, studies examining motor function demonstrated a small and non-significant effect (0.39 [-0.17, 0.94], p=0.17) in subjects with stroke and a large but non-significant effect (0.92 [-1.02, 2.87], p=0.35) in healthy subjects in favor of improvement in motor function. The results also indicate that efficacy of a-tDCS is dependent on current density and duration of application. A-tDCS increases corticomotor excitability in both healthy individuals and subjects with stroke. The results also show a trend in favor of motor function improvement following a-tDCS. A-tDCS is a non-invasive, cheap and easy-to-apply modality which could be used as a stand-alone technique or as an adds-on technique to enhance corticomotor excitability and the efficacy of motor training approaches. However, the small sample size of the included studies reduces the strength of the presented evidences and any conclusion in this regard should be considered cautiously. PMID:21978654

  20. Anode arc motion in high power arcjets

    NASA Technical Reports Server (NTRS)

    Harris, W. J.; O'Hair, E. A.; Hatfield, L. L.; Kristiansen, M.; Mankins, J. S.

    1992-01-01

    The long-term operational lifetime of most medium to high power arcjets is currently limited by the rapid deterioration of the arcjet electrodes. To a large extent, the rate of this deterioration is related to the motion of the arc discharge on the electrode surfaces. This paper details a series of experiments aimed at studying the temporal behavior of dc arcs on a water-cooled radially-segmented 30 kW class arcjet anode. The experimental anode used for these tests was made of copper, and was divided into four equivalent radial segments which were electrically isolated with aluminum oxide gaskets. The current carried by each segment was measured independently using four calibrated resistive shunts, and was analyzed by digital computer. The tests were limited to nitrogen propellant over a current range of 100-250 A dc. Results show that for the range of total currents considered here, the current distribution in the segmented arcjet anode is generally asymmetric, exhibiting random fluctuations over a wide range of frequencies.

  1. Anode arc motion in high power arcjets

    NASA Astrophysics Data System (ADS)

    Harris, W. J.; O'Hair, E. A.; Hatfield, L. L.; Kristiansen, M.; Mankins, J. S.

    1992-07-01

    The long-term operational lifetime of most medium to high power arcjets is currently limited by the rapid deterioration of the arcjet electrodes. To a large extent, the rate of this deterioration is related to the motion of the arc discharge on the electrode surfaces. This paper details a series of experiments aimed at studying the temporal behavior of dc arcs on a water-cooled radially-segmented 30 kW class arcjet anode. The experimental anode used for these tests was made of copper, and was divided into four equivalent radial segments which were electrically isolated with aluminum oxide gaskets. The current carried by each segment was measured independently using four calibrated resistive shunts, and was analyzed by digital computer. The tests were limited to nitrogen propellant over a current range of 100-250 A dc. Results show that for the range of total currents considered here, the current distribution in the segmented arcjet anode is generally asymmetric, exhibiting random fluctuations over a wide range of frequencies.

  2. Nickel anode electrode

    DOEpatents

    Singh, Prabhakar; Benedict, Mark

    1987-01-01

    A nickel anode electrode fabricated by oxidizing a nickel alloying material to produce a material whose exterior contains nickel oxide and whose interior contains nickel metal throughout which is dispersed the oxide of the alloying material and by reducing and sintering the oxidized material to form a product having a nickel metal exterior and an interior containing nickel metal throughout which is dispersed the oxide of the alloying material.

  3. Inert anodes for aluminum smelting

    SciTech Connect

    Weyand, J.D.; Ray, S.P.; Baker, F.W.; DeYoung, D.H.; Tarcy, G.P.

    1986-02-01

    The use of nonconsumable or inert anodes for replacement of consumable carbon anodes in Hall electrolysis cells for the production of aluminum has been a technical and commercial goal of the aluminum industry for many decades. This report summarizes the technical success realized in the development of an inert anode that can be used to produce aluminum of acceptable metal purity in small scale Hall electrolysis cells. The inert anode material developed consists of a cermet composition containing the phases: copper, nickel ferrite and nickel oxide. This anode material has an electrical conductivity comparable to anode carbon used in Hall cells, i.e., 150 ohm {sup {minus}1}cm{sup {minus}1}. Metal purity of 99.5 percent aluminum has been produced using this material. The copper metal alloy present in the anode is not removed by anodic dissolution as does occur with cermet anodes containing a metallic nickel alloy. Solubility of the oxide phases in the cryolite electrolyte is reduced by: (1) saturated concentration of alumina, (2) high nickel oxide content in the NiO-NiFe{sub 2}O{sub 4} composition, (3) lowest possible cell operating temperature, (4) additions of alkaline or alkaline earth fluorides to the bath to reduce solubilities of the anode components, and (5) avoiding bath contaminants such as silica. Dissolution rate measurements indicate first-order kinetics and that the rate limiting step for dissolution is mass transport controlled. 105 refs., 234 figs., 73 tabs.

  4. Fabrication of alumina films with laminated structures by ac anodization

    NASA Astrophysics Data System (ADS)

    Segawa, Hiroyo; Okano, Hironaga; Wada, Kenji; Inoue, Satoru

    2014-02-01

    Anodization techniques by alternating current (ac) are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50-200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials.

  5. Cu-Ni-Fe anodes having improved microstructure

    DOEpatents

    Bergsma, S. Craig; Brown, Craig W.

    2004-04-20

    A method of producing aluminum in a low temperature electrolytic cell containing alumina dissolved in an electrolyte. The method comprises the steps of providing a molten electrolyte having alumina dissolved therein in an electrolytic cell containing the electrolyte. A non-consumable anode and cathode is disposed in the electrolyte, the anode comprised of Cu--Ni--Fe alloys having single metallurgical phase. Electric current is passed from the anode, through the electrolyte to the cathode thereby depositing aluminum on the cathode, and molten aluminum is collected from the cathode.

  6. Performance variation according to anode-embedded orientation in a sediment microbial fuel cell employing a chessboard-like hundred-piece anode.

    PubMed

    An, Junyeong; Nam, Jonghyun; Kim, Bongkyu; Lee, Hyung-Sool; Kim, Byung Hong; Chang, In Seop

    2015-08-01

    The effect of two different anode-embedding orientations, lengthwise- and widthwise-embedded anodes was explored, on the performance of sediment microbial fuel cells (SMFCs) using a chessboard anode. The maximum current densities and power densities in SMFCs having lengthwise-embedded anodes (SLA1-SLA10) varied from 38.2mA/m(2) to 121mA/m(2) and from 5.5mW/m(2) to 20mW/m(2). In comparison, the maximum current densities and maximum power densities in SMFCs having anodes widthwise-embedded between 0cm to 8cm (SWA2-SWA5) increased from 82mA/m(2) to 140mA/m(2) and from 14.7mW/m(2) to 31.1mW/m(2) as the anode depth became deeper. Although there was a difference in the performance among SWA5-SWA10, it was considered negligible. Hence, it is concluded that it is important to embed anodes widthwise at the specific anode depths, in order to improve of SMFC performance. Chessboard anode used in this work could be a good option for the determination of optimal anode depths.

  7. An inert metal anode for magnesium electrowinning

    SciTech Connect

    Moore, J. F.; Hryn, J. N.; Pellin, M. J.; Calaway, W. F.; Watson, K.

    1999-12-01

    Results from the development of a novel type of anode for electrowinning Mg are reported. A tailored alloy system based on the binary Cu-Al can be made to form a thin alumina layer on its surface that is relatively impervious to attack by the molten chloride melt at high temperature. This barrier is thin enough (5--50 nm) to conduct electrical current without significant IR loss. As the layer slowly dissolves, the chemical potential developed at the surface drives the diffusion of aluminum from the bulk alloy to reform (heal) the protective alumina layer. In this way, an anode that generates Cl{sub 2} (melt electrolysis) and O{sub 2} (wet feed hydrolysis) and no chlorocarbons can be realized. Further, the authors expect the rate of loss of the anode to be dramatically less than the coke-derived carbon anodes typically in use for this technology, leading to substantial cost savings and ancillary pollution control by eliminating coke plant emissions, as well as eliminating chlorinated hydrocarbon emissions from Mg electrowinning cells.

  8. Process for anodizing aluminum foil

    SciTech Connect

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

    1984-11-06

    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/sup 0/ C. and then reanodizing the foil. The process is useful in anodizing foil to a voltage of up to 760 V.

  9. Corrosion of cermet anodes during low temperature electrolysis of alumina. Final report

    SciTech Connect

    Kozarek, R.L.; Ray, S.P.; Dawless, R.K.; LaCamera, A.F.

    1997-09-26

    Successful development of inert anodes to replace carbon anodes in Hall cells has the potential benefits of lower energy consumption,lower operating costs, and reduced CO{sub 2} and CO emissions. Using inert anodes at reduced current density and reduced operating temperature (800 C) has potential for decreasing the corrosion rate of inert anodes. It may also permit the use of new materials for containment and insulation. This report describes the fabrication characteristics and the corrosion performance of 5324-17% Cu Cermet anodes in 100 hour tests. Although some good results were achieved, the corrosion rate at low temperature (800 C) is varied and not significantly lower than typical results at high temperature ({approximately} 960 C). This report also describes several attempts at 200 hour tests, with one anode achieving 177 hours of continuous operation and another achieving a total of 235 hours but requiring three separate tests of the same anode. The longest run did show a lower wear rate in the last test; but a high resistance layer developed on the anode surface and forced an unacceptably low current density. It is recommended that intermediate temperatures be explored as a more optimal environment for inert anodes. Other electrolyte chemistries and anode compositions (especially high conductivity anodes) should be considered to alleviate problems associated with lower temperature operation.

  10. A dynamic inert metal anode.

    SciTech Connect

    Hryn, J. N.

    1998-11-09

    A new concept for a stable anode for aluminum electrowinning is described. The anode consists of a cup-shaped metal alloy container filled with a molten salt that contains dissolved aluminum. The metal alloy can be any of a number of alloys, but it must contain aluminum as a secondary alloying metal. A possible alloy composition is copper with 5 to 15 weight percent aluminum. In the presence of oxygen, aluminum on the metal anode's exterior surface forms a continuous alumina film that is thick enough to protect the anode from chemical attack by cryolite during electrolysis and thin enough to maintain electrical conductivity. However, the alumina film is soluble in cryolite, so it must be regenerated in situ. Film regeneration is achieved by the transport of aluminum metal from the anode's molten salt interior through the metal wall to the anode's exterior surface, where the transported aluminum oxidizes to alumina in the presence of evolving oxygen to maintain the protective alumina film. Periodic addition of aluminum metal to the anode's interior keeps the aluminum activity in the molten salt at the desired level. This concept for an inert anode is viable as long as the amount of aluminum produced at the cathode greatly exceeds the amount of aluminum required to maintain the anode's protective film.

  11. Investigation of mechanism of anode plasma formation in ion diode with dielectric anode

    SciTech Connect

    Pushkarev, A.

    2015-10-15

    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{sub 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°.

  12. Investigation of mechanism of anode plasma formation in ion diode with dielectric anode

    NASA Astrophysics Data System (ADS)

    Pushkarev, A.

    2015-10-01

    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 Br 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°.

  13. Engineering of highly ordered TiO2 nanopore arrays by anodization

    NASA Astrophysics Data System (ADS)

    Wang, Huijie; Huang, Zhennan; Zhang, Li; Ding, Jie; Ma, Zhaoxia; Liu, Yong; Kou, Shengzhong; Yang, Hangsheng

    2016-07-01

    Finite element analysis was used to simulate the current density distributions in the TiO2 barrier layer formed at the initial stage of Ti anodization. The morphology modification of the barrier layer was found to induce current density distribution change. By starting the anodization with proper TiO2 barrier layer morphology, the current density distribution can be adjusted to favor the formation of either nanotube arrays or nanopore arrays of anodic TiO2. We also found that the addition of sodium acetate into the electrolyte suppressed both the field-assisted chemical dissolution of TiO2 and the TiF62- hydrolysis induced TiO2 deposition during anodization, and thus further favored the nanopore formation. Accordingly, highly ordered anodic TiO2 nanopore arrays, similar to anodic aluminum oxide nanopore arrays, were successfully prepared.

  14. Carbon Nanofibers Modified Graphite Felt for High Performance Anode in High Substrate Concentration Microbial Fuel Cells

    PubMed Central

    Shen, Youliang; Zhou, Yan; Chen, Shuiliang; Yang, Fangfang; Zheng, Suqi; Hou, Haoqing

    2014-01-01

    Carbon nanofibers modified graphite fibers (CNFs/GF) composite electrode was prepared for anode in high substrate concentration microbial fuel cells. Electrochemical tests showed that the CNFs/GF anode generated a peak current density of 2.42 mA cm−2 at a low acetate concentration of 20 mM, which was 54% higher than that from bare GF. Increase of the acetate concentration to 80 mM, in which the peak current density of the CNFs/GF anode greatly increased and was up to 3.57 mA cm−2, was seven times as that of GF anode. Morphology characterization revealed that the biofilms in the CNFs/GF anode were much denser than those in the bare GF. This result revealed that the nanostructure in the anode not only enhanced current generation but also could tolerate high substrate concentration. PMID:24883348

  15. Specific features of an electric discharge operating between an electrolytic anode and a metal cathode

    NASA Astrophysics Data System (ADS)

    Gaisin, A. F.; Sarimov, L. R.

    2011-06-01

    Results are presented from experimental studies of a high-current electric discharge operating between an St45 steel cathode and a service water anode in a wide range of air pressures. Peculiarities of discharge ignition and specific features of cathode and anode spots were revealed. The behavior of the current density on a service water anode was investigated for the first time. Comparison of the current densities j on the steel cathode and service water anode shows that, in the parameter range under study, Hehl's law is not satisfied on the water anode. The two-dimensional distribution of the potential inside and on the surface of the service water anode was measured.

  16. Fabrication of highly ordered nanoporous alumina films by stable high-field anodization

    NASA Astrophysics Data System (ADS)

    Li, Yanbo; Zheng, Maojun; Ma, Li; Shen, Wenzhong

    2006-10-01

    Stable high-field anodization (1500-4000 A m-2) for the fabrication of highly ordered porous anodic alumina films has been realized in a H3PO4-H2O-C2H5OH system. By maintaining the self-ordering voltage and adjusting the anodizing current density, high-quality self-ordered alumina films with a controllable inter-pore distance over a large range are achieved. The high anodizing current densities lead to high-speed film growth (4-10 µm min-1). The inter-pore distance is not solely dependent on the anodizing voltage, but is also influenced by the anodizing current density. This approach is simple and cost-effective, and is of great value for applications in diverse areas of nanotechnology.

  17. Carbon nanofibers modified graphite felt for high performance anode in high substrate concentration microbial fuel cells.

    PubMed

    Shen, Youliang; Zhou, Yan; Chen, Shuiliang; Yang, Fangfang; Zheng, Suqi; Hou, Haoqing

    2014-01-01

    Carbon nanofibers modified graphite fibers (CNFs/GF) composite electrode was prepared for anode in high substrate concentration microbial fuel cells. Electrochemical tests showed that the CNFs/GF anode generated a peak current density of 2.42 mA cm(-2) at a low acetate concentration of 20 mM, which was 54% higher than that from bare GF. Increase of the acetate concentration to 80 mM, in which the peak current density of the CNFs/GF anode greatly increased and was up to 3.57 mA cm(-2), was seven times as that of GF anode. Morphology characterization revealed that the biofilms in the CNFs/GF anode were much denser than those in the bare GF. This result revealed that the nanostructure in the anode not only enhanced current generation but also could tolerate high substrate concentration.

  18. Specific features of an electric discharge operating between an electrolytic anode and a metal cathode

    SciTech Connect

    Gaisin, A. F.; Sarimov, L. R.

    2011-06-15

    Results are presented from experimental studies of a high-current electric discharge operating between an St45 steel cathode and a service water anode in a wide range of air pressures. Peculiarities of discharge ignition and specific features of cathode and anode spots were revealed. The behavior of the current density on a service water anode was investigated for the first time. Comparison of the current densities j on the steel cathode and service water anode shows that, in the parameter range under study, Hehl's law is not satisfied on the water anode. The two-dimensional distribution of the potential inside and on the surface of the service water anode was measured.

  19. Practical solid oxide fuel cells with anodes derived from self-assembled mesoporous-NiO-YSZ.

    PubMed

    Mamak, Marc; Coombs, Neil; Ozin, Geoffrey A

    2002-10-21

    Solid oxide fuel cells comprised of an anode made from sintered and reduced mesoporous-NiO-YSZ are shown to provide stable current and power densities at the operating temperature of 800 degrees C and show better performance than cells with anode cermets made from mechanical mixtures of NiO and YSZ, attributable to the unique anode microstructure.

  20. Interconnected hollow carbon nanospheres for stable lithium metal anodes.

    PubMed

    Zheng, Guangyuan; Lee, Seok Woo; Liang, Zheng; Lee, Hyun-Wook; Yan, Kai; Yao, Hongbin; Wang, Haotian; Li, Weiyang; Chu, Steven; Cui, Yi

    2014-08-01

    For future applications in portable electronics, electric vehicles and grid storage, batteries with higher energy storage density than existing lithium ion batteries need to be developed. Recent efforts in this direction have focused on high-capacity electrode materials such as lithium metal, silicon and tin as anodes, and sulphur and oxygen as cathodes. Lithium metal would be the optimal choice as an anode material, because it has the highest specific capacity (3,860 mAh g(-1)) and the lowest anode potential of all. However, the lithium anode forms dendritic and mossy metal deposits, leading to serious safety concerns and low Coulombic efficiency during charge/discharge cycles. Although advanced characterization techniques have helped shed light on the lithium growth process, effective strategies to improve lithium metal anode cycling remain elusive. Here, we show that coating the lithium metal anode with a monolayer of interconnected amorphous hollow carbon nanospheres helps isolate the lithium metal depositions and facilitates the formation of a stable solid electrolyte interphase. We show that lithium dendrites do not form up to a practical current density of 1 mA cm(-2). The Coulombic efficiency improves to ∼ 99% for more than 150 cycles. This is significantly better than the bare unmodified samples, which usually show rapid Coulombic efficiency decay in fewer than 100 cycles. Our results indicate that nanoscale interfacial engineering could be a promising strategy to tackle the intrinsic problems of lithium metal anodes.

  1. Mesoporous Silicon-Based Anodes

    NASA Technical Reports Server (NTRS)

    Peramunage, Dharmasena

    2015-01-01

    For high-capacity, high-performance lithium-ion batteries. A new high-capacity anode composite based on mesoporous silicon is being developed. With a structure that resembles a pseudo one-dimensional phase, the active anode material will accommodate significant volume changes expected upon alloying and dealloying with lithium (Li).

  2. Anodic Concentration Polarization in SOFCs

    SciTech Connect

    Williford, Rick E.; Chick, Lawrence A.; Maupin, Gary D.; Simner, Steve P.; Stevenson, Jeffry W.; Khaleel, Mohammad A.; Wachsman, ED, et al

    2003-08-01

    Concentration polarization is important because it determines the maximum power output of a solid oxide fuel cell (SOFC) at high fuel utilization. Anodic concentration polarization occurs when the demand for reactants exceeds the capacity of the porous ceramic anode to supply them by gas diffusion mechanisms. High tortuosities (bulk diffusion resistances) are often assumed to explain this behavior. However, recent experiments show that anodic concentration polarization originates in the immediate vicinity of the reactive triple phase boundary (TPB) sites near the anode/electrolyte interface. A model is proposed to describe how concentration polarization is controlled by two localized phenomena: competitive adsorption of reactants in areas adjacent to the reactive TPB sites, followed by relatively slow surface diffusion to the reactive sites. Results suggest that future SOFC design improvements should focus on optimization of the reactive area, adsorption, and surface diffusion at the anode/electrolyte interface.

  3. Recent Development on Anodes for Na-Ion Batteries

    SciTech Connect

    Bommier, C; Ji, XL

    2015-01-23

    New discoveries in anode materials for sodium ion batteries (NIBs) are highly necessary to achieve the goals of widespread applications, such as electric vehicles (EVs) and grid-level energy storage. Carbon-based materials are critical for this task as they are inexpensive, abundant, and versatile. They contain a plethora of structures and morphologies, ranging from highly ordered graphite or nanotubes to highly disordered amorphous carbon, thus making them very attractive for electrochemical energy storage. This review attempts to cover past and recent progress in the development of carbon-based anode materials for NIBs. To give a larger context, the article will briefly cover other anode materials for NIBs as well. The aim of this paper is to provide a timely update for researchers currently involved in the respective fields or to serve as a starting point for individuals who would like to gain a greater knowledge of new NIB anode materials.

  4. Perovskites for use as sulfur tolerant anodes

    NASA Astrophysics Data System (ADS)

    Howell, Thomas G.

    One of the major obstacles encountered when using solid oxide fuel cells with hydrocarbon fuels is sulfur poisoning. The current anode material used is Ni/YSZ and Ni is not sulfur tolerant; therefore, the performance of the cell will degrade over time due to the formation of NiS. Perovskites have demonstrated superior sulfur tolerance but lack the high conductivity and catalytic activity of Ni/YSZ cermets. One of the objectives of this effort is to explore the substitution of the A-site in an A2MgMoO 6 perovskite with Sr and Ba, to create Sr2MgMoO6 (SMMO) and Ba2MgMoO6 (BMMO), respectively, to improve the sulfur tolerance of solid oxide fuel cells (SOFCs). Sr2MgMoO 6, a double perovskite, has been previously studied and is suggested as a material of interest because of its relatively high conductivity and catalytic potential. Barium has not been previously studied and was selected as the dopant because the ionic radii (1.61 A) resulted in a calculated tolerance factor of 1.036 for BMMO when compared to SMMO, which has an ionic radii of 1.44 A and a calculated tolerance factor of 0.978. The tolerance factor for BaSrMgMoO6, a bi-substituted material synthesized for comparison as an intermediate formulation, was calculated to be 1.00. Another objective is to synthesize and characterize a series of lanthanum (La) doped Sr2MgMoO6 (SMMO) or La doped Sr2MgNbO 6 (SMNO) anode materials, which can be used in combination with electrolytes containing lanthanum to mitigate the effects of lanthanum poisoning in SOFCs. Currently, a La0.4Ce0.6O1.8 (LDC) transition layer is used with many perovskite-based anode materials to prevent La diffusion into the anode from the La0.8Sr0.2Ga0.8Mg 0.2O2.8 (LSGM) electrolyte, which can create a resistive La species that impedes electrochemical performance. To accomplish this, a new class of anode materials was synthesized with the goal of balancing La chemical potential between these neighboring materials. It was hypothesized that by

  5. Protection of MOS capacitors during anodic bonding

    NASA Astrophysics Data System (ADS)

    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. The anodic oxidation of p-benzoquinone and maleic acid

    SciTech Connect

    Bock, C.; MacDougall, B.

    1999-08-01

    The oxidation of organics, in particular of p-benzoquinone and maleic acid, at high anodic potentials has been studied using a range of anode materials such as noble-metal-based oxides and antimony-doped tin oxides. The influence of the current density was also investigated showing that the oxidation rate of p-benzoquinone increased only slightly with increasing current density. The efficiency of the p-benzoquinone oxidation was found to depend on several properties of the anode material, not just its chemical nature. Furthermore, efficiencies for the partial oxidation of p-benzoquinone using specially prepared noble-metal-oxide-based anodes were found to be only somewhat smaller or even as high as those observed for PbO{sub 2} or antimony-doped tin oxide anodes, respectively. The anodic electrolysis of maleic acid solutions was found to decrease the activity of IrO{sub 2} for the oxidation of organic compounds. This was not observed when PbO{sup 2} was employed for the oxidation of maleic acid.

  7. Report on the source of the electrochemical impedance on cermet inert anodes

    SciTech Connect

    Windisch, C.F. Jr.; Stice, N.D.

    1991-02-01

    the Inert Electrode Program at Pacific Northwest Laboratory (PNL) is supported by the Office of Industrial Processes of the US Department of Energy and is aimed at improving the energy efficiency of Hall-Heroult cells through the development of inert anodes. The inert anodes currently under study are composed of a cermet material of the general composition NiO-NiFe{sub 2}O{sub 4}-Cu. The program has three primary objectives: (a) to evaluate the anode material in a scaled-up, pilot cell facility, (b) to investigate the mechanisms of the electrochemical reactions at the anode surface, and (c) to develop sensors for monitoring anode and/or electrolyte conditions. This report covers the results of a portion of the studies on anode reaction mechanisms. The electrochemical impedances of cermet inert anodes in alumina-saturated molten cryolite as a function of frequency, current density, and time indicated that a significant component of the impedance is due to the gas bubbles produced at the anode during electrolysis. The data also showed a connection between surface structure and impedance that appears to be related to the effects of surface structure on bubble flow. Given the results of this work, it is doubtful that a resistive film contributes significantly to the electrochemical impedances on inert anodes. Properties previously assigned to such a film are more likely due to the bubbles and those factors that affect the properties and dynamics of the bubbles at the anode surface. 12 refs., 16 figs., 3 tabs.

  8. Optimization of Aluminum Anodization Conditions for the Fabrication of Nanowires by Electrodeposition

    NASA Technical Reports Server (NTRS)

    Fucsko, Viola

    2005-01-01

    Anodized alumina nanotemplates have a variety of potential applications in the development of nanotechnology. Alumina nanotemplates are formed by oxidizing aluminum film in an electrolyte solution.During anodization, aluminum oxidizes, and, under the proper conditions, nanometer-sized pores develop. A series of experiments was conducted to determine the optimal conditions for anodization. Three-micrometer thick aluminum films on silicon and silicon oxide substrates were anodized using constant voltages of 13-25 V. 0.1-0.3M oxalic acid was used as the electrolyte. The anodization time was found to increase and the overshooting current decreased as both the voltage and the electrolyte concentrations were decreased. The samples were observed under a scanning electron microscope. Anodizing with 25V in 0.3M oxalic acid appears to be the best process conditions. The alumina nanotemplates are being used to fabricate nanowires by electrodeposition. The current-voltage characteristics of copper nanowires have also been studied.

  9. Electrochemical aging of humectant-treated thermal-sprayed zinc anodes for cathodic protection

    SciTech Connect

    Covino, B.S. Jr.; Holcomb, G.R.; Bullard, S.J.; Russell, J.H.; Cramer, S.D.; Bennett, J.E.; Laylor, H.M.

    1999-07-01

    Humectants, substances that promote the retention of moisture, were studied to determine their effectiveness in improving the performance and extending the service life of both new and previously-aged thermal-sprayed Zn anodes used in impressed current (ICCP) and galvanic cathodic protection (GCP) systems for steel-reinforced concrete structures. Potassium acetate, lithium nitrate, and lithium bromide were applied to a series of thermal-sprayed Zn-coated concrete slabs before starting the ICCP or GCP experiment. All of the humectants altered the behavior of the thermal-sprayed Zn anodes. LiNO{sub 3} was the most beneficial for ICCP anodes and LiBr was the most beneficial for GCP anodes. Circuit resistances for ICCP anodes and galvanic current density for GCP anodes are compared on the basis of electrochemical aging, humidity, and type of humectant.

  10. Anion exchange polymer coated graphite granule electrodes for improving the performance of anodes in unbuffered microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Li, Dengfeng; Mao, Xuhui; Yu, Eileen Hao; Scott, Keith; Zhang, Enren; Wang, Dihua

    2016-10-01

    In this paper, graphite granule composite electrodes are prepared for microbial fuel cells (MFCs) by coating commercial graphite granules with the mixture of quaternary DABCO polysulfone or Nafion ion exchange polymer and carbon black. The results of electrochemical impedance spectroscopy (EIS) suggest that the addition of carbon black could significantly improve the electrical conductivity of graphite granule anodes. When phosphate buffer solution (PBS) is replaced by NaCl solution, the current densities of the pristine anode, 0.08 g Nafion coated anode and 0.16 g QDPSU coated anode decrease by 52.6%, 20.6% and 10.3% at -0.2 V (vs. Ag/AgCl), respectively. The solution resistance of ion exchange polymer coated anodes is more stable in comparison with that of pristine anode. After 40 operational days, the performance drop of 0.16 g QDPSU coated anode when switching the solution from PBS to NaCl is still smaller than that of pristine anode. However, 0.08 g Nafion coated anode shows the similar performance in NaCl solution to the pristine anode after long term operation. This study reveals that QDPSU anion exchange polymer is more suitable for the anode modification. The QDPSU coated anode promises a great potential for three-dimensional anode based MFCs to treat domestic wastewater.

  11. Performance of Zinc Anodes for Cathodic Protection of Reinforced Concrete Bridges

    SciTech Connect

    Covino, Bernard S. Jr.; Cramer, Stephen D.; Bullard, Sophie J.; Holcomb, Gordon R.; Russell, James H.; Collins, W. Keith; Laylor, Martin H.; Cryer, Curtis B.

    2002-03-01

    Operation of thermal spray zinc (Zn) anodes for cathodic protection (CP) of reinforced concrete structures was investigated in laboratory and field studies conducted by the Albany Research Center (ARC) in collaboration with the Oregon Department of Transportation. The purposes of the research presented in this report were: evaluate the need for preheating concrete to improve the adhesion of the anode; estimate the service life of thermal spray Zn CP anodes; determine the optimum thickness for Zn CP anodes; characterize the anode-concrete interfacial chemistry; and correlate field and laboratory results. Laboratory studies involved accelerated electrochemical aging of thermal sprayed Zn anodes on concrete slabs, some of which were periodically wetted while others were unwetted. Concrete used in the slabs contained either 1.2 or 3 kg NaCl /m3 (2 or 5 lbs NaCl /yd3) as part of the concrete mix design. The Zn anodes were applied to the slabs using the twin wire arc-spray technique. Half of the slabs were preheated to 120-160 C (250-320 F) to improve the initial Zn anode bond strength and the other half were not. Accelerated aging was done at a current density of 0.032 A/m2 (3 mA/ft2), 15 times that used on Oregon DOT Coastal bridges, i.e, . 0.0022 A/m2 (0.2 mA/ft2) Cores from the Cape Creek Bridge (OR), the Richmond San Rafael Bridge (CA), and the East Camino Underpass (CA) were used to study the anode-concrete interfacial chemistry, to relate the chemistry to electrochemical age at the time of sampling, and to compare the chemistry of the field anodes to the chemistry of anodes from the laboratory studies. Cores from a CALTRANS study of a silane sealant used prior to the application of the Zn anodes and cores with galvanized rebar from the Longbird Bridge (Bermuda) were also studied. Aged laboratory and field anodes were characterized by measuring some or all of the following parameters: thickness, bond strength, anode-concrete interfacial chemistry, bulk chemistry

  12. Multi-anode ionization chamber

    DOEpatents

    Bolotnikov, Aleksey E.; Smith, Graham; Mahler, George J.; Vanier, Peter E.

    2010-12-28

    The present invention includes a high-energy detector having a cathode chamber, a support member, and anode segments. The cathode chamber extends along a longitudinal axis. The support member is fixed within the cathode chamber and extends from the first end of the cathode chamber to the second end of the cathode chamber. The anode segments are supported by the support member and are spaced along the longitudinal surface of the support member. The anode segments are configured to generate at least a first electrical signal in response to electrons impinging thereon.

  13. Effect of electrolysis conditions on photocatalytic activities of the anodized TiO{sub 2} films

    SciTech Connect

    Onoda, Kinji; Yoshikawa, Susumu

    2007-12-15

    Photocatalytic activities of anodized TiO{sub 2} films for decomposition of gaseous acetaldehyde were investigated. The anodized TiO{sub 2} films were fabricated by galvanostatic anodization in a mixed electrolyte composed of H{sub 2}SO{sub 4}, H{sub 3}PO{sub 4}, and H{sub 2}O{sub 2}. Pre-nitridation treatment effectively enhanced the photocatalytic activity of the anodized TiO{sub 2} films. The electrolysis parameters such as anodization time, current density, electrolyte temperature, and electrolyte composition significantly affected the photocatalytic activity of the anodized TiO{sub 2} films. The improvement of photocatalytic activity of the anodized films is attributed to increase in surface areas of the anodized specimens. - Graphical abstract: The effect of concentration of H{sub 3}PO{sub 4} on the photocatalytic activity of the anodized TiO{sub 2} films was investigated. The pre-nitrided titanium plates were anodized in electrolyte of 1.5 M H{sub 3}PO{sub 4} and 0.3 M H{sub 2}O{sub 2} with varying H{sub 3}PO{sub 4} concentration in the range from 0 to 0.5 M. The highest photocatalytic activity was obtained at H{sub 3}PO{sub 4} concentration of 0.1 M.

  14. Electrically Conductive Anodized Aluminum Surfaces

    NASA Technical Reports Server (NTRS)

    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 < or = 10(exp 9) Omega-cm. The present treatment does this. The treatment is a direct electrodeposition process in which the outer 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

  15. Nano structural anodes for radiation detectors

    DOEpatents

    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.

  16. SnO2-Based Gas (Methane) Anodes for Electrowinning of Aluminum

    NASA Astrophysics Data System (ADS)

    Xiao, S.; Mokkelbost, T.; Paulsen, O.; Ratvik, A. P.; Haarberg, Geir Martin

    2013-10-01

    SnO2-based and carbon-based gas anodes were studied in molten Na3AlF6-AlF3-Al2O3 at 1123 K (850 °C) for aluminum electrolysis. Methane was introduced to the porous anodes to take part in a three-phase (anode/electrolyte/methane) boundary reaction. Carbon was used as the cathode. It was observed that the anode potential was reduced by 0.6 V and that the current was increased up to three times in galvanostatic and potentiostatic tests after the introduction of methane on SnO2-based anodes. A measurable depolarization effect and lower consumption of carbon after the introduction of methane on carbon anodes were also demonstrated.

  17. Cu--Ni--Fe anode for use in aluminum producing electrolytic cell

    DOEpatents

    Bergsma, S. Craig; Brown, Craig W.; Bradford, Donald R; Barnett, Robert J.; Mezner, Michael B.

    2006-07-18

    A method of producing aluminum in an electrolytic cell containing alumina dissolved in an electrolyte, the method comprising the steps of providing a molten salt electrolyte at a temperature of less than 900.degree. C. having alumina dissolved therein in an electrolytic cell having a liner for containing the electrolyte, the liner having a bottom and walls extending upwardly from said bottom. A plurality of non-consumable Cu--Ni--Fe anodes and cathodes are disposed in a vertical direction in the electrolyte, the cathodes having a plate configuration and the anodes having a flat configuration to compliment the cathodes. The anodes contain apertures therethrough to permit flow of electrolyte through the apertures to provide alumina-enriched electrolyte between the anodes and the cathodes. Electrical current is passed through the anodes and through the electrolyte to the cathodes, depositing aluminum at the cathodes and producing gas at the anodes.

  18. Effect of Anode Floating Voltage and its Applications in Characterizing Silicon Drift Detectors

    NASA Astrophysics Data System (ADS)

    Wu, Guang-Guo; Li, Hong-Ri; Liang, Kun; Yang, Ru; Cao, Xue-Lei; Wang, Huan-Yu; An, Jun-Ming; Hu, Xiong-Wei; Han, De-Jun

    2009-04-01

    Anode Boating voltage is predicted and investigated for silicon drift detectors (SDDs) with an active area of 5 mm2 fabricated by a double-side parallel technology. It is demonstrated that the anode Boating voltage increases with the increasing inner ring voltage, and is almost unchanged with the external ring voltage. The anode Boating voltage will not be affected by the back electrode biased voltage until it reaches the full-depleted voltage (-50 V) of the SDD. Theoretical analysis and experimental results show that the anode Boating voltage is equal to the sum of the inner ring voltage and the built-in potential between the p+ inner ring and the n+ anode. A fast checking method before detector encapsulation is proposed by employing the anode Boating voltage along with checking the leakage current, potential distribution and drift properties.

  19. Anodized Steel Electrodes for Supercapacitors.

    PubMed

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

    2016-03-01

    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. PMID:26891093

  20. Anodized Steel Electrodes for Supercapacitors.

    PubMed

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

    2016-03-01

    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.

  1. Formation of self-organized nanoporous anodic oxide from metallic gallium.

    PubMed

    Pandey, Bipin; Thapa, Prem S; Higgins, Daniel A; Ito, Takashi

    2012-09-25

    This paper reports the formation of self-organized nanoporous gallium oxide by anodization of solid gallium metal. Because of its low melting point (ca. 30 °C), metallic gallium can be shaped into flexible structures, permitting the fabrication of nanoporous anodic oxide monoliths within confined spaces like the inside of a microchannel. Here, solid gallium films prepared on planar substrates were employed to investigate the effects of anodization voltage (1, 5, 10, 15 V) and H(2)SO(4) concentration (1, 2, 4, 6 M) on anodic oxide morphology. Self-organized nanopores aligned perpendicular to the film surface were obtained upon anodization of gallium films in ice-cooled 4 and 6 M aqueous H(2)SO(4) at 10 and 15 V. Nanopore formation could be recognized by an increase in anodic current after a current decrease reflecting barrier oxide formation. The average pore diameter was in the range of 18-40 nm with a narrow diameter distribution (relative standard deviation ca. 10-20%), and was larger at lower H(2)SO(4) concentration and higher applied voltage. The maximum thickness of nanoporous anodic oxide was ca. 2 μm. In addition, anodic formation of self-organized nanopores was demonstrated for a solid gallium monolith incorporated at the end of a glass capillary. Nanoporous anodic oxide monoliths formed from a fusible metal will lead to future development of unique devices for chemical sensing and catalysis.

  2. Diagnostic Setup for Characterization of Near-Anode Processes in Hall Thrusters

    SciTech Connect

    L. Dorf; Y. Raitses; N.J. Fisch

    2003-09-08

    A diagnostic setup for characterization of near-anode processes in Hall-current plasma thrusters consisting of biased and emissive electrostatic probes, high-precision positioning system and low-noise electronic circuitry was developed and tested. Experimental results show that radial probe insertion does not cause perturbations to the discharge and therefore can be used for accurate near-anode measurements.

  3. A Thermally Conductive Separator for Stable Li Metal Anodes.

    PubMed

    Luo, Wei; Zhou, Lihui; Fu, Kun; Yang, Zhi; Wan, Jiayu; Manno, Michael; Yao, Yonggang; Zhu, Hongli; Yang, Bao; Hu, Liangbing

    2015-09-01

    Li metal anodes have attracted considerable research interest due to their low redox potential (-3.04 V vs standard hydrogen electrode) and high theoretical gravimetric capacity of 3861 mAh/g. Battery technologies using Li metal anodes have shown much higher energy density than current Li-ion batteries (LIBs) such as Li-O2 and Li-S systems. However, issues related to dendritic Li formation and low Coulombic efficiency have prevented the use of Li metal anode technology in many practical applications. In this paper, a thermally conductive separator coated with boron-nitride (BN) nanosheets has been developed to improve the stability of the Li metal anodes. It is found that using the BN-coated separator in a conventional organic carbonate-based electrolyte results in the Coulombic efficiency stabilizing at 92% over 100 cycles at a current rate of 0.5 mA/cm(2) and 88% at 1.0 mA/cm(2). The improved Coulombic efficiency and reliability of the Li metal anodes is due to the more homogeneous thermal distribution resulting from the thermally conductive BN coating and to the smaller surface area of initial Li deposition. PMID:26237519

  4. A Thermally Conductive Separator for Stable Li Metal Anodes.

    PubMed

    Luo, Wei; Zhou, Lihui; Fu, Kun; Yang, Zhi; Wan, Jiayu; Manno, Michael; Yao, Yonggang; Zhu, Hongli; Yang, Bao; Hu, Liangbing

    2015-09-01

    Li metal anodes have attracted considerable research interest due to their low redox potential (-3.04 V vs standard hydrogen electrode) and high theoretical gravimetric capacity of 3861 mAh/g. Battery technologies using Li metal anodes have shown much higher energy density than current Li-ion batteries (LIBs) such as Li-O2 and Li-S systems. However, issues related to dendritic Li formation and low Coulombic efficiency have prevented the use of Li metal anode technology in many practical applications. In this paper, a thermally conductive separator coated with boron-nitride (BN) nanosheets has been developed to improve the stability of the Li metal anodes. It is found that using the BN-coated separator in a conventional organic carbonate-based electrolyte results in the Coulombic efficiency stabilizing at 92% over 100 cycles at a current rate of 0.5 mA/cm(2) and 88% at 1.0 mA/cm(2). The improved Coulombic efficiency and reliability of the Li metal anodes is due to the more homogeneous thermal distribution resulting from the thermally conductive BN coating and to the smaller surface area of initial Li deposition.

  5. An analytical model for liquid-anode and vapor-anode AMTEC converters

    SciTech Connect

    Tournier, Jean-Michel; El-Genk, Mohamed S.; Schuller, Michael; Hausgen, Paul

    1997-01-10

    This paper describes a lumped analytical model of liquid-anode single-tube and vapor-anode multi-tube AMTEC cells. The model results agreed well with experimental data for Mo, NbN and TiN electrodes. Results showed that Mo and NbN electrodes exhibit high B values between 400 and 600 A.K{sup 1/2}/Pa.m{sup 2}, and have the potential for peak power densities slightly above 1 W/cm{sup 2}, with efficiencies as high as 28%. In contrast, TiN electrodes have lower temperature-independent exchange currents, between 120 and 135 A.K{sup 1/2}/Pa.m{sup 2}, lower peak power densities between 0.5 and 0.75 W/cm{sup 2}, and efficiencies below 24% at a BASE temperature of 1200 K. These values of B compare well with that reported by other investigators.

  6. Effects of Li4Ti5O12 Anode Electrode Thickness on the Cell Balancing of Hybrid Super Capacitor.

    PubMed

    Lee, Jong-Kyu; Yoon, Jung-Rag

    2015-03-01

    The hybrid super capacitor was prepared by controlling the anode electrode thickness to optimize cell balancing. With an increasing anode electrode thickness, the internal resistance increased, while the capacitance was not changed remarkably. The potential of the cathode increased and that of the anode was decreased with the working voltage. However, the potential variation of the cathode was larger than that of the anode due to the difference in the reaction mechanism of the cathode and anode. The discharge capacity retention as a function of the current rates increased and the cycle performance was improved with an increasing anode electrode thickness. The effects of the anode electrode thickness on the electrode potential are also discussed.

