Sample records for potentiostats

  1. Potentiostats

    NSDL National Science Digital Library

    This 52 page PDF document provides a comprehensive discussion including background history, theoretical considerations, electronic circuitry and design of potentiostats. The subject is treated in depth and would be a useful introduction to the topic.

  2. A portable and wireless data transmission potentiostat

    Microsoft Academic Search

    Chun-Yueh Huang; Huan-Yu Lin; Yu-Chien Wang; Wei-Yin Liao; Tse-Chuan Chou

    2004-01-01

    We propose a portable and wireless data transmission potentiostat and further exert the pH sensor to verify its performance. This potentiostat can be used to process the long-distance remote electrochemical signals of the amperometric sensor and the potentiometric sensor. Based on the popular general packet radio service (GPRS) communication systems, a personal digital assistant (PDA) cell phone, instead of personal

  3. An Inexpensive Field-Programmable Potentiostat

    NSDL National Science Digital Library

    Gopinath, Ashwini Vittal

    This article describes the practical design and construction of a small, inexpensive programmable potentiostat including a list of the components and circuitry for building a complete self-contained potentiostat - all for approximately $50 in component cost. Explanation is given about the basics and the operational characteristics of this potentiostat, illustrated by running cyclic voltammetric scans of potassium ferricyanide in a 3-electrode cell. The noise, as seen by the small oscillations on the voltammograms, may be lessened by the use of a shielded/grounded case with use of BNC connectors for attaching the electrodes to the potentiostat. Some of the components may no longer be manufactured and may have to substituted with equivalent available parts. Students interested in analytical instrumentation or electrochemistry, including projects involving field-portable electrochemical instrumentation, might also find this potentiostat useful. This is a good example of a practical instrument/ circuit design.

  4. Wireless Multichannel Integrated Potentiostat for Distributed Neurotransmitter Sensing

    E-print Network

    Cauwenberghs, Gert

    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- time multi-channel acquisition of dopamine concentration in vitro is performed with carbon fiber

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

    PubMed

    Steinberg, Matthew D; Kassal, Petar; Kerekovi?, Irena; Steinberg, Ivana Murkovi?

    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

  6. VLSI Potentiostat Array with Oversampling Gain Modulation for Wide-Range Neurotransmitter

    E-print Network

    Stanacevic, Milutin

    1 VLSI Potentiostat Array with Oversampling Gain Modulation for Wide-Range Neurotransmitter Sensing of neurotransmitter concentration. Index Terms-- Potentiostat, biomedical instrumentation, cur- rent measurement, require real- time and sensitive detection and monitoring of neurotransmit- ters. Neurotransmitters

  7. Variable gain CMOS potentiostat for dissolved oxygen sensor

    Microsoft Academic Search

    Mei Yee Ng; Yuzman Yusoff

    2010-01-01

    This paper presents a variable gain potetiostat designed for the electrochemical control of Dissolved Oxygen (DO) sensors. The design is targeted for implementation using MIMOS 0.35 um CMOS process technology at 3.3V. The potentiostat amplifier for dissolved oxygen utilizes three electrodes (working, reference and counter) which work together to form the electrochemical reaction. There are several types of DO sensor

  8. A micro-hole potentiostatic oxygen sensor for oceanic CTDs

    Microsoft Academic Search

    M. J. Atkinson; F. I. M. Thomas; N. Larson; E. Terrill; K. Morita; C. C. Liu

    1995-01-01

    A non-membrane, micro-hole, potentiostatic oxygen sensor was designed and tested for use on an oceanic CTD. The sensor consists of three electrodes: a carbon-fiber cathode, a Ag\\/ AgC1 reference and a platinum anode; all are mounted in a plexiglass flow duct. The carbon-fiber cathode is a bundle of 1000 carbon fibers recessed in epoxy and electroplated with platinum. The sensor

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

    SciTech Connect

    Roy, A.K. [Framatome Cogema Fuels, Livermore, CA (United States); Fleming, D.L.; Gordon, S.R. [Lawrence Livermore National Lab., CA (United States)

    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.

  10. Signal Integrity Analysis of a 2-D and 3-D Integrated Potentiostat for Neurotransmitter Sensing

    E-print Network

    Stanacevic, Milutin

    Signal Integrity Analysis of a 2-D and 3-D Integrated Potentiostat for Neurotransmitter Sensing for neurotransmitter sensing are investigated and compared. The potentiostat is implemented as current integrating with the neurotransmitter sensing circuit to generate an entire model to analyze signal integrity. Contrary

  11. Parametric optimization of a new combined refrigeration cycle – active thermal potentiostatting system

    Microsoft Academic Search

    Xingmei Ye; Jincan Chen; Guoxing Lin

    2007-01-01

    The active thermal potentiostatting system proposed by Martinovskii and Tsirlin is directly generalized to a more practical case, in which one intermediate chamber, besides a thermal potentiostatting chamber, and two irreversible refrigeration cycles are included and the influence of the thermal resistance between the working fluid and the reservoirs, the heat leakages from the environment to the intermediate chamber and

  12. Development of a computer controlled multichannel potentiostat for applications with flowing solution analysis

    Microsoft Academic Search

    Tang Fang; Michael McGrath; Dermot Diamond; Malcolm R. Smyth

    1995-01-01

    A 4-channel computer controlled potentiostat has been designed (expandable to 16 channels) for use with an amperometric array for analysis in flowing streams. The instrumentation developed to date has been used with both linear and radial flow cell configurations. Analogue and digital circuits for the independent control of 4 working electrodes have been fabricated, tested and integrated successfully to give

  13. Passive iron in acid medium. analysis of the anodic current transient under potentiostatic control

    Microsoft Academic Search

    R. M. Carranza; M. Chocron; J. R. Collet Lacoste; R. E. Gonnet

    1998-01-01

    Current transients for iron in its full passive state in acid media were studied under potentiostatic control. The experimental results were quantitatively interpreted through an analytical approximate equation relating the instationary-state current with the transient charge, based on Vetters electrode kinetics model of the passive iron interphase and the introduction of a potential distribution dependent on time across the passive

  14. Wide-Range, Picoampere-Sensitivity Multichannel VLSI Potentiostat for Neurotransmitter Sensing

    E-print Network

    Stanacevic, Milutin

    Wide-Range, Picoampere-Sensitivity Multichannel VLSI Potentiostat for Neurotransmitter Sensing@bme.jhu.edu, miki@jhu.edu, gert@jhu.edu Abstract-- Neurotransmitter sensing is critical in studying ner- vous neurotransmitters like dopamine, nitric oxide etc. The analog-to-digital converter design employs a current

  15. Potentiostatic study of reinforcing steel in chloride contaminated concrete powder solution extracts

    Microsoft Academic Search

    Chetan Kapat; Bulu Pradhan; B. Bhattacharjee

    2006-01-01

    This paper presents the findings of an experimental investigation of potentiostatic study on reinforcing steel in chloride contaminated concrete powder solution extracts. Various zones of corrosion for the steel reinforcement at various chloride levels have been identified. In addition the chloride concentration and pH value of these solutions were also measured. The major test variables include steel type, w\\/c ratio,

  16. Synthesis of Pt nanoparticles on electrochemically reduced graphene oxide by potentiostatic and alternate current methods

    SciTech Connect

    Molina, J.; Fernández, J.; Río, A.I. del; Bonastre, J.; Cases, F., E-mail: fjcases@txp.upv.es

    2014-03-01

    Reduced graphene oxide (RGO) has been synthesized on Pt wires by means of a potentiodynamic method between + 0.6 V and ? 1.4 V for 20 scans. Cyclic voltammetry characterization of the coatings showed the typical capacitative behavior of graphene. Pt nanoparticles were synthesized on Pt–RGO electrodes by means of potentiostatic methods and a comparison between different synthesis potentials (? 0.16, 0, + 0.2 and + 0.4 V) for the same synthesis charge (mC·cm{sup ?2}) was established. The electrodes obtained were characterized in 0.5 M H{sub 2}SO{sub 4} solution to observe the characteristic oxidation and reduction processes of the Pt surface. A 0.5 M H{sub 2}SO{sub 4}/0.5 M CH{sub 3}OH solution was used to measure the catalytic properties of the deposits against methanol oxidation. The most appropriate potential to perform the synthesis was 0 V followed by ? 0.16 V and + 0.2 V. The morphology of the coatings varied depending on the potential applied as observed by scanning electron microscopy. Alternate current methods were also used to synthesize Pt nanoparticles and compare the results with the traditional potentiostatic method. Different frequencies were used: 0.1, 1, 10, 100, 1000 and 10 000 Hz. Alternate current synthesis is more efficient than traditional potentiostatic methods, obtaining more electroactive coatings with less effective synthesis time. - Highlights: • Reduced graphene oxide has been obtained by electrochemical reduction on Pt wires. • Pt nanoparticles have been obtained potentiostatically at different potentials. • Pt nanoparticles have been obtained by ac methods with different frequencies. • ac synthesis is a better synthesis method than potentiostatic synthesis.

  17. 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

  18. An improved technique for dental alloy etching with a potentiostatic device.

    PubMed

    Hong, C Y

    1989-10-01

    Since a good retention of direct bonded retainers onto abutment teeth is the primary requirement for the fabrication of etched fixed partial dentures, successful formation of a micromechanical retentive architecture on the bonding surface is one of the most important procedures. For creating such a retentive dendritic pattern on nonprecious metal, a 2-electrode electrolytic method has been used. This equipment consists of a low-voltage DC power supply and two electrodes, namely, a working and a counter one. However, the current and voltage should be monitored during the entire processing time and the etching area must be pre-estimated. A potentiostat has been used to automatically stabilize the voltage across the working electrode and reference electrode by adjusting the current, as commonly employed in electro-chemical technology. A 3-electrode corrosion device originally developed for laboratory research was adapted for dental retainer etching in this study. The results revealed that the etching of dental nonprecious metal (Ni-Cr-Be alloy) could successfully be performed by using the system with a potentiostat. Moreover, the working potential was found to be approximately 1.3 volts by taking the midpoint between the breakdown and the critical potentials for passivation on the potentiostatic anode polarization curves. The optimal exposure time has been found to be in a range of 3 to 5 minutes and 4 minutes to be ideal as determined by SEM microphotographic observation which showed a uniform dendritic pattern with regular lattice form of alternating ridges and valleys.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2700236

  19. CheapStat: an open-source, "do-it-yourself" potentiostat for analytical and educational applications.

    PubMed

    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

  20. POTENTIOSTATIC DEPOSITION OF COPPER INDIUM DISULFIDE THIN FILMS: EFFECT OF CATHODIC POTENTIALS ON THE OPTICAL AND PHOTOELECTROCHEMICAL PROPERTIES

    Microsoft Academic Search

    Teo Sook Liang; Zulkarnain Zainal; Tan Wee Tee; Imad Hamadneh

    CuInS 2 thin films were one-step potentiostatically deposited onto indium tin oxide (ITO) coated glass from aqueous solution containing CuCl 2, InCl 3 and Na 2S2O3. The effect of cathodic potentials on the structural, photoelectrochemical and optical properties of the deposited film were studied. X-ray diffraction (XRD) patterns showed that the deposited CuInS 2 material was polycrystalline with tetragonal structure.

  1. Precision determination of copper in samples of high-Tc superconductors by potentiostatic coulometry

    SciTech Connect

    Markova, I.V. [V.I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Moscow (Russian Federation)

    1994-04-10

    An important task in the creation of high-Tc superconductors of required composition is the sufficiently accurate determination of the main components of high-Tc superconductors. One of the most widely encountered elements appearing in high-Tc superconductors is copper, whose precision determination is possible by coulometry. The coulometric determination of copper is generally accomplished by reducing Cu(II) or Cu(I) to the metal on electrodes prepared from various materials (Pt, C). There have been reports to the determination of macroscopic quantities of copper with the aid of coulometric titrations. The relative standard deviation (s{sub r}) in these procedures for determining copper exceeds 0.01. A procedure for the simultaneous determination of copper and indium in CuInS{sub 2} by controlled-potential coulometry on a large mercury electrode in NaCl solutions was proposed (s{sub r} did not exceed 0.05, and the range of determinable amounts of copper extended from 0.3 to 3 mg). The determination of copper by potentiostatic coulometry on an automated computer-controlled system using a gold indicator electrode was described by Subochev et al.. They proposed the use of 1 M HCl and the reversible reaction (1) CuCl {r_equilibrium} Cu{sup 2+} + Cl{sup {minus}} + e. for the coulometric determination of macroscopic and microgram quantities of copper. This case offers an optimal situation for coulometry, under which both forms of the redox system [the reactant and product forms, which are Cu(I) and Cu(II) in the present case], remain in the solution. This makes it possible to repeat determinations many times in single aliquot portion of the solution and thus to improve the metrological characteristics of the determinations. Here, the authors investigated the possibility of using reaction (1) and a Pt screen with a large surface as the working electrode to determine copper in high-Tc superconducting materials which also contain barium, yttrium, and thallium.

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

    SciTech Connect

    Lundblad, A.; Bjoernbom, P. (Royal Inst. of Tech., Stockholm (Sweden). 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.

  3. Integrated potentiostat for electrochemical sensing of urinary 3-hydroxyanthranilic acid with molecularly imprinted poly(ethylene-co-vinyl alcohol).

    PubMed

    Huang, Chun-Yueh; O'Hare, Danny; Chao, I-Jen; Wei, Hung-Wei; Liang, Yi-Fan; Liu, Bin-Da; Lee, Mei-Hwa; Lin, Hung-Yin

    2015-05-15

    Changing demographics, the rise of personalized medicine and increased identification of biomarkers for diagnosis and management of chronic disease have increased the demand for portable bioanalytical instrumentation and point-of-care. The recent development of molecularly imprinted polymers enables production of low cost and highly stable sensing chips; however, the commercially available and full functional instruments employed for electrochemical analysis have shortcomings in actual homecare applications. In this work, integrated circuits (ICs) for monolithic implementation of voltammeter potentiostat with a large dynamic current range (5 nA to 1.2 mA) and short conversion time (10 ms) were fabricated in a 0.35 ?m complementary metal-oxide-semiconductor (CMOS) process. The new instrumentation was tested with molecular imprinted sensors for 3-hydroxyanthranilic acid (3HAA) in urine. The sensor consisted of molecular imprinted of poly(ethylene-co-vinyl alcohol)s (abbreviated as EVALs) for implementation in a flow injection analysis system. The EVAL containing 32 ethylene mol% had the highest imprinting effectiveness for the target molecules. Fit-for-purpose figures of merit were achieved with a limit-of-detection (LOD) of 3.06 pg/mL. The measurements obtained in real undiluted urine samples fell within the reference concentration range of 50-550 ng/mL. PMID:25175746

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

    SciTech Connect

    Evans, Kenneth J. [Lawrence Livermore National Laboratory, Livermore, CA, 94550 (United States); Rebak, Raul B. [Chemistry and Materials Science, Lawrence Livermore National Laboratory, 7000 East Ave, L- 631, Livermore, CA, 94550 (United States)

    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)

  5. The use of a new potentiostat/coulometer in the controlled-potential coulometric determination of plutonium

    SciTech Connect

    Mendoza, P.G. Jr.; Temer, D.J.; Jackson, D.D.

    1993-10-01

    We evaluated a PAR 273 potentiostat and PAR 279 coulometer using iron as a stand-in for plutonium. Over 400 tuns consisting of electrical checks, blanks, and iron solutions were made. Manual operation of the instrumentation produced precisions better than 0.1%. Computer control of the instrumentation produced precisions better than 0.1%. Computer control of the instrumentation using a PC and a program written in QuickBASIC produced precisions of about 0.12%. The computer program automatically set up and controlled the instrumentation and recorded the data. The potentionstat`s current autoranging function caused erractic coulometer results. Use of the PAR 273`s low-pass filter (LPF) removed the amperometric end-point current noise, but it also biased the current. The PAR 273A`s LPF filtered the noise without introducing a bias. The coulometer functions, such as current integration and communication interface, occasionally locked up after a current overrange condition. The occasional procedural error revealed that the potentionstat`s ability to produce >1 A current can ruin the coulometer`s impact circuitry, which is protected up to 0.2 A for current ranges <1 A.

  6. Corrosion behavior of glassy Ni 55Co 5Nb 20Ti 10Zr 10 alloy in 1 N HCl solution studied by potentiostatic polarization and XPS

    Microsoft Academic Search

    Shu-jie Pang; Chan-hung Shek; Tao Zhang; Katsuhiko Asami; Akihisa Inoue

    2006-01-01

    Corrosion resistance of glassy Ni55Co5Nb20Ti10Zr10 (at.%) alloy in 1N HCl solution was investigated with respect to the electrochemical behavior and the compositions of the passive film and the underlying alloy surface just below the passive film. The potentiostatic polarization curve indicated that the alloy was spontaneously passivated with a low passive current density of the order of 10?3Am?2. The quantitative

  7. Stochastic approach to the pit growth kinetics of Inconel alloy 600 in Cl ? ion-containing thiosulphate solution at temperatures 25–150 °C by analysis of the potentiostatic current transients

    Microsoft Academic Search

    Jin-Ju Park; Su-Il Pyun

    2004-01-01

    The pit growth kinetics of Inconel alloy 600 in aqueous 0.1 M Na2S2O3+0.1 M NaCl solutions was investigated as a function of solution temperature by analysis of the potentiostatic current transient, based upon a stochastic theory. Potentiostatic current transients revealed that time necessary for pit embryo formation, tpit,form decreased with increasing solution temperature. Analysis of the statistical distribution of tpit,form

  8. Comparative corrosion performance of black oxide, sandblasted, and fine-drawn nitinol wires in potentiodynamic and potentiostatic tests: effects of chemical etching and electropolishing.

    PubMed

    Shabalovskaya, Svetlana; Rondelli, Gianni; Anderegg, James; Xiong, J P; Wu, Ming

    2004-05-15

    The corrosion performance of sandblasted (SB) and smooth fine-drawn (FD) medical-use nitinol wires was compared with the performance of wires with black oxide (BO) formed in air during their manufacture. Potentiodynamic and ASTM F746 potentiostatic tests in a 0.9 % NaCl solution were conducted on wires in their as-received, chemically etched, aged in boiling water, and electropolished states. As-received wires with various surface finishes revealed breakdown potentials in the range from -100 mV to +500 mV; similar passive current density, 10(-6) A/cm(2); and a wide hysteresis on the reverse scan, demonstrating strong susceptibility to localized corrosion. Chemically etched wires with original black oxide displayed consistent corrosion performance and surpassed, in corrosion resistance, electropolished wires that showed significantly lower breakdown (400-700 mV) and localized corrosion potentials ( approximately -50 to +113 mV). Sandblasted and fine-drawn wires exhibited rather inconsistent corrosion behavior. In potentiodynamic tests these wires could perform with equal probability either on the level of pretreated BO wires or rather similar to as-received wires. Both SB and FD wires revealed low breakdown potentials in the PS regime. SEM analysis performed before tests indicated that sandblasting was not efficient for the complete removal of the original scaling, and fine drawing aggravated the situation, resulting in a persistent scaling that contributed to the inferior corrosion performance. Inclusions (oxides, carbides, and oxidized carbides) inherited from the bulk and retained on electropolished surfaces are the cause of their inferior performance compared to chemically etched surfaces. In electropolished wires corrosion was initiated around inclusions. PMID:15116412

  9. PARSTAT 2273 Advanced Potentiostat/Galvanostat/FRA

    E-print Network

    Ulm, Universität

    systems will be measured. Applications · Research Electrochemistry · Corrosion · Sensors · Batteries Bus (USB), so there is no need for an additional card for your system. Electrochemistry Power for long term, heavy load operations #12;4 Applications Research Electrochemistry The physical nature

  10. 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

  11. VLSI POTENTIOSTAT ARRAY FOR DISTRIBUTED ELECTROCHEMICAL NEURAL Abhishek Bandyopadhyay1

    E-print Network

    Cauwenberghs, Gert

    A neurochemical sensor system is being developed to spa- tially sense and process neurotransmitters. This paper re system will be used to measure the concentration of nitric-oxide (NO), a diffusible neurotransmitter

  12. VLSI POTENTIOSTAT FOR AMPEROMETRIC MEASUREMENTS FOR ELECTROLYTIC Harpreet S. Narula and John G. Harris

    E-print Network

    Harris, John G.

    fixed po- tential between electrodes of the chemical reaction. Threats of chemical and biological terror chemical sensor. A technique of converting input currents into time for amperometric measurements is pro. Experimental results are reported showing the performance of the circuit as a chemical sensor. 2. INTRODUCTION

  13. Field calibration of a microhole potentiostatic oxygen sensor for oceanic CTDs

    NASA Astrophysics Data System (ADS)

    Thomas, F. I. M.; Atkinson, M. J.

    1995-04-01

    A new type of oxygen sensor for use on oceanic profiling CTDs has a response time that ranges from 0.4 to 0.7 s, depending on temperature. This oxygen (O2) sensor was calibrated in the field against O2 concentrations that were determined from Winkler titrations of Niskin-bottle water samples. Calibration coefficients were obtained from single casts and composite casts. When casts were calibrated separately, the mean error in predicting O2 concentrations was 1.22 +/- 0.72 micro(M) O2, n = 19 casts, and was not significantly different from the error between Niskin-bottle samples, which was 1.01 +/- 2.33 micro(M) O2, n = 33 triplicate or duplicate bottles. When casts were combined into a composite cast for an entire cruise, however, the mean error in the calibrations increased to 5.03 +/- 4.06 micro(m) O2, n = 19 casts. These results also indicate that only three Niskin bottles on a cast are requried to obtain an error of 1.0 micro(M) in predicted oxygen. For routine use, we recommend calibrating each cast separately using either three or four measured O2 concentrations to obtain calibration coefficients.

  14. Determination of the Crevice Repassivation Potential of Alloy 22 By a Potentiodynamic-Galvanostatic-Potentiostatic Method

    SciTech Connect

    K. Evans; L. Wong; R. Rebak

    2004-06-01

    Alloy 22 (N06022) is a nickel-based alloy highly resistant to corrosion. In some aggressive conditions of high chloride concentration, temperature and applied potential, Alloy 22 may suffer crevice corrosion, a form of localized corrosion. There are several electrochemical methods that can be used to determine localized corrosion in metallic alloys. One of the most popular for rapid screening is the cyclic potentiodynamic polarization (CPP). This work compares the results obtained by measuring the localized corrosion resistance of Alloy 22 using both CPP and the more cumbersome Tsujikawa-Hisamatsu Electrochemical (THE) method. The electrolytes used were 1 M NaCl and 5 M CaCl{sub 2}, both at 90 C. Results show that similar repassivation potentials were obtained for Alloy 22 using both methods. That is, in cases where localized corrosion is observed using the fast CPP method, there is no need to use THE method since it takes ten times longer to obtain comparable results in spite of the mode of corrosion attack is different in the tested specimens.

  15. A Novel Multi-Working Electrode Potentiostat for Electrochemical Detection of Metabolites

    E-print Network

    De Micheli, Giovanni

    metabolites and exogenous drugs in the blood or in the interstitial fluid. One of the challenges in this field in the same time, and the integration with the required electronics, can pave the way to smart systems used

  16. Study of Metal-NH[subscript 3] Interfaces (Metal= Cu, Ni, Ag) Using Potentiostatic Curves

    ERIC Educational Resources Information Center

    Nunes, Nelson; Martins, Angela; Leitao, Ruben Elvas

    2007-01-01

    Experiment is conducted to determine the kinetic parameters of metal-solution interfaces. During the experiment the kinetic parameters for the interfaces Cu-NH[subscript 3], Ag-NH[subscript 3] and Ni-NH[subscript 3] is easily determined.

  17. 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

  18. Ae response of 316L SS during SSR test under potentiostatic control fn1 fn1 This paper was presented at UK Corr. 1997

    Microsoft Academic Search

    Ahmet Cakir; Sabri Tuncell; Alptekin Aydin

    1999-01-01

    The acoustic emission (AE) response of an implant quality 316L stainless steel (SS) during slow strain rate tensile testing (SSRT) at a constant strain rate of 7.35×10?6 has been measured in Hanks solution with pH 4 at and around the pitting potential, Epit, of 110 mV(SCE). AE signals were detected by using a piezoelectric sensor. AE Signals recorded in the

  19. Electrochemical modeling of intercalation processes with phase field models

    E-print Network

    Ceder, Gerbrand

    Intermittent Titration Technique (GITT) and Potentiostatic Intermittent Titration Technique (PITT). We show Intermittent Titration Technique (GITT) and Potentiostatic Intermittent Titration Technique (PITT) methods [15

  20. 338 IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS, VOL. 7, NO. 3, JUNE 2013 CMOS Neurotransmitter Microarray: 96-Channel

    E-print Network

    Genov, Roman

    Neurotransmitter Microarray: 96-Channel Integrated Potentiostat With On-Die Microsensors Meisam Honarvar Nazari, Senior Member, IEEE Abstract--A 8 12 array of integrated potentiostats for on-CMOS neurotransmitter and an on-chip microfluidic network. It is experimentally validated in in-situ recording of neurotransmitter

  1. Mathematical modelling of electrochemical chloride extraction from concrete

    Microsoft Academic Search

    C. Andrade; J. M. Diez; A. Alamán; C. Alonso

    1995-01-01

    Equations to calculate the duration of electrochemical chloride extraction have been proposed and solved for the case of a constant chloride concentration in the concrete or for a concentration following the error function trend.In the case of constant initial chloride content, both potentiostatic and galvanostatic operation have being considered, while only the potentiostatic one was considered in the case of

  2. Influence of cell voltage and current on sulfur poisoning behavior of solid oxide fuel cells

    Microsoft Academic Search

    Zhe Cheng; Shaowu Zha; Meilin Liu

    2007-01-01

    The sulfur poisoning behavior of nickel-yttria stabilized zirconia (YSZ) cermet anodes in solid oxide fuel cells (SOFCs) was investigated under both potentiostatic and galvanostatic conditions. While the observed relative drop in cell power output caused by sulfur poisoning decreases as the cell-terminal voltage is lowered potentiostatically (thus more current passing through the cell), it increases as more current is drawn

  3. 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

  4. RESEARCH/RESEARCHERS MRS BULLETIN VOLUME 33 NOVEMBER 2008 www.mrs.org/bulletin 989

    E-print Network

    Lakhtakia, Akhlesh

    by potentiostatically anodizing 99.5%-pure titanium foils in a dimethylformamide electrolyte solution containing 0.5 wt such that the microstructure and nanostructure are captured. Butterfly wings are covered with scales to a density of 200

  5. Mixed Conduction in Rare-Earth Phosphates

    E-print Network

    Ray, Hannah Leung

    2012-01-01

    dc   measurements.     The   samples   were   placed  in  the  center  of  a  tube  furnace,  furnace.   The   Bio-­?Logic   potentiostat/galvanostat   and   EC-­?Lab   software   were   used   for   the   DC  

  6. Well-defined ultrathin Pd films on Pt(111): electrochemical preparation and interfacial chemistry 

    E-print Network

    Park, Yeon Su

    2005-08-29

    Well-defined ultrathin films of palladium, with coverages ranging from submonolayer, ?Pd = 0.5 monolayer (ML), to multilayer, ?P d = 8 ML, were electrochemically deposited on Pt(111) using potentiostatic and ...

  7. Effect of electrode configuration and electronic conductivity on current density distribution measurements in PEM fuel cells

    E-print Network

    Natarajan, Dilip; Van Nguyen, Trung

    2004-09-03

    of commercially available gas diffusion layers. Both galvanostatic and potentiostatic discharge modes were employed. Irrespective of the type of gas diffusion layer, when a common electrode was employed, significant performance variations were encountered between...

  8. 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...

  9. Development of Dual-Electrode Amperometric Detectors for Liquid Chromatography and Capillary Electrophoresis

    E-print Network

    Dorris, Megan

    2013-05-31

    .2.2.2.1 Cellulose Acetate Decoupler……………………………………………………………..…..77 3.2.2.2.2 Wireless Isolated Potentiostat and End Column Detection on PDMS Microchips…………………………………………………………………………………………….81 3.2.2.3 Instrumental Conditions………………………………………………………………………………..85...

  10. Educator's Reference Guide for Electrochemistry

    NSDL National Science Digital Library

    This is a 70 page primer on analytical electrochemistry of interest to faculty, students and practitioners wanting to learn basic concepts and applications of the topic. The material discusses voltammetry, major techniques and minor variations, the potentiostat and electrochemical cells.

  11. Evaluation of zirconium-iron-rhenium alloys as surrogates for a technetium alloy waste form

    E-print Network

    Mews, Paul Aaron

    2009-05-15

    wt% Re, 3) a rhenium-zirconium intermetallic, 4) another Fe-Zr intermetallic with very little Re, and 5) a Fe-Re intermetallic. Potentiostatic and potentiodynamic electrochemical tests were performed using sulfuric acid to evaluate the corrosion...

  12. Physicochemical properties of carbon steel with a vacuum-diffusion chromium coating

    Microsoft Academic Search

    E. P. Ponomarenko; L. I. Filina; V. P. Rebrunov; N. I. Shatalov

    1974-01-01

    The electrochemical investigations were made at 20 and 60~ with recording of anodic potentiostatic curves on the P-5827 potentiostat at the rate of 2.4 V\\/h and current-time curves at constant potentials. The measurements were made in a thermostatically controlled cell. Comparisons with a saturated calomel electrode, with a separate screen, were made at room temperature. The side surface and the

  13. Proceeding of the VI INTERNATIONAL CONFERENCE ON CLEAN TECHNOLOGIES FOR THE MINING INDUSTRY, University of Concepción, Chile RECYCLING PROCESS OF LI-ION BATTERIES AND FINAL ELECTROCHEMICAL PURIFICATION OF THE Co CONTAINING EXHAUSTED SOLUTIONS

    Microsoft Academic Search

    L. Criscuoli; C. Lupi; M. Pasquali

    The recycling process studied deals with cobalt electrolytic recovery from Li-ion batteries by means of both galvanostatic and potentiostatic electrowinning followed by an electrochemical purification of the exhausted electrolyte. A good Co metal deposit with a purity of 99.95% was produced by working at 250 A\\/m 2 current density and 50 °C temperature, while working in potentiostatic conditions (-0.9V vs.

  14. Electrochemical behavior of nitinol alloy in Ringer's solution.

    PubMed

    Sun, E X; Fine, S; Nowak, W B

    2002-10-01

    Corrosion behavior of Nitinol (nickel titanium) alloy has been examined in physiological Ringer's solution by means of electrochemical techniques (open-circuit potential measurement, potentiodynamic and potentiostatic polarizations) and capacitance measurements. The results show that the passive film is stable at open-circuit condition, but many of anodic current transients are observed at potentiodynamic and potentiostatic polarizations. The thickness of passive film decreased because of the occurrence of dissolution. PMID:15348190

  15. Fractal analysis of pit morphology of Inconel alloy 600 in sulphate, nitrate and bicarbonate ion-containing sodium chloride solution at temperatures of 25–100 °C

    Microsoft Academic Search

    Su-Il Pyun; Jin-Ju Park

    2004-01-01

    Pit morphology of Inconel alloy 600 in sulphate (SO 4 2-), nitrate (NO 3 -) and bicarbonate (HCO 3 -) ion-containing 0.5 M sodium chloride (NaCl) solution was analysed in terms of fractal geometry as functions of solution temperature and anion concentration using the potentiostatic current transient technique, scanning electron microscopy, image analysis and ac-impedance spectroscopy. Potentiostatic current transients revealed that

  16. A Study on Stress Corrosion Cracking of X70 Pipeline Steel in Carbonate Solution by EIS

    NASA Astrophysics Data System (ADS)

    Shahriari, A.; Shahrabi, T.; Oskuie, A. A.

    2013-05-01

    In this study, electrochemical impedance spectroscopy (EIS) simultaneously with the slow strain rate testing were used to investigate the stress corrosion cracking (SCC) behavior of X70 pipeline steel in high pH bicarbonate solution at different applied potentials. Potentiostatic EIS tests were also conducted at certain times to determine the changes associated with the SCC. Circuit models for the cracking were proposed by the use of the potentiostatic EIS measurements at different applied potentials. Finally, the results of the potentiostatic EIS tests and the SSR tests showed the decline of the circuit element resistance by increasing the stress which was related to the cracking. It was also observed that the X70 pipeline steel was most susceptible to SCC at potential of -650 mV versus SCE.

  17. 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.

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

    DOEpatents

    Frazzini, Thomas L. (Frankfort, IL); Holland, Michael K. (LaGrange Park, IL); Pietri, Charles E. (Downers Grove, IL); Weiss, Jon R. (Downers Grove, IL)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

  20. 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.

  1. Evaluation of Ti-6Al-4V Parts Produced with Rapid Prototyping Technology: Electron Beam Melting Machine

    E-print Network

    Abdeen, Dana

    2014-09-29

    The present study measured the corrosion properties of Ti-6Al-4V parts produced with Electron Beam Melting machine (EBM). Potentiodynamic and potentiostatic tests were applied on EBM Ti-6Al-4V in 3.5% mass NaCl solution, to determine the pitting...

  2. 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...

  3. Microstructural and electrochromic characteristics of electrodeposited and annealed WO 3 films

    Microsoft Academic Search

    A. K. Srivastava; M. Deepa; S. Singh; R. Kishore; S. A. Agnihotry

    2005-01-01

    Thin films of WO3 for electrochromic window applications have been potentiostatically electrodeposited from a precursor sol of acetylated peroxotungstic acid. Although the film annealed at 100 °C is amorphous to X-rays, transmission electron microscopy (TEM) findings reveal that the film is not only nanostructured but is also characterized by localized regions of amorphous phase and microcrystals of the hexagonal structure.

  4. Dependence of the Critical Pitting Temperature on surface roughness

    Microsoft Academic Search

    M. H. Moayed; N. J. Laycock; R. C. Newman

    2003-01-01

    It has been known for many years that highly alloyed stainless steels display a critical pitting temperature (CPT), which is the lowest temperature at which the growth of stable pits is possible. In the work reported here, the effect of varying surface roughness was investigated using potentiostatic and potentiodynamic CPT measurements on 904L stainless steel in 1 M NaCl. The

  5. Graphite electrodes as electron donors for anaerobic respiration

    Microsoft Academic Search

    Kelvin B. Gregory; Daniel R. Bond; Derek R. Lovley

    2004-01-01

    Summary It has been demonstrated previously that Geobacter species can transfer electrons directly to electrodes. In order to determine whether electrodes could serve as electron donors for microbial respiration, enrich- ment cultures were established from a sediment inoc- ulum with a potentiostat-poised graphite electrode as the sole electron donor and nitrate as the electron acceptor. Nitrate was reduced to nitrite

  6. Application of Bacterial Biocathodes in Microbial Fuel Cells Zhen He, Largus T. Angenent*

    E-print Network

    Review Application of Bacterial Biocathodes in Microbial Fuel Cells Zhen He, Largus T. Angenent breakthroughs are made. Keywords: Microbial fuel cell, Biofuel cell, Biocathode, Potentiostat-poised half cell, microbial fuel cells (MFCs) are special types of biofuel cells, producing electric power by utilizing

  7. Aerated Shewanella oneidensis in Continuously Fed Bioelectrochemical Systems for Power and

    E-print Network

    Angenent, Lars T.

    in a microbial fuel cell (MFC). The potentiostatic performance of aerated S. oneidensis was considerably enhanced; microbial electrolysis cell; microbial fuel cell; lactate; hydrogen Introduction Shewanella oneidensis MR-1 of BESs have broadened the application range from power generation with microbial fuel cells (MFCs

  8. The effect of water content on the electropolishing behavior of Inconel 718 alloy in perchloric–acetic acid mixtures

    Microsoft Academic Search

    Ching An Huang; Yu Chen Chen

    2009-01-01

    The electropolishing behavior of Inconel 718 alloy was studied in perchloric–acetic acid mixtures using a rotating disc electrode. The electropolishing behavior of an Inconel 718 weld, which was prepared with electron beam welding, was also investigated. A leveled but not brightened surface can be achieved when Inconel 718 alloy is potentiostatically polished in the acid mixture with 20vol.% perchloric acid.

  9. Wireless Integrated Voltametric and Amperometric Biosensing 1Mohsen Mollazadeh, 1Kartikeya Murari,1Christian Sauer, 2Milutin Stanacevic, 1Nitish Thakor,

    E-print Network

    Cauwenberghs, Gert

    foundry service. Potentiostat data sampled at Fs(pot) Field potential data sampled at Fs(fp) Data burst © RRX© FS(pot) Power/ clocks LSK modulated transmission at RTX Power © 4MHz / Power/ Data burst @ RRX r implantable scenario. The field potential chip is under testing. In this work, field potential data are played

  10. Conformal Metal Thin Films for H2 Purification and Fuel-Cell Catalyst Applications Tyler Munhollon, Coe College, SURF 2009 Fellow

    E-print Network

    Li, Mo

    use. A solution was made from nickel sulfate, boric acid, phosphorous acid, ethylene diamine, all the thin film membranes and then test the composition, as well as do electron imaging and XRD to find out the sides of the substrate. An Arbin potentiostat was used to run all of the test. The voltage ranged from

  11. Evaluation of Ti-6Al-4V Parts Produced with Rapid Prototyping Technology: Electron Beam Melting Machine 

    E-print Network

    Abdeen, Dana

    2014-09-29

    The present study measured the corrosion properties of Ti-6Al-4V parts produced with Electron Beam Melting machine (EBM). Potentiodynamic and potentiostatic tests were applied on EBM Ti-6Al-4V in 3.5% mass NaCl solution, to determine the pitting...

  12. A screen-printed amperometric dissolved oxygen sensor utilising an immobilised electrolyte gel and membrane

    Microsoft Academic Search

    Wendy Glasspool; John Atkinson

    1998-01-01

    An amperometric dissolved oxygen sensor based on potentiostatic operation has been designed and fabricated using thick film technology. Calibration of the sensor has shown a strong linear relationship with dissolved oxygen concentration. The devices have been bulk tested for long-term stability and good device to device repeatability has been observed within the batch. Results indicate that a repeatable response to

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

    Microsoft Academic Search

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

    2009-01-01

    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

  14. Electrodeposition of platinum-ruthenium nanoparticles on carbon nanotubes directly grown on carbon cloths for methanol oxidation

    Microsoft Academic Search

    Ming-Chi Tsai; Tsung-Kuang Yeh; Chuen-Horng Tsai

    2008-01-01

    Dense carbon nanotubes (CNTs) were grown via a thermal chemical vapor deposition (CVD) process on titanium treated carbon cloths. Platinum-ruthenium (Pt-Ru) nanoparticles were then deposited on the CNT surfaces by potentiostatic electrodeposition in mixed sulfuric acid and ethylene glycol (EG) containing aqueous electrolytes. After the deposition process, the surface morphology of prepared specimens was examined by scanning electron microscopy (SEM)

  15. Super-hydrophobic film prepared on zinc as corrosion barrier

    Microsoft Academic Search

    Peng Wang; Dun Zhang; Ri Qiu; Baorong Hou

    2011-01-01

    Potentiostatic electrolysis was carried out to prepare super-hydrophobic film on the surface of metallic zinc. The resultant film was examined by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, electrochemical measurements, and contact angle test. The super-hydrophobic property of the film results from the air trapped among the sheets of zinc tetradecanoate. This air behaves as a dielectric for

  16. Photovoltaic Powered Electrokinetic Restoration of Saline Soil

    Microsoft Academic Search

    Do-Hyung Kim; Ji-Min Jung; Sung-Ung Jo; Woo-Seung Kim; Kitae Baek

    2012-01-01

    Electrokinetic techniques are currently being explored as a means of extracting or removing contaminants from soils, sediments, and sludge. However, energy costs account for 25% of total operation costs. In this study, we investigated the efficiency of conventional electrokinetic and photovoltaic powered electrokinetic systems for the removal of salts from saline agricultural soils. We tested four different potentiostatic systems: a

  17. A new microcell or microreactor for material surface investigations at large current densities

    Microsoft Academic Search

    M. M Lohrengel; C Rosenkranz; I Klüppel; A Moehring; H Bettermann; B. Van den Bossche; J Deconinck

    2004-01-01

    The capillary-based droplet cell is well established in microelectrochemical surface analysis down to the ?m range. The potentiostatic 3-electrode arrangement allows all common techniques like cyclovoltammetry, impedance spectroscopy and current transients of potential steps. A limiting factor was the immobile electrolyte, which meant an accumulation of products or depletion of educts, especially at larger current densities. Reaction products like gases

  18. Cadmium electrode investigation. Final report, 16 July4 December 1979

    Microsoft Academic Search

    Buck

    1980-01-01

    Methods for improving the loading and utilization of active material in electrochemically impregnated cadmium electrodes were studied using sweep voltametry and galvanostatic pulse impregnation. Loading levels and utilization were found to decrease with cycling when the potentiostatic pulse method was used and impregnation times beyond one hour resulted in unacceptable surface loading. The use of galvanostatic pulse impregnation appeared to

  19. IEEE ENGINEERING IN MEDICINE AND BIOLOGY MAGAZINE NOVEMBER/DECEMBER 2005 23 STUDENTPAPERAWARD

    E-print Network

    Stanacevic, Milutin

    Integrated Potentiostat for Neurotransmitter Sensing A High Sensitivity, Wide Range VLSI Design and Chip-5175/05/$20.00©2005IEEE S ensing and measurement of neurotransmitters such as nitric oxide and dopamine may be invaluable called neurotransmitters, as shown in Figure 1. Detection and measurement of these molecules is of great

  20. Anodic electrochemistry of chalcopyrite

    Microsoft Academic Search

    T. Biegler; D. A. Swift

    1979-01-01

    The anodic behaviour of chalcopyrite in 1 M H2SO4 and 1 M HCl was studied by linear sweep voltammetry and potentiostatic electrolysis. Voltammograms with a fresh surface showed a small prewave, attributed to a surface oxidation process, followed by a region of active dissolution characterized by a steeply rising anodic current. At still higher potentials the behaviour differed in the

  1. 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…

  2. Análisis de la Amplitud de las Señales de Emisión Acústica Generadas por Corrosión Bajo Tensión en Latón-?

    Microsoft Academic Search

    P. A. Lapitz; J. Ruzzante; M. G. Alvarez; Agencia de Promoción Científica; Tecnológica Argentina

    2005-01-01

    The present work was aimed to characterize the acoustic emission (AE) response obtained during the propagation of stress corrosion cracks. The differences between the AE signals generated by transgranular and intergranular SCC were analyzed. For that purpose, slow strain rate tensile tests (SSRT) under potentiostatic control were performed. The systems studied were: 1) yellow brass in a 1M NaNO2 solution;

  3. Center for Nanostructured Biomimetic Interfaces Integrated Electrochemical and Optical Methods for Studying TRPV Channel Proteins

    E-print Network

    reservoir Laser Working electrode · Reconstitution of VR1 in the lipid bilayer in its functional form · VR1,*Department of Medicine, Michigan State University, East Lansing, Michigan RE Potentiostat Rubber gasket o-ring WE ITO counter slide Spacer Prism ITO working electrode spacer ITO counter electrode From syringe pump Exit

  4. Inhibition of acid corrosion of aluminum using vanillin

    Microsoft Academic Search

    A. Y. El-Etre

    2001-01-01

    The inhibition efficiency (IE) of vanillin towards the corrosion of aluminum in 5 M HCl solution was measured using weight loss measurement, hydrogen evolution method, thermometry and potentiostatic polarization techniques. The results drawn from the different techniques are comparable and exhibit a small discrepancy. It was found that vanillin acts as a good inhibitor for the corrosion of aluminum in

  5. 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…

  6. Corrosion behavior and electrical conductivity of niobium implanted 316L stainless steel used as bipolar plates in polymer electrolyte membrane fuel cells

    Microsoft Academic Search

    Kai Feng; Zhuguo Li; Xun Cai; Paul K. Chu

    2010-01-01

    The corrosion behavior and interfacial contact resistance (ICR) of niobium implanted SS316L used as the bipolar plate in a polymer electrolyte membrane fuel cell (PEMFC) are investigated. The ICR values of the bare and niobium implanted SS316L are measured to evaluate the electrical conductivity. The effects of ion implantation on the corrosion behavior are investigated by potentiodynamic and potentiostatic tests

  7. 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 ...

