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Yuan, Qifan. "Physical, electrical and electrochemical characterizations of transition metal compounds for electrochemical energy storage." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/71869.
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Electrochemical energy storage has been widely used in various areas, including new energy sources, auto industry, and information technology. However, the performance of current electrochemical energy storage devices does not meet the requirements of these areas that include both high energy and power density, fast recharge time, and long lifetime. One solution to meet consumer demands is to discover new materials that can substantially enhance the performance of electrochemical energy storage devices. In this dissertation we report four transition metal materials systems with potential applications in electrochemical energy storage.
Nanoscale and nanostructured materials are expected to play important roles in energy storage devices because of their enhanced and sometimes unique physical and chemical properties. Studied here is the comparative electrochemical cation insertion into a nanostructured vanadium oxide, a promising electrode material candidate, for the alkali metal ions Li+, Na+ and K+ and the organic ammonium ion, in aqueous electrolyte solutions. Observed are the distinctive insertion processes of the different ions, which yield a correlation between physical degradation of the material and a reduction of the calculated specific charge. The results reveal the potential of this nanostructured vanadium oxide material for energy storage. Vanadium based electrochemical systems are of general interest, and as models for vanadium based solid-state electrochemical processes, the solution state and the solid-state electrochemical properties of two cryolite-type compounds, (NH4)3VxGa1-xF6, and Na3VF6, are studied. The electrochemical behavior of (NH4)3VxGa1-xF6 explored the possibility of using this material as an electrolyte for solid state energy storage systems.
Zeolite-like materials have large surface to volume ratios, with ions and neutral species located in the nanometer sized pores of the 3-dimensional framework, potentially yielding high energy density storage capabilities. Yet the insulating nature of known zeolite-like materials has limited their use for electrical energy storage. Studied here are two vanadium based zeolite-like structures, the oxo-vanadium arsenate [(As6V15O51)-9]∞, and the oxo-vanadium phosphate [(P6V15O51)-9]∞, where the former shows electronic conduction in the 3-dimensional framework. Mixed electronic and ionic conductivity, from the framework and from the cations located within the framework, respectively, is measured in the oxo-vanadium arsenate, and allows the use of this material in electrochemical double-layer capacitor configuration for energy storage. By contrast, the oxo-vanadium phosphate shows ionic conduction only. Lastly, a new strontium manganese vanadate with a layered structure exhibiting mixed protonic and electronic conductivity is studied. The various transition metal compounds and materials systems experimentally studied in this thesis showcase the importance of novel materials in future energy storage schemes.Ph. D.
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Gopal, Venkatesh. "Synthesis, structural and electrochemical characterizations of new materials for li-ion batteries." Caen, 2013. http://www.theses.fr/2013CAEN2082.
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Ce travail de thèse est axée sur la découverte de nouveaux matériaux d'électrodes utilisées dans les batteries Li ou Na ion et rechargeables. Notre approche pour générer et identifier de nouveaux matériaux d'électrode à fort potentiel est basé sur la synthèse directe par chimie douce (précipitations, hydrothermale), échange d'ions et réactions électrochimiques d'oxydation/réduction. Dans le système des oxydes de vanadium, une nouvelle classe de matériau a été synthétisé avec la formule générale AVO3 (avec A = Li, Na, Ag, Cu). Dans le cas du lithium, nous avons observé la formation d’une nouvelle phase Li2VO3 de structure NaCl désordonnée délivrant une capacité spécifique réversible de 250 mAh/g à un potentiel moyen de 2,5 V vs Li/Li+. Un autre nouveau matériau d'électrode à base de phosphate de vanadium Na2VO(HPO4)2 a été préparé par échange ionique à partir du phosphate acide de vanadium VO(H2PO4)2. Ce composé est un conducteur ionique ( = 10-3S/cm à 200°C) et livré une capacité spécifique de 70 mAh/g à tension plus élevée ~ 3,9 V vs Li/Li+ avec une excellente réversibilité. A la recherche de nouvelles compositions dans le système Li-M-O, nous avons synthétisé la nouvelle phase Li5W2O7 à partir de la phase en ruban Li2W2O7 par insertion électrochimique de lithium. Cette phase présente une structure de type NaCl ordonnée et un comportement électrochimique attrayant avec une capacité spécifique initiale de 162 mAh/g. Nous avons étudié également la phase Ag2W2O7 iso-structurale qui offre quant à elle une capacité de 193 mAh/gThis thesis work is focused on the discovery of new electrode materials used in rechargeable lithium and sodium ion batteries. Our approach to generate and identify new high potential electrode materials is based on direct soft chemistry synthesis (precipitation, hydrothermal), ion exchange and electrochemical oxidation/reduction reactions. In the A-V-O system (A=Li, Na, Ag, Cu), a new class of material has been synthesized by lithium/sodium insertion with the general formula A2VO3. We found that the fully reduced phase Li2VO3 is showing a disordered rock-salt-type structure and delivered a reversible specific capacity of 250 mAh/g at an average potential of 2. 5 V vs. Li+/Li. Another candidate Li5W2O7 has been explored as new electrode material for Li-ion batteries in the A-W-O system. Starting from the ribbon-type structure Li2W2O7, the fully reduced phase Li5W2O7 is showing an ordered rock-salt-type structure and the electrochemical behavior of these new phases is attractive with an initial specific capacity of 162 mAh/g. We studied also the iso-structural phase Ag2W2O7 and it delivers a capacity of 193 mAh/g. Another new electrode material based on vanadium phosphate Na2VO(HPO4)2 has been prepared by ion exchange method starting from the acidic vanadium phosphate VO(H2PO4)2. This compound is an ionic conductor (=10-3S/cm at 200°C) and delivered a specific capacity of 70 mAh/g at higher voltage ~3. 9 V vs. Li/Li+ with an excellent reversibility
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Liu, Juan. "Electrochemical Characterizations and Theoretical Simulations of Transport Behaviors at Nanoscale Geometries and Interfaces." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/chemistry_diss/74.
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Since single nanopores were firstly proposed as a potential rapid and low-cost tool for DNA sequencing in 1990s (PNAS, 1996, 93, 13770), extensive studies on both biological and synthetic nanopores and nanochannels have been reported. Nanochannel based stochastic sensing at single molecular level has been widely reported through the detection of transient ionic current changes induced by geometry blockage due to analytes translocation. Novel properties, including ion current rectification (ICR), memristive and memcapacitive behaviors were reported. These fundamental properties of nanochannels arise from the nanoscale dimensions and enables applications not only in single molecule sensing, but also in drug delivery, electrochemical energy conversion, concentration enrichment and separation, nanoprecipitation, nanoelectronics etc. Electrostatic interactions at nanometer-scale between the fixed surface charges and mobile charges in solution play major roles in those applications due to high surface to volume ratio. However, the knowledge of surface charge density (SCD) at nanometer scale is inaccessible within nanoconfinement and often extrapolated from bulk planar values. The determination of SCD at nanometer scale is urgently needed for the interpretation of aforementioned phenomena. This dissertation mainly focuses on the determination of SCD confined at a nanoscale device with known geometry via combined electroanalytical measurements and theoretical simulation. The measured currents through charged nanodevices are different for potentials with the same amplitude but opposite polarities, which deviates away from linear Ohm's behavior, known as ICR. Through theoretical simulation of experiments by solving Poisson and Nernst-Planck equations, the SCD within nanoconfinement is directly quantified for the first time. An exponential gradient SCD is introduced on the interior surface of a conical nanopre based on the gradient distribution of applied electric field. The physical origin is proposed based on the facilitated deprotonation of surface functional groups by the applied electric field. The two parameters that describe the non-uniform SCD distribution: maximum SCD and distribution length are determined by fitting high- and low-conductivity current respectively. The model is validated and applied successfully for quantification and prediction of mass transport behavior in different electrolyte solutions. Furthermore, because the surface charge distribution, the transport behaviors are intrinsicaly heterogeneous at nanometer scale, the concept is extended to noninvasively determine the surface modification efficacy of individual nanopore devices. Preliminary results of single molecule sensing based on streptavidin-iminobiotin are included. The pH dependent binding affinity of streptavidin-iminobiotin binding is confirmed by different current change signals ("steps" and "spikes") observed at different pHs. Qualitative concentration and potential dependence have been established. The chemically modified nanopores are demonstrated to be reusable through regenerating binding surface.
