by Kong Lim Pun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Kong Lim Pun. / ABSTRACT --- p.i / 摘要 --- p.iii / ACNOWLEDGEMENT --- p.iv / TALE OF CONTENTS --- p.v / LIST OF FIGURES --- p.ix / LIST OF TABLES --- p.xi / Chapter CHAPTER 1 --- Introduction / Chapter 1.1 --- Nanoparticles and nanostructural materials --- p.1 / Chapter 1.2 --- Materials of copper-implanted and nickel-implanted fused silica --- p.4 / Chapter 1.2.1 --- Overview --- p.4 / Chapter 1.2.2 --- Formation of nanoparticles --- p.5 / Chapter 1.2.3 --- Optical properties of the material --- p.9 / Chapter 1.3 --- Goals of the project --- p.12 / Reference --- p.13 / Chapter CHAPTER 2 --- Background of Study / Chapter 2.1 --- Introduction --- p.15 / Chapter 2.2 --- Optical absorption of metal nanocluster composite glasses --- p.16 / Chapter 2.2.1 --- Dielectric constant --- p.16 / Chapter 2.2.2 --- The features of surface plasmon resonance peak --- p.16 / Chapter 2.3 --- Third-order optical nonlinearity of metal nanocluster composite glasses --- p.17 / Chapter 2.3.1 --- Classical field confinement --- p.19 / Chapter 2.3.2 --- Quantum confinement --- p.21 / Chapter 2.3.2.1 --- Intraband transitions --- p.21 / Chapter 2.3.2.2 --- Interband transitions --- p.22 / Chapter 2.3.2.3 --- Hot-electron transitions --- p.22 / Chapter 2.4 --- Preparation Methods of MNCG(s) --- p.23 / Chapter 2.4.1 --- Ion implantation --- p.23 / Chapter 2.4.2 --- Ion exchange --- p.23 / Chapter 2.4.3 --- Sputtering deposition --- p.24 / Chapter 2.4.4 --- Melt -quenching and heat-treatment processes --- p.25 / Chapter 2.4.5 --- Ion-beam assisted deposition --- p.25 / Chapter 2.5 --- Applications --- p.25 / Reference --- p.27 / Chapter CHAPTER 3 --- Instrumentation / Chapter 3.1 --- Introduction --- p.29 / Chapter 3.2 --- Metal Vapour Vacuum Arc (MEVVA) ion source implantation --- p.29 / Chapter 3.2.1 --- Background of MEVVA ion source --- p.29 / Chapter 3.2.2 --- Characteristics of MEVVA ion source --- p.32 / Chapter 3.2.3 --- Implantation conditions --- p.33 / Chapter 3.3 --- X-ray photoelectron spectroscopy --- p.34 / Chapter 3.3.1 --- Theory --- p.34 / Chapter 3.3.2 --- Qualitative analysis --- p.38 / Chapter 3.3.2.1 --- Chemical shift peaks --- p.40 / Chapter 3.3.2.2 --- Auger peaks --- p.40 / Chapter 3.3.2.3 --- Energy loss peaks --- p.40 / Chapter 3.3.3 --- Quantitative analysis --- p.41 / Chapter 3.3.3.1 --- Homogeneous system --- p.41 / Chapter 3.3.3.2 --- Determination of layer thickness --- p.45 / Chapter 3.3.4 --- Instrumental components of XPS --- p.47 / Chapter 3.3.4.1 --- Sample introduction system --- p.47 / Chapter 3.3.4.2 --- X-ray source --- p.49 / Chapter 3.3.5 --- Application to metal nanoclusters composite glasses --- p.49 / Chapter 3.3.5.1 --- Compositional analysis --- p.50 / Chapter 3.3.5.2 --- Depth profiling --- p.50 / Chapter 3.3.5.3 --- Auger parameter --- p.50 / Chapter 3.4 --- Transmission electron microscopy --- p.53 / Chapter 3.4.1 --- Basic instrumentation of TEM --- p.53 / Chapter 3.4.2 --- Preparation of TEM cross section specimen --- p.54 / Chapter 3.4.2.1 --- Cutting --- p.54 / Chapter 3.4.2.2 --- "Disc-cutting, grinding, dimpling " --- p.54 / Chapter 3.4.2.3 --- Ion beam thinning --- p.56 / Chapter 3.4.3 --- Image contrast of TEM --- p.56 / Chapter 3.4.4 --- Basic operations of TEM --- p.57 / Chapter 3.4.4.1 --- Bright field and dark field images --- p.57 / Chapter 3.4.4.2 --- Selected area diffraction (SAD) --- p.58 / Chapter 3.4.4.3 --- Convergent Beam Electron Diffraction --- p.59 / Reference --- p.60 / Chapter CHAPTER 4 --- Composition and Nano structure of Copper-implanted Fused Silica / Chapter 4.1 --- Introduction --- p.62 / Chapter 4.2 --- The Atomic Distribution and Chemical State of Copper Nanocluster --- p.64 / Chapter 4.3 --- TEM Studies of Copper Nanoclusters --- p.70 / Chapter 4.4 --- Theoretical Calculation on Ratio of Surface to Bulk Atoms of Copper Nanocluster --- p.73 / Chapter 4.5 --- Conclusions --- p.74 / Reference --- p.77 / Chapter CHAPTER 5 --- Composition and Nanostructure of Nickel-implanted Fused Silica / Chapter 5.1 --- Introduction --- p.79 / Chapter 5.2 --- The distribution of nickel nanoclusters --- p.80 / Chapter 5.3 --- TEM studies of nickel nanoclusters --- p.81 / Chapter 5.4 --- Chemical state of nickel clusters --- p.87 / Chapter 5.5 --- Discussion --- p.90 / Chapter 5.6 --- Conclusion --- p.90 / Reference --- p.92 / Chapter CHAPTER 6 --- Conclusions --- p.94

by Chow Yeung Ming = 化學鍍鎳層的表面性質與焊接能力之關係 / 周洋明. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 62-65). / Text in English; abstracts in English and Chinese. / by Chow Yeung Ming = Hua xue du nie ceng de biao mian xing zhi yu han jie neng li zhi guan xi / Zhou Yangming. / Abstract --- p.i / 論文摘要 --- p.ii / Acknowledgements --- p.iii / Table of Contents --- p.v / List of Figures --- p.viii / List of Tables --- p.ix / Abbreviations --- p.x / Chapter Chapter 1 --- INTRODUCTION / Chapter 1.1 --- Electroless Plating (Autocatalytic Deposition) --- p.1 / Chapter 1.2 --- Electroless Nickel (EN) Plating --- p.2 / Chapter 1.3 --- Types of Electroless Nickel Deposits --- p.2 / Chapter 1.4 --- Properties of Electroless Nickel --- p.5 / Chapter 1.5 --- Applications of Electroless Nickel in Electronic Packaging Industry --- p.7 / Chapter 1.6 --- Importance of Solderability --- p.8 / Chapter 1.7 --- Literature Review of Solderability Studies of Electroless Nickel --- p.9 / Chapter 1.8 --- Motivations & Aims of Studies --- p.10 / Chapter Chapter 2 --- EXPERIMENTAL & INSTRUMENTATION / Chapter 2.1 --- Electroless Nickel Plating --- p.11 / Chapter 2.2 --- Solderability Measurements / Chapter 2.2.1 --- Soldering --- p.13 / Chapter 2.2.2 --- Various test methods for solderability --- p.13 / Chapter 2.2.3 --- Wetting balance method --- p.15 / Chapter 2.2.4 --- Solderability measurements of electroless nickel deposits --- p.17 / Chapter 2.2.5 --- Assessment of wetting curves --- p.19 / Chapter 2.3 --- Surface Oxidation Studies / Chapter 2.3.1 --- Use of X-ray photoelectron spectroscopy (XPS) in surface characterization --- p.19 / Chapter 2.3.2 --- XPS system --- p.22 / Chapter 2.3.3 --- Surface composition of electroless nickel deposits --- p.22 / Chapter 2.3.4 --- Oxide thickness characterization by angle-resolved XPS --- p.25 / Chapter 2.3.5 --- Oxide thickness characterization by XPS depth profiling with low-energy-ion sputtering --- p.28 / Chapter 2.4 --- Surface Morphology Studies / Chapter 2.4.1 --- Surface morphology studies by scanning Auger electron microscopy (SAM) & atomic force microscopy (AFM) --- p.28 / Chapter 2.4.2 --- SAM studies of electroless nickel surfaces --- p.29 / Chapter 2.4.3 --- AFM studies of electroless nickel surfaces --- p.29 / Chapter 2.5 --- Oxide Quality Studies --- p.31 / Chapter Chapter 3 --- RESULTS & DISCUSSIONS / Chapter 3.1 --- Solderability Measurements by the Wetting Balance Method --- p.33 / Chapter 3.2 --- Surface Oxidation Studies / Chapter 3.2.1 --- Surface composition of electroless nickel deposits --- p.36 / Chapter 3.2.2 --- Oxide thickness characterization by angle-resolved XPS --- p.38 / Chapter 3.2.3 --- Oxide thickness characterization by XPS depth profiling with low-energy-ion sputtering --- p.44 / Chapter 3.2.4 --- Conclusion --- p.47 / Chapter 3.3 --- Surface Morphology Studies / Chapter 3.3.1 --- SAM studies of electroless nickel surfaces --- p.49 / Chapter 3.3.2 --- AFM studies of electroless nickel surface --- p.49 / Chapter 3.3.3 --- Conclusion --- p.53 / Chapter 3.4 --- Interpretation of Wetting Kinetics of Electroless Nickel --- p.54 / Chapter Chapter 4 --- CONCLUSIONS & FURTHER STUDIES / Chapter 4.1 --- Conclusions --- p.59 / Chapter 4.2 --- Further Studies --- p.60 / Appendix --- p.61 / References --- p.62

