Tesis: "Electrode de zinc"

1

Bass, Kevin. "Zinc electrode performance in modified electrolyte". Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/10348.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

2

Caldeira, Vincent. "Développement d'électrodes composites architecturées à base de zinc pour accumulateurs alcalins rechargeables". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI065.

Texto completo

Resumen

Ces travaux de thèse résultent d’une étude multidisciplinaire dont l’objectif final était d’élaborer une électrode négative à base de zinc pour accumulateur alcalin rechargeable. L’origine de l’étude tient en la découverte surprenante, par la société EASYL, d’un nouveau procédé de synthèse du zincate de calcium (CAZN), matière électrochimiquement active et connue pour ses bonnes caractéristiques de cyclabilité en générateur alcalin rechargeable. L’intérêt de cette découverte réside dans ses caractéristiques avantageuses : la synthèse ultra-rapide se fait en continu, n’utilise aucun système de chauffe ni de solution alcaline et conduit à une granulométrie et une pureté contrôlée du zincate de calcium ; la rendant compatible avec une production industrielle de ce matériau.L’utilisation de CAZN en batterie prismatique de 4 Ah a permis la découverte d’un fonctionnement des électrodes de type cœur-coquille, leur cœur actif étant riche en zinc et leur surface jouant le rôle de couche protectrice ; si la capacité nominale est choisie inférieure à la capacité théorique de la batterie, l’activité à cœur de l’électrode est maintenue sans que sa surface ne soit altérée, ce qui permet d’éviter (ou de ralentir) la formation de dendrite, un effet très bénéfique sur la cyclabilité de l’électrode.Cependant, l’utilisation du zincate de calcium comme seule source de matière active ne semble pas appropriée. En effet, la formation du cœur de zinc conduit à l’apparition d’une couche résistive d’hydroxyde de calcium à sa périphérie, diminuant les performances électrochimiques des électrodes. Aussi surprenant que cela puisse paraitre, il est cependant possible de régénérer une électrode vieillie ayant formé une couche riche en hydroxyde de calcium par un simple repos, soit un arrêt pur et simple de la batterie. La formation de cette couche résistive peut en outre être évitée par l’ajout d’oxyde de zinc sacrificiel au zincate de calcium, additif actif qui s’est avérée efficace tant d’un point de vue morphologique qu’électrochimique.En revanche, la formation contrôlée d’un cœur riche en zinc conduit à la densification du zinc sur lui-même, et diminue la surface de contact matière active/électrolyte et donc les performances électrochimiques. Partant de ce constat, la structure de l’électrode a été intégralement repensée pour permettre la formation, non pas d’un cœur de zinc, mais de plusieurs d’entre eux, par l’emploi de collecteurs de courant multicouches ; cette méthodologie, aussi simple qu’efficace, conduit à d’excellentes performances pratiques et une cyclabilité optimale de la batterie
The work presented in this document results from a multidisciplinary study, the unique goal of which is to develop a negative electrode for alkaline rechargeable batteries. At the origin of this thesis, is the surprising discovery by EASYL of a new way to synthesize calcium zincate (CAZN), an electrochemically active material known for its good cycling characteristics in alkaline batteries. The advantage of such a discovery resides in its unique characteristics: the ultra-fast synthesis is carried out continuously, uses neither heating system nor alkaline solutions, yields pure and tailored CAZN crystals; it is therefore compatible with an industrial production of this material.Its use in a 4 Ah prismatic batteries allowed to unveil a core-shell operation mechanism, in which the electrode evolves towards an active zinc-core surrounded by a protective shell. So, if the nominal capacity remains below the theoretical one, the core of the electrode can be kept active while the surface is maintained, thus avoiding (or at least slowing down) possible dendrite formation and yielding prolonged cycle life.However, the use of calcium zincate as the only active material source is not appropriate, because the formation of the zinc-core leads to the appearance of a resistive layer of calcium hydroxide at its periphery, which reduces the overall electrochemical performance. As surprising as it may seem, it is possible to regenerate an electrode having formed such a calcium hydroxide-rich layer by a simple rest such as a stop of the battery. Nevertheless, it is preferable to avoid the formation of this resistive layer and to do so, the use of a mixture of sacrificial zinc oxide combined with calcium zincate has proven very effective, both from a morphological and an electrochemical point-of-view.However, the controlled formation of a zinc-rich core leads to zinc densification on itself; this decreases the surface of contact between the active material and the electrolyte, and thus the electrochemical performance. This negative effect has been overcome by drastically rethinking the structure of the electrode, in order to allow the formation of multiple and tailored zinc cores. To that goal, multilayers of current collector were employed, which proved simple and effective to reach high-performance and high cyclability zinc electrodes for alkaline batteries

Los estilos APA, Harvard, Vancouver, ISO, etc.

3

Dong, Mengyang. "Heterostructured Electrocatalysts for Oxygen Electrode in Rechargeable Zinc-Air Batteries". Thesis, Griffith University, 2022. http://hdl.handle.net/10072/418672.

Texto completo

Resumen

Nowadays, under the background of environmental pollution and energy crisis, with the continuous development of various forms of new energy, energy conversion and storage devices are essential to the utilization of renewable energy. Among them, clean battery technology is developing rapidly. Compared with traditional batteries including lithium batteries, Zn-air batteries have unique advantages and face significant development opportunities due to their high theoretical energy density, safety and environmental protection. However, as a secondary battery, the rechargeable Zn-air battery is charged and discharged at the air cathode. The high overpotential and slow kinetic process of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which occur respectively, seriously affect the actual efficiency of the battery, which has become an essential obstacle for the commercial use of Zn-air batteries. In order to explore the excellent theoretical performance of Zn-air batteries, it is an essential mean to use electrocatalysts with ORR/OER dual catalytic function to improve the cathode reaction efficiency. Based on this, this thesis reviews the structure, reaction mechanism, structure and performance characteristics of various oxygen reaction electrocatalysts of Zn-air batteries, and analyzes the material factors affecting the performance of catalysts. Utilizing strategies such as porous carbon, heteroatom doping, transition metal oxides, single-atom modulation, and defect control, a series of composite materials with high ORR/OER dual catalytic activity were prepared. The structure, electrochemical properties and catalytic performance of the materials in Zn-air batteries were studied. In addition, this thesis also investigates the application of catalysts in miniature wearable solid-state Zn-air batteries combined with various new battery configuration designs. In this dissertation, a series of transition metal carbon-based bifunctional catalysts with excellent performance were prepared based on various building elements. However, the analysis and research in this thesis revealled the fine materials science contents such as the electronic state distribution of the adsorption and bonding of heteroatom-doped carbon to oxygen reaction intermediates, and the regulation pathway of adsorption sites caused by defects. Understanding these contents is very important for explaining the structure-activity relationship of catalytic materials. Studying a bifunctional catalyst for Zn-air batteries that can work stably and maintain a terrific constant charge-discharge potential gap, withstanding high current density, will eventually lead to a revolution in the battery industry. However, most of the reported electrocatalysts in high-rate Zn-air batteries to date do not have enough durability, suffering from unstable nanostructures, poor electrical conductivity, low active sites, and high overpotentials. In view of this, it is the ultimate proposition of the road to Zn-air batteries applications to pursuit ultrastable and cheap catalysts that can alleviate particle aggregation, have abundant active sites and low resistance. In addition, compared with liquid Zn-air batteries, the performance of all-solid-state Zn-air batteries in various reports, is often poor, which originates from the insufficient water retention and conductivity of solid-state electrolytes, improper catalyst loading method and battery configuration. Various factors such as design, especially the research and development of new solid-state electrolytes, are of great significance for the development of wearable rechargeable Zn-air batteries with both flexible mechanical properties and charge-discharge efficiency. In order to solve the above problems and these drawbacks of Zn-air batteries, different characterization techniques are used to determine the similarity or commonality of composite electrocatalysts with high efficiency and activity. The main research contents are as follows: (1) Spinel-type metal oxides, as a group of the transition metal oxides, are considered as one of the most promising bifunctional oxygen electrocatalysts due to its unique electronic structure, mixed metalic valence centres with redox behaviours, abundance and environmental friendliness. In the first work, a facile one-step hydrothermal method is reported for the synthesis of a high-performance bifunctional oxygen electrocatalyst, cobalt-doped Mn3O4 nanocrystals supported on graphene nanosheets (Co-Mn3O4/G). Compared to pristine Mn3O4, this Co-Mn3O4/G exhibits greatly enhanced electrocatalytic activity, delivering a half-wave potential of 0.866 V for the ORR and a low overpotential of 275 mV at 10 mA cm−2 for the OER. The Zn-air battery built with Co-Mn3O4/G shows a reduced charge–discharge voltage of 0.91 V at 10 mA cm−2, a peak power density of 115.24 mW cm−2 and excellent stability without any degradation after 945 cycles (315 h), outperforming the state-of-the-art Pt/C–Ir/C catalyst-based device. This work offers an efficient strategy to synthesize spinel-type complex oxide materials in high-performance bifunctional oxygen electrocatalyst areas. (2) In order to make the Zn-air batteries work well at a high current, structural optimization is imperative. In the second work, a rapid seeding synthesis strategy is reported for the fabrication of impregnated Co3O4-based carbon ultra-thin nanosheets (Co3O4/C-NS) architecture induced by CoMOF as a bifunctional electrocatalyst. The impregnated ultra-thin nanosheets network would provide prolific pathways for efficient mass transfer, which allows the inner active sites to be accessible to electrolyte and oxygen. Additionally, the MOF-derived carbon matrix would suppress the aggregation of Co3O4 nanoparticles and increase the stability of the catalyst during the high-density charge/discharge cycling. Our Co3O4/C-NS exhibits uniform morphology, high specific area, low internal resistance, and superior ORR and OER activity to the benchmark Pt/C and Ir/C, respectively. Furthermore, the Zn-air batteries fabricated with the assynthesized electrocatalyst afford remarkably stable charge/discharge at a high current density of 25 mA cm-2, surpassing most of the previously reported catalysts. The material engineering approach highlighted herein exemplifies a facile yet effective avenue towards stable, efficient and robust non-noble metal-based electrocatalysts. (3) Single-atom catalysts (SACs) have attracted great interest in the field of catalysis, mainly because SACs not only possess the advantages of homogeneous and heterogeneous catalysts, but also possess some unique properties. In the third work, NiCo-LDH with electrocatalytic Ni and Co were grown on Ni, Co-codoped, hierarchically ordered macroporous carbon (NiCo-LDH@NiCo-SAs/OPC) derived from pyrolysis of ZIFs via a facile method. The strong coupling between NiCo-LDH and NiCo- SAs/OPC not only sharply facilitates the electron transfer but also result in high chemical stability against the corrosion during charging and discharging processes. Additionally, interconnected hierarchically porous structures were involved in NiCo-SAs/OPC via introducing removable templates, which would serve as channels to accelerate mass transport (O2 and electrolytes) during electrochemical steps. The obtained hierarchically porous NiCo-LDH@NiCo-SAs/OPC possesses abundant atomically dispersed Ni-Nx, Co-Nx sites and continuous species/charge transport channels, and exhibits good bifunctional ORR/OER electrocatalytic performance, which is superior to the corresponding noble metals Pt/C and RuO2 catalysts. More importantly, the rechargeable Zn metal-air batteries assembled with NiCo-LDH@NiCo-SAs/OPC also exhibited good charge-discharge performance and long-term stability. (4) Alloy-based electrocatalysts have been studied as bifunctional catalysts for ORR/OER for a long-time. In the fourth work, NiCo bi-alloy particles are used to embed onto the carbonized MF framework (NiCo@CMF), which has shown excellent performance, providing a new idea for designing other non-precious metal ORR/OER bifunctional electrocatalysts. More importantly, NiCo@CMF electrode can be processed into various shapes, furthermore, the assembled Zn-air battery shows pretty good flexibility during application as well as an appreciable charge-discharge voltage gap. While maintaining high-efficiency battery performance, the battery exhibits excellent bending mechanical properties. These works provide the power supply for nextgeneration smart wearable devices. The unique machinable NiCo@CMF electrode will have many potential applications, providing more possibilities for the design of wearabletype Zn-air batteries, and the cost-effectiveness of the NiCo@CMF electrode allows it to be fabricated on a large scale, providing a more economically viable avenue to the Zn-air batteries technology. This strategy can even be extended to other wearable devices for wider promotion.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
Full Text

