Dissertations / Theses on the topic 'Electrode'
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Tavener, P. "Electron spectroscopy of electrode materials." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370304.
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Hoffrogge, Johannes Philipp. "A surface-electrode quadrupole guide for electrons." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-155503.
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Koep, Erik Kenneth. "A Quantitative Determination of Electrode Kinetics using Micropatterned Electrodes." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10524.
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Interfacial polarization resistances limit the performance of many thin film solid-state devices, especially at low temperatures. To improve performance, a fundamental understanding of the electrode kinetics that govern interfacial reaction rates must be developed. The goal of this work is to determine site-specific reaction mechanisms and the relative significance of various reactions in order to quantify optimum structural parameters within the cathode microstructure. Key parameters include the length of triple phase boundary (TPB), the quantity of exposed electrolyte/electrode surface, and the ratio of electrolyte to electrode material. These parameters, when studied in a specific system, can be incorporated into broader models, which will encompass the specific conductivity of each component to develop an optimized three-dimensional network.
The emphasis of this work is the systematic control and manipulation of potential cathodic reaction sites in order to develop an understanding of the relative importance of specific reaction sites. Since the physical dimensions of reaction sites are relatively small, an approach has been developed that utilizes micro-fabrication (similar to that used in integrated-circuit fabrication) to produce small and highly controlled microstructures.
Investigations were made into the nature and reactivity of Triple Phase Boundaries (hereafter TPB) through the use of patterned platinum electrodes since only the TPBs are active in these electrodes. After the processing details of micro-fabrication were established for the platinum electrodes, patterned Mixed-Ionic/Electronic Conducting (MIEC) electrodes were fabricated and studied using impedance spectroscopy to determine the contributions from the MIEC surface versus the TPB. Systematically changing the geometry of the MIEC electrodes (thickness and line width) allowed for the determination of the effect of ambipolar transport within the MIEC on the activity of MIEC surfaces versus the TPB. This information is critical to rational design of functionally graded electrodes (with optimal particle size, shape, porosity and conductivity). In addition to experimental studies, representative patterned electrode samples were made available for collaborative studies with surface scientists at other institutions to provide additional techniques (such as Raman Spectroscopy) on the carefully designed and controlled cathode surfaces.
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Taylor, M. E. "Substrate and electrode effects in inelastic electron tunnelling spectroscopy." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235265.
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Inelastic Electron Tunnelling Spectroscopy is a powerful and versatile technique for obtaining vibrational densities of states of amorphous materials and adsorbed molecules. The experimental device, or tunnel junction, consists of two metal electrodes separated by a thin (2nm) layer of the material under study. This thesis looks at features in the tunnelling spectrum due to electrode phonons, and also at the effects of substrate roughness on the spectrum. Two coupled linear chains are used to model the vibrational behaviour of joined lattices in order to consider the penetration of phonons of one material into the other; penetration does not occur unless the two chains have very similar properties. Work with Al-I-Al-Pb tunnel junctions confirms the model results, as no sign is seen of lead phonon peaks in the tunnelling spectrum. However, other workers have seen lead peaks in Al-I-Ag-Pb junctions, and invoked phonon penetration in explanation. Microscopic examination of similarly prepared silver films reveals that they are pinholed; and this, it is argued, gives rise to the lead peaks. Results are presented on the magnitudes of electrode phonon structure in tunnelling spectra, and models for the occurrence of these features are reviewed. It is argued, from comparison of the experimental data with bulk self energies from superconducting tunnelling, that the electron-phonon coupling responsible is characteristic of the bulk metal; interaction does not take place in the barrier. This is consistent with the linear chain model. The effects of roughening tunnel junctions with calcium fluoride substrates are studied. Little change is noted with undoped junctions, but investigation of formate-doped junctions confirms the loss in dopant peak intensity seen by other workers and some variation is noticed in the rate of loss of intensity between C-H and CO2 modes. The mechanism which best explains these observations is that roughening encourages penetration of the organic layer by atoms of the top electrode metal.
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Aixill, W. Joanne. "Electrode processes." Thesis, University of Oxford, 1998. http://ora.ox.ac.uk/objects/uuid:9578fd22-42fe-41cc-9d92-96f8272956d8.
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The work presented in this thesis first characterises a high speed channel flow cell and then applies the system to the electro-reduction of nitromethane in aqueous solution. Potential step transient measurements are carried out with the current-time transients simulated using a model based on the absence of axial diffusion. The excellent agreement between theory and experiment confirms the proposed mass transport model and further demonstrates that the combination of current-time transients recorded using the high speed channel flow cell and numerical simulations provide a powerful tool to access homogeneous rate constants of the order 1 x 106s̄¹. The high speed channel flow cell is then used in combination with a range of complementary electrochemical techniques, numerical modelling, in-situ ESR, single crystal experiments and kinetic isotope measurements to infer a mechanistic scheme for the complex electro-reduction pathway of nitromethane in aqueous solution. Platinum, gold, mercury/copper and mercury/gold electrodes are investigated enabling the most conclusive description of the reduction mechanism to date. The reaction pathway is shown to follow an ECEEE type process with the chemical step proceeding at the electrode surface. The heterogeneous rate constant, khet, describing the chemical step is calculated for each electrode surface. For platinum in the pH range 7.0 - 9.0 this value is 0.3 ± 0.06 cm s̄¹. For mercury/copper it is 0.18 cm s̄¹, for gold/mercury it is 0.06 cm s̄¹ and for Au it is 0.095 cm s̄¹. Consideration of these values shows a surprising independence of the heterogeneous rate constant on the chemical identity of the surface with all of the values being similar to within less than an order of magnitude. The reason for the apparent paradox of the observed surface indifference of the chemical reaction step is explained by a homogeneous H transfer from the carbon to the oxygen of the nitromethane radical anion, formed form the initial electron transfer step, occurring in the layer of solution immediately adjacent to the electrode solution as shown in the scheme below. The resulting species, •CH2 N(OH))ˉ then undergoes a rapid irreversible adsorption to the electrode surface and subsequent transformation to the final product the hydroxylamine, CH3NHOH. It is proposed that if the energy barrier to the adsorption of •CH2 N(OH))ˉ is less than that required for the H atom transfer then the reaction rate will be insensitive to the adsorption step and hence the chemical identity of the electrode. This introduces the concept of a whole new electrochemical process: the surface indifferent electrocatalytic reaction.