Solar water-splitting is a potentially transformative renewable energy technology. Slow kinetics of the oxygen evolution reaction (OER) limit the efficiency of solar-water-splitting devices, thus constituting a hurdle to widespread implementation of this technology. Catalysts must be stable under highly oxidizing conditions in aqueous electrolyte and minimally absorb light. A grand goal of OER catalysis research is the design of new materials with higher efficiencies enabled by comprehensive understanding of the fundamental chemistry behind catalyst activity. However, little progress has been made towards this goal to date. This dissertation details work addressing major challenges in the field of OER catalysis. Chapter I introduces the current state-of-the-art and challenges in the field. Chapter II highlights work using ultra-thin films as a platform for fundamental study and comparison of catalyst activity. Key results of this work are (1) the identification of a Ni0.9Fe0.1OOH catalyst displaying the highest OER activity in base to date and (2) that in base, many transition-metal oxides transform to layered oxyhydroxide materials which are the active catalysts. The latter result is critical in the context of understanding structure-activity relationships in OER catalysts. Chapter III explores the optical properties of these catalysts, using in situ spectroelectrochemistry to quantify their optical absorption. A new figure-of-merit for catalyst performance is developed which considers both optical and kinetic losses due to the catalyst and describes how these factors together affect the efficiency of composite semiconductor/catalyst photoanodes. In Chapter IV, the fundamental structure-composition-activity relationships in Ni1-xFexOOH catalysts are systematically investigated. This work shows that nearly all previous studies of Ni-based catalysts were likely affected by the presence of Fe impurities, a realization which holds significant weight for future study of Ni-based catalyst materials. Chapter V discusses the synthesis of tin-titanium oxide nanoparticles with tunable lattice constants. These materials could be used to make high-surface-area supports for thin layers of OER catalysts, which is important for maximizing catalyst surface area, minimizing the use of precious-metal catalysts, and optimizing 3D structure for enhanced mass/bubble transport. Finally, Chapter VI summarizes this work and outlines directions for future research. This work contains previously published and unpublished co-authored material. / 2015-03-29

Este trabalho descreve a síntese e caracterização de polímeros de coordenação (PC) e sua aplicação como fotocatalisadores heterogêneos ativos sob a radiação visível, visando a degradação de compostos orgânicos em água. Problemas ambientais têm ocupado posição de destaque na sociedade contemporânea. Dentre eles, o uso de combustíveis fósseis e a remoção de compostos poluentes do meio ambiente têm merecido especial atenção. Uma das alternativas mais indicadas como substituinte dos combustíveis fósseis é a energia solar, por ser limpa, renovável e presente em todo o planeta. O estudo de materiais fotoativos é essencial para aproveitar ao máximo essa