Dissertations / Theses on the topic 'Electrochemical impedance spectroscopy studies'
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1
Aaron, Douglas Scott. "Transport in fuel cells: electrochemical impedance spectroscopy and neutron imaging studies." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34699.
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Current environmental and energy sustainability trends have instigated considerable interest in alternative energy technologies that exhibit reduced dependence on fossil fuels. The advantages of such a direction are two-fold: reduced greenhouse gas emissions (notably CO2) and improved energy sustainability. Fuel cells are recognized as a potential technology that achieves both of these goals. However, improvements to fuel cell power density and stability must be realized to make them economically competitive with traditional, fossil-based technologies. The work in this dissertation is largely focused on the use of analytical tools for the study of transport processes in three fuel cell systems toward improvement of fuel cell performance.
Polymer electrolyte membrane fuel cells (PEMFCs) are fueled by hydrogen and oxygen to generate electrical current. Microbial fuel cells (MFCs) use bacteria to degrade carbon compounds, such as those found in wastewaters, and simultaneously generate an electric current. Enzyme fuel cells (EFCs) operate similarly to PEMFCs but replace precious metal catalysts, such as platinum, with biologically-derived enzymes. The use of enzymes also allows EFCs to utilize simple carbon compounds as fuel. The operation of all three fuel cell systems involves different modes of ion and electron transport and can be affected negatively by transport limitations. Electrochemical impedance spectroscopy (EIS) was used in this work to study the distribution of transport resistances in all three fuel cell systems. The results of EIS were used to better understand the transport resistances that limited fuel cell power output. By using this technique, experimental conditions (including operating conditions, construction, and materials) were identified to develop fuel cells with greater power output and longevity. In addition to EIS, neutron imaging was employed to quantify the distribution of water in PEMFCs and EFCs. Water content is an integral aspect of providing optimal power output from both fuel cell systems. Neutron imaging contributed to developing an explanation for the loss of water observed in an operating EFC despite conditions designed to mitigate water loss. The findings of this dissertation contribute to the improvement of fuel cell technology in an effort to make these energy devices more economically viable.
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Klett, Matilda. "Electrochemical Studies of Aging in Lithium-Ion Batteries." Doctoral thesis, KTH, Tillämpad elektrokemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145057.
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Lithium-ion batteries are today finding use in automobiles aiming at reducing fuel consumption and emissions within transportation. The requirements on batteries used in vehicles are high regarding performance and lifetime, and a better understanding of the interior processes that dictate energy and power capabilities is a key to strategic development. This thesis concerns aging in lithium-ion cells using electrochemical tools to characterize electrode and electrolyte properties that affect performance and performance loss in the cells. A central difficulty regarding battery aging is to manage the coupled effects of temperature and cycling conditions on the various degradation processes that determine the lifetime of a cell. In this thesis, post-mortem analyses on harvested electrode samples from small pouch cells and larger cylindrical cells aged under different conditions form the basis of aging evaluation. The characterization is focused on electrochemical impedance spectroscopy (EIS) measurements and physics-based EIS modeling supported by several material characterization techniques to investigate degradation in terms of properties that directly affect performance. The results suggest that increased temperature alter electrode degradation and limitations relate in several cases to electrolyte transport. Variations in electrode properties sampled from different locations in the cylindrical cells show that temperature and current distributions from cycling cause uneven material utilization and aging, in several dimensions. The correlation between cell performance and localized utilization/degradation is an important aspect in meeting the challenges of battery aging in vehicle applications. The use of in-situ nuclear magnetic resonance (NMR) imaging to directly capture the development of concentration gradients in a battery electrolyte during operation is successfully demonstrated. The salt diffusion coefficient and transport number for a sample electrolyte are obtained from Li+ concentration profiles using a physics-based mass-transport model. The method allows visualization of performance limitations and can be a useful tool in the study of electrochemical systems.QC 20140512
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Abdur, Rahman Abdur Rub. "CellMap: An Automated Multielectrode Array Cell Culture Analysis System Based on Electrochemical Impedance Spectroscopy." [Tampa, Fla] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002185.
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Kang, Jiho. "Electrochemical studies of coatings and thin films." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1138388240.
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Campos, Rui César de Almeida. "Studies of electron transfer in self-assembled monolayers and bilayer lipid membranes." Thesis, Durham University, 2012. http://etheses.dur.ac.uk/3899/.
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The work presented on this thesis is focused on studies of the kinetics of electron transfer in bilayer lipid membranes (BLMs). Three different types of BLM were studied: i) tethered, ii) pore suspended (commonly known as ‘black’) and iii) based on the avidin – biotin interaction (these are part of the wider group of polymer cushioned BLMs). In order to produce tethered BLMs (tBLMs) of the best quality possible, self – assembled monolayers (SAMs) of a thiolipid (1,2 dipalmitoyl-sn-glycero-phosphothioethanol (DPPTE)) and of the same thiolipid mixed with L α phosphatidylcholine (EggPC) were characterised and their behaviour compared to that of SAMs of two alkanethiols (1 – heptanethiol and 1 – dodecanethiol). The SAMs that were formed by a mixture of lipids (DPPTE+EggPC) presented better kinetic parameters and were the chosen to produce tBLMs. Tethered BLMs were made by using the SAM described above as the lower leaflet; the second leaflet was deposited by vesicle fusion, the vesicles were made of EggPC. tBLMs are commonly used as model membranes, however in biophysical studies free-standing membranes or ‘black’ lipid membranes are more realistic models of cellular processes. The rates of electron transfer in both types of bilayer lipid membranes are compared. These BLMs were modified using two very important mitochondrial membrane associated molecules – ubiquinone-10 (UQ10) and α-tocopherol (VitE). The studies involved the use three redox couples, Fe(CN)_6^(3-/4-), Ru(NH_3 )_6^(3+/2+) and NAD+/NADH using cyclic voltammetry and electrochemical impedance spectroscopy. The NAD+/NADH couple is of particular interest as it is the key to several important biochemical processes. The last type of BLM that was studied was the BLMs based on the avidin – biotin interaction. Avidin was deposited on a platinum surface by electrodeposition and then vesicles composed of EggPC and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(biotinyl) (sodium salt) (DOPE(B)) are burst by applying +0.7V (vs. Ag/AgCl, KCl 3.5M), leading to the formation of a supported BLM. The vesicles used had methylene blue (MB) inside; its release, when the vesicles burst, was monitored by cyclic voltammetry and UV-Vis. The kinetic parameters were determined based on the EIS measurements using Fe(CN)_6^(3-/4-) and Ru(NH_3 )_6^(3+/2+) as redox couples.
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Xu, Mingming. "Electrochemical Kinetics Studies of Copper Anode Materials in Lithium Battery Electrolyte." Ohio University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1127139833.
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Lopez-Sabando, Jaime. "Practical vibration evaluation and early warning of damage in post-tensioned tendons." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002311.
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Ocaña, Tejada Cristina. "Aptasensors based on electrochemical impedance spectroscopy." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/305103.