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Seon, Hongsun 1965. "Electrode erosion and arc stability in transferred arcs with graphite electrodes." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=108637.
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Arc stability and erosion behavior were studied on a hollow graphite DC cathode in an argon atmosphere at atmospheric pressure. It was found that the arc stability is associated with the electron emission mode transition of the cathode operation. Estimation of current densities, SEM pictures, Fast Fourier Transform (FFT) of total voltage, and measurement of cathode surface temperature supported this. Stable arcs are in the thermionic emission regime while unstable arcs in the thermofield emission regime. Higher argon gas flow rate is believed to cause the shift of the mode from the thermofield emission to the thermionic emission by increasing the arc root temperature through steepening the thermal gradient at the arc root and increasing ionization phenomena inside the arc. Sharp cathode tip geometry usually leads to the thermionic emission while a rounded tip geometry encourages the thermofield emission. For the unstable arcs, the high voltage fluctuation resulted from the jumping of the arc root between different cathode spots and changes in the arc length. In the stable arcs, however, the voltage was almost constant because of the absence of arc jumping. The standard deviation of the voltage was used as the arc stability indicator and was less than 3 V for the stable arc in this transferred arc system.The erosion rate of the cathode in this work ranged from 0.41 to 2.61 mug/C. At 150 A runs the arc stability strongly influenced the erosion rate; as the arc stability increased, the erosion rate decreased. Higher currents runs (300 and 400 A), however, showed the opposite trend because of the carbon vapor redeposition. The total erosion rates of 150 A runs were separated into the stable (Es) and the unstable (Eu) erosion rate. The Eu was more than 3 times higher in this work. It is believed that the thermofield emission of the unstable arcs produced more erosion because of the higher local heat flux to the cathode spots.
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Gardel, Emily Jeanette. "Microbe-electrode interactions: The chemico-physical environment and electron transfer." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11185.
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This thesis presents studies that examine microbial extracellular electron transfer that an emphasis characterizing how environmental conditions influence electron flux between microbes and a solid-phase electron donor or acceptor. I used bioelectrochemical systems (BESs), fluorescence and electron microscopy, chemical measurements, 16S rRNA analysis, and qRT-PCR to study these relationships among chemical, physical and biological parameters and processes.Engineering and Applied Sciences
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Euler, Luisa. "Impedance and Stimulation Comfort of Knitted Electrodes for Neuromuscular Electrical Stimulation (NMES) : Influence of electrode construction and pressure application to the electrode." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-23896.
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Neuromuscular electrical stimulation (NMES) is a modality of electrotherapy which is aiming to restore and improve muscle function by injecting small levels of current into the muscle using different types of electrodes. Advantages are seen in using textile electrodes which can be integrated into wearables. Previous research has been done for the development of textile stimulation electrodes. However, the focus has not been on the electrode construction itself. Therefore, the influence of electrode construction parameters of knitted electrodes as well as of the electrode condition, i.e. wet or dry, on the skin-electrode impedance and on the perceived stimulation comfort were analysed. Further, the application of pressure to the electrode was investigated. It was found that the electrode condition is the most important parameter for the electrode performance as a wet electrode showed a lower impedance and an improved stimulation comfort with a better skin contact. Followed by this, the pressure was the second most important factor, especially for dry electrodes. A higher pressure reduced the skin-electrode impedance and improved the skin contact in dry condition. Nevertheless, dry electrodes with a high applied pressure still performed worse than wet electrodes. Regarding the electrode design, the most important factor was the electrode size. A bigger size reduced the impedance. Nevertheless, for the application in NMES, a smaller electrode size is to be preferred as it improved the stimulation selectivity and thus, a lower NMES level was required to induce a plantarflexion without affecting the stimulation comfort. The other investigated construction parameters (binding, yarn density, shape) only showed minor influences on the electrode performance. Therefore, the possibilities of applying pressure to the electrode to improve the performance of dry textile electrodes should be further investigated.
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Brosel, Oliu Sergi. "Interdigitated electrode arrays (idea) impedimetric transducers for bacterial biosensing applications." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/666603.
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La tecnologia dels biosensors, basada en dispositius analítics que combinen un bioreceptor amb una unitat de transducció, s’ha aplicat en nombroses àrees de recerca per a la detecció de diferents analits d’interès. Els bacteris, especialment els bacteris patògens, són agents biològics importants per ser detectats en diversos camps com el diagnòstic clínic, la indústria alimentària o la qualitat de l’aigua per prevenir malalties en els éssers humans. No obstant això, els bacteris també es poden utilitzar en un ampli ventall d’aplicacions; per exemple, com a indicadors biològics per determinar la toxicitat de diversos compostos.
En aquesta tesi es proposa l’ús de transductors impedimètrics basats en elèctrodes de tipus interdigitat (interdigitated electrode arrays, IDEA de les sigles en anglès) com a instrument per al desenvolupament d’aplicacions biosensores bacterianes. L’espectroscòpia electroquímica d’impedància és una tècnica àmpliament estudiada per caracteritzar biosistemes perquè permet monitoritzar els fenòmens que tenen lloc a la superfície dels elèctrodes. Aquesta tècnica no requereix marcadors en el procés de transducció i pot ser usada en un mode d’operació sense marcatge addicional; així se simplifiquen els assajos de biomonitoratge. Entre els diferents tipus de transductors impedimètrics, els elèctrodes de tipus interdigitat són realment avantatjosos en termes de miniaturització, d’obtenció d’una resposta ràpida i estable o d’increment en la relació senyal-soroll. La utilització dels dispositius IDEA com a base de transducció per a un biosensor permet reduir el temps i cost per assaig. A més a més, en aquest treball es detalla i demostra l’aplicabilitat dels IDEA tridimensionals (3D-IDEA), en els quals els dígits dels elèctrodes estan separats per barreres aïllants, que permeten millorar la sensibilitat en el registre de canvis superficials si els comparem amb els IDEA convencionals per a la detecció de bactèries.
