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1

Time-Based Integrated Potentiostat.  

National Technical Information Service (NTIS)

An integrated potentiostat includes a voltage controller that maintains within a predetermined range a potential between a reference electrode and a working electrode in an electrochemical cell. The integrated potentiostat further includes a capacitor tha...

H. S. Narula J. G. Harris

2005-01-01

2

Potentiostat Circuits for Biomedical Instrumentations  

NASA Astrophysics Data System (ADS)

The potentiostat system consisting of a constant voltage driving negative feedback circuit is very useful in understanding of electrochemical interfacial phenomena. This paper proposes a designing method for a simplified potentiostat circuit for biomedical instrumentations and bio-sensors, by using conventional op-amplifiers and instrumentation amplifiers. The ranges are 10?V˜10mV, 0.1nA˜10mA in the frequency of 10Hz˜10kHz. Results of the loop frequency characteristics, the intrinsic noises and the Lissajous characteristic of a designed potentiostat consisting of low noise and low bias-current op-amps. and instrumentation amps. are shown.

Dendo, Isao

3

Simple, Low Cost Potentiostat for Corrosion Studies.  

National Technical Information Service (NTIS)

An inexpensive potentiostat with a fairly basic specifications is described which has been developed for long-term tests in sea water. The design uses, cheap, readily available integrated-circuit operational amplifiers and voltage stabilizers. Several ins...

P. E. Francis A. S. Dolphin

1984-01-01

4

Calibration Method and Apparatus for Potentiostats.  

National Technical Information Service (NTIS)

A system and method for potentiostat calibration includes a conductive substrate, a model film placed on the substrate, an electrolyte, and a potentionstat for obtaining calibration data from tests conducted on the model film. The electrolyte is disposed ...

B. R. Hinderliter G. P. Bierwagen V. S. Bonitz

2005-01-01

5

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

2010-01-01

6

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

7

Application of Coulostatic Charge Injection Techniques to Improve Potentiostat Risetimes.  

National Technical Information Service (NTIS)

The design of a potentiostat is given which is capable of applying large amounts of peak power (300 watts at 1 micro sec to an electrochemical cell. The design incorporates the use of a coulostat to initially charge the double layer while the potentiostat...

J. F. Davis N. Winograd

1972-01-01

8

VLSI multichannel track-and-hold potentiostat  

NASA Astrophysics Data System (ADS)

Simultaneous mapping of multiple electrical or chemical properties of neural activity facilitates understanding neurological phenomena and their underlying mechanisms. We present a track-and-hold potentiostat performing simultaneous acquisition of 16 independent channels of current ranging five orders of magnitude in dynamic range over four scales down to hundreds of picoamperes. Sampling rate ranges from DC to 200KHz. The system features programmable current gain control, configurable anti-aliasing log-domain filter, triggered current integration and provides differential output ready for asynchronous external analog-to-digital conversion over a compressed dynamic range. We present system description, circuit implementation and experimental results of real-time neurotransmitter concentration measurements from the 16-channel prototype fabricated in a 1.2 micron CMOS process.

Genov, Roman; Stanacevic, Milutin; Naware, Mihir; Cauwenberghs, Gert; Thakor, Nitish

2003-04-01

9

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

10

Development of a low cost potentiostat using ATXMEGA32  

NASA Astrophysics Data System (ADS)

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

Muid, Abdul; Djamal, Mitra; Wirawan, Rahadi

2014-03-01

11

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

12

Design of a CMOS Potentiostat Circuit for Electrochemical Detector Arrays  

PubMed Central

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

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

2010-01-01

13

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

14

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

15

Simulations of surface capacitance effects on potentiostat response following disruption of passivity.  

National Technical Information Service (NTIS)

Following depassivation of potentiostatically controlled metals, complex current transients arise because of the current distribution and the capacitance of the surrounding passive metal/solution interface. A computer simulation of the cross-section has b...

H. S. Isaacs A. J. Davenport G. S. Frankel

1991-01-01

16

DURIP 00 Thermal Analysis and Potentiostatic Instuments for Relaxor Ferroelectric Research.  

National Technical Information Service (NTIS)

The funds provided by this grant were used to purchase a thermoanalytical balance, with additional thermal analytical capabilities, and a general purpose potentiostat/galvanostat in support of ongoing research on the thermochemistry of ferroelectric relax...

W. Petuskey

2001-01-01

17

A highly-accurate low-power CMOS potentiostat for implantable biosensors  

Microsoft Academic Search

Current-mirror-based potentiostats suffer from systematic and random errors causing offset, gain and linearity error in reading out the sensor data. In this work, a new potentiostat topology is proposed to eliminate the systematic error via an error-cancellation loop. The loop takes advantage of an error-tracking amplifier connected to a transimpedance amplifier with adjustable input common-mode voltage. Due to the enhanced

Milad Razzaghpour; Saul Rodriguez; Eduard Alarcon; Ana Rusu

2011-01-01

18

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

19

Electrochemical degradation of aqueous solution of Amaranth azo dye on ACF under potentiostatic model  

Microsoft Academic Search

The Amaranth azo dye degradation with electrochemical method in aqueous solution has been studied under potentiostatic condition with activated carbon fiber (ACF) electrode. Cyclic voltammetry on platinum (Pt) wire and quasi-steady-state polarized curves on ACF held by a Pt wire were investigated at first. The mechanisms of the electrochemical processes for Amaranth on ACF were defined as adsorption, electrooxidation and

Li Fan; Yanwei Zhou; Weishen Yang; Guohua Chen; Fenglin Yang

2008-01-01

20

A Low-Noise Potentiostat for the Study of Small Amplitude Signals in Electrochemistry.  

National Technical Information Service (NTIS)

A low noise potentiostat, developed and built at NBS, is described. The instrument, which has built-in an ac current amplifier, is particularly suited for detecting small current fluctuations in the frequency range between 0.1 and 2000 Hz. The noise in th...

R. W. Shideler U. Bertocci

1980-01-01

21

High-Speed Non-Faradaic Resistance Compensation in Potentiostatic Techniques.  

National Technical Information Service (NTIS)

The general problem of the incorporation of IR compensation in a potentiostatic circuit is considered. The manner in which the number of time constants needed to describe the system affect the amount of stable positive feedback at short times or high freq...

A. A. Pilla R. B. Roe C. C. Herrmann

1969-01-01

22

Use of a new potentiostat/coulometer in the controlled-potential coulometric determination of plutonium.  

National Technical Information Service (NTIS)

We evaluated a PAR 273 potentiostat and PAR 279 coulometer using iron as a stand-in for plutonium. Over 400 turns consisting of electrical checks, blanks, and iron solutions were made. Manual operation of the instrumentation produced precisions better tha...

P. G. Mendoza D. J. Temer D. D. Jackson

1993-01-01

23

Preparation and characterisation of Cu–Co heterogeneous alloys by potentiostatic electrodeposition  

Microsoft Academic Search

Electrodeposition in the potentiostatic mode has been used to produce Cu–Co metastable alloys. The influence of different plating parameters, such as bath composition, working electrode voltage (vs. reference) and intensity of agitation, on the composition and properties of the deposit has been investigated. A broad range of compositions (2–26 at.% Co) are obtainable. In particular, the Co content in the

R. López Antón; M. L Fdez-Gubieda; A Garc??a-Arribas; J Herreros; M Insausti

2002-01-01

24

A low-cost miniaturized potentiostat for point-of-care diagnosis.  

PubMed

This paper presents a novel approach of using a miniaturized potentiostat (M-P) chip (LMP91000) to perform full range cyclic voltammetry (CV) measurements for the detection of biomarkers. The LMP91000 evaluation board was reconfigured to perform three-electrode CV measurements in order to achieve electrochemical cortisol immunosensing. The microelectrodes for cortisol estimation were fabricated by immobilizing monoclonal anti-cortisol antibody (Anti-M-Cab) onto self-assembled monolayer (SAM) modified Au microelectrodes. The results obtained using the M-P were compared to those obtained using a conventional potentiostat. The M-P was successful in measuring cortisol levels in the range of pM. The outcomes of the studies suggest that M-P can effectively perform biochemical measurements on three electrode systems, enabling the development of miniature systems for point-of-care (POC) diagnosis. PMID:25016332

Cruz, Andres Felipe Diaz; Norena, Nicolas; Kaushik, Ajeet; Bhansali, Shekhar

2014-12-15

25

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

2013-08-01

26

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

Microsoft Academic Search

A color interference film etching technique based on the principle of potentiostatic etching has been developed to distinguish, by optical metallography, between Cr-rich sigma and Mo-rich chi phases as well as with simultaneous identification of the ferrite and austenite phases in duplex stainless steels. The optical metallography results are confirmed by semiquantitative energy dispersive spectrometry analysis and back-scattered electron imaging.

E. M. L. E. M. Jackson; P. E. de Visser; L. A. Cornish

1993-01-01

27

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 -30°C, can be manufactured at relatively low cost ($600), thus, allowing for en-masse deployment at field sites. The MCU-based potentiostat was integrated with electrodes and a solar panel-based power system, and deployed as a biosensor to monitor microbial respiration in drained thaw lake basins outside Barrow, AK. At three different depths, the working electrode of a microbial three-electrode system (M3C) was maintained at potentials corresponding to the microbial reduction of iron(III) compounds and humic acids. Thereby, the working electrode mimics these compounds and is used by certain microbes as an electron acceptor. The sensors revealed daily cycles in microbial respiration. In the medium- and deep-depth electrodes the onset of these cycles followed a considerable increase in overall activity that corresponded to those soils reaching temperatures conducive to microbial activity as the summer thaw progressed. The BES biosensor is a valuable tool for studying microbial activity in situ in remote environments, and the cost-efficient design of the potentiostat allows for wide-scale use in remote areas. PMID:22209069

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

2012-02-15

28

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

2011-04-01

29

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

2013-09-15

30

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

PubMed Central

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

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

2012-01-01

31

Analysis of delamination in thin film electrodes under galvanostatic and potentiostatic operations with Li-ion diffusion from edge  

NASA Astrophysics Data System (ADS)

Progressive delamination driven by Li-ion diffusion in elastic disk-like thin film electrodes of Li-ion batteries is modeled based on the cohesive model. Axisymmetric diffusion model is considered under both galvanostatic and potentiostatic operations. The effect of edge diffusion on the delamination process is evaluated. It is found that the diffusion from edge leads to an earlier delamination initiation. The edge effect is significant for active disks with a small aspect ratio, but negligible for the case of large aspect ratio. The edge diffusion is weaker in the potentiostatic operation than in the galvanostatic operation.

Lu, Bo; Song, Yi-Cheng; Guo, Zhan-Sheng; Zhang, Jun-Qian

2013-06-01

32

Synthesis and photoelectrochemical properties of nanoporous iron (III) oxide by potentiostatic anodization  

NASA Astrophysics Data System (ADS)

We report the synthesis of self-organized nanoporous iron (III) oxide (haematite) via potentiostatic anodization of iron foil. Dependent upon the applied potential and electrolytic composition, the pore diameters range from 50 to 250 nm with a pore depth of approximately 500 nm. We examine the effect of electrolytic composition, anodization bath temperature and applied potential on the dimensions of the as-synthesized nanoporous structure. Crystallization and structural retention of the synthesized structure are achieved upon annealing the initial amorphous sample in a nitrogen atmosphere at 400 °C. The crystallized nanoporous film, having a 2.2 eV bandgap, exhibited a net photocurrent density of 0.51 mA cm-2 in 0.5 M H2O2+1 M NaOH at 0.6 V versus Ag/AgCl under simulated AM 1.5 sunlight. Factors limiting the photoresponse and strategies of improvement are discussed.

Prakasam, Haripriya E.; Varghese, Oomman K.; Paulose, Maggie; Mor, Gopal K.; Grimes, Craig A.

2006-09-01

33

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

34

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

2011-01-01

35

Urinalysis with molecularly imprinted poly(ethylene-co-vinyl alcohol) potentiostat sensors.  

PubMed

Among many important biomarkers excreted in urine are albumin, uric acid, glucose, urea, creatine and creatinine. In the growing elderly population, these biomarkers may be useful correlates with kidney dysfunction, infection and related problems such as glomerular, proximal, and distal convoluted tubule functions, diabetes, hypertension and proteinuria. This study employed solvent evaporation processing of poly(ethylene-co-vinyl alcohol), (EVAL) to form molecularly imprinted polymers (MIPs) that recognize creatinine, urea, and lysozyme. The mole ratio of ethylene to vinyl alcohol affected the performance: 27 mol% ethylene gave the highest imprinting effectiveness for creatinine and urea, while 44 mol% gave the highest effectiveness for lysozyme. Electrochemical examination using a home made potentiostat and imprinted polymer electrode showed electrical signals responsive to the target molecules. Finally, an actual urine sample was tested using the electrode. The test results were compared with those of the commercial instrument ARCHITECT ci 8200 system to precisely determine the accuracy of the molecularly imprinted polymer electrode for urinalysis. PMID:19230648

Huang, Chun-Yueh; Tsai, Tain-Chin; Thomas, James L; Lee, Mei-Hwa; Liu, Bin-Da; Lin, Hung-Yin

2009-04-15

36

In-channel electrochemical detection for microchip capillary electrophoresis using an electrically isolated potentiostat.  

PubMed

A new electrode configuration for microchip capillary electrophoresis (CE) with electrochemical (EC) detection is described. This approach makes it possible to place the working electrode directly in the separation channel. The "in-channel" EC detection was accomplished without the use of a decoupler through the utilization of a specially designed, electrically isolated potentiostat. The effect of the working electrode position on the separation performance (in terms of plate height and peak skew) of poly(dimethylsiloxane)-based microchip CEEC devices was evaluated by comparing the more commonly used end-channel configuration with this new in-channel approach. Using catechol as the test analyte, it was found that in-channel EC detection decreased the total plate height by a factor of 4.6 and lowered the peak skew by a factor of 1.3. A similar trend was observed for the small, inorganic ion nitrite. Furthermore, a fluorescent and electrochemically active amino acid derivative was used to directly compare the separation performance of in-channel EC detection to that of a widely used laser-induced fluorescence (LIF) detection scheme. In this case, it was found that the plate height and peak skew for both detection schemes were essentially equal, and the separation performance of in-channel EC detection is comparable to LIF detection. PMID:11924975

Martin, R Scott; Ratzlaff, Kenneth L; Huynh, Bryan H; Lunte, Susan M

2002-03-01

37

Reprint of: 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:24216205

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

2013-11-25

38

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

Microsoft Academic Search

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

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

39

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

Strømme, Maria; Frenning, Göran; Razaq, Aamir; Gelin, Kristina; Nyholm, Leif; Mihranyan, Albert

2009-04-01

40

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

41

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

42

XPS Spectroscopic Study of Potentiostatic and Galvanostatic Oxidation of Pt Electrodes in H2SO4 and HClO4.  

National Technical Information Service (NTIS)

The surface oxides produced from potentiostatic and galvanostatic oxidation of Pt electrodes in HClO4 and H2SO4 are examined using x-ray photoelectron spectroscopy. The oxide I species produced as the initial oxidation product by successively more anodic ...

J. S. Hammond N. Winograd

1976-01-01

43

A potentiostatic study of the solid-phase diffusion of the electronegative component during selective dissolution of Pb-In, Ag-Cd, and Sn-Zn alloys  

SciTech Connect

In this paper the authors have studied by a pulse potentiostatic method the selective dissolution (SD) of Pb-In (5, 10, 20 at .%), Sn-In (0.5, 1, 2.5, 4, 17 at .%), Ag-Cd (30 at .%), and Sn-Zn (1 at .%) alloys at potentials which are sufficient only for the dissolution of the electronegative component (ENC). Also considered is the effect of the ENC concentration in the alloy, of the duration of the SD process, and of the melting point of the alloy on the quantity D /SUB A/ (diffusion constant of ENC component A in alloy A-B). The experiments were carried out in deaerated solutions at 20/sup 0/C. Features of solid-phase diffusion of the A atoms during the SD of alloy A-B are described.

Pchel'nikov, A.P.; Losev, V.V.; Marshakov, A.I.

1986-01-01

44

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

PubMed Central

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

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

2012-01-01

45

Semi-real time electrochemical monitoring for influenza virus RNA by reverse transcription loop-mediated isothermal amplification using a USB powered portable potentiostat.  

PubMed

In this paper, the semi-real time electrochemical monitoring method using a screen-printed electrode, which employs reverse transcription loop-mediated isothermal amplification (RT-LAMP) for influenza virus RNA, is presented. The amplified DNA combined with methylene blue (MB), which was used as an electroactive DNA intercalator, and the electrochemical signal was monitored using square wave voltammetry in the presence of RT-LAMP reagent components. MB molecules binding to amplified DNA caused the reduction of the peak current due to the slow diffusion of MB-amplified DNA complex to the electrode surface. We successfully monitored the amplification process of DNA on the basis of RT-LAMP by measuring and analyzing the electrochemical signal of MB with only one screen-printed electrode that connected with a USB powered portable potentiostat. The peak height of the current was related to the extent of amplification of DNA and the amount of input RNA. Since laborious probe immobilization is not required and both the amplification and the monitoring are possible in a single tube, our method does not suffer from potential cross-contamination. Furthermore, our method provides a new rote for the development of electrochemical hand held biosensors. PMID:22010112

Nagatani, Naoki; Yamanaka, Keiichiro; Saito, Masato; Koketsu, Ritsuko; Sasaki, Tadahiro; Ikuta, Kazuyoshi; Miyahara, Toshiro; Tamiya, Eiichi

2011-12-21

46

Parallel recording of neurotransmitters release from chromaffin cells using a 10×10 CMOS IC potentiostat array with on-chip working electrodes.  

PubMed

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

Kim, Brian N; Herbst, Adam D; Kim, Sung J; Minch, Bradley A; Lindau, Manfred

2013-03-15

47

A simple, low cost potentiostat for corrosion studies  

Microsoft Academic Search

A potensiostat for long term tests in sea water was designed, using readily available integrated-circuit operational amplifiers and voltage stabilizers. Reference electrode to specimen voltage is + or - 2V. Specimen to counter electrode voltage is + or - 10V. Maximum output current is 0.1 A. Inputs are isolated from earth. Reference electrodes input impedance is 100 million ohms. It

P. E. Francis; A. S. Dolphin

1984-01-01

48

A simple, low cost potentiostat for corrosion studies  

NASA Astrophysics Data System (ADS)

A potensiostat for long term tests in sea water was designed, using readily available integrated-circuit operational amplifiers and voltage stabilizers. Reference electrode to specimen voltage is + or - 2V. Specimen to counter electrode voltage is + or - 10V. Maximum output current is 0.1 A. Inputs are isolated from earth. Reference electrodes input impedance is 100 million ohms. It has recording outputs for cell-current and specimen-to-reference potential. In performance tests, potential drift never exceeds 5 mV over a 50 day period.

Francis, P. E.; Dolphin, A. S.

1984-07-01

49

Intelligent potentiostat for identification of heavy metals in situ  

NASA Astrophysics Data System (ADS)

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

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

2006-01-01

50

Determination of Gold, Silver, and Copper in Gold-Base Alloys by Potentiostatic Coulometry  

Microsoft Academic Search

The working conditions for the simultaneous coulometric determination of 0.5 to 3 mg of gold, silver, and copper with a relative standard deviation of at most =0.5% were found in the study of the voltammetric behavior of Au(III), Ag(I), and Cu(II) at a platinum electrode in a 2 M HCl + 0.1 M KCNS solution. Fivefold mass amounts of gold

A. M. Demkin

2004-01-01

51

CONTROLLED ENVIRONMENT POTENTIOSTAT TO STUDY SOLID-AQUEOUS SYSTEMS. (R825549C051)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

52

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

53

Fatigue behavior in the potentiostatic passive corrosion regime of the iron-base superalloy A-286  

NASA Astrophysics Data System (ADS)

Surface crack initiation and propagation behavior of the iron-base superalloy A-286 were tested using smooth hourglass specimens under passive corrosion conditions. In the very underaged (VUA) condition, cracks were initiated at slip steps (stage I) and later propagated in a stage II mode, resulting in a minimum or dip in crack growth rate. For the highly overaged condition (HOA), cracks initiated at inclusions, and only stage II was observed; therefore, anomalies in crack growth behavior were not observed. A planar slip distribution, observed in VUA, was associated with a reduced crack growth rate. In general, the VUA microstructure was superior to HOA, as it exhibited an impressive combination of excellent mechanical properties, decreased susceptibility to corrosion, good resistance against crack initiation, and low crack growth rate, under corrosion fatigue conditions. Possible reasons for such behavior are discussed.

Daeubler, M. A.; Thompson, A. W.; Bernstein, I. M.

1991-02-01

54

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

ERIC Educational Resources Information Center

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

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

2007-01-01

55

Electroluminescence of heavily doped p-type porous silicon under electrochemical oxidation in the potentiostatic regime  

Microsoft Academic Search

Visible light emission is obtained during the anodic oxidation of heavily doped p-type porous silicon layers, with similar characteristics to the electroluminescence observed on lightly doped substrates. This indicates that the coarser structure of the heavily doped layers also presents a thinner structure, with crystallites of quantum sizes responsible for the emission. In this paper, the electroluminescence is studied in

S. Billat; F. Gaspard; R. Hérino; M. Ligeon; F. Muller; F. Romestain; J. C. Vial

1995-01-01

56

Supported Pt and Pt–Ru catalysts prepared by potentiostatic electrodeposition for methanol electrooxidation  

Microsoft Academic Search

Methanol electrooxidation was investigated on Pt–Ru electrocatalysts supported on glassy carbon. The catalysts were prepared\\u000a by electrodeposition from solutions containing chloroplatinic acid and ruthenium chloride. Bulk composition analysis of the\\u000a Pt–Ru catalyst was performed using an X-ray detector for energy dispersive spectroscopy analysis (EDX). Three different compositions\\u000a were analyzed in the range 0–20 at.% Ru content. Tafel plots for the oxidation

J. M. Sieben; M. M. E. Duarte; C. E. Mayer

2008-01-01

57

New GC\\/MS and Potentiostat and their Application to Photochrome Research  

Microsoft Academic Search

Photoinduced charge transfer (PICT) is a useful means of generating organic ion radicals. Cation radicals generated by PICT have relevance in a variety of applications of materials science interest, including new approaches to volume holographic data storage and 3D microfabrication. However a limitation to the use of PICT-initiated cation radical reactions is the persistence of photooxidant in the material subsequent

Kyndra Sluiter

2011-01-01

58

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

59

Potentiostatic Reversible Photoelectrochromism: An Effect Appearing in Nanoporous TiO2/Ni(OH)2 Thin Films.  

PubMed

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

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

2014-07-01

60

Potentiostatic-pulse study of the selective anodic dissolution of binary alloys involving multistep ionization of the electronegative component. indium-tin alloy  

Microsoft Academic Search

The laws of selective dissolution of an electronegative component A from A-B alloy at constant potential are analyzed while allowing for a multistep mechanism of the dissolution of A. The expression obtained for the time dependence of the overall dissolution rate of A from the alloy is analyzed for the case where the concentration of A on the alloy surface

A. I. Marshakov; V. V. Losev; A. P. Pchelnikov; Y. B. Skuratnik

1986-01-01

61

Potentiostatic-pulse study of the selective anodic dissolution of binary alloys involving multistep ionization of the electronegative component. indium-tin alloy  

SciTech Connect

The laws of selective dissolution of an electronegative component A from A-B alloy at constant potential are analyzed while allowing for a multistep mechanism of the dissolution of A. The expression obtained for the time dependence of the overall dissolution rate of A from the alloy is analyzed for the case where the concentration of A on the alloy surface is constant while the rate of the step A in equilibrium A /SUP n1+/ + n/sub 1/e is much higher than that of the step A /SUP n1+/ in equilibrium A /SUP n+/ + n/sub 2/e. The approach developed is used to study the laws of In dissolution from In-Sn alloy (17 atom % of In) in chloride solution.

Marshakov, A.I.; Losev, V.V.; Pchel'nikov, A.P.; Skuratnik, Y.B.

1986-09-01

62

Test Procedure to Evaluate the Relative Susceptibility of Materials to Stress Corrosion Cracking.  

National Technical Information Service (NTIS)

A stress corrosion test procedure that employs electrochemical potentiostatic polarization techniques has been presented. A potentiostatic stress corrosion life curve (PSCLC) was developed for various materials. The PSCLC can be used to show the effect of...

D. L. Dull L. Raymond

1972-01-01

63

Distributed neurochemical sensing: in vitro experiments  

Microsoft Academic Search

Experimental results characterizing a VLSI multi-channel potentiostat sensor system designed for sensing distributed neurotransmitter activity are presented. Neurotransmitter concentration is electrochemically transduced using an external carbon fiber electrode. Resultant current is processed by an integrated potentiostat, consisting of a current amplification stage, current-mode delta-sigma A\\/D converter, and counting decimator. Electrical characterization has shown that the VLSI potentiostat is sensitive to

G. Mulliken; Mihir Naware; A. Bandyopadhyay; Gert Cauwenberghs; Nitish Thakor

2003-01-01

64

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

PubMed Central

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

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

2010-01-01

65

SWEPT-POTENTIAL ELECTROCHEMICAL DETECTOR FOR FLOW STREAMS  

EPA Science Inventory

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

66

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

67

Electrochemical Etching of Titanium-Alloy Castings.  

National Technical Information Service (NTIS)

This study was conducted to determine whether a potentiostatic electrochemical method could be used to etch selectively either the dendrites or the interdendritic material from Ti cast structures and thereby reveal their microstructures. Cast binary titan...

J. C. Griess S. A. David R. J. Gray C. W. Houck

1983-01-01

68

The Variable Corrosion Resistance of 18CR-8NI Stainless Steels: I. Behavior of Commercial Alloys.  

National Technical Information Service (NTIS)

The electrochemical and corrosion characteristics of Types 303, 304 and 316 stainless steel in 1N H2SO4 were determined using precision potentiostatic polarization and conventional coupon exposure/weight change techniques. Factors increasing the magnitude...

B. E. Wilde N. D. Greene

1968-01-01

69

Educator's Reference Guide for Electrochemistry  

NSDL National Science Digital Library

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

2011-03-25

70

Intergranular Attack of Alloy 600: High-Temperature Electrochemical Tests. Final Report.  

National Technical Information Service (NTIS)

In some steam generators, intergranular attack (IGA) has occurred on Alloy 600 tubes in the tube-tube sheet crevice region. In order to evaluate the physico-chemical parameters which influence this type of corrosion, potentiostatic tests were implemented ...

G. Pinard-Legry G. Plante

1983-01-01

71

Extraction of Faradaic Signals from Flash Photocurrent Measurements--Benzophenone Photolysis.  

National Technical Information Service (NTIS)

The first paper in this series developed a theoretical model for characterizing the charging currents induced by changing faradaic currents measured under potentiostatic conditions. Of specific concern here are photoelectrochemical measurements, although ...

K. F. Dahnke S. S. Fratoni S. P. Perone

1975-01-01

72

Mechanism of formation and growth of sunflower-shaped imperfections in anodic oxide films on niobium  

Microsoft Academic Search

Anodizing of niobium has been investigated to develop niobium solid electrolytic capacitors. Chemically polished niobium specimens were anodized in a diluted phosphoric acid solution, initially galvanostatically at ia=4Am?2 up to Ea=100V, and then potentiostatically at Ea=100V for tpa=43.2ks. During the galvanostatic anodizing, the anode potential increased almost linearly with time, while, during potentiostatic anodizing, the anodic current decreased up to

K. Nagahara; M. Sakairi; H. Takahashi; K. Matsumoto; K. Takayama; Y. Oda

2007-01-01

73

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

74

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

75

A Real Time Measuring Method for Complex Impedance in Biomedical Instrumentations  

NASA Astrophysics Data System (ADS)

The author proposes a measuring method of complex bioimpedance in real time by using a potentiostat circuit and LabVIEW programming tools. In the system, 4-electrode method is applied on the dc-coupled potentiostat. Complex impedance is calculated from the frequency response function in LabVIEW. The resolutions of the resistive and reactive components are about 0.005% respectively. As a preliminary experiment, the complex impedance on a middle finger at 1kHz is measured with sampling time of 10ms. Pulse waves of resistive components which are synchronizing with ECG are clearly observed and very small reactive components.

Dendo, Isao

76

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

77

Characterization of electrochemically deposited polypyrrole using magnetoelastic material transduction elements  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

78

Electrodeposition of CdSe xTe 1 - x by periodic pulse technique  

NASA Astrophysics Data System (ADS)

Cadmium chalcogenides have been electrodeposited from an aqueous solution on titanium and graphite substrates by potentiostatic and periodic pulse techniques. Deposits have been characterized with X-ray diffractograms, surface micrographs, X-ray microprobe analysis and voltammetry. The mechanism and deposition kinetics of CdSe xTe 1 - x have been determined. The results are discussed.

