Dissertations / Theses: 'Analysis of natural materials'

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Kopec, Grant Michael. "Examining natural resource futures with material flow analysis." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709409.

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Hassel, Beatriz Ivón. "ANALYSIS OF NATURAL MATERIALS AND STRUCTURES BY NON-CONTACT STRAIN MEASUREMENT METHODS." Kyoto University, 2010. http://hdl.handle.net/2433/120467.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第15424号
農博第1809号
新制||農||979(附属図書館)
学位論文||H22||N4523(農学部図書室)
27902
京都大学大学院農学研究科森林科学専攻
(主査)教授小松幸平, 教授中野隆人, 教授矢野浩之
学位規則第4条第1項該当

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Guan, Juan. "Investigations on natural silks using dynamic mechanical thermal analysis (DMTA)." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:c16d816c-84e3-4186-8d6d-45071b9a7067.

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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.

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Ellis, Marguerite. "Investigation of Multiwalled Carbon Nanofiber - Graphite Layer Composites and Analysis of Natural Chalks." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/205417.

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The first part of this dissertation focuses on self-assembled composites. Self-assembled composites composed of vertically aligned multiwalled carbon nanofibers (VA-MWCNF) combined with a graphitic layer (GL) arranged perpendicular to MWCNF axes‘ have been produced at low temperature (445 °C) using low pressure thermal chemical vapor deposition (LPCVD). Electron microscopy and Raman spectroscopy were used to analyze composite morphology, structure and quality. It is found that different composite morphologies and modification of the GL structure can be obtained by varying the nickel (Ni) catalyst underlayer materials, the catalyst pre-treatment method, the gas recipe, the gas flow rates and the pressure conditions of the LPCVD process. Pre-treatment of the catalyst with H2 plasma or NH₃ gas was also investigated. It is found that even a short, one minute H2 plasma pre-treatment of the catalyst results in a significant break-down of the VA-MWCNF/GL composite structure. On the other hand, a one or ten minute catalyst pre-treatment with NH₃ gas results in a structural modification of the GL but retains the VA-MWCNF/GL composite structure. An increase in time of NH₃ gas pre-treatment leads to reduced VA-MWCNF/GL composite height. A growth mechanism for VA-MWCNF/GL composites was proposed. The focus, of the second part of this dissertation, is on the analysis of natural chalks used in traditional old master drawings. Scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) analysis were performed on bulk samples of natural black chalk, steatite and calcite natural white chalks and on samples of these chalks applied to paper using various techniques. Critical information was obtained about the morphology and sub-micron features of the chalk particles, the chalk/paper interaction of each application technique and elemental composition of the bulk chalk samples. It was found that the particle size and morphology of the natural white chalks reduced their ability to hold to the paper. This information provides insight as to why black chalk is more resistant to abrasion than the natural white chalks which is important for the conservation of extant chalk drawings.

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Scotter, Michael Joseph. "Aspects of the chemistry and analysis of the food colouring materials annatto and curcumin." Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327600.

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Fernandes, Fábio António Oliveira. "Biomechanical analysis of helmeted head impacts: novel materials and geometries." Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/21227.

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Doutoramento em Engenharia Mecânica
A cortiça é um material celular natural capaz de suster quantidades consideráveis de energia. Estas características tornam este material ideal para determinadas aplicações como a proteção de impactos. Considerando equipamentos de segurança passiva pessoal, os materiais sintéticos são hoje em dia os mais utilizados, em particular o poliestireno expandido. Este também é capaz de absorver razoáveis quantidades de energia via deformação permanentemente. Por outro lado, a cortiça além de ser um material natural, é capaz de recuperar grande parte da sua forma após deformada, uma característica desejada em aplicações com multi-impacto. Neste trabalho é efetuada uma avaliação da aplicabilidade da cortiça em equipamentos de segurança pessoal, especificamente capacetes. Vários tipos de cortiça aglomerada foram caracterizados experimentalmente. Impactos foram simulados numericamente para avaliar a validade dos modelos constitutivos e as propriedades utilizadas para simular o comportamento da cortiça. Capacetes foram selecionados como caso de estudo, dado as energias de impacto e repetibilidade de impactos a que estes podem ser sujeitos. Para avaliar os capacetes de um ponto de vista biomecânico, um modelo de cabeça humana em elementos finitos foi desenvolvido. Este foi validado de acordo com testes em cadáveres existentes na literatura. Dois modelos de capacete foram modelados. Um modelo de um capacete rodoviário feito de materiais sintéticos, o qual se encontra disponível no mercado e aprovado pelas principais normas de segurança de capacetes, que serve de referência. Este foi validado de acordo com os impactos da norma. Após validado, este foi avaliado com o modelo de cabeça humana em elementos finitos e uma análise ao risco de existência de lesões foi efetuado. Com este mesmo capacete, foi concluído que para incorporar cortiça aglomerada, a espessura teria de ser reduzida. Então um novo modelo de capacete foi desenvolvido, sendo este uma espécie de modelo genérico com espessuras constantes. Um estudo paramétrico foi realizado, variando a espessura do capacete e submetendo o mesmo a duplos impactos. Os resultados destes impactos e da análise com o modelo de cabeça indicaram uma espessura ótima de 40 mm de cortiça aglomerada, com a qual o capacete tem uma melhor resposta a vários impactos do que se feito de poliestireno expandido.
Cork is a natural cellular material capable of withstanding considerable amounts of energy. These features make it an ideal material for some applications, such as impact protection. Regarding personal safety gear, synthetic materials, particularly expanded polystyrene, are typically used. These are also able to absorb reasonable amounts of energy by deforming permanently. On the other hand, in addition to cork being a natural material, it recovers almost entirely after deformation, which is a desired characteristic in multi-impact applications. In this work, the applicability of agglomerated cork in personal safety gear, specifically helmets, is analysed. Different types of agglomerated cork were experimentally characterized. These experiments were simulated in order to assess the validity of the constitutive models used to replicate cork's mechanical behaviour. In order to assess the helmets from a biomechanical point of view, a finite element human head model was developed. This head model was validated by simulating the experiments performed on cadavers available in the literature. Two helmet models were developed. One of a motorcycle helmet made of synthetic materials, which is available on the market and certified by the main motorcycle helmets safety standards, being used as reference. This helmet model was validated against the impacts performed by the European standard. After validated, this helmet model was analysed with the human head model, by assessing its head injury risk. With this helmet, it was concluded that a thinner helmet made of agglomerated cork might perform better. Thus, a new helmet model with a generic geometry and a constant thickness was developed. Several versions of it were created by varying the thickness and subjecting them to double impacts. The results from these impacts and the analyses carried out with the finite element head model indicated an optimal thickness of 40 mm, with which the agglomerated cork helmet performed better than the one made of expanded polystyrene.

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Ghaderidosst, Melody, Grabe Vilma Hurtigh, Rebecka Norman, Adam Rosvall, and Evelina Wiksten. "Production Process for Tunnel Modeling : An Analysis of Composites for Water Applications." Thesis, Uppsala universitet, Institutionen för materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-444830.

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Hydroelectric power is a leading source of renewable energy where large turbines convert the kinetic energy of water into electricity. In order to not exceed the capacity limit of the turbine, excess water in the dams needs to be diverted away through spillways. In order to do in-house testing of the water flow, a 1:30 scale tunnel manufactured by an external supplier is used. The production of the tunnels is however preferred to be done in-house. In this thesis different material options and methods for the tunnel modeling production are examined. This has been achieved by a thorough literature study following practical experiments. Polymers are known for their strength and stiffness to weight ratio as well as low cost and availability. To further enhance its material properties for given applications, polymers can be reinforced with different fibers creating a composite. Several fibers were considered, however in order to support the set strategy of Vattenfall AB regarding environmental and sustainability goals, natural fibers, specifically hemp and flax deemed to be a good fit using epoxy as the matrix material. Based on the material properties tested for the composites, flax with epoxy was the resulting material used to model the tunnels. The final method for the production process using said material was based on three different methods that were tested. The conclusion was that using a flax-epoxy composite with a hand lay-up method using a negative mold made of Styrofoam gave the best results. It should, however, be noted that a definite production process for the tunnel could not be determined due to time limitations. A theoretical production process for tunnel modeling was nevertheless composed.

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de, las Heras Reverte Víctor. "Evaluation of natural materials in Sustainable Buildings : A potential solution to the European 2050 long-term strategy." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300115.

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Today, buildings consume 40% of total energy demand in the EU and are responsible for 36% of GHG emissions. For this reason, and due to the delicate situation of climate change that planet Earth is experiencing, solutions are being sought to make the building sector more sustainable. In the current project, the use of natural materials has been chosen as a solution in line with the EU 2050 long-term strategy. This research broadens the knowledge on sustainable building with natural materials as an alternative to conventional construction. To this end, first, an extensive state of the art has been carried out to gather information and identify research gaps on natural building materials and energy efficiency, proving the suitability of natural construction materials. Special emphasis has been put on straw bale construction and rammed earth construction, which have been studied individually. In addition, geometrically identical building models of both building techniques have been developed and simulated in Stockholm and Valencia in order to see how they would perform in different climates. Total energy demand for the straw-bale building of 140.22 kWh/(m2·year) in the case of Stockholm and 37.05 kWh/(m2·year) in the case of Valencia has been obtained. For the rammed earth building, a total demand of 301.82 kWh/(m2·year) has been obtained in Stockholm and 78.66 kWh/(m2·year) in Valencia. Once passive measures are applied in the different models, a reduction in demand for the straw bale building of 77.8% and 36.3% has been achieved for Stockholm and Valencia, respectively. In the rammed earth building, in contrast, the demand has been reduced by 86.3% in Stockholm and 73.9% in Valencia. Heat recovery ventilation and high insulation level have been identified as imperative needs in Stockholm, in contrast to Valencia. Other improvement strategies such as windows substitution, air permeability improvement, or natural ventilation for cooling have been implemented. Apart from that, better performance of the straw-bale buildings has been identified for both climates. Additionally, focusing on thermal inertia, its influence has been identified as not completely significant in terms of annual demand in the simulated climates.

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Windsor-Collins, Andrea Grace. "Resolving the morphological and mechanical properties of palm petioles : shape analysis methods for symmetric sections of natural form." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/13722.

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Palms support the largest leaves in the world and have evolved on Earth for over 120 million years. They are often reported to be the only structure left standing post-hurricane. Cross-sectional shapes of cantilevered structures are important design factors affecting torsional and bending performance. Understanding the shape contribution of natural sections such as palm petioles (modified leaf stalks) is more difficult than those for simple 2D shapes because conventional methods of calculating section properties are not well suited to these irregular shapes. The role of internal structure, material properties and external shape of palm petioles in cantilever performance has been investigated and three main contributions to knowledge result from this research. Firstly, 3D mapping, i.e., the size, orientation and position, of vascular bundles in the Trachycarpus fortunei palm petiole reveals the distributions of stress and Young’s modulus values, providing a more detailed understanding of petioles than previous work. Secondly, bulk elastic material properties along the longitudinal axis of the same petiole are then input to a bi-layered model of the same petiole establishing the Young’s modulus of the two layers without mechanically testing them individually and for determining that the outer layer is not lignified. Thirdly, the largest contribution is the introduction of modified shape transformers employing the use of circular envelopes, eliminating error caused by approximating second moment of area with the torsional constant. This leads to a novel Shape Edge Mapping (SEM) technique which deconstructs petiole cross section shape elements and enables the structural contribution of these elements to be calculated, improving the understanding of the petiole section and how it relates to its mechanical function. This thesis makes a valuable addition to the knowledge of palm function and presents novel techniques for non-destructive extraction of natural shape data for abstraction and use in preliminary engineering design.

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Palm, Viveka. "Material flow analyses in technosphere and biosphere – metals, natural resources and chemical products." Doctoral thesis, KTH, Civil and Environmental Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3318.

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Mendes, Luana Guabiraba. "Microencapsulation the natural dye annatto: an analysis of the efficiency of cashew gum as material wall." reponame:Repositório Institucional da UFC, 2012. http://www.repositorio.ufc.br/handle/riufc/17650.