Los estilos APA, Harvard, Vancouver, ISO, etc.

4

Gong, Minhui. "Etude des électrodes sur batterie zinc-air". Electronic Thesis or Diss., Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLC024.

Texto completo

Resumen

La batterie zinc-air devient une alternative potentielle à la batterie lithium-ion en raison de son avantage en termes de ressources, de sa densité d'énergie théorique élevée et de son faible potentiel de risque pour la sécurité. Ce travail met l'accent sur les problèmes conventionnels impliquant à la fois l'électrode à zinc et à air, visant à l'application.Pour l'électrode de zinc, deux configurations maison sont utilisées pour étudier la croissance des dendrites de zinc et l'évolution de l'hydrogène pendant le dépôt avec un électrolyte statique et en flux, respectivement. On trouve qu'une concentration élevée de zincate dans un électrolyte avec 7 M KOH (> 0,4 M ZnO) et la présence de circulation de l’électrolyte sont préférables pour réduire la croissance des dendrites. Cependant l'électrolyte en circulation générerait plus de dégagement d'hydrogène. Pour l'électrode à air, une étude de voltampèremètre cyclique détaillée de l'activité catalytique de pérovskites de lanthane- manganèse dopés au strontium (LSMO) vis-à-vis de la réaction de réduction de l'oxygène est menée. Une nouvelle méthodologie est proposée pour la comparaison de l'activité catalytique des LSMO. L'assemblage de la batterie zinc-air est également testé en formulant les électrodes avec un polymère PVDF-HFP prometteur dans les applications d’électrode à air
Zinc-air battery is becoming a potential alternative for lithium-ion battery owing to its resource stock advantage, high theoretical energy density, and low potential of safety risk. This work emphasizes the conventional issues involving both zinc and air electrode, aiming to application.For the zinc electrode, two homemade setups are used to study the zinc dendrite growth and hydrogen evolution during deposition with static and flowing electrolyte, respectively. It is found that high zincate concentration in electrolyte with 7 M KOH (>0.4 M ZnO) and flowing electrolyte are preferable for depressing dendrite growth. While flowing electrolyte would generate more hydrogen evolution. For the air electrode, a detailed cyclic voltametric investigation of the catalytic activity of lanthanum strontium manganese oxides (LSMO) towards oxygen reduction reaction is conducted. A new current normalization method is proposed for comparison of catalytic activity of the LSMOs. Zinc-air battery assembly is also tested, while remaining to be improved. Nevertheless, cost-effective PVDF-HFP is found to be a promising binder for air electrode formulation

Los estilos APA, Harvard, Vancouver, ISO, etc.

5

Dongui, Bini Kouame. "Electrode métallique négative pour générateurs électrochimiques "tout solide" à conduction protonique". Grenoble INPG, 1988. http://www.theses.fr/1988INPG0111.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

6

Ferreira, Jane Zoppas. "Electrocristallisation et dissolution du zinc dans un electrolite alcalinen circulation : cas d'une electrode poreuse et d'une electrode massive bombardee par des particules spheriques". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1991. http://hdl.handle.net/10183/170149.

Texto completo

Resumen

Le componement de deux types d'électrode de zinc en milieu alcalin a été étudié une électrode poreuse traversée par un électrolyte et une élect rode massive soumise à l'impact de billes mises en ci rculation avec l'élcctrolytc. A partir des mesures d'impédance électrochimique. on montre que l'élcctrode poreuse équivaut à un milieu constitué de pores cylindriques dont on suit les changements de texture en fonction de la polarisation. 11 s'avcrc que. mêrne avcc une circulation forcée, la pénétration du courant Jans lcs pores reste Ires faiblc notammcnt lorsque l'électrode débite du courant anodiquement ou cathodiquement. L'effet des chocs des billes sur une électrode massive polariséc cst étudié par analyse spectrale et temporelle des fluctuations. Les mcsurcs simultanées dcs fluctuations de potentiel et de rés istance d'é lectrolytc sont utilisées pour identifier les constantes de temps caractéristiques liées au tcm ps d'approchc des billes et à Ieur temps de séjour prcs du collecteur. Tandis que l'impact des billes de verre provoque uniquernent des cffets ohmiques sur les processus de dissolution et d'électrocristallisation du zinc. les billcs de zinc provoquent, cn plus, des fluctuations de potentiel dépola risantcs et apparaissant aux fréquences élevées. La modélisation de ces fluctuations montre qu'elles sont liées au temps de rccharge de la capacité du collecteur à travers l'impédancc faradique, qui suit I'échange rapide de charge électriquc provoqué par lcs chocs entre Ies billes de zinc et le collccteur. Les micrographies dcs élcct rodes polarisécs et Ies mesures d'impédance montrent que lcs chocs dcs billes cxcrccnt cn plus dcs effets sur les phénomcnes interfaciaux qui contrôlent les réactions se déroulant sur l'électrode de zinc.
In alkaline medium, the behaviour of two types of zinc electrodes has been studicd : a porous electrode flowed through by thc electrolyte and a solid one collided by sp herical particles circulating with the clcctrolyte. From clcctrochcmical impcdance measuremcnts, it is shown that the porous electrode behaves as a cylindrical pores clcctrode the tcxture of which changes with increasing polarisation. It was found that cvcn under forced electrolyte circulation. the current penetration in pores is shallow both under anodic and cathodic polarisations. The panicles impacts on the solid clcctrode result in a noise analyzcd both in the frequency and time domains. Simultaneous mcasurements of potcntial and electro lyte resistance fluctuations are used to identify the charactcristic time constants related to thc approach and rcsidence times of panicles within the electrode vicinity. While glass panicles gene rate only ohmic drop flutuations during the zinc dissolution or clcctrodcposition. zinc particles also induced potential fluctuations in the high frcqucncy domain. Modelling these fluctuations has concluded that they are related to thc recharging time of the electrode capacitance subsequent to the instantancous charge exchange taking place when zinc particles collide the electrodc. As rcvcalcd by impedance spectroscopy and electrode morphology, thesc collisions also influence the interfacial processes controlling the reactions on the zinc clectrode.

Los estilos APA, Harvard, Vancouver, ISO, etc.

7

Rodrigues, Joel da Silva. "Estudo da corrosão de revestimentos de zinco-ligas obtidos por imersão a quente sobre aços baixo-carbono". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/49059.

Texto completo

Resumen

O zinco vem sendo utilizado, já há bastante tempo, como revestimento protetor e decorativo para peças metálicas [1]. No entanto, cada vez mais a indústria busca revestimentos protetores que sejam mais resistentes à corrosão, que tenham boas características de soldabilidade, pintabilidade e, principalmente baixo custo. Os métodos mais comuns pelos quais os revestimentos de zinco são aplicados são imersão a quente, eletrodeposição e aspersão térmica. O presente trabalho tem como objetivo caracterizar a morfologia dos revestimentos Galvanized (GI), Galvannealed (GA) e Zn-55Al de zinco obtidos pelo processo de imersão a quente, verificar o comportamento eletroquímico e analisar o comportamento corrosivo dos revestimentos pelas técnicas de Potenciometria e Eletrodo Vibratório (SVET). Os resultados demonstraram que é possível a análise das fases por voltametria em microcélula no revestimento em que as fases foram crescidas, porém, não é possível aplicar a técnica nas diferentes fases formadas nos revestimentos industriais devido à espessura dos revestimentos. Não foi observado influência da luz Ultravioleta-visível na taxa de corrosão dos revestimentos estudados por SVET e esta técnica mostrou-se satisfatória para grandes aumentos e pequenas áreas. As análises por SVET demonstraram a possibilidade de analisar a corrosão localizada em diferentes fases intermetálicas nos revestimentos.
Zinc has been used for quite some time, as decorative and protective coating for metal parts. However, the industry increasingly seeks protective coatings that are more resistant to corrosion, have good weldability characteristics, and especially low cost. The most common methods by which zinc coatings are applied are hot dipping, electroplating and thermal spraying. The present work aims to characterize the morphology of the coatings Galvanized (GI), galvannealed (GA) and Zn-55Al of zinc obtained by hot dip process, check the electrochemical behavior and analyze the behavior of coatings for corrosion techniques of pots and Vibrating electrode (SVET). The results showed that it is possible to analyze the phases by microcell voltammetry in the coating in which the phases were grown, however, is not possible to apply the technique in the different phases formed in industrial coatings due to the thickness of coatings. There was no influence of UV-VIS in the corrosion rate of the coatings studied by SVET and this technique was satisfactory for large and small areas increases. The analysis by SVET demonstrated the possibility of analyzing the localized corrosion in different intermetalic phases in coatings.

Los estilos APA, Harvard, Vancouver, ISO, etc.

8

MacDonald, Gordon Alex. "Nanoscale Characterization of the Electrical Properties of Oxide Electrodes at the Organic Semiconductor-Oxide Electrode Interface in Organic Solar Cells". Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/347338.