  8. Journal of The Electrochemical Society, 158 (12) A1307-A1312 (2011) A1307 0013-4651/2011/158(12)/A1307/6/$28.00 The Electrochemical Society

    E-print Network

    Ceder, Gerbrand

    2011-01-01

    1307/6/$28.00 © The Electrochemical Society Electrochemical Properties of Monoclinic NaMnO2 Xiaohua Ma Institute of Technology, Cambridge, Massachusetts 02139, USA Monoclinic - NaMnO2 is re from NaMnO2 and 0.8 Na be intercalated back during potentiostatical intermittent charge and discharge

  9. Stripping voltammetry at preplated mercury coated microelectrodes in flowing solutions

    Microsoft Academic Search

    Fredrik Björefors; Leif Nyholm

    1996-01-01

    A flow system is described in which stable preplated mercury coatings on microelectrodes can be obtained due to minimised handling of the electrode and the fact that potentiostatic control can be maintained also between the experiments. Compared to the deposition of mercury and subsequent transfer of microelectrodes, the use of the flow system gives better control of the mercury deposition

  10. Anodic stripping potentiometric determination of antimony in environmental materials

    Microsoft Academic Search

    S. B. Adeloju; T. M. Young

    1995-01-01

    A method is described for sensitive and reliable determination of ultra-trace concentrations of antimony in environmental samples by anodic stripping potentiometry (ASP). The method involves potentiostatic deposition of antimony onto a glassy carbon mercury film electrode and the subsequent chemical oxidation (stripping) with mercury(II) ions. The optimum conditions for the reliable determination of antimony by this method are mixture of

  11. The Effect of Iron Addition on the Dry Sliding Wear and Corrosion Behavior of Cu Al Ni Shape Memory Alloy

    Microsoft Academic Search

    Abdul Raheem; K. Abid Ali; Zuheir T. Khulief

    2010-01-01

    In this paper, dry sliding wear and corrosion behavior of Cu + 13wt% Al + 3.8 wt% Ni was prepared by powder metallurgy. Dry sliding wear has been studied based on pin on disk at constant velocity and constant sliding distance .Corrosion behavior in 5 wt% NaOH solution based up on potentiostatic ( Tafel ) has been presented for base

  12. Studying localized corrosion using liquid cell transmission electron microscopy.

    PubMed

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

    2015-01-01

    Localized corrosion of Cu and Al thin films exposed to aqueous NaCl solutions was studied using liquid cell transmission electron microscopy (LCTEM). 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. PMID:25388023

  13. Rhodanine azosulpha drugs as corrosion inhibitors for corrosion of 304 stainless steel in hydrochloric acid solution

    Microsoft Academic Search

    M Abdallah

    2002-01-01

    The effect of rhodanine azosulpha drugs on the corrosion behaviour of 304 stainless steel in 1.0 M hydrochloric acid solution as corrosive medium has been investigated using weight loss and potentiostatic polarization techniques. Some corrosion parameters such as anodic and cathodic Tafel slope, corrosion potential, corrosion current, exchange current densities, surface coverage and inhibition efficiency were calculated. The polarization measurements

  14. Antibacterial drugs as corrosion inhibitors for corrosion of aluminium in hydrochloric solution

    Microsoft Academic Search

    M Abdallah

    2004-01-01

    The corrosion behavior of aluminium in 2 M HCl solution in the absence and presence of four compounds of antibacterial drug was investigated using hydrogen evolution, weight loss, and potentiostatic polarization techniques. It was found that, the inhibition efficiency of these compounds depends on their concentration and chemical structure. The inhibitive action of these compounds was discussed in terms of

  15. DISSOLUTION OF ZIRCONIUM IN HCl-METHANOL

    Microsoft Academic Search

    J. R. Aylward; E. M. Whitener

    1962-01-01

    The dissolution of zirconium in HCl-methanol was studied ; potentiostatically as a function of HCl concentration and temperature. At low ; overvoltages the reaction is activation controlled and the rate independent of ; HCl concentration. In this region preferential grain boundary attack results in ; etching and separation from the electrode of flnely divided panticles of alpha -; zirconium. At

  16. Electrochemical approach for passivating steel and other metals and for the simultaneous production of a biocide to render water potable

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Potentiostatic polarization curves indicated that the cathodic reactions in deaerated KI-I2 water solutions were due to iodine reduction and hydrogen evolution. In the presence of oxygen an additional reduction wave appeared. Anodic polarization curves revealed that iodine could be produced in the region of potential from +600 to +1000 nv vs. SCE.

  17. Evaluation of Corrosive Degradation in Coated Steel Using Alternating Current Impedance Spectroscopy

    Microsoft Academic Search

    D. F. Wei; D. A. Jones; I. F. Chatterjee

    1995-01-01

    Alternating current (AC) impedance spectroscopy was applied to measure the degradation of steel coatings previously exposed to corrosive solutions such as tap water and 3% sodium chloride (NaCl). The method used was simple and quick and did not utilize electrochemical (potentiostatic) control. Previously immersed specimens of three types of coated steel were sandwiched between metallic foil electrodes and connected to

  18. Electrochemistry Resources

    NSDL National Science Digital Library

    This is a general interest website in electrochemistry, offering answers to many common questions. Sections include impedance spectroscopy, quartz crystal microbalance, reference electrodes, simulation voltammetry, potentiostats and handling of mercury. A list of web and book references is available, as is a "contact us" tab for questions to the author.

  19. Electrodeposition of gold nanoparticles on fluorine-doped tin oxide: Control of particle density and size distribution

    Microsoft Academic Search

    Eoin Sheridan; Johan Hjelm; Robert J. Forster

    2007-01-01

    Electrodeposition of gold island films of nanometre dimensions (<100nm) on fluorine-doped tin oxide (FDTO) coated glass is reported. The effect of altering the overpotential of the potentiostatic transient, the use of both nucleation and growth pulses as well as the immobilisation of a spontaneously adsorbed monolayer of, 3-aminopropyldimethylmethoxysilane, is reported. Deposits ranging from isolated particles to dense arrays of nanometre

  20. Nanocrystalline zinc oxide thin films by novel double pulse single step electrodeposition

    Microsoft Academic Search

    A. I. Inamdar; A. C. Sonavane; S. K. Sharma; Hyunsik Im; P. S. Patil

    2010-01-01

    An attempt has been made to fabricate nanocrystalline zinc oxide thin films by using double pulse potentiostatic electrodeposition in oxygen saturated zinc acetate bath onto FTO coated conducting glass substrates. Zinc oxide formation mechanism has been studied by using linear sweep voltammetry (LSV) and electrochemical quartz crystal microbalance (EQCM) in presence of oxygen. The influence of pulse parameters like nucleation

  1. A new technique for online visualization of the electrode surface under electrochemical corrosion processes

    Microsoft Academic Search

    J. García-Antón; A. Igual-Muñoz; J. L. Guiñón; V. Pérez-Herranz

    2001-01-01

    A new method for the online visualization of corrosion processes has been developed. It relates two techniques, electrochemical studies (potentiodynamic, potentiostatic, chronoamperometric etc.) and image processing. The main advantage of this method is that it is possible to relate the morphological changes of the electrode surfaces to the electrochemical signal measured without disturbing the electrochemical system. The online visualization technique

  2. 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.

  3. An assessment of the crack tip potential of ?-titanium alloys during hydrogen environmentally assisted crack propagation based on crack tip and passive surface electrochemical measurements

    Microsoft Academic Search

    D. G Kolman; J. R Scully

    2000-01-01

    We have previously proposed a scenario for intergranular hydrogen-assisted crack initiation of metastable ?-titanium alloys exposed to aqueous chloride solution. This scenario requires the loss of potentiostatic control due to ohmic drop in solution such that the crack tip potential falls to a potential where hydrogen production is viable regardless of the applied potential. It is of interest to examine

  4. Stress corrosion cracking of stainless steels

    Microsoft Academic Search

    R. F. Hehemann

    1985-01-01

    The similarities and differences in the stress corrosion cracking response of ferritic and austenitic stainless steels in chloride solutions will be examined. Both classes of materials exhibit a cracking potential: similar transient response (to loading) of the potential in open circuit tests or the current in potentiostatic tests and similar enrichment of chromium and depletion of iron in the film

  5. 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

  6. Natural honey as corrosion inhibitor for metals and alloys. II. C-steel in high saline water

    Microsoft Academic Search

    A. Y. El-Etre; M. Abdallah

    2000-01-01

    The inhibtive action of natural honey on the corrosion of C-steel, which used in manufacturer of petroleum pipelines, in high saline water was evaluated. The inhibition efficiency was calculated using weight loss measurements and potentiostatic polarization technique. It was found that, natural honey exhibited a very good performance as inhibitor for steel corrosion in high saline water. The inhibition efficiency

  7. Effects of surface chromium depletion on the localized corrosion of Alloy 825 as a high-level waste container material

    SciTech Connect

    Dunn, D.S.; Sridhar, N.; Cragnolino, G.A. [Southwest Research Inst., San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses

    1994-12-31

    The effects of the chromium depleted mill finished surface on the localized corrosion resistance of alloy 825 were investigated. Tests conducted in solutions simulating the groundwater at Yucca Mountain with a higher concentration of chloride indicated that the breakdown and repassivation potentials for the mill finished surfaces were more active than those for polished surfaces. Potentiodynamic polarization tests indicated that pits can be initiated on the chromium depleted surface at potentials of 220 mV{sub SCE} in a solution containing 1,000 ppm chloride at 95 C. Potentiostatic tests identified a similar pit initiation potential for the mill finished surface. However, under longer term potentiostatic tests, a higher potential of 300 mV{sub SCE} was needed to sustain stable pit growth beyond the chromium depleted layer. An increase in the surface roughness decreased the localized corrosion resistance of the material.

  8. Effects of pulse voltage on the formation of nanoporous Ti oxides by dealloying amorphous TiCu alloy

    NASA Astrophysics Data System (ADS)

    Zhu, Shengli; Pi, Lele; Xie, Guoqiang; Cui, Zhenduo; Yang, Xianjin; Inoue, Akihisa

    2013-03-01

    In present study, we prepared nanoporous Ti oxides by potentiostat and pulse dealloying TiCu amorphous alloy in HNO3 solution. The influence of applied voltage on the morphology was investigated by SEM. The mechanism of dealloying was also discussed. A multilayer nanoporous structure was fabricated using pulse dealloying. The ideal nanoporous structure with mean pore diameter of about 50-100 nm and mean pore wall thickness of about 50 nm was obtained using pulse dealloying with initial voltage of 1.0 V and pulse size of 0.4 V. The static currents for pulse dealloying are higher than those for potentiostat dealloying under the same initial potentials. The nanoporous surface is mainly composed of TiO, Ti2O3 and TiO2.

  9. 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.

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

    SciTech Connect

    Jovancicevic, V. [W.R. Grace and Co., Columbia, MD (United States). Research Div.; Hartwick, D. [BetzDearborn, Mississauga, Ontario (Canada)

    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.

  11. Caustic Stress Corrosion Cracking of Mild Steel

    Microsoft Academic Search

    Douglas Singbeil; Desmond Tromans

    1982-01-01

    The stress corrosion cracking (SCC) behavior of cold worked mild steel in hot, aqueous, 33 pct NaOH solutions was studied\\u000a with prefatigue cracked double cantilever beam specimens. SCC kinetics were studied under freely corroding potentials (E\\u000a corr ? ?1.00 VSHE) and potentiostatic potentials of ?0.76 VSHE near the active-passive transition. The pH of the liquid within the crack was determined

  12. Long-Term Prediction of Localized Corrosion of Alloy 825 in High-Level Nuclear Waste Repository Environments

    Microsoft Academic Search

    D. S. Dunn; N. S. Sridhar; G. A. Cragnolino

    1996-01-01

    Long-term prediction of localized corrosion of high-level nuclear waste container materials is a necessary step in the performance assessment of the engineered barrier system. Localized corrosion of corrosion-resistant materials may occur if the containers are exposed to chloride-containing ground water at elevated temperatures. Potentiostatic tests conducted on alloy 825 (UNS NO8825), a candidate container material, have shown that the potential

  13. Surface Roughness and Metastable Pitting of Amorphous Nickel Alloy

    Microsoft Academic Search

    Y. Zuo; S. Fu

    1998-01-01

    The effects of surface finish on nucleation and growth of metastable pits on an amorphous Ni-Cr-Fe-Si-B alloy was studied using potentiostatic and potentiodynamic polarization tests. Nucleation of metastable pits on the amorphous alloy was facilitated significantly by a rougher surface. Both growth rate constants and peak currents of metastable pits followed a log-normal distribution. A rougher surface also promoted the

  14. Surface roughness and metastable pitting of amorphous nickel alloy

    SciTech Connect

    Zuo, Y.; Fu, S. [Beijing Univ. of Chemical Technology (China). Dept. of Applied Chemistry

    1998-04-01

    The effects of surface finish on nucleation and growth of metastable pits on an amorphous Ni-Cr-Fe-Si-B alloy was studied using potentiostatic and potentiodynamic polarization tests. Nucleation of metastable pits on the amorphous alloy was facilitated significantly by a rougher surface. Both growth rate constants and peak currents of metastable pits followed a log-normal distribution. A rougher surface also promoted the growth of metastable pits and led to a wider distribution in growth rates.

  15. Application of pyrolysed iron(II) phthalocyanine and CoTMPP based oxygen reduction catalysts as cathode materials in microbial fuel cells

    Microsoft Academic Search

    Feng Zhao; Falk Harnisch; Uwe Schröder; Fritz Scholz; Peter Bogdanoff; Iris Herrmann

    2005-01-01

    The performance of iron(II) phthalocyanine (FePc) and cobalt tetramethoxyphenylporphyrin (CoTMPP) based oxygen reduction catalysts was studied in view of the application as cathode materials in microbial fuel cells. Galvanostatic and potentiostatic experiments were performed in order to compare the proposed materials to platinum and hexacyanoferrate(III) based systems. Additionally, two-chamber microbial fuel cell experiments were carried out to demonstrate that the

  16. A study of the heat-affected zone (HAZ) of an Inconel 718 sheet welded with electron-beam welding (EBW)

    Microsoft Academic Search

    C. A. Huang; T. H. Wang; C. H. Lee; W. C. Han

    2005-01-01

    In this paper the heat-affected zones (HAZs) of the Inconel 718 sheets welded with electron-beam welding (EBW) were studied by using hardness measurement, metallographic etch and electrochemically potentiostatic etch methods. Before EBW, the Inconel 718 sheets were pretreated in three different conditions: as-received, solution- and precipitation-treatments. The results show that there is an obvious difference in the dimension of the

  17. Tribocorrosion behaviour of low temperature plasma carburised 316L stainless steel in 0.5 M NaCl solution

    Microsoft Academic Search

    Y. Sun; E. Haruman

    2011-01-01

    Experiments have been carried out to study the tribocorrosion behaviour of low temperature plasma carburised 316L stainless steel under unidirectional sliding in 0.5M NaCl solution, using a pin-on-disk tribometer integrated with a potentiostat for electrochemical control. It is found that the carburised layer exhibits much better resistance to material removal than the untreated specimen, particularly at anodic potentials. No corrosion

  18. Studies on electrodeposited silver sulphide thin films by double exposure holographic interferometry

    Microsoft Academic Search

    V. B. Prabhune; N. S. Shinde; V. J. Fulari

    2008-01-01

    Silver sulphide (Ag2S) thin films have been deposited on to stainless steel and fluorine doped tin oxide (FTO) glass substrates by the electrodeposition process, in potentiostatic mode using silver nitrate (AgNO3), sodium thiosulphate (Na2S2O3) as a precursor sources and Ethylene Diamine Tetra Acetic Acid (EDTA) was used as a complexing agent. The deposition potential of the compound was investigated by

  19. Electrosynthesis and characterization of Fe doped CdSe thin films from ethylene glycol bath

    Microsoft Academic Search

    S. M. Pawar; A. V. Moholkar; K. Y. Rajpure; C. H. Bhosale

    2007-01-01

    The CdSe and Fe doped CdSe (Fe:CdSe) thin films have been electrodeposited potentiostatically onto the stainless steel and fluorine doped tin oxide (FTO) glass substrates, from ethylene glycol bath containing (CH3COO)2·Cd·2H2O, SeO2, and FeCl3 at room temperature. The doping concentration of Fe is optimized by using (photo) electrochemical (PEC) characterization technique. The deposition mechanism and Fe incorporation are studied by

  20. Simple and rapid synthesis of NiO\\/PPy thin films with improved electrochromic performance

    Microsoft Academic Search

    A. C. Sonavane; A. I. Inamdar; D. S. Dalavi; H. P. Deshmukh; P. S. Patil

    2010-01-01

    Nickel oxide\\/polypyrrole (NiO\\/PPy) thin films were deposited by a two step process in which the NiO layer was electrodeposited potentiostatically from an aqueous solution of NiCl2·6H2O at pH 7.5 on fluorine doped tin oxide (FTO) coated conducting glass substrates, followed by the deposition of polypyrrole (PPy) thin films by chemical bath deposition (CBD) from pyrrole mixed with ammonium persulfate (APS).

  1. Analysis of cell impedance measured on the LiMn 2O 4 film electrode by PITT and EIS with Monte Carlo simulation

    Microsoft Academic Search

    Sung-Woo Kim; Su-Il Pyun

    2002-01-01

    Cell impedance measured on a LiMn2O4 film electrode was analyzed by using the potentiostatic intermittent titration technique (PITT) and electrochemical impedance spectroscopy (EIS) with Monte Carlo simulation. The plot of the resistance of the absorption–desorption of lithium ions at the electrolyte?electrode interface vs. the electrode potential measured by EIS coincided well with the plot of the cell impedance versus the

  2. Synthesis and characterization of electrochemically deposited nanocrystalline CdTe thin films

    Microsoft Academic Search

    Ragini Raj Singh; Diksha Painuly; R. K. Pandey

    2009-01-01

    Electrodeposition is emerging as a method for the synthesis of semiconductor thin films and nanostructures. In this work we prepared the nanocrystalline CdTe thin films on indium tin oxide coated glass substrate from aqueous acidic bath at the deposition temperature 50±1°C. The films were grown potentiostatically from ?0.60V to ?0.82V with respect to saturated calomel reference electrode. The structural, compositional,

  3. Development of a portable electroanalytical system for the stripping voltammetry of metals: Determination of copper in acetic acid soil extracts

    Microsoft Academic Search

    Valerio Beni; Vladimir I. Ogurtsov; Nikolai V. Bakunin; Damien W. M. Arrigan; Martin Hill

    2005-01-01

    The development, characterisation and evaluation of a prototype portable electrochemical trace metal analyser are presented. The instrument is a battery-powered microcontroller-based potentiostat, which implements anodic stripping voltammetry (ASV) at suitable sensor electrodes. It is capable of operating away from the laboratory, in the absence of an external power source and is usable by low-skilled personnel. The distinguishing feature of the

  4. Effect of organic dopants on electrodeposition and characteristics of polyaniline under the varying influence of H 2SO 4 and HClO 4 electrolyte media

    Microsoft Academic Search

    R. Murugesan; E. Subramanian

    2003-01-01

    Electrodeposition of conducting polyaniline (Pani) was made under potentiostatic condition at pH 1.0 in different electrolyte media (H2SO4 and HClO4) in the absence and presence of two organic dopants, disodium salts of naphthalene-1,5-disulphonic acid (NSA) and of catechol-3,5-disulphonic acid (CSA). The rate and yield of Pani deposition were dependent on the acid medium and the dopant employed. NSA in H2SO4

  5. Electrochemical behavior of thermally chromized steel in sodium chloride solutions

    Microsoft Academic Search

    I. I. Zaets; A. K. Gorbachev; N. S. Gorbunov; É. M. Tokareva

    1975-01-01

    Potentiodynamic measurements were carried out by means of a P-5827 potentiostat in which the potential was varied continuously at a rate of I W\\/h. A saturated calomel half-cell was used as reference electrode and a graphite rod as auxiliary electrode. The current was determined by M-82 and M-104 micro- and milliammeters. The rate of dissolution of thermally chromized steel in

  6. Corrosion resistance of chromized 316L stainless steel for PEMFC bipolar plates

    Microsoft Academic Search

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

    2008-01-01

    Corrosion resistance of the chromized 316L stainless steel was studied in a proton exchange membrane fuel cell (PEMFC) operating condition. Cr-rich surface layer was formed by pack cementation technique and electrochemical properties of the chromized surface were examined by potentiodynamic and potentiostatic tests. Results showed that the Cr-rich layers underneath the free surface passivated the surface and protect the surface

  7. Methanol oxidation efficiencies on carbon-nanotube-supported platinum and platinum–ruthenium nanoparticles prepared by pulsed electrodeposition

    Microsoft Academic Search

    Ming-Chi Tsai; Tsung-Kuang Yeh; Chuen-Horng Tsai

    2011-01-01

    Dense carbon nanotubes (CNTs, 30–50 nm in diameter, 6–8 ?m in length) were grown via a thermal chemical vapor deposition process on titanium treated carbon cloths. Catalysts in the form of either nano-scale platinum (Pt) or platinum-ruthenium (Pt–Ru) particles were then deposited on the CNT surfaces by pulse-mode potentiostatic electrodeposition. Surface morphologies of the prepared electrodes were examined by scanning electron microscopy

  8. SEMICONDUCTOR MATERIALS: Effect of bath temperature on the properties of CuInxGa1-x Se2 thin films grown by the electrodeposition technique

    Microsoft Academic Search

    Cao Jie; Qu Shengchun; Liu Kong; Wang Zhanguo

    2010-01-01

    Electrodeposition is a promising and low cost method to synthesize CuInx Ga1-x Se2 (CIGS)thin films as an absorber layer for solar cells. The effect of bath temperature on the properties of CIGS thin films was investigated in this paper. CIGS films of 1 mum thickness were electrodeposited potentiostatically from aqueous solution, containing trisodium citrate as a complexing agent, on Mo\\/glass

  9. Pore morphology and self-organization effects during etching of n-type GaP(100) in bromide solutions

    Microsoft Academic Search

    J. a b Wloka; K. a Mueller; P.a b Schmuki

    2005-01-01

    n-Type GaP was anodized in bromide-ion-containing solutions. In these solutions pores can be grown into the GaP substrate with morphologies that depend strongly on the electrochemical parameters. Under specific potentiostatic conditions highly defined rectangular pores can grow perpendicular to the (100) surface forming several micrometer thick well-defined porous layers on GaP. The etched channels show an etch stop at the

  10. Corrosion resistance tests on NiTi shape memory alloy

    Microsoft Academic Search

    Gianni Rondelli

    1996-01-01

    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

  11. Crack developmentrate and electromechanical characteristics of titanium alloy AT3 in certain media

    Microsoft Academic Search

    V. S. Fedchenko; A. M. Krutsan; R. K. Melekhov; V. E. Blashchuk

    1978-01-01

    TO determine the effect of the temperature factor and the composition of the working medium of the hydrolysis plant (0.5-0.7% sulfuric acid; 0.3-0.7% organic acids; 3.1-3.3% reducing sugar; 0.03-0.06% furfural; remainder -- water) on the tendency of AT-3 alloy to overall corrosion, we recorded the potentiostatic curves in 0.6% sulfuric acid at 20, 50, and 96~ and in a sulfuric

  12. Growth kinetics of passivating oxide film of Inconel alloy 600 in 0.1 M Na 2SO 4 solution at 25–300 °C using the abrading electrode technique and ac impedance spectroscopy

    Microsoft Academic Search

    Jin-Ju Park; Su-Il Pyun; Seung-Bok Lee

    2004-01-01

    The growth kinetics of passivating oxide film of Inconel alloy 600 has been investigated in aqueous 0.1M Na2SO4 solution at temperatures 25–300°C and at pressures 0.1–8MPa by analyses of potentiostatic current transients and ac impedance spectra. From the analysis of current transients, it was realized that the oxide film grown on the specimen has only one-layer structure below 60°C, but

  13. Preparation of Nano-Copper Modified Glassy Carbon Electrode and Its Catalytic Oxidation to Glucose

    Microsoft Academic Search

    Hai-Yun DING; Ye ZHOU; Shu-Jing ZHANG; Xue-Bo YIN; Yi-Jun LI; Xi-Wen HE

    2008-01-01

    Nano-Cu modified glassy carbon electrode (nano-Cu-GCE) fabrication by reduction of CuSO4 in the presence of cetyltrimethylammonium bromide (CTMAB), through potentiostatic process, and catalytic oxidation of glucose on the nano-Cu-GCE were proposed. Optimum potential and time for deposition of Cu were –100 mV and 8 min, respectively. The potential used for the determination of glucose was 400 mV. The results indicated

  14. An Environmental Automatic Monitoring System for Heavy Metals

    Microsoft Academic Search

    Shaofang Zou; Ping Xu; Weidong Xu; Yingle Fan

    2007-01-01

    An automatic monitoring system was developed for simultaneous determination of trace zinc, cadmium, lead, copper, iron and arsenic in environmental aqueous media using electrochemical stripping voltammetry. The sensor was mercury-film silver-based electrode. With a potentiostat, several pumps and valves controlled by computer, the system realized in-situ real-time detection of the six heavy metal ions mentioned above without manual operation. Quantitative

  15. Effects of boric acid on the electrodeposition of iron, nickel and iron-nickel

    Microsoft Academic Search

    K.-M. Yin; B.-T. Lin

    1996-01-01

    Iron (Fe), nickel (Ni), and iron-nickel (Fe?Ni) platings were carried out potentiostatically on rotating disk electrodes. The effects of boric acid on the iron and nickel reduction rates were evaluated. Experimental results support the surface competition of adsorption of ferrous and nickel ions on the electrode surface in Fe?Ni alloy deposition. Boric acid prevents the electrode surface passivation on nickel

  16. Polymerisation of methyl ethyl ketone formaldehyde resin modified with carbazole-9-carbonyl chloride

    Microsoft Academic Search

    Belkis Ustamehmeto?lu; Pelin Yaz?c?; Nilgun K?z?lcan

    2011-01-01

    Purpose – The purpose of this paper is to obtain a conductive polymer by using a fluorescence comonomer which is an insulator. In this study, methyl ethyl ketone formaldehyde resin (MEKFR) modified with carbazole-9-carbonyl chloride (CzCl) was synthesised via hydroxyl groups of MEKFR. Electrochemical polymerisation of Cz-MEKFR comonomer was carried out potentiostatically and a green, conductive polymer P(Cz-MEKFR) was obtained.

  17. In situ activation of cobalt cathodes in alkaline water electrolysis

    Microsoft Academic Search

    J. Y. Huot; L. Brossard

    1988-01-01

    The hydrogen evolution reaction (HER) on polished pure cobalt cathodes in 30 w\\/o KOH at 70°C in the presence of dissolved metallic impurities has been investigated in constant current and potential modes combined with the potential-sweep method. Potentiostatic tests show that the cell current decreases with time during the first 1000 s, which is tentatively attributed to the penetration of

  18. Characterization of the Ni–Mo catalyst formed in situ during hydrogen generation from alkaline water electrolysis

    Microsoft Academic Search

    Gvozden S. Tasic; Sladjana P. Maslovara; Dragana L. Zugic; Aleksandar D. Maksic; Milica P. Marceta Kaninski

    2011-01-01

    Objective of this work was to investigate the electrocatalytic efficiency using quasi-potentiostatic, galvanostatic and impedance spectroscopy techniques of the Ni–Mo catalysts obtained by in situ electrodeposition in an alkaline, 6 M KOH, electrolyser. In accordance to our previous studies, synergetic effect is observed, with its maximum at industrial conditions (high temperature and current density). The Tafel slopes are around 120 mV and

  19. The effects of inclusion of iodine in CdTe thin films on material properties and solar cell performance

    Microsoft Academic Search

    N. B Chaure; A. P Samantilleke; I. M Dharmadasa

    2003-01-01

    CdTe thin films were potentiostatically electrodeposited from a non-aqueous electrolytic bath containing ethylene glycol. In order to dope the CdTe using an n-type dopant according to a proposed new model, varying concentrations of iodine were added into the electrolytic bath. The resulting materials were studied for structural, morphological, optical and electrical properties. Structural analysis indicated the formation of CdTe layers

  20. Atomic emission spectroelectrochemistry applied to dealloying phenomena II. Selective dissolution of iron and chromium during active–passive cycles of an austenitic stainless steel

    Microsoft Academic Search

    K. Ogle; M. Mokaddem; P. Volovitch

    2010-01-01

    Atomic emission spectroelectrochemistry was used to investigate selective dissolution of a 304 austenitic stainless steel sample in 2M H2SO4. The partial dissolution rates of Fe, Cr, Ni, Mn, Mo, and Cu were measured as function of time during a series of potentiostatic triggered activation\\/passivation cycles. When first exposed to sulfuric acid solution, the steel sample was in a passive state

  1. 2Amino5-ethyl-1,3,4-thiadiazole as a corrosion inhibitor for copper in 3.0% NaCl solutions

    Microsoft Academic Search

    E. M. Sherif; Su-Moon Park

    2006-01-01

    2-Amino-5-ethyl-1,3,4-thiadiazole (AETDA) has been evaluated as a corrosion inhibitor for copper in 3.0% NaCl solutions using weight loss, pH, potentiodynamic polarization, potentiostatic current–time, and electrochemical impedance spectroscopic (EIS) measurements. The study was also complemented by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) investigations. Weight loss measurements gave an inhibition efficiency of about 60% with 1.0×10?3M AETDA present, increasing

  2. Evidence for Involvement of an Electron Shuttle in Electricity Generation by Geothrix fermentans

    Microsoft Academic Search

    Daniel R. Bond; Derek R. Lovley

    2005-01-01

    In experiments performed using graphite electrodes poised by a potentiostat (200 mV versus Ag\\/AgCl) or in a microbial fuel cell (with oxygen as the electron acceptor), the Fe(III)-reducing organism Geothrix fermen- tans conserved energy to support growth by coupling the complete oxidation of acetate to reduction of a graphite electrode. Other organic compounds, such as lactate, malate, propionate, and succinate

  3. Inhibition of Copper Corrosion with Schiff Base Derived from 3-Methoxysalicylaldehyde and O-Phenyldiamine in Chloride Media

    Microsoft Academic Search

    S. L. Li; R. L. Yu; S. B. Lei; H. Y. Ma; S. H. Chen; D. X. Liu

    1998-01-01

    The inhibiting effect of Schiff base N,Nâ²-o-phenylen-bis(3-methoxysalicylaldenimine), designated as V-ph-V, on corrosion of copper in 1.0 M hydrochloric acid (HCl) or 1.0 M sodium chloride (NaCl) solutions under various conditions was studied using the potentiostatic polarization method and for alternating current (AC) impedance technique. Results showed a remarkable decrease in the corrosion rate in the presence of V-ph-V (concentration =

  4. Corrosion of Iron in Acid Solutions with Hydrogen Sulfide

    Microsoft Academic Search

    X. L. Cheng; H. Y. Ma; X. L. Chen; H. Q. Yang; S. H. Chen; J. P. Zhang

    1998-01-01

    The influence of pH and the concentration of hydrogen sulfide (HâS) on corrosion of iron in acid solutions was studied using a potentiostatic polarization method. The alternating current (AC) impedance technique also was used to characterize the active dissolution process of iron. Results showed the dissolution process was accelerated by HâS. The anodic dissolution current (i{sub a}) increased with pH

  5. Mechanical and corrosion properties of rheocast and low-pressure cast A356-T6 alloy

    Microsoft Academic Search

    Chul Park; Sangshik Kim; Yongnam Kwon; Youngseon Lee; Junghwan Lee

    2005-01-01

    In this study, the mechanical and corrosion behavior of rheocast and low-pressure cast A356-T6 alloy were examined and compared with each other. Tensile, impact and high-cycle fatigue tests were conducted to characterizing the mechanical behavior. For the study of general corrosion and stress corrosion cracking behavior of A356-T6 alloy, polarization, potentiostatic and in situ slow strain rate tests were performed

  6. Initiation and growth of localized attack in nuclear waste package materials 011

    Microsoft Academic Search

    Roy

    1997-01-01

    Electrochemical potentiodynamic and potentiostatic polarization experiments were conducted on several candidate nuclear waste package container materials in an acidic brine containing 5 weight percent (wt%) NaCl at various temperatures. Substantial pitting and crevice corrosion was observed in Alloys 825 and G-3 in a 90°C brine at controlled potentials (E{sub cont}) that were noble compared to the critical pitting potential (E{sub

  7. Effect of macroalloying with Cu on the corrosion resistance of rapidly solidified NiAl intermetallic in 0.5 M H 2SO 4

    Microsoft Academic Search

    J. G. González-Rodriguez; J. C. Colín; S. Serna; B. Campillo; J. L. Albarran

    2007-01-01

    The effect of Cu contents on the corrosion resistance of NiAl intermetallic rapidly solidified in 0.5M H2SO4 at room temperature has been evaluated using electrochemical techniques. Cupper contents included 15, 20 and 25wt.% and techniques included potentiodynamic polarization curves, linear polarization resistance and potentiostatic tests. For comparison, the same tests were performed on a 316L type stainless steels. The results

  8. Electrochemical characterisation of biomedical alloys for surgical implants in simulated body fluids

    Microsoft Academic Search

    C. Valero Vidal; A. Igual Muñoz

    2008-01-01

    The aim of this research is to compare the electrochemical behaviour of two biomedical alloys, AISI 316L and CoCrMo in simulated body fluids. This comparison is focused on the influence of solution chemistry and immersion time on the passive behaviour using electrochemical techniques, potentiodynamic curves, potentiostatic tests and electrochemical impedance spectroscopy (EIS).Influence of albumin, used as model protein, on both

  9. Separation and concentration effect of f-MWCNTs on electrocatalytic responses of ascorbic acid, dopamine and uric acid at f-MWCNTs incorporated with poly (neutral red) composite films

    Microsoft Academic Search

    Umasankar Yogeswaran; Shen-Ming Chen

    2007-01-01

    A novel conductive composite film containing functionalized multi-walled carbon nanotubes (f-MWCNTs) with poly (neutral red) (PNR) was synthesized on glassy carbon electrodes (GC) by potentiostatic method. The composite film exhibited promising electrocatalytic oxidation of mixture of biochemical compounds such as ascorbic acid (AA), dopamine (DA) and uric acid (UA) in pH 4.0 aqueous solutions. It was also produced on gold

  10. The effect of crack- tip strain rate and potential on the propagation rate of stress corrosion crack for 321 stainless steel in boiling 42 Pct MgCl 2 solution

    Microsoft Academic Search

    D. Li; X. Mao

    1992-01-01

    The decay law of current with time on the bare surface of scratched 321 stainless steel in boiling 42 pct MgCl2 solution has been studied by the rapid scratching technique under potentiostatic condition. Based on the decay law and the\\u000a model of slip-bare metal dissolution-repassivation, a theoretical equation of stress corrosion crack propagation rate as a\\u000a function of crack-tip strain

  11. Stress corrosion cracking of stainless steels

    Microsoft Academic Search

    R. F. Hehemann

    1985-01-01

    The similarities and differences in the stress corrosion cracking response of ferritic and austenitic stainless steels in\\u000a chloride solutions will be examined. Both classes of materials exhibit a cracking potential: similar transient response (to\\u000a loading) of the potential in open circuit tests or the current in potentiostatic tests and similar enrichment of chromium\\u000a and depletion of iron in the film

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

    Microsoft Academic Search

    M. Yousefieh; M. Shamanian; A. Saatchi

    In the present work, the influence of step annealing heat treatment on the microstructure and pitting corrosion resistance\\u000a of super duplex stainless steel UNS S32760 welds have been investigated. The pitting corrosion resistance in chloride solution\\u000a was evaluated by potentiostatic measurements. The results showed that step annealing treatments in the temperature ranging\\u000a from 550 to 1000 °C resulted in a precipitation

  13. Electrochemical corrosion and metal ion release from Co-Cr-Mo prosthesis with titanium plasma spray coating

    Microsoft Academic Search

    Lucien Reclaru; Pierre-Yves Eschler; Reto Lerf; Andreas Blatter

    2005-01-01

    The corrosion behavior of CoCrMo implants with rough titanium coatings, applied by different suppliers by either sintering or vacuum plasma spraying, has been evaluated and compared with uncoated material. The open-circuit potential, corrosion current and polarization resistance were determined by electrochemical techniques. The Co, Cr and Ti ions released from the samples into the electrolyte during a potentiostatic extraction technique

  14. 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

  15. Over 95% of large-scale length uniformity in template-assisted electrodeposited nanowires by subzero-temperature electrodeposition

    PubMed Central

    2011-01-01

    In this work, we report highly uniform growth of template-assisted electrodeposited copper nanowires on a large area by lowering the deposition temperature down to subzero centigrade. Even with highly disordered commercial porous anodic aluminum oxide template and conventional potentiostatic electrodeposition, length uniformity over 95% can be achieved when the deposition temperature is lowered down to -2.4°C. Decreased diffusion coefficient and ion concentration gradient due to the lowered deposition temperature effectively reduces ion diffusion rate, thereby favors uniform nanowire growth. Moreover, by varying the deposition temperature, we show that also the pore nucleation and the crystallinity can be controlled. PMID:21781335

  16. Morphology-Controllable Synthesis of CeO2 on a Pt Electrode

    NASA Astrophysics Data System (ADS)

    Fu, Y.; Wei, Z. D.; Ji, M. B.; Li, L.; Shen, P. K.; Zhang, J.

    2008-11-01

    Nanoscale cerium dioxides with shape of nanoparticles, nanorods, and nanotubes were electrochemically synthesized. The morphology of CeO2 was modulated by changing electrode potential and potential direction. CeO2 nanorods and CeO2 nanotubes were synthesized via the potentiostatic and cyclic voltammeteric methods, respectively. The morphology and structure of the obtained CeO2 were characterized by field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). A possible formation mechanism has been suggested to illuminate the relationship between the preparation condition and the morphology of CeO2.

  17. 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

  18. Study of the corrosion behavior of titanium and some of its alloys for biomedical and dental implant applications

    Microsoft Academic Search

    J. E. G González; J. C Mirza-Rosca

    1999-01-01

    The influence of alloying elements and the potential on the corrosion resistance of Ti and other Ti-based biomedical implant alloys under simulated physiological conditions is presented. Ti and its following alloys: Ti?10Mo, Ti?10Mo?10Al, Ti?7Al?4.5V and Ti?5Al?4.5V and Ti?5Al?2.5Fe were studied. Electrochemical impedance spectroscopy was used and the experimental results were compared with those obtained by potentiostatic and potentiodynamic techniques. All

  19. Fabrication and nanostructure study of ultra thin electroplating constantan film on GaAs as a thermopower sensor

    NASA Astrophysics Data System (ADS)

    Kazeminezhad, I.; Khoshbakht, E.; Farbod, M.

    2008-03-01

    Ultra thin film of constantan was potentiostatically electrodeposited on n-type GaAs (111) from a citrate electrolyte containing both copper and nickel ions. SEM and EDX analyses were used to determine the film quality and composition. In order to fabricate high quality constantan alloy the optimum values of deposition potential and solution temperature were respectively found -1.45 V and 22-26 °C using the SEM analyses. The SEM images also showed that the grain size of the alloy extremely increases for the films with thickness of above 400 nm.

  20. Patterned electrochemical deposition of copper using an electron beam

    SciTech Connect

    Heijer, Mark den [Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden (Netherlands); Shao, Ingrid; Reuter, Mark C.; Ross, Frances M., E-mail: fmross@us.ibm.com [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598 (United States); Radisic, Alex [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium)

    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.

  1. Photoelectrochemical application of nanotubular titania photoanode

    Microsoft Academic Search

    Yibing Xie

    2006-01-01

    Titania\\/titanium (TiO2\\/Ti) electrodes with tailored surface structure have been fabricated by galvanostatic–potentiostatic anodization process. Highly ordered titania nanotubes array can be prepared by electrolyzing titanium foil at 20V for 40min in HF–H3PO4 electrolyte. Comparatively, micro-structured and crystallized TiO2 multiporous film can be prepared at 20–40V for 6h in H2SO4–H3PO4–H2O2–HF electrolyte. The morphological characteristics and crystal behaviors of both nanotubular and

  2. Pulsed amperometric detection of carbohydrates at gold electrodes with a two-step potential waveform

    SciTech Connect

    Neuburger, G.G.; Johnson, D.C.

    1987-01-01

    A two-step potential waveform is demonstrated for the detection of carbohydrates at a Au electrode in alkaline solutions for application in flow injection and liquid chromatography systems. Pulsed amperometric detection of carbohydrates previously based on a three-step waveform is now extended to potentiostats capable of programming an asymmetric square waveform (e.g., normal-pulse voltammetric waveforms). Detection limits for glucose, sorbitol, and sucrose are approximately 1 nmol in a 50-..mu..L sample (i.e., ca. 200 ng of glucose and 360 ng of sucrose) in a flow injection system.

  3. A comparative study of compositional and structural properties of CdTe thin films prepared by different electroplating techniques

    SciTech Connect

    Paulson, P.D.; Dutta, V.; Singh, C. [Indian Inst. of Tech., New Delhi (India)

    1994-12-31

    The structural and compositional properties of CdTe films, deposited from an aqueous solution of CdSO{sub 4} and TeO{sub 2} by Pulsed Electrodeposition, Potentiostatic and Galvanostatic Electrodeposition, have been studied. Polycrystalline films with a preferred <111> orientation are obtained in all techniques. However, films deposited by pulsed technique show the higher intensity for <111> peak. EDAX study shows that, for lower concentrations of CdSO{sub 4} in the electrolyte, pulsed films are more stoichiometric compared to films deposited by two other techniques.

  4. Morphological studies of the mechanism of pit growth of pure aluminum in sulfate ion- or nitrate ion-containing 0.1 M NaCl solutions

    Microsoft Academic Search

    Su-Il Pyun; Kyung-Hwan Na; Jin-Ju Park

    2001-01-01

    .   The mechanism of pit growth of pure aluminum (Al) in sulfate ion (SO4\\u000a 2–)- or nitrate ion (NO3\\u000a –)-containing 0.1 M sodium chloride solutions has been studied in terms of the morphological changes of artificial pits using\\u000a potentiodynamic polarization experiment, potentiostatic current transient technique and optical microscopy. The increase in\\u000a SO4\\u000a 2– and NO3\\u000a – ion concentrations in NaCl solution

  5. Formation of lithium-aluminum alloys at an aluminum electrode in propylene carbonate

    SciTech Connect

    Baranski, A.S.; Fawcett, W.R.

    1982-05-01

    The formation of lithium-aluminum alloys at pure aluminum has been studied by potentiostatic, ac impedance, and galvanostatic techniques. It is concluded that /beta/-LiAl is formed under most circumstances, some degree of nonstoichiometry being evident from the polarization curves. The diffusion coefficient for Li in /beta/-LiAl was also determined in the temperature range O to -40/sup 0/C Cycling efficiencies of the alloy electrode with respect to both lithium and aluminum were also investigated. 21 refs.

  6. Investigation into the susceptibility of corrosion resistant alloys to biocorrosion. Final report, 1 October 1995-30 September 1996

    SciTech Connect

    Clayton, C.R.

    1996-09-01

    The influence of sulfate-reducing bacteria (SRB) on the passivity of Mo-bearing (type 3 l7L) and low Mo content (type 304) austenitic stainless steels (55) was investigated by x-ray photoelectron spectroscopy (XPS), microbiological and electrochemical techniques. Samples were exposed to SRB, and then the resulting surfaces were analyzed by XPS, and the corrosion resistance by potentiodynamic polarization in deaerated 0.1 M HC 1. In order to further understand their passivity, the SRB-exposed samples were also analyzed by XPS after potentiostatic polarization at a passive potential in the hydrochloric solution.

  7. Separation of metal ions from aqueous solutions

    DOEpatents

    Almon, Amy C. (Augusta, GA)

    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.

  8. 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

  9. Electrodeposited magnetite with large magnetoresistive response at room temperature and low magnetic fields

    Microsoft Academic Search

    R. G. Delatorre; R. C. da Silva; J. S. Cruz; N. Garcia; A. A. Pasa

    2009-01-01

    Iron oxide layers were obtained by electrodeposition method on Cu substrates. The electrolyte containing Fe2(SO4)3, NaOH, and Triethanolamine was stirred at a temperature of 65 °C and the depositions were performed potentiostatically in\\u000a a conventional three electrode cell at a potential of ?1.1 V vs SCE. Parallel magnetoresistance values of ?6.2% at 3 kOe were\\u000a obtained for measurements at room temperature. The magnetoresistive

  10. The electrochemical behaviour of nitrogen-containing austenitic stainless steel in methanolic solution

    Microsoft Academic Search

    V. B. Singh; Monali Ray

    2007-01-01

    The corrosion behaviour of nitrogen-containing austenitic stainless steel in methanol containing different concentrations\\u000a of H2SO4, HCl, LiCl and H2SO4 + HCl has been investigated using a potentiostatic polarization method. The cathodic reaction in the H2SO4, HCl and H2SO4 + HCl solutions was proton reduction whereas in the neutral LiCl solution, oxygen reduction was the predominant cathodic\\u000a reaction. Active, passive and transpassive behaviours were observed

  11. 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

  12. Effects of surface chromium depletion on localized corrosion of alloy 825 as a high-level nuclear waste container material

    SciTech Connect

    Dunn, D.S.; Sridhar, N.; Cragnolino, G.A. [Southwest Research Institute, San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses

    1995-08-01

    Effects of the chromium-depleted, mill-finished surface on the localized corrosion resistance of alloy 825 (UNS N08825) were investigated. Tests were conducted in solutions based on the ground water at Yucca mountain, Nevada, but with a higher concentration of chloride. Results indicated that breakdown (E{sub p}) and repassivation (E{sub rp}) potentials for mill-finished surfaces were more active than those for polished surfaces. Potentiodynamic polarization tests indicated pits could be initiated on the chromium-depleted surface at potentials of 220 mV{sub SCE} in a solution containing 1,000 ppm Cl{sup {minus}} at 95 C. Potentiostatic tests identified a similar pit initiation potential for the mill-finished surface. However, under longterm potentiostatic tests, a higher potential of 300 mV{sub SCE} was needed to sustain stable pit growth beyond the chromium-depleted layer. An increase in surface roughness also was observed to decrease localized corrosion resistance of the material.

  13. 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.

  14. Electrochemical reaction of lithium with nanosized vanadium antimonate

    SciTech Connect

    Morales, Julian [Departamento de Quimica Inorganica e Ingenieria Quimica, Facultad de Ciencias, Campus de Rabanales, Edificio Marie Curie, Universidad de Cordoba, 14071 Cordoba (Spain); Sanchez, Luis [Departamento de Quimica Inorganica e Ingenieria Quimica, Facultad de Ciencias, Campus de Rabanales, Edificio Marie Curie, Universidad de Cordoba, 14071 Cordoba (Spain)]. E-mail: luis-sanchez@uco.es; Martin, Francisco [Laboratorio de Materiales y Superficie (Unidad Asociada al CSIC), Universidad de Malaga (Spain); Berry, Frank [Department of Chemistry, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)

    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.

  15. Effects of 2-amino-5-(ethylthio)-1,3,4-thiadiazole on copper corrosion as a corrosion inhibitor in 3% NaCl solutions

    NASA Astrophysics Data System (ADS)

    Sherif, El-Sayed M.

