Dissertations / Theses: 'Electric double layer capacitors'

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Cagle, Clint William. "Charging kinetics of electric double layer capacitors." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1263402254/.

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Premathilake, Dilshan V. "Vertically Oriented Graphene Electric Double Layer Capacitors." W&M ScholarWorks, 2017. https://scholarworks.wm.edu/etd/1516639673.

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Vertically oriented graphene nanosheets (VOGN) synthesized by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) have been fabricated as electrical double layer capacitors (EDLCs). The relatively open morphology of the films provided good frequency response, but had limited capacitance compared to present day activated carbon EDLCs. The objective of this research was to improve the capacitance of these films to a commercially viable level while maintaining sufficient frequency response for AC filtering. The growth of VOGN on Ni and Al substrates has been studied in this work. The native oxide on Ni was thinned at temperatures above ~600ºC with the oxygen from the surface oxide dissolving into the bulk, thus creating a low resistance ohmic contact that reduced the overall equivalent series resistance (ESR). Aluminum was studied because it is the primary substrate material used in electrolytic capacitors. However, it was much more difficult to work with because of its tenacious surface oxide. The maximum capacitance for a 10-minute VOGN/Ni growth observed was ~260µF/cm2, at temperature 850ºC, at 120 Hz, but the morphology was not very ordered. The best combination of capacitance (~160 µF/cm2) and frequency response (phase angle near -85º up to ~3000 Hz) was grown at 750ºC. The capacitance of VOGN/NI was further improved by using coatings of carbon black by an aerosol spray method. A capacitance of 2.3 mF/cm2 and frequency response phase angle near -90º at 120 Hz was achieved. It is the highest specific capacitance for an EDLC, reported in the literature, to date, suitable for AC filtering. Employing Al as a substrate required a novel method of plasma sputter cleaning of the oxide near the Al melting point (660ºC) and superimposing VOGN growth to prevent further oxidation. Initial results were ~80 µF/cm2 at a temperature of 620ºC with frequency response phase angle near -90º. Modeling of a uniform coating of carbon black (100 nm thick) on this underlying VOGN/Al architecture suggests that a capacitance of near 50 mF/cm2 can be achieved thus making this a potentially viable replacement for electrolytic capacitors. Another approach to commercialization of VOGN/Ni EDLCs has been studied by using a single substrate sheet interdigitated pattern design to create a low volume capacitor. A YAG laser was used to ablate resistance lines in the film resulting in a sinuous, square pattern on a VOGN/Ni coated alumina substrate and utilizing a gel electrolyte to create the EDLC.

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Fellman, Batya A. (Batya Ayala). "Carbon-based electric double layer capacitors for water desalination." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61603.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 68-72).
In capacitive deionization (CDI), salt water is passed through two polarized electrodes, whereby salt is adsorbed onto the electrode surface and removed from the water stream. This approach has received renewed interest for water desalination due to the development of new high-surface area, carbon-based nanomaterials. However, there is limited understanding as to how electrode geometry, surface properties, and capacitance affect ion capture. In this work, we experimentally investigated various standard carbon-based electrode materials, including activated carbon and carbon cloths, as well as microfabricated silicon structures for CDI. Electrochemical characterization through cyclic voltammetry was used to determine the electrochemical properties of each material. The capacitance values of the carbon materials tested were 40 F/g for 2000 m2 /g carbon cloth, 32 F/g for 1000 m2 /g carbon cloth, and 25 F/g for activated carbon. In addition, we constructed two iterations of flow test channels to perform parametric studies on ion capture. The first flow cell utilized a commercial conductivity probe to measure salt concentration after charging the electrodes without flow. We showed that the ion capture on both the carbon cloth and activated carbon electrodes were proportional to the applied voltage, however two orders of magnitude smaller than what is expected from the electrode charge. We addressed a significant experimental limitation in the second flow cell by integrating conductivity sensors into the flow channel to measure effluent salt concentration during electrode charging. We found that the salt adsorption increased from 33.1 pmol/g in the first flow cell to 63.5 pmol/g in the redesigned flow for an applied potential of 1.2 V. Future directions will focus on controlling electrode geometry and chemistry to help elucidate transport mechanisms and provide insight into the design of optimal materials for capacitive deionization.
by Batya A. Fellman.
S.M.

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Silva, Ricardo Manuel Fonseca Lopes. "Metal oxide/carbon nanotubes heterostructures for electric double layer capacitors." Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22962.

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Doutoramento em Ciência e Engenharia de Materiais
O presente estudo teve como objetivo principal a elaboração e caracterização de hétero-estruturas hibridas tridimensionais (3D) de nanotubos de carbono alinhados verticalmente e revestidos com óxido de manganês para aplicações em condensadores eletroquímicos como elétrodos livres de aditivos. Numa primeira fase, foram desenvolvidas metodologias para o crescimento de nanotubos de carbono puro e para nanotubos de carbono dopados com azoto, em substratos isoladores e metálicos, por deposição química em fase de vapor. Foi dada especial atenção ao crescimento direto de nanotubos de carbono alinhados verticalmente no substrato metálico (Inconel®600) e sua aplicação em elétrodos livres de aditivos à base de carbono. Posteriormente, foi desenvolvido um processo inovador para a deposição de óxido de manganês (Mn3O4) por deposição por camada atómica para o revestimento de nanoestruturas, como os nanotubos de carbono, para a elaboração de heteroestruturas. Estas foram devidamente caracterizadas como materiais para aplicações em eléctrodos. A eficiência electroquímica dos eléctrodos atinge um máximo para o nanocompósito de nanotubos de carbono puro/óxido de manganês revestidos com 600 ciclos por deposição por camada atómica e apresenta uma capacitância de 78.68 mF cm-2 a 5 mV s-1. Este resultado pode ser atribuído ao efeito cooperativo entre os componentes do nanocompósito e uma utilização eficaz dos materiais ativos. Provou-se que um material nanocompósito que englobe a capacitância da dupla camada elétrica, bem como a estrutura condutora dos nanotubos de carbono e a pseudocapacitância dos óxidos metálicos é de grande interesse devido ao seu mecanismo duplo de armazenamento de carga e as vantagens de cada mecanismo são exploradas nestes novos dipositivos híbridos. Este trabalho foi realizado na Universidade de Aveiro e na Universidade de Humboldt (Berlim), beneficiando das infraestruturas adequadas à execução do trabalho experimental de ambas as instituições e das competências complementares das equipas de investigação associadas. Devido à natureza multidisciplinar da área de investigação onde este doutoramento se insere, a colaboração com outras instituições internacionais valorizaram a discussão dos resultados obtidos e fundamentaram os novos materiais desenvolvidos
The purpose of this work was the elaboration and characterization of hybrid three-dimensional (3D) arrays of vertically aligned carbon nanotubes coated with manganese oxide heterostructures for application as binder-free electrodes in electrochemical capacitors. In the first stage, methodologies to grow pure and nitrogen doped vertically aligned carbon nanotubes arrays on nonmetallic and metallic substrates by thermal chemical vapor deposition have been developed. Particular attention was devoted to obtain vertically aligned carbon nanotubes arrays grown directly on metallic conductive substrates (Inconel®600) and their application in binderfree carbon-based electrodes. Subsequently, as one of the main points of this work, a novel manganese oxide (Mn3O4) atomic layer deposition process has been developed for coating nanostructures, such as carbon nanotubes, for the elaboration of heterostructures which were further used and characterized as electrodes materials. The electrochemical performance of the electrodes reaches a maximum for the pure carbon nanotubes/manganese oxide nanocomposite coated with 600 ALD cycles exhibiting a specific capacitance of 78.68 mF cm-2 at 5 mV s-1. This result could be attributed to the synergetic effect between the components in the nanocomposite and an effective utilization of the active materials. Therefore it was demonstrated that a nanocomposite material comprising electric double layer capacitance together with the conductive framework of the carbon nanotubes and pseudocapacitive metal oxides is of great interest due to its dual charge storage mechanism and the advantages of each mechanism are exploited in these new hybrid devices. This work was carried out at University of Aveiro and at Humboldt-Universität zu Berlin due to complementary avaivable expertises and equipments, and also benefits of several international collaborations due to the multidisciplinar nature of the research field.