fonte. A fotocatálise é um processo que utiliza a energia luminosa para realizar reações químicas. Os PC têm mostrado ótimos resultados na área. Esses são compostos poliméricos cujos monômeros são unidades de coordenação. Neste trabalho foram sintetizados PC formados por diferentes metais de transição e ligantes orgânicos. Dentre eles destacam-se níquel e benzenodicarboxilato (Ni-BDC). Os materiais foram caracterizados por FTIR, DRX, adsorção-dessorção de N2, DRS, TGA, MEV e ICP-OES. Os resultados sugerem a formação de PC inéditos, dotados de sítios de coordenação insaturados, com boa estabilidade térmica, porém com estabilidade em meio aquoso inferior. O ensaio de degradação fotocatalítica de corante evidencia que os materiais são fotoativos na luz visível, apesar da descoloração não ser completa. Este resultado é interessante, pois polímeros de coordenação de níquel ainda são pouco estudados como fotocatalisadores, e esse é um metal barato e abundante. / This work describes the synthesis and characterization of coordination polymers (CP) and their application as heterogeneous photocatalysts, under visible radiation, in degradation of organic compounds in water. Environmental issues have taken prominent position in contemporary society. Among them, fossil fuel usage and removal of hazardous compounds deserve special attention. One of the best alternatives to replace fossil fuels is the solar power, which is clean, renewable and ubiquitous throughout the planet. Research on photoactive materials is essential to improve this energy source use. Heterogeneous photocatalysis process uses light energy to induce chemical reactions. CP are exhibiting remarkable results in the field. These are polymeric compounds with coordination units as monomers. In the present work, CP based on different transition metals and organic ligands were synthesized, such as nickel benzenedicarboxylate (Ni-BDC). The materials were characterized by FTIR, XRD, N2 adsorption-desorption, DRS, TGA, SEM and ICPOES. The results suggest the formation of novel CP, endowed with unsaturated metal sites and good thermal stability, however with low stability in aqueous medium. The photocatalytic dye degradation experiments indicate the materials are photoactive under visible light, although the discoloration was not complete. This is an interesting result, considering that the research on nickel coordination polymers as photocatalysts is still scarce.

Alloys with good toughness and elevated temperature properties like A201 are expensive and can be more difficult to process. This results in the use of heavier but less expensive alternatives in many applications where toughness is of concern, such as steels. Common alloys such as A356 and E357 are relatively cheap and easy to work with. However, these alloys have considerably lower toughness than premium alloys. This research aims to investigate surface modification treatments that could yield better toughness at a low cost in a common aluminum alloy. The process must show significant improvement in said properties, be cost effective, and easily adaptable in a common foundry. Diffusion of coating material into the substrate was investigated with a variety of coating metals. The diffusion process was facilitated in the solutionizing step for the given substrate aluminum in order to strengthen the sub-surface region of the parts. This research aims to provide a platform for further research into the practical effects of the coating and tempering on impact and toughness properties. These samples were characterized by optical and scanning electron microscopy, EDS, impact testing, and tensile testing.

