Дисертації з теми "Raw earth materials"

This report has investigated the ethical issues associated with mining or processing of materials that make them considered as controversial. For each material, the main areas of use and the top producing countries are analysed, followed by social and/or environmental issues as well as potential problems in the future. In total, 13 materials are discussed, of which most are minerals. The overall issues, that are recurring throughout the report and are important to be aware of are: child labor, low safety standards, mining activity resulting in deforestation or harming biodiversity, mining processes that affect communities (e.g. because of large water consumption) and the risks associated with widespread illegal mining. The report also provides research about organisations and initiatives that aim to affect the problems, and gives a brief view over tools that can be used to increase awareness of these issues.

Att kunna mäta vår materialanvändning är centralt i omställningen till ett resurseffektivare samhälle och en cirkulär ekonomi. Inom EU används Domestic Material Consumption (DMC) som indikator för materialanvändning. Den beräknas genom att addera de material som ett land utvinner, plus de material som importeras, minus de material som exporteras. Det finns kritik mot DMC då den endast tar hänsyn till vikten på import- och exportprodukter då de korsar landsgränsen. DMC inkluderar inte de uppströms material som gått åt för att producera en produkt, men som inte syns i slutprodukten (den så kallade materialryggsäcken).   Den ökade globaliseringen har för många länder lett till en förflyttning av produktion utomlands, och för att beräkna dessa länders totala materialanvändning krävs det att hänsyn tas till importerade och exporterade produkters materialryggsäck. Raw Material Consumption (RMC) är en indikator som tar hänsyn till materialryggsäcken, men den har idag ingen standardiserad beräkningsmetod. Både RMC och DMC används inom Agenda 2030 för att följa upp FN:s hållbarhetsmål 12 ”Hållbar konsumtion och produktion”, samt hållbarhetsmål 8 ”Anständiga arbetsvillkor och ekonomisk tillväxt”. Endast DMC används idag inom EU.   Syftet med projektet var att beräkna Sveriges materialanvändning med hjälp av indikatorn Raw Material Consumption (RMC), samt att identifiera styrkor och svagheter hos RMC. Eurostats RME-verktyg användes för att beräkna RMC. Enligt RMC ökade Sveriges totala materialanvändning från 198 miljoner ton råmaterialekvivalenter (RME) år 2008, till 221 miljoner ton RME år 2015, motsvarande 21,4 ton RME per capita 2008 till 22,6 ton RME per capita 2015. Resultaten jämfördes med resultat för Sveriges DMC som Statistiska Centralbyrån tagit fram. RMC och DMC gav liknande resultat för Sveriges totala materialanvändning. Detta tros bero på att materialryggsäcken för den svenska importen är ungefär lika stor som för exporten och att den största materialkategorin, icke-metalliska mineraler, utgör en liten del av vår handelsbalans och därför inte påverkas i någon större utsträckning när importerade och exporterade produkters materialryggsäck inkluderas. På materialkategorinivå är dock skillnaderna mellan RMC och DMC större.   Resultat från Eurostats RME-verktyg som tagits fram i denna studie, har jämförts med resultat som OECD och UNEP tagit fram för Sveriges RMC. De har använt en annan beräkningsmetod än den RME-verktyget tillämpar. Skillnaden i total RMC för de olika beräkningsmetoderna är mellan 11 % och 22 %. På materialkategorinivå är skillnaderna större, över 50 % för fossila bränslen exempelvis. Liknande resultat har påvisats i en studie som jämförde Österrikes RMC för år 2007 med olika beräkningsmetoder.   Både DMC och RMC kan användas som indikatorer för resurseffektivitet och cirkulär ekonomi, men vid jämförelse mellan länder är RMC teoretiskt en mer lämplig indikator. Detta eftersom många länder idag har flyttat stora delar av sin produktion utomlands, och DMC därför riskerar att ge en skev bild över resurseffektivitet och frikoppling, när materialryggsäcken inte inkluderas.<br>Being able to measure the amount of materials used in society, is central in the transition to a resource-efficient and circular economy. Within the EU, Domestic Material Consumption (DMC) is currently used as indicator for material use. It is calculated by adding the materials that a country extracts, plus the materials imported, minus the materials being exported. There is criticism of DMC, as a measure, since it only considers the weight of imported and exported goods when they cross the country border. It does not consider the upstream materials needed to produce a product, which are not represented in the final product (the so-called material backpack). Globalisation has led to a geographical disconnection in production and consumption, and to consider net-importing countries’ total material consumption, it is necessary to include traded product’s material backpack. Raw Material Consumption (RMC) considers the material backpack, but is currently without a standardised calculation method. Both RMC and DMC are used in Agenda 2030 to follow up the UN Sustainability Development Goal 12 "Sustainable Consumption and Production", as well as Goal 8 "Decent Work Conditions and Economic Growth". Only DMC is used today in the EU.   The aim of this project was to calculate Sweden’s material consumption, using the indicator Raw Material Consumption (RMC), as well as identifying strengths and weaknesses of RMC. For calculating RMC, Eurostat’s RME-tool has been used. According to RMC, Sweden's total material usage increased from 2008 when it amounted to 198 million tonnes of raw material equivalents (RME), to 221 million tonnes RME in 2015. There has also been an increase per capita: 21,4 RME per capita in 2008 to 22,6 RME per capita in 2015. These results have been compared with the results for Sweden's DMC, calculated by SCB. RMC and DMC gave similar results for Sweden's total material consumption. This is believed to be due to the similar size of the material backpack of imports and exports. Another reason is believed to be due to Sweden’s largest material category, non-metallic minerals, is a small part of our trade balance, and therefore is not affected when the material backpack is included. At the material category level, however, the differences between RMC and DMC are greater.   Results from Eurostat's RME tool, calculated in this study, have been compared with results presented by the OECD and UNEP. They have used a different calculation method for Sweden’s RMC than the RME tool applies. The difference in total RMC for different calculation methods is between 11 % and 22 %. At material category level, the differences are greater, more than 50 % for fossil fuels, for example. Similar results have been presented in a study over Austria's RMC for the year 2007, using different calculation methods.   Both DMC and RMC can be used as policy-support for resource efficiency, but RMC is theoretically a more suitable indicator for comparison of countries. This is since many countries today have moved a significant share of their production abroad, and DMC therefore risks displaying a false perception of resource efficiency and decoupling, when the material backpack is not included.

