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Guldiken, Rasim Oytun. "Dual-electrode capacitive micromachined ultrasonic transducers for medical ultrasound applications." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31806.
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Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Degertekin, F. Levent; Committee Member: Benkeser, Paul; Committee Member: Berhelot, Yves; Committee Member: Brand, Oliver; Committee Member: Hesketh, Peter. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Ge, Kangkang. "New insights on charge storage mechanism in carbon-based capacitive electrode." Electronic Thesis or Diss., Université de Toulouse (2023-....), 2024. http://www.theses.fr/2024TLSES094.
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La compréhension de la formation et de la charge de la double couche électrique (EDL) des matériaux d'électrodes capacitives est cruciale pour développer les systèmes de stockage électrochimique de l'énergie de forte puissance, y compris en recharge. Cependant, les études expérimentales de la cinétique de charge des électrodes de carbone poreux, matériaux de choix pour les électrodes de supercondensateurs, posent d'importants défis en raison de la dynamique rapide des ions. Ce sont ces défis que nous proposons de relever dans ce travail. Dans un premier temps, nous nous sommes concentrés sur des carbones poreux de type CDC, c'est-à-dire des carbones dérivés de carbures (CDCs), et les avons caractérisés dans des électrolytes aqueux de différentes concentrations. En utilisant une micro-électrode à cavité, nous avons pu observer la déplétion de l'électrolyte lors de polarisations sous fortes surtensions, et avons analysé systématiquement son impact sur la cinétique de charge. Les résultats ont montré qu'une faible concentration d'électrolyte (10-3 M), une surtension élevée (> 200 mV) et une petite taille de pores de carbone (0,6 nm) exacerbent les gradients de concentration dans l'électrolyte, entraînant un transport ionique retardé. Dans un deuxième temps, nous avons étudié le mécanisme de stockage de charge dans un matériau de type oxyde de graphène réduit (rGO), toujours dans des électrolytes aqueux neutres. Les résultats de caractérisations électrochimiques operando par microbalance à quartz (EQCM) ont dépeint un mécanisme d'adsorption cationique en deux étapes : une adsorption de cations hydratés à faible surtension cathodique, suivie d'un mécanisme de déshydratation cationique pour des surtensions plus élevées (>200 mV). Notablement, une augmentation significative de la capacitance a été observée en raison de la déshydratation des cations, corrélée à une augmentation des interactions cation-rGO provenant de la charge de surface négative (potentiel zêta) du rGO. Ces résultats soulignent le rôle critique des interactions ion-électrode et de la désolvatation des cations dans les mécanismes de stockage de charge. Dans la dernière partie de cette thèse, nous avons caractérisé des matériaux de type réseaux métallo-organiques (MOFs) conducteurs lamellaires comme matériaux d'électrode. Des mesures par EQCM ont montré que le mécanisme de stockage de la charge dans ces MOFs en électrolyte non aqueux est dominé par l'adsorption des cations. Lorsque des cations de petites tailles sont utilisés (type tetraethylammonium), la capacité s'en trouve augmentée, tandis que l'utilisation de cations plus volumineux (tetrabutyl, hexyl) conduisent à une saturation des pores des électrodes MOF, entraînant une dynamique de charge plus lente avec une hystérésis, entraînant un déplacement important des molécules de solvant. Les résultats de cette thèse ont permis de développer notre compréhension de du transport et de l'adsorption ionique dans les milieux confinés, et du rôle de la dynamique des solvants, posant les bases pour concevoir des matériaux optimisés pour le stockage de l'énergie capacitiveUnderstanding the formation and structure of the electrical double layer (EDL) in state-of-the-art capacitive electrode materials is crucial for preparing the next-generation of fast charging and high-power energy storage systems. However, experimental investigations of the charging kinetics of porous carbon electrodes, the materials of choice for electrochemical capacitors, pose significant challenges due to rapid ion dynamics; this is the challenge we want to address in this work. This thesis starts with a focus on carbide-derived porous carbon (CDC), employing chronoamperometry in electrolytes of varying concentrations. Using a cavity micro-electrode setup, we were able to observe electrolyte depletion and we systematically analyzed its impacts on charging the kinetics. Results indicated that for low electrolyte concentration (10-3 M), high overpotential (> 200 mV), and small carbon pore size (0.6 nm) exacerbated electrolyte depletion, slowing down ion transportation. Then, we further investigated the charge storage mechanism in reduced graphene oxide (rGO) electrodes in near-neutral aqueous electrolytes. Operando EQCM results depicted a two-step cation adsorption mechanism with i) initial hydrated cation adsorption at low overpotential followed by cation dehydration for higher overvoltage(>200 mV). Notably, a significant increase in capacitance was observed due to cation dehydration, with the degree of enhancement correlating with non-electrostatic cation-rGO interactions due the negative charge of the rGO surface (zeta potential). These findings underscore the critical role of ion-electrode interactions and cation desolvation in modulating the charge storage mechanisms and capacitance. In a last part, we used conductive layered metal-organic frameworks (MOFs) as electrode materials. These MOFs revealed a cation-dominated charge storage mechanism in non-aqueous electrolytes via EQCM measurements. The use of small size cations (tetraethylammonium) resulted in improved capacity, while larger cations (butyl, hexyl ammonium) saturated MOF electrode pores, leading to asymmetric and sluggish charging dynamics, forcing solvent molecules to participate in the charge storage mechanism under nanopore confinement. The discoveries of this thesis significantly advance our understanding of ion electrosorption, ion transportation, and the role of solvent dynamics in confined pores, thus guiding the design of materials with improved performance for capacitive energy storage devices
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Dehkhoda, Amir Mehdi. "Development and characterization of activated biochar as electrode material for capacitive deionization." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57838.
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Biochar, a by-product of biomass pyrolysis, was investigated as a carbon-based electrode material for a water treatment method based on electrostatic adsorption/desorption of ions in electric double layers (EDLs) formed on the charged electrodes (capacitive deionization, CDI). Surface area, porous structure, and functional groups of biochar were developed, and corresponding effects on EDL capacitive performance were studied. A novel method was explored to tailor the micro- and meso-porous structures of activated biochar by exploiting the interaction between pre-carbonization drying conditions and carbonization temperature (475–1000 C) in a thermo-chemical process (KOH chemical activation). The mechanism of porosity development was investigated; results suggest that the conversion of KOH to K₂CO₃ under different drying conditions has a major role in tailoring the structure. The resultant surface area, micro- and meso-pore volumes were: 488–2670 m² g-¹, 0.04–0.72 cm³ g-¹, and 0.05–1.70 cm³ g-¹, respectively. Tailored biochar samples were investigated using physico-chemical surface characterization and electrochemical methods. For electrochemical testing, activated biochar was sprayed onto Ni mesh current collectors using Nafion® as binder. The majorly microporous activated biochar showed promising capacitances between 220 and 245 F g-¹ when 0.1 mol L-¹ NaCl/NaOH was used as the electrolyte. Addition of mesoporous structure resulted in significantly reduced electrode resistance (up to 80%) and improved capacitive behaviour due to enhanced ion transport within the pores.
CDI of NaCl and ZnCl₂ solutions was investigated in a batch-mode unit through the use of tailored biochar electrodes. For NaCl removal, all samples showed promising capacity (up to 5.13 mg NaCl g-¹) and durability through four consecutive cycles. In contrast, in the case of ZnCl₂, the microporous sample showed a considerable drop in removal capacity (>75%) from cycle 1 to 4, whereas the combined micro- and mesoporous sample exhibited relatively small electrosorption capacity. Interestingly, the sample with mostly mesoporous structure has shown the highest removal capacity (1.15 mg ZnCl₂ g-¹) and durability for Zn²⁺ removal. These results emphasize the importance of tailoring the porous structure of biochar as a function of the specific size of adsorbate ions to improve the CDI performance.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
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Hamer, Tyler Thomas. "Electrode arrays, test fixture, and system concept for high-bandwidth capacitive imaging." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108921.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 147-151).
Spot defects are a leading source of failure in the fabrication of integrated circuits (ICs). Thus, the IC industry inspects for defects at multiple stages of IC fabrication, especially the fabrication of IC photomasks. However, existing non-invasive imaging methods cannot image a modern photomask in a reasonable time-frame. Electroquasistatic (EQS) sensors are arrays of electrode pairs that capacitively couple to targets they sweep over. Utilizing high measurement frequencies and a number of parallel scanning electrode pairs, EQS sensors have been suggested as a potential high speed alternative for defect detection in IC fabrication. This thesis continues the investigation into EQS sensors for high speed imaging by exploring EQS sensors driven with high excitation frequencies. We develop electrode arrays that can be driven with high excitation frequencies and construct high frequency EQS sensors by attaching them to high frequency drive electronics. We also fabricate a test fixture for positioning these sensors relative to and sweeping them across targets on a conductive base. As the sensors sweep across targets, their impedance is measured from 1 - 500 MHz using an impedance analyzer and is later converted into the capacitance between the sensor's electrode array and the target. Capacitance changes are produced by a variable air gap and by a dielectric step, confirming these sensors can detect changes in a target's geometric and material properties with high excitation frequencies. Finally, we present concepts for a high speed measurement system which utilizes these sensors.
by Tyler Thomas Hamer.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Rommerskirchen, Alexandra Klara Elisabeth [Verfasser], Matthias [Akademischer Betreuer] Wessling, and Matthias [Akademischer Betreuer] Franzreb. "Continuous flow-electrode capacitive deionization / Alexandra Klara Elisabeth Rommerskirchen ; Matthias Wessling, Matthias Franzreb." Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1231911719/34.
