Science.gov

Sample records for potentiostats

  1. Instrumentation for potentiostatic corrosion studies with distilled water

    NASA Technical Reports Server (NTRS)

    Loess, R. E.; Youngdahl, C. A.

    1969-01-01

    Corrosion is studied potentiostatically in the corroding environment of distilled water with an instrument that measures the potential of the corroding specimen immediately after interruption of the polarizing current. No current is flowing. The process permits compensation for IR drops when potentiostatic control is used in high resistance systems.

  2. Wireless multichannel integrated potentiostat for distributed neurotransmitter sensing.

    PubMed

    Murari, Kartikeya; Sauer, Christian; Stanacevic, Milutin; Cauwenberghs, Gert; Thakor, Nitish

    2005-01-01

    Sensing neurotransmitters is critical in studying neural pathways and neurological disorders. An integrated device is presented which incorporates a potentiostat and a power harvesting and telemetry module. The potentiostat features 16 channels with multiple scales from microamperes to picoamperes. The wireless module is able to harvest power through inductively coupled coils and uses the same link to transmit data to and from the potentiostat. An integrated prototype is fabricated in CMOS technology, and experimentally characterized. Test results show RF powering introduces noise levels of 0.42% and 0.18% on potentiostat current scales of 500pA and 4nA respectively. Real-time multi-channel acquisition of dopamine concentration in vitro is performed with carbon fiber sensors. PMID:17281973

  3. A wireless potentiostat for mobile chemical sensing and biosensing.

    PubMed

    Steinberg, Matthew D; Kassal, Petar; Kereković, Irena; Steinberg, Ivana Murković

    2015-10-01

    Wireless chemical sensors are used as analytical devices in homeland defence, home-based healthcare, food logistics and more generally for the Sensor Internet of Things (SIoT). Presented here is a battery-powered and highly portable credit-card size potentiostat that is suitable for performing mobile and wearable amperometric electrochemical measurements with seamless wireless data transfer to mobile computing devices. The mobile electrochemical analytical system has been evaluated in the laboratory with a model redox system - the reduction of hexacyanoferrate(III) - and also with commercially available enzymatic blood-glucose test-strips. The potentiostat communicates wirelessly with mobile devices such as tablets or Smartphones by near-field communication (NFC) or with personal computers by radio-frequency identification (RFID), and thus provides a solution to the 'missing link' in connectivity that often exists between low-cost mobile and wearable chemical sensors and ubiquitous mobile computing products. The mobile potentiostat has been evaluated in the laboratory with a set of proof-of-concept experiments, and its analytical performance compared with a commercial laboratory potentiostat (R(2)=0.9999). These first experimental results demonstrate the functionality of the wireless potentiostat and suggest that the device could be suitable for wearable and point-of-sample analytical measurements. We conclude that the wireless potentiostat could contribute significantly to the advancement of mobile chemical sensor research and adoption, in particular for wearable sensors in healthcare and sport physiology, for wound monitoring and in mobile point-of-sample diagnostics as well as more generally as a part of the Sensor Internet of Things. PMID:26078146

  4. Development of a low cost potentiostat using ATXMEGA32

    NASA Astrophysics Data System (ADS)

    Muid, Abdul; Djamal, Mitra; Wirawan, Rahadi

    2014-03-01

    Potentiostat is principal devices in modern electrochemical research especially in the investigation of mechanism reaction which associated with the redox chemistry reaction and other chemical phenomena. Several applications measurement is developed based on this tool such as measurement of sample concentrations, quality test of food and medicine, environmental monitoring and biosensors or development of a protein sensor. We have developed a low cost, simple and portable potentiostat with a relatively small dimension. TLC2264 op-amp and ATMEGA32 microcontroller is used to build controller circuit system. Range potential measurement of this tool is between -1600mV and +1600mV within frequency range 1Hz - 1 kHz. The developed instrument has been tested for measuring samples using different voltammetry techniques, like cyclic, square wave, and linear sweep with relative error under 2.5%.

  5. Localized corrosion of container materials under potentiodynamic and potentiostatic controls

    SciTech Connect

    Roy, A.K.; Fleming, D.L.; Gordon, S.R.

    1996-05-01

    Potentiodynamic and potentiostatic polarization experiments were performed on ten candidate waste package container materials to evaluate their pitting tendency at ambient and elevated temperatures in aqueous environments relevant to the potential underground nuclear waste repository. Results indicate that of all the materials tested, Alloys G-30, C-4 and C-22, and Ti Gr-12 exhibited the maximum corrosion resistance, showing no pitting or observable dissolution in any environment tested. These experimental results will be used in identifying a group of potential container materials having the desired corrosion resistance.

  6. Metastable pitting of carbon steel under potentiostatic control

    SciTech Connect

    Cheng, Y.F.; Luo, J.L.

    1999-03-01

    The metastable pitting of A516-70 carbon steel was studied under potentiostatic control in solutions containing chloride ions. It was shown that there were different current fluctuation patterns and spectral slopes, that is, roll-off slopes, in passivity, general corrosion, and metastable pitting. Pits were often covered by a deposit which played an important role in the current fluctuation, with a quick current rise followed by a slow drop. There was a transitional potential (about 0 mV vs Ag/AgCl electrode) below which the metastable pitting initiation rate increased with the potential, because more sites would be activated. Above the transitional potential, the decay of the pitting occurrence rate with increased potential was due to the elimination of available pit sites. When the applied potential was between {minus}50 and 100 mV, pit growth kinetics was controlled by the potential drop through the deposit over the pit mouth. The potential dependence of repassivation time was mainly due to the effect of applied potential on the deposit over the pit mouth. There seemed to be good agreement between the calculated pit size and the measured values by optical microphotography. The assumption of hemispherical pit geometry was reasonable in calculating the pit radii.

  7. A Glucose Biosensor Using CMOS Potentiostat and Vertically Aligned Carbon Nanofibers.

    PubMed

    Al Mamun, Khandaker A; Islam, Syed K; Hensley, Dale K; McFarlane, Nicole

    2016-08-01

    This paper reports a linear, low power, and compact CMOS based potentiostat for vertically aligned carbon nanofibers (VACNF) based amperometric glucose sensors. The CMOS based potentiostat consists of a single-ended potential control unit, a low noise common gate difference-differential pair transimpedance amplifier and a low power VCO. The potentiostat current measuring unit can detect electrochemical current ranging from 500 nA to 7 [Formula: see text] from the VACNF working electrodes with high degree of linearity. This current corresponds to a range of glucose, which depends on the fiber forest density. The potentiostat consumes 71.7 [Formula: see text] of power from a 1.8 V supply and occupies 0.017 [Formula: see text] of chip area realized in a 0.18 [Formula: see text] standard CMOS process. PMID:27337723

  8. A comparison between potentiostatic circuits with grounded work or auxiliary electrode

    NASA Astrophysics Data System (ADS)

    Busoni, L.; Carlà, M.; Lanzi, L.

    2002-04-01

    Potentiostatic circuit configurations with work electrodes and auxiliary electrodes at ground potential have been reviewed and compared. Though the former is by far the best known and most used, the latter was more convenient and accurate in interfacial capacity measurements.

  9. DStat: A Versatile, Open-Source Potentiostat for Electroanalysis and Integration

    PubMed Central

    Dryden, Michael D. M.; Wheeler, Aaron R.

    2015-01-01

    Most electroanalytical techniques require the precise control of the potentials in an electrochemical cell using a potentiostat. Commercial potentiostats function as “black boxes,” giving limited information about their circuitry and behaviour which can make development of new measurement techniques and integration with other instruments challenging. Recently, a number of lab-built potentiostats have emerged with various design goals including low manufacturing cost and field-portability, but notably lacking is an accessible potentiostat designed for general lab use, focusing on measurement quality combined with ease of use and versatility. To fill this gap, we introduce DStat (http://microfluidics.utoronto.ca/dstat), an open-source, general-purpose potentiostat for use alone or integrated with other instruments. DStat offers picoampere current measurement capabilities, a compact USB-powered design, and user-friendly cross-platform software. DStat is easy and inexpensive to build, may be modified freely, and achieves good performance at low current levels not accessible to other lab-built instruments. In head-to-head tests, DStat’s voltammetric measurements are much more sensitive than those of “CheapStat” (a popular open-source potentiostat described previously), and are comparable to those of a compact commercial “black box” potentiostat. Likewise, in head-to-head tests, DStat’s potentiometric precision is similar to that of a commercial pH meter. Most importantly, the versatility of DStat was demonstrated through integration with the open-source DropBot digital microfluidics platform. In sum, we propose that DStat is a valuable contribution to the “open source” movement in analytical science, which is allowing users to adapt their tools to their experiments rather than alter their experiments to be compatible with their tools. PMID:26510100

  10. DStat: A Versatile, Open-Source Potentiostat for Electroanalysis and Integration.

    PubMed

    Dryden, Michael D M; Wheeler, Aaron R

    2015-01-01

    Most electroanalytical techniques require the precise control of the potentials in an electrochemical cell using a potentiostat. Commercial potentiostats function as "black boxes," giving limited information about their circuitry and behaviour which can make development of new measurement techniques and integration with other instruments challenging. Recently, a number of lab-built potentiostats have emerged with various design goals including low manufacturing cost and field-portability, but notably lacking is an accessible potentiostat designed for general lab use, focusing on measurement quality combined with ease of use and versatility. To fill this gap, we introduce DStat (http://microfluidics.utoronto.ca/dstat), an open-source, general-purpose potentiostat for use alone or integrated with other instruments. DStat offers picoampere current measurement capabilities, a compact USB-powered design, and user-friendly cross-platform software. DStat is easy and inexpensive to build, may be modified freely, and achieves good performance at low current levels not accessible to other lab-built instruments. In head-to-head tests, DStat's voltammetric measurements are much more sensitive than those of "CheapStat" (a popular open-source potentiostat described previously), and are comparable to those of a compact commercial "black box" potentiostat. Likewise, in head-to-head tests, DStat's potentiometric precision is similar to that of a commercial pH meter. Most importantly, the versatility of DStat was demonstrated through integration with the open-source DropBot digital microfluidics platform. In sum, we propose that DStat is a valuable contribution to the "open source" movement in analytical science, which is allowing users to adapt their tools to their experiments rather than alter their experiments to be compatible with their tools. PMID:26510100

  11. Potentiostatic and ac impedance studies of the hydrogen electrodes used in Ni/H2 batteries

    NASA Technical Reports Server (NTRS)

    Le Helloco, Jean-Guy; Bojkov, Hristo; Parthasarathy, Arvind; Srinivasan, Supramaniam; Appleby, A. J.

    1992-01-01

    In a study of electrode activity for hydrogen evolution and hydrogen ionization, knowledge of the detailed kinetics and of the surface coverage by adsorbed hydrogen is essential. In the Ni/H2 battery, the hydrogen electrode is subjected to high hydrogen pressure; elucidation of the variation of kinetic parameters with hydrogen pressure is therefore of interest. Potentiostatic and ac impedance spectroscopic techniques were used in the present study. The equivalent circuit of the reaction, the kinetic parameters, and their pressure dependence have been determined.

  12. A cost-effective and field-ready potentiostat that poises subsurface electrodes to monitor bacterial respiration.

    PubMed

    Friedman, Elliot S; Rosenbaum, Miriam A; Lee, Alexander W; Lipson, David A; Land, Bruce R; Angenent, Largus T

    2012-02-15

    Here, we present the proof-of-concept for a subsurface bioelectrochemical system (BES)-based biosensor capable of monitoring microbial respiration that occurs through exocellular electron transfer. This system includes our open-source design of a three-channel microcontroller-unit (MCU)-based potentiostat that is capable of chronoamperometry, which laboratory tests showed to be accurate within 0.95 ± 0.58% (95% Confidence Limit) of a commercial potentiostat. The potentiostat design is freely available online: http://angenent.bee.cornell.edu/potentiostat.html. This robust and field-ready potentiostat, which can withstand temperatures of -30°C, can be manufactured at relatively low cost ($600), thus, allowing for en-masse deployment at field sites. The MCU-based potentiostat was integrated with electrodes and a solar panel-based power system, and deployed as a biosensor to monitor microbial respiration in drained thaw lake basins outside Barrow, AK. At three different depths, the working electrode of a microbial three-electrode system (M3C) was maintained at potentials corresponding to the microbial reduction of iron(III) compounds and humic acids. Thereby, the working electrode mimics these compounds and is used by certain microbes as an electron acceptor. The sensors revealed daily cycles in microbial respiration. In the medium- and deep-depth electrodes the onset of these cycles followed a considerable increase in overall activity that corresponded to those soils reaching temperatures conducive to microbial activity as the summer thaw progressed. The BES biosensor is a valuable tool for studying microbial activity in situ in remote environments, and the cost-efficient design of the potentiostat allows for wide-scale use in remote areas. PMID:22209069

  13. A compact hybrid-multiplexed potentiostat for real-time electrochemical biosensing applications.

    PubMed

    Ramfos, Ioannis; Vassiliadis, Nikolaos; Blionas, Spyridon; Efstathiou, Konstantinos; Fragoso, Alex; O'Sullivan, Ciara K; Birbas, Alexios

    2013-09-15

    The architecture and design of a compact, multichannel, hybrid-multiplexed potentiostat for performing electrochemical measurements on continuously-biased electrode arrays is presented. The proposed architecture utilises a combination of sequential and parallel measurements, to enable high performance whilst keeping the system low-cost and compact. The accuracy of the signal readout is maintained by following a special multiplexing approach, which ensures the continuous biasing of all the working electrodes of an array. After sampling the results, a digital calibration technique factors out errors from component inaccuracies. A prototype printed circuit board (PCB) was designed and built using off-the-shelf components for the real-time measurement of the amperometric signal of 48 electrodes. The operation and performance of the PCB was evaluated and characterised through a wide range of testing conditions, where it exhibited high linearity (R(2)>0.999) and a resolution of 400pA. The effectiveness of the proposed multiplexing scheme is demonstrated through electrochemical tests using KCl and [Fe(CN)6](3-) in KCl solutions. The applicability of the prototype multichannel potentiostat is also demonstrated using real biosensors, which were applied to the detection of IgA antibodies. PMID:23624017

  14. In-channel amperometric detection for microchip electrophoresis using a wireless isolated potentiostat

    PubMed Central

    Gunasekara, Dulan B.; Hulvey, Matthew K.; Lunte, Susan M.

    2012-01-01

    The combination of microchip electrophoresis (ME) with amperometric detection leads to a number of analytical challenges that are associated with isolating the detector from the high voltages used for the separation. While methods such as end-channel alignment and the use of decouplers have been employed, they have limitations. A less common method has been to utilize an electrically isolated potentiostat. This approach allows placement of the working electrode directly in the separation channel without using a decoupler. This paper explores the use of microchip electrophoresis and electrochemical detection (ME-EC) with an electrically isolated potentiostat for the separation and in-channel detection of several biologically important anions. The separation employed negative polarity voltages and tetradecyltrimethylammonium bromide (TTAB, as a buffer modifier) for the separation of nitrite (NO2-), glutathione (GSH), ascorbic acid (AA), and tyrosine (Tyr). A half-wave potential (E½) shift of approximately negative 500 mV was observed for NO2- and H2O2 standards in the in-channel configuration compared to end channel. Higher separation efficiencies were observed for both NO2- and H2O2 with the in-channel detection configuration. The limits of detection were approximately two-fold lower and the sensitivity was approximately two-fold higher for in-channel detection of nitrite when compared to end-channel. The application of this microfluidic device for the separation and detection of biomarkers related to oxidative stress is described. PMID:21437918

  15. Distinguishing between chi and sigma phases in duplex stainless steels using potentiostatic etching

    SciTech Connect

    Jackson, E.M.L.E.M.; Visser, P.E. de . Physical Metallurgy Div.); Cornish, L.A. )

    1993-12-01

    A color interference film etching technique based on the principle of potentiostatic etching has been developed to distinguish, by optical metallography, between Cr-rich sigma and Mo-rich chi phases as well as with simultaneous identification of the ferrite and austenite phases in duplex stainless steels. The optical metallography results are confirmed by semiquantitative energy dispersive spectrometry analysis and back-scattered electron imaging. The technique is relatively simple and rapid, and makes use of low voltages and a hot etchant. Results have shown distinctively the sigma, chi, ferrite, and austenite phases, and enable observation of the microstructural development, morphology, and kinetics of formation of the phases in duplex alloys. The method, by giving excellent color contrast between sigma and chi, also facilitates quantitative image analysis of the sigma and chi volume fractions.

  16. VLSI Potentiostat Array With Oversampling Gain Modulation for Wide-Range Neurotransmitter Sensing.

    PubMed

    Stanacevic, M; Murari, K; Rege, A; Cauwenberghs, G; Thakor, N V

    2007-03-01

    A 16-channel current-measuring very large-scale integration (VLSI) sensor array system for highly sensitive electrochemical detection of electroactive neurotransmiters like dopamine and nitric-oxide is presented. Each channel embeds a current integrating potentiostat within a switched-capacitor first-order single-bit delta-sigma modulator implementing an incremental analog-to-digital converter. The duty-cycle modulation of current feedback in the delta-sigma loop together with variable oversampling ratio provide a programmable digital range selection of the input current spanning over six orders of magnitude from picoamperes to microamperes. The array offers 100-fA input current sensitivity at 3.4-muW power consumption per channel. The operation of the 3 mm times3 mm chip fabricated in 0.5-mum CMOS technology is demonstrated with real-time multichannel acquisition of neurotransmitter concentration. PMID:23851522

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

    NASA Astrophysics Data System (ADS)

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

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

  18. CheapStat: An Open-Source, “Do-It-Yourself” Potentiostat for Analytical and Educational Applications

    PubMed Central

    Rowe, Aaron A.; Bonham, Andrew J.; White, Ryan J.; Zimmer, Michael P.; Yadgar, Ramsin J.; Hobza, Tony M.; Honea, Jim W.; Ben-Yaacov, Ilan; Plaxco, Kevin W.

    2011-01-01

    Although potentiostats are the foundation of modern electrochemical research, they have seen relatively little application in resource poor settings, such as undergraduate laboratory courses and the developing world. One reason for the low penetration of potentiostats is their cost, as even the least expensive commercially available laboratory potentiostats sell for more than one thousand dollars. An inexpensive electrochemical workstation could thus prove useful in educational labs, and increase access to electrochemistry-based analytical techniques for food, drug and environmental monitoring. With these motivations in mind, we describe here the CheapStat, an inexpensive (<$80), open-source (software and hardware), hand-held potentiostat that can be constructed by anyone who is proficient at assembling circuits. This device supports a number of potential waveforms necessary to perform cyclic, square wave, linear sweep and anodic stripping voltammetry. As we demonstrate, it is suitable for a wide range of applications ranging from food- and drug-quality testing to environmental monitoring, rapid DNA detection, and educational exercises. The device's schematics, parts lists, circuit board layout files, sample experiments, and detailed assembly instructions are available in the supporting information and are released under an open hardware license. PMID:21931613

  19. Fabrication of triazinedithiol functional polymeric nanofilm by potentiostatic polymerization on aluminum surface

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Wang, Yabin; Li, Yanni; Wang, Qian

    2011-01-01

    The functional polymeric nanofilm of 6-(N-allyl-1,1,2,2-tetrahydroperfluorodecyl)amino-1,3,5-triazine-2,4-dithiol monosodium (AF17N) was prepared on pure aluminum surface by potentiostatic polymerization at different potentials. The thickness and weight of polymeric nanofilm increased proportionally to electro-polymerization potential following linear equation. The chemical structure of nanofilm was characterized by Fourier transform-infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Adsorption peaks in FT-IR and C1s, N1s, S2p, F1s and Al2p peaks in XPS spectra indicated that the polymeric nanofilm was poly(6-(N-allyl-1,1,2,2-tetrahydroperfluorodecyl)amino-1,3,5-triazine-2,4-disulfide) (PAF17). The morphologies of polymeric nanofilm were also observed by atomic force microscopy (AFM). All the results showed that the optimal electro-polymerization potential and time were 8 V and 20 s, respectively. Uniform and compact nanofilm of PAF17 could be obtained under these conditions. It is expected that this technique will be applied in the preparation of lubricating, dielectric and hydrophobic surface on aluminum substrate.

  20. Identification of the states of the processes at liquid cathodes under potentiostatic conditions using semantic diagram models

    NASA Astrophysics Data System (ADS)

    Smirnov, G. B.; Markina, S. E.; Tomashevich, V. G.

    2012-08-01

    A technique is described for constructing semantic diagram models of the electrolysis at a liquid cathode in a salt halide melt under potentiostatic conditions that are intended for identifying the static states of this system that correspond to certain combinations of the electrode processes or the processes occurring in the volumes of salt and liquid-metal phases. Examples are given for the discharge of univalent and polyvalent metals.

  1. Reprint of: Use of a mobile phone for potentiostatic control with low cost paper-based microfluidic sensors.

    PubMed

    Delaney, Jacqui L; Doeven, Egan H; Harsant, Anthony J; Hogan, Conor F

    2013-11-25

    By exploiting its ability to play sounds, a mobile phone with suitable software installed can serve the basic functions of a potentiostat in controlling an applied potential to oxidise ECL-active molecules, while the resultant photonic signal is monitored using the camera in video mode. In combination with paper microfluidic sensors this opens significant new possibilities for low-cost, instrument-free sensing. PMID:24216205

  2. Potentiostatic control of ionic liquid surface film formation on ZE41 magnesium alloy.

    PubMed

    Efthimiadis, Jim; Neil, Wayne C; Bunter, Andrew; Howlett, Patrick C; Hinton, Bruce R W; MacFarlane, Douglas R; Forsyth, Maria

    2010-05-01

    The generation of potentially corrosion-resistant films on light metal alloys of magnesium have been investigated. Magnesium alloy, ZE41 [Mg-Zn-Rare Earth (RE)-Zr, nominal composition approximately 4 wt % Zn, approximately 1.7 wt % RE (Ce), approximately 0.6 wt % Zr, remaining balance, Mg], was exposed under potentiostatic control to the ionic liquid trihexyl(tetradecyl)phosphonium diphenylphosphate, denoted [P(6,6,6,14)][DPP]. During exposure to this IL, a bias potential, shifted from open circuit, was applied to the ZE41 surface. Electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) were used to monitor the evolution of film formation on the metal surface during exposure. The EIS data indicate that, of the four bias potentials examined, applying a potential of -200 mV versus OCP during the exposure period resulted in surface films of greatest resistance. Both EIS measurements and scanning electron microscopy (SEM) imaging indicate that these surfaces are substantially different to those formed without potential bias. Time of flight-secondary ion mass spectrometry (ToF-SIMS) elemental mapping of the films was utilized to ascertain the distribution of the ionic liquid cationic and anionic species relative to the microstructural surface features of ZE41 and indicated a more uniform distribution compared with the surface following exposure in the absence of a bias potential. Immersion of the treated ZE41 specimens in a chloride contaminated salt solution clearly indicated that the ionic liquid generated surface films offered significant protection against pitting corrosion, although the intermetallics were still insufficiently protected by the IL and hence favored intergranular corrosion processes. PMID:20433137

  3. Wetting-in studies on alkaline-fuel-cell cathodes using a potentiostatic-galvanostatic experimental design

    SciTech Connect

    Lundblad, A.; Bjoernbom, P. . Dept. of Chemical Engineering and Technology)

    1994-06-01

    The influence of potential and current on electrolyte intrusion during the initiation phase of poly(tetrafluoroethylene)-(PTFE)-bonded carbon cathodes has been studied. A potentiostatic-galvanostatic experimental design was used. This was attained by varying the oxygen concentration using a computerized control circuit. The intrusion depth was determined by an electron microscope element-mapping method, and the amount of intruded electrolyte was determined by weighing. The wetting-in of the electrode was found to depend strongly on potential and less on applied current density. A combination of electrocapillarity and electro-osmosis is proposed as an explanation of the results. The experiments have also revealed interesting phenomena concerning electrolyte and three-dimensional current-density distribution during the initiation phase. From the results, a mechanism for the sudden failure (flooding) of PTFE-bonded carbon cathodes at the end of their service life is suggested.

  4. Identification of the states of the processes that occur on solid cathodes in the potentiostatic electrolysis mode using semantic diagram models

    NASA Astrophysics Data System (ADS)

    Smirnov, G. B.; Markina, S. E.; Tomashevich, V. G.

    2011-02-01

    A procedure is proposed to construct semantic diagram models for the electrolysis on a solid cathode in a salt halide melt under potentiostatic conditions. These models are intended to identify the static states of the system that correspond to a certain combination of the processes occurring on an electrode and in the system volume. Examples for discharging of univalent and polyvalent metals are given.

  5. A potentiostat featuring an integrator transimpedance amplifier for the measurement of very low currents—Proof-of-principle application in microfluidic separations and voltammetry

    NASA Astrophysics Data System (ADS)

    Koutilellis, G. D.; Economou, A.; Efstathiou, C. E.

    2016-03-01

    This work reports the design and construction of a novel potentiostat which features an integrator transimpedance amplifier as a current-monitoring unit. The integration approach addresses the limitations of the feedback resistor approach used for current monitoring in conventional potentiostat designs. In the present design, measurement of the current is performed by a precision switched integrator transimpedance amplifier operated in the dual sampling mode which enables sub-pA resolution. The potentiostat is suitable for measuring very low currents (typical dynamic range: 5 pA-4.7 μA) with a 16 bit resolution, and it can support 2-, 3- and 4-electrode cell configurations. Its operation was assessed by using it as a detection module in a home-made capillary electrophoresis system for the separation and amperometric detection of paracetamol and p-aminophenol at a 3-electrode microfluidic chip. The potential and limitations of the proposed potentiostat to implement fast potential-scan voltammetric techniques were demonstrated for the case of cyclic voltammetry.

  6. Re-passivation Potential of Alloy 22 in Chloride plus Nitrate Solutions using the Potentiodynamic-Galvano-static-Potentiostatic Method

    SciTech Connect

    Evans, Kenneth J.; Rebak, Raul B.

    2007-07-01

    In general, the susceptibility of Alloy 22 to suffer crevice corrosion is measured using the Cyclic Potentiodynamic Polarization (CPP) technique. This is a fast technique that gives rather accurate and reproducible values of re-passivation potential (ER1) in most cases. In the fringes of susceptibility, when the environment is not highly aggressive, the values of re-passivation potential using the CPP technique may not be highly reproducible, especially because the technique is fast. To circumvent this, the re-passivation potential of Alloy 22 was measured using a slower method that combines Potentiodynamic-Galvano-static-Potentiostatic steps (called here the Tsujikawa-Hisamatsu Electrochemical or THE method). The THE method applies the charge to the specimen in a more controlled way, which may give more reproducible re-passivation potential values, especially when the environment is not aggressive. The values of re-passivation potential of Alloy 22 in sodium chloride plus potassium nitrate solutions were measured using the THE and CPP methods. Results show that both methods yield similar values of re-passivation potential, especially under aggressive conditions. (authors)

  7. Comparative electron microscopy (SEM) examination of Fe, Au, and Zn electrode surfaces polarized in different regions of potentiostatic E/I behavior

    SciTech Connect

    Podesta, J.J.; Arvia, A.J.; Piatti, R.C.V.

    1982-12-01

    The surface morphology of some metals (Fe, Au, and Zn) after potentiostatic polarization was studied through SEM examination. The following electrochemical systems were investigated at 25C: (1) Fe/1 M H/sub 2/SO/sub 4/; (2) Au/1 M HCl; and (3) Zn/2 M NaOH. The polarization potentials were chosen in the active dissolution region, in the passivity region, and in the potential range where periodic oscillations of the anode current are observed. The changes in the morphologies of attack on the various metals were related to the film forming species and of anion adsorption.

  8. Comparison of Galvanic Currents Generated Between Different Combinations of Orthodontic Brackets and Archwires Using Potentiostat: An In Vitro Study

    PubMed Central

    Nayak, Rabindra S; Shafiuddin, Bareera; Pasha, Azam; Vinay, K; Narayan, Anjali; Shetty, Smitha V

    2015-01-01

    Background: Technological advances in wire selection and bracket design have led to improved treatment efficiency and allowed longer time intervals between appliance adjustments. The wires remain in the mouth for a longer duration and are subjected to electrochemical reactions, mechanical forces of mastication and generalized wear. These cause different types of corrosion. This study was done to compare the galvanic currents generated between different combinations of brackets and archwires commonly used in orthodontic practices. Materials and Methods: The materials used for the study included different commercially available orthodontic archwires and brackets. The galvanic current generated by individual materials and different combinations of these materials was tested and compared. The orthodontic archwires used were 0.019″ × 0.025″ heat-activated nickel-titanium (3M Unitek), 0.019″ × 0.025″ beta-titanium (3M Unitek) and 0.019″ × 0.025″ stainless steel (3M Unitek). The orthodontic brackets used were 0.022″ MBT laser-cut (Victory Series, 3M Unitek) and metal-injection molded (Leone Company) maxillary central incisor brackets respectively. The ligature wire used for ligation was 0.009″ stainless steel ligature (HP Company). The galvanic current for individual archwires, brackets, and the different bracket-archwire-ligature combinations was measured by using a Potentiostat machine. The data were generated using the Linear Sweep Voltammetry and OriginPro 8.5 Graphing and Data Analysis Softwares. The study was conducted in two phases. Phase I comprised of five groups for open circuit potential (OCP) and galvanic current (I), whereas Phase II comprised of six groups for galvanic current alone. Results: Mean, standard deviation and range were computed for the OCP and galvanic current (I) values obtained. Results were subjected to statistical analysis through ANOVA. In Phase I, higher mean OCP was recorded in stainless steel archwire, followed by beta

  9. Evaluation of in-channel amperometric detection using a dual-channel microchip electrophoresis device and a two-electrode potentiostat for reverse polarity separations

    PubMed Central

    Meneses, Diogenes; Gunasekara, Dulan B.; Pichetsurnthorn, Pann; da Silva, José A. F.; de Abreu, Fabiane C.; Lunte, Susan M.

    2015-01-01

    In-channel amperometric detection combined with dual-channel microchip electrophoresis is evaluated using a two-electrode isolated potentiostat for reverse polarity separations. The device consists of two separate channels with the working and reference electrodes placed at identical positions relative to the end of the channel, enabling noise subtraction. In previous reports of this configuration, normal polarity and a three-electrode detection system were used. In the two-electrode detection system described here, the electrode in the reference channel acts as both the counter and reference. The effect of electrode placement in the channels on noise and detector response was investigated using nitrite, tyrosine, and hydrogen peroxide as model compounds. The effects of electrode material and size and type of reference electrode on noise and the potential shift of hydrodynamic voltammograms for the model compounds were determined. In addition, the performance of two- and three-electrode configurations using Pt and Ag/AgCl reference electrodes was compared. Although the signal was attenuated with the Pt reference, the noise was also significantly reduced. It was found that lower LOD were obtained for all three compounds with the dual-channel configuration compared to single-channel, in-channel detection. The dual-channel method was then used for the detection of nitrite in a dermal microdialysis sample obtained from a sheep following nitroglycerin administration. PMID:25256669

  10. Investigation of the growth and local stoichiometric point group symmetry of titania nanotubes during potentiostatic anodization of titanium in phosphate electrolytes

    NASA Astrophysics Data System (ADS)

    Cummings, F. R.; Muller, T. F. G.; Malgas, G. F.; Arendse, C. J.

    2015-10-01

    Potentiostatic anodization of commercially pure, 50 μm-thick titanium (Ti) foil was performed in aqueous, phosphate electrolytes at increasing experimental timeframes at a fixed applied potential for the synthesis of titania nanotube arrays (TNAs). High resolution scanning electron microscopy images, combined with energy dispersive spectroscopy and x-ray diffraction spectra reveal that anodization of the Ti foil in a 1 M NaF+0.5 M H3PO4 electrolyte for 4 h yields a titanate surface with pore diameters ranging between 100 and 500 nm. The presence of rods on the Ti foil surface with lengths exceeding 20 μm and containing high concentrations of phosphor on the exterior was also detected at these conditions, along with micro-sized coral reef-like titanate balls. We propose that the formation of these structures play a major role during the anodization process and impedes nanotube growth during the anodization process. High spatially resolved scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) performed along the length of a single anodized TiO2 nanotube reveals a gradual evolution of the nanotube crystallinity, from a rutile-rich bottom to a predominantly anatase TiO2 structure along its length.

