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Sample records for electrochemical impedance spectra

  1. Investigation of the interaction between quercetin and human serum albumin by multiple spectra, electrochemical impedance spectra and molecular modeling.

    PubMed

    Dai, Jie; Zou, Ting; Wang, Li; Zhang, Yezhong; Liu, Yi

    2014-12-01

    Quercetin (Qu), a flavonoid compound, exists widely in the human diet and exhibits a variety of pharmacological activities. This work is aimed at studying the effect of Qu on the bioactive protein, human serum albumin (HSA) under simulated biophysical conditions. Multiple spectroscopic methods (including fluorescence and circular dichroism), electrochemical impedance spectra (EIS) and molecular modeling were employed to investigate the interaction between Qu and HSA. The fluorescence quenching and EIS experimental results showed that the fluorescence quenching of HSA was caused by formation of a Qu-HSA complex in the ground state, which belonged to the static quenching mechanism. Based on the calculated thermodynamic parameters, it concluded that the interaction was a spontaneous process and hydrogen bonds combined with van der Waal's forces played a major role in stabilizing the Qu-HSA complex. Molecular modeling results demonstrated that several amino acids participated in the binding process and the formed Qu-HSA complex was stabilized by H-bonding network at site I in sub-domain IIA, which was further confirmed by the site marker competitive experiments. The evidence from circular dichroism (CD) indicated that the secondary structure and microenvironment of HSA were changed. Alterations in the conformation of HSA were observed with a reduction in the amount of α helix from 59.9% (free HSA) to 56% (Qu-HSA complex), indicating a slight unfolding of the protein polypeptides. PMID:24801949

  2. Correlation of capacity fading processes and electrochemical impedance spectra in lithium/sulfur cells

    NASA Astrophysics Data System (ADS)

    Risse, Sebastian; Cañas, Natalia A.; Wagner, Norbert; Härk, Eneli; Ballauff, Matthias; Friedrich, K. Andreas

    2016-08-01

    The capacity fading of lithium/sulfur (Li/S) cells is one major challenge that has to be overcome for a successful commercialization of this electrochemical storage system. Therefore it is essential to detect the major fading mechanisms for further improvements of this system. In this work, the processes leading to fading are analyzed in terms of a linear four state model and correlated to the distribution of relaxation times calculated with a modified Levenberg-Marquardt algorithm. Additionally, the Warburg impedance and the solution resistance are also obtained by the same algorithm. The detailed analysis of intermediate states during the first cycle gives the distinction between relaxation processes at the sulfur cathode and at the lithium anode. The influence of the polysulfides on the impedance parameters was evaluated using symmetric cells; this yields a good correlation with the results obtained from the first discharge/charge experiment. A fast and a slow capacity fading process are observed for the charge and the discharge during 50 cycles. The fast fading process can be assigned to Faradaic reactions at the lithium anode.

  3. Electrochemical Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Retter, Utz; Lohse, Heinz

    Non-steady-state measuring techniques are known to be extremely suitable for the investigation of the electrode kinetics of more complex electrochemical systems. Perturbation of the electrochemical system leads to a shift of the steady state. The rate at which it proceeds to a new steady state depends on characteristic parameters (reaction rate constants, diffusion coefficients, charge transfer resistance, double-layer capacity). Due to non-linearities caused by the electron transfer, low-amplitude perturbation signals are necessary. The small perturbation of the electrode state has the advantage that the solutions of relevant mathematical equations used are transformed in limiting forms that are normally linear. Impedance spectroscopy represents a powerful method for investigation of electrical properties of materials and interfaces of conducting electrodes. Relevant fields of application are the kinetics of charges in bulk or interfacial regions, the charge transfer of ionic or mixed ionic-ionic conductors, semiconducting electrodes, the corrosion inhibition of electrode processes, investigation of coatings on metals, characterisation of materials and solid electrolyte as well as solid-state devices.

  4. Electrochemical Impedance Spectroscopy of Conductive Polymer Coatings

    NASA Technical Reports Server (NTRS)

    Calle, Luz Marina; MacDowell, Louis G.

    1996-01-01

    Electrochemical impedance spectroscopy (EIS) was used to investigate the corrosion protection performance of twenty nine proprietary conductive polymer coatings for cold rolled steel under immersion in 3.55 percent NaCl. Corrosion potential as well as Bode plots of the data were obtained for each coating after one hour immersion, All coatings, with the exception of one, have a corrosion potential that is higher in the positive direction than the corrosion potential of bare steel under the same conditions. Group A consisted of twenty one coatings with Bode plots indicative of the capacitive behavior characteristic of barrier coatings. An equivalent circuit consisting of a capacitor in series with a resistor simulated the experimental EIS data for these coatings very well. Group B consisted of eight coatings that exhibited EIS spectra showing an inflection point which indicates that two time constants are present. This may be caused by an electrochemical process taking place which could be indicitive of coating failing. These coatings have a lower impedance that those in Group A.

  5. Electrochemical Impedance Spectroscopy Of Metal Alloys

    NASA Technical Reports Server (NTRS)

    Macdowell, L. G.; Calle, L. M.

    1993-01-01

    Report describes use of electrochemical impedance spectroscopy (EIS) to investigate resistances of 19 alloys to corrosion under conditions similar to those of corrosive, chloride-laden seaside environment of Space Transportation System launch site. Alloys investigated: Hastelloy C-4, C-22, C-276, and B-2; Inconel(R) 600, 625, and 825; Inco(R) G-3; Monel 400; Zirconium 702; Stainless Steel 304L, 304LN, 316L, 317L, and 904L; 20Cb-3; 7Mo+N; ES2205; and Ferralium 255. Results suggest electrochemical impedance spectroscopy used to predict corrosion performances of metal alloys.

  6. Tracking of electrochemical impedance of batteries

    NASA Astrophysics Data System (ADS)

    Piret, H.; Granjon, P.; Guillet, N.; Cattin, V.

    2016-04-01

    This paper presents an evolutionary battery impedance estimation method, which can be easily embedded in vehicles or nomad devices. The proposed method not only allows an accurate frequency impedance estimation, but also a tracking of its temporal evolution contrary to classical electrochemical impedance spectroscopy methods. Taking into account constraints of cost and complexity, we propose to use the existing electronics of current control to perform a frequency evolutionary estimation of the electrochemical impedance. The developed method uses a simple wideband input signal, and relies on a recursive local average of Fourier transforms. The averaging is controlled by a single parameter, managing a trade-off between tracking and estimation performance. This normalized parameter allows to correctly adapt the behavior of the proposed estimator to the variations of the impedance. The advantage of the proposed method is twofold: the method is easy to embed into a simple electronic circuit, and the battery impedance estimator is evolutionary. The ability of the method to monitor the impedance over time is demonstrated on a simulator, and on a real Lithium ion battery, on which a repeatability study is carried out. The experiments reveal good tracking results, and estimation performance as accurate as the usual laboratory approaches.

  7. Impedance feedback control for scanning electrochemical microscopy.

    PubMed

    Alpuche-Aviles, M A; Wipf, D O

    2001-10-15

    A new constant-distance imaging method based on the relationship between tip impedance and tip-substrate separation has been developed for the scanning electrochemical microscope. The tip impedance is monitored by application of a high-frequency ac voltage bias between the tip and auxiliary electrode. The high-frequency ac current is easily separated from the dc-level faradaic electrochemistry with a simple RC filter, which allows impedance measurements during feedback or generation/collection experiments. By employing a piezo-based feedback controller, we are able to maintain the impedance at a constant value and, thus, maintain a constant tip-substrate separation. Application of the method to feedback and generation/collection experiments with tip electrodes as small as 2 microm is presented. PMID:11681463

  8. Method for conducting nonlinear electrochemical impedance spectroscopy

    DOEpatents

    Adler, Stuart B.; Wilson, Jamie R.; Huff, Shawn L.; Schwartz, Daniel T.

    2015-06-02

    A method for conducting nonlinear electrochemical impedance spectroscopy. The method includes quantifying the nonlinear response of an electrochemical system by measuring higher-order current or voltage harmonics generated by moderate-amplitude sinusoidal current or voltage perturbations. The method involves acquisition of the response signal followed by time apodization and fast Fourier transformation of the data into the frequency domain, where the magnitude and phase of each harmonic signal can be readily quantified. The method can be implemented on a computer as a software program.

  9. Impedance spectra of polypyrrole coated platinum electrodes.

    PubMed

    Onnela, Niina; Savolainen, Virpi; Hiltunen, Maiju; Kellomäki, Minna; Hyttinen, Jari

    2013-01-01

    Polypyrrole (PPy) coated electrodes may provide new solutions to increase the charge injection capacity and biocompatibility of metal electrodes in e.g., neural stimulus applications. In this study, electrical impedance spectra of PPy coated platinum (Pt) electrodes having three different coating thicknesses were measured and modeled. A suitable equivalent electrical circuit providing the material characteristics was chosen and the impedance data was analyzed using the model and data fitting. The modeled parameter values of different coating thicknesses were compared and our results demonstrated the changes in charge transfer properties and mechanisms of thin and thick PPy film coatings. PMID:24109743

  10. Corrosion Study Using Electrochemical Impedance Spectroscopy

    NASA Technical Reports Server (NTRS)

    Farooq, Muhammad Umar

    2003-01-01

    Corrosion is a common phenomenon. It is the destructive result of chemical reaction between a metal or metal alloy and its environment. Stainless steel tubing is used at Kennedy Space Center for various supply lines which service the orbiter. The launch pads are also made of stainless steel. The environment at the launch site has very high chloride content due to the proximity to the Atlantic Ocean. Also, during a launch, the exhaust products in the solid rocket boosters include concentrated hydrogen chloride. The purpose of this project was to study various alloys by Electrochemical Impedance Spectroscopy in corrosive environments similar to the launch sites. This report includes data and analysis of the measurements for 304L, 254SMO and AL-6XN in primarily neutral 3.55% NaCl. One set of data for 304L in neutral 3.55%NaCl + 0.1N HCl is also included.

  11. Mapping Electrochemical Heterogeneity at Iron Oxide Surfaces: A Local Electrochemical Impedance Study.

    PubMed

    Lucas, Marie; Boily, Jean-François

    2015-12-22

    Alternating current scanning electrochemical microscopy (AC-SECM) was used for the first time to map key electrochemical attributes of oriented hematite (α-Fe2O3) single crystal surfaces at the micron-scale. Localized electrochemical impedance spectra (LEIS) of the (001) and (012) faces provided insight into the spatial variations of local double layer capacitance (C(dl)) and charge transfer resistance (R(ad)). These parameters were extracted by LEIS measurements in the 0.4-8000 Hz range to probe the impedance response generated by the redistribution of water molecules and charge carriers (ions) under an applied AC. These were attributed to local variations in the local conductivity of the sample surfaces. Comparison with global EIS measurements on the same samples uncovered highly comparable frequency-resolved processes, that were broken down into contributions from the bulk hematite, the interface as well as the microelectrode/tip assembly. This work paves the way for new studies aimed at mapping electrochemical processes at the mesoscale on this environmentally and technologically important material. PMID:26625255

  12. Plasmonic-Based Electrochemical Impedance Spectroscopy: Application to Molecular Binding

    PubMed Central

    Lu, Jin; Wang, Wei; Wang, Shaopeng; Shan, Xiaonan; Li, Jinghong; Tao, Nongjian

    2012-01-01

    Plasmonic-based electrochemical impedance spectroscopy (P-EIS) is developed to investigate molecular binding on surfaces. Its basic principle relies on the sensitive dependence of surface plasmon resonance (SPR) signal on surface charge density, which is modulated by applying an AC potential to a SPR chip surface. The AC component of the SPR response gives the electrochemical impedance, and the DC component provides the conventional SPR detection. The plasmonic-based impedance measured over a range of frequency is in quantitative agreement with the conventional electrochemical impedance. Compared to the conventional SPR detection, P-EIS is sensitive to molecular binding taking place on the chip surface, and less sensitive to bulk refractive index changes or non-specific binding. Moreover, this new approach allows for simultaneous SPR and surface impedance analysis of molecular binding processes. PMID:22122514

  13. The Impedance Response of Semiconductors: An Electrochemical Engineering Perspective.

    ERIC Educational Resources Information Center

    Orazem, Mark E.

    1990-01-01

    Shows that the principles learned in the study of mass transport, thermodynamics, and kinetics associated with electrochemical systems can be applied to the transport and reaction processes taking place within a semiconductor. Describes impedance techniques and provides several graphs illustrating impedance data for diverse circuit systems. (YP)

  14. The evaluation of corrosion inhibitor film persistency using electrochemical impedance spectroscopy and electrochemical noise analysis

    SciTech Connect

    Tan, Y.J.; Kinsella, B.; Bailey, S.

    1996-10-01

    Electrochemical impedance spectroscopy (EIS) and electrochemical noise analysis (ENA) were used as combined techniques to study and evaluate the film persistency of several commercial batch treatment inhibitors which are used for protecting oil-wells, gas-wells or pipelines from CO{sub 2} corrosion. It was found that the inhibitors film deterioration was accompanied by typical changes in the EIS spectra, which could be used as indicators for monitoring inhibitor film breakdown. ENA was shown to be able to continuously follow and monitor the inhibitor film deterioration processes. The noise resistance (R{sub noise}) was confirmed to be strongly correlated to linear polarization resistance (R{sub p}) and this correlation was explained based on a concept called statistical linear polarization. The presence of the hydrocarbon phase and CO{sub 2} corrosion product scale were found to be factors which greatly affect batch treatment inhibitor film persistency.

  15. Electrochemical impedance measurement of a carbon nanotube probe electrode.

    PubMed

    Inaba, Akira; Takei, Yusuke; Kan, Tetsuo; Matsumoto, Kiyoshi; Shimoyama, Isao

    2012-12-01

    We measured and analyzed the electrochemical impedance of carbon nanotube (CNT) probe electrodes fabricated through the physical separation of insulated CNT bridges. The fabricated CNT electrodes were free-standing CNTs that were completely covered with an insulator, except for their tips. Typical dimensions of the nanoelectrodes were 1-10 nm in CNT diameter, 80-300 nm in insulator diameter, 0.5-4 μm in exposed CNT length and 1-10 μm in probe length. The electrochemical impedance at frequencies ranging from 40 Hz to 1 MHz was measured in physiological saline. The measured impedance of the CNT electrode was constant at 32 MΩ at frequencies below 1 kHz and was inversely proportional to frequency at frequencies above 10 kHz. By means of comparison with the parasitic capacitive impedance of the insulator membrane, we confirmed that the electrode was sufficiently insulated such that the measured constant impedance was given by the exposed CNT tip. Consequently, we can use the CNT electrode for highly localized electrochemical impedance measurements below 1 kHz. Considering an equivalent circuit and the nanoscopic dimensions of the CNT electrode, we demonstrated that the constant impedance was governed by diffusion impedance, whereas the solution resistance, charge-transfer resistance and double-layer capacitance were negligible. PMID:23124171

  16. Electrochemical Impedance Of Inorganic-Zinc-Coated Steel

    NASA Technical Reports Server (NTRS)

    Macdowell, Louis G.

    1992-01-01

    Report describes preliminary experiments to evaluate both direct-current and alternating-current electrochemical impedance measurements as candidate techniques for use in accelerated corrosion testing of mild-steel panels coated with inorganic zinc-rich primers and exposed to seaside air. Basic idea behind experiments to compare electrochemical impedance measurements with anticorrosion performances of coating materials to determine whether measurements can be used to predict performances. Part of continuing program to identify anticorrosion coating materials protecting steel panels adequately for as long as 5 years and beyond.

  17. Diagnosis of PEMFC stack failures via electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Merida-Donis, Walter Roberto

    Two failure modes related to water management in Proton Exchange Membrane fuel cells (dehydration and flooding) were investigated using electrochemical impedance spectroscopy as a diagnosis tool. It was hypothesised that each failure mode corresponds to changes in the overall stack impedance that are observable in different frequency ranges. This hypothesis was corroborated experimentally. The experimental implementation required new testing hardware and techniques. A four-cell stack capable of delivering individually conditioned reactants to each cell was designed, built, tested, and characterised under a variety of operating conditions. This stack is the first reported prototype of its type. The stack was used to perform galvanostatic, impedance measurements in situ. The measurements were made at three different temperatures (62, 70 and 80°C), covering the current density range 0.1 to 1.0 A cm-2 , and the frequency range 0.1 to 4 x 105 Hz. The recorded data represent the first reported set of measurements covering these ranges. The failure modes were simulated on individual cells within the stack. The effects on individual cell and stack impedance were studied by measuring the changes in stack and cell impedances under flooding or dehydration conditions. Dehydration effects were measurable over a wide frequency range (0.5 to 105 Hz). In contrast, flooding effects were measurable in a narrower frequency range (0.5 to 102 Hz). Using these results, separate or concurrent impedance measurements in these frequency ranges (or narrow bands thereof) can be used to discern and identify the two failure modes quasi-instantaneously. Such detection was not possible with pre-existing, do techniques. The measured spectra were modelled by a simple equivalent circuit whose time constants corresponded to ideal (RC) and distributed (Warburg) components. The model was robust enough to fit all the measured spectra (for single cells and the stack), under normal and simulated

  18. The use of electrochemical impedance spectroscopy (EIS) in the evaluation of the electrochemical properties of a microbial fuel cell.

    PubMed

    Manohar, Aswin K; Bretschger, Orianna; Nealson, Kenneth H; Mansfeld, Florian

    2008-04-01

    Electrochemical impedance spectroscopy (EIS) has been used to determine several electrochemical properties of the anode and cathode of a mediator-less microbial fuel cell (MFC) under different operational conditions. These operational conditions included a system with and without the bacterial catalyst and EIS measurements at the open-circuit potential of the anode and the cathode or at an applied cell voltage. In all cases the impedance spectra followed a simple one-time-constant model (OTCM) in which the solution resistance is in series with a parallel combination of the polarization resistance and the electrode capacitance. Analysis of the impedance spectra showed that addition of Shewanella oneidensis MR-1 to a solution of buffer and lactate greatly increased the rate of the lactate oxidation at the anode under open-circuit conditions. The large decrease of open-circuit potential of the anode increased the cell voltage of the MFC and its power output. Measurements of impedance spectra for the MFC at different cell voltages resulted in determining the internal resistance (R(int)) of the MFC and it was found that R(int) is a function of cell voltage. Additionally, R(int) was equal to R(ext) at the cell voltage corresponding to maximum power, where R(ext) is the external resistance that must be applied across the circuit to obtain the maximum power output. PMID:18294928

  19. Monitoring early zeolite formation via in situ electrochemical impedance spectroscopy.

    PubMed

    Brabants, G; Lieben, S; Breynaert, E; Reichel, E K; Taulelle, F; Martens, J A; Jakoby, B; Kirschhock, C E A

    2016-04-01

    Hitherto zeolite formation has not been fully understood. Although electrochemical impedance spectroscopy has proven to be a versatile tool for characterizing ionic solutions, it was never used for monitoring zeolite growth. We show here that EIS can quantitatively monitor zeolite formation, especially during crucial early steps where other methods fall short. PMID:27020096

  20. New impedance and electrochemical image techniques for biological applications

    NASA Astrophysics Data System (ADS)

    Tao, N. J.

    2010-03-01

    A method to image local surface impedance and electrochemical current optically is developed for biological applications. The principle of the impedance imaging is based on sensitive dependence of surface plasmon resonance (SPR) on local surface charge density. The technique can image local surface impedance and charge while providing simultaneously a conventional surface plasmon resonance (SPR) image. By applying a potential modulation to a sensor surface, it is possible to obtain an image of the DC component, and the amplitude and phase images of the AC component. The DC image provides local molecular binding, as found in the conventional SPR imaging technique. The AC images are directly related to the local impedance of the surface. This imaging capability may be used as a new detection platform for DNA and protein microarrays, a new method for analyzing local molecular binding and interfacial processes and a new tool for imaging cells and tissues.

  1. Tunable nanogap devices for ultra-sensitive electrochemical impedance biosensing.

    PubMed

    Lu, Yong; Guo, Zheng; Song, Jing-Jing; Huang, Qin-An; Zhu, Si-Wei; Huang, Xing-Jiu; Wei, Yan

    2016-01-28

    A wealth of research has been available discussing nanogap devices for detecting very small quantities of biomolecules by observing their electrical behavior generally performed in dry conditions. We report that a gold nanogapped electrode with tunable gap length for ultra-sensitive detection of streptavidin based on electrochemical impedance technique. The gold nanogap is fabricated using simple monolayer film deposition and in-situ growth of gold nanoparticles in a traditional interdigitated array (IDA) microelectrode. The electrochemical impedance biosensor with a 25-nm nanogap is found to be ultra-sensitive to the specific binding of streptavidin to biotin. The binding of the streptavidin hinder the electron transfer between two electrodes, resulting in a large increase in electron-transfer resistance (Ret) for operating the impedance. A linear relation between the relative Ret and the logarithmic value of streptavidin concentration is observed in the concentration range from 1 pM (picomolar) to 100 nM (nanomolar). The lowest detectable concentration actually measured reaches 1 pM. We believe that such an electrochemical impedance nanogap biosensor provides a useful approach towards biomolecular detection that could be extended to a number of other systems. PMID:26755137

  2. On-line corrosion monitoring with electrochemical impedance spectroscopy

    SciTech Connect

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

    1994-10-01

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

  3. Electrochemical impedance spectroscopy studies of lithium diffusion in doped manganese oxide

    SciTech Connect

    Johnson, B.J.; Doughty, D.H.; Voigt, J.A.; Boyle, T.J.

    1996-06-01

    Cathode performance is critical to lithium ion rechargeable battery performance; effects of doping lithium manganese oxide cathode materials on cathode performance are being investigated. In this paper, Li diffusion in Al-doped LiMn{sub 2}O{sub 4} was studied and found to be controlled by the quantity of Al dopant. Electrochemical cycling was conducted at 0.5mA/cm{sub 2}; electrochemical impedance spectra were taken at open circuit potential, with impedance being measured at 65 kHz-0.01 Hz. As the Al dopant level was increased, the Li diffusion rate decreased; this was attributed to the decreased lattice parameter of the doped oxide.

  4. Electrochemical cell design for the impedance studies of chlorine evolution at DSA(®) anodes.

    PubMed

    Silva, J F; Dias, A C; Araújo, P; Brett, C M A; Mendes, A

    2016-08-01

    A new electrochemical cell design suitable for the electrochemical impedance spectroscopy (EIS) studies of chlorine evolution on Dimensionally Stable Anodes (DSA(®)) has been developed. Despite being considered a powerful tool, EIS has rarely been used to study the kinetics of chlorine evolution at DSA anodes. Cell designs in the open literature are unsuitable for the EIS analysis at high DSA anode current densities for chlorine evolution because they allow gas accumulation at the electrode surface. Using the new cell, the impedance spectra of the DSA anode during chlorine evolution at high sodium chloride concentration (5 mol dm(-3) NaCl) and high current densities (up to 140 mA cm(-2)) were recorded. Additionally, polarization curves and voltammograms were obtained showing little or no noise. EIS and polarization curves evidence the role of the adsorption step in the chlorine evolution reaction, compatible with the Volmer-Heyrovsky and Volmer-Tafel mechanisms. PMID:27587166

  5. Time-domain fitting of battery electrochemical impedance models

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  6. High frequency impedance spectra on the chromium dioxide thin film

    SciTech Connect

    Fu, C. M.; Lai, C. J.; Wu, J. S.; Huang, J. C. A.; Wu, C.-C.; Shyu, S.-G.

    2001-06-01

    We report on the study of high frequency magnetotransport properties of the chromium dioxide (CrO{sub 2}) thin films, grown on Si substrate using chemical vapor deposition. The film exhibits a ferromagnetic transition with a Curie temperature near 390 K. The temperature dependent spontaneous magnetization follows Bloch{close_quote}s law. The impedance spectra, being analyzed based on the fundamental electrodynamics, are demonstrated to be in a low-loss dielectric limit along with the occurrence of dielectric relaxation and magnetization response. The specific features of impedance spectra, distinct from the usual metallic ferromagnet, are attributed to the half metallic nature of CrO{sub 2}. The results explore the possibility for high frequency device applications.

  7. Revisiting the electrochemical impedance spectroscopy of magnesium with online inductively coupled plasma atomic emission spectroscopy.

    PubMed

    Shkirskiy, Viacheslav; King, Andrew D; Gharbi, Oumaïma; Volovitch, Polina; Scully, John R; Ogle, Kevin; Birbilis, Nick

    2015-02-23

    The electrochemical impedance of reactive metals such as magnesium is often complicated by an obvious inductive loop with decreasing frequency of the AC polarising signal. The characterisation and ensuing explanation of this phenomenon has been lacking in the literature to date, being either ignored or speculated. Herein, we couple electrochemical impedance spectroscopy (EIS) with online atomic emission spectroelectrochemistry (AESEC) to simultaneously measure Mg-ion concentration and electrochemical impedance spectra during Mg corrosion, in real time. It is revealed that Mg dissolution occurs via Mg(2+) , and that corrosion is activated, as measured by AC frequencies less than approximately 1 Hz approaching DC conditions. The result of this is a higher rate of Mg(2+) dissolution, as the voltage excitation becomes slow enough to enable all Mg(2+) -enabling processes to adjust in real time. The manifestation of this in EIS data is an inductive loop. The rationalisation of such EIS behaviour, as it relates to Mg, is revealed for the first time by using concurrent AESEC. PMID:25425247

  8. A CMOS Electrochemical Impedance Spectroscopy (EIS) Biosensor Array.

    PubMed

    Manickam, Arun; Chevalier, Aaron; McDermott, Mark; Ellington, Andrew D; Hassibi, Arjang

    2010-12-01

    In this paper, we present a fully integrated biosensor 10 × 10 array in a standard complementary metal-oxide semiconducor process, which takes advantage of electrochemical impedance spectroscopy (EIS). We also show that this system is able to detect various biological analytes, such as DNA and proteins, in real time and without the need for molecular labels. In each pixel of this array, we implement a biocompatible Au electrode transducer and embedded sensor circuitry which takes advantage of the coherent detector to measure the impedance of the associated electrode-electrolyte interface. This chip is capable of concurrently measuring admittance values as small as 10(-8) Ω(-1) within the array with the detection dynamic range of more than 90 dB in the frequency range of 10 Hz-50 MHz. PMID:23850755

  9. Evaluation of non toxic alkyd primers by electrochemical impedance spectroscopy

    SciTech Connect

    Hernandez, L.S.; Garcia, G. |; Lopez, C.

    1998-12-31

    The purpose of this work was to compare the protective capacity of several alkyd primers pigmented with 12.1 volume percent either of calcium phosphate or micronized zinc phosphate as anticorrosive pigments. A paint containing zinc chromate was used as reference. The performance of these paints on steel was assessed through Electrochemical Impedance Spectroscopy (EIS) using a 3% NaCl solution. After 576 hr immersion, the paint with calcium phosphate and specially that with micronized zinc phosphate, showed a better behavior than paint with zinc chromate. Paint rating, using impedance parameters (ionic resistance and capacitance of the paint film, and breakpoint frequency), was in agreement with the visible paint deterioration and corrosion, In addition, there was a good correlation between these parameter and the open circuit corrosion potential of the metallic substrate.

  10. Organic electrochemical transistors for cell-based impedance sensing

    SciTech Connect

    Rivnay, Jonathan E-mail: owens@emse.fr; Ramuz, Marc; Hama, Adel; Huerta, Miriam; Owens, Roisin M. E-mail: owens@emse.fr; Leleux, Pierre

    2015-01-26

    Electrical impedance sensing of biological systems, especially cultured epithelial cell layers, is now a common technique to monitor cell motion, morphology, and cell layer/tissue integrity for high throughput toxicology screening. Existing methods to measure electrical impedance most often rely on a two electrode configuration, where low frequency signals are challenging to obtain for small devices and for tissues with high resistance, due to low current. Organic electrochemical transistors (OECTs) are conducting polymer-based devices, which have been shown to efficiently transduce and amplify low-level ionic fluxes in biological systems into electronic output signals. In this work, we combine OECT-based drain current measurements with simultaneous measurement of more traditional impedance sensing using the gate current to produce complex impedance traces, which show low error at both low and high frequencies. We apply this technique in vitro to a model epithelial tissue layer and show that the data can be fit to an equivalent circuit model yielding trans-epithelial resistance and cell layer capacitance values in agreement with literature. Importantly, the combined measurement allows for low biases across the cell layer, while still maintaining good broadband signal.

  11. Organic electrochemical transistors for cell-based impedance sensing

    NASA Astrophysics Data System (ADS)

    Rivnay, Jonathan; Ramuz, Marc; Leleux, Pierre; Hama, Adel; Huerta, Miriam; Owens, Roisin M.

    2015-01-01

    Electrical impedance sensing of biological systems, especially cultured epithelial cell layers, is now a common technique to monitor cell motion, morphology, and cell layer/tissue integrity for high throughput toxicology screening. Existing methods to measure electrical impedance most often rely on a two electrode configuration, where low frequency signals are challenging to obtain for small devices and for tissues with high resistance, due to low current. Organic electrochemical transistors (OECTs) are conducting polymer-based devices, which have been shown to efficiently transduce and amplify low-level ionic fluxes in biological systems into electronic output signals. In this work, we combine OECT-based drain current measurements with simultaneous measurement of more traditional impedance sensing using the gate current to produce complex impedance traces, which show low error at both low and high frequencies. We apply this technique in vitro to a model epithelial tissue layer and show that the data can be fit to an equivalent circuit model yielding trans-epithelial resistance and cell layer capacitance values in agreement with literature. Importantly, the combined measurement allows for low biases across the cell layer, while still maintaining good broadband signal.

  12. Theoretical models for electrochemical impedance spectroscopy and local ζ-potential of unfolded proteins in nanopores

    PubMed Central

    Vitarelli, Michael J.; Talaga, David S.

    2013-01-01

    Single solid-state nanopores find increasing use for electrical detection and/or manipulation of macromolecules. These applications exploit the changes in signals due to the geometry and electrical properties of the molecular species found within the nanopore. The sensitivity and resolution of such measurements are also influenced by the geometric and electrical properties of the nanopore. This paper continues the development of an analytical theory to predict the electrochemical impedance spectra of nanopores by including the influence of the presence of an unfolded protein using the variable topology finite Warburg impedance model previously published by the authors. The local excluded volume of, and charges present on, the segment of protein sampled by the nanopore are shown to influence the shape and peak frequency of the electrochemical impedance spectrum. An analytical theory is used to relate the capacitive response of the electrical double layer at the surface of the protein to both the charge density at the protein surface and the more commonly measured zeta potential. Illustrative examples show how the theory predicts that the varying sequential regions of surface charge density and excluded volume dictated by the protein primary structure may allow for an impedance-based approach to identifying unfolded proteins. PMID:24050368

  13. Investigation of polypyrrole degradation using electrochemical impedance spectroscopy.

    PubMed

    Marchesi, L F Q P; Simões, F R; Pocrifka, L A; Pereira, E C

    2011-08-11

    In this paper, the electrochemical degradation of polypyrrole film was studied by means of overpotential application. The overpotential was 0.58 V versus SCE, and after every 5 min of application of 0.58 V, a cyclic voltammogram was recorded in the range of -0.7 to 0.5 V as well as an electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance (EIS and EQCM). The main characteristic is the huge increase in the charge transfer resistance (r(ct)), which indicates that the insertion process of ions in the polymer matrix is hindered by the electrochemical degradation. Once the process of insertion is damaged, the number of intercalated ions in the matrix should decrease, which is expressed by the low-frequency capacitance, which is proportional to the number of intercalated ions in the polymeric matrix. The decrease of intercalated ions has an influence in the mass variation of the polymer film, which is confirmed by EQCM measurements. PMID:21721565

  14. AC impedance electrochemical modeling of lithium-ion positive electrodes.

    SciTech Connect

    Dees, D.; Gunen, E.; Abraham, D.; Jansen, A.; Prakash, J.; Chemical Engineering; IIT

    2004-01-01

    Under Department of Energy's Advanced Technology Development Program,various analytical diagnostic studies are being carried out to examine the lithium-ion battery technology for hybrid electric vehicle applications, and a series of electrochemical studies are being conducted to examine the performance of these batteries. An electrochemical model was developed to associate changes that were observed in the post-test analytical diagnostic studies with the electrochemical performance loss during testing of lithium ion batteries. While both electrodes in the lithium-ion cell have been studied using a similar electrochemical model, the discussion here is limited to modeling of the positive electrode. The positive electrode under study has a composite structure made of a layered nickel oxide (LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2}) active material, a carbon black and graphite additive for distributing current, and a PVDF binder all on an aluminum current collector. The electrolyte is 1.2M LiPF{sub 6} dissolved in a mixture of EC and EMC and a Celgard micro-porous membrane is used as the separator. Planar test cells (positive/separator/negative) were constructed with a special fixture and two separator membranes that allowed the placement of a micro-reference electrode between the separator membranes [1]. Electrochemical studies including AC impedance spectroscopy were then conducted on the individual electrodes to examine the performance and ageing effects in the cell. The model was developed by following the work of Professor Newman at Berkeley [2]. The solid electrolyte interface (SEI) region, based on post-test analytical results, was assumed to be a film on the oxide and an oxide layer at the surface of the oxide. A double layer capacity was added in parallel with the Butler-Volmer kinetic expression. The pertinent reaction, thermodynamic, and transport equations were linearized for a small sinusoidal perturbation [3]. The resulting system of differential

  15. Botulinum neurotoxin serotypes detected by electrochemical impedance spectroscopy.

    PubMed

    Savage, Alison C; Buckley, Nicholas; Halliwell, Jennifer; Gwenin, Christopher

    2015-05-01

    Botulinum neurotoxin is one of the deadliest biological toxins known to mankind and is able to cause the debilitating disease botulism. The rapid detection of the different serotypes of botulinum neurotoxin is essential for both diagnosis of botulism and identifying the presence of toxin in potential cases of terrorism and food contamination. The modes of action of botulinum neurotoxins are well-established in literature and differ for each serotype. The toxins are known to specifically cleave portions of the SNARE proteins SNAP-25 or VAMP; an interaction that can be monitored by electrochemical impedance spectroscopy. This study presents a SNAP-25 and a VAMP biosensors for detecting the activity of five botulinum neurotoxin serotypes (A-E) using electrochemical impedance spectroscopy. The biosensors are able to detect concentrations of toxins as low as 25 fg/mL, in a short time-frame compared with the current standard methods of detection. Both biosensors show greater specificity for their compatible serotypes compared with incompatible serotypes and denatured toxins. PMID:25954998

  16. Botulinum Neurotoxin Serotypes Detected by Electrochemical Impedance Spectroscopy

    PubMed Central

    Savage, Alison C.; Buckley, Nicholas; Halliwell, Jennifer; Gwenin, Christopher

    2015-01-01

    Botulinum neurotoxin is one of the deadliest biological toxins known to mankind and is able to cause the debilitating disease botulism. The rapid detection of the different serotypes of botulinum neurotoxin is essential for both diagnosis of botulism and identifying the presence of toxin in potential cases of terrorism and food contamination. The modes of action of botulinum neurotoxins are well-established in literature and differ for each serotype. The toxins are known to specifically cleave portions of the SNARE proteins SNAP-25 or VAMP; an interaction that can be monitored by electrochemical impedance spectroscopy. This study presents a SNAP-25 and a VAMP biosensors for detecting the activity of five botulinum neurotoxin serotypes (A–E) using electrochemical impedance spectroscopy. The biosensors are able to detect concentrations of toxins as low as 25 fg/mL, in a short time-frame compared with the current standard methods of detection. Both biosensors show greater specificity for their compatible serotypes compared with incompatible serotypes and denatured toxins. PMID:25954998

  17. Inductive phenomena at low frequencies in impedance spectra of proton exchange membrane fuel cells - A review

    NASA Astrophysics Data System (ADS)

    Pivac, Ivan; Barbir, Frano

    2016-09-01

    The results of electrochemical impedance spectroscopy of proton exchange membrane (PEM) fuel cells may exhibit inductive phenomena at low frequencies. The occurrence of inductive features at high frequencies is explained by the cables and wires of the test system. However, explanation of inductive loop at low frequencies requires a more detailed study. This review paper discusses several possible causes of such inductive behavior in PEM fuel cells, such as side reactions with intermediate species, carbon monoxide poisoning, and water transport, also as their equivalent circuit representations. It may be concluded that interpretation of impedance spectra at low frequencies is still ambiguous, and that better equivalent circuit models are needed with clearly defined physical meaning of each of the circuit elements.

  18. Electrochemical noise and impedance analysis of iron in chloride media

    SciTech Connect

    Mansfeld, F.; Xiao, H.

    1996-12-31

    Potential and current noise data have been collected for pure iron foils exposed to 0.5N sodium chloride (NaCl) that was aerated, deaerated, or aerated with sodium nitrite (NaNO{sub 2}) added as inhibitor. Potential and current noise data were obtained at the beginning of each hour over a 24-h period either sequentially or simultaneously. Statistical and spectral analyses were performed resulting in noise resistance values. For the noise resistance R{sub n} = {sigma}V/{sigma}I, where {sigma}V and {sigma}I are the standard deviation values of potential and current, respectively, similar values as for the polarization resistance R{sub p} determined with electrochemical impedance spectroscopy (EIS) at the end of the tests were obtained. The spectral noise resistance R{sub sn}{sup o} obtained from spectral analysis of simultaneously collected current and potential data agreed satisfactorily with R{sub p} and R{sub n} for aerated and inhibited solutions. Electrochemical noise and impedance data have also been obtained for two polymer coatings on cold-rolled steel during immersion in 0.5N NaCl for five months. The two types of measurements clearly distinguished between the relatively poor performance of the alkyd system and the excellent performance of the epoxy polyamide system. Similar trends with exposure time were observed for the pore resistance R{sub po} and R{sub p}, on the one hand, and R{sub n} and R{sub sn}{sup o} on the other hand. However, the numerical values of the parameters obtained with EIS were different from those obtained with electrochemical noise analysis (ENA).

  19. Electrochemical impedance spectroscopy based MEMS sensors for phthalates detection in water and juices

    NASA Astrophysics Data System (ADS)

    Zia, Asif I.; Mohd Syaifudin, A. R.; Mukhopadhyay, S. C.; Yu, P. L.; Al-Bahadly, I. H.; Gooneratne, Chinthaka P.; Kosel, Jǘrgen; Liao, Tai-Shan

    2013-06-01

    Phthalate esters are ubiquitous environmental and food pollutants well known as endocrine disrupting compounds (EDCs). These developmental and reproductive toxicants pose a grave risk to the human health due to their unlimited use in consumer plastic industry. Detection of phthalates is strictly laboratory based time consuming and expensive process and requires expertise of highly qualified and skilled professionals. We present a real time, non-invasive, label free rapid detection technique to quantify phthalates' presence in deionized water and fruit juices. Electrochemical impedance spectroscopy (EIS) technique applied to a novel planar inter-digital (ID) capacitive sensor plays a vital role to explore the presence of phthalate esters in bulk fluid media. The ID sensor with multiple sensing gold electrodes was fabricated on silicon substrate using micro-electromechanical system (MEMS) device fabrication technology. A thin film of parylene C polymer was coated as a passivation layer to enhance the capacitive sensing capabilities of the sensor and to reduce the magnitude of Faradic current flowing through the sensor. Various concentrations, 0.002ppm through to 2ppm of di (2-ethylhexyl) phthalate (DEHP) in deionized water, were exposed to the sensing system by dip testing method. Impedance spectra obtained was analysed to determine sample conductance which led to consequent evaluation of its dielectric properties. Electro-chemical impedance spectrum analyser algorithm was employed to model the experimentally obtained impedance spectra. Curve fitting technique was applied to deduce constant phase element (CPE) equivalent circuit based on Randle's equivalent circuit model. The sensing system was tested to detect different concentrations of DEHP in orange juice as a real world application. The result analysis indicated that our rapid testing technique is able to detect the presence of DEHP in all test samples distinctively.

  20. Impedance spectra of hot, dry silicate minerals and rocks: qualitative interpretation of spectra

    USGS Publications Warehouse

    Huebner, J.S.; Dillenburg, R.G.

    1995-01-01

    Impedance spectroscopy helps distinguish the contributions that grain interiors and grain boundaries make to electrical resistance of silicate minerals and rocks. Olivine, orthopyroxene, clinopyroxenes, and both natural and synthetic clinopyroxenite were measured. A network of electrical elements is presented for use in interpreting impedance spectra and conductive paths in hot or cold, wet or dry, minerals and rocks at any pressure. In dry rocks, a series network path predominates; in wet rocks, aqueous pore fluid and crystals both conduct. Finite resistance across the sample-electrode interface is evidence that electronic charge carriers are present at the surface, and presumably within, the silicate minerals and rocks measured. -from Authors

  1. An Electrochemical Impedance Spectroscopy System for Monitoring Pineapple Waste Saccharification

    PubMed Central

    Conesa, Claudia; Ibáñez Civera, Javier; Seguí, Lucía; Fito, Pedro; Laguarda-Miró, Nicolás

    2016-01-01

    Electrochemical impedance spectroscopy (EIS) has been used for monitoring the enzymatic pineapple waste hydrolysis process. The system employed consists of a device called Advanced Voltammetry, Impedance Spectroscopy & Potentiometry Analyzer (AVISPA) equipped with a specific software application and a stainless steel double needle electrode. EIS measurements were conducted at different saccharification time intervals: 0, 0.75, 1.5, 6, 12 and 24 h. Partial least squares (PLS) were used to model the relationship between the EIS measurements and the sugar determination by HPAEC-PAD. On the other hand, artificial neural networks: (multilayer feed forward architecture with quick propagation training algorithm and logistic-type transfer functions) gave the best results as predictive models for glucose, fructose, sucrose and total sugars. Coefficients of determination (R2) and root mean square errors of prediction (RMSEP) were determined as R2 > 0.944 and RMSEP < 1.782 for PLS and R2 > 0.973 and RMSEP < 0.486 for artificial neural networks (ANNs), respectively. Therefore, a combination of both an EIS-based technique and ANN models is suggested as a promising alternative to the traditional laboratory techniques for monitoring the pineapple waste saccharification step. PMID:26861317

  2. An Electrochemical Impedance Spectroscopy System for Monitoring Pineapple Waste Saccharification.

    PubMed

    Conesa, Claudia; Ibáñez Civera, Javier; Seguí, Lucía; Fito, Pedro; Laguarda-Miró, Nicolás

    2016-01-01

    Electrochemical impedance spectroscopy (EIS) has been used for monitoring the enzymatic pineapple waste hydrolysis process. The system employed consists of a device called Advanced Voltammetry, Impedance Spectroscopy & Potentiometry Analyzer (AVISPA) equipped with a specific software application and a stainless steel double needle electrode. EIS measurements were conducted at different saccharification time intervals: 0, 0.75, 1.5, 6, 12 and 24 h. Partial least squares (PLS) were used to model the relationship between the EIS measurements and the sugar determination by HPAEC-PAD. On the other hand, artificial neural networks: (multilayer feed forward architecture with quick propagation training algorithm and logistic-type transfer functions) gave the best results as predictive models for glucose, fructose, sucrose and total sugars. Coefficients of determination (R²) and root mean square errors of prediction (RMSEP) were determined as R² > 0.944 and RMSEP < 1.782 for PLS and R² > 0.973 and RMSEP < 0.486 for artificial neural networks (ANNs), respectively. Therefore, a combination of both an EIS-based technique and ANN models is suggested as a promising alternative to the traditional laboratory techniques for monitoring the pineapple waste saccharification step. PMID:26861317

  3. Non-destructive evaluation of TBC by electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Jianqi

    The objectives of this work focus on studying the feasibility of developing electrochemical impedance spectroscopy as an NDE methodology for quality assurance and post exposure inspection of TBC. Principally air plasma sprayed TBC was investigated while APS dense vertically cracked TBC and electron beam physical vapor deposition sprayed TBC were also studied using EIS. It has been found that EIS has a great promise in TBC quality assurance and post-exposure assessment. In the quality evaluation, EIS can detect TBC topcoat thickness, porosity, and kinds of defects (pore shape, cracks, or delamination). The TBC topcoat thickness shows a linear relationship with ceramic resistance. The TBC porosity has a linear relationship with ceramic capacitance. The kinds of defects in TBC topcoat can be assessed by the value of pore resistance. In the post-exposure inspection, EIS can monitor the evolution of defects in the topcoat, porosity, the growth of TGO and thermal conductivity of TBC. There is an exponential relationship between thermal conductivity and electrochemical impedance or a logarithmic relationship between thermal conductivity and electrochemical conductance. Investigation on thermal conductivity of TBC showed the specific heat or thermal conductivity of TBC has a logarithmic relationship with temperature, respectively. Exposure temperature and time are two important factors for an increase in thermal conductivity. The higher temperature and longer the exposure, the greater increase the thermal conductivity. High temperature exposure of TBC results in phase transformations, t-ZrO2 → m-ZrO2 and t-ZrO2 → c-ZrO2 and evolution of defect (ceramic sintering). Both the phase transformations and the sintering cause an increase in thermal conductivity. However, it has been found the phase transformations are only a conservative factor while the sintering is a substantial reason for an increase in thermal conductivity. A failure mode of TBC due to sintering was

  4. The application of electrochemical impedance spectroscopy for characterizing the degradation of Ni(OH)2/NiOOH electrodes

    NASA Technical Reports Server (NTRS)

    Macdonald, Digby D.

    1989-01-01

    The use of wide-band electrochemical impedance spectroscopy is described for characterizing the degradation of porous Ni(OH)2/NiOOH electrodes in concentrated KOH electrolyte solutions. The impedance spectra are interpreted in terms of a finite electrical transmission line and the changes in the components of the electrical analog are followed as a function of cycle number. The degradation of the capacity of rolled and bonded Ni(OH)2/NiOOH electrodes is caused by rupture of ohmic contacts within the active mass and by restructuring which results in a decrease in the number of active pores.

  5. Corrosion protection of copper by polypyrrole film studied by electrochemical impedance spectroscopy and the electrochemical quartz microbalance

    NASA Astrophysics Data System (ADS)

    Lei, Yanhua; Ohtsuka, Toshiaki; Sheng, Nan

    2015-12-01

    Polypyrrole (PPy) films were synthesized on copper in solution of sodium di-hydrogen phosphate and phytate for corrosion protection. The protection properties of PPy films were comparatively investigated in NaCl solution. During two months immersion, the PPy film doped with phytate anions, working as a cationic perm-selective membrane, inhibited the dissolution of copper to 1% of bare copper. Differently, the PPy film doped with di-hydrogen phosphate anions, possessing anionic perm-selectivity, was gradually reduced, and inhibited the dissolution to 7.8% of bare copper. Degradation of the PPy films was studied by comparing the electrochemical impedance spectroscopy change at different immersion time and Raman spectra change after immersion.

  6. Wavelet transformation to determine impedance spectra of lithium-ion rechargeable battery

    NASA Astrophysics Data System (ADS)

    Hoshi, Yoshinao; Yakabe, Natsuki; Isobe, Koichiro; Saito, Toshiki; Shitanda, Isao; Itagaki, Masayuki

    2016-05-01

    A new analytical method is proposed to determine the electrochemical impedance of lithium-ion rechargeable batteries (LIRB) from time domain data by wavelet transformation (WT). The WT is a waveform analysis method that can transform data in the time domain to the frequency domain while retaining time information. In this transformation, the frequency domain data are obtained by the convolution integral of a mother wavelet and original time domain data. A complex Morlet mother wavelet (CMMW) is used to obtain the complex number data in the frequency domain. The CMMW is expressed by combining a Gaussian function and sinusoidal term. The theory to select a set of suitable conditions for variables and constants related to the CMMW, i.e., band, scale, and time parameters, is established by determining impedance spectra from wavelet coefficients using input voltage to the equivalent circuit and the output current. The impedance spectrum of LIRB determined by WT agrees well with that measured using a frequency response analyzer.

  7. Electrochemical impedance study of the hematite/water interface.

    PubMed

    Shimizu, Kenichi; Lasia, Andrzej; Boily, Jean-François

    2012-05-22

    Reactions taking place on hematite (α-Fe(2)O(3)) surfaces in contact with aqueous solutions are of paramount importance to environmental and technological processes. The electrochemical properties of the hematite/water interface are central to these processes and can be probed by open circuit potentials and cyclic voltammetric measurements of semiconducting electrodes. In this study, electrochemical impedance spectroscopy (EIS) was used to extract resistive and capacitive attributes of this interface on millimeter-sized single-body hematite electrodes. This was carried out by developing equivalent circuit models for impedance data collected on a semiconducting hematite specimen equilibrated in solutions of 0.1 M NaCl and NH(4)Cl at various pH values. These efforts produced distinct sets of capacitance values for the diffuse and compact layers of the interface. Diffuse layer capacitances shift in the pH 3-11 range from 2.32 to 2.50 μF·cm(-2) in NaCl and from 1.43 to 1.99 μF·cm(-2) in NH(4)Cl. Furthermore, these values reach a minimum capacitance at pH 9, near a probable point of zero charge for an undefined hematite surface exposing a variety of (hydr)oxo functional groups. Compact layer capacitances pertain to the transfer of ions (charge carriers) from the diffuse layer to surface hydroxyls and are independent of pH in NaCl, with values of 32.57 ± 0.49 μF·cm(-2)·s(-φ). However, they decrease with pH in NH(4)Cl from 33.77 at pH 3.5 to 21.02 μF·cm(-2)·s(-φ) at pH 10.6 because of the interactions of ammonium species with surface (hydr)oxo groups. Values of φ (0.71-0.73 in NaCl and 0.56-0.67 in NH(4)Cl) denote the nonideal behavior of this capacitor, which is treated here as a constant phase element. Because electrode-based techniques are generally not applicable to the commonly insulating metal (oxyhydr)oxides found in the environment, this study presents opportunities for exploring mineral/water interface chemistry by EIS studies of single

  8. Electrochemical characterization of gelatinized starch dispersions: voltammetry and electrochemical impedance spectroscopy on platinum surface.

    PubMed

    Hernandez-Jaimes, C; Lobato-Calleros, C; Sosa, E; Bello-Pérez, L A; Vernon-Carter, E J; Alvarez-Ramirez, J

    2015-06-25

    The electrochemical properties of gelatinized starch dispersions (GSD; 5% w/w) from different botanical sources were studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests over a platinum surface. The phenomenological modelling of EIS data using equivalent circuits indicated that after gelatinization the electrical resistance was determined mainly by the resistance of insoluble material (i.e., ghosts). Sonication of the GSD disrupted the ghost microstructure, and produced an increase in electrical conductivity by reducing the resistance of the insoluble material. The CV data showed three oxidation peaks at potentials where glucose solutions displayed oxidation waves. It is postulated that hydrolysis at the bulk and electrocatalyzed oxidation on the Pt-surface are reactions involved in the starch transformation. Starches peak intensity increased with the amylose content, suggesting that the amylose-rich matrix played an important role in the charge transfer in the electrolytic system. PMID:25839788

  9. Formation, Structure and Electrochemical Impedance Analysis of Microporous Polyelectrolyte Multilayers

    NASA Astrophysics Data System (ADS)

    Lutkenhaus, Jodie; McEnnis, Kathleen; Hammond, Paula

    2007-03-01

    Microporous networks are of interest as electrolyte materials, gas separation membranes and catalytic nanoparticle templates. Here, we create microporous polyelectrolyte networks of tunable pore size and connectivity using the layer-by-layer (LBL) technique. In this method, a film is formed from the alternate adsorption of oppositely charged polyelectrolytes from aqueous solution to create a cohesive thin film. Using poly(ethylene imine) (PEI) and poly(acrylic acid) (PAA), LBL thin films of variable composition and charge density were assembled; then, the films were treated in an acidic bath, which ionizes PEI and de-ionizes PAA. This shift in charge density induces morphological rearrangement realized by a microporous network. Depending on the assembly pH and acidic bath pH, we are able to precisely tune the morphology, which is characterized by atomic force microscopy and scanning electron microscopy. To demonstrate the porous nature of the polyelectrolyte multilayer, the pores were filled with non-aqueous electrolyte (i.e. ethylene carbonate, dimethyl carbonate and lithium hexafluorophosphate) and probed with electrochemical impedance spectroscopy. These microporous networks exhibited two time constants, indicative of ions traveling through the liquid-filled pores and ions traveling through the polyelectrolyte matrix.

  10. Characterization of Molybdate Conversion Coatings for Aluminum Alloys by Electrochemical Impedance Spectroscopy

    NASA Technical Reports Server (NTRS)

    Calle, Luz Marina

    2000-01-01

    Electrochemical impedance spectroscopy (EIS) was used to investigate the corrosion inhibiting properties of newly developed proprietary molybdate conversion coatings on aluminum alloy 2024-T3 under immersion in aerated 5% (w/w) NaCl. Corrosion potential and EIS measurements were gathered for six formulations of the coating at several immersion times for two weeks. Nyquist as well as Bode plots of the data were obtained. The conversion-coated alloy panels showed an increase in the corrosion potential during the first 24 hours of immersion that later subsided and approached a steady value. Corrosion potential measurements indicated that formulations A, D, and F exhibit a protective effect on aluminum 2024-T3. The EIS spectra of the conversion-coated alloy were characterized by an impedance that is higher than the impedance of the bare alloy at all the immersion times. The low frequency impedance, Z(sub lf) (determined from the value at 0.05 Hz) for the conversion-coated alloy was higher at all the immersion times than that of the bare panel. This indicates improvement of corrosion resistance with addition of the molybdate conversion coating. Scanning electron microscopy (SEM) revealed the presence of cracks in the coating and the presence of cubic crystals believed to be calcium carbonate. Energy dispersive spectroscopy (EDS) of the test panels revealed the presence of high levels of aluminum, oxygen, and calcium but did not detect the presence of molybdenum on the test panels. X-ray photoelectron spectroscopy (XPS) indicated the presence of less than 0.01 atomic percent molybdenum on the surface of the coating.

  11. The application of electrochemical impedance spectroscopy for characterizing the degradation of Ni(OH)2/NiOOH electrodes

    NASA Technical Reports Server (NTRS)

    Macdonald, D. D.; Pound, B. G.; Lenhart, S. J.

    1989-01-01

    Electrochemical impedance spectra of rolled and bonded and sintered porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes for rolled and bonded electrodes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (non-porous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low. Transmission line modeling results suggest that porous rolled and bonded nickel electrodes undergo restructuring during charge/discharge cycling prior to failure.

  12. Constituent phases of the passive film formed on 2205 stainless steel by dynamic electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Cheng, Xue-Qun; Li, Cheng-Tao; Dong, Chao-Fang; Li, Xiao-Gang

    2011-02-01

    The passive film formed on 2205 duplex stainless steel (DSS) in 0.5 M NaHCO3+0.5 M NaCl aqueous solution was characterized by electrochemical measurements, including potentiodynamic anodic polarization and dynamic electrochemical impedance spectroscopy (DEIS). The results demonstrate that there is a great difference between the passive film evolutions of ferrite and austenite. The impedance values of ferrite are higher than those of austenite. The impedance peaks of ferritic and austenitic phases correspond to the potential of 0.15 and 0.25 V in the low potential range and correspond to 0.8 and 0.75 V in the high potential range. The evolutions of the capacitance of both phases are reverse compared to the evolutions of impedance. The thickness variations obtained from capacitance agree well with those of impedance analysis. The results can be used to explain why pitting corrosion occurs more easily in austenite phase than in ferrite phase.

  13. The influence of nanopore dimensions on the electrochemical properties of nanopore arrays studied by impedance spectroscopy.

    PubMed

    Kant, Krishna; Priest, Craig; Shapter, Joe G; Losic, Dusan

    2014-01-01

    The understanding of the electrochemical properties of nanopores is the key factor for better understanding their performance and applications for nanopore-based sensing devices. In this study, the influence of pore dimensions of nanoporous alumina (NPA) membranes prepared by an anodization process and their electrochemical properties as a sensing platform using impedance spectroscopy was explored. NPA with four different pore diameters (25 nm, 45 nm and 65 nm) and lengths (5 μm to 20 μm) was used and their electrochemical properties were explored using different concentration of electrolyte solution (NaCl) ranging from 1 to 100 μM. Our results show that the impedance and resistance of nanopores are influenced by the concentration and ion species of electrolytes, while the capacitance is independent of them. It was found that nanopore diameters also have a significant influence on impedance due to changes in the thickness of the double layer inside the pores. PMID:25393785

  14. Single cells and intracellular processes studied by a plasmonic-based electrochemical impedance microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Foley, Kyle; Shan, Xiaonan; Wang, Shaopeng; Eaton, Seron; Nagaraj, Vinay J.; Wiktor, Peter; Patel, Urmez; Tao, Nongjian

    2011-03-01

    Electrochemical impedance spectroscopy is a crucial tool for the detection and study of various biological substances, from DNA and proteins to viruses and bacteria. It does not require any labelling species, and methods based on it have been developed to study cellular processes (such as cell spreading, adhesion, invasion, toxicology and mobility). However, data have so far lacked spatial information, which is essential for investigating heterogeneous processes and imaging high-throughput microarrays. Here, we report an electrochemical impedance microscope based on surface plasmon resonance that resolves local impedance with submicrometre spatial resolution. We have used an electrochemical impedance microscope to monitor the dynamics of cellular processes (apoptosis and electroporation of individual cells) with millisecond time resolution. The high spatial and temporal resolution makes it possible to study individual cells, but also resolve subcellular structures and processes without labels, and with excellent detection sensitivity (~2 pS). We also describe a model that simulates cellular and electrochemical impedance microscope images based on local dielectric constant and conductivity.

  15. In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

    SciTech Connect

    Bertram, F. Evertsson, J.; Messing, M. E.; Mikkelsen, A.; Lundgren, E.; Zhang, F.; Pan, J.; Carlà, F.; Nilsson, J.-O.

    2014-07-21

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  16. In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Bertram, F.; Zhang, F.; Evertsson, J.; Carlà, F.; Pan, J.; Messing, M. E.; Mikkelsen, A.; Nilsson, J.-O.; Lundgren, E.

    2014-07-01

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  17. ELECTROCHEMICAL IMPEDANCE ANALYSIS OF beta-TITANIUM ALLOYS AS IMPLANTS IN RINGERS LACTATE SOLUTION

    SciTech Connect

    Bhola, Rahul; Bhola, Shaily M.; Mishra, Brajendra; Olson, David L.

    2010-02-22

    Commercially pure titanium and two beta-titanium alloys, TNZT and TMZF, have been characterized using various electrochemical techniques for their corrosion behavior in Ringers lactate solution. The variation of corrosion potential and solution pH with time has been discussed. Electrochemical Impedance Spectroscopy has been used to fit the results into a circuit model. The stability of the oxides formed on the surface of these alloys has been correlated with impedance phase angles. Cyclic Potentiodynamic Polarization has been used to compute the corrosion parameters for the alloys. TMZF is found to be a better beta-alloy as compared to TNZT.

  18. Electrochemical Impedance Analysis of β-TITANIUM Alloys as Implants in Ringers Lactate Solution

    NASA Astrophysics Data System (ADS)

    Bhola, Rahul; Bhola, Shaily M.; Mishra, Brajendra; Olson, David L.

    2010-02-01

    Commercially pure titanium and two β-titanium alloys, TNZT and TMZF, have been characterized using various electrochemical techniques for their corrosion behavior in Ringers lactate solution. The variation of corrosion potential and solution pH with time has been discussed. Electrochemical Impedance Spectroscopy has been used to fit the results into a circuit model. The stability of the oxides formed on the surface of these alloys has been correlated with impedance phase angles. Cyclic Potentiodynamic Polarization has been used to compute the corrosion parameters for the alloys. TMZF is found to be a better β-alloy as compared to TNZT.

  19. Investigation of water and ice by ac impedance using electrochemical properties cup.

    PubMed

    Chin, K B; Buehler, M G; Seshadri, S; Keymeulen, D; Anderson, R C; Dutz, S; Narayanan, S R

    2007-01-01

    Water and ice were investigated by ac impedance with the electrochemical properties cup in an effort to develop an in situ instrument for water characterization. In liquid water, the impedance modulus decreased with the increase in charge carriers. In the ice, the impedance measurements were characterized by the dielectric relaxation and its corresponding activation energy. The activation energy of 0.400 eV was determined for pure ice. With ice containing Cl(-) anions, the activation energy was 0.24 eV. H(+) and OH(-) doped ice has the lowest activation energy for dielectric relaxation. Results from previous works are similar to the results reported in this study. PMID:17503953

  20. A study on the impact of lithium-ion cell relaxation on electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Barai, Anup; Chouchelamane, Gael H.; Guo, Yue; McGordon, Andrew; Jennings, Paul

    2015-04-01

    Lithium-ion (Li-ion) batteries are of great interest to the automotive industry due to their higher power and energy density, higher cell voltage, longer cycle life and lower self-discharge compared to other battery chemistries. Electrochemical impedance spectroscopy is a powerful tool employed to investigate the fundamental electrochemical reactions within a Li-ion battery cell, which relates to state of charge, internal temperature and state of health. Its effectiveness has established it as a core method to study electrochemical behaviour of batteries in both off-line and on-line applications. In this work it is shown that in addition to state of charge, internal temperature and state of health, the time period between the removal of an electrical load and the impedance measurement affects the results. The study of five commercially available cells of varying capacities and electrode chemistries show that, regardless of cell type, maximum impedance change takes place within the first 4 h of the relaxation period. The root cause of this impedance change has been discussed from an electrochemical perspective.

  1. Estimation of parameters obtained by electrochemical impedance spectroscopy on systems containing high capacities.

    PubMed

    Stević, Zoran; Vujasinović, Mirjana Rajčić; Radunović, Milan

    2009-01-01

    Electrochemical systems with high capacities demand devices for electrochemical impedance spectroscopy (EIS) with ultra-low frequencies (in order of mHz), that are almost impossible to accomplish with analogue techniques, but this becomes possible by using a computer technique and accompanying digital equipment. Recently, an original software and hardware for electrochemical measurements, intended for electrochemical systems exhibiting high capacities, such as supercapacitors, has been developed. One of the included methods is EIS. In this paper, the method of calculation of circuit parameters from an EIS curve is described. The results of testing on a physical model of an electrochemical system, constructed of known elements (including a 1.6 F capacitor) in a defined arrangement, proved the validity of the system and the method. PMID:22400000

  2. Estimation of Parameters Obtained by Electrochemical Impedance Spectroscopy on Systems Containing High Capacities

    PubMed Central

    Stević, Zoran; Vujasinović, Mirjana Rajčić; Radunović, Milan

    2009-01-01

    Electrochemical systems with high capacities demand devices for electrochemical impedance spectroscopy (EIS) with ultra-low frequencies (in order of mHz), that are almost impossible to accomplish with analogue techniques, but this becomes possible by using a computer technique and accompanying digital equipment. Recently, an original software and hardware for electrochemical measurements, intended for electrochemical systems exhibiting high capacities, such as supercapacitors, has been developed. One of the included methods is EIS. In this paper, the method of calculation of circuit parameters from an EIS curve is described. The results of testing on a physical model of an electrochemical system, constructed of known elements (including a 1.6 F capacitor) in a defined arrangement, proved the validity of the system and the method. PMID:22400000

  3. Electrochemical detection of the amino-substituted naphthalene compounds based on intercalative interaction with hairpin DNA by electrochemical impedance spectroscopy.

    PubMed

    Liang, Gang; Li, Tao; Li, Xiaohong; Liu, Xinhui

    2013-10-15

    The amino-substituted naphthalene compounds, such as 1,8-diaminonaphthalene (1,8-DANAP), 2,3-diaminonaphthalene (2,3-DANAP), 1,5-diaminonaphthalene (1,5-DANAP), 1-naphthylamine (1-NAP) and 2-naphthylamine (2-NAP), were investigated by electrochemical impedance spectroscopy (EIS), which was based on the interaction with hairpin DNA immobilized on the gold electrodes. Upon hairpin DNA interacting with the target chemicals, the charge transfer resistance (RCT) of the hairpin DNA films was significantly decreased and the charge transfer resistance change (ΔR(CT)) decreased in a sequence of ΔR(CT) (1,8-DANAP)>ΔR(CT) (2,3-DANAP)>ΔR(CT) (1,5-DANAP)>ΔR(CT) (1-NAP)>ΔR(CT) (2-NAP). The ΔR(CT) changes were due to the difference in the binding constant (K(SV)) of the target chemicals to DNA. In addition, the interaction mechanism was further explored using 1,8-DANAP as a model analyte by fluorescence spectra, Raman spectroscopy, differential pulse voltammetry (DPV) and EIS, correspondingly. The results demonstrated that the amino-substituted naphthalene compounds intercalated into "stem" appearing in the hairpin DNA. Moreover, the hairpin DNA sensor exhibited high sensitivity to the amino-substituted naphthalene compounds with the detection limit of nano-mole, and maintained high selectivity over other selected environmental pollutants. Finally, the DNA sensor was challenged in natural water sample with a recovery of 96-102%, which offered a platform for prospective future development of a simple, rapid, sensitive and low-cost assay for the detection of target aromatic amine pollutants. PMID:23693094

  4. Analysis of bio-anode performance through electrochemical impedance spectroscopy.

    PubMed

    ter Heijne, Annemiek; Schaetzle, Olivier; Gimenez, Sixto; Navarro, Lucia; Hamelers, Bert; Fabregat-Santiago, Francisco

    2015-12-01

    In this paper we studied the performance of bioanodes under different experimental conditions using polarization curves and impedance spectroscopy. We have identified that the large capacitances of up to 1 mF·cm(-2) for graphite anodes have their origin in the nature of the carbonaceous electrode, rather than the microbial culture. In some cases, the separate contributions of charge transfer and diffusion resistance were clearly visible, while in other cases their contribution was masked by the high capacitance of 1 mF·cm(-2). The impedance data were analyzed using the basic Randles model to analyze ohmic, charge transfer and diffusion resistances. Increasing buffer concentration from 0 to 50mM and increasing pH from 6 to 8 resulted in decreased charge transfer and diffusion resistances; lowest values being 144 Ω·cm(2) and 34 Ω·cm(2), respectively. At acetate concentrations below 1 mM, current generation was limited by acetate. We show a linear relationship between inverse charge transfer resistance at potentials close to open circuit and saturation (maximum) current, associated to the Butler-Volmer relationship that needs further exploration. PMID:25869113

  5. Electrochemical impedance spectroscopy of lithium-titanium disulfide rechargeable cells

    NASA Technical Reports Server (NTRS)

    Narayanan, S. R.; Shen, D. H.; Surampudi, S.; Attia, A. I.; Halpert, G.

