Le stockage de l'énergie est un domaine en pleine évolution. Le développement des énergies renouvelable et les besoins croissants d'autonomie énergétique (ordinateur portable, Smartphone, voiture électrique) impliquent le développement de nouvelles technologies, plus performantes, moins coûteuses et écologiquement satisfaisantes. Les batteries lithium-air sont vues comme une alternative prometteuse aux batteries lithium- ion, car elles ont une capacité théorique de stockage 2-3 fois plus élevée. La structuration et la réactivité à la cathode est un verrou important. La présente étude se focalise sur le compartiment positif de la cellule, dans lequel les réactions de l’oxygène sont mises en jeu. Dans un premier temps, des modifications de la surface des électrodes de travail qui puissent agir comme fournisseurs de diènes, en utilisant le mécanisme Diels Alder, sont faites afin de changer les propriétés physico-chimiques de surfaces carbonées. Puis, la chimie click a été utilisée comme une deuxième technique de greffage en montrant que l’hydrophobicité des liquides ioniques influe sur la forme de greffage sur la surface des électrodes. Ensuite ces deux mécanismes de greffage sont utilisés pour étudier la réaction de réduction de l’oxygène et la réactivité du superoxyde à l’interface d’une électrode de carbone qui joue le rôle de cathode. / Energy storage is an evolving field. The development of renewable energies and the growing needs for energy autonomy (laptop, smartphone, and electric car) imply the development of new technologies that are more efficient, less costly and ecologically satisfactory. Lithium-air batteries are seen as a promising alternative to lithium-ion batteries, because they have a theoretical storage capacity 2-3 times higher. Structuring and reactivity at the cathode is an important lock. The present study focuses on the positive compartment of the cell, in which the reactions of oxygen are involved. In a first step, modifications of the surface of the working electrodes which can act as diene suppliers, using the Diels Alder mechanism in order to change the physicochemical properties of carbon surfaces. Then click chemistry was used as a second grafting technique showing that the hydrophobicity of the ionic liquids affects the grafting form on the surface of the electrodes. Then these two grafting mechanisms were used to study the oxygen reduction reaction and the reactivity of the superoxide at the interface of a carbon electrode which functions as a cathode.

Natural gas is stored as compressed natural gas (CNG) in heavy steel cylinders under pressures of 200-250 atm. However, such a method of storage has certain disadvantages which include multistage compression costs, limited driving range and safety aspects. Hence, alternative methods of storage such as adsorbed natural gas (ANG) which involve adsorbing natural gas at moderate pressures and room temperatures in a suitable nanoporous material are currently being explored. In this thesis, we have isolated model carbon nanostructures and defect geometries most likely to be found in these materials and investigated their specific interactions with methane. The thesis is concerned with ab-initio density functional theory calculations on these various model carbon nanostructures in order to identify the potential candidates that enhance methane adsorption. The adsorption energies of methane on graphite and graphene sheets were similar, with a value of 12.3 kJ/mol for graphene. The Stone-Wales defect in graphene was found to increase the methane adsorption energy to 37.2 kJ/mol, and small surface undulations on the graphene sheet resulted in a smaller increase (16 kJ/mol) in the adsorption energy relative to graphene. The presence of an interstitial carbon was found to significantly reduce the adsorption energy to 5.2 kJ/mol. The enhanced adsorption energy in the case of the Stone-Wales defect was attributed to the significant charge redistribution in the vicinity of the defect. A variety of functional groups such as carboxylic acid (COOH), carbonyl (CO), phenol (OH), pyran (-O-), phenone (=O), peroxide (OOH) and amine (NH2) groups have been observed on carbon surfaces. Extensive density functional calculations of methane adsorbed on various chemically functionalized graphene nanoribbons were carried out to evaluate their methane adsorption energies. A significant finding in this study, is the increased adsorption energies (relative to graphene) that occur for the functional groups containing the OH moiety. The adsorption energies for edge functionalized graphene nanoribbons are 27.6 and 69.7 kJ/mol for COOH and OOH functionalization. Additional computations reveal a strong correlation between the induced dipole moment on methane and the strength of the adsorption energies obtained for the extended nanoribbons. Adsorption isotherms for methane were obtained using grand canonical Monte Carlo simulations for slit-like graphitic pores with and without functional groups. For both OH and COOH functionalized graphite, we observe more than a 40 % increase in the volumetric loading over bare graphite for the highest weight % of the functional group and smallest pore width considered. The maximum volumetric loading decreases with a decrease in the wt% of the functional groups and with an increase in the pore width.