Babu, S. Moorthy; Rajalakshmi, T.; Dhanasekaran, R.; Ramasamy, P.

1991-03-01

79

Electrochemical migration tests of solder alloys in pure water  

Microsoft Academic Search

Electrochemical migration (ECM) tests on solder alloys were conducted by applying constant voltage with a power supply or sweeping the voltage at a constant rate with a potentiostat. Distilled water was used as the test environment. Time to short and short voltage were the measure of ECM susceptibility. Similar results were obtained in both test methods. In Sn?Pb alloy system,

T. Takemoto; R. M. LATANISIONI; T. W. EAGARt; A. Matsunawa

1997-01-01

80

Use of underpotential deposition of zinc to mitigate hydrogen absorption into Monel K500  

Microsoft Academic Search

Polarization experiments and a potentiostatic pulse technique have been used to show that a monolayer coverage of zinc effectively inhibits the absorption of hydrogen into Monel K500. By depositing a monolayer of zinc on Monel K500 the hydrogen, evolution reaction and hydrogen ingress flux rate were reduced by 60%.

G. Zheng; B. N. Popov; R. E. White

1994-01-01

81

Use of underpotential deposition of zinc to mitigate hydrogen absorption into Monel K500  

SciTech Connect

Polarization experiments and a potentiostatic pulse technique have been used to show that a monolayer coverage of zinc effectively inhibits the absorption of hydrogen into Monel K500. By depositing a monolayer of zinc on Monel K500 the hydrogen, evolution reaction and hydrogen ingress flux rate were reduced by 60%.

Zheng, G.; Popov, B.N.; White, R.E. (Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemical Engineering)

1994-05-01

82

AN ADVANCED FLUE GAS MONITOR FOR SO2 - PHASE I  

EPA Science Inventory

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

83

ESTUDO ELETROQUÍMICO DE RESISTÊNCIA À CORROSÃO LOCALIZADA DE AÇOS INOXIDÁVEIS PARA APLICAÇÕES COMO BIOMATERIAIS  

Microsoft Academic Search

Sandvik Bioline High-N and 316 LVM are two austenitic stainless steels specially developed to applications as biomaterials. Their localized corrosion resistance were investigated using electrochemical methods including potentiodynamics cyclic polarization and potentiostatic polarization, in a salt solution attenuated by fosfate and in solution for simulated crevices, i. e., solutions planned for tests of crevice corrosion. Sandvik SAF 2507 (a high-performance

C. Ulfvin

84

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

Microsoft Academic Search

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

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

2005-01-01

85

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

86

Implantable biosensor telemetry and interface using an optocoupler  

Microsoft Academic Search

This paper details the development of a miniature electronics package for implantable amperometric glucose sensors. The package includes a potentiostat to bias the glucose sensor with the proper excitation voltage, a transimpedance amplifier to develop voltage level data from sensor current, and an optocoupler device to interface to a commercially available telemetry unit which then transmits the glucose concentration data

Richard D. Beach; Francis MOUSSY

1999-01-01

87

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

88

Nanostructured electrode surfaces studied by electrochemical NMR  

Microsoft Academic Search

Electrochemical nuclear magnetic resonance (EC-NMR) is a powerful local probe, which combines solid state NMR with electrochemistry. It is a unique technique that permits a unified, electronic-level study of the metal and adsorbate side of the electrochemical interface. Experiments can be performed either under direct potentiostatic control and in situ potential adjustment, or with samples prepared in a separate electrochemical

P. K. Babu; Y. Y. Tong; H. S. Kim; A. Wieckowski

2002-01-01

89

Pulsed enhancement of the rate of coloration for tungsten trioxide based electrochromic devices  

Microsoft Academic Search

The rate of electrochromic coloration within tungsten oxide-based optical devices may be enhanced considerably by applying a progression of potentiostatically-controlled current pulses rather than applying a continuous current. The rate of coloration depends strongly on the pulse length employed, the optimum duration depending on the pulse amplitude. An additional advantage of this pulsing procedure is to enhance the durability of

Paul M. S. Monk; John A. Duffy; Malcolm D. Ingram

1998-01-01

90

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

National Technical Information Service (NTIS)

Mass transport and thermodynamic properties of LixCoO2 were studied by the potentiostatic intermittent titration technique (PITT) using solid-state thin-film batteries that provide a well-defined diffusion geometry. Both the chemical diffusion coefficient...

Y. I. Jang

2001-01-01

91

Influence of diffusion plane orientation on electrochemical properties of thin film LiCoO2 electrodes  

Microsoft Academic Search

Submicrometer LiCoO2 films have been prepared on silicon substrates with RF sputtering and pulsed laser deposition (PLD). The electrochemical activity of both types of thin film electrodes is compared using scanning cyclic voltammetry, galvanostatic and potentiostatic intermittent titration, and electrochemical impedance spectroscopy. The RF films exhibit a axis orientation and have an accessible diffusion plane alignment, unlike the c axis

P. J. Bouwman; B. A. Boukamp; H. J. M. Bouwmeester; P. H. L. Notten

2002-01-01

92

A fully integrated CMOS nanoscale biosensor microarray  

Microsoft Academic Search

This paper presents a fully integrated CMOS mi- croarray for biosensor applications. A 64-pixel working electrode array with optimized reference and counter electrode structure is proposed to improve symmetry, and the feature sizes of electrodes have been scaled down to 600nm. The circuit utilizes the decoding scheme of memories to simplify the pixel design while shares potentiostat opamp and current

Lei Zhang; Xiangqing He; Yan Wang; Zhiping Yu

2011-01-01

93

Cytochrome c dynamics at gold and glassy carbon surfaces monitored by in situ scanning tunnel microscopy  

Microsoft Academic Search

We have investigated the absorption of cytochrome c on gold and glassy carbon substrates by in situ scanning tunnel microscopy under potentiostatic control of both substrate and tip. Low ionic strength and potential ranges where no Faradaic current flows were used. Cyt c aggregates into flat composite structures of about 50 nm lateral extension at gold surfaces. The aggregates evolve

Jens E. T. Andersen; Per Møller; Marianne V. Pedersen; Jens Ulstrup

1995-01-01

94

Platinum particles deposited on synthetic boron-doped diamond surfaces. Application to methanol oxidation  

Microsoft Academic Search

Two methods have been used for the deposition of Pt particles on synthetic boron-doped diamond (BDD) surfaces: chemical deposition and electrodeposition under potentiostatic conditions. However, electrodeposition leads much higher platinum dispersion than chemical deposition. The mechanism of nucleation and growing of the electrodeposited platinum was investigated by means of chronoamperometric studies in acid medium. The electrodeposition on diamond surfaces shows

F. Montilla; E. Morallon; I. Duo; Ch. Comninellis; J. L. Vazquez

2003-01-01

95

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

96

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

97

New method for measuring the differential capacity in electrochemistry  

NASA Astrophysics Data System (ADS)

Electrical behavior of the ideally polarizable metal-solution interface is similar to a RC series circuit. The dc polarization, E, of the interface is potentiostatically controlled and differential capacity, C, measurements are carried out with a linear variation of E versus time. A precise measurement method of C is described in the case where the time constant of the circuit is rather high (~10-2 s). The principle of this method is to impose on the interface an ac current perturbation, I?, and to measure the ac potential response, E?. A system composed of a low bandwidth potentiostat (<1 Hz) and a galvanostat controls the dc potential, E, and produces the ac current, I?. In- and out-of-phase components of the ac potential response, E?, are analyzed by means of a lock-in amplifier. An ohmic drop compensation technique with suppression of the residual common mode is used to improve the determination of the E?(90°). Using a dummy cell, comparison between the new method and the classic potentiostatic technique is carried out. Results show that it is possible to measure C with a relative error less than 1% in a frequency range up to 2 kHz whereas with the classic potentiostatic technique the frequency range is limited to around 100 Hz.

Lecoeur, J.; Koehler, C.; Bellier, J. P.

1998-08-01

98

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

99

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

PubMed

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

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

2011-02-01

100

The Effect of Graphite-Epoxy Composites on the Galvanic Corrosion of Aerospace Alloys.  

National Technical Information Service (NTIS)

The galvanic corrosion rates of selected aerospace alloys coupled to graphite-epoxy composite materials (GECM) in aerated neutral (pH7) 3.5% NaCl at 22+1 C have been studied. Galvanic current was measured by the use of a potentiostat modified to operate a...

B. A. Miller, S. G. Lee

1976-01-01

101

Electrodeposition of silver nanoparticle arrays on ITO coated glass and their application as reproducible surface-enhanced Raman scattering substrate  

NASA Astrophysics Data System (ADS)

In this paper, a double-potentiostatic method is used for preparation of highly efficient and uniform surface-enhanced Raman scattering (SERS) substrate. The method takes advantage of the quick nucleation and slow growth process, yielding silver nanoparticle arrays (NAs) containing large amount of hot spots, which bring about these dense silver NAs for reproducible SERS application.

Bian, Jun-Cao; Li, Zhe; Chen, Zhong-Dong; He, Hai-Yan; Zhang, Xi-Wen; Li, Xiang; Han, Gao-Rong

2011-12-01

102

Electrodeposition of silver nanoparticle arrays on ITO coated glass and their application as reproducible surface-enhanced Raman scattering substrate  

Microsoft Academic Search

In this paper, a double-potentiostatic method is used for preparation of highly efficient and uniform surface-enhanced Raman scattering (SERS) substrate. The method takes advantage of the quick nucleation and slow growth process, yielding silver nanoparticle arrays (NAs) containing large amount of hot spots, which bring about these dense silver NAs for reproducible SERS application.

Jun-Cao Bian; Zhe Li; Zhong-Dong Chen; Hai-Yan He; Xi-Wen Zhang; Xiang Li; Gao-Rong Han

103

Inhibition of acidic corrosion of pure aluminum by some organic compounds  

Microsoft Academic Search

Inhibition of the corrosion of aluminum (Al) in hydrochloric acid (HCl) by sulfonic acid (SA), sodium cumene sulfonate (SCS), and sodium alkyl sulfate (SAS) has been studied using weight-loss and potentiostatic polarization methods. The results drawn from the two techniques are comparable and exhibit small discrepancy. The inhibition action depends on the chemical structure and the concentration of the inhibitors,

A. K. Maayta; N. A. F. Al-Rawashdeh

2004-01-01

104

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

105

Effect of particle size on the electrocatalytic activity of platinum dispersions in carbon matrix electrodes for phosphoric acid fuel cells  

Microsoft Academic Search

The loss in electrocatalytic activity of Pt particles in carbon matrix electrodes has been experimentally and theoretically investigated as a function of Pt particle size. The measurement of the cathodic potentiostatic current transient showed that a decrease in oxygen reduction current due to carboxyl group formation, relative to the oxygen reduction current in the absence of carboxyl group, increased with

S.-B. Lee; S.-I. Pyun

2000-01-01

106

Low-cost electrochemical impedance spectroscopy system for corrosion monitoring of metallic antiquities and works of art  

Microsoft Academic Search

Electrochemical impedance spectroscopy (EIS) is recognized to be a powerful and noninvasive technique to test the integrity of protective coatings on memorials, but commercial EIS systems are rather costly though versatile devices. This paper describes a low cost and portable EIS system that is based on a compact digital signal processor (DSP) board and embeds the potentiostatic function so that

A. Carullo; F. Ferraris; M. Parvis; A. Vallan; E. Angelini; P. Spinelli

2000-01-01

107

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

108

SEMICONDUCTOR MATERIALS: Morphology dependence of TiO2 nanotube arrays on anodization variables and buffer medium  

NASA Astrophysics Data System (ADS)

Vertically oriented TiO2 nanotube arrays were prepared by potentiostatic anodization of Ti foils in HF/acetic acid (HAC) aqueous solution. Anodization variables including anodization electrolyte concentration, anodization voltage, anodization time and buffer medium can be chosen and adjusted to manipulate the nanotube arrays to give the required length and morphology.

Xin, Wen; Meng, Cao; Jie, Wu; Junchao, Tao; Yan, Sun; Ning, Dai

2010-06-01

109

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

110

Optical characterization of bismuth reversible electrodeposition  

Microsoft Academic Search

Reversible electrodeposition of metallic bismuth onto transparent conducting substrates was studied with interest in the electrochromic phenomena produced by plating and stripping a thin metallic film. Different bismuth films were prepared potentiostatically by applying potential steps of different amplitude (whilst maintaining the electric charge at a constant value), and the change in transmittance was followed in situ simultaneously during the

S. I. Córdoba de Torresi; I. A. Carlos

1996-01-01

111

Annealing induced microstructural evolution of electrodeposited electrochromic tungsten oxide films  

Microsoft Academic Search

A significant influence of microstructure on the electrochromic and electrochemical performance characteristics of tungsten oxide (WO3) films potentiostatically electrodeposited from a peroxopolytungstic acid (PPTA) sol has been evaluated as a function of annealing temperature. Powerful probes like X-ray diffractometry (XRD), transmission electron microscopy (TEM), UV vis spectrophotometry, multiple step chronoamperometry and cyclic voltammetry have been employed for the thin film

M. Deepa; A. K. Srivastava; T. K. Saxena; S. A. Agnihotry

2005-01-01

112

Microstructural and electrochromic characteristics of electrodeposited and annealed WO 3 films  

Microsoft Academic Search

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

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

2005-01-01

113

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

114

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 ...

115

Effect of substrate surface treatment on the nucleation and crystal growth of electrodeposited copper and copper–indium alloys  

Microsoft Academic Search

Thin films of copper–indium alloy electroplated on molybdenum substrates show different morphologies related to the substrate treatment. An ammonia treatment of the molybdenum electrode can remove a thin oxide layer from the electrode surface, changing the morphological structure of the deposit. The nucleation kinetics of copper were investigated by potentiostatic current–time transients. The deposition process involves instantaneous nucleation for untreated

P. P Prosini; M. L Addonizio; A Antonaia

1997-01-01

116

Pulse technique for the electrochemical deposition of polymer films on electrode surfaces  

Microsoft Academic Search

Often, electrochemically-induced deposition of conducting polymer films on electrode surfaces fails using potentiostatic, galvanostatic or multisweep deposition procedures if bulky substituents at the monomer, nucleophilic attack at intermediate radical cations, hindered diffusional mass transport of the monomer to the electrode surface or the copolymerization of monomers with different oxidation potentials prevent fast chain propagation. A pulse profile for the electrochemical

Wolfgang Schuhmann; Christine Kranz; Heidi Wohlschläger; Johanna Strohmeier

1997-01-01

117

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

118

A gold-gold oil microtrench electrode for liquid-liquid anion transfer voltammetry.  

PubMed

Two flat gold electrodes are placed vis-à-vis with an epoxy spacer layer that is etched out to give a ca. 100 ?m-deep electrochemically active trench. A water-insoluble oil phase, here the redox system N,N-diethyl-N'N'-didodecyl-phenylenediamine (DDPD) in 4-(3-phenylpropyl)-pyridine (PPP), is immobilized into the trench to allow anion transfer upon oxidation of DDPD (oil) to DDP? (oil). In "mono-potentiostatic mode" quantitative transfer/expulsion of anions into the trench oil phase occurs. However, in "bi-potentiostatic mode" feedback currents dominated by rapid plate-to-plate diffusion normal to the electrode surfaces are observed. Comparison of "normal" diffusion and "lateral" diffusion shows that the rate of diffusion-migration charge transport across the oil film is anion hydrophobicity dependent. PMID:23670733

Dale, Sara E C; Chan, Yohan; Bulman Page, Philip C; Barnes, Edward O; Compton, Richard G; Marken, Frank

2013-07-01

119

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

120

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

121

Design and Fabrication of Complementary Metal-Oxide-Semiconductor Sensor Chip for Electrochemical Measurement  

NASA Astrophysics Data System (ADS)

An electrochemical sensor has been developed on a single chip in which potentiostat and sensor electrodes are integrated. Sensor chips were fabricated using 5.0 ?m complementary metal-oxide-semiconductor (CMOS) technology. All processes including the CMOS process, postprocessing for fabricating sensor electrodes and passivation layers, and packaging were performed at Toyohashi University of Technology. The integration makes it possible to measure electrochemical signals without having to use a bulky external electrochemical system. The potential between the working electrode and the reference electrode was controlled using an on-chip potentiostat composed of CMOS transistors. The chip characteristics were verified by electrochemical measurement, namely, by cyclic voltammetry. Potassium ferricyanide solution was measured to obtain results that fit well to the theoretical formula. A clear proportional relationship between peak height and the concentration of the sample solution was obtained using the proposed sensor chip, and the dynamic range obtained was 0.10 to 8.0 mM.

Tomoyuki Yamazaki,; Takaaki Ikeda,; Yoshiko Kano,; Hidekuni Takao,; Makoto Ishida,; Kazuaki Sawada,

2010-04-01

122

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

123

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

124

Investigation of passive films on alpha2 and gamma titanium aluminides by X-ray photoelectron spectroscopy  

SciTech Connect

Passive films on alpha2 and gamma titanium aluminide formed potentiostatically in sodium hydroxide (NaOH) and sulfuric acid (H2SO4) solutions were studied by x-ray photoelectron microscopy (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 H2SO4, 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 rate increased with increasing amounts of Al in the passive film for titanium aluminides.

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

1999-07-01

125

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

126

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

127

The kinetics of lithium transport through a composite electrode made of mesocarbon-microbeads heat-treated at 800 °C investigated by current transient analysis  

Microsoft Academic Search

  \\u000a Lithium transport through a mesocarbon-microbeads composite electrode was investigated in a 1 M LiPF6 solution in ethylene carbonate\\/diethyl carbonate (1:1 by vol%) using a galvanostatic intermittent titration technique and\\u000a a potentiostatic current transient technique. From analysis of the anodic current transient it is recognized that when the\\u000a potential step is small enough for the lithium extraction potential to be below

Seung-Bok Lee; Su-Il Pyun

2003-01-01

128

Normal and Anomalous Codeposition of Ni-Co-Fe-Zn Alloys from EMIC\\/EG in the Presence of an External Magnetic Field  

Microsoft Academic Search

The codeposition of Ni-Co-Fe-Zn alloys from a mixture of 1-ethyl-3-methylimidazolium chloride (EMIC)\\/ethylene glycol (EG)\\u000a was studied using potentiostatic electrodeposition in the potential range of –1.10 and –1.30 V vs saturated calomel electrode (SCE), using a permanent parallel magnetic field (PPMF) of 9 T. The uniform magnetic field was\\u000a aligned parallel to the cathode surface. It was found that both normal and

Mehdi Ebadi; Wan J. Basirun; Yatimah Alias; Mohammad R. Mahmoudian

2011-01-01

129

Normal and Anomalous Codeposition of Ni-Co-Fe-Zn Alloys from EMIC\\/EG in the Presence of an External Magnetic Field  

Microsoft Academic Search

The codeposition of Ni-Co-Fe-Zn alloys from a mixture of 1-ethyl-3-methylimidazolium chloride (EMIC)\\/ethylene glycol (EG) was studied using potentiostatic electrodeposition in the potential range of -1.10 and -1.30 V vs saturated calomel electrode (SCE), using a permanent parallel magnetic field (PPMF) of 9 T. The uniform magnetic field was aligned parallel to the cathode surface. It was found that both normal

Mehdi Ebadi; Wan J. Basirun; Yatimah Alias; Mohammad R. Mahmoudian

2011-01-01

130

Electrodeposition and characterization of Ni–Co–carbon nanotubes composite coatings  

Microsoft Academic Search

Ni–Co–carbon nanotubes composite coatings were prepared by electrodeposition in a Ni–Co plating bath containing carbon nanotubes (CNTs) 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 Ni–Co–CNTs composite coatings were evaluated on a UMT-2MT test rig in a ball-on-disk contact mode. The morphologies of

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

2006-01-01

131

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

132

Applicability of coagulation\\/flocculation and electrochemical processes to the purification of biologically treated vinasse effluent  

Microsoft Academic Search

We investigated the use of coagulation\\/flocculation (CF) and electrochemical oxidation (EO) processes to purify vinasse that had already been biologically treated (vinasse BT). The CF process was analyzed as a function of the concentration of the coagulant (FeCl3) and the pH of the vinasse BT. After the CF process, EO was performed by potentiostatic electrolysis with a Ti\\/RuPb(40%)Ox anode and

Teresa Zayas; Viviana Rómero; Leonardo Salgado; Mónica Meraz; Ulises Morales

2007-01-01

133

Modulation of dendrite growth of cuprous oxide by electrodeposition  

Microsoft Academic Search

Cuprous oxides with different dendrite morphologies were formed on F-doped tin oxide (FTO) covered glass substrates by potentiostatic deposition of cupric acetate. The effects of pH value (varied from 5.00 to 5.80) of electrolytes on the crystal morphologies of cuprous oxide were studied. Different crystal morphologies of cuprous oxides were obtained by the change of velocity of vertical growth and

Lijuan Wan; Zhiqiang Wang; Zaisan Yang; Wenjun Luo; Zhaosheng Li; Zhigang Zou

2010-01-01

134

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

135

Electronic conductivities of commercial ZrO 2 + 3 to 4 wt pct CaO electrolytes  

Microsoft Academic Search

Potentiostatic electrochemical experiments with liquid metal electrodes have been analyzed to provide values for the mixed\\u000a electrical conduction parameters (PMion, o?o, Oo , Po,P\\u000a o, and E O,C.) associated with commercial-grade ZrO2 + 3 to 4 wt pct CaO electrolytes. Good agreement between experimental and calculated values for the open-circuit cell voltage,E o. c., for relatively high oxygen concentrations in

Lawrence M. Friedman; Karl E. Oberg; William M. Boorstein; Robert A. Rapp

1973-01-01

136

Caustic Stress Corrosion Cracking of Mild Steel  

Microsoft Academic Search

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

Douglas Singbeil; Desmond Tromans

1982-01-01

137

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

138

Lithium Transport Through Sputter Deposited Lithium Cobalt Dioxide Thin Film Electrode  

Microsoft Academic Search

Lithium transport through lithium cobalt dioxide thin film electrode prepared by rf-magnetron sputtering was investigated in IM solution of LiClO4 in propylene carbonate using cyclic voltammetry, galvanostatic intermittent titration technique (GITT) and potentiostatic current transient technique. The cathodic and anodic current transients exhibited the non-Fickian behaviour of lithium transport when the applied potential steps encountered potential plateaus near 3.91 VLi\\/Li+'

Su-Il Pyun; Heon-Cheol Shin

2000-01-01

139

Effect of the protogenic nature of the medium on the rate of corrosion transformations in PT3V titanium alloy  

Microsoft Academic Search

Polarization was carried out using a P-5 827M potentiostat, and of volt-ampere graphs were recorded using a PDP-4 automatic recording device. Measurements were taken using the three-electrode method. The working electrode, whose radius was determined with an error to 1 ~m rotated at a frequency ~ = 2.4-27 sec -I. An auxiliary platinum electrode was placed in a side container

V. I. Pokhmurskii; O. S. Kalakhan

1992-01-01

140

Entrapment of live microbial cells in electropolymerized polyaniline and their use as urea biosensor  

Microsoft Academic Search

The lyophilized biomass of bacterium Brevibacterium ammoniagenes was immobilized in polystyrene sulphonate–polyaniline (PSS–PANI) conducting polymer on a Pt twin wire electrode by potentiostatic electropolymerization. The bacterial cells retained their viability as well as urease activity under entrapped state, as confirmed with bacterial live–dead fluorescent assay and enzymatic assays. The entrapped cells were visualized using scanning electron microscope. The immobilized cells

Sandeep Kumar Jha; Mandakini Kanungo; Archana Nath; Stanislaus F. D'Souza

2009-01-01

141

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

142

A low power sensor signal processing circuit for implantable biosensor applications  

Microsoft Academic Search

A low power sensor read-out circuit has been implemented in 0.35 µm CMOS technology that consumes only 400 µW of power and occupies an area of 0.66 mm2. The circuit is capable of converting the current signal from any generic biosensor into an amplitude shift keying (ASK) signal. The on-chip potentiostat biases the chemical sensor electrodes to create the sensor

Mo Zhang; Mohammad R. Haider; Mohammad A. Huque; Mohammad A. Adeeb; Shaela Rahman; Syed K. Islam

2007-01-01

143

A low power sensor signal processing circuit for implantable biosensor applications  

Microsoft Academic Search

A low power sensor read-out circuit has been implemented in 0.35m CMOS technology that consumes only 400W of power and occupies anarea of 0.66mm2. The circuit is capable of converting the current signal from any generic biosensor into an amplitude shift keying (ASK) signal. The on-chip potentiostat biases the chemical sensor electrodes to create the sensor current which is then

Mo Zhang; Mohammad R Haider; Mohammad A Huque; Mohammad A Adeeb; Shaela Rahman; Syed K Islam

2007-01-01

144

Some organic and inorganic compounds as inhibitors for carbon steel corrosion in 3.5 percent NaCl solution  

Microsoft Academic Search

Purpose – To study the effects of the sodium salts of molybdate, tungstate and monovanadate as well as some derivatives of Neville-Winter acid azo dyes on the corrosion of carbon steel in 3.5 percent NaCl solution. Design\\/methodology\\/approach – Open circuit potential measurement and potentiostatic polarization techniques have been used. Findings – It was found that all the compounds had inhibition

M. Abdallah; A. Y. El-Etre; M. G. Soliman; E. M. Mabrouk

2006-01-01

145

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

146

Effect of formation of surface hydroxide on hydrogen permeability of iron membranes and hydrogen embrittlement of high-strength steels  

Microsoft Academic Search

UDC 541.138:669.788 permeability of iron membranes. The working cell consisted of two parts separated by a bipolar electrode, i.e., an iron membrane. In the polarization part of the cell, contained in the examined solution, the membrane was hydrogen-charged in the potentiostatic condition. A potential of +0.3 V (here and in the rest of the article the potential is given with

V. A. Marichev; V. V. Molokanov

1992-01-01

147

Study of the input-side subsurface reorganization vs. the outside current density in hydrogen permeation under constant cell voltage through iron membrane according to R HC concept  

Microsoft Academic Search

In this work, hydrogen permeation tests were performed on pure iron membrane in 1M sodium hydroxide at 298K, subjected to hydrogen charging under “quasi-potentiostatic” polarization conditions, i.e. constant cell voltage applied between the cathode (membrane entry side) and the anode (counter electrode), which is a typical situation during metal electrodeposition or cathodic degreasing on steel in metal finishing industry.Two consecutive

M. DePetris-Wery; S. Wery; J. C. Catonne

2010-01-01

148

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

Microsoft Academic Search

The passive corrosion properties of a series of Ni–Cr–Mo 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 (25–85°C) 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 Noël; Stewart McIntyre; David W Shoesmith

2004-01-01

149

The voltammetric response of bipolar cells: Reversible electron transfer  

Microsoft Academic Search

The voltammetric response of a bipolar cell, formed by making electrical connection between two half-cells under overall potentiostatic control, is described. Experimental data obtained with reversible redox couples are compared with numerical simulations of the corresponding two-phase transport problem, where charge transfer may be limited by the transport of either, or both, of the redox-active couples. Preliminary experiments on the

Daniela Plana; Fran G. E. Jones; Robert A. W. Dryfe

2010-01-01

150

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

151

Vectorial electron injection into transparent semiconductor membranes and electric field effects on the dynamics of light-induced charge separation  

Microsoft Academic Search

Transparent titanium dioxide membranes (thickness 2.7 μm) were prepared by sintering of 8-nm colloidal anatase particles on a conducting glass support. The dynamics of charge recombination following electron injection from the excited state of RuLâ (L = 2,2â²-bipyridine-4,4â²-dicarboxylic acid) into the conduction band of the semiconductor were examined under potentiostatic control of the electric field within the space charge layer

B. ORegan; Jacques. Moser; M. Graetzel; M. Anderson

1990-01-01

152

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

153

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

SciTech Connect

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

Sadowski, R.A.; Chen, G.; Clayton, C.R.; Kearns, J.R. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Materials Science and Engineering; Gillow, J.B.; Francis, A.J. [Brookhaven National Lab., Upton, NY (United States). Biosystems and Process Sciences Div.