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Kim, Youngseok. "Characterizations of alloying Cu effect on electrochemical reactions of Al-Cu solid solution alloys." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1143130451.
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Venot, Timothée. "Matériaux optiques actifs en couches minces : élaboration et caractérisation de systèmes tout-solides électrochromes à émissivité infrarouge variable." Thesis, Tours, 2014. http://www.theses.fr/2014TOUR4006.
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Les dispositifs électrochromes sont des dispositifs qui permettent de moduler la réflexion ou la transmission de la lumière. Ils recouvrent une grande variété d’applications dans le domaine du visible (vitrages intelligents) et dans le domaine de l’infrarouge (protection thermique des satellites et discrétion optique infrarouge). Les travaux présentés dans ce manuscrit répondent essentiellement à une problématique visant à élaborer un dispositif électrochrome tout solide à émissivité infrarouge variable par un procédé unique de pulvérisation cathodique magnétron. Une nouvelle architecture d’empilement avec une électrode de travail monocouche bi fonctionnelle a été choisie pour réunir les propriétés apportées classiquement par deux couches ou plus sur le haut des empilements électrochromes. Cette nouvelle architecture a nécessité la mise en place d’un procédé de dépôt original de pulvérisation cathodique réactive hydratée. Ce procédé a permis d’obtenir une électrode monocouche à base de trioxyde de tungstène réunissant les propriétés optiques et électroniques souhaitées. Il a également permis de déposer les autres couches de l’empilement, la contre-électrode à base de trioxyde de tungstène et les électrolytes solides conducteurs protoniques à base d’oxyde de tantale ou de zirconium. L’étude de l’ajout d’une couche d’encapsulation à base de dioxyde de cérium a également été menée. Cette architecture a permis d’obtenir un empilement électrochrome tout solide fonctionnel. Ce dispositif complet ainsi élaboré présente de bonnes propriétés optiques dans l’infrarouge en terme de modulation d’émissivité dans les bandes spectrales d’intérêt, à savoir 13 % en bande II et 31 % en bande IIIElectrochromic materials are devices for modulating the reflection or transmission of light. They cover a wide variety of applications in the visible range (smart windows) and the infrared range (thermal protection for satellites and optical infrared discretion). The works presented in this manuscript were essentially responding to the problem of developping an all solid electrochromic device with a variable infrared emissivity by a single process of magnetron sputtering. A new stacking architecture with a working bi functional monolayer electrode was chosen to bring the properties conventionally made by two or more layers on top of electrochromic device. This new architecture has required the establishment of an original deposit process of hydrated reactive sputtering. This process yielded a monolayer electrode based on tungsten trioxide combining the desired optical and electronic properties. It allowed to deposit other layers of the stack, the counter electrode based on tungsten trioxide and the proton conductive solid electrolyte based on tantalum or zirconium oxide. The study of the addition of an encapsulation layer based on cerium dioxide was also conducted. This architecture has resulted in a functional all-solid electrochromic stack. The complete device thus prepared exhibits good optical properties in the infrared emissivity in terms of modulation and in particular in the spectral bands of interest, namely 13 % in MW and 31 % in LW
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Adonisi, Thobeka. "Electrochemical characterization of platinum based." Thesis, University of the Western Cape, 2012. http://hdl.handle.net/11394/3801.
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Fuel cells convert chemical energy from a fuel into electricity through chemical reaction with oxygen. This possesses some challenges like slow oxygen reduction reaction (ORR),
overpotential, and methanol fuel cross over in a direct methanol fuel cell (DMFC). These
challenges cause inefficiency and use of higher amounts of the expensive platinum catalyst. Several binary catalysts with better ORR activity have been reported. In this study we investigate
the best catalyst with better ORR and MOR performances and lower over-potentials for PEMFC and DMFC applications by comparing the in-house catalysts (10%Pt/C, 20%Pt/C,
30%Pt15%Ru/C, 40%Pt20%Ru/C, 30%PtCo/C, 20%Pt20%Cu/C and 20%PtSn/C) with the commercial platinum based catalysts (10%Pt/C, 20%Pt/C, 20%Pt10%Ru/C, 20%PtCo/C, 20%PtCu/C and 20%PtSn/C) using the cyclic voltammetry and the rotating disk electrode to determine their oxygen reduction reaction and methanol tolerance. HRTEM and XRD techniques were used to determine their particle size, arrangement and the atomic composition. It was observed that the 20%Pt/C in-house catalyst gave the best ORR activity and higher methanol oxidation current peaks compared to others catalysts followed by 20%Pt10%Ru/C commercial catalyst. The 20%PtCo/C commercial, 30%PtCo/C in-house and 20%PtSn/C in-house catalysts were found to be the most methanol tolerant catalysts making them the best catalysts for ORR in DMFC. It was observed that the ORR activity of 20%PtCo/C commercial and 30%PtCo/C inhouse
catalysts were enhanced when heat treated at 350 0C. From XRD and HRTEM studies, the particle sizes were between 2.72nm to 5.02nm with little agglomeration but after the heat treatment, the particles were nicely dispersed on the carbon support.>Magister Scientiae - MSc
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Wasala, KWM Milinda Prabath. "ELECTROCHEMICAL CHARACTERIZATION OF EXFOLIATED GRAPHENE." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1418.
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In this research we have investigated electrochemical and impedance characteristics of liquid phase exfoliated graphene electrodes. The exfoliated graphene electrodes were characterized in Electrochemical Double Layer Capacitors (EDLCs) geometry. Liquid phase exfoliation was performed on bulk graphite powder in order to produces few layer graphene flakes in large quantities. The exfoliation processes produced few layer graphene based materials with increased specific surface area and were found to have suitable electrochemical charge storage capacities. Electrochemical evaluation and performance of exfoliated graphene electrodes were tested with Cyclic Voltammetry, constant current charging discharging and Electrochemical Impedance Spectroscopy (EIS) at ambient conditions. We have used several electrolytes in order to evaluate the effect of electrolyte in charge storage capacities. Specific capacitance value of ~ 47F/g and ~ 262F/g was measured for aqueous and ionic electrolytes respectively. These values are at least an order of magnitude higher than those obtained by using EDLC's electrodes fabricated with the bulk graphite powder. In addition these EDLC electrodes give consistently good performance over a wide range of scan rates and voltage windows. These encouraging results illustrate the exciting potential for high performance electrical energy storage devices based on liquid phase exfoliated graphene electrodes.
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Wagner, Mary Elizabeth S. B. Massachusetts Institute of Technology. "Advanced electrochemical characterization of copper deposition." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/110960.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 51-52).
The electrodeposition of copper metal in a concentrated sulfuric acid solution is reported to occur through a four-step mechanism: (I) the dehydration of Cu2+ (H2O)6, (II) the reduction of Cu2+ to cu+, (III) the dehydration cu+ (H2O)6-x, (IV) the reduction of Cu+ to copper metal. The dehydration steps have been found to be responsible for the pH-dependence of the electrodeposition reaction. It is also reported, although not well understood, that the presence of Fe2+ ions affects the reaction kinetics. In this work, the kinetics of copper electrodeposition were studied using alternating current cyclic voltammetry. The reaction was studied at a copper rotating disk electrode with varying concentrations of Cu2+ and Fe2+ . At sufficiently low pH, and a sufficiently high concentration of Fe2+ , the deposition kinetics may be slowed enough to separately observe the two electron transfer steps involved in copper reduction. It was found that Fe2+ ions affect the electrodeposition kinetic by slowing down reaction kinetics, particularly the second electron transfer reaction.
by Mary Elizabeth Wagner.
S.B.
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Brown, Craig J. "Characterization of a parallel plate electrochemical reactor." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358040.