Orientador: Douglas Soares Galvão / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-07T20:03:25Z (GMT). No. of bitstreams: 1 Martins_BrunoVieiradaCunha_M.pdf: 9990355 bytes, checksum: 99ae9e77c86e165f825dfcd49bc23de6 (MD5) Previous issue date: 2006 / Resumo: Apresenta-se neste trabalho um estudo teórico baseado em uma nova familia de nanoestruturas de carbono, as chamadas nanofitas de carbono. Estas consistem em fitas delgadas de grafeno com a singular característica de possuírem uma conformação de equilíbrio na forma espiral, a qual pode ser mais estável que a conformação planar, viabilizada pelo delicado equilíbrio de forças entre a interação de van der Waals e a tensão elástica gerada pelo empenamento. Sua proximidade topológica com as nanoespirais, das quais foram inspiradas, permite o estabelecimento de paralelos estruturais e funcionais que orientam o trabalho. Os métodos de cálculo consistem em mecânica e dinâmica molecular clássicas utilizando o campo de força reativo de Brenner. O modelo, construído de acordo com princípios quânticos incorporados de forma paramétrica, permite a descrição da formação e quebra de ligações químicas a partir de informações sobre o ambiente onde o átomo está inserido. As simulações indicam a viabilidade da obtenção de espirais a partir de fitas para baixas temperaturas, o que em princípio permite que estas substituam as nanoespirais em suas aplicações como nanoatuadores. A possibilidade de formação de anéis a partir de condições geométricas especiais também é explorada. A diversidade topológica e a viabilidade de obtenção de estruturas diferenciadas em função da temperatura constituem propriedades únicas com um potencial de aplicação no desenvolvimento de nanoestruturas de formato variável. Em relação às nanoespirais, o trabalho soluciona o problema da formação de estruturas cônicas em processos dinâmicos. / Abstract: This work presents a theoretical study based on a novel family of carbon nanostructures, the carbon nanobelts. These structures consists in narrow graphene stripes having the spiral form as one of its equilibrium configurations, which may be more stable than the planar conformation. This stability condition is determined by a delicate balance between the van der Waals interactions and the elastic tension generated by the bending. Its topological proximity with the nanoscrolls, from which they were inspired, allows the obtention of their common structural and functional features. The calculation methods consist in classical molecular mechanics and dynamics using the reactive Brenner forcefield. The model, constructed in accordance with quantum principles incorporated in a parametric form, allows the description of formation and broken of chemical bonds from the informations about the environment where the atoms are inserted. The simulations points to the viability of obtaintion of spirals from belts at low temperatures, what in principle allows the substitution of nanoscrolls in its applications as nanoactuators. The possibility of formation of rings from special geometric conditions is explorated. The topological diversity and the viability of obtention of differentiated structures as a function of the temperature constitute unique properties with a potential application in the development of variable shape nanostructures. In relation to nanoscrolls, this work solves the problem of formation of conical structures in dynamical processes. / Mestrado / Física da Matéria Condensada / Mestre em Física

The main goal of this work is to search for new stable porous carbon-based materials, which have the ability to accommodate and store hydrogen gas. Theoretical and experimental studies suggest a close relation between the nano-scale structure of the material and its storage capacity. In order to design materials with a high storage capacity, a compromise between the size and the shape of the nanopores must be considered. Therefore, a number of different carbon-based materials have been investigated: carbon foams, dislocated graphite, graphite intercalated by C60 molecules, and metal-organic frameworks. The structures of interest include experimentally well-known as well as hypothetical systems. The studies were focused on the determination of important properties and special features, which may result in high storage capacities. Although the variety of possible pure carbon structures and metal-organic frameworks is almost infinite, the materials described in this work possess the main structural characteristics, which are important for gas storage.