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Andres, Britta. "Low-Cost, Environmentally Friendly Electric Double-Layer Capacitors : Conept, Materials and Production." Doctoral thesis, Mittuniversitetet, Avdelningen för naturvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-31539.

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Today’s society is currently performing an exit from fossilfuel energy sources. The change to sustainable alternativesrequires inexpensive and environmentally friendly energy storagedevices. However, most current devices contain expensive,rare or toxic materials. These materials must be replaced bylow-cost, abundant, nontoxic components.In this thesis, I suggest the production of paper-based electricdouble-layer capacitors (EDLCs) to meet the demand oflow-cost energy storage devices that provide high power density.To fulfill the requirements of sustainable and environmentallyfriendly devices, production of EDLCs that consist of paper,graphite and saltwater is proposed. Paper can be used as aseparator between the electrodes and as a substrate for theelectrodes. Graphite is suited for use as an active material in theelectrodes, and saltwater can be employed as an electrolyte.Westudied and developed different methods for the productionof nanographite and graphene from graphite. Composites containingthese materials and similar advanced carbon materialshave been tested as electrode materials in EDLCs. I suggest theuse of cellulose nanofibers (CNFs) or microfibrillated cellulose(MFC) as a binder in the electrodes. In addition to improvedmechanical stability, the nanocellulose improved the stabilityof graphite dispersions and the electrical performance of theelectrodes. The influence of the cellulose quality on the electricalproperties of the electrodes and EDLCs was investigated.The results showed that the finest nanocellulose quality is notthe best choice for EDLC electrodes; MFC is recommended forthis application instead. The results also demonstrated thatthe capacitance of EDLCs can be increased if the electrodemasses are adjusted according to the size of the electrolyte ions.Moreover, we investigated the issue of high contact resistancesat the interface between porous carbon electrodes and metalcurrent collectors. To reduce the contact resistance, graphitefoil can be used as a current collector instead of metal foils.Using the suggested low-cost materials, production methodsand conceptual improvements, it is possible to reduce the material costs by more than 90% in comparison with commercialunits. This confirms that paper-based EDLCs are apromising alternative to conventional EDLCs. Our findings andadditional research can be expected to substantially supportthe design and commercialization of sustainable EDLCs andother green energy technologies.
I dagens samhälle pågår en omställning från användning avfossila energikällor till förnybara alternativ. Denna förändringkräver miljövänliga och kostnadseffektiva elektriska energilagringsenheterför att möjliggöra en kontinuerlig energileverans.Dagens energilagringsenheter innehåller ofta dyra, sällsyntaeller giftiga material som behöver bytas ut för att nå hållbaralösningar.I denna avhandling föreslås att tillverka pappersbaseradesuperkondensatorer som möter kraven för kostnadseffektivaelektriska energilagrare med hög effekttäthet. För att nå kravenpå miljömässigt hållbara enheter föreslås användning avendast papper, grafit och saltvatten. Papper kan användas somseparator mellan elektroder likväl som substrat vid elektrodbestrykning.Grafit kan användas som aktivt elektrodmaterialoch saltvatten fungerar som elektrolyt. Olika metoder har härutvecklats för att producera nanografit och grafen från grafit.Dessa material har tillsammans med liknande, kommersiellt tillgängliga,avancerade kolmaterial testats i elektrodkompositerför superkondensatorer. Som bindemedel i dessa kompositerföreslås nanofibrillerad eller mikrofibrillerad cellulosa. Jaghar demonstrerat att nanocellulosa ökar dispersionsstabilitetensamt förbättrar den mekaniska stabiliteten och dom elektriskaegenskaperna i elektroderna. Hur cellulosans kvalitet påverkarelektroderna har undersökts och visar att den finaste kvaliteteninte är det bästa valet för superkondensatorer, istället rekommenderasmikrofibrillerad cellulosa. Utöver detta demonstrerasmöjligheten att öka superkondensatorernas kapacitans genomatt balansera elektrodernas massa med hänsyn till jonernasstorlek i elektrolyten. I avhandlingen diskuteras även svårigheternamed hög kontaktresistans i gränssnittet mellan porösakolstrukturer och metallfolie och hur detta kan undvikas omgrafitfolie används som kontakt.Genom att använda de material, produktionstekniker ochkonceptförbättringar som föreslås i avhandlingen är det möjligtatt reducera materialkostnaderna med mer än 90% i jämförelsemed kommersiella superkondensatorer. Detta bekräftar att pappersbaserade superkondensatorer är ett lovande alternativoch våra resultat tillsammans med vidare utveckling harstor potential att stödja övergången till miljömässigt hållbarasuperkondensatorer och annan grön energiteknik.

Vid tidpunkten för disputationen var följande delarbeten opublicerade: delarbete 6 inskickat.

At the time of the doctoral defence the following papers were unpublished: paper 6 submitted.

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New, David Allen 1976. "Double layer capacitors : automotive applications and modeling." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28337.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.
Includes bibliographical references (p. 223-227).
This thesis documents the work on the modeling of double layer capacitors (DLCs) and the validation of the modeling procedure. Several experiments were conducted to subject the device under test to a variety of charging/discharging profile and temperatures in an effort to simulate the various conditions such a device might encounter in an automotive type application. High and low current charging profiles were performed for both charge/discharge and charge/hold/discharge type experiments. Low temperature ([approx.] -25 ⁰C), room temperature ([approx.] 21 ⁰C), and high temperature experiments ([approx.] 50 ⁰C) were performed for the investigation of temperature effects on these devices. The derived DLC model was used in PSpice® and Matlab® simulations to determine how accurately the model could predict the performance of the device. The nonlinear characteristics of the device were also investigated and the nonlinear modeling information presented as an addition to the basic DLC model. Device variation was explored for a small sample of these devices in an effort to gain insight on the range of tolerances for modern devices. This work also presents an extensive look into the variety of electrochemical capacitor devices under investigation and in use today. An explanation of these devices and their distributed resistances and capacitance is included. This thesis gives a detailed look into the experimental setups and testing procedures used to test the devices, the simulations for the comparison, and presents the results of the comparison. Finally, this thesis documents the conclusion that this simple model procedure adequately predicts the performance of the device under these various performance profiles.
by David Allen New.
S.M.

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Wade, Timothy Lawrence. "High power carbon based supercapacitors /." Connect to thesis, 2006. http://repository.unimelb.edu.au/10187/439.

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Energy storage devices are generally evaluated on two main requirements; power and energy. In supercapacitors these two performance criteria are altered by the capacitance, resistance and voltage. (For complete abstract open document)

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Breitsprecher, Konrad [Verfasser], and Christian [Akademischer Betreuer] Holm. "Simulation studies on electrodes and electrolytes for electric double layer capacitors / Konrad Breitsprecher ; Betreuer: Christian Holm." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2018. http://d-nb.info/1176521616/34.

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Teuber, Moritz [Verfasser], Dirk Uwe [Akademischer Betreuer] Sauer, and Sandra [Akademischer Betreuer] Korte-Kerzel. "Lifetime assessment and degradation mechanisms in electric double-layer capacitors / Moritz Teuber ; Dirk Uwe Sauer, Sandra Korte-Kerzel." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/121155791X/34.

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Teuber, Moritz Verfasser], Dirk Uwe [Akademischer Betreuer] [Sauer, and Sandra [Akademischer Betreuer] Korte-Kerzel. "Lifetime assessment and degradation mechanisms in electric double-layer capacitors / Moritz Teuber ; Dirk Uwe Sauer, Sandra Korte-Kerzel." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/121155791X/34.

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Bodnar, Rares. "Fast charging techniques and compact integrated implementations for electrochemical double layer capacitors in portable applications." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/367559/.