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Huang, Jimin. "Characterization of Electrochemical Interfaces by INfrared Spectroscopy." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/30301.
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The properties of electrochemical interfaces are studied using Fourier transform infrared spectroscopy. Potential difference infrared spectroscopy (PDIRS) was used in the investigation of carbon monoxide adsorbed on polycrystalline platinum electrodes. It is found that the infrared peak position of adsorbed carbon monoxide is linearly dependent on the applied electrode potential, and that the Stark tuning rate is a function of system temperature. The change in Stark tuning rate is the result of the variation of the interfacial dielectric constant with temperature.
Self-assembled alkoxyalkanethiol monolayers were formed on gold substrates as surface modifiers of low dielectric constant designed to influence the interfacial capacitance. Polarization modulation infrared spectroscopy (PMIRS), ellipsometry, interfacial wetting, and cyclic voltammetry were conducted to characterize the modified interfaces. The interfacial capacitance is greatly reduced due to the adsorption of w-mercapto ethers on substrates. It was found that the solvation of the monolayer by solution is capable of improving the mass transport to maintain the Faradaic current while lowering the interfacial capacitance. The oxygen group in w-mercapto ethers at the monolayer-water interface interacts with water molecules to improve the monolayer solubility in water. The w-mercapto ether monolayers were found to be fluid-like in structure, giving better freedom to undergo structural change. The repulsion from the oxygen atoms in adjacent w-mercapto ether molecules adsorbed on the substrate introduces structural disorder to the alkyl chains in the monolayer, allowing better solvent permeation. This relieves some of the current blocking character of long chain alkanethiol monolayers. The interfacial contact angle to water for the w-mercapto ether monolayers is dependent on the oxygen position in the monolayer.
12-Methoxydodecanethiol has the lowest contact angle among all the w-mercapto ethers studied while 12-butoxydodecanethiol through 12-hexoxydodecanethiol have similar contact angles due to the ether oxygen being buried beneath several layers of methylene groups. The film thickness is roughly proportional to the total number of methylene groups in the two alkyl chains on w- mercapto ethers. w-Mercapto ethers that have a longer alkyl chain between the oxygen and thiol tend to form thicker monolayers on the substrates. In situ PMIRS measurements show that w-mercapto ether monolayers do not undergo structural change in the alkyl chains when in contact with either water or acetonitrile. The terminal methyl group, however, suffers from a shift in infrared peak position to lower frequency, and a decrease in peak height as the result of solvent load.Ph. D.
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Atcitty, Stanley. "Electrochemical Capacitor Characterization for Electric Utility Applications." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29613.
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Electrochemical capacitors (ECs) have received a significant level of interest for use in the electric utility industry for a variety of potential applications. For example, ECs integrated with a power conversion system can be used to assist the electric utility by providing voltage support, power factor correction, active filtering, and reactive and active power support. A number of electric utility applications have been proposed but, to date, ECs have not been very well characterized for use in these applications. Consequently, there is a need to gain a better understanding of ECs when used in electric utility applications. ECs are attractive for utility applications because they have higher energy density than conventional capacitors and higher power density than batteries. ECs also have higher cycle life than batteries, which results in longer life spans. To better understand the system dynamics when ECs are used for utility applications requires suitable models that can be incorporated into the variety of software programs currently used to create dynamic simulations for the applications, programs such as PSPICEâ ¢, MATLAB Simulinkâ ¢, and PSCADâ ¢. To obtain a relevant simulation with predictive capability, the behavior of the EC on which the model is based must be well defined; this necessitates a thorough understanding of the electrical characteristics of these devices.
This paper and the associated research focus on the use of the electrochemical impedance spectroscopy (EIS) to develop nonlinear equivalent circuit models to better understand and characterize symmetric ECs (SECs) for electric utility applications. It also focuses on the development of analytical solutions to better understand SEC efficiency and energy utilization.
Representative static synchronous compensator (StatCom) systems, with and with out SECs, were simulated and discussed. The temperature effects on device ionic resistance and capacitance are covered as is the effect of temperature on maximum power transfer to a resistive load. Experimental data showed that the SEC's double-layer capacitance and ionic resistance are voltage dependent. Therefore a voltage-dependent RC network model was developed and validated and the results showed that this type of model mimicked the experimental SEC better than traditional electrical models. Analytical solutions were developed for the efficiency and energy utilization of an SEC. The analytical solutions are a function of operating voltages, constant current, and ionic resistance. The operating voltage method is an important factor in system design because the power conversion interface is typically limited by a voltage window and thus can determine the performance of SECs during charge and discharge. If the operating voltage window is not properly selected the current rating of the system can be reduced thus limiting the SECs performance.Ph. D.
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BANGE, ADAM F. "DEVELOPMENT AND CHARACTERIZATION OF MINIATURIZED ELECTROCHEMICAL IMMUNOSENSORS." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1186764947.
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Lyons, Daniel Joseph. "Electrochemical Characterization of Ultra-Thin Silicon Films." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471727534.
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Subba, Rao Viruru Subbarao. "Electrochemical characterization of direct alcohol fuel cells using in-situ differential electrochemical mass spectrometry." kostenfrei, 2008. http://mediatum2.ub.tum.de/doc/645809/645809.pdf.
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Rao, Vineet. "Electrochemical characterization of direct alcohol fuel cells using in-situ differential electrochemical mass spectrometry." kostenfrei, 2008. http://mediatum2.ub.tum.de/doc/645809/645809.pdf.
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Korenblit, Yair. "Electrochemical characterization of ordered mesoporous carbide-derived carbons." Thesis, Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/34681.
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Porous carbon derived from an inorganic silicon carbide (SiC) precursor, termed SiC-derived carbon, is an attractive material for electrochemical energy storage applications, including electrodes for electrical double layer capacitors (EDLCs). The objective of this thesis is to investigate the effects that the carbide-derived carbon (CDC) microstructure and pore structure have on the energy and power characteristics of the EDLC electrodes.
Conventional SiC CDC is produced from non-porous crystalline SiC powder at temperatures above 800 °C. Here we studied the performance of SiC CDCs produced by chlorination at 700-900 °C of an ordered mesoporous SiC precursor, which was synthesized via a 1000 °C pyrolysis of polycarbosilane infiltrated into an SBA-15 silica template having ordered mesopores. The SiC CDC was purified from chlorine impurities by annealing in ammonia. The surface area and pore size of the purified SiC CDC was characterized via N2 and CO2 sorption using density functional theory (DFT) and Brunnauer, Emmet, and Teller (BET) theory. The specific capacitance, power and energy densities were characterized via electrochemical measurements of the SiC CDC electrodes in 1 M tetraethylammonium tetrafluoroborate (TEABF4) acetonitrile solution.
The SiC CDC exhibited a specific surface area (SSA) in excess of 2400 m2/g and gravimetric capacitance values of up to ~ 150 F/g, among the highest ever reported for any electrodes in this electrolyte. The ordered mesopores allowed for fast ion transport within each particle, resulting in excellent capacity retention under high current rates and ultra-fast frequency response, thus allowing for extremely high power and energy densities. The best overall performance was achieved in SiC CDC samples chlorinated at the lowest temperature of 700 °C.
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Alvi, Farah. "Synthesis and Characterization of Nanocomposites for Electrochemical Capacitors." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/3948.
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Presently there are deep concerns over the environmental consequences and the consumption of non-renewable energy sources, with the accelerated greenhouse effect, triggered enormous interest in the use of renewable energy sources e.g., solar, hydropower, wind and geothermal. However the intermittent nature of harvesting renewable energy sources has recently gained considerable attention in the alternative reliable, cost effective, and environmentally friendly energy storage devices. The supercapacitor and lithium ion batteries are considered more efficient electrical energy storage devices than conventional energy storage systems.