    1993-01-01

    The two-terminal alternating current impedance of Li/TiS2 rechargeable cells was studied as a function of frequency, state-of-charge, and extended cycling. Analysis based on a plausible equivalent circuit model for the Li/TiS2 cell leads to evaluation of kinetic parameters for the various physicochemical processes occurring at the electrode/electrolyte interfaces. To investigate the causes of cell degradation during extended cycling, the parameters evaluated for cells cycled 5 times were compared with the parameters of cells cycled over 600 times. The findings are that the combined ohmic resistance of the electrolyte and electrodes suffers a tenfold increase after extended cycling, while the charge-transfer resistance and diffusional impedance at the TiS2/electrolyte interface are not significantIy affected. The results reflect the morphological change and increase in area of the anode due to cycling. The study also shows that overdischarge of a cathode-limited cell causes a decrease in the diffusion coefficient of the lithium ion in the cathode.

  6. Predicting molecular scale skin-effect in electrochemical impedance due to anomalous subdiffusion mediated adsorption phenomenon

    NASA Astrophysics Data System (ADS)

    Kushagra, Arindam

    2016-02-01

    Anomalous subdiffusion governs the processes which are not energetically driven, on a molecular scale. This paper proposes a model to predict the response of electrochemical impedance due to such diffusion process. Previous works considered the use of fractional calculus to predict the impedance behaviour in response to the anomalous diffusion. Here, we have developed an expression which predicts the skin-effect, marked by an increase in the impedance with increasing frequency, in this regime. Negative inductances have also been predicted as a consequence of the inertial response of adsorbed species upon application of frequency-mediated perturbations. It might help the researchers in the fields of impedimetric sensors to choose the working frequency and those working in the field of batteries to choose the parameters, likewise. This work would shed some light into the molecular mechanisms governing the impedance when exposed to frequency-based perturbations like electromagnetic waves (microwaves to ionizing radiations) and in charge storage devices like batteries etc.

  7. Graphical analysis of electrochemical impedance spectroscopy data in Bode and Nyquist representations

    NASA Astrophysics Data System (ADS)

    Huang, Jun; Li, Zhe; Liaw, Bor Yann; Zhang, Jianbo

    2016-03-01

    Though it becomes a routine to fit impedance data to an equivalent electric circuit model (EECM) using complex nonlinear least square (CNLS) to extract physical parameters from impedance data, two formidable challenges still remain: to build a physically meaningful EECM and to find good initial estimates for model parameters. In this study, combining graphical analysis of impedance data in both Bode and Nyquist plots, a two-step procedure is proposed to address the challenges: (1) a frequency derivative phase angle method is developed in Bode plot to identify the number of time constants (or electrochemical processes); (2) graphical analysis of impedance data in Nyquist plot is used sequentially for initial parameter determination. Major graphical analysis methods are compared in terms of frequency resolution, accuracy and complexity using synthetic data. The superiority of the proposed procedure is illustrated using the experimental data of a three-electrode lithium-ion cell.

  8. Report on the source of the electrochemical impedance on cermet inert anodes

    SciTech Connect

    Windisch, C.F. Jr.; Stice, N.D.

    1991-02-01

    the Inert Electrode Program at Pacific Northwest Laboratory (PNL) is supported by the Office of Industrial Processes of the US Department of Energy and is aimed at improving the energy efficiency of Hall-Heroult cells through the development of inert anodes. The inert anodes currently under study are composed of a cermet material of the general composition NiO-NiFe{sub 2}O{sub 4}-Cu. The program has three primary objectives: (a) to evaluate the anode material in a scaled-up, pilot cell facility, (b) to investigate the mechanisms of the electrochemical reactions at the anode surface, and (c) to develop sensors for monitoring anode and/or electrolyte conditions. This report covers the results of a portion of the studies on anode reaction mechanisms. The electrochemical impedances of cermet inert anodes in alumina-saturated molten cryolite as a function of frequency, current density, and time indicated that a significant component of the impedance is due to the gas bubbles produced at the anode during electrolysis. The data also showed a connection between surface structure and impedance that appears to be related to the effects of surface structure on bubble flow. Given the results of this work, it is doubtful that a resistive film contributes significantly to the electrochemical impedances on inert anodes. Properties previously assigned to such a film are more likely due to the bubbles and those factors that affect the properties and dynamics of the bubbles at the anode surface. 12 refs., 16 figs., 3 tabs.

  9. Electrochemical Impedance Spectroscopy Investigation on the Clinical Lifetime of ProTaper Rotary File System

    PubMed Central

    Pirvu, Cristian; Demetrescu, Ioana

    2014-01-01

    The main objective of the current paper is to show that electrochemical impedance spectroscopy (EIS) could be a method for evaluating and predicting of ProTaper rotary file system clinical lifespan. This particular aspect of everyday use of the endodontic files is of great importance in each dental practice and has profound clinical implications. The method used for quantification resides in the electrochemical impedance spectroscopy theory and has in its main focus the characteristics of the surface titanium oxide layer. This electrochemical technique has been adapted successfully to identify the quality of the Ni-Ti files oxide layer. The modification of this protective layer induces changes in corrosion behavior of the alloy modifying the impedance value of the file. In order to assess the method, 14 ProTaper sets utilized on different patients in a dental clinic have been submitted for testing using EIS. The information obtained in regard to the surface oxide layer has offered an indication of use and proves that the said layer evolves with each clinical application. The novelty of this research is related to an electrochemical technique successfully adapted for Ni-Ti file investigation and correlation with surface and clinical aspects. PMID:24605336

  10. Effects of Nitrogen on Passivity of Nickel-Free Stainless Steels by Electrochemical Impedance Spectroscopy Analysis

    NASA Astrophysics Data System (ADS)

    Wu, Xinqiang; Fu, Yao; Ke, Wei; Xu, Song; Feng, Bing; Hu, Botao

    2015-09-01

    The effects of different nitrogen contents on the passivity of nickel-free stainless steels in 0.5 M sulfuric acid + 0.5 M sodium chloride solution were investigated by electrochemical impedance spectroscopy in the potential ranges of active dissolution and active-passive transition. A simplified reaction model containing adsorbed intermediates involved dissolution process, and passivation process was proposed to explain the impedance characteristics. Based on both equivalent circuit and mathematical model analysis, the effects of nitrogen on the passivity of stainless steels are discussed.

  11. Electrochemical impedance spectroscopy based-on interferon-gamma detection

    NASA Astrophysics Data System (ADS)

    Li, Guan-Wei; Kuo, Yi-Ching; Tsai, Pei-I.; Lee, Chih-Kung

    2014-03-01

    Tuberculosis (TB) is an ancient disease constituted a long-term menace to public health. According to World Health Organization (WHO), mycobacterium tuberculosis (MTB) infected nearly a third of people of the world. There is about one new TB occurrence every second. Interferon-gamma (IFN-γ) is associated with susceptibility to TB, and interferongamma release assays (IGRA) is considered to be the best alternative of tuberculin skin test (TST) for diagnosis of latent tuberculosis infection (LTBI). Although significant progress has been made with regard to the design of enzyme immunoassays for IFN-γ, adopting this assay is still labor-intensive and time-consuming. To alleviate these drawbacks, we used IFN-γ antibody to facilitate the detection of IFN-γ. An experimental verification on the performance of IGRA was done in this research. We developed two biosensor configurations, both of which possess high sensitivity, specificity, and rapid IFN-γ diagnoses. The first is the electrochemical method. The second is a circular polarization interferometry configuration, which incorporates two light beams with p-polarization and s-polarization states individually along a common path, a four photo-detector quadrature configuration to arrive at a phase modulated ellipsometer. With these two methods, interaction between IFN-γ antibody and IFN-γ were explored and presented in detail.

  12. Electrochemical impedance analysis of spray deposited CZTS thin film: Effect of Se introduction

    NASA Astrophysics Data System (ADS)

    Patil, Swati J.; Lokhande, Vaibhav C.; Lee, Dong-Weon; Lokhande, Chandrakant D.

    2016-08-01

    The present work deals with electrochemical impedance analysis of spray deposited Cu2ZnSnS4 (CZTS) thin films grown on fluorine doped tin oxide (FTO) substrates and effect of post Se introduction. The CZTS thin films are characterized using X-ray diffraction (XRD), X-Ray photo spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM) and UV-Vis spectroscopy techniques. The electrochemical measurements are carried out using impedance analysis spectroscopy. The strong peak in XRD pattern along (112) plane confirms the Kestrite crystal structure of CZTS film. The FE-SEM analysis reveals that nanoflakes contain crack-free surface microstructure changes with post Se introucation. The optical study reveals that absorption increases with Se dipping time and observed lower band gap of 1.31 eV. Introduction of Se in CZTS film results an improvement in the grain size and surface morphology which leads to increased electrical conductivity of CZTS film.

  13. Direct immobilization of antibodies on a new polymer film for fabricating an electrochemical impedance immunosensor.

    PubMed

    Zhang, Xiangyang; Shen, Guangyu; Shen, Youming; Yin, Dan; Zhang, Chunxiang

    2015-09-15

    A new polymer bearing aldehyde groups was designed and synthesized by grafting 4-pyridinecarboxaldehyde onto poly(epichlorohydrin). Antibodies can be directly immobilized on the surface of the polymer film through the covalent bonding of aldehyde groups of the film with amino groups of antibodies. In this study, human immunoglobulin G (IgG) was used as a model analyte for the fabrication of an electrochemical impedance immunosensor. Using the proposed immunosensor, IgG in the range from 0.1 to 80 ng ml(-1) was detected with a detection limit of 0.07 ng ml(-1) (signal/noise [S/N]=3). In addition, the electrochemical impedance immunosensor displays good stability and reproducibility. PMID:26072006

  14. Electrochemical impedance analysis of spray deposited CZTS thin film: Effect of Se introduction

    NASA Astrophysics Data System (ADS)

    Patil, Swati J.; Lokhande, Vaibhav C.; Lee, Dong-Weon; Lokhande, Chandrakant D.

    2016-08-01

    The present work deals with electrochemical impedance analysis of spray deposited Cu2ZnSnS4 (CZTS) thin films grown on fluorine doped tin oxide (FTO) substrates and effect of post Se introduction. The CZTS thin films are characterized using X-ray diffraction (XRD), X-Ray photo spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM) and UV-Vis spectroscopy techniques. The electrochemical measurements are carried out using impedance analysis spectroscopy. The strong peak in XRD pattern along (112) plane confirms the Kestrite crystal structure of CZTS film. The FE-SEM analysis reveals that nanoflakes contain crack-free surface microstructure changes with post Se introucation. The optical study reveals that absorption increases with Se dipping time and observed lower band gap of 1.31 eV. Introduction of Se in CZTS film results an improvement in the grain size and surface morphology which leads to increased electrical conductivity of CZTS film.

  15. Effective impedance spectra for predicting rough sea effects on atmospheric impulsive sounds.

    PubMed

    Boulanger, Patrice; Attenborough, Keith

    2005-02-01

    Two methods of calculating the effective impedance spectra of acoustically hard, randomly rough, two-dimensional surfaces valid for acoustic wavelengths large compared with the roughness scales have been explored. The first method uses the complex excess attenuation spectrum due to a point source above a rough boundary predicted by a boundary element method (BEM) and solves for effective impedance roots identified by a winding number integral method. The second method is based on an analytical theory in which the contributions from random distributions of surface scatterers are summed to obtain the total scattered field. Effective impedance spectra deduced from measurements of the complex excess attenuation above 2D randomly rough surfaces formed by semicylinders and wedges have been compared to predictions from the two approaches. Although the analytical theory gives relatively poor predictions, BEM-deduced effective impedance spectra agree tolerably well with measured data. Simple polynomials have been found to fit BEM-deduced spectra for surfaces formed by intersecting parabolas corresponding to average roughness heights between 0.25 and 7.5 m and for five incidence angles for each average height. Predicted effects of sea-surface roughness on sonic boom profiles and rise time are comparable to those due to turbulence and molecular relaxation effects. PMID:15759695

  16. A shock spectra and impedance method to determine a bound for spacecraft structural loads

    NASA Technical Reports Server (NTRS)

    Bamford, R.; Trubert, M.

    1974-01-01

    A method to determine a bound of structural loads for a spacecraft mounted on a launch vehicle is developed. The method utilizes the interface shock spectra and the relative impedance of the spacecraft and launch vehicle. The method is developed for single-degree-of-freedom models and then generalized to multidegree-of-freedom models.

  17. Evaluation of doped polyaniline as a carbon steel protective coating using electrochemical impedance spectroscopy

    SciTech Connect

    Calle, L.M.; MacDowell, L.G. III

    1997-12-01

    Electrochemical Impedance Spectroscopy (EIS) was used to evaluate the performance of two doped polyanilines, PAN, in the emeraldine base form, EB, as protective coatings for carbon steel under immersion in 3.55% NaCl. Coatings A and B consisted of EB doped with tetracyanoethylene (TCNE) and with p-toluenesulfonic acid (PTSA) respectively. The equivalent circuit R{sub e}(C{sub c}[R{sub c}(QR{sub 1})]) provided a satisfactory fit for the EIS data.

  18. Electrochemical impedance spectrum frequency optimization of bitter taste cell-based sensors.

    PubMed

    Hui, Guo-Hua; Ji, Peng; Mi, Shan-Shan; Deng, Shao-Ping

    2013-09-15

    Electrochemical impedance spectrum frequency optimization to bitter taste receptor cell-based sensors is discussed in this paper. The bitter taste receptor cells (the enteroendocrine STC-1 cells and the ICR mouse isolated taste bud cells) are cultured on carbon screen printed electrodes and used as sensing elements. The HEK-293 cells and dead isolated ICR mouse taste bud cells, without bitter taste receptor expression, are used in negative control experiments. The electrochemical impedance spectrum data is recorded and processed by bistable stochastic resonance for signal-to-noise ratio analysis. The bitter taste receptor cell-based sensor selectively responds to bitter tastants. The tastants species and concentrations can be decided by signal-to-noise ratio parameters. The signal-to-noise ratio eigen peak changes with the shift of electrochemical impedance spectrum frequencies. ICR mouse isolated taste bud cell-based sensor presents bitter tastants perception abilities. 9kHz is the optimal frequency for STC-1 cell-based sensor measurement. For isolated ICR mouse taste bud cells, 1.2kHz is the optimal frequency. Negative control experiments results indicate that cells with no taste receptor expression have no discriminating ability for tastant even if they are modulated by different frequencies. The taste cell-based sensor is of great practical value. PMID:23578970

  19. Electrochemical impedance spectroscopy of metal alloys in the space transportation system launch environment

    NASA Technical Reports Server (NTRS)

    Calle, Luz

    1990-01-01

    AC impedance measurements were performed to investigate the corrosion resistance of 18 alloys under conditions similar to the Space Transportation System (STS) launch environment. The alloys were: (1) zirconium 702; (2) Hastelloy C-22, C-276, C-4, and B-2; (3) Inconel 600 and 825; (4) Ferralium 255; (5) Inco Alloy G-3; (6) 20Cb-3; (7) SS 904L, 304LN, 316L, 317L, and 304L; (8) ES 2205; and (9) Monel 400. AC impedance data were gathered for each alloy at various immersion times in 3.55 percent NaCl-0.1N HCl. Polarization resistance values were obtained for the Nyguist plots at each immersion time using the EQUIVALENT CIRCUIT software package available with the 388 electrochemical impedance software. Hastelloy C-22 showed the highest overall values for polarization resistance while Monel 400 and Inconel 600 had the lowest overall values. There was good general correlation between the corrosion performance of the alloys at the beach corrosion testing site, and the expected rate of corrosion as predicted based on the polarization resistance values obtained. The data indicate that electrochemical impedance spectroscopy can be used to predict the corrosion performance of metal alloys.

  20. AC Impedance Studies of Polymer Light-emitting Electrochemical Cells and Light-emitting Diodes

    NASA Astrophysics Data System (ADS)

    Li, Yongfang; Gao, Jun; Heeger, Alan J.; Yu, Gang; Cao, Yong

    1998-03-01

    The alternating current (ac) impedance of polymer light-emitting electrochemical cells (LECs) is studied and compared with that of polymer light-emitting diodes(LEDs) in the frequency range from 100 Hz to 5 M Hz. The device capacitance, resistance and interface characteristics are analyzed using the frequency dependence of the impedance and plots of the imaginary component of the impedance (Z") vs. the real part (Z'). At low bias voltages, polymer LEDs behave as pure capacitors whereas the polymer blend in the LEC exhibits an ionic conductivity contribution to the impedance. With dc bias higher than the energy gap of the semiconducting polymer (eV > Eg), the Z" vs. Z' plot of the LEC is a flattened semicircle, while that of LED is a semicircle with a small tail at low frequencies. In the LED, the capacitance is independent of voltages, the film resistance decreases as the bias voltage is increased in forward bias due to charge injection at higher voltages. In the LEC, the capacitance increases at voltages sufficient to induce electrochemical redox and doping near the electrodes. From this increase, the thickness of the i-layer of the p-i-n junction is estimated to approximately 0.8 of the film thickness (at the bias voltage of 3 V). Thus, in the LEC under operating conditions, the crossover region from p-type occupies most of the film thickness.

  1. A new lithium-ion battery internal temperature on-line estimate method based on electrochemical impedance spectroscopy measurement

    NASA Astrophysics Data System (ADS)

    Zhu, J. G.; Sun, Z. C.; Wei, X. Z.; Dai, H. F.

    2015-01-01

    The power battery thermal management problem in EV (electric vehicle) and HEV (hybrid electric vehicle) has been widely discussed, and EIS (electrochemical impedance spectroscopy) is an effective experimental method to test and estimate the status of the battery. Firstly, an electrochemical-based impedance matrix analysis for lithium-ion battery is developed to describe the impedance response of electrochemical impedance spectroscopy. Then a method, based on electrochemical impedance spectroscopy measurement, has been proposed to estimate the internal temperature of power lithium-ion battery by analyzing the phase shift and magnitude of impedance at different ambient temperatures. Respectively, the SoC (state of charge) and temperature have different effects on the impedance characteristics of battery at various frequency ranges in the electrochemical impedance spectroscopy experimental study. Also the impedance spectrum affected by SoH (state of health) is discussed in the paper preliminary. Therefore, the excitation frequency selected to estimate the inner temperature is in the frequency range which is significantly influenced by temperature without the SoC and SoH. The intrinsic relationship between the phase shift and temperature is established under the chosen excitation frequency. And the magnitude of impedance related to temperature is studied in the paper. In practical applications, through obtaining the phase shift and magnitude of impedance, the inner temperature estimation could be achieved. Then the verification experiments are conduced to validate the estimate method. Finally, an estimate strategy and an on-line estimation system implementation scheme utilizing battery management system are presented to describe the engineering value.

  2. Impedance spectra classification for determining the state of charge on a lithium iron phosphate cell using a support vector machine

    NASA Astrophysics Data System (ADS)

    Jansen, P.; Vergossen, D.; Renner, D.; John, W.; Götze, J.

    2015-11-01

    An alternative method for determining the state of charge (SOC) on lithium iron phosphate cells by impedance spectra classification is given. Methods based on the electric equivalent circuit diagram (ECD), such as the Kalman Filter, the extended Kalman Filter and the state space observer, for instance, have reached their limits for this cell chemistry. The new method resigns on the open circuit voltage curve and the parameters for the electric ECD. Impedance spectra classification is implemented by a Support Vector Machine (SVM). The classes for the SVM-algorithm are represented by all the impedance spectra that correspond to the SOC (the SOC classes) for defined temperature and aging states. A divide and conquer based search algorithm on a binary search tree makes it possible to grade measured impedances using the SVM method. Statistical analysis is used to verify the concept by grading every single impedance from each impedance spectrum corresponding to the SOC by class with different magnitudes of charged error.

  3. A regenerating ultrasensitive electrochemical impedance immunosensor for the detection of adenovirus.

    PubMed

    Lin, Donghai; Tang, Thompson; Harrison, D Jed; Lee, William E; Jemere, Abebaw B

    2015-06-15

    We report on the development of a regenerable sensitive immunosensor based on electrochemical impedance spectroscopy for the detection of type 5 adenovirus. The multi-layered immunosensor fabrication involved successive modification steps on gold electrodes: (i) modification with self-assembled layer of 1,6-hexanedithiol to which gold nanoparticles were attached via the distal thiol groups, (ii) formation of self-assembled monolayer of 11-mercaptoundecanoic acid onto the gold nanoparticles, (iii) covalent immobilization of monoclonal anti-adenovirus 5 antibody, with EDC/NHS coupling reaction on the nanoparticles, completing the immunosensor. The immunosensor displayed a very good detection limit of 30 virus particles/ml and a wide linear dynamic range of 10(5). An electrochemical reductive desorption technique was employed to completely desorb the components of the immunosensor surface, then re-assemble the sensing layer and reuse the sensor. On a single electrode, the multi-layered immunosensor could be assembled and disassembled at least 30 times with 87% of the original signal intact. The changes of electrode behavior after each assembly and desorption processes were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy techniques. PMID:25562739

  4. On-line monitoring of the crystallization process: relationship between crystal size and electrical impedance spectra

    NASA Astrophysics Data System (ADS)

    Zhao, Yanlin; Yao, Jun; Wang, Mi

    2016-07-01

    On-line monitoring of crystal size in the crystallization process is crucial to many pharmaceutical and fine-chemical industrial applications. In this paper, a novel method is proposed for the on-line monitoring of the cooling crystallization process of L-glutamic acid (LGA) using electrical impedance spectroscopy (EIS). The EIS method can be used to monitor the growth of crystal particles relying on the presence of an electrical double layer on the charged particle surface and the polarization of double layer under the excitation of alternating electrical field. The electrical impedance spectra and crystal size were measured on-line simultaneously by an impedance analyzer and focused beam reflectance measurement (FBRM), respectively. The impedance spectra were analyzed using the equivalent circuit model and the equivalent circuit elements in the model can be obtained by fitting the experimental data. Two equivalent circuit elements, including capacitance (C 2) and resistance (R 2) from the dielectric polarization of the LGA solution and crystal particle/solution interface, are in relation with the crystal size. The mathematical relationship between the crystal size and the equivalent circuit elements can be obtained by a non-linear fitting method. The function can be used to predict the change of crystal size during the crystallization process.

  5. Evaluation of corrosion resistance of aluminium coating with and without annealing against molten carbonate using electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Ni, C. S.; Lu, L. Y.; Zeng, C. L.; Niu, Y.

    2014-09-01

    An arc ion plating (AIP) was used to fabricate a FeAl layer on 310S stainless steel to protect the sealing area being corroded by the molten carbonate in molten carbonate fuel cells (MCFCs). The degradation of aluminide coatings comes from both the corrosion of the coating in contact with the molten carbonate and the aluminium depletion due to the interdiffusion of aluminium and the substrate. The in-situ forming of aluminide in molten carbonate at 650 °C could be a possible way to reduce the inward diffusion of aluminium in the conventional pre-annealing at 850 °C. Electrochemical impedance spectroscopy (EIS) measurements were performed to model the corrosion of this pre-formed FeAl coating in comparison with the one formed in-situ in molten (0.62 Li+0.38 K)2CO3 at 650 °C. Although α-LiAlO2 is the corrosion product in both cases, the impedance spectra show distinct rate-limiting steps; the former is controlled by the charged particles passing through the scale, while the latter by their diffusion in the melt. The microstructure of the scale might be the reason for the difference in corrosion mechanism.

  6. Electrochemical Impedance Sensors for Monitoring Trace Amounts of NO3 in Selected Growing Media.

    PubMed

    Ghaffari, Seyed Alireza; Caron, William-O; Loubier, Mathilde; Normandeau, Charles-O; Viens, Jeff; Lamhamedi, Mohammed S; Gosselin, Benoit; Messaddeq, Younes

    2015-01-01

    With the advent of smart cities and big data, precision agriculture allows the feeding of sensor data into online databases for continuous crop monitoring, production optimization, and data storage. This paper describes a low-cost, compact, and scalable nitrate sensor based on electrochemical impedance spectroscopy for monitoring trace amounts of NO3- in selected growing media. The nitrate sensor can be integrated to conventional microelectronics to perform online nitrate sensing continuously over a wide concentration range from 0.1 ppm to 100 ppm, with a response time of about 1 min, and feed data into a database for storage and analysis. The paper describes the structural design, the Nyquist impedance response, the measurement sensitivity and accuracy, and the field testing of the nitrate sensor performed within tree nursery settings under ISO/IEC 17025 certifications. PMID:26197322

  7. Electrochemical Impedance Sensors for Monitoring Trace Amounts of NO3 in Selected Growing Media

    PubMed Central

    Ghaffari, Seyed Alireza; Caron, William-O.; Loubier, Mathilde; Normandeau, Charles-O.; Viens, Jeff; Lamhamedi, Mohammed S.; Gosselin, Benoit; Messaddeq, Younes

    2015-01-01

    With the advent of smart cities and big data, precision agriculture allows the feeding of sensor data into online databases for continuous crop monitoring, production optimization, and data storage. This paper describes a low-cost, compact, and scalable nitrate sensor based on electrochemical impedance spectroscopy for monitoring trace amounts of NO3− in selected growing media. The nitrate sensor can be integrated to conventional microelectronics to perform online nitrate sensing continuously over a wide concentration range from 0.1 ppm to 100 ppm, with a response time of about 1 min, and feed data into a database for storage and analysis. The paper describes the structural design, the Nyquist impedance response, the measurement sensitivity and accuracy, and the field testing of the nitrate sensor performed within tree nursery settings under ISO/IEC 17025 certifications. PMID:26197322

  8. Electrochemical impedance monitoring of immunochemical reactions using varying IDE geometries for signal enhancement

    NASA Astrophysics Data System (ADS)

    Page, Robin H.; McNeil, Calum

    2010-02-01

    Electrochemical Impedance Spectroscopy (EIS) has been applied to the detection of analytes for immunosensors [1-3]. The development of hand held devices based on this technique is a very promising prospect for point-of-care applications and is an attractive alternative to laboratory-based immunochemical analysis [1, 4]. The work in this paper will focus primarily on the development of an EIS method of transduction for immunoassay detection that could be potentially introduced into a hand held point-of-care device. Varying geometries of IDEs will be reported and discussed to improve the detection of antigen.

  9. A comparison of electrochemical noise and impedance spectroscopy for the detection of corrosion in reinforced concrete

    SciTech Connect

    Bertocci, U.

    1996-12-31

    Electrochemical impedance spectroscopy (EIS) and electrochemical noise measurements (ENM) were carried out on small concrete blocks with embedded steel rods, immersed in solutions of highway deicers, mainly sodium or magnesium chlorides with corrosion inhibitors added. Voltage and current fluctuations between identical electrodes were recorded, and different signal-processing schemes were tested. Various problems experienced in the course of the work are described. Corrosion polarization resistances obtained by EIS are compared with values of the ratio of the standard deviations of the voltage and current fluctuations. The results suggest that the type of ENM used in this work is subject to considerable uncertainties, and further work would be necessary before the method can be applied with sufficient confidence to corrosion monitoring.

  10. Investigation of the suppression effect of polyethylene glycol on copper electroplating by electrochemical impedance spectroscopy

    SciTech Connect

    Hung, C.-C.; Lee, W.-H.; Wang, Y.-L.; Chan, D.-Y.; Hwang, G.-J.

    2008-09-15

    Polyethylene glycol (PEG) is an additive that is commonly used as a suppressor in the semiconductor copper (Cu)-electroplating process. In this study, electrochemical impedance spectroscopy (EIS) was used to analyze the electrochemical behavior of PEG in the Cu-electroplating process. Polarization analysis, cyclic-voltammetry stripping, and cell voltage versus plating time were examined to clarify the suppression behavior of PEG. The equivalent circuit simulated from the EIS data shows that PEG inhibited the Cu-electroplating rate by increasing the charge-transfer resistance as well as the resistance of the adsorption layer. The presence of a large inductance demonstrated the strong adsorption of cuprous-PEG-chloride complexes on the Cu surface during the Cu-electroplating process. Increasing the PEG concentration appears to increase the resistances of charge transfer, the adsorption layer, and the inductance of the electroplating system.

  11. SURFACE SEGREGATION STUDIES OF SOFC CATHODES: COMBINING SOFT X-RAYS AND ELECTROCHEMICAL IMPEDENCE SPECTROSCOPY

    SciTech Connect

    Miara, Lincoln J.; Piper, L.F.J.; Davis, Jacob N.; Saraf, Laxmikant V.; Kaspar, Tiffany C.; Basu, Soumendra; Smith, K. E.; Pal, Uday B.; Gopalan, Srikanth

    2010-12-01

    A system to grow heteroepitaxial thin-films of solid oxide fuel cell (SOFC) cathodes on single crystal substrates was developed. The cathode composition investigated was 20% strontium-doped lanthanum manganite (LSM) grown by pulsed laser deposition (PLD) on single crystal (111) yttria-stabilized zirconia (YSZ) substrates. By combining electrochemical impedance spectroscopy (EIS) with x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy XAS measurements, we conclude that electrically driven cation migration away from the two-phase gas-cathode interface results in improved electrochemical performance. Our results provide support to the premise that the removal of surface passivating phases containing Sr2+ and Mn2+, which readily form at elevated temperatures even in O2 atmospheric pressures, is responsible for the improved cathodic performance upon application of a bias.

  12. Interface Design for CMOS-Integrated Electrochemical Impedance Spectroscopy (EIS) Biosensors

    PubMed Central

    Manickam, Arun; Johnson, Christopher Andrew; Kavusi, Sam; Hassibi, Arjang

    2012-01-01

    Electrochemical Impedance Spectroscopy (EIS) is a powerful electrochemical technique to detect biomolecules. EIS has the potential of carrying out label-free and real-time detection, and in addition, can be easily implemented using electronic integrated circuits (ICs) that are built through standard semiconductor fabrication processes. This paper focuses on the various design and optimization aspects of EIS ICs, particularly the bio-to-semiconductor interface design. We discuss, in detail, considerations such as the choice of the electrode surface in view of IC manufacturing, surface linkers, and development of optimal bio-molecular detection protocols. We also report experimental results, using both macro- and micro-electrodes to demonstrate the design trade-offs and ultimately validate our optimization procedures. PMID:23202170

  13. Label-Free Toxin Detection by Means of Time-Resolved Electrochemical Impedance Spectroscopy

    PubMed Central

    Chai, Changhoon; Takhistov, Paul

    2010-01-01

    The real-time detection of trace concentrations of biological toxins requires significant improvement of the detection methods from those reported in the literature. To develop a highly sensitive and selective detection device it is necessary to determine the optimal measuring conditions for the electrochemical sensor in three domains: time, frequency and polarization potential. In this work we utilized a time-resolved electrochemical impedance spectroscopy for the detection of trace concentrations of Staphylococcus enterotoxin B (SEB). An anti-SEB antibody has been attached to the nano-porous aluminum surface using 3-aminopropyltriethoxysilane/glutaraldehyde coupling system. This immobilization method allows fabrication of a highly reproducible and stable sensing device. Using developed immobilization procedure and optimized detection regime, it is possible to determine the presence of SEB at the levels as low as 10 pg/mL in 15 minutes. PMID:22315560

  14. Optimisation of the hot conditioning of carbon steel surfaces of primary heat transport system of Pressurized Heavy Water Reactors using electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Kiran Kumar, M.; Gaonkar, Krishna; Ghosh, Swati; Kain, Vivekanand; Bojinov, Martin; Saario, Timo

    2010-06-01

    Hot conditioning operation of the primary heat transport system is an important step prior to the commissioning of Pressurized Heavy Water Reactors. One of the major objectives of the operation is to develop a stable and protective magnetite layer on the inner surfaces of carbon steel piping. The correlation between stable magnetite film growth on carbon steel surfaces and the period of exposure to hot conditioning environment is generally established by a combination of weight change measurements and microscopic/morphological observations of the specimens periodically removed during the operation. In the present study, electrochemical impedance spectroscopy (EIS) at room temperature is demonstrated as an alternate, quantitative technique to arrive at an optimal duration of the exposure period. Specimens of carbon steel were exposed for 24, 35 and 48 h during hot conditioning of primary heat transport system of two Indian PHWRs. The composition and morphology of oxide films grown during exposure was characterized by X-ray diffraction and optical microscopy. Further, ex situ electrochemical impedance spectra of magnetite films formed after each exposure were measured, in 1 ppm Li + electrolyte at room temperature as a function of potential in a range of -0.8 to +0.3 VSCE. The defect density of the magnetite films formed after each exposure was estimated by Mott-Schottky analysis of capacitances extracted from the impedance spectra. Further the ionic resistance of the oxide was also extracted from the impedance spectra. Defect density was observed to decrease with increase in exposure time and to saturate after 35 h, indicating stabilisation of the barrier layer part of the magnetite film. The values of the ionic transport resistance start to increase after 35-40 h of exposure. The quantitative ability of EIS technique to assess the film quality demonstrates that it can be used as a supplementary tool to the thickness and morphological characterizations of samples

  15. High sensitivity and label-free detection of Enterovirus 71 by nanogold modified electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Fang-Yu; Li, Hsing-Yuan; Tseng, Shing-Hua; Cheng, Tsai-Mu; Chu, Hsueh-Liang; Yang, Jyh-Yuan; Chang, Chia-Ching

    2013-03-01

    Enterovirus 71 (EV71), which is the most fulminant and invasive species of enterovirus, can cause children neurologic complications and death within 2-3 days after fever and rash developed. Besides, EV71 has high sequence similarity with Coxsackie A 16 (CA16) that makes differential diagnosis difficult in clinic and laboratory. Since conventional viral diagnostic method cannot diagnose EV71 quickly and EV71 can transmit at low viral titer, the patients might delay in treatment. A quick, high sensitive, and high specific test for EV71 detection is pivotal. Electrochemical impedance spectroscopy (EIS) has been applied for detecting bio-molecules as biosensors recently. In this study, we try to build a detection platform for EV71 detection by nanogold modified EIS probe. The result shows that our probe can detect 3.6 VP1/50 μl (one EV71 particle has 60 VP1) in 3 minutes. The test can also distinguish EV71 from CA16 and lysozyme. Diagnosis of enterovirus 71 by electrochemical impedance spectroscopy has the potential to apply in clinic.

  16. Application of electrochemical impedance spectroscopy: A phase behavior study of babassu biodiesel-based microemulsions.

    PubMed

    Pereira, Thulio C; Conceição, Carlos A F; Khan, Alamgir; Fernandes, Raquel M T; Ferreira, Maira S; Marques, Edmar P; Marques, Aldaléa L B

    2016-11-01

    Microemulsions are thermodynamically stable systems of two immiscible liquids, one aqueous and the other of organic nature, with a surfactant and/or co-surfactant adsorbed in the interface between the two phases. Biodiesel-based microemulsions, consisting of alkyl esters of fatty acids, open a new means of analysis for the application of electroanalytical techniques, and is advantageous as it eliminates the required pre-treatment of a sample. In this work, the phase behaviours of biodiesel-based microemulsions were investigated through the electrochemical impedance spectroscopy (EIS) technique. We observed thatan increase in the amount of biodiesel in the microemulsion formulation increases the resistance to charge transfer at the interface. Also, the electrical conductivity measurements revealed that a decrease or increase in electrical properties depends on the amount of biodiesel. EIS studies of the biodiesel-based microemulsion samples showed the presence of two capacitive arcs: one high-frequency and the other low-frequency. Thus, the formulation of microemulsions plays an important role in estimating the electrical properties through the electrochemical impedance spectroscopy technique. PMID:27276278

  17. Selective detection of endotoxin using an impedance aptasensor with electrochemically deposited gold nanoparticles.

    PubMed

    Su, Wenqiong; Kim, Sung-Eun; Cho, MiSuk; Nam, Jae-Do; Choe, Woo-Seok; Lee, Youngkwan

    2013-01-01

    Using a single-stranded DNA (ssDNA) aptamer exhibiting high binding affinity (Kd = 12 nM) to endotoxin as a probe, an impedance sensor where aptamer-conjugated gold nanoparticles (AuNPs) were electrochemically deposited on a gold electrode was fabricated and its performance in regard to endotoxin detection assessed. AuNPs have been employed widely as biosensors because of their unique physical and chemical properties. In order to maximize the performance of the impedance aptasensor on endotoxin detection, some critical factors affecting aptamer conjugation to AuNPs and target recognition ability (i.e. concentrations of aptamer coupled with AuNPs, pH, ion strength and cation effect at the time of aptamer-endotoxin interaction) were optimized. Electrochemical impendence spectroscopy, cyclic voltametry, atomic force microscope, scanning electron microscope and quartz crystal microbalance were employed to characterize all the modification/detection procedures during the sensor fabrication. The developed aptasensor showed a broad linear dynamic detection range (0.01-10.24 ng/ml) with a very low detection limit for endotoxin (0.005 ng/ml), despite the presence of several biomolecules (e.g. plasmid DNA, RNA, serum albumin, Glc and sucrose) known to interfere with other endotoxin assays. The demonstrated aptasensor required a detection time of only 10 min, providing a simple and fast analytical method to specifically detect endotoxin from complex biological liqors. PMID:23165992

  18. Energy resolved electrochemical impedance spectroscopy for electronic structure mapping in organic semiconductors

    SciTech Connect

    Nádaždy, V. Gmucová, K.; Schauer, F.

    2014-10-06

    We introduce an energy resolved electrochemical impedance spectroscopy method to map the electronic density of states (DOS) in organic semiconductor materials. The method consists in measurement of the charge transfer resistance of a semiconductor/electrolyte interface at a frequency where the redox reactions determine the real component of the impedance. The charge transfer resistance value provides direct information about the electronic DOS at the energy given by the electrochemical potential of the electrolyte, which can be adjusted using an external voltage. A simple theory for experimental data evaluation is proposed, along with an explanation of the corresponding experimental conditions. The method allows mapping over unprecedentedly wide energy and DOS ranges. Also, important DOS parameters can be determined directly from the raw experimental data without the lengthy analysis required in other techniques. The potential of the proposed method is illustrated by tracing weak bond defect states induced by ultraviolet treatment above the highest occupied molecular orbital in a prototypical σ-conjugated polymer, poly[methyl(phenyl)silylene]. The results agree well with those of our previous DOS reconstruction by post-transient space-charge-limited-current spectroscopy, which was, however, limited to a narrow energy range. In addition, good agreement of the DOS values measured on two common π-conjugated organic polymer semiconductors, polyphenylene vinylene and poly(3-hexylthiophene), with the rather rare previously published data demonstrate the accuracy of the proposed method.

  19. Comprehensive characterization of all-solid-state thin films commercial microbatteries by Electrochemical Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Larfaillou, S.; Guy-Bouyssou, D.; le Cras, F.; Franger, S.

    2016-07-01

    Constant miniaturization of electronic devices opens the way to the development of thin film microbatteries (TFB). For this type of devices, the use of an all-solid-state thin film technology has many advantages over conventional lithium cells. These microbatteries are thin, bendable and can be produced with a customizable shape for integration in microelectronic devices. Moreover, without liquid electrolyte, they are safer. With the aim to support the industrial production of these TFBs, adequate tools for understanding the electrochemical behavior of the complete microbattery and the identification of their possible failures that can occur have to be developed. In this context, the Electrochemical Impedance Spectroscopy seems to be a good compromise for cells characterization. Widely used for the characterization of liquid electrolyte-based batteries, this technique has been less applied to all solid state batteries, mainly because of the difficulty to work with a two-electrode system. There has been no comprehensive study deeply explaining the impedance evolution during the entire life of a microbattery. In this paper, physical characterizations of individual active materials and aging experiments have been performed in order to undoubtedly assign each EIS contributions, and to propose a more comprehensive electrical model for this family of commercial all-solid-state microbatteries.

  20. Raman spectra of aligned carbon micro-coils and their impedance characteristics under loads

    SciTech Connect

    Tao, Wang; Yabo, Zhu Heliang, Fan; Zhicheng, Ju; Lei, Chen; Zhengyuan, Wang

    2014-02-21

    Scanning and transmission electron microscopy were used to characterize the morphology of the carbon microcoils (CMCs). The Raman spectra showed that CMCs had local regular structure as I{sub D}/I{sub G} = 0.841. Then, aligned CMCs/silicone–rubber composites (5 × 5 × 1 mm{sup 3}) were fabricated by coating of silicone rubber on the CMCs. Their alternating current impedance characteristics were measured as a function of applied load and the pressure sensitivity was discussed. The results showed that the impedance decreased as the increasing applied load, and the sample with less CMCs owned high pressure sensitivity, which indicated a novel composite film could act as an alternative of tactile sensor.

  1. Synthesis, characterization and electrochemical impedance spectroscopy of VOx-NTs/PPy composites

    NASA Astrophysics Data System (ADS)

    Cui, Chaojun; Wu, Guangming; Yang, Huiyu; She, Shifeng; Shen, Jun; Zhou, Bin; Zhang, Zhihua

    2010-10-01

    Composites consisting of vanadium oxide nanotubes (VOx-NTs) and polypyrrole (PPy) were synthesized by a two-steps method. VOx-NTs were firstly prepared by a combined sol-gel reaction and hydrothermal treatment procedure, in which V 2O 5 powder and H 2O 2 were used as raw materials and hexadecylamine as a structure-directing template. Then VOx-NTs/PPy composites were fabricated by a cationic exchange reaction between hexadecylamine and polypyrrole. The structure and morphology of the samples were investigated by SEM, TEM, XRD and FTIR techniques. The results confirmed that the template molecules were successfully substituted by the conducting polymers PPy without destroying the previous tubular structure. Electrochemical impedance spectroscopy (EIS) measurements were performed to evaluate the electrochemical kinetics of the samples. The results indicated that VOx-NTs/PPy composites had a lower charge transfer resistance and a faster lithium-ion diffusion speed than those of VOx-NTs, and the enhanced electrochemical kinetics could be attributed to the excellent electronic conductivity of polypyrrole.

  2. Dynamic Characterization of Dendrite Deposition and Growth in Li-Surface by Electrochemical Impedance Spectroscopy

    SciTech Connect

    Hernandez-Maya, R; Rosas, O; Saunders, J; Castaneda, H

    2015-01-13

    The evolution of dendrite formation is characterized by DC and AC electrochemical techniques. Interfacial mechanisms for lithium deposition are described and quantified by electrochemical impedance spectroscopy (EIS) between a lithium electrode and a graphite electrode. The initiation and growth of dendrites in the lithium surface due to the cathodic polarization conditions following anodic dissolution emulate long term cycling process occurring in the lithium electrodes. The dendrite initiation at the lithium/organic electrolyte interface is proposed to be performed through a combination of layering and interfacial reactions during different cathodic conditions. The growth is proposed to be performed by surface geometrical deposition. In this work, we use EIS in galvanostatic mode to assess the initiation and growth stages of dendrites by the accumulation of precipitates formed under different current conditions. The lithium/organic solvent experimental system using frequency domain techniques is validated by the theoretical approach using a deterministic model that accounts for the faradaic processes at the interface assuming a coverage fraction of the electrodic surface affected by the dendritic growth. (C) 2015 The Electrochemical Society. All rights reserved.

  3. In Situ Characterization of Ultrathin Films by Scanning Electrochemical Impedance Microscopy.

    PubMed

    Estrada-Vargas, Arturo; Bandarenka, Aliaksandr; Kuznetsov, Volodymyr; Schuhmann, Wolfgang

    2016-03-15

    Control over the properties of ultrathin films plays a crucial role in many fields of science and technology. Although nondestructive optical and electrical methods have multiple advantages for local surface characterization, their applicability is very limited if the surface is in contact with an electrolyte solution. Local electrochemical methods, e.g., scanning electrochemical microscopy (SECM), cannot be used as a robust alternative yet because their methodological aspects are not sufficiently developed with respect to these systems. The recently proposed scanning electrochemical impedance microscopy (SEIM) can efficiently elucidate many key properties of the solid/liquid interface such as charge transfer resistance or interfacial capacitance. However, many fundamental aspects related to SEIM application still remain unclear. In this work, a methodology for the interpretation of SEIM data of "charge blocking systems" has been elaborated with the help of finite element simulations in combination with experimental results. As a proof of concept, the local film thickness has been visualized using model systems at various tip-to-sample separations. Namely, anodized aluminum oxide (Al2O3, 2-20 nm) and self-assembled monolayers based on 11-mercapto-1-undecanol and 16-mercapto-1-hexadecanethiol (2.1 and 2.9 nm, respectively) were used as model systems. PMID:26871004

  4. Electrochemical impedance spectroscopy for lithium-ion cells: Test equipment and procedures for aging and fast characterization in time and frequency domain

    NASA Astrophysics Data System (ADS)

    Lohmann, Nils; Weßkamp, Patrick; Haußmann, Peter; Melbert, Joachim; Musch, Thomas

    2015-01-01

    New test equipment and characterization methods for aging investigations on lithium-ion cells for automotive applications are presented in this work. Electrochemical impedance spectroscopy (EIS) is a well-established method for cell characterization and analyzing electrochemical processes. In order to integrate this method into long-term aging studies with real driving currents, new test equipment is mandatory. The presented test equipment meets the demands for high current, wide bandwidth and precise measurement. This allows the cells to be cycled and characterized without interruption for changing the test device. The characterization procedures must be of short duration and have a minimum charge-throughput for negligible influence on the aging effect. This work presents new methods in the time and the frequency domain for obtaining the impedance spectrum which allow a flexible trade-off between measurement performance, time consumption and charge-throughput. In addition to sinusoidal waveforms, rectangular, Gaussian and sin(x)/x pulses are applied for EIS. The performance of the different methods is discussed. Finally, the time domain analysis is applied with real driving currents which provides impedance spectra for state of charge estimation considering aging effects in the car.

  5. Corrosion Resistance Characterization of Coating Systems Used to Protect Aluminum Alloys Using Electrochemical Impedance Spectroscopy and Artificial Neural Networks

    NASA Astrophysics Data System (ADS)

    Gambina, Federico

    In this study, the corrosion protection provided by of a number of chromate and chromate-free coatings systems was characterized in detail. High-solids SrCrO4-pigmented epoxy primers applied to 2024 and 7075 substrates were subject to salt spray exposure testing for 30 days. Samples were removed periodically and an electrochemical impedance measurement (EIS) was made. Although none of the coatings tested showed visual evidence of corrosion, the total impedance of the samples decreased by as much as two orders of magnitude. An analysis of capacitance showed that the primer coatings rapidly took up water from the exposure environment, but the coating-metal remained passive despite the fact that it was wet. These results support the idea that chromate coatings protect by creating a chromate-rich electrolyte within the coating that is passivating to the underlying metal substrate. They also suggest that indications of metal substrate passivity found in the low-frequency capacitive reactance of the impedance spectra are a better indicator of corrosion protection than the total impedance. The low-frequency capacitive reactance from EIS measurements is also good at assessing the protectiveness of chromate-free coatings systems. Fifteen different coatings systems comprising high-solids, chromate-free primers and chromate-free conversion coatings were applied to 2024 and 7075 substrates. These coatings were subject to salt spray exposure and EIS measurements. All coatings were inferior to coating systems containing chromate, but changes in the capacitive reactance measured in EIS was shown to anticipate visual indications of coating failure. A predictive model based on neural networks was trained to recognize the pattern in the capacitive reactance in impedance spectra measured after 48 hours of exposure and make an estimate of remaining coating life. A sensitivity analysis was performed to prune the impedance inputs. As a result of this analysis, a very simple but highly

  6. Acquiring impedance spectra from diode-coupled primary batteries to determine health and state of charge

    NASA Astrophysics Data System (ADS)

    Christophersen, Jon P.; Morrison, John L.; Morrison, William H.

    The U.S. Army uses BA5590 Lithium Sulfur Dioxide primary batteries for portable electronic systems. There remains a need, however, for technology that can rapidly assess these batteries and estimate their remaining state of health after being used without degrading them to determine if there is remaining useful life for additional missions. This allows the full range of charge to be consumed before the battery is recycled or disposed. Impedance spectroscopy measurements have been shown to be a useful diagnostic tool, but standard methods cannot be applied to the BA5590 batteries because of the up-front electronics. The BA5590 module is diode-coupled and a charge-neutral excitation signal would be half-wave rectified and completely corrupt the results. However, a rapid impedance spectrum measurement technique has been developed that can be used for the BA5590s based on the addition of a small discharge bias load super-imposed on the sinusoidal excitation signal. The feasibility of this approach was initially simulated and then successfully applied to cell strings on four fresh BA5590 modules. The results clearly showed consistent and repeatable impedance spectra with no significant impact on the SOC as a result of the measurement. Details of this measurement technique and discussion of the preliminary results are presented.

  7. Label-free Electrochemical Impedance Detection of C-reactive Protein

    NASA Astrophysics Data System (ADS)

    Whited, Allison; Singh, K.. V.; Solanki, Raj

    2009-05-01

    C-reactive protein, CRP, is a marker present in human serum indicating inflammation and infection. By measuring the amount present in serum, it is possible to monitor the effectiveness of a treatment or roughly gauge the risk of heart disease. Using a double antibody capture system immobilized on an interdigitated electrode array, a label-free device was developed to detect the presence of CRP present in buffer solution and various concentrations of human serum. Electrochemical impedance spectroscopy was used to measure the end point data of the binding signal as the assay was exposed to varying amounts of CRP in the presence of a constant concentration of anti-CRP. The sensor is able to achieve linear detection in both buffer solution and human serum spiked with CRP in the range of 1ng/ml to 1ug/ml. The sensor developed can be integrated into a portable microfluidic device.

  8. The Pt(111)/electrolyte interface under oxygen reduction reaction conditions: an electrochemical impedance spectroscopy study.

    PubMed

    Bondarenko, Alexander S; Stephens, Ifan E L; Hansen, Heine A; Pérez-Alonso, Francisco J; Tripkovic, Vladimir; Johansson, Tobias P; Rossmeisl, Jan; Nørskov, Jens K; Chorkendorff, Ib

    2011-03-01

    The Pt(111)/electrolyte interface has been characterized during the oxygen reduction reaction (ORR) in 0.1 M HClO(4) using electrochemical impedance spectroscopy. The surface was studied within the potential region where adsorption of OH* and O* species occur without significant place exchange between the adsorbate and Pt surface atoms (0.45-1.15 V vs RHE). An equivalent electric circuit is proposed to model the Pt(111)/electrolyte interface under ORR conditions within the selected potential window. This equivalent circuit reflects three processes with different time constants, which occur simultaneously during the ORR at Pt(111). Density functional theory (DFT) calculations were used to correlate and interpret the results of the measurements. The calculations indicate that the coadsorption of ClO(4)* and Cl* with OH* is unlikely. Our analysis suggests that the two-dimensional (2D) structures formed in O(2)-free solution are also formed under ORR conditions. PMID:21244087

  9. Impedance-derived electrochemical capacitance spectroscopy for the evaluation of lectin-glycoprotein binding affinity.

    PubMed

    Santos, Adriano; Carvalho, Fernanda C; Roque-Barreira, Maria-Cristina; Bueno, Paulo R

    2014-12-15

    Characterization of lectin-carbohydrate binding using label-free methods such as impedance-derived electrochemical capacitance spectroscopy (ECS) is desirable to evaluate specific interactions, for example, ArtinM lectin and horseradish peroxidase (HRP) glycoprotein, used here as a model for protein-carbohydrate binding affinity. An electroactive molecular film comprising alkyl ferrocene as a redox probe and ArtinM as a carbohydrate receptive center to target HRP was successfully used to determine the binding affinity between ArtinM and HRP. The redox capacitance, a transducer signal associated with the alkyl ferrocene centers, was obtained by ECS and used in the Langmuir adsorption model to obtain the affinity constant (1.6±0.6)×10(8) L mol(-1). The results shown herein suggest the feasibility of ECS application for lectin glycoarray characterization. PMID:24994505

  10. Energy Dispersive X-Ray and Electrochemical Impedance Spectroscopies for Performance and Corrosion Analysis of PEMWEs

    NASA Astrophysics Data System (ADS)

    Steen, S. M., Iii; Zhang, F.-Y.

    2014-11-01

    Proton exchange membrane water electrolyzers (PEMWEs) are a promising energy storage technology due to their high efficiency, compact design, and ability to be used in a renewable energy system. Before they are able to make a large commercial impact, there are several hurdles facing the technology today. Two powerful techniques for both in-situ and ex- situ characterizations to improve upon their performance and better understand their corrosion are electrochemical impedance spectroscopy and energy dispersive x-ray spectroscopy, respectively. In this paper, the authors use both methods in order to characterize the anode gas diffusion layer (GDL) in a PEMWE cell and better understand the corrosion that occurs in the oxygen electrode during electrolysis.

  11. Wide-Range Filter-Based Sinusoidal Wave Synthesizer for Electrochemical Impedance Spectroscopy Measurements.

    PubMed

    Chia-Ling Wei; Yi-Wen Wang; Bin-Da Liu

    2014-06-01

    A filter-based wide-range programmable sinusoidal wave synthesizer for electrochemical impedance spectroscopy measurement is proposed. The adopted filter is implemented with switched-capacitor circuits, so its corner frequency is accurate and adjustable by changing its switching frequency. The proposed sine wave synthesizer is implemented by using a 0.35 μm 2P4M 3.3 V mixed-signal polycide process. According to the measured results, the output frequency of the proposed synthesizer is 40 mHz-40 kHz . The measured total harmonic distortion is 0.073% at 10 Hz and 0.075% at 10 kHz, both of which are better than that of a typical function generator. PMID:24043398

  12. In Situ Representation of Soil/Sediment Conductivity Using Electrochemical Impedance Spectroscopy

    PubMed Central

    Li, Xiaojing; Wang, Xin; Zhao, Qian; Zhang, Yueyong; Zhou, Qixing

    2016-01-01

    The electrical conductivity (EC) of soil is generally measured after soil extraction, so this method cannot represent the in situ EC of soil (e.g., EC of soils with different moisture contents) and therefore lacks comparability in some cases. Using a resistance measurement apparatus converted from a configuration of soil microbial fuel cell, the in situ soil EC was evaluated according to the Ohmic resistance (Rs) measured using electrochemical impedance spectroscopy. The EC of soils with moisture content from 9.1% to 37.5% was calculated according to Rs. A significant positive correlation (R2 = 0.896, p < 0.01) between the soil EC and the moisture content was observed, which demonstrated the feasibility of the approach. This new method can not only represent the actual soil EC, but also does not need any pretreatment. Thus it may be used widely in the measurement of the EC for soils and sediments. PMID:27144567

  13. Protein-G-based human immunoglobulin G biosensing by electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Tsugimura, Kaiki; Ohnuki, Hitoshi; Endo, Hideaki; Tsuya, Daijyu; Izumi, Mitsuru

    2016-02-01

    A highly sensitive biosensor based on electrochemical impedance spectroscopy (EIS) was developed for the determination of human immunoglobulin G (IgG). Protein G, which specifically binds to IgG, was employed as the molecular receptor. Protein G was covalently immobilized on interdigitated electrodes through a mixed self-assembled monolayer (SAM) composed of 11-mercaptoundecanoic acid (MUA) and 6-mercaptohexanol. It was found that the mixing ratio of the SAM markedly affected the sensor performance. The sample prepared on 25% MUA SAM exhibited a linear behavior in the concentration range of 0.01-10 ng/mL, which is a record low detection for EIS-based IgG sensors. On the other hand, the sample on 100% MUA SAM showed no IgG-sensing action. A possible mechanism of the mixing ratio that affects the sensing performance was proposed.

  14. In Situ Representation of Soil/Sediment Conductivity Using Electrochemical Impedance Spectroscopy.

    PubMed

    Li, Xiaojing; Wang, Xin; Zhao, Qian; Zhang, Yueyong; Zhou, Qixing

    2016-01-01

    The electrical conductivity (EC) of soil is generally measured after soil extraction, so this method cannot represent the in situ EC of soil (e.g., EC of soils with different moisture contents) and therefore lacks comparability in some cases. Using a resistance measurement apparatus converted from a configuration of soil microbial fuel cell, the in situ soil EC was evaluated according to the Ohmic resistance (Rs) measured using electrochemical impedance spectroscopy. The EC of soils with moisture content from 9.1% to 37.5% was calculated according to Rs. A significant positive correlation (R² = 0.896, p < 0.01) between the soil EC and the moisture content was observed, which demonstrated the feasibility of the approach. This new method can not only represent the actual soil EC, but also does not need any pretreatment. Thus it may be used widely in the measurement of the EC for soils and sediments. PMID:27144567

  15. Electrochemical impedance spectroscopy and laser photoselectivity with gold nanoparticles for food applications

    NASA Astrophysics Data System (ADS)

    Chee, Grace

    With consistently higher and stricter standards for food quality and safety, it is becoming increasingly necessary to be able to quickly and easily determine certain properties of products in order to keep up with and maintain these standards. This master’s thesis is presented in three chapters. First, an overview of the theoretical background, current applications, and new technologies related to taking physiochemical property measurements of food, and various treatment methods used for food safety purposes. In the second chapter, electrochemical impedance spectroscopy (EIS) is used to find the dielectric (DE) constants and other physiochemical properties of potatoes in order to make quick adjustments to improve the microwave processing technique used for potato chipping. Finally, the third chapter introduces the use of a carbon dioxide laser system in conjunction with a two-ZnSe lens beam expander and functionalized gold nanoparticles to specifically target and kill E. coli in food samples.

  16. Corrosion Behavior of Stainless Steels in Neutral and Acidified Sodium Chloride Solutions by Electrochemical Impedance Spectroscopy

    NASA Technical Reports Server (NTRS)

    Calle, L. M.; Kolady, M. R.; Vinje, R. D.

    2004-01-01

    The objective of this work was to evaluate the corrosion performance of three alloys by Electrochemical Impedance Spectroscopy (EIS) and to compare the results with those obtained during a two-year atmospheric exposure study.' Three alloys: AL6XN (UNS N08367), 254SM0 (UNS S32154), and 304L (UNS S30403) were included in the study. 304L was included as a control. The alloys were tested in three electrolyte solutions which consisted of neutral 3.55% NaC1, 3.55% NaC1 in 0.lN HC1, and 3.55% NaC1 in 1.ON HC1. These conditions were expected to be less severe, similar, and more severe respectively than the conditions at NASA's Kennedy Space Center launch pads.

  17. Solid oxide electrolysis cell analysis by means of electrochemical impedance spectroscopy: A review

    NASA Astrophysics Data System (ADS)

    Nechache, A.; Cassir, M.; Ringuedé, A.

    2014-07-01

    High temperature water electrolysis based on Solid Oxide Electrolysis Cell (SOEC) is a very promising solution to produce directly pure hydrogen. However, degradation issues occurring during operation still represent a scientific and technological barrier in view of its development at an industrial scale. Electrochemical Impedance Spectroscopy (EIS) is a powerful in-situ fundamental tool adapted to the study of SOEC systems. Hence, after a quick presentation of EIS principle and data analysis methods, this review demonstrates how EIS can be used: (i) to characterize the performance and mechanisms of SOEC electrodes; (ii) as a complementary tool to study SOEC degradation processes for different cell configurations, in addition to post-test tools such as scanning electron microscopy (SEM) or X-ray diffraction (XRD). The use of EIS to establish a systematic SOEC analysis is introduced as well.

  18. A Realtime and Continuous Assessment of Cortisol in ISF Using Electrochemical Impedance Spectroscopy

    PubMed Central

    Arya, Sunil K.; Chornokur, Ganna; Bhansali, Shekhar

    2011-01-01

    This study describes the functioning of a novel sensor to measure cortisol concentration in the interstitial fluid (ISF) of a human subject. ISF is extracted by means of vacuum pressure from micropores created on the stratum corneum layer of the skin. The pores are produced by focusing a near infrared laser on a layer of black dye material attached to the skin. The pores are viable for approximately three days after skin poration. Cortisol measurements are based on electrochemical impedance (EIS) technique. Gold microelectrode arrays functionalized with Dithiobis (succinimidyl propionate) self-assembled monolayer (SAM) have been used to fabricate an ultrasensitive, disposable, electrochemical cortisol immunosensor. The biosensor was successfully used for in-vitro measurement of cortisol in ISF. Tests in a laboratory setup show that the sensor exhibits a linear response to cortisol concentrations in the range 1 pm to 100 nM. A small pilot clinical study showed that in-vitro immunosensor readings, when compared with commercial evaluation using enzyme-linked immunoassay (ELISA) method, correlated well with cortisol levels in saliva and ISF. Further, circadian rhythm could be established between the subject's ISF and the saliva samples collected over 24 hours time-period. Cortisol levels in ISF were found reliably higher than in saliva. This Research establishes the feasibility of using impedance based biosensor architecture for a disposable, wearable cortisol detector. The projected commercial in-vivo real-time cortisol sensor device, besides being minimally invasive, will allow continuous ISF harvesting and cortisol monitoring over 24 hours even when the subject is asleep. Forthcoming, this sensor could be interfaced to a wireless health monitoring system that could transfer sensor data over existing wide-area networks such as the internet and a cellular phone network to enable real-time remote monitoring of subjects. PMID:22163154

  19. Impedance Spectroscopic Investigation of Proton Conductivity in Nafion Using Transient Electrochemical Atomic Force Microscopy (AFM)

    PubMed Central

    Hink, Steffen; Wagner, Norbert; Bessler, Wolfgang G.; Roduner, Emil

    2012-01-01

    Spatially resolved impedance spectroscopy of a Nafion polyelectrolyte membrane is performed employing a conductive and Pt-coated tip of an atomic force microscope as a point-like contact and electrode. The experiment is conducted by perturbing the system by a rectangular voltage step and measuring the incurred current, followed by Fourier transformation and plotting the impedance against the frequency in a conventional Bode diagram. To test the potential and limitations of this novel method, we present a feasibility study using an identical hydrogen atmosphere at a well-defined relative humidity on both sides of the membrane. It is demonstrated that good quality impedance spectra are obtained in a frequency range of 0.2–1000 Hz. The extracted polarization curves exhibit a maximum current which cannot be explained by typical diffusion effects. Simulation based on equivalent circuits requires a Nernst element for restricted diffusion in the membrane which suggests that this effect is based on the potential dependence of the electrolyte resistance in the high overpotential region. PMID:24958175

  20. Corrosion characterization of durable silver coatings by electrochemical impedance spectroscopy and accelerated environmental testing.

    PubMed

    Chu, Chung-Tse; Fuqua, Peter D; Barrie, James D

    2006-03-01

    Highly reflective front-surface silver mirrors are needed for many optical applications. While various protective dielectric coating schemes have been developed, the long-term durability of Ag mirrors is still of great concern in the optics community for a variety of applications under harsh environments. The corrosion protection behavior of a SiNx-coated silver-mirror coating scheme was tested with electrochemical impedance spectroscopy (EIS) and accelerated environmental testing, including humidity and salt fog tests. The EIS data obtained were fitted with different equivalent circuit models. The results suggested that the 100A thick SiNx coating produced by rf magnetron sputtering was porous and acted as a leaky capacitor on the Ag film, whereas the addition of a NiCrNx interlayer as thin as 3A between SiNx and Ag films resulted in a much denser SiNx coating with a low-frequency impedance value of 2 orders of magnitude higher than that without the interlayer. Humidity and salt fog testing of different silver coatings showed similar results. The 100A SiNx/3A-NiCrNx/Ag coating exhibited excellent corrosion resistance against the corrosive environments used in this study. PMID:16539267

  1. Equivalent circuit model analysis on electrochemical impedance spectroscopy of lithium metal batteries

    NASA Astrophysics Data System (ADS)

    Gao, Peng; Zhang, Cuifen; Wen, Guangwu

    2015-10-01

    Lithium metal electrode is pretreated with 1,3-dioxolane or 1,4-dioxane to improve its properties. The components and morphology of the surface films formed in the above two pretreatment liquids are studied using FTIR and SEM respectively. Li-LiCoO2 coin cells are then fabricated and their cycle and discharge performance are tested. It is found that the battery performance is greatly improved by such pretreatment. Interestingly, the 1,4-dioxane pretreatment is more effective than 1,3-dioxolane in improving the lithium metal electrode performance. To explore the mechanism(s) behind, the electrochemical impedance spectroscopy (EIS) is employed and an equivalent circuit model is designed for EIS analysis. The fitting curves are aligned well with the experimental curves, suggesting that the proposed equivalent circuit model is an ideal model for lithium battery. Next, the corresponding relationship between the impedance components and every individual semicircle in the Nyquist curves is inferred theoretically and the result is satisfying. Based on the analysis using this model, we conclude that the structural stability of SEI film is increased and the interfacial compatibility between the lithium substrate and the SEI film is improved by 1,3-dioxolane or 1,4-dioxane pretreatment.

  2. Biological capacitance studies of anodes in microbial fuel cells using electrochemical impedance spectroscopy.

    PubMed

    Lu, Zhihao; Girguis, Peter; Liang, Peng; Shi, Haifeng; Huang, Guangtuan; Cai, Lankun; Zhang, Lehua

    2015-07-01

    It is known that cell potential increases while anode resistance decreases during the start-up of microbial fuel cells (MFCs). Biological capacitance, defined as the apparent capacitance attributed to biological activity including biofilm production, plays a role in this phenomenon. In this research, electrochemical impedance spectroscopy was employed to study anode capacitance and resistance during the start-up period of MFCs so that the role of biological capacitance was revealed in electricity generation by MFCs. It was observed that the anode capacitance ranged from 3.29 to 120 mF which increased by 16.8% to 18-20 times over 10-12 days. Notably, lowering the temperature and arresting biological activity via fixation by 4% para formaldehyde resulted in the decrease of biological capacitance by 16.9 and 62.6%, indicating a negative correlation between anode capacitance and anode resistance of MFCs. Thus, biological capacitance of anode should play an important role in power generation by MFCs. We suggest that MFCs are not only biological reactors and/or electrochemical cells, but also biological capacitors, extending the vision on mechanism exploration of electron transfer, reactor structure design and electrode materials development of MFCs. PMID:25656699

  3. Electrochemical impedance spectroscopy investigations of a microelectrode behavior in a thin-layer cell: Experimental and theoretical studies.