Els objectius d’aquest treball són l’elaboració i la validació d’estratègies de biodetecció, estables i reproduïbles, utilitzant IDEA i 3D-IDEA per a la identificació de bacteris com a analit d’interès o bé com a element de sensat. En el primer cas, s’ha dut a terme la detecció de bacteris o endotoxines bacterianes en mostres líquides, mentre que en el segon s’ha desenvolupat un biosensor del tipus microbià. Per tal de dur-ho a terme, els dispositius IDEA s’han (bio)funcionalitzat mitjançant diverses metodologies per desenvolupar en quatre aplicacions.Biosensor technology, consisting of analytical devices that conjugate a bioreceptor with a transducer unit, has been applied in numerous research areas for the detection of different analytes of interest. Bacteria, especially pathogenic bacteria, are important targets to be sensed and identified in many fields, like clinical diagnosis, food industry or water safety, to prevent a great number of diseases in humans. However, bacteria can be employed in a wide range of beneficial applications, such as their use as biological indicators to determine the toxicity of various compounds. In this thesis, the use of impedimetric transducers based on interdigitated electrode arrays (IDEA) has been proposed as a tool for the development of bacterial biosensing applications. Electrochemical Impedance Spectroscopy is a widely studied technique to characterize biosystems because it allows to monitor electrical events occurring on the surface of electrodes. This technique does not require additional markers for the transduction and can be used in a label-free operation mode and hence simplifying the biosensing assays. Among different types of impedimetric transducers interdigitated electrodes arrays are really advantageous in terms of easy-miniaturization, fast establishment of the steady-state signal response and increased signal-to-noise ratio. The utilization of IDEA devices as a base of a biosensor transducer permits reducing the time and cost per assay. In addition, the applicability of three-dimensional IDEA (3D-IDEA) is described and demonstrated, in which the electrode digits are separated by insulating barriers, to improve the sensitivity for the registration of superficial parameters compared with standard IDEA for bacteria sensing. The main aim of this work is the elaboration and testing of robust and reproducible biosensing strategies using IDEA and 3D-IDEA impedance transducers with bacteria, as an analyte target or as a sensing element. In the first case, the detection of bacteria or bacterial endotoxins in liquid samples may be performed and, in the second one, novel microbial-based biosensors may be developed. To this end, IDEA devices have been (bio)functionalized using various grafting schemes for their use in four different applications.
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Eklund, John C. "Electrode reaction dynamics." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297021.
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Wildgoose, Gregory G. "Modified electrode voltammetry." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432263.
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Sokolov, Stanislav V. "Electrode-particle impacts." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:92b60bce-79c9-4dc7-b1fe-15c1f8a7bdbb.
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The thesis is concerned with the study of particles by impact voltammetry. The use of the particle-impact technique is developed and extended beyond quantitative sizing of spherical metallic nanoparticles to complex systems involving quasi-spherical nanoparticles, reversible agglomeration processes and extremely low levels of analyte. Initially the assumption that the particles are spherical is challenged and a system of quasi-spherical citrate-capped nanoparticles has been analyzed. The combination of SEM imaging and electrochemical nano-impact experiments was demonstrated to allow sizing and characterization of the geometry of single silver nanoparticles and determine an icosahedral geometry. Next the agglomeration/aggregation state of silver nanoparticles is studied in a media of high ionic strength. Distinguishing agglomeration (reversible clustering of the particles) and aggregation (irreversible clustering) is a challenging task for conventional techniques, especially at arbitrary concentrations. Using the nano-impact technique in conjunction with light scattering techniques (nanoparticle tracking analysis and dynamic light scattering) it was demonstrated that even in high ionic strength environments, particles develop equilibria between agglomerated and monomeric species, which in practice means the transport behavior is dominated by the presence of fast-diusing monomers with high chemical reactivity. Having developed an understanding of the agglomeration and aggregation state of the particles and underlying mass transport, the causes of agglomeration were considered and developed using the idea of entropy of mixing driven clustering, a concept hitherto unexplored and an entirely new perspective. Through the use of maximization of entropy of mixing the expected agglomeration population in the absence of any enthalpy eects and the contribution to the entropy from the formation of dimers, trimers etc., was predicted even though their formation causes an overall reduction in particle numbers. For a system of citrate-capped silver nanoparticles entropy was shown to play a dominant role in the observed size distributions. The distribution predicted by the model and the experimentally observed particle size distributions demonstrated the strong entropy contribution. The last chapter is concerned with the design of an approach for the most sensitive electrochemical detection of nanoparticles, yet realized. The limit of detection is dependent on the mass transport of the particles to the electrode and the electroactive area of the electrode. The use of a hydrodynamic walljet flow causes high mass transport. Larger electroactive area increases the observed current magnitude but in order to detect individual particles low capacitance is a required and as a result traditional macroelectrodes cannot be used. Hence in order to increase the surface area and reduce the associated increase in capacitance we chose to use a random assembly of microelectrodes (RAM) which consist of hundreds of carbon fiber microelectrodes connected in parallel to a current collector, which results in large electroactive area and relatively low capacitance. Using this in-house manufactured cell we were able to demonstrate femtomolar limit of detection for 50 nm silver citrate-capped nanoparticles, which is substantially the lowest limit detection reported in the literature to date.
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Cocklin, E. M. "Surface X-ray diffraction studies of electrode/vacuum and electrode/electrolyte interfaces." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3011638/.
