9,880 research outputs found

    A Decision Support System for Economic Viability and Environmental Impact Assessment of Vertical Farms

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    Vertical farming (VF) is the practice of growing crops or animals using the vertical dimension via multi-tier racks or vertically inclined surfaces. In this thesis, I focus on the emerging industry of plant-specific VF. Vertical plant farming (VPF) is a promising and relatively novel practice that can be conducted in buildings with environmental control and artificial lighting. However, the nascent sector has experienced challenges in economic viability, standardisation, and environmental sustainability. Practitioners and academics call for a comprehensive financial analysis of VPF, but efforts are stifled by a lack of valid and available data. A review of economic estimation and horticultural software identifies a need for a decision support system (DSS) that facilitates risk-empowered business planning for vertical farmers. This thesis proposes an open-source DSS framework to evaluate business sustainability through financial risk and environmental impact assessments. Data from the literature, alongside lessons learned from industry practitioners, would be centralised in the proposed DSS using imprecise data techniques. These techniques have been applied in engineering but are seldom used in financial forecasting. This could benefit complex sectors which only have scarce data to predict business viability. To begin the execution of the DSS framework, VPF practitioners were interviewed using a mixed-methods approach. Learnings from over 19 shuttered and operational VPF projects provide insights into the barriers inhibiting scalability and identifying risks to form a risk taxonomy. Labour was the most commonly reported top challenge. Therefore, research was conducted to explore lean principles to improve productivity. A probabilistic model representing a spectrum of variables and their associated uncertainty was built according to the DSS framework to evaluate the financial risk for VF projects. This enabled flexible computation without precise production or financial data to improve economic estimation accuracy. The model assessed two VPF cases (one in the UK and another in Japan), demonstrating the first risk and uncertainty quantification of VPF business models in the literature. The results highlighted measures to improve economic viability and the viability of the UK and Japan case. The environmental impact assessment model was developed, allowing VPF operators to evaluate their carbon footprint compared to traditional agriculture using life-cycle assessment. I explore strategies for net-zero carbon production through sensitivity analysis. Renewable energies, especially solar, geothermal, and tidal power, show promise for reducing the carbon emissions of indoor VPF. Results show that renewably-powered VPF can reduce carbon emissions compared to field-based agriculture when considering the land-use change. The drivers for DSS adoption have been researched, showing a pathway of compliance and design thinking to overcome the ‘problem of implementation’ and enable commercialisation. Further work is suggested to standardise VF equipment, collect benchmarking data, and characterise risks. This work will reduce risk and uncertainty and accelerate the sector’s emergence