Requirements for increased operating efficiencies mean that future generations of aero-engines will need to operate at temperatures beyond the capabilities of current nickel-base superalloys. As a result, new alloy compositions for turbine disc applications are being developed. Optimising these alloy compositions requires balancing directly competing requirements. Increased Cr contents are needed to provide environmental resistance and increased concentrations of other refractory metals to improve solid solution strengthening. However, these elements compromise the alloyâs long-term microstructural stability by promoting the formation of topologically close-packed (TCP) phases, which are deleterious to alloy performance. High $\gamma^\prime$ volume fractions, which are needed to provide high-temperature strength, exacerbate the problem by increasing the concentration of these elements in the $\gamma$ phase. Therefore, an understanding of TCP formation and the compositional limits of stability is vital in the design of new alloys. This thesis presents a combination of fundamental studies of TCP phase formation in model alloys and microstructural assessment of the thermal stability of developmental alloy compositions. Knowledge of the effect of individual elements on thermal stability is important to enable the development of optimised alloy compositions. As a result, the first fundamental study investigated the effect of Co content on thermal stability. An unexpected transition in $\sigma$ precipitation behaviour after 500 hours at 800°C was observed between 12 and 16 at.\% Co. It is proposed that this behaviour may be due to the effect of Co on the $\gamma$/$\gamma^\prime$ partitioning behaviour of other elements. Preliminary results from further fundamental studies investigating the effect of the Mo/W ratio and B content on thermal stability are also presented. Decreasing the Mo/W ratio was found to reduce the quantity of $\sigma$ precipitation and promote the precipitation of a W-rich phase. B additions were found to promote the precipitation of the M$_3$B$_2$ phase. Thermodynamic predictions are frequently used to inform alloy design as an alternative to time-consuming and costly experiments. However, the accuracy of solvus temperature predictions for TCP phases has not been thoroughly considered. In this work, it was found that differential scanning calorimetry could be used as a means of measuring $\sigma$ solvus temperature in a series of alloys designed to be sufficiently unstable with respect to $\sigma$ precipitation. Comparison of experimental results with thermodynamic solvus temperature predictions revealed a significant underprediction of the $\sigma$ solvus temperatures for all of the studied alloys. This can inform our use of such predictions during alloy design. The ability to quantify the amount of TCP precipitation that occurs is extremely important when assessing the thermal stability of alloys. A new method was applied to the problem of TCP quantification, involving synchrotron X-ray diffraction of solid aged samples. This was an attempt to avoid some of the problems identified with the commonly used quantification method, which involves electrolytic extraction of minor phases, and assess the accuracy of the results produced by this method. Samples of a currently used commercial alloy, RR1000, were investigated following ageing for up to 5000 hours at 800°C, revealing the evolution of phases at this temperature. The presence of extremely low quantities of minor phases was successfully detected in the solid samples using this method. However, these quantities were too low for this to be a reliable method of quantification for commercial alloys. In parallel with these fundamental and technique-based studies, the thermal stability of a number of candidate alloys, which were developed during the design of a next-generation disc alloy by Rolls-Royce, was assessed. The alloys were characterised following a variety of thermal exposure temperatures and durations, which were determined by industrial needs at the time. Various minor phases were identified depending on the alloy compositions, including the TCP phases, $\sigma$ and $\mu$, as well as MC and M$_{23}$C$_6$ carbides and M$_3$B$_2$ borides.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Materials Science and Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Thomas Carson Tiearney, Jr. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Includes bibliographical references. / by Charles Hubert Smith. / Ph.D.

