Tesi: "Natural and technogenic materials"

1

Hostyn, Guillaume. "Contribution des fractions granulométriques grossières au fonctionnement des sols très anthropisés". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0088.

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Les approches de requalification de sites dégradés répondent de plus en plus à un double enjeu de dépollution et de valorisation. Les sols de ces sites, dits « sols très anthropisés », sont très souvent caractérisés par un fonctionnement dégradé lié aux processus anthropo-génétiques à l'œuvre dans ces contextes. Ces processus sont à l'origine de la présence dans ces sols de matériaux exogènes technogéniques ou naturels en quantités et natures variées. Dans ce contexte, les études et réflexions sur leur gestion s'effectuent classiquement sur la fraction fine, obtenue après tamisage à 2 mm, et laisse de côté la fraction dite « grossière », souvent surreprésentée (jusqu'à 50-60 % en masse). Or cette fraction, souvent considérée comme inerte, ne l'est pas nécessairement et sa présence peut éventuellement orienter le fonctionnement des écosystèmes et leur gestion future. Une approche méthodologique a alors été développée grâce à laquelle les dimensions et la nature des objets à étudier ont été précisément définis à travers l'utilisation d'une échelle granulométrique adaptée et la construction d'une typologie. Le couplage de cette approche à des caractérisations physico-chimiques a démontré la capacité de discrimination de la stratégie de tri mise en œuvre. La typologie a ainsi pu être amendées avec les informations liées aux composés caractéristiques des catégories de matériaux identifiées. Sur cette base, cinq matériaux modèles (anthracite, brique, calcaire, coke de pétrole et laitier de haut fourneau) ont été sélectionnés afin d'aider à la généralisation des résultats. Un processus d'adaptation des méthodes standardisées d'analyses de sol a alors été développé afin d'évaluer la réactivité des fractions granulométriques grossières. Ces dernières ne sont pas inertes et leur réactivité, bien qu'elle soit réduite par rapport à la fraction fine d'un point de vue massique, est uniquement dépendante du type de matériau et de la surface des particules. Pris seuls, les matériaux modèles sélectionnés présentent un niveau de fertilité insuffisant pour le développement du végétal et ne sont que marginalement à l'origine d'une toxicité. Ces résultats indiquent, qu'au sein du sol, les fractions grossières constituent un stock pérenne d'éléments mobilisables dans le temps à travers le processus d'altération mis en jeu par la pédogenèse. Ceci a été confirmé avec des essais de culture de végétaux sur des substrats à la formulation originale associant fractions grossières, fractions fines et matériaux inertes en conditions contrôlées en laboratoire et en lysimètres à l'échelle pilote de terrain. La contribution directe des fractions grossières à l'alimentation de la solution du sol en éléments puis à la nutrition minérale des végétaux est mise en évidence à court et à moyen termes. Ces fractions jouent également un rôle majeur dans le fonctionnement hydrique du sol en contribuant significativement à la rétention, au stockage de l'eau et à la libération d'éléments. Le type de matériau apparaît être le facteur principal gouvernant l'intensité de ces effets. Ces travaux de thèse ont ainsi permis de replacer les fractions granulométriques grossières dans un rôle actif dans le fonctionnement et l'évolution des sols très anthropisés. Les résultats obtenus apportent des connaissances nouvelles pour le génie pédologique et les acteurs de la gestion des sols très anthropisés. A cet effet, une procédure systématique de diagnostic des fractions granulométriques grossières a été proposée dont les effets doivent servir deux objectifs, i) enrichir les connaissances liées aux constituants des fractions grossières et ii) permettre une prise de décision éclairée, basée sur une connaissance plus complète du contenu d'un sol très anthropisé, autorisant une meilleure gestion en fonction du type de renaturation visée
The approaches of requalification of degraded sites increasingly answer the double challenge of depollution and valorization. The soils of these sites, known as "highly anthropized soils", are often characterized by a disturbed functioning due to anthropogenetic impacts. In particular, anthropic actives are responsible for the presence in these soils of exogenous materials, from both technogenic or natural origins, in varying quantities and natures. In this context, all the diagnoses and considerations regarding their management are carried out on the fine fraction, obtained after sieving at 2 mm, and ignore the so-called "coarse" fraction, which is often overrepresented (up to 50-60% by mass). This fraction, considered as inert, may not necessarily be so and its presence may have important consequences on the functioning of ecosystems and their future management.A dedicated methodological approach was developed. First, the dimensions and nature of the objects to be studied were precisely defined using an appropriate granulometric scale and the construction of a typology. This approach coupled to physico-chemical characterizations confirmed the efficiency of the tested screening strategy and fully enabled a precise and meaningful discrimination among coarse materials. The typology was thus implemented with composition characteristics of the material categories. On this basis, five reference materials (anthracite, brick, limestone, petroleum coke and blast furnace slag) were selected in order to allow for the generalization of the results. An adaptation process of standard soil analysis methods was then developed in order to assess the reactivity of coarse granulometric fractions. Results showed that coarse fractions are not inert. Their reactivity, although reduced compared to the fine fraction from a mass point of view, is only dependent on the type of material and the surface of the particles. Taken alone, the selected model materials present an insufficient level of fertility for plant development and are only marginally at the origin of toxicity. In an overall soil system, the coarse fraction constitutes a perennial stock of elements of interest that can be mobilized over time through the weathering processes generated by pedogenesis. The direct contribution of coarse fractions to plant nutrition was confirmed both under controlled conditions in the laboratory and in lysimeters at the pilot field scale. They also significantly contribute to water retention and storage. The type of material is the main factor governing the intensity of these effects.This thesis work has thus positioned the coarse granulometric fractions as being an active part of the functioning of highly anthropized soils. The results obtained provide new knowledge for stakeholders involved in soil engineering and highly anthropized soils management. To this end, a systematic procedure of diagnosis of coarse granulometric fractions has been proposed, the effects of which should serve two purposes, i) to enrich the knowledge related to the constituents of coarse fractions and ii) to allow an insightful decision-making process, based on a complete knowledge of the reality of a highly anthropized soil, authorizing an optimal and sensible management according to the targeted type of renaturation