    Gasificação direta de biomassa para produção de gás combustível

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    The excessive consumption of fossil fuels to satisfy the world necessities of energy and commodities led to the emission of large amounts of greenhouse gases in the last decades, contributing significantly to the greatest environmental threat of the 21st century: Climate Change. The answer to this man-made disaster is not simple and can only be made if distinct stakeholders and governments are brought to cooperate and work together. This is mandatory if we want to change our economy to one more sustainable and based in renewable materials, and whose energy is provided by the eternal nature energies (e.g., wind, solar). In this regard, biomass can have a main role as an adjustable and renewable feedstock that allows the replacement of fossil fuels in various applications, and the conversion by gasification allows the necessary flexibility for that purpose. In fact, fossil fuels are just biomass that underwent extreme pressures and heat for millions of years. Furthermore, biomass is a resource that, if not used or managed, increases wildfire risks. Consequently, we also have the obligation of valorizing and using this resource. In this work, it was obtained new scientific knowledge to support the development of direct (air) gasification of biomass in bubbling fluidized bed reactors to obtain a fuel gas with suitable properties to replace natural gas in industrial gas burners. This is the first step for the integration and development of gasification-based biorefineries, which will produce a diverse number of value-added products from biomass and compete with current petrochemical refineries in the future. In this regard, solutions for the improvement of the raw producer gas quality and process efficiency parameters were defined and analyzed. First, addition of superheated steam as primary measure allowed the increase of H2 concentration and H2/CO molar ratio in the producer gas without compromising the stability of the process. However, the measure mainly showed potential for the direct (air) gasification of high-density biomass (e.g., pellets), due to the necessity of having char accumulation in the reactor bottom bed for char-steam reforming reactions. Secondly, addition of refused derived fuel to the biomass feedstock led to enhanced gasification products, revealing itself as a highly promising strategy in terms of economic viability and environmental benefits of future gasification-based biorefineries, due to the high availability and low costs of wastes. Nevertheless, integrated techno economic and life cycle analyses must be performed to fully characterize the process. Thirdly, application of low-cost catalyst as primary measure revealed potential by allowing the improvement of the producer gas quality (e.g., H2 and CO concentration, lower heating value) and process efficiency parameters with distinct solid materials; particularly, the application of concrete, synthetic fayalite and wood pellets chars, showed promising results. Finally, the economic viability of the integration of direct (air) biomass gasification processes in the pulp and paper industry was also shown, despite still lacking interest to potential investors. In this context, the role of government policies and appropriate economic instruments are of major relevance to increase the implementation of these projects.O consumo excessivo de combustíveis fósseis para garantir as necessidades e interesses da sociedade conduziu à emissão de elevadas quantidades de gases com efeito de estufa nas últimas décadas, contribuindo significativamente para a maior ameaça ambiental do século XXI: Alterações Climáticas. A solução para este desastre de origem humana é de caráter complexo e só pode ser atingida através da cooperação de todos os governos e partes interessadas. Para isto, é obrigatória a criação de uma bioeconomia como base de um futuro mais sustentável, cujas necessidades energéticas e materiais sejam garantidas pelas eternas energias da natureza (e.g., vento, sol). Neste sentido, a biomassa pode ter um papel principal como uma matéria prima ajustável e renovável que permite a substituição de combustíveis fósseis num variado número de aplicações, e a sua conversão através da gasificação pode ser a chave para este propósito. Afinal, na prática, os combustíveis fósseis são apenas biomassa sujeita a elevada temperatura e pressão durante milhões de anos. Além do mais, a gestão eficaz da biomassa é fundamental para a redução dos riscos de incêndio florestal e, como tal, temos o dever de utilizar e valorizar este recurso. Neste trabalho, foi obtido novo conhecimento científico para suporte do desenvolvimento das tecnologias de gasificação direta (ar) de biomassa em leitos fluidizados borbulhantes para produção de gás combustível, com o objetivo da substituição de gás natural em queimadores industriais. Este é o primeiro passo para o desenvolvimento de biorrefinarias de gasificação, uma potencial futura indústria que irá providenciar um variado número de produtos de valor acrescentado através da biomassa e competir com a atual indústria petroquímica. Neste sentido, foram analisadas várias medidas para a melhoria da qualidade do gás produto bruto e dos parâmetros de eficiência do processo. Em primeiro, a adição de vapor sobreaquecido como medida primária permitiu o aumento da concentração de H2 e da razão molar H2/CO no gás produto sem comprometer a estabilidade do processo. No entanto, esta medida somente revelou potencial para a gasificação direta (ar) de biomassa de alta densidade (e.g., pellets) devido à necessidade da acumulação de carbonizados no leito do reator para a ocorrência de reações de reforma com vapor. Em segundo, a mistura de combustíveis derivados de resíduos e biomassa residual florestal permitiu a melhoria dos produtos de gasificação, constituindo desta forma uma estratégia bastante promissora a nível económico e ambiental, devido à elevada abundância e baixo custo dos resíduos urbanos. Contudo, devem ser efetuadas análises técnico-económicas e de ciclo de vida para a completa caraterização do processo. Em terceiro, a aplicação de catalisadores de baixo custo como medida primária demonstrou elevado potencial para a melhoria do gás produto (e.g., concentração de H2 e CO, poder calorífico inferior) e para o incremento dos parâmetros de eficiência do processo; em particular, a aplicação de betão, faialite sintética e carbonizados de pellets de madeira, demonstrou resultados promissores. Finalmente, foi demonstrada a viabilidade económica da integração do processo de gasificação direta (ar) de biomassa na indústria da pasta e papel, apesar dos parâmetros determinados não serem atrativos para potenciais investidores. Neste contexto, a intervenção dos governos e o desenvolvimento de instrumentos de apoio económico é de grande relevância para a implementação destes projetos.Este trabalho foi financiado pela The Navigator Company e por Fundos Nacionais através da Fundação para a Ciência e a Tecnologia (FCT).Programa Doutoral em Engenharia da Refinação, Petroquímica e Químic

    Predictive Maintenance of Critical Equipment for Floating Liquefied Natural Gas Liquefaction Process