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En els últims anys, a causa de la necessitat de diàgnostics ràpids i de millores en sensat, s’han utilitzat nous elements de reconeixement en biosensors. Un tipus d’aquests nous elements de reconeixement són els aptàmers. Els aptàmers són cadenes sintètiques de ADN o ARN les quals són seleccionades in vitro i tenen la capacitat d’unir-se a proteïnes, ions, cèl.lules, fàrmacs i lligands de baix pes molecular, reconeixent les seves molècules diana amb alta afinitat i especificitat. Diversos biosensors basats en aptàmers, també anomenats aptasensors, han sigut desenvolupats recentment. D’entre totes les tècniques de transducció utilitzades en biosensors, l’Espectrocòpia Electroquímica d’Impedància ha sigut àmpliament emprada como a eina per caracteritzar la superficies de sensors i estudiar esdeveniments en el biosensat en la superficie d’elèctrodes. La característica més important que presenta aquesta tècnica és que no requereix cap espècie marcada per a la transducció, per tant, aquesta tècnica de detecció pot utilitzar-se per dissenyar protocols de detecció directa sense marcatge, evitant assajos més cars i laboriosos.
El principal objectiu d’aquesta tesi doctoral va ser el desenvolupament d’aptasensors utilitzant la tècnica electroquímica d’impedància esmentada anteriorment. Per a això, diferents tipus d’elèctrodes van ser utilitzats, tals com elèctrodes de compòsit grafit-epoxi, elèctrodes de biocompòsit grafit-epoxi modificats amb molècules d’avidina i elèctrodes comercials serigrafiats de nanotubs de carboni de paret múltiple.
El treball es va dividir principalmente en dues parts d'acord amb la detecció de dues proteïnes diferents.
La primera part es va focalitzar en la detecció de trombina. Primer de tot, es van comparar i avaluar diversos aptasensors de detecció directa sense marcatge basat en diferents tècniques d'immobilització dels aptàmers, tals com: adsorció física humida, afinitat avidina-biotina i enllaç covalent mitjançant activació electroquímica de la superfície de l'elèctrode i mitjançant inserció electroquímica. Posteriorment, els elèctrodes de biocompòsit van ser comparats com a plataformes en genosensat i aptasensat. Amb la finalitat d'amplificar el senyal impedimètric obtingut utilitzant elèctrodes de biocompòsit, un protocol sàndwich va ser emprat incloent nanopartícules d'or modificades amb estreptavidina i tractament amplificador de plata.
La segona part de l'estudi es va basar en la detecció de citocrom c. Primerament, es va realitzar un simple aptasensor de detecció directa sense marcatge per a la detecció d'aquesta proteïna utilitzant la tècnica d'immobilització d'adsorció física humida. Finalment, i amb l'objectiu d'amplificar el señal impedimètric, es va desenvolupar un assaig tipus sándwich híbrid d’aptàmer i anticòs utilitzant elèctrodes serigrafiats de nanotubs de carboni de paret múltiple.
D'aquesta manera, la tesi explora i compara una àmplia gamma de procediments d'immobilització, l'ús de detecció directa sense marcatge o nanomaterial modificat amb biomolècules en diferents protocols directes o d'amplificació, i l'ús de reconeixement directe i sándwich per amplificar la sensibilitat i/o la selectivitat de l'assaig.In the recent years, due to the need for rapid diagnosis and improvements in sensing, new recognition elements are employed in biosensors. One kind of these new recognition elements are aptamers. Aptamers are synthetic strands of DNA or RNA which are selected in vitro and have the ability to bind to proteins, ions, whole cells, drugs and low molecular weight ligands recognizing their target with high affinity and specificity. Several aptamer-based biosensors, also called aptasensors, have been recently developed. Among all the transduction techniques employed in biosensors, Electrochemical Impedance Spectroscopy has widely used as a tool for characterizing sensor platforms and for studying biosensing events at the surface of the electrodes. The important feature presented by this technique is that it does not require any labelled species for the transduction; thus, this detection technique can be used for designing label-free protocols thus avoiding more expensive and time-consuming assays. The main aim of this PhD work was the development of aptasensors using the electrochemical impedance technique previously mentioned for protein detection. For that, different types of electrodes were used, such as Graphite Epoxy Composite electrodes (GECs), Avidin Graphite Epoxy Composite electrodes (AvGECs) and commercial Multi-Walled carbon nanotubes screen printed electrodes (MWCNT-SPE). The work was divided in two main parts according to the detection of the two different proteins. The first part was focused on thrombin detection. First of all, different impedimetric label-free aptasensors based on several aptamer immobilization techniques such as wet physical adsorption, avidin-biotin affinity and covalent bond via electrochemical activation of the electrode surface and via electrochemical grafting were developed and evaluated. Then, AvGECs electrodes were compared as a platform for genosensing and aptasensing. With the aim to amplying the obtained impedimetric signal using AvGECs, an aptamer sandwich protocol for thrombin detection was used including streptavidin gold-nanoparticles (Strep-AuNPs) and silver enhancement treatment. The second part of the study was based on cytochrome c detection. Firstly, a simple label-free aptasensor for the detection of this protein using a wet physical adsorption immobilization technique was performed. Finally, with the goal to amplify the impedimetric signal, a hybrid aptamer-antibody sandwich assay using MWCNT-SPE for the detection of the target protein was carried out. In this way, the thesis explores and compares a wide scope of immobilization procedures, the use of label-free or nanocomponent modified biomolecules in different direct or amplified protocols, and the use of direct recognition and sandwich alternatives to enhance sensitivity and/or selectivity of the assay
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Barton, Raymond Terence. "Characterisation of nickel electrodes by electrochemical impedance spectroscopy." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/12219.
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The thesis describes an electrochemical investigation of different types of nickel electrode used in nickel-cadmium cells, which are available commercially or currently under development. Impedance spectroscopy has been used to determine the electrochemical characteristics of these electrodes. The electrochemistry of the nickel electrodes was modelled by the electrical analogue method. Allowance was made within the model for porosity and adsorption effects. Component values were initially estimated by graphical techniques and the computer fitting procedure was then completed by an iterative process to provide kinetic parameters which were used to compare and contrast the characteristics of the nickel sintered, pocket and plastic bonded electrodes. The technological target of this work was establish a possible method by which the residual capacity remaining within nickel-cadmium cells could be determined. The kinetic parameters generated by the electrical analogue technique have provided data on which to base a measurement for the prediction of the state of charge in nickel-cadmium cells.
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Ma, Hongshen 1978. "Electrochemical Impedance Spectroscopy using adjustable nanometer-gap electrodes." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42240.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 151-154).
Electrochemical Impedance Spectroscopy (EIS) is a simple yet powerful chemical analysis technique for measuring the electrical permittivity and conductivity of liquids and gases. Presently, the limiting factor for using EIS as a portable chemical detection technology is the lack of absolute accuracy stemming from uncertainties in the geometrical factor used to convert measurable quantities of capacitance and conductance into the intrinsic parameters of permittivity and conductivity. The value of this geometrical conversion factor can be difficult to predict since it is easily affected by fringing electric fields, manufacturing variations, and surface chemistry. Existing impedance test cells typically address this problem using a calibration liquid with known permittivity and conductivity, however, this correction is not feasible in many applications since the calibration liquid may irreversibly contaminate the test electrodes. This thesis presents a technique for accurately measuring the permittivity and conductivity of liquids and gases without requiring the use of calibration liquids. This technique is made possible by precisely controlling the separation between two spherical electrodes to measure capacitance and conductance of the sample medium as a function of electrode separation. By leveraging the geometrical accuracy of the spherical electrodes and precise control of the electrode separation, the permittivity and conductivity of the sample can be determined without wet calibration. The electrode separation is adjusted using a flexure stage and a servomechanical actuator, which enables control the electrode separation with 0.25 nm resolution over a range of 50 gm. The nanometer smooth surfaces of the spherical electrodes also enable electrode gaps of less than 20 nm to be created.