Texto completo

Resumen

This dissertation focuses on characterizing the nanoscale and surface averaged electrical properties of transparent conducting oxide (TCO) electrodes such as indium tin oxide (ITO) and transparent metal-oxide (MO) electron selective interlayers (ESLs), such as zinc oxide (ZnO), the ability of these materials to rapidly extract photogenerated charges from organic semiconductors (OSCs) used in organic photovoltaic (OPV) cells, and evaluating their impact on the power conversion efficiency (PCE) of OPV devices. In Chapter 1, we will introduce the fundamental principles regarding the need for low cost power generation, the benefits of OPV technologies, as well as the key principles that govern the operation of OPV devices and the key innovations that have advanced this technology. In Chapter 2 of this dissertation, we demonstrate an innovative application of conductive probe atomic force microscopy (CAFM) to map the nanoscale electrical heterogeneity at the interface between an electrode, such as ITO, and an OSC such as the p-type OSC copper phthalocyanine (CuPc).(MacDonald et al. (2012) ACS Nano, 6, p. 9623) In this work we collected arrays of J-V curves, using a CAFM probe as the top contact of CuPc/ITO systems, to map the local J-V responses. By comparing J-V responses to known models for charge transport, we were able to determine if the local rate-limiting step for charge transport is through the OSC (ohmic) or the CuPc/ITO interface (nonohmic). These results strongly correlate with device PCE, as demonstrated through the controlled addition of insulating alkylphosphonic acid self-assembled monolayers (SAMs) at the ITO/CuPc interface. Subsequent chapters focus on the electrical property characterization of RF-magnetron sputtered ZnO (sp-ZnO) ESL films on ITO substrates. We have shown that the energetic alignment of ESLs and the organic semiconducting (OSC) active materials plays a critical role in determining the PCE of OPV devices and the appearance of, or lack thereof, UV light soaking sensitivity. For ZnO and fullerene interfaces, we have shown that either minimizing the oxygen partial pressure during ZnO deposition or exposure of ZnO to UV light minimizes the energetic offset at this interface and maximizes device PCE. We have used a combination of device testing, device modeling, and impedance spectroscopy to fully characterize the effects that energetic alignment has on the charge carrier transport and charge carrier distribution within the OPV device. This work can be found in Chapter 3 of this dissertation and is in preparation for publication. We have also shown that the local properties of sp-ZnO films varies as a function of the underlying ITO crystal face. We show that the local ITO crystal face determines the local nucleation and growth of the sp-ZnO films. We demonstrate that this effects the morphology, the chemical resistance to etching as well as the surface electrical properties of the sp-ZnO films. This is likely due to differences in the surface mobility of sputtered Zn and O atoms on these crystal faces during film nucleation. This affects the nanoscale distribution of electrical and chemical properties. As a result we demonstrate that the PCE, and UV sensitivity of the J-V response of OPVs using sp-ZnO ESLs are strongly impacted by the distribution of ITO crystal faces at the surface of the substrate. This work can be found in Chapter 4 of this dissertation and is in preparation for publication. These studies have contributed to a detailed understanding of the role that electrical heterogeneity, insulating barriers and energetic alignment at the MO/OSC interface play in OPV PCE.

Los estilos APA, Harvard, Vancouver, ISO, etc.

9

Holden, Nicholas John. "The improvement of weld quality in medium frequency direct current resistance spot welding". Thesis, Birmingham City University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312224.

Texto completo

Resumen

Zinc coated steels are widely used in the automotive industry, because of the improved protection against corrosion. Their use has consequences for the resistance welding process, which is the most widely used method of joining body panels. The zinc coating alloys with the copper electrode, resulting in increased electrode wear, and a reduction in electrode life. The welding current must be increased, because of the reduced contact resistance and thus heavier cables and power sources are required. A novel form of power source, the Medium Frequency Direct Current inverter, offers advantages over the traditional AC transformer. The higher operating frequency results in a lighter transformer, and a smaller welding current may be used, because the DC welding current generates heat at a constant rate, and is thus more effective than an AC power source. A potential advantage of this technology is that the increased frequency allows improved resolution in monitoring and control. Novel signal conditioning circuitry was developed, allowing significant improvement in the time resolution of the voltage and resistance signals. A series of welding trials was conducted, while monitoring the welding process. The correlation between weld quality and various process variables was assessed, and a control algorithm to compensate for electrode wear was proposed. This algorithm, based on a constant voltage principle, was implemented on a bespoke welding timer. A significant improvement in electrode life was obtained using this technique. The control algorithm was shown effective experimentally, but practical limitations do not permit testing under all possible conditions. A numerical model of the spot welding process, using Finite Difference technique, was developed. Following successful validation, the model was used to predict the performance of the control algorithm under various conditions of electrode wear. The results indicate that a constant voltage algorithm can compensate for an increase in electrode tip diameter, but that a change in contact resistance may result in unsatisfactory welds.

Los estilos APA, Harvard, Vancouver, ISO, etc.

10

Zoppas, Ferreira Jane. "Electrocristallation et dissolution du zinc dans un electrolyte alcalin en circulation : cas d'une electrode poreuse et d'une electrode massive bombardee par des particules spheriques". Paris 6, 1991. http://www.theses.fr/1991PA066392.

Texto completo

Resumen

Le comportement de deux types d'electrode de zinc en milieu alcalin a ete etudie: une electrode poreuse traversee par un electrolyte et une electrode massive soumise a l'impact de billes mises en circulation avec l'electrolyte. A partir des mesures d'impedance electrochimique, on montre que l'electrode poreuse equivaut a un milieu constitue de pores cylindriques dont on suit les changements de texture en fonction de la polarisation. L'effet des chocs des billes sur une electrode massive polarisee est etudie par analyse spectrale et temporelle des fluctuations. Les mesures simultanees des fluctuations de potentiel et de resistance d'electrolyte sont utilisees pour identifier les constantes de temps caracteristiques liees au temps d'approche des billes et a leur temps de sejour pres du collecteur. Tandis que l'impact des billes de verre provoque uniquement des effets ohmiques sur les processus de dissolution et d'electrocristallisation du zinc, les billes de zinc provoquent, en plus, des fluctuations de potentiel depolarisantes et apparaissant aux frequences elevees. La modelisation de ces fluctuations montre qu'elles sont liees au temps de recharge de la capacite du collecteur a travers l'impedance faradique, qui suit l'echange rapide de charge electrique provoque par les chocs entre les billes de zinc et le collecteur. Les micrographies des electrodes polarisees et les mesures d'impedance montrent que les chocs des billes exercent en plus des effets sur les phenomenes interfaciaux qui controlent les reactions se deroulant sur l'electrode de zinc

Los estilos APA, Harvard, Vancouver, ISO, etc.

11

Liu, Hanxiao. "Studies of efficient and stable organic solar cells based on aluminum-doped zine oxide transparent electrode". HKBU Institutional Repository, 2014. https://repository.hkbu.edu.hk/etd_oa/34.

Texto completo

Resumen

Organic solar cells (OSCs) have attracted significant attention due to their potential of large area solution fabrication capability at low-cost. For bulk heterojunction (BHJ) OSCs, a thin film of transparent conducting indium tin oxide (ITO), coated on glass or flexible plastic substrate, is widely used as a front electrode. However, indium is not abundant on Earth. Its price has increased continuously over the past 10 years and will likely become an obstacle for the commercialization of OSCs at low cost. Aluminum-doped zinc oxide (AZO) is a promising ITO alternative due to its advantages of high electric conductivity, optical transparency, non-toxicity and low cost. However, reports on OSCs using AZO electrode are quite limited, due to the relatively lower power conversion efficiency (PCE) of AZO-based OCSs as compared to that of ITO-based OCSs. This work focused on studies of high performance AZO-based OSCs through AZO surface modification, absorption enhancement and process optimization. The optical and electronic properties of AZO film including transmittance, sheet resistance, surface morphology and surface work function were characterized. AZO-based OSCs with conventional and inverted structures were fabricated. It was found that AZO-based OSCs with inverted structure demonstrated superior performance than the ones with conventional structure. The inverted structure avoids the use of acidic PEDOT:PSS hole transporting layer, allows the improving of the absorbance of the OSCs and therefore its efficiency. An AZO front transparent cathode was used for application in high performance inverted BHJ OSCs. The photoactive layer consisted a blend of poly[[4,8-bis[(2- ethylhexyl)oxy] benzo [1,2-b:4,5-b'] dithiophene-2,6- diyl][3-fluoro- 2-[(2-ethylhexyl) carbonyl]thieno[3,4-b]thiophenediyl]](PTB7):3'H-Cyclopropa[8,25][5,6]fullerene- C70- D5h(6)-3'-butanoicacid, 3'-phenyl-, methyl ester (PC70BM). A structurally identical control OSC having an ITO front cathode was also fabricated for comparison studies. The structure of OSCs was optimized to achieving absorption enhancement in the active layer. AZO and ITO were modified with a 10 nm thick solution-processed ZnO interlayer to facilitate the efficient electron extraction. The results revealed that bilayer AZO/ZnO and the ITO/ZnO cathodes possess similar electron extraction property. AZO layer has a transparency cutoff at wavelength < 380 nm, results in a slight decrease in the short-circuit current density (JSC). However, the decrease in JSC is very small because the main energy of solar irradiation falls in the spectrum with wavelength > 380 nm. It shows that AZO-based OSCs have a promising PCE of 6.15%, which is slightly lower than that of a control ITO-based OSC (6.57%). AZO-based OSCs, however, demonstrate an obvious enhancement in the stability under an ultraviolet (UV)-assisted acceleration aging test. The significant enhancement in the stability of AZO-based OSCs arises from the tailored absorption of AZO electrode in wavelength < 380 nm, which serves as a UV filter to inhibit an inevitable degradation process in ITO-based OSCs due to the UV irradiation. In order to further investigate the degradation mechanism of OSCs under UV exposure, the change in charge collection characteristics of the OSCs made with ITO/ZnO and AZO/ZnO front cathode before and after UV exposure was examined. It was found that there was an obvious decrease in the charge extraction efficiency of ITO-based OSCs after UV exposure, while there was no observable change in the charge extraction efficiency of OSCs made with AZO/ZnO cathode under the same acceleration aging test. This work demonstrates that AZO is a suitable ITO alternative for application in OSCs, offering an improved device stability, comparable PCE and cell fabrication processes with an attractive commercial potential.

Los estilos APA, Harvard, Vancouver, ISO, etc.

12

Wilson, Robert. "Spectroelectrochemical Sensing and Detection of Zinc in Serum by Anodic Stripping Voltammerty on a Bismuth Film Electrode". University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307320210.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

13

Pham, Ngoc Thach. "Cémentation électrochimique assistée par les ultrasons basse fréquence : application au couple cadmium/zinc". Grenoble INPG, 1999. http://www.theses.fr/1999INPG0014.