  11. An investigation into factors affecting the stability of carbons and carbon supported platinum and platinum/cobalt alloy catalysts during 1.2 V potentiostatic hold regimes at a range of temperatures

    NASA Astrophysics Data System (ADS)

    Ball, S. C.; Hudson, S. L.; Thompsett, D.; Theobald, B.

    To meet automotive targets for fuel cell operation and allow higher temperature operation an understanding of the factors affecting carbon and platinum stability is critical. The stability of both carbons and carbon supported platinum and platinum/cobalt alloy catalysts was studied during 1.2 V versus RHE potentiostatic hold tests using carbon and catalyst coated electrodes in a three-chamber wet electrolyte cell at a range of temperatures. At 80 °C the wt% of carbon corroded increases with increasing BET area. Surface oxidation was followed electrochemically using the quinone/hydroquinone redox couple. Increasing temperature, time at 1.2 V and wt% platinum on the carbon increases surface oxidation. Although increasing temperature was shown to increase the extent of carbon corrosion, catalysing the carbon did not significantly change how much carbon was corroded. Platinum stability was investigated by electrochemical metal area loss (ECA). Platinum catalysts on commercial carbons lost more ECA with increasing temperature. A platinum/cobalt alloy on a low surface area carbon was demonstrated to be more stable to both carbon corrosion and metal area loss at temperatures up to 80 °C than platinum catalysts on commercial carbons, making this material an excellent candidate for higher temperature automotive operation.

  12. Communication: Coordination structure of bromide ions associated with hexyltrimethylammonium cations at liquid/liquid interfaces under potentiostatic control as studied by total-reflection X-ray absorption fine structure

    NASA Astrophysics Data System (ADS)

    Nagatani, Hirohisa; Harada, Makoto; Tanida, Hajime; Sakae, Hiroki; Imura, Hisanori

    2014-03-01

    Total-reflection X-ray absorption fine structure (TR-XAFS) technique was applied for the first time to an interface between two immiscible electrolyte solutions under potentiostatic control. The hydration structure of bromide ions was investigated at polarized 2-octanone/water interfaces. TR-XAFS spectra at Br K-edge measured in the presence of hexyltrimethylammonium bromide (C6TAB) were slightly modified depending on the Galvani potential difference ({Δ }_o^w φ). The extended X-ray absorption fine structure analysis exposed hydration structure changes of bromide ions at the polarized interface. The coordination structure of bromide ions at the interface could be analyzed as compared with bromide ions dissolved in aqueous solution and Br--exchanged resin having quaternary ammonium groups. The results indicated that bromide ions were associated with C6TA+ at the polarized interface. The relative contribution of ion association form of bromide ions with quaternary ammonium groups was enhanced at a potential close to the ion transfer of C6TA+, where the interfacial concentration of C6TA+ is increased as a function of {Δ }_o^w φ.

  13. Conversion of an Agilent Chip Cube System and Adaptation of a ROXY EC Potentiostat for the Analysis of Proteolytic and Non-Proteolytic Protein Samples on a Thermo Finnigan LTQ-FT Ultra Mass Spectrometer.

    PubMed Central

    Crot, C.; Helseth, L.; Xu, H.; Davis, R.; Schilling, A.

    2010-01-01

    RP-48 High resolution, high mass accuracy analysis of peptide digests and proteins using hybrid instruments such as the Thermo Finnigan LTQ-FT Ultra instrument allow for faster unambiguous computer identification of proteins from peptide digests, accurate measurement of intact protein MW and detection of post translational modifications by top down methods and the use of auxiliary dissociation methods such as ECD to study disulfide bonds and crosslinked peptides as well as post-translational modifications such as phosphorylation. User demand for these instruments remains high in shared facilities like ours and efforts are always being made to improve sample throughput to increase instrument availability. Several vendors have released microfluidic based integrated chromatographic systems in the last few years that allow for relatively easy use in nanospray mode along with reductions in delay volumes and significant improvement in sample throughput and sensitivity. The current work reports on the successful integration of one such system, the Agilent Chip Cube system, originally designed to work only on MS instruments from that manufacturer, so that it will function routinely on the LTQ-FT Ultra MS. Using the chip cube's nanocolumn cartridge “chips”, our facility has been able to significantly shorten runtimes for digest based analyses of simple and complex fractionated samples while obtaining excellent peptide detection using smaller sample injection volumes. Details of the adaptation will be provided and examples will be shown using data from both CID and ECD based proteolytic workflows. In addition, we will present data generated using an online electrochemical potentiostat, the ROXY EC system, along with the chip cube on the LTQ FT Ultra allowing the detection of electrochemically generated peptide fragments from intact proteins as an adjunct/replacement for proteolysis in specific analytical problems where the use of nano-LC/MS/MS proteolytic analysis is

  14. Potentiostatic deposition of DNA for scanning probe microscopy.

    PubMed Central

    Lindsay, S M; Tao, N J; DeRose, J A; Oden, P I; Lyubchenko YuL; Harrington, R E; Shlyakhtenko, L

    1992-01-01

    We describe a procedure for reversible adsorption of DNA onto a gold electrode maintained under potential control. The adsorbate can be imaged by scanning probe microscopy in situ. Quantitative control of a molecular adsorbate for microscopy is now possible. We found a potential window (between 0 and 180 mV versus a silver wire quasi reference) over which a gold (111) surface under phosphate buffer is positively charged, but is not covered with a dense adsorbate. When DNA is present in these conditions, molecules adsorb onto the electrode and remain stable under repeated scanning with a scanning tunneling microscope (STM). They become removed when the surface is brought to a negative charge. When operated at tunnel currents below approximately 0.4 nA, the STM yields a resolution of approximately 1 nm, which is better than can be obtained with atomic force microscopy (AFM) at present. We illustrate this procedure by imaging a series of DNA molecules made by ligating a 21 base-pair oligonucleotide. We observed the expected series of fragment lengths but small fragments are adsorbed preferentially. Images FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 PMID:1617139

  15. Intelligent potentiostat for identification of heavy metals in situ

    NASA Astrophysics Data System (ADS)

    Christidis, K.; Gow, K.; Robertson, P.; Pollard, P.

    2006-01-01

    This article presents a low-cost portable electrochemical instrument capable of on-site identification of heavy metals. The instrument acquires metal-specific voltage and current signals by the application of differential pulse anodic stripping voltammetry. This technique enhances the analytical current and rejects the background current, resulting in a higher signal-to-noise ratio for a better detection limit. The identification of heavy metals is based on an intelligent machine-based method using a multilayer perceptron neural network consisting of three layers of neurons. The neural network is implemented using a 16 bit microcontroller. The system is developed for use in the field in order to avoid expensive and time-consuming procedures and can be used in a variety of situations to help environmental assessment and control.

  16. A potentiostatic study of the corrosion behavior of anodized and nonanodized aluminum alloy.

    PubMed

    White, K C; Svare, C W; Taylor, T D

    1985-06-01

    The clinical implication of this study is that some improvement in the corrosion resistance of denture bases made with aluminum alloy D-214 may be obtained by anodization. However, since this study does not exactly duplicate an oral environment or take into consideration the variation in oral environments, it cannot be assumed that the additional corrosion resistance would be discernible in a particular patient. PMID:3859652

  17. Potentiostatic controlled nucleation and growth modes of electrodeposited cobalt thin films on n-Si(1 1 1)

    NASA Astrophysics Data System (ADS)

    Mechehoud, Fayçal; Khelil, Abdelbacet; Eddine Hakiki, Nour; Bubendorff, Jean-Luc

    2016-08-01

    The nucleation and growth of Co electrodeposits on n-Si(1 1 1) substrate have been investigated as a function of the applied potential in a large potential range using electrochemical techniques (voltammetry and chrono-amperometry) and surface imaging by atomic force microscopy (AFM). The surface preparation of the sample is crucial and we achieve a controlled n-Si(1 1 1) surface with mono-atomic steps and flat terraces. Using Scharifker-Hills models for fitting the current-time transients, we show that a transition from an instantaneous nucleation process to a progressive one occurs when the overpotential increases. A good agreement between the nucleation and growth parameters extracted from the models and the AFM data's is observed. The growth is of the Volmer-Weber type with a roughness and a spatial extension in the substrate plane of the deposited islands that increase with thickness.

  18. Potentiostatic reversible photoelectrochromism: an effect appearing in nanoporous TiO2/Ni(OH)2 thin films.

    PubMed

    Cibrev, Dejan; Jankulovska, Milena; Lana-Villarreal, Teresa; Gómez, Roberto

    2014-07-01

    In the field of energy saving, finding composite materials with the ability of coloring upon both illumination and change of the applied electrode potential keeps on being an important goal. In this context, chemical bath deposition of Ni(OH)2 into nanoporous TiO2 thin films supported on conducting glass leads to electrodes showing both conventional electrochromic behavior (from colorless to dark brown and vice versa) together with photochromism at constant applied potential. The latter phenomenon, reported here for the first time, is characterized by fast and reversible coloration upon UV illumination. The bleaching kinetics shows first order behavior with respect to the Ni(III) centers in the film, and an order 1.2 with respect to electrons in the TiO2 film. From a more applied point of view, this study opens up the possibility of having two-mode smart windows showing not only conventional electrochromism but also reversible darkening upon illumination. PMID:24926989

  19. A potentiostatic study of oxygen transport through poly(2-ethoxyethyl methacrylate-co-2,3-dihydroxypropylmethacrylate) hydrogel membranes.

    PubMed

    Compañ, Vicente; Tiemblo, Pilar; García, F; García, J M; Guzmán, Julio; Riande, Evaristo

    2005-06-01

    The oxygen permeability and diffusion coefficients of hydrogel membranes prepared with copolymers of 2-ethoxyethyl methacrylate (EEMA)/2,3-dihydroxypropylmethacrylate (MAG) with mole fraction of the second monomer in the range between 0 and 0.75 are described. Values of the permeability and diffusion coefficients of oxygen are determined by using electrochemical procedures involving the measurement of the steady-state current in membranes prepared by radical polymerization of the monomers. The results obtained for the transport properties were analyzed taking into account the fractional free volumes, the cohesive energy densities and the glass transition temperatures of the hydrogels. PMID:15626426

  20. Aerated Shewanella oneidensis in Continuously-fed Bioelectrochemical Systems for Power and Hydrogen Production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We studied the effects of aeration of Shewanella oneidensis on potentiostatic current production, iron(III) reduction, hydrogen production in a microbial electrolysis cell, and electric power generation in a microbial fuel cell. The potentiostatic performance of aerated S. oneidensis was considerab...

  1. Electrochemical nitridation of metal surfaces

    SciTech Connect

    Wang, Heli; Turner, John A.

    2015-06-30

    Electrochemical nitridation of metals and the produced metals are disclosed. An exemplary method of electrochemical nitridation of metals comprises providing an electrochemical solution at low temperature. The method also comprises providing a three-electrode potentiostat system. The method also comprises stabilizing the three-electrode potentiostat system at open circuit potential. The method also comprises applying a cathodic potential to a metal.

  2. Electrochemical Microsensors for the Detection of Cadmium(II) and Lead(II) Ions in Plants

    PubMed Central

    Krystofova, Olga; Trnkova, Libuse; Adam, Vojtech; Zehnalek, Josef; Hubalek, Jaromir; Babula, Petr; Kizek, Rene

    2010-01-01

    Routine determination of trace metals in complex media is still a difficult task for many analytical instruments. The aim of this work was to compare three electro-chemical instruments [a standard potentiostat (Autolab), a commercially available miniaturized potentiostat (PalmSens) and a homemade micropotentiostat] for easy-to-use and sensitive determination of cadmium(II) and lead(II) ions. The lowest detection limits (hundreds of pM) for both metals was achieved by using of the standard potentiostat, followed by the miniaturized potentiostat (tens of nM) and the homemade instrument (hundreds of nM). Nevertheless, all potentiostats were sensitive enough to evaluate contamination of the environment, because the environmental limits for both metals are higher than detection limits of the instruments. Further, we tested all used potentiostats and working electrodes on analysis of environmental samples (rainwater, flour and plant extract) with artificially added cadmium(II) and lead(II). Based on the similar results obtained for all potentiostats we choose a homemade instrument with a carbon tip working electrode for our subsequent environmental experiments, in which we analyzed maize and sunflower seedlings and rainwater obtained from various sites in the Czech Republic. PMID:22219663

  3. SWEPT-POTENTIAL ELECTROCHEMICAL DETECTOR FOR FLOW STREAMS

    EPA Science Inventory

    An instrument has been designed, constructed, and evaluated for electrochemical measurements in flow streams. The instrument is basically a computer-controlled potentiostat with features that are necessary for measurements in flow streams. These features include real-time graphic...

  4. Selection of charge methods for lithium ion batteries by considering diffusion induced stress and charge time

    NASA Astrophysics Data System (ADS)

    Lu, Bo; Song, Yicheng; Zhang, Junqian

    2016-07-01

    This article demonstrates the design of charging strategies for lithium ion batteries with considering the balance between diffusion induced stress and total charge time for two- and three-stage charge methods. For the two-stage galvanostatic-potentiostatic charge method the low mechanical stress can be achieved without increasing total charge time by switching the galvanostatic to the potentiostatic at the time moment when the lithium concentration at the surface of particles reaches the limit cbarsurf = 0 . A three-stage method, which consists of an initial galvanostatic stage of high current, a galvanostatic stage of low current and a potentiostatic ending stage, is suggested. Employing the initial galvanostatic stage of high current is helpful not only in accelerating the charge process, but also in controlling the mechanical stress once the electrical current and time duration of the initial galvanostatic stage are properly designed.

  5. Apparatus for use in rapid and accurate controlled-potential coulometric analysis

    DOEpatents

    Frazzini, Thomas L.; Holland, Michael K.; Pietri, Charles E.; Weiss, Jon R.

    1981-01-01

    An apparatus for controlled-potential coulometric analysis of a solution includes a cell to contain the solution to be analyzed and a plurality of electrodes to contact the solution in the cell. Means are provided to stir the solution and to control the atmosphere above it. A potentiostat connected to the electrodes controls potential differences among the electrodes. An electronic circuit connected to the potentiostat provides analog-to-digital conversion and displays a precise count of charge transfer during a desired chemical process. This count provides a measure of the amount of an unknown substance in the solution.

  6. Plasma Arc Melting (PAM) and Corrosion Resistance of Pure NiTi Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Tuissi, A.; Rondelli, G.; Bassani, P.

    2015-03-01

    Plasma arc melting (PAM) as a suitable non-contaminating melting route for manufacturing high-quality NiTi alloy was successfully examined. The corrosion resistance of PAM Nitinol was evaluated by both potentiodynamic and potentiostatic tests and compared with lower purity NiTi produced by vacuum induction melting (VIM). For the electro-polished surfaces, excellent corrosion resistance of NiTi comparable with the Ti alloys was found with no pitting up to 800 mV versus saturated calomel electrode in simulated body fluid at 37 °C. Potentiostatic results of PAM Nitinol indicate slightly better corrosion resistance than the lower quality VIM alloy.

  7. Characterization of electrochemically deposited polypyrrole using magnetoelastic material transduction elements

    NASA Technical Reports Server (NTRS)

    Ersoz, Arzu; Ball, J. Christopher; Grimes, Craig A.; Bachas, Leonidas G.

    2002-01-01

    Magnetoelastic alloy films have been used as a working electrode in an electrochemical cell. This material allows magnetic interrogation of electrochemical deposition. This technique was used to monitor the electrochemical deposition of polypyrrole by multisweep (CV) and potentiostatic methods. Since the determination of the mass-sensitive magnetoelastic film's resonance frequency is based on magnetic transduction, an inherent advantage of this method is that it requires no electrical connections other than the working lead of the potentiostat. Increases in pyrrole deposition correlated with a decrease in the peak resonance frequency of the magnetoelastic alloy. This technique provides a novel approach by which one can monitor electrochemical processes.

  8. Algal biosensor array on a single electrode.

    PubMed

    Tatsuma, Tetsu; Yoshida, Yutaka; Shitanda, Isao; Notsu, Hideo

    2009-02-01

    An algal array was prepared on a single transparent electrode, and photosynthetic activity of each algal channel and its inhibition by a toxin were monitored with a single-channel potentiostat by successive light irradiation with a LED array. PMID:19173040

  9. Efficiencies of Bio-electrocatalytic Production of Hydrogen from Lactate Using Shewanella oneidensis MR-1

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shewanella oneidensis MR-1 was grown in a chemostatic, continuously-fed bioelectrochemical cell under slightly aerated conditions. The start-up phase was controlled potentiostatically (0.4 V vs. SHE). When a stable performance was achieved, the reactor was switched to bio-electrocatalytic producti...

  10. Electrochemical behavior of nano and femtosecond laser textured titanium alloy for implant surface modification.

    PubMed

    Jeong, Yong-Hoon; Kim, Won-Gi; Choe, Han-Cheol

    2011-02-01

    In this study, the electrochemical behavior of nano and femtosecond laser textured titanium alloy for implant surface modification has been researched using the potentiostat equipment. Cp-Ti and Ti-6Al-4V alloy, located on X-Y motorized stage, were irradiated using femtosecond laser. The corrosion properties were examined by a potentiodynamic and AC impedance test. PMID:21456241

  11. Cybernetic Control of an Electrochemical Repertoire.

    ERIC Educational Resources Information Center

    He, Peixin; And Others

    1982-01-01

    Describes major features of a computer-operated, cybernetic potentiostat and the development, design, and operation of the software in ROM. The instrument contains control circuitry and software making it compatible with the static mercury drop electrode produced by EG&G Princeton Applied Research Corporation. Sample results using the instrument…

  12. AN ADVANCED FLUE GAS MONITOR FOR SO2 - PHASE I

    EPA Science Inventory

    The development of an instrument for continuously monitoring SO2 levels in flue gas is proposed. The SO2 will be detected by means of an electrochemical sensor cell, which operates in a three-electrode potentiostatic mode. The proposed innovation is develop-ment of an advan...

  13. Overview of corrosion, corrosion protection, and stress-corrosion cracking of uranium and uranium alloys

    SciTech Connect

    Koger, J.W.

    1981-12-14

    This paper covers some basic definitions and provides some data. The 51 slides illustrates these definitions, crack initiation and propagation, sources of stress, types of specimens used for SCC, potentiostatic polarization, data for Mulberry and U-Nb alloys, effects of environment, and data for U-0.75 Ti and U-Mo alloys. (DLC)

  14. MICROFABRICATED ELECTROCHEMICAL ANALYSIS SYSTEM FOR HEAVY METAL DETECTION. (R825511C047)

    EPA Science Inventory

    A low power, hand-held system has been developed for the measurement of heavy metal ions in aqueous solutions. The system consists of an electrode array sensor, a high performance single chip potentiostat and a microcontroller circuit. The sensor is a microfabricated array of ...

  15. TiO(2) nanotube arrays: intrinsic peroxidase mimetics.

    PubMed

    Zhang, Lingling; Han, Lei; Hu, Peng; Wang, Li; Dong, Shaojun

    2013-11-18

    TiO2 nanotube arrays (NTA), prepared by potentiostatic anodization, were discovered to possess an intrinsic peroxidase-like activity. The colorimetric and electrochemical assays both demonstrated their excellent catalytic activity towards H2O2 reduction. On this basis, a simple and inexpensive electrochemical biosensor for glucose detection was developed. PMID:24084751

  16. Voltammetry at the Thin-Film Mercury Electrode (TFME).

    ERIC Educational Resources Information Center

    Pomeroy, R. S.; And Others

    1989-01-01

    Reviewed is the use of the Thin-Film Mercury Electrode for anodic stripping voltammetry, simple voltammetry of solution cations and cathodic stripping voltammetry for the determination of an environmentally important molecule, thiourea. The construction of a simple potentiostat and applications for student laboratory courses are included. (CW)

  17. In situ monitoring of the Li-O2 electrochemical reaction on nanoporous gold using electrochemical AFM.

    PubMed

    Wen, Rui; Byon, Hye Ryung

    2014-03-11

    The lithium-oxygen (Li-O2) electrochemical reaction on nanoporous gold (NPG) is observed using in situ atomic force microscopy (AFM) imaging coupled with potentiostatic measurement. Dense Li2O2 nanoparticles form a film at 2.5 V, which is decomposed at 3.8-4.0 V in an ether-based electrolyte. PMID:24469227

  18. Surface pK(sub a) of Self-Assembled Monolayers

    ERIC Educational Resources Information Center

    Hale, Penny S.; Maddox, Leone M.; Shapter, Joe G.

    2005-01-01

    The difference between solution and surface properties such as pK(sub a) is illustrated enabling students to understand the differences between nanoscale and macroscopic systems. Details regarding the usage of electrochemical instrumentation, such as a potentiostat, and of the technique such as cyclic voltammetry are given.

  19. Affordable Cyclic Voltammetry

    ERIC Educational Resources Information Center

    Stewart, Greg; Kuntzleman, Thomas S.; Amend, John R.; Collins, Michael J.

    2009-01-01

    Cyclic voltammetry is an important component of the undergraduate chemical curriculum. Unfortunately, undergraduate students rarely have the opportunity to conduct experiments in cyclic voltammetry owing to the high cost of potentiostats, which are required to control these experiments. By using MicroLab data acquisition interfaces in conjunction…

  20. Toward developing long-life water quality sensors for the ISS using planar REDOX and conductivity sensors

    NASA Technical Reports Server (NTRS)

    Buehler, M. G.; Kuhlman, G. M.; Keymeulen, D.; Myung, N.; Kounaves, S. P.

    2003-01-01

    REDOX and conductivity sensors are metal electrodes that are used to detect ionic species in solution by measuring the electrochemical cell current as the voltage is scanned. This paper describes the construction of the sensors, the potentiostat electronics, the measurement methodology, and applications to water quality measurements.

  1. Improvement in the Corrosion Resistance of Austenitic Stainless Steel 316L by Ion Implantation

    NASA Astrophysics Data System (ADS)

    Cai, Xun; Feng, Kai

    In the present work, austenitic stainless steel 316L (SS316L) samples were implanted with Ni and Ni-Cr. A nickel-rich layer about 100 nm in thickness and a Ni-Cr enriched layer about 60 nm thick are formed on the surface of SS316L. The effects of ion implantation on the corrosion performance of SS316L are investigated in a 0.5 M H2SO4 with 2 ppm HF solution at 80°C by open circuit potential (OCP), potentiodynamic and potentiostatic tests. The samples after the potentiostatic test are analyzed by XPS. The results indicate that the composition of the passive film change from a mixture of Fe oxides and Cr oxide to a Cr oxide dominated passive film after the potentiostatic test. The solutions after the potentiostatic test are analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). The results reveal that Fe is selectively dissolved in all cases and a proper Ni and Ni-Cr implant fluence can greatly improve the corrosion resistance of SS316L in the simulated polymer electrolyte membrane fuel cells (PEMFCS) environment. They are in agreement with the electrochemical test results that the bare SS316L has the highest dissolution rate in both cathode and anode environments and the Ni and Ni-Cr implantation reduce markedly the dissolution rate. After the potentiostatic test the interfacial contact resistance (ICR) values are also measured. Ni and Ni-Cr are enriched in the passive film formed in the simulated PEMFC cathode environment after ion implantation thereby providing better conductivity than that formed in the anode one. A significant improvement of ICR is achieved for the SS316L implanted with Ni and Ni-Cr as compared to the bare SS316L, which is attributed to the reduction in passive layer thickness caused by Ni and Ni-Cr implantation. The ICR values for implanted specimens increase with increasing dose.

  2. Electrodeposition of hafnium coatings from molten CsCl-HfCl{sub 4}

    SciTech Connect

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

    1992-04-20

    The electrode processes in the CsCl-HfCl{sub 4} melt were examined by potentiodynamic and potentiostatic methods with the use of P-5827 and PI-50.1.1 potentiostats. The potential sweep rates were varied form 0.005 to 1.0 V/sec. The recorders were KSP-4 and LKD-4-003 potentiometers and a PO-5122 oscillographic polarograph. The electrochemical cell was the traditional one for electrochemical studies. The reference electrode was Ag/NaCl-KCl-AgCl (2 mass %). The mass loss in the hafnium anode was used to determine the anode current yield and the mean degree of oxidation for the hafnium ion entering the melt. The anode products were identified by X-ray methods with a DRON-2 diffractometer and also by thermographic and chemical analysis. 15 refs., 4 figs., 1 tab.

  3. Template-assisted electrodeposition of indium-antimony nanowires - Comparison of electrochemical methods

    NASA Astrophysics Data System (ADS)

    Hnida, Katarzyna; Mech, Justyna; Sulka, Grzegorz D.

    2013-12-01

    Indium antimonide (InSb) is a III-V compound semiconductor that in a form of nanowires can possess improved thermoelectrical and optical properties compared to the corresponding bulk crystal. Here, we applied three electrodeposition techniques for a fast and inexpensive template-assisted fabrication of InSb nanowires from a sodium citrate-citric acid solution at room temperature. The home-made anodic aluminum oxide (AAO) templates with the pore diameter of 100 nm were used. InSb nanowires were synthesized by potentiostatic, galvanostatic and periodic pulse reverse techniques. The morphology, composition and crystallinity of as-obtained and annealed nanowires were investigated and compared with the literature data. It was found that the potentiostatic and pulse reverse methods gave crystalline nanowires. On the other hand, the constant current density deposition results in a partially amorphous nanowire material.

  4. Nano electrode arrays for in-situ identification and quantification of chemicals in water.

    SciTech Connect

    Gurule, Natalia J.; Kelly, Michael James; Brevnov, Dmitri A.; Ashby, Carol Iris Hill; Pfeifer, Kent Bryant; Yelton, William Graham

    2004-12-01

    The nano electrode arrays for in-situ identification and quantification of chemicals in water progress in four major directions. (1) We developed and engineering three nanoelectrode array designs which operate in a portable field mode or as distributed sensor network for water systems. (2) To replace the fragile glass electrochemical cells using in the lab, we design and engineered field-ready sampling heads that combine the nanoelectrode arrays with a high-speed potentiostat. (3) To utilize these arrays in a portable system we design and engineered a light weight high-speed potentiostat with pulse widths from 2 psec. to 100 msec. or greater. (4) Finally, we developed the parameters for an analytical method in low-conductivity solutions for Pb(II) detection, with initial studies for the analysis of As(III) and As(V) analysis in natural water sources.

  5. Corrosion resistance tests on NiTi shape memory alloy.

    PubMed

    Rondelli, G

    1996-10-01

    The corrosion performances of NiTi shape memory alloys (SMA) in human body simulating fluids were evaluated in comparison with other implant materials. As for the passivity current in potentiostatic conditions, taken as an index of ion release, the values are about three times higher for NiTi than for Ti6Al4V and austenitic stainless steels. Regarding the localized corrosion, while plain potentiodynamic scans indicated for NiTi alloy good resistance to pitting attack similar to Ti6Al4V, tests in which the passive film is abruptly damaged (i.e. potentiostatic scratch test and modified ASTM F746) pointed out that the characteristics of the passive film formed on NiTi alloy (whose strength can be related to the alloy's biocompatibility) are not as good as those on Ti6Al4V but are comparable or inferior to those on austenitic stainless steels. PMID:8894095

  6. Distributed effects of calcium ion contaminant on polymer electrolyte fuel cell performance

    NASA Astrophysics Data System (ADS)

    Uddin, Md Aman; Wang, Xiaofeng; Park, Jaehyung; Pasaogullari, Ugur; Bonville, Leonard

    2015-11-01

    Distributed performance of a polymer electrolyte fuel cell (PEFC) is studied both in galvanostatic and potentiostatic mode during in-situ injection of Ca2+ in the air stream using a segmented cell. In the galvanostatic mode, segments near the inlet are affected first by the contaminant resulting in decreased current density. At the same time, despite the presence of contaminants, current density for the other segments increases in order to maintain constant total current. In the potentiostatic mode, all segments are affected by the contaminants simultaneously and the current density in all segments decreases with time. The performance of the downstream segments is lower than the upstream segments. During both tests, the contaminant is found to precipitate on both the cathode flow field and the cathode GDL surface. As the test progresses, the contaminant penetrates into the GDL and deposits, causing mass transport losses.

  7. Selective dissolution in copper-tin alloys: Formation of corrosion- resistant patina on ancient Chinese bronze mirrors

    SciTech Connect

    Taube, M. |; Davenport, A.J.; King, A.H.; Chase, T. III

    1996-07-01

    Many ancient Chinese bronze mirrors have survived with a patina that leaves the delicate relief surface decorations intact. The microstructure of these ancient mirrors is two-phase and consists of acicular {alpha}-phase (Cu-rich) regions encased in a {delta}-phase (Sn-rich) matrix. At the surface, there is evidence of selective dissolution of the ct phase; the cc-phase regions are replaced pseudomorphically by a mineral product with the {delta} phase remaining metallic. Electrochemical polarization has been used to drive the copper dealloying process in modem, cast bronze. Synchrotron x-ray diffraction was employed to compare the ancient samples with those that were prepared potentiostatically. Poorly crystallized tin oxide (SnO{sub 2}) was found in the {alpha} replacement products of both sample types. The corrosion-resistance of the potentiostatically-treated bronze samples was tested by atmospheric exposure. Comparison with exposed, untreated samples indicated that the treatment was protective.

  8. A new electrochemical approach for evaluation of corrosion inhibitors in neutral aqueous solutions

    SciTech Connect

    Jovancicevic, V.; Hartwick, D.

    1997-12-01

    A new comprehensive electrochemical approach to corrosion inhibitor evaluation in neutral aqueous solutions has been developed. It consists of using concurrently three different but complementary electrochemical methods. Linear polarization resistance (LPR), concentration-step potentiostatic (CSP) and constant-concentration potentiostatic (CCP) methods are used to determine the overall corrosion rates, corrosion inhibition mechanism, and stability of the passive oxide film in the presence of corrosion inhibitors. This approach has been used successfully to evaluate corrosion inhibition of three organic inhibitor systems: a phosphonate-based corrosion inhibitor (hydroxyphosphonoacetic acid, HPA), a polymeric corrosion inhibitor (polyacrylic acid, PAA) and a non-phosphorus containing corrosion inhibitor (L-tartaric acid). Short-term CSP/CCP test results for these three inhibitors are in good agreement with long-term weight loss measurements.

  9. Preparation and characterisation of nearly stoichiometric CdTe films from a non-aqueous electrodeposition bath

    NASA Astrophysics Data System (ADS)

    Gore, R. B.; Pandey, Rajendra Kumar; Kumar, S. R.

    1991-06-01

    The cathodic polarisation characteristics and the growth behaviour of CdTe films in an ethylene-glycol-based bath have been studied. Conditions favouring stoichiometric deposition have been examined. The influence of the processing variables on the film properties has also been discussed with the help of the XRD, SEM and XPS studies. It has been shown that the films deposited potentiostatically at -0.8 V are stoichiometric and single phase.

  10. Teorell instability in concentration polarization

    NASA Astrophysics Data System (ADS)

    Abu-Rjal, Ramadan; Prigozhin, Leonid; Rubinstein, Isaak; Zaltzman, Boris

    2015-08-01

    We investigate the development of electro-osmotic (Teorell) oscillations at a weakly charged microporous membrane without a preimposed transmembrane electrolyte concentration drop. This drop, necessary for the occurrence of oscillations, develops spontaneously as a result of concentration polarization in the solution layers adjacent to the membrane. A three-layer model comprising a membrane flanked by two diffusion layers is proposed and analyzed for galvano- and potentiostatic regimes of operation.

  11. Proton transfer in oxidized adenosine self-aggregates.

    PubMed

    Capobianco, Amedeo; Caruso, Tonino; Celentano, Maurizio; La Rocca, Mario Vincenzo; Peluso, Andrea

    2013-10-14

    The UV-vis and the IR spectra of derivativized adenosine in dichloromethane have been recorded during potentiostatic oxidation at an optically transparent thin layer electrode. Oxidized adenosine shows a broad Zundel like absorption extending from 2800 up to 3600 cm(-1), indicating that a proton transfer process is occurring. Theoretical computations predict that proton transfer is indeed favored in oxidized 1:1 self-association complexes and allow to assign all the observed transient spectroscopic signals. PMID:24116647

  12. A Scanning Auger Microprobe analysis of corrosion products associated with sulfate reducing bacteria

    SciTech Connect

    Sadowski, R.A.; Chen, G.; Clayton, C.R.; Kearns, J.R.; Gillow, J.B.; Francis, A.J.