    PubMed

    Gabrielli, C; Keddam, M; Portail, N; Rousseau, P; Takenouti, H; Vivier, V

    2006-10-19

    Electrochemical impedance spectroscopy experiments were performed on a microdisk electrode in a thin-layer cell using a scanning electrochemical microscope for controlling the cell geometry. Experimental data showed that when the thin-layer thickness diminished, an additional low-frequency response appeared. It was ascribed to the radial diffusion of the electroactive species and was strongly dependent on the thin-layer dimensions (both thickness and diameter). Moreover, the numerical simulation of the impedance diagrams by finite element method calculations confirmed this behavior. An equivalent circuit based on a Randles-type circuit was proposed. Thus, the diffusion was described by introducing two electrical elements: one for the spherical diffusion and the other for the radial contribution. A nonlinear Simplex algorithm was used, and this circuit was shown to fit the impedance diagrams with a good accuracy. PMID:17034233

  4. The Performance of Dammar-based Paint System Evaluated by Electrochemical Impedance Spectroscopy (EIS) and Potential Time Measurement (PTM)

    NASA Astrophysics Data System (ADS)

    Omar, N. M.; Ahmad, A. Hanom

    2009-06-01

    The coating resistance of the Dammar-based paint system was determined by using Electrochemical Impedance Spectroscopy (EIS), whereas, the corrosion potential analysis was determined by using potential time measurement (PTM) method. Carotenoid pigment obtained from Capsicum Annum (dried chili pepper) was added into the mixture of dammar and acrylic polyol resin and the paint systems were proofed on Aluminium steel Q-panels as a substrate. Result shows that the paint system with a composition of 35% dammar (CD35%) possessed the higher corrosion resistance after 30 days of exposure in 3% NaCl solution for electrochemical impedance spectroscopy and also can withstand the longest time for delimitation protection in PTM analysis. The results prove that the developed organic paint system can improve the electrochemical and corrosion protection properties of a paint system.

  5. Impedance model of lithium ion polymer battery considering temperature effects based on electrochemical principle: Part I for high frequency

    NASA Astrophysics Data System (ADS)

    Xiao, Meng; Choe, Song-Yul

    2015-03-01

    Measurement of impedance is one of well-known methods to experimentally characterize electrochemical properties of Li-ion batteries. The measured impedance responses are generally fitted to an equivalent circuit model that is composed of linear and nonlinear electric components that mimic behaviors of different layers of a battery. However, the parameters do not provide quantitative statements on charge dynamics considering material properties. Therefore, electrochemical models are widely employed to study the charge dynamics, but have not included high frequency responses predominantly determined by double layers. Thus, we have developed models for the double layer and bulk that are integrated into the electrochemical model for a pouch type Li-ion battery. The integrated model is validated against the frequency response obtained from EIS equipment at different temperatures as well as the time response. The results show that the proposed model is capable of representing the responses at charging and discharging in time and frequency domain.

  6. A New Approach for Resolution of Complex Tissue Impedance Spectra in Hearts

    PubMed Central

    Barr, Roger C.

    2014-01-01

    This study was designed to test the feasibility of using sinusoidal approximation in combination with a new instrumentation approach to resolve complex impedance (uCI) spectra from heart preparations. To assess that feasibility, we applied stimuli in the 10–4000 Hz range and recorded potential differences (uPDs) in a four-electrode configuration that allowed identification of probe constants (Kp) during calibration that were in turn used to measure total tissue resistivity ρt from rabbit ventricular epicardium. Simultaneous acquisition of a signal proportional to the supplied current (Vstim) with uPD allowed identification of the V –I ratio needed for ρt measurement, as well as the phase shift from Vstim to uPD needed for uCI spectra resolution. Performance with components integrated to reduce noise in cardiac electrophysiologic experiments, in particular, and provide accurate electrometer-based measurements, in general, was first characterized in tests using passive loads. Load tests showed accurate uCI recovery with mean uPD SNRs between 101 and 103 measured with supplied currents as low as 10 nA. Comparable performance characteristics were identified during calibration of nine arrays built with 250 µm Ag/AgCl electrodes, with uCIs that matched analytic predictions and no apparent effect of frequency (F = 0.12, P = 0.99). The potential ability of parasitic capacitance in the presence of the electrode–electrolyte interface associated with the small sensors to influence the uCI spectra was therefore limited by the instrumentation. Resolution of uCI spectra in rabbit ventricle allowed measurement of ρt = 134 ± 53 Ω·cm. The rapid identification available with this strategy provides an opportunity for new interpretations of the uCI spectra to improve quantification of disease-, region-, tissue-, and species-dependent intercellular uncoupling in hearts. PMID:23625349

  7. Sensor spacing affects the tissue impedance spectra of rabbit ventricular epicardium

    PubMed Central

    Waits, Charlotte Mae K.; Barr, Roger C.

    2014-01-01

    This study was designed to test the hypothesis that a complex composite impedance spectra develops when stimulation and recording of cardiac muscle with sufficiently fine spatial resolution in a four-electrode configuration is used. With traditional (millimeter scale) separations, the ratio between the recorded interstitial central potential difference and total supplied interstitial current is constant at all frequencies. This occurs because the fraction of supplied current that redistributes to the intracellular compartment depends on effective membrane resistance between electrodes, which is low, to a much greater extent than effective membrane capacitance. The spectra should therefore change with finer separations at which effective membrane resistance increases, as supplied current will remain primarily interstitial at lower frequencies and redistribute between compartments at higher frequencies. To test this hypothesis, we built arrays with sensors separated (d) by 804 μm, 452 μm, and 252 μm; positioned those arrays across myocyte axes on rabbit ventricular epicardium; and resolved spectra in terms of resistivity (ρt) and reactivity (χt) over the 10 Hz to 4,000 Hz range. With all separations, we measured comparable spectra with predictions from passive membrane simulations that used a three-dimensional structural framework in which intracellular, interstitial, and membrane properties were prescribed based on the limited data available from the literature. At the finest separation, we found mean ρt at 100 Hz and 4,000 Hz that lowered from 395 Ω-cm to 236 Ω-cm, respectively, with maximal mean χt of 160 Ω-cm. This experimental confirmation of spectra development in whole heart experiments is important because such development is central to achieve measurements of intracellular and interstitial passive electrical properties in cardiac electrophysiological experiments using only interstitial access. PMID:24778170

  8. Electrochemical impedance immunosensor for sub-picogram level detection of bovine interferon gamma based on cylinder-shaped TiO₂ nanorods.

    PubMed

    Yang, Zhanjun; Jian, Zhiqin; Chen, Xiang; Li, Juan; Qin, Piya; Zhao, Jie; Jiao, Xin'an; Hu, Xiaoya

    2015-01-15

    Bovine interferon gamma (BoIFN-γ) released by T cells plays very important roles in early diagnosis of Mycobacterium tuberculosis (MTB) infections and control of bovine tuberculosis. In this work, a label-free electrochemical impedance immunosensor is for the first time developed for highly sensitive determination of BoIFN-γ. Cylinder-shaped TiO2 nanorods are synthesized by a facile hydrothermal method, and show high surface area and good hydrophicility. The immunosensor is fabricated by the immobilization of BoIFN-γ monoclonal antibody on the TiO2 nanorods modified glassy carbon electrode. The prepared TiO2 and immunosensor are characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, contact angle measurement, cyclic voltammetry, and electrochemical impedance spectra. The BoIFN-γ concentration is measured through the relative increase of impedance values in corresponding specific binding of BoIFN-γ antigen and BoIFN-γ antibody. The relative increased impedance values are proportional to the logarithmic value of BoIFN-γ concentrations in a wide range of 0.0001 to 0.1 ng/mL with a low detection limit of 0.1 pg/mL. The developed BoIFN-γ immunosensor shows a 249-fold decrease in detection limit in comparison with current enzyme-linked immunosorbent assay. This study provides a new, simple, and highly sensitive approach for very potential application in early diagnosis of MTB infections and control of bovine tuberculosis. PMID:25089816

  9. Effects of Bimolecular Recombination on Impedance Spectra in Organic Semiconductors: Analytical Approach.

    PubMed

    Takata, Masashi; Takagi, Kenichiro; Nagase, Takashi; Kobayashi, Takashi; Naito, Hiroyoshi

    2016-04-01

    An analytical expression for impedance spectra in the case of double injection (both electrons and holes are injected into an organic semiconductor thin film) has been derived from the basic transport equations (the current density equation, the continuity equation and the Possion's equation). Capacitance-frequency characteristics calculated from the analytical expression have been examined at different recombination constants and different values of mobility balance defined by a ratio of electron mobility to hole mobility. Negative capacitance appears when the recombination constant is lower than the Langevin recombination constant and when the value of the mobility balance approaches unity. These results are consistent with the numerical results obtained by a device simulator (Atlas, Silvaco). PMID:27451625

  10. Electrochemical Impedance Spectroscopy of Alloys in a Simulated Space Shuttle Launch Environment

    NASA Technical Reports Server (NTRS)

    Calle, L. M.; Kolody, M. R.; Vinje, R. D.; Whitten, M. C.; Li, D.

    2005-01-01

    Corrosion studies began at NASA/Kennedy Space Center in 1966 during the Gemini/Apollo Programs with the evaluation of long-term protective coatings for the atmospheric protection of carbon steel. An outdoor exposure facility on the beach near the launch pad was established for this purpose at that time. The site has provided over 35 years of technical information on the evaluation of the long-term corrosion performance of many materials and coatings as well as on maintenance procedures. Results from these evaluations have helped NASA find new materials and processes that increase the safety and reliability of our flight hardware, launch structures, and ground support equipment. The launch environment at the Kennedy Space Center (KSC) is extremely corrosive due to the combination of ocean salt spray, heat, humidity, and sunlight. With the introduction of the Space Shuttle in 1981, the already highly corrosive conditions at the launch pad were rendered even more severe by the acidic exhaust from the solid rocket boosters. Over the years, many materials have been evaluated for their corrosion performance under conditions similar to those found at the launch pads. These studies have typically included atmospheric exposure and evaluation with conventional electrochemical methods such as open circuit potential (OCP) measurements, polarization techniques, and electrochemical impedance spectroscopy (EIS). The atmosphere at the Space Shuttle launch site is aggressive to most metals and causes severe pitting in many of the common stainless steel alloys such as type 304L stainless steel (304L SS). A study was undertaken to find a more corrosion resistant material to replace the existing 304L SS tubing. This paper presents the results from atmospheric exposure as well as electrochemical measurements on the corrosion resistance of AL-6XN (UNS N08367) and 254-SMO (UNS S32154). Type 304L SS (UNS S30403) was used as a control. Conditions at the Space Shuttle launch pad were

  11. Charge Carrier Conduction Mechanism in PbS Quantum Dot Solar Cells: Electrochemical Impedance Spectroscopy Study.

    PubMed

    Wang, Haowei; Wang, Yishan; He, Bo; Li, Weile; Sulaman, Muhammad; Xu, Junfeng; Yang, Shengyi; Tang, Yi; Zou, Bingsuo

    2016-07-20

    With its properties of bandgap tunability, low cost, and substrate compatibility, colloidal quantum dots (CQDs) are becoming promising materials for optoelectronic applications. Additionally, solution-processed organic, inorganic, and hybrid ligand-exchange technologies have been widely used in PbS CQDs solar cells, and currently the maximum certified power conversion efficiency of 9.9% has been reported by passivation treatment of molecular iodine. Presently, there are still some challenges, and the basic physical mechanism of charge carriers in CQDs-based solar cells is not clear. Electrochemical impedance spectroscopy is a monitoring technology for current by changing the frequency of applied alternating current voltage, and it provides an insight into its electrical properties that cannot be measured by direct current testing facilities. In this work, we used EIS to analyze the recombination resistance, carrier lifetime, capacitance, and conductivity of two typical PbS CQD solar cells Au/PbS-TBAl/ZnO/ITO and Au/PbS-EDT/PbS-TBAl/ZnO/ITO, in this way, to better understand the charge carriers conduction mechanism behind in PbS CQD solar cells, and it provides a guide to design high-performance quantum-dots solar cells. PMID:27176547

  12. Rapid detection and quantification of free hemoglobin and haptoglobin by nanogold modified electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Lu, Yu-Ning; Li, Hsing-Yuan; Chu, Hsueh-Liang; Cheng, Tsia-Mu; Tseng, Shin-Hua; Chang, Chia-Ching

    2013-03-01

    Free Hemoglobin (Hb) is a metabolic substance that damage tissue and vessel. It is released from destructed red blood cell and causes infection or inflammatory of human body. In blood plasma, haptoglobin (Hp) binds free Hb with high affinity and prevents the damage which is caused by cell free Hb. Hp has three phenotypes, that are Hp1-1, Hp 2-1, and Hp 2-2. Different phenotypes of Hp has been different affinities to Hb. It is known that electrochemical impedance spectroscopy (EIS) provide more information for detecting the small amount bio-molecules, include protein and DNA. In this study, we have developed a simple, fast, reliable and sensitive platform to quantify concentration of free Hb and Hp. In this platform, detection probe has been modified with nano gold and the surface charge transfer resistance of Hb and Hp binding could be detected and quantified within 18 min. This is a whole new platform to quantify free Hb in the serum of human to our knowledge.

  13. Aptamer-based biosensor for label-free detection of ethanolamine by electrochemical impedance spectroscopy.

    PubMed

    Liang, Gang; Man, Yan; Jin, Xinxin; Pan, Ligang; Liu, Xinhui

    2016-09-14

    A label-free sensing assay for ethanolamine (EA) detection based on G-quadruplex-EA binding interaction is presented by using G-rich aptamer DNA (Ap-DNA) and electrochemical impedance spectroscopy (EIS). The presence of K(+) induces the Ap-DNA to form a K(+)-stabilized G-quadruplex structure which provides binding sites for EA. The sensing mechanism was further confirmed by circular dichroism (CD) spectroscopy and EIS measurement. As a result, the charge transfer resistance (RCT) is strongly increased as demonstrated by using the ferro/ferricyanide ([Fe(CN)6](3-/4-)) as a redox probe. Under the optimized conditions, a linear relationship between ΔRCT and EA concentration was obtained over the range of 0.16 nM and 16 nM EA, with a detection limit of 0.08 nM. Interference by other selected chemicals with similar structure was negligible. Analytical results of EA spiked into tap water and serum by the sensor suggested the assay could be successfully applied to real sample analysis. With the advantages of high sensitivity, selectivity and simple sensor construction, this method is potentially suitable for the on-site monitoring of EA contamination. PMID:27566359

  14. Generation of Small Single Domain Nanobody Binders for Sensitive Detection of Testosterone by Electrochemical Impedance Spectroscopy.

    PubMed

    Li, Guanghui; Zhu, Min; Ma, Lu; Yan, Junrong; Lu, Xiaoling; Shen, Yanfei; Wan, Yakun

    2016-06-01

    A phage display library of variable domain of the heavy chain only antibody or nanobody (Nb) was constructed after immunizing a bactrian camel with testosterone. With the smaller molecular size (15 kDa), improved solubility, good stability, high affinity, specificity, and lower immunogenicity, Nbs are a promising tool in the next generation of diagnosis and medical applications. Testosterone is a reproductive hormone, playing an important role in normal cardiac function and being the highly predictive marker for many diseases. Herein, a simple and sensitive immunosensor based on electrochemical impedance spectroscopy (EIS) and Nbs was successfully developed for the determination of testosterone. We successfully isolated the antitestosterone Nbs from an immune phage display library. Moreover, one of the Nbs was biotinylated according to in vivo BirA system, which showed the highest production yield and the most stable case. Further, the EIS immunosensor was set up for testosterone detection by applying the biotinylated antitestosterone Nb. As a result, the biosensor exhibited a linear working range from 0.05 to 5 ng mL(-1) with a detection limit of 0.045 ng mL(-1). In addition, the proposed immunosensor was successfully applied in determining testosterone in serum samples. In conclusion, the proposed immunosensor revealed high specificity of testosterone detection and showed as a potential approach for sensitive and accurate diagnosis of testosterone. PMID:27196036

  15. Rapid and highly sensitive detection of Enterovirus 71 by using nanogold-enhanced electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Hsing-Yuan; Tseng, Shing-Hua; Cheng, Tsai-Mu; Chu, Hsueh-Liang; Lu, Yu-Ning; Wang, Fang-Yu; Tsai, Li-Yun; Shieh, Juo-Yu; Yang, Jyh-Yuan; Juan, Chien-Chang; Tu, Lung-Chen; Chang, Chia-Ching

    2013-07-01

    Enterovirus 71 (EV71) infection is an emerging infectious disease causing neurological complications and/or death within two to three days after the development of fever and rash. A low viral titre in clinical specimens makes the detection of EV71 difficult. Conventional approaches for detecting EV71 are time consuming, poorly sensitive, or complicated, and cannot be used effectively for clinical diagnosis. Furthermore, EV71 and Coxsackie virus A16 (CA16) may cross react in conventional assays. Therefore, a rapid, highly sensitive, specific, and user-friendly test is needed. We developed an EV71-specific nanogold-modified working electrode for electrochemical impedance spectroscopy in the detection of EV71. Our results show that EV71 can be distinguished from CA16, Herpes simplex virus, and lysozyme, with the modified nanogold electrode being able to detect EV71 in concentrations as low as 1 copy number/50 μl reaction volume, and the duration between sample preparation and detection being 11 min. This detection platform may have the potential for use in point-of-care diagnostics.

  16. Evaluation of corrosion inhibitor film persistency by electrochemical impedance spectroscopy (EIS)

    SciTech Connect

    Chen, H.J.

    1996-08-01

    Film persistency of commercially available oilfield corrosion inhibitors has been evaluated in CO{sub 2}-saturated 5% sodium chloride solution using electrochemical impedance spectroscopy (EIS). The effect of inhibitor concentration and contact time on inhibitor film persistency was also investigated. This study demonstrates that EIS is a feasible method for evaluating and ranking inhibitor film persistency and can be used to monitor inhibitor film life. EIS can provide the corrosion rate and characteristics of the inhibited film and generate the parameters related to the specific inhibitor film. It was found that there is an excellent correlation between an EIS parameter, namely the high breakpoint frequency at a 45{degree} phase angle and inhibitor film persistency. The identification of this correlation, for which Chevron has been granted a patent, is significant because there are advantages associated with measuring this parameter. This discovery enables EIS to be used in the field to monitor and optimize corrosion inhibition programs, thus reducing the chemical and operation costs.

  17. Detection of methotrexate in a flow system using electrochemical impedance spectroscopy and multivariate data analysis.

    PubMed

    Tesfalidet, Solomon; Geladi, Paul; Shimizu, Kenichi; Lindholm-Sethson, Britta

    2016-03-31

    Methotrexate (MTX), a common pharmaceutical drug in cancer therapy and treatment of rheumatic diseases, is known to cause severe adverse side effects at high dose. As the side effect may be life threatening, there is an urgent need for a continuous, bed-side monitoring of the nominal MTX serum level in a patient while the chemical is being administered. This article describes a detection of MTX using a flow system that consists two modified gold electrodes. Interaction of MTX with the antibodies fixed on the electrode surface is detected by electrochemical impedance spectroscopy and evaluated using singular value decomposition (SVD). The key finding of this work is that the change in the electrode capacitance is found to be quantitative with respect to the concentration of MTX. Moreover a calibration curve constructed using the principal component regression method has a linear range of six orders of magnitude and a detection limit of 1.65 × 10(-10) M. PMID:26965322

  18. DNA Hybridization Sensors Based on Electrochemical Impedance Spectroscopy as a Detection Tool

    PubMed Central

    Park, Jin-Young; Park, Su-Moon

    2009-01-01

    Recent advances in label free DNA hybridization sensors employing electrochemical impedance spectroscopy (EIS) as a detection tool are reviewed. These sensors are based on the modulation of the blocking ability of an electrode modified with a probe DNA by an analyte, i.e., target DNA. The probe DNA is immobilized on a self-assembled monolayer, a conducting polymer film, or a layer of nanostructures on the electrode such that desired probe DNA would selectively hybridize with target DNA. The rate of charge transfer from the electrode thus modified to a redox indicator, e.g., [Fe(CN)6]3−/4−, which is measured by EIS in the form of charge transfer resistance (Rct), is modulated by whether or not, as well as how much, the intended target DNA is selectively hybridized. Efforts made to enhance the selectivity as well as the sensitivity of DNA sensors and to reduce the EIS measurement time are briefly described along with brief future perspectives in developing DNA sensors. PMID:22303136

  19. A label-free electrochemical impedance aptasensor for cylindrospermopsin detection based on thionine-graphene nanocomposites.

    PubMed

    Zhao, Zhen; Chen, Hongda; Ma, Lina; Liu, Dianjun; Wang, Zhenxin

    2015-08-21

    It is important to develop methods to determine cylindrospermopsin (CYN) at trace levels since CYN is a kind of widespread cyanobacterial toxin in water sources. In this study, a label-free impedimetric aptasensor has been fabricated for detecting CYN. In this case, the amino-substituted aptamer of CYN was covalently grafted onto the surface of the thionine-graphene (TH-G) nanocomposite through the cross-linker glutaraldehyde (GA). The reaction of the aptamer with CYN was monitored by electrochemical impedance spectroscopy because the CYN induced conformation change of the aptamer can cause a remarkable decrease of the electron transfer resistance. Under optimum conditions, the aptasensor exhibits high sensitivity and a low detection limit for CYN determination. The CYN can be quantified in a wide range of 0.39 to 78 ng mL(-1) with a good linearity (R(2) = 0.9968) and a low detection limit of 0.117 ng mL(-1). In addition, the proposed aptasensor displays excellent stability, reusability and reproducibility. PMID:26111280

  20. Salt transport properties of model reverse osmosis membranes using electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Feldman, Kathleen; Chan, Edwin; Stafford, Gery; Stafford, Christopher

    With the increasing shortage of clean water, efficient purification technologies including membrane separations are becoming critical. The main requirement of reverse osmosis in particular is to maximize water permeability while minimizing salt permeability. Such performance optimization has typically taken place through trial and error approaches. In this work, key salt transport metrics are instead measured in model reverse osmosis membranes using electrochemical impedance spectroscopy (EIS). As shown previously, EIS can provide both the membrane resistance Rm and membrane capacitance Cm, with Rm directly related to salt permeability. The membranes are fabricated in a molecular layer by layer approach, which allows for control over such parameters as thickness, surface and bulk chemistry, and network geometry/connectivity. Rm, and therefore salt permeability, follows the expected trends with thickness and membrane area but shows unusual behavior when the network geometry is systematically varied. By connecting intrinsic material properties such as the salt permeability with macroscopic performance measures we can begin to establish design rules for improving membrane efficiency and facilitate the creation of next-generation separation membranes.

  1. Electrochemical Impedance Spectroscopy (bio)sensing through hydrogen evolution reaction induced by gold nanoparticles.

    PubMed

    Mayorga-Martinez, Carmen C; Chamorro-Garcia, Alejandro; Merkoçi, Arben

    2015-05-15

    A new gold nanoparticle (AuNP) based detection strategy using Electrochemical Impedance Spectroscopy (EIS) through hydrogen evolution reaction (HER) is proposed. This EIS-HER method is used as an alternative to the conventional EIS based on [Fe(CN)6](3-/4-) or [Ru(NH3)6](3+/2+) indicators. The proposed method is based on the HER induced by AuNPs. EIS measurements for different amounts of AuNP are registered and the charge transfer resistance (Rct) was found to correlate and be useful for their quantification. Moreover the effect of AuNP size on electrical properties of AuNPs for HER using this sensitive technique has been investigated. Different EIS-HER signals generated in the presence of AuNPs of different sizes (2, 5, 10, 15, 20, and 50 nm) are observed, being the corresponding phenomena extendible to other nanoparticles and related catalytic reactions. This EIS-HER sensing technology is applied to a magneto-immunosandwich assay for the detection of a model protein (IgG) achieving improvements of the analytical performance in terms of a wide linear range (2-500 ng mL(-1)) with a good limit of detection (LOD) of 0.31 ng mL(-1) and high sensitivity. Moreover, with this methodology a reduction of one order of magnitude in the LOD for IgG detection, compared with a chroamperometric technique normally used was achieved. PMID:24953452

  2. Electrochemical impedance spectroscopy sensor for ascorbic acid based on copper(I) catalyzed click chemistry.

    PubMed

    Qiu, Suyan; Gao, Sen; Liu, Qida; Lin, Zhenyu; Qiu, Bin; Chen, Guonan

    2011-07-15

    Copper(I) species can be acquired from the reduction of copper(II) by ascorbic acid (AA) in situ, and which in turn quantitative catalyze the azides and alkynes cycloaddition reaction. In this study, propargyl-functionalized ferrocene (propargyl-functionalized Fc) has been modified on the electrode through reacting with azide terminal modified Au electrode via copper(I) catalyzed azides and alkynes cycloaddition (CuAAC) reaction. The electrochemical impedance spectroscopy (EIS) measurement has been applied to test the electron transfer resistance of the Au electrode before and after click reaction. The changes of the fractional surface coverage (θ) with different AA concentrations are characterized. It is found that the θ value has a linear response to the logarithm of AA concentration in the range of 5.0 pmol/L to 1.0 nmol/L with the detection limits of 2.6 pmol/L. The sensor shows a good stability and selectivity. And it has been successfully applied to the AA detection in the real samples (urine) with satisfactory results. PMID:21596552

  3. A highly selective electrochemical impedance spectroscopy-based aptasensor for sensitive detection of acetamiprid.

    PubMed

    Fan, Lifang; Zhao, Guohua; Shi, Huijie; Liu, Meichuan; Li, Zhengxin

    2013-05-15

    A simple aptasensor for sensitive and selective detection of acetamiprid has been developed based on electrochemical impedance spectroscopy (EIS). To improve sensitivity of the aptasensor, gold nanoparticles (AuNPs) were electrodeposited on the bare gold electrode surface by cycle voltammetry (CV), which was employed as a platform for aptamer immobilization. With the addition of acetamiprid, the formation of acetamiprid-aptamer complex on the AuNPs-deposited electrode surface resulted in an increase of electron transfer resistance (Ret). The change of Ret strongly depends on acetamiprid concentration, which is applied for acetamiprid quantification. A wide linear range was obtained from 5 to 600nM with a low detection limit of 1nM. The control experiments performed by employing the pesticides that may coexist or have similar structure with acetamiprid demonstrate that the aptasensor has only specific recognition to acetamiprid, resulting in high selectivity of the aptasensor. The dissociation constant, Kd of 23.41nM for acetamiprid-aptamer complex has been determined from the differential capacitance (Cd) by assuming a Langmuir isotherm, which indicates strong interaction between acetamiprid and aptamer, further proving high selectivity of the aptasensor. Besides, the applicability of the developed aptasensor has been successfully evaluated by determining acetamiprid in the real samples, wastewater and tomatoes. PMID:23274191

  4. Evaluation of inorganic zinc-rich primers using Electrochemical Impedance Spectroscopy (EIS)

    NASA Technical Reports Server (NTRS)

    Calle, Luz M.

    1993-01-01

    This investigation explores the use of Electrochemical Impedance Spectroscopy (EIS) in combination with beach exposure as a short term method for analyzing the performance of twenty-one zinc-rich primers. The twenty-one zinc-rich primers were: Carboline CZ-11, Ameron Devoe-Marine Catha-Coat 304, Briner V-65, Ameron D-21-9, Sherwin Williams Zinc Clad II, Carboline CZ-D7, Ameron D-4, Dupont Ganicin 347WB, Porter TQ-4374H, Inorganic Coatings IC-531, Subox Galvanox IV, Southern Coatings Chemtec 600, Glidden Glidzinc 5530, Byco SP-101, Tnemec 90E-75, Devoe Catha-Coat 302H, Glidden Glidzinc 5536, Koppers 701, Ameron D-21-5, Coronado 935-152, and Subox Galvanoz V. Data were also collected on galvanized steel for comparison purposes. A library of Bode magnitude plots was generated for each coating including curves for the initial time and after each week of atmospheric exposure as Beach Corrosion Test Site near the Space Shuttle launch pad at the Kennedy Space Center for up to three weeks. An examination of the variation of the Bode magnitude plots with atmospheric exposure revealed no clearly identifiable trend at this point that could distinguish between the good and the poor coatings. The test will be continued by including EIS measurements after six months and one year of atmospheric exposure.

  5. Probing the chemistry of nickel/metal hydride battery cells using electrochemical impedance spectroscopy

    NASA Technical Reports Server (NTRS)

    Isaac, Bryan J.

    1994-01-01

    Electrochemical Impedance Spectroscopy (EIS) is a valuable tool for investigating the chemical and physical processes occurring at electrode surfaces. It offers information about electron transfer at interfaces, kinetics of reactions, and diffusion characteristics of the bulk phase between the electrodes. For battery cells, this technique offers another advantage in that it can be done without taking the battery apart. This non-destructive analysis technique can thus be used to gain a better understanding of the processes occurring within a battery cell. This also raises the possibility of improvements in battery design and identification or prediction of battery characteristics useful in industry and aerospace applications. EIS as a technique is powerful and capable of yielding significant information about the cell, but it also requires that the many parameters under investigation can be resolved. This implies an understanding of the processes occurring in a battery cell. Many battery types were surveyed in this work, but the main emphasis was on nickel/metal hydride batteries.

  6. Human haptoglobin phenotypes and concentration determination by nanogold-enhanced electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Cheng, Tsai-Mu; Lee, Tzu-Cheng; Tseng, Shin-Hua; Chu, Hsueh-Liang; Pan, Ju-Pin; Chang, Chia-Ching

    2011-06-01

    Haptoglobin (Hp) is an acute phase protein that binds free hemoglobin (Hb), preventing Hb-induced oxidative damage in the vascular system. There are three phenotypes in human Hp, whose heterogeneous polymorphic structures and varying concentrations in plasma have been attributed to the cause of diseases and outcome of clinical treatments. Different phenotypes of Hp may be composed of the same subunits but different copy numbers, rendering their determination difficult by a single procedure. In this study, we have developed a simple, fast, reliable and sensitive method, using label-free nanogold-modified bioprobes coupled with self-development electrochemical impedance spectroscopy (EIS). By this method, probe surface charge transfer resistance is detected. The relative charge transfer resistance ratios for Hp 1-1, Hp 2-1 and Hp 2-2 were characterized. We were able to determine protein size difference within 3 nm, and the linear region of the calibration curve for Hp levels in the range of 90 pg ml - 1 and 90 µg ml - 1 (~1 fM to 1 pM). We surmise that similar approaches can be used to investigate protein polymorphism and altered protein-protein interaction associated with diseases.

  7. A Multilayer MEMS Platform for Single-Cell Electric Impedance Spectroscopy and Electrochemical Analysis

    PubMed Central

    Dittami, Gregory M.; Ayliffe, H. Edward; King, Curtis S.; Rabbitt, Richard D.

    2008-01-01

    The fabrication and characterization of a microchamber electrode array for electrical and electrochemical studies of individual biological cells are presented. The geometry was tailored specifically for measurements from sensory hair cells isolated from the cochlea of the mammalian inner ear. Conventional microelectromechanical system (MEMS) fabrication techniques were combined with a heat-sealing technique and polydimethylsiloxane micromolding to achieve a multilayered microfluidic system that facilitates cell manipulation and selection. The system allowed for electrical stimulation of individual living cells and interrogation of excitable cell membrane dielectric properties as a function of space and time. A three-electrode impedimetric system was incorporated to provide the additional ability to record the time-dependent concentrations of specific biochemicals in microdomain volumes near identified regions of the cell membrane. The design and fabrication of a robust fluidic and electrical interface are also described. The interface provided the flexibility and simplicity of a “cartridge-based” approach in connecting to the MEMS devices. Cytometric measurement capabilities were characterized by using electric impedance spectroscopy (1 kHz–10 MHz) of isolated outer hair cells. Chemical sensing capability within the microchannel recording chamber was characterized by using cyclic voltammetry with varying concentrations of potassium ferricyanide (K3Fe(CN)6). Chronoamperometric recordings of electrically stimulated PC12 cells highlight the ability of the platform to resolve exocytosis events from individual cells. PMID:19756255

  8. Effects of Operating Conditions on Internal Resistances in Enzyme Fuel Cells Studied via Electrochemical Impedance Spectroscopy

    SciTech Connect

    Aaron, D; Borole, Abhijeet P; Yiacoumi, Sotira; Tsouris, Costas

    2012-01-01

    Enzyme fuel cells (EFCs) offer some advantages over traditional precious-metal-catalyzed fuel cells, such as polymer electrolyte membrane fuel cells (PEMFCs). However, EFCs exhibit far less power output than PEMFCs and have relatively short life spans before materials must be replaced. In this work, electrochemical impedance spectroscopy (EIS) is used to analyze the internal resistances throughout the EFC at a variety of operating conditions. EIS analysis is focused primarily on the resistances of the anode, solution/membrane, and cathode. Increased enzyme loading results in improved power output and reductions in internal resistance. Conditions are identified for which enzyme loading does not limit the EFC performance. EIS experiments are also reported for EFCs operated continuously for 2 days; power output declines sharply over time, while all internal resistances increase. Drying of the cathode and enzyme/mediator degradation are believed to have contributed to this behavior. Finally, experiments are performed at varying air-humidification temperatures. Little effect on internal resistances or power output is observed. However, it is anticipated that increased air humidification can improve longevity by delivering more water to the cathode. Improvements to the enzymatic cathode are needed for EFC development. These improvements need to focus on improving transport rather than increasing enzyme loading.

  9. Two-Point Stretchable Electrode Array for Endoluminal Electrochemical Impedance Spectroscopy Measurements of Lipid-Laden Atherosclerotic Plaques.

    PubMed

    Packard, René R Sevag; Zhang, XiaoXiao; Luo, Yuan; Ma, Teng; Jen, Nelson; Ma, Jianguo; Demer, Linda L; Zhou, Qifa; Sayre, James W; Li, Rongsong; Tai, Yu-Chong; Hsiai, Tzung K

    2016-09-01

    Four-point electrode systems are commonly used for electric impedance measurements of biomaterials and tissues. We introduce a 2-point system to reduce electrode polarization for heterogeneous measurements of vascular wall. Presence of endoluminal oxidized low density lipoprotein (oxLDL) and lipids alters the electrochemical impedance that can be measured by electrochemical impedance spectroscopy (EIS). We developed a catheter-based 2-point micro-electrode configuration for intravascular deployment in New Zealand White rabbits. An array of 2 flexible round electrodes, 240 µm in diameter and separated by 400 µm was microfabricated and mounted on an inflatable balloon catheter for EIS measurement of the oxLDL-rich lesions developed as a result of high-fat diet-induced hyperlipidemia. Upon balloon inflation, the 2-point electrode array conformed to the arterial wall to allow deep intraplaque penetration via alternating current (AC). The frequency sweep from 10 to 300 kHz generated an increase in capacitance, providing distinct changes in both impedance (Ω) and phase (ϕ) in relation to varying degrees of intraplaque lipid burden in the aorta. Aortic endoluminal EIS measurements were compared with epicardial fat tissue and validated by intravascular ultrasound and immunohistochemistry for plaque lipids and foam cells. Thus, we demonstrate a new approach to quantify endoluminal EIS via a 2-point stretchable electrode strategy. PMID:26857007

  10. A general model of electrochemical impedance spectroscopy and its application to hydrogen storage materials

    NASA Astrophysics Data System (ADS)

    Tokash, Justin Charles

    organotin halides. To enable a closed-loop cycle, my task was then to be able to hydrogenate the organotin halides back to their hydride form. In addition to this experimental work, a parallel project was carried out to develop a new model of electrochemical impedance spectroscopy (EIS). The EIS technique is capable of probing complex chemical and electrochemical reactions, and this model was written into a computer code that allowed the input of experimental EIS data and the extraction of kinetic parameters based on a best-fit analysis of theoretical reaction schemes.

  11. A novel and simple cell-based electrochemical impedance biosensor for evaluating the combined toxicity of DON and ZEN.

    PubMed

    Gu, Wenshu; Zhu, Pei; Jiang, Donglei; He, Xingxing; Li, Yun; Ji, Jian; Zhang, Lijuan; Sun, Yange; Sun, Xiulan

    2015-08-15

    In this study, a novel and simple cell-based electrochemical biosensor was developed to assess the individual and combined toxicity of deoxynivalenol (DON) and zearalenone (ZEN) on BEL-7402 cells. The sensor was fabricated by modification with AuNPs, p-aminothiophenol, and folic acid in succession. The BEL-7402 cells which had a good activity were adhered on the electrode through the high affinity between the folate receptor and folic acid selectivity. We used the collagen to maintain the cell adhesion and viability. Electrochemical impedance spectroscopy (EIS) was developed to evaluate the individual and combined toxicity of DON and ZEN. Our results indicate that DON and ZEN caused a marked decrease in the cell viability in a dose-dependent manner. The value of electrochemical impedance spectroscopy decreased with the concentration of DON and ZEN in range of 0.1-20, 0.1-50 μg/ml with the detection limit as 0.03, 0.05 μg/ml, respectively, the IC50 for DON and ZEN as obtained by the proposed electrochemical method were 7.1 μg/ml and 24.6 μg/ml, respectively, and the combination of two mycotoxins appears to generate an additive response. The electrochemical cytotoxicity evaluation result was confirmed by biological assays. Compared to conventional methods, this electrochemical test is inexpensive, highly sensitive, and fast to respond, with long-term monitoring and real-time measurements. The proposed method provides a new avenue for evaluating the toxicity of mycotoxins. PMID:25863342

  12. Investigating Water Splitting with CaFe2O4 Photocathodes by Electrochemical Impedance Spectroscopy.

    PubMed

    Díez-García, María Isabel; Gómez, Roberto

    2016-08-24

    Artificial photosynthesis constitutes one of the most promising alternatives for harvesting solar energy in the form of fuels, such as hydrogen. Among the different devices that could be developed to achieve efficient water photosplitting, tandem photoelectrochemical cells show more flexibility and offer high theoretical conversion efficiency. The development of these cells depends on finding efficient and stable photoanodes and, particularly, photocathodes, which requires having reliable information on the mechanism of charge transfer at the semiconductor/solution interface. In this context, this work deals with the preparation of thin film calcium ferrite electrodes and their photoelectrochemical characterization for hydrogen generation by means of electrochemical impedance spectroscopy (EIS). A fully theoretical model that includes elementary steps for electron transfer to the electrolyte and surface recombination with photogenerated holes is presented. The model also takes into account the complexity of the semiconductor/solution interface by including the capacitances of the space charge region, the surface states and the Helmholtz layer (as a constant phase element). After illustrating the predicted Nyquist plots in a general manner, the experimental results for calcium ferrite electrodes at different applied potentials and under different illumination intensities are fitted to the model. The excellent agreement between the model and the experimental results is illustrated by the simultaneous fit of both Nyquist and Bode plots. The concordance between both theory and experiments allows us to conclude that a direct transfer of electrons from the conduction band to water prevails for hydrogen photogeneration on calcium ferrite electrodes and that most of the carrier recombination occurs in the material bulk. In more general vein, this study illustrates how the use of EIS may provide important clues about the behavior of photoelectrodes and the main strategies

  13. Electrochemical impedance spectroscopy system and methods for determining spatial locations of defects

    DOEpatents

    Glenn, David F.; Matthern, Gretchen E.; Propp, W. Alan; Glenn, Anne W.; Shaw, Peter G.

    2006-08-08

    A method and apparatus for determining spatial locations of defects in a material are described. The method includes providing a plurality of electrodes in contact with a material, applying a sinusoidal voltage to a select number of the electrodes at a predetermined frequency, determining gain and phase angle measurements at other of the electrodes in response to applying the sinusoidal voltage to the select number of electrodes, determining impedance values from the gain and phase angle measurements, computing an impedance spectrum for an area of the material from the determined impedance values, and comparing the computed impedance spectrum with a known impedance spectrum to identify spatial locations of defects in the material.

  14. Resolving Losses at the Negative Electrode in All-Vanadium Redox Flow Batteries Using Electrochemical Impedance Spectroscopy

    SciTech Connect

    Sun, Che Nan; Delnick, Frank M; Aaron, D; Mench, Matthew M; Zawodzinski, Thomas A

    2014-01-01

    We present an in situ electrochemical technique for the quantitative measurement and resolution of the ohmic, charge transfer and diffusion overvoltages at the negative electrode of an all-vanadium redox flow battery (VRFB) using electrochemical impedance spectroscopy (EIS). The mathematics describing the complex impedance of the V+2/V+3 redox reaction is derived and matches the experimental data. The voltage losses contributed by each process have been resolved and quantified at various flow rates and electrode thicknesses as a function of current density during anodic and cathodic polarization. The diffusion overvoltage was affected strongly by flow rate while the charge transfer and ohmic losses were invariant. On the other hand, adopting a thicker electrode significantly changed both the charge transfer and diffusion losses due to increased surface area. Furthermore, the Tafel plot obtained from the impedance resolved charge transfer overvoltage yielded the geometric exchange current density, anodic and cathodic Tafel slopes (135 5 and 121 5 mV/decade respectively) and corresponding transfer coefficients = 0.45 0.02 and = 0.50 0.02 in an operating cell.

  15. Failure of thin organic films by a combination of shearography and electrochemical impedance spectroscopy: the new concept of resistivity

    NASA Astrophysics Data System (ADS)

    Habib, Khaled

    2012-04-01

    A critical (steady state) value of the resistivity of different organic coatings was determined by a combination of optical shearography and electrochemical impedance spectroscopy (EIS). The behavior of organic coatings, i.e., ACE premiumgray enamel, white enamel, beige enamel (spray coatings), a yellow acrylic lacquer, and a gold nail polish on a metallic alloy, i.e., a carbon steel, was investigated over a temperature range of 20-60 °C. The value of the resistivity of coatings was determined by correlating the in-plan displacement of the coating (by shearography over a temperature range of 20- 60 °C) and the value of the alternating current (A.C) impedance of the coating by EIS in 3% NaCl solution. The integrity of the coatings with respect to time was assessed by comparison the measured value of resistivity to the critical (steady state) or asymptotic value of resistivity. In other words, by shearography, measurement of coating properties could be performed independent of parameters such as UV exposure, humidity, presence of chemical species, and other parameters which may normally interfere with conventional methods of the assessing of the integrity of coatings. Therefore, one may measure the resistivity of coatings, regardless of the history of the coating, in order to assess the integrity of coatings. Also, the obtained shearography data were found to be in a reasonable trend with the data of electrochemical impedance spectroscopy (EIS) in 3%NaCl solution.

  16. Electrochemical impedance spectroscopy of supercapacitors: A novel analysis approach using evolutionary programming

    NASA Astrophysics Data System (ADS)

    Oz, Alon; Hershkovitz, Shany; Tsur, Yoed

    2014-11-01

    In this contribution we present a novel approach to analyze impedance spectroscopy measurements of supercapacitors. Transforming the impedance data into frequency-dependent capacitance allows us to use Impedance Spectroscopy Genetic Programming (ISGP) in order to find the distribution function of relaxation times (DFRT) of the processes taking place in the tested device. Synthetic data was generated in order to demonstrate this technique and a model for supercapacitor ageing process has been obtained.

  17. Electrochemical and impedance investigation of the effect of lithium malonate on the performance of natural graphite electrodes in lithium-ion batteries

    SciTech Connect

    Sun, Xiao-Guang; Dai, Sheng

    2010-01-01

    Lithium malonate (LM) was coated on the surface of a natural graphite (NG) electrode, which was then tested as the negative electrode in the electrolytes of 0.9 M LiPF6/EC-PC-DMC (1/1/3, by weight) and 1.0 M LiBF4/EC-PC-DMC (1/1/3, by weight) under a current density of 0.075 mA cm-2. LM was also used as an additive to the electrolyte of 1.0 M LiPF6/EC-DMC-DEC (1/1/1, by volume) and tested on a bare graphite electrode. It was found that both the surface coating and the additive approach were effective in improving first charge discharge capacity and coulomb efficiency. Electrochemical impedance spectra showed that the decreased interfacial impedance was coupled with improved coulomb efficiency of the cells using coated graphite electrodes. Cyclic voltammograms (CVs) on fresh bare and coated natural graphite electrodes confirmed that all the improvement in the half-cell performance was due to the suppression of the solvent decomposition through the surface modification with LM. The CV data also showed that the carbonate electrolyte with LM as the additive was not stable against oxidation, which resulted in lower capacity of the full cell with commercial graphite and LiCoO2 electrodes.

  18. Impedance Characterization of a Model Au/Yttria-Stabilized Zirconia (YSZ)/Au Electrochemical Cell in Varying Oxygen and NOx Concentrations

    SciTech Connect

    Woo, L Y; Martin, L P; Glass, R S; Gorte, R J

    2006-11-01

    An electrochemical cell (Au/YSZ/Au) serves as a model system to investigate the effect of O{sub 2} and NO{sub x}. Possible mechanisms responsible for the response are presented. Two dense Au electrodes are co-located on the same side of a dense YSZ electrolyte and are separated from the electrolyte by a porous YSZ layer, present only under the electrodes. While not completely understood, the porous layer appears to result in enhanced NO{sub x} response. Impedance data were obtained over a range of frequencies (0.1 Hz to 1 MHz), temperatures (600 to 700 C), and oxygen (2 to 18.9%) and NO{sub x} (10 to 100 ppm) concentrations. Spectra were fit with an equivalent circuit, and values of the circuit elements were evaluated. In the absence of NO{sub x}, the effect of O{sub 2} on the low-frequency arc resistance could be described by a power law, and the temperature dependence by a single apparent activation energy at all O{sub 2} concentrations. When both O{sub 2} and NO{sub x} were present, however, the power-law exponent varied as a function of both temperature and concentration, and the apparent activation energy also showed dual dependence. Adsorption mechanisms are discussed as possibilities for the rate-limiting steps. Implications for impedance metric NO{sub x} sensing are also discussed.

  19. Electrochemical Impedance Spectroscopy of Alloys in a Simulated Space Shuttle Launch Environment

    NASA Technical Reports Server (NTRS)

    Calle, L. M.; Kolody, M. R.; Vinje, R. D.

    2004-01-01

    Type 304L stainless steel (304L SS) tubing is currently used in various supply lines that service the Orbiter at NASA's John F. Kennedy Space Center Launch Pads in Florida (USA). The atmosphere at the Space Shuffle launch site is very corrosive due to a combination of factors, such as the proximity of the Atlantic Ocean and the concentrated hydrochloric acid produced by the fuel combustion reaction in the solid rocket boosters. The acidic chloride environment is aggressive to most metals and causes severe pitting in many of the common stainless steel alloys such as 304L SS. Stainless steel tubing is susceptible to pitting corrosion that can cause cracking and rupture of both high-pressure gas and fluid systems. Outages in the systems where failures occur can impact the normal operation of the shuttle and launch schedules. The use of a more corrosion resistant tubing alloy for launch pad applications would greatly reduce the probability of failure, improve safety, lessen maintenance costs, and reduce downtime. A study which included ten alloys was undertaken to find a more corrosion resistant material to replace the existing 304L SS tubing. The study included atmospheric exposure at NASA's John F. Kennedy Space Center outdoor corrosion test site near the launch pads and electrochemical measurements in the laboratory which included DC techniques and electrochemical impedance spectroscopy (EIS). This paper presents the results from EIS measurements on three of the alloys: AL6XN (UN N08367), 254SMO (UNS S32l54), and 304L SS (UNS S30403). Type 304L SS was included in the study as a control. The alloys were tested in three electrolyte solutions which consisted of neutral 3.55% NaC1, 3.55% NaCl in O.1N HC1, and 3.55% NaCl in 1.ON HC1. The solutions were chosen to simulate environments that were expected to be less, similar, and more aggressive, respectively, than those present at the Space Shuttle launch pads. The results from the EIS measurements were analyzed to

  20. Establishment of equivalent circuits from electrochemical impedance spectroscopy study of corrosion inhibition of steel by pyrazine in sulphuric acidic solution

    NASA Astrophysics Data System (ADS)

    Kissi, M.; Bouklah, M.; Hammouti, B.; Benkaddour, M.

    2006-04-01

    This paper describes the use of the electrochemical impedance spectroscopy technique (EIS) in order to study the corrosion inhibition process of steel in 0.5 M H 2SO 4 solution at the open circuit potential (OCP). Diethyl pyrazine-2,3-dicarboxylate (Prz) as a non-ionic surfactant (NS) inhibitor has been examined. The Nyquist diagrams consisted of a capacitive semicircle at high frequencies followed by a well-defined inductive loop at low frequency values. The impedance measurements were interpreted according to suitable equivalent circuits. The results obtained showed that the Prz is a good inhibitor. The inhibition efficiency increases with an increase in the surfactant concentration to attain 80% at the 5 × 10 -3M. Prz is adsorbed on the steel surface according to a Langmuir isotherm adsorption model.

  1. Study of corrosion of super martensitic stainless steel under alternating current in artificial seawater with electrochemical impedance spectroscopy

    SciTech Connect

    Reyes, T.; Bhola, S.; Olson, D. L.; Mishra, B.

    2011-06-23

    The assessment of corrosion requires the use of tools able to quantify the corrosion but often times also qualify it. Electrochemical Impedance Spectroscopy (EIS) is a laboratory tool that can provide both qualification and quantification of corrosion. EIS was successfully used to compare the thickness of the corrosion products formed during the application of different alternating current (AC) densities as well as to characterize pitting. When EIS is applied at the open circuit potential, the technique is nondestructive and predicts the corrosion behavior of the electrode. It can also be used at cathodic potentials while still being nondestructive, providing information about the electrode reaction kinetics, diffusion and electrical double layer.

  2. The platinum microelectrode/Nafion interface - An electrochemical impedance spectroscopic analysis of oxygen reduction kinetics and Nafion characteristics

    NASA Technical Reports Server (NTRS)

    Parthasarathy, Arvind; Dave, Bhasker; Srinivasan, Supramaniam; Appleby, John A.; Martin, Charles R.

    1992-01-01

    The objectives of this study were to use electrochemical impedance spectroscopy (EIS) to study the oxygen-reduction reaction under lower humidification conditions than previously studied. The EIS technique permits the discrimination of electrode kinetics of oxygen reduction, mass transport of O2 in the membrane, and the electrical characteristics of the membrane. Electrode-kinetic parameters for the oxygen-reduction reaction, corrosion current densities for Pt, and double-layer capacitances were calculated. The production of water due to electrochemical reduction of oxygen greatly influenced the EIS response and the electrode kinetics at the Pt/Nafion interface. From the finite-length Warburg behavior, a measure of the diffusion coefficient of oxygen in Nafion and diffusion-layer thickness was obtained. An analysis of the EIS data in the high-frequency domain yielded membrane and interfacial characteristics such as ionic conductivity of the membrane, membrane grain-boundary capacitance and resistance, and uncompensated resistance.

  3. In situ monitoring of discharge/charge processes in Li-O2 batteries by electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Landa-Medrano, Imanol; Ruiz de Larramendi, Idoia; Ortiz-Vitoriano, Nagore; Pinedo, Ricardo; Ignacio Ruiz de Larramendi, José; Rojo, Teófilo

    2014-03-01

    Gaining insight into the reaction mechanisms underway during charge and discharge in Li-air batteries is essential to allow the target development of improved power and performance devices. This work reports the in situ monitoring of Li-air cells by electrochemical impedance spectroscopy and, for the first time, the development of an electrochemical model allowing the identification and attribution of the processes involved. The voltage at which each reaction product forms has been identified, including Li2O2 or Li2CO3 during discharge, together with the delithiation of the outer part of Li2O2 and oxidation reactions and electrolyte decomposition. The developed model can be used as a valuable tool for the optimisation of composition and structure of the air electrode through the investigation of the resistance associated with each process.

  4. Membrane Operational Impedance Spectra in Chara corallina Estimated by Laplace Transforms Analysis 1

    PubMed Central

    Homblé, Fabrice; Jenard, André

    1986-01-01

    The membrane operational impedance spectrum of Chara corallina Klein ex Willd. (R. Brown) cells is investigated using Laplace transform analysis. The spectrum changes with both amplitude and sign of the electrical stimulation when time- and voltage-dependent K+ channels contribute to the membrane conductance. We compare the advantages and disadvantage of this technique for studying membrane impedance with those of the alternating current method and the white noise method. PMID:16664925

  5. Label-free electrochemical impedance biosensor to detect human interleukin-8 in serum with sub-pg/ml sensitivity

    PubMed Central

    Sharma, R.; Deacon, S.E.; Nowak, D.; George, S.E.; Szymonik, M.P.; Tang, A.A.S.; Tomlinson, D.C.; Davies, A.G.; McPherson, M.J.; Wälti, C.

    2016-01-01

    Biosensors with high sensitivity and short time-to-result that are capable of detecting biomarkers in body fluids such as serum are an important prerequisite for early diagnostics in modern healthcare provision. Here, we report the development of an electrochemical impedance-based sensor for the detection in serum of human interleukin-8 (IL-8), a pro-angiogenic chemokine implicated in a wide range of inflammatory diseases. The sensor employs a small and robust synthetic non-antibody capture protein based on a cystatin scaffold that displays high affinity for human IL-8 with a KD of 35±10 nM and excellent ligand specificity. The change in the phase of the electrochemical impedance from the serum baseline, ∆θ(ƒ), measured at 0.1 Hz, was used as the measure for quantifying IL-8 concentration in the fluid. Optimal sensor signal was observed after 15 min incubation, and the sensor exhibited a linear response versus logarithm of IL-8 concentration from 900 fg/ml to 900 ng/ml. A detection limit of around 90 fg/ml, which is significantly lower than the basal clinical levels of 5–10 pg/ml, was observed. Our results are significant for the development of point-of-care and early diagnostics where high sensitivity and short time-to-results are essential. PMID:26897263

  6. Label-free electrochemical impedance biosensor to detect human interleukin-8 in serum with sub-pg/ml sensitivity.

    PubMed

    Sharma, R; Deacon, S E; Nowak, D; George, S E; Szymonik, M P; Tang, A A S; Tomlinson, D C; Davies, A G; McPherson, M J; Wälti, C

    2016-06-15

    Biosensors with high sensitivity and short time-to-result that are capable of detecting biomarkers in body fluids such as serum are an important prerequisite for early diagnostics in modern healthcare provision. Here, we report the development of an electrochemical impedance-based sensor for the detection in serum of human interleukin-8 (IL-8), a pro-angiogenic chemokine implicated in a wide range of inflammatory diseases. The sensor employs a small and robust synthetic non-antibody capture protein based on a cystatin scaffold that displays high affinity for human IL-8 with a KD of 35 ± 10 nM and excellent ligand specificity. The change in the phase of the electrochemical impedance from the serum baseline, ∆θ(ƒ), measured at 0.1 Hz, was used as the measure for quantifying IL-8 concentration in the fluid. Optimal sensor signal was observed after 15 min incubation, and the sensor exhibited a linear response versus logarithm of IL-8 concentration from 900 fg/ml to 900 ng/ml. A detection limit of around 90 fg/ml, which is significantly lower than the basal clinical levels of 5-10 pg/ml, was observed. Our results are significant for the development of point-of-care and early diagnostics where high sensitivity and short time-to-results are essential. PMID:26897263

  7. Exploring thermal spray gray alumina coating pore network architecture by combining stereological protocols and impedance electrochemical spectroscopy

    NASA Astrophysics Data System (ADS)

    Antou, G.; Montavon, G.; Hlawka, F.; Cornet, A.; Coddet, C.

    2006-12-01

    Complex multiscale pore network architecture characterized by multimodal pore size distribution and connectivity develops during the manufacture of ceramic thermal spray coatings from intra- and interlamellar cracks generated when each lamella spreads and solidifies to globular pores resulting from lamella stacking defects. This network significantly affects the coating properties and their in-service behaviors. De Hoff stereological analysis permits quantification of the three-dimensional (3D) distribution of spheroids (i.e., pores) from the determination of their two-dimensional (2D) distribution estimated by image analysis when analyzing the coating structure from a polished plane. Electrochemical impedance spectroscopy electrochemically examines a material surface by frequency variable current and potential and analyzes the complex impedance. When a coating covers the material surface, the electrolyte percolates through the more or less connected pore network to locally passivate the substrate. The resistive and capacitive characteristics of the equivalent electrical circuit will depend upon the connected pore network architecture. Both protocols were implemented to quantify thermal spray coating structures. Al2O3-13TiO2 coatings were atmospherically plasma sprayed using several sets of power parameters, are current intensity, plasma gas total flow rate, and plasma gas composition in order to determine their effects on pore network architecture. Particle characteristics upon impact, especially their related dimensionless numbers, such as Reynolds, Weber, and Sommerfeld criteria, were also determined. Analyses permitted identification of (a) the major effects of power parameters upon pore architecture and (b) the related formation mechanisms.

  8. Degradation of all-vanadium redox flow batteries (VRFB) investigated by electrochemical impedance and X-ray photoelectron spectroscopy: Part 2 electrochemical degradation

    NASA Astrophysics Data System (ADS)

    Derr, Igor; Bruns, Michael; Langner, Joachim; Fetyan, Abdulmonem; Melke, Julia; Roth, Christina

    2016-09-01

    Electrochemical degradation (ED) of carbon felt electrodes was investigated by cycling of a flow through all-vanadium redox flow battery (VRFB) and conducting half-cell measurements with two reference electrodes inside the test bench. ED was detected using half-cell and full-cell electrochemical impedance spectroscopy (EIS) at different states of charge (SOC). Reversing the polarity of the battery to recover cell performance was performed with little success. Renewing the electrolyte after a certain amount of cycles restored the capacity of the battery. X-ray photoelectron spectroscopy (XPS) reveals that the amount of surface functional increases by more than a factor of 3 for the negative side as well as for the positive side. Scanning electron microscope (SEM) images show a peeling of the fiber surface after cycling the felts, which leads to a loss of electrochemically active surface area (ECSA). Long term cycling shows that ED has a stronger impact on the negative half-cell [V(II)/V(III)] than the positive half-cell [V(IV)/V(V)] and that the negative half-cell is the rate-determining half-cell for the VRFB.

  9. Understanding Long-term Changes in Microbial Fuel Cell Performance Using Electrochemical Impedance Spectroscopy

    SciTech Connect

    Borole, Abhijeet P; Aaron, D; Hamilton, Choo Yieng; Tsouris, Costas

    2010-01-01

    Changes in the anode, cathode, and solution/membrane impedances during enrichment of an anode microbial consortium weremeasuredusing electrochemicalimpedancespectroscopy. The consortium was enriched in a compact, flow-through porous electrode chamber coupled to an air-cathode. The anode impedance initially decreased from 296.1 to 36.3 in the first 43 days indicating exoelectrogenic biofilm formation. The external load on the MFC was decreased in a stepwise manner to allow further enrichment. MFC operation at a final load of 50 decreased the anode impedance to 1.4 , with a corresponding cathode and membrane/solution impedance of 12.1 and 3.0 , respectively. An analysis of the capacitive element suggested that most of the three-dimensional anode surface was participating in the bioelectrochemical reaction. The power density of the air-cathode MFC stabilized after 3 months of operation and stayed at 422 ( 42 mW/m2 (33 W/m3) for the next 3 months. The normalized anode impedance for theMFCwas 0.017 k cm2, a 28-fold reduction over that reported previously. This study demonstrates a unique ability of biological systems to reduce the electron transfer resistance in MFCs, and their potential for stable energy production over extended periods of time.

  10. Impedances of electrochemically impregnated nickel electrodes as functions of potential, KOH concentration, and impregnation method

    NASA Technical Reports Server (NTRS)

    Reid, Margaret A.

    1989-01-01

    Impedances of fifteen electrodes form each of the four U.S. manufactures were measured at 0.200 V vs. the Hg/HgO reference electrode. This corresponds to a voltage of 1.145 for a Ni/H2 cell. Measurements were also made of a representative sample of these at 0.44 V. At the higher voltage, the impedances were small and very similar, but at the lower voltage there were major differences between manufacturers. Electrodes from the same manufacturers showed only small differences. The impedances of electrodes from two manufacturers were considerably different in 26 percent KOH from those in 31 percent KOH. These preliminary results seen to correlate with the limited data from earlier life testing of cells from these manufacturers. The impedances of cells being tested for Space Station Freedom are being followed, and more impendance measurements of electrodes are being performed as functions of manufacturer, voltage, electrolyte concentration, and cycle history in hopes of finding better correlations of impedance with life.

  11. Study of caffeine as corrosion inhibitors of carbon steel in chloride solution containing hydrogen sulfide using electrochemical impedance spectroscopy (EIS)

    NASA Astrophysics Data System (ADS)

    Solehudin, Agus; Berman, Ega Taqwali; Nurdin, Isdiriayani

    2015-09-01

    The corrosion behaviour of steel surface in the absence and presence of caffeine in 3.5% NaCl solution containing dissolved H2S gas is studied using electrochemical impedance spectroscopy (EIS). The experimental results of carbon steel corrosion in 3.5% NaCl solution containing 500 mg/l H2S at different caffeine concentrations showed that corrosion rate of carbon steel decreases with increasing of caffeine concentrations from 0 to 0,1 mmol/l. Whereas, the corrosion rate increase with increasing of caffeine concentrations from 1 to 10 mmol/l. It is clear that no inhibition efficiency increases with increasing inhibitor concentration. The optimum value of inhibition efficiency was 90% at a caffeine concentration of 0.1 mmol/l. This suggests that caffeine's performance as a corrosion inhibitor is more effective at a concentration of 0.1 mmol/l.

  12. Study of LiFeO 2 coated NiO as cathodes for MCFC by electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Huang, Bo; Yu, Qing-chun; Wang, Hui-min; Chen, Gang; Hu, Ke-ao

    LiFeO 2 was coated on porous NiO cathode using a simple combustion process. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed in the cathode characterizations. The electrochemical behaviors of LiFeO 2 coated NiO cathode (LFO-NiO) were also evaluated in a molten 62 mol% Li 2CO 3 + 38 mol% K 2CO 3 eutectic at 650 °C under the standard cathode gas condition by electrochemical impedance spectroscopy (EIS). The impedance response of the NiO and LFO-NiO at different immersion time is characterized by the presence of depressed semicircles in the high frequency range changing over into the lines with the angle of which observed with the real axis differing 45° or 90° in the low frequency range. The experimental Nyquist plots can be well analyzed theoretically with a modified model based on the well known Randles-Ershler equivalent circuit model. In the new model, the double layer capacity ( Cd) is replaced by the parallel combination of Cd and b/ ω to take into consideration the non-uniform of electric field at the electrode/electrolyte interface owing to the roughness of electrode surface. The LFO-NiO showed a lower dissolution and a good catalytic efficiency close to the state-of-the-art NiO value. In the unit cell test, the performance of the cell composed of LiFeO 2 coated NiO cathode maintained more stable values than that of the cell composed of NiO cathode. Thus the cathode prepared with coating method to coat LiFeO 2 on the surface of NiO cathode is able to reduce the solubility of NiO to lengthen the lifetime of MCFC while maintaining the advantages of NiO cathode.

  13. Characterization of Damp-Heat Degradation of CuInGaSe2 Solar Cell Components and Devices by (Electrochemical) Impedance Spectroscopy: Preprint

    SciTech Connect

    Pern, F. J. J.; Noufi, R.

    2011-09-01

    This work evaluated the capability of (electrochemical) impedance spectroscopy (IS, or ECIS as used here) to monitor damp heat (DH) stability of contact materials, CuInGaSe2 (CIGS) solar cell components, and devices. Cell characteristics and its variation of the CIGS devices were also examined by the ECIS.

  14. Real-time in situ monitoring of poly(lactide-co-glycolide) coating of coronary stents using electrochemical impedance spectroscopy.

    PubMed

    Zhong, Qi; Mao, Qunlong; Yan, Jin; Liu, Wenming; Zhang, Tao; Liu, Jianguo

    2015-04-01

    Monitoring erosion progress of biodegradable drug carrying polymer coated on coronary drug eluting stents (DES) is largely hindered because of the small amount of coating material as well as the irregular profile of coating, both of which make the monitoring using traditional methods highly challenging. In our study, electrochemical impedance spectroscopy (EIS), a widely used method in the study of metal corrosion, was used to address the challenges traditional methods face. In vitro, remained mass and molecular weight drop data of film-like poly(lactide-co-glycolide) (PLGA) samples due to degradation were monitored using traditional mass loss measurement and size exclusion chromatography (SEC) methods. The obtained data were compared to the changes of capacitance and impedance measured by EIS from PLGA-coated stainless slices with an equivalent electrical circuit model. The results showed that the changes of the resistance and capacitance obtained by EIS, which indicates transformations of PLGA coating, can be correlated to the degradation measured by traditional methods, such as SEC. Furthermore, EIS method was applied to monitor and evaluate the erosion progress of a real stent with PLGA coating. Our results suggested that EIS method can accurately monitor real-time erosion process of thin polymer coatings on DES in situ. PMID:25052293

  15. Sensitivity Enhancement of Bead-based Electrochemical Impedance Spectroscopy (BEIS) biosensor by electric field-focusing in microwells.