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MENDES, Luana Guabiraba. Microencapsulação do corante natural de urucum: uma análise da eficiência da goma do cajueiro com material de parede. 2012. 130 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Tecnologia de Alimentos, Fortaleza-CE, 2012
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Na prática, alguns corantes naturais, como a bixina, apresentam dificuldades tecnológicas de utilização, dificultando sua aplicação na indústria de alimentos. A microencapsulação pode amenizar essa situação, aumentando sua estabilidade e tornando possível sua incorporação em sistemas alimentícios sem a perda de suas propriedades. Assim, o objetivo dessa pesquisa foi microencapsular o corante natural de urucum, utilizando a goma de cajueiro como material de parede, aplicando os processos de liofilização e atomização, caracterizar as microcápsulas obtidas através de análises morfológicas, físico-quimicas, bem como determinar a eficiência da microencapsulação pela quantificação do teor de bixina total e superficial. Goma arábica foi utilizada como material de parede de referência, para efeito comparativo. Assim, foram preparadas três formulações, a saber: corante de urucum/ goma do cajueiro (U-GC) 4:1 m/m, corante de urucum /goma arábica (U-GA) 4:1 m/m e corante de urucum/ goma do cajueiro/ e goma arábica (1:1) 4:1 m/m (U-GCA). As suspensões, previamente preparadas também foram caracterizadas por análises físico-químicas. Na avaliação colorimétrica estudou-se a estabilidade do pigmento microencapsulado, em temperatura ambiente, a 25°C± 2°C na presença e na ausência de luz, durante 40 dias de armazenamento, em duas situações, ou seja, dissolvidos em solução-tampão pH 4,0 e na forma de pó. Nas três suspensões formuladas a análise colorimétrica e o pH não apresentaram grandes diferenças, mas já na viscosidade a suspensão goma do cajueiro/ corante de urucum, resultou em menor viscosidade (0,01746±0,000) nas mesmas concentrações de sólidos. As microcápsulas produzidas por atomização mostraram também formas irregulares com predominância circular e superfície dentada e, por liofilização, mostraram formas indefinidas e com tamanhos muito variáveis. Todas as microcápsulas mostraram-se solúveis em água. As microcápsulas elaboradas com goma arábica e goma do cajuerio/goma arábica (1:1) apresentaram as melhores eficiências na microencapsulação, 43,14 e 31,21%, respectivamente, além de conferirem maior estabilidade à bixina durante a exposição à luz e na estocagem no escuro. As diferentes formulações resultaram em diferentes teores do corante de urucum microencapsulado, sendo que a goma arábica apresentou maior eficiência e a goma do cajueiro menor eficiência, considerando os processos de liofilização e atomização. Houve uma maior degradação da bixina total, em torno de 65,79% e, da bixina superficial, em torno de 60,52%, nas microcápsulas armazenadas sob incidência de luz a 25°C±2°C, evidenciando o efeito deletério da luz sobre o corante de urucum. O método de microencapsulação por liofilização foi o que levou a menor degradação da bixina encapsulada. Dentre dos parâmetros de concentração utilizados e dos e dos métodos de microencsapsulação empregados, a goma do cajueiro, individualmente, não se apresentou como um eficiente material de parede. No entanto, a sua mistura com a goma arábica forneceu resultados promissores, os quais tornaram favorável a utilização desse material (U-GCA), como na indústria de alimentos, bem como em outros segmentos tecnologicos como os cosméticos e a farmacêutica.
In practice, some natural dyes, such as bixin present technological difficulties of use, hindering their application in the food industry. Microencapsulation can improve this situation by increasing their stability and making their incorporation in food systems possible without losing their properties. The objective of this research was to microencapsulate the natural dye annatto, using cashew gum as wall material, applying the freeze-drying and spray drying processes, to characterize the microcapsules obtained according to morphological and physico-chemical properties as well as to determine the effectiveness of the microencapsulation by quantification of the total bixin and surface bixin. Gum arabic was used as wall material, the reference for comparison. Thus, three formulations were prepared as follows: annatto colorant / cashew gum (U-GC) 4:1 w / w of annatto colorant / gum arabic (GA-U) 4:1 m / m of annatto colorant / cashew gum / gum arabic and (1:1) 4:1 m / m (U-GCA). The suspensions, which had been previously prepared, were also characterized in terms physical and chemical analyses. In colorimetric evaluation the stability of the microencapsulated pigment was studied, at a room temperature of 25 ° C ± 2 ° C in the presence and absence of light for 40 days storage in two situations, that is dissolved in buffer solution pH 4.0 and in powder form. In the three formulated suspensions , there were no major differences between the pH and colorimetric analyses, but the suspension viscosity cashew gum / dye annatto, resulted in lower viscosity (0.01746 ± 0.000) at the same concentrations of solids. The microcapsules produced by atomization also showed predominantly irregularly shaped circular and toothed surfaces, and lyophilization, show indefinite shapes and sizes vary widely. All the microspheres proved soluble in water. Microcapsules prepared with gum arabic and gum cajuerio / gum arabic (1:1) showed the best efficiency in the microencapsulation, 43.14 and 31.21%, respectivelyand this confers greater stability to the bixin during exposure to light and storage in the dark. The different formulations resulted in different concentrations of microencapsulated annatto dye, with the gum arabic being the most efficient and the cashew gum the least efficient in terms of lyophilization and spray drying. There was a greater total degradation of bixin, about 65.79% and the surface bixin, about 60.52%, in the microcapsules stored under light incidence at 25 ° C ± 2°C, demonstrating the detrimental effect of light on the dye annatto. The microencapsulation method by means of lyophilization is the one which led to the lowest levels of degradation of encapsulated bixin. Among the parameters used and the concentration and methods of microencapsulation employed, cashew gum, on its own, is not presented as an effective wall material. However, its mixture with gum arabic provided promising results, which favors making use of this material (U-GCA) in the food industry and in other technological sectors such as cosmetics and pharmaceuticals.

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Quixal, Martínez Martí. "Language learning tasks ans automatic analysis of learner language : connecting FLTL and NPL in the design of ICALL materials supporting effective use in real-life instruction." Doctoral thesis, Universitat Pompeu Fabra, 2012. http://hdl.handle.net/10803/104481.

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Esta investigación se encuentra en la encrucijada entre el Procesamiento del Lenguaje Natural y el Aprendizaje y Enseñanza de Lenguas Extranjeras y, en concreto, dentro del área denominada Aprendizaje de Lenguas Asistido por Ordenador con Inteliencia Artificial (en inglés, Intelligent Computer-Assisted Language Learning, abreviado ICALL). Nuestra investigación se centra en el diseño, la implemenación en entornos reales de materiales de ICALL para proveer a los estudiantes de lenguas extranjeras, y especialmente de inglés, de materiales que incorporen funcionalidades de corrección y evaluación automáticas de las respuestas. En esta tesis defendemos que, para que la integración de materiales de ICALL sea exitosa, hay que tener en cuenta por igual los requisitos pedagógicos y los computacionales ya en la fase de diseño de los materiales. Nuestros objetivos principales son dos. Por un lado, queremos integrar en el proceso de diseño de materiales tanto los principios fundamentales de la Adquisición de Segundas Lenguas y el Aprendizaje y Enseñanza de Lenguas Extranjeras como los principios fundamentales del modelado lingüístico. Por otro lado, queremos facilitar la integración o de los materiales de ICALL en contextos de instrucción reales, en contraste con los contextos de instrucción de investigación o de laboratorio, para capacitar a los docentes con la metodología y la tecnología necesarias para que puedan crear materiales de ICALL autónomamente. Para conseguir el primer objetivo, proponemos un proceso de diseño de materiales de ICALL que combina los principios básicos de la Enseñanza de Lenguas basado en Tareas y el Diseño de Tests basado en Tareas con el tipo de especificaciones requeridas por las herramientas de Procesamiento del Lenguaje Natural. Exploramos la relación entre los requisitos pedagógicos y computacionales desde tres puntos de vista: (i) las características formales de las actividades para el aprendizaje de lenguas extranjeras, (ii) la complejidad y la variabilidad de la lengua de los estudiantes, y (iii) la viabilidad de aplicar técnicas computacionales para el análisis y evaluación automáticas de las respuestas. Para lograr el segundo objetivo, proponemos una estrategia de evaluación automática que permite a los y las docentes adaptar los recursos lingüísticos computacionales necesarios para corregir automáticamente las actividades de ICALL sin la necesidad de aprender a programar. Para probar la viabilidad de la propuesta presentamos un experimento en que la aplicamos y la evaluamos en entornos de aprendizaje reales con docentes y aprendices de educación secundaria. Con esta tesis hacemos una contribuciones metodológicas y empíricas en el campo del ICALL, con una aproximación innovadora en el diseño de materiales que pone énfasis en la naturaleza multidisciplinar e iterativa del proceso. Los resultados que presentamos revelan el potencial de la caracteritzación de tareas de aprendizaje conjugando la perspectiva el Aprendizaje y Enseñanza de Lenguas Extranjeras y la de la Lingüística Computacional como un instrumento clave para describir formalmente las actividades de aprendizaje. Esta caracteritzación permite identificar los materiales de ICALL que sean a la vez pedagógicamente relevantes y computacionalmente viables. Los resultados demuestran que con la estrategia propuesta los y las docentes pueden caracterizar, crear y utilizar materiales de ICALL dentro de su programa de instrucción, y que el software computacional subyacente proporciona el procesamiento automático requerido con una calidad aceptable para el uso en contextos de instrucción reales. El software y la metodología propuestos resultan cruciales para la investigación y la práctica del ICALL: los docentes son capaces de diseñar actividades para los estudiantes sin depender de un experto en Procesamiento del Lenguaje Natural. Finalmente, los resultados también demuestran que los y las docentes valoran la experimentación muy positivamente en la medida en que les permite integrar nuevas tecnologías en el aula, al tiempo les permite comprender mejor la naturaleza de su tarea docente. Adem'as, los resultados demuestran que los estudiantes se sienten motivados por el hecho de poder utilizar una tecnología que permite una evaluación inmediata y personalizada de su actividad de aprendizaje.

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Adekunle, Kayode. "Bio-based Composites from Soybean Oil Thermosets and Natural Fibers." Doctoral thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-3587.

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In order to reduce over-dependency on fossil fuels and to create an environment that is free of non-degradable plastics, and most importantly to reduce greenhouse gas emission, bio-based products are being developed from renewable resources through intense research to substitute conventional petrochemical-based plastics with renewable alternatives and to replace synthetic fibers with natural fibers. Many authors have done quite a lot of work on synthesizing polymers from renewable origin. Polylactic acid (PLA) has been developed and characterized, and it was found that it has enormous potential and can serve as an alternative to conventional thermoplastics in many applications. Modification of the plant oil triglycerides has been discussed by many authors, and research is still going on in this area. The challenge is how to make these renewable polymers more competitive in the market, and if possible to make them 100% bio-based. There is also a major disadvantage to using a bio-based polymer from plant oils because of the high viscosity, which makes impregnation of fibers difficult. Although natural fibers are hydrophilic in nature, the problem of compatibility with the hydrophobic matrix must be solved; however, the viscosity of the bio-based resin from plant oils will complicate the situation even more. This is why many authors have reported blending of the renewable thermoset resin with styrene. In the process of solving one problem, i.e reducing the viscosity of the renewable thermoset resin by blending with reactive diluents such as styrene, another problem which we intended to solve at the initial stage is invariably being created by using a volatile organic solvent like styrene. The solution to this cycle of problems is to synthesize a thermoset resin from plant oils which will have lower viscosity, and at the same time have higher levels of functionality. This will increase the crosslinking density, and they can be cured at room temperature or relatively low temperature. In view of the above considerations, the work included in this thesis has provided a reasonable solution to the compounded problems highlighted above. Three types of bio-based thermoset resins were synthesized and characterized using NMR, DSC, TGA, and FT-IR, and their processability was studied. The three resins were subsequently reinforced with natural fibers (woven and non-woven), glass fibers, and Lyocell fiber and the resulting natural fiber composites were characterized by mechanical, dynamic mechanical, impact, and SEM analyses. These composites can be used extensively in the automotive industry, particularly for the interior components, and also in the construction and furniture industries. Methacrylated soybean oil (MSO), methacrylic anhydride-modified soybean oil (MMSO), and acetic anhydride-modified soybean oil (AMSO) were found to be suitable for manufacture of composites because of their lower viscosity. The MMSO and MSO resins were found to be promising materials because composites manufactured by using them as a matrix showed very good mechanical properties. The MMSO resin can completely wet a fiber without the addition of styrene. It has the highest number of methacrylates per triglyceride and high crosslink density.
Akademisk avhandling för avläggande av teknologie doktorsexamen vid Chalmers Tekniska högskola försvaras vid offentlig disputation, den 6:e maj, Chalmers, KE-salen, Kemigården 4, Göteborg, kl. 10.00.

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Guerrero, Catells Ángel. "Contribution to the advanced analysis and prevention of the mechanisms of natural fire induced structural collapse in highrise buldings." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/30710.