Texto completo

Resumen

Ce travail est consacre a l'etude de l'effet des ultrasons basse frequence (20 khz) sur la reaction de cementation cd(ii)/zn sur edt (electrode a disque tournant) et sur poudre en reacteur agite. Dans les deux configurations, et que ce soit avec ou sans ultrason, la reaction est controlee par le transfert de matiere liquide-solide des especes cementantes, du moins jusqu'a un taux de conversion de 80%. Sur edt, la cinetique de la reaction peut etre decrite par deux etapes du premier ordre dont la deuxieme est plus rapide que la premiere. Cette acceleration est liee a une modification de l'hydrodynamique a la surface de l'electrode resultant de l'evolution du depot sur les plans quantitatif (masse) et qualitatif (morphologie). L'apparition de cette rugosite critique depend de nombreux parametres operatoires tels que la vitesse d'agitation, la temperature ou bien encore les concentrations initiales en especes metalliques. D'autre part, l'apport des ultrasons sur la cinetique de la reaction est reduit par rapport aux resultats escomptes (gain d'un facteur 5-10) a partir d'une etude electrochimique du systeme redox etudie. Deux effets issus de la cavitation acoustique se compensent : l'amelioration du transfert de matiere (effet positif) et la regeneration de la surface reactionnelle (effet negatif). En effet, ce dernier conduit a la destruction du depot metallique dont la presence est l'agent accelerateur de la cinetique de cementation sans ultrason. En reacteur agite mecaniquement, les particules de zinc subissent une fragmentation conduisant, de part l'augmentation de surface reactionnelle, qui en resulte, a une amelioration de la cinetique. L'utilisation des ultrasons est egalement, dans cette configuration, peu probante sur la cinetique, les particules conservant une taille importante par fusion du depot de cadmium a leur surface. Cependant, elle permet a la reaction d'etre totale ce qui n'est pas le cas sans ultrason du fait d'une limitation en fin de reaction par le transport des especes zn(ii) oxydees du zinc des sites anodiques vers la solution. Une modelisation simplifiee de la reaction sur poudre en reacteur agite a permis de confirmer cette limitation. L'apport des ultrasons basse frequence sur la cementation cd(ii)/zn est donc globalement relativement limite d'autant plus que les energies mises en jeu sont importantes.

Los estilos APA, Harvard, Vancouver, ISO, etc.

14

Gourbeyre, Yannick. "Comportement vis-à-vis de la corrosion électrochimique d'un revêtement duplex, utilisé pour protéger les canalisations enterrées en fonte : élaboration d'un modèle physique". Châtenay-Malabry, Ecole centrale de Paris, 2004. http://www.theses.fr/2004ECAP0956.

Texto completo

Resumen

La recherche de tests permettant de qualifier des revêtements protecteurs de canalisations enterrées a été menée sur deux types de dépôt métallique recouverts d'une couche de finition organique : zinc+peinture bitumineuse, zinc-aluminium (85-15 % en masse)+peinture époxy. Au cours de ce travail, la grande complexité de structure et de répartition des phases, au sein des matériaux, a été mise en évidence. Celle-ci résultant du procédé de fabrication (projection à l'arc électrique) engendre aussi une complexité dans l'interprétation des résultats électrochimiques obtenus. L'environnement « sol » a été réduit à une solution simple mais agressive (NaCl 6 g. L 1). Quant aux incidents pouvant se produire lors de la mise en place des canalisations, ils ont été simulés par une blessure mettant à nue la fonte constituant les tuyaux et leurs raccords. Un modèle physico-chimique, exprimant les réactions électrochimiques du système duplex, a pu être établi à l'aide de la spectroscopie d'impédance électrochimique, en s'appuyant sur la théorie de l'électrode poreuse. L'effet cicatrisant des produits de corrosion du dépôt métallique a été évalué. Il s'avère que les mécanismes de corrosion sont plus rapides pour les revêtements à base de Zn+peinture bitumineuse que pour les revêtements Zn-Al+peinture époxy ; celui-ci est, à long terme, plus efficace dans le milieu choisi
The research of tests permitting to qualify protective coatings applied on buried pipelines was performed on two kinds of metallic deposit covered by a finishing organic coating : zinc + bituminous paint, zinc-aluminium (85-15% in weight) + epoxy paint. In this work, an important structure complexity of phase distributions was revealed inside of the investigated materials. This one results from the industrial process (projection by electric bow) and creates also a complexity of the interpretation of the electrochemical results. The “soil” environment was represented by a simple but aggresive solution (NaCl 6 g. L-1). The incident defects, resulting from the set up of the pipelines were simulated by a notch by which means the cast iron substrate was achieved. A physico-chemical model, expressing the electrochemical reactions of the duplex system, was established in terms of the porous electrode theory and with help of electrochemical impedance spectroscopy. A healing effect of the corrosion products of the metallic deposit was evaluated. It proves that the corrosion mechanisms are faster for the Zn+bituminous paint coating than the Zn+Al+epoxy paint coating. Consequently, Zn-Al+epoxy paint coating is a more efficient corrosion protection for longer immersion time in the chosen environment

Los estilos APA, Harvard, Vancouver, ISO, etc.

15

Fichou, Denis. "L'interface oxyde de zinc/électrolyte : étude des processus primaires". Paris 6, 1986. http://www.theses.fr/1986PA066259.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

16

Bannert, Tomáš. "Studium růstu ZnO krystalů ze supersaturovaného alkalického elektrolytu". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-319632.

Texto completo

Resumen

This thesis deals with the study of growth of zinc oxide crystals from supersaturated solutions using a scanning electron microscope and XRD methods. The work is divided into a theoretical and an experimental part. The theoretical part analyses issues related to the principle of operation of electrochemical cells with an emphasis on Ni-Zn batteries and phenomena limiting the life and efficiency of Ni-Zn batteries with a focus on phenomena that affect precipitation processes of zinc oxide crystals. It also analyses and compares the appropriateness of the methods that have been used to study the growth of the prepared zinc oxide crystals. The experimental part describes the preparation of a supersaturated solution, the process of each analysis and its evaluation. The results of each method are compared with the theoretical assumptions and among themselves. The experimental part also contains a chapter dealing with the design of in situ X-ray diffraction analysis methods of the obtained zinc oxide crystals.

Los estilos APA, Harvard, Vancouver, ISO, etc.

17

Messaoudi, Houssam mohammed. "Synthèse et caractérisation de membranes conductrices anioniques pour la protection d'électrode à air dans une batterie Zinc-Air fonctionnant sous air ambiant". Thesis, Cergy-Pontoise, 2016. http://www.theses.fr/2016CERG0864.

Texto completo

Resumen

Différentes membranes conductrices anioniques ont été développées pour protéger une électrode à air fonctionnant dans une batterie Zinc-Air alimentée par de l’air ambiant. Dans ces conditions, le dioxyde de carbone contenu dans l’air, en contact avec l’électrolyte basique, se transforme en carbonate de potassium qui précipite dans la structure poreuse de l’électrode. Cela provoque l’augmentation de sa résistance et la perte de son étanchéité, et l’électrode n’est alors stable que 80 heures. L’objectif de cette étude est donc de rendre stable une électrode à air pendant 3000 heures de fonctionnement.Pour cela, différents réseaux (semi-)interpénétrés de polymères ont donc été développés en associant un polyélectrolyte et un réseau partenaire neutre. La polyépichlorhydrine greffée avec du 1,4-diazabicyclo(2,2,2)octane et un polyélectrolyte fluoré ont été choisis comme polymère conducteur anionique. Des réseaux neutres à base de poly(méthacrylate de 2-hydroxyéthyle), d’alcool polyvinylique et de perfluoropolyéther leur ont été, tour à tour, associés. Les propriétés physico-chimiques des différentes membranes développées ont été caractérisées selon leur densité de charges et leur composition. Les membranes présentant les meilleures propriétés requises (conductivité anionique, prise en masse limitée, sélectivité, …) ont ensuite été assemblées sur des électrodes à air dont le potentiel et la stabilité ont été évalués au cours du fonctionnement en demi-cellule. Ainsi, une électrode à air modifiée avec de telles membranes peut présenter un potentiel stable pendant 6800 heures de fonctionnement à -30mA/cm²
Different anionic conducting membranes have been developed to protect an air electrode operating in a Zinc-Air battery fed with ambient air. Under those conditions, carbon dioxide from atmospheric air reacts with the alkaline electrolyte, and is then transformed into potassium carbonate. The precipitate of this carbonate inside the electrode porous structure leads to the increase of the system resistance and the loss of its sealing after 80 h of operation. The objective of this study focuses on the improvement of the stability of an air electrode for 3000 h of operation, by protecting it from carbonation reaction with a polymer membrane.For this, different (semi-)interpenetrating polymer networks have therefore been developed combining a polyelectrolyte and a neutral network partner. Polyepichlorohydrin grafted with 1,4-diazabicyclo (2,2,2) octane and a fluorinated polyelectrolyte were chosen as anionic conductive polymer. Neutral networks based on poly (2-hydroxyethyl methacrylate), polyvinyl alcohol and perfluoropolyether were then, alternately, associated to the polyelectrolyte. The physico-chemical properties of the various developed membranes were characterized according to their charge density and composition. The membranes with the best required properties (anionic conductivity, limited weight uptake, selectivity ...) were then assembled on air electrodes whose potential and stability have been evaluated during the operation in half-cell. Thus, an air electrode modified with such membranes maintains a stable potential during 6800 hours of running at -30mA / cm²

Los estilos APA, Harvard, Vancouver, ISO, etc.

18

Zanatta, Camilla dos Santos. "Preparação e caracterização de óxido de zinco nanoestruturado /". Bauru : [s.n.], 2009. http://hdl.handle.net/11449/88364.