  7. Development of an inert ceramic anode to reduce energy consumption in magnesium production. Final Report

    SciTech Connect

    1997-06-01

    The objective of this work is to develop a dimensionally stable ceramic anode for production of magnesium metal in electrolytic cells, replacing the graphite anodes currently used by The Dow Chemical Company magnesium business. The work is based on compositional and design technology for a ceramic anode developed in the former Central Research Inorganic Laboratory. The approach selected is to use a ceramic semiconductor tube as the material to interface with the bath and gaseous atmosphere in the cell. The testing goal was to demonstrate six anodes surviving a 30 day test lifetime with acceptable wear rates and electrical performance in a laboratory scale magnesium cell test. State of the art slip casting techniques were used and advanced in the pursuit of a virtually flaw free ceramic anode shell. Novel core materials were also invented to allow for the complete, crack free fabrication of the laboratory scale anode. Two successive anodes were tested and exceeded the 30 day cell lifetime goal with excellent wear characteristics. More aggressive testing of the ceramic anode revealed that the anode had a rather narrow operating region.

  8. Electrode patterns in arc discharge simulations: effect of anode cooling

    NASA Astrophysics Data System (ADS)

    Trelles, Juan Pablo

    2014-10-01

    Self-organized electrode patterns are often observed experimentally in diverse types of electrical discharges, including atmospheric-pressure electric arcs, but rarely captured in general-purpose computational plasma dynamics simulations. Time-dependent three-dimensional thermodynamic non-equilibrium (two-temperature) simulations reveal the spontaneous formation of self-organized anode attachment spot patterns in the free-burning arc, a canonical direct-current (dc) discharge with an axisymmetric electrode configuration and the absence of external forcing. The simulations are based on a monolithic fluid-electromagnetic plasma flow model numerically implemented within a second-order-accurate in space and time variational multiscale finite element framework. Simulation results show the gradual emergence of spot patterns with increasing levels of anode cooling: from a single diffuse spot for low cooling levels to the eventual coverage of the anode region by small spots for intense cooling. The characteristics of the patterns, such as the number, size and location of the spots, markedly depend on the imposed total current. Furthermore, the patterns transition from steady to dynamic with decreasing total current for high cooling levels. The pattern dynamics show the formation of new spots by the splitting of old ones occurring in the center of the plasma, as well as the movement and eventual extinction of spots at the plasma boundaries. The different types of anode patterns (from diffuse to self-organized spots) have a significant effect on the total voltage drop across the plasma column, but a minor effect on other plasma characteristics away from the anode region. The results indicate that thermal instability together with equilibration between heavy-species and electron energy have a dominant role in the formation of anode patterns in arc discharges.

  9. Alternative Anodes for the Electrolytic Reduction of Uranium Dioxide

    NASA Astrophysics Data System (ADS)

    Merwin, Augustus

    Reprocessing of spent nuclear fuel is an essential step in closing the nuclear fuel cycle. In order to consume current stockpiles, ceramic uranium dioxide spent nuclear fuel will be subjected to an electrolytic reduction process. The current reduction process employs a platinum anode and a stainless steel alloy 316 cathode in a molten salt bath consisting of LiCl-2wt% Li 2O and occurs at 700°C. A major shortcoming of the existing process is the degradation of the platinum anode under the severely oxidizing conditions encountered during electrolytic reduction. This work investigates alternative anode materials for the electrolytic reduction of uranium oxide. The high temperature and extreme oxidizing conditions encountered in these studies necessitated a unique set of design constraints on the system. Thus, a customized experimental apparatus was designed and constructed. The electrochemical experiments were performed in an electrochemical reactor placed inside a furnace. This entire setup was housed inside a glove box, in order to maintain an inert atmosphere. This study investigates alternative anode materials through accelerated corrosion testing. Surface morphology was studied using scanning electron microscopy. Surface chemistry was characterized using energy dispersive spectroscopy and Raman spectroscopy. Electrochemical behavior of candidate materials was evaluated using potentiodynamic polarization characteristics. After narrowing the number of candidate electrode materials, ferrous stainless steel alloy 316, nickel based Inconel 718 and elemental tungsten were chosen for further investigation. Of these materials only tungsten was found to be sufficiently stable at the anodic potential required for electrolysis of uranium dioxide in molten salt. The tungsten anode and stainless steel alloy 316 cathode electrode system was studied at the required reduction potential for UO2 with varying lithium oxide concentrations. Electrochemical impedance spectroscopy

  10. Anode-plasma expansion in pinch-reflex diodes

    SciTech Connect

    Colombant, D.G.; Goldstein, S.A.

    1983-10-24

    Anode-plasma expansion in pinch-reflex diodes is investigated with use of a one-dimensional magnetohydrodynamic model. Early in time, the plasma undergoes thermal expansion and its front is slowed down as a result of j x B. After the current has reached its maximum and for small radius where j and B are larger, j x B may accelerate the bulk of the anode plasma to large velocities. Good qualitative agreement is obtained with observations of the time dependence of the plasma velocity as well as its radial profile. The maximum expansion velocities reach tens of centimeters per microsecond.

  11. Structured photoluminescence spectrum in laterally anodized porous silicon

    NASA Astrophysics Data System (ADS)

    Fujiwara, Yasufumi; Nishitani, Hikaru; Nakata, Hiroyasu; Ohyama, Tyuzi

    1992-12-01

    Visible photoluminescence (PL) has been systematically investigated in laterally anodized porous silicon. The PL peak position was dependent on the distance from the meniscus and shifted towards a shorter wavelength with increasing anodization current density. A PL spectrum exhibiting several structures was observed inside the mirrorlike region on the sample surface, which was interpreted by multiple reflection of the luminescence, not by the quantum size effects. Through the analysis of the PL spectrum, the Si density of the porous layer was roughly estimated to be 37 percent by means of the effective-medium model.

  12. Alternative Anode Reaction for Copper Electrowinning

    SciTech Connect

    Not Available

    2005-07-01

    This report describes a project funded by the Department of Energy, with additional funding from Bechtel National, to develop a copper electrowinning process with lower costs and lower emissions than the current process. This new process also includes more energy efficient production by using catalytic-surfaced anodes and a different electrochemical couple in the electrolyte, providing an alternative oxidation reaction that requires up to 50% less energy than is currently required to electrowin the same quantity of copper. This alternative anode reaction, which oxidizes ferric ions to ferrous, with subsequent reduction back to ferric using sulfur dioxide, was demonstrated to be technically and operationally feasible. However, pure sulfur dioxide was determined to be prohibitively expensive and use of a sulfur burner, producing 12% SO{sub 2}, was deemed a viable alternative. This alternate, sulfur-burning process requires a sulfur burner, waste heat boiler, quench tower, and reaction towers. The electrolyte containing absorbed SO{sub 2} passes through activated carbon to regenerate the ferrous ion. Because this reaction produces sulfuric acid, excess acid removal by ion exchange is necessary and produces a low concentration acid suitable for leaching oxide copper minerals. If sulfide minerals are to be leached or the acid unneeded on site, hydrogen was demonstrated to be a potential reductant. Preliminary economics indicate that the process would only be viable if significant credits could be realized for electrical power produced by the sulfur burner and for acid if used for leaching of oxidized copper minerals on site.

  13. The effects of microstructure on the corrosion of glycine/nitrate processed cermet inert anodes: A preliminary study

    SciTech Connect

    Windisch, Jr, C F; Chick, L A; Maupin, G D; Stice, N D

    1991-07-01

    The Inert Electrodes Program at the Pacific Northwest Laboratory (PNL) is supported by the Office of Industrial Processes of the US Department of Energy and is aimed at improving the energy efficiency of Hall-Heroult cells through the development of inert anodes. The inert anodes currently under the study are composed of a cermet material of the general composition NiO-NiFe{sub 2}O{sub 4}-Cu. The program has three primary objectives: (a) to evaluate the anode material in a scaled-up, pilot cell facility, (b) to investigate the mechanisms of the electrochemical reactions at the anodes surface, and (c) to develop sensors for monitoring various anode and/or electrolyte conditions. This report covers the results of a portion of the studies on anode reaction mechanisms. The anode mechanism studies were focused in four areas in FY 1990 and FY 1991: (a) the determination of whether a film formed on cermet inert anodes and (if it existed) the characterization of this film, (b) the determination of the sources of the anode impedance, (c) the evaluation of the effects of silica and a precorroded state on anode corrosion, and (d) a preliminary study on the effect of microstructure on the corrosion properties of the anodes. This report discusses the results of the microstructure studies. 6 refs., 32 figs., 3 tabs.

  14. Recent Progress of Nanostructure Modified Anodes in Microbial Fuel Cells.

    PubMed

    Kim, Marie; Kim, Hyeon Woo; Nam, Joo-Youn; In, Su-Il

    2015-09-01

    Microbial fuel cell (MFC) is a bio-electrochemical system which converts chemical energy into electrical energy by catalytic activity of microorganisms. Electrons produced by microbial oxidation from substrates such as organic matter, complex or renewable biomass are transferred to the anode. Protons produced at the anode migrate to the cathode via the wire and combine with oxygen to form water. Therefore MFC technologies are promising approach for generating electricity or hydrogen gas and wastewater treatment. Electrode materials are one of the keys to increase the power output of MFCs. To improve the cost effective performance of MFCs, various electrodes materials, modifications and configurations have been developed. In this paper, among other recent advances of nanostructured electrodes, especially carbon based anodes, are highlighted. The properties of these electrodes, in terms of surface characteristics, conductivity, modifications, and options were reviewed. The applications, challenges and perspectives of the current MFCs electrode for future development in bio or medical field are briefly discussed. PMID:26716261

  15. Recent Progress of Nanostructure Modified Anodes in Microbial Fuel Cells.

    PubMed

    Kim, Marie; Kim, Hyeon Woo; Nam, Joo-Youn; In, Su-Il

    2015-09-01

    Microbial fuel cell (MFC) is a bio-electrochemical system which converts chemical energy into electrical energy by catalytic activity of microorganisms. Electrons produced by microbial oxidation from substrates such as organic matter, complex or renewable biomass are transferred to the anode. Protons produced at the anode migrate to the cathode via the wire and combine with oxygen to form water. Therefore MFC technologies are promising approach for generating electricity or hydrogen gas and wastewater treatment. Electrode materials are one of the keys to increase the power output of MFCs. To improve the cost effective performance of MFCs, various electrodes materials, modifications and configurations have been developed. In this paper, among other recent advances of nanostructured electrodes, especially carbon based anodes, are highlighted. The properties of these electrodes, in terms of surface characteristics, conductivity, modifications, and options were reviewed. The applications, challenges and perspectives of the current MFCs electrode for future development in bio or medical field are briefly discussed.

  16. Battery with modular air cathode and anode cage

    DOEpatents

    Niksa, Marilyn J.; Pohto, Gerald R.; Lakatos, Leslie K.; Wheeler, Douglas J.; Niksa, Andrew J.; Schue, Thomas J.; Turk, Thomas R.

    1988-01-01

    A battery assembly of the consumable metal anode type has now been constructed for ready assembly as well as disassembly. In a non-conductive and at least substantially inert cell body, space is provided for receiving an open-structured, non-consumable anode cage. The cage has an open top for facilitating insertion of an anode. A modular cathode is used, comprising a peripheral current conductor frame clamped about a grid reinforced air cathode in sheet form. The air cathode may be double gridded. The cathode frame can be sealed, during assembly, with electrolyte-resistant-sealant as well as with adhesive. The resulting cathode module can be assembled outside the cell body and readily inserted therein, or can later be easily removed therefrom.

  17. Battery with modular air cathode and anode cage

    DOEpatents

    Niksa, Marilyn J.; Pohto, Gerald R.; Lakatos, Leslie K.; Wheeler, Douglas J.; Niksa, Andrew J.; Schue, Thomas J.

    1987-01-01

    A battery assembly of the consumable metal anode type has now been constructed for ready assembly as well as disassembly. In a non-conductive and at least substantially inert cell body, space is provided for receiving an open-structured, non-consumable anode cage. The cage has an open top for facilitating insertion of an anode. A modular cathode is used, comprising a peripheral current conductor frame clamped about a grid reinforced air cathode in sheet form. The air cathode may be double gridded. The cathode frame can be sealed, during assembly, with electrolyte-resistant-sealant as well as with adhesive. The resulting cathode module can be assembled outside the cell body and readily inserted therein, or can later be easily removed therefrom.

  18. Nanostructured Anodic Multilayer Dielectric Stacked Metal-Insulator-Metal Capacitors.

    PubMed

    Karthik, R; Kannadassan, D; Baghini, Maryam Shojaei; Mallick, P S

    2015-12-01

    This paper presents the fabrication of Al2O3/TiO2/Al2O3 metal-insulator-metal (MIM) capacitor using anodization technique. High capacitance density of > 3.5 fF/μm2, low quadratic voltage coefficient of capacitance of < 115 ppm/V2 and a low leakage current density of 4.457 x 10(-11) A/cm2 at 3 V are achieved which are suitable for analog and mixed signal applications. We found that the anodization voltage played a major role in electrical and structural properties of the thin film. This work suggests that the anodization method can offer crystalline multilayer dielectric stack required for high performance MIM capacitor.

  19. Tested Demonstrations: Dyeing of Anodized Aluminum.

    ERIC Educational Resources Information Center

    Gilbert, George L., Ed.

    1983-01-01

    Provides a list of needed materials, required preparations, and instructions for demonstrating the dyeing of anodized aluminum. Discusses the chemistry involved and gives equations for reactions occurring at the anode and cathode. (JM)

  20. Anodes for Rechargeable Lithium-Sulfur Batteries

    SciTech Connect

    Cao, Ruiguo; Xu, Wu; Lu, Dongping; Xiao, Jie; Zhang, Jiguang

    2015-04-10

    In this work, we will review the recent developments on the protection of Li metal anode in Li-S batteries. Various strategies used to minimize the corrosion of Li anode and reducing its impedance increase will be analyzed. Other potential anodes used in sulfur based rechargeable batteries will also be discussed.

  1. Anode Fall Formation in a Hall Thruster

    SciTech Connect

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

    2004-06-29

    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.

  2. Anode binders for electrochemical cells

    SciTech Connect

    Ismail, M.I.

    1986-08-26

    An electrochemical cell is described comprised of an alkaline electrolyte, a manganese dioxide cathode and a gelled anode comprised of mercury amalgamated zinc, a starch graft copolymer gelling agent and a liquid petrolatum binder in amounts between 0.02% to 0.2% by weight thereof.

  3. Electrochemical cell with calcium anode

    DOEpatents

    Cooper, John F.; Hosmer, Pamela K.; Kelly, Benjamin E.

    1979-01-01

    An electrochemical cell comprising a calcium anode and a suitable cathode in an alkaline electrolyte consisting essentially of an aqueous solution of an hydroxide and a chloride. Specifically disclosed is a mechanically rechargeable calcium/air fuel cell with an aqueous NaOH/NaCl electrolyte.

  4. Improving the flexibility of microbial desalination cells through spatially decoupling anode and cathode.

    PubMed

    Ping, Qingyun; He, Zhen

    2013-09-01

    To improve the flexibility of microbial desalination cell (MDC) construction and operation, a new configuration with decoupled anode and cathode was developed and examined in this study. A higher salt concentration resulted in higher current generation, as well as a higher salt removal rate. The effect of the distance between the anode and the cathode on the MDC performance was not obvious, likely due to a sufficient conductivity in the salt solution. Because the cathode was identified as a limiting factor, adding one more cathode unit increased the current generation from 72.3 to 116.0 A/m(3), while installing additional anode units did not obviously alter the MDC current production. Changing the position of the anode/cathode units exhibited a weak influence on the MDC performance. Parallel connection of electrical circuits generally produced more current than the individual connections, and a strong competition was observed between multiple units sharing the same opposite unit.

  5. Effect of alloying elements Al and Ca on corrosion resistance of plasma anodized Mg alloys

    NASA Astrophysics Data System (ADS)

    Anawati, Asoh, Hidetaka; Ono, Sachiko

    2016-04-01

    Plasma anodizing is a surface treatment used to form a ceramic-type oxide film on Mg alloys by the application of a high anodic voltage to create intense plasma near the metal surface. With proper selection of the process parameters, the technique can produce high quality oxide with superior adhesion, corrosion resistance, micro-hardness, wear resistance and strength. The effect of alloying element Al on plasma anodizing process of Mg alloys was studied by comparing the anodizing curves of pure Mg, AZ31, and AZ61 alloys while the effect of Ca were studied on AZ61 alloys containing 0, 1, and 2 wt% Ca. Anodizing was performed in 0.5 M Na3PO4 solution at a constant current density of 200 Am-2 at 25°C. Anodic oxide films with lava-like structure having mix composition of amorphous and crystal were formed on all of the alloys. The main crystal form of the oxide was Mg3(PO4)2 as analyzed by XRD. Alloying elements Al and Ca played role in modifying the plasma lifetime during anodization. Al tended to extend the strong plasma lifetime and therefore accelerated the film thickening. The effect of Ca on anodizing process was still unclear. The anodic film thickness and chemical composition were altered by the presence of Ca in the alloys. Electrochemical corrosion test in 0.9% NaCl solution showed that the corrosion behavior of the anodized specimens depend on the behavior of the substrate. Increasing Al and Ca content in the alloys tended to increase the corrosion resistance of the specimens. The corrosion resistance of the anodized specimens improved significantly about two orders of magnitude relative to the bare substrate.

  6. Increased performance of a tubular microbial fuel cell with a rotating carbon-brush anode.

    PubMed

    Liao, Qiang; Zhang, Jun; Li, Jun; Ye, Dingding; Zhu, Xun; Zhang, Biao

    2015-01-15

    A novel method was proposed to improve the power output of microbial fuel cells (MFCs) by rotating the carbon-brush anode. The MFC with a rotating anode produced a peak power density of 210±3 W/m(3) and a maximum current density of 945±43 A/m(3), 1.4 and 2.7 times higher than those of the non-rotating case, respectively. The difference of the electrochemical impedance spectroscopy and cyclic voltammetry before and after anode rotation clearly suggested that the mass transfer to the spiral space was enhanced by the rotating anode. Furthermore, Tafel plots analysis also revealed that the rotating anode can improve the electrochemical activity of the biofilm. PMID:25168763

  7. Increased performance of a tubular microbial fuel cell with a rotating carbon-brush anode.

    PubMed

    Liao, Qiang; Zhang, Jun; Li, Jun; Ye, Dingding; Zhu, Xun; Zhang, Biao

    2015-01-15

    A novel method was proposed to improve the power output of microbial fuel cells (MFCs) by rotating the carbon-brush anode. The MFC with a rotating anode produced a peak power density of 210±3 W/m(3) and a maximum current density of 945±43 A/m(3), 1.4 and 2.7 times higher than those of the non-rotating case, respectively. The difference of the electrochemical impedance spectroscopy and cyclic voltammetry before and after anode rotation clearly suggested that the mass transfer to the spiral space was enhanced by the rotating anode. Furthermore, Tafel plots analysis also revealed that the rotating anode can improve the electrochemical activity of the biofilm.

  8. Improved Anode for a Direct Methanol Fuel Cell

    NASA Technical Reports Server (NTRS)

    Valdez, Thomas; Narayanan, Sekharipuram

    2005-01-01

    A modified chemical composition has been devised to improve the performance of the anode of a direct methanol fuel cell. The main feature of the modified composition is the incorporation of hydrous ruthenium oxide into the anode structure. This modification can reduce the internal electrical resistance of the cell and increase the degree of utilization of the anode catalyst. As a result, a higher anode current density can be sustained with a smaller amount of anode catalyst. These improvements can translate into a smaller fuel-cell system and higher efficiency of conversion. Some background information is helpful for understanding the benefit afforded by the addition of hydrous ruthenium oxide. The anode of a direct methanol fuel cell sustains the electro-oxidation of methanol to carbon dioxide in the reaction CH3OH + H2O--->CO2 + 6H(+) + 6e(-). An electrocatalyst is needed to enable this reaction to occur. The catalyst that offers the highest activity is an alloy of approximately equal numbers of atoms of the noble metals platinum and ruthenium. The anode is made of a composite material that includes high-surface-area Pt/Ru alloy particles and a proton-conducting ionomeric material. This composite is usually deposited onto a polymer-electrolyte (proton-conducting) membrane and onto an anode gas-diffusion/current-collector sheet that is subsequently bonded to the proton-conducting membrane by hot pressing. Heretofore, the areal density of noble-metal catalyst typically needed for high performance has been about 8 mg/cm2. However, not all of the catalyst has been utilized in the catalyzed electro-oxidation reaction. Increasing the degree of utilization of the catalyst would make it possible to improve the performance of the cell for a given catalyst loading and/or reduce the catalyst loading (thereby reducing the cost of the cell). The use of carbon and possibly other electronic conductors in the catalyst layer has been proposed for increasing the utilization of the

  9. Novel Sulfur-Tolerant Anodes for Solid Oxide Fuel Cells

    SciTech Connect

    Lei Yang; Meilin Liu

    2008-12-31

    One of the unique advantages of SOFCs over other types of fuel cells is the potential for direct utilization of hydrocarbon fuels (it may involve internal reforming). Unfortunately, most hydrocarbon fuels contain sulfur, which would dramatically degrade SOFC performance at parts-per-million (ppm) levels. Low concentration of sulfur (ppm or below) is difficult to remove efficiently and cost-effectively. Therefore, knowing the exact poisoning process for state-of-the-art anode-supported SOFCs with Ni-YSZ cermet anodes, understanding the detailed anode poisoning mechanism, and developing new sulfur-tolerant anodes are essential to the promotion of SOFCs that run on hydrocarbon fuels. The effect of cell operating conditions (including temperature, H{sub 2}S concentration, cell voltage/current density, etc.) on sulfur poisoning and recovery of nickel-based anode in SOFCs was investigated. It was found that sulfur poisoning is more severe at lower temperature, higher H{sub 2}S concentration or lower cell current density (higher cell voltage). In-situ Raman spectroscopy identified the nickel sulfide formation process on the surface of a Ni-YSZ electrode and the corresponding morphology change as the sample was cooled in H{sub 2}S-containing fuel. Quantum chemical calculations predicted a new S-Ni phase diagram with a region of sulfur adsorption on Ni surfaces, corresponding to sulfur poisoning of Ni-YSZ anodes under typical SOFC operating conditions. Further, quantum chemical calculations were used to predict the adsorption energy and bond length for sulfur and hydrogen atoms on various metal surfaces. Surface modification of Ni-YSZ anode by thin Nb{sub 2}O{sub 5} coating was utilized to enhance the sulfur tolerance. A multi-cell testing system was designed and constructed which is capable of simultaneously performing electrochemical tests of 12 button cells in fuels with four different concentrations of H{sub 2}S. Through systematical study of state-of-the-art anode

  10. Integrated main rail, feed rail, and current collector

    DOEpatents

    Petri, Randy J.; Meek, John; Bachta, Robert P.; Marianowski, Leonard G.

    1994-01-01

    A separator plate for a fuel cell comprising an anode current collector, a cathode current collector and a main plate, the main plate disposed between the anode current collector and the cathode current collector. The anode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the anode side of the separator plate and the cathode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the cathode side of the separator plate. In this manner, the number of components required to manufacture and assemble a fuel cell stack is reduced.

  11. Integrated main rail, feed rail, and current collector

    DOEpatents

    Petri, R.J.; Meek, J.; Bachta, R.P.; Marianowski, L.G.

    1994-11-08

    A separator plate is described for a fuel cell comprising an anode current collector, a cathode current collector and a main plate, the main plate disposed between the anode current collector and the cathode current collector. The anode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the anode side of the separator plate and the cathode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the cathode side of the separator plate. In this manner, the number of components required to manufacture and assemble a fuel cell stack is reduced. 9 figs.

  12. Probing anode degradation in automotive Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Kwon, Ou Jung

    circumstances, no more Li+ ions can be intercalated but should be reduced to metallic form on the anode particle surface. This is validated by calculating the distribution of Li concentration inside the anode particle with electrochemical modeling. In part three, a novel pulse charge protocol is developed, which consists of two steps. First high current charge/discharge pulses increase the cell temperature from a subzero temperature up to above room temperature in a short time, and next, high current charge provides the net charge capacity. Sluggish Li diffusion at low temperature becomes fast thanks to cell temperature elevation by high current pulses (1st step), which plays a role of preventing surface saturation during high current charge (2nd step). Thus, this charge protocol is not only Li deposition-free but also leads to rapid charge at subzero temperatures.

  13. [Vernier Anode Design and Image Simulation].

    PubMed

    Zhao, Ai-rong; Ni, Qi-liang; Song, Ke-fei

    2015-12-01

    Based-MCP position-sensitive anode photon-counting imaging detector is good at detecting extremely faint light, which includes micro-channel plate (MCP), position-sensitive anode and readout, and the performances of these detectors are mainly decided by the position-sensitive anode. As a charge division anode, Vernier anode using cyclically varying electrode areas which replaces the linearly varying electrodes of wedge-strip anode can get better resolution and greater electrode dynamic range. Simulation and design of the Vernier anode based on Vernier's decode principle are given here. Firstly, we introduce the decode and design principle of Vernier anode with nine electrodes in vector way, and get the design parameters which are the pitch, amplitude and the coarse wavelength of electrode. Secondly, we analyze the effect of every design parameters to the imaging of the detector. We simulate the electron cloud, the Vernier anode and the detector imaging using Labview software and get the relationship between the pitch and the coarse wavelength of the anode. Simultaneously, we get the corresponding electron cloud for the designing parameters. Based on the result of the simulation and the practical machining demand, a nine electrodes Vernier anode was designed and fabricated which has a pitch of 891 µm, insulation width of 25 µm, amplitude of 50 µm, coarse pixel numbers of 5. PMID:26964205

  14. [Vernier Anode Design and Image Simulation].

    PubMed

    Zhao, Ai-rong; Ni, Qi-liang; Song, Ke-fei

    2015-12-01

    Based-MCP position-sensitive anode photon-counting imaging detector is good at detecting extremely faint light, which includes micro-channel plate (MCP), position-sensitive anode and readout, and the performances of these detectors are mainly decided by the position-sensitive anode. As a charge division anode, Vernier anode using cyclically varying electrode areas which replaces the linearly varying electrodes of wedge-strip anode can get better resolution and greater electrode dynamic range. Simulation and design of the Vernier anode based on Vernier's decode principle are given here. Firstly, we introduce the decode and design principle of Vernier anode with nine electrodes in vector way, and get the design parameters which are the pitch, amplitude and the coarse wavelength of electrode. Secondly, we analyze the effect of every design parameters to the imaging of the detector. We simulate the electron cloud, the Vernier anode and the detector imaging using Labview software and get the relationship between the pitch and the coarse wavelength of the anode. Simultaneously, we get the corresponding electron cloud for the designing parameters. Based on the result of the simulation and the practical machining demand, a nine electrodes Vernier anode was designed and fabricated which has a pitch of 891 µm, insulation width of 25 µm, amplitude of 50 µm, coarse pixel numbers of 5.

  15. Fabrication of advanced design (grooved) cermet anodes

    NASA Astrophysics Data System (ADS)

    Windisch, C. F., Jr.; Huettig, F. R.

    1993-05-01

    Attempts were made to fabricate full-size anodes with advanced, or grooved, design using isostatic pressing, slip casting injection molding. Of the three approaches, isostatic pressing produced an anode with dimensions nearest to the target specifications, without serious macroscopic flaws. This approach is considered the most promising for making advanced anodes for aluminum smelting. However, significant work still remains to optimize the physical properties and microstructure of the anode, both of which were significantly different from that of previous anodes. Injection molding and slip casting yielded anode materials with serious deficiencies, including cracks and holes. Injection molding gave cermet material with the best intrinsic microstructure, i.e., the microstructure of the material between macroscopic flaws was very similar to that of anodes previously made at PNL. The reason for the similarity may have to do with amount of residual binder in the material prior to sintering.

  16. Fabrication of advanced design (grooved) cermet anodes

    SciTech Connect

    Windisch, C.F. Jr.; Huettig, F.R.

    1993-05-01

    Attempts were made to fabricate full-size anodes with advanced, or grooved, design using isostatic pressing, slip casting injection molding. Of the three approaches, isostatic pressing produced an anode with dimensions nearest to the target specifications, without serious macroscopic flaws. This approach is considered the most promising for making advanced anodes for aluminum smelting. However, significant work still remains to optimize the physical properties and microstructure of the anode, both of which were significantly different from that of previous anodes. Injection molding and slip casting yielded anode materials with serious deficiencies, including cracks and holes. Injection molding gave cermet material with the best intrinsic microstructure, i.e., the microstructure of the material between macroscopic flaws was very similar to that of anodes previously made at PNL. Reason for the similarity may have to do with amount of residual binder in the material prior to sintering.

  17. Anode spots acting as independent self-organized systems

    SciTech Connect

    Biborosch, L.; Toma, M.; Sanduloviciu, M.

    1995-12-31

    The time averaged current-voltage (I-V) characteristics between two anodes A and P of a glow discharge in helium were taken by means of a circuit containing a dc voltage supply U{sub 12} and a small load resistor R{sub 1} or only a variable load resistor R{sub v}. Here the current I{sub 1}, through the movable wire anode P (0, 1 mm in diameter and 2,5 mm in length) were measured versus their bias voltage U{sub 12} in respect to the grounded hollow anode A. Fig. 2 shows the profiles of the I-V characteristics obtained for different axial distances d{sub p} between A and P. Thus, we have introduced two new external parameters, namely the axial distance d{sub p} and the voltage bias U{sub 12} (or the load resistor R{sub v}) to control the occurrence and features of the coherent and well defined nearly spherical anode spots, formed in front of A or around the wire P, respectively.

  18. Experimental breakdown of selected anodized aluminum samples in dilute plasmas

    NASA Technical Reports Server (NTRS)

    Grier, Norman T.; Domitz, Stanley

    1992-01-01

    Anodized aluminum samples representative of Space Station Freedom structural material were tested for electrical breakdown under space plasma conditions. In space, this potential arises across the insulating anodized coating when the spacecraft structure is driven to a negative bias relative to the external plasma potential due to plasma-surface interaction phenomena. For anodized materials used in the tests, it was found that breakdown voltage varied from 100 to 2000 volts depending on the sample. The current in the arcs depended on the sample, the capacitor, and the voltage. The level of the arc currents varied from 60 to 1000 amperes. The plasma number density varied from 3 x 10 exp 6 to 10 exp 3 ions per cc. The time between arcs increased as the number density was lowered. Corona testing of anodized samples revealed that samples with higher corona inception voltage had higher arcing inception voltages. From this it is concluded that corona testing may provide a method of screening the samples.

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

    SciTech Connect

    Hu, Michael Z.; Lai, Peng; Bhuiyan, Md S; Tsouris, Costas; Gu, Baohua; Paranthaman, Mariappan Parans; Gabitto, Jorge; Harrison, L. D.

    2009-01-01

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

  20. Electrochemical Evaluation of Thin-Film Li-Si Anodes Prepared by Plasma Spraying

    SciTech Connect

    GUIDOTTI,RONALD A.; REINHARDT,FREDERICK W.; SCHARRER,GREGORY L.

    1999-09-08

    Thin-film electrodes of a plasma-sprayed Li-Si alloy were evaluated for use as anodes in high-temperature thermally activated (thermal) batteries. These anodes were prepared using 44% Li/56% Si (w/w) material as feed material in a special plasma-spray apparatus under helium or hydrogen, to protect this air- and moisture-sensitive material during deposition. Anodes were tested in single cells using conventional pressed-powder separators and lithiated pyrite cathodes at temperatures of 400 to 550 C at several different current densities. A limited number of 5-cell battery tests were also conducted. The data for the plasma-sprayed anodes was compared to that for conventional pressed-powder anodes. The performance of the plasma-sprayed anodes was inferior to that of conventional pressed-powder anodes, in that the cell emfs were lower (due to the lack of formation of the desired alloy phases) and the small porosity of these materials severely limited their rate capability. Consequently, plasma-sprayed Li-Si anodes would not be practical for use in thermal batteries.

  1. A Comparative Study of Anodized Titania Nanotube Architectures in Aqueous and Nonaqueous Solutions

    SciTech Connect

    Sturgeon, Matthew R; Lai, Peng; Hu, Michael Z.

    2011-01-01

    The unique and highly utilized properties of TiO2 nanotubes are a direct result of nanotube architecture. In order to create different engineered architectures, the effects of electrolyte solution, time, and temperature on the anodization of titanium foil were studied along with the resultant anodized titanium oxide (ATO) nanotube architectures encompassing nanotube length, pore diameter, wall thickness, smoothness, and ordered array structure. Titanium foil was anodized in three different electrolyte solutions: one aqueous (consisting of NH4F and (NH4)2SO4)) and two nonaqueous (glycerin or ethylene glycol, both containing NH4F) at varying temperatures and anodization times. Variation in anodization applied voltage, initial current, and effect of F- ion concentration on ATO nanotube architecture were also studied. Anodization in the aqueous electrolyte produced short, rough nanotube arrays, whereas anodization in organic electrolytes produced long, smooth nanotube arrays greater than 10 m in length. Anodization in glycerin at elevated temperatures for several hours presents the possibility of producing freely dispersed individual nanotubes.

  2. High-performance flexible nanoporous Si-carbon nanotube paper anodes for micro-battery applications.

    PubMed

    Biserni, Erika; Scarpellini, Alice; Bassi, Andrea Li; Bruno, Paola; Zhou, Yun; Xie, Ming

    2016-06-17

    Nanoporous Si has been grown by pulsed laser deposition on a free-standing carbon nanotube (CNT) paper sheet for micro-battery anodes. The Si deposition shows conformal coverage on the CNT paper, and the Si-CNT paper anodes demonstrate high areal capacity of ∼1000 μAh cm(-2) at a current density of 54 μA cm(-2), while 69% of its initial capacity is preserved when the current density is increased by a factor 10. Excellent stability without capacity decay up to 1000 cycles at a current density of 1080 μA cm(-2) is also demonstrated. After bending along the diameter of the circular paper disc many times, the Si-CNT paper anodes preserve the same morphology and show promising electrochemical performance, indicating that nanoporous Si-CNT paper anodes can find application for flexible micro-batteries.

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

    SciTech Connect

    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.

  4. High-performance flexible nanoporous Si-carbon nanotube paper anodes for micro-battery applications

    NASA Astrophysics Data System (ADS)

    Biserni, Erika; Scarpellini, Alice; Li Bassi, Andrea; Bruno, Paola; Zhou, Yun; Xie, Ming

    2016-06-01

    Nanoporous Si has been grown by pulsed laser deposition on a free-standing carbon nanotube (CNT) paper sheet for micro-battery anodes. The Si deposition shows conformal coverage on the CNT paper, and the Si-CNT paper anodes demonstrate high areal capacity of ˜1000 μAh cm-2 at a current density of 54 μA cm-2, while 69% of its initial capacity is preserved when the current density is increased by a factor 10. Excellent stability without capacity decay up to 1000 cycles at a current density of 1080 μA cm-2 is also demonstrated. After bending along the diameter of the circular paper disc many times, the Si-CNT paper anodes preserve the same morphology and show promising electrochemical performance, indicating that nanoporous Si-CNT paper anodes can find application for flexible micro-batteries.

  5. Variable anodic thermal control coating

    NASA Technical Reports Server (NTRS)

    Gilliland, C. S.; Duckett, J. (Inventor)

    1983-01-01

    A process for providing a thermal control solar stable surface coating for aluminum surfaces adapted to be exposed to solar radiation wherein selected values within the range of 0.10 to 0.72 thermal emittance (epsilon sub tau) and 0.2 to 0.4 solar absorptance (alpha subs) are reproducibly obtained by anodizing the surface area in a chromic acid solution for a selected period of time. The rate voltage and time, along with the parameters of initial epsilon sub tau and alpha subs, temperature of the chromic acid solution, acid concentration of the solution and the material anodized determines the final values of epsilon/tau sub and alpha sub S. 9 Claims, 5 Drawing Figures.

  6. Preventing Cracking of Anodized Coatings

    NASA Technical Reports Server (NTRS)

    He, Charles C.; Heslin, Thomas M.

    1995-01-01

    Anodized coatings have been used as optical and thermal surfaces in spacecraft. Particulate contamination from cracked coatings is a concern for many applications. The major cause for the cracking is the difference in the coefficient of thermal expansion between the oxide coatings and the aluminum substrate. The loss of water when the coating is exposed to a vacuum also could induce cracking of the coating. Hot-water sealing was identified as the major cause for the cracking of the coatings because of the large temperature change when the parts were immersed in boiling water and the water was absorbed in the coating. when the hot-water sealing process was eliminated, the cracking resistance of the anodized coatings was greatly improved. Also, it was found that dyed black coatings were more susceptible than clear coatings to cracking during thermo-vacuum cyclings.

  7. Struvite precipitation and phosphorus removal using magnesium sacrificial anode.

    PubMed

    Kruk, Damian J; Elektorowicz, Maria; Oleszkiewicz, Jan A

    2014-04-01

    Struvite precipitation using magnesium sacrificial anode as the only source of magnesium is presented. High-purity magnesium alloy cast anode was found to be very effective in recovery of high-quality struvite from water solutions and from supernatant of fermented waste activated sludge from a wastewater treatment plant that does not practice enhanced biological phosphorus removal. Struvite purity was strongly dependent on the pH and the electric current density. Optimum pH of the 24 mM phosphorus and 46 mM ammonia solution (1:1.9 P:N ratio) was in the broad range between 7.5 and 9.3, with struvite purity exceeding 90%. Increasing the current density resulted in elevated struvite purity. No upper limits were observed in the studied current range of 0.05-0.2 A. Phosphorus removal rate was proportional to the current density and comparable for tests with water solutions and with the supernatant from fermented sludge. The highest P-removal rate achieved was 4.0 mg PO4-P cm(-2) h(-1) at electric current density of 45 A m(-2). Initial substrate concentrations affected the rate of phosphorus removal. The precipitated struvite accumulated in bulk liquid with significant portions attached to the anode surface from which regular detachment occurred.

  8. Variation of anode grid surface morphology and its effect on operation of a triode virtual cathode oscillator

    SciTech Connect

    Xu Qifu; Cai Dan; Zhang Qiang; Zhao Xuelong; Zhao Qi; Cheng Guoxin; Liu Lie

    2012-10-15

    After repeatedly operation of a triode virtual cathode oscillator, the surface morphology of anode grid is studied by a scanning electron microscope. It is found that there are many quasi-periodic sawteeth formed on the anode grid, which are about 300-500 {mu}m in height, {approx}200 {mu}m in width, and 150-200 {mu}m in period. The formation of this sawteeth implies that there is possible Rayleigh-Taylor-like instability on the anode grid during the irradiation by high-current relativistic electron beam. These sawteeth enhance the electric field on anode grid, leading to more feasible of anode plasma generation, and more rapidly expansion of that plasma. As a result, the electron transmissivity of anode grid is decreased, the output microwave power of the virtual cathode oscillator is lowered and its operational performance is degraded.

  9. Anode and cathode materials characterization for a microbial fuel cell in half cell configuration.

    PubMed

    Pant, Deepak; Van Bogaert, Gilbert; Porto-Carrero, Christof; Diels, Ludo; Vanbroekhoven, Karolien

    2011-01-01

    Microbial fuel cells (MFCs) are novel bioelectrochemical devices for spontaneous conversion of biomass into electricity through the metabolic activity of the bacteria. Microbial production of electricity may become an important source of bioenergy in future because MFCs offer the possibility of extracting electric current from a wide range of soluble or dissolved complex organic wastes and renewable biomass. However, the materials used in these devices are still not economic and researchers use different materials as cathode and anode in MFCs. This results in variable performance which is difficult to compare. We tested several commercially available materials for their suitability as anode in an acetate fed MFC. Besides, a novel non-platinized activated carbon (AC) based, gas porous air cathode was also tested. Both the anode and cathode were tested in a half cell configuration. Carbon cloth, graphite cloth and dynamically stable anode (DSA) served as ideal anode material with carbon cloth and graphite mesh reaching the open circuit voltage (OCV) of acetate oxidation (-500 mV vs. Ag/AgCl). The effect of increasing concentration of acetate on anode OCV was also investigated and results showed that on increasing the acetate concentration from 10 mM to 40 mM has no adverse impact on the anodic activity towards electrochemical oxidation of acetate. The AC cathode showed stable current (-1.2 mA/cm2) over a period of 100 days. PMID:21977673

  10. Acid blue 29 decolorization and mineralization by anodic oxidation with a cold gas spray synthesized Sn-Cu-Sb alloy anode.

    PubMed

    do Vale-Júnior, Edilson; Dosta, Sergi; Cano, Irene Garcia; Guilemany, Josep Maria; Garcia-Segura, Sergi; Martínez-Huitle, Carlos Alberto

    2016-04-01

    The elevated cost of anodic materials used in the anodic oxidation for water treatment of effluents undermines the real application of these technologies. The study of novel alternative materials more affordable is required. In this work, we report the application of Sn-Cu-Sb alloys as cheap anodic material to decolorize azo dye Acid Blue 29 solutions. These anodes have been synthesized by cold gas spray technologies. Almost complete decolorization and COD abatement were attained after 300 and 600 min of electrochemical treatment, respectively. The influence of several variables such as supporting electrolyte, pH, current density and initial pollutant concentration has been investigated. Furthermore, the release and evolution of by-products was followed by HPLC to better understand the oxidative power of Sn-Cu-Sb electrodes.

  11. Effects of constant or dynamic low anode potentials on microbial community development in bioelectrochemical systems.

