Science.gov

Sample records for potentiostats

  1. Redox reaction rates using potentiostatic coulometry

    SciTech Connect

    Ramette, R.W.; Harris, R.Z.; Bengali, A.A.; Noll, R.J.

    1987-01-01

    A new method based on potentiostatic coulometry was used to study the kinetics of the aqueous redox reactions between the ions chlorate/iodide, bromate/iodide, and bromate/bromide. The halogen product was continuously and rapidly reduced back to halide at a large platinum gauze cathode, the current being a direct measure of reaction rate and the accumulated charge serving to measure the extent of reaction. The reactions were studied at several temperatures, and activation entropies and enthalpies were calculated.

  2. Wide dynamic range CMOS potentiostat for amperometric chemical sensor.

    PubMed

    Wang, Wei-Song; Kuo, Wei-Ting; Huang, Hong-Yi; Luo, Ching-Hsing

    2010-01-01

    Presented is a single-ended potentiostat topology with a new interface connection between sensor electrodes and potentiostat circuit to avoid deviation of cell voltage and linearly convert the cell current into voltage signal. Additionally, due to the increased harmonic distortion quantity when detecting low-level sensor current, the performance of potentiostat linearity which causes the detectable current and dynamic range to be limited is relatively decreased. Thus, to alleviate these irregularities, a fully-differential potentiostat is designed with a wide output voltage swing compared to single-ended potentiostat. Two proposed potentiostats were implemented using TSMC 0.18-?m CMOS process for biomedical application. Measurement results show that the fully differential potentiostat performs relatively better in terms of linearity when measuring current from 500 pA to 10 uA. Besides, the dynamic range value can reach a value of 86 dB. PMID:22294899

  3. Wide Dynamic Range CMOS Potentiostat for Amperometric Chemical Sensor

    PubMed Central

    Wang, Wei-Song; Kuo, Wei-Ting; Huang, Hong-Yi; Luo, Ching-Hsing

    2010-01-01

    Presented is a single-ended potentiostat topology with a new interface connection between sensor electrodes and potentiostat circuit to avoid deviation of cell voltage and linearly convert the cell current into voltage signal. Additionally, due to the increased harmonic distortion quantity when detecting low-level sensor current, the performance of potentiostat linearity which causes the detectable current and dynamic range to be limited is relatively decreased. Thus, to alleviate these irregularities, a fully-differential potentiostat is designed with a wide output voltage swing compared to single-ended potentiostat. Two proposed potentiostats were implemented using TSMC 0.18-?m CMOS process for biomedical application. Measurement results show that the fully differential potentiostat performs relatively better in terms of linearity when measuring current from 500 pA to 10 uA. Besides, the dynamic range value can reach a value of 86 dB. PMID:22294899

  4. Instrumentation for potentiostatic corrosion studies with distilled water

    NASA Technical Reports Server (NTRS)

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

    1969-01-01

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

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

    PubMed

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

    2015-10-01

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

  6. Development of a low cost potentiostat using ATXMEGA32

    NASA Astrophysics Data System (ADS)

    Muid, Abdul; Djamal, Mitra; Wirawan, Rahadi

    2014-03-01

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

  7. Design of a CMOS Potentiostat Circuit for Electrochemical Detector Arrays

    PubMed Central

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

    2010-01-01

    High-throughput electrode arrays are required for advancing devices for testing the effect of drugs on cellular function. In this paper, we present design criteria for a potentiostat circuit that is capable of measuring transient amperometric oxidation currents at the surface of an electrode with submillisecond time resolution and picoampere current resolution. The potentiostat is a regulated cascode stage in which a high-gain amplifier maintains the electrode voltage through a negative feedback loop. The potentiostat uses a new shared amplifier structure in which all of the amplifiers in a given row of detectors share a common half circuit permitting us to use fewer transistors per detector. We also present measurements from a test chip that was fabricated in a 0.5-?m, 5-V CMOS process through MOSIS. Each detector occupied a layout area of 35?m 15?m and contained eight transistors and a 50-fF integrating capacitor. The rms current noise at 2kHz bandwidth is ? 110fA. The maximum charge storage capacity at 2kHz is 1.26 106 electrons. PMID:20514150

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

    SciTech Connect

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

    1996-05-01

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

  9. Potentiostatic current and galvanostatic potential oscillations during electrodeposition of cadmium.

    PubMed

    López-Sauri, D A; Veleva, L; Pérez-Ángel, G

    2015-09-14

    Cathodic current and potential oscillations were observed during electrodeposition of cadmium from a cyanide electrolyte on a vertical platinum electrode, in potentiostatic and galvanostatic experiments. Electrochemical impedance spectroscopy experiments revealed a region of negative real impedance in a range of non-zero frequencies, in the second descending branch with a positive slope of the N-shape current-potential curve. This kind of dynamical behaviour is characteristic of the HN-NDR oscillators (oscillators with the N-Shape current-potential curve and hidden negative differential resistance). The oscillations could be mainly attributed to the changes in the real active cathodic area, due to the adsorption of hydrogen molecules and their detachment from the surface. The instabilities of the electrochemical processes were characterized by time series, Fast Fourier Transforms and 2-D phase portraits showing quasi-periodic oscillations. PMID:26243301

  10. Metastable pitting of carbon steel under potentiostatic control

    SciTech Connect

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

    1999-03-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

    Dryden, Michael D M; Wheeler, Aaron R

    2015-01-01

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

  13. 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.

    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.

  14. 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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

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

    SciTech Connect

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

    1993-12-01

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

  17. Measuring the Repassivation Potential of Alloy 22 Using the Potentiodynamic - Galvanostatic - Potentiostatic Method

    SciTech Connect

    Evans, K J; Rebak, R B

    2007-04-27

    Traditionally, the susceptibility of Alloy 22 (N06022) to suffer crevice corrosion has been measured using the Cyclic Potentiodynamic Polarization (CPP) technique (ASTM G 61). When the alloy is not very susceptible to crevice corrosion, the values of repassivation potential obtained using the CPP technique are not highly reproducible. To circumvent the large uncertainty in the values of the repassivation potential by the CPP method, the repassivation potential of Alloy 22 may be measured using a slower method that combines sequentially potentiodynamic, galvanostatic and potentiostatic treatments (this method is called the Tsujikawa-Hisamatsu Electrochemical or THE method). In the THE method the anodic charge is applied to the specimen in a more controlled manner, which avoids driving the alloy to transpassivity and therefore results in more reproducible repassivation potential values. Results using THE method under various testing conditions are presented. A new standard has been prepared for ASTM balloting for the THE method. The round robin matrix results are also discussed.

  18. Purification of supporting electrolyte by a moderate current pre-electrolysis potentiostat

    SciTech Connect

    Brown, B.B.; Paul, D.W.; Ridgway, T.H.; Heineman, W.R.

    1986-01-01

    Anodic stripping voltammetry (ASV) is a well known technique for determining ppb levels of metal ions in environmental samples. One problem in the determination of metal ions at this low concentration level is the contribution of comparatively large amounts of metal ions originating from supporting electrolyte that is added to the sample and used to prepare standards. Pre-electrolysis has been found to reduce the heavy metal content in supporting electrolyte solutions to a few ppb. A moderate current, low cost, potentiostat and an electrochemical cell have been developed for the purification of supporting electrolytes by pre-electrolysis. It provides the moderate current needed at the start of the electrolysis especially during double layer charging as well as the small faradaic current needed through the duration of the electrolysis.

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

    PubMed Central

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

    2011-01-01

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

  20. Anomalous codeposition of Fe-Ni alloys and Fe-Ni-SiO{sub 2} composites under potentiostatic conditions: Experimental study and mathematical model

    SciTech Connect

    Ramasubramanian, M.; Popova, S.N.; Popov, B.N.; White, R.E.; Yin, K.M.

    1996-07-01

    A mathematical model has been developed to describe the electrodeposition of Fe-Ni alloys and Fe-Ni-SiO{sub 2} composites under potentiostatic conditions. This model can be used to predict the polarization behavior, partial current densities, and alloy composition of each of the components as a function of the applied potential. Fe-Ni-SiO{sub 2} samples were deposited on platinum rotating disk electrodes from sulfate electrolytes under potentiostatic conditions, and the results obtained were compared to the model. The model predictions were found to agree well with the experimental observations for the Fe-Ni and Fe-Ni-SiO{sub 2} systems.

  1. Oscillatory instabilities during formic acid oxidation on Pt(100), Pt(110) and Pt(111) under potentiostatic control. II. Model calculations

    NASA Astrophysics Data System (ADS)

    Strasser, P.; Eiswirth, M.; Ertl, G.

    1997-07-01

    A kinetic model is developed for the electrocatalytic oxidation of formic acid on Pt under potentiostatic control. The model development proceeds stepwise via a simple model of the electrocatalytic CO oxidation. The full model consists of four coupled, nonlinear ordinary differential equations. The scanned and stationary current/outer potential (I/U) behavior, stationary current oscillations, two-parameter bifurcation diagrams and stirring effects are simulated using realistic model parameters. The numerical findings are found to be consistent with the experimental results given by Strasser et al. The model reproduces period-1 as well as mixed-mode oscillations. Furthermore, a mechanistic analysis of the model was performed: two suboscillators are identified whose characteristics allow a plausible interpretation of the observed dynamics. After a classification of the suboscillators into previously described categories, an attempt is made to identify the minimal mechanistic requirements for electrochemical current oscillations.

  2. Photoelectrochemical cell studies of Fe(2+) doped ZnSe nanorods using the potentiostatic mode of electrodeposition.

    PubMed

    Lohar, G M; Jadhav, S T; Takale, M V; Patil, R A; Ma, Y R; Rath, M C; Fulari, V J

    2015-11-15

    The Fe(2+) doped ZnSe nanorods are synthesized using simple potentiostatic mode of electrodeposition on the ITO substrate. In order to study the doping effect of Fe(2+) in ZnSe, varied the doing percent such as 0.5%, 1%, 1.5%. These films are characterized for structural, compositional, morphological, optical and electrochemical properties using the X-ray diffraction study (XRD), X-ray photoelectron spectroscopy, field emission scanning electron microscopy, UV-vis spectroscopy and electrochemical spectroscopy. Along with these Raman spectroscopy and photoluminescence spectroscopy have been studied for understanding the characteristics vibrations of ZnSe and luminescence of ZnSe nanorods. FE-SEM shows the nanorods like morphology. Photoelectrochemical cell performance studied using the J-V measurement and it shows the maximum efficiency at 1% Fe(2+) doped ZnSe nanorods. The observed maximum efficiency of Fe(2+) doped ZnSe nanorods is 0.32%. PMID:26210917

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  4. Potentiostatic pulse-deposition of calcium phosphate on magnesium alloy for temporary implant applications--an in vitro corrosion study.

    PubMed

    Kannan, M Bobby; Wallipa, O

    2013-03-01

    In this study, a magnesium alloy (AZ91) was coated with calcium phosphate using potentiostatic pulse-potential and constant-potential methods and the in vitro corrosion behaviour of the coated samples was compared with the bare metal. In vitro corrosion studies were carried out using electrochemical impedance spectroscopy and potentiodynamic polarization in simulated body fluid (SBF) at 37 C. Calcium phosphate coatings enhanced the corrosion resistance of the alloy, however, the pulse-potential coating performed better than the constant-potential coating. The pulse-potential coating exhibited ~3 times higher polarization resistance than that of the constant-potential coating. The corrosion current density obtained from the potentiodynamic polarization curves was significantly less (~60%) for the pulse-deposition coating as compared to the constant-potential coating. Post-corrosion analysis revealed only slight corrosion on the pulse-potential coating, whereas the constant-potential coating exhibited a large number of corrosion particles attached to the coating. The better in vitro corrosion performance of the pulse-potential coating can be attributed to the closely packed calcium phosphate particles. PMID:25427473

  5. 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

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

    SciTech Connect

    Evans, Kenneth J.; Rebak, Raul B.

    2007-07-01

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

  7. Finite element analysis of lithium insertion-induced expansion of a silicon thin film on a rigid substrate under potentiostatic operation

    NASA Astrophysics Data System (ADS)

    Liu, Ming

    2015-02-01

    Diffusion-induced stress and volumetric expansion under potentiostatic operation are investigated with an axisymmetric finite element model taking account of plastic yielding, coupling effects between diffusion and stress, diffusion from the edge surface, and concentration dependence of material properties. Significant differences on stresses, displacements, and fracture energies between purely elastic and elastic-plastic materials are found. Plasticity based on von-Mises criterion has no effect on concentration variation. The critical regions for fracture are the edge surface, and the regions near the edges on both the top surface and the interface.

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

    PubMed Central

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

    2015-01-01

    Background: Technological advances in wire selection and bracket design have led to improved treatment efficiency and allowed longer time intervals between appliance adjustments. The wires remain in the mouth for a longer duration and are subjected to electrochemical reactions, mechanical forces of mastication and generalized wear. These cause different types of corrosion. This study was done to compare the galvanic currents generated between different combinations of brackets and archwires commonly used in orthodontic practices. Materials and Methods: The materials used for the study included different commercially available orthodontic archwires and brackets. The galvanic current generated by individual materials and different combinations of these materials was tested and compared. The orthodontic archwires used were 0.019″ × 0.025″ heat-activated nickel-titanium (3M Unitek), 0.019″ × 0.025″ beta-titanium (3M Unitek) and 0.019″ × 0.025″ stainless steel (3M Unitek). The orthodontic brackets used were 0.022″ MBT laser-cut (Victory Series, 3M Unitek) and metal-injection molded (Leone Company) maxillary central incisor brackets respectively. The ligature wire used for ligation was 0.009″ stainless steel ligature (HP Company). The galvanic current for individual archwires, brackets, and the different bracket-archwire-ligature combinations was measured by using a Potentiostat machine. The data were generated using the Linear Sweep Voltammetry and OriginPro 8.5 Graphing and Data Analysis Softwares. The study was conducted in two phases. Phase I comprised of five groups for open circuit potential (OCP) and galvanic current (I), whereas Phase II comprised of six groups for galvanic current alone. Results: Mean, standard deviation and range were computed for the OCP and galvanic current (I) values obtained. Results were subjected to statistical analysis through ANOVA. In Phase I, higher mean OCP was recorded in stainless steel archwire, followed by beta-titanium archwire, heat-activated nickel titanium archwire, laser-cut bracket and metal-injection molded bracket, respectively. The difference in mean OCP recorded among the groups was found to be statistically significant in aerated phosphate buffered saline solution. The galvanic current (I) for metal-injection molded stainless steel brackets showed significantly higher values than all the other materials. Phase II results suggested that, in the couples formed by the archwire-bracket-ligature combinations, the bracket had more important contribution to the total galvanic current generated, since there were significant differences between galvanic current among the 2 brackets tested but not among the 3 wires. The galvanic current of the metal-injection molded bracket was significantly higher than that of laser-cut bracket. Highest mean current (I) was recorded in metal-injection molded bracket when used with heat-activated nickel titanium archwire while lowest mean current (I) was recorded in laser-cut bracket when used with beta-titanium archwire. Conclusion: The present study concluded that the bracket emerged to be the most important factor in determining the galvanic current (I). Higher mean current (I) was recorded in metal-injection molded bracket compared to laser-cut bracket. Among the three archwires, higher mean current (I) was recorded in heat-activated nickel-titanium, followed by stainless-steel and beta-titanium respectively. When coupled together; highest mean current (I) was recorded in metal-injection molded bracket when used with heat-activated nickel titanium archwire while lowest mean current (I) was recorded in laser-cut bracket when used with beta-titanium archwire. PMID:26229367

  9. Parallel Recording of Neurotransmitters Release from Chromaffin Cells Using a 10 10 CMOS IC Potentiostat Array with On-Chip Working Electrodes

    PubMed Central

    Kim, Brian Namghi; Herbst, Adam D.; Kim, Sung June; Minch, Bradley A.; Lindau, Manfred

    2012-01-01

    Neurotransmitter release is modulated by many drugs and molecular manipulations. We present an active CMOS-based electrochemical biosensor array with high throughput capability (100 electrodes) for on-chip amperometric measurement of neurotransmitter release. The high-throughput of the biosensor array will accelerate the data collection needed to determine statistical significance of changes produced under varying conditions, from several weeks to a few hours. The biosensor is designed and fabricated using a combination of CMOS integrated circuit (IC) technology and a photolithography process to incorporate platinum working electrodes on-chip. We demonstrate the operation of an electrode array with integrated high-gain potentiostats and output time-division multiplexing with minimum dead time for readout. The on-chip working electrodes are patterned by conformal deposition of Pt and lift-off photolithography. The conformal deposition method protects the underlying electronic circuits from contact with the electrolyte that covers the electrode array during measurement. The biosensor was validated by simultaneous measurement of amperometric currents from 100 electrodes in response to dopamine injection, which revealed the time course of dopamine diffusion along the surface of the biosensor array. The biosensor simultaneously recorded neurotransmitter release successfully from multiple individual living chromaffin cells. The biosensor was capable of resolving small and fast amperometric spikes reporting release from individual vesicle secretions. We anticipate that this device will accelerate the characterization of the modulation of neurotransmitter secretion from neuronal and endocrine cells by pharmacological and molecular manipulations of the cells. PMID:23084756

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  12. In vivo potentiostatic studies at the electrode tissue interface: filter properties of the monophasic action potential (Ag/AgCl) electrode in living rat heart.

    PubMed

    Chou, H A; Ovadia, M; Moskowitz, M; Zavitz, D H

    2000-03-01

    The monophasic action potential (Franz) catheter is regarded as the criterion standard for high fidelity recording of a class of physiological signals. However, its signal modulation characteristics have never been reported. Broadband impedance spectroscopy was performed in perfused living rat heart in a three-electrode potentiostatic configuration to determine the filtering characteristics of the MAP and model Ag/AgCl electrode-tissue interfaces. The filter transfer function H(f) (attenuation [dB] vs log(f) [log(Hz)]) was derived for the frequency range 10 Hz-10(6) Hz. As a filter, the MAP interface is characterized by two ranges of filtering behavior. At high frequency the MAP interface is a high-pass filter with passband frequency 54 kHz-549 kHz (median 321 kHz) and with -3 dB cutoff points ranging from 10 kHz to 302 kHz. In this high frequency range the transfer function is characterized by decreasing attenuation per decade. However, in the lower frequency range relevant to physiological signals (the monophasic action potential, 0.1-40 Hz), it is a severely attenuating nondiodic high-pass filter element with an average attenuation of 16.87 dB relative to passband. In this physiological range, rolloff is nonlinear with increasing attenuation per decade. While the MAP electrode and model Ag/AgCl electrodes are high-pass filters with robust transfer functions for high frequency signals in the living heart, the attenuation of signals in a frequency range relevant to in vivo physiological recording imparts extreme attenuation that may distort physiological signals unpredictably. This disadvantage may be mitigated by amplitude scaling to a calibrated pure tone signal within the physiological frequency band to recover a reproducible signal. PMID:10750142

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  14. Potentiostatic deposition of DNA for scanning probe microscopy.

    PubMed Central

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

    1992-01-01

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

  15. Intelligent potentiostat for identification of heavy metals in situ

    NASA Astrophysics Data System (ADS)

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

    2006-01-01

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

  16. 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. 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.

  18. Attofarad resolution potentiostat for electrochemical measurements on nanoscale biomolecular interfacial systems.

    PubMed

    Carminati, Marco; Ferrari, Giorgio; Sampietro, Marco

    2009-12-01

    We present an instrument that enables electrochemical measurements (cyclic voltammetry, impedance tracking, and impedance spectroscopy) on submicrometric samples. The system features a frequency range from dc to 1 MHz and a current resolution of 10 fA for a measurement time of 1 s, giving a sensitivity of few attofarads in terms of measurable capacitance with an applied voltage of only 100 mV. These performances are obtained using a low-noise wide-bandwidth integrator/differentiator stage to sense the input current and a modular approach to minimize the effect of input stray capacitances. A digitally implemented lock-in filter optimally extracts the impedance of the sample, providing time tracking and spectroscopy operating modes. This computer-based and flexible instrument is well suited for characterizing and tracking the electrical properties of biomolecules kept in the physiological solution down to the nanoscale. PMID:20059158

  19. Attofarad resolution potentiostat for electrochemical measurements on nanoscale biomolecular interfacial systems

    NASA Astrophysics Data System (ADS)

    Carminati, Marco; Ferrari, Giorgio; Sampietro, Marco

    2009-12-01

    We present an instrument that enables electrochemical measurements (cyclic voltammetry, impedance tracking, and impedance spectroscopy) on submicrometric samples. The system features a frequency range from dc to 1 MHz and a current resolution of 10 fA for a measurement time of 1 s, giving a sensitivity of few attofarads in terms of measurable capacitance with an applied voltage of only 100 mV. These performances are obtained using a low-noise wide-bandwidth integrator/differentiator stage to sense the input current and a modular approach to minimize the effect of input stray capacitances. A digitally implemented lock-in filter optimally extracts the impedance of the sample, providing time tracking and spectroscopy operating modes. This computer-based and flexible instrument is well suited for characterizing and tracking the electrical properties of biomolecules kept in the physiological solution down to the nanoscale.

  20. Determination of the Crevice Repassivation Potential of Alloy 22 by a Potentiodynamic-Galvanostatic-Potentiostatic Method

    SciTech Connect

    Evans, K J; Wong, L L; Rebak, R B

    2004-03-11

    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 that the mode of corrosion attack that results in the tested specimens are different.

  1. Oscillatory instabilities during formic acid oxidation on Pt(100), Pt(110) and Pt(111) under potentiostatic control. I. Experimental

    NASA Astrophysics Data System (ADS)

    Strasser, P.; Lbke, M.; Raspel, F.; Eiswirth, M.; Ertl, G.

    1997-07-01

    The experimental characterization of the current/outer potential (I/U) behavior during the electrochemical CO oxidation on Pt(100), Pt(110) and Pt(111) is used as the first step towards a thorough investigation of the processes occurring during the electrochemical formic acid oxidation. The CO study is followed by new cyclovoltammetric results during the electrochemical formic acid oxidation on the corresponding Pt single crystals. At high concentrations of formic acid, the cyclovoltammograms revealed a splitting of the large current peak observed on the cathodic sweep into two peaks whose dependence on scan rate and reverse potential was investigated. It turned out that the presence of a sufficiently large ohmic resistance R was crucial for oscillatory instabilities. Given an appropriate resistance, all three Pt surfaces were found to exhibit current oscillations at both low and high formic acid concentrations. On Pt(100) stable mixed-mode oscillations were observed. In addition, the sensitivity of the oscillations to stirring was investigated. Whereas the period-1 oscillations were found to be independent of stirring, the mixed-mode oscillations transformed into simple oscillations with stirring. The mechanism giving rise to instability and oscillations is described.

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

    PubMed

    Compa, Vicente; Tiemblo, Pilar; Garca, F; Garca, J M; Guzmn, Julio; Riande, Evaristo

    2005-06-01

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

  3. Rechargeable Li[sub 1+x]Mn[sub 2]O[sub 4]/carbon cells with a new electrolyte composition: Potentiostatic studies and application to practical cells

    SciTech Connect

    Guyomard, D.; Tarascon, J.M. )

    1993-11-01

    To improve the high temperature performance of Li[sub 1+x]Mn[sub 2]O[sub 4]/carbon rocking-chair secondary batteries the authors searched for and identified a new electrolyte composition whose range of stability extends up to 4.9 V vs Li at room temperature and 4.8 V vs Li at 55 C for the Li[sub x]Mn[sub 2]O[sub 4] material. The behavior of the M = LiMn[sub 2]O[sub 4] composite new electrolyte interface at high voltage (4.2 to 5.1 V vs Li) shows the superposition of two phenomena: (i) an irreversible behavior due to a very slow electrolyte oxidation caused by the large surface area of carbon black (mixed with the Li[sub x]Mn[sub 2]O[sub 4] active material to improve the conductivity) and (ii) two reversible Li deintercalation-intercalation processes in the Li[sub x]Mn[sub 2]O[sub 4] spinel structure. In order to evaluate the kinetics of the high voltage phenomena, the behavior of the LiMn[sub 2]O[sub 4]/new electrolyte interface was investigated as a function of time and temperature. The electrolyte oxidative degradation is a well-stabilized reaction with nontime evolving kinetics, and with an activation energy close to 8 kcal/mol. The self-discharge mechanism a local redox process involving electrolyte oxidation at the electrode surface and reversible intercalation of Li in the Li[sub x]Mn[sub 2]O[sub 4] spinel structure. The effective stability of this new electrolyte against oxidation allows for better performance of the rocking-chair cells, in terms of cycle-life and self-discharge, over a wider temperature range ([minus]20 to 55 C.)

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  5. Electrochemical nitridation of metal surfaces

    DOEpatents

    Wang, Heli; Turner, John A.

    2015-06-30

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

  6. Electrochemical microsensors for the detection of cadmium(II) and lead(II) ions in plants.

    PubMed

    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

  7. 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

  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. 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.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  12. 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.

  13. 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

  14. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  16. 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

  17. 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 ...

  18. 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  20. 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

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

    ERIC Educational Resources Information Center

    Pomeroy, R. S.; And Others

    1989-01-01

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

  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. Role of Preparation Method on the Microstructure and Mechanical Properties of PPy/Ni Organic-Inorganic Hybrid Bilayer Coatings on Carbon Steel

    NASA Astrophysics Data System (ADS)

    Torres-Huerta, A. M.; Dominguez-Crespo, M. A.; Alanis-Valdelamar, A.; Onofre-Bustamante, E.; Escudero, M. L.; Garca-Alonso, M. C.; Lois-Correa, J. A.

    2015-04-01

    The efficacy of the conducting polymers as coating on a metallic substrate is strongly dependent on the manner how they are applied. Polypyrrole (PPy)/Ni organic-inorganic hybrid coatings were electropolymerized on commercial carbon steel (AISI 1018) by combining potentiostatic and potentiodynamic techniques. In first instance, it was analyzed the electrodeposition of PPy using a constant potential regime and cyclic voltammetry techniques evaluating different synthesis parameters such as deposition time, applied potential, and potential cycles, respectively. Thereafter, it was used a potentiostatic method to obtain PPy/Ni bilayer films. The morphological, mechanical, and adhesion properties of these films depend on the synthesis parameters. The results revealed that polypyrrole films formed by both methods provide a globular-type structure, although coatings produced by cyclic voltammetry are denser and slightly thicker than those produced potentiostatically. Ni (oxide/hydroxide) particles are capable of sealing the pores of globular PPy coatings, thus increasing the hardness of the carbon steel (CS)/PPy/Ni system. As a result of the study, we have seen that PPy/Ni bilayer films are more uniform, compact and enhanced the hardness when the PPy is obtained by cyclic voltammetry than that observed for potentiostatic approach. Specifically, when four potential cycles are used to electropolymerized pyrrole, the more convenience properties in the CS/PPy/Ni arrangement are obtained.

  4. Corrosion and creep of dental amalgam.

    PubMed

    Gjerdet, N R; Espevik, S

    1978-01-01

    The influence of stress on corrosion was investigated by a potentiostatic technique. Amalgrams with low creep, both with and without gamma2-phase, revealed small increases in current with stress application while alloys with high creep exhibited large increases in current. Rupture of protective oxide due to increased strain for high creep alloys may explain the phenomenon. PMID:277492

  5. Effects of cathodic protection on corrosive wear of 304 stainless steel

    SciTech Connect

    Akonko, Saheed; Li, D.Y.; Ziomek-Moroz, M.

    2005-03-01

    Corrosive wear involves interaction of electrochemical and mechanical processes. The synergism of these two processes often results in significant material loss, compared to those caused by individual processes. Reduction of either corrosion or wear may effectively decrease material loss under certain circumstances. Since cathodic protection can reduce corrosion of metallic materials, it may also diminish corrosive wear if the corrosion process is suppressed. However, under a cathodic potential (potentiostatic condition) or enforced current (galvanosatic condition), properties of a material could be affected and thus its corrosive wear behavior could be different from what is expected. The present research demonstrated that cathodic protection under potentiostatic condition was beneficial under low wearing force but it became ineffective under higher wearing forces or more negative cathodic potentials. Hydrogen embrittlement could be responsible for this change.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    SciTech Connect

    Jovancicevic, V.; Hartwick, D.

    1997-12-01

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

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

    SciTech Connect

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

    1996-07-01

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

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

    SciTech Connect

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

    1995-10-01

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

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

    SciTech Connect

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

    1995-03-01

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

  11. Teorell instability in concentration polarization

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  12. Studying localized corrosion using liquid cell transmission electron microscopy

    SciTech Connect

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

    2014-11-07

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

  13. Studying localized corrosion using liquid cell transmission electron microscopy

    DOE PAGESBeta

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

    2014-11-07

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

  14. Demonstration of lithographic patterning in measurements of general and localized corrosion on alloy 22

    SciTech Connect

    Bedrossian, P J; Farmer, J C

    1999-07-01

    We have demonstrated a new technique capable of detecting generalized corrosion of metallographically-polished materials with nanometer-scale precision. After exposing a lithographically-patterned coupon of Alloy 22 to an electrolyte in a potentiostatically-controlled cell for twenty-four hours, we detected the loss of up to 130nm of metal. In addition, ''wormholes'' were detected at certain points of intersection of three grain boundaries.

  15. Highly Methanol Tolerant Cathode Based on PtAg for Use in Microfluidic Fuel Cell

    NASA Astrophysics Data System (ADS)

    Abrego-Martnez, J. C.; Mendoza-Huizar, L. H.; Ledesma-Garcia, J.; Arriaga, L. G.; Cuevas-Muiz, F. M.

    2015-12-01

    In the present work, a methanol tolerant cathode catalyst was developed through the electrodeposition of bimetallic nanoparticles PtAg on a glassy carbon electrode using potentiostatic and voltammetric techniques. The resulting particles were characterized by Scanning Electron Microscopy (SEM) and electrochemical techniques. According to the SEM study the synthetized nanoparticles have semi-spherical shape and their average diameter is 100 nm. This material shows catalytic activity to the oxygen reduction reaction with high tolerance to methanol.

  16. In vitro mechanical integrity of hydroxyapatite coated magnesium alloy.

    PubMed

    Kannan, M Bobby; Orr, Lynnley

    2011-08-01

    The mechanical integrity of resorbable implants during service, especially in load bearing orthopaedic applications, is critical. The high degradation rate of resorbable magnesium and magnesium-based implants in body fluid may potentially cause premature in-service failure. In this study, a magnesium alloy (AZ91) was potentiostatically coated with hydroxyapatite at different cathodic voltages in an attempt to enhance the mechanical integrity. The mechanical integrity of the uncoated and hydroxyapatite coated alloys was evaluated after in vitro testing of the coated samples in simulated body fluid (SBF). The uncoated alloy showed 40% loss in the mechanical strength after five days exposure to SBF. However, the hydroxyapatite coated alloy exposed to SBF showed 20% improvement in the mechanical strength as compared to that of the uncoated alloy. The alloy coated potentiostatically at -2 V performed better than the -3 V coated alloy. The cross-sectional analysis of the coatings revealed relatively uniform coating thickness for the -2 V coated alloy, whereas the -3 V coated alloy exhibited areas of uneven coating. This can be attributed to the increase in hydrogen evolution on the alloy during -3 V coating as compared to -2 V coating. The scanning electron micrographs of the in vitro tested alloy revealed that hydroxyapatite coating significantly reduced the localized corrosion of the alloy, which is critical for better in-service mechanical integrity. Thus, the study suggests that the in vitro mechanical integrity of resorbable magnesium-based alloy can be improved by potentiostatic hydroxyapatite coating. PMID:21636886

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

    PubMed

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

    2016-05-15

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

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

    PubMed

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

    2016-06-01

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

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

    PubMed Central

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

    2015-01-01

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

  20. 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

  1. Thin flexible intercalation anodes

    SciTech Connect

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

    1994-10-01

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

  2. Electrochemical techniques for the characterisation of expander materials

    NASA Astrophysics Data System (ADS)

    Francia, Carlotta; Maja, Mario; Spinelli, Paolo; Saez, Francisco; Martinez, Bruno; Marin, Dolores

    Characterisation of expander materials has been obtained by comparing the results of three different electrochemical techniques: cyclic voltammetry, potentiostatic transients and electrochemical impedance. It is shown that the evaluation of the expanders' performance carried out on the basis of the results of such techniques takes into account different important actions of the organic additives such as adsorption on lead and kinetics of electrochemical reactions. Seventeen different organic substances have been tested including both commercial materials used in the lead-acid battery industry, and other materials presenting physico-chemical similarities to known expanders.

  3. Corrosion resistance and electrochemical evaluation of silver mirrors

    NASA Astrophysics Data System (ADS)

    Pohlman, S. L.; Russell, P. M.

    1980-09-01

    Electrochemical methods including potentiostatic, potentiodynamic, and galvanic measurements were used to study the corrosion resistance of silver mirrors for use in solar energy concentrators. The potential driven modified scratch test appears promising as a rapid quality assurance evaluation technique. Galvanic measurements have shown that silver/copper is not an active galvanic couple and copper does provide only limited cathodic protection to the silver. Measurements have also shown that oxidation of tin or stannous ions and hydrogen formation at the silver/glass interface may occur.

  4. Template electrodeposition of ordered bismuth telluride nanowire arrays.

    PubMed

    Li, Shanghua; Liang, Yibin; Qin, Jian; Toprak, Muhammet; Muhammed, Mamoun

    2009-02-01

    Thermoelectric bismuth telluride nanowire arrays have been synthesized by direct-current electrode-position into porous anodic alumina membranes both galvanostatically and potentiostatically. The as-synthesized Bi2Te3 nanowire arrays are highly ordered in large area, stoichiometric, uniform, with high aspect ratio (above 100) and high filling ratio (>90%) of the membrane. The effects of different electrochemical deposition parameters on crystal structures, morphology and composition have been investigated. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) have been used to characterize the physical and chemical properties of the nanowires. PMID:19441566

  5. Electrodeposition of a tellurium-iodine compound

    SciTech Connect

    Bigelis, V.M.

    1988-01-01

    Forming more stable tellurium in iodide solution was investigated. Solutions with a large excess of iodide ions were prepared and radiotracers measured the current yields of tellurium. A platinum sheet was used as cathode, a tellurium rod was the anode, and a saturated silver-silver chloride electrode was the reference electrode. Electrodeposition and polarization measurements were conducted by a potentiostat. Polarization curves were obtained. Iodine 125 and tellurium 123m were used in the radiochemical analysis of the deposition yield and rate. Radioactivity measurements were made with a Ge(Li) detector.

  6. Reduction of Plutonium in Acidic Solutions by Mesoporous Carbons

    DOE PAGESBeta

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

    2015-12-19

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

  7. The ethanol electrooxidation at Pt layers deposited on polycrystalline Au.

    PubMed

    Prieto, Mauricio J; Rodrigues Filho, Ubirajara P; Landers, Richard; Tremiliosi-Filho, Germano

    2012-01-14

    The ethanol electro-oxidation reaction was evaluated using a polycrystalline Au substrate modified with two different amounts of Pt using the galvanic exchange methodology. FTIR results suggest that Pt deposits have a greater ability to break the C-C bond present in the ethanol molecule. However, under potentiostatic conditions both modified Au surfaces undergo faster deactivation in comparison with polycrystalline platinum as indicated by the chronoamperometric results. XPS results indicate the presence of two phases depending on the Pt content. These are: (i) Pt-Au alloy and (ii) segregated Pt. The structural and electronic properties of these phases were related to the differences observed in the catalytic activity. PMID:22116267

  8. Electrochemical apparatus for automatic measurement of carrier-concentration distribution in semiconductors

    SciTech Connect

    Belova, N.A.; Galchenkov, L.A.; Skvortsova, N.E.

    1986-06-01

    This paper describes apparatus for measuring the carrier-concentration depth (from 1 to 30-50 um) distribution of semiconductors in the concentration range of 10/sup 14/-10/sup 19/ cm/sup -3/. The measurement errors for concentration and depth are 10% and 5%. Measurements can be made in AgAs, InP, Si, and, with proper selection of the electrolyte, other semiconductors. Measurements are made automatically and the results are recorded with a plotter. Schematic diagrams are presented of the main units of the apparatus which include the capacitance meter, synchronous detector, potentiostat, automatic unit, and various circuits.

  9. Patterned electrochemical deposition of copper using an electron beam

    SciTech Connect

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

    2014-02-01

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

  10. Structural properties of single step electrochemically deposited ZnS nanofibers

    NASA Astrophysics Data System (ADS)

    Bhalerao, Anuradha B.; Wagh, B. G.; Lokhande, C. D.

    2013-06-01

    ZnS thin films are prepared by electro deposition technique over stainless steel substrates in potentiostatic mode from an aqueous acidic bath containing ZnSo4 and Na2S2O3. The growth kinetics of the film was studied and the deposition parameters such as electrolyte bath concentration, deposition time, deposition potential and pH of electrolyte bath are optimized. The X-ray diffraction (XRD) analysis of the deposited film showed presence of polycrystalline nature. The surface morphology studied by scanning electron microscope (SEM) shows fibrous morphology with well adherence and uniform distribution of nanosized fibers over the surface of substrate.

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

    SciTech Connect

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

    1997-04-01

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

  12. Simulation of an enzyme-based glucose sensor

    NASA Astrophysics Data System (ADS)

    Sha, Xianzheng; Jablecki, Michael; Gough, David A.

    2001-09-01

    An important biosensor application is the continuous monitoring blood or tissue fluid glucose concentration in people with diabetes. Our research focuses on the development of a glucose sensor based on potentiostatic oxygen electrodes and immobilized glucose oxidase for long- term application as an implant in tissues. As the sensor signal depends on many design variables, a trial-and-error approach to sensor optimization can be time-consuming. Here, the properties of an implantable glucose sensor are optimized by a systematic computational simulation approach.

  13. 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

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

    SciTech Connect

    Ortendahl, T.W.; Hoegstedt, P.O.; Odelius, H.; Noren, 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  16. Dynamics and Topography of QUASI-2D Needle-Like Silver Electrochemical Deposits Under a Quasi-Steady Regime

    NASA Astrophysics Data System (ADS)

    Pasquale, M. A.; Vicente, J. L.; Arvia, A. J.

    The electrochemical formation of single silver needles from aqueous silver sulfate was studied under both potentiostatic and galvanostatic conditions utilizing different quasi-2D cells. Under potentiostatic conditions, four (I-IV) stages of growth were distinguished. Stage III involved single needle growth under a quasi-steady-state (q-ss) regime in which, at the millimeter scale, the tip profile remained almost unchanged. Fast growing needles exhibited a truncated quasi-conical tip, and slow growing ones approached prolate hemispheroids. At stage III, the almost constant q-ss silver deposition rate was evaluated from the tip front displacement (dLz/dt) perpendicularly to the tangential plane of the tip. For the cathode to anode potential difference in the range -1.00 ? Ec-a ? -0.22 V, values of (dLz/dt) in the range 0.08-2.0 ?m s-1 were obtained. At the needle stem, the q-ss radial silver deposition rate (dLx/dt) was about two orders of magnitude lower than (dLz/dt). The transition from stage III to IV was characterized by tip thickening, i.e. a change in the tip q-conical profile to that of a prolate hemispheroid, and eventual tip splitting. Scanning electron micrographs at the micrometer scale of single silver needle tips from potentiostatic runs showed either a defined crystallography or an irregular topography covered by a large number of tiny crystals. In contrast, stems were always faceted. This difference indicated that surface relaxation processes following silver ion mass transport and discharge played a relevant role in the needle growth mode. At stage III, the growth regime is described utilizing a dual diffusion (D) and migration (M) model consisting of a DM direct contribution that becomes dominant at the needle stem, and a space charge (SC)-assisted DM contribution that operates at the tip apex. This explanation is consistent with the local cathodic current density values, the concentration ratio of silver clusters at the stem and tip apex surface, and the distinct kinetic behavior of needles produced from potentiostatic and galvanostatic runs. The complex link between mass transport phenomena of silver ions from the binary solution side, the silver ion discharge at the interface and the surface relaxation of silver adatoms and clusters at the metal lattice shed new light on the aspects of single silver needle formation.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  18. 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.

  19. Studies of passive film breakdown by detection and analysis of electrochemical noise

    NASA Astrophysics Data System (ADS)

    Bertocci, U.; Kruger, J.

    1980-12-01

    Random fluctuations in the passive current of electrodes under potentiostatic conditions have been measured on aluminum in boric acid: borate solution and on a Fe-Cr-Ni alloy, both in the amorphous and in the crystalline state, in sulfuric acid. The onset of pitting can be detected by thc large increase in current noise. The noise level is different in the amorphous and crystalline Fe-Cr-Ni alloy, indicating that the breakdown of the passive film differs in the two conditions. Thc experimental aspects involved in carrying out meaningful noise measurements in electrochemical systems are also discussed.

  20. Electrochemical array sensors for plating waste stream monitoring

    SciTech Connect

    Glass, R.S.; Hong, K.C.; Estill, J.C.; Reibold, R.A.; Thompson, W.M.; O'Brien, D.W.; Ciarlo, D.R. ); Granstaff, V.E. )

    1992-03-01

    Electrochemical sensors are being developed to aid in waste reduction efforts for plating operations and in environmental remediation. An important feature of these sensor systems are solid-state multielement microelectrode arrays. The individual elements of these arrays will be selected so that a variety of chemical species can be detected using a single device. In addition, we are developing a compact electronics package, consisting of a potentiostat, signal generator, and microcomputer with user-friendly software to use in conjunction with the arrays. This report discusses the selection process for array elements, advantages of the use of microelectrodes, and application to the analysis of actual plating rinse tank systems.

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

    PubMed

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

    2016-01-22

    The local microstructure of Fe-Ga nanowires is investigated considering dependence on the deposition technique. Using a complexed electrolyte, smooth and homogeneous Fe80Ga20 nanowires are deposited into anodic aluminum oxide templates by either applying pulse potential or potentiostatic deposition technique. At optimized deposition conditions the wires show the desired composition of Fe802Ga202 without a gradient along the growth direction. Composition distribution, structure and microstructure are examined in detail and reveal only minor differences. Line EELS and crystal lattice measurements reveal a negligible oxygen content for both preparation routines. Neither Fe/Ga oxides nor hydroxides were found. Both potentiostatically deposited as well as pulse deposited nanowires exhibit a preferred ?110? orientation, the latter with slightly larger crystals. Different contrast patterns were found by TEM that appear more pronounced in the case of pulse deposited wires. High resolution transmission electron microscopy analysis and comparison of differently prepared focused ion beam lamellas reveal that these contrasts are caused by defects in the alternating potential deposition itself and are not induced during the TEM preparation process. The alternating potential mode causes periodic growth thereby inducing different layers with reduced wire thickness/defects at the layer interfaces. PMID:26651087

  2. Effect of chemical composition on the corrosion behavior of Ni-Cr-Mo dental casting alloys.

    PubMed

    Huang, Her-Hsiung

    2002-06-01

    The objective of this investigation was to study the compositional influence on the corrosion behavior of Ni-Cr-Mo dental casting alloys in acidic artificial saliva. Cyclic potentiodynamic and potentiostatic tests were used to evaluate the corrosion behavior of different Ni-Cr-Mo dental casting alloys in deaerated artificial saliva with pH 5 at 37 degrees C. Optical microscope observations were made following the cyclic potentiodynamic tests. Surface chemical analyses were characterized by X-ray photoelectron spectroscopy and auger electron spectroscopy following the potentiostatic tests. The results show that the corrosion resistance of the Ni-Cr-Mo casting alloys investigated is associated with the formation of passive film containing Ni(OH)(2), NiO, Cr(2)O(3), and MoO(3), on the surface. The pitting potential and passive range, respectively, were statistically different among the different Ni-Cr-Mo alloys. The Ni-Cr-Mo alloys with higher Cr ( approximately 21%) and Mo ( approximately 8%) contents had a much larger passive range in the polarization curve and were immune to pitting corrosion due to the presence of high Cr (maximum approximately 31-35%) and Mo (maximum approximately 12%) contents in the surface passive film. The presence of Ti lower than 4% in the Ni-Cr-Mo casting alloy had no effect on corrosion resistance. A pitting resistance equivalent (PRE) of about 49 could provide the Ni-Cr-Mo alloy with a good pitting corrosion resistance. PMID:11920670

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  6. Mechanism of chloride corrosion of dental amalgam.

    PubMed

    Finkelstein, G F; Greener, E H

    1979-04-01

    Polarization of conventional dental amalgam in Ringer's solution produces a dissolution of the gamma 2 phase at--250 mV (SCE) and formation of Sn-Cl and Sn-O-Cl. This study was undertaken to determine the electrochemical nature of these reactions. Potentiostatic polarization scans were run at 4, 37 and 50 degrees C in several dilutions of aerated Ringer's solution. Manipulation of reactant concentrations and electrolyte temperature produced shifts in the potentiostatic profiles. At 50 degrees C, a gamma 2 dissolution peak shift to -300 mV was observed, and at 4 degrees C the peak shifted to -200 mV. Dilution of Ringer's solution with respect to [Cl-] over three orders of magnitude produced a linear shift in the noble direction of 500 mV. Cathodic polarization appears to be limited by the oxygen half cell reaction. Changes of [Cl] affect the shape of the peak, round out its approach to the current maximum. Shifts in peak potential due to temperature and concentration changes agreed with calculations based on critical pitting potential for gamma2 dissolution due to a chloride reaction. Polarization profiles in pooled saliva agreed with calculated potentials based on known saliva [Cl-]. PMID:35596

  7. Simplifying microbial electrosynthesis reactor design

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

    Gimkiewicz, Carla; Harnisch, Falk

    2013-01-01

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

  9. 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

  10. Intergranular corrosion in a martensitic stainless steel detected by electrochemical tests

    SciTech Connect

    Alonso-Falleiros, N.; Magri, M.; Falleiros, I.G.S.