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This thesis presents in situ Surface X-ray Diffraction (SXRD) studies of surfaces and interfaces, in both Ultra High Vacuum (UHV) and an electrochemical environment. Primarily Crystal Truncation Rod (CTR) measurements are utilised to determine a model for the atomic structure at the interface. A SXRD characterisation of the clean Ag(110) and Ag(111) surfaces in UHV were determined as a reference for the rest of the work in this thesis. Following this the growth conditions and structures of a silicene layer on Ag(111) were investigated, by Low Energy Electron Diffraction (LEED) and preliminary SXRD study of the interface structure is presented. A comprehensive study of the Ag(hkl)/alkaline interface is presented. X-ray Voltammetry (XRV) measurements have been performed to determine the potential dependence of the system. CTR measurements have been used to determine the structure at both the electrode and electrolyte sides of the interface. The results reveal large structural changes on the electrolyte side of the interface, with the response of relaxation of the surface layers in the metal. The presence of specifically adsorbed OH on the surface stabilises cations in a compact double layer through non-covalent interactions. The studies were extended to determine the effects of saturating the electrolyte gases, CO and O2 on the double layer structure. The results indicate that double layer structure is subtly perturbed, and hints at a change in the nature of bonding at the interface. Time resolved SXRD measurements are utilised to determine the dynamics of the restructuring of the electrolyte layering at the Ag(111)/Alkaline interface. In order to gain a comprehensive picture of the structural dynamics, two other systems are studied; the Au(111) reconstruction to determine the timescale of the (1 x 1) ↔ (p ×√3) reconstruction, and the underpotential deposition of Ag on Au(111). The results indicate that the mass transport of ions through electrolyte is on a timescale comparable to the charge transfer, whereas the ordering of ions and surface metal atoms occurs on much longer timescales.
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Hartley, Lee Fason. "Planar electrode dielectrophoresis systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq24718.pdf.
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Merrick, Ian. "Embedding at electrode surfaces." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/55969/.
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Electronic structure calculations are performed on metal surfaces using an embedding method. Firstly, Cu and Ni surfaces with adsorbates are studied. The O/Cu(00T) reconstruction is investigated, and it is found that atomic displacements increase bonding symmetry and is most likely the cause of reconstruction. The interaction between a single graphitic layer and the Ni(III) substrate is also studied, and it is found that interacting states are formed at Ni band gaps. The remainder of the thesis deals with steps on metal surfaces. First, the jellium model is used to calculate the work function dependence on step density. In the low step density limit, the work function varies linearly with step density. Further calculations are performed on realistic Pd and Pt surfaces. When electric fields are applied, the screening charge of stepped surfaces is mostly located at the step edge. This is explained by the increased fields associated with the edge. Field emission from Pd and Pt surfaces is also studied. It is found that Pd is a better emitter than Pt, owing to work function effects. Transmission is dependent on the surface parallel wavevector and decreases with increasing wavevector. The reduced work function also plays a role at stepped surfaces, although the major influence stems from the reduced local work function at the step site. The low effective potential at the step provides a locally reduced barrier to electron removal. In addition, an increase in transmission is seen from non-zero wavevectors for stepped surfaces. The result is that stepped Pd and Pt surfaces, with a step density of one step in every three (001) unit cells, show field emission increased by a factor of four compared with the flat (001) surfaces.
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Saidi, Eileen Semple. "Polymer electrolyte/electrode interfaces." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/1971.
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Kadiroglu, Umut. "Polymer electrolyte/electrode interfaces." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302347.
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Henstridge, Martin Carl. "Studies in electrode kinetics." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:562136fd-3a23-464e-8829-c1b37052a29a.
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This thesis is concerned with the study of electrode kinetics, which we shall examine via comparison between theory with experiment. As such the first two chapters outline the basic principles of electrochemical experiments and their simulation. First, we examine the properties of voltammetry at porous electrodes by means of both simulations and experiments. We then introduce the symmetric Marcus-Hush (SMH) model of electrode kinetics as an alternative to the empirical Butler-Volmer model. First, we examine different methods for modeling the voltammetry of kinetically inhomogeneous electroactive monolayers. Next, we perform a critical evaluation of the SMH model for solution-phase systems through extensive comparison to experiments under diffusion-only and convective mass transport conditions using both cyclic and square wave voltammetry. The model is compared with the Butler-Volmer model throughout and is ultimately found to be poorly suited to the parameterisation of electrode kinetics, despite its foundations in the microscopic Marcus theory. We then introduce the asymmetric Marcus-Hush model, which removes the assumption that the Gibbs energy curves for reactant and product have the same curvature. This modification results in an additional parameter which quantifies the asymmetry of the system. A similar evaluation of this model is then undertaken for both surface-bound and solution phase systems and the asymmetric model is found to be a great deal more successful than its symmetric predecessor. Finally we outline a novel technique for extracting kinetic information directly from experimental cyclic voltammetry. The method is simple to implement and is general to all electrode geometries with one-dimensional symmetry.
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Jeschull, Fabian. "Polymers at the Electrode-Electrolyte Interface : Negative Electrode Binders for Lithium-Ion Batteries." Doctoral thesis, Uppsala universitet, Strukturkemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-317739.
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We are today experiencing an increasing demand for high energy density storage devices like the lithium-ion battery for applications in portable electronic devices, electric vehicles (EV) and as interim storage for renewable energy. High capacity retention and long cycle life are prerequisites, particularly for the EV market. The key for a long cycle life is the formation of a stable solid-electrolyte interphase (SEI) layer on the surface of the negative electrode, which typically forms on the first cycles due to decomposition reactions at the electrode-electrolyte interface. More control over the surface layer can be gained when the layer is generated prior to the battery operation. Such a layer can be tailored more easily and can reduce the loss of lithium inventory considerably. In this context, water-soluble electrode binders, e.g. sodium carboxymethyl cellulose (CMC-Na) and poly(acrylic acid) (PAA), have proven themselves exceptionally useful. Since the binder is a standard component in composite electrodes anyway, its integration into the electrode fabrication process is easily accomplished. This thesis work investigates the parameters that govern binder distribution in elec-trode coatings, control the stability and electrochemical performance of the elec-trode and that determine the composition of the surface layer. Several commonly used electrode materials (graphite, silicon and lithium titanate) have been applied in order to study the impact of the binder on the electrode morphology and the differ-ent electrode-electrolyte interfaces. The results are correlated with the electrochemi-cal performance and with the SEI composition obtained by in-house and synchro-tron-based photoelectron spectroscopy (PES). The results demonstrate that the poor swellability of these water-soluble binders leads to a protection of the active material, given that the surface coverage is high and the binder evenly distributed. Although on the laboratory scale electrode formu-lations with a high binder content are common, they have little practical use in commercial devices due to the high content of inactive material. As the binder con-tent is decreased, complete surface coverage is more difficult to achieve and the binder distribution is more strongly coupled to the particle-binder interactions during the preparation process. Moreover, it is demonstrated in this thesis how these inter-actions are related to the surface area of the electrode components applied, the surface composition and the electrochemistry of the electrode. As a result of the smaller binder contents the benefits provided by CMC-Na and PAA at the electrode surface are compromised and the performance differs less distinctly from electrodes fabricated with the conventional binder, i.e. poly(vinylidene difluoride) (PVdF). Composites of alloying and conversion materials, on the other hand, typically em-ploy binders in larger amounts. Despite the frequently noted resiliency to volume expansion, which is also a positive side effect of the poor swellability of the binder in the electrolyte, the protection of the surface and the formation of a more stable interface are the major cause for the improved electrochemical behaviour, com-pared to electrodes employing PVdF binders.
