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1

Electrode Mounting for Potentiostatic Anodic Polarization Studies.  

National Technical Information Service (NTIS)

Samples of an arc melted, 10Cr- 10Ni- Fe alloy were mounted with the Stern-Makrides compression gasket assembly. Some electrodes were mounted directly, others were partially encased or coated with various resins prior to mounting. Potentiostatic anodic po...

N. D. Greene W. D. France B. E. Wilde

1965-01-01

2

Wide Dynamic Range CMOS Potentiostat for Amperometric Chemical Sensor  

PubMed Central

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.

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

2010-01-01

3

Wide dynamic range CMOS potentiostat for amperometric chemical sensor.  

PubMed

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

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

2010-03-04

4

Analysis of Mini-Potentiostat Design Options for Corrosion Research.  

National Technical Information Service (NTIS)

A design for a 'mini-potentiostat' for use in corrosion research has been developed and tested. This inexpensive device can replace currently available commercial instrumentation in conducting controlled experiments to determine the pitting resistance of ...

H. A. Newborn D. C. Bratlie

1978-01-01

5

Subminiature implantable potentiostat and modified commercial telemetry device for remote glucose monitoring  

Microsoft Academic Search

A subminiature implantable potentiostat and telemetry electronics package was developed to provide remote monitoring of implantable amperometric glucose sensors. Included are a new potentiostat for sensor biasing, a transimpedance amplifier to produce the sensor-current proportional voltage, and an optically coupled interface to the commercially available telemetry unit which transmits glucose concentration data to a corresponding receiver and computer. Potentiostat components

Richard D. Beach; F. v. Kuster; F. Moussy

1999-01-01

6

Limitations of potentiostatic control in stress corrosion crack growth measurements  

Microsoft Academic Search

The electrode potential distribution along a crack in a potentiostatically polarized specimen has been derived analytically\\u000a by including polarization behavior and solution conductance considerations. The analysis has been applied to the stress corrosion\\u000a cracks within low alloy steels in an 8M sodium hydroxide solution at 373 K and shows that the electrode potential at the tip\\u000a falls to the normal

P. Doig; P. E. J. Flewitt

1978-01-01

7

A micro-hole potentiostatic oxygen sensor for oceanic CTDs  

Microsoft Academic Search

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

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

1995-01-01

8

Localized corrosion of container materials under potentiodynamic and potentiostatic controls  

SciTech Connect

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.

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

1996-05-01

9

Potentiostatic electrodeposition of cuprous oxide thin films for photovoltaic applications  

Microsoft Academic Search

Potentiostatic deposition of Cu2O thin films on glass substrates coated with F-doped SnO2 from an alkaline electrolyte solution (pH 12.5) containing copper (II) sulfate and lactic acid was studied for fabrication of a Cu2O\\/Al-doped ZnO (AZO) heterojunction solar cell. The band gap of the electrodeposited Cu2O films was determined by photoelectrochemical measurements to be around 1.9eV irrespective of the applied

Wilman Septina; Shigeru Ikeda; M. Alam Khan; Takeshi Hirai; Takashi Harada; Michio Matsumura; Laurence M. Peter

2011-01-01

10

CMOS neurotransmitter microarray: 96-channel integrated potentiostat with on-die microsensors.  

PubMed

A 8 12 array of integrated potentiostats for on-CMOS neurotransmitter imaging is presented. Each potentiostat channel measures bidirectional redox currents proportional to the concentration of a neurochemical. By combining the current-to-frequency and the single-slope analog-to-digital converter (ADC) architectures a total linear dynamic range of 95 dB is achieved. A 3.8 mm 3.1 mm prototype fabricated in a 0.35 ?m standard CMOS technology was integrated with flat and 3D on-die gold microelectrodes and an on-chip microfluidic network. It is experimentally validated in in-situ recording of neurotransmitter dopamine. PMID:23853333

Nazari, Meisam Honarvar; Mazhab-Jafari, Hamed; Leng, Lian; Guenther, Axel; Genov, Roman

2013-06-01

11

Design of an integrated potentiostat circuit for CMOS bio sensor chips  

Microsoft Academic Search

A design strategy is presented for potentiostat circuits suitable for electronic bio sensors on CMOS. Guidelines are given to guarantee stable operation under the condition of widely varying and only roughly known electrochemical parameters. A concrete design example used in a fully electronic DNA sensor array CMOS chip is shown. Measurement results with a biological analyte applied to that chip

Alexander Frey; Martin Jenkner; Meinrad Schienle; Christian Paulus; Birgit Holzapfl; Petra Schindler-bauer; Franz Hofmann; D. Kuhlmeier; Jiirgen Krause; Jorg Albers; Walter Gumbrecht; Doris Schmitt-landsiedel; Roland Thewes

2003-01-01

12

Simple and Versatile Waveform Generator and Potentiostat Controller for Pulse Electrochemical Studies  

Microsoft Academic Search

A digitally controlled waveform generator and potentiostat controller, which is designed for rapid sweep electrochemical techniques such as cyclic staircase voltammetry at stationary electrodes, is described. It is a simple design, consisting of MOS memory coupled to a digital-to-analog converter for waveform generation and a crystal clock and a programmable interval timer for waveform and measurement timing. It can be

Palitha Jayaweera; Louis Ramaley

1988-01-01

13

A Molecular bio-wire based multi-array biosensor with integrated potentiostat  

Microsoft Academic Search

One of the important factors determining the sensitivity of any biosensing system is successful integration of bio- molecular transducers with peripheral signal processing circuitry. In this paper we present an architecture of a multi-array biosensor that integrates molecular bio-wires based immunosensor with a multi-channel potentiostat array. The biosensor operates by converting binding events between antigen and antibody into a measurable

Yang Liu; A. Gore; S. Chakrabartty; E. Alocilja

2007-01-01

14

A Portable Potentiostat with Molecularly Imprinted Polymeric Electrode for Dopamine Sensing  

Microsoft Academic Search

In this paper, we propose a low-cost and portable cyclic voltammetry potentiostat for the electrochemical dopamine biosensor designed with incorporation with artificial antibody (e.g. dopamine-imprinted polymers) as the sensing element. Its performance is evaluated by comparing the calibration curves of a dopamine biosensor with those obtained from very expensive commercial equipment. Experimental results show that good linearity and sensibility as

Chun-Yueh Huang; Mei-Hwa Lee; Zong-Huan Wu; Hong-Yi Tseng; Yu-Cheng Huang; Bin-Da Liu; Hung-Yin Lin

2009-01-01

15

Application of A Multichannel Potentiostat to Metal Ion Determinations in Flow Injection Analysis  

Microsoft Academic Search

A 4-channel potentiostat has been developed for use with an amperometric array and applied to the determination of a mixture of metal ions in flow injection analysis (FIA). The use of an array facilitates the acquisition of three dimensional electrochemical information in real-time (current vs. potential vs. time). The data acquired can be saved in ASCII format which facilitates post-run

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

1995-01-01

16

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

PubMed

By exploiting its ability to play sounds, a mobile phone with suitable software installed can serve the basic functions of a potentiostat in controlling an applied potential to oxidise ECL-active molecules, while the resultant photonic signal is monitored using the camera in video mode. In combination with paper microfluidic sensors this opens significant new possibilities for low-cost, instrument-free sensing. PMID:23870409

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

2013-06-19

17

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

PubMed

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 -30C, 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

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

2011-12-16

18

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

PubMed

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

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

2013-04-06

19

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

PubMed

The combination of microchip electrophoresis with amperometric detection leads to a number of analytical challenges that are associated with isolating the detector from the high voltages used for the separation. While methods such as end-channel alignment and the use of decouplers have been employed, they have limitations. A less common method has been to utilize an electrically isolated potentiostat. This approach allows placement of the working electrode directly in the separation channel without using a decoupler. This paper explores the use of microchip electrophoresis and electrochemical detection with an electrically isolated potentiostat for the separation and in-channel detection of several biologically important anions. The separation employed negative polarity voltages and tetradecyltrimethylammonium bromide (as a buffer modifier) for the separation of nitrite (NO??), glutathione, ascorbic acid, and tyrosine. A half-wave potential shift of approximately negative 500 mV was observed for NO?? and H?O? standards in the in-channel configuration compared to end-channel. Higher separation efficiencies were observed for both NO?? and H?O? with the in-channel detection configuration. The limits of detection were approximately two-fold lower and the sensitivity was approximately two-fold higher for in-channel detection of nitrite when compared to end-channel. The application of this microfluidic device for the separation and detection of biomarkers related to oxidative stress is described. PMID:21437918

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

2011-03-16

20

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

SciTech Connect

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.

Evans, K J; Rebak, R B

2007-04-27

21

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

PubMed

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

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

2011-09-13

22

The effect of contact configuration on the tribocorrosion of stainless steel in reciprocating sliding under potentiostatic control  

Microsoft Academic Search

The effect of electrode configuration on the tribocorrosion behavior of a ferritic stainless steel in sulfuric acid solution was investigated. A truncated cone was rubbed against a stationary plate using a reciprocating motion pin-on-plate tribometer under potentiostatic control. Three contact configurations were investigated consisting of a ceramic pin rubbing on a steel plate (I), a steel pin rubbing on a

M Stemp; S Mischler; D Landolt

2003-01-01

23

Reductive dechlorination of tetrachloroethene in a sand reactor using a potentiostat.  

PubMed

In this study, an electrochemical system was investigated to enhance abiotic dechlorination of chlorinated solvents in contaminated soil in situ. A potentiostatic electrolysis sand reactor was developed and tested to evaluate tetrachloroethene (PCE) dechlorination in saturated sand. When operated with recirculating nutrient-supplemented water the reactor sustained a low oxidation reduction potential (ORP) at the cathode (<-400 mV standard hydrogen electrode [SHE]), a pH less than 9.4, and electric current >5 mA at room temperature with the cathodic potential controlled at -950 mV SHE. Tetrachloroethene in the electrolysis reactor had a half-life of 6.8 d compared with the control bioreactor without electrolysis, which had a PCE half-life of 16.4 d. Ethane and ethene were the main dechlorination products in the test reactor, while trichloroethene (TCE) accumulated in the nutrient-amended control reactor without electrolysis. An electrolysis reactor operated with water not amended with nutrients showed a PCE half-life of 7.6 d, suggesting that most of dechlorination activity in the reactor was abiotic. Since complete dechlorination can be achieved under moderate pH and temperature, this type of electrolysis technology is attractive as a remedial method for subsurface chloroethene contamination. PMID:15998866

Shimomura, Tatsuo; Sanford, Robert A

2005-07-05

24

Electroreduction of hexavalent chromium using a polypyrrole-modified electrode under potentiostatic and potentiodynamic conditions.  

PubMed

Polypyrrole (ppy)-modified electrode was used for electroreduction of Cr(VI) and showed favorable advantage with extremely higher removal percentage and current efficiency over stainless steel (SS) electrode. In potentiostatic (PS) process and in stagnant solution, ppy electrode achieved a Cr(VI) removal efficiency of 16% and a current efficiency of 23% compared to 0 for SS electrode at a potential of -0.8V. In potentiodynamic (PD) process and in stagnant solutions, ppy electrode exhibited a Cr(VI) removal efficiency of 56% at a potential range from -0.8 to 0.8V whereas SS electrode presented none at the same conditions. Solution stirring promoted mass transportation and dramatically improved Cr(VI) removal efficiency, achieving 92% (ppy electrode) and 18% (SS electrode) in PS process and 100% (ppy electrode) and 36% (SS electrode) in PD process at 100rpm. ppy electrode exhibited an efficient Cr(VI) reduction at a wide potential range from -0.8 to 0.8V than the potential ranges of -0.8 to 0V and 0-0.8V. While ppy stability under PD condition of -0.8 to 0.8V was not as satisfactory as PS condition at -0.8V, but better than PS condition at 0.8V. These results demonstrate that ppy-modified electrode in PD process may be a promising alternative for Cr(VI) electroreduction. PMID:22609389

Tian, Ying; Huang, Liping; Zhou, Xiaohui; Wu, Chengbin

2012-04-28

25

Galvanostatic and potentiostatic deposition of bismuth telluride films from nitric acid solution: effect of chemical and electrochemical parameters  

Microsoft Academic Search

Composition modulated Bi2Te3 thin films have been deposited onto stainless-steel substrates using a potentiostatic or a galvanostatic process. The deposition potentials and current densities for different bath compositions and concentrations have been estimated from voltamperometric curves. Solutions with two Bi\\/Te ratios were studied. Only Bi3+ and HTeO2+ solutions in the volumetric proportion of 1:1 with equimolar solution concentrations of 0.01,

S. Michel; S. Diliberto; C. Boulanger; N. Stein; J. M. Lecuire

2005-01-01

26

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

27

Ionic motion in polypyrrole-cellulose composites: trap release mechanism during potentiostatic reduction.  

PubMed

This work investigates the movement of anions during potentiostatic controlled reduction of novel composite materials consisting of high surface area cellulose substrates, extracted from the Cladophora sp. algae, coated with thin ( approximately 50 nm) layers of the intrinsically conducting polymer (ICP) polypyrrole. The coating was achieved by chemical polymerization of pyrrole on the cellulose fibers with iron(III) chloride and phosphomolybdic acid, respectively. The composites are in the form of paper sheets and can be directly immersed into an electrolyte solution for ion absorption/desorption. The motion of glutamate and aspartate anions during cathodic polarization was investigated as a function of preceding anodic polarization at various potentials. The composite was found to exhibit memory effect as the response to a cathodic polarization of constant magnitude produced different responses depending on the magnitude of the preceding anodic potential. After the application of a cathodic potential to the composite, the reduction current curvesgenerated by anions leaving the compositewere found to initially increase in magnitude followed by a monotonic decay. A similar response has not been described and analyzed for electrochemical reduction of anion containing ICP materials earlier. A theoretical model was developed to aid the analysis of the experimental data. The model accounts for both freely mobile anions and anions that may be temporarily trapped in a contracting PPy network during cathodic polarization. By fitting the recorded reduction current curves to this model, detailed information about the ionic movement in the composite could be obtained, which may be used to further optimize the materials properties of conducting polymer systems aimed for specific electrochemical ion exchange processes. PMID:19338363

Strmme, Maria; Frenning, Gran; Razaq, Aamir; Gelin, Kristina; Nyholm, Leif; Mihranyan, Albert

2009-04-01

28

Polypyrrole-LiCF/sub 3/SO/sub 3/ composites formed by in situ pulsed potentiostatic electropolymerization  

SciTech Connect

Composites of polypyrrole and poly(ethylene oxide)*LiCF/sub 3/SO/sub 3/ were formed by in situ electropolymerization of polypyrrole at 0.8, 1.0 and 3.0 V vs. a platinum pseudo-reference electrode. The peak separation in solid state cyclic voltammograms under conditions placticized by acetonitrile for the in situ formed polypyrrole indicate that the resistance to ion transport within the composites is lower for composites formed by pulsed potentiostatic electropolymerization at 3.0 V, compared to composites grown by stepping the potential to 0.8, 1.0 or 3.0 V. 9 refs., 4 figs.

Harris, C.S.; Odegard, R.; Skotheim, T.A.

1988-01-01

29

Interfacing the AD5933 for bio-impedance measurements with front ends providing galvanostatic or potentiostatic excitation  

NASA Astrophysics Data System (ADS)

The AD5933 [1], a specialized single chip impedance analyzer, made by Analog Devices, is basically not intended for use with four electrode interface. Due to electrochemical phenomena at the electrodes connecting the material under test (MUT), especially in the low frequency region below 100 kHz, a two electrode interface generates considerable errors during the measurement. Thus, for most application in bio-impedance measurement only a four electrode interface can guarantee reliable results. Here we show how a four electrode interface with galvanostatic excitation but also for potentiostatic excitation can be realized by just a few external components.

Pliquett, Uwe; Barthel, Andreas

2012-12-01

30

Electrochemical potentiostatic activation for improvement of internal quantum efficiency of 385-nm ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

The electrochemical potentiostatic activation (EPA) method is proven to effectively improve the internal quantum efficiency (IQE) of 385-nm ultraviolet light-emitting diodes (UV-LEDs). UV-LEDs wafers were immersed into 1.0 M HCl solution, and an electric voltage of 3.0 V was applied to the p-type GaN layer in order to increase the hole concentration by breaking the MgH complex. Secondary ion mass spectroscopy analysis clearly indicates the successful removal of hydrogen atoms by the EPA process, which is a 35% reduction of the hydrogen concentration compared to the conventional N2 annealing. The light-output power was enhanced by 20% at an input current of 50 mA, which originated from an improvement of the IQE by 20%. The reverse leakage current was also lowered by about one order after the EPA process.

Choi, Hee Seok; Kim, Hak Jun; Lee, Jung Ju; Seo, Hyo Won; Tawfik, Wael Z.; Ha, Jun-Seok; Ryu, Sang-Wan; Jun, Seong Ran; Jeong, Tak; Lee, June Key

2013-10-01

31

Wetting-in studies of alkaline-fuel-cell cathodes using a potentiostatic-galvanostatic experimental design  

NASA Astrophysics Data System (ADS)

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

Lundblad, Anders; Bjornbom, Pehr

1994-06-01

32

Towards a miniature implantable in vivo telemetry monitoring system dynamically configurable as a potentiostat or galvanostat for two- and three-electrode biosensors  

Microsoft Academic Search

A miniature implantable and dynamically configurable potentiostat and galvanostat for two- and three-electrode biosensors with a telemetry electronics package was developed to provide remote monitoring of implantable amperometric and voltametric biosensors such as for glucose. Included are circuitry for sensor biasing, a transimpedance amplifier to produce the sensor proportional output signal, and a transceiver (transmitter and receiver) which can both

Richard D. Beach; Robert W. Conlan; Markham C. Godwin; Francis Moussy

2005-01-01

33

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

34

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

SciTech Connect

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

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

1993-10-01

35

Lithium transport through a solgel derived LiMn 2O 4 film electrode: analyses of potentiostatic current transient and linear sweep voltammogram by Monte Carlo simulation  

Microsoft Academic Search

Lithium transport through a solgel derived LiMn2O4 film electrode was theoretically investigated by analyses of the potentiostatic current transient and the linear sweep voltammogram in consideration of the interactions between lithium ions by using Monte Carlo simulation. The anodic current transients experimentally measured on the film electrode ran with the slope of logarithmic current with logarithmic time flatter than ?0.5

Sung-Woo Kim; Su-Il Pyun

2002-01-01

36

Attofarad resolution potentiostat for electrochemical measurements on nanoscale biomolecular interfacial systems  

NASA Astrophysics Data System (ADS)

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.

Carminati, Marco; Ferrari, Giorgio; Sampietro, Marco

2009-12-01

37

The comparison of galvanostatic and potentiostatic copper powder deposition on platinum and aluminium electrodes  

Microsoft Academic Search

Experiments have been carried out on copper powder electrodeposition by constant overpotential and constant current on aluminium, graphite, platinum and copper electrodes. It is shown that for one and the same quantity of electricity, electrode material, electrode surface area, electrolyte, temperature and time of deposition, different particle size distribution curves, current efficiency and specific energy consumption are obtained in galvanostatic

K. I. Popov; M. G. Pavlovi?; M. D. Maksimovi?; S. S. Krstaji?

1978-01-01

38

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

SciTech Connect

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.

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

2004-03-11

39

An investigation of the potentiostatic current oscillation during the anodic dissolution of iron in sulfuric acid  

NASA Astrophysics Data System (ADS)

A dynamical system analysis is presented to disclose the origin of current oscillation during the anodic dissolution of iron in sulfuric acid. The threshold of the electrochemical oscillatory dynamical regime is discussed in the parameter plane. The necessary electrode potential for oscillation increases as the stirring speed of the electrolyte solution increases and there is a critical stirring speed above which stable limit cycle oscillation cannot appear. The polarization curve is calculated and there is a limiting current plateau. There is an electrode potential interval within which the non-equilibrium steady state is unstable and the system oscillates before the potential reaches the limiting current plateau region. The limiting current increases with increasing stirring speed.

Hua, Dayin; Luo, Jiuli

1999-01-01

40

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

SciTech Connect

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.

K. Evans; L. Wong; R. Rebak

2004-06-01

41

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

PubMed

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

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

2005-06-01

42

An investigation on the optimum corrosion protection potential for minimization of cavitation damage using the potentiostatic method in seawater.  

PubMed

In this study, we replaced the expensive blade material with an aluminum-bronze alloy that has excellent corrosion resistance and cavitation characteristics and developed the corrosion protection method to improve durability using an electrochemical method. The objective of this study was to identify the electrochemical corrosion protection conditions to minimize cavitation damage due to generating hydrogen gas (2H?O + 2e? ? 2OH? + H?) by means of hydrogen overvoltage before the impact pressure of the cavity is transferred to the surface. In the constant potential experiment under the cavitation environment, the energy was reflected or cancelled out by collision of the cavities with the hydrogen gas generated by the hydrogen overvoltage. As a result, the optimal corrosion prevention potential in the dynamic state is assumed to be the range of -1.4 to -1.7 V, which is the range at which active polarization took place. PMID:23920179

Kim, Seong-Jong; Jang, Seok-Ki; Park, Jae-Cheul

2013-08-01

43

Potentiostatic formation of porous silicon in dilute HF: Evidence that nanocrystal size is not restricted by quantum confinement  

Microsoft Academic Search

The role that applied potential has in controlling the properties of porous silicon formed on highly conductive p-type silicon in diluted HF has been investigated by studying the photoluminescence characteristics along the currentvoltage curve and using high resolution transmission electron microscopy (HRTEM) evidence to support the conclusions drawn. A dramatic decrease in the average nanocrystal size was found to take

T. L. Sudesh L. Wijesinghe; E. J. Teo; D. J. Blackwood

2008-01-01

44

Achieving high electrode specific capacitance with materials of low mass specific capacitance: Potentiostatically grown thick micro-nanoporous PEDOT films  

Microsoft Academic Search

Electrode materials for supercapacitors are at present commonly evaluated and selected by their mass specific capacitance (CM, Fg?1). However, using only this parameter may be a misleading practice because the electrode capacitance also depends on kinetics, and may not increase simply by increasing material mass. It is therefore important to complement CM by the practically accessible electrode specific capacitance (CE,

Graeme A. Snook; Chuang Peng; Derek J. Fray; George Z. Chen

2007-01-01

45

Determination of the Crevice Repassivation Potential of Alloy 22 by a Potentiodynamic-Galvano static-Potentiostatic Method.  

National Technical Information Service (NTIS)

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 sever...

K. J. Evans L. L. Wong R. B. Rebak

2004-01-01

46

Bimetal and Multimetal Galvanic Corrosion Prediction Using Long- and Short-Term Polarization Curves.  

National Technical Information Service (NTIS)

Long-term potentiostatic polarization curves of up to 120-days duration were developed for the following materials: 90-10 copper-nickel; Monel 400; Inconel 625; Navy M-bronze; nickel-aluminum-bronze; and HY-80 steel. In addition, potentiostatic polarizati...

J. R. Scully

1984-01-01

47

The Electrochemical Behavior of Armco Iron in Sulfuric Acid.  

National Technical Information Service (NTIS)

The polarization behavior of Armco iron in sulfuric acid solutions was investigated. Anodic and cathodic polarization curves were obtained using aerated and deaerated solutions of 1N and pH1 sulfuric acid by galvanostatic and potentiostatic methods. (Auth...

H. A. Porte T. E. Nappier

1964-01-01

48

Raman and Infrared Spectroscopy of Aqueous Corrosion Films on Lead in O.1 M Sulfate Solutions.  

National Technical Information Service (NTIS)

This report contains the manuscript of a paper submitted for publication in the Journal of the Electrochemical Society. The Pb-H20-SO4 Pourbaix diagram was investigated by examining potentiostatically oxidized lead samples using Raman and infrared spectro...

R. Thibeau A. Goldfarb C. Brown R. Heidersbach

1979-01-01

49

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

National Technical Information Service (NTIS)

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 corro...

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

1995-01-01

50

Metalliding as an Electrochemical Process.  

National Technical Information Service (NTIS)

Controlled electrolysis in molten salts can improve the surface properties of metal alloys for wear and corrosion resistance. Surfaces of aluminum 1100 and carbon steel were modified by passage of cathodic current under potentiostatic and galvanostatic co...

D. O. Raleigh M. W. Kendig

1987-01-01

51

New Secondary Batteries Utilizing Electronically Conductive Polypyrrole Cathode.  

National Technical Information Service (NTIS)

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 potentiostatical...

T. Yeu

1991-01-01

52

Thin flexible intercalation anodes.  

National Technical Information Service (NTIS)

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 galva...

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

1994-01-01

53

Corrosion Protection of Solar-Collector Heat Exchangers with Electrochemically Deposited Films. Second Semi-Annual Report, 1 December 1978-31 May 1979.  

National Technical Information Service (NTIS)

A novel corrosion protection technique was demonstrated for the common solar collector metals Al, Cu, and Fe as mild steel. This involves the potentiostatic electrochemical deposition of thin, adherent polymer films on the interior of heat-exchanger tubes...

S. B. Brummer V. R. Koch G. H. Schnaper

1979-01-01

54

Electrochemical Aspects of Stress-Corrosion Cracking of Sensitized Stainless Steels.  

National Technical Information Service (NTIS)

The intergranular stress-corrosion cracking (SCC) of sensitized Type 304 stainless steel has been studied using sodium thiosulphate solutions at room temperature. Electrochemical aspects of the cracking have been examined using a potentiostatic scratching...

R. C. Newman K. Sieradzki H. S. Isaacs

1982-01-01

55

Anodic Polarization Behavior of Nickel 270 in H2-Saturated, in H2SO4.  

National Technical Information Service (NTIS)

Results are given of a round-robin potentiostatic anodic polarization test program for pure nickel in hydrogen-saturated, 1N H2SO4 at 25C using the experimental technique usually used in each participant's laboratory.

J. R. Myers

1967-01-01

56

Anodic Polarization Behavior of Cobalt-Chromium Alloys in Sulfuric Acid Solutions.  

National Technical Information Service (NTIS)

The anodic polarization behavior of annealed cobalt-chromium alloys in hydrogen saturated sulfuric acid solutions was investigated by using a potentiostatic technique. Polarization curves were obtained for eleven specimens, ranging from 100% cobalt to 100...

G. T. Seamon

1966-01-01

57

Research into the Chemical Behaviour of Surfaces of Single-Bi- and Tri-Crystals under Different Experimental Conditions.  

National Technical Information Service (NTIS)

Progress in the following research areas is summarized: (1) use of an electron emission microscope for the study of crystal surface reactivity; (2) potentiostatic studies of the electrochemical behavior of crystal surfaces.

P. Spinedi

1965-01-01

58

Electrocopolymerization of poly( o-toludine-co-metanilic acid) on mild steel surfaces and their physico-electrochemical characterizations  

Microsoft Academic Search

For the first time, poly(o-toludine-co-metanilic acid) (POM) layers have been deposited on mild steel (MS) substrate by galvanostatic (GS), potentiostatic (PS) and potentiodynamic (PD) methods. AC impedance of the electrodes has been analyzed. The shape and impedance parameters of galvanostatically prepared electrodes are similar to those of potentiostatically grown electrodes. The impedance spectra of potentiodynamically prepared electrode, however, are different.

P. Raja Kumar; D. Kalpana; N. G. Renganathan; S. Pitchumani

2007-01-01

59

Dynamics and Topography of QUASI2D Needle-Like Silver Electrochemical Deposits Under a Quasi-Steady Regime  

Microsoft Academic Search

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

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

2009-01-01

60

DYNAMICS AND TOPOGRAPHY OF QUASI2D NEEDLE-LIKE SILVER ELECTROCHEMICAL DEPOSITS UNDER A QUASISTEADY-STATE REGIME  

Microsoft Academic Search

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 (IIV) 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

M. A. PASQUALE; J. L. VICENTE; A. J. ARVIA

2009-01-01

61

Comparison of corrosion-resistance and hydrogen permeation properties of ZnNi, ZnNiCd and Cd coatings on low-carbon steel  

Microsoft Academic Search

ZnNiCd alloy was electroplated from an alkaline sulfate bath under potentiostatic conditions. The corrosion and hydrogen permeation characteristics of ZnNiCd alloy coatings electrodeposited from alkaline bath were studied and compared with those of Cd and ZnNi coatings obtained using commercial baths. ZnNiCd alloy was electroplated from an alkaline sulfate bath under potentiostatic conditions. The corrosion potential of this ZnNiCd coating

Hansung Kim; Branko N Popov; Ken S Chen

2003-01-01

62

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

DOEpatents

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.

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

63

Experimental procedure for crevice corrosion studies of Ni-Cr-Mo alloys in natural seawater  

NASA Astrophysics Data System (ADS)

An experimental procedure intended for crevice corrosion studies on Ni-Cr-Mo alloys is demonstrated. In this procedure a potentiostatic control of crevice corrosion specimens is applied to an immersible crevice cell design that uses a fluoroelastomer gasket crevice former. The procedure is demonstrated for a crevice susceptibility study on Alloy 625 in elevated temperature natural seawater, where crevice corrosion initiation and propagation are shown to be influenced by the electrochemical potential. Potentiostatic current monitoring establishes the crevice initiation time and rate of propagation, while post-mortem inspections confirm the extent of crevice damage.

Martin, F. J.; Lucas, K. E.; Hogan, E. A.

2002-03-01

64

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

Microsoft Academic Search

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 nonde- structive voltammetry techniques

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

2008-01-01

65

Special features in the electroreduction of oxidic molybdenum(VI) forms in tungstate melt  

Microsoft Academic Search

The electrochemical behavior of oxidic molybdenum in tungstate melt was studied under equilibrium and nonequilibrium conditions. Chronovoltammetry and transient polarization was used. The current-voltage curves were recorded with a pulse potentiostat and the experiments were performed in a quartz reactor with platinum and molybdenum electrodes and a platinum crucible served as the melt container and anode. The end product of

V. I. Shapoval; A. N. Baraboshkin; K. B. Kushkhov; V. V. Malyshev

1988-01-01

66

The inhibition of the corrosion of Armco iron in HCl solutions in the presence of surfactants of the type of N-alkyl quaternary ammonium salts  

Microsoft Academic Search

The polarization behaviour of Armco iron in aqueous solutions of HCl with and without inhibitors has been studied by the potentiostatic method. At lower overvoltage values, the dissolution process is controlled by activation, while at higher overvoltage values, the dissolution process is controlled by diffusion. The inhibition of this metal corrosion in the aqueous solutions of HCl has been studied

V Branzoi; F Branzoi; M Baibarac

2000-01-01

67

Silver electrocrystallization at polyaniline-coated electrodes  

Microsoft Academic Search

The initial stage of silver electrocrystallization is studied at polyaniline (PANI)-coated platinum electrodes by means of potentiostatic current transients and electron microscopic observations. Data for the nucleation frequency and the number of active sites for nucleation are obtained by interpreting of current transients according to the theory for nucleation and 3D growth under diffusion limitations. It is found that depending

S. Ivanov; V. Tsakova

2004-01-01

68

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

Microsoft Academic Search

The electrochemical performance and electrical contact resistance of chromized 316 stainless-steel (SS) are investigated under simulated operating condition in a proton-exchange membrane fuel cell (PEMFC). The corrosion resistance of the chromized stainless steel is assessed by potentiodynamic and potentiostatic tests and the interfacial contact resistance (ICR) is examined by measuring the electrical contact resistance as a function of the compaction

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

2009-01-01

69

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

Microsoft Academic Search

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

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

2010-01-01

70

Effect of Chemical Etching and Aging in Boiling Water on the Corrosion Resistance of Nitinol Wires with Black Oxide Resulting from Manufacturing Process  

Microsoft Academic Search

The effect of chemical etching in a HF\\/HNO3 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

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

71

Characterization of film failures by bismuth electrodepositionApplication to thin deformed fluorocarbon films for stent applications  

Microsoft Academic Search

A new approach for the detection and visualization of nano-scaled film defects, such as fissures and holes is described. The procedure is based on a selective electrochemical deposition of bismuth onto uncovered parts of stainless steel substrates due to film cracking after deformation. Cyclic voltammetry experiments enabled the identification of the bismuth redox signals, necessary for the subsequent potentiostatic electrodeposition.

Servaas Holvoet; Paula Horny; Stephane Turgeon; Pascale Chevallier; Jean-Jacques Pireaux; Diego Mantovani

2010-01-01

72

Rechargeable thin film batteries of polypyrrole and polyaniline  

Microsoft Academic Search

Thin films of polypyrrole (PPy) and polyaniline (PANi) were electrochemically deposited on stainless steel substrate under potentiostatic control. Secondary batteries were assembled using these polymers as active electrode materials and propylene carbonate (PC) solutions of tetraethyl ammonium perchlorate (TEAP) as the electrolyte. In repeated charge and discharge tests, the all PANi cells performed better than the PPy-PANi cells in voltage

J. Y. Lee; L. H. Ong; G. K. Chuah

1992-01-01

73

INHIBITION OF THE CORROSION OF NICKEL AND ITS ALLOYS BY NATURAL CLOVE OIL  

Microsoft Academic Search

The corrosion behavior of nickel, Inconel 600, and Inconel 690 in different concentrations of HCl solutions and its inhibition by clove oil was studied using potentiostatic polarization measurements. As the acid concentration increases, the rate of corrosion increases, indicating that HCl accelerates the dissolution of nickel and its alloys. The inhibition efficiency of the clove oil was found to increase

M. Abdallah; S. O. Al Karanee; A. A. Abdel Fattah

2009-01-01

74

Dependence of coating characteristics on deposition potential for electrodeposited ZnNi alloys  

Microsoft Academic Search

The electrodeposition of zincnickel alloys from ammonium chloride baths was studied on different substrates under potentiostatic and galvanostatic conditions, from low potentials\\/current densities where the codeposition was normal to the conditions where anomalous deposition took place. Anodic linear sweep voltammetry (ALSV) and ex situ techniques were used to characterize the coatings obtained in each condition. The results indicated that three

F Elkhatabi; M Benballa; M Sarret; C Mller

1999-01-01

75

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

Microsoft Academic Search

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

M Abdallah

2004-01-01

76

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

Microsoft Academic Search

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

M Abdallah

2002-01-01

77

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

Microsoft Academic Search

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

A. Y. El-Etre; M. Abdallah

2000-01-01

78

Effect of electrode potential on the tribocorrosion of tungsten  

Microsoft Academic Search

The tribocorrosion behavior of tungsten sliding against an alumina ball was evaluated in sulfuric acid under applied electrode potential. Surface chemistry of worn and unworn surfaces was evaluated using XPS and AES. Quasi-potentiostatic polarization curves and potential step measurements were performed under mass transport control to assess relevant corrosion factors. It was found that the tribocorrosion rate of tungsten varies

J. Stojadinovi?; D. Bouvet; M. Declercq; S. Mischler

2009-01-01

79

Tribocorrosion behaviour of ZrO xN y thin films for decorative applications  

Microsoft Academic Search

The aim of this work is the investigation of the tribocorrosion behaviour of single layered zirconium oxynitride, ZrOxNy, thin films in reciprocating sliding and immersed in an artificial sweat solution at room temperature. During the wear tests samples were kept under potentiostatic control and the corrosion current were monitored. Also, Electrochemical Impedance Spectroscopy (EIS) tests were performed before and after

S. C. Ferreira; E. Ariza; L. A. Rocha; J. R. Gomes; P. Carvalho; F. Vaz; A. C. Fernandes; L. Rebouta; L. Cunha; E. Alves; Ph. Goudeau; J. P. Rivire

2006-01-01

80

Investigation of the effect of impingement angle on tribocorrosion using single impacts  

Microsoft Academic Search

Using highly sensitive measurement and analog digital conversion devices it was possible to detect the repassivation transients after particle impingement on aluminium. Simultaneous use of a newly constructed slurry-jet and ?-electrodes as targets allowed the highly reproducible detection of single-particle impacts. This, in turn, allowed correlating the charge consumed during repassivation in a potentiostatic experiment with the damage caused. Variation

Andrew Jonathan Smith; Martin Stratmann; Achim Walter Hassel

2006-01-01

81

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 ...