(cont.) The technique for measuring permittivity and conductivity presented in this thesis could eventually be adapted to make miniaturized disposable impedance test cells for chemical analysis. Such systems could take advantage of conductivity assays to determine the presence and concentration of specific substances. The adjustable nanometer electrode gap can also be used to study the properties of chemical and biological systems in highly confined states. These studies are fundamentally important for understanding biochemical processes in natural systems where reactions often take place inside confined structures such as cells, organelles, and the intercellular matrix.
by Hongshen Ma.
Ph.D.
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Zheng, Linan. "DETECTION OF CHLAMYDIA TRACHOMATIS BY ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/1966.
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Chlamydia trachomatis is detected by electrochemical impedance spectroscopy using a mouse monoclonal IgG2a anti-MOMP antibody immobilized onto a Si electrode. Two types of electrochemical cells are used in this study, one with the electrode at the bottom and the other will the electrode on the side. Control experiments with Escherichia coli demonstrate this biosensor is not selective to Chlamydia trachomatis. Another control experiment with Chlamydia trachomatis immobilized onto mouse monoclonal IgG2a isotype antibody coated electrode obtains an increased charge transfer resistance (Rct) which is inversely proportional to the rate of electron transfer. These results demonstrate further investigations are needed to develop the Chlamydia trachomatis impedance biosensor.
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Xu, Mengyun. "Optimised label-free biomarker assays with electrochemical impedance spectroscopy." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:e527a06b-25e5-48fe-8be5-3c0c10210b74.
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There is huge academic interest and clinical need associated with the development of biomarker immunoassays where general aims are the generation of highly specific, convenient and sensitive sensing formats. In this project, a powerful electrochemical technique, electrochemical impedance spectroscopy (EIS), is applied in the establishment of powerful biomarker detecting protocols. Firstly, ultrasensitive, label-free and reusable insulin sensors, based on an antibody-PEGylated thiol self-assembly monolayer (PEG thiol SAM) interface, were produced and characterised via Faradaic EIS, presenting a detection limit (LOD) of 1.2 pM, a linear range across four orders of magnitude, and high sensitivity in even 50 % serum. By applying similar surface chemistry, a label-free biosensor, specific for the detection of α-synuclein antibodies, was fabricated. The α-synuclein interfaces used enabled the reliable detecting of this biomarker in patient sample serum. The concentration levels in the control and a patient group were determined to be significantly different, and, significantly, this difference was consistently across two different cohorts. Strikingly, this could potentially underpin an entirely new means of early Parkinson’s disease (PD) diagnosis. Non-Faradaic EIS methods were additionally applied to label-free insulin assays at both PEG thiol SAM and zwitterionic polymer film interfaces. The latter presented not only an exceptionally non-fouling interface, but also one seemingly both highly biocompatible and facilitating enhanced receptor: target binding. Finally, impedance assays, though potent, generally, operate by sampling only one of a limited number of available experimental variables, typically, Rct for Faradaic EIS, or C or Z for non-Faradaic EIS. Work carried out herein also explores the generation and utility of a portfolio of mathematically derived immittance functions all obtained from the same raw data sets. A particular focus was the examination of whether these were capable of increasing assay sensitivity and efficiency above normal impedance treatments.
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Foley, John J. "Microfluidic Electrical Impedance Spectroscopy." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1950.
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The goal of this study is to design and manufacture a microfluidic device capable of measuring changes in impedance valuesof microfluidic cell cultures. Tocharacterize this, an interdigitated array of electrodes was patterned over glass, where it was then bonded to a series of fluidic networks created in PDMS via soft lithography. The device measured ethanol impedance initially to show that values remain consistent over time. Impedance values of water and 1% wt. saltwater were compared to show that the device is able to detect changes in impedance, with up to a 60% reduction in electrical impedance in saltwater. Cells were introduced into the device, where changes in impedance were seen across multiple frequencies, indicating that the device is capable of detecting the presence of biologic elements within a system. Cell measurements were performed using NIH-3T3 fibroblasts.
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Formisano, Nello. "A study on the optimisation of electrochemical impedance spectroscopy biosensors." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687325.
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Electrochemical impedance spectroscopy (EIS) has been one of the most intensively studied electrochemical techniques for biosensing in recent decades. However, despite its great potential, real applications of EIS sensors still remain not as widely spread as other techniques because there are many factors that govern impedimetric signals. In particular, features such as the probe coverage density on the sensor surface, as well as the target size, charge and conformation, can assume significant importance. The aim of this study was to analyse both the limitations and the potential solutions for maximizing the EIS signals in certain possible systems which are characterised by having different types of target to detect. In order to reproduce different conditions, four types of molecular targets have been taken in consideration. These provided example systems where the approach for the development of an EIS sensor varied considerably. In the first system the importance of the surface conditions of an aptasensor for prostate specific antigen (PSA) using Faradaic processes was reported. It was demonstrated that the effect of the target binding combined with the relative surface charge modification can diminish the EIS signals. In the second system, a strategy for improving the sensitivity and selectivity of the assay for drug discovery applications was demonstrated. This was obtained by adopting ferrocene-crowned gold nanoparticles that specifically bind to the molecular targets and induced a transition from non-Faradaic to Faradaic processes. In the last two example systems, particular attention has also been given to non-Faradaic processes which are the least exploited in EIS systems although the technique can be simpler to implement compared to Faradaic EIS. Moreover, with non-Faradaic processes more effective results can be achieved under some specific conditions, such as exploiting the size and charge of molecular targets. On such premises, the current work wants to serve as a reference for overcoming the limitations met in several EIS systems and hopefully contribute as a support for enhancing the fields of applications of EIS sensors.
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Valenzuela, Jorge Ignacio. "Electrochemical impedance spectroscopy options for proton exchange membrane fuel cell diagnostics." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/266.
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Electrochemical impedance spectroscopy (EIS) has been exploited as a rich source of Proton Exchange Membrane Fuel Cell (PEMFC) diagnostic information for many years. Several investigators have characterized different failure modes for PEMFCs using EIS and it now remains to determine how this information is to be obtained and used in a diagnostic or control algorithm for an operating PEMFC.
This work utilizes the concept of impedance spectral fingerprints (ISF) to uniquely identify between failure modes in an operating PEMFC. Three well documented PEMFC failure modes, carbon monoxide (CO) poisoning, dehydration, and flooding were surveyed, modelled, and simulated in the time domain and the results were used to create a database of ISFs. The time domain simulation was realized with a fractional order differential calculus state space approach.
A primary goal of this work was to develop simple and cost effective algorithms that could be included in a PEMFC on-board controller. To this end, the ISF was discretized as coarsely as possible while still retaining identifying spectral features using the Goertzel algorithm in much the same way as in dual tone multi-frequency detection in telephony. This approach generated a significant reduction in computational burden relative to the classical Fast Fourier Transform approach.