1995-03-01

154

A novel non-enzymatic glucose sensor based on Cu nanoparticle modified graphene sheets electrode  

Microsoft Academic Search

A novel, stable and sensitive non-enzymatic glucose sensor was developed by potentiostatically electrodepositing metallic Cu nanoparticles on graphene sheets. The electrochemical performance of the Cu-graphene sheets electrode for detection of glucose was investigated by cyclic voltammetry and chronamperometry. The Cu-graphene sheets electrode displayed a synergistic effect of copper nanoparticles and graphene sheets towards the oxidation of glucose in alkaline solution,

Jing Luo; Sisi Jiang; Hongyan Zhang; Jinqiang Jiang; Xiaoya Liu

155

Modeling of the Current Distribution in Aluminum Anodization  

Microsoft Academic Search

The growth of porous anodic Al2O3 films, formed potentiostatically in continuously stirred 15 wt.% H2SO4 electrolyte was studied as a function of the anodization voltage (14–18 V), bath temperature (15–25 °C) and anodization time (15–35 min). The variation of the anodic surface overpotential with the current density was measured experimentally. The film thickness at the more accessible portions of the

Rohan Akolkar; Uziel Landau; Harry Kuo; Yar-Ming Wang

2004-01-01

156

Influence of bismuth on electrochemical behavior of sacrificial aluminum anode  

Microsoft Academic Search

Purpose – To evaluate bismuth, which is inexpensive and non-toxic, as a substitute for mercury, indium and gallium in Al-5%Zn-X sacrificial anode. Design\\/methodology\\/approach – The effect of bismuth on the electrochemical behavior of Al-5%Zn-Bi in the artificial sea water environment was investigated. Potentiodynamic, potentiostatic, galvanostatic, weight loss and efficiency test methods were employed. The surface of the specimens were studied

M. Karaminezhaad; A. H. Jafari; A. Sarrafi; Gh. Safi

2006-01-01

157

Electrochemical oxidation of aniline at boron-doped diamond electrodes  

Microsoft Academic Search

The electrochemical oxidation of aniline at boron-doped diamond (BDD) electrodes was investigated by cyclic voltammetry, steady-state polarization measurements and bulk electrolysis under potentiostatic control. It was found that acidic media is suitable for efficient electrochemical oxidation of aniline, because at low pH, the potential required for avoiding electrode fouling is lower than in neutral and alkaline media. The results of

M. Mitadera; N. Spataru; A. Fujishima

2004-01-01

158

Electrochemical deposition and studies on CdCr 2S 4 thin films  

Microsoft Academic Search

Cadmium chromium sulphide (CdCr2S4) thin films have prepared on indium doped tin oxide coated conducting glass (ITO) substrates from an aqueous electrolytic bath consists of CdSO4, Cr2O3 and Na2S2O3 using potentiostatic electrodeposition technique. The deposited films are characterized using X-ray diffraction, scanning electron microscopy, energy dispersive analysis by X-rays and optical absorption techniques, respectively. X-ray diffraction pattern reveals that the

T. Mahalingam; S. Thanikaikarasan; V. Dhanasekaran; R. Mariappan; P. Jayamurugan; S. Velumani; Jin-Koo Rhee

2010-01-01

159

Nuclear magnetic resonance spectroscopic study of the electrochemical oxidation product of methanol on platinum black  

Microsoft Academic Search

The absorbate resulting from the potentiostatic, catalytic decomposition of methanol (0.1 M CHâOH in 0.5 M HâSOâ) on a platinum black electrode has been studied via ¹³C 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 Tâ is dependent on surface coverage and

James B. Day; E. Oldfield; A. Wieckowski; P. A. Vuissoz; Jean-Philippe Ansermet

1996-01-01

160

The application of electroanalytical methods to the analysis of phase transitions during intercalation of ions into electrodes  

Microsoft Academic Search

Mechanisms of first-order phase transition induced by electrochemical intercalation of Li ions into composite graphite electrode\\u000a are studied both theoretically, in the framework of lattice gas models, and experimentally, by a combination of electroanalytical\\u000a techniques, such as cyclic voltammetry, potentiostatic intermittent titration (PITT), galvanostatic intermittent titration\\u000a (GITT), and electrochemical impedance spectroscopy (EIS). From the analysis of the mismatch between the

M. D. Levi; D. Aurbach

2007-01-01

161

Spatially resolved measurement of PEM fuel cells  

NASA Astrophysics Data System (ADS)

A measurement set-up is presented containing a multichannel frequency response analyser system together with a multichannel potentiostat that allows measurements of the local electrical impedance spectra of segmented fuel cells simultaneously. For evaluation the current and impedance distribution is combined with optical spatially resolved measurement and numerical simulation. Furthermore the multichannel frequency response analyser system is used for the measurement of impedance spectra of single cells in a fuel cell stack simultaneously.

Hakenjos, Alex; Hebling, Christopher

162

Effects Due to Uncompensated Resistance and Capacitance  

NASA Astrophysics Data System (ADS)

Electrochemists are aware of the annoying residual uncompensatedsolution resistance R u between the Luggin probe and the working electrode, see for example [74] . Although it is possible in principle to compensate fully for the iR error thus introduced [131, 132], this is rarely done, as it introduces, in practice, undesirable instrumental oscillations or, in the case of damped feedback [132], sluggish potentiostat response.

Britz, Dieter

163

Experimental Setup  

NASA Astrophysics Data System (ADS)

To run a successful electrochemical experiment it is essential that the experimental setup is electrically correct and appropriate for the experiment planned. There are several points that should be carefully considered before the experiments are started. They include proper choice of the working, reference and auxiliary electrodes, proper selection of the solvent and supporting electrolyte, proper selection of the electroanalytical technique and its parameters, proper wiring of the electrochemical circuit and, finally, proper setting of the parameters of the potentiostat/voltammograph used.

Stojek, Zbigniew

164

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; Murtomäki, Lasse; Johans, Christoffer; Girault, Hubert H; Kontturi, Kyösti

2013-02-01

165

Regulating noise-induced spiking using feedback.  

PubMed

We report successful manipulation of the noise provoked spiking behavior using delayed feedback control. Experiments were performed in a three electrode electrochemical cell under potentiostatic conditions. The uncontrolled system exhibited noise invoked oscillations whose regularity was quantified using normalized variance (NV). Superimposing delayed feedback, for appropriate values of delay (t), an enhancement in the regularity of the spike sequence was attained. Numerical simulations corroborated experimental observations. PMID:16711861

Escalera Santos, Gerardo J; Escalona, J; Parmananda, P

2006-04-01

166

Cathodic copper deposition at 65 °C in the absence and presence of Bi 3+ and Sb 3+ additives in acidified CuSO 4 aqueous solutions  

Microsoft Academic Search

An electrochemical study by cyclic voltammetry and potentiostatic pulse method of the cathodic deposition of copper on polycrystalline\\u000a copper electrode was carried out in acidic aqueous copper sulfate solution. Comparative electrochemical investigations were\\u000a performed in electrolytes in the absence and presence of Bi3+ and Sb3+ ions. All experiments were performed at 65 ?C. For bulk copper deposition, the results indicate

R. G. Barradas; M. Girgis

1991-01-01

167

Preparation and characterization of polyaniline film on stainless steel by electrochemical polymerization as a counter electrode of DSSC  

Microsoft Academic Search

Polyaniline (PANI) films were electrodeposited on stainless steel 304 (SS) from 0.5M H2SO4 solution containing 0.3M aniline by potentiostatic techniques to prepare a low cost and non-fragile counter electrode in dye-sensitized solar cell (DSSC). The compact layer, micro-particles, nanorods and fibrils were observed on the top of PANI films with different applied potentials (Eappl) by SEM. Then the conductivity and

Qi Qin; Jie Tao; Yan Yang

2010-01-01

168

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 37°C 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 stimulation–repassivation scheme in the presence of a crevice former. Susceptibility to crevice corrosion

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

2007-01-01

169

Analytical Characterization of Electrochemical Biosensor Test Strips for Measurement of Glucose in Low-Volume Interstitial Fluid Samples  

Microsoft Academic Search

Background: Minimally invasive interstitial fluid (ISF) sampling and glucose measurement technologies were integrated into a hand-held device for diabetic glucose monitoring investigations. Methods: Conventional electrochemical test strip tech- nology (Bayer Glucometer Elite®) was adapted to mea- sure glucose in small (0.5-2.0 mL) samples of ISF. Test strip glucose measurements were performed on a com- mercial potentiostat and were compared to

Michael E. Collison; Philip J. Stout; Tatyana S. Glushko; Kristen N. Pokela; Debra J. Mullins-Hirte; Joel R. Racchini; Melissa A. Walter; Steve P. Mecca; Joanna Rundquist; John J. Allen; Michael E. Hilgers; Thomas B. Hoegh

170

The effect of additives on the nucleation and growth of copper onto stainless steel cathodes  

Microsoft Academic Search

A potentiostatic technique has been used to study the effects of chloride ion, glue, and thiourea on the initial electrodeposition\\u000a of copper. A stainless steel (AISI 304) rotating disc electrode (RDE) with an electrolyte containing 40 g\\/1 Cu2+ and 180 g\\/1 H2SO4 at 40 ?C was employed. The current transients from the potential step measurements for the additive-free electrolyte could

M. Sun; T. J. O’Keefe

1992-01-01

171

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

Microsoft Academic Search

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

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

1996-01-01

172

Comparison of microbial electrolysis cells operated with added voltage or by setting the anode potential  

Microsoft Academic Search

Hydrogen production in a microbial electrolysis cell (MEC) can be achieved by either setting the anode potential with a potentiostat, or by adding voltage to the circuit with a power source. In batch tests the largest total gas production (46 ± 3 mL), lowest energy input (2.3 ± 0.3 kWh\\/m3 of H2 generated), and best overall energy recovery (?E+S = 58 ± 6%) was achieved at a set anode potential

Joo-Youn Nam; Justin C. Tokash; Bruce E. Logan

2011-01-01

173

Electropolymerization of poly( N-ethyl aniline) on mild steel: Synthesis, characterization and corrosion protection  

Microsoft Academic Search

Poly(N-ethylaniline) (PNEA) coatings on the mild steel electrode were synthesized by electrochemical oxidation of N-ethylaniline using aqueous oxalic acid solutions as reaction medium. Electrodeposition was carried out by potentiodynamic, potentiostatic and galvanostatic synthesis techniques. Smooth, adhesive and thick PNEA coatings on mild steel could be electrosynthesized during sequential scanning of the potential region between ?0.5 and 1.4V versus SCE, with

Aziz Ya?an; Nuran Özçiçek Pekmez; Attila Y?ld?z

2006-01-01

174

The inhibition effect of amino acids and hydroxy carboxylic acids on pitting corrosion of aluminum alloy 7075  

Microsoft Academic Search

Pitting corrosion of aluminum alloy 7075 in 0.05 M NaCl solution at pH values of 4, 5, 7 and 8 were examined by potentiostatic method. It was found that addition of 10?2 M hydroxy carboxylic acids or amino acids to NaCl solutions cause shifting of Epit values to noble directions. Amino acids are more effective in shifting Epit values to

G. Bereket; A. Yurt

2001-01-01

175

Electrochemical behavior of thermally chromized steel in sodium chloride solutions  

Microsoft Academic Search

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

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

1975-01-01

176

Investigation on the corrosion process of carbon steel coated by HVOF WC\\/Co cermets in neutral solution  

Microsoft Academic Search

The corrosion protection afforded to a carbon steel substrate by two cermet coatings (WC\\/12 wt.% Co and WC\\/17 wt.% Co; 0.05, 0.01 and 0.2 mm coating thickness), applied by high velocity oxygen fuel (HVOF) technique, has been studied in 3.5% NaCl solutions. Potentiodynamic polarization curves of cermet constituents, substrate and coated samples, iron and cobalt dissolution kinetics under potentiostatic conditions

C Monticelli; A Frignani; F Zucchi

2004-01-01

177

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

Microsoft Academic Search

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

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

2005-01-01

178

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 Schröder; Fritz Scholz; Peter Bogdanoff; Iris Herrmann

2005-01-01

179

Correlation between the haze ratio and the surface roughness of electrochemically deposited nanostructured ZnO films  

Microsoft Academic Search

This work reports the synthesis of nanostructured ZnO by electrochemical deposition on glass substrates covered by a thin film of SnO2 doped with F (SnO2:F). Nanostructured ZnO films are deposited by an electrochemical process using a three-electrode potentiostatic system with saturated calomel electrodes as reference electrodes from an aqueous solution containing ZnCl2, KCl, (pH 4.00) and an air flow or\\/and

K Lovchinov; O Angelov; H Nichev; V Mikli; D Dimova-Malinovska

2012-01-01

180

Electrodeposition of EuSe thin films onto different substrates  

Microsoft Academic Search

Electrodeposition and characterization of EuSe thin films onto different substrates such as stainless steel (SS), Ti, Cu, fluorine-doped tin oxide (F-SnO2) covered glasses is described. The films have been prepared in potentiostatic mode using aqueous acidic electrolyte containing Eu and Se precursors at 70°C bath temperature and pH 4. The disodium salt of ethylenediaminetetraacetic acid (Na2-EDTA) is used as a

N. S. Gaikwad; C. H. Bhosale

2002-01-01

181

Direct electrochemical synthesis of tungsten(VI) alkoxides  

Microsoft Academic Search

It is known that in organic solvents in presence of halide ions the anodic dissolution of tungsten does not occur. They have found that the electrolysis of solutions of (BuâN)Br in absolute MeOh and EtOH is accompanied by the anodic oxidation of the tungsten (anode) with the formation of the alkoxides W(OR)â, WO(OR)â, and WOâ(OR)â. A galvanostatic investigation (P-5848 potentiostat)

S. I. Kucheiko; N. Ya. Turova; V. A. Shreider

1986-01-01

182

Synergistic effect of polyethylene glycol 600 and polysorbate 20 on corrosion inhibition of zinc anode in alkaline batteries  

Microsoft Academic Search

Polyethylene glycol 600 (PEG 600) and polysorbate 20 (Tween 20) were used as a composite corrosion inhibitor of zinc in alkaline\\u000a solution for the first time. The effects of the composite and individual inhibitors on corrosion inhibition of zinc were evaluated\\u000a by weight-loss analysis and electrochemical methods including potentiodynamic, potentiostatic, and electrochemical impedance\\u000a spectroscopic measurements. It was found that there

Man Liang; Hebing Zhou; Qiming Huang; Shejun Hu; Weishan Li

183

Electrodeposition and characterization of PbSe films on indium tin oxide glass substrates  

Microsoft Academic Search

Electrodeposition of lead selenide (PbSe) thin films on indium tin oxide (ITO) covered glass is described. While disodium salt of ethylenediaminetetraaceticacid was used to complex the lead ions, well crystallized, nearly stoichiometric and mirror-like PbSe films were deposited on ITO glass in potentiostatic mode using aqueous acidic electrolyte containing Pb and Se precursors at different bath temperature. The improvement of

KunWei Li; XiaoTian Meng; Xue Liang; Hao Wang; Hui Yan

2006-01-01

184

The influence of water on the electrochemical activity of poly( N-vinylcarbazole) films  

Microsoft Academic Search

Poly(N-vinylcarbazole) (PVCz) films were prepared by potentiostatic deposition onto gold, platinum and indium tin oxide (ITO) electrodes from acetonitrile solutions of the monomer and LiClO4 supporting electrolyte. The redox behaviour of the polymer coated electrodes was studied in dry acetonitrile and in acetonitrile + water mixtures by cyclic voltammetry, in situ UV-visible spectrophotometry and ex situ Fourier transform IR spectroscopy.

Magdalena Skompska; Laurence M. Peter

1995-01-01

185

Electrodeposition of silicon from solutions of silicon halides in aprotic solvents  

Microsoft Academic Search

Amorphous silicon has been electrodeposited from nonaqueous baths using SiHClâ as the silicon source. A typical bath composition was 1.0M SiHClâ in propylene carbonate containing 0.1m tetrabutyl ammonium chloride as the supporting electrolyte. Deposits were made potentiostatically at around -2.5v vs. Pt reference at temperatures 35\\/degree\\/ -145\\/degree\\/C under an argon atmosphere. A variety of materials including Pt, Ti, Ti-6Al-4V alloy,

A. K. Agrawal; A. E. Austin

1981-01-01

186

Preparation of Zn–In–S film electrodes using chemical bath deposition for photoelectrochemical applications  

Microsoft Academic Search

Ternary zinc–indium–sulfide film electrodes were fabricated on fluorine doped tin oxide coated glass substrates using chemical bath deposition. New procedures for the growth of Zn–In–S films are presented. The physical and photoelectrochemical properties of the samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis spectroscopy, and a potentiostat. The XRD patterns and SEM images of samples reveal

Kong-Wei Cheng; Chia-Jui Liang

2010-01-01

187

Electropolymerized molecular imprinting on gold nanoparticle-carbon nanotube modified electrode for electrochemical detection of triazophos  

Microsoft Academic Search

An electrochemical sensor for pesticide triazophos (TAP) was prepared by deposition of gold nanoparticles (AuNPs) on carbon nanotubes (CNTs) modified glassy carbon (GC) electrode surface using a potentiostatic method, followed by electropolymerizing of o-hydroxyphenol at the AuNP\\/CNT\\/GC electrode surface in the presence of template triazophos via cyclic voltammetry. The electrochemical response of triazophos at the TAP-imprinted polyhydroxyphenol (PHP) modified AuNP\\/CNT\\/GC

Huaifen Li; Chenggen Xie; Shanqi Li; Ke Xu

188

Nanostructured thin film formation on femtosecond laser-textured Ti–35Nb–xZr alloy for biomedical applications  

Microsoft Academic Search

The aim of this study was to investigate the nanostructured thin film formation on femtosecond (FS) laser-textured Ti–35Nb–xZr alloy for biomedical applications. The initial surface roughening treatment involved irradiation with the FS laser in ambient air. After FS laser texturing, nanotubes were formed on the alloy surface using a potentiostat and a 1M H3PO4 solution containing 0.8wt.% NaF with an

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

2011-01-01

189

Preferential dissolution behaviour in Ni-Cr dental cast alloy  

Microsoft Academic Search

A Ni-Cr-Mo dental alloy was fabricated by three different casting methods, viz. centrifugal casting, high frequency induction\\u000a casting and vacuum pressure casting. The dependence of cast microstructure on the electrochemical corrosion behaviour was\\u000a investigated using potentiodynamic cyclic and potentiostatic polarization techniques, impedance spectroscopy and scanning\\u000a electron microscopy. The experimental results were compared and discussed with those obtained for a Co-Cr-Mo

Viswanathan S. Saji; Han Cheol Choe

2010-01-01

190

Electrochemical behavior of dental implant system before and after clinical use  

Microsoft Academic Search

Electrochemical behavior of dental implant system before and after clinical use (in vivo and in vitro) was researched by using abutment and titanium fixture. To simulate an oral environment, the samples of clinically used and non-used implant systems as a working electrode were exposed to artificial saliva at (36.5±1) °C. Electrochemical tests were carried out using a potentiostat. After electrochemical

Chae-Heon CHUNG; Hee-Jung KIM; Yong-Tae JEONG; Mee-Kyoung SON; Yong-Hoon JEONG; Han-Cheol CHOE

2009-01-01

191

Electrochemical corrosion behaviour of nanotubular Ti–13Nb–13Zr alloy in Ringer’s solution  

Microsoft Academic Search

Nanotubular oxide layer formation was achieved on biomedical grade Ti–13Nb–13Zr alloy using anodization technique in 1M H3PO4+0.5wt.% NaF. The as-formed and heat treated nanotubes were characterized using SEM, XRD and TEM. Corrosion behaviour of the nanotubular alloy was investigated employing potentiodynamic and potentiostatic polarization. The alloy after nanotubular oxide layer formation exhibited significantly higher corrosion current density than the bare

Viswanathan S. Saji; Han Cheol Choe

2009-01-01

192

Nanostructured surface changes of Ti–35Ta–xZr alloys with changes in anodization factors  

Microsoft Academic Search

The purpose of this study was to investigate the changes of the nanostructured surface of Ti–35Ta–xZr alloys for dental application resulting from changes in anodization factors. TiO2 nanotubes were formed on Ti–35Ta–xZr alloys by anodization in H3PO4-containing NaF solutions. Anodization was carried out using a scanning potentiostat. Microstructures of the alloys were examined by optical microscopy (OM), field emission scanning

Won-Gi Kim; Han-Cheol Choe; William A. Brantley

2011-01-01

193

Electrochemical behavior of TiN film coated Ti?Nb alloys for dental materials  

Microsoft Academic Search

In order to study the electrochemical behaviors of TiN film coated Ti?Nb alloys for dental materials, Ti containing Nb up\\u000a to 3, 20, and 40 wt.% was melted by a vacuum furnace and coated with TiN by EB-PVD. the electrochemical behaviors were investigated\\u000a using a potentiostat in 0.9% NaCl solution and the corrosion surface was observed using SEM and XPS.

Han-Cheol Choe; Yeong-Mu Ko; Ha-Ok Park

2006-01-01

194

Hydrogen trapping in high-strength steels  

Microsoft Academic Search

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 1mol\\/l acetic acid\\/1mol\\/l sodium acetate. The order of the k values for the three steels and two 18Ni maraging steels previously studied inversely parallels their threshold stress intensities

B. G. Pound

1998-01-01

195

Evaluation of a diffusion\\/trapping model for hydrogen ingress in high-strength alloys. Annual report, 15 September 1993-14 September 1994  

Microsoft Academic Search

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

Pound

1994-01-01

196

Single step electrosynthesis of Cu 2ZnSnS 4 (CZTS) thin films for solar cell application  

Microsoft Academic Search

The Cu2ZnSnS4 (CZTS) thin films have been electrodeposited onto the Mo coated and ITO glass substrates, in potentiostatic mode at room temperature. The deposition mechanism of the CZTS thin film has been studied using electrochemical techniques like cyclic voltammetery. For the synthesis of these CZTS films, tri-sodium citrate and tartaric acid were used as complexing agents in precursor solution. The

S. M. Pawar; B. S. Pawar; A. V. Moholkar; D. S. Choi; J. H. Yun; J. H. Moon; S. S. Kolekar; J. H. Kim

2010-01-01

197

AFM and XRD investigation of the effect of dissolved oxygen in electrolytes on electrodeposition of CdTe on HgCdTe  

Microsoft Academic Search

CdTe films have been deposited onto HgCdTe by potentiostatic electrodeposition at deposition potentials of -0.4 V and -0.5 V with respect to a saturated calomel reference electrode in ethylene glycol base electrolyte. Films deposited with and without nitrogen bubbling to reduce dissolved oxygen in electrolytes were investigated by atomic force microscopy (AFM) and x-ray diffraction (XRD). Significant reduction in roughness

Jong-Hwa Choi; Hee Chul Lee

2002-01-01

198

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

NASA Astrophysics Data System (ADS)

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

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

1991-06-01

199

The role of nucleation in the evolution of giant magnetoresistance with layer thicknesses in electrodeposited Co–Cu\\/Cu multilayers  

Microsoft Academic Search

Electrodeposited Co–Cu\\/Cu multilayers were prepared by a galvanostatic\\/potentiostatic (G\\/P) pulse sequence in which the Co-rich magnetic Co–Cu layer was deposited by current control and the non-magnetic Cu layer by potential control. The Cu deposition potential has been chosen so as to exclude the occurrence of a Co dissolution during the Cu deposition cycle. This ensured that the actual amounts of

Q. X. Liu; L. Péter; J. Tóth; L. F Kiss; Á. Cziráki; I. Bakonyi

2004-01-01

200

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

201

Electrochemical characterization of the Ni–W catalyst formed in situ during alkaline electrolytic hydrogen production—Part II  

Microsoft Academic Search

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

Milica P. Marceta Kaninski; Djordje P. Saponjic; Ivana M. Perovic; Aleksandar D. Maksic; Vladimir M. Nikolic

2011-01-01

202

Characterization of the Ni–Mo 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 Ni–Mo catalysts obtained by in situ electrodeposition in an alkaline, 6 M KOH, electrolyser. In accordance to our previous studies, synergetic effect is observed, with its maximum at industrial conditions (high temperature and current density). The Tafel slopes are around 120 mV and

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

2011-01-01

203

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

Microsoft Academic Search

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)

J. Pan; C. Karlen; C. Ulfvin

2000-01-01

204

Electrodeposition of polypyrrole on 316L stainless steel for corrosion prevention  

Microsoft Academic Search

The electrosynthesis of polypyrrole films onto 316L stainless steel from near neutral and alkaline solutions containing molybdate and nitrate is reported. The corrosion behavior of the coated electrodes was investigated in NaCl solutions by electrochemical techniques and scanning electron microscopy. The polymer formed potentiostatically in a solution of pH 12 is the most efficient in terms of adhesion and corrosion

M. B. González; S. B. Saidman

2011-01-01

205

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. Tamašauskait?-Tamaši?nait?; V. Pautienien?; Z. Jusys

2004-01-01

206

Efficient maximization of coloration by modification in morphology of electrodeposited NiO thin films prepared with different surfactants  

Microsoft Academic Search

In this paper, we report on the nickel oxide (NiO) thin films potentiostatically electrodeposited onto indium-doped tin oxide-coated\\u000a glass substrates by using two types of organic surfactants: (1) non-ionic: polyethylene glycol (PEG), polyvinylpyrrolidone\\u000a (PVP) and (2) anionic: sodium dodecyl sulfate (SDS). An aqueous solution containing nickel sulfate precursor and potassium\\u000a hydroxide buffer was used to grow the samples. The effect

Dhanaji S. Dalavi; Meenatai J. Suryavanshi; Sawanta S. Mali; Dipali S. Patil; Pramod S. Patil

207

Influence of different substrates on the electrochromic property of polyaniline films  

Microsoft Academic Search

The polyaniline (PANI) films doped with complex acid (sulfuric acid and sulfosalicylic acid) were prepared using the potentiostatic\\u000a method on bare nickel flake (NF) and flexible polyethylene terephthalate (PET)\\/indium tin oxide (ITO) substrates. The contents\\u000a of the PANI films, surface elements, electrochromic property and electrical conductivity were characterized by energy dispersive\\u000a X-ray spectrometer (EDS), cyclic voltammetry (CV) and electrochemical impedance

Li Ma; Ling He; Mengyu Gan; Haotian Ma; Wenyi Su; Jun Yan; Jianfeng Li; Deng Pan

2010-01-01

208

In-situ spectroscopic investigation of infrared transmissive\\/absorptive electrochromic devices  

Microsoft Academic Search

Novel transmissive\\/absorptive electrochromic (EC) devices have been assembled using conjugated polymers on infrared-transparent electrodes made of single-wall carbon nanotubes (SWNTs). We will present results on the design, fabrication and characterization of sandwich type EC devices using dioxythiophene-based conjugated polymers (PXDOT). The polymers were prepared on the SWNT films using a potentiostatic electropolymerization method. The transmittance of the samples was measured

Maria Nikolou; Aubrey L. Dyer

2005-01-01

209

Effects of deposition modes on the microstructure of copper deposits from an acidic sulfate bath  

Microsoft Academic Search

The electrodeposition of various copper deposits was carried out by means of cyclic voltammetric, potentiostatic, galvanostatic, pulse-rest and pulse-reverse plating modes in a simple acidic CuSO4 bath without any additives, although the 8 mM CuSO4 solution employed in this work was not practically applicable for electroplating. The morphologies of these Cu deposits were systematically compared by atomic force microscopy (AFM),

Chi-Chang Hu; Chi-Ming Wu

2003-01-01

210

Electrochemical formation and characterisation of poly(3-methylthiophene)\\/WO3 nanocomposite films  

Microsoft Academic Search

Stable poly(3-methylthiophene)\\/WO3 (PMeT\\/WO3) nanocomposite films have been prepared by a two-step electrochemical method. At first the WO3 film was grown by a potentiostatic method in tungsten electrolytes, and then PMeT was deposited on the WO3 film by a potentiodynamic polymerisation method in 2?M solutions of 3-methylthiophene in 1-butyl-3-metyllimidazolium hexafluorophosphate ([BMIM]PF6). The products are characterised in detail by multiform techniques: scanning

Xia Wang; Xu Chun Song; Yi Fan Zheng; Rong Ma; Hao Yong Yin

2012-01-01

211

Electrochromic properties of lithiated Co-oxide (Li x CoO 2) and Ni-oxide (Li x NiO 2) thin films prepared by the sol–gel route  

Microsoft Academic Search

Layered LixCoO2 and LixNiO2 thin films (x?1) were prepared by a peroxo wet chemistry route from Li(I), Co(II) and Ni(II) acetate precursors and the addition of H2O2. Structural changes during the processing of xerogel to final oxide were followed by X-ray diffraction and infrared spectroscopy. Electrochromic properties were determined with in-situ potentiodynamic, potentiostatic and galvanostatic spectroelectrochemical measurements. Single dipped films

Franc Švegl; Boris Orel; Ven?eslav Kau?i?