82

Thin flexible intercalation anodes  

Microsoft Academic Search

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.

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

1994-01-01

83

Critical crevice temperature for high-alloyed stainless steels in chlorinated seawater applications  

SciTech Connect

Eleven high-alloyed stainless steels (SS) were tested for application in chlorinated seawater. Critical crevice temperatures (CCT) were determined using a potentiostatic test method. Results were evaluated in terms of the critical crevice index (CCI) value of the alloys and compared to results of duplicate specimens in other tests.

Steinsmo, U.; Rogne, T.; Drugli, J.M.; Gartland, P.O. [SINTEF Corrosion Center, Trondheim (Norway)

1997-01-01

84

Electrochemistry Resources  

NSDL National Science Digital Library

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

2011-03-30

85

A simple current transducer for ultramicroelectrode measurements at a wide range of time scales  

Microsoft Academic Search

In this paper a simple current transducer is described which can measure pA currents at low scan rates in conjunction with a commercial potentiostat such as the one supplied by Bioanalytical Systems (BAS), and which will allow fast-scan voltammetry measurements up to 4000 V\\/s in conjunction with a waveform generator and a data acquisition system.

Chen Chan Hsueh; Anna Brajter-Toth

1996-01-01

86

Electrochemical behavior of silver sulfide  

Microsoft Academic Search

The electrochemical behavior of silver sulfide in sulfuric acid as well as in nitric acid was studied using electrodes made from synthetic silver sulfide. The primary techniques used were potentiostatic, potentiodynamic, galvanostatic and corrosion cell experiments. The cathodic reaction of silver sulfide produces silver and hydrogen sulfide. This reaction mechanism is a sequential two step charge transfer involving a single

Drouven

1982-01-01

87

Size Distributions of Silver and Copper Crystals as a Function of Electrocrystallization Conditions on Glassy Carbon  

Microsoft Academic Search

Specific features and regularities of size distributions of crystalline nuclei are studied using the electrocrystallization of copper and silver on glassy carbon as an example. For a potentiostatic nucleation mode, with increasing overvoltage, a nonuniform size distribution approaches a uniform one. For a galvanostatic nucleation mode, the most probable nuclei size decreases with increasing current density and decreasing concentration of

T. A. Arzhanova; A. P. Golikov

2002-01-01

88

Optimization of hydrogen uptake in AgCNTs electrodes with chargedischarge cyclic currents  

Microsoft Academic Search

Electrochemical storage of hydrogen in AgCNTs (silver and carbon nanotubes) electrodes has been studied by potentiostat\\/galvanostat method. Foamed silver has been employed as a mattress for the CNTs and it caused better connections between CNTs and the silver. Therefore the enhancements in the hydrogen storage capacities have been justified. Acidic and thermal methods have been used for purifying the CNTs

B. Khoshnevisan; M. Behpour; D. Kaveh

2009-01-01

89

Stress corrosion cracking of stainless steels  

Microsoft Academic Search

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

R. F. Hehemann

1985-01-01

90

The Stability of Methanephosphonate to Electro-Oxidation.  

National Technical Information Service (NTIS)

The stability of the carbon-phosphorus bond in the dispotassium salt of methanephosphonic acid was confirmed by its resistance to electrooxidation in aqueous solution at a platinum electrode up to a potential of + 3.0 v(nhe). Potentiostatic and potentiody...

L. F. G. Williams M. W. Jarvis

1973-01-01

91

Inhibition of acid corrosion of aluminum using vanillin  

Microsoft Academic Search

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

A. Y. El-Etre

2001-01-01

92

Electrode Passivation Studies.  

National Technical Information Service (NTIS)

Studies of the passivation of Zn-Fe, Zn-Mn, Zn-Co, and Zn-Ni alloys were made potentiostatically. Alloys of 90 Zn 10 Fe corrode at a high rate even when passive. Alloys of 83Zn-17 Mn have low, active dissolution currents. The 89 Zn - 11 Co alloys have hig...

S. B. Brummer A. C. Makrides J. Bradspies

1966-01-01

93

Hydrogen production under sunlight with an electrochemical photocell  

Microsoft Academic Search

Three methods of forming oxide film on metal, electrochemical formation, thermal formation in an electric furnace, and thermal formation by simple heating, were studied as possible means of producing titanium dioxide electrodes. The maximum photocurrents produced by potentiostatically or galvanically formed oxide film electrodes under anodic polarization were 1\\/10 that of single crystal rutile electrodes, and similar results were obtained

Akira Fujishima; K. Kohayakawa; K. Honda

1975-01-01

94

On the Mechanism of Pitting of Aluminum.  

National Technical Information Service (NTIS)

The Engell-Stolica potentiostatic method has been used for the kinetic study of the mechanism of pitting initiation of Al 1199. A statistical treatment of induction time has been developed in order to get meaningful data. Pitting initiation has been found...

T. H. Nguyen R. T. Foley

1979-01-01

95

LEACHING MECHANISMS AND KINETICS OF COMPLEX LOW-GRADE SULFIDIC COPPER ORES  

Microsoft Academic Search

The aim of the study was to examine the leaching kinetics of powdered chalcopyrite based concentrate and the formation potential of elemental sulphur by means of electrochemistry and chemical analysis. Anodic polarisation curves, cyclovoltammetry and potentiostatic measurements were carried out in 1 N sulphuric acid at temperatures 25-80 C. The working electrode was a carbon paste electrode, which gives good

Jari AROMAA; Petteri PESONEN

2007-01-01

96

Application of the electrochemical quartz crystal microbalance technique to copper sonoelectrochemistry  

Microsoft Academic Search

The applicability of the electrochemical quartz crystal microbalance technique in an ultrasonic field created by an ultrasound probe is demonstrated for the electrodeposition of copper. Cyclic voltammetry and potentiostatic depositions in acidic sulfate-based copper electrolytes were performed at different ultrasonic intensities. The electrochemical quartz crystal microbalance was operated in ultrasonic fields with intensities up to 30Wcm?2. For cyclic voltammetry, potential

Oliver Schneider; Sladjana Mati?; Christos Argirusis

2008-01-01

97

Graphite electrodes as electron donors for anaerobic respiration  

Microsoft Academic Search

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

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

2004-01-01

98

The effect of ultrasound upon the oxidation of thiosulphate on stainless steel and platinum electrodes  

Microsoft Academic Search

Ultrasound was found to increase the oxidation peak current and hence the decomposition rate of thiosulphate 50-fold compared to silent conditions. The effects of the ultrasonic frequency (20 and 38 kHz) and power upon the electrochemical oxidation of thiosulphate in aqueous KCl (1 moldm?3) at stationary stainless steel and platinum electrodes were studied chronoamperometrically and potentiostatically (at various scan rates).

B. G Pollet; J. P Lorimer; J.-Y Hihn; S. S Phull; T. J Mason; D. J Walton

2002-01-01

99

The evaluation of pitting corrosion from the spectrum slope of noise fluctuation on iron and 304 stainless steel electrodes  

Microsoft Academic Search

A parameter which represents the spectrum slope of noise current fluctuation describes the occurrence of pitting corrosion. The method is applied to analyses of anodic current fluctuation on pure iron and stainless steel electrodes using a low noise potentiostat. The parameter was obtained using the maximum entropy method (MEM). At a stable state, the slope number n is zero, which

T. Fukuda; T. Mizuno

1996-01-01

100

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

Microsoft Academic Search

Cathodic current trends on stainless steel samples with different surface percentages covered by biofilm and potentiostatically polarized in natural seawater were studied under oxygen concentration changes, temperature increases, and additions of enzymic inhibitors to the solution. The results showed that on each surface fraction covered by biofilm the oxygen reduction kinetics resembled a reaction catalyzed by an immobilised enzyme with

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

2011-01-01

101

Cybernetic Control of an Electrochemical Repertoire.  

ERIC Educational Resources Information Center

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

He, Peixin; And Others

1982-01-01

102

TiO2 nanotube arrays: intrinsic peroxidase mimetics.  

PubMed

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

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

2013-10-15

103

Affordable Cyclic Voltammetry  

ERIC Educational Resources Information Center

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

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

2009-01-01

104

Anodic Polarization Behavior of Titanium and Titanium Alloys in Sulfuric Acid Solutions.  

National Technical Information Service (NTIS)

The study was made to investigate the anodic polarization behavior of commercially-available titanium alloys in sulfuric acid solutions. Six materials were investigated at 22 plus or minus 1C using the potentiostatic technique. The electrolyte was 1, 5, a...

J. M. Peters

1966-01-01

105

Electrodeposited NiCo/Cu Superlattices  

SciTech Connect

NiCo/Cu superlattices were electrodeposited on polycrystalline Cu substrates from a single electrolyte under potentiostatic control. The X-ray diffraction (XRD) patterns showed that NiCo/Cu superlattices have the same crystal structure and texture as in their substrates. The films exhibited giant magnetoresistance (GMR) or anisotropic magnetoresistance (AMR), depending on the Cu layer thicknesses.

Safak, M.; Alper, M. [Department of Physics, Faculty of Science and Literature, University of Uludag, Goeruekle, Bursa (Turkey)

2007-04-23

106

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

ERIC Educational Resources Information Center

|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)|

Pomeroy, R. S.; And Others

1989-01-01

107

Dissolution of platinum: limits for the deployment of electrochemical energy conversion?  

PubMed

Platinum stability: Dissolution of Pt, which is one major degradation mechanism in, for example, hydrogen/air fuel cells, was monitored under potentiodynamic and potentiostatic conditions. The highly sensitive and time-resolving dissolution monitoring enables the distinction between anodic and cathodic dissolution processes during potential transient and chronoamperometric experiments, and the precise quantification of the amount of dissolved Pt. PMID:23124819

Topalov, Angel A; Katsounaros, Ioannis; Auinger, Michael; Cherevko, Serhiy; Meier, Josef C; Klemm, Sebastian O; Mayrhofer, Karl J J

2012-11-04

108

Effect of glassy carbon properties on the electrochemical deposition of platinum nano-catalyst and its activity for methanol oxidation  

Microsoft Academic Search

The effects of the properties of glassy carbon on the deposition of plati- num particles and the electrocatalytic activity of platinum supported on glassy car- bon (GC\\/Pt) for methanol oxidation in alkaline and acidic solutions were studied. Platinum was potentiostatically deposited on two glassy carbon samples, thermally treated at different temperatures, which were either polished or anodicaly polarised in acid

SANJA TERZI; VLADISLAVA M. JOVANOVI

109

Corrosion and creep of dental amalgam.  

PubMed

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

Gjerdet, N R; Espevik, S

1978-01-01

110

A low noise readout circuit for integrated electrochemical biosensor arrays  

Microsoft Academic Search

This paper presents a low noise electrochemical interface circuit that is tuned to the needs of protein-based biosensor arrays and compatible with the formation of fully integrated biochemical microsystems. The circuit includes an integrated potentiostat and highly sensitive amperometric readout amplifier. It achieves good noise performance while supporting biosensor output currents from 10 pA to 10 ?A to suit a

Jichun Zhang; Nicholas Trombly; Andrew Mason

2004-01-01

111

Affordable Cyclic Voltammetry  

ERIC Educational Resources Information Center

|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

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

2009-01-01

112

A model for the corrosion of steel subjected to synthetic produced water containing sulfate, chloride and hydrogen sulfide  

Microsoft Academic Search

A model was developed for the prediction of corrosion rates associated with steel subjected to synthetic produced water. The corrosive species included in the model, identified through water analysis conducted in the field, are sulfate, chloride and hydrogen sulfide. The effect on corrosion of these species was examined through polarization experimentation using a three electrode glass corrosion cell and potentiostat.

Peter Smith; Sudipta Roy; David Swailes; Stephen Maxwell; David Page; John Lawson

2011-01-01

113

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. Final report, 1 Sep 1972--31 Aug 1975  

Microsoft Academic Search

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

C. J. Huang; E. Yeager; W. E. Ogrady

1975-01-01

114

Electrochemical destruction of dilute cyanide by copper-catalyzed oxidation in a flow-through porous electrode  

Microsoft Academic Search

Aqueous cyanide-ion concentrations can be reduced from 100 ppm to below 1 ppm by oxidation in a porous flow-through reticulated vitreous carbon anode catalyzed by copper. Proper control of solution pH combined with potentiostatic operation maintains high current efficiency. A theoretical model that accounts for interactions between mass transfer and chemical reactions is capable of describing process performance.

Christopher S. Hofseth; T. W. Chapman

1999-01-01

115

Effect of the Nature of the Gas Phase and Alkali Additives on Corrosion and Passivation of Iron in Molten Carbonates.  

National Technical Information Service (NTIS)

Weight, potentiostatic, metallographic, and x-ray methods were used at 500-700 exp 0 C to study corrosion and passivation of iron in a pure eutectic mixture of Li, Na, K/CO sub 3 in the presence of 1 to 5 mol percent LiOH and NaOH under an atmosphere of C...

O. P. Penyagina I. N. Ozeryanaya S. D. Finkel'shtein N. D. Shamanova

1974-01-01

116

The Adsorption and Diffusion of Electrolytic Hydrogen in Palladium  

Microsoft Academic Search

A sensitive electrochemical technique, which permits the recording of the instantaneous rate of permeation of electrolytic hydrogen through palladium, is described. Results were obtained under conditions required by theory for the diffusion of hydrogen with the use of electronic potentiostats. Analysis of the results shows the validity of the equations previously deduced for the diffusion of hydrogen. No anomalies in

M. A. V. Devanathan; Z. Stachurski

1962-01-01

117

One-pot synthesis of benzoic acid by electrocatalytic reduction of bromobenzene in the presence of CO 2  

Microsoft Academic Search

The electrocatalytic properties of Ag for the reduction of organic halides have been exploited for one-pot electrosynthesis of benzoic acid. Among various investigated dipolar aprotic solvents, only dimethylformamide gives good results. The process has been investigated both under potentiostatic and galvanostatic control. In both cases, the reaction smoothly proceeds under mild conditions and lasts in a few hours, giving benzoic

Abdirisak A. Isse; Christian Durante; Armando Gennaro

2011-01-01

118

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

NASA Astrophysics Data System (ADS)

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

Cai, Xun; Feng, Kai

119

Synthesis of High Coercivity Core-Shell Nanorods Based on Nickel and Cobalt and Their Magnetic Properties  

PubMed Central

Hybrid magnetic nanostructures with high coercivity have immense application potential in various fields. Nickel (Ni) electrodeposited inside Cobalt (Co) nanotubes (a new system named Ni @ Co nanorods) were fabricated using a two-step potentiostatic electrodeposition method. Ni @ Co nanorods were crystalline, and they have an average diameter of 150 nm and length of ~15 ?m. The X-ray diffraction studies revealed the existence of two separate phases corresponding to Ni and Co. Ni @ Co nanorods exhibited a very high longitudinal coercivity. The general mobility-assisted growth mechanism proposed for the growth of one-dimensional nanostructures inside nano porous alumina during potentiostatic electrodeposition is found to be valid in this case too.

2010-01-01

120

Development of galvanostatic Fourier transform electrochemical impedance spectroscopy.  

PubMed

Here, we report development of the galvanostatic Fourier transform electrochemical impedance spectroscopy (FTEIS), which monitors impedance of electrochemical reactions activated by current steps. We first derive relevant relations for potential change upon application of a step current, obtain impedances theoretically from the relations by simulation, and verify them with experimental results. The validity of the galvanostatic FTEIS technique is demonstrated by measuring impedances of a semiconductive silicon wafer using the conventional frequency response analysis (FRA), the potentiostatic FTEIS, and the galvanostatic FTEIS methods, and the results are in excellent agreement with each other. This work is significant in that the galvanostatic FTEIS would allow one to record impedance changes during charge/discharge cycles of secondary batteries and fuel cells as well as electrochemically irreversible systems which may produce noise level chronoamperometric currents by potentiostatic techniques. PMID:23331177

Nam, Kwang-Mo; Shin, Dong-Hyup; Jung, Namchul; Joo, Moon G; Jeon, Sangmin; Park, Su-Moon; Chang, Byoung-Yong

2013-02-04

121

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

SciTech Connect

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.

Taube, M. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Materials Science and Engineering]|[Brookhaven National Lab., Upton, NY (United States); Davenport, A.J. [Brookhaven National Lab., Upton, NY (United States); King, A.H. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Materials Science and Engineering; Chase, T. III [Smithsonian Institution, Washington, D.C. (United States) Freer Gallery of Art, Dept. of Conservation and Scientific Research

1996-07-01

122

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

SciTech Connect

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

Gurule, Natalia J.; Kelly, Michael James; Brevnov, Dmitri A. (University of New Mexico, Albuquerque, NM); Ashby, Carol Iris Hill; Pfeifer, Kent Bryant; Yelton, William Graham

2004-12-01

123

Effects of cathodic protection on corrosive wear of 304 stainless steel  

SciTech Connect

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.

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

2005-03-01

124

Investigation of passive films on {alpha}{sub 2} and {gamma} titanium aluminides by X-ray photoelectron spectroscopy  

SciTech Connect

Passive films on {alpha}{sub 2} and {gamma} titanium aluminide formed potentiostatically in sodium hydroxide (NaOH) and sulfuric acid (H{sub 2}SO{sub 4}) solutions were studied by x-ray photoelectron spectroscopy (XPS). In NaOH, potentiostatic experiments showed that titanium aluminides had very similar passive current densities to that of Ti. XPS sputter depth profile showed nearly no Al present in the outer layer of the passive films. In H{sub 2}SO{sub 4}, passive current densities increased for specimens with increasing Al content. XPS sputter depth profile showed that Al was enriched in outer layers of the passive films. These results indicated that the passive film dissolution rates increased with increasing amounts of Al in the passive film for titanium aluminides.

Ziomek-Moroz, M.; Su, W.; Covino, B.S. Jr.

1999-07-01

125

Selective anodic dissolution of phases in copper-based alloys in citric acid solution  

Microsoft Academic Search

The anodic behaviour of as-cast and homogenized binary copper-based alloys with Zr, Cr, Al, Si and Sn in 50% citric acid solution has been studied by the potentiostatic method. At positive potentials all as-cast and homogenized alloys with low additions of alloying elements behave in a manner similar to that of copper. However, there is an essential difference between the

A. Mance; A. Mihajlovi?

1981-01-01

126

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

Microsoft Academic Search

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

Rachna Rawal; Sheetal Chawla; C. S. Pundir

2011-01-01

127

Anodic dissolution of chromium in acid ethanol solutions  

Microsoft Academic Search

The purpose of this work was to study the kinetics of the anodic dissolution of cast and hardened chromium with a purity of 99.9% in ethanol solutions of hydrogen chloride, containing various additions of water (up to 20%). The kinetics of anodic dissolution of chromium was studied at 20°C in a hydrogen atmosphere by potentiostat polarization of stationary and rotating

L. E. Tsygankova; V. I. Vigdorovich

1985-01-01

128

Molecular imprinting polymer electrosensor based on gold nanoparticles for theophylline recognition and determination  

Microsoft Academic Search

An electrochemical sensor for theophylline (ThPh) was prepared by electropolymerizing o-phenylenediamine on a glassy carbon electrode in the presence of ThPh via cyclic voltammetry, followed by deposition of gold\\u000a nanoparticles using a potentiostatic method. The effects of pH, ratio between template molecule and monomer, number of cycles\\u000a for electropolymerization, and of the solution for extraction were optimized. The current of

Xianwen Kan; Tingting Liu; Hong Zhou; Chen Li; Bin Fang

2010-01-01

129

Effects of preparing conditions on the electrodeposition of well-aligned ZnO nanorod arrays  

Microsoft Academic Search

By using a potentiostatic electrodeposition method, well-aligned ZnO nanorod arrays (ZNAs) were synthesized under different conditions. The effects of preparing conditions on the electrodeposition of ZNAs were systematically studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and absorbance spectroscopy. It is indicated that the electrodeposition parameters, such as electrodeposition potential, electrolyte pH, concentration of precursors, temperature of solution and

Min Guo; ChuanYu Yang; Mei Zhang; YanJun Zhang; Teng Ma; XiDong Wang; XinDong Wang

2008-01-01

130

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

SciTech Connect

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.

Bedrossian, P J; Farmer, J C

1999-07-01

131

Multichannel electrochemical detection system based on LabVIEW  

Microsoft Academic Search

In this work the design, construction, control and applications of a computerized portable multichannel detection system suitable for electrochemical measurements was developed. The detection system is based on integrated eight homemade miniature potentiostat powered by two 9V batteries. The electrochemical control programme, developed in LabVIEW 6.0, generated the modulation signal, scanned the potential of the working electrode, acquired the current

Huaqing Li; Xianbo Luo; Chunxiu Liu; Liying Jiang; Dafu Cui; Xinxia Cai; Qingde Yang

2004-01-01

132

Order and disorder in electrochemical deposits of copper on graphite  

Microsoft Academic Search

Electrochemical deposition of copper on highly oriented pyrolytic graphite (HOPG) from aqueous 0.05M H2SO4 and 0.1M NaCl media has been studied using cyclic voltammogram (CV), single-pulse potentiostatic current vs. time (i vs. t) transient, and in situ scanning tunneling microscopic (STM) techniques. At potentials positive to the Nernst reversible potential, Cu(II) ions tend to adsorb on the HOPG surface. In

R. Srinivasan; P. Gopalan

1995-01-01

133

Effect of Load Deflection on Corrosion Behavior of NiTi Wire  

Microsoft Academic Search

For dental orthodontic applications, NiTi wires are used under bending conditions in the oral environment for a long period. The purpose of this study was to investigate the effect of bending stress on the corrosion of NiTi wires using potentiodynamic and potentiostatic tests in artificial saliva. The results indicated that bending stress induces a higher corrosion rate of NiTi wires

I. H. Liu; T. M. Lee; C. Y. Chang; C. K. Liu

2007-01-01

134

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

Microsoft Academic Search

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

Sireerat Intarakamhang; Christian Leson; Wolfgang Schuhmann; Albert Schulte

2011-01-01

135

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

Microsoft Academic Search

The overcapacity mechanism and high voltage process of the Li-excess electrode material Li[LiNiMn]O are studied by solid-state NMR, X-ray diffraction, X-ray absorption spectroscopy, transmission electron microscopy, combined with galvanostatic and potentiostatic intermittent titration electrochemical measurements. The cycling performance is improved noticeably when the material is cycled between potential windows of 5.3-2.5 V compared to 4.6-2.5 V. Diffraction data show that

Meng Jiang; Baris Key; Ying S. Meng; Clare P. Grey

2009-01-01

136

Nitriding of 316 stainless steel in molten fluoride salt by an electrochemical technique  

Microsoft Academic Search

Electrochemical nitriding of type 316 stainless steel (316 SS) in molten fluoride salt (LiFKF, FLiK) containing Li3N was investigated. Formation of chromium nitride CrN and iron nitride ?-Fex(x>8)N was confirmed. Cyclic voltammogram measurements and electrolysis treatment were carried out using an AlLi alloy reference electrode at 873K. After potentiostatic treatment at 1.0V vs. Li\\/Li+ for 100min, the specimen was characterized

Takashi Watanabe; Masatoshi Kondo; Akio Sagara

137

Improvement in Oxidation Resistance of Stainless Steel by Molten-Salt Electrodeposition of La  

Microsoft Academic Search

Improvement in the oxidation resistance of SUS304 stainless steel was accomplished by electrodeposition of La in a molten salt. The electrolysis of La was conducted using a potentiostatic-polarization method in an equimolar NaClKCl melt containing 3.5mol. LaF 3 at 1023 K. Observation of the specimen surface after polarization at -1.8 V (vs. Ag\\/Ag+ (0.1)) for 0.18 ks showed that La

Michihisa Fukumoto; Rie Yamashita; Motoi Hara

2004-01-01

138

The effect of particle size and morphology on the rate capability of 4.7 V LiMn 1.5+ ? Ni 0.5? ? O 4 spinel lithium-ion battery cathodes  

Microsoft Academic Search

The electrochemical impact of lithium-ion diffusivity on the discharge rate capabilities of cation ordered (P4332) and disordered (Fd3m) LiMn1.5+?Ni0.5??O4 spinels were studied. Potentiostatic Intermittent Titration (PITT) measurements revealed up to 2 orders-of-magnitude lower lithium diffusion coefficient for the ordered spinel polymorph. The optimum structure of the high voltage spinel is resolved with respect to these ionic studies and our previous

M. Kunduraci; G. G. Amatucci

2008-01-01

139

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

Microsoft Academic Search

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

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

2011-01-01

140

Sulphur conductive solid electrolytes in MeSLn 2S 3 systems  

Microsoft Academic Search

The principal possibility of sulphide transfer in phases based on BaZrS3 and MLn2S4 has been considered. The regions of solid solutions based on tertiary compounds have been defined. The systematic study of these phases by methods of conductometry, EMF in chemical concentration chains with and without transfer, potentiostatic chronoamperometry has been performed. A possible defect forming mechanism at consecutive alloying

L. Kalinina; Ju. Ushakova; H. Fominykh; G. Shirokova; I. Murin; O. Medvedeva

2008-01-01

141

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

Microsoft Academic Search

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

Daniel R. Bond; Derek R. Lovley

2005-01-01

142

Electrochemical study on the inhibitory effect of the underpotential deposition of zinc on ZnCo alloy electrodeposition  

Microsoft Academic Search

ZnCo alloy electrodeposition from chloride baths containing different Zn2+\\/Co2+ ratios was investigated by cyclic voltammetry and anodic linear sweep voltammetry using a Pt electrode. The peaks were attributed by means of EDX analysis, SEM and TEM observations performed on some alloys potentiostatically deposited. In the range of potential where zinc deposits underpotential, cyclic voltammetry showed a complex cathodic peak with

G. Roventi; T. Bellezze; R. Fratesi

2006-01-01

143

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

Microsoft Academic Search

2-Amino-5-ethyl-1,3,4-thiadiazole (AETDA) has been evaluated as a corrosion inhibitor for copper in 3.0% NaCl solutions using weight loss, pH, potentiodynamic polarization, potentiostatic currenttime, and electrochemical impedance spectroscopic (EIS) measurements. The study was also complemented by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) investigations. Weight loss measurements gave an inhibition efficiency of about 60% with 1.010?3M AETDA present, increasing

E. M. Sherif; Su-Moon Park

2006-01-01

144

Electrodeposition and characterization of Y-Ba-Cu-O superconducting thin films  

Microsoft Academic Search

Precursor thin films of Y-Ba-Cu-O superconductor were produced by potentiostatic and pulse electrodeposition from the dissolved nitrate salts of Y, Ba, Cu in dimethylformamide (DMF). The films were deposited on metal foils such as Ag-coated Cu, Ag, Ni, and Zr. Films were also synthesized on Ag-coated SrTiO, CaTiO, and AlO. The electrodeposited films were heat treated in flowing O in

Weston

1991-01-01

145

An electrochemical noise study of tribocorrosion processes of AISI 304 L in Cl and SO_{4}^{2-} media  

Microsoft Academic Search

Electrochemical noise measurements were performed to investigate the intrinsically stochastic character of the tribocorrosion process. Unidirectional sliding tests (pin-on-disc) were performed using AISI 304L stainless steel sliding against corundum. Experiments were carried out in Cl- and SO_{4}^{2-} containing media under open-circuit and potentiostatic polarization conditions. The power spectral density (PSD) of the current and potential signals showed a strong dependence

A. Berradja; D. Dforge; R. P. Nogueira; P. Ponthiaux; F. Wenger; J.-P. Celis

2006-01-01

146

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

Microsoft Academic Search

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

Y. Sun; E. Haruman

2011-01-01

147

Influence of chelating agents on the tribocorrosion of tungsten in sulphuric acid solution  

Microsoft Academic Search

The corrosion and tribocorrosion of tungsten in 0.01M H2SO4, without and with the presence of lactic acid and phosphoric acid as chelating agents was studied here.The passive behaviour was characterised using potentiostatic polarization and potential step techniques combined with rotating disk electrodes. Surface analysis techniques (XPS, AES) were used to assess surface chemistry. The tribocorrosion of tungsten was investigated using

J. Stojadinovic; D. Bouvet; M. Declercq; S. Mischler

2011-01-01

148

Tribocorrosion behaviour of overlay welded NiCr 625 alloy in sulphuric and nitric acids: Electrochemical and chemical effects  

Microsoft Academic Search

The tribocorrosion behaviour of overlay welded NiCr 625 alloy sliding against alumina in 0.5M H2SO4 and 0.5M HNO3 solutions under potentiostatic conditions was investigated. The passivation of the samples in the two electrolytes at different potentials (?1.5, ?0.3 and +0.3 VMSE) was studied by means of potentiodynamic polarization curves and XPS. The tribocorrosion behaviour of the alloy in sulphuric acid

N. Espallargas; S. Mischler

2010-01-01

149

Electrochemically controlled proton-transfer-catalyzed reactions at liquid-liquid interfaces: nucleophilic substitution on ferrocene methanol.  

PubMed

The generation of ?-ferrocenyl carbocations from ferrocenyl alcohols for S(N)1 substitution at the water-organic solvent interface is initiated by the transfer of protons into the organic phase. The proton flux, and hence the reaction rate, can be controlled by addition of a suitable "phase-transfer catalyst" anion or by external polarization with a potentiostat, providing a new method for the synthesis of ferrocene derivatives. PMID:23225302

Peljo, Pekka; Qiao, Liang; Murtomki, Lasse; Johans, Christoffer; Girault, Hubert H; Kontturi, Kysti

2012-12-06

150

Chromium nitride\\/Cr coated 316L stainless steel as bipolar plate for proton exchange membrane fuel cell  

Microsoft Academic Search

Chromium nitride\\/Cr coating has been deposited on surface of 316L stainless steel to improve conductivity and corrosion resistance by physical vapor deposition (PVD) technology. Electrochemical behaviors of the chromium nitride\\/Cr coated 316L stainless steel are investigated in 0.05M H2SO4+2ppm F? simulating proton exchange membrane fuel cell (PEMFC) environments, and interfacial contact resistance (ICR) are measured before and after potentiostatic polarization

Rujin Tian

2011-01-01

151

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

Microsoft Academic Search

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

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

2005-01-01

152

Influence of fluoride ions on corrosion performance of 316L stainless steel as bipolar plate material in simulated PEMFC anode environments  

Microsoft Academic Search

Corrosion performance of 316L stainless steel as a bipolar plate material in proton exchange membrane fuel cell (PEMFC) is studied under different simulated PEMFC anode conditions. Solutions of 1נ10?5M H2SO4 with a wide range of different F? concentrations at 70C bubbled with hydrogen gas are used to simulate the PEMFC anode environments. Electrochemical methods, both potentiodynamic and potentiostatic, are employed

Ying Yang; Liejin Guo; Hongtan Liu

153

Testing various food-industry wastes for electricity production in microbial fuel cell  

Microsoft Academic Search

Three food-industry wastes: fermented apple juice (FAJ), wine lees and yogurt waste (YW) were evaluated in combination with two sources of inoculum, anaerobic sludge and garden compost, to produce electricity in microbial fuel cells. Preliminary potentiostatic studies suggested that YW was the best candidate, able to provide up to 250mA\\/m2 at poised potential +0.3V\\/SCE. Experiments conducted with two-chamber MFCs confirmed

Bibiana Cercado-Quezada; Marie-Line Delia; Alain Bergel

2010-01-01

154

Corrosion of similar and dissimilar metal crevices in the engineered barrier system of a potential nuclear waste repository  

Microsoft Academic Search

Crevice corrosion is considered possible if the corrosion potential (Ecorr) exceeds the repassivation potential for crevice corrosion (Ercrev). In this study, potentiodynamic polarization and potentiostatic hold were used to determine the Ercrev of similar and dissimilar metal crevices in the engineered barrier system of the potential Yucca Mountain repository in 0.5M NaCl, 4M NaCl, and 4M MgCl2 solutions at 95C.

X. He; D. S. Dunn; A. A. Csontos

2007-01-01

155

Correlation of Dental Amalgam Crevice Corrosion with Clinical Ratings  

Microsoft Academic Search

In vitro corrosion behavior of ?2-containing and ?2-free dental amalgams was examined under crevice conditions which simulated the amalgam-tooth interface. By means of potentiostatic testing, currentdensity\\/time behavior and integrated anodic current were measured for 16 hr. All of the amalgams demonstrated crevice corrosion susceptibility. Crevice corrosion propagation for ?2-free vs. ?2-containing amalgams was characterized by lower acceleration and maximum rates

E. J. Sutow; D. W. Jones; G. C. Hall

1989-01-01

156

An electrochemical study of the crevice corrosion resistance of NiTi in Hanks solution  

Microsoft Academic Search

The crevice corrosion resistance of NiTi in Hanks solution at 37C was assessed by employing electrochemical methods. NiTiCu, commercially pure Ti (cp Ti), Ti6Al4V, and 316L stainless steel were included in the study for comparison. The susceptibility to crevice corrosion was investigated by using a potentiostatically controlled stimulationrepassivation scheme in the presence of a crevice former. Susceptibility to crevice corrosion

F. T. Cheng; K. H. Lo; H. C. Man

2007-01-01

157

Initiation and repassivation of crevice corrosion of type 444 stainless steel in chloride solution  

Microsoft Academic Search

Effects of chloride ion concentrations, solution temperature, and crevice-forming materials on the crevice corrosion of type\\u000a 444 stainless steel were investigated using a potentiostatic method. Critical crevice potential (Ecrev) and repassivation potential (Er) of the creviced alloy decreased with an increase in chloride concentration [Cl?], satisfying the logarithmic relationship between E and [Cl?]. In addition, Ecrev and Er of the

Chan-Jin Park; Yong-Heon Lee

2004-01-01

158

Corrosion resistance and interfacial contact resistance of TiN coated 316L bipolar plates for proton exchange membrane fuel cell  

Microsoft Academic Search

TiN coating is successfully deposited on 316L by multi-arc ion plating. Corrosion behavior of TiN coated 316L is studied in 0.05M H2SO4+2ppmF? simulating proton exchange membrane fuel cell (PEMFC) environments using electrochemical method, and interfacial contact resistance (ICR) is measured before and after potentiostatic polarization at operation potential for PEMFC. The TiN coated 316L exhibits promising ICR and improved corrosion

Rujin Tian; Juncai Sun

2011-01-01

159

On-Chip pH-Regulator and its Application to Bio\\/Chemical Sensing  

Microsoft Academic Search

An on-chip pH-regulator based on an irregular use of an electrochemical thin-film three-electrode system will be presented. The device is operated using only an ordinary potentiostat. A pH-sensitive electrode was used for the reference electrode, whereas a non-polarizable Ag\\/AgCl electrode was used for the working electrode. Auxiliary electrode was placed around the working electrode, which worked as an actuator electrode.

Katsuya Morimoto; M. Toya; J. Fukuda; H. Suzuki

2006-01-01

160

Integrating data converters for picoampere currents from electrochemical transducers  

Microsoft Academic Search

This paper describes a current mode A\\/D converter designed for a maximum input current range of 5 nA and a resolution of the order of 1 pA. The converter is designed for a potentiostat for amperometric chemical sensors and provides a constant polarization voltage for the measuring electrode. A prototype chip using the dual slope conversion method has been fabricated

Madalina Breten; Torsten Lehmann; E. Braun

2000-01-01

161

Electrodeposition of polycrystalline and amorphous silicon for photovoltaic applications. Quarterly technical progress report No. 03, December 1, 1979February 29, 1980  

Microsoft Academic Search

The survey of Si precursors leading to electrodeposition of Si in organic solvents was extended this quarter to cover SiCl, (ClCH)SiCl, and Si(OEt). Plating experiments with SiHCL solutions in propylene carbonate with 0.1M tetrabutylammonium tetrafluoroborate were continued. Silicon was deposited on ITO glass (Nesatron) as well as Mo substrates at temperatures from 25-80°C. Both potentiostatic and galvanostatic conditions were used.