    1999-08-01

    Quenched and tempered martensitic stainless steel UNS S41000 was tested electrochemically for susceptibility to sensitization in specimens quenched from 975 C (1,248 K) and tempered for 2 h at different temperatures between 300 C (573 K) and 700 C (973 K). Besides an oxalic acid etch test, the following tests were performed using a potentiostat and 1 N sulfuric acid (H{sub 2}SO{sub 4}) solution: potentiokinetic polarization, potentiostatic etch, and electrochemical potentiokinetic reactivation in the double-loop version (DL-EPR). Tested surfaces were observed metallographically. The maximum susceptibility to intergranular corrosion was observed in the condition tempered at 550 C (823 K), and a sensitized structure was detected. For lower tempering temperatures, steel was less sensitized, or not at all, and for higher tempering temperatures, steel was less sensitized. All tests except for the oxalic acid etch were able to evaluate quantitatively different degrees of sensitization as a function of tempering temperature. The DL-EPR method was the best to discriminate degrees of sensitization.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    The local microstructure of FeGa nanowires is investigated considering dependence on the deposition technique. Using a complexed electrolyte, smooth and homogeneous Fe80Ga20 nanowires are deposited into anodic aluminum oxide templates by either applying pulse potential or potentiostatic deposition technique. At optimized deposition conditions the wires show the desired composition of Fe802Ga202 without a gradient along the growth direction. Composition distribution, structure and microstructure are examined in detail and reveal only minor differences. Line EELS and crystal lattice measurements reveal a negligible oxygen content for both preparation routines. Neither Fe/Ga oxides nor hydroxides were found. Both potentiostatically deposited as well as pulse deposited nanowires exhibit a preferred <110> orientation, the latter with slightly larger crystals. Different contrast patterns were found by TEM that appear more pronounced in the case of pulse deposited wires. High resolution transmission electron microscopy analysis and comparison of differently prepared focused ion beam lamellas reveal that these contrasts are caused by defects in the alternating potential deposition itself and are not induced during the TEM preparation process. The alternating potential mode causes periodic growth thereby inducing different layers with reduced wire thickness/defects at the layer interfaces.

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

    PubMed

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

    2015-09-01

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

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

    PubMed

    Wu, Grace; Zaman, Muhammad H

    2015-03-01

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

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

    PubMed

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

    2016-01-13

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

  15. Growth and etch rate study of low temperature anodic silicon dioxide thin films.

    PubMed

    Ashok, Akarapu; Pal, Prem

    2014-01-01

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

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

    PubMed Central

    Ashok, Akarapu; Pal, Prem

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

    The authors are working toward the design of a device for the detection of oxygen, following a discrete and an integrated instrumentation implementation. The discrete electronics are also used for preliminary analysis, to confirm the validity of the conception of system, and its set-up would be used in the characterization of the integrated device, waiting for the chip fabrication. This paper presents the design of a small and portable potentiostat integrated with electrodes, which is cheap and miniaturized, which can be applied for on-site measurements for the simultaneous detection of O2 and temperature in water systems. As a first approach a discrete PCB has been designed based on commercial discrete electronics and specific oxygen sensors. Dissolved oxygen concentration (DO) is an important index of water quality and the ability to measure the oxygen concentration and temperature at different positions and depths would be an important attribute to environmental analysis. Especially, the objective is that the sensor and the electronics can be integrated in a single encapsulated device able to be submerged in environmental water systems and be able to make multiple measurements. For our proposed application a small and portable device is developed, where electronics and sensors are miniaturized and placed in close proximity to each other. This system would be based on the sensors and electronics, forming one module, and connected to a portable notebook to save and analyze the measurements on-line. The key electronics is defined by the potentiostat amplifier, used to fix the voltage between the Working (WE) and Reference (RE) electrodes following an input voltage (Vin). Vin is a triangular signal, programmed by a LabViewinterface, which is also used to represent the CV transfers. To obtain a smaller and compact solution the potentiostat amplifier has also been integrated defining a full custom ASIC amplifier, which is in progress, looking for a point-of-care device. These circuits have been designed with a 0.13 μm technology from ST Microelectronics through the CMP-TIMA service.

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

    PubMed

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

    2016-02-10

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

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

    SciTech Connect

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

    2009-09-15

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

  1. Chemiresistive sensor based on polythiophene-modified single-walled carbon nanotubes for detection of NO2

    NASA Astrophysics Data System (ADS)

    Gaikwad, Sumedh; Bodkhe, Gajanan; Deshmukh, Megha; Patil, Harshada; Rushi, Arti; Shirsat, Mahendra D.; Koinkar, Pankaj; Kim, Yun-Hae; Mulchandani, Ashok

    2015-03-01

    In the present investigation, a chemiresistive sensor based on conducting polythiophene-modified single-walled carbon nanotubes (SWNTs) for NO2 detection has been reported. The SWNTs were aligned across 3 ?m gap between two gold microelectrodes on Si/SiO2 substrate. Alignment of SWNTs was carried out by using AC dielectrophoretic technique and it was confirmed by current-voltage (I-V) measurement. Aligned SWNTs were modified by conducting polythiophene using charge controlled potentiostatic deposition and it was confirmed by field-effect transistor (FET) and electrochemical measurements. Polythiophene-modified SWNT devices were used for the NO2 detection in chemiresistive modality. This sensor exhibited very good linear response range from 10 ppb to 10 ppm.

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

    PubMed

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2001-09-01

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

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

    SciTech Connect

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

    1988-07-01

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

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

    NASA Technical Reports Server (NTRS)

    Buehler, Martin (Inventor)

    2009-01-01

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

  6. Microdialysis Sampling Coupled to Microchip Electrophoresis with Integrated Amperometric Detection on an All Glass Substrate

    PubMed Central

    Scott, David E.; Grigsby, Ryan; Lunte, Susan M.

    2013-01-01

    The development of an all-glass separation-based sensor using microdialysis coupled to microchip electrophoresis with amperometric detection is described. The system includes a flow-gated interface to inject discrete sample plugs from the microdialysis perfusate into the microchip electrophoresis system. Electrochemical detection was accomplished with a platinum electrode in an in-channel configuration using a wireless electrically isolated potentiostat. To facilitate bonding around the in-channel electrode, a fabrication process was employed that produced a working and a reference electrode flush with the glass surface. Both normal and reversed polarity separations were performed with this sensor. The system was evaluated in vitro for the continuous monitoring of the production of hydrogen peroxide from the reaction of glucose oxidase with glucose. Microdialysis experiments were performed using a BASi loop probe with an overall lag time of approximately five minutes and a rise time of less than 60 seconds. PMID:23794474

  7. Corrosion protection ability of plasma-deposited amorphous hydrogenated carbon and fluorocarbon films

    NASA Astrophysics Data System (ADS)

    Srividya, C.; Sunkara, M.; Babu, S. V.

    1997-10-01

    Hydrogenated diamond-like carbon and fluorocarbon films, deposited in a radio-frequency (rf) plasma reactor, have high chemical inertness and high electrical resistivity. These films, deposited on aluminum and type 301 stainless steel substrates at several rf power and feed gas flow rates using different gas phase precursors, were characterized for their pinhole density and stability with exposure to 0.6 M NaCl and 0.1 M NaCl and 0.1 M Na2SO4 solutions using electrochemical impedance spectroscopy and potentiostatic techniques, respectively. The results from electrochemical characterizations with salt water exposure indicated that films with high effective pore resistances (>108 ? cm2)* and high stability with exposure (<10% changes in capacitance values) can be obtained over a narrow range of process conditions and gas phase compositions.

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

    PubMed

    Gwak, Jieun; Choun, Myounghoon; Lee, Jaeyoung

    2016-02-01

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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    A new liquid flow-cell designed for electronic structure investigations at the liquid-solid interface by soft X-ray absorption and emission spectroscopy is presented. A thin membrane serves simultaneously as a substrate for the working electrode and solid state samples as well as for separating the liquid from the surrounding vacuum conditions. In combination with counter and reference electrodes this approach allows in-situ studies of electrochemical deposition processes and catalytic reactions at the liquid-solid interface in combination with potentiostatic measurements. As model system in-situ monitoring of the deposition process of Co metal from a 10 mM CoCl2 aqueous solution by X-ray absorption and emission spectroscopy is presented.

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

    PubMed

    Sliozberg, Kirill; Schfer, 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. Tribo-electrochemical characterization of hafnium multilayer systems deposited on nitride/vanadium nitride AISI 4140 steel

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  13. 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.

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

    PubMed

    Kim, Eun-Sil; Choe, Han-Cheol

    2014-11-01

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

  15. Effect of growth potential on the electrodeposition of CIS thin films

    NASA Astrophysics Data System (ADS)

    Dhanwate, Vishakha N.; Chaure, N. B.

    2013-02-01

    Thin films of copper indium diselenide (CIS) were prepared in aqueous bath by low-cost potentiostatic electrodeposition technique onto Fluorine doped tin oxide substrates. The deposition potential was optimized using cyclic voltammetry study in a ternary Cu-In-Se system. The films were characterized systematically with the aid of UV-Vis spectroscopy, IV measurements, X-ray diffraction, Scanning electron microscopy and Energy dispersive X-ray analysis. CIS films deposited for different growth potential shows the tetragonal structure with (112) preferential orientation. Annealing of the films at temperature 400°C not only improves the crystallinity of layers, but it also increases the grain size, which is suitable for the development of high efficiency solar cells.

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

    SciTech Connect

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

    2003-08-01

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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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 that are produced by microbial biofilms and can affect their 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?mm2 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.

  19. Surface enhanced Raman scattering of a lipid Langmuir monolayer at the air-water interface.

    PubMed

    Mangeney, C; Dupres, V; Roche, Y; Felidj, N; Levi, G; Aubard, J; Bernard, S

    Surface enhanced Raman spectra were recorded from a phospholipid monolayer directly at the air-water interface. We used an organized monolayer of negatively charged tetramyristoyl cardiolipins as a template for the electrochemical generation of silver deposits. This two-dimensional electrodeposition of silver under potentiostatic control was the substrate for enhancement of Raman spectra. We report the optimized conditions for the Raman enhancement, the microscopic observations of the deposits, and their characterization by atomic force microscopy. Laser excitation at 514.5 nm leads to intense and reproducible surface enhanced Raman scattering spectra recorded in situ from one monolayer of cardiolipin, using 0.5 mol % of 10N nonyl acridine orange or 5 mol % of acridine in the film, and demonstrates the possibility of estimating the pH at the metal/phospholipidic film interface. PMID:15137111

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    PubMed Central

    2014-01-01

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

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

    PubMed

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

    2015-10-10

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

  3. Processing Ti-25Ta-5Zr Bioalloy via Anodic Oxidation Procedure at High Voltage

    NASA Astrophysics Data System (ADS)

    Ionita, Daniela; Grecu, Mihaela; Dilea, Mirela; Cojocaru, Vasile Danut; Demetrescu, Ioana

    2011-12-01

    The current paper reports the processing of Ti-25Ta-5Zr bioalloy via anodic oxidation in NH4BF4 solution under constant potentiostatic conditions at high voltage to obtain more suitable properties for biomedical application. The maximum efficiency of the procedure is reached at highest applied voltage, when the corrosion rate in Hank's solution is decreased approxomately six times. The topography of the anodic layer has been studied using atomic force microscopy (AFM), and the results indicated that the anodic oxidation process increases the surface roughness. The AFM images indicated a different porosity for the anodized surfaces as well. After anodizing, the hydrophilic character of Ti-25Ta-5Zr samples has increased. A good correlation between corrosion rate obtained from potentiodynamic curves and corrosion rate from ions release analysis was obtained.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

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

    PubMed

    Garca-Torres, J; Gispert, C; Gmez, E; Valls, 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

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

    SciTech Connect

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

    2014-10-15

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

  7. 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

  8. Electrochemical velocimetry on centrifugal microfluidic platforms.

    PubMed

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

    2013-08-21

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

  9. Copper-selective electrochemical filling of macropore arrays for through-silicon via applications

    PubMed Central

    2012-01-01

    In this article, the physico-chemical and electrochemical conditions of through-silicon via formation were studied. First, macropore arrays were etched through a low doped n-type silicon wafer by anodization under illumination into a hydrofluoric acid-based electrolyte. After electrochemical etching, ‘almost’ through-silicon macropores were locally opened by a backside photolithographic process followed by anisotropic etching. The 450 × 450-μm² opened areas were then selectively filled with copper by a potentiostatic electrochemical deposition. Using this process, high density conductive via (4.5 × 105 cm−²) was carried out. The conductive paths were then electrically characterized, and a resistance equal to 32 mΩ/copper-filled macropore was determined. PMID:22776559

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

    SciTech Connect

    Fukuda, Masaki; Iida, Chihiro; Nakayama, Masaharu

    2009-06-03

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

  11. Preparation and characterization of Sb2Se3 thin films by electrodeposition and annealing treatment

    NASA Astrophysics Data System (ADS)

    Lai, Yanqing; Chen, Zhiwei; Han, Can; Jiang, Liangxing; Liu, Fangyang; Li, Jie; Liu, Yexiang

    2012-11-01

    Antimony selenide (Sb2Se3) thin films were prepared on SnO2 coated glass substrates from acidic aqueous solution by potentiostatic electrodeposition and then post annealed at 300 C in Ar atmosphere. Cyclic voltammetry (CV), energy dispersive X-ray spectroscopy (EDS), and environmental scanning electron microscope (ESEM) studies were performed on as-deposited Sb2Se3 thin films to obtain suitable electrodeposition conditions. The annealed film shows improved crystallinity with a basic structure of orthorhombic Sb2Se3, and exhibits an optical absorption coefficient of higher than 105 cm-1 in the visible region and an optical band gap of 1.04 0.01 eV. Photoelectrochemical (PEC) tests confirm the p-type conductivity and good photovoltaic conversion characteristics of the annealed film.

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

    SciTech Connect

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

    2013-06-01

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

  13. Development of the high-temperature redox electrode and improved corrosion rate meter. Interim report for period ending September 1980

    SciTech Connect

    Danielson, M.J.; Koski, O.H.

    1981-09-01

    The oxidation-reduction (redox) electrode studies at Pacific Northwest Laboratory (PNL) were completed with the examination of the sulfide-sulfate system. This system is extremely reducing, and it was concluded that the redox electrode would still respond to the entry of oxygen even though sulfide is an oxygen getter. The corrosion rate of platinum in oxygenated brine was determined at 250/sup 0/C. It was concluded that the mechanism of response to oxygen fits a mixed potential model. Work began on the improved corrosion rate meter (ICR). A potentiostat and programmer were constructed and successfully tested. Corrosion tests were carried out in 25/sup 0/C brine with and without oxygen, and the ICR response was very good when compared to corrosion rates determined by weight loss. Future work will involve autoclave tests and development of microprocessor control of the electronics to simplify the measurements.

  14. Structural and compositional characterization of Bi1-xSbx nanowire arrays grown by pulsed deposition to improve growth uniformity

    NASA Astrophysics Data System (ADS)

    Cassinelli, M.; Mller, S.; Aabdin, Z.; Peranio, N.; Eibl, O.; Trautmann, C.; Toimil-Molares, M. E.

    2015-12-01

    Arrays of Bi1-xSbx nanowire with various compositions (0 ? x ? 1) are grown in etched ion-track membranes by pulsed electrochemical deposition. Nanowires of diameter from 130 nm down to 18 nm are characterized by means of X-ray diffraction and high-resolution electron microscopy combined with electron diffraction and energy dispersive X-ray analysis. Compared to potentiostatic deposition, the pulsed synthesis method leads to a more uniform growth and higher filling rate of the wires across the entire template. By tuning the deposition parameters, we demonstrate excellent control over the wire composition and crystallographic orientation. The deposition process presented facilitates the development of future nanowire-based thermoelectric sensors, which are expected to exhibit a higher sensitivity and a faster response compared to thin film sensors.

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

    PubMed

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

    2015-05-11

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

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

    SciTech Connect

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

    1998-08-01

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

  17. 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.

  18. Electrochemical and surface studies of zinc in alkaline solutions containing organic corrosion inhibitors

    NASA Astrophysics Data System (ADS)

    Ein-Eli, Y.; Auinat, M.; Starosvetsky, D.

    The electrochemical behavior of zinc in strong alkaline solutions containing 8.5 M of potassium hydroxide (KOH) and polymeric organic inhibitors was evaluated. The concentrations of the organic inhibitors studies were in the range of 400-4000 ppm and included polyethylene glycol (PEG), with a molecular weight of 600, and polyoxyethylen alkyl phosphate ester acid form (GAFAC RA600). The electrochemical studies included anodic, cathodic, and linear polarization along with potentiostatic studies. It was found that the inhibition properties of PEG, in the strong alkaline solution, are by far much more efficient than the inhibition capability of GAFAC RA600. Surface analysis obtained with the use of high resolution scanning electron microscopy (HRSEM) revealed different morphology characteristic developed at the zinc surface in the presence of the two inhibitors. A methodology employing electrochemical tests is proposed to quickly and conveniently evaluate inhibitors for Zn in alkaline media.

  19. Influence of sodium salts of organic acids as additives on localized corrosion of aluminum and its alloys

    SciTech Connect

    Raspini, I.A. )

    1993-10-01

    Localized pitting is best described by a characteristic parameter called the pitting potential values (E[sub p]). Although E[sub p] is governed by a number of factors, including alloy composition, metallurgical history, and the corrosive environment, the strongest effect on E[sub p] is produced by certain additives that differ from the aggressive anion and exert a beneficial effect. These are referred to as inhibitors. Potentiokinetic and potentiostatic anodic polarization curves were obtained on aluminum (Al) and Al alloys in mixed solutions containing sodium chloride with sodium benzoate, sodium acetate, or thioglycolic acid as inhibitors. Immersion time at the rest potential and corrosion products accumulated in the pits influenced the inhibition efficiency. Reliability of the polarization method was discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  2. Electrochemical generation of phosphorus-containing ion-radicals with simultaneous recording of EPR signal and electrochemical characteristics

    SciTech Connect

    Il'yasov, A.V.; Kadirov, M.K.; Kargin, Yu.M.

    1987-12-01

    The electrochemical generation of ion-radicals, especially under controlled conditions, widens the possibilities of a thorough theoretical analysis of the electronic structure of the compounds and of the rules governing the consecutive chemical reactions. In this work, the authors used a specially constructed three-electrode spiral vacuum cell to study at various temperatures certain unsaturated organophosphorus compounds containing two phosphorus atoms in the molecule. The possibility was envisaged of applying galvanometric pulses to the working electrode, containing the EPR spectrometer resonator, while controlling the potential, time, and intensity of the EPR signal, as well as poentiodynamic and potentiostatic pulses. The EPR spectra were recorded on a Bruker-Physik spectrometer. HFS constants are given for the ion-radicals studied.

  3. 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.

  4. Electrochemical durability of heat-treated carbon nanospheres as catalyst supports for proton exchange membrane fuel cells.

    PubMed

    Lv, Haifeng; Wu, Peng; Wan, Wei; Mu, Shichun

    2014-09-01

    Carbon nanospheres is wildly used to support noble metal nanocatalysts in proton exchange membrane (PEM) fuel cells, however they show a low resistance to electrochemical corrosion. In this study, the N-doped treatment of carbon nanospheres (Vulcan XC-72) is carried out in ammonia gas. The effect of heating treatment (up to 1000 degrees C) on resistances to electrochemical oxidation of the N-doped carbon nanospheres (HNC) is investigated. The resistance to electrochemical oxidation of carbon supports and stability of the catalysts are investigated with potentiostatic oxidation and accelerated durability test by simulating PEM fuel cell environment. The HNC exhibit a higher resistance to electrochemical oxidation than traditional Vulcan XC-72. The results show that the N-doped carbon nanospheres have a great potential application in PEM fuel cells. PMID:25924366

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

    PubMed Central

    2015-01-01

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

  6. Corrosion resistance of polyurethane-coated nitinol cardiovascular stents.

    PubMed

    Mazumder, M M; De, S; Trigwell, S; Ali, N; Mazumder, M K; Mehta, J L

    2003-01-01

    Corrosion of metal stents implanted inside an artery can have two adverse effects: (1) tissue reaction and possible toxic effects from the metal ions leaching out of the stent, and (2) loss of mechanical strength of the stent caused by corrosion. The corrosion resistance of Nitinol (Nickel-Titanium) stents and its modulation with different film thickness of polymer coating was studied against an artificial physiological solution using a Potentiostat/Galvanostat and an electrochemical corrosion cell. The corrosion rate decreased rapidly from 275 microm/year for an uncoated surface down to less than 13 microm/year for a 30 microm thick polyurethane coating. Stainless steel (316L) and Nitinol both contain potentially toxic elements, and both are subject to stress corrosion. Minimization of corrosion can significantly reduce both tissue reaction and structural degradation. PMID:14870939

  7. Nano/micro structure synthesis on semiconducting substrate and their characterization

    NASA Astrophysics Data System (ADS)

    Kaur, Jaskiran; Singh, Surinder; Kumar, Rajesh; Kanjilal, Dinakar; Chakarvarti, Shiv Kumar

    2011-12-01

    In this paper electrical and field emission properties of the randomly distributed copper, iron and nickel nanowires on GaAs substrate are presented. Semiconducting (GaAs) wafers, spin coated with thin polymeric films were irradiated with 50 MeV Li (+3) ions at a fluence of 8 10 7 ions/cm 2, followed by UV irradiation and chemically etching in aqueous NaOH (6N, at room temperature). The wires have been deposited potentiostatically into the pores of the track-etch polycarbonate membrane spin coated onto the GaAs substrate. The size, shape and morphology of the deposits are strongly dependent of the preparation conditions such as deposition potential, current density, electrolyte and etching conditions. Later, morphological, electrical and field emission properties of the so deposited nano-/micro-structures were studied.

  8. A nanostructured copper telluride thin film grown at room temperature by an electrodeposition method

    NASA Astrophysics Data System (ADS)

    Dhasade, S. S.; Han, S. H.; Fulari, V. J.

    2012-09-01

    Copper telluride onion flower like microstructures, constructed by quantum dots with various diameters, were obtained by a potentiostatic electrodeposition method at room temperature. The structural, optical, surface morphology, compositional analysis and Raman spectra properties of the deposited films have been studied using X-ray diffraction, optical absorption with scanning electron microscopy, EDAX, and Raman spectroscopy. The electrolyte concentration and deposition time can be used to control the diameter of the electrodeposited quantum dots to within a range of 50-55 nm. The films are found to be stoichiometric in composition. The optical constants such as the optical band gap energy and the optical absorption spectra show significant variation in their values with a change in deposition time. Upon deposition time the band gap energy increased from a value of 2.74 to 2.89 eV.

  9. 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.

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

    SciTech Connect

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

    2009-12-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  12. Electrochemical self-assembly of oriented zinc oxide film from polyethylene oxide containing electrolyte.

    PubMed

    Ju, Xiaohui; Feng, Wei; Fujii, Akihiko; Ozaki, Masanori

    2009-03-01

    Oriented nanopillar ZnO crystals were firstly fabricated by the potentiostatic cathodic electrodeposition technique on conducting glass substrates from polyethylene oxide (PEO) containing zinc nitrate solutions at low temperature (343 K). The mechanism for PEO-assisted electrochemical growth of ZnO hexagonal columus was proposed and confirmed by scanning electron microscopy, X-ray diffraction and UV-visible spectrophotometer measurements. It was observed that the concentration of PEO played an important role in the morphology and size of ZnO crystals. The structure and optical studies indicated that the addition of PEO not only influenced crystal growth habit but also improve the optical properties of ZnO. PMID:19435038

  13. 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.

  14. Relaxation phenomena in lithium ion insertion cells and simulation of the Sony cell

    SciTech Connect

    Fuller, T.F.; Doyle, M.; Newman, J.

    1994-12-31

    Relaxation phenomena in lithium-ion-insertion cells are modeled. Simulation results are presented for a dual lithium-ion-insertion cell and for a cell using a lithium-foil negative electrode. A period of relaxation after a charge or discharge can cause appreciable changes in the distribution of material in the insertion electrodes. Local concentration cells in the solution phase and an open-circuit potential that depends on state of charge for the solid phase drive the redistribution of material. Concentration profiles in solid and solution phases during relaxation are analyzed, and the consequences for cell performance are discussed. The model predicts the effects of relaxation time on multiple charge-discharge cycles and on peak power. Galvanostatic and potentiostatic charging are simulated; the results are compared to experimental data for a commercial battery.

  15. Inhibition of acidic corrosion of carbon steel by some mono and bis azo dyes based on 1,5 dihydroxynaphihalene.

    PubMed

    Abdallah, Metwally; Moustafa, Moustafa E

    2004-01-01

    Inhibition of the corrosion of carbon steel in hydrochloric acid solution by some mono- and bis-azo dyes based on 1,5-dihydroxynaphthalene was studied in relation to the concentration of inhibitors using weight loss and potentiostatic polarization techniques. The percentage inhibition efficiency calculated from two methods is in a good agreement with each other. The inhibition mechanism of the additives was ascribed to the formation of complex compound adsorbed on the metal surface. The adsorption process follows Freundlich adsorption isotherm. The formation of the complex compound was studied by conductometric and potentiometric titrations. The stability constants of the Fe-complexes were determined using the latter technique and related to the inhibition efficiency. PMID:15347207

  16. Khillah extract as inhibitor for acid corrosion of SX 316 steel

    NASA Astrophysics Data System (ADS)

    El-Etre, A. Y.

    2006-10-01

    The inhibitive effect of the extract of khillah ( Ammi visnaga) seeds, on the corrosion of SX 316 steel in HCl solution was determined using weight loss measurements as well as potentiostatic technique. It was found that the presence of the extract reduces markedly the corrosion rate of steel in the acid solution. The inhibition efficiency increases as the extract concentration is increased. The inhibitive effect of khillah extract was discussed on the basis of adsorption of its components on the metal surface. Negative values were calculated for the energy of adsorption indicating the spontaneity of the adsorption process. The formation of insoluble complexes as a result of interaction between iron cations and khellin, which present in the extract, was also discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  18. Microdialysis sampling coupled to microchip electrophoresis with integrated amperometric detection on an all-glass substrate.

    PubMed

    Scott, David E; Grigsby, Ryan J; Lunte, Susan M

    2013-07-22

    The development of an all-glass separation-based sensor using microdialysis coupled to microchip electrophoresis with amperometric detection is described. The system includes a flow-gated interface to inject discrete sample plugs from the microdialysis perfusate into the microchip electrophoresis system. Electrochemical detection was accomplished with a platinum electrode in an in-channel configuration using a wireless electrically isolated potentiostat. To facilitate bonding around the in-channel electrode, a fabrication process was employed that produced a working and a reference electrode flush with the glass surface. Both normal and reversed polarity separations were performed with this sensor. The system was evaluated in vitro for the continuous monitoring of the production of hydrogen peroxide from the reaction of glucose oxidase with glucose. Microdialysis experiments were performed using a BASi loop probe with an overall lag time of approximately five minutes and a rise time of less than 60 seconds. PMID:23794474

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    PubMed

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

    2016-02-01

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

  1. Electrochemical behaviour of Ti-Ni SMA and Co-Cr alloys in dynamic Tyrode's simulated body fluid.

    PubMed

    Liang, Chenghao; Zheng, Runfen; Huang, Naibao; Wu, Bo

    2010-05-01

    The electrochemical behaviour of Ti-Ni shape memory alloy and Co-Cr alloys were investigated in dynamic Tyrode's simulated body fluid on a Model CP6 Potentiostat/Galvanostat. The results indicated that, for all alloys, the anodic dissolution and the pitting sensitivity increased with the flow rate of the Tyrode's solution increasing while the open-circuit potentials and pitting corrosion potentials decreased with the Tyrode's solution increasing. Pitting corrosion of Ti-Ni alloy was easier than Co-Cr alloys. Since the solution's flow enhanced oxygen transform and made it easy to reach the surface of electrodes, the plateau of oxygen diffusion control was diminished. All these indicated that the cathodic reduction and the corrosion reaction, which was controlled by the electrochemical mass transport process, were all accelerated in dynamic Tyrode's simulated body fluid. PMID:20143135

  2. Corrosion behavior of sensitized duplex stainless steel.

    PubMed

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

    1998-01-01

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

  3. 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

  4. Crevice corrosion products of dental amalgam

    SciTech Connect

    Sutow, E.J.; Jones, D.W.; Hall, G.C.; Owen, C.G. )

    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.

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

    PubMed

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  7. 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.

  8. Studies on the electrodeposition of tin from acidic chloride-gluconate solutions

    NASA Astrophysics Data System (ADS)

    Rudnik, Ewa; W?och, Grzegorz

    2013-01-01

    Electrodeposition of tin from acidic chloride-gluconate baths was investigated. Equilibrium distribution of tin(II) species showed domination of Sn(II)-gluconate complexes, but for Sn2+ concentrations 50 mM or higher increased percentage of Sn(II)-chloride complexes was found. Cyclic voltammetry, anodic stripping analysis and potentiostatic measurements indicated that rate of the cathodic process is determined by the release of metal cations from gluconate complexes in diluted bath (5 mM), but for more concentrated solutions reduction of Sn(II) ions run under diffusion control. Studies of anodic response showed that it depends on the Sn(II)/Glu ratio in the bath and deposition potential due to development of different planes of metal crystal. Average effective diffusion coefficients of metal species were determined. Morphology and structure tin deposits were also presented.

  9. Polymer electrolyte fuel cell performance degradation at different synchrotron beam intensities.

    PubMed

    Eller, Jens; Bchi, Felix N

    2014-01-01

    The degradation of cell performance of polymer electrolyte fuel cells under monochromatic X-ray irradiation at 13.5?keV was studied in galvanostatic and potentiostatic operation modes in a through-plane imaging direction over a range of two orders of magnitude beam intensity at the TOMCAT beamline of the Swiss Light Source. The performance degradation was found to be a function of X-ray dose and independent of beam intensity, whereas the degradation rate correlates with beam intensity. The cell performance was more sensitive to X-ray irradiation at higher temperature and gas feed humidity. High-frequency resistance measurements and the analysis of product water allow conclusions to be drawn on the dominating degradation processes, namely change of hydrophobicity of the electrode and sulfate contamination of the electrocatalyst. PMID:24365920

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

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

    PubMed

    Liu, Xiaolin; Guo, Min; Cao, Jianjun; Lin, Jia; Tsang, Yuen Hong; Chen, Xianfeng; Huang, Haitao

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  15. 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.

  16. 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.

  17. Synthesis of nano-structured polypyrrole/copper electrodes for nitrate and nitrite electroreduction

    NASA Astrophysics Data System (ADS)

    Phuong Thoa Nguyen, Thi; Thinh Nguyen, Viet; Nguyen Bui, Nhat; Do, Duong Kim Bao; Pham, Anh Minh

    2010-09-01

    Nanostructured polypyrrole film was synthesized onto a copper electrode in solutions of oxalic and salicylic acids and their buffers. The electrooxidation of pyrrole to form polypyrrole film and the electroreduction of nitrate and nitrite ions at synthesized Ppy modified copper electrodes (Ppy/Cu) in potassium chloride aqueous solutions were studied using chronoamperometry. The nanoporous structure of the synthesized Ppy films was characterized by scanning electron microscopy (SEM). Nitrate and nitrite reduction were performed by an electrochemical method under potentiostatic conditions. The Ppy/Cu electrodes prepared in the oxalate buffer and salicylic acid solutions perform more stable catalytic activity for nitrate reduction; their service life is about ten times longer than that for the electrodes prepared in oxalic acid solution. After 20?h of electrolysis, the nitrite was reduced completely with 100% efficiency and the nitrate was reduced with 35% efficiency. Report submitted to the 5th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN, Hanoi, 9-12 November 2010.

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

    SciTech Connect

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

    2007-08-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

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

    PubMed

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

    2013-06-01

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

  1. Template-assisted electrochemical growth of polypyrrole nanotubes for development of high sensitivity glucose biosensor.

    PubMed

    Palod, Pragya Agar; Pandey, Shyam S; Hayase, Shuji; Singh, Vipul

    2014-10-01

    In this paper, we report the growth of polypyrrole (PPy) nanotube arrays using template-assisted electrochemical polymerization to fabricate enzymatic glucose biosensors. The PPy nanotubes were grown on platinum-coated alumina membranes (Anodiscs). By varying the polymerization time during the potentiostatic electropolymerization, the size/diameter of the PPy nanotubes were controlled, leading to changes in the subsequent enzyme immobilization (via physical adsorption). Enzyme electrode thus fabricated resulted in to the optimum sensitivity of 18.6mAcm(-2)M(-1), a wide range of linear operation (0.25-20mM) and the lowest detection limit of 0.25mM glucose concentration for the biosensor with the polymerization time of 40s. The effect of polymerization duration on the sensitivity has been explained on the basis of porosity and enzyme-loading capacity of polymerized electrodes. PMID:24912977

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

    NASA Technical Reports Server (NTRS)

    Ambrose, John R.

    1992-01-01

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

  3. Microstructural characterization of degradation in a high-chromium alloy in the sugar industry.

    PubMed

    Zumelzu, E; Parada, A; Goyos, L; Bobadilla, C

    2006-01-01

    A new high (24%)-chromium alloy was experimentally manufactured by combining the particular chemical composition of various materials with the use of thermal treatments to produce pump impellers for the sugar industry. The alloy metal was tested in situ in a sugar medium and then evaluated by electrochemical measurements; the two former procedures were associated with a nontraditional method to assess the susceptibility and resistance to corrosion. Potentiostatic and atomic absorption measurements were carried out to characterize the degradation and damage morphology by scanning electron microscopy (SEM) observations. The trials proved a good performance for the new alloy in the sugar medium in spite of nonsignificant localized damages involving erosion-corrosion mechanisms and surface microcrackings of the material. PMID:17181134

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

    PubMed

    Gutirrez Pineda, Eduart; Alcaide, Francisco; Rodrguez Presa, Mara J; Bolzn, Agustn 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  6. X-Ray Photoelectron Spectroscopy Depth Profiling of Electrochemically Prepared Thin Oxide Layers on Duplex Stainless Steel

    NASA Astrophysics Data System (ADS)

    Donik, ?rtomir; Kocijan, Aleksandra; Mandrino, Djordje; Jenko, Monika

    2011-10-01

    The surface oxidation of duplex stainless steel (DSS 2205) was studied by X-ray photoelectron spectroscopy (XPS). The experiments were performed on the alloy after controlled oxidation in a chloride-enriched solution at controlled potentials. The evolution of the passive film formed on the DSS in a chloride solution was studied using cyclic voltammetry with XPS surface characterization at selected potentials. The evolution of the oxide films and its specific compositions formed on the DSS was studied as a function of depth. Fe/Cr oxidized layers and oxide thicknesses were observed and correlated with the various potentiostatic potentials. The importance of Mo and Cr inside the oxide films in this article is studied and described, whereas their role in the protective layer, as oxides, is significant.

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

    NASA Astrophysics Data System (ADS)

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

    2005-06-01

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

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

    NASA Astrophysics Data System (ADS)

    da Silva, Paulo Srgio; Schmitz, Edinia P. Sartori; Spinelli, Almir; Garcia, Jarem Raul

    2012-07-01

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

  9. Cooperative stochastic behavior in localized corrosion. 2: Experiments

    SciTech Connect

    Lunt, T.T.; Pride, S.T.; Scully, J.R.; Hudson, J.L.; Mikhailov, A.S.

    1997-05-01

    Two types of experiments on metastable pitting are carried out in NaCl solutions, one with galvanically coupled Al-2% Cu and the second with 316L stainless steel under potentiostat control; the time dependence of the current is compared to simulated time series developed from the model of Part 1 of these two papers. The experimental and simulated time series are analyzed by several methods in order to extract defining characteristics, and specifically the degree to which interactions among metastable pitting events are present. The similarity between the model and the experiment, particularly of the stainless steel data, is strong, most important when the intermittent transitions between low and high activity metastable pitting regions are considered. Depending on the experimental conditions, large deviations from the Poissonian statistics are observed which agree with the predictions of the model.

  10. 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.

  11. Measurement of Li/sup +/ ion transport numbers in PEO-LiX complexes. Technical report No. 16, 15 July 1985-January 1988

    SciTech Connect

    Munshi, M.Z.; Owens, B.B.; Nguyen, S.

    1988-03-01

    Lithium-ion conducting-polymer materials are being intensively investigated in a number of research laboratories because of their potential use as solid electrolytes in high-energy-density solid-state lithium batteries. The most-widely used polymer were based on polyethylene oxide (PEO). The conduction mechanism in these polymer electrolytes has generally been assumed to be due to Li(+)ion transport from one lone pair site to another along the helical PEO strands. However, recent studies have shown that the Li(+) transport number is less than unity. The transport number for Li(+) ions in PEO-LiX complexes was measured using a potentiostatic polarization technique. The results indicate that the Li(+) ion transport is strongly influenced by the salt concentration and the type of counter ions.

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

    SciTech Connect

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

    1986-09-01

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

  13. 3D Printed Microfluidic Device with Integrated Biosensors for Online Analysis of Subcutaneous Human Microdialysate.

    PubMed

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

    2015-08-01

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

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

    DOE PAGESBeta

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

    2015-10-30

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

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

    PubMed Central

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

    2015-01-01

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

  16. 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

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

    SciTech Connect

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

    2015-03-30

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

  18. 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.

  19. Assessing the corrosion resistance of nonequilibrium magnesium-yttrium alloys

    SciTech Connect

    Miller, P.L.; Shaw, B.A.; Wendt, R.G.; Moshier, W.C.

    1995-12-01

    Magnesium-yttrium (Mg-Y) alloys containing 7 at% to 26 at% solute were fabricated using magnetron cosputter deposition. X-ray diffraction (XRD) revealed that no second phases were present in any of the alloys and that all but two of the alloys (Mg-7% Y and Mg-14% Y) were nanocrystalline and/or amorphous. Anodic potentiodynamic polarization performed in 0.1 M sodium chloride (NaCl) at both near-neutral and high pH values showed improved anodic polarization behavior for most of the alloys when compared to either pure Mg or one of the most corrosion-resistant commercial Mg alloys (alloy WE43 [UNS M18430]). In the high-pH solution, it was not uncommon for breakdown potentials (E{sub b}) of the Mg-Y alloys to be 2,000 mV higher than values for alloy WE43. Long-term galvanic and potentiostatic testing was performed on selected alloys to verify anodic polarization behavior. Potentiostatic testing also was performed in a pH 12 buffer solution. When defects did not affect corrosion behavior, low current density values were obtained, with one specimen exhibiting a current density of 0.9 {micro}A/cm{sup 2} (5.8 {micro}A/in.{sup 2}) at a potential > 300 mV{sub SCE}. X-ray photoelectron spectroscopy (XPS) conducted on Mg-22% Y revealed Y was enriched significantly in the passive film once the alloy was immersed in solution. This presence of oxidized Y in the passive film was believed to be responsible for the exceptional corrosion resistance of these alloys.

  20. 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

  1. Real-Time Telemetry System for Amperometric and Potentiometric Electrochemical Sensors

    PubMed Central

    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

  2. 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.

  3. 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.

  4. 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.

  5. Silver(I) ions ultrasensitive detection at carbon electrodes-analysis of waters, tobacco cells and fish tissues.

    PubMed

    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 μM. 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 μM) 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 μM) 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

  6. 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 μM. 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 μM) 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 μM) 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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    PubMed

    Kim, H; Johnson, J W

    1999-02-01

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

  9. 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

  10. An evaluation of the corrosion performance of magnesium-yttrium and yttrium-magnesium nonequilibrium alloys

    NASA Astrophysics Data System (ADS)

    Heidersbach, Krista Lynn

    1998-11-01

    In an effort to develop a corrosion-resistant light-weight metallic alloy, magnetron co-sputter deposition and electron beam physical vapor deposition (EB-PVD) have been employed to deposit binary magnesium-yttrium and yttrium-magnesium alloys. Yttrium was selected because it has been shown to significantly alter the passive film of magnesium and has been used in several commercially available alloys. The binary alloys, employed in this study, were evaluated for film structure, electrochemical performance and passive film composition and structure. The film's morphology was evaluated using scanning electron microscopy (SEM). Morphologies of the sputtered alloys ranged from zones 1 to zone T. X-ray diffraction (XRD) was used as a quick check for the presence of secondary phases that are detrimental to corrosion behavior. Although secondary phases were present, MgY particles, they did not affect the corrosion performance of the alloys. Electrochemical testing included potentiodynamic polarization, potentiostatic long term testing, and electrochemical impedance spectroscopy. All studies were performed using a standard three electrode technique in one of two solutions; pH 12 buffered solution containing 0.1M NaCl and 0.05M Nasb2Bsb4Osb7 with varied chloride concentration up to 3.5sp{w}/sb{o} NaCl (pH 9.2). Corrosion rates for all four alloys were a minimum of two orders of magnitude lower than either pure Mg or pure Y. The chemical composition of the air-formed oxides, the passive formed upon immersion in the pH 12 buffered solution with no applied potential, and the passive films formed by potentiostatic polarization in the same solution were characterized using XPS. The internal structure of these surface films was identified using transmission electron microscopy. Results from XPS indicated that a bi-layer oxide-hydroxide film was present on the surface of all the sputtered alloys. The inner layer of the film was found to be Ysb2Osb3. The outer layer was a mixture of Mg(OH)sb2 and Y(OH)sb3. TEM verified that this bi-layer film was present in both the air-formed oxides and the passive films formed on all four alloys. Yttrium oxide content increased as the polarization potential increased. It was this inner layer of yttrium oxide that was determined to be responsible for the improved corrosion resistance of these alloys.

  11. A XPS Study of the Passivity of Stainless Steels Influenced by Sulfate-Reducing Bacteria.

    NASA Astrophysics Data System (ADS)

    Chen, Guocun

    The influence of sulfate-reducing bacteria (SRB) on the passivity of type 304 and 317L stainless steels (SS) was investigated by x-ray photoelectron spectroscopy (XPS), microbiological and electrochemical techniques. Samples were exposed to SRB, and then the resultant surfaces were analyzed by XPS, and the corrosion resistance by potentiodynamic polarization in deaerated 0.1 M HCl. To further understand their passivity, the SRB-exposed samples were 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. Comparisons were made with control samples immersed in uninoculated medium. SRB caused a severe loss of the passivity of 304 SS through sulfide formation and possible additional activation to form hexavalent chromium. The sulfides included FeS, FeS_2, Cr_2S _3, NiS and possibly Fe_ {rm 1-x}S. The interaction took place nonuniformly, resulting in undercutting of the passive film and preferential hydration of inner surface layers. The bacterial activation of the Cr^{6+ }^ecies was magnified by subsequent potentiostatic polarization. In contrast, 317L SS exhibited a limited passivity. The sulfides were formed mainly in the outer layers. Although Cr^{6+}^ecies were observed after the exposure, they were dissolved upon polarization. Since 317L SS has a higher Mo content, its higher passivity was ascribed to Mo existing as molybdate on the surface and Mo^{5+} species in the biofilm. Consequently, the interaction of SRB with Mo was studied. It was observed that molybdate could be retained on the surfaces of Mo coupons by corrosion products. In the presence of SRB, however, a considerable portion of the molybdate interacted with intermediate sulfur -containing proteins, forming Mo(V)-S complexes and reducing bacterial growth and sulfate reduction. The limited insolubility of the Mo(V)-S complexes in 0.1 M HCl provided a certain protection so that the pitting potential of the SRB-exposed Mo coupons was not considerably decreased. The interaction of the sulfur-containing proteins with Mo also provided mechanistic information about the adhesion of biofilm to Mo-bearing steels. Additionally, the interactions of SRB with other alloying elements, Cr and Ni, were investigated.

  12. 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.

  13. 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.

  14. Quantifying capacity loss due to solid-electrolyte-interphase layer formation on silicon negative electrodes in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Nadimpalli, Siva P. V.; Sethuraman, Vijay A.; Dalavi, Swapnil; Lucht, Brett; Chon, Michael J.; Shenoy, Vivek B.; Guduru, Pradeep R.

    2012-10-01

    Charge lost per unit surface area of a silicon electrode due to the formation of solid-electrolyte-interphase (SEI) layer during initial lithiation was quantified, and the species that constitute this layer were identified. Coin cells made with Si thin-film electrodes were subjected to a combination of galvanostatic and potentiostatic lithiation and delithiation cycles to accurately measure the capacity lost to SEI layer formation. While the planar geometry of amorphous thin films allows accurate calculation of surface area, creation of additional surface by cracking was prevented by minimizing the thickness of the Si film. The cycled electrodes were analyzed with X-ray photoelectron spectroscopy to characterize the composition of the SEI layer. The charge lost due to SEI formation measured from coin cell experiments was found to be in good agreement with the first-cycle capacity loss during the initial lithiation of a Si(100) crystal with planar geometry. The methodology presented in this work is expected to provide a useful practical tool for battery-material developers in estimating the expected capacity loss due to first cycle SEI layer formation and in choosing an appropriate particle size distribution that balances mechanical integrity and the first cycle capacity loss in large volume expansion electrodes for lithium-ion batteries.

  15. Analysis of gas products from direct utilization of carbon in a solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Siengchum, Tritti; Guzman, Felipe; Chuang, Steven S. C.

    2012-09-01

    The evolution of gases from direct utilization of carbon in a solid oxide fuel cell (C-SOFC) was studied by potentiostatic/galvanostatic discharge of a fuel cell with coconut carbon, a carbonaceous material with low ash and sulfur content. Operation of C-SOFC at 750 °C produced less CO and more CO2 than those predicted by thermodynamic calculation using total Gibbs free energy minimization method. The addition of CO2 to the anode chamber increased CO formation and maximum power density from 0.09 W cm-2 to 0.13 W cm-2, indicating the occurrence of Boudouard reaction (CO2 + C ⇔ 2CO) coupling with CO electrochemical oxidation on the C-SOFC. Analysis of CO and CO2 concentration as a function of current and voltage revealed that electricity was mainly produced from the electrochemical oxidation of carbon at low current density and produced from the electrochemical oxidation of CO at high current density. The results suggest the electrochemical oxidation of solid carbon is more mass transfer limited than electrochemical oxidation of CO.

  16. Synthesis of dendritic silver nanostructures supported by graphene nanosheets and its application for highly sensitive detection of diazepam.