    PubMed

    Yan, Hengjing; Yates, Matthew D; Regan, John M

    2015-11-01

    In bioelectrochemical systems, exoelectrogenic bacteria respire with anode electrodes as their extracellular electron acceptor; therefore, lower anode potentials can reduce the energy gain to each microbe and select against ones that are not able to respire at a lower potential range. Often fully developed anode communities are compared across bioelectrochemical systems with set anode potentials or fixed external resistances as different operational conditions. However, the comparative effect of the resulting constantly low versus dynamically low anode potentials on the development of anode microbial communities as well as the final cathode microbial communities has not been directly demonstrated. In this study, we used a low fixed anode potential of -250 mV and a higher-current control potential of -119 mV vs. Standard Hydrogen Electrode to approximately correspond with the negative peak anode potential values obtained from microbial fuel cells operated with fixed external resistances of 1 kΩ and 47 Ω, respectively. Pyrosequencing data from a 2-month time series show that a lower set anode potential resulted in a more diverse community than the higher- and variable-potential systems, likely due to the hindered enrichment of a Geobacter-dominated community with limited energy gain at this set potential. In this case, it appears that the selective pressure caused by the low set potential was counteracted by the low energy gain over a 2-month time scale. The air cathode microbial community with constant low anode potentials showed delayed enrichment of denitrifiers or perchlorate-reducing bacteria compared to the fixed external resistance condition.

  12. Efficient organic light-emitting diode using semitransparent silver as anode

    SciTech Connect

    Peng Huajun; Zhu Xiuling; Sun Jiaxin; Xie Zhiliang; Xie Shuang; Wong Man; Kwok, H.-S.

    2005-10-24

    A semitransparent silver layer is investigated as the anode for organic light-emitting devices (OLEDs). By pretreating the silver layer in a CF{sub 4} plasma, hole injection into the hole-transport layer is greatly enhanced. A bottom-emitting OLED using the modified, semitransparent silver anode, demonstrates improved current density-voltage characteristics and a 20% higher external quantum efficiency, compared to a conventional OLED using indium tin oxide as an anode. The superior optical characteristics are attributed to a higher outcoupling efficiency in the microcavity structure.

  13. Chemically modified thermal-spray zinc anodes for galvanic cathodic protection

    SciTech Connect

    Covino, B.S. Jr.; Bullard, S.J.; Holcomb, G.R.; Russell, J.H.; Cramer, S.D.; Bennett, J.E.; Laylor, H.M.

    1999-12-01

    Humectants, substances that promote the retention of moisture, were applied to new and previously aged thermal-sprayed Zn anodes to improve the performance of galvanic cathodic protection systems. Anodes on steel-reinforced concrete were treated with aqueous solutions of the humectants lithium nitrate (LiNO{sub 3}) and lithium bromide (LiBr). LiBr was the most beneficial humectant, increasing the average galvanic current density of new thermal-sprayed Zn anodes by as much as a factor of six.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  15. High rate and stable cycling of lithium metal anode

    DOE PAGESBeta

    Qian, Jiangfeng; Henderson, Wesley A.; Xu, Wu; Bhattacharya, Priyanka; Engelhard, Mark H.; Borodin, Oleg; Zhang, Jiguang

    2015-02-20

    Lithium (Li) metal is an ideal anode material for rechargeable batteries. However, dendritic Li growth and limited Coulombic efficiency (CE) during repeated Li deposition/stripping processes have prevented the application of this anode in rechargeable Li metal batteries, especially for use at high current densities. Here, we report that the use of highly concentrated electrolytes composed of ether solvents and the lithium bis(fluorosulfonyl)imide (LiFSI) salt enables the high rate cycling of a Li metal anode at high CE (up to 99.1 %) without dendrite growth. With 4 M LiFSI in 1,2-dimethoxyethane (DME) as the electrolyte, a Li|Li cell can be cycledmore » at high rates (10 mA cm-2) for more than 6000 cycles with no increase in the cell impedance, and a Cu|Li cell can be cycled at 4 mA cm-2 for more than 1000 cycles with an average CE of 98.4%. These excellent high rate performances can be attributed to the increased solvent coordination and increased availability of Li+ concentration in the electrolyte. Lastly, further development of this electrolyte may lead to practical applications for Li metal anode in rechargeable batteries. The fundamental mechanisms behind the high rate ion exchange and stability of the electrolytes also shine light on the stability of other electrochemical systems.« less

  16. Fabrication of Porous Anodic Alumina with Ultrasmall Nanopores

    NASA Astrophysics Data System (ADS)

    Ding, Gu Qiao; Yang, Rong; Ding, Jian Ning; Yuan, Ning Yi; Zhu, Yuan Yuan

    2010-08-01

    Anodization of Al foil under low voltages of 1-10 V was conducted to obtain porous anodic aluminas (PAAs) with ultrasmall nanopores. Regular nanopore arrays with pore diameter 6-10 nm were realized in four different electrolytes under 0-30°C according to the AFM, FESEM, TEM images and current evolution curves. It is found that the pore diameter and interpore distance, as well as the barrier layer thickness, are not sensitive to the applied potentials and electrolytes, which is totally different from the rules of general PAA fabrication. The brand-new formation mechanism has been revealed by the AFM study on the samples anodized for very short durations of 2-60 s. It is discovered for the first time that the regular nanoparticles come into being under 1-10 V at the beginning of the anodization and then serve as a template layer dominating the formation of ultrasmall nanopores. Under higher potentials from 10 to 40 V, the surface nanoparticles will be less and less and nanopores transform into general PAAs.

  17. Controlling the Electron Energy Distribution Function Using an Anode

    NASA Astrophysics Data System (ADS)

    Baalrud, Scott D.; Barnat, Edward V.; Hopkins, Mathew M.

    2014-10-01

    Positively biased electrodes inserted into plasmas influence the electron energy distribution function (EEDF) by providing a sink for low energy electrons that would otherwise be trapped by ion sheaths at the chamber walls. We develop a model for the EEDF in a hot filament generated discharge in the presence of positively biased electrodes of various surface areas, and compare the model results with experimental Langmuir probe measurements and particle-in-cell simulations. In the absence of an anode, the EEDF is characterized by a cool trapped population at energies below the sheath energy, and a comparatively warm tail population associated with the filament primaries. Anodes that are small enough to collect a negligible fraction of the electrons exiting the plasma have little affect on the EEDF, but as the anode area approaches √{me /mi }Aw , where Aw is the chamber wall area, the anode collects most of the electrons leaving the plasma. This drastically reduces the density of the otherwise trapped population, causing an effective heating of the electrons and a corresponding density decrease. A global model is developed based on the EEDF model and current balance, which shows the interconnected nature of the electron temperature, density and the plasma potential. This work was supported by the Office of Fusion Energy Science at the U.S. Department of Energy under Contract DE-AC04-94SL85000, and by the University of Iowa Old Gold Program.

  18. High rate and stable cycling of lithium metal anode

    SciTech Connect

    Qian, Jiangfeng; Henderson, Wesley A.; Xu, Wu; Bhattacharya, Priyanka; Engelhard, Mark H.; Borodin, Oleg; Zhang, Jiguang

    2015-02-20

    Lithium (Li) metal is an ideal anode material for rechargeable batteries. However, dendritic Li growth and limited Coulombic efficiency (CE) during repeated Li deposition/stripping processes have prevented the application of this anode in rechargeable Li metal batteries, especially for use at high current densities. Here, we report that the use of highly concentrated electrolytes composed of ether solvents and the lithium bis(fluorosulfonyl)imide (LiFSI) salt enables the high rate cycling of a Li metal anode at high CE (up to 99.1 %) without dendrite growth. With 4 M LiFSI in 1,2-dimethoxyethane (DME) as the electrolyte, a Li|Li cell can be cycled at high rates (10 mA cm-2) for more than 6000 cycles with no increase in the cell impedance, and a Cu|Li cell can be cycled at 4 mA cm-2 for more than 1000 cycles with an average CE of 98.4%. These excellent high rate performances can be attributed to the increased solvent coordination and increased availability of Li+ concentration in the electrolyte. Lastly, further development of this electrolyte may lead to practical applications for Li metal anode in rechargeable batteries. The fundamental mechanisms behind the high rate ion exchange and stability of the electrolytes also shine light on the stability of other electrochemical systems.

  19. Metal-based anode for high performance bioelectrochemical systems through photo-electrochemical interaction

    NASA Astrophysics Data System (ADS)

    Liang, Yuxiang; Feng, Huajun; Shen, Dongsheng; Long, Yuyang; Li, Na; Zhou, Yuyang; Ying, Xianbin; Gu, Yuan; Wang, Yanfeng

    2016-08-01

    This paper introduces a novel composite anode that uses light to enhance current generation and accelerate biofilm formation in bioelectrochemical systems. The composite anode is composed of 316L stainless steel substrate and a nanostructured α-Fe2O3 photocatalyst (PSS). The electrode properties, current generation, and biofilm properties of the anode are investigated. In terms of photocurrent, the optimal deposition and heat-treatment times are found to be 30 min and 2 min, respectively, which result in a maximum photocurrent of 0.6 A m-2. The start-up time of the PSS is 1.2 days and the maximum current density is 2.8 A m-2, twice and 25 times that of unmodified anode, respectively. The current density of the PSS remains stable during 20 days of illumination. Confocal laser scanning microscope images show that the PSS could benefit biofilm formation, while electrochemical impedance spectroscopy indicates that the PSS reduce the charge-transfer resistance of the anode. Our findings show that photo-electrochemical interaction is a promising way to enhance the biocompatibility of metal anodes for bioelectrochemical systems.

  20. Relating MEC population dynamics to anode performance from DGGE and electrical data.

    PubMed

    Croese, Elsemiek; Keesman, Karel J; Widjaja-Greefkes, Aura H C A; Geelhoed, Jeanine S; Plugge, Caroline M; Sleutels, Tom H J A; Stams, Alfons J M; Euverink, Gert-Jan W

    2013-09-01

    The microbial electrolysis cell (MEC) is a promising system for H2 production, but little is known about the active microbial population in MEC systems. Therefore, the microbial community of five different MEC graphite felt anodes was analyzed using denaturing gradient gel electrophoresis (DGGE) profiling. The results showed that the bacterial population was very diverse and there were substantial differences between microorganisms in anolyte and anode samples. The archaeal population in the anolyte and at the anodes, and between the different MEC anodes, was very similar. SEM and FISH imaging showed that Archaea were mainly present in the spaces between the electrode fibers and Bacteria were present at the fiber surface, which suggested that Bacteria were the main microorganisms involved in MEC electrochemical activity. Redundancy analysis (RDA) and QR factorization-based estimation (QRE) were used to link the composition of the bacterial community to electrochemical performance of the MEC. The operational mode of the MECs and their consequent effects on current density and anode resistance on the populations were significant. The results showed that the community composition was most strongly correlated with current density. The DGGE band mostly correlated with current represented a Clostridium sticklandii strain, suggesting that this species had a major role in current from acetate generation at the MEC anodes. The combination of RDA and QRE seemed especially promising for obtaining an insight into the part of the microbial population actively involved in electrode interaction in the MEC.

  1. Microbial fuel cell with improved anode

    DOEpatents

    Borole, Abhijeet P.

    2010-04-13

    The present invention relates to a method for preparing a microbial fuel cell, wherein the method includes: (i) inoculating an anodic liquid medium in contact with an anode of the microbial fuel cell with one or more types of microorganisms capable of functioning by an exoelectrogenic mechanism; (ii) establishing a biofilm of the microorganisms on and/or within the anode along with a substantial absence of planktonic forms of the microorganisms by substantial removal of the planktonic microorganisms during forced flow and recirculation conditions of the anodic liquid medium; and (iii) subjecting the microorganisms of the biofilm to a growth stage by incorporating one or more carbon-containing nutritive compounds in the anodic liquid medium during biofilm formation or after biofilm formation on the anode has been established.

  2. Electrochemical cell design for the impedance studies of chlorine evolution at DSA anodes

    NASA Astrophysics Data System (ADS)

    Silva, J. F.; Dias, A. C.; Araújo, P.; Brett, C. M. A.; Mendes, A.

    2016-08-01

    A new electrochemical cell design suitable for the electrochemical impedance spectroscopy (EIS) studies of chlorine evolution on Dimensionally Stable Anodes (DSA®) has been developed. Despite being considered a powerful tool, EIS has rarely been used to study the kinetics of chlorine evolution at DSA anodes. Cell designs in the open literature are unsuitable for the EIS analysis at high DSA anode current densities for chlorine evolution because they allow gas accumulation at the electrode surface. Using the new cell, the impedance spectra of the DSA anode during chlorine evolution at high sodium chloride concentration (5 mol dm-3 NaCl) and high current densities (up to 140 mA cm-2) were recorded. Additionally, polarization curves and voltammograms were obtained showing little or no noise. EIS and polarization curves evidence the role of the adsorption step in the chlorine evolution reaction, compatible with the Volmer-Heyrovsky and Volmer-Tafel mechanisms.

  3. Electrochemical cell design for the impedance studies of chlorine evolution at DSA(®) anodes.

    PubMed

    Silva, J F; Dias, A C; Araújo, P; Brett, C M A; Mendes, A

    2016-08-01

    A new electrochemical cell design suitable for the electrochemical impedance spectroscopy (EIS) studies of chlorine evolution on Dimensionally Stable Anodes (DSA(®)) has been developed. Despite being considered a powerful tool, EIS has rarely been used to study the kinetics of chlorine evolution at DSA anodes. Cell designs in the open literature are unsuitable for the EIS analysis at high DSA anode current densities for chlorine evolution because they allow gas accumulation at the electrode surface. Using the new cell, the impedance spectra of the DSA anode during chlorine evolution at high sodium chloride concentration (5 mol dm(-3) NaCl) and high current densities (up to 140 mA cm(-2)) were recorded. Additionally, polarization curves and voltammograms were obtained showing little or no noise. EIS and polarization curves evidence the role of the adsorption step in the chlorine evolution reaction, compatible with the Volmer-Heyrovsky and Volmer-Tafel mechanisms.

  4. Electrochemical cell design for the impedance studies of chlorine evolution at DSA(®) anodes.

    PubMed

    Silva, J F; Dias, A C; Araújo, P; Brett, C M A; Mendes, A

    2016-08-01

    A new electrochemical cell design suitable for the electrochemical impedance spectroscopy (EIS) studies of chlorine evolution on Dimensionally Stable Anodes (DSA(®)) has been developed. Despite being considered a powerful tool, EIS has rarely been used to study the kinetics of chlorine evolution at DSA anodes. Cell designs in the open literature are unsuitable for the EIS analysis at high DSA anode current densities for chlorine evolution because they allow gas accumulation at the electrode surface. Using the new cell, the impedance spectra of the DSA anode during chlorine evolution at high sodium chloride concentration (5 mol dm(-3) NaCl) and high current densities (up to 140 mA cm(-2)) were recorded. Additionally, polarization curves and voltammograms were obtained showing little or no noise. EIS and polarization curves evidence the role of the adsorption step in the chlorine evolution reaction, compatible with the Volmer-Heyrovsky and Volmer-Tafel mechanisms. PMID:27587166

  5. Anode Sheath Switching in a Carbon Nanotube Arc Plasma

    SciTech Connect

    Abe Fetterman, Yevgeny Raitses, and Michael Keidar

    2008-04-08

    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.

  6. Novel trench gate field stop IGBT with trench shorted anode

    NASA Astrophysics Data System (ADS)

    Xudong, Chen; Jianbing, Cheng; Guobing, Teng; Houdong, Guo

    2016-05-01

    A novel trench field stop (FS) insulated gate bipolar transistor (IGBT) with a trench shorted anode (TSA) is proposed. By introducing a trench shorted anode, the TSA-FS-IGBT can obviously improve the breakdown voltage. As the simulation results show, the breakdown voltage is improved by a factor of 19.5% with a lower leakage current compared with the conventional FS-IGBT. The turn off time of the proposed structure is 50% lower than the conventional one with less than 9% voltage drop increased at a current density of 150 A/cm2. Additionally, there is no snapback observed. As a result, the TSA-FS-IGBT has a better trade-off relationship between the turn off loss and forward drop. Project supported by the National Natural Science Foundation of China (No. 61274080) and the Postdoctoral Science Foundation of China (No. 2013M541585).

  7. Electrochemical Treatment of Textile Dye Wastewater by Mild Steel Anode.

    PubMed

    Bhavya, J G; Rekha, H B; Murthy, Usha N

    2014-04-01

    This paper presents the results of the treatment of textile dye wastewater generated from a textile processing industry by electrochemical method. Experiments were conducted at current densities of 12, 24 and 48 A/m2 using mild steel as anode and cathode. During the various stages of electrolysis, parameters such as COD, color and BOD5 were determined in order to know the feasibility of electrochemical treatment. It was observed that increasing the electrolysis time and increased current density bring down the concentration of pollutants. Also COD removal rate and energy consumption during the electrolysis were calculated and presented in this paper. The present study proves the effectiveness of electrochemical treatment using MS as anode for TDW oxidation.

  8. Fabrication of the superhydrophobic surface on aluminum alloy by anodizing and polymeric coating

    NASA Astrophysics Data System (ADS)

    Liu, Wenyong; Luo, Yuting; Sun, Linyu; Wu, Ruomei; Jiang, Haiyun; Liu, Yuejun

    2013-01-01

    We reported the preparation of the superhydrophobic surface on aluminum alloy via anodizing and polymeric coating. Both the different anodizing processes and different polymeric coatings of aluminum alloy were investigated. The effects of different anodizing conditions, such as electrolyte concentration, anodization time and current on the superhydrophobic surface were discussed. The results showed that a good superhydrophobic surface was facilely fabricated by polypropylene (PP) coating after anodizing. The optimum conditions for anodizing were determined by orthogonal experiments. When the concentration of oxalic acid was 10 g/L, the concentration of NaCl was 1.25 g/L, anodization time was 40 min, and anodization current was 0.4 A, the best superhydrophobic surface on aluminum alloy with the contact angle (CA) of 162° and the sliding angle of 2° was obtained. On the other hand, the different polymeric coatings, such as polystyrene (PS), polypropylene (PP) and polypropylene grafting maleic anhydride (PP-g-MAH) were used to coat the aluminum alloy surface after anodizing. The results showed that the superhydrophobicity was most excellent by coating PP, while the duration of the hydrophobic surface was poor. By modifying the surface with the silane coupling agent before PP coating, the duration of the superhydrophobic surface was improved. The morphologies of the superhydrophobic surface were further confirmed by optical microscope (OM) and scanning electron microscope (SEM). Combined with the material of PP with the low surface free energy, the micro/nano-structures of the surface resulted in the superhydrophobicity of the aluminum alloy surface.

  9. 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

    NASA Astrophysics Data System (ADS)

    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.

  10. 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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    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.

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

    PubMed

    Garcia-Segura, Sergi; Keller, Jürg; Brillas, Enric; Radjenovic, Jelena

    2015-01-01

    Electrochemical advanced oxidation processes (EAOPs) have been widely investigated as promising technologies to remove trace organic contaminants from water, but have rarely been used for the treatment of real waste streams. Anodic oxidation with a boron-doped diamond (BDD) anode was applied for the treatment of secondary effluent from a municipal sewage treatment plant containing 29 target pharmaceuticals and pesticides. The effectiveness of the treatment was assessed from the contaminants decay, dissolved organic carbon and chemical oxygen demand removal. The effect of applied current and pH was evaluated. Almost complete mineralization of effluent organic matter and trace contaminants can be obtained by this EAOP primarily due to the action of hydroxyl radicals formed at the BDD surface. The oxidation of Cl(-) ions present in the wastewater at the BDD anode gave rise to active chlorine species (Cl2/HClO/ClO(-)), which are competitive oxidizing agents yielding chloramines and organohalogen byproducts, quantified as adsorbable organic halogen. However, further anodic oxidation of HClO/ClO(-) species led to the production of ClO3(-) and ClO4(-) ions. The formation of these species hampers the application as a single-stage tertiary treatment, but posterior cathodic reduction of chlorate and perchlorate species may reduce the risks associated to their presence in the environment.

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

    PubMed

    Garcia-Segura, Sergi; Keller, Jürg; Brillas, Enric; Radjenovic, Jelena

    2015-01-01

    Electrochemical advanced oxidation processes (EAOPs) have been widely investigated as promising technologies to remove trace organic contaminants from water, but have rarely been used for the treatment of real waste streams. Anodic oxidation with a boron-doped diamond (BDD) anode was applied for the treatment of secondary effluent from a municipal sewage treatment plant containing 29 target pharmaceuticals and pesticides. The effectiveness of the treatment was assessed from the contaminants decay, dissolved organic carbon and chemical oxygen demand removal. The effect of applied current and pH was evaluated. Almost complete mineralization of effluent organic matter and trace contaminants can be obtained by this EAOP primarily due to the action of hydroxyl radicals formed at the BDD surface. The oxidation of Cl(-) ions present in the wastewater at the BDD anode gave rise to active chlorine species (Cl2/HClO/ClO(-)), which are competitive oxidizing agents yielding chloramines and organohalogen byproducts, quantified as adsorbable organic halogen. However, further anodic oxidation of HClO/ClO(-) species led to the production of ClO3(-) and ClO4(-) ions. The formation of these species hampers the application as a single-stage tertiary treatment, but posterior cathodic reduction of chlorate and perchlorate species may reduce the risks associated to their presence in the environment. PMID:25464295

  13. Metallic anodes for next generation secondary batteries.

    PubMed

    Kim, Hansu; Jeong, Goojin; Kim, Young-Ugk; Kim, Jae-Hun; Park, Cheol-Min; Sohn, Hun-Joon

    2013-12-01

    Li-air(O2) and Li-S batteries have gained much attention recently and most relevant research has aimed to improve the electrochemical performance of air(O2) or sulfur cathode materials. However, many technical problems associated with the Li metal anode have yet to be overcome. This review mainly focuses on the electrochemical behaviors and technical issues related to metallic Li anode materials as well as other metallic anode materials such as alkali (Na) and alkaline earth (Mg) metals, including Zn and Al when these metal anodes were employed for various types of secondary batteries.

  14. Anode composite for molten carbonate fuel cell

    DOEpatents

    Iacovangelo, Charles D.; Zarnoch, Kenneth P.

    1983-01-01

    An anode composite useful for a molten carbonate fuel cell comprised of a porous sintered metallic anode component having a porous bubble pressure barrier integrally sintered to one face thereof, said barrier being comprised of metal coated ceramic particles sintered together and to said anode by means of said metal coating, said metal coating enveloping said ceramic particle and being selected from the group consisting of nickel, copper and alloys thereof, the median pore size of the barrier being significantly smaller than that of the anode.

  15. Physical model of anode glow patterns in elevated-pressure gas discharges

    NASA Astrophysics Data System (ADS)

    Islamov, R. Sh.

    2001-10-01

    A physical self-consistent model is developed to explain single spots or complex current structures at the anode of elevated-pressure parallel-plate dc discharges. The model is based on a fluid description of electron and ion transport coupled with Poisson's equation and involves a pair of coupled reaction-diffusion equations of an activator-inhibitor-type. This system of one-dimensional equations containing no phenomenological (adjustable) parameters allows one to find the current-density (activator) and anode potential drop (inhibitor) distributions on the anode surface. In a certain range of supply voltage, an anode glow stratification, resulting in the formation of separate glowing regions, takes place. However, the growth of perturbations and formation of a spatially periodic current pattern are complicated by competition between the current stripes, leading to suppressing of the neighboring current stripes. The bifurcation behavior of the model with respect to the characteristic electron energy, recombination coefficient, and discharge gap has been analyzed. The properties of a single anode current structure, including the normal current density effect, have been investigated. The application of these results to available findings in experiments and two-dimensional numerical simulations is discussed.

  16. Physical model of anode glow patterns in elevated-pressure gas discharges.

    PubMed

    Islamov, R S

    2001-10-01

    A physical self-consistent model is developed to explain single spots or complex current structures at the anode of elevated-pressure parallel-plate dc discharges. The model is based on a fluid description of electron and ion transport coupled with Poisson's equation and involves a pair of coupled reaction-diffusion equations of an activator-inhibitor-type. This system of one-dimensional equations containing no phenomenological (adjustable) parameters allows one to find the current-density (activator) and anode potential drop (inhibitor) distributions on the anode surface. In a certain range of supply voltage, an anode glow stratification, resulting in the formation of separate glowing regions, takes place. However, the growth of perturbations and formation of a spatially periodic current pattern are complicated by competition between the current stripes, leading to suppressing of the neighboring current stripes. The bifurcation behavior of the model with respect to the characteristic electron energy, recombination coefficient, and discharge gap has been analyzed. The properties of a single anode current structure, including the normal current density effect, have been investigated. The application of these results to available findings in experiments and two-dimensional numerical simulations is discussed.

  17. Anodic etching of p-type cubic silicon carbide

    NASA Technical Reports Server (NTRS)

    Harris, G. L.; Fekade, K.; Wongchotigul, K.

    1992-01-01

    p-Type cubic silicon carbide was anodically etched using an electrolyte of HF:HCl:H2O. The etching depth was determined versus time with a fixed current density of 96.4 mA/sq cm. It was found that the etching was very smooth and very uniform. An etch rate of 22.7 nm/s was obtained in a 1:1:50 HF:HCl:H2O electrolyte.

  18. Alternative anodic reactions in water splitting. Final report

    SciTech Connect

    Murphy, O.J.; Bockris, J. O'M.

    1984-10-01

    An anodic depolarization path to hydrogen production through water electrolysis has been examined, using lignite, grass and household wastes. Iron was removed from lignite by extensive washing. The degree of dissolution of lignite in 5 M H/sub 2/So/sub 4/ at 100/sup 0/C is ca. 0.1 wt %. Washed lignite dissolves less than unwashed material. Cyclic voltammograms showed peaks arising from dissolved organics. Increase of temperature produced more peaks. In alkaline solution, peaks disappeared. Oxidation currents were three times greater if the lignite particles were in contact with the electrode compared with their absence from solution. Platinum anodes oxidized lignite better than PbO/sub 2/. Redox systems, added to the electrolyte, helped compound formation. Grass and household wastes gave similar results but lower oxidation currents. Compounds present in solution prior to electrolysis dissolve off the internal surfaces of lignite particles. Increased oxidation currents, caused when lignite particles came in contact with the anode, arose, not because of enhanced electrochemical reactions, but from enhanced lignite dissolution following erosion. The organic compounds eventually form CO/sub 2/; the presence of heavy oils lasts for 10 hr. Current densities up to 750 mA cm/sup -2/ at ca. 1 V should be obtainable. The hydrocarbons are formed via a Kolbe mechanism from carboxylic acids. Speculative economic considerations show that the final cost of hydrogen produced, using lignite as an anode depolarizer, is considerably cheaper than that from natural gas: $0.40 per GJ, or less, compared to $5 per GJ.

  19. Gaseous Refining of Anode Copper

    NASA Astrophysics Data System (ADS)

    Goyal, Pradeep; Themelis, N. J.; Zanchuk, Walter A.

    1982-12-01

    The refining of blister copper prior to casting into anodes consists of oxidizing the copper melt to remove sulfur and then reducing its oxygen content. The age-old "wood poling" technique for deoxidation is gradually being replaced by the injection of reducing gases through one or two tuyeres. Thermodynamic and mass transfer analysis as well as laboratory tests have shown that the operating efficiency of gas injection can be improved considerably by enhancing mixing and gas-liquid mass transfer conditions within the copper bath. The injection of inert gas through porous plugs offers a viable industrial means for effecting such an improvement.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  1. An investigation of anode and cathode materials in photomicrobial fuel cells.

    PubMed

    Schneider, Kenneth; Thorne, Rebecca J; Cameron, Petra J

    2016-02-28

    Photomicrobial fuel cells (p-MFCs) are devices that use photosynthetic organisms (such as cyanobacteria or algae) to turn light energy into electrical energy. In a p-MFC, the anode accepts electrons from microorganisms that are either growing directly on the anode surface (biofilm) or are free floating in solution (planktonic). The nature of both the anode and cathode material is critical for device efficiency. An ideal anode is biocompatible and facilitates direct electron transfer from the microorganisms, with no need for an electron mediator. For a p-MFC, there is the additional requirement that the anode should not prevent light from perfusing through the photosynthetic cells. The cathode should facilitate the rapid reaction of protons and oxygen to form water so as not to rate limit the device. In this paper, we first review the range of anode and cathode materials currently used in p-MFCs. We then present our own data comparing cathode materials in a p-MFC and our first results using porous ceramic anodes in a mediator-free p-MFC. PMID:26755764

  2. Three-dimensional carbon nanotube-textile anode for high-performance microbial fuel cells.

    PubMed

    Xie, Xing; Hu, Liangbing; Pasta, Mauro; Wells, George F; Kong, Desheng; Criddle, Craig S; Cui, Yi

    2011-01-12

    Microbial fuel cells (MFCs) harness the metabolism of microorganisms, converting chemical energy into electrical energy. Anode performance is an important factor limiting the power density of MFCs for practical application. Improving the anode design is thus important for enhancing the MFC performance, but only a little development has been reported. Here, we describe a biocompatible, highly conductive, two-scale porous anode fabricated from a carbon nanotube-textile (CNT-textile) composite for high-performance MFCs. The macroscale porous structure of the intertwined CNT-textile fibers creates an open 3D space for efficient substrate transport and internal colonization by a diverse microflora, resulting in a 10-fold-larger anolyte-biofilm-anode interfacial area than the projective surface area of the CNT-textile. The conformally coated microscale porous CNT layer displays strong interaction with the microbial biofilm, facilitating electron transfer from exoelectrogens to the CNT-textile anode. An MFC equipped with a CNT-textile anode has a 10-fold-lower charge-transfer resistance and achieves considerably better performance than one equipped with a traditional carbon cloth anode: the maximum current density is 157% higher, the maximum power density is 68% higher, and the energy recovery is 141% greater.

  3. Corrosion Protection of Al/Au/ZnO Anode for Hybrid Cell Application

    PubMed Central

    Slaughter, Gymama; Stevens, Brian

    2015-01-01

    Effective protection of power sources from corrosion is critical in the development of abiotic fuel cells, biofuel cells, hybrid cells and biobateries for implantable bioelectronics. Corrosion of these bioelectronic devices result in device inability to generate bioelectricity. In this paper Al/Au/ZnO was considered as a possible anodic substrate for the development of a hybrid cell. The protective abilities of corrosive resistant aluminum hydroxide and zinc phosphite composite films formed on the surface of Al/Au/ZnO anode in various electrolyte environments were examined by electrochemical methods. The presence of phosphate buffer and physiological saline (NaCl) buffer allows for the formation of aluminum hyrdroxide and zinc phosphite composite films on the surface of the Al/Au/ZnO anode that prevent further corrosion of the anode. The highly protective films formed on the Al/Au/ZnO anode during energy harvesting in a physiological saline environment resulted in 98.5% corrosion protective efficiency, thereby demonstrating that the formation of aluminum hydroxide and zinc phosphite composite films are effective in the prevention of anode corrosion during energy harvesting. A cell assembly consisting of the Al/Au/ZnO anode and platinum cathode resulted in an open circuit voltage of 1.03 V. A maximum power density of 955.3 μW/ cm2 in physiological saline buffer at a cell voltage and current density of 345 mV and 2.89 mA/ cm2, respectively. PMID:26580661

  4. Enhanced osteoblast adhesion to drug-coated anodized nanotubular titanium surfaces

    PubMed Central

    Aninwene, George E; Yao, Chang; Webster, Thomas J

    2008-01-01

    Current orthopedic implants have functional lifetimes of only 10–15 years due to a variety of reasons including infection, extensive inflammation, and overall poor osseointegration (or a lack of prolonged bonding of the implant to juxtaposed bone). To improve properties of titanium for orthopedic applications, this study anodized and subsequently coated titanium with drugs known to reduce infection (penicillin/streptomycin) and inflammation (dexamethasone) using simple physical adsorption and the deposition of such drugs from simulated body fluid (SBF). Results showed improved drug elution from anodized nanotubular titanium when drugs were coated in the presence of SBF for up to 3 days. For the first time, results also showed that the simple physical adsorption of both penicillin/streptomycin and dexamethasone on anodized nanotubular titanium improved osteoblast numbers after 2 days of culture compared to uncoated unanodized titanium. In addition, results showed that depositing such drugs in SBF on anodized titanium was a more efficient method to promote osteoblast numbers compared to physical adsorption for up to 2 days of culture. In addition, osteoblast numbers increased on anodized titanium coated with drugs in SBF for up to 2 days of culture compared to unanodized titanium. In summary, compared to unanodized titanium, this preliminary study provided unexpected evidence of greater osteoblast numbers on anodized titanium coated with either penicillin/streptomycin or dexamethasone using simple physical adsorption or when coated with SBF; results which suggest the need for further research on anodized titanium orthopedic implants possessing drug-eluting nanotubes. PMID:18686785

  5. An investigation of anode and cathode materials in photomicrobial fuel cells.

    PubMed

    Schneider, Kenneth; Thorne, Rebecca J; Cameron, Petra J

    2016-02-28

    Photomicrobial fuel cells (p-MFCs) are devices that use photosynthetic organisms (such as cyanobacteria or algae) to turn light energy into electrical energy. In a p-MFC, the anode accepts electrons from microorganisms that are either growing directly on the anode surface (biofilm) or are free floating in solution (planktonic). The nature of both the anode and cathode material is critical for device efficiency. An ideal anode is biocompatible and facilitates direct electron transfer from the microorganisms, with no need for an electron mediator. For a p-MFC, there is the additional requirement that the anode should not prevent light from perfusing through the photosynthetic cells. The cathode should facilitate the rapid reaction of protons and oxygen to form water so as not to rate limit the device. In this paper, we first review the range of anode and cathode materials currently used in p-MFCs. We then present our own data comparing cathode materials in a p-MFC and our first results using porous ceramic anodes in a mediator-free p-MFC.

  6. Development of hollow anode penning ion source for laboratory application

    NASA Astrophysics Data System (ADS)

    Das, B. K.; Shyam, A.; Das, R.; Rao, A. D. P.

    2012-03-01

    The research work presented here focuses for the development of miniature penning type ion source. One hollow anode penning type ion source was developed in our laboratory. The size of the ion source is 38 mm diameter and 55 mm length. The ion source consists of two cathodes, a hollow anode and one piece of rare earth permanent magnet. The plasma was created in the plasma region between cathodes and the hollow anode. The J × B force in the region helps for efficient ionization of the gas even in the high vacuum region˜1×10 -5 Torr. The ions were extracted in the axial direction with help of the potential difference between the electrodes and the geometry of the extraction angle. The effect of the extraction electrode geometry for efficient extraction of the ions from the plasma region was examined. This ion source is a self extracted ion source. The self extracted phenomena reduce the cost and the size of the ion source. The extracted ion current was measured by a graphite probe. An ion current of more than 200 μA was observed at the probe placed 70 mm apart from the extraction electrode. In this paper, the structure of the ion source, effect of operating pressure, potential difference and the magnetic field on the extracted ion current is reported.

  7. Optimization and Domestic Sourcing of Lithium Ion Battery Anode Materials

    SciTech Connect

    Wood, III, D. L.; Yoon, S.

    2012-10-25

    The purpose of this Cooperative Research and Development Agreement (CRADA) between ORNL and A123Systems, Inc. was to develop a low-temperature heat treatment process for natural graphite based anode materials for high-capacity and long-cycle-life lithium ion batteries. Three major problems currently plague state-of-the-art lithium ion battery anode materials. The first is the cost of the artificial graphite, which is heat-treated well in excess of 2000°C. Because of this high-temperature heat treatment, the anode active material significantly contributes to the cost of a lithium ion battery. The second problem is the limited specific capacity of state-of-the-art anodes based on artificial graphites, which is only about 200-350 mAh/g. This value needs to be increased to achieve high energy density when used with the low cell-voltage nanoparticle LiFePO4 cathode. Thirdly, the rate capability under cycling conditions of natural graphite based materials must be improved to match that of the nanoparticle LiFePO4. Natural graphite materials contain inherent crystallinity and lithium intercalation activity. They hold particular appeal, as they offer huge potential for industrial energy savings with the energy costs essentially subsidized by geological processes. Natural graphites have been heat-treated to a substantially lower temperature (as low as 1000-1500°C) and used as anode active materials to address the problems described above. Finally, corresponding graphitization and post-treatment processes were developed that are amenable to scaling to automotive quantities.

  8. Anode heel affect in thoracic radiology: a visual grading analysis

    NASA Astrophysics Data System (ADS)

    Mearon, T.; Brennan, P. C.

    2006-03-01

    For decades, the antero-posterior (AP) projection of the thoracic spine has represented a substantial challenge. Patient thickness varies substantially along the cranio-caudal axis resulting in images that are too dark for the upper vertebrae and too light, or with excessive quantum mottle, towards the 9th to 12th thoracic vertebra. The anode heel affect is a well known phenomenon, however there is a paucity of reports demonstrating its exploitation in clinical departments for optimising images. The current work, using an adult, tissue-equivalent anthropomorphic phantom, explores if appropriate positioning ofthe anode can improve image quality for thoracic spine radiology. At each of 5 kVps (70, 81, 90, 102, 109) thirty AP thoracic spine images were produced, 15 with the anode end of the tube towards the cranial part of the phantom and 15 with the anode end of the tube facing caudally. Visual grading analysis of the resultant images demonstrated significant improvements in overall image quality and visualisation of specific anatomical features for the cranially facing anode compared with the alternative position, which were most pronounced for the 1st to 4th and 9th to 12th vertebrae. These improvements were evident at 70, 81 and 90 kVp, but not for the higher beam energies. The results demonstrate that correct positioning of the X-ray tube can improve image quality for thoracic radiology at specific tube potentials. Further work is ongoing to investigate whether this easy to implement and cost-free technique can be employed for other examinations.

  9. Brightness enhancement of plasma ion source by utilizing anode spot for nano applications.

    PubMed

    Park, Yeong-Shin; Lee, Yuna; Kim, Yoon-Jae; Park, Man-Jin; Moon, Dae Won; Chung, Kyoung-Jae; Hwang, Y S

    2012-02-01

    Anode spots are known as additional discharges on positively biased electrode immersed in plasmas. The anode spot plasma ion source (ASPIS) has been investigated as a high brightness ion source for nano applications such as focused ion beam (FIB) and nano medium energy ion scattering (nano-MEIS). The generation of anode spot is found to enhance brightness of ion beam since the anode spot increases plasma density near the extraction aperture. Brightness of the ASPIS has been estimated from measurement of emittance for total ion beam extracted through sub-mm aperture. The ASPIS is installed to the FIB system. Currents and diameters of the focused beams with∕without anode spot are measured and compared. As the anode spot is turned on, the enhancement of beam current is observed at fixed diameter of the focused ion beam. Consequently, the brightness of the focused ion beam is enhanced as well. For argon ion beam, the maximum normalized brightness of 12,300 A∕m(2) SrV is acquired. The ASPIS is applied to nano-MEIS as well. The ASPIS is found to increase the beam current density and the power efficiency of the ion source for nano-MEIS. From the present study, it is shown that the ASPIS can enhance the performance of devices for nano applications.

  10. Brightness enhancement of plasma ion source by utilizing anode spot for nano applications

    SciTech Connect

    Park, Yeong-Shin; Lee, Yuna; Chung, Kyoung-Jae; Hwang, Y. S.; Kim, Yoon-Jae; Park, Man-Jin; Moon, Dae Won

    2012-02-15

    Anode spots are known as additional discharges on positively biased electrode immersed in plasmas. The anode spot plasma ion source (ASPIS) has been investigated as a high brightness ion source for nano applications such as focused ion beam (FIB) and nano medium energy ion scattering (nano-MEIS). The generation of anode spot is found to enhance brightness of ion beam since the anode spot increases plasma density near the extraction aperture. Brightness of the ASPIS has been estimated from measurement of emittance for total ion beam extracted through sub-mm aperture. The ASPIS is installed to the FIB system. Currents and diameters of the focused beams with/without anode spot are measured and compared. As the anode spot is turned on, the enhancement of beam current is observed at fixed diameter of the focused ion beam. Consequently, the brightness of the focused ion beam is enhanced as well. For argon ion beam, the maximum normalized brightness of 12 300 A/m{sup 2} SrV is acquired. The ASPIS is applied to nano-MEIS as well. The ASPIS is found to increase the beam current density and the power efficiency of the ion source for nano-MEIS. From the present study, it is shown that the ASPIS can enhance the performance of devices for nano applications.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Surface modifications for enhanced enzyme immobilization and improved electron transfer of PQQ-dependent glucose dehydrogenase anodes.

    PubMed

    Lopez, Ryan J; Babanova, Sofia; Artyushkova, Kateryna; Atanassov, Plamen

    2015-10-01

    Pyrroloquinoline quinone dependent soluble glucose dehydrogenase (PQQ-sGDH) enzymatic MWCNT electrodes were p roduced using 1-pyrenecarboxylic acid (PCA) activated through carbodiimide functionalization and 1-Pyrenebutyric acid N-hydroxysuccinimide ester (PBSE) as tethering agents. At 600 mV potential, the current density generated by the activated-PCA tethered PQQ-sGDH anode was significantly greater than the current density generated by the untethered PQQ-sGDH and PBSE tethered anodes, and performance was nearly identical to the performance of a covalently bound PQQ-sGDH anode. A technique for covalently bonding heme-b (hemin), a natural quinohemoprotein porphyrin redox cofactor, to carbon nanotubes modified with arylamine groups is reported. The resulting performance of the covalently bound hemin PQQ-sGDH anode is considerably higher than that of any other PQQ-sGDH anodes tested.

  13. Anodization process produces opaque, reflective coatings on aluminum

    NASA Technical Reports Server (NTRS)

    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.

  14. Corrosion and Protection of Lead Anodes in Acidic Copper Sulphate Solutions

    NASA Astrophysics Data System (ADS)

    Cifuentes, L.; Astete, E.; Crisotomo, G.; Simpson, J.; Cifuentes, G.; Pilleux, M.