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Pennarun, Gaelle. "The micro-optical ring electrode : a new and novel electrode system for photoelectrochemistry." Thesis, University of Central Lancashire, 1999. http://clok.uclan.ac.uk/18843/.
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The design of a novel photoelectrochemical sensor, the micro-optical ring electrode (MORE), is described. Based on a thin-ring microelectrode and using at fibre-optic light guide as the insulating material interior of the ring, the MORE has been deisigned, constructed and developed to permit electrochemical investigation of photochemically generated solution species. Initial characterisation of the electrode behaviour in the dark has been ccomplished by the use of ferricyanide in conjunction with predictive mathematical models of the time dependence of the current at micro ring electrode. The photocharacterisation of the MORE has been achieved looking at the photochemical response of tris (2,2'biyridine)ruthenium(II) in presence of the quenching agent Fe3+ . Subsequent application of the MORE has been in the electrochemical investigation of photoactive drugs employed in Cancer Therapy. In the following study, the microelectrochemistry of methylene blue, a dye commonly employed on Photodynamic Therapy (PDT), has been characterised in the dark using, in the first instance, gold disc microelectrodes. The electrochemical behaviour of MB+ on gold disc microelectrodes has than been compared to the results obtained when using the MORE. Exploration of the photoelectrochemical response of the MORE is reported, achieved via the interrogation of the photoelectrochemistry of MB+. Photocurrent signals obtained during cyclic voltammetric and chronoamperometric studies of MB\ conducted with the MORE under illuminated conditions and in the absence of any deliberately added reducing agent, are attributed to the formation and subsequent detection of 3 MB+ within the diffusion layer of the microring electrode. The data demonstrate that the use of the MORE for direct electrochemical detection of photogenerated species with lifetimes of < 9 x 5 10- s is possible. The electrochemistry of 3MB+ over the applied potential range from -0.4 to +1.0 V versus SCE is elucidated and discussed in the context of the behaviour of photoexcited MB+ in the presence of deliberately added reducing agent Fe3+. In order to investigate the production of singlet oxygen associated with cancer treatment, an attempt was made to study the MB+/02 system. This part of the project has not been completed, however a preliminary study of the electrochemistry of the MB.
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Barron, Olivia. "Gas diffusion electrodes for high temperature polymer electrolyte membrane fuel cells membrane electrode assemblies." University of the Western Cape, 2014. http://hdl.handle.net/11394/4323.
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Philosophiae Doctor - PhDThe need for simplified polymer electrolyte membrane fuel cell (PEMFCs) systems, which do not require extensive fuel processing, has led to increased study in the field of high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) applications. Although these HT-PEMFCs can operate with less complex systems, they are not without their own challenges; challenges which are introduced due to their higher operation temperature. This study aims to address two of the main challenges associated with HT-PEMFCs; the need for alternative catalyst layer (CL) ionomers and the prevention of excess phosphoric acid (PA) leaching into the CL. The first part of the study involves the evaluation of suitable proton conducting materials for use in the CL of high temperature membrane electrode assemblies (HT-MEAs), with the final part of the study focusing on development of a novel MEA architecture comprising an acid controlling region. The feasibility of the materials in HT-MEAs was evaluated by comparison to standard MEA configurations.
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Hoffrogge, Johannes Philipp [Verfasser], and Peter [Akademischer Betreuer] Hommelhoff. "A surface-electrode quadrupole guide for electrons / Johannes Philipp Hoffrogge. Betreuer: Peter Hommelhoff." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1033270865/34.
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Blum, Richard Alan. "An Electronic System for Extracellular Neural Stimulation and Recording." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16192.
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A system for extracellular neural interfacing that had the capability for stimulation and recording at multiple electrodes was presented. As the core of this system was a custom integrated circuit (IC) that contained low-noise amplifiers, stimulation buffers, and artifact-elimination circuitry. The artifact-elimination circuitry was necessary to prevent the activity of the stimulation buffers from interfering with the normal functioning of the low-noise amplifiers.
The integrated circuits were fabricated in in a 0.35 micron CMOS process. We measured input-referred noise levels for the amplifiers as low as 3.50 microvolts (rms) in the in the bandwidth 30 Hz-3 kHz, corresponding to the frequency range of neural action potentials. The power consumption was 120 microwatts, corresponding to a noise-efficiency factor of 14.5. It was possible to resume recording signals within 2 ms of a stimulation, using the same electrode for both stimulation and recording.
A filtering algorithm to remove the post-discharge artifact was also presented. The filtering was implemented using a field-programmable gate array (FPGA). The filtering algorithm itself consisted of blanking for the duration of the stimulation and artifact-elimination, followed by a wavelet de-noising. The wavelet de-noising split the signal into frequency ranges, discarded those ranges that did not correspond to neural signals, applied a threshold to the retained signals, and recombined the different frequency ranges into a single signal. The combination of the filtering with the artifact-elimination IC resulted in the capability for artifact-free recordings.
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Henningsson, Anders. "Ion Insertion into Electrode Materials Studied with X-Ray and Electron Spectroscopic Methods." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2002. http://publications.uu.se/theses/91-554-5268-X/.
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Yoon, Kwansik. "The effect of the electrode composition on electron transfer through an electroactive monolayer." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=771.
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Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xi, 96 p. : ill. (some col.) Includes abstract. Includes bibliographical references.
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Xiao, Lei. "Nano-electrode materials for electroanalysis." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526413.
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Suwatchara, Danu. "Experimental advances in electrode kinetics." Thesis, University of Oxford, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639734.
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At the present, numerous kinetic theories are available to electrochemists in describing chemical reactions at the electrode. These exist in varying degree of complexity, ranging from simplistic empirical formulae to more rigorous models that account for microscopic physical phenomena pertiaining to the reactive species and their environment. However, experimental work documented in support of the validity and comparison between these theories is scarce. This is largely due to difficulty in attaining and controlling the experimental conditions where applicability of the theories break down. As such, the current work utilizes state-of-the-art · electrochemical experimental techniques in order to test some of the most prominent electrode kinetics theories via comparison to simulations. This is done with the aim of identifying their limitations and providing new insight into fundamental mechanistic processes that occur during an electrochemical reaction.
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Lowe, V. J. "The modification of electrode surfaces." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379931.
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Galloway, T. A. "Shining light on electrode interfaces." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3011709/.
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SETH, GAUTAM. "Adjustable Gap Micro-Electrode Biosensor." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1186371515.
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Ho, I.-Pin. "Instrumentation for Multi-Electrode Voltammetry." PDXScholar, 1990. https://pdxscholar.library.pdx.edu/open_access_etds/1141.
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When metal pollutants exist in natural water, their toxicity is dramatically dependent on the chemical species. Numerous sophisticated techniques and instruments have been developed to detect metal pollutants at very low concentration levels. However, one important factor is often ignored, i.e., rarely is species determination required. Electrochemical (EC) methods have the particular advantage of being, in principle, a species-sensitive method rather than an element-sensitive method for the study of metal speciation in natural waters.
The goal of this research was to develop an instrument using the EC technique for speciation and general voltammetric studies. It was accomplished by designing a flow-through EC cell containing multi-electrodes to which various fixed potentials over a selected range were applied. A special potentiostat was designed to supply a selected potential to each electrode in the cell. Potential control was provided by placing a combined counter-reference electrode at circuit ground and connecting each working electrode to the inverting input of a current follower which had a potential applied to its non-inverting input from two digital-to-analog converters and a resistor network. Integrating current followers were used for measuring signal currents generated by the electrolytes samples on each electrode. A multiplexing circuit, including an analog-to-digital converter, was used to fulfill data acquisition. These circuits were interfaced to a computer and the readout was a pseudo-voltammogram which is a plot of amperometric currents versus various applied fixed potentials on each electrode. Details of the instrumentation, software, and some initial results are described.
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Singh, Kanwardeep. "A comparison of electrode recruitment characteristics and muscle fatigue using intramuscular and nerve trunk electrodes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37980.pdf.
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Santana-Aguiar, Francisco Aurelio. "Characterisation of electrode microarrays produced photolithographically and with thiol self-assembled monolayers on gold electrodes." Thesis, Durham University, 2009. http://etheses.dur.ac.uk/45/.
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The macroscale electrochemical theory breaks down with microstructures smaller than the dimensions of the diffusion layer, showing that such electrodes have significant quantitative effects and qualitative advantages. The great advantage of microelectrodes over macroelectrodes is the minimisation of interference, which gives rise to much lower detection limits. Microelectrodes have much reduced ohmic drops and capacitive effects and can be used in the absence of supporting electrolyte. These features have opened a growing interest in the fabrication and application of microelectrodes in various areas. There are different microelectrode geometries, but disc type is the most used. Microelectrode arrays have been proposed as a way of increasing the magnitude of the current (produced for a single microelectrode), while maintaining the advantages of the single microelectrode. Although the inlaid microdisc microelectrode can be considered as one the most popular microelectrode geometry, there is also a need to consider conical recessed, recessed and protruding microdiscs as photolithographic microfabrication techniques often result in non-ideal geometries. It has been proved using surface imaging techniques such as scanning Kelvin nanoprobe (SKN), scanning electron microscopy (SEM) and white light interferometer microscopy that conical recessed electrodes with gradient potential along the recessed walls are formed during standard photolithographic methods for producing microelectrode arrays. Microarrays are ubiquitously used for high-throughput measurements using various signal transduction techniques. Ideally each sensor in a microarray platform should perform optimally to ensure an error free response. In this thesis, a simple method for designing a microelectrode array platform (MEA) is described, allowing a ‘defective’ cluster of sensing arrays to be easily identified. It is possible to extend this concept for multiple analyses on a single chip. Molecular electronic is a promising technology which would be an alternative. The concept of molecular electronics is the use of single molecules or arrays, or layers of molecules for the fabrication of electronic components such as wires, switches, and storage elements. Indeed, functionalised thiol monolayer-based microelectrode array may provide unique possibilities, facilitating electrochemical measurements involving electron transfer via electron tunnelling. The conjugated structure of rigid, linear molecule increases greatly the rate of electron transfer across the monolayer. Charge transfer and self-assembly characteristics of novel fully conjugated molecules molecular wires (synthesised at the Department of Chemistry and Centre for Molecular and Nanoscale Electronics, Durham University) assembled on flat gold electrodes are evaluated using Marcus model of electron-transfer and tunnelling theory. The behaviour of these wires is compared with heptanethiol and dodecanethiol SAMs. A preliminary study for application of self-assembled monolayer of molecular wires in microelectrode arrays for multiple analyses on a single chip has been successfully reached.
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Hanekom, Tania. "Modelling of the electrode-auditory nerve fibre interface in cochlear prostheses." Diss., University of Pretoria, 2001. http://hdl.handle.net/2263/27742.
