<p dir="ltr">The primary goal of this work is to gain a fundamental understanding on how growth conditions affect the morphology and crystallography orientation of CeO₂/Au vertically aligned nanocomposite (VAN) thin films. Focus has been placed on how the changes in morphology and crystallography translate to tunable optical properties. The morphological effects have been observed and analyzed via two main approaches: the change in morphology was observed at multiple points along the film thickness, and the morphology at the film/substrate interface has been analyzed with respect to total film thickness. The changes in Au crystallography orientations have been observed by measuring peak shift in XRD patterns and determining the resulting in- and out-of-plane strain. To observe additional effects of this morphology change, optical measurements have been taken for films at the bottom, middle, and top of the thickness range. Strong trends in transmittance, plasmonic absorption peak shifts and hyperbolic permittivity behavior are correlated with the film thickness. This tunability of optical properties likely arises from changes in both Au pillar phase morphology and crystal orientation. These findings demonstrate that changing film thickness may be a desirable method to easily tune the morphology and optical properties of VAN thin films.</p>

El proyecto se direcciona a aumentar la característica de revestimientos en muros de ladrillos, utilizando una mezcla de mortero que incorpora sulfato de calcio con ceniza Delonix. Para lograr este objetivo, se realizaron pruebas y ensayos para caracterizar las variantes de dosificaciones del mortero, la resistencia a compresión para espécimen de cúbicos, la permeabilidad en muretes recubiertos con ceniza Delonix, también un análisis de los costos unitario para la fabricación. Además, de evaluar los objetivos específicos para evaluar la resistencia de las perspectivas y encontrar la propuesta más efectiva de la mezcla para mejorar sus características. Los datos obtenidos de los ensayos se muestran con tablas y se describen los procedimientos para realizar ensayos de inundación simulada y medir la capacidad de los muros. En general, el proyecto busca una solución técnica para mejorar la resistencia y la permeabilidad de los revestimientos de muros de ladrillos en edificios en Perú. / The project is aimed at increasing the coating characteristics of brick walls, using a mortar mixture that incorporates calcium sulfate with Delonix ash. To achieve this objective, tests and trials were carried out to characterize the mortar dosage variants, the compressive strength for 50 mm cubic specimen, the permeability in walls coated with Delonix ash, as well as an analysis of the unit costs for manufacturing. In addition, to evaluate the specific objectives to evaluate the resistance of the prospects and to find the most effective proposal of the mixture to improve its characteristics. The data obtained from the tests are shown with tables and the procedures for performing simulated flood tests and measuring the capacity of the walls are described. In general, the project seeks a technical solution to improve the strength and permeability of brick wall cladding in buildings in Peru.

This thesis examines the dynamic mechanical properties of natural silk fibres, mainly from silkworm species Bombyx mori (B. mori) and spider species Nephila edulis, using dynamic mechanical thermal analysis, DMTA. The aim is not only to provide novel data on mechanical properties of silk, but also to relate these properties to the structure and morphology of silk. A systematic approach is adopted to evaluate the effect of the three principal factors of stress, temperature and hydration on the properties and structure of silk. The methods developed in this work are then used to examine commercially important aspects of the ‘quality’ of silk. I show that the dynamic storage modulus of silks increases with loading stress in the deformation through yield to failure, whereas the conventional engineering tensile modulus decreases significantly post-yield. Analyses of the effects of temperature and thermal history show a number of important effects: (1) the loss peak at -60 °C is found to be associated the protein-water glass transition; (2) the increase in the dynamic storage modulus of native silks between temperature +25 and 100 °C is due simply to water loss; (3) a number of discrete loss peaks from +150 to +220°C are observed and attributed to the glass transition of different states of disordered structure with different intermolecular hydrogen bonding. Excess environmental humidity results in a lower effective glass transition temperature (Tg) for disordered silk fractions. Also, humidity-dynamic mechanical analysis on Nephila edulis spider dragline silks has shown that the glass transition induces a partial supercontraction, called Tg contraction. This new finding leads to the conclusion of two independent mechanisms for supercontraction in spider dragline silks. Study of three commercial B. mori cocoon silk grades and a variety of processed silks or artificial silks shows that lower grade and poorly processed silks display lower Tg values, and often have a greater loss tangent at Tg due to increased disorder. This suggests that processing contributes significantly to the differences in the structural order among natural or unnatural silks. More importantly, dynamic mechanical thermal analysis is proposed to be a potential tool for quality evaluation and control in silk production and processing. In summary, I demonstrate that DMTA is a valuable analytical tool for understanding the structure and properties of silk, and use a systematic approach to understand quantitatively the important mechanical properties of silk in terms of a generic structural framework in silk proteins.