R. D. Rauh; T. L. Rose; R. A. Boudreau; T. O. Hoover; D. L. Natwig

1980-01-01

162

The effect of ultrasonic frequency and intensity upon electrode kinetic parameters for the Ag(S2O3)23?\\/Ag redox couple  

Microsoft Academic Search

This paper describes the effect of ultrasound on electrochemical parameters important in the removal of silver from photographic processing solutions. Decomposition voltages (obtained galvanostatically) and discharge potentials (obtained potentiostatically) for the reduction of the silver complex, Ag(S2O3)23- was studied in dilute aqueous Na2S2O3\\/NaHSO3 solution on stainless steel and carbon disc electrodes in both the absence and presence of ultrasound. Under

B. Pollet; J. P. Lorimer; S. S. Phull; T. J. Mason; D. J. Walton; J. Y. Hihn; V. Ligier; M. Wry

1999-01-01

163

Electrochemical synthesis of silver nanoparticles  

Microsoft Academic Search

Silver polarisation in non-aqueous solution of NaNO3 in ethanol was investigated by means of cyclic voltammetry and chronoamperometry. A deposit consisting of metallic silver nanoparticles has been obtained by both potentiostatic and galvanostatic method. The proposed mechanism assumes that both anodic dissolution of silver and its reduction to metallic state proceed during polarisation in ethanol. The described process is a

Maria Starowicz; Barbara Stypu?a; Jacek Bana?

2006-01-01

164

Stress corrosion cracking of stainless steels  

Microsoft Academic Search

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

R. F. Hehemann

1985-01-01

165

Electrodeposition and characterization of ZnSe semiconductor thin films  

Microsoft Academic Search

In this work, results on the preparation and characterization of ZnSe thin films obtained by electrodeposition are presented. Voltammetric curves were recorded in order to characterize the electrochemical behavior of the Zn+2\\/SeO2 system on different substrates. Thin films were deposited potentiostatically from an unstirred, deareated aqueous solution onto titanium, glass substrates coated with fluorine doped tin oxide and ITO glass

G Riveros; H Gmez; R Henr??quez; R Schrebler; R. E Marotti; E. A Dalchiele

2001-01-01

166

A new electroactive paper actuator using conducting polypyrrole  

Microsoft Academic Search

The construction of electromechanical actuator has been achieved by using the conducting polypyrrole films deposition onto a gold-coated cellophane paper. This is probably the first report of this type of paper actuator. The conducting polypyrrole was electro-generated using either galvanostatic or potentiostatic conditions at 0.5 mA\\/cm2 current density or 0.7 volts applied potential. The two types of actuators were constructed

Shripad D. Deshpande; Jaehwan Kim; Seong R. Yun

2004-01-01

167

New electro-active paper actuator using conducting polypyrrole: actuation behaviour in LiClO 4 acetonitrile solution  

Microsoft Academic Search

The construction of electromechanical actuator has been achieved by using the conducting polypyrrole films deposition onto a gold-coated cellophane paper. This is probably the first report of this type of paper actuator. The conducting polypyrrole was electro-generated using either galvanostatic or potentiostatic conditions at 0.5mA\\/cm2 current density or 0.7V applied potential, respectively. The two types of actuators were constructed, namely:

S. D. Deshpande; Jaehwan Kim; Sung-Ryul Yun

2005-01-01

168

Determining the Active Surface Area for Various Platinum Electrodes  

Microsoft Academic Search

Various methods, i.e., the adsorption\\/stripping of adsorbed probe species, such as hydrogen (H), copper (Cu), and carbon monoxide\\u000a (CO), oxygen and hydroxide (O\\/OH), potentiostatic CO\\/H displacement as well as double layer capacitance are exploited to evaluate\\u000a the electrochemically active surface areas (ECAs) of platinum (Pt) foils, chemically deposited Pt thin film, and carbon-supported\\u000a Pt nanoparticle electrodes. For the relatively smooth

Dong Chen; Qian Tao; Ling Wen Liao; Shao Xiong Liu; Yan Xia Chen; Shen Ye

169

Characterization of the NiMo catalyst formed in situ during hydrogen generation from alkaline water electrolysis  

Microsoft Academic Search

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

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

2011-01-01

170

Synthesis, characterisation and ion transport studies on polypyrrole\\/deoxyribonucleic acid conducting polymer membranes  

Microsoft Academic Search

Thin films composed of polypyrrole\\/deoxyribonucleic acid (PPy\\/DNA) were prepared by potentiodynamic, potentiostatic and galvanostatic methods from aqueous solutions containing pyrrole and salmon sperm DNA. This material was also grown as large free-standing membranes, and onto platinum sputter-coated polyvinylidene fluoride (PVDF) filters to form composite membranes. Electrochemical studies of this material indicated that it could be oxidised and reduced, inducing ion

V Misoska; W. E Price; S. F Ralph; G. G Wallace; N Ogata

2001-01-01

171

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

Microsoft Academic Search

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

Sung-Woo Kim; Su-Il Pyun

2002-01-01

172

The effects of applied potential and chloride ion on the repassivation kinetics of pure iron  

Microsoft Academic Search

The kinetics of repassivation on the bare surface of pure iron wire electrode in 0.5 M Na2SO4 solutions have been investigated as a function of applied anodic potential and chloride ion concentration by means of potentiostatic current transients obtained from the abrading electrode. At an applied anodic potential of ?0.6 V (SCE) near the Tafel region, the current transients showed

J.-D. Kim; S.-I. Pyun

1996-01-01

173

Isotope effects in ?-PdH(D) as an instrument for diagnosing bulk defects  

Microsoft Academic Search

. Protium and deuterium sorption in the ?-phase region is studied for highly defective palladium electrodeposits fabricated\\u000a under controllable potentiostatic modes, particularly in the region of concentrated hydride formation. An anomalously high\\u000a hydrogen content is observed for these samples in both ?- and ?-hydrides. On the basis of coulometry in the course of anodic\\u000a hydrogen extraction, the non-linear sorption isotherms

Maria Y. Rusanova; Michail Grden; Andrzej Czerwinski; Galina A. Tsirlina; Oleg A. Petrii; Tatyana Y. Safonova

2001-01-01

174

On the origin of electrodeposition mechanism of ZnO on ITO substrate  

Microsoft Academic Search

Zinc oxide (ZnO) was potentiostatically deposited on indium tin oxide (ITO) substrates. Comparing of the theoretical mass\\/charge\\u000a ratio with experimental value measured byin-situ electrochemical quartz crystal microbalance, the origin of deposition mechanism of ZnO could be explained as follows: (i)\\u000a surface pH enhancement due to the adsorption of hydroxide ion; (ii) the formation of intermediate species (i.e., zinc hydroxide (Zn(OH)+);

Jaeyoung Lee; Sang Cheol Nam; Yongsug Tak

2005-01-01

175

Analysis of stresses generated during hydrogen extraction from and injection into Ni(OH) 2\\/NiOOH film electrode  

Microsoft Academic Search

Stresses generated during the hydrogen extraction from and injection into a Ni(OH)2\\/NiOOH film electrode in 0.1 M KOH solution are analysed by means of a laser beam deflection technique combined with potentiostatic current transient and electrochemical quartz crystal microbalance (EQCM) techniques. From the measured values of the film thickness, the elapsed time for phase boundary movement (PBM) and the potential

Su-Il Pyun; Kwang-Hoon Kim; Jeong-Nam Han

2000-01-01

176

Electrochemical actuation of carbon nanotube yarns  

Microsoft Academic Search

We report on actuation in high tensile strength yarns of twist-spun multi-wall carbon nanotubes. Actuation in response to voltage ramps and potentiostatic pulses is studied to quantify the dependence of the actuation strain on the applied voltage. Strains of up to 0.5% are obtained in response to applied potentials of 2.5 V. The dependence of strain on applied voltage and

Tissaphern Mirfakhrai; Jiyoung Oh; Mikhail Kozlov; Eddie Chi Wah Fok; Mei Zhang; Shaoli Fang; Ray H. Baughman; John D. W. Madden

2007-01-01

177

Lithium Transport through a Sol-Gel Derived Li1 Mn2O4 Film Electrode : Analysis of Current Transient by Monte Carlo Simulation  

Microsoft Academic Search

Lithium transport through a sol-gel derived Li 1 Mn2O4 film electrode was theoretically investigated by the analysis of the potentiostatic current transient in consideration of the interactions between lithium ions using Monte Carlo simulation. The anodic current transient experimentally measured on the film electrode exhibited two inflection points. In order to analyze the experimental current transient in consideration of the

Su-Il Pyun; Sung-Woo Kim; Jang-Myoun Ko

178

5-(Phenyl)-4H-1,2,4-triazole-3-thiol as a corrosion inhibitor for copper in 3.5% NaCl solutions  

Microsoft Academic Search

5-(Phenyl)-4H-1,2,4-triazole-3-thiol (PTAT) was synthesized and tested as a corrosion inhibitor for copper in stagnant and stirred 3.5% NaCl solutions using potentiodynamic polarization, potentiostatic current time, weight loss and pH measurements along with Fourier transform infrared spectroscopy (FT-IR) investigation. Potentiodynamic polarization measurements indicated that the presence of PTAT in both stagnant and stirred solutions decreases cathodic, anodic and corrosion currents, polarization

El-Sayed M. Sherif; A. M. El Shamy; Mostafa M. Ramla; Ahmed O. H. El Nazhawy

2007-01-01

179

Characterization and corrosion behavior of injection molded 17-4 PH steel electrochemically coated with poly[ trans -dichloro(4-vinylpyridine)ruthenium  

Microsoft Academic Search

The present study describes preliminary results on the corrosion resistance of injection molded 17-4 PH stainless steel potentiostatically\\u000a coated with poly {trans-[RuCl2(vpy)4]}, where vpy (4-vinylpyridine) acts as a ligand. The coated electrodes were characterized by scanning electron microscopy\\u000a and energy dispersive spectroscopy, as well as by electrochemical techniques. The microstructural analysis indicated that\\u000a the films reached up to 100??m thickness.

A. V. C. Sobral; W. Ristow Jr.; S. C. Domenech; C. V. Franco

2000-01-01

180

Growth and characterization of ZnO nanowire arrays electrodeposited into anodic alumina templates in DMSO solution  

Microsoft Academic Search

ZnO nanowire arrays were grown by potentiostatic cathodic electrodeposition on aluminum anodic oxide template (AAO) from dimethyl\\u000a sulfoxide (DMSO) solutions containing zinc chloride and molecular oxygen as precursors. The nanowires presented high aspect\\u000a ratio and exhibited a very high crystallinity with a wurtzite crystal structure with preferential orientation along the (0001)\\u000a crystallographic axis. Chronoamperometric experiments were performed on gold bulk

Humberto Gomez; Gonzalo Riveros; Daniel Ramirez; Rodrigo Henriquez; Ricardo Schrebler; Ricardo Marotti; Enrique Dalchiele

181

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

Microsoft Academic Search

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

Feng Xu; Yinong Lu; Lili Xia; Yan Xie; Min Dai; Yunfei Liu

2009-01-01

182

Controlled growth of ZnO array on FTO glass substrate by electrodeposition  

Microsoft Academic Search

In this study, ZnO nanotube and nanorod array films were respectively synthesized directly on F-doped SnO2 glass substrate (FTO) using a direct electrodeposition from a simple aqueous zinc salt solution. The effects of potential\\u000a value, electrodeposition mode and solution stirring speed on the product morphology were investigated. Controlling the reaction\\u000a under potentiostatic condition of ?0.7 V at stirring speed of

Lijuan Luo; Gang L; Bihui Li; Zhenghua Chen; Yiwen Tang

2010-01-01

183

Electrodeposition of single and duplex layers of ZnO with different morphologies and electrical properties  

Microsoft Academic Search

ZnO films have been prepared by electrodeposition from aqueous solutions. Dense, nanostructured and doped samples can be prepared by changing the composition of the electrolytic bath and fine-tuning the electrochemical parameters. Duplex layers can also be produced, with a nanostructured ZnO layer electrodeposited using as the substrate a previously prepared dense or In-doped ZnO layer. The films are deposited potentiostatically

M. Berruet; M. Vzquez

2010-01-01

184

Electrochemical and chemical characterization of polypyrrole\\/phosphotungstate coatings electrosynthesized on carbon steel electrodes in acetonitrile medium  

Microsoft Academic Search

Hybrid material polypyrrole\\/PW12O403? was potentiostatically electrosynthesized on carbon steel electrodes in acetonitrile medium. The obtained coatings were characterized by cyclic voltammetry, FTIR-ATR, XPS, SEM and EDX techniques. Phosphotungstate as dopant agent, Fe oxides and polypyrrole chains are the compounds that form the hybrid material structure. The influence of the electrosynthesis potential was analysed. Oxidized and reduced state of the coatings

J. Bonastre; R. Lapuente; P. Garcs; F. Cases

2009-01-01

185

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

Microsoft Academic Search

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

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

2005-01-01

186

Cavitation erosion and pitting corrosion behaviour of laser surface-melted martensitic stainless steel UNS S42000  

Microsoft Academic Search

Surface modification of martensitic stainless steel UNS S42000 was achieved by laser surface-melting using a 3.5-kW continuous wave CO2 laser. The cavitation erosion and corrosion characteristics of laser surface-melted specimens in 3.5% NaCl solution at 23C were studied by means of a 20-kHz ultrasonic vibrator at a peak-to-peak amplitude of 30 ?m and a potentiostat, respectively. In a series of

C. T Kwok; H. C Man; F. T Cheng

2000-01-01

187

An examination of the electrochemical characteristics of two stainless steels (UNS S32654 and UNS S31603) under liquidsolid impingement  

Microsoft Academic Search

The erosioncorrosion resistance of high alloy stainless steel UNS S32654 and standard stainless steel UNS S31603 has been assessed under liquidsolid impingement conditions. The electrochemical characteristics of the two stainless steels have been examined via free corrosion potential measurements, anodic polarisation, linear polarisation and potentiostatic control in erosioncorrosion.It has been shown in this paper that high alloy stainless steel UNS

Xinming Hu; Anne Neville

2004-01-01

188

Active centers for Cu UPDOPD in acid sulfate solution on Pt(111) electrodes  

Microsoft Academic Search

A long-term study of Cu UPD and OPD kinetics on the Pt(111) electrode by cyclic voltammetry and potentiostatic current transient techniques has shown that copper oxides CuxO could be considered as the active centers of the adlayer growth and further bulk copper deposition. These species are formed by a slow surface reaction between the adsorbed oxygen and copper atoms or

A. I. Danilov; E. B. Molodkina; Yu. M. Polukarov; V. Climent; J. M. Feliu

2001-01-01

189

A Miniaturized Voltammetric Electronic Tongue  

Microsoft Academic Search

A miniaturized electronic tongue based on pulsed voltammetry has been developed. It was made by inserting three types of wires acting as working electrodes (gold, platinum, and rhodium; diameter 0.25mm) into a platinum tube acting as a counter electrode (diameter 2mm; length 4mm). The arrangement was connected to a potentiostat controlled by a computer. Due to the small size of

Fredrik Winquist; Ingemar Lundstrm

2008-01-01

190

Proton transfer in oxidized adenosine self-aggregates.  

PubMed

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

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

2013-10-14

191

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

Microsoft Academic Search

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

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

2008-01-01

192

Proton transfer in oxidized adenosine self-aggregates  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

193

Comparative study of hydrogen peroxide electro-generation on gas-diffusion electrodes in undivided and membrane cells  

Microsoft Academic Search

The generation of hydrogen peroxide by means of the cathodic reduction of oxygen at gas-diffusion electrodes with a near 100%\\u000a current efficiency was achieved in concentrations sufficient for the mineralization of refractory organics in Fenton treatment.\\u000a A decrease in current efficiency over time at high temperatures and high current densities was observed. The polarization\\u000a study carried out in potentiostatic, potentiodynamic

G. R. Agladze; G. S. Tsurtsumia; B.-I. Jung; J.-S. Kim; G. Gorelishvili

2007-01-01

194

High resolution TEM and triple-axis XRD investigation into porous silicon formed on highly conducting substrates  

Microsoft Academic Search

The microstructure of thin porous silicon films (?1?m) formed potentiostatically on p+-type silicon in dilute HF solutions is investigated via high resolution TEM and triple-axis XRD. Average pore diameters were found to increase with increasing etching potential, changing from a mixture of micro- and mesopores to predominately square macropores once oxide growth commences. It is postulated that these square pores

T. L. Sudesh L. Wijesinghe; Shi Qiang Li; Mark B. H. Breese; Daniel J. Blackwood

2009-01-01

195

In-situ x-ray investigation of hydrogen charging in thin film bimetallic electrodes  

Microsoft Academic Search

Hydrogen uptake and discharge by thin metallic films under potentiostatic control was studied using x-ray diffraction at the National Synchrotron Light Source (NSLS). The formation of metal-hydrogen phases in Pd, Pd-capped Nb and Pd\\/Nb multilayer electrode structures was deduced from x-ray diffraction data and correlated with the cyclic voltammetry (CV) peaks. The x-ray data was also used to construct a

Najeh M. Jisrawi; Harold Wiesmann; M. W. Ruckman; T. R. Thurston; G. Reisfeld; B. M. Ocko; Myron Strongin

1997-01-01

196

Cr, Mo and W alloying additions in Ni and their effect on passivity  

Microsoft Academic Search

The passive corrosion properties of a series of NiCrMo alloys were investigated. The alloys studied were C22, C2000, C276, C4 and 625. Potentiostatic experiments at potentials within the passive range were obtained as a function of temperature (2585C) for each alloy. Each specimen was subsequently analyzed by time-of-flight secondary ion mass spectrometry (TOF SIMS) and X-ray photoelectron spectroscopy (XPS). Results

Amy C Lloyd; James J Nol; Stewart McIntyre; David W Shoesmith

2004-01-01

197

The effect of prior Cl ? ion incorporation into native oxide film on pure aluminium in neutral chloride solution on pit initiation  

Microsoft Academic Search

The present work deals with the effect of pre-immersion treatment of a pure aluminium (Al) specimen in chloride solution in reference to distilled water on the pit initiation analysing potentiostatic anodic current transient, electrogravimetric curve measured during the open-circuit potential (OCP), and potentiodynamic polarisation curves. Pre-immersion treatment in distilled water hardly changed the number of available pit initiation sites, suggesting

S.-I Pyun; W.-J Lee

2001-01-01

198

Electrodeposited the gold\\/manganese oxides as nano supercapacitor  

Microsoft Academic Search

In this study, the nano-supercapacitors were electrodeposited the gold\\/manganese oxides thin film with potassium permanganate and gold chloride solution on ITO substrate. It was deposited for 200 s by potentiostatic method (0.7 V v.s. open circuit). The morphology and the microstructure of the films were examined by SEM (scan electron microscopy). The thickness of the thin films was about 30~100

Yi Hu; Jiun-Shing Liu

2010-01-01

199

Electrodeposition of PtRu nanoparticles on multi-walled carbon nanotubes: Application in sensitive voltammetric determination of methyldopa  

Microsoft Academic Search

A modified glassy carbon electrode, prepared by potentiostatic electrodeposition of platinumruthenium nanoparticles (PtRuNPs) onto a multi-walled carbon nanotube (MWCNT) layer, offers dramatic improvements in the stability and sensitivity of voltammetric responses toward methyldopa (m-dopa) compared to glassy carbon electrodes individually coated with MWCNT or PtRuNPs. The surface morphology and nature of the hybrid film (PtRuNPs\\/MWCNT) deposited on glassy carbon electrodes

Saeed Shahrokhian; Shokoufeh Rastgar

200

Effect of frequency and current density on A.C. etching of aluminum electrolytic capacitor foil  

Microsoft Academic Search

This work studies the effects of current frequency and current density on etching morphology, microstructure and static capacity\\u000a of the aluminum foils used in electrolytic capacitors. The behavior associated with electrochemical etching during an anodic\\u000a half cycle was investigated by a potentiostat. The oxide covering of the anode, which protected aluminum from etching, thickened\\u000a as the frequency increased. Increasing the

Yueh Lien Lee; Bin Lung Ou; Yi Hung Chiu

2007-01-01

201

Effect of acid concentration and current density on DC etching of aluminum electrolytic capacitor foil  

Microsoft Academic Search

This work studies the effects of acid concentration and current density on etching morphology, microstructure and static capacity\\u000a of the aluminum foils used in high-voltage electrolytic capacitors. The behavior associated with electrochemical etching was\\u000a investigated with a potentiostat. The aluminum etching type of DC etching is greatly influenced by the etching potential.\\u000a The static capacity increased to 0.65 uF\\/cm2 with

Chiu Yi Hung; Ou Bin Lung; Lee Yuoh Lien

2007-01-01

202

Corrosion resistance tests on NiTi shape memory alloy  

Microsoft Academic Search

The corrosion performances of NiTi shape memory alloys (SMA) in human body simulating fluids were evaluated in comparison with other implant materials. As for the passivity current in potentiostatic conditions, taken as an index of ion release, the values are about three times higher for NiTi than for Ti6Al4V and austenitic stainless steels. Regarding the localized corrosion, while plain potentiodynamic

Gianni Rondelli

1996-01-01

203

Macro, micro and nanostructure of TiO 2 anodised films prepared in a fluorine-containing electrolyte  

Microsoft Academic Search

The paper presents an electron microscopy study of the macro, micro and nanostructure of titania nano-tubes formed by electrochemical\\u000a anodisation of titanium in a fluorine containing electrolyte. Scanning electron microscopy (SEM) is used to examine the overall\\u000a structure of the nano-tubes formed under potentiostatic conditions. Transmission electron microscopy (TEM) has been used to\\u000a examine the structure of the oxide layer

Angkhana Jaroenworaluck; Domenico Regonini; Chris R. Bowen; Ron Stevens; Duncan Allsopp

2007-01-01

204

Graphitic mesoporous carbon as a durable fuel cell catalyst support  

Microsoft Academic Search

Highly stable graphitic mesoporous carbons (GMPCs) are synthesized by heat-treating polymer-templated mesoporous carbon (MPC) at 2600C. The electrochemical durability of GMPC as Pt catalyst support (Pt\\/GMPC) is compared with that of carbon black (Pt\\/XC-72). Comparisons are made using potentiostatic and cyclic voltammetric techniques on the respective specimens under conditions simulating the cathode environment of PEMFC (proton exchange membrane fuel cell).

Paul V. Shanahan; Lianbin Xu; Chengdu Liang; Mahesh Waje; Sheng Dai; Y. S. Yan

2008-01-01

205

Transient growth and thinning of the barrier oxide layer on iron measured by real-time spectroscopic ellipsometry  

Microsoft Academic Search

The transient growth and thinning of the passive film on iron was investigated in ethylenediaminetetraacetic acid, disodium salt (EDTA) containing borate buffer solutions of pH 8.4 using real-time spectroscopic ellipsometry under potentiostatic control. EDTA effectively suppressed the formation of the outer layer of the passive film, thereby rendering the barrier layer amenable to direct examination. It was shown that the

Zijie Lu; Digby D. Macdonald

2008-01-01

206

Electrochemical surface nitriding of pure iron by molten salt electrochemical process  

Microsoft Academic Search

Electrochemical surface nitriding of pure iron was investigated in molten LiClKClLi3N systems at 773K. An outer compound layer and an inner diffusion layer were obtained by means of potentiostatic electrolysis at 1.00V (versus Li+\\/Li). From XRD and SEM analyses, it was confirmed that the obtained compound layer consisted of ?-Fe23N and ??-Fe4N; the free energies of formation of the two

Hiroyuki Tsujimura; Takuya Goto; Yasuhiko Ito

2004-01-01

207

Effect of cyanine dye-solvent interaction on the electrochemical corrosion behaviour of low-carbon steel in acid medium  

Microsoft Academic Search

The effect of the solvent used in the preliminary treatment with 1-ethyl-2(2?-hydroxystyryl)quinolinium cyanine dye solution on the electrochemical corrosion behaviour of low-carbon steel in HCl solution as the corrosive medium has been studied. Weight loss measurements, anodic potentiostatic polarization curves and the cathodic current values showed that cyanine dye in protic solvents (isobutanol, isopropanol, n-butanol, water and methanol) gives a

M. Th. Makhlouf; G. K. Gomma; M. H. Wahdan; Z. H. Khalil

1995-01-01

208

Role of grain boundary precipitates and solute depleted zone in the intergranular corrosion of aluminum alloy AA7150  

Microsoft Academic Search

Aluminum alloys exhibit vastly different corrosion behavior depending on the temper. For instance, potentiodynamic scans on 7150-T6 and T7 indicated that the T6 temper exhibit two breakdown potentials whereas the T7 tempers exhibit only one breakdown potential. Potentiostatic testing of the T6 and T7 temper for 1 h and 24 h. The corrosion morphology of the T6 temper varied with

Thodla Ramgopal

2001-01-01

209

Kinetics of sensitization and de-sensitization of duplex 308 stainless steel  

Microsoft Academic Search

The kinetics of, and the factors responsible for, sensitization and de-sensitization were determined for duplex 308 stainless steel. Samples consisting of 10 vol.% of ferrite, balance austenite were heat treated at 600 and 550°C for times of 15 min-300h. The chromium contents of the ..cap alpha..-..gamma.. boundaries and ..gamma..-..gamma.. grain boundaries of heat treated samples were measured by a potentiostatic

T DEVINE

1988-01-01

210

Global coupling effects on spatiotemporal patterns on a ring electrode  

Microsoft Academic Search

Experimental results on spatiotemporal pattern formation on a ring electrode during the oscillatory electrodissolution of cobalt in 1.0M phosphoric acid are reported; the ring is the area between two non-concentric circles and its width thus varies continuously with angle. The experiments were controlled potentiostatically with the tip of the capillary of the reference electrode placed in the center of the

R. D. Otterstedt; N. I. Jaeger; P. J. Plath; J. L. Hudson

1999-01-01

211

Anodic oxidation of pyrrhotite in simulated CIP liquors  

Microsoft Academic Search

Natural pyrrhotite (Fe7S8) can be oxidized in alkali (pH 10) at 25C at potentials above ?0.2 V (SCE). The voltammetry of a ground pyrrhotite disc shows current peaks consistent with the formation of a ferric surface phase such as Fe(OH)3 by air oxidation or by potentiostatic oxidation. In unbuffered solution, proton production can be demonstrated implicating the formation of sulfate,

H. G. Linge

1995-01-01

212

A SERS investigation of the electrodeposition of Au in a phosphate solution  

Microsoft Academic Search

The spectroelectrochemical behaviour of cyanide and phosphate ions adsorbed on a Au electrode during electrodeposition and corrosion in a KAu(CN)2 phosphate bath was studied by in situ SERS (Surface Enhanced Raman Spectroscopy) and cyclic voltammetry. SERS spectra exhibiting features corresponding to CN? and PO4? vibrations were recorded under potentiostatic control in an interval from ?1600 to +1500mV vs. Ag\\/AgCl. Surface

Benedetto Bozzini; Vincenzo Romanello; Claudio Mele

2007-01-01

213

Modeling pit initiation rate as a function of environment for Aluminum alloy 7075-T651  

Microsoft Academic Search

Pit initiation in AA7075 was characterized by measuring metastable pits from potentiostatic testing. Environmental conditions included a range of temperatures (060C), chloride concentration (0.010.6M), electrolyte pH (2.510) and electrochemical potential (E). Metastable pit initiation rate, ?, was shown to have a dependence on all environmental variables, which is highly relevant to practical service. As a result of the wide variation

M. K. Cavanaugh; N. Birbilis; R. G. Buchheit

214

Underpotential deposition of cadmium onto (111) face of silver from chloride containing solution  

Microsoft Academic Search

The underpotential deposition (UPD) of cadmium and AgCd alloy formation on the (111) face of silver in chloride containing solutions were investigated by cyclic voltammetry and the potentiostatic pulse technique. It was shown that the UPD of cadmium commences at about ?400 mV versus SCE (300 mV vs. Cd2+\\/Cd) with the formation of ordered structure of the type (3x3)R30. Chloride

V. D Jovi?; B. M Jovi?

2002-01-01

215

Modification of a Pt surface by spontaneous Sn deposition for electrocatalytic applications. 2. Oxidation of CO, formaldehyde, formic acid, and methanol  

Microsoft Academic Search

The electrocatalytic activity of a spontaneously tin-modified Pt catalyst, fabricated through a simple dip-coating method under open-circuit conditions and characterized using surface analysis methods, was studied in electrooxidation reactions of a preadsorbed CO monolayer and continuous oxidation of methanol, formic acid, and formaldehyde in the potentiodynamic and potentiostatic modes. The catalytic activity of the tin-modified Pt surface is compared with

G. Stalnionis; L. Tamaauskait?-Tamai?nait?; V. Pautienien?; Z. Jusys

2004-01-01

216

Synthesis of TiO 2 submicro-rings and their application in dye-sensitized solar cell  

Microsoft Academic Search

In this paper, novel TiO2 submicro-rings were synthesized via potentiostatic anodization of titanium powder coated on transparent conducting oxide glass. The TiO2 submicro-rings film was characterized by SEM, XPS and 3D optical profiling. Accordingly, a possible growth mechanism of submicro-rings was discussed. The TiO2 submicro-rings based dye-sensitized solar cell (DSSC) with the film thickness of ca. 3.1?m was assembled and

Ming Li; Yong Liu; Hai Wang; Hui Shen

2011-01-01

217

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

PubMed

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

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

2003-07-15

218

Lithium insertion chemistry of phosphate phases with the lipscombite structure  

Microsoft Academic Search

The lithium insertion chemistry of an iron phosphate with the lipscombite structure, Fe1.19PO4F0.11(OH)0.46(H2O)0.43, was investigated by X-ray diffraction (XRD), galvanostatic cycling, and potentiostatic intermittent titration. The compound, prepared by a simple hydrothermal method, contains interconnecting chains of face-sharing FeO6 octahedra with about 60% Fe occupancy. Assuming that all the iron may be reduced, the theoretical capacity is about 180mAhg?1, similar

Mickael Doll; Sbastien Patoux; Thomas J. Richardson

2005-01-01

219

Special features in the electroreduction of oxidic molybdenum(VI) forms in tungstate melt  

SciTech Connect

The electrochemical behavior of oxidic molybdenum in tungstate melt was studied under equilibrium and nonequilibrium conditions. Chronovoltammetry and transient polarization was used. The current-voltage curves were recorded with a pulse potentiostat and the experiments were performed in a quartz reactor with platinum and molybdenum electrodes and a platinum crucible served as the melt container and anode. The end product of the oxidic molybdenum forms were shown to depend on the acid-base properties of the melt which allows for choosing the properties and controlling the electrode process.

Shapoval, V.I.; Baraboshkin, A.N.; Kushkhov, K.B.; Malyshev, V.V.

1988-01-01

220

Simulation of an enzyme-based glucose sensor  

NASA Astrophysics Data System (ADS)

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.

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

2001-09-01

221

Separation of metal ions from aqueous solutions  

DOEpatents

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.

Almon, Amy C. (Augusta, GA)

1994-01-01

222

Influence of electrochemical potential on the tribocorrosion behaviour of high carbon CoCrMo biomedical alloy in simulated body fluids by electrochemical impedance spectroscopy  

Microsoft Academic Search

The corrosion and tribocorrosion behaviour of a high carbon CoCrMo alloy sliding against alumina in simulated body fluids under potentiostatic conditions was investigated. The electrochemical behaviour of the sample in two electrolytes at different potentials (?1VAg\\/AgCl, ?0.5VAg\\/AgCl, +0.05VAg\\/AgCl, +0.5VAg\\/AgCl and +0.75VAg\\/AgCl) was studied by means of electrochemical impedance spectroscopy (EIS). The effects of solution chemistry and applied potential on the

Anna Igual Muoz; Leandre Casabn Julin

2010-01-01

223

Separation of metal ions from aqueous solutions  

DOEpatents

This invention is comprised of 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 flowing cell containing flowing 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 flowing cell and connected to the electrodes, and optionally a detector such as a chromatographic detector, positioned outside the flowing cell. This apparatus and its operation has significant application where trace amounts of metal ions are to be separated.

Almon, A.

1991-12-31

224

Template electrodeposition of ordered bismuth telluride nanowire arrays.  

PubMed

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

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

2009-02-01

225

Electrodeposited nickelcobalt composite coating containing nano-sized Si 3N 4  

Microsoft Academic Search

NiCo\\/Si3N4 composite coatings with various contents of Si3N4 nano-particulates were prepared by electrodeposition in a NiCo plating bath containing Si3N4 nano-particulates to be co-deposited. The shape and size of the Si3N4 nano-particulates were observed and determined on a transmission electron microscope. The polarization behavior of the composite plating bath was examined on a PAR-273A potentiostat\\/galvanostat device. The friction and wear

L. Shi; C. F. Sun; F. Zhou; W. M. Liu

2005-01-01

226

Electrodeposited nickelcobalt composite coating containing MoS 2  

Microsoft Academic Search

NiCo\\/MoS2 composite coatings were prepared by electrodeposition in a NiCo plating bath containing nano-sized MoS2 particles to be co-deposited. The polarization behavior of the composite plating bath was examined on a PAR-273A potentiostat\\/galvanostat device. The friction and wear behaviors of the NiCo\\/MoS2 composite coatings were evaluated with UMT-2MT test rig in a ball-on-disk contact mode. The morphologies of the original

Lei Shi; Chufeng Sun; Weimin Liu

2008-01-01

227

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

SciTech Connect

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

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

1987-01-01

228

The lithium-boron alloy anode in molten nitrate electrolytes  

Microsoft Academic Search

Potentiostatic studies of Li(B) anodes in molten LiNO at 300°C indicate that at 80% peak open-circuit voltage, a broad flat discharge at 780 mA cm⁻² is obtained. Galvanostatic discharge studies show stable anode potentials more negative than -3V (vs. Ag\\/sup +\\/\\/Ag) in LiNO at 300 mA cm⁻² over a temperature range of 270°⁻³⁵°sup 0\\/C. At temperatures above 350°C, deflagrations of

G. E. McManis; A. N. Fletcher; M. H. Miles

1984-01-01

229

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

NASA Astrophysics Data System (ADS)

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.

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

230

Electrical/thermoelectric characterization of electrodeposited Bi x Sb2- x Te3 thin films  

NASA Astrophysics Data System (ADS)

Bi x Sb2- x Te3 films were electrodeposited potentiostatically from acidic nitric baths at room temperature by controlling the electrodeposition parameters (i.e., the applied potential). Nearly stoichiometric Bi x Sb2- x Te3 thin films were obtained at applied potentials between -0.10 and -0.15 V versus the saturated calomel electrode (SCE). The electrical and thermoelectric properties of the as-deposited films were degraded at more negative deposition potentials; this might be attributed to the greater defect density formed. The post-annealing process in the reducing environment improved the electrical and thermoelectric properties, possibly because of a decrease in antistructure defects.