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The widespread increase in the range and types of portable electronic devices in the past decades has resulted in higher requirements for energy storage and conversion modules. Most of these devices use rechargeable batteries as energy storage elements. No matter what type of batteries are used (Ni-Cd, Ni-MH, Li-Ion, etc.) they all have one serious drawback in common, in terms of charging time. Electrochemical double layer capacitors (EDLCs) also known as ultracapacitors or supercapacitors seem to have overcome this disadvantage, at the cost of lower energy storage capacity. This work aims to explore the design of fast and compact integrated charging techniques for ultracapacitors using the AC mains network as the source. The main constraints that arise are the power dissipation on-chip and in the magnetic components due to the large amount of energy that has to be transferred in a very short time interval. Two other limitations come from the EDLC side due to the device parasitics and the widely varying voltages over the operational envelope. This will impose the need for a flexible control system providing high efficiency over the whole output voltage range. The structure of this thesis comprises five main parts: literature review, behavioural modelling of the control system (including matlab simulations); implementation of the device with discrete components; design of an analogue circuit implementation and design of a mixed signal circuit implementation. As ultracapacitors represent one of the newest solutions in the field of electrical energy storage there are very few designs for chargers from the mains network. Therefore the literature review will also examine the properties and the modelling of EDLCs, as well as the choice of converter topologies available and the characteristics of the magnetic devices required for the system. The behavioural model of the control module gives a preview of the system parameters, while the design chapter introduces a series of new control techniques. The simulations and measurements of the breadboard circuit come as a first confirmation of the design approach and make it a viable starting point for an IC implementation. The analogue IC design presents the integration of the algorithms in a medium-voltage process using the current mode approach, as a demonstrator for a fully monolithic high-voltage IC. Once the functionality of the system is demonstrated at IC level, the mixed-signal system aims to optimize the device and provide a broader flexibility for the system parameters and control algorithms.

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Turano, Stephan Parker. "Carbon Nanotubes chemical vapor deposition synthesis and application in electrochemical double layer supercapacitors /." Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-02242005-094827/unrestricted/turano%5Fstephan%5Fp%5F200505%5Fmast.pdf.

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Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2005.
Ready, Jud, Committee Co-Chair ; Carter, Brent, Committee Co-Chair ; Snyder, Bob, Committee Member ; Wang, Zhong Lin, Committee Member. Includes bibliographical references.

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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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Guidi, Giuseppe. "Energy management systems on board of electric vehicles, based on power electronics." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5270.

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The core of any electric vehicle (EV) is the electric drive train, intended as the energy conversion chain from the energy tank (typically some kind of rechargeable battery) to the electric motor that converts the electrical energy into the mechanical energy needed for the vehicle motion. The need for on-board electrical energy storage is the factor that has so far prevented pure electric vehicles from conquering significant market share. In fact electrochemical batteries, which are currently the most suitable device for electrical energy storage, have serious limitations in terms of energy and/or power density, cost and safety. All those characteristics reflect in pure electric vehicles being outperformed by standard internal combustion engine (ICE) based vehicles in terms of driving range, time needed to refuel and purchase cost. Electric vehicles do have their distinctive advantages, being intrinsically much more efficient, operating at zero emissions at the pipe, and offering a higher degree of controllability that can potentially enhance driving safety. No wonder then, that electric energy storage technology has attracted considerable R&D investments, resulting in new traction battery packs that are getting closer and closer to the industrial targets. In this scenario of EV technology gaining momentum, power electronics engineers have to come up with newer solutions allowing for more efficient and more reliable utilization of the precious on-board energy that comes in a form that cannot be directly utilized by the motor. At present, most of the research in the area of power electronics for automotive is focused in volume and cost reduction techniques. The increase in power density is pursued by developing components that can be operated at higher temperature, thus relieving the requirements on cooling. In this thesis, the focus is on the development of alternative topologies for the power electronics converters that make use of some peculiarities of the energy storage components and of the electrical drive train in general, rather than being a mere component-level optimization of well established topologies. A novel converter topology is proposed for hybridization of the energy source with a supercapacitor-based power buffer being used to assist the main traction battery. From the functional point of view, the topology implements a bidirectional DC/DC converter. Making use of the fact that the battery terminal voltage is close to constant, an arrangement for the supercapacitors is devised allowing for bidirectional power flow by using power electronics devices of lower ratings than the ones needed in conventional DC/DC converters. At the same time, much smaller magnetic components are needed. Theoretical analysis of the operation of the proposed converter is given, allowing for optimized design. A full-scale experimental prototype rated at 30 kW, intended for use in a pure EV, has been built and tested. Results validate the theory and show that no particular impediment exist to the deployment of the concept in practical applications. Another concept introduced in the thesis is an architecture where the traction inverter is embedded in the energy storage device. The latter is constituted by several modules, as in the case of modern Li-ion battery systems, and each module is equipped with a local power electronics interface, making it functionally equivalent to a controllable voltage source. The result is a modular, distributed system that can be engineered to have very high reliability and also to exhibit self-healing properties. A prototype with a minimum number of modules has been built and tested. Results confirm the effectiveness of the system, and make it a good candidate for deployment in applications where reliability is the most important requirement.

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Akle, Barbar Jawad. "Characterization and Modeling of the Ionomer-Conductor Interface in Ionic Polymer Transducers." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28682.

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Ionomeric polymer transducers consist of an ion-exchange membrane plated with conductive metal layers on its outer surfaces. Such materials are known to exhibit electromechanical coupling under the application of electric fields and imposed deformation (Oguro et al., 1992; Shahinpoor et al., 1998). Compared to other types of electromechanical transducers, such as piezoelectric materials, ionomeric transducers have the advantage of high-strain output (> 9% is possible), low-voltage operation (typically less than 5 V), and high sensitivity in the charge-sensing mode. A series of experiments on actuators with various ionic polymers such as Nafion and novel poly(Arylene ether disulphonate) systems (BPS and PATS) and electrode composition demonstrated the existence of a linear correlation between the strain response and the capacitance of the material. This correlation was shown to be independent of the polymer composition and the plating parameters. Due to the fact that the low-frequency capacitance of an ionomer is strongly related to charge accumulation at the electrodes, this correlation suggests a strong relationship between the surface charge accumulation and the mechanical deformation in ionomeric actuators. The strain response of water-hydrated transducers varies from 50 μstrain/V to 750 μstrain/V at 1Hz while the strain-to-charge response is between 9 ^μstrain_{^c_m²} and 15 ^μstrain_{^c_m²}. This contribution suggests a strong correlation between cationic motion and the strain in the polymer at the ionomer-conductor interface. A novel fabrication technique for ionic polymer transducers was developed for this dissertation for the purpose of quantifying the relationship between electrode composition and transducer performance. It consists of mixing an ionic polymer dispersion (or solution) with a fine conducting powder and attaching it to the membrane as an electrode. The Direct Assembly Process (DAP) allows the use of any type of ionomer, diluent, conducting powder, and counter ion in the transducer, and permits the exploration of any novel polymeric design. Several conducting powders have been incorporated in the electrode including single-walled carbon nanotubes (SWNT), polyaniline (PANI) powders, high surface area RuO2, and carbon black electrodes. The DAP provided the tool which enabled us to study the effect of electrode architecture on performance of ionic polymer transducers. The DAP allows the variation in the electrode architecture which enabled us to fabricate dry transducers with 50x better performance compared to transducers made using the state of the art impregnation-reduction technique. DAP fabricated transducers achieved a strain of 9.4% at a strain rate of 1%/s. Each electrode material had an optimal concentration in the electrode. For RuO2, the optimal loading was approximately 45% by volume. This study also demonstrated that carbon nanotubes electrodes have an optimal performance at loadings around 30 vol%, while PANI electrodes are optimized at 95 vol%. Extensional actuation in ionic polymer transducers was first reported and characterized in this dissertation. An electromechanical coupling model presented by Leo et al. (2005) defined the strain in the active areas as a function of the charge. This model assumed a linear and a quadratic term that produces a nonlinear response for a sine wave actuation input. The quadratic term in the strain generates a zero net bending moment for ionic polymer transducers with symmetric electrodes, while the linear term is canceled in extensional actuation for symmetric electrodes. Experimental results demonstrated strains on the order of 110 μstrain in the thickness direction compared to 1700 μstrain peak to peak on the external fibers for the same transducer, could be achieved when it is allowed to bend under +/-2V potential at 0.5 Hz. Extensional and bending actuation in ionic polymer transducers were explained using a bimorph active area model. Several experiments were performed to compare the bending actuation with the extensional actuation capability. The active area in the model was assumed to be the high surface area electrode. Electric double layer theory states that ions accumulate in a thin boundary layer close to the metal-polymer interface. Since the metal powders are evenly dispersed in the electrode area of the transducer, this area is expected to actuate evenly upon voltage application. This active area model emphasizes the importance the boundary layer on the conductor-ionomer interfacial area. Computing model parameters based on experimental results demonstrated that the active areas model collapses the bending data from a maximum variation of 200% for the strain per charge, to less than 68% for the model linear term. Furthermore, the model successfully predicted bending response from parameters computed using thickness experimental results. The prediction was particularly precise in estimating the trends of non-linearity as a function of the amount of asymmetry between the two electrodes.
Ph. D.