    It is known that lead anodes used in the industrial extraction of copper by electrolysis (electrowinning) suffer corrosion as a result of accidental or intended current interruptions. In order to improve understanding of the corrosion and protection of such anodes, the effects of the concentrations of copper, sulphuric acid, cobalt, iron, manganese, chloride and an organic additive (guar) on the corrosion of lead have been studied by means of weight loss tests and surface analysis techniques (X-ray photoelectron spectroscopy, X-ray diffraction, and wavelength dispersive spectroscopy). The rate of corrosion of lead during current interruptions increases with increasing concentration of sulphuric acid and copper, whereas it decreases markedly in the presence of cobalt and iron and, to a lesser extent, in the presence of chloride and the organic additive. Manganese is the only impurity whose presence does not reduce the rate of corrosion; it is also the only element which precipitates in significant amounts on the lead anode surface under the conditions studied. A method is proposed to establish the optimum anodic protection current density during current interruptions in electrowinning cells. Three current density ranges have been found, of which the 'high' protection range could be caused by the degree of compactness acquired by the PbO2 layer at applied anodic current densities in excess of 60 A m-2.

  15. An analytical model for liquid-anode and vapor-anode AMTEC converters

    SciTech Connect

    Tournier, J.; El-Genk, M.S.; Schuller, M.; Hausgen, P.

    1997-01-01

    This paper describes a lumped analytical model of liquid-anode single-tube and vapor-anode multi-tube AMTEC cells. The model results agreed well with experimental data for Mo, NbN and TiN electrodes. Results showed that Mo and NbN electrodes exhibit high B values between 400 and 600A.K{sup 1/2}/Pa.m{sup 2}, and have the potential for peak power densities slightly above 1W/cm{sup 2}, with efficiencies as high as 28{percent}. In contrast, TiN electrodes have lower temperature-independent exchange currents, between 120 and 135A.K{sup 1/2}/Pa.m{sup 2}, lower peak power densities between 0.5 and 0.75W/cm{sup 2}, and efficiencies below 24{percent} at a BASE temperature of 1200 K. These values of B compare well with that reported by other investigators. {copyright} {ital 1997 American Institute of Physics.}

  16. Interfacial morphology of low-voltage anodic aluminium oxide

    SciTech Connect

    Hu, Naiping; Dongcinn, Xuecheng; He, Xueying; Argekar, Sandip; Zhang, Yan; Browning, Jim; Schaefer, Dale

    2013-01-01

    X-ray reflectivity (XRR) and neutron reflectivity (NR), as well as ultra-smallangle X-ray scattering (USAXS), are used to examine the in-plane and surfacenormal structure of anodic films formed on aluminium alloy AA2024 and pure aluminium. Aluminium and alloy films up to 3500 A thick were deposited on Si wafers by electron beam evaporation of ingots. Porous anodic aluminium oxide (AAO) films are formed by polarizing at constant voltage up to 20 V noble to the open circuit potential. The voltage sweet spot (5 V) appropriate for constant-voltage anodization of such thin films was determined for both alloy and pure Al. In addition, a new concurrent voltage- and current-control protocol was developed to prepare films with larger pores (voltages higher than 5 V), but formed at a controlled current so that pore growth is slow enough to avoid stripping the aluminium substrate layer. USAXS shows that the pore size and interpore spacing are fixed in the first 10 s after initiation of anodization. Pores then grow linearly in time, at constant radius and interpore spacing. Using a combination of XRR and NR, the film density and degree of hydration of the films were determined from the ratio of scattering length densities. Assuming a chemical formula Al2O3xH2O, it was found that x varies from 0.29 for the native oxide to 1.29 for AAO grown at 20 V under concurrent voltage and current control. The average AAO film density of the porous film at the air surface is 2.45 (20) g cm3. The density of the barrier layer at the metal interface is 2.9 (4) g cm3, which indicates that this layer is also quite porous

  17. Effect of rolling technologies on the properties of Pb-0.06wt%Ca-1.2wt%Sn alloy anodes during copper electrowinning

    NASA Astrophysics Data System (ADS)

    Yang, Jian; Chen, Bu-ming; Hang, Hui; Guo, Zhong-cheng; Wang, Shuai

    2015-11-01

    The objective of this work was to study the effect of different rolling technologies on the properties of Pb-0.06wt%Ca-1.2wt%Sn anodes during copper electrowinning and to determine the relationship between the properties of the anodes and rolling techniques during copper electrowinning. The anode process was investigated via anodic polarization curves, cyclic voltammetry curves, electrochemical impedance spectra, and corrosion tests. The microscopic morphology and phase composition of the anodic oxide layers were observed by scanning electron microscopy and X-ray diffraction, respectively. Observable variations in the electrocatalytic activity and reaction kinetics of anodes during electrowinning indicated that the electrochemical behavior of the anodes was strongly affected by the rolling technology. An increase in the rolling number tended to decrease the oxygen evolution overpotential and the corrosion rate of the anodes. These trends are contrary to that of the apparent exchange current density. Furthermore, the intensities of diffraction peaks associated with PbO, PbOx, and α-PbO2 tended to increase with increasing rolling number. In addition, the rolled anodes exhibited a more uniform microstructure. Compared with one-way rolled anodes, the eight-time cross rolled anodes exhibited better electrocatalytic activity and improved corrosion resistance.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  19. Enhancing electrokinetic remediation of cadmium- contaminated soils with stepwise moving anode method.

    PubMed

    Chen, Xue J; Shen, Zhe M; Yuan, Tao; Zheng, Shen S; Ju, Bing X; Wang, Wen H

    2006-01-01

    This paper proposed an innovative approach by stepwise moving anode towards cathode to enhance the cadmium (Cd) removal from soil during the process of electrokinetic (EK) remediation. Fixed anode tests and moving anode tests were carried out for 60 hours to compare their performances. The anode-cathode spacing was 21 cm. Constant voltage grade of 1.0 V cm(-1) was applied in this study. The parameters included pH, electrical conductivity, current, Cd concentration and speciation distributions, energy consumptions, etc. It was found that the pH values in the moving anode tests were relatively lower than those of the fixed tests. In the moving anode test, the removal efficiency of Cd in the soils at the fraction of S4 was enhanced by 54.9% compared with that of the fixed anode tests. After 60 hours of treatment, approximately 80% of the spiked soils (100.63 mg x kg(-1) of Cd) in the system were successfully remedied in the moving anode tests; and the mean removal efficiency was 73% for actual field-contaminated soil (54.26 mg x kg(-1) of Cd). It is effective to remedy actual contaminated soils. In addition, the cumulative energy consumptions were 59.29 kWhm(-3) and 31.52 kWhm(-3) for the fixed and moving tests, respectively. The results revealed that the Cd removal efficiency was improved by the moving anode method. Moreover, less energy was consumed in the moving test. The proposed approach does not need to introduce extra chemicals nor adjust the pH in the system to enhance the Cd removal by EK remediation. The basic idea proposed in this paper provides a novel and environmental friendly method to enhance the EK remediation of heavy metals contaminated soils. PMID:17000543

  20. Spatially resolved confocal resonant Raman microscopic analysis of anode-grown Geobacter sulfurreducens biofilms.

    PubMed

    Lebedev, Nikolai; Strycharz-Glaven, Sarah M; Tender, Leonard M

    2014-02-01

    When grown on the surface of an anode electrode, Geobacter sulfurreducens forms a multi-cell thick biofilm in which all cells appear to couple the oxidation of acetate with electron transport to the anode, which serves as the terminal metabolic electron acceptor. Just how electrons are transported through such a biofilm from cells to the underlying anode surface over distances that can exceed 20 microns remains unresolved. Current evidence suggests it may occur by electron hopping through a proposed network of redox cofactors composed of immobile outer membrane and/or extracellular multi-heme c-type cytochromes. In the present work, we perform a spatially resolved confocal resonant Raman (CRR) microscopic analysis to investigate anode-grown Geobacter biofilms. The results confirm the presence of an intra-biofilm redox gradient whereby the probability that a heme is in the reduced state increases with increasing distance from the anode surface. Such a gradient is required to drive electron transport toward the anode surface by electron hopping via cytochromes. The results also indicate that at open circuit, when electrons are expected to accumulate in redox cofactors involved in electron transport due to the inability of the anode to accept electrons, nearly all c-type cytochrome hemes detected in the biofilm are oxidized. The same outcome occurs when a comparable potential to that measured at open circuit (-0.30 V vs. SHE) is applied to the anode, whereas nearly all hemes are reduced when an exceedingly negative potential (-0.50 V vs. SHE) is applied to the anode. These results suggest that nearly all c-type cytochrome hemes detected in the biofilm can be electrochemically accessed by the electrode, but most have oxidation potentials too negative to transport electrons originating from acetate metabolism. The results also reveal a lateral heterogeneity (x-y dimensions) in the type of c-type cytochromes within the biofilm that may affect electron transport to the

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

    SciTech Connect

    Anil V. Virkar

    2001-06-21

    A simple, approximate analysis of the effect of differing cathode and anode areas on the measurement of cell performance on anode-supported solid oxide fuel cells, wherein the cathode area is smaller than the anode area, is presented. It is shown that the effect of cathode area on cathode polarization, on electrolyte contribution, and on anode resistance, as normalized on the basis of the cathode area, is negligible. There is a small but measurable effect on anode polarization, which results from concentration polarization. Effectively, it is the result of a greater amount of fuel transported to the anode/electrolyte interface in cases wherein the anode area is larger than the cathode area. Experiments were performed on cells made with differing cathode areas and geometries. Cathodic and anodic overpotentials measured using reference electrodes, and the measured ohmic area specific resistances by current interruption, were in good agreement with expectations based on the analysis presented. At 800 C, the maximum power density measured with a cathode area of {approx}1.1 cm{sup 2} was {approx}1.65 W/cm{sup 2} compared to {approx}1.45 W/cm{sup 2} for cathode area of {approx}2 cm{sup 2}, for anode thickness of {approx}1.3 mm, with hydrogen as the fuel and air as the oxidant. At 750 C, the measured maximum power densities were {approx}1.3 W/cm{sup 2} for the cell with cathode area {approx}1.1 cm{sup 2}, and {approx}1.25 W/cm{sup 2} for the cell with cathode area {approx}2 cm{sup 2}.

  2. An oxygen pumping anode for electrowinning aluminium.

    PubMed

    Liu, Changqing; Ji, Xiaobo; Zhang, Pingmin; Chen, Qiyuan; Banks, Craig E

    2013-05-01

    The chemical potential of oxygen ions at the novel oxygen pumping anode for electrowinning aluminum was manipulated by the electromotive forces to create thermodynamic stability. It is our anticipation that this newly designed anode can be applied to electrochemical metallurgy of other metals, such as the direct electrochemical reduction of TiO2 in the FFC process. PMID:23519386

  3. Remote control for anode-cathode adjustment

    DOEpatents

    Roose, Lars D.

    1991-01-01

    An apparatus for remotely adjusting the anode-cathode gap in a pulse power machine has an electric motor located within a hollow cathode inside the vacuum chamber of the pulse power machine. Input information for controlling the motor for adjusting the anode-cathode gap is fed into the apparatus using optical waveguides. The motor, controlled by the input information, drives a worm gear that moves a cathode tip. When the motor drives in one rotational direction, the cathode is moved toward the anode and the size of the anode-cathode gap is diminished. When the motor drives in the other direction, the cathode is moved away from the anode and the size of the anode-cathode gap is increased. The motor is powered by batteries housed in the hollow cathode. The batteries may be rechargeable, and they may be recharged by a photovoltaic cell in combination with an optical waveguide that receives recharging energy from outside the hollow cathode. Alternatively, the anode-cathode gap can be remotely adjusted by a manually-turned handle connected to mechanical linkage which is connected to a jack assembly. The jack assembly converts rotational motion of the handle and mechanical linkage to linear motion of the cathode moving toward or away from the anode.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Anode power deposition in a MPD thruster with a magnetically annulled Hall parameter anode

    NASA Technical Reports Server (NTRS)

    Gallimore, Alec D.; Kelly, Arnold J.; Jahn, Robert G.

    1992-01-01

    Results from previous studies indicate that the anode fall increases monotonically with the electron Hall parameter. In an attempt to reduce the anode fall by decreasing the local electron Hall parameter, a proof-of-concept test was performed in which an array of 36 permanent magnets were imbedded within the anode of a high power quasi-steady MPD thruster to decrease the local azimuthal component of the induced magnetic field. The modified thruster was operated at power levels between 150 kW and 4 MW with Ar and He propellants. Terminal voltage, triple probe, floating probe, and magnetic probe measurements were made to characterize the performance of the thruster with new anode. Incorporation of the modified anode resulted in a reduction of the anode fall by up to 15 V with Ar and 20 V with He, which corresponded to decreased anode power fractions of 40 and 45 percent with Ar and He, respectively.

  6. One hundred anode microchannel plate ion detector

    SciTech Connect

    He Yi; Poehlman, John F.; Alexander, Andrew W.; Boraas, Kirk; Reilly, James P.

    2011-08-15

    A one-hundred-anode microchannel plate detector is constructed on a 10 cm x 15 cm printed circuit board and attached to a homebuilt matrix assisted laser desorption ionization (MALDI) time-of-flight mass spectrometer. Ringing and cross talk between anodes have been successfully eliminated and preliminary mass spectra of peptide ions recorded. With one hundred anodes on the printed circuit board, spatial information about the ion beam can also be readily determined with this detector. During operation, the detector anode assembly loses sensitivity after ions strike it for a considerable period of time due to charging of the non-conductive regions between anodes. However, this effect can be minimized by deflecting matrix ions away from the detector.

  7. Charge injection and accumulation in organic light-emitting diode with PEDOT:PSS anode

    SciTech Connect

    Weis, Martin; Otsuka, Takako; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

    2015-04-21

    Organic light-emitting diode (OLED) displays using flexible substrates have many attractive features. Since transparent conductive oxides do not fit the requirements of flexible devices, conductive polymer poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) has been proposed as an alternative. The charge injection and accumulation in OLED devices with PEDOT:PSS anodes are investigated and compared with indium tin oxide anode devices. Higher current density and electroluminescence light intensity are achieved for the OLED device with a PEDOT:PSS anode. The electric field induced second-harmonic generation technique is used for direct observation of temporal evolution of electric fields. It is clearly demonstrated that the improvement in the device performance of the OLED device with a PEDOT:PSS anode is associated with the smooth charge injection and accumulation.

  8. Evaluation of multi-brush anode systems in microbial fuel cells.

    PubMed

    Lanas, Vanessa; Logan, Bruce E

    2013-11-01

    The packing density of anodes in microbial fuel cells (MFCs) was examined here using four different graphite fiber brush anode configurations. The impact of anodes on performance was studied in terms of carbon fiber length (brush diameter), the number of brushes connected in parallel, and the wire current collector gage. MFCs with different numbers of brushes (one, three or six) set perpendicular to the cathode all produced similar power densities (1200 ± 40 mW/m(2)) and coulombic efficiencies (60% ± 5%). Reducing the number of brushes by either disconnecting or removing them reduced power, demonstrating the importance of anode projected area covering the cathode, and therefore the need to match electrode projected areas to maintain high performance. Multi-brush reactors had the same COD removal as single-brush systems (>90%). The use of smaller Ti wire gages did not affect power generation, which will enable the use of less metal, reducing material costs. PMID:24063821

  9. Effect of manganese additions on the performance of aluminum air-battery anode alloys

    SciTech Connect

    Scott, D.H.

    1982-05-05

    Lawrence Livermore Laboratories' (LLL) electrochemical evaluation of the experimental alloys previously cast indicated that the coulombic efficiency of an aluminum anode alloy with a nominal chemistry of 0.04% Fe, 0.04% Ga, and 0.8% Mg could be substantially improved by a 0.04% Mn addition. More recent elecrochemical testing of ingot sections performed by both Reynolds and LLL showed that the performance of an aluminum anode alloy, based on a nominal 0.04% Fe, could be improved by a high temperature homogenization. Based on these results, it was decided that the addition of manganese offered a very fruitful approach for providing improved anode performance. Thus the intent of the current work was to further investigate the effects of varying manganese/iron ratios and fabrication practices on the electro-chemical performance of an aluminum anode alloy containing a nominal 0.04% Fe. Results are presented and discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  11. Treatment of landfill leachate using microbial fuel cells: alternative anodes and semi-continuous operation.

    PubMed

    Ganesh, Krishnadas; Jambeck, Jenna R

    2013-07-01

    Microbial fuel cells were designed and operated to treat landfill leachate while continuously producing power. Two different anodes were tested in batch cycles using landfill leachate as a substrate without inoculation: an activated carbon anode and biochar anode. In addition, a semi-continuous serpentine design was evaluated. No significant difference of the mean was found for the peak voltage, current density or power densities between the batch cell with activated carbon or biochar. Similar COD reduction occurred at both the batch (with biochar) and semi-continuous scale (28% ± 8.8% and 21.7% ± 12.2%, respectively). The batch MFC with activated carbon anode had significantly higher COD removal (74.7% ± 5.5%). BOD was removed by the semi-continuous MFC, but ammonia was not removed in four of the five cycles. The results provide further information on the possibility of using MFCs in landfill leachate treatment systems.

  12. Determination of the cathode and anode voltage drops in high power low-pressure amalgam lamps

    SciTech Connect

    Vasilyak, L. M.; Vasiliev, A. I. Kostyuchenko, S. V.; Sokolov, D. V.; Startsev, A. Yu.; Kudryavtsev, N. N.

    2011-12-15

    For the first time, cathode and anode drops of powerful low-pressure amalgam lamps were measured. The lamp discharge current is 3.2 A, discharge current frequency is 43 kHz, linear electric power is 2.4 W/cm. The method of determination of a cathode drop is based on the change of a lamp operating voltage at variation of the electrode filament current at constant discharge current. The total (cathode plus anode) drop of voltage was measured by other, independent ways. The maximum cathode fall is 10.8 V; the anode fall corresponding to the maximal cathode fall is 2.4 V. It is shown that in powerful low pressure amalgam lamps the anode fall makes a considerable contribution (in certain cases, the basic one) to heating of electrodes. Therefore, the anode fall cannot be neglected, at design an electrode and ballast of amalgam lamps with operating discharge current frequency of tens of kHz.

  13. Acidity and aluminum toxicity caused by iron oxidation around anode bars

    SciTech Connect

    Shen, S.; Pepper, G.E.; Hassett, J.J.; Stucki, J.W.

    1998-08-01

    Soil acidity and aluminum toxicity are serious environmental problems often found in humid temperate and tropical regions or in areas with acid rain. Iron oxidation in soils can also cause high concentrations of H{sup +}, which, in turn, causes an increase of Al{sup 3+} in the soil solution. To examine this problem, a study was undertaken to discover the cause of crop damage in crops planted over buried anode bars. Anode bars are part of an impressed current cathodic protection system for pipelines near Decatur, Illinois. Soil samples were collected from the problem site and from a non-problem site for comparison. Results showed that Fe oxidation around anode bars at the problem site is stimulated by electric current, a situation that results in high concentrations of H{sup +} and reduces soil pH to less than 3.0. Under the low pH condition, the content of available Al is very high, and therefore, the soil solution becomes toxic for soybean roots. Exchangeable Al was 360 to 700 ppm in soil immediately adjacent to anode bars but only 3 ppm in the soil midway between anode bars. The damage to the plants, such as reduced vegetative growth and lowered seed yield, developed in a circular pattern over the anode bars. Factors contributing to the problem were soil Fe content, rectifier voltage, and soil drainage.

  14. Anode Biofilms of Geoalkalibacter ferrihydriticus Exhibit Electrochemical Signatures of Multiple Electron Transport Pathways.

    PubMed

    Yoho, Rachel A; Popat, Sudeep C; Rago, Laura; Guisasola, Albert; Torres, César I

    2015-11-17

    Thriving under alkaliphilic conditions, Geoalkalibacter ferrihydriticus (Glk. ferrihydriticus) provides new applications in treating alkaline waste streams as well as a possible new model organism for microbial electrochemistry. We investigated the electrochemical response of biofilms of the alkaliphilic anode-respiring bacterium (ARB) Glk. ferrihydriticus voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. We observed there to be at least four dominant electron transfer pathways, with their contribution to the overall current produced dependent on the set anode potential. These pathways appear to be manifested at midpoint potentials of approximately -0.14 V, -0.2 V, -0.24 V, and -0.27 V vs standard hydrogen electrode. The individual contributions of the pathways change upon equilibration from a set anode potential to another anode potential. Additionally, the contribution of each pathway to the overall current produced is reversible when the anode potential is changed back to the original set potential. The pathways involved in anode respiration in Glk. ferrihydriticus biofilms follow a similar, but more complicated, pattern as compared to those in the model ARB, Geobacter sulfurreducens. This greater diversity of electron transport pathways in Glk. ferrihydriticus could be related to its wider metabolic capability (e.g., higher pH and larger set of possible substrates, among others). PMID:26488071

  15. Anode Biofilms of Geoalkalibacter ferrihydriticus Exhibit Electrochemical Signatures of Multiple Electron Transport Pathways.

    PubMed

    Yoho, Rachel A; Popat, Sudeep C; Rago, Laura; Guisasola, Albert; Torres, César I

    2015-11-17

    Thriving under alkaliphilic conditions, Geoalkalibacter ferrihydriticus (Glk. ferrihydriticus) provides new applications in treating alkaline waste streams as well as a possible new model organism for microbial electrochemistry. We investigated the electrochemical response of biofilms of the alkaliphilic anode-respiring bacterium (ARB) Glk. ferrihydriticus voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. We observed there to be at least four dominant electron transfer pathways, with their contribution to the overall current produced dependent on the set anode potential. These pathways appear to be manifested at midpoint potentials of approximately -0.14 V, -0.2 V, -0.24 V, and -0.27 V vs standard hydrogen electrode. The individual contributions of the pathways change upon equilibration from a set anode potential to another anode potential. Additionally, the contribution of each pathway to the overall current produced is reversible when the anode potential is changed back to the original set potential. The pathways involved in anode respiration in Glk. ferrihydriticus biofilms follow a similar, but more complicated, pattern as compared to those in the model ARB, Geobacter sulfurreducens. This greater diversity of electron transport pathways in Glk. ferrihydriticus could be related to its wider metabolic capability (e.g., higher pH and larger set of possible substrates, among others).

  16. Electron and ion kinetics and anode plasma formation in two applied Br field ion diodes

    NASA Astrophysics Data System (ADS)

    Johnson, D. J.; Quintenz, J. P.; Sweeney, M. A.

    1985-02-01

    Two magnetically insulated ion diodes that utilize a radial applied-B field are described. Both diodes generate an annular beam that is extracted along the diode axis. The first diode operated at 1.2 MV and 600 kA for 25 ns and generated a 300-kA ion beam. The second operated at 300 kV, 100 kA and generated 15 kA of ion current. The first diode was used to study diode performance as a function of inner and outer anode-cathode gaps, the applied-B field, and transmission line current ratios. The second diode was used to study anode plasma formation. The diodes were operated below Bcrit, resulting in electron leakage to the anode, especially near the outer cathode. A definition of Bcrit applicable to extraction diodes is given and methods of improving ion production efficiency in these diodes are suggested. The strong correlation of ion production with visible light emission suggests, however, that the electron loss played an important role in anode turn-on. The breakdown of neutral gas desorbed by electron impact is thought to be the anode plasma production mechanism. The grazing incidence leakage electrons affect the breakdown by significantly enhancing space-charge-induced electric fields in the dielectric-filled anode grooves.

  17. Open circuit versus closed circuit enrichment of anodic biofilms in MFC: effect on performance and anodic communities.

    PubMed

    Larrosa-Guerrero, Amor; Scott, Keith; Katuri, Krishna P; Godinez, Carlos; Head, Ian M; Curtis, Thomas

    2010-08-01

    The influence of various carbon anodes; graphite, sponge, paper, cloth, felt, fiber, foam and reticulated vitreous carbon (RVC); on microbial fuel cell (MFC) performance is reported. The feed was brewery wastewater diluted in domestic wastewater. Biofilms were grown at open circuit or under an external load. Microbial diversity was analysed as a function of current and anode material. The bacterial community formed at open circuit was influenced by the anode material. However at closed circuit its role in determining the bacterial consortia formed was less important than the passage of current. The rate and extent of organic matter removal were similar for all materials: over 95% under closed circuit. The biofilm in MFCs working at open circuit and in the control reactors, increased COD removal by up to a factor of nine compared with that for baseline reactors. The average voltage output was 0.6 V at closed circuit, with an external resistor of 300 kOmega and 0.75 V at open circuit for all materials except RVC. The poor performance of this material might be related to the surface area available and concentration polarizations caused by the morphology of the material and the structure of the biofilm. Peak power varied from 1.3 mW m(-2) for RVC to 568 mW m(-2) for graphite with biofilm grown at closed circuit. PMID:20473665

  18. The Nitrogen-Nitride Anode.

    SciTech Connect

    Delnick, Frank M.

    2014-10-01

    Nitrogen gas N 2 can be reduced to nitride N -3 in molten LiCl-KCl eutectic salt electrolyte. However, the direct oxidation of N -3 back to N 2 is kinetically slow and only occurs at high overvoltage. The overvoltage for N -3 oxidation can be eliminated by coordinating the N -3 with BN to form the dinitridoborate (BN 2 -3 ) anion which forms a 1-D conjugated linear inorganic polymer with -Li-N-B-N- repeating units. This polymer precipitates out of solution as Li 3 BN 2 which becomes a metallic conductor upon delithiation. Li 3 BN 2 is oxidized to Li + + N 2 + BN at about the N 2 /N -3 redox potential with very little overvoltage. In this report we evaluate the N 2 /N -3 redox couple as a battery anode for energy storage.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  20. Conductive Anodic Filament (CAF) Formation

    NASA Astrophysics Data System (ADS)

    Caputo, Antonio

    Conductive anodic filament (CAF) is a failure mode in printed wiring boards (PWBs) which occurs under high humidity and high voltage gradient conditions. The filament, a copper salt, grows from anode to cathode along the epoxy-glass interface. Ready and Turbini (2000) identified this copper salt as the Cu 2(OH)3Cl, atacamite compound. This work has investigated the influence of polyethylene glycol (PEG) and polyethylene propylene glycol (PEPG) fluxing agents on the chemical nature of CAF. For coupons processed with PEPG flux, with and without chloride, a copper-chloride containing compound was formed in the polymer matrix. This compound was characterized using x-ray photoelectron spectroscopy (XPS) as CuCl and an electrochemical mechanism for the formation of the chloride-containing CAF has been proposed. For PEG flux, with and without chloride, it has been shown that CAF only formed, but no copper containing compound formed in the matrix. It appears for PEG fluxed coupons, a PEG-Cu-Cl complex forms, binds the available Cu and acts as a barrier to the formation of CuCl in the polymer matrix. Meeker and Lu Valle (1995) have previously proposed that CAF failure is best represented by two competing reactions -- the formation of a copper chloride corrosion compound (now identified as Cu2(OH)3Cl) and the formation of innocuous trapped chlorine compounds. Since no evidence of any trapped chloride compounds has been found, we propose that the formation of CAF is best represented by a single non-reversible reaction. For coupons processed with a high bromide-containing flux, bromide containing CAF was created and characterized using transmission electron microscopy (TEM) to be Cu2(OH)3Br. In addition, a copper-containing compound was formed in the polymer matrix and characterized using XPS as CuBr. An electrochemical mechanism for the formation of bromide-containing CAF has been proposed based on the XPS data.

  1. Autotrophic denitrification performance and bacterial community at biocathodes of bioelectrochemical systems with either abiotic or biotic anodes.

    PubMed

    Nguyen, Van Khanh; Hong, Sungsug; Park, Younghyun; Jo, Kyungmin; Lee, Taeho

    2015-02-01

    Two-chamber bioelectrochemical systems (BESs) have recently been developed for nitrate removal from nitrate-contaminated water. In this study, we compared the nitrate removal performance of biocathodes of BESs when using abiotic and biotic anodes. Acetate was used as electron donor in BESs with biotic anode, whereas a direct current power supply was used as energy source in BESs with abiotic anode. The nitrogen removal efficiency increased from 18.1% to 43.0% when the voltage supplied to the BES with abiotic anode increased from 0.7 V to 0.9 V, whereas no higher removal efficiency was obtained at a higher supplied voltage (1.1 V). The highest efficiency (78.0%) of autotrophic nitrogen removal was achieved when electron transfer from the biotic anode chamber of BESs was used. Unexpectedly, control of the cathode potential did not enhance nitrate removal in BESs with biotic anode. Special attention was paid to elucidate the differences of bacterial communities catalysing autotrophic denitrification in the biocathodes of BESs with abiotic and biotic anodes. Data from denaturing gradient gel electrophoresis and phylogenetic analysis suggested that denitrification in BESs with abiotic anode could be attributed to Nitratireductor sp., Shinella sp., and Dyella sp., whereas the dominant bacterial denitrifiers in BESs with biotic anode were found to be Pseudomonas sp., Curtobacterium sp., and Aeromonas sp. These results implied that biocathodes of BESs with biotic anode are more efficient than those of BESs with abiotic anode for nitrate removal from nitrate-contaminated water in practical applications.

  2. Anode materials for electrochemical waste destruction

    NASA Technical Reports Server (NTRS)

    Molton, Peter M.; Clarke, Clayton

    1990-01-01

    Electrochemical Oxidation (ECO) offers promise as a low-temperature, atmospheric pressure method for safe destruction of hazardous organic chemical wastes in water. Anode materials tend to suffer corrosion in the intensely oxidizing environment of the ECO cell. There is a need for cheaper, more resistant materials. In this experiment, a system is described for testing anode materials, with examples of several common anodes such as stainless steel, graphite, and platinized titanium. The ECO system is simple and safe to operate and the experiment can easily be expanded in scope to study the effects of different solutions, temperatures, and organic materials.

  3. CIRCUITS FOR CURRENT MEASUREMENTS

    DOEpatents

    Cox, R.J.

    1958-11-01

    Circuits are presented for measurement of a logarithmic scale of current flowing in a high impedance. In one form of the invention the disclosed circuit is in combination with an ionization chamber to measure lonization current. The particular circuit arrangement lncludes a vacuum tube having at least one grid, an ionization chamber connected in series with a high voltage source and the grid of the vacuum tube, and a d-c amplifier feedback circuit. As the ionization chamber current passes between the grid and cathode of the tube, the feedback circuit acts to stabilize the anode current, and the feedback voltage is a measure of the logaritbm of the ionization current.

  4. In-situ Raman spectroscopy mapping of Si based anode material lithiation

    NASA Astrophysics Data System (ADS)

    Yang, Junfeng; Kraytsberg, Alexander; Ein-Eli, Yair

    2015-05-01

    The lithiation/de-lithiation behavior of Cu-nanowire/Si nano-particle composite anodes with different copper current collectors is investigated using in-situ micro Raman spectroscopy. It is revealed that not all of the active material particles experience lithiation in the first cycle. It is suggested that a portion of the anode active material is electrically disconnected from the current collector to begin with. Mapping of the connectivity of the anode electrode, performed by in-situ micro-Raman revealed that the portion of the disconnected material depends on the type of the current collector and on the active material loading. The disconnected zones are distributed unevenly over the electrode area.

  5. Anode-biofilm electron transfer behavior and wastewater treatment under different operational modes of bioelectrochemical system.

    PubMed

    Wu, Baoguo; Feng, Chunhua; Huang, Liqiao; Lv, Zhisheng; Xie, Daohai; Wei, Chaohai

    2014-04-01

    Anode-biofilm electron transfer behavior was investigated during the advanced wastewater treatment process by three bioelectrochemical systems (BESs): microbial fuel cell (MFC), MFC operated under short circuit condition (MSC), and microbial electrolysis cell (MEC). Under different operational modes, current produced by the anode biofilm varied from 0.92, 4.15 to 8.21mA in the sequence of MFC, MSC and MEC, respectively. The cyclic voltammetry test on the anode biofilm suggested that the current generation was achieved via various bioelectroactive species with formal potentials at -0.473, -0.402 and -0.345V (vs. SCE). Gibbs free energy and charge transfer resistance data demonstrated that different amounts of available bioelectroactive species functioned in different BESs. The comparative investigation among MFC, MSC and MEC suggested that MEC was the only feasible operational mode for advanced wastewater treatment, because of its superior current generation capability.

  6. Anomalous - viscosity current drive

    DOEpatents

    Stix, Thomas H.; Ono, Masayuki

    1988-01-01

    An apparatus and method for maintaining a steady-state current in a toroidal magnetically confined plasma. An electric current is generated in an edge region at or near the outermost good magnetic surface of the toroidal plasma. The edge current is generated in a direction parallel to the flow of current in the main plasma and such that its current density is greater than the average density of the main plasma current. The current flow in the edge region is maintained in a direction parallel to the main current for a period of one or two of its characteristic decay times. Current from the edge region will penetrate radially into the plasma and augment the main plasma current through the mechanism of anomalous viscosity. In another aspect of the invention, current flow driven between a cathode and an anode is used to establish a start-up plasma current. The plasma-current channel is magnetically detached from the electrodes, leaving a plasma magnetically insulated from contact with any material obstructions including the cathode and anode.

  7. Gate modulation of anodically etched gallium arsenide nanowire random network

    NASA Astrophysics Data System (ADS)

    Aikawa, Shinya; Yamada, Kohei; Asoh, Hidetaka; Ono, Sachiko

    2016-06-01

    Gallium arsenide nanowires (GaAs NWs) formed by anodic etching show an electrically semi-insulating behavior because of charge carrier depletion caused by high interface state density. Here, we demonstrate the gate modulation of an anodically etched GaAs NW random network. By applying a reverse bias voltage after anodic etching of bulk GaAs, hydrogen ion exposure of the depleted NW region occurs, and then the interface state density is possibly decreased owing to the reduction in the amount of excess As generated at the interface between the amorphous Ga2O3 and GaAs layers. Consequently, the drain current of the thin-film transistor (TFT) with the GaAs NW random network was increased and was changed by the gate voltage. In contrast, the random network film remained in the insulator in the absence of reverse electrolysis treatment. The TFT performance is still insufficient but may be improved by optimizing the hydrogen ion exposure conditions.

  8. Inward Lithium-Ion Breathing of Hierarchically Porous Silicon Anodes

    SciTech Connect

    Xiao, Qiangfeng; Gu, Meng; Yang, Hui; Li, Bing; Zhang, Cunman; Liu, Yang; Liu, Fang; Dai, Fang; Yang, Li; Liu, Zhongyi; Xiao, Xingcheng; Liu, Gao; Zhao, Peng; Zhang, Sulin; Wang, Chong M.; Lu, Yunfeng; Cai, Mei

    2015-11-05

    Silicon has been identified as one of the most promising candidates as anode for high performance lithium-ion batteries. The key challenge for Si anodes is the large volume change induced chemomechanical fracture and subsequent rapid capacity fading upon cyclic charge and discharge. Improving capacity retention thus critically relies on smart accommodation of the volume changes through nanoscale structural design. In this work, we report a novel fabrication method for hierarchically porous Si nanospheres (hp-SiNSs), which consist of a porous shell and a hollow core. Upon charge/discharge cycling, the hp-SiNSs accommodate the volume change through reversible inward expansion/contraction with negligible particle-level outward expansion. Our mechanics analysis revealed that such a unique volume-change accommodation mechanism is enabled by the much stiffer modulus of the lithiated layer than the unlithiated porous layer and the low flow stress of the porous structure. Such inward expansion shields the hp-SiNSs from fracture, opposite to the outward expansion in solid Si during lithiation. Lithium ion battery assembled with this new nanoporous material exhibits high capacity, high power, long cycle life and high coulombic efficiency, which is superior to the current commercial Si-based anode materials. We find the low cost synthesis approach reported here provides a new avenue for the rational design of hierarchically porous structures with unique materials properties.

  9. Inward Lithium-Ion Breathing of Hierarchically Porous Silicon Anodes

    DOE PAGESBeta

    Xiao, Qiangfeng; Gu, Meng; Yang, Hui; Li, Bing; Zhang, Cunman; Liu, Yang; Liu, Fang; Dai, Fang; Yang, Li; Liu, Zhongyi; et al

    2015-11-05

    Silicon has been identified as one of the most promising candidates as anode for high performance lithium-ion batteries. The key challenge for Si anodes is the large volume change induced chemomechanical fracture and subsequent rapid capacity fading upon cyclic charge and discharge. Improving capacity retention thus critically relies on smart accommodation of the volume changes through nanoscale structural design. In this work, we report a novel fabrication method for hierarchically porous Si nanospheres (hp-SiNSs), which consist of a porous shell and a hollow core. Upon charge/discharge cycling, the hp-SiNSs accommodate the volume change through reversible inward expansion/contraction with negligible particle-levelmore » outward expansion. Our mechanics analysis revealed that such a unique volume-change accommodation mechanism is enabled by the much stiffer modulus of the lithiated layer than the unlithiated porous layer and the low flow stress of the porous structure. Such inward expansion shields the hp-SiNSs from fracture, opposite to the outward expansion in solid Si during lithiation. Lithium ion battery assembled with this new nanoporous material exhibits high capacity, high power, long cycle life and high coulombic efficiency, which is superior to the current commercial Si-based anode materials. We find the low cost synthesis approach reported here provides a new avenue for the rational design of hierarchically porous structures with unique materials properties.« less

  10. A new short-anoded IGBT with high emission efficiency

    NASA Astrophysics Data System (ADS)

    Weizhong, Chen; Bo, Zhang; Zehong, Li; Min, Ren; Zhaoji, Li

    2012-11-01

    A novel short-anoded insulated-gate bipolar transistor (SA-IGBT) with double emitters is proposed. At the on-state, the new structure shows extraordinarily high emission efficiency. Moreover, with a short-contacted anode, it further enhances the hole emission efficiency because of the crowding of the electrons. The forward voltage drop VF of this structure is 1.74 V at a current density 100 of A/cm2. Compared to the conventional NPT IGBT (1.94 V), segment-anode IGBT (SA-NPN 2.1 V), and conventional SA-IGBT (2.33 V), VF decreased by 10%, 17% and 30%, respectively. Furthermore, no NDR has been detected comparing to the SA-IGBT. At the off-state, there is a channel for extracting excessive carriers in the drift region. The turn-off loss Eoff of this proposed structure is 8.64 mJ/cm2. Compared to the conventional NPT IGBT (15.3 mJ/cm2), SA-NPN IGBT (12.8 mJ/cm2), and SA-IGBT (12.1 mJ/cm2), Eoff decreased by 43.7%, 32% and 28%, respectively.

  11. Inward lithium-ion breathing of hierarchically porous silicon anodes.

    PubMed

    Xiao, Qiangfeng; Gu, Meng; Yang, Hui; Li, Bing; Zhang, Cunman; Liu, Yang; Liu, Fang; Dai, Fang; Yang, Li; Liu, Zhongyi; Xiao, Xingcheng; Liu, Gao; Zhao, Peng; Zhang, Sulin; Wang, Chongmin; Lu, Yunfeng; Cai, Mei

    2015-11-05

    Silicon has been identified as a highly promising anode for next-generation lithium-ion batteries (LIBs). The key challenge for Si anodes is large volume change during the lithiation/delithiation cycle that results in chemomechanical degradation and subsequent rapid capacity fading. Here we report a novel fabrication method for hierarchically porous Si nanospheres (hp-SiNSs), which consist of a porous shell and a hollow core. On charge/discharge cycling, the hp-SiNSs accommodate the volume change through reversible inward Li breathing with negligible particle-level outward expansion. Our mechanics analysis revealed that such inward expansion is enabled by the much stiffer lithiated layer than the unlithiated porous layer. LIBs assembled with the hp-SiNSs exhibit high capacity, high power and long cycle life, which is superior to the current commercial Si-based anode materials. The low-cost synthesis approach provides a new avenue for the rational design of hierarchically porous structures with unique materials properties.

  12. Inward lithium-ion breathing of hierarchically porous silicon anodes

    PubMed Central

    Xiao, Qiangfeng; Gu, Meng; Yang, Hui; Li, Bing; Zhang, Cunman; Liu, Yang; Liu, Fang; Dai, Fang; Yang, Li; Liu, Zhongyi; Xiao, Xingcheng; Liu, Gao; Zhao, Peng; Zhang, Sulin; Wang, Chongmin; Lu, Yunfeng; Cai, Mei

    2015-01-01

    Silicon has been identified as a highly promising anode for next-generation lithium-ion batteries (LIBs). The key challenge for Si anodes is large volume change during the lithiation/delithiation cycle that results in chemomechanical degradation and subsequent rapid capacity fading. Here we report a novel fabrication method for hierarchically porous Si nanospheres (hp-SiNSs), which consist of a porous shell and a hollow core. On charge/discharge cycling, the hp-SiNSs accommodate the volume change through reversible inward Li breathing with negligible particle-level outward expansion. Our mechanics analysis revealed that such inward expansion is enabled by the much stiffer lithiated layer than the unlithiated porous layer. LIBs assembled with the hp-SiNSs exhibit high capacity, high power and long cycle life, which is superior to the current commercial Si-based anode materials. The low-cost synthesis approach provides a new avenue for the rational design of hierarchically porous structures with unique materials properties. PMID:26538181

  13. Development of a niobium-doped titania inert anode for titanium electrowinning in molten chloride salts.

    PubMed

    Snook, Graeme A; McGregor, Katherine; Urban, Andrew J; Lanyon, Marshall R; Donelson, R; Pownceby, Mark I

    2016-08-15

    The direct electrochemical reduction of solid titanium dioxide in a chloride melt is an attractive method for the production of titanium metal. It has been estimated that this type of electrolytic approach may reduce the costs of producing titanium sponge by more than half, with the additional benefit of a smaller environmental footprint. The process utilises a consumable carbon anode which releases a mixture of CO2 and CO gas during electrolysis, but suffers from low current efficiency due to the occurrence of parasitic side reactions involving carbon. The replacement of the carbon anode with a cheap, robust inert anode offers numerous benefits that include: elimination of carbon dioxide emissions, more efficient cell operation, opportunity for three-dimensional electrode configurations and reduced electrode costs. This paper reports a study of Nb-doped titania anode materials for inert anodes in a titanium electrolytic reduction cell. The study examines the effect of niobium content and sintering conditions on the performance of Nb-doped TiO2 anodes in laboratory-scale electrolysis tests. Experimental findings, including performance in a 100 h laboratory electrolysis test, are described. PMID:27265026

  14. Stable anodes for lithium ion batteries made of self-organized mesoporous silicon

    NASA Astrophysics Data System (ADS)

    Wolter, Sascha J.; Köntges, Marc; Bahnemann, Detlef; Brendel, Rolf

    2016-01-01

    Alloy-forming compounds, such as electrodes for lithium ion batteries, stand out in terms of their theoretical specific charge capacity while still lacking in mechanical stability due to significant volume changes during operation. Herein, we examine the approach of combining low structural dimensions of the active material with built-in expansion volumes and assess their benefit for silicon anodes in lithium ion batteries. Consequently, self-organized mesoporous silicon is prepared as a suitable anode material for lithium ion batteries without any pre-structuring methods. The anodes are made by employing electrochemical etching methods in a scalable process and are characterized by ellipsometry. Thermally evaporated copper is utilized as the current collector. A sheet of freestanding silicon in contact with copper is used as an anode material with a thickness of 3 μm. After an initialization phase, electrochemical characterization reveals an anode stability of more than 160 cycles with a specific charge capacity of 730 mAh/g. The mechanical stability of the anode is examined by taking SEM measurements of the used electrode material.