Texto completo

Resumen

Orientador: Dayse Iara dos Santos
Banca: Manuel Henrique Leite
Banca: Alejandra Hortencia Miranda González
Resumo: Materiais nanoestruturados vêm sendo amplamente estudados pela comunidade científica, devido às suas propriedades únicas obtidas com o controle da síntese dos materiais. Por meio do controle experimental, esses materiais podem ser utilizados em numerosas áreas, tais como na eletrônica e na fotônica. Dentre os vários métodos químicos, o processo poliol vem sendo utilizado devido à fácil obtenção de nanopartículas de óxidos e metais na sua forma elementar. O presente trabalho teve como objetivo a síntese do óxido de zinco nanoestruturado por meio do método poliol. Diferentes precursores metálicos, tais como acetato de zinco dihidratado, nitrato de zinco hexahidratado, sulfato de zinco monohidratado e cloreto de zinco anidro e diferentes tempos de permanência da síntese foram utilizados para verificar possíveis interferências dos ânions precursores na síntese e na morfologia do óxido de zinco quando obtido. Os materiais obtidos das sínteses foram caracterizados por difração de raios X (DRX), análises térmicas (TG/DTA), medidas de adsorção de gás nitrogênio, microscopia eletrônica de varredura (MEV), microscopia eletrônica de varredura de alta resolução (MEV-FEG) e cronopotenciometria. Por meio destas técnias mostrou-se a viabilidade da obtenção do óxido de zinco nanoestruturado dd maneira direta a partir do acetato de zinco, através de refluxo em etilenoglicol por 2, 4 e 8 horas seguido de lavagem e centrifugação. A menor nanoestrutura encontrada apresentou partículas com dimensão de aproximadamente 25 nm e formato poliédrico, as quais foram observadas pelo FEG. A técnica de cronopotenciometria, representada por meio das curvas de carga/descarga mostraram que a utilização do compósito contendo o óxido de zinco sintetizado apresenta melhores resultados quando comparados ao uso... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Nanostructered materials have been extensively studied by the scientific community due to their unique properties obtained by controlled synthesis of materials. By means of the control of parameters, this new materials can be used in a number of applications in electronic and photonic technology. Among the several methods to obtain nanoparticles or nanostructured materials, the polyol method has been applied because it shows easy procedures to produce nanostructured oxides and elemental metals. The aim of this work is the synthesis of nanostructured zinc oxide, one of the most multifunctional oxides, by the polyol method. Different precursors salts like zinc acetate dihydrate, zinc nitrate hexahydrate, zinc sulfate monohydrate and zinc chloride anhydrate, as well as several times of reflux, were used to investigate the influence of the precursos anions on the synthesis and on the morphology of the crystals of zinc oxide whenever produced. The obtained powders were characterized by X-ray diffraction (DRX), thermal analyses (TG/DTA), and measurements of 'N IND. 2' gas adsorption, scanning electronic and field emission microscopy (MEV and FEG) and chronopotentiometry. These techniques showed the possibility of producing nanostructured zinc oxide in direct way from the reflux in etylenglycol for 2, 4 and 8 hours, followed by washing and centrifugation. The smallest nanostructure observed by FEG presented around 25 nm polyhedral particles. The chronopotentiometry, present charge/discharge curves showing better results for the electrode made of polimer composite containing ZnO nanoparticles than the obtaining results for the oxide alone. The best results showed reversibility of the lithium-ion cell upon 20 cycles, applying 3 μΑ electric current and showing a charge potential up to 4.2 V.
O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp
Mestre

Los estilos APA, Harvard, Vancouver, ISO, etc.

19

Fillis, Ismarelda Rosaline. "Determination of Chromium(VI), Vanadium(V), Selenium(IV) and Zinc(II) in the City of Cape Town's potable water by stripping voltammetry at boron doped diamond electrodes". University of the Western Cape, 2011. http://hdl.handle.net/11394/5417.

Texto completo

Resumen

>Magister Scientiae - MSc
The main aim of this study is to investigate theelectrochemical determination of two beneficial (selenium and zinc) and two toxic (chromium and vanadium) metals in the potable water within the City of Cape Town's distribution area. The Water Laboratory of the City's Scientific Services Branch analyses for these metals in their elemental state, using the Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). This is a standard method used for the detection of trace metals. The most sensitive voltammetric method for determining these metals is by adsorptive stripping voltammetry, using a thin mercury film electrode with a glassy carbon support. This voltammetric method is used for quantitative determination of specific ionic species. Because of mercury's toxicity it is not really favoured for trace metals anymore. Many other possibilities are under investigation, e.g. bismuth-film, modified glassy carbon and antimony electrodes. The boron-doped diamond (BDD) electrode has distinct advantages when used to determine metal concentrations. Advantages of BDD electrodes include lower detection limit, speciation and wider potential window. In this study cyclic voltammetry (CV) was used to determine the copper, cadmium and lead concentrations in potable water by means of square wave voltammetry (SWV) and a bare glassy carbon electrode (GCE). Furthermore, a boron-doped diamond electrode (BDDE) was used to investigate the possibilities of determining selenium, chromium and vanadium by SWV. Real samples (potable water samples) were analysed electrochemically to qualify and quantify these metals and determine whether they comply with the SANS 241:2006 drinking water guidelines.The copper, cadmium, lead and selenium peaks appear very close to the theoretical values, which indicate that these metals can be detected by SWV method, but further analysis with more samples is advised. Even though responses were observed for vanadium and chromium, it was not reliable and requires further investigation. Further studies into the analyses of zinc are also advised.

Los estilos APA, Harvard, Vancouver, ISO, etc.

20

Andrade, Milton. "Heavy metal removal from bilge water by electrocoagulation treatment". ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/1092.

Texto completo

Resumen

The purpose of this research was to observe the removal efficiency for copper (Cu), nickel (Ni), and zinc (Zn) using Electrocoagulation (EC) technique in a continuous flow reactor with a synthetic bilge water emulsion; and additionally, to discuss the operation cost of the treatment. The optimal configuration for EC treatment used combined electrodes, aluminum and carbon steel; flow rate of 1 L/min; effluent recycling and 7.5 amps; this optimal configuration achieved 99% of zinc removal efficiency, 70% of both, copper and nickel removal efficiency, and low operation costs. The current intensity did not have significance incidence on the removal efficiency. The analysis of cost per gram of removed contaminant indicated that nickel had an average cost of $1.95 per gram removed, zinc and copper had $0.60 and $0.88 per gram removed, respectively. To develop additional experiments with the EC reactor are required in order to optimize metal removal efficiency.

Los estilos APA, Harvard, Vancouver, ISO, etc.

21

Zanatta, Camilla dos Santos [UNESP]. "Preparação e caracterização de óxido de zinco nanoestruturado". Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/88364.

Texto completo

Resumen

Made available in DSpace on 2014-06-11T19:23:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-07-31Bitstream added on 2014-06-13T18:09:34Z : No. of bitstreams: 1 zanatta_cs_me_bauru.pdf: 2567546 bytes, checksum: b92343b4c48fcdf306ed6a95bf902804 (MD5)
Materiais nanoestruturados vêm sendo amplamente estudados pela comunidade científica, devido às suas propriedades únicas obtidas com o controle da síntese dos materiais. Por meio do controle experimental, esses materiais podem ser utilizados em numerosas áreas, tais como na eletrônica e na fotônica. Dentre os vários métodos químicos, o processo poliol vem sendo utilizado devido à fácil obtenção de nanopartículas de óxidos e metais na sua forma elementar. O presente trabalho teve como objetivo a síntese do óxido de zinco nanoestruturado por meio do método poliol. Diferentes precursores metálicos, tais como acetato de zinco dihidratado, nitrato de zinco hexahidratado, sulfato de zinco monohidratado e cloreto de zinco anidro e diferentes tempos de permanência da síntese foram utilizados para verificar possíveis interferências dos ânions precursores na síntese e na morfologia do óxido de zinco quando obtido. Os materiais obtidos das sínteses foram caracterizados por difração de raios X (DRX), análises térmicas (TG/DTA), medidas de adsorção de gás nitrogênio, microscopia eletrônica de varredura (MEV), microscopia eletrônica de varredura de alta resolução (MEV-FEG) e cronopotenciometria. Por meio destas técnias mostrou-se a viabilidade da obtenção do óxido de zinco nanoestruturado dd maneira direta a partir do acetato de zinco, através de refluxo em etilenoglicol por 2, 4 e 8 horas seguido de lavagem e centrifugação. A menor nanoestrutura encontrada apresentou partículas com dimensão de aproximadamente 25 nm e formato poliédrico, as quais foram observadas pelo FEG. A técnica de cronopotenciometria, representada por meio das curvas de carga/descarga mostraram que a utilização do compósito contendo o óxido de zinco sintetizado apresenta melhores resultados quando comparados ao uso...
Nanostructered materials have been extensively studied by the scientific community due to their unique properties obtained by controlled synthesis of materials. By means of the control of parameters, this new materials can be used in a number of applications in electronic and photonic technology. Among the several methods to obtain nanoparticles or nanostructured materials, the polyol method has been applied because it shows easy procedures to produce nanostructured oxides and elemental metals. The aim of this work is the synthesis of nanostructured zinc oxide, one of the most multifunctional oxides, by the polyol method. Different precursors salts like zinc acetate dihydrate, zinc nitrate hexahydrate, zinc sulfate monohydrate and zinc chloride anhydrate, as well as several times of reflux, were used to investigate the influence of the precursos anions on the synthesis and on the morphology of the crystals of zinc oxide whenever produced. The obtained powders were characterized by X-ray diffraction (DRX), thermal analyses (TG/DTA), and measurements of 'N IND. 2' gas adsorption, scanning electronic and field emission microscopy (MEV and FEG) and chronopotentiometry. These techniques showed the possibility of producing nanostructured zinc oxide in direct way from the reflux in etylenglycol for 2, 4 and 8 hours, followed by washing and centrifugation. The smallest nanostructure observed by FEG presented around 25 nm polyhedral particles. The chronopotentiometry, present charge/discharge curves showing better results for the electrode made of polimer composite containing ZnO nanoparticles than the obtaining results for the oxide alone. The best results showed reversibility of the lithium-ion cell upon 20 cycles, applying 3 μΑ electric current and showing a charge potential up to 4.2 V.

Los estilos APA, Harvard, Vancouver, ISO, etc.

22

Duffield, Alan. "Optimisation of conductor-modified zinc electrodes". Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/28024.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

23

LEYGUE, ESTREME NADINE. "Macrocylisation en series lactame, lactone et thiolactone : mise en evidence d'un tetralactame comme complexant selectif du calcium". Toulouse 3, 1987. http://www.theses.fr/1987TOU30124.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

24

Sun, Xihe. "Novel carbon electrodes for zinc–bromine batteries". Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12844.

Texto completo

Resumen

Zinc-bromine batteries have long been considered one of the most suitable storage technologies due to their potential long life, deep discharge characteristics and potential low manufacturing cost, as well as very high theoretical specific energy density (~440 Wh/kg). However, there are still a number of challenges to their commercial success, including electrode lifetime, electrochemical efficiency and cost. The major purpose of this study is to investigate the property of both zinc and bromine electrodes in zinc bromine flow batteries, and to develop new materials for zinc bromine flow battery electrodes, suitable for utility scale use. Different carbon materials and high density polyethylene-carbon composites have been evaluated through physical and electrochemical methods. Calgon activated carbon, carbon cloth, multi-walled carbon nanotubes (MWCNTs), reduced graphene oxide (rGO) and cryogel carbon have been investigated as the electrocatalysts for the bromine/bromide redox couple reaction in the positive half-cell of the zinc bromine redox flow batteries. As for the zinc electrodes, high density polyethylene (HDPE)-carbon black (CB) and HDPE-multiwall carbon nanotubes (MWCNTs) composites have been studied with macroscopic and microscopic techniques. The MWCNTs shows the best performance of the five carbon candidates. The HDPE-CB composite electrode exhibits better zinc deposition than the HDPE-CNT composite electrode due to a lower nucleation overpotential and higher exchange current density. In addition, the interfacial structure of the electrode/electrolyte on the bromine electrode and zinc electrode in zinc bromine electrolyte has been illustrated for the first time using electrochemical impedance spectroscopy.