Yoo, In-Joon; Lim, Dong Chan; Myung, Nosang V.; Jeong, Young-Keun; Kim, Yang Do; Lee, Kyu Hwan; Lim, Jae-Hong

2013-09-01

231

Electrochemical behaviour of uranium (IV) in DMF at vitreous carbon  

Microsoft Academic Search

The electrochemical behaviour of UCl4 (0.01molL?1 up to 0.05molL?1) in 0.1molL?1 TBAPF6\\/DMF solution at vitreous carbon was studied, at room temperature, by cyclic voltammetry and potentiostatic techniques. The electrolytic solutions were analyzed by UV spectroscopy (UV), and the electrodeposited films were characterized by Rutherford Backscattering Spectroscopy (RBS) and X-ray diffraction (XRD). The cyclic voltammetric results, at low UCl4 concentrations (0.01molL?1),

M. L. Afonso; A. Gomes; A. Carvalho; L. C. Alves; F. Wastin; A. P. Gonalves

2009-01-01

232

Electrochemical preparation of In and Al doped ZnO thin films for CuInSe 2 solar cells  

Microsoft Academic Search

ZnO thin films doped with either In or Al were electrodeposited potentiostatically at 80 C from aqueous solutions containing Zn(NO3)2 and either InCl3 or Al(NO3)3. The films were used for the preparation of pn-junctions based on electrodeposited CuInSe2 thin films. The pn-junctions were prepared both with and without the chemical bath deposited CdS interlayer, thus demonstrating the possibility to make

Marianna Kemell; Frdric Dartigues; Mikko Ritala; Markku Leskel

2003-01-01

233

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

PubMed

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

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

2013-01-20

234

Enhanced performance as a lithium-ion battery cathode of electrodeposited V 2 O 5 thin films by e-beam irradiation  

Microsoft Academic Search

The influence of electron beam irradiation on the electrochemical properties of electrodeposited V2O5 thin films was investigated. V2O5 thin films were deposited electrochemically onto indium tin oxide-coated glass from an aqueous vanadyl sulfate hydrate (VOSO4?nH2O) solution using Pt and Ag\\/AgCl as the counter electrode and reference electrode, respectively. Electrodeposition was performed\\u000a potentiostatically at 1.7V vs. Ag\\/AgCl. Electrodeposited samples were then

Kyung-Hwa Kim; Dong-Kyun Roh; In Kyu Song; Byung-Cheol Lee; Sung-Hyeon Baeck

2010-01-01

235

Electrochemical aspects of stress-corrosion cracking of sensitized stainless steels  

SciTech Connect

The intergranular stress-corrosion cracking (SCC) of sensitized Type 304 stainless steel has been studied using sodium thiosulphate solutions at room temperature. Electrochemical aspects of the cracking have been examined using a potentiostatic scratching electrode technique applied to simulated grain boundary alloys. These results are compared with the current transients observed after intergranular fracture of embrittled specimens under the electrolyte. Dissolution kinetics within actual propagating cracks have been examined using load modulation. Rapid intergranular failure in a thiosulphate solution can be induced by successive load pulses of extremely short duration. Difficulties in accounting for the SCC velocities by an electrochemical mechanism are discussed.

Newman, R.C.; Sieradzki, K.; Isaacs, H.S.

1982-01-01

236

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

SciTech Connect

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.

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

1997-04-01

237

Chaos induction using a reference model assisted control.  

PubMed

A stable period two orbit in the parametric vicinity of a chaotic attractor is prevented from being reached, via the exclusion of trajectories from its near vicinity using a reference model based control strategy. This results in the inception of sustained chaotic dynamics. The reference model control strategy includes a predictive term enabling delimitation of precluded zones for the system dynamics. This technique for promotion of chaotic behavior is illustrated by using an experimental electrochemical cell involving the potentiostatic electro-dissolution of copper in phosphoric acid. PMID:21080697

Ramrez-lvarez, E; Rico-Martnez, R; Parmananda, P

2010-11-16

238

Coreduction of aluminium and lanthanide ions in molten fluorides: Application to cerium and samarium extraction from nuclear wastes  

Microsoft Academic Search

This work concerns the method of co-reduction process with aluminium ions in LiFCaF2 medium (7921mol.%) on tungsten electrode for cerium and samarium extraction. Electrochemical techniques such as cyclic and square wave voltammetries, and potentiostatic electrolyses were used to study the co-reduction of CeF3 and SmF3 with AlF3. For each of these elements, specific peaks of AlCe and AlSm alloys formation

M. Gibilaro; L. Massot; P. Chamelot; P. Taxil

2009-01-01

239

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

SciTech Connect

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

Jisrawi, N.M.; Wiesmann, H.; Ruckman, M.W.; Thurston, T.R.; Reisfeld, G.; Ocko, B.M.; Strongin, M. [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States)

1997-08-01

240

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

PubMed Central

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 -2.4C. 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.

2011-01-01

241

Preparation and evaluation of electrodeposited platinum nanoparticles on in situ carbon nanotubes grown carbon paper for proton exchange membrane fuel cells  

Microsoft Academic Search

Multi-walled carbon nanotubes (MWCNTs) based microporous layer on the non-woven carbon paper substrates was prepared by in situ growth in a chemical vapor deposition method. Pt with a loading of ?0.13mgcm?2 was electrodeposited at ?0.3, ?0.6, ?1.2, ?2.4, and ?3.6V vs SCE in a chloroplatinic acid (60g\\/L) and hydrochloric acid (10g\\/L) bath using a potentiostat. Scanning electron micrographs showed that

K. Saminathan; V. Kamavaram; V. Veedu; A. M. Kannan

2009-01-01

242

Al-Cd Alloy Formation by Aluminum Underpotential Deposition from AlCl3+NaCl Melts on Cadmium Substrate  

NASA Astrophysics Data System (ADS)

Aluminum was incorporated into a polycrystalline cadmium electrode surface by underpotential deposition from equimolar AlCl3+ NaCl melt at 473 K, 523 K, and 573 K (200 C, 250 C, and 300 C). The process was studied by linear sweep voltammetry and potentiostatic deposition/galvanostatic striping. The deposits were characterized X-ray diffraction (XRD), Auger electron spectroscopy (AES), and electron probe microanalyzer (EPMA). The electrochemical measurements showed evidence of Cd-Al alloys being formed but they could not be identified. The growth kinetics of the Cd-Al layers of various proportion and depths that depended on temperature and deposition time were described.

Jovi?evi?, Niko; Cvetkovi?, Vesna S.; Kamberovi?, eljko J.; Jovi?evi?, Jovan N.

2013-02-01

243

Oscillations and period-doubling bifurcations in the electrochemical oxidation of thiourea  

NASA Astrophysics Data System (ADS)

The electrochemical oxidation of thiourea on a Pt electrode was found to exhibit both simple and period-doubled oscillations. Measurements of the potentiostatic I/ behavior and impedance spectra suggest that the studied system belongs to the hidden negative differential resistance (HNDR) oscillator. The dependence of complex oscillations on initial compositions of the reaction mixture and temperature has also been characterized, which showed that: (1) lowering the reaction temperature facilitates the occurrence of complex oscillations; (2) the frequency of oscillation increases linearly with respect to the temperature; and (3) hydrochloric acid exhibits stronger influence on the reaction behavior than nitric acid.

Xu, Liangqin; Gao, Qingyu; Feng, Jiamin; Wang, Jichang

2004-10-01

244

Using electrochemical methods to determine alloy 22's crevice corrosion repassivation potential  

NASA Astrophysics Data System (ADS)

Alloy 22 (N06022) is a nickel-based alloy highly resistant to corrosion. In aggressive conditions of high chloride concentration, temperature, and applied potential, alloy 22 may suffer crevice corrosion, a form of localized corrosion. Several electrochemical methods can be used to detect localized corrosion in metallic alloys. One of the most popular for rapid screening is cyclic potentiodynamic polarization (CPP). This work compares the repassivation potentials obtained using CPP to repassivation potentials obtained using the Tsujikawa-Hisamatsu Electrochemical method and the potentiostatic method.

Evans, Kenneth J.; Yilmaz, Ahmet; Day, S. Daniel; Wong, Lana L.; Estill, John C.; Rebak, Ral B.

2005-01-01

245

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

NASA Astrophysics Data System (ADS)

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

Mathew, Anisha Mary; Neena, P.

2011-10-01

246

The anodic behavior of iron in hydrogen sulfide solutions  

Microsoft Academic Search

The anodic behavior of iron in 0.032 mol . L⁻¹ NaCl\\/0.003 mol . L⁻¹ NaHCO and 1 mol . L⁻¹ NaSO\\/0.003 mol . L⁻¹ NaHCO solutions containing 0.05 mol . L⁻¹ HS at ambient temperature was studied using cyclic voltammetry and the potentiostatic technique. In both solutions, a nonprotective film of mackinawite (Fe\\/sub 1+chi\\/S) was formed on the iron, but

B. G. Pound; G. A. Wright; R. M. Sharp

1989-01-01

247

Electrodeposition of ruthenium oxide on ferritic stainless steel bipolar plate for polymer electrolyte membrane fuel cells  

Microsoft Academic Search

The effect of RuO2 electrodeposition on ferritic stainless steel as a bipolar plate is evaluated in terms of the surface morphology, interfacial contact resistance (ICR), potentiostatic polarization, contact angle, and X-ray photoelectron spectroscopy. The surface morphology of deposited RuO2 is greatly stabilized by addition of HNO3 in 10mM RuCl3xH2O solution. The RuO2-deposition on stainless steel shows a high contact angle

Kwang Min Kim; Jong Hee Kim; Yun Yong Lee; Kyoo Young Kim

248

Kinetic characterization of Prussian Blue-modified graphite electrodes for amperometric detection of hydrogen peroxide  

Microsoft Academic Search

Prussian Blue-modified graphite electrodes (G\\/PB) with electrocatalytic activity toward H2O2 reduction were obtained by PB potentiostatic electrodeposition from a mixture containing 2.5mm FeCl3+2.5mm K3[Fe(CN)6] + 0.1m KCl +0.1m HCl. From cyclic voltammetric measurements, performed in KCl aqueous solutions of different concentrations (510?21 m), the rate constant for the heterogeneous electron transfer (k\\u000a s) was estimated by using the Laviron treatment.

Raluca C. Cretu; Delia M. Gligor; Laura Muresan; Ionel Catalin Popescu; Liana M. Muresan

2006-01-01

249

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

PubMed Central

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

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

2010-01-01

250

Crevice Corrosion on Ni-Cr-Mo Alloys  

SciTech Connect

Ni-Cr-Mo alloys were developed for their exceptional corrosion resistance in a variety of extreme corrosive environments. An alloy from this series, Alloy-22, has been selected as the reference material for the fabrication of nuclear waste containers in the proposed Yucca Mountain repository located in Nevada (US). A possible localized corrosion process under the anticipated conditions at this location is crevice corrosion. therefore, it is necessary to assess how this process may, or may not, propagate if the use of this alloy is to be justified. Consequently, the primary objective is the development of a crevice corrosion damage function that can be used to assess the evolution of material penetration rates. They have been using various electrochemical methods such as potentiostatic, galvanostatic and galvanic coupling techniques. Corrosion damage patterns have been investigated using surface analysis techniques such as scanning electron microscopy (SEM) and optical microscopy. All crevice corrosion experiments were performed at 120 C in 5M NaCl solution. Initiating crevice corrosion on these alloys has proven to be difficult; therefore, they have forced it to occur under either potentiostatic or galvanostatic conditions.

P. Jakupi; D. Zagidulin; J.J. Noel; D.W. Shoesmith

2006-05-12

251

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

PubMed

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

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

2013-04-08

252

Investigation of corrosion and stability of lead-brass alloy in acid and neutral solutions using electrochemical impedance spectroscopy  

SciTech Connect

The corrosion behavior of a lead-brass alloy (58% Cu, 1.8% Pb, and 42.2% Zn) was investigated in naturally aerated acid and neutral chloride and sulfate solutions under open-circuit and potentiostatic control conditions using electrochemical impedance spectroscopy (EIS). Corrosion under open-circuit conditions was caused mainly by the dissolved oxygen depolarizer, copper (I) chloride (CuCl) or copper (I) sulfate (Cu{sub 2}SO{sub 4}), together with some surface oxides, which were assumed to be corrosion products, leading to electrode passivation. Impedance spectra in the form of Nyquist plots consisted of depressed semicircles with different degrees of depression. These depressions increased with dilution of the electrolyte rather than with immersion time. This behavior was attributed partially to inhomogeneities and surface roughness. Data were analyzed in terms of the constant phase element model, which reduced to infinite Warburg diffusion in neutral solutions. At high cathodic overpotentials, reduction of hydrogen (H{sup +}) in acid media and of oxygen in neutral media seemed to be rate controlling. Potentiostatic polarization at potentials > {minus}0.5 V led to selective dissolution of zinc and accumulation of corrosion products. At potentials > {minus}0.2 V, pitting occurred.

Badawy, W.A.; El-Egamy, S.S.; Azab, A.S. [Univ. of Cairo, Giza (Egypt). Dept. of Chemistry

1997-11-01

253

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

PubMed

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

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

2013-06-13

254

Nanopore formation on the surface oxide of commercially pure titanium grade 4 using a pulsed anodization method in sulfuric acid.  

PubMed

Titanium and its alloys form a thin amorphous protective surface oxide when exposed to an oxygen environment. The properties of this oxide layer are thought to be responsible for titanium and its alloys biocompatibility, chemical inertness, and corrosion resistance. Surface oxide crystallinity and pore size are regarded to be two of the more important properties in establishing successful osseointegration. Anodization is an electrochemical method of surface modification used for colorization marking and improved bioactivity on orthopedic and dental titanium implants. Research on titanium anodization using sulphuric acid has been reported in the literature as being primarily conducted in molarity levels 3M and less using either galvanostatic or potentiostatic methods. A wide range of pore diameters ranging from a few nanometers up to 10?m have been shown to form in sulfuric acid electrolytes using the potentiostatic and galvanostatic methods. Nano sized pores have been shown to be beneficial for bone cell attachment and proliferation. The purpose of the present research was to investigate oxide crystallinity and pore formation during titanium anodization using a pulsed DC waveform in a series of sulfuric acid electrolytes ranging from 0.5 to 12M. Anodizing titanium in increasing sulfuric acid molarities showed a trend of increasing transformations of the amorphous natural forming oxide to the crystalline phases of anatase and rutile. The pulsed DC waveform was shown to produce pores with a size range from ?0.01 to 1?m(2). The pore size distributions produced may be beneficial for bone cell attachment and proliferation. PMID:23807314

Williamson, R S; Disegi, J; Griggs, J A; Roach, M D

2013-06-27

255

The corrosion behavior and microstructure of high-velocity oxy-fuel sprayed nickel-base amorphous/nanocrystalline coatings  

NASA Astrophysics Data System (ADS)

The corrosion characteristics of two Ni-Cr-Mo-B alloy powders sprayed by the high-velocity oxy-fuel (HVOF) process have been studied using potentiodynamic and potentiostatic corrosion analysis in 0.5 M H2SO4. The deposits were also microstructurally characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM) (utilizing both secondary electron and backscattered electron modes), and transmission electron microscopy (TEM). Results from the microstructural examination of the two alloys have revealed a predominantly amorphous/nanocrystalline face centered cubic (fcc) matrix containing submicron boride precipitates as well as regions of martensitically transformed laths. Apparent recrystallization of the amorphous matrix has also been observed in the form of cellular crystals with a fcc structure. The oxide stringers observed at splat boundaries were found to be columnar grained ?-Cr2O3, though regions of the spinel oxide NiCr2O4 with a globular morphology were also observed. The coatings of the two alloys exhibited comparable resistance to corrosion in 0.5 M H2SO4, as revealed by potentiodynamic tests. They both had rest potentials approximately equal to -300 mV saturated calomel electrode (SCE) and passive region current densities of 1 mA/cm2. Microstructural examination of samples tested potentiostatically revealed the prevalence of degradation at splat boundaries, especially those where significant oxidation of the deposit occurred.

Dent, A. H.; Horlock, A. J.; McCartney, D. G.; Harris, S. J.

1999-09-01

256

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

257

Applications of electrochemical methods for investigations of localized corrosion of nitrogen-molybdenium stainless steels  

SciTech Connect

Electrochemical methods were used to determine the localized corrosion resistance of 12 austenitic stainless steels (SS) with a composition range of 22%Cr-5%Ni-5%Mn-(1% to 5%)Mo-(0.0% to 0.7%)N-balance Fe in a deaerated 3.5 wt% sodium chloride (NaCl) solution from 10C to 97C. Potentiodynamic polarization was used to determine the critical pitting potential (CPP), protection potentials, and polarization resistance (Rp), and potentiostatic cyclic thermometry was used to determine the critical pitting temperature (CPT) and critical crevice temperature (CCT). The results of potentiodynamic polarization showed that all of the SS containing both N and Mo have CPP significantly higher than either Type 304 (UNS S30400) or Type 316L (UNS S31603) SS. Rp correlated with the pitting resistance equivalent (PRE) for PRE from 20 to 45; however, for PRE > 45 there was no correlation. Results obtained by potentiostatic cyclic thermometry showed that CPT and the CCT are both linear functions of PRE, and strongly dependent on both Mo and N concentration in the alloy.

Russell, James H.; Covino, Bernard S., Jr.; Bullard, Sophie J.

2001-04-01

258

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

SciTech Connect

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

Roy, A.K., LLNL

1997-11-01

259

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

NASA Astrophysics Data System (ADS)

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 LabView interface, 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 ?m technology from ST Microelectronics through the CMP-TIMA service.

Colomer-Farrarons, Jordi; Miribel-Catal, Pedro L.; Samitier, Josep; Arundell, Martin; Rodrguez, Ivn

2009-05-01

260

New methods for corrosion testing of aluminum alloys  

SciTech Connect

This symposium presents papers on a modification of the EXCO test method for exfoliation corrosion susceptibility in 7XXX, 2XXX, and aluminum-lithium alloys; materials evaluation using wet-dry mixed salt-spray tests; a comparison of potentiodynamic polarization tests with wet-dry mixed salt-spray testing of Al-Mg-Si alloy; an accelerated test for determining microbiological-influenced corrosion resistance of aluminum alloys; and corrosion of aluminum in Al alloys in nitric acid. Attention is also given to exfoliation corrosion testing of Al-Li alloys, damage-based assessment of stress corrosion performances among aluminum, and corrosion fatigue crack growth rate of Al-Li alloy sheet and its weldment. Other papers are on potentiometric and potentiostatic determination of the corrosion rate of welded 2519 aluminum alloy, time-lapse video techniques in the corrosion testing of aluminum alloys, and an examination of the influence of lithium on the repassivation rate of aluminum alloys.

Agarwala, V.S.; Ugiansky, G.M.

1992-01-01

261

Mechanisms and kinetics of WC-Co-Cr high velocity oxy-fuel thermal spray coating degradation in corrosive environments  

NASA Astrophysics Data System (ADS)

In this work, aspects of the corrosion behavior of WC-Co-Cr high velocity oxy-fuel (HVOF) thermal spray coatings have been assessed using a combination of x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to understand the corrosion mechanisms and, in particular, the electrochemical interactions between phases. Direct curent electrochemical accelerated corrosion techniques (potentiodynamic and potentiostatic tests) were performed to evaluate the corrosion kinetics of the coating. After the corrosion tests, the solution was analyzed using the inductively coupled plasma (ICP) technique, and a considerable amount of dissolved tungsten was detected. By combining information from XPS, SEM, ICP, and anodic polarization results, it is possible to propose a number of key reactions that can take place during WC-Co-Cr coating degradation, thus enabling the susceptible components of the coating to be identified. The implications of these findings for coating durability are discussed.

Souza, V. A. D.; Neville, A.

2006-03-01

262

Protection by DIGAZFEN-I hydrogen-sulfide corrosion inhibitor  

SciTech Connect

The performance of the new DIGAZFEN-I inhibitor for hydrogen sulfide corrosion in saline-hydrocarbon media, including the components (pyridine bases and fatty-acid aminoethers), was tested. Inhibition was determined gravimetrically on steel St3 in 3% NaCl solution and A-72 gasoline containing 1.5-2 g/liter hydrogen sulfide. Hydrogenation was determined indirectly from the plasticity changes in U9A steel strip specimens which were subsequently tested to failure. In parallel, potentiostatic measurements were made in 3% NaCl saturated with hydrogen sulfide with Armco iron. The inhibitor increased the hydrogen overvoltage and reduced the dissolution current while it also retarded both the anodic and cathodic processes.

Voloshin, V.F.; Golosova, O.P.; Mazalevskaya, L.A.; Bakumenko, V.S.; Sheinkman, A.K.

1988-07-01

263

Critical phenomena in magnetic nanowires.  

PubMed

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

Kamalakar, M Venkata; Raychaudhuri, A K

2009-09-01

264

Kinetics of the transpassive oxidation of pyrite. Technical progress report, July 1, 1992--October 20, 1992  

SciTech Connect

In the transpassive region, about 0.4 to 0.8 V (SCE), aggressive oxidation of pyrite occurred. The reaction products in this region were Fe(III) oxide, sulfate ion and partially oxidized sulfur intermediates. The growth kinetics of the reaction of pyrite were studied using chronoamperometry measurement with both stationary and rotating disk electrodes. The effect of electrode rotation speed, solution pH and temperature were examined. Potentiostatic measurements were well correlated by a paralinear rate equation, suggesting the formation of an intermediate passive film, associated with the simultaneous dissolution of the outer layer of the film. Activation energies of 66.17 kJ/mole (15.83 kcal/mole) and 38.67 kJ/mole (9.25 kcal/mole) were obtained for associated parabolic and linear rate constants respectively, at an applied potential of 0.6 V.

Hu, Weibai; Huang, Qinping; Zhu, Ximeng; Li, Jun; Bodily, D.M.; Wadsworth, M.E.

1992-12-31

265

A low-power wide range transimpedance amplifier for biochemical sensing.  

PubMed

This paper presents a novel low voltage and low power transimpedance amplifier for amperometric potentiostats. The power is optimized by having three different gain settings for different current ranges, which can be programmed with a biasing current. The voltage ranges have been optimized by using FGMOS transistors in a second voltage amplification stage that simultaneously allow for offset calibration as well as independent biasing of the gates. The circuit operates with input currents from 1 pA to 1 microA, with a maximum power supply voltage of 1.5 V and consumes 82.5 nW, 9.825 microW, 47.325 microW for currents varying from (1 pA, 0.25 nA), (0.25 nA, 62.5 nA) and (62.5 nA, 1 microA) respectively. PMID:18002545

Rodriguez-Villegas, Esther

2007-01-01

266

Characterization of blister formation and pitting of tungsten ion implanted aluminum  

SciTech Connect

the application of W implantation to Al1100 has resulted in improved resistance to pitting corrosion in a neutral pH, 1 wt% NaCl solution. Doses ranging from 3 {times} 10{sup 16} to 9 {times} 10{sup 16} ions/cm{sup 2} greatly enhanced the range of passivity during anodic polarization, and potentiostatic and immersion testing results indicated the implanted W acts to resist the growth of a nucleated pit. Although moderate increases in the pitting potential of Al 1100 (and also 99.9999% pure Al) have been realized, the extremely high pitting potentials achieved by co-sputtering thin films of Al and W were not reproducibly translated to bulk aluminum alloys. This discrepancy can possibly be traced to the morphology of the localized corrosion and breakdown of the passive film on ion-implanted Al, which takes the form of oxide blistering as a forerunner of pit growth.

Smith, P.P.; Buchanan, R.A. [Univ. of Tennessee, Knoxville, TN (United States); Williams, J.M. [Oak Ridge National Lab., TN (United States)

1995-06-15

267

Mixed LiCo(0.6)M(0.4)PO(4) (M = Mn, Fe, Ni) phosphates: cycling mechanism and thermal stability.  

PubMed

The electrochemical delithiation of LiCo(0.6)M(0.4)PO(4) phosphates (M = Mn, Fe, Ni) was studied by in situ synchrotron diffraction. In all three metallophosphates the oxidation-reduction of 3d-elements proceed via two-phase mechanisms leading to two-phase regions, corresponding to the Co(2+)/Co(3+) and M(2+)/M(3+) reactions. The Ni(2+)/Ni(3+) reaction was not revealed, neither by the potentiostatic intermittent titration technique (PITT) nor by diffraction. In the two-phase reaction, the olivine-like structure of the cathode remains preserved, which is characteristic of this type of materials. Pronounced solid-solution domains were observed during both lithium extraction and insertion. The thermal stability of the charged cathodes is limited by the presence of Co(3+) and its intrinsic instability in these compounds. PMID:19370224

Bramnik, Natalia N; Trots, Dmytro M; Hofmann, Heiko J; Ehrenberg, Helmut

2009-03-09

268

Anodic dissolution of chromium in acid ethanol solutions  

SciTech Connect

The purpose of this work was to study the kinetics of the anodic dissolution of cast and hardened chromium with a purity of 99.9% in ethanol solutions of hydrogen chloride, containing various additions of water (up to 20%). The kinetics of anodic dissolution of chromium was studied at 20/sup 0/C in a hydrogen atmosphere by potentiostat polarization of stationary and rotating disk electrodes with exposure at each potential for 2 min and increments of 20 mV. The authors postulate that in anhydrous solutions on account of the basic properties of water with respect to ethanol, only alcohol molecules participate in the process; in aqueous alcohol solutions there is a parallel ionization with the participation of both solvents, but with substantially different values of the rate constants of the corresponding processes.

Tsygankova, L.E.; Vigdorovich, V.I.

1985-09-01

269

Current-limited imposed-potential technique for inducing and monitoring metastable pitting events  

SciTech Connect

A technique has been developed to selectively induce metastable pitting while preventing the transition to stable pit growth. The current-limited imposed-potential (CLIP) technique limits available cathodic current to an initiated site using a resistor in series with the working electrode to form a voltage divider. Potentiodynamic CLIP testing yields a distribution of breakdown potentials from a single experiment. Potentiostatic CLIP testing yields induction time data, which can be used as input to a calculation of germination rate. Initial data indicate that a one-to-one correlation exists between electrochemical transients and observed pitting sites. The CLIP technique provides a consistent means of gathering quantitative potential and current transients associated with localized oxide breakdown.

Wall, F.D.

1999-11-24

270

An economical and convenient experiment setup for electrode investigation.  

PubMed

Electrodes are among the critical components of neural stimulation devices. Investigating electrode properties like electrode impedance, charge injection capacity, and electrode corrosion limits plays an important role in electrode development. There are many commercial devices available for this purpose. Although useful, these devices are usually expensive and often offer more functions than required. We propose a versatile setup, composed of a LabVIEW program, a National Instruments multifunctional board, and a circuit built of discrete commercial elements. The system offers basic functions used in electrochemical investigation like current and voltage injection, cyclic voltammetry, and impedance spectroscopy. It offers the functionalities of both a potentiostat and an arbitrary waveform generator. It has already been applied elsewhere. PMID:23366017

Aryan, Naser Pour; Rieger, Viola; Brendler, Christian; Rothermel, Albrecht

2012-01-01

271

Engineering PQS biosynthesis pathway for enhancement of bioelectricity production in pseudomonas aeruginosa microbial fuel cells.  

PubMed

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

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

2013-05-20

272

In Situ Characterization of Triboelectrochemical Effects on Topography of Patterned Copper Surfaces  

NASA Astrophysics Data System (ADS)

The topographic response of patterned copper surfaces to chemical-mechanical polishing (CMP) was investigated using a triboelectrochemical approach. Experimental methods include using a combined system containing a tribometer and a potentiostat. Results showed that more step height reduction and lower average surface roughness were obtained via CMP in acidic than in alkaline slurry. The increased contact area between wafer, pad, and abrasives was associated with the increase in friction. It was found that pH-dependent oxide formation and removal dominate the step height reduction for both acidic and alkaline slurries. The in situ approach pinpointed interactions between mechanical stimulation, chemical reaction, and electrochemical passivation. This research is beneficial to understanding triboelectrochemistry in Cu chemical-mechanical polishing of patterned wafers, an important application in semiconductor manufacturing.

Joo, Sukbae; Liang, Hong

2013-06-01

273

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

PubMed

Three-dimensional TiO2 with tunable morphology and crystalline phase was successfully prepared by the electrospinning technique and subsequent annealing. Porous-shaped anatase TiO2, cluster-shaped anatase TiO2, hierarchical-shaped rutile (minor) TiO2 and nano-necklace rutile (major) TiO2 were achieved at 500, 600, 700 and 800 C, respectively. The mechanism of the formation of these tailored morphologies and crystallinity was investigated. Lithium insertion properties were evaluated by galvanostatic and potentiostatic modes in half-cell configurations. By combining the large surface area, open mesoporosity and stable crystalline phase, the porous-shaped anatase TiO2 exhibited the highest capacity, best rate and cycling performance among the four samples. The present results demonstrated the usefulness of three-dimensional TiO2 as an anode for lithium storage with improved electrode performance. PMID:24056926

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

2013-09-06

274

A high precision CMOS weak current readout circuit  

NASA Astrophysics Data System (ADS)

This paper presents a high precision CMOS weak current readout circuit. This circuit is capable of converting a weak current into a frequency signal for amperometric measurements with high precision and further delivering a 10-bit digital output. A fast stabilization-enhanced potentiostat has been proposed in the design, which is used to maintain a constant bias potential for amperometric biochemical sensors. A technique based on source voltage shifting that reduces the leakage current of the MOS transistor to the reverse diode leakage level at room temperature was employed in the circuit. The chip was fabricated in the 0.35 ?m chartered CMOS process, with a single 3.3 V power supply. The interface circuit maintains a dynamic range of more than 100 dB. Currents from 1 pA to 300 nA can be detected with a maximum nonlinearity of 0.3% over the full scale.

Qisong, Wu; Haigang, Yang; Tao, Yin; Chong, Zhang

2009-07-01

275

Light addressable potentiometric sensor with an array of sensing regions  

NASA Astrophysics Data System (ADS)

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.

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

2001-09-01

276

Electrochemical behavior of superconducting Bi{sub 1.4}Pb{sub 0.6}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} in halide-containing acetate buffer  

SciTech Connect

Electrochemical responses of Bi{sub 1.4}Pb{sub 0.6}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} in various buffered halide solutions were studied. Electrochemical surface alterations in the anodic and cathodic potentials were investigated by x-ray diffraction of the surfaces after potentiostatic exposures in the different media. The principal electrochemical reactions involved in alteration of the surface of the superconductor were identified by considering its potentiodynamic response as well as the post-exposure surface constitution. Formation and stability of bismuth and bismuth trioxide were found to be significant in deciding the surface composition after electrochemical exposure in acetate buffer and buffers containing chloride and fluoride. The electrochemical process was controlled by chemical reaction and diffusion in the presence of iodide.

Chattoraj, I.; Pathak, L.C. [National Metallurgical Lab., Jamshedpur (India)

1998-06-01

277

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

Microsoft Academic Search

The inhibiting effect of some Schiff basesN,N?-o-phenylen-bis(3-methoxy-salicylidenimine) (VophV), N-2-hydroxyphenyl-(3-methoxy-salicylidenimine) (Vbso), N-4-phenylcarbazide-(3-methoxy-salicylidenimine) (Vpsd) N,N?-o-phenylen-bis(salicylidenimine) (SophS), N,N?-p-phenylen-bis(salicylidenimine) (SpphS), N-4-phenylcarbazide-(salicylidenimine) (Spsd) on the corrosion of copper in 1.0M NaCl solutions, under various conditions, has been studied by means of the potentiostatic polarization method and the AC impedance technique.In order to study the ability of quantum chemistry to select corrosion inhibitors, quantum chemical calculations

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

1999-01-01

278

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

PubMed Central

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

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

2013-01-01

279

Corrosion resistance of polyurethane-coated nitinol cardiovascular stents.  

PubMed

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

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

2003-01-01

280

Cooperative stochastic behavior in localized corrosion. 2: Experiments  

SciTech Connect

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.

Lunt, T.T.; Pride, S.T.; Scully, J.R.; Hudson, J.L. [Univ. of Virginia, Charlottesville, VA (United States); Mikhailov, A.S. [Max-Planck-Gesellschaft, Berlin (Germany). Fritz-Haber-Institut

1997-05-01

281

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

282

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

PubMed

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

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

2010-11-21

283

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

NASA Astrophysics Data System (ADS)

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.

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

2010-05-01

284

Distinguishing nanowire and nanotube formation by the deposition current transients.  

PubMed

High aspect ratio Ni nanowires (NWs) and nanotubes (NTs) were electrodeposited inside ordered arrays of self-assembled pores (approximately 50?nm in diameter and approximately 50??m in length) in anodic alumina templates by a potentiostatic method. The current transients monitored during each process allowed us to distinguish between NW and NT formation. The depositions were long enough for the deposited metal to reach the top of the template and form a continuous Ni film. The overfilling process was found to occur in two steps when depositing NWs and in a single step in the case of NTs. A comparative study of the morphological, structural, and magnetic properties of the Ni NWs and NTs was performed using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively. PMID:22650765

Proenca, Mariana P; Sousa, Clia T; Ventura, Joo; Vazquez, Manuel; Araujo, Joo P

2012-05-31

285

Electrochemical overcharge protection of rechargeable lithium batteries: II. Effect of lithium iodide-iodine additives on the behavior of lithium electrode in LiAsF/sub 6/-tetrahydrofuran solutions  

SciTech Connect

The effect of lithium iodide-iodine additives on the anodic and cathodic behavior of lithium in 1.5M LiAsF/sub 6//tetrahydrofuran (THF) solution has been investigated with the rotating disk and potentiostatic transient techniques. The formation of a passive film on the lithium surface at anodic potentials were found to allow a dissolution-precipitation mechanism. The addition of LiI-I/sub 2/ to the electrolyte decreased the stability of the passive film and increased the rate of lithium dissolution at the passive potentials. At the active anodic dissolution potentials as well as in the cathodic polarization regime, the current-potential relation of the lithium electrode was not affected by the presence of iodide-iodine additives in the electrolyte.

Behl, W.K.; Chin, D.T.

1988-01-01

286

Surface phenomena of hydroxyapatite film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants.  

PubMed

In this study, surface phenomena of hydroxyapatite (HA) film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants have been investigated by electron beam physical vapor deposition (EB-PVD), field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), potentiostat and contact angle. The microstructure of Ti-29Nb-xZr alloys exhibited equiaxed structure and alpha" phase decreased, whereas beta phase increased as Zr content increased. The increment of Zr contents in HA coated nanotubular Ti-29Nb-xZr alloys showed good corrosion potential in 0.9% NaCI solution. The wettability of HA coated nanotubular surface was higher than that of non-coated samples. PMID:23755573

Kim, Eun-Ju; Jeong, Yong-Hoon; Choe, Han-Cheol

2013-03-01

287

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

NASA Astrophysics Data System (ADS)

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.

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

2012-09-01

288

Current drain to cathodically protected stainless steels in seawater  

SciTech Connect

This paper describes tests conducted on small test panels in order to determine the current drain to cathodically protected stainless steels in seawater. The tests consisted of galvanostatic and potentiostatic polarization as well as galvanic coupling to sacrificial anodes. Cyclic polarization curves were recorded for some test samples. The steels investigated were AISI (13% chromium), AISI 316, ''Duples,'' and a high-alloyed 6% molybdenum steel. A reference sample of carbon steel was also included in the polarization tests. When polarized to -800mV and below vs Ag/AgCl/seawater reference electrode, the stainless steels require the same or slightly more current than carbon steels. With present cathodic protection design practices, stainless steel surfaces should be included in the total surface area and the same design current applied to all.

Lye, R.E. (Norsk Hydro, Research Centre, N-3900 Porsgrunn (NO))

1988-10-01

289

Efficient photoelectrochemical water splitting by anodically grown WO3 electrodes.  