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  17. Sacrificial anode stability and polarization potential variation in a ternary Al-xZn-xMg alloy in a seawater-marine environment

    NASA Astrophysics Data System (ADS)

    Muazu, Abubakar; Aliyu, Yaro Shehu; Abdulwahab, Malik; Idowu Popoola, Abimbola Patricia

    2016-06-01

    In this paper, the effects of zinc (Zn) and magnesium (Mg) addition on the performance of an aluminum-based sacrificial anode in seawater were investigated using a potential measurement method. Anodic efficiency, protection efficiency, and polarized potential were the parameters used. The percentages of Zn and Mg in the anodes were varied from 2% to 8% Zn and 1% to 4% Mg. The alloys produced were tested as sacrificial anodes for the protection of mild steel in seawater at room temperature. Current efficiency as high as 88.36% was obtained in alloys containing 6% Zn and 1% Mg. The polarized potentials obtained for the coupled (steel/Al-based alloys) are as given in the Pourbaix diagrams, with steel lying within the immunity region/cathodic region and the sacrificial anodes within the anodic region. The protection offered by the sacrificial anodes to the steel after the 7th and 8th week was measured and protection efficiency values as high as 99.66% and 99.47% were achieved for the Al-6%Zn-1%Mg cast anode. The microstructures of the cast anodes comprise of intermetallic structures of hexagonal Mg3Zn2 and body-centered cubic Al2Mg3Zn3. These are probably responsible for the breakdown of the passive alumina film, thus enhancing the anode efficiency.

  18. Anodic Bubble Behavior and Voltage Drop in a Laboratory Transparent Aluminum Electrolytic Cell

    NASA Astrophysics Data System (ADS)

    Zhao, Zhibin; Wang, Zhaowen; Gao, Bingliang; Feng, Yuqing; Shi, Zhongning; Hu, Xianwei

    2016-06-01

    The anodic bubbles generated in aluminum electrolytic cells play a complex role to bath flow, alumina mixing, cell voltage, heat transfer, etc., and eventually affect cell performance. In this paper, the bubble dynamics beneath the anode were observed for the first time from bottom view directly in a similar industrial electrolytic environment, using a laboratory-scale transparent aluminum electrolytic cell. The corresponding cell voltage was measured simultaneously for quantitatively investigating its relevance to bubble dynamics. It was found that the bubbles generated in many spots that increased in number with the increase of current density; the bubbles grew through gas diffusion and various types of coalescences; when bubbles grew to a certain size with their surface reaching to the anode edge, they escaped from the anode bottom suddenly; with the increase of current density, the release frequency increases, and the size of these bubbles decreases. The cell voltage was very consistent with bubble coverage, with a high bubble coverage corresponding to a higher cell voltage. At low current density, the curves of voltage and coverage fluctuated in a regularly periodical pattern, while the curves became more irregular at high current density. The magnitude of voltage fluctuation increased with current density first and reached a maximum value at current density of 0.9 A/cm2, and decreased when the current density was further increased. The extra resistance induced by bubbles was found to increase with the bubble coverage, showing a similar trend with published equations.

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

    PubMed

    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.

  20. Effects of anode material on arcjet performance

    NASA Technical Reports Server (NTRS)

    Sankovic, John M.; Curran, Frank M.; Larson, C. A.

    1992-01-01

    Anodes fabricated from four different materials were tested in a modular arcjet thruster at 1 kW power level on nitrogen/hydrogen mixtures. A two-percent thoriated tungsten anode served as the control. Graphite was chosen for its ease in fabrication, but experienced severe erosion in the constrictor and diverging side. Hafnium carbide and lanthanum hexaboride were chosen for their low work functions but failed due to thermal stress and reacted with the propellant. When compared to the thoriated tungsten nozzle, thruster performance was significantly lower for the lanthanum hexaboride insert and the graphite nozzle, but was slightly higher for the hafnium carbide nozzle. Both the lanthanum hexaboride and hafnium carbide nozzle operated at higher voltages. An attempt was made to duplicate higher performance hafnium carbide results, but repeated attempts at machining a second anode insert were unsuccessful. Graphite, hafnium carbide, and lanthanum hexaboride do not appear viable anode materials for low power arcjet thrusters.

  1. Test plan for the pilot cell test of inert anodes: Report on the June 1991 meeting at the Reynolds Metals Company facility

    NASA Astrophysics Data System (ADS)

    Windisch, C. F., Jr.; Alcorn, T. R.; Tabereaux, A. T.

    1991-09-01

    The Inert Electrodes Program at the Pacific Northwest Laboratory (PNL) is supported by the Office of Industrial Processes (OIP) of the U.S. Department of Energy (DOE) and is aimed at improving the energy efficiency of Hall-Heroult cells through the development of inert anodes. The inert anodes currently under study are composed of a cermet material of the general composition NiO-NiFe2O4-Cu. The program has three primary objectives: (1) evaluate the anode material in a pilot cell facility, (2) investigate the mechanisms of the electrochemical reactions at the anodes surface, and (3) develop sensors for monitoring various anode and/or electrolyte conditions. This report discusses a test plan that has been developed for the pilot cell test of the inert anodes.

  2. Test plan for the pilot cell test of inert anodes: Report on the June 1991 meeting at the Reynolds Metals Company facility

    SciTech Connect

    Windisch, C.F. Jr. ); Alcorn, T.R.; Tabereaux, A.T. . Mfg. Technology Lab.)

    1991-09-01

    The Inert Electrodes Program at the Pacific Northwest Laboratory (PNL) is supported by the Office of Industrial Processes (OIP) of the US Department of Energy (DOE) and is aimed at improving the energy efficiency of Hall-Heroult cells through the development of inert anodes. The inert anodes currently under study are composed of a cermet material of the general composition NiO-NiFe{sub 2}O{sub 4}-Cu. The program has three primary objectives: (1) evaluate the anode material in a pilot cell facility, (2) investigate the mechanisms of the electrochemical reactions at the anodes surface, and (3) develop sensors for monitoring various anode and/or electrolyte conditions. This report discusses a test plan that has been developed for the pilot cell test of the inert anodes. 6 refs., 7 figs., 4 tabs.

  3. High-performance electrode for medium-temperature solid oxide fuel cells. Control of microstructure of ceria-based anodes with highly dispersed ruthenium electrocatalysts

    SciTech Connect

    Uchida, Hiroyuki; Osuga, Takashi; Watanabe, Masahiro

    1999-05-01

    In order to enhance gas-diffusion rates in a mixed-conducting samaria-doped ceria (SDC) anode, micrometer-sized pores were prepared by sintering a SDC paste containing fine polymer beads (d = 1.2 {micro}m) coated on an yttria-stabilized zirconia electrolyte. SDC anodes prepared under different conditions were examined to determine their pore-size distribution, pore volume, ohmic resistance, polarization behavior, and morphological structure. Both the anodic overpotential and the ohmic resistance of SDC anodes were lowered appreciably by controlling their microstructures. The performance of a SDC anode with optimized microstructure was enhanced further with highly dispersed Ru catalysts at 3 wt % loading, especially at low operating temperatures at about 800 C. The current density on a Ru-SDC anode at an overpotential of 0.1 V was 0.5 A/cm{sup 2} at 800 C.

  4. Additive-free thick graphene film as an anode material for flexible lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Rana, Kuldeep; Kim, Seong Dae; Ahn, Jong-Hyun

    2015-04-01

    This work demonstrates a simple route to develop mechanically flexible electrodes for Li-ion batteries (LIBs) that are usable as lightweight effective conducting networks for both cathodes and anodes. Removing electrochemically dead elements, such as binders, conducting agents and metallic current collectors, from the battery components will allow remarkable progress in this area. To investigate the feasibility of using thick, additive-free graphene films as anodes for flexible LIBs, we have synthesized and tested thick, additive-free, freestanding graphene films as anodes, first in a coin cell and further in a flexible full cell. As an anode material in a half cell, it showed a discharge capacity of about 350 mA h g-1 and maintained nearly this capacity over 50 cycles at various current rates. This film was also tested as an anode material in a full cell with a LiCoO2 cathode and showed good electrochemical performance. Because the graphene-based flexible film showed good performance in half- and full coin cells, we used this film as a flexible anode for flexible LIBs. No conducting agent or binder was used in the anode side, which helped in realizing the flexible LIBs. Using this, we demonstrate a thin, lightweight and flexible lithium ion battery with good electrochemical performance in both its flat and bent states.This work demonstrates a simple route to develop mechanically flexible electrodes for Li-ion batteries (LIBs) that are usable as lightweight effective conducting networks for both cathodes and anodes. Removing electrochemically dead elements, such as binders, conducting agents and metallic current collectors, from the battery components will allow remarkable progress in this area. To investigate the feasibility of using thick, additive-free graphene films as anodes for flexible LIBs, we have synthesized and tested thick, additive-free, freestanding graphene films as anodes, first in a coin cell and further in a flexible full cell. As an anode

  5. Phase III Advanced Anodes and Cathodes Utilized in Energy Efficient Aluminum Production Cells

    SciTech Connect

    R.A. Christini; R.K. Dawless; S.P. Ray; D.A. Weirauch, Jr.

    2001-11-05

    During Phase I of the present program, Alcoa developed a commercial cell concept that has been estimated to save 30% of the energy required for aluminum smelting. Phase ii involved the construction of a pilot facility and operation of two pilots. Phase iii of the Advanced Anodes and Cathodes Program was aimed at bench experiments to permit the resolution of certain questions to be followed by three pilot cells. All of the milestones related to materials, in particular metal purity, were attained with distinct improvements over work in previous phases of the program. NiO additions to the ceramic phase and Ag additions to the Cu metal phase of the cermet improved corrosion resistance sufficiently that the bench scale pencil anodes met the purity milestones. Some excellent metal purity results have been obtained with anodes of the following composition: Further improvements in anode material composition appear to be dependent on a better understanding of oxide solubilities in molten cryolite. For that reason, work was commissioned with an outside consultant to model the MeO - cryolite systems. That work has led to a better understanding of which oxides can be used to substitute into the NiO-Fe2O3 ceramic phase to stabilize the ferrites and reduce their solubility in molten cryolite. An extensive number of vertical plate bench electrolysis cells were run to try to find conditions where high current efficiencies could be attained. TiB2-G plates were very inconsistent and led to poor wetting and drainage. Pure TiB2 did produce good current efficiencies at small overlaps (shadowing) between the anodes and cathodes. This bench work with vertical plate anodes and cathodes reinforced the importance of good cathode wetting to attain high current efficiencies. Because of those conclusions, new wetting work was commissioned and became a major component of the research during the third year of Phase III. While significant progress was made in several areas, much work needs to be

  6. Upcycling of Packing-Peanuts into Carbon Microsheet Anodes for Lithium-Ion Batteries.

    PubMed

    Etacheri, Vinodkumar; Hong, Chulgi Nathan; Pol, Vilas G

    2015-09-15

    Porous carbon microsheet anodes with Li-ion storage capacity exceeding the theoretical limit are for the first time derived from waste packing-peanuts. Crystallinity, surface area, and porosity of these 1 μm thick carbon sheets were tuned by varying the processing temperature. Anodes composed of the carbon sheets outperformed the electrochemical properties of commercial graphitic anode in Li-ion batteries. At a current density of 0.1 C, carbon microsheet anodes exhibited a specific capacity of 420 mAh/g, which is slightly higher than the theoretical capacity of graphite (372 mAh/g) in Li-ion half-cell configurations. At a higher rate of 1 C, carbon sheets retained 4-fold higher specific capacity (220 mAh/g) compared to those of commercial graphitic anode. After 100 charge-discharge cycles at current densities of 0.1 and 0.2 C, optimized carbon sheet anodes retained stable specific capacities of 460 and 370 mAh/g, respectively. Spectroscopic and microscopic investigations proved the structural integrity of these high-performance carbon anodes during numerous charge-discharge cycles. Considerably higher electrochemical performance of the porous carbon microsheets are endorsed to their disorderness that facilitate to store more Li-ions than the theoretical limit, and porous 2-D microstructure enabling fast solid-state Li-ion diffusion and superior interfacial kinetics. The work demonstrated here illustrates an inexpensive and environmentally benign method for the upcycling of packaging materials into functional carbon materials for electrochemical energy storage.

  7. Model for anodic film growth on aluminum with coupled bulk transport and interfacial reactions.

    PubMed

    DeWitt, Stephen; Thornton, Katsuyo

    2014-05-13

    Films grown through the anodic oxidation of metal substrates are promising for applications ranging from solar cells to medical devices, but the underlying mechanisms of anodic growth are not fully understood. To provide a better understanding of these mechanisms, we present a new 1D model for the anodization of aluminum. In this model, a thin space charge region at the oxide/electrolyte interface couples the bulk ionic transport and the interfacial reactions. Charge builds up in this region, which alters the surface overpotential until the reaction and bulk fluxes are equal. The model reactions at the oxide/electrolyte interface are derived from the Våland-Heusler model, with modifications to allow for deviations from stoichiometry at the interface and the saturation of adsorption sites. The rate equations and equilibrium concentrations of adsorbed species at the oxide/electrolyte interface are obtained from the reactions using Butler-Volmer kinetics, whereas transport-limited reaction kinetics are utilized at the metal/oxide interface. The ionic transport through the bulk oxide is modeled using a newly proposed cooperative transport process, the counter-site defect mechanism. The model equations are evolved numerically. The model is parametrized and validated using experimental data in the literature for the rate of ejection of aluminum species into the electrolyte, embedded charge at the oxide/electrolyte interface, and the barrier thickness and growth rate of porous films. The parametrized model predicts that the embedded charge at the oxide/electrolyte interface decreases monotonically for increasing electrolyte pH at constant current density. The parametrized model also predicts that the embedded charge during potentiostatic anodization is at its steady-state value; the embedded charge at any given time is equal to the embedded charge during galvanostatic anodization at the same current. In addition to simulations of anodized barrier films, this model can be

  8. Optimized Porous Anodic Alumina Membranes for Water Ultrafiltration of Pathogenic Bacteria (E. coli).

    PubMed

    Zimer, Alexsandro Mendes; Machado, Maria Manuela P; Dalla Costa Júnior, Lázaro José; Ike, Priscila Tomie Leme; Iemma Mônica R C; Yamamoto, Cíntia Fumi; Ferreira, Cauê Favero; Souza, Dulce H F; de Oliveira, Cauê Ribeiro; Pereira, Ernesto Chaves

    2016-06-01

    In this paper, we present the optimization of porous anodic alumina membranes for ultrafiltration prepared by anodically oxidized aluminum foils. The membranes were characterized by field-emission scanning electron microscopy to measure the pore diameter and the membrane thicknesses. The liquid fluxes were estimated through gas permeability measurements using Darcy's and Forchheimerś equations. A 2(3) factorial design we used to optimize the membrane properties: pore diameter, membrane thickness, and liquid flux using as control variables the applied current density, solution composition and concentration. It was observed that the most import variables to control the pore diameter were current density and electrolyte composition. After the anodization both, metallic aluminum substrate and the barrier layer of alumina were removed using adequate solutions to obtain the free standing membrane. Then, Escherichia coli a common bacterial contamination of drinking water was removed using these PAA membranes with 100% of efficiency to obtain bacteria-free water. PMID:27427747

  9. Optimized Porous Anodic Alumina Membranes for Water Ultrafiltration of Pathogenic Bacteria (E. coli).

    PubMed

    Zimer, Alexsandro Mendes; Machado, Maria Manuela P; Dalla Costa Júnior, Lázaro José; Ike, Priscila Tomie Leme; Iemma Mônica R C; Yamamoto, Cíntia Fumi; Ferreira, Cauê Favero; Souza, Dulce H F; de Oliveira, Cauê Ribeiro; Pereira, Ernesto Chaves

    2016-06-01

    In this paper, we present the optimization of porous anodic alumina membranes for ultrafiltration prepared by anodically oxidized aluminum foils. The membranes were characterized by field-emission scanning electron microscopy to measure the pore diameter and the membrane thicknesses. The liquid fluxes were estimated through gas permeability measurements using Darcy's and Forchheimerś equations. A 2(3) factorial design we used to optimize the membrane properties: pore diameter, membrane thickness, and liquid flux using as control variables the applied current density, solution composition and concentration. It was observed that the most import variables to control the pore diameter were current density and electrolyte composition. After the anodization both, metallic aluminum substrate and the barrier layer of alumina were removed using adequate solutions to obtain the free standing membrane. Then, Escherichia coli a common bacterial contamination of drinking water was removed using these PAA membranes with 100% of efficiency to obtain bacteria-free water.

  10. Method for providing uranium articles with a corrosion resistant anodized coating

    DOEpatents

    Waldrop, Forrest B.; Washington, Charles A.

    1982-01-01

    Uranium articles are provided with anodized oxide coatings in an aqueous solution of an electrolyte selected from the group consisting of potassium phosphate, potassium hydroxide, ammonium hydroxide, and a mixture of potassium tetraborate and boric acid. The uranium articles are anodized at a temperature greater than about 75.degree. C. with a current flow of less than about 0.036 A/cm.sup.2 of surface area while the pH of the solution is maintained in a range of about 2 to 11.5. The pH values of the aqueous solution and the low current density utilized during the electrolysis prevent excessive dissolution of the uranium and porosity in the film or watering. The relatively high temperature of the electrolyte bath inhibits hydration and the attendant deleterious pitting so as to enhance corrosion resistance of the anodized coating.

  11. Method for providing uranium articles with a corrosion-resistant anodized coating

    DOEpatents

    Waldrop, F.B.; Washington, C.A.

    1981-01-07

    Uranium articles are provided with anodized oxide coatings in an aqueous solution of an electrolyte selected from the group consisting of potassium phosphate, potassium hydroxide, ammonium hydroxide, and a mixture of potassium tetraborate and boric acid. The uranium articles are anodized at a temperature greater than about 75/sup 0/C with a current flow of less than about 0.036 A/cm/sup 2/ of surface area while the pH of the solution is maintained in a range of about 2 to 11.5. The pH values of the aqueous solution and the low current density utilized during the electrolysis prevent excessive dissolution of the uranium and porosity in the film or watering. The relatively high temperature of the electrolyte bath inhibits hydration and the attendant deleterious pitting so as to enhance corrosion resistance of the anodized coating.

  12. Compositional and structural changes at the anodic surface of thermally poled soda-lime float glass

    SciTech Connect

    Ziemath, E. C.; Araujo, V. D.; Escanhoela, C. A. Jr.

    2008-09-01

    Applying high dc electric fields at elevated temperatures on silicate glasses results in displacement of ions, causing compositional and structural changes in the anodic surface. In this work, the ionic displacement was accompanied by electric current measurements during poling. The thickness of the Na{sup +} depletion layer calculated from the current curves agrees with the thickness measured by EDS only if displacement of Ca{sup 2+} and O{sup -} are also taken into account. A depletion of Ca{sup 2+} in the anodic surface has in fact been observed. Structural changes were confirmed by infrared diffuse and specular reflectance spectroscopies. A narrowing of the band at about 1070 cm{sup -1} can be attributed to an increase in the structural ordering degree. Refractive index measurements confirm compositional changes and contact angle measurements indicate the existence of a negative charge density at the anodic surface.

  13. Child-Langmuir flow with periodically varying anode voltage

    SciTech Connect

    Rokhlenko, A.

    2015-02-15

    Using the Lagrangian technique, we study settled Child-Langmuir flows in a one dimensional planar diodes whose anode voltages periodically vary around given positive values. Our goal is to find analytically if the average currents in these systems can exceed the famous Child-Langmuir limit found for the stationary current a long time ago. The main result of our study is that in a periodic quasi-stationary regime the average current can be larger than the Child-Langmuir maximum even by 50% compared with its adiabatic average value. The cathode current in this case has the form of rectangular pulses which are formed by a very special triangular voltage modulation. This regime, i.e., periodicity, shape of pulses, and their amplitude, needs to be carefully chosen for the best performance.

  14. Electrochemical synthesis of hydrogen with depolarization of the anodic process

    NASA Astrophysics Data System (ADS)

    Tulskiy, Gennadiy; Tulskaya, Alena; Skatkov, Leonid; Gomozov, Valeriy; Deribo, Svetlana

    2016-05-01

    A new active composite coating for graphite gas diffusion electrode for hybrid sulfur cycle was proposed. The kinetics of oxidation of SO2 were studied on porous graphite anodes with different catalytic coatings. It was shown that the most efficient composite coating is based on activated carbon and platinum supported on graphite gas diffusion substrate. The voltage drop in the laboratory electrochemical cell was 1.3 V at a current density of 1000 A·m-2. This corresponds to a specific consumption of 3.1 kWh electric energy per 1 m3 of hydrogen.

  15. Studies of a granular aluminum anode in an alkaline fuel cell

    NASA Astrophysics Data System (ADS)

    Popovich, Neil A.; Govind, Rakesh

    A granular aluminum anode was investigated for use in an alkaline aluminum/hydrogen peroxide fuel cell. The fuel cell utilizes granules of aluminum (8-12 mm in diameter) as an anode, potassium hydroxide (KOH) as an anolyte and hydrogen peroxide as a catholyte. Granular anodes have a significantly higher surface area than planar surfaces, thereby resulting in higher utilization of the anode material. Polarization experiments were performed as well as closed circuit power production experiments. KOH concentrations were varied in the experiments. Polarization experiments achieved a current density of 10.02 mA/cm 2 using 2 M KOH and granular aluminum with a surface area of 205.6 cm 2. Power production experiments sustained a current density of 0.05 mA/cm 2 using 1.5 M KOH and granular aluminum with a surface area of 59.8 cm 2. Results indicate that granular metal anodes have potential for use in high energy density fuel cells.

  16. Anodic concentration loss and impedance characteristics in rotating disk electrode microbial fuel cells.

    PubMed

    Shen, Liye; Ma, Jingxing; Song, Pengfei; Lu, Zhihao; Yin, Yao; Liu, Yongdi; Cai, Lankun; Zhang, Lehua

    2016-10-01

    A rotating disk electrode (RDE) was used to investigate the concentration loss and impedance characteristics of anodic biofilms in microbial fuel cells (MFCs). Amperometric time-current analysis revealed that at the rotation rate of 480 rpm, a maximum current density of 168 µA cm(-2) can be achieved, which was 22.2 % higher than when there was no rotation. Linear sweep voltammetry and electrochemical impedance spectroscopy tests showed that when the anodic potential was set to -300 mV vs. Ag/AgCl reference, the power densities could increase by 59.0  %, reaching 1385 mW m(-2), the anodic resistance could reduce by 19  %, and the anodic capacitance could increase by 36 %. These results concur with a more than 85 % decrease of the diffusion layer thickness. Data indicated that concentration loss, diffusion layer thickness, and the mixing velocity play important roles in anodic resistance reduction and power output of MFCs. These findings could be helpful to the design of future industrial-scale MFCs with mixed bacteria biofilms. PMID:27282165

  17. Simulative research on the anode plasma dynamics in the high-power electron beam diode

    SciTech Connect

    Cai, Dan; Liu, Lie; Ju, Jin-Chuan; Zhang, Tian-Yang; Zhao, Xue-Long; Zhou, Hong-Yu

    2015-07-15

    Anode plasma generated by electron beams could limit the electrical pulse-length, modify the impedance and stability of diode, and affect the generator to diode power coupling. In this paper, a particle-in-cell code is used to study the dynamics of anode plasma in the high-power electron beam diode. The effect of gas type, dynamic characteristic of ions on the diode operation with bipolar flow model are presented. With anode plasma appearing, the amplitude of diode current is increased due to charge neutralizations of electron flow. The lever of neutralization can be expressed using saturation factor. At same pressure of the anode gas layer, the saturation factor of CO{sub 2} is bigger than the H{sub 2}O vapor, namely, the generation rate of C{sup +} ions is larger than the H{sup +} ions at the same pressure. The transition time of ions in the anode-cathode gap could be used to estimate the time of diode current maximum.

  18. New High-Energy Nanofiber Anode Materials

    SciTech Connect

    Zhang, Xiangwu; Fedkiw, Peter; Khan, Saad; Huang, Alex; Fan, Jiang

    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.

  19. Fortissimo: A Japanese Space Test Of Bare Wire Anode Tethers

    NASA Technical Reports Server (NTRS)

    Johnson, Les; Fujii, H. A.; Sanmartin, J. R.

    2008-01-01

    A Japanese led international team is developing a suborbital test of orbital-motion-limited (OML) bare wire anode current collection for application to electrodynamic tether (EDT) propulsion. The tether is a tape with a width of 25 mm, thickness of 0.05 mm, and is 300 m in length. This will be the first space test of OML theory. The mission will launch in the summer of 2009 using an S520 Sounding Rocket. During ascent, and above approx. 100 km in attitude, the tape tether will be deployed at a rate of approx. 8 m/s. Once deployed, the tape tether will serve as an anode, collecting ionospheric electrons. The electrons will be expelled into space by a hollow cathode device, thereby completing the circuit and allowing current to flow. The total amount of current collected will be used to assess the validity of OML theory. This paper will describe the objectives of the proposed mission, the technologies to be employed, and the application of the results to future space missions using EDTs for propulsion or power generation.

  20. Computational modeling of alkaline air-breathing microfluidic fuel cells with an array of cylinder anodes

    NASA Astrophysics Data System (ADS)

    Ye, Ding-Ding; Zhang, Biao; Zhu, Xun; Sui, Pang-Chieh; Djilali, Ned; Liao, Qiang

    2015-08-01

    A three-dimensional computational model is developed for an alkaline air-breathing microfluidic fuel cell (AMFC) with an array of cylinder anodes. The model is validated against experimental data from an in-house prototype AMFC. The distributions of fluid velocity, fuel concentration and current density of the fuel cell are analyzed in detail. The effect of reactant flow rate on the cell performance and electrode potentials is also studied. The model results suggest that fuel crossover is minimized by the fast electrolyte flow in the vicinity of the cathode. The current production of each anode is uneven and is well correlated with internal ohmic resistance. Fuel transfer limitation occurs at low flow rates (<100 μL min-1) but diminishes at high flow rates. The model results also indicate that cathode potential reversal takes place at combined low flow rate and high current density conditions, mainly due to the improved overpotential downstream where fuel starvation occurs. The anode reaction current distribution is found to be relatively uniform, which is a result of a compensating mechanism that improves the current production of the bottom anodes downstream.

  1. Asymmetric battery having a semi-solid cathode and high energy density anode

    DOEpatents

    Tan, Taison; Chiang, Yet-Ming; Ota, Naoki; Wilder, Throop; Duduta, Mihai

    2016-09-06

    Embodiments described herein relate generally to devices, systems and methods of producing high energy density batteries having a semi-solid cathode that is thicker than the anode. An electrochemical cell can include a positive electrode current collector, a negative electrode current collector and an ion-permeable membrane disposed between the positive electrode current collector and the negative electrode current collector. The ion-permeable membrane is spaced a first distance from the positive electrode current collector and at least partially defines a positive electroactive zone. The ion-permeable membrane is spaced a second distance from the negative electrode current collector and at least partially defines a negative electroactive zone. The second distance is less than the first distance. A semi-solid cathode that includes a suspension of an active material and a conductive material in a non-aqueous liquid electrolyte is disposed in the positive electroactive zone, and an anode is disposed in the negative electroactive zone.

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

    NASA Astrophysics Data System (ADS)

    Miller, Elizabeth C.

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

  3. Boat electrofishing relative to anode arrangement

    USGS Publications Warehouse

    Miranda, L.E.; Kratochvil, M.

    2008-01-01

    We assessed the effect of boom (i.e., anode) arrangement (a single boom and double booms spaced 1.3, 1.9, and 3.2 m apart) on the characteristics of the electric field formed ahead of an electrofishing boat as well as on fish catch. Anode arrangement affected the lengthwise and crosswise characteristics of the field. As a general rule, rearranging the anodes from a single boom located centrally to a double-boom system with broadly separated anodes shifted the strength of the field outward (away from the center) and forward (away from the boat). The highest voltage gradients occurred when the anodes had the greatest separation. Catch rates varied by boom arrangement, increasing as boom separation increased. Differences in species and length selectivity with respect to boom arrangement were minor. We suggest that the double-boom arrangement with the booms placed about 1.9 m apart (but no more than about 2.5 m) is suitable for most electrofishing applications. ?? Copyright by the American Fisheries Society 2008.

  4. Hierarchically Three-Dimensional Nanofiber Based Textile with High Conductivity and Biocompatibility As a Microbial Fuel Cell Anode.

    PubMed

    Tao, Yifei; Liu, Qiongzhen; Chen, Jiahui; Wang, Bo; Wang, Yuedan; Liu, Ke; Li, Mufang; Jiang, Haiqing; Lu, Zhentan; Wang, Dong

    2016-07-19

    Microbial fuel cells (MFCs) encompass complex bioelectrocatalytic reactions that converting chemical energy of organic compounds to electrical energy. Improving the anode configuration is thought to be a critical step for enhancing MFCs performance. In present study, a hierarchically structured textile polypyrrole/poly(vinyl alcohol-co-polyethylene) nanofibers/poly(ethylene terephthalate) (referred to PPy/NFs/PET) is shown to be excellent anode for MFCs. This hierarchical PPy/NFs/PET anode affords an open porous and three-dimensional interconnecting conductive scaffold with larger surface roughness, facilitating microbial colonization and electron transfer from exoelectrogens to the anode. The mediator-less MFC equipped with PPy/NFs/PET anode achieves a remarkable maximum power density of 2420 mW m(-2) with Escherichia coli as the microbial catalyst at the current density of 5500 mA m(-2), which is approximately 17 times higher compared to a reference anode PPy/PET (144 mW m(-2)). Considering the low cost, low weight, facile fabrication, and good winding, this PPy/NFs/PET textile anode promises a great potential for high-performance and cost-effective MFCs in a large scale. PMID:27294591

  5. Hierarchically Three-Dimensional Nanofiber Based Textile with High Conductivity and Biocompatibility As a Microbial Fuel Cell Anode.

    PubMed

    Tao, Yifei; Liu, Qiongzhen; Chen, Jiahui; Wang, Bo; Wang, Yuedan; Liu, Ke; Li, Mufang; Jiang, Haiqing; Lu, Zhentan; Wang, Dong

    2016-07-19

    Microbial fuel cells (MFCs) encompass complex bioelectrocatalytic reactions that converting chemical energy of organic compounds to electrical energy. Improving the anode configuration is thought to be a critical step for enhancing MFCs performance. In present study, a hierarchically structured textile polypyrrole/poly(vinyl alcohol-co-polyethylene) nanofibers/poly(ethylene terephthalate) (referred to PPy/NFs/PET) is shown to be excellent anode for MFCs. This hierarchical PPy/NFs/PET anode affords an open porous and three-dimensional interconnecting conductive scaffold with larger surface roughness, facilitating microbial colonization and electron transfer from exoelectrogens to the anode. The mediator-less MFC equipped with PPy/NFs/PET anode achieves a remarkable maximum power density of 2420 mW m(-2) with Escherichia coli as the microbial catalyst at the current density of 5500 mA m(-2), which is approximately 17 times higher compared to a reference anode PPy/PET (144 mW m(-2)). Considering the low cost, low weight, facile fabrication, and good winding, this PPy/NFs/PET textile anode promises a great potential for high-performance and cost-effective MFCs in a large scale.

  6. Operating conditions for the generation of stable anode spot plasma in front of a positively biased electrode

    SciTech Connect

    Park, Yeong-Shin; Lee, Yuna; Dang, Jeong-Jeung; Chung, Kyoung-Jae; Hwang, Y. S.

    2014-02-15

    Stability of an anode spot plasma, which is an additional high density plasma generated in front of a positively biased electrode immersed in ambient plasma, is a critical issue for its utilization to various types of ion sources. In this study, operating conditions for the generation of stable anode spot plasmas are experimentally investigated. Diagnostics of the bias current flowing into the positively biased electrode and the properties of ambient plasma reveal that unstable nature of the anode spot is deeply associated with the reduction of double layer potential between the anode spot plasma and the ambient plasma. It is found that stability of the anode spot plasma can be improved with increasing the ionization rate in ambient plasma so as to compensate the loss of electrons across the double layer or with enlarging the area of the biased electrode to prevent electron accumulation inside the anode spot. The results obtained from the present study give the guideline for operating conditions of anode spot plasmas as an ion source with high brightness.

  7. Enhanced electrical contact of microbes using Fe(3)O(4)/CNT nanocomposite anode in mediator-less microbial fuel cell.

    PubMed

    Park, In Ho; Christy, Maria; Kim, Pil; Nahm, Kee Suk

    2014-08-15

    A novel Fe(3)O(4)/CNT nanocomposite was synthesized and employed for the modification of carbon paper anode in a mediator-less microbial fuel cell (MFC) to enhance its performance. The Fe(3)O(4)/CNT composite modified anodes with various Fe(3)O(4) contents were investigated to find the optimum ratio of the nanocomposite for the best MFC performance. The Fe(3)O(4)/CNT modified anodes produced much higher power densities than unmodified carbon anode and the 30wt% Fe3O4/CNT modified anode exhibited a maximum power density of 830mW/m(2). In the Fe(3)O(4)/CNT composite modified anode, Fe(3)O(4) helps to attach the CNT on anode surface by its magnetic attraction and forms a multi layered network, whereas CNT offers a better nanostructure environment for bacterial growth and helps electron transfer from E.coli to electrode resulting in the increase in the current production with the catalytic activity of bacteria. The electrocatalytic behavior and all possible mechanism for their better performance are discussed in detail with the help of various structural and electrochemical techniques.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  9. Electrochemical Evaluation of Lead Base Composite Anodes Fabricated by Accumulative Roll Bonding Technique

    NASA Astrophysics Data System (ADS)

    Karbasi, Maryam; Keshavarz Alamdari, Eskandar

    2015-04-01

    Accumulative roll bonding is used for the first time in lead systems to fabricate advanced lead base composite anodes. For this purpose, Ag as the most common and effective additive, Co as the best metallic immiscible substitution for Ag, and MnO2 as the ceramic and electrocatalytic agent have been used as additives to produce anodes. The accumulative roll bonding processed sheets have been fabricated under determined conditions. The electrochemical properties of the prepared samples are investigated by Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, Polarization tests, electrowinning tests, and Scanning Electron Microscopy. The results indicate that the ARB-processed composite lead sheets can be perfectly used as novel developed anodes. The advantages include 5.51 times increase of current density, in the Pb-pct0.5Ag 9-pass sample compared to pure lead anode, decreased charge transfer resistance from 56.31 (Ω cm2) in pure lead anode to 17.5 (Ω cm2) in the Pb-pct2MnO2 8-pass sample (72 pct lower), and decreased oxygen evolution potential from 1.95 (V/SHE) in pure lead anode to 1.77 (V/SHE) in the Pb-pct2MnO2 8-pass sample (0.18 (V/SHE) lower). Electrowinning tests results reveal Pb-2 pctMnO2 8-pass showed best anodic performance withsignificant lower compared corrosion rate (75 pct), product and electrolyte contamination, slime formation, energy consumption and higher Zn deposit and energy conservation (to 294 kWh/t-Zn). Finest Zn deposit morphology (effective reduced grain size corresponding to smoothness and compaction) has been supplied by Pb-2 pctMnO2 8-pass sample resulted from enhanced growth rate of Zn in lack of Pb contaminations that could act as suitable nucleation sites.

  10. A POM–organic framework anode for Li-ion battery

    DOE PAGESBeta

    Yue, Yanfeng; Li, Yunchao; Bi, Zhonghe; Veith, Gabriel M.; Bridges, Craig A.; Guo, Bingkun; Chen, Jihua; Mullins, David R.; Surwade, Sumedh P.; Mahurin, Shannon M.; et al

    2015-10-12

    Rechargeable Li-ion batteries (LIBs) are currently the dominant power source for portable electronic devices and electric vehicles, and for small-scale stationary energy storage. However, one bottleneck of the anode materials for LIBs is the poor cycling performance caused by the fact that the anodes cannot maintain their integrity over several charge–discharge cycles. In this work, we demonstrate an approach to improving the cycling performance of lithium-ion battery anodes by constructing an extended 3D network of flexible redox active polyoxometalate (POM) clusters with redox active organic linkers, herein described as POMOF. In addition, this architecture enables the accommodation of large volumemore » changes during cycling at relatively high current rates. For example, the POMOF anode exhibits a high reversible capacity of 540 mA h g–1 after 360 cycles at a current rate of 0.25C and a long cycle life at a current rate of 1.25C (>500 cycles).« less

  11. A POM–organic framework anode for Li-ion battery

    SciTech Connect

    Yue, Yanfeng; Li, Yunchao; Bi, Zhonghe; Veith, Gabriel M.; Bridges, Craig A.; Guo, Bingkun; Chen, Jihua; Mullins, David R.; Surwade, Sumedh P.; Mahurin, Shannon M.; Liu, Hongjun; Paranthaman, M. Parans; Dai, Sheng

    2015-10-12

    Rechargeable Li-ion batteries (LIBs) are currently the dominant power source for portable electronic devices and electric vehicles, and for small-scale stationary energy storage. However, one bottleneck of the anode materials for LIBs is the poor cycling performance caused by the fact that the anodes cannot maintain their integrity over several charge–discharge cycles. In this work, we demonstrate an approach to improving the cycling performance of lithium-ion battery anodes by constructing an extended 3D network of flexible redox active polyoxometalate (POM) clusters with redox active organic linkers, herein described as POMOF. In addition, this architecture enables the accommodation of large volume changes during cycling at relatively high current rates. For example, the POMOF anode exhibits a high reversible capacity of 540 mA h g–1 after 360 cycles at a current rate of 0.25C and a long cycle life at a current rate of 1.25C (>500 cycles).

  12. Investigation of residual anode material after electrorefining uranium in molten chloride salt

    NASA Astrophysics Data System (ADS)

    Rose, M. A.; Williamson, M. A.; Willit, J.

    2015-12-01

    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% UCl3. 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 U3+ ion concentration in the diffusion layer surrounding the electrode rises precipitously to levels, which may at low temperatures exceed the solubility limit for UCl3 or in the case of the eutectic salt for K2UCl5. The reduction in current response observed at low temperature in eutectic salt is eliminated at 650 °C, where K2UCl5 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.

  13. Microwave processing of tantalum capacitor anodes

    SciTech Connect

    Lauf, R J; Hamby, C; Holcombe, C E; Vierow, W F

    1992-08-01

    Porous tantalum anodes were sintered at temperatures from 1600 to 1900{degrees}C using a conventional high-vacuum furnace as well as both 2.45 GHz fixed-frequency and 4--8 GHz variable-frequency microwave furnaces. Various insulation and casketing techniques were used to couple the microwave power to the tantalum compacts. Several types of tantalum powder were used to assess the effect of microwave processing on sintered surface area and impurity levels. Some microwave sintered anodes have an unusual surface rippling not seen on conventionally fired parts. The rippling suggests that a microscopic arcing or plasma might have been generated. Two important effects could be exploited if this phenomenon can be controlled. First, the effective tantalum surface area could be increased, yielding higher capacitance per volume. Second, surface impurities might be cleaned away, allowing the formation of a better dielectric film during the anodization process and, ultimately, higher working voltage.

  14. Nanocomposite protective coatings for battery anodes

    DOEpatents

    Lemmon, John P; Xiao, Jie; Liu, Jun

    2014-01-21

    Modified surfaces on metal anodes for batteries can help resist formation of malfunction-inducing surface defects. The modification can include application of a protective nanocomposite coating that can inhibit formation of surface defects. such as dendrites, on the anode during charge/discharge cycles. For example, for anodes having a metal (M'), the protective coating can be characterized by products of chemical or electrochemical dissociation of a nanocomposite containing a polymer and an exfoliated compound (M.sub.a'M.sub.b''X.sub.c). The metal, M', comprises Li, Na, or Zn. The exfoliated compound comprises M' among lamella of M.sub.b''X.sub.c, wherein M'' is Fe, Mo, Ta, W, or V, and X is S, O, or Se.

  15. Direct electrowinning of lead from suspension galena concentrate anode in different electrolytes

    NASA Astrophysics Data System (ADS)

    Paramguru, R. K.; Küzeci, E.; Kammel, R.

    1988-02-01

    Electrochemical extraction of lead from galena by suspension electrolysis has been examined. Galvanostatic studies with slurry electrode as well as voltametric studies with carbon paste electrode in various electrolytes have been made in order to evaluate bath performance. Sodium hydroxide has been found to result in poor dissolution whereas ionic conduction through the electrolyte as well as oxide formation at the anode hinders lead dissolution in perchlorate media. Acetate bath results in substantial amount of oxide formation at anode even though solid bed conduction dominates. Sodium chloride bath has been found to have good prospects for producing lead ions and elemental sulfur with good current efficiencies.

  16. Sulfur tolerant anode materials. Quarterly report, January 1--March 31, 1988

    SciTech Connect

    Not Available

    1988-05-01

    The goal of this program is the development of a molten carbonate fuel cell (MCFC) anode which is more tolerant of sulfur contaminants in the fuel than the current state-of-the-art nickel-based anode structures. This program addresses two different but related aspects of the sulfur contamination problem. The primary aspect is concerned with the development of a sulfur tolerant electrocatalyst for the fuel oxidation reaction. A secondary issue is the development of a sulfur tolerant water-gas-shift reaction catalyst and an investigation of potential steam reforming catalysts which also have some sulfur tolerant capabilities. These two aspects are being addressed as two separate tasks.