Both devices have many useful and important applications; they could be an excellent source for high power and high energy density, especially in portable electronic devices and Electrical Vehicles (EVs) or Hybrid Electrical Vehicles (HEVs). In order to make the efficient usage of these stationary energy storage devices, state of the art research on new and advanced electrode materials is highly needed. The aim of this dissertation is to investigate the scope of graphene/metal oxide-conducting polymer nanocomposites electrodes for light weight, high power density and wider voltage window supercapacitor devices.
The facile chemical polymerization approach was used to synthesize the aromatic and heterocyclic conducting polymer nanocomposites. For aromatic nanocomposites, several materials were synthesized includes ZnO-PANI, ZnO/G-PANI,RuO2-PANI and G-PANI. Subsequently these materials have been characterized by physical, structural techniques e.g Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Xray-Diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). In addition to material characterization the prepared material was also characterized by electrochemical measurements using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chrono potentiometry for supercapacitor electrodes. Since graphene is a two-dimensional single-atom-thick sp2 hybridized carbon structure due to its extraordinary characteristic, high electrical conductivity, chemical stability and large theoretical surface area (over 2600 m2 g−1) has gained immense interest in the future generation of renewable energy devices. Therefore, among all aromatic based nanocomposites, the Graphene-Polyaniline (G-PANI) rendered promisingly high specific capacitance around 440 F/g with the excellent cyclic stability. The higher specific capacitance of G-PANI might be due to the high conductivity and superior electrochemical properties of graphene in G-PANI nanocomposites.
However, besides the G-PANI, other aromatic nanocomposites e.g., RuO2-PANI, ZnO-PANI and G/ZnO-PANI also showed the potential of low cost and flexible supercapacitor electrodes with the reasonably good specific capacitance as 360 F/g, 300 F/g, and 275 F/g. We have further investigated the role of conductivity by adding different amount of graphene in G-PANI nanocomposites to optimize device performance with the specific capacitance and columbic efficiency of 440 F/g and 90% respectively.Further the other important parameters, relate with the electrode thickness, type of electrolytes, concentration of electrolytes and the effect of the solvent has also been studied to achieve the overall performance and reliability of the device. Moreover, in order to have the comprehensive study of conducting polymer besides the aromatic conducting polymer the heterocyclic polymers e.g., polythiophene and poly (3, 4-ethylenedioxythiophenes) (PEDOT) nanocomposites were studied at length to evaluate their role for the cost effective, large surface area and flexible green energy storage devices and has shown great prospects for commercial application. Therefore, G-Cps nanocomposites have proved to be a promising electrode material choice to facilitate the ionic diffusion and contact of the electrolytes to improve the specific capacitance and performance of the device.
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Hsiung, Chwan Hai H. (Chwan Hai Harold) 1982. "Synthesis and electrochemical characterization of lithium vanadium phosphate." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32730.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references (leaf 41).
In a world where the miniaturization and the portability of electronic devices is king, batteries play an ever-increasingly important role. They are vital components in many consumer electronics such as cell phones and PDAs, in medical devices, and in novel applications, such as unmanned vehicles and hybrids. As the power demands of these devices increases, battery performance must improve accordingly. This thesis is an introductory investigation into the electrochemical properties of a promising new battery cathode material: lithium vanadium phosphate (Li3V2(PO4)3) (LVP). Studies of other members of the phospho-olivine family, which LVP is a part of, indicate that the olivines have high lithium diffusivity but low electronic conductivity. LVP is part of the phosphor- olivine family, which traditionally has been shown to have high lithium diffusivity but low electronic conductivity. LVP was synthesized via a solid-state reaction and cast into composite cathodes. (90/5/5 ratio of LVP, Super P Carbon, and PVDF.) These composite cathodes were used in lithium anode, LiPF6 liquid electrolyte, Swage-type cells that were galvanostatically cycled from 3.OV to 4.2V and from 3.4V to 4.8V at C/20 rates. Electrochemical impedance spectroscopy was carried out on an LVP / liquid electrolyte / LVP cells from 0.01Hz to 1MHz. Finally, temperature conductivity measurements were taken from a die-pressed LVP bar. The results of the experimentation indicate that LVP has much promise as a new battery cathode material, but there are still a number of concerns to address.
(cont.) LVP has a higher operating voltage (4.78V) than the current Li-ion battery standard (3.6V), but there are issues with becoming amorphous, cycleability, and active material accessibility. From the EIS data, passivating films on the surface of the LVP cathode do not seem to be a factor in limiting performance. The conductivity data gives a higher than expected conductivity (4.62* 10-4 S/cm).
by Chwan Hai H. Hsiung.
S.B.
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Pereira, Joana Fernandes Alberto Wilton. "Electrochemical characterization of Dps, a DNA-protecting protein." Master's thesis, Faculdade de Ciências e Tecnologia, 2011. http://hdl.handle.net/10362/7820.
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Dissertação para obtenção do Grau de Mestre em
BiotecnologiaThe objectives of the present work were the purification and electrochemical characterization of Dps and study its iron incorporation mechanism in the presence of hydrogen peroxide. A bacterial miniferritin (Dps) from Pseudomonas (Ps.) nautica 617 was expressed in BL21(DE3) E. coli cells transformed with pET21c(+)-1dps plasmid vector. Protein overexpression was performed in nutritionally rich LB medium containing 100 μg/mL ampicillin. Recombinant Dps was purified through a two-step process: weak ionic exchange chromatography (DEAE Sepharose Fast Flow XK 26/40 resin) and strong ionic exchange chromatography (Q Resource resin). Protein concentration was determined through UV/Visible spectroscopy. The electrochemical study was performed through cyclic voltammetry, square wave voltammetry and chronoamperometry; Dps was either in solution or adsorbed to the working electrode. The chosen supporting electrolyte was 200 mM MOPS pH 7.1 buffer with 200 mM NaCl. Electrochemical assays were performed in aerobic and anaerobic environment and in the presence of Dps and Fe(II) and H2O2, both of Dps co-substrates. For the different assays, working electrodes made of gold, glassy carbon and graphite were used with different results and conclusions. The iron incorporation in the ferroxidase centers and mineral core formation were studied. Assay results were obtained through direct electron transfer. Among the observed results, iron oxidation during protein incubation and oxygen production during the catalytic mechanism were observed. DNA-Dps interaction results were inconclusive, although some unconfirmed evidence exists of DNA protection by Dps from electrochemical oxidation.
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Smiechowski, Matthew F. "Electrochemical Characterization of Lubricants for Microfabricated Sensor Applications." Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1121349361.
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Mcdermott, Mark Thomas. "Electrochemical and structural characterization of ordered graphite electrodes /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487846354484867.
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Cabrera, Catherine Regina. "Microfluidic electrochemical flow cells : design, fabrication, and characterization /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/8012.
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Lachal, Marie. "Etude des mécanismes d'insertion/désinsertion des cations alcalins (Li+/Na+) au sein de la structure olivine FePO4 pour accumulateurs Li-ion et Na-ion." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI035/document.