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The objective of this thesis is to provide additional insight into the electrode array-nerve fibre interface that exists in the implanted cochlea and to facilitate investigation of new electrode arrays in interaction with the cochlea and auditory nerve fibres. The focus is on potential distributions and excitation profiles generated by different electrode array types and factors that could have an influence on these distributions and profiles. Research contributions made by the thesis are the creation of a detailed 3-D model of the implanted cochlea that accurately predicts measurable effects in cochlear implant wearers and facilitates effortless simulation of existing and new electrode array variations; the establishment of the important anatomical structures required in a 3-D representation of the implanted cochlea; establishment of evidence that array location is the primary parameter that controls spread of excitation; definition of the critical focussing intensity of intracochlear electrode pairs; confirmation thatmonopolar stimulation could deliver focussed stimulation to approximately the same degree than that delivered by widely spaced electrode configurations and that the use of monopolar configurations over bipolar configurations are therefore advantageous under certain conditions; explanation of the effect that encapsulation tissue around cochlear implant electrodes could have on neural excitation profiles; extension of the information available on the focussing ability of multipolar intracochlear electrode configurations; and establishment of evidence that a higher lateral electrode density could facilitate better focussing of excitation, continuous shaping of excitation profiles and postoperative customization of electrode arrays for individual implant wearers.Dissertation (PhD(Electronic Engineering))--University of Pretoria, 2001.
Electrical, Electronic and Computer Engineering
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Myedi, Noluthando. "Electrochemical kinetics and sensing of conjugated dienes in acetonitrile." University of the Western Cape, 2011. http://hdl.handle.net/11394/5424.
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>Magister Scientiae - MScThis thesis focuses on the electroanalysis of some dienes (2-methyl-1.3-butadiene (MBD), tran-1.3-pentadiene (PD), 1.3-cyclohexadiene (CHD) and 3-cyclooctadiene (COD)) found in gasoline and the development of simple electrochemical diene sensors. The detection of dienes in fuels is important as they readily polymerise and form gum in fuel tanks. The electroctivity of the dienes was studied with glassy carbon electrode (GCE) and Pt electrode in tetrabutylammonium perchlorate (TBAP)/acetonitrile solution. Polyaniline-polystyrene sulfonic acid (PANi-PSSA) composite films were electro-deposited or drop-coated on GCE, with and without gold nanoparticles (AuNPs) and characterized by cyclic voltammetry (CV), high resolution transmission electron microscopy (HRTEM) and ultraviolet-visible (UV-vis) spectroscopy. Both composite polymers were found to be of nanofibral structure, and the spherical gold nanoparticles were dispersed uniformly within the polymer. The dienes exhibited no redox peaks on GCE/PANi-PSSA and GCE/PANi-PSSA/AuNPs electrode systems from -1.0 V to +1.5 V, beyond which PANi would overoxidize and lose its electroactivity. Therefore, cyclic voltammetry and steady state amperometry of the four dienes (MBD, PD, CHD and COD) were studied with unmodified Pt and GCE electrodes. Subtractively normalised interfacial-fourier transform infra-red (SNIFTIR) spectroscopic studies of the dienes were performed with Pt electrode. SNIFTIR data showed that there was a definite electro-oxidation of 1.3-cyclohexadiene as electrode potential was changed from E = 770 mV to E = 1638 mV. Severe electrode fouling was observed when steady state amperometric detection of CHD, as a representative diene, was performed on Pt electrode. Randel-Sevčik analysis of the CVs of the dienes on Pt electrode gave diffusion coefficient (Dox) values of 10.65 cm²/s, 9.55 cm²/s, 3.20 cm²/s and 3.96 cm²/s for CHD, COD, PD, and MBD, respectively. The corresponding detection limits (3σn-1) were 0.0106 M, 0.0111 M, 0.0109 M, and 0.0107 M.
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Zan, Lingxing [Verfasser]. "Metal-air Batteries: RRDE and EC-SPM Studies of Electrode Kinetics and Electrode Structure / Lingxing Zan." Bonn : Universitäts- und Landesbibliothek Bonn, 2017. http://d-nb.info/1149154039/34.
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Lawrence, Emma Charlotte Dorothy. "Investigations of electrode surfaces and enzyme/polymer electrode systems using scanning electrochemical microscopy and impedimetric techniques." Thesis, Cranfield University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426111.
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Blidberg, Andreas. "Iron Based Materials for Positive Electrodes in Li-ion Batteries : Electrode Dynamics, Electronic Changes, Structural Transformations." Doctoral thesis, Uppsala universitet, Strukturkemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-317014.
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Li-ion battery technology is currently the most efficient form of electrochemical energy storage. The commercialization of Li-ion batteries in the early 1990’s revolutionized the portable electronics market, but further improvements are necessary for applications in electric vehicles and load levelling of the electric grid. In this thesis, three new iron based electrode materials for positive electrodes in Li-ion batteries were investigated. Utilizing the redox activity of iron is beneficial over other transition metals due to its abundance in the Earth’s crust. The condensed phosphate Li2FeP2O7 together with two different LiFeSO4F crystal structures that were studied herein each have their own advantageous, challenges, and scientific questions, and the combined insights gained from the different materials expand the current understanding of Li-ion battery electrodes. The surface reaction kinetics of all three compounds was evaluated by coating them with a conductive polymer layer consisting of poly(3,4-ethylenedioxythiophene), PEDOT. Both LiFeSO4F polymorphs showed reduced polarization and increased charge storage capacity upon PEDOT coating, showing the importance of controlling the surface kinetics for this class of compounds. In contrast, the electrochemical performance of PEDOT coated Li2FeP2O7 was at best unchanged. The differences highlight that different rate limiting steps prevail for different Li-ion insertion materials. In addition to the electrochemical properties of the new iron based energy storage materials, also their underlying material properties were investigated. For tavorite LiFeSO4F, different reaction pathways were identified by in operando XRD evaluation during charge and discharge. Furthermore, ligand involvement in the redox process was evaluated, and although most of the charge compensation was centered on the iron sites, the sulfate group also played a role in the oxidation of tavorite LiFeSO4F. In triplite LiFeSO4F and Li2FeP2O7, a redistribution of lithium and iron atoms was observed in the crystal structure during electrochemical cycling. For Li2FeP2O7, and increased randomization of metal ions occurred, which is similar to what has been reported for other iron phosphates and silicates. In contrast, triplite LiFeSO4F showed an increased ordering of lithium and iron atoms. An electrochemically induced ordering has previously not been reported upon electrochemical cycling for iron based Li-ion insertion materials, and was beneficial for the charge storage capacity of the material.