PubMed

The potentiostatic anodization of metallic tungsten has been investigated in different solvent/electrolyte compositions with the aim of improving the water oxidation ability of the tungsten oxide layer. In the NMF/H(2)O/NH(4)F solvent mixture, the anodization leads to highly efficient WO(3) photoanodes, which, combining spectral sensitivity, an electrochemically active surface, and improved charge-transfer kinetics, outperform, under simulated solar illumination, most of the reported nanocrystalline substrates produced by anodization in aqueous electrolytes and by sol-gel methods. The use of such electrodes results in high water electrolysis yields of between 70 and 90% in 1 M H(2)SO(4) under a potential bias of 1 V versus SCE and close to 100% in the presence of methanol. PMID:21542603

Cristino, Vito; Caramori, Stefano; Argazzi, Roberto; Meda, Laura; Marra, Gian Luigi; Bignozzi, Carlo Alberto

2011-05-04

290

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

NASA Astrophysics Data System (ADS)

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

Nam, Nguyen Dang; Kim, Jung-Gu

2008-08-01

291

Macromolecules for inhibition of corrosion and wear. Progress report  

SciTech Connect

The phthalocyanines and Schiff base compounds are uniquely qualified inhibitors for corrosion. They are high electron density molecules for interaction with the metal surface, and possess large spatially arranged structures to serve as environmental barriers. Additionally, these compounds do stack-up as layered structures which provides shear planes, thus serving as lubricants. A number of these compounds have been synthesized and studied. Both electrochemical impedance spectroscopic and potentiostatic polarization techniques were used to determine their corrosion inhibition efficiencies. Wear studies were made using grease lubricated stainless steel miniature bearings. The results have shown that Schiff base compounds can be good additives for greases as they enhance wear life of bearings and inhibit corrosion by at least and order of magnitude. Although phthalocyanines, both monomers and polymers, provided a significant corrosion inhibition efficiencies (> 90%), they were not effective lubricants compared to the Schiff bases.... Schiff Base, Phthalocyanine, Additives, Fluorinated grease.

Conte, A.A.; Agarwala, V.S.

1992-12-14

292

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

PubMed

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

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

2013-06-01

293

Electropolymerization of pyrrole in the presence of fluoborate  

SciTech Connect

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

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

1982-08-01

294

Electrodeposited Ag nanoparticles on TiO2 nanorods for enhanced UV visible light photoreduction CO2 to CH4  

NASA Astrophysics Data System (ADS)

We employed the double-potentiostatic methodology to electrodeposit Ag nanoparticles on oriented single-crystalline rutile TiO2 nanorods synthesized by hydrothermal method. The synthesized composites were used as the photocatalyst to reduce CO2 to CH4 under UV irradiation, and tested by SEM, XRD, TEM, XPS, UV-vis and photoluminescence. Deposition with Ag nanoparticles was observed to enhance the photocatalytic activity (?1.5-2.64 ?mol (gcatal h)-1) up to 5 times with respect to undecorated TiO2 nanorods (?0.5 ?mol (gcatal h)-1). The increase in the CH4 yield was correlated with the surface morphology and structure of TiO2 nanorods.

Kong, Dan; Tan, Jeannie Ziang Yie; Yang, Fei; Zeng, Jieliang; Zhang, Xiwen

2013-07-01

295

High frequency reference electrode  

DOEpatents

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.

Kronberg, J.W.

1994-05-31

296

Electrochemical behavior of CrN coating for polymer electrolyte membrane fuel cell  

NASA Astrophysics Data System (ADS)

CrN films on a bipolar plate in polymer electrolyte membrane fuel cells have several advantages owing to their excellent corrosion resistance and mechanical properties. Three CrN samples deposited at various radio frequency (RF) powers by RF magnetron sputtering were evaluated under potentiodynamic, potentiostatic and electrochemical impedance spectroscopy conditions. The electrochemical impedance spectroscopy data were monitored for 168 h in a corrosive environment at 70 C to determine the coating performance at +600 mVSCE under simulated cathodic conditions in a polymer electrolyte membrane fuel cell. The electrochemical behavior of the coatings increased with decreasing RF power. CrN films on the AISI 316 stainless steel substrate showed high protective efficiency and charge transfer resistance, i.e. increasing corrosion resistance with decreasing RF power. X-ray diffraction confirmed the formation of a CrN(200) preferred orientation at low RF power.

Nam, N. D.; Park, I. J.; Kim, J. G.; Tai, P. H.; Yoon, D. H.

2010-05-01

297

Sputtered TiN thin films for improved corrosion resistance  

NASA Astrophysics Data System (ADS)

The general corrosion characteristics of TiN thin films deposited onto type 304 and 316 stainless steel by RF sputtering from a compound TiN target was investigated. In general, TiN film morphology and stoichiometry can vary considerably from film to film depending on deposition parameters and thus can play a major role in the corrosion behaviors of these films. Parametric models of the sputtering process were developed using statistial methods for design and analysis and studying the influence of a combination of variables on the properties of the TiN. The process parameters included RF power, N 2 partial presure, total gas pressure, substrate temperature and bias. A number of optimum conditions based on different responses were selected and corrosion testing of these films was carried out potentiostatically in 0.1N HCI and 0.1M NaCl solutions at 25C.

Bhardwaj, P.; Gregory, O. J.; Bragga, K.; Richman, M. H.

1991-06-01

298

Electro-Mechanical Actuation of Carbon Nanotube Yarns, Sheets, Composites  

NASA Astrophysics Data System (ADS)

We report preparation of highly conductive carbon nanotube yarns and sheets. The materials aim at such applications as electronic textiles, electro-mechanical actuators, and conductive coatings. The electro-mechanical response of the specimens was measured using custom made force transducer operating in an isometric mode. The measurements were carried out at room temperature in aqueous and organic electrolytes; square-wave potential of variable amplitude was applied with a potentiostat. It was found that the maximum isometric stress generated by nanotube actuators could be as large as 12 MPa. This approaches the stress generation capability of commercial ferroelectrics and is significantly larger than that of natural muscles. A variety of applications of the materials is discussed.

Oh, Jiyoung; Kozlov, Mikhail; Zhang, Mei; Fang, Shaoli; Baughman, Ray

2011-03-01

299

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

NASA Astrophysics Data System (ADS)

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

Winkler, Gates R.; Winkler, Jay R.

2011-11-01

300

Synergy effect over electrodeposited submicron Cu2O films in photocatalytic degradation of methylene blue  

NASA Astrophysics Data System (ADS)

In the study, we report a simple method to fabricate semiconductor Cu2O films by using a potentiostatic method. The obtained thin films have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM). The obtained Cu2O films are composed of submicron particles with sizes in the range from tens to several hundreds of nanometers. The photocatalytic activity over the Cu2O films was investigated under simulated solar light. A strong synergy effect between H2O2 and Cu2O films in the photocatalytic degradation of methylene blue has been observed. The binary H2O2/Cu2O systems exhibit high catalytic ability under the solar irradiation. The results show that Cu2O films can be used as a reliable platform for environmental remediation by using solar energy.

Xu, Ling; Xu, Haiyan; Wu, Shibiao; Zhang, Xinyi

2012-03-01

301

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

PubMed

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

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

302

Electrochemical removal of tannins from aqueous solutions  

SciTech Connect

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.

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

2000-02-01

303

High frequency reference electrode  

DOEpatents

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.

Kronberg, J.W.

1991-03-05

304

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

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

305

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

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

306

Distinguishing nanowire and nanotube formation by the deposition current transients  

PubMed Central

High aspect ratio Ni nanowires (NWs) and nanotubes (NTs) were electrodeposited inside ordered arrays of self-assembled pores (approximately 50?nm in diameter and approximately 50??m in length) in anodic alumina templates by a potentiostatic method. The current transients monitored during each process allowed us to distinguish between NW and NT formation. The depositions were long enough for the deposited metal to reach the top of the template and form a continuous Ni film. The overfilling process was found to occur in two steps when depositing NWs and in a single step in the case of NTs. A comparative study of the morphological, structural, and magnetic properties of the Ni NWs and NTs was performed using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively.

2012-01-01

307

Comparison between several methods for determining the depassivation threshold value for corrosion onset  

NASA Astrophysics Data System (ADS)

Numerous studies have been already carried out to study the chloride threshold value for depassivation of the steel embedded in concrete. Most of them were based on natural penetration of chlorides, whose main disadvantage is that it is very time consuming and makes necessary a long time to obtain reliable data. Other methods used are the potentiostatic tests that, depending on the potential applied, may also take very long. Recently, an accelerated method to determine the threshold value of corrosion of steel by application of electrical fields has been developed. In this paper, results obtained, for the same concrete, using every method are given as well as a comparison of the advantages and drawbacks of each of them.

de Viedma, P. G.; Castellote, M.; Andrade, C.

2006-11-01

308

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

NASA Astrophysics Data System (ADS)

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

Bhrara, Kalpana; Singh, Gurmeet

2006-11-01

309

Khillah extract as inhibitor for acid corrosion of SX 316 steel  

NASA Astrophysics Data System (ADS)

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.

El-Etre, A. Y.

2006-10-01

310

Giant cationic polyelectrolytes generated via electrochemical oxidation of single-walled carbon nanotubes.  

PubMed

Previously, reduced single-walled carbon nanotube anions have been used for effective processing and functionalization. Here we report individually separate and distinct (that is, discrete) single-walled carbon nanotube cations, directly generated from a pure anode using a non-aqueous electrochemical technique. Cyclic voltammetry provides evidence for the reversibility of this nanoion electrochemisty, and can be related to the complex electronic density of states of the single-walled carbon nanotubes. Fixed potentiostatic oxidation allows spontaneous dissolution of nanotube cations ('nanotubium'); Raman spectroscopy and transmission electron microscopy show that sequential fractions are purified, separating amorphous carbon and short, defective single-walled carbon nanotubes, initially. The preparation of nanotubium, in principle, enables a new family of nucleophilic grafting reactions for single-walled carbon nanotubes, exploited here, to assemble nanotubes on amine-modified Si surfaces. Other nanoparticle polyelectrolyte cations may be anticipated. PMID:23764646

Hodge, Stephen A; Bayazit, Mustafa K; Tay, Hui Huang; Shaffer, Milo S P

2013-01-01

311

Surface Morphology of Si(111) during Electrochemical Oxidation  

NASA Astrophysics Data System (ADS)

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

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

1997-03-01

312

Correlation of dental amalgam crevice corrosion with clinical ratings.  

PubMed

In vitro corrosion behavior of gamma 2-containing and gamma 2-free dental amalgams was examined under crevice conditions which simulated the amalgam-tooth interface. By means of potentiostatic testing, current-density/time behavior and integrated anodic current were measured for 16 hr. All of the amalgams demonstrated crevice corrosion susceptibility. Crevice corrosion propagation for gamma 2-free vs. gamma 2-containing amalgams was characterized by lower acceleration and maximum rates during the most dynamic period. Integrated anodic current results were correlated with marginal breakdown ratings reported in two clinical investigations. Strong and significant coefficients were found between integrated current and marginal breakdown ratings when gamma 2-containing and gamma 2-free amalgams were correlated as a single group, but not when correlated separately. PMID:2918139

Sutow, E J; Jones, D W; Hall, G C

1989-02-01

313

Corrosion of titanium/cobalt-chromium alloy couples.  

PubMed

Because of the increasing use of dissimilar metal combinations in the human body, we undertook an in vitro study to determine the compatibility and tendency to accelerate crevice corrosion of galvanic couples of cobalt-chromium alloy with either titanium, titanium alloy, or stainless steel. We employed an electrochemical open-circuit potential measurement test and a potentiostatic passive film-corrosion measurement test. The results demonstrated that the chromium alloy/stainless-steel couple was unstable. The cobalt-chromium alloy/titanium alloy couple was stable. Clinical Relevance: Cobalt-chromium alloys should not be used in combination with stainless steel but may be used in combination with titanium alloy. All usage of metal couples should be approached with the utmost caution. PMID:6630255

Kummer, F J; Rose, R M

1983-10-01

314

Crevice corrosion products of dental amalgam.  

PubMed

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. PMID:2066490

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

1991-07-01

315

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

NASA Astrophysics Data System (ADS)

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

Mndroiu, Mihaela; Ungureanu, Camelia; Ion, Raluca; Prvu, Cristian

2013-07-01

316

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

317

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

SciTech Connect

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.

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

2009-06-03

318

X-ray diffraction analysis of multilayer porous InP(001) structure  

SciTech Connect

Multilayer structures composed of four porous bilayers have been studied by high-resolution X-ray diffraction using synchrotron radiation, and the photoluminescence of these structures has been investigated at 4 K. The porous structures were formed by anodic oxidation of InP(001) substrates in aqueous HCl solution. The structural parameters of the sublayers were varied by changing the electrochemical etching mode (potentiostatic/galvanostatic). The X-ray scattering intensity maps near the InP 004 reflection are obtained. A model for scattering from such systems is proposed based on the statistical dynamical diffraction theory. Theoretical scattering maps have been fitted to the experimental ones. It is shown that a mathematical analysis of the scattering intensity maps makes it possible to determine the structural parameters of sublayers. The reconstructed parameters (thickness, strain, and porosity of sublayers and the shape and arrangement of pores) are in satisfactory agreement with the scanning electron microscopy data.

Lomov, A. A., E-mail: a.lomov@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Punegov, V. I. [Russian Academy of Sciences, Komi Research Center, Ural Division (Russian Federation); Vasil'ev, A. L. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Nohavica, D.; Gladkov, P. [Academy of Sciences of the Czech Republic, Institute of Photonics and Electronics (Czech Republic); Kartsev, A. A.; Novikov, D. V. [German Electron Synchrotron DESY (Germany)

2010-03-15

319

Platinum particles dispersed poly(diphenylamine) modified electrode for methanol oxidation  

NASA Astrophysics Data System (ADS)

A modified potentiostatic method, termed the pulse pontentiostatic method (PPSM) was used to get nano fibrillar poly(diphenylamine) (PDPA) film on Indium tin oxide (ITO) coated glass electrode and also for making modified electrode with platinum particles dispersed in PDPA. Platinum clusters were electrodispersed under constant potential on PDPA films to obtain catalytic electrodes for methanol oxidation. Energy dispersive analysis of X-rays (EDAX) results showed that the Pt microparticles are deposited into PDPA film. Scanning electron micrograph, SEM images show that the deposition results spherical catalytic particles. X-ray photoelectron spectroscopy (XPS) results inform that the net electronic charge on carbon atom and also the imine/amine ratio was not affected by Pt loadings. The modification of electrode surface by nano fibular PDPA improves the electrocatalytic activity for methanol oxidation.

Santhosh, P.; Gopalan, A.; Vasudevan, T.; Lee, Kwang-Pill

2006-09-01

320

A New PC and LabVIEW Package Based System for Electrochemical Investigations  

PubMed Central

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

Stevic, Zoran; Andjelkovic, Zoran; Antic, Dejan

2008-01-01

321

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

322

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

SciTech Connect

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.

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

2003-08-01

323

Electrodeposition and Characterization of Bismuth Telluride Nanowires  

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

324

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

325

Effect of electrochemical deposition parameters on the synthesis, structure and properties of polyaniline-polypyrrole composite coatings on steel  

NASA Astrophysics Data System (ADS)

Polyaniline-polypyrrole composite coatings were formed on low carbon steel using oxalic acid as electrolyte by aqueous potentiostatic electrodeposition. Potentiostatic method is a powerful technique that can force simultaneous polymerization of both pyrrole and aniline. A passive layer of iron (II) oxalate is deposited on the steel surface prior to the formation of composite coatings. The electrochemical deposition process shows three distinct regimes---dissolution of steel, formation of passive layer and formation of polymeric composite coatings. These three regimes have been studied in depth using spectroscopic techniques and electron microscopy. Quantitative analysis of the Current-time transient (I-t) curves show that the nucleation and growth of the passive layer occur by diffusion controlled 3-D instantaneous nucleation. It has also been shown that the morphology and the chemical structure of the composite coatings depend upon the electrochemical deposition (ECD) parameters. The ECD parameters that affect the formation of the coatings are the applied potential; molar feed ratio of monomers and the reaction time. The development of the composite coatings on steel was studied in depth using Infrared Spectroscopy, Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy. For equimolar feed ratio of monomers (aniline and pyrrole), it was shown that polypyrrole starts to form on the steel surface prior to the incorporation of polyaniline. Corrosion resistance and adhesion strength of the coatings were evaluated using DC polarization tests and Lap Joint tests respectively. It was shown that the electrochemical deposition parameters (molar feed ratio of monomers, applied potential and reaction time) influence the corrosion and adhesion performance of the coatings. In general, polyaniline-polypyrrole composite coatings show much better performance than the homopolymers. Especially, the coatings formed using equimolar feed ratio of monomers showed better results than those formed at all other feed ratios.

Rajagopalan, Ramakrishnan

326

Evidence for slow droplet formation during cubic-to-tetragonal phase transition in Li{sub x}M{sub 2}O{sub 4} spinel  

SciTech Connect

The authors studied the electroanalytical response of Li{sub x}Mn{sub 2}O{sub 4} electrodes around 3 V (vs. Li/Li{sup +}) using slow scan rate cyclic voltammetry (SSCV), potentiostatic intermittent titration technique, and electrochemical impedance spectroscopy. Broad anodic and cathodic peaks of typical 50 to 60 mV half-peak width, and a surprisingly large peak potential separation (ca. 150 mV and higher) appear on the SSCV curves of thin Li{sub x}Mn{sub 2}O{sub 4} electrodes around 3 V (vs. Li/Li{sup +}). The subsequent potentiostatic titrations performed at 10 mV steps revealed quite an unusual response; an increase in the current with time at 2.94 and 3.00 V (vs. Li/Li{sup +}) during discharge and charge, respectively. The above features of the cyclic voltammograms (at slow scan rate) and the current vs. time response can be understood in terms of a phase transition controlled by slow formation of droplets of a new phase in the bulk of the old one. A model describing such a process, based on the refined Frumkin-type sorption isotherm, which relates to both the electronic and the ionic species which participate in the intercalation reaction, is developed. The SSCV curves simulated according to this model agree well with the experimental ones. The authors also show a semiquantitative comparison of the electroanalytical characteristics of Li{sub x}Mn{sub 2}O{sub 4} electrodes around 3 and 4 V (vs. Li/Li{sup +}).

Levi, M.D.; Gamolsky, K.; Aurbach, D.; Heider, U.; Oesten, R.

2000-01-01

327

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

NASA Astrophysics Data System (ADS)

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.

Kim, Won-Gi; Choe, Han-Cheol

2012-01-01

328

Effects of Crystallographic Orientation on Corrosion Behavior of Magnesium Single Crystals  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

329

Real-Time Telemetry System for Amperometric and Potentiometric Electrochemical Sensors  

PubMed Central

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.

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

330

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

PubMed

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

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

2011-09-02

331

System-based approach for an advanced drug delivery platform  

NASA Astrophysics Data System (ADS)

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.

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

2006-04-01

332

Variation of slow strain rate test fracture mode of type 304L stainless steel in 288 C water  

SciTech Connect

Potentiostatic slow strain rate tests (SSRT) were performed to investigate the susceptibility to intergranular stress corrosion cracking (IGSCC) of type 304L (UNS S30403) stainless steel (SS) in 299 C water, focusing on corrosion potential and the degree of sensitization. The degrees of sensitization was examined by means of metallographic observation, double-loop electrochemical potentiokinetic reactivation (DL-EPR) technique, and grain boundary analysis with a transmission electron microscopy. The SSRT fracture mode changed from ductile {r{underscore}arrow} transgranular stress corrosion cracking (TGSCC) {r{underscore}arrow} TGSCC (granulated) {r{underscore}arrow} IGSCC, with increasing corrosion potential, water conductivity, and the electrochemical potentiokinetic reactivation (EPR) value. The IGSCC onset occurred at 375 mV vs. standard hydrogen electrode (SHE) of corrosion potential for type 304L SS with the EPR value > 3%, but it did not occur when the EPR value < 1%. Even though the microstructure exhibited a step structure, slight chromium depletion and the precipitation of Cr{sub 23}C{sub 6} were observed at grain boundaries after sensitization heat treatment. The variation of minimum corrosion potential for IGSCC onset is presented semi-quantitatively, considering the effects of aqueous impurity and degree of sensitization.

Saito, N.; Tsuchiya, Y.; Kano, F.; Tanaka, N.

2000-01-01

333

Corrosion protection and improved cytocompatibility of biodegradable polymeric layer-by-layer coatings on AZ31 magnesium alloys.  

PubMed

Composite coatings of electrostatically assembled layer-by-layer anionic and cationic polymers combined with an Mg(OH)2 surface treatment serve to provide a protective coating on AZ31 magnesium alloy substrates. These ceramic conversion coating and layer-by-layer polymeric coating combinations reduced the initial and long-term corrosion progression of the AZ31 alloy. X-ray diffraction and Fourier transform infrared spectroscopy confirmed the successful application of coatings. Potentiostatic polarization tests indicate improved initial corrosion resistance. Hydrogen evolution measurements over a 2week period and magnesium ion levels over a 1week period indicate longer range corrosion protection and retention of the Mg(OH)2 passivation layer in comparison to the uncoated substrates. Live/dead staining and DNA quantification were used as measures of biocompatibility and proliferation while actin staining and scanning electron microscopy were used to observe the cellular morphology and integration with the coated substrates. The coatings simultaneously provided improved biocompatibility, cellular adhesion and proliferation in comparison to the uncoated alloy surface utilizing both murine pre-osteoblast MC3T3 cells and human mesenchymal stem cells. The implementation of such coatings on magnesium alloy implants could serve to improve the corrosion resistance and cellular integration of these implants with the native tissue while delivering vital drugs or biological elements to the site of implantation. PMID:23684762

Ostrowski, Nicole; Lee, Boeun; Enick, Nathan; Carlson, Benjamin; Kunjukunju, Sangeetha; Roy, Abhijit; Kumta, Prashant N

2013-05-16

334

UV/Vis/NIR Spectroelectrochemistry  

NASA Astrophysics Data System (ADS)

Voltammetric techniques used in electrochemistry monitor the flow of current as a function of potential, time, and mass transport. A huge variety of different experiments are possible, giving information about reaction energies, reaction intermediates, and the kinetics of a process [1-4]. However, additional data are often required and are accessible, in particular, via in situ spectroelectrochemical approaches. By coupling a spectroscopic technique such as UV/Vis/NIR spectroscopy [5, 6] to an electrochemical experiment, a wealth of complementary information as a function of the potential, time, and mass transport is available. In a recently published book dedicated to spectroelectrochemical techniques [7] the diversity of methods and new chemical information obtained is apparent. Both spectroscopic information about short-lived unstable intermediates and spectroscopic information disentangling the composition of complex mixtures of reactants can be obtained. Figure II.6.1 shows a schematic diagram for the case of a computer-controlled potentiostat system connected to a conventional electrochemical cell (working electrode WE, reference electrode RE, counter electrode CE) and simultaneously controlling the emitter and detector of a spectrometer. This kind of experimental arrangement allows the electrochemical and the spectroscopic data to be recorded simultaneously and, therefore, in contrast to the analysis of two independent data sets, direct correlation of data as a function of time and potential is possible.

Neudeck, Andreas; Marken, Frank; Compton, Richard G.

335

Kinetic enhancement in nanoscale electrochemical systems caused by non-normal distributions of the electrode potential  

NASA Astrophysics Data System (ADS)

We have recently shown [Proc. Natl. Acad. Sci. U.S.A. 107, 4528 (2010)] that the discreteness and stochasticity of an electron transfer event on a resistively coupled nanoelectrode causes mesoscopic fluctuations in time of the electrode potential. These fluctuations give rise to a time-average faradaic current density substantially larger than in the macroscopic limit. The deviations result to a large extent from the potentiostatic control, which imposes a constraint on the evolution of the electrode potential that leads to non-normal distributions. The degree of freedom of the electrode potential requires a resistance between nanoelectrode and metallic support. In this article, we study the dependence of the mesoscopic stochastic dynamics on this resistance (assumed to be ohmic). We show that the enhancement of the reaction rate vanishes in both limits, zero and infinite resistance. The distribution of the electrode potential continuously transforms from a normal distribution at infinite resistance (the galvanostatic limit), through a more and more peaked distribution with increasingly important rare events to the deterministic behavior at zero resistance.

Garca-Morales, Vladimir; Krischer, Katharina

2011-06-01

336

Design and applications of an in situ electrochemical NMR cell  

NASA Astrophysics Data System (ADS)

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.

Zhang, Xiaocan; Zwanziger, Josef W.

2011-01-01

337

Porous NiTi surfaces for biomedical applications  

NASA Astrophysics Data System (ADS)

In this study, the NiTi shape memory alloy was surface modified by plasma electrolytic oxidation (PEO) in Na3PO4 with the aim to produce porous NiTi surfaces for biomedical applications. The oxidation was performed potentiostatically and the characteristics of the resultant surfaces were compared with those obtained in NaAlO2/NaPO2H2 under similar conditions.Surfaces with sub-micron sized pores could be produced in Na3PO4 electrolyte at 300 V. The process was accompanied by intense gas evolution and enhanced thermal effects relative to the NaAlO2/NaPO2H2 electrolyte. The EDS analyses revealed the presence of O, Ti, P, Ni, and a Ni/Ti atomic ratio of 0.4 suggesting preferential oxidation of titanium during the process and depletion of Ni from the surface. No crystalline oxide phases were detected by X-ray diffraction (XRD). By comparison, the layers formed in NaAlO2/NaPO2H2 consisted of crystalline Al2O3 and the Ni/Ti atomic ratio was 0.74. Following oxidation, the wettability and surface free energy of NiTi increased significantly.The findings of this study indicate that the PEO process shows potential for expanding the biofunctionality of NiTi.

Huan, Z.; Fratila-Apachitei, L. E.; Apachitei, I.; Duszczyk, J.

2012-04-01

338

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

SciTech Connect

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.

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

2009-08-05

339

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

PubMed

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

Shabalovskaya, Svetlana A

2002-01-01

340

Architecture-dependent surface chemistry for Pt monolayers on carbon-supported Au.  

PubMed

Pt monolayers were grown by surface-limited redox replacement (SLRR) on two types of Au nanostructures. The Au nanostructures were fabricated electrochemically on carbon fiber paper (CFP) by either potentiostatic deposition (PSD) or potential square wave deposition (PSWD). The morphology of the Au/CFP heterostructures, examined using scanning electron microscopy (SEM), was found to depend on the type of Au growth method employed. The properties of the Pt deposit, as studied using X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and cyclic voltammetry (CV), were found to depend strongly on the morphology of the support. Specifically, it was found that smaller Au morphologies led to a higher degree of cationicity in the resulting Pt deposit, with Pt(4+) and Pt(2+) species being identified using XPS and XAS. For fuel-cell catalysts, the resistance of ultrathin catalyst deposits to surface area loss through dissolution, poisoning, and agglomeration is critical. This study shows that an equivalent of two monolayers (ML) is the low-loading limit of Pt on Au. At 1 ML or below, the Pt film decreases in activity and durability very rapidly due to presence of cationic Pt. PMID:21919511

Cheng, Shuang; Rettew, Robert E; Sauerbrey, Marc; Alamgir, Faisal M

2011-10-04

341

Virtual electrochemical nitric oxide analyzer using copper, zinc superoxide dismutase immobilized on carbon nanotubes in polypyrrole matrix.  

PubMed

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 ?M to 1 mM with a detection limit of 0.1 ?M and high sensitivity of 1.1 ?A ?M(-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

Madasamy, Thangamuthu; Pandiaraj, Manickam; Balamurugan, Murugesan; Karnewar, Santosh; Benjamin, Alby Robson; Venkatesh, Krishna Arun; Vairamani, Kanagavel; Kotamraju, Srigiridhar; Karunakaran, Chandran

2012-08-31

342

Two-step electrodeposition construction of flower-on-sheet hierarchical cobalt hydroxide nano-forest for high-capacitance supercapacitors.  

PubMed

A novel flower-on-sheet hierarchical morphology of ?-Co(OH)2 nanostructures was achieved via an easy two-step synthesis strategy. The method is based on first a galvanostatic electrodeposition (GE) of vertically aligned interconnected Co(OH)2 nanosheets to form a branch layer and second a potentiostatic electrodeposition (PE) of Co(OH)2 microflowers on the obtained branch layer from the secondary growth of their sheet-like precursors. The formation mechanism of this special PE time-dependent nanostructure was proposed and their morphology-dependent supercapacitor properties were also investigated. For a given areas mass loading, high specific capacitances of 1822 F g(-1) have been achieved for the electrode obtained after 200 s GE followed by a 300 s PE in a three-electrode configuration, and it maintained 91% of its initial capacity after 1000 constant-current charge/discharge cycles. Even when the discharge current density was increased from 1 to 50 mA cm(-2), the capacitance was still as high as 1499 F g(-1), indicating an excellent rate performance of the fabricated electrodes. The high performances of the electrodes are attributed to the special porous structure, 3D hierarchical morphology, vertical aligned orientation, and low contact resistance between active material and charge collector. PMID:24048435

Yang, Wanlu; Gao, Zan; Ma, Jing; Wang, Jun; Zhang, Xingming; Liu, Lianhe

2013-10-22

343

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

SciTech Connect

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.

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

2004-05-13

344

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

SciTech Connect

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

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

2012-06-12

345

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

PubMed

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. PMID:22129016

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

2011-11-01

346

Low-melting-point titanium-base brazing alloyspart 2: Characteristics of brazing Ti-21Ni-14Cu on Ti-6Al-4v substrate  

NASA Astrophysics Data System (ADS)

Filler metal of a low-melting-point (917 C) Ti-21Ni-14Cu was brazed onto the substrate of Ti-6Al-4V alloy at 960 C for 2,4, and 8 h to investigate the microstructural evolution and electrochemical characteristics of the brazed metal as a function of the period of brazing time. Optical microscopy, scanning and transmission electron microscopy, and x-ray diffractometry were used to characterize the microstructure and phase of the brazed metal; also, the potentiostat was used for corrosion study. Experimental results indicate that diffusion of copper and nickel from the filler metal into the equiaxed a plus intergranular ? structure of Ti-6Al-4V substrate causes the lamellar Widmansttten structure to form. The intermetallic Ti2Ni phase existing in the prior filler metal diminishes, while the Ti2Cu phase can be identified for the metal brazed at 960 C for 2 h, but the latter phase decreases with time. Advantage might be taken from the evidence of faster diffusion of nickel than copper along the ? phase to the substrate. In deaerated Hanks solution, corrosion potential, corrosion current density, and critical potential for active-to-passive transition decrease while the passivation range broadens with the period of brazing time. However, all the brazed metals, immersed for different periods in oxygen-saturated Hanks solution, show similar corrosion behavior, irrespective of the brazing time.

Chang, E.; Chen, C.-H.

1997-12-01

347

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

348

Graphite electrodes as electron donors for anaerobic respiration.  

PubMed

It has been demonstrated previously that Geobacter species can transfer electrons directly to electrodes. In order to determine whether electrodes could serve as electron donors for microbial respiration, enrichment cultures were established from a sediment inoculum with a potentiostat-poised graphite electrode as the sole electron donor and nitrate as the electron acceptor. Nitrate was reduced to nitrite with the consumption of electrical current. The stoichiometry of electron and nitrate consumption and nitrite accumulation were consistent with the electrode serving as the sole electron donor for nitrate reduction. Analysis of 16 rRNA gene sequences demonstrated that the electrodes supplied with current were specifically enriched in microorganisms with sequences most closely related to the sequences of known Geobacter species. A pure culture of Geobacter metallireducens was shown to reduce nitrate to nitrite with the electrode as the sole electron donor with the expected stoichiometry of electron consumption. Cells attached to the electrode appeared to be responsible for the nitrate reduction. Attached cells of Geobacter sulfurreducens reduced fumarate to succinate with the electrode as an electron donor. These results demonstrate for the first time that electrodes may serve as a direct electron donor for anaerobic respiration. This finding has implications for the harvesting of electricity from anaerobic sediments and the bioremediation of oxidized contaminants. PMID:15142248

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

2004-06-01

349

Kinetics and mechanism of electroless deposition of copper  

SciTech Connect

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

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

1996-02-01

350

An electrochemical noise study of tribocorrosion processes of AISI 304 L in Cl- and SO_{4}^{2-} media  

NASA Astrophysics Data System (ADS)

Electrochemical noise measurements were performed to investigate the intrinsically stochastic character of the tribocorrosion process. Unidirectional sliding tests (pin-on-disc) were performed using AISI 304L stainless steel sliding against corundum. Experiments were carried out in Cl- and SO_{4}^{2-} containing media under open-circuit and potentiostatic polarization conditions. The power spectral density (PSD) of the current and potential signals showed a strong dependence on the sliding frequency but did not depend significantly on the normal load between 5 and 20 N. The fluctuations of the tangential and normal loads were also recorded, and a critical comparison between the PSD of the electrochemical response and the PSD of the mechanical solicitation (load) is proposed. At high frequencies (f > 0.1 Hz), the PSD of current or potential fluctuations have significantly different shapes than the PSD of load signals: the electrochemical signal PSD is governed by the dynamic balance between local depassivation and repassivation which only depends on the kinetics of the electrochemical phenomena. For lower frequencies, a plateau is observed for both the electrochemical PSD and the load PSD. The electrochemical signal is then governed by the continuous depassivation induced by sliding which appears as a low frequency component. These results suggest that the electrochemical noise technique investigated in the frequency domain might be a promising electrochemical tool for successfully unfolding tribocorrosion signatures for material parings in sliding-corrosion tests.

Berradja, A.; Dforge, D.; Nogueira, R. P.; Ponthiaux, P.; Wenger, F.; Celis, J.-P.

2006-08-01

351

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

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

Gil, Roberto Alonso; Muoz, Anna Igual

2011-07-28

352

Discrete electrochemical transients of aluminium alloys generated by slurry jet impingement  

NASA Astrophysics Data System (ADS)

Slurry impingement is a type of tribocorrosion resulting from simultaneous mechanical and electrochemical surface degradation. In order to understand the elementary process of slurry impingement and the effect of mechanical damage on passive films, electrochemical responses associated with passive film breakdown by particle impacts and following repassivation were measured during slurry impingement on Al and Al-1wt%Si alloy microelectrodes. Measurements were made using a slurry jet system which consists of a pump, a microelectrode, a potentiostat suited for measurements of fast transients of small currents and a high frequency data acquisition system. Current transients corresponding to separated single particle impacts have been successfully measured. The current transient sharply rises and gradually decays following a high field model of oxide growth. It is shown that pure Al repassivates faster after particle impact than the Al-1 wt% Si alloy. This type of erodent particle had an influence on the apparent repassivation rate of these electrodes, and both Al and Al-1 wt% Si alloy showed slower current decay after the impact of angular SiC particle than after the impact of spheroidal zirconia particle. The SiC particles made deep scars and scratches, and the zirconia particles made shallow depressions.

Akiyama, Eiji; Stratmann, Martin; Hassel, Achim Walter

2006-08-01

353

Exploring electrosorption at iron electrode with in situ surface-enhanced infrared absorption spectroscopy.  

PubMed

Surface-enhanced infrared absorption spectroscopy (SEIRAS) in attenuated total reflection (ATR) configuration has been extended to the Fe electrode/electrolyte interface in neutral and weakly acidic solutions for the first time. The SEIRA-active Fe film electrode was obtained through a potentiostatic electrodeposition of a virtually pinhole-free 40 nm-thick Fe overfilm onto a 60 nm-thick Au underfilm chemically predeposited on the reflecting plane of an ATR Si prism. The infrared absorption for CO adlayer at the Fe film electrode measured with ATR-SEIRAS was enhanced by a factor of larger than 34, as compared to that at a Fe bulk electrode with external infrared absorption spectroscopy in the literature. More importantly, the unipolar band shape enabled the reliable determination of the Stark tuning rates of CO adlayer at Fe electrode. In situ ATR-SEIRAS was also applied to study the electrosorption of a typical corrosion inhibitor benzotriazole (BTAH) on Fe electrode as a function of potential, providing additional spectral information at positive potentials in support of the formation of a polymer-like surface complex Fe(II)(m)(BTA)(n) as the corrosion-resistant layer. PMID:20481439

Huo, Sheng-Juan; Wang, Jin-Yi; Yao, Jian-Lin; Cai, Wen-Bin

2010-06-15

354

Voltage-induced morphological modifications in oocyte membranes containing exogenous K+ channels studied by electrochemical scanning force microscopy.  