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第23243号 / 農博第2450号 / 新制||農||1084(附属図書館) / 学位論文||R3||N5333(農学部図書室) / 京都大学大学院農学研究科応用生命科学専攻 / (主査)教授 白井 理, 教授 三芳 秀人, 教授 森 直樹 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Solar thermal energy is emerging as an important source of renewable energy for meeting the ever-increasing energy requirements of the world. Solar selective coatings are known to enhance the efficiency of the photo thermal energy conversion. An ideal solar selective coating has zero reflectance in the solar spectrum region (i.e., 0.3-2.5 µm) and 100% reflectance in the infrared (IR) region (i.e. 2.5-50 µm). In this thesis, novel carbon nanotubes (CNT) and graphene based absorbers have been developed for photo thermal applications. Carbon nanotubes have good optical properties (i.e., α and ε close to 1), high aspect ratios (> 150), high surface area (470 m2/g) and high thermal conductivity (> 3000 W/mK), which enable rapid heat transfer from the CNTs to the substrates. Similarly, graphene also exhibits high transmittance (97%), low reflectance, high thermal conductivity (5000 W/mK) and high oxidation resistance behaviour. The major drawback of using CNTs for photothermal applications is that it exhibits poor spectral selectivity (i.e., α/ε = 1). In other words, it acts as a blackbody absorber. On the other hand, graphene exhibits poor intrinsic absorption behaviour (α - 2.3%) in a broad wavelength range (UV-Near IR). The main objective of the present study is to develop CNT and graphene based absorbers for photothermal conversion applications. The growth of CNT and graphene was carried out using chemical vapour deposition and sputtering techniques. An absorber-reflector tandem concept was used to develop the CNT based tandem absorber (Ti/Al2O3/Co/CNT). The transition from blackbody absorber to solar selective absorber was achieved by varying the CNT thicknesses and by using a suitable underlying absorber (Ti/Al2O3). A simple multilayer heat mirror concept was used to develop the graphene based multilayer absorber (SiO2/graphene/Cu/graphene). The transition from high transmitance to high absorptance was achieved by varying the Cu thickness. The refractive indices and the extinction coefficients of Ti/Al2O3, AlTiO and graphene samples were determined by the phase-modulated spectroscopic ellipsometric technique. Finally, the optical properties (i.e., absorptance and the emittance) of the CNT and graphene based absorbers were investigated. Chapter 1 gives a brief introduction about solar thermal energy, spectrally selective coating and photothermal conversion. The different types of absorbers used to achieve the spectral selectivity have also been discussed shortly. A brief description about the carbon-based materials/allotropes and their properties are outlined. The properties of carbon nanotubes and graphene which are the 1-D and 2-D allotropes of carbon, respectively are tabulated. A detailed literature survey was carried out in order to identify the potential candidates for the photothermal conversion applications. The objectives and the scope of the thesis are also discussed in this chapter. Chapter 2 discusses the deposition and characterization techniques used for the growth and the study of 1-D and 2-D carbon nanostructures. Atmospheric pressure chemical vapour deposition (CVD) and hot filament CVD techniques were used to grow CNT and graphene, respectively. The magnetron sputtering technique was used for the growth of ‘Ti’, ‘Al2O3’ and Co layers which were needed to grow the CNT based tandem absorber on stainless steel (SS) substrates. The important characterization techniques used to examine various properties of the 1-D and 2-D carbon nanostructures include: X-ray diffraction, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), phase modulated ellipsometry, UV-VIS-NIR spectrophotometer, Fourier-infrared spectroscopy (FTIR), micro-Raman spectroscopy and solar spectrum reflectometer and emissometer. Chapter 3 describes the design and development of Ti/Al2O3 coating for the growth of CNT-based tandem absorber on SS substrates. The power densities of the aluminum and titanium targets and the oxygen flow rates were optimized to deposit the Ti/Al2O3 coatings. The optimized Ti/Al2O3 coating with a Co catalyst on top was used as an underlying substrate to grow the CNT-based tandem absorber at 800°C in Ar+H2 atmosphere (i.e., CNT/Co/Al2O3/Ti/SS). The formation of aluminum titanium oxide (AlTiO) was observed during the CNT growth process and this layer enhances the optical properties of the CNT based tandem absorber. The optical constants of Ti, Al2O3 and AlTiO coatings were measured using phase modulated spectroscopic ellipsometry in the wavelength range of 300-900 nm. The experimentally measured ellipsometric parameters have been fitted with the simulated spectra using the Tauc-Lorentz model for generating the dispersion of the optical constants of the Al2O3 and the AlTiO layers. The Ti and Al2O3 layer thicknesses play a major role in the design of the CNT based tandem absorber with good optical properties. Chapter 4 describes the synthesis and characterization of the CNT based tandem absorber (Ti/AlTiO/CoO/CNTs) deposited on SS substrates. CNTs at different thicknesses were grown on Ti/AlTiO/CoO coated