Chaque année, des millions de tonnes de terre sont excavées sur les chantiers du BTP en France. Actuellement, ces terres sont majoritairement valorisées dans le secteur du bâtiment, sous forme d’éléments de remplissage (brique en terre comprimée, adobe, bauge…), tandis que leur usage reste limité dans le secteur des travaux publics.L’objectif de ce travail de recherche est de développer de nouveaux éco-matériaux à base de terre crue et de sédiments de dragage, destinés à certaines applications en travaux publics, comme les bordures de trottoir, les blocs lego ou les glissières de sécurité. Différentes techniques de stabilisations, par compactage et stabilisation chimique, ont été explorées pour la confection des éprouvettes aux échelles du laboratoire et semi-industrielle. Différentes formulations, optimisées, ont fait l’objet de caractérisations physico-chimiques, mécaniques et microstructurales. Une analyse de cycle de vie est aussi réalisée afin de comparer les nouveaux matériaux développés aux matériaux traditionnels.Dans une première approche, la stabilisation chimico-mécanique de la terre crue et du sédiment de dragage est réalisée en utilisant un ciment Portland avec un compactage statique. L’optimisation des propriétés mécaniques et physiques à l’échelle de l’éprouvette cylindrique 5 x 10 cm2 (diamètre × hauteur) a permis d’aboutir à une formulation optimale composée de 75% de terre crue, 20% de sédiment et 5% de ciment, et compactée à 5 MPa. Cependant, lors du passage à l’échelle de la bordure de type P1 (33 × 20 × 8 cm3), des limitations de cette méthode sont constatées, notamment en raison de la non uniformité de la contrainte de compactage en raison de l’effet paroi.Pour surmonter ces obstacles, une stabilisation avec un liant géopolymère à base de métakaolin a été explorée. Plusieurs facteurs ont été étudiés : optimisation des propriétés mécaniques, analyse de l’influence des argiles, durabilité et analyse de cycle de vie. L’optimisation des propriétés mécaniques a été réalisée à travers un plan d’expériences à trois facteurs (SiO2/Al2O3, Na2O/Al2O3 et H2O/Na2O), suivi d’une variation du rapport massique métakaolin sur terre crue (MK/TC) entre 0.33 et 0.16. Cette optimisation réalisée à l’échelle de l’éprouvette prismatique 4 × 4 × 16 cm3 a permis de retenir deux formulations optimales à la fois sur le plan mécanique et environnemental. Ces formulations ont été ensuite exploitées à une échelle semi-industrielle, avec la fabrication et la pose de 30 mètres de bordures de type P1 (50 × 20 × 8 cm3) sur un chantier expérimental à Narbonne<br>Every year, millions of tonnes of soil are excavated on construction sites in France. Currently, most of these soils are reused in the construction sector, in products such as compressed earth bricks, adobe, paving stones, etc.), while its use remains limited in the field of public works.This study aims to develop new eco-friendly materials based on raw earth and dredged sediments in some civil engineering applications such as kerbs, Lego-like blocks, and guardrails. Various stabilization techniques, including compaction and chemical stabilization, were explored to produce laboratory-scale and semi-industrial-scale samples. Optimized formulations were then subjected to physicochemical, mechanical, and microstructural characterizations. A life cycle analysis was also conducted to compare these new materials with traditional ones.Initially, cement was used for the stabilization of raw earth and dredged sediments through static compaction. Optimization of the mechanical and physical properties on a cylindrical sample of 5 cm in diameter and 10 cm in height led to an optimal formulation consisting of 75% raw earth, 20% sediment, and 5% cement, compacted at 5 MPa. However, scaling up to a P1 kerbs (33 × 20 × 8 cm³) showed some limitations, notably due to a non-uniform compaction load caused by the wall effect.To overcome these limitations, stabilization using metakaolin-based geopolymer binder was explored. Several factors were studied, including mechanical properties, the effect of clays, durability, and life cycle analysis. Mechanical optimization was carried out using a three-factor experimental design (SiO2/Al2O3, Na2O/Al2O3, and H2O/Na2O), with subsequent variation of the metakaolin to raw earth weight ratio (MK/TC) between 0.33 and 0.16. This optimization, carried out on a 4 × 4 × 16 cm³ prismatic specimen, identified two optimal formulations in terms of mechanical and environmental performance. These formulations were then evaluated on a semi-industrial scale, resulting in the production and installation of 30 meters of P1 kerbs (50 × 20 × 8 cm³) on an experimental site