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    Predictive Maintenance of Critical Equipment for Liquefied Natural Gas Liquefaction Process Meeting global energy demand is a massive challenge, especially with the quest of more affinity towards sustainable and cleaner energy. Natural gas is viewed as a bridge fuel to a renewable energy. LNG as a processed form of natural gas is the fastest growing and cleanest form of fossil fuel. Recently, the unprecedented increased in LNG demand, pushes its exploration and processing into offshore as Floating LNG (FLNG). The offshore topsides gas processes and liquefaction has been identified as one of the great challenges of FLNG. Maintaining topside liquefaction process asset such as gas turbine is critical to profitability and reliability, availability of the process facilities. With the setbacks of widely used reactive and preventive time-based maintenances approaches, to meet the optimal reliability and availability requirements of oil and gas operators, this thesis presents a framework driven by AI-based learning approaches for predictive maintenance. The framework is aimed at leveraging the value of condition-based maintenance to minimises the failures and downtimes of critical FLNG equipment (Aeroderivative gas turbine). In this study, gas turbine thermodynamics were introduced, as well as some factors affecting gas turbine modelling. Some important considerations whilst modelling gas turbine system such as modelling objectives, modelling methods, as well as approaches in modelling gas turbines were investigated. These give basis and mathematical background to develop a gas turbine simulated model. The behaviour of simple cycle HDGT was simulated using thermodynamic laws and operational data based on Rowen model. Simulink model is created using experimental data based on Rowen’s model, which is aimed at exploring transient behaviour of an industrial gas turbine. The results show the capability of Simulink model in capture nonlinear dynamics of the gas turbine system, although constraint to be applied for further condition monitoring studies, due to lack of some suitable relevant correlated features required by the model. AI-based models were found to perform well in predicting gas turbines failures. These capabilities were investigated by this thesis and validated using an experimental data obtained from gas turbine engine facility. The dynamic behaviours gas turbines changes when exposed to different varieties of fuel. A diagnostics-based AI models were developed to diagnose different gas turbine engine’s failures associated with exposure to various types of fuels. The capabilities of Principal Component Analysis (PCA) technique have been harnessed to reduce the dimensionality of the dataset and extract good features for the diagnostics model development. Signal processing-based (time-domain, frequency domain, time-frequency domain) techniques have also been used as feature extraction tools, and significantly added more correlations to the dataset and influences the prediction results obtained. Signal processing played a vital role in extracting good features for the diagnostic models when compared PCA. The overall results obtained from both PCA, and signal processing-based models demonstrated the capabilities of neural network-based models in predicting gas turbine’s failures. Further, deep learning-based LSTM model have been developed, which extract features from the time series dataset directly, and hence does not require any feature extraction tool. The LSTM model achieved the highest performance and prediction accuracy, compared to both PCA-based and signal processing-based the models. In summary, it is concluded from this thesis that despite some challenges related to gas turbines Simulink Model for not being integrated fully for gas turbine condition monitoring studies, yet data-driven models have proven strong potentials and excellent performances on gas turbine’s CBM diagnostics. The models developed in this thesis can be used for design and manufacturing purposes on gas turbines applied to FLNG, especially on condition monitoring and fault detection of gas turbines. The result obtained would provide valuable understanding and helpful guidance for researchers and practitioners to implement robust predictive maintenance models that will enhance the reliability and availability of FLNG critical equipment.Petroleum Technology Development Funds (PTDF) Nigeri

    Socio-endocrinology revisited: New tools to tackle old questions

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    Animals’ social environments impact their health and survival, but the proximate links between sociality and fitness are still not fully understood. In this thesis, I develop and apply new approaches to address an outstanding question within this sociality-fitness link: does grooming (a widely studied, positive social interaction) directly affect glucocorticoid concentrations (GCs; a group of steroid hormones indicating physiological stress) in a wild primate? To date, negative, long-term correlations between grooming and GCs have been found, but the logistical difficulties of studying proximate mechanisms in the wild leave knowledge gaps regarding the short-term, causal mechanisms that underpin this relationship. New technologies, such as collar-mounted tri-axial accelerometers, can provide the continuous behavioural data required to match grooming to non-invasive GC measures (Chapter 1). Using Chacma baboons (Papio ursinus) living on the Cape Peninsula, South Africa as a model system, I identify giving and receiving grooming using tri-axial accelerometers and supervised machine learning methods, with high overall accuracy (~80%) (Chapter 2). I then test what socio-ecological variables predict variation in faecal and urinary GCs (fGCs and uGCs) (Chapter 3). Shorter and rainy days are associated with higher fGCs and uGCs, respectively, suggesting that environmental conditions may impose stressors in the form of temporal bottlenecks. Indeed, I find that short days and days with more rain-hours are associated with reduced giving grooming (Chapter 4), and that this reduction is characterised by fewer and shorter grooming bouts. Finally, I test whether grooming predicts GCs, and find that while there is a long-term negative correlation between grooming and GCs, grooming in the short-term, in particular giving grooming, is associated with higher fGCs and uGCs (Chapter 5). I end with a discussion on how the new tools I applied have enabled me to advance our understanding of sociality and stress in primate social systems (Chapter 6)