    PubMed

    Shin, Kyeong-Sik; Ji, Jae Hoon; Hwang, Kyo Seon; Jun, Seong Chan; Kang, Ji Yoon

    2016-11-15

    This paper reports a novel electrochemical impedance spectroscopy (EIS) biosensors that uses magnetic beads trapped in a microwell array to improve the sensitivity of conventional bead-based EIS (BEIS) biosensors. Unloading the previously measured beads by removing the magnetic bar enables the BEIS sensor to be used repeatedly by reloading it with new beads. Despite its recyclability, the sensitivity of conventional BEIS biosensors is so low that it has not attracted much attentions from the biosensor industry. We significantly improved the sensitivity of the BEIS system by introducing of a microwell array that contains two electrodes (a working electrode and a counter electrode) to concentrate the electric field on the surfaces of the beads. We confirmed that the performance of the BEIS sensor in a microwell array using an immunoassay of prostate specific antigen (PSA) in PBS buffer and human plasma. The experimental results showed that a low concentration of PSA (a few tens or hundreds of fg/mL) were detectable as a ratio of the changes in the impedance of the PBS buffer or in human plasma. Therefore, our BEIS sensor with a microwell array could be a promising platform for low cost, high-performance biosensors for applications that require high sensitivity and recyclability. PMID:27152445

  16. Measurement of Small Molecule Binding Kinetics on a Protein Microarray by Plasmonic-Based Electrochemical Impedance Imaging

    PubMed Central

    2015-01-01

    We report on a quantitative study of small molecule binding kinetics on protein microarrays with plasmonic-based electrochemical impedance microscopy (P-EIM). P-EIM measures electrical impedance optically with high spatial resolution by converting a surface charge change to a surface plasmon resonance (SPR) image intensity change, and the signal is not scaled to the mass of the analyte. Using P-EIM, we measured binding kinetics and affinity between small molecule drugs (imatinib and SB202190) and their target proteins (kinases Abl1 and p38-α). The measured affinity values are consistent with reported values measured by an indirect competitive binding assay. We also found that SB202190 has weak bindings to ABL1 with KD > 10 μM, which is not reported in the literature. Furthermore, we found that P-EIM is less prone to nonspecific binding, a long-standing issue in SPR. Our results show that P-EIM is a novel method for high-throughput measurement of small molecule binding kinetics and affinity, which is critical to the understanding of small molecules in biological systems and discovery of small molecule drugs. PMID:25153794

  17. The promise of electrochemical impedance spectroscopy as novel technology for the management of patients with diabetes mellitus.

    PubMed

    Adamson, Teagan Leigh; Eusebio, Francis Ang; Cook, Curtiss B; LaBelle, Jeffrey T

    2012-09-21

    Self-monitoring of blood glucose is the standard of care in management of hyperglycemia among patients with diabetes mellitus. To increase the sensitivity and specificity of current devices, a novel method of detecting glucose using electrochemical impedance spectroscopy (EIS) technology is explored. The enzyme glucose oxidase (GOx) was fixed to gold electrodes and a sine wave of sweeping frequencies was induced using a wide range of concentrations of glucose. Each frequency in the impedance sweep was analyzed for the highest response and R-squared value. The frequency with both factors optimized is specific for the glucose-GOx binding interaction and was determined to be 1.17 kHz in purified solutions in both higher and lower ranges of glucose. The correlation between the impedance response and concentration at the low range of detection (0-100 mg dL(-1) of glucose) was determined to be 3.53 ohm/ln (mg dL(-1)) with an R-squared value of 0.90 with a 39 mg dL(-1) lower limit of detection. The same frequency of 1.17 kHz was verified in whole blood under the same glucose range. The above data confirm that EIS offers a new method of glucose detection as an alternative to current technology in use by patients. Additionally, the unique frequency response of individual markers allows for modulation of signals so that several other markers important in the management of diabetes could be measured with a single sensor. PMID:22842610

  18. Interpreting impedance spectra of organic photovoltaic cells—Extracting charge transit and recombination rates

    SciTech Connect

    Mullenbach, Tyler K.; Zou, Yunlong; Holmes, Russell J.; Holst, James

    2014-09-28

    Impedance spectroscopy has been widely used to extract the electron-hole recombination rate constant in organic photovoltaic cells (OPVs). This technique is typically performed on OPVs held at open-circuit. Under these conditions, the analysis is simplified with recombination as the only pathway for the decay of excess charge carriers; transit provides no net change in the charge density. In this work, we generalize the application and interpretation of impedance spectroscopy for bulk heterojunction OPVs at any operating voltage. This, in conjunction with reverse bias external quantum efficiency measurements, permits the extraction of both recombination and transit rate constants. Using this approach, the transit and recombination rate constants are determined for OPVs with a variety of electron donor-acceptor pairings and compositions. It is found that neither rate constant individually is sufficient to characterize the efficiency of charge collection in an OPV. It is demonstrated that a large recombination rate constant can be accompanied by a large transit rate constant, thus fast recombination is not necessarily detrimental to OPV performance. Extracting the transit and recombination rate constants permits a detailed understanding of how OPV architecture and processing conditions impact the transient behavior of charge carriers, elucidating the origin of optimum device configurations.

  19. A Label-Free Electrochemical Impedance Cytosensor Based on Specific Peptide-Fused Phage Selected from Landscape Phage Library.

    PubMed

    Han, Lei; Liu, Pei; Petrenko, Valery A; Liu, Aihua

    2016-01-01

    One of the major challenges in the design of biosensors for cancer diagnosis is to introduce a low-cost and selective probe that can recognize cancer cells. In this paper, we combined the phage display technology and electrochemical impedance spectroscopy (EIS) to develop a label-free cytosensor for the detection of cancer cells, without complicated purification of recognition elements. Fabrication steps of the cytosensing interface were monitored by EIS. Due to the high specificity of the displayed octapeptides and avidity effect of their multicopy display on the phage scaffold, good biocompatibility of recombinant phage, the fibrous nanostructure of phage, and the inherent merits of EIS technology, the proposed cytosensor demonstrated a wide linear range (2.0 × 10(2) - 2.0 × 10(8) cells mL(-1)), a low limit of detection (79 cells mL(-1), S/N = 3), high specificity, good inter-and intra-assay reproducibility and satisfactory storage stability. This novel cytosensor designing strategy will open a new prospect for rapid and label-free electrochemical platform for tumor diagnosis. PMID:26908277

  20. Corrosion Behavior of Surface-Treated Implant Ti-6Al-4V by Electrochemical Polarization and Impedance Studies

    NASA Astrophysics Data System (ADS)

    Paul, Subir; Yadav, Kasturi

    2011-04-01

    Implant materials for orthopedic and heart surgical services demand a better corrosion resistance material than the presently used titanium alloys, where protective oxide layer breaks down on a prolonged stay in aqueous physiological human body, giving rise to localized corrosion of pitting, crevice, and fretting corrosion. A few surface treatments on Ti alloy, in the form of anodization, passivation, and thermal oxidation, followed by soaking in Hank solution have been found to be very effective in bringing down the corrosion rate as well as producing high corrosion resistance surface film as reflected from electrochemical polarization, cyclic polarization, and Electrochemical Impedance Spectroscopy (EIS) studies. The XRD study revealed the presence of various types of oxides along with anatase and rutile on the surface, giving rise to high corrosion resistance film. While surface treatment of passivation and thermal oxidation could reduce the corrosion rate by 1/5th, anodization in 0.3 M phosphoric acid at 16 V versus stainless steel cathode drastically brought down the corrosion rate by less than ten times. The mechanism of corrosion behavior and formation of different surface films is better understood from the determination of EIS parameters derived from the best-fit equivalent circuit.

  1. A Label-Free Electrochemical Impedance Cytosensor Based on Specific Peptide-Fused Phage Selected from Landscape Phage Library

    PubMed Central

    Han, Lei; Liu, Pei; Petrenko, Valery A.; Liu, Aihua

    2016-01-01

    One of the major challenges in the design of biosensors for cancer diagnosis is to introduce a low-cost and selective probe that can recognize cancer cells. In this paper, we combined the phage display technology and electrochemical impedance spectroscopy (EIS) to develop a label-free cytosensor for the detection of cancer cells, without complicated purification of recognition elements. Fabrication steps of the cytosensing interface were monitored by EIS. Due to the high specificity of the displayed octapeptides and avidity effect of their multicopy display on the phage scaffold, good biocompatibility of recombinant phage, the fibrous nanostructure of phage, and the inherent merits of EIS technology, the proposed cytosensor demonstrated a wide linear range (2.0 × 102 − 2.0 × 108 cells mL−1), a low limit of detection (79 cells mL−1, S/N = 3), high specificity, good inter-and intra-assay reproducibility and satisfactory storage stability. This novel cytosensor designing strategy will open a new prospect for rapid and label-free electrochemical platform for tumor diagnosis. PMID:26908277

  2. A Label-Free Electrochemical Impedance Cytosensor Based on Specific Peptide-Fused Phage Selected from Landscape Phage Library

    NASA Astrophysics Data System (ADS)

    Han, Lei; Liu, Pei; Petrenko, Valery A.; Liu, Aihua

    2016-02-01

    One of the major challenges in the design of biosensors for cancer diagnosis is to introduce a low-cost and selective probe that can recognize cancer cells. In this paper, we combined the phage display technology and electrochemical impedance spectroscopy (EIS) to develop a label-free cytosensor for the detection of cancer cells, without complicated purification of recognition elements. Fabrication steps of the cytosensing interface were monitored by EIS. Due to the high specificity of the displayed octapeptides and avidity effect of their multicopy display on the phage scaffold, good biocompatibility of recombinant phage, the fibrous nanostructure of phage, and the inherent merits of EIS technology, the proposed cytosensor demonstrated a wide linear range (2.0 × 102 - 2.0 × 108 cells mL-1), a low limit of detection (79 cells mL-1, S/N = 3), high specificity, good inter-and intra-assay reproducibility and satisfactory storage stability. This novel cytosensor designing strategy will open a new prospect for rapid and label-free electrochemical platform for tumor diagnosis.

  3. In situ investigation of pore clogging during discharge of a Li/O2 battery by electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Bardenhagen, Ingo; Yezerska, Olga; Augustin, Matthias; Fenske, Daniela; Wittstock, Arne; Bäumer, Marcus

    2015-03-01

    The behavior of three gas diffusion electrodes (GDE) with macro- and mesopores is investigated by in situ electrochemical impedance spectroscopy (EIS) in the Li/O2 battery system while discharging. Using a three electrode setup the current response from the anode (Li metal) and cathode (GDE) can be separated and the changes of the electrochemical processes at the GDE during discharge can be observed, exclusively. We identify up to four processes with different time constants which we assign to the lithium ion migration through a surface layer, the charge-transfer from the carbon surface to the molecular oxygen, the lithium ion and oxygen diffusion towards the cathode surface and, in case of the mesoporous materials, the lithium ion movement inside the pores, along the pore axis. The latter finding reflects that pore clogging of such is a limiting factor for the discharge of the Li/O2 battery. A large mesopore volume as in the xerogel electrode, however, allows for a high storage capability and a long and constant oxygen reduction. We demonstrate that the three electrode EIS proves to be a powerful in situ diagnostic tool to determine the state and, hence, the reversibility of the reactions at the cathode.

  4. Calculation of the energy loss in giant magnetic impedance elements using the complex magnetic permeability spectra

    NASA Astrophysics Data System (ADS)

    Rustemaj, Driton; Mukherjee, Debashis

    2013-01-01

    The giant magnetic impedance (GMI) effect in ferromagnetic materials has been investigated for sensing applications. The GMI properties were evaluated via numerical solution of the complex magnetic permeability of the material. MATLAB simulation was carried out to study the frequency dependence of magnetic permeability via obtaining solutions of the Landau-Lifshitz-Gilbert (LLG) and the Maxwell's equations. The results indicate that the complex magnetic permeability peaks at a frequency of 6 GHz, corresponding to the ferromagnetic resonant (FMR) frequency, where the energy loss is maximum. A variation of the Gilbert damping parameter (α) associated with the LLG equation inversely affects this peak value. The area under the curve of complex magnetic permeability, calculated through counting the number of pixels within the image, provides an estimate of the average energy loss density within the material and appears to be consistent with the variation of the peak intensity.

  5. The identification of pitting and crevice corrosion spectra in electrochemical noise using an artificial neural network

    SciTech Connect

    Barton, T.F.; Tuck, D.L.; Wells, D.B.

    1996-12-31

    An artificial neural network has been developed to identify the onset and classify the type of localized corrosion from electrochemical noise spectra. The multilayer feedforward (MLF) network was trained by classical back-propagation to identify corrosion from the characteristics of the initial current ramp. Using 50 training files and 39 test files taken from measurements on Type 304 stainless steel in a dilute chloride electrolyte, the network accurately detected and classified 96% of the data and reported no misclassifications. Experiments with high levels of adventitious noise superimposed on the original data have been carried out to examine the noise tolerance of the network.

  6. Interpretation of observations made using local electrochemical impedance mapping (LEIM) on organic coated aluminum alloy 2024-T3

    NASA Astrophysics Data System (ADS)

    Mierisch, Amber Menemsha

    2001-08-01

    Local Electrochemical Impedance Mapping (LED4) was used to investigate local underfilm corrosion of organic coated (epoxy, polyurethane, vinyl) aluminum alloy 2024- T3 substrates immersed in chloride solutions. Several interesting features in LEIM were observed that would provide insight into the local breakdown processes of coated metals if they reflected actual electrochemical phenomena. Contribution to measurements from' artifact or quantities unrelated to breakdown, and the general effect of the dielectric layer on LEIM, were evaluated by comparison of analytical and numerical modeling to LEIM of fabricated electrodes. An equipotential disk was used to model underfilm corrosion. The fields calculated for these models were correlated with LEIM of both bare and coated fabricated electrodes (Au, Pt, Al, Cu). Numerical modeling predicted that a dielectric layer would dull edge effects and severely dampen the magnitude of the field emanating from the substrate surface. A salt film beneath the coating was predicted to have no significant effect on the field. LEIM of coated disk electrodes showed no evidence of the underfilm electrode with two exceptions: (1)underfilm corrosion occurring on pure aluminum, and (2)a copper electrode, which has a very active surface. The discrepancy between modeling and experimental results of coated systems prompted further experimental investigation to isolate the roles of current density and coating defects. Blisters were created on coated gold samples by placing NaCl and AlCl3 salt islands beneath the coating for various coating and substrate configurations. LEIM recorded a peak in admittance only over an acidic blister in polyurethane where local hydrolysis had occurred. It was determined that one of two criteria is required to measure electrochemical activity through a film: (1)the substrate must be actively corroding to produce a current density sufficient to generate a measurable field, or (2)a low resistivity defect must exist

  7. Evaluation of inorganic zinc-rich primers using Electrochemical Impedance Spectroscopy (EIS) in combination with atmospheric exposure

    NASA Technical Reports Server (NTRS)

    Calle, Luz M.

    1994-01-01

    This investigation explored the use of Electrochemical Impedance Spectroscopy (EIS) in combination with atmospheric exposure as a short term method for analyzing the performance of twenty-one commercially available zinc-rich primers. The twenty-one zinc-rich primers were: Carboline CZ-11, Ameron Devoe-Marine Catha-Coat 304, Briner V-65, Ameron D-21-9, Sherwin Williams Zinc Clad II, Carboline CZ-D7, Ameron D-4, Dupont Ganicin 347WB, Porter TQ-4374H, Inorganic Coatings IC-531, Subox Galvanox IV, Southern Coatings Chemtec 600, GLidden Glidzinc 5530, Byco SP-101, Tnemec 90E-75, Devoe Catha-Coat 302H, Glidden Glidzinc 5536, Koppers 701, Ameron D-21-5, Coronado 935-152, and Subox Galvanox V. Data were also collected on galvanized steel for comparison purposes. A library of Bode magnitude plots was generated for each coating including curves for the initial time and after each week of atmospheric exposure at the Beach Corrosion Test site near the Space Shuttle launch pad at the Kennedy Space Center for up to four weeks. Subsequent measurements were collected after 8 weeks and after one year of atmospheric exposure. Analysis of the impedance data was performed with the purpose of identifying parameters that could be used to predict the long-term performance of zinc-rich primers. It has been shown that there is a correlation between the long-term performance of zinc-rich primers and several parameters obtained from EIS measurements in combination with atmospheric exposure. The equivalent circuit R2(R2C(R3W)) provided a satisfactory fit for the EIS data. The corrosion potential and the R2 resistance are parameters indicative of the galvanic mechanism of protection. The capacitance of the coating is related to the barrier mechanism of protection.

  8. Sensitivity improvement of a miniaturized label-free electrochemical impedance biosensor by electrode edge effect

    NASA Astrophysics Data System (ADS)

    Kuo, Yi-Ching; Chen, Ching-Sung; Chang, Ku-Ning; Lin, Chih-Ting; Lee, Chih-Kung

    2014-07-01

    Point-of-care (PoC) biosensors continue to gain popularity because of the desire to improve cost performance in today's health care industry. As cardiovascular disease (CVD) remains one of the top three leading causes of death in Asia, a tool that can help to detect CVDs is highly sought after. We present a high-sensitivity PoC biosensor that can be used to detect CVD biomarkers. To meet the requirements of a PoC biosensor, we adopted electrochemical methods as the basis of the detection. A more stable three-electrode configuration was miniaturized and put onto a biochip. To improve the detection sensitivity associated with the reduced size in the biochip, computer simulation was used to investigate several potential effective possibilities. We found that the electrolyte current density on the edge near the working electrode (WE) and counter electrode (CE) was higher. This was verified using an atomic force microscope to measure the surface potential. We then experimented with the configuration by lengthening the edge of the WE and CE without changing the area of the WE and CE and maintained the gap between the two electrodes. We found improved measurement efficiency with our newly developed biochip.

  9. An Electrochemical Impedance Spectroscopy-Based Technique to Identify and Quantify Fermentable Sugars in Pineapple Waste Valorization for Bioethanol Production

    PubMed Central

    Conesa, Claudia; García-Breijo, Eduardo; Loeff, Edwin; Seguí, Lucía; Fito, Pedro; Laguarda-Miró, Nicolás

    2015-01-01

    Electrochemical Impedance Spectroscopy (EIS) has been used to develop a methodology able to identify and quantify fermentable sugars present in the enzymatic hydrolysis phase of second-generation bioethanol production from pineapple waste. Thus, a low-cost non-destructive system consisting of a stainless double needle electrode associated to an electronic equipment that allows the implementation of EIS was developed. In order to validate the system, different concentrations of glucose, fructose and sucrose were added to the pineapple waste and analyzed both individually and in combination. Next, statistical data treatment enabled the design of specific Artificial Neural Networks-based mathematical models for each one of the studied sugars and their respective combinations. The obtained prediction models are robust and reliable and they are considered statistically valid (CCR% > 93.443%). These results allow us to introduce this EIS-based technique as an easy, fast, non-destructive, and in-situ alternative to the traditional laboratory methods for enzymatic hydrolysis monitoring. PMID:26378537

  10. Electrochemical Impedance Spectroscopy and Corrosion Behavior of Co/CeO2 Nanocomposite Coatings in Simulating Body Fluid Solution

    NASA Astrophysics Data System (ADS)

    Benea, Lidia

    2013-02-01

    A series of Co/CeO2 (25 nm) nanocomposite coating materials by electrodeposition were successfully prepared containing different cerium oxide composition in the cobalt-plating bath. Stainless steel (304L) was used as support material for nanocomposite coatings. The nano-CeO2 is uniformly incorporated into cobalt matrix, and the effect on surface morphologies was identified by scanning electron microscopy with energy-dispersive X-ray analysis. Codeposition of nano-CeO2 particles with cobalt disturbs the regular surface morphology of the cobalt coatings. It should be noted that the as-prepared Co/CeO2 nanocomposite coatings were found to be much superior in corrosion resistance over those of pure cobalt coatings materials based on a series of electrochemical impedance spectroscopy measurements in simulating body fluid solution. With increase in the nano-CeO2 particles concentration in the cobalt electrolyte, it is observed that the corrosion resistance of Co/CeO2 increases. Co/CeO2 nanocomposite coatings have higher polarization resistance as compared with pure cobalt layers in simulating body fluid solution.

  11. Study of benzotriazole as corrosion inhibitors of carbon steel in chloride solution containing hydrogen sulfide using electrochemical impedance spectroscopy (EIS)

    SciTech Connect

    Solehudin, Agus; Nurdin, Isdiriayani

    2014-03-24

    Corrosion and inhibition studies on API 5LX65 carbon steel in chloride solution containing various concentrations of benzotriazole has been conducted at temperature of 70°C using Electrochemical Impedance Spectroscopy (EIS). Corroded carbon steel surface with and without inhibitor have been observed using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDS). The objectives of this research are to study the performance of benzotriazole as corrosion inhibitors. The experimental results of carbon steel corrosion in 3.5% NaCl solution containing 500 mg/l H{sub 2}S at different BTAH concentrations showed that corrosion rate of carbon steel decreases with increasing of BTAH concentrations from 0 to 10 mmol/l. The inhibition efficiency of BTAH was found to be affected by its concentration. The optimum efficiency obtained of BTAH is 93% at concentration of 5 mmol/l. The result of XRD and EDS analysis reveal the iron sulfide (FeS) formation on corroded carbon steel surface without inhibitor. The EDS spectrum show the Nitrogen (N) bond on carbon steel surface inhibited by BTAH.

  12. Study of benzotriazole as corrosion inhibitors of carbon steel in chloride solution containing hydrogen sulfide using electrochemical impedance spectroscopy (EIS)

    NASA Astrophysics Data System (ADS)

    Solehudin, Agus; Nurdin, Isdiriayani

    2014-03-01

    Corrosion and inhibition studies on API 5LX65 carbon steel in chloride solution containing various concentrations of benzotriazole has been conducted at temperature of 70°C using Electrochemical Impedance Spectroscopy (EIS). Corroded carbon steel surface with and without inhibitor have been observed using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDS). The objectives of this research are to study the performance of benzotriazole as corrosion inhibitors. The experimental results of carbon steel corrosion in 3.5% NaCl solution containing 500 mg/l H2S at different BTAH concentrations showed that corrosion rate of carbon steel decreases with increasing of BTAH concentrations from 0 to 10 mmol/l. The inhibition efficiency of BTAH was found to be affected by its concentration. The optimum efficiency obtained of BTAH is 93% at concentration of 5 mmol/l. The result of XRD and EDS analysis reveal the iron sulfide (FeS) formation on corroded carbon steel surface without inhibitor. The EDS spectrum show the Nitrogen (N) bond on carbon steel surface inhibited by BTAH.

  13. An Electrochemical Impedance Spectroscopy-Based Technique to Identify and Quantify Fermentable Sugars in Pineapple Waste Valorization for Bioethanol Production.

    PubMed

    Conesa, Claudia; García-Breijo, Eduardo; Loeff, Edwin; Seguí, Lucía; Fito, Pedro; Laguarda-Miró, Nicolás

    2015-01-01

    Electrochemical Impedance Spectroscopy (EIS) has been used to develop a methodology able to identify and quantify fermentable sugars present in the enzymatic hydrolysis phase of second-generation bioethanol production from pineapple waste. Thus, a low-cost non-destructive system consisting of a stainless double needle electrode associated to an electronic equipment that allows the implementation of EIS was developed. In order to validate the system, different concentrations of glucose, fructose and sucrose were added to the pineapple waste and analyzed both individually and in combination. Next, statistical data treatment enabled the design of specific Artificial Neural Networks-based mathematical models for each one of the studied sugars and their respective combinations. The obtained prediction models are robust and reliable and they are considered statistically valid (CCR% > 93.443%). These results allow us to introduce this EIS-based technique as an easy, fast, non-destructive, and in-situ alternative to the traditional laboratory methods for enzymatic hydrolysis monitoring. PMID:26378537

  14. On the sensitivity improvement of a miniaturized label-free electrochemical impedance biosensor

    NASA Astrophysics Data System (ADS)

    Kuo, Yi-Ching; Chou, Shin-Ting; Tsai, Pei-I.; Li, Guan-Wei; Lin, Chih-Ting; Lee, Chih-Kung

    2014-03-01

    Development of point-of-care biosensors continues to gain popularity due to the demand of improving the cost performance in today's health care. As cardiovascular disease induced death remains on the top 3 death causes for most Asian countries, this paper is to present a high-sensitivity point-of-care biosensor for the detection of cardiovascular disease biomarkers. To meet the point-of-care biosensors requirements, which include characteristics such as small size, low cost, and ease of operation, we adopted electrochemical methods as the basis of detection. The 4-aminothiophenol was adopted as the bio-linkers to facilitate the antibody-antigen interaction. A more stable three-electrode configuration was miniaturized and laid out onto a biochip. A microfluidics subsystem based on opto-piezoelectronic technology was also integrated to create the microfluidic biochip system. To improve the detection sensitivity associated with the reduction in biochip size, electrochemistry simulation was used to investigate several potentially effective means. We found that the electric field on the edge near working electrode and counter electrode was higher, which was verified by using atomic force microscopy to measure the surface potential. With the successful verification, we explored the configuration, i.e., lengthened the edge of working electrode and counter electrode without changing the areas of working electrode and counter electrode and the gap between these two electrodes, so as to evaluate the possibility of improving the measurement efficiency in our newly developed biochips. Detailed design, simulation and experimental results, improved design identified, etc. were all presented in detail.

  15. Alternating current impedance imaging of high-resistance membrane pores using a scanning electrochemical microscope. Application of membrane electrical shunts to increase measurement sensitivity and image contrast.

    PubMed

    Ervin, Eric Nathan; White, Henry S; Baker, Lane A; Martin, Charles R

    2006-09-15

    Whether an individual pore in a porous membrane can be imaged using scanning electrochemical microscopy (SECM), operated in ac impedance mode, is determined by the magnitude of the change in the total impedance of the imaging system as the SECM tip is scanned over the pore. In instances when the SECM tip resistance is small relative to the internal pore resistance, the total impedance changes by a negligible amount, rendering the pore invisible during impedance imaging. A simple solution to this problem is to introduce a low-impedance electrical shunt (i.e., a salt bridge) across the membrane. This principle is demonstrated by imaging polycarbonate membranes (6-12-microm thickness) containing between 1 and 2000 conical-shaped pores (60-nm- and 2.5-microm-diameter openings) using an approximately 1-microm-radius Pt tip. Theory and experiments show that image contrast (the change in ac current measured as the probe is scanned over the pore) is inversely proportional to the total resistance of the membrane and can be increased by a factor of approximately 50x by introducing a low-resistance electrical shunt across the membrane. Remarkably, SECM images of membranes containing a single high-resistance (approximately 1 G Omega) pore can only be imaged by short-circuiting the membrane. Image contrast also becomes independent of membrane resistance when an electrical shunt is used, allowing for more quantitative comparisons of the features in ac impedance images of different membranes. PMID:16970331

  16. Assessment of the Effects of Flow Rate and Ionic Strength on Microbial Fuel Cell Performance Using Electrochemical Impedance Spectroscopy

    SciTech Connect

    Aaron, D; Tsouris, Costas; Hamilton, Choo Yieng; Borole, Abhijeet P

    2010-01-01

    Impedance changes of the anode, cathode and solution were examined for a microbial fuel cell (MFC) under varying conditions in order to improve its performance. An MFC inoculated with a pre-enriched microbial culture resulted in a startup time of ten days. Over this period, the anode impedance decreased below the cathode impedance, suggesting a cathode limited power output. Decreasing the anode flow rate did not impact the anode impedance significantly, while it increased the cathode impedance by 65% . Reducing the anode-medium ionic strength from 100% to 10% increased the cathode impedance by 48%.

  17. Measurement of surface resistivity/conductivity of different organic thin films by a combination of optical shearography and electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Habib, Khaled

    2013-11-01

    Shearography techniques were applied again to measure the surface resistivity/conductivity of different organic thin films on a metallic substrate. The coatings were ACE premium-grey enamel (spray coating), a yellow Acrylic lacquer, and a gold nail polish on a carbon steel substrate. The investigation was focused on determining the in-plane displacement of the coatings by shearography between 20 and 60 °C. Then, the alternating current (AC) impedance (resistance) of the same coated samples was determined by electrochemical impedance spectroscopy (EIS) in 3.0% NaCl solution at room temperature. As a result, the proportionality constant (resistivity or conductivity = 1/surface resistivity) between the determined AC impedance and the in-plane displacement was obtained. The obtained resistivity of all investigated coatings, 40:15 × 106-24:6 × 109Ωcm, was found in the insulator range.

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

    SciTech Connect

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

    2015-01-15

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

  19. Evaluation of an Oxide Layer on NI-CR-MO-W Alloy Using Electrochemical Impedance Spectroscopy and Surface Analysis

    SciTech Connect

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

    2006-12-21

    High corrosion resistance under very aggressive conditions is a distinguishing property of Ni-Cr-Mo-W alloys. One such alloy, Alloy 22, is a candidate material for fabrication of the outer layer of high-level nuclear waste (HLNW) packages for the proposed HLNW repository at Yucca Mountain, Nevada, USA. We are using Electrochemical Impedance Spectroscopy (EIS), ex-situ X-Ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectroscopy (ToF SIMS) to characterize the electrochemical properties and composition of the protective oxide formed on Alloy 22 surfaces. These studies have been conducted at temperatures up to 90 C at potentials from -0.8 V to 0.8 V (vs. Ag/AgCl (sat'd KCl)) in deaerated 5 mol L{sup -1} NaCl solution. Using this combination of techniques, we can correlate the electrical (from EIS) and compositional properties (from XPS, ToF SIMS) of the oxide. At more negative potentials (-0.8 V to -0.4 V) the film exhibits a low charge transfer resistance and high capacitance, indicating the presence of a very defective film with a high concentration of electronic defects. The presence of additional elements in the equivalent circuit, corresponding to water reduction, supports this suggestion. At these potentials, surface analysis techniques show a thin oxide layer with a low concentration of Cr203. Increasing the potential (to between -0.2 and 0.2 V) leads to a major increase in overall interfacial resistance consistent with the formation of an oxide with a small concentration of electronic defects. At the same time, the surface analysis techniques show increases in the film thickness and the Cr{sub 2}O{sub 3} content. A further increase in potential to 0.8 V, in general, leads to a decrease in interfacial resistance throughout the film. When the Cr{sub 2}O{sub 3} barrier layer is degraded, then the higher oxidation states of Mo and W species (MO{sup VI}, W{sup VI}) increase in concentration and are stored in the outer part of the film

  20. A sensitive electrochemical impedance immunosensor for determination of malachite green and leucomalachite green in the aqueous environment.

    PubMed

    Zhu, Dan; Li, Qiangqiang; Pang, Xiumei; Liu, Yue; Wang, Xue; Chen, Gang

    2016-08-01

    Application of malachite green (MG) and leucomalachite green (LMG) in fish farm water causes an environmental problem. This study proposes for the first time a sensitive and convenient electrochemical impedance spectroscopy (EIS) method for determining MG and LMG by a bovine serum albumin-decorated gold nanocluster (BSA-AuNC)/antibody composite film-based immunosensor. In order to improve the analytical performance, the glassy carbon electrode (GCE) was modified with 1, 4-phenylenediamine to form a stable layer, and then, BSA-AuNCs were covalently bound to the GCE. An adequate quantity of the polyclonal antibody of LMG was immobilized onto the surface of the BSA-AuNCs by the chemical reaction of EDC/NHS. The sensors can respond to the specific target based on specific covalent bonding. The experimental parameters, such as the pH, incubating concentration, and time, have been investigated and optimized. The calibration curve for LMG was linear in the range of 0.1~10.0 ng/mL with the limit of detection (LOD) 0.03 ng/mL. Furthermore, the sum of MG and LMG was detected in fish farm water by MG reduction. The recovery was between 89.7 % and 99.2 % in spiked samples. The EC sensor method was also compared with the ELISA method and validated by the LC-MS/MS method, which proves its great promise as a field instrument for the rapid monitoring of MG and LMG pollution. Graphical abstract 1, 4-Phenylenediamine and BSA-AuNC/antibody-decorated glassy carbon electrodes have been used for the impedimetric detection of the sum of malachite green and leucomalachite green via specific immuno-binding. PMID:27277811

  1. A correlation between salt spray and electrochemical impedance spectroscopy test results for conversion-coated aluminum alloys

    SciTech Connect

    Buchheit, R.G.; Cunningham, M.; Jensen, H.; Kendig, M.W.; Martinez, M.A.

    1998-01-01

    The corrosion resistance of 33 inorganic conversion coatings applied to five aluminum alloys was tested by salt spray exposure and electrochemical impedance spectroscopy (EIS). Results were evaluated to determine if a relationship existed. Individual salt spray test panels, with an area of 30 in.{sup 2} (194 cm{sup 2}), were inspected visually at regular intervals up to 168 h of exposure. At each inspection interval, panels were assigned a pass rank if <5 pits were observed, or a fail rank if >5 pits were observed. EIS data were analyzed using a simple equivalent circuit which yielded a coating resistance (R{sub c}), which was used as a figure of merit to assess coating performance. Examination of the data showed both tests could be sensitive discriminators of corrosion protection, but that EIS was more discriminating in the extremes of coating performance. Analysis showed the probability of achieving a passing salt spray result increased as R{sub c} increased. In the regimes where both tests were sensitive, regression analysis showed a linear relationship existed for each alloy substrate between the log of R{sub c} and the probability of a coating meeting the pass/fail criterion in salt spray. Based upon these relationships, threshold R{sub c} values were proposed to define the minimum value for which a given coating can be expected to attain a passing result in a 168-h salt spray test. These values were 2 {times} 10{sup 6} {Omega}-cm{sup 2} to 5 {times} 10{sup 6} {Omega}-cm{sup 2} for Al 356 (UNS A13560), Al 2024-T3 (UNS A92024), and Al 6061-T6 (UNS A96061); 1.5 {times} 10{sup 7} for Al 7075-T6 (UNS A97075); and 2.3 {times} 10{sup 6} {Omega}-cm{sup 2} for Al 3003 (UNS A93003).

  2. Microstructural and electrochemical impedance characterization of bio-functionalized ultrafine ZnS nanocrystals-reduced graphene oxide hybrid for immunosensor applications

    NASA Astrophysics Data System (ADS)

    Mishra, Sujeet K.; Srivastava, Avanish K.; Kumar, Devendra; Biradar, Ashok M.; Rajesh, Affa

    2013-10-01

    We report a mercaptopropionic acid capped ZnS nanocrystals decorated reduced graphene oxide (RGO) hybrid film on a silane modified indium-tin-oxide glass plate, as a bioelectrode for the quantitative detection of human cardiac myoglobin (Ag-cMb). The ZnS nanocrystals were anchored over electrochemically reduced GO sheets through a cross linker, 1-pyrenemethylamine hydrochloride, by carbodiimide reaction and have been characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The transmission electron microscopic characterization of the ZnS-RGO hybrid shows the uniform distribution of ultra-fine nanoparticles of ZnS in nano-sheets of GO throughout the material. The protein antibody, Ab-cMb, was covalently linked to ZnS-RGO nanocomposite hybrid for the fabrication of the bioelectrode. A detailed electrochemical immunosensing study has been carried out on the bioelectrode towards the detection of target Ag-cMb. The optimal fitted equivalent circuit model that matches the impedance response has been studied to delineate the biocompatibility, sensitivity and selectivity of the bioelectrode. The bioelectrode exhibited a linear electrochemical impedance response to Ag-cMb in a range of 10 ng to 1 μg mL-1 in PBS (pH 7.4) with a sensitivity of 177.56 Ω cm2 per decade. The combined synergistic effects of the high surface-to-volume ratio of ZnS(MPA) nanocrystals and conducting RGO has provided a dominant charge transfer characteristic (Ret) at the lower frequency region of <10 Hz showing a good biocompatibility and enhanced impedance sensitivity towards target Ag-cMb. The impedance response sensitivity of the ZnS-RGO hybrid bioelectrode towards Ag-cMb has been found to be about 2.5 fold higher than that of a bare RGO modified bioelectrode.

  3. Studies of the Use of Electrochemical Impedance Spectroscopy to Characterize and Assess the Performance of Lacquers Used to Protect Aluminum Sheet and Can Ends

    NASA Astrophysics Data System (ADS)

    Ali, Mohammad

    This study involved investigating the feasibility of using Electrochemical Impedance Spectroscopy to assess the performance of coatings used to protect aluminum in beverage containers, and developing an accelerated testing procedure. In the preliminary investigation, tests were performed to ensure that the EIS systems at hand are capable, functional and consistent. This was followed by EIS testing of kitchen-aluminum foil and high-impedance epoxy polymer as a baseline for chemically-active and chemically-inert systems. The ability of EIS to differentiate between intact and flawed coatings was tested by investigating deliberately damaged coatings. The effects of varying the pH and oxygen content on the performance of the coated aluminum samples were also tested. From this investigation, it has been concluded that EIS can be used to differentiate between intact and flawed coatings and detect corrosion before it is visually observable. Signatures of corrosion have been recorded and a preliminary testing procedure has been drawn.

  4. Electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes: FFT-impedance spectroscopy of the growth process and magnetic properties

    NASA Astrophysics Data System (ADS)

    Gerngross, Mark-Daniel; Carstensen, Jürgen; Föll, Helmut

    2014-06-01

    The electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes has been investigated by fast Fourier transform-impedance spectroscopy (FFT-IS) in the frequency range from 75 Hz to 18.5 kHz. The impedance data could be fitted very well using an electric circuit equivalent model with a series resistance connected in series to a simple resistor-capacitor ( RC) element and a Maxwell element. Based on the impedance data, the Co deposition in ultra-high aspect ratio InP membranes can be divided into two different Co deposition processes. The corresponding share of each process on the overall Co deposition can be determined directly from the transfer resistances of the two processes. The impedance data clearly show the beneficial impact of boric acid on the Co deposition and also indicate a diffusion limitation of boric acid in ultra-high aspect ratio InP membranes. The grown Co nanowires are polycrystalline with a very small grain size. They show a narrow hysteresis loop with a preferential orientation of the easy magnetization direction along the long nanowire axis due to the arising shape anisotropy of the Co nanowires.

  5. Electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes: FFT-impedance spectroscopy of the growth process and magnetic properties

    PubMed Central

    2014-01-01

    The electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes has been investigated by fast Fourier transform-impedance spectroscopy (FFT-IS) in the frequency range from 75 Hz to 18.5 kHz. The impedance data could be fitted very well using an electric circuit equivalent model with a series resistance connected in series to a simple resistor-capacitor (RC) element and a Maxwell element. Based on the impedance data, the Co deposition in ultra-high aspect ratio InP membranes can be divided into two different Co deposition processes. The corresponding share of each process on the overall Co deposition can be determined directly from the transfer resistances of the two processes. The impedance data clearly show the beneficial impact of boric acid on the Co deposition and also indicate a diffusion limitation of boric acid in ultra-high aspect ratio InP membranes. The grown Co nanowires are polycrystalline with a very small grain size. They show a narrow hysteresis loop with a preferential orientation of the easy magnetization direction along the long nanowire axis due to the arising shape anisotropy of the Co nanowires. PMID:25050088

  6. A ladder network modelling the electrochemical impedance of the diffusion and reaction processes in semi-infinite space.

    PubMed

    Moya, A A

    2016-02-01

    The Gerischer impedance, i.e., the diffusion-reaction impedance of an ionic species in semi-infinite space, has been modelled by means of a novel simple equivalent ladder electric circuit constituted by a finite number of resistors and capacitors, which corresponds to the Cauer structure obtained from development into continued fractions. The Nyquist plots of the impedance of the ladder network or Cauer circuit and the deviation with respect to the Gerischer impedance have been originally analysed as a function of the number of circuit elements. From the Cauer equivalent circuit, a new and simple expression modelling the Gerischer impedance at the limit of the lowest frequencies has been derived. PMID:26763107

  7. Electrochemical impedance spectroscopy study on the corrosion of the weld zone of 3Cr steel welded joints in CO2 environments

    NASA Astrophysics Data System (ADS)

    Xu, Li-ning; Zhu, Jin-yang; Lu, Min-xu; Zhang, Lei; Chang, Wei

    2015-05-01

    The welded joints of 3Cr pipeline steel were fabricated with commercial welding wire using the gas tungsten arc welding (GTAW) technique. Potentiodynamic polarization curves, linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS) were used to investigate the corrosion resistance and the growth of a corrosion film on the weld zone (WZ). The changes in electrochemical characteristics of the film were obtained through fitting of the EIS data. The results showed that the average corrosion rate of the WZ in CO2 environments first increased, then fluctuated, and finally decreased gradually. The formation of the film on the WZ was divided into three stages: dynamic adsorption, incomplete-coverage layer formation, and integral layer formation.

  8. Negative resistance for methanol electro-oxidation on platinum/carbon (Pt/C) catalyst investigated by an electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Cai, Guang-Xu; Guo, Jian-Wei; Wang, Jia; Li, Song

    2015-02-01

    The poisoning of Pt-based catalyst occurs generally during methanol electro-oxidation. Though traditional electrochemical techniques have probed these issues intensively, it is amazing to find that the negative resistance presents in the intermediate potential zone during an electrochemical impedance spectroscopy (EIS) measurement. Based on the chemical reaction analysis, we establish an EIS model and make some numerical analyses, thus determining the specific EIS shapes and equivalent circuits relating to various potential zones. These results not only compensate the drawback for traditional electrochemical approaches, but also reveal the dynamic adsorption of CO and OH species on Pt surfaces, providing a chance for understanding bifunctional mechanism towards quantitative manners. Significantly, we clarify that the negative resistance begins from the maximum catalysis of methanol electro-catalysis and ends in the initial passive state on Pt surfaces, offering a tool for further improvement. Interestingly, our discovery for negative resistance is consistent with that in general electrochemical system, facilitating its extension and direction in future.

  9. Impedance spectra of Fe-doped SrTiO3 thin films upon bias voltage: inductive loops as a trace of ion motion.

    PubMed

    Taibl, S; Fafilek, G; Fleig, J

    2016-08-01

    Mass and charge transport properties of slightly Fe-doped SrTiO3 (Fe:STO) thin films on a conducting substrate were investigated by means of impedance spectroscopy under different bias voltages and I-V measurements with varying scan rates. At measurement temperatures between 325 °C and 700 °C the applied bias voltage caused an unusual "inductive loop" in the low frequency range of impedance spectra. DC measurements showed that current-voltage curves strongly depend on the scan rate, indicating that different states of the sample became accessible to probe. Both findings can be understood in terms of bias induced ion motion, i.e. by stoichiometry polarization within the Fe:STO thin films upon voltage. Hence, the appearance of an "inductive loop" in the impedance spectra is considered a very general feature that might exist for many materials, particularly in oxide thin films. It may indicate ion motion and stoichiometry variations taking place in the corresponding frequency range. PMID:27088884

  10. Combinatorial materials research applied to the development of new surface coatings X: a high-throughput electrochemical impedance spectroscopy method for screening organic coatings for corrosion inhibition.

    PubMed

    He, Jie; Bahr, James; Chisholm, Bret J; Li, Jun; Chen, Zhigang; Balbyshev, Séva N; Bonitz, Verena; Bierwagen, Gordon P

    2008-01-01

    The objective of the study was to develop a high-throughput electrochemical impedance spectroscopy (HT-EIS) method for rapid and quantitative evaluation of corrosion protective coatings. A 12-element, spatially addressable electrochemical platform was designed, fabricated, and validated. This platform was interfaced to a commercial EIS instrument through an automated electronic switching unit. The HT-EIS system enables four parallel EIS measurements to be run simultaneously, which significantly reduces characterization time compared to that of serial EIS measurements using a multiplexer. The performance of the HT-EIS system was validated using a series of model systems, including a Randles equivalent circuit, an electrochemical reaction (Ti/K4FeCN6, K3FeCN6), a highly uniform polymer film, and several polymer coatings. The results of the validation studies showed that the HT-EIS system enables a major reduction in characterization time and provides high quality data comparable to data obtained with conventional, single-cell EIS measurement systems. PMID:18582116

  11. Electrolyte ion adsorption and charge blocking effect at the hematite/aqueous solution interface: an electrochemical impedance study using multivariate data analysis.

    PubMed

    Shimizu, K; Nyström, J; Geladi, P; Lindholm-Sethson, B; Boily, J-F

    2015-05-01

    A model-free multivariate analysis using singular value decomposition is employed to refine an equivalent electrical circuit model in order to probe the electrochemical properties of the hematite/water interface in dilute NaCl and NH4Cl solutions using electrochemical impedance spectroscopy. The result shows that the surface protonation is directly related to the mobility and trapping of charge carriers at the mineral surface. Moreover, the point of zero charge can be found at pH where the charge transfer resistance is the highest, in addition to the minimum double layer capacitance. The inner-sphere interaction of the NH4(+) ion with the surface is indicated by an increase of capacitance for charge carrier trapping from the protonated surface as well as lower double layer capacitance and open circuit potential. It is clear that the intrinsic electrochemical activity of hematite depends on the degree of surface (de)protonation and other inner-sphere adsorption, as these processes affect the charge carrier density in the surface state. This work also highlights an important synergistic effect of the two spectral analyses that enables EIS to be utilized in an in-depth investigation of mineral/water interfaces. PMID:25857599

  12. An electrochemical study of corrosion protection by primer-topcoat systems on 4130 steel with ac impedance and dc methods

    NASA Technical Reports Server (NTRS)

    Mendrek, M. J.; Higgins, R. H.; Danford, M. D.

    1988-01-01

    To investigate metal surface corrosion and the breakdown of metal protective coatings, the ac impedance method is applied to six systems of primer coated and primer topcoated 4130 steel. Two primers were used: a zinc-rich epoxy primer and a red lead oxide epoxy primer. The epoxy-polyamine topcoat was used in four of the systems. The EG and G-PARC Model 368 ac impedance measurement system, along with dc measurements with the same system using the polarization resistance method, were used to monitor changing properties of coated 4230 steel disks immersed in 3.5 percent NaCl solutions buffered at pH 5.4 over periods of 40 to 60 days. The corrosion system can be represented by an electronic analog called an equivalent circuit consisting of resistors and capacitors in specific arrangements. This equivalent circuit parallels the impedance behavior of the corrosion system during a frequency scan. Values for the resistors and capacitors, that can be assigned in the equivalent circuit following a least-squares analysis of the data, describe changes that occur on the corroding metal surface and in the protective coatings. Two equivalent circuits have been determined that predict the correct Bode phase and magnitude of the experimental sample at different immersion times. The dc corrosion current density data are related to equivalent circuit element parameters. Methods for determining corrosion rate with ac impedance parameters are verified by the dc method.

  13. Electrochemical impedance spectroscopy study on polymerization of L-lysine on electrode surface and its application for immobilization and detection of suspension cells.

    PubMed

    Huang, Baozhen; Jia, Ningming; Chen, Lina; Tan, Liang; Yao, Shouzhuo

    2014-07-15

    Poly-L-lysine (PLL), which has been employed as a conductive polymer in the construction of some electrochemical sensors, can be prepared using L-lysine by cyclic voltammetry (CV) with a wide potential range. However, the presented explanation and description about its polymerization mechanism seems oversimplified because the self-reaction of electrode and the electrolysis of solvent at high potential are ignored. This work presents an intensive investigation on the relevant reactions during the process of PLL-polymerization using CV, X-ray photoelectron spectroscopy, Fourier transform-infrared spectroscopy, and electrochemical impedance spectroscopy. At a higher positive potential, the transfer from lysine molecules to cation radicals and the polymerization reaction on the glassy carbon electrode (GCE) could be achieved, accompanied by the activation of GCE, the formation of oxygen-containing functional groups, and the generation of oxygen derived from the oxidation of water. The adsorbed oxygen had a seriously negative effect on the formation of PLL unless it suffered reduction at a lower negative potential. The charge transfer through the electrochemical polymerized PLL film was seriously hindered by the immobilization of suspension cells due to the electrostatic interaction. The charge-transfer resistance difference (ΔR(ct)) was increased with the enhancement of the cell number (N(cells)) and the 1/ΔR(ct) value displayed a linear response with 1/N(cells) in the range of 5.0 × 10(2)-1.0 × 10(5) cells with a detection limit of 180 cells estimated at a signal-to-noise ratio of 3. A sensitive electrochemical sensor for the quantitative detection of suspension cells was developed. PMID:24939429

  14. Electrochemical exfoliation of carbon dots with the narrowest full width at half maximum in their fluorescence spectra in the ultraviolet region using only water as electrolyte.

    PubMed

    Li, Xuehua; Zhao, Zhiwei; Pan, Chen

    2016-08-01

    Here, a novel kind of CDs were electrochemically exfoliated from graphite rods using distilled water as the only electrolyte. The as-exfoliated CDs showed two significant features: the narrowest fluorescence spectra with a FWHM of only 10 nm and ultraviolet fluorescence spectra in the region up to 360 nm. PMID:27376467

  15. X-ray and Electrochemical Impedance Spectroscopy Diagnostic Investigations of Liquid Water in Polymer Electrolyte Membrane Fuel Cell Gas Diffusion Layers

    NASA Astrophysics Data System (ADS)

    Antonacci, Patrick

    In this thesis, electrochemical impedance spectroscopy (EIS) and synchrotron x-ray radiography were utilized to characterize the impact of liquid water distributions in polymer electrolyte membrane fuel cell (PEMFC) gas diffusion layers (GDLs) on fuel cell performance. These diagnostic techniques were used to quantify the effects of liquid water visualized on equivalent resistances measured through EIS. The effects of varying the thickness of the microporous layer (MPL) of GDLs were studied using these diagnostic techniques. In a first study on the feasibility of this methodology, two fuel cell cases with a 100 microm-thick and a 150 microm-thick MPL were compared under constant current density operation. In a second study with 10, 30, 50, and 100 microm-thick MPLs, the liquid water in the cathode substrate was demonstrated to affect mass transport resistance, while the liquid water content in the anode (from back diffusion) affected membrane hydration, evidenced through ohmic resistance measurements.

  16. Non-uniform temperature distribution in Li-ion batteries during discharge - A combined thermal imaging, X-ray micro-tomography and electrochemical impedance approach

    NASA Astrophysics Data System (ADS)

    Robinson, James B.; Darr, Jawwad A.; Eastwood, David S.; Hinds, Gareth; Lee, Peter D.; Shearing, Paul R.; Taiwo, Oluwadamilola O.; Brett, Dan J. L.

    2014-04-01

    Thermal runaway is a major cause of failure in Li-ion batteries (LIBs), and of particular concern for high energy density transport applications, where safety concerns have hampered commercialisation. A clear understanding of electro-thermal properties and how these relate to structure and operation is vital to improving thermal management of LIBs. Here a combined thermal imaging, X-ray tomography and electrochemical impedance spectroscopy (EIS) approach was applied to commercially available 18650 cells to study their thermal characteristics. Thermal imaging was used to characterise heterogeneous temperature distributions during discharge above 0.75C; the complementary information provided by 3D X-ray tomography was utilised to evaluate the internal structure of the battery and identify the regions causing heating, specifically the components of the battery cap.

  17. A study of X100 pipeline steel passivation in mildly alkaline bicarbonate solutions using electrochemical impedance spectroscopy under potentiodynamic conditions and Mott-Schottky

    NASA Astrophysics Data System (ADS)

    Gadala, Ibrahim M.; Alfantazi, Akram

    2015-12-01

    The key steps involved in X100 pipeline steel passivation in bicarbonate-based simulated soil solutions from the pre-passive to transpassive potential regions have been analyzed here using a step-wise anodizing-electrochemical impedance spectroscopy (EIS) routine. Pre-passive steps involve parallel dissolution-adsorption in early stages followed by clear diffusion-adsorption control shortly before iron hydroxide formation. Aggressive NS4 chlorides/sulfate promote steel dissolution whilst inhibiting diffusion in pre-passive steps. Diffusive and adsorptive effects remain during iron hydroxide formation, but withdraw shortly thereafter during its removal and the development of the stable iron carbonate passive layer. Passive layer protectiveness is evaluated using EIS fitting, current density analysis, and correlations with semiconductive parameters, consistently revealing improved robustness in colder, bicarbonate-rich, chloride/sulfate-free conditions. Ferrous oxide formation at higher potentials results in markedly lower impedances with disordered behavior, and the involvement of the iron(III) valence state is observed in Mott-Schottky tests exclusively for 75 °C conditions.

  18. A catalyst layer optimisation approach using electrochemical impedance spectroscopy for PEM fuel cells operated with pyrolysed transition metal-N-C catalysts

    NASA Astrophysics Data System (ADS)

    Malko, Daniel; Lopes, Thiago; Ticianelli, Edson A.; Kucernak, Anthony

    2016-08-01

    The effect of the ionomer to carbon (I/C) ratio on the performance of single cell polymer electrolyte fuel cells is investigated for three different types of non-precious metal cathodic catalysts. Polarisation curves as well as impedance spectra are recorded at different potentials in the presence of argon or oxygen at the cathode and hydrogen at the anode. It is found that a optimised ionomer content is a key factor for improving the performance of the catalyst. Non-optimal ionomer loading can be assessed by two different factors from the impedance spectra. Hence this observation could be used as a diagnostic element to determine the ideal ionomer content and distribution in newly developed catalyst-electrodes. An electrode morphology based on the presence of inhomogeneous resistance distribution within the porous structure is suggested to explain the observed phenomena. The back-pressure and relative humidity effect on this feature is also investigated and supports the above hypothesis. We give a simple flowchart to aid optimisation of electrodes with the minimum number of trials.

  19. Electrochemical and impedance characterization of Microbial Fuel Cells based on 2D and 3D anodic electrodes working with seawater microorganisms under continuous operation.

    PubMed

    Hidalgo, D; Sacco, A; Hernández, S; Tommasi, T

    2015-11-01

    A mixed microbial population naturally presents in seawater was used as active anodic biofilm of two Microbial Fuel Cells (MFCs), employing either a 2D commercial carbon felt or 3D carbon-coated Berl saddles as anode electrodes, with the aim to compare their electrochemical behavior under continuous operation. After an initial increase of the maximum power density, the felt-based cell reduced its performance at 5 months (from 7 to 4 μW cm(-2)), while the saddle-based MFC exceeds 9 μW cm(-2) (after 2 months) and maintained such performance for all the tests. Electrochemical impedance spectroscopy was used to identify the MFCs controlling losses and indicates that the mass-transport limitations at the biofilm-electrolyte interface have the main contribution (>95%) to their internal resistance. The activation resistance was one order of magnitude lower with the Berl saddles than with carbon felt, suggesting an enhanced charge-transfer in the high surface-area 3D electrode, due to an increase in bacteria population growth. PMID:26166463

  20. Disposable MMP-9 sensor based on the degradation of peptide cross-linked hydrogel films using electrochemical impedance spectroscopy.

    PubMed

    Biela, Anna; Watkinson, Michael; Meier, Ute C; Baker, David; Giovannoni, Gavin; Becer, C Remzi; Krause, Steffi

    2015-06-15

    Matrix metalloproteinase-9 (MMP-9) plays an important role in both physiological and pathological processes. This enzyme is a peripheral biomarker of neuroinflammation in multiple sclerosis (MS), a chronic autoimmune disease of the central nervous system. Presently, expensive magnetic resonance imaging (MRI) studies are used to monitor subclinical disease activity in MS. An alternative to costly MRI scans could be the detection of MMP-9, using a low-cost, disposable sensor system for MMP-9 suitable for home-monitoring of inflammation. This would allow an early prediction of the failure of anti-inflammatory therapies and more timely clinical intervention to limit neuronal damage and prevent disability. Herein we present the development of a disposable sensor for fast and straightforward detection of MMP-9. Biosensors were produced by coating electrodes with oxidized dextran and subsequent cross-linking with peptides containing specific cleavage sites for MMP-9. Exposure of the films to the enzyme resulted in the degradation of the films, which was monitored using impedance measurements. Sensor response was rapid, a significant impedance change was usually observed within 5 min after the addition of MMP-9. Sensors showed a negligible response to matrix metalloproteinase-2 (MMP-2), a protease which may interfere with MMP-9 detection. The peptide sequence with the highest sensitivity and selectivity Leu-Gly-Arg-Met-Gly-Leu-Pro-Gly-Lys was selected to construct calibration curves. MMP-9 was successfully detected in a clinically relevant range from 50 to 400 ng/ml. Two different processes of hydrogel degradation were observed on electrode surfaces with different roughness, and both appeared suitable to monitor MMP-9 activity. The sensor materials are generic and can be easily adopted to respond to other proteases by selecting peptide cross-linkers with suitable cleavage sites. PMID:25660510

  1. Characterization of gold-thiol-8-hydroxyquinoline self-assembled monolayers for selective recognition of aluminum ion using voltammetry and electrochemical impedance spectroscopy.

    PubMed

    Shervedani, Reza Karimi; Rezvaninia, Zeinab; Sabzyan, Hassan; Boeini, Hassan Zali

    2014-05-12

    Gold electrode surface is modified via covalent attachment of a synthesized thiol functionalized with 8-hydroxyquinoline, p-((8-hydroxyquinoline)azo) benzenethiol (SHQ), for the first time. The behavior of the nanostructured electrode surface (Au-SHQ) is characterized by electrochemical techniques including cyclic and differential pulse voltammetry (CV and DPV), and electrochemical impedance spectroscopy (EIS). The modified surface is stable in a wide range of potentials and pHs. A surface pKa of 6.0±0.1 is obtained for Au-SHQ electrode using surface acid/base titration curves constructed by CV and EIS measurements as a function of pH. These results helped to determine the charge state of the surface as a function of pH. The gold modified electrode surface showed good affinity for sensing the Al(III) ion at pH 5.5. The sensing process is based on (i) accumulation and complex formation between Al(III) from the solution phase and 8HQ function on the Au electrode surface (recognition step) and (ii) monitoring the impedance of the Au-SHQ-Al(III) complex against redox reaction rate of parabenzoquinone (PBQ) (signal transduction step). The PBQ is found to be a more suitable probe for this purpose, after testing several others. Thus, the sensor was tested for quantitative determination of Al(III) from the solution phase. At the optimized conditions, a linear response, from 1.0×10(-11) to 1.2×10(-5) M Al(III) in semi-logarithmic scale, with a detection limit of 8.32×10(-12) M and mean relative standard deviation of 3.2% for n=3 at 1.0×10(-7) M Al(III) is obtained. Possible interferences from coexisting cations and anions are also studied. The results show that many ions do not interfere significantly with the sensor response for Al(III). Validity of the method and applicability of the sensor are successfully tested by determination of Al(III) in human blood serum samples. PMID:24767148

  2. Selective label-free electrochemical impedance measurement of glycated haemoglobin on 3-aminophenylboronic acid-modified eggshell membranes.

    PubMed

    Boonyasit, Yuwadee; Heiskanen, Arto; Chailapakul, Orawan; Laiwattanapaisal, Wanida

    2015-07-01

    We propose a novel alternative approach to long-term glycaemic monitoring using eggshell membranes (ESMs) as a new immobilising platform for the selective label-free electrochemical sensing of glycated haemoglobin (HbA1c), a vital clinical index of the glycaemic status in diabetic individuals. Due to the unique features of a novel 3-aminophenylboronic acid-modified ESM, selective binding was obtained via cis-diol interactions. This newly developed device provides clinical applicability as an affinity membrane-based biosensor for the identification of HbA1c over a clinically relevant range (2.3 - 14 %) with a detection limit of 0.19%. The proposed membrane-based biosensor also exhibited good reproducibility. When analysing normal and abnormal HbA1c levels, the within-run coefficients of variation were 1.68 and 1.83%, respectively. The run-to-run coefficients of variation were 1.97 and 2.02%, respectively. These results demonstrated that this method achieved the precise and selective measurement of HbA1c. Compared with a commercial HbA1c kit, the results demonstrated excellent agreement between the techniques (n = 15), demonstrating the clinical applicability of this sensor for monitoring glycaemic control. Thus, this low-cost sensing platform using the proposed membrane-based biosensor is ideal for point-of-care diagnostics. PMID:25956596

  3. The testing of batteries linked to supercapacitors with electrochemical impedance spectroscopy: A comparison between Li-ion and valve regulated lead acid batteries

    NASA Astrophysics Data System (ADS)

    Ferg, Ernst; Rossouw, Claire; Loyson, Peter

    2013-03-01

    For electric vehicles, a supercapacitor can be coupled to the electrical system in order to increase and optimize the energy and power densities of the drive system during acceleration and regenerative breaking. This study looked at the charge acceptance and maximum discharge ability of a valve regulated lead acid (VRLA) and a Li-ion battery connected in parallel to supercapacitors. The test procedure evaluated the advantage of using a supercapacitor at a 2 F:1 Ah ratio with the battery types at various states of charge (SoC). The results showed that about 7% of extra charge was achieved over a 5-s test time for a Li-ion hybrid system at 20% SoC, whereas at the 80% SoC the additional capacity was approximately 16%. While for the VRLA battery hybrid system, an additional charge of up to 20% was achieved when the battery was at 80% SoC, with little or no benefit at the 20% SoC. The advantage of the supercapacitor in parallel with a VRLA battery was noticeable on its discharge ability, where significant extra capacity was achieved for short periods of time for a battery at the 60% and 40% SoC when compared to the Li-ion hybrid system. The study also made use of Electrochemical Impedance Spectroscopy (EIS) with a suitable equivalent circuit model to explain, in particular, the internal resistance and capacitance differences observed between the different battery chemistries with and without a supercapacitor.

  4. A comparison of corrosion, tribocorrosion and electrochemical impedance properties of pure Ti and Ti6Al4V alloy treated by micro-arc oxidation process

    NASA Astrophysics Data System (ADS)

    Fazel, M.; Salimijazi, H. R.; Golozar, M. A.; Garsivaz jazi, M. R.

    2015-01-01

    In this paper, the micro-arc oxidation (MAO) coatings were performed on pure Ti and Ti6Al4V samples at 180 V. The results indicated that unlike the volcanic morphology of oxide layer on pure Ti, a cortex-like morphology with irregular vermiform slots was seen on MAO/Ti6Al4V sample. According to polarization curves, the corrosion resistance of untreated samples was significantly increased by MAO process. The electrochemical impedance spectroscopy analysis showed a lower capacitance of barrier layer (led to higher resistance) for MAO/Ti specimens. This indicates that corrosive ions diffusion throughout the oxide film would be more difficult resulted in a higher corrosion resistance. Tribocorrosion results illustrated that the potential of untreated samples was dropped sharply to very low negative values. However, the lower wear volume loss was achieved for Ti6Al4V alloy. SEM images of worn surfaces demonstrated the local detachment of oxide layer within the wear track of MAO/Ti sample. Conversely, no delamination was detected in MAO/Ti6Al4V and a mild abrasive wear was the dominant mechanism.

  5. Kinetics of oxidation of Fe-Cr-Al alloy Characterization by electrochemical spectroscopy of impedance in a 3% medium NaCl

    NASA Astrophysics Data System (ADS)

    Chadli, H.; Retima, M.; Khenioui, Y.

    2009-11-01

    The film growths kinetic study developed on the Fe-Cr-Al alloy oxidation under ambient air has been studied due to its tremendous uses in the automobile industry, specifically in catalytic exhaust. In this work, we report on its behavior as a function of various parameters such as the temperature, the oxidation duration, elaboration mode or the substrate nature and geometry. It has been shown that the growth, the morphology or the adherence of the formed layers are strongly affected by these parameters. At high temperature (900-1100 ∘C), the formed protective film for the materials studied in this work is primarily consisted of alumina. Below these temperatures, several phases may coexist, namely, the γ phase and the θ phase. The extension of this alloy application has led us to perform spectroscopic measurements of electrochemical impedance (SEI) in an aqueous environment 3% (NaCl). These measurements have shown that sane coatings preserve excellent insulating properties and the corrosion risks are related to defects in the layers while are formed.

  6. Combined operando X-ray diffraction-electrochemical impedance spectroscopy detecting solid solution reactions of LiFePO4 in batteries.

    PubMed

    Hess, Michael; Sasaki, Tsuyoshi; Villevieille, Claire; Novák, Petr

    2015-01-01

    Lithium-ion batteries are widely used for portable applications today; however, often suffer from limited recharge rates. One reason for such limitation can be a reduced active surface area during phase separation. Here we report a technique combining high-resolution operando synchrotron X-ray diffraction coupled with electrochemical impedance spectroscopy to directly track non-equilibrium intermediate phases in lithium-ion battery materials. LiFePO4, for example, is known to undergo phase separation when cycled under low-current-density conditions. However, operando X-ray diffraction under ultra-high-rate alternating current and direct current excitation reveal a continuous but current-dependent, solid solution reaction between LiFePO4 and FePO4 which is consistent with previous experiments and calculations. In addition, the formation of a preferred phase with a composition similar to the eutectoid composition, Li0.625FePO4, is evident. Even at a low rate of 0.1C, ∼20% of the X-ray diffractogram can be attributed to non-equilibrium phases, which changes our understanding of the intercalation dynamics in LiFePO4. PMID:26345306

  7. Combined operando X-ray diffraction-electrochemical impedance spectroscopy detecting solid solution reactions of LiFePO4 in batteries

    NASA Astrophysics Data System (ADS)

    Hess, Michael; Sasaki, Tsuyoshi; Villevieille, Claire; Novák, Petr

    2015-09-01

    Lithium-ion batteries are widely used for portable applications today; however, often suffer from limited recharge rates. One reason for such limitation can be a reduced active surface area during phase separation. Here we report a technique combining high-resolution operando synchrotron X-ray diffraction coupled with electrochemical impedance spectroscopy to directly track non-equilibrium intermediate phases in lithium-ion battery materials. LiFePO4, for example, is known to undergo phase separation when cycled under low-current-density conditions. However, operando X-ray diffraction under ultra-high-rate alternating current and direct current excitation reveal a continuous but current-dependent, solid solution reaction between LiFePO4 and FePO4 which is consistent with previous experiments and calculations. In addition, the formation of a preferred phase with a composition similar to the eutectoid composition, Li0.625FePO4, is evident. Even at a low rate of 0.1C, ~20% of the X-ray diffractogram can be attributed to non-equilibrium phases, which changes our understanding of the intercalation dynamics in LiFePO4.

  8. Combined operando X-ray diffraction–electrochemical impedance spectroscopy detecting solid solution reactions of LiFePO4 in batteries

    PubMed Central

    Hess, Michael; Sasaki, Tsuyoshi; Villevieille, Claire; Novák, Petr

    2015-01-01

    Lithium-ion batteries are widely used for portable applications today; however, often suffer from limited recharge rates. One reason for such limitation can be a reduced active surface area during phase separation. Here we report a technique combining high-resolution operando synchrotron X-ray diffraction coupled with electrochemical impedance spectroscopy to directly track non-equilibrium intermediate phases in lithium-ion battery materials. LiFePO4, for example, is known to undergo phase separation when cycled under low-current-density conditions. However, operando X-ray diffraction under ultra-high-rate alternating current and direct current excitation reveal a continuous but current-dependent, solid solution reaction between LiFePO4 and FePO4 which is consistent with previous experiments and calculations. In addition, the formation of a preferred phase with a composition similar to the eutectoid composition, Li0.625FePO4, is evident. Even at a low rate of 0.1C, ∼20% of the X-ray diffractogram can be attributed to non-equilibrium phases, which changes our understanding of the intercalation dynamics in LiFePO4. PMID:26345306

  9. X-ray photoelectron spectroscopic and electrochemical impedance spectroscopic analysis of RuO2-Ta2O5 thick film pH sensors.

