This thesis explores the theory of electron energy-loss spectroscopy (EELS) in atomic resolution electron microscopy. / The first unequivocal evidence of the effective nonlocal potential in momentum-transfer-resolved EELS is presented. For suitable geometries, the nonlocal potential can be well approximated by a local potential. In scanning transmission electron microscopy (STEM) the validity of this is mainly influenced by the detector size and, contrary to conventional wisdom, a thin annular detector does not allow direct image interpretation. It is found that the best way to ensure the potential is well approximated by a local potential is to use a detector with a large collection angle. / To simplify computation and interpretation it is desirable to make the single-channelling approximation. In this approximation only the elastic scattering of the probe before the ionisation event is modelled. It is shown how this approximation breaks down for the small detectors used in momentum-transfer-resolved EELS and this is confirmed with experimental results. Double-channelling calculations, where the channelling of the probe both before and after the ionisation event are modelled, can also be simulated. An alternative approximation for small detectors that includes double channelling and is more applicable for momentum-transfer-resolved EELS is also presented. / Beyond chemical information, the fine structure of an absorption edge gives bonding and electronic information. Incorporating fine structure into channelling theory allows the exploration of the effects of channelling on fine structure. The weighting of the two different spectra in graphite, as a function of incident probe tilt in momentum-transfer-resolved EELS, is calculated using double-channelling simulations. This is combined with experimental data and multivariate statistical analysis to extract the two physical spectra, greatly simplifying the analysis of a large data set. / The effect of the nonlocal potential and channelling on site-specific electronic structure analysis by channelling EELS is examined. It is found that using a large on-axis detector can make the interaction effectively local, leading to a greater change in the spectra as a function of sample tilt. Alternatively offsetting the detector can achieve similar results but at the cost of greater statistical noise. Channelling calculations were combined with the program FEFF and the full energy differential cross section was calculated from first principles for the aluminium K edge as a function of sample tilt in nickel aluminate spinel. Qualitative agreement with experiment was found but quantitative agreement will require further investigation. / The theory of fine structure in STEM was examined, using strontium titanate to see how the high spatial resolution of STEM can be used in conjunction with energy-loss near-edge spectroscopy measurements. The possibility of imaging unoccupied electron molecular orbitals using STEM was also examined.