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El progresivo incremento de la altura de los Edificios de Gran Altura (EGA) ha aumentado las consecuencias reales y potenciales cuando irrumpen en ellos incendios naturales. A la vista de dichas pérdidas, el objeto principal de esta Tesis es la contribución al análisis avanzado y prevención de los mecanismos de colapso estructural en EGAs inducidos por incendios naturales, mejorando el conocimiento actual de los fenómenos involucrados en los mecanismos de fallo estructural introducidos por la acción de dichos incendios naturales y de las consecuencias de ciertas estrategias de extinción de incendios. Durante el calentamiento del Hormigón de Alta Resistencia (HSC), tienen lugar diversos fenómenos complejos, con interacciones físicas, químicas y mecánicas que resultan en cambios significativos de sus propiedades, comportando una pérdida de la capacidad portante y de otras características de servicio de las estructuras de HSC. Un fenómeno significativo conducente a un mecanismo de fallo estructural específico de los HSCs es el Spalling Térmico. Esta Tesis fija el citado objeto, en primer lugar, en los dominios del análisis computacional del Spalling Térmico por medio del software de análisis higro-termo-quimo-mecánico (HTCM) más avanzado y basado en el denominado Modelo de Padua, el software High Temperature Concrete and Spalling o HITECOSP con los objetivos de: Desarrollar un abanico de nomogramas de Spalling con el objeto de evaluar la sensibilidad de los procesos HTCM involucrados en el comportamiento de los HSC, bajo condiciones de incendio natural, a determinados parámetros relevantes; Analizar si el Spalling es energéticamente viable en un abanico de casos reales; Discernir cuál es la contribución energética al Spalling Térmico por parte del gas comprimido y cuál es la correspondiente a la energía elástica constreñida (los dos factores clave conducentes, conjuntamente, al Spalling Térmico). Se han desarrollado más de 91 análisis HTCM, resultantes de la combinación de los valores de los parámetros considerados, a saber: el contenido inicial de humedad del HSC, su permeabilidad intrínseca, la intensidad del fuego, la resistencia a compresión, el conjunto de propiedades del HSC y el espesor del elemento estructural. Otra materia escasamente estudiada en relación con el objeto de la Tesis, es el análisis del efecto de las estrategias de extinción en el estado estructural de los EGAs durante incendios naturales. El choque térmico inducido por la aplicación de un chorro de agua sobre la superficie de un elemento estructural, produce una reducción significativa de la resistencia a flexión y a compresión, mientras que fenómenos de Spalling (Post-Spalling) pueden tener lugar durante y después de la extinción. Esta Tesis fija por tanto su objeto, en segundo lugar, en el dominio del análisis del efecto de un espectro de procesos de enfriamiento en el estado HTCM de un elemento estructural de nuevo con HITECOSP con los siguientes objetivos: Analizar el efecto de un espectro de procesos de enfriamiento en el estado HTCM de un elemento estructural, fabricado con HSC, durante el desarrollo de un incendio natural en un EGA; Desarrollar un análisis comparativo del estado HTCM final de un elemento estructural después de diferentes tipos y subtipos de procesos de enfriamiento, incluyendo la comparación de enfriamientos ambientales y de superficie, diferentes instantes de inicio y velocidades de los procesos de enfriamiento; Proporcionar suficiente información para analizar la influencia en el comportamiento HTCM de un elemento estructural, durante los procesos de enfriamiento, de diversos parámetros no relacionados con los propios procesos de enfriamiento. Dos casos de referencia han sido seleccionados y analizados en profundidad incluyendo numerosas variaciones de: tipo de enfriamiento bien enfriando los gases del escenario bien la superficie del elemento estructural, instante de inicio del proceso de enfriamiento y su velocidad. Este segundo encuadre de objetivos incluye el desarrollo de más de 20 Simulaciones de Dinámica de Fluidos Computacional por medio del software Fire Dynamics Simulator (FDS) para extraer la evolución de la temperatura en las superficies de los elementos estructurales durante diversas acciones de extinción. Finalmente se incluye un análisis heurístico del efecto de los procesos de enfriamiento en el estado HTCM de una columna cuadrada, fabricada con HSC, durante el desarrollo de un incendio natural en un EGA, entendiéndose como una extensión introductoria de los anteriores análisis a casos con flujos 2D como las columnas cuadradas, en las cuales el Spalling de esquina es el más peligroso.
The progressive gain of height of High-Rise Buildings (HRB) has increased the actual and potential consequences when natural fires irrupt. In sight of these losses, the major aim of this Thesis is to contribute to the advanced analysis and prevention of the mechanisms of natural fire-induced structural collapse in HRB, by improving the current knowledge of both the phenomena involved in the structural failure mechanisms introduced by natural fires action and of the consequences of certain fire fighting strategies developed during these fires. During heating of High Strength Concrete (HSC), there take place several complex, interacting physical, chemical and mechanical phenomena resulting in significant changes of the material inner structure and properties, leading to a loss of the load bearing capacity and of other important service features of concrete structures. A significant phenomenon leading to a structural failure mechanism very specific for the HSC used in HRBs and of a great practical importance is the Thermal Spalling. This Thesis settles, first, the abovementioned major aim in the domain of the computational Thermal Spalling analysis by means of the most advanced hygrothermo chemo-mechanical (HTCM) analysis software based on the so-called Model of Padova, High Temperature Concrete and Spalling software (HITECOSP) – with the objectives of: Develop a spectrum of spalling nomograms addressed to evaluate the sensitivity of the HTCM processes involved on the HSCs behaviour under a natural fire to some relevant parameters; Analyze if spalling is energetically possible in a variety of actual cases; Discern what is the energetic contribution of compressed gas to Thermal Spalling and what is that corresponding to the constrained elastic energy (namely, the two key factors leading, together, to Thermal Spalling). There are developed more than 91 HTCM analyses resulting from combinations of the parameters’ values initially considered: the initial moisture content of concrete, its intrinsic permeability, the rate of temperature increase, the porosity, compressive strength and, in general, the whole set of properties of concrete and the thickness of the structural element. Another scarcely studied matter related to the major aim of this Thesis is the analysis of the effect of fire fighting strategies on the structural state of the HRB during natural fires. Thermal shock, induced by the application of water jets on the surface of structural elements, produces a significant reduction in both the flexural strength the compressive strength, whereas Post-cooling spalling may occur after the fire is over, after cooling down or maybe even during extinguishing (especially those containing calcareous aggregates). This Thesis settles, second, the major aim in the domain of the analysis of the effect of a spectrum of cooling processes on the HTCM state of a structural element, manufactured with HSC, during the development of a natural fire in a HRB again with HITECOSP with the objectives of: Analyze the effect of a spectrum of cooling processes on the HTCM state of a structural element, manufactured with HSC, during the development of a natural fire in a HRB; Develop a comparative analysis to compare the final HTCM state of a structural element after the development of different types and subtypes of cooling processes, including comparisons about the Environment vs. Structural element’s Surface cooling attacks, among different start instants and for several velocities of the cooling processes; Provide enough information to analyze the influence on the HTCM behaviour of the structural element during the cooling processes of several parameters non-related to the own cooling processes. Two reference cases are selected where the extinguishing actions conditions are varied in order to cover the widest possible range of situations found by Fire-Fighting Services during a natural fire extinguishment: the type of cooling, the cooling start instant and its rate. This second settling of objectives also includes the development of more than 20 Computational Fluid Dynamics simulations by means of Fire Dynamics Simulator software (FDS) in order to work out the evolution of temperature at surfaces during several extinguishing actions. To conclude, the development of a heuristic analysis of the effect of cooling processes on the HTCM state of a square column, manufactured with HSC, during the development of a natural fire in a HRB, is also included, being understood as an introductory extension of the abovementioned analyses to cases with 2D fluxes such as square columns, where Corner Thermal Spalling is the most dangerous type.

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Ngo, Thi Tuyen. "Analysis of the Interaction of Halide Perovskite with Other Materials and its Effect on the Performance of Optoelectronic Devices." Doctoral thesis, Universitat Jaume I, 2019. http://hdl.handle.net/10803/668130.

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Halide perovskites (HPs) have been demonstrated as promising materials for the preparation of efficient solar cells, LEDs and other optoelectronic devices. In addition, HPs can be prepared using low-cost techniques. However some issues such as low stability or hysteresis are hindering their commercialization. As illustrated, combining materials with different natures has been a successful strategy to develop new materials with enhanced properties. In this Doctoral Thesis we analysed the interaction of HPs with other materials, looking for the potential application. The results pointed out that (1) proper preparation of ETMs can significantly improve both the performance and long term stability of solar cells. (2) Better HP film quality can be achieved by combining HP with either QDs or organic molecules, resulting an enhancement in the device performance of solar cells, LEDs and light amplifiers. (3) New property, exciplex emission, can be obtained from the combination of HP and QDs.
Las perovskitas de haluro (HP) han demostrado ser materiales prometedores para la preparación de células solares (CS), LED y otros dispositivos optoelectrónicos eficientes, utilizando técnicas de preparación de bajo costo. Empero, problemas como la baja estabilidad e histéresis obstaculizan su comercialización. Como se ilustra, la combinación de materiales con diferentes naturalezas es una estrategia exitosa para mejorar las propiedades. En esta Tesis Doctoral analizamos la interacción de los HP con otros materiales, buscando aplicaciones potenciales. Los resultados señalaron que (1) la preparación adecuada de ETM mejora significativamente tanto el rendimiento como la estabilidad a largo plazo de las CS. (2) Se puede lograr una mejor calidad de película HP combinando HP con QD o moléculas orgánicas, lo que resulta en una mejora en el rendimiento de CS, LED y amplificadores de luz. (3) Se puede obtener una nueva propiedad, la emisión de exciplex, de la combinación de HP y QD.

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Sztankovics, Linda. "Shifting powers, prospects and perspectives? : A critical reading of the European Union’s geopolitical reasoning on critical raw materials." Thesis, Försvarshögskolan, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:fhs:diva-9700.

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Global energy transitions and rises in demand for critical raw materials (CRMs) are predicted to reshape global politics in yet uncertain but profound ways. With CRMs being vital for Europe’s decarbonization process, the present study sets out to examine the EU’s geopolitical discourse by taking an inquisitive yet critical stance focusing particularly on the new “geopolitical” Commission’s geopolitical reasoning on CRMs. Building upon critical geopolitics, a discourse analysis was conducted on 9 European Commission communications (2019–2020). Three key observations were made: first, a ‘geopolitical’ and ‘assertive’ EU is crucial in an increasingly ‘fragile’, ‘polarized’ and ‘competitive’ world. Second, securing CRMs is a ‘security question’, requiring ‘strategic approaches and partnerships’, notably with ‘resource–rich regions’ and particularly with Africa. Third, the EU’s narrative is ambiguous. While classical geopolitical assumptions are distinguishable, it remains questionable whether the EU will depart from its familiar path of liberal cooperation, multilateralism and trade when scouting for CRMs, although its role as a “benign ally” can be questioned. Further studies on the EU’s geopolitical reasoning, along with its actual practice in the area of CRMs, are warranted. Likewise, a critical reading of reports and foresight preceding EU policymaking is encouraged, to better comprehend how the EU’s dominating geopolitical discourse on CRMs and subsequent practice is produced in the first place.

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Shea, Lauren. "Microstructural and textural analysis of naturally deformed granulites in the Mount Hay block of central Australia: Implications for the rheology of polyphase lower crustal materials." Thesis, Boston College, 2019. http://hdl.handle.net/2345/bc-ir:108578.

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Thesis advisor: Seth C. Kruckenberg
Quantitatively describing the deformational behavior (i.e. the rheology) of lower crustal materials has proven challenging due to the highly variable nature of structural and compositional fabrics in the lower crust. Further, many flow laws describing the rheology of monophase aggregates are experimentally derived and do not necessarily apply to polyphase materials, such as gabbro, that dominate the lower crust. Here, we present the results of integrated microstructural analysis and electron backscatter diffraction (EBSD) textural analysis from exhumed lower crustal granulites in the Mount Hay block of central Australia. The preservation of heterogeneous mafic and felsic granulites containing monophase and/or polyphase mixtures of anorthite, pyroxene, and quartz (interlayered on the mm- to m-scale) make this region uniquely suited for advancing our knowledge of the processes that affect deformation and the rheology of the lower crust. Forty-two samples from distinct structural and compositional domains were chosen to compare the microstructural record of deformation, the development of crystallographic textures, and to provide estimates of lower crustal rheology and deformation conditions. Full thin-section maps of crystallographic texture were produced using EBSD methods. The resultant orientation maps were processed to characterize crystallographic textures in all constituent phases, and all other quantifiable aspects of the rock microstructure (e.g., grain size, grain shape, misorientation axes). The EBSD analysis reveals the presence of strong crystallographic preferred orientations (CPO) in nearly all constituent phases, suggesting deformation dominated by dislocation creep. Differential stresses during deformation are calculated using grain size piezometry for all major phases, and range between 34-54 MPa in quartz within monophase layers. Two-pyroxene geothermometry was used to constrain deformation temperatures to ca. 780-810 C. Based on the estimated CPO patterns, stress, and temperature, we quantify strain rates and effective viscosities of all major phases through application of monophase flow laws. Monophase strain rates range from 2.10 x 10-12 s-1 to 1.56 x 10-11 s-1 for quartz, 4.68 x 10-15 s-1 to 2.48 x 10-13 s-1 for plagioclase feldspar, 1.56 x 10-18 s-1 to 1.64 x 10-16 s-1 for enstatite, and 5.66 x 10-16 s-1 to 1.00 x 10-14 s-1 for diopside. The determined flow law variables used for monophase calculations were subsequently applied to two different models – the Minimized Power Geometric model of Huet et al. (2014) and the Asymptotic Expansion Homogenization (AEH) method of Cook (2006) – in order to calculate a bulk aggregate viscosity of the polyphase material. At a strain rate of 10-14 s-1, polyphase effective viscosities for our samples range from 3.07 x 1020 to 2.74 x 1021 Pa·s. We find that the bulk viscosity of heterogeneous, gabbroic lower crust in the Mount Hay region lies between that of monophase plagioclase and monophase quartz, and varies as a function of composition. These results are consistent with past modeling studies and geophysical estimates
Thesis (MS) — Boston College, 2019
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Earth and Environmental Sciences

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Huang, Weichun. "Acoustic properties of natural materials." Thesis, Le Mans, 2018. http://www.theses.fr/2018LEMA1031/document.

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Dans cette thèse, nous étudions un métamatériau inspiré de la paille de blé pour l'absorption parfaite du son. Une botte de paille estidéalisée comme un milieu poreux anisotrope, composé d’un arrangement périodique très concentré de tubes creux cylindriques. L’approche théorique de ce métamatériau repose sur l'homogénéisation asymptotique à deux échelles d'un réseau perméable de résonateursparfaitement rigides dont la physique est enrichi par des résonances internes. Les principales caractéristiques de ce milieu poreux sont lacompressibilité effective négative autour de la résonance du tube et la réduction drastique de la vitesse de propagation du son (slowsound) à très basse fréquence. Une configuration optimale est conçue, basée sur la condition de couplage critique, pour laquelle la fuited’énergie du système résonnant ouvert est parfaitement compensée par les pertes intrinsèques induites par les pertes viscothermiques.Des mesures en tube à impédance sont effectuées sur des échantillons fabriqués par impression additive pour valider les résultatsthéoriques. Nous montrons que ce métamatériau est un absorbeur sub-longueur d'onde capable d’une absorption parfaite à très bassefréquence et d'introduire une quasi-bande interdite autour de la résonance du tube. De plus, la nature anisotrope de ce matériau conduit àune absorption globalement élevée à basse fréquence et ce pour toutes les incidences. Cette étude offre la possibilité de concevoir unabsorbeur acoustique sélectif en angle et en fréquence. Pour conclure, les résultats de cette thèse montrent que la paille est un boncandidat pour une absorption acoustique parfaite
Straw-inspired metamaterials for sound absorption are investigated in this Thesis. A straw stack is idealized as a highly concentratedresonant anisotropic porous medium constituted of a periodic arrangement of densely packed cylindrical hollow tubes. The approach tothis metamaterial relies on the two-scale asymptotic homogenization of a permeable array of perfectly rigid resonators, where the physicsis further enriched by tailoring inner resonances. The main features of such sound absorbing medium are the possibility for the effectivecompressibility to become negative around the tube resonance and the drastic reduction of the effective sound speed (slow sound) at verylow frequency in the system. Moreover, an optimal configuration for sound absorption is designed, based on the critical couplingcondition, in which the energy leakage out of the open resonant system is perfectly compensated by the intrinsic losses induced by thevisco-thermal losses both in the anisotropic matrix and in the resonators. Impedance tube measurements are performed on 3-D printedsamples with controlled parameters to validate the theoretical results. This metamaterial is a sub-wavelength absorber that can achievetotal absorption at a very low frequency and possesses a quasi-band-gap around the tube resonance. Furthermore, the anisotropic nature ofthe configuration gives rise to high absorption at low-frequency range for all incidences and diffuse field excitation. It paves the way tothe design of angular and frequency selective sound absorber. To conclude, the results of this Thesis show that straw is a good candidatefor perfect sound absorption

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Wegst, Ulrike G. K. "The mechanical performance of natural materials." Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/272820.