Los estilos APA, Harvard, Vancouver, ISO, etc.

25

Napier, Stuart A. "Electron correlation and spin-dependent effects in the electron impact excitation of zinc atoms". University of Western Australia. School of Physics, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0098.

Texto completo

Resumen

[Truncated abstract] This work investigated electron correlation and spin-dependent effects in electron scattering from zinc for incident electron energies from the lowest excitation threshold at 4.003 eV to 50 eV. Experiments were performed using a crossed-beams electron impact spectrometer, which included an unpolarised electron gun, and also a spin-polarised electron gun. The apparatus was tested, and shown to be operating well, by repeating past studies of electron scattering from helium and argon. Emission cross sections for the 4s4p 3P1, 4s4p 1P1, 4s5s 3S1, 4s4d; 5d; 6d 3D1;2;3 and 4s4d; 5d 1D2 states were measured from the respective thresholds to 50 eV. These were compared with Convergent Close-Coupling (CCC) and B-spline R-matrix (BSRM) calculations of the 4s4p 3P1, 4s4p 1P1, 4s5s 3S1, 4s4d 1D2 and 4s4d 3D1;2;3 emission cross sections. There are serious discrepancies between the theories, and between the theories and experiment, which indicates strong continuum coupling and innershell excitation effects in the electron excitation of zinc. The differential elastic scattering signal at scattering angles of 30 , 54 , 90 and 110 was measured for incident electron energies from just below the lowest excitation threshold at 4.003 eV, to the ionisation threshold at 9.394 eV. Some assignments given by Sullivan et al [1] and Zatsarinny and Bartschat [2] were confirmed by the present experiment. An area of disagreement in the literature concerning the nature of a feature observed at the 4s4p 1P1 threshold at 5.796 eV was resolved in favour of Zatsarinny and Bartschat, who assign the feature as a cusp. ... Below the ionisation threshold, the 4s4p 3P1 photon excitation function supports the assignment of the near-4s4p 1P1 threshold feature as a cusp. Some of the overlapping negative-ion resonances which were observed near 7.5 eV in the 4s4p 3P1, 4s4p 1P1 and 4s5s 3S1 photon excitation functions were assigned with the assistance of the BSRM calculations of Zatsarinny and Bartschat. However, continuum coupling effects above 8 eV seem to cause the theoretical negative-ion resonance predictions to break down. Above the ionisation threshold, the near-11 eV negative-ion resonance effects depend on the configuration n, L and S of the neutral state excitation observed. This may be due to the properties of the mixed negative ion component states. Postcollision interaction (PCI) effects the 4s5s 3S1, 4s4d; 5d; 6d 3D1;2;3 and 4s4d; 5d 1D2 photon excitation functions. The PCI mechanism can populate the 4s4d; 5d; 6d 3D1;2;3 and 4s4d; 5d 1D2 states because the scattered and ejected electrons have a similar energy, and can thus exchange a large amount of orbital angular momentum. The present work demonstrates that electron correlation effects, especially those associated with innershell excitation, are very significant in electron scattering from zinc. Existing theoretical models of electron scattering from zinc inadequately treat electron correlations, and as a result of this are inaccurate, as shown here. The studies presented here should guide the development of models that accurately describe the innershell excitation effects, which are important for zinc and a great many other atoms.

Los estilos APA, Harvard, Vancouver, ISO, etc.

26

Pravica, Luka. "Polarised electron studies of spin-dependent interactions in zinc and krypton atoms". University of Western Australia. School of Physics, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0063.

Texto completo

Resumen

[Truncated abstract.] An apparatus has been built, tested and characterised with greatly increased precision and accuracy to enable spin-polarised electron impact explorations of angular momentum effects in atoms. A combination of experimental, computational and interpretative studies has revealed new phenomena. In zinc the polarisation of the radiated photons from excited and ionised-with-excited atoms was measured in terms of integrated Stokes parameters (P1, P2 and P3) and related to electron exchange and spin-orbit interaction using normalised state multipoles.

Los estilos APA, Harvard, Vancouver, ISO, etc.

27

Zhou, Taojun y 周濤俊. "All-electron and full-potential positron annihilation calculations forintrinsic and defective zinc and zinc oxide". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39634164.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

28

Holtzhausen, David Jacobus. "The development of a reactor for the manufacture of zinc electrodes for a silver oxide-zinc battery". Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51958.

Texto completo

Resumen

Dissertation (PhD)--University of Stellenbosch, 2000.
ENGLISH ABSTRACT: Silver/Zinc batteries are extensively used for applications where a power source with a high energy density is needed. A reactor was developed to manufacture the zinc electrodes for these batteries. The parameters for the control of this reactor were identified. The interaction and relationships between the set of parameters were established and quantified. The novel design of the reactor includes features such as continuous replenishment of the constituting chemicals, parallel flow of the plating fluid, inert anodes and a serial electrical layout. The controlling parameters consist of both chemical and physical parameters. They are - zincate concentration, hydroxyl concentration, density, temperature, flow rate of the plating fluid, and current density. The unique solubility characteristics of zinc oxide in potassium hydroxide lend themselves to a novel approach for the determination of the zincate concentration in· the plating solution. A set of conditions for the manufacturing of electrodes, with the required characteristics, was identified. The requirements are densely packed zinc dendrite morphology with high porosity and mechanical stability. The designed reactor complies with the industries safety requirements. The batteries were successfully applied in their operational domain (torpedoes) after this extensive research project was completed.
AFRIKAANSE OPSOMMING: Silwer/Sink batterye word intensief aangewend in gebruike waar 'n kragbron met hoë energie digtheid benodig word. 'n Reaktor is ontwikkel wat die sink elektrodes van die tipes batterye vervaardig. Die veranderlikes vir die beheer van die reaktor is bepaal. Die interaksie en verwantskap tussen die stel veranderlikes is verkry en gekwantifiseer. Die unieke ontwerp van die reaktor het die volgende karakteristieke, nl. aaneenlopende vervanging van die chemikalië verbruik, parallelle vloei van die plateringsvloeistof, inerte anodes en elektriese uitleg in serie. Die chemiese en fisiese veranderlikes is beide beherende veranderlikes. Hierdie fisiese en chemiese veranderlikes wat die proses beheer is die sinkaat konsentrasie, hidroksiel konsentrasie, digtheid, temperatuur, vloeitempo van die plateringsvloeistof en die stroomdigtheid. Die unieke oplossingskarakteristieke van sinkoksied in kalsium· hidroksied leen hom tot die unieke proses om die sinkaat konsentrasie in die plateringsvloeistof te bepaal. 'n Steloperasionele kondisies vir die vervaardiging van die elektrodes met die spesifieke spesifikasies soos verlang, is geïdentifiseer. Hierdie kondisies is die diggepakte sinkdendriet morfologie met 'n hoë porositeit en meganiese stabiliteit. Die ontwerpte reaktor voldoen aan die industriële veiligheidsvereistes en die ergonomiese maatstawwe. Die batterye is suksesvol gebruik in hulle industriële aanwending as gevolg van die suksesvolle afhandeling van die stuk navorsing.

Los estilos APA, Harvard, Vancouver, ISO, etc.

29

Zhou, Taojun. "All-electron and full-potential positron annihilation calculations for intrinsic and defective zinc and zinc oxide". Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B39634164.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

30

Климов, Олексій Володимирович, Алексей Владимирович Климов, Oleksii Volodymyrovych Klymov, Денис Ігорович Курбатов, Денис Игоревич Курбатов, Denys Ihorovych Kurbatov, Анатолій Сергійович Опанасюк et al. "Raman investigation and electro-physical properties of II-VI wide-band gap films". Thesis, Publishing House of Bucharest University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/29353.

Texto completo

Resumen

В даній роботі розглядались електро-фізичні властивості сполук групи А2В6 та їх дослідження за допомогою раманівської спектроскопії. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/29353
В данной работе рассматривались электро-физические свойства соединений группы А2В6 и их исследования с помощью рамановского спектроскопии. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/29353
In this work shown electro-physical properties of the compounds of group A2B6 and their research using Raman spectroscopy. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/29353

Los estilos APA, Harvard, Vancouver, ISO, etc.

31

Verma, Ved P. "Enhanced Zinc Oxide and Graphene Nanostructures for Electronics and Sensing Applications". FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/245.

Texto completo

Resumen

Zinc oxide and graphene nanostructures are important technological materials because of their unique properties and potential applications in future generation of electronic and sensing devices. This dissertation investigates a brief account of the strategies to grow zinc oxide nanostructures (thin film and nanowire) and graphene, and their applications as enhanced field effect transistors, chemical sensors and transparent flexible electrodes. Nanostructured zinc oxide (ZnO) and low-gallium doped zinc oxide (GZO) thin films were synthesized by a magnetron sputtering process. Zinc oxide nanowires (ZNWs) were grown by a chemical vapor deposition method. Field effect transistors (FETs) of ZnO and GZO thin films and ZNWs were fabricated by standard photo and electron beam lithography processes. Electrical characteristics of these devices were investigated by nondestructive surface cleaning, ultraviolet irradiation treatment at high temperature and under vacuum. GZO thin film transistors showed a mobility of ~5.7 cm 2/ V•s at low operation voltage of ~0.5 V with a sub threshold swing of ~85 mV/decade. Bottom gated FET fabricated from ZNWs exhibit a very high on-to-off ratio (~10 6) and mobility (∼28 cm 2 /V•s). A bottom gated FET showed large hysteresis of ~5.0 to 8.0 V which was significantly reduced to ~1.0 V by the surface treatment process. The results demonstrate charge transport in ZnO nanostructures strongly depends on its surface environmental conditions and can be explained by formation of depletion layer at the surface by various surface states. A nitric oxide (NO) gas sensor using single ZNW, functionalized with Cr nanoparticles was developed. The sensor exhibited average sensitivity of ~46% and a minimum detection limit of ~1.5 ppm for NO gas. The sensor also is selective towards NO gas as demonstrated by a cross sensitivity test with N2, CO and CO2 gases. Graphene film on copper foil was synthesized by chemical vapor deposition method. A hot press lamination process was developed for transferring graphene film to flexible polymer substrate. The graphene/polymer film exhibited a high quality, flexible transparent conductive structure with unique electrical-mechanical properties; ~88.80 % light transmittance and ~1.1742 kΩ/sq sheet resistance. The application of a graphene/polymer film as a flexible and transparent electrode for field emission displays was demonstrated.

Los estilos APA, Harvard, Vancouver, ISO, etc.