2

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

3

Kozii, Ivan, e Іван Козій. "Using a highly efficient gas cleaning equipment for reduction technogenic impact on the environment". Thesis, National Aviation University, 2021. https://er.nau.edu.ua/handle/NAU/50966.

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1. Matus K.J., Nam K.-M., Selin N.E., Lamsal L.N., Reilly J.M. Health Damages from Air Pollution in China. Global Environmental Chang, 2012, vol. 22, no. 2, pp. 55-66. 2. Tronvil P. Developing standards: Global standards for air cleaning equipment. Filtration & Separation, 2008, vol. 45, no. 9, pp. 28-31. 3. Hession M. Incinerator and gas cleaning equipment overview. Health Estate J., 1997, vol.51, no. 8, pp. 6-7.
Growth in the scale of economic activity leads to increased human impacts and disturbance of equilibrium in the environment. Along with the depletion of natural resources increases environmental pollution, in particular water and air. This significantly undermines the natural resource potential of the state’s development, negatively affects the welfare and health of the population, and poses a threat to environmental safety. Consuming natural resources, industrial enterprises are sources of complex environmental contamination. Activities of industrial enterprises has a negative impact on the state of ecosystems surrounding areas. Deposition of contaminants from the waste gases results in contamination of the soil and migration of heavy metals in the groundwater and surface water. The problem is compounded by the fact that the exhaust gases contain different by dispersion of the solid particles. This poses the problem of the development of environmental protection measures for air protection from emissions of industrial enterprises. One way to reduce the amount of pollutants released into the air with the flue gases is the selection of highly efficient gas-cleaning equipment, which must take into account several factors: physical and chemical characteristics of the carrier gas, the characteristics of chemical and particulate contaminants.
Зростання масштабів економічної діяльності призводить до посилення людського впливу та порушення рівноваги в навколишньому середовищі. Разом з виснаженням природних ресурсів збільшується забруднення навколишнього середовища, зокрема води та повітря. Це суттєво підриває природно-ресурсний потенціал розвитку держави, негативно впливає на добробут та здоров’я населення та створює загрозу екологічній безпеці. Споживаючи природні ресурси, промислові підприємства є джерелами складного забруднення навколишнього середовища. Діяльність промислових підприємств негативно впливає на стан екосистем навколишніх територій. Відкладення забруднень із відпрацьованих газів призводить до забруднення ґрунту та міграції важких металів у підземні та поверхневі води. Проблема ускладнюється тим, що вихлопні гази містять різні за рахунок дисперсії твердих частинок. Це ставить проблему розробки природоохоронних заходів щодо захисту повітря від викидів промислових підприємств. Одним із способів зменшити кількість забруднюючих речовин, що викидаються в повітря з димовими газами, є підбір високоефективного газоочисного обладнання, яке повинно враховувати декілька факторів: фізичні та хімічні характеристики газу-носія, характеристики хімічних та твердих частинок забруднювачі.