The ISF database was used to diagnose simulated experimental PEMFC failures into one of five levels of failure: none (normal operation), mild, moderate, advanced, and extreme from one of the three catalogued failure modes. The described ISF recognition algorithm was shown to correctly identify failure modes to a lower limit of SNR = 1dB.
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Bhatnagar, Purva. "A microcontroller-based Electrochemical Impedance Spectroscopy Platform for Health Monitoring Systems." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439307617.
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Argyle, Hillary McKenna. "Sensitivity of Electrochemical Impedance Spectroscopy Measurements to Concrete Bridge Deck Properties." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/3963.
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Numerous methods have been developed to measure corrosion potential relating to chloride infiltration in concrete, including an emerging application of electrochemical impedance spectroscopy (EIS). EIS involves measurements of electrical impedance to evaluate the corrosion potential of steel reinforcement in concrete. With EIS, current is injected vertically into the concrete bridge deck between the surface and the embedded reinforcing steel, usually the top mat, to evaluate the degree to which the reinforcing steel is protected from chloride infiltration by the entire bridge deck system. The objectives of this research were to 1) investigate the sensitivity of EIS measurements obtained at various frequencies to specific deck properties, 2) recommend a particular frequency or range in frequency at which impedance measurements can differentiate among various levels of corrosion protection for reinforcing steel in concrete bridge decks, and 3) compare impedance values measured at the recommended frequency(ies) to more traditional test measurements relating to corrosion of reinforcing steel in concrete bridge decks. This research involved impedance testing of 25 concrete slabs, divided into five sets. The effects of sealant presence, curing time, temperature, moisture content, cover depth, water-to-cementitious materials ratio, air content, chloride concentration, and epoxy coating condition on individual impedance measurements were evaluated. For the controlled laboratory experiments, sealant presence, curing time, temperature, moisture content, cover depth, water-to-cementitious materials ratio, air content, and epoxy coating condition were shown to have a statistically significant effect on impedance measurements, with p-values less than 0.05. The statistical analyses indicated that impedance testing in the frequency range of approximately 100 Hz to 1 kHz would be expected to provide the best data about the degree to which the reinforcing steel is protected from chloride infiltration by a bridge deck system. In this frequency range, a high level of differentiation among levels of corrosion protection is expected, and a high speed of data collection is also possible. For the uncontrolled laboratory experiments, a single frequency of 200 Hz was selected for impedance testing. Statistical analyses were performed to compare impedance with more traditional test measurements relating to corrosion of reinforcing steel in concrete bridge decks. Longitudinal and transverse cover, dry and wet resistivity, dry and wet half-cell potential, dry linear polarization, and chloride concentration were determined to be correlated with impedance, with p-values less than 0.15.
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Baumeister, Carl Robert. "Electrochemical impedance spectroscopy and surface plasmon resonance for diagnostic antibody detection." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/31495.
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The successful use of biomarker antibody detection for disease diagnosis is currently
restricted to cases where the antibody affinity and specificity of interaction with
antigen is high. Evanescent field biosensing, e.g. Surface Plasmon Resonance (SPR),
and electrochemical detection, in particular Electrochemical Impedance Spectroscopy
(EIS), have been shown viable for detection of lower affinity antibodies, based on the
principle that these technologies allow the measurement of antibody binding to
immobilized antigen, i.e. without the need to wash away excess, non-bound
antibodies or using labelled antibodies. Proof of principle for this in the case of
detection of biomarker anti-mycolic acid antibodies for TB diagnosis has been
provided in the Mycolic acid Antibody Real-Time Inhibition assay (MARTI) by our
research group. Although already patented and published, MARTI is not yet a feasible
diagnostic test due to slow sample turn-around time, affordability and technical
vulnerability associated with unstable lipid antigen surface chemistry and the
difficulty of standardization of liposome carriers of mycolic acids used for measuring
the binding inhibition of serum antibodies to immobilized antigen. Here, these
challenges were addressed by investigating the use of a magnetic field for more stable
lipid antigen immobilization, new phospholipid compositions to generate more stable
liposome carriers for lipid antigen in solution and the use of screen-printed electrodes
(SPE) in EIS to address affordability of diagnosis and improve sample turn-around
time. The latter approach appeared quite promising in distinguishing a TB positive
and a TB negative patient serum and is amenable to automation by means of a flow
injection system.Dissertation (MSc)--University of Pretoria, 2012.
Biochemistry
MSc
Unrestricted
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Piippo, Juha. "Electrochemical characterization of inorganic coatings : titanium nitride and aluminium oxide coatings characterized using electrochemical impedance spectroscopy /." [S.l.] : [s.n.], 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10309.
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Liu, Xing, and s3072856@student rmit edu au. "Electrical Impedance Spectroscopy Applied in Plant Physiology Studies." RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080428.092529.
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Electrical Impedance Spectroscopy (EIS) is a relatively new method applied to food quality assessment. EIS allows relatively inexpensive assessment, is fast, easy to operate and non-invasive. It has been adopted for investigation of fundamental electrical properties of plant tissues. Although the applications of EIS for food quality determination have been reported previously, the analytical relationships between electrical impedance properties and quality criteria have not yet been fully developed. Further exploration is thus important in acquiring more data on electrical impedance characteristics of fruits and vegetables and researching new approaches for determination of their quality. This dissertation aims to investigate the electrical impedance properties of fruits and vegetables, and explore the relationship between impedance and quality criteria. In particular, the present dissertation outlines experimental research conducted on relationships between impedance properties and fruit tastes as well as the impedance changes observed during ripening process. Impedance measurement to monitor moisture content changes in the progress of drying is also included in this research. In summary, the impedance properties have merits in fruits and vegetables quality assessment. The current used subjective visual inspection and assessment could be replaced by the EIS based approach as it is a more precise measurement of food quality. Further study is required to give this method practical value.
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Lu, Yuan S. B. Massachusetts Institute of Technology. "Using electrochemical impedance spectroscopy to characterize vertically-aligned carbon nanotube forest porosimetry." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98662.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 55-56).
Carbon nanotubes have generated much research interest and potential applications due to their unique properties such as their high tensile strength, high thermal conductivity, and unique semiconductor properties. Vertically-aligned carbon nanotubes (VA-CNTs) have been used in applications for electrochemical systems in energy storage systems and desalination systems. Typical methods of characterizing the morphology and composition of CNTs are limited in providing information on the packing density of CNTs, and therefore, an effective method for in situ characterization of VA-CNT electrodes is needed. This method explores the use of impedance spectroscopy and other electrochemical methods to characterize VA-CNTs in situ. VA-CNTs forests were grown via chemical vapor densification on pre-oxidized silicon wafers, mechanically densified to achieve varying volume fractions (1%, 2%, 5%, and 10%), and tested in a three-electrode electrochemical cell. Electrochemical techniques (cyclic voltammetry, impedance spectroscopy, and potentiostatic techniques) were used to measure the performance of the VA-CNTs in 1 M and 500 mM electrolyte solutions. Optimization of the experimental setup design and data collection methods yielded data that resulted in the expected cyclic voltammetry response and impedance behavior of porous electrodes. A transmission line model-pore size distribution (TLM-PSD) model was applied to the data collected in order to predict and model porosimetry characteristics. Porous behavior was observed in the VA-CNT electrodes of all volume fractions tested, and the impedance spectra showed that the volume fraction affected the overall impedance but not the characteristic shape of the spectra. Comparison between the impedance data collected in 1 M NaCl and 500 mM NaCl showed the expected corresponding inverse correlation with solution conductivity. Parameters that describe the VA-CNT electrode porosity were calculated and predicted using electrochemical data and the TLM-PSD model. The porous volume Vtot and total ionic conductance Yp values calculated using the model applied to the impedance spectroscopy data showed trends as expected for the different volume fractions of VA-CNT. The results show that electrochemical impedance spectroscopy can be used to characterize certain physical characteristics of the VA-CNT electrodes and further development of the model can yield insights into the porous geometry of VA-CNT forests.
by Yuan Lu.
S.B.
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Gruden, Roman, Andreas Buchholz, and Olfa Kanoun. "Electrochemical analysis of water and suds by impedance spectroscopy and cyclic voltammetry." Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-149036.
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Optimum detergent dosage during a washing process depends on water quality, degree of pollution and quantity of laundry. Particularly, water quality is an important factor. Other parameters like carbonate- or non-carbonate hardness and calcium / magnesium (Ca / Mg) ratio in addition to total hardness of water have an impact on the amount of detergent. This work discusses the possibilities realizing a detergent sensor that measures important parameters for the washing process and assess the ideal necessary amount of detergent during the washing process. The approach is to combine impedance spectroscopy with cyclic voltammetry in order to determine both water quality and concentration of detergent in the suds which build up the basis for an optimum detergent dosage. The results of cyclic voltammetry show that it is possible to identify the Ca / Mg ratio and the carbonate hardness separately, which is necessary for the optimization of the washing process. Impedance measurements identify total hardness and detergent concentrations.
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Fredlén, Alexander. "Electrochemical impedance spectroscopy on NMC811 at varying temperature and state of charge." Thesis, KTH, Tillämpad elektrokemi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299455.
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I detta arbete har elektrokemisk impedansspektroskopi använts för att producera reproducerbara impedansdata för katodmaterialet NMC811. Data som skulle kunna användas som basen för parametrisering och konstruktionen av en fysik-baserad modell. Dessutom har effekten av laddningstillstånd, temperatur, och historian av cellen på impedansen undersökts. Baserat på resultaten av preliminära test så har experiment konstruerats i vilka katodens impedans i en NMC811//Grafit cell har undersökts vid olika temperaturer och laddningstillstånd, både efter laddning och urladdning av cellen. Reproducerbara resultat kunde erhållas och det visades hur laddningstillstånd och temperatur har en stor påverkan på impedansen. Tyvärr så kunde inget sägas om hystereseffekten på grund av dålig stabilitet i lågfrekvensområdet av impedansmätningarna.In this work, electrochemical impedance spectroscopy has been used to try and produce reproducible impedance data for the cathode material NMC811. Data that could serve as the basis of parameter extraction for the construction of a physics-based model. Furthermore, the effect of state of charge, temperature, and history of the cell on the impedance has been analysed. Based on the results of preliminary tests, an experimental cycle was constructed in which the cathode impedance of a NMC811//Graphite cell was measured at varying temperatures and state of charge, both following charge and discharge of the cell. Reproducible results were achieved, and it was shown how the state of charge and temperature of the cell had a major effect on the measured impedance. Unfortunately, no conclusions could be made about the history effect on impedance due to poor stability in the low frequency regions of the impedance measurements.
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Lai, Wei Haile Sossina M. "Impedance spectroscopy as a tool for electrochemical study of mixed conducting ceria /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-12072006-123745.
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Pali, Madhavi L. "Detection of Small Molecule Analytes with Biosensors based on Electrochemical Impedance Spectroscopy." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/dissertations/1651.
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Several different approaches were studied to improve and understand the sensitivity and detection limit that could be obtained for biosensors that utilize electrochemical impedance spectroscopy (EIS) for signal transduction. The first project involves the detection of fish hormones by applying Electrochemical impedance spectroscopy (EIS) & Quartz crystal microbalance (QCM) techniques. Detection of three fish hormones, cortisol, insulin-like growth factor 1 (IGF-1), and vitellogenin is studied by both electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM), and the EIS (QCM) detection limits are 7.9 (0.50) μM, 3.0 (2.4) nM, and 43 (13) pM, respectively, in PBS buffer. Thus, the two detection methods, EIS and QCM, have similar sensitivity, but QCM is four times more in magnitude while it comes to sensitiveness consideration, which is consistent with the published literature. The molecular weights of cortisol, IGF-1, and vitellogenin are 362.5 Da, 7.3 kDa, and 440.5 kDa, respectively. For both EIS and QCM, the sensitivity and detection limit improve dramatically with increasing molecular weight, reflecting the larger change in polymer-protein film thickness at the Au electrode upon recognition and binding of larger analytes. Potential applications to the understanding of fish physiology are discussed, including hormone detection in fish blood plasma, and ambient water.
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Coignet, Philippe. "Transport-reaction modeling of the impedance response of a fuel cell." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0526104-151500/.
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Ateh, Davidson Day. "Study of epithelial cells on polypyrrole based conducting polymers using electrochemical impedance spectroscopy." Thesis, Queen Mary, University of London, 2005. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1749.
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Polypyrrole (PPy) is a conjugated polymer that displays special electronic properties including conductivity. It may be electrogenerated with the incorporation of any anionic species including negatively charged biological molecules such as proteins and polysaccharides. For this thesis, variously loaded-PPy films were prepared on gold sputter-coated coverslips. The growth and characteristics of epithelial cells, namely keratinocytes, were studied on these films by microscopy, biochemical assay, immunocytochemistry and electrochemical impedance spectroscopy. Keratinocyte viability was found to be PPy-load dependent. For chloride, polyvinyl sulphate, dermatan sulphate and collagen-loaded PPy films, polycarbonate and gold, keratinocyte viability, as assessed by the AlamarBlueTM assay, was respectively 47%, 60%, 88% and 23%, 75% and 61% of tissue culture polystyrene controls after 5 days. This was found to require a previously unreported polymer washing step prior to cell seeding due to the observed toxicity of untreated films. Keratinocytes stained positive for proliferation (PCNA), suprabasal differentiation (K10) and hyperproliferation (K16) markers although cell morphology was poor for organotypical cultures on dermatanloaded PPy compared with de-epidermalised dermis. Cell-induced impedance changes were detected in a three-electrode format over PPy modified electrodes. Results obtained showed the effects of cell density, cell type and monitoring frequencies. In particular, it was seen that lower cell densities could be detected on PPy compared to unmodified gold electrodes. Keratinocyte confluence as determined by impedimetric analysis was reached more rapidly on PPy than bare gold in agreement with AlamarBlueTM measurements. Electrical equivalent circuit analysis using parameters whose contributions may be directly mapped to intracellular and intercellular spaces, and membrane components suggested that the technique can be extended to cell morphology discrimination. This work shows that PPy biocomposites are attractive candidates for tissue engineering applications since they may incorporate biomolecules and are electrically addressable with the potential to both direct and report on cell activities.
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Williams, Brian J. "Applications of Electrochemical Impedance Spectroscopy in In Vivo Corrosion Monitoring and Tissue Discrimination." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1311605422.
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Mohammad, Naim Nur Nafisah. "Modelling the ageing behaviour of supercapacitors using electrochemical impedance spectroscopy for dynamic applications." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/29169/.
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Diagnosis of ageing mechanisms in supercapacitors is made difficult by the enforcement of various ageing factors in the current ageing tests. The thesis presents the exact determination of the ageing mechanism by separating the impacts of high temperature, current cycling and constant voltage applications in accelerated ageing tests. The state of health (SOH) of the supercapacitors are monitored periodically with electrochemical impedance spectroscopy, cyclic voltammetry and constant current test to observe the evolution of ageing. The thesis identifies patterns of ageing from the changes at supercapacitor impedance. The thesis also presents the cause of the increase in ESR and the loss of capacitance in supercapacitors. High temperature application causes the appearance of high frequency semicircle which reflects the damage at the electrode-current collector interface. A tilt of the impedance line at low frequencies reflects modifications of electrodes and it is most sensitive to current cycling and constant voltage applications. The increase in ESR is observed to be caused by a single ageing mechanism while the capacitance loss is caused by multiple interactions of these ageing mechanisms at the same time. The thesis develops a supercapacitor model by means of electrical equivalent circuit. The model is divided into two parts based on the changes in its SOH: the baseline model represents the early stage of the supercapacitor life and the ageing model represents the phase of ageing. The models show dynamic interactions between ageing process and supercapacitor electrical performance. The supercapacitor model, in the form of fractional-order model, reduces the number of circuit components and shows excellent electrical behaviour particularly at the open circuit voltage decay and voltage recovery period. The parameterisation of model parameters shows that aged supercapacitors experience an increase of distributed resistance in the electrode pores and an increase of diffusion impedance at high temperature.
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Day, M. J. "Mechanistic studies using in situ electrochemical-ESR spectroscopy." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384356.
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Smila-Castro, Ornella. "X-ray absorption spectroscopy studies of electrochemical processes." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3766/.
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Electron transfer is a key part of many chemical, biological and physical processes, that is commonly studied by electrochemical methods, which give insight into reaction mechanisms but no structural information. It is necessary to combine electroanalysis with another technique to gain essential knowledge of metal-ligand bond length and oxidation states. X-ray absorption spectroscopy (XAS) can provide these data for species in dilute solution and, if combined with electrochemistry, could potentially provide powerful insight into electron transfer reactions. This dissertation describes the development and application of techniques for the study of electrochemical intermediates by XAS. Chapters 2 and 3 introduce the theory and practice of electrochemistry and spectroscopy with emphasis on XAS. Chapter 4 describes the development of variable-temperature spectroelectrolysis cells for the study of electrochemical intermediates. In Chapter 5, the electrochemical behaviour of Cp\( \ast \)Rh(CO)\(_2\), is investigated as an organometallic compound representative of the redox chemistry studied in this thesis. Chapter 6 describes a new approach to the study of electrochemical intermediates in which a miniature electrolysis cell is combined with a microdispenser so that electrochemical intermediates can be generated and then dispensed, quenched at low temperature prior to study by XAS. Chapter 7 contains final conclusions.
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La, Mantia Fabio. "Characterization of electrodes for lithium-ion batteries through electrochemical impedance spectroscopy and mass spectrometry /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17848.
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Husain, Adel Abdulmajeed. "Paint coated steel in Kuwaiti corrosion environment : surface corrosion mapping & electrochemical impedance spectroscopy." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336601.
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Pavlacky, Drew Adam. "Electrochemical Impedance Spectroscopy Study of the Ultraviolet Exposure of Ballistic Resistant Polymer Matrix Composites." Thesis, North Dakota State University, 2012. https://hdl.handle.net/10365/26755.
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This study examined the effect of ultraviolet radiation on ballistic resistant polymer matrix composites. Two composite systems studied included a phenolic matrix with either S2 Glass? or Kevlar? fiber laminates. These composites were weathered in ultraviolet conditions and the effects were quantified with multiple destructive and non-destructive testing. Electrochemical impedance spectroscopy (EIS) was used as a non-destructive evaluation method which is a commonly used experiment in the corrosion community. Circuit modeling the EIS spectra produced both resistive and capacitive characteristics inherent of the composite materials. Surface characterization was performed to determine if degradation was occurring at the composite surface. Techniques included: color, gloss, surface profilometry, and water contact angle. Tensile and flexural destructive experimentation revealed the influence of the ultraviolet exposure on the mechanical properties. It was determined that the resistive portion of the EIS response correlated well with the ultimate tensile strength of the S2 Glass? fiber composites.Army Research Laboratory
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taki, motahareh. "DEVELOPING PROBES FOR LABEL-FREE DETECTION OF HEXANUCLEOTIDE GGGGCC REPEATS BY ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2634.
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DNA repeat expansion sequences cause a myriad of neurological diseases when they expand beyond a critical threshold. Previous electrochemical approaches focused on the detection of trinucleotide repeats (CAG, CGG, and GAA) and relied on labeling of the probe and/or target strands or enzyme-linked assays. However, detection of expanded GC-rich sequences is challenging because they are prone to forming secondary structures such as cruciforms and quadruplexes. Here, we present label-free detection of hexanucleotide GGGGCC repeat sequences, which cause the leading genetic form of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). The approach relies on capturing targets by surface-bound oligonucleotide probes with a different number of complementary repeats, which proportionately translates the length of the target strands into charge transfer resistance (RCT) signal measured by electrochemical impedance spectroscopy (EIS). The probe carrying three tandem repeats transduces the number of repeats into RCT with a 3× higher calibration sensitivity and detection limit. Chronocoulometric measurements show a decrease in surface density with increasing repeat length, which is opposite of the impedance trend. This implies that the length of the target itself can contribute to amplification of the impedance signal independent of the surface density. Moreover, the probe can distinguish between a control and patient sequences while remaining insensitive to non-specific Huntington’s disease (CAG) repeats in the presence of a complementary target. This label-free strategy might be applied to detect the length of other neurodegenerative repeat sequences using short probes with a few complementary repeats.
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Waligo, Alfred. "Condition monitoring of lithium-ion batteries using broadband multisine excitation and electrochemical impedance spectroscopy." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/28109.
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Electrochemical Impedance Spectroscopy (EIS) is a well-known technique that has been employed on various electrochemical cells to obtain their impedance spectra. Lithium-ion(Li-ion) cells are some of the cells to which it has been applied. The impedance spectra obtained from EIS can be used to estimate various batteries State of Health (SOH) and State of Charge (SOC) characteristics. The lengthy acquisition time associated with standard EIS makes it unsuitable for rapid on-line impedance measurements. Alternative methods that take a shorter time have therefore been proposed. This study compares the spectra obtained by the Harmonic Compensated Synchronous Detection (HCSD) broadband signal technique with the EIS and a custom Broadband Impedance Spectroscopy (BIS) technique, at different states of charge, which mimic a real-time load. The test cells are industry standard Nickel-Cobalt and Manganese Oxide (NCM) Li-ion cells. The BIS technique is like HCSD in the selection of frequencies; however, the amplitude of the excitation broadband signal is varied to match the impedance magnitude response of the cell. Also, parameter extraction is performed on both EIS and BIS techniques for fault detection purposes.
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Wang, Peng. "Corrosion behaviour of zirconium alloys in high temperature aqueous environment by electrochemical impedance spectroscopy." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/corrosion-behaviour-of-zirconium-alloys-in-high-temperature-aqueous-environment-by-electrochemical-impedance-spectroscopy(e1bf6a9f-c8ca-45db-8e05-14ee723886d9).html.