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Kim, Edward Soo. "Data-mining natural language materials syntheses." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122075.

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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Discovering, designing, and developing a novel material is an arduous task, involving countless hours of human effort and ingenuity. While some aspects of this process have been vastly accelerated by the advent of first-principles-based computational techniques and high throughput experimental methods, a vast ocean of untapped historical knowledge lies dormant in the scientific literature. Namely, the precise methods by which many inorganic compounds are synthesized are recorded only as text within journal articles. This thesis aims to realize the potential of this data for informing the syntheses of inorganic materials through the use of data-mining algorithms. Critically, the methods used and produced in this thesis are fully automated, thus maximizing the impact for accelerated synthesis planning by human researchers.
There are three primary objectives of this thesis: 1) aggregate and codify synthesis knowledge contained within scientific literature, 2) identify synthesis "driving factors" for different synthesis outcomes (e.g., phase selection) and 3) autonomously learn synthesis hypotheses from the literature and extend these hypotheses to predicted syntheses for novel materials. Towards the first goal of this thesis, a pipeline of algorithms is developed in order to extract and codify materials synthesis information from journal articles into a structured, machine readable format, analogous to existing databases for materials structures and properties. To efficiently guide the extraction of materials data, this pipeline leverages domain knowledge regarding the allowable relations between different types of information (e.g., concentrations often correspond to solutions).
Both unsupervised and supervised machine learning algorithms are also used to rapidly extract synthesis information from the literature. To examine the autonomous learning of driving factors for morphology selection during hydrothermal syntheses, TiO₂ nanotube formation is found to be correlated with NaOH concentrations and reaction temperatures, using models that are given no internal chemistry knowledge. Additionally, the capacity for transfer learning is shown by predicting phase symmetry in materials systems unseen by models during training, outperforming heuristic physically-motivated baseline stratgies, and again with chemistry-agnostic models. These results suggest that synthesis parameters possess some intrinsic capability for predicting synthesis outcomes. The nature of this linkage between synthesis parameters and synthesis outcomes is then further explored by performing virtual synthesis parameter screening using generative models.
Deep neural networks (variational autoencoders) are trained to learn low-dimensional representations of synthesis routes on augmented datasets, created by aggregated synthesis information across materials with high structural similarity. This technique is validated by predicting ion-mediated polymorph selection effects in MnO₂, using only data from the literature (i.e., without knowledge of competing free energies). This method of synthesis parameter screening is then applied to suggest a new hypothesis for solvent-driven formation of the rare TiO₂ phase, brookite. To extend the capability of synthesis planning with literature-based generative models, a sequence-based conditional variational autoencoder (CVAE) neural network is developed. The CVAE allows a materials scientist to query the model for synthesis suggestions of arbitrary materials, including those that the model has not observed before.
In a demonstrative experiment, the CVAE suggests the correct precursors for literature-reported syntheses of two perovskite materials using training data published more than a decade prior to the target syntheses. Thus, the CVAE is used as an additional materials synthesis screening utility that is complementary to techniques driven by density functional theory calculations. Finally, this thesis provides a broad commentary on the status quo for the reporting of written materials synthesis methods, and suggests a new format which improves both human and machine readability. The thesis concludes with comments on promising future directions which may build upon the work described in this document.
by Edward Soo Kim.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering

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Ramirez, Cadavid David A. "Development of Processes for the Extraction of Industrial Grade Rubber and Co-Products from the Roots of Taraxacum kok-saghyz (TK)." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512060296142347.

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Lowe, David James. "Natural rubber/organoclay nanocomposites." Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/2971.

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Natural rubber (NR)/organoclay nanocomposites were prepared using organomontmorillonite (OMMT) and organo-sepiolite (OSEP). Both were found to improve modulus significantly more than equivalent amounts of conventional fillers such as carbon black for strains up to 100%. OSEP was found to increase modulus more than OMMT for a given filler content, and NR/OSEP nanocomposites also had potentially anisotropic physical properties. OMMT had more effect on vulcanisation than OSEP, although both produced considerable acceleration. The tensile stress-strain behaviour of NR/OMMT and NR/OSEP nanocomposites were studied using a number of different micromechanical models. Some models were found to give a good empirical fit with experimental data, with the best results given by the Halpin-Tsai model. Furthermore, by analysis of the vulcanisation behaviour using rheometry, and particle morphology using transmission electron microscopy (TEM), it was possible to accurately estimate the Young's modulus of a nanocomposite from knowledge of the cure onset time and the shape factor of the particles. It was discovered that unmodified montmorillonite and sepiolite clays could undergo organic modi cation in situ during mixing into NR following the addition of a suitable modifier. This resulted in vulcanisates with very similar physical properties to those found when using pre-modified OMMT or OSEP. TEM and X-ray diffraction showed that the exfoliation state of the clay modified in situ was also similar to that of pre-modified organoclay. Silane coupling agents were also used with NR/OMMT and NR/OSEP nanocomposites, producing significant increases in modulus. However, the increased modulus was only observed above 40% strain for OMMT and above 25% for OSEP. The coupling agents strengthens the rubber- ller interface preventing interfacial slippage and cavitation in the nanocomposite, and these mechanisms only begin to operate when the interfacial stress reaches a significant level. The most effective coupling agent used was bis[triethoxysilylpropyl] tetrasulfide due to its relatively high reactivity.

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Holcroft, Neal. "Natural fibre insulation materials for retrofit applications." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707590.

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Improving the thermal performance of existing domestic buildings can have multiple benefits: reducing greenhouse gas emissions, reducing the cost of heating and therefore fuel poverty, improving comfort and health. Solid wall buildings constitute around 30% of UK housing stock, and are among the least efficient. However, the installation of solid wall insulation, while improving thermal performance can significantly affect the moisture balance of the building. This can result in mould growth, which can cause structural damage and lead to health problems for the occupants. This thesis explores the use of Natural Fibre Insulation (NFI) materials for internal solid wall insulation. The hygrothermal properties of a range of NFI materials are characterised in order to assess their potential for retrofit applications. This is followed by large-scale testing, which compares three solid wall insulation systems in controlled conditions, the results of which are used to validate a heat and moisture transfer model to further assess performance. Experimental results showed that the risk of interstitial condensation is significantly reduced by the application of natural fibre insulation in comparison to a conventional rigid foam system. Simulation of a solid wall exposed to climatic conditions for the UK revealed that the relative humidity at the interface between the masonry and insulation layers remained at 69% when internally insulated with hemp-lime and 96% with rigid foam insulation, while average moisture content of the masonry was 48% lower when hemp-lime was used. Field tests were also conducted to determine the thermal performance of two solid walls internally insulated with 80 mm of hemp-lime when exposed to real weather conditions. The thermal conductivity of the hemp-lime was found to be 30% higher than when measured in dry stead-state laboratory conditions due to the high moisture content of the masonry. However, its application still resulted in 66% and 68% reductions in the U-value compared to the uninsulated wall from 2.73 and 2.65 W/m2K to 0.93 and 0.86 W/m2K.

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Brakus, Josko. "Mechanical properties of natural materials : an overview." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11553.

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Souayfane, Farah. "Modèle simplifié de changement de phase en présence de convection et rayonnement : application à un mur translucide associant superisolation et stockage d'énergie thermiques." Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4043/document.

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Cette thèse vise à étudier l'exploitation du rayonnement solaire grâce à un nouveau concept de mur capteur passif. Dans ce contexte, le comportement thermique d’un mur solaire semi-transparent a été étudié. Le mur fournit un éclairage naturel et est composé d’une couche d’aérogel de silice assurant une isolation thermique et acoustique, et d’un MCP. Ce dernier est contenu dans des briques de verre assurant l’absorption, le stockage et la restitution de chaleur. Ce mur a été caractérisé expérimentalement au centre PERSEE à Sophia. Il a été remarqué que la performance thermique du mur est élevée en hiver, tandis qu’une surchauffe estivale a été rencontrée. Un modèle numérique simplifié a été développé pour modéliser la convection naturelle et le rayonnement pendant la fusion du MCP. Ce modèle est validé à l’aide d’un modèle CFD, et des résultats de Benchmark. Pour optimiser la performance du mur en été, un modèle numérique du transfert de chaleur à travers le mur a été développé sous MATLAB. Ce modèle a été couplé à TRNSYS afin d’évaluer la performance thermique de l'ensemble du bâtiment. Le modèle couplé a été validé expérimentalement. Le comportement thermique du mur est testé dans des différents climats, et des solutions passives sont proposées pour assurer le confort thermique. Enfin, ce modèle a permis d'étudier le comportement thermique annuel d’un bâtiment intégrant un mur MCP- aérogel dans son enveloppe et une étude économique a été réalisée. Ces études ont confirmé l'intérêt du mur vis-à-vis de l'amélioration des performances énergétiques du bâtiment. La faisabilité économique de l'application du mur dépend du climat, du coût d’énergie, et du coût d'investissement
This thesis aims to study the exploitation of solar radiation thanks to a new concept of passive sensor wall. In this context, the thermal behavior of a novel semi-transparent solar wall has been studied. The wall is composed of glazing, silica aerogel (TIM) and glass bricks filled with fatty acids (PCM). This wall provides storage and restitution of heat, thermal-acoustic insulation and daylighting. The thermal performance of the TIM-PCM wall is tested in a full-sized test cell located in Sophia, PERSEE center. In winter, particularly in sunny cold days, the PCM absorbs solar radiation, melts, and then releases the stored heat to the building at night. During summer, overheating is encountered, the PCM remains in its liquid state and is unable to release the stored heat. A simplified model for PCM melting in presence of natural convection and radiation is developed and validated using a CFD model, and benchmark solutions. Then, a numerical model describing the heat transfer mechanisms through the wall is developed. This model is linked to TRNSYS to assess the thermal performance of the whole building. The MATLAB-TRNSYS model is then validated experimentally. The thermal behavior of the wall is tested under different climates, and passive solutions are proposed to ensure thermal comfort in summer. Finally, the validated model is used to study the annual thermal behavior of a building integrating TIM-PCM wall and an economic study is conducted. These studies confirm the interest of the wall vis-à-vis the improvement of energy performance of the building. The economic feasibility of applying the TIM-PCM wall depends mainly on climate, energy costs, and investment cost

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26

Turvill, Michael W. "The synthesis of natural and synthetic colouring materials." Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280103.

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27

FILHO, ROMILDO DIAS TOLEDO. "COMPOSITE MATERIALS REINFORCED WITH NATURAL FIBRES: EXPERIMENTAL CHARACTERIZATION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1997. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2144@1.

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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
BRITISH COUNCIL
UNIVERSIDADE FEDERAL DA PARAÍBA
A presente tese estuda as propriedades de curta e londa duração de argamassas de cimento reforçadas com fibras de coco e sisal. O trabalho experimental visou a determinação das propriedades físicas e mecânicas do reforço e o estudo da influência do tipo, fração volumétrica e tamanho de fibra, orientação e composição da matriz nas propriedades mecânicas do compósito. Estudos foram executados com o objetivo de se determinar a influência do reforço na retração plástica, com e sem restrições, das matrizes de argamassa. Fissurações resultantes da imposição das restrições e o fenômeno de cicatrização das fissuras foram também investigados. O modo de ruptura e as propriedades de aderência interfacial fibra-matriz foram determinados através de ensaios de arrancamento. As propriedades de longa duração dos compósitos foram determinadas através dos ensaios de fluência, retração e durabilidade. A influência da adição de várias frações volumétricas e tamanhos de fibras na fluência das matrizes de argamassa foi determinada usando-se corpos de prova, selados e não selados, submetidos a uma pressão de 14,4 MPa durante um período de 210-350 dias. Recuperações das deformações elásticas foram monitoradas por um período de 56-180 dias. A influência dos tipos de fibra, fração volumétrica, tamanho de fibra, tipo de cura, traço da argamassa e substituição parcial do cimento Portland por micro-sílica e escória de alto forno na estabilidade dimensional das matrizes de argamassa foi determinada com o uso de ensaios de retração por um período de 320 dias. A durabilidade das fibras de coco e sisal, imersas em soluções alcalinas de hidróxido de cálcio e de sódio e em água de torneira, foi determinada através da realização de ensaios de resistência à tração em idades variando de 30-420 dias. A durabilidade das argamassas reforçadas com fibras naturais após 320-360 dias imersas em água, expostas a ciclos de molhagem e secagem bem como ao ambiente natural foi determinada através de resultados de ensaios de flexão e de observações de imagens obtidas com o uso de microscopia eletrônica. Um mapeamento de elementos químicos foi realizado com o objetivo de se verificar possíveis migrações de produtos da matriz de cimento Portland para o lúmen e paredes das fibras. Tratamentos para garantir a durabilidade dos compósitos foram estudados, a saber: (a) modificações na matriz através da substituição parcial do cimento Portland por micro-sílica e escória de alto orno; (b) carbonatação da matriz de cimento Portland; (c) imersão das fibras em micro-sílica líquida antes de serem incorporadas à matriz de cimento Portand.
This thesis studies both the short-term and long- term behaviour of sisal and coconut fibre reinforced mortar composites.The experimental work involved extensive laboratory testing to determine the physical and mechanical properties of the fibre reinforcement and to study the influence of fibre type, volume fraction, fibre length, fibre arrangement and matrix composition on the mechanical properties of the composite.Studies were also made to determine the influence of fibre reinforcement in controlling free and restrained shrinkage during the early age of mortar mixes. Cracking due to restraint and the phenomenon of crack self-healing were also investigated. The mode of failure and the properties of the resistance to fibre-matrix interfacial bonding were determined using the single fibre pull-out test.The long-term properties of the sisal and coconut fibre reinforced-mortar composites were assessed throughout creep, shrinkage and durability tests. The influence of the addition of sisal and coconut fibres, of various volume fraction and lengths, on the creep of a mortar matrix was determined using sealed and unsealed specimens subjected to a pressure of 14.4 MPa over a period of 210-350 days. Recovery strains were recorded for a period of 56-180 days.The influence of fibre types, volume fraction, fibre lengths, cure types, mix proportions and replacement of OPC by slag and silica fume on the dimensional stability of mortar matrices was determined using drying shrinkage tests for a period of 320 days. The durability of sisal and coconut fibres exposed to alkaline solutions of calcium and sodium hydroxide and stored in tap water was measured as strength loss over a period of 420 days. The durability of fibre-reinforced mortars after 320 to 360 days, stored under water, exposed to cycles of wetting and drying as well as to the natural weather,was assessed from results of flexural tests and from observations of the photomicrographs obtained using backscattered imaging and secondary electron imaging. Dotting maps of chemical elements were obtained in order to verify possible migration of cement products from the matrix to the lumen and voids within of the fibres. Treatments to enhance the durability performance of the composites were studied,including: (a) modifications to the matrix through the replacement of Portland cement by undensified silica fume and by blast-furnace slag; (b) carbonation of the cementitious matrix and (c) immersion of the fibres in slurry silica fume prior to being incorporated into the Portland cement matrix.