    PubMed

    Manjakkal, Libu; Cvejin, Katarina; Kulawik, Jan; Zaraska, Krzysztof; Socha, Robert P; Szwagierczak, Dorota

    2016-08-10

    The paper reports on investigation of the pH sensing mechanism of thick film RuO2-Ta2O5 sensors by using X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Interdigitated conductimetric pH sensors were screen printed on alumina substrates. The microstructure and elemental composition of the films were examined by scanning electron microscopy and energy dispersive spectroscopy. The XPS studies revealed the presence of Ru ions at different oxidation states and the surface hydroxylation of the sensing layer increasing with increasing pH. The EIS analysis carried out in the frequency range 10 Hz-2 MHz showed that the electrical parameters of the sensitive electrodes in the low frequency range were distinctly dependent on pH. The charge transfer and ionic exchange occurring at metal oxide-solution interface were indicated as processes responsible for the sensing mechanism of thick film RuO2-Ta2O5 pH sensors. PMID:27282750

  10. Microelectromechanical System-Based Sensing Arrays for Comparative in Vitro Nanotoxicity Assessment at Single Cell and Small Cell-Population Using Electrochemical Impedance Spectroscopy.

    PubMed

    Shah, Pratikkumar; Zhu, Xuena; Zhang, Xueji; He, Jin; Li, Chen-Zhong

    2016-03-01

    The traditional in vitro nanotoxicity assessment approaches are conducted on a monolayer of cell culture. However, to study a cell response without interference from the neighbor cells, a single cell study is necessary; especially in cases of neuronal, cancerous, and stem cells, wherein an individual cell's fate is often not explained by the whole cell population. Nonetheless, a single cell does not mimic the actual in vivo environment and lacks important information regarding cell communication with its microenvironment. Both a single cell and a cell population provide important and complementary information about cells' behaviors. In this research, we explored nanotoxicity assessment on a single cell and a small cell population using electrochemical impedance spectroscopy and a microelectromechanical system (MEMS) device. We demonstrated a controlled capture of PC12 cells in different-sized microwells (to capture a different number of cells) using a combined method of surface functionalization and dielectrophoresis. The present approach provides a rapid nanotoxicity response as compared to other conventional approaches. This is the first study, to our knowledge, which demonstrates a comparative response of a single cell and small cell colonies on the same MEMS platform, when exposed to metaloxide nanoparticles. We demonstrated that the microenvironment of a cell is also accountable for cells' behaviors and their responses to nanomaterials. The results of this experimental study open up a new hypothesis to be tested for identifying the role of cell communication in spreading toxicity in a cell population. PMID:26860350

  11. Novel electrochemical nickel metallization in silicon impedance engineering for mixed-signal system-on-chip crosstalk isolation

    NASA Astrophysics Data System (ADS)

    Zhang, Xi

    One of the major challenges for single chip radio frequency integrated circuits (RFIC's) built on Si is the RE crosstalk through the Si substrate. Noise from switching transient in digital circuits can be transmitted through Si substrate and degrades the performance of analog circuit elements. A highly conductive moat or Faraday cage type structure of through-the-wafer thickness in the Si substrate was demonstrated to be effective in shielding electromagnetic interference thereby reducing RE cross-talk in high performance mixed signal integrated circuits. Such a structure incorporated into the p- Si substrate was realized by electroless Ni metallization over selected regions with ultra-high-aspect-ratio macropores that was etched electrochemically in p- Si substrates. The metallization process was conducted by immersing the macroporous Si sample in an alkaline aqueous solution containing Ni2+ without a reducing agent. It was found that working at slightly elevated temperature, Ni 2+ was rapidly reduced and deposited in the macropores. During the wet chemical process, conformal metallization on the pore wall was achieved. The entire porous Si skeleton was gradually replaced by Ni along the extended duration of immersion. In a p-/p+ epi Si substrate used for high performance digital CMOS, the suppression of crosstalk by the arrayed metallic Ni via structure fabricated from the front p side was significant that the crosstalk went down to the noise floor of the conventional measurement instruments. The process and mechanism of forming such a Ni structure over the original Si were studied. Theoretical computation relevant to the process was carried out to show a good consistency with the experiments.

  12. Characterization of damp heat degradation of CuInGaSe2 solar cell components and devices by (electrochemical) impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Pern, F. J. John; Noufi, Rommel

    2011-09-01

    This work evaluated the capability of (electrochemical) impedance spectroscopy (IS, or ECIS as used here) to monitor damp heat (DH) stability of contact materials, CuInGaSe2 (CIGS) solar cell components, and devices. Cell characteristics and its variation of the CIGS devices were also examined by the ECIS. Bare and encapsulated sample sets were separately prepared and exposed in an environmental chamber at 85°C and 85% relative humidity (RH). The ECIS results from bare samples tested within 50-100 h of DH exposure allowed the determination of the use of a conducting Ag paste and a low-melting-point solder alloy for making a DH-stable external connection with Au wires. Bare Mo and AlNi grid degraded (corroded) rapidly while Ni was DH-stable. The moisture-dampened Al-doped ZnO (AZO) and bilayer ZnO (BZO) likely underwent hydrolytic "capacitor-forming" reaction by DH, resulting in "transient" behavior of very high resistance in ECIS that was not detected by four-point probe. Using an encapsulation test structure that allowed moisture ingress control, DH-induced degradation (resistance increase) rates of BZO on glass decreased from 0.21 ohm/h using a moisture-permeable Tedlar/Polyester/Tedlar (TPT) backsheet to 1.0 x 10-3 ohm/h using a moisture barrier FG-200 film, while Mo on glass did not exhibit the same conducting degradation and corrosion as the bare samples after over 1270 h DH exposure. CIGS solar cells encapsulated with a TPT backsheet degraded irregularly over 774 h DH exposure. Key resistance and capacitance parameters extracted by curve fitting of impedance data clearly showed the variation and impact of DH exposure on cell characteristics. Profound "depression" or shorting of the "p-n junction capacitor" by DH was evident. ECIS results are shown to correlate reasonably well with the solar cells' currentvoltage (I-V) degrading trends. Furthermore, ECIS analysis was capable of differentiating cell degradation due to "junction capacitor" shorting, damage or

  13. An immobilization-free electrochemical impedance biosensor based on duplex-specific nuclease assisted target recycling for amplified detection of microRNA.

    PubMed

    Zhang, Jing; Wu, Dong-Zhi; Cai, Shu-Xian; Chen, Mei; Xia, Yao-Kun; Wu, Fang; Chen, Jing-Hua

    2016-01-15

    An immobilization-free electrochemical impedance biosensor for microRNA detection was developed in this work, which was based on both the duplex-specific nuclease assisted target recycling (DSNATR) and capture probes (Cps) enriched from the solution to electrode surface via magnetic beads (MBs). In the absence of miR-21, Cps cannot be hydrolyzed due to the low activity of duplex-specific nuclease (DSN) against ssDNA. Therefore, the intact Cps could be attached to the surface of magnetic glass carbon electrode (MGCE), resulting in a compact negatively charged layer as well as a large charge-transfer resistance. While in the presence of miR-21, it hybridized with Cp to form a DNA-RNA heteroduplex. Due to the considerable cleavage preference for DNA in DNA-RNA hybrids, DSN hydrolyzed the target-binding part of the Cp while liberating the intact miR-21 to hybridize with a new Cp and initiate the second cycle of hydrolysis. In this way, a single miR-21 was able to trigger the permanent hydrolysis of multiple Cps. Finally, all Cps were digested. Thus, the negatively charged layer could not be formed, resulting in a small charge-transfer resistance. By employing the above strategy, the proposed biosensor achieved ultrahigh sensitivity toward miR-21 with a detection limit of 60aM. Meanwhile, the method showed little cross-hybridization among the closely related miRNA family members even at the single-base-mismatched level. Successful attempts were made in applying the approach to detect miR-21 in human serum samples of breast cancer patients. PMID:26363493

  14. Electrochemical impedance spectroscopy of biofilms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Microbial activity that leads to the formation of biofilms on process equipment can accelerate corrosion, reduce heat transfer rates, and generally decrease process efficiencies. Additional concerns arise in the food and pharma industries where product quality and safety are a high priority. Pharmac...

  15. Fabrication of TiO2-NTs and TiO2-NTs covered honeycomb lattice and investigation of carrier densities in I-/I3- electrolyte by electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Baran, Evrim; Yazıcı, Birgül

    2015-12-01

    The TiO2 nanotubes (NTs) were produced by one-step (1S) and two-step (2S) anodization technique. Effects of various anodization potential and times on the growth of TiO2-NTs were investigated by using Field Emission-Scanning Electron Microscopy (FE-SEM). The crystal structure of the electrodes was determined with X-ray powder diffractometry (XRD). The most suitable potential and time for TiO2-NTs obtained by both of anodization methods were found to be 21 V and 4 h. XRD results indicated that 2S anodization technique provided better crystallinity. The electrochemical behaviors of the electrodes in acetonitrile electrolyte contained I-/I3- were examined by utilizing electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) techniques. Electrochemical results showed that 2S anodization technique increases the carrier densities (ND) value of TiO2-NTs, and flat band potential is shifted by 50 mV to more negative values.

  16. Application of impedance spectroscopy to SOFC research

    SciTech Connect

    Hsieh, G.; Mason, T.O.; Pederson, L.R.

    1996-12-31

    With the resurgence of interest in solid oxide fuel cells and other solid state electrochemical devices, techniques originally developed for characterizing aqueous systems are being adapted and applied to solid state systems. One of these techniques, three-electrode impedance spectroscopy, is particularly powerful as it allows characterization of subcomponent and interfacial properties. Obtaining accurate impedance spectra, however, is difficult as reference electrode impedance is usually non-negligible and solid electrolytes typically have much lower conductance than aqueous solutions. Faidi et al and Chechirlian et al have both identified problems associated with low conductivity media. Other sources of error are still being uncovered. Ford et al identified resistive contacts with large time constants as a possibility, while Me et al showed that the small contact capacitance of the reference electrode was at fault. Still others show that instrument limitations play a role. Using the voltage divider concept, a simplified model that demonstrates the interplay of these various factors, predicts the form of possible distortions, and offers means to minimize errors is presented.

  17. Electrochemical Performance and Stability of the Cathode for Solid Oxide Fuel Cells. I. Cross Validation of Polarization Measurements by Impedance Spectroscopy and Current-Potential Sweep

    SciTech Connect

    Zhou, Xiao Dong; Pederson, Larry R.; Templeton, Jared W.; Stevenson, Jeffry W.

    2009-12-09

    The aim of this paper is to address three issues in solid oxide fuel cells: (1) cross-validation of the polarization of a single cell measured using both dc and ac approaches, (2) the precise determination of the total areal specific resistance (ASR), and (3) understanding cathode polarization with LSCF cathodes. The ASR of a solid oxide fuel cell is a dynamic property, meaning that it changes with current density. The ASR measured using ac impedance spectroscopy (low frequency interception with real Z´ axis of ac impedance spectrum) matches with that measured from a dc IV sweep (the tangent of dc i-V curve). Due to the dynamic nature of ASR, we found that an ac impedance spectrum measured under open circuit voltage or on a half cell may not represent cathode performance under real operating conditions, particularly at high current density. In this work, the electrode polarization was governed by the cathode activation polarization; the anode contribution was negligible.

  18. Electron Impedances

    SciTech Connect

    P Cameron

    2011-12-31

    It is only recently, and particularly with the quantum Hall effect and the development of nanoelectronics, that impedances on the scale of molecules, atoms and single electrons have gained attention. In what follows the possibility that characteristic impedances might be defined for the photon and the single free electron is explored is some detail, the premise being that the concepts of electrical and mechanical impedances are relevant to the elementary particle. The scale invariant quantum Hall impedance is pivotal in this exploration, as is the two body problem and Mach's principle.

  19. Original implementation of Electrochemical Impedance Spectroscopy (EIS) in symmetric cells: Evaluation of post-mortem protocols applied to characterize electrode materials for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Gordon, Isabel Jiménez; Genies, Sylvie; Si Larbi, Gregory; Boulineau, Adrien; Daniel, Lise; Alias, Mélanie

    2016-03-01

    Understanding ageing mechanisms of Li-ion batteries is essential for further optimizations. To determine performance loss causes, post-mortem analyses are commonly applied. For each type of post-mortem test, different sample preparation protocols are adopted. However, reports on the reliability of these protocols are rare. Herein, Li-ion pouch cells with LiNi1/3Mn1/3Co1/3O2 - polyvinylidene fluoride positive electrode, graphite-carboxymethyl cellulose-styrene rubber negative electrode and LiPF6 - carbonate solvents mixture electrolyte, are opened and electrodes are recovered following a specified protocol. Negative and positive symmetric cells are assembled and their impedances are recorded. A signal analysis is applied to reconstruct the Li-ion pouch cell impedance from the symmetric cells, then comparison against the pouch cell true impedance allows the evaluation of the sample preparation protocols. The results are endorsed by Transmission Electronic Microscopy (TEM) and Gas Chromatography - Mass Spectrometry (GC-MS) analyses. Carbonate solvents used to remove the salt impacts slightly the surface properties of both electrodes. Drying electrodes under vacuum at 25 °C produces an impedance increase, particularly very marked for the positive electrode. Drying at 50 °C under vacuum or/and exposition to the anhydrous room atmosphere is very detrimental.

  20. Microstructures and electrochemical behaviors of the friction stir welding dissimilar weld.

    PubMed

    Shen, Changbin; Zhang, Jiayan; Ge, Jiping

    2011-06-01

    By using optical microscope, the microstructures of 5083/6082 friction stir welding (FSW) weld and parent materials were analyzed. Meanwhile, at ambient temperature and in 0.2 mol/L NaHS03 and 0.6 mol/L NaCl solutionby gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation, the electrochemical behavior of 5083/6082 friction stir welding weld and parent materials were comparatively investigated by gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation. The results indicated that at given processing parameters, the anti-corrosion property of the dissimilar weld was superior to those of the 5083 and 6082 parent materials. PMID:25084589

  1. Electrochemical impedance based chiral analysis of anti-ascorbutic drug: l-Ascorbic acid and d-ascorbic acid using C-dots decorated conductive polymer nano-composite electrode.

    PubMed

    Pandey, Indu; Kant, Rama

    2016-03-15

    Clinical manifestations owing to l-ascorbic acid for scurvy as comparison to d-ascorbic acid and challenges of chiral purity are overcome by using chiral selective conductive polymer nanocomposite which mimics antibodies and enzymes. A novel chiral selective imprinted polyaniline-ferrocene-sulfonic acid film has been electrochemically fabricated on C-dots modified pencil graphite electrode. The performance of the obtained l-ascorbic acid or d-ascorbic acid chiral selective sensor was investigated by electrochemical impedance spectroscopy, cyclic and differential pulse voltammetry. The surface characteristics of the C-dots, chiral sensor before and after the de-doping of chiral d- and l-ascorbic acid were characterized by scanning electron microscopy, Raman spectroscopy and X-ray diffraction spectroscopy. Excellent recognition results were obtained by difference in electron transfer resistance. The proposed chiral sensor is capable of measuring d-ascorbic acid or l-ascorbic acid in aqueous as well as in real and commercial samples within the range of 0.020-0.187 nM and 0.003-0.232 nM with detection limit of 0.00073 nM and 0.00016 nM, respectively. The proposed method has also been examined for the chiral selective recognition of ascorbic acid isomers (d- and l-) quantitatively, in complicated matrices of real samples. PMID:26499067

  2. La2NiO4+δ infiltrated into gadolinium doped ceria as novel solid oxide fuel cell cathodes: Electrochemical performance and impedance modelling

    NASA Astrophysics Data System (ADS)

    Nicollet, C.; Flura, A.; Vibhu, V.; Rougier, A.; Bassat, J. M.; Grenier, J. C.

    2015-10-01

    This paper is devoted to the study of composite cathodes of La2NiO4+δ infiltrated into a Gd-doped ceria backbone. Porous Gd-doped ceria backbones are screen printed onto yttria-stabilized zirconia or Gd-doped ceria dense electrolytes, and infiltrated with a La and Ni nitrate solution (2:1 stoichiometry ratio). The influence of the preparation parameters on the polarization resistance, such as the concentration of the infiltration solution, the amount of infiltrated phase, the annealing temperature, the thickness of the electrode, and the nature of the electrolyte, is characterized by impedance spectroscopy performed on symmetrical cells. The optimization of these parameters results in a decrease of the polarization resistance down to 0.15 Ω cm2 at 600 °C. Using the Adler-Lane-Steele model, the modelling of the impedance diagrams leads to the determination of the ionic conductivity as well as the surface exchange rate of the infiltrated electrode.

  3. A physical interpretation of impedance at conducting polymer/electrolyte junctions

    SciTech Connect

    Stavrinidou, Eleni; Sessolo, Michele; Sanaur, Sébastien; Malliaras, George G.; Winther-Jensen, Bjorn

    2014-01-15

    We monitor the process of dedoping in a planar junction between an electrolyte and a conducting polymer using electrochemical impedance spectroscopy performed during moving front measurements. The impedance spectra are consistent with an equivalent circuit of a time varying resistor in parallel with a capacitor. We show that the resistor corresponds to ion transport in the dedoped region of the film, and can be quantitatively described using ion density and drift mobility obtained from the moving front measurements. The capacitor, on the other hand, does not depend on time and is associated with charge separation at the moving front. This work offers a physical description of the impedance of conducting polymer/electrolyte interfaces based on materials parameters.

  4. Monitoring of microbial adhesion and biofilm growth using electrochemical impedancemetry.

    PubMed

    Dheilly, A; Linossier, I; Darchen, A; Hadjiev, D; Corbel, C; Alonso, V

    2008-05-01

    Electrochemical impedance spectroscopy was tested to monitor the cell attachment and the biofilm proliferation in order to identify characteristic events induced on the metal surface by Gram-negative (Pseudomonas aeruginosa PAO1) and Gram-positive (Bacillus subtilis) bacteria strains. Electrochemical impedance spectra of AISI 304 electrodes during cell attachment and initial biofilm growth for both strains were obtained. It can be observed that the resistance increases gradually with the culture time and decreases with the biofilm detachment. So, the applicability of electric cell-substrate impedance sensing (ECIS) for studying the attachment and spreading of cells on a metal surface has been demonstrated. The biofilm formation was also characterized by the use of scanning electron microscopy and confocal laser scanning microscopy and COMSTAT image analysis. The electrochemical results roughly agree with the microscope image observations. The ECIS technique used in this study was used for continuous real-time monitoring of the initial bacterial adhesion and the biofilm growth. It provides a simple and non-expensive electrochemical method for in vitro assessment of the presence of biofilms on metal surfaces. PMID:18330564

  5. Electrochemical Impedance Immunosensor Based on Self-Assembled Monolayers for Rapid Detection of Escherichia coli O157:H7 with Signal Amplification Using Lectin.

    PubMed

    Li, Zhanming; Fu, Yingchun; Fang, Weihuan; Li, Yanbin

    2015-01-01

    Escherichia coli O157:H7 is a predominant foodborne pathogen with severe pathogenicity, leading to increasing attention given to rapid and sensitive detection. Herein, we propose an impedance biosensor using new kinds of screen-printed interdigitated microelectrodes (SPIMs) and wheat germ agglutinin (WGA) for signal amplification to detect E. coli O157:H7 with high sensitivity and time-efficiency. The SPIMs integrate the high sensitivity and short response time of the interdigitated electrodes and the low cost of the screen-printed electrodes. Self-assembling of bi-functional 3-dithiobis-(sulfosuccinimidyl-propionate) (DTSP) on the SPIMs was investigated and was proved to be able to improve adsorption quantity and stability of biomaterials. WGA was further adopted to enhance the signal taking advantage of the abundant lectin-binding sites on the bacteria surface. The immunosensor exhibited a detection limit of 102 cfu·mL(-1), with a linear detection range from 10(2) to 10(7) cfu·mL(-1) (r2 = 0.98). The total detection time was less than 1 h, showing its comparable sensitivity and rapid response. Furthermore, the low cost of one SPIM significantly reduced the detection cost of the biosensor. The biosensor may have great promise in food safety analysis and lead to a portable biosensing system for routine monitoring of foodborne pathogens. PMID:26251911

  6. Electrochemical Impedance Immunosensor Based on Self-Assembled Monolayers for Rapid Detection of Escherichia coli O157:H7 with Signal Amplification Using Lectin

    PubMed Central

    Li, Zhanming; Fu, Yingchun; Fang, Weihuan; Li, Yanbin

    2015-01-01

    Escherichia coli O157:H7 is a predominant foodborne pathogen with severe pathogenicity, leading to increasing attention given to rapid and sensitive detection. Herein, we propose an impedance biosensor using new kinds of screen-printed interdigitated microelectrodes (SPIMs) and wheat germ agglutinin (WGA) for signal amplification to detect E. coli O157:H7 with high sensitivity and time-efficiency. The SPIMs integrate the high sensitivity and short response time of the interdigitated electrodes and the low cost of the screen-printed electrodes. Self-assembling of bi-functional 3-dithiobis-(sulfosuccinimidyl-propionate) (DTSP) on the SPIMs was investigated and was proved to be able to improve adsorption quantity and stability of biomaterials. WGA was further adopted to enhance the signal taking advantage of the abundant lectin-binding sites on the bacteria surface. The immunosensor exhibited a detection limit of 102 cfu·mL−1, with a linear detection range from 102 to 107 cfu·mL−1 (r2 = 0.98). The total detection time was less than 1 h, showing its comparable sensitivity and rapid response. Furthermore, the low cost of one SPIM significantly reduced the detection cost of the biosensor. The biosensor may have great promise in food safety analysis and lead to a portable biosensing system for routine monitoring of foodborne pathogens. PMID:26251911

  7. Sensitivity improvement of a sandwich-type ELISA immunosensor for the detection of different prostate-specific antigen isoforms in human serum using electrochemical impedance spectroscopy and an ordered and hierarchically organized interfacial supramolecular architecture.

    PubMed

    Gutiérrez-Zúñiga, Gabriela Guadalupe; Hernández-López, José Luis

    2016-01-01

    A gold millielectrode (GME) functionalized with a mixed (16-MHA + EG3SH) self-assembled monolayer (SAM) was used to fabricate an indirect enzyme-linked immunosorbent assay (ELISA) immunosensor for the sensitive detection of prostate-specific antigen (PSA), a prostate cancer (PCa) biomarker, in human serum samples. To address and minimize the issue of non-specific protein adsorption, an organic matrix (amine-PEG3-biotin/avidin) was assembled on the previously functionalized electrode surface to build up an ordered and hierarchically organized interfacial supramolecular architecture: Au/16-MHA/EG3SH/amine-PEG3-biotin/avidin. The electrode was then exposed to serum samples at different concentrations of a sandwich-type immunocomplex molecule ((Btn)Ab-AgPSA-(HRP)Ab), and its interfacial properties were characterized using electrochemical impedance spectroscopy (EIS). Calibration curves for polarization resistance (RP) and capacitance (1/C) vs. total and free PSA concentrations were obtained and their analytical quality parameters were determined. This approach was compared with results obtained from a commercially available ELISA immunosensor. The results obtained in this work showed that the proposed immunosensor can be successfully applied to analyze serum samples of patients representative of the Mexican population. PMID:26703258

  8. Current density distribution in cylindrical Li-Ion cells during impedance measurements

    NASA Astrophysics Data System (ADS)

    Osswald, P. J.; Erhard, S. V.; Noel, A.; Keil, P.; Kindermann, F. M.; Hoster, H.; Jossen, A.

    2016-05-01

    In this work, modified commercial cylindrical lithium-ion cells with multiple separate current tabs are used to analyze the influence of tab pattern, frequency and temperature on electrochemical impedance spectroscopy. In a first step, the effect of different current tab arrangements on the impedance spectra is analyzed and possible electrochemical causes are discussed. In a second step, one terminal is used to apply a sinusoidal current while the other terminals are used to monitor the local potential distribution at different positions along the electrodes of the cell. It is observed that the characteristic decay of the voltage amplitude along the electrode changes non-linearly with frequency, where high-frequent currents experience a stronger attenuation along the current collector than low-frequent currents. In further experiments, the decay characteristic is controlled by the cell temperature, driven by the increasing resistance of the current collector and the enhanced kinetic and transport properties of the active material and electrolyte. Measurements indicate that the ac current distribution depends strongly on the frequency and the temperature. In this context, the challenges for electrochemical impedance spectroscopy as cell diagnostic technique for commercial cells are discussed.

  9. A multiplexed three-dimensional paper-based electrochemical impedance device for simultaneous label-free affinity sensing of total and glycated haemoglobin: The potential of using a specific single-frequency value for analysis.

    PubMed

    Boonyasit, Yuwadee; Chailapakul, Orawon; Laiwattanapaisal, Wanida

    2016-09-14

    A novel three-dimensional paper-based electrochemical impedance device (3D-PEID) is first introduced for measuring multiple diabetes markers. Herein, a simple 3D-PEID composed of a dual screen-printed electrode on wax-patterned paper coupled with a multilayer of magnetic paper was fabricated for label-free electrochemical detection. The results clearly demonstrated in a step-wise manner that the haptoglobin (Hp)-modified and 3-aminophenylboronic acid (APBA)-modified eggshell membranes (ESMs) were highly responsive to a clinically relevant range of total (0.5-20 g dL(-1); r(2) = 0.989) and glycated haemoglobin (HbA1c) (2.3%-14%; r(2) = 0.997) levels with detection limits (S/N = 3) of 0.08 g dL(-1) and 0.21%, respectively. The optimal binding frequencies of total haemoglobin and HbA1c to their specific recognition elements were 5.18 Hz and 9.99 Hz, respectively. The within-run coefficients of variation (CV) were 1.84%, 2.18%, 1.72%, and 2.01%, whereas the run-to-run CVs were 2.11%, 2.41%, 2.08%, and 2.21%, when assaying two levels of haemoglobin and HbA1c, respectively. The CVs for the haemoglobin and HbA1c levels measured on ten independently fabricated paper-based sheets were 1.96% and 2.10%, respectively. These results demonstrated that our proposed system achieved excellent precision for the simultaneous detection of total haemoglobin and HbA1c, with an acceptable reproducibility of fabrication. The long-term stability of the Hp-modified eggshell membrane (ESM) was 98.84% over a shelf-life of 4 weeks, enabling the possibility of storage or long-distance transport to remote regions, particularly in resource-limited settings; however, for the APBA-modified ESM, the stability was 92.35% over a one-week period. Compared with the commercial automated method, the results demonstrated excellent agreement between the techniques (p-value < 0.05), thus permitting the potential application of 3D-PEID for the monitoring of the glycaemic status in diabetic

  10. Impedance Noise Identification for State-of-Health Prognostics

    SciTech Connect

    Jon P. Christophersen; Chester G. Motloch; John L. Morrison; Ian B. Donnellan; William H. Morrison

    2008-07-01

    Impedance Noise Identification is an in-situ method of measuring battery impedance as a function of frequency using a random small signal noise excitation source. Through a series of auto- and cross-correlations and Fast Fourier Transforms, the battery complex impedance as a function of frequency can be determined. The results are similar to those measured under a lab-scale electrochemical impedance spectroscopy measurement. The lab-scale measurements have been shown to correlate well with resistance and power data that are typically used to ascertain the remaining life of a battery. To this end, the Impedance Noise Identification system is designed to acquire the same type of data as an on-board tool. A prototype system is now under development, and results are being compared to standardized measurement techniques such as electrochemical impedance spectroscopy. A brief description of the Impedance Noise Identification hardware system and representative test results are presented.

  11. Impedance magnetocardiogram.

    PubMed

    Kandori, A; Miyashita, T; Suzuki, D; Yokosawa, K; Tsukada, K

    2001-02-01

    We have developed an impedance magnetocardiogram (IMCG) system to detect the change of magnetic field corresponding to changes in blood volume in the heart. A low magnetic field from the electrical activity of the human heart--the so-called magnetocardiogram (MCG)--can be simultaneously detected by using this system. Because the mechanical and electrical functions in the heart can be monitored by non-invasive and non-contact measurements, it is easy to observe the cardiovascular functions from an accurate sensor position. This system uses a technique to demodulate induced current in a subject. A flux-locked circuit of a superconducting quantum interference device has a wide frequency range (above 1 MHz) because a constant current (40 kHz) is fed through the subject. It is shown for the first time that the system could measure IMCG signals at the same time as MCG signals. PMID:11229740

  12. Opto-electrochemical spectroscopy of metals in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Habib, K.

    2016-03-01

    In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the electrical resistance of aluminium samples during the initial stage of anodisation processes in aqueous solution. In fact, because the resistance values in this investigation were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the resistance was called electrical resistance-emission spectroscopy. The anodisation process of the aluminium samples was carried out by electrochemical impedance spectroscopy (EIS) in different sulphuric acid concentrations (1.0%-2.5% H2SO4) at room temperature. In the meantime, the real time holographic interferometry was used to determine the difference between the electrical resistance of two subsequent values, dR, as a function of the elapsed time of the EIS experiment for the aluminium samples in 1.0%, 1.5%, 2.0%, and 2.5% H2SO4 solutions. The electrical resistance-emission spectra of the present investigation represent a detailed picture of not only the rate change of the electrical resistance throughout the anodisation processes but also the spectra represent the rate change of the growth of the oxide films on the aluminium samples in different solutions. As a result, a new spectrometer was developed based on the combination of the holographic interferometry and electrochemical impedance spectroscopy for studying in situ the electrochemical behavior of metals in aqueous solutions.

  13. Microfabricated Thin Film Impedance Sensor & AC Impedance Measurements

    PubMed Central

    Yu, Jinsong; Liu, Chung-Chiun

    2010-01-01

    Thin film microfabrication technique was employed to fabricate a platinum based parallel-electrode structured impedance sensor. Electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis of the small amplitude (±5 mV) AC impedance measurements (frequency range: 1 MHz to 0.1 Hz) at ambient temperature were carried out. Testing media include 0.001 M, 0.01 M, 0.1 M NaCl and KCl solutions, and alumina (∼3 μm) and sand (∼300 μm) particulate layers saturated with NaCl solutions with the thicknesses ranging from 0.6 mm to 8 mm in a testing cell, and the results were used to assess the effect of the thickness of the particulate layer on the conductivity of the testing solution. The calculated resistances were approximately around 20 MΩ, 4 MΩ, and 0.5 MΩ for 0.001 M, 0.01 M, and 0.1 M NaCl solutions, respectively. The presence of the sand particulates increased the impedance dramatically (6 times and 3 times for 0.001 M and 0.1 M NaCl solutions, respectively). A cell constant methodology was also developed to assess the measurement of the bulk conductivity of the electrolyte solution. The cell constant ranged from 1.2 to 0.8 and it decreased with the increase of the solution thickness. PMID:22219690

  14. Rapid and molecular selective electrochemical sensing of phthalates in aqueous solution.

    PubMed

    Zia, Asif I; Mukhopadhyay, Subhas Chandra; Yu, Pak-Lam; Al-Bahadly, I H; Gooneratne, Chinthaka P; Kosel, J Rgen

    2015-05-15

    Reported research work presents real time non-invasive detection of phthalates in spiked aqueous samples by employing electrochemical impedance spectroscopy (EIS) technique incorporating a novel interdigital capacitive sensor with multiple sensing thin film gold micro-electrodes fabricated on native silicon dioxide layer grown on semiconducting single crystal silicon wafer. The sensing surface was functionalized by a self-assembled monolayer of 3-aminopropyltrietoxysilane (APTES) with embedded molecular imprinted polymer (MIP) to introduce selectivity for the di(2-ethylhexyl) phthalate (DEHP) molecule. Various concentrations (1-100 ppm) of DEHP in deionized MilliQ water were tested using the functionalized sensing surface to capture the analyte. Frequency response analyzer (FRA) algorithm was used to obtain impedance spectra so as to determine sample conductance and capacitance for evaluation of phthalate concentration in the sample solution. Spectrum analysis algorithm interpreted the experimentally obtained impedance spectra by applying complex nonlinear least square (CNLS) curve fitting in order to obtain electrochemical equivalent circuit and corresponding circuit parameters describing the kinetics of the electrochemical cell. Principal component analysis was applied to deduce the effects of surface immobilized molecular imprinted polymer layer on the evaluated circuit parameters and its electrical response. The results obtained by the testing system were validated using commercially available high performance liquid chromatography diode array detector system. PMID:25218198

  15. ADVANCES IN IMPEDANCE THEORY

    SciTech Connect

    Stupakov, G.; /SLAC

    2009-06-05

    We review recent progress in the following areas of the impedance theory: calculation of impedance of tapers and small angle collimators; optical approximation and parabolic equation for the high-frequency impedance; impedance due to resistive inserts in a perfectly conducting pipe.

  16. A novel broadband impedance method for detection of cell-derived microparticles

    PubMed Central

    Lvovich, Vadim; Srikanthan, Sowmya; Silverstein, Roy L.

    2010-01-01

    A novel label-free method is presented to detect and quantify cell-derived microparticles (MPs) by the electrochemical potential-modulated electrochemical impedance spectroscopy (EIS). MPs are present in elevated concentrations during pathological conditions and play a major role in the establishment and pathogenesis of many diseases. Considering this, accurate detection and quantification of MPs is very important in clinical diagnostics and therapeutics. A combination of bulk solution electrokinetic sorting and interfacial impedance responses allows achieving detection limits as low as several MPs per µL. By fitting resulting EIS spectra with an equivalent electrical circuit, the bulk solution electrokinetic and interfacial impedance responses were characterized. In the bulk solution two major relaxations were prominent - β-relaxation in low MHz region due to the MP capacitive membrane bridging, and α-relaxation at ∼ 10 kHz due to counter ions diffusion. At low frequencies (10-0.1 Hz) at electrochemical potentials exceeding −100 mV, a facile interfacial Faradaic process of oxidation in MPs coupled with diffusion and non Faradaic double layer charging dominate, probably due to oxidation of phospholipids and/or proteins on the MP surface and MP lysis. Buffer influence on the MP detection demonstrated that that a relatively low conductivity Tyrode’s buffer background solution is preferential for the MP electrokinetic separation and characterization. This study also demonstrated that standard laboratory methods such as flow cytometry underestimate MP concentrations, especially those with smaller average sizes, by as much as a factor of 2 to 40. PMID:20729061

  17. Effect of low-temperature conditions on passive layer growth in Li intercalation materials: In situ impedance study

    SciTech Connect

    Barsoukov, E.; Kim, J.H.; Kim, J.H.; Yoon, C.O.; Lee, H.

    1998-08-01

    Electrochemical impedance spectroscopy has been applied to investigate the formation of insulating layers at the surfaces of microscopic particles of mesocarbon microbeads (MCMB), graphite, and hard carbon during the first Li-intercalation into these materials at ambient temperature as well as at {minus}20 C. Investigations were carried out in a three-electrode sandwich cell, designed for impedance measurements in the frequency range 64 kHz to 5 mHz. The impedance spectra, obtained in the potential range 1.5 and 0.02 V during the first charge, were analyzed by complex nonlinear least square fits. A new model, taking into account the porous structure of the intercalation material, electrochemical processes at the interface, as well as spherical diffusion of Li ions toward the centers of the particles, has been used for this analysis. The first intercalation at {minus}20 C results in formation of an insulating layer, which is about 90 times thinner than in the room-temperature case, as concluded from an analysis of experimental results. The irreversible capacity loss, which is 1.3 times larger at {minus}20 C that at room temperature, is ascribed to the formation of a porous precipitate of electrolyte decomposition products on the particle surface. Additional Li intercalation at room temperature results in an irreversible capacity loss of 26% from the initial value, and formation of a composite layer, including low-temperature and room-temperature deposited components.

  18. Impedance analysis of nanocarbon DSSC electrodes

    NASA Astrophysics Data System (ADS)

    Gagliardi, S.; Giorgi, L.; Giorgi, R.; Lisi, N.; Dikonimos Makris, Th.; Salernitano, E.; Rufoloni, A.

    2009-07-01

    Carbon nanoparticles and multiwall carbon nanotubes were deposited on an Optically Transparent Electrode (OTE) for application in Dye Sensitised Solar Cells (DSSCs) as counter electrode materials. Electrochemical Impedance Spectroscopy (EIS) was used to evaluate the behaviour in a I3-/I electrolyte solution. Results were compared to commercial Pt catalysed OTE and polycrystalline graphite. Multiwalled carbon nanotubes show low series resistance and low charge transfer resistance promising an improved fill factor (and efficiency) in DSSCs assembled with such materials as counter electrodes.

  19. Crystal structures, UV spectra of solid iodide anionic water clusters I(-)(H2O)(1-4), and electrochemical reaction of I(-)(H2O)(1-4) → I· + e(-)(H2O)(1-4).

    PubMed

    Qiu, Yanxuan; Yang, Meng; Chen, Wenbin; Su, Yuzhi; Ouyang, Zhenjie; Yan, Hua; Gao, Feixian; Dong, Wen

    2013-05-16

    Four iodide anionic water clusters of I(-)(H2O)1-4 in two supramolecular complexes of [Fe(phen)3][I2(H2O)3] (1) and [Zn(phen)3][I2(H2O)4.5] (2) have been determined by single-crystal X-ray diffraction analysis. The diffuse reflectance spectra for the solid iodide anionic water clusters of I(-)(H2O)1-4 were investigated, and their absorption bands were demonstrated by denisty functional theory calculation. The electrochemical reaction of I(-)(H2O)1-4 → I· + e(-)(H2O)1-4 with the oxidation potential of Ep = 0.61 eV was first found and reported in two aqueous solutions (1 mmol·dm(-3)) of 1 and 2. PMID:23614806

  20. UNIVERSAL AUTO-CALIBRATION FOR A RAPID BATTERY IMPEDANCE SPECTRUM MEASUREMENT DEVICE

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; William H. Morrison

    2014-03-01

    Electrochemical impedance spectroscopy has been shown to be a valuable tool for diagnostics and prognostics of energy storage devices such as batteries and ultra-capacitors. Although measurements have been typically confined to laboratory environments, rapid impedance spectrum measurement techniques have been developed for on-line, embedded applications as well. The prototype hardware for the rapid technique has been validated using lithium-ion batteries, but issues with calibration had also been identified. A new, universal automatic calibration technique was developed to address the identified issues while also enabling a more simplified approach. A single, broad-frequency range is used to calibrate the system and then scaled to the actual range and conditions used when measuring a device under test. The range used for calibration must be broad relative to the expected measurement conditions for the scaling to be successful. Validation studies were performed by comparing the universal calibration approach with data acquired from targeted calibration ranges based on the expected range of performance for the device under test. First, a mid-level shunt range was used for calibration and used to measure devices with lower and higher impedance. Next, a high excitation current level was used for calibration, followed by measurements using lower currents. Finally, calibration was performed over a wide frequency range and used to measure test articles with a lower set of frequencies. In all cases, the universal calibration approach compared very well with results acquired following a targeted calibration. Additionally, the shunts used for the automated calibration technique were successfully characterized such that the rapid impedance measurements compare very well with laboratory-scale measurements. These data indicate that the universal approach can be successfully used for onboard rapid impedance spectra measurements for a broad set of test devices and range of

  1. Characterization of protein-immobilized polystyrene nanoparticles using impedance spectroscopy.

    PubMed

    Park, Soo-In; Lee, Sang-Yup

    2014-10-01

    A novel approach for characterization of non-conductive protein-immobilized nanoparticles using AC impedance spectroscopy combined with conductive atomic force microscopy was examined. As AC impedance spectroscopy can provide information on diverse electrical properties such as capacitance and inductance, it is applicable to the characterization of non-conductive substances. Several non-conductive protein-immobilized polystyrene nanoparticles were analyzed using AC impedance spectroscopy, and their impedance spectra were used as markers for nanoparticle identification. Analyses of impedance signals using an electrical circuit model established that the capacitance and inductance of each nanoparticle changed with the adsorbed protein and that impedance spectral differences were characteristic properties of the proteins. From this study, AC impedance spectroscopy was shown to be a useful tool for characterization of non-conductive nanoparticles and is expected to be applicable to the development of sensors for nanomaterials. PMID:25942903

  2. Robust impedance shaping telemanipulation

    SciTech Connect

    Colgate, J.E.

    1993-08-01

    When a human operator performs a task via a bilateral manipulator, the feel of the task is embodied in the mechanical impedance of the manipulator. Traditionally, a bilateral manipulator is designed for transparency; i.e., so that the impedance reflected through the manipulator closely approximates that of the task. Impedance shaping bilateral control, introduced here, differs in that it treats the bilateral manipulator as a means of constructively altering the impedance of a task. This concept is particularly valuable if the characteristic dimensions (e.g., force, length, time) of the task impedance are very different from those of the human limb. It is shown that a general form of impedance shaping control consists of a conventional power-scaling bilateral controller augmented with a real-time interactive task simulation (i.e., a virtual environment). An approach to impedance shaping based on kinematic similarity between tasks of different scale is introduced and illustrated with an example. It is shown that an important consideration in impedance shaping controller design is robustness; i.e., guaranteeing the stability of the operator/manipulator/task system. A general condition for the robustness of a bilateral manipulator is derived. This condition is based on the structured singular value ({mu}). An example of robust impedance shaping bilateral control is presented and discussed.

  3. Electrochemical analysis of lithium polymer batteries

    NASA Astrophysics Data System (ADS)

    Han, Yong-Bong

    Lithium batteries consist of lithium anode, polymer electrolyte separator, and the porous, composite cathode. Lithium batteries have been very attractive to the battery industries because lithium metal has an extremely high energy density. The use of lithium metal can cause dendrite formation by uneven electro-deposition during charge. The lithium battery can explode in a liquid electrolyte when it is shorted by the dendrite. It has been reported that the mechanical properties of a polymer electrolyte can retard the dendrite initiation. We have attempted to study the dendrite initiation quantitatively by developing a mathematical model that evaluates the behavior of the interface and by performing dendrite-initiation experiments with the use of cross-linked polymer electrolytes to vary the mechanical properties of the electrolyte. Cross-linking the polymer backbone may decrease the transport properties of the polymer electrolyte. The transport properties are diffusion coefficient, ionic conductivity, and transference number of the electrolyte. When poor transport properties of the polymer electrolyte cause salt depletion at the cathode at low salt concentrations, side reactions and dendrite initiation can be accelerated. In order to study how cross-linking the polymer backbone affects the transport properties, the transport properties are measured experimentally by LBNL method which is based on concentrated solution theory. Porous electrodes are commonly used as the cathode in lithium battery systems. Because the electrochemical reaction occurs at the active particles in the porous, composite cathode during charge and discharge, the kinetics of the electrochemical reaction at the active particles in the cathode affects the battery performance. AC impedance has been broadly used to study the kinetics of the electrochemical reaction in the cathode. However, the AC impedance spectra have been analyzed by regarding the porous cathode as a planar electrode by most

  4. Influence of overcharge and over-discharge on the impedance response of LiCoO2|C batteries

    NASA Astrophysics Data System (ADS)

    Erol, Salim; Orazem, Mark E.; Muller, Richard P.

    2014-12-01

    This paper provides the results of impedance measurements on commercially available LiCoO2|C coin-type cells. The impedance response was shown to be extremely sensitive to state-of-charge, overcharge, and over-discharge. Interestingly, the impedance showed a persistent change to the electrochemical characteristics of a coin cell subject to overcharge; whereas, the electrochemical characteristics returned to normal for a coin cell subject to over-discharge. A measurement model analysis was used to show the reversibility of the impedance behavior of an over-discharged cell and the irreversibility of the impedance response of an overcharged cell.

  5. Impedance of a nanoantenna

    SciTech Connect

    Greffet, Jean-Jacques; Laroche, Marine; Marquier, Francois

    2009-10-07

    We introduce a generalized definition of the impedance of a nanoantenna that can be applied to any system. We also introduce a definition of the impedance of a two level system. Using this framework, we establish a link between the electrical engineering and the quantum optics picture of light emission.

  6. Method of estimating pulse response using an impedance spectrum

    SciTech Connect

    Morrison, John L; Morrison, William H; Christophersen, Jon P; Motloch, Chester G

    2014-10-21

    Electrochemical Impedance Spectrum data are used to predict pulse performance of an energy storage device. The impedance spectrum may be obtained in-situ. A simulation waveform includes a pulse wave with a period greater than or equal to the lowest frequency used in the impedance measurement. Fourier series coefficients of the pulse train can be obtained. The number of harmonic constituents in the Fourier series are selected so as to appropriately resolve the response, but the maximum frequency should be less than or equal to the highest frequency used in the impedance measurement. Using a current pulse as an example, the Fourier coefficients of the pulse are multiplied by the impedance spectrum at corresponding frequencies to obtain Fourier coefficients of the voltage response to the desired pulse. The Fourier coefficients of the response are then summed and reassembled to obtain the overall time domain estimate of the voltage using the Fourier series analysis.

  7. Interface electric properties of Si/organic hybrid solar cells using impedance spectroscopy analysis

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Zhu, Juye; Ding, Li; Gao, Pingqi; Pan, Xiaoyin; Sheng, Jiang; Ye, Jichun

    2016-05-01

    The internal resistance and capacitance of Si/organic hybrid solar cells (Si-HSC) based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) are investigated by electrochemical impedance spectroscopy (EIS). Three types of Nyquist plots in Si-HSC are observed firstly at different bias voltages, while suitable equivalent circuit models are established to evaluate the details of interface carrier transfer and recombination. In particular, the carrier transport property of the PEDOT:PSS film responds at a high frequency (6 × 104-1 × 106 Hz) in three-arc spectra. Therefore, EIS could help us deeply understand the electronic properties of Si-HSC for developing high performance devices.

  8. Study of Body Composition by Impedance Analysis

    NASA Astrophysics Data System (ADS)

    González-Solís, J. L.; Vargas-Luna, M.; Sosa-Aquino, M.; Bernal-Alvarado, J.; Gutiérrez-Juárez, G.; Huerta-Franco, R.; Sanchis-Sabater, A.

    2002-08-01

    This work presents a set of impedance measurements and preliminary results on the analysis of body composition using impedance spectroscopy. This study is made using a pork meat sample and spectra from fat and flesh region were independently obtained using the same electrodes array. From these measurements, and theoretical considerations, it is possible to explain the behavior of the composite sample flesh-fat-flesh and, fitting the electrical parameters of the model, it shows the plausibility of a physical and quantitative application to human corporal composition.

  9. Effect of Feeding and Suction on Gastric Impedance Spectroscopy Measurements.

    PubMed

    Beltran, Nohra E; Sánchez-Miranda, Gustavo; Sacristan, Emilio

    2015-01-01

    A specific device and system has been developed and tested for clinical monitoring of gastric mucosal reactance in the critically ill as an early warning of splanchnic hypoperfusion associated with shock and sepsis. This device has been proven effective in clinical trials and is expected to become commercially available next year. The system uses a combination nasogastric tube and impedance spectroscopy probe as a single catheter. Because this device has a double function, the question is: Does enteral feeding or suction affect the gastric reactance measurements? This study was designed to evaluate the effect of feeding and suction on the measurement of gastric impedance spectroscopy in healthy volunteers. Impedance spectra were obtained from the gastric wall epithelia of 18 subjects. The spectra were measured for each of the following conditions: postinsertion of gastric probe, during active suction, postactive suction, and during enteral feeding (236 ml of nutritional supplement). Impedance spectra were reproducible in all volunteers under all conditions tested. There was a slight increase in impedance parameters after suction, and a decrease in impedance after feeding; however, these observed differences were insignificant compared to patient-to-patient variability, and truly negligible compared with previously observed changes associated with splanchnic ischemia in critically ill patients. Our results demonstrate that suction or feeding when using the impedance spectro-metry probe/nasogastric tube does not significantly interfere with gastric impedance spectrometer measurements. PMID:26226020

  10. AC impedance study of degradation of porous nickel battery electrodes

    NASA Technical Reports Server (NTRS)

    Lenhart, Stephen J.; Macdonald, D. D.; Pound, B. G.

    1987-01-01

    AC impedance spectra of porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (nonporous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low.

  11. Overview Of Impedance Sensors

    NASA Astrophysics Data System (ADS)

    Abele, John E.

    1989-08-01

    Electrical impedance has been one of the many "tools of great promise" that physicians have employed in their quest to measure and/or monitor body function or physiologic events. So far, the expectations for its success have always exceeded its performance. In simplistic terms, physiologic impedance is a measure of the resistance in the volume between electrodes which changes as a function of changes in that volume, the relative impedance of that volume, or a combination of these two. The history and principles of electrical impedance are very nicely reviewed by Geddes and Baker in their textbook "Principles of Applied Biomedical Instrumentation". It is humbling, however, to note that Cremer recorded variations in electrical impedance in frog hearts as early as 1907. The list of potential applications includes the measurement of thyroid function, estrogen activity, galvanic skin reflex, respiration, blood flow by conductivity dilution, nervous activity and eye movement. Commercial devices employing impedance have been and are being used to measure respiration (pneumographs and apneamonitors), pulse volume (impedance phlebographs) and even noninvasive cardiac output.

  12. High-temperature "spectrochronopotentiometry": correlating electrochemical performance with in situ Raman spectroscopy in solid oxide fuel cells.

    PubMed

    Kirtley, John D; Halat, David M; McIntyre, Melissa D; Eigenbrodt, Bryan C; Walker, Robert A

    2012-11-20

    Carbon formation or "coking" on solid oxide fuel cell (SOFC) anodes adversely affects performance by blocking catalytic sites and reducing electrochemical activity. Quantifying these effects, however, often requires correlating changes in SOFC electrochemical efficiency measured during operation with results from ex situ measurements performed after the SOFC has been cooled and disassembled. Experiments presented in this work couple vibrational Raman spectroscopy with chronopotentiometry to observe directly the relationship between graphite deposited on nickel cermet anodes and the electrochemical performance of SOFCs operating at 725 °C. Raman spectra from Ni cermet anodes at open circuit voltage exposed to methane show a strong vibrational band at 1556 cm(-1) assigned to the "G" mode of highly ordered graphite. When polarized in the absence of a gas-phase fuel, these carbon-loaded anodes operate stably, oxidizing graphite to form CO and CO(2). Disappearance of graphite intensity measured in the Raman spectra is accompanied by a steep ∼0.8 V rise in the cell potential needed to keep the SOFC operating under constant current conditions. Continued operation leads to spectroscopically observable Ni oxidation and another steep rise in cell potential. Time-dependent spectroscopic and electrochemical measurements pass through correlated equivalence points providing unequivocal, in situ evidence that identifies how SOFC performance depends on the chemical condition of its anode. Chronopotentiometric data are used to quantify the oxide flux necessary to eliminate the carbon initially present on the SOFC anode, and data show that the oxidation mechanisms responsible for graphite removal correlate directly with the electrochemical condition of the anode as evidenced by voltammetry and impedance measurements. Electrochemically oxidizing the Ni anode damages the SOFC significantly and irreversibly. Anodes that have been reconstituted following electrochemical oxidation of

  13. Microfabricated AC impedance sensor

    DOEpatents

    Krulevitch, Peter; Ackler, Harold D.; Becker, Frederick; Boser, Bernhard E.; Eldredge, Adam B.; Fuller, Christopher K.; Gascoyne, Peter R. C.; Hamilton, Julie K.; Swierkowski, Stefan P.; Wang, Xiao-Bo

    2002-01-01

    A microfabricated instrument for detecting and identifying cells and other particles based on alternating current (AC) impedance measurements. The microfabricated AC impedance sensor includes two critical elements: 1) a microfluidic chip, preferably of glass substrates, having at least one microchannel therein and with electrodes patterned on both substrates, and 2) electrical circuits that connect to the electrodes on the microfluidic chip and detect signals associated with particles traveling down the microchannels. These circuits enable multiple AC impedance measurements of individual particles at high throughput rates with sufficient resolution to identify different particle and cell types as appropriate for environmental detection and clinical diagnostic applications.

  14. Effect of grain-boundary corrosion on impedance characteristics of an aluminum-zinc-indium alloy in 3.5% sodium chloride solution

    SciTech Connect

    Venugopal, A.; Angal, R.D.; Raja, V.S.

    1996-02-01

    Applications of Al alloy sacrificial anodes for cathodic protection (CP) of steel structures in marine environments are well known. Small changes in composition and heat treatment can affect the corrosion behavior of the alloy substantially. However, characterization of the alloy anodes in relation to such changes is lacking in the literature. Electrochemical impedance spectroscopy (EIS) was used to understand the dissolution behavior of an Al-Zn-In alloy in 3.5% sodium chloride (NaCl) solution as a function of time after the alloy was subjected to galvanostatic dissolution. Compared to optical microscopy, the changing trend in impedance spectra reflected the preferential dissolution of the alloy along the grain boundaries. The usefulness of EIS as a tool to indicate the current efficiency loss from grain-boundary attack was illustrated.

  15. FTIR spectra and normal-mode analysis of a tetranuclear Manganese adamantane-like complex in two electrochemically prepared oxidation states: Relevance to the oxygen-evolving complex of Photosystem II

    SciTech Connect

    Visser, Hendrik; Dube, Christopher E.; Armstrong, William H.; Sauer, Kenneth; Yachandra, Vittal K.

    2002-03-19

    The IR spectra and normal-mode analysis of the adamantane-like compound [Mn4O6(bpea)4]n+ in two oxidation states, MnIV4 and MnIIIMnIV3, that are relevant to the oxygen-evolving complex of photosystem II are presented. Mn-O vibrational modes are identified with isotopic exchange, 16O->18O, of the mono-(mu)-oxo bridging atoms in the complex. IR spectra of the MnIIIMnIV3 species are obtained by electrochemical reduction of the MnIV4 species using a spectroelectrochemical cell, based on attenuated total reflection [Visser et al. Anal Chem 2001, 73, 4374-4378]. A novel method of subtraction is used to reduce background contributions from solvent and ligand modes, and the difference and double-difference spectra are used in identifying Mn-O bridging modes that are sensitive to oxidation state change. Two strong IR bands are observed for the MnIV4 species at 745 and 707 cm-1 and a weaker band at 510 cm-1. Upon reduction, the MnIIIMnIV3 species exhibits two strong IR bands at 745 and 680 cm-1, and several weaker bands are observed in the 510 - 425 cm-1 range. A normal mode analysis is performed to assign all the relevant bridging modes in the oxidized MnIV4 and reduced MnIIIMnIV3 species. The calculated force constants for the MnIV4 species are = 3.15 mdynAngstrom, = 0.55 mdyn/Angstrom, and = 0.20 mdyn/Angstrom. The force constants for the MnIIIMnIV3 species are = 3.10 mdyn/Angstrom, = 2.45 mdyn/Angstrom, = 0.40, and = 0.15 mdyn/Angstrom. This study provides insights for the identification of Mn-O modes in the IR spectra of the photosynthetic oxygen-evolving complex during its catalytic cycle.

  16. Spectral, thermal and electrochemical investigation of carbohydrazone derived ionophore as Fe(III) ion selective electrode

    NASA Astrophysics Data System (ADS)

    Chandra, Sulekh; Deepshikha; Sarkar, Anjana

    2013-04-01

    Dibenzoylmethane bis(carbohydrazone) (BMBC) has been synthesized and structurally characterized on the basis of IR, 1H NMR, mass, UV spectra and thermogravimetric analyses. BMBC has been analysed electrochemically and explored as new N, N Schiff base. It plays the role of an excellent ion carrier in the construction of iron(III) ion selective membrane sensor. This sensor shows very good selectivity and sensitivity towards iron ion over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The response mechanism was discussed in the view of UV-spectroscopy and Electrochemical Impedance Spectroscopy (EIS). The proposed sensor was successfully used for the determination of iron in different samples.

  17. Electrochemical Study of Corrosion Behavior of Wrought Stellite Alloys in Sodium Chloride and Green Death Solutions

    NASA Astrophysics Data System (ADS)

    Zhang, X. Z.; Liu, R.; Chen, K. Y.; Yao, M. X.; Collier, R.

    2015-09-01

    Corrosion behavior of wrought Stellite 6B and Stellite 6K, which have similar chemical composition but contain different carbon content, in 3.5 wt.% NaCl solution and in Green Death solution is investigated using various electrochemical methods, including potentiodynamic polarization, cyclic polarization, and electrochemical impedance spectroscopy (EIS). The obtained potentiodynamic polarization curves, cyclic polarization curves, and EIS spectra for these alloys are in good agreement, showing that Stellite 6K with higher carbon content is easier corroded due to its larger volume fraction of carbides but the Cr2O3 film formed on this alloy is stronger and more stable than that on Stellite 6B. Further immersion tests on these alloys show that Stellite 6K has less resistance to pitting corrosion.

  18. Growth, characterization and electrochemical properties of hierarchical CuO nanostructures for supercapacitor applications

    SciTech Connect

    Krishnamoorthy, Karthikeyan; Kim, Sang-Jae

    2013-09-01

    Graphical abstract: - Highlights: • Hierarchical CuO nanostructures were grown on Cu foil. • Monoclinic phase of CuO was grown. • XPS analysis revealed the presence of Cu(2p{sub 3/2}) and Cu(2p{sub 1/2}) on the surfaces. • Specific capacitance of 94 F/g was achieved for the CuO using cyclic voltammetry. • Impedance spectra show their pseudo capacitor applications. - Abstract: In this paper, we have investigated the electrochemical properties of hierarchical CuO nanostructures for pseudo-supercapacitor device applications. Moreover, the CuO nanostructures were formed on Cu substrate by in situ crystallization process. The as-grown CuO nanostructures were characterized using X-ray diffraction (XRD), Fourier transform-infra red spectroscopy (FT-IR), X-ray photoelectron spectroscopy and field emission-scanning electron microscope (FE-SEM) analysis. The XRD and FT-IR analysis confirm the formation of monoclinic CuO nanostructures. FE-SEM analysis shows the formation of leave like hierarchical structures of CuO with high uniformity and controlled density. The electrochemical analysis such as cyclic voltammetry and electrochemical impedance spectroscopy studies confirms the pseudo-capacitive behavior of the CuO nanostructures. Our experimental results suggest that CuO nanostructures will create promising applications of CuO toward pseudo-supercapacitors.

  19. Wake potentials and impedances for the ATA (Advanced Test Accelerator) induction cell

    SciTech Connect

    Craig, G.D.

    1990-09-04

    The AMOS Wakefield Code is used to calculate the impedances of the induction cell used in the Advanced Test Accelerator (ATA) at Livermore. We present the wakefields and impedances for multipoles m = 0, 1 and 2. The ATA cell is calculated to have a maximum transverse impedance of approximately 1000 {Omega}/m at 875 MHz with a quality factor Q = 5. The sensitivity of the impedance spectra to modeling variations is discussed.

  20. Vascular impedance analysis in human pulmonary circulation.

    PubMed

    Zhou, Qinlian; Gao, Jian; Huang, Wei; Yen, Michael

    2006-01-01

    Vascular impedance is determined by morphometry and mechanical properties of the vascular system, as well as the rheology of the blood. The interactions between all these factors are complicated and difficult to investigate solely by experiments. A mathematical model representing the entire system of human pulmonary circulation was constructed based on experimentally measured morphometric and elasticity data of the vessels. The model consisted of 16 orders of arteries and 15 orders of veins. The pulmonary arteries and veins were considered as elastic tubes and their impedance was calculated based on Womersley's theory. The flow in capillaries was described by the "sheet-flow" theory. The model yielded an impedance modulus spectrum that fell steeply from a high value at 0 Hz to a minimum around 1.5 Hz. At about 4 Hz, it reached a second high and then oscillated around a relatively small value at higher frequencies. Characteristic impedance was 27.9 dyn-sec/cm5. Influence of variations in vessel geometry and elasticity on impedance spectra was analyzed. Simulation results showed good agreement with experimental measurements. PMID:16817653

  1. Electrochemical biosensors and nanobiosensors.

    PubMed

    Hammond, Jules L; Formisano, Nello; Estrela, Pedro; Carrara, Sandro; Tkac, Jan

    2016-06-30

    Electrochemical techniques have great promise for low-cost miniaturised easy-to-use portable devices for a wide range of applications-in particular, medical diagnosis and environmental monitoring. Different techniques can be used for biosensing, with amperometric devices taking the central role due to their widespread application in glucose monitoring. In fact, glucose biosensing takes an approximately 70% share of the biosensor market due to the need for diabetic patients to monitor their sugar levels several times a day, making it an appealing commercial market.In this review, we present the basic principles of electrochemical biosensor devices. A description of the different generations of glucose sensors is used to describe in some detail the operation of amperometric sensors and how the introduction of mediators can enhance the performance of the sensors. Electrochemical impedance spectroscopy is a technique being increasingly used in devices due to its ability to detect variations in resistance and capacitance upon binding events. Novel advances in electrochemical sensors, due to the use of nanomaterials such as carbon nanotubes and graphene, are presented as well as future directions that the field is taking. PMID:27365037

  2. Electrochemical biosensors and nanobiosensors

    PubMed Central

    Hammond, Jules L.; Formisano, Nello; Carrara, Sandro; Tkac, Jan

    2016-01-01

    Electrochemical techniques have great promise for low-cost miniaturised easy-to-use portable devices for a wide range of applications–in particular, medical diagnosis and environmental monitoring. Different techniques can be used for biosensing, with amperometric devices taking the central role due to their widespread application in glucose monitoring. In fact, glucose biosensing takes an approximately 70% share of the biosensor market due to the need for diabetic patients to monitor their sugar levels several times a day, making it an appealing commercial market. In this review, we present the basic principles of electrochemical biosensor devices. A description of the different generations of glucose sensors is used to describe in some detail the operation of amperometric sensors and how the introduction of mediators can enhance the performance of the sensors. Electrochemical impedance spectroscopy is a technique being increasingly used in devices due to its ability to detect variations in resistance and capacitance upon binding events. Novel advances in electrochemical sensors, due to the use of nanomaterials such as carbon nanotubes and graphene, are presented as well as future directions that the field is taking. PMID:27365037

  3. Battery electrochemical nonlinear/dynamic SPICE model

    SciTech Connect

    Glass, M.C.

    1996-12-31

    An Integrated Battery Model has been produced which accurately represents DC nonlinear battery behavior together with transient dynamics. The NiH{sub 2} battery model begins with a given continuous-function electrochemical math model. The math model for the battery consists of the sum of two electrochemical process DC currents, which are a function of the battery terminal voltage. This paper describes procedures for realizing a voltage-source SPICE model which implements the electrochemical equations using behavioral sources. The model merges the essentially DC non-linear behavior of the electrochemical model, together with the empirical AC dynamic terminal impedance from measured data. Thus the model integrates the short-term linear impedance behavior, with the long-term nonlinear DC resistance behavior. The long-duration non-Faradaic capacitive behavior of the battery is represented by a time constant. Outputs of the model include battery voltage/current, state-of-charge, and charge-current efficiency.

  4. Impedance of accelerator components

    SciTech Connect

    Corlett, J.N.

    1996-05-01

    As demands for high luminosity and low emittance particle beams increase, an understanding of the electromagnetic interaction of these beams with their vacuum chamber environment becomes more important in order to maintain the quality of the beam. This interaction is described in terms of the wake field in time domain, and the beam impedance in frequency domain. These concepts are introduced, and related quantities such as the loss factor are presented. The broadband Q = 1 resonator impedance model is discussed. Perturbation and coaxial wire methods of measurement of real components are reviewed.

  5. Superconducting active impedance converter

    DOEpatents

    Ginley, D.S.; Hietala, V.M.; Martens, J.S.

    1993-11-16

    A transimpedance amplifier for use with high temperature superconducting, other superconducting, and conventional semiconductors allows for appropriate signal amplification and impedance matching to processing electronics. The amplifier incorporates the superconducting flux flow transistor into a differential amplifier configuration which allows for operation over a wide temperature range, and is characterized by high gain, relatively low noise, and response times less than 200 picoseconds over at least a 10-80 K. temperature range. The invention is particularly useful when a signal derived from either far-IR focal plane detectors or from Josephson junctions is to be processed by higher signal/higher impedance electronics, such as conventional semiconductor technology. 12 figures.

  6. Superconducting active impedance converter

    DOEpatents

    Ginley, David S.; Hietala, Vincent M.; Martens, Jon S.

    1993-01-01

    A transimpedance amplifier for use with high temperature superconducting, other superconducting, and conventional semiconductor allows for appropriate signal amplification and impedance matching to processing electronics. The amplifier incorporates the superconducting flux flow transistor into a differential amplifier configuration which allows for operation over a wide temperature range, and is characterized by high gain, relatively low noise, and response times less than 200 picoseconds over at least a 10-80 K. temperature range. The invention is particularly useful when a signal derived from either far-IR focal plane detectors or from Josephson junctions is to be processed by higher signal/higher impedance electronics, such as conventional semiconductor technology.

  7. Validation of an Impedance Education Method in Flow

    NASA Technical Reports Server (NTRS)

    Watson, Willie R.; Jones, Michael G.; Parrott, Tony L.

    2004-01-01

    This paper reports results of a research effort to validate a method for educing the normal incidence impedance of a locally reacting liner, located in a grazing incidence, nonprogressive acoustic wave environment with flow. The results presented in this paper test the ability of the method to reproduce the measured normal incidence impedance of a solid steel plate and two soft test liners in a uniform flow. The test liners are known to be locally react- ing and exhibit no measurable amplitude-dependent impedance nonlinearities or flow effects. Baseline impedance spectra for these liners were therefore established from measurements in a conventional normal incidence impedance tube. A key feature of the method is the expansion of the unknown impedance function as a piecewise continuous polynomial with undetermined coefficients. Stewart's adaptation of the Davidon-Fletcher-Powell optimization algorithm is used to educe the normal incidence impedance at each Mach number by optimizing an objective function. The method is shown to reproduce the measured normal incidence impedance spectrum for each of the test liners, thus validating its usefulness for determining the normal incidence impedance of test liners for a broad range of source frequencies and flow Mach numbers. Nomenclature

  8. Statistical Properties of Antenna Impedance in an Electrically Large Cavity

    SciTech Connect

    WARNE,LARRY K.; LEE,KELVIN S.H.; HUDSON,H. GERALD; JOHNSON,WILLIAM A.; JORGENSON,ROY E.; STRONACH,STEPHEN L.