32

Lee, You-Shin. "Studies on Suppression of Dendrite Formation for Rechargeable Zinc Electrodes in Alkaline Solutions". 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/202719.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

33

Li, Sonny X. "Nitrogen doped zinc oxide thin film". Berkeley, Calif. : Oak Ridge, Tenn. : Lawrence Berkeley National Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2003. http://www.osti.gov/servlets/purl/821916-VLVAK9/native/.

Texto completo

Resumen

Thesis (M.S.); Submitted to the University of California, Berkeley, 210 Hearst Mining Memorial Bldg., Berkeley, CA 94720 (US); 15 Dec 2003.
Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--54116" Li, Sonny X. USDOE Director. Office of Science. Basic Energy Sciences (US) 12/15/2003. Report is also available in paper and microfiche from NTIS.

Los estilos APA, Harvard, Vancouver, ISO, etc.

34

Menezes, Eduardo Serralta Hurtado de. "Síntese e passivação de nanofios de óxido de zinco". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/159201.

Texto completo

Resumen

Neste trabalho se realiza a síntese e caracterização de nanofios de óxido de zinco. Adicionalmente se apresenta o processo de montagem de um dispositivo para medidas elétricas deste material. Estuda-se complementarmente o efeito do tratamento de plasma sobre as propriedades de fotoluminescência do material. Nanofios foram sintetizados pelo mecanismo vapor-líquido-sólido (VLS), utilizando ouro como catalizador e safira c-plane como substrato. As amostras foram caracterizadas utilizando microscopia eletrônica de varredura, fotoluminescência a temperatura ambiente, difração de raios X, e microscopia eletrônica de transmissão. Os nanofios obtidos têm seção transversal com formato quase hexagonal, e larguras de aproximadamente 46 nm. O comprimento deles varia de 3 a 10 μm. Os resultados de difração de raios x e microscopia eletrônica de transmissão mostram que eles são monocristalinos com rede cristalina tipo wurtzita, e com direção de crescimento no eixo c. Foram estudados os efeitos da potência de plasma de oxigênio (O2) na fotoluminescência dos nanofios a temperatura ambiente. A diferença na fotoluminescência após diferentes tratamentos de plasma de O2 mostra que a razão entre a emissão da região do band gap e da banda do visível pode ser modificada pelo tratamento. Este efeito corrobora com a hipótese de que a banda verde de luminescência está relacionada às vacâncias de zinco. A variação percentual da razão entre as duas regiões apresenta uma dependência linear com a potência do plasma.
In this work, we performed the synthesis and characterization of zinc oxide nanowires. We also report an assembly process to measure the electrical properties of this material. We study the plasma treatment effect on the photoluminescence spectra of the nanowires. Nanowires were synthesized via vapor-liquid-solid mechanism, using gold as catalyst and c-plane sapphire as substrate. The samples were characterized using scanning electron microscopy, room temperature photoluminescence, x-rays diffraction and transmission electron microscopy. Our nanowires show a quasi-hexagonal cross section, with diameters of approximately 46 nm. Their lengths ranged from 3 to 10 μm. Our results show monocrystalline wurtzite crystal nanowires with c growth direction. We also study the plasma power effect of oxygen (O2) plasma treatment on the room temperature photoluminescence spectra of the nanowires. Our results show that the deep level emission to near band emission ratio decreases with the plasma treatment. This effect supports the hypothesis that claims the green band luminescence is related to the oxygen vacancies. Furthermore, the relative ratio change depends linearly on the plasma power.

Los estilos APA, Harvard, Vancouver, ISO, etc.

35

Tiwale, Nikhil. "Zinc oxide nanowire field effect transistors for sensor applications". Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/268227.

Texto completo

Resumen

A wide variety of tunable physio-chemical properties make ZnO nanowires a promising candidate for functional device applications. Although bottom-up grown nanowires are producible in volume, their high-throughput device integration requires control over dimensions and, more importantly, of precise placement. Thus development of top-down fabrication routes with accurate device positioning is imperative and hence pursued in this thesis. ZnO thin film transistors (TFT) were fabricated using solution based precursor zinc neodecanoate. A range of ZnO thin films were prepared by varying process parameters, such as precursor concentrations and annealing temperatures, and then analysed for their optical and electrical characteristics. ZnO TFTs prepared from a 15 % precursor concentration and annealing at 700 $^\circ$C exhibited best device performance with a saturation mobility of 0.1 cm$^2$/V.s and an on/off ratio of 10$^7$. Trap limited conduction (TLC) transport was found to be dominant in these devices. A direct-write electron beam lithography (EBL) process was developed using zinc naphthenate and zinc neodecanoate precursors for the top-down synthesis of ZnO nanowires. Nanoscale ZnO patterns with a resolution of 50 nm and lengths up to 25 $\mu$m were fabricated. A linear mobility of 0.5 cm$^2$/V.s and an on/off ratio of $\sim$10$^5$ was achieved in the micro-FETs with 50 $\mu$m channel width. Interestingly, on scaling down the ZnO channel width down to 100 nm, almost two orders of magnitude enhancement in the linear mobility was observed, which reached $\sim$33.75 cm$^2$/V.s. Such increment in the device performance was attributed to the formation of larger grains and thus reduction in the grain-boundary scattering. Six volatile organic compounds (VOCs) were sensed at room temperature using the direct-write EBL fabricated ZnO devices under UV sensitisation. As the surface-to-volume ratio increases with the decreasing channel width (from 50 $\mu$m to 100 nm), sensing response of the ZnO devices becomes more significant. Ppm level detection of various VOCs was observed; with a 25 ppm level Anisole detection being the lowest concentration. Additionally, using 100 nm device, detection of 10 ppm NO$_2$ was achieved at room temperature. The sensing response towards NO$_2$ was found to be increased with UV illumination and sensor temperature. This led to exhibit $\sim$171 % sensing response for a 2.5 ppm level of NO$_2$.

Los estilos APA, Harvard, Vancouver, ISO, etc.

36

Ma, Jun. "The deposition and electro-optical properties of thin film zinc sulphide phosphors". Thesis, University of Ulster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388877.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

37

Khan, Aurangzeb. "Synthesis, Characterization and Luminescence Properties of Zinc Oxide Nanostructures". Ohio University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1150470597.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

38

Holder, Jenna Ka Ling. "Quantum structures in photovoltaic devices". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:d23c2660-bdba-4a4f-9d43-9860b9aabdb8.

Texto completo

Resumen

A study of three novel solar cells is presented, all of which incorporate a low-dimensional quantum confined component in a bid to enhance device performance. Firstly, intermediate band solar cells (IBSCs) based on InAs quantum dots (QDs) in a GaAs p-i-n structure are studied. The aim is to isolate the InAs QDs from the GaAs conduction band by surrounding them with wider band gap aluminium arsenide. An increase in open circuit voltage (V_OC) and decrease in short circuit current (J_sc) is observed, causing no overall change in power conversion efficiency. Dark current - voltage measurements show that the increase in V_OC is due to reduced recombination. Electroreflectance and external quantum efficiency measurements attribute the decrease in J_sc primarily to a reduction in InGaAs states between the InAs QD and GaAs which act as an extraction pathway for charges in the control device. A colloidal quantum dot (CQD) bulk heterojunction (BHJ) solar cell composed of a blend of PbS CQDs and ZnO nanoparticles is examined next. The aim of the BHJ is to increase charge separation by increasing the heterojunction interface. Different concentration ratios of each phase are tested and show no change in J_sc, due primarily to poor overall charge transport in the blend. V_OC increases for a 30 wt% ZnO blend, and this is attributed largely to a reduction in shunt resistance in the BHJ devices. Finally, graphene is compared to indium tin oxide (ITO) as an alternative transparent electrode in squaraine/ C₇₀ solar cells. Due to graphene’s high transparency, graphene devices have enhanced J_sc, however, its poor sheet resistance increases the series resistance through the device, leading to a poorer fill factor. V_OC is raised by using MoO₃ as a hole blocking layer. Absorption in the squaraine layer is found to be more conducive to current extraction than in the C₇₀ layer. This is due to better matching of exciton diffusion length and layer thickness in the squaraine and to the minority carrier blocking layer adjacent to the squaraine being more effective than the one adjacent to the C₇₀.

Los estilos APA, Harvard, Vancouver, ISO, etc.

39

Yang, Yang y 楊暘. "Atomic structure studies of zinc oxide (0001) polar surface by low energy electron diffraction at multiple incident angles". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48199515.

Texto completo

Resumen

Zinc oxide surfaces have been of considerable interest because of their favorable properties, such as high electron mobility, good transparency, large electronic breakdown field and wide bandgap. Knowing the surface structure of ZnO is the key to better understand the above phenomena and to further develop its applications. In this thesis, the Patterson Function was evaluated by inversion of LEED I-V spectra at multiple incident angles to determine the surface structure of the ZnO(0001) polar surface. The sample was prepared by degassing and then 15 cycles of argon sputtering and annealing. The experimental LEED I-V spectra from multiple incident angles were taken from the sample. After processing the data by a macro program in OPTIMAS and a Matlab program, a clean Patterson Function map showing the inter-atomic pair distances was obtained. It was then compared with the simulated Patterson Function map of the proposed 1×1 bare surface model. As a result, the spots positions in the simulated Patterson Function map matched well with that of the experimental Patterson Function map. On the other hand, the LEED I-V curve fitting work was done by the surface science group of City University of Hong Kong. Six models were proposed by them and normal incidence theoretical LEED I-V spectra were calculated to fit with the experimental LEED I-V curves provided by us. Among the six models 2×2 Zn point defect model was fitted to be the best model with the R-factor 0.244. We also compared the multiple scattering simulated Patterson Function map of 2×2 Zn point defect model with the experimental one to verify the validity of the model. As a result, the model fit the experimental data. So we conclude that in general 1×1 model support the order part, and 2×2 top layer Zn defect model best fits the random missing part.
published_or_final_version
Physics
Master
Master of Philosophy

Los estilos APA, Harvard, Vancouver, ISO, etc.

40

Puli, Surendra K. "Design and synthesis of fluorescent sensors for zinc based on photoinduced electron transfer (PET) /". Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1136090161&sid=2&Fmt=2&clientId=1509&RQT=309&VName=PQD.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

41

Lox, Josephine F. L., Zhiya Dang, Anh Mai Lê, Eileen Hollinger y Vladimir Lesnyak. "Colloidal Cu–Zn–In–S-Based Disk-Shaped Nanocookies". American Chemical Association, 2019. https://tud.qucosa.de/id/qucosa%3A74324.