4

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

6

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.

7

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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Flores, Ramírez Eleonora [Verfasser], Martin [Akademischer Betreuer] Kaupenjohann, Martin [Gutachter] Kaupenjohann, Grabach Christina [Gutachter] Siebe e Jean Louis [Gutachter] Morel. "Purpose-designed technogenic materials for sustainable urban greening / Eleonora Flores Ramírez ; Gutachter: Martin Kaupenjohann, Christina Siebe Grabach, Jean Louis Morel ; Betreuer: Martin Kaupenjohann". Berlin : Technische Universität Berlin, 2018. http://d-nb.info/1169210341/34.

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10

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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11

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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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.

13

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.

14

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 (sommario):

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.

15

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.

16

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.

17

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.

18

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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19

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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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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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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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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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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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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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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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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Yang, Hong-Seok. "Outdoor noise control by natural/sustainable materials in urban areas". Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4484/.

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This study explores the effects of natural and sustainable materials including vegetation, green roof systems and green walls on outdoor noise control in urban areas. The concept of this study starts with a hypothesis that well-planned use of the natural materials on building and urban surfaces can achieve useful reductions in noise levels and reverberation in urban spaces. Firstly, this study examines random-incidence absorption and scattering coefficients of vegetation through a series of measurements in a reverberation chamber in order to characterise the effects of various designable factors such as soil depths, soil water content and vegetation densities. This data is used later in acoustic computer simulations. To quantify the scattering effect of trees and to allow including it in numerical predictions, a series of measurements are carried out for individual trees in an open field. Green roof systems are placed on a low profiled structure to examine sound transmission through the vegetated low barrier. To suggest noise abatement schemes in relatively small urban spaces, the acoustic effects of landscape designs using vegetation in a courtyard are studied through a case study. As a preliminary study on the noise reduction effect of vegetation in relatively large urban spaces, field measurements are carried out at outdoor spaces in high-rise apartment complexes. Based on the measurement results, the noise reduction effect of vegetation in apartment complexes is also predicted. The overall results for each research topic can be summarised as follows: It is shown that low-growing vegetation can be an effective measure for absorbing/scattering sound energy, especially at high frequencies. Results of field measurements show that tree reverberation exerts an influence only on frequencies above 1 kHz. At 4 kHz, RT (reverberation time) can be as long as 0.28 sec. Measurements made near the same deciduous tree with and without leaves indicate that leaves increase reverberation at 4 kHz by 0.08 sec. The results on sound transmission over the low barrier with green roof systems suggest that SPL attenuation increases with the increasing green roof areas. The extra SPL (sound pressure level) attenuation caused by green roof systems could be up to 9.5 dB at certain frequencies. With well-planned application of landscape designs in a courtyard, speech levels and RT at 500 Hz are decreased by 9.3 dBA and 81 %, respectively. In outdoor spaces of apartment complexes, RT is generally rather long, over 4 sec at 500 Hz, influenced by many factors such as openness, source-receiver distance and building height. In terms of SPL distribution, the measured SPL is up to 8 dB higher compared to the semi-free field situation. It is also found that vegetation at the apartment complex can be effective in reducing RT by 0.95 sec (46 % decrease).

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Poompradub, Sirilux. "Structure and physical properties of natural rubber based composite materials". 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144559.

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Lotfi, Amirhossein. "Study on the Machinability of Natural Fiber Reinforced Composite Materials". Thesis, Griffith University, 2020. http://hdl.handle.net/10072/396146.