  17. Sulfur tolerant anode materials. Quarterly report, October 1--December 31, 1987

    SciTech Connect

    Not Available

    1988-02-01

    The goal of this program is the development of a molten carbonate fuel cell (MCFC) anode which is more tolerant of sulfur contaminants in the fuel than the current state-of-the-art nickel-based anode structures. This program addresses two different but related aspects of the sulfur contamination problem. The primary aspect is concerned with the development of a sulfur tolerant electrocatalyst for the fuel oxidation reaction. A secondary issue is the development of a sulfur tolerant water-gas-shift reaction catalyst and an investigation of potential steam reforming catalysts which also have some sulfur tolerant capabilities. These two aspects are being addressed as two separate tasks.

  18. Lead dioxide film sonoelectrodeposition in acidic media: Preparation and performance of stable practical anodes.

    PubMed

    Sáez, V; Esclapez, M D; Frías-Ferrer, A J; Bonete, P; Tudela, I; Díez-García, M I; González-García, J

    2011-07-01

    Practical lead dioxide anodes have been obtained by electrodeposition on glassy carbon and titanium substrates in the presence and in the absence of an ultrasound field. The films obtained by mechanical agitation on glassy carbon are strongly improved when the electrodeposition process is carried out with the ultrasound field, providing adherent deposits free from nodules and stress, but with pores appearing occasionally. These enhanced properties were not achieved by mechanical conditions, even when optimization of temperature, current density, additives and geometrical aspects was attempted. The best practical anodes were obtained by sonoelectrodeposition using specially treated titanium as substrate, providing comparable behavior to commercial electrodes. PMID:21195010

  19. Sulfur tolerant anode materials. Quarterly report, October 1--December 31, 1986

    SciTech Connect

    Not Available

    1987-02-01

    The goal of this program is the development of a molten carbonate fuel cell (MCFC) anode which is more tolerant of sulfur contaminants in the fuel than the current state-of-the-art nickel-based anode structures. This program addresses two different but related aspects of the sulfur contamination problem. The primary aspect is concerned with the development of a sulfur tolerant electrocatalyst for the fuel oxidation reaction. A secondary issue is the development of a sulfur tolerant water-gas-shift reaction catalyst and an investigation of potential steam reforming catalysts which also have some sulfur tolerant capabilities. These two aspects are being addressed as two separate tasks.

  20. Carbon-Coated SnO2 Nanorod Array for Lithium-Ion Battery Anode Material

    PubMed Central

    2010-01-01

    Carbon-coated SnO2 nanorod array directly grown on the substrate has been prepared by a two-step hydrothermal method for anode material of lithium-ion batteries (LIBs). The structural, morphological and electrochemical properties were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical measurement. When used as anodes for LIBs with high current density, as-obtained array reveals excellent cycling stability and rate capability. This straightforward approach can be extended to the synthesis of other carbon-coated metal oxides for application of LIBs. PMID:20672094

  1. An Insoluble Titanium-Lead Anode for Sulfate Electrolytes

    SciTech Connect

    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

  2. Polarization-Induced Interfacial Reactions between Nickel and Selenium in Ni/Zirconia SOFC Anodes and Comparison with Sulfur Poisoning

    SciTech Connect

    Marina, Olga A.; Pederson, Larry R.; Coyle, Christopher A.; Thomsen, Edwin C.; Edwards, Danny J.

    2011-01-10

    Three distinctly different characteristic responses of a nickel/yttria-stabilized zirconia (Ni/YSZ) cermet anode to the presence of hydrogen selenide in synthetic coal gas were observed, depending on temperature (650-800oC), H2Se concentration (0-40 ppm), and especially on the extent of anodic polarization (0 to ~0.5 V). The first level of response was characterized by a rapid but modest decrease in power density to a new steady state, with no further degradation observed in tests up to 700 hours in duration. Mostly observed at high temperatures, low H2Se concentrations, and low anodic polarizations, this response level was similar to effects caused by the presence of H2S, but with slower onset and lower reversibility. Higher anodic polarization at a constant current could trigger a second level of response characterized by oscillatory behavior involving cycles of rapid performance loss followed by rapid recovery. Oscillations at the constant current density were accompanied by the appearance and disappearance of a new feature in the electrochemical impedance spectrum with a summit frequency of ~100 Hz. Oscillatory behavior ceased when the current density was lowered. Such behavior was not observed for cells operated at a constant potential of similar magnitude, though. A third level of response, irreversible cell failure, could be induced by further increases in anodic polarization, additionally favored by low temperature and high H2Se concentration. Post-test analyses of failed cells by electron microscopy revealed the extensive microstructural changes including the appearance of nickel oxide and nickel selenide alteration phases, only at the anode/electrolyte interface. From bulk thermochemical considerations the formation of nickel selenides could not be expected. Local chemical conditions created at the anode/electrolyte interface appear to be of overriding importance with respect to the extent of Ni/YSZ anode interactions with H2Se in coal gas.

  3. The low current domain of the aluminum/sulfur battery

    SciTech Connect

    Licht, S.; Hwang, J.; Light, T.S.; Dillon, R.

    1997-03-01

    A variety of factors including solution-phase modification, aluminum composition, temperature, and anolyte volume, modify anodic behavior in the approach to the low current density domain of the aluminum/sulfur battery. A relatively low level [0.4% Hg(NO{sub 3}){sub 2} by weight in the anolyte] of mercury provides an amalgam film on the aluminum anode which minimizes the parasitic chemical consumption of aluminum anode which aluminum, providing anodic faradaic efficiencies in excess of 80%. Anodic overpotential losses are high for aluminum immersed in mercury-containing electrolytes. However, at lower current densities, their absolute magnitude is several hundred millivolts or smaller and does not substantially impair the cell potential. Aluminum/sulfur battery discharge times up to several hundred hours are demonstrated for 0.2 mA/cm{sup 2} current density cells.

  4. Pulsed klystrons with feedback controlled mod-anode modulators

    SciTech Connect

    Reass, William A; Baca, David M; Jerry, Davis L; Rees, Daniel E

    2009-01-01

    This paper describes a fast rise and fall, totem-pole mod-anode modulators for klystron application. Details of these systems as recently installed utilizing a beam switch tube ''on-deck'' and a planar triode ''off-deck'' in a grid-catch feedback regulated configuration will be provided. The grid-catch configuration regulates the klystron mod-anode voltage at a specified set-point during switching as well as providing a control mechanism that flat-top regulates the klystron beam current during the pulse. This flat-topped klystron beam current is maintained while the capacitor bank droops. In addition, we will review more modern on-deck designs using a high gain, high voltage planar triode as a regulating and switching element. These designs are being developed, tested, and implemented for the Los Alamos Neutron Science Center (LANSCE) accelerator refurbishment project, ''LANSCE-R''. An advantage of the planar triode is that the tube can be directly operated with solid state linear components and provides for a very compact design. The tubes are inexpensive compared to stacked semiconductor switching assemblies and also provide a linear control capability. Details of these designs are provided as well as operational and developmental results.

  5. Cathodic and anodic biofilms in Single Chamber Microbial Fuel Cells.

    PubMed

    Cristiani, P; Carvalho, M L; Guerrini, E; Daghio, M; Santoro, C; Li, B

    2013-08-01

    The oxygen reduction due to microaerophilic biofilms grown on graphite cathodes (biocathodes) in Single Chamber Microbial Fuel Cells (SCMFCs) is proved and analysed in this paper. Pt-free cathode performances are compared with those of different platinum-loaded cathodes, before and after the biofilm growth. Membraneless SCMFCs were operating in batch-mode, filled with wastewater. A substrate (fuel) of sodium acetate (0.03 M) was periodically added and the experiment lasted more than six months. A maximum of power densities, up to 0.5 W m(-2), were reached when biofilms developed on the electrodes and the cathodic potential decreased (open circuit potential of 50-200 mV vs. SHE). The power output was almost constant with an acetate concentration of 0.01-0.05 M and it fell down when the pH of the media exceeded 9.5, independently of the Pt-free/Pt-loading at the cathodes. Current densities varied in the range of 1-5 Am(-2) (cathode area of 5 cm(2)). Quasi-stationary polarization curves performed with a three-electrode configuration on cathodic and anodic electrodes showed that the anodic overpotential, more than the cathodic one, may limit the current density in the SCMFCs for a long-term operation. PMID:23474690

  6. Space Test of Bare-Wire Anode Tethers

    NASA Technical Reports Server (NTRS)

    Johnson, L.; Fujii, H. A.; Sanmartin, J. R.

    2007-01-01

    An international team, lead by Tokyo Metropolitan University, is developing a mission concept for a suborbital test of orbital-motion-limited (OML) bare-wire anode current collection for application to electrodynamic tether propulsion. The tether is a tape with a 50-mm width, 0.05-mm thickness, and 1-km length. This will be the first space test of the OML theory. In addition, by being an engineering demonstration (of space tethers), the mission will demonstrate electric beam generation for "sounding" determination of the neutral density profile in the ionospheric "E-layer." If selected by the Institute of Space and Astronautical Science/Japanese Aerospace Exploration Agency (JAXA), the mission will launch in early 2009 using an $520 Sounding Rocket. During ascent, and above =100 km in attitude, the 1-km tape tether will be deployed at a rate of 8 m/s. Once deployed, the tape tether will serve as an anode, collecting ionospheric electrons. The electrons will be expelled into space by a hollow cathode device, thereby completing the circuit and allowing current to flow.This paper will describe the objectives of the proposed mission, the technologies to be employed, and the application of the results to future space missions using electrodynamic tethers for propulsion or power generation.

  7. Silicon Whisker and Carbon Nanofiber Composite Anode

    NASA Technical Reports Server (NTRS)

    Lang, Christopher M.

    2015-01-01

    Phase II Objectives: Demonstrate production levels of grams per batch; Achieve full cell anode capacity of greater than 1,000 mAh/g at a charge rate of 10 (C/10) and 0 degree C; Establish a full cell cycle life of over 300 cycles; Display an operating temperature of negative 30 degrees C to plus 30 degrees C; Demonstrate a rate capability of C/5 or higher; Deliver to NASA three 2.5 Ah cells (energy density greater than 220 Wh/kg); Exhibit the safety features of the anode and full cells; Design a 1 kWh prismatic battery pack.

  8. High capacity tin-iron oxide-carbon nanostructured anode for advanced lithium ion battery

    NASA Astrophysics Data System (ADS)

    Verrelli, Roberta; Hassoun, Jusef

    2015-12-01

    A novel nanostructured Sn-Fe2O3-C anode material, prepared by high-energy ball milling, is here originally presented. The anode benefits from a unique morphology consisting in Fe2O3 and Sn active nanoparticles embedded in a conductive buffer carbon matrix of micrometric size. Furthermore, the Sn metal particles, revealed as amorphous according to X-ray diffraction measurement, show a size lower than 10 nm by transmission electron microscopy. The optimal combination of nano-scale active materials and micrometric electrode configuration of the Sn-Fe2O3-C anode reflects into remarkable electrochemical performances in lithium cell, with specific capacity content higher than 900 mAh g-1 at 1C rate (810 mA g-1) and coulombic efficiency approaching 100% for 100 cycles. The anode, based on a combination of lithium conversion, alloying and intercalation reactions, exhibits exceptional rate-capability, stably delivering more than 400 mAh g-1 at the very high current density of 4 A g-1. In order to fully confirm the suitability of the developed Sn-Fe2O3-C material as anode for lithium ion battery, the electrode is preliminarily studied in combination with a high voltage LiNi0.5Mn1.5O4 cathode in a full cell stably and efficiently operating with a 3.7 V working voltage and a capacity exceeding 100 mAh g-1.

  9. Effect of nickel impregnated hollow fiber anode for micro tubular solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    He, Beibei; Ling, Yihan; Xu, Jianmei; Zhao, Ling; Cheng, Jigui

    2014-07-01

    A micro tubular solid oxide fuel cells (MT-SOFCs) with a cell configuration of Ni impregnated Ni-Gd0.1Ce0.9O1.95 (GDC)/GDC/La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF)-GDC has been prepared by the phase inversion and impregnation technique. A special asymmetrical structure consisting of a sponge-like layer and a finger-like porous layer for hollow fiber anode is obtained by the phase inversion. Fine Ni specie particles are then coated on the surface of anode using impregnation method. The enhancement in electronic conductivity of anode by Ni modification is beneficial to current collection of MT-SOFCs. Meanwhile, the catalytic activity of anode is also improved due to the introduction of Ni nano-particles. Thus, the Ni modified MT-SOFCs exhibit high power densities, such as 0.69 W cm-2 at 600 °C. The encouraging results demonstrate that the Ni impregnation is an effective way to improve anode microstructure of MT-SOFCs.

  10. Facile incorporation of hydroxyapatite onto an anodized Ti surface via a mussel inspired polydopamine coating

    NASA Astrophysics Data System (ADS)

    Zhe, Wang; Dong, Chaofang; Sefei, Yang; Dawei, Zhang; Kui, Xiao; Xiaogang, Li

    2016-08-01

    Inspired by the porous morphology of anodized Ti and the adhesive versatility of polydopamine (PDA), which can induce apatite mineralization, we fabricated a novel interface by coating a porous anodized TiO2 layer with PDA to rapidly immobilize HA on Ti-based substrates. It was found that the as-prepared PDA/anodized (HD) surface exhibited nanoscale roughness, which possessed an excellent ability to form apatite when immersed in 1.5× simulated body fluid (SBF), as observed by AFM and FE-SEM. The morphology and composition of each layer were further confirmed by XPS, XRD and FTIR. The corrosion resistance of the multilayer was investigated using potentiodynamic polarization curve and electrochemical impedance spectra (EIS) measurements in a 0.9 wt% NaCl solution, the results suggested that the HA/PDA/anodized (HDA) layer increased the corrosion resistance of pure Ti with higher corrosion potential and lower passive current, the surface wettability was also enhanced with the incorporation of HA. In vitro cellular assays showed that the HDA layer stimulated cell attachment and improved the alkaline phosphate (ALP) activity. Overall, the PDA/anodized treatment provided a viable method to quickly integrate HA, and the obtained HDA layer improved both corrosion resistance and biocompatibility of the Ti surface.

  11. Impact of Anodic Respiration on Biopolymer Production and Consequent Membrane Fouling.

    PubMed

    Ishizaki, So; Terada, Kotaro; Miyake, Hiroshi; Okabe, Satoshi

    2016-09-01

    Microbial fuel cells (MFCs) have recently been integrated with membrane bioreactors (MBRs) for wastewater treatment and energy recovery. However, the impact of integration of the two reactors on membrane fouling of MBR has not been reported yet. In this study, MFCs equipped with different external resistances (1-10 000 ohm) were operated, and membrane-fouling potentials of the MFC anode effluents were directly measured to study the impact of anodic respiration by exoelectrogens on membrane fouling. It was found that although the COD removal efficiency was comparable, the fouling potential was significantly reduced due to less production of biopolymer (a major foulant) in MFCs equipped with lower external resistance (i.e., with higher current generation) as compared with aerobic respiration. Furthermore, it was confirmed that Geobacter sulfurreducens strain PCA, a dominant exoelectrogen in anode biofilms of MFCs in this study, produced less biopolymer under anodic respiration condition than fumarate (anaerobic) respiration condition, resulting in lower membrane-fouling potential. Taken together, anodic respiration can mitigate membrane fouling of MBR due to lower biopolymer production, suggesting that development of an electrode-assisted MBR (e-MBR) without aeration is feasible.

  12. Porous aluminum room temperature anodizing process in a fluorinated-oxalic acid solution

    NASA Astrophysics Data System (ADS)

    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.

  13. Effects of Anode Flow Field Design on CO(2) Bubble Behavior in μDMFC.

    PubMed

    Li, Miaomiao; Liang, Junsheng; Liu, Chong; Sun, Gongquan; Zhao, Gang

    2009-01-01

    Clogging of anode flow channels by CO(2) bubbles is a vital problem for further performance improvements of the micro direct methanol fuel cell (μDMFC). In this paper, a new type anode structure using the concept of the non-equipotent serpentine flow field (NESFF) to solve this problem was designed, fabricated and tested. Experiments comparing the μDMFC with and without this type of anode flow field were implemented using a home-made test loop. Results show that the mean-value, amplitude and frequency of the inlet-to-outlet pressure drops in the NESFF is far lower than that in the traditional flow fields at high μDMFC output current. Furthermore, the sequential images of the CO(2) bubbles as well as the μDMFC performance with different anode flow field pattern were also investigated, and the conclusions are in accordance with those derived from the pressure drop experiments. Results of this study indicate that the non-equipotent design of the μDMFC anode flow field can effectively mitigate the CO(2) clogging in the flow channels, and hence lead to a significant promotion of the μDMFC performance.

  14. Nanopore gradients on porous aluminum oxide generated by nonuniform anodization of aluminum.

    PubMed

    Kant, Krishna; Low, Suet P; Marshal, Asif; Shapter, Joseph G; Losic, Dusan

    2010-12-01

    A method for surface engineering of structural gradients with nanopore topography using the self-ordering process based on electrochemical anodization of aluminum is described. A distinct anodization condition with an asymmetrically distributed electric field at the electrolyte/aluminum interface is created by nonparallel arrangement between electrodes (tilted by 45°) in an electrochemical cell. The anodic aluminum oxide (AAO) porous surfaces with ordered nanopore structures with gradual and continuous change of pore diameters from 80 to 300 nm across an area of 0.5-1 cm were fabricated by this anodization using two common electrolytes, oxalic acid (0.3 M) and phosphoric acid (0.3 M). The formation of pore gradients of AAO is explained by asymmetric and gradual distribution of the current density and temperature variation generated on the surface of Al during the anodization process. Optical and wetting gradients of prepared pore structures were confirmed by reflective interferometric spectroscopy and contact angle measurements showing the ability of this method to generate porous surfaces with multifunctional gradients (structural, optical, wetting). The study of influence of pore structures on cell growth using the culture of neuroblastoma cells reveals biological relevance of nanopore gradients and the potential to be applied as the platform for spatially controllable cell growth and cell differentiation.

  15. Effects of Anode Flow Field Design on CO2 Bubble Behavior in μDMFC

    PubMed Central

    Li, Miaomiao; Liang, Junsheng; Liu, Chong; Sun, Gongquan; Zhao, Gang

    2009-01-01

    Clogging of anode flow channels by CO2 bubbles is a vital problem for further performance improvements of the micro direct methanol fuel cell (μDMFC). In this paper, a new type anode structure using the concept of the non-equipotent serpentine flow field (NESFF) to solve this problem was designed, fabricated and tested. Experiments comparing the μDMFC with and without this type of anode flow field were implemented using a home-made test loop. Results show that the mean-value, amplitude and frequency of the inlet-to-outlet pressure drops in the NESFF is far lower than that in the traditional flow fields at high μDMFC output current. Furthermore, the sequential images of the CO2 bubbles as well as the μDMFC performance with different anode flow field pattern were also investigated, and the conclusions are in accordance with those derived from the pressure drop experiments. Results of this study indicate that the non-equipotent design of the μDMFC anode flow field can effectively mitigate the CO2 clogging in the flow channels, and hence lead to a significant promotion of the μDMFC performance. PMID:22412313

  16. Impact of Anodic Respiration on Biopolymer Production and Consequent Membrane Fouling.

    PubMed

    Ishizaki, So; Terada, Kotaro; Miyake, Hiroshi; Okabe, Satoshi

    2016-09-01

    Microbial fuel cells (MFCs) have recently been integrated with membrane bioreactors (MBRs) for wastewater treatment and energy recovery. However, the impact of integration of the two reactors on membrane fouling of MBR has not been reported yet. In this study, MFCs equipped with different external resistances (1-10 000 ohm) were operated, and membrane-fouling potentials of the MFC anode effluents were directly measured to study the impact of anodic respiration by exoelectrogens on membrane fouling. It was found that although the COD removal efficiency was comparable, the fouling potential was significantly reduced due to less production of biopolymer (a major foulant) in MFCs equipped with lower external resistance (i.e., with higher current generation) as compared with aerobic respiration. Furthermore, it was confirmed that Geobacter sulfurreducens strain PCA, a dominant exoelectrogen in anode biofilms of MFCs in this study, produced less biopolymer under anodic respiration condition than fumarate (anaerobic) respiration condition, resulting in lower membrane-fouling potential. Taken together, anodic respiration can mitigate membrane fouling of MBR due to lower biopolymer production, suggesting that development of an electrode-assisted MBR (e-MBR) without aeration is feasible. PMID:27427998

  17. Adsorption behavior of low concentration carbon monoxide on polymer electrolyte fuel cell anodes for automotive applications

    NASA Astrophysics Data System (ADS)

    Matsuda, Yoshiyuki; Shimizu, Takahiro; Mitsushima, Shigenori

    2016-06-01

    The adsorption behavior of CO on the anode around the concentration of 0.2 ppm allowed by ISO 14687-2 is investigated in polymer electrolyte fuel cells (PEFCs). CO and CO2 concentrations in the anode exhaust are measured during the operation of a JARI standard single cell at 60 °C cell temperature and 1000 mA cm-2 current density. CO coverage is estimated from the gas analysis and CO stripping voltammetry. The cell voltage decrease as a result of 0.2 ppm CO is 29 mV and the CO coverage is 0.6 at the steady state with 0.11 mg cm-2 of anode platinum loading. The CO coverage as a function of CO concentration approximately follows a Temkin-type isotherm. Oxygen permeated to the anode through a membrane is also measured during fuel cell operation. The exhaust velocity of oxygen from the anode was shown to be much higher than the CO supply velocity. Permeated oxygen should play an important role in CO oxidation under low CO concentration conditions.

  18. Long-term testing of in-situ cerium oxide coated anodes for aluminum electrowinning

    SciTech Connect

    King, H.L.

    1989-10-01

    The ELTECH Anode Phase 2 Project (Contract Number AC07-86ID12655), as supported by the Department of Energy (DOE) from December 1988 through April 1989, focused on long-term testing of in-situ anodically deposited cerium oxide (CEROX) coatings on nickel ferrite/Cu cermets. The specific objective of this research was to determine the effectiveness of the CEROX coating in reducing the transfer of cermet components to the produced aluminum. A dosing regimen was first established for the minimum addition of cerium to the cell necessary to produce targeted CEROX coatings on the cermet anode and the periodic additions necessary to maintain coating thicknesses. The effects of the addition of CeF{sub 3} on CEROX coating formation was evaluated for targeted coating thicknesses at three different current densities. Analytical procedures were identified for determining alumina concentrations and the cryolite bath ratio for quasi-commercial baths.

  19. Cobalt-based metal organic framework with superior lithium anodic performance

    NASA Astrophysics Data System (ADS)

    Hu, Xiaoshi; Hu, Huiping; Li, Chao; Li, Tian; Lou, Xiaobing; Chen, Qun; Hu, Bingwen

    2016-10-01

    The reversible charging of a Co-1,4-benzenedicarboxylate MOF (Co-BDC MOF) prepared via an one-pot solvothermal method was studied for use as the anode in a Li-ion cell. It was found that this MOF anode provides high reversible capacities (1090 and 611 mA h g-1 at current densities of 0.2 and 1 A g-1, respectively), and an impressive rate performance. Such an outstanding Li-ion storage property has not been reported previously for the LIB anodes within the MOFs category. Ex-situ X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) studies of this material at different state of charge suggest that cobalt stays at Co2+ state during discharge/charge process, so that in this case Li+ may be inserted into the organic moiety without the direct participation of cobalt ions.

  20. Cross-Linked Chitosan as an Efficient Binder for Si Anode of Li-ion Batteries.

    PubMed

    Chen, Chao; Lee, Sang Ha; Cho, Misuk; Kim, Jaehoon; Lee, Youngkwan

    2016-02-01

    We investigate the use of chitosan (CS) as a new cross-linkable and water-soluble binder for the Si anode of Li-ion batteries. In contrast to the traditional binder utilizing a hydrogen bond and/or van der Waals force-linked anode electrodes, CS can easily form a 3D network to limit the movement of Si particles through the cross-linking between the amino groups of CS and the dialdehyde of glutaraldehyde (GA). Chemical, mechanical, and morphological analyses are conducted by Fourier transform infrared spectroscopy, tensile testing, and scanning electron microscopy. The cross-linked Si/CS-GA anode exhibits an initial discharge capacity of 2782 mAh g(-1) with a high initial Coulombic efficiency of 89% and maintained a capacity of 1969 mAh g(-1) at the current density of 500 mA g(-1) over 100 cycles. PMID:26745390

  1. Chemical Fouling Reduction of a Submersible Steel Spectrophotometer in Estuarine Environments Using a Sacrificial Zinc Anode.

    PubMed

    Tait, Zachary S; Thompson, Megan; Stubbins, Aron

    2015-07-01

    The availability of in situ spectrophotometers, such as the S::CAN spectro::lyser, has expanded the possibilities for high-frequency water quality data collection. However, biological and chemical fouling can degrade the performance of in situ spectrophotometers, especially in saline environments with rapid flow rates. A complex freshwater washing system has been previously designed to reduce chemical fouling for the S::CAN spectro::lyser spectrophotometer. In the current study, we present a simpler, cheaper alternative: the attachment of a sacrificial zinc anode. Results are presented detailing the S::CAN spectro::lyser performance with and without the addition of the sacrificial anode. Attachment of the zinc anode provided efficient corrosion protection during 2-wk deployments in a highly dynamic (average tidal range, 2.5 m) saline tidal saltmarsh creek at Groves Creek, Skidaway Institute of Oceanography, Savannah, GA.

  2. High energy density amorphous silicon anodes for lithium ion batteries deposited by DC sputtering

    NASA Astrophysics Data System (ADS)

    Farmakis, Filippos; Elmasides, Costas; Fanz, Patrik; Hagen, Markus; Georgoulas, Nikolaos

    2015-10-01

    As more and more applications require high energy density electrochemical storage systems that deliver more than 200 Wh/kg, Lithium-ion batteries with silicon-based anodes provide promising electrochemical properties especially high specific capacity. In this paper, we present micro-grain structured silicon deposited by DC sputtering on special copper foil that serves as current collector. It is demonstrated that high-density silicon anodes are obtained with more than 2000 mAh g-1 and 2.0 mAh cm-2 that can be considered as a commercial value. In addition, irreversible capacity during the first galvanostatic cycle can be lower than 20% for such anodes. Finally, it is found that there exists a clear correlation between the grain-size and the texture of the amorphous silicon to the electrochemical performance of half-cells.

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

    PubMed

    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. PMID:26952447

  4. Reduced Graphene Oxide Anodes for Potential Application in Algae Biophotovoltaic Platforms

    PubMed Central

    Ng, Fong-Lee; Jaafar, Muhammad Musoddiq; Phang, Siew-Moi; Chan, Zhijian; Salleh, Nurul Anati; Azmi, Siti Zulfikriyah; Yunus, Kamran; Fisher, Adrian C.; Periasamy, Vengadesh

    2014-01-01

    The search for renewable energy sources has become challenging in the current era, as conventional fuel sources are of finite origins. Recent research interest has focused on various biophotovoltaic (BPV) platforms utilizing algae, which are then used to harvest solar energy and generate electrical power. The majority of BPV platforms incorporate indium tin oxide (ITO) anodes for the purpose of charge transfer due to its inherent optical and electrical properties. However, other materials such as reduced graphene oxide (RGO) could provide higher efficiency due to their intrinsic electrical properties and biological compatibility. In this work, the performance of algae biofilms grown on RGO and ITO anodes were measured and discussed. Results indicate improved peak power of 0.1481 mWm−2 using the RGO electrode and an increase in efficiency of 119%, illustrating the potential of RGO as an anode material for applications in biofilm derived devices and systems. PMID:25531093

  5. A nanoporous metal recuperated MnO2 anode for lithium ion batteries.

    PubMed

    Guo, Xianwei; Han, Jiuhui; Zhang, Ling; Liu, Pan; Hirata, Akihiko; Chen, Luyang; Fujita, Takeshi; Chen, Mingwei

    2015-10-01

    Lithium-ion batteries (LIBs) have been intensively studied to meet the increased demands for the high energy density of portable electronics and electric vehicles. The low specific capacity of the conventional graphite based anodes is one of the key factors that limit the capacity of LIBs. Transition metal oxides, such as NiO, MnO2 and Fe3O4, are known to be promising anode materials that are expected to improve the specific capacities of LIBs for several times. However, the poor electrical conductivity of these oxides significantly restricts the lithium ion storage and charge/discharge rate. Here we report that dealloyed nanoporous metals can realize the intrinsic lithium storage performance of the oxides by forming oxide/metal composites. Without any organic binder, conductive additive and additional current collector, the hybrid electrodes can be directly used as anodes and show highly reversible specific capacity with high-rate capability and long cyclic stability.

  6. Effect of Sulfuric Acid Concentration on Electrochemical Characteristics of Nano Porous Structure Formed by Anodizing Process.

    PubMed

    Lee, Jung-Hyung; Lee, Seung-Jun; Kim, Seong-Jong

    2016-02-01

    Aluminum alloy is a very strong reactivity material, but it has excellent corrosion resistance due to protective oxide film created in air. However, it is not practical because the film thickness is uneven and varies depending on the generation condition. Therefore, aluminum anodizing was performed to form film with commercially applicable hardness, corrosion resistance, and wear resistance. This offers such advantages as commercial applicability to large areas and low prices. In this study, the electrochemical characteristics with concentration of sulfuric acid electrolyte were compared with the two-step anodizing method which is widely used. A surface observation revealed regular structures and pores with the size of several tens of nm, and the anodized film presented excellent corrosion resistance with considerably low corrosion current density in sea water. PMID:27433656

  7. Cross-Linked Chitosan as an Efficient Binder for Si Anode of Li-ion Batteries.

    PubMed

    Chen, Chao; Lee, Sang Ha; Cho, Misuk; Kim, Jaehoon; Lee, Youngkwan

    2016-02-01

    We investigate the use of chitosan (CS) as a new cross-linkable and water-soluble binder for the Si anode of Li-ion batteries. In contrast to the traditional binder utilizing a hydrogen bond and/or van der Waals force-linked anode electrodes, CS can easily form a 3D network to limit the movement of Si particles through the cross-linking between the amino groups of CS and the dialdehyde of glutaraldehyde (GA). Chemical, mechanical, and morphological analyses are conducted by Fourier transform infrared spectroscopy, tensile testing, and scanning electron microscopy. The cross-linked Si/CS-GA anode exhibits an initial discharge capacity of 2782 mAh g(-1) with a high initial Coulombic efficiency of 89% and maintained a capacity of 1969 mAh g(-1) at the current density of 500 mA g(-1) over 100 cycles.

  8. Chemical Fouling Reduction of a Submersible Steel Spectrophotometer in Estuarine Environments Using a Sacrificial Zinc Anode.

    PubMed

    Tait, Zachary S; Thompson, Megan; Stubbins, Aron

    2015-07-01

    The availability of in situ spectrophotometers, such as the S::CAN spectro::lyser, has expanded the possibilities for high-frequency water quality data collection. However, biological and chemical fouling can degrade the performance of in situ spectrophotometers, especially in saline environments with rapid flow rates. A complex freshwater washing system has been previously designed to reduce chemical fouling for the S::CAN spectro::lyser spectrophotometer. In the current study, we present a simpler, cheaper alternative: the attachment of a sacrificial zinc anode. Results are presented detailing the S::CAN spectro::lyser performance with and without the addition of the sacrificial anode. Attachment of the zinc anode provided efficient corrosion protection during 2-wk deployments in a highly dynamic (average tidal range, 2.5 m) saline tidal saltmarsh creek at Groves Creek, Skidaway Institute of Oceanography, Savannah, GA. PMID:26437114

  9. Effect of Sulfuric Acid Concentration on Electrochemical Characteristics of Nano Porous Structure Formed by Anodizing Process.

    PubMed

    Lee, Jung-Hyung; Lee, Seung-Jun; Kim, Seong-Jong

    2016-02-01

    Aluminum alloy is a very strong reactivity material, but it has excellent corrosion resistance due to protective oxide film created in air. However, it is not practical because the film thickness is uneven and varies depending on the generation condition. Therefore, aluminum anodizing was performed to form film with commercially applicable hardness, corrosion resistance, and wear resistance. This offers such advantages as commercial applicability to large areas and low prices. In this study, the electrochemical characteristics with concentration of sulfuric acid electrolyte were compared with the two-step anodizing method which is widely used. A surface observation revealed regular structures and pores with the size of several tens of nm, and the anodized film presented excellent corrosion resistance with considerably low corrosion current density in sea water.

  10. Reduced graphene oxide anodes for potential application in algae biophotovoltaic platforms.

    PubMed

    Ng, Fong-Lee; Jaafar, Muhammad Musoddiq; Phang, Siew-Moi; Chan, Zhijian; Salleh, Nurul Anati; Azmi, Siti Zulfikriyah; Yunus, Kamran; Fisher, Adrian C; Periasamy, Vengadesh

    2014-01-01

    The search for renewable energy sources has become challenging in the current era, as conventional fuel sources are of finite origins. Recent research interest has focused on various biophotovoltaic (BPV) platforms utilizing algae, which are then used to harvest solar energy and generate electrical power. The majority of BPV platforms incorporate indium tin oxide (ITO) anodes for the purpose of charge transfer due to its inherent optical and electrical properties. However, other materials such as reduced graphene oxide (RGO) could provide higher efficiency due to their intrinsic electrical properties and biological compatibility. In this work, the performance of algae biofilms grown on RGO and ITO anodes were measured and discussed. Results indicate improved peak power of 0.1481 mWm(-2) using the RGO electrode and an increase in efficiency of 119%, illustrating the potential of RGO as an anode material for applications in biofilm derived devices and systems. PMID:25531093

  11. Fuel cell system shutdown with anode pressure control

    DOEpatents

    Clingerman, Bruce J.; Doan, Tien M.; Keskula, Donald H.

    2002-01-01

    A venting methodology and pressure sensing and vent valving arrangement for monitoring anode bypass valve operating during the normal shutdown of a fuel cell apparatus of the type used in vehicle propulsion systems. During a normal shutdown routine, the pressure differential between the anode inlet and anode outlet is monitored in real time in a period corresponding to the normal closing speed of the anode bypass valve and the pressure differential at the end of the closing cycle of the anode bypass valve is compared to the pressure differential at the beginning of the closing cycle. If the difference in pressure differential at the beginning and end of the anode bypass closing cycle indicates that the anode bypass valve has not properly closed, a system controller switches from a normal shutdown mode to a rapid shutdown mode in which the anode inlet is instantaneously vented by rapid vents.

  12. 4. Anode Building. View is to the east. This facility, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. Anode Building. View is to the east. This facility, which was used for the cleaning and manufacture of anodes, was documented prior to demolition in 1993. - Sullivan Electrolytic Zinc Plant, Government Gulch, Kellogg, Shoshone County, ID

  13. Humectants To Augment Current From Metallized Zinc Cathodic Protection Systems on Concrete

    SciTech Connect

    Holcomb, Gordon R.; Covino Jr., Bernard S.; Cramer, Stephen D.; Russell, James H. Russell; Bullard, Sophie J.; Collins, W. Keith; Bennett, Jack E.; Soltesz, Steven M.; Laylor, H. Martin

    2002-12-01

    Cathodic protection (CP) systems using thermal-sprayed zinc anodes are employed to mitigate the corrosion process in reinforced concrete structures. However, the performance of the anodes is improved by moisture at the anode-concrete interface. Research was conducted to investigate the effect of hydrophilic chemical additives, humectants, on the electrical performance and service life of zinc anodes. Lithium bromide and lithium nitrate were identified as feasible humectants with lithium bromide performing better under galvanic CP and lithium nitrate performing better under impressed current CP. Both humectants improved the electrical operating characteristics of the anode and increased the service life by up to three years.

  14. Rational engineering of nanoporous anodic alumina optical bandpass filters

    NASA Astrophysics Data System (ADS)

    Santos, Abel; Pereira, Taj; Law, Cheryl Suwen; Losic, Dusan

    2016-08-01

    Herein, we present a rationally designed advanced nanofabrication approach aiming at producing a new type of optical bandpass filters based on nanoporous anodic alumina photonic crystals. The photonic stop band of nanoporous anodic alumina (NAA) is engineered in depth by means of a pseudo-stepwise pulse anodisation (PSPA) approach consisting of pseudo-stepwise asymmetric current density pulses. This nanofabrication method makes it possible to tune the transmission bands of NAA at specific wavelengths and bandwidths, which can be broadly modified across the UV-visible-NIR spectrum through the anodisation period (i.e. time between consecutive pulses). First, we establish the effect of the anodisation period as a means of tuning the position and width of the transmission bands of NAA across the UV-visible-NIR spectrum. To this end, a set of nanoporous anodic alumina bandpass filters (NAA-BPFs) are produced with different anodisation periods, ranging from 500 to 1200 s, and their optical properties (i.e. characteristic transmission bands and interferometric colours) are systematically assessed. Then, we demonstrate that the rational combination of stacked NAA-BPFs consisting of layers of NAA produced with different PSPA periods can be readily used to create a set of unique and highly selective optical bandpass filters with characteristic transmission bands, the position, width and number of which can be precisely engineered by this rational anodisation approach. Finally, as a proof-of-concept, we demonstrate that the superposition of stacked NAA-BPFs produced with slight modifications of the anodisation period enables the fabrication of NAA-BPFs with unprecedented broad transmission bands across the UV-visible-NIR spectrum. The results obtained from our study constitute the first comprehensive rationale towards advanced NAA-BPFs with fully controllable photonic properties. These photonic crystal structures could become a promising alternative to traditional optical

  15. Self-cleaning rotating anode X-ray source

    DOEpatents

    Paulikas, Arvydas P.

    1989-01-01

    A self-cleaning rotating anode x-ray source comprising an evacuable housing, a rotatable cylindrical anode within the housing, a source of electrons within the housing which electrons are caused to impinge upon the anode to produce x-rays, and means for ionizing residual particles within the housing and accelerating such ions so as to impinge upon the anode to sputter impurities from the surface thereof.

  16. Salt passivation during anodic iridium dissolution in chloride melts

    SciTech Connect

    Saltykova, N.A.; Pechorskaya, L.S.; Baraboshkin, A.N.; Kotovskii, S.N.; Kosikhin, L.T.

    1986-11-01

    Anodic iridium dissolution in chloride melts at 500-700/sup 0/C was studied by potentiostatic, potentiodynamic, and galvanostatic techniques. It was found that an iridium anode is passivated by hexachloroiridates, first by the iridium (III) salt and at more positive potentials by the iridium (IV) salt. Values for anode resistance during passivation by salt films were calculated. It was shown that the morphology of the dissolving anode surface is determined by the value of polarization.

  17. Dissipation factor as a predictor of anodic coating performance

    DOEpatents

    Panitz, Janda K. G.

    1995-01-01

    A dissipation factor measurement is used to predict as-anodized fixture performance prior to actual use of the fixture in an etching environment. A dissipation factor measurement of the anodic coating determines its dielectric characteristics and correlates to the performance of the anodic coating in actual use. The ability to predict the performance of the fixture and its anodized coating permits the fixture to be repaired or replaced prior to complete failure.

  18. Self-cleaning rotating anode x-ray source

    DOEpatents

    Paulikas, A.P.

    1987-06-02

    A self-cleaning rotating anode x-ray source comprising and evacuable housing, a rotatable cylindrical anode within the housing, a source of electrons within the housing which electrons are caused to impinge upon the anode to produce x-rays, and means for ionizing residual particles within the housing and accelerating such ions so as to impinge upon the anode to sputter impurities from the surface thereof. 2 figs.

  19. The research of anodic microdischarges in plasma-electrolyte processing

    NASA Astrophysics Data System (ADS)

    Kashapov, L. N.; Kashapov, N. F.; Kashapov, R. N.

    2015-06-01

    The article is devoted to the topic of anodic microdischarges in plasma-electrolyte processing. The aim of this work is to research the conditions of anodic micro-discharges during the plasma-electrolytic treatment and the influence they have on the surface of metals. As a result of experimental researches, was made a mechanism of influence anodic microdischarges on the surface of the electrode, burning of anodic microdischarges occur in the voltage range of 40-100 W.

  20. Electrochemical surface modification of carbon mesh anode to improve the performance of air-cathode microbial fuel cells.

    PubMed

    Luo, Jianmei; Chi, Meiling; Wang, Hongyu; He, Huanhuan; Zhou, Minghua

    2013-12-01

    A convenient and promising alternative to surface modification of carbon mesh anode was fulfilled by electrochemical oxidation in the electrolyte of nitric acid or ammonium nitrate at ambient temperature. It was confirmed that such an anode modification method was low cost and effective not only in improving the efficiency of power generation in microbial fuel cells (MFCs) for synthetic wastewater treatment, but also helping to reduce the period for MFCs start-up. The MFCs with anode modification in electrolyte of nitric acid performed the best, achieving a Coulombic efficiency enhancement of 71 %. As characterized, the electrochemical modification resulted in the decrease of the anode potential and internal resistance but the increase of current response and nitrogen-containing and oxygen-containing functional groups on the carbon surface, which might contribute to the enhancement on the performances of MFCs.