    PubMed

    Majidi, Mir Reza; Ghaderi, Seyran; Asadpour-Zeynali, Karim; Dastangoo, Hossein

    2015-12-01

    In this paper, preparation, characterization and application of a new sensor for fast and simple determination of trace amount of diazepam were described. This sensor is based on Ag nanodendrimers (AgNDs) supported by graphene nanosheets modified glassy carbon electrode (GNs/GCE). The AgNDs were directly electrodeposited on the surface of electrode via potentiostatic method without using any templates, surfactants, or stabilizers. The structure of the synthesized AgNDs/GNs was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) techniques. The nanodendrimers with tree-like and hierarchical structures have a fascinating structure for fabrication of effective electrocatalysts. The experimental results confirmed that AgNDs/GNs/GC electrode has good electrocatalytic activity toward the reduction of diazepam. A low detection limit of 8.5610(-8)M and a wide linear detection range of 1.010(-7) to 1.010(-6)M and 1.010(-6) to 2010(-6)M were achieved via differential pulse voltammetry (DPV). The proposed electrode displayed excellent repeatability and long-term stability and it was satisfactorily used for determination of diazepam in real samples (commercially tablet, injection and human blood plasma) with high recovery. PMID:26354262

  17. Short-term canine implantation of a glucose monitoring-telemetry device.

    PubMed

    Atanasov, P; Yang, S; Salehi, C; Ghindilis, A L; Wilkins, E

    1996-12-01

    In this study we report the development and short-term in vivo evaluation of an integrated implantable device consisting of an amperometric glucose biosensor, a miniature potentiostat, a FM signal transmitter, and power supply. The device (dimensions: 5.0 x 7.0 x 1.5 cm) was implanted under the skin of medium-size anaesthetized dog. The experimental set-up included several methods for data collection: analog recording via wired X-T chart recorders; data collection by wearable microprocessor--data logger, and remote data collection via antenna and receiver linked to a computer-based data acquisition system. The device (sensor) performance was evaluated in vitro prior to implantation, using different model solutions simulating the physiological environment. A linear response to glucose concentration was obtained up to 25 mM glucose, with a sensitivity of 0.5 microA/mM. The results of short-term subcutaneous implantation of the integrated device reveal adequate monitoring of an artificially-induced glycaemia. The delay-time was 3-7 minutes. These tests demonstrate the feasibility of data transmission by the telemetry system through the skin of a medium-sized dog and allow the commencement of chronic in vivo experimentation. PMID:8953555

  18. 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-μm CMOS process occupies an area of 1.2 mm ×2 mm and consumes 50 μW. 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

  19. A Portable Liquid Chromatograph with a Battery-operated Compact Electroosmotic Pump and a Microfluidic Chip Device with a Reversed Phase Packed Column.

    PubMed

    Ishida, Akihiko; Fujii, Mitsutaka; Fujimoto, Takehiro; Sasaki, Shunsuke; Yanagisawa, Ichiro; Tani, Hirofumi; Tokeshi, Manabu

    2015-01-01

    A compact and lightweight liquid chromatography system is presented with overall dimensions of 26 cm width 18 cm length 21 cm height and weight of 2 kg. This system comprises a battery-operated compact electroosmotic pump, a manual injector, a microfluidic chip device containing a packed column and an electrochemical detector, and a USB bus-powered potentiostat. The pumping system was designed for microfluidic-based reversed-phase liquid chromatography in which an electroosmotically generated water stream pushes the mobile phase via a diaphragm for the output. The flow rate ranged from 0 to 10 ?L/min and had a high degree of precision. The pumping system operated continuously for over 24 h with dry batteries. The column formed in the microfluidic device was packed with 3-?m ODS particles with a length of 30 mm and a diameter of 0.8 mm. The results presented herein demonstrate the performance of the pumping system and the column using alkylphenols, catecholamine, catechin, and amino acids. PMID:26561261

  20. Repassivation behavior of 316L stainless steel in borate buffer solution: Kinetics analysis of anodic dissolution and film formation

    NASA Astrophysics Data System (ADS)

    Xu, Haisong; Sun, Dongbai; Yu, Hongying

    2015-12-01

    The repassivation behavior of metals or alloys after oxide film damage determines the development of local corrosion and corrosion resistance. In this work, the repassivation kinetics of 316L stainless steel (316L SS) are investigated in borate buffer solution (pH 9.1) by using the abrading electrode technique. The current densities flowing from bare 316L SS surface are measured by potentiostatic method and analyzed to characterize repassivation kinetics. The initial stages of current decay (t < 500 ms) are discussed according to a film growth model, which describes the initial current transient should be divided into substrate dissolution current and passive film formation current based on Avrami kinetics. Then the two independent components are analyzed individually. The film formation rate and the thickness of film are compared in different applied potential. It is shown that anodic dissolution dominates the repassivation for a short time during the early times, and a higher applied potential will promote the anodic dissolution of metal. The film growth rate increases slightly with increasing in potential. Correspondingly, increase in applied potential from 0 VSCE to 0.8 VSCE results in thicker monolayer, which covers the whole bare surface at the time of θ = 1. The electric field strengths through the thin passive film could reach 3.97 × 106 V cm-1.

  1. 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 (615 at %) and Ni (513 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: 14901499, 2012

  2. Electrodeposition of Nanocrystalline Chromium Coatings Based on 1-Butyl-3-Methylimidazolium-Bromide Ionic Liquid.

    PubMed

    He, Xinkuai; Zhu, Qingyun; Hou, Bailong; Cai, Youxing; Li, Chen; Fu, Liqin; Wu, Luye

    2015-12-01

    The electrochemical behavior of trivalent chromium reduction from 1-butyl-3-methylimidazolium-bromide ([BMIM]Br) ionic liquid is studied. The result of cyclic voltammetry shows that the Cr(III) reduction is irreversible and occurs in two steps, Cr(III)to Cr(II), and Cr(II) to Cr(0), respectively. In the electrochemical impedance spectroscopy measurements, the preferable equivalent circuit is made to fit the experimental data. The effects of electroplating parameters on coating thickness and electrodepositon rate are investigated by potentiostatic method on Cu electrode from Cr(III)-[BMIM]Br solution. The results show that the temperature and depositing potential have great effect on the coating thickness and electrodeposition rate. The surface morphology and composition of deposited Cr are investigated using scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS). SEM analysis shows that chromium electrodeposits obtained on Cu electrodes present a ball-like structure. EDS analysis shows that the coatings are composed of Cr. Moreover, the corrosion resistance of the as-deposited chromium layer is evaluated using polarization curves. The results show that the corrosion resistance of the chromium coatings obtained at higher potential is better. PMID:26682363

  3. Strong Photo-Amplification Effects in Flexible Organic Capacitors with Small Molecular Solid-State Electrolyte Layers Sandwiched between Photo-Sensitive Conjugated Polymer Nanolayers

    PubMed Central

    Lee, Hyena; Kim, Jungnam; Kim, Hwajeong; Kim, Youngkyoo

    2016-01-01

    We demonstrate strong photo-amplification effects in flexible organic capacitors which consist of small molecular solid-state electrolyte layers sandwiched between light-sensitive conjugated polymer nanolayers. The small molecular electrolyte layers were prepared from aqueous solutions of tris(8-hydroxyquinoline-5-sulfonic acid) aluminum (ALQSA3), while poly(3-hexylthiophene) (P3HT) was employed as the light-sensitive polymer nanolayer that is spin-coated on the indium-tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) film substrates. The resulting capacitors feature a multilayer device structure of PET/ITO/P3HT/ALQSA3/P3HT/ITO/PET, which were mechanically robust due to good adhesion between the ALQSA3 layers and the P3HT nanolayers. Results showed that the specific capacitance was increased by ca. 3-fold when a white light was illuminated to the flexible organic multilayer capacitors. In particular, the capacity of charge storage was remarkably (ca. 250-fold) enhanced by a white light illumination in the potentiostatic charge/discharge operation, and the photo-amplification functions were well maintained even after bending for 300 times at a bending angle of 180o. PMID:26846891

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

    PubMed

    Zahn, Raphael; Vrs, Jnos; 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

  5. Optical properties of electrochemically synthesized polypyrrole thin films: the electrolyte effect

    NASA Astrophysics Data System (ADS)

    Thombare, J. V.; Shinde, S. K.; Lohar, G. M.; Chougale, U. M.; Dhasade, S. S.; Dhaygude, H. D.; Relekar, B. P.; Fulari, V. J.

    2014-06-01

    Polypyrrole thin films are prepared by the potentiostatic mode of electrodeposition at +0:7 V versus a saturated calomel electrode (SCE). The polypyrrole films are prepared in the presence of different electrolytes such as: p-toluene sulphonic acid (PTS), oxalic acid and H2SO4. The prepared films are characterized by UVvis absorption spectroscopy and normal reflectance measurements. The electrochemically synthesized films are semiconductor in nature. The band gap energy of polypyrrole thin films is found to be 1.95, 1.92 and 1.79 eV for H2SO4, oxalic acid and p-toluene sulphonic acid, respectively. The normal reflectance spectroscopy of polypyrrole films shows that the maximum reflectance is in the presence of p-toluene sulphonic acid; this is may be due to a more distinct microstructure than the others. The optical constants such as the extinction coefficient, refractive index, optical conductivity, etc. are calculated and studied with various electrolytes.

  6. 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.; Baroux, B.

    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.

  7. Electrochemical noise measurement: The definitive in-situ technique for corrosion applications?

    SciTech Connect

    Dawson, J.L.

    1996-12-31

    A review is presented of electrochemical noise (EN), the generic term given to fluctuations of current and potential seen in high-temperature corrosion, molten salt corrosion, and aqueous corrosion. EN levels in corrosion and particularly localized corrosion are significantly greater than EN observed in redox systems. EN associated with corrosion is the result of stochastic pulses of current generated by, for example, sudden film rupture, crack propagation, discrete events involving metal dissolution at etch pits, grain boundaries and kink sites, and hydrogen discharge with gas bubble formation and detachment. EN in corrosion includes low-frequency, nonstationary, and weakly stationary processes; transients; and cyclic or oscillatory phenomena. The use of EN, obtained either by potentiostatic/galvanostatic measurements or at freely corroding potentials, has been shown to offer advantages over conventional DC and AC techniques in research studies, testing, and corrosion monitoring. In many cases, reaction mechanisms can be elucidated and corrosion rate information can be obtained. Assessment of individual transients, use of signal analysis techniques, modeling of ensembles of transients as developed for electrocrystallization studies, and use of the chaos theory have all been used in EN evaluations.

  8. Submicron patterned metal hole etching

    DOEpatents

    McCarthy, Anthony M. (Menlo Park, CA); Contolini, Robert J. (Lake Oswego, OR); Liberman, Vladimir (Needham, MA); Morse, Jeffrey (Martinez, CA)

    2000-01-01

    A wet chemical process for etching submicron patterned holes in thin metal layers using electrochemical etching with the aid of a wetting agent. In this process, the processed wafer to be etched is immersed in a wetting agent, such as methanol, for a few seconds prior to inserting the processed wafer into an electrochemical etching setup, with the wafer maintained horizontal during transfer to maintain a film of methanol covering the patterned areas. The electrochemical etching setup includes a tube which seals the edges of the wafer preventing loss of the methanol. An electrolyte composed of 4:1 water: sulfuric is poured into the tube and the electrolyte replaces the wetting agent in the patterned holes. A working electrode is attached to a metal layer of the wafer, with reference and counter electrodes inserted in the electrolyte with all electrodes connected to a potentiostat. A single pulse on the counter electrode, such as a 100 ms pulse at +10.2 volts, is used to excite the electrochemical circuit and perform the etch. The process produces uniform etching of the patterned holes in the metal layers, such as chromium and molybdenum of the wafer without adversely effecting the patterned mask.

  9. A 1000-cell SOFC reactor for domestic cogeneration

    NASA Astrophysics Data System (ADS)

    Alston, T.; Kendall, K.; Palin, M.; Prica, M.; Windibank, P.

    A cogeneration system was built using 1000 cells with the intention of supplying 30 kW of hot water and 500 W of power. The basis of the cogenerator was the small tubular SOFC design. 8Y zirconia was mixed into a plastic paste and extruded to form thin-walled tubes. The process produced a zirconia material with high strength and good electrical properties. After drying and firing to full density, electrodes were coated onto the inner and outer surfaces of the electrolyte, then sintered. Current collecting wires were wound around the tubular cells and the tubes were assembled into a reactor. Either hydrogen or a premix of natural gas and air was fed through the tubes and ignited by a hot wire. The ignition shock did not damage the cells in any way. Cycling was achieved within minutes. A steel heat exchanger/recuperator was used to feed hot air to the cell stack. The electrical output was measured via a potentiostat.

  10. Experimental investigation of the effect of indium content on the CuIn{sub 5}S{sub 8} electrodes using electrochemical impedance spectroscopy

    SciTech Connect

    Gannouni, M. Assaker, I. Ben; Chtourou, R.

    2015-01-15

    This paper reports on the use of electrochemical impedance spectroscopy to investigate the electrochemical behavior of spinel CuIn{sub 5}S{sub 8}/electrolyte interface. The CuIn{sub 5}S{sub 8} spinel films have been potentiostatically deposited onto indium tin oxide (ITO)-coated glass substrate. CuCl{sub 2} and InCl{sub 3} mixed solutions with different [Cu]/[In] ratios were used as cation precursor and Na{sub 2}S{sub 2}O{sub 3} as the anion precursor in acidic solution and at room temperature. The effect of the [Cu]/[In] ratio in the precursor solution on the structural, chemical stoichiometry, and morphological properties of prepared samples, as well as the electrochemical behavior of the CuIn{sub 5}S{sub 8}/electrolyte interface was investigated. The electrochemical impedance spectroscopy data have been modeled using an equivalent circuit approach. Several parameters such as, flat-band potential and free carrier concentration were determined by the change in the Mott–Schottky plots.

  11. Unveiling the Hard Anodization Regime of Aluminum: Insight into Nanopores Self-Organization and Growth Mechanism.

    PubMed

    Vega, Vctor; Garca, Javier; Montero-Moreno, Josep M; Hernando, Blanca; Bachmann, Julien; Prida, Vctor M; Nielsch, Kornelius

    2015-12-30

    Pores growth mechanism and their self-ordering conditions are investigated for nanoporous alumina membranes synthesized by hard anodization (HA) of Al in a broad range of anodic conditions, covering oxalic acid electrolytes with concentrations from 0.300 M down to 0.075 M and potentiostatic anodization voltages between 120 and 225 V. The use of linear sweep voltammetry (LSV) and scanning and transmission electron microscopy, together with image analysis techniques allow one to characterize the intrinsic nature of the HA regime. HA of aluminum is explained on the basis of a phenomenological model taking into account the role of oxalate ions and their limited diffusion through alumina nanochannels from a bulk electrolyte. The depletion of oxalate ions at the bottom of the pores causes an increased growth of the alumina barrier layer at the oxide/electrolyte interface. Furthermore, an innovative method has been developed for the determination of the HA conditions leading to self-ordered pore growth in any given electrolyte, thus allowing one to extend the available range of interpore distances of the highly ordered hexagonal pore arrangement in a wide range of 240-507 nm, while keeping small pore diameters of 50-60 nm. PMID:26646814

  12. Electrodeposited ZnO films with high UV emission properties

    SciTech Connect

    Matei, Elena; Enculescu, Ionut

    2011-11-15

    Highlights: {yields} Electrodeposition of ZnO from nitrate baths is investigated. {yields} The influence of process parameters on morphological and optical properties is studied. {yields} Experimental conditions to fabricate ZnO films with high UV emission were found. -- Abstract: We report here our results in the preparation of ZnO films with high UV band to band characteristic luminescence emission by potentiostatic electrodeposition. Zinc nitrate aqueous baths with different concentration and additives were employed for the preparation of the films on platinum substrates. We focused our research in determining how the electrodeposition bath composition, i.e. zinc nitrate concentration and addition of KCl or polyvinyl pyrolidone and applied overpotential influence the morphological and optical properties of the oxide films. Scanning electron microscopy was employed for characterizing the films in terms of morphology. Optical reflection, photoluminescence spectroscopy and cathodoluminescence were used for determining the optical characteristics of the samples. The morphology of the deposit varies from hexagonal prisms to platelets as a function of the deposition rate. This experimental parameter also influences the luminescence properties. We found that at low deposition rates high UV luminescent material is obtained.

  13. Preparation of Supercapacitors on Flexible Substrates with Electrodeposited PEDOT/Graphene Composites.

    PubMed

    Lehtimki, Suvi; Suominen, Milla; Damlin, Pia; Tuukkanen, Sampo; Kvarnstrm, Carita; Lupo, Donald

    2015-10-14

    Composite films consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) were electrochemically polymerized by electrooxidation of EDOT in ionic liquid (BMIMBF4) onto flexible electrode substrates. Two polymerization approaches were compared, and the cyclic voltammetry (CV) method was found to be superior to potentiostatic polymerization for the growth of PEDOT/GO films. After deposition, incorporated GO was reduced to rGO by a rapid electrochemical method of repetitive cathodic potential cycling, without using any reducing reagents. The films were characterized in 3-electrode configuration in BMIMBF4. Symmetric supercapacitors with aqueous electrolyte were assembled from the composite films and characterized through cyclic voltammetry and galvanostatic discharge tests. It was shown that PEDOT/rGO composites have better capacitive properties than pure PEDOT or the unreduced composite film. The cycling stability of the supercapacitors was also tested, and the results indicate that the specific capacitance still retains well over 90% of the initial value after 2000 consecutive charging/discharging cycles. The supercapacitors were demonstrated as energy storages in a room light energy harvester with a printed organic solar cell and printed electrochromic display. The results are promising for the development of energy-autonomous, low-power, and disposable electronics. PMID:26381462

  14. A novel automated electrochemical ascorbic acid assay in the 24-well microtiter plate format.

    PubMed

    Intarakamhang, Sireerat; Leson, Christian; Schuhmann, Wolfgang; Schulte, Albert

    2011-02-14

    Automatic ascorbic acid (AA) voltammetry was established in 24-well microtiter plates. The assay used a movable assembly of a pencil rod working, an Ag/AgCl reference and a Pt counter electrode with differential pulse voltammetry (DPV) for concentration-dependent current generation. A computer was in command of electrode (z) and microtiter plate (x, y) positioning and timed potentiostat operation. Synchronization of these actions supported sequential approach of all wells and subsequent execution of electrode treatment procedures or AA voltammetry at defined intervals in a measuring cycle. DPV in well solutions offered a linear current/concentration range between 0.1 and 8.0 mM, a sensitivity of about 1 ?A mM(-1) AA, and a detection limit of 50 ?M. When used with a calibration curve or standard addition, automated voltammetry of samples with added known amounts of AA demonstrated good recovery rates. Also, the assay achieved the accurate determination of the AA content of vitamin C tablets, a fruit juice and an herbal tea extract. Robotic AA voltammetry has the advantage of conveniently handling multiple samples in a single measuring run without the continuous attention of laboratory personnel. It is a good option when the goal is cost-effective AA screening of sample libraries and has potential for applications in health care and the food processing, cosmetic and pharmaceutical industries. PMID:21241840

  15. Preparation of Cu2O/TiO2 nanotube heterojunction arrays with enhanced photoelectrocatalysis performance

    NASA Astrophysics Data System (ADS)

    Zhang, Jianfang; Wang, Yan; Shen, Tiankuo; Bian, Haidong; Shu, Xia; Wu, Yucheng; Chen, Zhong

    2013-12-01

    Highly ordered TiO2 nanotube arrays (TNAs) were firstly fabricated by two-step anodization process. Then the Cu2O nanoparticles were deposited onto the as-fabricated TNAs via potentiostatic electrochemical deposition method in a three-electrode cell (the TNAs, Ag/AgCl and graphite performed as working electrode, reference electrode and counter electrode, respectively). The field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were adopted for the morphology characterization, the crystalline phases and composition analyzation of the as-prepared Cu2O/TNAs heterojunctions, repectively. The photoelectrochemical performance of the Cu2O/TNAs samples was evaluated by measuring the enhanced photocurrent response under intermittent Xe lamp irradiation. Then the photocatalytic properties were further investigated based on the photocatalytic degradation of methyl orange (MO) solution under simulated visible light. The results indicated that the inner surface and interface of the TNAs had been successfully modified with uniformly distributed Cu2O nanoparticles, which further ameliorated the photoelectrochemical and photocatalytic activities.

  16. Structural and optical properties of electrochemically deposited ZnO films in electrolyte containing Al2(SO4)3

    NASA Astrophysics Data System (ADS)

    Lovchinov, K.; Ganchev, M.; Rachkova, A.; Nichev, H.; Angelov, O.; Mikli, V.; Dimova-Malinovska, D.

    2012-12-01

    The present work concerns the electrochemical deposition of aluminium doped ZnO nanostructured thin films on SnO2:F covered glass substrates. Doped with Al nanostructured ZnO (ZnO:Al) films are obtained by an electrochemical process using a three-electrode potentiostatic system with a saturated calomel electrode as reference electrode, in aqueous solution containing ZnCl2, KCl and Al2(SO4)3. The influence of the deposition parameters on the structural properties of the obtained ZnO:Al layers is investigated by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM). Energy Dispersive X-ray Analysis (EDAX) is applied for measurement of the Al content in the films. The SEM micrographs and AFM pictures show that the ZnO:Al films consist of nanograins with a shape of walls. The XRD spectra demonstrate (100), (002), (101), (110) and (103) the characteristic reflexes of the ZnO. Influence of the Al concentration on the IR reflectance spectra and haze ratio of ZnO:Al thin films are presented and discussed.

  17. In-channel electrochemical detection in the middle of microchannel under high electric field.

    PubMed

    Kang, Chung Mu; Joo, Segyeong; Bae, Je Hyun; Kim, Yang-Rae; Kim, Yongseong; Chung, Taek Dong

    2012-01-17

    We propose a new method for performing in-channel electrochemical detection under a high electric field using a polyelectrolytic gel salt bridge (PGSB) integrated in the middle of the electrophoretic separation channel. The finely tuned placement of a gold working electrode and the PGSB on an equipotential surface in the microchannel provided highly sensitive electrochemical detection without any deterioration in the separation efficiency or interference of the applied electric field. To assess the working principle, the open circuit potentials between gold working electrodes and the reference electrode at varying distances were measured in the microchannel under electrophoretic fields using an electrically isolated potentiostat. In addition, "in-channel" cyclic voltammetry confirmed the feasibility of electrochemical detection under various strengths of electric fields (?400 V/cm). Effective separation on a microchip equipped with a PGSB under high electric fields was demonstrated for the electrochemical detection of biological compounds such as dopamine and catechol. The proposed "in-channel" electrochemical detection under a high electric field enables wider electrochemical detection applications in microchip electrophoresis. PMID:22148852

  18. Development of an on-animal separation-based sensor for monitoring drug metabolism in freely roaming sheep.

    PubMed

    Scott, David E; Willis, Sean D; Gabbert, Seth; Johnson, David; Naylor, Erik; Janle, Elsa M; Krichevsky, Janice E; Lunte, Craig E; Lunte, Susan M

    2015-06-01

    The development of an on-animal separation-based sensor that can be employed for monitoring drug metabolism in a freely roaming sheep is described. The system consists of microdialysis sampling coupled to microchip electrophoresis with electrochemical detection (MD-ME-EC). Separations were accomplished using an all-glass chip with integrated platinum working and reference electrodes. Discrete samples from the microdialysis flow were introduced into the electrophoresis chip using a flow-gated injection approach. Electrochemical detection was accomplished in-channel using a two-electrode isolated potentiostat. Nitrite was separated by microchip electrophoresis using reverse polarity and a run buffer consisting of 50 mM phosphate at pH 7.4. The entire system was under telemetry control. The system was first tested with rats to monitor the production of nitrite following perfusion of nitroglycerin into the subdermal tissue using a linear probe. The data acquired using the on-line MD-ME-EC system were compared to those obtained by off-line analysis using liquid chromatography with electrochemical detection (LC-EC), using a second microdialysis probe implanted parallel to the first probe in the same animal. The MD-ME-EC device was then used on-animal to monitor the subdermal metabolism of nitroglycerin in sheep. The ultimate goal is to use this device to simultaneously monitor drug metabolism and behavior in a freely roaming animal. PMID:25697221

  19. On-chip multi-electrochemical sensor array platform for simultaneous screening of nitric oxide and peroxynitrite.

    PubMed

    Quinton, Damien; Girard, Aurlie; Thi Kim, Loan To; Raimbault, Vincent; Griscom, Laurent; Razan, Florence; Griveau, Sophie; Bedioui, Fethi

    2011-04-01

    In this work we report on the design, microfabrication and analytical performances of a new electrochemical sensor array (ESA) which allows for the first time the simultaneous amperometric detection of nitric oxide (NO) and peroxynitrite (ONOO(-)), two biologically relevant molecules. The on-chip device includes individually addressable sets of gold ultramicroelectrodes (UMEs) of 50 m diameter, Ag/AgCl reference electrode and gold counter electrode. The electrodes are separated into two groups; each has one reference electrode, one counter electrode and 110 UMEs specifically tailored to detect a specific analyte. The ESA is incorporated on a custom interface with a cell culture well and spring contact pins that can be easily interconnected to an external multichannel potentiostat. Each UME of the network dedicated to the detection of NO is electrochemically modified by electrodepositing thin layers of poly(eugenol) and poly(phenol). The detection of NO is performed amperometrically at 0.8 V vs. Ag/AgCl in phosphate buffer solution (PBS, pH = 7.4) and other buffers adapted to biological cell culture, using a NO-donor. The network of UMEs dedicated to the detection of ONOO(-) is used without further chemical modification of the surface and the uncoated gold electrodes operate at -0.1 V vs. Ag/AgCl to detect the reduction of ONOOH in PBS. The selectivity issue of both sensors against major biologically relevant interfering analytes is examined. Simultaneous detection of NO and ONOO(-) in PBS is also achieved. PMID:21321748

  20. Morphological Evolution of Nanocluster Aggregates and Single Crystals in Alkaline Zinc Electrodeposition

    SciTech Connect

    Desai, D; Turney, DE; Anantharaman, B; Steingart, DA; Banerjee, S

    2014-04-24

    The morphology of Zn electrodeposits is studied on carbon-coated transmission electron microscopy grids. At low over-potentials (eta = -50 mV), the morphology develops by aggregation at two distinct length scales: similar to 5 nm diameter monocrystalline nanoclusters form similar to 50 nm diameter polycrystalline aggregates, and the aggregates form a branched network. Epitaxial (00 (0) over bar2) growth above an overpotential of vertical bar eta(c)vertical bar > 125 mV leads to the formation of hexagonal single crystals up to 2 mu m in diameter. Potentiostatic current transients were used to calculate the nucleation rate from Scharifker et al.'s model. The exp(eta) dependence of the nucleation rates indicates that atomistic nucleation theory explains the nucleation process better than Volmer-Weber theory. A kinetic model is provided using the rate equations of vapor solidification to simulate the evolution of the different morphologies. On solving these equations, we show that aggregation is attributed to cluster impingement and cluster diffusion while single-crystal formation is attributed to direct attachment.

  1. Influence of porosity on corrosion behaviour of Ti-39Nb alloy for dental applications.

    PubMed

    Fojt, Jaroslav; Joska, Ludek

    2013-01-01

    Porous materials allow for easier osseointegration of implants and their firmer connection with the bone. The presence of pores in a material may become a source of both mechanical and corrosion problems. The presented study explored a Ti-39Nb alloy with a porosity of 0-33%. Specimens were exposed in the physiological solution of two pH values. In view of this material's possible use in dental applications, the effect of fluoride ions on its corrosion behaviour was studied. The open circuit potential and polarization resistance were measured. Data concerning susceptibility to crevice corrosion were obtained from potentiostatic measurements based on the ASTM F746 standard. In terms of corrosion behaviour, specimens with a lower porosity were not much different from the non-porous material. Porosity produced its effect at the level of 24 and 33%. It is obvious that porosity affects corrosion behaviour of this type of material. This conclusion was confirmed by measurements of susceptibility to crevice corrosion which grew with the specimens' increasing porosity. Corrosion resistance of the Ti-39Nb alloy was comparable with that of the compact material, but the presence of pores initiated a local attack of the material. PMID:23629532

  2. The electrochemical behaviors of Mg, Mg-Li-Al-Ce and Mg-Li-Al-Ce-Y in sodium chloride solution

    NASA Astrophysics Data System (ADS)

    Lv, Yanzhuo; Xu, Yan; Cao, Dianxue

    2011-10-01

    The electrochemical performances of magnesium, magnesium-lithium-aluminum-cerium and magnesium-lithium-aluminum-cerium-yttrium as the anode of magnesium-hydrogen peroxide semi-fuel cells have been studied by methods of potentiodynamic, potentiostatic and electrochemical impedence measurements. The surface morphologies of magnesium and its alloys have been examined by scanning electron microscopy (SEM). It has been found that magnesium-lithium-aluminum-cerium and magnesium-lithium-aluminum-cerium-yttrium electrodes are less corrosion resistant than that of magnesium electrode in 0.7 mol L-1 NaCl solution and the corrosion current density decreases with the following order: magnesium < magnesium-lithium-aluminum-cerium-yttrium < magnesium-lithium-aluminum-cerium. The magnesium-lithium-aluminum-cerium-yttrium anode is more active than magnesium-lithium-aluminum-cerium and magnesium. The magnesium-hydrogen peroxide semi-fuel cell with magnesium-lithium-aluminum-cerium-yttrium anode shows better performance than that with Mg-Li-Al-Ce and Mg.

  3. Electrochemical Oscillations of Nickel Electrodissolution in an Epoxy-Based Microchip Flow Cell

    PubMed Central

    Cioffi, Alexander G.; Martin, R. Scott; Kiss, Istvn Z.

    2011-01-01

    We investigate the nonlinear dynamics of transpassive electrodissolution of nickel in sulfuric acid in an epoxy-based microchip flow cell. We observed bistability, smooth, relaxation, and period-2 waveform current oscillations with external resistance attached to the electrode in the microfabricated electrochemical cell with 0.05 mm diameter Ni wire under potentiostatic control. Experiments with 1mm 0.1 mm Ni electrode show spontaneous oscillations without attached external resistance; similar surface area electrode in macrocell does not exhibit spontaneous oscillations. Combined experimental and numerical studies show that spontaneous oscillation with the on-chip fabricated electrochemical cell occurs because of the unusually large ohmic potential drop due to the constrained current in the narrow flow channel. This large IR potential drop is expected to have an important role in destabilizing negative differential resistance electrochemical (e.g., metal dissolution and electrocatalytic) systems in on-chip integrated microfludic flow cells. The proposed experimental setup can be extendend to multi-electrode configurations; the epoxy-based substrate procedure thus holds promise in electroanalytical applications that require collector-generator multi-electrodes wires with various electrode sizes, compositions, and spacings as well as controlled flow conditions. PMID:21822407

  4. Electrodeposition of Cu-Pd alloys onto electrophoretic deposited carbon nanotubes for nitrate electroreduction

    NASA Astrophysics Data System (ADS)

    Zhang, Qiu; Ding, Liang; Cui, Hao; Zhai, Jianping; Wei, Zhongbo; Li, Qin

    2014-07-01

    Copper-palladium (Cu-Pd) alloys have been electrodeposited onto carbon nanotubes, which were uniformly and stably deposited on Ti plates via electrophoretic deposition. Electrodes with a wide range of Cu/Pd atomic ratios were fabricated by potentiostatic coelectrodeposition of Cu and Pd onto Ti/CNTs. They were characterized by energy-dispersive X-ray analyzer, X-ray diffraction and tested for nitrate electroreduction. The electrode deposited in bath with 5 mM Cu2+ and 5 mM Pd2+ (Ti/CNTs/Cu5-Pd5) possessed outstanding stability as well as the highest electrocatalytic activity with the best nitrate conversion yield and proper N2 selectivity, indicating a synergistic effect of Cu and Pd. X-ray photoelectron spectroscopy and scanning electron microscopy analysis of Ti/CNTs/Cu5-Pd5 and Ti/Cu5-Pd5 revealed that CNTs played a remarkable role in the homogeneous formation of the bimetal, significantly improving the alloy's electrocatalytic activity and stability. The fabricated Ti/CNTs/Cu5-Pd5 was proved to be a promising electrode for nitrate electroreduction.

  5. Electrochemistry combined on-line with electrospray mass spectrometry

    SciTech Connect

    Zhou, F.; Berkel, G.J.V.

    1995-10-15

    In this paper a variety of methods to couple electrochemistry on-line with electrospray mass spectrometry (EC/ES-MS) are presented, and the fundamental and analytical utility of this hybrid technique is illustrated. The major problems encountered in coupling EC and ES-MS are discussed, and means to overcome them are presented. Three types of electrochemical flow cells, viz., a thin-layer electrode flow-by cell, a tubular electrode flow-through cell, and a porous electrode flow-through cell, are discussed in regard to their suitability for this coupling. Methods for coupling each of these electrochemical cells on-line with ES-MS, either floated at or decoupled from the ES high voltage and controlled by a constant current supply, a constant potential supply, or a potentiostat are presented. Three applications are used to illustrate the utility and versatility of the EC/ES-MS combination: (1) the ionization of neutral analytes (i.e., perylene) for detection by ES-MS, (2) the study of the products of electrode reactions (i.e., nickel(II) octaethylporphyrin oxidation products), including relatively short-lived products (i.e., {Beta}-carotene oxidation products), and (3) the enhanced determination of metals (i.e., elemental silver) achieved by coupling anodic stripping voltammetry on-line with ES-MS. 52 refs., 6 figs.

  6. Carbon nanotube-based supercapacitors using low cost collectors

    NASA Astrophysics Data System (ADS)

    Amirhoseiny, Maryam; Zandi, Majid; Mosayyebi, Abolghasem; Khademian, Mehrzad

    2016-01-01

    In this work, electrochemical double layer supercapacitors were fabricated using multiwalled carbon nanotube (MWCNT) composite microfilm as electrode. To improve the electrochemical properties, MWCNTs were functionalized with ‑COOH by acid treatments. CNT/PVA films have been deposited on different current collectors by spin coating to drastically enhance the electrode performance. Electrode fabrication involved various stages preparing of the CNT composite, and coating of the CNT/PVA paste on different substrates which also served as current collector. Al, Ni and graphite were used and compared as current collectors. The surface morphology of the fabricated electrodes was investigated with scanning electrode microscopy (SEM). Overall cell performance was evaluated with a multi-channel potentiostat/galvanostat analyzer. Each supercapacitor cell was subjected to charge-discharge cycling study at different current rates from 0.2Ag‑1 to 1Ag‑1. The results showed that graphite-based electrodes offer advantages of significantly higher conductivity and superior capacitive behavior compared to thin film electrodes formed on Ni and Al current collectors. The specific capacitance of graphite based electrode is found to be 29Fg‑1.

  7. Linking optical and electrical small amplitude perturbation techniques for dynamic performance characterization of dye solar cells.

    PubMed

    Halme, Janne

    2011-07-21

    This paper unifies the analytical models used widely but thus far mostly separately for electrical and optical small amplitude perturbation measurements of nanostructured electrochemical dye solar cells (DSC): electrochemical impedance spectroscopy (EIS), intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS). The models are linked by expressing the kinetic boundary condition used for solving the time-dependent continuity equation of electrons in IMPS and IMVS analysis in terms of the series and parallel impedance components found in the complete equivalent circuit impedance model of DSC. As a result, analytical expressions are derived for potentiostatic IMPS and galvanostatic IMVS transfer functions of complete DSCs that are applicable at any operating point along the solar cell current-voltage (IV) curve. In agreement with the theory, impedance spectrum calculated as a ratio of IMVS and IMPS transfer functions measured near the maximum power point matches exactly with the impedance spectrum measured directly with EIS. Consequently, both IMPS-IMVS and EIS yield equal estimates for the electron diffusion length. The role of the chemical capacitance of the nanostructured semiconductor photoelectrode in the interpretation of the so-called RC attenuation of the IMPS response is clarified, as well as the capacitive frequency dispersion in IMPS and IMVS. PMID:21655592

  8. Microbial Biofilm Voltammetry: Direct Electrochemical Characterization of Catalytic Electrode-Attached Biofilms?

    PubMed Central

    Marsili, Enrico; Rollefson, Janet B.; Baron, Daniel B.; Hozalski, Raymond M.; Bond, Daniel R.

    2008-01-01

    While electrochemical characterization of enzymes immobilized on electrodes has become common, there is still a need for reliable quantitative methods for study of electron transfer between living cells and conductive surfaces. This work describes growth of thin (<20 ?m) Geobacter sulfurreducens biofilms on polished glassy carbon electrodes, using stirred three-electrode anaerobic bioreactors controlled by potentiostats and nondestructive voltammetry techniques for characterization of viable biofilms. Routine in vivo analysis of electron transfer between bacterial cells and electrodes was performed, providing insight into the main redox-active species participating in electron transfer to electrodes. At low scan rates, cyclic voltammetry revealed catalytic electron transfer between cells and the electrode, similar to what has been observed for pure enzymes attached to electrodes under continuous turnover conditions. Differential pulse voltammetry and electrochemical impedance spectroscopy also revealed features that were consistent with electron transfer being mediated by an adsorbed catalyst. Multiple redox-active species were detected, revealing complexity at the outer surfaces of this bacterium. These techniques provide the basis for cataloging quantifiable, defined electron transfer phenotypes as a function of potential, electrode material, growth phase, and culture conditions and provide a framework for comparisons with other species or communities. PMID:18849456

  9. Kinetics and mechanism of the electrochemical formation of iron oxidation products on steel immersed in sour acid media.

    PubMed

    Hernndez-Espejel, Antonio; Palomar-Pardav, Manuel; Cabrera-Sierra, Romn; Romero-Romo, Mario; Ramrez-Silva, Mara Teresa; Arce-Estrada, Elsa M

    2011-03-01

    From electrochemical techniques (cyclic voltammetry, potential steps, and EIS), XRD, and SEM-EDX, the kinetics and mechanism of anodic film formation applying anodic potential steps on steel immersed in sour acid media was determined. It was found, from a thermodynamic analysis, based on equilibrium phase diagrams of the system considered in this work, that iron oxidation may produce different new solid phases, depending on the applied potential, the first being the iron oxidation associated with formation of FeS((c)) species, which in turn can be reoxidized to FeS(2(c)) or even to Fe(2)O(3(c)) at higher potential values. From analysis of the corresponding experimental potentiostatic current density transients, it was concluded that the electrochemical anodic film formation involves an E(1)CE(2) mechanism, whereby the first of the two simultaneous processes were the Fe electrochemical oxidation (E(1)) followed by FeS precipitation (C) that occurs by 3D nucleation and growth limited by mass transfer reaction and FeS oxidation (E(2)) forming a mix of different stoichiometry iron sulphides and oxides. From EIS measurements, it was revealed that the anodic film's charge transfer resistance diminishes as the potential applied for its formation becomes more anodic, thus behaving poorly against corrosion. PMID:21302956

  10. 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.

  11. SEM method for direct visual tracking of nanoscale morphological changes of platinum based electrocatalysts on fixed locations upon electrochemical or thermal treatments.

    PubMed

    Zorko, Milena; Jozinovi?, Barbara; Bele, Marjan; Hodnik, Nejc; Gaber?ek, Miran

    2014-05-01

    A general method for tracking morphological surface changes on a nanometer scale with scanning electron microscopy (SEM) is introduced. We exemplify the usefulness of the method by showing consecutive SEM images of an identical location before and after the electrochemical and thermal treatments of platinum-based nanoparticles deposited on a high surface area carbon. Observations reveal an insight into platinum based catalyst degradation occurring during potential cycling treatment. The presence of chloride clearly increases the rate of degradation. At these conditions the dominant degradation mechanism seems to be the platinum dissolution with some subsequent redeposition on the top of the catalyst film. By contrast, at the temperature of 60C, under potentiostatic conditions some carbon corrosion and particle aggregation was observed. Temperature treatment simulating the annealing step of the synthesis reveals sintering of small platinum based composite aggregates into uniform spherical particles. The method provides a direct proof of induced surface phenomena occurring on a chosen location without the usual statistical uncertainty in usual, random SEM observations across relatively large surface areas. PMID:24662366

  12. The effect of expanders on lead-sulphate formation and reduction

    NASA Astrophysics Data System (ADS)

    Francia, Carlotta; Maja, Mario; Spinelli, Paolo

    The influence of some organic expanders on the formation of lead-sulphate has been studied by means of potentiostatic transients. The experimental data have been discussed according to the theories which have been proposed in the literature for the electro-crystallisation of lead-sulphate and lead. The discussion of the data obtained confirms the inhibiting effect of the expanders on lead sulphation. In fact, the tests showed that, when the expanders are added to the electrolyte, a longer time is required to reach the current maximum of the i( t) curve and a reduction of its intensity. According to the theoretical interpretation, this finding indicates a decreasing of the kinetic constant of the solid state process. The analysis of the i( t) transients obtained during the sulphate reduction revealed an influence of expanders only when the sulphate layers has been formed in their presence. Thus, it seems that the adsorption of the organic expanders on lead is of primary importance for their action while adsorption on lead-sulphate appears to be negligible.

  13. Analytical detection of biological thiols in a microchip capillary channel.

    PubMed

    Chand, Rohit; Jha, Sandeep Kumar; Islam, Kamrul; Han, Dawoon; Shin, Ik-Soo; Kim, Yong-Sang

    2013-02-15

    Sulfur-containing amino acids, such as cysteine and homocysteine play crucial roles in biological systems for the diagnosis of medical states. In this regard, this paper deals with separation, aliquot and detection of amino thiols on a microchip capillary electrophoresis with electrochemical detection in an inverted double Y-shaped microchannel. Unlike the conventional capillary electrophoresis, the modified microchannel design helps in storing the separated thiols in different reservoirs for further analysis, if required; and also eliminates the need of electrodes regeneration. The device was fabricated using conventional photolithographic technique which consisted of gold microelectrodes on a soda lime glass wafer and microchannels in PDMS mold. Multiple detections were performed using in-house fabricated dual potentiostat. Based on amperometric detection, cysteine and homocysteine were analyzed in 105 s and 120 s, respectively after diverting in branched channels. Repeated experiments proved the good reproducibility of the device. The device produced a linear response for both cysteine and homocysteine in electrochemical analysis. To prove the practicality of device, we also analyzed cysteine and homocysteine in real blood samples without any pre-treatment. Upon calculation, the device showed a very low limit of detection of 0.05 ?M. The modified microchip design shall find a broad range of analytical applications involving assays of thiols and other biological compounds. PMID:22940195

  14. Tyrosinase conjugated reduced graphene oxide based biointerface for bisphenol A sensor.

    PubMed

    Reza, K Kamil; Ali, Md Azahar; Srivastava, Saurabh; Agrawal, Ved Varun; Biradar, A M

    2015-12-15

    We have fabricated a nanocomposite of reduced graphene oxide (rGO) sheets and chitosan (Cn) polymer based highly sensitive electrochemical biosensor for detection of bisphenol A (BPA). The two-dimensional structure and chemical functionality of rGO and Cn provide an excellent electrode surface for loading of tyrosinase enzyme molecules. This rGO-Cn nanocomposite is capable of effectively utilizing their superior conductivity, larger effective surface area and superior electrochemical performance due to its synergistic effect between rGO and Cn. The structural, morphological and electrochemical characterizations of nanocomposite sheets have been performed by electron microscopy, X-ray diffraction, FTIR and Potentiostat/Galvanostat techniques. This fabricated biosensor is sensitive to nanomolar (0.74 nM) concentration of BPA and detection time is 10s compared to conventional BPA ELISA kit (0.3 g/L and 2.5h). The rGO-Cn based biosensor exhibits a higher sensitivity (83.3 A nM(-1) cm(-2)), wider linearity (0.01-50 M) with good selectivity towards BPA. This biosensor is capable to quantify real sample of BPA using packaged drinking water bottles. This rGO-Cn nanocomposite sheets emerges as a potential electrode material for detection of other estrogenic substrate. PMID:26201981

  15. In vitro biocorrosion of Co-Cr-Mo implant alloy by macrophage cells.

    PubMed

    Lin, Hsin-Yi; Bumgardner, Joel D

    2004-11-01

    We hypothesized that macrophage cells and their released reactive chemical species (RCS) affect Co-Cr-Mo alloy's corrosion properties and that alloy corrosion products change macrophage cell behavior. A custom cell culture corrosion cell was used to evaluate how culture medium, cells, and RCS altered alloy corrosion in 3-day tests. Corrosion was evaluated by measuring total charge transfer at a constant potential using a potentiostat and metal ion release by atomic emission spectroscopy. Viability, proliferation, and NO (nitric oxide) and IL-1beta (interlukin-1beta) release were used to assess cellular response to alloy corrosion products. In the presence of activated cells, total charge transfers and Co ion release were the lowest (p < 0.05). This was attributed to an enhancement of the surface oxide by RCS. Cr and Mo release were not different between cells and activated cells. Low levels of metal ions did not affect cell viability, proliferation, or NO release, though IL-1beta released from the activated cells was higher on the alloy compared to the controls. These data support the hypothesis that macrophage cells and their RCS affect alloy corrosion. Changes in alloy corrosion by cells may be important to the development of host responses to the alloy and its corrosion products. PMID:15475202

  16. Influence of the sliding velocity and the applied potential on the corrosion and wear behavior of HC CoCrMo biomedical alloy in simulated body fluids.

    PubMed

    Gil, Roberto Alonso; Muñoz, Anna Igual

    2011-11-01

    The corrosion and tribocorrosion behavior of an as-cast high carbon CoCrMo alloy immersed in phosphate buffered solution (PBS) and phosphate buffered solution with bovine serum albumin (PBS+BSA) have been analyzed by electrochemical techniques and surface microscopy. After the electrochemical characterization of the alloy in both solutions, the sample was studied tribo-electrochemically (by open circuit potential, OCP measurements, potentiodynamic curves and potentiostatic tests) in a ball-on-disk tribometer rotating in different sliding velocities. The influence of solution chemistry, sliding velocity and applied potential on the corrosion and tribocorrosion behavior of the CoCrMo alloy has been studied. Anodic current density increases with sliding velocity but wear rate does not change at an applied anodic potential; on the other hand, BSA modifies the wear debris behavior (by agglomerating the debris formed by mechanical removal of particles) thus increasing the mechanical wear volume. Under cathodic conditions, cathodic current density also increases during mechanical contact while the wear rate decreases with sliding velocity and BSA lubricates the contact thus reducing the total wear volume with respect to the non-containing BSA solution. The work shows how the electrode potential critically affects the corrosion and tribocorrosion rates by increasing the wear coefficients at applied anodic potentials due to severe wear accelerated corrosion. PMID:22098909

  17. 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

  18. Corrosion and Erosion-Corrosion Processes of Metal-Matrix Composites in Slurry Conditions

    NASA Astrophysics Data System (ADS)

    Flores, J. F.; Neville, A.; Kapur, N.; Gnanavelu, A.