Recent trends in energy production have led to a renewed interest in improving grid level energy storage solutions. Flywheel energy storage is an attractive option for grid level storage, however, it suffers from high parasitic loss. This study investigates the extent to which passive diamagnetic bearings, a form of electromagnetic bearing, can help reduce this parasitic loss. Such bearings require three main components: a weight compensation mechanism (lifter-floater), a stabilizing mechanism and an electrical machine. This study makes use of a new radial modification of an existing linear multi-plattered diamagnetic bearing. Here a prototype is built and analytical expressions derived for each of the three main components. These expressions provide a method of estimating displacements, fields, forces, energy and stiffness in the radial diamagnetic bearing. The built prototype solution is found to lift a 30 [g] mass using six diamagnetic platters for stabilization (between ring magnets) with a disc lifter and spherical floater for weight compensation. The relationship between mass and number of platters was found to be linear, suggesting that, up to a point, increases in mass are likely possible and indicating that significant potential exists for these bearings where high stiffness is not needed – for instance in flywheel energy storage. The study examines methods of reducing bearing (parasitic) losses and demonstrates that losses occur in three main forms during idling: air-friction losses, electrical machine losses, stabilizing machine losses. Low speed (158 [rpm]) air-friction losses are found to be the dominant loss at 0.1 [W/m3]. The focus of this study, however, is on loss contributions resulting from the bearing’s electrical machine and stabilizing machine. Stabilizing machine losses are found to be very low at: 1 × 10−6 [W/m3] – this leaves electrical machine losses as the dominant loss. Such electrical machine losses are analysed and divided into eddy current loss and hysteresis loss. Two components of hysteresis loss are remanent field related cogging loss and remagetization loss. Eddy current losses in silicon steel laminations in an electrical machine are quite high, especially at high speeds, with losses in the order of 1 × 105 [W/m3]. Noting the further high cost of producing single unit quantities of custom lamination-based electrical machine prototypes, this high loss prompts a look at potentially lower cost ferrite materials for building these machines. A commercial sample of soft magnetite ferrite is shown to have equivalent eddy current losses of roughly 1 × 10−13 [W/m3]. The study notes that micro-structured magnetite has significant hysteresis loss. Such loss is in the order of 1 × 10−3 [W/m3] when referring to both remanence related cogging and remagnetization. This study, thus, extends its examination of loss to nano-structured magnetite. Magnetite nano-particles have shown superparamagnetic (no hysteresis) behaviour that promises the elimination of hysteresis losses. A co-precipitation route to the synthesis of these nano-particles is examined. A detailed examination involving a series of 31 experiments is shown to demonstrate only two pathways providing close-to-superparamagnetic behaviour. After characterization by Scanning Electron Microscope (SEM), X-Ray Diffractometer (XRD), Superconducting Quantum Interference Device (SQUID) and crude colorimetry, the lowest coercivity and remanence found in any given sample falls at −0.17 [Oe] (below error) and 0.00165 [emu/g] respectively. These critical points can be used to estimate hysteresis related power loss, however, to produce bulk ferrite a method of sintering or bonding synthesized powder is needed. A microwave sintering solution promises to preserve nano-structure when taking synthesized powders to bulk material. A set of proof-of-concept experiments provide the ground work for proposing a future microwave sintering approach to such bulk material production. The study uses critical points measured by way of SEM, XRD, SQUID characterization (e.g. remanence and coercivity) to implement a modified Jiles-Atherton model for hysteresis curve fitting. The critical points and curve fitting model allow estimation of power loss resulting from remanent related cogging and remagnetization effects in nano-structured magnetite. Such nano-structured magnetite is shown to exhibit hysteresis losses in the order of 1 × 10−4 [W/m3] from remagnetization and 1 × 10−7[W/m3] from remanence related cogging drag. These losses are lower than those of micro-structured samples, suggesting that nano-structured materials have a significant positive effect in reducing electrical machine losses for the proposed radial multi-plattered diamagnetic bearing solution. The lower parasitic loss in these bearings suggests excellent compatibility with flywheel energy storage applications.

Submitted by Maike Costa (maiksebas@gmail.com) on 2017-10-02T13:44:12Z No. of bitstreams: 1 arquivototal.pdf: 2230662 bytes, checksum: e5c9108ece6cc0732bd25a644daad838 (MD5) / Made available in DSpace on 2017-10-02T13:44:12Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2230662 bytes, checksum: e5c9108ece6cc0732bd25a644daad838 (MD5) Previous issue date: 2017-02-23 / The measure of efficiency of the productive process is productivity, which consists of maximizing the results, using the same volume of resources or maintaining the result and reducing the volume of resources. Faced with the need to minimize environmental problems and rationalize the use of resources, the use of Energy Efficiency (EE) in the industrial sector has become an alternative to raise productivity, mainly by reducing energy losses. This work had as its general objective to analyze a relationship between productivity and energy efficiency in a graphic company in Paraíba, identifying a productivity, verifying the existing points of energy losses, evaluating the potential of energy consumption improvements and measuring the launch of Productivity and Energy Efficiency, after reducing energy losses. This work was characterized by Qualitative-Quantitative applied research, regarding the objectives of the study and descriptive. The instruments for data collection for a bibliographical research, analysis of input resources (MWh) and output (T - Production) for a calculation of productivity (T / MWh) and direct observation. After a collect of consumption, production and energy profile data, the data are tabulated and analyzed by means of the indicators, to estimate a reduction in consumption. It was verified that the productivity of the company is affected by seasonality, confirmed from the test in the F test, the coefficient of determination indicated that 63.2% of the variation of the electric energy consumption by variation of production. On the other hand, 36.8% of the variation of energy consumed cannot be explained by production, indicating that there are other process factors that do not affect production and explain consumption. As to dimensions indicated that: energy management, driving system, lighting system, cooling system and compressed air system, are responsible for 84.54% of total electricity consumption. After an evaluation of the potential for improvements, we have: energy management (6.00%), motor system (7.57%), lighting system (5.57%), refrigeration system (0.55%) and Compressed air (5.40%), corresponding to a saving of 9.39% in the company's total electricity consumption. Leading to increased productivity Gain (T / MWh) of 10.39%. In billing, a representative reduction of an annual savings of around R$ 445 thousand. It can be concluded that when there is an increase in energy efficiency, increasing productivity in a ratio, proportional, which impacts on increasing the competitiveness of the company. / A medida de eficiência do processo produtivo é a produtividade, que consiste na maximização dos resultados, utilizando o mesmo volume de recursos ou mantendo o resultado e reduzindo o volume de recursos. Diante da necessidade de minimizar os problemas ambientais e racionalizar a utilização dos recursos, o uso da Eficiência Energética (EE) no setor industrial tornou-se uma alternativa para elevar o índice de produtividade, principalmente, reduzindo das perdas energéticas. Este trabalho teve como o objetivo geral analisar a relação entre produtividade e eficiência energética em uma empresa gráfica na Paraíba, identificando a produtividade, verificando os pontos de perdas energéticas existentes, avaliando a potencialidade de melhorias do consumo energético e mensurando o nível de Produtividade e Eficiência Energética, após a redução destas perdas energéticas. Este trabalho foi caracterizado como por pesquisa aplicada Qualitativa-Quantitativa, quanto aos objetivos do estudo é descritivo. Os instrumentos para coleta de dados foi a pesquisa bibliográfica, análise documentos dos recursos de entrada (Energia elétrica – MWh) e saída (Produção – T) para a realização do cálculo de produtividade (T/MWh) e da observação direta. Após a coleta dos dados de consumo, produção e perfil energético, os dados serão tabulados e analisados por meios dos indicadores, para estimar a redução de consumo. Verificou-se que a produtividade da empresa é afetada pela sazonalidade, confirmada a partir do teste t e o teste F, o coeficiente de determinação indicou que 63,2% da variação do consumo de energia é explicada pela variação da produção. Por outro lado,36,8% da variação da energia consumida não pode ser explicada pela produção, indicando que há outros fatores do processo que não afetam a produção e que explicam aquele consumo. Sobre as dimensões indicou que: gestão energética, sistema motriz, sistema de iluminação, sistema de refrigeração e sistema de ar comprimido, são responsáveis por 84,54% do consumo total de energia elétrica. Após a avaliação do potencial das melhorias, temos: gestão energética (6,00%), sistema motriz (7,57%), sistema de iluminação (5,57%), sistema de refrigeração (0,55%) e sistema de ar comprimido (5,40%), correspondendo a uma economia de 9,39% no consumo total de energia elétrica da referida empresa. Levando a um incremento de ganho de produtividade (T/MWh) estimado de 10,39%. No faturamento, a redução representou uma economia anual da ordem de R$ 445 mil reais. Pode-se concluir que quando há aumento da eficiência energética, aumentando de produtividade em uma relação diretamente proporcional, o que impacta no aumento de competitividade da empresa.

abstract: Topological insulators with conducting surface states yet insulating bulk states have generated a lot of interest amongst the physics community due to their varied characteristics and possible applications. Doped topological insulators have presented newer physical states of matter where topological order co&ndashexists; with other physical properties (like magnetic order). The electronic states of these materials are very intriguing and pose problems and the possible solutions to understanding their unique behaviors. In this work, we use Electron Energy Loss Spectroscopy (EELS) – an analytical TEM tool to study both core&ndashlevel; and valence&ndashlevel; excitations in Bi2Se3 and Cu(doped)Bi2Se3 topological insulators. We use this technique to retrieve information on the valence, bonding nature, co-ordination and lattice site occupancy of the undoped and the doped systems. Using the reference materials Cu(I)Se and Cu(II)Se we try to compare and understand the nature of doping that copper assumes in the lattice. And lastly we utilize the state of the art monochromated Nion UltraSTEM 100 to study electronic/vibrational excitations at a record energy resolution from sub-nm regions in the sample. / Dissertation/Thesis / M.S. Materials Science and Engineering 2013

Abstract Experimental synchrotron radiation induced electron- and ion spectroscopies together with electron-ion and ion-ion coincidence techniques as well as electron energy loss spectroscopy have been used to study the electronic properties of several vapor phase samples. In this thesis studies of the electronic structure and fragmentation of Sb4 clusters, photo- and Auger electron spectroscopy of atomic Si and Pb as well as ultra high resolution VUV absorption of vapor phase KF molecules have been performed. The instrumentation and techniques used in the studies, especially the electron energy loss apparatus and the newly built ultra high resolution FINEST beamline branch, are presented.