    2006-10-01

    Effects of 2-amino-5-(ethylthio)-1,3,4-thiadiazole (ATD) on copper corrosion as a corrosion inhibitor in de-aerated, aerated and oxygenated 3% NaCl solutions have been studied using potentiodynamic polarization, potentiostatic current-time, electrochemical impedance spectroscopic (EIS), weight loss and pH measurements along with scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) investigations. Potentiodynamic polarization measurements indicated that the presence of ATD in these solutions greatly decreases cathodic, anodic and corrosion currents. Potentiostatic current-time measurements and SEM/EDX investigations also showed that the ATD molecules are strongly adsorbed on the copper surface preventing it from being corroded easily. EIS measurements revealed that the charge transfer resistance increases due to the presence of ATD, and this effect increases with oxygen content in the solution. Weight loss measurements gave an inhibition efficiency of about 83% with 1.0 mM ATD present, increasing to about 94% at the ATD concentration of 5.0 mM. Results together are internally consistent with each other, showing that ATD is a good mixed-type inhibitor for copper corrosion with its inhibition efficiency increasing in the order of oxygenated > aerated > de-aerated 3% NaCl solutions.

  16. Initiation and growth of localized attack in nuclear waste package materials 011

    SciTech Connect

    Roy, A.K., LLNL

    1997-11-01

    Electrochemical potentiodynamic and potentiostatic polarization experiments were conducted on several candidate nuclear waste package container materials in an acidic brine containing 5 weight percent (wt%) NaCl at various temperatures. Substantial pitting and crevice corrosion was observed in Alloys 825 and G-3 in a 90{degrees}C brine at controlled potentials (E{sub cont}) that were noble compared to the critical pitting potential (E{sub pit}) measured by the potentiodynamic polarization method in a similar environment. The results of potentiostatic polarization experiments performed in a 30{degrees}C brine at E{sub cont} values that were noble compared to the corrosion potential (E{sub corr}) indicate that Alloys 825, G-30, C-4 and 625 suffered from crevice corrosion. Alloy C-22 became susceptible to crevice corrosion at 60{degrees}C under controlled potentials which were sufficiently noble compared to E{sub corr}, suggesting that it had a higher critical crevice corrosion temperature compared to that of the other high-nickel alloys tested. No pitting was observed at 30{degrees}C and 60{degrees}C on any tested materials. But Alloy 625 showed surface cracks in the crevice region. Ti Grade- 12 was immune to localized attach. Tests are ongoing.

  17. 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.

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

    SciTech Connect

    Stein, D.J.; Cecchi, J.L. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Chemical and Nuclear Engineering; Hetherington, D.; Guilinger, T. [Sandia National Labs., Albuquerque, NM (United States)

    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.

  19. 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

  20. Electrodeposition of tin-cobalt and tin-cadmium-cobalt alloys from fluoride-chloride electrolytes

    SciTech Connect

    Yakovleva, S.V.; Krasikov, B.S.; Solov'eva, L.V.

    1988-09-10

    The use of fluoride-chloride electrolytes, intended for the deposition of tin-cadmium alloys, on introduction of cobalt(II) compounds into them, apparently makes it possible to obtain ternary alloys and to evaluate some of their physicomechanical characteristics, as well as the character of polarization in the codeposition of cobalt in alloys. A study was carried out by the method of taking partial polarization curves under standard (both galvanostatic and also potentiostatic) regimes in a cell with separated electrode compartments. Electrolytes studied, in which tin(II), cadmium(II), and cobalt(II) were introduced in the form of chlorides and ammonium fluoride served as the background component (ligand with respect to tin), are shown. To unify electrolyte compositions, a constant composition of the solutions was maintained with respect to the surface-active substances introduced - phenol, gelatin, and thiourea.

  1. Electrochemical removal of tannins from aqueous solutions

    SciTech Connect

    Buso, A.; Balbo, L.; Giomo, M.; Farnia, G.; Sandona, G.

    2000-02-01

    The application of electrochemical methods to remove tannins from wastewater was investigated. Gallotannic acid was used as the reference substance. Electrochemical experiments were performed using platinum electrodes. Macroscale potentiostatic or galvanostatic electrolyses were carried out with sodium sulfate or sodium chloride as supporting electrolytes, to analyze direct and indirect oxidation processes. Operating variables such as pH and chloride concentration were considered to determine their influence on the efficiency and energy consumption of the process. The simulation of a pilot plant was carried out with a mathematical model, the parameters of which were determined by fitting of experimental profiles. The results of a preliminary investigation on the oxidation-coagulation process using sacrificial electrodes are also reported.

  2. Preparation of Nickel Oxide Embedded Self Organized Titania Nanotubes Array by New Alginate Method as a Supercapacitor Electrode

    NASA Astrophysics Data System (ADS)

    Dabaghi, Habibeh Hadad; Kazemzad, Mahmood; Ganjkhanlou, Yadolah; Eskandari, Rahmatollah

    2013-12-01

    Potentiostatic two step anodizing of titanium utilized for preparation of self organized titania nanotubes arrays with diameter of 150 nm. Then the new alginate method has been applied for incorporation of NiO into the nanotubes. The prepared hybrid materials have been characterized by various methods including field emission scanning electron microscopy, X-ray diffractometry and cyclic voltammetry analyses. The X-ray diffraction patterns of samples were also studied by Rietveld's method. Results showed that the prepared electrode containing anatase, rutile and NiO phases with fraction of 70, 8, and 22%, respectively. It was found that by application of the new method, porous NiO uniformly coated on nanotubes surface and great enhancement of specific capacitance from 0.14 to 3.8 mF cm-2 could be obtained. The prepared nanocomposites are promising materials for supercapacitance application and also for solar energy harvesting systems.

  3. Electrochemical and Crystallographic Aspects of Lead Granular Growth

    NASA Astrophysics Data System (ADS)

    Nikoli?, Nebojša D.; Ivanovi?, Evica R.; Brankovi?, Goran; La?njevac, Uroš ?.; Stevanovi?, Sanja I.; Stevanovi?, Jasmina S.; Pavlovi?, Miomir G.

    2015-06-01

    Lead granules synthesized by the potentiostatic regime of electrolysis were characterized by the scanning electron microscopy technique. Effect of the different parameters of electrolysis, such as solution composition, overpotential of electrodeposition, and quantity of the electricity, on lead granular growth has been systematically investigated. Aside from the electrochemical aspects of lead granular growth, crystallographic aspects of the obtained granules were also analyzed. In the dependence of the electrodeposition conditions, granules of various shapes were obtained. The granules, such as octahedrons and hexagons, as well as many various types of twinned particles: single-twinned, multiply-twinned, lamellar-twinned, and many other complicated shapes denoted as polyparticles, were synthesized through regulation of the parameters of electrolysis. Increasing both the concentration of Pb2+ ions and overpotential of the electrodeposition favored the formation of more complicated forms. Formation of granules of specified crystallographic characteristics was also correlated with the basic principle of metal electrocrystallization.

  4. 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.

  5. 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.

  6. Localized corrosion initiation, propagation, and repassivation of corrosion resistant high-level nuclear waste container materials

    SciTech Connect

    Dunn, D.S.; Cragnolino, G.A.; Sridhar, N. [Southwest Research Inst., San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses

    1996-10-01

    The initiation and repassivation of pitting and crevice corrosion of two candidate high-level nuclear waste container materials, type 316L stainless steel and alloy 825, were examined under a range of environmental conditions possible in a repository. The initiation and repassivation potentials for localized corrosion in short-term tests were determined to be a function of temperature, chloride concentration, and potential. Under long-term potentiostatic conditions, pitting and crevice corrosion were initiated at potentials much lower than those measured in short-term tests. Crevice corrosion occurred preferentially over pitting corrosion. Similar results were obtained when creviced specimens were connected through a zero resistance ammeter to a boldly exposed cathode of the same material. Localized corrosion was only observed when the potential of the creviced specimen was higher than the repassivation potential.

  7. Long-term prediction of localized corrosion of alloy 825 in high-level nuclear waste repository environments

    SciTech Connect

    Dunn, D.S.; Sridhar, N.; Cragnolino, G.A. [Center for Nuclear Waste Regulatory Analyses, San Antonio, TX (United States)

    1996-02-01

    Long-term prediction of localized corrosion of high-level nuclear waste container materials is a necessary step in the performance assessment of the engineered barrier system. Localized corrosion of corrosion-resistant materials may occur if the containers are exposed to chloride-containing ground water at elevated temperatures. Potentiostatic tests conducted on alloy 825 (UNS NO8825), a candidate container material, have shown that the potential at which localized corrosion can be initiated is a function of surface conditions and exposure time. The initiation potentials for localized corrosion measured in short-term tests with polished specimens overestimated the long-term initiation potentials by as much as 300 mV. On the other hand, the repassivation potential obtained from short-term tests on deep pits can be used to predict the initiation of localized corrosion in long-term tests.

  8. Modelling the influence of ionic and fluid transport on rebars corrosion in unsaturated cement systems

    NASA Astrophysics Data System (ADS)

    Dridi, W.; Dangla, P.; Foct, F.; Petre-Lazar, I.

    2006-11-01

    This paper deals with numerical modelling of rebar corrosion kinetics in unsaturated concrete structures. The corrosion kinetics is investigated in terms of mechanistic coupling between reaction rates at the steel surface and the ionic transport processes in the concrete pore system. The ionic and mass transport model consists of time-dependent equations for the concentration of dissolved species, the liquid pressure and the electrical potential. The complete set of nonlinear equations is solved using the finite-volume method. The nonlinear boundary conditions dealing with corrosion are introduced at the steel-concrete interface where they are implicitly coupled with the mass transport model in the concrete structure. Both the case of free corrosion and potentiostatic polarisation are discussed in a one dimensional model.

  9. Alginate electrodeposition onto three-dimensional porous Co-Ni films as drug delivery platforms.

    PubMed

    García-Torres, J; Gispert, C; Gómez, E; Vallés, E

    2015-01-21

    Three-dimensional porous Co-Ni films/alginate hybrid materials have been successfully prepared by electrodeposition to be used as a steerable magnetic device for drug delivery. Firstly, 3D porous Co-Ni films were prepared as substrates for the subsequent electrodeposition of the alginate biopolymer. Cyclic voltammetry, galvanostatic and potentiostatic studies were performed to establish the best conditions to obtain porous Co-Ni films. The electrochemical experiments were carried out in an electrolyte containing the metal salts and ammonium chloride at low pHs. In a second stage, the electrochemical deposition of alginate as a biocompatible polymer drug delivery carrier was performed. The characteristics of the alginate matrix were investigated in terms of electrochemical properties, morphology and drug release. The hybrid material obtained showed soft-magnetic behavior and drug release indicating its suitability to be used as a steerable magnetic drug delivery device. PMID:25437927

  10. Electropolymerization of pyrrole in the presence of fluoborate

    SciTech Connect

    Prejza, J.; Lundstrom, I.; Skotheim, T.

    1982-08-01

    The formation of polypyrrole on some metallic films (Pt,Pd,Ti,Au,Ni,Cr,In,Al,Fe,Ag, etc.) has been studied under potentiostatic and galvanostatic conditions. The role of pyrrole and the fluoborate ion in the polymerization process has been investigated at room temperature. From the analysis of galvanostatic current-potential curves it has been possible to distinguish the particular processes: initiator formation, polymerization, polymer degradation, and gas evolution. The polymerization in acetonitrile is indirectly initiated with a reaction order of /approximately equals/1 with respect to the BF/sub 4//sup -/ concentration. There are at least two different kinds of polypyrrole, depending on polymerization potential, that differ structurally. The formation of polymers on nonpolarized electrodes has also been observed. This work is pertinent to solar cells. 23 refs.

  11. Electrochemical preparation and characterization of polypyrrole/stainless steel electrodes decorated with gold nanoparticles.

    PubMed

    Gutiérrez Pineda, Eduart; Alcaide, Francisco; Rodríguez Presa, María J; Bolzán, Agustín E; Gervasi, Claudio A

    2015-02-01

    The electrosynthesis and characterization of polypyrrole(PPy)/stainless steel electrodes decorated with gold nanoparticles and the performance of the composite electrode for sensing applications is described. PPy films were grown in potassium perchlorate and sodium salicylate solutions under comparable electropolymerization conditions. Polymer films prepared in the presence of perchlorate ions exhibited worm-like structures, whereas columnar structures were obtained in salicylate-containing solutions. Voltammetric response of PPy films prepared in salicylate solutions was more reversible. PPy films were decorated with gold nanoparticles obtained by a double step potentiostatic electrodeposition routine that allowed fine control of deposit characteristics. Analysis of deposits was performed by means of SEM and confocal Raman spectroscopy. The electrocatalytic activity of the Au/PPy electrodes was assessed for the electro-oxidation of hydrazine and hydroxylamine. Results showed a successful optimization of the route of synthesis that rendered nanocomposite electrode materials with promising applications in electrochemical sensing. PMID:25569325

  12. Large-diameter titanium dioxide nanotube arrays as a scattering layer for high-efficiency dye-sensitized solar cell

    PubMed Central

    2014-01-01

    Large-sized titanium dioxide (TiO2) nanotube arrays with an outer diameter of approximately 500 nm have been successfully synthesized by potentiostatic anodization at 180 V in a used electrolyte with the addition of 1.5 M lactic acid. It is found that the synthesized large-diameter TiO2 nanotube array shows a superior light scattering ability, which can be used as a light scattering layer to significantly enhance the efficiency of TiO2 nanoparticle-based dye-sensitized solar cells from 5.18% to 6.15%. The remarkable light scattering ability makes the large-diameter TiO2 nanotube array a promising candidate for light management in dye-sensitized solar cells (DSSCs). PMID:25114652

  13. Photo-electrochemical sensor for dissolved oxygen, based on a poly(3,4-ethylenedioxythiophene)/iron oxalate hybrid electrode.

    PubMed

    Bencsik, Gábor; Lukács, Zsófia; Visy, Csaba

    2010-02-01

    In this work a poly(3,4-ethylenedioxythiophene) (PEDOT)/iron oxalate composite was synthesized by electrochemical polymerization. The layer was deposited potentiostatically from the monomer-containing solution in the presence of iron(II) oxalate. Similarly to the polypyrrole/iron oxalate electrode--presented in a recent paper--the layer gave a negative photocurrent, which depended on the oxygen concentration of the electrolyte. This cathodic photocurrent--taken as the differences between the values registered under illumination and in the dark at -750 mV potential on the cathodic part of the voltammetric cycles--confirmed the sensitivity of the PEDOT/iron oxalate electrode for dissolved oxygen. Stationary photocurrents were determined also from chronoamperometric measurements, and they exhibited a linear behaviour with the dissolved oxygen concentration to below 1 ppm. The photo-effect of the PEDOT/iron oxalate layer can be attributed to the excitation of the neutral form of the film. PMID:20098773

  14. 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.

  15. Anticorrosion characteristics of a Zn-primer coating in a ballast tank under various chloride concentrations

    NASA Astrophysics Data System (ADS)

    Kim, Seong-Jong; Lee, Seung-Jun

    2010-05-01

    At an open-circuit potential, the anodic polarization curves had very similar values, and no significant differences were observed among the conditions. In the cathodic polarization curves, total residual chloride (TRC) reacted with the Zn-primer coating and created a film that had anticorrosion properties. Therefore, the anticorrosion property improved. With an increase in applied potential in the potentiostatic experiment, the observed surface corrosion occurred due to the dissolution reaction. From Tafel analysis, the corrosion current density had the highest value in natural seawater and the lowest value in the 2 ppm solution. Generally, metals corrode faster with increasing TRC concentration, but with the formation of Zn(OH)2, which has anticorrosion properties, the corrosion resistance of a Zn-primer-coated specimen in seawater can be improved.

  16. 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.

  17. 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

  18. 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.

  19. A light emitting diode based photoelectrochemical screener for distributed combinatorial materials discovery

    NASA Astrophysics Data System (ADS)

    Winkler, Gates R.; Winkler, Jay R.

    2011-11-01

    Combinatorial approaches for targeted discovery of new materials require rapid screening systems to evaluate large numbers of new material compositions. High-throughput combinatorial materials discovery is a capital-intensive undertaking requiring sophisticated robotic sample preparation and rapid screening assays. A distributed approach to combinatorial materials discovery can achieve similar goals by increasing the breadth of participation and reducing the size of the capital investment. The discovery of new photoactive materials for solar fuels production demands a screening device to probe materials for electrochemical current production upon irradiation with visible light. We have developed a system that uses an array of pulsed light-emitting diodes (LEDs) synchronized with a two-electrode potentiostat that can measure the photoelectrochemical responses of combinatorial sample arrays deposited on conducting glass plates. Compared to raster scanning methods, this LED system trades spatial resolution for a substantial reduction in scan time.

  20. Electrochemical corrosion and metal ion release from Co-Cr-Mo prosthesis with titanium plasma spray coating.

    PubMed

    Reclaru, Lucien; Eschler, Pierre-Yves; Lerf, Reto; Blatter, Andreas

    2005-08-01

    The corrosion behavior of CoCrMo implants with rough titanium coatings, applied by different suppliers by either sintering or vacuum plasma spraying, has been evaluated and compared with uncoated material. The open-circuit potential, corrosion current and polarization resistance were determined by electrochemical techniques. The Co, Cr and Ti ions released from the samples into the electrolyte during a potentiostatic extraction technique were analyzed using ICP-MS. The Ti coatings from the different suppliers showed a different porous morphology, and the implants exhibited a distinct corrosion activity, underlining the importance of the coating process parameters. Among the titanium coated samples, the one with the sintered overcoat turned out to be the most resistant. Yet, on an absolute scale, they all showed a corrosion resistance inferior to that of uncoated CoCrMo or wrought titanium. PMID:15763254

  1. A New PC and LabVIEW Package Based System for Electrochemical Investigations

    PubMed Central

    Stevi?, Zoran; Andjelkovi?, Zoran; Anti?, Dejan

    2008-01-01

    The paper describes a new PC and LabVIEW software package based system for electrochemical research. An overview of well known electrochemical methods, such as potential measurements, galvanostatic and potentiostatic method, cyclic voltammetry and EIS is given. Electrochemical impedance spectroscopy has been adapted for systems containing large capacitances. For signal generation and recording of the response of investigated electrochemical cell, a measurement and control system was developed, based on a PC P4. The rest of the hardware consists of a commercially available AD-DA converter and an external interface for analog signal processing. The interface is a result of authors own research. The software platform for desired measurement methods is LabVIEW 8.2 package, which is regarded as a high standard in the area of modern virtual instruments. The developed system was adjusted, tested and compared with commercially available system and ORCAD simulation.

  2. Chemical versus electrochemical synthesis of carbon nano-onion/polypyrrole composites for supercapacitor electrodes.

    PubMed

    Mykhailiv, Olena; Imierska, Monika; Petelczyc, Martyna; Echegoyen, Luis; Plonska-Brzezinska, Marta E

    2015-04-01

    The development of high-surface-area carbon electrodes with a defined pore size distribution and the incorporation of pseudo-active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano-onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission- and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800?F?g(-1) for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300?F?g(-1) for the CNOs/Ppy bilayer (electrochemical deposition). PMID:25736714

  3. Comprehensive dissolution current noise analysis during stress corrosion cracking of Cu{sub 3}Au alloys

    SciTech Connect

    Malki, B.; Legris, A.; Pastol, J.L.; Gorse, D.

    1999-10-01

    Potentiostatic electrochemical noise measurements are performed on Cu{sub 3}Au polycrystals over the whole duration of slow strain rate tensile testes up to brittle cracking in acidic sulfate medium. According to previous works, three different potential testing conditions are chosen, which lead to a more or less enhanced embrittlement. At first glance, one observes successively silent and active electrochemical zones over the whole duration of the mechanical test. Qualitative signal analysis using deterministic chaos theories reveals that (i) the electrochemical behavior of the strained specimen is purely deterministic, (ii) the local maximum Lyapunov exponent, {lambda}{sub 1}, is sensitive to corrosion-deformation interactions, and (iii) there is a clear tendency of {lambda}{sub 1} to decrease well before entering in the crack propagation regime, regardless of the electrochemical conditions used.

  4. SCC behavior and anodic dissolution of Inconel 600 in low concentration thiosulfate

    NASA Astrophysics Data System (ADS)

    Hsu, S. S.; Tsai, S. C.; Kai, J. J.; Tsai, C. H.

    1991-09-01

    The anodic dissolution behavior and the resistance to stress corrosion cracking of Inconel 600 in low concentration thiosulfate were studied utilizing the potentiodynamic polarization and constant load test methods under potential control. It was found that sensitized Inconel 600 was susceptible to IGSCC in thiosulfate solution only when pH was lower than 3. There existed an optimum combination of dissolution/repassivation rates that shortest failure time occured, which corresponded well with the maximum potentiostatic current at onset of abrupt current increase. The constant load test results for samples of different heat treatment also showed that the grain boundary chromium concentration and the crack tip electrochemical potential control the anodic dissolution behavior and thereby determine the stress corrosion resistance of Inconel 600.

  5. Oxidation of chalcopyrite by in-situ electrogenerated Fe{sup III}and Cu{sup II} using an ion exchange membrane

    SciTech Connect

    Ivanaj, S.; Gaballah, I. [Lab. d`Environnement et de Mineralurgie, Vandoeuvre (France); [Ecole Nationale Superieure de Geologie, Vandoeuvre (France); [Centre National de la Recherche Scientifique, Paris (France); [Inst. National Polytechnique de Lorraine, Vandoeuvre (France)

    1995-08-01

    Oxidation of chalcopyrite from a copper concentrate in an electrochemical cell having separate anodic and cathodic compartments was studied by potentiodynamic, potentiostatic and galvanostatic experiments. Oxidation of chalcopyrite particles was mainly realized by in-situ electrogenerated Fe{sup III} and Cu{sup II} ions. The use of an ion exchange membrane, in this experimental set, avoids the reduction of the ferric and cupric ions. The effects of particle size, current feeder potential, current intensity and pulp density were studied to optimize the oxidation parameters. Selective complete oxidation of chalcopyrite was achieved. Oxidation of pyrite was negligible. More than 85% of sulfur was obtained in its elemental form. This may allow selective extraction of copper from the chalcopyrite concentrate without sulfur dioxide emissions. 49 refs.

  6. Investigation into the susceptibility of corrosion resistant alloys to biocorrosion. Final report, September 1991-October 1995

    SciTech Connect

    Clayton, C.R.

    1996-02-02

    The influence of sulfate-reducing bacteria (SRB) on the passivity of Mo-bearing (type 317L) and low Mo content (type 304) austenitic stainless steels (SS) was investigated by x-ray photoelectron spectroscopy (XPS), microbiological and electrochemical techniques. Samples were exposed to SRB, and then the resulting surfaces were analyzed by XPS, and the corrosion resistance by potentiodynamic polarization in deaerated 0.1 M HCI. In order to further understand their passivity, the SRB-exposed samples were also analyzed by XPS after potentiostatic polarization at a passive potential in the hydrochloric solution. The characterization was performed under two surface conditions: unrinsed and rinsed by deaerated alcohol and deionized water.

  7. A wound-type lithium/polyaniline secondary cell

    NASA Astrophysics Data System (ADS)

    Li, Changzhi; Zhang, Borong; Wang, Baochen

    1992-07-01

    A wound-type cell with a polyaniline (PAn) positive electrode, a LiClON4-propylene carbonate (PC) electrolyte, and a lithium-foil negative electrode is constructed. The two electrodes are separated by a polypropylene separator. The PAn is deposited on carbon felt from a HClON4 solution containing aniline by galvanostatic or potentiostatic electrolysis. Using cyclic voltammetry charge/discharge cycles and charge/retention tests, the following results are obtained: (1) reversibility of the charge/discharge reaction of the PAn electrode is very good; (2) more than 50 charge/discharge cycles at 80 percent charge/discharge efficiency and 260 W h/kg discharge energy density can be achieved at 50 mA between 2 and 4 V; (3) the open-circuit voltage and the capacity retention of the battery after storage at open-circuit for 60 days are 3.4 V and 33 percent, respectively.

  8. 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 [Department of Applied Chemistry, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611 (Japan); Nakayama, Masaharu, E-mail: nkymm@yamaguchi-u.ac.jp [Department of Applied Chemistry, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611 (Japan)

    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.

  9. Effect of microstructure and strain on the degradation behavior of novel bioresorbable iron-manganese alloy implants.

    PubMed

    Heiden, Michael; Kustas, Andrew; Chaput, Kevin; Nauman, Eric; Johnson, David; Stanciu, Lia

    2015-02-01

    Advancing the understanding of microstructural effects and deformation on the degradability of Fe-Mn bioresorbable alloys (specifically, Fe-33%Mn) will help address the current problems associated with designing degradable fracture fixation implants for hard tissues. Potentiostatic polarization tests were conducted on a wide variety of metal samples to examine how different deformation processes affect the instantaneous rate of degradation of Fe-Mn alloys. Large-strain machining (LSM), a novel severe plastic deformation (SPD) technique was utilized during these experiments to modify the degradation properties of the proposed Fe-Mn alloy. It was discovered that Fe-33%Mn after LSM with a rake angle of 0° (effective strain?=?2.85) showed the most promising increase in degradation rate compared to as-cast, annealed, and additional deformation conditions (rolled and other LSM parameters) for the same alloy. The mechanisms for enhancement of the corrosion rate are discussed. PMID:24825402

  10. Crevice corrosion products of dental amalgam

    SciTech Connect

    Sutow, E.J.; Jones, D.W.; Hall, G.C.; Owen, C.G. (Division of Dental Biomaterials Science, Faculty of Dentistry, Dalhousie University, Halifax, Nova Scotia (Canada))

    1991-07-01

    The objective of this study was to determine the in vitro corrosion products that resulted from crevice corrosion of low- and high-copper dental amalgams. Specimens were potentiostatically polarized in a chloride-containing electrolyte while set against a PTFE surface to form a crevice. After 16 h, corrosion products were examined by light microscopy, SEM, EDS, and XRD. Analysis showed the presence of three previously reported products (Sn4(OH)6Cl2, SnO, and Cu2O) and a new product, CuCl, which formed on high-copper, {gamma} 2-free amalgams. Thermodynamic considerations show that CuCl is stable for the reported in vivo potentials of amalgam restorations and the high acidity and high chloride ion concentration associated with crevice corrosion.

  11. 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

  12. The inhibition of corrosion of mild steel in 0.5 M sulfuric acid solution in the presence of benzyl triphenyl phosphonium bromide

    NASA Astrophysics Data System (ADS)

    Bhrara, Kalpana; Singh, Gurmeet

    2006-11-01

    Benzyl triphenyl phosphonium bromide (BTPPB) has been evaluated as a corrosion inhibitor for mild steel in aerated 0.5 M sulfuric acid solution by galvanostatic polarization and potentiostatic polarization methods. The effect of BTPPB on the corrosion current is measured at various temperatures and concentrations. The inhibitor efficiencies, effective activation energies and heat of adsorption have been calculated. The inhibition efficiency increases with increase in inhibitor concentration to reach 99.3% for 10 -2 M. The nature of adsorption of BTPPB on the metal surface has also been examined. Probable mode of adsorption on the metal surface has been proposed using infrared spectroscopic studies. The electrochemical results have also been supplemented by surface morphological studies and quantum chemical analysis.

  13. 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.

  14. Some aspects of quantum chemical calculations for the study of Schiff base corrosion inhibitors on copper in NaCl solutions

    Microsoft Academic Search

    S. L Li; Y. G Wang; S. H Chen; R Yu; S. B Lei; H. Y Ma; De X Liu

    1999-01-01

    The inhibiting effect of some Schiff bases—N,N?-o-phenylen-bis(3-methoxy-salicylidenimine) (V–oph–V), N-2-hydroxyphenyl-(3-methoxy-salicylidenimine) (V–bso), N-4-phenylcarbazide-(3-methoxy-salicylidenimine) (V–psd) N,N?-o-phenylen-bis(salicylidenimine) (S–oph–S), N,N?-p-phenylen-bis(salicylidenimine) (S–pph–S), N-4-phenylcarbazide-(salicylidenimine) (S–psd) on the corrosion of copper in 1.0M NaCl solutions, under various conditions, has been studied by means of the potentiostatic polarization method and the AC impedance technique.In order to study the ability of quantum chemistry to select corrosion inhibitors, quantum chemical calculations

  15. High frequency reference electrode

    DOEpatents

    Kronberg, James W. (Aiken, SC)

    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.

  16. Lab-on-a-chip sensor for measuring Zn by stripping voltammetry

    NASA Astrophysics Data System (ADS)

    Pei, Xing; Kang, Wenjing; Yue, Wei; Bange, Adam; Wong, Hector R.; Heineman, William R.; Papautsky, Ian

    2012-03-01

    This work reports on continuing development of a lab-on-a-chip sensor for electrochemical detection of heavy metal zinc in blood serum. The sensor consists of a three electrode system, including an environmentally-friendly bismuth working electrode, a Ag/AgCl reference electrode, and a gold auxiliary electrode. By optimizing the electrodeposition of bismuth film, better control of fabrication steps and improving interface between the sensor and potentiostat, repeatability and sensitivity of the lab-on-a-chip sensor has been improved. Through optimization of electrolyte and stripping voltammetry parameters, limits of detection were greatly improved. The optimized sensor was able to measure zinc in in the physiological range of 65-95 ?g/dL. Ultimately, with further development and integrated sample preparation sensor system will permit rapid (min) measurements of zinc from a sub-mL sample (a few drops of blood) for bedside monitoring.

  17. 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.

  18. Applicability of repassivation potential for long-term prediction of localized corrosion of Alloy 825 and type 316L stainless steel

    SciTech Connect

    Sridhar, N.; Cragnolino, G.A. (Southwest Research Inst., San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses)

    1993-11-01

    Repassivation potential (E[sub rp]) was investigated for use as a parameter in the long-term prediction of pitting resistance of two Fe-Ni-Cr-Mo alloys that are candidate materials for high-level nuclear waste containers. This potential was found to be independent of the extent of prior pit growth for alloy 825 (UNS N08825) and type 316 L (UNS S31603) stainless steel (SS). Repassivation potential decreased by an increase in backward scan rate after pits were grown under potentiostatic conditions. This was related to the effect of potential on repassivation time. The corrosion potential (E[sup corr]) in simulated pit-crevice solutions increased with a decrease in pH and was independent of chloride (CL[sup [minus

  19. 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.

  20. 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 ?A cm(-2) after template dissolution. PMID:24481549

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

    SciTech Connect

    Wixtrom, Alex I. [Christopher Newport University, Newport News, VA (United States); Buhler, Jessica E. [Christopher Newport University, Newport News, VA (United States); Reece, Charles E. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Abdel-Fattah, Tarek M. [Christopher Newport University, Newport News, VA (United States)

    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.

  2. Integrated circuit-based electrochemical sensor for spatially resolved detection of redox-active metabolites in biofilms

    PubMed Central

    Bellin, Daniel L.; Sakhtah, Hassan; Rosenstein, Jacob K.; Levine, Peter M.; Thimot, Jordan; Emmett, Kevin; Dietrich, Lars E. P.; Shepard, Kenneth L.

    2014-01-01

    Despite advances in monitoring spatiotemporal expression patterns of genes and proteins with fluorescent probes, direct detection of metabolites and small molecules remains challenging. A technique for spatially resolved detection of small molecules would benefit the study of redox-active metabolites produced by microbial biofilms, which can drastically affect colony development. Here we present an integrated circuit-based electrochemical sensing platform featuring an array of working electrodes and parallel potentiostat channels. “Images” over a 3.25 × 0.9 mm area can be captured with a diffusion-limited spatial resolution of 750 ?m. We demonstrate that square wave voltammetry can be used to detect, identify, and quantify (for concentrations as low as 2.6 ?M) four distinct redox-active metabolites called phenazines. We characterize phenazine production in both wild-type and mutant Pseudomonas aeruginosa PA14 colony biofilms, and find correlations with fluorescent reporter imaging of phenazine biosynthetic gene expression. PMID:24510163

  3. Stationary anodic process at platinum in KF-NaF-AlF3-Al2O3 melts

    NASA Astrophysics Data System (ADS)

    Nekrasov, V. N.; Limanovskaya, O. V.; Suzdal'tsev, A. V.; Khramov, A. P.; Zaikov, Yu. P.

    2014-08-01

    The kinetics of the anodic process at platinum in KF-NaF-AlF3-Al2O3 melts in the temperature range 725-800°C is studied using potentiostatic polarization. Platinum is considered as an indifferent oxygen-evolving electrode, and a two-stage scheme is proposed for the anodic process on it. According to this scheme, primary charge transfer with the formation of adsorbed Oads particles is accompanied by their desorption according to a physical or an electrochemical mechanism. The polarization dependences of the anodic process on platinum are calculated under stationary conditions with allowance for the predominance of different stages of the process and a desorption mechanism. The calculated and experimental stationary anodic polarization dependences are compared.

  4. Preselection of Ni-Cr(-Mo) alloys as potential canister materials for vitrified high active nuclear waste by electrochemical testing

    NASA Astrophysics Data System (ADS)

    Bort, H.; Wolf, I.; Leistikow, S.

    1987-07-01

    Several Ni-Cr(-Mo) alloys (Hastelloy C4, Inconel 625, Sanicro 28, Incoloy 825, Inconel 690) were tested by electrochemical methods to characterize their corrosion behavior in chloride containing solutions at various temperatures and pH-values in respect to their application as canister materials for final radioactive waste storage. Especially, Hastelloy C4 was tested by potentiodynamic, potentiostatic and galvanostic measurements. As electrolytes H 2SO 4 solutions were used, as parameters temperature, chloride content and pH-value were varied. All tested alloys showed a clearly limited resistance against pitting corrosion phenomena; under severe conditions even crevice corrosion phenomena were observed. The best corrosion behavior, however, is shown by Hastelloy C4, which has the lowest passivation current density of all tested alloys and the largest potential region with protection against local corrosion phenomena.

  5. 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

  6. 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.

  7. 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-?m 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 ?A, 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

  8. 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 temperature controlled cells for potentiostatic and potentiodynamic testing (Figure 2).

  9. Power management systems for sediment microbial fuel cells in high power and continuous power applications

    NASA Astrophysics Data System (ADS)

    Donovan, Conrad Koble

    The objective of this dissertation was to develop power management systems (PMS) for sediment microbial fuel cells (SFMCs) for high power and continuous applications. The first part of this dissertation covers a new method for testing the performance of SMFCs. This device called the microbial fuel cell tester was developed to automatically test power generation of PMS. The second part focuses on a PMS capable of delivering high power in burst mode. This means that for a small amount of time a large amount of power up to 2.5 Watts can be delivered from a SMFC only generating mW level power. The third part is aimed at developing a multi-potentiostat laboratory tool that measures the performance at fixed cell potentials of microbial fuel cells so that I can optimize them for use with the PMS. This tool is capable of controlling the anode potential or cathode potential and measuring current of six separate SMFCs simultaneously. By operating multiple potentiostats, I was able to run experiments that find ideal operating conditions for the sediment microbial fuel cells, and also I can optimize the power management system for these conditions. The fourth part of the dissertation is targeting a PMS that was able to operate a sensor continuously which was powered by an SMFC. In pervious applications involving SMFCs, the PMS operated in batch mode. In this PMS, the firmware on the submersible ultrasonic receiver (SUR) was modified for use with my PMS. This integration of PMS and SUR allowed for the continuous operation of the SUR without using a battery. Finally, the last part of the dissertation recommends a scale-up power management system to overcome the linearity scale up issue of SMFCs as future work. Concluding remarks are also added to summarize the goal and focus of this dissertation.

  10. 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

  11. 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.

  12. Silver(I) Ions Ultrasensitive Detection at Carbon Electrodes—Analysis of Waters, Tobacco Cells and Fish Tissues

    PubMed Central

    Krizkova, Sona; Krystofova, Olga; Trnkova, Libuse; Hubalek, Jaromir; Adam, Vojtech; Beklova, Miroslava; Horna, Ales; Havel, Ladislav; Kizek, Rene

    2009-01-01

    We used carbon paste electrodes and a standard potentiostat to detect silver ions. The detection limit (3 Signal/Noise ratio) was estimated as 0.5 ?M. A standard electrochemical instrument microanalysis of silver(I) ions was suggested. As a working electrode a carbon tip (1 mL) or carbon pencil was used. Limits of detection estimated by dilution of a standard were 1 (carbon tip) or 10 nM (carbon pencil). Further we employed flow injection analysis coupled with carbon tip to detect silver(I) ions released in various beverages and mineral waters. During first, second and third week the amount of silver(I) ions releasing into water samples was under the detection limit of the technique used for their quantification. At the end of a thirteen weeks long experiment the content of silver(I) ions was several times higher compared to the beginning of release detected in the third week and was on the order of tens of nanomoles. In subsequent experiments the influence of silver(I) ions (0, 5 and 10 ?M) on a plant model system (tobacco BY-2 cells) during a four-day exposition was investigated. Silver(I) ions were highly toxic to the cells, which was revealed by a double staining viability assay. Moreover we investigated the effect of silver(I) ions (0, 0.3, 0.6, 1.2 and 2.5 ?M) on guppies (Poecilia reticulata). Content of Ag(I) increased with increasing time of the treatment and applied concentrations in fish tissues. It can be concluded that a carbon tip or carbon pencil coupled with a miniaturized potentiostat can be used for detection of silver(I) ions in environmental samples and thus represents a small, portable, low cost and easy-to-use instrument for such purposes. PMID:22399980

  13. 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].

  14. 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.

  15. Utilization of subsurface microbial electrochemical systems to elucidate the mechanisms of competition between methanogenesis and microbial iron(III)/humic acid reduction in Arctic peat soils

    NASA Astrophysics Data System (ADS)

    Friedman, E. S.; Miller, K.; Lipson, D.; Angenent, L. T.

    2012-12-01

    High-latitude peat soils are a major carbon reservoir, and there is growing concern that previously dormant carbon from this reservoir could be released to the atmosphere as a result of continued climate change. Microbial processes, such as methanogenesis and carbon dioxide production via iron(III) or humic acid reduction, are at the heart of the carbon cycle in Arctic peat soils [1]. A deeper understanding of the factors governing microbial dominance in these soils is crucial for predicting the effects of continued climate change. In previous years, we have demonstrated the viability of a potentiostatically-controlled subsurface microbial electrochemical system-based biosensor that measures microbial respiration via exocellular electron transfer [2]. This system utilizes a graphite working electrode poised at 0.1 V NHE to mimic ferric iron and humic acid compounds. Microbes that would normally utilize these compounds as electron acceptors donate electrons to the electrode instead. The resulting current is a measure of microbial respiration with the electrode and is recorded with respect to time. Here, we examine the mechanistic relationship between methanogenesis and iron(III)- or humic acid-reduction by using these same microbial-three electrode systems to provide an inexhaustible source of alternate electron acceptor to microbes in these soils. Chamber-based carbon dioxide and methane fluxes were measured from soil collars with and without microbial three-electrode systems over a period of four weeks. In addition, in some collars we simulated increased fermentation by applying acetate treatments to understand possible effects of continued climate change on microbial processes in these carbon-rich soils. The results from this work aim to increase our fundamental understanding of competition between electron acceptors, and will provide valuable data for climate modeling scenarios. 1. Lipson, D.A., et al., Reduction of iron (III) and humic substances plays a major role in anaerobic respiration in an Arctic peat soil. Journal of Geophysical Research-Biogeosciences, 2010. 115. 2. Friedman, E.S., et al., A cost-effective and field-ready potentiostat that poises subsurface electrodes to monitor bacterial respiration. Biosensors and Bioelectronics, 2012. 32(1): p. 309-313.

  16. System-based approach for an advanced drug delivery platform

    NASA Astrophysics Data System (ADS)

    Kulinsky, Lawrence; Xu, Han; Tsai, Han-Kuan A.; Madou, Marc

    2006-03-01

    Present study is looking at the problem of integrating drug delivery microcapsule, a bio-sensor, and a control mechanism into a biomedical drug delivery system. A wide range of medical practices from cancer therapy to gastroenterological treatments can benefit from such novel bio-system. Drug release in our drug delivery system is achieved by electrochemically actuating an array of polymeric valves on a set of drug reservoirs. The valves are bi-layer structures, made in the shape of a flap hinged on one side to a valve seat, and consisting of thin films of evaporated gold and electrochemically deposited polypyrrole (PPy). These thin PPy(DBS) bi-layer flaps cover access holes of underlying chambers micromachined in a silicon substrate. Chromium and polyimide layers are applied to implement "differential adhesion" to obtain a voltage induced deflection of the bilayer away from the drug reservoir. The Cr is an adhesion-promoting layer, which is used to strongly bind the gold layer down to the substrate, whereas the gold adheres weakly to polyimide. Drug actives (dry or wet) were pre-stored in the chambers and their release is achieved upon the application of a small bias (~ 1V). Negative voltage causes cation adsorption and volume change in PPy film. This translates into the bending of the PPy/Au bi-layer actuator and release of the drug from reservoirs. This design of the drug delivery module is miniaturized to the dimensions of 200?m valve diameter. Galvanostatic and potentiostatic PPy deposition methods were compared, and potentiostatic deposition method yields film of more uniform thickness. PPy deposition experiments with various pyrrole and NaDBS concentrations were also performed. Glucose biosensor based on glucose oxidase (GOx) embedded in the PPy matrix during elechtrochemical deposition was manufactured and successfully tested. Multiple-drug pulsatile release and continuous linear release patterns can be implemented by controlling the operation of an array of valves. Varying amounts of drugs, together with more complex controlling strategies would allow creation of more complex drug delivery patterns.

  17. Degradation and failure susceptibility of carbon steels in simulated Yucca Mountain nuclear repository environments

    NASA Astrophysics Data System (ADS)

    Yilmaz, Ahmet

    Environmental degradation and cracking of medium carbon steel (MCS) rock bolts and low carbon steel (LCS) I-beam have been investigated by experimental methods such as linear polarization, impedance spectroscopy, weight loss measurements, and electro-mechanical dynamic slow strain rate tensile (SSRT) tests, along with potentiostatic in-situ potential-current monitoring techniques. The experiments were conducted in concentrated aqueous environments of various temperatures, which simulated the conditions at the Yucca Mountain (YM) nuclear waste repository site, where the candidate structural materials introduced above, will be used for supporting the waste repository tunnels. MCS corroded at medium general rates approximately around 40 mum/year to 200 mum/year in de-aerated simulated YM waters of various temperatures and concentrations. Increased temperatures increased the corrosion rates in the all de-aerated waters. Increased concentrations of overall species in the simulated waters also increased the corrosion rates, but only slightly. Impedance spectroscopy revealed similar trends for temperature and concentration effects on the rates in both aerated and deaerated environments. Aeration increased corrosion rates significantly in dilute (1X) and ten times concentrated (10X) waters at all temperatures. However, inhibitive precipitates on the specimens formed by oxygen-environment reactions at higher temperatures (up to 85°C) in hundred times concentrated (100X) waters decreased corrosion rates drastically, resulting some localized corrosion and pitting. The average rates were determined to be between approximately 100 mu/year and 1000 mu/year in the entire concentration and temperature range tested. Electrochemical results showed slightly higher rates compared to the other tests because of their much shorter testing period, therefore in general they should be taken as conservative upper bounds. SSRT on LCS under various imposed metal-electrolyte interface potentials revealed strain aging embrittlement (SAE) and hydrogen induced cracking (HIC) at 85°C in simulated de-aerated 100X YM waters. The failures were brittle and of sharp cracks which always inclined in ˜45° to the load axis. Ductile failures along secondary trans-granular cracks around the main cracks occurred at room temperature (25°C) with some anodic and cathodic over-potentials around Ecorr, revealing susceptibility of LCS to stress corrosion cracking (SCC) in the simulated repository environments. SSRT combined with in-situ current and potential monitoring by potentiostatic methods revealed that Portevin LeChatelier (PLC) effect in LCS starts at ˜55°C, and showed precise correlations with open circuit potential Ecorr and the corresponding current. Therefore, SSRT along the in-situ potential-current monitoring in aqueous environments becomes a powerful diagnostic research tool especially for investigating dynamic strain aging (Portevin-LeChatelier Effect) phenomena of metals in aqueous environments.

  18. Morphology and performances of the anodic oxide films on Ti6Al4V alloy formed in alkaline-silicate electrolyte with aminopropyl silane addition under low potential

    NASA Astrophysics Data System (ADS)

    Chen, Jiali; Wang, Jinwei; Yuan, Hongye

    2013-11-01

    Oxide films on Ti6Al4V alloy are prepared using sodium hydroxide-sodium silicate as the base electrolyte with addition of aminopropyl trimethoxysilane (APS) as additive by potentiostatic anodizing under 10 V. APS is incorporated into the films during anodizing and the surface morphology of the oxide films is changed from particle stacked to honeycomb-like porous surfaces as shown by scanning electron microscopy (SEM) with Energy Disperse Spectroscopy (EDX). The surface roughness and aminopropyl existence on the oxide films result in their differences in wettability as tested by the surface profile topography and contact angle measurements. The anti-abrasive ability of the anodic films is improved with the addition of APS due to its toughening effects and serving as lubricants in the ceramic oxide films as measured by ball-on-disk friction test. Also, potentiodynamic corrosion test proves that their anticorrosive ability in 3.5 wt.% NaCl is greatly improved as reflected by their much lower corrosion current (Icorr) and higher corrosion potential (Ecorr) than those of the substrate.