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Dans le cadre du développement des technologies Na-ion, le composé NaFePO4, équivalent chimiquedu matériau très attractif LiFePO4, représente une alternative intéressante aux problèmes deressourcement du lithium. Toutefois, les composés LiFePO4 et NaFePO4 de structure olivineprésentent des divergences de comportement structural et électrochimique lors de l'insertioncationique. Ce travail présente une analyse des mécanismes de (dés)insertion des ions Li+ et Na+ ausein de la phase FePO4 par voie chimique et électrochimique. Les échantillons de LiFePO4 ont étésynthétisés par deux méthodes différentes (hydrothermale et précipitation), puis délithiéschimiquement via différents procédés. Dans un premier temps, les analyses structurales (DRX)associées aux analyses nucléaires ont permis d'effectuer un suivi de la cinétique de réaction. Nousavons montré que la présence de joints de grains, issus du traitement thermique effectué, limitefortement la vitesse de délithiation. L'analyse de l’évolution des domaines de cohérences a permis deproposer un mécanisme de délithiation original de type "Coeur-Coquille" avec un coeur de LiFePO4,confirmé par HRTEM et STEM-EELS. Dans un deuxième temps, afin de comparer les mécanismes dedélithiation chimique et électrochimique, l’insertion et la cyclabilité des ions Li+ et Na+ ont étécaractérisées en demi-cellules lithium et sodium. Bien que la signature électrochimique des matériauxLiFePO4 et NaFePO4 soit différente, les performances en termes de capacité restituée ou de tenue enpuissance s'avèrent similaires. Enfin, l'insertion électrochimique des ions Li+ et Na+ au sein d'unepoudre comportant des défauts structuraux a été caractérisée par DRX Operando durant un cycle decharge / décharge effectué à régime lent. Ces analyses ont révélées que la co-insertion cationiques'effectue via une solution solide de type LixNayFePO4 (0As part of the development of Na-ion technology, NaFePO4 compound, chemical equivalent of theattractive LiFePO4 material, would be a promising option facing possible lithium shortage. However,olivine-type LiFePO4 and NaFePO4 display different structural and electrochemical behaviors duringcationic insertion. This thesis presents an analysis of the (de)insertion mechanisms of Li+ and Na+ ionswithin olivine-type FePO4 by chemical and electrochemical means. Samples of LiFePO4 weresynthesized by two different methods (hydrothermal and precipitation), then chemically delithiated bydifferent processes. In a first step, structural analysis (XRD) associated with nuclear analyses enabledfollowing the reaction kinetics. We have pointed out that the presence of grain boundaries, resultingfrom the heat treatment, strongly limits the delithiation kinetics. The analysis of the evolution of thecoherency domains enabled us to propose an original "Shrinking Core" type delithiation mechanismwith a core of LiFePO4, observed by HRTEM and STEM-EELS. In a second step, in order to comparechemical and electrochemical mechanisms, insertion and cyclability of Li+ and Na+ were characterizedin lithium and sodium half-cells. Although the electrochemical signature of LiFePO4 and NaFePO4materials is different, the performances in terms of restored capacity or power capability are similar.Finally, electrochemical insertion of Li+ and Na+ in a powder comprising structural defects wascharacterized by operando XRD, during a charge / discharge cycle performed at low rate. Theseanalyses revealed that the cationic co-insertion takes place via a solid solution LixNayFePO4(0
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Lascaud, Julie. "Elaboration de couches minces atténuantes en silicium poreux : Application aux transducteurs ultrasonores capacitifs micro-usinés." Thesis, Tours, 2017. http://www.theses.fr/2017TOUR4026/document.
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Les transducteurs ultrasonores capacitifs micro-usinés (CMUT) représentent aujourd’hui une réelle alternative aux technologies piézoélectriques dans le domaine de l’imagerie échographique médicale. Au cours des années, les procédés de fabrication des transducteurs se sont enrichis en vue d’améliorer leurs performances. A contrario le choix du substrat, généralement en silicium, a été peu étudié. Il est cependant reconnu que le support contribue à la signature acoustique du dispositif ultrasonore. L’objectif de ces travaux de thèse a été d’intégrer une couche de silicium poreux afin d’absorber une partie des ondes élastiques qui se propagent dans le substrat et interfèrent avec le signal acoustique émis. Nous montrons alors qu’il été possible de réaliser une couche de silicium poreux en face arrière de composants, sur plaquettes 6 pouces, sans dégrader leurs performances. Finalement, par l’intermédiaire de caractérisations acoustiques et des signatures impulsionnelles des transducteurs, nous révélons le potentiel prometteur de ce matériaux pour la réalisation de milieu arrière atténuant dédié à la transduction ultrasonoreCapacitive micromachined ultrasonic transducers (CMUT) have emerged as a potential alternative to traditional piezoelectric transducers for ultrasound imaging. Along the years, CMUT processes have been evolved to enhance the device performances. In the meantime, no particular attention was paid on the silicon substrate, even if it is well-known that it could contribute to the transducer efficiency. The aim of this PhD thesis was to use porous silicon as a backing material for ultrasonic transducers to absorb a piece of the acoustic wave propagating in the substrate and which induce crosstalks in the acoustic signal. We show that porous silicon layer can be obtained on the rear side of already processed wafers without any damage on the performances of capacitive micromachined ultrasonic transducers. Finally, by means of acoustic characterizations and the transducer electroacoustic responses, we reveal the potential interest of porous silicon as backing material for ultrasonic transducers
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Liu, Ran. "Synthesis, characterization and properties of nanostructured materials by template-directed method." ScholarWorks@UNO, 2004. http://louisdl.louislibraries.org/u?/NOD,141.
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Thesis (M.S.)--University of New Orleans, 2004.Title from electronic submission form. "A thesis ... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Chemistry."--Thesis t.p. Vita. Includes bibliographical references.
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SAMARAO, ASHWIN K. "AMPEROMETRIC CHARACTERIZATION OF A NANO INTERDIGITATED ARRAY (nIDA) ELECTRODE AS AN ELECTROCHEMICAL SENSOR." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154451638.
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Yau, Chun Ho. "Silver electrochemical-deposition on silicon nanowires, characterization & application." access abstract and table of contents access full-text, 2006. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21456306a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2006."Master of Science in Materials Engineering & Nanotechnology dissertation." Title from title screen (viewed on Nov. 21, 2006) Includes bibliographical references.
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Dogan, Bahadir. "Synthesis And Characterization Of Semiconductor Nanowires Via Electrochemical Technique." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12611335/index.pdf.
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This thesis aims to investigate structural, optical and photoelectrochemical behavior of CdS nanowires and their heterojunctions with CdTe and polypyrrole nanowires. In the first part, CdS nanowires have been synthesized via electrochemical template-based route. It has been observed that synthesis conditions, such as bias voltage and deposition time, affect the morphology, optical and photoelectrochemical characteristics of CdS nanowires. Depending on the deposition time, length of the CdS nanowires changed from 100-200 nm to 3-4 m. Also the diameter of the nanowires increased with increasing the deposition time. Structure of the CdS nanowires has been confirmed by X-ray diffraction spectrometry and EDX analysis. Phototelectrochemical performances of the CdS nanowires have been changed dramatically with bias voltage and deposition time.In the second part of this thesis, CdTe nanostructures have been deposited on CdS nanowires. Change in optical and photoelectrochemical behavior of CdS nanowires after CdTe deposition has been investigated. Organic semiconductors and their composites with inorganic materials have been gaining attention due to tunable optical, electrical and magnetic properties. Also, ease of fabrication techniques, and therefore, low cost made these materials attractive for lots of applications including photovoltaic devices and flexible electronics. In the last part of this thesis, heterojunctions of CdS and Polypyrrole (Ppy) nanowires have been synthesized. Like CdS/CdTe heteronanostructures, first the CdS nanowires have been electrochemically deposited in anodized alumina template and then Ppy has been successfully deposited on CdS nanowires. In order to investigate the effects of polypyrrole synthesis conditions on CdS/Ppy heteronanostructures, CdS nanowire synthesis conditions have been kept constant. It has been observed that morphology and photoelectrochemical behavior of the Ppy nanowires has been affected from Ppy synthesis conditions. The photoelectrochemical performance changes of CdS/Ppy heteronanostructures have been also investigated in this part.
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Siegesmund, Øyvind. "Development and electrochemical characterization of ultra-microsensors using nanotechnology." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kjemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-6851.
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Rao, Ashwin K. "Preparation and characterization of macroporous electrodes for electrochemical bioassays." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1211388576/.
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Simper, Jessica Mary. "Electrochemical characterization of aqueous chlorine and inorganic chloramine species." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311946.
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Blanton, Gabriel G. (Gabriel Garrison) 1982. "Design considerations and characterization of Origami [TM] electrochemical capacitors." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32801.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaf 23).
Electrochemical capacitors, also known as supercapacitors, ultracapacitors, and electric double-layer capacitors, have recently received attention as electrical energy storage devices. The devices are both high power and high energy, making them ideally suited for load balancing applications in such demanding applications as electric vehicles, transmission devices, and other systems with intermittent peaks in power. Recent trends in miniaturization have created applications where size and weight constraints are critical. Micropower devices such as microelectromechanical systems (MEMS) and miniature remote sensors with consumption in the range of milliWatts to Watts are increasingly common. To help meet the power demands of these miniature devices, micron-scale electrochemical capacitors are being developed that utilize traditional two dimensional fabrication techniques combined with folding methods to form the third dimension. Devices produced in this manner allow for close packing of multiple layers, resulting in high power and energy densities. This work examines the scientific fundamentals governing electrochemical capacitors and the design, fabrication, and testing of devices produced at the Massachusetts Institute of Technology utilizing the Origami[TM] technique.
by Gabriel G. Blanton.
S.B.
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Makinde, Zainab Olusola. "Spectroscopic and electrochemical characterization of thio binuclear phthalocyanine complexes." Thesis, Rhodes University, 2017. http://hdl.handle.net/10962/59287.
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Chykyda, T. Y., and A. V. Krushevskyi. "Synthesis, characterization, and electrochemical studies of chemically synthesized NaFePO4." Thesis, Київський національний університет технологій та дизайну, 2018. https://er.knutd.edu.ua/handle/123456789/10799.
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Kelly, Brett. "Electrochemical Method for Characterization and Ranking of Corrosion Inhibitors." Thesis, North Dakota State University, 2017. https://hdl.handle.net/10365/28657.
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One of the most cost-effective methods in mitigating corrosion effects is through the use of corrosion inhibitors. This work studied the performance of eight organic inhibitors on mild steel substrate through electrochemical characterization techniques, with the primary goal of incorporating a screening process to sift through the large selection of potential inhibitors without having to fully characterize them. The test methodology developed was successful at screening the potential corrosion inhibitors through linear polarization resistance (LPR) testing in NaCl electrolyte, narrowing the collection of inhibitors to the three most-promising chemicals, adrenalone, 3,4-dihydroxyphenylacetic acid and dopamine. The screened inhibitors proved effective in HCl electrolyte, reducing the corrosion rates of mild steel by over 85%. X-ray photoelectron spectroscopy (XPS) and quartz crystal microbalance (QCM) testing were used to confirm surface adsorption of the molecules to the substrate, indicating the formation of a protective barrier film as the means of corrosion protection.
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Moats, Michael Scott 1970. "Electrochemical characterization of anode passivation mechanisms in copper electrorefining." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282777.
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Anode passivation can decrease productivity and quality while increasing costs in modern copper electrorefineries. This investigation utilized electrochemical techniques to characterize the passivation behavior of anode samples from ten different operating companies. It is believed that this collection of anodes is the most diverse set ever to be assembled to study the effect of anode composition on passivation. Chronopotentiometry was the main electrochemical technique, employing a current density of 3820 A m⁻². From statistical analysis of the passivation characteristics, increasing selenium, tellurium, silver, lead and nickel were shown to accelerate passivation. Arsenic was the only anode impurity that inhibited passivation. Oxygen was shown to accelerate passivation when increased from 500 to 1500 ppm, but further increases did not adversely affect passivation. Nine electrolyte variables were also examined. Increasing the copper, sulfuric acid or sulfate concentration of the electrolyte accelerated passivation. Arsenic in the electrolyte had no effect on passivation. Chloride and optimal concentrations of thiourea and glue delayed passivation. Linear sweep voltammetry, cyclic voltammetry, and impedance spectroscopy provided complementary information. Analysis of the electrochemical results led to the development of a unified passivation mechanism. Anode passivation results from the formation of inhibiting films. Careful examination of the potential details, especially those found in the oscillations just prior to passivation, demonstrated the importance of slimes, copper sulfate and copper oxide. Slimes confine dissolution to their pores and inhibit diffusion. This can lead to copper sulfate precipitation, which blocks more of the surface area. Copper oxide forms because of the resulting increase in potential at the interface between the copper sulfate and anode. Ultimate passivation occurs when the anode potential is high enough to stabilize the oxide film in the bulk electrolyte. The effect of anode impurities or electrolyte concentrations can be related to the formation of one of these films. Reactions occurring after passivation have also been examined. Post-passivation reactions are believed to include silver dissolution, transformation of lead sulfate to lead oxide, and oxygen evolution. Following the sharp potential increase caused by the passivation, silver that has accumulated on the anode surface will dissolve into the electrolyte at a potential between 1.0 and 1.3 V. After the silver has dissolved, the potential increases again at which point the oxidation of lead sulfate to lead oxide occurs. The formation of lead oxide provides a surface with a lower oxygen evolution overpotential. The presence of kupferglimmer also results in a stable lower oxygen evolution potential occurring at approximately 2.0 V.
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Rami, Soukaina. "Synthesis, Characterization, and Electrochemical Properties of Polyaniline Thin Films." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5563.
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Conjugated polymers have been used in various applications (battery, supercapacitor, electromagnetic shielding, chemical sensor, biosensor, nanocomposite, light-emitting-diode, electrochromic display etc.) due to their excellent conductivity, electrochemical and optical properties, and low cost. Polyaniline has attracted the researchers from all disciplines of science, engineering, and industry due to its redox properties, environmental stability, conductivity, and optical properties. Moreover, it is a polymer with fast electroactive switching and reversible properties displayed at low potential, which is an important feature in many applications. The thin oriented polyaniline films have been fabricated using self-assembly, Langmuir-Blodgett, in-situ self-assembly, layer-by-layer, and electrochemical technique. The focus of this thesis is to synthesize and characterize polyaniline thin films with and without dyes. Also, the purpose of this thesis is to find the fastest electroactive switching PANI electrode in different electrolytic medium by studying their electrochemical properties. These films were fabricated using two deposition techniques: in-situ self-assembly and electrochemical deposition. The characterization of these films was done using techniques such as Fourier Transform Infrared Spectroscopy (FTIR), UV-spectroscopy, Scanning Electron Microscope (SEM), and X-Ray Diffraction (XRD). FTIR and UV-spectroscopy showed similar results in the structure of the polyaniline films. However, for the dye incorporated films, since there was an addition in the synthesis of the material, peak locations shifted, and new peaks corresponding to these materials appeared. The 1 layer PANI showed compact film morphology, comparing to other PANI films, which displayed a fiber-like structure. Finally, the electrochemical properties of these thin films were studied using cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) in different scenarios. These scenarios included the study in different acid based electrolytes and different gel based electrolytes. The ultra-thin self-assembled PANI films were shown to have a faster switching time, especially for the 1 layer PANI, whereas the color contrast could be observed for the film containing the dye molecule. Also, HCl based electrolyte gave the best electrochemical reversibility compared to other acids used. For the gelatin and PVA based electrolytes, having the same concentration, the results were similar. Hence, the change in the electrolyte consistencies, from liquid to semi-solid, did not change the electrochemical properties of the films. Finally, in the EIS, it was shown that these PANI thin films exhibit a pseudo-capacitance behavior, and as the film thickness grew, the capacitance increased.
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Sairi, Masniza Binti. "The preparation and electrochemical characterization of nanopore array membranes." Thesis, Curtin University, 2014. http://hdl.handle.net/20.500.11937/2587.
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This thesis aimed to examine the behaviour of nanoscale and microscale liquid interfaces for chemical detection. Nanoporous membranes were prepared by various methods and characterised by ion-transfer electrochemistry at the membrane-modified interfaces between two immiscible electrolyte solutions. The detection of model analytes and ionised drug substances indicate that these miniaturised interfaces provide viable platforms for the detection of ions of chemical and biochemical importance.
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Islam, Gazi Jahirul. "Electrochemical Detection and Characterization at Liquid/Liquid micro-Interfaces." Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/88488.
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The purpose of this research is to investigate the electrochemical detection and characterization of different substances at liquid/liquid micro-interfaces which were created at the tips of the glass micropipettes. In this way, per- and polyfluoroalkyl substances (PFAS), PAMAM dendrimers and sulphate ions were investigated by voltammetric analysis. The successful detection of all substances provides the basis for improved analytical processes and various electrochemical properties were analysed to elucidate their transfer mechanisms at the interfaces.
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SARTO, FRANCESCA. "Electrochemical characterization of electrode materials for hydrogen-energy applications." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2014. http://hdl.handle.net/2108/203430.
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YU, CHE-CHIA, and 游哲嘉. "Synthesis, optical and electrochemical characterizations of imine-containing polydithienylpyrroles." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/u7aq9p.
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碩士國立雲林科技大學
化學工程與材料工程系
105
Three polydithienylpyrroles with thiophene, thiazole, and pyridine units attached by an imine linkage to dithienylpyrrole group are synthesized electrochemically, which are denominated as PDTPTA, PDTPZA and PDTPPA, respectively. A cathodically coloring material PProDOT-Ph is also synthesized using electrochemical polymerization. The optical and electrochemical properties of three anodically coloring materials (PDTPTA, PDTPZA and PDTPPA) and a cathodically coloring material (PProDOT-Ph), such as optical contrast, color variations, optical stability, coloration efficiency, electrochemical stability, and optical memory properties are characterized. The maximum optical contrast of PDTPTA film is 36.8 % at 1286 nm in an ionic liquid solution, and the coloration efficiency of the PDTPTA film is 203.90 cm2 C-1 at the wavelength of 1286 nm. In the neutral state, PDTPTA film is earthy yellow (0.2 V), it turns into dark yellow (0.8 V), grey (1.0 V), and bluish-grey (1.2 V) at doped state upon oxidation. Electrochromic devices (ECD) based on PDTPTA, PDTPZA, and PDTPPA as anodic polymers and PProDOT-Et2, PProDOT-Bz2, and PProDOT-Ph as cathodic polymers are constructed. PDTPTA /PProDOT-Bz2 ECD shows the highest optical contrast (70.2 %) and the highest coloration efficiency (736.20 cm2/C) at 622 nm. PProDOT-Ph-based ECDs show higher electrochemical cycling stability than those of PProDOT-Et2- and PProDOT-Bz2-based ECDs, 86% of electroactivity is retained after 1000 cycles for PProDOT-Ph-based ECDs. PProDOT-Bz2-based ECDs display higher optical memory effects than those of PProDOT-Et2- and PProDOT-Ph-based ECDs, and PDTPTA /PProDOT-Bz2 ECD shows good optical memory with less than 2.5% transmittance change in coloring state.
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YU, YA-HAN, and 游雅涵. "Synthesis and Electrochemical Characterizations of high-capacity LiNiCoO2 Cathode Materials." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/03273854194908170382.
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碩士輔仁大學
化學系
103
We have successfully synthesized the concentration-gradient cathode materials of LiNi0.95Co0.05O2 ((G)C5-LN), LiNi0.9Co0.1O2 ((G)C10-LN), LiNi0.8Co0.2O2 ((G)C20-LN) and LiNi0.81Co0.19O2 ((G)C10-LNC10) via a co-precipitation route. According to the analysis of physical, electrochemical, and thermal propeties, the concentration-gradient cathode material has a structure with different chemical compositions of primary particles from the surface toward core of each of the secondary particles. The primary particle with rich Co content on the surface and the primary particle with rich Ni content in the core of secondary particle of the concentration-gradient cathode materials have provided the advantages of high safety and high capacity. For the synthesis of (G)C10-LNC10, 10% mol. Co(OH)2 is uniformly coated on the surface of 90% mol. Ni0.9Co0.1(OH)2, and mixed with lithium hydroxide, then high temperature sintered. The mole ratio of Co in the core of (G)C10-LNC10 cathode material is at least 10% mol, and the mole ratio of Co on the surface of (G)C10-LNC10 cathode materia is higher than 25% mol.. The (G)C10-LNC10 has a better concentration-gradient structure, so it can provide the best electrochemical performences.
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Shih, Cheng-Mei, and 施正美. "Synthesis and Electrochemical Characterizations of Spherical C/LiFe0.99Mg0.01PO4for Lithium battery." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/17288484861822996400.
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碩士輔仁大學
化學系
98
In this study, the high-performance C/LiFeMgPO4 had been synthesized via both co-precipitation and spray-drying method. Under the scanning electron microscope observations, the synthesized C/LiFeMgPO4 is shown the perfectly spherical particle, thus having higher tap-density (0.93 g/cm3); the primary -particle size of C/LiFeMgPO4 is about 200 nm, which could reduce the diffusion path of lithium ion and improve the effect of mass-transfer. In the process of spray-drying, it was carried out doping metal into material and coating carbon on the surface of material to enhance the electrical conductivity of C/LiFeMgPO4 , which increases to 5.24×10-3 S/cm. C/LiFeMgPO4 shows initial specific discharge capacity of 125.3mAh/cm3 at discharge of 0.1C and the capacity of 67.41% at a high discharge-rate of 8C. During the cycle-life test, there is no obvious decay in capacity even after 50 cycles at 0.5C. After analyzing the EIS experimental data, it is concluded that C/LiFeMgPO4 cathode material via co-precipitation and spray-drying has the smaller charge-transfer resistance (24.81Ω) due to its own the better electric conductivity and degree of crystallization. The apparent diffusion-coefficient of lithium ion (DLi+) is larger (5.2×10-13cm2/s) compared to other synthesized method.
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Lin, Congmin, and 林琮閔. "Synthesis And Electrochemical Characterizations Of High-Voltage LiNi0.5Mn1.5O4 Cathode Material." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/33860374735679497428.
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碩士輔仁大學
化學系
100
The spherical LiNi0.5Mn1.5O4 cathode materials have been successfully synthesized by a co-precipitation method and LiNi0.5Mn1.5O4 were modified with Mg element to improve the electrochemical performance. According to analyzing the ICP and EDX results, LiNi0.5Mn1.5O4 had been gradient-doped 2 mol% Mg element and the LiNi0.5Mn1.5O4 powder particles have a structure comprising different Mg ratio from the nano-particle on a surface of the powder particle toward the nano-particle in the core of the powder particle. The rich Mg content on the surface of the cathode material powder makes the LiNi0.5Mn1.5O4 able to have the advantages of high thermal stability and high electrochemical performances. Electrochemical testing results showed that discharge capacities of Mg-modified LiNi0.5Mn1.5O4 are 122 and 92 mAh g-1 at discharging rates of 0.1 and 4C, respectively. The corresponding values for pristine are 126 and 26 mAh g-1. The Mg-modified LiNi0.5Mn1.5O4 half-cells lost only ~17% of initial capacities, while the pristine half-cells lost ~24% of capacity after 50 charge/discharge cycles at room temperature. High temperature (55 ºC) cycling results showed that Mg-modified LiNi0.5Mn1.5O4 has a lower capacity-lost (8%) than pristine (24%) after 20 cycles. For DSC analysis, the exothermic peak of the Mg-modified LiNi0.5Mn1.5O4 charged at 4.9V was shifted to higher temperature and the exothermic heat had decreased, compared to the pristine.
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HSIEH, YUN-CHUN, and 謝雲君. "Synthesis and Electrochemical Characterizations of Spinel Sr-doped LiNi0.5Mn1.5O4 Cathode Material." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/42g5q6.
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碩士輔仁大學
化學系
105
The spherical LiNi0.5Mn1.5O4 (LNMO) cathode materials have been successfully synthesized by a co-precipitation method and were doped with the 2 mol% or 5 mol% Sr to promote the electrochemical performances. At the discharging rate of 0.1C, the initial discharge capacity of pristine LNMO, 2% Sr-LNMO, and 5% Sr-LNMO are 135.9, 130.6, and 107.8 mAh g−1, respectively. At the discharging rate of 3.0C, the 2% Sr-LNMO shows an improved electrochemical performance with the discharge capacity of 94.6 mAhg−1 at 4.9 V. On the other hand, the corresponding value for the pristine LNMO sample is 87.5 mAhg−1. The cycling performance with capacity retention of pristine LNMO, 2% Sr-LNMO, and 5% Sr-LNMO are 92.5%, 87.6%, and 104.7%, respectively, at room temperature after 60 charge/discharge cycles. Electrochemical impedance spectroscopy (EIS) reveals that the Sr modification decreases the total resistance and enhances Li ion diffusion rates which further proves that the Sr modification can improve the electrochemical performance of LiNi0.5Mn1.5O4 (LNMO) cathode materials. Our work promotes the practical application of LiNi0.5Mn1.5O4 cathode material in high voltage lithium-ion batteries with high energy density and power performance.
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Chang, Shao-Tao, and 張卲韜. "Synthesis and Electrochemical Characterizations of Mg Gradient-Doped LiNi0.5Co0.2Mn0.3O2 Cathode Material." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/83804347538538673236.
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碩士輔仁大學
化學系
102
In the present study, LiNi0.5Co0.2Mn0.3O2 (LNCMO) cathode material gradient-doped with Mg is successfully synthesized via a co-precipitation method. The Mg element was doped at a molar ratio of Mg/LNCMO = 1.7 % using an inductively coupled plasma optical emission spectroscope (ICP-OES). Mg gradient-doped LNCMO (Mg(GD-LNCMO)) particle cross-section use Energy Dispersive Spectrometer (EDS) to detect the amount of the Mg, the particle doped with Mg has 2.5 mol% ratio on the surface and gradually reduce to 0.5 mol% ratio in the core. The initial discharge capacity of Mg(GD)-LNCMO compare to LNCMO didn’t shows serious decay(4.3 V: 160.3 mAh g-1/ 162.6 mAh g-1 , 4.5 V: 188.3 mAh g-1/189.9 mAh g-1). Mg(GD)-LNCMO shows an improved electrochemical performance in the rate capability and cycle life. At discharging rate of 7.0 C, improvement effect is as follows 4.3 V: 72.5 % → 78.4 % / 4.5 V: 76.4 % → 82.2 %. After 70 charge/discharge cycles, improvement effect is as follows 4.3 V: 83.6 % → 91.7 % / 4.5 V: 71.3 % → 86.7 %. When the cell operation voltage to raise, the improvement effect also increase. Differential scanning calorimetry (DSC) analysis shows that exothermic pick of the Mg(GD)-LNCMO is shifted at higher temperatures and that the amount of heat is decreased by comparison with LNCMO. The improvements of both electrochemical retention and thermal stability were possibly attributed to the reduced reaction between the electrodes and electrolytes, and increase the stability of the structure.
47
Shao-Sheng, Lu, and 呂紹聖. "Electrochemical Characterizations of Iron Porphyrins and the Preparation of Modified Electrodes." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/20050755015662604163.
Full textAbstract:
碩士國立暨南國際大學
應用化學系
95
A series of symmetric porphyrin rings bearing phenyl, mesityl, 2,6-dichlorophenyl and triphenylamine (TPA) pendant groups and their iron complexes were synthesized. Cyclic voltammetry and spectral methods were used to examine the redox potentials and optical properties of these compounds. The formal electrode potentials of iron porphyrins are in agreement with the electron-donating-withdrawing properties of the substituents on the phenyl groups. The B and Q bands of FeTDPAPP(Cl) are located at higher wavelengths and the bandwidths become broader compared with those of the other porphyrins, indicating the peripheral TPA affects the electronic configuration of iron porphyrins. Titration of iron porphyrins with tetra-n-butylammonium hydroxide (TBAOH) as the axial ligands was monitored by spectrophotometry and cyclic voltammetry. The preparation method and characterization of iron porphyrin modified electrode was also studied. It was observed that FeTDPAPP(Cl) monomer can be electropolymerized and incorporated onto the electrode surfaces. The other three iron porphyrins can be used as dopant molecules when electropolymerable monomer (EDOT) was co-existed as mixtures. The polymeric films were characterized by electrochemical and spectral measurements.
48
Jhang, Bing-Cheng, and 張秉丞. "Synthesis and Electrochemical Characterizations of Al Gradient-doped LiCoO2 Cathode Material." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/y6p3pt.
Full textAbstract:
碩士輔仁大學
化學系
107
In this study, an Al gradient-doped LiCoO2 (LCO) cathode was prepared via chemical co-precipitation followed by calcination. The average doping concentration of Al in the Al(GD)-LCO was ~2 mol.% with ~4 mol.% on the particle surface. Al(GD)-LCO returned values for initial efficiency, rate capability and cycle-life that were superior to those of LCO. The AC-impedance and PITT results indicate that the Al-rich surface of Al(GD)-LCO reduced the charge-transfer resistance(Rct) and enhanced the diffusion of Li+ by minimizing the side reactions with the electrolyte. All the results showed that the Al gradient-doped LCO cathode material effectively improve the electrochemical performances of LCO cathode material at high voltage.
49
Sung, Wei-Cheng, and 宋煒晟. "Synthesis And Electrochemical Characterizations Of Nanostructured LiMn2O4 For Lithium-Ion Battery." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/34577928761433815295.
Full textAbstract:
碩士輔仁大學
化學系
98
Porous (P-) and dense (D-) nano-structured lithium manganese oxide (LiMn2O4) powders have been synthesized by carbonate and hydroxide co-precipitation, respectively. Electrochemical testing results at room temperature showed that discharge capacities of P-LiMn2O4 are 121 and 55 mAh g-1 at discharging rates of 0.1 and 10C, respectively. The corresponding values for D-LiMn2O4 are 119 and 38 mAh g-1. EIS analysis showed that the Li-ion diffusion coefficient of P-LiMn2O4 electrode film (9.0x10-13 cm2 s-1) is much higher than that of D-LiMn2O4 electrode film (3.0x10-13 cm2 s-1), which was attributed to the higher surface area and shorter path for Li-ion diffusion in the P-LiMn2O4. The Re+Rct of D-LiMn2O4 (19.4Ω) at 4.20V is little lower than that of P-Li Mn2O4 (24.4Ω) due to better electric-connection between primary particles. These observations reveal that the porous nanostructure of P-LiMn2O4 improved the high-rate performance, which could be predominated by Li-ion diffusion.
50
Chung, Hsin-Hua, and 鍾欣樺. "Synthesis, optical and electrochemical characterizations of inden and 1,2,5-thiadiazole-containing polydithienylpyrrole." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/n7j4pe.
Full textAbstract:
碩士國立雲林科技大學
化學工程與材料工程系
103
Inden (DIT) and 1,2,5-thiadiazole (BDTA ) - based electrochromic materials are synthesized PDIT and PBDTA homopolymers are prepared by electropolymerizing DIT and BDTA monomers, respectively. Moreover, P(DIT-TTPA ),P(BDT-TTPA) , P(DIT-DTP), and P(BDTA-DTP) copolymers are prepared by electropolymerizing DIT and BDTA with TTPA and DTP units. Their optical and electrochemical properties, such as optical contrast, color variation, electrochemical stability, coloration efficiency, and optical memory properties are investigated. Six polymer films are studied inaliquid state electrolyte ([EPI+][TFSI-]) and in electrochromic devices (ECDs). Upon application of specific potentials, the state of homopolymers (PDIT and PBDTA) changes from neutral to oxidation state. These homopolymer films are not only reversibly oxidized and reduced but also accompanied by obvious color change (yellow, green, and blue). Compare the colors with homopolymer films, the colors of their corresponding copolymer films show slight variations. Maximum optical contrast (ΔT max) of P(DIT-TTPA ) films are measured as 60.3% at 1042 nm in [EPI+][TFSI-] solution, and the maximum coloration efficiency (η) of P(BDTA- TTPA) films are calculated to be 217.8 cm2/C. The ECDs are fabricated using anodic polymer films, gel state electrolytes, and cathodic PProDOT-Et2 films. PDIT/ PProDOT-ET2 ECD shows the highest ΔT max (50.3%) at 590nm, P(BDTA-TTPA)/ PProDOT-Et2 ECD shows the highest η (649.4 cm2/C) at 590 nm, and PBDTA / PProDOT-Et2 ECD shows the best optical memories (ΔT max is 1.5% in the oxidation state ). In addition, ECDs show satisfactory redox stability.