SS substrates using atmospheric CVD at various growth durations. The transition from blackbody absorber to solar selective absorber was achieved by varying the thicknesses of the CNTs and by suitably designing the bottom tandem absorber. At thicknesses > 10 µm, the CNT forest acts as near-perfect blackbody absorber, whereas, at thicknesses ≤ 0.36 µm, the IR reflectance of the coating increases (i.e., ε = 0.20) with slight decrease in the absorptance (i.e., α = 0.95). A spectral selectivity (α/ε) of 4.75 has been achieved for the 0.36 µm-thick CNTs grown on SS/Ti/AlTiO/CoO tandem absorber. Chapter 5 discusses the growth of graphene on polycrystalline copper (Cu) foils (1 cm × 1 cm) using hot filament CVD. The roles of the process parameters such as gas flow rates (methane and hydrogen), growth temperatures (filament and substrate) and durations on the growth of graphene were studied. The process parameters were also optimized to grow monolayer, bilayer and multilayer graphene in a controlled manner and the growth mechanism was deduced from the experimental results. The presence of graphene on Cu foils was confirmed using XPS, micro-Raman spectroscopy, FESEM and TEM techniques. The FESEM data clearly confirmed that graphene starts nucleating as hexagonal islands which later evolves into dendritic lobe shaped islands with an increase in the supersaturation. The TEM data substantiated further the growth of monolayer, bilayer and multilayer graphene. The intensity of 2D and G peak ratio (i.e., I2D/IG = 2) confirmed the presence of the monolayer graphene and the absence of the ‘D’ peak in the Raman spectrum indicated the high purity of graphene grown on Cu foils. The results show that the polycrystalline morphology of the copper foil has negligible effect on the growth of monolayer graphene. In Chapter 6, the design and development of graphene/Cu/graphene multilayer absorber and the study of its optical properties are discussed. The multilayer graphene grown on Cu foils has been transferred on quartz and SiO2 substrates in order to fabricate the graphene/Cu/graphene multilayer absorber. The sputtering technique was used to deposit copper on top of graphene/quartz substrates. The uniformity of the transferred multilayer graphene films was confirmed using Raman mapping. A simple multilayer heat mirror concept was used to develop the graphene/Cu/graphene absorber on quartz substrates and the transition from high transmittance to high absorptance was achieved. In order to further enhance the absorption, the graphene/Cu/graphene multilayer coating was fabricated on SiO2 substrates. The thickness of the Cu layer plays a major role in creating destructive interference, which results in high absorptance and low emittance. A high specular absorptance of 0.91 and emittance of 0.22 was achieved for the SiO2 graphene/Cu/graphene multilayer absorber. The specular reflectance of the multilayer absorber coatings was measured using the universal reflectance accessory of the UV-VIS-NIR spectrophotometer. Chapter 7 summarizes the major findings of the present investigation and also suggests future aspects for experimentation and analysis. The results obtained from the present work clearly indicate that both CNT and graphene based absorbers can be used as potential candidates for photothermal applications. In particular, the CNT based tandem absorber can be used for high temperature solar thermal applications and the graphene based multilayer absorber finds applications in the area of photodetectors and optical broadband modulators.

Die vorliegende Promotion beinhaltet die Untersuchung von irregulären Kohlenstoff-Nanostrukturen, die mittels Hochenergie-Kugelmahlen hergestellt wurden. Die wissenschaftliche Herausforderung besteht darin, die strukturelle Vielfalt dieser Nanostrukturen experimentell zu erfassen, zu klassifizieren und bezüglich ausgewählter Eigenschaften zu bewerten, sowie mit den Herstellungsparametern in Zusammenhang zu bringen. Die Pulver konnten nach den Mahlungen hinsichtlich ihrer Struktur in zwei grundsätzliche Typen eingeteilt werden: (I) ein Nanopulver, das aus graphitischen Stapelpaketen besteht, welche in eine amorphe Matrix eingebettet sind, (II) ein vollständig amorphisiertes Pulver. Die Strukturanalyse in Bezug auf die Mahlbedingungen (Mahlatmosphäre, Mahltemperatur) zeigt, dass die Dauer der Nanostrukturierung sowie die Anzahl und Größe von graphitischen Stapelpaketen gezielt beeinflusst werden kann. Außerdem konnten Hinweise gefunden werden, die darauf hindeuten, dass Mahlen bei tiefen Temperaturen oder unter Wasserstoffatmosphäre die Agglomeration der Nanopartikel verringern kann. Das Kugelmahlen ermöglicht es ebenfalls, die spezifische Oberfläche des Graphitpulvers von 5,5 m2/g auf 725 m2/g innerhalb von fünf Mahlstunden zu erhöhen. Der Anteil der Verunreinigungen (Fe) liegt dabei nicht höher als 0,05 wt%. Es ist jedoch zu beachten, dass sämtliche Eigenschaften