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King, Harrison Raymond. "Electrode Geometry Effects in an Electrothermal Plasma Microthruster." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1899.
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Nanosatellites, such as Cubesats, are a rapidly growing sector of the space industry. Their popularity stems from their low development cost, short development cycle, and the widespread availability of COTS subsystems. Budget-conscious spacecraft designers are working to expand the range of missions that can be accomplished with nanosatellites, and a key area of development fueling this expansion is the creation of micropropulsion systems. One such system, originally developed at the Australian National University (ANU), is an electrothermal plasma thruster known as Pocket Rocket (PR). This device heats neutral propellant gas by exposing it to a Capacitively Coupled Plasma (CCP), then expels the heated gas to produce thrust. Significant work has gone towards understanding how PR creates and sustains a plasma and how this plasma heats the neutral gas. However, no research has been published on varying in the device's geometry. This thesis aims to observe how the size of the RF electrode affects PR operation, and to determine if it can be adjusted to improve performance. To this end, a thruster has been built which allows the geometry of the RF electrode to be easily varied. Measurements of the plasma density at the exit of this thruster with different sizes of electrode were then used to validate a Computational Fluid Dynamics (CFD) model capable of approximately reproducing experimental measurements from both this study and from the ANU team. From this CFD, the number of argon ions in the thruster was found for each geometry, since collisions between argon ions and neutrals are primarily responsible for the heating observed in the thruster. A geometry using a 10.5 mm electrode was observed to produce a 23% increase in the quantity of ions produced compared to the baseline 5 mm electrode size, and a 3.5 mm electrode appears to produce 88% more ions.
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Wu, Nan. "Capacitive reverse electrodialysis cells for osmotic energy harvesting : Toward real brines and power enhancement." Electronic Thesis or Diss., Université Paris sciences et lettres, 2024. http://www.theses.fr/2024UPSLS019.
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Face aux problèmes de réchauffement climatique, trouver des ressources énergétiques propres et durables pour remplacer les combustibles fossiles conventionnels est d'une importance capitale. L'énergie osmotique demeure une ressource énergétique inexploitée avec un potentiel significatif. Dans ce travail, nous parvenons à une conversion efficace de l'énergie osmotique en électricité grâce à un processus de mélange bien contrôlé utilisant un système d'électrodialyse inverse capacitif (CRED). Il est démontré qu'un écart substantiel de densité de puissance existe entre le système CRED et la valeur maximale théorique, principalement en raison de l'efficacité de conversion faible du flux ionique-électronique dans les électrodes capacitifs. Pour pallier cette limitation, nous proposons la stratégie de boosting pour optimiser le régime de fonctionnement du système CRED. Des expériences et des modélisations confirment une amélioration de la performance énergétique du système CRED. Pour avancer vers des applications réelles, nous évaluons les performances du système CRED sous des solutions composées de mélanges ioniques complexes. Contrairement à la chute significative de la densité de puissance observée dans les systèmes RED classiques, le système CRED ne présente qu'une légère diminution lorsqu'il est soumis à des solutions avec un mélange d'ions divalents. Ce phénomène est attribué au renversement périodique des solutions dans les compartiments, qui atténue l'effet d'empoisonnement de la membrane. Ce résultat est ensuite validé par des tests à long terme avec des solutions réelles. Pour généraliser le système CRED dans un spectre plus large, nous proposons une cellule de gradient de pH avec des électrodes de MnO2 à pseudo-capacité. Elle utilise l'énergie osmotique établie dans un processus de capture de CO2 basé sur un électrolyte et vise à réduire le coût global du processus de capture de carbone. La cellule de gradient de pH présente une augmentation inattendue de la densité de puissance sous la stratégie de boosting. Cela est dû à la contribution de tension supplémentaire des électrodes en raison du changement de couverture fractionnelle lié aux réactions d'oxydoréduction. Cependant, elle reste dans le cadre du régime capacitif et est bien décrite par une modélisation CRED adaptéeGiven the global warming issues, finding clean and sustainable energy resources to replace conventional fossil fuels is of paramount importance. Osmotic energy remains an untapped energy resource with significant potential. In this work, we achieve efficient conversion of osmotic energy into electricity through a well-controlled mixing process using a capacitive reverse electrodialysis (CRED) system. It is demonstrated that a substantial power density gap exists between the CRED system and the theoretical maximum value, primarily due to the low ionic-electronic flux conversion efficiency in capacitive electrodes. To address this limitation, we propose the boosting strategy to optimize the working regime of the CRED system. Both experiments and modeling confirm an enhanced energy performance of the CRED system. To advance towards real-world applications, we assess the performance of the CRED system under solutions composed of complex ion mixing. In contrast to the significant power density drop observed in classic RED systems, the CRED system exhibits only a minor decrease when subjected to solutions with divalent ion mixing. This phenomenon is attributed to the periodic water chamber reversal, which mitigates the membrane poisoning effect. This result is further validated through long-term testing with real-world solutions. To generalize the CRED system into a broader spectrum, we propose a pH gradient cell with MnO2 electrodes of pseudo capacitance. It uses the osmotic energy established within an electrolyte based CO2 capturing process and aims to reduce the overall cost of carbon capturing process. The pH gradient cell presents unexpected power density increase under boosting strategy. This is due to the additional electrode voltage contribution due to fractional coverage change related to redox reactions. However, it stays in the framework of capacitive regime and remains well described by an adapted CRED modeling
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Smith, Nafeesah. "Development of capacitive deionisation electrodes: optimization of fabrication methods and composition." University of the Western Cape, 2020. http://hdl.handle.net/11394/7710.
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>Magister Scientiae - MScMembrane Capacitive Deionisation (MCDI) is a technology used to desalinate water where a potential is applied to an electrode made of carbonaceous materials resulting in ion adsorption. Processes and materials for the production of electrodes to be applied in Membrane Capacitive Deionisation processes were investigated. The optimal electrode composition and synthesis approached was determined through analysis of the salt removal capacity and the rate at which the electrodes absorb and desorb ions. To determine the conductivity of these electrodes, the four point probe method was used. Contact angle measurements were performed to determine the hydrophilic nature of the electrodes. N2 adsorption was done in order to determine the surface area of carbonaceous materials as well as electrodes fabricated in this study. Scanning electron microscopy was utilised to investigate the morphology. Electrodes were produced with a range of research variables; (i) three different methods; slurry infiltration by calendaring, infiltration ink dropwise and spray-coating, (ii) electrodes with two different active material/binder ratios and a constant conductive additive ratio were produced in order to find the optimum, (iii) two different commercially available activated carbon materials were used in this study (YP50F and YP80F), (iv) two different commercially available electrode substrates were utilised (JNT45 and SGDL), (v) different slurry mixing times were investigated showing the importance of mixing, and (vi) samples were treated at three different temperatures to establish the optimal drying conditions. Through optimization of the various parameters, the maximum adsorption capacity of the electrode was incrementally increased by 36 %, from 16 mg·g-1 at the start of the thesis to 25 mg·g-1 at the end of the study.
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Oh, Yoontaek. "Effects of Electrochemical Reactions on Sustainable Power Generation from Salinity Gradients using Capacitive Reverse Electrodialysis." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin161375277977973.
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Brahmi, Youcef. "Nouveau concept pour améliorer l'extraction d'énergie bleue par des couches capacitives." Electronic Thesis or Diss., Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLS099.
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Pour lutter efficacement contre le réchauffement climatique, il est nécessaire d'augmenter la production d'énergies propres et renouvelables. L'énergie solaire, l'énergie éolienne, l’hydroélectrique et l'énergie marémotrice sont des technologies matures. L'augmentation de la production d'énergie renouvelable nécessite l'utilisation de sources d'énergie peu ou pas exploitées, comme l’énergie bleue. Cette forme d’énergie correspond à l’énergie générée lors du mélange d'eau douce et d'eau salée. Cependant, les procédés actuels d’extraction d'énergie à partir de gradients de sel restent inefficaces, principalement parce que les membranes sélectives commerciales sont peu performantes comme le cas de l’électrodialyse inverse ou l’Osmose à pression retardée qui ne sont toujours pas économiquement rentable. Les espoirs de membranes non sélectives dotées de canaux nanofluidiques chargés qui ont été conçus pour réduire la résistance interne de la cellule semblent être vains. Une nouvelle solution est proposée qui consiste à augmenter le potentiel de circuit ouvert de la membrane en y attachant des électrodes capacitives avec des groupements fonctionnels chargés négativement qui permet l’adsorption des ions, essentiellement les ions positifs. Une telle configuration nous permet de doubler le potentiel du circuit ouvert de la cellule sans trop modifier la résistance ohmique globale et donc de multiplier par 4 la puissance brute potentiellement récupérable.Après une étude approfondie réalisée dans le but de caractériser le procédé et une optimisation de la consommation énergique due aux pertes de charge, nous présentons un dispositif de quelques centimètres carrés avec une seule membrane récoltant une densité de puissance nette de 2 Watts par mètre carré de membrane (densité de puissance potentielle nette estimée à 5.4 W.m-2, ce qui rend le système économiquement viableTo effectively combat global warming, it is necessary to increase the production of clean, renewable energy. Solar, wind power, hydroelectric dams and tidal power plants are mature technologies. Increasing the production of this energy requires the use of energy sources that are little or not exploited like the blue energy which is the a less-known source with enormous potential that can be generated directly from the mixing of fresh and salt water. However, current processes for energy harvesting from salt gradients remain inefficient mainly because commercial selective membranes have poor performance as in the reverse electrodialysis or in the pressure retarded osmosis and still not economically viable. Hopes for nonselective membranes with charged nanofluidic channels which have been designed to reduce the internal resistance of the cell seem to be in vain. Here we present a novel solution that involves increasing the open circuit potential of the membrane by attaching tailored capacitive layers with negatively charged functional groups on the surface that adsorb ions, mainly the positive ones. Such a configuration allows us to double the potential of the open circuit of the cell without modifying too much the global ohmic resistance and thus to multiply by 4 the potentially recoverable power.After a thorough study carried out in order to characterize the process and an optimization of the energy consumption caused by the hydraulic pressure drop, we display a device of a few squared centimeters with only one membrane harvesting a net power density of 2 Watts per square meter of the membrane (estimated net potential power density 5.4 W.m−2 ) which makes the system economically viable
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CAMPIONE, Antonino. "Electrodialysis modelling for low energy desalination." Doctoral thesis, Università degli Studi di Palermo, 2020. http://hdl.handle.net/10447/395212.
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Mutha, Heena K. "Carbon nanotube electrodes for capacitive deionization." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85478.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 80-85).
Capacitive deionization (CDI) is a desalination method where voltage is applied across high surface area carbon, adsorbing salt ions and removing them from the water stream. CDI has the potential to be more efficient than existing desalination technologies for brackish water, and more portable due to its low power requirements. In order to optimize salt adsorption in CDI, we need a better understanding of salt adsorption and the electrode properties involved in ion removal. Current materials are highly porous, with tortuous geometeries, overlapping double layers, and subnanometer diameters. In this work, we design ordered-geometry, vertically-aligned carbon nanotube electrodes. The CNTs in this study have 2-3 walls, inner diameter of 5.6 nm and outer diameter of 7.7 nm. The capacitance and charging dynamics were investigated using three-electrode cell testing in sodium chloride solution. We found that the material capacitance was 20-40 F/g and the charging time varies linearly with CNT height. The data was matched with the Gouy-Chapman-Stern model indicating that porous effects were negligible. Charging rates of CNTs compared to microporous activated carbon fiber, show that CNTs are more efficient at charging by weight. However, densification and surface functionalization will be necessary to enhance CNT performance by planar area. Future work will involve investigating electrodes in a flow-through cell to use salt adsorption data to determine the influence on electrode thickness on salt adsorption in channel flow.
by Heena K. Mutha.
S.M.
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Gonçalves, José Miguel Pino. "Laser-induced graphene electrodes for capacitive deionization." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/23658.
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Mestrado em Engenharia FísicaEste trabalho tem como objetivo a síntese de elétrodos à base de grafeno induzido por laser (LIG) para serem explorados pela primeira vez num sistema de desionização capacitiva (CDI) para remoção de iões da água. O trabalho foi desenvolvido em colaboração com a Bosch Termotecnologia S.A. Aveiro no âmbito de um projeto em Co-promoção. A síntese dos elétrodos de LIG foi realizada utilizando um polímero comercial, Kapton, sobre o qual se fez incidir um feixe laser de CO2. O trabalho focou-se no estudo da influência de vários parâmetros de processamento a laser para a otimização dos elétrodos. A caracterização do material foi feita usando as técnicas de microscopia eletrónica de varrimento (SEM), medição da superfície específica (BET), espectroscopia de Raman, medidas de resistência elétrica pela técnica de Van der Pauw e testes de estabilidade em fluxo de água. Paralelamente a este estudo foram também caracterizados quatro elétrodos comerciais. Para a caracterização dos elétrodos foi desenvolvido um sistema que permite avaliar o comportamento no processo de desionização capacitiva nos modos de corrente (CC) e tensão (CV) constantes. O desempenho do material desenvolvido foi avaliado através da análise de ciclos de carga/descarga, e comparado com o comportamento dos dois melhores elétrodos comerciais. Os testes realizados permitiram observar a operação de CDI em todos os elétrodos, embora com diferentes níveis de desempenho. Os elétrodos de LIG revelaram uma curva de carga/descarga tipicamente capacitiva, não obstante o seu desempenho ser inferior aos elétrodos comerciais. Os resultados obtidos neste estudo exploratório, aliados ao método de produção a laser de baixo custo, põem em evidência o potencial destes elétrodos para uma aplicação CDI industrial requerendo, no entanto, a sua otimização.
The goal of this work is the synthesis of electrodes based on laser induced graphene (LIG) to be explored for the first time in a capacitive deionization (CDI) system for ion removal from water. The work was developed in cooperation with Bosch Thermotechnology S.A Aveiro in the ambit of a project in Co-promotion. The LIG’s electrodes synthesis was done using a commercial polymer, Kapton, in which a CO2 laser beam was irradiated. The work focused on the study of the influence of various laser processing parameters for the optimization of the electrodes. The characterization of the material was done using techniques such as scanning electron microscopy (SEM), specific surface adsorption measurements (BET), Raman spectroscopy, Van der Pauw electrical resistance sheet measurements and stability tests in the presence of a water flow. In parallel with this study, four commercial electrodes were also characterized. For the characterization of the electrodes was developed a system which allowed to evaluate their behaviour in the process of capacitive deionization in the operation modes of constant current (CC) and voltage (CV). The performance of the developed material was assessed via the analysis of the charge/discharge cycles, and comparing them to the behaviour of two other commercial electrodes. The test executed showed the CDI operation in all of the electrodes, although with different levels of performance. The LIG electrodes revealed a charge/discharge curve typically capacitive, regardless of showing inferior performance results compared to the commercial electrodes. The results obtained in this exploratory work, allied to the LIG’s electrode production at low cost, evidences the potential of these electrodes for an industrial CDI application requiring, however, further optimization.
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Nkuna, Shonny. "Development of capacitive deionisation electrodes: optimization of fabrication methods and composition." University of the Western Cape, 2017. http://hdl.handle.net/11394/5980.
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Magister Scientiae - MSc (Chemistry)The objective of this research was to optimize the fabrication methods for and compositions of electrodes for the Membrane Capacitive Deionisation (MCDI) system. Two electrode fabrication methods were developed, namely a spray coating- and a casting method. The compositions of the electrodes were varied yielding a total of 14 different electrode in an attempt to optimize the fabrication methods and compositions of the electrodes. Three activated carbons were utilized in this study, TOB, YP50F and YP80F, these activated carbons have different surface areas and porosity therefore were affected different by the materials added in the ink. Carbon black and carbon nanotubes were used as conductivity additives to enhance the conductivity of the electrodes. Lastly a polymer binder was added to increase the mechanical integrity of the electrode, this polymer was typically PVDF. For some electrodes, PVDF was replaced with ion exchange polymers in an attempt to provide ion conductive properties to the electrodes. To establish the charge capacity of the electrodes Cyclic Voltammetry was used, BET analysis evaluated the surface area and porosity of the raw materials and fabricated electrodes. Scanning Electron Microscopy was used to verify surface morphology and uniformity. Ion adsorption capacity measurements were performed using a specially designed MCDI cell. The objectives of this study were achieved, the fabrication methods were optimized with the casting method producing superior electrodes. Apart from fulfilling the research objectives, the current research work generated significant scientific value by revealing how the production method impacts the electrode's surface area and electrode adsorption capacity.
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Yazicioglu, Refet Firat. "Surface Micromachined Capacitive Accelerometers Using Mems Technology." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1093475/index.pdf.
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Micromachined accelerometers have found large attention in recent years due
to their low-cost and small size. There are extensive studies with different
approaches to implement accelerometers with increased performance for a number of
military and industrial applications, such as guidance control of missiles, active
suspension control in automobiles, and various consumer electronics devices. This
thesis reports the development of various capacitive micromachined accelerometers
and various integrated CMOS readout circuits that can be hybrid-connected to
accelerometers to implement low-cost accelerometer systems.
Various micromachined accelerometer prototypes are designed and optimized
with the finite element (FEM) simulation program, COVENTORWARE, considering
a simple 3-mask surface micromachining process, where electroplated nickel is used
as the structural layer. There are 8 different accelerometer prototypes with a total of
65 different structures that are fabricated and tested. These accelerometer structures occupy areas ranging from 0.2 mm2 to 0.9 mm2 and provide sensitivities in the range
of 1-69 fF/g.
Various capacitive readout circuits for micromachined accelerometers are
designed and fabricated using the AMS 0.8 µm n-well CMOS process, including a single-ended and a fully-differential switched-capacitor readout circuits that can operate in both open-loop and close-loop. Using the same process, a buffer circuit with 2.26fF input capacitance is also implemented to be used with micromachined gyroscopes. A single-ended readout circuit is hybrid connected to a fabricated accelerometer to implement an open-loop accelerometer system, which occupies an area less than 1 cm2 and weighs less than 5 gr. The system operation is verified with various tests, which show that the system has a voltage sensitivity of 15.7 mV/g, a nonlinearity of 0.29 %, a noise floor of 487 Hz µ
g , and a bias instability of 13.9 mg, while dissipating less than 20 mW power from a 5 V supply. The system presented in this research is the first accelerometer system developed in Turkey, and this research is a part of the study to implement a national inertial measurement unit composed of low-cost micromachined accelerometers and gyroscopes.
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Abdel-Fattah, E., and H. Sugai. "Electron heating mode transition observed in a very high frequency capacitive discharge." American Institute of Physics, 2003. http://hdl.handle.net/2237/7247.
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Sadat, David. "Simulation of a Capacitive Micromachined Ultrasonic Transducer with a Parylene Membrane and Graphene Electrodes." Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5476.
Full textAbstract:
Medical ultrasound technology accounts for over half of all imaging tests performed worldwide. In comparison to other methods, ultrasonic imaging is more portable and lower cost, and is becoming more accessible to remote regions where traditionally no medical imaging can be done. However, conventional ultrasonic imaging systems still rely on expensive PZT-based ultrasound probes that limit broader applications. In addition, the resolution of PZT based transducers is low due to the limitation in hand-fabrication methods of the piezoelectric ceramics. Capacitive Micromachined Ultrasonic Transducers (CMUTs) appears as an alternative to the piezoelectric (PZT) ceramic based transducer for ultrasound medical imaging. CMUTs show better ultrasound transducer design for batch fabrication, higher axial resolution of images, lower fabrication costs of the elements, ease of fabricating large arrays of cells using MEMS fabrication, and the extremely important potential to monolithically integrate the 2D transducer arrays directly with IC circuits for real-time 3D imaging. Currently most efforts on CMUTs are silicon based. Problems with current silicon-based CMUT designs include low pressure transmission and high-temperature fabrication processes. The pressure output from the silicon based CMUTs cells during transmission are too low when compared to commercially available PZT transducers, resulting in relatively blurry ultrasound images. The fabrication of the silicon-based cells, although easier than PZT transducers, still suffers from inevitable high temperature process and require specialized and expensive equipment. Manufacturing at an elevated temperature hinders the capability of fabricating front end analog processing IC circuits, thus it is difficult to achieve true 3D/4D imaging. Therefore novel low temperature fabrication with a low cost nature is needed. A polymer (Parylene) based CMUTs transducer has been investigated recently at UCF and aims to overcome limitations posted from the silicon based counterparts. This thesis describes the numerical simulation work and proposed fabrication steps of the Parylene based CMUT. The issue of transducer cost and pressure transmission is addressed by proposing the use of low cost and low temperature Chemical Vapor Deposition (CVD) fabrication of Parylene-C as the structural membrane plus graphene for the membrane electrodes. This study focuses mainly on comparing traditional silicon-based CMUT designs against the Parylene-C/Graphene CMUT based transducer, by using MEMS modules in COMSOL. For a fair comparison, single CMUT cells are modeled and held at a constant diameter and the similar operational frequency at the structural center. The numerical CMUT model is characterized for: collapse voltage, membrane deflection profile, center frequency, peak output pressure transmission over the membrane surface, and the sensitivity to the change in electrode surface charge. This study took the unique approaches in defining sensitivity of the CMUT by calculating the membrane response and the change in the electrode surface charge due to an incoming pressure wave. Optimal design has been achieved based on the simulation results. In comparison to silicon based CMUTs, the Parylene/Graphene based CMUT transducer produces 55% more in volume displacement and more than 35% in pressure output. The thesis has also laid out the detailed fabrication processes of the Parylene/Graphene based CMUT transducers. Parylene/Graphene based ultrasonic transducers can find wide applications in both medical imaging and Non destructive evaluation (NDE).ID: 031001393; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Title from PDF title page (viewed May 28, 2013).; Thesis (M.S.M.E.)--University of Central Florida, 2012.; Includes bibliographical references (p. 105-113).
M.S.M.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering; Miniature Engineering Systems
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Caudill, Landon S. "PRESSURE-DRIVEN STABILIZATION OF CAPACITIVE DEIONIZATION." UKnowledge, 2018. https://uknowledge.uky.edu/me_etds/113.
Full textAbstract:
The effects of system pressure on the performance stability of flow-through capacitive deionization (CDI) cells was investigated. Initial data showed that the highly porous carbon electrodes possessed air/oxygen in the micropores, and the increased system pressure boosts the gases solubility in saline solution and carries them out of the cell in the effluent. Upon applying a potential difference to the electrodes, capacitive-based ion adsorption occurs in competition with faradaic reactions that consume oxygen. Through the addition of backpressure, the rate of degradation decreases, allowing the cell to maintain its salt adsorption capacity (SAC) longer. The removal of oxygen from the pore space of the electrodes makes it no longer immediately accessible to faradaic reactions, thus hindering the rate of reactions and giving the competing ion adsorption an advantage that is progressively seen throughout the life of the cell. A quick calculation shows that the energy penalty to power the pump is fairly insignificant, especially in comparison to the cost of replacing the electrodes in the cell. Thus, operating at elevated pressures is shown to be cost effective for continuous operation through the reduced electrode replenishment costs.
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Newill, Paul Anthony. "Imaging of soil moisture in the root zone using capacitively coupled electrodes." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/imaging-of-soil-moisture-in-the-root-zone-using-capacitively-coupled-electrodes(24dbb858-3a0f-4fd7-8956-0070d2e47283).html.
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This research explores the use of insulated electrodes to determine electrical impedance distributions within soil cores. It is used to infer the effect of roots on soil moisture which, in turn, can provide knowledge relating to crop breeding programmes. These programmes are becoming increasingly important in order to address challenges posed by global population growth and climate change. Direct contact electrical impedance measurements in soil are frequently used but these are vulnerable to electrochemical effects and corrosion. Insulated electrodes are used in the present work to overcome these difficulties and a modified electrode model has been proposed. Measurements require the acquisition of spectroscopic complex impedance and extraction of the real impedance to infer soil moisture content. Calculated and simulated impedance, from the analytical solution and an FEM model respectively, were compared to measurements performed within a parallel-plate test cell containing saline solutions. The effects of moisture, compaction and temperature on soil impedance measurements have been explored. Finally, two growth trials using maize plants and control vessels were performed to create 2D images of impedance distributions, from which moisture placement was inferred. Results show that for saline electrolytes, the insulated electrode method was capable of estimating the impedance of tap water to within 10% of calibrated laboratory equipment. For soil based measurements, the variation of moisture content from 5-30% resulted in a 1000-fold decrease in impedance. The change was most significant in drier soils. For compaction based testing, at 5% moisture content soil impedance decreased by approximately 40%, compared to only 20% in the wettest samples. Temperature testing revealed an impedance change of approximately 2%/ °C, in agreement with earlier reports. Plant growth trials revealed increases in electrical impedance due to soil drying from an initial value of 1-2kΩ when the soil was wetted to field capacity, to as much as 60kΩ when dry. Only small changes were evident in the control vessels. It was also found that areas exposed to potential evaporation, such as at the surface closest to the plant stem, suffered significant losses in moisture content, reaching as high as 15-20kΩ. This research utilises a measurement technique which has not previously been used to measure soil impedance to infer moisture content. The research also found that the scaling of a thin layer within an FEM model can significantly reduce computational demands, while retaining accuracy, and allow more complex FEM simulations to be performed on a less powerful computer.
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Rjagopal, Ramasubramaniam. "Correlated single electron transport in capacitively coupled tunnel junction arrays /." view abstract or download file of text, 1999. http://wwwlib.umi.com/cr/uoregon/fullcit?p9957570.
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Thesis (Ph. D.)--University of Oregon, 1999.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 95-97). Also available for download via the World Wide Web; free to University of Oregon users. Address:http://wwwlib.umi.com/cr/uoregon/fullcit?p9957570.
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Nazari, Asl Sara [Verfasser], Meinhard [Akademischer Betreuer] Schilling, and Peter [Akademischer Betreuer] Werning. "Development of a non-contact EEG hat using textile capacitive electrodes / Sara Nazari Asl ; Meinhard Schilling, Peter Werning." Braunschweig : Technische Universität Braunschweig, 2020. http://d-nb.info/1206334347/34.
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Costa, i. Bricha Elm. "Computer simulation of a capacitively coupled GEC cell." Thesis, Queen's University Belfast, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368881.
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Abrahams, Dhielnawaaz. "Charge Transfer and Capacitive Properties of Polyaniline/ Polyamide Thin Films." University of the Western Cape, 2018. http://hdl.handle.net/11394/6361.
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Magister Scientiae - MSc (Chemistry)Blending polymers together offers researchers the ability to create novel materials that have a combination of desired properties of the individual polymers for a variety of functions as well as improving specific properties. The behaviour of the resulting blended polymer or blend is determined by the interactions between the two polymers. The resultant synergy from blending an intrinsically conducting polymer like polyaniline (PANI), is that it possesses the electrical, electronic, magnetic and optical properties of a metal while retaining the poor mechanical properties, solubility and processibility commonly associated with a conventional polymer. Aromatic polyamic acid has outstanding thermal, mechanical, electrical, and solvent resistance properties that can overcome the poor mechanical properties and instability of the conventional conducting polymers, such as polyaniline.
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Engstrom, Allison Michelle. "Vanadium Oxide Electrochemical Capacitors| An Investigation into Aqueous Capacitive Degradation, Alternate Electrolyte-Solvent Systems, Whole Cell Performance and Graphene Oxide Composite Electrodes." Thesis, University of California, Berkeley, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3616666.
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Vanadium oxide has emerged as a potential electrochemical capacitor material due to its attractive pseudocapacitive performance; however, it is known to suffer from capacitive degradation upon sustained cycling. In this work, the electrochemical cycling behavior of anodically electrodeposited vanadium oxide films with various surface treatments in aqueous solutions is investigated at different pH. Quantitative compositional analysis and morphological studies provide additional insight into the mechanism responsible for capacitive degradation. Furthermore, the capacitance and impedance behavior of vanadium oxide electrochemical capacitor electrodes is compared for both aqueous and nonaqueous electrolyte-solvent systems. Alkali metal chloride and bromide electrolytes were studied in aqueous systems, and nonaqueous systems containing alkali metal bromides were studied in polar aprotic propylene carbonate (PC) or dimethyl sulfoxide (DMSO) solvents. The preferred aqueous and nonaqueous systems identified in the half-cell studies were utilized in symmetric vanadium oxide whole-cells. An aqueous system utilizing a 3.0 M NaCl electrolyte at pH 3.0 exhibited an excellent 96% capacitance retention over 3000 cycles at 10 mV s-1. An equivalent system tested at 500 mV s-1 displayed an increase in capacitance over the first several thousands of cycles, and eventually stabilized over 50,000 cycles. Electrodes cycled in nonaqueous 1.0 M LiBr in PC exhibited mostly non-capacitive charge-storage, and electrodes cycled in LiBr-DMSO exhibited a gradual capacitive decay over 10,000 cycles at 500 mV s-1. Morphological and compositional analyses, as well as electrochemical impedance modeling, provide additional insight into the cause of the cycing behavior. Lastly, reduced graphene oxide and vanadium oxide nanowire composites have been successfully synthesized using electrophoretic deposition for electrochemical capacitor electrodes. The composite material was found to perform with a higher capacitance than electrodes containing only vanadium oxide nanowires by a factor of 4.0 at 10 mV s-1 and 7.5 at 500 mV s-1. The thermally reduced composite material was examined in both symmetric and asymmetric whole cell electrochemical capacitor devices, and although the asymmetric cell achieved both higher energy and power density, the symmetric cell retained a higher capacitance over 50,000 cycles at 200 mV s-1.
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Kloub, Hussam Abdelhamid [Verfasser], and Yiannos [Akademischer Betreuer] Manoli. "High effectiveness micro electro mechanical capacitive transducer for kinetic energy harvesting = Hocheffizienter mikroelektromechanischer kapazitiver Wandler für bewegungsbasiertes Energy Harvesting." Freiburg : Universität, 2011. http://d-nb.info/1123468230/34.
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Brousse, Kevin. "Intégration de micro-supercondensateurs à hautes performances sur puce de silicium et substrats flexibles." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30090/document.
Full textAbstract:
Le développement de l'internet des objets au service des " Smart Cities " requière des sources d'énergie miniaturisées. Ces travaux concernent la préparation de micro- supercondensateurs à hautes performances par voies sèches. Des films minces de carbure de titane ont été déposés sur wafer de silicium par pulvérisation, puis convertis par chloration partielle en films de carbone dérivé de carbure microporeux adhérents. 205 mF.cm-2 / 410 F.cm-3 ont été délivrés en milieu 1M H2SO4, et 170 F.cm-3 dans un mélange de liquide ionique et d'acétonitrile en contrôlant la taille des micropores. Les micro-supercondensateurs préparés sur wafer par cette voie, compatible avec les techniques de microfabrication utilisées dans l'industrie des semi-conducteurs, surpassent les performances des micro-supercondensateurs sur puce rapportées jusqu'alors. Enfin, l'écriture laser d'oxydes commerciaux sur polyimide s'est avérée prometteuse pour la préparation de micro-supercondensateurs flexiblesThe development of the internet of things, serving the concept of Smart Cities, demands miniaturized energy storage devices. Electrochemical double layer capacitors (or so called EDLCs) are a good candidate as they can handle fast charge and discharge over 1,000,000 cycles. This work focuses on the preparation of high performance micro- supercapacitors using non wet processing routes. Titanium carbide (TiC) thin films were first deposited on silicon wafer by non-reactive DC magnetron sputtering. The deposition parameters, such as pressure and temperature, were optimized to prepare dense and thick TiC films. Then, microporous carbide-derived carbon (CDC) films with sub-nanometer pore diameters were obtained by removing the metallic atoms of the TiC films under chlorine atmosphere. Partial chlorination led to strongly adherent TiC-CDC films which could be used as electrode in aqueous electrolyte. Capacitance values of 205 mF.cm-2 / 410 F.cm-3 were delivered in 1M H2SO4, and were stable over 10,000 cycles. In order to increase the energy density of the on-chip electrodes, the pore sizes were increased to accommodate the larger ions of organic electrolytes, by performing chlorination at higher temperatures. The 700°C chlorinated TiC-CDC electrodes delivered up to 72 mF.cm-2 within a 3 V potential window in an ionic liquid / acetonitrile mixture. Another strategy consisted in the grafting of anthraquinone (AQ) molecules, which brought additional faradic contribution to the capacitive current. Electrochemical grafting by pulsed chronoamperometry allowed to double the TiC-CDC capacitance in aqueous electrolyte (1M KOH). On-chip CDC-based micro-supercapacitors were successfully prepared via reactive ion etching/ inductive coupled plasma procedure followed by chlorination. This non-wet processing route is fully compatible with the microfabrication techniques used in the semi-conductor industry, and the as-prepared micro-devices outperforms the current state of art of on-chip micro-supercapacitors. Aside, the preparation of flexible micro-supercapacitors was achieved via direct laser-writing, which provided a facile and scalable engineering with low cost. Ruthenium oxide (RuO2)-based interdigitated electrodes were obtained from laser-writing of a commercial RuO2.xH2O / cellulose acetate mixture spin-coated onto KaptonTM. Capacitance values of ~30 mF.cm-2 were recorded in 1M H2SO4 for the flexible device. This work open the way for the design of high performance micro-devices at a large scale
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Otsuka, Salinas Kenjo. "Evaluación de la deionización capacitiva de NaCl acuoso empleando un electrodo de carbón activado modificado con hexafluorofosfatro de 1-butil-3-metilimidazolio." Master's thesis, Pontificia Universidad Católica del Perú, 2018. http://tesis.pucp.edu.pe/repositorio/handle/123456789/12577.
Full textAbstract:
En el presente trabajo de tesis, se presenta la síntesis, caracterización y aplicación de un
electrodo de carbón activado y carbón activado modificado con el líquido iónico
hexafluorofosfato de 1-butil-3-metilimidazolio en la remoción de cloruro de sodio mediante el
proceso de deionización capacitiva (CDI) en soluciones acuosas salinas preparadas de 200,
500 y 1000 ppm y aplicando potenciales de 0,8; 1,0 y 1,2 V. El desarrollo de la tecnología
de deionización capacitiva (CDI) para la desalinización de soluciones electrolíticas es un
área bastante prometedora, registrándose hasta la fecha múltiples trabajos a escala de
laboratorio e industrial. El proceso de deionización capacitiva (CDI) depende directamente
de la capacitancia eléctrica de los materiales empleado como electrodos, la humectabilidad
de estos, así como el potencial de trabajo aplicado entre los electrodos. Los materiales
carbonosos al ser modificados con líquido iónico presentan un incremento de la
capacitancia eléctrica, gran estabilidad electroquímica, así como una mejora de la
humectabilidad. Ante esto, surge la siguiente interrogante: ¿será posible desarrollar un
electrodo que contribuya a la mejora de la remoción de cloruro de sodio en el campo de la
deionización capacitiva (CDI)?. Mediante voltametría cíclica se calcula la capacitancia
eléctrica del carbón activado modificado y carbón activado; siendo 58,40 F/g y 44,20 F/g,
respectivamente. Mediante la medición del ángulo de contacto se obtiene una mejora de la
humectabilidad de 112,00° para el electrodo sin modificar a 61,90° para el electrodo
modificado. Finalmente, se logra determinar que a una concentración salina de 1240 ppm y
un potencial de 1,0 V se obtiene la mayor capacidad de remoción de 13,79 mg/g.In the present thesis is presented the synthesis, characterization and application of an activated carbon electrode and activated carbon modified with ionic liquid 1-butyl-3- methylimidazolium hexafluorophosphate for the removal of sodium chloride in prepared aqueous saline solutions of 200, 500 and 1000 ppm and applying potentials of 0,8; 1,0 and 1,2 V by means of capacitive deionization process (CDI). The development of capacitive deionization (CDI) technology for the desalination of electrolytic solutions is a quite promising field, with multiple laboratory and industrial scale work being recorded to date. The capacitive deionization process (CDI) directly depends on the electrical capacitance of the materials used as electrodes, wettability, as well as the applied work potential between the electrodes. The carbonaceous materials modified with ionic liquid exhibit an increase in electrical capacitance, great electrochemical stability, as well as an improvement in wettability. Given this, the following question arises: will it be possible to develop an electrode that contributes to the improvement of the removal of sodium chloride in the field of capacitive deionization (CDI)? Through cyclic voltammetry technique, the electrical capacitance of modified activated carbon and activated carbon is calculated as 58,40 F/g and 44,20 F/g, respectively. By measuring the contact angle, an improvement in wettability is obtained from 112,00° for the unmodified electrode to 61,90° for the modified electrode. Finally, it is determined that the highest removal capacity of 13,79 mg/g is obtained at a saline concentration of 1240 ppm and a working potential of 1,0 V.
Tesis
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Hamet, Jean-François. "Etude de bicristaux de silicium par spectroscopie capacitive, influence des traitementsthermiques et des impuretes." Caen, 1989. http://www.theses.fr/1989CAEN2001.
Full textAbstract:
Etude des proprietes electriques des joints de grain par dlts, tscap et egalement par des mesures de recombinaison ebic. L'activite electrique des joints est liee a la presence de precipites a caractere metallique le long des joints
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Trnkócy, Tomáš. "Návrh a realizace testovacího zařízení manipulačního mechanismu vzorku pro elektronový mikroskop." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230625.
Full textAbstract:
Práce se zabývá návrhem a implementací testovacího zařízení pro manipulačnínmechanismus vzorku v elektronovém mikroskopu. Testovací zařízení a jeho software zajištuje meření několika parametrů mechanismu, jejich statistické vyhodnocení a porovnání se specifikací. Cílem je vytvořit komplexní testovací zařízení s jednoduchým uživatelským rozhraním, s požadavkem náhrady stávajícího nemodulárního a nestabilního řešení a jeho rozšíření o testování dalších parametrů.
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Murray, Franck. "Developpement des methodes de spectroscopie capacitive et applications a la caracterisation de defauts d'interface et de volume dans les semiconducteurs." Caen, 1987. http://www.theses.fr/1987CAEN2013.
Full textAbstract:
Conditions d'utilisation de spectrometrie transitoire de niveau profond classique et optique. Cas des etats d'interface isolant-semiconducteur, effet de la densite. Etude des structures mis et mos. Dans le cas de defauts d'irradiaiton par les ions lourds de forte energie dans le silicium, trois pieges a porteurs majoritaires et six pieges a porteurs minoritaires ont ete identifies par spectrometrie transitoire de niveau profond normale et optique
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Lakhdari, Hacène. "Etude par technique spectroscopique de capacite transitoire des defauts a l'interface semiconducteur-isolant." Paris 6, 1988. http://www.theses.fr/1988PA066341.
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Explication du comportement inhabituel de certaines structures mos en dlts (non-saturation du spectre dlts pour un remplissage total de la densite d'etats d'interface) par une interaction par effet tunnel entre les porteurs libres du semiconducteur et les defauts des premieres couches d'oxyde (etats lents). Etude de la degradation des interfaces si-sio::(2) sous injection d'electrons chauds en comparant la cinetique de creation des etats lents et rapides. Etude des defauts induits par plasma ionique reactif
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BERNABEU, PATRICIA. "Adsorption de proteines plasmatiques sur une electrode a disque tournant : etude des parametres cinetiques a partir de l'analyse des variations de la capacite de double couche electrochimique." Paris 6, 1989. http://www.theses.fr/1989PA066050.
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Hwang, Gwo-Jen, and 黃國貞. "Three-Electrode Silicon Capacitive Pressure Sensor." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/27610021402028924551.
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Pierce, Kena Marie. "Electrode separation effects in capacitive deionization desalination systems." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-08-6357.
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A more energy efficient and sustainable method of desalinating water is needed due to increasing water shortages and contamination of current freshwater sources. Capacitive deionization (CDI), a new emerging technology, is a type of electric desalination that uses an applied voltage to pull the salt ions out of the salty solution and store the ions in porous carbon electrodes. CDI uses less applied energy than more commonly used methods of desalination like reverse osmosis and multi-flash distillation and has the added advantage of energy recovery. This report details experiments conducted to analyze the effect of different separation distances between the electrodes on salt ion adsorption for a high concentration solution under various flow rates and a 1 V voltage potential difference.
The testing was performed in the Multiscale Thermal-Fluids Laboratory at The University of Texas at Austin using a uniquely fabricated CDI cell. Voltage, elapsed time, and electrical conductivity measurements were taken during the testing. Electrical conductivity was used to signify salinity of the solution. Two different separation distances were created by placing either one 2mm mesh between the electrodes or by using two 2 mm meshes between the electrodes. The results did not agree with the expectation that the one-mesh tests would adsorb twice the amount of salt ions as the two-mesh tests because of the differences in the electric field between the two types of tests. This is believed to be due to the high concentration tested. Future testing should include repeating these tests to verify the results and performing the tests for lower concentrations to see if they followed the expectation.text
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Lai, Chung-Wen, and 賴俊文. "Computer Aided Design of Electrode Pattern in Capacitive Touch Panel." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/05654285939490493089.
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碩士國立成功大學
航空太空工程學系碩博士班
94
This thesis aims at developing an efficient method for designing the electrode pattern in capacitive touch panel. The linearity of the electrical field on the capacitive touch panel is very important to the quality of the touch panel, and the distribution of silver electrodes on the panel is the key to improve the electric field. A parametric design tool is established under the Visual Basic for Application (VBA) program language. The dimensions of the silver electrode are parameterized in this parametric design tool. The electrode pattern can be established by defining these parameters. This tool not only can shorten the time of designing the electrode pattern, but also can adjust the geometry of silver electrodes easily. A 12.2 inch electrode pattern is designed by using this parametric design tool to prove the feasibility of this tool. Seven kinds of element geometry test can be used to adjust the layout of the silver electrodes for good linearity. Finally, a 10.2 inch electrode pattern is fabricated and validated.
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Tsai, Hung-Ming, and 蔡鴻銘. "Optimal Design of Electrode Pattern for Projected Capacitive Touch Panel." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/22486639885159977811.
Full textAbstract:
碩士國立交通大學
電控工程研究所
101
This study proposes the optimal design for a projected capacitive touch panel. The panel consists of two parallel Indium Tin Oxide (ITO) film layers which are separated by a sensor glass layer. Our goal is to optimize the touch sensitivity for the projected capacitive touch panel, where capacitance shifts due to environmental disturbance are commonly presented to make successful touch detections difficult. A simulation model of projected capacitive touch panel is built by COMSOL. Numerical values of touch sensing signal of different touch panel design can be simulated by this model to provide a reference for touch panel controller design. Design guidelines of ITO electrode pattern are distilled herein to improve the detection sensitivity for projected capacitive touch panel. Also, the cost of designing the touch panel is optimized for super sensitivity. Finally, the relationship between the time constant and detection sensitivity has been studied to achieve balance in the design of the projected capacitive touch panel.
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Yu-ChunChen and 陳玉純. "Electrode Binders to Upgrade the Capacitive Performance of Activated Carbon." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/89zw99.
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Du, Fang-Yi, and 杜芳儀. "Characterization on Capacitive Performance of Nanocomposite Electrode Based on Mesoporous Carbons." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/52783777943446158576.
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碩士國立成功大學
化學系碩博士班
97
There are three major topics discussed in this thesis. In the first part, mesoporous carbons of different pore size were synthesized. The effect of the pores size and on the supercapacitor characteristics were investigated systematically by means of cyclic voltammetry. In the second part, electrode nanocomposite materials of ruthenium oxide@ mesoporous carbons were synthesized and characterized its electrochemical behavior. The third part is to prepare hollow-shape materials of various morphologies, which used gelatin as surface active agent. Part I：Investigate the pore size effect on capacitive performance based on mesoporous carbon materials Mesoporous carbons with high surface area and large pore size demonstrate potential application in high-power supercapacitors. It is also well known that the key factor of capacitive performance directly depends on pore size of carbon materials. To investigate the correlation between the pore size and capacitive behaviour of carbon materials, we used the Gelatin-PR620 blending method to synthesize hollow-sphere mesoporous carbons(HSC) with various pore size which can control by hydrothermal treatment at 1 atm, 100℃ condition. The pore width of HSC, ranged from 2.8 to 12nm, have notable increment as hydrothermal time extended. The capacitive performance of HSC with hydrothermal treatment was significantly improved due to the large pore size, which enable ions to pass through easily at high charge/discharge state. The HSC with hydrothermal treatment for 2 days exhibit ideal capacitive property which of capcative performance was 71.2 % obtained from the CV charaterization between the scan rate 50mvs-1 and 3000mvs-1. Moreover, surface area and condicitivity of HSCs are not directly relative to the hydrothermal time. The proe size of mesoporous carbon and utilation of macropore might be the key factor to decide the performance of supcapacitor behaviour. Part II：Synthesize RuO2@silk-like carbon composite in supercapacitor application. In order to promote the SC value (or energy density) in real application, RuO2@silk-like carbon composite materials were synthesized easily via hydrothermal treatment rather than traditional incorporation method. According to TGA analysis, the weight percentage of RuO2@silk-like carbon composite materials was about 25 %. The specific capacitive value of the RuO2@silk-like carbon composite was much high by four times than of the pristine carbon by means of cyclic voltmammetry. The utilation of ruthenium oxide of the comoposite was up to 544 Fg-1 at scan rate of 25 mVs-1. Besides, the capacitive retention of the RuO2@silk-like carbon composite were 46.2 % (ranged from the scan rate of 25 to 1000 mVs-1), demonstrating excellent prpoerity of high power density. Further, it was found that capacitive performance of composite greatly deponds on pore size and morphology of the pristine carbon. These results demonstrate the RuO2@silk-like carbon composite to be an excellent candidate for pracital application. Part III：Preparation hollow-structure materials with gelatin by Hard-template method In this study, a hard-template method was used to fabricate the hollow-structure materials with different morphology. However, in previous reports about hard-template method, the step of coating the templates with designed materials is generally regarded as the most challenging because it usually requires complicated surface modification process. Instead of typical and complicated surface modification, gelatine was used to active surface of which could simplfy the experiment process. Further, because this surface active method operated through the solution environment, the uniformity and dispersion of the products are significantly improved than that of reported.
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Lin, Pin-cheng, and 林品成. "Capacitive properties of cobalt/manganese oxide electrode prepared by hydrothermal method." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/22178024412991538534.
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碩士逢甲大學
材料科學與工程學系
103
In the present study, the preparation of Co/Mn (cobalt/manganese) oxide electrode was mainly based on three steps. First, Co-oxide nanostructure was prepared on a graphite substrate by hydrothermal process as a function of hydrothermal time. Experimental results showed that the hydrothermal synthesized Co-oxide exhibited a snowflake-like morphology with a hierarchical structure. Second, the snowflake-like Co-oxide was post heated at 300°C and 350°C in an ambient atmosphere. Subsequently, the Mn-oxide was deposited onto the surface of the Co-oxide nanostructure to form a Co/Mn oxide core-shell structure by a secondary hydrothermal process. The resulting Co/Mn oxide core-shell structures were characterized using XRD, SEM, TEM, XPS and electrochemical analyses. The effect of post heat treatment on the material characteristics and pseudocapacitive performance of the core-shell structure were investigated. The dimension of hydrothermal synthesized Co-oxide with a snowflake-like morphology varied with the post heat treatment conditions. The Co-oxide nanostructure served as a template for the growth of Mn-oxide films. A highest specific capacitance (SC) of 196 F/g and a relatively good electrochemical reversibility can be obtained when the composite electrode was calcined at 300ºC for 4 h. More than 90% capacitance retained after 1200 CV (cyclic voltammetry) cycles. The Co/Mn oxide core/shell structure exhibited a better electrochemical stability, being one of the promising active materials in pseudocapacitor applications.
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Wang, Yi-Siou, and 汪意修. "Capacitive properties of manganese/vanadium oxide electrode prepared by anodic deposition." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/54983928266918775690.
Full textAbstract:
碩士逢甲大學
材料科學與工程學系
101
In this research, manganese oxide and vanadium oxide electrodes are manufactured by anodic deposition process. Various ratios of manganese and vanadium were mixed with vanadyl sulfate and manganese acetate solution, then deposited onto graphite substrate in aqueous solution at different potentials. Besides, XRD, SEM, TEM, EDS were conducted to analyze the electrochemical characteristics of composite films. Meanwhile, the influences of the combination of Mn- and V-oxides on the capacitance characteristics of film electrode are being discussed. According to the experimental results, the deposition potential resulted in the alteration of the equilibrium phase, as well as the crystallinity, surface morphology, composition and capacitance characteristics of the film. The microstructural observation shows that the particle size of the anodic-deposited vanadium oxide electrodes is about 10 nm. The surface structure tends to become denser with the increase of deposition potential, resulting in the difficulty of electrolyte penetration reaction. Therefore, the highest capacitance value is merely 121 F/g and the capacitive stability remains 75%. This is likely due to the repetitive redox reaction during CV process causing the flattened surface of the film, the redox reaction area is thus declined. In terms of manganese oxide electrode, no significant change is observed in the structural size with the increase of deposition potential. The crystallite size distribution is about 20-30 nm. At the deposition potential of 1.0 V, the majority phase is amorphous MnO2, showing a loose porous structure on the film surface. The electrolyte can easily penetrate and cause the reaction with the electrodes. The maximum capacitance value can be as high as 245 F/g. In the wake of the compound with vanadium, the maximum capacitance value of the composite film is only 145 F/g at a Mn/V ratio of 1/3 and a deposition potential of 1.0 V. Though the capacitance value is not increased, the capacitance stability is quite excellent. There is no recession phenomenon after 1200-cycle test. The experiment data suggest that instead of showing relatively good capacitance characteristics, the Mn/V oxide compound exhibits a tremendous electrochemical stability. Key－words: Supercapacitor; Anodic deposition; Manganese oxide; Vanadium oxide; Electrochemical stability
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廖宜仁. "Design and Characterization of CMOS-MEMS Dual-Electrode Capacitive Micromachined Ultrasonic Transducers." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/sdfkaf.
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Amaral, Eliana Patrícia da Conceição. "Redox-free reverse electrodialysis using capacitive electrodes for energy generation." Master's thesis, 2020. http://hdl.handle.net/10362/113080.
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The increasing demand for fossil fuels and arising concerns about their impact on the environment creates the need to develop sustainable technologies that make use of natural sources to generate energy, like reverse electrodialysis (RED) that makes use of salinity gradient power (SGP). In this thesis, a possible optimization of the electrode system applied in RED is introduced, including the preparation and study of capacitive slurry electrodes to replace redox electrodes commonly used.
Three slurries were prepared with different carbon concentrations (15 %, 20 %, and 22.4 %) in 1 M aqueous solution of NaCl. When pumped through a single membrane cell, it was possible to conclude about their resistance, and without being pumped their capacitance was obtained. The 22.4 %cwt slurry allowed the lowest electro-resistance at different conditions, while the 20 %cwt slurry achieved the highest specific capacitance of 34.52 F/g after 100 cycles. Pumping the slurries through the RED cell at 300 mL/min, while using the 20 %cwt slurry resulted in the best electrochemical performance, since the best trade-off between power density 1.56 W/m2, and energy efficiency 15.6 %, was achieved.
The results obtained demonstrate that it is possible to efficiently operate a redox-free RED cell. Further investigation on slurry preparation, charge percolation mechanism, and cell design, should be done aiming for complete validation of capacitive slurries application in RED, thus promoting its industrial application.
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Yan, Bo-Kai, and 顏伯凱. "A CMOS MEMS capacitive tactile sensor with polymer gap and metal sensing electrode." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/50126597817918409228.
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Lian, Bing-Xu, and 連炳旭. "Fabrication and characterization of Titanium dioxide/carbon aerogel electrode for capacitive deionization applications." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/03433397482177634679.
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碩士國立勤益科技大學
化工與材料工程系
100
Carbon aerogel is an ideal electrode material because of its low electrical resistivity, high specific surface area, and controllable pore size distribution. Carbon Aerogel were prepared using resorcinol and formaldehyde catalyzed by KOH in a sol–gel process followed by carbonization, during which the KOH serves as an activating agent and increase specific surface area, and it was modified by adding mesopore titania to carbon precursor for increase mesopore volum. The electrode was fabricated by polymer binder and conductive filler, which to probe into the effect of electrochemical performance . The results show that molar ratio of Resorcinol and Formaldehyde were 1:2 that has the highest surface area of 1208.8 m2 g-1, and found that 10wt% polytetrafluoroethene content by cyclic voltammetry and galvanostatic charge-discharge test have largest capacitance were 195 and 227 F/g. The saturation monolayer adsorption capacity of Langmuir isotherms was 4.2641 mg/g. For activation by KOH , with an increase of mass ratio of KOH to resorcinol from 2 to 5, both the specific surface area and the pore volume of the carbons aerogel increased, from 1208.8 to 1948 m2/g and 0.6324 to 0.9406 cm3/g, respectively. The optimum mass ratio of KOH to resorcinol was 4, because the too high content of KOH lead to turn off . The specific surface area of 1929 m2/g and the highest specific capacitance of up to 255 F/g were obtained with the mass ratio of KOH to resorcinol of 4, for the same sample, the saturation monolayer adsorption capacity of Langmuir isotherms was 5.0751 mg/g. For the modified by adding mesopore titania, the highest specific capacitance of TiO2/ carbon aerogel electrode was 277 F/g by cyclic voltammetry. The highest of saturation monolayer adsorption capacity of Langmuir isotherms was 10.325 mg/g , indicate increases in the number of ions per adsorption capacity and in capactive deionization electrode strength of ions by titania incorporation. For the results , electrosorption of Na ion on the carbon aerogel was significantly increased by titania incorporation,resulting in an improved performance of the TiO2-Carbon Aerogel as a CDI electrode.
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Huang, Jing-Ting, and 黃靖婷. "Electrodeposited MnO2 on Electrospun Carbon Nanofibers as an Electrode for Membrane Capacitive Deionization." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/8z73r6.
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碩士國立臺灣大學
環境工程學研究所
106
Membrane capacitive deionization (MCDI) is a promising desalination technology with low energy input and high water recovery. Electrode materials play an important role for determination of the desalination performance. Generally, there are two fundamental mechanisms: (1) capacitive electrosorption using highly porous carbons, and (2) pseudocapacitive ion storage using redox materials (i.e., MnO2). Most recently, to achieve high salt adsorption capacity (SAC) of electrode materials, many efforts have been made on the development of pseudocapacitive materials, such as transition metal oxides and conductive polymers, for the applications of CDI and MCDI. To investigate the dominant species between the electric double layer capacitor, pseudocapacitor and hybrid capacitor, the raw materials of binder-free electrodes (electrospun) were fabricated by electrospinning, and then were electrodeposited with MnO2. Carbonization and activation processes were further conducted to manufacture activated carbon nanofiber (ACF) with high specific surface area and carbon nanofiber (CNF) with high conductivity from electrospun. After manganese dioxide (MnO2) was electrodeposited on both materials, pseudocapacitive (MnO2/CNF) and hybrid (MnO2/ACF) electrodes were obtained. Material characterization (i.e., accelerated surface area and porosimetry system, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectrometer, X-ray diffractometer, thermogravimetric analysis and contact angle meter) confirmed the presence of MnO2 electrodeposited on the substrates. Cyclic voltammetry and electrochemical impedance spectra measurements were conducted to determine the specific capacitance and electrical conductivity of electrodes. According to the results obtained by cyclic voltammetry, the specific capacitance (at 5 mV s−1) of MnO2/ACF (70.33 F g−1) was higher than ACF (59.96 F g−1). On the other side, the specific capacitance (at 5 mV s−1) of MnO2/CNF (52.16 F g−1) was 10-fold higher than CNF (4.7 F g−1). To investigate the desalination performance, the fabricated electrode materials were tested in a batch-mode MCDI at 1.0 V for 10 mM NaCl. Here, the anode was MnO2/CNF or MnO2/ACF, while the cathode was ACF. As demonstrated, the SAC of MnO2/CNF and MnO2/ACF were 11.7 and 13.2 mg g−1, respectively, which were both higher than that of ACF (9.17 mg g−1). Therefore, the desalination performance can be enhanced by Faradaic ion storage via incorporation of redox-MnO2 with carbon electrode materials. Note that the MnO2/ACF presents the highest SAC among these materials. This reflects that the combination of capacitive electrosorption and pseudocapacitive ion storage is much preferred for MCDI applications. These results can provide a strategy to prepare high-performance capacitive electrodes based on electrospun carbon nanofibers.
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Li, Yi-Chieh, and 李怡潔. "Reduction of organic fouling in capacitive deionization by TNT modified activated carbon electrode." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/327w32.
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碩士國立中央大學
環境工程研究所
107
Capacitive deionization (CDI) is a rising technology for water desalination. CDI is based on the electrosorption of ions onto the electrical double layer (EDL) of electrode surface which formed by applying low voltage, and the desorption is processed easily by removing voltage. There has been a dearth of research about the CDI performance when there is organic compounds in wastewater for reuse. The biologically treated still contains dissolved organic matter (DOM) which cannot be treated completely by the secondary process, and it will block the pores of carbon nano-material and make poor deionization efficiency. The titanate nanotube (TNT) modified activated carbon electrode (TNTAC electrode) has been developed in this study to reduce the adverse effect which is from organic compounds in aqueous solution. In this study, TNTAC electrodes with 5 wt.% of Ti and hydrothermal temperature of 150°C has the best deionization efficiency. The adsorption-desorption has been carried out for the mixture of fulvic acid and NaCl. The results show that the TNTAC electrode prepared in this study can be reused up to 9 times, and both the deionization efficiency and the ability of fulvic acid adsorption are superior to the activated carbon electrode. The composition of the chemical state for the surface of electrode after reuse is determined by X-ray photoelectron spectroscopy (XPS). It is found that the TNTAC electrode may decompose fulvic acid and limit the fouling of electrode at the same time, and effectively extend the working time of electrodes.
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LUO, HONG-JYUN, and 羅弘駿. "The Removal of Potassium Hydrogen Phthalate via Capacitive Deionization Using TiO2/AC Composite Electrode." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/84xmdq.
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碩士國立中央大學
環境工程研究所
106
The sources of organic pollution in the environment mainly include the wastewater from food factories, petrochemicals, pesticides, plastics, dyes, and etc. The impact of organic compounds for environmental, including the decline of dissolved oxygen in aquaculture, difficult to resolve in water and creature, and etc. To prepare of activated carbon electrode to remove organic compound (potassium hydrogen phthalate, KHP) via CDI experiment from aqueous solutions. On the other hand, the influences of flow rate, initial concentration and applied voltage are investigated. TiO2/AC composite powder was prepared with the sol–gel method and further discuss about the addition of TiO2 whether enhance CDI desalination efficiency than the carbon electrode. Four kinetic models, including pseudo-first-order, pseudo-second-order, Elovich, and intra-particle diffusion models, were employed to fit the electrosorption kinetic of KHP. All the mesopore ratios of electrode material are higher than 80%, which indicate that the mesopore play an important role in this study. From XRD analysis of the TiO2/AC composite electrode indicates that can obtain a good anatase crystalline by the sol-gel method and the optimum anatase crystal strength was prepared at the 500℃. It is possible to know from the CDI experiment that the best operating conditions of AC electrode for removing KHP were the flow rate of 60 ml/min and the initial concentration of 50 ppm. The adsorption kinetics could be described by the pseudo-second-order model. The 10 wt.% TiO2/AC composite electrode has better removal amount of KHP than the AC electrode, which means the addition of titanium dioxide has the effect of improving the activated carbon. In addition, the adsorption cycle performance of CDI indicates that 10 wt.% TiO2/AC composite electrode has better durability and stability than AC electrode.
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Liu, Po I., and 劉柏逸. "Microwave-assisted ionothermal synthesis of titanium dioxide/activated carbon composite electrode materials for capacitive deionization." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/j7999k.
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Lo, Che-Wei, and 羅哲偉. "Enhanced Desalination Efficiency of Activated Carbon Electrode Coated with Ion-exchange Layer for Membrane Capacitive Deionization." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/12888188098089087519.
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碩士國立臺灣大學
環境工程學研究所
104
Membrane capacitive deionization (MCDI) is an alternative desalination technology, which combined with the ion-exchange membrane (IEM) in front of electrodes. Based on the principle of capacitive deionization (CDI), the ions are removed by applying electric field and ions, which stored in the surface of porous carbon electrodes from aqueous solution. During the process of electrosorption, the IEM plays an important role to exclude the co-ion effect due to the characteristic of permselective. A membrane that completely blocks transport of co-ions while allowing transport of counter-ions simultaneously. However, the IEM is expensive, requires strong physical pressure between membrane and electrodes. In order to solve the problems of contact resistance and thickness of electrodes, the heterogeneous membrane/activated carbon electrode (RMCDI) was developed by adhering the powder of ion-exchange resin (IER) on the surface of electrodes directly. The electrodes were characterized by electrochemical analysis, contact angle and surface structure analysis. The results show IER layer can not only reduce the resistance between electrode and IEM but also improve the hydrophilic properties. In addition, the results also show the functional groups of IER will not be destroyed during product process. For the cyclic voltammetry, the specific capacitance still keeps up after coating IER layer. From the electrosorption experiments of 5 mM NaCl at applied potential of 1.2 V over 30 min period in RMCDI system, the electrosorption capacity (6.21 mg/g-carbon) is 40 % higher than the un-coating electrode and also have good performance of charge efficiency (71.4%) and lower energy consumption (0.0434 kWh/mole). Furthermore, a cyclic test was performance for continuous operation of RMCDI including electrosorption and desorption process for 5 cycles. The electrosorption capacity was measured between 5.91 and 6.23 mg/g-carbon over the repeat operations. This implies that the RMCDI system would have stable performance and good generation of electrodes over the repeated operation
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Chuang, Chieh-lung, and 莊杰龍. "A flow-through module of capacitive deionization with activated carbon/carbon black composite electrode for the desalination of aqueous solution." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/n6ce3q.
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碩士國立交通大學
環境工程系所
105
Capacitive deionization (CDI) technology is the use of an external voltage for generation of electrode capacitance, thereby removing ions from the aqueous solution. Carbon material applied in the CDI technology include activated carbon, mesoporous carbon material and carbon nanotubes, which store charge with the mechanism of electrical double layer capacitance. Activated carbon processes a very high specific surface area, however, due to poor conductivity of activated carbon, carbon black can be then incorporated therein to improve the overall specific capacitance. Therefore, incorporate different proportions of carbon black in the activated carbon was conducted to prepare capacitive deionization electrode. With those electrodes, the specific capacitance and electrosorption capacity for the activated carbon with different proportions of carbon black could be compared, and screened out a best performance electrode. A Flow-through modular with this preferred electrode was then applied to evaluate its performance on the desalination of NaCl solution. This study can be divided into two parts, the first part is to realize the relationship between the specific capacitance and the desalting amount. Activated carbon (AC) were mixed with carbon black (CB) by using a polymer binder (PVdF), and then landed on the titanium mesh via dip coating method. The mesh AC electrodes with different the ratio of CB were prepared and their changes in the specific capacitance as well as electrically adsorption capacity were investigated. The second part is flow-through modules were operated at different voltages and flow rates for the evaluation of their performances. The results showed that 10% PVdF performed the best coating. With the increase of carbon black, the specific capacitance of CDI electrode has indeed improved due to pseudocapacitance contributed by oxygen-containg functional groups (C=O). The results also showed that flow-through type of CDI modules assembly with 10% of CB laden AC mesh electrode performs the best desalination capacity, especially at the operating voltage of 1.2 V and the flow rate of 20 ml/min.