    Hunting Wildlife in the Tropics and Subtropics

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    The hunting of wild animals for their meat has been a crucial activity in the evolution of humans. It continues to be an essential source of food and a generator of income for millions of Indigenous and rural communities worldwide. Conservationists rightly fear that excessive hunting of many animal species will cause their demise, as has already happened throughout the Anthropocene. Many species of large mammals and birds have been decimated or annihilated due to overhunting by humans. If such pressures continue, many other species will meet the same fate. Equally, if the use of wildlife resources is to continue by those who depend on it, sustainable practices must be implemented. These communities need to remain or become custodians of the wildlife resources within their lands, for their own well-being as well as for biodiversity in general. This title is also available via Open Access on Cambridge Core

    The expansion of Brachypodium rupestre in western Pyrenees: fungal endophytes and loss of ecosystem services

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    En esta tesis se plantean dos líneas de investigación que han quedado recogidas en los tres trabajos científicos que la conforman: • Capítulo 1) La primera línea de investigación desarrolla un modo de cuantificar económicamente la pérdida del servicio ecosistémico de aprovisionamiento ligado a la expansión de B. rupestre, con el objetivo de sensibilizar a los sectores implicados y fomentar acciones medioambientales dirigidas a promover la conservación de los pastos de montaña, ecosistemas ambiental y económicamente valiosos. Para ello, se realizó una adaptación del método de valoración económica por sustitución y se llevaron a cabo inventarios florísticos en cubiertas de alta y baja diversidad florística. El registro de estos datos nos permitió generar unos valores pastorales transformables en cantidad de forraje disponible para los animales, tras un detallado cálculo de la superficie viable de ser pastada (200,05 ha tras excluir las zonas con grandes pendientes). Con censos de animales y con información detallada y exhaustiva del consumo de energía que tiene cada tipo de animal que pasta las estivas del valle (ovejas, vacas y caballos) se determinaron las raciones de alimento necesarias en una temporada de pastoreo estival (50007 raciones) y su coste monetario (21146€; 107€/ha). De este modo, se estimó el coste que supone la pérdida del valor de aprovisionamiento debido a la expansión de B. rupestre y que va ligado en este caso a la pérdida de riqueza y diversidad florística de las comunidades vegetales que lo constituyen. • Capítulo 2 y 3) La segunda línea de investigación engloba dos trabajos en los que se caracteriza la desconocida comunidad de hongos endófitos de individuos de B. rupestre desarrollándose en comunidades de alta y baja diversidad florística. El estudio de los microorganismos en su ambiente natural es una disciplina relativamente nueva, dado que su interés se ha centrado tradicionalmente en las enfermedades que afectan a los humanos, los animales o las plantas. Sin embargo, los grandes avances tecnológicos y científicos de las últimas décadas nos están permitiendo conocer su altísima diversidad y las complejas redes ecológicas en las que están involucrados. El conocimiento sobre los hongos endófitos, que crecen en el interior de casi todas las plantas sin desarrollar enfermedades, está demostrando numerosas ventajas adaptativas que estos pueden llegar a conferir a su huésped ante numerosas situaciones de estrés (salinidad, herbivorismo, patógenos, etc.).This thesis encompasses two research lines comprised in three scientific papers: • Chapter 1) First chapter quantifies economically the loss of the provisioning service related to the B. rupestre expansion, with the aim of raising awareness among stakeholders and promote environmental actions for grassland restauration. For this purpose, we adapted the substitution economic approach, that we based on field floristic surveys done in high-diversity and low-diversity grasslands. The data collected allowed the estimation of the pastoral values, that were related to energy values and eventually to animal feed rations (50007 rations). We estimated the available surface for grazing (200.05 ha excluding steep slopes) and we compiled summer livestock censuses for determining the energy needs of each type of animal (sheep, cows and horses). Eventually, we estimated the economic cost of the loss of the provisioning service related to the B. rupestre expansion (21146€; 107€/ha). • Chapter 2 and 3) The second line of research encompasses two papers that characterize the fungal endophytic community of B. rupestre from plants developing in communities of high and low- floristic diversity. The study of microorganisms in their natural environment is a new discipline, considering that the research has usually focused on human, animal or plant diseases. The technological and scientific advances in the last decades have broadened our knowledge on the high diversity and the complex ecological networks in which they are involved. In particular, the study of fungal endophytes, which grow inside plants without developing diseases, is demonstrating the numerous adaptive advantages they confer to their host in different stressing situations (salinity, herbivory, pathogens, etc.).Ayudas de nueva solicitud para la Formación de Personal Investigador en la Universidad Pública de Navarra, convocatoria 2017. Ayudas de movilidad de doctorado 2021 para la realización de una estancia internacional en la Universidad de Camerino (Italia). Interreg Sudoe Programme, European Regional Development Fund, Open2preserve Project 108 (SOE2/P5/E0804). Libera 2017, SEO y Ecoembes - Apadrinamiento de espacios naturales. La degradación de los ecosistemas pascícolas de la Selva de Irati: Comportamiento invasivo de especies endémicas bajo condiciones de cambio global. Libera 2018, SEO y Ecoembes-Apadrinamiento de espacios naturales. La degradación de los ecosistemas pascícolas: ZEC Roncesvalles-Selva de Irati. Proyecto de investigación en centros escolares (Gobierno de Navarra, 2018). Formando futuras investigadoras: introduciendo la ciencia ecológica y ambiental al mundo escolar.Programa de Doctorado en Agrobiología Ambiental (RD 99/2011)Ingurumen Agrobiologiako Doktoretza Programa (ED 99/2011