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28

Song, Juha. "Multiscale materials design of natural exoskeletons : fish armor." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69670.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 261-282).
Biological materials have developed hierarchical and heterogeneous material nanostructures and microstructures to provide protection against various environmental threats that, in turn, provide bioinspired clues to man-made, protective material designs. In particular, designs of dermal fish armor are a tradeoff between protection and mobility. A comprehensive knowledge base of the materials and mechanical design principles of fish armor has broad applicability to the development of synthetic engineered protective/flexible materials. In this thesis, two fish armor model systems have been investigated by means of structure-property-function relationships, ultimately answering how the armor systems have been designed in response to their environmental threats. The first model system, Polypterus senegalus are descendants of ancient fish and their body is covered by a natural armor consisting of small bony scales. The quadlayered armor scales are composed of ganoine, dentin, isopedine and bone, to protect against predatory biting attacks. First of all, multilayer design principles of P. senegalus scales were understood with respect to penetration resistance by the multiscale experimental and computational study. The quad-layered scales exhibit mechanical gradient within and between material layers and have geometrically corrugated junctions with an undetectable gradation; all of which lead to effective penetration resistance including load-dependent effective material properties, circumferential surface cracking, plastic dissipation in the underlying dentin layer, stress redistribution around the interfaces with suppression of interfacial failure. Secondly, since the outmost ganoine is structurally anisotropic, the roles of anisotropy of ganoine in the entire system have been investigated by combining orientation-dependant indentation and mechanical modeling. The elastic-plastic anisotropy of the ganoine layer enhances the load-dependent penetration resistance of the multilayered armor compared with the isotropic ganoine layer mainly by (i) enhancing the transmission of stress and dissipation to the underlying dentin layer, (ii) lowering the ganoine/dentin interfacial stresses and hence reducing any propensity toward delamination, and (iii) providing discrete structural pathways for cracks to propagate normal to the surface for easy arrest by the underlying dentin layer. Inspired by P. senegalus scales, threat-protection interaction and structurefunction relationships among various layered armor systems have been investigated using parametric studies with finite element (FE) models. Geometry, microstructure and mechanical properties of a threat system significantly influence its ability to effectively penetrate into the armor system or to be defeated by the armor. Simultaneously, three structure parameters of multilayered armor designs are mainly considered: (i) the thickness of the outmost layer; (ii) the quad-layered vs. bilayer structure; and (iii) the sequence of the outer two layers. The role of the armor microstructure in defeating threats as well as providing avenues of energy dissipation to withstand biting attacks is identified. Microstructural length scale and material property matching between the threat and armor is clearly observed. Bilayered and quadlayred models are mechanically comparable, but the quad-layer model achieves a weight reduction. Studies of predatorprey threat-protection interactions may lead to insights into tunability in mechanical functionality of each system in conjunction with adaptive phenotypic plasticity of the tooth and scale microstructure and geometry, "adaptive stalemates," and the so-called evolutionary "arms race." The second model system, Gasterosteus aculeatus, is well-known for light-weight and morphologically varied armor structure among different G. aculeatus populations. Marine and freshwater G. aculeatus armor structures have been assessed quantitatively by micro-computed tomography ([mu]CT) technique. The convolution of plate geometry in conjunction with plate-to-plate overlap allows a relatively constant armor thickness to be maintained throughout the assembly, promoting spatially homogeneous protection and thereby avoiding weakness at the armor unit interconnections. Plate-to-plate junctures act to register and join the plates while permitting compliance in sliding and rotation in selected directions. SEM and [mu]CT revealed a porous, sandwich-like cross-section of lateral plates beneficial for bending stiffness and strength at minimum weight. Moreover, the structural parameters of the pelvic assemblies were also quantified via pCT, which include the spatial dependence of the suture amplitude and frequency, the suture plate inclination angle, and the suture gap. Significant differences in these structural parameters were observed between the different G. aculeatus populations. Composite analytical and finite element computational models were developed and used in conjunction with the pCT data to simulate the mechanical behavior of the pelvic assembly, to predict the effective suture stiffness and to understand the conformational change of the pelvic assembly from the "rest" to "offensive" states. This study elucidates the structural and functional differences between different divergent populations of G. aculeatus and serves as a model for other systems of interest in evolutionary biology.
by Juha Song.
Ph.D.

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29

Ghidan, Osama Yousef Ali. "The isotopic composition of Zn in natural materials." Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/1215.

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This work represents the most recent development of Zn isotopic measurements, and the first identification of Zn isotopic fractionation in natural materials using Thermal Ionisation Mass Spectrometry (TIMS). The procedures developed in this research systematically evaluates and solves several critical analytical issues involved in TIMS Zn isotopic measurements such as, reducing the size of sample needed to perform an accurate and precise measurement, minimizing the effect of interferences on the Zn fractionation, reducing the blank associated with the analyses, dissolution and purification of different natural samples, and the generally ignored issue of the effect of the ion exchange chemistry (Zn separation) to the fractionation of Zn. These procedures have allowed sub-permil fractionations in the isotopic composition of Zn to be revealed in small Zn sample (1µg), and the determination of low level (ng) elemental abundance of Zn in samples to be measured accurately by the means of isotope dilution mass spectrometry IDMS. This thesis uses the rigorous double spike technique to measure fractionation, relative to the internationally proposed absolute Zn isotopic reference material (δ zero), based on a high purity Alfa Aesar 10759, now available to the international isotope community. All the isotopic measurements in natural materials were performed on bulk samples purified by ion exchange chemistry.The isotopic composition of the Zn minerals and igneous rocks agreed with that of the absolute reference material, which makes it possible to consider this reference material as being representative of “bulk Earth” Zn. Significant and consistent fractionation of ~+0.3 ‰ per amu were found in 5 sediments from a range of localities. The consistency of this is attributed to conveyor type oceanic circulations effects. The results from the two metamorphic samples indicate that the fractionation of Zn in these rocks is the same as found in igneous rocks but are different from the Zn found in sedimentary rocks. This supports the widely held assumption that high temperature and pressure processes do not fractionate the isotopic composition of chalcophile elements, such as has been found for Cd. Clay sample TILL-3 appears to exhibit a consistently slightly positive Zn fractionation of +0.12 ± 0.10 ‰ amu-1, although inside the uncertainties of both igneous and sedimentary rocks, which is not surprising since Till is thought to be a formed from a range of mixed glacial sediments The isotopic composition of Zn was measured in two plants and one animal sample. The fractionation of (-0.088 ± 0.070 ‰ amu-1) of Zn in the Rice (a C3 type plant material) sample suggested that Zn may be used to study Zn systematics in plants. The result obtained for MURST-Iss-A2 (Antarctic Krill) was +0.21 ± 0.11 ‰ amu-1 relative to the laboratory standard which is similar to the average Zn fractionation results of +0.281 ± 0.083 ‰ amu-1 obtained for marine sediments.In this work, the isotopic composition of Zn was measured in five stone and two iron meteorites. The range of Zn fractionation in stone meteorites was between -0.287 ± 0.098 and + 0.38 ± 0.16 ‰ amu-1, and was consistent with previous work, although more measurements would be needed to generalize this to all stone meteorites. In iron meteorites; Canyon Diablo was found to have the greatest fractionation of +1.11 ± 0.11 ‰ amu-1 relative to the laboratory standard. Of all the meteorites studied, Redfields clearly showed an anomalous isotopic composition indicating that this meteorite possesses a significantly different Zn isotopic composition compared to all of the other natural materials measured. Using 64Zn as a reference isotope, significant differences relative to the laboratory standard were found of +5.6 ± 0.4‰, +4.4 ± 3.6 ‰, and +21.0± 0.9 ‰ and +27.4 ± 18.8 ‰ on 66Zn and 67Zn, 68Zn and 70Zn respectively. These significant “Redfields anomalies” can be interpreted in a number of ways in relation to their nucleosynthetic production. Whether Redfields is a primitive type of iron meteorite or not, the Redfields anomaly strongly suggests wide spread isotopic heterogeneity of at least one part of the Solar System and does not support the suggestion that “Zn was derived from an initially single homogeneous reservoir in the early Solar System”. A pilot study to determine the concentration and the isotopic composition of Zn in River and tap water was performed.The concentration of Zn in River water averaged 6.9 ± 0.8 ngg-1, while for tap water it ranged from 13.1 ngg-1 to 5.2 μgg-1. River water was fractionated by -1.09 ± 0.70 ‰ amu-1, while restrained tap water yielded the maximum fractionation of -6.39 ± 0.62 ‰ amu-1 relative to the laboratory standard. The Zn fractionation of tap water is much larger than all other natural samples, although the uncertainty is also significantly greater due to the use of the less precise Daly detector used for these preliminary experimental measurements. The fractionation of Zn in seven ultra pure Zn standard materials was measured relative to the laboratory standard and found to range from -5.11 ± 0.36 ‰ amu-1 for AE 10760 to +0.12 ± 0.16 ‰ amu-1 for Zn IRMM 10440. There appears to be some evidence for a relationship between Zn fractionation and its purity. As well as natural materials, the fractionation of Zn was measured in a number of processed materials. None of these results or those obtained for natural materials impact on the currently IUPAC accepted value for the atomic weight of Zn. Along with fractionation determinations, the concentration of Zn was also measured by Isotope Dilution Mass Spectrometry in all of the samples. The concentration of Zn in five stony meteorites ranged from 26 ± 13 to 302 ± 14 μgg-1 for Plainview and Orgueil respectively. For ordinary Chondrites, the concentration of Zn in the three samples analysed ranged from 26 ± 13 to 64 ± 34 μgg-1 for Plainview and Brownfield 1937 respectively.The concentration of Zn was measured in two metamorphic rocks standard materials; the maximum concentration was 101.5 ± 1.7 µgg-1 in SDC-1. The concentration of Zn present in plant samples studied in this research was 22.15 ± 0.42, 14.62 ± 0.27 µgg-1 for Rice IMEP-19 and Sargasso NIES-Number 9 respectively which is within the normal range of Zn concentrations. Except for meteorites, the final uncertainties consistently cover the ranges of individual concentration measurements and indicate the homogeneity of the samples, including samples from different bottles where available. The final fractional uncertainties obtained for SRMs were all less than 2.8 %, demonstrating the high level of precision possible using IDMS.

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30

Ghidan, Osama Yousef Ali. "The isotopic composition of Zn in natural materials." Curtin University of Technology, School of Science and Computing, Department of Imaging and Applied Physics, 2008. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=116055.