PubMed

We report on a novel use of electrochemical scanning force microscopy (SFM) for the investigation of morphological modifications occurring in plasma membranes containing voltage-gated ion channels, on membrane potential variation. Membrane patches of Xenopus laevis oocytes microinjected with exogenous KAT1 cRNA, deposited by a stripping method at the surface of a derivatized gold film in inside-out configuration, have been imaged by SFM in an electrochemical cell. A potentiostat was used to maintain a desired potential drop across the membrane. Performing imaging at potential values corresponding to open (-120 mV) and closed (+20 mV) states for KAT1, morphological differences in localized sample zones were observed. Particularly, cross-shaped features involving a significant membrane portion appear around putative channel locations. The reported approach constitutes the first demonstration of an SPM-based experimental technique suitable to investigate the rearrangements occurring to the plasma membrane containing voltage-gated channels on transmembrane potential variation. PMID:18058826

Alessandrini, Andrea; Gavazzo, Paola; Picco, Cristiana; Facci, Paolo

2008-04-01

355

Parametric study on electrochemical deposition of copper nanoparticles on an ultrathin polypyrrole film deposited on a gold film electrode.  

PubMed

Monoshaped and monosized copper nanostructured particles have been prepared by potentiostatic electrochemical deposition on an ultrathin polypyrrole (PPY) film, electrochemically grown on a Si(100) substrate sputter-coated with a thin gold film or gold-film electrode (GFE). The crystal size and the number density of the copper nanocrystals have been examined by varying several deposition parameters, including the thickness of the gold film, the PPY film thickness, the applied potential, and the Cu2+ and the electrolyte concentrations for copper deposition. Optimal conditions for uniform growth ofnanocrystals well-dispersed on the GFE have been determined, along with insight into the mechanism of crystal growth. A minimum gold film thickness of 80 nm is required to eliminate the effects of the gold-silicon interface. The PPY film thickness and homogeneity principally affect the shape uniformity of the nanocrystals, while the copper deposition potential could be used to regulate the size and number density of the nanocrystals. Both the Cu2+ and electrolyte concentrations are also found to play important roles in controlling the electrodeposition of nanocrystal growth. PMID:15984275

Zhou, X J; Harmer, A J; Heinig, N F; Leung, K T

2004-06-01

356

Electropolymerization of nano-dimensioned polypyrrole micro-ring arrays on gold substrates prepared using submerged micro-contact printing  

NASA Astrophysics Data System (ADS)

Cobaltabisdicarbollide-doped polypyrrole (PPy-[Co(C2B9H11)2]) nanostructures have been produced by directed, potentiostatic electropolymerization using a patterned combination of conducting and insulating thiols (4-aminothiophenol and octadecylmercaptan, respectively). The different conducting characters of both self-assembled monolayers guides the PPy-[Co(C2B9H11)2] deposition over the pattern. In this way we have produced doped, nanostructured annular polypyrrole rings, ~400 nm high and ~200 nm wide at full width-half maximum height. Two processes are thought to affect the polypyrrole growth; primarily, the different conducting characters of the self-assembled thiol monolayers, but also the hydrophobic interactions between the electrolyte and the self-assembled monolayer. The effects of the hydrophobicity of the doping anion were also studied by comparing the microstructures obtained for polypyrrole doped with the lipophilic [Co(C2B9H11)2]- anion and those doped with hydrophilic Cl- and ClO4- anions.

Errachid, Abdelhamid; Caballero, David; Crespo, Eulalia; Bessueille, Franois; Pla-Roca, Mateu; Mills, Christopher A.; Teixidor, Francesc; Samitier, Josep

2007-12-01

357

Simultaneous analysis of dopamine and homovanillic acid by high-performance liquid chromatography with wall-jet/thin-layer electrochemical detection.  

PubMed

Wall-jet/thin-layer amperometric electrochemical detection (ECD) coupled with high-performance liquid chromatography (HPLC) was used here for the simultaneous analysis of dopamine (DA) and homovanillic acid (HVA) at a glassy carbon electrode. Compared with the conventional thin-layer mode and wall-jet mode, the presented wall-jet/thin-layer ECD has the advantages of enhanced capture of electroactive DA and HVA on the working electrode to give enhanced responses and more convenient washing/refreshment of the working electrode surface. Under optimized conditions, the HPLC-ECD calibration curves show good linearity from 0.01 to 100 ?M for DA and HVA, and the limits of detection (LODs) obtained were 1.1 nM for DA and 0.7 nM for HVA which are lower than those obtained with an UV-vis detector and a commercial electrochemical detector. The method was tested on human urine with satisfactory results. The balance of response-signal, signal-background and noise level for our HPLC-ECD system is also discussed. In addition, a demethylation electrooxidation mechanism for HVA is suggested through potentiostatic bulk electrolysis, electrospray ionization-mass spectrometry, fluorescent spectrophotometry and cyclic voltammetry studies. PMID:24116372

Zhou, Yaping; Yan, Hongling; Xie, Qingji; Huang, Siyu; Liu, Jiali; Li, Zou; Ma, Ming; Yao, Shouzhuo

2013-10-10

358

Testing various food-industry wastes for electricity production in microbial fuel cell.  

PubMed

Three food-industry wastes: fermented apple juice (FAJ), wine lees and yogurt waste (YW) were evaluated in combination with two sources of inoculum, anaerobic sludge and garden compost, to produce electricity in microbial fuel cells. Preliminary potentiostatic studies suggested that YW was the best candidate, able to provide up to 250 mA/m(2) at poised potential +0.3V/SCE. Experiments conducted with two-chamber MFCs confirmed that wine lees were definitely not suitable. FAJ was not able to start an MFC by means of its endogenous microflora, while YW was. Both FAJ and YW were suitable fuels when anaerobic sludge or compost leachate was used as inoculum source. Sludge-MFCs had better performance using YW (54 mW/m(2) at 232 mA/m(2)). In contrast, compost-leachate MFCs showed higher power density with FAJ (78 mW/m(2) at 209 mA/m(2)) than with YW (37 mW/m(2) at 144 mA/m(2)) but YW gave more stable production. Under optimized operating conditions, compost-leachate MFCs fueled with YW gave up to 92 mW/m(2) at 404 mA/m(2) and 44 mW/m(2) in stable conditions. PMID:20034785

Cercado-Quezada, Bibiana; Delia, Marie-Line; Bergel, Alain

2010-04-01

359

Coupling EELS/EFTEM Imaging with Environmental Fluid Cell Microscopy  

SciTech Connect

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].

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

2012-01-01

360

Overpotential-Dependent Phase Transformation Pathways  

SciTech Connect

An objective in battery development for higher storage energy density is the design of compounds that can accommodate maximum changes in ion concentration over useful electrochemical windows. Not surprisingly, many storage compounds undergo phase transitions in situ, including production of metastable phases. Unique to this environment is the frequent application of electrical over- and underpotentials, which are the electrical analogs to undercooling and superheating. Surprisingly, overpotential effects on phase stability and transformation mechanisms have not been studied in detail. Here we use synchrotron X-ray diffraction performed in situ during potentiostatic and galvanostatic cycling, combined with phase-field modeling, to reveal a remarkable dependence of phase transition pathway on overpotential in the model olivine Li{sub 1-x}FePO{sub 4}. For a sample of particle size {approx}113 nm, at both low (e.g., <20 mV) and high (>75 mV) overpotentials a crystal-to-crystal olivine transformation dominates, whereas at intermediate overpotentials a crystalline-to-amorphous phase transition is preferred. As particle sizes decrease to the nanoscale, amorphization is further emphasized. Implications for battery use and design are considered.

Y Kao; M Tang; N Meethong; J Bai; W Carter; Y Chiang

2011-12-31

361

The influence of dichromate ions on aluminum dissolution kinetics in artificial crevice electrode cells  

SciTech Connect

Dissolution kinetics for pits and crevices in aluminum and the effect of dichromate ions on the dissolution kinetics were investigated by using artificial crevice electrodes. The aluminum artificial crevice electrodes were potentiostatically polarized over a range of potential in 0.1 M NaCl solution with and without dichromate ions. The anodic dissolution charge, and cathodic charges for the hydrogen and dichromate reduction reactions, were measured. The addition of dichromate ions did not suppress the active dissolution. This indicates that the mechanism of localized corrosion inhibition by dichromates is something other than anodic inhibition of Al dissolution in the pit or crevice environment. The relative amount of local cathodic reactions on Al was increased by the addition of dichromate because of the dichromate reduction. The initial dissolution of aluminum in a crevice was ohmic controlled. From the change in the dissolution current with time, the conductivity of the crevice and potential at the bottom of crevice were estimated. The conductivity and the bottom potential decreased with the ratio of cathodic charge of hydrogen evolution to anodic dissolution charge. The conductivity in the crevice and thus the dissolution current seem to be controlled by hydrogen evolution and only indirectly by dichromate concentration.

Akiyama, E.; Frankel, G.S.

1999-11-01

362

Electrochemical study of resistance to localized corrosion of stainless steels for biomaterial applications  

SciTech Connect

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.

Pan, J.; Karlen, C.; Ulfvin, C.

2000-03-01

363

The electrocatalytic hydrogenation of glucose; 1: Kinetics of hydrogen evolution and glucose hydrogenation on Raney nickel powder  

SciTech Connect

The kinetics of H[sub 2] evolution and glucose reduction to sorbitol was investigated using a batch slurry reactor containing Raney nickel powder catalyst. In the presence and absence of glucose, hydrogen evolution proceeds via a Volmer-Heyrovsky mechanism, with both steps simultaneously rate controlling at low overpotentials and the Volmer reaction rate limiting at high cathodic overvoltages. A kinetic model for the electrocatalytic hydrogenation of glucose with simultaneous H[sub 2] generation was developed and tested. The model contains rate equations for the individual Volmer, Heyrovsky, and glucose hydrogenation steps, a Langmuir adsorption isotherm for glucose, an equation describing the shift in open-circuit potential due to glucose adsorption on the nickel catalyst, and steady-state atomic hydrogen and charge balance relationships. The theory accurately predicted potentiostatic polarization data and glucose hydrogenation rates. The results indicate that the mechanism for sorbitol formation with electrogenerated atomic hydrogen on Raney nickel is the same as that for the high temperature and pressure chemical catalytic hydrogenation process.

Anantharaman, V.; Pintauro, P.N. (Tulane Univ., New Orleans, LA (United States). Dept. of Chemical Engineering)

1994-10-01

364

On the electrochemical formation of Pu-Al alloys in molten LiCl-KCl  

NASA Astrophysics Data System (ADS)

Properties of Pu-Al alloys were investigated in connection with development of pyrochemical methods for reprocessing of spent nuclear fuel. Electroseparation techniques in molten LiCl-KCl are being developed in ITU to group-selectively recover actinides from the mixture with fission products. In the process, actinides are electrochemically reduced on solid aluminium cathodes, forming solid actinide-aluminium alloys. This article is focused on electro-chemical characterisation of Pu-Al alloys in molten LiCl-KCl, on electrodeposition of Pu on solid Al electrodes and on determination of chemical composition and structure of the formed alloys. Cyclic voltammetry and chronopotentiometry were used to study Pu-Al alloys in the temperature range 400-550 C. Pu is reduced to metal in one reduction step Pu3+/Pu0 on an inert W electrode. On a reactive Al electrode, the reduction of Pu3+ to Pu0 occurs at a more positive potential due to formation of Pu-Al alloys. The open circuit potential technique was used to identify the alloys formed. Stable deposits were obtained by potentiostatic electrolyses of LiCl-KCl-PuCl3 melts on Al plates. XRD and SEM-EDX analyses were used to characterise the alloys, which were composed mainly of PuAl4 with some PuAl3. In addition, the preparation of PuCl3 containing salt by carbochlorination of PuO2 is described.

Mendes, E.; Malmbeck, R.; Nourry, C.; Sou?ek, P.; Glatz, J.-P.

2012-01-01

365

Analyses of the genotoxic and mutagenic potential of the products formed after the biotransformation of the azo dye Disperse Red 1.  

PubMed

Azo dyes constitute the largest class of synthetic dyes. Following oral exposure, these dyes can be reduced to aromatic amines by the intestinal microflora or liver enzymes. This work identified the products formed after oxidation and reduction of the dye Disperse Red 1, simulating hepatic biotransformation and evaluated the mutagenic potential of the resultant solution. Controlled potential electrolysis was carried out on dye solution using a Potentiostat/Galvanostat. HPLC-DAD and GC/MS were used to determine the products generated after the oxidation/reduction process. The Salmonella/microsome assay with the strains TA98 and YG1041 without S9, and the mouse lymphoma assay (MLA) using the thymidine kinase (Tk) gene, were used to evaluate the mutagenicity of the products formed. Sulfate 2-[(4-aminophenyl)ethylamino]-ethanol monohydrate, nitrobenzene, 4-nitro-benzamine and 2-(ethylphenylamino)-ethanol were detected. This dye has already being assigned as mutagenic in different cell system. In addition, after the oxidation/reduction process the dye still had mutagenic activity for the Salmonella/microsome assay. Nevertheless, both the original dye Disperse Red 1 and its treated solutions showed negative results in the MLA. The present results suggest that the ingestion of water and food contaminated with this dye may represent human and environmental health problem, due to the generation of harmful compounds after biotransformation. PMID:21907275

Chequer, Farah Maria Drumond; Lizier, Thiago Mescoloto; de Felcio, Rafael; Zanoni, Maria Valnice Boldrin; Debonsi, Hosana Maria; Lopes, Norberto Peporine; Marcos, Ricard; de Oliveira, Danielle Palma

2011-08-30

366

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

PubMed

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

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

2011-01-01

367

Formation of metallic periodic nanostructures by spontaneous oscillation in self-organized electrocrystallization  

NASA Astrophysics Data System (ADS)

A unique electrodeposition system is designed to self-organize metallic periodic nanostructures on the surface of solid substrate, which consists of an ultrathin electrolyte layer about 300 nm in thickness. In this system the metal electrodeposits (copper, cobalt, zinc and silver) are formed robustly on the solid substrate (silicon wafer or glass plate), possess considerably low branching rate, and usually cover with periodic metal/metal oxide nano-nodules. Both potentiostatic and galvanostatic modes can be applied to generate such structures. Following issues are focused in this presentation: (1) The mechanism for the formation of the periodic nanostructures on the filaments; (2) The experimental conditions to control the periodicity of these periodic spatio-temporal structures; (3) The electric properties of this nano-nodules chains. References: [1] Yu-Yan Weng, et al. Phys. Rev. E 73, 051601 (2006) [2] Yuan Wang, Yu Cao, Mu Wang, et al., Phys. Rev. E, 69, 021607 (2004) [3] M. Zhang, et al., Adv. Mater. 16, 409 (2004) [4] S. Zhong, Y. Wang, Mu Wanget al., Phys. Rev. E, 67, 061601 (2003)

Wang, Mu; Peng, Ruwen; Ma, Guobin; Hao, Xiping; Ming, Naiben

2007-03-01

368

Electrochemical behavior of silver sulfide  

SciTech Connect

The electrochemical behavior of silver sulfide in sulfuric acid as well as in nitric acid was studied using electrodes made from synthetic silver sulfide. The primary techniques used were potentiostatic, potentiodynamic, galvanostatic and corrosion cell experiments. The cathodic reaction of silver sulfide produces silver and hydrogen sulfide. This reaction mechanism is a sequential two step charge transfer involving a single electron in each step. Silver ions are produced from silver sulfide upon applying an anodic potential. The dissolution rate of silver sulfide can be so high that the formation of silver sulfate occurs which partially covers the silver sulfide surface and inhibits a further rate increase. The sulfur from the silver sulfide will be oxidized at low overpotentials to elemental sulfur; at high overpotentials, the oxidation to sulfate or bisulfate is observed. The results suggest that the catalysis of chalcopyrite by the addition of silver ions is caused by the formation and subsequent dissolution of silver sulfide leaving a porous layer behind. The understanding of the reaction mechanism of silver sulfide dissolution and its optimization will significantly improve the economic evaluation of industrial processes using the catalyzed leaching of chalcopyrite. The present knowledge of the catalysis indicates that other ions may be substituted for silver ions which would increase the feasibility of hydrometallurgical processes.

Drouven, B.U.E.

1982-01-01

369

Nucleation in electrochemical growth of the Ag(100) crystal face: Determining the nucleus size via the nucleation theorem  

NASA Astrophysics Data System (ADS)

We employ the nucleation theorem for a model-independent determination of the size of the two-dimensional (2D) Ag nucleus with the aid of experimental data for the nucleation-mediated electrochemical growth of the Ag(100) crystal face in aqueous solution of AgNO3 at 318 K. These data are for the stationary rate of 2D nucleation, for the initial portion of the potentiostatic current transient pertaining to atomically smooth face, and for the galvanostatic current corresponding to stationary growth of the face. It turns out that the 2D nucleus is constituted of 17-64 Ag atoms when the overpotential is in the range of 12-22.4 mV. Upon expressing the overpotential in terms of supersaturation, it is found that the experimental data for the size of the 2D Ag nucleus are in conformity with existing simulation data for the size of the 2D nucleus on the (100) face of Kossel crystal (the simulation nucleus contains 1-30 atoms). It is found as well that the Gibbs-Thomson equation of the classical theory of 2D nucleation describes very well the supersaturation dependence of the size of both the Ag and the simulation nucleus.

Kashchiev, Dimo; Bostanov, Vesselin

2007-12-01

370

The effect of oxidizing water on metallic restorations in the mouth: in vitro reduction behavior of oxidizing water.  

PubMed

Mouth-rinsing with oxydized water which contains electrolytically generated chlorine is known to hinder dental plaque formation and growth, but it also accelerates the deterioration of metallic restorations in the mouth. The present work consists of an in vitro study to elucidate the electrochemical reactions involved in the reduction of oxydized water on dental alloys through a systematic investigation of the potentiostatic polarization behavior of dental alloy electrodes. The five dental alloys selected for investigation were gold alloy, gold alloy containing platinum, silver-palladium-gold alloy, conventional amalgam and high copper amalgam. The corrosion potentials of all dental alloy electrodes were shown to be more noble in oxydized water than in 0.1N sodium chloride solution. The potential differences between the corrosion potentials were relatively small in the case of amalgam electrodes. The polarization curves for all of the dental alloy electrodes in oxydized water revealed reduction currents of chlorine, hypochlorous acid, dissolved oxygen and oxonium ion. The reduction of chlorine and hypochlorous acid started at a more noble potential than that of dissolved oxygen. The dental alloys studied, except the amalgams, did not dissolve excessively at the corrosion potentials in oxydized water. PMID:9198335

Nishida, T

1997-03-01

371

Improved kinetics of LiNi(1/3)Mn(1/3)Co(1/3)O2 cathode material through reduced graphene oxide networks.  

PubMed

An electronically conducting 3D network of reduced graphene oxide (RGO) was introduced into LiNi(1/3)Mn(1/3)Co(1/3)O(2) (LNMC) cathode material in a special nano/micro hierarchical structure. The rate test and cycling measurement showed that the hierarchical networks remarkably improve the high rate performance of LNMC electrode for lithium-ion batteries. The effect of RGO conducting networks on kinetic property was investigated by electrochemical impedance spectroscopy (EIS) and potentiostatic intermittent titration (PITT). The EIS results reveal that the RGO network greatly decreases the resistance of lithium batteries, especially the charge transfer resistance which can be attributed to the significantly improved conducting networks. The enhancement of apparent diffusion coefficient by the RGO conducting networks is shown by PITT. The power performance was found to be limited by the electrical conduction in the two-phase region, which can be greatly facilitated by the hierarchical RGO network together with carbon black. The as-obtained LNMC/RGO cathode exhibits an outstanding electrochemical property supporting the design idea of electronically conducting 3D networks for the high-energy and high-power lithium-ion batteries. PMID:22274568

Jiang, Ke-Cheng; Xin, Sen; Lee, Jong-Sook; Kim, Jaekook; Xiao, Xiao-Ling; Guo, Yu-Guo

2012-01-25

372

Electrochemical activity and bacterial diversity of natural marine biofilm in laboratory closed-systems.  

PubMed

Even if a widely shared mechanism actually does not exist, it is now generally accepted that, in aerobic conditions, marine electrochemically active biofilms (MEABs) induce faster oxygen reduction on stainless steel immersed in seawater. This phenomenon has been widely studied, but nearly all the experiments found in literature have been conducted in open-systems (i.e. experimental environments where seawater is constantly renewed). In this work we tried to obtain, in open circuit and potentiostatic conditions, MEABs in different laboratory closed-systems without water renewal (mesocosms), in order to verify the relationship between electrochemical activity and biofilm composition. The diversity of the microbial populations of biofilms obtained by our new kind of approach was examined by the DGGE technique (denaturing gradient gel electrophoresis). MEABs were obtained in all the mesocosms from 2000 to 2 L, showing in some cases electrochemical performances comparable to those of open-systems, and a very high genetic variability. Our DGGE results underline the difficulty in finding a correlation between electrochemical activity and composition of microbial populations. PMID:19481980

Faimali, Marco; Chelossi, Elisabetta; Pavanello, Giovanni; Benedetti, Alessandro; Vandecandelaere, Ilse; De Vos, Paul; Vandamme, Peter; Mollica, Alfonso

2009-05-18

373

Electrochemical Testing of Ni-Cr-Mo-Gd Alloys  

SciTech Connect

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.

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

2005-10-01

374

A new electrochemical sensor for OH radicals detection.  

PubMed

A new, cheap modified electrode for indirect detection of OH radical is described. A glassy carbon (GC) electrode was modified with a polyphenol film prepared by oxidative potentiostatic electropolymerization of 0.05M phenol in 1M H2SO4. The film having a thickness of ~10nm perfectly covered the GC surface and inhibited the charge transfer of many redox species. The degradation of the polyphenol film, that was induced by OH radicals generated by Fenton reaction or by H2O2 photolysis, is the analytical signal and it was evaluated by cyclic voltammetry and chronoamperometry using the redox probe Ru(NH3)6(3+). Some simulations of the kinetics of the reactions occurring in the solution bulk and near the electrode surface were carried out to fully understand the processes that lead to the analytical signal. The modified electrode was used to evaluate the performances of different TiO2-based photocatalysts and the results were successfully compared with those obtained from a traditional HPLC method that is based on the determination of the hydroxylation products of salicylic acid. PMID:24054662

Gualandi, Isacco; Tonelli, Domenica

2013-06-29

375

Low-melting-point titanium-base brazing alloys. Part 2: Characteristics of brazing Ti-21Ni-14Cu on Ti-6Al-4V substrate  

SciTech Connect

Filler metal of a low-melting-point (917 C) Ti-21Ni-14Cu was brazed onto the substrate of Ti-6Al-4V alloy at 960 C for 2, 4, and 8 h to investigate the microstructural evolution and electrochemical characteristics of the brazed metal as a function of the period of brazing time. Optical microscopy, scanning and transmission electron microscopy, and x-ray diffractometry were used to characterize the microstructure and phase of the brazed metal; also, the potentiostat was used for corrosion study. Experimental results indicate that diffusion of copper and nickel from the filler metal into the equiaxed {alpha} plus intergranular {beta} structure of Ti-6Al-4V substrate causes the lamellar Widmanstaetten structure to form. The intermetallic Ti{sub 2}Ni phase existing in the prior filler metal diminishes, while the Ti{sub 2}Cu phase can be identified for the metal brazed at 960 C for 2 h, but the latter phase decreases with time. Advantage might be taken from the evidence of faster diffusion of nickel than copper along the {beta} phase to the substrate. In deaerated Hank`s solution, corrosion potential, corrosion current density, and critical potential for active-to-passive transition decrease while the passivation range broadens with the period of brazing time. However, all the brazed metals, immersed for different periods in oxygen-saturated Hank`s solution, show similar corrosion behavior, irrespective of the brazing time.

Chang, E.; Chen, C.H. [National Cheng-Kung Univ., Tainan (Taiwan, Province of China). Dept. of Materials Science and Engineering

1997-12-01

376

Fabrication of free-standing Cu nanorod arrays on Cu disc by template-assisted electrodeposition  

NASA Astrophysics Data System (ADS)

Free-standing Cu nanorod arrays on Cu foil have been fabricated by a template-assisted method. Cu nanorods were potentiostatically deposited on mechanically polished Cu foil using anodized aluminum oxide templates as the deposition mask. Three electrolyte systems were compared, including two acid copper sulfate based solutions and one alkaline solution. The most uniform nanorods were achieved in the alkaline electrolyte. The weight gain per unit area after electrodeposition has been used as a direct measure of average length of deposited Cu nanorods. It was found that our control over the uniformity in nanorod length across the array is important in reaching the maximized aspect ratio without aggregation. Through controlling the weight change it was possible to control the aspect ratio of nanorods and to avoid aggregation of nanorods. Our capability to fabricate free-standing Cu nanorod arrays of uniform height with maximized aspect ratio on Cu foil is especially important in applying this nanostructured Cu as a current collector in Li ion batteries.

Chen, Xiangping; Duan, Huanan; Zhou, Zhentao; Liang, Jianyu; Gnanaraj, Joe

2008-09-01

377

Study of the reaction of lithium with isostructural A{sub 2}B and various Al{sub x}B alloys  

SciTech Connect

The electrochemical alloying reaction of Li with isostructural A{sub 2}B and Al-based alloys has been investigated. The binary A{sub 2}B alloys the authors selected (Sb{sub 2}Ti, Sb{sub 2}V, Sn{sub 2}Co, Sn{sub 2}Mn, Sn{sub 2}Fe, Al{sub 2}Cu, and Ge{sub 2}Fe) are isostructural (Al{sub 2}Cu type) and comprise an active element (A) that alloys with lithium, and an inactive one (B) that does not. These compounds were prepared by mechanical alloying and have small grain size (10--20 nm). With the exception of Al{sub 2}Cu, the authors observed a full reaction of A with lithium (A{sub 2}B + 2xLi {yields} B + 2Li{sub x}A, where the theoretical values of x are 1 for Al, 3 for Sb, and 4.4 for Si, Ge, and Sn). Extremely slow electrochemical cycling at 55 C and potentiostatic tests at lithium potential proved the total inactivity of the Al{sub 2}Cu vs. lithium. However, thermodynamic considerations predict that the reaction of Al{sub 2}Cu with Li should occur and that the formation of LiAl should be observed. Other Al-transition metal intermetallics were studied and were also found to be inert toward Li, suggesting that the Al-transition metal bond has unique features.

Larcher, D.; Beaulieu, L.Y.; Mao, O.; George, A.E.; Dahn, J.R.

2000-05-01

378

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

PubMed Central

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

Rao, Srinivasa B.; Chowdhary, Ramesh

2011-01-01

379

Amperometric Sensor for Detection of Chloride Ions  

PubMed Central

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 ?M, 100 ?M and 10 ?M 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.

Trnkova, Libuse; Adam, Vojtech; Hubalek, Jaromir; Babula, Petr; Kizek, Rene

2008-01-01

380

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

PubMed Central

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.

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

2011-01-01

381

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

PubMed

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

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

2013-01-25

382

Electrodeposition of p-Type Sb x Te y Thermoelectric Films  

NASA Astrophysics Data System (ADS)

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.

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

2011-05-01

383

Potential COntrol Under Thin Aqueous Layers Using a Kelvin Probe  

SciTech Connect

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.

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

2006-08-17

384

In-vitro corrosion and wear of titanium alloys in the biological environment.  

PubMed

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

Khan, M A; Williams, R L; Williams, D F

1996-11-01

385

Wireless voltammetry recording in unanesthetised behaving rats.  

PubMed

In vivo voltammetry is a valuable technique for rapid measurement of dopamine in the brain of freely behaving rats. Using a conventional voltammetry system, however, behavioural freedom is restricted by cables connecting the head assembly to the measurement system. To overcome these difficulties, we developed a wireless voltammetry system utilizing radio waves. This system consisted of a potentiostat and transmitter system that was mounted on the back of the rat, and a receiver and analysis system. A single-step pulse (100-250 mV) was applied at 4 Hz after an activation pulse to a carbon fibre recording electrode (diameter: 7 microm). Measurement of dopamine (detection limit: 2.7 x 10(-7)M) was demonstrated in vitro. In vivo experiment was performed at least 1 week after the recording electrode was implanted in the rat striatum. Administration of 2-phenylethylamine to rats increased dopamine signal current, which was consistent with the result in the microdialysis measurement. During a resident-intruder test, dopamine signal current in a resident rat increased upon introduction of an intruder rat. These results show that the present wireless system is useful for a long-term measurement of dopamine in behaving rats. PMID:17983679

Kagohashi, Maki; Nakazato, Taizo; Yoshimi, Kenji; Moizumi, Shunjiro; Hattori, Nobutaka; Kitazawa, Shigeru

2007-10-03

386

A fully implantable telemetry system for the chronic monitoring of brain tissue oxygen in freely moving rats.  

PubMed

The ability to monitor tissue oxygen concentration in a specific region of the brain in a freely moving animal could provide a new paradigm in neuroscience research. We have developed a fully implantable telemetry system for the continuous and chronic recording of brain tissue oxygen (PO(2,BR)) in conscious animals. A telemetry system with a sampling rate of 2kHz was combined with a miniaturized potentiostat to amperiometrically detect oxygen concentration with carbon paste electrodes. Wireless power was employed to recharge the telemeter battery transcutaneously for potential lifetime monitoring. Rats were implanted with the telemeter in the peritoneal cavity and electrodes stereotaxically implanted into the brain (striatum or medulla oblongata). While the animals were living in their home cages the sensitivity to changes in oxygen was validated by repeatedly altering the inspired oxygen (10%, 100%, respectively) or a pharmacological stimulus (carbonic anhydrase inhibitor: acetazolamide 50mg/kg IP). Basal level of PO(2,BR) was monitored for 3weeks and showed good overall stability and good correlation to movement such as grooming. During hypoxia, PO(2,BR) decreased significantly by -51%2% from baseline, whereas it increased by 34%3% during hyperoxia. Following the systemic administration of acetazolamide, PO(2,BR) increased by 38%4%. We propose this new technology provides a robust method to measure changes in oxygen concentration in specific areas of the brain, in conscious freely moving rats. The ability to track long term changes with disease progression or drug treatment may be enabled. PMID:22123353

Russell, David M; Garry, Emer M; Taberner, Andrew J; Barrett, Carolyn J; Paton, Julian F R; Budgett, David M; Malpas, Simon C

2011-11-19

387

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

388

Hydrogen trapping in high-strength steels  

SciTech Connect

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.

Pound, B.G. [SRI International, Menlo Park, CA (United States). Materials Research Center

1998-10-09

389

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

390

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

391

Environmental cracking susceptibility of AISI 422 stainless steel in NH[sub 4]HCO[sub 3]/NH[sub 4]OH solution at 70 C  

SciTech Connect

The environmentally assisted cracking (EAC) susceptibility of AISI 422 (UNS S42200) stainless steel (SS) turbine blades was examined in an aerated NH[sub 4]HCO[sub 3]/NH[sub 4]OH solution at 70 C. Exposure in this solution is intended to simulate a cleaning procedure used to remove deposited copper from turbine blades in commercial power plants. EAC susceptibility is a strong function of the electrochemical potential; hence, it is necessary to compare the potential of contaminated blades to potential ranges such as the active-passive transition, which might promote EAC susceptibility. The ranking of open-circuit or mixed potentials experienced by the various materials/electrolyte combinations relative to the active-passive transition was polished SS/aerated > copper + SS/aerated > copper/aerated = SS active to passive transition > polished SS/deaerated. Constant extension rate tests were conducted by potentiostatically polarizing AISI 422 specimens to these potentials. For the displacement rate chosen, both tensile test parameters as well as scanning electron fractography revealed little differences between the environmental results and those obtained in air, except at the potential associated with the active-passive transition of the SS. However, this potential is 0.3 V more negative than the potential of the Cu-contaminated AISI 422 SS turbine blade. Hence, the chemical cleaning procedure does not promote EAC of AISI 422 SS unless the mixed potential experienced by the Cu-contaminated blades becomes more negative than expected.

Scully, J.R.; Scully, H.S. (Univ. of Virginia, Charlottesville (United States))

1993-02-01

392

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

SciTech Connect

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.

Pound, B.G.

1990-11-14

393

Growth and characterization of electrodeposited Cu2O thin films  

NASA Astrophysics Data System (ADS)

This work demonstrates the electrodeposition of cuprous oxide (Cu2O) thin films onto a fluorine-doped tin oxide (FTO)-coated conducting glass substrates from Cu(II) sulfate solution with C6H8O7 chelating agent. During cyclic voltammetry experiences, the potential interval where the electrodeposition of Cu2O is carried out was established. The thin films were obtained potentiostatically and were characterized through different techniques. From the MottSchottky measurements, the flat-band potential and the acceptor density for the Cu2O thin films are determined. All the films showed a p-type semiconductor character with a carrier density varying between 2.41 1018 cm?3 and 5.38 1018 cm?3. This little difference is attributed to the increase of the stoichiometric defects in the films with the deposition potential. Atomic force microscopy analysis showed that the Cu2O thin films obtained at high potential are more homogenous in appearance and present lower crystallites size. X-ray diffraction measurements indicate a cubic structure with good crystallization state and the deposition potential was found to have an influence on the size of the crystallites. The optical measurements show a direct band gap between 2.072.49 eV depending on the applied potential.

Laidoudi, S.; Bioud, A. Y.; Azizi, A.; Schmerber, G.; Bartringer, J.; Barre, S.; Dinia, A.

2013-11-01

394

Preparation and capacitance behavior of nickel oxide-titania nanocomposite  

NASA Astrophysics Data System (ADS)

Titania nanotube array with an average tube diameter of 110 nm and length of 700 nm was fabricated by a potentiostatic anodization on titanium metal sheet. Nickel oxide was then loaded into titania nanotubes by electrodepositon-electrooxidation and heating treatment processes. The morphology and microstructure of the nanocomposite were investigated by field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and energy dispersive x-ray (EDX) analysis. Nickel oxide could well coat on titania nanotubes from inner wall to pore mouth with a high loading amount up to 36.4% of nickel-to-titanium atom ratio. Such a well-defined nickel oxide-titania/titanium nanotubular composite was designed as a functional electrode for an electrochemical capacitance application. The result of electrochemical characterization exhibits a highly reversible redox peaks by cyclic voltammetry in sodium hydroxide aqueous solution. High specific supercapacitance was accordingly achieved up to 7.8 mF cm-2 due to the intensive loading of nickel oxide.

Xie, Yibing; Huang, Chuanjun; Zhou, Limin; Huang, Haitao; Lu, Jian

2007-10-01

395

An in vitro investigation of the anodic polarization and capacitance behavior of 316-L stainless steel.  

PubMed

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

Sutow, E J; Pollack, S R; Korostoff, E

1976-09-01

396

Electrochemical Fractionation of Molybdenum Stable Isotopes  

NASA Astrophysics Data System (ADS)

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.

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

2008-12-01

397

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

SciTech Connect

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)

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

1992-05-01

398

The effect of Fe content in electrodeposited CoFe/Cu multilayers on structural, magnetic and magnetoresistance characterizations.  

PubMed

A series of CoFe/Cu multilayers were electrodeposited on Ti substrates from the electrolytes containing their metal ion under potentiostatic control, but the Fe concentration in the electrolytes was changed from 0.0125 M to 0.2 M. The deposition was carried out in a three-electrode cell at room temperature. The deposition of Cu layers was made at a cathode potential of -0.3 V with respect to saturated calomel electrode (SCE), while the ferromagnetic CoFe layers were deposited at -1.5 V versus SCE. The structural studies by X-ray diffraction revealed that the multilayers have face-centered-cubic structure. The magnetic characteristics of the films were investigated using a vibrating sample magnetometer and their easy-axis was found to be in film plane. Magnetoresistance measurements were carried out using the Van der Pauw method at room temperature with magnetic fields up to +/- 12 kOe. All multilayers exhibited giant magnetoresistance (GMR) and the GMR values up to 8% were obtained. PMID:21138032

Tekgl, Atakan; Alper, Mrsel; Kockar, Hakan; Safak, Mr?ide; Karaagac, Oznur

2010-11-01

399

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

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.