  19. Corrosion inhibitor storage and release property of TiO{sub 2} nanotube powder synthesized by rapid breakdown anodization method

    SciTech Connect

    Arunchandran, C.; Ramya, S.; George, R.P. [Corrosion Science and Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)] [Corrosion Science and Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Kamachi Mudali, U., E-mail: kamachi@igcar.gov.in [Corrosion Science and Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ? TiO{sub 2} nanotube powders were synthesized by rapid breakdown anodization method. ? Benzotriazole was loaded into the TiO{sub 2} nanotube powders. ? Low pH induced release of benzotriazole from TiO{sub 2} nanotube powders was proved. -- Abstract: Titanium dioxide (TiO{sub 2}) is one of the most studied substances in material science due to its versatile properties and diverse applications. In this study titanium dioxide nanotube powder were synthesized by rapid breakdown anodization (RBA) method. The synthesis involved potentiostatic anodization of titanium foil in 0.1 M HClO{sub 4} electrolyte under an applied voltage of 20 V and rapid stirring. The morphology and the phase of titanium dioxide nanotube powder were studied using field emission scanning electron microscopy, laser Raman spectroscopy and high resolution transmission electron microscopy. Benzotriazole was chosen as model inhibitor to evaluate TiO{sub 2} nanotube powder's corrosion inhibitor loading and releasing properties. The storage and release properties of TiO{sub 2} nanotube powder were studied using UV–visible spectroscopy and thermogravimetric analysis.

  20. Bioelectrocatalytic application of titania nanotube array for molecule detection.

    PubMed

    Xie, Yibing; Zhou, Limin; Huang, Haitao

    2007-06-15

    A bioelectrocatalysis system based on titania nanotube electrode has been developed for the quantitative detection application. Highly ordered titania nanotube array with inner diameter of 60 nm and total length of 540 nm was formed by anodizing titanium foils. The functionalization modification was achieved by embedding glucose oxidases inside tubule channels and electropolymerizing pyrrole for interfacial immobilization. Morphology and microstructure characterization, electrochemical properties and bioelectrocatalytic reactivities of this composite were fully investigated. The direct detection of hydrogen peroxide by electrocatalytic reduction reaction was fulfilled on pure titania nanotube array with a detection limit up to 2.0 x 10(-4)mM. A biosensor based on the glucose oxidase-titania/titanium electrode was constructed for amperometric detection and quantitative determination of glucose in a phosphate buffer solution (pH 6.8) under a potentiostatic condition (-0.4V versus SCE). The resulting glucose biosensor showed an excellent performance with a response time below 5.6s and a detection limit of 2.0 x 10(-3)mM. The corresponding detection sensitivity was 45.5 microA mM(-1)cm(-2). A good operational reliability was also achieved with relative standard deviations below 3.0%. This novel biosensor exhibited quite high response sensitivity and low detection limit for potential applications. PMID:17188856

  1. Enhanced durability of a proton conducting oxide fuel cell with a purified yttrium-doped barium zirconate-cerate electrolyte

    NASA Astrophysics Data System (ADS)

    Hakim, Muhammad; Yoo, Chung-Yul; Joo, Jong Hoon; Yu, Ji Haeng

    2015-03-01

    The aim of this study is to investigate the effect of yttrium-doped barium zirconate-cerate (BaZr0.3Ce0.5Y0.2O3-?, BZCY) refinement on cell stability under operational fuel cell conditions. For this purpose, anode-supported cells, comprised of a nickel oxide (NiO)-BZCY anode, a BZCY electrolyte, and a BZCY-La0.6Sr0.4Co0.2Fe0.8O3-? composite cathode are successfully prepared with refined or as-calcined BZCY powder. The long-term fuel cell performance is evaluated under a potentiostatic measurement at 600 °C. The cell with the refined BZCY electrolyte shows a modest power density of 47 mW cm-2 at a 600 °C operating temperature over 480 h without any significant performance loss, whereas the cell with the as-calcined BZCY electrolyte displays a rapid degradation of cell performance over 110 h. A post-testing analysis of the cell with the refined BZCY does not reveal any evidence of delamination resulting from electrolyte surface decomposition. These results demonstrate that the refinement process significantly enhances the chemical stability of BZCY-based proton conducting fuel cells, which produce a high content of water vapor on the cathode side.

  2. An Implantable RFID Sensor Tag toward Continuous Glucose Monitoring.

    PubMed

    Xiao, Zhibin; Tan, Xi; Chen, Xianliang; Chen, Sizheng; Zhang, Zijian; Zhang, Hualei; Wang, Junyu; Huang, Yue; Zhang, Peng; Zheng, Lirong; Min, Hao

    2015-05-01

    This paper presents a wirelessly powered implantable electrochemical sensor tag for continuous blood glucose monitoring. The system is remotely powered by a 13.56-MHz inductive link and utilizes an ISO 15693 radio frequency identification (RFID) standard for communication. This paper provides reliable and accurate measurement for changing glucose level. The sensor tag employs a long-term glucose sensor, a winding ferrite antenna, an RFID front-end, a potentiostat, a 10-bit sigma-delta analog to digital converter, an on-chip temperature sensor, and a digital baseband for protocol processing and control. A high-frequency external reader is used to power, command, and configure the sensor tag. The only off-chip support circuitry required is a tuned antenna and a glucose microsensor. The integrated chip fabricated in SMIC 0.13- ?m CMOS process occupies an area of 1.2 mm ×2 mm and consumes 50 ?W. The power sensitivity of the whole system is -4 dBm. The sensor tag achieves a measured glucose range of 0-30 mM with a sensitivity of 0.75 nA/mM. PMID:25823049

  3. Electrochemically reduced graphene oxide-based electrochemical sensor for the sensitive determination of ferulic acid in A. sinensis and biological samples.

    PubMed

    Liu, Linjie; Gou, Yuqiang; Gao, Xia; Zhang, Pei; Chen, Wenxia; Feng, Shilan; Hu, Fangdi; Li, Yingdong

    2014-09-01

    An electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE) was used as a new voltammetric sensor for the determination of ferulic acid (FA). The morphology and microstructure of the modified electrodes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy analysis, and the electrochemical effective surface areas of the modified electrodes were also calculated by chronocoulometry method. Sensing properties of the electrochemical sensor were investigated by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that ERGO was electrodeposited on the surface of GCE by using potentiostatic method. The proposed electrode exhibited electrocatalytic activity to the redox of FA because of excellent electrochemical properties of ERGO. The transfer electron number (n), electrode reaction rate constant (ks) and electron-transfer coefficient (?) were calculated as 1.12, 1.24s(-1), and 0.40, respectively. Under the optimized conditions, the oxidation peak current was proportional to FA concentration at 8.49 × 10(-8)mol L(-1) to 3.89 × 10(-5)mol L(-1) with detection limit of 2.06 × 10(-8)mol L(-1). This fabricated sensor also displayed acceptable reproducibility, long-term stability, and high selectivity with negligible interferences from common interfering species. The voltammetric sensor was successfully applied to detect FA in A. sinensis and biological samples with recovery values in the range of 99.91%-101.91%. PMID:25063114

  4. Affinity sensor using 3-aminophenylboronic acid for bacteria detection.

    PubMed

    Wannapob, Rodtichoti; Kanatharana, Proespichaya; Limbut, Warakorn; Numnuam, Apon; Asawatreratanakul, Punnee; Thammakhet, Chongdee; Thavarungkul, Panote

    2010-10-15

    Boronic acid that can reversibly bind to diols was used to detect bacteria through its affinity binding reaction with diol-groups on bacterial cell walls. 3-aminophenylboronic acid (3-APBA) was immobilized on a gold electrode via a self-assembled monolayer. The change in capacitance of the sensing surface caused by the binding between 3-APBA and bacteria in a flow system was detected by a potentiostatic step method. Under optimal conditions the linear range of 1.5×10(2)-1.5×10(6) CFU ml(-1) and the detection limit of 1.0×10(2) CFU ml(-1) was obtained. The sensing surface can be regenerated and reused up to 58 times. The method was used for the analysis of bacteria in several types of water, i.e., bottled, well, tap, reservoir and wastewater. Compared with the standard plate count method, the results were within one standard deviation of each other. The proposed method can save both time and cost of analysis. The electrode modified with 3-APBA would also be applicable to the detection of other cis-diol-containing analytes. The concept could be extended to other chemoselective ligands, offering less expensive and more robust affinity sensors for a wide range of compounds. PMID:20801635

  5. Surfactant-dependent macrophage response to polypyrrole-based coatings electrodeposited on Ti6Al7Nb alloy.

    PubMed

    Mindroiu, Mihaela; Ion, Raluca; Pirvu, Cristian; Cimpean, Anisoara

    2013-08-01

    In this study, polypyrrole (PPy) films were successfully synthesized on Ti6Al7Nb alloy by potentiostatic polymerization in the presence of poly(sodium 4-styrenesulfonate) (NaPSS), t-octylphenoxy polyethoxyethanol (Triton X-100) and N-dodecyl-?-D-maltoside (DM) surfactants. Atomic force microscopy (AFM) analysis of the PPy/surfactant composite films revealed a granular structure characterized by a lower surface roughness than un-modified PPy films. The results demonstrated that addition of surfactants, namely Triton X-100 and DM, can improve electrochemical film stability and corrosion resistance. Further, Triton X-100 enhanced the adhesive strength of PPy films to the substrate. The surfactant type also showed a great influence on the surface wettability, the highest hydrophilic character being observed in the case of PPy/PSS film. Few studies have been devoted to the elucidation of inflammatory cell response to PPy-based materials. Therefore, RAW 264.7 macrophages were cultured on PPy-surfactant films to determine whether they elicit a differential cell behavior in terms of cell adhesion, proliferation, cellular morphology and cytokine secretion. Our results highlight the dependence of macrophage response on the surfactants used in the pyrrole polymerization process and suggest that the immune response to biomaterials coated with PPy films might be controlled by the choice of surfactant molecules. PMID:23706221

  6. A comparison of the corrosion behaviour and surface characteristics of vacuum-brazed and heat-treated Ti6Al4V alloy.

    PubMed

    Lee, T M; Chang, E; Yang, C Y

    1998-08-01

    The corrosion characteristics of the brazed Ti6Al4V specimens were analysed and compared with respect to the conventionally heat-treated specimens by an electrochemical corrosion test. The object of this research was to explore the potentiality of the brazed titanium for biomaterials. The characteristics of the 1300 degrees C heat-treated and the 970 degrees C brazed specimens, with passivation and sterilization treatment, were evaluated by measurement of corrosion potential, Ecorr, corrosion current densities, Icorr, polarization resistance of the reacted surface films, Rp, in a potentiodynamic test. The experimental results show that the corrosion rates of the heat-treated and the brazed samples are similar at Ecorr, and the value of Ecorr for the brazed sample is noble to the heat-treated samples. The passive current density of the brazed specimen is either lower or higher than the heat-treated specimen, depending on the polarization potential. By Auger electron spectroscopic and high-resolution X-ray photoelectron spectroscopic analysis on specimens from the potentiostatic test, the elements of copper and nickel in the brazing filler were not detected while less alumina was found in the reacted film of the brazed specimens when compared with the heat-treated specimens. The implication of the results is discussed. PMID:15348855

  7. Quasi-in-situ single-grain photoelectron microspectroscopy of Co/PPy nanocomposites under oxygen reduction reaction.

    PubMed

    Bocchetta, Patrizia; Amati, Matteo; Bozzini, Benedetto; Catalano, Massimo; Gianoncelli, Alessandra; Gregoratti, Luca; Taurino, Antonietta; Kiskinova, Maya

    2014-11-26

    This paper reports an investigation into the aging of pyrolyzed cobalt/polypyrrole (Co/PPy) oxygen reduction reaction (ORR) electrocatalysts, based on quasi-in-situ photoelectron microspectroscopy. The catalyst precursor was prepared by potentiostatic reverse-pulse coelectrodeposition from an acetonitrile solution on graphite. Accelerated aging was obtained by quasi-in-situ voltammetric cycling in an acidic electrolyte. Using photoelectron imaging and microspectroscopy of single Co/PPy grains at a resolution of 100 nm, we tracked the ORR-induced changes in the morphology and chemical state of the pristine material, consisting of uniformly distributed ?20 nm nanoparticles, initially consisting of a mixture of Co(II) and Co(III) oxidation states in almost equal amounts. The evolution of the Co 2p, O 1s, and N 1s spectra revealed that the main effects of aging are a gradual loss of the Co present at the surface and the reduction of Co(III) to Co(II), accompanied by the emergence and growth of a N 1s signal, corresponding to electrocatalytically active C-N sites. PMID:25369153

  8. Influence of post-treatment temperature of TNTa photoelectrodes on photoelectrochemical properties and photocatalytic degradation of 4-nonylphenol

    NASA Astrophysics Data System (ADS)

    Xin, Yanjun; Liu, Huiling; Li, Junjing; Chen, Qinghua; Ma, Dong

    2013-03-01

    TiO2/Ti Nanotube array (TNTa) photoelectrodes were prepared by galvanostatic and potentiostatic anodization technique, and annealed at different temperature. The morphology and structure were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectra. Optical properties and photoelectrochemical (PECH) properties were investigated by surface photovoltage (SPV), ultra UV-vis diffuse reflectance spectra (UV/vis/DRS), open-circuit potential (OCP) and transient photocurrent. Photodecomposition performances were evaluated by the yield of •OH radicals and photocatalytic (PC) degradation rate of 4-nonylphenol (4-NP) under xenon light. The results showed that with the increase of post-treatment temperature, PECH and PC properties increased gradually and then decreased. The photocurrent densities, yield of *OH radicals and photodecomposition rates of 4-NP were following the trend of TNT-823>TNT-873>TNT-773>TNT-673>TNT-973>TNT-298. When the annealing temperature was 823 K, the photoelectrodes were composed of mixed crystal structure and ordered nanotube array, which exhibited superior PECH properties. When the annealed temperature arrived to 973 K, the nanotube collapsed and the PECH and PC properties of TNTa photoelectrodes decreased. For TNT-823 photoelectrodes, after the assistant potential was applied, the degradation rate of 4-NP increased significantly from 77% to 97% after 120 min illumination.

  9. Comparison of Electrochemical Methods to Determine Crevice Corrosion Repassivation Potential of Alloy 22 in Chloride Solutions

    SciTech Connect

    K. Evans; A. Yilmaz; S. Day; L. Wong; J. Estill

    2004-08-23

    Alloy 22 (N06022) is a nickel-based alloy highly resistant to corrosion. In some aggressive conditions of high chloride concentration, temperature and applied potential, Alloy 22 may suffer crevice corrosion, a form of localized corrosion. There are several electrochemical methods that can be used to determine localized corrosion in metallic alloys. One of the most popular for rapid screening is the cyclic potentiodynamic polarization (CPP). This work compares the repassivation potentials obtained using CPP to related repassivation potential values obtained using the Tsujikawa-Hisamatsu Electrochemical (THE) method and the potentiostatic (POT) method. Studied variables included temperature and chloride concentration. The temperature was varied from 30 C and 120 C and the chloride concentration was varied between 0.0005 M to 4 M. Results show that similar repassivation potentials were obtained for Alloy 22 using CPP and THE methods. Generally, under more aggressive conditions, the repassivation potentials were more conservative using the CPP method. POT tests confirmed the validity of the repassivation potential as a threshold below which localized corrosion does not nucleate. The mode of attack in the tested specimens varied depending if the test method was CPP or THE; however, the repassivation potential remained the same.

  10. Electrodeposited NiFeCu/Cu multilayers: Effect of Fe ion concentration on properties

    NASA Astrophysics Data System (ADS)

    Kuru, Hilal; Kockar, Hakan; Alper, Mursel

    2015-01-01

    A series of 125[NiFeCu(3 nm)/Cu(1 nm)] multilayers were electrodeposited on strong (110) textured Cu substrates from electrolytes containing different Fe ion concentrations under potentiostatic control. The compositional analysis by energy dispersive X-ray spectroscopy demonstrated that as the Fe ion concentration in the electrolyte is increased, the Fe content of the multilayers increased. X-ray diffraction measurements indicated that all samples exhibited a face-centred cubic structure with a strong (110) texture as their substrates. The surface images obtained by scanning electron microscopy disclosed that all films have smooth surfaces. Magnetoresistance measurements were carried out at room temperature with magnetic fields up to ±12 kOe. All samples exhibited giant magnetoresistance (GMR) and the maximum GMR value of 5% was obtained in the multilayer grown from the electrolyte containing 0.0036 M Fe ion concentration. The GMR magnitude changed depending on the film contents arising from the variation of the Fe ion concentration in the electrolyte. The magnetic properties studied with the vibrating sample magnetometer showed that the saturation magnetisation changed, and the coercivities decreased with varying Fe ion concentration in the electrolyte. The changes observed in the properties were ascribed to the variations observed in the film composition caused by the Fe ion concentration of the electrolyte.

  11. Properties of electrodeposited CoFe/Cu multilayers: The effect of Cu layer thickness

    NASA Astrophysics Data System (ADS)

    Sahin, Turgut; Kockar, Hakan; Alper, Mursel

    2015-01-01

    CoFe/Cu multilayers were potentiostatically electrodeposited on Ti substrates as a function of different non-magnetic (Cu) layer thicknesses, and their characterizations were investigated. The compositional analysis performed by energy dispersive X-ray spectroscopy disclosed that the Cu content in the multilayers increased and the Co content decreased as non-magnetic layer was increased. However, the Fe content was almost stable. The scanning electron microscopy studies showed that the surface morphology of the films is strongly affected by the non-magnetic layer thickness, and X-ray diffraction was used to analyse the structural properties of the multilayers and revealed that the multilayers have face-centred cubic (fcc) structure and their preferred orientations change depending on the Cu layer thickness. In the case of magnetoresistance measurements of the multilayers performed at room temperature, the highest giant magnetoresistance (GMR) values exhibited for the films with the Cu layer thickness (6.0 nm) whereas the lowest GMR magnitudes were observed for the films without Cu layer. Therefore, the variations of the Cu layer thicknesses were observed to have a significant effect on the GMR of multilayers. The differences observed in the magnetotransport properties were attributed to the microstructural changes caused by the Cu layer thickness.

  12. A Portable Luminometer with a Disposable Electrochemiluminescent Biosensor for Lactate Determination

    PubMed Central

    Martínez-Olmos, Antonio; Ballesta-Claver, Julio; Palma, Alberto J.; Valencia-Mirón, Maria del Carmen; Capitán-Vallvey, Luis Fermin

    2009-01-01

    A hand-held luminometer for measuring electrochemiluminescence (ECL) for lactate determination and based on one-shot biosensors fabricated using screen-printed electrodes is described. The lactate recognition system is based on lactate oxidase and the transduction system consists of electro-oxidation of luminol, with all the reagents immobilized in a Methocel membrane. The membrane composition and reaction conditions have been optimized to obtain adequate sensitivity. The luminometer is based on a large silicon photodiode as detector and includes a programmable potentiostat to initialize the chemical reaction and signal processing circuitry, designed to acquire a low level photocurrent with offset cancelation, low pass filtering for noise attenuation and adjustable gain up to 1012 V/A. The one-shot biosensor responds to lactate rapidly, with an acquisition time of 2.5 min, obtaining a linear dependence from 8 × 10?6 to 2 × 10?4 M, a detection limit of 2.4 × 10?6 M and a sensor-to-sensor reproducibility (relative standard deviation, RSD) of around 7–10 % at the medium level of the range. PMID:22408475

  13. Probing electric fields inside microfluidic channels during electroosmotic flow with fast-scan cyclic voltammetry.

    PubMed

    Forry, Samuel P; Murray, Jacqueline R; Heien, Michael L A V; Locascio, Laurie E; Wightman, R Mark

    2004-09-01

    Fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes was used in microfluidic channels. This method offers the advantage that it can resolve electroactive species not separated in the channel. In addition, this method provides a route to investigate the distribution of applied electrophoretic fields in microfluidic channels. To probe this, microelectrodes were inserted at various distances into channels and cyclic voltammograms recorded at 300 V/s were repeated at 0.1-s intervals. The use of a battery-powered laptop computer and potentiostat provided galvanic isolation between the applied electrophoretic field and the electrochemical measurements. In the absence of an external field, the peak potential for oxidation of the test solute, Ru(bpy)3(2+), was virtually unaltered by insertion of the microelectrode tip into the channel. When an electrophoretic field was applied, the peak potential for Ru(bpy)3(2+) oxidation shifted to more positive potentials in a manner that was directly proportional to the field in the channel. The shifts in peak potential observed with FSCV enabled direct compensation of the applied electrochemical potential. This approach was used to explore the electrophoretic field at the channel terminus. It was found to persist for more than 50 microm from the channel terminus. In addition, the degree of analyte dispersion was found to depend critically on the electrode position outside the channel. PMID:15373427

  14. Evaluation of a diffusion/trapping model for hydrogen ingress in high-strength alloys. Final technical report, November 1988-November 1990

    SciTech Connect

    Pound, B.G.

    1990-11-14

    The objective of this research was to obtain the hydrogen ingress and trapping characteristics for a range of microstructures and so identify the dominant type of irreversible trap in different alloys. A diffusion/trapping model was used in conjunction with a potentiostatic pulse technique to study the ingress of hydrogen in three precipitation-hardened alloys (Inconel 718, Incoloy 925, and 18Ni maraging steel), two work-hardened alloys (Inconel 625 and Hastelloy C-276), titanium (pure and grade 2), and copper-enriched AISI 4340 steel in 1 mol/L acetic acid-1 mol/L sodium acetate containing 15 ppm arsenic oxide. In all cases except pure titanium, the data were shown to fit the interface-control form of the model and values were determined for the irreversible trapping constants (k) and the flux of hydrogen into the alloys. The density of irreversible trap defects were calculated from k and generally found to be in close agreement with the concentration of a specific heterogeneity in each alloy. Moreover, the trapping constants for the alloys were found to be consistent with their relative susceptibilities to hydrogen embrittlement.

  15. Square wave anodic stripping voltammetric determination of Cd²? and Pb²? at bismuth-film electrode modified with electroreduced graphene oxide-supported thiolated thionine.

    PubMed

    Li, Zou; Chen, Li; He, Fang; Bu, Lijuan; Qin, Xiaoli; Xie, Qingji; Yao, Shouzhuo; Tu, Xinman; Luo, Xubiao; Luo, Shenglian

    2014-05-01

    Graphene oxide (GO)-thionine (TH) nanocomposite was prepared by ?-? stacking. The nanocomposite was cast-coated on a glassy carbon electrode (GCE) to prepare an electroreduced GO (ERGO)-TH/GCE, then 2-mercaptoethanesulfonate (MES) was covalently tethered to ERGO-TH by potentiostatic anodization to form an ERGO-TH-MES/GCE. The thiolation reaction was monitored by electrochemical quartz crystal microbalance (EQCM). Square wave anodic stripping voltammetry (SWASV) was used to determine Cd(2+) and Pb(2+) at the ERGO-TH-MES/GCE further modified with Nafion and Bi. Under the optimal conditions, the linear calibration curves for Cd(2+) and Pb(2+) are from 1 to 40 ?g L(-1), with limits of detection (S/N=3) of 0.1 ?g L(-1) for Cd(2+) and 0.05 ?g L(-1) for Pb(2+), respectively. The electrode was used for the simultaneous analysis of Cd(2+) and Pb(2+) in water samples with satisfactory recovery. PMID:24720997

  16. Preliminary corrosion studies of candidate materials for supercritical water oxidation reactor systems. Master's thesis

    SciTech Connect

    Orzalli, J.C.

    1994-05-01

    An experimental test facility has been designed and constructed for investigation of the corrosion behavior of candidate materials in a supercritical water oxidation environment. The high temperatures (500 deg C) and high pressures (300 atm) required in this process, made the experimental apparatus construction and control a complex engineering problem. The facility consists of two systems. The first is an exposure autoclave internal volume 850 ml, with associated monitoring and control systems for conducting long term exposure testing of test coupons and U-bends. The second is an electrochemical cell with a potentiostat and frequency response analyzer for conducting Electronic Impedance Spectroscopy (EIS) in the supercritical water environment. Exposure testing of three candidate materials; Inconel 625, Hastelloy C-276 and 316 stainless steel was conducted at three temperature regimes corresponding to three locations in a SCWO waste treatment system. Preliminary results are presented in an environment of demineralized water as a control. Experimental results indicate evidence of a film on the materials characterized by slight weight gain. Light and confocal laser light microscopic evaluations revealed the presence of localized pitting corrosion on the Inconel 625.

  17. Electrochemical preparation of Photosystem I-polyaniline composite films for biohybrid solar energy conversion.

    PubMed

    Gizzie, Evan A; LeBlanc, Gabriel; Jennings, G Kane; Cliffel, David E

    2015-05-13

    In this work, we report for the first time the entrapment of the biomolecular supercomplex Photosystem I (PSI) within a conductive polymer network of polyaniline via electrochemical copolymerization. Composite polymer-protein films were prepared on gold electrodes through potentiostatic electropolymerization from a single aqueous solution containing both aniline and PSI. This study demonstrates the controllable integration of large membrane proteins into rapidly prepared composite films, the entrapment of such proteins was observed through photoelectrochemical analysis. PSI's unique function as a highly efficient biomolecular photodiode generated a significant enhancement in photocurrent generation for the PSI-loaded polyaniline films, compared to pristine polyaniline films, and dropcast PSI films. A comprehensive study was then performed to separately evaluate film thickness and PSI concentration in the initial polymerization solution and their effects on the net photocurrent of this novel material. The best performing composite films were prepared with 0.1 ?M PSI in the polymerization solution and deposited to a film thickness of 185 nm, resulting in an average photocurrent density of 5.7 ?A cm(-2) with an efficiency of 0.005%. This photocurrent output represents an enhancement greater than 2-fold over bare polyaniline films and 200-fold over a traditional PSI multilayer film of comparable thickness. PMID:25897977

  18. Enhanced low-temperature power density of solid oxide fuel cell by nickel nanoparticle infiltration into pre-fired Ni/yttria-stabilized zirconia anode.

    PubMed

    Kang, Lee-Seung; Park, Jae Layng; Lee, Sungkyu; Jin, Yun-Ho; Hong, Hyun-Seon; Lee, Chan-Gi; Kim, Bum Sung

    2014-12-01

    The Ni/yttria-stabilized zirconia (YSZ) anode morphology of an anode-supported solid oxide fuel cell (SOFC) unit cell was improved by nickel nanoparticle infiltration. A colloidal route was selected for efficient fabrication of nickel metal nanoparticles and subsequent infiltration into the Ni/YSZ anode of a pre-fired SOFC unit cell. The power density of the anode-supported SOFC unit cell was measured by the potentiostatic method to investigate the effect of nickel nanoparticle infiltration. The increase in the power density of the Ni/YSZ anode with nickel nanoparticle infiltration became gradually less significant as the SOFC operating temperature increased from 700 to 800 degrees C. The improved performance of the Ni/YSZ anode with nickel nanoparticle infiltration compared to that of an anode without nickel nanoparticles is tentatively attributed to two factors: The discretely distributed nanoparticles on the nanostructured electrodes exhibited significant catalytic effects on the electrochemical performance of the electrodes, in addition to substantially increasing the triple phase boundary lengths. PMID:25970993

  19. Photoelectrode characteristics of partially hydrolyzed aluminum phthalocyanine chloride/fullerene C?? composite nanoparticles working in a water phase.

    PubMed

    Zhang, Shuai; Abe, Toshiyuki; Iyoda, Tomokazu; Nagai, Keiji

    2012-01-01

    Photoelectrochemical measurements were used to study the photoelectrode characteristics of composite nanoparticles composed of fullerene C?? and partially hydrolyzed aluminum phthalocyanine chloride (AlPc). In cyclic voltammetry measurements, the electrodes coated with the composite nanoparticles were found to have photoanodic [electron donor: 2-mercaptoethanol (ME)] and photocathodic (electron acceptor: O?) characteristics similar to those of the vapor-deposited p/n junction electrode. Their photoanodic features were further investigated with respect to the transient photocurrent response to light irradiation and the dependence on ME concentration (under potentiostatic conditions), from which it was noted that there was a decrease in the initial spiky photocathodic current and saturation of the steady-state photoanodic current at a higher ME concentration. Thus, the reaction kinetics was probably dominated by charge transport process. Moreover, external and internal quantum efficiency spectrum measurements indicated that the composite nanoparticles responded to the full spectrum of visible light ( < 880 nm) for both the photoanodic and photocathodic current. The present research will assist comprehension of photocatalytic behavior of the composite nanoparticles. PMID:22964498

  20. Improvement in glucose biosensing response of electrochemically grown polypyrrole nanotubes by incorporating crosslinked glucose oxidase.

    PubMed

    Palod, Pragya Agar; Singh, Vipul

    2015-10-01

    In this paper a novel enzymatic glucose biosensor has been reported in which platinum coated alumina membranes (Anodisc™s) have been employed as templates for the growth of polypyrrole (PPy) nanotube arrays using electrochemical polymerization. The PPy nanotube arrays were grown on Anodisc™s of pore diameter 100nm using potentiostatic electropolymerization. In order to optimize the polymerization time, immobilization of glucose oxidase (GOx) was first performed using physical adsorption followed by measuring its biosensing response which was examined amperometrically for increasing concentrations of glucose. In order to further improve the sensing performance of the biosensor fabricated for optimum polymerization duration, enzyme immobilization was carried out using cross-linking with glutaraldehyde and bovine serum albumin (BSA). Approximately six fold enhancement in the sensitivity was observed in the fabricated electrodes. The biosensors also showed a wide range of linear operation (0.2-13mM), limit of detection of 50?M glucose concentration, excellent selectivity for glucose, notable reliability for real sample detection and substantially improved shelf life. PMID:26117773

  1. Corrosion and Fretting Corrosion Studies of Medical Grade CoCrMo Alloy in a Clinically Relevant Simulated Body Fluid Environment

    NASA Astrophysics Data System (ADS)

    Ocran, Emmanuel K.; Guenther, Leah E.; Brandt, Jan-M.; Wyss, Urs; Ojo, Olanrewaju A.

    2015-06-01

    In modular hip implants, fretting corrosion at the head/neck and neck/stem interfaces has been identified as a major cause of early revision in hip implants, particularly those with heads larger than 32 mm. It has been found that the type of fluid used to simulate the fretting corrosion of biomedical materials is crucial for the reliability of laboratory tests. Therefore, to properly understand and effectively design against fretting corrosion damage in modular hips, there is the need to replicate the human body environment as closely as possible during in vitro testing. In this work, corrosion and fretting corrosion behavior of CoCrMo in 0.14 M NaCl, phosphate buffered saline, and in a clinically relevant novel simulated body fluid was studied using a variety of electrochemical characterization techniques and tribological experiments. Electrochemical, spectroscopy and tribo-electrochemical techniques employed include Potentiodynamic polarization, Potentiostatic polarization, Electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, augur electron spectroscopy, inductively coupled plasma mass spectroscopy, and pin-on-disk wear simulation. The presence of phosphate ions in PBS accounted for the higher corrosion rate when compared with 0.14 M NaCl and the clinically relevant novel simulated body fluid. The low corrosion rates and the nature of the protective passive film formed in the clinically relevant simulated body fluid make it suitable for future corrosion and fretting corrosion studies.

  2. Real-time, multiplexed electrochemical DNA detection using an active complementary metal-oxide-semiconductor biosensor array with integrated sensor electronics

    PubMed Central

    Levine, Peter M.; Gong, Ping; Levicky, Rastislav; Shepard, Kenneth L.

    2009-01-01

    Optical biosensing based on fluorescence detection has arguably become the standard technique for quantifying extents of hybridization between surface-immobilized probes and fluorophore-labeled analyte targets in DNA microarrays. However, electrochemical detection techniques are emerging which could eliminate the need for physically bulky optical instrumentation, enabling the design of portable devices for point-of-care applications. Unlike fluorescence detection, which can function well using a passive substrate (one without integrated electronics), multiplexed electrochemical detection requires an electronically-active substrate to analyze each array site and benefits from the addition of integrated electronic instrumentation to further reduce platform size and eliminate the electromagnetic interference that can result from bringing non-amplified signals off chip. We report on an active electrochemical biosensor array, constructed with a standard complementary metal-oxide-semiconductor (CMOS) technology, to perform quantitative DNA hybridization detection on chip using targets conjugated with ferrocene redox labels. A 4×4 array of gold working electrodes and integrated potentiostat electronics, consisting of control amplifiers and current-input analog-to-digital converters, on a custom-designed 5×3 mm2 CMOS chip drive redox reactions using cyclic voltammetry, sense DNA binding, and transmit digital data off chip for analysis. We demonstrate multiplexed and specific detection of DNA targets as well as real-time monitoring of hybridization, a task that is difficult, if not impossible, with traditional fluorescence-based microarrays. PMID:19054661

  3. Change of electrochemical impedance spectra (EIS) with time during CO-poisoning of the Pt-anode in a membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Wagner, N.; Gülzow, E.

    This paper focuses on the electrochemical characterisation, e.g. current-voltage-measurement and time resolved electrochemical impedance spectroscopy (TREIS) of polymer electrolyte fuel cells (PEFCs) during operation of the fuel cell with oxygen and H 2+100 ppm CO respectively. Due to the poisoning effect of carbon monoxide, the system changes its state during the experiment. The reconstruction of quasi-causal impedance spectra was made by using enhanced numerical procedures. The reconstructed impedance spectra recorded at constant load, in galvanostatic mode of operation of the fuel cell show a strong time dependence and exhibit pseudo-inductive contributions at the low frequency part of the spectra which increase during the experiment. The analysis of the spectra suggests that the pseudo-inductive behaviour can be attributed to a surface relaxation process of the anode. Furthermore, the influence of the carbon monoxide on the electrochemical behaviour of the contaminated fuel cell may be interpreted by means of a Faraday impedance in addition with a potential-dependent hindrance of the charge transfer. Otherwise, the impedance spectra recorded during CO poisoning of the anode at constant cell voltage, in the potentiostatic mode of operation of the fuel cell, show also a strong time dependence, but no pseudo-inductive contribution in the low frequency part of the spectra.

  4. Microstructure and corrosion behavior of as-cast and heat-treated Al-4.5 Wt pct Cu-2.0 wt pct Mn alloys

    NASA Astrophysics Data System (ADS)

    Skolianos, S. M.; Kattamis, T. Z.; Devereux, O. F.

    1989-11-01

    The microstructure and corrosion behavior of as-cast and heat-treated Al-4.5 pct Cu-2.0 pct Mn alloy specimens solidified at various cooling rates were investigated. The equilibrium phases Al6Mn and ?-Al2Cu, which are observed in the conventionally solidified alloy in the as-cast condition, were not detected in rapidly solidified (melt-spun) material. Instead, the ternary compound Al20Cu2Mn3 was present in addition to the ? phase, which was present in all cases. The morphological and kinetic nature of corrosion was investigated metallographically and through potentiostatic techniques in 3.5 wt pct NaCl aqueous solution. Corrosion of the as-cast material was described by two anodic reactions: corrosion of the intermetallic phases and pitting of the ?-Al solid solution. The corrosion rate increased with cooling rate from that for the furnace-cooled alloy to that for the copper mold-cast alloy and, subsequently, decreased in the rapidly solidified alloy. In the heat-treated material, corrosion could be described by two anodic reactions: corrosion of Al20Cu2Mn3 precipitate particles and pitting of the ?-Al matrix.

  5. Photoelectrocatalytic oxidation of glucose at a ruthenium complex modified titanium dioxide electrode promoted by uric acid and ascorbic acid for photoelectrochemical fuel cells

    NASA Astrophysics Data System (ADS)

    Lu, Shuo-Jian; Ji, Shi-Bo; Liu, Jun-Chen; Li, Hong; Li, Wei-Shan

    2015-01-01

    The simultaneous presence of uric acid (UA) and ascorbic acid (AA) is first found to largely promote the photoelectrocatalytic oxidation of glucose (GLU) at an indium-tin oxide (ITO) or TiO2 nanoparticles/ITO electrode modified with [Ru(tatp)3]2+ (tatp = 1,4,8,9-tetra-aza-triphenylene) possessing good redox activity and nanoparticle size distribution. A well-defined electrocatalytic peak for GLU oxidation is shown at 0.265 V (vs. SCE) under approximate physiological conditions upon incorporation of UA and AA. The [Ru(tatp)3]2+/ITO electrode exhibits attractive amperometric oxidation responses towards GLU, UA and AA, while controlled potentiostatically at 0.3 V, 0.7 V and 1.0 V, respectively, indicating high sensitivity and excellent reproducibility. On basis of the photoelectrocatalysis of [Ru(tatp)3]2+/TiO2/ITO anode, a GLU concentration-dependent photoelectrochemical fuel cell vs. SCE is elaborately assembled. The proposed free-enzyme photoelectrochemical fuel cell employing 0.1 M GLU associated with 0.01 M UA and 0.01 M AA as fuel shows open-circuit photovoltage of 0.608 V, short-circuit photocurrent density of 124.5 ?A cm-2 and maximum power density of 21.75 ?W cm-2 at 0.455 V, fill factor of 0.32 and photoenergy conversion efficiency of 36.65%, respectively.

  6. Fatigue crack growth rates in a pressure vessel steel under various conditions of loading and the environment

    NASA Astrophysics Data System (ADS)

    Hicks, P. D.; Robinson, F. P. A.

    1986-10-01

    Corrosion fatigue (CF) tests have been carried out on SA508 Cl 3 pressure vessel steel, in simulated P.W.R. environments. The test variables investigated included air and P.W.R. water environments, frequency variation over the range 1 Hz to 10 Hz, transverse and longitudinal crack growth directions, temperatures of 20 °C and 50 °C, and R-ratios of 0.2 and 0.7. It was found that decreasing the test frequency increased fatigue crack growth rates (FCGR) in P.W.R. environments, P.W.R. environment testing gave enhanced crack growth (vs air tests), FCGRs were greater for cracks growing in the longitudinal direction, slight increases in temperature gave noticeable accelerations in FCGR, and several air tests gave FCGR greater than those predicted by the existing ASME codes. Fractographic evidence indicates that FCGRs were accelerated by a hydrogen embrittlement mechanism. The presence of elongated MnS inclusions aided both mechanical fatigue and hydrogen embrittlement processes, thus producing synergistically fast FCGRs. Both anodic dissolution and hydrogen embrittlement mechanisms have been proposed for the environmental enhancement of crack growth rates. Electrochemical potential measurements and potentiostatic tests have shown that sample isolation of the test specimens from the clevises in the apparatus is not essential during low temperature corrosion fatigue testing.

  7. Engineering bamboo-type TiO2 nanotube arrays to enhance their photocatalytic property.

    PubMed

    Guan, Dongsheng; Hymel, Paul J; Zhou, Chengjun; Wang, Ying

    2014-06-01

    Bamboo-type TiO2 nanotube arrays with high surface area can be synthesized by alternating voltage (AV) anodization for their important use as photocatalytic medium. Their morphologies are highly dependent on preparation parameters including anodization time and electrolyte composition. Minimum time of high-voltage steps required for forming desired bamboo ridge spacing on these nanotubes can be calculated from current-time profiles recorded during potentiostatic anodization at the voltage. Water content in NH4F-containing ethylene glycol (EG) electrolytes is optimized simply from analyses of current transients or current-voltage relations for anodization in EG electrolytes with different amount of water, in order to achieve efficient electrochemical growth of TiO2 nanotubes for large ridge density and long tube length. Two types of bamboo-type TiO2 nanotubes with the same length of 5.46 microm but different ridge spacing are synthesized for photocatalytic degradation of methylene blue (MB) under UV radiation. Both of the bamboo-type nanotube arrays show improved photo catalysis compared to smooth TiO2 nanotubes of the same length, due to their larger surface area favorable for heterogeneous catalytic processes. In particular, the apparent rate constant of photocatalytic degradation on bamboo-type nanotubes is up to 29.4% higher than that for degradation on smooth ones. PMID:24738426

  8. Ternary chalcogenide-based photoelectrochemical cells. II - The n-CdIn2Se4/aqueous polysulfide system

    NASA Astrophysics Data System (ADS)

    Tenne, R.; Mirovsky, Y.; Greenstein, Y.; Cahen, D.

    1982-07-01

    The behavior of CdIn2Se4, a ternary analog of CdSe, as a photoanode in an aqueous polysulfide photoelectrochemical cell is investigated. Measurements of I-V curves in the dark and under illumination show that potentiostatic photoetching under large reverse bias leads to a dramatic increase in cell photocurrent (up to about 15 mA/sq cm under reverse bias of 400 mV) and a decrease in the dark currents under reverse bias as well as an improvement in output stability. Spectral response measurements reveal a considerable subbandgap photocurrent for the etched electrode, most of which disappears after photoetching, accompanied by an order of magnitude increase in the response to supra-bandgap excitation. Analysis of the shape of the spectral response reveals two distinct transition modes: an indirect transition at 1.55 eV and a direct transition at 1.72 eV. Finally, preliminary tests on thin film polycrystalline electrodes demonstrate an encouraging performance for polycrystalline material.

  9. Tribocorrosion mechanisms of Ti6Al4V biomedical alloys in artificial saliva with different pHs

    NASA Astrophysics Data System (ADS)

    Licausi, M. P.; Igual Muñoz, A.; Amigó Borrás, V.

    2013-10-01

    Titanium and its alloys has been widely used for the design of dental implants because of its biocompatibility, mechanical properties and corrosion resistance. The powder-metallurgy process is a promising alternative to the casting fabrication process of titanium alloys for bone implants design as the porous structure mimics the natural bone structures, allowing the bone to grow into the pores which results in a better fixation of the artificial implant. However, under in vivo conditions the implants are subjected to tribocorrosion phenomenon, which consists in the degradation mechanisms due to the combined effect of wear and corrosion. The aim of this study is to evaluate the tribocorrosion behaviour of cast and sintered Ti6Al4V biomedical alloy for dental applications using the cast material as reference. Titanium samples were tested in artificial human saliva solution with three different pHs (3, 6, 9) and in an acidic saliva with 1000 ppm fluorides (AS-3-1000F-) by different electrochemical techniques (potentiodynamic curves, potentiostatic tests and tribo-electrochemical tests). Cast and sintered titanium alloys exhibit the same tribocorrosion mechanisms in AS independently of the pH which consists in plastic deformation with passive dissolution, but the addition of fluorides to the acidified solution changes the degradation mechanism towards active dissolution of the titanium alloys.

  10. Microelectrospotting as a new method for electrosynthesis of surface-imprinted polymer microarrays for protein recognition.

    PubMed

    Bosserdt, Maria; Erd?ssy, Júlia; Lautner, Gergely; Witt, Julia; Köhler, Katja; Gajovic-Eichelmann, Nenad; Yarman, Aysu; Wittstock, Gunther; Scheller, Frieder W; Gyurcsányi, Róbert E

    2015-11-15

    Here we introduce microelectrospotting as a new approach for preparation of protein-selective molecularly imprinted polymer microarrays on bare gold SPR imaging chips. During electrospotting both the gold chip and the spotting tip are electrically connected to a potentiostat as working and counter electrodes, respectively. The spotting pin encloses the monomer-template protein cocktail that upon contacting the gold surface is in-situ electropolymerized resulting in surface confined polymer spots of ca. 500µm diameter. By repeating this procedure at preprogrammed locations for various composition monomer-template mixtures microarrays of nanometer-thin surface-imprinted films are generated in a controlled manner. We show that the removal and rebinding kinetics of the template and various potential interferents to such microarrays can be monitored in real-time and multiplexed manner by SPR imaging. The proof of principle for microelectrospotting of electrically insulating surface-imprinted films is made by using scopoletin as monomer and ferritin as protein template. It is shown that microelectrospotting in combination with SPR imaging can offer a versatile platform for label-free and enhanced throughput optimization of the molecularly imprinted polymers for protein recognition and for their analytical application. PMID:26056955

  11. Role of surfactant-mediated electrodeposited titanium oxide substrate in improving electrocatalytic features of supported platinum particles

    NASA Astrophysics Data System (ADS)

    Sp?taru, Tan?a; Preda, Loredana; Osiceanu, Petre; Munteanu, Cornel; Anastasescu, Mihai; Marcu, Maria; Sp?taru, Nicolae

    2014-01-01

    A new hybrid system with improved photocatalytic and electrocatalytic performances was obtained by two-step potentiostatic deposition on highly boron-doped diamond (BDD) substrate. First, hydrated TiO2 was anodically deposited from a TiCl3 aqueous solution, both in the presence and in the absence of sodium dodecyl sulfate (SDS). The study of the UV irradiation effect evidenced that titanium oxide coatings obtained by surfactant-assisted electrodeposition (TiO2:SDS) exhibit enhanced photocurrent, due to its very rough texture and presumably to better efficiency of charge carrier separation. Electrochemical deposition of platinum on the oxide-coated BDD was carried out in a second step and AFM, SEM and XPS measurements have shown that, on the TiO2:SDS substrate, Pt particles are smaller, more uniformly distributed, and tend to form clusters, leading to a specific surface area of the electrocatalyst of ca. 6.55 m2 g-1. Carbon monoxide stripping experiments demonstrated that, when deposited on TiO2:SDS, Pt particles are also less sensitive to CO-poisoning during methanol anodic oxidation.

  12. Disposable electrochemical sensor to evaluate the phytoremediation of the aquatic plant Lemna minor L. toward Pb(2+) and/or Cd(2+).