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Abstract:

This work represents the most recent development of Zn isotopic measurements, and the first identification of Zn isotopic fractionation in natural materials using Thermal Ionisation Mass Spectrometry (TIMS). The procedures developed in this research systematically evaluates and solves several critical analytical issues involved in TIMS Zn isotopic measurements such as, reducing the size of sample needed to perform an accurate and precise measurement, minimizing the effect of interferences on the Zn fractionation, reducing the blank associated with the analyses, dissolution and purification of different natural samples, and the generally ignored issue of the effect of the ion exchange chemistry (Zn separation) to the fractionation of Zn. These procedures have allowed sub-permil fractionations in the isotopic composition of Zn to be revealed in small Zn sample (1µg), and the determination of low level (ng) elemental abundance of Zn in samples to be measured accurately by the means of isotope dilution mass spectrometry IDMS. This thesis uses the rigorous double spike technique to measure fractionation, relative to the internationally proposed absolute Zn isotopic reference material (δ zero), based on a high purity Alfa Aesar 10759, now available to the international isotope community. All the isotopic measurements in natural materials were performed on bulk samples purified by ion exchange chemistry.
The isotopic composition of the Zn minerals and igneous rocks agreed with that of the absolute reference material, which makes it possible to consider this reference material as being representative of “bulk Earth” Zn. Significant and consistent fractionation of ~+0.3 ‰ per amu were found in 5 sediments from a range of localities. The consistency of this is attributed to conveyor type oceanic circulations effects. The results from the two metamorphic samples indicate that the fractionation of Zn in these rocks is the same as found in igneous rocks but are different from the Zn found in sedimentary rocks. This supports the widely held assumption that high temperature and pressure processes do not fractionate the isotopic composition of chalcophile elements, such as has been found for Cd. Clay sample TILL-3 appears to exhibit a consistently slightly positive Zn fractionation of +0.12 ± 0.10 ‰ amu-1, although inside the uncertainties of both igneous and sedimentary rocks, which is not surprising since Till is thought to be a formed from a range of mixed glacial sediments The isotopic composition of Zn was measured in two plants and one animal sample. The fractionation of (-0.088 ± 0.070 ‰ amu-1) of Zn in the Rice (a C3 type plant material) sample suggested that Zn may be used to study Zn systematics in plants. The result obtained for MURST-Iss-A2 (Antarctic Krill) was +0.21 ± 0.11 ‰ amu-1 relative to the laboratory standard which is similar to the average Zn fractionation results of +0.281 ± 0.083 ‰ amu-1 obtained for marine sediments.
In this work, the isotopic composition of Zn was measured in five stone and two iron meteorites. The range of Zn fractionation in stone meteorites was between -0.287 ± 0.098 and + 0.38 ± 0.16 ‰ amu-1, and was consistent with previous work, although more measurements would be needed to generalize this to all stone meteorites. In iron meteorites; Canyon Diablo was found to have the greatest fractionation of +1.11 ± 0.11 ‰ amu-1 relative to the laboratory standard. Of all the meteorites studied, Redfields clearly showed an anomalous isotopic composition indicating that this meteorite possesses a significantly different Zn isotopic composition compared to all of the other natural materials measured. Using 64Zn as a reference isotope, significant differences relative to the laboratory standard were found of +5.6 ± 0.4‰, +4.4 ± 3.6 ‰, and +21.0± 0.9 ‰ and +27.4 ± 18.8 ‰ on 66Zn and 67Zn, 68Zn and 70Zn respectively. These significant “Redfields anomalies” can be interpreted in a number of ways in relation to their nucleosynthetic production. Whether Redfields is a primitive type of iron meteorite or not, the Redfields anomaly strongly suggests wide spread isotopic heterogeneity of at least one part of the Solar System and does not support the suggestion that “Zn was derived from an initially single homogeneous reservoir in the early Solar System”. A pilot study to determine the concentration and the isotopic composition of Zn in River and tap water was performed.
The concentration of Zn in River water averaged 6.9 ± 0.8 ngg-1, while for tap water it ranged from 13.1 ngg-1 to 5.2 μgg-1. River water was fractionated by -1.09 ± 0.70 ‰ amu-1, while restrained tap water yielded the maximum fractionation of -6.39 ± 0.62 ‰ amu-1 relative to the laboratory standard. The Zn fractionation of tap water is much larger than all other natural samples, although the uncertainty is also significantly greater due to the use of the less precise Daly detector used for these preliminary experimental measurements. The fractionation of Zn in seven ultra pure Zn standard materials was measured relative to the laboratory standard and found to range from -5.11 ± 0.36 ‰ amu-1 for AE 10760 to +0.12 ± 0.16 ‰ amu-1 for Zn IRMM 10440. There appears to be some evidence for a relationship between Zn fractionation and its purity. As well as natural materials, the fractionation of Zn was measured in a number of processed materials. None of these results or those obtained for natural materials impact on the currently IUPAC accepted value for the atomic weight of Zn. Along with fractionation determinations, the concentration of Zn was also measured by Isotope Dilution Mass Spectrometry in all of the samples. The concentration of Zn in five stony meteorites ranged from 26 ± 13 to 302 ± 14 μgg-1 for Plainview and Orgueil respectively. For ordinary Chondrites, the concentration of Zn in the three samples analysed ranged from 26 ± 13 to 64 ± 34 μgg-1 for Plainview and Brownfield 1937 respectively.
The concentration of Zn was measured in two metamorphic rocks standard materials; the maximum concentration was 101.5 ± 1.7 µgg-1 in SDC-1. The concentration of Zn present in plant samples studied in this research was 22.15 ± 0.42, 14.62 ± 0.27 µgg-1 for Rice IMEP-19 and Sargasso NIES-Number 9 respectively which is within the normal range of Zn concentrations. Except for meteorites, the final uncertainties consistently cover the ranges of individual concentration measurements and indicate the homogeneity of the samples, including samples from different bottles where available. The final fractional uncertainties obtained for SRMs were all less than 2.8 %, demonstrating the high level of precision possible using IDMS.

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31

Buchholt, Kristina. "Nanostructured materials for gas sensing applications." Doctoral thesis, Linköpings universitet, Tillämpad Fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-69641.

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In this Thesis I have investigated the use of nanostructured films as sensing and contact layers for field effect gas sensors in order to achieve high sensitivity, selectivity, and long term stability of the devices in corrosive environments at elevated temperatures. Electrochemically synthesized Pd and Au nanoparticles deposited as sensing layers on capacitive field effect devices were found to give a significant response to NOx with small, or no responses to H2, NH3, and C3H6. Pt nanoparticles incorporated in a TiC matrix are catalytically active, but the agglomeration and migration of the Pt particles towards the substrate surface reduces the activity of the sensing layer. Magnetron sputtered epitaxial films from the Ti-Si-C and the Ti-Ge-C systems were grown on 4H-SiC substrates in order to explore their potential as high temperature stable ohmic contact materials to SiC based field effect gas sensors. Ti3SiC2 thin films deposited on 4H-SiC substrates were found to yield ohmic contacts to n-type SiC after a high temperature rapid thermal anneal at 950 ºC. Investigations on the growth mode of Ti3SiC2 thin films with varying Si content on 4H-SiC substrates showed the growth to be lateral step-flow with the propagation of steps with a height as small as half a unit cell. The amount of Si present during deposition leads to differences in surface faceting of the films and Si-supersaturation conditions gives growth of Ti3SiC2 films with the presence of TiSi2 crystallites. Current-voltage measurements of the as-deposited Ti3GeC2 films indicate that this material is also a promising candidate for achieving long term stable contact layers to 4H-SiC for operation at elevated temperatures in corrosive environments. Further investigations into the Ti-Ge-C system showed that the previously unreported solid solutions of (Ti,V)2GeC, (Ti,V)3GeC2 and (Ti,V)4GeC3 can be synthesized, and it was found that the growth of these films is affected by the nature of the substrate.

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32

Darros, Andressa Bella. "Compósitos de matrizes poliméricas com mantas aleatórias de fibras vegetais de sisal e de coco." Universidade Federal de São Carlos, 2013. https://repositorio.ufscar.br/handle/ufscar/1175.

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Made available in DSpace on 2016-06-02T19:19:56Z (GMT). No. of bitstreams: 1 DARROS_Andressa_2013.pdf: 2489179 bytes, checksum: f31dd28ac3f9d3703a4ab312265e2f12 (MD5) Previous issue date: 2013-03-15
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The search for new materials in order to alleviate the environmental problems have encouraged the use of raw materials of natural origin to replace, at least partially, to synthetically produced. Vegetable fibers may be used for incorporation into composites of polymer matrices, being renewable, biodegradable and non-toxic. However, generally vegetable fibers exhibit lower mechanical and thermal properties due to the components present in the fiber (cellulose, hemicellulose and lignin) when compared with high performance fibers such as glass fibers and carbon. In general, polymeric matrices can be of three types; thermoset, thermoplastic and thermoplastic biodegradable. In this paper, polymeric matrices and composites of polymer matrices were obtained with the use of random webs of coconut fibers and sisal fibers by compression molding in a hydraulic press. This study involved a comparative study of composites molded polymer matrices with their epoxy resin, polypropylene (PP), and polyhydroxybutyrate (PHB) without fiber. Were performed some types of thermal and mechanical tests for all molded materials. The techniques used were differential scanning calorimetry (DSC), thermogravimetry (TG), dynamic mechanical thermal analysis (DMTA) in bending mode, and mechanical tests of flexural and tensile before and after conditioning in air chamber, with temperature and humidity. The results of flexural tests to room temperature for composites of epoxy resin and PHB values were similar in the resistance of materials when compared to the respective polymer matrix without fibers. The composite of PP / sisal fibers showed a higher resistance when compared to PP without fiber, related to good fiber-matrix interaction. Flexural and tensile tests of specimens after the conditioning chamber for acclimatization showed decreases in resistance of all materials, being more pronounced for composites due to high moisture absorption of natural fibers. The results of DMTA before conditioning showed an increase in E' of the composites of epoxy resin as compared to the epoxy resin without fibers, because the fibers restrict the movement of the molecular chains located at the interfacial region. Relative to PP, composite PP / sisal fibers had an E' greater. The PHB without fibers showed a modulus greater than the composites containing coconut fiber and sisal fibers. DMTA analyzes performed on materials post conditioning decreased in modules, due to weakening of the fiber-matrix interactions.
A busca por novos materiais visando amenizar os problemas ambientais têm incentivado a utilização de matérias-primas de origem natural em substituição, pelo menos parcial, às sinteticamente produzidas. As fibras vegetais podem ser utilizadas para incorporação em compósitos de matrizes poliméricas, por serem de fontes renováveis, biodegradáveis e não tóxicas. Entretanto, geralmente, as fibras vegetais apresentam propriedades mecânicas e térmicas inferiores devido aos componentes presentes na fibra (celulose, hemicelulose e lignina), quando comparadas às fibras de alto desempenho, como fibras de vidro e de carbono. Em geral, as matrizes poliméricas podem ser de três tipos; termorrígida, termoplástica e termoplástica biodegradável. Neste trabalho, matrizes poliméricas e compósitos de matrizes poliméricas foram obtidos com a utilização de mantas aleatórias de fibras de coco e de fibras de sisal através da moldagem por compressão em prensa hidráulica. Assim, este trabalho envolveu um estudo comparativo dos compósitos moldados com suas respectivas matrizes poliméricas (resina epóxi, polipropileno (PP), e polihidroxibutirato (PHB)). Foram realizados alguns tipos de análises térmicas e ensaios mecânicos para todos os materiais moldados. As técnicas utilizadas foram a calorimetria exploratória diferencial (DSC), termogravimetria (TG), análise térmica dinâmico-mecânica (DMTA) no modo de flexão, e ensaios mecânicos de flexão e de tração antes e pós-condicionamento em câmara de climatização, com temperatura e umidade. Os resultados dos ensaios mecânicos de flexão à temperatura ambiente dos compósitos de resina epóxi e do PHB obtiveram valores similares nas resistências dos materiais quando comparados às respectivas matrizes poliméricas, sem fibras vegetais. viii O compósito de PP/Fibras de sisal apresentou uma resistência mais elevada quando comparado ao PP sem fibras, relacionado a uma boa interação fibra-matriz. Os ensaios de flexão e de tração de corpos-de-prova após o condicionamento em câmara de climatização apresentaram decréscimos nas resistências de todos os materiais, sendo mais acentuados para os compósitos devido a elevada absorção de umidade das fibras vegetais. Os resultados de DMTA antes do condicionamento apresentaram aumento no E dos compósitos de resina epóxi em comparação com a resina epóxi sem fibras, devido às fibras limitarem a movimentação das cadeias moleculares localizadas na região interfacial. Em relação ao PP, o compósito PP/fibras de sisal apresentou um E mais elevado. O PHB sem fibras apresentou um módulo maior que os compósitos contendo mantas de fibras de coco e de fibras de sisal. As análises de DMTA realizadas nos materiais pós-condicionamento apresentaram decréscimos nos módulos, devido ao enfraquecimento das interações fibra-matriz.

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33

Squires, Timothy Richard. "Efficient numerical methods for ultrasound elastography." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:332c7b2b-10c3-4dff-b875-ac1ee2c5d4fb.

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In this thesis, two algorithms are introduced for use in ultrasound elastography. Ultrasound elastography is a technique developed in the last 20 years by which anomalous regions in soft tissue are located and diagnosed without the need for biopsy. Due to this, the relativity cheap cost of ultrasound imaging and the high level of accuracy in the methods, ultrasound elastography methods have shown great potential for the diagnosis of cancer in soft tissues. The algorithms introduced in this thesis represent an advance in this field. The first algorithm is a two-step iteration procedure consisting of two minimization problems - displacement estimation and elastic parameter calculation that allow for diagnosis of any anomalous regions within soft tissue. The algorithm represents an improvement on existing methods in several ways. A weighting factor is introduced for each different point in the tissue dependent on the confidence in the accuracy of the data at that point, an exponential substitution is made for the elasticity modulus, an adjoint method is used for efficient calculation of the gradient vector and a total variation regularization technique is used. Most importantly, an adaptive mesh refinement strategy is introduced that allows highly efficient calculation of the elasticity distribution of the tissue though using a number of degrees of freedom several orders lower than methods that use a uniform mesh refinement strategy. Results are presented that show the algorithm is robust even in the presence of significant noise and that it can locate a tumour of 4mm in diameter within a 5cm square region of tissue. Also, the algorithm is extended into 3 dimensions and results are presented that show that it can calculate a 3 dimensional elasticity distribution efficiently. This extension into 3-d is a significant advance in the field. The second algorithm is a one-step algorithm that seeks to combine the two problems of elasticity distribution and displacement calculation into one. As in the two-step algorithm, a weighting factor, exponential substitution for the elasticity parameter, adjoint method for calculation of the gradient vector, total variation regularization and adaptive mesh refinement strategy are incorporated. Results are presented that show that this original approach can locate tumours of varying sizes and shapes in the presence of varying levels of added artificial noise and that it can determine the presence of a tumour in images taken from breast tissue in vivo.

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Espert, Ana. "Natural fibres/polypropylene composites from residual and recycled materials." Licentiate thesis, KTH, Fibre and Polymer Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1667.

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Natural fibres fulfil all the requirements in order toreplace inorganic fillers in thermoplastic composites. Naturalfibres are inexpensive, renewable, biodegradable, present lowerdensity and their mechanical properties can be compared tothose of inorganic fillers. However, several disadvantagesappear when natural fibres are used for composites. First ofall, the poor compatibility between the hydrophilic fibres withthe hydrophobic thermoplastic matrix leads to a weak interface,which results in poor mechanical properties. On the other hand,the hydrophilic nature of the fibres makes them very sensitivetowards water absorption, which leads also to the loss ofproperties and the swelling and dimensional instability.