Levi, M.D.; Salitra, G.; Markovsky, B.; Teller, H.; Aurbach, D. [Bar-Ilan Univ., Ramat-Gan (Israel). Dept. of Chemistry; Heider, U.; Heider, L. [Merck KGaA, Darmstadt (Germany)

1999-04-01

400

Enhanced pitting corrosion resistance of aluminum alloy 7075 in the presence of oxalate anions  

SciTech Connect

The presence of oxalate in chloride-containing corrosive aqueous media was found to protect aluminum alloy AA 7075 (UNS A95075). The effect of 0.05 M sodium oxalate on induction times for the initiation of pit formation was measured on AA 7075 specimens. The variance and the mean value of the induction times measured increased with the time of specimen immersion at the open circuit potential (OCP). Statistical analysis was done by potentiostatic measurement of several specimens using electrochemical instrumentation controlled by a personal computer. Pit generation rates were found to be inversely proportional to the duration of the immersion period at OCP. Therefore, it was concluded that prolonged exposure of the tested specimens to sodium oxalate solutions enhanced their resistance to corrosion. Impedance measurements confirmed this finding. The increased resistance was attributed to the retardation of the process by which the surface protective layer would have been destroyed. This retardation may have been ascribable to the formation of surface complexes between Al{sup 3+} and oxalates from the bulk solution. Polarization of the specimens at anodic potentials reduced the corrosion resistance of AA 7075, possibly because of the destabilization of the surface complexes formed between Al and the oxalate ions.

Kobotiatis, L.; Tsikrikas, C.; Koutsoukos, P.G. [Univ. of Patras (Greece)

1995-01-01

401

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)

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 0.8 V 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 10-11-10-10 cm2/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.

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

2008-01-01

402

Application of electrochemical techniques for machining titanium aluminide-based alloys  

SciTech Connect

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

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

1997-01-01

403

Corrosion behavior of mild steel in acetic acid solutions  

SciTech Connect

The corrosion behavior of mild steel in acetic acid (CH{sub 3}COOH) solutions was studied by weight loss and potentiostatic polarization techniques. The variation in corrosion rate of mild steel with concentrations of CH{sub 3}COOH, evaluated by weight loss and electrochemical techniques, showed marked resemblance. From both techniques, the maximum corrosion rate was observed for 20% CH{sub 3}COOH solution at all three experimental temperatures (25, 35, and 45 C). Anodic polarization curves showed active-passive behavior at each concentration, except at 80% CH{sub 3}COOH. Critical current density (i{sub c}) passive current density (I{sub n}), primary passivation potential (E{sub pp}), and potential for passivity (E{sub p}) had their highest values in 20% CH{sub 3}COOH solution. With an increase in temperature, while the anodic polarization curves shifted toward higher current density region at each concentration, the passive region became progressively less distinguishable. With the addition of sodium acetate (NaCOOCH{sub 3}) as a supporting electrolyte, the passive range was enlarged substantially. However, the transpassive region commenced at more or less the same potential. Cathodic polarization curves were almost identical irrespective of the concentration of CH{sub 3}COOH or temperature.

Singh, M.M.; Gupta, A.

2000-04-01

404

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

PubMed

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

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

2012-09-10

405

Electrostatic field measurements and band flattening during electron-transfer processes at single-crystal TiO[sub 2] electrodes by electric field-induced optical second harmonic generation  

SciTech Connect

Optical second harmonic generation (SHG) is employed as a local, time-resolved measurement of the electrostatic fields at the surface of single-crystal TiO[sub 2] electrodes in contact with aqueous electrolyte solutions. The interfacial SHG at a fundamental wavelength of 584 nm is dominated by the electric field-induced second harmonic (EFISH) response from the first 20 nm of the space charge layer at the surface of the semiconductor. A substantial decrease in the amount of SHG from the electrode while under potentiostatic control is observed upon illumination of the surface with UV light (320 nm) whose energy is above the bandgap for TiO[sub 2] (3.0 eV or 410 nm). Comparisons of the drop in SHG upon UV illumination with photovoltage measurements for TiO[sub 2] electrodes at open circuit verify that this decrease is due to a reduction in the strength of the electrostatic fields ([open quotes]band flattening[close quotes]) within the space charge region upon UV illumination. The EFISH response from the surface decreases with increasing power of the UV illumination, corresponding to a band flattening of up to 70% for the highest power densities. Upon termination of the UV illumination, a slow (10-12 s) rise time is observed for the return of the surface SHG to its normal levels. 50 refs., 8 figs.

Lantz, J.M.; Corn, R.M. (Univ. of Wisconsin, Madison, WI (United States))

1994-05-05

406

Electrochemical corrosion behavior of modified 9Cr-1Mo alloy  

SciTech Connect

The electrochemical corrosion behavior of modified 9Cr-1Mo alloy was studied in aqueous sulfate solution, with emphasis on the active dissolution, active-passive transition and passive film growth as a function of electrode potential, electrolyte pH and temperature. The primary electrochemical techniques employed were potentiodynamic, potentiostatic and galvanostatic polarization measurements supplemented by ESCA measurements of the anodic oxide film formed at various potentials. Passivation potential and critical current density of modified 9Cr-1Mo alloy were found to be significantly lower than those of pure iron, indicating alloying iron with chromium facilitates passivation. The oxidative dissolution of chromium oxide, the secondary passivation, and oxygen evolution were observed at the relatively higher oxidizing potentials. The anodic current under conditions of controlled constant potential decreased with increasing pH. Evidenced by ESCA, the excellent corrosion resistance of the iron-chromium alloy is strongly believed to be due to the enrichment of chromium on the surface which blocks the dissolution of iron.

Ahn, J.H.

1988-01-01

407

Dye Sensitized Solar Cells Based on Free-standing TiO2 Nanotube  

NASA Astrophysics Data System (ADS)

Dye-sensitized solar cells based on free-standing TiO2 nanotube arrays as electrodes have been fabricated. It was shown that highly ordered vertically oriented TiO2 nanotube arrays offer a large surface area for adsorption of dye molecules or quantum dots and provide a direct pathway for fast electron transport. This cuts down carrier recombination and enhances photoconversion efficiency. TiO2 nanotube arrays were obtained by potentiostatic anodization of titanium foil in fluoride-based ehylene glycol electrolyte. TiO2 nanotube arrays can be detached from the titanium foil by chemical etching and annealed at high temperatures to obtain highly crystalline anatase phase without cracking, since there is no strain induced between TiO2 and Ti foil. Solar cells based on free-standing dye-sensitized solar cells reveal much higher overall efficiency than those with nanotubes attached to the Ti foil, due to the improved crystallinity and front side illumination. J. Phys. Chem. C 2009, 113, 6310--6314

Kim, Chaehyun; Delikanli, Savas; Perera, Samanthe; Zeng, Hao

2010-03-01

408

Design of a high-speed electrochemical scanning tunneling microscope  

NASA Astrophysics Data System (ADS)

In this paper, we present a bottom-up approach to designing and constructing a high-speed electrochemical scanning tunneling microscope (EC-STM). Using finite element analysis (FEA) calculations of the frequency response of the whole mechanical loop of the STM, we analyzed several geometries to find the most stable one that could facilitate fast scanning. To test the FEA results, we conducted measurements of the vibration amplitudes using a prototype STM setup. Based on the FEA analysis and the measurement results, we identified the potentially most disturbing vibration modes that could impair fast scanning. By modifying the design of some parts of the EC-STM, we reduced the amplitudes as well as increased the resonance frequencies of these modes. Additionally, we designed and constructed an electrochemical flow-cell that allows STM imaging in a flowing electrolyte, and built a bi-potentiostat to achieve electrochemical potential control during the measurements. Finally, we present STM images acquired during high-speed imaging in air as well as in an electrochemical environment using our newly-developed EC-STM.

Yanson, Y. I.; Schenkel, F.; Rost, M. J.

2013-02-01

409

New Ni-free superelastic alloy for orthodontic applications.  

PubMed

A potential new Ni-free Ti alloy for biomedical applications was assessed in order to investigate the superelastic behavior, corrosion resistance and the biocompatibility. The alloy studied was Ti19.1Nb8.8Zr. The chemical composition was determined by X-ray microanalysis, the thermoelastic martensitic transformation was characterized by high sensitivity calorimeter. The critical stresses were determined by electromechanical testing machine and the corrosion behavior was analyzed by potentiostatic equipment in artificial saliva immersion at 37C. The results were compared with six different NiTi orthodontic archwire brands. The biocompatibility was studied by means of cultures of MG63 cells. Ni-free Ti alloy exhibits thermoelastic martensitic transformation with Ms=45C. The phase present at 37C was austenite which under stress can induce martensite. The stress-strain curves show a superelastic effect with physiological critical stress (low and continuous) and a minimal lost of the recovery around 150 mechanical cycles. The corrosion resistance improves the values obtained by different NiTi alloys avoiding the problem of the Ni adverse reactions caused by Ni ion release. Cell culture results showed that adhered cell number in new substrate was comparable to that obtained in a commercially pure Ti grade II or beta-titanium alloy evaluated in the same conditions. Consequently, the new alloy presents an excellent in-vitro response. PMID:23706217

Arciniegas, M; Manero, J M; Espinar, E; Llamas, J M; Barrera, J M; Gil, F J

2013-04-11

410

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

NASA Astrophysics Data System (ADS)

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

Chen, Jiali; Wang, Jinwei; Yuan, Hongye

2013-11-01

411

Assessment of corrosion rate in prestressed concrete with acoustic emission  

NASA Astrophysics Data System (ADS)

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.

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

2011-03-01

412

Wafer Scale Integration of CMOS Chips for Biomedical Applications via Self-Aligned Masking  

PubMed Central

This paper presents a novel technique for the integration of small CMOS chips into a large area substrate. A key component of the technique is the CMOS chip based self-aligned masking. This allows for the fabrication of sockets in wafers that are at most 5 m larger than the chip on each side. The chip and the large area substrate are bonded onto a carrier such that the top surfaces of the two components are flush. The unique features of this technique enable the integration of macroscale components, such as leads and microfluidics. Furthermore, the integration process allows for MEMS micromachining after CMOS die-wafer integration. To demonstrate the capabilities of the proposed technology, a low-power integrated potentiostat chip for biosensing implemented in the AMI 0.5 m CMOS technology is integrated in a silicon substrate. The horizontal gap and the vertical displacement between the chip and the large area substrate measured after the integration were 4 m and 0.5 m, respectively. A number of 104 interconnects are patterned with high-precision alignment. Electrical measurements have shown that the functionality of the chip is not affected by the integration process.

Uddin, Ashfaque; Milaninia, Kaveh; Chen, Chin-Hsuan; Theogarajan, Luke

2011-01-01

413

Wafer Scale Integration of CMOS Chips for Biomedical Applications via Self-Aligned Masking.  

PubMed

This paper presents a novel technique for the integration of small CMOS chips into a large area substrate. A key component of the technique is the CMOS chip based self-aligned masking. This allows for the fabrication of sockets in wafers that are at most 5 m larger than the chip on each side. The chip and the large area substrate are bonded onto a carrier such that the top surfaces of the two components are flush. The unique features of this technique enable the integration of macroscale components, such as leads and microfluidics. Furthermore, the integration process allows for MEMS micromachining after CMOS die-wafer integration. To demonstrate the capabilities of the proposed technology, a low-power integrated potentiostat chip for biosensing implemented in the AMI 0.5 m CMOS technology is integrated in a silicon substrate. The horizontal gap and the vertical displacement between the chip and the large area substrate measured after the integration were 4 m and 0.5 m, respectively. A number of 104 interconnects are patterned with high-precision alignment. Electrical measurements have shown that the functionality of the chip is not affected by the integration process. PMID:22400126

Uddin, Ashfaque; Milaninia, Kaveh; Chen, Chin-Hsuan; Theogarajan, Luke

2011-12-01

414

Dissolution and corrosion inhibition of copper, zinc, and their alloys  

SciTech Connect

The corrosion behavior of copper, zinc, and their alloys in sulfuric acid (H{sub 2}SO{sub 4}) solutions with oxygen and ferric ions (Fe{sup 3+}) was studied using a potentiostat. Oxygen and Fe{sup 3+} ions were shown to play an important role in corrosion of copper and copper-zinc alloys. Cathodic reduction of oxygen mainly was controlled by chemical reaction, and that of Fe{sup 3+} ions was controlled by diffusion. The overall cathodic process was the summation of the reduction of oxygen and Fe{sup 3+} ions. Corrosion of zinc was controlled mainly by reduction of water. Corrosion inhibition using benzotriazole (BTAH) also was investigated in aerated and deaerated solutions. BTAH was found to be a useful inhibitor, and the inhibition layer was shown to be stable and persistent. Morphology of the surface of copper, zinc, and brasses after corrosion in the presence and absence of BTAH was examined by scanning electron microscopy. BTAH formed a protective layer on the surface, thereby inhibiting corrosion. Solution analysis of the dissolution of brasses showed that zinc dissolved preferentially in the initial stages, followed by simultaneous dissolution of copper and zinc.

Jinturkar, P.; Guan, Y.C.; Han, K.N. [South Dakota School of Mines and Technology, Rapid City, SD (United States). Dept. of Metallurgical Engineering

1998-02-01

415

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

SciTech Connect

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.

Luo, H.; Han, K.N. [South Dakota School of Mines and Technology, Rapid City, SD (United States). Dept. of Metallurgical Engineering; Guan, Y.C. [Bateman Engineering, Inc., Denver, CO (United States)

1998-09-01

416

Inhibitive Effect of L-Oh on the Corrosion of Austenitic Chromium-Nickel Steel in H2SO4 Solution  

NASA Astrophysics Data System (ADS)

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.

Hosseini, S. M. A.; Amiri, M.; Momeni, A.

417

Packaged Au-PPy valves for drug delivery systems  

NASA Astrophysics Data System (ADS)

The most common methods for the drug delivery are swallowing pills or receiving injections. However, formulations that control the rate and period of medicine (i.e., time-release medications) are still problematic. The proposed implantable devices which include batteries, sensors, telemetry, valves, and drug storage reservoirs provide an alternative method for the responsive drug delivery system [1]. Using this device, drug concentration can be precisely controlled which enhances drug efficiency and decreases the side effects. In order to achieve responsive drug delivery, a reliable release valve has to be developed. Biocompatibility, low energy consumption, and minimized leakage are the main requirements for such release method. A bilayer structure composed of Au/PPy film is fabricated as a flap to control the release valve. Optimized potentiostatic control to synthesize polypyrrole (PPy) is presented. The release of miniaturize valve is tested and showed in this paper. A novel idea to simultaneously fabricate the device reservoirs as well as protective packaging is proposed in this paper. The solution of PDMS permeability problem is also mentioned in this article.

Tsai, Han-Kuan A.; Ma, Kuo-Sheng; Zoval, Jim; Kulinsky, Lawrence; Madou, Marc

2006-04-01

418

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

SciTech Connect

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.

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

2004-08-23

419

Electrochemical oxidation of La2CuO4 in fused nitrates  

NASA Astrophysics Data System (ADS)

La2CuO4 has been electrochemically oxidized in fused alkali nitrates, a medium that stabilizes peroxo and superoxo groups. The oxidation takes place either in neutral (NaClO4 electrolyte) or basic (KOH, Na2O electrolytes) media, in the presence or absence of protons, and in the presence or absence of added oxo groups (e.g. NaClO4). The oxidation potentials are lower as the basicity of the medium increases (NaClO4 > KOH > Na2O). The resulting La2CuO4+? materials have large superconductivity fractions when the oxidation is performed at 150C, and very small fractions (along with phase decomposition into CuO) when it is performed at 235C. The oxidized materials are totally unreactive versus iodide. That, along with the reported existence of peroxo and superoxo groups in this media, suggests that intercalation of oxygen in intermediate -1 and/or - oxidation states takes place. However, the existence of such reaction in the absence of protons eliminates the possibility of a mechanism by which OH- groups are being intercalated. Potentiostatic experiments yield a phase-segregated material with phases of Tc 45 and 35 K, while galvanostatic experiments allow to prepare the 35 K phase by itself.

Michel, C. R.; Casa-Pastor, N.

1997-02-01

420

The effect of surface treatments on the fretting behavior of Ti-6Al-4V alloy.  

PubMed

Stem modularity in total hip replacement introduces an additional taper joint between Ti-6Al-4V stem components with the potential for fretting corrosion processes. One possible way to reduce the susceptibility of the Ti-6Al-4V/Ti-6Al-4V interface to fretting is the surface modification of the Ti-6Al-4V alloy. Among the tested, industrially available surface treatments, a combination of two deep anodic spark deposition treatments followed by barrel polishing resulted in a four times lower material release with respect to untreated, machined fretting pad surfaces. The fretting release has been quantified by means of radiotracers introduced in the alloy surface by proton irradiation. In a simple sphere on flat geometry, the semispherical fretting pads were pressed against flat, dog-bone shaped Ti-6Al-4V fatigue samples cyclically loaded at 4 Hz. In this way a cyclic displacement amplitude along the surfaces of 20 mum has been achieved. A further simplification consisted in the use of deionized water as lubricant. A comparison of the radiotracer results with an electrochemical material characterization after selected treatments by potentiostatic tests of modular stems in 0.9% NaCl at 40 degrees C for 10 days confirmed the benefit of deep anodic spark deposition and subsequent barrel polishing for improving the fretting behavior of Ti-6Al-4V. PMID:18161779

Dalmiglio, Matteo; Schaaff, Petra; Holzwarth, Uwe; Chiesa, Roberto; Rondelli, Gianni

2008-08-01

421

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

PubMed Central

Optical biosensing based on fluorescence detection has arguably become the standard technique for quantifying extents of hybridization between surface-immobilized probes and fluorophore-labeled analyte targets in DNA microarrays. However, electrochemical detection techniques are emerging which could eliminate the need for physically bulky optical instrumentation, enabling the design of portable devices for point-of-care applications. Unlike fluorescence detection, which can function well using a passive substrate (one without integrated electronics), multiplexed electrochemical detection requires an electronically-active substrate to analyze each array site and benefits from the addition of integrated electronic instrumentation to further reduce platform size and eliminate the electromagnetic interference that can result from bringing non-amplified signals off chip. We report on an active electrochemical biosensor array, constructed with a standard complementary metal-oxide-semiconductor (CMOS) technology, to perform quantitative DNA hybridization detection on chip using targets conjugated with ferrocene redox labels. A 44 array of gold working electrodes and integrated potentiostat electronics, consisting of control amplifiers and current-input analog-to-digital converters, on a custom-designed 53 mm2 CMOS chip drive redox reactions using cyclic voltammetry, sense DNA binding, and transmit digital data off chip for analysis. We demonstrate multiplexed and specific detection of DNA targets as well as real-time monitoring of hybridization, a task that is difficult, if not impossible, with traditional fluorescence-based microarrays.

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

2009-01-01

422

Synthesis of single-walled carbon nanotubes and graphene composite in arc for ultracapacitors  

NASA Astrophysics Data System (ADS)

Arc discharge supported by the erosion of graphite anode is considered as one of the most practical and efficient methods to synthesize various carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene with minimal defects and large yield due to the relatively high synthesis temperature and eco-friendly growth mechanism. By introducing a non-uniform magnetic field during synthesis process, large-scale graphene and high-purity SWCNT can be obtained in one step. In addition, the yield of graphene can be controlled by external parameters, such as the type and pressure of buffer gas, the temperature of substrate, and so on. Possessing the properties of highly accessible surface area and good electrical conductivity, the composite of graphene and SWCNT are promising nanomaterials for the electrodes of ultracapacitor, which can store electric energy with high level of capacitance. In this work, we fabricated electrodes of ultracapacitor based on nanostructures composite by wire-wound rod coating method, characterized them by SEM, EDX and Raman spectroscopy, and tested the performance by a potentiostat/galvanostat.

Li, Jian; Cheng, Xiaoqian; Shashurin, Alexey; Keidar, Michael

2012-10-01

423

Influence of the sulfur species reactivity on biofilm conformation during pyrite colonization by Acidithiobacillus thiooxidans.  

PubMed

Massive pyrite (FeS?) electrodes were potentiostatically modified by means of variable oxidation pulse to induce formation of diverse surface sulfur species (S(n)?, S?). The evolution of reactivity of the resulting surfaces considers transition from passive (e.g., Fe(1-x )S?) to active sulfur species (e.g., Fe(1-x )S(2-y ), S?). Selected modified pyrite surfaces were incubated with cells of sulfur-oxidizing Acidithiobacillus thiooxidans for 24 h in a specific culture medium (pH 2). Abiotic control experiments were also performed to compare chemical and biological oxidation. After incubation, the attached cells density and their exopolysaccharides were analyzed by confocal laser scanning microscopy (CLMS) and atomic force microscopy (AFM) on bio-oxidized surfaces; additionally, S(n)?/S? speciation was carried out on bio-oxidized and abiotic pyrite surfaces using Raman spectroscopy. Our results indicate an important correlation between the evolution of S(n)?/S? surface species ratio and biofilm formation. Hence, pyrite surfaces with mainly passive-sulfur species were less colonized by A. thiooxidans as compared to surfaces with active sulfur species. These results provide knowledge that may contribute to establishing interfacial conditions that enhance or delay metal sulfide (MS) dissolution, as a function of the biofilm formed by sulfur-oxidizing bacteria. PMID:22113561

Lara, Ren H; Garca-Meza, J Viridiana; Cruz, Roel; Valdez-Prez, Donato; Gonzlez, Ignacio

2011-11-24

424

Galvanic corrosion of dental cobalt-chromium alloys and dental amalgam in artificial saliva.  

PubMed

When two or more metals or alloys are placed in contact with one another inside the oral cavity, galvanic coupling may occur which may lead to galvanic corrosion. Galvanic corrosion may release elements from the alloy into the oral cavity with possible harm to the patient. This in vitro study was conducted to determine the extent of galvanic corrosion where different dental amalgams and Co-Cr alloy combinations were placed in contact with artificial saliva as an electrolyte. The tests were conducted with potential measurements as well as potentiodynamic and potentio-static polarisation techniques. Results showed that the galvanic corrosion current density is much lower than the corrosion current density, indicating that galvanic coupling of the samples does not have a substantial effect on the overall corrosion of the samples. The corrosion potential differences between three of the four couples were above the minimum 50 mV potential difference, which is considered a potential harmful level, with only the Wironium Plus and Dispersalloy combination being under 50 mV potential difference. It is concluded that: Galvanic corrosion does not pose a greater threat to the alloys than ordinary corrosion. A Wironium Plus and Dispersalloy combination may be the safest where a Co-Cr and amalgam combination is required in the mouth of a patient. PMID:18543740

van Vuuren, L Jansen; Odendaal, J S J; Pistorius, P C

2008-02-01

425

Miniaturized electrochemical system for cholinesterase inhibitor detection.  

PubMed

The utility of a simple, low-cost detection platform for label-free electrochemical characterization of acetylcholinesterase (AChE) inhibition is demonstrated as a potential tool for screening of small-molecule therapeutic agents for Alzheimer's disease (AD). Technique validation was performed against the standard Ellman's colorimetric assay using the clinically established cholinesterase inhibitor (ChEI), Donepezil (Aricept()). Electrochemical measurements were obtained by differential pulse voltammetry (DPV) performed using a portable potentiostat system for detection of the enzymatic product, thiocholine (TCh), by direct oxidation on unmodified gold screen-printed electrodes. The IC50 profiles for Donepezil measured in vitro were found to be comparable between both colorimetric and electrochemical detection methods for the analysis of purified human erythrocyte-derived AChE (287 nM by DPV; 268 nM by Ellman's method). The selectivity of this unmodified electrode system was compared to a range of biological sulfur-containing compounds including cysteine, homocysteine, glutathione and methionine as well as ascorbic acid. Preliminary studies also demonstrated the potential applicability of this electrochemical technique for the analysis of Donepezil in crude cholinesterase samples from anterior cortex homogenates of C57BL/6J mice. PMID:23567119

Veloso, Anthony J; Nagy, Paul M; Zhang, Biao; Dhar, Devjani; Liang, Anqi; Ibrahim, Tarek; Mikhaylichenko, Svetlana; Aubert, Isabelle; Kerman, Kagan

2013-03-13

426

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

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.

Economou, Anastasios; Voulgaropoulos, Anastasios

2003-01-01

427

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

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

Economou, Anastasios; Voulgaropoulos, Anastasios

2003-01-01

428

Development of molten carbonate fuel cell power plant technology  

NASA Astrophysics Data System (ADS)

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.

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

429

SnO2:F Coated Ferritic Stainless Steels for PEM Fuel Cell Bipolar Plates  

SciTech Connect

Ferrite stainless steels (AISI441, AISI444, and AISI446) were successfully coated with 0.6 {micro}m thick SnO{sub 2}:F by low-pressure chemical vapor deposition and investigated in simulated PEMFC environments. The results showed that a SnO{sub 2}:F coating enhanced the corrosion resistance of the alloys in PEMFC environments, though the substrate steel has a significant influence on the behavior of the coating. ICP results from the testing solutions indicated that fresh AISI441 had the highest dissolution rates in both environments, and coating with SnO2:F significantly reduced the dissolution. Coating AISI444 also improved the corrosion resistance. Coating AISI446 steel further improved the already excellent corrosion resistance of this alloy. For coated steels, both potentiostatic polarizations and ICP results showed that the PEMFC cathode environment is much more corrosive than the anode one. More dissolved metallic ions were detected in solutions for PEMFC cathode environment than those in PEMFC anode environment. Sn{sup 2+} was detected for the coated AISI441 and AISI444 steels but not for coated AISI446, indicating that the corrosion resistance of the substrate has a significant influence on the dissolution of the coating. After coating, the ICR values of the coated steels increased compared to those of the fresh steels. The SnO{sub 2}:F coating seems add an additional resistance to the native air-formed film on these stainless steels.

Wang, H.; Turner, J. A.

2007-01-01

430

Electrochemically driven organic monolayer formation on silicon surfaces using alkylammonium and alkylphosphonium reagents  

NASA Astrophysics Data System (ADS)

The functionalization of silicon surfaces with organic monolayers, bound through Si C bonds, is an area of wide interest due to the technological promise of organosilicon hybrid devices, but also to investigate fundamental surface reactivity. In this paper, the use of alkylammonium and alkylphosphonium cations as sources of organic moieties to bind to hydrogen-terminated flat and porous silicon is demonstrated. Tetraalkylammonium, tetraalkyl/arylphosphonium reagents, and alkyl pyridinium salts can be utilized, but trialkylammonium salts cannot as they yield substantial surface oxidation. Under electrochemical conditions, either potentiostatic or galvanostatic modes, alkyl groups derived from the ammonium or phosphonium salts are grafted to the silicon surface and are bound through Si C bonds. Covalent attachment of the organic monolayers to the surface was demonstrated by XPS, AFM scribing, and FTIR. The mechanism may proceed via reduction of the ammonium salt yielding alkyl radicals, R, which may be reduced to R- and attack surface Si Si bonds, leading to Si C bonds, or the formation of silyl anions (?Si-) under the cathodic conditions followed by nucleophilic attack on the trialkylammonium cation.

Wang, Dong; Buriak, Jillian M.

2005-10-01

431

Photocatalytic degradation of gaseous toluene over Ag-doping TiO? nanotube powder prepared by anodization coupled with impregnation method.  

PubMed

In this work, Ag-doping TiO(2) nanotubes were prepared and employed as the photocatalyst for the degradation of toluene. The TiO(2) nanotube powder was produced by the rapid-breakdown potentiostatic anodization of Ti foil in chloride-containing electrolytes, and then doped with Ag through an incipient wetness impregnation method. The samples were characterized by scanning electron microscope, high-resolution transmission electron microscopy, X-ray diffraction, surface photovoltage measurements, X-ray photoelectron spectroscopy and N(2) adsorption. The nanotubular TiO(2) photocatalysts showed an outer diameter of approximately 40nm, fine mesoporous structure and high specific surface area. The photocatalytic activity of Ag-doping TiO(2) nanotube powder was evaluated through photooxidation of gaseous toluene. The results indicated that the degradation efficiency of toluene could get 98% after 4h reaction using the Ag-doping TiO(2) nanotubes as the photocatalyst under UV light illumination, which was higher than that of the pure TiO(2) nanotubes, Ag-doping P25 or P25. Benzaldehyde species could be observed during the photocatalytic oxidation monitored by in situ FTIR, and the formed benzaldehyde intermediate during reaction would be partially oxidized into CO(2) and H(2)O. PMID:21435692

Li, Xinyong; Zou, Xuejun; Qu, Zhenping; Zhao, Qidong; Wang, Lianzhou

2011-03-23

432

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

433

Degradation mechanisms of carbon-based electrocatalyst support materials and development of an advanced support based on electrically conducting diamond  

NASA Astrophysics Data System (ADS)

In this dissertation, the degradation mechanisms of sp 2-bonded carbon electrocatalyst supports were studied under potential and temperature conditions relevant to the polymer electrolyte membrane fuel cell (PEMFC). In addition, an alternative support was fabricated in two forms: electrically conducting diamond powder and paper to overcome current material stability issues in the PEMFC. Two structurally well-characterized sp2-bonded carbon powders, graphite (structurally well-ordered) and glassy carbon (GC, structurally disordered) were studied under potentiostatic polarization from 1.0 to 1.6 V vs. Ag/AgCl at 25, 50, and 80C. Characterization of the surface oxidation and microstructural changes (i.e., increase in the exposed edge plane density) provided evidence for the so-called order/disorder mechanism where structurally disordered carbons corrode more severely because of oxidation and gasification of the exposed edge plane. Microstructural changes for graphite were heterogeneously distributed across the electrode surface. This is indicative of a nucleation and growth process, where disordered regions and defects serve as active sites for electrochemical corrosion, while other, more structurally ordered regions do not corrode. Preliminary results for a high-surface-area carbon black, Vulcan XC-72, are presented that show changes in the surface oxide content and also discuss the effect of polarization potential on Pt activity. The physical and electrochemical properties of two commercial boron-doped diamond thin-film electrodes were compared with microcrystalline and nanocrystalline boron-doped diamond thin film deposited in our laboratory. The electrochemical response for Fe(CN)63-/4-, Ru(NH3)6 3+/2+, IrCl62-/3-, 4-methylcatechol, and Fe3+/2+ was quite reproducible from electrode type-to-type and from film-to-film for a given type. DeltaEp, ipox, and ip red values for Fe(CN)63-/4-, Ru(NH 3)63+/2+ on all electrodes were relatively unaffected by pH. Electrically conducting diamond powder was prepared by coating insulating diamond powder (8-12 mum diam) with a thin boron-doped diamond layer using microwave-assisted chemical vapor deposition (CVD). Increases in the electrical conductivity after growth confirmed that a conductive diamond overlayer formed. The charge passed during anodic polarization at 1.6 V vs. Ag/AgCl and 25C for 1 h was largest for GC powder (0.88 C/cm2) and smallest for conductive diamond powder (0.18 C/cm2), illustrating the dimensional stability of diamond powder compared to sp2-bonded carbon powder. Boron-doped nanocrystalline diamond (BND) was coated on Toray RTM carbon paper (TCP) via microwave-assisted CVD. Pt nanoparticles were deposited on TCP and BND using a pulsed galvanostatic method. The stability of the bare TCP and BND substrates and the composite Pt/TCP and Pt/BND electrodes were studied using potentiostatic polarization in 0.1 M HClO4. The BND electrode exhibited superior morphological and microstructural stability over TCP at 1.6 V vs. Ag/AgCl. Evidence was found for dissolution and redeposition of Pt on composite electrodes, particularly for Pt/TCP.

Fischer, Anne Elizabeth

434

Electrochemical properties of suprastructures galvanically coupled to a titanium implant.  

PubMed

In recent years, dental implants have been widely used for the aesthetic and functional restoration of edentulous patients. Dental implants and restorative alloys are required with high corrosion resistance. Suprastructures and implants of different compositions in electrical contact may develop galvanic or coupled corrosion problems. In addition to galvanic corrosion, crevice and pitting corrosion may occur in the marginal gap between dental implant assemblies. In this study, gold, silver-palladium, cobalt-chromium, and nickel-chromium suprastructures were used to investigate their galvanic and crevice corrosion characteristics in combination with titanium (Ti) implants. Potentiodynamic and potentiostatic testing were performed in artificial saliva at 37 degrees C. Potentiodynamic testing was carried out at the potential scan rate of 1 mV/s in the range of -600-1600 mV (SCE). Potentiostatic testing was performed with an open-circuit potential and current densities at -250, 0, and 250 mV (SCE) in artificial saliva. After electrochemical testing, surface morphologies and cross-sections were examined using micrographs of the samples. Potentiodynamic test results indicated that suprastructure/Ti implant couples produced passive current densities in the range of 0.5-12 microA/cm(2); Ti abutment/Ti implant and gold/Ti implant couples exhibited relatively low passive current densities; Co-Cr/Ti implant couples the highest. Co-Cr and Ni-Cr/Ti implant couples showed breakdown potentials of 700 and 570 mV (SCE), respectively. The open-circuit potentials of silver, Ti abutment, gold, Ni-Cr, and Co-Cr/Ti implant couples were -93.2 +/- 93.9, -123.7 +/- 58.8, -140.0 +/- 80.6, -223.5 +/- 35.1, and -312.7 +/- 29.8 mV (SCE), respectively, and did not change with immersion time. The couples exhibited cathodic current densities at -250 mV (SCE); in particular, gold and silver alloys showed high cathodic current densities of -3.18 and -6.63 microA/cm(2), respectively. At 250 mV (SCE), Ti abutment/Ti implant couples exhibited a minimum current density of 9.48 x 10(-2) microA/cm(2), but gold, Ni-Cr, Co-Cr, and silver/Ti implant couples exhibited 0.313, 1.27, 5.60, and 8.06 microA/cm(2), respectively. All couples exhibited relatively low current densities at 0 mV (SCE). Photomicrographs after electrochemical testing showed crevice or pitting corrosion in the marginal gap and at the suprastructure surface. Although of the tested samples Co-Cr/Ti implant couples showed the possibility of galvanic corrosion, its degree was not significant. However, it should be borne in mind that galvanic corrosion can accelerate localized corrosion, such as crevice or pitting corrosion. PMID:15264315

Oh, Keun-Taek; Kim, Kyoung-Nam

2004-08-15

435

Self-assembled monolayers of n-alkanethiols suppress hydrogen evolution and increase the efficiency of rechargeable iron battery electrodes.  

PubMed

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. PMID:23237487

Malkhandi, Souradip; Yang, Bo; Manohar, Aswin K; Prakash, G K Surya; Narayanan, S R

2012-12-24

436

Reversible detection of heparin and other polyanions by pulsed chronopotentiometric polymer membrane electrode.  