O processo de fosfatização é amplamente utilizado na indústria de tratamento de superfície de metais, especialmente de placas de baixa espessura, melhorando a aderência entre a superfície do metal e o revestimento de tinta, e aumentando a durabilidade dos sistemas de pintura contra ataques corrosivos. Os fosfatos tricatiônicos contendo zinco, níquel e manganês são comumente aplicados em aço, e muito se discute sobre a substituição do níquel por outro elemento com o objetivo de obter um fosfato mais amigável ao meio ambiente, tanto em seus processos como para as pessoas envolvidas. O nióbio tem sido avaliado nesse sentido. Os impactos ambientais mais significativos dos fosfatos estão relacionados com a presença do níquel e do cromo hexavalente utilizado no processo, devido a exposição ao contato humano e a contaminação residual da água e do solo. Seguindo a linha de pesquisa que estudou a substituição do níquel por nióbio em camadas formadas sobre o aço carbono, o presente estudo avaliou e caracterizou camadas de fosfato contendo zinco, manganês e nióbio, formadas em aço galvanizado, comparando os resultados com o fosfato de zinco, manganês e níquel, bem como com o fosfato de zinco e manganês, sem a adição de nióbio. Embora o uso de cromo não seja recomendado mundialmente, ainda hoje é utilizado no processo de selagem da porosidade da camada de fosfato, em banhos contendo cromo hexavalente, que é reconhecido por ser carcinogênico, estando associado a várias doenças. Devido às características passivantes do nióbio, este estudo também avaliou o banho tricatiônico contendo oxalato amoniacal de nióbio, como etapa de passivação das camadas, tanto em banhos bicatiônicos, quanto nos tricatiônicos, com resultados muito interessantes como opção de substituição do cromo hexavalente. Os resultados obtidos neste trabalho são promissores, pois algumas das formulações contendo nióbio se apresentaram equivalentes ao fosfato contendo níquel, tanto em morfologia, verificadas em microscopia eletrônica de varredura, ensaios gravimétricos, de porosidade e de aderência, quanto nas características de proteção anticorrosivas, verificadas nos ensaios eletroquímicos e em câmara de névoa salina. Embora apresentando eficácia compatível com fosfato contendo níquel, ajustes na estabilidade dos banhos ainda são necessários e mais estudos utilizando técnicas voltadas para o entendimento dos fenômenos que ocorrem na base dos poros, devem orientar as próximas etapas da linha de pesquisa. / The phosphating processes are widely used in industry as surface treatments for metals, especially for low thickness plates, improving the adhesion between the metallic surface and the paint coating, and increasing the durability of paint systems against corrosion attacks. The tricationic phosphates containing zinc, nickel and manganese are commonly applied on steel. There is much discussion about the replacement of nickel by another element in order to have an environmentally friendly phosphating process. Niobium as a replacement for nickel has been evaluated. The most significant environmental impacts of phosphating processes are related to the presence of nickel and hexavalent chromium used in the process, this last as a passivation treatment. Nickel and hexavalent chromium are harmful to human and environment leading to contamination of water and soil. In the present study phosphate layers containing zinc, manganese and niobium have been evaluated and characterized on galvanized steel, and the results were compared with phosphates containing zinc, manganese and nickel, or a bicationic phosphate layer with zinc and manganese. Although the use of hexavalent chromium is not recommended worldwide, it is still used in processes for sealing the porosity of phosphate layers. This element is carcinogenic and has been associated with various diseases. Due to the passivation characteristics of niobium, this study also evaluated the tricationic bath containing niobium ammonium oxalate as a passivation treatment. The results showed that it could act as a replacement for the hexavalent chromium. The results of the present study showed that formulations containing niobium are potential replacements for hexavalent chromium and similar corrosion protection was obtained for the phosphate containing nickel or that with niobium. The morphology observed by scanning electron microscopy, gravimetric tests, porosity and adhesion evaluation results indicated that the phosphate obtained with passivation treatment in niobium containing solution could be considered as a promising alternative to replace passivation with hexavalent chromium ions. Despite of the promising results, adjustments in the baths to obtain stability are still needed and should guide the next steps of the subject of this research.