    2012-03-01

    The corrosion and erosion-corrosion (EC) processes of four metal-matrix composites (MMCs) in a simulated cooling water environment have been assessed in this article. The MMCs consisted of two Ni-base and two Fe-base matrices alloyed with different concentrations of chromium, molybdenum, boron, silicon, and carbon; the matrices were reinforced with tungsten carbide (WC) particles. The corrosion behavior has been investigated using a combination of potentiostatic polarization and post-tests surface analysis. The EC processes were studied by in situ electrochemical techniques measuring the current density and corrosion potential response at different slurry temperatures and sand content. At static conditions it was found that as the temperature increased, there was a transition from a homogeneous corrosion of the matrix to an interfacial corrosion mechanism. The Ni-base MMCs showed a better corrosion resistance and interestingly a highly alloyed matrix did not significantly improved MMC's corrosion resistance. In the in situ EC tests, the Fe-base MMCs showed a constant increase in the current density at all sand contents. Whereas, significant changes were not observed in the Ni-base MMCs below 0.5 g/L. Although sand content had an effect on the monitored current density (the current increased as the sand content increased) this effect was less pronounced above 3 g/L.

  19. Automated analysis of food-borne pathogens using a novel microbial cell culture, sensing and classification system.

    PubMed

    Xiang, Kun; Li, Yinglei; Ford, William; Land, Walker; Schaffer, J David; Congdon, Robert; Zhang, Jing; Sadik, Omowunmi

    2016-02-01

    We hereby report the design and implementation of an Autonomous Microbial Cell Culture and Classification (AMC(3)) system for rapid detection of food pathogens. Traditional food testing methods require multistep procedures and long incubation period, and are thus prone to human error. AMC(3) introduces a "one click approach" to the detection and classification of pathogenic bacteria. Once the cultured materials are prepared, all operations are automatic. AMC(3) is an integrated sensor array platform in a microbial fuel cell system composed of a multi-potentiostat, an automated data collection system (Python program, Yocto Maxi-coupler electromechanical relay module) and a powerful classification program. The classification scheme consists of Probabilistic Neural Network (PNN), Support Vector Machines (SVM) and General Regression Neural Network (GRNN) oracle-based system. Differential Pulse Voltammetry (DPV) is performed on standard samples or unknown samples. Then, using preset feature extractions and quality control, accepted data are analyzed by the intelligent classification system. In a typical use, thirty-two extracted features were analyzed to correctly classify the following pathogens: Escherichia coli ATCC#25922, Escherichia coli ATCC#11775, and Staphylococcus epidermidis ATCC#12228. 85.4% accuracy range was recorded for unknown samples, and within a shorter time period than the industry standard of 24 hours. PMID:26818563

  20. Electrochemical preparation of nanostructured lanthanum using lanthanum chloride as a precursor in 1-butyl-3-methylimidazolium dicyanamide ionic liquid.

    PubMed

    Zhang, Q B; Yang, C; Hua, Y X; Li, Y; Dong, P

    2015-02-14

    Nanostructured lanthanum was electrochemically prepared on a platinum (Pt) substrate in the room temperature ionic liquid 1-butyl-3-methylimidazolium dicyanamide (BMI-DCA) containing anhydrous LaCl3 at 333 K. The electrochemical reduction behavior of La(iii) was investigated using cyclic voltammetry and chronoamperometry techniques. Cyclic voltammogram revealed that the reduction of La(iii) in BMI-DCA involved an irreversible process controlled by diffusion. Chronoamperometric transient analysis confirmed the diffusion controlled electrodeposition process with the diffusion coefficient of La(iii) species in the range of 10(-10) cm(2) s(-1). The strong complexing capability of DCA(-) anions facilitated the displacement of chloride ligands and induced the solubility of LaCl3. The subsequent coordination of La(iii) and DCA(-) anions forming [La(DCA)4](-) complex anions was monitored by designing amperometric titration experiments. Potentiostatically deposited La-deposits with different nanostructures were characterized by SEM, XRD and XPS analyses. The electrodeposition potential was found to play an important role in controlling the nucleation and growth kinetics of the nanocrystal during the electrodeposition process. Depending on the deposition potential, metallic lanthanum with either nanoparticles or nanoporous structures was obtained. PMID:25589210

  1. Free-standing aluminium nanowire architectures made in an ionic liquid.

    PubMed

    Zein el-Abedin, Sherif; Endres, Frank

    2012-01-16

    We report on the electrochemical synthesis of free-standing aluminium nanowire architectures through a template-assisted electrodeposition technique. For this purpose, nuclear track-etched polycarbonate membranes were employed as templates. One side of the template was sputtered with a thin gold film to serve as a working electrode. Subsequently the nanowires were made in the ionic liquid 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl)/AlCl(3) (40/60 mol?%) under potentiostatic conditions. Two different electrodeposition procedures were employed to fabricate strongly adherent Al nanowire structures on an electrodeposited Al layer. In the first procedure, electrodeposition simultaneously occurs along the pores of the template and on the Au-sputtered side of the template. In the second procedure, electrodeposition takes place in two different steps: first a thick supporting film of Al is deposited on the sputtered side of the membrane and second Al nanowires are grown within the pores. After chemical dissolution of the membrane in dichloromethane, an aluminium foil of a controlled thickness with a three-dimensional nanowire structure on one side was obtained. Different nanowire architectures, such as free-standing nanowires, vertically aligned tree-shaped arrays, and bunched nanowire films, were obtained. Such nanowire architectures are of particular interest for applications in Li-ion micro-batteries. PMID:22120955

  2. LabVIEW-based sequential-injection analysis system for the determination of trace metals by square-wave anodic and adsorptive stripping voltammetry on mercury-film electrodes

    PubMed Central

    Economou, Anastasios; Voulgaropoulos, Anastasios

    2003-01-01

    The development of a dedicated automated sequential-injection analysis apparatus for anodic stripping voltammetry (ASV) and adsorptive stripping voltammetry (AdSV) is reported. The instrument comprised a peristaltic pump, a multiposition selector valve and a home-made potentiostat and used a mercury-film electrode as the working electrodes in a thin-layer electrochemical detector. Programming of the experimental sequence was performed in LabVIEW 5.1. The sequence of operations included formation of the mercury film, electrolytic or adsorptive accumulation of the analyte on the electrode surface, recording of the voltammetric current-potential response, and cleaning of the electrode. The stripping step was carried out by applying a square-wave (SW) potential-time excitation signal to the working electrode. The instrument allowed unattended operation since multiple-step sequences could be readily implemented through the purpose-built software. The utility of the analyser was tested for the determination of copper(II), cadmium(II), lead(II) and zinc(II) by SWASV and of nickel(II), cobalt(II) and uranium(VI) by SWAdSV. PMID:18924623

  3. Wearable salivary uric acid mouthguard biosensor with integrated wireless electronics.

    PubMed

    Kim, Jayoung; Imani, Somayeh; de Araujo, William R; Warchall, Julian; Valdés-Ramírez, Gabriela; Paixão, Thiago R L C; Mercier, Patrick P; Wang, Joseph

    2015-12-15

    This article demonstrates an instrumented mouthguard capable of non-invasively monitoring salivary uric acid (SUA) levels. The enzyme (uricase)-modified screen printed electrode system has been integrated onto a mouthguard platform along with anatomically-miniaturized instrumentation electronics featuring a potentiostat, microcontroller, and a Bluetooth Low Energy (BLE) transceiver. Unlike RFID-based biosensing systems, which require large proximal power sources, the developed platform enables real-time wireless transmission of the sensed information to standard smartphones, laptops, and other consumer electronics for on-demand processing, diagnostics, or storage. The mouthguard biosensor system offers high sensitivity, selectivity, and stability towards uric acid detection in human saliva, covering the concentration ranges for both healthy people and hyperuricemia patients. The new wireless mouthguard biosensor system is able to monitor SUA level in real-time and continuous fashion, and can be readily expanded to an array of sensors for different analytes to enable an attractive wearable monitoring system for diverse health and fitness applications. PMID:26276541

  4. Template assisted electrodeposition of germanium and silicon nanowires in an ionic liquid.

    PubMed

    Al-Salman, R; Mallet, J; Molinari, M; Fricoteaux, P; Martineau, F; Troyon, M; Zein El Abedin, S; Endres, F

    2008-11-01

    In this paper we report for the first time on the room temperature template synthesis of germanium and silicon nanowires by potentiostatic electrochemical deposition from the air- and water stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py(1,4)]Tf(2)N) containing GeCl(4) and SiCl(4) as a Ge and Si source, respectively. Commercially-available track-etched polycarbonate membranes (PC) with an average nominal pore diameter of 90-400 nm were used as templates. Ge and Si nanowires with an average diameter corresponding to the nanopores' diameter and lengths of a few micrometres were reproducibly obtained. Structural characterization of the nanowires was performed by EDX, TEM, HR-SEM and Raman spectroscopy. Despite the rough surface of the nanowires, governed mostly by the original shape of the nanopore's wall of the commercially-available PC membrane, preliminary structural characterizations demonstrate the promising prospective of this innovative elaboration process compared to constraining high vacuum and high temperature methods. PMID:18936846

  5. Effects of environment on localized corrosion of copper-based, high-level waste container materials

    SciTech Connect

    Sridhar, N.; Cragnolino, G.A.

    1993-12-01

    Effects of environmental factors on localized corrosion of copper (Cu)-based materials that are candidates for use in high-level nuclear waste containers were examined. Effects of bicarbonate (HCO{sub 3}{sup {minus}}), chloride (Cl{sup {minus}}), and sulfate (SO{sub 4}{sup 2{minus}}), which are present in the ground water near the proposed Yucca Mountain site for a high-level waste repository, were studied. Localized corrosion was observed only at low temperatures in environments involving combinations of high HCO{sub 3}{sup {minus}} with high Cl{sup {minus}} or high SO{sub 4}{sup 2{minus}}. Uniform corrosion was observed at low concentrations of HCO{sup {minus}}{sub 3} (< {approximately}2,000 ppm), especially when Cl{sup {minus}} or SO{sub 4}{sup 2{minus}} concentration was high. A passive behavior without localized corrosion was observed at high HCO{sub 3}{sup {minus}} concentrations at temperatures > 80 C, irrespective of the Cl{sup {minus}} and SO{sub 4}{sup 2{minus}} concentrations. Localized corrosion observed in the Cu-based alloys was much shallower than in stainless steels and nickel (Ni)-based alloys and tended to broaden with time under potentiostatic conditions. Oxygen-free Cu (CDA-102, UNS C10200) exhibited a greater tendency toward localized corrosion than a 70% Cu-30% Ni alloy (CDA-715, UNS C71500).

  6. Electrodeposition of PVA-protected PtCo electrocatalysts for the oxygen reduction reaction in H2SO4

    NASA Astrophysics Data System (ADS)

    Gasparotto, Luiz H. S.; Ciapina, Eduardo G.; Ticianelli, Edson A.; Tremiliosi-Filho, Germano

    2012-01-01

    In this paper we report the electrosynthesis of PVA-protected PtCo films (PVA = poly(vinylalcohol)) and their activities towards the oxygen reduction reaction (ORR). PtCo electrodeposits were potentiostatically obtained in the presence and absence of PVA at distinct potentials. The film morphology and composition were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), which revealed that the use of PVA in the electrodeposition of PtCo films was decisive to achieve better film composition control. Cyclic voltammetry for PVA-protected PtCo films showed that the electrochemical surface area is dependent on the electrodeposition potentials and suggested different adsorption strengths of oxygen-containing species. Films produced in the presence of PVA presented the following activity order towards ORR as a function of the electrodeposition potential (vs. Ag/AgCl): -0.9 V > -0.8 V > -1.0 V > -0.7 V. In contrast, PtCo films electrodeposited in the absence of PVA displayed very similar activities regardless of the electrodeposition potential. The simplicity of the electrodeposition method combined with its effectiveness enabled the production of model electrodes for investigating the fundamental aspects of the reactions taking place in the fuel cell cathodes.

  7. Electrochemical deposition and microstructural characterization of AlCrFeMnNi and AlCrCuFeMnNi high entropy alloy thin films

    NASA Astrophysics Data System (ADS)

    Soare, V.; Burada, M.; Constantin, I.; Mitrică, D.; Bădiliţă, V.; Caragea, A.; Târcolea, M.

    2015-12-01

    Al-Cr-Fe-Mn-Ni and Al-Cr-Cu-Fe-Mn-Ni high entropy alloy thin films were prepared by potentiostatic electrodeposition and the microstructure of the deposits was investigated. The thin films were co-deposited in an electrolyte based on a DMF (N,N-dimethylformamide)-CH3CN (acetonitrile) organic compound. The energy dispersive spectrometry investigation (EDS) indicated that all the five respectively six elements were successfully co-deposited. The scanning electron microscopy (SEM) analysis revealed that the film consists of compact and uniform particles with particle sizes of 500 nm to 4 μm. The X-ray diffractometry (XRD) patterns indicated that the as-deposited thin films were amorphous. Body-centered-cubic (BCC) structures were identified by XRD after the films were annealed at various temperatures under inert Ar atmosphere. The alloys adhesion on the substrate was determined by the scratch-testing method, with higher values obtained for the Al-Cr-Cu-Fe-Mn-Ni alloy.

  8. Electrochemical formation and characterization of Au nanostructures on a highly ordered pyrolytic graphite surface

    NASA Astrophysics Data System (ADS)

    Gómez, José J. Arroyo; Zubieta, Carolina; Ferullo, Ricardo M.; García, Silvana G.

    2016-02-01

    The electrochemical formation of Au nanoparticles on a highly ordered pyrolytic graphite (HOPG) substrate using conventional electrochemical techniques and ex-situ AFM is reported. From the potentiostatic current transients studies, the Au electrodeposition process on HOPG surfaces was described, within the potential range considered, by a model involving instantaneous nucleation and diffusion controlled 3D growth, which was corroborated by the microscopic analysis. Initially, three-dimensional (3D) hemispherical nanoparticles distributed on surface defects (step edges) of the substrate were observed, with increasing particle size at more negative potentials. The double potential pulse technique allowed the formation of rounded deposits at low deposition potentials, which tend to form lines of nuclei aligned in defined directions leading to 3D ordered structures. By choosing suitable nucleation and growth pulses, one-dimensional (1D) deposits were possible, preferentially located on step edges of the HOPG substrate. Quantum-mechanical calculations confirmed the tendency of Au atoms to join selectively on surface defects, such as the HOPG step edges, at the early stages of Au electrodeposition.

  9. 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.

  10. 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 (Anodiscs) have been employed as templates for the growth of polypyrrole (PPy) nanotube arrays using electrochemical polymerization. The PPy nanotube arrays were grown on Anodiscs of pore diameter 100 nm 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 (0.2-13 mM), 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

  11. Non-destructive Patterning of Carbon Electrodes by Using the Direct Mode of Scanning Electrochemical Microscopy.

    PubMed

    Stratmann, Lutz; Clausmeyer, Jan; Schuhmann, Wolfgang

    2015-11-01

    Patterning of glassy carbon surfaces grafted with a layer of nitrophenyl moieties was achieved by using the direct mode of scanning electrochemical microscopy (SECM) to locally reduce the nitro groups to hydroxylamine and amino functionalities. SECM and atomic force microscopy (AFM) revealed that potentiostatic pulses applied to the working electrode lead to local destruction of the glassy carbon surface, most likely caused by etchants generated at the positioned SECM tip used as the counter electrode. By applying galvanostatic pulses, and thus, limiting the current during structuring, corrosion of the carbon surface was substantially suppressed. After galvanostatic patterning, unambiguous proof of the formation of the anticipated amino moieties was possible by modulation of the pH value during the feedback mode of SECM imaging. This patterning strategy is suitable for the further bio-modification of microstructured surfaces. Alkaline phosphatase, as a model enzyme, was locally bound to the modified areas, thus showing that the technique can be used for the development of protein microarrays. PMID:26316379

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

    PubMed Central

    Martnez-Olmos, Antonio; Ballesta-Claver, Julio; Palma, Alberto J.; Valencia-Mirn, Maria del Carmen; Capitn-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 710 % at the medium level of the range. PMID:22408475

  13. Niobized AISI 304 stainless steel bipolar plate for proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Wang, Lixia; Sun, Juncai; Li, Pengbin; Jing, Bo; Li, Song; Wen, Zhongsheng; Ji, Shijun

    2012-06-01

    AISI 304 stainless steel (SS) has been niobized by a plasma surface diffusion alloying method. A 3 ?m niobized layer with dominant niobium elements has been formed on the 304 SS surface and the performances of the niobized 304 SS has been examined and evaluated as bipolar plate for proton exchange membrane fuel cell (PEMFC). Results show that the average contact angle with water for the niobized 304 SS is about 90.4, demonstrating better hydrophobicity as compared with the untreated 304 SS (68.1). The corrosion resistance of the 304 SS is considerably improved by the niobized layer with the corrosion current densities decreased at 0.2 and 0.4 ?A cm-2 in simulated PEMFC anode purged with hydrogen and the cathode purged with air condition (0.05 M H2SO4 + 2 ppm F- solution at 70 C), respectively. The interfacial contact resistance (ICR) for the as-prepared niobized 304 SS is 10.53 m? cm2 at the compaction of 140 N cm-2. Furthermore, after 4 h potentiostatic tests, the niobizied specimens exhibit much lower ICR than that for the untreated ones. Thus, the niobized layer can act as a conductively protective layer of the 304 SS bipolar plate for PEMFC.

  14. 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

  15. Ultrathin, Stretchable, Multiplexing pH Sensor Arrays on Biomedical Devices With Demonstrations on Rabbit and Human Hearts Undergoing Ischemia

    PubMed Central

    Chung, Hyun-Joong; Sulkin, Matthew S.; Kim, Jong-Seon; Goudeseune, Camille; Chao, Hsin-Yun; Song, Joseph W.; Yang, Sang Yoon; Hsu, Yung-Yu; Ghaffari, Roozbeh

    2014-01-01

    Stable pH is an established biomarker of health, relevant to all tissues of the body, including the heart. Clinical monitoring of pH in a practical manner, with high spatiotemporal resolution, is particularly difficult in organs such as the heart due to its soft mechanics, curvilinear geometry, heterogeneous surfaces and continuous, complex rhythmic motion. The results presented here illustrate that advanced strategies in materials assembly and electrochemical growth can yield interconnected arrays of miniaturized IrOx pH sensors encapsulated in thin, low-modulus elastomers to yield conformal monitoring systems capable of non-invasive measurements on the surface of the beating heart. A thirty channel custom data acquisition system enables spatiotemporal pH mapping with a single potentiostat. In-vitro testing reveals super-Nernstian sensitivity with excellent uniformity (69.9 2.2 mV/pH), linear response to temperature (?1.6 mV/C), and minimal influence of extracellular ions (< 3.5 mV). Device examples include sensor arrays on balloon catheters and on skin-like stretchable membranes. Real-time measurement of pH on the surfaces of explanted rabbit hearts and a donated human heart during protocols of ischemia-reperfusion illustrate some of the capabilities. Envisioned applications range from devices for biological research, to surgical tools and long-term implants. PMID:23868871

  16. Improvement in direct methanol fuel cell performance by treating the anode at high anodic potential

    NASA Astrophysics Data System (ADS)

    Joghee, Prabhuram; Pylypenko, Svitlana; Wood, Kevin; Corpuz, April; Bender, Guido; Dinh, Huyen N.; O'Hayre, Ryan

    2014-01-01

    This work investigates the effect of a high anodic potential treatment protocol on the performance of a direct methanol fuel cell (DMFC). DMFC membrane electrode assemblies (MEAs) with PtRu/C (Hi-spec 5000) anode catalyst are subjected to anodic treatment (AT) at 0.8 V vs. DHE using potentiostatic method. Despite causing a slight decrease in the electrochemical surface area (ECSA) of the anode, associated with ruthenium dissolution, AT results in significant improvement in DMFC performance in the ohmic and mass transfer regions and increases the maximum power density by 15%. Furthermore, AT improves the long-term DMFC stability by reducing the degradation of the anode catalyst. From XPS investigation, it is hypothesized that the improved performance of AT-treated MEAs is related to an improved interface between the catalyst and Nafion ionomer. Among potential explanations, this improvement may be caused by incorporation of the ionomer within the secondary pores of PtRu/C agglomerates, which generates a percolating network of ionomer between PtRu/C agglomerates in the catalyst layer. Furthermore, the decreased concentration of hydrophobic CF2 groups may help to enhance the hydrophilicity of the catalyst layer, thereby increasing the accessibility of methanol and resulting in better performance in the high current density region.

  17. The use of differential measurements with a glucose biosensor for interference compensation during glucose determinations by flow injection analysis.

    PubMed

    McGrath, M J; Iwuoha, E I; Diamond, D; Smyth, M R

    1995-01-01

    A novel detection system for the determination of glucose in the presence of clinically important interferents, based on the use of dual sensors and flow-injection analysis (FIA), is described. The normalisation methodology involves measurement of the interference signal at a reference sensor; this signal can then be subtracted from the glucose sensor signal (post-run) to give a corrected measurement of the glucose concentration. The detection system consists of a thin layer with dual glassy carbon working electrodes. One electrode was surface modified to act as a glucose biosensor by immobilisation of glucose oxidase (GOx) (from Aspergillus niger) with 1% glutaraldehyde and bovine serum albumin. The second electrode (glucose oxidase omitted) was utilised to measure the interference signal responding only to electroactive species present in the injected sample. A computer controlled multichannel potentiostat was used for potential application and current monitoring duties. The sensor responses were saved in ASCII format to facilitate post-run analysis in Microsoft Excel. Cyclic voltammetry (CV) was utilised to investigate the manner in which the interference signal contributed to the total signal obtained at the biosensor in the presence of glucose. The kinetics parameters Imax and the apparent Michaelis-Menten constant, K'm, were calculated for the sensor operating under flow-injection conditions. PMID:8652108

  18. 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

  19. Electrochemical sensing method for point-of-care cortisol detection in human immunodeficiency virus-infected patients

    PubMed Central

    Kaushik, Ajeet; Yndart, Adriana; Jayant, Rahul Dev; Sagar, Vidya; Atluri, Venkata; Bhansali, Shekhar; Nair, Madhavan

    2015-01-01

    A novel electrochemical sensing method was devised for the first time to detect plasma cortisol, a potential psychological stress biomarker, in human immunodeficiency virus (HIV)-positive subjects. A miniaturized potentiostat (reconfigured LMP91000 chip) interfaced with a microfluidic manifold containing a cortisol immunosensor was employed to demonstrate electrochemical cortisol sensing. This fully integrated and optimized electrochemical sensing device exhibited a wide cortisol-detection range from 10 pg/mL to 500 ng/mL, a low detection limit of 10 pg/mL, and sensitivity of 5.8 ?A (pg mL)?1, with a regression coefficient of 0.995. This cortisol-selective sensing system was employed to estimate plasma cortisol in ten samples from HIV patients. The electrochemical cortisol-sensing performance was validated using an enzyme-linked immunosorbent assay technique. The results obtained using both methodologies were comparable within 2%5% variation. The information related to psychological stress of HIV patients can be correlated with disease-progression parameters to optimize diagnosis, therapeutic, and personalized health monitoring. PMID:25632229

  20. Strong Photo-Amplification Effects in Flexible Organic Capacitors with Small Molecular Solid-State Electrolyte Layers Sandwiched between Photo-Sensitive Conjugated Polymer Nanolayers

    NASA Astrophysics Data System (ADS)

    Lee, Hyena; Kim, Jungnam; Kim, Hwajeong; Kim, Youngkyoo

    2016-02-01

    We demonstrate strong photo-amplification effects in flexible organic capacitors which consist of small molecular solid-state electrolyte layers sandwiched between light-sensitive conjugated polymer nanolayers. The small molecular electrolyte layers were prepared from aqueous solutions of tris(8-hydroxyquinoline-5-sulfonic acid) aluminum (ALQSA3), while poly(3-hexylthiophene) (P3HT) was employed as the light-sensitive polymer nanolayer that is spin-coated on the indium-tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) film substrates. The resulting capacitors feature a multilayer device structure of PET/ITO/P3HT/ALQSA3/P3HT/ITO/PET, which were mechanically robust due to good adhesion between the ALQSA3 layers and the P3HT nanolayers. Results showed that the specific capacitance was increased by ca. 3-fold when a white light was illuminated to the flexible organic multilayer capacitors. In particular, the capacity of charge storage was remarkably (ca. 250-fold) enhanced by a white light illumination in the potentiostatic charge/discharge operation, and the photo-amplification functions were well maintained even after bending for 300 times at a bending angle of 180o.

  1. Ion transport in polycarbonate based solid polymer electrolytes: experimental and computational investigations.

    PubMed

    Sun, Bing; Mindemark, Jonas; V Morozov, Evgeny; Costa, Luciano T; Bergman, Martin; Johansson, Patrik; Fang, Yuan; Furó, István; Brandell, Daniel

    2016-03-30

    Among the alternative host materials for solid polymer electrolytes (SPEs), polycarbonates have recently shown promising functionality in all-solid-state lithium batteries from ambient to elevated temperatures. While the computational and experimental investigations of ion conduction in conventional polyethers have been extensive, the ion transport in polycarbonates has been much less studied. The present work investigates the ionic transport behavior in SPEs based on poly(trimethylene carbonate) (PTMC) and its co-polymer with ε-caprolactone (CL) via both experimental and computational approaches. FTIR spectra indicated a preferential local coordination between Li(+) and ester carbonyl oxygen atoms in the P(TMC20CL80) co-polymer SPE. Diffusion NMR revealed that the co-polymer SPE also displays higher ion mobilities than PTMC. For both systems, locally oriented polymer domains, a few hundred nanometers in size and with limited connections between them, were inferred from the NMR spin relaxation and diffusion data. Potentiostatic polarization experiments revealed notably higher cationic transference numbers in the polycarbonate based SPEs as compared to conventional polyether based SPEs. In addition, MD simulations provided atomic-scale insight into the structure-dynamics properties, including confirmation of a preferential Li(+)-carbonyl oxygen atom coordination, with a preference in coordination to the ester based monomers. A coupling of the Li-ion dynamics to the polymer chain dynamics was indicated by both simulations and experiments. PMID:26984668

  2. Electrochemical nucleophilic synthesis of di-tert-butyl-(4-[18F]fluoro-1,2-phenylene)-dicarbonate.

    PubMed

    He, Qinggang; Wang, Ying; Alfeazi, Ines; Sadeghi, Saman

    2014-09-01

    An electrochemical method with the ability to conduct (18)F-fluorination of aromatic molecules through direct nucleophilic fluorination of cationic intermediates is presented in this paper. The reaction was performed on a remote-controlled automatic platform. Nucleophilic electrochemical fluorination of tert-butyloxycarbonyl (Boc) protected catechol, an intermediate model molecule for the positron emission tomography (PET) probe (3,4-dihydroxy-6-[(18)F]fluoro-L-phenylalanine), was performed. Fluorination was achieved under potentiostatic anodic oxidation in acetonitrile containing Et3N3HF and other supporting electrolytes. Radiofluorination efficiency was influenced by a number of variables, including the concentration of the precursor, concentration of Et3N3HF, type of supporting electrolyte, temperature and time, as well as applied potentials. Radio-fluorination efficiency of 10.40.6% (n=4) and specific activity of up to 43GBq/mmol was obtained after 1h electrolysis of 0.1M of 4-tert-butyl-diboc-catechol in the acetonitrile solution of Et3N3HF (0.033M) and NBu4PF6 (0.05M). Density functional theory (DFT) was employed to explain the tert-butyl functional group facilitation of electrochemical oxidation and subsequent fluorination. PMID:25000498

  3. Effect of gelling on the impedance parameters of Pb/PbSO 4 electrode in maintenance-free lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Vinod, M. P.; Vijayamohanan, K.

    The impedance parameters of Pb/PbSO 4 electrode in 4.8 M sulfuric acid have been measured potentiostatically under open-circuit conditions over a wide range of frequencies (10 -2 to 10 4 Hz) under both deep-discharged (state-of-charge, SoC=0) and fully charged (SoC=1) conditions. Immobilization of the electrolyte by adding sodium silicate (5 g/l) on the impedance of Pb/PbSO 4 electrode shows significant difference in comparison with the flooded system. Four equivalent circuits have been formulated for overcharged and deep-discharged electrodes in gelled and flooded electrolytes, respectively. Impedance parameters are calculated using a phenomenological model, which indicates that in the case of gelled electrolytes, the electrochemical reactions are mass-transfer controlled, in contrast to the flooded electrolyte cells, where the process is known to be charge-transfer controlled. The study provides a non-destructive investigation of the effect of gelling on the electrical performance of sealed maintenance-free lead-acid batteries.

  4. Exploratory development of an electrically rechargeable lithium battery

    NASA Astrophysics Data System (ADS)

    Abraham, K. M.; Goldman, J. L.; Dempsey, M. D.; Holleck, G. L.

    1980-10-01

    The cathodic behavior or V6013 was investigated in rechargeable Li cells of the type, Li/2Me-THF,LiAsF6/V6013,C. Two forms of V6013 were synthesized and characterized. These were a stoichiometric form, i.e., V02.17, and a slightly non-stoichiometric form, i.e., V02.19. Stoichiometric V6013 was prepared by heating requisite quantities of V205 and V powder for 24 hrs. at 650 C. The slightly non-stoichiometric V6013 was prepared by the thermal decomposition of NH4V03 at 450 C. The discharge characteristics of the stoichiometric oxide at 60 C were similar to that of non-stoichiometric oxide at room temperature. The rechargeability of both the oxides were found to be sensitive to the lower voltage cutoff. The safest limits of cycling were 3.0 and 1.9V. Potentiostatic discharges of the oxides between 1.9 and 1.3V revealed a high capacity irreversible reduction process at about 1.6V. Three types of hermetically sealed cells were constructed and tested. In a high capacity (5Ah) prismatic cell utilizing the non-stoichiometric oxide, energy densities of 106 Whr/kg and 190 Whr/DM3 were achieved.

  5. Preparation of electrodeposited Zn–Ni–B alloy coatings

    NASA Astrophysics Data System (ADS)

    Sakai, Taro; Kamimoto, Yuki; Ichino, Ryoichi

    2016-01-01

    We prepared Zn–Ni–B alloys with high Zn content and high corrosion resistance. The composition of the alloys was controlled by potentiostatic electrolysis. In the electroplating bath, dimethylamineborane was used as the B source. The characterization of the alloys and corrosion resistance evaluation were carried out by X-ray diffraction (XRD) analysis, optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma–atomic emission spectrometry (ICP-AES), Tafel plots, and cyclic corrosion tests. All films were categorized into three groups on the basis of the results of XRD analysis, and it was found by TEM analysis that the Ni–B-type showed an amorphous structure. The Ni–B-type could contain up to 50.6 mol % Zn and showed similar or better anticorrosion properties than the amorphous Ni–B films. In the Ni–B-type, the higher the Zn content, the higher the corrosion resistance. The Zn–Ni–B alloys had almost the same electrochemical corrosion resistance and Zn content as the Zn–Ni–P alloys.

  6. 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 α" phase to β 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

  7. Effects of Osseointegration by Bone Morphogenetic Protein-2 on Titanium Implants In Vitro and In Vivo

    PubMed Central

    Teng, Fu-Yuan; Chen, Wen-Cheng; Wang, Yin-Lai; Hung, Chun-Cheng; Tseng, Chun-Chieh

    2016-01-01

    This study designed a biomimetic implant for reducing healing time and achieving early osseointegration to create an active surface. Bone morphogenetic protein-2 (BMP-2) is a strong regulator protein in osteogenic pathways. Due to hardly maintaining BMP-2 biological function and specificity, BMP-2 efficient delivery on implant surfaces is the main challenge for the clinic application. In this study, a novel method for synthesizing functionalized silane film for superior modification with BMP-2 on titanium surfaces is proposed. Three groups were compared with and without BMP-2 on modified titanium surfaces in vitro and in vivo: mechanical grinding; electrochemical modification through potentiostatic anodization (ECH); and sandblasting, alkali heating, and etching (SMART). Cell tests indicated that the ECH and SMART groups with BMP-2 markedly promoted D1 cell activity and differentiation compared with the groups without BMP-2. Moreover, the SMART group with a BMP-2 surface markedly promoted early alkaline phosphatase expression in the D1 cells compared with the other surface groups. Compared with these groups in vivo, SMART silaning with BMP-2 showed superior bone quality and created contact areas between implant and surrounding bones. The SMART group with BMP-2 could promote cell mineralization in vitro and osseointegration in vivo, indicating potential clinical use. PMID:26977141

  8. Immobilization of lysine oxidase on a gold-platinum nanoparticles modified Au electrode for detection of lysine.

    PubMed

    Chauhan, N; Narang, J; Sunny; Pundir, C S

    2013-04-10

    A commercial lysine oxidase (LyOx) from Trichoderma viride was immobilized covalently onto gold nanoparticles (AuNPs) and platinum nanoparticles (PtNPs) electrodeposited onto Au electrode using 3-aminopropyltriethoxy silane (3-APTES) and glutaraldehyde cross linking chemistry. A lysine biosensor was fabricated using LyOx/3-APTES/AuNPs-PtNPs/Au electrode as a working electrode, Ag/AgCl (3M KCl) as standard electrode and Pt wire as auxiliary electrode connected through a potentiostat. The enzyme electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The cumulative effect of AuNPs and PtNPs showed excellent electrocatalytic activity at low applied potential for detection of H2O2, a product of LyOx reaction. The sensor showed its optimum response within 4s, when polarized at 0.2V vs. Ag/AgCl in 0.1M phosphate buffer, pH 7.5 at 30C. The linear range and detection limit of the sensor were 1.0-600?M and 1.0?M (S/N=3), respectively. Biosensor measured lysine level in sera, milk and amino acid tablet, which correlated well with those by standard HPLC method. The enzyme electrode lost 50% of its initial activity after 200 uses over a period of 4 months. PMID:23540929

  9. A mechanistic model for oxide growth and dissolution during corrosion of Cr-containing alloys.

    PubMed

    Momeni, M; Wren, J C

    2015-01-01

    We have developed a corrosion model that can predict metal oxide growth and dissolution rates as a function of time for a range of solution conditions. Our model considers electrochemical reactions at the metal/oxide and oxide/solution interfaces, and the metal cation flux from the metal to the solution phase through a growing oxide layer, and formulates the key processes using classical chemical reaction rate or flux equations. The model imposes mass and charge balance and hence, is labeled as the Mass Charge Balance (MCB) model. Mass and charge balance dictate that at any given time the oxidation (or metal cation) flux must be equal to the sum of the oxide growth flux and the dissolution flux. For each redox reaction leading to the formation of a specific oxide, the metal oxidation flux is formulated using a modified Butler-Volmer equation with an oxide-thickness-dependent effective overpotential. The oxide growth and dissolution fluxes have a first-order dependence on the metal cation flux. The rate constant for oxide formation also follows an Arrhenius dependence on the potential drop across the oxide layer and hence decreases exponentially with oxide thickness. This model is able to predict the time-dependent potentiostatic corrosion behaviour of both pure iron, and Co-Cr and Fe-Ni-Cr alloys. PMID:25912738

  10. Development of a commercial micro corrosion monitoring system

    NASA Astrophysics Data System (ADS)

    Niblock, Trevor G. E.; Surangalikar, Harshal S.; Morse, Jeffrey; Laskowski, Bernard C.; Castro-Cedeno, Mario H.; Wilson, Alan R.

    2002-11-01

    Analatom Inc. in conjunction with the DSTO (Defence Science & Technology Organisation) has been developing a micro Linear Polarization Resistance (LPR) system for assessing the integrity of high value structures. The device operates on the principle that as a metal corrodes, the oxide formed effectively creates an anodic cell. Hence, if the metal can be separated into two sections, a potential and resistance can be measured between each section. These values can be used to compute the effective mass loss of the device. By matching the material properties of the device with that of the structure whose "health" is being monitored, it is possible to establish a corrosion rate of the structure. Previous research at DSTO has shown that such a system can be fabricated and operated on the micro scale. The task has now been to develop the device into a commercially viable system; it is this development that is examined in this paper. In the original system, a potentiostat is used to evaluate the device for data relating the mass loss during corrosion. This system is now replaced with simplified electronics to reduce both the cost and size of the device. Signal conditioning into the LPR is critical as potentials over 20mV across the terminals can be a source of corrosion of the device. Micro controllers and small board computers are used to run this signal conditioning process and the LPR interface circuit.

  11. Multifrequency impedance measurement technique for wireless characterization of microbiological cell cultures

    NASA Astrophysics Data System (ADS)

    Wissenwasser, J.; Vellekoop, M. J.; Kapferer, W.; Lepperdinger, G.; Heer, R.

    2011-11-01

    An impedance measurement system with probe signal frequencies up to 50 kHz with AC-probe voltages below 30 mV rms was integrated for wireless and battery-free monitoring of microbiological cell cultures. The here presented modular design and the use of state-of-the-art components greatly eases adoptions to a wide range of biotechnological applications without the need of bulky LCR-meters or potentiostats. The device had a power consumption of less than 2.5 mA at a 3.3 V single power supply and worked trouble-free within the humid environment of a cell culture incubator. Measurements on lumped RC-elements showed an error of less than 1% for absolute values and less than 1 regarding the phase of the complex impedance. The performance of sensor devices with interdigitated electrode structures for the measurement of adherent cell cultures was tested in the presence of phosphate-buffered saline solution in the humid atmosphere of an incubator for biological cell cultures.

  12. 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.

  13. 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.

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

    SciTech Connect

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

    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].

  15. Electrochemical oxidation of tramadol in low-salinity reverse osmosis concentrates using boron-doped diamond anodes.

    PubMed

    Lütke Eversloh, Christian; Schulz, Manoj; Wagner, Manfred; Ternes, Thomas A

    2015-04-01

    The electrochemical treatment of low-salinity reverse osmosis (RO) concentrates was investigated using tramadol (100 μM) as a model substance for persistent organic contaminants. Galvanostatic degradation experiments using boron-doped diamond electrodes at different applied currents were conducted in RO concentrates as well as in ultra-pure water containing either sodium chloride or sodium sulfate. Kinetic investigations revealed a significant influence of in-situ generated active chlorine besides direct anodic oxidation. Therefore, tramadol concentrations decreased more rapidly at elevated chloride content. Nevertheless, reduction of total organic carbon (TOC) was found to be comparatively low, demonstrating that transformation rather than mineralization was taking place. Early stage product formation could be attributed to both direct and indirect processes, including demethylation, hydroxylation, dehydration, oxidative aromatic ring cleavage and halogenation reactions. The latter led to various halogenated derivatives and resulted in AOX (adsorbable organic halogens) formation in the lower mg/L-range depending on the treatment conditions. Characterisation of transformation products (TPs) was achieved via MS(n) experiments and additional NMR measurements. Based on identification and quantification of the main TPs in different matrices and on additional potentiostatic electrolysis, a transformation pathway was proposed. PMID:25660808

  16. Lab-on-a-bird: biophysical monitoring of flying birds.

    PubMed

    Gumus, Abdurrahman; Lee, Seoho; Ahsan, Syed S; Karlsson, Kolbeinn; Gabrielson, Richard; Guglielmo, Christopher G; Winkler, David W; Erickson, David

    2015-01-01

    The metabolism of birds is finely tuned to their activities and environments, and thus research on avian systems can play an important role in understanding organismal responses to environmental changes. At present, however, the physiological monitoring of bird metabolism is limited by the inability to take real-time measurements of key metabolites during flight. In this study, we present an implantable biosensor system that can be used for continuous monitoring of uric acid levels of birds during various activities including flight. The system consists of a needle-type enzymatic biosensor for the amperometric detection of uric acid in interstitial fluids. A lightweight two-electrode potentiostat system drives the biosensor, reads the corresponding output current and wirelessly transfers the data or records to flash memory. We show how the device can be used to monitor, in real time, the effects of short-term flight and rest cycles on the uric acid levels of pigeons. In addition, we demonstrate that our device has the ability to measure uric acid level increase in homing pigeons while they fly freely. Successful application of the sensor in migratory birds could open up a new way of studying birds in flight which would lead to a better understanding of the ecology and biology of avian movements. PMID:25880904

  17. Lab-on-a-Bird: Biophysical Monitoring of Flying Birds

    PubMed Central

    Gumus, Abdurrahman; Lee, Seoho; Ahsan, Syed S.; Karlsson, Kolbeinn; Gabrielson, Richard; Guglielmo, Christopher G.; Winkler, David W.; Erickson, David

    2015-01-01

    The metabolism of birds is finely tuned to their activities and environments, and thus research on avian systems can play an important role in understanding organismal responses to environmental changes. At present, however, the physiological monitoring of bird metabolism is limited by the inability to take real-time measurements of key metabolites during flight. In this study, we present an implantable biosensor system that can be used for continuous monitoring of uric acid levels of birds during various activities including flight. The system consists of a needle-type enzymatic biosensor for the amperometric detection of uric acid in interstitial fluids. A lightweight two-electrode potentiostat system drives the biosensor, reads the corresponding output current and wirelessly transfers the data or records to flash memory. We show how the device can be used to monitor, in real time, the effects of short-term flight and rest cycles on the uric acid levels of pigeons. In addition, we demonstrate that our device has the ability to measure uric acid level increase in homing pigeons while they fly freely. Successful application of the sensor in migratory birds could open up a new way of studying birds in flight which would lead to a better understanding of the ecology and biology of avian movements. PMID:25880904

  18. Effect of composition on corrosion resistance of high-alloy austenitic stainless steel weld metals

    SciTech Connect

    Marshall, P.I. ); Gooch, T.G. )

    1993-06-01

    The corrosion resistance of stainless steel weld metal in the ranges of 17 to 28% chromium (Cr), 6 to 60% nickel (Ni), 0 to 9% molybdenum (Mo), and 0.0 to 0.37% nitrogen (N) was examined. Critical pitting temperatures were determined in ferric chloride (FeCl[sub 3]). Passive film breakdown potentials were assessed from potentiodynamic scans in 3% sodium chloride (NaCl) at 50 C. Potentiodynamic and potentiostatic tests were carried out in 30% sulfuric acid (H[sub 2]SO[sub 4]) ar 25 C, which was representative of chloride-free acid media of low redox potential. Metallographic examination and microanalysis were conducted on the test welds. Because of segregation of alloying elements, weld metal pitting resistance always was lower than that of matching composition base steel. The difference increased with higher Cr, Mo, and N contents. Segregation also reduced resistance to general corrosion in H[sub 2]SO[sub 4], but the effect relative to the base steel was less marked than with chloride pitting. Segregation of Cr, Mo, and N in fully austenitic deposits decreased as the Ni[prime][sub eq-]Cr[prime][sub eq] ratio increased. Over the compositional range studied, weld metal pitting resistance was dependent mainly on Mo content and segregation. N had less effect than in wrought alloys. Both Mo and N enhanced weld metal corrosion resistance in H[sub 2]SO[sub 4].

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

    NASA Astrophysics Data System (ADS)

    Licausi, M. P.; Igual Muoz, A.; Amig Borrs, 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.

  20. Deformation and fracture of aluminum-lithium alloys: The effect of dissolved hydrogen

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    The effects of dissolved hydrogen on the mechanical properties of 2090 and 2219 alloys are studied. The work done during this semi-annual period consists of the hydrogen charging study and some preliminary mechanical tests. Prior to SIMS analysis, several potentiostatic and galvanostatic experiments were performed for various times (going from 10 minutes to several hours) in the cathodic zone, and for the two aqueous solutions: 0.04N of HCl and 0.1N NaOH both combined with a small amount of As2O3. A study of the surface damage was conducted in parallel with the charging experiments. Those tests were performed to choose the best charging conditions without surface damage. Disk rupture tests and tensile tests are part of the study designed to investigate the effect of temperature, surface roughness, strain rate, and environment on the fracture behavior. The importance of the roughness and environment were shown using the disk rupture test as well as the importance of the strain rate under hydrogen environment. The tensile tests, without hydrogen effects, have not shown significant differences between low and room temperature.

  1. Electrochemical Fractionation of Molybdenum Stable Isotopes

    NASA Astrophysics Data System (ADS)

    Crawford, J.; Black, J.; Wasylenki, L.; Gordon, G.; Anbar, A.; Kavner, A.

    2008-12-01

    Stable isotope signatures were measured from Molybdenum (Mo) electrodeposited from aqueous solution. As potential varied from -1.35 V to -2.00 V (relative to Ag/AgCl), fractionation decreases from ?97/95Mo = -1.3 to -0.9 (?97/95Mo defined as the difference in the 97Mo/95Mo ratio of deposited Mo relative to aqueous Mo). Natural variations of ?97/95Mo span a range of ~ 3 [Barling, J. and Anbar, A. D., EPSL. 2004, 217: 315], therefore, charge transfer driven fractionation may be responsible for some of the observed variation in Mo stable isotope geochemistry. Following previous approaches with Fe and Zn [Kavner, A. et al. Geochim. Cosmochim. Acta. 2005, 69: 2971; 2008, 72: 1731], Mo was plated in a three-electrode cell from a neutral to slightly alkaline solution (pH ~ 8.7). Voltage was held constant during electrodeposition using an Autolab Potentiostat. In all experiments, less than 0.5 % of the Mo was deposited, which insures that the plating reservoir remains at an approximately constant isotopic composition. Plated Mo was then recovered in acid, and the isotopic composition of samples and stock solutions were measured using a Thermo Scientific Neptune MC-ICP-MS. These experiments show that the redox process induces an isotopic signature with respect to the starting material, with a trend showing that fractionation decreases as a function of applied voltage.