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Interest in natural fiber reinforced composites (NFRCs) is increasing rapidly thanks to their numerous advantages such as low cost, biodegradability, eco-friendly nature, relatively good mechanical properties, and a growing emphasis on the environmental and sustainability aspects of engineering materials. However, large scale use of NFRCs is still considered as challenging due to the difficulties in manufacturing, limited knowledge of its machinability and appropriate parameter settings, and being prone to machining-induced defects. These materials are known as hard-to-machine materials due to their heterogeneous structure, mechanical anisotropy and tendency to damage while exposed to mechanical stresses. High rejection rate of composite parts at the assembly stage because of poor quality hole due to several vital drilling induced damages such as matrix cracking, fiber pull-out, delamination, fiber and matrix separation and thermal degradation is a serious concern for manufacturing industries. Among all these defects, delamination was found to be the most vital life-limiting factor which affects the mechanical strength and structural integrity of the component significantly in terms of dimensional tolerances and load carrying capability. Therefore, the main objective of this research is investigating the influence of drilling process parameters on the machinability of flax/poly(lactic acid) bio-composites along with characterization, modelling, and condition monitoring of drilling operation through extensive experimental and analytical investigations. The effect of key drilling parameters and tool geometry such as cutting speed, feed rate, drill diameter, drill material and point angle at different levels were studied experimentally to analyse the relations between resultant quality of the produced holes, cutting forces and size of delamination. Damages and defects associated with the drilling process such as delamination, fiber breakage, fiber pull-out, and matrix cracking were studied through qualitative measurements, optical microscopy and scanning electron microscopy examination. Experimental results revealed that the choice of drill bit in terms of diameter, material and point angle has a considerable effect on the machinability and hole performance. Drilling with HSS drills resulted in nearly 60% lower thrust force and better hole quality compared to that with carbide drills. In addition, the analysis of variance (ANOVA) was applied to identify the significance of each individual cutting parameter. Analytical model was developed to predict the critical thrust force related to the onset of delamination propagation during drilling FF/PLA laminates. The delamination zone was modelled as an elliptical plate, with clamped edge and the analytical model developed based on theory of virtual work, LEFM methodology and theory of plate bending. An experimental investigation was carried out, in addition to the analytical model, through a punching test on different configurations of blind hole to characterize the critical thrust force at the onset of delamination. The developed model has been verified by experimental data and compared with the results of existing models and the presented model considering the effect chisel edge and cutting edges. Based on the results, the predicted values by the proposed model present better correlation with the experimental values than those predicted by other models. A relationship exists between cutting variables (thrust and cutting forces), tool wear and the final quality of the drilled hole. Accordingly, the quality of drilled holes can be improved by in-process monitoring in order to record the whole process status through measuring the thrust force and other indicators. An experimental investigation on online monitoring and non-destructive evaluation of drilling operation using vibration, acoustic emission and thrust force signals was conducted and the correlation between the cutting parameters, delamination, cutting thrust force and the pattern of the signals was detected. The response of material through acceleration, force and AE signals were analysed using different signal analysis tools and statistical parameters to derive the features of signals that can express the key characteristics of machining condition. It is observed that the AE rms values are affected by variation in the cutting parameters and it follows a similar trend as observed in the case of drilling thrust force by varying cutting conditions. The variation of vibration and acoustic emission signals were in correlation with delamination factor and damage severity. Four major damage mechanisms have been identified generally as the main sources of AE energy wave in drilling of FF/PLA composites namely fiber breakage, delamination, matrix cracking and friction. A process for detection and discrimination of various damage mechanisms can be correlated to the frequency of damages. Furthermore, among several statistical parameters applied on the effective segment of the time signals, Kurtosis was found the most competent statistical parameter for condition monitoring of the drilling process to to differentiate between poor and good quality of the drilled holes and enhance the quality of composite component. The findings from this research concluded that damage severity can be assessed through AE parameter analysis and it has a considerable potential for the application of in-process monitoring.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
Full Text

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Buraglio, Nadia. "Accelerator mass spectrometry of 129I and its applications in natural water systems". Doctoral thesis, Uppsala universitet, Institutionen för materialvetenskap, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1077.