In order to enhance the compatibility fibre-matrix, thefibres were chemically surface modified by five differentmethods: a) graft copolymerisation withpolypropylene-graftedmaleic anhydride copolymer (PPgMA), b)modification by PPgMA during processing, c) modification byorganosilanes, d) acetylation, e) modification with peroxideoligomers. Modified fibres led to improved mechanicalproperties and thermal behaviour when used in composites withpost-industrial polypropylene (PP) containing ethylene vinylacetate copolymer (EVA). Modification with peroxide oligomersshowed very promising results, but modification with PPgMA waschosen for further preparation of composites due to itssimplicity.

Two sets of composites were prepared using two differentpolypropylene types as matrix: virgin polypropylene (PP) andthe above mentioned post-industrial polypropylene (PP/EVA).Four different types of cellulosic fibres were used as fillers:cellulose fibres from pulping, sisal fibres, coir fibres andLuffa sponge fibres. The mechanical properties of thecomposites were dependent mostly on the fibre loading andslightly on the type of fibre. The fibers changed thecharacteristics of the material leading a higher stiffness buta lower toughness.

Water absorption of composites was studied at threedifferent temperatures: 23°C, 50°C and 70°C. Thewater absorption kinetics were studied and it was found thatwater is absorbed in composites following the kineticsdescribed by the Fickian diffusion theory. After absorption, animportant loss of properties was observed, due to thedestruction of the fibre structure due to the waterabsorbed.

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Zhao, Wen. "The Control of Water Contaminants Assisted by Natural Materials." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/7114.

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Natural materials can be used to remove water contaminants by applying proper physical, chemical, and biological water treatment processes. This study involves using natural materials, as they are considered to be more environmentally benign and cost-effective than synthetic materials. This dissertation concentrates on monitoring five major water quality parameters—ammonia, fluoride, turbidity, pH, and fecal indicator bacteria (FIB) —in two major applications where clean water is needed. The focus is on meeting the water quality requirements for each contaminant. The overall objective of this study is to control the levels of ammonia in aquaculture wastewater, and adjust fluoride, turbidity, pH, and FIB in drinking water by using natural materials. To accomplish this objective, this dissertation study is divided into two parts. Part I is about ammonia removal in aquaculture wastewater. Zeolite was the representative natural material that was used in this study. The methodologies presented include ion exchange and chemical neutralization processes. Part II is about fluoride, turbidity, pH and fecal indicator bacteria control in drinking water. Pumice stone was used in this study. The methodologies utilized in this work include biofiltration and adsorption. In Part I, the methods of ion exchange and chemical neutralization as a function of ammonia removal efficiency, toxicity, and daily cost were compared. All these methods were found to remove ammonia by a simple drop-off system. Chabazite, a natural zeolite, was the ion exchanger source. Similarly, we compared the effectiveness of commercialized neutralizers versus a novel neutralizer prepared for this work. The ion exchanger (chabazite) had the highest ammonia removal in freshwater, but no significant ammonia removal in seawater was observed after in-vivo trials. However, for commercial water neutralizers, the in-vivo trials showed that they are not able to control ammonia levels in either freshwater or seawater. The novel neutralizer was found to have higher ammonia removal efficiencies in both freshwater and seawater. In terms of toxicity, the AmmoSorb can be considered non-toxic. To safely use the novel neutralizer, it is recommended to control its daily dose at 1 g/L/day followed by a two-thirds volume of water change every day. A comprehensive cost analysis also showed that the novel neutralizer was the least expensive ammonia remover. In Part II, drinking water was treated by a bench-scale biosand filter system that included different filtration technologies, biological disinfection, and adsorption. The filtration technologies analyzed in this work include Aluminum Oxide Coated Pumice (AOCP) and sand. The AOCP also works as adsorption media to remove fluoride in water. As results, the AOCP imbedded biosand filter (BSF) can efficiently control fluoride, turbidity, and pH level to meet the WHO standards. In addition, the exhausted BSF can be regenerated by recoating the pumice with additional layers of aluminum oxide. The fluoride, turbidity, pH, as well as fecal indicator bacteria levels controlled by the regenerated BSF also meet the WHO standard for about one-month operation. The overall contribution of this research is providing new methods to treat water at an affordable cost and an easy operational procedure with potential health benefits to the specific applications that require ammonia, fluoride, turbidity, pH, and E. coli levels to be controlled.

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Mahony, Oliver. "Silica-Natural Polymer Hybrid Materials for Human Tissue Regeneration." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526370.

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37

Lees, Joan Anne. "Modelling the magnetic properties of natural and environmental materials." Thesis, Coventry University, 1994. http://curve.coventry.ac.uk/open/items/aa273a60-0c0d-a613-81b9-b95cc2ec3fdd/1.

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Magnetic properties have been used to characterize natural and environmental materials. An evaluation of magnetic properties, for the modelling of sources of materials and minerals, has been completed. A methodological framework has been developed for the application of magnetic techniques to studies involving the quantification of sources of materials and minerals in any environment. the framework includes the idntification of sources using magnetic reconnaissance and multi-variate statistical classification techniques. magnetic measurements used are susceptibility (both field and laboratory), remanence and magnetization measurements. the linear additivity of magnetic measurements, and classification and linear modelling techniques, ahve been tested using datea for artificial laboratory mixtures and hypothetical mixing experimentrs. The limitations of using magnetic properties with these statistical and mathematical techniques are defined. the famework allows for hte testing of suitabililty of manetic modelling techniques in any sourceing study.

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38

Ferreira, Pinto Da Silva Carla Florbela. "Interactions between volatile organic compounds and natural building materials." Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760948.

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There is increasing concern regarding the indoor air quality of energy efficient buildings. Indoor air pollutants, such as volatile organic compounds (VOCs) and particulates, commonly found in buildings, can be harmful to human health. Interior materials are known to be one of the main contributors to poor indoor air quality. There is a need to develop natural materials and systems in order to minimise the level of indoor air pollutants, or even reduce them to near zero through the use of VOC-free emitters and exploitation of the sink effect for airborne pollutants. Natural building materials are considered to possess low embodied energy and are environmentally-friendly. The aim of this research was to investigate the physical and chemical interactions between natural building materials and VOCs in new or refurbished buildings (e.g. dwellings, offices, hospitals, schools and retail outlets). Key to this was the identification of low VOC emission materials with the added benefit of passively improving the indoor air quality. Comprehensive chemical and physical characterisation of materials was undertaken in order to understand the mechanisms involved in the capture of VOCs by three classes of natural building materials: insulation, coatings and wood panels. In order to understand the interactions between VOCs and building materials, adsorption and desorption experiments were carried out in laboratory-scale environmental chambers and in a real size room with a volume of 30 m3, all with controlled temperature, relative humidity and air flow-rate. Four organic pollutants commonly found in indoor environments were selected for this study according to their physico-chemical properties: formaldehyde, toluene, limonene and dodecane. In the first stage of this research, TVOC and formaldehyde emissions from 18 commercially available natural building materials were analysed (six insulation materials, six coatings and six wood-based panels). These materials included natural wool, hemp fibres, wood fibres, gypsum, lime mortars, clay-based plasters and wood-based plasters. Four of these materials were selected to investigate their adsorption and desorption behaviour towards the selected organic pollutants. It was observed that, in general, all natural building materials showed very low, or even zero, VOC emissions. In the case of formaldehyde, this organic pollutant was found to be emitted by the wood-based panels due to the formaldehyde-based resins used to glue the wood fibres. In the case of coated wood panels, the resin impregnated paper coating was shown to act as a barrier to formaldehyde emission and as a result this showed lower emission levels compared to an equivalent uncoated material. With regard to the adsorption and desorption behaviour it was observed that highly porous materials such as lime mortar and MDF panels have good capacity to remove VOCs and formaldehyde from the indoor air due to their high surface area. They allow the diffusion of the organic pollutants through their bigger pores. Natural wool, classed as an insulation material, showed good affinity to adsorb formaldehyde due to chemisorption by the proteins present in the fibres. The later stages of this research involved the investigation of the adsorption/desorption behaviour of newly developed natural building materials incorporating bio-based additives with optimised capacity to remove VOCs from the air. The incorporations were as follows: walnut shell within MDF panels; hemp sheaves, pumice and brick powder within clay-based plasters; and cellulose flakes, natural wool and photocatalytic TiO2 particles within lime mortar. The combination of two materials was also used because of the affinity of each material with different VOCs, for example the incorporation of natural wool in a lime mortar formulation. The outcomes of this research demonstrate that, if careful consideration is given to materials selection when constructing a new building or during a refurbishment process, the old judgment “building materials are the main contributors to a poor indoor air quality” is not true. This is achieved by selecting materials with low- or zero-VOC emissions and with the capacity to remove organic pollutants from the indoor air. Therefore, these materials contribute to a better indoor air quality by releasing low or negligible emissions and by facilitating the removal of airborne pollutants.

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39

Karlsson, Oskar. "Ferulic Acid – A Valuable Natural Compound for Sustainable Materials." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290233.

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One of the largest problems that stands before us is the quest to find sustainable alternatives to fossil-based materials. Fossil-based products can be found all around us in our society. This quest has forced us to look for new ways to build materials. Synthetic polymer materials have traditionally been produced from fossil-based starting materials however, in modern times studies regarding biobased superseders for the unsustainable starting materials has been conducted. One of these new potential building blocks is ferulic acid (FA) that is an aromatic cinnamic acid. FA has previously been used as an antioxidant but since it in addition is aromatic, have more than two functional groups and contains a double bond between two carbons it holds a large potential for polymeric synthesis. FA has been isolated from agricultural side streams such as sugar beet pulp, flax shives, wheat- and corn bran through enzymatic release and pressurised low-polarity water extraction (PLPW). One of the largest areas of use regarding FA is the biological applications. It has been proven to be effective protection against UV-radiation which open up possible uses in the textile industry, cosmetics and skincare. FA has also shown biomedical properties such as antiallergic, anti-inflammatory, anti-diabetic, anticarcinogenic and antiviral properties among others. Two of the most common polymerization methods are free radical- and step-wise polymerization. FA shows great promise for the possibility to polymerize through both these methods since it has a double bond and more than two functional groups. Polymer materials produced from FA has been done with step-wise polymerization. The polymers showed thermostable and possibly biodegradable properties. Free-radical polymerization requires a monomer with a sterically unhindered double bond and for that reason the FA must be modified in order to polymerize using free radicals. This modified monomer has been produced in a small laboratory scale and can in theory be polymerized through radical polymerization.
Ett av de största problemen som vi står inför i modern tid är hur vi ska ersätta material som är producerade från fossila bränslen. Dessa material finns överallt i vårt moderna samhälle och spelar en betydelserik roll i vår infrastruktur. Detta har tvingat oss att undersöka andra miljövänligare källor för att se om dessa kan ersätta de fossila. Polymera material är ett exempel på material som tidigare har haft en fossil bas. På grund av detta har dessa material och hur dem kan producerats undersökt för att se om det finns en alternativ biobaserad källa. Ferulsyra är en aromatisk kanelsyra som är mest känd för att ha antioxidatiova egenskaper. Utöver detta innehåller ferulsyra en dubbelbindning mellan två kol och dessutom fler än två funktionella grupper vilket indikerar att den kan vara en möjlig monomer för polymersyntes. Ferulsyra kan produceras från sidoströmmar från jordbruksindustrin så som till exemper sockerbetsmassa, linhår och vete, både genom enzymatiska reaktioner eller med hjälp av extraktion med ett lösningsmedel. En av de största användningsområdena gällande ferulsyra är inom biologiska applikationer. Den kan bland annat användas som solskydd, både inom hudvårdsindustrin och som ytbeläggning i textilier. Ferulsyra har också uppvisat medicinska egenskaper som visar på att det kan användas mot allergier, inflammationer, diabetes, canser och virussjukdomar. De två vanligaste metoderna för polymersyntes är fri radikalpolymerisation och stegvis polymerisation. Ferulsyra uppvisar stor potential för att kunna användas som monomer i båda metoderna då den innehåller en dubbelbindning mellan två kol och fler än två funktionella grupper. Syntes av ferulsyra genom stegvis polymerisation har genomförts. Resultatet var att de producerade materialen uppvisade termostabila och biologiskt nedbrytbara egenskaper. För att fri radikalpolymerisation ska vara möjligt med ferulsyra som monomer krävs det att dubbelbindningen inte är steriskt hindrad. Detta innebär att ferulsyra först måste modifieras innan polymerisationen är möjlig. Dessa modifieringar har genomförts på labbskala och den producerade monomeren är teoretiskt sätt möjlig att polymerisera genom fri radikalpolymerisation.

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40

Hasbach, Ximena. "Natural carbonaceous materials for use in transparent Joule heaters." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122181.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (page 35).
Natural carbonaceous materials have the potential to be used in a new class of more economically and environmentally sound electronic devices due to their tunable conductivity as well as robust mechanical and thermal properties. This study aims to explore the potential of steam cracker tar (SCT), a byproduct of ethylene production, for use in conductive applications, specifically transparent Joule heaters. The SCT was made into thin films using both rod-rolling and spray-coating methods. After the superior uniformity of the rod-rolled films was observed, a 2 laser cutter was used to anneal the rod-rolled films with the intention of increasing their sp² content and thus improving their conductivity. First the power and then the z-defocusing of the laser were varied, and the ability of the resulting films to heat was tested with an applied voltage. To test the conductivity and heating capabilities of the annealed SCT films, 60 volts were applied, the current measured, and the number of degrees heated measured with a thermal camera software. A combination of Raman spectroscopy and profilometry was used to characterize the films. The film with the best heating capabilities was found to be the one annealed with 8% laser power and 0.2 inch z-defocus. This film was observed to heat to 35 degrees Celsius, and was demonstrated to efficiently de-ice a frozen sheet of tempered glass. Future work in this study will focus on finding ways to improve conductivity in SCT films with better transparency.
by Ximena Hasbach.
S.B.
S.B. Massachusetts Institute of Technology, Department of Materials Science and Engineering

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41

Zolfaghari, Mohammad Esmail. "The morphological, flow and failure characteristics of fractionated natural bulk material : evaluation of flowability of fractionated powdered liquorice using a specially designed flowmeter : the particle morphology was assessed by computer image analysis and the failure properties by shear cell testing." Thesis, University of Bradford, 1986. http://hdl.handle.net/10454/4353.