L'objectif de ce travail est de comprendre comment la forme intrinsèque des fibres individuelles contrôle les propriétés collectives des empilements, en particulier leurs propriétés mécaniques (élasticité) et électriques. Nous nous intéressons à des fibres longues, alignées selon une direction privilégiée et présentent un désordre de forme important. Notre étude est expérimentale et numérique. Nous proposons un modèle à deux dimensions, de champ moyen auto-cohérent, décrivant l'élasticité collective de l'empilement à partir des propriétés individuelles des fibres : leurs distribution de désordre ainsi que leurs module de courbure. Nous obtenons une équation d'état qui décrit avec un bon accord l'élasticité de nos empilements de fibres, sans paramètre ajustable, mais à un facteur multiplicatif près. Nous obtenons des résultats comparables entre les études expérimentale et numérique. / The purpose of this work is to understand how intrinsic shape of individual fibers controls the collective behavior of fiber stacks, in particular the mechanical (elasticity) and electrical properties. We consider long fibers, aligned towards one preferential direction with a significant disorder shape. Our study is experimental and numerical. We propose a two dimensions self consistent mean field model which describes the collective elasticity from the individual properties of fibers : the disorder distribution and the bending modulus. We obtain an equation of state which describes with a good agreement the stacks elasticity, without any fit parameters, however up to a multiplicative constant. We obtain similar results between experimental and numerical studies.

O objetivo deste trabalho é identificar e correlacionar as propriedades mecânicas do concreto e da argamassa de assentamento com o comportamento estrutural de blocos vazados de concreto, prismas e paredes, por meio de modelagem física e numérica. Realizou-se detalhada investigação experimental, recorrendo à premissa metodológica de se utilizar um mesmo concreto, de consistência plástica, para a moldagem de blocos vazados e corpos-de-prova cilíndricos, para assegurar propriedades idênticas dos materiais em cada série de ensaios. Analisou-se o efeito de confinamento que se apresenta nos ensaios de blocos isolados, o qual induz uma distribuição não-uniforme de deformações e acarreta aumento da sua capacidade resistente em relação à resistência à compressão do concreto. Em ensaios nos quais se reduziu o efeito de confinamento, constatou-se que os blocos apresentam menor capacidade resistente e alteração do modo de ruína, decorrente da distribuição mais uniforme das deformações, similar àquela que se observa nos blocos centrais dos prismas e paredes. Analisou-se também a influência do efeito de confinamento e do processo de cura das juntas de argamassa e se associou parâmetros indicativos do seu comportamento à capacidade resistente e ao modo de ruína de prismas e paredes. As propriedades mecânicas dos materiais, obtidas experimentalmente, foram implementadas em um modelo numérico de elementos finitos, que se mostrou capaz de representar o comportamento dos diversos elementos de alvenaria submetidos à compressão, com boa predição da resistência, deformabilidade e modo de ruína. Com base nos resultados numéricos e experimentais, estabeleceu-se um modelo de interpretação da distribuição de tensões e deformações nos blocos vazados de concreto, o que resultou na recomendação de um procedimento para determinação de sua rigidez axial. Associou-se também o efeito da resistência e da deformabilidade da argamassa no comportamento estrutural dos prismas e paredes. Correlações e formulações algébricas foram estabelecidas para análise do comportamento e previsão quantitativa da resistência e da deformabilidade de blocos, prismas e paredes. / This work aims to identify and correlate the mechanical properties of concrete and bedding mortar to the structural behavior of hollow concrete blocks, prisms and walls, by mean of physical and numerical modeling. A detailed experimental investigation was carried out by assuming as a premise the use of plastic consistency concrete to produce hollow blocks and cylindrical samples. This was done to assure the same material properties in each test series. Confinement effect in block compression tests causes a non-uniform strain distribution through face-shells and webs. This effect induces an increase of the block ultimate load. Modified block tests by reducing the confinement effect were performed. The results showed that confinement reduction brings a more uniform strain distribution, which is similar to the observed one in the central blocks of prisms and walls. A decrease of compressive strength and changes the failure mode were also evidenced. Confinement effect and influence of water loss during the curing of mortar joints were also considered. Indicative parameters about bedding mortar behavior were obtained and the resistant capacity and the failure mode of prisms and walls were associated to them. The mechanical properties of materials obtained in tests were implemented in a finite elements numerical model to analyze the behaviour of masonry elements under compression. The numerical analysis gave good predictions of strength, deformability and failure mode. Based on the numerical and experimental results, a stress and strain distribution model was realized, which enabled an experimental procedure for the determination of the block axial stiffness. Correlations and algebraic formulation were proposed for the behavior analysis and quantitative evaluation of strength and deformability of blocks, prisms and walls.