    Multifunctional Lightweight Structures of Silicon Carbide Nanowires

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    Silicon carbide (SiC) as a type of ceramic material possesses unique properties such as high hardness, good high temperature strength, and excellent oxidation resistance. However, the intrinsic shortcomings of ceramic-based materials, such as high brittleness, low recoverable compressibility, and low fatigue resistance, prevent their utilisations as structural or functional components. To overcome these issues, highly porous lightweight and flexible SiC ceramics constructed by nanowires are promising alternatives for advanced engineering applications. The aim of this thesis is therefore to fabricate highly porous lightweight and flexible SiC nanowire structures by three novel approaches: (1) in-situ chemical-blowing; (2) melamine foam-based replica template; (3) electrospinning and explore their properties towards different applications. The overview, including the aims and objectives of this thesis is outlined in Chapter 1. The existing knowledge about lightweight SiCNW structures including crystallography, synthesis approaches, physical properties (mechanical strength, thermal conductivity, high temperature stability), and well-developed energy and environment-related applications (piezoresistive sensors, catalyst support, absorbers, and filters) is documented in Chapter 2. The generic information of the starting materials, synthesis techniques, equipment, and method used for the fabrication of 3D SiCNW structures, characterisation of their microstructural features, and evaluation of the various aspects of their multifunctionalities is descripted in Chapter 3. To identify suitable techniques to assemble SiC nanowires (SiCNWs) into 3D architectures, Chapter 4 provides a selection of advanced manufacturing approaches for lightweight SiCNW structures with easy and precise control of the overall shape and growth of SiCNWs. Followed with the demonstration of the exciting properties of the as-obtained three SiCNW structures including mechanical properties, thermal insulation performance, thermo-oxidation resistance, and fire-retardance in Chapter 5. Finally, based on their own characteristics, the applications of the SiCNW structures such as piezoresistive sensors, catalyst support, and efficient absorbents for oil and organic solvents are present in Chapter 6. A guidance in the manufacturing of advanced ceramic nanowire structures with desired microstructures and properties tailored for specific applications will be eventually provided. I first demonstrated the creation of SiCNW sponges by a facile template/catalyst-free sugar-blowing technique, by reacting SiO2 with sustainable kitchen sugar, using NH4Cl as a blowing agent. The as-grown, highly porous SiCNW sponges exhibited a core-shell structure, the core part with a density of 115-125 mg cm-3 was comprised of short and tangled SiC whiskers with SiC flakes embedded, while the shell layer with an ultralow density of ~25 mg cm-3 consisted of numerous smooth SiCNWs. These sponges exhibited a compressive modulus of ~389 kPa, recoverability under cyclic compression loading for 100 cycles at a strain of 20% and a thermal conductivity of 42-92 mW m-1K-1. Secondly, I reported the fabrication of SiCNW scaffolds with tuneable microstructures, densities, and therefore properties, by regulating the solid loading content in the reticulated melamine foam (MF) template. The resulting samples exhibited high strength (modulus up to ~167.3 kPa), good recoverability (11% residual strain and 72% maximum stress after 100 compressive cycles at a ε = 20%), and low thermal conductivity of 32-54 mW m-1K-1. Finally, I successfully created 3D SiCNW aerogels by using a Mille crêpe stacking and sintering of the electrospun PAN/SiO2 fibres for the first time. The resulting aerogels made of interconnected SiCNWs displayed an ultralight density of 29 mg cm-3, excellent compressive recoverability and fatigue resistance. Meanwhile, the SiCNW aerogels exhibited a thermal conductivity of 24 mW m-1K-1, even lower than that of the air, suggesting its superinsulation capability. Benefitting