Actuellement, les supercondensateurs sont au centre de beaucoup de recherches. Ils offrent une solution potentielle pour le stockage réversible de l´énergie que ce soit pour le domaine spatial, aéronautique ou encore le transport (véhicules hybrides). Un axe de recherche important, visant à augmenter les densités d'énergie et de puissance, est consacré aux systèmes oxydes de métaux de transition /charbon actif (C) asymétriques. Les systèmes à base de RuO2 présentent les capacités les plus élevées, supérieures à 700 F/g, mais leur coût et leur toxicité limitent leur application aux petits appareils électroniques. Des oxydes moins coûteux tels que les oxydes de cobalt (notamment Co3O4), MnO2, V2O5, Fe3O4, NiO, Ni(OH)2, ainsi que des polymères conducteurs électroniques, ont été étudiés de manière approfondie au cours des dernières décennies jusqu’à être utilisés, pour certains, dans des dispositifs commerciaux. Mais aucun système n’a été aussi étudié que le C / MnO2. En effet, il a été démontré que ce dernier est particulièrement intéressant car il peut fonctionner dans des milieux aqueux à des tensions pouvant aller jusqu’à 2V tout en gardant une bonne stabilité électrochimique durant le vieillissement. Néanmoins, les performances du système, en particulier en termes de densité de puissance, sont limitées à cause de la mauvaise conductivité électronique du MnO2. Il est possible de surmonter ce problème en ajoutant à l’oxyde de manganèse, des matériaux conducteurs à base de carbone (noir de carbone, nanotubes de carbone…) ou encore, en développant des stratégies de greffage ou de décoration plus élaborées. La combinaison d’oxydes avec des espèces carbonées est très largement rapportée dans la littérature alors que le mélange d’oxydes de différente nature l’est beaucoup moins. Nous proposons dans ce projet de synthétiser et de développer des matériaux originaux améliorant, par un effet synergique, les propriétés intéressantes du manganèse, du cobalt et de l'oxyde / hydroxyde de nickel. Les inconvénients de chaque composant étant compensés par les bonnes propriétés complémentaires des autres. Nous cherchons à réunir en un seul matériau (ou composite), le bon comportement pseudocapacitif du manganèse, la bonne conductivité électronique associée aux oxydes de cobalt, la grande capacité de l'hydroxyde de nickel ainsi que les propriétés de conduction du carbone. Ce projet de doctorat vise à concevoir et à fabriquer de nouvelles classes d'électrodes composites hybrides basées sur des assemblages de graphène (pour la capacitance renforcée à double couche) et d'oxydes poreux de métaux de transition (pour une capacité faradique supplémentaire due à de multiples processus rédox réversibles). Les avantages combinés du graphène et des oxydes de métaux de transition permettront aux supercondensateurs à haute densité d'énergie de travailler dans des électrolytes aqueux respectueux de l'environnement ce qui est, aujourd’hui, un besoin reconnu. / Supercapacitors are the focus of much research at the present time. They offer a potential solution for reversible energy storage in the fields of space, aircrafts or transportation (hybrid vehicles). An important research line, aiming at increasing both energy and power densities, is devoted to asymmetric transition metal oxides / activated carbon (C) systems. RuO2-based devices exhibit the highest capacitance, more than 700 F/g, but their cost limits the applications to small electronic devices. Less expensive oxides such as cobalt oxides (especially Co3O4), MnO2, V2O5, Fe3O4, NiO, Ni(OH)2, as well as electrically conducting polymers, have been extensively studied in the past decades, or used in commercial devices; they EACH exhibit each drawbacks and advantages with regard to applications. But no system has been investigated as much as the C/MnO2 one, which is particularly interesting because it can work in aqueous media at tensions up to 2 V, and high stability in ageing has been demonstrated. Nevertheless, the performances of the system, especially in terms of power density, are limited by the poor electronic conductivity of MnO2. This problem is usually solved by simply mixing conductive carbon materials (carbon black, CNTs…) with MnO2 or by developing more elaborated grafting or decoration strategies. The combination of oxide and carbonaceous species is widely reported in the literature, whereas combining oxides with different natures is less frequently encountered. We propose in this project to synthesize and develop original materials enhancing, through a synergistic effect, the interesting properties of manganese, cobalt