    2000-12-13

    This paper presents models and measurements of antenna input impedance in resonant cavities at high frequencies.The behavior of input impedance is useful in determining the transmission and reception characteristics of an antenna (as well as the transmission characteristics of certain apertures). Results are presented for both the case where the cavity is undermoded (modes with separate and discrete spectra) as well as the over moded case (modes with overlapping spectra). A modal series is constructed and analyzed to determine the impedance statistical distribution. Both electrically small as well as electrically longer resonant and wall mounted antennas are analyzed. Measurements in a large mode stirred chamber cavity are compared with calculations. Finally a method based on power arguments is given, yielding simple formulas for the impedance distribution.

  9. Electrochemical corrosion studies in low conductivity propellants

    NASA Technical Reports Server (NTRS)

    Blue, G. D.; Moran, C. M.; Distefano, S.

    1986-01-01

    The Jet Propulsion Laboratory is investigating the possibility of developing advanced electrochemical techniques as accelerated compatibility tests for metal/propellant systems which overcome the problems associated with the low conductivity of the liquid propellants (e.g., hydrazines, nitrogen tetroxide). Both DC techniques and AC electrochemical impedance spectroscopy are being evaluated. Progress has been made in experiments involving stainless steel with hydrazine and nitrogen tetroxide propellants.

  10. Impedance cardiography: recent advancements.

    PubMed

    Cybulski, Gerard; Strasz, Anna; Niewiadomski, Wiktor; Gąsiorowska, Anna

    2012-01-01

    The aim of this paper is the presentation of recent advancements in impedance cardiography regarding methodical approach, applied equipment and clinical or research implementations. The review is limited to the papers which were published over last 17 months (dated 2011 and 2012) in well recognised scientific journals. PMID:23042327

  11. Impedances of Tevatron separators

    SciTech Connect

    K. Y. Ng

    2003-05-28

    The impedances of the Tevatron separators are revisited and are found to be negligibly small in the few hundred MHz region, except for resonances at 22.5 MHz. The later are contributions from the power cables which may drive head-tail instabilities if the bunch is long enough.

  12. Longitudinal impedance of RHIC

    SciTech Connect

    Blaskiewicz, M.; Brennan, J. M.; Mernick, K.

    2015-05-03

    The longitudinal impedance of the two RHIC rings has been measured using the effect of potential well distortion on longitudinal Schottky measurements. For the blue RHIC ring Im(Z/n) = 1.5±0.2Ω. For the yellow ring Im(Z/n) = 5.4±1Ω.

  13. A Batteryless Sensor ASIC for Implantable Bio-Impedance Applications.

    PubMed

    Rodriguez, Saul; Ollmar, Stig; Waqar, Muhammad; Rusu, Ana

    2016-06-01

    The measurement of the biological tissue's electrical impedance is an active research field that has attracted a lot of attention during the last decades. Bio-impedances are closely related to a large variety of physiological conditions; therefore, they are useful for diagnosis and monitoring in many medical applications. Measuring living tissues, however, is a challenging task that poses countless technical and practical problems, in particular if the tissues need to be measured under the skin. This paper presents a bio-impedance sensor ASIC targeting a battery-free, miniature size, implantable device, which performs accurate 4-point complex impedance extraction in the frequency range from 2 kHz to 2 MHz. The ASIC is fabricated in 150 nm CMOS, has a size of 1.22 mm × 1.22 mm and consumes 165 μA from a 1.8 V power supply. The ASIC is embedded in a prototype which communicates with, and is powered by an external reader device through inductive coupling. The prototype is validated by measuring the impedances of different combinations of discrete components, measuring the electrochemical impedance of physiological solution, and performing ex vivo measurements on animal organs. The proposed ASIC is able to extract complex impedances with around 1 Ω resolution; therefore enabling accurate wireless tissue measurements. PMID:26372646

  14. Testing and analyses of electrochemical cells using frequency response

    NASA Technical Reports Server (NTRS)

    Norton, O. A., Jr.; Thomas, D. L.

    1992-01-01

    The feasibility of electrochemical impedance spectroscopy as a method for analyzing battery state of health and state of charge was investigated. Porous silver, zinc, nickel, and cadmium electrodes as well as silver/zinc cells were studied. State of charge could be correlated with impedance data for all but the nickel electrodes. State of health was correlated with impedance data for two silver/zinc cells, one apparently good and the other dead. The experimental data were fit to equivalent circuit models.

  15. Recycler short kicker beam impedance

    SciTech Connect

    Crisp, Jim; Fellenz, Brian; /Fermilab

    2009-07-01

    Measured longitudinal and calculated transverse beam impedance is presented for the short kicker magnets being installed in the Fermilab Recycler. Fermi drawing number ME-457159. The longitudinal impedance was measured with a stretched wire and the Panofsky equation was used to estimate the transverse impedance. The impedance of 3319 meters (the Recycler circumference) of stainless vacuum pipe is provided for comparison. Although measurements where done to 3GHz, impedance was negligible above 30MHz. The beam power lost to the kicker impedance is shown for a range of bunch lengths. The measurements are for one kicker assuming a rotation frequency of 90KHz. Seven of these kickers are being installed.

  16. High-precision impedance spectroscopy: a strategy demonstrated on PZT.

    PubMed

    Boukamp, Bernard A; Blank, Dave H A

    2011-12-01

    Electrochemical impedance spectroscopy (EIS) has been recognized as a very powerful tool for studying charge and mass transport and transfer in a wide variety of electrically or electrochemically active systems. Sophisticated modeling programs make it possible to extract parameters from the impedance data, thus contributing to a better understanding of the system or material properties. For an accurate analysis, a correct modeling function is needed; this is often in the form of an equivalent circuit. It is not always possible to define the modeling function from visual inspection of the impedance dispersion. Small contributions to the overall dispersion can be masked, and hence overlooked. In this publication, a strategy is presented for high-precision impedance data analysis. A Kramers-Kronig test is used for the essential data validation. An iterative process of partial analysis and subtraction assists in deconvoluting the impedance spectrum, yielding both a vi- able model function and a set of necessary starting values for the full complex nonlinear least squares (CNLS) modeling. The advantage and possibilities of this strategy are demonstrated with an analysis of the ionic and electronic conductivity of lead zirconate titanate (PZT) as functions of temperature and oxygen partial pressure. PMID:23443688

  17. Piezoelectric impedance-based strength gain monitoring in concrete

    NASA Astrophysics Data System (ADS)

    Guo, Zhigang; Sun, Zhi

    2012-04-01

    This paper presented an experimental study on piezoelectric impedance based cubic and axial compressive strength gain monitoring in concrete during curing process. The piezoceramic (PZT) patch was attached on the concrete specimen to collect the monitoring signal. The electro-mechanical impedance (EMI) spectra of surface bonded PZT patch were collected using an impedance analyzer by sweeping the frequency. A regression analysis is conducted to establish the empirical relationship between the relative strength gain of concrete and the monitored relative resonant frequency change of the EMI spectra. The established empirical formula is used for concrete strength monitoring via EMI spectra. The results tell that the EMI technique is a practical and reliable nondestructive test method for concrete strength gain monitoring.

  18. Thermodynamic and Kinetic Properties of the Electrochemical Cell.

    ERIC Educational Resources Information Center

    Smith, Donald E.

    1983-01-01

    Describes basic characteristics of the electrochemical cell. Also describes basic principles of electrochemical procedures and use of these concepts to explain use of the term "primarily" in discussions of methods primarily responsive to equilibrium cell potential, bulk ohmic resistance, and the Faradaic impedance. (JN)

  19. Sulfur nanocrystals anchored graphene composite with highly improved electrochemical performance for lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Dong, Zimin; Wang, Xiuli; Zhao, Xuyang; Tu, Jiangping; Su, Qingmei; Du, Gaohui

    2014-12-01

    Two kinds of graphene-sulfur composites with 50 wt% of sulfur are prepared using hydrothermal method and thermal mixing, respectively. Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectra mapping show that sulfur nanocrystals with size of ∼5 nm dispersed on graphene sheets homogeneously for the sample prepared by hydrothermal method (NanoS@G). While for the thermal mixed graphene-sulfur composite (S-G mixture), sulfur shows larger and uneven size (50-200 nm). X-ray Photoelectron Spectra (XPS) reveals the strong chemical bonding between the sulfur nanocrystals and graphene. Comparing with the S-G mixture, the NanoS@G composite shows highly improved electrochemical performance as cathode for lithium-sulfur (Li-S) battery. The NanoS@G composite delivers an initial capacity of 1400 mAh g-1 with the sulfur utilization of 83.7% at a current density of 335 mA g-1. The capacity keeps above 720 mAh g-1 over 100 cycles. The strong adherence of the sulfur nanocrystals on graphene immobilizes sulfur and polysulfides species and suppressed the "shuttle effect", resulting higher coulombic efficiency and better capacity retention. Electrochemical impedance also suggests that the strong bonding enabled rapid electronic/ionic transport and improved electrochemical kinetics, therefore good rate capability is obtained. These results demonstrate that the NanoS@G composite is a very promising candidate for high-performance Li-S batteries.

  20. Electrochemical immunosensor constructed using TiO2 nanotubes as immobilization scaffold and tracing tag.

    PubMed

    Huo, Xiaohe; Liu, Peipei; Zhu, Jie; Liu, Xiaoqiang; Ju, Huangxian

    2016-11-15

    A ternary TiO2 nanotube (TNT) composite and a signal antibody and horseradish peroxidase (HRP) functionalized TNT were designed as an electrode scaffold for immobilization of high quantity of capture antibody and a tracing tag for immunosensing, respectively. The polyaniline (PANI) was coated on TNTs by chemical oxidative polymerization, and gold nanoparticles were deposited on TNT-PANI with a routine chemical reduction. Various techniques including scanning electron microscopy, energy dispersive X-ray, transmission electron microscope, X-ray diffraction, Fourier transform infrared spectra, X-ray photoelectron spectra, impedance and electrochemical techniques were used to characterize the nano-materials. Using bis(sulfosuccinimidyl) suberate as amino cross-linker, the TNT composite could be further functionalized with protein G' for oriented immobilization of capture antibody on electrode surface. Upon sandwich-type immunoreaction, the signal antibody on the tracing tag was quantitatively captured on the surface to generate sensitive electrochemical response with a H2O2 mediated HRP catalytic reaction. With α-fetoprotein as an analyte model, the immunosensor showed a linear range of 0.01-350ngmL(-1) with a detection limit of 1.5pgmL(-1). The accelerated electron transfer by the ternary composite, oriented immobilization of capture antibody and high loading of HRP on the TNT tracing tag greatly amplified the electrochemical signal, and led to the superior performance of the immunoassay. PMID:27261885

  1. Platinum nanoparticles functionalized nitrogen doped graphene platform for sensitive electrochemical glucose biosensing.

    PubMed

    Yang, Zhanjun; Cao, Yue; Li, Juan; Jian, Zhiqin; Zhang, Yongcai; Hu, Xiaoya

    2015-04-29

    In this work, we reported an efficient platinum nanoparticles functionalized nitrogen doped graphene (PtNPs@NG) nanocomposite for devising novel electrochemical glucose biosensor for the first time. The fabricated PtNPs@NG and biosensor were characterized using transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, static water contact angle, UV-vis spectroscopy, electrochemical impedance spectra and cyclic voltammetry, respectively. PtNPs@NG showed large surface area and excellent biocompatibility, and enhanced the direct electron transfer between enzyme molecules and electrode surface. The glucose oxidase (GOx) immobilized on PtNPs@NG nanocomposite retained its bioactivity, and exhibited a surface controlled, quasi-reversible and fast electron transfer process. The constructed glucose biosensor showed wide linear range from 0.005 to 1.1mM with high sensitivity of 20.31 mA M(-1) cm(-2). The detection limit was calculated to be 0.002 mM at signal-to-noise of 3, which showed 20-fold decrease in comparison with single NG-based electrochemical biosensor for glucose. The proposed glucose biosensor also demonstrated excellent selectivity, good reproducibility, acceptable stability, and could be successfully applied in the detection of glucose in serum samples at the applied potential of -0.33 V. This research provided a promising biosensing platform for the development of excellent electrochemical biosensors. PMID:25847159

  2. Bioelectrical impedance analysis of bovine milk fat

    NASA Astrophysics Data System (ADS)

    Veiga, E. A.; Bertemes-Filho, P.

    2012-12-01

    Three samples of 250ml at home temperature of 20°C were obtained from whole, low fat and fat free bovine UHT milk. They were analysed by measuring both impedance spectra and dc conductivity in order to establish the relationship between samples related to fat content. An impedance measuring system was developed, which is based on digital oscilloscope, a current source and a FPGA. Data was measured by the oscilloscope in the frequency 1 kHz to 100 kHz. It was showed that there is approximately 7.9% difference in the conductivity between whole and low fat milk whereas 15.9% between low fat and free fat one. The change of fatness in the milk can be significantly sensed by both impedance spectra measurements and dc conductivity. This result might be useful for detecting fat content of milk in a very simple way and also may help the development of sensors for measuring milk quality, as for example the detection of mastitis.

  3. Impedance calculation for ferrite inserts

    SciTech Connect

    Breitzmann, S.C.; Lee, S.Y.; Ng, K.Y.; /Fermilab

    2005-01-01

    Passive ferrite inserts were used to compensate the space charge impedance in high intensity space charge dominated accelerators. They study the narrowband longitudinal impedance of these ferrite inserts. they find that the shunt impedance and the quality factor for ferrite inserts are inversely proportional to the imaginary part of the permeability of ferrite materials. They also provide a recipe for attaining a truly passive space charge impedance compensation and avoiding narrowband microwave instabilities.

  4. Impedance Measurement Box

    ScienceCinema

    Christophersen, Jon

    2013-05-28

    Energy storage devices, primarily batteries, are now more important to consumers, industries and the military. With increasing technical complexity and higher user expectations, there is also a demand for highly accurate state-of-health battery assessment techniques. IMB incorporates patented, proprietary, and tested capabilities using control software and hardware that can be part of an embedded monitoring system. IMB directly measures the wideband impedance spectrum in seconds during battery operation with no significant impact on service life. It also can be applied to batteries prior to installation, confirming health before entering active service, as well as during regular maintenance. For more information about this project, visit http://www.inl.gov/rd100/2011/impedance-measurement-box/

  5. Impedance Measurement Box

    Energy Science and Technology Software Center (ESTSC)

    2014-11-20

    The IMB 50V software provides functionality for design of impedance measurement tests or sequences of tests, execution of these tests or sequences, processing measured responses and displaying and saving of the results. The software consists of a Graphical User Interface that allows configuration of measurement parameters and test sequencing, a core engine that controls test sequencing, execution of measurements, processing and storage of results and a hardware/software data acquisition interface with the IMB hardware system.

  6. Gynecologic electrical impedance tomograph

    NASA Astrophysics Data System (ADS)

    Korjenevsky, A.; Cherepenin, V.; Trokhanova, O.; Tuykin, T.

    2010-04-01

    Electrical impedance tomography extends to the new and new areas of the medical diagnostics: lungs, breast, prostate, etc. The feedback from the doctors who use our breast EIT diagnostic system has induced us to develop the 3D electrical impedance imaging device for diagnostics of the cervix of the uterus - gynecologic impedance tomograph (GIT). The device uses the same measuring approach as the breast imaging system: 2D flat array of the electrodes arranged on the probe with handle is placed against the body. Each of the 32 electrodes of the array is connected in turn to the current source while the rest electrodes acquire the potentials on the surface. The current flows through the electrode of the array and returns through the remote electrode placed on the patient's limb. The voltages are measured relative to another remote electrode. The 3D backprojection along equipotential surfaces is used to reconstruct conductivity distribution up to approximately 1 cm in depth. Small number of electrodes enables us to implement real time imaging with a few frames per sec. rate. The device is under initial testing and evaluation of the imaging capabilities and suitability of usage.

  7. Acoustic ground impedance meter

    NASA Technical Reports Server (NTRS)

    Zuckerwar, A. J.

    1981-01-01

    A compact, portable instrument was developed to measure the acoustic impedance of the ground, or other surfaces, by direct pressure-volume velocity measurement. A Helmholz resonator, constructed of heavy-walled stainless steel but open at the bottom, is positioned over the surface having the unknown impedance. The sound source, a cam-driven piston of known stroke and thus known volume velocity, is located in the neck of the resonator. The cam speed is a variable up to a maximum 3600 rpm. The sound pressure at the test surface is measured by means of a microphone flush-mounted in the wall of the chamber. An optical monitor of the piston displacement permits measurement of the phase angle between the volume velocity and the sound pressure, from which the real and imaginary parts of the impedance can be evaluated. Measurements using a 5-lobed cam can be made up to 300 Hz. Detailed design criteria and results on a soil sample are presented.

  8. High input impedance amplifier

    NASA Technical Reports Server (NTRS)

    Kleinberg, Leonard L.

    1995-01-01

    High input impedance amplifiers are provided which reduce the input impedance solely to a capacitive reactance, or, in a somewhat more complex design, provide an extremely high essentially infinite, capacitive reactance. In one embodiment, where the input impedance is reduced in essence, to solely a capacitive reactance, an operational amplifier in a follower configuration is driven at its non-inverting input and a resistor with a predetermined magnitude is connected between the inverting and non-inverting inputs. A second embodiment eliminates the capacitance from the input by adding a second stage to the first embodiment. The second stage is a second operational amplifier in a non-inverting gain-stage configuration where the output of the first follower stage drives the non-inverting input of the second stage and the output of the second stage is fed back to the non-inverting input of the first stage through a capacitor of a predetermined magnitude. These amplifiers, while generally useful, are very useful as sensor buffer amplifiers that may eliminate significant sources of error.

  9. Impedance spectroscopy analysis of human odorant binding proteins immobilized on nanopore arrays for biochemical detection.

    PubMed

    Lu, Yanli; Zhang, Diming; Zhang, Qian; Huang, Yixuan; Luo, Senbiao; Yao, Yao; Li, Shuang; Liu, Qingjun

    2016-05-15

    Human odorant-binding proteins (hOBPs) not only can bind and transport odorants in the surrounding environment for sensing smells, but also play important roles in transmitting lots of biomolecules in different organs. Utilizing the properties of hOBPs, an electrochemical biosensor with nanopore array was developed to detect specific biomolecular ligands, such as aldehydes and fatty acids. The highly ordered nanopores of anodic aluminum oxide with diameter of 20-40 nm were fabricated with two-step oxidation. Through 2-carboxyethyl phosphonic acid, hOBPs were self-assembled on nanopores as the sensing membrane. With nanopore arrays, the impedance spectra showed quite different electron transfer processes in the frequency spectra, which could be characterized by the electron transfer resistance and electrical resistance of the porous membrane. Under stimulation of biomolecular ligands, series resistance of nanopores and hOBPs increased and showed a concentration-dependence feature, while the electron transfer resistance hardly changed. The nanopore based biosensor could sensitively detect biological ligands of benzaldehyde, docosahexaenoic acid, and lauric acid, which were closely related to or were potential biomarkers for cancers and other serious diseases. Equipped with hOBPs, the sensor exhibited promising potentials both in odorant and biomolecule detection for olfactory biosensing and in disease diagnosis and evaluation for biochemical detection. PMID:26710343

  10. Impedance characterization of microarray recording electrodes in vitro.

    PubMed

    Merrill, Daniel R; Tresco, Patrick A

    2005-11-01

    The mechanisms underlying performance degradation of chronically implanted silicon microelectrode arrays in the central nervous system (CNS) remain unclear. Humoral and cellular components of the brain foreign body response were evaluated to determine whether their presence on the electrode surface results in increased electrical impedance. Iridium oxide microelectrode recording arrays were electrically characterized in saline, culture media with 10% fetal bovine serum, and coated with various CNS cell types isolated from rat brain. Electrochemical impedance spectroscopy and cyclic voltammetry were performed using a three-electrode system. Potential cycling caused an immediate decrease in electrical impedance, which increased with time toward precycling values, with the effect of cycling remaining significant for several days. The addition of serum caused a significant increase in impedance of up to 28% relative to the saline control. Microelectrodes coated with various cell types known to participate in the foreign body response caused a 20%-80% increase in impedance immediately after contact that remained constant or gradually increased for several weeks. Our findings suggest that the attachment of molecular and cellular species following microelectrode implantation into brain tissue likely contribute to increases in impedance, but do not appear sufficient to hinder recording performance. PMID:16285400

  11. Electrochemical behavior of a magnesium galvanic anode under ASTM test method G 97-89 conditions

    SciTech Connect

    Genesca, J.; Betancourt, L.; Rodriguez, C.

    1996-07-01

    The electrochemical behavior of a magnesium galvanic anode in an aerated 5 g/L calcium sulfate + 0.1 g/L magnesium hydroxide solution was investigated by measuring electrochemical impedance under the conditions of ASTM Test Method G 97-89. Impedance spectra showed the capacitance of a porous layer (C{sub po}) in the high-frequency region, the resistive component (R{sub po}) of the porous layer (R{sub po}) in the frequency range between 100 Hz and 1,000 Hz, and the resistance of charge transfer (R{sub t}) in the low-frequency region. R{sub po} and R{sub t} increased with time, whereas C{sub po} decreased with immersion time. Since the resistance of a film is proportional to its resistivity and thickness, an increase in R{sub po} was interpreted to mean passivation increased with immersion time. This increase in protection with time provided evidence for the existence of a protective layer over the magnesium anode surface. This layer was identified as Mg(OH){sub 2} using x-ray diffraction of corrosion products formed on the magnesium anode.

  12. Detecting Corrosion Resistance of Coated Steel Rebars by Electrochemical Technique (eis)

    NASA Astrophysics Data System (ADS)

    Ryou, J.; Shah, S.

    Electrochemical impedance spectroscopy (EIS) is one of the electrochemical techniques used in materials science. The present measurements are used to evaluate the corrosion resistance of new types of coated steel rebar used in reinforced concrete. In this study, Si-based coating materials are used and evaluated, because adding Si to metals and alloys, including steel, generally increases their corrosion, oxidation, and erosion resistance. The result suggests that electrochemical impedance spectroscopy may be useful for monitoring corrosion activity on coated steel rebars. Based upon impedance changes, it appears that the silicon powder coating bonds well to the steel, and that the coating has a good performance.

  13. Enhanced Electrochemical Catalytic Efficiencies of Electrochemically Deposited Platinum Nanocubes as a Counter Electrode for Dye-Sensitized Solar Cells

    NASA Astrophysics Data System (ADS)

    Wei, Yu-Hsuan; Tsai, Ming-Chi; Ma, Chen-Chi M.; Wu, Hsuan-Chung; Tseng, Fan-Gang; Tsai, Chuen-Horng; Hsieh, Chien-Kuo

    2015-12-01

    Platinum nanocubes (PtNCs) were deposited onto a fluorine-doped tin oxide glass by electrochemical deposition (ECD) method and utilized as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). In this study, we controlled the growth of the crystalline plane to synthesize the single-crystal PtNCs at room temperature. The morphologies and crystalline nanostructure of the ECD PtNCs were examined by field emission scanning electron microscopy and high-resolution transmission electron microscopy. The surface roughness of the ECD PtNCs was examined by atomic force microscopy. The electrochemical properties of the ECD PtNCs were analyzed by cyclic voltammetry, Tafel polarization, and electrochemical impedance spectra. The Pt loading was examined by inductively coupled plasma mass spectrometry. The DSSCs were assembled via an N719 dye-sensitized titanium dioxide working electrode, an iodine-based electrolyte, and a CE. The photoelectric conversion efficiency (PCE) of the DSSCs with the ECD PtNC CE was examined under the illumination of AM 1.5 (100 mWcm-2). The PtNCs in this study presented a single-crystal nanostructure that can raise the electron mobility to let up the charge-transfer impedance and promote the charge-transfer rate. In this work, the electrocatalytic mass activity (MA) of the Pt film and PtNCs was 1.508 and 4.088 mAmg-1, respectively, and the MA of PtNCs was 2.71 times than that of the Pt film. The DSSCs with the pulse-ECD PtNC CE showed a PCE of 6.48 %, which is higher than the cell using the conventional Pt film CE (a PCE of 6.18 %). In contrast to the conventional Pt film CE which is fabricated by electron beam evaporation method, our pulse-ECD PtNCs maximized the Pt catalytic properties as a CE in DSSCs. The results demonstrated that the PtNCs played a good catalyst for iodide/triiodide redox couple reactions in the DSSCs and provided a potential strategy for electrochemical catalytic applications.

  14. Enhanced Electrochemical Catalytic Efficiencies of Electrochemically Deposited Platinum Nanocubes as a Counter Electrode for Dye-Sensitized Solar Cells.

    PubMed

    Wei, Yu-Hsuan; Tsai, Ming-Chi; Ma, Chen-Chi M; Wu, Hsuan-Chung; Tseng, Fan-Gang; Tsai, Chuen-Horng; Hsieh, Chien-Kuo

    2015-12-01

    Platinum nanocubes (PtNCs) were deposited onto a fluorine-doped tin oxide glass by electrochemical deposition (ECD) method and utilized as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). In this study, we controlled the growth of the crystalline plane to synthesize the single-crystal PtNCs at room temperature. The morphologies and crystalline nanostructure of the ECD PtNCs were examined by field emission scanning electron microscopy and high-resolution transmission electron microscopy. The surface roughness of the ECD PtNCs was examined by atomic force microscopy. The electrochemical properties of the ECD PtNCs were analyzed by cyclic voltammetry, Tafel polarization, and electrochemical impedance spectra. The Pt loading was examined by inductively coupled plasma mass spectrometry. The DSSCs were assembled via an N719 dye-sensitized titanium dioxide working electrode, an iodine-based electrolyte, and a CE. The photoelectric conversion efficiency (PCE) of the DSSCs with the ECD PtNC CE was examined under the illumination of AM 1.5 (100 mWcm(-2)). The PtNCs in this study presented a single-crystal nanostructure that can raise the electron mobility to let up the charge-transfer impedance and promote the charge-transfer rate. In this work, the electrocatalytic mass activity (MA) of the Pt film and PtNCs was 1.508 and 4.088 mAmg(-1), respectively, and the MA of PtNCs was 2.71 times than that of the Pt film. The DSSCs with the pulse-ECD PtNC CE showed a PCE of 6.48 %, which is higher than the cell using the conventional Pt film CE (a PCE of 6.18 %). In contrast to the conventional Pt film CE which is fabricated by electron beam evaporation method, our pulse-ECD PtNCs maximized the Pt catalytic properties as a CE in DSSCs. The results demonstrated that the PtNCs played a good catalyst for iodide/triiodide redox couple reactions in the DSSCs and provided a potential strategy for electrochemical catalytic applications. PMID:26625891

  15. Electrochemical Techniques

    SciTech Connect

    Chen, Gang; Lin, Yuehe

    2008-07-20

    Sensitive and selective detection techniques are of crucial importance for capillary electrophoresis (CE), microfluidic chips, and other microfluidic systems. Electrochemical detectors have attracted considerable interest for microfluidic systems with features that include high sensitivity, inherent miniaturization of both the detection and control instrumentation, low cost and power demands, and high compatibility with microfabrication technology. The commonly used electrochemical detectors can be classified into three general modes: conductimetry, potentiometry, and amperometry.

  16. Quartz tuning fork based microwave impedance microscopy

    NASA Astrophysics Data System (ADS)

    Cui, Yong-Tao; Ma, Eric Yue; Shen, Zhi-Xun

    2016-06-01

    Microwave impedance microscopy (MIM), a near-field microwave scanning probe technique, has become a powerful tool to characterize local electrical responses in solid state samples. We present the design of a new type of MIM sensor based on quartz tuning fork and electrochemically etched thin metal wires. Due to a higher aspect ratio tip and integration with tuning fork, such design achieves comparable MIM performance and enables easy self-sensing topography feedback in situations where the conventional optical feedback mechanism is not available, thus is complementary to microfabricated shielded stripline-type probes. The new design also enables stable differential mode MIM detection and multiple-frequency MIM measurements with a single sensor.

  17. Ionospheric effects to antenna impedance

    NASA Technical Reports Server (NTRS)

    Bethke, K. H.

    1986-01-01

    The reciprocity between high power satellite antennas and the surrounding plasma are examined. The relevant plasma states for antenna impedance calculations are presented and plasma models, and hydrodynamic and kinetic theory, are discussed. A theory from which a variation in antenna impedance with regard to the radiated power can be calculated for a frequency range well above the plasma resonance frequency is give. The theory can include photo and secondary emission effects in antenna impedance calculations.

  18. Electrochemical process combined with UV light irradiation for synergistic degradation of ammonia in chloride-containing solutions.

    PubMed

    Xiao, Shuhu; Qu, Jiuhui; Zhao, Xu; Liu, Hujuan; Wan, Dongjin

    2009-03-01

    An electrochemical process combined with ultraviolet light irradiation (UPE) using nonphotoactive dimensionally stable anodes (DSAs) like RuO2/Ti and IrO2/Ti in the presence of chlorides was investigated for ammonia degradation. In this process, the in situ electrogenerated active chlorine and in situ photogenerated chlorine radicals were responsible for the high efficiency of ammonia degradation. More than 97% of ammonia was converted to nitrogen and a significantly synergistic effect was confirmed. Compared with the single electrochemical (E) and photochemical (P) process, the degradation rates of ammonia and the average current efficiencies (ACEs) of the UPE process increased by 1.5 and 1.7 times using RuO2/Ti and IrO2/Ti electrodes, respectively. On the basis of the linear voltammograms, Electrochemical Impedance Spectra (EIS), UV-vis spectra, Electron Spin Resonance (ESR) analysis and a series of experiments designed, the synergistic mechanism was investigated. In addition, this unique process succeeded in transferring the reaction from the electrode surface to the bulk of the solution compared with the conventional photoelectrocatalytic (PEC) process. The loss of chloride decreased from 21.0% to 7.2% and the recycle of chloride was accelerated in the UPE process. Finally the effects of initial pH, current density and ammonia-nitrogen concentration were discussed. Results indicated that pH and ammonia concentration exerted little influences on the degradation rates and current density was the "rate-determining" factor. PMID:19135227

  19. Optically stimulated differential impedance spectroscopy

    DOEpatents

    Maxey, Lonnie C; Parks, II, James E; Lewis, Sr., Samuel A; Partridge, Jr., William P

    2014-02-18

    Methods and apparatuses for evaluating a material are described. Embodiments typically involve use of an impedance measurement sensor to measure the impedance of a sample of the material under at least two different states of illumination. The states of illumination may include (a) substantially no optical stimulation, (b) substantial optical stimulation, (c) optical stimulation at a first wavelength of light, (d) optical stimulation at a second wavelength of light, (e) a first level of light intensity, and (f) a second level of light intensity. Typically a difference in impedance between the impedance of the sample at the two states of illumination is measured to determine a characteristic of the material.

  20. IMPEDANCE OF FINITE LENGTH RESISTOR

    SciTech Connect

    KRINSKY, S.; PODOBEDOV, B.; GLUCKSTERN, R.L.

    2005-05-15

    We determine the impedance of a cylindrical metal tube (resistor) of radius a, length g, and conductivity {sigma}, attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency, k >> 1/a. In the equilibrium regime, , the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity {sigma}. In the transient regime, ka{sup 2} >> g, we derive analytic expressions for the impedance and wakefield.

  1. Monolithically compatible impedance measurement

    DOEpatents

    Ericson, Milton Nance; Holcomb, David Eugene

    2002-01-01

    A monolithic sensor includes a reference channel and at least one sensing channel. Each sensing channel has an oscillator and a counter driven by the oscillator. The reference channel and the at least one sensing channel being formed integrally with a substrate and intimately nested with one another on the substrate. Thus, the oscillator and the counter have matched component values and temperature coefficients. A frequency determining component of the sensing oscillator is formed integrally with the substrate and has an impedance parameter which varies with an environmental parameter to be measured by the sensor. A gating control is responsive to an output signal generated by the reference channel, for terminating counting in the at least one sensing channel at an output count, whereby the output count is indicative of the environmental parameter, and successive ones of the output counts are indicative of changes in the environmental parameter.

  2. Bioelectrical impedance analysis revisited.

    PubMed

    Mikes, D M; Cha, B A; Dym, C L; Baumgaertner, J; Hartzog, A G; Tacey, A D; Calabria, M R

    1999-12-01

    Although total limb volume measurements are used to track the progress of lymphedema and its treatment, these measurements can be confounded by changes other than fluid excess namely muscle or fat gain. Bioelectrical impedance analysis (BIA) is a technique that specifically quantifies both total body fluid and extracellular fluid in extremities. Whereas BIA has potential as a quick, inexpensive, and quantitative technique to measure directly fluid gain or loss from lymphedema, it also has certain shortcomings that must be addressed before it can be validated. this paper examines the back-ground that explains why measuring total limb volume is insufficient to quantify the extent of peripheral lymphedema and explores the advantages and drawbacks of using BIA for this purpose. PMID:10652699

  3. Facile route to covalently-jointed graphene/polyaniline composite and it's enhanced electrochemical performances for supercapacitors

    NASA Astrophysics Data System (ADS)

    Qiu, Hanxun; Han, Xuebin; Qiu, Feilong; Yang, Junhe

    2016-07-01

    A polyaniline/graphene composite with covalently-bond is synthesized by a novel approach. In this way, graphene oxide is functionalized firstly by introducing amine groups onto the surface with the reduction of graphene oxide in the process and then served as the anchor sites for the growth of polyaniline (PANI) via in-situ polymerization. The composite material is characterized by electron microscopy, the resonant Raman spectra, X-ray diffraction, transform infrared spectroscopy and X-ray photoelectron spectroscopy. The electrochemical properties of the composite are measured by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charging/discharging. With the functionalization process, the graphene/polyaniline composite electrode exhibits remarkably enhanced electrochemical performance with specific capacitance of 489 F g-1 at 0.5 A g-1, which is superior to those of its individual components. The outstanding electrochemical performance of the hybrid can be attributed to its covalently synergistic effect between graphene and polyaniline, suggesting promising potentials for supercapacitors.

  4. In vitro electrochemical corrosion and cell viability studies on nickel-free stainless steel orthopedic implants.

    PubMed

    Salahinejad, Erfan; Hadianfard, Mohammad Jafar; Macdonald, Digby Donald; Sharifi-Asl, Samin; Mozafari, Masoud; Walker, Kenneth J; Rad, Armin Tahmasbi; Madihally, Sundararajan V; Tayebi, Lobat

    2013-01-01

    The corrosion and cell viability behaviors of nanostructured, nickel-free stainless steel implants were studied and compared with AISI 316L. The electrochemical studies were conducted by potentiodynamic polarization and electrochemical impedance spectroscopic measurements in a simulated body fluid. Cytocompatibility was also evaluated by the adhesion behavior of adult human stem cells on the surface of the samples. According to the results, the electrochemical behavior is affected by a compromise among the specimen's structural characteristics, comprising composition, density, and grain size. The cell viability is interpreted by considering the results of the electrochemical impedance spectroscopic experiments. PMID:23630603

  5. In Vitro Electrochemical Corrosion and Cell Viability Studies on Nickel-Free Stainless Steel Orthopedic Implants

    PubMed Central

    Salahinejad, Erfan; Hadianfard, Mohammad Jafar; Macdonald, Digby Donald; Sharifi-Asl, Samin; Mozafari, Masoud; Walker, Kenneth J.; Rad, Armin Tahmasbi; Madihally, Sundararajan V.; Tayebi, Lobat

    2013-01-01

    The corrosion and cell viability behaviors of nanostructured, nickel-free stainless steel implants were studied and compared with AISI 316L. The electrochemical studies were conducted by potentiodynamic polarization and electrochemical impedance spectroscopic measurements in a simulated body fluid. Cytocompatibility was also evaluated by the adhesion behavior of adult human stem cells on the surface of the samples. According to the results, the electrochemical behavior is affected by a compromise among the specimen's structural characteristics, comprising composition, density, and grain size. The cell viability is interpreted by considering the results of the electrochemical impedance spectroscopic experiments. PMID:23630603

  6. Electrochemical performance of a solid oxide fuel cell with an anode based on Cu-Ni/CeO2 for methane direct oxidation

    NASA Astrophysics Data System (ADS)

    Hornés, Aitor; Escudero, María J.; Daza, Loreto; Martínez-Arias, Arturo

    2014-03-01

    A CuNi-CeO2/YSZ/LSF solid oxide fuel cell has been fabricated and tested with respect to its electrochemical activity for direct oxidation of dry methane. The electrodes have been prepared by impregnation of corresponding porous YSZ layers, using reverse microemulsions as impregnating medium for the anode (constituted by Cu-Ni at 1:1 atomic ratio in combination with CeO2). On the basis of I-V electrochemical testing complemented by impedance spectroscopy (IS) measurements it is shown the ability of the SOFC for direct oxidation of methane in a rather stable way. Differences in the behavior as a function of operating temperature (1023-1073 K) are also revealed and examined on the basis of analysis of IS spectra.

  7. Frequency response of electrochemical cells

    NASA Technical Reports Server (NTRS)

    Thomas, Daniel L.

    1989-01-01

    Impedance concepts can be applied to the analysis of battery electrodes, yielding information about the structure of the electrode and the processes occurring in the electrode. Structural parameters such as the specific area (surface area per gram of electrode) can be estimated. Electrode variables such as surface overpotential, ohmic losses, and diffusion limitations may be studied. Nickel and cadmium electrodes were studied by measuring the ac impedance as a function of frequency, and the specific areas that were determined were well within the range of specific areas determined from BET measurements. Impedance spectra were measured for the nickel and cadmium electrodes, and for a 20 A-hr NiCd battery as functions of the state of charge. More work is needed to determine the feasibility of using frequency response as a nondestructive testing technique for batteries.

  8. The in-situ characterization of a transesterification reaction using electrical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Cho, Sungjin

    ) for different samples at various reaction conditions during transesterfication were calculated. It was found that all electrical impedance data and FTIR spectras at particular region, which is carbonyl functional group of fatty acid methyl ester, depends on temperatures, methanol molar ratio to oil, concentration of catalyst and reaction time. In particular, the time constant, tau b, decreases with an increase in temperature for all samples and its dependence follows the Arrhenius relation. Therefore, in-situ monitoring of these electrochemical characterizations are very significant to the mass production of biodiesel in the future.

  9. Characterisation of CFRP adhesive bonds by electromechanical impedance

    NASA Astrophysics Data System (ADS)

    Malinowski, Pawel H.; Wandowski, Tomasz; Ostachowicz, Wieslaw M.

    2014-03-01

    In aircraft industry the Carbon Fiber Reinforced Polymer (CFRP) elements are joint using rivets and adhesive bonding. The reliability of the bonding limits the use of adhesive bonding for primary aircraft structures, therefore it is important to assess the bond quality. The performance of adhesive bonds depends on the physico-chemical properties of the adhered surfaces. The contamination leading to weak bonds may have various origin and be caused by moisture, release agent, hydraulic fluid, fuel, poor curing of adhesive and so on. In this research three different causes of possible weak bonds were selected for the investigation: 1. Weak bond due to release agent contamination, 2. Weak bond due to moisture contamination, 3. Weak bond due to poor curing of the adhesive. In order to assess the bond quality electromechanical impedance (EMI) technique was selected and investigation was focused on the influence of bond quality on electrical impedance of piezoelectric transducer. The piezoelectric transducer was mounted at the middle of each sample surface. Measurements were conducted using HIOKI Impedance Analyzer IM3570. Using the impedance analyzer the electrical parameters were measured for wide frequency band. Due to piezoelectric effect the electrical response of a piezoelectric transducer is related to mechanical response of the sample to which the transducers is attached. The impedance spectra were investigated in order to find indication of the weak bonds. These spectra were compared with measurements for reference sample using indexes proposed in order to assess the bond quality.

  10. Electrochemical cell

    DOEpatents

    Redey, L.I.; Vissers, D.R.; Prakash, J.

    1996-07-16

    An electrochemical cell is described having a bimodal positive electrode, a negative electrode of an alkali metal, and a compatible electrolyte including an alkali metal salt molten at the cell operating temperature. The positive electrode has an electrochemically active layer of at least one transition metal chloride at least partially present as a charging product, and additives of bromide and/or iodide and sulfur in the positive electrode or the electrolyte. Electrode volumetric capacity is in excess of 400 Ah/cm{sup 3}; the cell can be 90% recharged in three hours and can operate at temperatures below 160 C. There is also disclosed a method of reducing the operating temperature and improving the overall volumetric capacity of an electrochemical cell and for producing a positive electrode having a BET area greater than 6{times}10{sup 4}cm{sup 2}/g of Ni. 6 figs.

  11. Electrochemical cell

    DOEpatents

    Redey, Laszlo I.; Vissers, Donald R.; Prakash, Jai

    1994-01-01

    An electrochemical cell having a bimodal positive electrode, a negative electrode of an alkali metal, and a compatible electrolyte including an alkali metal salt molten at the cell operating temperature. The positive electrode has an electrochemically active layer of at least one transition metal chloride at least partially present as a charging product, and additives of bromide and/or iodide and sulfur in the positive electrode or the electrolyte. Electrode volumetric capacity is in excess of 400 Ah/cm.sup.3 ; the cell can be 90% recharged in three hours and can operate at temperatures below 160.degree. C. There is also disclosed a method of reducing the operating temperature and improving the overall volumetric capacity of an electrochemical cell and for producing a positive electrode having a BET area greater than 6.times.10.sup.4 cm.sup.2 /g of Ni.

  12. Electrochemical cell

    DOEpatents

    Redey, Laszlo I.; Vissers, Donald R.; Prakash, Jai

    1996-01-01

    An electrochemical cell having a bimodal positive electrode, a negative electrode of an alkali metal, and a compatible electrolyte including an alkali metal salt molten at the cell operating temperature. The positive electrode has an electrochemically active layer of at least one transition metal chloride at least partially present as a charging product, and additives of bromide and/or iodide and sulfur in the positive electrode or the electrolyte. Electrode volumetric capacity is in excess of 400 Ah/cm.sup.3 ; the cell can be 90% recharged in three hours and can operate at temperatures below 160.degree. C. There is also disclosed a method of reducing the operating temperature and improving the overall volumetric capacity of an electrochemical cell and for producing a positive electrode having a BET area greater than 6.times.10.sup.4 cm.sup.2 /g of Ni.

  13. Electrochemical cell

    DOEpatents

    Redey, L.I.; Vissers, D.R.; Prakash, J.

    1994-02-01

    An electrochemical cell is described having a bimodal positive electrode, a negative electrode of an alkali metal, and a compatible electrolyte including an alkali metal salt molten at the cell operating temperature. The positive electrode has an electrochemically active layer of at least one transition metal chloride at least partially present as a charging product, and additives of bromide and/or iodide and sulfur in the positive electrode or the electrolyte. Electrode volumetric capacity is in excess of 400 Ah/cm[sup 3]; the cell can be 90% recharged in three hours and can operate at temperatures below 160 C. There is also disclosed a method of reducing the operating temperature and improving the overall volumetric capacity of an electrochemical cell and for producing a positive electrode having a BET area greater than 6[times]10[sup 4] cm[sup 2]/g of Ni. 8 figures.

  14. Impedance in School Screening Programs.

    ERIC Educational Resources Information Center

    Robarts, John T.

    1985-01-01

    This paper examines the controversy over use of impedance screening in public schools to identify students with hearing problems, including otitis media, a common ear condition in infants and young children. It cites research that questions the value of pure tone screening as a single test and raises critics' objections to the use of impedance,…

  15. Ultra-wideband impedance sensor

    DOEpatents

    McEwan, Thomas E.

    1999-01-01

    The ultra-wideband impedance sensor (UWBZ sensor, or Z-sensor) is implemented in differential and single-ended configurations. The differential UWBZ sensor employs a sub-nanosecond impulse to determine the balance of an impedance bridge. The bridge is configured as a differential sample-and-hold circuit that has a reference impedance side and an unknown impedance side. The unknown impedance side includes a short transmission line whose impedance is a function of the near proximity of objects. The single-ended UWBZ sensor eliminates the reference side of the bridge and is formed of a sample and hold circuit having a transmission line whose impedance is a function of the near proximity of objects. The sensing range of the transmission line is bounded by the two-way travel time of the impulse, thereby eliminating spurious Doppler modes from large distant objects that would occur in a microwave CW impedance bridge. Thus, the UWBZ sensor is a range-gated proximity sensor. The Z-sensor senses the near proximity of various materials such as metal, plastic, wood, petroleum products, and living tissue. It is much like a capacitance sensor, yet it is impervious to moisture. One broad application area is the general replacement of magnetic sensors, particularly where nonferrous materials need to be sensed. Another broad application area is sensing full/empty levels in tanks, vats and silos, e.g., a full/empty switch in water or petroleum tanks.

  16. Ultra-wideband impedance sensor

    DOEpatents

    McEwan, T.E.

    1999-03-16

    The ultra-wideband impedance sensor (UWBZ sensor, or Z-sensor) is implemented in differential and single-ended configurations. The differential UWBZ sensor employs a sub-nanosecond impulse to determine the balance of an impedance bridge. The bridge is configured as a differential sample-and-hold circuit that has a reference impedance side and an unknown impedance side. The unknown impedance side includes a short transmission line whose impedance is a function of the near proximity of objects. The single-ended UWBZ sensor eliminates the reference side of the bridge and is formed of a sample and hold circuit having a transmission line whose impedance is a function of the near proximity of objects. The sensing range of the transmission line is bounded by the two-way travel time of the impulse, thereby eliminating spurious Doppler modes from large distant objects that would occur in a microwave CW impedance bridge. Thus, the UWBZ sensor is a range-gated proximity sensor. The Z-sensor senses the near proximity of various materials such as metal, plastic, wood, petroleum products, and living tissue. It is much like a capacitance sensor, yet it is impervious to moisture. One broad application area is the general replacement of magnetic sensors, particularly where nonferrous materials need to be sensed. Another broad application area is sensing full/empty levels in tanks, vats and silos, e.g., a full/empty switch in water or petroleum tanks. 2 figs.

  17. Electrochemical storage

    NASA Technical Reports Server (NTRS)

    Thaller, L. H.

    1984-01-01

    The source of the problem within the individual single cell which is related to the stochastic properties of cell populations and to the actual electrochemistry and chemistry taking place is described. The complications which arise in multicell batteries to show how different electrochemistries might alleviate or accentuate these problems is described. The concept of the electrochemical system is introduced to show how certain shortcomings of the single cell/battery string concept can be circumvented. Some of these electrochemical systems permit performance characteristics that are impossible by using conventional battery design philosophies. Projections for energy density and performance characteristics of the concepts are addressed.

  18. Electrochemical micromachining

    PubMed

    Schuster; Kirchner; Allongue; Ertl

    2000-07-01

    The application of ultrashort voltage pulses between a tool electrode and a workpiece in an electrochemical environment allows the three-dimensional machining of conducting materials with submicrometer precision. The principle is based on the finite time constant for double-layer charging, which varies linearly with the local separation between the electrodes. During nanosecond pulses, the electrochemical reactions are confined to electrode regions in close proximity. This technique was used for local etching of copper and silicon as well as for local copper deposition. PMID:10884233

  19. Electromagnetic scattering by impedance structures

    NASA Technical Reports Server (NTRS)

    Balanis, Constantine A.; Griesser, Timothy

    1987-01-01

    The scattering of electromagnetic waves from impedance structures is investigated, and current work on antenna pattern calculation is presented. A general algorithm for determining radiation patterns from antennas mounted near or on polygonal plates is presented. These plates are assumed to be of a material which satisfies the Leontovich (or surface impedance) boundary condition. Calculated patterns including reflection and diffraction terms are presented for numerious geometries, and refinements are included for antennas mounted directly on impedance surfaces. For the case of a monopole mounted on a surface impedance ground plane, computed patterns are compared with experimental measurements. This work in antenna pattern prediction forms the basis of understanding of the complex scattering mechanisms from impedance surfaces. It provides the foundation for the analysis of backscattering patterns which, in general, are more problematic than calculation of antenna patterns. Further proposed study of related topics, including surface waves, corner diffractions, and multiple diffractions, is outlined.

  20. Electrochemical methods for monitoring performance of corrosion inhibitor under multiphase flow

    SciTech Connect

    Chen, Y.; Gopal, M.

    1999-07-01

    The corrosion inhibitor is the main tool for preventing internal corrosion in carbon steel pipelines, which are used to transport multiphase mixtures from oil production. This paper presents results of an imidazoline based inhibitor using the Electrochemical Noise (ECN) and Electrochemical Impedance Spectroscopy (EIS) techniques in a multiphase flow pipeline. ECN and EIS measurements were made simultaneously in a 101.6mm I.D., 15m long acrylic pipeline using saltwater and carbon dioxide mixtures. Full pipe flow was studied for liquid velocity of 1.25 m/s and slug flow for Froude numbers 6 and 9. Experiments were carried out at a constant pressure of 136kPa and temperature of 40 C. The ECN signals and EIS spectra of blank and inhibition tests were obtained. The ECN technique is able to monitor the inhibitor film formation continuously. The current noise fluctuation is correlated to the corrosion rate for both blank test and inhibitor test. The higher current fluctuation indicates higher corrosion rates. Different EIS spectra were obtained for blank and inhibitor studies. The simple charge transfer process was seen to occur for blank tests while charge transfer and diffusion processes were taking place under inhibitor effects.

  1. In situ characterization of natural pyrite bioleaching using electrochemical noise technique

    NASA Astrophysics Data System (ADS)

    Chen, Guo-bao; Yang, Hong-ying; Li, Hai-jun

    2016-02-01

    An in situ characterization technique called electrochemical noise (ECN) was used to investigate the bioleaching of natural pyrite. ECN experiments were conducted in four active systems (sulfuric acid, ferric-ion, 9k culture medium, and bioleaching solutions). The ECN data were analyzed in both the time and frequency domains. Spectral noise impedance spectra obtained from power spectral density (PSD) plots for different systems were compared. A reaction mechanism was also proposed on the basis of the experimental data analysis. The bioleaching system exhibits the lowest noise resistance of 0.101 MΩ. The bioleaching of natural pyrite is considered to be a bio-battery reaction, which distinguishes it from chemical oxidation reactions in ferric-ion and culture-medium (9k) solutions. The corrosion of pyrite becomes more severe over time after the long-term testing of bioleaching.

  2. Impedance Eduction in Sound Fields With Peripherally Varying Liners and Flow

    NASA Technical Reports Server (NTRS)

    Watson, W. R.; Jones, M. G.

    2015-01-01

    A two-dimensional impedance eduction theory is extended to three-dimensional sound fields and peripherally varying duct liners. The approach is to first measure the acoustic pressure field at a series of flush-mounted wall microphones located around the periphery of the flow duct. The numerical solution for the acoustic pressure field at these microphones is also obtained by solving the three-dimensional convected Helmholtz equation using the finite element method. A quadratic objective function based on the difference between the measured and finite element solution is constructed and the unknown impedance function is obtained by minimizing this objective function. Impedance spectra educed for two uniform-structure liners (a wire-mesh and a conventional liner) and a hard-soft-hard peripherally varying liner (for which the soft segment is that of the conventional liner) are presented. Results are presented at three mean flow Mach numbers and fourteen sound source frequencies. The impedance spectra of the uniform-structure liners are also computed using a two-dimensional impedance eduction theory. The primary conclusions of the study are: 1) when measured data is used with the uniform-structure liners, the three-dimensional theory reproduces the same impedance spectra as the two-dimensional theory except for frequencies corresponding to very low or very high liner attenuation; and 2) good agreement between the educed impedance spectra of the uniform structure conventional liner and the soft segment of the peripherally varying liner is obtained.

  3. Electrochemical construction

    DOEpatents

    Einstein, Harry; Grimes, Patrick G.

    1983-08-23

    An electrochemical cell construction features a novel co-extruded plastic electrode in an interleaved construction with a novel integral separator-spacer. Also featured is a leak and impact resistant construction for preventing the spill of corrosive materials in the event of rupture.

  4. Electrochemical Deburring

    NASA Technical Reports Server (NTRS)

    Burley, R. K.

    1983-01-01

    Electrochemical deburring removes burrs from assembled injector tubes. Since process uses liquid anodic dissolution in liquid electrolyte to proide deburring action, smoothes surfaces and edges in otherwise inaccessible areas. Tool consists of sleeve that contains metallic ring cathode. Sleeve is placed over tube, and electrolytic solution is forced to flow between tube and sleeve. The workpiece serves an anode.

  5. Electrochemical Engineering.

    ERIC Educational Resources Information Center

    Alkire, Richard C.

    1983-01-01

    Discusses engineering ramifications of electrochemistry, focusing on current/potential distribution, evaluation of trade-offs between influences of different phenomena, use of dimensionless numbers to assist in scale-over to new operating conditions, and economics. Also provides examples of electrochemical engineering education content related to…

  6. Electrochemical capacitor

    DOEpatents

    Anderson, Marc A.; Liu, Kuo -Chuan; Mohr, Charles M.

    1999-10-05

    An inexpensive porous metal oxide material having high surface area, good conductivity and high specific capacitance is advantageously used in an electrochemical capacitor. The materials are formed in a sol-gel process which affords control over the properties of the resultant metal oxide materials.

  7. Electrochemical device

    DOEpatents

    Grimes, Patrick G.; Einstein, Harry; Bellows, Richard J.

    1988-01-12

    A tunnel protected electrochemical device features channels fluidically communicating between manifold, tunnels and cells. The channels are designed to provide the most efficient use of auxiliary power. The channels have a greater hydraulic pressure drop and electrical resistance than the manifold. This will provide a design with the optimum auxiliary energy requirements.

  8. An electric impedance based microelectromechanical system flow sensor for ionic solutions

    PubMed Central

    Ayliffe, H Edward; Rabbitt, RD

    2008-01-01

    Microfluidic devices with channel cross sections measuring 4 × 10 μm2 instrumented with gold microelectrodes were used to sense flow rates of ionic solutions on the basis of electric impedance (EI) measured perpendicular to the flow. Negative pressures were applied to access ports of the microdevices to generate flow of saline solutions (physiologic concentrations 0.9%) through the micro-EI recording zone with flow rates between 2.4 and 4.8 μl min−1. The EI spectra (100 Hz–20 MHz) recorded under flow conditions were compared with the no-flow condition. Changes in the magnitude of EI (at 350 Hz) for flow rates as low as 2.4 μl min−1 were statistically significant compared with the no-flow condition. The observed dependence of EI on flow rate is attributed to the relative difference between the rate of migration of charge-balancing electrolyte ions to the electrode surface and the rate of removal of the same ions by forced convection. An electrochemical convection–diffusion model was used to study the observed dependence on flow. Simulations support the conceptual model that passing DC current from the gold electrodes into the ionic solution results in an increase in ionic concentration near the electrode surface (due to the inward migration of counter-balancing ions). When the fluid flow rates increase, these counter-balancing ions are replaced by the bulk solution, thereby lowering the average ionic concentration within the recording zone. This local concentration drop results in an increase in the real part of the impedance. PMID:19672321

  9. I/O impedance controller

    DOEpatents

    Ruesch, Rodney; Jenkins, Philip N.; Ma, Nan

    2004-03-09

    There is disclosed apparatus and apparatus for impedance control to provide for controlling the impedance of a communication circuit using an all-digital impedance control circuit wherein one or more control bits are used to tune the output impedance. In one example embodiment, the impedance control circuit is fabricated using circuit components found in a standard macro library of a computer aided design system. According to another example embodiment, there is provided a control for an output driver on an integrated circuit ("IC") device to provide for forming a resistor divider network with the output driver and a resistor off the IC device so that the divider network produces an output voltage, comparing the output voltage of the divider network with a reference voltage, and adjusting the output impedance of the output driver to attempt to match the output voltage of the divider network and the reference voltage. Also disclosed is over-sampling the divider network voltage, storing the results of the over sampling, repeating the over-sampling and storing, averaging the results of multiple over sampling operations, controlling the impedance with a plurality of bits forming a word, and updating the value of the word by only one least significant bit at a time.

  10. Impedance-estimation methods, modeling methods, articles of manufacture, impedance-modeling devices, and estimated-impedance monitoring systems

    DOEpatents

    Richardson, John G.

    2009-11-17

    An impedance estimation method includes measuring three or more impedances of an object having a periphery using three or more probes coupled to the periphery. The three or more impedance measurements are made at a first frequency. Three or more additional impedance measurements of the object are made using the three or more probes. The three or more additional impedance measurements are made at a second frequency different from the first frequency. An impedance of the object at a point within the periphery is estimated based on the impedance measurements and the additional impedance measurements.

  11. Enhanced capacitance of composite TiO2 nanotube/boron-doped diamond electrodes studied by impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Siuzdak, K.; Bogdanowicz, R.; Sawczak, M.; Sobaszek, M.

    2014-12-01

    We report on novel composite nanostructures based on boron-doped diamond thin films grown on top of TiO2 nanotubes. The nanostructures made of BDD-modified titania nanotubes showed an increase in activity and performance when used as electrodes in electrochemical environments. The BDD thin films (~200-500 nm) were deposited using microwave plasma assisted chemical vapor deposition (MW PA CVD) onto anodically fabricated TiO2 nanotube arrays. The influence of boron-doping level, methane admixture and growth time on the performance of the Ti/TiO2/BDD electrode was studied in detail. Scanning electron microscopy (SEM) was applied to investigate the surface morphology and grain size distribution. Moreover, the chemical composition of TiO2/BDD electrodes was investigated by means of micro-Raman spectroscopy. The composite electrodes TiO2/BDD are characterized by a significantly higher capacitive current compared to BDD films deposited directly onto a Ti substrate. The novel composite electrode of TiO2 nanotube arrays overgrown by boron-doped diamond (BDD) immersed in 0.1 M NaNO3 can deliver a specific capacitance of 2.10, 4.79, and 7.46 mF cm-2 at a scan rate of 10 mV s-1 for a [B]/[C] ratio of 2k, 5k and 10k, respectively. The substantial improvement of electrochemical performance and the excellent rate capability could be attributed to the synergistic effect of TiO2 treatment in CH4 : H2 plasma and the high electrical conductivity of BDD layers. The analysis of electrochemical impedance spectra using an electric equivalent circuit allowed us to determine the surface area on the basis of the value of constant phase element.

  12. Electrical impedance imaging of water distribution in the root zone

    NASA Astrophysics Data System (ADS)

    Newill, P.; Karadaglić, D.; Podd, F.; Grieve, B. D.; York, T. A.

    2014-05-01

    The paper describes a technique that is proposed for imaging water transport in and around the root zone of plants using distributed measurements of electrical impedance. The technique has the potential to analyse sub-surface phenotypes, for instance drought tolerance traits in crop breeding programmes. The technical aim is to implement an automated, low cost, instrument for high-throughput screening. Ultimately the technique is targeted at in-field, on-line, measurements. For demonstration purposes the present work considers measurements on laboratory scale rhizotrons housing growing maize plants. Each rhizotron is fitted with 60 electrodes in a rectangular array. To reduce electrochemical effects the capacitively coupled contactless conductivity (C4D) electrodes have an insulating layer on the surface and the resistance of the bulk material is deduced from spectroscopic considerations. Electrical impedance is measured between pairs of electrodes to build up a two-dimensional map. A modified electrical model of such electrodes is proposed which includes the resistive and reactive components of both the insulating layer and the bulk material. Measurements taken on a parallel-plate test cell containing water confirm that the C4D technique is able to measure electrical impedance. The test cell has been used to explore the effects of water content, compaction and temperature on measurements in soil. Results confirm that electrical impedance measurements are very sensitive to moisture content. Impedance fraction changes up to 20% are observed due to compaction up to a pressure of 0.21 kg cm-2 and a temperature fraction sensitivity of about 2%/°C. The effects of compaction and temperature are most significant under dry conditions. Measurements on growing maize reveal the changes in impedance across the rhizotron over a period of several weeks. Results are compared to a control vessel housing only soil.

  13. Numerical Analysis of the Impedance of Fractal Electrodes

    NASA Astrophysics Data System (ADS)

    Cao, Qi-Zhong

    The constant-phase-angle (CPA) impedance observed in electrochemical cells is often thought to be due to fractal roughness on the electrode surface. This idea was pursued by numerous theoretical and experimental studies in the last decade but there is no consensus on the quantitative relationship between the roughness and the impedance. In this study, we consider the partial differential equations that govern the electrostatic potential and the concentrations of anions and cations between two blocking electrodes which have no chemical reactions. We assume that diffusion and conduction are the only transport mechanisms and the Poisson -Boltzmann equation is obeyed. These equations are linearized and solved analytically in one dimension and numerically in two dimensions. For the latter, we used electrodes shaped like Koch curves and saw-tooth curves. A special grid was generated by conformal mapping to fit these boundaries with singularities and the equations are solved by finite -difference method on this grid. The numerical results are compared to the one-dimensional solution that give the behavior of the flat electrode. We find that the only observable effect of surface roughness is that it increases the interfacial capacitance due to the increased surface area. No evidence of the CPA impedance could be seen in our numerical data. We also studied the problem with the boundary-element method. It confirms that the numerical results are rigorously correct in the high and low frequency limit. Requiring the impedance in the intermediate frequency regime to match smoothly with these limits rule out the possibility of a CPA impedance. We suggest that the CPA impedance observed in many experiments is caused either by the adsorption and desorption of ions on the surface, or by oxidation and corrosion on the surface that changed the boundary conditions in the system.

  14. Mechanical impedance and acoustic mobility measurement techniques of specifying vibration environments

    NASA Technical Reports Server (NTRS)

    Kao, G. C.

    1973-01-01

    Method has been developed for predicting interaction between components and corresponding support structures subjected to acoustic excitations. Force environments determined in spectral form are called force spectra. Force-spectra equation is determined based on one-dimensional structural impedance model.

  15. Electrochemical cell

    DOEpatents

    Redey, Laszlo I.; Vissers, Donald R.; Prakash, Jai

    1994-01-01

    An electrochemical cell having an alkali metal negative electrode such as sodium and a positive electrode including Ni or transition metals, separated by a .beta." alumina electrolyte and NaAlCl.sub.4 or other compatible material. Various concentrations of a bromine, iodine and/or sulfur containing additive and pore formers are disclosed, which enhance cell capacity and power. The pore formers may be the ammonium salts of carbonic acid or a weak organic acid or oxamide or methylcellulose.

  16. Coupling impedance for modern accelerators

    SciTech Connect

    Heifets, S.A.; Kheifets, S.A. )

    1992-03-10

    A systematic review of theoretical results for the longitudinal and transverse impedances obtained by different methods is presented. The paper comprises definitions, general theorems, modal analysis, a diffraction model, and analytical results. Several new results are included. In particular, necessary and sufficient conditions are given for the independence of the impedance from the beam longitudinal direction. The impedances of two basic simple structures---that of a {ital cavity} and that of a {ital step}---are studied in detail. The transition from the regime of a cavity to the regime of a step is explained, an approximate formula describing this transition is given, and the criterion for determining the applicability of each regime is established. The asymptotic behavior of the impedance for a finite number {ital M} of periodically arranged cavities as a function of {ital M} is studied. The different behaviors of the impedance for a single cavity and that for an infinite number of cavities are explained as resulting from the interference of the diffracted waves. A criterion for determining the transition in the impedance behavior from small {ital M} to large {ital M} is presented.

  17. Electrochemical cell

    DOEpatents

    Redey, Laszlo I.; Myles, Kevin M.; Vissers, Donald R.; Prakash, Jai

    1996-01-01

    An electrochemical cell with a positive electrode having an electrochemically active layer of at least one transition metal chloride. A negative electrode of an alkali metal and a compatible electrolyte including an alkali metal salt molten at cell operating temperature is included in the cell. The electrolyte is present at least partially as a corrugated .beta." alumina tube surrounding the negative electrode interior to the positive electrode. The ratio of the volume of liquid electrolyte to the volume of the positive electrode is in the range of from about 0.1 to about 3. A plurality of stacked electrochemical cells is disclosed each having a positive electrode, a negative electrode of an alkali metal molten at cell operating temperature, and a compatible electrolyte. The electrolyte is at least partially present as a corrugated .beta." alumina sheet separating the negative electrode and interior to the positive electrodes. The alkali metal is retained in a porous electrically conductive ceramic, and seals for sealing the junctures of the electrolyte and the adjacent electrodes at the peripheries thereof.

  18. Electrochemical cell

    DOEpatents

    Redey, L.I.; Myles, K.M.; Vissers, D.R.; Prakash, J.

    1996-07-02

    An electrochemical cell is described with a positive electrode having an electrochemically active layer of at least one transition metal chloride. A negative electrode of an alkali metal and a compatible electrolyte including an alkali metal salt molten at cell operating temperature is included in the cell. The electrolyte is present at least partially as a corrugated {beta}{double_prime} alumina tube surrounding the negative electrode interior to the positive electrode. The ratio of the volume of liquid electrolyte to the volume of the positive electrode is in the range of from about 0.1 to about 3. A plurality of stacked electrochemical cells is disclosed each having a positive electrode, a negative electrode of an alkali metal molten at cell operating temperature, and a compatible electrolyte. The electrolyte is at least partially present as a corrugated {beta}{double_prime} alumina sheet separating the negative electrode and interior to the positive electrodes. The alkali metal is retained in a porous electrically conductive ceramic, and seals for sealing the junctures of the electrolyte and the adjacent electrodes at the peripheries thereof. 8 figs.

  19. Electrochemical cell

    DOEpatents

    Nagy, Zoltan; Yonco, Robert M.; You, Hoydoo; Melendres, Carlos A.