2000-01-01

212

Annealing induced microstructural evolution of electrodeposited electrochromic tungsten oxide films  

Microsoft Academic Search

A significant influence of microstructure on the electrochromic and electrochemical performance characteristics of tungsten oxide (WO3) films potentiostatically electrodeposited from a peroxopolytungstic acid (PPTA) sol has been evaluated as a function of annealing temperature. Powerful probes like X-ray diffractometry (XRD), transmission electron microscopy (TEM), UV–vis spectrophotometry, multiple step chronoamperometry and cyclic voltammetry have been employed for the thin film characterization.

M. Deepa; A. K. Srivastava; T. K. Saxena; S. A. Agnihotry

2005-01-01

213

Corrosion behaviour of nano structured sol-gel alumina coated 9Cr–1Mo ferritic steel in chloride bearing environments  

Microsoft Academic Search

A stable boehmite sol was synthesized using Al-isopropoxide as a precursor in an appropriate ratio with water. Afterwards, the 9Cr–1Mo steel specimens were coated with prepared boehmite sol by dip coating technique. AFM analysis of the coated specimens confirmed the presence of nano sized particles (8–12nm) in the coating. Electrochemical measurements like potentiodynamic and potentiostatic polarisations, electrochemical impedance spectroscopy (EIS)

G. Ruhi; O. P. Modi; I. B. Singh

2009-01-01

214

Electrolytic nickel recovery from lithium-ion batteries  

Microsoft Academic Search

Lithium\\/cobalt\\/nickel oxide (LiCoxNi1?xO2, 0potentiostatic electrowinning. Operative

Carla Lupi; Mauro Pasquali

2003-01-01

215

Reduction of Tantalum Pentoxide Using Graphite and Tin-Oxide-Based Anodes via the FFC-Cambridge Process  

Microsoft Academic Search

An investigation into the electrochemical reduction of tantalum pentoxide (Ta2O5) to tantalum metal in molten calcium chloride was performed. The oxide was made the cathode, and either graphite or tin oxide\\u000a rods were selected as the anodes. The experiments were terminated after 8 hours of potentiostatic electrolysis using a two-electrode\\u000a setup, with the current and anodic potential recorded. The cathode products

Roger Barnett; Kamal Tripuraneni Kilby; Derek J. Fray

2009-01-01

216

High frequency stage I corrosion fatigue of austenitic stainless steel (316L)  

Microsoft Academic Search

High frequency (123 Hz) fatigue crack propagation studies were conducted under rising ?K conditions (R-ratio = 0.22) on single edge notch specimens of austenitic stainless steel (type 316L) that contained an annealed precrack.\\u000a Tests were conducted in near neutral (pH 5.5) solutions of 1 M NaCl and 1 M NaCl + 0.01 M Na2S2O3 under potentiostatically controlled conditions and in

Clinton Fong; Desmond Tromans

1988-01-01

217

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

218

A photoelectrochemical method for determining the kinematics of moving particles using an array of individually addressable electrodes.  

PubMed

We present the novel use of photoelectrochemistry to detect and monitor the trajectory of moving spheres. Using an array of individually addressable electrodes under illumination and potentiostatted so that a photocurrent is generated, the motion of a sphere is detected by means of measuring "dark" transients as the shadow cast by the moving sphere passes over each electrode. The method can used to determine the size and velocity of a single ball, or simultaneously track two spheres in collision. PMID:19533674

Rees, Neil V; Compton, Richard G

2009-08-01

219

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

220

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 95°C.

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

2007-01-01

221

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

Microsoft Academic Search

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

Dimo Kashchiev; Vesselin Bostanov

2007-01-01

222

Mechanistic study on electrochemical codeposition of mixed zinc–erbium oxide films on the cathodic surface  

Microsoft Academic Search

Erbium doped zinc oxide thin films were prepared from aqueous solutions containing Zn(NO3)2 and Er(NO3)3 by the potentiostatic technique using a three-electrode system. The pH changes at the cathode\\/solution interface were in-situ measured during the electrodeposition process of mixed erbium–zinc hydroxide or oxide films. The solution- and solid-phase speciation distributions of the two metal ions and their hydroxides as a

Jian-Min Zhang; Xiang-Ming Feng

2008-01-01

223

Nickel and cobalt recycling from lithium-ion batteries by electrochemical processes.  

PubMed

The presence of LiCoO(2) and LiCo(x)Ni((1-x))O(2) in the cathodic material of Li-ion and Li-polymer batteries has stimulated the recovery of Co and Ni by hydrometallurgical processes. In particular, the two metals were separated by SX method and then recovered by electrochemical (galvanostatic and potentiostatic) processes. The metallic Ni has been electrowon at 250 A/m(2), pH 3-3.2 and 50 degrees C, with 87% current efficiency and 2.96 kWh/kg specific energy consumption. Potentiostatic electrolysis produces a very poor Ni powder in about 1 h with current efficiency changing from 70% to 45% depending on Ni concentration in the electrolyte. Current efficiency of 96% and specific energy consumption of 2.8 kWh/kg were obtained for Co at 250 A/m(2), pH 4-4.2 and 50 degrees C, by using a solution containing manganese and (NH(4))(2)SO(4). The Co powder, produced in potentiostatic conditions (-0.9 V vs. SCE, pH 4, room temperature) appears particularly suitable for Co recycling as cobaltite in new batteries. PMID:15737721

Lupi, C; Pasquali, M; Dell'era, A

2005-01-01

224

Mechanism of the passivation of zirconium in low-pH solutions  

NASA Astrophysics Data System (ADS)

The passivation of zirconium alloys Zr-702 and Zr-704 was investigated using electrochemical and surface analysis techniques. The techniques used in this research include electrochemical experiments, such as potentiodynamic, potentiostatic, and electrochemical impedance spectroscopy (EIS), optical and scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS). The electrochemical experiments results showed that both alloys passivated in sulfuric acid. This passivity was modified by reducing the water content of the solution by adding methanol to the electrolyte. Both alloys showed transpassive behavior in hydrochloric acid and aqueous-methanolic sulfuric acid. Microscopic analysis of samples after the potentiostatic experiments in hydrochloric acid showed pitting. Potentiostatic measurements showed that both alloys remain passive in hydrochloric acid. SEM/EDS and XPS chemical analyses showed that the passive film consisted of only zirconium and oxgyen. The XPS results showed that the zirconium in the film was in either the 0 or +4 state. Additionally, XPS showed that the thickest films we formed in aqueous sulfuric acid. Films formed in hydrochloric acid showed no thickness increase over air-formed films. EIS analyses showed that the passive films formed on both alloys in sulfuric and hydrochloric acid grow under diffusion control. Mott-Schottky EIS analyses showed that the passive films formed were semiconductor in nature, and had donor densities on the order of 1019 cm-3.

Vanwinkle, James Arthur

225

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

226

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

227

Hydrophobic ionic liquids based on the 1-butyl-3-methylimidazolium cation for lithium\\/seawater batteries  

Microsoft Academic Search

Two hydrophobic ionic liquids (room temperature molten salts) based on 1-butyl-3-methylimidazolium cation (BMI+), BMI+PF6? and BMI+Tf2N?, were used in developing a highly efficient lithium anode system for lithium\\/seawater batteries. The lithium anode system was composed of lithium metal\\/ionic liquid\\/Celgard membrane. Both BMI+PF6?and BMI+Tf2N? maintained high apparent anodic efficiency (up to 100%) under potentiostatic polarization (at +0.5V versus open-circuit potential (OCP))

Yancheng Zhang; Mirna Urquidi-Macdonald

2005-01-01

228

Impedance experimentation for an electrode interface in human fetal tissue: Novel pathological régime of anomalous diffusion  

NASA Astrophysics Data System (ADS)

Impedance spectroscopic experimentation at the superfused electrode|living tissue interface for human fetal skin was performed in three-electrode potentiostatic configuration for noble metal electrodes, with spectral analysis of the current. The impedance plane locus observed, reflects a diffusional element frequently in series with a distributed element of Havriliak-Negami type. In a minority of experiments no impedance could be defined, due to the presence of an additional peak in every cycle in the shoulder of the current waveform. This nonlinearity has never been reported before for a system of the present type, and may represent a novel pathological régime of anomalous diffusion.

Ovadia, Marc; Fayn, Evgueni; Zavitz, Daniel H.

2006-06-01

229

Electrodeposited nickel–cobalt composite coating containing MoS 2  

Microsoft Academic Search

Ni–Co\\/MoS2 composite coatings were prepared by electrodeposition in a Ni–Co 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 Ni–Co\\/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

230

Electrodeposited nickel–cobalt composite coating containing nano-sized Si 3N 4  

Microsoft Academic Search

Ni–Co\\/Si3N4 composite coatings with various contents of Si3N4 nano-particulates were prepared by electrodeposition in a Ni–Co 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

231

Modulation of dendrite growth of cuprous oxide by electrodeposition  

NASA Astrophysics Data System (ADS)

Cuprous oxides with different dendrite morphologies were formed on F-doped tin oxide (FTO) covered glass substrates by potentiostatic deposition of cupric acetate. The effects of pH value (varied from 5.00 to 5.80) of electrolytes on the crystal morphologies of cuprous oxide were studied. Different crystal morphologies of cuprous oxides were obtained by the change of velocity of vertical growth and lateral growth through varying the pH value of electrolyte. The processes of Cu 2O dendrite crystal growth were analyzed through SEM images at different deposition times. Photoelectrochemical properties of the Cu 2O thin films prepared in the system are also studied.

Wan, Lijuan; Wang, Zhiqiang; Yang, Zaisan; Luo, Wenjun; Li, Zhaosheng; Zou, Zhigang

2010-10-01

232

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

233

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?, Željko J.; Jovi?evi?, Jovan N.

2013-02-01

234

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

Microsoft Academic Search

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

J. E. G González; J. C Mirza-Rosca

1999-01-01

235

Diffusivity, activity and solubility of oxygen in liquid lead and lead bismuth eutectic alloy by electrochemical methods  

NASA Astrophysics Data System (ADS)

The diffusivity of oxygen in liquid lead and lead-bismuth eutectic (LBE) alloy was measured by a potentiostatic method and is given by log(DOPb/ cm2 s-1)=-2.554-2384/T (±0.070), 818-1061 K, and log(DOLBE/ cm2 s-1)=-0.813-3612/T (±0.091), 811-980 K. The activity of oxygen in lead and LBE was determined by coulometric titration experiments. Using the measured data, the standard free energy of dissolution of oxygen in liquid lead and LBE was derived and is given by

Ganesan, Rajesh; Gnanasekaran, T.; Srinivasa, Raman S.

2006-02-01

236

Diagnosis of foot-and-mouth disease by electrochemical enzyme-linked immunoassay.  

PubMed

The development of an inmunosensor for the point-of-care detection of the foot-and-mouth cattle disease is presented. The detector is based on an ELISA method with electrochemical detection. A non-structural protein, 3ABC, is used to selectively detect antibodies is used to selectively detect anti-3ABC antibodies produced after infection. The biological test is performed onto a screen printed electrodes. A dedicated small, portable potentiostat is employed for the control of the sensors, as well as data acquisition, processing, and storage. PMID:21095891

Longinotti, Gloria; Ybarra, Gabriel; Lloret, Paulina; Moina, Carlos; Ciochinni, Andres; Serantes, Diego Rey; Malatto, Laura; Roberti, Mariano; Tropea, Salvador; Fraigi, Liliana

2010-01-01

237

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

238

Electrochemical Reactions During Ru Chemical Mechanical Planarization and Safety Considerations  

NASA Astrophysics Data System (ADS)

We analyzed electrochemical reactions during ruthenium (Ru) chemical mechanical planarization (CMP) using a potentiostat and a quartz crystal microbalance, and considered the potential safety issues. We evaluated the valence number derived from Faraday's law using the dissolution mass change of Ru and total coulomb consumption in the electrochemical reactions for Ru in acidic solution and slurry. The valence numbers of dissolved Ru ions were distributed in the range of 2 to 3.5. As toxic ruthenium tetroxide (RuO4) has a valence number of 8, we were able to conclude that no toxic RuO4 was produced in the actual Ru CMP.

Shima, Shohei; Wada, Yutaka; Tokushige, Katsuhiko; Fukunaga, Akira; Tsujimura, Manabu

2011-05-01

239

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

NASA Astrophysics Data System (ADS)

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

Malkhandi, Sauradip; Bonnefont, Antoine; Krischer, Katharina

2009-06-01

240

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/Ø 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

241

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

Microsoft Academic Search

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 H3PO4 solution, and crystallized at 300 and 500°C. Corrosion experiments were carried out using a potentiostat in 0.15 M NaCl solution\\u000a at 36.5 ± 1°C. The Ti–xHf alloys exhibited the ?? and anatase phases. The pore size

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

2011-01-01

242

Surface characteristics of HA coated Ti30Ta-xZr and Ti30Nb-xZr alloys after nanotube formation  

Microsoft Academic Search

In this study, surface characteristics of hydroxyapatite(HA) coated Ti-30Ta-xZr and Ti-30Nb-xZr alloys after nanotube formation have been investigated by EB-PVD, FE-SEM, XRD and potentiostat. The microstructures of the Ti-30Ta-xZr alloy had a needle-like morphology, and the thickness of this needle-like structure increased as the Zr content increased. The microstructures of the Ti-30Nb-xZr alloy had an equiaxed grain structure. The nanotubes

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

2010-01-01

243

Characterization of hydrogen ingress in high-strength alloys. Final report, 15 September 1993-14 September 1995  

Microsoft Academic Search

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

Pound

1995-01-01

244

Control of composition and conduction type of CdTe film electrodeposited from ammonia alkaline aqueous solutions  

Microsoft Academic Search

Potentiostatic cathodic electrodeposition of CdTe films was studied using aqueous ammonia-alkaline electrolytic baths in which Cd(II)- and Te(IV)-species were dissolving to form Cd(NHâ)â{sup 2+} and TeOâ²⁻ ions, respectively. Deposition of three kinds of films, i.e., Te-rich amorphous, Te-rich polycrystalline CdTe, and Cd-rich polycrystalline CdTe films, can be controlled by changing the pH (pH 10.5--12.2) and Cd(II)\\/Te(IV) concentration ratio of the

Kuniaki Murase; Hiroto Watanabe; Shiro Mori; Tetsuji Hirato; Yasuhiro Awakura

1999-01-01

245

Effects of minor additions of ruthenium on the passivation of duplex stainless-steel corrosion in concentrated hydrochloric acid solutions  

Microsoft Academic Search

The effects of minor additions of ruthenium (0.14%, 0.22%, and 0.28%) on the passivation of duplex stainless-steel (DSS, Fe–22%Cr–9%Ni–3%Mo)\\u000a corrosion in 2 M HCl solutions have been studied using open-circuit potential (OCP), potentiodynamic cyclic polarization,\\u000a potentiostatic current–time, electrochemical impedance spectroscopy (EIS), and weight loss measurements. OCP measurements\\u000a showed an increased shift in the corrosion potential to more positive values with increasing

El-Sayed M. Sherif; J. H. Potgieter; J. D. Comins; L. Cornish; P. A. Olubambi; C. N. Machio

2009-01-01

246

Synthesis and characterization of a new soluble conducting polymer and its electrochromic devices  

Microsoft Academic Search

A new polythiophene derivative was synthesized by both chemical and electrochemical oxidative polymerization of 1-(perfluorophenyl)-2,5-di(2-thienyl)-1H-pyrrole (FPTPy). The structures of both the monomer and the soluble polymer were elucidated by nuclear magnetic resonance (1H-NMR) and fourier transform infrared (FTIR). Polymer of FPTPy was also synthesized via potentiostatic electrochemical polymerization in acetonitrile (AN)\\/NaClO4\\/LiClO4 (0.1M:0.1M) solvent–electrolyte couple. Characterizations of the resulting insoluble polymer

Elif Sahin; Ertugrul Sahmetlioglu; Idris M. Akhmedov; Cihangir Tanyeli; Levent Toppare

2006-01-01

247

Synthesis, characterization and optoelectrochemical properties of poly(1,6-bis(2,5-di(thiophen-2-yl)-1 H-pyrrol-1-yl)hexane) and its copolymer with EDOT  

Microsoft Academic Search

A new polythiophene derivative was synthesized by electrochemical oxidative polymerization of 1,6-bis(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)hexane (TPH). The structure of the monomer was elucidated by 1H, 13C, FTIR and mass analyses. The polymer P(TPH) and its copolymer with 3,4-ethylenedioxythiophene (P(TPH-co-EDOT)) were synthesized via potentiostatic electrochemical polymerization. Characterizations of the resulting polymers were performed by cyclic voltammetry (CV), FTIR, UV–vis spectroscopies and conductivity measurements. Moreover,

Metin Ak; Ertu?rul ?ahmetlio?lu; Levent Toppare

2008-01-01

248

Electrochemical array sensors for plating waste stream monitoring  

SciTech Connect

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

Glass, R.S.; Hong, K.C.; Estill, J.C.; Reibold, R.A.; Thompson, W.M.; O`Brien, D.W.; Ciarlo, D.R. [Lawrence Livermore National Lab., CA (United States); Granstaff, V.E. [Sandia National Labs., Albuquerque, NM (United States)

1992-03-01

249

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

2013-05-01

250

Patterned electrochemical deposition of copper using an electron beam  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

251

Structural properties of single step electrochemically deposited ZnS nanofibers  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

252

Structural and magnetic transformation in electrochemically synthesized FePt thin films on Si/Pt electrodes  

NASA Astrophysics Data System (ADS)

FePt films were prepared by electrochemical deposition on to the platinum coated Si substrate. The appropriate composition of alloy was achieved by carrying out the potentiostatic deposition at -800 mV. After deposition, films were subjected to different annealing temperatures for 1h. Structural and magnetic studies were performed to investigate the phase transformation. At low annealing temperatures, presence of FePt3 was observed along with FePt phase. An increase in coercivity and squareness was observed with annealing temperature. A highest coercivity of 7.8 kOe was obtained after annealing at 700°C for 1h indicating the L10 phase formation.

Gupta, Rekha; Goyal, Rajan; Medwal, Rohit; Annapoorni, S.

2014-04-01

253

A photoelectrochemical method for tracking the motion of Daphnia magna in water.  

PubMed

We present the novel use of photoelectrochemistry to detect and monitor the motion of a single Daphnia magna swimming in a confined volume of water. Using an array of individually-addressable electrodes under illumination and potentiostatted so that a photocurrent is generated, the motion of the daphnid is detected by means of measuring "dark" transients as the shadow cast by the moving sphere passes over each electrode. The method can be used to determine the size and speed of a single daphnid. PMID:19684900

Rees, Neil V; Compton, Richard G

2009-09-01

254

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 -2.4°C. Decreased diffusion coefficient and ion concentration gradient due to the lowered deposition temperature effectively reduces ion diffusion rate, thereby favors uniform nanowire growth. Moreover, by varying the deposition temperature, we show that also the pore nucleation and the crystallinity can be controlled.

2011-01-01

255

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

256

Metal chelate catalysts for fuel cells  

NASA Astrophysics Data System (ADS)

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

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

1981-07-01

257

Metal chelate catalysts for fuel cells. Annual report Jul 80-Jun 81  

SciTech Connect

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

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

1981-07-01

258

Wearable electrochemical sensors for in situ analysis in marine environments.  

PubMed

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

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

2011-07-21

259

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

PubMed

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

Ashok, Akarapu; Pal, Prem

2014-01-01

260

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

PubMed Central

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

Ashok, Akarapu; Pal, Prem

2014-01-01

261

An approach to an inhibition electronic tongue to detect on-line organophosphorus insecticides using a computer controlled multi-commuted flow system.  

PubMed

An approach to an inhibition bioelectronic tongue is presented. The work is focused on development of an automated flow system to carry out experimental assays, a custom potentiostat to measure the response from an enzymatic biosensor, and an inhibition protocol which allows on-line detections. A Multi-commuted Flow Analysis system (MCFA) was selected and developed to carry out assays with an improved inhibition method to detect the insecticides chlorpyrifos oxon (CPO), chlorfenvinfos (CFV) and azinphos methyl-oxon (AZMO). The system manifold comprised a peristaltic pump, a set of seven electronic valves controlled by a personal computer electronic interface and software based on LabView® to control the sample dilutions into the cell. The inhibition method consists in the injection of the insecticide when the enzyme activity has reached the plateau of the current; with this method the incubation time is avoided. A potentiostat was developed to measure the response from the enzymatic biosensor. Low limits of detection of 10 nM for CPO, CFV, and AZMO were achieved. PMID:22163822

Alonso, Gustavo A; Dominguez, Rocio B; Marty, Jean-Louis; Muñoz, Roberto

2011-01-01

262

An electrochromic film device to teach polymer electrochemical physics  

NASA Astrophysics Data System (ADS)

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

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

2007-09-01

263

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

2013-07-01

264

Waste water derived electroactive microbial biofilms: growth, maintenance, and basic characterization.  

PubMed

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

Gimkiewicz, Carla; Harnisch, Falk

2013-01-01

265

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

PubMed

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 mus integration time is ~0.11 pA and is negligible compared to the inherent electrode noise. PMID:20514361

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

2010-04-01

266

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

267

Development and application of a real-time capacitive sensor.  

PubMed

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

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

2011-01-15

268

Spatial bifurcations of fixed points and limit cycles during the electrochemical oxidation of H2 on Pt ring-electrodes.  

PubMed

Pattern formation during the oscillatory oxidation of H2 on Pt ring-electrodes in the presence of electrosorbing ions was studied under potentiostatic control for three different positions of the reference electrode (RE). The position of the RE crucially affects the degree of the global feedback which is imposed by the potentiostatic operation mode, and the three configurations selected corresponded to zero, maximum and intermediate global coupling. In the absence of global coupling, 'communication' among different positions occurs exclusively through migration coupling (the electrochemical counterpart to diffusion in reaction-diffusion systems). In this case, spatially inhomogeneous oscillations that were attributed to a spatial bifurcation of the homogeneous limit cycle were observed throughout. This implies that the system is Benjamin-Feir unstable. For the strongest global coupling adjustable, travelling pulses were found that emerged in a wave bifurcation with n = 1 from the homogeneous steady state. The pulses exhibited modulations in velocity and width that most likely resulted from the interaction between inhomogeneities of the catalytic surface and the nonlinear reaction dynamics. In the case of an intermediate global coupling strength, a diversity of spatio-temporal motions was observed. The dynamics ranged from pulses over target patterns and so-called asymmetric target patterns to mixed states where two or three of these states alternate. For some parameters these mixed states were in addition separated by bursts of the system to a nearly homogeneous unreactive state. PMID:11901673

Grauel, P; Varela, H; Krischer, K

2001-01-01

269

Electrochemical etching of titanium-alloy castings  

SciTech Connect

This study was conducted to determine whether a potentiostatic electrochemical method could be used to etch selectively either the dendrites or the interdendritic material from Ti cast structures and thereby reveal their microstructures. Cast binary titanium alloys containing Mo, Ta, Nb, Al, and Cr and one multicomponent alloy containing Al, Ta, Nb, and Mo were polarized in sulfuric, oxalic, and fluosilicic acids and in a potassium hydroxide solution. Potentiostatic anodic polarization curves were obtained for each alloy. Results showed that the electrode potential for passivation was nearly the same for all alloys in a given acid, although the current density at the passivation potential varied from alloy to alloy. Generally for most alloying elements, the current density at the passivation potential decreased as the concentration of the alloying element increased, but not linearly. In the alkaline solution only the Ti-15% Cr alloy underwent significant dissolution, which occurred in the transpassive potential region. We were able to develop the dendritic structure with only the Ti-15% Mo, Ti-15% Ta, and Ti-15% Cr alloys. Possible reasons for our inability to delineate the dendritic structure in other alloys are discussed.

Griess, J.C.; David, S.A.; Gray, R.J.; Houck, C.W.

1983-10-01

270

Influence of dissolved hydrogen on aluminum-lithium alloy fracture behavior  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

271

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

272

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

SciTech Connect

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

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

1998-09-01

273

Origins of Nanoscale Damage to Glass-Sealed Platinum Electrodes with Submicrometer and Nanometer Size  

PubMed Central

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 UMEs 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 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 size are pivotal for reliable and quantitative nanoelectrochemical measurements.

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

2013-01-01

274

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

NASA Astrophysics Data System (ADS)

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

McCann, Kevin

275

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

PubMed Central

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

Gimkiewicz, Carla; Harnisch, Falk

2013-01-01

276

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

277

Electrodeposition of Bi(x)Fe(1-x) intermetallic compound nanowire arrays and their magnetic properties.  

PubMed

There have been few reports on Bi-Fe intermetallic compounds because Bi and Fe are immiscible in the equilibrium states and neither alloy nor intermetallic compound exists in the binary system. In this paper, we show that, by using the nanometer-scale templates based synthesis in conjunction with the electrochemical deposition, it is possible to mix in solid solution elements that are immiscible in traditional fabrication methods. The preparation of Bi-Fe intermetallic compound nanowire arrays was investigated via an electrodeposition route by using a polycarbonate (PC) membrane template. Cyclic voltammetry, potentiostatic transient, and potentiostatic stripping were used to study the formation of Bi(x)Fe(1-x) intermetallic compounds. The compositions of Bi(1-x)Fe(x) intermetallic compound nanowire arrays were sensitive to the bath compositions and the electrodeposition potentials, and the length could be easily adjusted by varying the electrodeposition time. The electrodeposited Bi(1-x)Fe(x) intermetallic compound nanowire arrays had a parallel-to-the-wire easy magnetization. Furthermore, the spin-glass such as behavior and an unusually large characteristic time, which was about 5.26 h, were found in Bi(1-x)Fe(x) intermetallic compound nanowire arrays at room temperature. PMID:16671702

Li, Gao-Ren; Tong, Ye-Xiang; Kay, Lin-Gang; Liu, Guan-Kun

2006-05-11

278

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-Català, Pedro L.; Samitier, Josep; Arundell, Martin; Rodríguez, Ivón

2009-05-01

279

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

SciTech Connect

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

Lim, Jae-Hong; Park, MiYeong; Lim, Dong-Chan [Materials Processing Division, Korea Institute of Materials Science, 66, Sangnam-dong, Changwon 641-010 (Korea, Republic of)] [Materials Processing Division, Korea Institute of Materials Science, 66, Sangnam-dong, Changwon 641-010 (Korea, Republic of); Myung, Nosang V. [Department of Chemical and Environmental Engineering, University of California-Riverside, Riverside, CA 92521 (United States)] [Department of Chemical and Environmental Engineering, University of California-Riverside, Riverside, CA 92521 (United States); Lee, Jung-Ho [Division of Materials and Chemical Engineering, Hanyang University, Kyeonggi 426-791 (Korea, Republic of)] [Division of Materials and Chemical Engineering, Hanyang University, Kyeonggi 426-791 (Korea, Republic of); Jeong, Young-Keun [Hybrid Materials Solution NCRC, Pusan National University, Busan 609-735 (Korea, Republic of)] [Hybrid Materials Solution NCRC, Pusan National University, Busan 609-735 (Korea, Republic of); Yoo, Bongyoung, E-mail: byyoo@hanyang.ac.kr [Division of Materials and Chemical Engineering, Hanyang University, Kyeonggi 426-791 (Korea, Republic of)] [Division of Materials and Chemical Engineering, Hanyang University, Kyeonggi 426-791 (Korea, Republic of); Lee, Kyu Hwan, E-mail: lgh1636@kims.re.kr [Materials Processing Division, Korea Institute of Materials Science, 66, Sangnam-dong, Changwon 641-010 (Korea, Republic of)

2012-10-15

280

Novel Pt nanowires modified screen-printed gold electrode by electrodeposited method  

NASA Astrophysics Data System (ADS)

In this work, the preparation and characterization of novel Pt nanowires (Pt NWs) on the screen-printed gold electrode (SPGE) surface are reported. Firstly the mesoporous template was prepared by the electro-assisted self-assembly (EASA) method on the manual SPGE. Then, in the potentiostatic condition, Pt NWs were electrodeposited in the meosoporous channel on the Au electrode surface using the chronopotentiometry (CP) method at room temperature. The synthesized Pt NWs were characterized by cyclic voltammetry (CV), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) spectrometer. The results indicated that Pt NWs were successfully electrodeposited on the SPGE substrate, even the diameter of each Pt NWs could reach 3.2 nm. Furthermore, the SPGE could be mass produced conveniently and cost low which had very promising application prospect. And it is significant that the Pt NWs modified SPGE could function as an electrode in an electrochemical biosensor.