Graphene, a one-atom thick sheet of carbon, is the thinnest, strongest and most electrically conductive material ever discovered. Alongside carbon nanotubes it is part of the group of nanocarbons whose unique properties have sparked huge interest in possible applications, including electronic devices, solar cells and biosensors. Doping of these materials allows for the modification of their optical and electronic properties,which is crucial to realising these applications. Studying the properties of these doped materials at atomic resolution and finding controllable and industrially scalable routes to doping, such as low energy ion implantation, are thus essential if they are to becomethe materials of the future. In this thesis, highly localised optical enhancements in metal doped graphene are studied using energy-filtered transmission electron microscopy in a monochromated and aberration corrected electron microscope. The ideal conditions for imaging the low energy loss region of graphene using EFTEM are discussed and new methods to compensate for image artifacts when using this technique at high resolution are presented. Density functional theory is used to reveal new visible spectrum plasmon excitations in the electron energy loss spectra of boron and nitrogen doped nanocarbons. Atomic resolution scanning transmission electron microscopy and nanoscale electron energy loss spectroscopy are used to investigate controllable and defect-free substitutional doping of suspended graphene films through low energy ion implantation. Computational methods for filtering high angle annular dark field images are shown and software for the automated processing and spectroscopic analysis of these images is developed.

Scanning transmission electron microscopy is one of the essential techniques suitable not only for imaging of nanostructures, but also for various kinds of spectroscopy and, as it was recently demonstrated, nanomanipulation. In this thesis, we deal with an interaction of fast electrons and metallic spherical nanoparticles, specifically aluminium and gold nanospheres. First, we present both analytical and numerical calculations of electron energy loss spectra and their analysis for different parameters. The main part of the thesis is devoted to theoretical calculations of forces acting on the nanosphere due to the electron passing in its close proximity. Based on our novel results revealing a time evolution of the mechanical force, we also propose a possible mechanism responsible for the nanoparticle movement in electron microscopes.

This is a study about how to improve the building envelope from a group of housing belonging to The Million Programme, a housing programme implanted in the Sweden around 70’s. Massive buildings made of concrete, which were constructed really fast because of the pressing time Schedule and were not developed as they should. This renovation study is explained with examples and drawings and it basically shows how to add thermal insulation on the most conflictive points of the building envelope. It is done in order to improve climatic conditions inside housing, trying to make thermal bridges disappear and reducing energy loss.

No description available.

Two-dimensional (2D) materials have properties that are often different from their three-dimensional (3D) bulk form. Many of these materials are stable at ambient conditions, which allows them to be integrated with other 2D- or 3D-materials to form heterostructures. Integration of various dimensional materials attains unique electrical and optical properties that aid in developing novel electronic devices. The interface of the heterogeneous integration of these films can exhibit a weak van der Waals-like bonding. In this thesis, an advanced characterization (from atomic to millimeter resolution) of various dimensional materials with weakly bonded interfaces is developed and employed to understand their behavior at scale. First, a large-area single-crystal cadmium telluride thin film is grown incommensurately and strain-free to a sapphire substrate despite a significant 3.7% lattice mismatch. The film remarkably delaminates as a bulk single crystal film due to an atomically thin tellurium that spontaneously forms at the interface. Aberration-corrected electron microscopy and spectroscopy reveal both the van der Waals-like structure and bonding at the film/substrate interface. Second, a large-area atomically thin gallium is intercalated at the interface of epitaxial graphene. Correlative microscopy workflows are applied to understand the thickness uniformity and area coverage of the 2D–gallium over few millimeters of the sample. Utilizing multiple correlative methods, SEM image contrast is found to be directly related to the presence of the intercalated gallium. The origin of the SEM contrast is investigated as a function of the surface potential. Then, the heterostructure characterization is scaled up over a few square millimeter areas by segmenting SEM images, each acquired with nanometer-scale resolution. Additionally, transmission electron microscopy is applied to investigate the interface of gallium–SiC, the gallium air–stability, and the role of the substrate on the heteroepitaxial growth of 2D–gallium, which charts a path for further development of these materials. / Thesis / Doctor of Philosophy (PhD)