    PubMed

    Neagu, Daniela; Arduini, Fabiana; Quintana, Josefina Calvo; Di Cori, Patrizia; Forni, Cinzia; Moscone, Danila

    2014-07-01

    In this work a miniaturized and disposable electrochemical sensor was developed to evaluate the cadmium and lead ion phytoremediation potential by the floating aquatic macrophyte Lemna minor L. The sensor is based on a screen-printed electrode modified "in-situ" with bismuth film, which is more environmentally friendly than the mercury-based sensor usually adopted for lead and cadmium ion detection. The sensor was coupled with a portable potentiostat for the simultaneous measurement of cadmium and lead ions by stripping analysis. The optimized analytical system allows the simultaneous detection of both heavy metals at the ppb level (LOD equal to 0.3 and 2 ppb for lead and cadmium ions, respectively) with the advantage of using a miniaturized and cost-effective system. The sensor was then applied for the evaluation of Pb(2+) or/and Cd(2+) uptake by measuring the amount of the heavy metals both in growth medium and in plant tissues during 1 week experiments. In this way, the use of Lemna minor coupled with a portable electrochemical sensor allows the set up of a model system able both to remove the heavy metals and to measure "in-situ" the magnitude of heavy metal removal. PMID:24899412

  13. In situ Fourier transform infrared-diffuse reflection spectroscopy of direct methanol fuel cell anodes and cathodes

    SciTech Connect

    Fan, Q.; Pu, C.; Smotkin, E.S. [Illinois Inst. of Tech., Chicago, IL (United States). Dept. of Chemical and Environmental Engineering

    1996-10-01

    In situ Fourier transform infrared-diffuse reflection spectroscopy (FTIR-DRS) was used to study both the adsorbed and desorbed species produced on high surface area anodes and cathodes of direct methanol/oxygen fuel cells. The authors investigated platinum-ruthenium and platinum black as anodes. The cathodes studied were platinum black. The primary product detected on both Pt-black and Pt-Ru anodes at low methanol/water vapor ratios (P{sub methanol}: 15.2 kPa) was CO{sub 2}. Consistent with previous work, CO adsorption is more prevalent on Pt-black than on Pt-RU. In addition to CO and CO{sub 2}, vibrational modes due to formic acid, methylformate, and formaldehyde are detected by FTIR-DRS under potentiostatic control. At higher methanol/water vapor ratios (P{sub methanol}: 38.0 kPa) and low potentials (0.10 to 0.50 V), formaldehyde is the only product at the Pt-Ru anode. Methylformate and formic acid vibrational modes appear at potentials from 0.60 to 0.80 V. CO{sub 2} and methanol are observed at open circuit on the cathode side as a result of methanol permeation from the anode to the cathode region. CO{sub 2} increases in the cathode region with increasing anode potential.

  14. Comparative study of the shape-dependent electrocatalytic activity of platinum multipods, discs, and hexagons: applications for fuel cells.

    PubMed

    Subhramannia, Mahima; Ramaiyan, Kannan; Pillai, Vijayamohanan K

    2008-04-01

    We here demonstrate a remarkable potential-dependent morphological evolution of platinum mesostructures in the form of multipods, discs, and hexagons using a porous anodic alumina membrane (PAAM). These structures prepared potentiostatically at -0.7, -0.5 and -0.3 V, respectively, reveal unique shape-dependent electrocatalytic activity toward both formic acid and ethanol oxidation reactions. A comparison of the electrooxidation kinetics of these structures illustrates that hexagons show better performance toward formic acid oxidation whereas, for ethanol oxidation, multipods show significantly enhanced activity. Interestingly, the enhancement factor (R) for these mesostructures with respect to that of commercial platinized carbon toward formic acid oxidation ranges up to 2000% for hexagons whereas for multipods and disc they are about 700% and 300%, respectively. Similarly, for ethanol oxidation, the calculated value of R varies up to 600% for multipods while for disc and hexagons these values are 500% and 200%, respectively. These shape-dependent electrocatalytic activity of Pt mesostructures have been further correlated with XRD results. Thus, the present results demonstrate the importance of precise control of morphology by an electric field and their potential benefits especially for fuel cell applications since designing a better electrocatalyst for many fuel cell reactions continues to be an important challenge. PMID:18281997

  15. Nanotube nucleation phenomena on Ti-25Ta-xZr alloys for implants using ATO technique.

    PubMed

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

    2014-10-01

    The purpose of this study was to investigate nanotube nucleation phenomena on the Ti-25Ta-xZr alloys for implant materials, using an anodic titanium oxide (ATO) technique. Ti-25Ta-(0 wt.%-15 wt.%) Zr alloys were prepared using a vacuum arc-melting furnace. The Ti-25Ta-xZr alloys were then homogenized for 12 hr at 1000 degrees C, followed by water quenching. Formation of the nanotubular oxide surface structure was achieved initially on the Ti-25Ta-xZr alloys by anodization in a 1 M H3PO4 electrolyte containing 0.8 wt.% NaF at room temperature, using a potentiostat. After the first formation of the nanotubes was achieved, this initial nanotube layer was eliminated, and further anodization was carried out repeatedly. The microstructure, phase transformation, and morphology of nanotubular Ti-25Ta-xZr alloys and the process of nanotube growth using this ATO method were analyzed by X-ray diffraction, field-emission scanning electron microscopy, and energy dispersive X-ray spectroscopy. Microstructures of the Ti-25Ta-xZr alloys changed from ?" phase to ? phase. Nanotubes formed with the ATO technique had pit-like top holes, with thinner walls and lower contact angle, compared to the initially formed nanotubes. PMID:25942827

  16. Influence of the cathode architecture in the frequency response of self-breathing proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Ferreira-Aparicio, P.; Chaparro, A. M.

    2014-12-01

    Self-breathing proton exchange membrane fuel cells are apparently simple devices, but efficient water management is critical for their performance. The cathode configuration should guarantee balanced rates between O2 accessibility from the circumventing air and H2O removal, and a good electric contact between catalyst layers and current collectors at the same time. By applying progressive modifications to the initial concept of a conventional PEMFC, the effect of the cathode architecture on cell performance has been analyzed. Frequency response analyses of the cell during steady-state potentiostatic stepping have yielded relevant information regarding limitations originated by the cathode impedance under high current load conditions. The primitive cell design has been optimized for self-breathing operation by means of this diagnostic tool. The thickness of the perforated plate in the cathode has been found to be one of the main factors contributing to limit oxygen accessibility when a high current load is demanded. Adequate cathode architecture is critical for reducing mass transport limitations in the catalytic layer and enhancing performance under self-breathing conditions.

  17. Influence of fluoride content and pH on corrosion and tribocorrosion behaviour of Ti13Nb13Zr alloy in oral environment.

    PubMed

    Golvano, I; Garcia, I; Conde, A; Tato, W; Aginagalde, A

    2015-09-01

    CpTi and Ti6Al4V alloy are the most widely used materials for implant application, but the release of toxic elements (e.g. Al and V) and the so-called stress-shielding effect are still a concern. In recent years, ? and near-? titanium alloys have been developed, which overcome these issues with reduced modulus of elasticity and biocompatible alloying elements. However, literature is scarce studying the tribocorrosion behaviour of these alloys for dental implantology. The present work studies the tribocorrosion behaviour of the near-? Ti13Nb13Zr alloy in oral environment, using CpTi4 for comparison purposes. To that end, the influence of the pH and fluoride concentration in artificial saliva was analysed. Reciprocating sliding corrosion tests were carried out under open circuit potential and potentiostatic conditions. Results reveal a negative influence of the increase of fluoride concentration and the acidified artificial saliva on the material degradation. Moreover, some light has been shed on the different tribocorrosion mechanisms of Ti13Nb13Zr and CpTi4 in simulated oral environment. PMID:26042765

  18. Dithionite/air direct ion liquid fuel cell

    NASA Astrophysics Data System (ADS)

    Noack, Jens; Tübke, Jens; Pinkwart, Karsten

    2015-07-01

    The feasibility of an alkaline S2O42-/air-fuel cell was evaluated at room temperature, using a cell with an anion exchange membrane and a platinum oxygen reduction reaction catalyst. The tests performed were open circuit voltage analysis, linear sweep voltammetry, discharge analysis and electrochemical impedance spectroscopy (EIS) with registration of anode half-cell potential. With 0.85 M Na2S2O4 in 2 M KOH, the cell achieved a maximum power density of 2 mW cm-2, and the open circuit cell voltage was about 0.9 V. In a potentiostatic discharging at 0.2 V cell voltage, an energy efficiency of 12.3% was achieved at an energy density of 8.6 Wh L-1. The low power density was mainly due to the low reaction kinetics of dithionite oxidation at graphite electrodes. The low energy efficiency was mainly caused by a low cathode potential, which probably resulted from mixed potential formation and the low anode kinetics.

  19. On-site analysis of arsenic in groundwater using a microfabricated gold ultramicroelectrode array

    PubMed

    Feeney; Kounaves

    2000-05-15

    Rapid on-site analysis of arsenic in groundwater was achieved with a small battery-powered unit in conjunction with a microfabricated gold ultramicroelectrode array (Au-UMEA). The sensor, consisting of 564 UME disks with a unique gold surface created by electron beam evaporation, was demonstrated to be highly sensitive to low-ppb As3+ using square wave anodic stripping voltammetry. The influence of the square wave frequency, pulse amplitude, and deposition potential on the arsenic peak stripping current was investigated. Varying those theoretical parameters yielded results surprisingly similar to those for the thin Hg film case. The performance of the Au-UMEA was evaluated for reproducibility and reliability. Three stability tests showed an average relative standard deviation of 2.5% for 15 consecutive runs. Limits of detection were investigated, and 0.05 ppb As3+ could be measured while maintaining a S/N of 3:1. Interference studies were performed in the presence of 50-500 ppb of Cu2+, Hg2+, and Pb2+. On-site analysis of groundwater containing arsenic was performed with a small battery-powered potentiostat. Quantification was done through standard additions, and these results were compared to the standard EPA methodology. PMID:10845367

  20. Electrochemical removal of hydrogen atoms in Mg-doped GaN epitaxial layers

    NASA Astrophysics Data System (ADS)

    Lee, June Key; Hyeon, Gil Yong; Tawfik, Wael Z.; Choi, Hee Seok; Ryu, Sang-Wan; Jeong, Tak; Jung, Eunjin; Kim, Hyunsoo

    2015-05-01

    Hydrogen atoms inside of an Mg-doped GaN epitaxial layer were effectively removed by the electrochemical potentiostatic activation (EPA) method. The role of hydrogen was investigated in terms of the device performance of light-emitting diodes (LEDs). The effect of the main process parameters for EPA such as solution type, voltage, and time was studied and optimized for application to LED fabrication. In optimized conditions, the light output of 385-nm LEDs was improved by about 26% at 30 mA, which was caused by the reduction of the hydrogen concentration by ˜35%. Further removal of hydrogen seems to be involved in the breaking of Ga-H bonds that passivate the nitrogen vacancies. An EPA process with high voltage breaks not only Mg-H bonds that generate hole carriers but also Ga-H bonds that generate electron carriers, thus causing compensation that impedes the practical increase of hole concentration, regardless of the drastic removal of hydrogen atoms. A decrease in hydrogen concentration affects the current-voltage characteristics, reducing the reverse current by about one order and altering the forward current behavior in the low voltage region.

  1. Corrosion resistance, chemistry, and mechanical aspects of Nitinol surfaces formed in hydrogen peroxide solutions.

    PubMed

    Shabalovskaya, Svetlana A; Anderegg, James W; Undisz, Andreas; Rettenmayr, Markus; Rondelli, Gianni C

    2012-08-01

    Ti oxides formed naturally on Nitinol surfaces are only a few nanometers thick. To increase their thickness, heat treatments are explored. The resulting surfaces exhibit poor resistance to pitting corrosion. As an alternative approach to accelerate surface oxidation and grow thicker oxides, the exposure of Nitinol to strong oxidizing H(2)O(2) aqueous solutions (3 and 30%) for various periods of time was used. Using X-Ray Photoelectron Spectroscopy (XPS) and Auger spectroscopy, it was found that the surface layers with variable Ti (6-15 at %) and Ni (5-13 at %) contents and the thickness up to 100 nm without Ni-enriched interfaces could be formed. The response of the surface oxides to stress in superelastic regime of deformations depended on oxide thickness. In the corrosion studies performed in both strained and strain-free states using potentiodynamic and potentiostatic polarizations, the surfaces treated in H(2)O(2) showed no pitting in corrosive solution that was assigned to higher chemical homogeneity of the surfaces free of secondary phases and inclusions that assist better biocompatibility of Nitinol medical devices. PMID:22689286

  2. Surface, corrosion and biocompatibility aspects of Nitinol as an implant material.

    PubMed

    Shabalovskaya, Svetlana A

    2002-01-01

    The present review surveys studies on physical-chemical properties and biological response of living tissues to NiTi (Nitinol) carried out recently, aiming at an understanding of the place of this material among the implant alloys in use. Advantages of shape memory and superelasticity are analyzed in respect to functionality of implants in the body. Various approaches to surface treatment, sterilization procedures, and resulting surface conditions are analyzed. A review of corrosion studies conducted both on wrought and as-cast alloys using potentiodynamic and potentiostatic techniques in various corrosive media and in actual body fluids is also given. The parameters of localized and galvanic corrosion are presented. The corrosion behavior is analyzed with respect to alloy composition, phase state, surface treatment, and strain and compared to that of conventional implant alloys. Biocompatibility of porous Nitinol, Ni release and its effect on living cells are analyzed based on understanding of the surface conditions and corrosion behavior. Additionally, the paper offers a brief overview of the comparative toxicity of metals, components of commonly used medical alloys, indicating that the biocompatibility profile of Nitinol is conducive to present in vivo applications. PMID:11847410

  3. Effects of lead oxide addition on the electrochemical properties of alloy 600 in aqueous 1 M sodium hydroxide solution

    SciTech Connect

    Pyun, S.I.; Lee, W.J.; Park, J.J.

    1999-12-01

    Effects of lead oxide (PbO) addition on the electrochemical properties of alloy 600 (UNS N06600) have been studied in aqueous 1 M sodium hydroxide (NaOH) solution at room temperature using surface analytical techniques and electrochemical methods. For the comparative study on the different roles of the surface layers in the electrochemical properties of alloy 600, two kinds of electrodes were potentiostatically prepared at the anodic and cathodic potential peaks observed in cyclic voltammograms obtained in PbO-containing caustic solution; lead dioxide (PbO{sub 2}) film-covered and Pb deposit-covered alloy electrodes. The crystal structures and morphologies of the two kinds of the surface layers were characterized by x-ray diffractometry and scanning electron microscopy. From the open-circuit potential (OCP) transients and galvanic current transients. It was inferred that Ni and Fe among alloy 600 constituents as anodic sites were dissolved selectively in caustic solution caused by the lower OCP value where there was no PbO{sub 2} alloy. Based upon the experimental results, it was suggested that an enhanced dissolution of Ni and Fe in alloy 600 in caustic solution at room temperature was a consequence of PbO{sub 2}-induced corrosion.

  4. Effect of Fluoride on Nickel-Titanium and Stainless Steel Orthodontic Archwires: An In-Vitro Study

    PubMed Central

    Heravi, Farzin; Moayed, Mohamad Hadi; Mokhber, Nima

    2015-01-01

    Objectives: The commonly used Nickel-Titanium (NiTi) archwires in orthodontic treatment are often exposed to fluoride-containing mouthwashes. The aim of this in-vitro study was to evaluate and compare the corrosion resistance of three commercially available NiTi archwires exposed to 0.05 wt% and 0.2 wt% fluoride mouthwashes. Materials and Methods: Three different types of NiTi archwires, 0.016? in diameter, from Dentaurum, Global, and GAC, and a stainless steel archwire from Dentaurum were examined to assess their corrosion resistance in Fusayama-Meyer artificial saliva and in two other artificial saliva containing 0.05 wt% and 0.2 wt% sodium fluoride (NaF). After the primary setup of wires, they were tested by potentiodynamic and potentiostatic polarization and corrosion potential/time analyses. Their surfaces were evaluated using a scanning electronic microscope (SEM). Results: The results showed that all the wires were passive in artificial saliva. In contrast, by adding fluoride ions to the solution, the decrease in the archwires’ corrosion resistance was in direct proportion to the increase in fluoride concentration. Conclusion: The NiTi wires experienced deterioration of their corrosion properties under the effect of fluoride but not as much as the stainless steel archwires. PMID:26005454

  5. Mechanical performance of PPy helix tube microactuator

    NASA Astrophysics Data System (ADS)

    Bahrami Samani, Mehrdad; Spinks, Geoffrey M.; Cook, Christopher

    2004-02-01

    Conducting polymer actuators with favourable properties such as linearity, high power density and compliance are of increasing demand in micro applications. These materials generate forces over two times larger than produced by mammalian skeletal muscles. They operate to convert electro chemical energy to mechanical stress and strain. On the other hand, the application of conducting polymers is limited by the lack of a full description of the relation between four essential parameters: stress, strain, voltage and current. In this paper, polypyrrole helix tube micro actuator mechanical characteristics are investigated. The electrolyte is propylene carbonate and the dopant is TBA. PF6. The experiments are both in isotonic and isometric conditions and the input parameters are both electrical and mechanical. A dual mode force and length control and potentiostat / galvanostat are utilized for this purpose. Ultimately, the viscoelastic behaviour of the actuator is presented in this paper by a standard stress relaxation test. The effect of electrical stimulus on mechanical parameters is also explored by cyclic voltametry at different scan rates to obtain the best understanding of the actuation mechanism. The results demonstrate that the linear viscoelastic model, which performed well on conducting polymer film actuators, has to be modified to explain the mechanical behaviour of PPy helix tube fibre micro actuators. Secondly, the changes in mechanical properties of PPy need to be considered when modelling electromechanical behaviour.

  6. Development of Amperometric Biosensors Based on Nanostructured Tyrosinase-Conducting Polymer Composite Electrodes

    PubMed Central

    Lupu, Stelian; Lete, Cecilia; Balaure, Paul C?t?lin; Caval, Dan Ion; Mihailciuc, Constantin; Lakard, Boris; Hihn, Jean-Yves; del Campo, Francisco Javier

    2013-01-01

    Bio-composite coatings consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and tyrosinase (Ty) were successfully electrodeposited on conventional size gold (Au) disk electrodes and microelectrode arrays using sinusoidal voltages. Electrochemical polymerization of the corresponding monomer was carried out in the presence of various Ty amounts in aqueous buffered solutions. The bio-composite coatings prepared using sinusoidal voltages and potentiostatic electrodeposition methods were compared in terms of morphology, electrochemical properties, and biocatalytic activity towards various analytes. The amperometric biosensors were tested in dopamine (DA) and catechol (CT) electroanalysis in aqueous buffered solutions. The analytical performance of the developed biosensors was investigated in terms of linear response range, detection limit, sensitivity, and repeatability. A semi-quantitative multi-analyte procedure for simultaneous determination of DA and CT was developed. The amperometric biosensor prepared using sinusoidal voltages showed much better analytical performance. The Au disk biosensor obtained by 50 mV alternating voltage amplitude displayed a linear response for DA concentrations ranging from 10 to 300 ?M, with a detection limit of 4.18 ?M. PMID:23698270

  7. Self-Organized Growth of Single Crystalline Copper Nanobead Strings by Electrodeposition

    NASA Astrophysics Data System (ADS)

    Meng, Cong; Peng, Ruwen; Wang, Mu

    2013-03-01

    Here we report a self-organized growth of single-crystalline strings of nano sized copper beads electrodeposited from an ultrathin layer of CuSO4 electrolyte solution without adding any additives. Spontaneous oscillation of voltage/current has been observed when potentiostatic/galvanostatic mode is applied. Scanning electron microscopy indicates that the filaments developed from the cathode are made of smooth copper beads a few hundreds of nanometers in size connected by thin single-crystalline rods. The periodicity along the string may vary from 500nm to one micron, and the spatial periodicity is strict up to hundreds of microns. To pinpoint the growth mechanism, we intentionally terminate the growth at different stage of the spontaneous oscillation of the voltage across the electrodes, and established the relation of the microscopic deposit morphology and the voltage oscillations. A growth mechanism is proposed based on the experimental observations. Structural and luminescent properties of the copper strings have been investigated, and the possible applications of such a unique structure have been discussed.

  8. Effect of metallurgical factors on the electrochemical noise measured on AISI Type 430 stainless steels in chloride-containing media

    SciTech Connect

    Gorse, D.; Boulleret, C. [CECM-CNRS, Vitry sur Seine (France); Baroux, B. [Inst. National Polytechnique de Grenoble, Saint Martin d`Heres (France)

    1996-12-31

    Potentiostatic noise measurements are performed on a series of AISI 430 type ferritic stainless steels containing controlled amounts of sulfur (from 8 up to 47 ppm) and titanium (up to 0.37 wt%), in 0.02M sodium chloride (NaCl) aqueous solution (pH 6.6), in a range of potentials below the pitting potential. The authors focus on the evolution of the shape of the current transients, going from a titanium (Ti) free and 41-ppm sulfur-containing alloy to different Ti-bearing alloys with comparable amount of sulfur ({approximately}40 ppm). The results are compared to the case of a Ti-free and low sulfur (8-ppm) containing alloy. The shape of the anodic current transients obeys a power law, t{sup n}. The authors distinguish two different situations, with n either less or larger than 1, which can be associated with the Ti and sulfur content in the steel. The influence of the exposure time under polarization is also discussed. It appears that for the manganese sulfide (MnS)-containing alloys, after prolonged polarization, the shape of the metastable pitting events evolves toward that found for MnS-free alloys (Ti-bearing), or low-sulfur-containing alloys. Attention is drawn to the possible relationship between the shape of the current transients and the metallurgical defects acting as pitting initiation sites.

  9. Hot Risers in the North Sea: a parametric study of CP and corrosion characteristics of hot steel in cold seawater

    SciTech Connect

    Fischer, K.P.; Hansen, A.H.; Mehdizadeh, P.; Solheim, P.S.

    1983-05-01

    In recent years doubts have been expressed regarding the adequacy of the design criteria for cathodic protection of hot oil risers in the North Sea area. Therefore it was decided to study some of the fundamental aspects of corrosion and corrosion control of hot steel in cold seawater. For studying these phenomena a specially designed channel flow system was constructed. Seawater was pumped into the laboratory facilities and through the flow channel. Here the flow rate, the steel surface temperature and the polarisation characteristics of the mounted steel probes could be controlled. The progressive current density at potentiostatic polarisation was found to be a sensitive function of the development of the calcareous deposit on hot steel. Thus on hot steel in cold seawater the initial current density will be very high. Subsequently, due to the build up of the calcareous deposit, the current will decrease to a value in the range as found for steel in seawater at ambient temperature. The acquired data on the cathodic polarisation behaviour of hot steel in cold seawater should be applicable for the designers of protection systems of marine risers.

  10. Delayed feedback induced multirhythmicity in the oscillatory electrodissolution of copper

    NASA Astrophysics Data System (ADS)

    Nagy, Timea; Verner, Erika; Gáspár, Vilmos; Kori, Hiroshi; Kiss, István Z.

    2015-06-01

    Occurrence of bi- and trirhythmicities (coexistence of two or three stable limit cycles, respectively, with distinctly different periods) has been studied experimentally by applying delayed feedback control to the copper-phosphoric acid electrochemical system oscillating close to a Hopf bifurcation point under potentiostatic condition. The oscillating electrode potential is delayed by ? and the difference between the present and delayed values is fed back to the circuit potential with a feedback gain K. The experiments were performed by determining the period of current oscillations T as a function of (both increasing and decreasing) ? at several fixed values of K. With small delay times, the period exhibits a sinusoidal type dependence on ?. However, with relatively large delays (typically ? ? T) for each feedback gain K, there exists a critical delay ?crit above which birhythmicity emerges. The experiments show that for weak feedback, K?crit is approximately constant. At very large delays, the dynamics becomes even more complex, and trirhythmicity could be observed. Results of numerical simulations based on a general kinetic model for metal electrodissolution were consistent with the experimental observations. The experimental and numerical results are also interpreted by using a phase model; the model parameters can be obtained from experimental data measured at small delay times. Analytical solutions to the phase model quantitatively predict the parameter regions for the appearance of birhythmicity in the experiments, and explain the almost constant value of K?crit for weak feedback.

  11. Comparison of Pt and Pd catalysts for hydrogen pump separation from reformate

    NASA Astrophysics Data System (ADS)

    Wu, Xuemei; Benziger, Jay; He, Gaohong

    2012-11-01

    Hydrogen recovery from CO2/H2 reformate mixtures by selective electrochemical pumping was compared from carbon supported Pt and Pd catalysts. Catalyst coated membranes were prepared by air-brushing a suspension of commercially available 20 wt% Pt/C or 20 wt% Pd/C catalysts and solubilized Nafion in methanol onto Nafion 115 membranes. Electrochemical activity and separation efficiency for the different catalyst layer formulations were evaluated by cyclic voltammetry, polarization and potentiostatic hydrogen pumping. The effective membrane-electrode-assembly (MEA) resistance increased due to dilution of H2 by CO2; the effective MEA resistance was greater for Pd/C catalysts than for Pt/C catalysts. CO2 adsorbed more strongly to Pd catalysts than Pt catalysts reducing the electrochemical active surface area available for hydrogen oxidation/reduction. Pd/C catalysts had an energy efficiency for hydrogen recovery from reformate mixtures approximately 80% that of Pt catalysts. Because Pd is ten times less costly than Pt the results presented here suggest that Pd/C catalysts would be a promising candidate for hydrogen pumps to recover H2 from reformate mixtures.

  12. Application of electrochemical techniques for machining titanium aluminide-based alloys

    SciTech Connect

    Ziomek-Moroz, M.; Su, W; Alman, David E.; Hawk, Jeffrey A.

    1997-01-01

    Intermetallic materials with excellent resistance to high-temperature oxidation have been considered as potential replacements for superalloys used as aerospace materials. Titanium aluminides are especially attractive for this role. However, further commercialization of titanium aluminides requires the development of non-conventional machining, such as electrochemical machining (ECM). As a first attempt in the development of the ECM process, the corrosion behavior of arc-melted gamma TiAl and alpha 2 Ti3Al was investigated along with pure titanium and aluminum in deaerated and non-deaerated solutions of sulfuric acid, sodium sulfate, and sodium hydroxide. Two types of electrochemical experiments were carried out, namely, potentiodynamic and potentiostatic. In the Na2SO4 solution, the highest current was found for Al and the lowest for TiAl. The shape of the polarization curves indicates that the intermetallics show similar behavior to that of Ti. It has been found that, in sulfuric acid, current values decrease with increasing titanium content. In the sodium sulfate and sodium hydroxide solutions, current values initially decrease with increasing titanium content and remain unchanged for higher concentrations of titanium.

  13. Electrosynthesis of polyaniline–mutilwalled carbon nanotube nanocomposite films in the presence of sodium dodecyl sulfate for glucose biosensing

    NASA Astrophysics Data System (ADS)

    Huyen Le, Trong; Thang Trinh, Ngoc; Nguyen, Le Huy; Binh Nguyen, Hai; Nguyen, Van Anh; Tran, Dai Lam; Dung Nguyen, Tuan

    2013-06-01

    Polyaniline–mutilwalled carbon nanotube (PANi–MWCNT) nanocomposites were electropolymerized in the presence of sodium dodecyl sulfate (SDS) onto interdigitated platinum-film planar microelectrodes (ID?E). The MWCNTs were first dispersed in SDS solution then mixed with aniline and H2SO4. This mixture was used to electro-synthesize PANi–MWCNT films with potentiostatic method at E = + 0.90 V (versus SCE). The PANi–MWCNT films were characterized by cyclic voltammetry (CV) and scanning electron microscopy (SEM). The results show that the PANi–MWCNT films have a high electroactivity, and a porous and branched structure that can increase the specific surface area for biosensing application. In this work the PANi–MWCNT films were applied for covalent immobilization of glucose oxidase (GOx) via glutaraldehyde agent. The GOx/PANi–MWCNT/ID?E was studied using cyclic voltammetric and chronoamperometric techniques. The effect of several interferences, such as ascorbic acid (AA), uric acid (UA), and acetaminophen (AAP) on the glucosensing at +0.6 V (versus SCE) is not significant. The time required to reach 95% of the maximum steady-state current was less than 5 s. A linear range of the calibration curve for the glucose concentration lies between 1 and 12 mM which is a suitable level in the human body.

  14. Zinc oxide nanostructures for electrochemical cortisol biosensing

    NASA Astrophysics Data System (ADS)

    Vabbina, Phani Kiran; Kaushik, Ajeet; Tracy, Kathryn; Bhansali, Shekhar; Pala, Nezih

    2014-05-01

    In this paper, we report on fabrication of a label free, highly sensitive and selective electrochemical cortisol immunosensors using one dimensional (1D) ZnO nanorods (ZnO-NRs) and two dimensional nanoflakes (ZnO-NFs) as immobilizing matrix. The synthesized ZnO nanostructures (NSs) were characterized using scanning electron microscopy (SEM), selective area diffraction (SAED) and photoluminescence spectra (PL) which showed that both ZnO-NRs and ZnO-NFs are single crystalline and oriented in [0001] direction. Anti-cortisol antibody (Anti-Cab) are used as primary capture antibodies to detect cortisol using electrochemical impedance spectroscopy (EIS). The charge transfer resistance increases linearly with increase in cortisol concentration and exhibits a sensitivity of 3.078 K?. M-1 for ZnO-NRs and 540 ?. M -1 for ZnO-NFs. The developed ZnO-NSs based immunosensor is capable of detecting cortisol at 1 pM. The observed sensing parameters are in physiological range. The developed sensors can be integrated with microfluidic system and miniaturized potentiostat to detect cortisol at point-of-care.

  15. Electrodeposition technique-dependent photoelectrochemical and photocatalytic properties of an In2S3/TiO2 nanotube array.

    PubMed

    Li, Yue; Luo, Shenglian; Wei, Zhendong; Meng, Deshui; Ding, Mingyue; Liu, Chengbin

    2014-03-01

    Electrodeposition is a very versatile tool to fabricate multicomponent TiO2 nanotube array (NTA) composites. However, the understanding of the correlation between the component structure and the fabrication technique has not been clearly investigated yet, though it has been observed that the performance of composites is bound up with the component structure. In this work, the photoelectrochemical properties of In2S3-TiO2 NTA composites prepared by CV electrodeposition, potentiostatic electrodeposition and pulse electrodeposition, respectively, were investigated. The results revealed that the as-prepared photoelectrodes exhibited electrodeposition technique-dependent properties, and the pulse prepared In2S3-TiO2 yielded the highest and stable photocurrent response, consequently exhibiting a superior photocatalytic activity in the degradation of p-nitrophenol (PNP). This may be attributed to the homogeneous, ultra-fine structure of In2S3 nanoparticles (NPs), which brings about a high charge separation efficiency. Furthermore, the trapping tests showed that both radicals and holes were the main active species in the photocatalytic degradation of PNP. This work not only provided a firm basis for maximizing photocatalytic activity via tuning fabrication techniques but also gave a deep insight into the photocatalytic mechanism. PMID:24457830

  16. Pulse electrodeposition of adherent nickel coatings onto anodized aluminium surfaces

    NASA Astrophysics Data System (ADS)

    Frantz, Cédric; Vichery, Charlotte; Zechner, Johannes; Frey, Damian; Bürki, Gerhard; Cebeci, Halil; Michler, Johann; Philippe, Laetitia

    2015-03-01

    Aluminium is one of the mostly used elements in the industry because of its abundance and low weight. However, the deposition of a metallic coating requires performing the so-called zincate pre-treatment in order to allow the formation of inter-metallic bonds and thereby achieving sufficient adherence. In this work, porous anodic aluminium oxide (AAO) is used as an anchoring intermediate layer for nickel coatings. AAO is grown anodically in sulfuric acid and nickel coatings are deposited by potentiostatic reverse pulse electrodeposition onto as-anodized aluminium surfaces. The electrodeposition of nickel is initiated onto the electrochemically thinned barrier layer of AAO and pursued until the complete covering of the oxide. The electrochemical behavior of Watts and sulfamate baths is investigated by cyclic voltammetry for different barrier layer thickness, allowing to validate the thinning conditions and to determine the appropriate deposition potential of nickel. GD-OES measurements show that low duty cycles are necessary to achieve high filling ratio of the AAO. SEM micrographs show that a smooth uniform coating is obtained when nickel is deposited in presence of additives.

  17. Electrodeposition and Characterization of Yttrium Barium Copper Oxide Superconducting Thin Films

    NASA Astrophysics Data System (ADS)

    Weston, Alan James

    Precursor thin films of Y-Ba-Cu-O superconductor were produced by potentiostatic and pulse electrodeposition from the dissolved nitrate salts of Y, Ba, Cu in dimethylformamide (DMF). The films were deposited on metal foils such as Ag-coated Cu, Ag, Ni, and Zr. Films were also synthesized on Ag-coated SrTiO_3, CaTiO _3, and Al_2O _3. The electrodeposited films were heat treated in flowing O_2 in order to produce the superconducting phase. The film composition as a function of the salt concentration in DMF was determined by energy dispersive x-ray analysis. Surface compositions were obtained by Auger electron spectroscopy. Crystal structure and phases were identified by means of x-ray diffraction. The superconducting dimagnetic behaviour has been observed in magnetic measurements. Films formed by pulse plating on the titanates and on Zr exhibited the best uniformity with highest T_{rm c}. Y-Ba-Cu-O films formed on Zr had highest T_{rm c} onset at 93 K (resistance measurement). The pulse plating process was extended to the synthesis of Er-Ba-Cu-O films. On Zr, the latter resulted in a T_{rm c} onset at 80 K.

  18. Evolution of novel bioresorbable iron-manganese implant surfaces and their degradation behaviors in vitro.

    PubMed

    Heiden, Michael; Walker, Emily; Nauman, Eric; Stanciu, Lia

    2015-01-01

    The purpose of this study is to advance understanding of surface degradation kinetics for Fe-Mn bioresorbable alloys (specifically Fe-20%Mn) and target degradable fracture fixation implants for hard tissues. This study addresses how arc melted Fe-20%Mn discs degrade in a static, osteogenic medium for up to a 3 month time span. Degradation behavior of these bulk alloys was investigated using both mass loss tests for measuring long-term corrosion rates and potentiostatic tests for following the instantaneous rate of degradation. It was discovered that cold-rolling Fe-20%Mn to 77% cold work (CW) suppressed the instantaneous corrosion rate compared with the cast structure. It was also found that an unstable iron-rich oxide layer forms on the entire surface of these bulk samples and the act of machining the bulk metal into a defined shape may affect the morphology of the oxide layer on the outer edge of the samples during degradation. The mechanisms behind the surface evolution of these potential orthopedic implants are investigated in detail. PMID:24616416

  19. Direct electrochemical sensor for label-free DNA detection based on zero current potentiometry.

    PubMed

    Wu, Nai-ying; Gao, Wei; He, Xu-lun; Chang, Zhu; Xu, Mao-tian

    2013-01-15

    A direct electrochemical DNA biosensor based on zero current potentiometry was fabricated by immobilization of ssDNA onto gold nanoparticles (AuNPs) coated pencil graphite electrode (PGE). One ssDNA/AuNPs/PGE was connected in series between clips of working and counter electrodes of a potentiostat, and then immersed into the solution together with a reference electrode, establishing a novel DNA biosensor for specific DNA detection. The variation of zero current potential difference (?E(zcp)) before and after hybridization of the self-assembled probe DNA with the target DNA was used as a signal to characterize and quantify the target DNA sequence. The whole DNA biosensor fabrication process was characterized by cyclic voltammetry and electrochemical impedance spectroscopy with the use of ferricyanide as an electrochemical redox indicator. Under the optimized conditions, ?E(zcp) was linear with the concentrations of the complementary target DNA in the range from 10nM to 1?M, with a detection limit of 6.9nM. The DNA biosensor showed a good reproducibility and selectivity. Prepared DNA biosensor is facile and sensitive, and it eliminates the need of using exogenous reagents to monitor the oligonucleotides hybridization. PMID:22884003

  20. Fluorescence confocal laser scanning microscopy as a probe of pH gradients in electrode reactions and surface activity.

    PubMed

    Rudd, Nicola C; Cannan, Susan; Bitziou, Eleni; Ciani, Ilenia; Whitworth, Anna L; Unwin, Patrick R

    2005-10-01

    The application of fluorescence confocal laser scanning microscopy (CLSM) to quantify three-dimensional pH gradients near electrode surfaces is described. The methodology utilizes a trace quantity of a fluorescent dye, fluorescein, in solution, which fluoresces strongly above pH 6.5, to map the pH adjacent to various ultramicroelectrodes undergoing electrochemical processes that lead to pH changes. The experimental fluorescence profiles, determined by CLSM, have been compared to models by solving the underlying mass transport equations, including the effect of natural convection, using the finite element method. The methodology has been validated through studies of the galvanostatic reduction of water at both disk and ring ultramicroelectrodes. The fluorescence profiles were found to be highly sensitive to both the initial bulk solution pH and applied current in a predictable fashion. The potentiostatic reduction of oxygen has been investigated at 25- and 10-microm-diameter platinum electrodes to confirm the effective number of electrons transferred in the reaction. Finally, the application of this methodology to observe defects in microelectrode arrays, particularly those that cannot be seen by optical microscopy, is described. PMID:16194080

  1. The influence of complexing agent and proteins on the corrosion of stainless steels and their metal components.

    PubMed

    Kocijan, Aleksandra; Milosev, Ingrid; Pihlar, Boris

    2003-01-01

    The present work is devoted to the problem of biodegradation of orthopaedic implants manufactured from stainless steel. In vitro simulations of the biocompatibility of two types of stainless steel, AISI 304 and AISI 316L, and their individual metal components, i.e. iron, chromium, nickel and molybdenum, were carried out in simulated physiological solution (Hank's) containing complexing agents. Knowledge of the effects of the chemical and biological complexing agents, EDTA and proteins, respectively, on the corrosion resistance of a metal should provide a better understanding of the processes occurring in vivo on its surface. The behavior of stainless steels and metal components was studied under open circuit and under potentiostatic conditions. The concentration of dissolved corrosion products in the form of released ions was determined by differential pulse polarography (DPP) and atomic emission spectrometry using inductively coupled plasma (ICP-AES). The composition of solid corrosion products formed on the surface was analyzed by energy dispersive X-ray spectroscopy (EDS) and their morphology was viewed by scanning electron microscopy (SEM). The addition of EDTA and proteins to physiological solution increased the dissolution of pure metals and stainless steels. The effect of particular protein differs on different metals and alloys. PMID:15348541

  2. Microprocessor-controlled anodic stripping voltammeter for trace metal analysis in tap water

    NASA Astrophysics Data System (ADS)

    Clem, R. G.; Park, F. W.; Kirsten, F. A.; Phillips, S. L.; Binnall, E. P.

    1984-06-01

    The construction and use of a portable, microprocessor controlled anodic stripping voltammeter for on-site simultaneous metal analysis of copper, lead and cadmium in tap water is discussed. The instrumental system is comprised of a programmable controller which permits keying in analytical parameters such as sparge time and plating time: a rotating cell for efficient oxygen removal and amalgam formation; and, data handling via a minicomputer or analog pen recorder. Plating and stripping potentials are controlled by a digital potentiostat; stripping is done using a staircase waveform with measurement of the current after a one msec delay. In this way charging current effects are minimized. Results of tap water analysis showed 3 plus or minus 1 (MU)g/L lead, 22 plus or minus 0.3 (MU)g/L copper, and less than 0.2 (MU)g/L cadmium for a Berkeley, California tap water, and 1-1000 (MU)g/L Cu, 1 -2 (MU)g/L Pb for ten samples of Seattle, Washington tap water. Recommendations are given for a next generation instrument system.

  3. Coatings on NiTi Alloy

    NASA Astrophysics Data System (ADS)

    Kei, C. C.; Yu, Y. S.; Racek, J.; Vokoun, D.; Šittner, P.

    2014-07-01

    Atomic layer deposition is introduced as a method suitable for preparation of Al2O3 layers on the surface of NiTi medical devices such as stents because of the excellent thickness control and conformal protective coating on complex structures. The corrosion properties of NiTi plates with Al2O3 coatings of various thicknesses in an environment similar to that occurring in the human body were studied using open circuit potential, potentiostatic electrochemical impedance spectroscopy, and cyclic polarization tests. It shows that the layer thickness plays a key role in the inhibition of corrosion. The thinner layers are more diffuse and make it easier for anodic reaction of passive NiTi with protective TiO2 underneath of Al2O3, while the thicker layers have the barrier effect with local pores initiating pitting corrosion. The results of our electrochemical experiments consistently show that corrosion properties of thick Al2O3 coatings on NiTi plate are inferior compared to the thin layers.

  4. Nucleation and growth in electrodeposition of thin copper films on pyrolytic graphite

    SciTech Connect

    Kinaci, F.S.; Muller, R.H.

    1992-05-01

    Electrodeposition of Cu on graphite electrodes was studied, with emphasis on nucleation. Various ex-situ and in-situ methods were investigated for determining the number density of nuclei. Two direct methods were studied (scanning electron microscopy and scanning tunneling microscopy); indirect determinations included Raman spectroscopy and analysis of potentiostatic current transients. Though some of the techniques correctly predicted the nucleation densities under special conditions, SEM was the most reliable tool. The large scatter in the data necessitated steps to minimize this effect. To electrodeposit Cu on graphite, a nucleation overpotential of 250 mV was measured with cyclic voltammetry; such a large overpotential does not occur on a Pt or on a Cu-covered graphite electrode. The deposition potential is the dominant parameter governing nucleation density. There is a sharp increase in the nucleation density with applied potential. Cu can be deposited on highly oriented pyrolytic graphite only between the nucleation overpotential and the hydrogen evolution potential. To increase the Cu nucleation density, while avoiding excessive H evolution, a double pulse potential technique was used; nucleation densities on the order of 10{sup 10} nuclei/cm{sup 2} were achieved. The use of inhibitors (PVA, benzotriazole) was also investigated. Deposition on conducting polymer electrodes was also studied; initial results with polyaniline show promise. 57 figs, 6 tabs, refs. (DLC)

  5. Dye-sensitized nanostructured p-type nickel oxide film as a photocathode for a solar cell

    SciTech Connect

    He, J.; Lindstroem, H.; Hagfeldt, A.; Lindquist, S.E.

    1999-10-21

    Nanostructured NiO film was prepared by depositing nickel hydroxide slurry on conducting glass and sintering at 500 C to a thickness of about 1 {micro}m. The photocurrent-voltage (IV) characteristics of the plain nanostructured NiO electrode recorded potentiostatically in a standard three-electrode setup upon UV illumination demonstrate p-type behavior, while the IV characteristics of a dye-sensitized nanostructured NiO electrode coated with erythrosin B show cathodic photocurrent under visible light illumination. The highest incident photon-to-current conversion efficiencies of tetrakis(4-carboxyphenyl)porphyrin (TPPC) and erythrosin B-coated NiO films were 0.24% and 3.44%, respectively. In sandwich solar cells with a platinized conducting glass as counter electrode exposed to light from a sun simulator (light intensity: 68 mW/cm{sup 2}), a short-circuit cathodic photocurrent density (I{sub SC}) of 0.079 mA/cm{sup 2} and an open-circuit voltage (V{sub OC}) of 98.5 mV for TPPC-coated NiO electrode were achieved. Similarly, I{sub SC} = 0.232 mA/cm{sup 2} and V{sub OC} = 82.8 mV were registered when the NiO electrode was coated with erythrosin B. The cathodic photocurrent is explained by hole injection from dye molecule to the valence band of the p-NiO electrode.

  6. Phosphate Detection through a Cost-Effective Carbon Black Nanoparticle-Modified Screen-Printed Electrode Embedded in a Continuous Flow System.

    PubMed

    Talarico, Daria; Cinti, Stefano; Arduini, Fabiana; Amine, Aziz; Moscone, Danila; Palleschi, Giuseppe

    2015-07-01

    An automatable flow system for the continuous and long-term monitoring of the phosphate level has been developed using an amperometric detection method based on the use of a miniaturized sensor. This method is based on the monitoring of an electroactive complex obtained by the reaction between phosphate and molybdate that is consequently reduced at the electrode surface. The use of a screen-printed electrode modified with carbon black nanoparticles (CBNPs) leads to the quantification of the complex at low potential, because CBNPs are capable of electrocatalitically enhancing the phosphomolybdate complex reduction at +125 mV versus Ag/AgCl without fouling problems. The developed system also incorporates reagents and waste storage and is connected to a portable potentiostat for rapid detection and quantification of phosphate. Main analytical parameters, such as working potential, reagent concentration, type of cell, and flow rate, were evaluated and optimized. This system was characterized by a low detection limit (6 ?M). Interference studies were carried out. Good recovery percentages comprised between 89 and 131.5% were achieved in different water sources, highlighting its suitability for field measurements. PMID:26066782

  7. Tuning the electrochemical swelling of polyelectrolyte multilayers toward nanoactuation.

    PubMed

    Zahn, Raphael; Vörös, János; Zambelli, Tomaso

    2014-10-14

    We discuss physicochemical determinants of electrochemical polyelectrolyte multilayer swelling that are relevant to actuator usage. We used electrochemical quartz crystal microbalance with dissipation monitoring (EC-QCM-D) and cyclic voltammetry to compare the electrochemical swelling of two types of ferrocyanide-containing polyelectrolyte multilayers, poly(l-glutamic acid)/poly(allylamine hydrochloride) (PGA/PAH), and carboxymethyl cellulose/poly(diallyldimethylammonium chloride) (CMC/PDDA). We showed that ferrocyanide oxidation causes the swelling of PGA/PAH multilayers whereas it results in the contraction of CMC/PDDA multilayers. This behavior can be attributed to the presence of a positive and a negative Donnan potential in the case of PGA/PAH and CMC/PDDA multilayers, respectively. Using multilayers consisting of PGA and poly(allylamine) ferrocene (PGA/PAH-FC), we applied EC-QCM-D and demonstrated potentiostatic thickness control with nanometer precision and showed that the multilayer's thickness depends linearly on the applied potential within a certain potential range. PMID:25229875

  8. Localized corrosion effects and modifications of acidic and alkaline slurries on copper chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Tsai, Tzu-Hsuan; Yen, Shi-Chern

    2003-04-01

    This study demonstrates the CMP performance can be enhanced by modifying the corrosion effects of acidic and alkaline slurries on copper. A corrosion test-cell with a polishing platform is connected with the potentiostat to investigate the corrosion behaviors of copper CMP in various alumina slurries. Experiments show that the slurry needs to be maintained in acidic pH<4.56 or alkaline pH>9.05 surroundings and thus better dispersion of alumina particles and less residual contaminant on copper surface can be obtained. The surface defects after copper CMP using acidic and alkaline slurries are described by pitting corrosion mechanisms, and these mechanisms can be regarded as a basis to modify their corrosion effects. Experimental results indicate that it is necessary to modify the dissolution of HNO 3 and oxidization of NH 4OH for copper CMP slurries. Consequently, the slurries of 5 wt.% HNO 3 by adding 0.1 wt.% BTA or 5 wt.% KNO 3 by adding 1 wt.% NH 4OH achieve good CMP performance for copper with higher CMP efficiency factor (CMPEF), 1460 and 486, and lower surface roughness ( Rq), 4.019 and 3.971 nm, respectively. It is found that AFM micrographs can support the effectiveness of corrosion modifications for copper CMP in various slurry chemistries.