  2. Effects of concentration-dependent elastic modulus on Li-ions diffusion and diffusion-induced stresses in spherical composition-gradient electrodes

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Li, Yong; Zheng, Bailin

    2015-09-01

    The composition-gradient electrode material is considered as one of the most promising materials for lithium-ion batteries because of its excellent electrochemical performance and thermal stability. In this work, the effects of concentration-dependent elastic modulus on Li-ions diffusion and diffusion-induce stress in the composition-gradient electrodes were studied. The coupling equations of elasticity and diffusion under both potentiostatic charging and galvanostatic charging were developed to obtain the distributions of both the Li-ions concentration and the stress. The results indicated that the effects of the concentration-dependent elastic modulus on the Li-ions diffusion and the diffusion-induce stresses are controlled by the lithiation induced stiffening factor in the composition-gradient electrodes: a low stiffening factor at the center and a high stiffening factor at the surface lead to a significant effect, whereas a high stiffening factor at the center and a low stiffening factor at the surface result in a minimal effect. The results in this work provide guidance for the selection of electrode materials.

  3. Fabrication and magnetic properties of La-X (X = Co, Ni, and Fe) nanotube arrays prepared by electrodeposition methods

    NASA Astrophysics Data System (ADS)

    Chen, J. Y.; Shi, D. W.; Ahmad, N.; Liu, D. P.; Zhou, W. P.; Han, X. F.

    2013-08-01

    Well-ordered La-X (X = Co, Ni and Fe) nanotubes, with the average diameter of 200 nm, wall thicknesses of 40 nm, have been fabricated into anodized aluminum oxide template by potentiostatic electrodeposition method. Various composition of La-X nanotubes were obtained by tuning the applied deposition potential. Magnetization measurements reveal that doped La could enhance the coercivity (Hc) of La-X nanotubes and their easy axis is perpendicular to the nanotube axis. There is a transition from the curling to transverse mode with increase of angle. Temperature dependent magnetization indicates the existence of superparamagnetic nanoparticles and that the surface effect results in the increase of saturation magnetization (Ms) at low temperature. Abnormal behavior of temperature dependent Hc may result from thermal excitation, magnetoelastic anisotropy, as well as oxide layer of nanotube inner surface induced coupling. These one-dimensional rare-earth transition metal nanostructures could have potential applications in novel spintronics device, ultra-small magnetic media, drug delivery, or other nanodevice.

  4. 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

  5. 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.; Glzow, 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.

  6. 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

  7. Quantitative DEMS study of ethanol oxidation: effect of surface structure and Sn surface modification.

    PubMed

    Mostafa, Ehab; Abd-El-Latif, Abd-El-Aziz A; Ilsley, Richard; Attard, Gary; Baltruschat, Helmut

    2012-12-14

    Using the dual thin layer flow through cell, a semi-quantitative analysis of the volatile products during the electrooxidation of adsorbed and bulk solution of 0.01 M ethanol at polycrystalline platinum, smooth, roughened and Sn modified Pt(11,1,1), Pt(311) electrodes has been done by on-line differential electrochemical mass spectroscopy (DEMS). In addition to the current efficiency of CO(2), that of acetaldehyde was determined as a function of the flow rate. At polycrystalline platinum, ethanol oxidation produces only acetaldehyde; the amount of acetaldehyde further oxidized to acetic acid is negligible due to convection conditions. For comparison and for calibration purposes, i-propanol oxidation was examined for which acetone is the only oxidation product. At Pt(11,1,1), the main oxidation product is acetaldehyde. At Pt(311), in addition to acetaldehyde, acetic acid was also formed. Surface modification with Sn did not increase the reactivity of Pt(11,1,1) instead it led to inhibition of the ethanol oxidation. In the case of Pt(311), the onset potential of oxidation was shifted negatively by 0.2 V in the presence of Sn. The results of the potentiostatic measurements showed that this shift is not associated with the production of CO(2); rather acetic acid and acetaldehyde are the main oxidation products. PMID:23108295

  8. In situ Measurements of the Solid Electrolyte Interphase in Li-Ion Batteries Using Neutron Reflectometry

    NASA Astrophysics Data System (ADS)

    Dura, Joseph; Owejan, Jeanette; Decaluwe, Steven; Owejan, Jon

    2013-03-01

    The huge advantages of Li-ion batteries, i.e. high energy density and specific power are due not only to the low mass of Li, but also a direct result of the high operating voltage provided by the large electrochemical potential of Li. However, these advantages come at a cost, as all known electrolytes are unstable at these potentials. Li-ion batteries are only made possible by the solid electrolyte interphase, SEI, a passivation layer that forms from the decomposition products of certain electrolytes. Ideally the SEI offers sufficient electronic resistance when it has grown thick enough to stop additional electrolyte decomposition. However, slow continued SEI growth leads to capacity fade and increased cell resistance. Despite the SEI's critical significance, currently structural characterization is incomplete because of the reactive and delicate nature of the SEI and the electrolyte system in which it forms. Here we present the first in situ neutron reflectometry measurements of the SEI layer as function of potential in a working lithium half-cell. The SEI layer after 10 and 20 CV cycles is 4.0 and 4.5 nm, respectively, growing to 8.9 nm after a series of potentiostatic holds that approximates a charge/discharge cycle. Specified data sets show uniform mixing of SEI components.

  9. 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

  10. 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.

  11. 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

  12. 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

  13. Spatiotemporal norepinephrine mapping using a high-density CMOS microelectrode array.

    PubMed

    Wydallis, John B; Feeny, Rachel M; Wilson, William; Kern, Tucker; Chen, Tom; Tobet, Stuart; Reynolds, Melissa M; Henry, Charles S

    2015-10-21

    A high-density amperometric electrode array containing 8192 individually addressable platinum working electrodes with an integrated potentiostat fabricated using Complementary Metal Oxide Semiconductor (CMOS) processes is reported. The array was designed to enable electrochemical imaging of chemical gradients with high spatiotemporal resolution. Electrodes are arranged over a 2 mm × 2 mm surface area into 64 subarrays consisting of 128 individual Pt working electrodes as well as Pt pseudo-reference and auxiliary electrodes. Amperometric measurements of norepinephrine in tissue culture media were used to demonstrate the ability of the array to measure concentration gradients in complex media. Poly(dimethylsiloxane) microfluidics were incorporated to control the chemical concentrations in time and space, and the electrochemical response at each electrode was monitored to generate electrochemical heat maps, demonstrating the array's imaging capabilities. A temporal resolution of 10 ms can be achieved by simultaneously monitoring a single subarray of 128 electrodes. The entire 2 mm × 2 mm area can be electrochemically imaged in 64 seconds by cycling through all subarrays at a rate of 1 Hz per subarray. Monitoring diffusional transport of norepinephrine is used to demonstrate the spatiotemporal resolution capabilities of the system. PMID:26333296

  14. 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

  15. 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.

  16. Determination of solid phase chemical diffusion coefficient and density of states by electrochemical methods: Application to iridium oxide-based thin films

    NASA Astrophysics Data System (ADS)

    Backholm, Jonas; Georn, Peter; Niklasson, Gunnar A.

    2008-01-01

    Potentiostatic intermittent titration technique (PITT) and electrochemical impedance spectroscopy (EIS) were investigated as methods to determine solid phase chemical diffusion coefficient (D) and electronic density of states (DOS). These techniques were then applied to iridium oxide (IrOx) and iridium-tantalum oxide (IrTaOx) thin films prepared by sputter deposition. The experiments, performed in 1M propionic acid between -0.2 and 0.8V vs Ag /AgCl, showed effects of interfacial side reactions, whose contribution to the electrochemical response could be identified and corrected for in the case of PITT as well as EIS. It was found that D is strongly underestimated when using PITT with the common Cottrell formalism, which follows from non-negligible interfacial charge transfer and Ohmic resistances. EIS indicated an anomalous diffusion mechanism, and D was determined to be in the 10-11-10-10cm2/s range for IrOx and IrTaOx. Both PITT and EIS showed that the intercalated charge as a function of potential exhibits a shape that resembles the theoretical DOS of crystalline iridium oxide, especially for IrTaOx.

  17. 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.

  18. Facile synthesis of polypyrrole functionalized nickel foam with catalytic activity comparable to Pt for the poly-generation of hydrogen and electricity

    NASA Astrophysics Data System (ADS)

    Tang, Tiantian; Li, Kan; Shen, Zhemin; Sun, Tonghua; Wang, Yalin; Jia, Jinping

    2016-01-01

    Polypyrrole functionalized nickel foam is facilely prepared through the potentiostatic electrodeposition. The PPy-functionalized Ni foam functions as a hydrogen-evolution cathode in a rotating disk photocatalytic fuel cell, in which hydrogen energy and electric power are generated by consuming organic wastes. The PPy-functionalized Ni foam cathode exhibits stable catalytic activities after thirteen continuous runs. Compared with net or plate structure, the Ni foam with a unique three-dimensional reticulate structure is conducive to the electrodeposition of PPy. Compared with Pt-group electrode, PPy-coated Ni foam shows a satisfactory catalytic performance for the H2 evolution. The combination of PPy and Ni forms a synergistic effect for the rapid trapping and removal of proton from solution and the catalytic reduction of proton to hydrogen. The PPy-functionalized Ni foam could be applied in photocatalytic and photoelectrochemical generation of H2. In all, we report a low cost, high efficient and earth abundant PPy-functionalized Ni foam with a satisfactory catalytic activities comparable to Pt for the practical application of poly-generation of hydrogen and electricity.

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

    PubMed

    Nagy, Timea; Verner, Erika; Gspr, Vilmos; Kori, Hiroshi; Kiss, Istvn 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. PMID:26117133

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

    NASA Astrophysics Data System (ADS)

    Nagy, Timea; Verner, Erika; Gspr, Vilmos; Kori, Hiroshi; Kiss, Istvn 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.

  1. Recycling of Magnesium Alloy Employing Refining and Solid Oxide Membrane (SOM) Electrolysis

    NASA Astrophysics Data System (ADS)

    Guan, Xiaofei; Zink, Peter A.; Pal, Uday B.; Powell, Adam C.

    2013-04-01

    Pure magnesium was recycled from partially oxidized 50.5 wt pct Mg-Al scrap alloy and AZ91 Mg alloy (9 wt pct Al, 1 wt pct Zn). Refining experiments were performed using a eutectic mixture of MgF2-CaF2 molten salt (flux). During the experiments, potentiodynamic scans were performed to determine the electrorefining potentials for magnesium dissolution and magnesium bubble nucleation in the flux. The measured electrorefining potential for magnesium bubble nucleation increased over time as the magnesium content inside the magnesium alloy decreased. Potentiostatic holds and electrochemical impedance spectroscopy were employed to measure the electronic and ionic resistances of the flux. The electronic resistivity of the flux varied inversely with the magnesium solubility. Up to 100 pct of the magnesium was refined from the Mg-Al scrap alloy by dissolving magnesium and its oxide into the flux followed by argon-assisted evaporation of dissolved magnesium and subsequently condensing the magnesium vapor. Solid oxide membrane electrolysis was also employed in the system to enable additional magnesium recovery from magnesium oxide in the partially oxidized Mg-Al scrap. In an experiment employing AZ91 Mg alloy, only the refining step was carried out. The calculated refining yield of magnesium from the AZ91 alloy was near 100 pct.

  2. Development of an amperometric sulfite biosensor based on SO(x)/PBNPs/PPY modified ITO electrode.

    PubMed

    Rawal, Rachna; Pundir, C S

    2012-11-01

    A sulfite oxidase (SO(x)) (EC 1.8.3.1) purified from Syzygium cumini leaves was immobilized onto prussian blue nanoparticles/polypyrrole composite (PBNPs/PPY) electrodeposited onto the surface of indium tin oxide (ITO) electrode. An amperometric sulfite biosensor was fabricated using SO(x)/PBNPs/PPY/ITO electrode as working electrode, Ag/AgCl as standard and Pt wire as auxiliary electrode connected through a potentiostat. The working electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of SO(x). The biosensor showed optimum response within 2s, when operated at 20 mV s? in 0.1M Tris-HCl buffer, pH 8.5 and at 35 C. Linear range and minimum detection limit were 0.5-1000 ?M and 0.12 ?M (S/N=3) respectively. There was good correlation (r=0.99) between red wine samples sulfite value by standard DTNB method and the present method. The sensor was evaluated with 97% recovery of added sulfite in red wine samples and 2.2% and 4.3% within and between batch coefficients of variation respectively. The sensor was employed for determination of sulfite level in red and white wine samples. The enzyme electrode was used 200 times over a period of 3 months when stored at 4 C. PMID:22705572

  3. 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.; Kamachi Mudali, U.

    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 UVvisible spectroscopy and thermogravimetric analysis.

  4. Corrosion inhibition of a mild steel by aniline and alkylamines in acidic solutions

    SciTech Connect

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

    1998-09-01

    Corrosion inhibition of a mild steel in acid solutions by alkylamines (ALK-AM) and aniline hydrochloric (ANL-HCl) salts was investigated in the presence of sodium sulfate (Na{sub 2}SO{sub 4}) and sodium chloride (NaCl) using a potentiostat, a contact-angle goniometer, a scanning electron microscope (SEM), a Fourier transform infrared spectrometer (FTIR), and an atomic force microscope (AFM). Results showed chloride ions (Cl{sup {minus}}) had a pronounced effect on inhibition of amines and ANL for corrosion of mild steel. In the presence of Cl{sup {minus}} ions, cationic types of surfactants (ALK-AM and ANL) were attached to the surface through formation of chloride precipitate at the surface. In the absence of the organic inhibitors, corrosion initiated along grain boundaries of ferrite and pearlite structures. In the presence of the organic inhibitor, however, the steel surface was covered by an organic salt precipitation, and the corrosion rate was reduced significantly.

  5. Corrosion inhibition of copper with benzotriazole and other organic surfactants

    SciTech Connect

    Ling, Y.; Guan, Y.; Han, K.N.

    1995-05-01

    The corrosion behavior of copper with various organic inhibitors in aerated solutions at pH 1 to pH 2 was studied using a potentiostat. The inhibitors studied included benzotriazole (BTAH), hydroxy benzophenoximes, L-hydroxy-5-nonylacetophenone oxime, and sodium octyl hydroxamate (SOH). BTAH was shown to be the most effective of the inhibitors tested. Morphology of the copper substrate after corrosion in the presence and absence of BTAH was examined using scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) was used to identify the spectra of the adsorbed complexes (BTA). The surface film was identified as a polymeric Cu(I)-BTA complex that totally covered the copper surface, exhibiting strong corrosion inhibition. The formation of Cu(I)-BTA was found to have been accomplished after the adsorption of BTAH on the copper surface. The effect of annealing of copper plate on the rate of corrosion also was investigated, and results indicated that the annealed copper exhibited better corrosion resistance than copper plate that had not been annealed.

  6. 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

  7. Polyion Selective Polymeric Membrane-Based Pulstrode as a Detector in Flow-Injection Analysis

    PubMed Central

    2015-01-01

    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

  8. Relevance of an electrochemical process prior to a biological treatment for the removal of an organophosphorous pesticide, phosmet.

    PubMed

    Salles, Nara Alonso; Fourcade, Florence; Geneste, Florence; Floner, Didier; Amrane, Abdeltif

    2010-09-15

    The aim of this study was to examine the feasibility of coupling an electrochemical pre-treatment with a biological step in order to degrade phosmet, an organophosphorous pesticide. Preliminary biodegradation experiments showed that the target molecule was not assimilated by activated sludge. The pre-treatment consisted of potentiostatic electrolysis (-1.3 V/SCE) in a flow cell. After only one pass (1 mL min(-1)), cyclic voltammetry with a vitreous carbon electrode showed a total phosmet reduction in neutral medium confirmed by thin layer chromatography, which also highlighted the presence of several by-products. H NMR spectra of the main by-product showed the absence of the aromatic ring, only the phosphorus part of phosmet has been identified and phosmet-oxon, a very toxic derivative, was not formed. Lower toxicity and higher biodegradability characterized the electrolyzed solution, EC(50) value increased from 7% to 58% and BOD(5) value increased from 4 to 9 mg O(2) L(-1) after electrolysis leading to an increase of the BOD(5) on COD ratio from 0.19 to 0.42 (limit of biodegradability, 0.4). These encouraging results were confirmed during activated sludge culture since an almost total mineralization of the electrolyzed solution was recorded (97%), confirming the feasibility of the proposed coupled process. PMID:20538412

  9. Eliminating Electrochromic Degradation in Amorphous TiO2 through Li-Ion Detrapping.

    PubMed

    Wen, Rui-Tao; Niklasson, Gunnar A; Granqvist, Claes G

    2016-03-01

    The quest for superior and low-cost electrochromic (EC) thin films, for applications in smart windows, remains strong because of their large importance for energy-efficient buildings. Although the development of new EC materials for improved devices is important, diminishing or reversing degradation is another key issue, and electrical rejuvenation of degraded EC materials can offer new opportunities. Here we demonstrate that cathodically coloring EC thin films of TiO2, which normally suffer from ion-trapping-induced degradation of charge capacity and optical modulation upon extensive electrochemical cycling, can recover their initial EC performance by a rejuvenation procedure involving Li(+) ion detrapping. Thus, the initial performance can be regained, and refreshed TiO2 films exhibit the same degradation features as as-deposited films upon prolonged electrochemical cycling. The rejuvenation was carried out by using either galvanostatic or potentiostatic treatments. Our study may open avenues to explore the recovery not only of EC materials and devices based on those but also for other ion-exchange-based devices. PMID:26910644

  10. 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.

  11. 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 MottSchottky analysis a donor concentration of 2.3נ1020cm?3 and a flat band potential of 1.00V 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 1.4S cm?1. PMID:25843970

  12. Strong Photo-Amplification Effects in Flexible Organic Capacitors with Small Molecular Solid-State Electrolyte Layers Sandwiched between Photo-Sensitive Conjugated Polymer Nanolayers.

    PubMed

    Lee, Hyena; Kim, Jungnam; Kim, Hwajeong; Kim, Youngkyoo

    2016-01-01

    We demonstrate strong photo-amplification effects in flexible organic capacitors which consist of small molecular solid-state electrolyte layers sandwiched between light-sensitive conjugated polymer nanolayers. The small molecular electrolyte layers were prepared from aqueous solutions of tris(8-hydroxyquinoline-5-sulfonic acid) aluminum (ALQSA3), while poly(3-hexylthiophene) (P3HT) was employed as the light-sensitive polymer nanolayer that is spin-coated on the indium-tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) film substrates. The resulting capacitors feature a multilayer device structure of PET/ITO/P3HT/ALQSA3/P3HT/ITO/PET, which were mechanically robust due to good adhesion between the ALQSA3 layers and the P3HT nanolayers. Results showed that the specific capacitance was increased by ca. 3-fold when a white light was illuminated to the flexible organic multilayer capacitors. In particular, the capacity of charge storage was remarkably (ca. 250-fold) enhanced by a white light illumination in the potentiostatic charge/discharge operation, and the photo-amplification functions were well maintained even after bending for 300 times at a bending angle of 180(o). PMID:26846891

  13. Passivation dynamics in the anisotropic deposition and stripping of bulk magnesium electrodes during electrochemical cycling

    SciTech Connect

    Wetzel, David J.; Malone, Marvin A.; Haasch, Richard T.; Meng, Yifei; Vieker, Henning; Hahn, Nathan; Golzhauser, Armin; Zuo, Jian-Min; Zavadil, Kevin R.; Gewirth, Andrew A.; Nuzzo, Ralph G.

    2015-08-10

    Rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, though little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pit densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 μm in height. Finally, the passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte.

  14. Effects of passive films on corrosion resistance of uncoated SS316L bipolar plates for proton exchange membrane fuel cell application

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Ning, Xiaohui; Tang, Hongsheng; Guo, Liejin; Liu, Hongtan

    2014-11-01

    The effects of passive films on the corrosion behaviors of uncoated SS316L in anode and cathode environments of proton exchange membrane fuel cells (PEMFCs) are studied. Potentiodynamic and potentiostatic polarizations are employed to study the corrosion behavior; Mott-Schottky measurements are used to characterize the semiconductor properties of passive films; X-ray photoelectron spectroscopy (XPS) analyses are used to identify the compositions and the depth profiles of passive films. The passive films formed in the PEMFC anode and cathode environments under corresponding conditions both behave as n-type semiconductor. The passive film formed in the anode environment has a single-layer structure, Cr is the major element (Cr/Fe atomic ratio > 1), and the Cr/Fe atomic ratio decreases from the surface to the bulk; while the passive film formed in the PEMFC cathode environment has a bi-layer structure, Fe is the major element (Cr/Fe atomic ratio < 0.5), and in the external layer of the bi-layer structure Fe content increases rapidly and gradually in the internal layer. SS316L shows better corrosion resistance owing to both the high content of Cr oxide in the passive film and low band bending in normal PEMFC anode environments.

  15. Assessment of corrosion rate in prestressed concrete with acoustic emission

    NASA Astrophysics Data System (ADS)

    Mangual, Jes; ElBatanouny, Mohamed K.; Vlez, William; Ziehl, Paul; Matta, Fabio; Gonzlez, Miguel

    2011-04-01

    Acoustic Emission (AE) sensing was employed to assess the rate of corrosion of steel strands in small scale concrete block specimens. The corrosion process was accelerated in a laboratory environment using a potentiostat to supply a constant potential difference with a 3% NaCl solution as the electrolyte. The embedded prestressing steel strand served as the anode, and a copper plate served as the cathode. Corrosion rate, half-cell potential measurements, and AE activity were recorded continuously throughout each test and examined to assess the development of corrosion and its rate. At the end of each test the steel strands were cleaned and re-weighed to determine the mass loss and evaluate it vis--vis the AE data. The initiation and propagation phases of corrosion were correlated with the percentage mass loss of steel and the acquired AE signals. Results indicate that AE monitoring may be a useful aid in the detection and differentiation of the steel deterioration phases, and estimation of the locations of corroded areas.

  16. Admittance spectroscopy of sealed secondary batteries

    NASA Astrophysics Data System (ADS)

    Bari, M. A.; Jonscher, A. K.

    1986-05-01

    The admittance of sintered NiCd alkaline and Pb-acid-sealed batteries was investigated in the frequency range 0.01 to 10,000 Hz at 253, 293, and 323 K, with small signals of 1-10 mV amplitude under potentiostatic control to keep the direct current to a minimum value. Fully charged and fully discharged states of these batteries were investigated, the latter corresponding to relatively 'slow' and 'fast' discharges. The spectra of the real and imaginary components of the complex capacitance C(omega) are shown as functions of frequency, and equivalent circuits are derived using as circuit elements resistors and 'universal' dispersive capacitors obeying the power law frequency dependence Cn(omega) = An(i omega)exp n-1 with n in the range 0,1. The results are discussed in terms of known electrochemical reactions in these two types of batteries and assignments are made of the bulk eletrolyte resistance, the interfacial electrochemical reaction, and the transport of ionic species through the pores of the nonconducting matter surrounding the electrodes, as well as a 'structural' inductance term. The analysis shows clear evidence of dispersive processes but no trace of direct current conduction, at least down to 0.01 Hz, which is rather surprising. The results open a number of fundamental questions relating to the processes governing the dynamic response of secondary batteries which are at present not well understood.

  17. Stress-corrosion behavior of aluminum-lithium alloys in aqueous salt environments

    NASA Technical Reports Server (NTRS)

    Pizzo, P. P.; Galvin, R. P.; Nelson, H. G.

    1984-01-01

    The stress corrosion susceptibility of two powder metallurgy (P/M) alloys, Al-Li-Cu and Al-Li-Cu-Mg; two mechanically attrited (M/A) alloys, Al-Li-Cu and Al-Li-Mg; and two wrought, ingot alloys, X-2020 and AA7475, are compared. Time-dependent fracture in an aqueous sodium chloride environment under alternate immersion condition was found to vary significantly between alloys. The stress corrosion behavior of the two powder metallurgy processed alloys was studied in detail under conditions of crack initiation, static crack growth, and fatigue crack growth. A variety of stress corrosion tests were performed including smooth surface, time-to-failure tests; potentiostatic tests on smooth surfaces exposed to constant applied strain rates; and fracture mechanics-type tests under static and cyclic loads. Both alloys show surface pitting and subsequent intergranular corrosion. Pitting is more severe in the magnesium-bearing alloy and is associated with stringer particles strung along the extrusion direction as a result of P/M processing.

  18. Design and applications of an in situ electrochemical NMR cell

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaocan; Zwanziger, Josef W.

    2011-01-01

    A device using a three-electrode electrochemical cell (referred to as an ECNMR cell) was successfully constructed that could be used in a standard 5 mm NMR probe to acquire high-resolution NMR spectra while the working electrode was held at a constant electrical potential. The working electrode was a 20 nm thick gold film thermally coated on the outside of an inner 3 mm glass tube. An underlayer consisting of (3-mercaptopropyl)trimethoxy-silane was coated on the glass surface in order to improve its adhesion to gold. Tests showed prolonged life of the gold film. Details of the design and construction of the ECNMR cell are described. The ECNMR cell could be routinely used in a multi-user service high-resolution NMR instrument under oxygen-free conditions in both aqueous and non-aqueous solvents. Different approaches were applied to suppress the noise transmitted between the potentiostat and the NMR spectrometer. These approaches were shown to be effective in reducing background noise in the NMR spectra. The electrochemical and NMR performance of the ECNMR cell is presented. The reduction of 1,4-benzoquinone in both aqueous and non-aqueous solvents was used for testing. The evolution of the in situ ECNMR spectra with time demonstrated that use of the ECNMR cell was feasible. Studies of caffeic acid and 9-chloroanthracene using this ECNMR cell were undertaken to explore its applications, such as monitoring reactions and studying their reaction mechanisms.

  19. Electrolytic recovery of gallium from dilute solutions employing microelectrodes

    SciTech Connect

    Cahen, G.L.; Gileadi, E.; Paciej, R.C.; Stoner, G.E.

    1985-06-01

    The recovery of gallium from dilute solutions is known to be slow and inefficient due to competing hydrogen evolution and the limitations of mass transport. Methods used to improve the process include pulse plating, inhibition of hydrogen evolution by suitable additives, increasing the pH, and conducting the process at temperatures above the melting point of gallium. In the present work, an alternative approach was taken employing microelectrodes to enhance the rate of mass transport and thus to increase the rate of gallium recovery. Potentiostatic plating and stripping experiments were performed using electrodes ranging in diameter from 1 cm down to 45 ..mu..m. The effect of electrode diameter on the rate and efficiency of the plating of gallium was studied at different potentials and under different conditions of mass transport. The effect of plating time was also determined, and the conditions for the optimum recovery of gallium in terms of the overall rate as well as the current efficiency were evaluated. Carbon fiber epoxy composites can serve as ensembles of microelectrodes. It was shown that, with a typical radius of 3-5 ..mu..m for the individual fibers, considerable enhancement of the rate of recovery of metals from dilute solutions can be expected.

  20. Specific and efficient electrochemical selection of Geoalkalibacter subterraneus and Desulfuromonas acetoxidans in high current-producing biofilms.

    PubMed

    Pierra, Mlanie; Carmona-Martnez, Alessandro A; Trably, Eric; Godon, Jean-Jacques; Bernet, Nicolas

    2015-12-01

    Two different saline sediments were used to inoculate potentiostatically controlled reactors (a type of microbial bioelectrochemical system, BES) operated in saline conditions (35 gNaCl l(-1)). Reactors were fed with acetate or a mixture of acetate and butyrate at two pH values: 7.0 or 5.5. Electroactive biofilm formation lag-phase, maximum current density production and coulombic efficiency were used to evaluate the overall performance of reactors. High current densities up to 8.5 A m(-2) were obtained using well-defined planar graphite electrodes. Additionally, biofilm microbial communities were characterized by CE-SSCP and 454 pyrosequencing. As a result of this procedure, two anode-respiring bacteria (ARB) always dominated the anodic biofilms: Geoalkalibacter subterraneus and/or Desulfuromonas acetoxidans. This suggests that a strong electrochemically driven selection process imposed by the applied potential occurs in the BES system. Moreover, the emergence of Glk. subterraneus in anodic biofilms significantly contributes to broaden the spectrum of high current producing microorganisms electrochemically isolated from environmental samples. PMID:25717030

  1. Electrodeposition of p-Type Sb x Te y Thermoelectric Films

    NASA Astrophysics Data System (ADS)

    Lim, Jae-Hong; Park, Mi Yeong; Lim, Dong Chan; Yoo, Bongyoung; Lee, Jung-Ho; Myung, Nosang V.; Lee, Kyu Hwan

    2011-05-01

    Thermoelectric Sb x Te y films were potentiostatically electrodeposited in aqueous nitric acid electrolyte solutions containing different concentrations of TeO2. Stoichiometric Sb x Te y films were obtained by applying a voltage of -0.15 V versus saturated calomel electrode (SCE) using a solution consisting of 2.4 mM TeO2, 0.8 mM Sb2O3, 33 mM tartaric acid, and 1 M HNO3. The nearly stoichiometric Sb2Te3 films had a rhombohedral structure, Rbar{3}m , with a preferred orientation along the (015) direction. The films had hole concentration of 5.8 1018/cm3 and exhibited mobility of 54.8 cm2/Vs. A more negative potential resulted in higher Sb content in the deposited Sb x Te y films. Furthermore, it was observed that the hole concentration and mobility decreased with increasingly negative deposition potential, and eventually showed insulating properties, possibly due to increased defect formation. The absolute value of the Seebeck coefficient of the as-deposited Sb2Te3 thin film at room temperature was 118 ?V/K.

  2. Experimental and Quantum Studies on Adsorption and Corrosion Inhibition Effect of Imidazole Derivatives on N80 Steel in Hydrochloric Acid

    NASA Astrophysics Data System (ADS)

    Yadav, M.; Kumar, Sumit; Sharma, Dipti; Yadav, P. N.

    2013-12-01

    The inhibition effect of synthesized N?-(phenylmethylidene)-2-(2-methyl-1H-benzimidazol-1-yl)acetohydrazides, N?-(4-methylphenylmethylidene)-2-(2-methyl-1H-benzimidazol-1-yl)acetohydrazides, and N?-(4-methoxyphenylmethylidene)-2-(2-methyl-1H-benzimidazol-1-yl)acetohydrazides on the corrosion behaviour of N80 steel in 15% hydrochloric acid solution was investigated using weight loss, potentiostatic polarization and electrochemical impedance spectroscopy methods. The inhibition efficiency increased as the concentration of the inhibitors was increased. The effect of temperature on corrosion inhibition was investigated by weight loss method and thermodynamic parameters were calculated. Potentiodynamic polarization measurements show that all the three studied inhibitors act as mixed inhibitor. The adsorption of inhibitors on N80 steel surface obeys Langmuir adsorption isotherm. The structure of inhibitors was optimized using semiemperical AM1 method. Theoretical parameters such as the highest occupied molecular orbital (EHOMO), lowest unoccupied molecular orbital (ELUMO) energy levels, energy gap (?E = ELUMO - EHOMO), dipole moment (?), global hardness (?), softness (?), binding energy, molecular surface area and the fraction of electrons transferred (?N) were calculated and the adsorption mechanism was discussed. Scanning electron microscopy was used to characterize the surface marphology of the N80 steel.

  3. Effect of Nitrate on the Critical Potentials of Alloy 22 in Chloride Containing Environments

    SciTech Connect

    G. Ilevbare; K. King; S. Gordon; G. Gdowski; H. Elayat; T. Summers

    2004-05-13

    The study of Alloy 22 has been undertaken in several selected nitrate/chloride (NO{sub 3}Cl{sup -}) electrolytes. These electrolytes include chloride concentrations [Cl{sup -}] of 1.0, 3.5 and 6.0 metal with NO{sub 3}/Cl{sup -} ratios of 0.05, 0.15 and 0.5 at various temperatures. Alloy 22 maintains is passivity in most industrial environments. As a result, it is highly desirable for numerous industrial applications including underground waste disposal systems. Alloy 22 possesses remarkably low general corrosion rates. It has exceptional resistance so localized corrosion including environmentally assisted cracking [1-7]. Alloy 22 (N06022) is a nickel(Ni)-alloy and contains 22% chromium (Cr), 13% molybdenum (Mo), 3% tungsten (W) and about 3% iron (Fe). The goal of this study was to determine the levels of NO{sub 3} required for effective inhibition of crevice corrosion at Alloy 22. To achieve this, carefully designed statistical cost matrices covering the selected range of CT compositions and temperatures were employed in carrying out the experiments. Specimens for three experiments were in the form of multiple crevice assemblies (MCA), optimized with 24 artificial crevice sites. Tests used in this investigation involved open circuit potential monitoring, polarization resistance, and cyclic polarization experiments. Potentiostatic polarization test were also employed.

  4. Inhibitive action of ferricyanide complex anion on both corrosion and passivation of zinc and zinc-nickel alloy in the alkaline solution

    NASA Astrophysics Data System (ADS)

    El-Sayed, Abdel-Rahman; Mohran, Hossnia S.; Abd El-Lateef, Hany M.

    2011-08-01

    The corrosion of zinc and Zn-0.5Ni alloy in strong alkaline solution (7 M KOH) in the absence and presence of [Fe(CN)6]3- complex anion (1 10-3-1 10-2 M) as inhibitor has been studied. Tafel plot, potentiodynamic, potentiostatic and electrochemical impedance spectroscopy (EIS) techniques were used, and complementary by EDX and SEM investigation. It is observed that, the corrosion current density (Icorr) decreases, and the inhibition efficiency (IE%) increases as the concentration of inhibitor is increased. The shift of breakdown potential to less positive direction, indicating that the reduction of oxide layer on the alloy surface occurs somewhat easier in the presence of [Fe(CN)6]3- complex anion. The impedance measurements have shown that the increase of the inhibitor concentration in the alkaline solution reduces the corrosion rate in the active region. Accordingly, addition of [Fe(CN)6]3- complex anion to KOH solution can be considered as an important criteria for a good battery anodes. This behavior is due to its high negative open-circuit potential, less corrosion rate and higher self-catalysis in the passive region compared with those in its absence.

  5. Solid-state electrochemical kinetics of Li-ion intercalation into Li{sub 1{minus}x}CoO{sub 2}: Simultaneous application of electroanalytical techniques SSCV, PITT, and EIS

    SciTech Connect

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

    1999-04-01

    The electroanalytical behavior of thin Li{sub 1{minus}x}CoO{sub 2} electrodes is elucidated by the simultaneous application of three electroanalytical techniques: slow-scan-rate cyclic voltammetry (SSCV), potentiostatic intermittent titration technique, and electrochemical impedance spectroscopy. The data were treated within the framework of a simple model expressed by a Frumkin-type sorption isotherm. The experimental SSCV curves were well described by an equation combining such an isotherm with the Butler-Volmer equation for slow interfacial Li-ion transfer. The apparent attraction constant was {minus}4.2, which is characteristic of a quasi-equilibrium, first-order phase transition. Impedance spectra reflected a process with the following steps: Li{sup +} ion migration in solution, Li{sup +} ion migration through surface films, strongly potential-dependent charge-transfer resistance, solid-state Li{sup +} diffusion, and accumulation of the intercalants into the host materials. An excellent fit was found between these spectra and an equivalent circuit, including a Voigt-type analog (Li{sup +} migration through multilayer surface films and charge transfer) in series with a finite-length Warburg-type element (Li{sup +} solid-state diffusion), and a capacitor (Li accumulation). In this paper, the authors compare the solid-state diffusion time constants and the differential intercalation capacities obtained by the three electroanalytical techniques.

  6. A new method for determining the acid number of biodiesel based on coulometric titration.

    PubMed

    Barbieri Gonzaga, Fabiano; Pereira Sobral, Sidney

    2012-08-15

    A new method is proposed for determining the acid number (AN) of biodiesel using coulometric titration with potentiometric detection, basically employing a potentiostat/galvanostat and an electrochemical cell containing a platinum electrode, a silver electrode, and a combination pH electrode. The method involves a sequential application of a constant current between the platinum (cathode) and silver (anode) electrodes, followed by measuring the potential of the combination pH electrode, using an isopropanol/water mixture as solvent and LiCl as the supporting electrolyte. A preliminary evaluation of the new method, using acetic acid for doping a biodiesel sample, showed an average recovery of 100.1%. Compared to a volumetric titration-based method for determining the AN of several biodiesel samples (ranging from about 0.18 to 0.95 mg g(-1)), the new method produced statistically similar results with better repeatability. Compared to other works reported in the literature, the new method presented an average repeatability up to 3.2 times better and employed a sample size up to 20 times smaller. PMID:22841067

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

    NASA Astrophysics Data System (ADS)

    Kuo, Hsin-Hui; Kuo, Chin-Guo; Yen, Chia-Ying; Yang, Cheng-Fu

    2014-02-01

    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 - x Te3 + 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 - x Te3 + x -based materials and grow the nanowires in anodic aluminum oxide (AAO) templates.

  8. Dual-electrode oxidation used for aniline degradation in aqueous electrolyte.

    PubMed

    Yan-Yang, Chu; Ling-Ling, Li; Mao-Juan, Bai

    2011-01-01

    The electrochemical degradation of aniline in aqueous electrolyte has been studied by dual-electrode oxidation process using Ti/SnO2-Sb2O5 for anodic oxidation and graphite cathode to produce H2O2 in situ. The linear voltammograms were employed to obtain reasonable anodic and cathodic potential values for the purpose of restraining side reactions. The influence of Fe2+ on aniline degradation was investigated under potentiostatic condition with a three-electrode system. It was found that an anodic potential range of 2.0 +/- 0.1 V and a cathodic potential of -0.65 V could favor anodic oxidation and H2O2 generation. Anodic oxidation was accounted for aniline degradation in the absence of Fe2+, while in the presence of Fe2+ both electro-Fenton oxidation and anodic oxidation (dual-electrode oxidation) could degradate aniline effectively. When cathodic potential values were -0.65 and -0.80 V, the optimum Fe2+ concentration were 0.50 and 0.30 mM, respectively. 77.5% COD removal and 70.4% TOC removal with a current efficiency (CE) of 96-100% were achieved under the optimum conditions. This work indicates that dual-electrode oxidation process characterized by a high CE is feasible for the degradation of organic compounds. PMID:22049752

  9. Polyphenol biosensor based on laccase immobilized onto silver nanoparticles/multiwalled carbon nanotube/polyaniline gold electrode.

    PubMed

    Rawal, Rachna; Chawla, Sheetal; Pundir, C S

    2011-12-15

    Laccase purified from Ganoderma sp. was immobilized covalently onto electrochemically deposited silver nanoparticles (AgNPs)/carboxylated multiwalled carbon nanotubes (cMWCNT)/polyaniline (PANI) layer on the surface of gold (Au) electrode. A polyphenol biosensor was fabricated using this enzyme electrode (laccase/AgNPs/cMWCNT/PANI/Au electrode) as the working electrode, Ag/AgCl as the reference electrode, and platinum (Pt) wire as the auxiliary electrode connected through a potentiostat. The biosensor showed optimal response at pH 5.5 (0.1 M acetate buffer) and 35°C when operated at a scan rate of 50 mV s(-1). Linear range, response time, and detection limit were 0.1-500 μM, 6 s, and 0.1 μM, respectively. The sensor was employed for the determination of total phenolic content in tea, alcoholic beverages, and pharmaceutical formulations. The enzyme electrode was used 200 times over a period of 4 months when stored at 4°C. The biosensor has an advantage over earlier enzyme sensors in that it has no leakage of enzyme during reuse and is unaffected by the external environment due to the protective PANI microenvironment. PMID:21855525

  10. Time-domain fitting of battery electrochemical impedance models

    NASA Astrophysics Data System (ADS)

    Alavi, S. M. M.; Birkl, C. R.; Howey, D. A.

    2015-08-01

    Electrochemical impedance spectroscopy (EIS) is an effective technique for diagnosing the behaviour of electrochemical devices such as batteries and fuel cells, usually by fitting data to an equivalent circuit model (ECM). The common approach in the laboratory is to measure the impedance spectrum of a cell in the frequency domain using a single sine sweep signal, then fit the ECM parameters in the frequency domain. This paper focuses instead on estimation of the ECM parameters directly from time-domain data. This may be advantageous for parameter estimation in practical applications such as automotive systems including battery-powered vehicles, where the data may be heavily corrupted by noise. The proposed methodology is based on the simplified refined instrumental variable for continuous-time fractional systems method ('srivcf'), provided by the Crone toolbox [1,2], combined with gradient-based optimisation to estimate the order of the fractional term in the ECM. The approach was tested first on synthetic data and then on real data measured from a 26650 lithium-ion iron phosphate cell with low-cost equipment. The resulting Nyquist plots from the time-domain fitted models match the impedance spectrum closely (much more accurately than when a Randles model is assumed), and the fitted parameters as separately determined through a laboratory potentiostat with frequency domain fitting match to within 13%.

  11. A liquid-junction-free reference electrode based on a PEDOT solid-contact and ionogel capping membrane.

    PubMed

    Zuliani, Claudio; Matzeu, Giusy; Diamond, Dermot

    2014-07-01

    Liquid-junction-free reference electrodes have been prepared on screen printed substrates using poly-3,4-ethylenedioxythiophene (PEDOT) as solid-contact and novel ionogels as capping membrane. The chemico-physical properties of the PEDOT layer were tuned by changing the electropolymerization media and the electrodeposition technique. Electrodepositing PEDOT films potentiostatically or potentiodynamically were found to have a significant impact on the stability of the electrodes during the conditioning step. Optimization of the capping membrane formulation, e.g., acrylate monomers, ionic liquid, cross-linkers and photo-initiators, produced electrodes with properties almost equivalent with a commercial reference electrode. Thus, calibration plots of Na(+) ion-selective electrodes against the optimized solid-contact ionogel reference electrodes (SCI-REs) or against a double-liquid junction Ag/AgCl electrode did not present any significant difference. Such SCI-REs may provide an effective route to the generation of future low-cost components for potentiometric sensing strips. PMID:24840415

  12. 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

  13. Corrosion behaviour of magnesium alloys coated with TiN by cathodic arc deposition in NaCl and Na{sub 2}SO{sub 4} solutions

    SciTech Connect

    Altun, Hikmet Sinici, Hakan

    2008-03-15

    Magnesium-based light-metal alloys belong to a class of structural materials with increasing industrial attention. Magnesium alloys show the lowest density among the engineering metallic materials, low cost and large availability. However, the limitations according to mechanical strength and the low corrosion resistance restrict their practical application. In this study, TiN was coated on magnesium-based AZ91 magnesium-aluminium-zinc alloy using cathodic arc PVD process. The corrosion behaviours of uncoated and coated magnesium alloys in 1% NaCl, 3% NaCl and 3% Na{sub 2}SO{sub 4} solutions and the influence of the coatings on the corrosion behaviour of the substrate were investigated utilizing potentiodynamic polarization tests. A potentiostat for electrochemical corrosion tests, a cathodic arc physical vapour deposition coating system for coating processes, a scanning electron microscopy for surface examination and elemental analysis of the coatings were used in this study. It was determined that corrosion resistance of magnesium alloys can be increased with TiN coating on the alloys using cathodic arc PVD process.

  14. Passivation Dynamics in the Anisotropic Deposition and Stripping of Bulk Magnesium Electrodes During Electrochemical Cycling

    SciTech Connect

    Wetzel, David J.; Malone, Marvin A.; Haasch, Richard T.; Meng, Yifei; Vieker, Henning; Hahn, Nathan; Golzhauser, Armin; Zuo, Jian-Min; Zavadil, Kevin R.; Gewirth, Andrew A.; Nuzzo, Ralph G.

    2015-08-10

    Rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, though little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pit densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 ?m in height. Finally, the passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte.

  15. 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.

  16. Environmental factors affecting corrosion of munitions

    SciTech Connect

    Bundy, K.; Bricka, M.; Morales, A.

    1995-12-31

    Spent small arms munitions have accumulated for years at outdoor firing ranges operated by the DoD and other groups. Used bullets are often subjected to moisture sources. There is increasing concern that accumulations of lead-based munitions represent potential sources of water and soil pollution. To understand both the severity of and solutions to this problem, it is necessary to measure how rapidly bullets corrode and to determine the soil variables affecting the process. In this study M16 bullets were buried in samples of soil taken from Louisiana army firing ranges. Four environmental conditions were simulated; rain water, acid rain, sea water, and 50% sea water/50% acid rain. The three electrode technique was used to measure the bullet corrosion. Graphite rods served as counter electrodes. A saturated calomel reference electrode was used along with a specially constructed salt bridge. Electrochemical measurements were conducted using a computer-controlled potentiostat to determine corrosion potential, soil resistance, and corrosion current. The rate of corrosion was found to markedly increase with decreasing soil pH and increasing chloride and moisture contents, with the chloride content being the most influential variable. High soil resistance and noble corrosion potential were found to be associated with low corrosion rates. This is important since both parameters can be readily measured in the field.

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

    SciTech Connect

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

    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.

  18. Amperometric determination of acetylcholine-A neurotransmitter, by chitosan/gold-coated ferric oxide nanoparticles modified gold electrode.