  1. Rational engineering of nanoporous anodic alumina optical bandpass filters.

    PubMed

    Santos, Abel; Pereira, Taj; Law, Cheryl Suwen; Losic, Dusan

    2016-08-01

    Herein, we present a rationally designed advanced nanofabrication approach aiming at producing a new type of optical bandpass filters based on nanoporous anodic alumina photonic crystals. The photonic stop band of nanoporous anodic alumina (NAA) is engineered in depth by means of a pseudo-stepwise pulse anodisation (PSPA) approach consisting of pseudo-stepwise asymmetric current density pulses. This nanofabrication method makes it possible to tune the transmission bands of NAA at specific wavelengths and bandwidths, which can be broadly modified across the UV-visible-NIR spectrum through the anodisation period (i.e. time between consecutive pulses). First, we establish the effect of the anodisation period as a means of tuning the position and width of the transmission bands of NAA across the UV-visible-NIR spectrum. To this end, a set of nanoporous anodic alumina bandpass filters (NAA-BPFs) are produced with different anodisation periods, ranging from 500 to 1200 s, and their optical properties (i.e. characteristic transmission bands and interferometric colours) are systematically assessed. Then, we demonstrate that the rational combination of stacked NAA-BPFs consisting of layers of NAA produced with different PSPA periods can be readily used to create a set of unique and highly selective optical bandpass filters with characteristic transmission bands, the position, width and number of which can be precisely engineered by this rational anodisation approach. Finally, as a proof-of-concept, we demonstrate that the superposition of stacked NAA-BPFs produced with slight modifications of the anodisation period enables the fabrication of NAA-BPFs with unprecedented broad transmission bands across the UV-visible-NIR spectrum. The results obtained from our study constitute the first comprehensive rationale towards advanced NAA-BPFs with fully controllable photonic properties. These photonic crystal structures could become a promising alternative to traditional optical

  2. Structural transformation of nickel hydroxide films during anodic oxidation

    SciTech Connect

    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.

  3. Modeling graphite anodes with serial and transmission line models

    NASA Astrophysics Data System (ADS)

    Illig, J.; Ender, M.; Weber, A.; Ivers-Tiffée, E.

    2015-05-01

    Electrochemical impedance spectroscopy (EIS) is an indispensable technique for the investigation of polarization processes in Lithium-ion Batteries. These cause performance limitation or degradation. A physically meaningful impedance model is key when drawing conclusions on further cell improvement. This study introduces an in-depth impedance analysis of a commercial high-power graphite anode. The impedance spectra measured between 0 °C and 30 °C and 0%-100% SOC were analyzed by the distribution of relaxation times (DRT-method), enabling a separation of loss processes by their individual time constants. Using this method, we separated charge transfer resistance and solid electrolyte interface resistance at medium frequencies (10 Hz-200 Hz) and the contact resistance anode/current collector in the at high frequency range (5 kHz-100 kHz). Two fundamentally different model structures were set up, either (i) two modifications of a serial model connecting RQ-elements and a Warburg element for solid state diffusion, or (ii) three modifications of a transmission line model with one-path or two-path design. The suitability of all serial and TLM model structures was tested, and the fitting procedure was supported using microstructure parameters gained from x-ray tomography. The favored one-path transmission line model reveals that the lithium-ion transport in the electrolyte contributes more to polarization than expected. Impediment of lithium-ion transport is caused by the pore structure and the tortuosity of the high-power graphite anode, and has to be considered for meaningful interpretation of impedance spectra.

  4. Coaxial anode improves sensitivity of gas radiation counters

    NASA Technical Reports Server (NTRS)

    Kraushaar, W. L.

    1974-01-01

    Anode wire itself is enclosed by three segments. Two on ends are rejector segments, and middle one is primary charge-detecting segment. Anode wire is made from tungsten and is surrounded by enamel insulation. Enamel is covered by segments of vapor-deposited gold. At one point in center segment, gold layer makes direct contact with anode wire.

  5. Lifetime of anode polymer in magnetically insulated ion diodes for high-intensity pulsed ion beam generation

    SciTech Connect

    Zhu, X. P.; Dong, Z. H.; Han, X. G.; Xin, J. P.; Lei, M. K.

    2007-02-15

    Generation of high-intensity pulsed ion beam (HIPIB) has been studied experimentally using polyethylene as the anode polymer in magnetically insulated ion diodes (MIDs) with an external magnetic field. The HIPIB is extracted from the anode plasma produced during the surface discharging process on polyethylene under the electrical and magnetic fields in MIDs, i.e., high-voltage surface breakdown (flashover) with bombardments by electrons. The surface morphology and the microstructure of the anode polymer are characterized using scanning electron microscopy and differential scanning calorimetry, respectively. The surface roughening of the anode polymer results from the explosive release of trapped gases or newly formed gases under the high-voltage discharging, leaving fractured surfaces with bubble formation. The polyethylene in the surface layer degrades into low-molecular-weight polymers such as polyethylene wax and paraffin under the discharging process. Both the surface roughness and the fraction of low molecular polymers apparently increase as the discharging times are prolonged for multipulse HIPIB generation. The changes in the surface morphology and the composition of anode polymer lead to a noticeable decrease in the output of ion beam intensity, i.e., ion current density and diode voltage, accompanied with an increase in instability of the parameters with the prolonged discharge times. The diode voltage (or surface breakdown voltage of polymer) mainly depends on the surface morphology (or roughness) of anode polymers, and the ion current density on the composition of anode polymers, which account for the two stages of anode polymer degradation observed experimentally, i.e., stage I which has a steady decrease of the two parameters and stage II which shows a slow decrease, but with an enhanced fluctuation of the two parameters with increasing pulses of HIPIB generation.

  6. Hybrid anode for semiconductor radiation detectors

    DOEpatents

    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).

  7. Silicon Whisker and Carbon Nanofiber Composite Anode

    NASA Technical Reports Server (NTRS)

    Ma, Junqing (Inventor); Newman, Aron (Inventor); Lennhoff, John (Inventor)

    2015-01-01

    A carbon nanofiber can have a surface and include at least one crystalline whisker extending from the surface of the carbon nanofiber. A battery anode composition can be formed from a plurality of carbon nanofibers each including a plurality of crystalline whiskers.

  8. Anode for rechargeable ambient temperature lithium cells

    NASA Technical Reports Server (NTRS)

    Huang, Chen-Kuo (Inventor); Surampudi, Subbarao (Inventor); Attia, Alan I. (Inventor); Halpert, Gerald (Inventor)

    1994-01-01

    An ambient room temperature, high density, rechargeable lithium battery includes a Li(x)Mg2Si negative anode which intercalates lithium to form a single crystalline phase when x is up to 1.0 and an amorphous phase when x is from 1 to 2.0. The electrode has good reversibility and mechanical strength after cycling.

  9. Anode materials for lithium-ion batteries

    DOEpatents

    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.

  10. Passive and transpassive anodic behavior of chalcopyrite in acid solutions

    NASA Astrophysics Data System (ADS)

    Warren, G. W.; Wadsworth, M. E.; El-Raghy, S. M.

    1992-01-01

    The electrochemical oxidation of CuFeS2 in various acid solutions was studied using electrodes made from massive samples. The primary techniques employed were potentiodynamic polarization and constant potential experiments supplemented by capacitance measurements. It was the purpose of this study to investigate the behavior of: (1) several sources of CuFeS2 in H2SO4 electrolytes, and (2) a single source of CuFeS2 in various dilute acids. Electrochemical characterization of CuFeS2 from various locations was performed in 1 M H2SO4 which showed significant differences in their behavior. All samples exhibited passive-like response during anodic polarization. The current density in this passive region was reproducible and showed differences of up to two orders of magnitude between samples from different sources which has been attributed mainly to the presence of impurities in some of the samples. During anodic polarization CuFeS2 was found to be sensitive to pH at higher potential, but insensitive at low potential in sulfate solution. In addition, current decay measurements at constant potential in the low potential-passive region were found to follow the Sato-Cohen (logarithmic) model for solid film formation. Based on current and mass balance measurements, two intermediate sulfide phases appeared to form in the sequence CuFeS2 → S, → S2. At higher potentials, in the transpassive region, the observed increase in current is compatible with the decomposition of water to form chemisorbed oxygen which releases copper and forms sulfate ions.

  11. Passive and transpassive anodic behavior of chalcopyrite in acid solutions

    NASA Astrophysics Data System (ADS)

    Warren, G. W.; Wadsworth, M. E.; El-Raghy, S. M.

    1982-12-01

    The electrochemical oxidation of CuFeS2 in various acid solutions was studied using electrodes made from massive samples. The primary techniques employed were potentiodynamic polarization and constant potential experiments supplemented by capacitance measurements. It was the purpose of this study to investigate the behavior of: (1) several sources of CuFeS2 in H2SO4 electrolytes, and (2) a single source of CuFeS2 in various dilute acids. Electrochemical characterization of CuFeS2 from various locations was performed in 1 M H2SO4 which showed significant differences in their behavior. All samples exhibited passive-like response during anodic polarization. The current density in this passive region was reproducible and showed differences of up to two orders of magnitude between samples from different sources which has been attributed mainly to the presence of impurities in some of the samples. During anodic polarization CuFeS2 was found to be sensitive to pH at higher potential, but insensitive at low potential in sulfate solution. In addition, current decay measurements at constant potential in the low potential-passive region were found to follow the Sato-Cohen (logarithmic) model for solid film formation. Based on current and mass balance measurements, two intermediate sulfide phases appeared to form in the sequence CuFeS2→S1→S2. At higher potentials, in the transpassive region, the observed increase in current is compatible with the decomposition of water to form chemisorbed oxygen which releases copper and forms sulfate ions.

  12. Microbial fuel cells as discontinuous portable power sources: syntropic interactions with anode-respiring bacteria.

    PubMed

    Gao, Yaohuan; An, Junyeong; Ryu, Hodon; Lee, Hyung-Sool

    2014-04-01

    For microbial fuel cells (MFCs) to work as portable power sources used in a discontinuous manner, anode-respiring bacteria (ARB) should survive for at least several days in the absence of exogenous electron donors, and immediately generate current upon addition of an electron donor. Here, we proved that biopolymer-accumulating bacteria provide substrate (fuel) for ARB to generate current in lack of exogenous electron donor in 4 days, which allows MFCs to be used as portable power sources.

  13. Nanostructured ion beam-modified Ge films for high capacity Li ion battery anodes

    SciTech Connect

    Rudawski, N. G.; Darby, B. L.; Yates, B. R.; Jones, K. S.; Elliman, R. G.; Volinsky, A. A.

    2012-02-20

    Nanostructured ion beam-modified Ge electrodes fabricated directly on Ni current collector substrates were found to exhibit excellent specific capacities during electrochemical cycling in half-cell configuration with Li metal for a wide range of cycling rates. Structural characterization revealed that the nanostructured electrodes lose porosity during cycling but maintain excellent electrical contact with the metallic current collector substrate. These results suggest that nanostructured Ge electrodes have great promise for use as high performance Li ion battery anodes.

  14. "Thermal Stability of Anodic Hafnium Oxide Nanotube Arrays"

    SciTech Connect

    Qiu, Xiaofeng; Howe, Jane Y; Mayer, Harry A; Paranthaman, Mariappan Parans; Tuncer, Enis

    2011-01-01

    Thermal stability of highly ordered Hafnium oxide, HfO2 nanotube arrays prepared through electrochemical anodization approach in the presence of ammonium fluoride is investigated in a temperature range of room temperature to 900 C in flowing Argon atmosphere. The formation of the HfO2 nanotube arrays was monitored by current density transient characteristics during anodization of hafnium metal foil. Morphologies of the as grown and post-annealed HfO2 nanotube arrays were analyzed by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). Although monoclinic HfO2 is thermally stable up to 2000K in bulk, the morphology HfO2 nanotube arrays degraded at 900 C. Detailed X-ray photoelectron spectroscopy (XPS) study revealed that the thermal treatment significantly impact the composition and chemical environment of the core elements (Hf, O and F) of HfO2. Possible reasons for the degradation of the nanotube morphology were discussed based on XPS study and possible future improvements were suggested briefly.

  15. Single-Wall Carbon Nanotube Anodes for Lithium Cells

    NASA Technical Reports Server (NTRS)

    Hepp, Aloysius F.; Raffaelle, Ryne; Gennett, Tom; Kumta, Prashant; Maranchi, Jeff; Heben, Mike

    2006-01-01

    In recent experiments, highly purified batches of single-wall carbon nanotubes (SWCNTs) have shown promise as superior alternatives to the graphitic carbon-black anode materials heretofore used in rechargeable thin-film lithium power cells. The basic idea underlying the experiments is that relative to a given mass of graphitic carbon-black anode material, an equal mass of SWCNTs can be expected to have greater lithium-storage and charge/discharge capacities. The reason for this expectation is that whereas the microstructure and nanostructure of a graphitic carbon black is such as to make most of the interior of the material inaccessible for intercalation of lithium, a batch of SWCNTs can be made to have a much more open microstructure and nanostructure, such that most of the interior of the material is accessible for intercalation of lithium. Moreover, the greater accessibility of SWCNT structures can be expected to translate to greater mobilities for ion-exchange processes and, hence, an ability to sustain greater charge and discharge current densities.

  16. Modeling and Performance of Anode-Supported SOFC

    SciTech Connect

    Chick, Lawrence A.; Stevenson, Jeffry W.; Meinhardt, Kerry D.; Simner, Steven P.; Jaffe, John E.; Williford, Rick E.

    2001-02-28

    A "one-dimensional", steady-state model of an SOFC stack was needed to support the design of balance-of-plant components for a 5 kW mobile SOFC system. This "stack module" was required to predict appropriate stack voltage responses to changes in fuel composition, fuel flow rate, stack temperature and current demand, with response characteristics that were adjustable to changes in stack component materials and dimensions as well as to electrode porosity. The spreadsheet-based stack module was derived from the work by Kim, Virkar et al (see J. Electrochem. Soc. 146(1) 69-78 (1999)), with modifications suggested by Riess and Schoonman, p291 in CRC Handbook of Electrochemistry (1997) CRC Press. The usual overpotential terms account for ohmic resistance of the cell components, losses due to charge transfer at the electrodes, and losses due to diffusion of reactants into and products out of the porous electrodes. Response of the module is compared to published cell and stack data. After fitting adjustable parameters to match particular cell performance characteristics, the module responds reasonably well to changes in temperature and fuel concentration. The module is used to analyze the performance of anode-supported cells that were fabricated at PNNL (see abstract submitted by Stevenson, Meinhardt, Simner, Habeger and Canfield, "Fabrication and Testing of Anode-Supported SOFC").

  17. Production of energetic neutral particles and low energy electrons from four anode rods ion source

    SciTech Connect

    Mostafa, O. A.; El-Khabeary, H.; Abdel Reheem, A. M.

    2013-11-15

    The factors affecting the energetic neutral current, the low energy electron current, and the positive ion current emerging from a four-anode-rods ion source have been studied using argon gas. The neutral and electron current were measured using a simple, new technique. It was found that the energetic neutral current and the electron current depend on the positive ion current and the gas pressure. The ratio of the neutral and electron current to the positive ion current increases by increasing the gas pressure. Also it was found that at a pressure equal to 9 × 10{sup −4} mmHg, the ratio of the neutral to the positive ion current reaches 2.34 while the ratio of the electron current to the positive ion current reaches 1.7.

  18. Fabrication and characterization of anode-supported micro-tubular solide oxide fuel cell by phase inversion method

    NASA Astrophysics Data System (ADS)

    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.

  19. Composit, Nanoparticle-Based Anode material for Li-ion Batteries Applied in Hybrid Electric (HEV's)

    SciTech Connect

    Dr. Malgorzata Gulbinska

    2009-08-24

    Lithium-ion batteries are promising energy storage devices in hybrid and electric vehicles with high specific energy values ({approx}150 Wh/kg), energy density ({approx}400 Wh/L), and long cycle life (>15 years). However, applications in hybrid and electric vehicles require increased energy density and improved low-temperature (<-10 C) performance. Silicon-based anodes are inexpensive, environmentally benign, and offer excellent theoretical capacity values ({approx}4000 mAh/g), leading to significantly less anode material and thus increasing the overall energy density value for the complete battery (>500 Wh/L). However, tremendous volume changes occur during cycling of pure silicon-based anodes. The expansion and contraction of these silicon particles causes them to fracture and lose electrical contact to the current collector ultimately severely limiting their cycle life. In Phase I of this project Yardney Technical Products, Inc. proposed development of a carbon/nano-silicon composite anode material with improved energy density and silicon's cycleability. In the carbon/nano-Si composite, silicon nanoparticles were embedded in a partially-graphitized carbonaceous matrix. The cycle life of anode material would be extended by decreasing the average particle size of active material (silicon) and by encapsulation of silicon nanoparticles in a ductile carbonaceous matrix. Decreasing the average particle size to a nano-region would also shorten Li-ion diffusion path and thus improve rate capability of the silicon-based anodes. Improved chemical inertness towards PC-based, low-temperature electrolytes was expected as an additional benefit of a thin, partially graphitized coating around the active electrode material.

  20. Nanostructured hybrid silicon/carbon nanotube heterostructures: reversible high-capacity lithium-ion anodes.

    PubMed

    Wang, Wei; Kumta, Prashant N

    2010-04-27

    Lithium-ion batteries have witnessed meteoric advancement the last two decades. The anode area has seen unprecedented research activity on Si and Sn, the two anode alternatives to currently used carbon following the initial seminal work by Fuji on tin oxide nanocomposites. Recent reports on silicon nanowires, porous Si, and amorphous Si coatings on graphite nanofibers (GNF) have been very encouraging. High capacity and long cycle life anodes are still, however, elusive and much needed to meet the ever increasing energy storage demands of modern society. Herein, we report for the first time the synthesis of novel 1D heterostructures comprising vertically aligned multiwall CNTs (VACNTs) containing nanoscale amorphous/nanocrystalline Si droplets deposited directly on VACNTs with clearly defined spacing using a simple two-step liquid injection CVD process. A hallmark of these single reactor derived heterostructures is an interfacial amorphous carbon layer anchoring the nanoscale Si clusters directly to the VACNTs. The defined spacing of nanoscale Si combined with their tethered CNT architecture allow for the silicon to undergo reversible electrochemical alloying and dealloying with Li with minimal loss of contact with the underlying CNTs. The novel heterostructures thus exhibit impressive reversible stable capacities approximately 2050 mAh/g with very good rate capability and an acceptable first cycle irreversible loss approximately 20% comparable to graphitic anodes indicating their promise as high capacity Li-ion anodes. Although warranting further research, particularly with regard to long-term cycling, it can be envisaged that optimization of this simple approach could lead to reversible high capacity next generation Li-ion anodes.

  1. Methods for determining the degree of baking in anodes

    SciTech Connect

    Hughes, C.P.

    1996-10-01

    Anode baking temperature is recognized as a critical factor in determining anode quality and performance. It is difficult and costly to measure directly and an indirect method, the coke L{sub c} technique, is often used. In this technique, baking temperature is estimated from the average crystallite size in the c direction (L{sub c}) of a coke sample placed in the anode stubhole. The paper details the results of a large statistically designed experimental program in which coke L{sub c} results were compared to anode properties routinely measured by smelters. Anode thermal conductivity and air and carboxy reactivity were found to correlate well with baking temperature. A direct anode L{sub c} measurement technique was also strongly associated with temperature, particularly at high baking temperatures. Recommendations are given on the usefulness and simplicity of traditional anode property measurements for assessing baking temperatures as alternatives to the coke L{sub c} method.

  2. Methods for making anodes for lithium ion batteries

    SciTech Connect

    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.

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

    SciTech Connect

    Frankel, G.S.; Schrott, A.G.; Horkans, J.; Andricacos, P.C.; Isaacs, H.S.

    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.

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

    SciTech Connect

    Frankel, G.S.; Schrott, A.G.; Horkans, J.; Andricacos, P.C. . Thomas J. Watson Research Center); Isaacs, H.S. )

    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.

  5. Anodal tDCS targeting the right orbitofrontal cortex enhances facial expression recognition.

    PubMed

    Willis, Megan L; Murphy, Jillian M; Ridley, Nicole J; Vercammen, Ans

    2015-12-01

    The orbitofrontal cortex (OFC) has been implicated in the capacity to accurately recognise facial expressions. The aim of the current study was to determine if anodal transcranial direct current stimulation (tDCS) targeting the right OFC in healthy adults would enhance facial expression recognition, compared with a sham condition. Across two counterbalanced sessions of tDCS (i.e. anodal and sham), 20 undergraduate participants (18 female) completed a facial expression labelling task comprising angry, disgusted, fearful, happy, sad and neutral expressions, and a control (social judgement) task comprising the same expressions. Responses on the labelling task were scored for accuracy, median reaction time and overall efficiency (i.e. combined accuracy and reaction time). Anodal tDCS targeting the right OFC enhanced facial expression recognition, reflected in greater efficiency and speed of recognition across emotions, relative to the sham condition. In contrast, there was no effect of tDCS to responses on the control task. This is the first study to demonstrate that anodal tDCS targeting the right OFC boosts facial expression recognition. This finding provides a solid foundation for future research to examine the efficacy of this technique as a means to treat facial expression recognition deficits, particularly in individuals with OFC damage or dysfunction.

  6. Electrochemical incineration of sulfanilic acid at a boron-doped diamond anode.

    PubMed

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

    2012-06-01

    The anodic oxidation of sulfanilic acid solutions has been studied in acidic medium using a divided cell with a boron-doped diamond (BDD) anode and a stainless steel cathode. Overall mineralization was achieved under all experimental conditions tested due to the efficient destruction of sulfanilic acid and all its by-products with hydroxyl radicals generated at the BDD anode from water oxidation. The alternative use of an undivided cell with the same electrodes gave rise to the coating of the cathode with polymeric compounds, thus preventing the complete electrochemical incineration of sulfanilic acid. The solutions treated in the anodic compartment of the divided cell were degraded at similar rate under pH regulation within the pH interval 2.0-6.0. The mineralization current efficiency was enhanced when the applied current decreased and the initial substrate concentration increased. The decay of sulfanilic acid was followed by reversed-phase HPLC, showing a pseudo first-order kinetics. Hydroquinone and p-benzoquinone were identified as aromatic intermediates by gas chromatography-mass spectrometry and/or reversed-phase HPLC. Maleic, acetic, formic, oxalic and oxamic acids were detected as generated carboxylic acids by ion-exclusion HPLC. Ionic chromatographic analysis of electrolyzed solutions revealed that the N content of sulfanilic acid was mainly released as NH(4)(+) ion and in much smaller proportion as NO(3)(-) ion.

  7. Air-breathing direct formic acid microfluidic fuel cell with an array of cylinder anodes

    NASA Astrophysics Data System (ADS)

    Zhu, Xun; Zhang, Biao; Ye, Ding-Ding; Li, Jun; Liao, Qiang

    2014-02-01

    An air-breathing direct formic acid membraneless microfluidic fuel cell using graphite cylinder arrays as the anode is proposed. The three dimensional anode volumetrically extends the reactive surface area and improves fuel utilization. The effects of spacer configuration, fuel and electrolyte concentration as well as reactant flow rate on the species transport and cell performance are investigated. The dynamic behavior of generated CO2 bubbles is visualized and its effect on current generation is discussed. The results show that the absence of two spacers adjacent to the cathode surface improves the cell performance by reducing the proton transfer resistance. The CO2 gas bubbles are constrained within the anode array and expelled by the fluid flow periodically. Proper reactant concentration and flow rate are crucial for cell operation. At optimum conditions, a maximum current density of 118.3 mA cm-3 and a peak power density of 21.5 mW cm-3 are obtained. In addition, benefit from the volumetrically stacked anodes and enhanced fuel transfer, the maximum single pass fuel utilization rate reaches up to 87.6% at the flow rate of 1 mL h-1.

  8. Copper Nanoparticle-Incorporated Carbon Fibers as Free-Standing Anodes for Lithium-Ion Batteries

    NASA Astrophysics Data System (ADS)

    Han, Pan; Yuan, Tao; Yao, Long; Han, Zhuo; Yang, Junhe; Zheng, Shiyou

    2016-03-01

    Copper-incorporated carbon fibers (Cu/CF) as free-standing anodes for lithium-ion batteries are prepared by electrospinning technique following with calcination at 600, 700, and 800 °C. The structural properties of materials are characterized by X-ray diffraction (XRD), Raman, thermogravimetry (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM), and energy dispersive X-ray spectrometry (EDS). It is found that the Cu/CF composites have smooth, regular, and long fibrous morphologies with Cu nanoparticles uniformly dispersed in the carbon fibers. As free-standing anodes, the unique structural Cu/CF composites show stable and high reversible capacities, together with remarkable rate and cycling capabilities in Li-ion batteries. The Cu/CF calcined at 800 °C (Cu/CF-800) has the highest charge/discharge capacities, long-term stable cycling performance, and excellent rate performance; for instance, the Cu/CF-800 anode shows reversible charge/discharge capacities of around 800 mAh g-1 at a current density of 100 mA g-1 with stable cycling performance for more than 250 cycles; even when the current density increases to 2 A g-1, the Cu/CF-800 anode can still deliver a capacity of 300 mAh g-1. This excellent electrochemical performance is attributed to the special 1D structure of Cu/CF composites, the enhanced electrical conductivity, and more Li+ active positions by Cu nanoinclusion.

  9. Enhanced electrochemical performance and carbon anti-coking ability of solid oxide fuel cells with silver modified nickel-yttrium stabilized zirconia anode by electroless plating

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoyan; Tian, Yu; Zhang, Jun; Zuo, Wei; Kong, Xiaowei; Wang, Jinghui; Sun, Kening; Zhou, Xiaoliang

    2016-01-01

    In this paper, silver (Ag) particles are introduced into the conventional Ni/YSZ anode by utilizing electroless plating method to improve its carbon anti-coking ability in hydrocarbons. The experimental results show that electrochemical performances of the decorated cells in H2, CH4 and C2H6 are all increased as compared to the cell with unmodified Ni/YSZ anode, which are verified by impedance spectrums as well. The durability experiment is carried out for as long as 24 h at the current density of 0.33 A/cm2 where the modified anode is subjected to dry C2H6 indicating the anti-coking ability of the anode is greatly improved. Scanning electron microscope shows that the slight decreasing in the cell terminal voltage can be attributed to the minimized carbon deposition which maybe resulted from the aggregation of silver particles at high temperature. Energy-dispersive X-ray spectroscopy line scanning results after long-term stability operation of the anode suggest that the carbon deposition can be depressed effectively both inside the anode and on the surface of the anode. Therefore, the results show that silver is a promising candidate material for modifying the Ni/YSZ anode with regard to improving electrochemical performance and suppressing the carbon deposition when taking the hydrocarbons as fuels.

  10. Anodic nanoporous SnO2 grown on Cu foils as superior binder-free Na-ion battery anodes

    NASA Astrophysics Data System (ADS)

    Bian, Haidong; Zhang, Jie; Yuen, Muk-Fung; Kang, Wenpei; Zhan, Yawen; Yu, Denis Y. W.; Xu, Zhengtao; Li, Yang Yang

    2016-03-01

    We present a convenient, low-cost strategy to fabricate one-dimensional, vertically oriented nanoporous assembly of SnO2 upon a Cu substrate as a potentially promising anode system for Na-ion batteries application. The major novelty of the fabrication stage resides in anodizing a Sn/Cu bilayer film that is created by a facile cold-rolling procedure amenable to large-scale production. The open, nanoporous morphology of SnO2 facilitates the diffusion of electrolytes to access the SnO2 surface. The high porosity of the SnO2 phase also provides large void space to effectively accommodate the volume expansion/contraction during sodiation/desodiation. As a result, the 1-D nanoporous SnO2 thus assembled on the Cu substrate can be directly used as an effective electrode system for Na-ion storage-without the need for additives, delivering a remarkable capacity of 326 mA h g-1 over 200 cycles at a current rate of 0.2 C.

  11. Electrochemical incineration of diclofenac in neutral aqueous medium by anodic oxidation using Pt and boron-doped diamond anodes.

    PubMed

    Brillas, Enric; Garcia-Segura, Sergi; Skoumal, Marcel; Arias, Conchita

    2010-04-01

    The degradation of diclofenac, a common non-steroidal anti-inflammatory drug, in aqueous medium has been studied by anodic oxidation (AO) using an undivided cell with a Pt or boron-doped diamond (BDD) anode. Operating without pH regulation, AO with Pt acidifies the solution with precipitation of its protonated form, whereas using BDD, the solution becomes alkaline and only attains partial mineralization. Total incineration of low contents of the drug is feasible by AO with BDD in a neutral buffer medium of pH 6.5. Comparative treatment with Pt gives poor decontamination. The diclofenac decay always follows a pseudo first-order reaction. The increase in current for AO with BDD accelerates the degradative process, but decreases its efficiency. 2-Hydroxyphenylacetic acid, 2,5-dihydroxyphenylacetic acid, 2,6-dichloroaniline and 2,6-dichlorohydroquinone have been identified as aromatic intermediates. For AO with Pt, high amounts of malic, succinic, tartaric and oxalic acids are accumulated in the bulk and the N-derivatives produced are rapidly destroyed with loss of NH4+. When BDD is employed, some carboxylic acids are also accumulated in small extent, with a larger persistence of oxalic and oxamic acids. The process involves the formation of different N-derivatives that slowly release NH4+ and NO3(-) ions. Chloride ion is lost in all cases.

  12. Polyaniline-Coated Carbon Nanotube Ultrafiltration Membranes: Enhanced Anodic Stability for In Situ Cleaning and Electro-Oxidation Processes.

    PubMed

    Duan, Wenyan; Ronen, Avner; Walker, Sharon; Jassby, David

    2016-08-31

    Electrically conducting membranes (ECMs) have been reported to be efficient in fouling prevention and destruction of aqueous chemical compounds. In the current study, highly conductive and anodically stable composite polyaniline-carbon nanotube (PANI-CNT) ultrafiltration (UF) ECMs were fabricated through a process of electropolymerization of aniline on a CNT substrate under acidic conditions. The resulting PANI-CNT UF ECMs were characterized by scanning electron microscopy, atomic force microscopy, a four-point conductivity probe, cyclic voltammetry, and contact angle goniometry. The utilization of the PANI-CNT material led to significant advantages, including: (1) increased electrical conductivity by nearly an order of magnitude; (2) increased surface hydrophilicity while not impacting membrane selectivity or permeability; and (3) greatly improved stability under anodic conditions. The membrane's anodic stability was evaluated in a pH-controlled aqueous environment under a wide range of anodic potentials using a three-electrode cell. Results indicate a significantly reduced degradation rate in comparison to a CNT-poly(vinyl alcohol) ECM under high anodic potentials. Fouling experiments conducted with bovine serum albumin demonstrated the capacity of the PANI-CNT ECMs for in situ oxidative cleaning, with membrane flux restored to its initial value under an applied potential of 3 V. Additionally, a model organic compound (methylene blue) was electrochemically transformed at high efficiency (90%) in a single pass through the anodically charged ECM. PMID:27525344

  13. Increased Power in Sediment Microbial Fuel Cell: Facilitated Mass Transfer via a Water-Layer Anode Embedded in Sediment

    PubMed Central

    Lee, Yoo Seok; An, Junyeong; Kim, Bongkyu; Park, HyunJun; Kim, Jisu; Chang, In Seop

    2015-01-01

    We report a methodology for enhancing the mass transfer at the anode electrode of sediment microbial fuel cells (SMFCs), by employing a fabric baffle to create a separate water-layer for installing the anode electrode in sediment. The maximum power in an SMFC with the anode installed in the separate water-layer (SMFC-wFB) was improved by factor of 6.6 compared to an SMFC having the anode embedded in the sediment (SMFC-woFB). The maximum current density in the SMFC-wFB was also 3.9 times higher (220.46 mA/m2) than for the SMFC-woFB. We found that the increased performance in the SMFC-wFB was due to the improved mass transfer rate of organic matter obtained by employing the water-layer during anode installation in the sediment layer. Acetate injection tests revealed that the SMFC-wFB could be applied to natural water bodies in which there is frequent organic contamination, based on the acetate flux from the cathode to the anode. PMID:26714176

  14. Increased Power in Sediment Microbial Fuel Cell: Facilitated Mass Transfer via a Water-Layer Anode Embedded in Sediment.

    PubMed

    Lee, Yoo Seok; An, Junyeong; Kim, Bongkyu; Park, HyunJun; Kim, Jisu; Chang, In Seop

    2015-01-01

    We report a methodology for enhancing the mass transfer at the anode electrode of sediment microbial fuel cells (SMFCs), by employing a fabric baffle to create a separate water-layer for installing the anode electrode in sediment. The maximum power in an SMFC with the anode installed in the separate water-layer (SMFC-wFB) was improved by factor of 6.6 compared to an SMFC having the anode embedded in the sediment (SMFC-woFB). The maximum current density in the SMFC-wFB was also 3.9 times higher (220.46 mA/m2) than for the SMFC-woFB. We found that the increased performance in the SMFC-wFB was due to the improved mass transfer rate of organic matter obtained by employing the water-layer during anode installation in the sediment layer. Acetate injection tests revealed that the SMFC-wFB could be applied to natural water bodies in which there is frequent organic contamination, based on the acetate flux from the cathode to the anode.

  15. Pd-catalytic hydrodechlorination of chlorinated hydrocarbons in groundwater using H2 produced by a dual-anode system.

    PubMed

    Xie, Shiwei; Yuan, Songhu; Liao, Peng; Jia, Mengqi; Wang, Yin

    2015-12-01

    Water electrolysis has been employed for in situ supplying H2 to Pd-catalytic treatment of groundwater, but the treatment efficiency is greatly inhibited by the concomitant production of O2. In this study, a new dual-anode system is proposed to improve the efficiency. An inert anode and an iron anode are used simultaneously to produce O2 and Fe(II), respectively. The quick oxidative precipitation of Fe(II) by O2 removes both Fe(II) and O2, improving the utilization of cathodic H2 for the subsequent Pd-catalytic hydrodechlorination. Feasibility tests in the lab show that Pd-catalytic hydrodechlorination of trichloroethylene (TCE) was considerably increased by the addition of an iron anode to the conventional two-electrode system. Scale-up tests at an abandoned chemical site demonstrated that chlorobenzenes in the groundwater were largely hydrodechlorinated to benzene, showing a maximum efficiency with the currents of 0.24 and 0.16 A applied to the inert and iron anodes, respectively, at the flow rate of 6 L/h. In a 3-month intermittent field test, Pd normalized rate constants of hydrodechlorinating three chlorobenzenes are comparable to the conventional means of H2 supply, while the cost for hydrodechlorination normalized by one mole [H] is much lower. The dual-anode system is an effective means to supplying H2 in situ for Pd-catalytic treatment.

  16. Computational modeling of air-breathing microfluidic fuel cells with flow-over and flow-through anodes

    NASA Astrophysics Data System (ADS)

    Zhang, Biao; Ye, Ding-ding; Sui, Pang-Chieh; Djilali, Ned; Zhu, Xun

    2014-08-01

    A three-dimensional computational model for air-breathing microfluidic fuel cells (AMFCs) with flow-over and flow-through anodes is developed. The coupled multiphysics phenomena of fluid flow, species transport and electrochemical reactions are resolved numerically. The model has been validated against experimental data using an in-house AMFC prototype with a flow-through anode. Characteristics of fuel transfer and fuel crossover for both types of anodes are investigated. The model results reveal that the fuel transport to the flow-over anode is intrinsically limited by the fuel concentration boundary layer. Conversely, fuel transport for the flow-through anode is convectively enhanced by the permeate flow, and no concentration boundary layer is observed. An unexpected additional advantage of the flow-through anode configuration is lower parasitic (crossover) current density than the flow-over case at practical low flow rates. Cell performance of the flow-through case is found to be limited by reaction kinetics. The present model provides insights into the fuel transport and fuel crossover in air-breathing microfluidic fuel cells and provides guidance for further design and operation optimization.

  17. Polyaniline-Coated Carbon Nanotube Ultrafiltration Membranes: Enhanced Anodic Stability for In Situ Cleaning and Electro-Oxidation Processes.

    PubMed

    Duan, Wenyan; Ronen, Avner; Walker, Sharon; Jassby, David

    2016-08-31

    Electrically conducting membranes (ECMs) have been reported to be efficient in fouling prevention and destruction of aqueous chemical compounds. In the current study, highly conductive and anodically stable composite polyaniline-carbon nanotube (PANI-CNT) ultrafiltration (UF) ECMs were fabricated through a process of electropolymerization of aniline on a CNT substrate under acidic conditions. The resulting PANI-CNT UF ECMs were characterized by scanning electron microscopy, atomic force microscopy, a four-point conductivity probe, cyclic voltammetry, and contact angle goniometry. The utilization of the PANI-CNT material led to significant advantages, including: (1) increased electrical conductivity by nearly an order of magnitude; (2) increased surface hydrophilicity while not impacting membrane selectivity or permeability; and (3) greatly improved stability under anodic conditions. The membrane's anodic stability was evaluated in a pH-controlled aqueous environment under a wide range of anodic potentials using a three-electrode cell. Results indicate a significantly reduced degradation rate in comparison to a CNT-poly(vinyl alcohol) ECM under high anodic potentials. Fouling experiments conducted with bovine serum albumin demonstrated the capacity of the PANI-CNT ECMs for in situ oxidative cleaning, with membrane flux restored to its initial value under an applied potential of 3 V. Additionally, a model organic compound (methylene blue) was electrochemically transformed at high efficiency (90%) in a single pass through the anodically charged ECM.

  18. Fuel cell anode configuration for CO tolerance

    DOEpatents

    Uribe, Francisco A.; Zawodzinski, Thomas A.

    2004-11-16

    A polymer electrolyte fuel cell (PEFC) is designed to operate on a reformate fuel stream containing oxygen and diluted hydrogen fuel with CO impurities. A polymer electrolyte membrane has an electrocatalytic surface formed from an electrocatalyst mixed with the polymer and bonded on an anode side of the membrane. An anode backing is formed of a porous electrically conductive material and has a first surface abutting the electrocatalytic surface and a second surface facing away from the membrane. The second surface has an oxidation catalyst layer effective to catalyze the oxidation of CO by oxygen present in the fuel stream where at least the layer of oxidation catalyst is formed of a non-precious metal oxidation catalyst selected from the group consisting of Cu, Fe, Co, Tb, W, Mo, Sn, and oxides thereof, and other metals having at least two low oxidation states.

  19. Molybdenum dioxide-based anode for solid oxide fuel cell applications

    NASA Astrophysics Data System (ADS)

    Kwon, Byeong Wan; Ellefson, Caleb; Breit, Joe; Kim, Jinsoo; Grant Norton, M.; Ha, Su

    2013-12-01

    The present paper describes the fabrication and performance of a molybdenum dioxide (MoO2)-based anode for liquid hydrocarbon/oxygenated hydrocarbon-fueled solid oxide fuel cells (SOFCs). These fuel cells first internally reform the complex liquid fuel into carbon fragments and hydrogen, which are then electrochemically oxidized to produce electrical energy without external fuel processors. The MoO2-based anode was fabricated on to an yttria-stabilized zirconia (YSZ) electrolyte via combined electrostatic spray deposition (ESD) and direct painting methods. The cell performance was measured by directly feeding liquid fuels such as n-dodecane (i.e., a model diesel/kerosene fuel) or biodiesel (i.e., a future biomass-based liquid fuel) to the MoO2-based anode at 850 °C. The maximum initial power densities obtained from our MoO2-based SOFC were 34 mW cm-2 and 45 mW cm-2 using n-dodecane and biodiesel, respectively. The initial power density of the MoO2-based SOFC was improved up to 2500 mW cm-2 by optimizing the porosity of the MoO2-based anode. To test the long-term stability of the MoO2-based anode SOFC against coking, n-dodecane was continuously fed into the cell for 24 h at the open circuit voltage (OCV). During long-term testing, voltage-current density (V-I) plots were periodically obtained and they showed no significant changes over the operation time. Microstructural examination of the tested cells indicated that the MoO2-based anode displayed negligible coke formation, which explains its stability. On the other hand, SOFCs with conventional nickel (Ni)-based anodes under the same operating conditions showed a significant amount of coke formation on the metal surface, which led to a rapid drop in cell performance. Hence, the present work demonstrates that MoO2-based anodes exhibit outstanding tolerance to coke formation. This result opens up the opportunity for more efficiently generating electrical energy from both existing transportation and next generation

  20. High performance anode for advanced Li batteries

    SciTech Connect

    Lake, Carla

    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. Lithium Metal Anodes for Rechargeable Batteries

    SciTech Connect

    Xu, Wu; Wang, Jiulin; Ding, Fei; Chen, Xilin; Nasybulin, Eduard N.; Zhang, Yaohui; Zhang, Jiguang

    2013-10-29

    Rechargeable lithium metal batteries have much higher energy density than those of lithium ion batteries using graphite anode. Unfortunately, uncontrollable dendritic lithium growth inherent in these batteries (upon repeated charge/discharge cycling) and limited Coulombic efficiency during lithium deposition/striping has prevented their practical application over the past 40 years. With the emerging of post Li-ion batteries, safe and efficient operation of lithium metal anode has become an enabling technology which may determine the fate of several promising candidates for the next generation of energy storage systems, including rechargeable Li-air battery, Li-S battery, and Li metal battery which utilize lithium intercalation compounds as cathode. In this work, various factors which affect the morphology and Coulombic efficiency of lithium anode will be analyzed. Technologies used to characterize the morphology of lithium deposition and the results obtained by modeling of lithium dendrite growth will also be reviewed. At last, recent development in this filed and urgent need in this field will also be discussed.

  2. Chromic acid anodizing of aluminum foil

    NASA Technical Reports Server (NTRS)

    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.

  3. High efficiency current regulator for ring laser gyroscope

    SciTech Connect

    Ljung, B.H.

    1981-08-04

    A method and apparatus for regulating the anode current of a gas lasing system with reduced power dissipation is disclosed. According to this invention a feedback loop is connected between the anode circuitry and the high voltage power supply such that the anode current regulator has a much lower voltage across itself than has been the case in the past. Since the voltage across the current regulator is reduced, there is not nearly as much power for the regulator to dissipate. In addition, because of the smaller power handling requirements, a stabilized anode current can be achieved at about half the level required by prior art circuitry. Thus, the power dissipation can be reduced even further.

  4. Luminescence characteristics of nanoporous anodic alumina annealed at different temperatures

    NASA Astrophysics Data System (ADS)

    Ilin, D. O.; Vokhmintsev, A. S.; Weinstein, I. A.

    2016-09-01

    Anodic aluminum oxide (AAO) membranes with 100 µm thickness were synthesized in oxalic acid solution under constant current density. Grown samples were annealed in 500-1250 °C range for 5 h in air. Average pore diameter was evaluated using quantitative analysis of SEM images and appeared to be within 78-86 nm diapason. It was found there was a broad emission band in the 350-620 nm region of photoluminescence (PL) spectra in amorphous membranes which is attributed to F-type oxygen deficient centers or oxalic ions. It was shown that intensive red emission caused by Cr3+ (696 nm) and Mn4+ (680 nm) impurities dominates in PL of AAO samples with crystalline α- and δ-phases after annealing at 1100-1250 °C temperatures.