Zhao, Hongli; Zhou, Changxiang; Teng, Yuanjie; Chen, Chen; Lan, Minbo

2011-02-01

281

Corrosion behavior of sensitized duplex stainless steel.  

PubMed

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

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

1998-01-01

282

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

NASA Astrophysics Data System (ADS)

In this article, the physico-chemical and electrochemical conditions of through-silicon via formation were studied. First, macropore arrays were etched through a low doped n-type silicon wafer by anodization under illumination into a hydrofluoric acid-based electrolyte. After electrochemical etching, `almost' through-silicon macropores were locally opened by a backside photolithographic process followed by anisotropic etching. The 450 × 450-?m² opened areas were then selectively filled with copper by a potentiostatic electrochemical deposition. Using this process, high density conductive via (4.5 × 105 cm-²) was carried out. The conductive paths were then electrically characterized, and a resistance equal to 32 m?/copper-filled macropore was determined.

Defforge, Thomas; Billoué, Jérôme; Diatta, Marianne; Tran-Van, François; Gautier, Gaël

2012-07-01

283

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

PubMed

In this article, the physico-chemical and electrochemical conditions of through-silicon via formation were studied. First, macropore arrays were etched through a low doped n-type silicon wafer by anodization under illumination into a hydrofluoric acid-based electrolyte. After electrochemical etching, 'almost' through-silicon macropores were locally opened by a backside photolithographic process followed by anisotropic etching. The 450?×?450-?m² opened areas were then selectively filled with copper by a potentiostatic electrochemical deposition. Using this process, high density conductive via (4.5?×?105?cm-²) was carried out. The conductive paths were then electrically characterized, and a resistance equal to 32 m?/copper-filled macropore was determined. PMID:22776559

Defforge, Thomas; Billoué, Jérôme; Diatta, Marianne; Tran-Van, François; Gautier, Gaël

2012-01-01

284

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

SciTech Connect

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

Wan Jun [College of Life Science and Pharmaceutical Engineering, Nanjing University of Technology, 210093 Nanjing, Jiangsu (China); Key Laboratory of Eco-chemical Engineering, Ministry of Education, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China); Yan Xia; Ding Junjie; Wang Meng [Key Laboratory of Eco-chemical Engineering, Ministry of Education, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China); Hu Kongcheng, E-mail: wanjundz@sohu.com [College of Life Science and Pharmaceutical Engineering, Nanjing University of Technology, 210093 Nanjing, Jiangsu (China)

2009-12-15

285

Periodic behavior in the iron/sulfuric acid system  

SciTech Connect

Potentiostatic current oscillations observed during the anodic dissolution of an iron electrode in a sulfuric acid electrolyte are considered. This behavior has been experimentally characterized with respect to its potential dependence. A new mechanism has been developed that is consistent with observed behaviors and trends. This mechanism combines previously developed ideas concerning periodic behavior and passivation of iron with a new interpretation of precipitated salt-film behavior. The salt film is taken to be nonporous, serving as both a necessary precursor to oxide passivation as well as an effective passivating species itself. The mechanism is well corroborated by results from a mathematical model which also highlights the necessity of salt-film precipitation for the development of periodic behavior. Additionally, the issue of coherence is explicitly considered.

Rush, B.; Newman, J. [Lawrence Berkeley Lab., CA (United States). Energy and Environment Division]|[Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering

1995-11-01

286

Recovery of the actinides by electrochemical methods in molten chlorides using solid aluminium cathode  

SciTech Connect

An electrorefining process in molten chloride salts is being developed at ITU to reprocess the spent nuclear fuel. According to the thermochemical properties of the system, aluminium is the most promising electrode material for the separation of actinides (An) from lanthanides (Ln). The actinides are selectively reduced from the fission products and stabilized by the formation of solid and compact actinide-aluminium alloys with the reactive cathode material. In this work, the maximum loading of aluminium with actinides was investigated by potentiostatic and galvano-static electrorefining of U-Pu- Zr alloys. A very high aluminium capacity was achieved, as the average loading was 1.6 g of U and Pu into 1 g of aluminium and the maximum achieved loading was 2.3 g. For recovery of the actinides from aluminium, a process based on chlorination and a subsequent sublimation of AlCl{sub 3} is proposed. (authors)

Malmbeck, R.; Mendes, E.; Serp, J.; Soucek, P.; Glatz, J.P. [European Commission, JRC, Institute for Transuranium Elements, Postfach 2340, 76125 Karlsruhe (Germany); Cassayre, L. [Laboratoire de Genie Chimique - LGC, Universite Paul Sabatier, UMR 5503, 118 route de Narbonne, 31062 Toulouse Cedex 04 (France)

2007-07-01

287

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

288

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

NASA Astrophysics Data System (ADS)

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

Nicic, Igor; Macdonald, Digby D.

2008-09-01

289

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

290

Iron dissolution in aqueous AOT solution.  

PubMed

The effects of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) on the electrochemical behavior of iron were studied by potentiodynamic and potentiostatic techniques and open-circuit potential measurements. Experiments were made in both neutral and alkaline AOT solutions (pH 7 and pH 12). It was found that AOT-assisted dissolution is initiated on a passivated iron surface and that the oxidation current leads to the formation of a gel-like film on the electrode surface. This dissolution process was investigated as a function of pH, potential, and electrode rotation rate and the corrosion products were characterized by polarizing microscopy, SEM/EDX, and IR spectroscopy. The gel-like material is a mixed NaAOT-Fe(AOT)3 lamellar mesophase and a structure for this mesophase is proposed. PMID:17126850

Lehr, I L; Saidman, S B; Schulz, P C

2007-02-15

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

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

SciTech Connect

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

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

2013-06-01

293

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

NASA Astrophysics Data System (ADS)

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

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

1987-07-01

294

Electrochemical stability of Co-Mo intermetallic compound electrodes for hydrogen oxidation reaction in hot KOH solution  

NASA Astrophysics Data System (ADS)

In order to obtain a hydrogen electrode with high-performance and stability for H 2-O 2 alkaline fuel cells, Brewer-type Co-Mo alloys are manufactured in the 35 to 57 wt.% Mo composition range by an arc-melting method. The electrochemical stability of alloys composed of Co 3Mo and Co 7Mo 6 phases is investigated in hot KOH solution deaerated with N 2 gas by means of electrochemical methods such as cyclic voltammetry, potentiostatic polarization and potentiodynamic polarization. Co-Mo alloy is extensively dissolved because the cobalt in alloy is soluble in hot KOH solution. The dissolution current of the alloys increases with increasing electrolyte temperature, electrolyte concentration and Mo content in the alloy.

Lee, Chang Rae; Kang, Sung Goon

295

A model for pore growth in anodically etched gallium phosphide  

NASA Astrophysics Data System (ADS)

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

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

2005-06-01

296

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

SciTech Connect

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

Jang, Y.-I.

2001-10-02

297

Mechanistic study of photoelectrochemical reactions at a p-gap electrode  

SciTech Connect

The photocurrent-potential relations of a p-GaP electrode in various solutions are studied potentiostatically. Both the cathodic and anodic photocurrents are observed, i.e., the sign of photocurrent changes at a certain potential which we name the potential of zero photocurrent, V/sub zp/. The potential of zero photocurrent is close but not equal to the flatband potential. The origin of the anodic photocurrent is presented. The log (photocurrent)-potential relations follow the Tafel line at medium bias potentials and deviate from it at large and small bias potentials. The mechanism of the cathodic reactions is proposed based on the experimental results. The rate-determining step is the supply of photoexcited electrons to the semiconductor surface at large bias potentials and is the electrochemical, i.e., surface, process at medium and small bias potentials. 34 refs.

Uosaki, K.; Kita, H.

1981-10-01

298

Pharmacokinetic study of medicinal polymers: models based on dextrans  

SciTech Connect

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

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

1986-09-01

299

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

300

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

NASA Astrophysics Data System (ADS)

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

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

301

Chaos during the growth of an artificial pit  

SciTech Connect

This paper reports that the current vs. time behavior of a silver electrode in a one-dimensional artificial pit configuration was followed under potentiostatic control in 1M HClO{sub 4}. The current decay followed power law behavior in time, i {congruent} t{sup {minus}y}, with y {congruent} 0.5. Within specific regimes of applied potential and pit depth, the current was found to oscillate both periodically and chaotically with time. The oscillations result from an instability of a salt film on the metal surface. Owing to the instability of the salt film, a porous metal laver develops on the electrode surface, and this has a variety of implications in the field of corrosion.

Corcoran, S.G.; Sieradzki, K. (Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Materials Science and Engineering)

1992-06-01

302

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

SciTech Connect

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

Tan Hua; Jiang Yiming; Deng Bo; Sun Tao; Xu Juliang [Department of Material Science, Fudan University, Shanghai 200433 (China); Li Jin, E-mail: jinli@fudan.edu.cn [Department of Material Science, Fudan University, Shanghai 200433 (China)

2009-09-15

303

Elucidation of band structure of charge storage in conducting polymers using a redox reaction.  

PubMed

A novel technique to investigate charge storage characteristics of intrinsically conducting polymer films has been developed. A redox reaction is conducted on a polymer film on a rotating disk electrode under potentiostatic condition so that the rate of charging of the film equals the rate of removal of the charge by the reaction. The voltammogram obtained from the experiment on polyaniline film using Fe(2+)/Fe(3+) in HCl as the redox system shows five distinct linear segments (bands) with discontinuity in the slope at specific transition potentials. These bands are the same as those indicated by electron spin resonance (ESR)/Raman spectroscopy with comparable transition potentials. From the dependence of the slopes of the bands on concentration of ferrous and ferric ions, it was possible to estimate the energies of the charge carriers in different bands. The film behaves as a redox capacitor and does not offer resistance to charge transfer and electronic conduction. PMID:24915486

Contractor, Asfiya Q; Juvekar, Vinay A

2014-07-01

304

Mechanism of localized corrosion of 7075 alloy plate  

NASA Astrophysics Data System (ADS)

Investigation of localized corrosion in 7075 aluminum alloy plate shows that the mechanism of corrosion can be rationalized on the basis of potentiokinetic anodic polarization behavior. 7075 alloy in cold water quenched W temper has been shown to be susceptible to both pitting and intergranular corrosion. Aging to peak strength condition (T651 temper) increases the susceptibility to intergranular corrosion. The preferential anodic path is presumed to be solute enrichment (Zn and Mg) in the vicinity of grain boundaries. This is substantiated by the observation of two distinct pitting potentials in the anodic polarization curve for the T651 temper. Overaging to the T7351 temper decreases susceptibility, both by the reduction in the difference between the two pitting potentials and by the reduction in the amount of solute atoms segregated. Metallographic cross-sections of potentiostatically polarized specimens substantiate the proposed mechanism.

Maitra, S.; English, G. C.

1981-03-01

305

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

306

An electronic pollen detection method using Coulter counting principle  

NASA Astrophysics Data System (ADS)

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

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

307

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

PubMed

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. PMID:22128993

Winkler, Gates R; Winkler, Jay R

2011-11-01

308

Corrosion behavior of boride layers evaluated by the EIS technique  

NASA Astrophysics Data System (ADS)

The corrosion behavior of boride layers at the AISI 304 steel surface is evaluated in the present study. Electrochemical impedance spectroscopy (EIS) technique was used for the evaluation of the polarization resistance at the steel surface, with the aid of AUTOLAB potentiostat. Samples were treated with boron paste thickness of 4 and 5 mm, in the range of temperatures 1123 ? T ? 1273 K and exposed time of 4 and 6 h. The electrochemical technique employed 10 mV AC with a frequency scan range from 8 kHz to 3 mHz in deaerated 0.1 M NaCl solution. Nyquist diagrams show that the highest values of corrosion resistance are present in the samples borided at the temperature of 1273 K, with treatment time of 4 h and 4 mm of boron paste thickness. The values of corrosion resistance on borided steels are compared with the porosity exhibited in the layers.

Campos, I.; Palomar-Pardavé, M.; Amador, A.; VillaVelázquez, C.; Hadad, J.

2007-09-01

309

Electrochemical velocimetry on centrifugal microfluidic platforms.  

PubMed

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

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

2013-08-21

310

Nanoparticle based DNA biosensor for tuberculosis detection using thermophilic helicase-dependent isothermal amplification.  

PubMed

The present study describes the development of a DNA based biosensor to detect Mycobacterium tuberculosis using thermophilic helicase-dependent isothermal amplification (tHDA) and dextrin coated gold nanoparticles (AuNPs) as electrochemical reporter. The biosensor is composed of gold nanoparticles (AuNPs) and amine-terminated magnetic particles (MPs) each functionalized with a different DNA probe that specifically hybridize with opposite ends of a fragment within the IS6110 gene, which is M. tuberculosis complex (MTC) specific. After hybridization, the formed complex (MP-target-AuNP) is magnetically separated from the solution and the AuNPs are electrochemically detected on a screen printed carbon electrode (SPCE) chip. The obtained detection limit is 0.01 ng/?l of isothermally amplified target (105 bp). This biosensor system can be potentially implemented in peripheral laboratories with the use of a portable, handheld potentiostat. PMID:21616654

Torres-Chavolla, Edith; Alocilja, Evangelyn C

2011-07-15

311

Electron transfer mechanism in Shewanella loihica PV-4 biofilms formed at graphite electrode.  

PubMed

Electron transfer mechanisms in Shewanella loihica PV-4 viable biofilms formed at graphite electrodes were investigated in potentiostat-controlled electrochemical cells poised at oxidative potentials (0.2V vs. Ag/AgCl). Chronoamperometry (CA) showed a repeatable biofilm growth of S. loihica PV-4 on graphite electrode. CA, cyclic voltammetry (CV) and its first derivative shows that both direct electron transfer (DET) mediated electron transfer (MET) mechanism contributes to the overall anodic (oxidation) current. The maximum anodic current density recorded on graphite was 90 ?A cm(-2). Fluorescence emission spectra shows increased concentration of quinone derivatives and riboflavin in the cell-free supernatant as the biofilm grows. Differential pulse voltammetry (DPV) show accumulation of riboflavin at the graphite interface, with the increase in incubation period. This is the first study to observe a gradual shift from DET to MET mechanism in viable S. loihica PV-4 biofilms. PMID:22281091

Jain, Anand; Zhang, Xiaoming; Pastorella, Gabriele; Connolly, Jack O; Barry, Niamh; Woolley, Robert; Krishnamurthy, Satheesh; Marsili, Enrico

2012-10-01

312

Portable electrochemical surface-enhanced Raman spectroscopy system for routine spectroelectrochemical analysis.  

PubMed

A simple, portable electrochemical surface-enhanced Raman spectroscopy (SERS) system is reported, consisting of a small benchtop Raman spectrometer, a laptop computer, and a portable USB potentiostat. Screen printed electrodes modified with silver colloidal nanoparticles are used as the SERS-active electrode, which exhibit long-term stability once prepared. Spectroelectrochemical analyses of para-aminothiophenol and melamine as model systems was conducted. In both cases, an increase in SERS signal is observed upon modulation of the applied voltage, indicating an inherent benefit of such a system wherein the surface charge can be easily tuned. Given the low cost, rapid analysis time, and good sensitivity of this system, this simple setup could be implemented for many on-site sensing applications, ranging from food and drug analysis to environmental monitoring and to chemical and biological warfare agent detection. PMID:22242894

Robinson, A M; Harroun, S G; Bergman, J; Brosseau, C L

2012-02-01

313

Rapid fabrication of bimetallic spherical motors.  

PubMed

Catalytic bimetallic nanomotors can swim at 100 body lengths per second as well as pick up, haul, and release micrometer-scale cargo. The electrokinetic locomotion of bimetallic nanomotors is driven by the electrocatalytic decomposition of hydrogen peroxide. The motors are typically fabricated by electrodeposition-based template synthesis techniques that result in heterogeneous samples and require specialized knowledge of electrochemistry, a three-electrode potentiostat setup, cyanide-based chemistry, and porous membranes. This paper presents a rapid and facile method for fabrication of spherical bimetallic motors that only requires access to metal deposition equipment and commercially available microspheres. The resulting spherical motors swim at speeds comparable to rod-shaped motors with the same dimensions and composition. The spherical motors' velocity increases with fuel concentration and decreasing diameter. PMID:20695541

Wheat, Philip M; Marine, Nathan A; Moran, Jeffrey L; Posner, Jonathan D

2010-08-17

314

Microstructure and properties of ultrafine grain nickel 200 after hydrostatic extrusion processes  

NASA Astrophysics Data System (ADS)

This paper presents the results of the studies of the structure and properties of ultrafine grained nickel 200 obtained by hydrostatic extrusion processes. Microstructure was characterized by means of optical microscopy and electron transmission microscopy. Corrosion resistance was studied by impedance and potentiodynamic methods using an AutoLab PGSTAT 100 potentiostat in 0.1 M Na2SO4 solution and in acidified (by addition of H2SO4) 0.1 M NaCl solution at pH = 4.2 at room temperature. Microhardness tests were also performed. The results showed that hydrostatic extrusion produces a heterogeneous, ultrafine-grained microstructure in nickel 200. The corrosive resistance tests showed that the grain refinement by hydrostatic extrusion is accompanied by a decreased corrosive resistance of nickel 200.

Sitek, R.; Krajewski, C.; Kami?ski, J.; Spychalski, M.; Garbacz, H.; Pachla, W.; Kurzyd?owski, K. J.

2012-09-01

315

Optimization of hydrogen uptake in Ag-CNTs electrodes with charge-discharge cyclic currents  

NASA Astrophysics Data System (ADS)

Electrochemical storage of hydrogen in Ag-CNTs (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 and the outputs have been characterized by XRD and Raman spectroscopy. It has been observed that in cyclic charge and discharge (C&D) procedures the amount of stored hydrogen in the electrodes (the discharge capacity) is very sensitive to the cyclic regulated currents and it is shown that the optimum value is about 326 mA h/g at 9 mA. This optimization can be attributed to two competitive phenomena: (i) re-alignment of the CNTs, and (ii) oxidation of the electrode's surface.

Khoshnevisan, B.; Behpour, M.; Kaveh, D.

2009-06-01

316

Combinatorial electrochemical synthesis and screening of Pt-WO3 catalysts for electro-oxidation of methanol  

NASA Astrophysics Data System (ADS)

An automated system for high-throughput electrochemical synthesis and screening of fuel cell electro-oxidation catalysts is described. This system consists of an electrode probe that contains counter and reference electrodes that can be positioned inside an array of electrochemical cells created within a polypropylene block. The electrode probe is attached to an automated of X-Y-Z motion system. An externally controlled potentiostat is used to apply the electrochemical potential to the catalyst substrate. The motion and electrochemical control are integrated using a user-friendly software interface. During automated synthesis the deposition potential and/or current may be controlled by a pulse program triggered by the software using a data acquisition board. The screening includes automated experiments to obtain cyclic voltammograms. As an example, a platinum-tungsten oxide (Pt-WO3) library was synthesized and characterized for reactivity towards methanol electro-oxidation.

Jayaraman, Shrisudersan; Baeck, Sung-Hyeon; Jaramillo, Thomas F.; Kleiman-Shwarsctein, Alan; McFarland, Eric W.

2005-06-01

317

Improving the signal-to-noise ratio of an ECL-based sensor using ad hoc carbon nanotube electrodes  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate that mechanically modified cylinder-shaped carbon nanotube (CNT) working electrodes (WEs), combined with an averaging processing algorithm, can increase electrogenerated chemiluminescence (ECL) limit of detection by more than one order of magnitude, compared to gold electrodes. With CNT WEs, we obtained a stable light emission that lasts for hundreds of voltammetric cycles. This stability was further exploited to increase the detection limit with a simple algorithm, based on mean calculation. Ad hoc fabricated sensors are characterized with a full-custom potentiostat testbed and software platform, using tris(2,2-bipyridyl)ruthenium (II) as ECL labels. Our measurement results show that the signal-to-noise ratio (SNR) improves by a factor of larger than 20 compared to standard gold WEs to reach a detection limit up to 40 pg ?l-1.

Sanginario, A.; Giorcelli, M.; Tagliaferro, A.; Demarchi, D.

2012-07-01

318

New Cyclic Voltammetry Method for Examining Phase Transitions on Electrodes: Simulated Results  

NASA Astrophysics Data System (ADS)

We propose a new experimental technique for cyclic voltammetry, based on the first-order reversal curve (FORC) method for analysis of systems undergoing hysteresis. The advantages of this technique are demonstrated by applying it to dynamical models of electrochemical adsorption. The method can not only differentiate between discontinuous and continuous phase transitions, but can also quite accurately recover equilibrium behavior from dynamic analysis of systems with a continuous phase transition. The FORC diagram for a discontinuous phase transition is characterized by a negative (unstable) region separating two positive (stable) regions, while such a negative region does not exist for continuous phase transitions. Experimental data for Electrochemical FORC (EC-FORC) analysis could easily be obtained by simple reprogramming of a potentiostat designed for conventional cyclic-voltammetry experiments.I. Abou Hamad, D.T. Robb, P.A. Rikvold, J. Electroanal. Chem., in press.

Abou Hamad, Ibrahim; Robb, Daniel; Rikvold, Per Arne

2007-03-01

319

First-Principles Molecular Dynamics at a Constant Electrode Potential  

NASA Astrophysics Data System (ADS)

A simulation scheme for performing first-principles molecular dynamics at a constant electrode potential is presented, opening the way for a more realistic modeling of voltage-driven devices. The system is allowed to exchange electrons with a reservoir at fixed potential, and dynamical equations for the total electronic charge are derived by using the potential energy of the extended system. In combination with a thermostat, this potentiostat scheme reproduces thermal fluctuations of the charge with the correct statistics, implying a realistic treatment of the potential as a control variable. Practically, the dynamics of the charge are decoupled from the electronic structure calculations, making the scheme easily implementable in existing first-principles molecular dynamics codes. Our approach is demonstrated on a test system by considering various test cases.

Bonnet, Nicéphore; Morishita, Tetsuya; Sugino, Osamu; Otani, Minoru

2012-12-01

320

Giant magnetoresistance in electrodeposited Co87Fe13/Cu compositionally modulated alloys  

NASA Astrophysics Data System (ADS)

In this paper we report on the giant magnetoresistance effect and oscillatory exchange coupling in electrodeposited Co87Fe13/Cu compositionally modulated alloys. The alloys are compositionally modulated over nanometre length scales with ferromagnetic Co87Fe13 (Cu) alloy layers and non-magnetic Cu layers. Co87Fe13/Cu multilayered thin films were electrodeposited from a single sulfate plating solution containing all metallic ions of interest under computer-controlled potentiostat switching on (111)-textured Cu buffers previously evaporated on Si(111). Electrodeposits present a polycrystalline character with coexistence of face-centred cubic (fcc) and hexagonal close-packed (hcp) structures. Magnetoresistance effects as high as 8% were observed at room temperature. The dependence of the magnetoresistance effect on Cu spacer layer thickness shows an oscillation period around 1.0 nm.

Kakuno, E. M.; da Silva, R. C.; Mattoso, N.; Schreiner, W. H.; Mosca, D. H.; Teixeira, S. R.

1999-06-01

321

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

322

Scanning droplet cell for high throughput electrochemical and photoelectrochemical measurements.  

PubMed

High throughput electrochemical techniques are widely applied in material discovery and optimization. For many applications, the most desirable electrochemical characterization requires a three-electrode cell under potentiostat control. In high throughput screening, a material library is explored by either employing an array of such cells, or rastering a single cell over the library. To attain this latter capability with unprecedented throughput, we have developed a highly integrated, compact scanning droplet cell that is optimized for rapid electrochemical and photoeletrochemical measurements. Using this cell, we screened a quaternary oxide library as (photo)electrocatalysts for the oxygen evolution (water splitting) reaction. High quality electrochemical measurements were carried out and key electrocatalytic properties were identified for each of 5456 samples with a throughput of 4 s per sample. PMID:23464227

Gregoire, John M; Xiang, Chengxiang; Liu, Xiaonao; Marcin, Martin; Jin, Jian

2013-02-01

323

First-principles molecular dynamics at a constant electrode potential.  

PubMed

A simulation scheme for performing first-principles molecular dynamics at a constant electrode potential is presented, opening the way for a more realistic modeling of voltage-driven devices. The system is allowed to exchange electrons with a reservoir at fixed potential, and dynamical equations for the total electronic charge are derived by using the potential energy of the extended system. In combination with a thermostat, this potentiostat scheme reproduces thermal fluctuations of the charge with the correct statistics, implying a realistic treatment of the potential as a control variable. Practically, the dynamics of the charge are decoupled from the electronic structure calculations, making the scheme easily implementable in existing first-principles molecular dynamics codes. Our approach is demonstrated on a test system by considering various test cases. PMID:23368585

Bonnet, Nicéphore; Morishita, Tetsuya; Sugino, Osamu; Otani, Minoru

2012-12-28

324

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 500°C. Corrosion experiments were carried out using a potentiostat in 0.15 M NaCl solution at 36.5 ± 1°C. The Ti-xHf alloys exhibited the ?' 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

2011-01-01

325

Electrochemical fabrication and characterization of nanocontacts and nm-sized gaps  

NASA Astrophysics Data System (ADS)

Copper nanocontacts and molecular-sized nanogaps were prepared and characterized at electrified solid/liquid interfaces employing lithographic and electrochemical techniques. A dedicated four-electrode potentiostat was developed for controlling the electrochemical fabrication process and for monitoring the electrical characteristics of the nanostructures created. The formation and breaking of Cu nanocontacts exhibits conductance quantization characteristics. The statistical analysis of conductance histograms revealed a preferential stability of nanocontacts with integer values of G0, with a clear preference for 1 G0, 2 G0 and 3 G0. The growth of molecular-sized gaps shows quantized tunneling current, which is attributed to the discrete nature of Cu atoms, water molecules, and specifically adsorbed ions.

Mészáros, G.; Kronholz, S.; Karthäuser, S.; Mayer, D.; Wandlowski, T.

2007-06-01

326

Spectroscopic investigation of an electrochemically controlled conducting polymer-solid electrolyte junction  

NASA Astrophysics Data System (ADS)

We have recently reported a hybrid conducting polymer-solid electrolyte heterojunction in which electronic channel current is controlled by ionic diffusion and redox reactions involving doped polyethyleneoxide and doped polyaniline (PANI). In this paper we demonstrate on the microscopic level the validity of the model we proposed to interpret the electronic behavior of the device we fabricated. In particular, we used resonance and vicinity (surface-enhanced-Raman-scattering like) enhanced micro-Raman spectroscopy to map out the redox state of PANI along the conducting channel, simultaneously with the determination of the voltamperometric characteristics in a potentiostat configuration. The Raman data were complemented as appropriate by the optical and Fourier transform infrared absorption spectroscopies.

Berzina, Tatiana; Erokhin, Victor; Fontana, M. P.

2007-01-01

327

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

328

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

329

Computer-controlled instrumentation for fast voltammetry at ultramicroelectrodes  

NASA Astrophysics Data System (ADS)

In this article we describe an electrochemical experimental setup for cyclic voltammetry operating from low (1 V/s) to very high (200 kV/s) scan rates. The system is designed to achieve an acceptable cost and to be user friendly for nonexperts. The instrumentation is based on a commercial arbitrary wave form generator, a digital oscilloscope, a general purpose interface bus interface to a PC, and a laboratory-built potentiostat. There are no complicated manual operations, instead the software creates dialog with an operator to control commands for the instruments. Requirements for the wave form synthesis and the data acquisition are given. Various data-smoothing methods for treating 8-bit fast scan data are evaluated. The performance was tested on the oxidation of ferrocene in acetonitrile. The estimated value of the standard heterogeneous rate constant, k0=0.8+/-0.1 cm s-1, is in reasonable agreement with the most recent reports from other laboratories.

Pospíšil, L.; Fiedler, J.; Fanelli, N.

2000-04-01

330

Polypyrrole/gold bilayer characterization  

NASA Astrophysics Data System (ADS)

Polypyrrole/gold bilayer microactuators are being developed in our laboratory for biomedical applications such as microvalves. To fully open and close the valves, the bilayer hinges must be able to rotate between 0° and 180° within a few seconds against external forces. The layer thicknesses and hinge lengths must therefore be properly designed for the application. However, existing models fail to predict the correct behavior of microfabricated PPy/Au bilayer microactuators. Therefore, additional experimental data are needed to correctly forecast their performance. Bilayer actuators were fabricated with ranges of PPy thicknesses and hinge lengths. Bending angles were recorded through a stereomicroscope in the fully oxidized and reduced states. Isometric forces exerted by the hinges were measured with a force transducer, the output of which was read by a potentiostat and correlated with the applied potentials.