and nickel oxide/hydroxide, the drawbacks of each component being overbalanced by the good complementary properties of the other components. We aim at gathering in one single material (or composite), the good pseudocapacitive behavior of manganese, the good electronic conductivity associated to cobalt oxides, the high capacity of nickel hydroxide, as well as the enhanced conduction properties of carbon. The present PhD project aims at designing and manufacturing new classes of hybrid composite electrodes based on assemblies of graphene (for enhanced double layer capacitance) and porous transition metals oxides (for additional faradaic capacitance due to multiple reversible redox processes) directly applied on metallic current collectors. The combined advantages of graphene with those of transition metals oxides will enable supercapacitors with high energy density, working in environmentally friendly aqueous electrolytes, which are an acknowledged need. / A procura crescente de energia em setores distintos, como residencial, transporte e industrial, bem como a proliferação de fontes renováveis de produção de energia, exigem novos e mais eficientes dispositivos de armazenamento de energia. Consequentemente, tem-se observado um interesse crescente na produção e engenharia de materiais para armazenamento de energia. Muito dos esforços de R&D estão centrados no desenvolvimento de materiais nanoestruturados que possam responder aos requisitos da aplicação, tais como densidade de energia, densidade de potência e estabilidade face à ciclagem do dispositivo. Presentemente são muitos os materiais investigados como potenciais candidatos para elétrodos para dispositivos de armazenamento de energia por via eletroquímia, nomeadamente baterias, condensadores, pseudocondensadores ou supercondensadores. O objetivo do presente trabalho é produzir e estudar novos materiais com uma resposta eletroquímica intermédia entre um elétrodo típico de supercondensador e um elétrodo típico de bateria, também conhecidos como elétrodos híbridos. Por essa razão, selecionaram-se hidróxidos e óxidos de níquel e cobalto devido à sua elevada atividade eletroquímica e baixo custo. Estes materiais foram combinados com derivados de grafeno, que exibem alta condutividade e elevada área superficial ativa. Portanto, este trabalho foca a síntese e caracterização fisico química e eletroquímica de hidróxidos e óxidos de níquel-cobalto nanoestruturados e sua combinação com óxido de grafeno reduzido para aplicações de armazenamento de energia. A síntese foi efectuada por duas vias distintas: eletrodeposição e exfoliação. A eletrodeposição é usada para obter hidróxidos e óxidos de níquel-cobalto em combinação com óxido de grafeno reduzido. Os resultados evidenciam um efeito sinérgico quando o óxido de grafeno reduzido é combinado com o (hidr)óxido de níquel- cobalto, isto é, um aumento na capacidade, condutividade e estabilidade do compósito quando comparado com o (hidr)óxido de níquel-cobalto. Neste trabalho é dada especial atenção à espectroscopia de impedância eletroquímica que foi utilizada para avaliar os fenômenos que ocorrem durante a carga e descarga contínua e compreender os processos que ocorrem no material ativo e que resultam na sua degradação. O hidróxido de níquel-cobalto é também preparado por exfoliação, em meio aquoso, por meio da intercalação de lactato, enquanto o tetra-butilamónio é utilizado na exfoliação do óxido de níquel-cobalto. A resposta eletroquímica é avaliada em diferentes eletrólitos após reconstrução. Os resultados revelam a influência das espécies intercaladas durante o processo de exfoliação: quando a exfoliação é realizada para fins de armazenamento de energia, as espécies intercaladas e a força da interação com o material ativo devem ser consideradas de antemão para evitar o bloqueio superficial ou inibição da interação elétrodo-eletrólito. Os resultados mostraram que a exfoliação é uma rota promissora para aumentar a área de superfície ativa dos materiais, um parâmetro crítico no desempenho eletroquímico dos materiais dos eletrodos. Nesta dissertação é também estudado o mecanismo de carga-descarga do hidróxido de níquel-cobalto, que ainda não está completamente entendido. Assim, compreender esse mecanismo é um passo crítico para otimizar a morfologia e o desempenho do material e para projetar futuros dispositivos de armazenamento de energia. Para esclarecer os processos que ocorrem durante a carga, aplica-se o modelo de Mott-Schottky foi aplicado parade modo a avaliar a variação da conductividade do material e da sua capacidade na interface elétrodo-eletrólito. [...]