stark von den verschiedenen Mahlparametern (Mahltemperatur, Mahlmaterial) abhängen. Die für Adsorptionsuntersuchungen optimalen Eigenschaften (große spezifische Oberfläche, erhöhte Reaktivität, geringe Verunreinigungen) werden schon nach kurzer Mahldauer erreicht. Wiederholungsmahlungen und Wiederholungsmessungen verschiedener Eigenschaften (spezifische Oberfläche, Verbrennungstemperatur) machen deutlich, dass die Ergebnisse reproduzierbar sind, und dass keine Alterungserscheinungen während der Lagerung unter Argonatmosphäre im Zeitraum von einem Jahr auftreten. Die Wasserstoffspeicherung an nanostrukturierten Kohlenstoffpulvern konnte nachgewiesen werden. Die maximalen Speicherkapazitäten für Temperaturen nahe 77 K lagen bei 1,5 wt%. Für niedrigere Temperaturen Tist = 35 K zeigten sich höhere Speicherkapazitäten von bis zu 5 wt%. Die Korrelation der ermittelten Speicherkapazitäten mit den theoretisch erreichbaren Werten in Bezug auf die Oberfläche der Proben zeigt, dass im Experiment deutlich höhere Werte erhalten werden. Dies lässt den Schluss zu, dass neben der Speicherung an der Oberfläche der Pulver ein weiterer Speichermechanismus innerhalb der Mikroporen der Proben stattfindet.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nanostructured carbon materials production can constitute an alternative for a sustainable management of residues originated from petrochemical waste and agriculture activities, toward the development of multifunctional ―green‖ materials. The coconut processing industry generate a significant amount of waste (45% of mass). The shell, fibers and coconut coir dust have been studied extensively to produce conventional carbon materials. The goal of this work was to produce carbon-clay nanocomposites and carbon nanostructures by hydrothermal route. By using coconut fiber residue as carbonaceous precursor along with lamellar (montmorillonite and kaolinite) and fibrous clays (sepiolite and attapulgite).The obtained materials were characterized by X-ray diffraction, Raman and Infrared spectroscopy, thermogravimetry, scanning and transmission electron microscopy and area and porosity measurements by BET. Carbon phase formation was indicated by infrared results with bands at ~ 1444 cm-1 and ~ 1512 cm-1 assigned to C=C of aromatic groups. Raman spectroscopy results showed presence of carbonaceous species by the appearance of D and G bands assigned to disordered and graphitic crystallites, respectively. The estimated particle size based on Raman bands was found between 8-33 nm. SEM results showed that the morphology of coconut coir dust was preserved and all materials showed overlapping sheets and plates formation. In transmission electron microscopy (TEM) images it was possible to observe three types of carbon nanostructures: sheets, fibers and nanoparticles. It was observed the formation of very thin amorphous sheets, as well as the presence of partially ordered graphitic domains and disperse carbon nanoparticles. / A produção de materiais de carbono nanoestruturados pode constituir uma alternativa para a reutilização de resíduos provenientes da indústria petroquímica e atividades agrícolas, abrindo um caminho para o desenvolvimento de materiais ―verdes‖ multifuncionais. Da indústria do processamento do coco, origina-se uma quantidade significativa de resíduos (45% do fruto). A casca, fibras e pó de coco são estudados extensivamente para a produção de materiais de carbono convencionais. A proposta deste trabalho foi produzir nanocompósitos de carbono-argila e nanoestruturas de carbono, via rota hidrotérmica. Para tanto foi utilizado o pó de coco in natura como precursor carbonáceo e argilas lamelares (montmorillonita e caulinita) e fibrosas (atapulgita e sepiolita). Os materiais obtidos foram caracterizados por difração de Raios-X, espectroscopia Raman e no Infravermelho, Termogravimetria, Microscopia eletrônica de Varredura (MEV) e Transmissão (MET), e medidas de área superficial e porosidade por BET. A formação de carbono foi indicada pelos resultados de infravermelho com bandas em ~1444 cm-1 e ~1512 cm-1 atribuídas a C=C de grupos aromáticos. Os resultados de espectroscopia Raman evidenciaram a presença de espécies carbonáceas pelo aparecimento das bandas D e G atribuídas, respectivamente, a presença de desordem e cristalitos de grafite. A faixa de tamanho de partícula estimada a partir das bandas Raman está entre 8-33 nm. Os resultados de MEV mostraram que a morfologia do pó de coco foi preservada e todos os materiais obtidos apresentaram a formação de folhas sobrepostas e placas. Nas imagens de microscopia eletrônica de transmissão (MET) foi possível observar a formação de três tipos de nanoestruturas de carbono: folhas, fibras e nanopartículas. Observou-se a formação de folhas muito finas, de caráter predominantemente amorfo, bem como a presença de domínios grafiticos parcialmente ordenados, e nanopartículas de carbono dispersas.

Orientadores: Rubens Maciel Filho, André Luiz Jardini Munhoz / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-17T01:50:40Z (GMT). No. of bitstreams: 1 MaciasMacias_Carolina_M.pdf: 33756712 bytes, checksum: 756466b4de64af3709bb1a7410020b1a (MD5) Previous issue date: 2010 / Resumo: Após a descoberta dos nanotubos de Carbono, o estudo de novos materiais de Carbono surgiu como um fascinante assunto de pesquisa para a comunidade científica. As propriedades excepcionais destes materiais os fazem potenciais aditivos para lubrificantes, suportes para catalisadores, materiais para estocagem de energia, e materiais para dispositivos nanoeletrônicos. Técnicas de síntese muito versáteis como o método Laser-Forno e o método de Deposição Química de Vapor são usadas para produzir vários tipos de materiais de Carbono como nanotubos, esferas e fibras a partir de hidrocarbonetos líquidos e gasosos e de outras matérias-primas. Por outro lado, o processamento do petróleo gera resíduos que vêm sendo tratados por meio de processos inovadores como a Destilação Molecular visando à obtenção de produtos finais de alto valor agregado. Porém, esta técnica gera resíduos ainda mais pesados (ultrapesados) de petróleo de composição rica em hidrocarbonetos, resinas, asfaltenos, aromáticos e heteroátomos, característica que lhes confere potencial como precursores de estruturas carbonosas, mas paralelamente impõe desafios tecnológicos em função da sua complexidade. Neste contexto, o resíduo ultrapesado da destilação molecular aplicada ao resíduo de vácuo foi avaliado como matéria prima para a síntese de estruturas de carbono. Em razão disso, foi construído um reator bifuncional para a síntese de materiais carbonosos por meio do método Laser- Forno e do método de Deposição Química de Vapor. Com o projeto adequado do reator foram desenvolvidas políticas e condições operacionais que possibilitaram a síntese de esferas de Carbono. Estas foram caracterizadas e foi possível demonstrar a potencialidade do resíduo da destilação molecular como material precursor de nanoestruturas de Carbono, abrindo um novo caminho de pesquisa que envolve o processamento de resíduos com a obtenção de produtos de alto valor agregado. / Abstract: Since the discovery of carbon nanotubes and related carbon materials, an intense scientific activity around these new structures has been stimulated. Because of the exceptional properties showed by these materials, they have been investigated as lubricant additives, catalyst supports, energy storage materials and nanoelectronic devices. Various methods, including Chemical Vapor Deposition and Laser-Furnace technique, have been developed for the production of carbon nanomaterials (nanotubes, spheres and fibers) from liquid and gaseous hydrocarbons, and other carbon precursors. Additionally, petroleum processing generates oil wastes that have been treated by various innovative processes as Molecular Distillation, with the intention of producing high value final products as gasoline and lubricant oils. Nevertheless, this technique generates oil wastes even heavier (ultraheavy oil), that exhibit a complex chemical composition based on saturates, resins, asphalthenes, aromatics and heteroatoms compounds. This feature suggests that Molecular Distillation Residua could be used as a carbon precursor for carbon nanostructures, but additionally imposes process challenges. In this context, the ultraheavy oil residue from Molecular Distillation of vacuum residue was assessed as raw material for the synthesis of carbon nanostructures. The performance evaluation experiments were carried out in a reactor for carbon materials production by Chemical Vapor Deposition and Laser-Furnace technique, built for that purpose. There were developed policies and operational conditions that made possible the Carbon Spheres production. The as-produced Carbon Spheres were characterized by various techniques, and the potential of Molecular Distillation Residue, as carbon nanostructures precursor, was demonstrated. Finally, a new branch of research involving oil wastes processing and carbon nanomaterials synthesis was successfully initiated. / Mestrado / Desenvolvimento de Processos Químicos / Doutor em Engenharia Química

No description available.