  9. Corrosion resistance, chemistry, and mechanical aspects of Nitinol surfaces formed in hydrogen peroxide solutions

    SciTech Connect

    Shabalovskay, Svetlana A.; Anderegg, James W.; Undisz, Andreas; Rettenmayr, Markus; Rondelli, Gianni C.

    2012-06-12

    Ti oxides formed naturally on Nitinol surfaces are only a few nanometers thick. To increase their thickness, heat treatments are explored. The resulting surfaces exhibit poor resistance to pitting corrosion. As an alternative approach to accelerate surface oxidation and grow thicker oxides, the exposure of Nitinol to strong oxidizing H2O2 aqueous solutions (3 and 30%) for various periods of time was used. Using X-Ray Photoelectron Spectroscopy (XPS) and Auger spectroscopy, it was found that the surface layers with variable Ti (6–15 at %) and Ni (5–13 at %) contents and the thickness up to 100 nm without Ni-enriched interfaces could be formed. The response of the surface oxides to stress in superelastic regime of deformations depended on oxide thickness. In the corrosion studies performed in both strained and strain-free states using potentiodynamic and potentiostatic polarizations, the surfaces treated in H2O2 showed no pitting in corrosive solution that was assigned to higher chemical homogeneity of the surfaces free of secondary phases and inclusions that assist better biocompatibility of Nitinol medical devices. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 100B: 1490–1499, 2012

  10. Electrochemical Testing of Ni-Cr-Mo-Gd Alloys

    SciTech Connect

    T. E. Lister; R. E. Mizia; H. Tian

    2005-10-01

    The waste package site recommendation design specified a boron-containing stainless steel, Neutronit 976/978, for fabrication of the internal baskets that will be used as a corrosion-resistant neutron-absorbing material. Recent corrosion test results gave higher-than-expected corrosion rates for this material. The material callout for these components has been changed to a Ni-Cr-Mo-Gd alloy (ASTM-B 932-04, UNS N06464) that is being developed at the Idaho National Laboratory. This report discusses the results of initial corrosion testing of this material in simulated in-package environments that could contact the fuel baskets after breach of the waste package outer barrier. The corrosion test matrix was executed using the potentiodynamic and potentiostatic electrochemical test techniques. The alloy performance shows low rates of general corrosion after initial removal of a gadolinium-rich second phase that intersects the surface. The high halide-containing test solutions exhibited greater tendencies toward initiation of crevice corrosion.

  11. Corrosion resistance studies on grain-boundary etched drug-eluting stents.

    PubMed

    Rettig, Ralf; Kunze, Julia; Stöver, Michael; Wintermantel, Erich; Virtanen, Sannakaisa

    2007-07-01

    In this paper we compare the influence of different microstructures on the corrosion resistance of new drug-eluting stainless steel stents, which have been produced by grain-boundary-selective electrochemical etching processes. The morphology of the stent surfaces was analysed by scanning electron microscopy (SEM), and the surface composition was investigated with Auger electron spectroscopy (AES) as well as with energy dispersive X-ray analysis (EDX). The passivity of the different microstructured stents was studied by cyclovoltammetry in Ringer solution. Release of nickel and chromium was assessed after potentiostatic experiments in Ringer solution by analysing the collected electrolyte with AAS. For stents produced by different two-step etching procedures bringing about ideal morphologies regarding the mechanical and biological properties of the surface, no significant differences in the passivation behaviour could be observed. A two-step process using first nitric acid and oxalic acid in a second step produces stent surfaces with very good corrosion properties: electrochemical analysis shows that the range of stable passivity is the same as for conventional stent surfaces, and low rates of nickel and chromium release are observed. The etching procedures do not seem to change the surface oxide layer composition. PMID:17277971

  12. Physical electrochemistry of nanostructured devices.

    PubMed

    Bisquert, Juan

    2008-01-01

    This Perspective reviews recent developments in experimental techniques and conceptual methods applied to the electrochemical properties of metal-oxide semiconductor nanostructures and organic conductors, such as those used in dye-sensitized solar cells, high-energy batteries, sensors, and electrochromic devices. The aim is to provide a broad view of the interpretation of electrochemical and optoelectrical measurements for semiconductor nanostructures (sintered colloidal particles, nanorods, arrays of quantum dots, etc.) deposited or grown on a conducting substrate. The Fermi level displacement by potentiostatic control causes a broad change of physical properties such as the hopping conductivity, that can be investigated over a very large variation of electron density. In contrast to traditional electrochemistry, we emphasize that in nanostructured devices we must deal with systems that depart heavily from the ideal, Maxwell-Boltzmann statistics, due to broad distributions of states (energy disorder) and interactions of charge carriers, therefore the electrochemical analysis must be aided by thermodynamics and statistical mechanics. We discuss in detail the most characteristic densities of states, the chemical capacitance, and the transport properties, specially the chemical diffusion coefficient, mobility, and generalized Einstein relation. PMID:18075682

  13. Effect of Acidified Feronia elephantum Leaf Extract on the Corrosion Behavior of Mild Steel

    NASA Astrophysics Data System (ADS)

    Muthukrishnan, Pitchaipillai; Prakash, Periakaruppan; Ilayaraja, Murugan; Jeyaprabha, Balasubramanian; Shankar, Karikalan

    2015-03-01

    Mild steel is used as a structural material for pipes, tank, reaction vessels, etc. which are known to corrode invariably in contact with various solvents. From the view point of a nation's economy and financial implications of corrosion hazard, it is necessary to adopt appropriate means and ways to reduce the losses due to corrosion. The use of eco-friendly corrosion inhibitors are increasing day by day. Feronia elephantum leaf extract (FELE) has been tested as eco-friendly corrosion inhibitor for A262 mild steel in 1 M H2SO4 and 1 M HCl solutions using non-electrochemical (Gravimetric, X-ray diffraction analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy) and electrochemical techniques (open circuit potential, potentiostatic polarization, and electrochemical impedance measurements). The protection efficiency is found to increase with increase in FELE concentration but decrease with temperature, which is suggestive of physical adsorption mechanism. The adsorption of FELE on mild steel surface obeys the Langmuir adsorption isotherm. SEM results confirm the formation of a protective layer by FELE over mild steel surface.

  14. Corrosion of Carbon Steel and Corrosion-Resistant Rebars in Concrete Structures Under Chloride Ion Attack

    NASA Astrophysics Data System (ADS)

    Mohamed, Nedal; Boulfiza, Mohamed; Evitts, Richard

    2013-03-01

    Corrosion of reinforced concrete is the most challenging durability problem that threatens reinforced concrete structures, especially structures that are subject to severe environmental conditions (i.e., highway bridges, marine structures, etc.). Corrosion of reinforcing steel leads to cracking and spalling of the concrete cover and billions of dollars are spent every year on repairing such damaged structures. New types of reinforcements have been developed to avoid these high-cost repairs. Thus, it is important to study the corrosion behavior of these new types of reinforcements and compare them to the traditional carbon steel reinforcements. This study aimed at characterizing the corrosion behavior of three competing reinforcing steels; conventional carbon steel, micro-composite steel (MMFX-2) and 316LN stainless steel, through experiments in carbonated and non-carbonated concrete exposed to chloride-laden environments. Synthetic pore water solutions have been used to simulate both cases of sound and carbonated concrete under chloride ions attack. A three-electrode corrosion cell is used for determining the corrosion characteristics and rates. Multiple electrochemical techniques were applied using a Gamry PC4™ potentiostat manufactured by Gamry Instruments (Warminster, PA). DC corrosion measurements were applied on samples subjected to fixed chloride concentration in the solution.

  15. In situ scanning tunneling microscopy in electrolyte solutions

    NASA Astrophysics Data System (ADS)

    Itaya, Kingo

    1998-07-01

    Until recently, there had been only few in situ methods available for the structural determination of an electrode surface in solution at the atomic level. Now, several recent investigations have demonstrated scanning tunneling microscopy (STM) to be a powerful new technique for in situ characterization, with atomic resolution, of surfaces under potentiostatic control. The object of this review is to highlight some of the recent progress made, mainly, but not exclusively, in the author's laboratory, on in situ STM with atomic resolution. The review is focused on several selected topics, including structures of specifically adsorbed anions, underpotential deposition, adsorption of organic molecules, and electrochemical dissolution of metals and semiconductors. A combination of in situ STM and ex situ ultrahigh vacuum techniques has revealed detailed atomic structures of various adlayers, particularly iodine adlayers on Au, Ag, and Pt electrodes. It was recently demonstrated that aromatic molecules such as benzene adsorbed on Rh, Pt, and Cu can be clearly “seen” while the electrode is immersed in electrolytic solution. The atomic structures of semiconductor surfaces of Si, GaAs, and InP were successfully imaged in solution. Furthermore, it has been established that dynamic processes of electrochemical etching of metals and semiconductors can be followed by in situ STM. The work on semiconductors may well form the basis of development of a technology for preparing atomically flat substrate surfaces, which are expected to be required by the semiconductor industry of the next generation.

  16. Kinetics and mechanism of electroless deposition of copper

    SciTech Connect

    Mishra, K.G.; Paramguru, R.K. [Council of Scientific and Industrial Research, Orissa (India). Regional Research Lab.

    1996-02-01

    This paper describes investigations on the role of electrolyte composition on the mechanism of the electroless copper deposition process. Both potentiostatic and galvanostatic polarization curves as well as steady-state plots are used in these investigations. Actual deposition rates are also measured through gravimetrically determined weight gain for comparison. The observation indicates that the two-compartment cell gives the mixed potential, E{sub m}, values closer to that of the actual plating, whereas the deposition rate determined from the mixed current, i{sub m}, value is lower than that of the actual one. The mechanism of electroless copper deposition changes from anodic to cathodic control as well as from diffusion to activation control depending on the concentration of Cu{sup ++} and HCHO. The mechanism in each case could be determined through the application of the Butler-Volmer equation to the half-cell reactions depending on the position of E{sub m} in the polarization plots of the individual half-cell reactions.

  17. Polyion selective polymeric membrane-based pulstrode as a detector in flow-injection analysis.

    PubMed

    Bell-Vlasov, Andrea K; Zajda, Joanna; Eldourghamy, Ayman; Malinowska, Elzbieta; Meyerhoff, Mark E

    2014-04-15

    A method for the detection of polyions using fully reversible polyion selective polymeric membrane type pulstrodes as detectors in a flow-injection analysis (FIA) system is examined. The detection electrode consists of a plasticized polymeric membrane doped with 10 wt % of tridodecylmethylammonium-dinonylnaphthalene sulfonate (TDMA/DNNS) ion-exchanger salt. The pulse sequence used involves a short (1 s) galvanostatic pulse, an open-circuit pulse (0.5 s) during which the EMF of the cell is measured, and a longer (15 s) potentiostatic pulse to return the membrane to its original chemical composition. It is shown that total pulse sequence times can be optimized to yield reproducible real-time detection of injected samples of protamine and heparin at up to 20 samples/h. Further, it is shown that the same membrane detector can be employed for FIA detection of both polycations at levels ?10 ?g/mL and polyanions at levels of ?40 ?g/mL by changing the direction of the galvanostatic pulse. The methodology described may also be applicable in the detection of polyionic species at low levels in other flowing configurations, such as in liquid chromatography and capillary electrophoresis. PMID:24650129

  18. Degradation of SS316L bipolar plates in simulated fuel cell environment: Corrosion rate, barrier film formation kinetics and contact resistance

    NASA Astrophysics Data System (ADS)

    Papadias, Dionissios D.; Ahluwalia, Rajesh K.; Thomson, Jeffery K.; Meyer, Harry M.; Brady, Michael P.; Wang, Heli; Turner, John A.; Mukundan, Rangachary; Borup, Rod

    2015-01-01

    A potentiostatic polarization method is used to evaluate the corrosion behavior of SS316L in simulated anode and cathode environments of polymer electrolyte fuel cells. A passive barrier oxide film is observed to form and reach steady state within ?10 h of polarization, after which time the total ion release rates are low and nearly constant at ?0.4 ?g cm-2 h-1 for all potentials investigated. The equilibrium film thickness, however, is a function of the applied potential. The main ionic species dissolved in the liquid are predominately Fe followed by Ni, that account for >90% of the steady-state corrosion current. The dissolution rate of Cr is low but increases systematically at potentials higher than 0.8 V. The experimental ion release rates can be correlated with a point defect model using a single set of parameters over a broad range of potentials (0.2-1 V) on the cathode side. The interfacial contact resistance measured after 48 h of polarization is observed to increase with increase in applied potential and can be empirically correlated with applied load and oxide film thickness. The oxide film is substantially thicker at 1.5 V possibly because of alteration in film composition to Fe-rich as indicated by XPS data.

  19. Role of the electrolyte in cathodic lead dioxide reduction

    SciTech Connect

    Lyamina, L.I.; Gorbunova, K.M.; Tarasova, N.I.

    1985-09-01

    The electrolyte composition and particularly the anions are thought to be important in cathodic lead dioxide reduction. Data are reported for the process in 0.1 M Na/sub 2/B/sub 4/O/sub 7/, Na/sub 2/HPO/sub 4/, KOH, and KC1 solution and in 0.3 M K/sub 2/SO/sub 4/ solution. Deposits of alpha-PbO/sub 2/ were produced electrolytically on nickel. The potentials are reported on the hydrogen scale. The electrochemical behavior of lead dioxide in said solutions was evaluated from charging curves and from potentiodynamic curves obtained with a P-5848 potentiostat. The first stage of lead dioxide reduction in all solutions results in the formation of an intermediate oxide having the composition of PbO/sub 1/ /sub 43/ to PbO/sub 1/ /sub 24/. The second stage (reduction of the intermediate oxide to metallic lead) depends on the nature of the electrolyte. An examination of the results obtained action of lead dioxide with the electrophilic component increases in the order of KOH yields KC1 yields Na/sub 2/B/sub 4/O/sub 7/ yields Na/sub 2/HPO/sub 4/ yields K/sub 2/SO/sub 4/.

  20. Poly(3,4-ethylenedioxythiophene)/multiwall carbon nanotube composite coatings for improving the stability of microelectrodes in neural prostheses applications.

    PubMed

    Zhou, Haihan; Cheng, Xuan; Rao, Li; Li, Tao; Duan, Yanwen Y

    2013-05-01

    With the purpose of improving the stability of microelectrodes under continuous high charge density stimulation, which is required for neural prostheses applications such as visual prostheses, multiwall carbon nanotube (MWCNT)-doped poly(3,4-ethylenedioxythiophene) (PEDOT) composite films were coated onto a platinum microelectrode by electrochemical polymerization. Galvanostatically polymerized PEDOT/MWCNT films demonstrated superior characteristics compared to polystyrene sulfonate doping and potentiostatic polymerization, including a three-dimensional cone morphology and enhanced electrochemical performance (the safe charge injection limit reached 6.2 mC cm(-2) for cathodic-first pulses). Most important of all, the improved stability of the coatings has been revealed through stimulation for 96 h using 3.0 mCc m(-2) current pulses in bicarbonate- and phosphate-buffered saline solution. Cell assays revealed that PEDOT/MWCNT films could promote the adhesion and neurite outgrowth of rat pheochromocytoma cells. Finally, platinum wires coated with PEDOT/MWCNT films were implanted into rat cortex for 6 weeks for histological evaluation. Glial fibrillary acidic protein and neuronal nuclei staining revealed that the films elicit a lower tissue response compared to platinum implants. These results suggest that the galvanostatically polymerized PEDOT/MWCNT films can improve the stability of stimulation microelectrodes and that PEDOT/MWCNT is an excellent candidate material for electrode coating for neural prostheses applications. PMID:23402765

  1. Amperometric determination of xanthine in fish meat by zinc oxide nanoparticle/chitosan/multiwalled carbon nanotube/polyaniline composite film bound xanthine oxidase.

    PubMed

    Devi, Rooma; Yadav, Sandeep; Pundir, C S

    2012-02-01

    Xanthine oxidase (XOD) was immobilized on a composite film of zinc oxide nanoparticle/chitosan/carboxylated multiwalled carbon nanotube/polyaniline (ZnO-NP/CHIT/c-MWCNT/PANI) electrodeposited over the surface of a platinum (Pt) electrode. A xanthine biosensor was fabricated using XOD/ZnO-NP/CHIT/c-MWCNT/PANI/Pt as working electrode, Ag/AgCl as reference electrode and Pt wire as auxiliary electrode connected through a potentiostat. The ZnO-NPs were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the enzyme electrode was characterized by cyclic voltammetry, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response within 4 s at 0.5 V potential, pH 7.0, 35 °C and linear range 0.1-100 ?M with a detection limit of 0.1 ?M. The enzyme electrode was employed for determination of xanthine in fish meat during storage. The electrode lost 30% of its initial activity after 80 uses over one month, when stored at 4 °C. PMID:22135777

  2. Electrochemical Polishing Applications and EIS of a Vitamin B{sub 4}-Based Ionic Liquid

    SciTech Connect

    Wixtrom, Alex I. [Christopher Newport University, Newport News, VA (United States); Buhler, Jessica E. [Christopher Newport University, Newport News, VA (United States); Reece, Charles E. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Abdel-Fattah, Tarek M. [Christopher Newport University, Newport News, VA (United States)

    2013-01-01

    Modern particle accelerators require minimal interior surface roughness for Niobium superconducting radio frequency (SRF) cavities. Polishing of the Nb is currently achieved via electrochemical polishing with concentrated mixtures of sulfuric and hydrofluoric acids. This acid-based approach is effective at reducing the surface roughness to acceptable levels for SRF use, but due to acid-related hazards and extra costs (including safe disposal of used polishing solutions), an acid-free method would be preferable. This study focuses on an alternative electrochemical polishing method for Nb, using a novel ionic liquid solution containing choline chloride, also known as Vitamin B{sub 4} (VB{sub 4}). Potentiostatic electrochemical impedance spectroscopy (EIS) was also performed on the VB4-based system. Nb polished using the VB4-based method was found to have a final surface roughness comparable to that achieved via the acid-based method, as assessed by atomic force microscopy (AFM). These findings indicate that acid-free VB{sub 4}-based electrochemical polishing of Nb represents a promising replacement for acid-based methods of SRF cavity preparation.

  3. Seed layer-free electrodeposition of well-aligned ZnO submicron rod arrays via a simple aqueous electrolyte

    SciTech Connect

    Xu Feng [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Materials Science and Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing 210009 (China); Lu Yinong, E-mail: ynlu@njut.edu.cn [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Materials Science and Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing 210009 (China); Xia Lili; Xie Yan; Dai Min; Liu Yunfei [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Materials Science and Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing 210009 (China)

    2009-08-05

    A potentiostatic electrodeposition technique was used to directly fabricate large-scale, well-aligned, and single-crystalline submicron ZnO rod arrays on tin doped indium oxide glass substrate without a pre-prepared seed layer of ZnO from an aqueous solution only containing zinc nitrate. The effects of electrochemical parameters, such as electrodeposition potential, electrodeposition duration, solution temperature, and precursor concentration, on the orientation, morphology, aspect ratio, and growth rate of ZnO rod arrays were systematically investigated. Results show that submicron ZnO rod arrays with (0 0 0 2) preferred orientation and perfect crystallization were obtained when electrodeposition potential was in the range from -0.6 to -1.1 V and solution temperature was controlled above 60 deg. C. Both high solution temperature and low precursor concentration resulted in the decrease in rod diameters. Photoluminescence measures showed that small diameter and nanotips of ZnO rod arrays should be responsible for strong and sharp ultraviolet emission in the room temperature photoluminescence spectra.

  4. Low modulus Ti-Nb-Hf alloy for biomedical applications.

    PubMed

    González, M; Peña, J; Gil, F J; Manero, J M

    2014-09-01

    ?-Type titanium alloys with a low elastic modulus are a potential strategy to reduce stress shielding effect and to enhance bone remodeling in implants used to substitute failed hard tissue. For biomaterial application, investigation on the mechanical behavior, the corrosion resistance and the cell response is required. The new Ti25Nb16Hf alloy was studied before and after 95% cold rolling (95% C.R.). The mechanical properties were determined by tensile testing and its corrosion behavior was analyzed by potentiostatic equipment in Hank's solution at 37°C. The cell response was studied by means of cytotoxicity evaluation, cell adhesion and proliferation measurements. The stress-strain curves showed the lowest elastic modulus (42GPa) in the cold worked alloy and high tensile strength, similar to that of Ti6Al4V. The new alloy exhibited better corrosion resistance in terms of open circuit potential (EOCP), but was similar in terms of corrosion current density (iCORR) compared to Ti grade II. Cytotoxicity studies revealed that the chemical composition of the alloy does not induce cytotoxic activity. Cell studies in the new alloy showed a lower adhesion and a higher proliferation compared to Ti grade II presenting, therefore, mechanical features similar to those of human cortical bone and, simultaneously, a good cell response. PMID:25063170

  5. Evaluation on the Corrosion of the Three Ni-Cr Alloys with Different Composition

    PubMed Central

    Rao, Srinivasa B.; Chowdhary, Ramesh

    2011-01-01

    Dental casting alloys are widely used in contact with oral tissue for many years now. With the development of new dental alloys over the past 15 years, many questions remain unanswered about their biologic safety. Concepts and current issues concerning the response to the biologic effects of dental casting alloys are presented. In this paper, samples of three commercially available nickel-chrome (Ni-cr) casting alloys (Dentaurum, Bego, Sankin) were taken to assess their corrosion behavior, using potentiodynamic polarization method (electrochemical method) with fusayama artificial saliva as an electrolyte medium to check for their biocompatibility. The parameters for corrosion rate and corrosion resistance were obtained from computer-controlled corrosion schematic instrument, namely, potentiostat through corrosion software (power CV). The results obtained were analyzed by classic Tafel analysis. Statistical analysis was done by Student's t-test and ANOVA test. It was concluded that Dentarum and Bego showed satisfactory corrosive behavior, with exception of Sankin which depicted higher corrosion rate and least resistance to corrosion. Thus, the selection of an alloy should be made on the basis of corrosion resistance and biologic data from dental manufactures. PMID:21461232

  6. On the electroanalytical characterization of Li{sub x}CoO{sub 2}, Li{sub x}NiO{sub 2} and LiMn{sub 2}O{sub 4} (spinel) electrodes in repeated lithium intercalation-deintercalation processes

    SciTech Connect

    Aurbach, D.; Levi, M.D.; Levi, E.; Markovsky, B.; Salitra, G.; Teller, H.; Heider, U.; Heider, L.

    1998-07-01

    This paper reports on electroanalytical studies of the intercalation-deintercalation of lithium into lithiated transition metal oxides which are used as cathodes for Li ion batteries. These include Li{sub x}CoO{sub 2} Li{sub x}NiO{sub 2} and Li{sub x}Mn{sub 2}O{sub 4} spinel. The basic electroanalytical response of these systems in LiAsF{sub 6} 1M/EC-DMC solutions was obtained from the simultaneous use of slow and fast scan cyclic voltammetry (SSCV), potentiostatic intermittent titration (PITT) (from which D vs. E was calculated), and impedance spectroscopy (EIS). Surface sensitive FTIR spectroscopy and XRD were also used for surface and 3D characterization, respectively. A large and important denominator was found in the electrochemical behavior of lithium intercalation-deintercalation into these transition metal oxides and graphite. The use of the electroanalytical response of these systems as a tool for the study of stabilization and failure mechanisms of these materials as cathodes in rechargeable Li batteries is demonstrated and discussed.

  7. Compact Electrochemical System Using On-Chip Sensor Electrodes and Integrated Devices

    NASA Astrophysics Data System (ADS)

    Yamazaki, Tomoyuki; Ikeda, Takaaki; Ishida, Makoto; Sawada, Kazuaki

    2011-04-01

    We report a compact electrochemical sensing system to implement cyclic voltammetry. This type of sensor needs a working electrode, counter electrode, and reference electrode, all of which were integrated on a single chip. The electrochemical system also needs a potentiostat and an input voltage-generating circuit, which were developed using on-chip active devices and a few discrete passive components. This is the first sensor system incorporating electrode-side input voltage generation for electrochemical measurements using an on-chip operational amplifier, which replaces a bulky external voltage controller. A continuous cyclic voltammetry measurement was conducted with a well-studied ferricyanide solution to demonstrate the operation of the intelligent sensor chip. A clear peak was observed and linearity to the target chemical concentration was obtained between the peak height and concentration of the ferricyanide solution. With potential for mass production and small size, this sensor chip could be the best candidate to realize point-of-care testing. This sensor chip is a milestone of a fully integrated electrochemical sensor chip.

  8. Variation of Nd and Vfb for different compositions of CdSe xTe 1-x thin films by pulse plating technique

    NASA Astrophysics Data System (ADS)

    Saaminathan, V.; Murali, K. R.

    2006-03-01

    CdSe xTe 1-x thin films with 0potentiostatic mode with CdSO 4, SeO 2, TeO 2 and H 2SO 4 as precursors. As-deposited and annealed films coated on Ti, Ni and SS were characterized by X-ray diffraction technique and SEM, and their electrical properties were studied. The as-deposited films exhibited a cubic structure; those after heat treatment at 500 °C in air exhibited a hexagonal structure. Variation of donor concentration and the flat band potential for different values of ‘ x’ and duty cycles were studied for CdSe xTe 1-x thin films. The semiconductor parameters for all compositions coated on Ti, Ni and SS were estimated. It showed good agreement with the earlier reports.

  9. Halogen-free boron based electrolyte solution for rechargeable magnesium batteries

    NASA Astrophysics Data System (ADS)

    Zhu, Jinjie; Guo, Yongsheng; Yang, Jun; Nuli, Yanna; Zhang, Fan; Wang, Jiulin; Hirano, Shin-ichi

    2014-02-01

    All halogen containing electrolytes for Mg battery are apt to corrode conventional metal current collectors. In this paper, a new type of halogen-free boron based electrolyte (Mg[Mes3BPh]2/THF) is designed and prepared. Electrochemical tests show that this electrolyte system possesses high ion conductivity (1.5 × 10-3 S cm-1) and good Mg deposition-dissolution reversibility. More importantly, the same electrochemical window (2.6 V vs. Mg RE) of the electrolyte on Pt and stainless steel electrodes indicates that halogen-free electrolyte indeed lessens the corrosion to conventional metal current collectors. The surface morphologies of stainless steel, aluminum and copper are further observed after their anodic potentiostatic polarization in 0.25 mol L-1 Mg[Mes3BPh]2/THF electrolyte solution for 2 days. A comparison with halogen containing electrolytes proves that the presence of halogen in electrolyte is the reason for corrosion. This work provides a stepping stone for developing new halogen-free electrolyte systems for rechargeable Mg batteries.

  10. In situ measurement of active catalyst surface area in fuel cell stacks

    NASA Astrophysics Data System (ADS)

    Brightman, E.; Hinds, G.; O'Malley, R.

    2013-11-01

    Measurement of electrochemical surface area (ECSA) of fuel cell electrodes is a key diagnostic of performance and gives a useful parameter for monitoring degradation and state of health in polymer electrolyte membrane fuel cells (PEMFCs). However, conventional methods for determining ECSA require potentiostatic control of the cell, which is impractical in a fuel cell stack. Here we demonstrate for the first time the practical application of a galvanostatic technique that enables in situ monitoring of ECSA in each cell throughout the lifetime of a stack. The concept is demonstrated at single cell level using both H adsorption and CO stripping, and the H adsorption (cathodic current) method is extended to stack testing. The undesirable effects of H2 crossover on the measurement may be minimised by appropriate selection of current density and by working with dilute H2 on the anode electrode. Good agreement is achieved with ECSA values determined using conventional single cell voltammetry across a range of MEA designs. The technique is straightforward to implement and provides an invaluable tool for state of health monitoring during PEMFC stack lifetime studies.

  11. Polymer film selection for corrosion protection of data storage magnetic materials.

    PubMed

    Chatruprachewin, Santi; Supadee, Laddawan; Titiroongruang, Wisut

    2011-12-01

    Due to the current requirement of high recording density of hard disk drive, the thickness of DLC layer which is the protective layer is needed to be reduced. Therefore, the corrosion of read-write elements that are fabricated from soft magnetic materials is more critical. During the photolithography process, polymer photoresist is playing the major role on controlling the corrosion of soft magnetic materials. Two different types of polymer photoresists are selected to investigate, noted as wet photoresist and dry photoresist, respectively. Contact angle measurement, AFM and SEM are techniques using to determine the quality of polymer photoresists. Furthermore, the direct corrosion is also studied by using potentiostat/galvanostat-based measurements. The result suggested that the wet photoresist, AZ4999 Clariant, is better as compared to that of dry photoresist. No surface degradation as well as surface defects of the wet photoresist was found after lithography process. The corrosion rate of the specimen coated by this corresponding wet film is found to be only 1.44 x 10(-6) mm/y. In addition, the wet photoresist surface is hydrophobic posed of more than 75 degree of contact angle. PMID:22408952

  12. Coupling EELS/EFTEM Imaging with Environmental Fluid Cell Microscopy

    SciTech Connect

    Unocic, Raymond R [ORNL; Baggetto, Loic [ORNL; Veith, Gabriel M [ORNL; Dudney, Nancy J [ORNL; More, Karren Leslie [ORNL

    2012-01-01

    Insight into dynamically evolving electrochemical reactions and mechanisms encountered in electrical energy storage (EES) and conversion technologies (batteries, fuel cells, and supercapacitors), materials science (corrosion and oxidation), and materials synthesis (electrodeposition) remains limited due to the present lack of in situ high-resolution characterization methodologies. Electrochemical fluid cell microscopy is an emerging in-situ method that allows for the direct, real-time imaging of electrochemical processes within a fluid environment. This technique is facilitated by the use of MEMS-based biasing microchip platforms that serve the purpose of sealing the highly volatile electrolyte between two electron transparent SiNx membranes and interfacing electrodes to an external potentiostat for controlled nanoscale electrochemislly experiments [!]. In order to elucidate both stmctural and chemical changes during such in situ electrochemical experiments, it is impmtant to first improve upon the spatial resolution by utilizing energy-filtered transmission electron microscopy (EFTEM) (to minimize chromatic aben ation), then to detennine the chemical changes via electron energy loss spectroscopy (EELS). This presents a formidable challenge since the overall thickness through which electrons are scattered through the multiple layers of the cell can be on the order of hundreds of nanometers to microns, scattering through which has the deleterious effect of degrading image resolution and decreasing signal-to noise for spectroscopy [2].

  13. Characterization of local electrochemical doping of high performance conjugated polymer for photovoltaics using scanning droplet cell microscopy?

    PubMed Central

    Gasiorowski, Jacek; Mardare, Andrei Ionut; Sariciftci, Niyazi Serdar; Hassel, Achim Walter

    2013-01-01

    The electrochemical oxidation of a next generation low bandgap high performance photovoltaic material namely poly[4,8-bis-substituted-benzo[1,2-b:4,5-b0]dithiophene-2,6-diyl-alt-4-substituted-thieno[3,4-b] thiophene-2,6-diyl] (PBDTTT-c) thin film was investigated using a scanning droplet cell microscope. Cyclic voltammetry was used for the basic characterization of the oxidation/doping of PBDTTT-c. Application of the different final potentials during the electrochemical study provides a close look to the oxidation kinetics. The electrical properties of both doped and undoped PBDTTT-c were analyzed in situ by electrochemical impedance spectroscopy giving the possibility to correlate the changes in the doping level with the subsequent changes in the resistance and capacitance. As a result one oxidation peak was found during the cyclic voltammetry and in potentiostatic measurements. From Mott–Schottky analysis a donor concentration of 2.3 × 1020 cm?3 and a flat band potential of 1.00 V vs. SHE were found. The oxidation process resulted in an increase of the conductivity by two orders of magnitude reaching a maximum for the oxidized form of 1.4 S cm?1. PMID:25843970

  14. Enhanced electrocatalytic activity of the Au-electrodeposited Pt nanoparticles-coated conducting oxide for the quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Yoon, Yeung-Pil; Kim, Jae-Hong; Kang, Soon-Hyung; Kim, Hyunsoo; Choi, Chel-Jong; Kim, Kyong-Kook; Ahn, Kwang-Soon

    2014-08-01

    Au was electrodeposited potentiostatically at 0.3 V for 5 min on nanoporous Pt nanoparticle-coated F-doped SnO2 (FTO/Pt) substrates. For comparison, Au-electrodeposited FTO (FTO/Au) and Au-uncoated FTO/Pt were prepared. FTO/Au showed large-sized Au clusters dispersed sparsely over FTO, which resulted in lower electrocatalytic activity than FTO/Pt. In contrast, FTO/Pt exhibited poor stability unlike FTO/Au due to poisoning by the adsorption of sulfur species. The Au-electrodeposited FTO/Pt (FTO/Pt/Au) consisted of small Au clusters deposited over the entire area of Pt due to the effective Au nucleation provided by nanoporous metallic Pt. FTO/Pt/Au exhibited enhanced electrocatalytic activity and excellent stability because the small Au particles well-dispersed over the nanoporous metallic Pt network provided numerous electrochemical reaction sites, and the Pt surface was not exposed to the electrolyte. When FTO/Pt/Au was used as the counter electrode (CE) of a quantum dot-sensitized solar cell, the significantly enhanced electrocatalytic activity of the FTO/Pt/Au CE facilitated the reduction reaction of Sn2- + 2e- (CE) ? Sn-12- + S2- at the CE/electrolyte interface, resulting in a significantly hindered recombination reaction, Sn2- + 2e- (TiO2 in the photoanode) ? Sn-12- + S2-, and significantly improved overall energy conversion efficiency.

  15. Electrical Conductivity Measurement and Anisotropy of Mylonite and Cataclasite

    NASA Astrophysics Data System (ADS)

    Omura, K.

    2001-12-01

    Resent studies of electromagnetic survey reveal the electrical conductivity structure at the deeper part of faults. There seems to be high conductivity region around the focal areas. The high conductivity may be related to the existence of water in rocks, which affect the strength and activity of faults, i.e., earthquake. Investigations on the electrical conductivity structure suggest important clues on the mechanism and conditions of earthquake occurrence. Rocks at the focal zone of a fault are expected to suffer from hard deformation and/or fracturing with alteration. Rocks have characteristic fabrics. They are called fault-related rocks, such as mylonite and cataclasite. We collected mylonite and cataclasite samples from the Hatagawa fracture zone in northeast Japan. The Hatagawa fracture zone is regarded as a major exhumed fault. We can observe the mylonite and cataclasite at a surface now that were produced from granitic rocks at the focal depth region in the past. We conducted measurements of electrical conductivities of the fault-related rocks at ambient condition, as a first step. We connected a frequency response analyzer and a potentiostat to measure AC impedance spectra. The combination of the two instruments performs sine wave correlation between signals passing trough a sample and a reference resistance. In addition, the potentiostat can measure a micro current. As a result, the measurement system is basically resistant to an electrical noise around the sample under severe condition and is able to measure up to 109 ? . We observed clearly foliations and lineations in mylonite samples. We cut each mylonite sample into three cylindrical chips parallel to three directions: parallel to both the foliation and the lineation (x-axis), parallel to the foliation and perpendicular to the lineation (y-axis), perpendicular to the foliation (z-axis). We did not observe any planar or linear fabric on the cataclasite samples. Porosities of the samples were less than 1 %. The conductivities at 1 Hz of samples under dry condition (samples are heated at 120 degree C for 6 hours) are about 10-8 1/? m and have little difference among samples. Under wet condition at the same frequency (samples were forcibly saturated by distilled water in a vacuum chamber), conductivities of all samples increased by more than one order of magnitude, but conductivities along three direction of mylonite are significantly different. The conductivity along x-axis and y -axis was higher by about one order and several times, respectively, than that along z-axis. This result suggests the distribution and connectivity of cracks in mylonite are anisotropic and more conductive water than rock matrix connected along x-axis. At focal deep region along a fault, cracks must be compacted, but, if thin sheets of water are distributed anisotropically in mylonite zone, some anisotropic conductivity structure may be detected.

  16. Redox competition mode of scanning electrochemical microscopy (RC-SECM) for visualisation of local catalytic activity.

    PubMed

    Eckhard, Kathrin; Chen, Xingxing; Turcu, Florin; Schuhmann, Wolfgang

    2006-12-01

    In order to locally analyse catalytic activity on modified surfaces a transient redox competition mode of scanning electrochemical microscopy (SECM) has been developed. In a bi-potentiostatic experiment the SECM tip competes with the sample for the very same analyte. This leads to a current decrease at the SECM tip, if it is positioned in close proximity to an active catalyst site on the surface. Specifically, local catalytic activity of a Pt-catalyst modified sample with respect to the catalytic reduction of molecular oxygen was investigated. At higher local catalytic activity the local 02 partial pressure within the gap between accurately positioned SECM tip and sample is depleted, leading to a noticeable tip current decrease over active sites. A flexible software module has been implemented into the SECM to adapt the competition conditions by proper definition of tip and sample potentials. A potential pulse profile enables the localised electrochemically induced generation of molecular oxygen prior to the competition detection. The current decay curves are recorded over the entire duration of the applied reduction pulse. Hence, a time resolved processing of the acquired current values provides movies of the local oxygen concentration against x,y-position. The SECM redox competition mode was verified with a macroscopic Pt-disk electrode as a test sample to demonstrate the feasibility of the approach. Moreover, highly dispersed electro-deposited spots of gold and platinum on glassy carbon were visualised using the redox competition mode of SECM. Catalyst spots of different nature as well as activity inhomogeneities within one spot caused by local variations in Pt-loading were visualised successfully. PMID:19810414

  17. Electrochemical incineration of wastes

    NASA Technical Reports Server (NTRS)

    Bhardwaj, R. C.; Sharma, D. K.; Bockris, J. OM.

    1990-01-01

    The novel technology of waste removal in space vehicles by electrochemical methods is presented to convert wastes into chemicals that can be eventually recycled. The important consideration for waste oxidation is to select a right kind of electrode (anode) material that should be stable under anodic conditions and also a poor electrocatalyst for oxygen and chlorine evolution. On the basis of long term electrolysis experiments on seven different electrodes and on the basis of total organic carbon reduced, two best electrodes were identified. The effect of redox ions on the electrolyte was studied. Though most of the experiments were done in mixtures of urine and waste, the experiments with redox couples involved 2.5 M sulfuric acid in order to avoid the precipitation of redox ions by urea. Two methods for long term electrolysis of waste were investigated: (1) the oxidation on Pt and lead dioxide electrodes using the galvanostatic methods; and (2) potentiostatic method on other electrodes. The advantage of the first method is the faster rate of oxidation. The chlorine evolution in the second method is ten times less then in the first. The accomplished research has shown that urine/feces mixtures can be oxidized to carbon dioxide and water, but current densities are low and must be improved. The perovskite and Ti4O7 coated with RuO2 are the best electrode materials found. Recent experiment with the redox agent improves the current density, however, sulphuric acid is required to keep the redox agent in solution to enhance oxidation effectively. It is desirable to reduce the use of acid and/or find substitutes.

  18. Multiple redox states of multiheme cytochromes may enable bacterial response to changing redox environments

    NASA Astrophysics Data System (ADS)

    Arbour, T.; Wrighton, K. C.; Mullin, S. W.; Castelle, C.; Luef, B.; Gilbert, B.; Banfield, J. F.

    2013-12-01

    Multiheme c-type cytochromes (MHCs) are key components in electron-transport pathways that enable some microorganisms to transfer electron byproducts of metabolism to a variety of minerals. As a response to changes in mineral redox potential, microbial communities may shift their membership, or individual organisms may adjust protein expression. Alternatively, the ability to respond may be conferred by the innate characteristics of certain electron-transport-chain components. Here, we used potentiostat-controlled microbial fuel cells (MFCs) to measure the timescale of response to imposed changes in redox conditions, thus placing constraints on the importance of these different mechanisms. In the experiments, a solid electrode acts as an electron-accepting mineral whose redox potential can be precisely controlled. We inoculated duplicate MFCs with a sediment/groundwater mixture from an aquifer at Rifle, Colorado, supplied acetate as an electron donor, and obtained stable, mixed-species biofilms dominated by Geobacter and a novel Geobacter-related family. We poised the anode at potentials spanning the range of natural Fe(III)-reduction, then performed cyclic voltammetry (CV) to characterize the overall biofilm redox signature. The apparent biofilm midpoint potential shifted directly with anode set potential when the latter was changed within the range from about -250 to -50 mV vs. SHE. Following a jump in set potential by 200 mV, the CV-midpoint shift by ~100 mV over a timescale of ~30 minutes to a few hours, depending on the direction of the potential change. The extracellular electron transfer molecules, whose overall CV signature is very similar to those of purified MHCs, appear to span a broad redox range (~200 mV), supporting the hypothesis that MHCs confer substantial redox flexibility. This flexibility may be a principle reason for the abundance of MHCs expressed by microorganisms capable of extracellular electron transfer to minerals.

  19. Nanostructuring effect of multi-walled carbon nanotubes on electrochemical properties of carbon foam as constructive electrode for lead acid battery

    NASA Astrophysics Data System (ADS)

    Kumar, Rajeev; Kumari, Saroj; Mathur, Rakesh B.; Dhakate, Sanjay R.

    2015-01-01

    In the present study, nanostructuring effect of multi-walled carbon nanotubes (MWCNTs) on electrochemical properties of coal tar pitch (CTP) based carbon foam (CFoam) was investigated. The different weight fractions of MWCNTs were mixed with CTP and foam was developed from the mixture of CTP and MWCNTs by sacrificial template technique and heat treated at 1,400 and 2,500 °C in inert atmosphere. These foams were characterized by scanning electron microscopy, X-ray diffraction, and potentiostat PARSTAT for cyclic voltammetry. It was observed that, bulk density of CFoam increases with increasing MWCNTs content and decreases after certain amount. The MWCNTs influence the morphology of CFoam and increase the width of ligaments as well as surface area. During the heat treatment, stresses exerting at MWCNTs/carbon interface accelerate ordering of the graphene layer which have positive effect on the electrochemical properties of CFoam. The current density increases from 475 to 675 mA/cm2 of 1,400 °C heat treated and 95 to 210 mA/cm2 of 2,500 °C heat-treated CFoam with 1 wt% MWCNTs. The specific capacitance was decreases with increasing the scan rate from 100 to 1,000 mV/s. In case of 1 % MWCNTs content CFoam the specific capacitance at the scan rate 100 mV/s was increased from 850 to 1,250 ?F/cm2 and 48 to 340 ?F/cm2 of CFoam heat treated at 1,400 °C and 2,500 °C respectively. Thus, the higher value surface area and current density of MWCNTs-incorporated CFoam heat treated to 1,400 °C can be suitable for lead acid battery electrode with improved charging capability.

  20. Synthesis Structure Property Relations in Layered, Li-excess Oxides Electrode Materials Li[Li1/3-2x/3NixMn2/3-x/3]O2 (x=1/3, 1/4 and 1/5)

    SciTech Connect

    Fell, Christopher [University of Florida, Gainesville; Carroll, Kyler [Virginia Commonwealth University, Richland; Chi, Miaofang [ORNL; Meng, Ying Shirley [University of Florida, Gainesville

    2010-01-01

    Relations between synthesis conditions, detailed crystal structures, and electrochemical properties of the Li-excess layered oxides Li[Ni{sub x}Li{sub 1/3-2x/3}Mn{sub 2/3-x/3}]O{sub 2}(0 < x < 1/2) are studied by X-ray diffraction, scanning electron microscopy (EELS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electron energy-loss spectrometry, combined with electrochemical property measurements including potentiostatic intermittent titration technique (PITT). Optimal synthesis conditions are obtained for stoichiometric samples sintered at 1000 C in air followed by furnace cooling. The materials exhibit capacities of {approx}250, 230, and 200 mAh/g within a voltage range of 2-4.8 V on discharge for x = 1/5, 1/4 and 1/3, respectively. Diffraction data of electrochemically cycled electrode materials show an expanded c/a lattice ratio and changing Li/Ni interlayer mixing indicating peculiar cation migration in the structures. High resolution TEM images and XPS spectra show obvious differences in the surface characteristics of the samples synthesized with stoichiometric and excess amount of LiOH, suggesting that surface characteristics is one of the contributing factors to the difference in electrochemical properties. Our results suggest that the first cycle irreversible capacity is affected by both the bulk and surface characteristics of pristine materials, which is strongly influenced by precursor chemistry. The PITT results suggest that cation rearrangement during the charge/discharge has a significant impact on the lithium chemical diffusivity.