    PubMed

    Chauhan, Nidhi; Pundir, C S

    2014-11-15

    An amperometric acetylcholine biosensor was constructed by co-immobilizing covalently, a mixture of acetylcholinesterase (AChE) and choline oxidase (ChO) onto nanocomposite of chitosan (CHIT)/gold-coated ferric oxide nanoparticles (Fe@AuNPs) electrodeposited onto surface of a Au electrode and using it as a working electrode, Ag/AgCl as reference electrode and Pt wire as auxiliary electrode connected through potentiostat. The biosensor is based on electrochemical measurement of H2O2 generated from oxidation of choline by immobilized ChO, which in turn is produced from hydrolysis of acetylcholine by immobilized AChE. The biosensor exhibited optimum response within 3s at +0.2V, pH 7.0 and 30°C. The enzyme electrode had a linear working range of 0.005-400 µM, with a detection limit of 0.005 µM for acetylcholine. The biosensor measured plasma acetylcholine in apparently healthy and persons suffering from Alzheimer's disease. The enzyme electrode was unaffected by a number of serum substances but lost 50% of its initial activity after its 100 uses over a period of 3 months, when stored at 4°C. PMID:24836212

  19. Construction of an uricase nanoparticles modified au electrode for amperometric determination of uric acid.

    PubMed

    Chauhan, Nidhi; Kumar, Arun; Pundir, C S

    2014-10-01

    A method is described for preparation of uricase nanoparticles (100 nm in size) and their direct immobilization onto the Au electrode. The enzyme electrode along with Ag/AgCl as reference and Pt as auxiliary electrode were connected through potentiostat/galvanostat to construct an amperometric uric acid biosensor. The enzyme electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and electrochemical impedance spectroscopy (EIS). The enzyme electrode detected uric acid level as low as 5.0 μM at a signal-to-noise ratio of 3, within 7 s at pH 8.5 and 40 °C. The biosensor showed a linear working range, 0.005 to 0.8 mM for uric acid with a sensitivity of 0.03 mA μM(-1) cm(-2). The biosensor was evaluated. The biosensor lost only 15 % of its initial activity over a period of 7 months, when stored at 4 °C. The fabricated biosensor was successfully employed for determination of uric acid in human serum and urine. PMID:25141984

  20. Potential COntrol Under Thin Aqueous Layers Using a Kelvin Probe

    SciTech Connect

    G.S. Frankel; B. Maier; M. Stratman; M. Rohwerder; A. Michalik; J. Dora; M. Wicinski

    2006-08-17

    Kelvin Probes can be modified to control as well as monitor potential. The design and operation of two different Kelvin Probe Potentiostats (KPPs) are described in this paper. One approach uses a permanent magnet and double coil to oscillate the needle at a fixed frequency, an AC backing potential, and software analysis and control schemes. This technique can also control the distance between the tip and sample, thereby tracking the topography of the sample. Both KPPs were used to make measurements on Type 304L stainless steel under thin layers of electrolyte. Cathodic polarization curves exhibited a limiting current density associated with oxygen reduction. The limiting current density varied with solution layer thickness over a finite range of thickness. Anodic polarization curves on 304L in a thin layer of chloride solution resulted in pitting corrosion. The breakdown potential did not vary with solution layer thickness. However, the thin layer was observed to increase in volume remarkably during pit growth owing to the absorption of water from the high humidity environment into the layer with ionic strength increased by the pit dissolution. The open circuit potential (OCP) and solution layer thickness were monitored during drying out of a thin electrolyte layer. Pitting corrosion initiated, as indicated by a sharp drop in the OCP, as the solution thinned and increased in concentration.

  1. Development of molten carbonate fuel cell power plant technology

    NASA Astrophysics Data System (ADS)

    Bushnell, C. L.; Davis, C. L.; Dayton, J. E.; Johnson, C. K.; Katz, M.; Krasij, M.; Kunz, H. R.; Maricle, D. L.; Meyer, A. P.; Pivar, J. C.

    1984-09-01

    A prototype molten carbonate fuel cell stack which meets the requirements of a 1990's-competitive, coal-fired electrical utility central station, or industrial cogeneration power plant was developed. Compressive creep testing of the present anode is continuedl the samples and support the earlier data showing improved creep resistance. Testing to define the operating limits that are suitable for extending the life of nickel oxide cathodes to an acceptable level is continuing. The mechanical characteristics of several one-piece cathode current collector candidates are measured for suitability. Metallographic evaluation of stack separators was initiated. Posttest characterization of surface treated INCO 825 was completed, retort corrosion testing of this material is continuing, potentiostatic immersion testing of alternative single piece cathode current collector materials is initiated. The 20-cell Stack No. 3 progressed from completion and delivery of the Test Plan through Design Review, assembly, and initial heat-up for the start of testing. Manufacture of separator plates for the upcoming 20-cell Stack No. 4 has begun. The primary objective of this follow-on test is stack cost reduction.

  2. 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

  3. Construction and application of an amperometric xanthine biosensor based on zinc oxide nanoparticles-polypyrrole composite film.

    PubMed

    Devi, Rooma; Thakur, Manish; Pundir, C S

    2011-04-15

    Zinc oxide nanoparticles (ZnO-NPs) were synthesized from zinc nitrate by simple and efficient method in aqueous media at 55°C without any requirement of calcinations step. A mixture of ZnO-NPs and pyrrole was eletropolymerized on Pt electrode to form a ZnO-NPs-polypyrrole (PPy) composite film. Xanthine oxidase (XOD) was immobilized onto this nanocomposite film through physiosorption. The ZnO-NPs/polypyrrole/Pt electrode was characterized by Fourier transform infrared (FTIR), cyclic voltammetry (CV), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of XOD. The XOD/ZnO-NPs-PPy/Pt electrode as working electrode, Ag/AgCl as reference electrode and Pt wire as auxiliary electrode were connected through a potentiostat to construct a xanthine biosensor. The biosensor exhibited optimum response within 5s at pH 7.0, 35°C and linearity from 0.8 μM to 40 μM for xanthine with a detection limit 0.8 μM (S/E=3). Michaelis Menten constant (K(m)) for xanthine oxidase was 13.51 μM and I(max) 0.071 μA. The biosensor measured xanthine in fish meat and lost 40% of its initial activity after its 200 uses over 100 days, when stored at 4°C. PMID:21324666

  4. Amperometric Sensor for Detection of Chloride Ions†

    PubMed Central

    Trnkova, Libuse; Adam, Vojtech; Hubalek, Jaromir; Babula, Petr; Kizek, Rene

    2008-01-01

    Chloride ion sensing is important in many fields such as clinical diagnosis, environmental monitoring and industrial applications. We have measured chloride ions at a carbon paste electrode (CPE) and at a CPE modified with solid AgNO3, a solution of AgNO3 and/or solid silver particles. Detection limits (3 S/N) for chloride ions were 100 μM, 100 μM and 10 μM for solid AgNO3, solution of AgNO3 and/or solid silver particles, respectively. The CPE modified with silver particles is the most sensitive to the presence chloride ions. After that we approached to the miniaturization of the whole electrochemical instrument. Measurements were carried out on miniaturized instrument consisting of a potentiostat with dimensions 35 × 166 × 125 mm, screen printed electrodes, a peristaltic pump and a PC with control software. Under the most suitable experimental conditions (Britton-Robinson buffer, pH 1.8 and working electrode potential 550 mV) we estimated the limit of detection (3 S/N) as 500 nM.

  5. Applications of Planar ITO Electrodes for Studying of Some Biochemical Activities

    NASA Astrophysics Data System (ADS)

    Learngarunsri, P.; Chaiyen, P.; Srikhirin, T.; Veerasai, W.; Dangtip, S.

    Trends in disposable and handheld biosensors have called for miniaturized and planar electrodes in the place of conventional bulky ones. In this work, thin tin-doped indium oxide (ITO) film coated on glass were used as a based electrode in a three-electrode electrochemical system to follow some biochemical activities, such as NADH and phenol activity. The reference electrode is made on ITO layer by electro-deposition of thin nickel layer and silver layer, consecutively, followed by chlorination of silver surface by electrochemical potentiostatic method. The plain planar ITO-coated glasses were used as both counter electrode and working electrodes. Cyclic-voltammetry measurements; which follow an oxidation of 200 ?M nicotinamide adenine dinucleotide (NADH) in 0.1 M KCl, show current peak of 8.5 ?A. Another case was also to follow the NADH oxidation but in competition with its coupling activity with flavin mononucleotide (FMN). In this case, cyclic-voltammetry measurements were carried out of 200 ?M NADH in 50 mM sodium phosphate; current peak of 1.3 ?A was observed.

  6. The corrosion of iron rotating hemispheres in 1 M sulfuric acid: An electrochemical impedance study

    SciTech Connect

    Haili, C.C.

    1987-06-01

    This research project consists of experimental investigation and theoretical analysis of the corrosion of iron in sulfuric acid. Objectives were: to elucidate the processes governing the complex behavior of the iron-sulfuric acid system, particularly the reaction mechanism, the passivation process, and the observed limiting current and electrochemical oscillations; to improve our fundamental understanding of metal corrosion and passivation phenomena; and to demonstrate the application of the electrochemical impedance method as a tool for the study of electrochemical systems. Experiments carried out were: (1) potentiodynamic experiments to determine the anodic polarization curve, especially the passivation curve; (2) potentiostatic experiments recording the sustained current oscillations that occur within a certain potential range on the limiting current plateau; (3) measurement of the ac impedance of the system at several points along the anodic polarization curve, using a frequency response analyser. Rotating hemispherical iron electrodes were used in most of these experiments. The Kramers-Kronig relations were applied to the electrochemical impedance. The experimental results were compared with theoretical predictions in order to elucidate the behavior of the iron-sulfuric acid system. A concentrated-solution model was used to calculate the impedance, in addition to analytic calculations using infinitely-dilute-solution theory. The calculated results for the reaction mechanism and conditions tested did not agree with the experimental results. 226 refs., 5 figs.

  7. Effect of Fluid Flow on Zinc Electrodeposits from Acid Chloride Electrolytes. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Abdelmassir, A. A.

    1982-01-01

    Zinc was deposited potentiostatically from acid chloride baths. Once bath chemistry and electrochemistry were controlled, the study was focused on convective mass transfer at horizontal electrodes and its effect on cell performance. A laser schlieren imaging technique allowed in situ observations of flow patterns and their correlation with current transients. Convection was turbulent and mass transfer as a function of Rayleigh number was well correlated by: Sh = 0.14 R to the 1/3 power. Similarly, convection initiation time was correlated by DT/d squared = 38 Ra to the -2/3 power. Time scale of fluctuations was about half the initiation time. Taking the boundary layer thickness as a characteristic length, a critical Rayleigh number for the onset of convection was deduced: Ra sub CR = 5000. Placing the anode on the top of the cathode completely changed the flow pattern but kept the I-t curves identical whereas the use of a cathode grid doubled the limiting current. A well defined plateau in the current voltage curves suggested that hydrogen evolution has been successfully inhibited. Finally, long time deposition showed that convection at horizontal electrodes increased the induction time for dentrite growth by at least a factor of 2 with respect to a vertical wire.

  8. Electrochemical generation of oxygen. 1: The effects of anions and cations on hydrogen chemisorption and anodic oxide film formation on platinum electrode. 2: The effects of anions and cations on oxygen generation on platinum electrode

    NASA Technical Reports Server (NTRS)

    Huang, C. J.; Yeager, E.; Ogrady, W. E.

    1975-01-01

    The effects were studied of anions and cations on hydrogen chemisorption and anodic oxide film formation on Pt by linear sweep voltammetry, and on oxygen generation on Pt by potentiostatic overpotential measurement. The hydrogen chemisorption and anodic oxide film formation regions are greatly influenced by anion adsorption. In acids, the strongly bound hydrogen occurs at more cathodic potential when chloride and sulfate are present. Sulfate affects the initial phase of oxide film formation by produced fine structure while chloride retards the oxide-film formation. In alkaline solutions, both strongly and weakly bound hydrogen are influenced by iodide, cyanide, and barium and calcium cations. These ions also influence the oxide film formation. Factors considered to explain these effects are discussed. The Tafel slope for oxygen generation was found to be independent on the oxide thickness and the presence of cations or anions. The catalytic activity indicated by the exchange current density was observed decreasing with increasing oxide layer thickness, only a minor dependence on the addition of certain cations and anions was found.

  9. Effects of Zn amount on the properties of Zn-Zu2O composite films grown for PEC photoelectrodes by using electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Kim, Tae Gyoum; Lee, Hu Joong; Ryu, Hyukhyun; Lee, Won-Jae

    2015-10-01

    In this study, Zn-Cu2O composite films were grown on fluorine-doped tin-oxide (FTO) substrates by using the electrochemical deposition method. Various amounts of Zinc (Zn) were added to grow the Zn-Cu2O composite films. We analyzed the morphological, structural, optical energy band gap and photocurrent density properties of the Zn-Cu2O composite films by using various measurements such as field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), UV-visible spectrophotometry and potentiostat/galvanostat measurements, respectively. As a result, the highest photocurrent density value of -4.04 mA/cm2 was obtained for the 30-wt% sample, which had the lowest Cu2O (111)/ ZnO (101) XRD peak intensity ratio. The highest photocurrent density value from the 30-wt% sample was approximately 2.35 times higher than that from the non-composite Cu2O film (0-wt% sample). From this study, we found that adding Zn could improve the photocurrent values of Zn-Cu2O composite films.

  10. The influence of Cu2O crystal structure on the Cu2O/ZnO heterojunction photovoltaic performance

    NASA Astrophysics Data System (ADS)

    Elfadill, Nezar G.; Hashim, M. R.; Chahrour, Khaled M.; Qaeed, M. A.; Bououdina, M.

    2015-09-01

    Cuprous oxide (Cu2O) films were potentiostatically electrodeposited onto platinum (Pt) film coated onto silicon (Si) wafer from lactic solution at pH 9. The influence of applied potential on Cu2O crystal structure was carefully examined. At higher electrochemical applied potential, a polycrystalline structure was observed, and then as the applied potential decreased, a single crystalline structure oriented along (1 1 1) was obtained. Further decrease in the applied potential leads to the formation of a polycrystalline structure and finally at much lower applied potential, a single crystalline structure growing along (2 0 0) orientation (equivalent to (1 0 0) orientation) was revealed. Cu2O/ZnO heterojunction photodiodes based on these three crystal structures were fabricated and studied under dark and illuminated conditions. The best performance of the solar cell efficiency was achieved by the heterojunction based on (1 1 1) oriented Cu2O film (≈1.45%) compared to other structures (0.34% and 0.25%), which may be attributed to the formation of high quality heterojunction interface due to the heteroepitaxial-like growth of (0 0 2) oriented ZnO.

  11. Inhibitive Effect of L-Oh on the Corrosion of Austenitic Chromium-Nickel Steel in H2SO4 Solution

    NASA Astrophysics Data System (ADS)

    Hosseini, S. M. A.; Amiri, M.; Momeni, A.

    The corrosion behavior of the austenitic chromium-nickel steel in different concentrations (0.001, 0.002, 0.005, and 0.01 M) of dimethyl 2-(2-hydroxy phenyl amino)-3-(triphenyl phosphoranilidin) butane dioate (L-OH) in 0.5 M H2SO4 was investigated by potentiostatic polarization measurements. The effect of concentration and temperature on inhibition properties was determined. It was found that the presence of L-OH reduces markedly the corrosion rate of steel in the acid solution. The inhibition efficiency increases as the L-OH concentration is increased. Maximum inhibition efficiency (95%) was obtained for alloy in acid solution containing 0.01 M of L-OH. Thermodynamic parameters for adsorption of L-OH are calculated. It was found that the inhibitor is adsorbed on the steel surface and the experimental results are in agreement with Timken's isotherm. Negative values of the free energy of adsorption were obtained indicating the spontaneity of adsorption process. Scanning electron microscopy was done from the surface of exposed sample indicating uniform film on the surface of the alloy.

  12. Understanding the fundamentals of redox mediators in Li-O2 batteries: a case study on nitroxides.

    PubMed

    Bergner, Benjamin J; Hofmann, Christine; Schürmann, Adrian; Schröder, Daniel; Peppler, Klaus; Schreiner, Peter R; Janek, Jürgen

    2015-12-21

    The development of aprotic lithium-oxygen (Li-O2) batteries suffers from high charging overvoltages. Dissolved redox mediators, like nitroxides, providing increased energy efficiency and longer lifetime are promising tools to overcome this challenge. Since this auspicious concept is still in its infancy, the underlying chemical reactions as well as the impact of the different (electro)chemical parameters are poorly understood. Herein, we derive an electrochemical model for the charging reactions, which is validated by potentiostatic measurements. The model elucidates the impact of the major factors including basic cell parameters and the chemical properties of the redox mediator. The model is applied to the promising class of nitroxides, which is systematically investigated by using derivatives of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy), AZADO (2-azaadamantane-N-oxyl), and an azaphenalene based nitroxide. The nitroxides are electrochemically characterized by cyclic voltammetry and their performance as redox mediators is studied in Li-O2 batteries with an ether-based electrolyte. Based on the presented model, the charging profiles of the different nitroxide redox mediators are correlated with their molecular structures. PMID:26563563

  13. Hydrogen trapping in high-strength steels

    SciTech Connect

    Pound, B.G.

    1998-10-09

    Hydrogen trapping in three high-strength steels -- AerMet 100 and AISI 4340 and H11 -- was studied using a potentiostatic pulse technique. Irreversible trapping constants (k) and hydrogen entry fluxes were determined for these alloys in 1 mol/1 acetic acid/1 mol/1 sodium acetate. The order of the k values for the three steels and two 18Ni maraging steels previously studies inversely parallels their threshold stress intensities for stress corrosion cracking (K{sub 1SCC}). Irreversible trapping in AerMet 100 varies with aging temperature and appears to depend on the type of carbide (Fe{sub 3}C or M{sub 2}C) present. For 4340 steel, k can be correlated with K{sub 1SCC} over a range of yield strengths. The change in k is consistent with a change in the principal type of irreversible trap from matrix boundaries to incoherent Fe{sub 3}C. The principal irreversible traps in H11 at high yield strengths are thought to be similar to those in 4340 steel.

  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. 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.

  16. On-site in-situ determination of heavy metals in groundwater using an electrochemically-based sensor

    SciTech Connect

    Herdan, J.; Feeney, R.; Kounaves, S.P.

    1997-12-31

    An electrochemically-based probe has been developed for rapid in-situ or on-site detection of heavy metals in contaminated groundwater. The transducer consists of a microlithographically fabricated iridium ultramicroelectrode array (UMEA) which is used in conjunction with the high speed electrochemical preconcentration technique of square wave anodic stripping voltammetry (SWASV). The UMEA is connected to an integrated potentiostat which is controlled by a laptop computer. The entire probe, measuring only two inches in diameter, can be inserted downhole to measure such metal ions as Cu, Cd, Ph, and Zn, at the parts-per-billion level. The utility of this probe for rapid on site screening of metals was shown by conducting a proof-of-concept field demonstration at a metals-contaminated site at Hanscom Air Force Base in Massachusetts. Sampling was performed both, directly in-situ, and on-site by bringing the sample to the surface. Acidified samples where also taken back to the laboratory where they were measured both electrochemically using a mercury film glassy carbon electrode with SWASV, and by ICP Spectroscopy using EPA method 200.7. Excellent correlation was obtained between all of the measurement techniques, and the data for total and ionic forms was also in good agreement.

  17. Electrodeposited platinum thin films with preferential (100) orientation: Characterization and electrocatalytic properties for ammonia and formic acid oxidation

    NASA Astrophysics Data System (ADS)

    Bertin, Erwan; Garbarino, Sbastien; Guay, Daniel; Solla-Gulln, Jos; Vidal-Iglesias, Francisco J.; Feliu, Juan M.

    2013-03-01

    The electrocatalytic activity of preferentially oriented {100} Pt electrodes for the electro-oxidation of ammonia (0.2 M NaOH + 0.1 M NH3) and formic acid (0.5 M HCOOH + 0.5 M H2SO4) was assessed. They were prepared without using any surfactant through potentiostatic deposition (Ed = -0.10 V vs RHE, [HCl] = 10 mM and [Na2PtCl66H2O] = 0.5 mM) and by varying the deposition charge. For comparison, polycrystalline Pt thin films were prepared using the same solution but with Ed = +0.10 V vs RHE. Quantification of the fraction of (111) and (100) sites was performed by bismuth irreversible adsorption and deconvolution of the hydrogen region, respectively. Samples with as much as 47% of (100) surface sites were obtained. The preferential orientation was further confirmed by CO stripping voltammetry that exhibits similar characteristic features, as well as a similar potential of zero total charge than those expected for a preferential (100) surface. As compared to polycrystalline Pt, the occurrence of Pt (100) surface sites leads to an electrocatalytic activity enhancement by a factor of 4.8 and 2.6 (expressed as ?A cmPt-2) for the oxidation of ammonia and formic acid, respectively.

  18. CO electrooxidation on well-characterized Pt-Ru alloys

    SciTech Connect

    Gasteiger, H.A.; Markovic, N.; Ross, P.N. Jr.; Cairns, E.J. Lawrence Berkeley Lab., CA )

    1994-01-13

    The electrocatalytic activity of well-characterized Pt-Ru alloy electrodes toward the electrooxidation of CO in acidic electrolyte at room temperature was measured on alloy surfaces prepared in UHV (ultrahigh vacuum). Clearly defined surface composition was determined via LEIS (low-energy ion scattering). Electrocatalytic activities were measured by CO stripping voltammetry as well as by potentiostatic oxidation of adsorbed CO. It was found that the property of Ru atoms to nucleate oxygen-containing species at low potentials produced a strong enhancement in the catalytic activity of sputter-cleaned Pt-Ru alloy electrodes compared to pure Pt, thereby supporting the concept of the bifunctional character of the oxidation process of these alloys. A further synergistic effect of the alloy with a Ru surface composition of approximately 50 atom % Ru was observed, with a catalytic shift in the CO electrooxidation current of -0.25 and -0.15 V compared to those of pure Pt and pure Ru surfaces, respectively. This synergism was attributed to a uniquely active state of OH[sub ads] on Pt-Ru pair sites. The different electrocatalytic activities of sputter-cleaned versus annealed Pt-Ru alloy electrodes with essentially identical Ru surface compositions are discussed in terms of Ru clustering during annealing. 48 refs., 8 figs., 1 tab.

  19. TiO2 membranes for concurrent photocatalytic organic degradation and corrosion protection

    NASA Astrophysics Data System (ADS)

    Liang, Robert; Hatat-Fraile, Melisa; He, Horatio; Arlos, Maricor; Servos, Mark R.; Zhou, Y. Norman

    2015-10-01

    Organic contaminants and corrosion in water treatment effluents are a current global problem and the development of effective methods to facilitate the removal of organic contaminants and corrosion control strategies are required to mitigate this problem. TiO2 nanomaterials that are exposed to UV light can generate electron-hole pairs, which undergo redox reactions to produce hydroxyl radicals from adsorbed molecular oxygen. They hydroxyl radicals are able to oxidize organic contaminants in water. This same process can be used in conjunction to protect metals from corrosion via cathodic polarization. In this work, TiO2 nanomaterials were synthesized and electrophoretically deposited on conductive substrates to serve as films or membranes. An illuminated TiO2 film on a conductive surface served as the photoanode and assisted in the cathodic protection of stainless steel (SS304) and the degradation of organic pollutants, in this case glucose. This proof-of-concept relied on photoelectrochemical experiments conducted using a potentiostat and a xenon lamp illumination source. The open-circuit potential changes that determine whether a metal is protected from corrosion under illumination was observed; and the electrical characteristics of the TiO2 film or membrane under dark and arc lamp illumination conditions were also analyzed. Furthermore, the effect of organic contaminants on the photocathodic protection mechanism and the oxidation of glucose during this process were explored.

  20. A novel non-enzymatic glucose sensor based on Cu nanoparticle modified graphene sheets electrode.

    PubMed

    Luo, Jing; Jiang, Sisi; Zhang, Hongyan; Jiang, Jinqiang; Liu, Xiaoya

    2012-01-01

    A novel, stable and sensitive non-enzymatic glucose sensor was developed by potentiostatically electrodepositing metallic Cu nanoparticles on graphene sheets. The electrochemical performance of the Cu-graphene sheets electrode for detection of glucose was investigated by cyclic voltammetry and chronamperometry. The Cu-graphene sheets electrode displayed a synergistic effect of copper nanoparticles and graphene sheets towards the oxidation of glucose in alkaline solution, showing higher oxidation current and negative shift in peak potential. At detection potential of 500 mV, the Cu-graphene electrode sensor presented a wide linear range up to 4.5mM glucose with a detection limit of 0.5 ?M (signal/noise=3). In addition, the sensor responds very quickly (<2s) with addition of glucose. Furthermore, the Cu-graphene sheets electrode exhibits high stability and selectivity to glucose, and the poisoning by chloride ion as well as interference from the oxidation of common interfering species (ascorbic, dopamine, uric acid and carbohydrate) are effectively avoided. The Cu-graphene sheets electrode allows highly selective and sensitive, stable and fast amperometric sensing of glucose, which is promising for the development of non-enzymatic glucose sensor. PMID:22122930

  1. Batch-injection analysis with amperometric detection of the DPPH radical for evaluation of antioxidant capacity.

    PubMed

    Oliveira, Gracy K F; Tormin, Thiago F; Sousa, Raquel M F; de Oliveira, Alberto; de Morais, Srgio A L; Richter, Eduardo M; Munoz, Rodrigo A A

    2016-02-01

    This work proposes the application of batch-injection analysis with amperometric detection to determine the antioxidant capacity of real samples based on the measurement of DPPH radical consumption. The efficient concentration or EC50 value corresponds to the concentration of sample or standard required to scavenge 50% DPPH radicals. For the accurate determination of EC50, samples were incubated with DPPH radical for 1h because many polyphenolic compounds typically found in plants and responsible for the antioxidant activity exhibit slow kinetics. The BIA system with amperometric detection using a glassy-carbon electrode presented high precision (RSD = 0.7%, n = 12), low detection limit (1 ?mol L(-1)) and selective detection of DPPH (free of interferences from antioxidants). These contributed to low detection limits for the antioxidant (0.015 and 0.19 ?mol L(-1) for gallic acid and butylated hydroxytoluene, respectively). Moreover, BIA methods show great promise for portable analysis because battery-powered instrumentation (electronic micropipette and potentiostats) is commercially available. PMID:26304399

  2. Ion and gas chromatography mass spectrometry investigations of organophosphates in lithium ion battery electrolytes by electrochemical aging at elevated cathode potentials

    NASA Astrophysics Data System (ADS)

    Weber, Waldemar; Wagner, Ralf; Streipert, Benjamin; Kraft, Vadim; Winter, Martin; Nowak, Sascha

    2016-02-01

    The electrochemical aging of commercial non-aqueous lithium hexafluorophosphate (LiPF6)/organic carbonate solvent based lithium ion battery electrolyte has been investigated in view of the formation of ionic and non-ionic alkylated phosphates. Subject was a solvent mixture of ethylene carbonate/ethyl methyl carbonate EC:EMC (1:1, by wt.) with 1 M LiPF6 (LP50 Selectilyte™, BASF). The analysis was carried out by ion chromatography coupled with electrospray ionization mass spectrometry (ESI-MS) for ionic compounds and (headspace) gas chromatography mass spectrometry ((HS)-GC-MS) for non-ionic compounds. The electrochemical aging was performed by galvanostatic charge/discharge cycling and potentiostatic experiments with LiNi0.5Mn1.5O4 (LMNO) as cathode material at increased cut-off potentials (>4.5 V vs. Li/Li+). A strong dependence of the formation of organophosphates on the applied electrode potential was observed and investigated by quantitative analysis of the formed phosphates. In addition, new possible "fingerprint" compounds for describing the electrolyte status were investigated and compared to existing compounds.

  3. In-vitro corrosion and wear of titanium alloys in the biological environment.

    PubMed

    Khan, M A; Williams, R L; Williams, D F

    1996-11-01

    Cyclic anodic polarization studies were undertaken for several titanium alloys of varying composition and phase structures. All materials were exposed to an accelerated corrosion test using a potentiostat and their electrochemical behaviour was analysed within a potential range of 0 to 5000 mV. The electrolyte used was a phosphate buffered saline (PBS) solution at pH = 5, 7.4 and 9. The polarization curves obtained represented both the passive and active regions of the materials and these curves were used to compare the resistance to pitting corrosion of each material. The sliding-wear of these materials was studied in both non-corrosive and corrosive environments. A simple pin-on-disc type wear apparatus was designed and built to simulate the co-joint action of corrosion and sliding-wear. Using this apparatus, it was also possible to evaluate the effect of wear-accelerated corrosion, which was also evaluated by wearing the surface of the specimens prior to corrosion. It was evident that the mixed phase alpha-beta alloys (Ti-6AI-4V and Ti-6AI-7Nb) possessed the best combination of both corrosion and wear resistance, although commercially pure titanium and the near-beta (Ti-13Nb-13Zr) and beta (Ti-15Mo) alloys displayed the best corrosion resistant properties. PMID:8922597

  4. Study of the magnetization behavior of ferromagnetic nanowire array: Existence of growth defects revealed by micromagnetic simulations

    NASA Astrophysics Data System (ADS)

    Nguyen Vien, G.; Rioual, S.; Gloaguen, F.; Rouvellou, B.; Lescop, B.

    2016-03-01

    High aspect ratio nanowires were electrodeposited in nanoporous anodic alumina template by a potentiostatic method. The angular dependence of the coercive field and remanence magnetization extracted from magnetometry measurements are compared with micromagnetic simulations. Inclusion of magnetostatic interactions between Ni nanowires in simulations is required to explain some of the properties of the magnetization reversal. However, it is not sufficient to reproduce fully the angular dependence of the coercive field. Due to the polycrystalline nature of nanowires and thus to the presence of grain boundaries, defects are included in simulations. A good agreement between theory and experiment is then clearly highlighted, in particular in the nanowire easy axis direction. The achieved results allow a description of several experimental data published in the literature and consequently to get a better understanding of reversal mechanisms that operate in such nanowire arrays. A complementary study of composite nanowire array is successfully performed to prove the adequacy of the simulations method to describe the magnetic properties of nanowire array.

  5. 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.

  6. Synergistic effects in the inhibition of copper corrosion

    SciTech Connect

    Gonzalez, S.; Laz, M.M.; Souto, R.M. . Dept. de Quimica Fisica); Salvarezza, R.C.; Arvia, A.J. )

    1993-06-01

    Benzotriazole (BTA), thiourea (TU), and potassium ethylxanthate (KEX), behave as copper (Cu) corrosion inhibitors under certain conditions. These chemicals have been investigated to establish whether they provided synergistic effects. The Cu corrosion inhibition was followed through changes in electrochemical characteristics. Cu specimens were tested at 25 C in two aggressive media, 0.1 M NaCl and 1 M NaClO[sub 4] using the linear potential sweep technique at 0.001 V/s and by scanning electron microscopy of Cu specimens subjected to potentiodynamic and potentiostatic routines. A comparative behavior of the different substances for Cu was presented in the 6.6 [le] pH [le] 11 range. For KEX-BTA mixtures, synergistic inhibition effects were found in 0.1 M NaCl (7 [le] pH [le] 11). The apparent synergistic inhibition was explained tentatively by an increase in the compactness of the polymer-like passivating layer of KEX-Cu, which formed in the presence of BTA and Cl[minus] ions.

  7. 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.

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

    SciTech Connect

    Xu Feng; Lu Yinong; Xia Lili; Xie Yan; Dai Min; Liu Yunfei

    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.

  9. Electrodeposition and characterization of HgSe thin films

    SciTech Connect

    Mahalingam, T. . E-mail: maha51@rediffmail.com; Kathalingam, A.; Sanjeeviraja, C.; Chandramohan, R.; Chu, J.P.; Kim, Yong Deak; Velumani, S.

    2007-08-15

    In this article we present the results on the electrochemical synthesis of mercury selenide (HgSe), an interesting II-VI material. HgSe thin films were deposited potentiostatically on conducting glass substrates from an aqueous bath containing HgCl{sub 2} and SeO{sub 2}. The prepared films were characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), scanning electron microscope (SEM) and optical absorption techniques. Stoichiometric polycrystalline HgSe films were obtained at a deposition potential around - 0.7 V vs SCE, at a temperature 60 deg. C and a pH value of 3.5. The as-grown films exhibited a direct optical band gap of 0.78 eV. This report deals with the growth mechanism and a study related to the influence of electrolyte bath composition, deposition potential, temperature and pH on the properties of HgSe thin films.

  10. 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.

  11. Fabrication of CIGS Films by Electrodeposition Method for Photovoltaic Cells

    NASA Astrophysics Data System (ADS)

    Lee, Hyunju; Yoon, Hyukjoo; Ji, Changwook; Lee, Dongyun; Lee, Jae-Ho; Yun, Jae-Ho; Kim, Yangdo

    2012-12-01

    Cu(InGa)Se2 (CIGS) thin films were fabricated by electrochemical deposition in a single bath containing Cu, In, Ga, and Se ions. The electrolyte was prepared by dissolving CuCl2, InCl3, GaCl3, H2SeO3, and LiCl in deionized water. The potentiostatic deposition process was achieved by applying a voltage ranging from -0.5 V to -0.8 V versus Ag/AgCl. The effects of different chemical bath concentrations on the film composition and morphology were investigated. Stoichiometric CIGS film composition could be achieved by controlling the chemical compositions of the bath and the voltage. Gelatin was added to the solution to improve the surface and microstructures of the CIGS film. The as-deposited films were annealed at 500C in Ar atmosphere for crystallization. The structural, morphological, and compositional properties of the CIGS thin films before and after annealing were examined by x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. This study showed that the composition of the CIGS films is dependent on the bath concentration, whereas the applied potential had relatively less effect on the CIGS film composition. In addition, the use of gelatin helped in the fabrication of crack-free CIGS thin films with greatly improved surface morphology.

  12. Facultative nitrate reduction by electrode-respiring Geobacter metallireducens biofilms as a competitive reaction to electrode reduction in a bioelectrochemical system.

    PubMed

    Kashima, Hiroyuki; Regan, John M

    2015-03-01

    Alternative metabolic options of exoelectrogenic biofilms in bioelectrochemical systems (BESs) are important not only to explain the fundamental ecology and performance of these systems but also to develop reliable integrated nutrient removal strategies in BESs, which potentially involve substrates or intermediates that support/induce those alternative metabolisms. This research focused on dissimilatory nitrate reduction as an alternative metabolism to dissimilatory anode reduction. Using the exoelectrogenic nitrate reducer Geobacter metallireducens, the critical conditions controlling those alternative metabolisms were investigated in two-chamber, potentiostatically controlled BESs at various anode potentials and biofilm thicknesses and challenged over a range of nitrate concentrations. Results showed that anode-reducing biofilms facultatively reduced nitrate at all tested anode potentials (-150 to +900 mV vs Standard Hydrogen Electrode) with a rapid metabolic shift. The critical nitrate concentration that triggered a significant decrease in BES performance was a function of anode biofilm thickness but not anode potential. This indicates that these alternative metabolisms were controlled by the availability of nitrate, which is a function of nitrate concentration in bulk solution and its diffusion into an anode-reducing biofilm. Coulombic recovery decreased as a function of nitrate dose due to electron-acceptor substrate competition, and nitrate-induced suspended biomass growth decreased the effluent quality. PMID:25622928

  13. Effect of Non-ionic Surfactants and Its Role in K Intercalation in Electrolytic Manganese Dioxide

    NASA Astrophysics Data System (ADS)

    Biswal, Avijit; Tripathy, B. C.; Subbaiah, T.; Meyrick, D.; Ionescu, Mihail; Minakshi, Manickam

    2014-09-01

    The effect of non-ionic surface active agents (surfactants) Triton X-100 (TX-100) and Tween-20 (Tw-20) and their role in potassium intercalation in electrolytic manganese dioxide (EMD) produced from manganese cake has been investigated. Electrosynthesis of MnO2 in the absence or presence of surfactant was carried out from acidic MnSO4 solution obtained from manganese cake under optimized conditions. A range of characterization techniques, including field emission scanning electron microscopy, transmission electron microscopy (TEM), Rutherford back scattering (RBS), and BET surface area/porosity studies, was carried out to determine the structural and chemical characteristics of the EMD. Galvanostatic (discharge) and potentiostatic (cyclic voltammetric) studies were employed to evaluate the suitability of EMD in combination with KOH electrolyte for alkaline battery applications. The presence of surfactant played an important role in modifying the physicochemical properties of the EMD by increasing the surface area of the material and hence, enhancing its electrochemical performance. The TEM and RBS analyses of the discharged EMD (?-MnO2) material showed clear evidence of potassium intercalation or at least the formation of a film on the MnO2 surface. The extent of intercalation was greater for EMD deposited in the presence of TX-100. Discharged MnO2 showed products of Mn2+ intermediates such as MnOOH and Mn3O4.

  14. A reusable capacitive immunosensor based on a CuS ultrathin film constructed by using a surface sol-gel technique.

    PubMed

    Wu, Zhan; Cao, Zhong; Zeng, Ju-Lan; Zhang, Ling; Chu, Xia; Shen, Guo-Li; Yu, Ru-Qin

    2010-01-01

    A capacitive sensing method based on a CuS ultrathin film modified electrode prepared by a surface sol-gel technique has been developed for the direct detection of human IgA. The resulting CuS film was investigated with cyclic voltammetry (CV), impedance spectroscopy, and quartz crystal microbalance (QCM). CV and impedance examinations showed that the CuS film formed on the gold electrode surface was insulated, and was applicable to form an insulating layer of a capacitive immunosensor. With QCM measurements, the thickness of the CuS film was evaluated to be 5.8 nm. The capacitance change was greatly increased by a CuS nanofilm-based immunosensor, which was initiated by the recognition of an immobilized antibody and the target antigen. The capacitance of the immunosensor corresponding to the concentration of human IgA was investigated by potentiostatic-step measurements. A linear calibration curve was obtained in the range of 1.81 - 90.5 ng ml(-1) with a detection limit of 1.81 ng ml(-1). There were no obvious interferences from the nonspecific adsorption of other proteins. With nice reproducibility and regeneration capacity, the CuS ultrathin film modified immunosensor could be used for the detection of human IgA in serum samples with a recovery of 96.1 - 104.4%, showing its promising applicability and reliability. PMID:20834134

  15. Stress-corrosion behavior of aluminum-lithium alloys in aqueous environments

    NASA Technical Reports Server (NTRS)

    Pizzo, P. P.; Galvin, R. P.; Nelson, H. G.

    1983-01-01

    The stress corrosion susceptibility of two powder metallurgy (P/M) alloys, Al-Li-Cu and Al-Li-Cu-Mg two mechanically attrited (M/A) alloys, Al-Li-Cu and Al-Li-Mg; and two wrought, ingot alloys, X-2020 and AA7475, are compared. Time-dependent fracture in an aqueous sodium chloride environment under alternate immersion condition was found to vary significantly between alloys. The stress corrosion behavior of the two powder metallurgy processed alloys was studied in detail under conditions of crack initiation, static crack growth, and fatigue crack growth. A variety of stress corrosion tests were performed including smooth surface, time-to-failure tests; potentiostatic tests on smooth surfaces exposed to constant applied strain rates; and fracture mechanics-type tests under static and cyclic loads. Both alloys show surface pitting and subsequent intergranular corrosion. Pitting is more severe in the magnesium-bearing alloy and is associated with stringer particles strung along the extrusion direction as a result of P/M processing.

  16. Passivation Dynamics in the Anisotropic Deposition and Stripping of Bulk Magnesium Electrodes During Electrochemical Cycling.

    PubMed

    Wetzel, David J; Malone, Marvin A; Haasch, Richard T; Meng, Yifei; Vieker, Henning; Hahn, Nathan T; Glzhuser, Armin; Zuo, Jian-Min; Zavadil, Kevin R; Gewirth, Andrew A; Nuzzo, Ralph G

    2015-08-26

    Although rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pit densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 ?m in height. The passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte. PMID:26258957

  17. 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

  18. New Secondary Batteries Utilizing Electronically Conductive Polypyrrole Cathode. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Yeu, Taewhan

    1991-01-01

    To gain a better understanding of the dynamic behavior in electronically conducting polypyrroles and to provide guidance toward designs of new secondary batteries based on these polymers, two mathematical models are developed; one for the potentiostatically controlled switching behavior of polypyrrole film, and one for the galvanostatically controlled charge/discharge behavior of lithium/polypyrrole secondary battery cell. The first model is used to predict the profiles of electrolyte concentrations, charge states, and electrochemical potentials within the thin polypyrrole film during switching process as functions of applied potential and position. Thus, the detailed mechanisms of charge transport and electrochemical reaction can be understood. Sensitivity analysis is performed for independent parameters, describing the physical and electrochemical characteristic of polypyrrole film, to verify their influences on the model performance. The values of independent parameters are estimated by comparing model predictions with experimental data obtained from identical conditions. The second model is used to predict the profiles of electrolyte concentrations, charge state, and electrochemical potentials within the battery system during charge and discharge processes as functions of time and position. Energy and power densities are estimated from model predictions and compared with existing battery systems. The independent design criteria on the charge and discharge performance of the cell are provided by studying the effects of design parameters.

  19. Wearable salivary uric acid mouthguard biosensor with integrated wireless electronics

    PubMed Central

    Kim, Jayoung; Imani, Somayeh; de Araujo, William R.; Warchall, Julian; Valdés-Ramírez, Gabriela; Paixão, Thiago R.L.C.; Mercier, Patrick P.; Wang, Joseph

    2016-01-01

    This article demonstrates an instrumented mouthguard capable of non-invasively monitoring salivary uric acid (SUA) levels. The enzyme (uricase)-modified screen printed electrode system has been integrated onto a mouthguard platform along with anatomically-miniaturized instrumentation electronics featuring a potentiostat, microcontroller, and a Bluetooth Low Energy (BLE) transceiver. Unlike RFID-based biosensing systems, which require large proximal power sources, the developed platform enables real-time wireless transmission of the sensed information to standard smartphones, laptops, and other consumer electronics for on-demand processing, diagnostics, or storage. The mouthguard biosensor system offers high sensitivity, selectivity, and stability towards uric acid detection in human saliva, covering the concentration ranges for both healthy people and hyperuricemia patients. The new wireless mouthguard biosensor system is able to monitor SUA level in real-time and continuous fashion, and can be readily expanded to an array of sensors for different analytes to enable an attractive wearable monitoring system for diverse health and fitness applications. PMID:26276541

  20. 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 μA cm-2 and maximum power density of 21.75 μW cm-2 at 0.455 V, fill factor of 0.32 and photoenergy conversion efficiency of 36.65%, respectively.

  1. New secondary batteries utilizing electronically conductive polypyrrole cathode

    NASA Astrophysics Data System (ADS)

    Yeu, Taewhan

    1991-05-01

    To gain a better understanding of the dynamic behavior in electronically conducting polypyrroles and to provide guidance toward designs of new secondary batteries based on these polymers, two mathematical models are developed; one for the potentiostatically controlled switching behavior of polypyrrole film, and one for the galvanostatically controlled charge/discharge behavior of lithium/polypyrrole secondary battery cell. The first model is used to predict the profiles of electrolyte concentrations, charge states, and electrochemical potentials within the thin polypyrrole film during switching process as functions of applied potential and position. Thus, the detailed mechanisms of charge transport and electrochemical reaction can be understood. Sensitivity analysis is performed for independent parameters, describing the physical and electrochemical characteristic of polypyrrole film, to verify their influences on the model performance. The values of independent parameters are estimated by comparing model predictions with experimental data obtained from identical conditions. The second model is used to predict the profiles of electrolyte concentrations, charge state, and electrochemical potentials within the battery system during charge and discharge processes as functions of time and position. Energy and power densities are estimated from model predictions and compared with existing battery systems. The independent design criteria on the charge and discharge performance of the cell are provided by studying the effects of design parameters.

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

    SciTech Connect

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

    2015-10-30

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

  3. Recreation of Marine Atmospheric Corrosion Condition on Weathering Steel in Laboratory

    NASA Astrophysics Data System (ADS)

    Guchhait, S. K.; Dewan, S.; Saha, J. K.; Mitra, P. K.

    2014-04-01

    Salt spray test, autoclave corrosion test, SO2 salt spray test, and Relative humidity test are generally used to assess atmospheric corrosion in laboratories at accelerated rates. However, no test can absolutely simulate the service condition. One can get only approximate corrosion rates using the aforesaid tests which serve as an indicative of corrosion behavior of the material in a service condition. The present work is aimed at creating specific environmental condition in laboratory to get the corrosion test done in short duration to compare with on field exposure test which would otherwise take years to complete. In this work recreation of atmospheric environment of Digha was tried and it was simulated in such a manner that the results of laboratory test could be compared with long time field exposure at Digha. Weathering steel (WS) was taken for experimentations. Potentiostatic electrochemical tests route was adopted to simulate atmospheric condition of Digha. Laboratory test results compared well with 18 month field exposure data in terms of corrosion rate, SEM and Ramon Spectroscopy matching.

  4. 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.

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

    PubMed

    Bosserdt, Maria; Erd?ssy, Jlia; Lautner, Gergely; Witt, Julia; Khler, Katja; Gajovic-Eichelmann, Nenad; Yarman, Aysu; Wittstock, Gunther; Scheller, Frieder W; Gyurcsnyi, Rbert 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. 500 m 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

  6. 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)

  7. Coatings on NiTi Alloy

    NASA Astrophysics Data System (ADS)

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

  8. Marine phototrophic consortia transfer electrons to electrodes in response to reductive stress.

    PubMed

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

    2016-03-01

    This work studies how extracellular electron transfer (EET) from cyanobacteria-dominated marine microbial biofilms to solid electrodes is affected by the availability of inorganic carbon (Ci). The EET was recorded chronoamperometrically in the form of electrical current by a potentiostat in two identical photo-electrochemical cells using carbon electrodes poised at a potential of +0.6 V versus standard hydrogen electrode under 12/12 h illumination/dark cycles. The Ci was supplied by the addition of NaHCO3 to the medium and/or by sparging CO2 gas. At high Ci conditions, EET from the microbial biofilm to the electrodes was observed only during the dark phase, indicating the occurrence of a form of night-time respiration that can use insoluble electrodes as the terminal electron acceptor. At low or no Ci conditions, however, EET also occurred during illumination suggesting that, in the absence of their natural electron acceptor, some cyanobacteria are able to utilise solid electrodes as an electron sink. This may be a natural survival mechanism for cyanobacteria to maintain redox balance in environments with limiting CO2 and/or high light intensity. PMID:26407568

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

    SciTech Connect

    Lee, June Key E-mail: hskim7@jbnu.ac.kr; Hyeon, Gil Yong; Tawfik, Wael Z.; Choi, Hee Seok; Ryu, Sang-Wan; Jeong, Tak; Jung, Eunjin; Kim, Hyunsoo E-mail: hskim7@jbnu.ac.kr

    2015-05-14

    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.

  10. Electrochemical study of resistance to localized corrosion of stainless steels for biomaterial applications

    SciTech Connect

    Pan, J.; Karlen, C.; Ulfvin, C.

    2000-03-01

    Sandvik Bioline High-N and 316 LVM are two austenitic stainless steels especially developed for biomaterial applications. Their resistance to localized corrosion was investigated by electrochemical methods including cyclic potentiodynamic polarization and potentiostatic polarization measurements in a phosphate-buffered saline solution and in a simulated crevice solution, i.e., designed for crevice corrosion testing. Sandvik SAF 2507 (a high-performance super duplex stainless steel) was included in the tests as a reference material High-N, higher alloyed than 316 LVM, demonstrated excellent resistance to pitting initiation and a strong tendency to repassivation. High-N proved to have an equivalent or even higher resistance to localized corrosion than SAF 2507. The latter is known for its impressive corrosion properties, particularly in chloride containing environments. While 316 LVM may run the risk of crevice corrosion in implant applications, the risk seems negligible for High-N. In view of the fact that also the mechanical properties are superior to those of 316 LVM, High-N is a very attractive implant material.

  11. An in vitro investigation of the anodic polarization and capacitance behavior of 316-L stainless steel.

    PubMed

    Sutow, E J; Pollack, S R; Korostoff, E

    1976-09-01

    Determinations were made of how the corrosion-resistant properties of the passive film on 316-L stainless steel are influenced by the material's mechanical and surface states, and the variable pH and PO2 conditions of the interstitial fluid. Cold-rolled and annealed specimens were surface-prepared, commercially and in the laboratory, respectively, as if for orthopedic implantation. Passive film behavior was studied by the anodic polarization and pulse-potentiostatic capacitance methods. The pH and PO2 of the Ringer's test solution were varied to include interstitial fluid values occurring postoperatively and onto recovery. The anodic polarization behavior of all specimens was found to be pH- and PO2-independent. Breakdown potentials of annealed specimens were 800-950 mV (SCE), in contrast to previously reported values of approximately 350 mV. This substantial increase is related to the influence of surface preparation and, in particular, to the optimization of electropolishing time which acts to produce a microscopically smooth surface, free of debris and disarrayed material. Capacitance behavior of annealed material for potentials greater than 400 mV was consistent with a model involving the entry of chloride and metal ions (mostly Fe) into the passive film. This entry is related to the onset of pitting. PMID:10307

  12. MIC on stainless steels in wastewater treatment plants

    SciTech Connect

    Iversen, A.

    1999-11-01

    Field tests of stainless steels were carried out at five wastewater treatment plants for one year. Three stainless steel grades i.e. AISI 304 (UNS S30400), AISI 316 (UNS S31600) and duplex 2205 (UNS S31803) were tested in the final settling tank in the plants. The time dependence of the open circuit potential (OCP) was measured for all coupons. Ennoblement of the OCP, similar to that reported from investigations in seawater, was found in one of the plants. Waters from three of the exposure sites, containing dispersed deposits from exposed coupons, were chemically analyzed. Pitting corrosion was observed after the field test on steel grade AISI 304 in three of the five plants, and on AISI 316 in one plant. No corrosion was found on 2205 in any of the plants. Laboratory measurements of the OCP were carried out for AISI 304, AISI 316 and 2205 in water collected from one of the plants. Cathodic polarization curves were determined as well in wastewater from the same plant. The cathodic reaction rate increased at the highest OCP. Simulation of the ennoblement was carried out by potentiostatic polarization in a 600 ppm chloride solution. The current response indicated corrosion on AISI 304 welded material and on AISI 304, AISI 316 in crevice assemblies after a long period of induction time.

  13. Passivation Behavior of Ultrafine-Grained Pure Copper Fabricated by Accumulative Roll Bonding (ARB) Process

    NASA Astrophysics Data System (ADS)

    Fattah-alhosseini, Arash; Imantalab, Omid

    2016-01-01

    In this study, passivation behavior of ultrafine-grained (UFG) pure copper fabricated by ARB process in 0.01 M borax solution has been investigated. Before any electrochemical measurements, evaluation of microstructure was obtained by transmission electron microscopy (TEM). TEM observations revealed that with increasing the number of ARB passes, the grain size of specimens decrease. Also, TEM images showed that UFGs with average size of below 100 nm appeared after 7 passes of ARB. To investigate the passivation behavior of the specimens, electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis was carried out. For this purpose, three potentials within the passive region were chosen for potentiostatic passive film growth. EIS results showed that both passive film and charge-transfer resistance increases with increasing the number of ARB passes. Moreover, Mott-Schottky analysis revealed that with increasing the number of ARB passes, the acceptor density of the passive films decreased. In conclusion, increasing the number of ARB passes offers better conditions for forming the passive films with higher protection behavior, due to the growth of a much thicker and less defective films.

  14. 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/.

  15. Virtual electrochemical nitric oxide analyzer using copper, zinc superoxide dismutase immobilized on carbon nanotubes in polypyrrole matrix.

    PubMed

    Madasamy, Thangamuthu; Pandiaraj, Manickam; Balamurugan, Murugesan; Karnewar, Santosh; Benjamin, Alby Robson; Venkatesh, Krishna Arun; Vairamani, Kanagavel; Kotamraju, Srigiridhar; Karunakaran, Chandran

    2012-10-15

    In this work, we have designed and developed a novel and cost effective virtual electrochemical analyzer for the measurement of NO in exhaled breath and from hydrogen peroxide stimulated endothelial cells using home-made potentiostat. Here, data acquisition system (NI MyDAQ) was used to acquire the data from the electrochemical oxidation of NO mediated by copper, zinc superoxide dismutase (Cu,ZnSOD). The electrochemical control programs (graphical user-interface software) were developed using LabVIEW 10.0 to sweep the potential, acquire the current response and process the acquired current signal. The Cu,ZnSOD (SOD1) immobilized on the carbon nanotubes in polypyrrole modified platinum electrode was used as the NO biosensor. The electrochemical behavior of the SOD1 modified electrode exhibited the characteristic quasi-reversible redox peak at the potential, +0.06 V vs. Ag/AgCl. The biological interferences were eliminated by nafion coated SOD1 electrode and then NO was measured selectively. Further, this biosensor showed a wide linear range of response over the concentration of NO from 0.1 μM to 1 mM with a detection limit of 0.1 μM and high sensitivity of 1.1 μA μM(-1). The electroanalytical results obtained here using the developed virtual electrochemical instrument were also compared with the standard cyclic voltammetry instrument and found in agreement with each other. PMID:23141325

  16. 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

  17. 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.

  18. 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

  19. Study on Electro-polymerization Nano-micro Wiring System Imitating Axonal Growth of Artificial Neurons towards Machine Learning

    NASA Astrophysics Data System (ADS)

    Dang, Nguyen Tuan; Akai-Kasada, Megumi; Asai, Tetsuya; Saito, Akira; Kuwahara, Yuji; Hokkaido University Collaboration

    2015-03-01

    Machine learning using the artificial neuron network research is supposed to be the best way to understand how the human brain trains itself to process information. In this study, we have successfully developed the programs using supervised machine learning algorithm. However, these supervised learning processes for the neuron network required the very strong computing configuration. Derivation from the necessity of increasing in computing ability and in reduction of power consumption, accelerator circuits become critical. To develop such accelerator circuits using supervised machine learning algorithm, conducting polymer micro/nanowires growing process was realized and applied as a synaptic weigh controller. In this work, high conductivity Polypyrrole (PPy) and Poly (3, 4 - ethylenedioxythiophene) PEDOT wires were potentiostatically grown crosslinking the designated electrodes, which were prefabricated by lithography, when appropriate square wave AC voltage and appropriate frequency were applied. Micro/nanowire growing process emulated the neurotransmitter release process of synapses inside a biological neuron and wire's resistance variation during the growing process was preferred to as the variation of synaptic weigh in machine learning algorithm. In a cooperation with Graduate School of Information Science and Technology, Hokkaido University.

  20. The Prediction of Long-Term Coating Performance from Short-Term Electrochemical Data. Part 2; Comparison of Electrochemical Data to Field Exposure Results for Coatings on Steel

    NASA Technical Reports Server (NTRS)

    Contu, F.; Taylor, S. R.; Calle, L. M.; Hintze, P. E.; Curran, J. P.; Li, W.

    2009-01-01

    The pace of coatings development is limited by the time required to assess their corrosion protection properties. This study takes a step f orward from Part I in that it correlates the corrosion performance of organic coatings assessed by a series of short-term electrochemical measurement with 18-month beachside exposure results of duplicate pan els. A series of 19 coating systems on A36 steel substrates were test ed in a completely blind study using the damage tolerance test (DTT). In the DTT, a through-film pinhole defect is created, and the electro chemical characteristics of the defect are then monitored over the ne xt 4 to 7 days while immersed in 0.SM NaCl. The open circuit potentia l, anodic potentiostatic polarization tests and electrochemical imped ance spectroscopy were used to study the corrosion behavior of the co ating systems. The beachside exposure tests were conducted at the Ken nedy Space Center according to ASTM D610-01. It was found that for 79 % of the coatings systems examined, the 18 month beachside exposure r esults could be predicted by two independent laboratory tests obtained within 7 days.

  1. Reduction of CO2 to low carbon alcohols on CuO FCs/Fe2O3 NTs catalyst with photoelectric dual catalytic interfaces

    NASA Astrophysics Data System (ADS)

    Li, Peiqiang; Wang, Huying; Xu, Jinfeng; Jing, Hua; Zhang, Jun; Han, Haixiang; Lu, Fusui

    2013-11-01

    In this paper, the CuO FCs/Fe2O3 NTs catalyst was obtained after Fe2O3 nanotubes (Fe2O3 NTs) were decorated with CuO flower clusters (CuO FCs) by the pulse electrochemical deposition method. The in situ vertically aligned Fe2O3 NTs were prepared on the ferrous substrate by a potentiostatic anodization method. The SEM result showed the volcano-like Fe2O3 NTs were arranged in order and the CuO FCs constituted of flaky CuO distributed on the Fe2O3 NTs surface uniformly. After CuO FCs were loaded on Fe2O3 NTs, the absorption of visible light was enhanced noticeably, and its band gap narrowed to 1.78 eV from 2.03 eV. The conduction band and valence band locating at -0.73 eV and 1.05 eV, respectively were further obtained. In the PEC reduction of CO2 process, methanol and ethanol were two major products identified by chromatography. Their contents reached 1.00 mmol L-1 cm-2 and 107.38 ?mol L-1 cm-2 after 6 h, respectively. This high-efficiency catalyst with photoelectric dual catalytic interfaces has a great guidance and reference significance for CO2 reduction to liquid carbon fuels.In this paper, the CuO FCs/Fe2O3 NTs catalyst was obtained after Fe2O3 nanotubes (Fe2O3 NTs) were decorated with CuO flower clusters (CuO FCs) by the pulse electrochemical deposition method. The in situ vertically aligned Fe2O3 NTs were prepared on the ferrous substrate by a potentiostatic anodization method. The SEM result showed the volcano-like Fe2O3 NTs were arranged in order and the CuO FCs constituted of flaky CuO distributed on the Fe2O3 NTs surface uniformly. After CuO FCs were loaded on Fe2O3 NTs, the absorption of visible light was enhanced noticeably, and its band gap narrowed to 1.78 eV from 2.03 eV. The conduction band and valence band locating at -0.73 eV and 1.05 eV, respectively were further obtained. In the PEC reduction of CO2 process, methanol and ethanol were two major products identified by chromatography. Their contents reached 1.00 mmol L-1 cm-2 and 107.38 ?mol L-1 cm-2 after 6 h, respectively. This high-efficiency catalyst with photoelectric dual catalytic interfaces has a great guidance and reference significance for CO2 reduction to liquid carbon fuels. Electronic supplementary information (ESI) available: Reduction of CO2 to low carbon alcohols on CuO FCs/Fe2O3 NTs catalyst with photoelectric dual catalytic interfaces. See DOI: 10.1039/c3nr03352j

  2. Lipopolysaccharide inhibits or accelerates biomedical titanium corrosion depending on environmental acidity

    PubMed Central

    Yu, Fei; Addison, Owen; Baker, Stephen J; Davenport, Alison J

    2015-01-01

    Titanium and its alloys are routinely used as biomedical implants and are usually considered to be corrosion resistant under physiological conditions. However, during inflammation, chemical modifications of the peri-implant environment including acidification occur. In addition certain biomolecules including lipopolysaccharide (LPS), a component of Gram-negative bacterial cell walls and driver of inflammation have been shown to interact strongly with Ti and modify its corrosion resistance. Gram-negative microbes are abundant in biofilms which form on dental implants. The objective was to investigate the influence of LPS on the corrosion properties of relevant biomedical Ti substrates as a function of environmental acidity. Inductively coupled plasma mass spectrometry was used to quantify Ti dissolution following immersion testing in physiological saline for three common biomedical grades of Ti (ASTM Grade 2, Grade 4 and Grade 5). Complementary electrochemical tests including anodic and cathodic polarisation experiments and potentiostatic measurements were also conducted. All three Ti alloys were observed to behave similarly and ion release was sensitive to pH of the immersion solution. However, LPS significantly inhibited Ti release under the most acidic conditions (pH 2), which may develop in localized corrosion sites, but promoted dissolution at pH 47, which would be more commonly encountered physiologically. The observed pattern of sensitivity to environmental acidity of the effect of LPS on Ti corrosion has not previously been reported. LPS is found extensively on the surfaces of skin and mucosal penetrating Ti implants and the findings are therefore relevant when considering the chemical stability of Ti implant surfaces in vivo. PMID:25634122

  3. Fabrication of multiwalled carbon nanotubes/polyaniline modified Au electrode for ascorbic acid determination.

    PubMed

    Chauhan, Nidhi; Narang, Jagriti; Pundir, C S

    2011-05-01

    An ascorbate oxidase (AsOx) (E.C.1.10.3.3) purified from Lagenaria siceraria fruit was immobilized covalently onto a carboxylated multiwalled carbon nanotubes and polyaniline (c-MWCNT/PANI) layer electrochemically deposited on the surface of an Au electrode. The diffusion coefficient of ascorbic acid was determined as 3.05 10(-4) cm(2) s(-1). The behavior of different electrolytes on electro-deposition was also studied. An ascorbate biosensor was fabricated using a AsOx/c-MWCNT/PANI/Au electrode as a working electrode, Ag/AgCl (3 M/saturated KCl) as standard and Pt wire as an auxiliary electrode connected through a potentiostat. Linear range, response time and detection limit were 2-206 ?M, 2 s and 0.9 ?M respectively. The biosensor showed optimum response at pH 5.8 and in a broader temperature range (30-45 C), when polarized at +0.6 V. The biosensor was employed for determination of ascorbic acid level in sera, fruit juices and vitamin C tablets. The sensor was evaluated with 91% recovery of added ascorbic acid in sera and 6.5% and 11.4% within and between batch coefficients of variation respectively for five serum samples. There was a good correlation (r = 0.98) between fruit juice ascorbic acid values by the standard 2,6-dichlorophenolindophenol (DCPIP) method and the present method. The enzyme electrode was used 200 times over a period of two months, when stored at 4 C. The biosensor has advantages over earlier enzyme sensors in that it has no leakage of enzyme, due to the covalent coupling of enzyme with the support, lower response time, wider working range, higher storage stability and no interference by serum substances. PMID:21416096

  4. 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.

  5. Functionalization and Characterization of Nanomaterial Gated Field-Effect Transistor-Based Biosensors and the Design of a Multi-Analyte Implantable Biosensing Platform

    NASA Astrophysics Data System (ADS)

    Croce, Robert A., Jr.

    Advances in semiconductor research and complementary-metal-oxide semiconductor fabrication allow for the design and implementation of miniaturized metabolic monitoring systems, as well as advanced biosensor design. The first part of this dissertation will focus on the design and fabrication of nanomaterial (single-walled carbon nanotube and quantum dot) gated field-effect transistors configured as protein sensors. These novel device structures have been functionalized with single-stranded DNA aptamers, and have shown sensor operation towards the protein Thrombin. Such advanced transistor-based sensing schemes present considerable advantages over traditional sensing methodologies in view of its miniaturization, low cost, and facile fabrication, paving the way for the ultimate realization of a multi-analyte lab-on-chip. The second part of this dissertation focuses on the design and fabrication of a needle-implantable glucose sensing platform which is based solely on photovoltaic powering and optical communication. By employing these powering and communication schemes, this design negates the need for bulky on-chip RF-based transmitters and batteries in an effort to attain extreme miniaturization required for needle-implantable/extractable applications. A complete single-sensor system coupled with a miniaturized amperometric glucose sensor has been demonstrated to exhibit reality of this technology. Furthermore, an optical selection scheme of multiple potentiostats for four different analytes (glucose, lactate, O 2 and CO2) as well as the optical transmission of sensor data has been designed for multi-analyte applications. The last part of this dissertation will focus on the development of a computational model for the amperometric glucose sensors employed in the aforementioned implantable platform. This model has been applied to single-layer single-enzyme systems, as well as multi-layer (single enzyme) systems utilizing glucose flux limiting layer-by-layer assembled outer membranes. The concentration of glucose and hydrogen peroxide within the sensor geometry, the transient response and the device response time has been simulated for both systems.

  6. Reference and counter electrode positions affect electrochemical characterization of bioanodes in different bioelectrochemical systems.

    PubMed

    Zhang, Fang; Liu, Jia; Ivanov, Ivan; Hatzell, Marta C; Yang, Wulin; Ahn, Yongtae; Logan, Bruce E

    2014-10-01

    The placement of the reference electrode (RE) in various bioelectrochemical systems is often varied to accommodate different reactor configurations. While the effect of the RE placement is well understood from a strictly electrochemistry perspective, there are impacts on exoelectrogenic biofilms in engineered systems that have not been adequately addressed. Varying distances between the working electrode (WE) and the RE, or the RE and the counter electrode (CE) in microbial fuel cells (MFCs) can alter bioanode characteristics. With well-spaced anode and cathode distances in an MFC, increasing the distance between the RE and anode (WE) altered bioanode cyclic voltammograms (CVs) due to the uncompensated ohmic drop. Electrochemical impedance spectra (EIS) also changed with RE distances, resulting in a calculated increase in anode resistance that varied between 17 and 31?? (-0.2?V). While WE potentials could be corrected with ohmic drop compensation during the CV tests, they could not be automatically corrected by the potentiostat in the EIS tests. The electrochemical characteristics of bioanodes were altered by their acclimation to different anode potentials that resulted from varying the distance between the RE and the CE (cathode). These differences were true changes in biofilm characteristics because the CVs were electrochemically independent of conditions resulting from changing CE to RE distances. Placing the RE outside of the current path enabled accurate bioanode characterization using CVs and EIS due to negligible ohmic resistances (0.4??). It is therefore concluded for bioelectrochemical systems that when possible, the RE should be placed outside the current path and near the WE, as this will result in more accurate representation of bioanode characteristics. PMID:24729040

  7. Influence of the physical, structural and chemical properties on the photoresponse property of magnetron sputtered TiO2 for the application of water splitting.

    PubMed

    Rahman, M; MacElroy, J M D; Dowling, D P

    2011-10-01

    The production of hydrogen from water (called "water splitting"), utilises sunlight as an energy source (solar-hydrogen) in a photoelectrochemical (PEC) solar cell, is a promising source of green energy. In this work, a PEC was used, for evaluating the photoactivity of a thin film TiO2 based photoanode by measuring photocurrent (which is comparable to hydrogen production rate by water splitting process in PEC). The main focus of this work is to study the effect of the TiO2 nanosurface and bulk properties on the photoresponse properties of the photoanode. The TiO2 coatings (360-400 nm) were deposited using a closed field reactive magnetron sputtering system. The structure and morphology of the TiO2 coatings were systematically altered by varying the deposition pressure between 5 x 10(-4) to 1 x 10(-2) mbar. The properties of the deposited nano-coatings were determined using Ellipsometry, SEM, AFM, profilometry, XPS, Raman and X-ray diffraction (XRD). Coating properties were correlated with the light absorption and photocurrent performance which were evaluated using UV-Vis spectroscopy and tri-electrode potentiostat measurements respectively. It was concluded from this study that the coating deposition pressure has a pronounced effect on the TiO2 photoanode properties leading to a significant enhancement in the photoactivity in PEC cell. Over a six fold increase in photocurrent at applied potential 0 V was observed for TiO2 photoanode prepared at 4 x 10(-3) mbar as compared to 5 x 10(-4) mbar. A correlation has been established between the deposition pressure, nano surface morphology and bulk properties, UV-Vis light absorbance and bandgap value, and the consequently higher (i) photocurrent density, (ii) negative flat band, and (iii) open circuit potential measured in Photoelectrochemical (PEC) cell. PMID:22400237

  8. Nanotubular oxide surface and layer formed on the Ti-35Ta-xZr alloys for biomaterials.

    PubMed

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

    2011-08-01

    Titanium and its alloys are widely used as a dental implant material in clinical dentistry and as an orthopedic implant materials due to their good mechanical properties, corrosion resistance, and biocompatibility. In this study, nanotubular oxide surface and layer formed on the Ti-35Ta-xZr alloys for biomaterials have been investigated by using electrochemical methods. Ti-35Ta-xZr alloys were prepared by arc melting and heat treated for 24 hr at 1000 degrees C in argon atmosphere, and then water quenching. Ti oxide nanotubes were formed on the Ti-35Ta-xZr alloys by anodizing in H3PO4 containing 0.8 wt% NaF solution at 25 degrees C. Anodization was carried out using a scanning potentiostat. Microstructures of the alloys and nanotube surface were examined by FE-SEM, EDX, and XRD. Crystallization treatment of nanotube surface was carried out for 3 hr at 450 degrees C. Microstructures of the Ti-35Ta-xZr alloys were changed from beta phase to alpha'' phase, and changed from an equiaxed to a needle-like structure with increasing Zr content. Nanotubular oxide surface and layers consisting of highly ordered nanotubes with a wide range of diameters (approximately 150-200 nm) and lengths (approximately 4-10 microm) can be formed on alloys in the Ti-35Ta-xZr alloys with Zr content. As the Zr content increased from 3% to 15%, length of step between the bamboo knob-like had increasing values of approximately 50 nm, 80 nm, and 140 nm, respectively. The nanotubes formed on the Ti-35Ta-xZr alloy surface were amorphous structure before heat treatment, but oxide surface had mainly an anatase structure by heat treatment. PMID:22103213

  9. Environment-assisted cracking of a nickel-based superalloy in hydrogen-producing solutions

    NASA Astrophysics Data System (ADS)

    Lillard, Jennifer Anne

    The environment assisted cracking (EAC) of nickel-based superalloy 718 was characterized in acidic chloride solutions under hydrogen-producing conditions using a rising-load fracture mechanics method. The stress intensity at the onset of crack growth (KTH) was used to measure EAC susceptibility as a function of applied electrode potential and solution chemistry. For all test conditions KTH was reduced from the air fracture initiation toughness (KICi). EAC susceptibility depended on both the electrode potential and solution pH. When the electrode potential was constant, susceptibility increased as the solution pH decreased. When the solution pH was constant, there was a minimum in KTH at intermediate electrode potentials. The appearance of the fracture surface gradually changed from voids and transgranular facets to voids with transgranular and intergranular facets as KTH decreased. The amount of plasticity associated with the voids and transgranular facets decreased as KTH decreased. Transgranular cracking dominated the onset of crack growth and occurred primarily by slip band fracture. A ductile fracture model, based on a critical fracture strain as measured by void growth, accurately predicted KTH and microstructure effects, suggesting that absorbed hydrogen lowered KTH from K ICi by promoting secondary microvoid nucleation which lead to intravoid strain localization and transgranular cracking. An empirical model of hydrogen production and absorption, based on a local crack chemistry that was less acidic than the bulk, was developed and used to predict the pH dependence of KTH at -1.0 VSCE . Gaseous hydrogen embrittlement data from the literature, hydrogen charging results, potentiostatic and potentiodynamic polarization data, and data from a buffered solution were combined to predict KTH of Alloy 718 as a function of solution pH at -1.0 VSCE in acidic chloride environments. The model accurately predicted KTH over the pH range studied.

  10. Impedance study of tea with added taste compounds using conducting polymer and metal electrodes.

    PubMed

    Dhiman, Mopsy; Kapur, Pawan; Ganguli, Abhijit; Singla, Madan Lal

    2012-09-01

    In this study the sensing capabilities of a combination of metals and conducting polymer sensing/working electrodes for tea liquor prepared by addition of different compounds using an impedance mode in frequency range 1 Hz-100 KHz at 0.1 V potential has been carried out. Classification of six different tea liquor samples made by dissolving various compounds (black tea liquor + raw milk from milkman), (black tea liquor + sweetened clove syrup), (black tea liquor + sweetened ginger syrup), (black tea liquor + sweetened cardamom syrup), (black tea liquor + sweet chocolate syrup) and (black tea liquor + vanilla flavoured milk without sugar) using six different working electrodes in a multi electrode setup has been studied using impedance and further its PCA has been carried out. Working electrodes of Platinum (Pt), Gold (Au), Silver (Ag), Glassy Carbon (GC) and conducting polymer electrodes of Polyaniline (PANI) and Polypyrrole (PPY) grown on an ITO surface potentiostatically have been deployed in a three electrode set up. The impedance response of these tea liquor samples using number of working electrodes shows a decrease in the real and imaginary impedance values presented on nyquist plots depending upon the nature of the electrode and amount of dissolved salts present in compounds added to tea liquor/solution. The different sensing surfaces allowed a high cross-selectivity in response to the same analyte. From Principal Component Analysis (PCA) plots it was possible to classify tea liquor in 3-4 classes using conducting polymer electrodes; however tea liquors were well separated from the PCA plots employing the impedance data of both conducting polymer and metal electrodes. PMID:23035436

  11. Influence of compressible aerogel electrodes on the properties of an electrochemical cell

    NASA Astrophysics Data System (ADS)

    Sponheimer, Christopher

    In the biomedical field the need for intra organ pressure measurement can only be facilitated by adapting existing pressure sensing technology to the specific tissues under test. The customization of these sensors has only driven up cost and the need to explore new technologies has become increasingly more important. For this dissertation, we explore the use of a new technology, particularly electrochemical pressure sensing to provide a low-cost pressure sensor to fill this need. Preliminary testing showed that electrically conductive polymers exhibited a change in voltage when pressurized if bubbles were first electrolyzed in the gel creating an aerogel, and that this effect was virtually undetectable without the bubbles present. Using electrochemical impedance spectroscopy (EIS) and model fitting, it was shown that this effect occurs at the electrode interface. Theoretical derivation supported by potentiostatic voltage measurements indicated that a change in the electrode surface area in contact with the fluid was responsible for the effect. Optical micrographs were taken as a bubble along the electrode was pressurized. Using image analysis, the relationship of the change in surface area of the bubble correlated to the relationship of the change in impedance of the electrochemical cell (ECC). The results further demonstrated that the electrochemical response to pressure of a gelatin aerogel electrode was linear for the pressure range of 0 to1034 mmHg. This finding lends itself well for use in medical devices. A new device was invented along with a manufacturing process for an electrochemical pressure transducer (EPT). The EPT was subject to in vitro testing using simulated gastric fluid to create a baseline efficacy of the device for use in the gastrointestinal tract. Multiple design specific techniques were developed to improve sensor performance during physiological conditions.

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

    PubMed

    Garca-Meza, J V; Fernndez, J J; Lara, R H; Gonzlez, 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 Sn? 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?/Sn? 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 Sn?/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

  13. Identifying the microbial communities and operational conditions for optimized wastewater treatment in microbial fuel cells.

    PubMed

    Ishii, Shun'ichi; Suzuki, Shino; Norden-Krichmar, Trina M; Wu, Angela; Yamanaka, Yuko; Nealson, Kenneth H; Bretschger, Orianna

    2013-12-01

    Microbial fuel cells (MFCs) are devices that exploit microorganisms as "biocatalysts" to recover energy from organic matter in the form of electricity. MFCs have been explored as possible energy neutral wastewater treatment systems; however, fundamental knowledge is still required about how MFC-associated microbial communities are affected by different operational conditions and can be optimized for accelerated wastewater treatment rates. In this study, we explored how electricity-generating microbial biofilms were established at MFC anodes and responded to three different operational conditions during wastewater treatment: 1) MFC operation using a 750 ? external resistor (0.3 mA current production); 2) set-potential (SP) operation with the anode electrode potentiostatically controlled to +100 mV vs SHE (4.0 mA current production); and 3) open circuit (OC) operation (zero current generation). For all reactors, primary clarifier effluent collected from a municipal wastewater plant was used as the sole carbon and microbial source. Batch operation demonstrated nearly complete organic matter consumption after a residence time of 8-12 days for the MFC condition, 4-6 days for the SP condition, and 15-20 days for the OC condition. These results indicate that higher current generation accelerates organic matter degradation during MFC wastewater treatment. The microbial community analysis was conducted for the three reactors using 16S rRNA gene sequencing. Although the inoculated wastewater was dominated by members of Epsilonproteobacteria, Gammaproteobacteria, and Bacteroidetes species, the electricity-generating biofilms in MFC and SP reactors were dominated by Deltaproteobacteria and Bacteroidetes. Within Deltaproteobacteria, phylotypes classified to family Desulfobulbaceae and Geobacteraceae increased significantly under the SP condition with higher current generation; however those phylotypes were not found in the OC reactor. These analyses suggest that species related to family Desulfobulbaceae and Geobacteraceae are correlated with the electricity generation in the biofilm and may be key players for optimizing wastewater treatment rates and energy recovery in applied MFC systems. PMID:24183402

  14. Automated Controlled-Potential Coulometer for the IAEA

    SciTech Connect

    Cordaro, J.V.; Holland, M.K.; Fields, T.

    1998-01-29

    An automated controlled-potential coulometer has been developed at the Savannah River Site (SRS) for the determination of plutonium for use at the International Atomic Energy Agency`s (IAEA) Safeguards Analytical Laboratory in Siebersdorf, Austria. The system is functionally the same as earlier systems built for use at the Savannah River Site`s Analytical Laboratory. All electronic circuits and printed circuits boards have been upgraded with state-of-the-art components. A higher amperage potentiostat with improved control stability has been developed. The system achieves electronic calibration accuracy and linearity of better than 0.01 percent, with a precision and accuracy better than 0.1 percent has been demonstrated. This coulometer features electrical calibration of the integration system, electrolysis current background corrections, and control-potential adjustment capabilities. These capabilities allow application of the system to plutonium measurements without chemical standards, achieving traceability to the international measurement system through electrical standards and Faraday`s constant. the chemist is provided with the capability to perform measurements without depending upon chemical standards, which is a significant advantage for applications such as characterization of primary and secondary standards. Additional benefits include reducing operating cost to procure, prepare and measure calibration standards and the corresponding decrease in radioactive waste generation. The design and documentation of the automated instrument are provided herein. Each individual module`s operation, wiring, layout, and alignment are described. Interconnection of the modules and system calibration are discussed. A complete set of prints and a list of associated parts are included.

  15. Bioresorbable silicon electronic sensors for the brain.

    PubMed

    Kang, Seung-Kyun; Murphy, Rory K J; Hwang, Suk-Won; Lee, Seung Min; Harburg, Daniel V; Krueger, Neil A; Shin, Jiho; Gamble, Paul; Cheng, Huanyu; Yu, Sooyoun; Liu, Zhuangjian; McCall, Jordan G; Stephen, Manu; Ying, Hanze; Kim, Jeonghyun; Park, Gayoung; Webb, R Chad; Lee, Chi Hwan; Chung, Sangjin; Wie, Dae Seung; Gujar, Amit D; Vemulapalli, Bharat; Kim, Albert H; Lee, Kyung-Mi; Cheng, Jianjun; Huang, Younggang; Lee, Sang Hoon; Braun, Paul V; Ray, Wilson Z; Rogers, John A

    2016-02-01

    Many procedures in modern clinical medicine rely on the use of electronic implants in treating conditions that range from acute coronary events to traumatic injury. However, standard permanent electronic hardware acts as a nidus for infection: bacteria form biofilms along percutaneous wires, or seed haematogenously, with the potential to migrate within the body and to provoke immune-mediated pathological tissue reactions. The associated surgical retrieval procedures, meanwhile, subject patients to the distress associated with re-operation and expose them to additional complications. Here, we report materials, device architectures, integration strategies, and in vivo demonstrations in rats of implantable, multifunctional silicon sensors for the brain, for which all of the constituent materials naturally resorb via hydrolysis and/or metabolic action, eliminating the need for extraction. Continuous monitoring of intracranial pressure and temperature illustrates functionality essential to the treatment of traumatic brain injury; the measurement performance of our resorbable devices compares favourably with that of non-resorbable clinical standards. In our experiments, insulated percutaneous wires connect to an externally mounted, miniaturized wireless potentiostat for data transmission. In a separate set-up, we connect a sensor to an implanted (but only partially resorbable) data-communication system, proving the principle that there is no need for any percutaneous wiring. The devices can be adapted to sense fluid flow, motion, pH or thermal characteristics, in formats that are compatible with the body's abdomen and extremities, as well as the deep brain, suggesting that the sensors might meet many needs in clinical medicine. PMID:26779949

  16. 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.

  17. Mechanical characterization of conducting polymer actuated neural probes under physiological settings

    NASA Astrophysics Data System (ADS)

    Daneshvar, Eugene D.; Smela, Elisabeth; Kipke, Daryl R.

    2010-04-01

    Most implantable chronic neural probes have fixed electrode sites on the shank of the probe. Neural probe shapes and insertion methods have been shown to have considerable effects on the resulting chronic reactive tissue response that encapsulates probes. We are developing probes with controllable articulated electrode projections, which are expected to provoke less reactive tissue response due to the projections being minimally sized, as well as to permit a degree of independence from the probe shank allowing the recording sites to "float" within the brain. The objective of this study was to predict and analyze the force-generating capability of conducting polymer bilayer actuators under physiological settings. Custom parylene beams 21 ?m thick, 1 cm long, and of varying widths (200 - 1000 ?m) were coated with Cr/Au. Electroplated weights were fabricated at the ends of the beams to apply known forces. Polypyrrole was potentiostatically polymerized to varying thicknesses onto the Au at 0.5 V in a solution of 0.1 M pyrrole and 0.1 M dodecylbenzenesulfonate (DBS). Using cyclic voltammetry, the bilayer beams were cycled in artificial cerebrospinal fluid (aCSF) at 37 C, as well as in aqueous NaDBS as a control. Digital images and video were analyzed to quantify the deflections. The images and the cyclic voltammograms showed that divalent cations in the aCSF interfered with polymer reduction. By integrating polypyrrole-based conducting polymer actuators, we present a type novel neural probe. We demonstrate that actuating PPy(DBS) under physiological settings is possible, and that the technique of microfabricating weights onto the actuators is a useful tool for studying actuation forces.

  18. Electrodeposition of layered manganese oxide nanocomposites intercalated with strong and weak polyelectrolytes.

    PubMed

    Nakayama, Masaharu; Tagashira, Hiroki

    2006-04-11

    Multilayered manganese oxide nanocomposites intercalated with strong (poly(diallyldimethylammonium) chloride, PDDA) and weak (poly(allylamine hydrochloride), PAH) polyelectrolytes can be produced on polycrystalline platinum electrode in a thin film form by a simple, one-step electrochemical route. The process involves a potentiostatic oxidation of aqueous Mn2+ ions at around +1.0 V (vs Ag/AgCl) in the presence of polyelectrolytes. Fully charged PDDA polycations are accommodated tightly in the interlayer space by electrostatic interaction with negative charges on the manganese oxide layers, leading to an interlayer distance of 0.97 nm. The layered film prepared with PAH has a larger polymer content (PAH/Mn molar ratio of 0.98) than that (PDDA/Mn molar ratio of 0.43) made with PDDA because of the smaller charging degree of PAH, exhibiting a larger interlayer distance (1.19 nm). The interlayer PAH contains neutral (-NH2) and positively charged (-NH3(+)) amine groups, and the -NH3(+) groups are associated with Cl- (to generate -NH3(+) Cl- ion pairs) as well as the negatively charged manganese oxide layers. Both polyelectrolytes once incorporated were not ion exchanged with small cations in solution. The layered structure of PDDA/MnO(x) was collapsed during the reduction process in a KCl electrolyte solution, accompanying an expansion of the interlayer as a result of incorporation of K+ ions for charge neutrality. On the contrary, the layered PAH/MnO(x) film showed a good electrochemical response due to the redox reaction of Mn3+/Mn4+ couple with no change in the structure. X-ray photoelectron spectroscopy revealed that, in this case, excess negative charges generated on the manganese oxide layers upon reduction can be balanced by the protons being released from the -NH3(+) Cl- sites in the interlayer PAH; the Cl- anions becoming unnecessary are inevitably excluded from the interlayer, and vice versa upon oxidation. PMID:16584268

  19. Corrosion behavior of aluminium composite coatings

    SciTech Connect

    Deuis, R.L.; Green, L.; Subramanian, C.; Yellup, J.M.

    1997-11-01

    The corrosion behavior of metal-matrix composite (MMC) coatings (3 mm to 5 mm [0.12 in. to 0.2 in.] thick) fabricated by the plasma-transferred arc (PTA) surfacing process was investigated by potentiostatic and immersion techniques. The test electrolyte was a 3.5 wt% sodium chloride (NaCl) solution. Composites were reinforced with angular particles of aluminum oxide (Al{sub 2}O{sub 3}), silicon carbide (SiC), or titanium carbide (TiC) of varying volume fractions (V{sub f} {approx} 2.5% to 40%) and of two sizes (70 {micro}m and 140 {micro}m). The matrix was predominantly aluminium with 2 wt% Ni, which was added to enhance the matrix`s wear resistance. The reinforcement type significantly influenced corrosion behavior of the MMC coatings. The immersion study showed the corrosion rate increased in the following order of reinforcement addition: Al{sub 2}O{sub 3} < SiC < TiC. Al{sub 2}O{sub 3} particles appeared to play no role in the corrosion process, whereas SiC and TiC particles participated actively. Reinforcement surface area appeared to be a significant parameter influencing the corrosion mechanism of the SiC- and TiC-reinforced composites. An increase in V{sub f} generally resulted in a higher corrosion rate for the SiC- and TiC-reinforced composites. Coating porosity, electrical conductivity of the reinforcement, and the presence of nickel aluminide (NiAl{sub 3}, formed during the surfacing process) all influenced corrosion behavior.

  20. Tuning the crystallinity of thermoelectric Bi(2)Te(3) nanowire arrays grown by pulsed electrodeposition.

    PubMed

    Lee, Jongmin; Farhangfar, Shadyar; Lee, Jaeyoung; Cagnon, Laurent; Scholz, Roland; Gsele, Ulrich; Nielsch, Kornelius

    2008-09-10

    Arrays of thermoelectric bismuth telluride (Bi(2)Te(3)) nanowires were grown into porous anodic alumina (PAA) membranes prepared by a two-step anodization. Bi(2)Te(3) nanowire arrays were deposited by galvanostatic, potentiostatic and pulsed electrodeposition from aqueous solution at room temperature. Depending on the electrodeposition method and as a consequence of different growth mechanisms, Bi(2)Te(3) nanowires exhibit different types of crystalline microstructure. Bi(2)Te(3) nanowire arrays, especially those grown by pulsed electrodeposition, have a highly oriented crystalline structure and were grown uniformly as compared to those grown by other electrodeposition techniques used. X-ray diffraction (XRD) analyses are indicative of the existence of a preferred growth orientation. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) confirm the formation of a preferred orientation and highly crystalline structure of the grown nanowires. The nanowires were further analyzed by scanning electron microscopy (SEM). Energy dispersive x-ray spectrometry (EDX) indicates that the composition of Bi-Te nanowires can be controlled by the electrodeposition method and the relaxation time in the pulsed electrodeposition approach. The samples fabricated by pulsed electrodeposition were electrically characterized within the temperature range 240K?T?470K. Below T?440K, the nanowire arrays exhibited a semiconducting behavior. Depending on the relaxation time in the pulsed electrodeposition, the semiconductor energy gaps were estimated to be 210-290meV. At higher temperatures, as a consequence of the enhanced carrier-phonon scattering, the measured electrical resistances increased slightly. The Seebeck coefficient was measured for every Bi(2)Te(3) sample at room temperature by a very simple method. All samples showed a positive value (12-33VK(-1)), indicating a p-type semiconductor behavior. PMID:21828882

  1. Li3V2(PO4)3 encapsulated flexible free-standing nanofabric cathodes for fast charging and long life-cycle lithium-ion batteries.

    PubMed

    Sun, Pingping; Zhao, Xueying; Chen, Renpeng; Chen, Tao; Ma, Lianbo; Fan, Qi; Lu, Hongling; Hu, Yi; Tie, Zuoxiu; Jin, Zhong; Xu, Qingyu; Liu, Jie

    2016-03-31

    Lithiated transition metal phosphates with large theoretical capacities have emerged as promising cathode materials for rechargeable lithium-ion batteries. However, the poor kinetic properties caused by their low intrinsic electronic and ionic conductivity greatly hinder their practical applications. In this work, we demonstrate a novel strategy to prepare monoclinic lithium vanadium phosphate nanoparticles implanted in carbon nanofibers as the cathodes of Li-ion cells with high capacity, flexibility, long cycle stability and significantly improved high-rate performance. The composite nanofibers were obtained by electrospinning using polyacrylonitrile and Li3V2(PO4)3 nanoparticles, followed by annealing and coating with a thin layer of carbon by plasma enhanced chemical vapor deposition. The Li3V2(PO4)3 nanocrystals with the monoclinic phase were uniformly distributed in the composite nanofibers. The electrochemical performances of the as-prepared binder-free fibrous cathodes were characterized by potentiostatic and galvanostatic tests. At the rate of 0.5 C in the range of 3.0-4.3 V, the composite displayed an initial discharge capacity of 128 mA h g(-1) (96.2% of the theoretical capacity). A discharge capacity of 120 mA h g(-1) was observed even at a high rate of 10 C, and a capacity retention of 98.9% was maintained after 500 cycles at 5 C, indicating excellent high-rate capability and capacity retention. Compared to the control samples without a carbon outer-layer, the composite nanofibers with carbon coating demonstrated much better electrochemical performances. It indicates that the carbon coating can further protect the structural integrity of nanofabric electrodes during the charge/discharge processes without hindering the Li-ion mobility and also can prevent undesired side reactions with an electrolyte, thus greatly improving the rate performance and cyclic stability of the cathode. PMID:26990080

  2. Dye-sensitized solar cells based on free-standing titanium dioxide nanotube arrays

    NASA Astrophysics Data System (ADS)

    Kim, Chaehyun

    Dye-sensitized solar cells (DSSCs) are photoelectrochemical cells using wide band gap nanoporous oxide semiconductors sensitized by dey molecules. DSSCs generally consist of photosensitive dye molecules and a titanium dioxide (TiO2) nanoparticle network. DSSCs convert light energy to electrical energy through photo-excitation of dye molecules anchored to the surface of TiO2 nanoparticles, electron injection and transport in the TiO 2 nanoparticle network. DSSCs attracted great attention due to their respectable efficiency with very low fabrication cost, good performance under diffuse light conditions, semi-transparency and multi color range possibilities, and the ability to be fabricated on flexible substrates. Its main efficiency limiting factor is the random hopping of electrons within the TiO2 nanoparticle network, which causes carrier trapping and recombination. The charge transport and collection can be enhanced by employing ordered nanostructures such as nanowire or nanotube arrays. However, DSSCs based on nanowire or nanotube arrays with power conversion efficiency higher than 11.18% achieved from the conventional DSSCs have yet to be demonstrated. This dissertation focuses on the development of DSSCs using highly crystalline free-standing TiO2 nanotube (FSTNT) arrays to enhance charge transport and collection, and hence, power conversion efficiency. TiO2 nanotube arrays were obtained by potentiostatic anodization of titanium foil in fluoride-based ethylene glycol electrolyte. TiO2 nanotube arrays were detached from the titanium foil by chemical etching and annealed at high temperatures to obtain highly crystalline anatase phase FSTNT arrays. DSSCs based on FSTNT arrays revealed high power conversion efficiency of 13.2% and short-circuit photocurrent density comparable to that of monocrystalline silicon solar cell.

  3. 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.

  4. A Miniaturized Transcutaneous System for Continuous Glucose Monitoring

    PubMed Central

    Croce, Robert A.; Vaddiraju, SanthiSagar; Kondo, Jun; Wang, Yan; Zuo, Liang; Zhu, Kai; Islam, Syed K.; Burgess, Diane; Papadimitrakopoulos, Fotios; Jain, Faquir C.

    2012-01-01

    Implantable sensors for continuous glucose monitoring hold great potential for optimal diabetes management. This is often undermined by a variety of issues associated with: (1) negative tissue response; (2) poor sensor performance; and (3) lack of device miniaturization needed to reduce implantation trauma. Herein, we report our initial results towards constructing an implantable device that simultaneously address all three aforementioned issues. In terms of device miniaturization, a highly miniaturized CMOS (complementary metal-oxide-semiconductor) potentiostat and signal processing unit was employed (with a combined area of 0.665 mm2). The signal processing unit converts the current generated by a transcutaneous, Clark-type amperometric sensor to output frequency in a linear fashion. The Clark-type amperometric sensor employs stratification of five functional layers to attain a well-balanced mass transfer which in turn yields a linear sensor response from 0 to 25 mM of glucose concentration, well beyond the physiologically observed (2 to 22 mM) range. In addition, it is coated with a thick polyvinyl alcohol (PVA) hydrogel with embedded poly(lactic-co-glycolic acid) (PLGA) microspheres intended to provide continuous, localized delivery of dexamethasone to suppress inflammation and fibrosis. In vivo evaluation in rat model has shown that the transcutaneous sensor system reproducibly tracks repeated glycemic events. Clarke’s error grid analysis on the as –obtained glycemic data has indicated that all of the measured glucose readings fell in the desired Zones A & B and none fell in the erroneous Zones C, D and E. Such reproducible operation of the transcutaneous sensor system, together with low power (140 μW) consumption and capability for current-to-frequency conversion renders this a versatile platform for continuous glucose monitoring and other biomedical sensing devices. PMID:22992979

  5. Real-Time Measurements of the Redox States of c-Type Cytochromes in Electroactive Biofilms: A Confocal Resonance Raman Microscopy Study

    PubMed Central

    Virdis, Bernardino; Millo, Diego; Donose, Bogdan C.; Batstone, Damien J.