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During recent decades, huge amount of radioactive waste has been dumped into the earth's surface environments. 129I (T1/2 = 15.6 My) is one of the radioactive products that has been produced through a variety of processes, including atomic weapon testing, reprocessing of nuclear fuel and nuclear accidents. This thesis describes development of the Accelerator Mass Spectrometry (AMS) ultra-sensitive atom counting technique at Uppsala Tandem Laboratory to measure 129I and discusses investigations of its distribution in the hydrosphere (marine and fresh water) and precipitation. The AMS technique provides a method for measuring long-lived radioactive isotopes in small samples, relative to other conventional techniques, and thus opens a new line of research. The optimization of the AMS system at Uppsala included testing a time of flight detector, evaluation of the most appropriate charge-state, reduction of molecular interference and imporvement of the detection limit. Furthermore, development of a chemical procedure for separation of iodine from natural water samples has been accomplished. The second part of the thesis reports investigations of 129I in natural waters and indicates that high concentrations of 129I (3-4 orders of magnitude higher than in the pre-nuclear era) are found in most of the considered natural waters. Inventory calculations and results of measurements suggest that the major sources of radioactive iodine are the two main European nuclear reprocessing facilities at Sellafield (U.K.) and La Hague (France). This information provides estimates of the transit time and vertical mixing of water masses in the central Arctic Ocean. Results from precipitation, lakes and runoff are used to elucidate mechanisms of transport of 129I from the point sources and its pathways in the hydrological environment. This study also shows the need for continuous monitoring of the 129I level in the hydrosphere and of its future variability.

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Dahlqvist, Martin. "Materials Design from First Principles : stability and magnetism of nanolaminates". Doctoral thesis, Linköpings universitet, Tunnfilmsfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-104764.

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In this thesis, first-principles calculations within density functional theory are presented, with a principal goal to investigate the phase stability of so called Mn+1AXn (MAX) phases. MAX phases are a group of nanolaminated materials comprised of a transition metal (M), a group 12-16 element (A), and carbon or nitrogen (X). They combine ceramic and metallic characteristics, and phase stability studies are motivated by a search for new phases with novel properties, such as magnetism, and for the results to be used as guidance in attempted materials synthesis in the lab. To investigate phase stability of a hypothetical material, a theoretical approach has been developed, where the essential part is to identify the set of most competing phases relative to the material of interest. This approach advance beyond more traditional evaluation of stability, where the energy of formation of the material is generally calculated relative to its single elements, or to a set of ad hoc chosen competing phases. For phase stability predictions to be reliable, validation of previous experimental work is a requirement prior to investigations of new, still hypothetical, materials. It is found that the predictions from the developed theoretical approach are consistent with experimental observations for a large set of MAX phases. The predictive power is thereafter demonstrated for the new phases Nb2GeC and Mn2GaC, which subsequently have been synthesized as thin films. It should be noted that Mn is used for the first time as sole M-element in a MAX phase. Hence, the theory is successfully used to find new candidates, and to guide experimentalists in their work on novel promising materials. Phase stability is also evaluated for MAX phase alloys. Incorporation of oxygen in different M2AlC phases are studied, and the results show that oxygen prefer different sites depending on M-element, through the number of available non-bonding M d-electrons. The theory also predicts that oxygen substituting for carbon in Ti2AlC stabilizes the material, which explains the experimentally observed 12.5 at% oxygen (x = 0.5) in Ti2Al(C1-xOx). Magnetism is a recently attained property of MAX phase materials, and a direct result of this Thesis work. We have demonstrated the importance of choice of magnetic spin configuration and electron correlations approximations for theoretical evaluation of the magnetic ground state of Cr2AC (A = Al, Ga, Ge). Furthermore, alloying Cr2AlC with Mn to obtain the first magnetic MAX phase have been theoretically predicted and experimentally verified. Using Mn2GaC as model system, Heisenberg Monte Carlo simulations have been used to explore also noncollinear magnetism, suggesting a large set of possible spin configurations (spin waves and spin spirals) to be further investigated in future theoretical and experimental work.

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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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Boglaienko, Daria. "Capture and Densification of Floating Hydrophobic Liquids by Natural Granular Materials". FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3261.