from intrinsic properties of SiC, experimental results have shown that all the as-obtained SiCNW structures exhibited good thermal insulation performance, exceptional high-temperature stability, fire-retardance, and temperature-invariant elasticity. Furthermore, I have explored the best-suited functional applications for each SiCNW structure. The SiCNW sponges and aerogels with better compressive recoverability and mechanical stability exhibited interesting electromechanical sensing capability. The sponge-based sensor exhibited a gauge factor up to 87 and stable wide-range compression-resistance responses. Whilst the aerogel-based strain sensor with higher recoverable strains presented stable sensing behaviour at different strains, frequencies, elevated temperatures over 200 °C and excellent repeatability over 2000 cycles. Owing to the cellular structure with the co-existence of SiC nanowires and struts, good interconnectivity, and competent mechanical strength and stability, the SiCNW scaffolds demonstrated the exclusive suitability as excellent support for MOF-derived TiO2-C catalyst, with ~35% enhanced in-situ loading of the catalyst, enabling a superior photocatalytic performance and good repeatability for at least 3 cycles. I further examined the SiCNW structures as organic solvent/oil absorbent. They exhibited rapid absorption of various organic solvents and oils. Typically, the SiCNW aerogels possess the highest absorption capacity of 32-86 g g-1, as well as robust recoverability. Meanwhile, the absorbed content can be easily removed by squeezing, distillation, and combustion, while the SiCNW structures remain unchanged. These features have shown that the SiCNW structures are promising for applications for the potential removal of chemical spills and oil leakage, with the advantage of easy recycling. All these remarkable findings will not only provide an important opportunity to advance the understanding of lightweight SiCNWs structures and make original contributions to utilise them as multifunctional devices, but also bring us the new ways to reshape the manufacturing of porous ceramics for future energy and environment-related applications

    Deposição de filmes do diamante para dispositivos electrónicos

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    This PhD thesis presents details about the usage of diamond in electronics. It presents a review of the properties of diamond and the mechanisms of its growth using hot filament chemical vapour deposition (HFCVD). Presented in the thesis are the experimental details and discussions that follow from it about the optimization of the deposition technique and the growth of diamond on various electronically relevant substrates. The discussions present an analysis of the parameters typically involved in the HFCVD, particularly the pre-treatment that the substrates receive- namely, the novel nucleation procedure (NNP), as well as growth temperatures and plasma chemistry and how they affect the characteristics of the thus-grown films. Extensive morphological and spectroscopic analysis has been made in order to characterise these films.Este trabalho discute a utilização de diamante em aplicações electrónicas. É apresentada uma revisão detalhada das propriedades de diamante e dos respectivos mecanismos de crescimento utilizando deposição química a partir da fase vapor com filament quente (hot filament chemical vapour deposition - HFCVD). Os detalhes experimentais relativos à otimização desta técnica tendo em vista o crescimento de diamante em vários substratos com relevância em eletrónica são apresentados e discutidos com detalhe. A discussão inclui a análise dos parâmetros tipicamente envolvidos em HFCVD, em particular do pré-tratamento que o substrato recebe e que é conhecido na literatura como "novel nucleation procedure" (NNP), assim como das temperaturas de crescimento e da química do plasma, bem como a influência de todos estes parâmetros nas características finais dos filmes. A caracterização morfológica dos filmes envolveu técnicas de microscopia e espetroscopia.Programa Doutoral em Engenharia Eletrotécnic
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