    1995-03-01

    A Scanning Auger Microprobe analysis was performed on the corrosion products of an austenitic AISI type 304 SS after a potentiostatic polarization of one volt for ten minutes in a modified Postgate`s C media containing sulfate reducing bacteria. The corrosion products were characterized and mapped in local regions where pitting was observed. A critical evaluation of the applicability of this technique for the examination of microbially influenced corrosion (MIC) is presented.

  13. Studying localized corrosion using liquid cell transmission electron microscopy

    SciTech Connect

    Chee, See Wee; Pratt, Sarah H.; Hattar, Khalid; Duquette, David; Ross, Frances M.; Hull, Robert

    2014-11-07

    Using liquid cell transmission electron microscopy (LCTEM), localized corrosion of Cu and Al thin films immersed in aqueous NaCl solutions was studied. We demonstrate that potentiostatic control can be used to initiate pitting and that local compositional changes, due to focused ion beam implantation of Au+ ions, can modify the corrosion susceptibility of Al films. Likewise, a discussion on strategies to control the onset of pitting is also presented.

  14. On-line corrosion monitoring with electrochemical impedance spectroscopy

    SciTech Connect

    Roberge, P.R. . Dept. of Chemistry and Chemical Engineering); Sastri, V.S. )

    1994-10-01

    Electrochemical impedance spectroscopy (EIS) has been found to be a rapid and accurate technique for measuring corrosion rates in the most difficult situations and for yielding information concerning the occurrence of localized corrosion. When used in the absence of potentiostatic control, the technique carries less instrumental overhead, and the danger of damaging the probe by accidental polarization is reduced. Results from two field tests were presented to illustrate the advantages of using EIS for on-line monitoring of general and localized corrosion.

  15. Teorell instability in concentration polarization.

    PubMed

    Abu-Rjal, Ramadan; Prigozhin, Leonid; Rubinstein, Isaak; Zaltzman, Boris

    2015-08-01

    We investigate the development of electro-osmotic (Teorell) oscillations at a weakly charged microporous membrane without a preimposed transmembrane electrolyte concentration drop. This drop, necessary for the occurrence of oscillations, develops spontaneously as a result of concentration polarization in the solution layers adjacent to the membrane. A three-layer model comprising a membrane flanked by two diffusion layers is proposed and analyzed for galvano- and potentiostatic regimes of operation. PMID:26382404

  16. Studying localized corrosion using liquid cell transmission electron microscopy

    DOE PAGESBeta

    Chee, See Wee; Pratt, Sarah H.; Hattar, Khalid; Duquette, David; Ross, Frances M.; Hull, Robert

    2014-11-07

    Using liquid cell transmission electron microscopy (LCTEM), localized corrosion of Cu and Al thin films immersed in aqueous NaCl solutions was studied. We demonstrate that potentiostatic control can be used to initiate pitting and that local compositional changes, due to focused ion beam implantation of Au+ ions, can modify the corrosion susceptibility of Al films. Likewise, a discussion on strategies to control the onset of pitting is also presented.

  17. A CMOS Amperometric System for Multi-Neurotransmitter Detection.

    PubMed

    Massicotte, Genevieve; Carrara, Sandro; Di Micheli, Giovanni; Sawan, Mohamad

    2016-06-01

    In vivo multi-target and selective concentration monitoring of neurotransmitters can help to unravel the brain chemical complex signaling interplay. This paper presents a dedicated integrated potentiostat transducer circuit and its selective electrode interface. A custom 2-electrode time-based potentiostat circuit was fabricated with 0.13 μm CMOS technology and provides a wide dynamic input current range of 20 pA to 600 nA with 56 μ W, for a minimum sampling frequency of 1.25 kHz. A multi-working electrode chip is functionalized with carbon nanotubes (CNT)-based chemical coatings that offer high sensitivity and selectivity towards electroactive dopamine and non-electroactive glutamate. The prototype was experimentally tested with different concentrations levels of both neurotransmitter types, and results were similar to measurements with a commercially available potentiostat. This paper validates the functionality of the proposed biosensor, and demonstrates its potential for the selective detection of a large number of neurochemicals. PMID:26761882

  18. Electrochemical behavior of nanocrystalline Ta/TaN multilayer on 316L stainless steel: Novel bipolar plates for proton exchange membrane fuel-cells

    NASA Astrophysics Data System (ADS)

    Alishahi, M.; Mahboubi, F.; Mousavi Khoie, S. M.; Aparicio, M.; Hübner, R.; Soldera, F.; Gago, R.

    2016-08-01

    Insufficient corrosion resistance and surface conductivity are two main issues that plague large-scale application of stainless steel (SS) bipolar plates in proton exchange membrane fuel cells (PEMFCs). This study explores the use of nanocrystalline Ta/TaN multilayer coatings to improve the electrical and electrochemical performance of polished 316L SS bipolar plates. The multilayer coatings have been deposited by (reactive) magnetron sputtering and characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The electrochemical behavior of bare and coated substrates has been evaluated in simulated PEMFC working environments by potentiodynamic and potentiostatic polarization tests at ambient temperature and 80 °C. The results show that the Ta/TaN multilayer coating increases the polarization resistance of 316L SS by about 30 and 104 times at ambient and elevated temperatures, respectively. The interfacial contact resistance (ICR) shows a low value of 12 mΩ × cm2 before the potentiostatic test. This ICR is significantly lower than for the bare substrate and remains mostly unchanged after potentiostatic polarization for 14 h. In addition, the high contact angle (92°) with water for coated substrates indicates a hydrophobic character, which can improve the water management within the cell in PEMFC stacks.

  19. A Low-Cost Smartphone-Based Electrochemical Biosensor for Point-of-Care Diagnostics

    PubMed Central

    Sun, Alexander; Wambach, Travis; Venkatesh, A. G.; Hall, Drew A.

    2015-01-01

    This paper describes the development of a smartphone-based electrochemical biosensor module. The module contains a low power potentiostat that interfaces and harvests power from a smartphone through the phone’s audio jack. A prototype with two different potentiostat designs was constructed and used to conduct proof of concept cyclic voltammetry experiments with potassium ferro-/ferricyanide (K4[Fe(CN)6] / K3[Fe(CN)6]) in a side-by-side comparison with a laboratory grade instrument. Results show that the module functions within the available power budget and that the recovered voltammogram data matches well with the data from an expensive bench top tool. Excluding the loses from supply rectification and regulation, the module consumes either 5.7 mW or 4.3 mW peak power, depending on which of the two discussed potentiostat designs is used. At single quantity pricing, the hardware for the prototype device costs less than $30. PMID:26097899

  20. Electrochemical sensing of nuclear matrix protein 22 in urine with molecularly imprinted poly(ethylene-co-vinyl alcohol) coated zinc oxide nanorod arrays for clinical studies of bladder cancer diagnosis.

    PubMed

    Lee, Mei-Hwa; Thomas, James L; Chang, Yu-Chia; Tsai, Yuh-Shyan; Liu, Bin-Da; Lin, Hung-Yin

    2016-05-15

    In 1996 and 2000, the US Food and Drug Administration (FDA) approved the use of Nuclear matrix protein 22 (NMP22) as a monitoring tool for predicting the recurrence/clearing of bladder cancer, and for screening undiagnosed individuals who have symptoms of, or are at risk for, that disease. The fabrication of electrodes for sensing NMP22 and their integration with a portable potentiostat in a homecare system may have great value. This work describes a sensing element comprised of molecularly imprinted polymers (MIPs) for the specific recognition of NMP22 target molecules. Zinc oxide (ZnO) nanorods (214 ± 45 nm in diameter and 1.08 ± 0.11 μm long) were hydrothermally grown on the sensing electrodes to increase the surface area to be coated with MIPs. A portable potentiostat was assembled and a data acquisition (DAQ) card and the Labview program were utilized to monitor electrochemical reaction to sense NMP22 in urine samples. Finally, in phase 0 clinical trials, measurements were made of samples from a few patients with bladder cancer using the NMP22 MIP-coated ZnO nanorods electrodes that were integrated into a portable potentiostat, revealing NMP 22 concentrations in the range 128 ± 19 to 588 ± 53 ng/mL. PMID:26774095

  1. Effect of chemical etching and aging in boiling water on the corrosion resistance of Nitinol wires with black oxide resulting from manufacturing process.

    PubMed

    Shabalovskaya, S; Rondelli, G; Anderegg, J; Simpson, B; Budko, S

    2003-07-15

    The effect of chemical etching in a HF/HNO(3) acid solution and aging in boiling water on the corrosion resistance of Nitinol wires with black oxide has been evaluated with the use of potentiodynamic, modified potentiostatic ASTM F746, and scratch tests. Scanning-electron microscopy, elemental XPS, and Auger analysis were employed to characterize surface alterations induced by surface treatment and corrosion testing. The effect of aging in boiling water on the temperatures of martensitic transformations and shape recovery was evaluated by means of measuring the wire electroresistance. After corrosion tests, as-received wires revealed uniformly cracked surfaces reminiscent of the stress-corrosion-cracking phenomenon. These wires exhibited negative breakdown potentials in potentiostatic tests and variable breakdown potentials in potentiodynamic tests (- 100 mV to + 400 mV versus SCE). Wires with treated surfaces did not reveal cracking or other traces of corrosion attacks in potentiodynamic tests up to + 900-1400-mV potentials and no pitting after stimulation at + 800 mV in potentiostatic tests. They exhibited corrosion behavior satisfactory for medical applications. Significant improvement of corrosion parameters was observed on the reverse scans in potentiodynamic tests after exposure of treated wires to potentials > 1000 mV. In scratch tests, the prepared surfaces repassivated only at low potentials, comparable to that of stainless steel. Tremendous improvement of the corrosion behavior of treated Nitinol wires is associated with the removal of defect surface material and the growth of stable TiO(2) oxide. The role of precipitates in the corrosion resistance of Nitinol-scratch repassivation capacity in particular-is emphasized in the discussion. PMID:12808592

  2. Effects of magnetic fields from underwater electrical cutting on in vitro corrosion of dental amalgam.

    PubMed

    Ortendahl, T W; Högstedt, P; Odelius, H; Norén, J G

    1988-11-01

    Metallic taste has been reported from divers working with underwater electric welding and cutting. An in vitro model was designed to simulate the intraoral situation of the divers with respect to the magnetic field. Potentiostatic analyses were performed on amalgam samples exposed to AC and DC magnetic fields. Morphologic changes were analyzed using differential interference light microscopy and scanning electron microscopy. Chemical changes on the surface of the amalgam samples were analyzed with secondary ion mass spectrometry. Results demonstrated that dental amalgams exposed to a specific AC magnetic field underwent morphologic and chemical changes in the superficial amalgam layers. PMID:3227577

  3. Patterned electrochemical deposition of copper using an electron beam

    SciTech Connect

    Heijer, Mark den; Shao, Ingrid; Reuter, Mark C.; Ross, Frances M.; Radisic, Alex

    2014-02-01

    We describe a technique for patterning clusters of metal using electrochemical deposition. By operating an electrochemical cell in the transmission electron microscope, we deposit Cu on Au under potentiostatic conditions. For acidified copper sulphate electrolytes, nucleation occurs uniformly over the electrode. However, when chloride ions are added there is a range of applied potentials over which nucleation occurs only in areas irradiated by the electron beam. By scanning the beam we control nucleation to form patterns of deposited copper. We discuss the mechanism for this effect in terms of electron beam-induced reactions with copper chloride, and consider possible applications.

  4. Investigation of the electrochemically active surface area and lithium diffusion in graphite anodes by a novel OsO4 staining method

    NASA Astrophysics Data System (ADS)

    Pfaffmann, Lukas; Birkenmaier, Claudia; Müller, Marcus; Bauer, Werner; Mitsch, Tim; Feinauer, Julian; Krämer, Yvonne; Scheiba, Frieder; Hintennach, Andreas; Schleid, Thomas; Schmidt, Volker; Ehrenberg, Helmut

    2016-03-01

    Negative electrodes of lithium-ion batteries generally consist of graphite-based active materials. In order to realize batteries with a high current density and therefore accelerated charging processes, the intercalation of lithium and the diffusion processes of these carbonaceous materials must be understood. In this paper, we visualized the electrochemical active surface area for three different anode materials using a novel OsO4 staining method in combination with scanning electron microscopy techniques. The diffusion behavior of these three anode materials is investigated by potentiostatic intermittent titration technique measurements. From those we determine the diffusion coefficient with and without consideration of the electrochemical active surface area.

  5. The effect of potential upon the high-temperature fatigue crack growth response of low-alloy steels. Part 1: Crack growth results

    SciTech Connect

    James, L.A.; Moshier, W.C.

    1997-04-01

    Corrosion-fatigue crack propagation experiments were conducted on several low-alloy steels in elevated temperature aqueous environments, and experimental parameters included temperature, sulfur content of the steel, applied potential level, and dissolved hydrogen (and in one case, dissolved oxygen) concentration in the water. Specimen potentials were controlled potentiostatically, and the observation (or non-observation) of accelerated fatigue crack growth rates was a complex function of the above parameters. Electrochemical results and the postulated explanation for the complex behavior are given in Part II.

  6. Microfluidic platform for neurotransmitter sensing based on cyclic voltammetry and dielectrophoresis for in vitro experiments.

    PubMed

    Mathault, Jessy; Zamprogno, Pauline; Greener, Jesse; Miled, Amine

    2015-08-01

    This paper presents a new microfluidic platform that can simultaneously measure and locally modulate neurotransmitter concentration in a neuron network. This work focuses on the development of a first prototype including a potentiostat and electrode functionalization to detect several neurotransmitter's simultaneously. We tested dopamine as proof of concept to validate functionality. The system is based on 320 bidirectional electrode array for dielectrophoretic manipulation and cyclic voltammetry. Each electrode is connected to a mechanical multiplexer in order to reduce noise interference and fully isolate the electrode. The multiplexing rate is 476 kHz and each electrode can drive a signal with an amplitude of 60 V pp for dielectrophoretic manipulation. PMID:26736720

  7. Comparative study on corrosion behaviour of Nitinol and stainless steel orthodontic wires in simulated saliva solution in presence of fluoride ions.

    PubMed

    Mirjalili, M; Momeni, M; Ebrahimi, N; Moayed, M H

    2013-05-01

    Localized corrosion and effects of pre-passivation treatment of Nitinol and SS304 orthodontic wires in simulated saliva solution in the presence and absence of fluoride ions were investigated by means of potentiodynamic and potentiostatic polarisations. Results revealed that Nitinol does not show pitting corrosion in saliva solution however, SS304 shows pitting corrosion. Meanwhile fluoride ion has deteriorative effect on pitting corrosion of Nitinol, while its effect on SS304 was marginally constructive. Additionally, the presence of artificial crevice has no effect on corrosion behaviour in the presence of fluoride. Pre-passivation treatment has positive influence on pitting corrosion of both alloys in the presence of F(-) ions. PMID:23498236

  8. Extensive study of shape and surface structure formation in the mercury beating heart system.

    PubMed

    Ramírez-Álvarez, E; Ocampo-Espindola, J L; Montoya, Fernando; Yousif, F; Vázquez, F; Rivera, M

    2014-11-13

    A phenomenological study of the mercury beating heart system in a three electrode electrochemical cell configuration forced with a harmonic perturbation is presented. The system is controlled via a potentiostat, where the mercury drop is electrically connected to a platinum wire and acts as the working electrode. This configuration exhibits geometrical shapes and complex surface structures when a harmonic signal is superimposed to the working electrode potential. This study involves a wide range of frequencies and amplitudes of the forcing signal. Differents levels of structure complexity are observed as a function of the parameters of the applied perturbation. At certain amplitudes and frequencies, rotational behavior is also observed. PMID:25343208

  9. Effect of Applied Potential on the Electrochemical Deposition of Styrene-Butadiene Co-Polymer Based Conducting Polymer Composite

    NASA Astrophysics Data System (ADS)

    Mathew, Anisha Mary; Neena, P.

    2011-10-01

    Homogeneous conducting polymer composite films with improved electrical properties are synthesized via electrochemical polymerization of polyaniline on Styrene butadiene rubber coated steel electrode. The electrochemical polymerization is carried out by potentiostatic method using an aqueous solution of 0.2 M aniline and 1.5 M sulphuric acid as electrolyte in a single compartment electrochemical cell. The optical studies show successful incorporation of polyaniline into the matrix polymer film. The effect of applied potential on the electrodeposition of composite is studied by cyclic voltammetry and by impedance spectroscopic measurements.

  10. Separation of metal ions from aqueous solutions

    DOEpatents

    Almon, Amy C.

    1994-01-01

    A process and apparatus for quantitatively and selectively separating metal ions from mixtures thereof in aqueous solution. The apparatus includes, in combination, a horizontal electrochemical flow cell containing flow bulk electrolyte solution and an aqueous, metal ion-containing solution, the cell containing a metal mesh working electrode, a counter electrode positioned downstream from the working electrode, an independent variable power supply/potentiostat positioned outside of the flow cell and connected to the electrodes, and optionally a detector such as a chromatographic detector, positioned outside the flow cell. This apparatus and its operation has significant application where trace amounts of metal ions are to be separated.

  11. Novel Approach to Surface Plasmon Resonance: A Third Dimension in Data Interpretation Through Surface Roughness Changes.

    PubMed

    Manole, Claudiu Constantin; Pîrvu, C; Maury, F; Demetrescu, I

    2016-06-01

    In a Surface Plasmon Resonance (SPR) experiment two key parameters are classically recorded: the time and the angle of SPR reflectivity. This paper brings into focus a third key parameter: SPR reflectivity. The SPR reflectivity is proved to be related to surface roughness changes. Practical investigations on (i) gold anodizing and (ii) polypyrrole film growth in presence of oxalic acid is detailed under potentiostatic conditions. These experimental results reveal the potential of using the SPR technique to investigate real-time changes both on the gold surface, but also in the gold film itself. This extends the versatility of the technique in particular as sensitive in-situ diagnostic tool. PMID:27427713

  12. The Structure and Properties of Inductively Coupled Plasma Assisted Magnetron Sputtered Nanocrystalline NbN Coatings in Corrosion Protective Die Casting Molds.

    PubMed

    Chun, Sung-Yong

    2016-02-01

    Niobium nitride coatings for the surface modified die casting molds with various ICP powers have been prepared using ICP assisted magnetron sputtering. The applied ICP power was varied from 0 to 200 W. The deposited coatings were characterized post-deposition using X-ray diffractometry (XRD) and atomic force microscopy (AFM). Single NbN phased coatings with nano-grain sized (<7.6 nm) were identified. The corrosion resistance and hardness of each coating were evaluated from potentiostat and nanoindentator. Superior corrosion protective coatings in excess of 13.9 GPa were deposited with assistance of ICP plasma during sputtering. PMID:27433719

  13. Morphology, structure, and magnetism of FeCo thin films electrodeposited on hydrogen-terminated Si(111) surfaces.

    PubMed

    Zarpellon, J; Jurca, H F; Mattoso, N; Klein, J J; Schreiner, W H; Ardisson, J D; Macedo, W A A; Mosca, D H

    2007-12-15

    In this work we describe the fabrication of FeCo alloy (less than 10 at% Co) thin films from aqueous ammonium sulfate solutions onto n-type Si(111) substrates using potentiostatic electrodeposition at room temperature. The incorporation of Co into the deposits tends to inhibit Fe silicide formation and to protect deposits against oxidation under air exposure. As the incorporation of Co was progressively increased, the sizes of nuclei consisting of FeCo alloy increased, leading to films with a highly oriented body-centered cubic structure with crystalline texture, where (110) planes remain preferentially oriented parallel to the film surface. PMID:17900605

  14. Synthesis and characterization of porous structured ZnO thin film for dye sensitized solar cell applications

    NASA Astrophysics Data System (ADS)

    Marimuthu, T.; Anandhan, N.; Mummoorthi, M.; Dharuman, V.

    2016-05-01

    Zinc oxide (ZnO) and zinc oxide/eosin yellow (ZnO/EY) thin films were potentiostatically deposited onto fluorine doped tin oxide (FTO) glass substrate. Effect of eosin yellow dye on structural, morphological and optical properties was studied. X-ray diffraction patterns, micro Raman spectra and photoluminescence (PL) spectra reveal hexagonal wurtzite structure with less atomic defects in 101 plane orientation of the ZnO/EY film. Scanning electron microscopy (SEM) images show flower for ZnO and porous like structure for ZnO/EY thin film, respectively. DSSC was constructed and evaluated by measuring the current density verses voltage curve.

  15. Reduction of Plutonium in Acidic Solutions by Mesoporous Carbons

    SciTech Connect

    Parsons-Moss, Tashi; Jones, Stephen; Wang, Jinxiu; Wu, Zhangxiong; Uribe, Eva; Zhao, Dongyuan; Nitsche, Heino

    2015-12-19

    Batch contact experiments with several porous carbon materials showed that carbon solids spontaneously reduce the oxidation state of plutonium in 1-1.5 M acid solutions, without significant adsorption. The final oxidation state and rate of Pu reduction varies with the solution matrix, and also depends on the surface chemistry and surface area of the carbon. It was demonstrated that acidic Pu(VI) solutions can be reduced to Pu(III) by passing through a column of porous carbon particles, offering an easy alternative to electrolysis with a potentiostat.

  16. Thin flexible intercalation anodes

    SciTech Connect

    Levy, S.C.; Cieslak, W.R.; Klassen, S.E.; Lagasse, R.R.

    1994-10-01

    Poly(acrylonitrile) fibers have been pyrolyzed under various conditions to form flexible carbon yarns capable of intercalating lithium ions. These fibers have also been formed into both woven and non woven cloths. Potentiostatic, potentiodynamic and galvanostatic tests have been conducted with these materials in several electrolytes. In some tests, a potential hold was used after each constant current charge and discharge. These tests have shown some of these flexible materials to reversibly intercalate lithium ions to levels that are suitable for use as a practical battery anode.

  17. Pitting of steam-generator tubing alloys in solutions containing thiosulfate and sulfate or chloride.

    PubMed

    Zhang, William; Carcea, Anatolie G; Newman, Roger C

    2015-01-01

    The pitting of nuclear steam generator tubing alloys 600, 690 and 800 was studied at 60 °C using dilute thiosulfate solutions containing excess sulfate or (for Alloy 600) chloride. A potentiostatic scratch method was used. In sulfate solutions, all alloys pitted at low potentials, reflecting their lack of protective Mo. The alloys demonstrated the most severe pitting at a sulfate : thiosulfate concentration ratio of ∼40. Alloy 600 pitted worst at a chloride : thiosulfate ratio of ∼2000. The results are interpreted through the mutual electromigration of differently charged anions into a pit nucleus, and differences in the major alloy component. PMID:25898311

  18. {ital In-situ} x-ray investigation of hydrogen charging in thin film bimetallic electrodes

    SciTech Connect

    Jisrawi, N.M.; Wiesmann, H.; Ruckman, M.W.; Thurston, T.R.; Reisfeld, G.; Ocko, B.M.; Strongin, M.

    1997-08-01

    Hydrogen uptake and discharge by thin metallic films under potentiostatic control was studied using x-ray diffraction at the National Synchrotron Light Source (NSLS). The formation of metal-hydrogen phases in Pd, Pd-capped Nb and Pd/Nb multilayer electrode structures was deduced from x-ray diffraction data and correlated with the cyclic voltammetry (CV) peaks. The x-ray data was also used to construct a plot of the hydrogen concentration as a function of cell potential for a multilayered thin film. {copyright} {ital 1997 Materials Research Society.}

  19. Convection of tin in a Bridgman system. II - An electrochemical method for detecting flow regimes

    NASA Technical Reports Server (NTRS)

    Sears, B.; Fripp, A. L.; Debnam, W. J., Jr.; Woodell, G. A.; Anderson, T. J.; Narayanan, R.

    1992-01-01

    An ampoule was designed in order to obtain local flow behavior of the flow fields for convection of tin in a vertical Bridgman configuration. Multiple electrochemical cells were located along the periphery of the ampoule. Oxygen was titrated into the ampoule at one of the cell locations using a potentiostat and the concentration of oxygen was monitored at the other cell locations by operating the cells in a galvanic mode. Onset of oscillations were detected by means of thermocouples. We conclude that the flows are generally three dimensional for an aspect ratio of 5. Results on oscillations concurred with those of earlier workers. Suggestions for improved designs were made.

  20. Dynamic instabilities during the continuous electro-oxidation of CO on poly- and single crystalline Pt electrodes

    NASA Astrophysics Data System (ADS)

    Malkhandi, Sauradip; Bonnefont, Antoine; Krischer, Katharina

    2009-06-01

    Dynamic instabilities during bulk CO electro-oxidation on poly- and single crystalline rotating Pt electrodes in different electrolytes were investigated experimentally. In sulphuric and perchloric electrolytic media, only bistability is observed. The dependence of the width of the bistable regime on some parameters is discussed. The addition of small amounts of chloride ions induces current oscillations under potentiostatic conditions on polycrystalline Pt, Pt(1 1 0) and Pt(1 0 0) electrodes. Existence range, shape and mean frequency of the mainly irregular kinetic oscillations vary significantly with the crystallographic structure of the electrode surface.

  1. Calculation of mass transfer in multiphase flow

    SciTech Connect

    Wang, L.; Gopal, M.

    1998-12-31

    This paper summarizes the results of mass transfer mechanisms under disturbed liquid-gas flow in 10 cm diameter pipe using electrochemical limiting current density and potentiostatic noise technique. The solution used is potassium ferro/ferricyanide dissolve in 1.3 N sodium hydroxide system. Mass transfer coefficients in full pipe flow and slug flow are obtained. The relationship between mass transfer coefficient with full pipe flow velocities and with slug flow Froude numbers are studied. The impact of bubbles in slugs on the mass transfer coefficient is revealed, The impact of flow disturbance, including weld beads and pits, are discussed for both full pipe flow and slug flow.

  2. Electrochemical reaction of lithium with nanosized vanadium antimonate

    SciTech Connect

    Morales, Julian; Sanchez, Luis . E-mail: luis-sanchez@uco.es; Martin, Francisco; Berry, Frank

    2006-08-15

    Nanometric vanadium antimonate, VSbO{sub 4}, was prepared by mechanical milling from Sb{sub 2}O{sub 3} and V{sub 2}O{sub 5} and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Mossbaueer spectroscopy (MS) and X-ray photoelectron spectroscopy (XPS) techniques. Its reactivity towards lithium was examined by testing Li/VSbO{sub 4} cells under galvanostatic and potentiostatic regimes. The amount of Li inserted was found to be consistent with a two-step process involving the reactions (i) VSbO{sub 4}+8 Li{sup {yields}}Sb+V+4 Li{sub 2}O and (ii) Sb+3 Li{sup {yields}}Li{sub 3}Sb, the former being virtually irreversible and the latter reversible as suggested by the shape of the anodic and cathodic curves. Ex situ XPS measurements of the discharged and charged electrode provided direct evidence of the formation of alloyed Sb and confirmed the results of the potentiostatic curves regarding the irreversible or reversible character of the previous reactions. The Li/VSbO{sub 4} cell exhibited acceptable electrochemical performance, which surpassed that of other Sb-based compounds as the likely result of the formation of V and its associated enhanced electrode conductivity. - Graphical abstract: TEM image of nanosized VSbO{sub 4} sample.

  3. Miniaturized neural sensing and optogenetic stimulation system for behavioral studies in the rat

    NASA Astrophysics Data System (ADS)

    Kim, Min Hyuck; Nam, Ilho; Ryu, Youngki; Wellman, Laurie W.; Sanford, Larry D.; Yoon, Hargsoon

    2015-04-01

    Real time sensing of localized electrophysiological and neurochemical signals associated with spontaneous and evoked neural activity is critically important for understanding neural networks in the brain. Our goal is to enhance the functionality and flexibility of a neural sensing and stimulation system for the observation of brain activity that will enable better understanding from the level of individual cells to that of global structures. We have thus developed a miniaturized electronic system for in-vivo neurotransmitter sensing and optogenetic stimulation amenable to behavioral studies in the rat. The system contains a potentiostat, a data acquisition unit, a control unit, and a wireless data transfer unit. For the potentiostat, we applied embedded op-amps to build single potential amperometry for electrochemical sensing of dopamine. A light emitting diode is controlled by a microcontroller and pulse width modulation utilized to control optogenetic stimulation within a sub-millisecond level. In addition, this proto-typed electronic system contains a Bluetooth module for wireless data communication. In the future, an application-specific integrated circuit (ASIC) will be designed for further miniaturization of the system.

  4. Integrated Nanopore Detectors in a Standard Complementary Metal-Oxide-Semiconductor Process

    NASA Astrophysics Data System (ADS)

    Uddin, Ashfaque; Chen, Chin-Hsuan; Yemenicioglu, Sukru; Milaninia, Kaveh; Corigliano, Ellie; Varma, Madoo; Theogarajan, Luke

    2012-02-01

    High-bandwidth and low-noise nanopore sensor and detection electronics are crucial in achieving single-DNA base resolution. A potential way to accomplish this goal is to integrate solid-state nanopores within a CMOS platform, in close proximity to the biasing electrodes and custom-designed amplifier electronics. Here we report the development of solid-state nanopore devices in a commercial CMOS potentiostat chip implemented in On-Semiconductor's 0.5 micron technology. By using post-CMOS micromachining, a free-standing oxide membrane and electrodes are fabricated utilizing the N+ polysilicon/oxide/N+ polysilicon capacitor structure available in the aforementioned process. Nanopores with sub-5 nm diameter are drilled in the membrane using a Transmission Electron Microscope. The integrity of pores is validated by measuring current-voltage and noise characteristics. DNA translocation experiments are also performed utilizing these on-chip pores. In addition, electrical tests performed on the CMOS potentiostat circuitry show that the post-CMOS micromachining process does not have any detrimental effect on the CMOS circuitry.

  5. Wearable electrochemical sensors for in situ analysis in marine environments.

    PubMed

    Malzahn, Kerstin; Windmiller, Joshua Ray; Valdés-Ramírez, Gabriela; Schöning, Michael J; Wang, Joseph

    2011-07-21

    The development of wearable screen-printed electrochemical sensors on underwater garments comprised of the synthetic rubber neoprene is reported. These wearable sensors are able to determine the presence of environmental pollutants and security threats in marine environments. Owing to its unique elastic and superhydrophobic morphology, neoprene is an attractive substrate for thick-film electrochemical sensors for aquatic environments and offers high-resolution printing with no apparent defects. The neoprene-based sensor was evaluated for the voltammetric detection of trace heavy metal contaminants and nitroaromatic explosives in seawater samples. We also describe the first example of enzyme (tyrosinase) immobilization on a wearable substrate towards the amperometric biosensing of phenolic contaminants in seawater. Furthermore, the integration of a miniaturized potentiostat directly on the underwater garment is demonstrated. The wearable sensor-potentiostat microsystem provides a visual indication and alert if the levels of harmful contaminants have exceeded a pre-defined threshold. The concept discussed here is well-suited for integration into dry- and wetsuits worn by divers and recreational surfers/swimmers, thereby providing them with the ability to continuously assess their surroundings for environmental contaminants and security hazards. PMID:21637863

  6. Simplifying microbial electrosynthesis reactor design

    PubMed Central

    Giddings, Cloelle G. S.; Nevin, Kelly P.; Woodward, Trevor; Lovley, Derek R.; Butler, Caitlyn S.

    2015-01-01

    Microbial electrosynthesis, an artificial form of photosynthesis, can efficiently convert carbon dioxide into organic commodities; however, this process has only previously been demonstrated in reactors that have features likely to be a barrier to scale-up. Therefore, the possibility of simplifying reactor design by both eliminating potentiostatic control of the cathode and removing the membrane separating the anode and cathode was investigated with biofilms of Sporomusa ovata. S. ovata reduces carbon dioxide to acetate and acts as the microbial catalyst for plain graphite stick cathodes as the electron donor. In traditional ‘H-cell’ reactors, where the anode and cathode chambers were separated with a proton-selective membrane, the rates and columbic efficiencies of microbial electrosynthesis remained high when electron delivery at the cathode was powered with a direct current power source rather than with a potentiostat-poised cathode utilized in previous studies. A membrane-less reactor with a direct-current power source with the cathode and anode positioned to avoid oxygen exposure at the cathode, retained high rates of acetate production as well as high columbic and energetic efficiencies. The finding that microbial electrosynthesis is feasible without a membrane separating the anode from the cathode, coupled with a direct current power source supplying the energy for electron delivery, is expected to greatly simplify future reactor design and lower construction costs. PMID:26029199

  7. Influence of dissolved hydrogen on aluminum-lithium alloy fracture behavior

    NASA Technical Reports Server (NTRS)

    Rivet, F. C.; Swanson, R. E.

    1989-01-01

    The objective of this work is to study the effects of dissolved hydrogen on the mechanical properties of 2090 and 2219 alloys. Prior to mechanical testing, potentiostatic and potentiodynamic tests were performed using NaCl/HCl solutions varying in pH from 1.5 to 7.5 (3.5 pct NaCl in deionized water). After analysis of the potentiodynamic curve for each solution, several potentiostatic experiments were conducted for various times (from 10 minutes to several hours) with a cathodic overpotential of 300 mV. These experiments were performed to select charging conditions. It is shown that the fracture of L-S and T-S orientations proceeds via slipping of layers in the S-T direction. The T-S and L-S orientations fractured with substantially higher propagation energy that the L-T and T-L orientations, due in large part to the extensive delamination propagation of the fracture.

  8. Origins of nanoscale damage to glass-sealed platinum electrodes with submicrometer and nanometer size.

    PubMed

    Nioradze, Nikoloz; Chen, Ran; Kim, Jiyeon; Shen, Mei; Santhosh, Padmanabhan; Amemiya, Shigeru

    2013-07-01

    Glass-sealed Pt electrodes with submicrometer and nanometer size have been successfully developed and applied for nanoscale electrochemical measurements such as scanning electrochemical microscopy (SECM). These small electrodes, however, are difficult to work with because they often lose a current response or give a low SECM feedback in current-distance curves. Here we report that these problems can be due to the nanometer-scale damage that is readily and unknowingly made to the small tips in air by electrostatic discharge or in electrolyte solution by electrochemical etching. The damaged Pt electrodes are recessed and contaminated with removed electrode materials to lower their current responses. The recession and contamination of damaged Pt electrodes are demonstrated by scanning electron microscopy and X-ray energy dispersive spectroscopy. The recessed geometry is noticeable also by SECM but is not obvious from a cyclic voltammogram. Characterization of a damaged Pt electrode with recessed geometry only by cyclic voltammetry may underestimate electrode size from a lower limiting current owing to an invalid assumption of inlaid disk geometry. Significantly, electrostatic damage can be avoided by grounding a Pt electrode and nearby objects, most importantly, an operator as a source of electrostatic charge. Electrochemical damage can be avoided by maintaining potentiostatic control of a Pt electrode without internally disconnecting the electrode from a potentiostat between voltammetric measurements. Damage-free Pt electrodes with submicrometer and nanometer sizes are pivotal for reliable and quantitative nanoelectrochemical measurements. PMID:23763642

  9. San copolymer membranes with ion exchangers for Cu(II) removal from synthetic wastewater by electrodialysis.

    PubMed

    Caprarescu, Simona; Corobea, Mihai Cosmin; Purcar, Violeta; Spataru, Catalin Ilie; Ianchis, Raluca; Vasilievici, Gabriel; Vuluga, Zina

    2015-09-01

    Heterogeneous membranes were obtained by using styrene-acrylonitrile copolymer (SAN) blends with low content of ion-exchanger particles (5wt.%). The membranes obtained by phase inversion were used for the removal of copper ions from synthetic wastewater solutions by electrodialytic separation. The electrodialysis was conducted in a three cell unit, without electrolyte recirculation. The process, under potentiostatic or galvanostatic control, was followed by pH and conductivity measurements in the solution. The electrodialytic performance, evaluated in terms of extraction removal degree (rd) of copper ions, was better under potentiostatic control then by the galvanostatic one and the highest (over 70%) was attained at 8V. The membrane efficiency at small ion-exchanger load was explained by the migration of resin particles toward the pores surface during the phase inversion. The prepared membranes were characterized by various techniques i.e. optical microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and differential thermal analysis and contact angle measurements. PMID:26354689

  10. Growth and Etch Rate Study of Low Temperature Anodic Silicon Dioxide Thin Films

    PubMed Central

    Ashok, Akarapu; Pal, Prem

    2014-01-01

    Silicon dioxide (SiO2) thin films are most commonly used insulating films in the fabrication of silicon-based integrated circuits (ICs) and microelectromechanical systems (MEMS). Several techniques with different processing environments have been investigated to deposit silicon dioxide films at temperatures down to room temperature. Anodic oxidation of silicon is one of the low temperature processes to grow oxide films even below room temperature. In the present work, uniform silicon dioxide thin films are grown at room temperature by using anodic oxidation technique. Oxide films are synthesized in potentiostatic and potentiodynamic regimes at large applied voltages in order to investigate the effect of voltage, mechanical stirring of electrolyte, current density and the water percentage on growth rate, and the different properties of as-grown oxide films. Ellipsometry, FTIR, and SEM are employed to investigate various properties of the oxide films. A 5.25 Å/V growth rate is achieved in potentiostatic mode. In the case of potentiodynamic mode, 160 nm thickness is attained at 300 V. The oxide films developed in both modes are slightly silicon rich, uniform, and less porous. The present study is intended to inspect various properties which are considered for applications in MEMS and Microelectronics. PMID:24672287

  11. Fabrication of the CuO/Cu2O heterojunction using an electrodeposition technique for solar cell applications

    NASA Astrophysics Data System (ADS)

    Wijesundera, R. P.

    2010-04-01

    Thin films of n-type cuprous oxide (Cu2O) were potentiostatically electrodeposited on a Ti substrate in an acetate bath. Cu2O thin films were annealed at 500 °C for 30 min in air for growing p-type cupric oxide (CuO) thin films. n-Cu2O thin films were potentiostatically electrodeposited in an acetate bath on Ti/CuO electrodes in order to fabricate the p-CuO/n-Cu2O heterojunction. The structural, morphological and optoelectronic properties of the CuO/Cu2O heterojunction were studied using x-ray diffraction (XRD), scanning electron micrographs (SEMs) and dark and light current-voltage characteristics. XRD and SEM reveal that well-covered single phase polycrystalline Cu2O thin film on the Ti/CuO electrode can be possible at the deposition potential of -550 mV versus the saturated calomel electrode (SCE) in an acetate bath. Photovoltaic characteristics further established the formation of the CuO/Cu2O heterojunction.

  12. TEM investigations on the local microstructure of electrodeposited galfenol nanowires.

    PubMed

    Pohl, D; Damm, C; Pohl, D; Schultz, L; Schlörb, H

    2016-01-22

    The local microstructure of Fe-Ga nanowires is investigated considering dependence on the deposition technique. Using a complexed electrolyte, smooth and homogeneous Fe80Ga20 nanowires are deposited into anodic aluminum oxide templates by either applying pulse potential or potentiostatic deposition technique. At optimized deposition conditions the wires show the desired composition of Fe80±2Ga20±2 without a gradient along the growth direction. Composition distribution, structure and microstructure are examined in detail and reveal only minor differences. Line EELS and crystal lattice measurements reveal a negligible oxygen content for both preparation routines. Neither Fe/Ga oxides nor hydroxides were found. Both potentiostatically deposited as well as pulse deposited nanowires exhibit a preferred 〈110〉orientation, the latter with slightly larger crystals. Different contrast patterns were found by TEM that appear more pronounced in the case of pulse deposited wires. High resolution transmission electron microscopy analysis and comparison of differently prepared focused ion beam lamellas reveal that these contrasts are caused by defects in the alternating potential deposition itself and are not induced during the TEM preparation process. The alternating potential mode causes periodic growth thereby inducing different layers with reduced wire thickness/defects at the layer interfaces. PMID:26651087

  13. TEM investigations on the local microstructure of electrodeposited galfenol nanowires

    NASA Astrophysics Data System (ADS)

    Pohl, D.; Damm, C.; Pohl, D.; Schultz, L.; Schlörb, H.

    2016-01-01

    The local microstructure of Fe-Ga nanowires is investigated considering dependence on the deposition technique. Using a complexed electrolyte, smooth and homogeneous Fe80Ga20 nanowires are deposited into anodic aluminum oxide templates by either applying pulse potential or potentiostatic deposition technique. At optimized deposition conditions the wires show the desired composition of Fe80±2Ga20±2 without a gradient along the growth direction. Composition distribution, structure and microstructure are examined in detail and reveal only minor differences. Line EELS and crystal lattice measurements reveal a negligible oxygen content for both preparation routines. Neither Fe/Ga oxides nor hydroxides were found. Both potentiostatically deposited as well as pulse deposited nanowires exhibit a preferred <110> orientation, the latter with slightly larger crystals. Different contrast patterns were found by TEM that appear more pronounced in the case of pulse deposited wires. High resolution transmission electron microscopy analysis and comparison of differently prepared focused ion beam lamellas reveal that these contrasts are caused by defects in the alternating potential deposition itself and are not induced during the TEM preparation process. The alternating potential mode causes periodic growth thereby inducing different layers with reduced wire thickness/defects at the layer interfaces.

  14. Facile production of thermoelectric bismuth telluride thick films in the presence of polyvinyl alcohol.

    PubMed

    Lei, C; Burton, M R; Nandhakumar, I S

    2016-06-01

    Bismuth telluride is currently the best performing thermoelectric material for room temperature operations in commercial thermoelectric devices. We report the reproducible and facile production of 600 micron thick bismuth telluride (Bi2Te3) layers by low cost and room temperature pulsed and potentiostatic electrodeposition from a solution containing bismuth and tellurium dioxide in 2 M nitric acid onto nickel in the presence of polyvinyl alcohol (PVA). This was added to the electrolyte to promote thick layer formation and its effect on the structure, morphology and composition of the electrodeposits was investigated by SEM and EDX. Well adherent, uniform, compact and stoichiometric n-type Bi2Te3 films with a high Seebeck coefficient of up to -200 μV K(-1) and a high electrical conductivity of up to 400 S cm(-1) resulting in a power factor of 1.6 × 10(-3) W m(-1) K(-2) at film growth rates of 100 μm h(-1) for potentiostatic electrodeposition were obtained. The films also exhibited a well defined hexagonal structure as determined by XRD. PMID:27166737

  15. Corrosion resistance of stressed NiTi and stainless steel orthodontic wires in acid artificial saliva.

    PubMed

    Huang, Her-Hsiung

    2003-09-15

    The purpose of this study was to investigate the corrosion resistance of stressed NiTi and stainless steel orthodontic wires using cyclic potentiodynamic and potentiostatic tests in acid artificial saliva at 37 degrees C. An atomic force microscope was used to measure the 3-D surface topography of as-received wires. Scanning electron microscope observations were carried out before and after the cyclic potentiodynamic tests. The surface chemical analysis was characterized using X-ray photoelectron spectroscopy and Auger electron spectroscopy after the potentiostatic tests. The cyclic potentiodynamic test results showed that the pH had a significant influence on the corrosion parameters of the stressed NiTi and stainless steel wires (p < 0.05). The pitting potential, protection potential, and passive range of stressed NiTi and stainless steel wires decreased on decreasing pH, whereas the passive current density increased on decreasing pH. The load had no significant influence on the above corrosion parameters (p > 0.05). For all pH and load conditions, stainless steel wire showed higher pitting potential and wider passive range than NiTi wire (p < 0.001), whereas NiTi wire had lower passive current density than stainless steel wire (p < 0.001). The corrosion resistance of the stressed NiTi and stainless steel wires was related to the surface characterizations, including surface defect and passive film. PMID:12926035

  16. Development and application of a real-time capacitive sensor.

    PubMed

    Wongkittisuksa, Booncharoen; Limsakul, Chusak; Kanatharana, Proespichaya; Limbut, Warakorn; Asawatreratanakul, Punnee; Dawan, Supaporn; Loyprasert, Suchera; Thavarungkul, Panote

    2011-01-15

    A real-time capacitive sensor based on a potentiostatic step method was developed. It can display in real-time the evoked current waveform, capacitance and the electrical resistance of elements serially connected to the insulation layer on the electrode as a function of time as well as the ohmic resistance of the insulation layer. These features enable the user to observe the association and dissociation of the affinity binding pairs and to evaluate the insulating property of the electrode surface during measurement. The system allows the setting of potential pulse height, pulse interval, gain, filter, and sampling frequency, enabling the system to be more flexible. The performance of the system was firstly evaluated with equivalent circuits. Under suitable parameter settings it provided good accuracy of both the capacitance and resistance. Using the affinity binding pair of human serum albumin (HSA) and anti human serum albumin (anti-HSA) the measured capacitance change was used for the direct detection of HSA. The developed system provided the same sensitivity as the commercially available potentiostat (P>0.05). The proposed system was then applied to analyse HSA in real urine samples and the results agreed well with the immunoturbidimetric assay (P>0.05). The proposed system can be applied for capacitance measurement to directly detect other target analytes using different affinity binding pairs. Other applications such as kinetics analysis of the interaction between affinity bindings, thickness analysis, and the study of the insulation property of the modified layer are also promising. PMID:21087852

  17. Electrochemical extraction of neodymium by co-reduction with aluminum in LiCl-KCl molten salt

    NASA Astrophysics Data System (ADS)

    Yan, Yong-De; Xu, Yan-Lu; Zhang, Mi-Lin; Xue, Yun; Han, Wei; Huang, Ying; Chen, Qiong; Zhang, Zhi-Jian

    2013-02-01

    The electrochemical behavior of Nd(III) ions in LiCl-KCl and LiCl-KCl-AlCl3 melts on a Mo electrode at 723 K was studied by various electrochemical techniques. The results showed that Nd(III) ions are reduced to Nd(0) through two consecutive steps, and the underpotential deposition of neodymium on pre-deposited Al electrode formed two kinds of Al-Nd intermetallic compounds in LiCl-KCl-AlCl3 solutions. The electrochemical extraction of neodymium was carried out in LiCl-KCl-AlCl3 melts on a Mo electrode at 873 K by potentiostatic and galvanostatic electrolysis. The extraction efficiency was 99.25% after potentiostatic electrolysis for 30 h. Al-Li-Nd bulk alloy was obtained by galvanostatic electrolysis. X-ray diffraction (XRD) suggested that Al2Nd and Al3Nd phases were formed in Al-Li-Nd alloy. The microstructure and micro-zone chemical analysis of Al-Li-Nd alloy were characterized by scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), respectively.

  18. Electrochemical behaviour of silver in borate buffer solutions

    NASA Astrophysics Data System (ADS)

    Zaky, Ayman M.; Assaf, Fawzi H.; Abd El Rehim, Sayed S.; Mohamed, Basheer M.

    2004-01-01

    The electrochemical behaviour of Ag in aqueous 0.15 M borax and 0.15 M boric acid buffer solution was studied under various conditions using cyclic voltammetry and potentiostatic techniques. It was found that the anodic polarization curve of Ag in borate buffer solution was characterized by the appearance of two potential regions, active and passive, prior to the oxygen evolution reaction. The active potential region was characterized by the appearance of three anodic peaks, the first two peaks A 1 and A 2 correspond to the oxidation of Ag and formation of [Ag(OH) 2] - soluble compound and a passive film of Ag 2O on the electrode surface. The third anodic peak corresponds to the conversion of both [Ag(OH) 2] - and Ag 2O to Ag 2O 2. X-ray diffraction patterns confirmed the existence of Ag 2O and Ag 2O 2 passive layers on the electrode surface potentiodynamically polarized up to 800 mV. Potentiostatic current transient measurements showed that the formation of Ag 2O and Ag 2O 2 involves a nucleation and growth mechanism under diffusion control.

  19. Aqueous corrosion characteristics and corrosion-related cracking susceptibilities of Fe sub 3 Al-type iron aluminides

    SciTech Connect

    Buchanan, R.A.; Kim, J.G. . Dept. of Materials Science and Engineering)

    1991-04-01

    In certain fossil-energy applications, iron aluminides may be subjected to ambient-temperature aqueous corrosion conditions. In the present project, the aqueous corrosion characteristics and the cracking tendencies under aqueous-corrosion conditions were studied. In these studies, electrochemical, immersion and electrochemical-mechanical evaluation techniques were employed. For a range of iron-aluminide compositions, cyclic anodic polarization tests were conducted in a number of electrolytes to provide information on anodic dissolution characteristics including tendencies for either active uniform corrosion, localized corrosion, or passivation. Average corrosion penetration rates were determined by application of Tafel methods or the polarization-resistance method in combination with Faraday's law. Immersion test methods were employed to verify corrosion behavior as determined by electrochemical methods and to evaluate localized-corrosion initiation times. U-bend corrosion tests were conducted at open-circuit corrosion potentials and at potentiostatically-controlled anodic and cathodic potentials to investigate the cracking tendencies of selected iron aluminides and to provide information on the cracking mechanism. And finally, slow-strain-rate corrosion tests were conducted at open-circuit and potentiostatically-controlled cathodic potentials to study the ductility response as related to cracking tendencies and the mechanism responsible. 32 refs., 19 figs., 11 tabs.

  20. An electrochromic film device to teach polymer electrochemical physics

    NASA Astrophysics Data System (ADS)

    Huang, Mei-Rong; Tao, Tao; Li, Xin-Gui; Gong, Qian-Cheng

    2007-09-01

    We discuss the background associated with an electrochromic device that can reversibly change its color and optical density at a specific potential. We discuss the underlying science needed to make a new polyaniline (PAN)/polyvinyl alcohol(PVA) electrochromic composite film on an indium-tin oxide (ITO) conducting glass by electropolymerization and describe a reversible redox transition of the PAN. The experiment gives students an opportunity to fabricate an electrochromic device containing PAN, one of the most important conducting polymers. The experimental conditions are flexible so that each group of students can construct their own electrochromic device with particular behavior. Two techniques for polymerizing the PAN and three methods of demonstrating the electrochromism are given, depending on the available apparatus. A sophisticated three-electrode potentiostat or a crude apparatus containing a battery, wire, a variable resistor, and a voltage meter is used to synthesize the PAN deposit. The electrochromic property is repetitively observed by reversibly changing the applied potentials on the device. A potentiostatic apparatus, a single flashlight battery, or a flashlight battery accompanied by a variable resistor allows students to observe multicolor electrochromism. The experiments significantly enhance students' understanding of polymer chemicophysics principles and their appreciation of novel variable colorful films. The experiments are safe and easy to perform, provided that appropriate precautions are taken.

  1. Amperometric measurements of ethanol on paper with a glucometer.

    PubMed

    Wu, Grace; Zaman, Muhammad H

    2015-03-01

    Recent advances in electrochemical analysis on filter paper exemplify the versatility of this substrate for high performance testing. Its low-cost, light-weight, and environmentally friendly properties make it particularly attractive for applications in addressing health and environmental safety needs in low-resource settings and developing countries. However, the main drawback to sensitive electrochemical testing is the use of a potentiostat, a bench-top instrument that is extremely expensive, thereby negating the some of the benefits of paper-based devices. Hence there is a need to develop paper-devices for use with handheld, portable device readers that can extract quantitative readouts. In this study, we developed a method to use micro-paper electrochemical devices, or µPEDs, with a glucose meter, which are used for personal monitoring of blood glucose levels. Ethanol was chosen as a model target analyte due to its importance in the global issue of road safety. µPEDs were simple in design and could be tested with a potentiostat. We observed that inclusion of the stabilizer trehalose was critical to preparing µPEDs for later analysis. In addition, an NAD(+)-dependent enzyme was used to impart selectivity to the biosensor, which also represents a class of enzymes with targets relevant to the health and food industry. PMID:25618657

  2. Three-Dimensional Growth of Li2S in Lithium-Sulfur Batteries Promoted by a Redox Mediator.

    PubMed

    Gerber, Laura C H; Frischmann, Peter D; Fan, Frank Y; Doris, Sean E; Qu, Xiaohui; Scheuermann, Angelique M; Persson, Kristin; Chiang, Yet-Ming; Helms, Brett A

    2016-01-13

    During the discharge of a lithium-sulfur (Li-S) battery, an electronically insulating 2D layer of Li2S is electrodeposited onto the current collector. Once the current collector is enveloped, the overpotential of the cell increases, and its discharge is arrested, often before reaching the full capacity of the active material. Guided by a new computational platform known as the Electrolyte Genome, we advance and apply benzo[ghi]peryleneimide (BPI) as a redox mediator for the reduction of dissolved polysulfides to Li2S. With BPI present, we show that it is now possible to electrodeposit Li2S as porous, 3D deposits onto carbon current collectors during cell discharge. As a result, sulfur utilization improved 220% due to a 6-fold increase in Li2S formation. To understand the growth mechanism, electrodeposition of Li2S was carried out under both galvanostatic and potentiostatic control. The observed kinetics under potentiostatic control were modeled using modified Avrami phase transformation kinetics, which showed that BPI slows the impingement of insulating Li2S islands on carbon. Conceptually, the pairing of conductive carbons with BPI can be viewed as a vascular approach to the design of current collectors for energy storage devices: here, conductive carbon "arteries" dominate long-range electron transport, while BPI "capillaries" mediate short-range transport and electron transfer between the storage materials and the carbon electrode. PMID:26691496

  3. Metal chelate catalysts for fuel cells

    NASA Astrophysics Data System (ADS)

    Darby, R.; White, R.; Yamana, M.; Tsutsue, M.

    1981-07-01

    A variety of metal chelates were synthesized and evaluated for their activity as oxygen cathode electrocatalysts in strong acidic electrolytes. It was found that Cobalt tetraazaanulene (CoTAA) and iron phthalocyanine (FePc) exhibit the best activity of all the metal chelates synthesized, but have very limited stability. The proposed solution to this problem is the synthesis of polymeric forms of these chelates, with comparable active and considerably greater stability than the monomers. Three methods for stability testing were developed: (1) Potentiostatic, with periodic measurement of the current potential characteristic; (2) potentiostatic, with continuous monitoring of the current, and; (3) galvanostatic, with continuous monitoring of potential. Each method provides a good evaluation of activity versus time, and the method to be used depends upon the objective of the test. A polymeric form of Co(TAA) was synthesized by means of an acetylene terminated monomer, which in turn was made via a Co(TAA)Br2 intermediate. The activity of the polymer was found to be comparable to that of Co(TAA) monomer, and significantly greater than that of either the stacked or sheet polymeric forms of Cobalt tetraphenylporphrine (CoTPP) previously synthesized and tested.

  4. In situ electrochemical investigation of tungsten electrochemical behavior during chemical mechanical polishing

    SciTech Connect

    Stein, D.J.; Cecchi, J.L.; Hetherington, D.; Guilinger, T.

    1998-09-01

    The electrochemical behavior of tungsten during chemical mechanical polishing (CMP) was observed in order to investigate a proposed blanket passivation and abrasion mechanism for tungsten removal. The experiments were performed in a cell that allowed electrochemical measurements to be made during polish. Polish rates were determined from the same samples used in the cell. Alumina-based polish slurries containing potassium iodate, ferric nitrate, or ammonium persulfate were used. DC polarization experiments show no evidence of passive film formation on the tungsten during polish. Tungsten oxidation rates measured during polish account for removal rates that are 1 to 2 orders of magnitude below the measured polish rate. Values of the charge-transfer resistance (measured by ac impedance spectroscopy) during polish are 1 to 2 orders of magnitude higher than expected from the polish rate, thus corroborating the dc-based data. Polish rates under potentiostatic conditions were also measured. The current required to maintain the metal anodic of the open-circuit potential is well below the current expected from measured polish rates, assuming complete oxidation of the tungsten. The polish rate during cathodic potentiostatic conditions ({minus}0.5 V with regard to the open-circuit potential) was similar to the polish rate at open circuit. The authors conclude that the formation of a blanket passive layer does not significantly contribute to tungsten removal during CMP.

  5. Cathodic processes of neodymium(iii) in LiF-NdF3-Nd2O3 melts.

    PubMed

    Huang, Chao; Liu, Xiaolong; Gao, Yuan; Liu, Shizhe; Li, Bing

    2016-08-15

    In this paper, cyclic voltammetry and square wave voltammetry are applied to characterize the cathode processes of neodymium ions on a W electrode in LiF-NdF3 melts with or without the metal Nd. The results indicate that neodymium ions in the LiF-NdF3 (2 wt%) melt are reduced in two steps, i.e. Nd(3+) → Nd(2+) and Nd(2+) → Nd(0), corresponding to starting reduction potentials of 0.35 V vs. Li(+)/Li and 0.1 V vs. Li(+)/Li, respectively. The Nd(3+) → Nd(2+) process is controlled by mass transfer and the Nd(2+) → Nd(0) process is controlled by both an interfacial step and mass transfer. But in the LiF-NdF3 melt with excess metal Nd equilibrium, the kinetics of the above two processes are controlled by mass transfer. After potentiostatic electrolysis at 0.35 V in the LiF-NdF3-Nd2O3 melt NdF2 is formed on the Mo cathode, and metallic Nd is obtained by potentiostatic electrolysis at 0.1 V in the LiF-NdF3-Nd2O3-Nd melt, which validates the above electrochemical reduction results. PMID:27197114

  6. Sensitive Bioanalysis Based on in-Situ Droplet Anodic Stripping Voltammetric Detection of CdS Quantum Dots Label after Enhanced Cathodic Preconcentration.

    PubMed

    Qin, Xiaoli; Wang, Linchun; Xie, Qingji

    2016-01-01

    We report a protocol of CdS-labeled sandwich-type amperometric bioanalysis with high sensitivity, on the basis of simultaneous chemical-dissolution/cathodic-enrichment of the CdS quantum dot biolabel and anodic stripping voltammetry (ASV) detection of Cd directly on the bioelectrode. We added a microliter droplet of 0.1 M aqueous HNO₃ to dissolve CdS on the bioelectrode and simultaneously achieved the potentiostatic cathodic preconcentration of Cd by starting the potentiostatic operation before HNO₃ addition, which can largely increase the ASV signal. Our protocol was used for immunoanalysis and aptamer-based bioanalysis of several proteins, giving limits of detection of 4.5 fg·mL(-1) for human immunoglobulin G, 3.0 fg·mL(-1) for human carcinoembryonic antigen (CEA), 4.9 fg·mL(-1) for human α-fetoprotein (AFP), and 0.9 fM for thrombin, which are better than many reported results. The simultaneous and sensitive analysis of CEA and AFP at two screen-printed carbon electrodes was also conducted by our protocol. PMID:27563894

  7. A simple approach for producing colloidal noble metal nanocrystals: Alternating voltage induced electrochemical synthesis

    NASA Astrophysics Data System (ADS)

    McCann, Kevin

    Intense research has been focused on developing bottom-up nanocrystal synthesis techniques to obtain nanocrystals with sophisticated compositions and enhanced perfomances. Three popular methods are: 1) the reduction of metal complex ions or molecules with selected reducing agents, 2) the decomposition of metal compounds at elevated temperatures, and 3) the electrochemical reduction of metal ions using specialized potentiostats. The first two require expensive metal salt precursors while the last requires specialized potentiostats and either employ a single sacrificial electrode or metal salt precursors. To resolve these issues, we have focused on a facile and generic approach to generate nanocrystals by an alternating voltage induced electrochemical synthesis (AVIES) method. Nanocrystals are produced when an alternating voltage is applied by a common laboratory transformer to two sacrificial electrodes that are inserted in an electrolyte solution containing capping ligands. This work focuses on the ability of the AVIES approach to synthesize Au, Pd, and Pt noble metal nanocrystals. The nanocrystals synthesized were found to be dependent on the electrolyte identity, capping ligand, applied voltage, reaction temperature. The ability of AVIES to produce alloyed nanocrystals starting with alloyed electrodes will be discussed. The AVIES approach requires neither expensive metal compounds nor specialized instruments, is environmentally benign, and can be easily adoptable to any research lab.

  8. Preparation of corrosion-resistant and conductive trivalent Cr-C coatings on 304 stainless steel for use as bipolar plates in proton exchange membrane fuel cells by electrodeposition

    NASA Astrophysics Data System (ADS)

    Wang, Hsiang-Cheng; Sheu, Hung-Hua; Lu, Chen-En; Hou, Kung-Hsu; Ger, Ming-Der

    2015-10-01

    In this study, Cr-C-coated bipolar plates are produced by electroplating on the SS304 plates with a machined flow channel. The resulting plates were tested using potentiodynamic and potentiostatic measurements in simulated PEMFC environments, which show that the bipolar plate coated with Cr-C exhibited good anticorrosion performance. The corrosive current density of the Cr-C coating formed for a plating time of 10 min for 10 h exhibits a low stable value of 1.51 × 10-10 A/cm2 during the potentiostatic test in a 0.5 M H2SO4 + 2 ppm HF solution at 70 °C with an air purge, indicating that the Cr-C coating plated for 10 min is stable in a cathode environment. The interfacial contact resistance (ICR) of the bipolar plate with the Cr-C coating clearly improved, presenting an ICR of 19.52 mΩ cm2 at a pressure of 138 N/cm2. The results from scanning electron microscopy (SEM) and ICR before and after the corrosion tests indicate that the bipolar plate with the Cr-C coating is electrochemically stable. In this study, the maximum power density (212.41 mW/cm2) is obtained at a cell temperature of 80 °C and a gas flow rate of 300 standard cubic centimeters per minute (sccm) when Cr-C coated SS304 bipolar plates were used.

  9. Synthesis of mesoporous carbon-silica-polyaniline and nitrogen-containing carbon-silica films and their corrosion behavior in simulated proton exchange membrane fuel cells environment

    NASA Astrophysics Data System (ADS)

    Wang, Tao; He, Jianping; Sun, Dun; Guo, Yunxia; Ma, Yiou; Hu, Yuan; Li, Guoxian; Xue, Hairong; Tang, Jing; Sun, Xin

    In this study, polyaniline is deposited onto mesoporous carbon-silica-coated 304 stainless steel using electropolymerization method. Variation of the electropolymerization time and applied potential can affect the growth of polyaniline, and lead to different structural and electrochemical properties of the films. Nitrogen-containing groups are successfully introduced onto the mesoporous carbon-silica film by pyrolyzing treatment under N 2 atmosphere and the electrical conductivity is improved observably compared with the carbon-silica film. The electrochemical properties of the mesoporous carbon-silica-polyaniline films and nitrogen-containing carbon-silica composite films are examined by using potentiodynamic polarization, potentiostatic polarization and electrochemical impedance spectroscopy. The corrosion tests in 0.5 M H 2SO 4 system display that the carbon-silica-polyaniline films show the optimal protective performance. However, according to potentiostatic polarization process, nitrogen-containing carbon-silica film with a water contact angle 95° is extremely stable and better for the protection of stainless steel in simulated fuel cell environment compared to carbon-silica-polyaniline film. Therefore, the nitrogen-containing carbon-silica-coated 304 stainless steel is a promising candidate for bipolar plate materials in PEMFCs.

  10. Corrosion behaviour of austenitic stainless steel as a function of methanol concentration for direct methanol fuel cell bipolar plate

    NASA Astrophysics Data System (ADS)

    Wang, Lixia; Kang, Bin; Gao, Na; Du, Xiao; Jia, Linan; Sun, Juncai

    2014-05-01

    The corrosion behaviour of an AISI 304 stainless steel (304 SS) is investigated in aqueous acid methanol solutions (0.5 M H2SO4 + 2 ppm HF + x M CH3OH, x = 0, 1, 5, 10 and 20) at 50 °C to simulate the varied anodic operating conditions of direct methanol fuel cells. Electrochemical measurements including potentiodynamic polarisation, potentiostatic polarisation and electrochemical impedance spectroscopy tests, are employed to analyse the corrosion behaviour. The results reveal that the corrosion resistance of 304 SS is enhanced in solutions with higher methanol content. Scanning electron microscopy and inductively coupled plasma atomic emission spectrometry data indicate that the surface corrosion on 304 SS is alleviated when the methanol concentration is increased. According to the X-ray photoelectron spectroscopy and Mott-Schottky analyses, the passive films formed on the 304 SS after potentiostatic tests in all the test solutions are composed of a duplex electronic structure with an external n-type semiconductor layer and an internal p-type semiconductor layer. Further analyses of the surface conductivity conducted by measuring the interfacial contact resistance between the 304 SS and carbon paper reveal that the passive film formed in the solution with higher methanol content exhibits lower conductivity.

  11. Electrochemical behaviour and surface conductivity of niobium carbide-modified austenitic stainless steel bipolar plate

    NASA Astrophysics Data System (ADS)

    Wang, Lixia; Sun, Juncai; Kang, Bin; Li, Song; Ji, Shijun; Wen, Zhongsheng; Wang, Xiaochun

    2014-01-01

    A niobium carbide diffusion layer with a cubic NbC phase surface layer (∼6 μm) and a Nb and C diffusion subsurface layer (∼1 μm) is fabricated on the surface of AISI 304 stainless steel (304 SS) bipolar plate in a proton exchange membrane fuel cell (PEMFC) using plasma surface diffusion alloying. The electrochemical behaviour of the niobium carbide diffusion-modified 304 SS (Nb-C 304 SS) is investigated in simulated PEMFC environments (0.5 M H2SO4 and 2 ppm HF solution at 80 °C). Potentiodynamic, potentiostatic polarisation and electrochemical impedance spectroscopy measurements reveal that the niobium carbide diffusion layer considerably improves the corrosion resistance of 304 SS compared with untreated samples. The corrosion current density of Nb-C 304 SS is maintained at 0.058 μA cm-2 and 0.051 μA cm-2 under simulated anodic and cathodic conditions, respectively. The interfacial contact resistance of Nb-C 304 SS is 8.47 mΩ cm2 at a compaction force of 140 N cm-2, which is significantly lower than that of the untreated sample (100.98 mΩ cm2). Moreover, only a minor increase in the ICR of Nb-C 304 SS occurs after 10 h potentiostatic tests in both cathodic and anodic environments.

  12. Aerated Shewanella oneidensis in continuously fed bioelectrochemical systems for power and hydrogen production.

    PubMed

    Rosenbaum, Miriam; Cotta, Michael A; Angenent, Largus T

    2010-04-01

    We studied the effects of aeration of Shewanella oneidensis on potentiostatic current production, hydrogen production in a microbial electrolysis cell, and electric power generation in a microbial fuel cell (MFC). The potentiostatic performance of aerated S. oneidensis was considerably enhanced to a maximum current density of 0.45 A/m(2) or 80.3 A/m(3) (mean: 0.34 A/m(2), 57.2 A/m(3)) compared to anaerobically grown cultures. Biocatalyzed hydrogen production rates with aerated S. oneidensis were studied within the applied potential range of 0.3-0.9 V and were highest at 0.9 V with 0.3 m(3) H(2)/m(3) day, which has been reported for mixed cultures, but is approximately 10 times higher than reported for an anaerobic culture of S. oneidensis. Aerated MFC experiments produced a maximum power density of 3.56 W/m(3) at a 200-Omega external resistor. The main reasons for enhanced electrochemical performance are higher levels of active biomass and more efficient substrate utilization under aerobic conditions. Coulombic efficiencies, however, were greatly reduced due to losses of reducing equivalents to aerobic respiration in the anode chamber. The next challenge will be to optimize the aeration rate of the bacterial culture to balance between maximization of bacterial activation and minimization of aerobic respiration in the culture. PMID:19998276

  13. Post-CMOS fabrication of Working Electrodes for On-Chip Recordings of Transmitter Release

    PubMed Central

    Ayers, Sunitha; Berberian, Khajak; Gillis, Kevin D.; Lindau, Manfred; Minch, Bradley A.

    2010-01-01

    The release of neurotransmitters and hormones from secretory vesicles plays a fundamental role in the function of the nervous system including neuronal communication. High-throughput testing of drugs modulating transmitter release is becoming an increasingly important area in the fields of cell biology, neurobiology, and neurology. Carbon-fiber amperometry, provides high-resolution measurements of amount and time course of transmitter release from single vesicles, and their modulation by drugs and molecular manipulations. However, such methods do not allow the rapid collection of data from a large number of cells. To allow such testing, we have developed a CMOS potentiostat circuit that can be scaled to a large array. In this paper, we present two post-CMOS fabrication methods to incorporate the electrochemical electrode material. We demonstrate by proof of principle the feasibility of on-chip electrochemical measurements of dopamine, and catecholamine release from adrenal chromaffin cells. The measurement noise is consistent with the typical electrode noise in recordings with external amplifiers. The electronic noise of the potentiostat in recordings with 400 μs integration time is ~0.11 pA and is negligible compared to the inherent electrode noise. PMID:20514361

  14. Simplifying microbial electrosynthesis reactor design.

    PubMed

    Giddings, Cloelle G S; Nevin, Kelly P; Woodward, Trevor; Lovley, Derek R; Butler, Caitlyn S

    2015-01-01

    Microbial electrosynthesis, an artificial form of photosynthesis, can efficiently convert carbon dioxide into organic commodities; however, this process has only previously been demonstrated in reactors that have features likely to be a barrier to scale-up. Therefore, the possibility of simplifying reactor design by both eliminating potentiostatic control of the cathode and removing the membrane separating the anode and cathode was investigated with biofilms of Sporomusa ovata. S. ovata reduces carbon dioxide to acetate and acts as the microbial catalyst for plain graphite stick cathodes as the electron donor. In traditional 'H-cell' reactors, where the anode and cathode chambers were separated with a proton-selective membrane, the rates and columbic efficiencies of microbial electrosynthesis remained high when electron delivery at the cathode was powered with a direct current power source rather than with a potentiostat-poised cathode utilized in previous studies. A membrane-less reactor with a direct-current power source with the cathode and anode positioned to avoid oxygen exposure at the cathode, retained high rates of acetate production as well as high columbic and energetic efficiencies. The finding that microbial electrosynthesis is feasible without a membrane separating the anode from the cathode, coupled with a direct current power source supplying the energy for electron delivery, is expected to greatly simplify future reactor design and lower construction costs. PMID:26029199

  15. Waste Water Derived Electroactive Microbial Biofilms: Growth, Maintenance, and Basic Characterization

    PubMed Central

    Gimkiewicz, Carla; Harnisch, Falk

    2013-01-01

    The growth of anodic electroactive microbial biofilms from waste water inocula in a fed-batch reactor is demonstrated using a three-electrode setup controlled by a potentiostat. Thereby the use of potentiostats allows an exact adjustment of the electrode potential and ensures reproducible microbial culturing conditions. During growth the current production is monitored using chronoamperometry (CA). Based on these data the maximum current density (jmax) and the coulombic efficiency (CE) are discussed as measures for characterization of the bioelectrocatalytic performance. Cyclic voltammetry (CV), a nondestructive, i.e. noninvasive, method, is used to study the extracellular electron transfer (EET) of electroactive bacteria. CV measurements are performed on anodic biofilm electrodes in the presence of the microbial substrate, i.e. turnover conditions, and in the absence of the substrate, i.e. nonturnover conditions, using different scan rates. Subsequently, data analysis is exemplified and fundamental thermodynamic parameters of the microbial EET are derived and explained: peak potential (Ep), peak current density (jp), formal potential (Ef) and peak separation (ΔEp). Additionally the limits of the method and the state-of the art data analysis are addressed. Thereby this video-article shall provide a guide for the basic experimental steps and the fundamental data analysis. PMID:24430581

  16. Design of a miniaturized electrochemical instrument for in-situ O2 monitoring

    NASA Astrophysics Data System (ADS)

    Colomer-Farrarons, Jordi; Miribel-Català, Pedro L.; Samitier, Josep; Arundell, Martin; Rodríguez, Ivón

    2009-05-01

    The authors are working toward the design of a device for the detection of oxygen, following a discrete and an integrated instrumentation implementation. The discrete electronics are also used for preliminary analysis, to confirm the validity of the conception of system, and its set-up would be used in the characterization of the integrated device, waiting for the chip fabrication. This paper presents the design of a small and portable potentiostat integrated with electrodes, which is cheap and miniaturized, which can be applied for on-site measurements for the simultaneous detection of O2 and temperature in water systems. As a first approach a discrete PCB has been designed based on commercial discrete electronics and specific oxygen sensors. Dissolved oxygen concentration (DO) is an important index of water quality and the ability to measure the oxygen concentration and temperature at different positions and depths would be an important attribute to environmental analysis. Especially, the objective is that the sensor and the electronics can be integrated in a single encapsulated device able to be submerged in environmental water systems and be able to make multiple measurements. For our proposed application a small and portable device is developed, where electronics and sensors are miniaturized and placed in close proximity to each other. This system would be based on the sensors and electronics, forming one module, and connected to a portable notebook to save and analyze the measurements on-line. The key electronics is defined by the potentiostat amplifier, used to fix the voltage between the Working (WE) and Reference (RE) electrodes following an input voltage (Vin). Vin is a triangular signal, programmed by a LabViewinterface, which is also used to represent the CV transfers. To obtain a smaller and compact solution the potentiostat amplifier has also been integrated defining a full custom ASIC amplifier, which is in progress, looking for a point

  17. The alkaline zinc electrode as a mixed potential system

    NASA Technical Reports Server (NTRS)

    Fielder, W. L.

    1979-01-01

    Cathodic and anodic processes for the alkaline zinc electrode in 0.01 molar zincate electrolyte (9 molar hydroxide) were investigated. Cyclic voltammograms and current-voltage curves were obtained by supplying pulses through a potentiostat to a zinc rotating disk electrode. The data are interpreted by treating the system as one with a mixed potential; the processes are termed The zincate and corrosion reactions. The relative proportions of the two processes vary with the supplied potential. For the cathodic region, the cathodic corrosion process predominates at higher potentials while both processes occur simultaneously at a lower potential (i.e., 50 mV). For the anodic region, the anodic zincate process predominates at higher potentials while the anodic corrosion process is dominant at lower potential (i.e., 50 mV) if H2 is present.

  18. Microfluidic in-channel multi-electrode platform for neurotransmitter sensing

    NASA Astrophysics Data System (ADS)

    Kara, A.; Mathault, J.; Reitz, A.; Boisvert, M.; Tessier, F.; Greener, J.; Miled, A.

    2016-03-01

    In this project we present a microfluidic platform with in-channel micro-electrodes for in situ screening of bio/chemical samples through a lab-on-chip system. We used a novel method to incorporate electrochemical sensors array (16x20) connected to a PCB, which opens the way for imaging applications. A 200 μm height microfluidic channel was bonded to electrochemical sensors. The micro-channel contains 3 inlets used to introduce phosphate buffer saline (PBS), ferrocynide and neurotransmitters. The flow rate was controlled through automated micro-pumps. A multiplexer was used to scan electrodes and perform individual cyclic voltammograms by a custom potentiostat. The behavior of the system was linear in terms of variation of current versus concentration. It was used to detect the neurotransmitters serotonin, dopamine and glutamate.

  19. A straightforward implementation of in situ solution electrochemical ¹³C NMR spectroscopy for studying reactions on commercial electrocatalysts: ethanol oxidation.

    PubMed

    Huang, L; Sorte, E G; Sun, S-G; Tong, Y Y J

    2015-05-11

    Identifying and quantifying electrocatalytic-reaction-generated solution species, be they reaction intermediates or products, are highly desirable in terms of understanding the associated reaction mechanisms. We report herein a straightforward implementation of in situ solution electrochemical (13)C NMR spectroscopy for the first time that enables in situ studies of reactions on commercial fuel-cell electrocatalysts (Pt and PtRu blacks). Using ethanol oxidation reaction (EOR) as a working example, we discovered that (1) the complete oxidation of ethanol to CO2 only took place dominantly at the very beginning of a potentiostatic chronoamperometric (CA) measurement and (2) the PtRu had a much higher activity in catalysing oxygen insertion reaction that leads to acetic acid. PMID:25868425

  20. A microfluidic paper-based electrochemical biosensor array for multiplexed detection of metabolic biomarkers

    NASA Astrophysics Data System (ADS)

    Zhao, Chen; Thuo, Martin M.; Liu, Xinyu

    2013-10-01

    Paper-based microfluidic devices have emerged as simple yet powerful platforms for performing low-cost analytical tests. This paper reports a microfluidic paper-based electrochemical biosensor array for multiplexed detection of physiologically relevant metabolic biomarkers. Different from existing paper-based electrochemical devices, our device includes an array of eight electrochemical sensors and utilizes a handheld custom-made electrochemical reader (potentiostat) for signal readout. The biosensor array can detect several analytes in a sample solution and produce multiple measurements for each analyte from a single run. Using the device, we demonstrate simultaneous detection of glucose, lactate and uric acid in urine, with analytical performance comparable to that of the existing commercial and paper-based platforms. The paper-based biosensor array and its electrochemical reader will enable the acquisition of high-density, statistically meaningful diagnostic information at the point of care in a rapid and cost-efficient way.

  1. Enhanced removal of 8-quinolinecarboxylic acid in an activated carbon cloth by electroadsorption in aqueous solution.

    PubMed

    López-Bernabeu, S; Ruiz-Rosas, R; Quijada, C; Montilla, F; Morallón, E

    2016-02-01

    The effect of the electrochemical treatment (potentiostatic treatment in a filter-press electrochemical cell) on the adsorption capacity of an activated carbon cloth (ACC) was analyzed in relation with the removal of 8-quinolinecarboxylic acid pollutant from water. The adsorption capacity of an ACC is quantitatively improved in the presence of an electric field (electroadsorption process) reaching values of 96% in comparison to 55% in absence of applied potential. In addition, the cathodic treatment results in higher removal efficiencies than the anodic treatment. The enhanced adsorption capacity has been proved to be irreversible, since the removed compound remains adsorbed after switching the applied potential. The kinetics of the adsorption processes is also improved by the presence of an applied potential. PMID:26433936

  2. Synthesis and thermoelectric/electrical characterization of electrodeposited Sb{sub x}Te{sub y} thin films

    SciTech Connect

    Lim, Jae-Hong; Park, MiYeong; Lim, Dong-Chan; Myung, Nosang V.; Lee, Jung-Ho; Jeong, Young-Keun; Yoo, Bongyoung; Lee, Kyu Hwan

    2012-10-15

    Sb{sub x}Te{sub y} films were potentiostatically electrodeposited from acidic nitric baths at room temperature by controlling the applied potential. Near-stoichiometric Sb{sub 2}Te{sub 3} thin films were obtained at applied potentials between −0.15 and −0.30 V vs. saturated calomel electrode (SCE). Post-annealing in a reducing environment resulted in an improvement in the crystal structure without the evaporation of the Te element. This result was indicated by a significant reduction in the electrical resistance and decrease in the FWHM of the main diffraction peaks. The power factor (σS{sup 2}) increased from 44.2 to 372.1 μW/m K{sup 2} after annealing at 473 K.

  3. Improvement of corrosion resistance of Nisbnd Mo alloy coatings: Effect of heat treatment

    NASA Astrophysics Data System (ADS)

    Mousavi, R.; Bahrololoom, M. E.; Deflorian, F.; Ecco, L.

    2016-02-01

    In this paper, Nisbnd Mo alloy coatings were deposited from bath containing sodium citrate, nickel sulphate, and sodium molybdate. Essentially, this work is divided into two mains parts: (i) the optimization on the coatings deposition parameters and (ii) the effect of the heat treatment. Polarization curves and electrochemical impedance spectroscopy were acquired using potentiostat/galvanostat and a frequency response analyzer, respectively. Morphology and chemical composition of the coatings were investigated by scanning electron microscopy and energy dispersive spectroscopy, respectively. Polarization curves at different condition revealed that electroplating at temperature 40 oC, pH 9 provides a dense coating with high efficiency. Following the optimization of the deposition parameters, the coatings were annealed at 200, 400, and 600 oC for 25 min. The results showed that the coatings obtained at temperature 40 oC, pH 9, and annealing at 600 oC has the highest corrosion resistance and microhardness.

  4. Electro-active sensor, method for constructing the same; apparatus and circuitry for detection of electro-active species

    NASA Technical Reports Server (NTRS)

    Buehler, Martin (Inventor)

    2009-01-01

    An electro-active sensor includes a nonconductive platform with a first electrode set attached with a first side of a nonconductive platform. The first electrode set serves as an electrochemical cell that may be utilized to detect electro-active species in solution. A plurality of electrode sets and a variety of additional electrochemical cells and sensors may be attached with the nonconductive platform. The present invention also includes a method for constructing the aforementioned electro-active sensor. Additionally, an apparatus for detection and observation is disclosed, where the apparatus includes a sealable chamber for insertion of a portion of an electro-active sensor. The apparatus allows for monitoring and detection activities. Allowing for control of attached cells and sensors, a dual-mode circuitry is also disclosed. The dual-mode circuitry includes a switch, allowing the circuitry to be switched from a potentiostat to a galvanostat mode.

  5. In vitro biocompatibility response of Ti-Zr-Si thin film metallic glasses

    NASA Astrophysics Data System (ADS)

    Ke, J. L.; Huang, C. H.; Chen, Y. H.; Tsai, W. Y.; Wei, T. Y.; Huang, J. C.

    2014-12-01

    In this study, the bio-electrochemical response of the Ti-Zr-Si thin film metallic glasses (TFMGs) in simulated body fluid with different contents of titanium is measured via potentiostat. According to the results of bio-corrosion potential and current, as well as the polarization resistance, it is concluded that the Ti66Zr25Si9 TFMGs possess the highest bio-electrochemical resistance. With increasing content of titanium, the corrosion resistance becomes progressively higher. The passive current results reveal that amorphous alloys can form a more protective and denser passive film on the metallic glass surface than the crystalline materials. In addition, the mechanical performance of the Ti-Zr-Si TFMGs is better than the crystalline counterparts. As a result, the Ti-based TFMGs are considered to be potential materials for bio-coating applications.

  6. Relation between energetic and utilization coefficients in the positive plates of automotive lead/acid batteries

    NASA Astrophysics Data System (ADS)

    D'Alkaine, C. V.; Carubelli, A.; Fava, H. W.; Sanhueza, A. C.

    A new experimental method to distinguish between energetic and structural materials and to characterize the manufacturing technology for positive plates in lead/acid batteries is discussed. This new method proposes the evaluation of the energetic β-coefficient from plots of capacity versus very low current densities under galvanostatic conditions and using real-size positive plates in 2.3-6.9 M H 2SO 4 solutions. The results are identical to those obtained previously from potentiostatic measurements, and they fit a new equation as opposed to Peukert's equation. The independence of the β-coefficient with H 2SO 4 concentration indicates that the discharge of PbO 2 to its products proceeds via a solid-state reaction mechanism.

  7. Adhesion and proliferation of osteoblast-like cells on anodic porous alumina substrates with different morphology.

    PubMed

    Salerno, Marco; Caneva-Soumetz, Federico; Pastorino, Laura; Patra, Niranjan; Diaspro, Alberto; Ruggiero, Carmelina

    2013-06-01

    We have fabricated nanoporous alumina surfaces by means of anodization in oxalic acid in different conditions and used them as the substrates for the growth of cells from a human osteoblast-like cell line. The rough nanoporous alumina substrates have been compared both with smooth standard Petri dishes used as the control and with commercial substrates of similar material. The viability of the cells has been assessed at different culture times of 4, 11, 18, and 25 days in vitro. It turned out that the porous side of the galvanostatically fabricated alumina performed similar to the control and better than the commercial porous alumina, whereas the potentiostatically fabricated porous alumina performed better than all the other substrates at all times, and in particular at the two shortest time periods of 4 and 11 days in vitro. The best performance of the substrates is associated with intermediate surface roughness and feature spacing. PMID:23722279

  8. Corrosion behavior of sensitized duplex stainless steel.

    PubMed

    Torres, F J; Panyayong, W; Rogers, W; Velasquez-Plata, D; Oshida, Y; Moore, B K

    1998-01-01

    The present work investigates the corrosion behavior of 2205 duplex stainless steel in 0.9% NaCl solution after various heat-treatments, and compares it to that of 316L austenitic stainless steel. Both stainless steels were heat-treated at 500, 650, and 800 degrees C in air for 1 h, followed by furnace cooling. Each heat-treated sample was examined for their microstructures and Vickers micro-hardness, and subjected to the X-ray diffraction for the phase identification. Using potentiostatic polarization method, each heat-treated sample was corrosion-tested in 37 degrees C 0.9% NaCl solution to estimate its corrosion rate. It was found that simulated sensitization showed an adverse influence on both steels, indicating that corrosion rates increased by increasing the sensitization temperatures. PMID:9713683

  9. Influence of Step Annealing Temperature on the Microstructure and Pitting Corrosion Resistance of SDSS UNS S32760 Welds

    NASA Astrophysics Data System (ADS)

    Yousefieh, M.; Shamanian, M.; Saatchi, A.

    2011-12-01

    In the present work, the influence of step annealing heat treatment on the microstructure and pitting corrosion resistance of super duplex stainless steel UNS S32760 welds have been investigated. The pitting corrosion resistance in chloride solution was evaluated by potentiostatic measurements. The results showed that step annealing treatments in the temperature ranging from 550 to 1000 °C resulted in a precipitation of sigma phase and Cr2N along the ferrite/austenite and ferrite/ferrite boundaries. At this temperature range, the metastable pits mainly nucleated around the precipitates formed in the grain boundary and ferrite phase. Above 1050 °C, the microstructure contains only austenite and ferrite phases. At this condition, the critical pitting temperature of samples successfully arrived to the highest value obtained in this study.

  10. Electrodeposition and Characterization of Bismuth Telluride Nanowires

    NASA Astrophysics Data System (ADS)

    Frantz, C.; Stein, N.; Gravier, L.; Granville, S.; Boulanger, C.

    2010-09-01

    In this work, we report thermoelectric measurements on electroplated bismuth telluride nanowires. Porous polycarbonate membranes, obtained by ion-track irradiation lithography, were chosen as electroplating templates. Bismuth telluride nanowires were achieved in acidic media under potentiostatic conditions at -100 mV versus saturated silver chloride electrode. The filling ratio of the pores was increased to 80% by adding dimethyl sulfoxide to the electrolyte. Whatever the experimental conditions, the nanowires were polycrystalline in the rhombohedral phase of Bi2Te3. Finally, the power output of arrays of bismuth telluride nanowires was analyzed as a function of load resistance. The results were strongly dependent on the internal resistance, which can be significantly reduced by the presence of dimethyl sulfoxide during electroplating.

  11. Corrosion inhibition of mild steel in acidic media using newly synthesized heterocyclic organic molecules: Correlation between inhibition efficiency and chemical structure

    NASA Astrophysics Data System (ADS)

    Ouici, H. B.; Benali, O.; Guendouzi, A.

    2015-03-01

    The corrosion inhibition of mild steel in 5% HCl solutions by some new synthesized organic compounds namely 3-(2-methoxyphenyl) 5-mercapto-1. 2. 4-triazole (2-MMT), 3-(3-methoxyphenyl) 5-mercapto-1. 2. 4-triazole (3-MMT) and 3-(2-hydroxyphenyl) 5-mercapto-1. 2. 4-triazole (2-HMT) was investigated using weight loss and potentiostatic polarization techniques. These measurements reveal that the inhibition efficiency obtained by these compounds increased by increasing their concentration. The inhibition efficiency follows the order 2-MMT >3-MMT >2-HMT. Polarization studies show that these compounds are of the mixed type but dominantly act as a cathodic inhibitors for mild steel in 5% HCl solutions. These inhibitors function through adsorption following Langmuir isotherm. Activation energy and Gibbs free energy for adsorption of inhibitors are calculated. Molecular modeling has been conducted to correlate the corrosion inhibition properties with the calculated quantum chemical parameters.

  12. Light addressable potentiometric sensor with an array of sensing regions

    NASA Astrophysics Data System (ADS)

    Liang, Weiguo; Han, JingHong; Zhang, Hong; Chen, Deyong

    2001-09-01

    This paper describes the mechanism of light addressable poteniometric sensors (LAPS) from the viewpoints of Semiconductor Physics, and introduces the fabrication of a multi-parameter LAPS chip. The MEMS technology is applied to produce a matrix of sensing regions on the wafer. By doing that, the cross talk among these regions is reduced, and the precision of the LAPS is increased. An IR-LED matrix is used as the light source, and the flow-injection method is used to input samples. The sensor system is compact and highly integrated. The measure and control system is composed of a personal computer, a lock-in amplifier, a potentiostat, a singlechip system, and an addressing circuit. Some experiments have been done with this device. The results show that this device is very promising for practical use.

  13. Preparation and Characterization of the Porous (TiO2) Oxide Films of Nanostructure for Biological and Medical Applications

    SciTech Connect

    Fadl-Allah, Sahar A.; El Sherief, Rabab M.; Badawy, Waheed A.

    2007-02-14

    In this paper, galvanostatically and potentiostatically formed surface oxide film on titanium in H2O2 free and H2O2 containing H2SO4 solutions were investigated. Conventional electrochemical techniques and electrochemical impedance spectroscopy (EIS) measurements beside the scanning electron microscope (SEM) were used. In absence of H2O2, the impedance response indicated a stable thin oxide film which depends on the mode of anodization of the metal. However, the introduction of H2O2 into the solution resulted in significant changes in the film characteristics, which were reflected in the EIS results. The film characteristics were found to be affected by the mode of oxide film growth and polarization time. The H2O2 addition to the solution has led to a significant decrease in the corrosion resistance of the passive film. The electrochemical and the use of equivalent circuit models have led to the understanding of the film characteristics under different conditions.

  14. Recovering Silver from Photographic Process Wastes

    NASA Astrophysics Data System (ADS)

    Sathaiyan, N.; Adaikkalam, P.; Abdul Kader, J. A. M.; Visvanathan, S.

    1990-10-01

    Spent color bleach-fix solution (CBFS), a product of photographic processing operations, is a potential source of silver. Of the extraction reactors used in recovering this silver, the rotating cylindrical electrode (RCE) has an advantage in that it provides improved mass transfer with an extended effective surface area. In addition, the application of a potentiostatic technique allows the silver deposition reaction to take place preferentially, without the formation of silver sulfide. The process consists of prior physical treatment, subsequent chemical reduction of the ferric-EDTA (ethylene diamine tetra-acetic acid) complex present in the CBFS with sodium dithionite (monitored by measuring the redox potential of Fe3+/Fe2+ couple), followed by electrodeposition of silver in a divided cell using a cation exchange membrane. The combined procedure results in increased current efficiency and reduced electrolysis time.

  15. Electrochemical Polishing Applications and EIS of a Novel Choline Chloride-Based Ionic Liquid

    SciTech Connect

    Wixtrom, Alex I.; Buhler, Jessica E.; Reece, Charles E.; Abdel-Fattah, Tarek M.

    2013-06-01

    Minimal surface roughness is a critical feature for high-field superconducting radio frequency (SRF) cavities used to engineer particle accelerators. Current methods for polishing Niobium cavities typically utilize solutions containing a mixture of concentrated sulfuric and hydrofluoric acid. Polishing processes such as these are effective, yet there are many hazards and costs associated with the use (and safe disposal) of the concentrated acid solutions. An alternative method for electrochemical polishing of the cavities was explored using a novel ionic liquid solution containing choline chloride. Potentiostatic electrochemical impedance spectroscopy (EIS) was used to analyze the ionic polishing solution. Final surface roughness of the Nb was found to be comparable to that of the acid-polishing method, as assessed by atomic force microscopy (AFM). This indicates that ionic liquid-based electrochemical polishing of Nb is a viable replacement for acid-based methods for preparation of SRF cavities.

  16. Li Diffusion and High-Voltage Cycling Behavior of Thin-Film LiCoO2 Cathodes

    SciTech Connect

    Jang, Y.-I.

    2001-10-02

    Mass transport and thermodynamic properties of Li{sub x}CoO{sub 2} were studied by the potentiostatic intermittent titration technique (PITT) using solid-state thin-film batteries that provide a well-defined diffusion geometry. Both the chemical diffusion coefficient and the thermodynamic factor have minima at the phase boundaries of the Li/vacancy ordered phase ''Li{sub 0.5}CoO{sub 2}''. The self-diffusion coefficient of Li has a minimum at x = 0.5 associated with the Li/vacancy ordering. As the degree of ordering increases, the nonmonotonic variations become more pronounced when approaching x = 0.5 in Li{sub x}CoO{sub 2}. We also show that thin-film LiCoO{sub 2} cathodes having grains of sub-micrometer size combined with the Li upon electrolyte exhibit excellent capacity retention when charged up to 4.5 V.

  17. Microbial characterization of anode-respiring bacteria within biofilms developed from cultures previously enriched in dissimilatory metal-reducing bacteria.

    PubMed

    Pierra, Mélanie; Carmona-Martínez, Alessandro A; Trably, Eric; Godon, Jean-Jacques; Bernet, Nicolas

    2015-11-01

    This work evaluated the use of a culture enriched in DMRB as a strategy to enrich ARB on anodes. DMRB were enriched with Fe(III) as final electron acceptor and then transferred to a potentiostatically-controlled system with an anode as sole final electron acceptor. Three successive iron-enrichment cultures were carried out. The first step of enrichment revealed a successful selection of the high current-producing ARB Geoalkalibacter subterraneus. After few successive enrichment steps, the microbial community analysis in electroactive biofilms showed a significant divergence with an impact on the biofilm electroactivity. Enrichment of ARB in electroactive biofilms through the pre-selection of DMRB should therefore be carefully considered. PMID:26182995

  18. Permeability improvements of electropolymerized polypyrrole films using dissolvable nano-CaCO3 particle templates.

    PubMed

    Popescu Mandoc, Luisa-Roxana; Gorgy, Karine; Ungureanu, Eleonora-Mihaela; Buica, George-Octavian; Holzinger, Michael; Cosnier, Serge

    2014-03-21

    The electropolymerisation of N-substituted pyrroles on a dissolvable calcium carbonate nanoparticle template was investigated in order to improve the film permeabilities in aqueous solution. After deposition of CaCO3 nanoparticles on the electrode surface, poly(pyrrole-ammonium) or poly(pyrrole-NTA) (NTA: nitrilotriacetic acid) were electrogenerated around the template structures of the electrodes using potentiostatic methods. The dissolution of nanoparticles in acidic medium leads to the formation of nano-porous structures increasing, therefore, the polypyrrole permeability in aqueous solutions. Histidine-tagged glucose oxidase, chosen as an enzyme model, was immobilised on the modified polypyrrole-NTA via the NTA-Cu(2+)-histidine interactions to validate the proposed method. The described setup led to a twofold increase in the maximum current density from 5 to 10 μA cm(-2) after template dissolution. PMID:24481549

  19. Exfoliation corrosion susceptibility and mechanisms of Al -- Li 2060 T8E30 aluminum lithium alloy in acidic media

    NASA Astrophysics Data System (ADS)

    Karayan, Ahmad Ivan

    The Al - Li 2060 aluminum lithium alloy was first launched in 2011. This alloy is a potential candidate for the use at wing/fuselage forgings, lower wing, and fuselage/pressure cabin. However, since its first launching, the corrosion properties of this alloy has not been extensively explored. There are three common laboratory tests for assessing the exfoliation corrosion (EFC) susceptibility of aluminum alloy 2XXX, namely EFC test in EXCO, modified EXCO and MASTMAASIS media. The objectives of this work is to study the susceptibility and mecahnism of corrosion of this alloy in EXCO, modified EXCO and MATSMAASIS media. These three media are acid. In the EXCO solution, this alloy suffers EFC after a 96-hour EFC test. The pH dramatically increases in the first 11 hours from 0.25 to 0.30. The pH then slightly increases and tends to remain constant at pH of 3.45 after 96 hours. The cyclic potentiodynamic polarization (CPP) test results show the presence of negative hysteresis and one breakdwon potential. This negative hysteresis suggests the absence of pitting corrosion due to the breakdown of passive film. The potentiostatic tests at potentials below and above the breakdown potential show an abrupt increase in potential in the first minutes and the presence of current transients. The scanning electron microscopy (SEM)-energy dispersive x-ray spectroscopy (EDS) examination confirms that the Al 20Cu2Mn3 particles preferentially dissolve, leaving the pitting after a potentiostatic test below the breakdown potential. From the potentiostatic test at a potential above the breakdown potential and an SEM examination after this potentiostatic test, intergranular corrosion (IGC) was observed. The electrochemical impedance spectroscopy (EIS) test and mathematical modeling indicates that the adsorption of intermediates in reduction of hydrogen ions is dominant in the first hours of immersion. The two time constants are observed when EFC occurs. The video capture microscopy

  20. Evidence of enzymatic catalysis of oxygen reduction on stainless steels under marine biofilm.

    PubMed

    Faimali, Marco; Benedetti, Alessandro; Pavanello, Giovanni; Chelossi, Elisabetta; Wrubl, Federico; Mollica, Alfonso

    2011-04-01

    Cathodic current trends on stainless steel samples with different surface percentages covered by biofilm and potentiostatically polarized in natural seawater were studied under oxygen concentration changes, temperature increases, and additions of enzymic inhibitors to the solution. The results showed that on each surface fraction covered by biofilm the oxygen reduction kinetics resembled a reaction catalyzed by an immobilised enzyme with high oxygen affinity (apparent Michaelis-Menten dissociation constant close to K(O(2))(M)  ≈ 10 μM) and low activation energy (W ≈ 20 KJ mole(-1)). The proposed enzyme rapidly degraded when the temperature was increased above the ambient (half-life time of ∼1 day at 25°C, and of a few minutes at 50°C). Furthermore, when reversible enzymic inhibitors (eg sodium azide and cyanide) were added, the cathodic current induced by biofilm growth was inhibited. PMID:21526439

  1. Some views on the erosion corrosion response of bulk chromium carbide based cermets

    NASA Astrophysics Data System (ADS)

    Stack, M. M.; Antonov, M. M.; Hussainova, I.

    2006-08-01

    Chromium carbide/nickel based composites are applicable in many environments involving tribo-corrosion due to their combined ability to resist wear and corrosion. Hence, they are candidate materials for use either in bulk as surface coatings in crude oil (offshore) or in power and marine industries. The aim of this work was to study the effect of material parameters such as composition and surface roughness, together with test conditions such as abrasive particle concentration, applied potential, temperature and time of experiment on the performance of chromium carbide based cermets. Potentiodynamic and potentiostatic tests were carried out as part of this work. SEM studies were also conducted to establish the mechanisms of the material degradation processes. Finally, erosion-corrosion maps were constructed based on the results. Material wastage, synergy and regime maps were developed for these materials and demonstrated that the performance of the cermet depends on the interplay of material and process variables.

  2. Abiotic systems for the catalytic treatment of solvent-contaminated water

    SciTech Connect

    Betterton, E.A.; Arnold, R.G.; Liu, Zhijie; Hollan, N.

    1996-12-31

    Three abiotic systems are described that catalyze the reductive dehalogenation of heavily halogenated environmental pollutants, including carbon tetrachloride, trichloroethene, and perchloroethene. These systems include (a) an electrolytic reactor in which the potential on the working electrode (cathode) is fixed by using a potentiostat, (b) a light-driven system consisting of a semiconductor and (covalently attached) macrocycle that can accept light transmitted via an optical fiber, and a light-driven, two-solvent (isopropanol/acetone) system that promotes dehalogenation reactions via an unknown mechanism. Each is capable of accelerating reductive dehalogenation reactions to very high rates under laboratory conditions. Typically, millimolar concentrations of aqueous-phase targets can be dehalogenated in minutes to hours. The description of each system includes the elements of reaction mechanism (to the extent known), typical kinetic data, and a discussion of the feasibility of applying this technology for the in situ destruction of hazardous compounds. 14 refs., 11 figs., 2 tabs.

  3. Highly sensitive DNA sensor based on polypyrrole nanowire

    NASA Astrophysics Data System (ADS)

    Mai, Anh Tuan; Duc, Thanh Pham; Thi, Xuan Chu; Nguyen, Minh Hieu; Nguyen, Hoang Hai

    2014-08-01

    This paper describes the development of a DNA sensor based on polypyrrole nanowire. By using potentiostatic technique, in the presence of gelatin as the soft mold, the polypyrrole nanowires were synthesized on the surface of the micro-sensor. The surface enhanced Raman spectroscopy shows that the Nsbnd H ends of the polypyrrole nanowires orientate upward from the surface facilitating the DNA probe immobilization through the simple linkage with the phosphate groups of the probe DNA. The label-free signal readout was carried out by lock-in amplifier technique. The response time of the DNA sensor is 10 s and the measurement time was 5 min. The lowest detectable concentration of Escherichia coli DNA was 0.1 nM.

  4. Electrochemical synthesis of core-shell magnetic nanowires

    NASA Astrophysics Data System (ADS)

    Ovejero, Jesús G.; Bran, Cristina; Vilanova, Enrique; Kosel, Jürgen; Morales, María P.; Vazquez, Manuel

    2015-09-01

    (Fe, Ni, CoFe) @ Au core-shell magnetic nanowires have been synthesized by optimized two-step potentiostatic electrodeposition inside self-assembled nanopores of anodic aluminium templates. The optimal electrochemical parameters (e.g., potential) have been firstly determined for the growth of continuous Au nanotubes at the inner wall of pores. Then, a magnetic core was synthesized inside the Au shells under suitable electrochemical conditions for a wide spectrum of single elements and alloy compositions (e.g., Fe, Ni and CoFe alloy). Novel opportunities offered by such nanowires are discussed particularly, the magnetic behavior of (Fe, Ni, CoFe) @ Au core-shell nanowires was tested and compared with that of bare nanowires. These core-shell nanowires can be released from the template thereby opening novel opportunities for biofunctionalization of individual nanowires.

  5. Improved corrosion resistance and interfacial contact resistance of 316L stainless-steel for proton exchange membrane fuel cell bipolar plates by chromizing surface treatment

    NASA Astrophysics Data System (ADS)

    Lee, S. B.; Cho, K. H.; Lee, W. G.; Jang, H.

    The electrochemical performance and electrical contact resistance of chromized 316 stainless-steel (SS) are investigated under simulated operating condition in a proton-exchange membrane fuel cell (PEMFC). The corrosion resistance of the chromized stainless steel is assessed by potentiodynamic and potentiostatic tests and the interfacial contact resistance (ICR) is examined by measuring the electrical contact resistance as a function of the compaction force. The results show that the chromizing surface treatment improves the corrosion resistance of the stainless steel due to the high-chromium concentration in the diffuse coating layer. On the other hand, the excess Chromium content on the surface increases the contact resistance of the steel plate to a level that is excessively high for commercial applications. This study examines the root cause of the high-contact resistance after chromizing and reports the optimum process to improve the corrosion resistance without sacrificing the ICR by obtaining a chrome carbide on the outer layer.

  6. The passivity of Type 316L stainless steel in borate buffer solution

    NASA Astrophysics Data System (ADS)

    Nicic, Igor; Macdonald, Digby D.

    2008-09-01

    The passivity of Type 316 SS in borate buffer solution (pH 8.35), in the steady-state, has been explored using a variety of electrochemical techniques, including potentiostatic polarization, Mott Schottky analysis, and electrochemical impedance spectroscopy. The study shows that the passive film is an n-type semiconductor with a donor density that is essentially independent of voltage across the passive state. The passive current density is also found to be voltage-independent, but the thickness of the barrier layer depends linearly on the applied voltage. These observations are consistent with the predictions of the Point Defect Model, noting that the point defects within the barrier layer of the passive film are metal interstitials or oxygen vacancies, or both. No evidence for p-type behavior was obtained, indicating that cation vacancies do not have a significant population density in the film compared with the two donors (cation interstitials and oxygen vacancies).

  7. Electrochemical deposition and characterization of Ni-P alloy thin films

    SciTech Connect

    Mahalingam, T. . E-mail: maha51@rediffmail.com; Raja, M.; Thanikaikarasan, S.; Sanjeeviraja, C.; Velumani, S.; Moon, Hosun; Kim, Yong Deak

    2007-08-15

    Nickel phosphorus (Ni-P) alloy thin films were prepared by electrodeposition on pre-cleaned copper substrates using a potentiostatic cathodic electrodeposition method from sulfate electrolyte baths at various sodium hypophosphite (NaH{sub 2}PO{sub 2}) concentrations. X-ray diffraction studies reveal polycrystalline cubic alloys at low concentrations of phosphorus (< 13.5 at.%) and these transformed into amorphous alloys at higher concentrations. X-ray photoelectron spectra show the presence of Ni{sub 2}p and P{sub 2}p lines corresponding to their binding energies. Scanning electron microscopic studies reveal spherical shaped grains at low phosphorus contents and modules of cauliflower type morphology at higher phosphorus concentrations. The effects of phosphorus concentration on the crystal structure, composition and morphology are studied and discussed.

  8. A novel method for the modification of zinc powder by ultrasonic impregnation in cerium nitrate solution.

    PubMed

    Zhu, Liqun; Zhang, Hui

    2008-04-01

    This work is devoted to an extensive study of cerium deposits distributed directly on zinc particles by simple impregnation or ultrasonic impregnation for the modification of zinc powder. Meantime, the characterization of modified zinc powder and the influence of ultrasound parameters in the modification process upon the dendritic growth, the corrosion behavior and the cyclic performance of zinc are investigated using scanning electron microscopy, energy dispersion spectrometry, potentiostatic polarization, potentiodynamic polarization and cyclic voltammetry. Compared with simple impregnation, the assistance of ultrasonic irradiation is found to have a significant effect on the sedimentary state and favorable properties of cerium deposits in a protective way. Besides the cyclic voltammetry measurements display that the application of ultrasound also improves the cyclic performance of zinc electrode containing modified zinc powder mainly because the cerium deposits formed under ultrasonic irradiation can greatly hinder the dissolution and diffusion of the oxidation product of zinc in the electrolyte and effectively favor the capacity maintenance of zinc electrode. PMID:18024152

  9. Synthesis of gold nanowires with controlled crystallographic characteristics

    NASA Astrophysics Data System (ADS)

    Karim, S.; Toimil-Molares, M. E.; Maurer, F.; Miehe, G.; Ensinger, W.; Liu, J.; Cornelius, T. W.; Neumann, R.

    2006-09-01

    The controlled fabrication of poly- and single-crystalline Au nanowires is reported. In polycarbonate templates, prepared by heavy-ion irradiation and subsequent etching, Au nanowires with diameters down to 25 nm are electrochemically synthesized. Four-circle X-ray diffraction and transmission electron microscopy measurements demonstrate that wires deposited potentiostatically at a voltage of -1.2 V at 65 °C are single-crystalline and oriented along the [110] direction. By reverse-pulse electrodeposition, wires oriented along the [100] direction are grown. The wires are cylindrical over their whole length. The morphology of the caps growing on top of poly- and single-crystalline wires is a strong indication of the particular crystalline structure of the nanowires.

  10. Structure and dye-sensitized solar cell application of TiO2 nanotube arrays fabricated by the anodic oxidation method

    NASA Astrophysics Data System (ADS)

    Ok, Seon-Yeong; Cho, Kwon-Koo; Kim, Ki-Won; Ryu, Kwang-Sun

    2010-05-01

    Well-ordered TiO2 nanotube arrays were fabricated by the potentiostatic anodic oxidation method using pure Ti foil as a working electrode and ethylene glycol solution as an electrolyte with the small addition of NH4F and H2O. The influence of anodization temperature and time on the morphology and formation of TiO2 nanotube arrays was examined. The TiO2 nanotube arrays were applied as a photoelectrode to dye-sensitized solar cells. Regardless of anodizing temperature and time, the average diameter and wall thickness of TiO2 nanotube arrays show a similar value, whereas the length increases with decreasing reaction temperature. The conversion efficiency is very low, which is due to a morphology breaking of the TiO2 nanotube arrays in the manufacturing process of a photoelectrode.

  11. 3D Printed Microfluidic Device with Integrated Biosensors for Online Analysis of Subcutaneous Human Microdialysate.

    PubMed

    Gowers, Sally A N; Curto, Vincenzo F; Seneci, Carlo A; Wang, Chu; Anastasova, Salzitsa; Vadgama, Pankaj; Yang, Guang-Zhong; Boutelle, Martyn G

    2015-08-01

    This work presents the design, fabrication, and characterization of a robust 3D printed microfluidic analysis system that integrates with FDA-approved clinical microdialysis probes for continuous monitoring of human tissue metabolite levels. The microfluidic device incorporates removable needle type integrated biosensors for glucose and lactate, which are optimized for high tissue concentrations, housed in novel 3D printed electrode holders. A soft compressible 3D printed elastomer at the base of the holder ensures a good seal with the microfluidic chip. Optimization of the channel size significantly improves the response time of the sensor. As a proof-of-concept study, our microfluidic device was coupled to lab-built wireless potentiostats and used to monitor real-time subcutaneous glucose and lactate levels in cyclists undergoing a training regime. PMID:26070023

  12. A CMOS detection chip for amperometric sensors with chopper stabilized incremental ΔΣ ADC

    NASA Astrophysics Data System (ADS)

    Min, Chen; Yuntao, Liu; Jingbo, Xiao; Jie, Chen

    2016-06-01

    This paper presents a low noise complimentary metal–oxide-semiconductor (CMOS) detection chip for amperometric electrochemical sensors. In order to effectively remove the input offset of the cascaded integrators and the low frequency noise in the modulator, a novel offset cancellation chopping scheme was proposed in the Incremental ΔΣ analog to digital converter (IADC). A novel low power potentiostat was employed in this chip to provide the biasing voltage for the sensor while mirroring the sensor current out for detection. The chip communicates with FPGA through standard built in I2C interface and SPI bus. Fabricated in 0.18-μm CMOS process, this chip detects current signal with high accuracy and high linearity. A prototype microsystem was produced to verify the detection chip performance with current input as well as micro-sensors. Project supported by the State Key Development Program for Basic Research of China (No. 2015CB352100).

  13. Correlation between electronic and corrosion properties of the passive oxide film on nitinol.

    PubMed

    Katić, Jozefina; Metikoš-Huković, Mirjana

    2014-01-01

    The oxide film (TiO(2)) was formed on Nitinol potentiostatically in an acetic acid solution. Deep understanding of electronic properties of this film is needed to predict long-term corrosion properties of Nitinol implant material in simulated body fluid conditions. The capacitance measurements were performed under depletion conditions to study electronic (semiconducting) properties. The space charge, formed at the solid|liquid interface, creates the barrier for the corrosion processes in aggressive (bio)environment. According to the results of electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis (MS), the passive film on Nitinol behaves as amorphous highly-doped n-type semiconductor. The values of electronic structure parameters (the flat-band potential, E(fb) and the carrier (donor) density, N(D)) were corrected for frequency dispersion. PMID:25125118

  14. A model for pore growth in anodically etched gallium phosphide

    NASA Astrophysics Data System (ADS)

    Ricci, P. C.; Salis, M.; Anedda, A.

    2005-06-01

    The electrochemical etching process of porous gallium phosphide was studied by means of the characteristic current-potential (I-V) curves. Measurements were performed in H2SO4 0.5-M aqueous solution both in the dark and by illuminating the samples with the 351-nm line of an argon laser. Raman spectroscopy was applied to investigate the surface morphology of the samples prepared under different anodizing conditions within the potentiostatic regime. Based on a few reasonable assumptions, a simple model of pore growth is proposed. The enhancing effect in current intensity due to the branching of pores and the opposite effect due to a concomitant decrease in the effective cross area available for carrier transport are accounted for to explain the main features of the recorded I -V curves.

  15. Tribo-electrochemical characterization of hafnium multilayer systems deposited on nitride/vanadium nitride AISI 4140 steel

    NASA Astrophysics Data System (ADS)

    Mora, M.; Vera, E.; Aperador, W.

    2016-02-01

    In this work is presented the synergistic behaviour among corrosion/wear (tribocorrosion) of the multilayer coatings hafnium nitride/vanadium nitride [HfN/VN]n. The multilayers were deposited on AISI 4140 steel using the technique of physical vapor deposition PVD magnetron sputtering, the tests were performed using a pin-on-disk tribometer, which has an adapted potentiostat galvanostat with three-electrode electrochemical cell. Tribocorrosive parameters such as: Friction coefficient between the coating and the counter body (100 Cr6 steel ball); Polarization resistance by means of electrochemical impedance spectroscopy technique and corrosion rate by polarization curves were determined. It was observed an increase in the polarization resistance, a decrease in the corrosion rate and a low coefficient of friction in comparison with the substrate, due to an increase on the number of bilayers.

  16. Improvement of flexible lithium battery shelf life by pre-discharging

    NASA Astrophysics Data System (ADS)

    Lim, Seung-Gyu; Jin, En Mei; Zhao, Xing Guan; Park, Kyung-Hee; Kim, Nam-In; Gu, Hal-Bon; Park, Bok-Kee

    Poly (methyl methacrylate) (PMMA)-based gel electrolyte has been used in flexible lithium batteries. These batteries are flexible and less than 0.5 mm thick, which make them suitable as power sources for smart cards and radio frequency identification (RFID) tags. We investigated the electrochemical properties of flexible lithium batteries using an impedance analyzer and potentiostat/galvanostat to evaluate the electrical capacities. To prevent the formation of gas by decomposition of electrolyte solvent, the batteries had to be pre-discharged about 5% of theoretical MnO 2 capacity. Of the three kinds of pre-discharging methods, especially, battery two-step pre-discharging method was performed showed the best electrical properties after storage at 60 °C for 60 days.

  17. Novel integrated and portable endotoxin detection system based on an electrochemical biosensor.

    PubMed

    Zuzuarregui, Ana; Souto, David; Pérez-Lorenzo, Eva; Arizti, Fernando; Sánchez-Gómez, Susana; Martínez de Tejada, Guillermo; Brandenburg, Klaus; Arana, Sergio; Mujika, Maite

    2015-01-21

    This paper describes the design, implementation and validation of a sensitive and integral technology solution for endotoxin detection. The unified and portable platform is based on the electrochemical detection of endotoxins using a synthetic peptide immobilized on a thin-film biosensor. The work covers the fabrication of an optimized sensor, the biofunctionalization protocol and the design and implementation of the measuring and signalling elements (a microfluidic chamber and a portable potentiostat-galvanostat), framed ad hoc for this specific application. The use of thin-film technologies to fabricate the biosensing device and the application of simple immobilization and detection methods enable a rapid, easy and sensitive technique for in situ and real time LPS detection. PMID:25431806

  18. Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure.

    PubMed

    May, Matthias M; Lewerenz, Hans-Joachim; Lackner, David; Dimroth, Frank; Hannappel, Thomas

    2015-01-01

    Photosynthesis is nature's route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis. Here a combined chemical surface transformation of a tandem structure and catalyst deposition at ambient temperature yields photocurrents approaching the theoretical limit of the absorber and results in a solar-to-hydrogen efficiency of 14%. The potentiostatically assisted photoelectrode efficiency is 17%. Present benchmarks for integrated systems are clearly exceeded. Details of the in situ interface transformation, the electronic improvement and chemical passivation are presented. The surface functionalization procedure is widely applicable and can be precisely controlled, allowing further developments of high-efficiency robust hydrogen generators. PMID:26369620

  19. Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure

    PubMed Central

    May, Matthias M.; Lewerenz, Hans-Joachim; Lackner, David; Dimroth, Frank; Hannappel, Thomas

    2015-01-01

    Photosynthesis is nature's route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis. Here a combined chemical surface transformation of a tandem structure and catalyst deposition at ambient temperature yields photocurrents approaching the theoretical limit of the absorber and results in a solar-to-hydrogen efficiency of 14%. The potentiostatically assisted photoelectrode efficiency is 17%. Present benchmarks for integrated systems are clearly exceeded. Details of the in situ interface transformation, the electronic improvement and chemical passivation are presented. The surface functionalization procedure is widely applicable and can be precisely controlled, allowing further developments of high-efficiency robust hydrogen generators. PMID:26369620

  20. Self-organized highly ordered TiO{sub 2} nanotubes in organic aqueous system

    SciTech Connect

    Wan Jun; Yan Xia; Ding Junjie; Wang Meng; Hu Kongcheng

    2009-12-15

    A simple method to achieve self-organized, freestanding TiO{sub 2} nanotube array was constructed, free of corrosive etching process which was traditionally employed to separate TiO{sub 2} nanotubes from the metallic Ti substrate. The TiO{sub 2} nanotube arrays were constructed through potentiostatic anodization of Ti foil in aqueous electrolyte containing NH{sub 4}F and ethylene glycol. The nanotubes in the array were of 45 {mu}m lengths and 100 nm average pore diameters. The effect of NH{sub 4}F concentration on the length of the self-organized nanotube arrays was investigated. Electrochemical and spectroscopic measurements showed that the as-prepared nanotubes possessed large surface areas, good uniformity, and were ready for enzyme immobilization. The as-prepared nanotube arrays were amorphous, but crystallized with annealing at elevated temperatures, as demonstrated by X-ray diffraction (XRD).

  1. Corrosion of some chromium-nickel steels and alloys in sulfuric acid solutions of sodium sulfite

    SciTech Connect

    Kopeliovich, D.K.; Glagolenko, Yu.V.; Ermolinskii, S.P.

    1988-05-01

    Steels 12Kh18N1OT and 10Kh17N13M3T and alloys 06KhN28MDT and 46KhNM were studied in sulfuric acid solutions containing sodium sulfite and sulfur dioxide to determine the effects of different concentrations of the corrosive constituents on the anodic and cathodic active and passive corrosion behavior of the metals. Polarization curves were obtained with a P-5827 M potentiostat. Addition of sulfite facilitated both electrode processes and the region of the reactive state was broadened due to the shift of passivation potentials to more positive values. The activating effect of sulfite reduction products were confirmed by tests of alloys in spent solutions. This increased likelihood of activation and the decrease of the solutions's own corrosion potential were both attributed to retardation of the cathodic process by lower valence sulfur compounds.

  2. Hydrogen storage materials, batteries, and electrochemistry; Proceedings of the Symposium, Phoenix, AZ, Oct. 14-17, 1991

    SciTech Connect

    Corrigan, D.A.; Srinivasan, S.

    1992-01-01

    Various papers on hydrogen storage materials, batteries, and electrode chemistry are presented. Individual topics addressed include: development of hydrogen-absorbing alloys for nickel metal hydride secondary batteries, capacity retention in hydrogen storage alloys, sealed metal-hydride batteries for aerospace applications, nickel-hydrogen battery self-discharge mechanism and methods for its inhibition, studies on the self-discharge mechanism of Ni/H2 cells. Also discussed are: characterization of IPV nickel electrodes by means of an integrated cycling and electrochemical impedance spectroscopy technique, characterization of IPV nickel electrodes by means of an integrated electrochemical impedance spectroscopy technique, low cost electrocatalytic gas diffusion membrane electrodes of metal-hydrogen batteries, potentiostatic and ac impedance studies of the hydrogen electrodes used in Ni/H2 batteries.

  3. Electrodeposition of Zn and Zn-Mn alloy coatings from an electrolytic bath prepared by recovery of exhausted zinc-carbon batteries

    NASA Astrophysics Data System (ADS)

    da Silva, Paulo Sérgio; Schmitz, Edinéia P. Sartori; Spinelli, Almir; Garcia, Jarem Raul

    2012-07-01

    The electrodeposition of galvanic coatings was performed using a chloride-based acidic electrolytic bath containing polyethylene glycol (PEG) as an additive. The electrolytic bath was prepared using Zn and Mn recovered from exhausted zinc-carbon batteries by means of acid leaching with HCl. The coatings were obtained potentiostatically at -1.2 V and -1.6 V (vs. Ag/AgCl) and galvanostatically with a current density of -10 mA cm-2. The results indicated that the presence of PEG in the bath during galvanostatic deposition favored the formation of a coating containing a mixture of Zn and Zn-Mn alloy with an Mn content of around 2 wt%.

  4. The electrochemical behaviour of 316L austenitic stainless steel in Cl- containing environment under different H2S partial pressures

    NASA Astrophysics Data System (ADS)

    Ding, Jinhui; Zhang, Lei; Lu, Minxu; Wang, Jing; Wen, Zhibin; Hao, Wenhui

    2014-01-01

    In oil-gas production environments, presence of H2S-Cl- can induce deterioration of the passive film, leading to pitting corrosion of stainless steels. In this paper, by using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and capacitance measurements (Mott-Schottky analysis), the electrochemical behaviour of AISI 316L austenitic stainless steel was investigated in Cl- solutions under different H2S partial pressures (from 0 to 1.0 bar). The results indicated that presence of H2S in Cl- solution can accelerate both the cathodic and anodic current density, leading to a metastable passive state in higher passive potential range, changing the semiconductor behaviour from p-type to n-type, increasing its susceptibility to corrosion. XPS analysis was employed to characterize the surface film after potentiostatic polarization, whose results provide good evidences for the electrochemical measurements.

  5. 3D Printed Microfluidic Device with Integrated Biosensors for Online Analysis of Subcutaneous Human Microdialysate

    PubMed Central

    2015-01-01

    This work presents the design, fabrication, and characterization of a robust 3D printed microfluidic analysis system that integrates with FDA-approved clinical microdialysis probes for continuous monitoring of human tissue metabolite levels. The microfluidic device incorporates removable needle type integrated biosensors for glucose and lactate, which are optimized for high tissue concentrations, housed in novel 3D printed electrode holders. A soft compressible 3D printed elastomer at the base of the holder ensures a good seal with the microfluidic chip. Optimization of the channel size significantly improves the response time of the sensor. As a proof-of-concept study, our microfluidic device was coupled to lab-built wireless potentiostats and used to monitor real-time subcutaneous glucose and lactate levels in cyclists undergoing a training regime. PMID:26070023

  6. Biocompatibility of nanotube formed Ti-30Nb-7Ta alloys.

    PubMed

    Kim, Eun-Sil; Choe, Han-Cheol

    2014-11-01

    The purpose of this study was to investigate the biocompatibility of Ti-30Nb-7Ta alloy surface decorated with TiO2 nanotubes by anodization in an electrolyte containing 1 M H3PO4 and 0.8 wt.% NaF with an applied voltage of 10 V for 2 h. The anodization was carried out using a scanning potentiostat. The microstructures of alloys and morphology of the nanotubes were investigated by optical microscopy, field emission scanning electron microscopy, and X-ray diffractometry. In comparison to the Ti-30Nb-3Ta alloy, the Ti-30Nb-7Ta alloy contained a lower amount of α" phase, while the β phase was higher. In this study, we observed the formation of a spongy porous layer on the Ti-30Nb-7Ta alloy, while the Ti-30Nb and Ti-30Nb-3Ta alloys showed an absence of such a spongy layer. PMID:25958540

  7. Investigation on the Oxidation and Reduction of Titanium in Molten Salt with the Soluble TiC Anode

    NASA Astrophysics Data System (ADS)

    Wang, Shulan; Wan, Chaopin; Liu, Xuan; Li, Li

    2015-12-01

    To reveal the oxidation process of titanium from TiC anode and the reduction mechanism of titanium ions in molten NaCl-KCl, the polarization curve of TiC anode in molten NaCl-KCl and cyclic voltammograms of the molten salt after polarization were studied. Investigation on the polarization curve shows that titanium can be oxidized and dissociated from the TiC anode at very low potential. The cyclic voltammograms demonstrated that the reduction reaction of titanium ions in the molten salt is a one-step process. By potentiostatic electrolysis, dendritic titanium is obtained on the steel plate. The work promotes the understanding on the process of electrochemical oxidization/dissociation of titanium from TiC anode and the reduction mechanism of titanium ions in molten salt.

  8. Electrochemical co-deposition of magnesium with lithium from quaternary ammonium-based ionic liquid

    NASA Astrophysics Data System (ADS)

    Shimamura, Osamu; Yoshimoto, Nobuko; Matsumoto, Mami; Egashia, Minato; Morita, Masayuki

    Electrochemical deposition of magnesium (Mg) has been successfully achieved from an ionic liquid (IL) solution based on quaternary ammonium salt containing lithium (Li) salt. Irreversible electrochemical behavior was generally observed in the IL-based electrolytes containing simple Mg salt. In the IL-based electrolyte dissolving both Mg and Li salts, electrochemical reduction and oxidation of magnesium cation (Mg 2+) have become detectable. Such reversible processes correspond respectively to cathodic deposition and anodic dissolution of metallic Mg, which are accompanied by the co-deposition/co-dissolution of Li. Potentiostatic electrolysis of IL dissolving binary Mg and Li salts gave metallic deposit consisting of both elements with total current efficiency of ca. 52%.

  9. Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure

    NASA Astrophysics Data System (ADS)

    May, Matthias M.; Lewerenz, Hans-Joachim; Lackner, David; Dimroth, Frank; Hannappel, Thomas

    2015-09-01

    Photosynthesis is nature's route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis. Here a combined chemical surface transformation of a tandem structure and catalyst deposition at ambient temperature yields photocurrents approaching the theoretical limit of the absorber and results in a solar-to-hydrogen efficiency of 14%. The potentiostatically assisted photoelectrode efficiency is 17%. Present benchmarks for integrated systems are clearly exceeded. Details of the in situ interface transformation, the electronic improvement and chemical passivation are presented. The surface functionalization procedure is widely applicable and can be precisely controlled, allowing further developments of high-efficiency robust hydrogen generators.

  10. High-throughput screening of thin-film semiconductor material libraries I: system development and case study for Ti-W-O.

    PubMed

    Sliozberg, Kirill; Schäfer, Dominik; Erichsen, Thomas; Meyer, Robert; Khare, Chinmay; Ludwig, Alfred; Schuhmann, Wolfgang

    2015-04-13

    An automated optical scanning droplet cell (OSDC) enables high-throughput quantitative characterization of thin-film semiconductor material libraries. Photoelectrochemical data on small selected measurement areas are recorded including intensity-dependent photopotentials and -currents, potentiodynamic and potentiostatic photocurrents, as well as photocurrent (action) spectra. The OSDC contains integrated counter and double-junction reference electrodes and is fixed on a precise positioning system. A Xe lamp with a monochromator is coupled to the cell through a thin poly(methyl methacrylate) (PMMA) optical fiber. A specifically designed polytetrafluoroethylene (PTFE) capillary tip is pressed on the sample surface and defines through its diameter the homogeneously illuminated measurement area. The overall and wavelength-resolved irradiation intensities and the cell surface area are precisely determined and calibrated. System development and its performance are demonstrated by means of screening of a TiWO thin film. PMID:25727402

  11. Effect of annealing temperature on the pitting corrosion resistance of super duplex stainless steel UNS S32750

    SciTech Connect

    Tan Hua; Jiang Yiming; Deng Bo; Sun Tao; Xu Juliang; Li Jin

    2009-09-15

    The pitting corrosion resistance of commercial super duplex stainless steels SAF2507 (UNS S32750) annealed at seven different temperatures ranging from 1030 deg. C to 1200 deg. C for 2 h has been investigated by means of potentiostatic critical pitting temperature. The microstructural evolution and pit morphologies of the specimens were studied through optical/scanning electron microscope. Increasing annealing temperature from 1030 deg. C to 1080 deg. C elevates the critical pitting temperature, whereas continuing to increase the annealing temperature to 1200 deg. C decreases the critical pitting temperature. The specimens annealed at 1080 deg. C for 2 h exhibit the best pitting corrosion resistance with the highest critical pitting temperature. The pit morphologies show that the pit initiation sites transfer from austenite phase to ferrite phase as the annealing temperature increases. The aforementioned results can be explained by the variation of pitting resistance equivalent number of ferrite and austenite phase as the annealing temperature changes.

  12. The relationship between induction time for pitting and pitting potential for high purity aluminum.

    SciTech Connect

    Wall, Frederick Douglas; Vandenavyle, Justin J.; Martinez, Michael A.

    2003-08-01

    The objective of this study was to determine if a distribution of pit induction times (from potentiostatic experiments) could be used to predict a distribution of pitting potentials (from potentiodynamic experiments) for high-purity aluminum. Pit induction times were measured for 99.99 Al in 50 mM NaCl at potentials of -0.35, -0.3, -0.25, and -0.2 V vs. saturated calomel electrode. Analysis of the data showed that the pit germination rate generally was an exponential function of the applied potential; however, a subset of the germination rate data appeared to be mostly potential insensitive. The germination rate behavior was used as an input into a mathematical relationship that provided a prediction of pitting potential distribution. Good general agreement was found between the predicted distribution and an experimentally determined pitting potential distribution, suggesting that the relationships presented here provide a suitable means for quantitatively describing pit germination rate.

  13. Electrochemical velocimetry on centrifugal microfluidic platforms.

    PubMed

    Abi-Samra, Kameel; Kim, Tae-Hyeong; Park, Dong-Kyu; Kim, Nahui; Kim, Jintae; Kim, Hanshin; Cho, Yoon-Kyoung; Madou, Marc

    2013-08-21

    Expanding upon recent applications of interfacing electricity with centrifugal microfluidic platforms, we introduce electrochemical velocimetry to monitor flow in real-time on rotating fluidic devices. Monitoring flow by electrochemical techniques requires a simple, compact setup of miniaturized electrodes that are embedded within a microfluidic channel and are connected to a peripherally-located potentiostat. On-disc flow rates, determined by electrochemical velocimetry, agreed well with theoretically expected values and with optical measurements. As an application of the presented techniques, the dynamic process of droplet formation and release was recorded, yielding critical information about droplet frequency and volume. Overall, the techniques presented in this work advance the field of centrifugal microfluidics by offering a powerful tool, previously unavailable, to monitor flow in real-time on rotating microfluidic systems. PMID:23787459

  14. Influence of surface modification of nitinol with silicon using plasma-immersion ion implantation on the alloy corrosion resistance in artificial physiological solutions

    NASA Astrophysics Data System (ADS)

    Kashin, O. A.; Borisov, D. P.; Lotkov, A. I.; Abramova, P. V.; Korshunov, A. V.

    2015-10-01

    Cyclic voltammetry and potentiostatic polarization have been applied to study electrochemical behavior and to determine corrosion resistance of nitinol, which surface was modified with silicon using plasma-immersion ion implantation, in 0.9% NaCl solution and in artificial blood plasma. It was found out that continuous, and also homogeneous in composition, thin Si-containing layers are resistant to corrosion damage at high positive potentials in artificial physiological solutions due to formation of stable passive films. Breakdown potential Eb of Si-modified NiTi depends on the character of silicon and Ni distribution at the alloy surface, Eb values amounted to 0.9-1.5 V (Ag/AgCl/KCl sat.) for the alloy samples with continuous Si-containing surface layers and with decreased Ni surface concentration.

  15. Improving the corrosion resistance of nitinol by plasma-immersion ion implantation with silicon for biomedical applications

    NASA Astrophysics Data System (ADS)

    Abramova, P. V.; Korshunov, A. V.; Lotkov, A. I.; Kashin, O. A.; Borisov, D. P.

    2015-11-01

    Cyclic voltammetry and potentiostatic polarization have been applied to study electrochemical behavior and to determine corrosion resistance of nitinol, which surface was modified with silicon using plasma-immersion ion implantation, in 0.9 % NaCl solution and in artificial blood plasma. It was found out that continuous, and also homogeneous in composition thin Si-containing layers are resistant to corrosion damage at high positive potentials in artificial physiological solutions due to formation of stable passive films. Breakdown potential Eb of Si-modified NiTi depends on the character of silicon and Ni distribution at the alloy surface, Eb values amounted to 0.9-1.5 V (Ag/AgCl/KCl sat.) for the alloy samples with continuous Si-containing surface layers and with decreased Ni surface concentration.

  16. Electrocatalytic activities of cathode electrodes for water electrolysis using tetra-alkyl-ammonium-sulfonic acid ionic liquid as electrolyte

    NASA Astrophysics Data System (ADS)

    Fiegenbaum, Fernanda; de Souza, Michèle O.; Becker, Márcia R.; Martini, Emilse M. A.; de Souza, Roberto F.

    2015-04-01

    The hydrogen evolution reaction (HER) performed with platinum (Pt), nickel (Ni), stainless steel 304 (SS) or glassy carbon (GC) cathodes in 0.1 M 3-triethylammonium-propanesulfonic acid tetrafluoroborate (TEA-PS.BF4) solution is studied using quasi-potentiostatic and impedance spectroscopy techniques. The objective is to compare the catalytic effect on the cathode using different materials to obtain hydrogen by water electrolysis. Furthermore, the catalytic effect of the ionic liquid (IL) on the cathode compared with that of a hydrochloric acid (HCl) solution with same pH value (0.8) is reported. A low activation energy (Ea) of 8.7 kJ mol-1 is found for the glassy carbon cathode. Tafel plots obtained with TEA-PS.BF4 IL suggest the formation of an electroactive layer of IL on the cathode, which may be responsible for the catalytically enhanced performance observed.

  17. Reduction mechanism of sulfur in lithium-sulfur battery: From elemental sulfur to polysulfide

    NASA Astrophysics Data System (ADS)

    Zheng, Dong; Zhang, Xuran; Wang, Jiankun; Qu, Deyu; Yang, Xiaoqing; Qu, Deyang

    2016-01-01

    The polysulfide ions formed during the first reduction wave of sulfur in Li-S battery were determined through both in-situ and ex-situ derivatization of polysulfides. By comparing the cyclic voltammetric results with and without the derivatization reagent (methyl triflate) as well as the in-situ and ex-situ derivatization results under potentiostatic condition, in-situ derivatization was found to be more appropriate than its ex-situ counterpart, since subsequent fast chemical reactions between the polysulfides and sulfur may occur during the timeframe of ex-situ procedures. It was found that the major polysulfide ions formed at the first reduction wave of elemental sulfur were the S4 2 - and S5 2 - species, while the widely accepted reduction products of S8 2 - and S6 2 - for the first reduction wave were in low abundance.

  18. Corrosion inhibition of mild steel in acidic media using newly synthesized heterocyclic organic molecules: Correlation between inhibition efficiency and chemical structure

    SciTech Connect

    Ouici, H. B. Guendouzi, A.; Benali, O.

    2015-03-30

    The corrosion inhibition of mild steel in 5% HCl solutions by some new synthesized organic compounds namely 3-(2-methoxyphenyl) 5-mercapto-1. 2. 4-triazole (2-MMT), 3-(3-methoxyphenyl) 5-mercapto-1. 2. 4-triazole (3-MMT) and 3-(2-hydroxyphenyl) 5-mercapto-1. 2. 4-triazole (2-HMT) was investigated using weight loss and potentiostatic polarization techniques. These measurements reveal that the inhibition efficiency obtained by these compounds increased by increasing their concentration. The inhibition efficiency follows the order 2-MMT >3-MMT >2-HMT. Polarization studies show that these compounds are of the mixed type but dominantly act as a cathodic inhibitors for mild steel in 5% HCl solutions. These inhibitors function through adsorption following Langmuir isotherm. Activation energy and Gibbs free energy for adsorption of inhibitors are calculated. Molecular modeling has been conducted to correlate the corrosion inhibition properties with the calculated quantum chemical parameters.

  19. A Complementary Type of Electrochromic Device by Radio Frequency Magnetron Sputtering System

    NASA Astrophysics Data System (ADS)

    Oksuz, Lutfi; Kiristi, Melek; Bozduman, Ferhat; Uygun Oksuz, Aysegul

    2014-10-01

    Electrochromic (EC) devices can change their optical properties reversibly in the visible region (400-800 nm) upon charge insertion/extraction reactions according to the applied voltage. A complementary type of EC device composes of two electrochromic layers, which is separated by an ionic conduction layer (electrolyte). In this work, the EC device was fabricated using vanadium oxide (V2O5) and titanium doped tungsten oxide (WO3-TiO2) electrodes. The EC electrodes were deposited as thin film structures by a reactive RF magnetron sputtering system in a medium of gas mixture of argon and oxygen. surface morphology of the films was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Electrochemical property and durability of the EC device was investigated by a potentiostat system. Optical measurement was examined under applied voltages of +/- 2.5 V by a computer-controlled system, constantly.

  20. Electrochemical behavior of 0.2 to 3 molar ferrous chloride-ferric chloride mixtures on edge-on pyrolytic graphite rotated disk electrodes

    NASA Technical Reports Server (NTRS)

    Miller, R. O.

    1977-01-01

    Potentiostatic determinations in various mixtures of FeCl2-FeCl3 with excess HCl show rest potentials that are 0.1 V less electropositive than the theoretical values from the formulated ratios of FeII to FeIII (probably as a result of complexing). The standard rate constant sub s. ranges between 0.0001 and 0.000 cm/sec. Tafel slopes b of roughly 0.12V per decade indicate single-electron exchange kinetics. No significant trend in either b or sub s was attributed to mixture composition. The higher sub s. values occurred with and edge-on pyrolytic graphite that had undergone a permanent surface change.

  1. Simultaneous telemetric monitoring of brain glucose and lactate and motion in freely moving rats.

    PubMed

    Rocchitta, Gaia; Secchi, Ottavio; Alvau, Maria Domenica; Farina, Donatella; Bazzu, Gianfranco; Calia, Giammario; Migheli, Rossana; Desole, Maria Speranza; O'Neill, Robert D; Serra, Pier A

    2013-11-01

    A new telemetry system for simultaneous detection of extracellular brain glucose and lactate and motion is presented. The device consists of dual-channel, single-supply miniature potentiostat-I/V converter, a microcontroller unit, a signal transmitter, and a miniaturized microvibration sensor. Although based on simple and inexpensive components, the biotelemetry device has been used for accurate transduction of the anodic oxidation currents generated on the surface of implanted glucose and lactate biosensors and animal microvibrations. The device was characterized and validated in vitro before in vivo experiments. The biosensors were implanted in the striatum of freely moving animals and the biotelemetric device was fixed to the animal's head. Physiological and pharmacological stimulations were given in order to induce striatal neural activation and to modify the motor behavior in awake, untethered animals. PMID:24102201

  2. Reduction mechanism of sulfur in lithium-sulfur battery: From elemental sulfur to polysulfide

    DOE PAGESBeta

    Zheng, Dong; Yang, Xuran; Zhang, Xiaoqing; Wang, Jiankun; Qu, Deyu; Qu, Deyang

    2015-10-30

    In this study, the polysulfide ions formed during the first reduction wave of sulfur in Li–S battery were determined through both in-situ and ex-situ derivatization of polysulfides. By comparing the cyclic voltammetric results with and without the derivatization reagent (methyl triflate) as well as the in-situ and ex-situ derivatization results under potentiostatic condition, in-situ derivatization was found to be more appropriate than its ex-situ counterpart, since subsequent fast chemical reactions between the polysulfides and sulfur may occur during the timeframe of ex-situ procedures. It was found that the major polysulfide ions formed at the first reduction wave of elemental sulfurmore » were the S42– and S52– species, while the widely accepted reduction products of S82– and S62– for the first reduction wave were in low abundance.« less

  3. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.

  4. An assessment of the formation of electrodeposited scales using scanning electron and atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Morizot, A. P.; Neville, A.; Taylor, J. D.

    2002-04-01

    The deposition of insoluble salts onto surfaces in process systems represents an important operational problem. Mineral scale formation (e.g. CaCO 3 and BaSO 4) can result from fluid streams becoming supersaturated when incompatible waters combine (e.g. in oil recovery) or can be formed when cathodic protection is applied and electrodeposition occurs. In this study, electrodeposition is studied on metal rotating disk electrodes (RDE) in artificial seawater under static conditions and under rotation at 400 rpm. Also, a Ca-free brine and a Mg-free brine of the same dissolved solids level were used in static tests. The focus of the study is the assessment of the electrochemical response of the system under potentiostatic control and correlation of the current versus time measurements to the characteristics of the scale determined via scanning electron microscopy and atomic force microscopy analysis.

  5. An electronic pollen detection method using Coulter counting principle

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng; Zhe, Jiang; Chandra, Santanu; Hu, Jun

    A method for detecting and counting pollen particles based on Coulter counting principle is presented. This approach also provides information on the size and surface charges of the micro particles, allowing for preliminary differentiation of pollens from other micro particles. Three samples are studied: polymethyl methacrylate particles, tree pollens from Juniperus Scopulorum and grass pollens from Secale Cerale. The samples, suspended in diluted KCl aqueous solutions in an electrochemical cell, were allowed to pass through a microchannel and the conductance of the microchannel was sampled with a Gamry ® Potentiostat. The changes in the conductance due to the passing of the micro particles was thus recorded and analyzed. The experimental results showed that tree pollens and grass pollens display distinctive behaviors. The phenomena may be attributed to the differences in the surface characteristics of the pollens and is potentially useful for counting and differentiating different micro particles.

  6. Electrochemical flowcell for in-situ investigations by soft x-ray absorption and emission spectroscopy

    SciTech Connect

    Schwanke, C.; Lange, K. M.; Golnak, R.; Xiao, J.

    2014-10-15

    A new liquid flow-cell designed for electronic structure investigations at the liquid-solid interface by soft X-ray absorption and emission spectroscopy is presented. A thin membrane serves simultaneously as a substrate for the working electrode and solid state samples as well as for separating the liquid from the surrounding vacuum conditions. In combination with counter and reference electrodes this approach allows in-situ studies of electrochemical deposition processes and catalytic reactions at the liquid-solid interface in combination with potentiostatic measurements. As model system in-situ monitoring of the deposition process of Co metal from a 10 mM CoCl{sub 2} aqueous solution by X-ray absorption and emission spectroscopy is presented.

  7. Synthesis and microstructural studies of annealed Cu(2)O/Cu(x)S bilayer as transparent electrode material for photovoltaic and energy storage devices.

    PubMed

    Taleatu, B A; Arbab, E A A; Omotoso, E; Mola, G T

    2014-10-01

    Cu2 O thin film and a transparent bilayer have been fabricated by electrodeposition method. The growths were obtained in potentiostatic mode with gradual degradation of anodic current. X-ray diffraction (XRD) study showed that the bilayer is polycrystalline and it possesses mixture of different crystallite phases of copper oxides. Surface morphology of the films was investigated by scanning electron microscopy (SEM). The SEM images revealed that the films were uniformly distributed and the starting material (Cu2 O) had cubical structure. Grains agglomeration and crystallinity were enhanced by annealing. Optical studies indicated that all the samples have direct allowed transition. Energy band gap of the bilayer film was reduced by annealing treatment thus corroborating quantum confinement upshot. PMID:25088932

  8. Corrosion behavior of PIRAC nitrided Ti-6Al-4V surgical alloy.

    PubMed

    Starosvetsky, D; Shenhar, A; Gotman, I

    2001-02-01

    Hard titanium nitride (TiN) coatings were obtained on the surface of Ti-6Al-4V alloy using an original PIRAC nitriding method, based on annealing the samples under a low pressure of monatomic nitrogen created by selective diffusion of N from the atmosphere. PIRAC nitrided samples exhibited excellent corrosion resistance in Ringer's solution in both potentiodynamic and potentiostatic tests. The anodic current and metal ion release rate of PIRAC nitrided Ti-6Al-4V at the typical corrosion potential values were significantly lower than those of the untreated alloy. This, together with the excellent adhesion and high wear resistance of the TiN coatings, makes PIRAC nitriding an attractive surface treatment for Ti-6Al-4V alloy surgical implants. PMID:15348321

  9. Development of sulfur-tolerant components for the molten carbonate fuel cell

    NASA Astrophysics Data System (ADS)

    Sammells, A. F.; Nicholson, S. B.; Ang, P. G. P.

    1980-02-01

    The sulfur tolerance of candidate anode and anode current collector materials for the molten carbonate fuel cell were evaluated in an electrochemical half-cell using both steady-state and transient potentiostatic techniques. Hydrogen sulfide was introduced into the fuel at concentrations of 50 and 1000 ppm; at the higher sulfur concentration nickel and cobalt underwent a negative shift in their open-circuit potentials, and high anodic and cathodic currents were observed compared with clean fuels. Exchange currents were not greatly affected by 50 ppm H2S; but, at higher sulfur concentrations, higher apparent exchange currents were observed, indicating a probable sulfidation reaction. New anode materials including TiC showed good stability in the anodic region. Of the anode current collector materials evaluated, high stabilities were found for 410 and 310 stainless steels.

  10. Use of cyclic current reversal polarization voltammetry for investigating the relationship between corrosion resistance and heat-treatment induced variations in microstructures of 400 C martensitic stainless steels

    NASA Technical Reports Server (NTRS)

    Ambrose, John R.

    1992-01-01

    Software for running a cyclic current reversal polarization voltammagram has been developed for use with a EG&G Princeton Applied Research Model 273 potentiostat/galvanostat system. The program, which controls the magnitude, direction and duration of an impressed galvanostatic current, will produce data in ASCII spreadsheets (Lotus, Quattro) for graphical representation of CCRPV voltammograms. The program was used to determine differences in corrosion resistance of 440 C martenstic stainless steel produced as a result of changes in microstructure effected by tempering. It was determined that tempering at all temperatures above 400 F resulted in increased polarizability of the material, with the increased likelihood that pitting would be initiated upon exposure to marine environments. These results will be used in development of remedial procedures for lowering the susceptibility of these alloys toward the stress corrosion cracking experienced in bearings used in high pressure oxygen turbopumps used in the main engines of space shuttle orbiters.

  11. Synthesis of mesoporous nanocomposites for their application in solid oxide electrolysers cells: microstructural and electrochemical characterization.

    PubMed

    Torrell, M; Almar, L; Morata, A; Tarancón, A

    2015-01-01

    Fabrication routes for new SOEC mesoporous nanocomposite materials as electrodes are presented in this paper. NiO-CGO and SDC-SSC are described as possible new materials and their synthesis and the cell fabrication are discussed. The obtained materials are microstructurally characterised by SEM, TEM and XRD, where the mesoporous structures are observed and analysed. The obtained samples are electrochemically analysed by I-V polarisation curves and EIS analysis, showing a maximum current density of 330 mA cm(-2) at 1.7 V. A degradation of the cell performance is evidenced after a potentiostatic test at 1.4 V after more than 40 hours. Oxygen electrode delaminating is detected, which is most probably the main cause of ageing. Even taking into account the lack of durability of the fabricated cells, the mesoporous electrodes do not seem to be altered, opening the possibility for further studies devoted to this high stability material for SOEC electrodes. PMID:26212761

  12. Alkaline Ammonia Electrolysis on Electrodeposited Platinum for Controllable Hydrogen Production.

    PubMed

    Gwak, Jieun; Choun, Myounghoon; Lee, Jaeyoung

    2016-02-19

    Ammonia is beginning to attract a great deal of attention as an alternative energy source carrier, because clean hydrogen can be produced through electrolytic processes without the emission of COx . In this study, we deposited various shapes of Pt catalysts under potentiostatic mode; the electrocatalytic oxidation behavior of ammonia using these catalysts was studied in alkaline media. The electrodeposited Pt was characterized by both qualitative and quantitative analysis. To discover the optimal structure and the effect of ammonia concentration, the bulk pH value, reaction temperature, and applied current of ammonia oxidation were investigated using potential sweep and galvanostatic methods. Finally, ammonia electrolysis was conducted using a zero-gap cell, producing highly pure hydrogen with an energy efficiency over 80 %. PMID:26530809

  13. High frequency reference electrode

    DOEpatents

    Kronberg, James W.

    1994-01-01

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or "halo" at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes.

  14. An ultrasensitive electrochemical genosensor for Brucella based on palladium nanoparticles.

    PubMed

    Rahi, A; Sattarahmady, N; Heli, H

    2016-10-01

    Palladium nanoparticles were potentiostatically electrodeposited on a gold surface at a highly negative potential. The nanostructure, as a transducer, was utilized to immobilize a Brucella-specific probe and the process of immobilization and hybridization was detected by electrochemical methods. The proposed method for detection of the complementary sequence and a non-complementary sequence was applied. The fabricated genosensor was evaluated for the assay of the bacteria in the cultured and human samples with and without PCR. The genosensor could detect the complementary sequence with a sensitivity of 0.02 μA dm(3) mol(-1), a linear concentration range of 1.0 × 10(-12) to 1.0 × 10(-19) mol dm(-3), and a detection limit of 2.7 × 10(-20) mol dm(-3). PMID:27423961

  15. Motion-driven electrochromic reactions for self-powered smart window system.

    PubMed

    Yeh, Min-Hsin; Lin, Long; Yang, Po-Kang; Wang, Zhong Lin

    2015-05-26

    The self-powered system is a promising concept for wireless networks due to its independent and sustainable operations without an external power source. To realize this idea, the triboelectric nanogenerator (TENG) was recently invented, which can effectively convert ambient mechanical energy into electricity to power up portable electronics. In this work, a self-powered smart window system was realized through integrating an electrochromic device (ECD) with a transparent TENG driven by blowing wind and raindrops. Driven by the sustainable output of the TENG, the optical properties, especially the transmittance of the ECD, display reversible variations due to electrochemical redox reactions. The maximum transmittance change at 695 nm can be reached up to 32.4%, which is comparable to that operated by a conventional electrochemical potentiostat (32.6%). This research is a substantial advancement toward the practical application of nanogenerators and self-powered systems. PMID:25808880

  16. Critical phenomena in magnetic nanowires.

    PubMed

    Kamalakar, M Venkata; Raychaudhuri, A K

    2009-09-01

    In this paper we report the first experimental study of critical phenomena in case of magnetic nanowires of nickel near the ferromagnetic-paramagnetic transition from the electrical transport properties. Nickel nanowire arrays, prepared by potentiostatic electrodeposition of nickel inside pores of nanoporous anodic alumina template were well characterized by X-ray Diffraction, Transmission electron microscopy and Energy dispersive Spectroscopy. Precise electrical resistance measurement of the nanowire arrays of wire diameter 20 nm have been done in the temperature range between 300 K to 700 K. We see a drop in the Curie temperature as observed from the resistivity anomaly. We analyzed the resistance data near the critical region and extracted the critical exponent alpha directly from the resistance. We observed a decrease in the critical part of the resistivity including a decrease in the magnitude of the critical exponent alpha and severe modification in the correction to scaling. PMID:19928208

  17. Modeling and analysis of a molten salt electrowinning system with liquid cadmium cathode

    SciTech Connect

    Kim, K.R.; Ahn, D.H.; Paek, S.; Kwon, S.W.; Kim, S.H.; Shim, J.B.; Chung, H.; Kim, E.H.

    2007-07-01

    In the present work, an electrowinning process in the LiCl-KCl/Cd system is considered to model and analyze the equilibrium behavior and electro-transport of the actinide and rare-earth elements. Equilibrium distributions of the actinide and rare-earth elements in a molten salt and liquid cadmium system have been estimated for an infinite potentiostatic electrolysis from the thermodynamic data and material balance. A simple dynamic modeling of this process was performed by taking into account the material balances and diffusion-controlled electrochemical reactions in a diffusion layer at an electrode interface between the molten salt and liquid cadmium cathode. This model demonstrated a prediction of the concentration behaviors, a faradic current of each element and an electrochemical potential as function of the time up to the corresponding electro-transport satisfying a given applied current based on a galvano-static electrolysis. (authors)

  18. 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.

  19. Sustainable Electrochemically-Mediated Atom Transfer Radical Polymerization with Inexpensive Non-Platinum Electrodes.

    PubMed

    Fantin, Marco; Lorandi, Francesca; Isse, Abdirisak A; Gennaro, Armando

    2016-08-01

    Electrochemically-mediated atom transfer radical polymerization (eATRP) of oligo(ethylene oxide) methyl ether methacrylate in water is investigated on glassy carbon, Au, Ti, Ni, NiCr and SS304. eATRPs are performed both in divided and undivided electrochemical cells operating under either potentiostatic or galvanostatic mode. The reaction is fast, reaching high conversions in ≈4 h, and yields polymers with dispersity <1.2 and molecular weights close to the theoretical values. Most importantly, eATRP in a highly simplified setup (undivided cell under galvanostatic mode) with inexpensive nonnoble metals, such as NiCr and SS304, as cathode is well-controlled. Additionally, these electrodes neither release harmful ions in solution nor react directly with the CX chain end and can be reused several times. It is demonstrated that Pt can be replaced with cheaper, and more readily available materials without negatively affecting eATRP performance. PMID:27333068

  20. Use of array of conducting polymers for differentiation of coconut oil products.

    PubMed

    Rañola, Rey Alfred G; Santiago, Karen S; Sevilla, Fortunato B

    2016-01-01

    An array of chemiresistors based on conducting polymers was assembled for the differentiation of coconut oil products. The chemiresistor sensors were fabricated through the potentiostatic electrodeposition of polyaniline (PANi), polypyrrole (PPy) and poly(3-methylthiophene) (P-3MTp) on the gap separating two planar gold electrodes set on a Teflon substrate. The change in electrical resistance of the sensors was measured and observed after exposing the array to the headspace of oil samples. The sensor response was found rapid, reversible and reproducible. Different signals were obtained for each coconut oil sample and pattern recognition techniques were employed for the analysis of the data. The developed system was able to distinguish virgin coconut oil (VCO) from refined, bleached & deodorised coconut oil (RBDCO), flavoured VCO, homemade VCO, and rancid VCO. PMID:26695237

  1. Dissolution of amorphous Ti-Zr-Si alloy during anodic oxidation with formation of barrier films

    SciTech Connect

    Isaev, N.I.; Yakovlev, V.B.; Iovdal'skii, A.A.; Gorshkov, T.P.

    1988-07-01

    Radiometric analysis of a solution has been used to study kinetic mechanisms for dissolution of amorphous alloy components in acid aqueous solutions with anodic oxidation in different regimes. In a galvanostatic regime for alloy and crystalline Ti, Zr, and Ta two sections are detected: an initial section of accelerated dissolution and a steady section. An increase in dissolution of zirconium from the alloy has been revealed compared with pure crystalline zirconium. Potentiostatic oxidation is accompanied by a slowdown in dissolution similar to a change in current. Current yield has been analyzed for dissolution of the main elements and nonrectifying impurities of the alloy (for example copper). Gamma spectroscopy using the gamma radiation from neutron-activated isotopes of the components and impurities was performed.

  2. Surface Morphology of Si(111) during Electrochemical Oxidation

    NASA Astrophysics Data System (ADS)

    Ando, A.; Miki, K.; Sakamoto, K.; Matsumoto, K.; Morita, Y.; Tokumoto, H.

    1997-03-01

    Topographical changes of hydrogen terminated Si(111) during electrochemical oxidation in a 0.2 M H_2SO4 aqueous solution have been investigated using atomic force microscopy (AFM). The hydrogen terminated surface with atomically flat terraces was prepared by dipping into a NH_4F aqueous solution. Electrochemical oxidation has been performed by a potentiostatic (constant potential) or a galvanostatic (constant current) method. AFM images show that the oxidation occured on the terraces and proceeded homogeneously. The surface became rough as the oxidation proceeded. However, step edges were still observed even after the charge of 50 mC/cm^2 was applied. Quantitative analysis of a relation between the charge and surface morphology will be discussed. the address below:

  3. Considerations on electrical impedance measurements of electrolyte solutions in a four-electrode cell

    NASA Astrophysics Data System (ADS)

    Chaparro, C. V.; Herrera, L. V.; Meléndez, A. M.; Miranda, D. A.

    2016-02-01

    A tetrapolar probe to measure the electrical properties of electrolyte solutions was implemented with gold electrodes according to the van der Pauw method. Electrical impedance spectroscopy (EIS) measurements of different concentrations of phosphate buffer saline (PBS) solution and an oral mucosal tissue sample dispersed in PBS were performed in the galvanostatic mode using a four-electrode cell (tetrapolar probe). Taking advantage of using a potentiostat/galvanostat for carrying out the electrical measurements, a simple and rapid method using a three-electrode electrochemical cell is described for: a) cleaning of electrodes, b) verification of surface chemical state of electrode material and c) choice of current supplied to electrodes for EIS measurements. Results of this research shown a depolarization effect due to the addition of oral mucosa tissue cells into the PBS solution.

  4. Electrochemical Behavior of CrN Coated on 316L Stainless Steel in Simulated Cathodic Environment of Proton Exchange Membrane Fuel Cell

    NASA Astrophysics Data System (ADS)

    Nam, Nguyen Dang; Kim, Jung-Gu

    2008-08-01

    Four types of CrN coating were deposited on type 316L stainless steel by magnetron sputtering physical vapor deposition (PVD) for use in bipolar plates. Four samples deposited at various bias voltages were evaluated under potentiodynamic, potentiostatic, and electrochemical impedance spectroscopy (EIS) conditions. EIS data were monitored for 96 h in an aerated corrosive environment at 70 °C to determine coating performance at +600 mV application. The electrochemical behavior of the coatings was enhanced with decreasing bias voltage. The CrN films on the 316L stainless steel substrate exhibited high protective efficiency, that is, increasing corrosion resistance with decreasing bias voltage. X-ray diffraction (XRD) analysis confirmed the formation of crystalline-refined CrN(200) at a low bias voltage.

  5. Engineering PQS Biosynthesis Pathway for Enhancement of Bioelectricity Production in Pseudomonas aeruginosa Microbial Fuel Cells

    PubMed Central

    Cao, Bin; Seviour, Thomas; Nesatyy, Victor J.; Marsili, Enrico; Kjelleberg, Staffan; Givskov, Michael; Tolker-Nielsen, Tim; Song, Hao; Loo, Joachim Say Chye; Yang, Liang

    2013-01-01

    The biosynthesis of the redox shuttle, phenazines, in Pseudomonas aeruginosa, an ubiquitous microorganism in wastewater microflora, is regulated by the 2-heptyl-3,4-dihydroxyquinoline (PQS) quorum-sensing system. However, PQS inhibits anaerobic growth of P. aeruginosa. We constructed a P. aeruginosa strain that produces higher concentrations of phenazines under anaerobic conditions by over-expressing the PqsE effector in a PQS negative ΔpqsC mutant. The engineered strain exhibited an improved electrical performance in microbial fuel cells (MFCs) and potentiostat-controlled electrochemical cells with an approximate five-fold increase of maximum current density relative to the parent strain. Electrochemical analysis showed that the current increase correlates with an over-synthesis of phenazines. These results therefore demonstrate that targeting microbial cell-to-cell communication by genetic engineering is a suitable technique to improve power output of bioelectrochemical systems. PMID:23700414

  6. Pharmacokinetic study of medicinal polymers: models based on dextrans

    SciTech Connect

    Kulakov, V.N.; Pimenova, G.N.; Matveev, V.A.; Sedov, V.V.; Vasil'ev, A.E.

    1986-09-01

    The authors study the pharmacokinetics of dextrans with various molecular masses modified by fluorescein isothiocyanate (FITC) using a radioisotope method. The radionuclide /sup 125/I was selectively bound to a FITC residue attached to the polysaccharide by electrochemical iodination under potentiostatic conditions. In the experiments, dextrans modified by FITC were labeled with /sup 125/I (DF-/sup 125/I) by electrochemical iodination. The separation of DF-/sup 125/I and FITC from ionic forms of the radionuclide not bound to the polymer was carried out. The properties of the samples obtained are presented. The radioactivity accumulated in the rate organs and urine studied are shown. The features of DF-/sup 125/I behavior in the blood and liver are examined.

  7. The effect of deposition electrolyte on polypyrrole surface interaction with biological environment

    NASA Astrophysics Data System (ADS)

    Mîndroiu, Mihaela; Ungureanu, Camelia; Ion, Raluca; Pîrvu, Cristian

    2013-07-01

    The effects of electrolyte type used in electrodeposition of polypyrrole (PPy) films on Ti6Al7Nb alloy was studied in order to design a titanium modified surface with enhanced antibacterial activity and better biocompatibility. Therefore, the polypyrrole coatings were synthesized by potentiostatic electrochemically technique from pyrrole and lithium perchlorate (LiClO4) using aqueous and non-aqueous solutions. The both PPy films were characterized by electrochemical methods in Hank's Balanced Salt Solution (HBSS), and surface characterization by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) analysis, adhesion test and contact angle measurements. A correlation between the film stability and surface properties, synthesis parameters and the interaction with biological environment was established. The physical-chemical properties of the studied PPy films are in direct related with the doping level and have an important influence of the biocompatibility and antibacterial activity.

  8. Inhibition of mild steel corrosion by sodium dodecyl benzene sulfonate and sodium oleate in acidic solutions

    SciTech Connect

    Luo, H.; Han, K.N.; Guan, Y.C.

    1998-08-01

    Inhibition of mild steel corrosion by sodium dodecyl benzene sulfonate (C{sub 12}H{sub 25}C{sub 6}H{sub 4}SO{sub 3}Na [SDBS]) and sodium oleate (CH{sub 3}[CH{sub 2}]{sub 7}CH{double_bond}CH[CH{sub 2}]{sub 7}COONa) in acidic solutions was investigated using a potentiostat, a lock-in amplifier, a contact angle goniometer, A fourier transform infrared (FTIR) spectrometer, and an ultraviolet (UV)/visible spectrophotometer. In the presence of the organic inhibitors, the corrosion rate was reduced significantly, Anionic SDBS was adsorbed on the positively charged mild steel surface through the electrostatic attraction. However, for sodium oleate, the soluble oleic acid (CH{sub 3}[CH{sub 2}]{sub 7}CH{double_bond}CH[CH]{sub 7}COOH) chemisorbed on the steel surface at the first stage. Then, insoluble colloid adsorbed on the chemisorbed surface through van der Waals forces.

  9. Corrosion characteristics of anodized Ti-(10-40wt%)Hf alloys for metallic biomaterials use.

    PubMed

    Jeong, Yong-Hoon; Choe, Han-Cheol; Brantley, William A

    2011-01-01

    The effect of anodizing on corrosion resistance of Ti-xHf alloys has been investigated. Ti-xHf alloys were prepared and anodized at 120, 170 and 220 V in 1 M H(3)PO(4) solution, and crystallized at 300 and 500°C. Corrosion experiments were carried out using a potentiostat in 0.15 M NaCl solution at 36.5 ± 1°C. The Ti-xHf alloys exhibited the α' and anatase phases. The pore size on the anodized surface increases as the applied voltage is increased, whereas the pore size decreases as the Hf content is increased. The anodized Ti-xHf alloys exhibited better corrosion resistance than non-anodized Ti-xHf alloys. PMID:21104193

  10. Tuning the characteristics of electrochemically fabricated gold nanowires.

    PubMed

    Karim, S; Ensinger, W; Cornelius, T W; Khan, E U; Neumann, R

    2008-11-01

    We have developed different electrochemical procedures for the production of gold nanowires with variable and controllable crystallographic and morphological properties using etched ion track templates. The texture of the nanowires is tuned by the variation of the electrodeposition parameters. Potentiostatic plating at low overvoltage provides strongly (110) textured wires for diameters below 100 nm. With the increase in diameter above 100 nm, this texture decreases and the signal from ({111} planes becomes more pronounced. Under reverse pulse deposition conditions, (100) textured wires are generated. The growth mechanism is discussed in detail in terms of the surface energy minimum principle. In addition, wires are shaped in a reliable way from cylindrical to conical geometry by engineering the pore structure in the template. PMID:19198285

  11. Redox mechanism in the binary transition metal phosphide Cu3P

    NASA Astrophysics Data System (ADS)

    Mauvernay, B.; Doublet, M.-L.; Monconduit, L.

    2006-05-01

    The electrochemical behaviour of the binary transition metal phosphide Cu3P towards lithium is investigated through galvano- and potentiostatic measurements. Obtained through high-temperature synthesis, this system shows a better volumetric capacity than graphite and a good capacity retention. In situ X-ray diffraction and first-principles electronic structure calculations are combined with the electrochemical results to show that the complete insertion of 3Li+ in the Cu3P electrode proceeds with the formation of three intermediate phases of lithium composition LixCu(3-x)P (x=1,2,3). The extra capacity previously observed in discharge is now clearly assigned to lithium insertion into the CuP2 impurity and to SEI reactions.

  12. One-step through-mask electrodeposition of a porous structure composed of manganese oxide nanosheets with electrocatalytic activity for oxygen reduction

    SciTech Connect

    Fukuda, Masaki; Iida, Chihiro; Nakayama, Masaharu

    2009-06-03

    Potentiostatic electrolysis of a mixed aqueous solution of Bu{sub 4}NBr and MnSO{sub 4} at +1.0 V (vs. Ag/AgCl) on Pt electrode led to the oxidation of Br{sup -} and Mn{sup 2+} ions. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and X-ray diffraction (XRD) revealed that this anodic process was followed by the deposition of insulating crystals of bromide salt of Bu{sub 4}N{sup +} and the subsequent formation of layered manganese oxide in the interstitial spaces of the bromide grains already grown. Dissolution of the bromide crystals in water left a well-dispersed porous texture composed of manganese oxide nanosheets. The resulting MnO{sub x}-modified electrode exhibited a larger catalytic current for the reduction of oxygen in alkaline solution, compared to the bare Pt electrode.

  13. A portable hypergolic oxidizer vapor sensor for NASA's Space Shuttle program

    NASA Technical Reports Server (NTRS)

    Helms, W. R.

    1978-01-01

    The design and performance characteristics of an electrochemical NO2 sensor selected by NASA for the space shuttle program is described. The instrument consists of a sample pump, an electrochemical cell, and control and display electronics. The pump pushes the sample through the electrochemical cell where the vapors are analyzed and an output proportional to the NO2 concentration is produced. The output is displayed on a panel meter, and is also available at a recorder jack. The electrochemical cell is made up of a polypropylene chamber covered with teflon membrane faceplates. Plantinum electrodes are bonded to the faceplates, and the sensing and counter electrodes are potentiostatically controlled at -200 mV with respect to the reference electrode. The cell is filled with electrolyte, consisting of 13.5 cc of 23% solution of KOH.

  14. Reproducible and recyclable SERS substrates: Flower-like Ag structures with concave surfaces formed by electrodeposition

    NASA Astrophysics Data System (ADS)

    Bian, Juncao; Shu, Shiwei; Li, Jianfu; Huang, Chao; Li, Yang Yang; Zhang, Rui-Qin

    2015-04-01

    Direct synthesis of three-dimensional Ag structures on solid substrates for the purposes of producing reproducible and recyclable surface-enhanced Raman scattering (SERS) applications remains challenging. In this work, flower-like Ag structures with concave surfaces (FACS) were successfully electrodeposited onto ITO glass using the double-potentiostatic method. The FACS, with an enhancement factor of the order of 108, exhibited a SERS signal intensity 3.3 times stronger than that measured from Ag nanostructures without concave surfaces. A cleaning procedure involving lengthy immersion of the sample in ethanol and KNO3 was proposed to recycle the substrate and confirmed by using rhodamine 6G, adenine, and 4-aminothiophenol as target molecules. The findings can help to advance the practical applications of Ag nanostructure-based SERS substrates.

  15. Photoelectrochemical and Electrochemical Characterization of Sub-Micro-Gram Amounts of Organic Semiconductors Using Scanning Droplet Cell Microscopy.

    PubMed

    Kollender, Jan Philipp; Gasiorowski, Jacek; Sariciftci, Niyazi S; Mardare, Andrei I; Hassel, Achim Walter

    2014-07-31

    A model organic semiconductor (MDMO-PPV) was used for testing a modified version of a photoelectrochemical scanning droplet cell microscope (PE-SDCM) adapted for use with nonaqueous electrolytes and containing an optical fiber for localized illumination. The most attractive features of the PE-SDCM are represented by the possibility of addressing small areas on the investigated substrate and the need of small amounts of electrolyte. A very small amount (ng) of the material under study is sufficient for a complete electrochemical and photoelectrochemical characterization due to the scanning capability of the cell. The electrochemical behavior of the polymer was studied in detail using potentiostatic and potentiodynamic investigations as well as electrochemical impedance spectroscopy. Additionally, the photoelectrochemical properties were investigated under illumination conditions, and the photocurrents found were at least 3 orders of magnitude higher than the dark (background) current, revealing the usefulness of this compact microcell for photovoltaic characterizations. PMID:25101149

  16. Photoelectrochemical and Electrochemical Characterization of Sub-Micro-Gram Amounts of Organic Semiconductors Using Scanning Droplet Cell Microscopy

    PubMed Central

    2014-01-01

    A model organic semiconductor (MDMO-PPV) was used for testing a modified version of a photoelectrochemical scanning droplet cell microscope (PE-SDCM) adapted for use with nonaqueous electrolytes and containing an optical fiber for localized illumination. The most attractive features of the PE-SDCM are represented by the possibility of addressing small areas on the investigated substrate and the need of small amounts of electrolyte. A very small amount (ng) of the material under study is sufficient for a complete electrochemical and photoelectrochemical characterization due to the scanning capability of the cell. The electrochemical behavior of the polymer was studied in detail using potentiostatic and potentiodynamic investigations as well as electrochemical impedance spectroscopy. Additionally, the photoelectrochemical properties were investigated under illumination conditions, and the photocurrents found were at least 3 orders of magnitude higher than the dark (background) current, revealing the usefulness of this compact microcell for photovoltaic characterizations. PMID:25101149

  17. Enhanced performance of hexavalent chromium reducing cathodes in the presence of Shewanella oneidensis MR-1 and lactate.

    PubMed

    Xafenias, Nikolaos; Zhang, Yue; Banks, Charles J

    2013-05-01

    Biocathodes for the reduction of the highly toxic hexavalent chromium (Cr(VI)) were investigated using Shewanella oneidensis MR-1 (MR-1) as a biocatalyst and performance was assessed in terms of current production and Cr(VI) reduction. Potentiostatically controlled experiments (-500 mV vs Ag/AgCl) showed that a mediatorless MR-1 biocathode started up under aerated conditions in the presence of lactate, received 5.5 and 1.7 times more electrons for Cr(VI) reduction over a 4 h operating period than controls without lactate and with lactate but without MR-1, respectively. Cr(VI) reduction was also enhanced, with a decrease in concentration over the 4 h operating period of 9 mg/L Cr(VI), compared to only 1 and 3 mg/L, respectively, in the controls. Riboflavin, an electron shuttle mediator naturally produced by MR-1, was also found to have a positive impact in potentiostatically controlled cathodes. Additionally, a microbial fuel cell (MFC) with MR-1 and lactate present in both anode and cathode produced a maximum current density of 32.5 mA/m(2) (1000 Ω external load) after receiving a 10 mg/L Cr(VI) addition in the cathode, and cathodic efficiency increased steadily over an 8 day operation period with successive Cr(VI) additions. In conclusion, effective and continuous Cr(VI) reduction with associated current production were achieved when MR-1 and lactate were both present in the biocathodes. PMID:23517384

  18. Corrosion of stainless steel, nickel-titanium, coated nickel-titanium, and titanium orthodontic wires.

    PubMed

    Kim, H; Johnson, J W

    1999-02-01

    Orthodontic wires containing nickel have been implicated in allergic reactions. The potential for orthodontic wires to cause allergic reactions is related to the pattern and mode of corrosion with subsequent release of metal ions, such as nickel, into the oral cavity. The purpose of this study was to determine if there is a significant difference in the corrosive potential of stainless steel, nickel titanium, nitride-coated nickel titanium, epoxy-coated nickel titanium, and titanium orthodontic wires. At least two specimens of each wire were subjected to potentiostatic anodic dissolution in 0.9% NaCl solution with neutral pH at room temperature. Using a Wenking MP 95 potentiostat and an electrochemical corrosion cell, the breakdown potential of each wire was determined. Photographs were taken of the wire speci mens using a scanning electron microscope, and surface changes were qualitatively evaluated. The breakdown potentials of stainless steel, two nickel titanium wires, nitride-coated nickel titanium, epoxy-coated nickel titanium, and titanium were 400 mV, 300 mV, 750 mV, 300 mV, 1800 mV, and >2000 mV, respectively. SEM photographs revealed that some nickel titanium and stainless steel wires were susceptible to pitting and localized corrosion. The results indicate that corrosion occurred readily in stainless steel. Variability in breakdown potential of nickel titanium alloy wires differed across vendors' wires. The nitride coating did not affect the corrosion of the alloy, but epoxy coating decreased corrosion. Titanium wires and epoxy-coated nickel titanium wires exhibited the least corrosive potential. For patients allergic to nickel, the use of titanium or epoxy-coated wires during orthodontic treatment is recommended. PMID:10022183

  19. Electrochemically and bioelectrochemically induced ammonium recovery.

    PubMed

    Gildemyn, Sylvia; Luther, Amanda K; Andersen, Stephen J; Desloover, Joachim; Rabaey, Korneel

    2015-01-01

    Streams such as urine and manure can contain high levels of ammonium, which could be recovered for reuse in agriculture or chemistry. The extraction of ammonium from an ammonium-rich stream is demonstrated using an electrochemical and a bioelectrochemical system. Both systems are controlled by a potentiostat to either fix the current (for the electrochemical cell) or fix the potential of the working electrode (for the bioelectrochemical cell). In the bioelectrochemical cell, electroactive bacteria catalyze the anodic reaction, whereas in the electrochemical cell the potentiostat applies a higher voltage to produce a current. The current and consequent restoration of the charge balance across the cell allow the transport of cations, such as ammonium, across a cation exchange membrane from the anolyte to the catholyte. The high pH of the catholyte leads to formation of ammonia, which can be stripped from the medium and captured in an acid solution, thus enabling the recovery of a valuable nutrient. The flux of ammonium across the membrane is characterized at different anolyte ammonium concentrations and currents for both the abiotic and biotic reactor systems. Both systems are compared based on current and removal efficiencies for ammonium, as well as the energy input required to drive ammonium transfer across the cation exchange membrane. Finally, a comparative analysis considering key aspects such as reliability, electrode cost, and rate is made. This video article and protocol provide the necessary information to conduct electrochemical and bioelectrochemical ammonia recovery experiments. The reactor setup for the two cases is explained, as well as the reactor operation. We elaborate on data analysis for both reactor types and on the advantages and disadvantages of bioelectrochemical and electrochemical systems. PMID:25651406

  20. Analysis of electrochemical noise from metastable pitting in aluminum, aged Al-2%Cu, and AA 2024-T3

    SciTech Connect

    Pride, S.T.; Scully, J.R.; Hudson, J.L.

    1996-12-31

    The authors compare methods of analyzing electrochemical current (ECN) and potential (EPN) noise data associated with metastable pitting and the transition from metastable to stable pitting. Various analysis methods were applied to electrochemical noise data associated with metastable pit events on aluminum, aged Al-2%Cu, and AA 2024-T3 ST. Two experimental approaches were used. High-purity Al, roughly simulating copper-depleted grain boundary zones in aged Al-Cu alloys, was potentiostatically polarized so that current spikes associated with individual pitting events could be analyzed. Second, the coupling current between nominally identical galvanically coupled Al, aged Al-2%Cu, and AA 2024-T3 ST electrodes was recorded in conjunction with couple potential using a saturated calomel reference electrode. Pit stabilization occurred when individual pits exceeded a threshold of I{sub pit}/r{sub pit} > 10{sup {minus}2} A/cm at all times during pit growth as established from potentiostatic measurements. The magnitude of this ratio is linked directly to the concentration of the aggressive solution within pits. Two related statistical pit stabilization factors (I{sub rms}/r{sub pit total} from ECN data and the mean of (I{sub peak}-I{sub ox})/r{sub pit} values from each pit current spike) were obtained from galvanic ECN data containing a large number of pit current spikes. These parameters provided a better indication of the transition to stable pitting than the pitting index or noise resistance but also had shortcomings. Spectral analysis using current and potential spectral power density (SPD) data provided qualitative information on pit susceptibility. However, the transition to stable pitting could not be accurately defined because of a lack of information on pit sizes in spectral data.

  1. Prediction of Failure Due to Thermal Aging, Corrosion and Environmental Fracture in Amorphous and Titanium Alloys

    SciTech Connect

    Farmer, J C

    2003-04-15

    DARPA is exploring a number of advanced materials for military applications, including amorphous metals and titanium-based alloys. Equipment made from these materials can undergo degradation due to thermal aging, uniform corrosion, pitting, crevice corrosion, denting, stress corrosion cracking, corrosion fatigue, hydrogen induced cracking and microbial influenced corrosion. Amorphous alloys have exceptional resistance to corrosion, due in part to the absence of grain boundaries, but can undergo crystallization and other phase instabilities during heating and welding. Titanium alloys are extremely corrosion resistant due to the formation of a tenacious passive film of titanium oxide, but is prone to hydrogen absorption in crevices, and hydrogen induced cracking after hydrogen absorption. Accurate predictions of equipment reliability, necessary for strategic planning, requires integrated models that account for all relevant modes of attack, and that can make probabilistic predictions. Once developed, model parameters must be determined experimentally, and the validity of models must be established through careful laboratory and field tests. Such validation testing requires state-of-the-art surface analytical techniques, as well as electrochemical and fracture mechanics tests. The interaction between those processes that perturb the local environment on a surface and those that alter metallurgical condition must be integrated in predictive models. The material and environment come together to drive various modes of corrosive attack (Figure 1). Models must be supported through comprehensive materials testing capabilities. Such capabilities are available at LLNL and include: the Long Term Corrosion Test Facility (LTCTF) where large numbers of standard samples can be exposed to realistic test media at several temperature levels; a reverse DC machine that can be used to monitor the propagation of stress corrosion cracking (SCC) in situ; and banks of potentiostats with

  2. A combined electrochemical and optical trapping platform for measuring single cell respiration rates at electrode interfaces

    SciTech Connect

    Gross, Benjamin J.; El-Naggar, Mohamed Y.

    2015-06-15

    Metal-reducing bacteria gain energy by extracellular electron transfer to external solids, such as naturally abundant minerals, which substitute for oxygen or the other common soluble electron acceptors of respiration. This process is one of the earliest forms of respiration on earth and has significant environmental and technological implications. By performing electron transfer to electrodes instead of minerals, these microbes can be used as biocatalysts for conversion of diverse chemical fuels to electricity. Understanding such a complex biotic-abiotic interaction necessitates the development of tools capable of probing extracellular electron transfer down to the level of single cells. Here, we describe an experimental platform for single cell respiration measurements. The design integrates an infrared optical trap, perfusion chamber, and lithographically fabricated electrochemical chips containing potentiostatically controlled transparent indium tin oxide microelectrodes. Individual bacteria are manipulated using the optical trap and placed on the microelectrodes, which are biased at a suitable oxidizing potential in the absence of any chemical electron acceptor. The potentiostat is used to detect the respiration current correlated with cell-electrode contact. We demonstrate the system with single cell measurements of the dissimilatory-metal reducing bacterium Shewanella oneidensis MR-1, which resulted in respiration currents ranging from 15 fA to 100 fA per cell under our measurement conditions. Mutants lacking the outer-membrane cytochromes necessary for extracellular respiration did not result in any measurable current output upon contact. In addition to the application for extracellular electron transfer studies, the ability to electronically measure cell-specific respiration rates may provide answers for a variety of fundamental microbial physiology questions.

  3. A combined electrochemical and optical trapping platform for measuring single cell respiration rates at electrode interfaces

    NASA Astrophysics Data System (ADS)

    Gross, Benjamin J.; El-Naggar, Mohamed Y.

    2015-06-01

    Metal-reducing bacteria gain energy by extracellular electron transfer to external solids, such as naturally abundant minerals, which substitute for oxygen or the other common soluble electron acceptors of respiration. This process is one of the earliest forms of respiration on earth and has significant environmental and technological implications. By performing electron transfer to electrodes instead of minerals, these microbes can be used as biocatalysts for conversion of diverse chemical fuels to electricity. Understanding such a complex biotic-abiotic interaction necessitates the development of tools capable of probing extracellular electron transfer down to the level of single cells. Here, we describe an experimental platform for single cell respiration measurements. The design integrates an infrared optical trap, perfusion chamber, and lithographically fabricated electrochemical chips containing potentiostatically controlled transparent indium tin oxide microelectrodes. Individual bacteria are manipulated using the optical trap and placed on the microelectrodes, which are biased at a suitable oxidizing potential in the absence of any chemical electron acceptor. The potentiostat is used to detect the respiration current correlated with cell-electrode contact. We demonstrate the system with single cell measurements of the dissimilatory-metal reducing bacterium Shewanella oneidensis MR-1, which resulted in respiration currents ranging from 15 fA to 100 fA per cell under our measurement conditions. Mutants lacking the outer-membrane cytochromes necessary for extracellular respiration did not result in any measurable current output upon contact. In addition to the application for extracellular electron transfer studies, the ability to electronically measure cell-specific respiration rates may provide answers for a variety of fundamental microbial physiology questions.

  4. Real-time telemetry system for amperometric and potentiometric electrochemical sensors.

    PubMed

    Wang, Wei-Song; Huang, Hong-Yi; Chen, Shu-Chun; Ho, Kuo-Chuan; Lin, Chia-Yu; Chou, Tse-Chuan; Hu, Chih-Hsien; Wang, Wen-Fong; Wu, Cheng-Feng; Luo, Ching-Hsing

    2011-01-01

    A real-time telemetry system, which consists of readout circuits, an analog-to-digital converter (ADC), a microcontroller unit (MCU), a graphical user interface (GUI), and a radio frequency (RF) transceiver, is proposed for amperometric and potentiometric electrochemical sensors. By integrating the proposed system with the electrochemical sensors, analyte detection can be conveniently performed. The data is displayed in real-time on a GUI and optionally uploaded to a database via the Internet, allowing it to be accessed remotely. An MCU was implemented using a field programmable gate array (FPGA) to filter noise, transmit data, and provide control over peripheral devices to reduce power consumption, which in sleep mode is 70 mW lower than in operating mode. The readout circuits, which were implemented in the TSMC 0.18-μm CMOS process, include a potentiostat and an instrumentation amplifier (IA). The measurement results show that the proposed potentiostat has a detectable current range of 1 nA to 100 μA, and linearity with an R2 value of 0.99998 in each measured current range. The proposed IA has a common-mode rejection ratio (CMRR) greater than 90 dB. The proposed system was integrated with a potentiometric pH sensor and an amperometric nitrite sensor for in vitro experiments. The proposed system has high linearity (an R2 value greater than 0.99 was obtained in each experiment), a small size of 5.6 cm × 8.7 cm, high portability, and high integration. PMID:22164093

  5. Effects of Crystallographic Orientation on Corrosion Behavior of Magnesium Single Crystals

    NASA Astrophysics Data System (ADS)

    Shin, Kwang Seon; Bian, Ming Zhe; Nam, Nguyen Dang

    2012-06-01

    The corrosion behavior of magnesium single crystals with various crystallographic orientations was examined in this study. To identify the effects of surface orientation on the corrosion behavior in a systematic manner, single-crystal specimens with ten different rotation angles of the plane normal from the [0001] direction to the [ 10overline{1} 0] direction at intervals of 10° were prepared and subjected to potentiodynamic polarization and potentiostatic tests as well as electrochemical impedance spectroscopy (EIS) measurements in 3.5 wt.% NaCl solution. Potentiodynamic polarization results showed that the pitting potential ( E pit) first decreased from -1.57 V SCE to -1.64 V SCE with an increase in the rotation angle from 0° to 40°, and then increased to -1.60 V SCE with a further increase in the rotation angle to 90°. The results obtained from potentiostatic tests are also in agreement with the trend in potentiodynamic polarization tests as a function of rotation angle. A similar trend was also observed for the depressed semicircle and the total resistances in the EIS measurements due to the facile formation of MgO and Mg(OH)2 passive films on the magnesium surface. In addition, the amount of chloride in the passive film was found first to increase with an increase in rotation angle from 0° to 40°, then decrease with a further increase in rotation angle, indicating that the tendency to form a more protective passive film increased for rotation angle near 0° [the (0001) plane] or 90° [the ( 10overline{1} 0) plane].

  6. A combined electrochemical and optical trapping platform for measuring single cell respiration rates at electrode interfaces.

    PubMed

    Gross, Benjamin J; El-Naggar, Mohamed Y

    2015-06-01

    Metal-reducing bacteria gain energy by extracellular electron transfer to external solids, such as naturally abundant minerals, which substitute for oxygen or the other common soluble electron acceptors of respiration. This process is one of the earliest forms of respiration on earth and has significant environmental and technological implications. By performing electron transfer to electrodes instead of minerals, these microbes can be used as biocatalysts for conversion of diverse chemical fuels to electricity. Understanding such a complex biotic-abiotic interaction necessitates the development of tools capable of probing extracellular electron transfer down to the level of single cells. Here, we describe an experimental platform for single cell respiration measurements. The design integrates an infrared optical trap, perfusion chamber, and lithographically fabricated electrochemical chips containing potentiostatically controlled transparent indium tin oxide microelectrodes. Individual bacteria are manipulated using the optical trap and placed on the microelectrodes, which are biased at a suitable oxidizing potential in the absence of any chemical electron acceptor. The potentiostat is used to detect the respiration current correlated with cell-electrode contact. We demonstrate the system with single cell measurements of the dissimilatory-metal reducing bacterium Shewanella oneidensis MR-1, which resulted in respiration currents ranging from 15 fA to 100 fA per cell under our measurement conditions. Mutants lacking the outer-membrane cytochromes necessary for extracellular respiration did not result in any measurable current output upon contact. In addition to the application for extracellular electron transfer studies, the ability to electronically measure cell-specific respiration rates may provide answers for a variety of fundamental microbial physiology questions. PMID:26133851

  7. (Titanium, chromium) nitride coatings for bipolar plate of polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Choi, H. S.; Han, D. H.; Hong, W. H.; Lee, J. J.

    (Titanium, chromium) nitride [(Ti,Cr)N] coatings are synthesized on a 316L stainless-steel substrate by inductively-coupled, plasma-assisted, reactive direct current magnetron sputtering. The chemical and electrical properties of the coating are investigated from the viewpoint of it application to bipolar plates. Nanocrystallized Cr-Ti films are formed in the absence of nitrogen gas, while a hexagonal β-(Ti,Cr) 2N phase is observed at N 2 = 1.2 sccm. Well-crystallized (Ti,Cr)N films are obtained at N 2 > 2.0 sccm. The corrosion resistance of the coating is examined by potentiodynamic and potentiostatic tests in 0.05 M H 2SO 4 + 0.2 ppm HF solution at 80 °C, which simulates the operation conditions of a polymer electrolyte membrane fuel cell. The Davies method is used to measure the interfacial contact resistance between the sample and carbon paper. The (Ti,Cr)N coating exhibits the highest corrosion potential and lowest current density. In a cathode environment, the corrosion potential and current density are 0.33 V (vs. SCE) and <5 × 10 -7 A cm -2 (at 0.6 V), respectively. In an anode environment the corresponding values are 0.16 V and <-5 × 10 -8 A cm -2 at -0.1 V. The (Ti,Cr)N coatings exhibit excellent stability during potentiostatic polarization tests in both anode and cathode environments. The interfacial contact resistance decreases with deposition of the (Ti,Cr)N film, and a minimum value of 4.5 mΩ cm 2 is obtained at a compaction force of 150 N cm -2, which indicates that the formation of oxide films can be successfully prevented by the (Ti,Cr)N film. Analysis with Auger electron spectroscopy reveals that the oxygen content at the surface decreases with increase in the nitrogen content.

  8. Statistic analysis of operational influences on the cold start behaviour of PEM fuel cells

    NASA Astrophysics Data System (ADS)

    Oszcipok, M.; Riemann, D.; Kronenwett, U.; Kreideweis, M.; Zedda, M.

    For portable fuel cell systems a multitude of applications have been presented over the past few years. Most of these applications were developed for indoor use, and not optimised for outdoor conditions. The key problem concerning this case is the cold start ability of the polymer electrolyte membrane fuel cell (PEMFC). This topic was first investigated by the automotive industry, which has the same requirements for alternative traction systems as for conventional combustion engines. The technical challenge is the fact that produced water freezes to ice after shut-down of the PEMFC and during start-up when the temperature is below 0 °C. To investigate the basic cold start behaviour isothermal, potentiostatic single cell experiments were performed and the results are presented. The cold start behaviour is evaluated using the calculated cumulated charge transfer through the membrane which directly corresponds with the amount of produced water in the PEMFC. The charge transfer curves were mathematically fitted to obtain only three parameters describing the cold start-up with the cumulated charge transfer density and the results are analysed using the statistical software Cornerstone 4.0. The results of the statistic regression analyses are used to establish a statistic-based prediction model of the cold start behaviour which describes the behaviour of the current density during the experiment. The regression shows that the initial start current mainly depends on the membrane humidity and the operation voltage. After the membrane humidity has reached its maximum, the current density drops down to zero. The current decay also depends on the constant gas flows of the reactant gases. Ionic conductivity of the membrane and charge transfer resistance were investigated by a series of ac impedance spectra during potentiostatic operation of the single cell at freezing temperatures. Cyclic voltammetry and polarisation curves between cold start experiments show degradation

  9. Effects of TiN coating on the corrosion of nanostructured Ti-30Ta-xZr alloys for dental implants

    NASA Astrophysics Data System (ADS)

    Kim, Won-Gi; Choe, Han-Cheol

    2012-01-01

    Electrochemical characteristics of a titanium nitride (TiN)-coated/nanotube-formed Ti-Ta-Zr alloy for biomaterials have been researched by using the magnetic sputter and electrochemical methods. Ti-30Ta-xZr (x = 3, 7 and 15 wt%) alloys were prepared by arc melting and heat treated for 24 h at 1000 °C in an argon atmosphere and then water quenching. The formation of oxide nanotubes was achieved by anodizing a Ti-30Ta-xZr alloy in H3PO4 electrolytes containing small amounts of fluoride ions at room temperature. Anodization was carried out using a scanning potentiostat, and all experiments were conducted at room temperature. The microstructure and morphology of nanotube arrays were characterized by optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The TiN coatings were obtained by the radio-frequency (RF) magnetron sputtering technique. The depositions were performed from pure Ti targets on Ti-30Ta-xZr alloys substrates. The corrosion properties of the specimens were examined using potentiodynamic test in a 0.9% NaCl solution by using potentiostat. The microstructures of Ti-30Ta-xZr alloys were changed from an equiaxed to a needle-like structure with increasing Zr content. The interspace between the nanotubes was approximately 20, 80 and 200 nm for Zr contents of 3, 7 and 15 wt%, respectively. The corrosion resistance of the TiN-coated on the anodized Ti-30Ta-xZr alloys was higher than that of the untreated Ti alloys, indicating a better protective effect.

  10. Improved lithium storage properties of electrospun TiO2 with tunable morphology: from porous anatase to necklace rutile

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Wang, Haiying; Zhou, Qiwen; Kong, Mengqi; Ye, Haitao; Yang, Gang

    2013-10-01

    Three-dimensional TiO2 with tunable morphology and crystalline phase was successfully prepared by the electrospinning technique and subsequent annealing. Porous-shaped anatase TiO2, cluster-shaped anatase TiO2, hierarchical-shaped rutile (minor) TiO2 and nano-necklace rutile (major) TiO2 were achieved at 500, 600, 700 and 800 °C, respectively. The mechanism of the formation of these tailored morphologies and crystallinity was investigated. Lithium insertion properties were evaluated by galvanostatic and potentiostatic modes in half-cell configurations. By combining the large surface area, open mesoporosity and stable crystalline phase, the porous-shaped anatase TiO2 exhibited the highest capacity, best rate and cycling performance among the four samples. The present results demonstrated the usefulness of three-dimensional TiO2 as an anode for lithium storage with improved electrode performance.Three-dimensional TiO2 with tunable morphology and crystalline phase was successfully prepared by the electrospinning technique and subsequent annealing. Porous-shaped anatase TiO2, cluster-shaped anatase TiO2, hierarchical-shaped rutile (minor) TiO2 and nano-necklace rutile (major) TiO2 were achieved at 500, 600, 700 and 800 °C, respectively. The mechanism of the formation of these tailored morphologies and crystallinity was investigated. Lithium insertion properties were evaluated by galvanostatic and potentiostatic modes in half-cell configurations. By combining the large surface area, open mesoporosity and stable crystalline phase, the porous-shaped anatase TiO2 exhibited the highest capacity, best rate and cycling performance among the four samples. The present results demonstrated the usefulness of three-dimensional TiO2 as an anode for lithium storage with improved electrode performance. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02819d