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The corrosion behaviour of zirconium based alloys has been primarily investigated by electrochemical impedance spectroscopy (EIS). In-situ autoclave EIS experiments were performed in simulated primary coolant conditions in order to study the high temperature water corrosion of zirconium alloys in PWRs. In-situ impedance response of the corroding material was recorded throughout first kinetic transition. A physical model of the zirconium oxide was proposed in accordance with the microstructural observation' made by SEM analysis. Electrical properties of the oxide was evaluated with equivalent circuit model (ECM) which was constructed according to the physical oxide model. Evolution of various oxide parameters obtained from ECM was analysed in accordance with the microstructure observation made by SEM. A two layer structure consists of a outer porous oxide and an inner barrier oxide, was found to be the most accurate description for the autoclave formed oxide. Supporting evidence from the SEM cross-section and surface analysis of the oxide had shown cracks and pores that were linked and connected with the environment. This observation is also confirmed by the in-situ EIS measurement which has shown porous electrode behaviour throughout the course of oxidation. The porous oxide behaviour was also confirmed by the ex-situ soaking experiment on samples with incremental exposure time. Evolution of inner barrier layer oxide thickness was found to be correlated with kinetic transition which was determined from weight gain measurement. This indicated that barrier layer maybe the oxidation rate controlling layer and its thickness maybe reduced during transition. Thus, a thinner barrier layer would resulted in a rapid corrosion of zirconium alloys. Furthermore, maintaining the barrier layer thickness maybe the possible route to improve zirconium alloy corrosion resistance.
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Jeffers, Kenneth E. "Electrochemical impedance spectroscopy for the characterization of corrosion and cathodic protection of buried pipelines." [Florida] : State University System of Florida, 1999. http://etd.fcla.edu/etd/uf/1999/amj9949/jeffers.pdf.
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Thesis (M.S.)--University of Florida, 1999.Title from first page of PDF file. Document formatted into pages; contains xx, 206 p.; also contains graphics. Vita. Includes bibliographical references (p. 202-205).
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Lu, Yunxiang. "Study of electrochemical performance of strontium doped lanthanum cobalt oxides using electrochemical impedance spectroscopy and microelectrode array cell design /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9818.
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Medina, Francelys A. Lanagan Michael Thomas. "Impedance spectroscopy studies of silica-titania glasses and glass-ceramics." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/PSUonlyIndex/ETD-4566/index.html.
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Jayaraj, Balaji. "Correlating microstructural development and failure mechanisms to photo stimulated luminescence spectroscopy and electrochemical impedance spectroscopy in thermal barrier coatings." Doctoral diss., University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4948.
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Thermal barrier coatings (TBCs) are widely used for thermal protection of hot section components in turbines for propulsion and power generation. Applications of TBCs based on a clearer understanding of failure mechanisms can help increase the performance and life-cycle cost of advanced gas turbine engines. Development and refinement of robust nondestructive evaluation techniques can also enhance the reliability, availability and maintainability of hot section components in gas turbines engines. In this work, degradation of TBCs was non-destructively examined by photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) as a function of furnace thermal cycling carried out in air with 10-minute heat-up, 0.67, 9.6 and 49.6 - hour dwell duration at 1121[degree]C (2050[degree]F), and 10-minute forced-air quench. TBCs examined in this study consisted of either electron beam physical vapor deposited and air plasma sprayed yttria-stabilized zirconia (YSZ) on a variety of bond coat / superalloy substrates including bond coats of NiCoCrAlY and (Ni,Pt)Al, and superalloys of CMSX-4, Rene'N5, Haynes 230 and MAR-M-509. Detailed microstructural characterization by scanning electron microscopy and energy dispersive spectroscopy was carried out to document the degradation and failure characteristics of TBC failure, and correlate results of PSLS and EIS. Mechanisms of microstructural damage initiation and progression varied as a function of TBC architecture and thermal cycling dwell time, and included undulation of the interface between the thermally grown oxide (TGO) and bond coats, internal oxidation of the bond coats, and formation of Ni/Co-rich TGO. These microstructural observations were correlated to the evolution in compressive residual stress in the TGO scale determined by PSLS shift. Correlations include stress-relief and corresponding luminescence shift towards stress-free luminescence (i.e. v= 14402 cm[super-1] and v = 14432 cm[super]-1) associated with subcritical cracking of the TGO scale and stress-relaxation associated with gradual shift in the luminescence towards stress-free luminescence (i.e. v = 14402 cm[super-1] and v = 14432 cm[super-1]) is related to the undulation of TGO/bondcoat interface (e.g., rumpling and ratcheting). Microstructural changes in TBCs such as YSZ sintering, TGO growth, and subcritical damages within the YSZ and TGO scale were also correlated to the changes in electrochemical resistance and capacitance of the YSZ and TGO, respectively. With thermal exposure the YSZ/TGO resistance and capacitance increased and decreased as result of sintering and TGO growth. With progressive thermal cycling damages in the TGO was related to the TGO capacitance showing a continuous increase and at failure TGO capacitance abruptly increased with the exposure of bondcoat. Further correlations among the microstructural development, PSLS and EIS are documented and discussed, particularly as a function of dwell time used during furnace thermal cycling test, with due respect for changes in failure characteristics and mechanisms for various types of TBCs.ID: 029810158; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 213-217).
Ph.D.
Doctorate
Mechanical, Materials, and Aerospace Engineering
Engineering and Computer Science
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Khani, Meynaq Mohammad Yaser. "Electrochemical investigations on lipid cubic phases." Doctoral thesis, Umeå universitet, Kemiska institutionen, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-130174.