Fanning, Steven; Liu, Yingkai; Christophersen, Marc; Duerkop, Matthias; Smela, Elisabeth; Shapiro, Benjamin

2005-05-01

331

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

332

Single-step electrochemical nanolithography of metal thin films by localized etching with an AFM tip  

NASA Astrophysics Data System (ADS)

This work introduces electrochemical nanolithography (ENL), a single-step method in which a metal thin film is locally etched without application of a mask on a 100 nm length scale with an electrochemical atomic force microscope (AFM). The method requires the application of ultra-short voltage pulses on the tip (nanosecond range duration, 2-4 V amplitude), while both the sample and the metalized tip are under independent potentiostatic control for full control of interface reactions in an AFM electrochemical cell. It is demonstrated that Cu films as well as Co and Cu/Co sandwich magnetic films can be patterned if negative voltage pulses are applied to the tip. This method also applies to films deposited on an insulating substrate. Moreover the lateral dimension of lithographed structures is tunable, from a few micrometers down to 150 nm, by appropriate choice of ENL conditions. Simulation of the dissolution process is discussed.

de Abril, O.; Gündel, A.; Maroun, F.; Allongue, P.; Schuster, R.

2008-08-01

333

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

334

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

335

Electrochemical deposition and characterization of Ni-P alloy thin films  

SciTech Connect

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

Mahalingam, T. [Department of Physics, Alagappa University, Karaikudi, 630 003 (India) and Department of Electrical and Computer Engineering, College of Information Technology, Ajou University, Suwon 443-749 (Korea, Republic of)]. E-mail: maha51@rediffmail.com; Raja, M. [Department of Physics, Alagappa University, Karaikudi, 630 003 (India); Thanikaikarasan, S. [Department of Physics, Alagappa University, Karaikudi, 630 003 (India); Sanjeeviraja, C. [Department of Physics, Alagappa University, Karaikudi, 630 003 (India); Velumani, S. [Departamento de Fisica, ITESM-Campus Monterrey, Nuevo Leon, C.P. 64849 (Mexico); Moon, Hosun [Department of Electrical and Computer Engineering, College of Information Technology, Ajou University, Suwon 443-749 (Korea, Republic of); Kim, Yong Deak [Department of Electrical and Computer Engineering, College of Information Technology, Ajou University, Suwon 443-749 (Korea, Republic of)

2007-08-15

336

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

PubMed Central

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

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

2013-01-01

337

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

338

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

PubMed

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

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

2010-05-01

339

Scanning droplet cell for high throughput electrochemical and photoelectrochemical measurements  

NASA Astrophysics Data System (ADS)

High throughput electrochemical techniques are widely applied in material discovery and optimization. For many applications, the most desirable electrochemical characterization requires a three-electrode cell under potentiostat control. In high throughput screening, a material library is explored by either employing an array of such cells, or rastering a single cell over the library. To attain this latter capability with unprecedented throughput, we have developed a highly integrated, compact scanning droplet cell that is optimized for rapid electrochemical and photoeletrochemical measurements. Using this cell, we screened a quaternary oxide library as (photo)electrocatalysts for the oxygen evolution (water splitting) reaction. High quality electrochemical measurements were carried out and key electrocatalytic properties were identified for each of 5456 samples with a throughput of 4 s per sample.

Gregoire, John M.; Xiang, Chengxiang; Liu, Xiaonao; Marcin, Martin; Jin, Jian

2013-02-01

340

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

341

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

NASA Astrophysics Data System (ADS)

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

Rudnik, Ewa; W?och, Grzegorz

2013-01-01

342

A wound-type lithium/polyaniline secondary cell  

NASA Astrophysics Data System (ADS)

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

Li, Changzhi; Zhang, Borong; Wang, Baochen

1992-07-01

343

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

344

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

PubMed

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

Abdallah, Metwally; Moustafa, Moustafa E

2004-01-01

345

Electrodeposition of silicon from solutions of silicon halides in aprotic solvents  

SciTech Connect

Amorphous silicon has been electrodeposited from nonaqueous baths using SiHCl/sub 3/ as the silicon source. A typical bath composition was 1.0M SiHCl/sub 3/ in propylene carbonate containing 0.1m tetrabutyl ammonium chloride as the supporting electrolyte. Deposits were made potentiostatically at around -2.5v vs. Pt reference at temperatures 35/degree/ -145/degree/C under an argon atmosphere. A variety of materials including Pt, Ti, Ti-6Al-4V alloy, n-Si, and indium-tin oxide coated fused silica were used for the substrate. The as-deposited silicon contains some hydrogen bonded as SiH/sub 2/ or SiH. The quality and hydrogen content of the deposits are controllable by selecting the proper bath composition and operating temperature. This work is pertinent to solar cells. 9 refs.

Agrawal, A.K.; Austin, A.E.

1981-11-01

346

Effect of growth potential on the electrodeposition of CIS thin films  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

347

AFM and XRD investigation of the effect of dissolved oxygen in electrolytes on electrodeposition of CdTe on HgCdTe  

NASA Astrophysics Data System (ADS)

CdTe films have been deposited onto HgCdTe by potentiostatic electrodeposition at deposition potentials of -0.4 V and -0.5 V with respect to a saturated calomel reference electrode in ethylene glycol base electrolyte. Films deposited with and without nitrogen bubbling to reduce dissolved oxygen in electrolytes were investigated by atomic force microscopy (AFM) and x-ray diffraction (XRD). Significant reduction in roughness (>1 orders) was observed by bubbling the electrolyte with 6 N nitrogen gas and the resulting films were highly oriented. The reduction in roughness is believed to be the result of the suppression of the reduction reaction whereby the dissolved molecular oxygen is converted to hydrogen peroxide and water that disturbs the ordered CdTe electrodeposition onto HgCdTe wafers.

Choi, Jong-Hwa; Lee, Hee Chul

2002-03-01

348

In-situ spectroscopic investigation of infrared transmissive/absorptive electrochromic devices.  

NASA Astrophysics Data System (ADS)

Novel transmissive/absorptive electrochromic (EC) devices have been assembled using conjugated polymers on infrared-transparent electrodes made of single-wall carbon nanotubes (SWNTs). We will present results on the design, fabrication and characterization of sandwich type EC devices using dioxythiophene-based conjugated polymers (PXDOT). The polymers were prepared on the SWNT films using a potentiostatic electropolymerization method. The transmittance of the samples was measured over the infrared through visible energy range. To extract the optical constants of the polymer, we modeled all layers of this multilayer thin film structure using a Drude-Lorentz model. From the parameters obtained, we compute optical constants which yield information about the electronic structure of the neutral and doped states of the polymer. Evidence for polaron states at low doping and bipolaron states at maximum doping will be discussed.

Nikolou, Maria; Dyer, Aubrey L.

2005-03-01

349

Zur beeinflussung des korrosionsverhaltens von brennelement-hüllenmaterial aus ZrNb1 durch mechanische oberflächenbehandlung  

NASA Astrophysics Data System (ADS)

The reactivity of the outer surface of cladding material of the alloy Zr-1%Nb is significantly increased above the well-known state of chemically or electrochemically polished specimens by abrasive surface treatments. Out-of-reactor oxidation in water resulted in heterogenous oxide films on liquid honed and belt ground samples. An effect of intensity of mechanical treatment on the degree of the surface reactivity increase was found in voltammetric and potentiostatic investigations. The change of surface activity is due to different electronic conduction of the oxide film. The results are explained on the basis of Thiessen's triboplasma model. Increased reactivity is a consequence of tribochemical reactions including the interacting materials, molecules of Sorption layers, and the surrounding atmospherical milieu. The production and distribution of intermetallic reaction products are supposed to play an important role in this process. The forces of mechanical loading determine the induced excess energy, which controls both probability and selection of the tribochemical reactions.

Naumann, G.

1983-06-01

350

Bioelectrochemical reduction of CO(2) to CH(4) via direct and indirect extracellular electron transfer by a hydrogenophilic methanogenic culture.  

PubMed

This study describes the performance of a microbial biocathode, based on a hydrogenophilic methanogenic culture, capable of reducing carbon dioxide to methane, at high rates (up to 0.055 + or - 0.002 mmol d(-1) mgVSS(-1)) and electron capture efficiencies (over 80%). Methane was produced, at potentials more negative than -650 mV vs. SHE, both via abiotically produced hydrogen gas (i.e., via hydrogenophilic methanogenesis) and via direct extracellular electron transfer. The relative contribution of these two mechanisms was highly dependent on the set cathode potential. Both cyclic voltammetry tests and batch potentiostatic experiments indicated that the capacity for extracellular electron transfer was a constitutive trait of the hydrogenophilic methanogenic culture. In principle, both electrons and carbon dioxide required for methane production could be obtained from a bioanode carrying out the oxidation of waste organic substrates. PMID:20074943

Villano, Marianna; Aulenta, Federico; Ciucci, Costanza; Ferri, Tommaso; Giuliano, Antonio; Majone, Mauro

2010-05-01

351

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

352

On-site fuel electroanalysis: Determination of lead, copper and mercury in fuel bioethanol by anodic stripping voltammetry using screen-printed gold electrodes.  

PubMed

The potential application of commercial screen-printed gold electrodes (SPGEs) for the trace determination of lead, copper, and mercury in fuel bioethanol is demonstrated. Samples were simply diluted in 0.067molL(-1) HCl solution prior to square-wave anodic stripping voltammetry (SWASV) measurements recorded with a portable potentiostat. The proposed method presented a low detection limit (<2?gL(-1)) for a 240s deposition time, linear range between 5 and 300?gL(-1), and adequate recovery values (96-104%) for spiked samples. This analytical method shows great promise for on-site trace metal determination in fuel bioethanol once there is no requirement for sample treatment or electrode modification. PMID:25000856

Almeida, Eduardo S; Richter, Eduardo M; Munoz, Rodrigo A A

2014-07-21

353

Efficient production of ultrapure manganese oxides via electrodeposition.  

PubMed

A new process for the production of electrolytic amorphous nanomanganese oxides (EAMD) with uniform size and morphology is described. EAMD are produced for the first time by cathodic deposition from a basic aqueous solution of potassium permanganate at a constant temperature of 16°C. The synthesized materials are characterized by XRD, SEM, TEM, and HRTEM. The materials produced at 5.0 V at constant temperature are amorphous with homogeneous size and morphology with an average particle size around 20 nm, which appears to be much lesser than the previously reported anodic EAMD. A potentiostatic electrodeposition with much lesser deposition rate (with respect to previously reported anodic depositions) is considered to be the reason behind the very low and homogenous particle size distribution due to the lesser agglomeration of our as-synthesized nanoparticles. PMID:22595552

Cheney, Marcos A; Joo, Sang Woo; Banerjee, Arghya; Min, Bong-Ki

2012-08-01

354

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

PubMed

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

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

2009-03-01

355

Fabrication of all-solid-state electrochemical microcapacitors  

NASA Astrophysics Data System (ADS)

All-solid-state electrochemical microcapacitors are fabricated using photolithography, electrochemical polymerization and solution casting techniques. Gold microelectrode arrays are fabricated by ultraviolet photolithography and a wet-etching method. Conducting polymers such as polypyrrole (PPy) are potentiostatically synthesized on these microelectrodes. A microcapacitor is made up of 50 parallel-connected pairs of microelectrodes. The width of the microelectrodes and the distance between them are each 50 ?m. Two types of polymer electrolytes are applied, defined by the polymer matrix and ion-conducting media. Cell capacitance can be controlled by the total synthesis charge of the conducting polymers and a cell potential of 0.6 V is obtained. The electrochemical performance and charging-discharging mechanisms of all-solid-state microcapacitors are studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and constant-current discharge and the results are compared with those of microcapacitors with liquid electrolyte.

Sung, Joo-Hwan; Kim, Se-Joon; Lee, Kun-Hong

356

Fabrication of microcapacitors using conducting polymer microelectrodes  

NASA Astrophysics Data System (ADS)

Conducting polymer microcapacitors are fabricated by means of photolithography and electrochemical polymerization techniques. Gold or platinum microelectrode arrays are prepared by UV photolithography and a wet etching method. Conducting polymers such as polypyrrole (PPy) and poly-(3-phenylthiophene) (PPT) are synthesized potentiostatically on these microelectrodes. A microcapacitor is made up of 50 parallel-connected pairs of microelectrodes. The width of the microelectrodes and the distance between them are both 50 ?m. Three types of cell are constructed in aqueous and non-aqueous electrolytes, and cell potentials between 0.6 and 1.4 V can be obtained depending upon the type of conducting polymers and electrolytes. Cell capacitance can be controlled easily by the total synthesis charge of the conducting polymers.

Sung, Joo-Hwan; Kim, Se-Joon; Lee, Kun-Hong

357

Synthesis of gold nanowires with controlled crystallographic characteristics  

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

358

High-density nickel nanowire arrays for data storage applications  

NASA Astrophysics Data System (ADS)

This paper is dedicated to a study of magnetic properties (magnetic anisotropy, coercive force and remanent magnetization) of spatially ordered high-density Ni nanowire arrays. The magnetic nanowires were prepared by electrodeposition of nickel from simple sulfate solutions into anodic aluminum oxide (AAO) nanoporous templates (with diameter of d = 20 and 40 nm) fabricated by potentiostatic anodization. We show that Ni nanowires have strong out-of-plane axial magnetic anisotropy (normal to the substrate plane) along with an in-plane anisotropy caused by hexagonal spatial distribution of nanowires in an array. An existence of the six-fold in-plane anisotropy proofs the long-range hexagonal order of nanowires. High quality of nanowire arrays makes possible of its usage as high-density (up to 2Tb/in2) magnetic recording media.

Samardak, A. S.; Sukovatitsina, E. V.; Ognev, A. V.; Chebotkevich, L. A.; Mahmoodi, R.; Peighambari, S. M.; Hosseini, M. G.; Nasirpouri, F.

2012-02-01

359

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

NASA Astrophysics Data System (ADS)

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

Donovan, Conrad Koble

360

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 H 3PO 4 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

361

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

2011-01-01

362

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

NASA Astrophysics Data System (ADS)

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

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

363

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

NASA Astrophysics Data System (ADS)

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

Yilmaz, Ahmet

364

Study of corrosion pits in chloride solution  

NASA Astrophysics Data System (ADS)

A laser technique was used to initiate single corrosion pits as well as geometrically ordered arrays of pit on nickel (99.99%) immersed in 0.5 M NaCl solutions under potentiostatic condition. The current was measured during pit growth and the shape of each pit was recorded upon termination of each experiment. It was found that single pits had smooth surfaces and they were slightly shallower than hemispheres and for applied potentials between 0.5 and 0.6 V SCE, and for growth time greater than 20 s. Experimental measurements of pit radius and current density as a function of time at t ? 100 s agreed with calculations based on the hypothesis that the pit growth rate was limited by the diffusion controlled dissolution rate of a salt film. A transport model, which included both migration and diffusion, was used to interpret experimental results. The model predicted that the local environment inside the pit cavity was aggressive enough that a salt film might precipitate at the early stage of pit growth. Current interruption experiments demonstrated that pit stability was determined by the extent of relaxation of the pit environment. A critical concentration adjacent to the pit surface is required for the pit to maintain active. It was found to be independent of the pit size, but dependent on the applied potential. The critical applied potential above which pits continued to grow decreased with pit size. It was observed that the growth rate of pits at an applied potential of 0.5 V SCE decreased in the presence of flow, and pits repassivated at Pe number greater than 1000. A two-dimensional trench model predicted rinsing of cavity at Pe > 1000, which was in qualitative agreement with the experimental observations. Controlled multiple pits experiments demonstrated that pits do interact with each other within a critical distance. It was found that the neighboring pits enhanced the growth of the central pit in the lateral direction and the total current also increased under potentiostatic condition. The critical distance was affected by the bulk concentration of chloride.

Zhu, Lei

365

Triboelectrochemical characterization of microelectronic materials  

NASA Astrophysics Data System (ADS)

Non-uniformity in chemical-mechanical planarization (CMP) due to diverse pattern geometry in copper damascene structures has been a critical limit to process yield. Fundamental understanding in tribology and electrochemistry is crucial to solve this problem. This research develops novel triboelectrochemical techniques to characterize the polished wafer surface and to understand mechanisms of materials removal. There are two approaches in this research. Experimentally, a setup containing a tribometer and a potentiostat was built. It enabled simultaneous measurement in friction coefficient and electrochemical response of wafer materials. Theoretically, electrochemical reactions and Hertzian contact were analyzed on ECMPed wafers in terms of mechanisms of step height reduction in anodic and cathodic ECMP in corresponds to surface chemistry. Results revealed the nature of limitation of ECMP for global planarization. In order to further the fundamental investigation of ECMP, the potentiostatic electrochemical impedance spectroscopy (EIS) was utilized to study the interface kinetics. It was revealed that the formation of Cu oxide films was affected by the electrical potentials. Through in situ measurement, it was found that the tribological behavior depend on the surface chemistry and surface morphology under the influence of anodic potentials. The potentiodynamic polarization results explained the removal and formation mechanisms of interface. The results showed that the cycle of passivation/removal was a function of mechanical factor such as the load and speed. The new model was developed via material removal rate (MRR) in both electrochemical and mechanical aspects. The quantitative contribution of iii electrochemical potential to overall removal was established for the first time. It was further confirmed by Ru and the electrochemical constant j was developed for metal ECMP. This dissertation includes seven chapters. Chapter I Introduction and II Motivation and Objectives are followed by the materials setup and testing conditions discussed in Chapter III. The tribological and electrochemical characterization of the Cu patterned geometry is discussed in Chapter IV. Chapter V discusses the kinetics of the interface during polishing and its removal mechanisms. Chapter VI discusses the synergism of ECMP, followed by Conclusions and Future work.

Joo, Suk Bae

366

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

NASA Astrophysics Data System (ADS)

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

Chen, Guocun

367

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

PubMed

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

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

2014-03-01

368

Interface effect on the electropolymerized polypyrrole films with hollow micro/nanohorn arrays.  

PubMed

Polypyrrole (PPy) films with hollow micro/nanohorn arrays were controllably synthesized in p-toluenesulfonate aqueous solutions by template-free electrochemical methods. The micelles which consist of pyrrole monomers and the surfactants provided the soft templates during the polymerization process. The polymerization potential and pH value of the solutions cooperatively influenced the shape of the micelles at the substrate/electrolyte interface and further controlled the morphologies of PPy films. PPy grew along the soft templates during the high potential periods of a pulse potentiostatic (PPS) method, while the pH value and the low potential were varied to modulate the shape of the soft templates. It has been shown to be most appropriate to fabricate hollow micro/nanohorn PPy films with the highest electrical conductivity (190 S cm(-1)) via PPS at pH ?1.5. A diagram was also introduced in order to illustrate the polymerization potential and pH value dependence of nanohorn PPy morphologies. This work proposed a potential method to the in situ growth of conducting polymers with high conductivity and high specific surface area. PMID:24611811

Bai, Yang; Xu, Youlong; Wang, Jie; Gao, Mingqi; Wang, Jingping

2014-04-01

369

The open-circuit ennoblement of alloy C-22 and other Ni-Cr-Mo alloys  

NASA Astrophysics Data System (ADS)

The open-circuit corrosion and anodic oxidation behavior of the C-series of Ni-Cr-Mo alloys (C-4, C-276, C-2000, and C-22) and alloy 625 have been studied at 25°C and 75°C in 1.0 mol·L-1 NaCl+1.0 mol·L-1 H2SO4. A combination of open-circuit potential, potentiostatic polarization, and electrochemical impedance spectroscopy were employed in the study. The composition of the films formed was determined by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Passive oxide film resistances increase and defect oxide film concentrations decrease as films thicken and chromium and molybdenum segregate to the alloy/oxide and oxide/solution interfaces, respectively. The high-chromium alloys exhibit higher film resistances and lower film defect concentrations consistent with the more positive potentials observed on these alloys. The results show that the observed ennoblement in corrosion potentials with time is coupled to the Cr/Mo segregation process and the suppression of defect injection at the alloy/oxide interface. By all measures, C-22 exhibited the best passive properties.

Lloydis, A. C.; Noël, J. J.; Shoesmith, D. W.; McIntyre, N. S.

2005-01-01

370

Electrochemistry combined on-line with electrospray mass spectrometry  

SciTech Connect

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

Zhou, F.; Berkel, G.J.V. [Oak Ridge National Lab., TN (United States)

1995-10-15

371

Amperometric bienzyme screen-printed biosensor for the determination of leucine.  

PubMed

Leucine plays an important role in protein synthesis, brain functions, building muscle mass, and helping the body when it undergoes stress. Here, we report a new amperometric bienzyme screen-printed biosensor for the determination of leucine, by coimmobilizing p-hydroxybenzoate hydroxylase (HBH) and leucine dehydrogenase (LDH) on a screen-printed electrode with NADP(+) and p-hydroxybenzoate as the cofactors. The detection principle of the sensor is that LDH catalyzes the specific dehydrogenation of leucine by using NADP(+) as a cofactor. The product, NADPH, triggers the hydroxylation of p-hydroxybenzoate by HBH in the presence of oxygen to produce 3,4-dihydroxybenzoate, which results in a change in electron concentration at the working carbon electrode, which is detected by the potentiostat. The sensor shows a linear detection range between 10 and 600 ?M with a detection limit of 2 ?M. The response is reproducible and has a fast measuring time of 5-10 s after the addition of a given concentration of leucine. PMID:24220759

Labroo, Pratima; Cui, Yue

2014-01-01

372

Hydrogen ingress into copper-nickel alloys  

SciTech Connect

Hydrogen (H) ingress into two copper (Cu)-nickel (Ni) alloys -- a commercial 77% Cu-15% Ni alloy (aged) and alloy K-500 (UNS N05500, aged and unaged) --- was studied using a technique referred to as hydrogen ingress analysis by potentiostatic pulsing (HIAPP). Anodic current transients obtained for these alloys in an acetate buffer (1 mol/L acetic acid + 1 mol/L sodium acetate [NaAc]) were analyzed using a diffusion-trapping model to determine trapping constants and H entry fluxes. A small increase was observed in the irreversible trapping constant for alloy K-500 with aging. Trapping constants of the aged alloys were similar within the limits of uncertainty, but H entry flux for the 77% Cu alloy was lower than that for aged or unaged alloy K-500. The lower flux may have accounted at least partly, for the Cu alloy's higher resistance to H embrittlement. Trap densities were consistent qualitatively with levels of sulfur (S) and phosphorus (P) in the two alloys. This finding supported an assumption that S and P provided the primary irreversible traps.

Pound, B.G. (SRI International, Menlo Park, CA (United States). Materials Research Center)

1994-04-01

373

Synthesis and enhanced electrochemical performance of Li2CoPO4F cathodes under high current cycling.  

PubMed

Lithium cobalt fluorophosphate, Li(2)CoPO(4)F, is successfully synthesized by a solid state reaction under Ar flow at 700 °C. X-ray diffraction and scanning electron microscopic studies are utilized to analyze the structural and morphological features of the synthesized materials, respectively. The presence of fluorine is also supported by energy-dispersive X-ray spectroscopy. The electrochemical properties are evaluated by means of Li/Li(2)CoPO(4)F half-cell configurations in both potentiostatic and galvanostatic modes. The Li/Li(2)CoPO(4)F cell delivers an initial discharge capacity of 132 mA h g(-1) at a current density of 0.1 mA cm(-2) between 2.0 and 5.1 V at room temperature. Due to the higher operating potential of the Co(2+/3+) couple in the fluorophosphate matrix, this cell shows a capacity retention of only 53% after 20 cycles, still the material delivered 108 mA h g(-1) at a high current rate of 1 C. Cyclic voltammetric studies corroborate the insertion and extraction of Li(+) ions by a single phase reaction mechanism during cycling. PMID:22832971

Amaresh, S; Kim, G J; Karthikeyan, K; Aravindan, V; Chung, K Y; Cho, B W; Lee, Y S

2012-09-14

374

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

375

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

376

Submicron patterned metal hole etching  

DOEpatents

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

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

2000-01-01

377

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

PubMed

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

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

2014-09-01

378

Voltammetric studies on the electrochemical determination of methylmercury in chloride medium at carbon microelectrodes.  

PubMed

Electroanalytical techniques have been used to determine methylmercury at low levels in environmental matrices. The electrochemical behaviour of methylmercury at carbon microelectrodes in a hydrochloric acid medium using cyclic, square wave and fast-scan linear-sweep voltammetric techniques has been investigated. The analytical utility of the methylmercury reoxidation peak has been explored, but the recorded peak currents were found to be poorly reproducible. This is ascribed to two factors: the adsorption of insoluble chloromercury compounds on the electrode surface, which appears to be an important contribution to hinder the voltammetric signal of methylmercury; and the competition between the reoxidation of the methylmercury radical and its dimerization reaction, which limits the reproducibility of the methylmercury peak. These problems were successfully overcome by adopting the appropriate experimental conditions. Fast-scan rates were employed and an efficient electrochemical regeneration procedure of the electrode surface was achieved, under potentiostatic conditions in a mercury-free solution containing potassium thiocyanate--a strong complexing agent. The influence of chloride ion concentration was analysed. Interference by metals, such as lead and cadmium, was considered. Calibration plots were obtained in the micromolar and submicromolar concentration ranges, allowing the electrochemical determination of methylmercury in trace amounts. An estuarine water sample was analysed using the new method with a glassy carbon microelectrode. PMID:17723747

Ribeiro, F; Neto, M M M; Rocha, M M; Fonseca, I T E

2006-10-10

379

Electrochromic properties of electrodeposited tungsten oxide (WO3) thin film  

NASA Astrophysics Data System (ADS)

In this work, we report on a potentiostatic electrochemical procedure employing an ethanolic solution of peroxotungstic acid yielded tungsten oxide (WO3) films specifically for transmissive electrochromic devices (ECDs) such as ``smart windows''. WO3 film was confirmed from the binding energy determination by X-ray photoelectron spectroscopic studies. The diffusion coefficient during intercalation and deintercalation was found to be 2.59×10-10 and 2.40×10-10 cm2/C. Electrodeposited WO3 produce high color/bleach transmittance difference up to 74% at 630 nm. On reduction of WO3, the CIELAB 1931 2% color space coordinates show the transition from colorless to the deep blue state (L=95.18, a=2.12, b=0.3138, and L=57.78, a=-21.79, b=0.244) with steady decrease in relative luminance. The highest coloration efficiency (CE) of 92 cm2/C and good response time of 10.28 for coloration (reduction) and 3.2 s for bleaching (oxidation) was observed with an excellent reversibility of 89%.

Dalavi, D. S.; Kalagi, S. S.; Mali, S. S.; More, A. J.; Patil, R. S.; Patil, P. S.

2012-06-01

380

Enhancing the electrochemical oxidation of acid-yellow 36 azo dye using boron-doped diamond electrodes by addition of ferrous ion.  

PubMed

This work shows preliminary results on the electrochemical oxidation process (EOP) using boron-doped diamond (BDD) electrode for acidic yellow 36 oxidation, a common azo dye used in textile industry. The study is centred in the synergetic effect of ferrous ions and hydroxyl free radicals for improving discoloration of azo dye. The assays were carried out in a typical glass cell under potentiostatic conditions. On experimental conditions, the EOP was able to partially remove the dye from the reaction mixture. The reaction rate increased significantly by addition of Fe(2+) (1mM as ferrous sulphate) to the system and by (assumed) generation of ferrate ion [Fe(VI)] over BDD electrode. Ferrate is considered as a highly oxidizing reagent capable of removing the colorant from the reaction mixture, in synergistic action with the hydroxyl radicals produced on the BDD surface. Further increases in the Fe(2+) concentration lead to depletion of the reaction rate probably due to the hydroxyl radical scavenging effect of Fe(2+) excess in the system. PMID:19195775

Villanueva-Rodríguez, M; Hernández-Ramírez, A; Peralta-Hernández, J M; Bandala, Erick R; Quiroz-Alfaro, Marco A

2009-08-15

381

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, François; Pla-Roca, Mateu; Mills, Christopher A.; Teixidor, Francesc; Samitier, Josep

2007-12-01

382

Inhibition of copper corrosion with Schiff base derived from 3-methoxysalicylaldehyde and O-phenyldiamine in chloride media  

SciTech Connect

The inhibiting effect of Schiff base N,N{prime}-o-phenylen-bis(3-methoxysalicylaldenimine), designated as V-ph-V, on corrosion of copper in 1.0 M hydrochloric acid (HCl) or 1.0 M sodium chloride (NaCl) solutions under various conditions was studied using the potentiostatic polarization method and for alternating current (AC) impedance technique. Results showed a remarkable decrease in the corrosion rate in the presence of V-ph-V (concentration = 10{sup 4} M) in 1.0 M NaCl solution at 40 C. To study the nature of the solid products formed under free corrosion conditions or with the additive V-ph-V, the surface morphology at the end of the immersion tests was examined using scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) also was used to identify the spectra of the adsorbed complex. The surface film was identified as a polymeric Cu(II)-(V-ph-V)-H{sub 2}O. Cu(II)-(V-ph-V)-H{sub 2}O complex totally covered the copper surface, exhibiting strong corrosion inhibition. Formation of Cu(II)-(V-ph-V)-H{sub 2}O was accomplished after adsorption of V-ph-V on the copper surface. The complex also was synthesized from V-ph-V with Cu(II), and its single crystal structure was determined using a diffractometer.