  1. Electronic, Structural, and Electrochemical Properties of LiNi[subscript x]Cu[subscript y]Mn[subscript 2?x?y]O[subscript 4] (0 ; x ; 0.5, 0 ; y ; 0.5) High-Voltage Spinel Materials

    SciTech Connect

    Yang, Ming-Che; Xu, Bo; Cheng, Ju-Hsiang; Pan, Chun-Jern; Hwang, Bing-Joe; Meng, Ying S. (Florida); (UCSD); (NTU)

    2011-09-06

    First principles computation is carried out for investigating the electronic, structural, and electrochemical properties of LiM{sub 1/2}Mn{sub 3/2}O{sub 4} (M = Ti, V, Cr, Fe, Co, Ni, and Cu). The computation results suggest that doping with Co or Cu can potentially lower Li diffusion barrier as compared to Ni doping. Our experimental research has focused on LiNi{sub x}Cu{sub y}Mn{sub 2-x-y}O{sub 4} (0 < x < 0.5, 0 < y < 0.5), and we found that the amount of Cu will affect the lattice parameters, the cation disorder in the spinel lattice, the particle morphology, as well as the electrochemical properties. Crystal structures, electronic structures, and electrochemical properties of LiNi{sub x}Cu{sub y}Mn{sub 2-x-6}O{sub 4} (0 < x < 0.5, 0 < y < 0.5) are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray absorption spectroscopy (XAS), and electrochemical measurements including potentiostatic intermittent titration technique (PITT). With detailed electrochemical measurements and in situ XAS experiments of LiNi{sub 0.25}Cu{sub 0.25}Mn{sub 1.50}O{sub 4}, the proposed explanation of the voltage profile by the first principles computation was proven, a second plateau at 4.2 V originates from the oxidation of Cu{sup 2+} to Cu{sup 3+}, and the plateau at 4.95 V may originate from extra electrons provided by oxygen ions. Although the reversible discharge capacity decreases with increasing Cu amount, optimized composition such as LiCu{sub 0.25}Ni{sub 0.25}Mn{sub 1.5}O{sub 4} exhibits high capacities at high rates.

  2. Electrochemical and Structural Study of the Layered, 'Li-Excess' Lithium-Ion Battery Electrode Material Li[Li[subscript 1/9]Ni[subscript 1/3]Mn[subscript 5/9

    SciTech Connect

    Jiang, Meng; Key, Baris; Meng, Ying S.; Grey, Clare P.; (SBU); (Florida)

    2009-09-15

    The overcapacity mechanism and high voltage process of the Li-excess electrode material Li[Li{sub 1/9}Ni{sub 1/3}Mn{sub 5/9}]O{sub 2} are studied by solid-state NMR, X-ray diffraction, X-ray absorption spectroscopy, transmission electron microscopy, combined with galvanostatic and potentiostatic intermittent titration electrochemical measurements. The cycling performance is improved noticeably when the material is cycled between potential windows of 5.3-2.5 V compared to 4.6-2.5 V. Diffraction data show that structural changes occur at high voltages, the solid-state NMR data of the same samples indicating that the high voltage processes above 4.4 V are associated with Li removal from the structure, in addition to electrolyte decomposition. The NMR spectra of the discharged samples show that cation rearrangements in the transition metal layers have occurred. The XAS spectra confirm that the Mn oxidation state remains unchanged at 4+, whereas Ni{sup 2+} is oxidized to Ni{sup 4+} on charging to 4.4 V, returning to Ni{sup 2+} on discharge, independent of the final charge voltage. A significant change of the shape of the Ni edge is observed in the 4.6-5.3 V potential range on charge, which is ascribed to a change in the Ni local environment. No O{sub 2} evolution was detected based on ex situ analysis of the gases evolved in the batteries, the TEM data showing that thick passivating films form on the electrodes. The results suggest that at least some of the oxygen loss from these lithium-excess materials occurs via a mechanism involving electrolyte decomposition.

  3. Oxygen reduction at the platinum/Nafion{reg_sign} interface: Electrode kinetics and mass transport

    SciTech Connect

    Parthasarathy, A.

    1992-12-31

    Research in solid polymer electrolyte fuel cells is gaining momentum because of the prospects of attaining high energy efficiencies and power densities, essential for transportation and space applications. The most advanced solid polymer electrolytes for these fuel cells are the perfluorosulfonate ionomers (PFSIs) such as duPont`s Naflon and the Dow PFSIs. The high oxygen solubility, chemical stability, proton conductivity and permselectivity exhibited by Naflon and the Dow PFSI`s make them ideal candidates as electrolytes for fuel cells. Furthermore, the minimal anion adsorption on electrodes from fluorinated acids enhances oxygen reduction kinetics. The primary objectives of this work were to determine the concentration and diffusion coefficient of oxygen in Naflon, and the electrode kinetic parameters for the reduction of oxygen at the Pt/Nafion interface under totally solid-state conditions. Cyclic voltammetric and potentiostatic transient measurements were made at the Pt/Nafion interface. Slow sweep voltammograms yielded Tafel parameters for oxygen reduction. From the two-section Tafel, plot, the calculated exchange current densities were found to be higher than those obtained at any other Pt/acid interface. From an analysis of the transients, the values of oxygen solubility and diffusion coefficient in Naflon were determined. Electrochemical impedance spectroscopic (EIS) investigations were then used to study oxygen reduction under lower humidfication conditions. EIS clearly permits the discrimination of electrode kinetics, mass transport of O{sub 2} and the electrical characteristics of the membrane. A temperature-dependence study in the range of 30{degrees}C to 80{degrees}C yielded the activation energy for oxygen reduction at the Pt/Naflon interface. The diffusion coefficient of oxygen in Nafion increases with temperature while its solubility decreases. the pressure-dependence of oxygen reduction kinetics shows that the reaction order of oxygen is unity.

  4. High-Performance and Stable Gel-State Dye-Sensitized Solar Cells Using Anodic TiO2 Nanotube Arrays and Polymer-Based Gel Electrolytes.

    PubMed

    Seidalilir, Zahra; Malekfar, Rasoul; Wu, Hui-Ping; Shiu, Jia-Wei; Diau, Eric Wei-Guang

    2015-06-17

    Highly ordered and vertically oriented TiO2 nanotube (NT) arrays were synthesized with potentiostatic anodization of Ti foil and applied to fabricate gel-state dye-sensitized solar cells (DSSCs). The open structure of the TiO2 NT facilitates the infiltration of the gel-state electrolyte; their one-dimensional structural feature provides effective charge transport. TiO2 NTs of length L = 15-35 ?m were produced on anodization for periods of t = 5-15 h at a constant voltage of 60 V, and sensitized with N719 for photovoltaic characterization. A commercially available copolymer, poly(methyl methacrylate-co-ethyl acrylate) (PMMA-EA), served as a gelling agent to prepare a polymer-gel electrolyte (PGE) for DSSC applications. The PGE as prepared exhibited a maximum conductivity of 4.58 mS cm(-1) with PMMA-EA (7 wt %). The phase transition temperature (Tp) of the PGE containing PMMA-EA at varied concentrations was determined on the basis of the viscosities measured at varied temperatures. Tp increased with increasing concentration of PMMA-EA. An NT-DSSC with L = 30 ?m assembled using a PGE containing PMMA-EA (7 wt %) exhibited an overall power conversion efficiency (PCE) of 6.9%, which is comparable with that of a corresponding liquid-type device, PCE = 7.1%. Moreover, the gel-state NT-DSSC exhibited excellent thermal and light-soaking enduring stability: the best device retained ?90% of its initial efficiency after 1000 h under 1 sun of illumination at 50 °C, whereas its liquid-state counterpart decayed appreciably after light soaking for 500 h. PMID:25984747

  5. Electrochemically assisted self-assembly of ordered and functionalized mesoporous silica films: impact of the electrode geometry and size on film formation and properties.

    PubMed

    Herzog, Grégoire; Sibottier, Emilie; Etienne, Mathieu; Walcarius, Alain

    2013-01-01

    Surfactant-templated mesoporous silica thin films can be deposited onto solid electrode surfaces by electrochemically assisted self-assembly (EASA). The method involves a cathodically triggered self-assembly of cationic surfactants (cetyltrimethyl ammonium bromide, CTAB) and local pH increase leading to the polycondensation of silica precursors (i.e., tetraethoxysilane, alone or in the presence of (3-mercaptopropyl) trimethoxysilane (MPTMS)) and concomitant growth of the ordered mesoporous silica or organosilica film. The present work shows that the EASA method can be applied to film deposition on electrode supports of various morphologies, geometries and sizes (large and flat discs or non-flat streaked supports, i.e., gold CD-trodes, as well as several kinds of ultramicroelectrodes, including carbon fibers, platinum wires, and platinum microdiscs). Galvanostatic conditions were mainly preferred to potentiostatic conditions to avoid problems related to various overpotentials and surface areas experienced with the various working electrodes used here. The results indicate that film deposition was possible on each electrode support but also that both the film formation and properties were dependent on the experimental conditions for EASA. For example, passing from large electrodes to ultramicroelectrodes required the application of larger current densities to ensure film deposition, which can be due to faster loss of the hydroxyl species in solution in the case of radial or spherical diffusion, in comparison to the linear. Highly porous deposits were obtained after template removal, as ascertained by cyclic voltammetry using Ru(NH3)6(3+) as a redox probe. The advantage of better signal-to-background current ratios for ultramicroelectrodes relative to the macroscopic ones was maintained after film deposition, also resulting in higher sensitivity when used in conditions of preconcentration electroanalysis (using silver(I) or mercury(II) as a probe being accumulated by complexation to MPTMS-based films). PMID:24466668

  6. Electrochemical investigation of chromium oxide-coated Ti-6Al-4V and Co-Cr-Mo alloy substrates.

    PubMed

    Swaminathan, Viswanathan; Zeng, Haitong; Lawrynowicz, Daniel; Zhang, Zongtao; Gilbert, Jeremy L

    2011-08-01

    Hard coatings for articulating surfaces of total joint replacements may improve the overall wear resistance. However, any coating approach must take account of changes in corrosion behavior. This preliminary assessment analyzes the corrosion kinetics, impedance and mechanical-electrochemical stability of 100 ?m thick plasma sprayed chromium oxide (Cr?O?) coatings on bearing surfaces in comparison to the native alloy oxide films on Co-Cr-Mo and Ti-6Al-6V. Cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, and mechanical abrasion under potentiostatic conditions were performed on coated and substrate surfaces in physiological saline. SEM analysis characterized the coating morphology. The results showed that the corrosion current density values of chromium oxide coatings (0.4-1.2 ?A/cm²) were of the same order of magnitude as Ti-6Al-4V alloy. Mechanical abrasion did not increase corrosion rates of chromium oxide coatings but did for uncoated Co-Cr-Mo and Ti-6Al-4V. The impedance response of chromium oxide coatings was very different than Co-Cr-Mo and Ti-6Al-4V native oxides characterized by a defected coating model. More of a frequency-independent purely resistive response was seen in mid-frequency range for the coatings (CPE(coat) : 40-280 nF/cm² (rad/s)(1-?) , ?: 0.67-0.83) whereas a more capacitive character is seen for Co-Cr-Mo and Ti-6Al-4V (CPE(ox) around 20 ?F/cm² (rad/s)(1-?) , ? around 0.9). Pores, interparticle gaps and incomplete fusion typical for thermal spray coatings were present in these oxides which could have influenced corrosion resistance. The coating microstructure could have allowed some fluid penetration. Overall, these coatings appear to have suitable corrosion properties for wear surfaces. PMID:21648063

  7. Effect of bicarbonate ion additives on pitting corrosion of type 316L stainless steel in aqueous 0.5 M sodium chloride solution

    SciTech Connect

    Park, J.J.; Pyun, S.I.; Lee, W.J. [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Materials Science and Engineering; Kim, H.P. [Korea Atomic Energy Research Inst., Taejon (Korea, Republic of)

    1999-04-01

    The effect of bicarbonate ions (HCO{sub 3}{sup {minus}}) on pitting corrosion of type 316L stainless steel (SS, UNS S3 1603) was investigated in aqueous 0.5 M sodium chloride (NaCl) solution using potentiodynamic polarization, the abrading electrode technique, alternating current (AC) impedance spectroscopy combined with x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Addition of HCO{sub 3}{sup {minus}} ions to NaCl solutions extended the passive potential region in width and, at the same time, raised the pitting potential in value on the potentiodynamic polarization curve. Potentiostatic current transients obtained from the moment just after interrupting the abrading action showed the repassivation rate of propagating pits increased and that the pit growth rate decreased with increasing HCO{sub 3}{sup {minus}} ion concentration. Over the whole applied potential, the oxide film resistance was higher in the presence of HCO{sub 3}{sup {minus}} ions. The pit number density decreased with increasing HCO{sub 3}{sup {minus}} ion concentration. Moreover, addition of HCO{sub 3}{sup {minus}} ions to NaCl solutions retarded lateral pit growth, while promoting downward pit growth from the surface. The bare surface of the specimen repassivated preferentially along the pit mouth and walls, compared to the pit bottom, as a result of formation of a surface film with a high content of protective mixed ferrous-chromous carbonate ([Fe,Cr]CO{sub 3}) that formed from preferential adsorption of HCO{sub 3}{sup {minus}} ions.

  8. Model for anodic film growth on aluminum with coupled bulk transport and interfacial reactions.

    PubMed

    DeWitt, Stephen; Thornton, Katsuyo

    2014-05-13

    Films grown through the anodic oxidation of metal substrates are promising for applications ranging from solar cells to medical devices, but the underlying mechanisms of anodic growth are not fully understood. To provide a better understanding of these mechanisms, we present a new 1D model for the anodization of aluminum. In this model, a thin space charge region at the oxide/electrolyte interface couples the bulk ionic transport and the interfacial reactions. Charge builds up in this region, which alters the surface overpotential until the reaction and bulk fluxes are equal. The model reactions at the oxide/electrolyte interface are derived from the Våland-Heusler model, with modifications to allow for deviations from stoichiometry at the interface and the saturation of adsorption sites. The rate equations and equilibrium concentrations of adsorbed species at the oxide/electrolyte interface are obtained from the reactions using Butler-Volmer kinetics, whereas transport-limited reaction kinetics are utilized at the metal/oxide interface. The ionic transport through the bulk oxide is modeled using a newly proposed cooperative transport process, the counter-site defect mechanism. The model equations are evolved numerically. The model is parametrized and validated using experimental data in the literature for the rate of ejection of aluminum species into the electrolyte, embedded charge at the oxide/electrolyte interface, and the barrier thickness and growth rate of porous films. The parametrized model predicts that the embedded charge at the oxide/electrolyte interface decreases monotonically for increasing electrolyte pH at constant current density. The parametrized model also predicts that the embedded charge during potentiostatic anodization is at its steady-state value; the embedded charge at any given time is equal to the embedded charge during galvanostatic anodization at the same current. In addition to simulations of anodized barrier films, this model can be extended to multiple dimensions to simulate anodic nanostructure growth. PMID:24739021

  9. Microbial production of hydrogen and ethanol from glycerol-containing wastes discharged from a biodiesel fuel production plant in a bioelectrochemical reactor with thionine.

    PubMed

    Sakai, Shinsuke; Yagishita, Tatsuo

    2007-10-01

    H(2) and ethanol production from glycerol-containing wastes discharged from a biodiesel fuel production plant by Enterobacter aerogenes NBRC 12010 was demonstrated in bioelectrochemical cells. Thionine as an exogenous electron transfer mediator was reduced by E. aerogenes, and was re-oxidized by a working electrode applied at +0.2 V against a Ag/AgCl reference electrode by a potentiostat (electrode system). At the initial glycerol concentration of 110 mM, 92.9 mM glycerol was consumed in the electrode system with 2 mM thionine after 48 h. On the other hand, the concentration of glycerol consumed was only 50.3 mM under the control conditions without thionine and the electrodes (normal fermentation). There are no differences in the yields of H(2) and ethanol against glycerol consumed between the control conditions and the conditions with the electrode system. A pH of 6.0 was suitable for the H(2) production in the range between pH 6 and pH 7.5 in the electrode system. At pH values of 7.0 and 7.5, H(2) production decreased and formate was remarkably produced in the reaction solution. The rates of both glycerol consumption and the H(2) and ethanol production increased as the thionine concentration and the surface area of the working electrode increased. After 60 h, 154 mM of the initial 161 mM glycerol concentration in the wastes was consumed in the electrode system, which is a 2.6-fold increase compared to the control experiment. Biotechnol. Bioeng. 2007;98: 340-348. (c) 2007 Wiley Periodicals, Inc. PMID:17390385

  10. Electrochemical behavior of cobalt-chromium alloys in a simulated physiological solution.

    PubMed

    Pound, Bruce G

    2010-07-01

    Several cobalt-chromium alloys such as MP35N are used for biomedical implants. The electrochemical behavior of these alloys in the passive range differs from that of other biomedical alloys. In particular, their cyclic potentiodynamic polarization curves exhibit an increase in current at a potential of about 0.4 V (SCE). This study examined the electrochemical behavior of MP35N in phosphate-buffered saline (PBS). Tests were performed on mechanically polished MP35N rod and electropolished MP35N wire using cyclic potentiodynamic polarization, potentiostatic polarization, and electrochemical impedance spectroscopy. In both cases, the surface oxide was shown to undergo two distinct changes as the potential is increased. The first change appears to be associated with solid-state oxidation reactions involving the conversion of Cr(III) to Cr(VI) and of Co(II) to Co(III) at similar potentials. The second change involves transpassive dissolution that results in the release of chromate and nickel ions. At potentials below where these reactions occur, the impedance spectra showed near-capacitive behavior, and the data could be fitted by a parallel resistance-capacitance (as a constant phase element) circuit associated with the passive oxide film. The thickness of the oxide was determined from the capacitance and found to be consistent with surface analytical results reported in the literature. Resistivities obtained from resistance values indicated changes in the film composition as the potential was increased, particularly after the onset of the solid-state reactions. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res 2010. PMID:20128010

  11. Surface layer expansion due to proton insertion during reduction of RuO{sub 2}(100) single crystal electrodes.

    SciTech Connect

    Chu, Y. S.; Lister, T. E.; You, H.; Tanzer, J.; Mitchell, J.; Yonco, R.; Nagy, Z.

    1999-03-29

    Ruthenium dioxide has received much interest due to its nearly ideal properties for use as the active material in ultracapacitors. Ultracapacitors,a new type of energy storage device, share similarities to both conventional capacitors in that energy is stored by separation of charge and to batteries where charge is stored in chemical reactions. The chemical charge storage mechanism is referred to as pseudo-capacitance, as the Faradaic charge is distributed relatively even across a large portion of the operating voltage range. This property, which is unlike most reversible electrochemical reactions, results in charge-discharge curves for these materials being very similar to a capacitor. Despite many conventional studies of these materials, much is not known about the electrochemical reactions and the structural aspects of the reactions. The goal of our study is to investigate the modification of the surface structure accompanied by the pseudo-capacitance reactions on RuO{sub 2} electrodes. In order to study the surface structure, we performed x-ray diffraction rod measurements on single crystal surfaces. RuO{sub 2} single crystals were grown by open-flow chemical transport method with the evaporation temperature of 1350 C and the oxygen flow of 60 cc/min. These samples were analyzed in-situ in a solution of 0.5 M H{sub 2}SO{sub 4} under potential control using a conventional three-electrode potentiostat configuration. X-ray measurements were carried out at National Synchrotron Light Source (X6B, X10A, and X25A) and Advanced Photon Source (12BM) using focused optics.

  12. Electrochemical photovoltaic cells. Project 65021 quarterly technical progress report, October 15, 1979-January 15, 1980

    SciTech Connect

    Ang, P.G.P.; Remick, R.J.; Sammells, A.F.

    1980-03-01

    During the third quarter of this program, liquid junction devices based upon the semiconductors MoSe/sub 2/, MoS/sub 2/, GaAs, and CdSe have been evaluated. Lifetime testing of MoSe/sub 2/ and MoS/sub 2/ materials in acidic halogen electrolytes at constant current densities of 5 mA/cm/sup 2/ have shown excellent stability to date. For MoSe/sub 2/ single crystals in the electrolyte 1M HBr + 1M Br/sub 2/, short-circuit currents of 63 mA/cm/sup 2/ were achieved with a power conversion efficiency of 6.7% for 200 mW/cm/sup 2/ xenon light illumination. Transient potentiostatic measurements made on MoSe/sub 2/ in this electrolyte indicated little diffusion control, with exchange currents being of the order of 1 to 10 mA/cm/sup 2/. Good photoresponse of MoS/sub 2/ has been observed in 1M HBr + 1M Br/sub 2/. The performance of the natural crystal is comparable to the performance of a single-crystal MoS/sub 2/ in this electrolyte. CdSe thermally evaporated onto porous titanium gave efficiencies of about 4% with 100 mW/cm/sup 2/ xenon illumination. Experimental work was initiated on the dye sensitization of Fe/sub 2/O/sub 3/ and TiO/sub 2/ materials. Of the twelve dyes evaluated, little enhancement of the photoresponse of these materials was noted. Solid-state photoelectrochemical cells have been fabricated, based upon LiI. Cells of the configuration - cond. glass CdSe/LiI + PbI/sub 2//LiI/LiI + C + PbI/sub 2//cond. glass - were fabricated. Photoresponses up to 150 mV were observed.

  13. Changes in biofilm structure during the colonization of chalcopyrite by Acidithiobacillus thiooxidans.

    PubMed

    García-Meza, J V; Fernández, J J; Lara, R H; González, I

    2013-07-01

    Biofilms of Acidithiobacillus thiooxidans were grown on the surface of massive chalcopyrite electrodes (MCE) where different secondary sulfur phases were previously formed by potentiostatic oxidation of MCE at 0.780?Ean?0.965 V (electrooxidized MCE, eMCE). The formation of mainly S? and minor amounts of CuS and Sn²? were detected on eMCEs. The eMCEs were incubated with A. thiooxidans cells for 1, 12, 24, 48, and 120 h in order to temporally monitor changes in eMCE's secondary phases, biofilm structure, and extracellular polymeric substance (EPS) composition (lipids, proteins, and polysaccharides) using microscopic, spectroscopic, electrochemical, and biochemical techniques. The results show significant cell attachments with stratified biofilm structure since the first hour of incubation and EPS composition changes, the most important being production after 48-120 h when the highest amount of lipids and proteins were registered. During 120 h, periodic oxidation/formation of S?/Sn²? was recorded on biooxidized eMCEs, until a stable CuS composition was formed. In contrast, no evidence of CuS formation was observed on the eMCEs of the abiotic control, confirming that CuS formation results from microbial activity. The surface transformation of eMCE induces a structural transformation of the biofilm, evolving directly to a multilayered biofilm with more hydrophobic EPS and proteins after 120 h. Our results suggest that A. thiooxidans responded to the spatial and temporal distribution and chemical reactivity of the Sn²?/S?/CuS phases throughout 120 h. These results suggested a strong correlation between surface speciation, hydrophobic domains in EPS, and biofilm organization during chalcopyrite biooxidation by A. thiooxidans. PMID:23053079

  14. Microbially-influenced corrosion capability of Yucca Mountain bacterial isolates

    SciTech Connect

    Pitonzo, B.; Castro, P.; Amy, P. [Univ. of Nevada, Las Vegas, NV (United States)] [and others

    1996-12-01

    Microorganisms implicated in microbially-influenced corrosion have been isolated from the deep subsurface at Yucca Mt. Iron-oxidizing (FeOx), sulfate-reducing (SRB), and exopolymer (EPS)-producing bacteria were found. Microbial corrosion rate was monitored electrochemically. The test system was composed of a 1020 carbon steel coupon immersed in soft R2A agar prepared with simulated groundwater (J-13). A KCl bridge was used to connect the test and reference cell (calomel electrode). A platinum counter-electrode was used to apply a potential to the coupon and the corrosion process was measured by a potentiostat (Gamry). Corrosion cells (3x) were inoculated with purified cultures of EPS-producing bacteria and enrichment cultures of FeOx and SRB bacteria. Test cells were inoculated with microorganisms separately, as well as in various combinations. An uninoculated control cell was prepared to assess abiotic corrosion. Average corrosion rates were measured in milli-inches per year (mpy) against time. The control, and cells containing EPS-producing, FeOx or SRB bacteria alone or in combination demonstrated a rapid decrease in corrosion rate by 3 days. The corrosion rates stabilized, and at 35 days peaked at 2.25 mpy (FeOx), 3.30 mpy (SRB), and 2.80 mpy (EPS). AU of these values were significantly higher than the corrosion rate observed in the control cell, 1.30 mpy at 35 days. The various combinations demonstrated higher corrosion rates than any bacterial group alone. Coupons were cleaned, revealing surface pits. 200 pits/sq. in. were counted on a coupon previously exposed to a mixture of EPS-producing and FeOx microorganisms. Pit diameter ranged from 0.25 to 2.75 mm. The results indicate that Yucca Mountain microorganisms, alone and in combination, are capable of causing corrosion of 1020 carbon steel.

  15. Kinetic insights over a PEMFC operating on stationary and oscillatory states.

    PubMed

    Mota, Andressa; Gonzalez, Ernesto R; Eiswirth, Markus

    2011-12-01

    Kinetic investigations in the oscillatory state have been carried out in order to shed light on the interplay between the complex kinetics exhibited by a proton exchange membrane fuel cell fed with poisoned H(2) (108 ppm of CO) and the other in serie process. The apparent activation energy (E(a)) in the stationary state was investigated in order to clarify the E(a) observed in the oscillatory state. The apparent activation energy in the stationary state, under potentiostatic control, rendered (a) E(a) ? 50-60 kJ mol(-1) over 0.8 V < E < 0.6 V and (b) E(a) ? 10 kJ mol(-1) at E = 0.3 V. The former is related to the H(2) adsorption in the vacancies of the surface poisoned by CO and the latter is correlated to the process of proton conductivity in the membrane. The dependence of the period-one oscillations on the temperature yielded a genuine Arrhenius dependence with two E(a) values: (a) E(a) around 70 kJ mol(-1), at high temperatures, and (b) E(a) around 10-15 kJ mol(-1), at lower temperatures. The latter E(a) indicates the presence of protonic mass transport coupled to the essential oscillatory mechanism. These insights point in the right direction to predict spatial couplings between anode and cathode as having the highest strength as well as to speculate the most likely candidates to promote spatial inhomogeneities. PMID:22017227

  16. Surface Analysis by Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Coury, Louis A., Jr.; Johnson, Mario; Murphy, Tammy J.

    1995-12-01

    In both student projects a Burleigh Instruments ARIS-2200E STM was employed to image polycrystalline gold electrodes before and after deposition of a second metal onto the surface. Students prepared their own tungsten STM tips using an A.C.-etching procedure in 5% NaNO2. The electrodes used were available commercailly (AAI-AbTech, Yardley, PA) and consisted of 1000 of Au over a 100 adhesion layer of Ti on electronics-grade borosilicate glass. Electrodes were affixed to the STM sample holder using conductive carbon tape (SPI, West Chester, PA) and imaged in air. Modified electrodes were prepared by sonochemical deposition of 300 nm-Cu particles onto the Au surface in a procedure described elsewhere (2) or by the electrolytic deposition of various metals used in dental amalgams from acidic media using a Cypress Systems CS-1087 potentiostat. ResultsIn a typical image obtained for an unmodified Au surface (see image below), small crystallites (~500 to 1000 in diameter) of Au formed during the sputtering process during electrode fabrication are clearly visible. Images of modified electrodes (not shown) always show a markedly different morphology, with visible characteristic surface features ranging in size from hundreds of nanometers to several microns. The concepts students learn in these studies include electron tunneling, electroplating, nucleation phenomena, and amalgam chemistry. Although primarily touted as a method for atomic resolution imaging, STM clearly has utility for examining surfaces with features in the 100-nm to 1-micrometer size regime. Because of the recent availability of inexpensive instruments with user-friendly software, we encourage others to consider incorporating STM into the undergraduate curriculum. AcknowledgmentThis project was supported partially by a grant, DUE-9351426, from the National Science Foundation Division of Undergraduate Education Instrumentation and Laboratory Improvement Program. Literature Cited Lederman, L. Science 1991, 251, 1S--20S. Madigan, N. A.; Murphy, T. J.; Fortune, J. M.; Hagan, C. R. S.; Coury, L. A. submitted.

  17. Corrosion probes for fireside monitoring in coal-fired boilers

    SciTech Connect

    Covino, Bernard S., Jr.; Bullard, Sophie J.; Ziomek-Moroz, M.; Holcomb, Gordon R.

    2005-01-01

    Corrosion probes are being developed and combined with an existing measurement technology to provide a tool for assessing the extent of corrosion of metallic materials on the fireside in coal-fired boilers. The successful development of this technology will provide power plant operators the ability to (1) accurately monitor metal loss in critical regions of the boiler, such as waterwalls, superheaters, and reheaters; and (2) use corrosion rates as process variables. In the former, corrosion data could be used to schedule maintenance periods and in the later, processes can be altered to decrease corrosion rates. The research approach involves laboratory research in simulated environments that will lead to field tests of corrosion probes in coal-fired boilers. Laboratory research has already shown that electrochemically-measured corrosion rates for ash-covered metals are similar to actual mass loss corrosion rates. Electrochemical tests conducted using a potentiostat show the corrosion reaction of ash-covered probes at 500?C to be electrochemical in nature. Corrosion rates measured are similar to those from an automated corrosion monitoring system. Tests of corrosion probes made with mild steel, 304L stainless steel (SS), and 316L SS sensors showed that corrosion of the sensors in a very aggressive incinerator ash was controlled by the ash and not by the alloy content. Corrosion rates in nitrogen atmospheres tended to decrease slowly with time. The addition of oxygen-containing gases, oxygen and carbon dioxide to nitrogen caused a more rapid decrease in corrosion rate, while the addition of water vapor increased the corrosion rate.

  18. Measurements and mechanisms of localized aqueous corrosion in aluminum-lithium-copper alloys

    NASA Technical Reports Server (NTRS)

    Wall, Douglas; Stoner, Glenn E.

    1991-01-01

    Summary information is included for electrochemical aspects of stress corrosion cracking in alloy 2090 and an introduction to the work to be initiated on the new X2095 (Weldalite) alloy system. Stress corrosion cracking (SCC) was studied in both S-T and L-T orientations in alloy 2090. A constant load TTF test was performed in several environments with a potentiostatically applied potential. In the same environments the electrochemical behavior of phases found along subgrain boundaries was assessed. It was found that rapid failure due to SCC occurred when the following criteria was met: E(sub BR,T1) is less than E(sub applied) is less than E(sub Br, matrix phase). Although the L-T orientation is usually considered more resistant to SCC, failures in this orientation occurred when the stated criteria was met. This may be due to the relatively isotropic geometry of the subgrains which measure approximately 12 to 25 microns in diameters. Initial studies of alloy X2095 includes electrochemical characterization of three compositional variations each at three temperatures. The role of T(sub 1) dissolution in SCC behavior is addressed using techniques similar to those used in the research of 2090 described. SCC susceptibility is also studied using alternate immersion facilities at Reynolds Metals Corporation. Pitting is investigated in terms of stability, role of precipitate phases and constituent particles, and as initiation sites for SCC. In all research endeavors, attempts are made to link electrochemistry to microstructure. Previous work on 2090 provides a convenient basis for comparison since both alloys contain T(sub 1) precipitates but with different distributions. In 2090 T(sub 1) forms preferentially on subgrain boundaries whereas in X2095 the microstructure appears to be more homogeneous with finer T(sub 1) particles. Another point for comparison is the delta prime strengthening phase found in 2090 but absent in X2095.

  19. Liquid infused porous surfaces for mineral fouling mitigation.

    PubMed

    Charpentier, Thibaut V J; Neville, Anne; Baudin, Sophie; Smith, Margaret J; Euvrard, Myriam; Bell, Ashley; Wang, Chun; Barker, Richard

    2015-04-15

    Prevention of mineral fouling, known as scale, is a long-standing problem in a wide variety of industrial applications, such as oil production, water treatment, and many others. The build-up of inorganic scale such as calcium carbonate on surfaces and facilities is undesirable as it can result in safety risks and associated flow assurance issues. To date the overwhelming amount of research has mainly focused on chemical inhibition of scale bulk precipitation and little attention has been paid to deposition onto surfaces. The development of novel more environmentally-friendly strategies to control mineral fouling will most probably necessitate a multifunctional approach including surface engineering. In this study, we demonstrate that liquid infused porous surfaces provide an appealing strategy for surface modification to reduce mineral scale deposition. Microporous polypyrrole (PPy) coatings were fabricated onto stainless steel substrates by electrodeposition in potentiostatic mode. Subsequent infusion of low surface energy lubricants (fluorinated oil Fluorinert FC-70 and ionic liquid 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm)) into the porous coatings results in liquid-repellent slippery surfaces. To assess their ability to reduce surface scaling the coatings were subjected to a calcium carbonate scaling environment and the scale on the surface was quantified using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). PPy surfaces infused with BMIm (and Fluorinert to a lesser extent) exhibit remarkable antifouling properties with the calcium carbonate deposition reduced by 18 times in comparison to untreated stainless steel. These scaling tests suggest a correlation between the stability of the liquid infused surfaces in artificial brines and fouling reduction efficiency. The current work shows the great potential of such novel coatings for the management of mineral scale fouling. PMID:25585291

  20. Using anodic aluminum oxide templates and electrochemical method to deposit BiSbTe-based thermoelectric nanowires

    PubMed Central

    2014-01-01

    In this study, the cyclic voltammetry method was first used to find the reduced voltages and anodic peaks of Bi3+, Sb3+, and Te4+ ions as the judgments for the growth of the (Bi,Sb)2 - x Te3 + x-based materials. Ethylene glycol (C2H6O2) was used as a solvent, and 0.3 M potassium iodide (KI) was used to improve the conductivity of the solution. Two different electrolyte formulas were first used: (a) 0.01 M Bi(NO3)3-5H2O, 0.01 M SbCl3, and 0.01 M TeCl4 and (b) 0.015 M Bi(NO3)3-5H2O, 0.005 M SbCl3, and 0.0075 M TeCl4. The potentiostatic deposition process was first used to find the effect of reduced voltage on the variation of compositions of the (Bi,Sb)2 - xTe3 + x-based materials. After finding the better reduced voltage, 0.01 M Bi(NO3)3-5H2O, 0.01 M SbCl3, and 0.01 M TeCl4 were used as the electrolyte formula. The pulse deposition process was successfully used to control the composition of the (Bi,Sb)2 - xTe3 + x-based materials and grow the nanowires in anodic aluminum oxide (AAO) templates. PMID:24502697

  1. Characterization of Nonmetallic Inclusions in High-Manganese and Aluminum-Alloyed Austenitic Steels

    NASA Astrophysics Data System (ADS)

    Park, Joo Hyun; Kim, Dong-Jin; Min, Dong Joon

    2012-07-01

    The effects of Al and Mn contents on the size, composition, and three-dimensional morphologies of inclusions formed in Fe- xMn- yAl ( x = 10 and 20 mass pct, y = 1, 3, and 6 mass pct) steels were investigated to enhance our understanding of the inclusion formation behavior in high Mn-Al-alloyed steels. By assuming that the alumina is a dominant oxide compound, the volume fraction of inclusions estimated from the chemical analysis, i.e., insoluble Al, in the Fe-Mn-3Al steels was larger than the inclusion volume fractions in the Fe-Mn-1Al and Fe-Mn-6Al steels. A similar tendency was found in the analysis of inclusions from a potentiostatic electrolytic extraction method. This finding could be explained from the terminal velocities of the compounds, which was affected by the thermophysical properties of Fe-Mn-Al steels. The inclusions formed in the Fe-Mn-Al-alloyed steels are classified into seven types according to chemistry and morphology: (1) single Al2O3 particle, (2) single AlN or AlON particle, (3) MnAl2O4 single galaxite spinel particle, (4) Al2O3(-Al(O)N) agglomerate, (5) single Mn(S,Se) particle, (6) oxide core with Mn(S,Se) skin (wrap), and (7) Mn(S,Se) core with Al2O3(-Al(O)N) aggregate (or bump). The Mn(S,Se) compounds were formed by the contamination of the steels by Se from the electrolytic Mn. Therefore, the raw materials (Mn) should be used carefully in the melting and casting processes of Fe-Mn-Al-alloyed steels.

  2. Defect properties of anodic oxide films on titanium and impact of oxygen vacancy on oxygen electrode reactions

    NASA Astrophysics Data System (ADS)

    Roh, Bumwook

    2007-05-01

    The anodic titanium oxide film formed on titanium substrate is studied with the experimental techniques of ellipsometry, Mott-Schottky analysis, electrochemical impedance spectroscopy (EIS), and the EIS modeling with the Point Defect Model (PDM), in order to characterize the defective and semiconductive structure of the oxide film and investigate the impact of the defects of the oxide barrier layer on the oxygen electrode reactions. Ellipsometry is used to measure the thickness of the oxide film, and the model used to analyze the thickness in ellipsometry is applied to determine the structure of the oxide film that it is single-layered. The EIS model with the PDM is proposed to determine whether the oxygen vacancy is the major type of oxide defect. The expression of film thickness/potential from the PDM combined with the solution to the Nernst-Plank equation is proposed to investigate the oxygen vacancy diffusion coefficient. The effect of oxygen vacancies in the anodic oxide film on the kinetics of the oxygen electrode reaction has been studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Oxide films of different donor density are prepared galvano-potentiostatically at various current densities. The semiconductive properties of the oxide films are characterized using EIS and Mott-Schottky analysis. The film thickness is found to be almost constant, but Mott-Schottky analysis shows that the donor (oxygen vacancy) density decreased sharply with increasing oxide film formation rate (current density). With regard to the relationships between the rates of oxygen reduction/evolution and the donor density, the results show that the rates of both the reactions are higher for passive films having higher donor densities. Possible explanation, including enhancement of the conductivity of the film due to the vacancies facilitating charge transfer and enrichment of the reaction sites of the surface oxygen vacancies acting as catalytic sites, are discussed. The possible mechanisms for the oxygen electrode reactions where oxygen vacancies are acting as catalytic reaction sites are proposed. Finally, the oxygen vacancy profile and the surface oxygen vacancy concentration are provided by the advanced EIS modeling with the PDM.

  3. Direct electrochemical oxidation of ammonia on graphite as a treatment option for stored source-separated urine.

    PubMed

    Zöllig, Hanspeter; Fritzsche, Cristina; Morgenroth, Eberhard; Udert, Kai M

    2015-02-01

    Electrolysis can be a viable technology for ammonia removal from source-separated urine. Compared to biological nitrogen removal, electrolysis is more robust and is highly amenable to automation, which makes it especially attractive for on-site reactors. In electrolytic wastewater treatment, ammonia is usually removed by indirect oxidation through active chlorine which is produced in-situ at elevated anode potentials. However, the evolution of chlorine can lead to the formation of chlorate, perchlorate, chlorinated organic by-products and chloramines that are toxic. This study focuses on using direct ammonia oxidation on graphite at low anode potentials in order to overcome the formation of toxic by-products. With the aid of cyclic voltammetry, we demonstrated that graphite is active for direct ammonia oxidation without concomitant chlorine formation if the anode potential is between 1.1 and 1.6 V vs. SHE (standard hydrogen electrode). A comparison of potentiostatic bulk electrolysis experiments in synthetic stored urine with and without chloride confirmed that ammonia was removed exclusively by continuous direct oxidation. Direct oxidation required high pH values (pH > 9) because free ammonia was the actual reactant. In real stored urine (pH = 9.0), an ammonia removal rate of 2.9 ± 0.3 gN·m(-2)·d(-1) was achieved and the specific energy demand was 42 Wh·gN(-1) at an anode potential of 1.31 V vs. SHE. The measurements of chlorate and perchlorate as well as selected chlorinated organic by-products confirmed that no chlorinated by-products were formed in real urine. Electrode corrosion through graphite exfoliation was prevented and the surface was not poisoned by intermediate oxidation products. We conclude that direct ammonia oxidation on graphite electrodes is a treatment option for source-separated urine with three major advantages: The formation of chlorinated by-products is prevented, less energy is consumed than in indirect ammonia oxidation and readily available and cheap graphite can be used as the electrode material. PMID:25497427

  4. Fretting corrosion of CoCrMo and Ti6Al4V interfaces.

    PubMed

    Swaminathan, Viswanathan; Gilbert, Jeremy L

    2012-08-01

    Mechanically assisted corrosion (fretting corrosion, tribocorrosion etc.,) of metallic biomaterials is a primary concern for numerous implant applications, particularly in the performance of highly-loaded medical devices. While the basic underlying concepts of fretting corrosion or tribocorrosion and fretting crevice corrosion are well known, there remains a need to develop an integrated systematic method for the analysis of fretting corrosion involving metal-on-metal contacts. Such a method can provide detailed and quantitative information on the processes present and explore variations in surfaces, alloys, voltages, loadings, motion and solution conditions. This study reports on development of a fretting corrosion test system and presents elements of an in-depth theoretical fretting corrosion model that incorporates both the mechanical and the electrochemical aspects of fretting corrosion. To demonstrate the capabilities of the new system and validate the proposed model, experiments were performed to understand the effect of applied normal load on fretting corrosion performance of Ti6Al4V/Ti6Al4V, CoCrMo/Ti6Al4V, and CoCrMo/CoCrMo material couples under potentiostatic conditions with a fixed starting surface roughness. The results of this study show that fretting corrosion is affected by material couples, normal load and the motion conditions at the interface. In particular, fretting currents and coefficient of friction (COF) vary with load and are higher for Ti6Al4V/Ti6Al4V couple reaching 3 mA/cm(2) and 0.63 at about 73 MPa nominal contact stress, respectively. Ti6Al4V coupled with CoCrMo displayed lower currents (0.6 mA/cm(2)) and COF (0.3), and the fretting corrosion behavior was comparable to CoCrMo/CoCrMo couple (1.2 mA/cm(2) and 0.3, respectively). Information on the mechanical energy dissipated at the interface, the sticking behavior, and the load dependence of the inter-asperity distance calculated using the model elucidated the influence of mechanical factors on the experimental results. It was observed that the lowest amount of work was required to generate some of the highest fretting corrosion currents in Ti6Al4V/Ti6Al4V couples compared to the other combinations. The elements of the model presented here provide an excellent basis to explain many of the observed behaviors of these interfaces. PMID:22575833

  5. Electrochemical microfluidic biosensor for the detection of nucleic acid sequences.

    PubMed

    Goral, Vasiliy N; Zaytseva, Natalya V; Baeumner, Antje J

    2006-03-01

    A microfluidic biosensor with electrochemical detection for the quantification of nucleic acid sequences was developed. In contrast to most microbiosensors that are based on fluorescence for signal generation, it takes advantage of the simplicity and high sensitivity provided by an amperometric and coulorimetric detection system. An interdigitated ultramicroelectrode array (IDUA) was fabricated in a glass chip and integrated directly with microchannels made of poly(dimethylsiloxane) (PDMS). The assembly was packaged into a Plexiglas housing providing fluid and electrical connections. IDUAs were characterized amperometrically and using cyclic voltammetry with respect to static and dynamic responses for the presence of a reversible redox couple-potassium hexacyanoferrate (ii)/hexacyanoferrate (iii) (ferri/ferrocyanide). A combined concentration of 0.5 microM of ferro/ferricyanide was determined as lower limit of detection with a dynamic range of 5 orders of magnitude. Background signals were negligible and the IDUA responded in a highly reversible manner to the injection of various volumes and various concentrations of the electrochemical marker. For the detection of nucleic acid sequences, liposomes entrapping the electrochemical marker were tagged with a DNA probe, and superparamagnetic beads were coated with a second DNA probe. A single stranded DNA target sequence hybridized with both probes. The sandwich was captured in the microfluidic channel just upstream of the IDUA via a magnet located in the outside housing. Liposomes were lysed using a detergent and the amount of released ferro/ferricyanide was quantified while passing by the IDUA. Optimal location of the magnet with respect to the IDUA was investigated, the effect of dextran sulfate on the hybridization reaction was studied and the amount of magnetic beads used in the assay was optimized. A dose response curve using varying concentrations of target DNA molecules was carried out demonstrating a limit of detection at 1 fmol assay(-1) and a dynamic range between 1 and 50 fmol. The overall assay took 6 min to complete, plus 15-20 min of pre-incubation and required only a simple potentiostat for signal recording and interpretation. PMID:16511625

  6. Electrochemical Detection of Multiple Bioprocess Analytes

    NASA Technical Reports Server (NTRS)

    Rauh, R. David

    2010-01-01

    An apparatus that includes highly miniaturized thin-film electrochemical sensor array has been demonstrated as a prototype of instruments for simultaneous detection of multiple substances of interest (analytes) and measurement of acidity or alkalinity in bioprocess streams. Measurements of pH and of concentrations of nutrients and wastes in cell-culture media, made by use of these instruments, are to be used as feedback for optimizing the growth of cells or the production of desired substances by the cultured cells. The apparatus is designed to utilize samples of minimal volume so as to minimize any perturbation of monitored processes. The apparatus can function in a potentiometric mode (for measuring pH), an amperometric mode (detecting analytes via oxidation/reduction reactions), or both. The sensor array is planar and includes multiple thin-film microelectrodes covered with hydrous iridium oxide. The oxide layer on each electrode serves as both a protective and electrochemical transducing layer. In its transducing role, the oxide provides electrical conductivity for amperometric measurement or pH response for potentiometric measurement. The oxide on an electrode can also serve as a matrix for one or more enzymes that render the electrode sensitive to a specific analyte. In addition to transducing electrodes, the array includes electrodes for potential control. The array can be fabricated by techniques familiar to the microelectronics industry. The sensor array is housed in a thin-film liquid-flow cell that has a total volume of about 100 mL. The flow cell is connected to a computer-controlled subsystem that periodically draws samples from the bioprocess stream to be monitored. Before entering the cell, each 100-mL sample is subjected to tangential-flow filtration to remove particles. In the present version of the apparatus, the electrodes are operated under control by a potentiostat and are used to simultaneously measure the pH and the concentration of glucose. It is anticipated that development of procedures for trapping more enzymes into hydrous iridium oxide (and possibly into other electroactive metal oxides) and of means for imparting long-term stability to the transducer layers should make it possible to monitor concentrations of products of many enzyme reactions for example, such key bioprocess analytes as amino acids, vitamins, lactose, and acetate.