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With the technological development in biologically orientated industries more and more natural products in powdered form are being handled and processed. Three differently comminuted liquorice rhizome products were classified into 23 narrow size fractions to investigate the particle and bulk characteristics of the material, and to study the influence of particle shape on powder flowability. The morphology of the fibrous particulate was investigated by using a Quantimet 720 Image Analyser. The perimeter (P), projected area (A), breadth (B), length (L), horizontal and vertical projected lengths (P V and Pi) and the horizontal and vertical Feret diameters (FV FH) were measured from which four dimensionless shape factors were evaluated, [P2/47rA, PHxPV/A, L/B, FV/FH]. The surface texture of the particles was measured by fractal analysis. The influence of particle shape and size on the mean flow rate, coefficient of flow variation and flow uniformity were measured using a specially designed inclined tube flowmeter. The failure properties of powdered liquorice when sheared under known normal compressive stresses were measured and from a series of yield loci the unconfined yield strength, major consolidation stress and effective angle of internal friction were obtained. The effects of particle shape and size on the angle of internal friction, wall friction, bulk and packed densities were. investigated and the experimental correlations expressed in terms of mathematical equations. These relationships, together with the failure function plots, indicate that comminuted liquorice powder behaves as a "simple" powder.

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42

Garkhail, Sanjeev Kumar. "Composites based on natural fibres and thermoplastic matrices." Thesis, Queen Mary, University of London, 2002. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1700.

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This thesis examines the possibility of reinforcing thermoplastic matrices, notably polypropylene (PP) and polyhydroxyalkanoates (PHAs), by (a vegetable fibre) flax. An effort is made to enhance/optimise the mechanical properties of flax, PP composites through a micromechanical and macromechanical study. The fibrc'matrix interface is modified via chemical modifications as well as modifications in processing parameters (transcrystallinity). Effects of parameters like fibre length, fibre volume fraction and fibre-matrix interface modification on the mechanical properties of long flax fibre reinforced PP composites (compression moulded) as well as short flax fibre based composites (injection moulded) are studied. In order to get a better insight in the importance of these different parameters for the optimisation of composite performance, the experimental results are compared with model predictions using micromechanical models for random short-fibre-reinforced composites. For the injection moulded composites, different compounding routes are used and compared. The moisture resistance (pick-up and diffusivity) as well as dimensional stability (swelling) of natural fibre mat reinforced thermoplastics (NMTs), based on different kinds of flax fibres and PPs, are studied. The effects of a novel fibre upgrading method for flax fibres (DuralinTM) on the moisture pick-up and residual tensile properties of NMT composites are explored. Biodegradable composites based on flax fibre and PHAs are analysed. It is observed that addition of (cheap) flax fibre to polyhydroxybutyrate (PHB) could be advantageous as far as cost-performance of biopolymer composites is concerned. especially for stiffness critical applications. Mechanical properties of `biocomposites' manufactured through different routes (i. e. injection moulding and compression moulding) are compared. Addition of cheap flax fibres to an expensive and brittle PI IA composite leads to enhanced toughness of the composites. Abstract A life cycle assessment (LCA) study on glass-fibre-mat-reinforced-thermoplastic (GMT) and NMT manufactured by a current production method for thermoplastic prepregs followed by compression moulding into an automotive and non-automotive part is carried out.

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43

Montoya, Armisén Pedro. "Characterization of 2D materials." Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-416436.

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Cochrane, Emma Louise. "Natural biosorbent materials for the remediation of copper contaminated wastewaters." Thesis, University of Aberdeen, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540478.

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In this study, three biosorbents, crab carapace, the macroalgae Fucus vesiculosus and peat were compared with an activated-carbon and an ion-exchange resin for the removal of Cu²⁺ from synthetic solutions and distillery wastewater. Sorption of Cu²⁺ was evaluated and best represented by the pseudo-second order rate model for all materials. Langmuir and Freudlich isotherms were used to describe the sorption equilibrium data with maximum uptake values of 79.4, 114.9 and 71.4 mg g^-1 obtained for crab carapace, Fucus vesiculosus and ion-exchange resin respectively. The removal efficiencies of crab carapace and Fucus vesiculosus were >95 % i.e. comparable with those achieved using ion-exchange resin. Metal uptake was found to proceed via a number of mechanisms including absorption on the material surface, ion-exchange and micro-precipitation. It was observed by GG-ATR FTIR that a number of different functional groups present in the materials were also involved in metal uptake and removal. Plant trials set up to provide a preliminary investigation into the application of Cu²⁺ enriched crab carapace to a Cu²⁺ deficient soil showed that although the addition of crab carapace enriched with Cu²⁺ does not immediately help deficiency problems, it is possible that there is scope for such an application as a route for disposal. Crab carapace is an effective and efficient biosorbent for the removal of Cu²⁺ from aqueous solutions and may be considered a viable alternative to activated-carbon and ion-exchange resin. As a waste material from the fishing industry it also presents the most economically and environmentally sound material for biosorption.

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45

Zhao, Shengjie. "Natural frequency based damage identification of beams using piezoelectric materials." ASME 2015 International Mechanical Engineering Congress and Exposition, 2015. http://hdl.handle.net/1993/31652.

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Following the studies of natural frequency based damage detection methods, an advanced technique for damage detection and localization in beam-type structures using a vibration characteristic tuning procedure is developed by an optimal design of piezoelectric materials. Piezoelectric sensors and actuators are mounted on the surface of the host beam to generate excitations for the tuning via a feedback process. The excitations induced by the piezoelectric effect are used to magnify the effect of the damage on the change of the natural frequencies of the damaged structure to realize the high detection sensitivity. Based on the vibration characteristic tuning procedure, a scan-tuning methodology for damage detection and localization is proposed. From analytical simulations, both crack and delamination damage in the beams are detected and located with over 20% change in the natural frequencies. Finite element method (FEM) simulations are conducted to verify the effectiveness of the proposed methodology.
October 2016

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Escalera, Edwin. "Characterization of some natural and synthetic materials with silicate structures." Licentiate thesis, Luleå tekniska universitet, Materialvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25679.

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The present thesis deals with characterization of silicate structures with a determined morphology and structure such as ordered mesoporous silica and layered silicates. Mesoporous silica groups are amorphous solids exhibiting highly ordered pore structures with narrow pore size distributions and large surface areas. Porous materials are used in various applications such as in adsorption, separation, removal of pollution treatments, molds for templating, etc.Another interesting group of layered materials are crystal silicates with minerals of natural origin. The silicates have a structure that consists of staked layers in which planes of oxygen atoms coordinate to cations such as Si4+, Al3+, Mg2+, Fe3+ to form two dimensional sheets. The coordination of cations in adjacent sheets typically alternates between tetrahedral and octahedral. The properties and uses of the clays vary widely due to the differences in their structure and composition. Some important applications are paints, adsorption, intercalation, removal of pollutants from water and in ceramic industry.The thesis consists of two parts. In the first study characterization of synthesized and functionalized ordered mesoporous silica were performed. Mesoporous silica with a large surface area on which organic functional groups are grafted was used to synthesize cobalt nanoparticles. Investigation by SEM and TEM showed hexagonal particles, with a pore size about 10 nm. The functionalization of the silica was studied by FTIR and TG/DTA techniques and the obtained nanoparticles were characterized by XRD, TEM and EDX analysis. In the second study, an extended literature review on properties of clays is presented. Samples from three different clay deposits, Ivirgarzama (IC), Entre Rios (EC) and Uspha-Uspha (U) from Bolivia were characterized by different experimental techniques in order to assess their relevant features. The chemical and mineralogical analysis showed that the clays consist mainly of kaolinite and illite along with quartz in different amounts. Also, certain amounts of feldspar, iron and magnesium are present in the clays and with predominance in the EC clay. Thermal analysis (DSC/TG and dilatometer) and XRD were used to study the phase transformations and their microstructural evolution at sintering. The EC clay with a high alkali and iron content influenced both the onset of liquid formation and the onset of sintering. Mullite is a crystalline phase that strengthens the ceramics and it was formed in all the studied clays. Based on these results, the EC and U clays provide required characteristics that enable them for use in the fabrication of products with red tonality, especially bricks, roofing tiles and rustic floor tiles. The IC clay with relatively low iron content and with relatively good refractoriness can be used for production of firebricks and also for partially replacing kaolin and silica in white firing ceramics. Thus, the clays from Ivirgarzama, Entre Rios and Uspha-Uspha are promising raw materials and they should be considered as valuable resources for the production of building ceramics.
Godkänd; 2013; 20130118 (edwesc); Tillkännagivande licentiatseminarium 2013-01-30 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Edwin Escalera Mejia Ämne: Konstruktionsmaterial/Engineering Materials Uppsats: Characterization of Some Natural and Synthetic Materials With Silicate Structures Examinator: Docent Marta-Lena Antti, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Dr Farid Akhtar, Dept of Materials and Environmental Chemistry, Stockholm University Tid: Onsdag den 20 februari 2013 kl 10.15 Plats: E246, Luleå tekniska universitet

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47

Guidetti, Giulia. "Cellulose photonics : designing functionality and optical appearance of natural materials." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277918.

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Cellulose is the most abundant biopolymer on Earth as it is found in every plant cell wall; therefore, it represents one of the most promising natural resources for the fabrication of sustainable materials. In plants, cellulose is mainly used for structural integrity, however, some species organise cellulose in helicoidal nano-architectures generating strong iridescent colours. Recent research has shown that cellulose nanocrystals, CNCs, isolated from natural fibres, can spontaneously self-assemble into architectures that resemble the one producing colouration in plants. Therefore, CNCs are an ideal candidate for the development of new photonic materials that can find use to substitute conventional pigments, which are often harmful to humans and to the environment. However, various obstacles still prevent a widespread use of cellulose-based photonic structures. For instance, while the CNC films can display a wide range of colours, a precise control of the optical appearance is still difficult to achieve. The intrinsic low thermal stability and brittleness of cellulose-based films strongly limit their use as photonic pigments at the industrial scale. Moreover, it is challenging to integrate them into composites to obtain further functionality while preserving their optical response. In this thesis, I present a series of research contributions that make progress towards addressing these challenges. First, I use an external magnetic field to tune the CNC films scattering response. Then, I demonstrate how it is possible to tailor the optical appearance and the mechanical properties of the films as well as to enhance their functionality, by combining CNCs with other polymers. Finally, I study the thermal properties of CNC films to improve the retention of the helicoidal arrangement at high temperatures and to explore the potential use of this material in industrial fabrication processes, such as hot-melt extrusion.

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Barrera, Martinez Cindy Sofia. "Novel Renewable Materials from Natural Rubber and Agro-Industrial Residues." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480540955796333.

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O'Neill-Williams, Barrie. "The use of natural site derived materials as concrete aggregate." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/12178.

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Includes abstract.
Includes bibliographical references.
This thesis focuses on the use of site-derived fine material, in its natural form, as aggregate in concrete construction. It is proposed that the utilisation of this type of concrete aggregate will lead to; the preservation of natural materials that would otherwise have to be beneficiated off site, the reduction of waste material produced on a construction site, and an overall energy saving.

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Connell, Louise Stephanie. "Natural and synthetic polymer-based hybrid materials for tissue regeneration." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24820.

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The world's population is aging and cases of debilitating degenerative diseases are increasing. Bone is the second most transplanted tissue after blood but natural bone grafts are in short supply. Bioglass, which is a particular composition of bioactive glass, stimulates more bone repair than other synthetic bone grafts. However, it is brittle so cannot be used in cyclically loaded sites. A promising solution is the use of hybrid materials that can potentially combine the toughness of polymers with the stiffness and bioactivity of the glass through interpenetrating inorganic-organic networks. Hybrids have the unique feature of tuneable mechanical properties and degradation rates. In this thesis, two very different polymers were investigated as the organic component of hybrids; chitosan and poly(2-hydroxyethyl methacrylate-co-(3-trimethoxysilane)propyl methacrylate). The natural polymer chitosan was incorporated into the silica sol-gel process to produce hybrids and scaffolds were fabricated using freeze drying and foaming techniques. The chemical, morphological, mechanical and degradation properties of the scaffolds were studied. In order to covalently bond the organic and inorganic components, the chitosan was functionalised with an alkoxysilane crosslinker, 3-glycidoxypropyl trimethoxysilane. Using NMR and FTIR, the functionalisation reaction and side-reactions were characterised, discovering that the reaction was only 20% efficient at all pH values. To avoid the inefficient functionalisation reactions and concerns over the reproducibility of natural polymers, the synthetic co-polymer poly(2-hydroxyethyl methacrylate-co-(3-trimethoxysilane)propyl methacrylate) was synthesised by controlled polymerisation techniques (ATRP and ARGET ATRP) and typical free radical polymerisation (FRP). ATRP gave good control over molecular weight distributions, but the copper catalyst had serious implications on the chemical and architectural structure of the polymers. An NMR kinetics study was used to identify alternative polymerisation routes that could avoid the problems associated with the copper catalyst. The polymers were introduced into the sol-gel process to produce entirely synthetic hybrids with non-brittle (tough) behaviour and dissolution rates controlled by the polymer composition. The hybrids also exhibited hydroxyapatite precipitation in simulated body fluid, indicative of potential bioactivity in vivo. Hence, the aim of producing non-brittle, bioactive materials with controllable degradation rates was achieved.

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Dissertations / Theses on the topic 'Analysis of natural materials'

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