    1992-01-01

    An electrochemical cell has a layer-type or sandwich configuration with a Teflon center section that houses working, reference and counter electrodes and defines a relatively narrow electrolyte cavity. The center section is surrounded on both sides with thin Teflon membranes. The membranes are pressed in place by a pair of Teflon inner frames which are in turn supported by a pair of outer metal frames. The pair of inner and outer frames are provided with corresponding, appropriately shaped slits that are in plane generally transverse to the plane of the working electrode and permit X-ray beams to enter and exit the cell through the Teflon membranes that cover the slits so that the interface between the working electrode and the electrolyte within the cell may be analyzed by transmission geometry. In one embodiment, the center section consists of two parts, one on top of the other. Alternatively, the center section of the electrochemical cell may consist of two intersliding pieces or may be made of a single piece of Teflon sheet material. The electrolyte cavity is shaped so that the electrochemical cell can be rotated 90.degree. in either direction while maintaining the working and counter electrodes submerged in the electrolyte.

  20. Electrochemical cell

    DOEpatents

    Nagy, Z.; Yonco, R.M.; You, H.; Melendres, C.A.

    1992-08-25

    An electrochemical cell has a layer-type or sandwich configuration with a Teflon center section that houses working, reference and counter electrodes and defines a relatively narrow electrolyte cavity. The center section is surrounded on both sides with thin Teflon membranes. The membranes are pressed in place by a pair of Teflon inner frames which are in turn supported by a pair of outer metal frames. The pair of inner and outer frames are provided with corresponding, appropriately shaped slits that are in plane generally transverse to the plane of the working electrode and permit X-ray beams to enter and exit the cell through the Teflon membranes that cover the slits so that the interface between the working electrode and the electrolyte within the cell may be analyzed by transmission geometry. In one embodiment, the center section consists of two parts, one on top of the other. Alternatively, the center section of the electrochemical cell may consist of two intersliding pieces or may be made of a single piece of Teflon sheet material. The electrolyte cavity is shaped so that the electrochemical cell can be rotated 90[degree] in either direction while maintaining the working and counter electrodes submerged in the electrolyte. 5 figs.

  1. Electrochemical cyclability mechanism for MnO 2 electrodes utilized as electrochemical supercapacitors

    NASA Astrophysics Data System (ADS)

    Wei, Weifeng; Cui, Xinwei; Chen, Weixing; Ivey, Douglas G.

    The electrochemical cyclability mechanism of nanocrystalline MnO 2 electrodes with rock salt-type and hexagonal ɛ-type structures was investigated to determine the relationship between physicochemical feature evolution and the corresponding electrochemical behaviour of MnO 2 electrodes. Rock salt MnO 2 and hexagonal ɛ-MnO 2 electrodes, with fibrous and porous morphologies, evolve into the antifluorite-type MnO 2 with a petal-shaped nanosheet structure after electrochemical cycling, similar to that observed in nanocrystalline antifluorite-type MnO 2 electrodes after electrochemical cycling. However, a different impedance response was observed for the rock salt MnO 2 and hexagonal ɛ-MnO 2 electrodes during the charge-discharge cycles, compared with the improved impedance response observed for the cycled antifluorite-type MnO 2. A dissolution-redeposition mechanism is proposed to account for the impedance response of the MnO 2 electrodes with different morphologies and crystal structures.

  2. Label-free impedance detection of cancer cells.

    PubMed

    Venkatanarayanan, Anita; Keyes, Tia E; Forster, Robert J

    2013-02-19

    Ovarian cancer cells, SKOV3, have been immobilized onto platinum microelectrodes using anti-EPCAM capture antibodies and detected with high sensitivity using electrochemical impedance. The change in impedance following cell capture is strongly dependent on the supporting electrolyte concentration. By controlling the concentration of Dulbecco's phosphate buffered saline (DPBS) electrolyte, the double layer thickness can be manipulated so that the interfacial electric field interacts with the bound cells, rather than simply decaying across the antibody capture layer. Significantly, the impedance changes markedly upon cell capture over the frequency range from 3 Hz to 90 kHz. For example, using an alternating-current (ac) amplitude of 25 mV, a frequency of 81.3 kHz, and an open circuit potential (OCP) as the direct-current (dc) voltage, a detection limit of 4 captured cells was achieved. Assuming an average cell radius of 5 μm, the linear dynamic range is from 4 captured cells to 650 ± 2 captured cells, which is approximately equivalent to fractional coverages from 0.1% to 29%. An equivalent circuit that models the impedance response of the cell capture is discussed. PMID:23331159

  3. Investigating the low-temperature impedance increase of lithium-ion cells.

    SciTech Connect

    Abraham, D. P.; Heaton, J. R.; Kang, S.-H.; Dees, D. W.; Jansen, A. N.; Chemical Engineering

    2008-01-01

    Low-temperature performance loss is a significant barrier to commercialization of lithium-ion cells in hybrid electric vehicles. Increased impedance, especially at temperatures below 0 C, reduces the cell pulse power performance required for cold engine starts, quick acceleration, or regenerative braking. Here we detail electrochemical impedance spectroscopy data on binder- and carbon-free layered-oxide and spinel-oxide electrodes, obtained over the +30 to ?30 C temperature range, in coin cells containing a lithium-preloaded Li{sub 4/3}Ti{sub 5/3}O{sub 4} composite (LTOc) counter electrode and a LiPF{sub 6}-bearing ethylene carbonate/ethyl methyl carbonate electrolyte. For all electrodes studied, the impedance increased with decreasing cell temperature; the increases observed in the midfrequency arc dwarfed the increases in ohmic resistance and diffusional impedance. Our data suggest that the movement of lithium ions across the electrochemical interface on the active material may have been increasingly hindered at lower temperatures, especially below 0 C. Low-temperature performance may be improved by modifying the electrolyte-active material interface (for example, through electrolyte composition changes). Increasing surface area of active particles (for example, through nanoparticle use) can lower the initial electrode impedance and lead to lower cell impedances at -30 C.

  4. Combined electromechanical impedance and fiber optic diagnosis of aerospace structures

    NASA Astrophysics Data System (ADS)

    Schlavin, Jon; Zagrai, Andrei; Clemens, Rebecca; Black, Richard J.; Costa, Joey; Moslehi, Behzad; Patel, Ronak; Sotoudeh, Vahid; Faridian, Fereydoun

    2014-03-01

    Electromechanical impedance is a popular diagnostic method for assessing structural conditions at high frequencies. It has been utilized, and shown utility, in aeronautic, space, naval, civil, mechanical, and other types of structures. By contrast, fiber optic sensing initially found its niche in static strain measurement and low frequency structural dynamic testing. Any low frequency limitations of the fiber optic sensing, however, are mainly governed by its hardware elements. As hardware improves, so does the bandwidth (frequency range * number of sensors) provided by the appropriate enabling fiber optic sensor interrogation system. In this contribution we demonstrate simultaneous high frequency measurements using fiber optic and electromechanical impedance structural health monitoring technologies. A laboratory specimen imitating an aircraft wing structure, incorporating surfaces with adjustable boundary conditions, was instrumented with piezoelectric and fiber optic sensors. Experiments were conducted at different structural boundary conditions associated with deterioration of structural health. High frequency dynamic responses were collected at multiple locations on a laboratory wing specimen and conclusions were drawn about correspondence between structural damage and dynamic signatures as well as correlation between electromechanical impedance and fiber optic sensors spectra. Theoretical investigation of the effect of boundary conditions on electromechanical impedance spectra is presented and connection to low frequency structural dynamics is suggested. It is envisioned that acquisition of high frequency structural dynamic responses with multiple fiber optic sensors may open new diagnostic capabilities for fiber optic sensing technologies.

  5. Au-F127 strawberry-like nanospheres as an electrochemical interface for sensitive detection of carcinoembryonic antigen in real sample.

    PubMed

    Li, Juan; Xie, Hangqing; Liu, Yuhong; Ren, Hang; Zhao, Wenbo; Huang, Xiaohua

    2015-11-01

    Nanomaterial-based signal-amplification strategies hold a great promise in realizing sensitive biological detection. A simple label-free electrochemical immunosensor for sensitive detection of carcinoembryonic antigen (CEA) was developed by immobilizing anti-CEA antibodies onto the Au-F127 strawberry-like nanospheres modified glassy carbon electrode (Au-F127/GCE). The Au-F127 strawberry-like nanospheres offered a large surface and multifunctional substrate for the effective immobilization of anti-CEA and the existence of Au could accelerate electron transfer and make the electrochemical signal amplified. The Au-F127 nanocomposites and anti-CEA were characterized by transmission electron microscopy (TEM), polycrystalline electron diffraction ring pattern, ultra-violet visible (UV-vis) spectra and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra. Electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) were employed to verify the stepwise assembly of the immunosensor and evaluated the analytical performance of the fabricated immunosensor, respectively. The immunosensor showed a wide liner response range between 0.01 and 80 ng mL(-1) with a low detection limit of 0.24 pg mL(-1) at a signal-to-noise (S/N) ratio of 3. Additionally, the proposed method was successfully applied to determine CEA in human serum samples with satisfactory results. PMID:26452840

  6. Sensitive immunodetection through impedance measurements onto gold functionalized electrodes.

    PubMed

    Ameur, S; Martelet, C; Jaffrezic-Renault, N; Chovelon, J M

    2000-01-01

    This article deals with a direct electrochemical method of detecting antigens using new methods of functionalization of gold electrodes. Based on the reacting ability of gold with sulfhydryl groups, three protocols for the fixation of antibodies have been explored. They are based on either the self-assembling properties of functional thiols bearing long alkyl chains or the possibility of a direct coupling of antibody moieties. Coverage rates as high as 97% can be reached. The analysis of the electrochemical impedance behavior of such layers can lead to a sensitive method for the direct detection of the antibody/antigen interaction. The addition of a redox couple in the tested solution, acting as an amplifier, allowed detection limits for the antigens as low as a few picograms/milliliter to be reached. PMID:11209460

  7. Determination of Electrochemical Performance and Thermo-Mechanical-Chemical Stability of SOFCs from Defect Modeling

    SciTech Connect

    Eric Wachsman; Keith L. Duncan

    2006-09-30

    room temperature. The results reveal that the flexural strength decreases significantly after heat treatment in very low oxygen partial pressure environments; however, in contrast, fracture toughness is increased by 30-40% when the oxygen partial pressure was decreased to 10{sup -20} to 10{sup -22} atm range. Fractographic studies show that microcracks developed at 800 oC upon hydrogen reduction are responsible for the decreased strength. To understand the role of microstructure on electrochemical performance, electrical impedance spectra from symmetric LSM/YSZ/LSM cells was de-convoluted to obtain the key electrochemical components of electrode performance, namely charge transfer resistance, surface diffusion of reactive species and bulk gas diffusion through the electrode pores. These properties were then related to microstructural features, such as triple-phase boundary length and tortuosity. From these experiments we found that the impedance due to oxygen adsorption obeys a power law with pore surface area, while the impedance due to charge transfer is found to obey a power-law with respect to triple phase boundary length. A model based on kinetic theory explaining the power-law relationships observed was then developed. Finally, during our EIS work on the symmetric LSM/YSZ/LSM cells a technique was developed to improve the quality of high-frequency impedance data and their subsequent de-convolution.

  8. Cervical cancer detection by electrical impedance in a Colombian setting

    NASA Astrophysics Data System (ADS)

    Miranda, David A.; Corzo, Sandra P.; González Correa, C. A.

    2013-04-01

    Electrical properties of normal and neoplastic cervical tissues in a heterogeneous group of 56 Colombian women were studied by electrical impedance spectroscopy and a model based on the Generalized Effective-Medium Theory of Induced Polarization (GEMTIP). Differences between the electrical bioimpedance spectra were correlated with cellular and tissue parameters. The analysis performed by the proposed model suggest that the number of different types of cellular layers that form the biological tissue, the intracellular and extracellular conductivity could be used to explain the differences between electrical bioimpedance spectra in normal and neoplastic tissues.

  9. Noncontact scanning electrical impedance imaging.

    PubMed

    Liu, Hongze; Hawkins, Aaron; Schultz, Stephen; Oliphant, Travis E

    2004-01-01

    We are interested in applying electrical impedance imaging to a single cell because it has potential to reveal both cell anatomy and cell function. Unfortunately, classic impedance imaging techniques are not applicable to this small scale measurement due to their low resolution. In this paper, a different method of impedance imaging is developed based on a noncontact scanning system. In this system, the imaging sample is immersed in an aqueous solution allowing for the use of various probe designs. Among those designs, we discuss a novel shield-probe design that has the advantage of better signal-to-noise ratio with higher resolution compared to other probes. Images showing the magnitude of current for each scanned point were obtained using this configuration. A low-frequency linear physical model helps to relate the current to the conductivity at each point. Line-scan data of high impedance contrast structures can be shown to be a good fit to this model. The first two-dimensional impedance image of biological tissues generated by this technique is shown with resolution on the order of 100 mum. The image reveals details not present in the optical image. PMID:17271930

  10. [Monitoring cervical dilatation by impedance].

    PubMed

    Salvat, J; Lassen, M; Sauze, C; Baud, S; Salvat, F

    1992-01-01

    Several different physics procedures have been tried to mechanize the recording of partograms. Can a measure of impedance of tissue Z using potential difference V, according to Ohm's law V = Z1, and 1 is a constant, be correlated with a measure of cervical dilatation using vaginal examination? This was our hypothesis. The tissue impedance meter was made to our design and applied according to a bipolar procedure. Our work was carried out on 28 patients. 10 patients were registered before labour started in order to test the apparatus and to record the impedance variations without labour taking place, and 18 patients were registered in labour to see whether there was any correlation. The level of impedance in the cervix without labour was 302.7 Ohms with a deviation of 8.2. Using student's t tests it was found that there was a significant correlation (p less than 0.001) in four measurements between the impedance measure and measures obtained by extrapolating the degrees of dilatation calculated from vaginal examination. This is a preliminary study in which we have defined the conditions that are necessary to confirm these first results and to further develop the method. PMID:1401774

  11. Electrochemical cell

    DOEpatents

    Kaun, T.D.

    An improved secondary electrochemical cell is disclosed having a negative electrode of lithium aluminum, a positive electrode of iron sulfide, a molten electrolyte of lithium chloride and potassium chloride, and the combination that the fully charged theoretical capacity of the negative electrode is in the range of 0.5 to 1.0 that of the positive electrode. The cell thus is negative electrode limiting during discharge cycling. Preferably, the negative electrode contains therein, in the approximate range of 1 to 10 volume % of the electrode, an additive from the materials of graphitized carbon, aluminum-iron alloy, and/or magnesium oxide.

  12. Electrochemical cell

    DOEpatents

    Redey, L.I.; Vissers, D.R.; Prakash, J.

    1994-08-23

    An electrochemical cell is described having an alkali metal negative electrode such as sodium and a positive electrode including Ni or transition metals, separated by a [beta] alumina electrolyte and NaAlCl[sub 4] or other compatible material. Various concentrations of a bromine, iodine and/or sulfur containing additive and pore formers are disclosed, which enhance cell capacity and power. The pore formers may be the ammonium salts of carbonic acid or a weak organic acid or oxamide or methylcellulose. 6 figs.

  13. Electrochemical cell

    DOEpatents

    Kaun, Thomas D.

    1984-01-01

    An improved secondary electrochemical cell is disclosed having a negative electrode of lithium aluminum, a positive electrode of iron sulfide, a molten electrolyte of lithium chloride and potassium chloride, and the combination that the fully charged theoretical capacity of the negative electrode is in the range of 0.5-1.0 that of the positive electrode. The cell thus is negative electrode limiting during discharge cycling. Preferably, the negative electrode contains therein, in the approximate range of 1-10 volume % of the electrode, an additive from the materials of graphitized carbon, aluminum-iron alloy, and/or magnesium oxide.

  14. Ultrafast electrochemical preparation of graphene/CoS nanosheet counter electrodes for efficient dye-sensitized solar cells

    SciTech Connect

    Zhu, Chongyang; Zhu, Yimei; Min, Huihua; Xu, Feng; Chen, Jing; Dong, Hui; Tong, Ling; Sun, Litao

    2015-10-05

    Utilizing inexpensive, high-efficiency counter electrodes (CEs) to replace the traditional platinum counterparts in dye-sensitized solar cells (DSSCs) is worthwhile. In this paper, we detail how we synchronously prepared composite CEs of CoS nanosheet arrays and reduced graphene oxide (rGO) layers for the first time via a low temperature, ultrafast one-step electrochemical strategy. With this approach, the whole fabrication process of the composite CEs was only a small percentage of the average time (~15 hours) using other methods. The DSSC assembled with the rGO–CoS composite CE achieved an enhanced power conversion efficiency (PCE) of 8.34%, which is dramatically higher than 6.27% of pure CoS CE-based DSSC and even exceeds 7.50% of Pt CE-based DSSC. The outstanding PCE breakthrough is undoubtedly attributed to the enhancement in electrocatalytic ability of the rGO–CoS composite CE due to the incorporation of highly conducting rGO layers and the GO layers-induced growth of CoS nanosheet arrays with higher density and larger surface area. Therefore, lower charge-transfer resistance and higher exchange current density can be achieved as corroborated by the electrochemical impedance spectra (EIS) and Tafel polarization curves (TPCs). As a result, further experiments also proved that the electrochemical strategy exhibited its universality of fabricating other graphene-enhanced chalcogenide functional composite films.

  15. Electrochemical behavior of rutin on a multi-walled carbon nanotube and ionic liquid composite film modified electrode.

    PubMed

    Liu, Xiuhui; Li, Li; Zhao, Xueping; Lu, Xiaoquan

    2010-11-01

    In this paper, the electrochemical behaviors of rutin at the MWNTs-IL-Gel/glassy carbon electrode (GCE) were investigated. Good electrocatalysis behavior towards the oxidation of rutin with enhancement of the redox peak current and decrease of the peak-to-peak separation was demonstrated. The electrochemical parameters of rutin were calculated giving values of the charge-transfer coefficient (alpha) and the electrode reaction standard rate constant (k(s)) as 0.47 and 0.2s(-1), respectively. In addition, the MWNTs-IL-Gel/GCE was characterized by different methods including electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), clay film thickness, and UV-vis spectra. The oxidation peak currents of rutin in such modified electrode increased linearly with the concentration of rutin in the range from 7.2 x 10(-8) to 6.0 x 10(-6) mol L(-1) with a detection limit of 2.0 x 10(-8) mol L(-1). These results suggest that the proposed electrode can be used for sensitive, simple and rapid determination of rutin. PMID:20708387

  16. Ultrafast electrochemical preparation of graphene/CoS nanosheet counter electrodes for efficient dye-sensitized solar cells

    DOE PAGESBeta

    Zhu, Chongyang; Zhu, Yimei; Min, Huihua; Xu, Feng; Chen, Jing; Dong, Hui; Tong, Ling; Sun, Litao

    2015-10-05

    Utilizing inexpensive, high-efficiency counter electrodes (CEs) to replace the traditional platinum counterparts in dye-sensitized solar cells (DSSCs) is worthwhile. In this paper, we detail how we synchronously prepared composite CEs of CoS nanosheet arrays and reduced graphene oxide (rGO) layers for the first time via a low temperature, ultrafast one-step electrochemical strategy. With this approach, the whole fabrication process of the composite CEs was only a small percentage of the average time (~15 hours) using other methods. The DSSC assembled with the rGO–CoS composite CE achieved an enhanced power conversion efficiency (PCE) of 8.34%, which is dramatically higher than 6.27%more » of pure CoS CE-based DSSC and even exceeds 7.50% of Pt CE-based DSSC. The outstanding PCE breakthrough is undoubtedly attributed to the enhancement in electrocatalytic ability of the rGO–CoS composite CE due to the incorporation of highly conducting rGO layers and the GO layers-induced growth of CoS nanosheet arrays with higher density and larger surface area. Therefore, lower charge-transfer resistance and higher exchange current density can be achieved as corroborated by the electrochemical impedance spectra (EIS) and Tafel polarization curves (TPCs). As a result, further experiments also proved that the electrochemical strategy exhibited its universality of fabricating other graphene-enhanced chalcogenide functional composite films.« less

  17. Electrochemical corrosion and modeling studies of types 7075 and 2219 aluminum alloys in a nitric acid + ferric sulfate deoxidizer solution

    NASA Astrophysics Data System (ADS)

    Savas, Terence P.

    The corrosion behavior of types 7075-T73 and 2219-T852 high strength aluminum alloys have been investigated in a HNO3 + Fe2(SO 4)3 solution. The materials are characterized in the time domain using the electrochemical noise resistance parameter (Rn) and in the frequency-domain using the spectral noise impedance parameter ( Rsn). The Rsn parameter is derived from an equivalent electrical circuit model that represents the corrosion test cell schematic used in the present study. These calculated parameters are correlated to each other, and to corresponding scanning electron microscopy (SEM) examinations of the corroded surfaces. In addition, energy dispersive spectroscopy (EDS) spectra are used in conjunction with SEM exams for particle mapping and identification. These constituent particles are characterized with respect to their size and composition and their effect on the localized corrosion mechanisms taking place. Pitting mechanisms are identified as 'circumferential' where the particles appeared noble with respect to the aluminum matrix and by 'selective dissolution' where they are anodic to the aluminum matrix. The electrochemical data are found to be in good agreement with the surface examinations. Specifically, the electrochemical parameters Rn and Rsn were consistent in predicting the corrosion resistance of 7075-T73 to be lower than for the 2219-T852 alloy. Other characteristic features used in understanding the corrosion mechanisms include the open circuit potential (OCP) and coupling-current time records.

  18. Enhanced electrochemical performance of mesoporous NiCo2O4 as an excellent supercapacitive alternative energy storage material

    NASA Astrophysics Data System (ADS)

    Bhojane, Prateek; Sen, Somaditya; Shirage, Parasharam M.

    2016-07-01

    Here we report the supercapacitive properties of mesoporous nickel cobalt oxide (NiCo2O4) synthesized by fast, inexpensive and facile chemical bath method, by avoiding high pressure, high temperature and chemical complexity. Physico-chemical characterization techniques such as X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Raman Spectra, and nitrogen adsorption-desorption isotherm analysis is performed to characterize the electrode material. Brunauer-Emmett-Teller (BET) measurements reveal the surface area 52.86 m2 g-1 and from Barrett-Joyner-Halenda (BJH), typical pores size ranges between 10 and 50 nm, also confirms the mesoporosity. The electrochemical properties are measured by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charging/discharging. The synthesized material exhibits remarkably enhanced electrochemical performance with specific capacitance of 1130 F g-1 at 1 mV s-1 sweep rate and 1125 F g-1 at current density of 0.05 A g-1, highest without supporting base like carbon cloth, Ni-foam, Ti- foil used for direct growth (deposition) of electrode material. It is superior to those of its individual and hybrid components prepared by similar technique. Ragone plot shows high specific energy density (49.25 Wh kg-1) and corresponding specific power density (1851.31 W kg-1) even at high current density of 0.5 A g-1.

  19. Influence of implantation on the electrochemical properties of smooth and porous TiN coatings for stimulation electrodes

    NASA Astrophysics Data System (ADS)

    Meijs, S.; Sørensen, C.; Sørensen, S.; Rechendorff, K.; Fjorback, M.; Rijkhoff, N. J. M.

    2016-04-01

    Objective. To determine whether changes in electrochemical properties of porous titanium nitride (TiN) electrodes as a function of time after implantation are different from those of smooth TiN electrodes. Approach. Eight smooth and 8 porous TiN coated electrodes were implanted in 8 rats. Before implantation, voltage transients, cyclic voltammograms and impedance spectra were recorded in phosphate buffered saline (PBS). After implantation, these measurements were done weekly to investigate how smooth and porous electrodes were affected by implantation. Main results. The electrode capacitance of the porous TiN electrodes decreased more than the capacitance of the smooth electrodes due to acute implantation under fast measurement conditions (such as stimulation pulses). This indicates that protein adhesion presents a greater diffusion limitation for counter-ions for the porous than for the smooth electrodes. The changes in electrochemical properties during the implanted period were similar for smooth and porous TiN electrodes, indicating that cell adhesion poses a similar diffusion limitation for smooth and porous electrodes. Significance. This knowledge can be used to optimize the porous structure of the TiN film, so that the effect of protein adhesion on the electrochemical properties is diminished. Alternatively, an additional coating could be applied on the porous TiN that would prevent or minimize protein adhesion.

  20. Impedances of Laminated Vacuum Chambers

    SciTech Connect

    Burov, A.; Lebedev, V.; /Fermilab

    2011-06-22

    First publications on impedance of laminated vacuum chambers are related to early 70s: those are of S. C. Snowdon [1] and of A. G. Ruggiero [2]; fifteen years later, a revision paper of R. Gluckstern appeared [3]. All the publications were presented as Fermilab preprints, and there is no surprise in that: the Fermilab Booster has its laminated magnets open to the beam. Being in a reasonable mutual agreement, these publications were all devoted to the longitudinal impedance of round vacuum chambers. The transverse impedance and the flat geometry case were addressed in more recent paper of K. Y. Ng [4]. The latest calculations of A. Macridin et al. [5] revealed some disagreement with Ref. [4]; this fact stimulated us to get our own results on that matter. Longitudinal and transverse impendances are derived for round and flat laminated vacuum chambers. Results of this paper agree with Ref. [5].

  1. An electrochemistry-based impedance model for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Li, Shengbo Eben; Wang, Baojin; Peng, Huei; Hu, Xiaosong

    2014-07-01

    Accurate models of lithium-ion batteries are important for analyzing and predicting battery dynamics and aging. This paper presents an electrochemistry-based impedance model for lithium-ion batteries to better understand the relationship between battery internal dynamics and external measurement. The proposed impedance model is a modified single particle model which balances between simplicity and accuracy. The model includes electrochemical impedance due to charge-transfer reaction, diffusion dynamics in the electrodes, effects of ion concentration, capacitance dispersion in the double layer, and anode insulating film growth, etc. The impedance tests for model validation were performed on two lithium-ion cells at ambient temperature and at different SOC levels. A particle swarm optimization method is employed to identify model parameters. The model accuracy under different conditions is compared with that of conventional Randles model and the parameter variations at different stage of the aging process are studied.

  2. Electrochemical attosyringe

    PubMed Central

    Laforge, François O.; Carpino, James; Rotenberg, Susan A.; Mirkin, Michael V.

    2007-01-01

    The ability to manipulate ultrasmall volumes of liquids is essential in such diverse fields as cell biology, microfluidics, capillary chromatography, and nanolithography. In cell biology, it is often necessary to inject material of high molecular weight (e.g., DNA, proteins) into living cells because their membranes are impermeable to such molecules. All techniques currently used for microinjection are plagued by two common problems: the relatively large injector size and volume of injected fluid, and poor control of the amount of injected material. Here we demonstrate the possibility of electrochemical control of the fluid motion that allows one to sample and dispense attoliter-to-picoliter (10−18 to 10−12 liter) volumes of either aqueous or nonaqueous solutions. By changing the voltage applied across the liquid/liquid interface, one can produce a sufficient force to draw solution inside a nanopipette and then inject it into an immobilized biological cell. A high success rate was achieved in injections of fluorescent dyes into cultured human breast cells. The injection of femtoliter-range volumes can be monitored by video microscopy, and current/resistance-based approaches can be used to control injections from very small pipettes. Other potential applications of the electrochemical syringe include fluid dispensing in nanolithography and pumping in microfluidic systems. PMID:17620612

  3. Rapid Impedance Spectrum Measurements for Onboard State-of-Health Applications

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; Chinh D. Ho

    2012-06-01

    Rapid impedance measurements can provide a useful online tool for improved state-of-health estimation. A validation study has been initiated at the Idaho National Laboratory for a rapid impedance technique known as Harmonic Compensated Synchronous Detection. This technique enables capturing the impedance spectra over a broad frequency range within about ten seconds. Commercially available lithium-ion cells are being calendar-life aged at 50°C with reference performance tests at 30°C every 32.5 days to gauge degradation The cells have completed the first set of reference performance tests and preliminary results are presented. The spectra change as a function of temperature and depth-of-discharge condition, as expected. The data indicate that the rapid impedance measurement technique is a benign measurement tool that can be successfully used to gauge changes in the corresponding pulse resistance.

  4. An instrument for simultaneous EQCM impedance and SECM measurements.

    PubMed

    Gollas, B; Bartlett, P N; Denuault, G

    2000-01-15

    A novel combination of an electrochemical quartz crystal microbalance (EQCM) and a scanning electrochemical microscope (SECM) has been built. Unlike conventional EQCMs, the instrument described here allows rapid in situ measurement of the modulus of the quartz crystal's transfer function. Data analysis in the complex plane for the Butterworth-Van Dyke (BVD) equivalent circuit yields the real and the imaginary components R (damping resistance) and XL (reactive inductance) of the crystal's electroacoustic impedance around its resonant frequency of 10 MHz. The influence of different tip shapes of an approaching microelectrode on the electroacoustic impedance of the quartz crystal was studied and found to be minimal for certain geometries. The capability of the EQCM/SECM instrument was tested in cyclic voltammetric plating/stripping experiments using a copper(I) chloride solution of high concentration in 1 M HCl. Four parameters, XL, R, the substrate, and the tip current, can be recorded simultaneously. Depletion layer effects were observed and could be corrected for to yield accurate current efficiencies for potentiodynamic and potentiostatic copper plating. The amperometric response of the SECM tip positioned closely to the substrate reflects the concentration changes of electroactive ions in the diffusion layer of the substrate electrode. PMID:10658330

  5. Characteristic impedance of microstrip lines

    NASA Technical Reports Server (NTRS)

    Bailey, M. C.; Deshpande, M. D.

    1989-01-01

    The dyadic Green's function for a current embedded in a grounded dielectric slab is used to analyze microstrip lines at millimeter wave frequencies. The dyadic Green's function accounts accurately for fringing fields and dielectric cover over the microstrip line. Using Rumsey's reaction concept, an expression for the characteristic impedance is obtained. The numerical results are compared with other reported results.

  6. The Aberdeen Impedance Imaging System.

    PubMed

    Kulkarni, V; Hutchison, J M; Mallard, J R

    1989-01-01

    The Aberdeen Impedance Imaging System is designed to reconstruct 2 dimensional images of the average distribution of the amplitude and phase of the complex impedance within a 3 dimensional region. The system uses the four electrode technique in a 16 electrode split-array. The system hardware consists of task-orientated electronic modules for: driving a constant current, multiplexing the current drive, demultiplexing peripheral voltages, differential amplification, phase sensitive detection and low-pass filtration, digitisation with a 14 bit analog to digital converter (ADC), and -control logic for the ADC and multiplexors. A BBC microprocessor (Master series), initiates a controlled sequence for the collection of a number of data sets which are averaged and stored on disk. Image reconstruction is by a process of convolution-backprojection similar to the fan-beam reconstruction of computerised tomography and is also known as Equipotential Backprojection. In imaging impedance changes associated with fracture healing the changes may be large enough to allow retrieval of both the amplitude and phase of the complex impedance. Sequential imaging of these changes would necessitate monitoring electronic and electrode drift by imaging an equivalent region of the contralateral limb. Differential images could be retrieved when the image of the normal limb is the image template. Better characterisation of tissues would necessitate a cleaner retrieval of the quadrature signal. PMID:2742979

  7. Experimental impedance investigation of an ultracapacitor at different conditions for electric vehicle applications

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Hu, Xiaosong; Wang, Zhenpo; Sun, Fengchun; Dorrell, David G.

    2015-08-01

    Ultracapacitors (UCs) are being increasingly deployed as a short-term energy storage device in various energy systems including uninterruptable power supplies, electrified vehicles, renewable energy systems, and wireless communication. They exhibit excellent power density and energy efficiency. The dynamic behavior of a UC, however, strongly depends on its impedance characteristics. In this paper, the impedance characteristics of a commercial UC are experimentally investigated through the well-adopted Electrochemical Impedance Spectroscopy (EIS) technique. The implications of the UC operating conditions (i.e., temperature and state of charge (SOC)) to the impedance are systematically examined. The results show that the impedance is highly sensitive to the temperature and SOC; and the temperature effect is more significant. In particular, the coupling effect between the temperature and SOC is illustrated, as well as the high-efficiency SOC window, which is highlighted. To further verify the reliability of the EIS-based investigation and to probe the sensitivity of UC parameters to the operating conditions, a dynamic model is characterized by fitting the collected impedance data. The interdependence of UC parameters (i.e., capacitance and resistance elements) on the temperature and SOC is quantitatively revealed. The impedance-based model is demonstrated to be accurate in two driving-cycle tests.

  8. Electrochemical supercapacitors

    DOEpatents

    Rudge, Andrew J.; Ferraris, John P.; Gottesfeld, Shimshon

    1996-01-01

    A new class of electrochemical capacitors provides in its charged state a positive electrode including an active material of a p-doped material and a negative electrode including an active material of an n-doped conducting polymer, where the p-doped and n-doped materials are separated by an electrolyte. In a preferred embodiment, the positive and negative electrode active materials are selected from conducting polymers consisting of polythiophene, polymers having an aryl group attached in the 3-position, polymers having aryl and alkyl groups independently attached in the 3- and 4-positions, and polymers synthesized from bridged dimers having polythiophene as the backbone. A preferred electrolyte is a tetraalykyl ammonium salt, such as tetramethylammonium trifluoromethane sulphonate (TMATFMS), that provides small ions that are mobile through the active material, is soluble in acetonitrile, and can be used in a variety of capacitor configurations.

  9. Calibration of electrical impedance tomography

    SciTech Connect

    Daily, W; Ramirez, A

    2000-05-01

    Over the past 10 years we have developed methods for imaging the electrical resistivity of soil and rock formations. These technologies have been called electrical resistance tomography of ERT (e.g. Daily and Owen, 1991). Recently we have been striving to extend this capability to include images of electric impedance--with a new nomenclature of electrical impedance tomography or EIT (Ramirez et al., 1999). Electrical impedance is simply a generalization of resistance. Whereas resistance is the zero frequency ratio of voltage and current, impedance includes both the magnitude and phase relationship between voltage and current at frequency. This phase and its frequency behavior is closely related to what in geophysics is called induced polarization or (Sumner, 1976). Why is this phase or IP important? IP is known to be related to many physical phenomena of importance so that image of IP will be maps of such things as mineralization and cation exchange IP (Marshall and Madden, 1959). Also, it is likely that IP, used in conjunction with resistivity, will yield information about the subsurface that can not be obtained by either piece of information separately. In order to define the accuracy of our technologies to image impedance we have constructed a physical model of known impedance that can be used as a calibration standard. It consists of 616 resistors, along with some capacitors to provide the reactive response, arranged in a three dimensional structure as in figure 1. Figure 2 shows the construction of the network and defines the coordinate system used to describe it. This network of components is a bounded and discrete version of the unbounded and continuous medium with which we normally work (the subsurface). The network has several desirable qualities: (1) The impedance values are known (to the accuracy of the component values). (2) The component values and their 3D distribution is easily controlled. (3) Error associated with electrode noise is eliminated. (4

  10. Direct and environmentally benign synthesis of manganese oxide/graphene composites from graphite for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Lee, Hae-Min; Jeong, Gyoung Hwa; Kang, Doo Won; Kim, Sang-Wook; Kim, Chang-Koo

    2015-05-01

    We develop a direct and environmentally benign method to prepare manganese oxide (Mn3O4)/graphene composites via one-step hydrothermal synthesis from graphite without using strong acids and toxic reducing agents. Structural and morphological analyses reveals that the irregularly shaped Mn3O4 nanoparticles are well-dispersed on the graphene flakes. Cyclic voltammetry and galvanostatic charge-discharge tests indicate that the charge-storing mechanism of the Mn3O4/graphene composites is pseudocapacitive. The Mn3O4/graphene composite exhibits a specific capacitance of 367 F/g at a current density of 5 A/g. After 3000 charge-discharge cycles, the Mn3O4/graphene electrode retains 91.8% of its initial specific capacitance. From electrochemical impedance spectra, it is evident that the changes in both the equivalent series resistance and charge-transfer resistance of the Mn3O4/graphene electrode before and after 3000 charge-discharge cycles are small, indicating good cycling and electrochemical stability of the Mn3O4/graphene electrode.

  11. Evaluation of Wall Boundary Conditions for Impedance Eduction Using a Dual-Source Method

    NASA Technical Reports Server (NTRS)

    Watson, W. R.; Jones, M. G.

    2012-01-01

    The accuracy of the Ingard-Myers boundary condition and a recently proposed modified Ingard-Myers boundary condition is evaluated for use in impedance eduction under the assumption of uniform mean flow. The evaluation is performed at three centerline Mach numbers, using data acquired in a grazing flow impedance tube, using both upstream and downstream propagating sound sources, and on a database of test liners for which the expected behavior of the impedance spectra is known. The test liners are a hard-wall insert consisting of 12.6 mm thick aluminum, a linear liner without a facesheet consisting of a number of small diameter but long cylindrical channels embedded in a ceramic material, and two conventional nonlinear liners consisting of a perforated facesheet bonded to a honeycomb core. The study is restricted to a frequency range for which only plane waves are cut on in the hard-wall sections of the flow impedance tube. The metrics used to evaluate each boundary condition are 1) how well it educes the same impedance for upstream and downstream propagating sources, and 2) how well it predicts the expected behavior of the impedance spectra over the Mach number range. The primary conclusions of the study are that the same impedance is educed for upstream and downstream propagating sources except at the highest Mach number, that an effective impedance based on both the upstream and downstream measurements is more accurate than an impedance based on the upstream or downstream data alone, and that the Ingard-Myers boundary condition with an effective impedance produces results similar to that achieved with the modified Ingard-Myers boundary condition.

  12. Impedance analysis of different cell monolayers grown on gold-film electrodes.

    PubMed

    Reiss, Bjoern; Wegener, Joachim

    2015-08-01

    Impedance analysis of mammalian cells grown on planar film electrodes provides a label-free, non-invasive and unbiased observation of cell-based assays addressing the biological response to drugs, toxins or stressors in general. Whereas the time course of the measured impedance at one particular frequency has been used a lot for quantitative monitoring, in-depth analysis of the frequency-dependent impedance spectra is rarely performed. This study summarizes and validates the existing model for spectral analysis by applying it to eight different cell types from different mammalian tissues. Model parameters correctly predict the functional and/or structural properties of the individual cells under study. PMID:26737923

  13. Processing, microstructural evolution and electrochemical performance relationships in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Sarikaya, Ayhan

    The relationships between the processing parameters, microstructures and electrochemical performance of solid oxide fuel cell (SOFC) components were investigated. The operating regimes (i.e., reducing vs. oxidizing) as well as the elevated temperatures (e.g. 800°C) for their operation introduce several material challenges. Therefore, composite materials are employed to withstand operating conditions while providing sufficient electrochemical performance for fuel cell operation. Analyses on lanthanum-strontium manganite (LSM) - yttria stabilized zirconia (YSZ) compositions (45 vol%-55 vol%) by impedance spectroscopy demonstrated that two competing polarization mechanisms (i.e. charge-exchange and surface adsorption-diffusion of oxygen) limit performance. Optimization of microstructures resulted in total resistances as low as 0.040 Ohm cm2. Studies on Ag composites revealed that incorporation of up to 25 vol% oxide particles (LSM and YSZ) with sizes comparable to the Ag grains (~0.5 microm) can minimize the densification and coarsening of the Ag matrix. While the powder based oxide additions increased the stability limit of porous Ag composites from <550°C to 800°C, the use of nanostructured coatings increased the stability limit to 900°C for cathodes and current collectors. Investigations of Ni-YSZ anode microstructures demonstrated that uniform distribution of percolating isometric pores (>5 microm) allows forming desired continuous percolation of all phases (Ni, YSZ and pores) lowering activation polarization below 0.100 Ohm cm2 and maintaining significant electrical conductivity (>1000 S/cm). Identification of polarization mechanisms by deconvolution of impedance spectra and tailoring the corresponding microstructures was demonstrated as an effective method for optimization of SOFC components.

  14. A comprehensive impedance journey to continuous microbial fuel cells.

    PubMed

    Sevda, Surajbhan; Chayambuka, Kudakwashe; Sreekrishnan, T R; Pant, Deepak; Dominguez-Benetton, Xochitl

    2015-12-01

    The aim of the present work was to characterize the impedance response of an air-cathode MFC operating in a continuous mode and to determine intrinsic properties that define its performance which are crucial to be controlled for scalability purposes. The limiting step on electricity generation is the anodic electrochemically-active biofilm, independently of the external resistance, Rext, utilized. However, for Rext below 3 kΩ the internal impedance of the bioanode remained invariable, in good correspondence to the power density profile. The hydraulic retention time (HRT) had an effect on the impedance of both the bioanode and the air-cathode and especially on the overall MFC. The lowest HRT at which the MFC was operable was 3h. Yet, the variation on the HRT did not have a significant impact on power generation. A two constant phase element-model was associated with the EIS response of both bioanode and air-cathode, respectively. Consistency was found between the CPE behaviour and the normal power-law distribution of local resistivity with a uniform dielectric constant, which represented consistent values with the electrical double layer, the Nernst diffusion layer and presumably the biofilm thickness. These results have future implications on MFC monitoring and control, as well as in providing critical parameters for scale-up. PMID:25921205

  15. Impedance spectroscopy study of anodic growth of zirconium oxide film in NaOH medium

    NASA Astrophysics Data System (ADS)

    Pauporté, T.; Finne, J.; Lincot, D.

    2005-06-01

    The growth of anodic oxide films on zirconium metal has been followed up to 300 V by electrochemical impedance spectroscopy and scanning electron microscopy. The maximum layer thickness is 720 nm, the dielectric constant of the film is measured at 19.5 and the growth constant is 2.4 nm V-1. Above 50 V, the presence of two impedance relaxations between 1 Hz and 200 kHz reveals a bilayered structure. This may be a consequence of a lower resistivity of the outer layer induced by some electrolytic solution infiltration into film defects.

  16. Determination of Complex Microcalorimeter Parameters with Impedance Measurements

    NASA Technical Reports Server (NTRS)

    Saab, T.; Bandler, S. R.; Chervenak, J.; Figueroa-Feliciano, E.; Finkbeiner, F.; Iyomoto, N.; Kelley, R.; Kilbourne, C. A.; Lindeman, M. A.; Porter, F. S.; Sadleir, J.

    2005-01-01

    The proper understanding and modeling of a microcalorimeter s response requires the accurate knowledge of a handful of parameters, such as C, G, alpha, . . . . While a few of these, such 8s the normal state resistance and the total thermal conductance to the heat bath (G) are directly determined from the DC IV characteristics, some others, notoriously the heat capacity (C) and alpha, appear in degenerate combinations in most measurable quantities. The case of a complex microcalorimeter, i.e. one in which the absorber s heat capacity is connected by a finite thermal impedance to the sensor, and subsequently by another thermal impedance to the heat bath, results in an added ambiguity in the determination of the individual C's and G's. In general, the dependence of the microcalorimeter s complex impedance on these parameters varies with frequency. This variation allows us to determine the individual parameters by fitting the prediction of the microcalorimeter model to the impedance data. We describe in this paper our efforts at characterizing the Goddard X-ray microcalorimeters. Using the parameters determined with this method we them compare the pulse shape and noise spectra predicted by the microcalorimeter model to data taken with the same devices.

  17. Study the effects of moisture content on the electrical properties of technical textiles by impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Lusis, A.; Pentjuss, E.; Bajars, G.; Gabrusenoks, J.; Janeliukštis, R.; Zandersons, J.

    2012-08-01

    Application of metal coatings for the functionalization of technical fibres and fabrics faced with influence of moisture on functional properties, e.g., the impedance of the metal coated K-glass fabrics have strong dependence of content absorbed water or moisture. The paper devoted to develop methodology for characterisation functional materials based on fabrics and model for interpretation of the electrical impedance spectra to obtained functional characteristics of technical textile fabrics. Model based on analyses of 3D plot of imaginary part of complex modulus spectra versus sample mass. Methodology helps to control content of adsorbed water in fabric and influence of moisture on the functional characteristics.

  18. Electrochemical Sensors and Biosensors Based on Nanomaterials and Nanostructures

    SciTech Connect

    Zhu, Chengzhou; Yang, Guohai; Li, He; Du, Dan; Lin, Yuehe

    2014-10-29

    We report that considerable attention has been devoted to the integration of recognition elements with electronic elements to develop electrochemical sensors and biosensors.Various electrochemical devices, such as amperometric sensors, electrochemical impedance sensors, and electrochemical luminescence sensors as well as photoelectrochemical sensors, provide wide applications in the detection of chemical and biological targets in terms of electrochemical change of electrode interfaces. Here, this review focuses on recent advances in electrochemical sensors and biosensors based on nanomaterials and nanostructures during 2013 to 2014. The aim of this effort is to provide the reader with a clear and concise view of new advances in areas ranging from electrode engineering, strategies for electrochemical signal amplification, and novel electroanalytical techniques used in the miniaturization and integration of the sensors. Moreover, the authors have attempted to highlight areas of the latest and significant development of enhanced electrochemical nanosensors and nanobiosensors that inspire broader interests across various disciplines. Electrochemical sensors for small molecules, enzyme-based biosensors, genosensors, immunosensors, and cytosensors are reviewed herein (Figure 1). Such novel advances are important for the development of electrochemical sensors that open up new avenues and methods for future research. In conclusion, we recommend readers interested in the general principles of electrochemical sensors and electrochemical methods to refer to other excellent literature for a broad scope in this area.(3, 4) However, due to the explosion of publications in this active field, we do not claim that this Review includes all of the published works in the past two years and we apologize to the authors of excellent work, which is unintentionally left out.

  19. Electrochemical Sensors and Biosensors Based on Nanomaterials and Nanostructures

    DOE PAGESBeta

    Zhu, Chengzhou; Yang, Guohai; Li, He; Du, Dan; Lin, Yuehe

    2014-10-29

    We report that considerable attention has been devoted to the integration of recognition elements with electronic elements to develop electrochemical sensors and biosensors.Various electrochemical devices, such as amperometric sensors, electrochemical impedance sensors, and electrochemical luminescence sensors as well as photoelectrochemical sensors, provide wide applications in the detection of chemical and biological targets in terms of electrochemical change of electrode interfaces. Here, this review focuses on recent advances in electrochemical sensors and biosensors based on nanomaterials and nanostructures during 2013 to 2014. The aim of this effort is to provide the reader with a clear and concise view of new advancesmore » in areas ranging from electrode engineering, strategies for electrochemical signal amplification, and novel electroanalytical techniques used in the miniaturization and integration of the sensors. Moreover, the authors have attempted to highlight areas of the latest and significant development of enhanced electrochemical nanosensors and nanobiosensors that inspire broader interests across various disciplines. Electrochemical sensors for small molecules, enzyme-based biosensors, genosensors, immunosensors, and cytosensors are reviewed herein (Figure 1). Such novel advances are important for the development of electrochemical sensors that open up new avenues and methods for future research. In conclusion, we recommend readers interested in the general principles of electrochemical sensors and electrochemical methods to refer to other excellent literature for a broad scope in this area.(3, 4) However, due to the explosion of publications in this active field, we do not claim that this Review includes all of the published works in the past two years and we apologize to the authors of excellent work, which is unintentionally left out.« less

  20. The quantum Hall impedance standard

    NASA Astrophysics Data System (ADS)

    Schurr, J.; Kučera, J.; Pierz, K.; Kibble, B. P.

    2011-02-01

    Alternating current measurements of double-shielded quantum Hall devices have revealed a fascinating property of which only a quantum effect is capable: it can detect its own frequency dependence and convert it to a current dependence which can be used to eliminate both of them. According to an experimentally verified model, the residual frequency dependence is smaller than the measuring uncertainty of 1.3 × 10-9 kHz-1. In this way, a highly precise quantum standard of impedance can be established, without having to correct for any calculated frequency dependence and without the need for any artefact with a calculated frequency dependence. Nothing else like that is known to us and we hope that our results encourage other national metrology institutes to also apply it to impedance metrology and further explore its beautiful properties.

  1. FXR accelerator cavity impedance experiments

    SciTech Connect

    Avalle, C.A.

    1998-01-05

    One of the goals of the present Flash X-Ray (FXR) accelerator upgrade effort [1][2] at Lawrence Livermore National Laboratory (LLNL) is to reduce the cavity transverse impedance, since it has been shown that beam stability is significantly affected by this parameter [3]. Recently, we have evaluated various techniques and cell modifications to accomplish that, both through lab measurements and computer models. A spare cell, identical in every way to cells in the accelerator, was specially modified for the experiments. The impedance measurements were done without the beam, by applying twin-wire techniques. This report describes the results of these experiments and suggests possible cell modifications to improve their performance. The techniques and modifications which are suggested might also be applicable to AHF and DARHT-2 long-pulse accelerator development.

  2. Impedance based automatic electrode positioning.

    PubMed

    Miklody, Daniel; Hohne, Johannes

    2015-08-01

    The position of electrodes in electrical imaging and stimulation of the human brain is an important variable with vast influences on the precision in modeling approaches. Nevertheless, the exact position is obscured by many factors. 3-D Digitization devices can measure the distribution over the scalp surface but remain uncomfortable in application and often imprecise. We demonstrate a new approach that uses solely the impedance information between the electrodes to determine the geometric position. The algorithm involves multidimensional scaling to create a 3 dimensional space based on these impedances. The success is demonstrated in a simulation study. An average electrode position error of 1.67cm over all 6 subjects could be achieved. PMID:26736345

  3. 21 CFR 870.2770 - Impedance plethysmograph.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral...

  4. 21 CFR 870.2750 - Impedance phlebograph.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of...

  5. 21 CFR 870.2770 - Impedance plethysmograph.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral...

  6. 21 CFR 870.2750 - Impedance phlebograph.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of...

  7. 21 CFR 870.2750 - Impedance phlebograph.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of...

  8. 21 CFR 870.2750 - Impedance phlebograph.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of...

  9. 21 CFR 870.2750 - Impedance phlebograph.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of...

  10. 21 CFR 870.2770 - Impedance plethysmograph.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral...

  11. 21 CFR 870.2770 - Impedance plethysmograph.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral...

  12. 21 CFR 870.2770 - Impedance plethysmograph.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral...

  13. Impedance analysis of acupuncture points and pathways

    NASA Astrophysics Data System (ADS)

    Teplan, Michal; Kukučka, Marek; Ondrejkovičová, Alena

    2011-12-01

    Investigation of impedance characteristics of acupuncture points from acoustic to radio frequency range is addressed. Discernment and localization of acupuncture points in initial single subject study was unsuccessfully attempted by impedance map technique. Vector impedance analyses determined possible resonant zones in MHz region.

  14. Cathodic and anodic pre-treated boron doped diamond with different sp2 content: Morphological, structural, and impedance spectroscopy characterizations

    NASA Astrophysics Data System (ADS)

    Baldan, M. R.; Azevedo, A. F.; Couto, A. B.; Ferreira, N. G.

    2013-12-01

    In this work, the influence of cathodic (Red) and anodic (Ox) pre-treatment on boron doped diamond (BDD) films grown with different sp2/sp3 ratios was systematically studied. The sp2/sp3 ratios were controlled by the addition of CH4 of 1,3,5 and 7 sccm in the gas inlet during the growth process. The electrodes were treated in 0.5 mol L-1 H2SO4 at -3 and 3 V vs Ag/AgCl, respectively, for 30 min. The electrochemical response of BDD films was investigated using electrochemical impedance spectroscopy (EIS) and Mott-Schottky Plot (MSP) measurements. Four film sample sets were produced in a hot filament chemical vapor deposition reactor. During the growth process, an additional H2 line passing through a bubbler containing the B2O3 dissolved in methanol was used to carry the boron. The scanning electron microscopy morphology showed well faced films with a small decrease in their grain size as the CH4 concentration increased. The Raman spectra depicted a pronounced sp2 band, mainly for films with 5 and 7 sccm of CH4. MSP showed a decrease in the acceptor concentration as the CH4 increased indicating the CH4 influence on the doping process for Red-BDD and Ox-BDD samples. Nonetheless, an apparent increase in the acceptor concentrations for both Ox-BDD samples was observed compared to that for Red-BDD samples, mainly attributed to the surface conductive layer (SCL) formation after this strong oxidation process. The EIS Nyquist plots for Red-BDD showed a capacitance increase for the films with higher sp2 content (5 and 7 sccm). On the other hand, the Nyquist plots for Ox-BDD can be described as semicircles near the origin, at high frequencies, where their charge transfer resistance strongly varied with the sp2 increase in such films.

  15. Electrochemical hydrogen Storage Systems

    SciTech Connect

    Dr. Digby Macdonald

    2010-08-09

    closed-loop cycle, our task was then to be able to hydrogenate the organotin halides back to their hydride form. In addition to this experimental work, a parallel project was carried out to develop a new model of electrochemical impedance spectroscopy (EIS) that could be used to define the mechanisms of the electrochemical hydrogenation reactions. The EIS technique is capable of probing complex chemical and electrochemical reactions, and our model was written into a computer code that allowed the input of experimental EIS data and the extraction of kinetic parameters based on a best-fit analysis of theoretical reaction schemes. Finally, electrochemical methods for hydrogenating organic and metallo-organic materials have been explored.

  16. Microfluidic electrochemical reactors

    DOEpatents

    Nuzzo, Ralph G.; Mitrovski, Svetlana M.

    2011-03-22

    A microfluidic electrochemical reactor includes an electrode and one or more microfluidic channels on the electrode, where the microfluidic channels are covered with a membrane containing a gas permeable polymer. The distance between the electrode and the membrane is less than 500 micrometers. The microfluidic electrochemical reactor can provide for increased reaction rates in electrochemical reactions using a gaseous reactant, as compared to conventional electrochemical cells. Microfluidic electrochemical reactors can be incorporated into devices for applications such as fuel cells, electrochemical analysis, microfluidic actuation, pH gradient formation.

  17. Electrochemical behaviour and surface characterisation of Zr exposed to an SBF solution containing glycine, in view of dental implant applications.

    PubMed

    Bozzini, Benedetto; Carlino, Paolo; Mele, Claudio

    2011-01-01

    Zr and Ti alloys are extensively used in the biomedical field owing to their optimal mechanical properties and excellent corrosion resistance. Fully ceramic implants based on zirconia are appealing with respect to the traditional Ti-based metallic ones for several reasons, such as: (i) improved aesthetic impact, (ii) better biocompatibility and (iii) better osteointegration. Nevertheless, fully ceramic implants exhibit serious mechanical and clinical drawbacks, chiefly brittleness and impossibility of post-implant position adjustments. In this paper we propose the novel approach of using a metal-based system, consisting of metallic Zr, for the bulk of the implant and an electrochemically grown zirconia coating, ensuring contact of the ceramic with the biological environment and isolation from the underlying metal. This solution combines the outstanding mechanical properties of the metal in the bulk with the optimal biochemical properties exclusively where they are needed: at the surface. The present paper-focussed on the electrochemical behaviour of the proposed system at the implant-wound and implant-growing bone interface-reports a time-dependent electrochemical corrosion study of zirconia-coated zirconium, performed in the following ways: (i) exposure and measurements in SBF (simulating the inorganic part of human plasma, relevant to wound chemistry), (ii) exposure and measurements in SBF with added glycine (the simplest, ubiquitous amino acid found in proteins), (iii) exposure in SBF with added glycine and measurements in SBF. Electrochemical impedance spectra were measured and interpreted with the equivalent-circuit approach, yielding estimates of the time-variation of the oxide film thickness and resistance were estimated. FT-IR, Surface Raman and VIS reflectance spectroscopies were used to characterise the surface before and after the exposure to SBF solutions. Spectroelectrochemical measurements revealed an higher corrosion resistance of the oxide films

  18. Constant current loop impedance measuring system that is immune to the effects of parasitic impedances

    NASA Technical Reports Server (NTRS)

    Anderson, Karl F. (Inventor)

    1994-01-01

    A constant current loop measuring system is provided for measuring a characteristic of an environment. The system comprises a first impedance positionable in the environment, a second impedance coupled in series with said first impedance and a parasitic impedance electrically coupled to the first and second impedances. A current generating device, electrically coupled in series with the first and second impedances, provides a constant current through the first and second impedances to produce first and second voltages across the first and second impedances, respectively, and a parasitic voltage across the parasitic impedance. A high impedance voltage measuring device measures a voltage difference between the first and second voltages independent of the parasitic voltage to produce a characteristic voltage representative of the characteristic of the environment.

  19. Buffered Electrochemical Polishing of Niobium

    SciTech Connect

    Gianluigi Ciovati; Tian, Hui; Corcoran, Sean

    2011-03-01

    The standard preparation of superconducting radio-frequency (SRF) cavities made of pure niobium include the removal of a 'damaged' surface layer, by buffered chemical polishing (BCP) or electropolishing (EP), after the cavities are formed. The performance of the cavities is characterized by a sharp degradation of the quality factor when the surface magnetic field exceeds about 90 mT, a phenomenon referred to as 'Q-drop.' In cavities made of polycrystalline fine grain (ASTM 5) niobium, the Q-drop can be significantly reduced by a low-temperature (? 120 °C) 'in-situ' baking of the cavity if the chemical treatment was EP rather than BCP. As part of the effort to understand this phenomenon, we investigated the effect of introducing a polarization potential during buffered chemical polishing, creating a process which is between the standard BCP and EP. While preliminary results on the application of this process to Nb cavities have been previously reported, in this contribution we focus on the characterization of this novel electrochemical process by measuring polarization curves, etching rates, surface finish, electrochemical impedance and the effects of temperature and electrolyte composition. In particular, it is shown that the anodic potential of Nb during BCP reduces the etching rate and improves the surface finish.

  20. Joint Impedance Decreases during Movement Initiation

    PubMed Central

    Ludvig, Daniel; Antos, Stephen A.; Perreault, Eric J.

    2013-01-01

    The mechanical properties of the joint influence how we interact with our environment and hence are important in the control of both posture and movement. Many studies have investigated how the mechanical properties—specifically the impedance—of different joints vary with different postural tasks. However, studies on how joint impedance varies with movement remain limited. The few studies that have investigated how impedance varies with movement have found that impedance is lower during movement than during posture. In this study we investigated how impedance changed as people transitioned from a postural task to a movement task. We found that subjects’ joint impedances decreased at the initiation of movement, prior to increasing at the cessation of movement. This decrease in impedance occurred even though the subjects’ torque and EMG levels increased. These findings suggest that during movement the central nervous system may control joint impedance independently of muscle activation. PMID:23366632

  1. Storm Spectra

    NASA Technical Reports Server (NTRS)

    2007-01-01

    portion is defined by the day/night boundary (known as the terminator).

    These two images illustrate only a small fraction of the information contained in a single LEISA scan, highlighting just one aspect of the power of infrared spectra for atmospheric studies.

  2. Electrical Impedance Spectroscopy for Electro-Mechanical Characterization of Conductive Fabrics

    PubMed Central

    Bera, Tushar Kanti; Mohamadou, Youssoufa; Lee, Kyounghun; Wi, Hun; Oh, Tong In; Woo, Eung Je; Soleimani, Manuchehr; Seo, Jin Keun

    2014-01-01

    When we use a conductive fabric as a pressure sensor, it is necessary to quantitatively understand its electromechanical property related with the applied pressure. We investigated electromechanical properties of three different conductive fabrics using the electrical impedance spectroscopy (EIS). We found that their electrical impedance spectra depend not only on the electrical properties of the conductive yarns, but also on their weaving structures. When we apply a mechanical tension or compression, there occur structural deformations in the conductive fabrics altering their apparent electrical impedance spectra. For a stretchable conductive fabric, the impedance magnitude increased or decreased under tension or compression, respectively. For an almost non-stretchable conductive fabric, both tension and compression resulted in decreased impedance values since the applied tension failed to elongate the fabric. To measure both tension and compression separately, it is desirable to use a stretchable conductive fabric. For any conductive fabric chosen as a pressure-sensing material, its resistivity under no loading conditions must be carefully chosen since it determines a measurable range of the impedance values subject to different amounts of loadings. We suggest the EIS method to characterize the electromechanical property of a conductive fabric in designing a thin and flexible fabric pressure sensor. PMID:24892493

  3. Non-destructive determination of impedance spectrum of fruit flesh under the skin

    NASA Astrophysics Data System (ADS)

    Vozáry, E.; Benkó, P.

    2010-04-01

    Impedance spectrum of fresh (intact) apples and of artificially bruised (pressed) apples was determined on the surface of skin with ECG electrodes (Fiab Spa). The magnitude and the phase angle of impedance were measured with a HP 4284A precision LCR meter. The open-short corrected spectra were approached a model consisting of serial resultant of an ohmic resistance and three distributed elements. Approach was performed with complex nonlinear least squares method by MathLab program. Variance analysis was performed (P<0.05) on impedance parameters (SPSS 12.0 for Windows). Parameters of the first distributed element can describe the impedance of apple skin, and parameters of the second and the third element can characterize the impedance of apple flesh. Parameters of the second and the third element are in good agreement with impedance parameters obtained from spectra measured directly on apple flesh without skin. The value of parameters resulted from measurement on apples with skin are sensitive to the degree of artificial bruises.

  4. Electrochemical deposition of conductive and adhesive polypyrrole-dopamine films

    PubMed Central

    Kim, Semin; Jang, Lindy K.; Park, Hyun S.; Lee, Jae Young

    2016-01-01

    Electrode surfaces have been widely modified with electrically conductive polymers, including polypyrrole (PPY), to improve the performance of electrodes. To utilize conductive polymers for electrode modification, strong adhesion between the polymer films and electrode substrates should be ensured with high electrical/electrochemical activities. In this study, PPY films were electrochemically polymerized on electrodes (e.g., indium tin oxide (ITO)) with dopamine as a bio-inspired adhesive molecule. Efficient and fast PPY electrodeposition with dopamine (PDA/PPY) was found; the resultant PDA/PPY films exhibited greatly increased adhesion strengths of up to 3.7 ± 0.8 MPa and the modified electrodes had electrochemical impedances two to three orders of magnitude lower than that of an unmodified electrode. This electrochemical deposition of adhesive and conductive PDA/PPY offers a facile and versatile electrode modification for various applications, such as biosensors and batteries. PMID:27459901

  5. Electrochemical deposition of conductive and adhesive polypyrrole-dopamine films.

    PubMed

    Kim, Semin; Jang, Lindy K; Park, Hyun S; Lee, Jae Young

    2016-01-01

    Electrode surfaces have been widely modified with electrically conductive polymers, including polypyrrole (PPY), to improve the performance of electrodes. To utilize conductive polymers for electrode modification, strong adhesion between the polymer films and electrode substrates should be ensured with high electrical/electrochemical activities. In this study, PPY films were electrochemically polymerized on electrodes (e.g., indium tin oxide (ITO)) with dopamine as a bio-inspired adhesive molecule. Efficient and fast PPY electrodeposition with dopamine (PDA/PPY) was found; the resultant PDA/PPY films exhibited greatly increased adhesion strengths of up to 3.7 ± 0.8 MPa and the modified electrodes had electrochemical impedances two to three orders of magnitude lower than that of an unmodified electrode. This electrochemical deposition of adhesive and conductive PDA/PPY offers a facile and versatile electrode modification for various applications, such as biosensors and batteries. PMID:27459901

  6. Electrochemical deposition of conductive and adhesive polypyrrole-dopamine films

    NASA Astrophysics Data System (ADS)

    Kim, Semin; Jang, Lindy K.; Park, Hyun S.; Lee, Jae Young

    2016-07-01

    Electrode surfaces have been widely modified with electrically conductive polymers, including polypyrrole (PPY), to improve the performance of electrodes. To utilize conductive polymers for electrode modification, strong adhesion between the polymer films and electrode substrates should be ensured with high electrical/electrochemical activities. In this study, PPY films were electrochemically polymerized on electrodes (e.g., indium tin oxide (ITO)) with dopamine as a bio-inspired adhesive molecule. Efficient and fast PPY electrodeposition with dopamine (PDA/PPY) was found; the resultant PDA/PPY films exhibited greatly increased adhesion strengths of up to 3.7 ± 0.8 MPa and the modified electrodes had electrochemical impedances two to three orders of magnitude lower than that of an unmodified electrode. This electrochemical deposition of adhesive and conductive PDA/PPY offers a facile and versatile electrode modification for various applications, such as biosensors and batteries.

  7. Rapid Impedance Spectrum Measurements for State-of-Health Assessment of Energy Storage Devices

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; Chester G. Motloch; William H. Morrison

    2012-04-01

    Harmonic compensated synchronous detection (HCSD) is a technique that can be used to measure wideband impedance spectra within seconds based on an input sum-of-sines signal having a frequency spread separated by harmonics. The battery (or other energy storage device) is excited with a sum-of-sines current signal that has a duration of at least one period of the lowest frequency. The voltage response is then captured and synchronously detected at each frequency of interest to determine the impedance spectra. This technique was successfully simulated using a simplified battery model and then verified with commercially available Sanyo lithium-ion cells. Simulations revealed the presence of a start-up transient effect when only one period of the lowest frequency is included in the excitation signal. This transient effect appears to only influence the low-frequency impedance measurements and can be reduced when a longer input signal is used. Furthermore, lithium-ion cell testing has indicated that the transient effect does not seem to impact the charge transfer resistance in the mid-frequency region. The degradation rates for the charge transfer resistance measured from the HCSD technique were very similar to the changes observed from standardized impedance spectroscopy methods. Results from these studies, therefore, indicate that HCSD is a viable, rapid alternative approach to acquiring impedance spectra.

  8. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba

    2002-08-30

    This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD

  9. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba; Christopher J. Ziolkowski

    2004-10-29

    This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or non-metallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging

  10. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba

    2004-05-03

    This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging

  11. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba

    2004-02-01

    This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging

  12. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba; Christopher J. Ziolkowski

    2005-01-17

    This project aimed at developing a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GTI. GTI proposed to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or non-metallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment

  13. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba

    2003-10-01

    This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging

  14. Bilateral Impedance Control For Telemanipulators

    NASA Technical Reports Server (NTRS)

    Moore, Christopher L.

    1993-01-01

    Telemanipulator system includes master robot manipulated by human operator, and slave robot performing tasks at remote location. Two robots electronically coupled so slave robot moves in response to commands from master robot. Teleoperation greatly enhanced if forces acting on slave robot fed back to operator, giving operator feeling he or she manipulates remote environment directly. Main advantage of bilateral impedance control: enables arbitrary specification of desired performance characteristics for telemanipulator system. Relationship between force and position modulated at both ends of system to suit requirements of task.