  5. Transparent nanotubular capacitors based on transplanted anodic aluminum oxide templates.

    PubMed

    Zhang, Guozhen; Wu, Hao; Chen, Chao; Wang, Ti; Wu, Wenhui; Yue, Jin; Liu, Chang

    2015-03-11

    Transparent AlZnO/Al2O3/AlZnO nanocapacitor arrays have been fabricated by atomic layer deposition in anodic aluminum oxide templates transplanted on the AlZnO/glass substrates. A high capacitance density of 37 fF/μm(2) is obtained, which is nearly 5.8 times bigger than that of planar capacitors. The capacitance density almost remains the same in a broad frequency range from 1 kHz to 200 kHz. Moreover, a low leakage current density of 1.7 × 10(-7) A/cm(2) at 1 V has been achieved. The nanocapacitors exhibit an average optical transmittance of more than 80% in the visible range, and thus open the door to practical applications in transparent integrated circuits.

  6. Electrochemical performance of Si anode modified with carbonized gelatin binder

    NASA Astrophysics Data System (ADS)

    Jiang, Ying; Mu, Daobin; Chen, Shi; Wu, Borong; Cheng, Kailin; Li, Luyu; Wu, Feng

    2016-09-01

    Gelatin is alternatively adopted as the binder to modify Si anode coupling with its carbonization treatment. The binder can provide good bonding and uniform dispersion of the particles besides its environmental benignancy. Importantly, the carbonized binder containing nitrogen will be advantageous to the electrical conductivity of the electrode. In addition, some spaces are formed in the electrode due to the decomposition and shrinkage of the gelatin binder during heat-treatment, which may facilitate electrolyte penetration and accommodate volume change during cycling. All these merits make contribution to the good electrochemical performance of the modified Si electrode. It exhibits a reversible capacity of 990.3 mA h g-1 after 70 cycles at a current density of 100 mA g-1 and 904 mA h g-1 after 100 cycles at 400 mA g-1.

  7. A novel CZT detector using strengthened electric field line anode

    NASA Astrophysics Data System (ADS)

    Fu, Jian-Qiang; Li, Yu-Lan; Zhang, Lan; Niu, Li-Bo; Jiang, Hao; Li, Yuan-Jing

    2014-12-01

    In this paper, we report on the design, simulation and testing of a novel CZT detector with an electrode named the Strengthened Electric Field Line Anode (SEFLA). The Strengthened Electric Field (SEF) technique and Single Polarity Charge Sensing (SPCS) technique are implemented. It could achieve the same performance as Coplanar Grid, Pixel Array CZT detectors but requires only a simple readout system. Geant4, Ansoft Maxwell and a self-developed Induced Current Calculator (ICC) package are used to develop an understanding of how the energy spectrum is formed, and the parameters of the detector are optimized. A prototype is fabricated. Experimental results demonstrate the effectiveness of this design. The test shows that the SEFLA detector achieves a FWHM of 6.0% @59.5 keV and 1.6% @662 keV, which matches well with the simulations.

  8. LiVP2O7/C: A New Insertion Anode Material for High-Rate Lithium-Ion Battery Applications.

    PubMed

    Mani, Vellaisamy; Kalaiselvi, Nallathamby

    2016-04-18

    LiVP2O7/C, popularly known so far as an environmentally compatible and economically viable lithium battery cathode material, was exploited for the first time as an anode through the current study. LiVP2O7/C was synthesized by adopting oxalyl dihydrazide assisted solution combustion method and explored as an anode material in rechargeable lithium cell assembly. Notably, an initial capacity of 600 mAh g(-1) was exhibited by LiVP2O7/C anode, at the rate of 0.5 C along with an excellent Coulombic efficiency of 99% up to 150 cycles. The title anode demonstrates its suitability for high capacity and high rate applications by way of exhibiting appreciable capacity values of 200, 150, 120, and 110 mAh g(-1), under the influence of 2, 4, 6, and 8 C rates, respectively. Further, LiVP2O7/C anode, when subjected to a high current 10 C rate, exhibits an acceptable capacity of 107 mAh g(-1) up to 500 cycles, which is closer to its theoretical capacity value of 117 mAh g(-1). The study demonstrates the possibility of exploiting LiVP2O7/C as yet another potential anode and thereby opens a newer avenue to explore wide variety of LiMP2O7/C composites for their probable anode behavior in rechargeable lithium batteries.

  9. Bacterial Community Analysis, New Exoelectrogen Isolation and Enhanced Performance of Microbial Electrochemical Systems Using Nano-Decorated Anodes

    NASA Astrophysics Data System (ADS)

    Xu, Shoutao

    Microbial electrochemical systems (MESs) have attracted much research attention in recent years due to their promising applications in renewable energy generation, bioremediation, and wastewater treatment. In a MES, microorganisms interact with electrodes via electrons, catalyzing oxidation and reduction reactions at the anode and the cathode. The bacterial community of a high power mixed consortium MESs (maximum power density is 6.5W/m2) was analyzed by using denature gradient gel electrophoresis (DGGE) and 16S DNA clone library methods. The bacterial DGGE profiles were relatively complex (more than 10 bands) but only three brightly dominant bands in DGGE results. These results indicated there are three dominant bacterial species in mixed consortium MFCs. The 16S DNA clone library method results revealed that the predominant bacterial species in mixed culture is Geobacter sp (66%), Arcobacter sp and Citrobacter sp. These three bacterial species reached to 88% of total bacterial species. This result is consistent with the DGGE result which showed that three bright bands represented three dominant bacterial species. Exoelectrogenic bacterial strain SX-1 was isolated from a mediator-less microbial fuel cell by conventional plating techniques with ferric citrate as electron acceptor under anaerobic conditions. Phylogenetic analysis of the 16S rDNA sequence revealed that it was related to the members of Citrobacter genus with Citrobacter sp. sdy-48 being the most closely related species. The bacterial strain SX-1 produced electricity from citrate, acetate, glucose, sucrose, glycerol, and lactose in MFCs with the highest current density of 205 mA/m2 generated from citrate. Cyclic voltammetry analysis indicated that membrane associated proteins may play an important role in facilitating electron transfer from the bacteria to the electrode. This is the first study that demonstrates that Citrobacter species can transfer electrons to extracellular electron acceptors

  10. Magnetic dipole discharges. II. Cathode and anode spot discharges and probe diagnostics

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.; Ionita, C.; Schrittwieser, R.

    2013-08-15

    The high current regime of a magnetron-type discharge has been investigated. The discharge uses a permanent magnet as a cold cathode which emits secondary electrons while the chamber wall or a grounded electrode serves as the anode. As the discharge voltage is increased, the magnet develops cathode spots, which are short duration arcs that provide copious electrons to increase the discharge current dramatically. Short (1 μs), high current (200 A) and high voltage (750 V) discharge pulses are produced in a relaxation instability between the plasma and a charging capacitor. Spots are also observed on a negatively biased plane Langmuir probe. The probe current pulses are as large as those on the magnet, implying that the high discharge current does not depend on the cathode surface area but on the properties of the spots. The fast current pulses produce large inductive voltages, which can reverse the electrical polarity of the magnet and temporarily operate it as an anode. The discharge current may also oscillate at the frequency determined by the charging capacitor and the discharge circuit inductance. Each half cycle of high-current current pulses exhibits a fast (≃10 ns) current rise when a spot is formed. It induces high frequency (10–100 MHz) transients and ringing oscillations in probes and current circuits. Most probes behave like unmatched antennas for the electromagnetic pulses of spot discharges. Examples are shown to distinguish the source of oscillations and some rf characteristics of Langmuir probes.

  11. Electrochemical Aging of Thermal-Sprayed Zinc Anodes on Concrete

    SciTech Connect

    Holcomb, G.R.; Bullard, S.J.; Covino, B.S. Jr.; Cramer, S.D.; Cryer, C.B.; McGill, G.E.

    1996-10-01

    Thermal-sprayed zinc anodes are used in impressed current cathodic protection systems for some of Oregon's coastal reinforced concrete bridges. Electrochemical aging of zinc anodes results in physical and chemical changes at the zinc-concrete interface. Concrete surfaces heated prior to thermal-spraying had initial adhesion strengths 80 pct higher than unheated surfaces. For electrochemical aging greater than 200 kC/m{sup 2} (5.2 A h/ft{sup 2}), there was no difference in adhesion strengths for zinc on preheated and unheated concrete. Adhesion strengths decreased monotonically after about 400 to 600 kC/m{sup 2} (10.4 to 15.6 A-h/ft{sup 2}) as a result of the reaction zones at the zinc-concrete interface. A zone adjacent to the metallic zinc (and originally part of the zinc coating) was primarily zincite (ZnO), with minor constituents of wulfingite (Zn(OH){sub 2}), simonkolleite (Zn{sub 5}(OH) {sub 8}C{sub l2}{sup .}H{sub 2}O), and hydrated zinc hydroxide sulfates (Zn{sub 4}SO{sub 4}(OH){sub 6}{sup .}xH{sub 2}O). This zone is the locus for cohesive fracture when the zinc coating separates from the concrete during adhesion tests. Zinc ions substitute for calcium in the cement paste adjacent to the coating as the result of secondary mineralization. The initial estimate of the coating service life based on adhesion strength measurements in accelerated impressed current cathodic protection tests is about 27 years.

  12. Using live algae at the anode of a microbial fuel cell to generate electricity.

    PubMed

    Xu, Chang; Poon, Karen; Choi, Martin M F; Wang, Ruihua

    2015-10-01

    Live green microalgae Chlorella pyrenoidosa was introduced in the anode of a microbial fuel cell (MFC) to act as an electron donor. By controlling the oxygen content, light intensity, and algal cell density at the anode, microalgae would generate electricity without requiring externally added substrates. Two models of algal microbial fuel cells (MFCs) were constructed with graphite/carbon electrodes and no mediator. Model 1 algal MFC has live microalgae grown at the anode and potassium ferricyanide at the cathode, while model 2 algal MFC had live microalgae in both the anode and cathode in different growth conditions. Results indicated that a higher current produced in model 1 algal MFC was obtained at low light intensity of 2500 lx and algal cell density of 5 × 10(6) cells/ml, in which high algal density would limit the electricity generation, probably by increasing oxygen level and mass transfer problem. The maximum power density per unit anode volume obtained in model 1 algal MFC was relatively high at 6030 mW/m(2), while the maximum power density at 30.15 mW/m(2) was comparable with that of previous reported bacteria-driven MFC with graphite/carbon electrodes. A much smaller power density at 2.5 mW/m(2) was observed in model 2 algal MFC. Increasing the algal cell permeability by 4-nitroaniline would increase the open circuit voltage, while the mitochondrial acting and proton leak promoting agents resveratrol and 2,4-dinitrophenol would increase the electric current production in algal MFC.

  13. Using live algae at the anode of a microbial fuel cell to generate electricity.

    PubMed

    Xu, Chang; Poon, Karen; Choi, Martin M F; Wang, Ruihua

    2015-10-01

    Live green microalgae Chlorella pyrenoidosa was introduced in the anode of a microbial fuel cell (MFC) to act as an electron donor. By controlling the oxygen content, light intensity, and algal cell density at the anode, microalgae would generate electricity without requiring externally added substrates. Two models of algal microbial fuel cells (MFCs) were constructed with graphite/carbon electrodes and no mediator. Model 1 algal MFC has live microalgae grown at the anode and potassium ferricyanide at the cathode, while model 2 algal MFC had live microalgae in both the anode and cathode in different growth conditions. Results indicated that a higher current produced in model 1 algal MFC was obtained at low light intensity of 2500 lx and algal cell density of 5 × 10(6) cells/ml, in which high algal density would limit the electricity generation, probably by increasing oxygen level and mass transfer problem. The maximum power density per unit anode volume obtained in model 1 algal MFC was relatively high at 6030 mW/m(2), while the maximum power density at 30.15 mW/m(2) was comparable with that of previous reported bacteria-driven MFC with graphite/carbon electrodes. A much smaller power density at 2.5 mW/m(2) was observed in model 2 algal MFC. Increasing the algal cell permeability by 4-nitroaniline would increase the open circuit voltage, while the mitochondrial acting and proton leak promoting agents resveratrol and 2,4-dinitrophenol would increase the electric current production in algal MFC. PMID:26018284

  14. Sharp transition between two regimes of operation of dc discharge with two anodes and thermionic emission from cathode

    SciTech Connect

    Mustafaev, A. S.; Grabovskiy, A.; Demidov, V. I.; Kaganovich, I. D.; Koepke, M. E.

    2014-05-15

    In a dc discharge plasma with two anodes and thermionic emission from cathode, the two anodes are used for plasma control. The main anode is placed between the cathode and the other auxiliary anode has a circular opening for passing electron current from the cathode to the second anode. It is experimentally demonstrated that a plasma may exhibit a sudden transition between two quasi-stable conditions as one increases the cathode-electron current collected by the auxiliary anode through an aperture, i.e., hole, in the main anode. In one regime, a bright glowing “ball-shaped double layer” appears on the plasma side having a potential drop of 10–15 eV and concomitant ionization in the neighboring region attached to the opening. The second regime is characterized by a uniform potential profile in plasma and an absence of the ball-shaped double layer. The transition between these regimes is accompanied by a significant change in plasma properties, such as the electron energy distribution function (EEDF). Controlling the EEDF is a valuable capability in technological applications. Increasing the gas pressure leads to the elimination of the first regime for sufficiently high gas pressure, the threshold being a few Torr. The disappearance of a regime transition can be explained by invoking an EEDF transition, from being nonlocal at low pressure to becoming local at high pressure. Local EEDF is determined by local values of electric field. Nonlocal EEDF is determined by electric field values elsewhere, and the electron can travel without energy loss over a path much longer than the discharge dimension.

  15. Structural tuning of photoluminescence in nanoporous anodic alumina by hard anodization in oxalic and malonic acids

    NASA Astrophysics Data System (ADS)

    Santos, Abel; Alba, Maria; Rahman, Mahbubur M.; Formentín, Pilar; Ferré-Borrull, Josep; Pallarès, Josep; Marsal, Lluis F.

    2012-04-01

    We report on an exhaustive and systematic study about the photoluminescent properties of nanoporous anodic alumina membranes fabricated by the one-step anodization process under hard conditions in oxalic and malonic acids. This optical property is analysed as a function of several parameters (i.e. hard anodization voltage, pore diameter, membrane thickness, annealing temperature and acid electrolyte). This analysis makes it possible to tune the photoluminescent behaviour at will simply by modifying the structural characteristics of these membranes. This structural tuning ability is of special interest in such fields as optoelectronics, in which an accurate design of the basic nanostructures (e.g. microcavities, resonators, filters, supports, etc.) yields the control over their optical properties and, thus, upon the performance of the nanodevices derived from them (biosensors, interferometers, selective filters, etc.)

  16. Controlling Pore Geometries and Interpore Distances of Anodic Aluminum Oxide Templates via Three-Step Anodization.

    PubMed

    Lim, Jin-Hee; Wiley, John B

    2015-01-01

    Porous alumina membranes have attracted much attention because they are very useful templates for the fabrication of various nanostructures important to nanotechnology. However, there are challenges in controlling pore geometries and interpore distances in alumina templates while maintaining highly ordered hexagonal pore structures. Herein, a three-step anodization method is utilized to prepare anodic alumina templates with various pore morphologies (e.g., arched-shape, tree-like, branched-shape) and tunable interpore distances. Such structures are not found within the more traditional alumina templates fabricated by a two-step anodization of aluminum films. The range of interpore distances and pore diameters within the modified templates increases with increasing voltages. In contrast, under decreasing voltages, hexagonally ordered pores can also branch into several pores with smaller sizes and reduced interpore distances. Electrochemical growth of metal nanowires in the modified templates helps to highlight details of the pore structures and which pore channels are active.

  17. Investigation of Metal Oxide/Carbon Nano Material as Anode for High Capacity Lithium-ion Cells

    NASA Technical Reports Server (NTRS)

    Wu, James Jianjun; Hong, Haiping

    2014-01-01

    NASA is developing high specific energy and high specific capacity lithium-ion battery (LIB) technology for future NASA missions. Current state-of-art LIBs have issues in terms of safety and thermal stability, and are reaching limits in specific energy capability based on the electrochemical materials selected. For example, the graphite anode has a limited capability to store Li since the theoretical capacity of graphite is 372 mAh/g. To achieve higher specific capacity and energy density, and to improve safety for current LIBs, alternative advanced anode, cathode, and electrolyte materials are pursued under the NASA Advanced Space Power System Project. In this study, the nanostructed metal oxide, such as Fe2O3 on carbon nanotubes (CNT) composite as an LIB anode has been investigated.

  18. Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties.

    PubMed

    Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

    2016-03-24

    In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA.

  19. Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties.

    PubMed

    Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

    2016-01-01

    In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA. PMID:27023546

  20. Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties

    PubMed Central

    Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

    2016-01-01

    In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA. PMID:27023546

  1. Critical importance of humidification of the anode in miniature air-breathing polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Hamel, Simon; Fréchette, Luc G.

    2011-08-01

    Although water management at the cathode is known to be critical in miniature polymer electrolyte membrane fuel cells (mPEMFCs), this study shows that control of water transport towards the anode is a determining factor to increase air-breathing mPEMFC performances. An analytical 1D model is developed to capture the water transport and water content profile in the membrane. It shows that drying at the anode and flooding at the cathode can happen simultaneously, mainly due to dominant electro-osmotic drag at low cell temperatures. Experimental results demonstrate that injecting water at the anode, at a rate of 3 times the amount produced at the cathode, increases the cell performances at high current densities. By this method, the limiting current and maximum power densities have been raised by 100% and 30% respectively.

  2. Transcranial direct current stimulation modulates efficiency of reading processes.

    PubMed

    Thomson, Jennifer M; Doruk, Deniz; Mascio, Bryan; Fregni, Felipe; Cerruti, Carlo

    2015-01-01

    Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that offers promise as an investigative method for understanding complex cognitive operations such as reading. This study explores the ability of a single session of tDCS to modulate reading efficiency and phonological processing performance within a group of healthy adults. Half the group received anodal or cathodal stimulation, on two separate days, of the left temporo-parietal junction while the other half received anodal or cathodal stimulation of the right homologue area. Pre- and post-stimulation assessment of reading efficiency and phonological processing was carried out. A larger pre-post difference in reading efficiency was found for participants who received right anodal stimulation compared to participants who received left anodal stimulation. Further, there was a significant post-stimulation increase in phonological processing speed following right hemisphere anodal stimulation. Implications for models of reading and reading impairment are discussed.

  3. Three-dimensional Sn-graphene anode for high-performance lithium-ion batteries.

    PubMed

    Wang, Chundong; Li, Yi; Chui, Ying-San; Wu, Qi-Hui; Chen, Xianfeng; Zhang, Wenjun

    2013-11-01

    Tin (Sn) has been considered as one of the most promising anode materials for high-capacity lithium-ion batteries (LIBs) due to its high energy density, abundance, and environmentally benign nature. However, the problems of fast capacity fading at prolonged cycling and poor rate capacity hinder its practical use. Herein, we report the development of a novel architecture of Sn nanoparticle-decorated three-dimensional (3D) foothill-like graphene as an anode in LIBs. Electrochemical measurements demonstrated that the 3D Sn-graphene anode delivered a reversible capacity of 466 mA h g(-1) at a current density of 879 mA g(-1) (1 C) after over 4000 cycles and 794 mA h g(-1) at 293 mA g(-1) (1/3 C) after 400 cycles. The capacity at 1/3 C is over 200% that of conventional graphite anodes, suggesting that the 3D Sn-graphene structure enables a significant improvement in the overall performance of a LIB in aspects of capacity, cycle life, and rate capacity.

  4. Characteristics and electrochemical mechanisms of a nanosilver solution formed by anodic dissolution with high DC voltage

    NASA Astrophysics Data System (ADS)

    Hung, Nguyen Duc; Thuy, Nguyen Minh; Nhi Tru, Nguyen

    2013-08-01

    Nanosilver solution, prepared by anodic dissolution with high DC voltage in doubly distilled water, is free of undesirable chemicals and forms a highly pure product which is suitable for different applications, especially in the medical and pharmaceutical fields. In this study high DC voltage electrolysis was implemented to form nanosilver solutions with varying electrode diameters, anode-cathode distances, and electrolysis duration. The process was monitored while the cell was in operation, and the characteristics of the resulting solution were analysed afterwards. Cell reactions included: colour changes in the solution bulk due to the reduction of silver ions forming nanoparticles, anodic dissolution of silver, intense gas evolution at both electrodes, and chemical reactions in the solution causing nanosilver formation. UV-Vis characteristics, particle size distribution, transmission electron microscopy (TEM) images, solution concentrations, conductivities, and ζ-potentials were all found to depend on the electrode's distances, temperature, electrolysis duration, and current density. Nanosilver preparation can thus be considered a combination of electrochemical reactions (such as silver dissolution at anode and water decomposition to generate hydrogen and oxygen), and chemical reactions between the electrolytic products from the solution bulk.

  5. Graphene/silicon nanocomposite anode with enhanced electrochemical stability for lithium-ion battery applications

    NASA Astrophysics Data System (ADS)

    Maroni, F.; Raccichini, R.; Birrozzi, A.; Carbonari, G.; Tossici, R.; Croce, F.; Marassi, R.; Nobili, F.

    2014-12-01

    A graphene/silicon nanocomposite has been synthesized, characterized and tested as anode active material for lithium-ion batteries. A morphologically stable composite has been obtained by dispersing silicon nanoparticles in graphene oxide, previously functionalized with low-molecular weight polyacrylic acid, in eco-friendly, low-cost solvent such as ethylene glycol. The use of functionalized graphene oxide as substrate for the dispersion avoids the aggregation of silicon particles during the synthesis and decreases the detrimental effect of graphene layers re-stacking. Microwave irradiation of the suspension, inducing reduction of graphene oxide, and the following thermal annealing of the solid powder obtained by filtration, yield a graphene/silicon composite material with optimized morphology and properties. Composite anodes, prepared with high-molecular weight polyacrylic acid as green binder, exhibited high and stable reversible capacity values, of the order of 1000 mAh g-1, when cycled using vinylene carbonate as electrolyte additive. After 100 cycles at a current of 500 mA g-1, the anode showed a discharge capacity retention of about 80%. The mechanism of reversible lithium uptake is described in terms of Li-Si alloying/dealloying reaction. Comparison of the impedance responses of cells tested in electrolytes with or without vinylene carbonate confirms the beneficial effects of the additive in stabilizing the composite anode.

  6. Carbonized textile with free-standing threads as an efficient anode material for bioelectrochemical systems

    NASA Astrophysics Data System (ADS)

    Wang, Zejie; Zheng, Zhiyong; Zheng, Suqi; Chen, Shuiliang; Zhao, Feng

    2015-08-01

    Efficiency of bioelectrochemical systems (BESs) is generally limited by the performance of bioanode, resulted from the nature of microbial electron transfer and the character of the anode substrate. In the present study, a 3D structured anode material is fabricated using a towel as precursor through high-temperature carbonization. The 3D electrode is resulted from freely standing threads, twisted by fibers with diameter at micrometer scale, on a woven textile substrate. The open structure provides easy accesses for microbial to attach on the fiber surface. Furthermore, the prepared materials possess a high capacitive character which is beneficial for electron storage and contributes to the performance of bioanode. When tested in BESs, the prepared material achieves a current density of 0.80 ± 0.06 mA cm-2, larger than conventional anodes, e.g. graphite felt (0.55 ± 0.01 mA cm-2), carbon cloth (0.06 ± 0.01 mA cm-2), and carbon mesh (0.02 ± 0.00 mA cm-2). The present study provides a novel 3D anode substrate that can effectively promote the performance of BESs.

  7. Uncertainty studies of real anode surface area in computational analysis for molten salt electrorefining

    NASA Astrophysics Data System (ADS)

    Choi, Sungyeol; Park, Jaeyeong; Hoover, Robert O.; Phongikaroon, Supathorn; Simpson, Michael F.; Kim, Kwang-Rag; Hwang, Il Soon

    2011-09-01

    This study examines how much cell potential changes with five differently assumed real anode surface area cases. Determining real anode surface area is a significant issue to be resolved for precisely modeling molten salt electrorefining. Based on a three-dimensional electrorefining model, calculated cell potentials compare with an experimental cell potential variation over 80 h of operation of the Mark-IV electrorefiner with driver fuel from the Experimental Breeder Reactor II. We succeeded to achieve a good agreement with an overall trend of the experimental data with appropriate selection of a mode for real anode surface area, but there are still local inconsistencies between theoretical calculation and experimental observation. In addition, the results were validated and compared with two-dimensional results to identify possible uncertainty factors that had to be further considered in a computational electrorefining analysis. These uncertainty factors include material properties, heterogeneous material distribution, surface roughness, and current efficiency. Zirconium's abundance and complex behavior have more impact on uncertainty towards the latter period of electrorefining at given batch of fuel. The benchmark results found that anode materials would be dissolved from both axial and radial directions at least for low burn-up metallic fuels after active liquid sodium bonding was dissolved.

  8. Direct anodic hydrochloric acid and cathodic caustic production during water electrolysis

    NASA Astrophysics Data System (ADS)

    Lin, Hui-Wen; Cejudo-Marín, Rocío; Jeremiasse, Adriaan W.; Rabaey, Korneel; Yuan, Zhiguo; Pikaar, Ilje

    2016-02-01

    Hydrochloric acid (HCl) and caustic (NaOH) are among the most widely used chemicals by the water industry. Direct anodic electrochemical HCl production by water electrolysis has not been successful as current commercially available electrodes are prone to chlorine formation. This study presents an innovative technology simultaneously generating HCl and NaOH from NaCl using a Mn0.84Mo0.16O2.23 oxygen evolution electrode during water electrolysis. The results showed that protons could be anodically generated at a high Coulombic efficiency (i.e. ≥ 95%) with chlorine formation accounting for 3 ~ 5% of the charge supplied. HCl was anodically produced at moderate strengths at a CE of 65 ± 4% together with a CE of 89 ± 1% for cathodic caustic production. The reduction in CE for HCl generation was caused by proton cross-over from the anode to the middle compartment. Overall, this study showed the potential of simultaneous HCl and NaOH generation from NaCl and represents a major step forward for the water industry towards on-site production of HCl and NaOH. In this study, artificial brine was used as a source of sodium and chloride ions. In theory, artificial brine could be replaced by saline waste streams such as Reverse Osmosis Concentrate (ROC), turning ROC into a valuable resource.

  9. Uncertainty Studies of Real Anode Surface Area in Computational Analysis for Molten Salt Electrorefining

    SciTech Connect

    Sungyeol Choi; Jaeyeong Park; Robert O. Hoover; Supathorn Phongikaroon; Michael F. Simpson; Kwang-Rag Kim; Il Soon Hwang

    2011-09-01

    This study examines how much cell potential changes with five differently assumed real anode surface area cases. Determining real anode surface area is a significant issue to be resolved for precisely modeling molten salt electrorefining. Based on a three-dimensional electrorefining model, calculated cell potentials compare with an experimental cell potential variation over 80 hours of operation of the Mark-IV electrorefiner with driver fuel from the Experimental Breeder Reactor II. We succeeded to achieve a good agreement with an overall trend of the experimental data with appropriate selection of a mode for real anode surface area, but there are still local inconsistencies between theoretical calculation and experimental observation. In addition, the results were validated and compared with two-dimensional results to identify possible uncertainty factors that had to be further considered in a computational electrorefining analysis. These uncertainty factors include material properties, heterogeneous material distribution, surface roughness, and current efficiency. Zirconium's abundance and complex behavior have more impact on uncertainty towards the latter period of electrorefining at given batch of fuel. The benchmark results found that anode materials would be dissolved from both axial and radial directions at least for low burn-up metallic fuels after active liquid sodium bonding was dissolved.

  10. Direct anodic hydrochloric acid and cathodic caustic production during water electrolysis

    PubMed Central

    Lin, Hui-Wen; Cejudo-Marín, Rocío; Jeremiasse, Adriaan W.; Rabaey, Korneel; Yuan, Zhiguo; Pikaar, Ilje

    2016-01-01

    Hydrochloric acid (HCl) and caustic (NaOH) are among the most widely used chemicals by the water industry. Direct anodic electrochemical HCl production by water electrolysis has not been successful as current commercially available electrodes are prone to chlorine formation. This study presents an innovative technology simultaneously generating HCl and NaOH from NaCl using a Mn0.84Mo0.16O2.23 oxygen evolution electrode during water electrolysis. The results showed that protons could be anodically generated at a high Coulombic efficiency (i.e. ≥ 95%) with chlorine formation accounting for 3 ~ 5% of the charge supplied. HCl was anodically produced at moderate strengths at a CE of 65 ± 4% together with a CE of 89 ± 1% for cathodic caustic production. The reduction in CE for HCl generation was caused by proton cross-over from the anode to the middle compartment. Overall, this study showed the potential of simultaneous HCl and NaOH generation from NaCl and represents a major step forward for the water industry towards on-site production of HCl and NaOH. In this study, artificial brine was used as a source of sodium and chloride ions. In theory, artificial brine could be replaced by saline waste streams such as Reverse Osmosis Concentrate (ROC), turning ROC into a valuable resource. PMID:26848031

  11. Nb-doped rutile TiO₂: a potential anode material for Na-ion battery.

    PubMed

    Usui, Hiroyuki; Yoshioka, Sho; Wasada, Kuniaki; Shimizu, Masahiro; Sakaguchi, Hiroki

    2015-04-01

    The electrochemical properties of the rutile-type TiO2 and Nb-doped TiO2 were investigated for the first time as Na-ion battery anodes. Ti(1-x)Nb(x)O2 thick-film electrodes without a binder and a conductive additive were prepared using a sol-gel method followed by a gas-deposition method. The TiO2 electrode showed reversible reactions of Na insertion/extraction accompanied by expansion/contraction of the TiO2 lattice. Among the Ti(1-x)Nb(x)O2 electrodes with x = 0-0.18, the Ti(0.94)Nb(0.06)O2 electrode exhibited the best cycling performance, with a reversible capacity of 160 mA h g(-1) at the 50th cycle. As the Li-ion battery anode, this electrode also attained an excellent rate capability, with a capacity of 120 mA h g(-1) even at the high current density of 16.75 A g(-1) (50C). The improvements in the performances are attributed to a 3 orders of magnitude higher electronic conductivity of Ti(0.94)Nb(0.06)O2 compared to that of TiO2. This offers the possibility of Nb-doped rutile TiO2 as a Na-ion battery anode as well as a Li-ion battery anode.

  12. Electrochemical treatment of cork boiling wastewater with a boron-doped diamond anode.

    PubMed

    Fernandes, Annabel; Santos, Diana; Pacheco, Maria José; Ciríaco, Lurdes; Simões, Rogério; Gomes, Arlindo C; Lopes, Ana

    2015-01-01

    Anodic oxidation at a boron-doped diamond anode of cork boiling wastewater was successfully used for mineralization and biodegradability enhancement required for effluent discharge or subsequent biological treatment, respectively. The influence of the applied current density (30-70 mA/cm2) and the background electrolyte concentration (0-1.5 g/L Na2SO4) on the performance of the electrochemical oxidation was investigated. The supporting electrolyte was required to achieve conductivities that enabled anodic oxidation at the highest current intensities applied. The results indicated that pollutant removal increased with the applied current density, and after 8 h, reductions greater than 90% were achieved for COD, dissolved organic carbon, total phenols and colour. The biodegradability enhancement was from 0.13 to 0.59 and from 0.23 to 0.72 for the BOD/COD ratios with BOD of 5 and 20 days' incubation period, respectively. The tests without added electrolyte were performed at lower applied electrical charges (15 mA/cm2 or 30 V) with good organic load removal (up to 80%). For an applied current density of 30 mA/cm2, there was a minimum of electric conductivity of 1.9 mS/cm (corresponding to 0.75 g/L of Na2SO4), which minimized the specific energy consumption.

  13. Electrochemical treatment of cork boiling wastewater with a boron-doped diamond anode.

    PubMed

    Fernandes, Annabel; Santos, Diana; Pacheco, Maria José; Ciríaco, Lurdes; Simões, Rogério; Gomes, Arlindo C; Lopes, Ana

    2015-01-01

    Anodic oxidation at a boron-doped diamond anode of cork boiling wastewater was successfully used for mineralization and biodegradability enhancement required for effluent discharge or subsequent biological treatment, respectively. The influence of the applied current density (30-70 mA/cm2) and the background electrolyte concentration (0-1.5 g/L Na2SO4) on the performance of the electrochemical oxidation was investigated. The supporting electrolyte was required to achieve conductivities that enabled anodic oxidation at the highest current intensities applied. The results indicated that pollutant removal increased with the applied current density, and after 8 h, reductions greater than 90% were achieved for COD, dissolved organic carbon, total phenols and colour. The biodegradability enhancement was from 0.13 to 0.59 and from 0.23 to 0.72 for the BOD/COD ratios with BOD of 5 and 20 days' incubation period, respectively. The tests without added electrolyte were performed at lower applied electrical charges (15 mA/cm2 or 30 V) with good organic load removal (up to 80%). For an applied current density of 30 mA/cm2, there was a minimum of electric conductivity of 1.9 mS/cm (corresponding to 0.75 g/L of Na2SO4), which minimized the specific energy consumption. PMID:25409580

  14. Impact of gas products around the anode on the performance of a direct carbon fuel cell using a carbon/carbonate slurry

    NASA Astrophysics Data System (ADS)

    Watanabe, Hirotatsu; Umehara, Daisuke; Hanamura, Katsunori

    2016-10-01

    This paper investigates the impact of gas products around the anode on cell performance via an in situ observation. In a direct carbon fuel cell used this study, the anode is inserted into the carbon/carbonate slurry. The current-voltage (I-V) curves are measured before and after a long discharge in the constant current discharge mode. An in situ observation shows that the anode is almost completely covered by gas bubbles when the voltage becomes nearly 0 V in the constant current discharge at 40 mA/cm2; this indicates that gas products such as CO2 prevent the carbon particles and ions from reaching the anode. Meanwhile, the long discharge at 20 mA/cm2 is achieved for 30 min, even though the anode is covered by the CO2 bubbles at 15 min. The I-V curves at 1 min after the termination of the long discharge at 20 mA/cm2 are lower than those prior to the long discharge. The overpotential significantly increases at higher current densities, where mass transport becomes the limiting process. The cell performance is significantly influenced by the gas products around the anode.

  15. Hydrogenotrophic denitrification process efficiency and the number of denitrifying bacteria (MPN) in the sequencing batch biofilm reactor (SBBR) with platinum and carbon anodes.

    PubMed

    Kłodowska, Izabella; Rodziewicz, Joanna; Janczukowicz, Wojciech; Gotkowska-Płachta, Anna; Cydzik-Kwiatkowska, Agnieszka

    2016-01-01

    This work reports on the effect of electric current density and anode material (platinum, carbon) on the concentration of oxidized and mineral forms of nitrogen, on physical parameters (pH, redox potential, electrical conductivity) and the number of denitrifying bacteria in the biofilm (MPN). Experiments were conducted under anaerobic conditions without and with the flow of electric current (with density of 79 mA · m(-2) and 132 mA · m(-2)). Results obtained in the study enabled concluding that increasing density of electric current caused a decreasing concentration of nitrate in the reactor with platinum anode (R1) and carbon anode (R2). Its concentration depended on anode material. The highest hydrogenotrophic denitrification efficiency was achieved in R2 in which the process was aided by inorganic carbon (CO2) that originated from carbon anode oxidation and the electrical conductivity of wastewater increased as a result of the presence of HCO3(-) and CO3(2-) ions. Strong oxidizing properties of the platinum anode (R1) prevented the accumulation of adverse forms of nitrogen, including nitrite and ammonia. The increase in electric current density affected also a lower number of denitrifying bacteria (MPN) in the biofilm in both reactors (R1 and R2). Metal oxides accumulated on the surface of the cathode had a toxic effect upon microorganisms and impaired the production of a hydrogen donor.

  16. Hydrogenotrophic denitrification process efficiency and the number of denitrifying bacteria (MPN) in the sequencing batch biofilm reactor (SBBR) with platinum and carbon anodes.

    PubMed

    Kłodowska, Izabella; Rodziewicz, Joanna; Janczukowicz, Wojciech; Gotkowska-Płachta, Anna; Cydzik-Kwiatkowska, Agnieszka

    2016-01-01

    This work reports on the effect of electric current density and anode material (platinum, carbon) on the concentration of oxidized and mineral forms of nitrogen, on physical parameters (pH, redox potential, electrical conductivity) and the number of denitrifying bacteria in the biofilm (MPN). Experiments were conducted under anaerobic conditions without and with the flow of electric current (with density of 79 mA · m(-2) and 132 mA · m(-2)). Results obtained in the study enabled concluding that increasing density of electric current caused a decreasing concentration of nitrate in the reactor with platinum anode (R1) and carbon anode (R2). Its concentration depended on anode material. The highest hydrogenotrophic denitrification efficiency was achieved in R2 in which the process was aided by inorganic carbon (CO2) that originated from carbon anode oxidation and the electrical conductivity of wastewater increased as a result of the presence of HCO3(-) and CO3(2-) ions. Strong oxidizing properties of the platinum anode (R1) prevented the accumulation of adverse forms of nitrogen, including nitrite and ammonia. The increase in electric current density affected also a lower number of denitrifying bacteria (MPN) in the biofilm in both reactors (R1 and R2). Metal oxides accumulated on the surface of the cathode had a toxic effect upon microorganisms and impaired the production of a hydrogen donor. PMID:26809836

  17. Fundamental Investigation of Si Anode in Li-Ion Cells

    NASA Technical Reports Server (NTRS)

    Wu, James J.; Bennett, William R.

    2012-01-01

    Silicon is a promising and attractive anode material to replace graphite for high capacity lithium ion cells since its theoretical capacity is approximately 10 times of graphite and it is an abundant element on earth. However, there are challenges associated with using silicon as Li-ion anode due to the significant first cycle irreversible capacity loss and subsequent rapid capacity fade during cycling. In this paper, cyclic voltammetry and electrochemical impedance spectroscopy are used to build a fundamental understanding of silicon anodes. The results show that it is difficult to form the SEI film on the surface of Si anode during the first cycle, the lithium ion insertion and de-insertion kinetics for Si are sluggish, and the cell internal resistance changes with the state of lithiation after electrochemical cycling. These results are compared with those for extensively studied graphite anodes. The understanding gained from this study will help to design better Si anodes.

  18. Materials characterization of cermet anodes tested in a pilot cell

    SciTech Connect

    Windisch, C.F. Jr.; Strachan, D.M.; Henager, C.H. Jr.; Alcorn, T.R.; Tabereaux, A.T.; Richards, N.E.

    1993-02-01

    Cermet anodes were evaluated as nonconsumable substitutes for carbon anodes using a pilot-scale reduction cell at the Reynolds Manufacturing Technology Laboratory. After pilot cell testing, tile anodes were subjected to extensive materials characterization and physical properties measurements at the Pacific Northwest Laboratory. Significant changes in the composition of the cermet anodes were observed including the growth of a reaction layer and penetration of electrolyte deep into the cermet matrix. Fracture strength and toughness were measured as a function of temperature and the ductile-brittle transition wasreduced by 500C following pilot cell testing. These results imply difficulties with anode material and control of operating conditions in the pilot cell, and suggest that additional development work be performed before the cermet anodes are used in commercial reduction cells. The results also highlight specific fabrication and operational considerations that should be addressed in future testing.

  19. Electrostatic spray deposition of porous SnO₂/graphene anode films and their enhanced lithium-storage properties.

    PubMed

    Jiang, Yinzhu; Yuan, Tianzhi; Sun, Wenping; Yan, Mi

    2012-11-01

    Porous SnO₂/graphene composite thin films are prepared as anodes for lithium ion batteries by the electrostatic spray deposition technique. Reticular-structured SnO₂ is formed on both the nickel foam substrate and the surface of graphene sheets according to the scanning electron microscopy (SEM) results. Such an assembly mode of graphene and SnO₂ is highly beneficial to the electrochemical performance improvement by increasing the electrical conductivity and releasing the volume change of the anode. The novel engineered anode possesses 2134.3 mA h g⁻¹ of initial discharge capacity and good capacity retention of 551.0 mA h g⁻¹ up to the 100th cycle at a current density of 200 mA g⁻¹. This anode also exhibits excellent rate capability, with a reversible capacity of 507.7 mA h g⁻¹ after 100 cycles at a current density of 800 mA g⁻¹. The results demonstrate that such a film-type hybrid anode shows great potential for application in high-energy lithium-ion batteries. PMID:23106602

  20. Enhanced lithium ion battery cycling of silicon nanowire anodes by template growth to eliminate silicon underlayer islands.

    PubMed

    Cho, Jeong-Hyun; Picraux, S Tom

    2013-01-01

    It is well-known that one-dimensional nanostructures reduce pulverization of silicon (Si)-based anode materials during Li ion cycling because they allow lateral relaxation. However, even with improved designs, Si nanowire-based structures still exhibit limited cycling stability for extended numbers of cycles, with the specific capacity retention with cycling not showing significant improvements over commercial carbon-based anode materials. We have found that one important reason for the lack of long cycling stability can be the presence of milli- and microscale Si islands which typically form under nanowire arrays during their growth. Stress buildup in these Si island underlayers with cycling results in cracking, and the loss of specific capacity for Si nanowire anodes, due to progressive loss of contact with current collectors. We show that the formation of these parasitic Si islands for Si nanowires grown directly on metal current collectors can be avoided by growth through anodized aluminum oxide templates containing a high density of sub-100 nm nanopores. Using this template approach we demonstrate significantly enhanced cycling stability for Si nanowire-based lithium-ion battery anodes, with retentions of more than ~1000 mA·h/g discharge capacity over 1100 cycles.