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Wang, Weijian. "Electrode shape optimization of piezoelectric transducers." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001041.
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Nakagawa, Harumichi, Masatoshi Yamazaki, Motoki Nihei, Ryoko Niwa, Tatsuhiko Arafune, Akira Mishima, Shiho Nashimoto, et al. "Virtual Electrode Polarization-Induced Reentrant Activity." Research Institute of Environmental Medicine, Nagoya University, 2003. http://hdl.handle.net/2237/7595.
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Cornell, Ann. "Electrode reactions in the chlorate process." Doctoral thesis, KTH, Kemiteknik, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3442.
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Bass, Kevin. "Zinc electrode performance in modified electrolyte." Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/10348.
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Blackham, Ian George. "Scanning tunneling microscopy of electrode surfaces." Thesis, University of Oxford, 1992. https://ora.ox.ac.uk/objects/uuid:f9d27595-1177-406f-89a2-1448ac654dd3.
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A scanning tunneling microscope (STM) suitable for the in-situ study of electrode surfaces under electrochemical control has been developed. The system consists of commercially available software and feedback electronics, with a custom-built stage and electrochemical control. The stage incorporates an automatic coarse approach mechanism for ease of operation. Gold single crystal spheres (SCS) and gold on mica thin films have been studied as surfaces potentially suitable for samples in in-situ electrochemical STM experiments. Characteristic features of each surface have been identified. High resolution in-situ STM imaging of the electro-oxidation of a gold surface in a sulphuric acid electrolyte has been achieved. Surface rearrangement at potentials positive of the double layer region has been observed and correlated with cyclic voltammetry. As yet unexplained features resulting from biasing the surface at potentials negative of the double layer region are reported. In phosphate electrolyte, bulk surface oxide formation and the surface resulting from reduction of the oxide have been imaged. Some aspects of the direct electrochemistry of cytochrome c at 4,4' dithiodipyridine (SSBPY) modified gold electrodes have been investigated. In-situ FTIR showed the potential dependent orientation of adsorbed thiopyridine species, while ex-situ and in-situ STM studies showed a novel surface pitting process to be active. It is hypothesised the STM experiment itself induces the process to take place. Features attributable to cytochrome c molecules have been observed. Rearrangement of gold on mica surfaces, on exposure to certain aqueous solutions has been observed and the process is attributed to the interaction of the solutions with the original surface structure present.
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Rao, Girish. "Enzyme electrode studies of bile acids." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/11881.
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Hákonardóttir, Stefanía. "Prosthetic Control using Implanted Electrode Signals." Thesis, KTH, Skolan för teknik och hälsa (STH), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147699.
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This report presents the design and manufacturing process of a bionic signal messagebroker (BSMB), intended to allow communication between implanted electrodes andprosthetic legs designed by Ossur. The BSMB processes and analyses the data intorelevant information to control the bionic device. The intention is to carry out eventdetection in the BSMB, where events in the muscle signal are matched to the events ofthe gait cycle (toe-o, stance, swing).The whole system is designed to detect muscle contraction via sensors implantedin residual muscles and transmit the signals wireless to a control unit that activatesassociated functions of a prosthetic leg. Two users, one transtibial and one transfemoral,underwent surgery in order to get electrodes implantable into their residual leg muscles.They are among the rst users in the world to get this kind of implanted sensors.A prototype of the BSMB was manufactured. The process took more time thanexpected, mainly due to the fact that it was decided to use a ball grid array (BGA)microprocessor in order to save space. That meant more complicated routing and higherstandards for the manufacturing of the board. The results of the event detection indicatethat the data from the implanted electrodes can be used in order to get sucient controlover prosthetic legs. These are positive ndings for users of prosthetic legs and shouldincrease their security and quality of life.It is important to keep in mind when the results of this report are evaluated that allthe testing carried out were only done on one user each.
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Thomas, Glyn Rees. "Counter electrode materials for electrochromic windows." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261513.
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Sim, Koon Weng. "An enzyme electrode for alcohol analysis." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38159.
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Dvorson, Leonard 1974. "Field emitters with integrated focusing electrode." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/80243.
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Shake, Tyler Joseph. "Embedded Passivated-electrode Insulator-based Dielectrophoresis." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/46809.
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Pathogens in drinking water are the cause of over 1.5 million deaths around the world every year, mostly in developing countries. Practical, cheap, and effective tools for detection of these pathogens are critical to advance public health in many areas around the globe. Micro electro-mechanical systems (MEMS) are miniaturized structures that can be used for a variety of purposes, including, but not limited to, small scale sensors. Therefore, MEMS can be used in place of expensive laboratory equipment and offer a cheap and practical tool for pathogen detection.
The presented work's research objective is to introduce a new technique called embedded passivated-electrode insulator-based dielectrophoresis (EπDEP) for preconcentration, separation, or enrichment of bioparticles, including living cells. This new method combines traditional electrode-based DEP and insulator-based DEP with the objective of enhancing the electric field strength and capture efficiency within the microfluidic channel while alleviating direct contact between the electrode and the fluid. The EπDEP chip contains embedded electrodes within the microfluidic channel covered by a thin passivation layer of only 4 μm. The channel was designed with two nonaligned vertical columns of insulated microposts (200 μm diameter, 50 μm spacing) located between the electrodes (600 μm wide, 600 μm horizontal spacing) to generate the nonuniform electric field lines to concentrate cells while maintaining steady flow in the channel. The performance of the chip was demonstrated using Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterial pathogens in aqueous media. Trapping efficiencies of 100% were obtained for both pathogens at an applied AC voltage of 50 V peak-to-peak and flow rates as high as 10 uL/min.Master of Science
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Lin, Chia-Hua. "A Microfabricated Deep Brain Stimulation Electrode." Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1244061398.
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