  15. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba; Christopher J. Ziolkowski

    2004-06-30

    This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging

  16. Impedance spectroscopy of food mycotoxins

    NASA Astrophysics Data System (ADS)

    Bilyy, Oleksandr I.; Yaremyk, Roman Ya.; Kotsyumbas, Ihor Ya.; Kotsyumbas, Halyna I.

    2012-01-01

    A new analytical method of high-selective detection of mycotoxins in food and feed are considered. A method is based on optical registration the changes of conduct of the electric polarized bacterial agents in solution at the action of the external gradient electric fields. Measuring are conducted in integrated electrode-optical cuvette of the special construction, which provides the photometric analysis of forward motion of the objects registration in liquid solution under act of the enclosed electric field and simultaneous registration of kinetics of change of electrical impedance parameters solution and electrode system.

  17. Electrochemical characteristics of lithium-ion cells

    SciTech Connect

    Nagasubramanian, C.; Roth, P.; Jungst, R.G.; Clark, N.

    1998-01-01

    The authors describe below the electrochemical performance characteristics, including charge-discharge characteristics at different rates, of cylindrical 18650 (18 mm diameter, 65 mm high) and prismatic lithium ion cells at ambient and sub-ambient temperatures. Ragone plots of power and energy data for these cells are compared and indicate that at room temperature the prismatic lithium ion cells (approx. 500 mAh) exhibit higher specific power and power density than the 18650 cells (approx. 1,100 mAhr). The cell impedance was measured between 35 C and {minus}40 C at three open circuit voltages: 4.1 v (fully charged), 3.6 v (partially discharged), and 3.1 v (almost completely discharged). Over the temperature range from 35 C to {minus}20 C, the cell impedance is nearly constant for both cell types and increases by 2 to 3 times at {minus}40 C. The impedance doesn`t vary significantly with open circuit voltage (OCV). These cells show very little voltage drop at room temperature for current pulses up to 1 A. The charge-discharge characteristics of the cells are being studied at different rates as a function of temperature to compute the power, energy, and capacity outputs. This will not only broaden the database on lithium ion cells, but will also allow us to evaluate the suitability of the cells as power sources for low temperature applications. Other electrochemical characteristics of these cells including pulse response are being evaluated. Impedance measurements of the cells under load are planned to make meaningful correlations between the voltage drop and the current pulse amplitude.

  18. Four-electrode impedance spectrometer for investigation of solid ion conductors.

    PubMed

    Kežionis, A; Butvilas, P; Šalkus, T; Kazlauskas, S; Petrulionis, D; Žukauskas, T; Kazakevičius, E; Orliukas, A F

    2013-01-01

    An impedance spectrometer capable of accurately measuring solid ion conducting sample impedance spectra by two- or four-electrode methods in either time or frequency domain has been built. The four-electrode measurement mode is implemented by constructing a differential amplifier with a very high input impedance and common mode rejection ratio over a wide frequency range. All of the measurements can be performed in frequencies ranging from 10 Hz to 2 MHz and sample temperatures up to 800 K. The working principle of the spectrometer as well as its technical parameters and accuracy estimation are presented in this paper. The advantage of four-electrode over two-electrode measurement mode is shown by an example of Ce(0.9)Gd(0.1)O(1.95) solid electrolyte ceramic impedance measurements. PMID:23387663

  19. Four-electrode impedance spectrometer for investigation of solid ion conductors

    NASA Astrophysics Data System (ADS)

    Kežionis, A.; Butvilas, P.; Šalkus, T.; Kazlauskas, S.; Petrulionis, D.; Žukauskas, T.; Kazakevičius, E.; Orliukas, A. F.

    2013-01-01

    An impedance spectrometer capable of accurately measuring solid ion conducting sample impedance spectra by two- or four-electrode methods in either time or frequency domain has been built. The four-electrode measurement mode is implemented by constructing a differential amplifier with a very high input impedance and common mode rejection ratio over a wide frequency range. All of the measurements can be performed in frequencies ranging from 10 Hz to 2 MHz and sample temperatures up to 800 K. The working principle of the spectrometer as well as its technical parameters and accuracy estimation are presented in this paper. The advantage of four-electrode over two-electrode measurement mode is shown by an example of Ce0.9Gd0.1O1.95 solid electrolyte ceramic impedance measurements.

  20. Analysis of the transverse SPS beam coupling impedance with short and long bunches

    SciTech Connect

    Salvant,B.; Calaga, R.; de Maria, R.; Arduini, G.; Burkhardt, H.; Damerau, H.; Hofle, W.; Metral, E.; Papotti, G.; Rumolo, G.; Tomas, R.; White, S.

    2009-05-04

    The upgrade of the CERN Large Hadron Collider (LHC) would require a four- to five-fold increase of the single bunch intensity presently obtained in the Super Proton Synchrotron (SPS). Operating at such high single bunch intensities requires a detailed knowledge of the sources of SPS beam coupling impedance, so that longitudinal and transverse impedance reduction campaigns can be planned and performed effectively if needed. In this paper, the transverse impedance of the SPS is studied by injecting a single long bunch into the SPS, and observing its decay without RF. Longer bunches allow for higher frequency resolution of the longitudinal and transverse bunch spectra acquired with strip line couplers connected to a fast data acquisition. It also gives access to the frequency content of the transverse impedance. Results from measurements with short and long bunches in the SPS performed in 2008 are compared with simulations.

  1. Impedance spectroscopy investigation of electrophysical characteristics of the electrode-liquid crystal interface

    NASA Astrophysics Data System (ADS)

    Belyaev, B. A.; Drokin, N. A.

    2015-01-01

    The behavior of frequency dependences of the impedance of a capacitive measuring cell with a liquid crystal has been investigated in the frequency range from 10-1 to 105 Hz. A method for determining electrophysical characteristics of the liquid crystal in the bulk and at the liquid crystal-metal electrode interface has been proposed and tested for liquid crystals of the alkyl cyanobiphenyl series, which are doped with ionic surfactants. The method is based on the use of an equivalent electrical circuit, which makes it possible to approximate the impedance spectra with the required accuracy, and also on the determination of the frequency at the singular point in the impedance spectra, at which the reactive component of the electric current flowing through the liquid-crystal cell is negligible compared to the active component.

  2. Spheromak Impedance and Current Amplification

    SciTech Connect

    Fowler, T K; Hua, D D; Stallard, B W

    2002-01-31

    It is shown that high current amplification can be achieved only by injecting helicity on the timescale for reconnection, {tau}{sub REC}, which determines the effective impedance of the spheromak. An approximate equation for current amplification is: dI{sub TOR}{sup 2}/dt {approx} I{sup 2}/{tau}{sub REC} - I{sub TOR}{sup 2}/{tau}{sub closed} where I is the gun current, I{sub TOR} is the spheromak toroidal current and {tau}{sub CLOSED} is the ohmic decay time of the spheromak. Achieving high current amplification, I{sub TOR} >> I, requires {tau}{sub REC} <<{tau}{sub CLOSED}. For resistive reconnection, this requires reconnection in a cold zone feeding helicity into a hot zone. Here we propose an impedance model based on these ideas in a form that can be implemented in the Corsica-based helicity transport code. The most important feature of the model is the possibility that {tau}{sub REC} actually increases as the spheromak temperature increases, perhaps accounting for the ''voltage sag'' observed in some experiments, and a tendency toward a constant ratio of field to current, B {proportional_to} I, or I{sub TOR} {approx} I. Program implications are discussed.

  3. A Comparative Study of Four Impedance Eduction Methodologies Using Several Test Liners

    NASA Technical Reports Server (NTRS)

    Watson, Willie R.; Jones, Michael G.

    2013-01-01

    A comparative study of four commonly used impedance eduction methods is presented for a range of liner structures and test conditions. Two of the methods are restricted to uniform flow while the other two accommodate both uniform and boundary layer flows. Measurements on five liner structures (a rigid-wall insert, a ceramic tubular liner, a wire mesh liner, a low porosity conventional liner, and a high porosity conventional liner) are obtained using the NASA Langley Grazing Flow Impedance Tube. The educed impedance of each liner is presented for forty-two test conditions (three Mach numbers and fourteen frequencies). In addition, the effects of moving the acoustic source from upstream to downstream and the refractive effects of the mean boundary layer on the wire mesh liner are investigated. The primary conclusions of the study are that: (1) more accurate results are obtained for the upstream source, (2) the uniform flow methods produce nearly identical impedance spectra at and below Mach 0.3 but significant scatter in the educed impedance occurs at the higher Mach number, (3) there is better agreement in educed impedance among the methods for the conventional liners than for the rigid-wall insert, ceramic, or wire mesh liner, and (4) the refractive effects of the mean boundary layer on the educed impedance of the wire mesh liner are generally small except at Mach 0.5.

  4. Noninvasive electrical impedance sensor for in vivo tissue discrimination at radio frequencies.

    PubMed

    Dai, Yu; Du, Jun; Yang, Qing; Zhang, Jianxun

    2014-09-01

    Compared to traditional open surgery, minimally invasive surgery (MIS) allows for a more rapid and less painful recovery. However, the lack of significant haptic feedback in MIS can make tissue discrimination difficult. This paper tests a noninvasive electrical impedance sensor for in vivo discrimination of tissue types in MIS. The sensor consists of two stainless steel spherical electrodes used to measure the impedance spectra over the frequency range of 200 kHz to 5 MHz. The sensor helps ensure free movement on an organ surface and prevents soft tissues from being injured during impedance measurement. Since the recorded electrical impedance is correlated with the force pressed on the electrode and the mechanical property of the tissue, the electrode-tissue contact impedance is calculated theoretically. We show that the standard deviation of the impedance ratio at each frequency point is sufficient to distinguish different tissue types. Both in vitro experiment in a pig kidney and in vivo experiment in rabbit organs were performed to demonstrate the feasibility of the electrical impedance sensor. The experimental results indicated that the sensor, used with the proposed data-processing method, provides accurate and reliable biological tissue discrimination. PMID:24764269

  5. Impedance studies on Li-ion cathodes

    SciTech Connect

    NAGASUBRAMANIAN, GANESAN

    2000-04-17

    This paper describes the author's 2- and 3-electrode impedance results of metal oxide cathodes. These results were extracted from impedance data on 18650 Li-ion cells. The impedance results indicate that the ohmic resistance of the cell is very nearly constant with state-of-charge (SOC) and temperature. For example, the ohmic resistance of 18650 Li-ion cells is around 60 m{Omega} for different SOCS (4.1V to 3.0V) and temperatures from 35 C to {minus}20 C. However, the interfacial impedance shows a modest increase with SOC and a huge increase of between 10 and 100 times with decreasing temperature. For example, in the temperature regime (35 C down to {minus}20 C) the overall cell impedance has increased from nearly 200 m{Omega} to 8,000 m{Omega}. Most of the increase in cell impedance comes from the metal oxide cathode/electrolyte interface.

  6. Electrochemical processes at solid electrode-electrolyte-gas interfaces

    SciTech Connect

    Youngblood, G.E.; Weber, W.J; Bates, J.L.

    1991-05-01

    Electrochemical reactions at solid electrolyte-electrode-gas interfaces are being investigated with ac impedance and dc polarization techniques using an unbonded interface cell (UIC). The UIC approach eliminates influence of sample size and interface morphology resulting from electrode-electrolyte fabrication. The electrochemical reactions of oxygen with solid electrode (La{sub 1-x}Sr{sub x}MnO{sub 3} or Pt) and solid electrolyte (0.08Y{sub 2}O{sub 3} - 0.92ZrO{sub 2}) interfaces are described. 6 refs., 4 figs., 2 tabs.

  7. Facile synthesis of tetragonal columnar-shaped TiO2 nanorods for the construction of sensitive electrochemical glucose biosensor.

    PubMed

    Yang, Zhanjun; Tang, Yan; Li, Juan; Zhang, Yongcai; Hu, Xiaoya

    2014-04-15

    A tetragonal columnar-shaped TiO2 (TCS-TiO2) nanorods are synthesized via a facile route for the immobilization of glucose oxidase (GOx). A novel electrochemical glucose biosensor is constructed based on the direct electrochemistry of GOx at TCS-TiO2 modified glassy carbon electrode. The fabricated biosensor is characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, electrochemical impedance spectra and cyclic voltammetry. The immobilized enzyme molecules on TCS-TiO2 nanorods retain its native structure and bioactivity and show a surface controlled, quasi-reversible and fast electron transfer process. The TCS-TiO2 nanorods have large surface area and provide a favorable microenvironment for enhancing the electron transfer between enzyme and electrode surface. The constructed glucose biosensor shows wide linear range from 5.0×10(-6) to 1.32×10(-3) M with a high sensitivity of 23.2 mA M(-1) cm(-2). The detection limit is calculated to be 2.0×10(-6) M at signal-to-noise of 3. The proposed glucose biosensor also exhibits excellent selectivity, good reproducibility, and acceptable operational stability. Furthermore, the biosensor can be successfully applied in the detection of glucose in serum sample at the applied potential of -0.50 V. The TCS-TiO2 nanorods provide an efficient and promising platform for the immobilization of proteins and development of excellent biosensors. PMID:24325982

  8. In situ one-pot synthesis of graphene-polyaniline nanofiber composite for high-performance electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Jin, Yuhong; Fang, Mou; Jia, Mengqiu

    2014-07-01

    In this work, graphene-polyaniline nanofiber (G/PANI-F) composite is prepared through a new and one-pot method that includes the reduction of graphene oxide (GO) by aniline and then followed by in-situ polymerization. Aniline plays the two roles in this method: as a chemical reducing agent to reduce GO to graphene and as a monomer to prepare polyaniline nanofiber (PANI-F). Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy and transmission electron microscopy are employed to confirm that GO can be reduced by aniline and PANI-F can be deposited on the surface of graphene. The electrochemical properties of G/PANI-F composite electrode are measured by using cyclic voltammetry, galvanostatic charge-discharge test and electrochemical impedance spectroscopy. The G/PANI-F composite electrode exhibits enhanced specific capacitance of 965 F g-1 at 0.5 A g-1 and the capacity retention is 90% after 2000 cycles.

  9. Facile synthesis and electrochemical characterization of Sn4Ni3/C nanocomposites as anode materials for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Ma, Ruguang; Lu, Zhouguang; Yang, Shiliu; Xi, Liujiang; Wang, Chundong; Wang, H. E.; Chung, C. Y.

    2012-12-01

    Sn4Ni3/C nanocomposites were synthesized by a pyrolyzing-annealing two-step strategy. The phase structure, carbon content and morphology of the nanocomposites were investigated. The results reveal that the crystallinity, carbon structure and purity were enhanced obviously after heat-treatment. Electrochemical performance was evaluated by cyclic voltammograms (CV), galvanostatic discharge/charge and electrochemical impedance spectra (EIS). The annealed Sn4Ni3/C powders deliver an initial charge capacity of 525.2 mA h g-1, 400 mA h g-1 over 10 cycles at 36 mA g-1, >300 mA h g-1 after 40 cycles at 72 mA g-1 and maintain 240 mA h g-1 for 40 cycles at 150 mA g-1. TEM investigation of the cycled electrodes shows the discharge/charge process neither destroyed the structure of nanocomposites nor changed the crystallinity of the materials. So the high capacity and stable cyclability are ascribed to the synergetic effect of ductile nickel and conductive carbon constituent and the influence of heat-treatment.

  10. TRANSVERSE IMPEDANCE MEASUREMENT AT THE RHIC.

    SciTech Connect

    ZHANG,S.Y.; HUANG,H.; CAMERON,P.; DREES,A.; FLILLER,R.; SATOGATA,T.

    2002-06-02

    The RHIC transverse impedance was measured during the last operation run. Measurement of the imaginary part of the broadband impedance was the main goal. No large difference between the two rings was found nor in either plane. The measured tune shift is larger than the expected by a factor of 2.5 to 3. Several other issues such as the real part impedance measurement are also presented.

  11. Graphitic carbon nitride (g-C3N4) coated titanium oxide nanotube arrays with enhanced photo-electrochemical performance.

    PubMed

    Sun, Mingxuan; Fang, Yalin; Kong, Yuanyuan; Sun, Shanfu; Yu, Zhishui; Umar, Ahmad

    2016-08-01

    Herein, we report the successful formation of graphitic carbon nitride coated titanium oxide nanotube array thin films (g-C3N4/TiO2) via the facile thermal treatment of anodized Ti sheets over melamine. The proportion of C3N4 and TiO2 in the composite can be adjusted by changing the initial addition mass of melamine. The as-prepared samples are characterized by several techniques in order to understand the morphological, structural, compositional and optical properties. UV-vis absorption studies exhibit a remarkable red shift for the g-C3N4/TiO2 thin films as compared to the pristine TiO2 nanotubes. Importantly, the prepared composites exhibit an enhanced photocurrent and photo-potential under both UV-vis and visible light irradiation. Moreover, the observed maximum photo-conversion efficiency of the prepared composites is 1.59 times higher than that of the pristine TiO2 nanotubes. The optical and electrochemical impedance spectra analysis reveals that the better photo-electrochemical performance of the g-C3N4/TiO2 nanotubes is mainly due to the wider light absorption and reduced impedance compared to the bare TiO2 nanotube electrode. The presented work demonstrates a facile and simple method to fabricate g-C3N4/TiO2 nanotubes and clearly revealed that the introduction of g-C3N4 is a new and innovative approach to improve the photocurrent and photo-potential efficiencies of TiO2. PMID:27443233

  12. Dielectric and impedance spectroscopic studies of neodymium gallate

    NASA Astrophysics Data System (ADS)

    Sakhya, Anup Pradhan; Dutta, Alo; Sinha, T. P.

    2016-05-01

    The AC electrical properties of a polycrystalline neodymium gallate, NdGaO3 (NGO), synthesized by the sol-gel method have been investigated by employing impedance spectroscopy in the frequency range from 42 Hz to 5 MHz and in the temperature range from 323 K to 593 K. The X-ray diffraction analysis shows that the compound crystallizes in the orthorhombic phase with Pbnm space group at room temperature. Two relaxation processes with different relaxation times are observed from the impedance as well as modulus spectroscopic measurements, which have been attributed to the grain and the grain boundary effects at different temperatures in NGO. The complex impedance data are analyzed by an electrical equivalent circuit consisting of a resistance and a constant phase element in parallel. It has been observed that the value of the capacitance and the resistance associated with the grain boundary is higher than those associated with the grain. The temperature dependent electrical conductivity shows the negative temperature coefficient of resistance. The frequency dependent conductivity spectra are found to follow the power law.

  13. Electrochemical Investigation of Interaction between a Bifunctional Probe and GG Mismatch Duplex.

    PubMed

    Li, Jiao; He, Hanping; Peng, Xiaoqian; Huang, Min; Zhang, Xiuhua; Wang, Shengfu

    2015-01-01

    A bifunctional probe (FecNC), containing a recognition part and an electrochemical active center, was applied to electrochemical detection of GG mismatch duplexes. The preparation of gold electrodes modified by mismatch and complementatry duplexes was characterized by electrochemical impedance spectroscopy (EIS) and optimized for better detection in terms of self-assembly time, hybridization time, and incubation time. The interaction between FecNC and DNA duplexes modified on the surface of a gold electrode was explored by square wave voltammetry (SWV) and EIS. The results showed that the DNA duplexes with GG mismatch on the surface of a gold electrode was easily detected by the largest electrochemical signal of the bifunctional probe because of its selective binding to GG mismatches. The bifunctional probe could offer a simple, effective electrochemical detection of GG mismatches, and theoretical bases for development of electrochemical biosensors. Further, the method would be favorable for diagnosis of genetic diseases. PMID:26165289

  14. Adaptive Impedance Control Of Redundant Manipulators

    NASA Technical Reports Server (NTRS)

    Seraji, Homayoun; Colbaugh, Richard D.; Glass, Kristin L.

    1994-01-01

    Improved method of controlling mechanical impedance of end effector of redundant robotic manipulator based on adaptive-control theory. Consists of two subsystems: adaptive impedance controller generating force-control inputs in Cartesian space of end effector to provide desired end-effector-impedance characteristics, and subsystem implementing algorithm that maps force-control inputs into torques applied to joints of manipulator. Accurate control of end effector and effective utilization of redundancy achieved simultaneously by use of method. Potential use to improve performance of such typical impedance-control tasks as deburring edges and accommodating transitions between unconstrained and constrained motions of end effectors.

  15. Electrical Impedance Tomography of Electrolysis

    PubMed Central

    Meir, Arie; Rubinsky, Boris

    2015-01-01

    The primary goal of this study is to explore the hypothesis that changes in pH during electrolysis can be detected with Electrical Impedance Tomography (EIT). The study has relevance to real time control of minimally invasive surgery with electrolytic ablation. To investigate the hypothesis, we compare EIT reconstructed images to optical images acquired using pH-sensitive dyes embedded in a physiological saline agar gel phantom treated with electrolysis. We further demonstrate the biological relevance of our work using a bacterial E.Coli model, grown on the phantom. The results demonstrate the ability of EIT to image pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E.coli model. The results are promising, and invite further experimental explorations. PMID:26039686

  16. Impedance Spectroscopy of Human Blood

    NASA Astrophysics Data System (ADS)

    Mesa, Francisco; Bernal, José J.; Sosa, Modesto A.; Villagómez, Julio C.; Palomares, Pascual

    2004-09-01

    The blood is one of the corporal fluids more used with analytical purposes. When the blood is extracted, immediately it is affected by agents that act on it, producing transformations in its elements. Among the effects of these transformations the hemolysis phenomenon stands out, which consists of the membrane rupture and possible death of the red blood cells. The main purpose of this investigation was the quantification of this phenomenon. A Solartron SI-1260 Impedance Spectrometer was used, which covers a frequency range of work from 1 μHz to 10 MHz, and its accuracy has been tested in the accomplishment of several applications. Measurements were performed on 3 mL human blood samples, from healthy donors. Reactive strips for sugar test of 2 μL, from Bayer, were used as electrodes, which allow gathering a portion of the sample, to be analyzed by the spectrometer. Preliminary results of these measurements are presented.

  17. Improvement of impedance spectroscopy methods: resonance analysis of samples

    NASA Astrophysics Data System (ADS)

    Balmus, Sorin-Bogdan; Ciomaga, Cristina E.; Horchidan, Nadejda; Mitoseriu, Liliana; Dumitru, Ioan

    2015-06-01

    An impedance spectroscopy method, using an Agilent E4991A RF Impedance/Material Analyzer, was employed for the investigation of radiofrequency and microwave dielectric characteristics for some ceramic materials with high dielectric permittivity. Experimental observations recorded single, double and even triple resonances in the permittivity spectra, while for the selected samples significantly different values of permittivity from the ones found in existing literature were directly measured and observed in the frequency range of 100 MHz-1 GHz. The specified material analyzer is designed to work within certain permittivity-frequency domains; working outside these limits leads to significant errors when carrying out direct measurements of permittivity. Having observed that the resonance measurements are not associated with the intrinsic material properties but with the sample resonances, we proposed a dielectric resonance cavity model for sample purposes and we determined the dielectric permittivity at different resonance frequencies. A scaling procedure, based on the computed values of permittivity, was applied in order to correct the directly measured permittivity spectra where the frequency was outside the resonance domains. The corrected data are in good agreement with those measured using other techniques and suggest that the proposed procedure extends the spectroscopy method currently used for high permittivity measurements. The sources of error for the proposed method were investigated.

  18. RF discharge impedance measurements using a new method to determine the stray impedances

    SciTech Connect

    Bakker, L.P.; Kroesen, G.M.W.; Hoog, F.J. de )

    1999-06-01

    The impedance of a capacitively coupled radio frequency discharge in a tubular fluorescent lamp filled with neon and mercury is measured. The stray impedances in the electrical network are determined using a new method that requires no extra instruments. The reflection of power is used to determine the stray impedances. Making use of a simple discharge impedance model, the electron density in the lamp is estimated.

  19. Volume dependence of respiratory impedance in infants.

    PubMed

    Peták, F; Hayden, M J; Hantos, Z; Sly, P D

    1997-10-01

    We previously studied low-frequency respiratory impedance (Zrs) data at an elevated lung volume to separate airway and tissue mechanical properties in normal infants (Am. I. Respir. Crit. Care Med. 1996; 154:161-166). The aim of the present study was to determine the volume dependence of the airway and tissue mechanics by extending Zrs measurements to lower lung volumes. Zrs spectra between 0.5 and 21 Hz were measured in supine sleeping infants (n = 8; 7 to 26 mo of age) at mean transrespiratory pressures (Ptr[mean]) of 20, 10, and 0 cm H2O, during periods of apnea induced by inflating the infants' lungs to a pressure of 20 cm H2O through a face mask. At each inflation pressure, a model containing airway resistance (Raw) and inertance (law) and tissue damping (G) and elastance (H) was fitted to Zrs data. At FRC, the values of Raw, law, G, and H were 20.6+/-4.9 (SD) cm H2O x s/L, 0.037+/-0.014 cm H2O x s2/L, 39.6+/-10.3 cm H2O/L, and 147+/-35 cm H2O/L, respectively. Increase of Ptr(mean) caused a monotonous decrease in Raw (42+/-7% of the value at FRC), while law remained constant. The tissue parameters were minimal at a Ptr(mean) of 10 cm H2O (68+/-10% and 78+/-6% in G and H, respectively) and significantly higher at both 0 and 20 cm H2O. Although Zrs measurements can be made in most infants at lung volumes as low as FRC, an inflation pressure of 20 cm H2O provides a higher success rate and is therefore a more suitable condition for general use. PMID:9351618

  20. Gold nanotip array for ultrasensitive electrochemical sensing and spectroscopic monitoring.

    PubMed

    Jiang, Yueyue; Meng, Fanben; Qi, Dianpeng; Cai, Pingqiang; Yin, Zongyou; Shao, Fangwei; Zhang, Hua; Boey, Freddy; Chen, Xiaodong

    2013-07-01

    A gold nanotip array platform with a combination of ultrasensitive electrochemical sensing and spectroscopic monitoring capability is reported. Adenosine triphosphate is detected down to 1 pM according to the impedance changes in response to aptamer-specific binding. Furthermore, the local molecular information can be monitored at the individual plasmonic nanotips, and hence provide the capability for a better understanding of complex biological processes. PMID:23362212

  1. A Sensitive and simple macrophage-based electrochemical biosensor for evaluating lipopolysaccharide cytotoxicity of pathogenic bacteria.

    PubMed

    Wang, Xiumei; Zhu, Pei; Pi, Fuwei; Jiang, Hui; Shao, Jingdong; Zhang, Yinzhi; Sun, Xiulan

    2016-07-15

    In this study, a sensitive and simple electrochemical murine macrophage (Ana-1) cell sensor has been developed for early detection of lipopolysaccharides (LPS) to evaluate the toxicity of pathogenic bacteria. Magnetic glassy carbon electrode (MGCE), which possesses excellent reproducibility and regeneration qualities, was modified with a nanocomposite to improve electrochemical signals and enhance the sensitivity. The synthesized magnetic nanoparticles (MNPs) were internalized into murine macrophages, which completed the immobilization of macrophages onto the modified electrode for evaluating the cytotoxicity of LPS by electrochemical impedance spectroscopy (EIS). The MNPs facilitated reusability of the proposed sensor by allowing removal of the magnetic core from the electrode. Our results indicated that LPS caused a marked decrease in electrochemical impedance in a dose-dependent manner in range of 1-5μg/mL. By SEM, we found that microvilli on the plasma membrane became scarce and the membrane became smooth on cells incubated with LPS, which lessens the absorption of cells to reduce the impedance. And biological assay indicated that EIS patterns were correlated with the calcium concentration in cells, and suggested that [Ca(2+)]i production increased in cells incubated with LPS and its mobilization altered electrochemical signals. Compared with conventional methods, this electrochemical test is inexpensive, highly sensitive, and has a quick response, and thus provides a new avenue for evaluating the cytotoxicity of pathogens. PMID:26991601

  2. An Analysis of Electrical Impedance Measurements Applied for Plant N Status Estimation in Lettuce (Lactuca sativa)

    PubMed Central

    Muñoz-Huerta, Rafael F.; de J. Ortiz-Melendez, Antonio; Guevara-Gonzalez, Ramon G.; Torres-Pacheco, Irineo; Herrera-Ruiz, Gilberto; Contreras-Medina, Luis M.; Prado-Olivarez, Juan; Ocampo-Velazquez, Rosalia V.

    2014-01-01

    Nitrogen plays a key role in crop yields. Hence, farmers may apply excessive N fertilizers to crop fields, inducing environmental pollution. Crop N monitoring methods have been developed to improve N fertilizer management, most of them based on leaf or canopy optical-property measurements. However, sensitivity to environmental interference remains an important drawback. Electrical impedance has been applied to determine the physiological and nutritional status of plant tissue, but no studies related to plant-N contents are reported. The objective of this article is to analyze how the electrical impedance response of plants is affected by their N status. Four sets of lettuce (Lactuca sativa L.) with a different N-source concentrations per set were used. Total nitrogen and electrical impedance spectra (in a 1 to 100 kHz frequency range) were measured five times per set, three times every other day. Minimum phase angles of impedance spectra were detected and analyzed, together with the frequency value in which they occurred, and their magnitude at that frequency. High and positive correlation was observed between plant N content and frequency values at minimum phase angle with no significant variations detected between days of measurement. These results suggest that electrical impedance can be sensitive to plant N status. PMID:25057134

  3. Far-infrared embedding impedance measurements

    NASA Technical Reports Server (NTRS)

    Neikirk, D. P.; Rutledge, D. B.

    1984-01-01

    A technique which allows the measurement of detector embedding impedance has been developed. By using a bismuth microbolometer as a variable resistance load the impedance of one element in a bow-tie antenna array operating at 94 GHz was inferred. The technique is frequency insensitive, and could be used throughout the far-infrared.

  4. How good is the impedance boundary condition?

    NASA Technical Reports Server (NTRS)

    Lee, Shung-Wu; Gee, W.

    1987-01-01

    The impedance boundary condition (IBC) is often used in scattering problems involving material-coated conducting bodies. It is shown that for some commonly encountered coating configurations, the value of the impedance varies significantly as functions of the incident angle and polarization. Hence, the use of IBC in a rigorously formulated problem may affect the accuracy of the final solution.

  5. FDTD modeling of thin impedance sheets

    NASA Technical Reports Server (NTRS)

    Luebbers, Raymond J.; Kunz, Karl S.

    1991-01-01

    Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. In this paper it is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods.

  6. Esophageal Impedance Monitoring: Clinical Pearls and Pitfalls.

    PubMed

    Ravi, Karthik; Katzka, David A

    2016-09-01

    The development of intraluminal esophageal impedance monitoring has improved our ability to detect and measure gastroesophageal reflux without dependence on acid content. This ability to detect previously unrecognized weak or nonacid reflux episodes has had important clinical implications in the diagnosis and management of gastroesophageal reflux disease (GERD). In addition, with the ability to assess bolus transit within the esophageal lumen, impedance monitoring has enhanced the recognition and characterization of esophageal motility disorders in patients with nonobstructive dysphagia. The assessment of the intraluminal movement of gas and liquid has also been proven to be of diagnostic value in conditions such as rumination syndrome and excessive belching. Further, alternative applications of impedance monitoring, such as the measurement of mucosal impedance, have provided novel insights into assessing esophageal mucosal integrity changes as a consequence of inflammatory change. Future applications for esophageal impedance monitoring also hold promise in esophageal conditions other than GERD. However, despite all of the clinical benefits afforded by esophageal impedance monitoring, important clinical and technical shortcomings limit its diagnostic value and must be considered when interpreting study results. Overinterpretation of studies or application of impedance monitoring in patients can have deleterious clinical implications. This review will highlight the clinical benefits and limitations of esophageal impedance monitoring and provide clinical pearls and pitfalls associated with this technology. PMID:27325223

  7. Possibilities of electrical impedance tomography in gynecology

    NASA Astrophysics Data System (ADS)

    V, Trokhanova O.; A, Chijova Y.; B, Okhapkin M.; V, Korjenevsky A.; S, Tuykin T.

    2013-04-01

    The paper describes results of comprehensive EIT diagnostics of mammary glands and cervix. The data were obtained from examinations of 170 patients by EIT system MEM (multi-frequency electrical impedance mammograph) and EIT system GIT (gynecological impedance tomograph). Mutual dependence is discussed.

  8. Active impedance matching of complex structural systems

    NASA Technical Reports Server (NTRS)

    Macmartin, Douglas G.; Miller, David W.; Hall, Steven R.

    1991-01-01

    Viewgraphs on active impedance matching of complex structural systems are presented. Topics covered include: traveling wave model; dereverberated mobility model; computation of dereverberated mobility; control problem: optimal impedance matching; H2 optimal solution; statistical energy analysis (SEA) solution; experimental transfer functions; interferometer actuator and sensor locations; active strut configurations; power dual variables; dereverberation of complex structure; dereverberated transfer function; compensators; and relative power flow.

  9. Impedance of finite length resistive cylinder

    NASA Astrophysics Data System (ADS)

    Krinsky, S.; Podobedov, B.; Gluckstern, R. L.

    2004-11-01

    We determine the impedance of a cylindrical metal tube (resistor) of radius a, length g, and conductivity σ attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency (k≫1/a). In the equilibrium regime, ka2≪g, the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity σ. In the transient regime, ka2≫g, where the contribution of transition radiation arising from the discontinuity in conductivity is important, we derive an analytic expression for the impedance and compute the short-range wakefield. The analytic results are shown to agree with numerical evaluation of the impedance.

  10. Electrochemical methane sensor

    DOEpatents

    Zaromb, S.; Otagawa, T.; Stetter, J.R.

    1984-08-27

    A method and instrument including an electrochemical cell for the detection and measurement of methane in a gas by the oxidation of methane electrochemically at a working electrode in a nonaqueous electrolyte at a voltage about 1.4 volts vs R.H.E. (the reversible hydrogen electrode potential in the same electrolyte), and the measurement of the electrical signal resulting from the electrochemical oxidation.

  11. Electrochemical Biosensors - Sensor Principles and Architectures

    PubMed Central

    Grieshaber, Dorothee; MacKenzie, Robert; Vörös, Janos; Reimhult, Erik

    2008-01-01

    Quantification of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. However, converting the biological information to an easily processed electronic signal is challenging due to the complexity of connecting an electronic device directly to a biological environment. Electrochemical biosensors provide an attractive means to analyze the content of a biological sample due to the direct conversion of a biological event to an electronic signal. Over the past decades several sensing concepts and related devices have been developed. In this review, the most common traditional techniques, such as cyclic voltammetry, chronoamperometry, chronopotentiometry, impedance spectroscopy, and various field-effect transistor based methods are presented along with selected promising novel approaches, such as nanowire or magnetic nanoparticle-based biosensing. Additional measurement techniques, which have been shown useful in combination with electrochemical detection, are also summarized, such as the electrochemical versions of surface plasmon resonance, optical waveguide lightmode spectroscopy, ellipsometry, quartz crystal microbalance, and scanning probe microscopy. The signal transduction and the general performance of electrochemical sensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale. The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor. New nanotechnology-based approaches, such as the use of engineered ion-channels in lipid bilayers, the encapsulation of enzymes into vesicles, polymersomes, or polyelectrolyte capsules provide additional possibilities for signal amplification. In particular, this review highlights the importance of the precise control over the delicate

  12. On the Use of Experimental Methods to Improve Confidence in Educed Impedance

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Watson, Willie R.

    2011-01-01

    Results from impedance eduction methods developed by NASA Langley Research Center are used throughout the acoustic liner community. In spite of recent enhancements, occasional anomalies persist with these methods, generally at frequencies where the liner produces minimal attenuation. This investigation demonstrates an experimental approach to educe impedance with increased confidence over a desired frequency range, by combining results from successive tests with different cavity depths. A series of tests is conducted with three wire-mesh facesheets, for which the results should be weakly dependent on source sound pressure level and mean grazing flow speed. First, a raylometer is used to measure the DC flow resistance of each facesheet. These facesheets are then mounted onto a frame and a normal incidence tube is used to determine their respective acoustic impedance spectra. A comparison of the acoustic resistance component with the DC flow resistance for each facesheet is used to validate the measurement process. Next, each facesheet is successively mounted onto three frames with different cavity depths, and a grazing flow impedance tube is used to educe their respective acoustic impedance spectra with and without mean flow. The no-flow results are compared with those measured in the normal incidence tube to validate the impedance eduction method. Since the anti-resonance frequency varies with cavity depth, each sample provides robust results over a different frequency range. Hence, a combination of results can be used to determine the facesheet acoustic resistance. When combined with the acoustic reactance, observed to be weakly dependent on the source sound pressure level and grazing flow Mach number, the acoustic impedance can be educed with increased confidence. Representative results of these tests are discussed, and the complete database is available in electronic format upon request.

  13. Symmetric cell approach and impedance spectroscopy of high power lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Liu, J.; Amine, K.

    High power lithium-ion cells are a very promising energy source for practical hybrid vehicles. It is found that the impedance of the 18650 high-power cells using LiNi 0.8Co 0.2O 2 chemistry increases with time during the beginning period of storage. A symmetric cell approach is developed to distinguish the anode and cathode effects on the impedance rise. Cathode impedance, especially charge-transfer resistance, is identified as the main component of the cell impedance and is most responsible for the rise of the cell impedance during storage at room temperature. With analysis of impedance spectra from a variety of cells, the charge-transfer process is thought to take place at the interface between the electrolyte solution and the surface of surface layers on the electrode. We also propose that the surface layers might be mixed conductors of electrons and lithium ions, instead of pure lithium-ion conductors. The nature of the surface layers on the cathode is likely different from that of the surface layers on the anode.

  14. Symmetric cell approach and impedance spectroscopy of high power lithium-ion batteries.

    SciTech Connect

    Chen, C. H.; Liu, J.; Amine, K.; Chemical Engineering

    2001-06-15

    High power lithium-ion cells are a very promising energy source for practical hybrid vehicles. It is found that the impedance of the 18650 high-power cells using LiNi{sub 0.8}Co{sub 0.2}O{sub 2} chemistry increases with time during the beginning period of storage. A symmetric cell approach is developed to distinguish the anode and cathode effects on the impedance rise. Cathode impedance, especially charge-transfer resistance, is identified as the main component of the cell impedance and is most responsible for the rise of the cell impedance during storage at room temperature. With analysis of impedance spectra from a variety of cells, the charge-transfer process is thought to take place at the interface between the electrolyte solution and the surface of surface layers on the electrode. We also propose that the surface layers might be mixed conductors of electrons and lithium ions, instead of pure lithium-ion conductors. The nature of the surface layers on the cathode is likely different from that of the surface layers on the anode.

  15. Development and Validation of an Interactive Liner Design and Impedance Modeling Tool

    NASA Technical Reports Server (NTRS)

    Howerton, Brian M.; Jones, Michael G.; Buckley, James L.

    2012-01-01

    The Interactive Liner Impedance Analysis and Design (ILIAD) tool is a LabVIEW-based software package used to design the composite surface impedance of a series of small-diameter quarter-wavelength resonators incorporating variable depth and sharp bends. Such structures are useful for packaging broadband acoustic liners into constrained spaces for turbofan engine noise control applications. ILIAD s graphical user interface allows the acoustic channel geometry to be drawn in the liner volume while the surface impedance and absorption coefficient calculations are updated in real-time. A one-dimensional transmission line model serves as the basis for the impedance calculation and can be applied to many liner configurations. Experimentally, tonal and broadband acoustic data were acquired in the NASA Langley Normal Incidence Tube over the frequency range of 500 to 3000 Hz at 120 and 140 dB SPL. Normalized impedance spectra were measured using the Two-Microphone Method for the various combinations of channel configurations. Comparisons between the computed and measured impedances show excellent agreement for broadband liners comprised of multiple, variable-depth channels. The software can be used to design arrays of resonators that can be packaged into complex geometries heretofore unsuitable for effective acoustic treatment.

  16. Ac Impedance Spectroscopy Of Al/A-Sic/C-Si(P)/Al Heterostructure under Illumination

    NASA Astrophysics Data System (ADS)

    Perný, Milan; Šály, Vladimír; Váry, Michal; Mikolášek, Miroslav; Huran, Jozef; Packa, Juraj

    2014-05-01

    The amorphous silicon carbide/crystalline silicon heterojunction was prepared and analyzed. The current-voltage (I - V ) measurements showed the barrier properties of prepared sample. Biased impedance spectra of Al/a-SiC/c-Si(p)/Al heterojunction under the standard illumination are reported and analyzed. AC measurements in the illuminated conditions were processed in order to identify electronic behavior using equivalent AC circuit which was suggested and obtained by fitting the measured impedance data. A phenomenon of negative capacitance/resistance in certain frequency range has been observed.

  17. Effects of Nb-doped on the structure and electrochemical performance of LiFePO{sub 4}/C composites

    SciTech Connect

    Ma, Zhipeng; Shao, Guangjie; Wang, Guiling; Zhang, Ying; Du, Jianping

    2014-02-15

    The olivine-type niobium doping Li{sub 1−x}Nb{sub x}FePO{sub 4}/C (x=0, 0.005, 0.010, 0.015, 0.025) cathode materials were synthesized via a two-step ball milling solid state reaction. The effects of Nb doping were charactered by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), galvanostatic intermittent titration technique (GITT), cyclic voltammetry (CV), electrochemical impedance spectra (EIS) and galvanostatic charge–discharge. It is found that Nb doping enlarges the interplanar distance of crystal plane parallel to [0 1 0] direction in LiFePO{sub 4}. In other words, it widens the one dimensional diffusion channels of Li{sup +} along the [0 1 0] direction. Electrochemical test results indicate that the Li{sub 0.99}Nb{sub 0.01}FePO{sub 4}/C composite exhibits the best electrochemical performance with initial special discharge capacity of 139.3 mA h g{sup −1} at 1 C rate. The present synthesis route is promising in making the solid state reaction method more practical for preparation of the LiFePO{sub 4} material. - Graphical abstract: The proper amount of Nb doping widens the one dimensional diffusion channels of Li{sup +} along the [0 1 0] direction. Display Omitted - Highlights: • The Nb doping LiFePO{sub 4}/C is prepared by a facile two-step ball milling solid state reaction. • The sample possesses the better high-rate performance. • The tap density of Li{sub 0.99}Nb{sub 0.01}FePO{sub 4}/C sample is 1.76 g cm{sup −3}.

  18. Chronic impedance spectroscopy of an endovascular stent-electrode array

    NASA Astrophysics Data System (ADS)

    Opie, Nicholas L.; John, Sam E.; Rind, Gil S.; Ronayne, Stephen M.; Grayden, David B.; Burkitt, Anthony N.; May, Clive N.; O’Brien, Terence J.; Oxley, Thomas J.

    2016-08-01

    Objective. Recently, we reported a minimally invasive stent-electrode array capable of recording neural signals from within a blood vessel. We now investigate the use of electrochemical impedance spectroscopy (EIS) measurements to infer changes occurring to the electrode–tissue interface from devices implanted in a cohort of sheep for up to 190 days. Approach. In a cohort of 15 sheep, endovascular stent-electrode arrays were implanted in the superior sagittal sinus overlying the motor cortex for up to 190 days. EIS was performed routinely to quantify viable electrodes for up to 91 days. An equivalent circuit model (ECM) was developed from the in vivo measurements to characterize the electrode–tissue interface changes occurring to the electrodes chronically implanted within a blood vessel. Post-mortem histological assessment of stent and electrode incorporation into the wall of the cortical vessels was compared to the electrical impedance measurements. Main results. EIS could be used to infer electrode viability and was consistent with x-ray analysis performed in vivo, and post-mortem evaluation. Viable electrodes exhibited consistent 1 kHz impedances across the 91 day measurement period, with the peak resistance frequency for the acquired data also stable over time. There was a significant change in 100 Hz phase angles, increasing from ‑67.8° ± 8.8° at day 0 to ‑43.8° ± 0.8° at day 91, which was observed to stabilize after eight days. ECM’s modeled to the data suggested this change was due to an increase in the capacitance of the electrode–tissue interface. This was supported by histological assessment with >85% of the implanted stent struts covered with neointima and incorporated into the blood vessel within two weeks. Conclusion. This work demonstrated that EIS could be used to determine the viability of electrode implanted chronically within a blood vessel. Impedance measurements alone were not observed to be a useful predictor of alterations

  19. One-step electrochemical synthesis of a graphene–ZnO hybrid for improved photocatalytic activity

    SciTech Connect

    Wei, Ang; Xiong, Li; Sun, Li; Liu, Yanjun; Li, Weiwei; Lai, Wenyong; Liu, Xiangmei; Wang, Lianhui; Huang, Wei; Dong, Xiaochen

    2013-08-01

    Graphical abstract: - Highlights: • Graphene–ZnO hybrid was synthesized by one-step electrochemical deposition. • Graphene–ZnO hybrid presents a special structure and wide UV–vis absorption spectra. • Graphene–ZnO hybrid exhibits an exceptionally higher photocatalytic activity for the degradation of dye methylene blue. - Abstract: A graphene–ZnO (G-ZnO) hybrid was synthesized by one-step electrochemical deposition. During the formation of ZnO nanostructure by cathodic electrochemical deposition, the graphene oxide was electrochemically reduced to graphene simultaneously. Scanning electron microscope images, X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectra, and UV–vis absorption spectra indicate the resulting G-ZnO hybrid presents a special structure and wide UV–vis absorption spectra. More importantly, it exhibits an exceptionally higher photocatalytic activity for the degradation of dye methylene blue than that of pure ZnO nanostructure under both ultraviolet and sunlight irradiation.

  20. Electrochemical Corrosion of Stainless Steel in Thiosulfate Solutions Relevant to Gold Leaching

    NASA Astrophysics Data System (ADS)

    Choudhary, Lokesh; Wang, Wei; Alfantazi, Akram

    2016-01-01

    This study aims to characterize the electrochemical corrosion behavior of stainless steel in the ammoniacal thiosulfate gold leaching solutions. Electrochemical corrosion response was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy, while the semi-conductive properties and the chemical composition of the surface film were characterized using Mott-Schottky analysis and X-ray photoelectron spectroscopy, respectively. The morphology of the corroded specimens was analyzed using scanning electron microscopy. The stainless steel 316L showed no signs of pitting in the ammoniacal thiosulfate solutions.

  1. Solid-phase electrochemical reduction of graphene oxide films in alkaline solution

    PubMed Central

    2013-01-01

    Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO. PMID:24059434

  2. TECHNICAL NOTE: Portable audio electronics for impedance-based measurements in microfluidics

    NASA Astrophysics Data System (ADS)

    Wood, Paul; Sinton, David

    2010-08-01

    We demonstrate the use of audio electronics-based signals to perform on-chip electrochemical measurements. Cell phones and portable music players are examples of consumer electronics that are easily operated and are ubiquitous worldwide. Audio output (play) and input (record) signals are voltage based and contain frequency and amplitude information. A cell phone, laptop soundcard and two compact audio players are compared with respect to frequency response; the laptop soundcard provides the most uniform frequency response, while the cell phone performance is found to be insufficient. The audio signals in the common portable music players and laptop soundcard operate in the range of 20 Hz to 20 kHz and are found to be applicable, as voltage input and output signals, to impedance-based electrochemical measurements in microfluidic systems. Validated impedance-based measurements of concentration (0.1-50 mM), flow rate (2-120 µL min-1) and particle detection (32 µm diameter) are demonstrated. The prevailing, lossless, wave audio file format is found to be suitable for data transmission to and from external sources, such as a centralized lab, and the cost of all hardware (in addition to audio devices) is ~10 USD. The utility demonstrated here, in combination with the ubiquitous nature of portable audio electronics, presents new opportunities for impedance-based measurements in portable microfluidic systems.

  3. Rotor damage detection by using piezoelectric impedance

    NASA Astrophysics Data System (ADS)

    Qin, Y.; Tao, Y.; Mao, Y. F.

    2016-04-01

    Rotor is a core component of rotary machinery. Once the rotor has the damage, it may lead to a major accident. Thus the quantitative rotor damage detection method based on piezoelectric impedance is studied in this paper. With the governing equation of piezoelectric transducer (PZT) in a cylindrical coordinate, the displacement along the radius direction is derived. The charge of PZT is calculated by the electric displacement. Then, by the use of the obtained displacement and charge, an analytic piezoelectric impedance model of the rotor is built. Given the circular boundary condition of a rotor, annular elements are used as the analyzed objects and spectral element method is used to set up the damage detection model. The Electro-Mechanical (E/M) coupled impedance expression of an undamaged rotor is deduced with the application of a low-cost impedance test circuit. A Taylor expansion method is used to obtain the approximate E/M coupled impedance expression for the damaged rotor. After obtaining the difference between the undamaged and damaged rotor impedance, a rotor damage detection method is proposed. This method can directly calculate the change of bending stiffness of the structural elements, it follows that the rotor damage can be effectively detected. Finally, a preset damage configuration is used for the numerical simulation. The result shows that the quantitative damage detection algorithm based on spectral element method and piezoelectric impedance proposed in this paper can identify the location and the severity of the damaged rotor accurately.

  4. Estimates of Acausal Joint Impedance Models

    PubMed Central

    Perreault, Eric J.

    2013-01-01

    Estimates of joint or limb impedance are commonly used in the study of how the nervous system controls posture and movement, and how that control is altered by injury to the neural or musculoskeletal systems. Impedance characterizes the dynamic relationship between an imposed perturbation of joint position and the torques generated in response. While there are many practical reasons for estimating impedance rather than its inverse, admittance, it is an acausal representation of the limb mechanics that can lead to difficulties in interpretation or use. The purpose of this study was to explore the acausal nature of nonparametric estimates of joint impedance representations to determine how they are influenced by common experimental and computational choices. This was accomplished by deriving discrete-time realizations of first-and second-order derivatives to illustrate two key difficulties in the physical interpretation of impedance impulse response functions. These illustrations were provided using both simulated and experimental data. It was found that the shape of the impedance impulse response depends critically on the selected sampling rate, and on the bandwidth and noise characteristics of the position perturbation used during the estimation process. These results provide important guidelines for designing experiments in which nonparametric estimates of impedance will be obtained, especially when those estimates are to be used in a multistep identification process. PMID:22907963

  5. Estimates of acausal joint impedance models.

    PubMed

    Westwick, David T; Perreault, Eric J

    2012-10-01

    Estimates of joint or limb impedance are commonly used in the study of how the nervous system controls posture and movement, and how that control is altered by injury to the neural or musculoskeletal systems. Impedance characterizes the dynamic relationship between an imposed perturbation of joint position and the torques generated in response. While there are many practical reasons for estimating impedance rather than its inverse, admittance, it is an acausal representation of the limb mechanics that can lead to difficulties in interpretation or use. The purpose of this study was to explore the acausal nature of nonparametric estimates of joint impedance representations to determine how they are influenced by common experimental and computational choices. This was accomplished by deriving discrete-time realizations of first- and second-order derivatives to illustrate two key difficulties in the physical interpretation of impedance impulse response functions. These illustrations were provided using both simulated and experimental data. It was found that the shape of the impedance impulse response depends critically on the selected sampling rate, and on the bandwidth and noise characteristics of the position perturbation used during the estimation process. These results provide important guidelines for designing experiments in which nonparametric estimates of impedance will be obtained, especially when those estimates are to be used in a multistep identification process. PMID:22907963

  6. Measurements of electrical impedance of biomedical objects.

    PubMed

    Frączek, Marcin; Kręcicki, Tomasz; Moron, Zbigniew; Krzywaźnia, Adam; Ociepka, Janusz; Rucki, Zbigniew; Szczepanik, Zdzisław

    2016-01-01

    Some basic problems related to measurements of electrical impedance of biological objects (bioimpedance) have been presented in this paper. Particularly problems arising from impedance occurring at the sensor-tissue interface (interfacial impedances) in contact measuring methods have been discussed. The influence of finite values of impedances of the current source and voltage measuring device has also been taken into consideration. A model of the impedance sensor for the four-electrode measurement method containing the interfacial, source and measuring device impedances has been given and its frequency characteristics obtained by the computer simulation have been presented. The influence of these impedances on the shape of frequency characteristic of the sensor model has been discussed. Measurements of bioimpedance of healthy and anomalous soft tissues have been described. Some experimental results, particularly the frequency characteristics of bioimpedance, have been shown. The presented results of measurement show that bioimpedance can be a valuable source of information about the tissues, so measurement of bioimpedance can be a useful supplement to other medical diagnostic methods. PMID:27151250

  7. Electrochemical behavior of chemically synthesized selenium thin film.

    PubMed

    Patil, A M; Kumbhar, V S; Chodankar, N R; Lokhande, A C; Lokhande, C D

    2016-05-01

    The facile and low cost simple chemical bath deposition (CBD) method is employed to synthesize red colored selenium thin films. These selenium films are characterized for structural, morphological, topographical and wettability studies. The X-ray diffraction (XRD) pattern showed the crystalline nature of selenium thin film with hexagonal crystal structure. The scanning electron microscopy (SEM) study displays selenium nanoparticles ranging from 20 to 475nm. A specific surface area of 30.5m(2)g(-1) is observed for selenium nanoparticles. The selenium nanoparticles hold mesopores in the range of 1.39nm, taking benefits of the good physicochemical stability and excellent porosity. Subsequently, the electrochemical properties of selenium thin films are deliberated by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) techniques. The selenium thin film shows specific capacitance (Cs) of 21.98Fg(-1) with 91% electrochemical stability. PMID:26896773

  8. Fabrication and electrochemical performance of graphene—ZnO nanocomposites

    NASA Astrophysics Data System (ADS)

    Li, Zhen-Peng; Men, Chuan-Ling; Wang, Wan; Cao, Jun

    2014-05-01

    Graphene—ZnO nanocomposites were synthesized successfully through a one-step solvothermal approach. The morphology, structure, and composition of the prepared nanocomposites were investigated by scanning electron microscopy (SEM), transmission electron microscope (TEM), laser micro Raman spectroscopy, and Fourier transform infra-red spectroscopy (FT-IR). The outcomes confirmed that this approach is comparatively steady, practicable, and operable compared with other reported methods. The electrochemical performance of the graphene-ZnO electrodes was analyzed through cyclic voltammetry, altering-current (AC) impedance, and chronopotentiometry tests. The graphene—ZnO electrodes exhibited an improved electrode performance with higher specific capacitance (115 F·g-1), higher electrochemical stability, and higher energy density than the graphene electrodes and most reported graphene—ZnO electrodes. Graphene—ZnO nanocomposites have a steady reversible charge/discharge behavior, which makes them promising candidates for electrochemical capacitors (ECs).

  9. Single Mode Theory for Impedance Eduction in Large-Scale Ducts with Grazing Flow

    NASA Technical Reports Server (NTRS)

    Watson, Willie R.; Gerhold, Carl H.; Jones, Michael G.; June, Jason C.

    2014-01-01

    An impedance eduction theory for a rigid wall duct containing an acoustic liner with an unknown impedance and uniform grazing flow is presented. The unique features of the theory are: 1) non-planar waves propagate in the hard wall sections of the duct, 2) input data consist solely of complex acoustic pressures acquired on a wall adjacent to the liner, and 3) multiple higher-order modes may exist in the direction perpendicular to the liner and the opposite rigid wall. The approach is to first measure the axial propagation constant of a dominant higher-order mode in the liner sample section. This axial propagation constant is then used in conjunction with a closed-form solution to a reduced form of the convected Helmholtz equation and the wall impedance boundary condition to educe the liner impedance. The theory is validated on a conventional liner whose impedance spectrum is educed in two flow ducts with different cross sections. For the frequencies and Mach numbers of interest, no higher-order modes propagate in the hard wall sections of the smaller duct. A benchmark method is used to educe the impedance spectrum in this duct. A dominant higher-order vertical mode propagates in the larger duct for similar test conditions, and the current theory is applied to educe the impedance spectrum. Results show that when the theory is applied to data acquired in the larger duct with a dominant higher-order vertical mode, the same impedance spectra is educed as that obtained in the small duct where only the plane wave mode is present and the benchmark method is used. This result holds for each higher-order vertical mode that is considered.

  10. An impedance study of two types of stainless steel in Ringer physiological solution containing complexing agents.

    PubMed

    Slemnik, Mojca; Milosev, Ingrid

    2006-10-01

    The effect of complexing agents EDTA and citric acid on the electrochemical behaviour of AISI 304 and orthopaedic stainless steels in Ringer physiological solution was investigated by potentiodynamic polarization method and electrochemical impedance spectroscopy (EIS). The content of Mo has a pronounced effect on the corrosion resistance, as evident by the broader passive range of the orthopaedic stainless steel containing Mo. The addition of complexing agents induces significant changes in polarization and impedance characteristics, i.e., the shift of corrosion and breakdown potentials in a more negative direction, an increase in current density, and a significant decrease in charge transfer resistance. The results were interpreted by the formation of soluble complexes of metal ions with chelating agents, especially EDTA, which suppressed the formation of the outer Fe(III) layer of the passive film. The impact of complexing agent on the electrochemical parameters was found to be related to its concentration in electrolyte and the stability constant of the complex formed with the related metal ion. PMID:16977388

  11. Electrochemical oxidation of cholesterol

    PubMed Central

    2015-01-01

    Summary Indirect cholesterol electrochemical oxidation in the presence of various mediators leads to electrophilic addition to the double bond, oxidation at the allylic position, oxidation of the hydroxy group, or functionalization of the side chain. Recent studies have proven that direct electrochemical oxidation of cholesterol is also possible and affords different products depending on the reaction conditions. PMID:25977713

  12. Electrochemical cell stack assembly

    DOEpatents

    Jacobson, Craig P.; Visco, Steven J.; De Jonghe, Lutgard C.

    2010-06-22

    Multiple stacks of tubular electrochemical cells having a dense electrolyte disposed between an anode and a cathode preferably deposited as thin films arranged in parallel on stamped conductive interconnect sheets or ferrules. The stack allows one or more electrochemical cell to malfunction without disabling the entire stack. Stack efficiency is enhanced through simplified gas manifolding, gas recycling, reduced operating temperature and improved heat distribution.

  13. Summary of the impedance working group

    SciTech Connect

    Chao, A.W.

    1995-05-01

    The impedance working group concentrated on the LHC design during the workshop. They look at the impedance contributions of liner, beam position monitors, shielded bellows, experimental chambers, superconducting cavities, recombination chambers, space charge, kickers, and the resistive wall. The group concluded that the impedance budgeting and the conceptual designs of the vacuum chamber components looked basically sound. It also noted, not surprisingly, that a large amount of studies are to be carried out further, and it ventured to give a partial list of these studies.

  14. FDTD modeling of thin impedance sheets

    NASA Technical Reports Server (NTRS)

    Luebbers, Raymond; Kunz, Karl

    1991-01-01

    Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. It is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods. These sheets are characterized by a discontinuity in the tangential magnetic field on either side of the sheet but no discontinuity in tangential electric field. This continuity, or single valued behavior of the electric field, allows the sheet current to be expressed in terms of an impedance multiplying this electric field.

  15. Koch fractal boundary patch over reactive impedance

    NASA Astrophysics Data System (ADS)

    Reddy V, Venkateshwar; Sarma, N. V. S. N.

    2013-04-01

    This paper describes the enhancement of bandwidth and miniaturization for patch antennas. Introduction of fractal structure (Square Koch) over reactive impedance surface (RIS) is used to enhance impedance bandwidth while minimizing the patch size. Comparison has been made with those of a single-layer (sub1) antenna and the corresponding dual-layer (RIS) antenna. Approximately double the impedance bandwidth is achieved with the proposed RIS Square Koch antenna 1 when compared with Square Koch antenna 1without RIS. There is a 55 % reduction in the patch size. The simulated results indicate that the presented antennas provide gain of about 2.5dBi over the entire band of frequencies.

  16. RHIC ABORT KICKER WITH REDUCED COUPLING IMPEDANCE.

    SciTech Connect

    HAHN,H.; DAVINO,D.

    2002-06-02

    Kicker magnets typically represent the most important contributors to the transverse impedance budget of accelerators and storage rings. Methods of reducing the impedance value of the SNS extraction kicker presently under construction and, in view of a future performance upgrade, that of the RHIC abort kicker have been thoroughly studied at this laboratory. In this paper, the investigation of a potential improvement from using ferrite different from the BNL standard CMD5005 is reported. Permeability measurements of several ferrite types have been performed. Measurements on two kicker magnets using CMD5005 and C2050 suggest that the impedance of a magnet without external resistive damping, such as the RHIC abort kicker, would benefit.

  17. Effect of Resonator Axis Skew on Normal Incidence Impedance

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Jones, Michael G.; Homeijer, Brian

    2003-01-01

    High by-pass turbofan engines have fewer fan blades and lower rotation speeds than their predecessors. Consequently, the noise suppression at the low frequency end of the noise spectra has become an increasing concern. This has led to a renewed emphasis on improving noise suppression efficiency of passive, duct liner treatments at the lower frequencies. For a variety of reasons, passive liners are comprised of locally-reacting, resonant absorbers. One reason for this design choice is to satisfy operational and economic requirements. The simplest liner design consists of a single layer of honeycomb core sandwiched between a porous facesheet and an impervious backing plate. These resonant absorbing structures are integrated into the nacelle wall and are very ef- ficient over a limited bandwidth centered on their resonance frequency. Increased noise suppression bandwidth and greater suppression at lower frequencies is typically achieved for conventional liners by increasing the liner depth and incorporating thin porous septa into the honeycomb core. However, constraints on liner depth in modern high by-pass engine nacelles severely limit the suppression bandwidth extension to lower frequencies. Also, current honeycomb core liners may not be suitable for irregular geometric volumes heretofore not considered. It is of interest, therefore, to find ways to circumvent liner depth restrictions and resonator cavity shape constraints. One way to increase effective liner depth is to skew the honeycomb core axis relative to the porous facesheet surface. Other possibilities are to alter resonator cavity shape, e.g. high aspect ratio, narrow channels that possibly include right angle bends, 180. channel fold-backs, and splayed channel walls to conform to irregular geometric constraints. These possibilities constitute the practical motivation for expanding impedance modeling capability to include unconventional resonator orientations and shapes. The work reported in this paper is

  18. Optimal multisine excitation design for broadband electrical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Sanchez, B.; Vandersteen, G.; Bragos, R.; Schoukens, J.

    2011-11-01

    Electrical impedance spectroscopy (EIS) can be used to characterize biological materials in applications ranging from cell culture to body composition, including tissue and organ state. The emergence of cell therapy and tissue engineering opens up a new and promising field of application. While in most cases classical measurement techniques based on a frequency sweep can be used, EIS based on broadband excitations enables dynamic biological systems to be characterized when the measuring time and injected energy are a constraint. Myocardial regeneration, cell characterization in micro-fluidic systems and dynamic electrical impedance tomography are all examples of such applications. The weakness of such types of fast EIS measuring techniques resides in their intrinsic loss of accuracy. However, since most of the practical applications have no restriction over the excitation used, the input power spectrum can be appropriately designed to maximize the accuracy obtained from the measurements. This paper deals with the problem of designing the optimal multisine excitation for electrical bioimpedance measurements. The optimal multisine is obtained by the minimization of the Cramer-Rao lower bound, or what is the same, by maximizing the accuracy obtained from the measurements. Furthermore, because no analytical solution exists for global optimization involving time and frequency domains jointly, this paper presents the multisine optimization approach partially in both domains and then combines the results. As regards the frequency domain approach, a novel contribution is made for the multisine amplitude power spectrum. In the time domain, multisine is optimized by reducing its crest factor. Moreover, the impact on the information and accuracy of the impedance spectrum obtained from using different multisine amplitude power spectra is discussed, as well as the number of frequencies and frequency distributions. The theory is supported by a set of validation measurements when

  19. Carbon-Based Materials for Lithium-Ion Batteries, Electrochemical Capacitors, and Their Hybrid Devices.

    PubMed

    Yao, Fei; Pham, Duy Tho; Lee, Young Hee

    2015-07-20

    A rapidly developing market for portable electronic devices and hybrid electrical vehicles requires an urgent supply of mature energy-storage systems. As a result, lithium-ion batteries and electrochemical capacitors have lately attracted broad attention. Nevertheless, it is well known that both devices have their own drawbacks. With the fast development of nanoscience and nanotechnology, various structures and materials have been proposed to overcome the deficiencies of both devices to improve their electrochemical performance further. In this Review, electrochemical storage mechanisms based on carbon materials for both lithium-ion batteries and electrochemical capacitors are introduced. Non-faradic processes (electric double-layer capacitance) and faradic reactions (pseudocapacitance and intercalation) are generally explained. Electrochemical performance based on different types of electrolytes is briefly reviewed. Furthermore, impedance behavior based on Nyquist plots is discussed. We demonstrate the influence of cell conductivity, electrode/electrolyte interface, and ion diffusion on impedance performance. We illustrate that relaxation time, which is closely related to ion diffusion, can be extracted from Nyquist plots and compared between lithium-ion batteries and electrochemical capacitors. Finally, recent progress in the design of anodes for lithium-ion batteries, electrochemical capacitors, and their hybrid devices based on carbonaceous materials are reviewed. Challenges and future perspectives are further discussed. PMID:26140707

  20. Electrochemical thermodynamic measurement system

    DOEpatents

    Reynier, Yvan; Yazami, Rachid; Fultz, Brent T.

    2009-09-29

    The present invention provides systems and methods for accurately characterizing thermodynamic and materials properties of electrodes and electrochemical energy storage and conversion systems. Systems and methods of the present invention are configured for simultaneously collecting a suite of measurements characterizing a plurality of interconnected electrochemical and thermodynamic parameters relating to the electrode reaction state of advancement, voltage and temperature. Enhanced sensitivity provided by the present methods and systems combined with measurement conditions that reflect thermodynamically stabilized electrode conditions allow very accurate measurement of thermodynamic parameters, including state functions such as the Gibbs free energy, enthalpy and entropy of electrode/electrochemical cell reactions, that enable prediction of important performance attributes of electrode materials and electrochemical systems, such as the energy, power density, current rate and the cycle life of an electrochemical cell.