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Electrochemical Impedance Spectroscopy (EIS) was used to develop a novel methodology for studying ionic interaction with lipids arranged in a lipid cubic phase (LCP). Studying different types of ions, both cations and anions, validated the method. A free-standing LCP membrane was formed between two cell compartments and impedance experiments were carried out in a 2-electrode setup to estimate dielectric properties of the membrane, exposed to the following electrolyte solutions at different concentrations: KCl, CsBr, CaCl2, MgCl2, CsCl, NaCl, NaOAc and NaTryptophan. Two different LCP were used in this setup, i.e: Monoloein/water and the ternary system of monoolein/dioleoylphosphatidylcholine/water (MO/DOPC/H2O). SAXRD measurements were performed to determine the space group of the cubic phase and confirm the stability of the LCP during measurements. Membrane resistances and capacitances were found from equivalent circuit fitting to the impedance data. The membrane resistance was shown to be related to ionic interaction with the lipid head group in the water channels of the LCP. Membrane capacitance were correlating to condensing and swelling effect of LCP due to the exposure of ions. The results correlated well with the SAXRD results and earlier published data. The results also indicate that these membranes become less permeable to ions as they increase in size as well as in charge or polarity. Cyclic voltammetry was used to study the applications of a LCP for modification of the bioanode in a biofuel cell. The monoolein cubic phase was used to host Glucose oxidase (GOx) and a freely diffusing ferrocene carboxylate was used as mediator. The supported cubic phase had an intrinsic resistance in the same order of magnitude as the freestanding MO-LCP membrane as measured with EIS.Elektrokemisk impedans spektroskopi har använts för att utveckla en ny metod för att studera joners växelverkan med lipider som bildat en kubisk fas. Olika typer av joner, både positiva och negativa, användes för att validera metoden. Ett fristående membran uppbyggt av en kubisk fas separerade två avdelningar i en elektrokemisk cell. Cellen fylldes med elektrolyt-lösningar och impedansmätningar kunde utföras mellan två platina elektroder placerade i vardera avdelning. Membranet exponerades för följande elektrolytlösningar av olika koncentration: KCl, CsBr, CaCl2, MgCl2, CsCl, NaCl, NaOAc and NaTryptofan. Två olika kubiska faser användes i denna uppställning, dvs: Monoloein/vatten och det ternära systemet monoolein/dioleoylfosfatidylkolin/vatten(MO/DOPC/H2O). Med hjälp av SAXRD kunde den kubiska fasens kristallstruktur bestämmas och dess stabilitet under mätningarna bekräftas. De dielektriska egenskaperna hos membranet bestämdes genom att anpassa impedansspektrat till en ekvivalent krets bestående av resistanser, kapacitanser och konstant-faselement. Membranresistansen visade sig vara relaterad till jonernas växelverkan med lipidhuvudgruppen i vattenkanalerna i kubiska fasen. Ju starkare växelverkan desto högre var resistansen. Membrankapacitansen kunde korreleras med kondenserande och uppsvällande effekter på kubiska fasen förorsakade av exponeringen till joner. Resultaten bekräftades av SAXRD mätningar och även tidigare publicerade data. Resultaten indikerar också tydligt att permeabiliteten hos membranet minskar med ökad jonstorlek, jonladdningoch polaritet hos jonen. Cyklisk voltammetri användes för att studera en tillämpning av kubiska fasen i en tänkt applikation som bioanod i en biobränslecell. Elektroden modifierades med en kubisk fas innehållande GOx och tillsammans med en fritt diffunderande ferrocen karboxylat som mediator, där oxidation av glukos studeras. Det visade sig att den kubiska fasen hade en resistans av samma storleksordning som det fristående membranet uppmätt med impedansspektroskopi.
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Wasala, KWM Milinda Prabath. "ELECTROCHEMICAL CHARACTERIZATION OF EXFOLIATED GRAPHENE." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1418.
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In this research we have investigated electrochemical and impedance characteristics of liquid phase exfoliated graphene electrodes. The exfoliated graphene electrodes were characterized in Electrochemical Double Layer Capacitors (EDLCs) geometry. Liquid phase exfoliation was performed on bulk graphite powder in order to produces few layer graphene flakes in large quantities. The exfoliation processes produced few layer graphene based materials with increased specific surface area and were found to have suitable electrochemical charge storage capacities. Electrochemical evaluation and performance of exfoliated graphene electrodes were tested with Cyclic Voltammetry, constant current charging discharging and Electrochemical Impedance Spectroscopy (EIS) at ambient conditions. We have used several electrolytes in order to evaluate the effect of electrolyte in charge storage capacities. Specific capacitance value of ~ 47F/g and ~ 262F/g was measured for aqueous and ionic electrolytes respectively. These values are at least an order of magnitude higher than those obtained by using EDLC's electrodes fabricated with the bulk graphite powder. In addition these EDLC electrodes give consistently good performance over a wide range of scan rates and voltage windows. These encouraging results illustrate the exciting potential for high performance electrical energy storage devices based on liquid phase exfoliated graphene electrodes.
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Skoorka, Michelle E. "The effect of humidity on composite lap joints and an electrochemical study on coatings and galvanic systems /." View online ; access limited to URI, 2004. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3135915.
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Protsailo, Lesia V. "Characterization of the electrode/SAM/electrolyte interface and intermolecular interactions in solutions using electrochemical impedance spectroscopy and ATR-FTIR spectroscopy /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
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Smiechowski, Matthew F. "Electrochemical Characterization of Lubricants for Microfabricated Sensor Applications." Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1121349361.
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Yuan, Qifan. "Physical, electrical and electrochemical characterizations of transition metal compounds for electrochemical energy storage." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/71869.
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Electrochemical energy storage has been widely used in various areas, including new energy sources, auto industry, and information technology. However, the performance of current electrochemical energy storage devices does not meet the requirements of these areas that include both high energy and power density, fast recharge time, and long lifetime. One solution to meet consumer demands is to discover new materials that can substantially enhance the performance of electrochemical energy storage devices. In this dissertation we report four transition metal materials systems with potential applications in electrochemical energy storage.
Nanoscale and nanostructured materials are expected to play important roles in energy storage devices because of their enhanced and sometimes unique physical and chemical properties. Studied here is the comparative electrochemical cation insertion into a nanostructured vanadium oxide, a promising electrode material candidate, for the alkali metal ions Li+, Na+ and K+ and the organic ammonium ion, in aqueous electrolyte solutions. Observed are the distinctive insertion processes of the different ions, which yield a correlation between physical degradation of the material and a reduction of the calculated specific charge. The results reveal the potential of this nanostructured vanadium oxide material for energy storage. Vanadium based electrochemical systems are of general interest, and as models for vanadium based solid-state electrochemical processes, the solution state and the solid-state electrochemical properties of two cryolite-type compounds, (NH4)3VxGa1-xF6, and Na3VF6, are studied. The electrochemical behavior of (NH4)3VxGa1-xF6 explored the possibility of using this material as an electrolyte for solid state energy storage systems.
Zeolite-like materials have large surface to volume ratios, with ions and neutral species located in the nanometer sized pores of the 3-dimensional framework, potentially yielding high energy density storage capabilities. Yet the insulating nature of known zeolite-like materials has limited their use for electrical energy storage. Studied here are two vanadium based zeolite-like structures, the oxo-vanadium arsenate [(As6V15O51)-9]∞, and the oxo-vanadium phosphate [(P6V15O51)-9]∞, where the former shows electronic conduction in the 3-dimensional framework. Mixed electronic and ionic conductivity, from the framework and from the cations located within the framework, respectively, is measured in the oxo-vanadium arsenate, and allows the use of this material in electrochemical double-layer capacitor configuration for energy storage. By contrast, the oxo-vanadium phosphate shows ionic conduction only. Lastly, a new strontium manganese vanadate with a layered structure exhibiting mixed protonic and electronic conductivity is studied. The various transition metal compounds and materials systems experimentally studied in this thesis showcase the importance of novel materials in future energy storage schemes.Ph. D.
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Boychuk, O. V. "Electrochemical Impedance Spectroscopy Study In-Situ State of Health of the Alkaline Zn-Mno2 Batteriesunder Changing of Thermal Modes." Thesis, Київський національний університет технологій та дизайну, 2017. https://er.knutd.edu.ua/handle/123456789/8396.
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Raghunathan, Anand. "Electrochemical impedance spectroscopy as a method of predict delamination of coated steel in cathodic disbondment tests." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43449.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1997.Vita.
Includes bibliographical references (leaves 66-67).
by Anand Raghunathan.
M.S.
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Kwiecien, Monika [Verfasser], Dirk Uwe [Akademischer Betreuer] Sauer, and Julia [Akademischer Betreuer] Kowal. "Electrochemical impedance spectroscopy on lead-acid cells during aging / Monika Kwiecien ; Dirk Uwe Sauer, Julia Kowal." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1211960137/34.
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