O objetivo deste trabalho é identificar e correlacionar as propriedades mecânicas do concreto e da argamassa de assentamento com o comportamento estrutural de blocos vazados de concreto, prismas e paredes, por meio de modelagem física e numérica. Realizou-se detalhada investigação experimental, recorrendo à premissa metodológica de se utilizar um mesmo concreto, de consistência plástica, para a moldagem de blocos vazados e corpos-de-prova cilíndricos, para assegurar propriedades idênticas dos materiais em cada série de ensaios. Analisou-se o efeito de confinamento que se apresenta nos ensaios de blocos isolados, o qual induz uma distribuição não-uniforme de deformações e acarreta aumento da sua capacidade resistente em relação à resistência à compressão do concreto. Em ensaios nos quais se reduziu o efeito de confinamento, constatou-se que os blocos apresentam menor capacidade resistente e alteração do modo de ruína, decorrente da distribuição mais uniforme das deformações, similar àquela que se observa nos blocos centrais dos prismas e paredes. Analisou-se também a influência do efeito de confinamento e do processo de cura das juntas de argamassa e se associou parâmetros indicativos do seu comportamento à capacidade resistente e ao modo de ruína de prismas e paredes. As propriedades mecânicas dos materiais, obtidas experimentalmente, foram implementadas em um modelo numérico de elementos finitos, que se mostrou capaz de representar o comportamento dos diversos elementos de alvenaria submetidos à compressão, com boa predição da resistência, deformabilidade e modo de ruína. Com base nos resultados numéricos e experimentais, estabeleceu-se um modelo de interpretação da distribuição de tensões e deformações nos blocos vazados de concreto, o que resultou na recomendação de um procedimento para determinação de sua rigidez axial. Associou-se também o efeito da resistência e da deformabilidade da argamassa no comportamento estrutural dos prismas e paredes. Correlações e formulações algébricas foram estabelecidas para análise do comportamento e previsão quantitativa da resistência e da deformabilidade de blocos, prismas e paredes. / This work aims to identify and correlate the mechanical properties of concrete and bedding mortar to the structural behavior of hollow concrete blocks, prisms and walls, by mean of physical and numerical modeling. A detailed experimental investigation was carried out by assuming as a premise the use of plastic consistency concrete to produce hollow blocks and cylindrical samples. This was done to assure the same material properties in each test series. Confinement effect in block compression tests causes a non-uniform strain distribution through face-shells and webs. This effect induces an increase of the block ultimate load. Modified block tests by reducing the confinement effect were performed. The results showed that confinement reduction brings a more uniform strain distribution, which is similar to the observed one in the central blocks of prisms and walls. A decrease of compressive strength and changes the failure mode were also evidenced. Confinement effect and influence of water loss during the curing of mortar joints were also considered. Indicative parameters about bedding mortar behavior were obtained and the resistant capacity and the failure mode of prisms and walls were associated to them. The mechanical properties of materials obtained in tests were implemented in a finite elements numerical model to analyze the behaviour of masonry elements under compression. The numerical analysis gave good predictions of strength, deformability and failure mode. Based on the numerical and experimental results, a stress and strain distribution model was realized, which enabled an experimental procedure for the determination of the block axial stiffness. Correlations and algebraic formulation were proposed for the behavior analysis and quantitative evaluation of strength and deformability of blocks, prisms and walls.

<p dir="ltr">Photovoltaics are leading devices in green energy production. Understanding the fundamental physics behind energy transport in candidate materials for future photovoltaic and optoelectronic devices is necessary to both realize material limitations and improve efficiency. Excitons, which are bound electron-hole pairs, are central to determining how energy propagates throughout semiconductors. Exciton transport is greatly influenced by material dimensionality. In highly ordered quantum dot (QD) systems, electronic coupling between individual QDs can lead to coherent exciton transport, whereas in two-dimensional heterostructures, excitons can form at the interface of a heterojunction, creating charge-transfer excitons.</p><p dir="ltr">This dissertation is dedicated to summarizing the studies of exciton transport and behavior in two systems: perovskite QD superlattices and transition metal dichalcogenide (TMDC)/polyacene heterostructures. Chapter 1 provides readers with details on these materials in addition to information on the fundamental concepts (i.e., excitons, phonons, energy transfer) needed to best appreciate further chapters. Chapter 2 summarizes the spectroscopic techniques (photoluminescence and transient absorption spectroscopy and microscopy) used to examine exciton behavior. Next, the effects of disorder and dephasing pathways on the ability of perovskite QDs to coherently couple is investigated through the lens of superradiance in Chapter 3. After this, the temperature-dependent exciton transport within perovskite QD superlattices is imaged with high spatial and temporal resolutions in Chapter 4. The experimental transport data on these superlattices provides evidence for environment-assisted quantum transport, which, until this study, had yet to be realized in solid-state systems. In Chapter 5, attention is switched to verifying the existence and deepening the understanding of the behavior of several spatially separated interlayer excitons in a tungsten disulfide/tetracene heterostructure. Finally, Chapter 6 summarizes the preliminary results obtained through transient absorption spectroscopy on other TMDC/polyacene heterostructures where separation of the triplet pair state is attempted. </p><p dir="ltr">It is this author’s hope that this dissertation will not only summarize their graduate work but will also serve as inspiration for others to continue learning and contribute to the advancement of the energy research field.</p>

<p dir="ltr">Metamaterials are artificially engineered nanoscale systems with a three-dimensional repetitive arrangement of certain components, and present exceptional optical properties for applications in nanophotonics, solar cells, plasmonic devices, and more. Self-assembled oxide-metal vertically aligned nanocomposites (VANs), with metallic phase as nanopillars embedded in the matrix oxide, have been recently proposed as a promising candidate for metamaterial applications. However, precise microstructural control and the structure-property relationships in VANs are still in high demand. Thus, by employing multiple approaches for structural design, this dissertation attempts to investigate the mechanisms of nanostructure evolutions and the corresponding optical responses.</p><p dir="ltr">In this dissertation, the precise control over the nanostructures has been demonstrated through morphology tuning, nanopillar orderings, and strain engineering. Firstly, Au, a well-known plasmonic mediator, has been selected as the metallic phase that forms nanopillars. Based on the previously proposed strain compensation model which describes the basic formation mechanism of VAN morphology, two oxides were then considered: La_0.7Sr_0.3MnO₃(LSMO) and CeO₂. In the first two chapters of this dissertation, LSMO was considered due to its similar lattice (a_LSMO= 3.87 Å, a_Au= 4.08 Å) and its enormous potential in nanoelectronics and spintronics. Deposited on SrTiO₃ (001) substrate through pulsed laser deposition (PLD), LSMO-Au nanocomposites exhibit ideal VAN morphology as well as promising hyperbolic dispersions in response to the incident illuminations. By substrate surface treatment of annealing at 1000°C, and variation of STO substate orientations from (001), to (111) and (110), the improved and tunable in-plan orderings of Au nanopillars have been successfully achieved. In the third chapter, a new oxide-metal VAN system of <a href="" target="_blank">CeO₂</a>-Au (a_CeO2= 5.411 Å, and a_CeO2/= 3.83 Å) has been deposited. The intriguing 45° rotated in-plan epitaxy presents an unexpected update to the strain compensation model, and tuning of Au morphology from nanopillars, nanoantennas, to nanoparticles also shows an effective modulation of the LSPR responses. COMSOL simulations have been exploited to reveal the relationships between Au morphologies and optical responses. In the last chapter, the two VAN systems of LSMO-Au and CeO₂-Au have been combined to form a complex layered VAN thin film. Investigations into the strain states, the nature of complex interfaces, and the according hybrid properties, show dramatic possibilities for further strain engineering. In summary, this dissertation has provided multiple routes for highly tailorable oxide-metal nanocomposite designs. And the two proposed material systems present great potential in optical metamaterial applications including biosensors, photovoltaics, super lenses, and more.</p>

<p dir="ltr">Transitioning to a carbon-neutral future will require a broad portfolio of green energy generation and storage solutions. With the abundant availability of solar radiation across the Earth’s surface, energy generation from photovoltaics (PVs) will be an important part of this green energy portfolio. While silicon-based solar cells currently dominate the PV market, temperatures exceeding 1000 °C are needed for purification of silicon, and batch processing of silicon wafers limits how rapidly Si-based PV can be deployed. Furthermore, silicon’s indirect band gap necessitates absorber layers to exceed 100 µm thick, limiting its applications to rigid substrates.</p><p dir="ltr">Solution processed thin-film solar cells may allow for the realization of continuous, high-throughput manufacturing of PV modules. Thin-film absorber materials have direct band gaps, allowing them to absorb light more efficiently, and thus, they can be as thin as a few hundred nanometers and can be deposited on flexible substrates. Solution deposition of these absorber materials utilizing molecular precursor-based inks could be done in a roll-to-roll format, drastically increasing the throughput of PV manufacturing, and reducing installation costs. In this dissertation, solution processed synthesis and the characterization of two emerging direct band gap absorber materials consisting of earth abundant elements is discussed: the enargite phase of Cu₃AsS₄ and the distorted perovskite phase of BaZrS₃.</p><p dir="ltr">The enargite phase of Cu₃AsS₄ (ENG) is an emerging PV material with a 1.42 eV band gap, making it an ideal single-junction absorber material for photovoltaic applications. Unfortunately, ENG-based PV devices have historically been shown to have low power conversion efficiencies, potentially due to defects in the material. A combined computational and experimental study was completed where DFT-based calculations from collaborators were used inform synthesis strategies to improve the defect properties of ENG utilizing new synthesis techniques, including silver alloying, to reduce the density of harmful defects.</p><p dir="ltr">Chalcogenide perovskites are viewed as a stable alternative to halide perovskites, with BaZrS₃ being the most widely studied. With a band gap of 1.8 eV, BaZrS₃ could be an excellent wide-bandgap partner for a silicon-based tandem solar cell.Historically, sputtering, and solid-state approaches have been used to synthesize chalcogenide perovskites, but these methods require synthesis temperatures exceeding 800 °C, making them incompatible with the glass substrates and rear-contact layers required to create a PV device. In this dissertation, these high synthesis temperatures are bypassed through the development of a solution-processed deposition technique.A unique chemistry was developed to create fully soluble molecular precursor inks consisting of alkaline earth metal dithiocarboxylates and transition metal dithiocarbamates for direct-to-substrate synthesis of BaZrS₃ and BaHfS₃ at temperatures below 600 °C.</p><p dir="ltr">However, many challenges must be overcome before chalcogenide perovskites can be used for the creation of photovoltaic devices including oxide and Ruddlesden-Popper secondary phases, isolated grain growth, and deep level defects. Nevertheless, the development of a moderate temperature solution-based synthesis route makes chalcogenide perovskite research accessible to labs which do not have high temperature furnaces or sputtering equipment, further increasing research interest in this quickly developing absorber material.</p>

Die Sicherheit von Straßen-, Schienenfahrzeugen sowie von Flugzeugen erfordert hochbelastbare Bauteile aus Stahl, Eisen, Aluminium und Magnesium. Während des Herstellungsprozesses können Verunreinigungen in der Metallschmelze auftreten, die zu Defekten in Form von Einschlüssen führen. Die Reduzierung oder Entfernung dieser Einschlüsse ist schwierig oder manchmal sogar unmöglich. Der Sonderforschungsbereich 920 „Multifunktionale Filter für die Metallschmelzefiltration – ein Beitrag zu Zero Defect Materials“ konzentrierte sich auf die Erforschung einer neuen Generation von Metallqualitäten – auch beim Recycling – durch Schmelzefiltration mit überlegenen mechanischen Eigenschaften für höchstbeanspruchbare Komponenten in Sicherheits- und Leichtbaukonstruktionen. Der SFB 920 wurde von 2011 bis 2023 an der Technischen Universität Bergakademie Freiberg von der Deutschen Forschungsgemeinschaft (DFG) gefördert (Projektnummer 169148856 – SFB 920) und nach 12 Jahren intensiver Forschungsarbeit erfolgreich beendet. Der Abschlussbericht des SFB 920 fasst die wichtigsten Publikationen und ausgewählte Ergebnisse zusammen.:1 Zusammenfassung / Summary 1 2 Die 50 wichtigsten veröffentlichten Ergebnisse 2 2.1 Publikationen mit wissenschaftlichen Qualitätssicherung 2 2.2 Weitere Publikationen und öffentlich gemachte Ergebnisse 4 3 Übersicht der Teilprojekte 5 4 Wissenschaftliche Entwicklung des Sonderforschungsbereichs 7 4.1 Einleitung, Vision und Thesen 7 4.2 Ausgewählte Ergebnisse 8 4.2.1 „Stahlschmelze-Filtration“ 8 4.2.2 „Aluminiumschmelze-Filtration“ 16 4.2.3 „Magnesiumschmelzefiltration“ 17 4.2.4 Beiträge der Simulation 18 4.2.5 Harz- und pechfreies Bindemittel für umweltfreundliche, reaktive Filter 20 4.2.6 Generatives Hybrid-Flammspritzverfahren 20 4.2.7 Transferprojekte 21 4.2.8 Zusammenfassende Bemerkungen 22 4.2.9 Management der Forschungsdaten 24 4.2.10 Literatur 24 4.3 Wissenschaftliche Veranstaltungen und Wissenschaftskommunikation 26 4.4 Nationale und internationale Kooperationen 28 5 Schwerpunktbildung und internationale Sichtbarkeit 31 / The safety of road and railway vehicles as well as aircrafts requires highly stressable components made of steel, iron, aluminum and magnesium. During the production process, contaminations can occur in the metal melt, which lead to defects in the form of inclusions. Reducing or removing these inclusions is difficult or sometimes impossible. The Collaborative Research Center 920 “Multi-functional filters for metal melt filtration – a contribution towards zero defect materials” focussed on research into a new generation of metal qualities - also during recycling - via melt filtration with superior mechanical properties for use in high-demand construction materials and light-weight structures. The CRC 920 was funded by the German Research Foundation (DFG, Deutsche Forschungsgemeinschaft) from 2011 to 2023 at the Technische Universität Bergakademie Freiberg (Project-ID 169148856 – SFB 920) and was successfully completed after 12 years of intensive research work. The final report of the CRC 920 presents the most important publications and selected results.:1 Zusammenfassung / Summary 1 2 Die 50 wichtigsten veröffentlichten Ergebnisse 2 2.1 Publikationen mit wissenschaftlichen Qualitätssicherung 2 2.2 Weitere Publikationen und öffentlich gemachte Ergebnisse 4 3 Übersicht der Teilprojekte 5 4 Wissenschaftliche Entwicklung des Sonderforschungsbereichs 7 4.1 Einleitung, Vision und Thesen 7 4.2 Ausgewählte Ergebnisse 8 4.2.1 „Stahlschmelze-Filtration“ 8 4.2.2 „Aluminiumschmelze-Filtration“ 16 4.2.3 „Magnesiumschmelzefiltration“ 17 4.2.4 Beiträge der Simulation 18 4.2.5 Harz- und pechfreies Bindemittel für umweltfreundliche, reaktive Filter 20 4.2.6 Generatives Hybrid-Flammspritzverfahren 20 4.2.7 Transferprojekte 21 4.2.8 Zusammenfassende Bemerkungen 22 4.2.9 Management der Forschungsdaten 24 4.2.10 Literatur 24 4.3 Wissenschaftliche Veranstaltungen und Wissenschaftskommunikation 26 4.4 Nationale und internationale Kooperationen 28 5 Schwerpunktbildung und internationale Sichtbarkeit 31