Li, S.L.; Ma, H.Y.; Lei, S.B.; Yu, R.; Chen, S.H.; Liu, D.X. [Shandong Univ., Jinan (China). Dept. of Chemistry

1998-12-01

383

Iron oxide nanotube layer fabricated with electrostatic anodization for heterogeneous Fenton like reaction.  

PubMed

Iron oxide nanotubes (INT) were fabricated with potentiostatic anodization of zero valent iron foil in 1M Na2SO4 containing 0.5wt% NH4F electrolyte, holding the potential at 20, 40, and 60V for 20min, respectively. Field emission scanning electron microscopy and X-ray diffractometry were used to evaluate the morphology and crystalline structure of the INT film. The potential of 40V for 20min was observed to be optimal to produce an optimal catalytic film. Cyanide dissolved in water was degraded through the Fenton-like reaction using the INT film with hydrogen peroxide (H2O2). In case of INT-40V in the presence of H2O2 3%, the first-order rate constant was found to be 1.7×10(-2)min(-1), and 1.2×10(-2)min(-1) with commercial hematite powder. Degradation of cyanide was much less with only H2O2. Therefore, this process proposed in this work can be an excellent alternative to traditional catalysts for Fenton-like reaction. PMID:24704548

Jang, Jun-Won; Park, Jae-Woo

2014-05-30

384

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

385

Recreation of Marine Atmospheric Corrosion Condition on Weathering Steel in Laboratory  

NASA Astrophysics Data System (ADS)

Salt spray test, autoclave corrosion test, SO2 salt spray test, and Relative humidity test are generally used to assess atmospheric corrosion in laboratories at accelerated rates. However, no test can absolutely simulate the service condition. One can get only approximate corrosion rates using the aforesaid tests which serve as an indicative of corrosion behavior of the material in a service condition. The present work is aimed at creating specific environmental condition in laboratory to get the corrosion test done in short duration to compare with on field exposure test which would otherwise take years to complete. In this work recreation of atmospheric environment of Digha was tried and it was simulated in such a manner that the results of laboratory test could be compared with long time field exposure at Digha. Weathering steel (WS) was taken for experimentations. Potentiostatic electrochemical tests route was adopted to simulate atmospheric condition of Digha. Laboratory test results compared well with 18 month field exposure data in terms of corrosion rate, SEM and Ramon Spectroscopy matching.

Guchhait, S. K.; Dewan, S.; Saha, J. K.; Mitra, P. K.

2014-04-01

386

Development of a commercial micro corrosion monitoring system  

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

387

Electrodeposition and characterization of HgSe thin films  

SciTech Connect

In this article we present the results on the electrochemical synthesis of mercury selenide (HgSe), an interesting II-VI material. HgSe thin films were deposited potentiostatically on conducting glass substrates from an aqueous bath containing HgCl{sub 2} and SeO{sub 2}. The prepared films were characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), scanning electron microscope (SEM) and optical absorption techniques. Stoichiometric polycrystalline HgSe films were obtained at a deposition potential around - 0.7 V vs SCE, at a temperature 60 deg. C and a pH value of 3.5. The as-grown films exhibited a direct optical band gap of 0.78 eV. This report deals with the growth mechanism and a study related to the influence of electrolyte bath composition, deposition potential, temperature and pH on the properties of HgSe thin films.

Mahalingam, T. [Department of Physics, Alagappa University, Karaikudi - 630 003 (India) and Department of Electrical and Computer Engineering, College of Information Technology, Ajou University, Suwon 443-749 (Korea, Republic of)]. E-mail: maha51@rediffmail.com; Kathalingam, A. [Department of Physics, Alagappa University, Karaikudi - 630 003 (India); Sanjeeviraja, C. [Department of Physics, Alagappa University, Karaikudi - 630 003 (India); Chandramohan, R. [Physics Department, National Chang-Hua University of Education, Chang-Hua 50058, Taiwan (China); Chu, J.P. [Institute of Materials Engineering, National Taiwan Ocean University, Keelung 202, Taiwan (China); Kim, Yong Deak [Department of Electrical and Computer Engineering, College of Information Technology, Ajou University, Suwon 443-749 (Korea, Republic of); Velumani, S. [Departamento de Fisica, ITESM - Campus Monterrey, Nuevo Leon, C.P.64849 (Mexico)

2007-08-15

388

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

389

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

SciTech Connect

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

Orzalli, J.C.

1994-05-01

390

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

391

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

392

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

393

Removal of tarnishing and roughness of copper surface by electropolishing treatment  

NASA Astrophysics Data System (ADS)

Tarnishing and roughness of copper surface can be removed by electropolishing treatment (EP) imparting a bright and smooth surface at suitable conditions, e.g. current density, time, temperature, and viscosity. It was carried out by using an electrolytic cell containing phosphoric acid 55% as the electrolytic solution. Both copper working electrode and lead counter electrode, and reference electrode (SCE) were connected to a Potentiostat/Galvanostat to allow an electric current to pass through the solution. Some additives such as soluble starch, ethylene glycol, and methanol were added to reduce defects formed on the copper surface during EP process. The results showed that the highest gloss value was obtained by applying electric potential 1.5 V at the passive region of polarization curve. The surface was investigated after EP treatment, where SEM and EDX showed lower roughness in case of addition of both soluble starch and ethylene glycol more than methanol. Moreover, AFM analysis showed the lowest roughness in case of soluble starch more than other additives.

Awad, A. M.; Ghany, N. A. Abdel; Dahy, T. M.

2010-04-01

394

Effects of cooling time and alloying elements on the microstructure of the gleeble-simulated heat-affected zone of 22% Cr duplex stainless steels  

NASA Astrophysics Data System (ADS)

The effects of austenite stabilizers, such as nitrogen, nickel, and manganese, and cooling time on the microstructure of the Gleeble simulated heat-affected zone (HAZ) of 22% Cr duplex stainless steels were investigated. The submerged are welding was performed for comparison purposes. Optical microscopy (OM) and transmission electron microscopy (TEM) were used for microscopic studies. The amount of Cr2N precipitates in the simulated HAZ was determined using the potentiostatic electrolysis method. The experimental results indicate that an increase in the nitrogen and nickel contents raised the ? to transformation temperature and also markedly increased the amount of austenite in the HAZ. The lengthened cooling time promotes the reformation of austenite. An increase in the austenite content reduces the supersaturation of nitrogen in ferrite matrix as well as the precipitation tendency of Cr2N. The optimum cooling time from 800 to 500 °C (? t 8/5) obtained from the Gleeble simulation is between 30 and 60 s, which ensures the austenite content in HAZ not falling below 25% and superior pitting and stress corrosion cracking resistance for the steels. The effect of manganese on the formation of austenite can be negligible.

Hsieh, Rong-Iuan; Liou, Horng-Yih; Pan, Yeong-Tsuen

2001-10-01

395

A metal-decorated nickel foam-inducing regulatable manganese dioxide nanosheet array architecture for high-performance supercapacitor applications.  

PubMed

Three dimensional manganese dioxide/Pt/nickel foam (shortened to MnPtNF) hybrid electrodes were prepared by double-pulse polarization and potentiostatic deposition technologies for supercapacitor applications. The decoration of Pt nanoparticles onto nickel foam varies the nucleation mechanism of the manganese dioxide species, inducing the formation of manganese dioxide nanosheets. Additionally, controlling the size of the Pt nanoparticles leads to modulated nanosheet architecture and electrochemical properties of the manganese dioxide electrode, as revealed by XRD, Raman spectra, SEM, TEM, cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The nanosheet architecture of the MnPtNF electrode favors the transportation of electrons and ions, which results in the enhanced electrochemical properties. Importantly, the optimized MnPtNF electrode obtains a maximum specific capacitance of 1222 F g(-1) at 5 A g(-1) (89% of the theoretical specific capacitance of MnO2) and 600 F g(-1) at 100 A g(-1). Moreover, the presence of Pt nanoparticles in the MnO2 electrode effectively improves its cycling stability, which is confirmed by the increase of the specific capacitance retention from 14.7% to 90% after 600 cycles. PMID:23887746

Tang, Peng-Yi; Zhao, Yong-Qing; Wang, Yin-Mei; Xu, Cai-Ling

2013-09-01

396

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)²?, 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)²?/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)²?/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, René H; García-Meza, J Viridiana; Cruz, Roel; Valdez-Pérez, Donato; González, Ignacio

2012-08-01

397

Electrically evoking and electrochemically resolving quantal release on a microchip.  

PubMed

A microchip was applied to electrically depolarize rat pheochromocytoma (PC12) cells and to simultaneously detect exocytotic catecholamine release amperometrically. Results demonstrate exocytosis elicited by flowing cells through an electric field generated by a potentiostat circuit in a microchannel, as well as exocytosis triggered by application of an extracellular voltage pulse across. Electrical finite element model (FEM) analysis illustrated that larger cells experienced greater depolarizing excitation from the extracellular electric fields due to the smaller shunt path and higher resistance to current flow in the channel around the cell. Consistent with these simulations, data recorded from cell clusters and large cells exhibited increased release rates relative to data from the smaller cells. Overall, the system was capable of resolving single vesicle quantal release, in the zeptomole range, as well as the kinetics associated with the vesicle fusion process. Analysis of spike population statistics suggested detection of catecholamines from multiple release sites around the cells. The potential for such a device to be used in flow cytometry to evoke and detect exocytosis was demonstrated. PMID:20024047

Dittami, Gregory M; Rabbitt, Richard D

2010-01-01

398

A low power sensor signal processing circuit for implantable biosensor applications  

NASA Astrophysics Data System (ADS)

A low power sensor read-out circuit has been implemented in 0.35 µm CMOS technology that consumes only 400 µW of power and occupies an area of 0.66 mm2. The circuit is capable of converting the current signal from any generic biosensor into an amplitude shift keying (ASK) signal. The on-chip potentiostat biases the chemical sensor electrodes to create the sensor current which is then integrated and buffered to generate a square wave with a frequency proportional to the sensor current level. A programmable frequency divider is incorporated to fix the ASK envelope frequency to be inbetween 20 Hz and 20 kHz, which is within the audible range of human hearing. The entire transmitter block operates with a supply voltage as low as 1.5 V, and it can be easily powered up by an external RF source. Test results emulate the simulation results with good agreement and corroborate the efficacy of the designed system.

Zhang, Mo; Haider, Mohammad R.; Huque, Mohammad A.; Adeeb, Mohammad A.; Rahman, Shaela; Islam, Syed K.

2007-04-01

399

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

2012-03-15

400

Transport, phase reactions, and hysteresis of iron fluoride and oxyfluoride conversion electrode materials for lithium batteries.  

PubMed

Potentiostatic intermittent titration technique (PITT) was applied to FeF2, FeF3, and FeO0.67F1.33 to gain insight into the transport-related aspects of the conversion reaction by quantitative analysis of Li(+) diffusion and hysteresis. PITT derived diffusion coefficient measurements were benchmarked relative to values extracted by electrochemical impedance spectroscopy (EIS). A reverse-step PITT methodology was used to evaluate true hysteresis by eliminating nucleation induced overpotentials. This method evaluates the minimum potential hysteresis and allowed an accurate representation of the potential required to move conversion reactions forward at C/1000 rates in both lithiation and delithiation. The high resolution PITT data were also used to gain further insight into reaction mechanisms involved in the reversible conversion reactions. Physical evidence, based on pair distribution function (PDF) structural analysis, and electrochemical evidence are presented regarding a new step in the reaction during the rutile FeF2 reconversion reaction. PMID:24708435

Ko, Jonathan K; Wiaderek, Kamila M; Pereira, Nathalie; Kinnibrugh, Tiffany L; Kim, Joshua R; Chupas, Peter J; Chapman, Karena W; Amatucci, Glenn G

2014-07-23

401

Electrochemical regeneration of activated carbon cloth exhausted with bentazone.  

PubMed

The electrochemical regeneration of an activated carbon cloth exhausted with a common herbicide (bentazone) was investigated under different operating conditions. The reversibility of the desorption process was confirmed by monitoring the UV spectra of the solution while cathodic polarization is being applied. Neither nanotextural nor chemical changes are produced in the carbon cloth upon polarization in the absence of the adsorbate. Upon cathodic polarization of a carbon cloth working electrode preloaded with bentazone, negative charges appear on the surface. A partial bentazone desorption results from repulsive electrostatic interactions between the negative charges on the carbon cloth and bentazone. When the electrode potential is below the thermodynamic value for cathodic decomposition of water, hydroxyl ions are liberated. Such ions provoke local pH changes that are responsible of the dissociation of bentazone and carbon surface groups to their anionic form. As a consequence of the pH increase, an almost reversible desorption of bentazone is observed. The effects of several operating parameters on the regeneration efficiency were evaluated. Higher regeneration efficiencies were attained under potentiostatic as compared to galvanostatic conditions, as OH- production strongly depends on the applied potential. PMID:18605577

Ania, Conchi O; Béguin, François

2008-06-15

402

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.

403

Pulsed galvanostatic control of solid-state polymeric ion-selective electrodes.  

PubMed

We report on galvanostatically controlled solid-state reversible ion-selective sensors for cationic analytes utilizing a conducting polymer as a transduction layer between the polymeric membrane and electron-conductive substrate. The instrumental control of polymeric membrane ion-selective electrodes based on electrochemically induced periodic ion extraction in alternating galvanostatic/potentiostatic mode was introduced recently creating exciting possibilities to detect clinically relevant polyions such as heparin and protamine and drastically improve the sensitivity of ion-selective sensors limited by the Nernst equation. The present study forms the basis for development of reliable, robust, and possibly maintenance-free sensors that can be fabricated using screen-printing technology. Various aspects of the development of solid-contact galvanostatically controlled ion-selective electrodes with a conducting polymer as a transduction layer are considered in the present work on the example of a model system based on a sodium-selective membrane. The protamine-selective solid-contact sensor was fabricated and characterized, which represents the next step toward commercially viable polyion sensing technology. A substantial improvement of a low detection limit (0.03 mg L-1) was achieved. A simplified diffusion-based theoretical model is discussed predicting the polarization at the interface of the conducting polymer and the membrane, which can cause the disruption of the sensor response function at relatively small current densities. PMID:17488093

Perera, Hasini; Fordyce, Katherine; Shvarev, Alexey

2007-06-15

404

A 1000-cell SOFC reactor for domestic cogeneration  

NASA Astrophysics Data System (ADS)

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

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

405

Development of amperometric biosensors based on nanostructured tyrosinase-conducting polymer composite electrodes.  

PubMed

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

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

2013-01-01

406

Theoretical approach to ion penetration into pores with pore fractal characteristics during double-layer charging/discharging on a porous carbon electrode.  

PubMed

The effects of pore fractal characteristics on the kinetics of double-layer charging/discharging on a porous carbon electrode were investigated by using theoretical calculations of potentiostatic current transients (PCTs) and cyclic voltammograms (CVs). Prior to theoretical calculation, it was experimentally evidenced that pore fractality is clearly possessed by the porous carbon electrode. From the analyses of the PCTs and the CVs theoretically calculated at various values of pore fractal dimension dF,pore, inner cutoff length rmin, and outer cutoff length rmax of the pore fractality, it was found that as dF,pore increased, the absolute values of the derivatives of the logarithmic PCTs decreased to 0.5, and the current decayed more slowly with time. The rate capability gamma decreases with increasing dF,pore over the whole scan-rate range, which leads to the lower power density. As rmin increased, the current decayed more rapidly in the later stage of the PCT, which is mainly limited by the smaller pores. On the other hand, as rmax increased, the current decayed more rapidly in the earlier stage of the PCT, which is mainly determined by the larger pores. Moreover, the larger values of rmin and rmax enhance the rate capability gamma as well, but they reduce the double-layer capacitance. The beneficial contribution of the larger pores to the power density competes with the detrimental contribution of those pores to the energy density. PMID:17129044

Lee, Gyoung-Ja; Pyun, Su-Il

2006-12-01

407

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

408

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

2013-12-01

409

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

NASA Astrophysics Data System (ADS)

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

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

1986-10-01

410

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 Muñoz, A.; Amigó Borrás, V.

2013-10-01

411

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 2 week period and magnesium ion levels over a 1 week 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

2013-11-01

412

Electrochemical generation of oxygen. 1: The effects of anions and cations on hydrogen chemisorption and anodic oxide film formation on platinum electrode. 2: The effects of anions and cations on oxygen generation on platinum electrode  

NASA Technical Reports Server (NTRS)

The effects were studied of anions and cations on hydrogen chemisorption and anodic oxide film formation on Pt by linear sweep voltammetry, and on oxygen generation on Pt by potentiostatic overpotential measurement. The hydrogen chemisorption and anodic oxide film formation regions are greatly influenced by anion adsorption. In acids, the strongly bound hydrogen occurs at more cathodic potential when chloride and sulfate are present. Sulfate affects the initial phase of oxide film formation by produced fine structure while chloride retards the oxide-film formation. In alkaline solutions, both strongly and weakly bound hydrogen are influenced by iodide, cyanide, and barium and calcium cations. These ions also influence the oxide film formation. Factors considered to explain these effects are discussed. The Tafel slope for oxygen generation was found to be independent on the oxide thickness and the presence of cations or anions. The catalytic activity indicated by the exchange current density was observed decreasing with increasing oxide layer thickness, only a minor dependence on the addition of certain cations and anions was found.

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

1975-01-01

413

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

SciTech Connect

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

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

1996-10-01

414

Nickel-based 3D electrocatalyst layers for production of hydrogen by water electrolysis in an acidic medium.  

PubMed

Electrocatalytic activity of three-dimensional nickel-based layers in the hydrogen evolution reaction (HER) was investigated in an acidic medium. It was demonstrated that patterning of a glassy carbon electrode substrate with a 3D polyaniline (PANI) matrix is a convenient way of increasing the electrocatalytically active surface area of electrodeposited Ni, and hence its apparent electrocatalytic activity. The optimized PANI/Ni electrocatalyst layer showed a significantly higher activity in the HER then a two-dimensional control Ni-plate surface. It was also demonstrated that it is possible to produce a Ni-based HER electrocatalyst layer by synthesizing Ni nanoparticles and supporting them on Vulcan carbon. This electrocatalyst also offered a significantly higher electrocatalytic activity in the HER then the control surface, but lower then the optimized PANI/Ni electrocatalyst. The electrocatalytic activity of the optimized PANI/Ni layer was also compared to the activity of a 3D catalyst produced by coating a porous RVC cube substrate with Ni. This electrocatalyst showed the highest HER electrocatalytic activity among the investigated layers when tested under potentiodynamic polarization conditions. However, under the potentiostatic conditions, the optimized PANI/Ni layer showed the highest electrocatalytic activity. PMID:19437992

Bou-Saleh, Ziad; Omanovic, Sasha

2009-04-01

415

Electrochemical monitoring of the metabolic activity of mycobacteria in culture.  

PubMed

Mycobacterial metabolic activity is typically measured using time-consuming manual methods based on nutrient consumption, nucleic acid synthesis or reduction of tetrazolium salts. In this study, we propose much simpler electrochemical methods for continuous monitoring of the metabolic activity of mycobacteria in culture. Chronoamperometry and chronopotentiometry were used to detect metabolic activity of both slow-growing and fast-growing mycobacteria using a potentiostat with 2D-electrochemical cell. Electrochemical measurements were able to detect statistically significant differences in the metabolic activity of approximately 10(7) mycobacteria in different growth conditions, within less than 24 h of mycobacterial culture. The metabolic activity of mycobacteria measured by the used electrochemical methods correlated well with changes in general respiratory conditions within the cells as it was evaluated by different biochemical tests. Chronoamperometry and chronopotentiometry allowed measurement of mycobacterial metabolic activity without invasive chemical reactions, at minimal bacterial load and when metabolic response of mycobacteria occurs quickly. The proposed methodology is simple, rapid and cost-effective, and it is expected that both in vitro and in vivo metabolic activity of human mycobacterial pathogens as Mycobacterium tuberculosis can be measured when the implementation of this method to analyze virulent strains is adapted. PMID:22453520

Rodríguez, Jimmy; Ramírez, Ana-S; Suárez, Marco-Fidel; Soto, Carlos-Yesid

2012-06-01

416

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 Felício, Rafael; Zanoni, Maria Valnice Boldrin; Debonsi, Hosana Maria; Lopes, Norberto Peporine; Marcos, Ricard; de Oliveira, Danielle Palma

2011-12-01

417

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

NASA Astrophysics Data System (ADS)

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

Tsai, Tzu-Hsuan; Yen, Shi-Chern

2003-04-01

418

Fabrication of vertically aligned Pd nanowire array in AAO template by electrodeposition using neutral electrolyte  

NASA Astrophysics Data System (ADS)

A vertically aligned Pd nanowire array was successfully fabricated on an Au/Ti substrate using an anodic aluminum oxide (AAO) template by a direct voltage electrodeposition method at room temperature using diluted neutral electrolyte. The fabrication of Pd nanowires was controlled by analyzing the current-time transient during electrodeposition using potentiostat. The AAO template and the Pd nanowires were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) methods and X-Ray diffraction (XRD). It was observed that the Pd nanowire array was standing freely on an Au-coated Ti substrate after removing the AAO template in a relatively large area of about 5 cm2, approximately 50 nm in diameter and 2.5 ?m in length with a high aspect ratio. The nucleation rate and the number of atoms in the critical nucleus were determined from the analysis of current transients. Pd nuclei density was calculated as 3.55 × 108 cm-2. Usage of diluted neutral electrolyte enables slower growing of Pd nanowires owing to increase in the electrodeposition potential and thus obtained Pd nanowires have higher crystallinity with lower dislocations. In fact, this high crystallinity of Pd nanowires provides them positive effect for sensor performances especially.

Ta?alt?n, Nevin; Öztürk, Sadullah; K?l?nç, Necmettin; Yüzer, Hayrettin; Öztürk, Zafer Ziya

2010-07-01

419

Amperometric creatinine biosensor based on covalently coimmobilized enzymes onto carboxylated multiwalled carbon nanotubes/polyaniline composite film.  

PubMed

A mixture of commercial creatinine amidohydrolase (CA), creatine amidinohydrolase (CI), and sarcosine oxidase (SO) was coimmobilized covalently via N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) chemistry onto carboxylated multiwalled carbon nanotube (c-MWCNT)/polyaniline (PANI) nanocomposite film electrodeposited over the surface of a platinum (Pt) electrode. A creatinine biosensor was fabricated using enzyme/c-MWCNT/PANI/Pt as working electrode, Ag/AgCl as reference electrode, and Pt wire as auxiliary electrode connected through potentiostat. The enzyme electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and electrochemical impedance spectroscopy (EIS). The biosensor detected creatinine levels as low as 0.1 ?M, estimated at a signal-to-noise ratio of 3, within 5s at pH 7.5 and 35°C. The optimized biosensor showed a linear response range of 10 to 750 ?M creatinine with sensitivity of 40 ?A/mM/cm(2). The fabricated biosensor was successfully employed for determination of creatinine in human serum. The biosensor showed only 15% loss in its initial response after 180 days when stored at 4°C. PMID:21906581

Yadav, Sandeep; Kumar, Ashok; Pundir, C S

2011-12-15

420

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

PubMed

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

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

2013-01-15

421

Formation of the Microstructure of TiO2 Film Through Anodic Oxidation of Titanium  

NASA Astrophysics Data System (ADS)

Recent titanium oxide nanotube arrays have attracted attention for their applications. Titanium oxide nanotubes were prepared under potentiostat conditions (10 - 60 V) for various times (1 min - 3 hr). SEM observations revealed that the pore sizes of the nanotubes have a tendency to increase with an increase in the applied potential in the NH4F-glycerol-H2O electrolyte. Some corrosive pores were observed on the surface of titanium substrate at 40 V for 1 minute at 40°C. The pores covered the surface of the titanium substrate after 10 minutes, and some small pores were observed in the inner part of the pores, which should correspond to the combining of some small adjacent pores into a large one. The combining of the tubes were observed after 2 h and 3 h anodization times, and the nanotube arrays seem to be formed upward from the SEM side-views. The photocatalytic activity of the titanium oxide nanotubes was evaluated according to the JIS standard (JIS R 1703-2). The R factor of the titanium oxide nanotube arrays formed at 40 V and 40°C for a 3h the anodization time was 9.71 n mol/l·min, which was twice that of the titanium oxide thin film obtained by the rf-sputtering method.

Yokogawa, Y.; Yasuki, T.; Hirotomi, T.; Nakamura, A.; Kishida, I.

2011-04-01

422

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.

423

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 µm 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 µm 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 µm and 0.5 µm, 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

424

Design and applications of an in situ electrochemical NMR cell.  

PubMed

A device using a three-electrode electrochemical cell (referred to as an ECNMR cell) was successfully constructed that could be used in a standard 5mm 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 3mm 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. PMID:21067948

Zhang, Xiaocan; Zwanziger, Josef W

2011-01-01

425

Optimal set anode potentials vary in bioelectrochemical systems.  

PubMed

In bioelectrochemical systems (BESs), the anode potential can be set to a fixed voltage using a potentiostat, but there is no accepted method for defining an optimal potential. Microbes can theoretically gain more energy by reducing a terminal electron acceptor with a more positive potential, for example oxygen compared to nitrate. Therefore, more positive anode potentials should allow microbes to gain more energy per electron transferred than a lower potential, but this can only occur if the microbe has metabolic pathways capable of capturing the available energy. Our review of the literature shows that there is a general trend of improved performance using more positive potentials, but there are several notable cases where biofilm growth and current generation improved or only occurred at more negative potentials. This suggests that even with diverse microbial communities, it is primarily the potential of the terminal respiratory proteins used by certain exoelectrogenic bacteria, and to a lesser extent the anode potential, that determines the optimal growth conditions in the reactor. Our analysis suggests that additional bioelectrochemical investigations of both pure and mixed cultures, over a wide range of potentials, are needed to better understand how to set and evaluate optimal anode potentials for improving BES performance. PMID:20704197

Wagner, Rachel C; Call, Douglas F; Logan, Bruce E

2010-08-15

426

Electrodeposited nickel-cobalt composite coating containing MoS 2  

NASA Astrophysics Data System (ADS)

Ni-Co/MoS 2 composite coatings were prepared by electrodeposition in a Ni-Co plating bath containing nano-sized MoS 2 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 Ni-Co/MoS 2 composite coatings were evaluated with UMT-2MT test rig in a ball-on-disk contact mode. The morphologies of the original and worn surfaces of the composite coatings were observed on scanning electron microscope (SEM). It was found that the introduction of MoS 2 nano-particulates in the electrolyte caused the shift towards larger negatives of the reduction potential of the Ni-Co alloy coating, and the co-deposited MoS 2 showed no significant effect on the electrodeposition process of the Ni-Co alloy coating. However, the co-deposited MoS 2 led to changes in the surface morphology and structure of the composite coating as well. Namely, the peak width of the Ni-Co solid solution for the composite coating is broader as compared to that of the Ni-Co alloy coating. The co-deposited MoS 2 particulates were uniformly distributed in the Ni-Co matrix and contributed to increase tribological properties of the Ni-Co alloy coating.