Texto completo

Resumen

We present a colloidal synthesis of quaternary Cu–Zn–In–S (CZIS) nanoplatelets (NPLs) by means of partial cation exchange. Starting with the synthesis of highly monodisperse binary CuS NPLs with lateral dimensions of ∼64 nm and thickness of ∼5 nm, we further performed a cation exchange reaction in which copper was partly replaced by indium, leading to Cu–In–S NPLs. To enhance the stability of the resulting NPLs and to improve their optical properties, we carried out the ZnS shell growth via both the heterogeneous nucleation of ZnS on the NPLs and via partial cation exchange on the surface of the particles. The latter reaction resulted, however, in rather an alloyed than the core/shell structure, whereas the reaction between zinc and sulfur precursors yielded unusual cookie-like hexagonal shaped structure, in which ZnS trigonal extensions grew only on one of the basal planes of the plates along the thickness direction. Upon ZnS growth, the lateral dimensions of the resulting core/shell CZIS/ZnS and alloyed CZIS NPLs distinctly increased to ∼80 and ∼75 nm, respectively. The analysis of the optical properties of the alloyed CZIS NPLs showed photoluminescence (PL) in the range from 780 to 820 nm depending on the reaction time and temperature. This PL signal originated mainly from small nanoparticles formed as a byproduct in the synthesis. In contrast to the alloyed NPLs, PL measurements of the core/shell CZIS/ZnS platelets showed a weak emission in the near-infrared region (PL maximum at approx. 1110 nm), which so far has rarely been reported for the copper chalcogenide-based two-dimensional structures.

Los estilos APA, Harvard, Vancouver, ISO, etc.

42

Johansen, Jonathan Frederick. "Mathematical modelling of primary alkaline batteries". Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16412/1/Jonathan_Johansen_Thesis.pdf.

Texto completo

Resumen

Three mathematical models, two of primary alkaline battery cathode discharge, and one of primary alkaline battery discharge, are developed, presented, solved and investigated in this thesis. The primary aim of this work is to improve our understanding of the complex, interrelated and nonlinear processes that occur within primary alkaline batteries during discharge. We use perturbation techniques and Laplace transforms to analyse and simplify an existing model of primary alkaline battery cathode under galvanostatic discharge. The process highlights key phenomena, and removes those phenomena that have very little effect on discharge from the model. We find that electrolyte variation within Electrolytic Manganese Dioxide (EMD) particles is negligible, but proton diffusion within EMD crystals is important. The simplification process results in a significant reduction in the number of model equations, and greatly decreases the computational overhead of the numerical simulation software. In addition, the model results based on this simplified framework compare well with available experimental data. The second model of the primary alkaline battery cathode discharge simulates step potential electrochemical spectroscopy discharges, and is used to improve our understanding of the multi-reaction nature of the reduction of EMD. We find that a single-reaction framework is able to simulate multi-reaction behaviour through the use of a nonlinear ion-ion interaction term. The third model simulates the full primary alkaline battery system, and accounts for the precipitation of zinc oxide within the separator (and other regions), and subsequent internal short circuit through this phase. It was found that an internal short circuit is created at the beginning of discharge, and this self-discharge may be exacerbated by discharging the cell intermittently. We find that using a thicker separator paper is a very effective way of minimising self-discharge behaviour. The equations describing the three models are solved numerically in MATLABR, using three pieces of numerical simulation software. They provide a flexible and powerful set of primary alkaline battery discharge prediction tools, that leverage the simplified model framework, allowing them to be easily run on a desktop PC.

Los estilos APA, Harvard, Vancouver, ISO, etc.

43

Johansen, Jonathan Frederick. "Mathematical modelling of primary alkaline batteries". Queensland University of Technology, 2007. http://eprints.qut.edu.au/16412/.

Texto completo

Resumen

Three mathematical models, two of primary alkaline battery cathode discharge, and one of primary alkaline battery discharge, are developed, presented, solved and investigated in this thesis. The primary aim of this work is to improve our understanding of the complex, interrelated and nonlinear processes that occur within primary alkaline batteries during discharge. We use perturbation techniques and Laplace transforms to analyse and simplify an existing model of primary alkaline battery cathode under galvanostatic discharge. The process highlights key phenomena, and removes those phenomena that have very little effect on discharge from the model. We find that electrolyte variation within Electrolytic Manganese Dioxide (EMD) particles is negligible, but proton diffusion within EMD crystals is important. The simplification process results in a significant reduction in the number of model equations, and greatly decreases the computational overhead of the numerical simulation software. In addition, the model results based on this simplified framework compare well with available experimental data. The second model of the primary alkaline battery cathode discharge simulates step potential electrochemical spectroscopy discharges, and is used to improve our understanding of the multi-reaction nature of the reduction of EMD. We find that a single-reaction framework is able to simulate multi-reaction behaviour through the use of a nonlinear ion-ion interaction term. The third model simulates the full primary alkaline battery system, and accounts for the precipitation of zinc oxide within the separator (and other regions), and subsequent internal short circuit through this phase. It was found that an internal short circuit is created at the beginning of discharge, and this self-discharge may be exacerbated by discharging the cell intermittently. We find that using a thicker separator paper is a very effective way of minimising self-discharge behaviour. The equations describing the three models are solved numerically in MATLABR, using three pieces of numerical simulation software. They provide a flexible and powerful set of primary alkaline battery discharge prediction tools, that leverage the simplified model framework, allowing them to be easily run on a desktop PC.

Los estilos APA, Harvard, Vancouver, ISO, etc.

44

Sekhosana, Kutloano Edward. "Photophysical properties of zinc carboxy phthalocyanine-quantum dot conjugates". Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001652.

Texto completo

Resumen

This thesis presents work based on the interactions of water soluble caboxylated zinc phthalocyanines (Pcs) and coreshell quantum dots (QDs). The Pcs are ZnPc(COOH)₈ and ZnPc(COOH)₄ and coreshell QDs are CdTe@ZnS-GSH. GSH = L-glutathione. Characterization and photophysical studies of conjugates were carried out. The approach of coordinating Pcs to QDs was achieved using an organic cross linker, N-N’-dicyclohexylcarbodiimide (DCC) at pH 10 at room temperature. Employing atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, infrared and X-ray photoelectron spectroscopies, the formation of the conjugates was confirmed. Upon conjugation with Pc derivatives, the fluorescence quantum yield of CdTe@ZnS-GSH decreased due to energy transfer from the QDs to the Pc. The average fluorescence lifetime of the CdTe@ZnS-GSH QD also decreased upon conjugation. The föster resonance energy transfer (FRET) behaviour of CdTe@ZnS-GSH-ZnPc(COOH)₄ conjugates was compared to that of CdTe@ZnS-GSH-ZnPc(COOH)₈. Higher FRET efficiencies were observed for CdTe@ZnS-GSH-ZnPc(COOH)₄-mixed or CdTe@ZnS-GSH-ZnPc(COOH)₄-linked compared to the corresponding CdTe@ZnS-GSH-ZnPc(COOH)₈-mixed or CdTe@ZnS-GSH-ZnPc(COOH)₈-linked. Triplet quantum yield (ΦT) and lifetime (ΤT) of ZnPc(COOH)₈ were found to increase in the presence of coreshell QDs. Though the singlet quantum yield (ΦΔ) value of ZnPc(COOH)8 was lower than ΦT , there was a slight upsurge in the ΦT in the presence of QDs.
Microsoft� Word 2010
Adobe Acrobat 9.53 Paper Capture Plug-in

Los estilos APA, Harvard, Vancouver, ISO, etc.

45

To, Chun-kit y 杜俊傑. "Defect studies of single crystal and thin film zinc oxide by positron annihilation spectroscopy and cathodoluminescence". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B4608955X.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

46

Longworth, Sarennah Jane Pearce. "Transmission electron microscopy of potentials at grain boundaries in strontium titanate and zinc oxide electroceramics". Thesis, University of Cambridge, 2007. https://www.repository.cam.ac.uk/handle/1810/252058.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

47

FERREIRA, CARLOS ARTHUR. "Electrosynthese de couches de polypyrrole sur electrodes de fer et de zinc. Application a la protection des metaux". Paris 7, 1991. http://www.theses.fr/1991PA077301.

Texto completo

Resumen

Dans cette these, j'ai montre pour la premiere fois qu'il etait possible de deposer par electropolymerisation anodique du ppy des films de polypyrrole (ppy) epais et extremement adherent sur des metaux oxydables. Cet objectif n'a pu etre atteint qu'apres avoir mis au point des traitements de surface specifiques a chaque metal et qu'apres optimisation du milieu. Dans ce travail j'ai etudie en detail le processus d'electropolymerisation du pyrrole sur des electrodes de fer ou d'acier doux dans differents milieux organiques et montre que le comportement electrochimique du metal etait lie a la basicite du milieu. Le traitement prealable de la surface des electrodes par hno#3 dilue m'a permis de deposer en milieu aqueux et par oxydation electrochimique du pyrrole des films de ppy extremement adherents a la surface du metal. Dans le cas des aciers zingues, nous avons egalement reussi a ralentir suffisamment la corrosion du zinc, grace a un traitement optimal de la surface et a deposer des films de polypyrrole en milieu organique et aqueux. En introduisant par ailleurs dans le milieu d'electrolyte une faible proportion de pyrroles fonctionnalises en position 2 par des groupes cooh et nh#2, j'ai montre une amelioration considerable des proprietes de protection de ces films de ppy contre la corrosion. Le comportement de l'acier recouvert de ppy, puis d'une couche de cataphorese organique est alors comparable a celui du metal phosphate, revetu de la meme couche de cataphorese. En realisant l'etude (ir, xps) des films ppy et des surfaces metalliques j'ai propose une interpretation coherente de ces phenomenes de deposition et d'adherence des films de ppy sur les metaux oxydables

Los estilos APA, Harvard, Vancouver, ISO, etc.

48

Fernando, Joseph F. S. "Crystal seeding and photochemistry of gold-zinc oxide hybrid nanoparticles". Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/101206/1/Joseph_Fernando_Thesis.pdf.

Texto completo

Resumen

This project investigated the synthesis of hybrid nanoparticles of gold and zinc oxide by using photodeposition and crystal seeding approach. The study extended our understanding of the factors that determine nanocrystal size, shape and ratio of gold and zinc oxide in the hybrid system. Control at this scale is important from a materials-engineering viewpoint and for technological applications such as nonlinear optics, photocatalysis and photovoltaics. This research found that nonlinear optical absorption of zinc oxide can be enhanced by several orders of magnitude by coupling zinc oxide nanoparticles to gold nanoparticles.

Los estilos APA, Harvard, Vancouver, ISO, etc.

49

Halls, Daniel Charles. "Remote Electron Beam Induced Current (REBIC) and cathodoluminescence studies of some zinc oxide and varistor ceramics". Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/8008.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

50

Cook, Charles D. "Design and synthesis of photo-induced electron transfer based fluorescent probes for pyruvate and zinc detection /". Available to subscribers only, 2007. http://proquest.umi.com/pqdweb?did=1407498711&sid=5&Fmt=2&clientId=1509&RQT=309&VName=PQD.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

Tesis sobre el tema "Electrode de zinc"

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros