Tesis sobre el tema "Cathodes hybrides"

La pollution de l'eau par les nitrates représente un défi environnemental majeur et constitue l'une des dix violations les plus courantes de la qualité de l'eau dans le monde. Ce défi offre une opportunité pour l'économie circulaire, car l'électrolyse des nitrates a été proposée comme une méthode durable pour la valorisation des effluents contaminés par les nitrates grâce à la production décentralisée et simultanée d'ammoniac (un produit chimique de base). En particulier, la réduction électrochimique des nitrates (REN) est une stratégie prometteuse et durable pour résoudre le problème critique de la pollution des sources d'eau par les nitrates. Plusieurs matériaux abondants sur Terre, tels que le cuivre et l'étain, ont été proposés comme matériaux électrocatalytiques adaptés pour la REN. Jusqu'à présent, la plupart des études électrochimiques fondamentales ont été menées dans des conditions potentiostatiques. En revanche, cette étude présente une évaluation de la REN dans des conditions galvanostatiques pour atteindre des conditions opérationnelles plus représentatives pour des systèmes ingénierisés de plus grande envergure. Cependant, cela provoque l'apparition de la réaction concomitante de dégagement de l'hydrogène (HER), qui se produit à un potentiel thermodynamique similaire à celui de la REN. Ainsi, l'efficacité faradique de la REN diminue considérablement dans des conditions galvanostatiques réalistes en raison de la concurrence avec la HER. Ce projet aborde ce défi fondamental en électrocatalyse et propose une nouvelle stratégie basée sur l'immobilisation de molécules ioniques à base d'imidazolium sur la surface de la cathode pour inhiber sélectivement la HER et améliorer la REN. Notamment, cette recherche explore une gamme de matériaux de cathodiques hybrides, y compris des électrodes à base de carbone et de métal sous forme de plaques 2D et de mousses 3D, reconnues pour leur potentiel dans les applications réelles de la REN. Le succès de l'immobilisation de la couche organique ionique sur les cathodes a été confirmé par différentes techniques de caractérisation physico-chimiques et par une évaluation subséquente de l'activité et de la sélectivité électrocatalytiques, démontrant une sélectivité et une efficacité faradique améliorées pour la production d'ammoniac sur les cathodes hybrides, deux fois supérieures à celles du matériau d'électrode nu pour la REN dans les mêmes conditions expérimentales
Nitrate pollution in water represents a significant environmental challenge and is one of the top ten most common water quality violations worldwide. This challenge offers an opportunity for the circular economy as nitrate electrolysis has been suggested as a sustainable method for valorization of nitrate-contaminated effluents by simultaneous decentralized ammonia production (a commodity chemical). In particular, the electrochemical reduction of nitrate (ERN) is a promising and sustainable strategy for addressing the critical issue of nitrate pollution in water sources. Several earth abundant materials such as copper and tin have been suggested as suitable electrocatalytic materials for ERN. Mostly fundamental electrochemical studies under potentiostatic conditions are reported so far. In contrast, this study presents ERN evaluation under galvanostatic conditions for achieving more representative operational conditions for larger engineered systems. However, this provokes the appearance of the concomitant hydrogen evolution reaction (HER), which takes place at a similar thermodynamic potential than ERN. Thus, faradaic efficiency for ERN significantly diminishes under realistic galvanostatic conditions due to the competition with HER. This project addresses this fundamental challenge in electrocatalysis and proposes a novel strategy based on the immobilization of imidazolium-based ionic molecules on the surface of the cathode to selectively inhibit HER and enhance ERN. Notably, this research explores a range of hybrid cathode materials, including 2D plate and 3D foam carbon- and metal-based electrodes, which are recognized for their potential in real world applications for ERN. The success of the ionic organic layer immobilization onto the cathodes was confirmed through different physicochemical characterization techniques and subsequent electrocatalytic activity and selectivity evaluation, which demonstrated an enhanced selectivity and faradaic efficiency for ammonia production on hybrid cathodes twice as much as the bare electrode material for ERN under the same experimental conditions

The proton exchange membrane fuel cell (PEMFC) is considered to be a promising power device with a broad range of applications. However, there are still a number of challenges especially concerning performance, cost, and reliability of these systems. The redox flow battery utilizes fundamentally simpler chemistry, but has limitations in terms of membranes/materials used in system construction and in terms of redox regeneration requirements. The hybridization of a PEMFC anode with a redox flow battery cathode, replacing the limiting oxygen electrode, leads to both advantages and compromises in performance. Although there are improvements in kinetics, cell and systems design, and cost, there are restrictions imposed by the regeneration method and membrane contamination. In this work, the Fe³⁺/Fe²⁺ redox fuel cell cathode is characterized over a range of electrolyte concentrations, operating conditions, and electrode materials. A Fe³⁺/Fe²⁺ simulated bio-electrolyte and a simple electrolyte catholyte are studied using CV and ETS to determine kinetic parameters for the electrolyte cathode redox couple, while a prototype single cell fuel cell is used to demonstrate actual fuel cell performance. Electrochemical data shows the effect of ferric ion complexation! polymerization on the operation of both electrolyte systems. The results show that the heterogeneous electron transfer rate constant and diffusion coefficient as well as interface properties all increase with the ratio of total anion species (S0₄²⁻,HS0₄⁻)to ferric species. Fuel cell testing showed no significant difference in performance between the two systems opening up various possibilities for redox species regeneration. Improvements are also achieved through optimization of cathode materials and operating conditions. This hybrid system, part of a strategic NSERC grant (Novel biofuel cell - methane reforming reactor system for electricity generation, #GHGPJ 269967 — 03)(1), showed promising performance even though components such as the membrane were not optimized. Power densities of greater than 0.25 W/cm² were achieved with no platinum group metals on the cathode. In addition, the liquid redox cathode eliminates the need for external humidification and separate cooling for the fuel cell and provides greater design flexibility. Different aspects of the redox cathode were characterized and showed opportunity for further performance improvement.

Increasing mechanical, economic and environmental requirements lead to multi material designs, wherein different classes of materials and manufacturing processes are merged to realize lightweight components with a high level of functional integration. Particularly in automotive industry the use of corresponding technologies will rise in the near future, as they can provide a significant contribution to weight reduction, energy conservation and therefore to the protection of natural resources. Especially the use of continuous fiber reinforced polymers (FRP) with thermoplastic matrices offers advantages for automotive components, due to its good specific characteristics and its suitability for mass production. In conjunction with isotropic materials, such as steel or aluminum, optimized lightweight structures can be produced, whose properties can be easily adapted to the given component requirements. The present paper deals with the development of innovative hybrid laminates with low residual stresses, made of thin-walled steel sheets and glass fiber reinforced thermoplastic (GFRP) prepregs layers. Thereby the interlaminar shear strength (ILSS) was increased by an optimization of the FRP/metal-interfaces, carried out by examining the influence of several pre-operations like sanding, cleaning with organic solvents and applying primer systems. Based on these findings optimized compound samples were prepared and tested under realistic Cathodic dip paint conditions to determine the influence on the ILSS.

This thesis presents experimental and modelling research on atmospheric pressure hollow cathodes and hollow electrodes. Experiments with the hybrid hollow electrode activated discharge (H-HEAD), which is a combination of a hollow cathode and a microwave plasma source, is presented. The experiments show that this source is able to produce long plasma columns in air and nitrogen at atmospheric pressure and at very low gas flow rates. Measurements of the vibrational temperature of the nitrogen molecules are also presented in this thesis. The vibrational temperature is an indication of the electron temperature in the plasma, an important characteristic of the plasma. Modelling work on the hollow cathode at atmospheric pressure with fluid equations is also presented. It is shown that the inclusion of fast and secondary electrons, characteristic of the hollow cathode plasmas, increases the sheath width. The sheath width was found to be of the order of 100 μm. By modelling the plasma as highly collisional by using the drift-diffusion approximation, it was shown that the increase in sheath thickness was larger at lower pressures than at higher pressures. Still, the sheath width can be of the order of 100 μm. A pulsed atmospheric plasma in a hollow electrode geometry was also modelled by the drift-diffusion fluid equations, with the addition of the energy equation for electrons. Rate and transport coefficients for the electrons were calculated from the solution to the Boltzmann equation as functions of mean electron energy. The dynamics of the plasma at pulse rise time showed large electron density and mean energy peaks at the cathode ends, but also that these quantities were enhanced at the centre of the discharge, between the cathode plates.

Cette thèse est consacrée à la fabrication ascendante (bottom-up) de matériaux nanostructurés hybrides hiérarchisés à base de nanotubes de carbone alignés verticalement (VACNTs) décorés par des nanoparticules (NPs). En fonction de leur utilisation comme cathode ou anode, des nanoparticules de soufre (S) ou silicium (Si) ont été déposées. En raison de leur structure unique et de leurs propriétés électroniques, les VACNTs agissent comme une matrice de support et un excellent collecteur de courant, améliorant ainsi les voies de transport électroniques et ioniques. La nanostructuration et le contact du S avec un matériau hôte conducteur améliore sa conductivité, tandis que la nanostructuration du Si permet d'accommoder plus facilement les variations de volume pendant les réactions électrochimiques. Dans la première partie de la thèse, nous avons synthétisé des VACNTs par une méthode de dépôt chimique en phase vapeur (HF-CVD) directement sur des fines feuilles commerciales d'aluminium et de cuivre sans aucun prétraitement des substrats. Dans la deuxième partie, nous avons décoré les parois latérales des VACNTs avec différents matériaux d'électrode, dont des nanoparticules de S et de Si. Nous avons également déposé et caractérisé des nanoparticules de nickel (Ni) sur les VACNTs en tant que matériaux alternatifs pour l'électrode positive. Aucun additif conducteur ou aucun liant polymère n'a été ajouté à la composition d'électrode. La décoration des nanotubes de carbone a été effectuée par deux méthodes différentes: méthode humide par électrodéposition et méthode sèche (par dépôt physique en phase vapeur (PVD) ou par CVD). Les structures hybrides obtenues ont été testées électrochimiquement séparément dans une pile bouton contre une contre-électrode de lithium. A notre connaissance, il s'agit de la première étude de l'évaporation du soufre sur les VACNTs et de la structure résultante (appelée ici S@VACNTs). Des essais préliminaires sur les cathodes nanostructurées obtenues (S@VACNTs revêtus d'alumine ou de polyaniline) ont montré qu'il est possible d'atteindre une capacité spécifique proche de la capacité théorique du soufre. La capacité surfacique de S@VACNTs, avec une masse de S de 0.76 mg cm-2, à un régime C/20 atteint une capacité de 1.15 mAh cm-2 au premier cycle. Pour les anodes nanostructurées au silicium (Si@VACNTs), avec une masse de Si de 4.11 mg cm-2, on montre une excellente capacité surfacique de 12.6 mAh cm-2, valeur la plus élevée pour les anodes à base de silicium nanostructurées obtenues jusqu'à présent. Dans la dernière partie de la thèse, les électrodes nanostructurées fabriquées ont été assemblées afin de réaliser la batterie complète (Li2S/Si) et sa performance électrochimique a été testée. Les capacités surfaciques obtenues pour les électrodes nanostructurées de S et de Si ouvrent la voie à la réalisation d'une LIB à haute densité d'énergie, entièrement nanostructurée, et démontrent le grand potentiel du concept proposé à base d'électrodes nanostructurées hybrides hiérarchisées
This thesis is devoted to the bottom-up fabrication of hierarchical hybrid nanostructured materials based on active vertically aligned carbon nanotubes (VACNTs) decorated with nanoparticles (NPs). Owing to their unique structure and electronic properties, VACNTs act as a support matrix and an excellent current collector, and thus enhance the electronic and ionic transport pathways. The nanostructuration and the confinement of sulfur (S) in a conductive host material improve its conductivity, while the nanostructuration of silicon (Si) accommodates better the volume change during the electrochemical reactions. In the first part of the thesis, we have synthesized VACNTs by a hot filament chemical vapor deposition (HF-CVD) method directly over aluminum and copper commercial foils without any pretreatment of the substrates. In the second part, we have decorated the sidewalls and the surface of the VACNT carpets with various LIB's active electrode materials, including S and Si NPs. We have also deposited and characterized nickel (Ni) NPs on CNTs as alternative materials for the cathode electrode. No conductive additives or any polymer binder have been added to the electrode composition. The CNTs decoration has been done systematically through two different methods: wet method by electrodeposition and dry method by physical vapor deposition (PVD). The obtained hybrid structures have been electrochemically tested separately in a coin cell against a lithium counter-electrode. Regarding the S evaporationon VACNTs, and the S@VACNTs structure, these topics are investigated for the first time to the best of our knowledge.Preliminary tests on the obtained nanostructured cathodes (S@VACNTs coated with alumina or polyaniline) have shown that it is possible to attain a specific capacity close to S theoretical storage capacity. The surface capacity of S@VACNTs, with 0.76 mg cm-2 of S, at C/20 rate reaches 1.15 mAh cm-2 at the first cycle. For the nanostructured anodes Si@VACNTs, with 4.11 mg cm-2 of Si showed an excellent surface capacity of 12.6 mAh cm-2, the highest value for nanostructured silicon anodes obtained so far. In the last part of the thesis, the fabricated nanostructured electrodes have been assembled in a full battery (Li2S/Si) and its electrochemical performances experimentally tested. The high and well-balanced surface capacities obtained for S and Si nanostructured electrodes pave the way for realization of high energy density, all-nanostructured LIBs and demonstrate the large potentialities of the proposed hierarchical hybrid nanostructures' concept

Galvanic anode technology has in recent years come to the fore as a cost-effective method of successfully mitigating the corrosion of reinforcing steel in concrete structures. Developments in the field of cathodic protection have included the introduction of a novel Hybrid anode system, which uses the same sacrificial anode to pass a short-term impressed current before being connected to the steel directly to provide a long-term galvanic current. Galvanic and hybrid technologies are often seen as less powerful solutions in the treatment of reinforcement corrosion, and the test methodologies which determine the efficacy of cathodic protection systems favour impressed current technologies. The work completed has investigated the application of traditional and novel corrosion assessment techniques to laboratory samples to assess the protection offered by the hybrid treatment methodology in both treatment phases. In addition, the response of both galvanic and hybrid anodes to environmental conditions has been recorded and assessed before being discussed in the context of steel protection criteria. Finally, an investigation is presented into the on-site deterioration of commercially pure titanium feeder wire installed as part of the hybrid anode system and potential solutions to the problem have been documented. The research undertaken found that the hybrid anode system is capable of protecting steel in challenging, aggressive environments. This was confirmed by steel corrosion rate and indicative steel potential measurements. The responsive behaviour investigation showed that the current output of galvanic and hybrid anodes responds rapidly to changes in the corrosion risk posed to the steel and that this has a direct effect on anode system lifetimes. An assessment of the polarisation-based protection criteria applied to steel in concrete has found that the standard inhibits the use of responsive behaviour, and that revisions which consider the present risk of steel corrosion by considering the corrosion current resulting from the relative aggressivity of the concrete environment would be more valid in their application. A cathodic protection system based on the concepts of pit re-alkalisation and pH maintenance can fully utilise galvanic anode responsive behaviour. It was discovered that the deterioration of commercially pure titanium feeder wire seen on site installations was due to anodising in the presence of chloride media which had the potential to lead to pitting corrosion. The pitting risk varied depending on the duration of the treatment and proximity to the installed anode. An anodically grown oxide delayed the onset of corrosion in aqueous KBr solution, but did not significantly increase the pitting potential.

Magister Scientiae - MSc (Chemistry)
This research was based on the development and characterization of graphenised lithium iron phosphate-lithium manganese silicate (LiFePO4-Li2MnSiO4) hybrid cathode materials for use in Li-ion batteries. Although previous studies have mainly focused on the use of a single cathode material, recent works have shown that a combination of two or more cathode materials provides better performances compared to a single cathode material. The LiFePO4- Li2MnSiO4 hybrid cathode material is composed of LiFePO4 and Li2MnSiO4. The Li2MnSiO4 contributes its high working voltage ranging from 4.1 to 4.4 V and a specific capacity of 330 mA h g-1, which is twice that of the LiFePO4 which, in turn, offers its long cycle life, high rate capacity as well as good electrochemical and thermal stability. The two cathode materials complement each other's properties however they suffer from low electronic conductivities which were suppressed by coating the hybrid material with graphene nanosheets. The synthetic route entailed a separate preparation of the individual pristine cathode materials, using a sol-gel protocol. Then, the graphenised LiFePO4-Li2MnSiO4 and LiFePO4-Li2MnSiO4 hybrid cathodes were obtained in two ways: the hand milling (HM) method where the pristine cathodes were separately prepared and then mixed with graphene using a pestle and mortar, and the in situ sol-gel (SG) approach where the Li2MnSiO4 and graphene were added into the LiFePO4 sol, stirred and calcined together.
2021-04-30

Cette thèse s’insère dans un projet d’élaboration et de caractérisation des cellules photovoltaïques organiques classiques et inverses, plus précisément il s’agit d’améliorer les performances des cellules via des couches tampons anodiques et cathodiques originales. Nous avons commencé d’améliorer les couches tampons cathodiques avec différents donneurs d’électrons: phtalocyanine de cuivre CuPc, subphtalocyanine SubPc et dérivés de thiophène organiques. Dans le premier cas de donneur d’électrons (CuPc), nous avons mis en évidence l’effet d’une fine couche d’un composé de césium, utilisée comme couche tampon cathodique dans des cellules inverses, sur la collecte des électrons après un traitement thermique. Nous avons montré aussi que la couche tampon cathodique hybride, Alq3 (9nm) / Ca (3nm) améliore les performances des cellules quelque soit le donneur d’électrons et sans nécessité de recuit. Dans le cas de drivés de thiophène, nous avons montré comment la morphologie de surface des couches organiques peut influencer les performances des cellules photovoltaïques organiques. Et dans le cas de SubPc utilisé dans des cellules inverses, nous avons étudié l’effet de la vitesse de dépôt de la couche SubPc sur sa morphologie. Concernant l’amélioration de la couche tampon anodique, nous avons étudié des cellules classiques à base SubPc et du pentathiophene (5T). Après l’optimisation de l’épaisseur des donneurs d’électrons, nous avons montré que la bicouche MoO3 (3 nm) / Cul (1,5 nm) utilisée comme couche tampon anodique, permet d'améliorer les performances des cellules, quelque soit le donneur d’électrons. Dans le cas du SubPc, nous avons obtenu un rendement qui approche de 5%
This thesis concerns elaboration and characterization of classical and inverse organic photovoltaic cells, specifically improving the anodic and cathodic buffer layers. We started by improving the cathode buffer layers with different electron donors: copper phthalocyanine CuPc, subphtalocyanine SubPc and thiophene derivatives (BSTV and BOTV). In the first case of electron donor (CuPc), we highlighted the effect of the thin layer of cesium compound, used as a cathodic buffer layer in inverse cells, on the collection of electrons after heat treatment.We have also shown that the hybrid cathodic buffer layer, Alq3 (9 nm) / Ca (3nm) improves the cell performance whatever the electron donor without annealing. In the case of thiophene derivatives, we have shown how the morphology of the organic layers surface can influence the performance of organic photovoltaic cells. In the case of SubPc used in inverse cells, we studied the effect of the deposition rate of the layer on the morphology of SubPc surface.Regarding the improvement of the anodic buffer layers, we investigated those based on the SubPc and pentathiophene (5T) in classical cells. After optimization of the electron donors thickness, we have shown that the bilayer MoO3 (3 nm) / CuI (1.5 nm) used as an anodic buffer layer, improves cell performances, whatever the electron donor. In the case of SubPc, we obtained a efficiency approaching 5%

The Z-accelerator at Sandia National Laboratories (SNL), is a high-current pulsed power machine used to drive a range of high energy density physics (HEDP) experiments [1]. To achieve peak currents of >20MA, in a rise time of ~100ns, the current is split over four levels of transmission line, before being added in parallel in a double-post-hole convolute (DPHC) and delivered to the load through a single inner magnetically insulated transmission line (MITL). The electric field on the cathode electrode, >107Vm-1, drives the desorption and ionisation of neutral contaminants to form a plasma from which electrons are emitted into the anode-cathode (a-k) gap. The current addition path in the DPHC forms magnetic 'null' regions, across which electrons are lost to the anode, shunting current from the inner MITL and load. In experiment, current losses of >10% have been measured within the convolute; this reduces the power delivered to the load, negatively impacting the load performance, as well as complicating the prediction of the Poynting flux used to drive detailed magneto-hydrodynamic (MHD) simulations [2, 3]. In this thesis we develop 3-dimensional (3D) Particle-in-Cell (PIC) and hybrid fluid-PIC computer models to simulate the plasma evolution in the DPHC and inner MITL. The expected experimental current loss at peak current was matched in simulations where Hydrogen plasma was injected from the cathode elec- trode at a rate of 0.0075mlns-1 (1ml=1015cm-2), with an initial temperature of 3eV. The simulated current loss was driven by plasma penetrating the downstream side of the anode posts, reducing the effective a-k gap spacing and enhancing electron losses to the anode. The current loss at early time (<10MA), was matched in simulations where space-charge-limited (SCL) electron emission was allowed directly from the cathode; to match the loss over the entire current pulse, a delay model is motivated. Here, plasma injection was delayed after the start of SCL emission, based on realistic plasma expansion velocities of ~3cmμs-1. The PIC model, which was necessary to accurately simulate the kinetic behaviour of the lower density plasma and charged particle sheaths, was computationally intensive such that the spatial resolutions achieved in the 3D simulations were relatively poor. With the aim of reducing the computational overhead, allowing finer spatial resolutions to be accessed, we investigate the applicability of hybrid techniques to simulating the cathode plasma in the convolute. Our PIC model was both implemented in the resistive MHD code, Gorgon, where part of the plasma was modelled in the single fluid approximation, and extended to include an inertial two-fluid description of the plasma. The hybrid models were applied to the DPHC simulations, the results from which are used to motivate a three component model; here, the densest part of the convolute plasma is modelled using the single fluid MHD approximation, transitioning to a fully kinetic PIC description of the lower density plasma and charged particle sheaths, linked by a two-fluid description.

In our proton exchange membrane (PEM) fuel cells, the electrolyte is a catalyst platinum (Pt) coated nafion membrane. In order to increase the electrochemically active catalyst area to enhance the cell performance but without sacrificing the electrical conductivity of the membrane, carbon thin films were deposited onto the membrane by using the filtered cathodic vacuum arc deposition (FCVAD) technique. With varying the deposition conditions, it was possible to form porous carbon films and nanoisland and nanorod structure surface which increased the catalyst area when a higher He working gas pressure and a low number of pulses were used. Based on this result, hybrid C-Mo thin films were deposited for further enhancing the Pt catalytic effect. Under the varied deposition conditions, the surface morphology and C and Mo grain sizes of the hybrid thin films were measured and their relations with the catalytic performance were studied. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34867

Les matériaux nanocomposites présentent des propriétés physico-chimiques uniques qui ne peuvent être obtenues en utilisant un seul composant. Ainsi, l'amélioration des propriétés de ces matériaux a suscité un intérêt majeur dans différents domaines. Les matériaux nanocomposites diélectriques à haute densité d'énergie présentent des performances prometteuses pour les applications de stockage d'énergie. Des efforts importants ont été menés pour combiner la constante diélectrique élevée de la céramique avec la flexibilité et la facilité de mise en œuvre des polymères. Ainsi, cette thèse porte sur le développement et la caractérisation de nanocomposites à base de céramique BaTiO3 et de polymères fluorés. Dans un premier temps, la synthèse de PVDF-g-BaTiO3 a été réalisée en utilisant la polymérisation RAFT du VDF à partir de la surface des nanoparticules fonctionnalisées, en utilisant différentes concentrations en BaTiO3, et l'effet de ce pourcentage sur les propriétés finales a été étudié. Les résultats ont montré que le greffage du PVDF a été réalisé avec succès, conduisant à des nanocomposites avec une stabilité thermique améliorée. De plus, le succès du greffage du PVDF a été principalement prouvé par la spectroscopie RMN HRMAS, qui a été utilisée pour la première fois pour caractériser les nanocomposites préparés. Les propriétés diélectriques de ces matériaux ont été étudiés et révèlent l'existence de trois relaxations : la première a été attribué à la relaxation secondaire β dans le PVDF, la seconde a été liée à la fraction cristalline dans le polymère, tandis que la troisième relaxation a été attribué à la polarisation interfaciale résultant de la présence de charges et d'impuretés dans le système. Cependant, la relaxation liée à la température de transition vitreuse n'a pas pu être observé en raison de la cristallinité élevée du polymère. Le procédé de mélange en solution a été également utilisé pour préparer des matériaux nanocomposites constitués de PVDF-g-BaTiO3/P(VDF-co-HFP) et les films préparés ont été entièrement caractérisés. La dispersion uniforme des nanocomposites PVDF-g-BaTiO3 dans la matrice de copolymère a conduit à des performances mécaniques améliorées. Ensuite, pour fournir une application pour les nanocomposites PVDF-g-BaTiO3 préparés, ces derniers ont été utilisés comme liant pour préparer un matériau de cathode pour les batteries. La procédure de calandrage a été utilisée pour préparer les films d'électrode et a permis d'obtenir une structure uniforme et des performances de cyclage améliorées
Nanocomposite materials present unique physic-chemical properties that cannot be obtained using one component. Thus, the improvement in the properties of such materials have resulted in major interest for versatile fields. Dielectric nanocomposite materials with high energy density exhibit promising performances for energy storage applications. Major efforts have been conducted to combine the efficient properties and high dielectric constant of ceramics with the flexibility and easy processing of polymers. Thus, this thesis focuses on the development and characterizations of nanocomposites based on BaTiO3 ceramic and fluoropolymers. First, the synthesis of PVDF-g-BaTiO3 was realized using RAFT polymerization of VDF from the surface of functionalized nanoparticles, using different BaTiO3 concentrations, and the effect of such percentage on the final properties was studied. Results showed the successful grafting of PVDF leading to nanocomposites with enhanced thermal stability. Furthermore, the successful grafting of PVDF onto the functionalized nanoparticles was mainly proved by HRMAS NMR spectroscopy, which was used for the first time to characterize the prepared nanocomposites. The dielectric properties of such materials were investigated, and reveals the existence of three relaxations: the first one was attributed to the well-known β secondary relaxation in PVDF, the second one was assigned to the crystalline fraction in the polymer, while the third relaxation was assigned to interfacial polarization arising from the presence of fillers and impurities in the system. However, the relaxation related to glass transition temperature could not be observed due to the high crystallinity of the polymer. Solution blending strategy was also used to prepare nanocomposite materials consisting of PVDF-g-BaTiO3/P(VDF-co-HFP) and the prepared films were fully characterized. The uniform distribution of PVDF-g-BaTiO3 nanocomposites in the copolymer matrix leads to enhanced mechanical performances resulting in increased Young’s modulus. Then, to supply an application for the prepared PVDF-g-BaTiO3 nanocomposites, those later were used as binder to prepare cathode material for batteries. Calendering procedure was used to prepare the electrode films and enabled to obtain uniform structure and enhanced cycling performances

Mestrado em Engenharia Física
Os objetivos principais deste trabalho são a produção de nanoestruturas híbridas de carbono compostas por grafeno e agregados de diamante nanocristalino, bem como a sua caracterização estrutural, morfológica e como cátodos frios. Estas estruturas híbridas poderão ter um interesse tecnológico muito elevado uma vez que reúnem no mesmo material estruturas de carbono com propriedades físicas muito distintas. Entre as várias aplicações possíveis destes híbridos destaca-se a sua utilização na fabricação de dispositivos baseados na emissão de eletrões por efeito de campo (Field Emission Devices - FEDs). Para cumprir os objetivos do trabalho fez-se a síntese simultânea do grafeno com agregados de diamante nanocristalino (NCD) utilizando a técnica de deposição química em fase de vapor ativada por micro-ondas (MPCVD) e explorou-se o método de fluxo pulsado para controlar a quantidade de metano e desta forma a densidade e tamanho dos agregados. Os substratos utilizados são de Cu policristalino sobre os quais se cresceu um filme fino de grafeno com agregados de NCD. As estruturas desenvolvidas foram caracterizadas recorrendo à microscopia eletrónica de varrimento e à espetroscopia de Raman. Foi ainda avaliada a densidade de corrente em função do campo elétrico da emissão eletrónica por efeito de campo de todas as amostras sintetizadas. Os resultados obtidos demonstraram que é possível crescer em simultâeo os dois tipos de alótropos de carbono (agregados de NCD e grafeno) e que é possível controlar o diâmetro e a densidade de agregados de NCD. Em particular, detetou-se experimentalmente o aumento da densidade e diâmetro de agregados em função de número de ciclos, o aumento da densidade de agregados e diminuição do seu diâmetro tanto em função do tempo de CH4 (tempo do On) como do valor do seu fluxo. O estudo da emissão por efeito de campo mostrou uma correlação entre a densidade de agregados e a densidade de corrente elétrica, tendo-se atingido valores da ordem dos 10-5 A/cm2. É de notar que se detetou uma diminuição no campo elétrico de ativação e um aumento na densidade máxima de corrente com o nº de ciclos e com o tempo de CH4 introduzido na síntese. Por outro lado, observou-se um aumento do fator de amplificação de campo em função do nº de ciclos e a sua diminuição em função de tempo de CH4. O estudo efetuado neste trabalho revelou que este híbrido tem um bom potencial para ser usado como cátodo frio, nomeadamente no que concerne à corrente máxima de emissão. Contudo, o desenvolvimento de um dispositivo com base neste material requer ainda um processo de otimização.
The main objectives of this work are the production of a hybrid carbon nanostructure composed by graphene and monocrystalline diamond clusters along with their structural and morphological characterization and as a cold cathode. This hybrid structure may have a very large technological interest since it congregates on the same material phases with very different physical properties. Among the many possible applications for this hybrid the manufacture of Field Emission Devices (FEDs) stands out. To fulfill the work objectives, the simultaneous synthesis of graphene with nanocrystalline diamond clusters (NCD) was done using the chemical vapor deposition technique activated by microwave plasma CVD (MPCVD) and the pulsed flow method was explored for controlling methane delivery. The used substrates were polycrystalline Cu on which it was deposited a thin film of graphene with NCD clusters. The developed structures were characterized using scanning electron microscopy (SEM) and Raman spectroscopy. The field emission current density was measured as a function of the electric field for all synthetized samples. The results demonstrated that it is possible to grow simultaneously the two types of carbon allotropes (NCD clusters and graphene) and to control the diameter and density of NCD. In particular, it was experimentally detected an increase of both clusters’ density and diameter with the number of cycles. Alongside, an increase of clusters´ density and a decrease of clusters´ diameter were observed with CH4 duty cycle and total flow. The study of field emission puts in evidence a correlation between the clusters density and the emission current, attaining densities in the order of 10-5 A/cm2. It is noteworthy a decrease of the activation current electric field and an increase of the current´s density maximum value with the number of cycles and CH4 duty cycle. On the other hand, the field enhancement factor was observed to increase with the number of cycles and to decrease with the methane duty cycle. The study undertaken in this work revealed that this hybrid has a high potential to be used as cold cathode, namely in what concerns the maximum emission current. However, a full development of a device based on this hybrid material still requires a process optimization.

Le travail de cette thèse, financé l’ANR-20-CE05-0012 ADELINE, porte sur l’élaboration d’unenouvelle génération de lampes fluorescentes exemptes de Hg et Ga. Elle s’appuie sur l’émission UV + Visibled’une décharge moléculaire à basse pression et sur la conversion subséquente dans le domaine du Visible par desluminophores adaptés au spectre d’émission de la décharge. L’utilisation d’émetteurs moléculaires, généralementréactifs à haute température, exige le remplacement de la cathode chaude telle qu’utilisée dans les lampesfluorescentes Ar-Hg. L’originalité de ce travail consiste dans sa substitution par un applicateur d’onde de hautefréquence (HF) pour produire un plasma comparable à celui de lueur négative (LN), mais à chute cathodiquefortement réduite (cathode froide sans bombardement ionique). Ce plasma peut être avantageusement complétépar un plasma de colonne positive (CP) obtenu lorsqu’une alimentation hybride HF&DC est appliquée. Dans cetravail, une décharge HF à onde de surface obtenue par un changement de configuration de l’applicateur estégalement proposée et étudiée pour l’application à l’éclairage. L’objectif était la maximisation de l’efficacitélumineuse de la lampe, ce qui passe par l’optimisation à la fois du flux énergétique de la décharge et de laconversion UV-Visible par les luminophores. Une part importante du travail de thèse a été donc consacrée à ladétermination, par différentes approches expérimentales et numériques, des conditions opératoires (géométrie del’applicateur d’onde HF et du tube de décharge, tension DC) en vue de l’optimisation du flux énergétique de ladécharge. L’étude conduite dans l’Ar pur a démontré l’apport énergétique favorable du plasma de CP(rendement énergétique de 6% pour une décharge HF&DC contre 1,5 % pour une décharge HF), apport d’autantplus bénéfique que la longueur de la CP est grande. Toutefois, l’écart important d’émission obtenu dans nosconditions de travail entre les différentes zones de la décharge (LN et CP) rend finalement les décharges HF àonde de surface plus appropriées à l’application visée (rendement énergétique de 12% pour une décharge HF àonde de surface contre 6% pour une décharge HF&DC). L’étude de mélanges réactifs a clairement démontrél’avantage du mélange Ar-S₂ sur le mélange Ar-N₂/O₂. Cet avantage résulte d’une meilleure répartition spectralede l’émission pour Ar-S2 avec un impact avantageux, d’une part, sur le rendement énergétique d’émission de ladécharge dans le domaine UV+Visible (émission IR réduite) et, d’autre part, sur le rendement de conversion parles luminophores. Un mélange approprié de luminophores d’absorption UV a permis l’élaboration d’un dispositifde lampe (décharge HF à onde de surface en tube scellé) des performances visuelles proches de celles deslampes Ar-Hg. Comparativement, l’efficacité lumineuse de la lampe à onde de surface mise en œuvre estnettement inférieure à cause de deux principaux facteurs : rendement électrique de la décharge HF et rendementénergétique d’émission. Le 1er est fortement limité par des contraintes technologiques qui, par exemple, n’ontpas permis d’éradiquer les fuites de rayonnement HF et le 2ème est inhérent à la dépense énergétique requise pourla dissociation de S₈ en S₂
This thesis, funded by the ANR-20-CE05-0012 ADELINE project, focuses on the development of anew generation of mercury- and gallium-free fluorescent lamps. It is based on the UV + Visible emission from alow-pressure molecular discharge and its conversion into the visible range through phosphors suited to theemission spectrum of the discharge. The use of molecular emitters, typically reactive at high temperatures,requires the replacement of the hot cathode, as used in Ar-Hg fluorescent lamps. This work lies in thesubstitution of the hot cathode with a high-frequency (HF) wave applicator, which generates a plasmacomparable to that of a negative glow (NG) but with a significantly reduced cathode fall. This plasma can beadvantageously used with a positive column (PC) plasma, achieved when a hybrid HF&DC power supply isapplied. Additionally, a surface-wave HF discharge, obtained by modifying the applicator configuration, isproposed and studied for lighting applications. The aim was to maximize the luminous efficiency of the lamp,which involved optimizing both the energy flux of the discharge and the UV-to-visible conversion by thephosphors. A significant part of this work was dedicated to the determination with experimental and numericalapproaches, of the operating conditions (HF wave applicator and discharge tube geometry, DC voltage) thatoptimize the energy flux of the discharge. The study conducted in pure argon demonstrated the beneficial energycontribution of the PC plasma (6% energy efficiency for an HF&DC discharge versus 1.5% for an HFdischarge), a benefit that increases with the length of the PC. However, the significant emission differenceobserved under our working conditions between the various regions of the discharge (NG and PC). This madesurface-wave HF discharges more suitable for the intended application. The study of reactive mixtures clearlyshowed the advantage of the Ar-S₂ mixture over the Ar-N₂/O₂ mixture. This advantage is due to a better spectralemission distribution for Ar-S₂. This has a favorable impact on both the energy efficiency of the dischargeemission in the UV+Visible range (reduced IR emission) and the conversion efficiency by the phosphors. Asuitable combination of UV-absorbing phosphors enabled the development of a lamp device (surface-wave HFdischarge in a sealed tube) with visual performance close to that of Ar-Hg lamps. However, the luminousefficiency of the implemented surface-wave lamp remains significantly lower due to two main factors: theelectrical efficiency of the HF discharge and the energy efficiency of emission. The former is strongly limited bytechnological constraints, such as the inability to eliminate HF radiation leaks, while the latter is inherent to theenergy required for the dissociation of S₈ into S₂

博士
大同大學
化學工程學系(所)
103
In recent years, nanostructure metal sulfides have been widely employed as electrode materials in hybrid supercapacitors (SCs) due to their high specific capacity and excellent electrochemical stability. Generally, the metal sulfides are usually prepared by using chemical method, such as chemical precipitation and hydrothermal methods. However, the metal sulfide powders still need polymer binder, conducting agent and high pressure coating on the conductive substrate, which could contribute extra contact resistances. In the chapter 3 of this thesis, metal sulfides (cobalt sulfide and nickel sulfide) were successfully deposited on Ni foam substrates by the facile potentiodynamic (PD) deposition method. The CoS and Ni3S2 electroactive materials delivered remarkable specific capacity up to 224.7 mAhg-1 at 4 A g-1 and 99.6 Fg-1 at 2 Ag-1, respectively. Moreover, the CoS electrode exhibited about 100% retention of specific capacity around and 99% Columbic efficiency after consecutive 1000 cycles with a fairly high current density of 8 A g-1.As for the Ni3S2 flaky electrode, it can still possess specific capacity retention around 91% after cycling of 500-1000 cycles at a high current density of 4 Ag-1. In the chapter 4 of this thesis, the corresponding deposition mechanism of metal sulfides has been investigated by using cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The CV results suggested that the partial metal (M=Ni2+, Co2+) ions complexes with the electroreduced product of TU in the form of [MTU]2+ and the formation of electroreduction of [MTU]2+ complexes onto the Ni foam surface. Then the [MTU]2+ would further reduce to MS onto the Ni foam surface. In order to comprehend the electrodeposition mechanism of MS, the XPS analyses were carried out the results. The Ni3S2 is successfully prepared on a Ni foam substrate by the proposed potentiodynamic, the required power-supply equipment for the PD deposition is relatively expansive. It would be unfeasible for practical applications. Therefore, the pulse reversal deposition technique have been developed to prepare Ni3S2 electrode in the chapter 5 of this thesis. The NSPR-2 electrode delivered remarkable specific capacity up to 179.5mAhg-1 at 2 A g-1 and 105.9 mAhg-1 at 32 A g-1 charge–discharge current density in 1.0 M KOH aqueous electrolyte. Furthermore, a hybrid SC with the flaky Ni3S2 as the positive electrode material and carbon fiber cloth (CFC) as the negative electrode, exhibited a high energy density (26.4 W h kg−1) at an power density of 1978 W kg−1.

碩士
國立聯合大學
環境與安全衛生工程學系碩士班
104
Lithium-ion battery becomes the most important energy supplier with the rapid development of the portable electric and electronic products. However overheating, fire and explosion accidents occurred from time to time owing to battery thermal runaway. One of the possible reasons is the exothermic reaction between the lithiated cathode materials and electrolytes. In this study thermal curves of eight lithiated cathode materials reacted with different electrolytes that are commonly used in lithium-ion battery are performed in a Mettler TA-4000 System coupled with a differential scanning calorimetry (DSC822) measuring cell. Disposable crucible (ME-26732) which can withstand up to 100 bars is used for detecting thermal curves. Data are acquired and stored for further evaluation. Scanning rate is selected to be 4K min-1 in programmatic ramp up to 500℃ for the reason of sustaining better thermal equilibrium inside the crucible. Electrolytes, namely, ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and mixtures of DMC/EC and DEC/EC with the ratio of 1：1 reacted with eight cathode materials, i.e., lithium iron phosphate (LiFePO4), lithium manganese oxide (LiMn2O4), lithium nickel manganese cobalt oxide (LiNi1/3Mn1/3Co1/3O2, NMC333), LiNi0.5Mn0.3Co0.2O2, NMC532), (LiNi0.8Co0.2O2, NCA ), etc. are measured and accessed, respectively. Results indicate that the lowest onset temperature occurred at the reaction of lithium manganese oxide (LiMn2O4) with DMC as well as DMC/EC mixture. In addition, lithium iron phosphate (LiFePO4) reacted with electrolytes do not exhibit exothermic behaviors and turns out to have the best thermal stability than other lithited cathode materials. Furthermore electrolyte mixtures seem to have better thermal stability than the single electrolyte alone. These phenomena provide much more clear sights for searching the root causes to explain or link the incidents of overheating, fire or explosion encountered in lithium-ion batteries. Keywords: lithiated cathode material, onset temperature, thermal instability, electrolyte

Lithium ion batteries have been regarded as one of the most promising and intriguing energy storage devices in modern society since 1990s. A lithium ion battery contains three main components, cathode, anode, and electrolyte, and the performance of battery depends on each component and the compatibility between them. Electrolyte acts as a lithium ions conduction medium and two electrodes contribute mainly to the electrochemical performance. Generally, cathode is the limiting factor in terms of capacity and cell potential, which attracts significant research interests in this field.Different from conventional slurry thick film cathodes with additional electrochemically inactive additives, binder-free thin film cathode has become a promising candidate for advanced high-performance lithium ion batteries towards applications such as all-solid-state battery, portable electronics, and microelectronics. However, these electrodes generally require modifications to improve the performance due to intrinsically slow kinetics of cathode materials.

In this thesis work, pulsed laser deposition has been applied to design thin film cathode electrodes with advanced nanostructures and improved electrochemical performance. Both single-phase nanostructure designs and multi-phase nanocomposite designs are explored. In terms of materials, the thesis focuses on manganese based layered oxides because of their high electrochemical performance. In Chapter 3 of the nanocomposite cathode work, well dispersed Au nanoparticles were introduced into highly textured LiNi_0.5Mn_0.3Co_0.2O₂ (NMC532) matrix to act as localized current collectors and decrease the charge transfer resistance. To further develop this design, in Chapter 4, tilted Au pillars were incorporated into Li₂MnO₃ with more effective conductive Au distribution using simple one-step oblique angle pulsed laser deposition. In Chapter 5, the same methodology was also applied to grow 3D Li₂MnO₃ with tilted and isolated columnar morphology, which largely increase the lithium ion intercalation and the resulted rate capability. Finally, in Chapter 6, direct cathode integration of NMC532 was attempted on glass substrates for potential industrial applications.

ZnO nanowire arrays (NWAs) and Al-doped ZnO (AZO) cathodes were applied in hybrid organic / inorganic solar cells for lower-cost solar energy. Parameters for the electrodeposition of ZnO NWAs and the fabrication of NWA-free baseline devices were systematically optimized using ITO as the cathodes. High efficiencies of up to 5.4% were achieved. Incorporation of the ZnO NWAs into the baseline devices significantly reduced their efficiencies due to possible shorting in the active layer. Devices fabricated using AZO cathodes were characterized. The AZO-based devices achieved efficiencies of up to ~4.8%, showing promising results for the application of AZO as an ITO alternative. Formation of numerous large nanoplatelets was observed during the electrodeposition of ZnO NWAs on AZO cathodes. The NWAs grown on AZO cathodes were also non-uniform. Future studies were proposed to address the issues with incorporation of ZnO NWAs in hybrid solar cells and their combination with AZO cathodes.

碩士
義守大學
電子工程學系
102
In this study, we deposit Ag nanoparticles (Ag NPs)-doped carbon nanotube (CNT) suspension on metal by spray technique to produce a high current density carbon nanotube field emission electron source substrate. Field emission organic light-emitting diodes (FEOLEDs) are fabricated by combining the CNT field emission electron source with organic light-emitting diodes (OLEDs), which demonstrate a higher luminous efficiency than OLEDs. The study of a CNT field emission electron source substrate is to enhance the field emission characteristics. First, Cu, Ag or Al is evaporated on the glass substrate to form the cathode. Ag NPs-doped multi-walled carbon nanotubes (MWCNTs) are deposited onto cathodes by spray technique. Doping Ag NPs into CNTs can improve the conductivity of CNTs film to further enhance the field emission properties. Experimental results reveal that a current density of 62.5 mA/cm2 at 1.78 V/μm has been obtained when Cu is used as a cathode and 6.6 wt% Ag NPs is doped into CNTs. When the above electron emitting source used as a substrate combines an OLED device to form a FEOLED, the luminance intensity is enhanced from 5857 cd/m2 to 7386 cd/m2 and the luminous efficiency is enhanced from 9.327 cd/A to 11.76 cd/A.

碩士
國立清華大學
工程與系統科學系
104
Abstract This thesis describes the development of microplasma devices architecture by hybrid diamond as cathode. These microplasma devices are suitable for UV emission sources and corresponding applications. The cathode boundary layer (CBL) discharge device structure has been implemented in this study, which consist of 2 mm cylindrical cavity in the centre of anode. Here, two types of devices were fabricated, such as two electrode and novel three electrode devices. These devices were tested with Ar (10 %) + N2 (90 %) gas used as discharge medium for generation of UV emissions. The current – voltage relationship and optical emission spectra were studied for two devices, while HiD (nanocrystalline diamond/ultrananocrystalline diamond) coated Si tip cathode. The microplasma illumination behavior was investigated for different diamond films including microcrystalline diamond (MCD), ultrananocrystalline diamond UNCD, planar HiD and HiD coated Si tip cathodes for the case of two-electrode microplasma device. From these results, the HiD coated over Si tip shows the better plasma illumination intensity compared with other electrodes due to its excellent electron field emission property (E0 = 9.1; Je = 4.53 @ 18.1 V/µm; β = 1605). The lifetime stability of the microplasma devices were studied by means of electrode degradation by plasma damage and variation of plasma intensity for two-electrode device. However, the electrode degradation causes the limitation of the lifetime stability in two electrode device due to high filed strength on cathode, which leads to ion bombardment. To overcome this problem, the third electrode has been added to the two electrode devices, which results in lower applied voltages on diamond cathode for longer lifetime. The cathode material in case of the three electrode microplasma device has been exhibited longer lifetime than the two electrode device. In case of the HiD/Si tip based two-electrode device operated at current density of ~ 3.5 mA/cm2 with applied voltage of 500 V, the device shown the lifetime stability of 2.9 hr. In case of the three-electrode device, which operated at anode current density (Ja) = 3.2 mA/cm2 (applied voltage 440 V) and cathode current density (Jc) = 1.8 mA/cm2 (applied voltage 160 V), the stability of the device came up to 4.3 hr without any decay in current density. The plasma intensity of the three electrode device was markedly higher in comparison with two electrode device due to the additional third electrode, which results in generation of extended positive column. We observed the near UV emissions for both devices, which arising from N2 second positive. The resultant near UV emissions attained at wavelengths of 296.5 nm, 315.5 nm, 336.5 nm, 353.1 nm, 357.3 nm, 375.1 nm and 379.8 nm. Therefore, this hybrid diamond based three electrode CBL device has great potential for practical applications as a robust UV source.

The simultaneous synthesis of nanocarbon allotropes is a challenging issue. In this work, chemical vapor deposition (CVD) is demonstrated to be a successful strategy to obtain hybrid functional thin films, which are employed in prototypes in the fields of microelectronics and biomedicine. Three types of nanocarbon hybrids are explored: intimate mixtures of nanocrystalline diamond (NCD) and carbon nanotubes (CNTs) (NCD-CNTs), NCD and graphene (GDHs), and NCD and nanographite in platelet-like morphology (DGNPs or DNPs) are obtained by microwave-plasma CVD (MPCVD) in rapid and singlestep procedures. NCD-CNTs hybrids are composed of non-bundling multi-walled CNTs in a network arrangement, interconnecting NCD clusters in porous morphologies or fully embedded in a dense NCD matrix. Changing the amount of catalyst allowed a qualitative control the CNTs content. Optimized NCD-CNTs thin films are patterned into microelectromechanical resonators, constituting the first attempt to produce such devices from these hybrid materials. Regarding the GDHs films, the nucleation density of NCD clusters on top of a smooth, highly crystalline few layer graphene is shown to be tunable from c.a. 106/cm2 to at least 5x106/cm2 using a CH4 pulsed flow modulation method. Moreover, this is accomplished whilst maintaining the fundamental morphology and structure of the constituents. Electron field emission studies reveal activation fields ranging from 4.6 to 8.4 V/μm, decreasing with increasing NCD cluster density. Two emission regimes are observed, attributable to the background graphene and the protruded NCD clusters. The graphene phase helps in the heat removal from the emitting sites, yielding stable operation for several hours. On the other hand, DGNPs are constituted by a thin (5 nm) inner diamond platelet covered by a nanographite coating. These hybrids provide preferential vertical alignment, enhanced surface area, chemical inertness, biocompatibility, amenability to functionalization, facile faradaic charge transfer and low and tailorable electrical resistivity. Indeed, increasing the amount of N2 during growth lowers the films’ electrical resistivity by over one order of magnitude (down to c.a. 10-5 Ω.m), triggers the nanoplatelet vertical growth, leads to higher nanographite crystallinity and enhances charge transfer rate constants up to 6x10-3 cm.s-1 in 10 mM PBS/[Fe(CN)6]4- solution. Enhanced proliferation and metabolism is observed for preosteoblasts cultured in DGNPs surfaces, accompanied by high cell viability after small magnitude DC stimulus. In the absence of DC stimulation, an up-regulating effect of preosteoblastic maturation intrinsically exerted by the DGNPs is observed. Moreover, DGNPs label-free impedimetric biosensors are developed, using avidin detection as a proof of concept. Avidin quantification is attained within the 10 to 1000 μg.mL-1 range, and the limits of detection and of quantitation corrected by the non-specific response are 2.3 and 13.8 μg.mL-1, respectively. These findings suggest that DGNPs are excellent materials for biomedical sensing and actuating devices. Additionally, DGNPs thin films are shown to enhance the thermal dissipation under convection-governed conditions when compared to smooth NCD films, thus constituting valid alternatives for heat dissipation at conditions where purely diamond surfaces cannot be employed.
A síntese simultânea de nano-alótropos de carbono constitui, atualmente, um grande desafio tecnológico. Neste trabalho demonstra-se que a técnica de deposição química em fase de vapor (CVD) constitui uma estratégia válida para obter híbridos sob a forma de filmes finos funcionais, posteriormente aplicados em protótipos nas áreas da microelectrónica e biomedicina. Três tipos de híbridos de nanocarbonos são explorados: misturas íntimas de diamante nanocristalino (NCD) e nanotubos de carbono (CNTs) (NCD-CNTs), NCD e grafeno (GDHs), e NCD e nanografite em morfologias de plaquetas (DGNPs ou DNPs). Estes híbridos são obtidos por CVD ativado por plasma de micro-ondas (MPCVD) em procedimentos rápidos e de passo único. Os híbridos de NCD-CNTs são compostos por uma rede de CNTs de múltipla parede não agrupados, interligando agregados de NCD numa morfologia porosa ou numa matriz densa de NCD. A quantidade de CNTs pode ser controlada pela quantidade de catalisador. Filmes finos de NCD-CNTs são otimizados para a microfabricação de ressoadores micro-electromecânicos, constituindo a primeira tentativa de produzir tais dispositivos a partir destes materiais. Relativamente aos filmes de GDHs, é demonstrado que a densidade de nucleação de agregados de NCD em cima de grafeno de poucas camadas é controlável desde c.a. 106/cm2 até pelo menos 5x106/cm2, usando o método de modulação pulsada de fluxo de CH4. Esse controlo é conseguido mantendo a estrutura e morfologia fundamental dos constituintes. Estudos de emissão de eletrões por efeito de campo demonstram campos de ativação desde 4,6 até 8,4 V/μm, decrescendo com o aumento da densidade dos agregados de NCD. Dois regimes de emissão são observados, atribuíveis ao grafeno e às protusões de NCD. O grafeno promove a remoção de calor dos sítios emissores, resultando em desempenhos estáveis por várias horas. Por outro lado, as DGNPs são constituídas por plaquetas finas (5 nm) de diamante revestido por um filme de nanografite. Estes híbridos exibem alinhamento vertical preferencial, área de superfície amplificada, inércia química, biocompatibilidade, possibilidade de funcionalização, rápida transferência de carga faradaica, bem como resistividade elétrica baixa e controlável. O aumento da concentração de N2 durante o crescimento diminui a resistividade elétrica dos filmes em uma ordem de grandeza (até c.a. 10-5 Ω.m), induz o desenvolvimento vertical das nanoplaquetas, contribui para uma cristalinidade superior da nanografite e aumenta as constantes da taxa de transferência de carga até 6x10-3 cm.s-1 numa solução de 10 mM PBS/[Fe(CN)6]4-. Uma proliferação e metabolismo amplificados são observados em préosteoblastos cultivados em superfícies de DGNPs, acompanhados por uma elevada viabilidade celular após estímulos elétricos DC de baixa magnitude. Na ausência de estimulação DC, é observado um efeito de regulação antecipada da maturação pré-osteoblástica, intrinsecamente exercida pelas DGNPs. Paralelamente, são desenvolvidos biossensores impedimétricos sem etiqueta à base de DGNPs usando a avidina como prova de conceito. A quantificação de avidina é conseguida na gama dos 10 até aos 1000 μg.mL-1 com limites de deteção e quantificação de 2,3 e 13,8 μg.mL-1, respetivamente. Estes resultados sugerem que as DGNPs constituem excelentes materiais para dispositivos de deteção e atuação biomédica. Adicionalmente, é também demonstrado que filmes de DGNPs amplificam a dissipação térmica sob condições de convecção natural quando comparados com filmes de NCD de baixa rugosidade, constituindo, portanto, alternativas válidas para a dissipação térmica em condições onde superfícies puramente de diamante não podem ser aplicadas.
Programa Doutoral em Nanociências e Nanotecnologia

碩士
國立中央大學
機械工程學系
104
p‒SOFC is an appropriate fuel cell type to be applied in the power generating system. p‒SOFC is combined with MGT and CHP to utilize the hydrogen and oxygen unreacted from the stack. Some parameters are fixed by using Matlab / Simulink such as 50 cells, membrane area of 0.1 m2. Furthermore, three cases, cases 1, 2, and 3, are analyzed, and the best case, case 2, is installed with anode and cathode recycling, to increase system performance. Some parameters are varied to be analyzed such as fuel utilization, steam to fuel, air stoichiometry, and fuel stoichiometry. In case comparison, case 2 shows the better performance than case 1 and case 3, where installation of a fuel heat exchanger before reformer is highly recommended in order to increase the reaction rate in reformer. Operating temperature in each component in every case is difference. Case 1 produces higher hydrogen production than case 2 and case 3 due to heat used to heat the reformer in case 1 is higher than other cases, however, the power in case 1 is lower than case 2 due to heat output of reformer in case 1 is lower than other cases. Furthermore, the result of exergy analysis shows that case 2 has lower exergy destruction (5.193 kW) than case 1 (6.170 kW) and case 3 (6.635 kW), where installation of heat exchanger can decrease exergy destruction around 0.977 kW. For parameters analysis results: First, the result of fuel utilization shows that increasing fuel utilization from 60 % to 90 % can increase p‒SOFC power output from 3 kW to 3.9 kW due to stack consumes more fuel, however, MGT power output decreases from 1.9 kW to 1.4 kW due to decreasing fuel unreacted in the combustor. The efficiency of p‒SOFC, power system, and CHP increases from 45 % to 58 %, 66 % to 73 %, and 72 % to 79 %, respectively. Second, increasing steam to fuel from 3 to 3.5 can increase p‒SOFC power output from 3.7 kW to 3.8 kW due to increasing hydrogen production from 28.7 mmol/s to 29.1 mmol/s. However, increasing steam to fuel ratio from 3.5 to 5 can decrease p‒SOFC power output from 3.8 kW to 3.4 kW due to fuel dilution in the reformer, and decreasing hydrogen production from 29 mmol/s to 26.9 mmol/s. The efficiency of p‒SOFC, power system, and CHP decreases from 57 % to 52 %, from 72 % to 68 %, and 79 % to 74 %, respectively. Third, increasing air stoichiometry from 2 to 4 can decrease p‒SOFC power output from 3.9 kW to 3.1 kW due to decreasing hydrogen production from 27.6 mmol/s to 27.2 mmol/s. Consequently, p‒SOFC electrical current decreases from 95.92 A to 94.54 A. In another hand, MGT power output increases from 1.4 kW to 2.1 kW due to increasing mass flow rate from 100 mmol/s to 150 mmol/s, however, compressor power also increases from 0.5 kW to 1 kW. The efficiency of p‒SOFC, power system, and CHP decreases from 58 % to 47 %, from 73 % to 65 %, and from 79 % to 71 %, respectively. Fourth, increasing fuel stoichiometry from 1 to 1.3 can increase p‒SOFC power out from 3 kW to 4 kW due to increasing hydrogen production from 22 mmol/s to 33 mmol/s, where there is an increase significantly of p‒SOFC power output when fuel stoichiometry is set from 1.0 to 1.2, and p‒SOFC efficiency increases from 53 % to 58 %. However, fuel stoichiometry from 1.2 to 1.3 can decrease p‒SOFC efficiency from 58 % to 54 % due to fuel is not balance with water in the reformer. Consequently, hydrogen production only increases slightly. Briefly, the optimum parameters are fuel utilization of 83 %, steam to fuel ratio of 3, air stoichiometry of 2, and fuel stoichiometry of 1.2. The last, Combination between cathode recycling and anode recycling shows promising performance, where power system efficiency increases up to 6.81 % due to increasing hydrogen production, increasing operating temperature in each component, and decreasing compressor work. Keywords: air stoichiometry, CHP, ethanol, fuel stoichiometry, fuel utilization, MGT, p‒SOFC, Recycling, and steam to fuel

abstract: The automotive industry is committed to moving towards sustainable modes of transportation through electrified vehicles to improve the fuel economy with a reduced carbon footprint. In this context, battery-operated hybrid, plug-in hybrid and all-electric vehicles (EVs) are becoming commercially viable throughout the world. Lithium-ion (Li-ion) batteries with various active materials, electrolytes, and separators are currently being used for electric vehicle applications. Specifically, lithium-ion batteries with Lithium Iron Phosphate (LiFePO4 - LFP) and Lithium Nickel Manganese Cobalt Oxide (Li(NiMnCo)O2 - NMC) cathodes are being studied mainly due to higher cycle life and higher energy density values, respectively. In the present work, 26650 Li-ion batteries with LFP and NMC cathodes were evaluated for Plug-in Hybrid Electric Vehicle (PHEV) applications, using the Federal Urban Driving Schedule (FUDS) to discharge the batteries with 20 A current in simulated Arizona, USA weather conditions (50 ⁰C & <10% RH). In addition, 18650 lithium-ion batteries (LFP cathode material) were evaluated under PHEV mode with 30 A current to accelerate the ageing process, and to monitor the capacity values and material degradation. To offset the high initial cost of the batteries used in electric vehicles, second-use of these retired batteries is gaining importance, and the possibility of second-life use of these tested batteries was also examined under constant current charge/discharge cycling at 50 ⁰C. The capacity degradation rate under the PHEV test protocol for batteries with NMC-based cathode (16% over 800 cycles) was twice the degradation compared to batteries with LFP-based cathode (8% over 800 cycles), reiterating the fact that batteries with LFP cathodes have a higher cycle life compared to other lithium battery chemistries. Also, the high frequency resistance measured by electrochemical impedance spectroscopy (EIS) was found to increase significantly with cycling, leading to power fading for both the NMC- as well as LFP-based batteries. The active materials analyzed using X-ray diffraction (XRD) showed no significant phase change in the materials after 800 PHEV cycles. For second-life tests, these batteries were subjected to a constant charge-discharge cycling procedure to analyze the capacity degradation and materials characteristics.
Dissertation/Thesis
Masters Thesis Materials Science and Engineering 2017

碩士
國立中央大學
化學學系
101
Economic and environmental requirements have motivated research in energy generation. Here, hybrid biofuel cell have been developed to meet the need. The cathode composed of laccase immobilized on CNT (CNT-Laccase), while the anode is Pt bimetallic alloy deposited on polyaniline-coated carbon nanotube (PANICNT). CNT-Laccase was characterized by Fourier Transform Infrared (FTIR) Spectrophotometry, Surface Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). CNT-Laccase FTIR spectra showed that the structure contain several functional groups, such as hydroxyl, amine and amide. SEM figures revealed that immobilization didn’t destroy tube structure of CNT, but it promoted aggregation. Elemental analysis of the structure displayed oxygen and nitrogen atoms distribution indicating the presence of Laccase. Therefore, FTIR and SEM reasserted successful immobilization. TGA reveal CNT-Laccase possesses two decomposition temperatures at 310ºC and 670ºC, that are related to decomposition of Laccase part and CNT part of CNT-Laccase, respectively. Laccase immobilization has changed CNT thermo stability. Immobilization also affected Laccase enzymatic activity where it boosts the stability at high temperature and neutral pH. At temperature 65ºC, free Laccase completely loss its activity, while CNT-Laccase still retaining 57.12% of its activity at 45ºC. The activity of CNT laccase at pH 7 was 7.04% of activity at pH 5 which was higher than that of free Laccase. CNT-Laccase was not able to perform oxygen electroreduction without addition ABTS (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) as mediator. In our case, ABTS was needed to shuttle electrons from electrode to Laccase active site. Performance of oxygen electroreduction activity was also determined by type and composition of binding polymer. Nafion was able to provide better environment for oxygen electroreduction activity compare to polyvinyl alcohol (PVA). Current density resulted in using Nafion in ratio 1:10 to buffer volume was 1.31 mA/cm2, which was higher than that of PVA (1.01 mA/cm2). Increasing binding polymer ratio into 1:2 and 1:1 undermined oxygen electroreduction activity. On the anode side, the alloy such as PtSn, Pt3Sn, Pt, and PtPb were tested to analyze their activity toward glucose electrooxidation. The formation of alloy was confirmed by shifted Pt fcc patterns on X-ray Diffraction (XRD) analysis. The alloys were able to be deposited on PANICNT surface as confirmed by Transmission Electron Microscopy (TEM) images. All the metal alloys were able to oxidize glucose in neutral and basic solution. The activity is affected by the presence of secondary atom. PtSn/PANICNT showed the highest activity as reflected by the highest current density and highest sensitivity. The current density was about 8.27 mA/cm2 and 8.27 mA/cm2 at basic and neutral pH, respectively. The highest sensitivity for PtSn/PANICNT was achieved at potential 0.0 V and 0.1 V, which were about 39.64 μAcm-2mM-1 and 39.54 μAcm-2mM-1 respectively. On the other hand, PtPb/PANICNT shifted glucose electrooxidation to lower potential as the highest sensitivity (40.33 μAcm-2mM-1) was achieved at -0.1 V.

碩士
逢甲大學
材料科學與工程學系
106
Hybrid organic−inorganic halide perovskite solar cells (PeSCs) are currently at the forefront of emerging photovoltaic technologies due to their potential for providing cost-effective highly efficient solar energy conversion. The interfacial layers play an important role in determining the efficiency and stability of PeSCs. In this work, a solution-processed cross-linkable hybrid composite film composed of N,Ndimethyl-N-octadecyl(3-aminopropyl)-trimethoxysilyl chloride silane (DMOAP)-doped [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) is demonstrated as an effective cathode interfacial layer for PeSCs. The hydrolyzable alkoxysilane groups on DMOAP enable moisture cross-linking through the formation of stable siloxane bonds, which is effective in ensuring uniform film coverage of PC61BM on the perovskite layer and preventing the undesirable reaction between the mobile halide ions and Ag electrode. On the other hand, the quaternary ammonium cations on DMOAP can induce the formation of favorable interfacial dipoles, allowing the high work-function Ag layer to act as the cathode. Importantly, our results show that the chloride anions (Cl-) on DMOAP can cause efficient n-doping of PC61BM via anioninduced electron transfer, increasing the conductivity of PC61BM film by more than 2 orders of magnitude. With these desired properties, the resulting devices show a remarkable power conversion efficiency (PCE) of 18.06%, which is superior to those of the devices with undoped PC61BM film (PCE = 4.34%) and a state-of-the-art ZnO nanoparticles (NPs) interfacial layer (PCE = 10.40%). More encouragingly, combining this interfacial layer with an effective thin-film encapsulation layer, the resulting devices exhibit promising long-term ambient stability, with negligible (<5%) loss in PCE after more than 5700 h of aging. To the best of our knowledge, the device stability obtained in this study is one of the best results for PeSCs.