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Areir, Milad. "Development of 3D printed flexible supercapacitors : design, manufacturing, and testing." Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/16659.

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The development of energy storage devices has represented a significant technological challenge for the past few years. Electrochemical double-layer capacitors (EDLCs), also named as supercapacitors, are a likely competitor for alternative energy storage because of their low-cost, high power density, and high fast charge/discharge rate. The recent development of EDLCs requires them to be lightweight and flexible. There are many fabrication techniques used to manufacture flexible EDLCs, and these methods can include pre-treatment to ensure more efficient penetration of activated carbon (AC) patterns onto the substrate, or those that utilise masks for the definitions of patterns on substrates. However, these methods are inconvenient for building cost-effective devices. Therefore, it was necessary to find a suitable process to reduce the steps of manufacture and to be able to print multiple materials uniformly. This research work describes the first use of a 3D printing technology to produce flexible EDLCs for energy storage. In this research work, the four essential elements for the EDLCs substrate, current collector, activated electrode, and gel electrolyte were investigated. The AC powder was milled by ball milling to optimise the paste deposition and the electrochemical performance. A flexible composite EDLC was designed and manufactured by 3D printing. The electrochemical performance of the flexible composite EDLCs was then examined. Being highly flexible is one of the critical demands for the recent development of EDLCs. Therefore, highly flexible EDLCs were designed and manufactured by only one single extrusion process. The 3D highly flexible EDLC maintains significant electrochemical performance under a mechanical bending test. To meet the power and energy requirements, the EDLCs were connected and tested in series and parallel circuits. A supercapacitor based on printed AC material displays an area specific capacitance of 1.48 F/cm2 at the scan rate of 20 mV/s. The coulombic efficiency for the flexible EDLC was found to be 59.91%, and the cycling stability was achieved to be 56% after 500 cycles. These findings indicate that 3D printing technology may be increasingly used to develop more sophisticated flexible wearable electronic devices.

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Kovařík, Jakub. "Superkapacitory pro akumulaci energie." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-318193.

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This paper describes the design of DC/DC converters designed for charging supercapacitors and subsequent transformation of voltage to the desired value. In the text are presented decreasing and increasing switched-mode voltage converter including the calculation of the individual components and also the design of converter that combines both types. Using simulation software has been verified the function of each circuits, which can serves as a lower power backup supply.

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Andres, Britta. "Paper-based Supercapacitors." Licentiate thesis, Mittuniversitetet, Avdelningen för naturvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-22410.

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The growing market of mobile electronic devices, renewable off-grid energy sources and electric vehicles requires high-performance energy storage devices. Rechargeable batteries are usually the first choice due to their high energy density. However, supercapacitors have a higher power density and longer life-time compared to batteries. For some applications supercapacitors are more suitable than batteries. They can also be used to complement batteries in order to extend a battery's life-time. The use of supercapacitors is, however, still limited due to their high costs. Most commercially available supercapacitors contain expensive electrolytes and costly electrode materials. In this thesis I will present the concept of cost efficient, paper-based supercapacitors. The idea is to produce supercapacitors with low-cost, green materials and inexpensive production processes. We show that supercapacitor electrodes can be produced by coating graphite on paper. Roll-to-roll techniques known from the paper industry can be employed to facilitate an economic large-scale production. We investigated the influence of paper on the supercapacitor's performance and discussed its role as passive component. Furthermore, we used chemically reduced graphite oxide (CRGO) and a CRGO-gold nanoparticle composite to produce electrodes for supercapacitors. The highest specific capacitance was achieved with the CRGO-gold nanoparticle electrodes. However, materials produced by chemical synthesis and intercalation of nanoparticles are too costly for a large-scale production of inexpensive supercapacitor electrodes. Therefore, we introduced the idea of producing graphene and similar nano-sized materials in a high-pressure homogenizer. Layered materials like graphite can be exfoliated when subjected to high shear forces. In order to form mechanical stable electrodes, binders need to be added. Nanofibrillated cellulose (NFC) can be used as binder to improve the mechanical stability of the porous electrodes. Furthermore, NFC can be prepared in a high-pressure homogenizer and we aim to produce both NFC and graphene simultaneously to obtain a NFC-graphene composite. The addition of 10% NFC in ratio to the amount of graphite, increased the supercapacitor's capacitance, enhanced the dispersion stability of homogenized graphite and improved the mechanical stability of graphite electrodes in both dry and wet conditions. Scanning electron microscope images of the electrode's cross section revealed that NFC changed the internal structure of graphite electrodes depending on the type of graphite used. Thus, we discussed the influence of NFC and the electrode structure on the capacitance of supercapacitors.

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Zubieta, Bernal Luis Eduardo. "Characterization of double-layer capacitors for power electronics applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ28861.pdf.

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Morossi, Ilaria. "Modellazione e analisi in frequenza di celle a supercondensatore." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.

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Tra le diverse tipologie di sistemi di accumulo energetico, i supercondensatori, grazie alla elevata densità di potenza, alla scarsa manutenzione richiesta e alla lunga vita utile in termini di numero di cicli, vedono grande flessibilità e possibilità di applicazione in molteplici settori del mercato, sia in utilizzo esclusivo sia all’interno di sistemi ibridi, dove vengono affiancati ad un'altra tecnologia di accumulo con caratteristiche complementari in grado di migliorarne le performance. Nell’ottica di estendere le applicazioni e ottimizzare il progetto e le prestazioni dei sistemi a supercondensatore è fondamentale lo sviluppo di modelli efficaci, in grado di simulare in maniera fedele il comportamento reale. L’elaborazione di modelli permette di eseguire test e simulare diverse condizioni operative, anche estreme, contenendo i costi e senza generare situazioni di pericolo. In questa tesi vengono esposti i principali modelli elettrici di celle a supercondensatore (SCs) presenti in letteratura e ne viene proposta l’implementazione in ambiente Matlab-Simulink, avvalendosi anche degli strumenti forniti dalle librerie Stateflow e Simscape. La procedura di stima dei parametri viene condotta attraverso la apposita toolbox di Simulink e i risultati dei modelli ottimizzati vengono confrontati con i profili sperimentali, ricavati da test eseguiti in laboratorio su un supercondensatore Maxwell Technologies BCAP3000. Infine, vista la possibilità offerta dai SC di sopportare veloci cicli di carica e scarica, viene eseguita un’analisi della risposta in frequenza, sempre in ambiente Simulink, in cui si realizza il diagramma complesso di impedenza nel range di frequenza da 1 mHz a 100 kHz. Tale analisi consentirà di individuare i valori di frequenza limite oltre i quali il supercondensatore non risulta più efficiente e sarà completata da un’interpretazione sia elettrica circuitale, sia fisica dei grafici di impedenza.

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Ljungberg, Stefan. "High Frequency Oscillations at an Electric Double Layer." Thesis, KTH, Rymd- och plasmafysik, 1995. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91579.

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Wang, Hao. "Mechanistic studies of electrochemical double layer capacitors using solid-state NMR spectroscopy." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708302.

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Lin, J. F. (Jhih-Fong). "Multi-dimensional carbonaceous composites for electrode applications." Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526208459.