    2014-01-01

    Confocal Resonance Raman Microscopy (CRRM) was used to probe variations of redox state of c-type cytochromes embedded in living mixed-culture electroactive biofilms exposed to different electrode polarizations, under potentiostatic and potentiodynamic conditions. In the absence of the metabolic substrate acetate, the redox state of cytochromes followed the application of reducing and oxidizing electrode potentials. Real-time monitoring of the redox state of cytochromes during cyclic voltammetry (CV) in a potential window where cytochromes reduction occurs, evidenced a measurable time delay between the oxidation of redox cofactors probed by CV at the electrode interface, and oxidation of distal cytochromes probed by CRRM. This delay was used to tentatively estimate the diffusivity of electrons through the biofilm. In the presence of acetate, the resonance Raman spectra of young (10 days, j?=?20849 A cm?2) and mature (57 days, j?=?26773 A cm?2) biofilms show that cytochromes remained oxidized homogeneously even at layers as far as 70 m from the electrode, implying the existence of slow metabolic kinetics that do not result in the formation of a redox gradient inside the biofilm during anode respiration. However, old biofilms (80 days, j?=?19037 A cm?2) with thickness above 100 m were characterized by reduced catalytic activity compared to the previous developing stages. The cytochromes in these biofilm were mainly in the reduced redox state, showing that only aged mixed-culture biofilms accumulate electrons during anode respiration. These results differ substantially from recent observations in pure Geobacter sulfurreducens electroactive biofilms, in which accumulation of reduced cytochromes is already observed in thinner biofilms, thus suggesting different bottlenecks in current production for mixed-culture and G. sulfurreducens biofilms. PMID:24587123

  6. 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.; Kim, H.P.

    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.

  7. 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

  8. Angstrom-resolved real-time dissection of electrochemically active noble metal interfaces.

    PubMed

    Shrestha, Buddha R; Baimpos, Theodoros; Raman, Sangeetha; Valtiner, Markus

    2014-06-24

    Electrochemical solid|liquid interfaces are critically important for technological applications and materials for energy storage, harvesting, and conversion. Yet, a real-time Angstrom-resolved visualization of dynamic processes at electrified solid|liquid interfaces has not been feasible. Here we report a unique real-time atomistic view into dynamic processes at electrochemically active metal interfaces using white light interferometry in an electrochemical surface forces apparatus. This method allows simultaneous deciphering of both sides of an electrochemical interface-the solution and the metal side-with microsecond resolution under dynamically evolving reactive conditions that are inherent to technological systems in operando. Quantitative in situ analysis of the potentiodynamic electrochemical oxidation/reduction of noble metal surfaces shows that Angstrom thick oxides formed on Au and Pt are high-ik materials; that is, they are metallic or highly defect-rich semiconductors, while Pd forms a low-ik oxide. In contrast, under potentiostatic growth conditions, all noble metal oxides exhibit a low-ik behavior. On the solution side, we reveal hitherto unknown strong electrochemical reaction forces, which are due to temporary charge imbalance in the electric double layer caused by depletion/generation of charged species. The real-time capability of our approach reveals significant time lags between electron transfer, oxide reduction/oxidation, and solution side reaction during a progressing electrode process. Comparing the kinetics of solution and metal side responses provides evidence that noble metal oxide reduction proceeds via a hydrogen adsorption and subsequent dissolution/redeposition mechanism. The presented approach may have important implications for designing emerging materials utilizing electrified interfaces and may apply to bioelectrochemical processes and signal transmission. PMID:24826945

  9. 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.

  10. Real-time in vivo uric acid biosensor system for biophysical monitoring of birds.

    PubMed

    Gumus, A; Lee, S; Karlsson, K; Gabrielson, R; Winkler, D W; Erickson, D

    2014-02-21

    Research on birds has long played an important role in ecological investigations, as birds are relatively easily observed, and their high metabolic rates and diurnal habits make them quite evidently responsive to changes in their environments. A mechanistic understanding of such avian responses requires a better understanding of how variation in physiological state conditions avian behavior and integrates the effects of recent environmental changes. There is a great need for sensor systems that will allow free-flying birds to interact with their environment and make unconstrained decisions about their spatial location at the same time that their physiological state is being monitored in real time. We have developed a miniature needle-based enzymatic sensor system suitable for continuous real-time amperometric monitoring of uric acid levels in unconstrained live birds. The sensor system was constructed with Pt/Ir wire and Ag/AgCl paste. Uricase enzyme was immobilized on a 0.7 mm sensing cavity of Nafion/cellulose inner membrane to minimize the influences of background interferents. The sensor response was linear from 0.05 to 0.6 mM uric acid, which spans the normal physiological range for most avian species. We developed a two-electrode potentiostat system that drives the biosensor, reads the output current, and wirelessly transmits the data. In addition to extensive characterization of the sensor and system, we also demonstrate autonomous operation of the system by collecting in vivo extracellular uric acid measurements on a domestic chicken. The results confirm our needle-type sensor system's potential for real-time monitoring of birds' physiological state. Successful application of the sensor in migratory birds could open up a new era of studying both the physiological preparation for migration and the consequences of sustained avian flight. PMID:24326318

  11. Alloy 33, a new material resisting marine corrosion

    SciTech Connect

    Agarwal, D.C.; Koehler, M.

    1997-12-01

    A new austenitic chromium-based material alloyed with nominally (wt.%) 33 Cr, 32 Fe, 31 Ni, 1.6 Mo, 0.6 Cu and 0.4 N, having a pitting resistance equivalent of 50, has been developed recently. The alloy exhibits excellent local corrosion resistance in chloride-bearing media. When tested in 10% FeCl{sub 3} {center_dot} 6 H{sub 2}O solution, a critical pitting temperature of 85 C was determined. Low segregation in the matching weld metal means that the critical pitting temperature of a 5 mm PAW weld seam is only 10 C lower. Potentiostatic corrosion tests in artificial seawater at 0.3 V (SCE) with additions of 0.5 mol NaCl reveal no pitting corrosion at 85 C, and crevice corrosion in artificial seawater at 0.3 V (SCE) has not been observed at temperatures below 55 C. In saturated CaCl{sub 2} solutions at 125 C under constant load conditions the resistance to stress corrosion cracking of Alloy 33 is superior even to that of Alloy 926. The combination of excellent corrosion resistance to a broad variety of media with high yield strength, 30% above that of the nitrogen-alloyed 6% Mo stainless steels, not only offers a cost-effective alternative to higher-cost nickel alloys, but also allows for light weight structures in the Offshore Industry. Alloy 33 (UNS R20033) has been approved by ASME and VdTUEV for pressure vessels in the temperature range of {minus}196 C to 450 C and can be manufactured to all semi-finished products used in the marine and chemical industries.

  12. Self-Assembled Monolayers of n-Alkanethiols Suppress Hydrogen Evolution and Increase the Efficiency of Rechargeable Iron Battery Electrodes

    SciTech Connect

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

    2013-01-09

    Iron-based rechargeable batteries, because of their low cost, eco-friendliness, and durability, are extremely attractive for large-scale energy storage. A principal challenge in the deployment of these batteries is their relatively low electrical efficiency. The low efficiency is due to parasitic hydrogen evolution that occurs on the iron electrode during charging and idle stand. In this study, we demonstrate for the first time that linear alkanethiols are very effective in suppressing hydrogen evolution on alkaline iron battery electrodes. The alkanethiols form self-assembled monolayers on the iron electrodes. The degree of suppression of hydrogen evolution by the alkanethiols was found to be greater than 90%, and the effectiveness of the alkanethiol increased with the chain length. Through steady-state potentiostatic polarization studies and impedance measurements on high-purity iron disk electrodes, we show that the self-assembly of alkanethiols suppressed the parasitic reaction by reducing the interfacial area available for the electrochemical reaction. We have modeled the effect of chain length of the alkanethiol on the surface coverage, charge-transfer resistance, and double-layer capacitance of the interface using a simple model that also yields a value for the interchain interaction energy. We have verified the improvement in charging efficiency resulting from the use of the alkanethiols in practical rechargeable iron battery electrodes. The results of battery tests indicate that alkanethiols yield among the highest faradaic efficiencies reported for the rechargeable iron electrodes, enabling the prospect of a large-scale energy storage solution based on low-cost iron-based rechargeable batteries.

  13. Passivation dynamics in the anisotropic deposition and stripping of bulk magnesium electrodes during electrochemical cycling

    DOE PAGESBeta

    Wetzel, David J.; Malone, Marvin A.; Haasch, Richard T.; Meng, Yifei; Vieker, Henning; Hahn, Nathan; Golzhauser, Armin; Zuo, Jian-Min; Zavadil, Kevin R.; Gewirth, Andrew A.; et al

    2015-08-10

    Rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, though little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pitmore » densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 μm in height. Finally, the passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte.« less

  14. 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

  15. Anodized ZnO nanostructures for photoelectrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Huang, Mao-Chia; Wang, TsingHai; Wu, Bin-Jui; Lin, Jing-Chie; Wu, Ching-Chen

    2016-01-01

    Zinc oxide (ZnO) nanostructures were fabricated on the polished zinc foil by anodic deposition in an alkaline solution containing 1.0 M NaOH and 0.25 M Zn(NO3)2. Potentiostatic anodization was conducted at two potentials (-0.7 V in the passive region and -1.0 V in the active region vs. SCE) which are higher than the open circuit potential (-1.03 V vs. SCE) and as-obtained ZnO nanostrcutures were investigated focusing on their structural, optical, electrical and photoelectrochemical (PEC) characteristics. All samples were confirmed ZnO by X-ray photoelectron spectroscopy and Raman spectra. Observations in the SEM images clearly showed that ZnO nanostructures prepared at -0.7 V vs. SCE were composed of nanowires at while those obtained at -1.0 V vs. SCE possessed nanosheets morphology. Result from transmission electron microscope and X-ray diffraction patterns suggested that the ZnO nanowires belonged to single crystalline with a preferred orientation of (0 0 2) whereas the ZnO nanosheets were polycrystalline. Following PEC experiments indicated that ZnO nanowires had higher photocurrent density of 0.32 mA/cm2 at 0.5 V vs. SCE under 100 mW/cm2 illumination. This value was about 1.9 times higher than that of ZnO nanosheets. Observed higher photocurrent was likely due to the single crystalline, preferred (0 0 2) orientation, higher carrier concentration and lower charge transfer resistance.

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

    SciTech Connect

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

    2014-08-25

    Au was electrodeposited potentiostatically at 0.3 V for 5 min on nanoporous Pt nanoparticle-coated F-doped SnO{sub 2} (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 S{sub n}{sup 2− }+ 2e{sup −} (CE) → S{sub n−1}{sup 2−} + S{sup 2−} at the CE/electrolyte interface, resulting in a significantly hindered recombination reaction, S{sub n}{sup 2− }+ 2e{sup −} (TiO{sub 2} in the photoanode) → S{sub n-1}{sup 2−} + S{sup 2−}, and significantly improved overall energy conversion efficiency.

  17. Electrochemical incineration of wastes

    NASA Astrophysics Data System (ADS)

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

    1990-08-01

    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. The effect of dopant concentration on properties of transparent conducting Al-doped ZnO thin films for efficient Cu2ZnSnS4 thin-film solar cells prepared by electrodeposition method

    NASA Astrophysics Data System (ADS)

    Mkawi, E. M.; Ibrahim, K.; Ali, M. K. M.; Farrukh, M. A.; Mohamed, A. S.

    2015-11-01

    Al-doped ZnO (AZO) thin films were potentiostatically deposited on indium tin oxide substrates. The influence of the doping level of the ZnO:Al films was investigated. The results of the X-ray diffraction and scanning electron microscopy analysis revealed that the structural properties of the AZO films were found polycrystalline with a hexagonal wurtzite-type structure along the (002) plane. The grain size of the AZO films was observed as approximately 3 μm in the film doping with 4 mol% ZnO:Al concentration. The thin films also exhibited an optical transmittance as high as 90 % in the wavelength range of 100-1,000 nm. The optical band gap increased from 3.33 to 3.45 eV. Based on the Hall studies, the lowest resistivity (4.78 × 10-3 Ω cm) was observed in the film doping with 3 mol% ZnO:Al concentration. The sheet resistant, carrier concentration and Hall mobility values were found as 10.78 Ω/ square, 9.03 × 1018 cm-3 and 22.01 cm2/v s, respectively, which showed improvements in the properties of AZO thin films. The ZnO:Al thin films were used as a buffer layer in thin-film solar cells with the structure of soda-lime glass/Mo/Cu2ZnSnS4/ZnS/ZnO/Al grid. The best solar cell efficiency was 2.3 % with V OC of 0.430 V, J SC of 8.24 mA cm-2 and FF of 68.1 %.

  19. 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.

  20. Part I. Carbon and mercury-carbon optically transparent electrodes. Part II. Investigation of redox properties of technetium by cyclic voltammetry and thin layer spectroelectrochemistry

    SciTech Connect

    Hurst, R.W.

    1980-01-01

    A carbon optically transparent electrode (C OTE) has been prepared by vapor-deposithing a thin carbon film (150 to 310 A thick) on glass and quartz. Optical transparency is good throughout the ultraviolet-visible region. Electrochemical and spectroelectrochemical measurements were made with ferricyanide and o-tolidine respectively. The C OTE serves as a good substrate for deposition of a thin mercury film to form a mercury film transparent electrode (Hg-C OTE). The Hg-C OTE exhibits electrochemical properties of conventional mercury film electrodes as evidenced by Pb/sup 2 +/ cyclic voltammograms. The Hg-C OTE exhibits electrochemical properties of conventional mercury film electrodes as evidenced by Pb/sup 2 -/ cyclic VOHammograms. The Hg-C OTE enabled the spectrochemical characterization of cysteine oxidation, which was shown to involve the oxidation of mercury to form mercurous cysteinate. An 8080 based microcomputer has been interfaced with a Harrick oscillating mirror rapid scanning uv-visible spectrophotometer. Two different approaches are compared for controlling the galvanometer. The first utilizes the digital hardware on the Harrick processing module to derive the mirror drive waveform, while the second creates the waveform under direct software control. A potentiostat is also interfaced and the system is demonstrated by the spectroelectrochemical determination of the redox potential of o-tolidine. Redox potentials are also determined for a series of technetium complexes by the spectropotentiostatic technique. These include hexahalogens, ditertiary arsine, and 1,2-bis(diphenylphosphino) ethane complexes of technetium. Transient hexavalent technetium is produced, detected, and characterized in aqueous alkaline media by pulse radiolysis and very fast scan cyclic voltammetry. The lifetime is of the order of milliseconds. This species is potentially useful in the preparation of technetium radiopharmaceuticals.

  1. Experimental Study on the pH of Pore water in Compacted Bentonite under Reducing Conditions with Electromigration

    SciTech Connect

    Nessa, S.A.; Idemitsu, K.; Yamazaki, S.; Ikeuchi, H.; Inagaki, Y.; Arima, T.

    2008-07-01

    Compacted bentonite and carbon steel are considered a good buffer and over-pack materials in the repositories of high-level radioactive waste disposal. Sodium bentonite, Kunipia-F contains approximately 95 wt% of montmorillonite. Bentonites prominent properties of high swelling, sealing ability and cation exchange capacity provide retardation against the transport of radionuclides from the waste into the surrounding rocks in the repository and its properties determine the behavior of bentonite. In this regards, the pH of pore water in compacted bentonite is measured with pH test paper wrapped with semi-permeable membrane of collodion sheet under reducing conditions. On 30 days, the pH test paper in the experimental apparatus indicated that the pH of pore water in compacted bentonite is around 8.0 at saturated state. The carbon steel coupon is connected as the working electrode to the potentiostat and is held at a constant supplied potential between +300 and -300 mV vs. Ag/AgCl electrode for up to 7 days. During applying electromigration the pH of pore water in bentonite decreased and it reached 6.0{approx}6.0 on 7 days. The concentration of iron and sodium showed nearly complementary distribution in the bentonite specimen after electromigration. It is expected that iron could migrate as ferrous ion through the interlayer of montmorillonite replacing exchangeable sodium ions in the interlayer. Semi-permeable membrane of collodion sheet does not affect the color change of pH test paper during the experiment. (authors)

  2. Tribocorrosive behaviour of commonly used temporomandibular implants in a synovial fluid-like environment: Ti-6Al-4V and CoCrMo

    NASA Astrophysics Data System (ADS)

    Royhman, D.; Yuan, J. C.; Shokuhfar, T.; Takoudis, C.; Sukotjo, C.; Mathew, M. T.

    2013-10-01

    The temporomandibular joint implant metal alloys, Ti6Al4V and CoCrMo, (n = 3/group) were tested under free-potential and potentiostatic conditions using a custom-made tribocorrosion apparatus. Sliding duration (1800 cycles), frequency (1.0 Hz) and load (16 N) mimicked the daily mastication process. Synovial-like fluid (bovine calf serum, pH = 7.6 at 37 C) was used to simulate the in vivo environment. Changes in friction coefficient were monitored throughout the sliding process. Changes in surface topography, total weight loss and roughness values were calculated using scanning electron microscopy and white-light interferometry. Finally, statistical analyses were performed using paired t-tests to determine significance between regions within each metal type and also independent sample t-tests to determine statistical significance between metal alloy types. Ti6Al4V demonstrated a greater decrease of potential than CoCrMo, a higher weight loss from wear (Kw = 257.8 versus 2.62 g p < 0.0001), a higher weight loss from corrosion (Kc = 17.44 versus 0.14 g p < 0.0001) and a higher weight loss from the combined effects of wear and corrosion (Kwc = 275.28 versus 2.76 g p < 0.0001). White-light interferometry measurements demonstrated a greater difference in surface roughness inside the wear region in Ti6Al4V than CoCrMo after the sliding (Ra = 323.80 versus 70.74 nm p < 0.0001). In conclusion, CoCrMo alloy shows superior anti-corrosive and biomechanical properties.

  3. Electrochemical behavior of polypyrrol/AuNP composites deposited by different electrochemical methods: sensing properties towards catechol.

    PubMed

    Garca-Hernndez, Celia; Garca-Cabezn, Cristina; Medina-Plaza, Cristina; Martn-Pedrosa, Fernando; Blanco, Yolanda; de Saja, Jos Antonio; Rodrguez-Mndez, Mara Luz

    2015-01-01

    Two different methods were used to obtain polypyrrole/AuNP (Ppy/AuNP) composites. One through the electrooxidation of the pyrrole monomer in the presence of colloidal gold nanoparticles, referred to as trapping method (T), and the second one by electrodeposition of both components from one solution containing the monomer and a gold salt, referred to as cogeneration method (C). In both cases, electrodeposition was carried out through galvanostatic and potentiostatic methods and using platinum (Pt) or stainless steel (SS) as substrates. Scanning electron microscopy (SEM) demonstrated that in all cases gold nanoparticles of similar size were uniformly dispersed in the Ppy matrix. The amount of AuNPs incorporated in the Ppy films was higher when electropolymerization was carried out by chronopotentiometry (CP). Besides, cogeneration method allowed for the incorporation of a higher number of AuNPs than trapping. Impedance experiments demonstrated that the insertion of AuNPs increased the conductivity. As an electrochemical sensor, the Ppy/AuNp deposited on platinum exhibited a strong electrocatalytic activity towards the oxidation of catechol. The effect was higher in films obtained by CP than in films obtained by chronoamperometry (CA). The influence of the method used to introduce the AuNPs (trapping or cogeneration) was not so important. The limits of detection (LOD) were in the range from 10(-5) to 10(-6) mol/L. LODs attained using films deposited on platinum were lower due to a synergy between AuNPs and platinum that facilitates the electron transfer, improving the electrocatalytic properties. Such synergistic effects are not so pronounced on stainless steel, but acceptable LOD are attained with lower price sensors. PMID:26665076

  4. Corrosion behavior of carbon steel in the monoethanolamine-H{sub 2}O-CO{sub 2}-O{sub 2}-SO{sub 2} system

    SciTech Connect

    Kladkaew, N.; Idem, R.; Tontiwachwuthikul, P.; Saiwan, C.

    2009-10-15

    The effects of operating parameters on the corrosion of carbon steel in the monoethanolamine (MEA)-H{sub 2}O-CO{sub 2}-O{sub 2}-SO{sub 2} system were investigated using two different corrosion measurement techniques. The corrosion studies were conducted using a 273A potentiostat using MEA, O{sub 2}, and SO{sub 2} concentrations and CO{sub 2} loading in the ranges of 1-7 kmol/m{sup 3}, 0-100%, 0-204 ppm, and 0-0.5 mol CO{sub 2}/mol MEA, respectively, at corrosion temperatures in the range of 303-353 K. The experimental results showed, for the first time, that a higher concentration of SO{sub 2} in a simulated flue gas stream induces a higher corrosion rate essentially because of the increase in the hydrogen ion concentration generated by reactions of SO{sub 2} and H{sub 2}O as well as SO{sub 2}, O{sub 2}, and H{sub 2}O. Also, an increase in oxygen concentration in the simulated flue gas stream causes a higher corrosion rate due to the increasing solubility of oxygen and, in turn, a higher amount of dissolved oxygen in the liquid phase. The results further show that an increase in the concentrations of MEA, O{sub 2}, and SO{sub 2} as well as CO{sub 2} loading will cause the generation of higher amounts of hydrogen or hydronium ions, as well as carbonic acid and bicarbonate ions, and this is what leads to a higher corrosion rate.

  5. The effect of grain boundary chemistry on Intergranular stress corrosion cracking of Ni-Cr-Fe alloys in 50 Pct NaOH at 140 C

    NASA Astrophysics Data System (ADS)

    Sung, J. K.; Koch, J.; Angeliu, T.; Was, G. S.

    1992-10-01

    The role of chromium, carbon, chromium carbides, and phosphorus on the intergranular stress corrosion cracking (IGSCC) resistance of Ni-Cr-Fe alloys in 50 pct NaOH at 140 C is studied using controlled-purity alloys. The effect of carbon is studied using heats in which the carbon level is varied between 0.002 and 0.063 wt pct while the Cr level is fixed at 16.8 wt pct. The effect of Cr is studied using alloys with Cr concentrations between 5 and 30 wt pct. The effect of grain boundary Cr and C together is studied by heat-treating the nominal alloy composition of Ni-16Cr-9Fe-0.035C, and the effect of P is studied using a high-purity, P-doped alloy and a carbon-containing, P-doped alloy. Constant extension rate tensile (CERT) results show that the crack depth increases with decreasing alloy Cr content and increasing alloy C content. Crack- ing severity also correlates inversely with thermal treatment time at 700 C, during which the grain boundary Cr content rises and the grain boundary C content falls. Phosphorus is found to have a slightly beneficial effect on IG cracking susceptibility. Potentiodynamic polarization and potentiostatic current decay experiments confirm that Cr depletion or grain boundary C enhances the dissolution at the grain boundary. Results support a film rupture-anodic dissolution model in which Cr depletion or grain boundary C (independently or additively) enhances dissolution of nickel from the grain boundary region and leads to increased IG cracking.

  6. 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 MgCl2 solution

    NASA Astrophysics Data System (ADS)

    Li, D.; Mao, X.

    1992-10-01

    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 model of slip-bare metal dissolution-repassivation, a theoretical equation of stress corrosion crack propagation rate as a function of crack-tip strain rate and potential for 321 stainless steel in boiling 42 pct MgCl2 solution has been proposed as da/dt = 3.6 104 M/zF? ?/Nnb? 4+6E/0.03- E [1-exp(-Nnb?(0.03-)/?)] The theoretical calculation shows that when the crack-tip strain rate changes from 10-4/s to 10-2/s, the crack propagation rate changes from 0.01 mm/h to 3 mm/h at natural corrosion potential (-0.35 V(SEC)). If the crack-tip strain rate is above 10-2/s, the crack propagation rate should correspond to the upper bound determined by the maximum metal dissolution rate. When the crack-tip strain rate is below 10-4 s-1, the crack propagation rate is below 0.01 mm/h. The sensitive potential Ec to cracking is -0.35 V(SEC); above the sensitive potential Ec, the crack propagation rate varies slowly with potential. However, below Ec, the crack propagation rate decreases rapidly with potential decreases. The crack propagation rate of 321 stainless steel in 42 pct MgCl2 solution has been measured using a slow strain rate test technique. The the- oretical calculation is consistent with the experimental results.

  7. Methane Emission in a Specific Riparian-Zone Sediment Decreased with Bioelectrochemical Manipulation and Corresponded to the Microbial Community Dynamics

    PubMed Central

    Friedman, Elliot S.; McPhillips, Lauren E.; Werner, Jeffrey J.; Poole, Angela C.; Ley, Ruth E.; Walter, M. Todd; Angenent, Largus T.

    2016-01-01

    Dissimilatory metal-reducing bacteria are widespread in terrestrial ecosystems, especially in anaerobic soils and sediments. Thermodynamically, dissimilatory metal reduction is more favorable than sulfate reduction and methanogenesis but less favorable than denitrification and aerobic respiration. It is critical to understand the complex relationships, including the absence or presence of terminal electron acceptors, that govern microbial competition and coexistence in anaerobic soils and sediments, because subsurface microbial processes can effect greenhouse gas emissions from soils, possibly resulting in impacts at the global scale. Here, we elucidated the effect of an inexhaustible, ferrous-iron and humic-substance mimicking terminal electron acceptor by deploying potentiostatically poised electrodes in the sediment of a very specific stream riparian zone in Upstate New York state. At two sites within the same stream riparian zone during the course of 6 weeks in the spring of 2013, we measured CH4 and N2/N2O emissions from soil chambers containing either poised or unpoised electrodes, and we harvested biofilms from the electrodes to quantify microbial community dynamics. At the upstream site, which had a lower vegetation cover and highest soil temperatures, the poised electrodes inhibited CH4 emissions by ∼45% (when normalized to remove temporal effects). CH4 emissions were not significantly impacted at the downstream site. N2/N2O emissions were generally low at both sites and were not impacted by poised electrodes. We did not find a direct link between bioelectrochemical treatment and microbial community membership; however, we did find a correspondence between environment/function and microbial community dynamics. PMID:26793170

  8. A Versatile Coating Strategy to Highly Improve the Electrochemical Properties of Layered Oxide LiMO2 (M = Ni0.5Mn0.5 and Ni1/3Mn1/3Co1/3).

    PubMed

    Zhao, Enyue; Chen, Minmin; Chen, Dongfeng; Xiao, Xiaoling; Hu, Zhongbo

    2015-12-16

    This work provides a convenient, effective and highly versatile coating strategy for the layered oxide LiMO2 (M = Ni0.5Mn0.5 and Ni1/3Mn1/3Co1/3). Here, layered oxide LiMO2 (M = Ni0.5Mn0.5 and Ni1/3Mn1/3Co1/3) has been successfully coated with ion conductor of Li2SiO3 by in situ hydrolysis of tetraethyl orthosilicate (TEOS) followed by the lithiation process. The discharge capacity, cycle stability, rate capability, and some other electrochemical performances of layered cathode materials LiMO2 can be highly enhanced through surface-modification by coating appropriate content of Li2SiO3. Particularly, the 3 mol % Li2SiO3 coated LiNi1/3Mn1/3Co1/3O2 exhibits approximately a discharge capacity of 111 mAh/g after 300 cycles at the current density of 800 mA/g (5 C). Potentiostatic intermittent titration technique (PITT) test was carried out to investigate the mechanism of the improvement in the electrochemical properties. The diffusion coefficient of Li(+)-ion (DLi) of Li2SiO3 coated layered oxide materials has been greatly increased. We believe our methodology provides a convenient, effective and highly versatile coating strategy, which can be expected to open the way to ameliorate the electrochemical properties of electrode materials for lithium ion batteries. PMID:26599838

  9. Synthesis of dendritic silver nanostructures supported by graphene nanosheets and its application for highly sensitive detection of diazepam

    PubMed Central

    Majidi, Mir Reza; Ghaderi, Seyran; Asadpour-Zeynali, Karim; Dastangoo, Hossein

    2015-01-01

    In this paper, preparation, characterization and application of a new sensor for fast and simple determination of trace amount of diazepam were described. This sensor is based on Ag nanodendrimers (AgNDs) supported by graphene nanosheets modified glassy carbon electrode (GNs/GCE). The AgNDs were directly electrodeposited on the surface of electrode via potentiostatic method without using any templates, surfactants, or stabilizers. The structure of the synthesized AgNDs/GNs was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) techniques. The nanodendrimers with tree-like and hierarchical structures have a fascinating structure for fabrication of effective electrocatalysts. The experimental results confirmed that AgNDs/GNs/GC electrode has good electrocatalytic activity toward the reduction of diazepam. A low detection limit of 8.56 × 10− 8 M and a wide linear detection range of 1.0 × 10− 7 to 1.0 × 10− 6 M and 1.0 × 10− 6 to 20 × 10− 6 M were achieved via differential pulse voltammetry (DPV). The proposed electrode displayed excellent repeatability and long-term stability and it was satisfactorily used for determination of diazepam in real samples (commercially tablet, injection and human blood plasma) with high recovery. PMID:26354262

  10. 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

  11. Electrochemical behavior of polypyrrol/AuNP composites deposited by different electrochemical methods: sensing properties towards catechol

    PubMed Central

    García-Hernández, Celia; Medina-Plaza, Cristina; Martín-Pedrosa, Fernando; Blanco, Yolanda; de Saja, José Antonio

    2015-01-01

    Summary Two different methods were used to obtain polypyrrole/AuNP (Ppy/AuNP) composites. One through the electrooxidation of the pyrrole monomer in the presence of colloidal gold nanoparticles, referred to as trapping method (T), and the second one by electrodeposition of both components from one solution containing the monomer and a gold salt, referred to as cogeneration method (C). In both cases, electrodeposition was carried out through galvanostatic and potentiostatic methods and using platinum (Pt) or stainless steel (SS) as substrates. Scanning electron microscopy (SEM) demonstrated that in all cases gold nanoparticles of similar size were uniformly dispersed in the Ppy matrix. The amount of AuNPs incorporated in the Ppy films was higher when electropolymerization was carried out by chronopotentiometry (CP). Besides, cogeneration method allowed for the incorporation of a higher number of AuNPs than trapping. Impedance experiments demonstrated that the insertion of AuNPs increased the conductivity. As an electrochemical sensor, the Ppy/AuNp deposited on platinum exhibited a strong electrocatalytic activity towards the oxidation of catechol. The effect was higher in films obtained by CP than in films obtained by chronoamperometry (CA). The influence of the method used to introduce the AuNPs (trapping or cogeneration) was not so important. The limits of detection (LOD) were in the range from 10−5 to 10−6 mol/L. LODs attained using films deposited on platinum were lower due to a synergy between AuNPs and platinum that facilitates the electron transfer, improving the electrocatalytic properties. Such synergistic effects are not so pronounced on stainless steel, but acceptable LOD are attained with lower price sensors. PMID:26665076

  12. An amperometric biosensor based on acetylcholinesterase immobilized onto iron oxide nanoparticles/multi-walled carbon nanotubes modified gold electrode for measurement of organophosphorus insecticides.

    PubMed

    Chauhan, Nidhi; Pundir, Chandra Shekhar

    2011-09-01

    An acetylcholinesterase (AChE) purified from maize seedlings was immobilized covalently onto iron oxide nanoparticles (Fe(3)O(4)NP) and carboxylated multi walled carbon nanotubes (c-MWCNT) modified Au electrode. An organophosphorus (OP) biosensor was fabricated using this AChE/Fe(3)O(4)/c-MWCNT/Au electrode as a working electrode, Ag/AgCl as standard and Pt wire as an auxiliary electrode connected through a potentiostat. The biosensor was based on inhibition of AChE by OP compounds/insecticides. The properties of nanoparticles modified electrodes were studied by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), cyclic voltammograms (CVs) and electrochemical impedance spectroscopy (EIS). The synergistic action of Fe(3)O(4)NP and c-MWCNT showed excellent electrocatalytic activity at low potential (+0.4V). The optimum working conditions for the sensor were pH 7.5, 35°C, 600 μM substrate concentration and 10 min for inhibition by pesticide. Under optimum conditions, the inhibition rates of OP pesticides were proportional to their concentrations in the range of 0.1-40 nM, 0.1-50 nM, 1-50 nM and 10-100 nM for malathion, chlorpyrifos, monocrotophos and endosulfan respectively. The detection limits were 0.1 nM for malathion and chlorpyrifos, 1 nM for monocrotophos and 10nM for endosulfan. The biosensor exhibited good sensitivity (0.475 mA μM(-1)), reusability (more than 50 times) and stability (2 months). The sensor was suitable for trace detection of OP pesticide residues in milk and water. PMID:21763810

  13. Nature and extent of electrogenic microbial communities recovered from Juan de Fuca hydrothermal sulfides

    NASA Astrophysics Data System (ADS)

    Girguis, P. R.; Nielsen, M. E.

    2011-12-01

    Microbes have evolved a variety of metabolic strategies to survive in anaerobic environments, including extracellular electron transfer (EET). Here we present laboratory and in situ experiments revealing that hydrothermal vent microbes employ and depend upon EET to access spatially remote oxidants via semi-conductive pyrite. To simulate the physical and electrochemical conditions in vent sulfides, we constructed a two-chamber flow-through bioelectrochemical reactor in which a pyrite electrode was enclosed in one chamber and subject to simulated hydrothermal conditions. Electroactive biofilms formed solely on pyrite in electrical continuity with oxygenated water. Phylogenetic and metagenomic analyses revealed a diversity of autotrophic and heterotrophic archaea and bacteria, markedly different in composition from the control (pyrite without electrical continuity). To further characterize this phenomenon, we deployed a bioelectrochemical experiment in situ at the hydrothermal vent sulfide "Roane" (2200 m water depth, at the Mothra hydrothermal field, Juan de Fuca ridge). A graphite anode was inserted into a borehole drilled into the base of a hydrothermal sulfide, and connected through a potentiostat to a carbon-fiber cathode on the outside of the vent structure. The in situ experiment produced sustained current and enriched for a distinct microbial community likely associated with EET. The data presented herein reveal the nature and extent of microbial communities that use conductive minerals such as pyrite, though fully reduced, to facilitate the reduction of spatially remote oxidants while maintaining chemical discontinuity. Thus EET, by enabling sustained access to terminal electron acceptors while maintaining the functioning of strictly anaerobic metabolisms, may alleviate the limitations commonly associated with anaerobic environs, namely the depletion of oxidants.

  14. Advanced carbon manufacturing for energy and biological applications

    NASA Astrophysics Data System (ADS)

    Turon Teixidor, Genis

    The science of miniaturization has experienced revolutionary advances during the last decades, witnessing the development of the Integrated Circuit and the emergence of MEMS and Nanotechnology. Particularly, MEMS technology has pioneered the use of non-traditional materials in microfabrication by including polymers, ceramics and composites to the well known list of metals and semiconductors. One of the latest additions to this set of materials is carbon, which represents a very important inclusion given its significance in electrochemical energy conversion systems and in applications where it is used as sensor probe material. For these applications, carbon is optimal in several counts: It has a wide electrochemical stability window, good electrical and thermal conductivity, high corrosion resistance and mechanical stability, and is available in high purity at a low cost. Furthermore carbon is biocompatible. This thesis presents several microfabricated devices that take advantage of these properties. The thesis has two clearly differentiated parts. In the first one, applications of micromachined carbon in the field of energy conversion and energy storage are presented. These applications include lithium ion micro batteries and the development of new carbon electrodes with fractal geometries. In the second part, the focus shifts to biological applications. First, the study of the interaction of living cells with micromachined carbon is presented, followed by the description of a sensor based on interdigitated nano-electrode arrays, and finally the development of the new instrumentation needed to address arrays of carbon electrodes, a multiplexed potentiostat. The underlying theme that connects all these seemingly different topics is the use of carbon microfabrication techniques in electrochemical systems.

  15. Hydrophobic ionic liquids based on the 1-butyl-3-methylimidazolium cation for lithium/seawater batteries

    NASA Astrophysics Data System (ADS)

    Zhang, Yancheng; Urquidi-Macdonald, Mirna

    Two hydrophobic ionic liquids (room temperature molten salts) based on 1-butyl-3-methylimidazolium cation (BMI +), BMI +PF 6- and BMI +Tf 2N -, were used in developing a highly efficient lithium anode system for lithium/seawater batteries. The lithium anode system was composed of lithium metal/ionic liquid/Celgard membrane. Both BMI +PF 6-and BMI +Tf 2N - maintained high apparent anodic efficiency (up to 100%) under potentiostatic polarization (at +0.5 V versus open-circuit potential (OCP)) in a 3% NaCl solution. Eventually, traces of water contaminated the ionic liquid and a bilayer film (LiH and LiOH) on the lithium surface was formed, decreasing the rate of lithium anodic reaction and hence the discharge current density. BMI +Tf 2N - prevented traces of water from reaching the lithium metal surface longer than BMI +PF 6- (60 h versus 7 h). However, BMI +PF 6- was better than BMI +Tf 2N - in keeping a constant current density (0.2 mA cm -2) before the traces of water contaminated the lithium surface due to the non-reactivity of BMI +PF 6- with the lithium metal that kept the bare lithium surface. During the discharge process, BMI +PF 6- and BMI +Tf 2N - acted as ion transport media of Li +, Cl -, OH - and H 2O, but did not react with them because of the excellent chemical stability, high conductivity, and high hydrophobicity of these two ionic liquids. Both BMI +PF 6- and BMI +Tf 2N - gels were tentative approaches used to delay the traces of water coming in contact with the lithium surface.

  16. Nuclear magnetic resonance spectroscopic study of the electrochemical oxidation product of methanol on platinum black

    SciTech Connect

    Day, J.B.; Oldfield, E.; Wieckowski, A.; Vuissoz, P.A.; Ansermet, J.P.

    1996-12-25

    The absorbate resulting from the potentiostatic, catalytic decomposition of methanol (0.1 M CH{sub 3}OH in 0.5 M H{sub 2}SO{sub 4}) on a platinum black electrode has been studied via {sup 13}C nuclear magnetic resonance spectroscopy, at open cell potential. Cyclic voltammetry results indicate that coverage is a function of electrodecomposition time and potential. The spin-spin relaxation time T{sub 2} is dependent on surface coverage and ranges from {approx}3 to {approx}1.8 ms at coverages ranging from 0.3 to 0.75 ML, due to the increased effectiveness of {sup 13}C-{sup 13}C dipolar interactions at high coverage. At 0.5 ML, the temperature dependence of the {sup 13}CO T{sub 2} (in a {sup 2}H{sub 2}O-exchanged electrolyte system) has been determined from 80 to 250 K. There is a well-defined peak in relaxation rate at {approx}170 K which can be modeled using a simple diffusional model having an activation energy of 7.9 {+-} 2.0 kcal/ mol. Spin-lattice relaxation results from 10 to 250 K reveal Korringa behavior, with a T{sub 1}T product (and Knight shift) that is independent of surface coverage, and has the same value for the electrochemical adsorbate as gas phase CO adsorbed on Pt. The similarity in T{sub 1}T, T{sub 2}, Knight shift, and activation energy for surface diffusion are in general accord with values previously measured in gas phase heterogeneous catalyst systems and strongly support the idea of primarily on top CO with C-down, on one major type of surface site. 18 refs., 8 figs., 2 tabs.

  17. Effects of the nitro-group on the mutagenicity and toxicity of some benzamines

    SciTech Connect

    Chung, K.T.; Murdock, C.A.; Zhou, Y.

    1995-11-01

    The Ames Salmonella/microsomal assay was employed to test the mutagenicity of some benzamines and their nitro-derivatives using strains TA98 and TA100, and their nitro-reductase deficient mutants, TA98NR and TA100 NR, in the presence and absence of Aroclor 1254 induced rat S9 mix. Aniline was not mutagenic to any tester strains; whereas p-nitroaniline was directly mutagenic to TA98, but not to TA98NR. 2-Nitro-p-phenylenediamine and 4-nitro-o-phenylenediamine were strongly mutagenic to all strains with or without S9 mix, whereas p-phenylenediamine was weakly mutagenic to TA98 and TA98NR after metabolic activation. 3-Nitro-o-phenylendiamine was a weak mutagen to all strains; and o-phenylenediamine was mutagenic to TA98, TA98NR, and TA100 with activation. The addition of the nitro-group to benzamines thus converts them into direct mutagens; the position of the nitro-group is crucial for mutagenic activity. Cytoxicity of these compounds were also examined using Chinese hamster ovary cells. The oxidation potentials of these compounds were measured using PARC EGG 273 Potentiostat/Gavonostat equipped with a PC computer. Physical properties such as the energy difference between the Lowest Unoccupied Molecular Orbital and the Highest Occupied Molecular Orbital, ionization potential and dipole moment were calculated. The mutagenicity or toxicity of these compounds was not related to any of these physical properties. The effect of the nitro-group on the mutagenicity of benzamines is unclear.

  18. Low temperature operation and influence parameters on the cold start ability of portable PEMFCs

    NASA Astrophysics Data System (ADS)

    Oszcipok, M.; Zedda, M.; Riemann, D.; Geckeler, D.

    The start up behaviour of PEM fuel cells below 0 °C is one of the most challenging tasks to be solved before commercialisation. The automotive industry started to develop solutions to reduce the start up time of fuel cell systems in the middle of the nineties. The strategies varied from catalytic combustion of hydrogen on the electrode catalyst to fuel starvation or external stack heating via cooling loops to increase the stack temperature. Beside the automotive sector the cold start ability is as well important for portable PEMFC applications for outdoor use. But here the cold start issue is even more complicated, as the fuel cell system should be operated as passive as possible. Below 0 °C freezing of water inside the PEMFC could form ice layers in the electrode and in the gas diffusion layer. Therefore the cell reaction is limited or even inhibited. Product water during the start up builds additional barriers and leads to a strong decay of the output power at isothermal operating conditions. In order to find out which operational and hardware parameters affect this decay, potentiostatic experiments on single cells were performed at isothermal conditions. These experiments comprise investigations of the influence of membrane thickness and different GDL types as well as the effect of gas flow rates and humidification levels of the membrane. As pre stage to physical based models, empirical based prediction models are used to gain a better understanding of the main influence parameters during cold start. The results are analysed using the statistical software Cornerstone 4.0. The experience of single cell investigations are compared to start up behaviour of portable fuel cell stacks which are operated in a climate chamber at different ambient temperatures below 0 °C. Additional flow sharing problems in the fuel cell stack could be seen during cold start up experiments.

  19. Microscopy of hierarchically organized TiO2 photoelectrode for dye solar cells

    NASA Astrophysics Data System (ADS)

    Eskandar, A.; Mohamed, N. M.

    2015-07-01

    Research on improving the performance of dye solar cells has various aspects of the device being investigated. This paper analyzes the deliberately hierarchized photoelectrode configuration for DSC applications to improve the performance of DSCs. Multiple layers of differently composed TiO2 particle types namely aggregates and nanoparticles were deposited to form a photoelectrode with thickness of about 12 m. The photoelectrodes were assembled into working DSCs with an active area of 1 cm2. Measurement for solar power conversion performance was measured under 1 sun at AM1.5 spectrum simulated sunlight. Electron microscopy for photoelectrode analysis was conducted using Field Emission Scattering Electron Microscopy with enhanced resolution. External Quantum Efficiency was measured using a purpose built instrument. Kinetics were investigated using the Electrochemical Impedance Spectroscopy (EIS) measurement with a potentiostat. The best performing DSC is of the hierarchically organized photoelectrode with a photoconversion efficiency of 4.58%, an increase of 14% in comparison to the reference samples with fully aggregates configuration. Short circuit current density, Jsc increases by about 2.223 mA cm-2 relative to the blanks. The electron microscopy confirmed expected thickness at around 10 m and layers forming the photoelectrode being hierarchically deposited with 20 nm TiO2 nanoparticles and 450 nm TiO2 aggregates mixture composition. EQE improved especially for visible region of 500-550 nm light wavelengths with 12 % increase in the response of in that region. Improvement to the diffusion coefficient as measured by the EIS contributed to the performance increase of the photoelectrode configuration under investigation.

  20. A Wireless FSCV Monitoring IC With Analog Background Subtraction and UWB Telemetry.

    PubMed

    Dorta-Quinones, Carlos I; Wang, Xiao Y; Dokania, Rajeev K; Gailey, Alycia; Lindau, Manfred; Apsel, Alyssa B

    2016-04-01

    A 30- μW wireless fast-scan cyclic voltammetry monitoring integrated circuit for ultra-wideband (UWB) transmission of dopamine release events in freely-behaving small animals is presented. On-chip integration of analog background subtraction and UWB telemetry yields a 32-fold increase in resolution versus standard Nyquist-rate conversion alone, near a four-fold decrease in the volume of uplink data versus single-bit, third-order, delta-sigma modulation, and more than a 20-fold reduction in transmit power versus narrowband transmission for low data rates. The 1.5- mm(2) chip, which was fabricated in 65-nm CMOS technology, consists of a low-noise potentiostat frontend, a two-step analog-to-digital converter (ADC), and an impulse-radio UWB transmitter (TX). The duty-cycled frontend and ADC/UWB-TX blocks draw 4 μA and 15 μA from 3-V and 1.2-V supplies, respectively. The chip achieves an input-referred current noise of 92 pArms and an input current range of ±430 nA at a conversion rate of 10 kHz. The packaged device operates from a 3-V coin-cell battery, measures 4.7 × 1.9 cm(2), weighs 4.3 g (including the battery and antenna), and can be carried by small animals. The system was validated by wirelessly recording flow-injection of dopamine with concentrations in the range of 250 nM to 1 μM with a carbon-fiber microelectrode (CFM) using 300-V/s FSCV. PMID:26057983