PubMed

The first fully reversible polymeric membrane-based sensor for the anticoagulant heparin and other polyanions using a pulsed chronopotentiometry (pulstrode) measurement mode is reported. Polymeric membranes containing a lipophilic inert salt of the form R(+)R(-) (where R(+) and R(-) are tridodecylmethylammonium (TDMA(+)) and dinonylnaphthalene sulfonate (DNNS(-)), respectively) are used to suppress unwanted spontaneous ion extractions under zero-current equilibrium conditions. An anodic galvanostatic current pulse applied across the membrane perturbs the equilibrium lipophilic ion distribution within the membrane phase in such a way that anions/polyanions are extracted into the membrane from the sample. The membrane is then subjected to an open-circuit zero current state for a short period, and finally a 0 V vs reference electrode potentiostatic pulse is applied to restore the membrane to its initial full equilibrium condition. Potentials are sampled as average values during the last 10% of the 0.5 s open circuit phase of the measurement cycle. Fully reversible and reproducible electromotive force (emf) responses are observed for heparin, pentosan polysulfate (PPS), chondroitin sulfate (CS), and oversulfated chondroitin sulfate (OSCS), with the magnitude of the potentiometric response proportional to charge density of the polyanions. The sensor provides an emf response related to heparin concentrations in the range of 1-20 U/mL. The responses to variations in heparin levels and toward other polyanions of the pulstrode configuration are analogous to the already established single-use, nonreversible potentiometric polyion sensors based on membranes doped only with the lipophilic anion exchanger TDMA(+). PMID:20121058

Gemene, Kebede L; Meyerhoff, Mark E

2010-03-01

437

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

SciTech Connect

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

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

2009-09-15

438

Determination of the critical potentials for pitting, protection, and stress corrosion cracking of 67-33 brass in fluoride solutions  

SciTech Connect

Pitting potentials and protection potentials have been determined for {alpha}-brass (33% Zn) using a cyclic polarization method. Increasing the F{sup {minus}} concentration shifts the critical potential to more active values. The pitting potentials, E{sub p}, and protection potentials, E{sub pp}, depend on the logarithmic concentration of F{sup {minus}} ions according to the equations: E{sub p} = a + b log [F{sup {minus}}] and E{sub pp} = a + b log [F{sup {minus}}]. Slow strain rate tests (SSRT), at a strain rate of 5 {times} 10{sup {minus}5} s{sup {minus}1}, were performed under open-circuit and potentiostatic conditions to study the stress corrosion cracking (SCC) characteristics of the {alpha}-brass in NaF solutions of various concentrations (pH 6.8) at 25 C. The minimum concentration of NaF that caused intergranular stress corrosion cracking (IGSCC) was 1 {times} 10{sup {minus}4} M. This concentration, was also the critical level for repassivation, observed in cyclic polarization tests. These results demonstrate a good correlation between the electrical and the mechanical breakdown of the passive film. In the presence of 10{sup {minus}1}M NaF the potential range for IGSCC was {minus}150 to {minus}50 mV (SCE). These critical potentials were restricted to the stable passive potential range and also fell within the potential-pH region where Cu{sub 2}O was stable. The formation of a Cu{sub 2}O film on the brass after polarization in the passive region was confirmed by X-ray diffraction (XRD). At more noble potentials and at cathodic potentials below the Cu{sub 2}O domain, the failure mode was ductile fracture. These observations of IGSCC of the brass in fluoride solutions support a film rupture-dissolution mechanism.

Lee, C.K.; Shih, H.C. [National Tsing Hua Univ., Hsinchu (Taiwan, Province of China). Dept. of Materials Science and Engineering

1995-03-01

439

Microstructure and corrosion behavior of porous coatings on titanium alloy by vacuum-brazed method.  

PubMed

The microstructural evolution and electrochemical characteristics of brazed porous-coated Ti-6Al-4V alloy were analyzed and compared with respect to the conventionally 1300 degrees C sintering method. The titanium filler metal of low-melting-point (934 degrees C) Ti-15Cu-15Ni was used to braze commercially pure (CP) titanium beads onto the substrate of Ti-6Al-4V alloy at 970 degrees C for 2 and 8 h. Optical microscopy, scanning and transmission electron microscopy, and X-ray diffractometry (XRD) were used to characterize the microstructure and phase of the brazed metal; also, the potentiostat was used for corrosion study. Experimental results indicate that the bead/substrate contact interface of the 970 degrees C brazed specimens show larger contact area and higher radius curvature in comparison with 1300 degrees C sintering method. The microstructure of brazed specimens shows the Widmansttten structure in the brazed zone and equiaxed alpha plus intergranular beta in the Ti-6Al-4V substrate. The intermetallic Ti2Ni phase existing in the prior filler metal diminishes, while the Ti2Cu phase can be identified for the substrate at 970 for 2 h, but the latter phase decrease with time. In Hank's solution at 37 degrees C, the corrosion rates of the 1300 degrees C sintering and the 970 degrees C brazed samples are similar at corrosion potential (E(corr)) in potentiodynamic test, and the value of E(corr) for the brazed sample is noble to the sintering samples. The current densities of the brazed specimens do not exceed 100 microA/cm2 at 3.5 V (SCE). These results suggest that the vacuum-brazed method exhibits the potentiality to manufacture the porous-coated specimens for biomedical application. PMID:16278850

Lee, T M; Chang, E; Yen, C H

2006-05-01

440

A new electroactive paper actuator using conducting polypyrrole  

NASA Astrophysics Data System (ADS)

The construction of electromechanical actuator has been achieved by using the conducting polypyrrole films deposition onto a gold-coated cellophane paper. This is probably the first report of this type of paper actuator. The conducting polypyrrole was electro-generated using either galvanostatic or potentiostatic conditions at 0.5 mA/cm2 current density or 0.7 volts applied potential. The two types of actuators were constructed namely: 1.Ppy/Cellophane bilayer 2. Ppy/ Cellophane paper /Ppy trilayer using electrochemical technique. These actuators showed a reversible and reproducible displacement in acetonitrile solution containing LiClO4 (1M). The maximum displacement of 9.1 mm was recorded for tri-layer device and 3.5 mm for bi-layer device in 1M LiClO4 acetonitrile solutions. The prepared actuator devices were investigated for their mechanical actuation in air medium. The actuation in air is comparatively less than in solution actuation, but still it showed significant movement in air also. The results obtained in acetonitrile solution containing 1M LiClO4 shows that the actuator requires very low excitation voltages of 0.2 MV m-1 at 0.5 Hz frequencies. The effect of humidity on the actuation properties was addressed. The humidity measurement was carried out between 60% to 95% humidity with the help of humidity-temperature controlled chamber. The resonating frequency of 3 Hz at 6 volts had shown 1.8 mm displacement at 95% humidity for gold-coated cellophane sample without polypyrrole.

Deshpande, Shripad D.; Kim, Jaehwan; Yun, Seong R.

2004-07-01

441

Metastable pitting of aluminum and Al-Cu alloys  

NASA Astrophysics Data System (ADS)

Metastable pitting behavior and the transition from metastable to stable pitting on high purity aluminum and two Al-Cu alloys (aged Al-2%Cu and AA2024-T3) were investigated. Experiments on pure Al were done potentiostatically, and nominally identical electrodes galvanic coupling experiments were conducted with the Al-Cu alloys. Applied potential, chloride concentration, and exposure time were the variables used to establish the critical potentials for pit stabilization and signature time series of metastable and stable pitting events. A distribution of pitting and repassivation (transition) potentials were observed at each Clsp- concentration. Factors controlling the transition from metastable to stable pitting were identified by comparing the electrochemical behavior of stable pits at elapsed times equal to the mean lifetime of metastable pits. This comparison also provided insight on the origins of statistical distributions of pitting potentials. A key criterion for pit stabilization is that individual pits exceed a threshold of Isbpit/rsbpit > 10sp{-2} A/cm at all times during pit growth. This parameter was linked to pit growth and mass transport conditions leading to the formation of a depassivating pit chemistry. Methods from electrochemical noise analyses were compared using the galvanic coupling time series. Isbpit/rsbpit analysis of the metastable pit current spikes provided a better indication of the transition to stable pitting than the pitting index and electrochemical noise resistance. Power spectral density plots of the current and potential time series provided qualitative information on pit susceptibility. Temporal analyses of the galvanic coupling current time series provided evidence that some correlation may exist between individual metastable pitting events. The metastable pitting events were found to deviate from Poisson behavior with increasing activity. Metastable pitting events may have an influence on subsequent pitting events at higher activity.

Pride, Sheldon Tyrone

442

Automated Controlled-Potential Coulometer for the IAEA  

SciTech Connect

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.

Cordaro, J.V. [Westinghouse Savannah River Company, AIKEN, SC (United States); Holland, M.K.; Fields, T.

1998-01-29

443

Preparation, structure, and electrochemistry of a polypyrrole film doped with manganese(III)-substituted Dawson-type phosphopolyoxotungstate.  

PubMed

The fabrication, structure, electrochemical properties, and electrocatalytic properties of a manganese(III)-substituted Dawson-type phosphopolyoxotungstate, alpha 2-K7P2W17O61(Mn3+.OH2).12H2O (P2W17Mn), entrapped in polypyrrole (PPy) film have been studied. The hybrid film was prepared by potentiostatic polymerization from aqueous solution containing 20 mM pyrrole (Py) and 2 mM P2W17Mn on a pyrolytic graphite (PG) surface. Chronoamperometry, Raman spectroscopy, UV-visible absorption spectroscopy, and cyclic voltammetry were used to monitor and characterize the growth, structure, and properties of the film. The chronoamperometric curve shows that P2W17Mn can catalyze the electrochemical polymerization of Py. The Raman spectrum suggests that the doped P2W17Mn has little effect on the structure of PPy film. The P2W17Mn/PPy film exhibits good voltammetric response in both the acidic aqueous and acetonitrile solutions. At pH 1.0, the molar ratio of pyrrole to P2W17Mn7- in the hybrid film is 21.1:1, quite close to the expected ratio of 21.2:1 for a PPy film with a +0.33 oxidation level per pyrrole moiety and doped with an anion with a charge of 7. The influence of solution pH on P2W17Mn7- in the film is much smaller than that in the aqueous solution. During the potential scanning in 0.1 M LiClO4 acetonitrile solution, P2W17Mn7- was slowly released from the hybrid film and electrolyte ions (Li+ and ClO4-) were inserted into the film. This was identified by cyclic voltammetry and UV-visible spectroscopy. Additionally, the hybrid film can effectively catalyze the reduction of hydrogen peroxide and nitrite. PMID:16851272

Tao, Wenyan; Li, Zhenfeng; Pan, Dawei; Nie, Lihua; Yao, Shouzhuo

2005-02-24

444

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

PubMed

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

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

2011-06-06

445

Electrochemical investigations of pitting corrosion in nitrogen-bearing type 316LN stainless steel  

SciTech Connect

Nitrogen (N) alloying was found to inhibit active dissolution and to introduce a secondary loop with fluctuating currents in the anodic polarization curve of type 316LN stainless steel (SS) (UNS S31653) in 1 N hydrochloric acid (HCl) solution. Potentiostatic tests in this potential range confirmed the occurrence of current transients as a result of metastable pits, resulting in secondary loop formation. Higher minimum chloride (Cl{sup {minus}}) concentration and low acidic pH were shown to be required for stable pit formation in type 316LN SS compared to similar alloys without N alloying. Results showed no selective anodic dissolution of any of the alloying elements in actively growing pits in type 316LN SS. Although ammonium ions (NH{sub 4}{sup +}) were found within pits under suitable applied potentials in 1 N HCl and under natural corrosion in ferric chloride (FECl{sub 3}) solutions, the more anodic the potential, the less was its yield. The formation of NH{sup +}{sub 2} ions was found to be greater at more active potentials under uniformly dissolving conditions, and an apparent Tafel slope for the reduction reaction N + 4H{sup +} + 3e {r_arrow}NH{sub 4}{sup +} for the dissolution of N from the steel was estimated to be 0.125 V. Significant enrichments of N, chromium (CR), and nickel (Ni) to a marginal extent were observed by Auger electron spectroscopy (AES) of the actively growing pitted surface. The iron (Fe) component, however, showed considerable depletion. The unattacked surface region surrounding the pit maintained normal passive film characteristic. Based on observations, a mechanism elaborating the beneficial effect of alloyed N on pitting corrosion resistance of SS was developed.

Palit, G.C.; Kain, V.; Gadiyar, H.S. [Bhabha Atomic Research Centre, Bombay (India). Metallurgy Div.

1993-12-01

446

Characterization of native and anodic oxide films formed on commercial pure titanium using electrochemical properties and morphology techniques  

NASA Astrophysics Data System (ADS)

Potentiostatically anodized oxide films on the surface of commercial pure titanium (cp-Ti) formed in sulfuric (0.5 M H 2SO 4) and in phosphoric (1.4 M H 3PO 4) acid solutions under variables anodizing voltages were investigated and compared with the native oxide film. Potentiodynamic polarization and electrochemical impedance spectroscopy, EIS, were used to predicate the different in corrosion behavior of the oxide film samples. Scanning electron microscope, SEM, and electron diffraction X-ray analysis, EDX, were used to investigate the difference in the morphology between different types of oxide films. The electrochemical characteristics were examined in phosphate saline buffer solution, PSB (pH 7.4) at 25 C. Results have been shown that the nature of the native oxide film is thin and amorphous, while the process of anodization of Ti in both acid solutions plays an important role in changing the properties of passive oxide films. Significant increase in the corrosion resistance of the anodized surface film was recorded after 3 h of electrode immersion in PSB. On the other side, the coverage ( ?) of film formed on cp-Ti was differed by changing the anodized acid solution. Impedance results showed that both the native film and anodized film formed on cp-Ti consist of two layers. The resistance of the anodized film has reached to the highest value by anodization of cp-Ti in H 3PO 4 and the inner layer in the anodized film formed in both acid solutions is also porous.

Fadl-allah, Sahar A.; Mohsen, Q.

2010-08-01

447

Nanotubular oxide surface and layer formed on the Ti-35Ta-xZr alloys for biomaterials.  

PubMed

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

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

2011-08-01

448

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

SciTech Connect

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

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

1980-03-01

449

Extension of logarithmic growth of Thiobacillus ferrooxidans by potential controlled electrochemical reduction of Fe(III).  

PubMed

In this study, we demonstrated that the period of logarithmic growth for Thiobacillus ferrooxidans could be extended when optimal conditions for cell growth were maintained using potential controlled electrochemical cultivation with sufficient aeration. The optimal pH and Fe(II) concentration for the electrolytic cultivation were determined to be 2.0 and 150 mM, respectively. When the potential was set to 0.0V vs Ag/AgCl, the Pt electrode reduced Fe(III) to Fe(II) with an efficiency of 95%. A porous glass microbubble generator was used to maintain adequate levels of dissolved oxygen, which was the electron acceptor for T. ferrooxidans when the cell density in the medium was high. Under these conditions, cells at an initial density of 10(7) cells/mL grew logarithmically for 4days until the cell density was 4 x 10(9) cells/mL. This corresponded to a period of logarithmic growth that was 3 times longer than was observed in batch cultures without electrolysis. In addition, the final cell density reached 10(10) cells/mL after 6 days of electrochemical cultivation, which was a 50-fold increase over conventional batch culture. Under conditions of increasing cell density, potentiostatic electrolysis made it possible to remove Fe(III), which causes product inhibition, at an increasing rate and to correspondingly increase the production rate of Fe(II), which is the electron donor for T. ferrooxidans. Thus, our cultivation system provides a sufficient supply of electron donor and acceptor for T. ferrooxidans, thereby elongating the period of logarithmic growth and producing very high cell densities. PMID:10417221

Matsumoto, N; Nakasono, S; Ohmura, N; Saiki, H

1999-09-20

450

Nature and extent of electrogenic microbial communities recovered from Juan de Fuca hydrothermal sulfides  

NASA Astrophysics Data System (ADS)

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.

Girguis, P. R.; Nielsen, M. E.

2011-12-01

451

Electrochemical formation of Dy alloy films in a molten LiCl-KCl-DyCl3 system  

NASA Astrophysics Data System (ADS)

As to the electrochemical formation of Dy-Ni alloy films in a molten LiCl-KCl-DyCl3 system at 700 K, the growth of DyNi2 film and behavior of anodic dissolution of Dy from the formed DyNi2 film were investigated. The DyNi2 films were formed by potentiostatic electrolysis at 0.55, 0.62 and 0.70 V with Ni electrodes. The growth rates of DyNi2 films are higher at less noble potential, i.e., 0.47 8m min-1 at 0.55 V, 0.32 8m min-1 at 0.62 V and 0.14 8m min-1 at 0.70 V. From RBS analysis, it was suggested that the Dy-Ni alloy film was formed for 10 or 30 s during electrodepositing Dy at 0.30 V with a Ni electrode. Moreover, the growth rate of Dy-Ni alloy film was faster than that of Dy-Fe alloy film. Anodic electrolysis of the formed DyNi2 film with thickness of 15 ?m was conducted at 0.90 V, 1.30 V and 1.90 V, respectively. The formed DyNi2 were transformed to other phases, i.e., DyNi3, DyNi5 and Ni, by selective anodic dissolution of Dy. The transformed Ni film was about 10 ?m in thickness and had a porous structure with a pore diameter of 1~2 ?m.

Konishi, H.; Usui, T.; Nohira, T.; Ito, Y.

2009-05-01

452

The lithium-boron alloy anode in molten nitrate electrolytes  

SciTech Connect

Potentiostatic studies of Li(B) anodes in molten LiNO/sub 3/ at 300/sup 0/C indicate that at 80% peak open-circuit voltage, a broad flat discharge at 780 mA cm/sup -2/ is obtained. Galvanostatic discharge studies show stable anode potentials more negative than -3V (vs. Ag/sup +//Ag) in LiNO/sub 3/ at 300 mA cm/sup -2/ over a temperature range of 270/sup 0/-350/sup 0/C. At temperatures above 350/sup 0/C, deflagrations of the anode were often observed, particularly after deep discharge. Electrolyte composition is a key factor in determining the current density-potential and potential-temperature characteristics of the Li(B) anode in molten nitrates. Experiments in equimolar LiNO/sub 3/-KNO/sub 3/ exhibit open-circuit anode potentials up to 0.2V less electronegative to that seen in equimolar LiNO/sub 3/-NaNO/sub 3/ electrolyte. In a like fashion at 300 mA cm/sup -2/ and 300/sup 0/C, the use of LiNO/sub 3/-KNO/sub 3/ equimolar electrolyte results in Li(B) anode potentials up to 0.45V more positive than those seen in LiNO/sub 3/-NaNO/sub 3/ equilmolar electrolyte and up to 0.85V more positive than that seen in LiNO/sub 3/ electrolyte. Single cell tests integrating the Li(B) anode with existing silver ion cathode technology exhibit stable cell potentials in excess of 3V at 300 mA cm/sup -2/ at 300/sup 0/C. The two phase composition of the Li(B) alloy allows for exceptional anode stability at the high anode potential of elemental lithium.

McManis, G.E.; Fletcher, A.N.; Miles, M.H.

1984-02-01

453

Electrodeposition of polycrystalline and amorphous silicon for photovoltaic applications. Quarterly technical progress report No. 03, December 1, 1979-February 29, 1980  

SciTech Connect

The survey of Si precursors leading to electrodeposition of Si in organic solvents was extended this quarter to cover SiCl/sub 4/, (ClC/sub 3/H/sub 6/)SiCl/sub 3/, and Si(OEt)/sub 4/. Plating experiments with SiHCL/sub 3/ solutions in propylene carbonate with 0.1M tetrabutylammonium tetrafluoroborate were continued. Silicon was deposited on ITO glass (Nesatron) as well as Mo substrates at temperatures from 25-80/sup 0/C. Both potentiostatic and galvanostatic conditions were used. The high resistance of the films (10/sup 6/-10/sup 8/ ..cap omega..-cm) limited the thickness which could be deposited by either method to less than 5 ..mu..m. X-ray analysis of the films confirmed that they were amorphous. SEM analysis of the films revealed a very porous structure with nodules about 1 ..mu..m in diameter. Annealing the deposit at 400/sup 0/C in an Ar:H/sub 2/ atmosphere resulted in a slightly smoother surface but the nodules remained. The films deposited on ITO glass had a band gap of about 1.0 eV and an EO/sub 4/ value of 1.5-2.0 eV. The Auger analysis of the films showed the presence of large amounts of oxygen in the samples that had been exposed to air. The first silicon deposits were obtained from the high temperature fluoride molten salts. Plating on a platinum cathode resulted in silicide formation which suggests a method of making a PtSi alloy for use as a stable reference electrode in the fluoride melts containing silicon (IV). Galvanostatic deposition on silver substrates in general gave thick, uneven, and poorly adherent deposits.

Rauh, R.D.; Rose, T.L.; Boudreau, R.A.; Hoover, T.O.; Natwig, D.L.

1980-07-01

454

Carbon Nanotube Microwell Array for Sensitive Electrochemiluminescent Detection of Cancer Biomarker Proteins  

PubMed Central

This paper describes fabrication of a novel electrochemiluminescent (ECL) immunosensor array featuring capture-antibody-decorated single-wall carbon nanotube forests (SWCNT) residing in the bottoms of 10 L wells with hydrophobic polymer walls. Silica nanoparticles containing [Ru(bpy)3]2+ and secondary antibodies (RuBPY-silica-Ab2) are employed in this system for highly sensitive two-analyte detection. Antibodies to PSA and IL-6 were attached to the same RuBPY-silica-Ab2 particle. The array was fabricated by forming the wells on a conductive pyrolytic graphite chip (1 1 in.) with a single connection to a potentiostat to achieve ECL. The sandwich immunoassay protocol employs antibodies attached to SWCNTs in the wells to capture analyte proteins. Then RuBPY-silica-Ab2 is added to bind to the captured proteins. ECL is initiated in the microwells by electrochemical oxidation of tripropyl amine (TprA), which catalytically reduces [Ru(bpy)3]2+ in the 100 nm particles, and is measured with a coupled charged device (CCD) camera. Separation of the analytical spots by the hydrophobic wall barriers enabled simultaneous immunoassays for two proteins in a single sample without cross-contamination. Detection limit (DL) for prostate specific antigen (PSA) was 1 pg mL?1 and for interleukin-6 (IL-6) was 0.25 pg mL?1 (IL-6) in serum. Array determinations of PSA and IL-6 in patient serum were well-correlated with single-protein ELISAs. These microwell SWCNT immunoarrays provide a simple, sensitive approach to detection of two or more proteins.

Sardesai, Naimish P.; Barron, John C.; Rusling, James F.

2011-01-01

455

High-performance Supercapacitor cells with Activated Carbon/MWNT nanocomposite electrodes  

NASA Astrophysics Data System (ADS)

The purpose of this work was to investigate and improve the performance of supercapacitor cells with carbon-based nanocomposite electrodes. The electrode structure comprised activated carbon (AC), four types of multi-wall nanotubes (MWNTs) and two alternative polymer binders, Polyvinyl alcohol (PVA) or Polyvinylidene fluoride (PVDF). Electrode fabrication involved various stages of mixing and dispersion of the AC powder and carbon nanotubes, rolling and coating of the AC/MWNT/binder paste on an aluminium substrate which also served as current collector. The organic electrolyte utilised was 1M tetraethylammonium tetrafluoroborate (TEABF4) fully dissolved in propylene carbonate (PC). All devices were of the electrochemical double layer capacitor (EDLC) type, incorporating four layers of tissue paper as separator material. The surface topography of the so fabricated electrodes was investigated with scanning electrode microscopy (SEM). Overall cell performance was evaluated with a multi-channel potentiostat/galvanostat/impedance analyser. Each supercapacitor cell was subjected to Cyclic Voltammetry (CV) at various scan rates from 0.01 V/s to 1 V/s, Charge-Discharge at a fixed current steps (2 mA) and Electrochemical Impedance Spectroscopy (EIS) with frequency range from 10 mHz to 1 MHz. It was established that an AC-based supercapacitor with 0.15%w/w MWNT content and 30 ?m roll-coated, nanocomposite electrodes provided superior energy and power and energy densities while the cells was immersed in the electrolyte; well above those generated by the AC-based EDLC cells.

Markoulidis, F.; Lei, C.; Lekakou, C.; Figgemeier, E.; Duff, D.; Khalil, S.; Martorana, B.; Cannavaro, I.

2012-09-01

456

In situ monitoring of electrochemical reactions by surface enhanced Raman scattering. Final report 1 Jul 80-31 Aug 82  

SciTech Connect

Several aspects of the recently discovered surface enhanced Raman scattering (SERS) from molecules adsorbed on a metal-liquid or metal-gas interface were investigated. Since the physical origins of such a large enhancement factor 10,000 - 1,000,000 times on Ag surfaces) are not yet fully understood, the authors pursued the topic of SERS from the basic science aspect, concentrating mainly on the electromagnetic 'antenna' enhancement effect and on the adatom-related resonance effect. They also pursued the topic of SERS from the applications aspect, concentrating mainly on the correlation between the SERS spectra of adsorbed molecular species and the electrochemical cyclic voltammograms. This ability to provide molecular specific information on ions and molecules adsorbed on noble metal (Ag, Au, and Cu) electrodes, immersed in various electrolytes and controlled by a potentiostat, has eventual relevance to the H/sub 2//O/sub 2/ Pt-acid fuel cell system. In addition, they applied SERS to the monitoring of adsorbed molecules catalytically formed on Ag powder catalysts which had been briefly exposed to SO/sub 2/, O/sub 2/, O/sub 3/, NO, or NO/sub 2/ gas introduced into a purging He gas stream. Since SERS can detect catalytically formed SO/sub 3//sup -2/, SO/sub 4//sup -2/, NO/sub 2//sup -1/ and NO/sub 3//sup -1/ ions on Ag powder, they believe that SERS may one day be useful as an in situ diagnostic probe to provide molecular information on absorbed products/intermediates during actual catalytic reaction conditions. Whether SERS observed on the noble metals can be extended to transition metal surfaces (e.g., Pt, Pd, Ir, and Os), remains to be investigated.

Chang, R.K.

1982-11-01

457

Branched and interconnected bismuth telluride nanowire arrays for thermoelectric power generation  

NASA Astrophysics Data System (ADS)

Thermoelectric generators can be used to extract waste heat energy and convert it into usable electrical energy. For decades, the thermoelectric figure of merit (ZT), which is a function of the Seebeck coefficient, electrical conductivity and thermal conductivity, has been limited to values of about 1 for practical bulk thermoelectric materials because in bulk thermoelectric materials, the parameters of ZT are interdependent. The challenge is to find materials whose thermal and electrical properties can be altered independently. Recent progress shows that in advanced bulk materials and low dimensional systems, the electrical and thermal parameters can be modulated independently allowing us to attain ZT values >1. In principle, the nanowire topology allows manipulation of the power factor in addition to reduction in thermal conductivity by increased phonon scattering from free surfaces. The focus of this work is the fabrication of nanowire arrays that can be used to form a thermoelectric device in order to exploit the benefits offered by nanowires and increase the figure of merit of the device. Emphasis is placed on resolving challenges faced during fabrication of templates as well as the nanowires, and to achieve scalable synthesis at low cost, comparable to bulk, while retaining nanoscale control of composition. 300-350 mum thick, Branched Porous Anodic Alumina (BPAA) templates were fabricated for subsequent electrodeposition of bismuth telluride nanowires. The nanowires of diameter 100nm, length exceeding 100mum were fabricated using potentiostatic pulsed electrodeposition (2s-6s pulses) providing good filling factors and uniform deposition. The Bi2Te3 nanowire core was annealed in Se to form a Bi2(Se,Te)3 shell, after equilibration of point defects by annealing in a Te vapor overpressure. This structure is designed to scatter long-wavelength phonons, lowering the thermal conductivity, while electrostatically repelling electrons from the free surfaces to reduce defect scattering and enhance mobility. Thus, it is anticipated that the resulting material may exhibit enhanced ZT, forming the n-type leg of a bulk thermoelectric device.

Tewari, Pranati

458

Doped overoxidized polypyrrole microelectrodes as sensors for the detection of dopamine released from cell populations.  

PubMed

A surface modification of interdigitated gold microelectrodes (IDEs) with a doped polypyrrole (PPy) film for detection of dopamine released from populations of differentiated PC12 cells is presented. A thin PPy layer was potentiostatically electropolymerized from an aqueous pyrrole solution onto electrode surfaces. The conducting polymer film was doped during electropolymerization by introducing counter-ions in the monomer solution. Several counter-ions were tested and the resulting electrode modifications were characterized electrochemically to find the optimal dopant that increases sensitivity in dopamine detection. Overoxidation of the PPy films was shown to contribute to a significant enhancement in sensitivity to dopamine. The changes caused by overoxidation in the electrochemical behavior and electrode morphology were investigated using cyclic voltammetry and SEM as well as AFM, respectively. The optimal dopant for dopamine detection was found to be polystyrene sulfonate anion (PSS(-)). Rat pheochromocytoma (PC12) cells, a suitable model to study exocytotic dopamine release, were differentiated on IDEs functionalized with an overoxidized PSS(-)-doped PPy film. The modified electrodes were used to amperometrically detect dopamine released by populations of cells upon triggering cellular exocytosis with an elevated K(+) concentration. A comparison between the generated current on bare gold electrodes and gold electrodes modified with overoxidized doped PPy illustrates the clear advantage of the modification, yielding 2.6-fold signal amplification. The results also illustrate how to use cell population based dopamine exocytosis measurements to obtain biologically significant information that can be relevant in, for instance, the study of neural stem cell differentiation into dopaminergic neurons. PMID:23628978

Sasso, Luigi; Heiskanen, Arto; Diazzi, Francesco; Dimaki, Maria; Castillo-Len, Jaime; Vergani, Marco; Landini, Ettore; Raiteri, Roberto; Ferrari, Giorgio; Carminati, Marco; Sampietro, Marco; Svendsen, Winnie E; Emnus, Jenny

2013-07-01

459

A mechanistic study of copper electropolishing in phosphoric acid solutions  

NASA Astrophysics Data System (ADS)

The microelectronics industry is using copper as the interconnect material for microchips. A study of copper electropolishing is important for the process development of a new, low downforce approach, which is being developed to replace chemical mechanical polishing (CMP) of the copper overburden. A promising technology is a combination of electropolishing with conventional CMP. Electropolishing of copper in phosphoric acid has been studied for, more than 70 years. Previous work has shown that the polishing rate, as measured by current density is directly related to the viscosity of the electrolyte. Also, the limiting species is water. In this study, a multidimensional design of experiments was performed to develop an in-depth model of copper electropolishing. Phosphoric acid was mixed with alcohols of different molecular weight and related viscosity to investigate how the solvents' properties affected polishing. The alcohols used were methanol, ethanol, isopropanol, butanol, ethylene glycol, and glycerol. The limiting current densities and electrochemical behavior of each solution was measured by potentiodynamic and potentiostatic experiments. Also, the kinematic viscosity and density were measured to determine the dynamic viscosity to investigate the relationship of current density and viscosity. Water, methanol, ethanol, and isopropanol solutions were also examined at 20C to 60C. Next, the relative percentage of dissociated phosphoric acid was measured by Raman spectroscopy for each polishing solution. Raman spectroscopy was also used to measure the relative dissociation of phosphoric acid inside the polishing film. Additionally, wafers were electropolished and electrochemical mechanically polished to investigate the effects of the different solvents, fluid flow, current, and potential. The results of these experiments have shown that the molecular mass and the ability of the solvent to dissociate phosphoric acid are the primary electrolyte properties that control copper electropolishing. The dependence of the polishing rate on viscosity seen in previous studies is purely consequential. Therefore, by controlling the type and concentration of alcohol in the electropolishing solution the polishing rate can be controlled.

Mansson, Andrew

460

Characterization of hydrogen ingress in high-strength alloys. Final report, 15 September 1993-14 September 1995  

SciTech Connect

The ingress of hydrogen (H) in various high-strength alloys was investigated with a view to characterizing their susceptibility to hydrogen embrittlement (HE). A potentiostatic pulse technique was applied to three Fe-base alloys (AerMet 100, H11, and A-286), two Cu-containing alloys (Be-Cu and alloy K-500), a superferritic stainless steel (Sea-Cure), and three Beta-Ti alloys (Ti-15V-3Cr-3Al-3Sn, Beta-21S, and Beta-C) in 1 mol/L acetic acid-1 mol/L sodium acetate. The data were analyzed using a diffusion/trapping model to obtain the irreversible trapping constant (k) and H entry flux for each alloy. The order of the k values for AerMet 100, H11, and two high-strength steels previously studied (4340 and 18Ni) inversely parallels their threshold stress intensities for stress corrosion cracking. Likewise, the k values for the other alloys can be correlated with their observed resistances to HE according to the following groups: (1) alloy A-286,18Ni steel, H11, Be-Cu, and also alloy 718 from earlier work; (2) annealed/aged and direct aged alloy K-500; and (3) Ti alloys. The trapping characteristics of Sea-Cure could not be determined. However, the propensity of the S44660 alloy to undergo HE at cathodic protection potentials can be attributed to changes in the oxide that lead to a less restricted entry of H.

Pound, B.G.

1995-11-01

461

Evaluation of a diffusion/trapping model for hydrogen ingress in high-strength alloys. Annual report, 15 September 1993-14 September 1994  

SciTech Connect

The ingress of hydrogen in various high-strength alloys was investigated with a view to characterizing their susceptibility to hydrogen embrittlement (HE). A potentiostatic pulse technique was applied to two precipitation-hardened iron-base alloys (AerMet 100 and alloy A-286), two Cu-containing alloys (Be-Cu and alloy K-500), and a superferritic stainless steel (UNS 544660) in 1 mol/L acetic acid-1 mol/L sodium acetate. The data were analyzed using a diffusion/trapping model to obtain the irreversible trapping constant (k) and hydrogen entry flux for each alloy. Irreversible trapping was negligible in overaged AerMet 100 but pronounced in the aged alloy. The order of the k values for AerMet 100 and two steels (4340 and 1 18Ni) previously studied inversely parallels their threshold stress intensities for stress corrosion cracking. Likewise, the k values of alloy A-286, 18Ni steel, and also alloy 718 from earlier work are consistent with test data for their relative resistance to HE. The results for AerMet 100 and alloy A-286 extend the previously reported correlation between k and HE resistance. Unaged Be-Cu is intrinsically more susceptible to HE than unaged alloy K- 500. The type of heat treatment has a marked effect on the rapping behavior of alloy K-500. The intrinsic susceptibility of the annealed and aged alloy is twice that or the direct-aged alloy. The propensity of the S44660 alloy to undergo HE at cathodic protection potentials can be attributed to the absence of an oxide and hence the relatively unrestricted entry of H.

Pound, B.G.

1994-11-01

462

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

SciTech Connect

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.

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

1999-04-01

463

Impedance study of tea with added taste compounds using conducting polymer and metal electrodes.  

PubMed

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

Dhiman, Mopsy; Kapur, Pawan; Ganguli, Abhijit; Singla, Madan Lal

2012-09-01

464

Nuclear magnetic resonance spectroscopic study of the electrochemical oxidation product of methanol on platinum black  

SciTech Connect

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.

Day, J.B. [Univ. of Illinois, Urbana, IL (United States)]|[Ecole Polytechnique Federale de Lausanne (Switzerland); Oldfield, E.; Wieckowski, A. [Univ. of Illinois, Urbana, IL (United States); Vuissoz, P.A.; Ansermet, J.P. [Ecole Polytechnique Federale de Lausanne (Switzerland)

1996-12-25

465

Microstructure and anodic polarization behavior of experimental Ag-18Cu-15Pd-12Au alloy in aqueous sulfide solution.  

PubMed

The anodic corrosion behavior of an experimental Ag-15Pd-18Cu-12Au alloy in 0.1% Na(2)S solution in relation to its microstructure was investigated using potentiodynamic and potentiostatic polarization techniques with analyses of corrosion products by X-ray diffractometry, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. The role of Pd in improvement of the corrosion resistance was also investigated. In the potential/current density curve, three distinct current peaks, at -520 mV (peak I), -425 mV (peak II) and -175 mV (peak III), were observed. The Ag-rich alpha(2) matrix with coarse Cu and Pd-rich lamellae was the most corrosion-susceptible region, and this region was preferentially corroded at peak I with the formation of granular deposits of Ag(2)S. A small amount of Ag-Cu mixed sulfide deposited on the Cu and Pd-rich coarse particles and dissolution of Ag as AgO(-) might have occurred in parallel with Ag(2)S formation at peak II. Enrichment of Pd on the alloy surface occurred at peak III due to preferential dissolution of Ag and Cu. A high level of corrosion resistance was attained with the formation of a thin Pd-rich sulfide film, which enhanced the passivity of the alloy in an alkaline sulfide solution. It was found that passivity is an important phenomenon not only for base metal alloys but also for noble metal alloys to maintain high levels of resistance to corrosion and tarnishing in sulfide environments. PMID:15348446

Endo, Kazuhiko; Ohno, Hiroki; Asakura, Shukuji

2003-05-01