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Abstract The objective of this thesis is to demonstrate multi-dimensional carbon nanotube (CNT) structures in combination with various active materials in order to evaluate their performance in electrode applications such as cold emitters, electric double-layer capacitors (EDLC), and electrochemical sensor/catalyst devices. As the host materials for other active materials, the construction of multi-dimensional CNT nanostructures in this thesis is achieved by two different approaches. In the first, direct growth of 3-dimensional carbon nanostructures by catalytic chemical deposition to produce filamentary carbon as well as vertically aligned forests was applied. The second route that was utilized encompassed the immobilization of CNTs from dispersions to form 2-dimensional surface coatings as well as self-supporting porous buckypapers. Carbonaceous nanocomposites of the active materials are obtained by a number of different methods such as (i) growing nanotubes and filamentous structures on porous Ni catalyst structures, (ii) impregnating CNTs with organic receptor molecules or with Pd nanoparticles, (iii) plating and replacing Cu with Pd on the nanotubes by chemical and galvanic reactions, (iv) annealing W evaporated on CNTs to form CNT-WC composites in solid-solid reactions and (v) reacting S vapor with W coated on CNTs to synthesize CNT-WS2 edge-on lamellar structures of the dichalcogenide in the vertically aligned CNT forests. The 3-dimensional carbon-Raney®Ni composite electrodes show reasonable specific capacitance of ~12 F·g-1 in electric double-layer capacitors as well as a low turn-on field (<1.0 V·µm-1) in field emitter devices. CNT-Nafion®-trifluoroacetylazobenzene coatings on glassy carbon electrodes outperform their Nafion®-trifluoroacetylazobenzene counterparts in electrochemical sensing of different amine compounds (e.g. 10 mM cadaverine, putrescine or ammonia). Cu and CuPd/buckypaper composites display catalytic activity in electrocatalytic oxidation of methanol in alkaline media. On the other hand, nanocomposites of WC and WS2 with aligned CNT forest exhibit a promising performance in hydrogen evolution reactions with an overpotential between -0.5 and -0.7 V at pH~1. In addition, these respective CNT forest aligned nanocomposites also demonstrate a novel method to obtain macroscopic 3-dimensional catalytic electrode assemblies. The results in this thesis elucidate the combination of carbon based nanostructures with organic and inorganic materials as a feasible and versatile approach to produce electrodes for several applications. The following studies of each active carbonaceous composite are expected to boost the technological innovation in relevant fields and initiate further development for commercial exploitation
Tiivistelmä Työn tavoitteena oli demonstroida moniulotteisia hiilinanoputkirakenteita (CNT), joihin yhdistetään erilaisia aktiivisia materiaaleja sekä arvioida niiden suorituskykyä elektrodisovelluksissa, kuten kenttäemitterissä, sähköisissä kaksoiskerroskondensaattoreissa ja sähkökemiallisissa anturi- ja katalyyttikomponenteissa. Moniulotteisten CNT-nanorakenteiden konstruoiminen muiden aktiivisten materiaalien isäntämateriaaliksi toteutettiin kahdella tavalla. Ensimmäisessä toteutuksessa sovellettiin katalyyttis-kemiallista pinnoitusta, jolla kasvatettiin suoraan kolmiulotteisia hiilinanorakenteita sekä kuitumaisena hiilenä että pystysuuntaan orientoituneina hiilinanoputkimetsinä. Toinen päämenetelmä oli hiilinanoputkien immobilisointi dispersioista kaksiulotteisiksi pinnoitteiksi ja itsetukeutuviksi huokoisiksi hiilinanoputkipapereiksi. Hiiltä sisältäviä aktiivisten materiaalien nanokomposiitteja valmistettiin useilla menetelmillä, kuten (i) kasvattamalla nanoputkia ja kuitumaisia rakenteita huokoisiin Ni-katalyyttirakenteisiin, (ii) kyllästämällä hiilinanoputkia orgaanisilla reseptorimolekyyleillä tai Pd-nanopartikkeleilla, (iii) pinnoittamalla ja korvaamalla nanoputkien päällä olevaa kuparia palladiumilla kemiallisten ja galvaanisten reaktioiden avulla, (iv) hehkuttamalla hiilinanoputkien pinnalle höyrystettyä wolframia (W) muodostamaan CNT-WC-komposiitteja kiinteä–kiinteä-reaktiolla sekä (v) antamalla rikkihöyryn reagoida W-pinnoitettujen hiilinanoputkien kanssa lamellaaristen CNT-WS2-kalkogenidirakenteiden syntetisoimiseksi pystysuuntaan orientoituneisiin CNT-metsiin. Kolmiulotteisilla hiili–Raney®Ni-komposiittielektrodeilla saavutetaan kohtuullinen ominaiskapasitanssi (~12 F·g-1) sähköisissä kaksoiskerroskondensaattoreissa ja pieni kytkeytymiskenttä (<1,0 V·μm-1) kenttäemitterikomponenteissa. CNT-Nafion®-trifluoroasetyyliatsobentseeni-pinnoitteet lasimaisilla hiilielektrodeilla ovat selvästi parempia erilaisten amiiniyhdisteiden (esimerkiksi 10 mM kadaveriini, putreskiini tai ammoniakki) sähkökemiallisessa havaitsemisessa kuin vastaavat Nafion®-trifluoroasetyyliatsobentseeni-pinnoitteet. Cu- ja CuPd-hiilinanoputkipaperikomposiitit osoittavat katalyyttistä aktiivisuutta metanolin sähkökatalyyttisessä hapettumisessa emäksisessä väliaineessa. Toisaalta WC- ja WS2-yhdisteiden ja orientoituneiden CNT-metsien muodostamat nanokomposiitit osoittavat lupaavaa suorituskykyä vedynmuodostamisreaktiossa -0,5…-0,7 V ylipotentiaalilla, ja nämä myös demonstroivat uutta menetelmää makroskooppisten kolmiulotteisten katalyyttisten elektrodirakenteiden toteuttamiseksi. Väitöskirjan tulokset osoittavat, että hiilipohjaisten nanorakenteiden ja orgaanisten/epäorgaanisten materiaalien yhdistäminen on toteuttamiskelpoinen ja monipuolinen lähestymistapa elektrodien valmistamiseksi useisiin sovelluksiin. Kunkin työssä esitetyn aktiivista hiiltä sisältävän komposiitin tutkimuksen odotetaan lisäävän kyseisen alan teknisiä innovaatioita ja synnyttävän lisää kehitystyötä tutkimuksen kaupalliseksi soveltamiseksi

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Tian, Xu [Verfasser]. "Towards the realization of powerful and energetic electrochemical double layer capacitors / Xu Tian." Ulm : Universität Ulm. Fakultät für Naturwissenschaften, 2015. http://d-nb.info/1080562915/34.

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Ratniyomchai, Tosaphol. "Optimal design and control of stationary electrochemical double-layer capacitors for light railways." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7133/.

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The optimisation algorithm has been further investigated to understand the influence of the weight coefficients that affect the solution of all the optimisation problems and it is very often overlooked in the traditional approach. In fact, the choice of weight coefficients leading to the optimum among different optimal solutions also presents a challenge and this specific problem does not give any a priori indications. This challenge has been tackled using both genetic algorithms and particle swarm optimisations, which are the best methods when there are multiple local optima and the number of parameters is large. The results show that, when the optimal set of coefficients are used and the optimal positions and capacitances of EDLCs are selected, the energy savings can be up to 42%. The second problem of the control of the storage has been tackled with a linear state of charge control based on a piece-wise linear characteristic between the current and the voltage deviation from the nominal voltage of the supply at the point of connection of the storage. The simulations show that, regardless of the initial state of charge, the control maintain the state of charge of EDLCs within the prescribed range with no need of using the on-board braking resistor and, hence, dissipating braking energy. The robustness of the control algorithm has been verified by changing the characteristics of the train loading and friction force, with an energy saving between 26-27%.

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Ku, Daniel C. (Daniel Chung-Ming) 1985. "Methodology, morphology, and optimization of carbon nanotube growth for improved energy storage in a double layer capacitor." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/63028.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 77-80).
The goal of this thesis is to optimize the growth of carbon nanotubes (CNTs) on a conducting substrate for use as an electrode to improve energy density in a double-layer capacitor. The focus has been on several areas, such as substrate material, growth conditions, catalyst variations, and thin-film deposition techniques in order to achieve growth of a high density, vertically-aligned carbon nanotube array suitable for use as an electrode. This thesis describes the methodology of modifying a significant number of parameters in order to achieve all of the targeted electrode specifications, with the exception of nanotube density. The successful growth of a CNT array on an aluminum foil substrate marks an important milestone for realizing a future commercial product.
by Daniel C. Ku.
S.M.

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Shah, Rakesh Kumar. "Synthesis and Characterization of Electrochemical Double Layer Capacitors Using Aligned Architectures of Carbon Nanotubes." Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1674103521&sid=9&Fmt=2&clientId=1509&RQT=309&VName=PQD.

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Shiu, Huan-Ruei. "Effects of Electric Double Layer on Bypass Transition in Microchannel Flow." Université Joseph Fourier (Grenoble), 2004. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0401200516434500.

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Hou, Chia-Hung. "Electrical double layer formation in nanoporous carbon materials." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22698.

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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Sotira Yiacoumi; Committee Co-Chair: Costas Tsouris; Committee Member: Ching-Hua Huang; Committee Member: Sankar Nair; Committee Member: Spyros G. Pavlostathis.

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Yang, Kun-Lin. "Electrical double-layer formation at the nanoscale : molecular modeling and applications." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20123.

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Meige, Albert, and albert@meige net. "Numerical modeling of low-pressure plasmas: applications to electric double layers." The Australian National University. Research School of Physical Sciences and Engineering, 2006. http://thesis.anu.edu.au./public/adt-ANU20070111.002333.

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Inductive plasmas are simulated by using a one-dimensional particle-in-cell simulation including Monte Carlo collision techniques (pic/mcc). To model inductive heating, a non-uniform radio-frequency (rf) electric field, perpendicular to the electron motion is included into the classical particle-in-cell scheme. The inductive plasma pic simulation is used to confirm recent experimental results that electric double layers can form in current-free plasmas. These results differ from previous experimental or simulation systems where the double layers are driven by a current or by imposed potential differences. The formation of a super-sonic ion beam, resulting from the ions accelerated through the potential drop of the double layer and predicted by the pic simulation is confirmed with nonperturbative laser-induced fluorescence measurements of ion flow. It is shown that at low pressure, where the electron mean free path is of the order of, or greater than the system length, the electron energy distribution function (eedf) is close to Maxwellian, except for its tail which is depleted at energies higher than the plasma potential. Evidence supporting that this depletion is mostly due to the high-energy electrons escaping to the walls is given. ¶ A new hybrid simulation scheme (particle ions and Boltzmann/particle electrons), accounting for non-Maxwellian eedf and self-consistently simulating low-pressure high-density plasmas at low computational cost is proposed. Results obtained with the improved hybrid model are in much better agreement with the full pic simulation than the classical non self-consistent hybrid model. This model is used to simulate electronegative plasmas and to provide evidence supporting the fact that propagating double layers may spontaneously form in electronegative plasmas. It is shown that critical parameters of the simulation were very much aligned with critical parameters of the experiment.

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Thompson, David. "The local Coulombic Monte Carlo algorithm : applications to the electric double layer." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/32355.

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A reformulation of the Coulomb problem, using a local Coulomb algorithm based on auxiliary fields, has been extended to slab and quasi-2D geometries. It has been implemented using Metropolis Monte Carlo and Gaussian charge interpolation functions. We have established the accuracy of the algorithm by generating effective pair potentials. Using this implementation, the Gouy-Chapman problem was numerically resolved for constant potential slab boundaries. In the low coupling limit, we find excellent aggreement with analytic solutions. In the high coupling regime, we find agreement with the analytic theory in the limit of large wall separation. Using the contact value theorem, we calculate the pressure experienced by like-charged equipotential walls. The parameter space we consider pertains to many interesting biomaterials ranging from monovalent biomembranes to spermidine DNA. The numerical results show attractions mediated by counter-ions between the like-charged equipotential slab boundaries. We also extend the implementation to allow for inhomogeneous dielectric backgrounds. The effect of a thin adsorbed layer of solvent is considered for an electrolyte system bounded by isolated electrodes. We show that a reduction in the dielectric value of this adsorbed layer results in a depletion of ions near the electrodes, even though the electrodes carry zero total charge. The applications considered show the versatility and accuracy of our implementation.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

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Asante, Jerry Bamfo [Verfasser]. "Nanostructured Ni(OH)2 and MnO2 cathode designs for aqueous asymmetric double layer capacitors / Jerry Bamfo Asante." Ulm : Universität Ulm, 2019. http://d-nb.info/1184989842/34.

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Zubieta, Luis Eduardo. "Design of a propulsion system with double-layer power capacitors and soft-switched converters for a hybrid automobile." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58962.pdf.

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Drillkens, Julia Verfasser], Dirk Uwe [Akademischer Betreuer] [Sauer, and Ulrike [Akademischer Betreuer] Krewer. "Aging in electrochemical double layer capacitors : an experimental and modeling approach / Julia Drillkens ; Dirk Uwe Sauer, Ulrike Krewer." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1171323751/34.

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Oschatz, Martin, S. Boukhalfa, W. Nickel, J. T. Lee, S. Klosz, L. Borchardt, A. Eychmüller, G. Yushin, and Stefan Kaskel. "Kroll-carbons based on silica and alumina templates as high-rate electrode materials in electrochemical double-layer capacitors." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-151345.

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Hierarchical Kroll-carbons (KCs) with combined micro- and mesopore systems are prepared from silica and alumina templates by a reductive carbochlorination reaction of fumed silica and alumina nanoparticles inside a dense carbon matrix. The resulting KCs offer specific surface areas close to 2000 m2 g−1 and total pore volumes exceeding 3 cm3 g−1, resulting from their hierarchical pore structure. High micropore volumes of 0.39 cm3 g−1 are achieved in alumina-based KCs due to the enhanced carbon etching reaction being mainly responsible for the evolution of porosity. Mesopore sizes are uniform and precisely controllable over a wide range by the template particle dimensions. The possibility of directly recycling the process exhaust gases for the template synthesis and the use of renewable carbohydrates as the carbon source lead to a scalable and efficient alternative to classical hard- and soft templating approaches for the production of mesoporous and hierarchical carbon materials. Silica- and alumina-based Kroll-carbons are versatile electrode materials in electrochemical double-layer capacitors (EDLCs). Specific capacitances of up to 135 F g−1 in an aqueous electrolyte (1 M sulfuric acid) and 174 F g−1 in ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate) are achieved when measured in a symmetric cell configuration up to voltages of 0.6 and 2.5 V, respectively. 90% of the capacitance can be utilized at high current densities (20 A g−1) and room temperature rendering Kroll-carbons as attractive materials for EDLC electrodes resulting in high capacities and high rate performance due to the combined presence of micro- and mesopores.

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Drillkens, Julia [Verfasser], Dirk Uwe [Akademischer Betreuer] Sauer, and Ulrike [Akademischer Betreuer] Krewer. "Aging in electrochemical double layer capacitors : an experimental and modeling approach / Julia Drillkens ; Dirk Uwe Sauer, Ulrike Krewer." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1171323751/34.

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SCALIA, ALBERTO. "New devices for energy harvesting and storage: integrated third generation photovoltaic solar cells and electrochemical double layer capacitors." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2724022.

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A worldwide conversion towards renewable energy sources has to be implemented in order to hopefully avoid the irreversible consequences of the global temperature increment caused by the greenhouse gases production. In addition, the current need to benefit from electricity in every moment of daily life, mainly in case of limited access to the electric grid, is forcing the scientific community to an intensive effort towards the production of integrated energy harvesting and storage devices. The topic of this PhD thesis is to investigate and propose innovative solutions for the integration of third generation photovoltaic (PV) cells and electrochemical double layer capacitors (EDLCs), the so-called photo-capacitors. Different photo-capacitor structures have been studied and experimentally fabricated. At first, flexibility was explored, as it is a mandatory requirement to cover non-planar or bendable surfaces, which are more and more common in nowadays portable electronics. Easily scalable fabrication processes have been used for both the harvester and the storage units, employing photopolymer membranes as electrolytes and metallic grids as current collectors and electrodes substrates. For this configuration, the best overall conversion and storage efficiency ever reported for a flexible Dye sensitized solar cell (DSSC)-based photo-capacitor was demonstrated. Subsequently, observing in the literature an evident lack in the exploitation of high voltage photo-capacitors, EDLC electrolytes with broad voltage windows have been examined. These electrolytes allowed to fabricate stable and reliable devices integrating the EDLC with a PV module and not only with a single solar cell, as normally is done. High voltage values, up to 2.5 V, have been obtained employing an ionic liquid electrolyte (Pyr14TFSI) or –alternatively- a solid state electrolyte (PEO-Pyr14TFSI) for storage section fabrication. Moreover, novel electrolyte mixtures of organic solvents and ionic liquids with good physical and electrochemical properties have been employed with the aim to increase energy density and voltage with respect to commercial EDLCs. Finally, a novel polymer-based platform has been suggested for the fabrication of an innovative “two-electrodes” self-powered device. The multifunctional polymeric layer, made of two poly(ethylene glycol)-based sections separated by a perfluorinated barrier, was obtained by oxygen-inhibited UV-light crosslinking procedure. For the energy harvesting section, one side of the polymeric layer was adapted to enable iodide/triiodide diffusion in a DSSC, while the other side empowered sodium/chloride ions diffusion and was used for on-board charge storage. The resulting photo-capacitor results in a planar architecture appreciably simplified with respect to other recently proposed solutions and is definitely more easily exploitable in low power electronics.

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Lim, Jong Il. "Transient finite element analysis of electric double layer using Nernst-Planck-Poisson equations with a modified stern layer." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4703.

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Finite element analysis of electric double layer capacitors using a transient nonlinear Nernst-Planck-Poisson (NPP) model and Nernst-Planck-Poisson-modified Stern layer (NPPMS) model are presented in 1D and 2D. The NPP model provided unrealistic ion concentrations for high electrode surface potential. The NPPMS model uses a modified Stern layer to account for finite ion size, resulting in realistic ion concentrations even at high surface potential. The finite element solution algorithm uses the Newton-Raphson method to solve the nonlinear problem and the alpha family approximation for time integration to solve the NPP and NPPMS models for transient cases. Cubic Hermite elements are used for interfacing the modified Stern and diffuse layers in 1D while serendipity elements are used for the same in 2D. Effects of the surface potential and bulk molarity on the electric potential and ion concentrations are studied. The ability of the models to predict energy storage capacity is investigated and the predicted solutions from the 1D NPP and NPPMS models are compared for various cases. It is observed that NPPMS model provided realistic and correct results for low and high values of surface potential. Furthermore, the 1D NPPMS model is extended into 2D. The pore structure on the electrode surface, the electrode surface area and its geometry are important factors in determining the performance of the electric double layer capacitor. Thus 2D models containing a porous electrode are modeled and analyzed for understanding of the behavior of the electric double layer capacitor. The effect of pore radius and pore depth on the predicted electric potential, ion concentrations, surface charge density, surface energy density, and charging time are discussed using the 2D Nernst-Planck-Poissonmodified Stern layer (NPPMS) model.

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Sillars, Fiona B. "High energy density electrochemical double layer capacitors : the effect of pore size distribution on the performance of room temperature ionic liquids." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=13310.

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Huffstutler, Jacob Danial. "AN ANALYSIS OF ELECTROCHEMICAL ENERGY STORAGE USING ELECTRODES FABRICATED FROM ATOMICALLY THIN 2D STRUCTURES OF MOS2, GRAPHENE AND MOS2/GRAPHENE COMPOSITES." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1583.

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The behavior of 2D materials has become of great interest in the wake of development of electrochemical double-layer capacitors (EDLCs) and the discovery of monolayer graphene by Geim and Novoselov. This study aims to analyze the response variance of 2D electrode materials for EDLCs prepared through the liquid-phase exfoliation method when subjected to differing conditions. Once exfoliated, samples are tested with a series of structural characterization methods, including tunneling electron microscopy, atomic force microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. A new ionic liquid for EDLC use, 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate is compared in performance to 6M potassium hydroxide aqueous electrolyte. Devices composed of liquid-phase exfoliated graphene / MoS2 composites are analyzed by concentration for ideal performance. Device performance under cold extreme temperatures for the ionic fluid is presented as well. A brief overview of by-layer analysis of graphene electrode materials is presented as-is. All samples were tested with cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy, with good capacitive results. The evolution of electrochemical behavior through the altered parameters is tracked as well.

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42

Ellis, William Joseph. "Application of statistical mechanics to a model neuron /." Title page, contents and abstract only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phe479.pdf.

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43

Katakura, Seiji. "Electric double layer structure in ionic liquids studied using molecular dynamics simulations and interface-selective experimental techniques." Kyoto University, 2020. http://hdl.handle.net/2433/253294.

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44

Shi, Bobo. "The Electrical Double Layer at the Water-Silica Interface: Structure, Dynamics, Response to External Fields, and Biomolecules Adsorption." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461256456.

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45

Hoffmann, Viola [Verfasser]. "Conductive advanced carbon materials from biomass for the application in energy storage and conversion technologies (Electrochemical Double-Layer Capacitors and Direct Carbon Fuel Cells) / Viola Hoffmann." Düren : Shaker, 2020. http://d-nb.info/1222396181/34.

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46

Yang, Guomin. "Interfacial properties of calcium montmorillonite in aqueous solutions : Density functional theory and classical molecular dynamics studies on the electric double layer." Doctoral thesis, KTH, Kemisk apparatteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-204648.

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The swelling properties of Bentonite are highly affected by clay content and the clay-water interactions that arise from the ion distribution in the diffuse double layer formed near the charged montmorillonite (or smectite) surfaces. Existing continuum models describing the electric double layers, such as classical Poisson-Boltzmann and DLVO theory, ignore the ion-ion correlations, which are especially important for multivalent ions at high surface charge and ionic strength. To better understand the clay-water interactions, atomistic models were developed using both density functional theory of fluids (DFT) as well as classical molecular dynamics (MD) methods. In order to increase our understanding of water-saturated, swelling smectite clays, a DFT, technique was initially developed that allowed more accurate predictions of important thermodynamic properties of the diffuse double layers. This DFT approach was then extended to handle systems with mixtures of different sizes and charges. The extended DFT model was verified against experiments and Monte-Carlo simulations. One practical application was to predict the ion exchange equilibria in Bentonite clays, which have wide practical usage in different areas. Nevertheless, in the DFT work it was realized that DFT demands that the particles, ions in this case, which are described as hard spheres, realistically cannot be described as such at low water loadings, when ion specific hydration forces govern the electric double layer properties. To study how the deformation of the hydration shells of Ca2+ influences the properties of compacted smectite clays, MD simulations using the CLAYFF forcefield were employed in order to account for the deformation of the hydration shells. Comparisons of DFT and MD modeling then allowed to demonstrate under which conditions DFT modeling becomes increasingly inaccurate and when it still can give accurate results.
Under senare år har mycket forskning ägnats åt att förstå egenskaperna hos svällande leror som används för att skydda mot läckage av föroreningar från kontaminerade områden och från framtida slutförvar av radionuklider. Den fria svällningen förorsakas av de starka osmotiska krafter som uppstår när vatten tränger in mellan de tunna elektriskt negativt laddade lermineralskikten och löser de laddningskompenserande jonerna i det diffusa dubbelskiktet. I flera arbeten användandes av sk. kontinuum-teori har vattenmolekylens form, specifika orientering och bindning till katjonerna i de nanometerstora utrymmen mellan lerpartiklarna ej beaktats samt ej heller hur de hydratiserade jonerna orienteras på de atomärt ojämna ytorna. Detta möjliggörs dock genom modellering av de enskilda atomernas och jonernas interaktioner med molekyldynamik simuleringar, MD. I detta arbete har programmet Gromacs använts tillsammans med kraftfältet CLAYFF för att studera dessa fenomen i montmorillonitleror med natrium- och kalciumjoner. Simuleringarna visar att natrium bildar transienta innersfärkomplex vilka orienterar sig i bi-triangulära fördjupningar på ytan, ungefär 3.8 Å från mitt-planet mellan lerytorna. Denna orientering observeras ända upp till att avståndet mellan ytorna ökat till större än motsvarande fem lager vattenmolekyler mellan lerpartiklarnas ytor. Detta sker inte med kalcium, oberoende av avståndet mellan ytorna. Natriumjoner koordineras med fyra vattenmolekyler och en syreatom på leran vid ett lager vatten mellan ytorna och med fem till sex vattenmolekyler, ortogonalt orienterade med ökande mängd vatten mellan ytorna, och med en hydratiserad jon-radie av 3.1 Å. Kalcium koordinerar till sju vattenmolekyler vid ett vattenlager mellan ytorna, men ökar till åtta ortogonalt orienterade vattenmolekyler med en jonradie på 3.3 Å vid större avstånd. Generellt visas att när avståndet mellan lerytorna är mindre än ca 10 Å, deformeras de annars symmetriskt hydratiserade jonerna. En jämförelse mellan MD simuleringar och med klassisk täthetsfunktionalteori, DFT, visar att den senare inte kan beskriva hur yttersfärkomplexen samverkar med laddningarna bundna närmast ytan, dvs i Stern-lagret.

QC 20170403

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47

Taboada-Serrano, Patricia L. "Colloidal interactions in aquatic environments effect of charge heterogeneity and charge asymmetry /." Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-11102005-102942/.

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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006.
Yiacoumi, Sotira, Committee Chair ; Tsouris, Costas, Committee Co-Chair ; Pavlostathis, Spyros, Committee Member ; Tannenbaum, Rina, Committee Member ; Sherrill, David, Committee Member.

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48

Taboada-Serrano, Patricia Larisse. "Colloidal Interactions in Aquatic Environments: Effect of Charge Heterogeneity and Charge Asymmetry." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7521.

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The classical theory of colloids and surface science has universally been applied in modeling and calculations involving solid-liquid interfaces encountered in natural and engineered environments. However, several discrepancies between the observed behavior of charged solid-liquid interfaces and predictions by classical theory have been reported in the past decades. The hypothesis that the mean-field, pseudo-one-component approximation adopted within the framework of the classical theory is responsible for the differences observed is tested in this work via the application of modeling and experimental techniques at a molecular level. Silica and silicon nitride are selected as model charged solid surfaces, and mixtures of symmetric and asymmetric indifferent and non-indifferent electrolytes are used as liquid phases. Canonical Monte Carlo simulations (CMC) of the electrical double layer (EDL) structure of a discretely charged planar silica surface, embedded in solutions of indifferent electrolytes, reveal the presence of a size exclusion effect that is enhanced at larger values of surface charge densities. That effect translates into an unexpected behavior of the interaction forces between a charged planar surface and a spherical particle. CMC simulations of the electrostatic interactions and calculations of the EDL force between a spherical particle and a planar surface, similarly charged, reveal the presence of two attractive force components: a depletion effect almost at contact and a long-range attractive force of electrostatic origin due to ion-ion correlation effects. Those two-force components result from the consideration of discreteness of charge in the interaction of solid-liquid interfaces, and they contradict the classical theory predictions of electrostatic repulsive interaction between similarly charged surfaces. Direct interaction force measurements between a charged planar surface and a colloidal particle, performed by atomic force microscopy (AFM), reveal that, when indifferent and non-indifferent electrolytes are present in solution, surface charge modification occurs in addition to the effects on the EDL behavior reported for indifferent electrolytes. Non-uniformity and even heterogeneity of surface charge are detected due to the action of non-indifferent, asymmetric electrolytes. The phenomena observed explain the differences between the classical theory predictions and the experimental observations reported in the open literature, validating the hypothesis of this work.

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Thakore, Vaibhav. "Nonlinear dynamic modeling, simulation and characterization of the mesoscale neuron-electrode interface." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5529.

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Extracellular neuroelectronic interfacing has important applications in the fields of neural prosthetics, biological computation and whole-cell biosensing for drug screening and toxin detection. While the field of neuroelectronic interfacing holds great promise, the recording of high-fidelity signals from extracellular devices has long suffered from the problem of low signal-to-noise ratios and changes in signal shapes due to the presence of highly dispersive dielectric medium in the neuron-microelectrode cleft. This has made it difficult to correlate the extracellularly recorded signals with the intracellular signals recorded using conventional patch-clamp electrophysiology. For bringing about an improvement in the signal-to-noise ratio of the signals recorded on the extracellular microelectrodes and to explore strategies for engineering the neuron-electrode interface there exists a need to model, simulate and characterize the cell-sensor interface to better understand the mechanism of signal transduction across the interface. Efforts to date for modeling the neuron-electrode interface have primarily focused on the use of point or area contact linear equivalent circuit models for a description of the interface with an assumption of passive linearity for the dynamics of the interfacial medium in the cell-electrode cleft. In this dissertation, results are presented from a nonlinear dynamic characterization of the neuroelectronic junction based on Volterra-Wiener modeling which showed that the process of signal transduction at the interface may have nonlinear contributions from the interfacial medium. An optimization based study of linear equivalent circuit models for representing signals recorded at the neuron-electrode interface subsequently proved conclusively that the process of signal transduction across the interface is indeed nonlinear. Following this a theoretical framework for the extraction of the complex nonlinear material parameters of the interfacial medium like the dielectric permittivity, conductivity and diffusivity tensors based on dynamic nonlinear Volterra-Wiener modeling was developed. Within this framework, the use of Gaussian bandlimited white noise for nonlinear impedance spectroscopy was shown to offer considerable advantages over the use of sinusoidal inputs for nonlinear harmonic analysis currently employed in impedance characterization of nonlinear electrochemical systems. Signal transduction at the neuron-microelectrode interface is mediated by the interfacial medium confined to a thin cleft with thickness on the scale of 20-110 nm giving rise to Knudsen numbers (ratio of mean free path to characteristic system length) in the range of 0.015 and 0.003 for ionic electrodiffusion. At these Knudsen numbers, the continuum assumptions made in the use of Poisson-Nernst-Planck system of equations for modeling ionic electrodiffusion are not valid. Therefore, a lattice Boltzmann method (LBM) based multiphysics solver suitable for modeling ionic electrodiffusion at the mesoscale neuron-microelectrode interface was developed. Additionally, a molecular speed dependent relaxation time was proposed for use in the lattice Boltzmann equation. Such a relaxation time holds promise for enhancing the numerical stability of lattice Boltzmann algorithms as it helped recover a physically correct description of microscopic phenomena related to particle collisions governed by their local density on the lattice. Next, using this multiphysics solver simulations were carried out for the charge relaxation dynamics of an electrolytic nanocapacitor with the intention of ultimately employing it for a simulation of the capacitive coupling between the neuron and the planar microelectrode on a microelectrode array (MEA). Simulations of the charge relaxation dynamics for a step potential applied at t = 0 to the capacitor electrodes were carried out for varying conditions of electric double layer (EDL) overlap, solvent viscosity, electrode spacing and ratio of cation to anion diffusivity. For a large EDL overlap, an anomalous plasma-like collective behavior of oscillating ions at a frequency much lower than the plasma frequency of the electrolyte was observed and as such it appears to be purely an effect of nanoscale confinement. Results from these simulations are then discussed in the context of the dynamics of the interfacial medium in the neuron-microelectrode cleft. In conclusion, a synergistic approach to engineering the neuron-microelectrode interface is outlined through a use of the nonlinear dynamic modeling, simulation and characterization tools developed as part of this dissertation research.
Ph.D.
Doctorate
Physics
Sciences
Physics

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50

Chen, Yin-Chang, and 陳垠璋. "High-Power Matrerials for Electric Double layer Capacitors." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/63q3h2.

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碩士
國立臺北科技大學
有機高分子研究所
102
In this study, the high surface area of activated meso-carbonemicro-beads and the carbon nanotube for use as modern composite supercapacitor electrodes. The activated mesocarbonemicrobeads will be porous in internal and external part for high performance electrode materials. The aMCMB electrode has a high energy storage capacity. This capacitance of electrode is 350 F g-1 under current is 0.02A g-1. The capacitance of electrode will decrease to 155 F g-1 under current is 0.6A g-1. The study was decreased transfer path of internal ion and raise particle touch for power output of supercapacitor and high rate charge-discharge ability. This capacitance of electrode is 372 F g-1 under current is 0.02A g-1. The capacitance of electrode will decrease to 153 F g-1 under current is 0.6A g-1. The CNTs was added to milling process for raising electron transport and inter-granular pore. This capacitance of electrode is 292 F g-1 under current is 0.02A g-1. The capacitance of electrode will decrease to 177 F g-1 under current is 0.6A g-1.

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Dissertations / Theses on the topic 'Electric double layer capacitors'

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