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Densification and submergence of floating crude oil is proposed as a novel oil spills treatment method. Surface application of dry granular materials (e.g., quartz sand, limestone) on top of a floating oil layer increases the density of the floating oil phase/granule mixture and leads to formation of relatively large and stable aggregates with significant amounts of captured oil. The aggregates separate from the floating hydrophobic phase and settle by gravity. Implementation of this method will reduce the impact radius of a spill and its mobility, preventing direct contamination of beaches, coastal flora and fauna. The major objective of this research was to examine interactions of particles with hydrophobic liquid-water interface from different perspectives. The important characteristics of the process, such as oil removal efficiencies, optimal particle-to-oil ratios and particle size ranges, were experimentally defined. A series of experiments was conducted to investigate aggregation and dissolution rate constants of the submerged hydrophobic liquids in salt water and deionized water, and to study the impact of the surface porosity of the granular particles on oil capture efficiencies. In addition to crude oil (South Louisiana crude, MC 252), aggregation volumes of quartz sand with other hydrophobic liquids (alkanes and aromatics) were analyzed in relation to wetting characteristics and physical properties of the liquids. A classification of the main types of oil-particle aggregates was developed based on the formation characteristics of the aggregates. Moreover, under specific conditions, depending on the application rates of the granular materials, unique interactions of the particles with the hydrophobic liquid-water interface were observed and defined (bowl formation and roping). These concepts can be utilized to control surface mobility of floating oils, especially during the initial stages of an oil spill, while the oil layer is intact, and when other treatment methods may not be suitable near coastal areas, where transport of floating oils can significantly impact coastal ecosystems.

39

Roy, Debashish. "Natural-synthetic hybrid functional materials from cellulose via the RAFT process". Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441327.

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40

Abbas, Shah Rukh. "Preliminary investigation of natural materials for use in ultrasound contrast agents". Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708316.

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41

Matsuo, Miyuki. "Color Change of Lignocellulosic Materials during Natural Aging and Heat Treatment". Kyoto University, 2012. http://hdl.handle.net/2433/157700.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第16909号
農博第1925号
新制||農||999(附属図書館)
学位論文||H24||N4670(農学部図書室)
29584
京都大学大学院農学研究科森林科学専攻
(主査)教授川井秀一, 教授杉山淳司, 准教授仲村匡司
学位規則第4条第1項該当

42

Nelson, Andrew Wyatt. "Naturally occurring radioactive materials associated with unconventional drilling for natural gas". Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/5579.

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As unconventional drilling has emerged as a major industry in the US and around the world, many environmental health and pollution risks have surfaced. One emerging concern is the risk of environmental contamination arising from unconventional wastes that are enriched in naturally-occurring radioactive materials (NORM). Although NORM has been a well-documented contaminant of oil and gas wastes for decades, there are new challenges associated with unconventional drilling. This thesis discusses several of these challenges, focusing on NORM from black shale formations. Chapter 1 provides background information on environmental radioactivity and unconventional drilling. Chapter 2 describes the potential for NORM to migrate into groundwater around unconventional drilling operations. Chapters 3 and 4 describe radiochemical methods developed for the analysis of Marcellus Shale unconventional drilling wastes. Chapter 5 describes environmental partitioning of Marcellus Shale unconventional drilling wastes. Collectively, this thesis attempts to broaden the scientific understanding of NORM in unconventional drilling wastes so that potential environmental impacts may be mitigated.

43

Kalyankar, Rahul R. "Natural fiber reinforced structural insulated panels for panelized construction". Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2010r/kalyankar.pdf.

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44

Mital, D., J. Zajac, F. Botko, M. Hatala, Z. Mitalova, S. Radchenko, Віталій Олександрович Іванов, Виталий Александрович Иванов e Vitalii Oleksandrovych Ivanov. "Measuring of roundness of WPC materials after turning". Thesis, Sumy State University, 2016. http://essuir.sumdu.edu.ua/handle/123456789/48030.

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Natural fibers offer several advantages. They are renewable, inexpensive, can be used to isolate a sound and have got a low density. The disadvantages of these materials are: susceptibility to moisture, low fire resistance, and sensitivity to biodegradation. Their disadvantages are possible to eliminate by using of thermosetting and thermoplastic matrixes obtaining the plastics filled by organic fillers. Nowadays is preferred a usage of thermoplastic matrixes (especially in WPC product).

45

Li, Weiyao. "Understanding UV Protection Mechanism of Natural and Synthetic Eumelanin". University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1491930546268438.

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46

Скиданенко, Юлія Павлівна, Юлия Павловна Скиданенко e Yuliia Pavlivna Skydanenko. "Науково-методичні підходи до визначення економічної сутності наслідків надзвичайних ситуацій природного характеру". Thesis, Видавництво СумДУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/26759.

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Сучасний стан розвитку суспільства пов'язаний з подоланням природних та техногенних небезпек. Їх подолання та попередження є достатньо складною проблемою, яка потребує подальшого розвитку та удосконалення. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/26759

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Rahman, Muhammad Ziaur. "Mechanical Performance of Natural / Natural Fiber Reinforced Hybrid Composite Materials Using Finite Element Method Based Micromechanics and Experiments". DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6482.

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A micromechanical analysis of the representative volume element (RVE) of a unidirectional flax/jute fiber reinforced epoxy composite is performed using finite element analysis (FEA). To do so, first effective mechanical properties of flax fiber and jute fiber are evaluated numerically and then used in evaluating the effective properties of ax/jute/epoxy hybrid composite. Mechanics of Structure Genome (MSG), a new homogenization tool developed in Purdue University, is used to calculate the homogenized effective properties. Numerical results are compared with analytical solution based on rule of mixture, Halpin-Tsai as well as Tsai-Hahn equations. The effect of the volume fraction of the two different fibers is studied. Mechanical performance of hybrid composite is compared with the mechanical performance of single fiber composites. Synergistic effect due to hybridization is studied using analytical method given in literature, finite element method based MSG and Classical Lamination Theory (CLT). It is found that, when Poisson ratio is taken into consideration, elastic modulus shows synergy due to hybridization. Finally, impact properties of ax/jute/epoxy hybrid composite material are studied using Charpy impact testing.

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Burström, Karin. "Metal Oxide Composites with Carbon Materials : Synthesis, Characterisation and Preliminary Catalytic Applications". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75791.

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Nanoparticles combining metal oxides TiO2 and graphene derivatives (reduced graphene oxide and multi-walled carbon nanotubes) were synthesised via wet chemistry methods. The materials were investigated through a series of techniques (scanning electron microscopy, X-ray diffraction, photoluminescence and UV-visible spectrophotometry). The electronic features of the materials were examined by cyclic voltammetry, and some photocatalysis testing was performed, using a solar light simulator and Rhodamine B as a pollutant in water. It was found that addition of the graphene derivative enhanced the electrical properties of the substance, which theoretically should reflect positively in the photocatalytic skill. However, photocatalysis was not found more efficient with the composites, compared to the pristine materials. Further, SnO2@ZnO core@shell nanoparticles were synthesised by wet chemistry methods. These materials were investigated by the mentioned methods and preliminary photocatalysis testing was executed, where the composites were found functional, although further testing is required.

49

Buraglio, Nadia. "Accelerator mass spectrometry of ¹²⁹I and its applications in natural water systems". Doctoral thesis, Uppsala University, Department of Materials Science, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1077.

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During recent decades, huge amount of radioactive waste has been dumped into the earth's surface environments. ¹²⁹I (T_1/2= 15.6 My) is one of the radioactive products that has been produced through a variety of processes, including atomic weapon testing, reprocessing of nuclear fuel and nuclear accidents. This thesis describes development of the Accelerator Mass Spectrometry (AMS) ultra-sensitive atom counting technique at Uppsala Tandem Laboratory to measure ¹²⁹I and discusses investigations of its distribution in the hydrosphere (marine and fresh water) and precipitation. The AMS technique provides a method for measuring long-lived radioactive isotopes in small samples, relative to other conventional techniques, and thus opens a new line of research. The optimization of the AMS system at Uppsala included testing a time of flight detector, evaluation of the most appropriate charge-state, reduction of molecular interference and imporvement of the detection limit. Furthermore, development of a chemical procedure for separation of iodine from natural water samples has been accomplished.

The second part of the thesis reports investigations of ¹²⁹I in natural waters and indicates that high concentrations of ¹²⁹I (3-4 orders of magnitude higher than in the pre-nuclear era) are found in most of the considered natural waters. Inventory calculations and results of measurements suggest that the major sources of radioactive iodine are the two main European nuclear reprocessing facilities at Sellafield (U.K.) and La Hague (France). This information provides estimates of the transit time and vertical mixing of water masses in the central Arctic Ocean. Results from precipitation, lakes and runoff are used to elucidate mechanisms of transport of ¹²⁹I from the point sources and its pathways in the hydrological environment. This study also shows the need for continuous monitoring of the ¹²⁹I level in the hydrosphere and of its future variability.

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Santim, Ricardo Hidalgo [UNESP]. "Síntese e caracterização de blendas borracha natural/polianilina e borracha natural/polipirrol obtidas por polimerização in situ". Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/126367.

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Made available in DSpace on 2015-08-20T17:09:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2015. Added 1 bitstream(s) on 2015-08-20T17:26:47Z : No. of bitstreams: 1 000844408_20200123.pdf: 201500 bytes, checksum: b24d7b49916a5f2728c18c6608fa6acc (MD5)
Os polímeros geralmente são muito conhecidos por serem materiais leves, flexíveis e de fácil processamento. Cada vez mais a área tecnológica tem a demanda dessas propriedades associadas a condutividade elétrica ajustável. Nessa perspectiva, há trabalhos que se empenham em associar Polímeros Condutores Intrínsecos (PCI) com matrizes de boa propriedade mecânica. Entre os PCI, o polipirrol (PPy) e a polianilina (PAni) têm se destacado devido à fácil síntese, alta estabilidade ambiental, alta condutividade (10 2 S/cm) e baixo custo dos monômeros. Uma das limitações nas aplicações tecnológica desses polímeros condutores está na sua pobre propriedade mecânica e baixa solubilidade. Uma das alternativas para contornar esses problemas é fazer a polimerizão in situ dos polímeros condutores na presença de um polímero com boas propriedades mecânicas. Dessa forma, o objetivo desse trabalho foi preparar blendas de borracha natural (BN) com PAni e BN com PPy através da polimerização in situ da anilina e do pirrol, respectivamente, no látex de seringueira, natural e prevulcanizado. Foram estudadas as propriedades morfológicas, estruturais, elétricas, mecânicas e térmicas dessas amostras. As análises dos espectros de infravermelho e UV-Vis- NIR evidenciaram a síntese, em meio látex, da polianilina no estado sal de esmeraldina (dopada) e do polipirrol no estado dopado. As blendas apresentaram condutividade elétrica na faixa de 10 -14 a 10 -2 S/cm que variou em função da razão borracha/monômero. Na maioria dos casos, obteve-se maior condutividade elétrica quando utilizou-se o látex prevulcanizado. A tensão na ruptura aumentou com a diminuição da razão de BN/monômero para as blendas obtidas a partir de látex natural e também de látex prevulcanizado. Para a mesma condição de síntese, a tensão de ruptura foi superior para as blendas obtidas a partir do látex...
The polymers are generally known to be very lightweight materials, flexible and easy processing. Each year, more and more the technology area has the demand for these properties associated with adjustable electrical conductivity. From this perspective, there are studies that seek to associate intrinsically conducting polymers (ICP) with polymer matrices that has good mechanical property. Among those ICP, polypyrrole (PPy) and polyaniline (PAni) has received much attention due to easy of synthesis, high environmental stability, high conductivity (10 2 S/cm) and low cost of monomers. However, they have poor mechanical property and low solubility. An alternative to overcome these problems is to make in situ polymerization of the conductive polymer in the presence of another polymer that possesses good mechanical properties. In this way, the aim of this study was to obtain natural rubber (NR) composites with PAni and NR with PPY by in situ polymerization of aniline and pyrrole, respectively, in the natural and prevulcanized natural rubber latex. Morphological, structural, electrical, mechanical and thermal properties these samples were studied. Analysis of infrared and UV-Vis-NIR spectra showed the polyaniline and polypyrrole are in doped state. The electrical conductivity of the composites showed to be dependent on the ratio rubber/ monomer, staying in the range of 10 -14 to 10 -2 S/cm. In most cases, higher conductivity occurred when prevulcanized latex was used. The strain at break of the composites increases with decreasing rubber/monomer ratio. For the same synthesis conditions the strain at break was higher to the composites obtained from prevulcanized latex. In some polymerization condition it was evident the occurrence of encapsulation of prevulcanized rubber particles with the conducting polymers mainly to low rubber/monomer ratio

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