Shi, Lei; Sun, Chufeng; Liu, Weimin

2008-08-01

427

Effects of Potential and Mechanical Stimulation on Oxidation of Tantalum During Electrochemical Mechanical Polishing  

NASA Astrophysics Data System (ADS)

Metal oxidation under stress plays a significant role in many industrial applications, particularly in chemical mechanical polishing (CMP). Here we report effects of mechanical stimulation on tantalum (Ta) oxidation during CMP. A tantalum surface was polished at various anodic potentials and under different mechanical forces. A potentiostat was used to measure the anodic reaction current during electrochemical mechanical polishing (ECMP). The material removal rate (MRR) measured using atomic force microscopy (AFM) was compared with that calculated using Faraday's law. Relationship was linked (or established) between the anodic potential and a mechanical force. The MRR was a second-order polynomial function of potential at constant mechanical force, followed by a logarithmic function. It was found that more suboxides were present at extreme potentials (low and high), while substantial pentoxide was generated under intermediate potentials. A model is proposed to explain the oxidation process of Ta during ECMP. The oxidation of Ta was a function of the anodic potential and mechanical force. The ex situ method used in this study fulfilled the in situ observation on Ta oxidation in polishing. Additionally, this technique can be used to investigate oxidation of other metals.

Gao, F.; Liang, Hong

2012-03-01

428

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

PubMed

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

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

2012-02-01

429

Miniaturized voltammetric stripping on screen printed gold electrodes for field determination of copper in atmospheric deposition.  

PubMed

The applicability of commercial screen-printed gold electrodes (SPGEs) connected to a portable potentiostat and a laptop has been explored to optimize a new square wave anodic stripping voltammetric method for on-site determination of soluble Cu(II) in atmospheric deposition samples taken around an industrial complex. Electrode conditioning procedures, chemical and instrumental variables have been optimized to develop a reliable method capable of measuring dissolved copper with a detection limit of 3.7 ng mL(-1), useful for pollution monitoring or screening purposes. The proposed method was tested with the SLRS-5 River Water for Trace Metals (recoveries 109.9-113.1%) and the SPS-SW2 Batch 121 Elements in Surface Waters (recoveries 93.2-97.6%). The method was applied to soluble Cu(II) measurement in liquid samples taken by a total atmospheric deposition collector modified with a quartz filter for soluble and insoluble elemental speciation. The voltammetric measurements on field samples were tested in the lab by a reference ICP-MS method, with good agreement. The proposed method proved capability for field operation during a two weeks monitoring campaign. PMID:23158345

Rueda-Holgado, F; Bernalte, E; Palomo-Marín, M R; Calvo-Blázquez, L; Cereceda-Balic, F; Pinilla-Gil, E

2012-11-15

430

Construction of amperometric uric acid biosensor based on uricase immobilized on PBNPs/cMWCNT/PANI/Au composite.  

PubMed

A chitosan-glutaraldehyde crosslinked uricase was immobilized onto Prussian blue nanoparticles (PBNPs) absorbed onto carboxylated multiwalled carbon nanotube (c-MWCNT) and polyaniline (PANI) layer, electrochemically deposited on the surface of Au electrode. The nanohybrid-uricase electrode was characterized by scanning electron microscopic (SEM), Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry. An amperometric uric acid biosensor was fabricated using uricase/c-MWCNT/PBNPs/Au electrode as working electrode, Ag/AgCl as standard and Pt wire as auxiliary electrode connected through a potentiostat. The biosensor showed optimum response within 4s at pH 7.5 and 40°C, when operated at 0.4V vs. Ag/AgCl. The linear working range for uric acid was 0.005-0.8 mM, with a detection limit of 5 ?M. The sensor was evaluated with 96% recovery of added uric acid in sera and 4.6 and 5.4% within and between batch of coefficient of variation respectively and a good correlation (r=0.99) with standard enzymic colorimetric method. This sensor measured uric acid in real serum samples. The sensor lost only 37% of its initial activity after its 400 uses over a period of 7 months, when stored at 4°C. PMID:22020190

Rawal, Rachna; Chawla, Sheetal; Chauhan, Nidhi; Dahiya, Tulika; Pundir, C S

2012-01-01

431

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

PubMed

Zinc oxide nanoparticles (ZnO-NPs) were synthesized from zinc nitrate by simple and efficient method in aqueous media at 55°C without any requirement of calcinations step. A mixture of ZnO-NPs and pyrrole was eletropolymerized on Pt electrode to form a ZnO-NPs-polypyrrole (PPy) composite film. Xanthine oxidase (XOD) was immobilized onto this nanocomposite film through physiosorption. The ZnO-NPs/polypyrrole/Pt electrode was characterized by Fourier transform infrared (FTIR), cyclic voltammetry (CV), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of XOD. The XOD/ZnO-NPs-PPy/Pt electrode as working electrode, Ag/AgCl as reference electrode and Pt wire as auxiliary electrode were connected through a potentiostat to construct a xanthine biosensor. The biosensor exhibited optimum response within 5s at pH 7.0, 35°C and linearity from 0.8 ?M to 40 ?M for xanthine with a detection limit 0.8 ?M (S/E=3). Michaelis Menten constant (K(m)) for xanthine oxidase was 13.51 ?M and I(max) 0.071 ?A. The biosensor measured xanthine in fish meat and lost 40% of its initial activity after its 200 uses over 100 days, when stored at 4°C. PMID:21324666

Devi, Rooma; Thakur, Manish; Pundir, C S

2011-04-15

432

Room-temperature epitaxial electrodeposition of single-crystalline germanium nanowires at the wafer scale from an aqueous solution.  

PubMed

Direct epitaxial growth of single-crystalline germanium (Ge) nanowires at room temperature has been performed through an electrodeposition process on conductive wafers immersed in an aqueous bath. The crystal growth is based on an electrochemical liquid-liquid-solid (ec-LLS) process involving the electroreduction of dissolved GeO2(aq) in water at isolated liquid gallium (Ga) nanodroplet electrodes resting on single-crystalline Ge or Si supports. Ge nanowires were electrodeposited on the wafer scale (>10 cm(2)) using only common glassware and a digital potentiostat. High-resolution electron micrographs and electron diffraction patterns collected from cross sections of individual substrate-nanowire contacts in addition to scanning electron micrographs of the orientation of nanowires across entire films on substrates with different crystalline orientations, supported the notion of epitaxial nanowire growth. Energy dispersive spectroscopic elemental mapping of single nanowires indicated the Ga(l) nanodroplet remains affixed to the tip of the growing nanowire throughout the nanowire electrodeposition process. Current-voltage responses measured across many individual nanowires yielded reproducible resistance values. The presented data cumulatively show epitaxial growth of covalent group IV nanowires is possible from the reduction of a dissolved oxide under purely benchtop conditions. PMID:24417670

Fahrenkrug, Eli; Gu, Junsi; Jeon, Sunyeol; Veneman, P Alexander; Goldman, Rachel S; Maldonado, Stephen

2014-02-12

433

Low-melting-point titanium-base brazing alloys—part 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 Widmanstätten 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 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.

1997-12-01

434

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 (28±7 nM by DPV; 26±8 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

2013-04-24

435

Properties of the nano-thick Pt/W bilayered catalytic layer employed dye sensitized solar cells  

NASA Astrophysics Data System (ADS)

A Pt/W bilayered catalytic layer on a flat glass substrate was used as a counter electrode to improve the energy conversion efficiency of a dye-sensitized solar cell device with the structure of 0.45 cm2 effective area of glass/FTO/blocking layer/TiO2/N719 (dye)/electrolyte/50 nm Pt/50 nm W/glass. For comparison, 100 nm-thick Pt and W counter electrodes on flat glass substrates were also prepared using the same procedure. The photovoltaic properties, such as the short circuit current density, open circuit voltage, fill factor, energy conversion efficiency and impedance were characterized using a solar simulator and potentiostat. The phases and microstructures of the catalytic layers were examined by x-ray diffraction and field emission electron microscopy. The measured energy conversion efficiencies of the dye-sensitized solar cell devices with Pt only and Pt/W bilayer counter electrodes were 4.60% and 6.54%, respectively. The interface resistance at the interface between the counter electrode and electrolyte decreased when a Pt/W bilayered thin film was applied. The increase in efficiency resulted from the effect of compressive strain field formed by the intermetallic layer of Pt2W at Pt and W layer interface. This suggests that the use of Pt/W bilayered catalytic layers improves the efficiency of the dye-sensitized solar cells compared to those using the conventional Pt layers.

Noh, Yunyoung; Song, Ohsung

2014-05-01

436

Thermal impedance spectroscopy for Li-ion batteries using heat-pulse response analysis  

NASA Astrophysics Data System (ADS)

Novel characterization of the thermal properties of batteries have been introduced by defining their frequency-dependent thermal impedance functions. The thermal impedance function can be approximated as a thermal impedance spectrum by analyzing the experimental temperature transient which is related to the thermal impedance function through Laplace transformation. In order to obtain the temperature transient, a process has been devised to generate an external heat pulse with heating wire and to measure the response of the battery. This process is used to study several commercial Li-ion batteries of cylindrical type. Thermal impedance measurements have been performed using a potentiostat/galvanostat controlled by a digital signal processor, which is more commonly available than a flow-meter usually applied for thermal property measurements. Thermal impedance spectra obtained for batteries produced by different manufacturers are found to differ considerably. Comparison of spectra at different states-of-charge indicates an independence of the thermal impedance on the charge state of the battery. It is shown that the thermal impedance spectrum can be used to obtain simultaneously the thermal capacity and the thermal conductivity of the battery by non-linear complex least-squares fit of the spectrum to the thermal impedance model.

Barsoukov, Evgenij; Jang, Jee Hwan; Lee, Hosull

437

Mechanical performance of PPy helix tube microactuator  

NASA Astrophysics Data System (ADS)

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

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

2004-02-01

438

Electrochromic properties of nano-structured nickel oxide thin film prepared by spray pyrolysis method  

NASA Astrophysics Data System (ADS)

In this study, we present a simple method to improve the electrochromic properties of a nickel oxide thin film. The method involves a three-step process—(a) conducting indium tin oxide (ITO) nano-particles were first sprayed onto a conducting substrate to form a porous nano-structured ITO layer, (b) nickel oxide film was then deposited onto the nano-structured ITO layer by a spray pyrolysis technique, and (c) the substrate, ITO nano-particles layer and nickel oxide film were annealed at high temperature of 300 °C to improve adhesion of these three layers. The microstructure of the resulting electrochromic cell was investigated using scanning electron microscopy. It is evident that the nickel oxide film covers the surface of the ITO nano-particle layer and forms a nano-structured nickel oxide (NSNO) film. The switching time and contrast were characterized by Autolab PGSTAT12 potentiostat and Jasco V-570 spectrophotometer. The results suggest that the transmittance contrast and switching time of NSNO are slightly superior to those of a conventional nickel oxide (CNO) film. However, the cycling durability of NSNO can be much better than that of CNO.

Lin, Sheng-Hui; Chen, Fu-Rong; Kai, Ji-Jung

2008-01-01

439

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

PubMed

A sulfite oxidase (SO(x)) (EC 1.8.3.1) purified from Syzygium cumini leaves was immobilized onto prussian blue nanoparticles/polypyrrole composite (PBNPs/PPY) electrodeposited onto the surface of indium tin oxide (ITO) electrode. An amperometric sulfite biosensor was fabricated using SO(x)/PBNPs/PPY/ITO electrode as working electrode, Ag/AgCl as standard and Pt wire as auxiliary electrode connected through a potentiostat. The working electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of SO(x). The biosensor showed optimum response within 2s, when operated at 20 mV s?¹ in 0.1M Tris-HCl buffer, pH 8.5 and at 35 °C. Linear range and minimum detection limit were 0.5-1000 ?M and 0.12 ?M (S/N=3) respectively. There was good correlation (r=0.99) between red wine samples sulfite value by standard DTNB method and the present method. The sensor was evaluated with 97% recovery of added sulfite in red wine samples and 2.2% and 4.3% within and between batch coefficients of variation respectively. The sensor was employed for determination of sulfite level in red and white wine samples. The enzyme electrode was used 200 times over a period of 3 months when stored at 4 °C. PMID:22705572

Rawal, Rachna; Pundir, C S

2012-11-01

440

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

441

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

442

Stretchable, multiplexed pH sensors with demonstrations on rabbit and human hearts undergoing ischemia.  

PubMed

Stable pH is an established biomarker of health, relevant to all tissues of the body, including the heart. Clinical monitoring of pH in a practical manner, with high spatiotemporal resolution, is particularly difficult in organs such as the heart due to its soft mechanics, curvilinear geometry, heterogeneous surfaces, and continuous, complex rhythmic motion. The results presented here illustrate that advanced strategies in materials assembly and electrochemical growth can yield interconnected arrays of miniaturized IrOx pH sensors encapsulated in thin, low-modulus elastomers to yield conformal monitoring systems capable of noninvasive measurements on the surface of the beating heart. A thirty channel custom data acquisition system enables spatiotemporal pH mapping with a single potentiostat. In vitro testing reveals super-Nernstian sensitivity with excellent uniformity (69.9 ± 2.2 mV/pH), linear response to temperature (-1.6 mV °C(-1) ), and minimal influence of extracellular ions (<3.5 mV). Device examples include sensor arrays on balloon catheters and on skin-like stretchable membranes. Real-time measurement of pH on the surfaces of explanted rabbit hearts and a donated human heart during protocols of ischemia-reperfusion illustrate some of the capabilities. Envisioned applications range from devices for biological research, to surgical tools and long-term implants. PMID:23868871

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

2014-01-01

443

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

PubMed

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

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

2011-02-14

444

High-resolution neutron powder diffractometer SPODI at research reactor FRM II  

NASA Astrophysics Data System (ADS)

SPODI is a high-resolution thermal neutron diffractometer at the research reactor Heinz Maier-Leibnitz (FRM II) especially dedicated to structural studies of complex systems. Unique features like a very large monochromator take-off angle of 155° and a 5 m monochromator-sample distance in its standard configuration achieve both high-resolution and a good profile shape for a broad scattering angle range. Two dimensional data are collected by an array of 80 vertical position sensitive 3He detectors. SPODI is well suited for studies of complex structural and magnetic order and disorder phenomena at non-ambient conditions. In addition to standard sample environment facilities (cryostats, furnaces, magnet) specific devices (rotatable load frame, cell for electric fields, multichannel potentiostat) were developed. Thus the characterisation of functional materials at in-operando conditions can be achieved. In this contribution the details of the design and present performance of the instrument are reported along with its specifications. A new concept for data reduction using a 2 ? dependent variable height for the intensity integration along the Debye-Scherrer lines is introduced.

Hoelzel, M.; Senyshyn, A.; Juenke, N.; Boysen, H.; Schmahl, W.; Fuess, H.

2012-03-01

445

Amperometric choline biosensor based on multiwalled carbon nanotubes/zirconium oxide nanoparticles electrodeposited on glassy carbon electrode.  

PubMed

A bienzymatic choline biosensor was constructed by coimmobilizing acetylcholinesterase (AChE) and choline oxidase (ChO) onto nanocomposite of carboxylated multiwalled carbon nanotubes (c-MWCNTs) and zirconium oxide nanoparticles (ZrO(2)NPs) electrodeposited on the surface of a glassy carbon electrode (GCE) and using it (AChE-ChO/c-MWCNT/ZrO(2)NPs/GCE) as working electrode, Ag/AgCl as reference 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, and cyclic voltammetry (CV) studies, optimized, and evaluated. The biosensor exhibited optimum response within 4 s at +0.2V, pH 7.4, and 25 °C. The detection limit and working range of the biosensor were 0.01 ?M and 0.05 to 200 ?M, respectively. The half-life of the enzyme electrode was 60 days at 4 °C. The serum choline level, as measured by the biosensor, was 9.0 to 12.8 ?mol/L (with a mean of 10.81 ?mol/L) in apparently healthy persons and 5.0 to 8.4 ?mol/L (with a mean of 6.53 ?mol/L) in persons suffering from Alzheimer's disease. The enzyme electrode was unaffected by a number of serum substances. PMID:22561918

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

2012-08-01

446

Submersible voltammetric probes for in situ real-time trace element measurements in surface water, groundwater and sediment-water interface  

NASA Astrophysics Data System (ADS)

A summary of the state of the art in the development of two submersible voltammetric probes performed by us to allow continuous, real-time monitoring of trace elements (Cu(II), Pb(II), Cd(II), Zn(II) and Mn(II), Fe(II)) in natural aquatic ecosystems is given. The first one, called the voltammetric in situ (VIP) profiling system, allowed in situ measurements in surface water and groundwater down to 500 m. Its construction required the development of: (i) a gel-integrated, either single or interconnected, array microsensor, (ii) a submersible probe and (iii) hardware, firmware and software for control of the whole system: i.e. data transmission and acquisition, data processing and maintenance operations. The second system, called the sediment-water interface voltammetric in situ profiling (SIVIP) system, has been developed to allow real-time, high spatial resolution trace elements concentration profile measurements at the sediment-water interface. Its construction required the development of: (i) a gel-integrated microsensor array with 64 individually addressable lines, (ii) a voltammetric probe based on powerful double multiplexing system and single potentiostat allowing simultaneous measurements over the 64 sensor lines, and (iii) hardware, firmware and software for control of the whole system. A general description of both systems as well as examples of laboratory characterization and/or field applications are reported.

Tercier-Waeber, M.-L.; Buffle, J.; Confalonieri, F.; Riccardi, G.; Sina, A.; Graziottin, F.; Fiaccabrino, G. C.; Koudelka-Hep, M.

1999-12-01

447

Immobilization of rat brain acetylcholinesterase on porous gold-nanoparticle-CaCO? hybrid material modified Au electrode for detection of organophosphorous insecticides.  

PubMed

An acetylcholinesterase (AChE) purified from rat brain was immobilized onto gold nanoparticles (AuNPs) assembled on the surface of porous calcium carbonate (CaCO(3)) microsphere. The resulting AChE-AuNPs-CaCO(3) bioconjugate was mounted on the surface of Au electrode with the help of silica sol-gel matrix to prepare the working electrode. This electrode was connected to Ag/AgCl (3M/saturated KCl) as standard and Pt wire as an auxiliary electrode through a potentiostat to construct an organophosphorus (OP) biosensor. The biosensor was based on inhibition of AChE by OP compounds/insecticides. The biosensor showed optimum response at pH 7.0, 30°C, when polarized at +0.2V. Two OP compounds, malathion and chlorpyrifos could be detected in the range of 0.1-100 nM and 0.1-70 nM, respectively at 2.0-3.0% inhibition level of AChE. The sensor was reactivated by immersing it in 0.1 mM 2-pyridine aldoxime for 10 min. The detection limit of the sensor was 0.1 nM for both malathion and chlorpyrifos. The biosensor exhibited good reusability (50 times without considerable loss) and storage stability (50% within 60 days, when stored at 4°C). PMID:21856330

Chauhan, Nidhi; Narang, Jagriti; Pundir, C S

2011-12-01

448

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

449

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

PubMed

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

Barbieri Gonzaga, Fabiano; Pereira Sobral, Sidney

2012-08-15

450

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

2012-10-15

451

Determination of charge transfer resistance and capacitance of microbial fuel cell through a transient response analysis of cell voltage.  

PubMed

An alternative method for determining the charge transfer resistance and double-layer capacitance of microbial fuel cells (MFCs), easily implemented without a potentiostat, was developed. A dynamic model with two parameters, the charge transfer resistance and double-layer capacitance of electrodes, was derived from a linear differential equation to depict the current generation with respect to activation overvoltage. This model was then used to fit the transient cell voltage response to the current step change during the continuous operation of a flat-plate type MFC fed with acetate. Variations of the charge transfer resistance and the capacitance value with respect to the MFC design conditions (biocatalyst existence and electrode area) and operating parameters (acetate concentration and buffer strength in the catholyte) were then determined to elucidate the validity of the proposed method. This model was able to describe the dynamic behavior of the MFC during current change in the activation loss region; having an R(2) value of over 0.99 in most tests. Variations of the charge transfer resistance value (thousands of Omega) according to the change of the design factors and operational factors were well-correlated with the corresponding MFC performances. However, though the capacitance values (approximately 0.02 F) reflected the expected trend according to the electrode area change and catalyst property, they did not show significant variation with changes in either the acetate concentration or buffer strength. PMID:20036528

Ha, Phuc Thi; Moon, Hyunsoo; Kim, Byung Hong; Ng, How Yong; Chang, In Seop

2010-03-15

452

Evaluation on the corrosion of the three ni-cr alloys with different composition.  

PubMed

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

Rao, Srinivasa B; Chowdhary, Ramesh

2011-01-01

453

Design of a high-speed electrochemical scanning tunneling microscope.  

PubMed

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. PMID:23464213

Yanson, Y I; Schenkel, F; Rost, M J

2013-02-01

454

Carbon nanotube enhanced mediator-type biosensor for real-time monitoring of glucose concentrations in fish.  

PubMed

We have developed a mediator-type biosensor to rapidly monitor blood glucose concentrations in fish, which are an indicator of stress. Glucose oxidase was used to detect glucose concentrations and ferrocene was used to limit the effect of oxygen. We also improved the sensitivity and durability of the sensor for better performance. Single-walled carbon nanotubes were used to enhance sensor sensitivity. Affixing the carbon nanotubes (30 mg ml(-1)) to the working electrode increased the sensor sensitivity to 61.9 mM nA(-1) mm(-2), twice the value for the sensor without single-walled carbon nanotubes. A fabricated mediator-type biosensor sensor was used to perform real-time in vivo measurements. The sensor was implanted into the interstitial fluid of a fish eyeball, and detection was transmitted to a personal computer by a wireless potentiostat. Continuous measurement of the glucose concentration was possible for 78 hours. Stress was artificially applied to the fish during the measurement, and the change of blood glucose concentrations were observed. Our proposed sensor is applicable for effectively monitoring stress in free-swimming fish. PMID:22427105

Takase, Mai; Yoneyama, Yohei; Murata, Masataka; Hibi, Kyoko; Ren, Huifeng; Endo, Hideaki

2012-05-01

455

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

456

Microchip electrophoresis with amperometric detection for the study of the generation of nitric oxide by NONOate salts.  

PubMed

Microchip electrophoresis (ME) with electrochemical detection was used to monitor nitric oxide (NO) production from diethylammonium (Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (DEA/NO) and 1-(hydroxyl-NNO-azoxy)-L-proline disodium salt (PROLI/NO). NO was generated through acid hydrolysis of these NONOate salts. The products of acid hydrolysis were introduced into a 5-cm separation channel using gated injection. The separation was accomplished using reverse polarity and a background electrolyte consisting of 10 mM boric acid and 2 mM tetradecyltrimethylammonium bromide, pH 11. Electrochemical detection was performed using an isolated potentiostat in an in-channel configuration. Potentials applied to the working electrode, typically higher than +1.0 V vs. Ag/AgCl, allowed the direct detection of nitrite, NO, DEA/NO, and PROLI/NO. Baseline resolution was achieved for the separation of PROLI/NO and NO while resolution between DEA/NO and NO was poor (1.0 ± 0.2). Nitrite was present in all samples tested. PMID:22415023

Gunasekara, Dulan B; Hulvey, Matthew K; Lunte, Susan M; da Silva, José Alberto Fracassi

2012-06-01

457

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

PubMed

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

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

2012-01-17

458

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

459

Selective functionalization of gold arms of a surface plasmon polariton Mach-Zehnder interferometer for biosensing  

NASA Astrophysics Data System (ADS)

In long range surface plasmon polariton (LRSPP) sensing, in a Mach-Zehnder interferometer (MZI) configuration, gold arms have to respond differently to the analyte as to form layers with different refractive indices. This can be achieved if the arms are coated with different thiol-based self-assembled monolayers (SAMs), one of which should block adsorption and the other should specifically adsorb the analyte of interest. Since the MZI arms' width and the distance between them are in the micron range, such a chemical differentiation is a challenging task which nevertheless could be achieved with two techniques (1) Microspotting trough droplet confinement and manipulation using a solvophilic guide and (2) Toposelective electrochemical desorption of SAMs where the arms are subjected to different potentials. We found the latter approach the most promising because of its scalability to the wafer level. During the electrochemical desorption the potentials of both arms have to be independently controlled with a multi-channel potentiostat. Subsequent deposition of another SAM on the freed MZI arm is accomplished with minimal thiol exchange. The resulting MZI was analyzed and imaged by time-of-flight secondary ion mass spectrometry (ToF- SIMS) and with phase shift atomic force microscopy which confirms the desired MZI structure in which only one arm has specific affinity to one protein while the other would block any interaction.

Tencer, Michal; Berini, Pierre

2009-06-01

460

Integrated electrochemical transistor as a fast recoverable gas sensor.  

PubMed

A new design of conductometric chemical sensors based on conducting polymers as chemosensitive elements was suggested. The sensor includes six electrodes. Four inner electrodes coated by chemosensitive polymer are used for simultaneous two- and four-point resistance measurements thus providing information on the bulk polymer resistance and on the resistance of the polymer/electrode contacts. Two outer electrodes wired to inner electrodes by polymeric electrolyte are used for electrical control of redox state of the chemosensitive polymer. The outer electrodes are connected to potentiostat as reference and counter electrodes. It allows us to control redox state of the inner (working) electrodes. This new measurement configuration, resembling chemosensitive electrochemical transistors, provides an internal test of the sensor integrity and an electrically driven sensor regeneration. It was tested as a sensor for the detection of nitrogen dioxide. Polythiophene or polyaniline was used as receptors. Cyclic voltammograms of these polymers on the sensor surface measured in air atmosphere were very similar to that measured in aqueous electrolyte. A control of conductivity of these chemosensitive polymers by electrical potential applied vs. incorporated reference electrode was demonstrated. This effect was used for the regeneration of the chemosensitive material after exposure to nitrogen dioxide: in comparison to usual chemiresistors displaying an irreversible behavior in such test even in the time scale of hours, a completely reversible sensor regeneration within few minutes was observed. PMID:21241841

Lange, Ulrich; Mirsky, Vladimir M

2011-02-14

461

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

PubMed

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

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

2011-04-01

462

Characterization of YSZ solid oxide fuel cells electrolyte deposited by atmospheric plasma spraying and low pressure plasma spraying  

NASA Astrophysics Data System (ADS)

Yttria doped zirconia has been widely used as electrolyte materials for solid oxide fuel cells (SOFC). Plasma spraying is a cost-effective process to deposit YSZ electrolyte. In this study, the 8 mol% Y2O3 stabilized ZrO2 (YSZ) layer was deposited by low pressure plasma spraying (LPPS) and atmospheric plasma spraying (APS) with fused-crushed and agglomerated powders to examine the effect of spray method and particle size on the electrical conductivity and gas permeability of YSZ coating. The microstructure of YSZ coating was characterized by scanning electron microscopy and x-ray diffraction analysis. The results showed that the gas permeability was significantly influenced by powder structure. The gas permeability of YSZ coating deposited by fused-crushed powder is one order lower in magnitude than that by agglomerated powder. Moreover, the gas permeability of YSZ deposited by LPPS is lower than that of APS YSZ. The electrical conductivity of the deposits through thickness direction was measured by potentiostat/galvanostat based on three-electrode assembly approach. The electrical conductivity of YSZ coating deposited by low pressure plasma spraying with fused-crushed powder of small particle size was 0.043 S cm-1 at 100 °C, which is about 20% higher than that of atmospheric plasma spraying YSZ with the same powder.

Zhang, C.; Liao, H. L.; Li, W. Y.; Zhang, G.; Coddet, C.; Zhang, C.; Li, C. J.; Li, C. X.; Ning, X. J.

2006-12-01

463

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-á-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, Jesé; Elbatanouny, Mohamed K.; Vélez, William; Ziehl, Paul; Matta, Fabio; González, Miguel

2011-03-01

464

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 30°C. 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

2013-04-10

465

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

PubMed

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

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

2011-12-15

466

Energy-efficient treatment of organic wastewater streams using a rotatable bioelectrochemical contactor (RBEC).  

PubMed

A membraneless bioelectrochemical system - rotatable bio-electrochemical contactor (RBEC) consists of an array of rotatable electrode disks was developed to convert the chemical energy from wastewater organics (acetate) directly into electricity. Each rotatable electrode disk had an upper-air exposing and a lower-water submerging halves. Intermittent rotation (180°) enabled each halve to alternately serve as anode and cathode. Removal of chemical oxygen demand (COD) was increased by 15% (from 0.79 to 0.91 kg COD m(-3) d(-1)) by allowing electron flow from the lower to the upper disk halves. Coupling with a potentiostat could alleviate cathodic limitation and increased COD removal to 1.32 kg COD m(-3) day(-1) (HRT 5h). About 40% of the COD removed was via current, indicating that the biofilm could use the lower half disk as electron acceptor. The RBEC removed COD more energy-efficiently than conventional activated sludge processes as active aeration is not required (0.47 vs. 0.7-2.0 kW h kg COD(-1)). PMID:22209129

Cheng, Ka Yu; Ho, Goen; Cord-Ruwisch, Ralf

2012-12-01

467