  7. Growth mechanism of surface roughed platinum nanowires through electrodeposition current control and their electrochemical applications

    NASA Astrophysics Data System (ADS)

    Ruan, Dajiang

    The aim of this work is to investigate the effect of current density on the grain size and surface morphology of electrodeposited platinum nanowires and their applications. Platinum (Pt) nanowires were fabricated by a galvanostatic electrodeposition method in a porous anodic alumina oxide (AAO) template with different current densities. Both direct current and pulse current electrodeposition were used to synthesize the Pt nanowires. The grain size and surface morphology of the Pt nanowires were studied by field emission scanning electron microscopy (FE-SEM), transmission electron microcopy (TEM) and X-ray diffraction (XRD). The experimental results showed that the current density was the key factor to control the surface roughness. The surface of the Pt nanowires became rougher and the grain sizes were increased by increasing the current densities. From the experimental results, a growth mechanism of Pt nanowires based on progressive nucleation and crystallization was proposed in order to find out the relationship between the surface morphology and current density. The electrochemical properties and catalytic activities of these surface roughed Pt nanowires were investigated in the detection of H20 2 and for the methanol oxidation. Cyclic voltammograms of Pt nanowire modified electrodes were obtained using a potentiostat, which showed that rougher Pt nanowires have higher response and better activity than that of smooth nanowires. For H202 detection, the effect of scan rate and H202 concentration were studied and it was found that the peak current for hydrogen peroxide reduction became larger with the increasing of either scan rate or H202 concentration. It can be inferred that the process of electrocatalytic hydrogen peroxide reduction may be controlled by diffusion of hydrogen peroxide and the Pt nanowire modified glassy carbon electrode (GCE) is well suited for the detection of H202. From the relationship between the peak current and square root of scan rates for methanol oxidation, it can be inferred that the process of electrocatalytic methanol oxidation was controlled by diffusion of methanol. To understand the effect of the morphological feature on the electrocatalytic activity of the Pt nanowire catalysts, the electrochemically active surface area (ECSA) as a function of deposited current density was investigated, which suggests that Pt nanowire catalysts deposited at highest current density had the most ECSA surface morphology of the Pt nanowires. The chronoamperometric curves and electrochemical impedance spectroscopy (EIS) results confirmed that the Pt nanowire catalyst synthesized at higher current density possessed longer durability and gave more efficient electrochemical performance.

  8. Direct Electrolytic Deposition of Mats of Mn(x)O(y) Nanowires

    NASA Technical Reports Server (NTRS)

    Myung, Nosang; West, William; Whitacre, Jay; Bugga, Ratnakumar

    2004-01-01

    Mats of free-standing manganese oxide (MnxOy) nanowires have been fabricated as experimental electrode materials for rechargeable electrochemical power cells and capacitors. Because they are free-standing, the wires in these mats are electrochemically accessible. The advantage of the mat-of-nanowires configuration, relative to other configurations of electrode materials, arises from the combination of narrowness and high areal number density of the wires. This combination offers both high surface areas for contact with electrolytes and short paths for diffusion of ions into and out of the electrodes, thereby making it possible to charge and discharge at rates higher than would otherwise be possible and, consequently, to achieve greater power densities. The nanowires are fabricated in an electrolytic process in which there is no need for an electrode binder material. Moreover, there is no need to incorporate an electrically conductive additive into the electrode material; the only electrically conductive material that must be added is a thin substrate contact film at the anchored ends of the nanowires. Hence, the mass fraction of active electrode material is close to 100 percent, as compared with about 85 percent in conventional electrodes made from a slurry of active electrode material, binder, and conductive additive pressed onto a metal foil. The locations and sizes of the nanowires are defined by holes in templates in the form of commercially available porous alumina membranes. In experiments to demonstrate the present process, alumina membranes of various pore sizes and degrees of porosity were used. First, a film of Au was sputtered onto one side of each membrane. The membranes were then attached, variously, to carbon tape or a gold substrate by use of silver or carbon paste. Once thus attached, the membranes were immersed in a plating solution comprising 0.01 M MnSO4 + 0.03 M (NH4)2SO4. The pH of the solution was kept constant at 8 by addition of H2SO4 or NH4OH as needed. Mn(x)O(y) nanowires were potentiostatically electrodeposited in the pores in the alumina templates. Depending on the anodic deposition potentials, Mn(x)O(y) was deposited in various oxidation states [divalent (Mn3O4), trivalent (Mn2O3), or tetravalent (MnO2)]. The Mn(x)O(y) wires were made free-standing (see figure) by dissolving the alumina templates, variously, in KOH or NaOH at a concentration of 20 volume percent.

  9. Phenomena of nanotube nucleation and growth on new ternary titanium alloys.

    PubMed

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

    2010-07-01

    Ti-30Nb-xZr and Ti-30Ta-xNb alloys have been investigated using various methods of surface nanotube formation. Ternary Ti-30Nb-xZr (x = 3 and 15 wt%) and Ti-30Ta-xNb (x = 3 and 15 wt%) alloys were prepared by using high-purity sponge Ti (Grade 4, G&S Titanium, USA), Ta, Zr and Nb spheres. The two groups of ternary Ti alloys were prepared using a vacuum arc melting furnace. Nanotube formation was carried out with a conventional three-electrode configuration with the Ti alloy specimen, a platinum counterelectrode, and a saturated calomel (SCE) reference electrode. Experiments were performed in 1 M H3PO4 with small additions of NaF (0.1-0.8 wt%), using a potentiostat. Nanotubes formed on the surfaces of the two ternary Ti alloys were examined by field emission scanning electron microscopy, EDS and XRD. The Ti-30Ta-xZr alloys had microstructure with entirely needle-like constituents; the thickness of the needle-like alpha-phase increased as the Zr content increased. The Ti-30Nb-xZr alloys had equiaxed microstructures of the beta-phase, and increasing amounts of the needle-like alpha phase appeared at the grain boundaries of the beta-phase as the Zr content increased. The nanotubes were nucleated and grew mainly on the beta phase for the Ti-30Ta-3Zr and Ti-30Nb-3Zr alloys, which had nanotubes with uniform shape, but the nanotubes were nucleated at the alpha phase for the Ti-30Ta-15Zr and Ti-30Nb-15Zr alloys, which had nanotubes with irregular shape and diameters of two sizes. The diameter and depth of the nanotubes could be controlled, depending upon the alloy composition and composition of the surface oxide films (TiO2, Nb2O5, Ta2O5, and ZrO2). It is concluded that this research that selection of the appropriate alloying element can allow significant control of the nanotopography of these Ti alloy surfaces and that it is possible to control the surface nanotube size to promote long-term osseointegration for clinical dental or orthopedic use. PMID:21128479

  10. Characteristic corrosion resistance of nanocrystalline TiN films prepared by high density plasma reactive magnetron sputtering.

    PubMed

    Kim, J H; Kang, C G; Kim, Y T; Cheong, W S; Song, P K

    2013-07-01

    Nanocytalline TiN films were deposited on non-alkali glass and Al substrates by reactive DC magnetron sputtering (DCMS) with an electromagnetic field system (EMF). The microstructure and corrosion resistance of the TiN-coated Al substrates were estimated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical methods. All the TiN films shows that they have a (111) preferred orientation at room temperature. TiN films deposited on Al substrate using only DCMS 400 W showed a sheet resistance of 3.22 x 10-1 omega/symbol see texts (resistivity, 3.22 x 10-5 omegacm). On the other hand, a relatively low sheet resistance of 1.91 x 10-1 omega/symbol see text (1.91 x 10-5 omegacm) was obtained for the dense nanocrystalline TiN film deposited on Al substrate using DCMS 375 W+ EMF 25 W, indicating that the introduction of an EMF system enhanced the electrical properties of the TiN film. TiN films deposited on Al substrate at 400 degreesC had a (200) preferred orientation with the lowest sheet resistance of 1.28x10-1 omega/symbol see texts (1.28 x 10-5 omegacm) which was attributed to reduced nano size defects and an improvement of the crystallinity. Potentiostatic and Potentiodynamic tests with a TiN-coated Al showed good corrosion resistance (l/corr, = 2.03 microA/cm2, Ecorr = -348 mV) compared to the uncoated Al substrate (/corr = 4.45 microA/cm2, Ecorr = -650 mV). Furthermore, EMF system showed that corrosion resistance of the TiN film also was enhanced compared to DCMS only. For the TiN film deposited on Al substrate at 400 degreesC, corrosion current and potential was 0.63 micro/cm2 and -1.5 mV, respectively. This improved corrosion resistance of the TiN film could be attributed to the densification of the film caused by enhancement of nitrification with increasing high reactive nitrogen radicals. PMID:23901480

  11. Evaluating cathodic protection reliability on steel pipe in microbially active soils

    SciTech Connect

    Kajiyama, F.; Okamura, K. [Tokyo Gas Co. Ltd. (Japan). Fundamental Technology Research Lab.

    1999-01-01

    Cathodic protection (CP) has been recognized as the most effective method of preventing corrosion of coated-steel pipelines in soils. However, evaluation of CP reliability on steel pipe in microbially active soils has not yet been performed well. Primarily, this has resulted from lack of understanding of bacterial behavior under cathodically protected conditions. The reliability of CP of steel pipe in soils in the presence of bacteria, such as iron bacteria (IB) and sulfate-reducing bacteria (SRB), was evaluated using steel specimens exposed to bacteria-containing soils and potentiostatically polarized in the potential range from {minus}0.65 V vs a copper-copper sulfate (Cu-CuSo{sub 4}) electrode to {minus}1.3 V{sub Cu-CuSo{sub 4}}. In the case of sandy soil containing IB, when the cathodic polarization potential was applied more negatively than the generally accepted protection potential of {minus}0.85 V{sub Cu-CuSO{sub 4}}, CP was achieved substantially by a decrease in the number of living IB as a result of environmental changes, including a decrease in the redox potential (E{sub h}) and an increase in pH caused by cathodic reaction. In clay containing SRB, when the cathodic polarization potential was applied more negatively than the recommended protection criteria for active SRB clay of {minus}0.95 v{sub Cu-CuSo{sub 4}}, CP was achieved in the potential range from {minus}0.95 V{sub Cu-CuSo{sub 4}}, to {minus}1.1 V{sub Cu-CuSo{sub 4}} to {minus}1.1 V{sub Cu-CuSo{sub 4}}. SRB thrived actively, resulting in formation of adherent iron sulfide (FeS) layers on the steel surface. CP was achieved through their temporary protective properties without ruptures. At potentials more negative than {minus}1.1 V{sub Cu-CuSo{sub 4}}, sufficient CP was achieved through formation of excessive hydroxyl (OH{sup {minus}}) ions generated by enhanced cathodic reaction.

  12. A study of photocatalytic graphene–TiO{sub 2} synthesis via peroxo titanic acid refluxed sol

    SciTech Connect

    Low, Wasu, E-mail: masterwasulow@hotmail.com [The Joint Graduate School of Energy and Environment, King Mongkut's University of Technology Thonburi, Bangkok 10140 (Thailand); Boonamnuayvitaya, Virote, E-mail: virote.boo@kmutt.ac.th [Department of Chemical Engineering, King Mongkut's University of Technology Thonburi, Bangkok 10140 (Thailand)

    2013-08-01

    Graphical abstract: - Highlights: • TiO{sub 2} synthesized via PTA as a precursor demonstrates exclusively anatase phase. • The TEM image of GR–TiO{sub 2} (PTA) demonstrates that TiO{sub 2} nanoparticles are successfully loaded onto graphene sheet. • The specific surface area seems to increase with increasing weight ratio of graphene oxide. It was observed that GR–TiO{sub 2} showed higher adsorption compared to bare TiO{sub 2} (PTA). • The GR–TiO{sub 2} (PTA, 1:50) catalyst showed higher photocatalytic activity than any other catalyst. - Abstract: In the present work, graphene–TiO{sub 2} (GR–TiO{sub 2}) photocatalyst with various weight ratios of graphene was synthesized using peroxo titanic acid solution (PTA) as a precursor for TiO{sub 2}. Graphene oxide prepared by Hummer's method was converted to graphene under ultraviolet (UV) irradiation in ethanol–water solvent for 48 h. The as-prepared GR–TiO{sub 2} composites were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV–vis spectrophotometry, and transmission electron microscopy (TEM). The automated potentiostat was applied to measure the photocurrent generations of prepared catalysts. The photocatalytic activities of GR–TiO{sub 2} (PTA) catalysts were determined by measuring the percentage methylene blue (MB) degradation. The results showed that TiO{sub 2} nanoparticles were successfully loaded onto graphene sheet and the surface area of catalysts increased with increasing weight ratio of graphene. In addition, GR–TiO{sub 2} (PTA, 1:50) exhibited the highest photocatalytic activity among the catalysts under UV and visible light irradiation. The adsorption edge of GR–TiO{sub 2} was shifted to a longer wavelength of 400 nm in comparison with that of pure TiO{sub 2} (PTA). The increase in the photocatalytic performance of GR–TiO{sub 2} (PTA) catalyst may be attributed to the increase in surface area, the extension of light absorption in the visible light region, and prevention of charge recombination.

  13. The use of microelectrodes in the study of localized corrosion of aluminum 6111-like alloys

    NASA Astrophysics Data System (ADS)

    Abdullah, Aboubakr M.

    This thesis is classified into four chapters. While chapter 1 is only an introductory chapter that summarizes the two mechanisms that are trying to explain localized corrosion of metals and alloys, Chapter 4 is the conclusions and future work chapter that presents the new achievements that have been added to the field of corrosion science by this work besides the proposed work to be done in the future. In chapter 2, Crevice corrosion of an experimental Al 6111-like alloy with 0.68% Cu has been studied using potentiodynamic and potentiostatic techniques in different concentrations of sodium chloride and in 0.1M nitric acid solutions. Potentiodynamic experiments show that the alloy has an active/passive transition in a saturated sodium chloride solution at elevated temperatures (90 and 70°C). Also, a steep electrode potential gradient, E(x), within the crevice has been measured using a microprobe connected to a SCE and controlled by a 3-D manipulator, and the observed locations of corrosion on the crevice wall are similar to the locations seen previously for systems in which it was clear that the shift of E(x) into the active peak region of the polarization curve on the crevice wall stabilized the crevice corrosion process. In chapter 3, focuses on the corrosion of a peak aged aluminum 6111-like alloy of 1.47% copper using the artificial pit configuration (pencil electrode) with relatively larger specimens in the form of plates rather than wires. The sample which was flush with the surface of the epoxy resin mount was anodically polarized in neutral NaCl solutions of different concentrations and pH 6.9. The alloy dissolved uniformly at a certain rate to form a local cell with epoxy resin walls and the alloy surface as its bottom. The potential drop profile within the cavity was recorded on a daily basis. It showed that the total potential drop is in the order of 50 mV. The pH in the local cell was measured using a commercial mono pH microelectrode coupled with a homemade Pyrex (glassy) microprobe connected to a SCE and controlled by a 3-D manipulator. pH measurements showed the medium within the cavity is alkaline with a pH ranges from 9--12. Also, the chloride ion concentration within the local cell was measured using a mono Ag/AgCl microelectrode coupled with the same glassy microprobe, which is connected to a SCE. (Abstract shortened by UMI.)

  14. Electrochemical growth behavior, surface properties, and enhanced in vivo bone response of TiO2 nanotubes on microstructured surfaces of blasted, screw-shaped titanium implants

    PubMed Central

    Sul, Young-Taeg

    2010-01-01

    TiO2 nanotubes are fabricated on TiO2 grit-blasted, screw-shaped rough titanium (ASTM grade 4) implants (3.75 × 7 mm) using potentiostatic anodization at 20 V in 1 M H3PO4 + 0.4 wt.% HF. The growth behavior and surface properties of the nanotubes are investigated as a function of the reaction time. The results show that vertically aligned nanotubes of ?700 nm in length, with highly ordered structures of ?40 nm spacing and ?15 nm wall thickness may be grown independent of reaction time. The geometrical properties of nanotubes increase with reaction time (mean pore size, pore size distribution [PSD], and porosity ?90 nm, ?40–127 nm and 45%, respectively for 30 minutes; ?107 nm, ?63–140 nm and 56% for one hour; ?108 nm, ?58–150 nm and 60% for three hours). It is found that the fluorinated chemistry of the nanotubes of F-TiO2, TiOF2, and F-Ti-O with F ion incorporation of ?5 at.%, and their amorphous structure is the same regardless of the reaction time, while the average roughness (Sa) gradually decreases and the developed surface area (Sdr) slightly increases with reaction time. The results of studies on animals show that, despite their low roughness values, after six weeks the fluorinated TiO2 nanotube implants in rabbit femurs demonstrate significantly increased osseointegration strengths (41 vs 29 Ncm; P = 0.008) and new bone formation (57.5% vs 65.5%; P = 0.008) (n = 8), and reveal more frequently direct bone/cell contact at the bone–implant interface by high-resolution scanning electron microscope observations as compared with the blasted, moderately rough implants that have hitherto been widely used for clinically favorable performance. The results of the animal studies constitute significant evidence that the presence of the nanotubes and the resulting fluorinated surface chemistry determine the nature of the bone responses to the implants. The present in vivo results point to potential applications of the TiO2 nanotubes in the field of bone implants and bone tissue engineering. PMID:20463928

  15. Increased carbon uptake in marine sediment enabled by naturally occurring electrical conductors

    NASA Astrophysics Data System (ADS)

    Nielsen, M. E.; Cahoon, D. P.; Girguis, P. R.

    2011-12-01

    Reduction-oxidation (redox) gradients are common across marine sediment-water interfaces and result from microbially-mediated reactions such as the oxidation of organic matter coupled to reduction of electron acceptors. Most microbes living in sediments do not have direct access to oxygen in their immediate environment, however it has recently been shown that sulfide-oxidizing microbes may employ extracellular electron transfer (EET) to couple the oxidation of sulfide in the anoxic zone to reduction of oxygen at the sediment-water interface located several centimeters away. However, no mechanisms for this observed phenomenon have been validated. Accordingly, we tested the hypothesis that conductive minerals in marine sediment (specifically pyrite) can couple spatially separated redox reactions such as anaerobic respiration and oxygen reduction. Marine sediment was amended with naturally occurring pyrite in varying concentrations (0, 2, 10 and 50 weight-percent) and then incubated with 10 ?M 13C-labeled acetate. After six hours, the treatments with the greatest amount of added pyrite showed the greatest incorporation of acetate from the labeled pool. The fraction of labeled acetate incorporation more than doubled in the 10 and 50 weight-percent treatments compared to the control sediment. We also designed a circuit to investigate the electrical conductivity of the sediment treatments as a function of added pyrite. A potentiostat was used to establish a known voltage across a sediment column and current was measured. Resistance (the inverse of conductance) was calculated from a linear fit of current data over a range of voltages ranging from 0.5 to 1.0 V. The treatments with added pyrite had lower resistance than background sediment, with the lowest resistance corresponding to the 50% pyrite treatment. We also examined the effect of varying pyrite content on microbial community composition using massively parallel 16S rRNA sequencing. Microbial community analyses reveal that the majority of microbes in the sediment belong to the deltaproteobacteria or gammaproteobacteria classes, which have been previously implicated in EET in laboratory and field-based bioelectrochemical studies. These data force us to reconsider the role of EET and conductive minerals in organic carbon cycling -particularly in metaliferous sediments- and suggest that EET-enabled anaerobic metabolism may represent a significant contribution to marine carbon cycling.

  16. Sodium molybdate - an additive of choice for enhancing the performance of AC/AC electrochemical capacitors in a salt aqueous electrolyte.

    PubMed

    Abbas, Q; Ratajczak, P; Béguin, F

    2014-01-01

    Sodium molybdate (Na2MoO4) has been used as an additive to 1 mol L(-1) lithium sulfate electrolyte for electrochemical capacitors based on activated carbon (AC) electrodes, in order to reduce the corrosion of stainless steel current collectors. We demonstrate that the MoO4(2-) anions improve the overall capacitance owing to pseudofaradaic processes. In a two-electrode cell, capacitance values of 121 F g(-1) have been achieved up to 1.6 V using 1 mol L(-1) Li2SO4 + 0.1 mol L(-1) Na2MoO4, as compared to 103 F g(-1) when 1 mol L(-1) Li2SO4 is used. Further, by using a two-electrode setup equipped with a reference electrode, we could demonstrate that, at 1.6 V, the positive electrode potential reaches a value of 0.96 V vs. NHE in 1 mol L(-1) Li2SO4, crossing the thermodynamic potential limit of oxygen evolution (Eox = 0.846 V vs. NHE), and the pitting potential, Epit = 0.95 V vs. NHE. By contrast, in 1 mol L(-1) Li2SO4 + 0.1 mol L(-1) Na2MoO4, the pseudofaradaic contribution occurring at -0.05 V vs. NHE due to MoO4(2-) anions drives the positive electrode to reach only 0.798 V vs. NHE. Hence, the oxidation of the AC and corrosion of the stainless steel current collector at the positive electrode are unlikely in Li2SO4 + Na2MoO4 when the capacitor operates at 1.6 V. During potentiostatic floating of the capacitor at 1.6 V for 120 hours in Li2SO4 + Na2MoO4, the capacitance and resistance remain constant at 125 F g(-1) and ~1.0 ?, respectively, while the resistance increases from 1.4 ? to 3.1 ? in Li2SO4. Overall, the addition of MoO4(2-) anions to Li2SO4 aqueous electrolyte allows the capacitance to be enhanced, corrosion of the positive stainless steel current collector to be inhibited and the AC/AC electrochemical capacitor to demonstrate stable performance up to 1.6 V. PMID:25427248

  17. Mechanistic, kinetic, and processing aspects of tungsten chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Stein, David

    This dissertation presents an investigation into tungsten chemical mechanical polishing (CMP). CMP is the industrially predominant unit operation that removes excess tungsten after non-selective chemical vapor deposition (CVD) during sub-micron integrated circuit (IC) manufacture. This work explores the CMP process from process engineering and fundamental mechanistic perspectives. The process engineering study optimized an existing CMP process to address issues of polish pad and wafer carrier life. Polish rates, post-CMP metrology of patterned wafers, electrical test data, and synergy with a thermal endpoint technique were used to determine the optimal process. The oxidation rate of tungsten during CMP is significantly lower than the removal rate under identical conditions. Tungsten polished without inhibition during cathodic potentiostatic control. Hertzian indenter model calculations preclude colloids of the size used in tungsten CMP slurries from indenting the tungsten surface. AFM surface topography maps and TEM images of post-CMP tungsten do not show evidence of plow marks or intergranular fracture. Polish rate is dependent on potassium iodate concentration; process temperature is not. The colloid species significantly affects the polish rate and process temperature. Process temperature is not a predictor of polish rate. A process energy balance indicates that the process temperature is predominantly due to shaft work, and that any heat of reaction evolved during the CMP process is negligible. Friction and adhesion between alumina and tungsten were studied using modified AFM techniques. Friction was constant with potassium iodate concentration, but varied with applied pressure. This corroborates the results from the energy balance. Adhesion between the alumina and the tungsten was proportional to the potassium iodate concentration. A heuristic mechanism, which captures the relationship between polish rate, pressure, velocity, and slurry chemistry, is presented. In this mechanism, the colloid reacts with the chemistry of the slurry to produce active sites. These active sites become inactive by removing tungsten from the film. The process repeats when then inactive sites are reconverted to active sites. It is shown that the empirical form of the heuristic mechanism fits all of the data obtained. The mechanism also agrees with the limiting cases that were investigated.

  18. Revisiting the crevice corrosion of stainless steel and aluminum in chloride solutions---The role of electrode potential

    NASA Astrophysics Data System (ADS)

    Deforce, Brian S.

    Although the crevice corrosion of stainless steel and aluminum in chloride solutions has been studied extensively, there is little agreement on the mechanism of crevice corrosion for these materials. The present study attempted to resolve the ambiguity of the crevice corrosion mechanism by first reviewing previous relevant studies and then, by conducting an in-depth study of crevice corrosion with a focus on electrode potential and the IR mechanism. The crevice corrosion of aluminum (99.999 wt. %, AA2024) and stainless steel (304 and 444) in neutral and mildly acidic chloride solutions was investigated. For each alloy system, polarization curves were generated in simulated crevice solutions and potentiostatic crevice corrosion experiments with varying crevice gap opening dimensions were performed. Current and electrode potential along the crevice wall were measured. In-situ photographs of the developing crevice corrosion were obtained and in-situ and ex-situ pH measurements were performed. For the stainless steels, potentiodynamic and potentiostatic methods, including a novel applied potential shift method, were used in an attempt of detect the development of an anodic peak in a passive system, prior to the onset of crevice corrosion. Crevice corrosion of aluminum in a pH 6, 0.6M NaCl solution was not found to occur under open circuit or polarized conditions. Polarization curves in simulated crevice solutions did not show an anodic peak. Based on the polarization behavior, the IR mechanism correctly predicts the absence of crevice corrosion for this system. Crevice corrosion was observed for aluminum in a mildly acidic (pH 3), chloride free solution and found to be consistent with the IR mechanism. In this solution, crevice corrosion resulting in severe material loss was observed and a high current (10 mA) was measured. This is the first time crevice corrosion of aluminum, as indicated by significant material loss and high measured current, has been reported. Also of importance, is the fact that the corrosion occurred in the absence of pitting corrosion. The cause of corrosion in this case can be explained by alkalization of the crevice due to a high rate of hydrogen evolution reaction, driven by a potential drop within the crevice. For stainless steels, crevice corrosion was clearly demonstrated in a neutral 0.6M NaCl solution and in two mildly acidic simulated crevice solutions: pH 2, 0.6M NaCl and pH 1, 3M NaCl. The conclusive evidence of the occurrence of crevice corrosion was a high measured current and photographic evidence of showing severe material loss within the crevice and no attack on the uncreviced surfaces. All observations of the propagation of crevice corrosion for 304 and 444 were consistent with the IR mechanism. Additional efforts to understand the mechanism of stainless steel crevice corrosion focused on studying the initiation. No evidence was found to suggest initiation occurs due to a reduction of the pitting potential from chloride accumulation. Initiation of crevice corrosion was found to occur after the development of an anodic peak. This is the first time an anodic peak has been detected prior to the onset of crevice corrosion. This novel observation provides proof that an anodic peak can develop in a passive system. Since the IR mechanism requires an anodic peak, this observation provides convincing evidence for the applicability of IR mechanism in a passive system. Equally important, the observation shows that while compositional change is required to develop the anodic peak, another step is necessary to initiate crevice corrosion. Crevice corrosion mechanisms that rely solely on compositional change are inadequate in that they do not provide an explanation for the additional step. However, the IR mechanism clearly defines this additional step as the initiation event, IR>Deltaphi*, at which point the crevice wall in contact with the acidified crevice solution is activated and crevice corrosion begins. In summary, crevice corrosion of aluminum and stainless steels was clearly demonstrated

  19. Reductive electrochemical remediation of emerging and regulated disinfection byproducts.

    PubMed

    Radjenovi?, Jelena; Farré, Maria José; Mu, Yang; Gernjak, Wolfgang; Keller, Jurg

    2012-04-15

    Long-term exposure to low concentrations of disinfection byproducts (DBPs) in drinking water has been associated with increased human-health risks of bladder cancer and adverse reproductive outcomes. In this study, we investigated electrochemical reduction utilizing a resin-impregnated graphite cathode for the degradation of 17 DBPs (i.e. halomethanes, haloacetonitriles, halopropanones, chloral hydrate and trichloronitromethane) at low ?g L(-1) concentration levels. The reduction experiments were potentiostatically controlled at cathode potentials -700, -800 and -900 mV vs Standard Hydrogen Electrode (SHE) during 24 h. At the lowest potential applied (i.e. -900 mV vs SHE), the disappearance of DBPs from the solution after 24 h of reduction was >70%, except for chloroform (32%), 1,1-dichloropropanone (48%), and chloral hydrate (31%). Due to the participation of several removal mechanisms (e.g. electrochemical reduction, adsorption, volatilization and/or hydrolysis) it was not possible to distinguish the removal efficiencies of electrochemical reduction of individual compounds. Adsorption of the more hydrophilic DBPs (i.e. haloacetonitriles, chloral hydrate, and 1,1-dichloropropanone) onto the electrode seems to be affected by the cathode polarization, as the removals observed in the open circuit experiments were significantly higher than the ones obtained in electrochemical reduction under the same conditions. The overall efficiency of reduction was estimated based on the analyses of the released Cl(-), Br(-) and I(-) ions. Nearly complete C-I bond cleavage was achieved at all three potentials applied, and from the theoretically predicted release of I(-) ions, calculated based on the removed DBPs, 86 ± 9 to 92 ± 1% was measured in the catholyte solution at -700 to -900 mV vs SHE. Debromination efficiencies obtained were 74 ± 3, 79 ± 6 and 68 ± 4% at -700, -800 and -900 mV vs SHE, while for C-Cl bond cleavage the obtained values were 69 ± 1, 72 ± 1 and 76 ± 4%, respectively. Nevertheless, dechlorination efficiencies are to be considered as approximate, since an increase in Cl(-) concentration was observed in the open circuit experiments due to the hydrolysis of some of the chlorine-containing DBPs. Although the Coulombic efficiencies for DPBs dehalogenation were only 1.9 ± 0.3 (-900 mV vs SHE) -4.1 ± 0.2% (-700 mV vs SHE), relatively low energy consumption of the process was observed, estimated at 72 ± 2 Wh m(-3) at -900 mV vs SHE for the concentration range of DBPs in this study (i.e. 65.3-129.7 ?g L(-1)). The study demonstrated that reductive electrochemical treatment has the potential to be a modern remediation technology for the removal of low concentrations of halogenated DBPs in water. PMID:22265615

  20. Coupled Multi-Electrode Investigation of Crevice Corrosion of 316 Stainless Steel and NiCrMo Alloy 625

    SciTech Connect

    F. Bocher; F.J. Presuel-Moreno; J.R. Scully

    2006-06-08

    Crevice corrosion is currently mostly studied using either one of two techniques depending on the information desired. The first method involves two multicrevice formers or washers fastened on both sides of a sample plate. This technique provides exposure information regarding the severity of crevice corrosion (depth, position, frequency of attack) but delivers little or no electrochemical information. The second method involves the potentiodynamic or potentiostatic study of an uncreviced sample in a model crevice solution or under a crevice former in aggressive solution where crevice corrosion may initiate and propagate and global current is recorded. However, crevice corrosion initiation and propagation behavior is highly dependent on exact position in the crevice over time. The distance from the crevice mouth will affect the solution composition, the pH, the ohmic potential drop and the true potential in the crevice. Coupled multi-electrode arrays (MEA) were used to study crevice corrosion in order to take in account spatial and temporal evolution of electrochemistry simultaneously. Scaling laws were used to rescale the crevice geometry while keeping the corrosion electrochemical properties equivalent to that of a natural crevice at a smaller length scale. one of the advantages was to be able to use commercial alloys available as wires electrode and, in the case of MEA, to spread the crevice corrosion over many individual electrodes so each one of them will have a near homogeneous electrochemical behavior. The initial step was to obtain anodic polarization curves for the relevant material in acid chloride solution which simulated the crevice electrolyte. using the software Crevicer{trademark}, the potential distribution inside the crevice as a function of the distance from the crevice mouth was determined for various crevice gaps and applied potentials, assuming constant chemistry throughout the crevice. The crevice corrosion initiation location x{sub crit} is the position where the potential drops to E{sub Flade}. Figure 1 illustrates the resulting x{sub crit} vs. G scaling laws for 316 Stainless Steel in 1 M HCl at 50 C. The coupled multi-wire array is composed of one hundred identical 316 Stainless Steel wires in a five by twenty formation inserted in a groove of a 316 Stainless Steel rod such that the ends of the wires are flush mounted with the rod. The 100 wires are coupled electrically through in-line zero resistance ammeters. The diameter of the wires (250 {micro}m) was chosen so that x{sub crit} (critical initiation distance from the crevice mouth) and the expected zone of crevice corrosion (predicted from the scaling law) would be larger than the radius of a single wire. The array created a flush mounted planar electrode with the surface/volume ratio obtained in planar crevices. The observation of the current evolution as a function of position inside and outside the crevice as function of time was made possible as illustrated in Figure 2 in 0.6 M NaCl at 50 C.

  1. Effect of slurry chemicals on chemical-mechanical planarization of copper

    NASA Astrophysics Data System (ADS)

    Hong, Youngki

    An important component of the slurries used in chemical mechanical planarization (CMP) is an appropriately chosen corrosion/dissolution inhibitor, which facilitates selective material removal from protrusions while protecting recessed regions of the surface. The present work demonstrates the utility of two environmentally benign anionic surfactants, sodium dodecyl sulfate (SDS) and ammonium dodecyl sulfate (ADS) as dissolution inhibitors. Using these surfactants in a standard slurry (1 wt% glycine with 5 wt% H2O 2 at pH = 4.0) typically used for Cu CMP, and combining measurements of open circuit potentials and contact angles with those of Cu removal rates, we show that both SDS and ADS suppress chemical dissolution and polish rates of Cu. The dissolution inhibition efficiencies of ADS and SDS measured in these experiments are found to be superior to those of benzotriazole (BTA), a traditional inhibiting agent used for copper CMP. It has been demonstrated that ADS can also be utilized as an inhibiting agent for the application in electrochemical-mechanical planarization (ECMP) of copper. Using an acidic electrolyte of glycine and H2O 2, and small Cu discs, we show that the corrosion inhibition efficiency of ADS is superior to that of benzotriazole even in ECMP application. The relation between PE of Cu patterns and complexing agents has been investigated by measuring removal rates and surface topographies from patterns created on blanket Cu films. It has been observed that PE is dependent on the step height and drops significantly beyond a threshold step height that is in the range of 1000 A. Since the same type of polishing pad (IC 1400) was used in all the experiments, it might be the complexing agent that determines this characteristic PE threshold. Also, the huge increase in Cu dissolution rate for the citric acid system with increasing temperature appears to be responsible for the low PE values measured for this system. The synergetic effect of mixtures of ADS and BTA on Cu planarization has also been demonstrated. A model slurry containing a mixture of 3 mM ADS and 0.5 mM BTA shows much lower dissolution rate of Cu than that containing 10 mM BTA while sustaining similar polish rates of Cu at 2 psi. The planarization efficiency evaluated using the topographies created on Cu film surface (width: ˜ 15mum, depth: ˜ 5000 A) also shows better results while using the mixture of 3mM ADS and 0.5 mM BTA compared to 10 mM BTA. The relation between the copper dissolution rate and planarization efficiency is shown to be inversely logarithmically proportional to each other. The information from potentiostatic polarization, contact angle, UV/VIS spectroscopy and FTIR spectroscopy suggests that the synergetic effect of the mixture of BTA and ADS is due to electrostatic attraction between Cu/Cu-BTA complex and dodecyl sulfate as well as the complexation of Cu-BTA-dodecyl sulfate.

  2. Modeling the environmental dependence of localized corrosion evolution in AA7075-T651

    NASA Astrophysics Data System (ADS)

    Cavanaugh, Mary Katherine

    In this work, the localized corrosion of AA7075-T651 as a function of environment is empirically modeled using neural network approaches. The modeling approach is divided into three stages: pit initiation, corrosion mode differentiation, and propagation. This study characterized the effect of temperature (0-60°C), pH (2.5-12.5), [Cl-] (0.01-0.6M NaCl), electrochemical potential (-780 to -640mVSCE), orientation (LS, ST), time (1-720h), and alloy microstructure on each stage. Examination of metastable pits during potentiostatic testing was employed to study pit initiation, while differentiation and propagation were investigated by extensive observation of corrosion after immersion exposure using optical profilometry and scanning electron microscopy (SEM). Pit initiation rate, lambda, was shown to have an exponential dependence on electrochemical potential, E, a logarithmic dependence on [Cl-], an exponential dependence on temperature, and peaked at intermediate pH. Additionally, lambda scaled with the number density of intermetallic particles. Pitting event intensity (related to the peak current sustained) was also an important parameter in this study. Combining the effects of pit initiation rate and event intensity, [Cl-] and temperature had a profound impact on the total damage incurred (the total charge passed from pitting events). It was established that pit location was determined by the alloy microstructure, while the environment determined the severity of damage. Unlike previous studies that indicate lambda decreases exponentially with time, the pit initiation rate was shown to remain constant with time for most of the conditions studied. A trained neural network model was able to accurately predict lambda as a function of environmental variables. The neural network was able to reflect previously observed trends in this work and in the literature. Pitting was determined to be the main mode of localized attack in this study, since no intergranular corrosion (IGC) was detected. Grain boundary attack (distinguished from IGC by presenting on the exposed face rather than in the cross-section), uniform corrosion, and pits forming at both anodic and cathodic particles were observed. Circumferential pits were shown to occur when the reduction current on cathodic particles was ˜10 times larger than icorr in a given environment. Solution pH was shown to have a large effect on the corrosion morphology, while temperature and exposure time affected the severity of damage. [Cl-] and orientation had a limited effect on the damage accumulation in this alloy. The number of pit sites after 720h exposure was determined to be ˜100-200/mm 2 in all environments investigated. Tested neural network models were able to predict, not only the maximum pit depth and diameter as a function of environment, but also entire pit depth and diameter distributions. Pit growth kinetics varied depending on the exposure conditions, but most environments followed t1/3 kinetics, which is within the range reported in the literature.

  3. Technological aspects of corrosion control in metallic systems

    NASA Astrophysics Data System (ADS)

    Taylor, Matthew Logan

    Three corrosion control technologies were investigated, including the effect of nitrogen on the passivity of chromium in sulfate solutions, possible issues associated with the use of amines in steam turbine environments and the microstructure of naval advanced amorphous coatings. Nitrogen (N) is a minor alloying element commonly used to increase the strength of steels by stabilizing the austenite phase. Physical vapor deposited chromium + nitrogen (0, 6.8 and 8.9 at.%N) coatings were investigated as a model system, to test the model. Because Cr passive films have been observed to be generally n-type semiconductors, an impedance function containing a n-type Faradaic impedance was constructed and optimized to electrochemical impedance spectra for the model system at pH 4,7 and 10 1M sulfate solution at 30°C. An apparent deviation from theory was observed, however. The n-type model predicted steady state currents which were independent of potential, while the observed current densities had a positive correlation with potential. Mott-Schottky analysis revealed that the test potentials were within the n-p transition and p-type potential range, which resolves the apparent deviation. Despite this difficulty, however, the impedance model produced reasonably accurate results, calculating current densities to within one order of magnitude of the measured steady state currents where anodic currents were available and passive film thicknesses on the order of 1-2 nm. Various amines are commonly used to inhibit corrosion in thermal power generation systems, including steam turbines, by increasing the pH. However, during the shutdown phase of the power plant, it is possible for these inhibitors to concentrate and cause corrosion of the turbine rotor. The effect of two ammine inhibitors (monoethanolamine and dimethylamine) on the passivity of ASTM A470/471 steel is investigated in a simulated turbine environment at pH 7, and temperatures of 95°C and at 175°C. Potentiodynamic scans and potentiostatic measurements revealed that the steel depassivated with high (0.1M) concentrations of monoethanolamine, in combination with acetate. Because the steel depassivated at low potentials and at neutral pH, it is unlikely to be acid or transpassive depassivation. The proposed mechanism for this depassivation is resistive depassivation, whereby the potential drop incurred by the precipitated outer-layer robs the barrier layer of the passive film of the potential required to maintain a finite film thickness. High velocity oxy-fuel (HFOV) coatings are employed in maritime environments to protect against corrosion and wear. The performance of such coatings is dominated by flaws in the microstructure, such as porosity, delamination and secondary phases. A nondestructive evaluation technique that is capable of determining the quality of a HVOF coating was developed, based on electrochemical impedance spectroscopy (EIS). The EIS measurement was correlated to the microstructure observed via scanning electron microscopy (SEM). Because a transmission line model was unable to provide discriminatory information, a convenient mathematical impedance function was constructed, with two separated time constants defined by constant phase elements, with time constants for a "fast" and a "slow" process. Enabling the impedance studies above is a new software package for fitting complicated impedance functions of up to 50 parameters to complex impedance data, developed specifically for this work. The curve-fitting software utilizes differential evolution, an evolutionary algorithm which is relatively new to the field of impedance modeling, enabling the operator to obtain high quality fits without the need for excellent starting guesses, taking trial and error out of the curve-fitting process and vastly improving the man-hour efficiency involved in optimizing complicated impedance functions such as the Faradaic impedance of the Point Defect Model. (Abstract shortened by UMI.)

  4. Portable Hand-Held Electrochemical Sensor for the Transuranics

    SciTech Connect

    Dale D. Russell, William B. Knowlton, Ph.D.; Russel Hertzog, Ph.D

    2005-11-25

    During the four-year period of the grant all of the goals of the originally proposed work were achieved, and some additional accomplishments are here reported. Two types of sensors were designed and built in the lab, capable of detecting uranium, plutonium and thorium at the 10 part-per-trillion level. The basis of both sensor types is a specially designed polymer having selective binding sites for actinyl ions of the form MO{sub 2}{sup 2+}(aq), where M is any actinide in the +6 oxidation state. This binding site also traps ions of the form MO{sub 2}{sup +}(aq), where M is any actinide in the +4 oxidation state. In this way, the polymer is responsive to the two most common water-soluble ions of the actinide series. The chelating ring responsible for binding the actinyl ions was identified from the literature, calix[n]arene where n = 6. Several versions of this sensing polymer were coated on conductive substrates and demonstrated for actinide sensing. An optimized sensor was developed and is fully described in this report. It has a polymer bilayer, fabricated under the particular conditions given below. Two different operating modes were demonstrated having different capabilities. One is the chemFET mode (a FET is a field effect transistor) and the other is the voltammetric mode. These two sensors give complementary information regarding the actinide species in a sample. Therefore our recommendation is that both be used together in a probe. A detailed design for such a probe has been filed as a patent application with the United States Patent Office, and is patent pending. The sensing polymer incorporating this actinyl-chelating ring was tested under a variety of conditions and the operating limits were determined. A full factorial experiment testing the polymerization method was conducted to optimize performance and characteristics of this polymer. The actinyl-sensing polymer was also deposited on the gate of a field effect transistor (FET) and demonstrated as a sensitive detector for uranium. Millimeter scale electrodes, operated by a hand-held instrument assembled in this lab and operated in the voltammetric mode, were transported to the DOE-Nevada test site (Las Vegas, NV) where field detection and quantitation of plutonium, uranium, and a mixture of these two elements was also demonstrated. Several probe designs were prepared, built and tested including probes with movable protective windows. A miniature, battery powered potentiostat was designed, built and demonstrated for use in a hand-held field portable instrument. This work was performed largely by undergraduates who gained valuable research experience, and many of them have continued on to graduate schools. In addition, they all gained exposure to and appreciation for national security research, in particular non-proliferation research. Four graduate students participated and one earned the MS degree on this project.

  5. Anode materials for hydrogen sulfide containing feeds in a solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Roushanafshar, Milad

    SOFCs which can directly operate under high concentration of H2S would be economically beneficial as this reduces the cost of gas purification. H2S is highly reactive gas specie which can poison most of the conventional catalysts. As a result, developing anode materials which can tolerate high concentrations of H2S and also display high activity toward electrochemical oxidation of feed is crucial and challenging for this application. The performance of La0.4Sr0.6TiO3+/-delta -Y0.2Ce0.8O2-delta (LST-YDC) composite anodes in solid oxide fuel cells significantly improved when 0.5% H2 S was present in syngas (40% H2, 60% CO) or hydrogen. Gas chromatography and mass spectrometry analyses revealed that the rate of electrochemical oxidation of all fuel components improved when H2S containing syngas was present in the fuel. Electrochemical stability tests performed under potentiostatic condition showed that there was no power degradation for different feeds, and that there was power enhancement when 0.5% H2S was present in various feeds. The mechanism of performance improvement by H2S was discussed. Active anodes were synthesized via wet chemical impregnation of different amounts of La0.4Ce0.6O1.8 (LDC) and La 0.4Sr0.6TiO3 (L4ST) into porous yttria-stabilized zirconia (YSZ). Co-impregnation of LDC with LS4T significantly improved the performance of the cell from 48 mW.cm-2 (L4ST) to 161 mW.cm -2 (LDC-L4ST) using hydrogen as fuel at 900 °C. The contribution of LDC to this improvement was investigated using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). EIS measurements using symmetrical cells showed that the polarization resistance decreased from 3.1¦O.cm 2 to 0.5 O.cm2 when LDC was co-impregnated with LST, characterized in humidified H2 (3% H2O) at 900 °C. In addition, the microstructure of the cell was modified when LDC was impregnated prior to L4ST into the porous YSZ. TEM and SEM results showed that the L4ST particles were finely distributed into the anode structure in the presence of LDC when compared to the L4ST alone. The rate of electrochemical oxidation of H2 and CH4 feeds over L0.4Sr0.6TiO3+/-delta and La0.4Ce0.6O1.8-La0.4Sr0.6 TiO3+/-delta impregnated solid oxide fuel cell anodes increased significantly when H2S (0.5%) was present. There was recovery of the fuel cell under galvanostatic conditions at 40 mA.cm -2 and 800 °C in both H2S (0.5%)-H2 and H2S (0.5%)-CH4 after switching to H2 as fuel. Mass spectrometry analysis revealed the effect of H2S (0.5%) on the enhancement of CH4 electrochemical oxidation.