New and more efficient magnetic materials for energy applications are a big necessity for sustainable future. Whether the application is energy conversion or refrigeration, materials based on sustainable elements should be used, which discards all rare earth elements. For energy conversion, permanent magnets with high magnetisation and working temperature are needed whereas for refrigeration, the entropy difference between the non-magnetised and magnetised states should be large. For this reason, magnetic materials have been synthesised with high temperature methods and structurally and magnetically characterised with the aim of making a material with potential for large scale applications. To really determine the cause of the physical properties the connections between structure (crystalline and magnetic) and, mainly, the magnetic properties have been studied thoroughly. The materials that have been studied have all been iron based and exhibit properties with potential for the applications in mind. The first system, for permanent magnet applications, was Fe5SiB2. It was found to be unsuitable for a permanent magnet, however, an interesting magnetic behaviour was studied at low temperatures. The magnetic behaviour arose from a change in the magnetic structure which was solved by using neutron diffraction. Substitutions with phosphorus (Fe5Si1-xPxB2) and cobalt (Fe1-xCox)5PB2 were then performed to improve the permanent magnet potential. While the permanent magnetic potential was not improved with cobalt substitutions the magnetic transition temperature could be greatly controlled, a real benefit for magnetic refrigeration. For this purpose AlFe2B2 was also studied, and there it was found, conclusively, that the material undergoes a second order transition, making it unsuitable for magnetic cooling. However, the magnetic structure was solved with two different methods and was found to be ferromagnetic with all magnetic moments aligned along the crystallographic a-direction. Lastly, the origin of magnetic cooling was studied in Fe2P, and can be linked to the interactions between the magnetic and atomic vibrations.

2007/2008<br>In the course of this thesis I present an experimental investigation into various strongly correlated transition metal and rare earth compounds using core-level spectroscopic techniques, which have augmented the understanding of the electronic properties of these different systems. I will discuss the orbital occupation and the symmetry of the states near the Fermi level, responsible for the variety of ground states shown by a variety of strongly correlated systems such as misfit cobaltates, strontium ruthenates, metallic manganese and rare earth compounds.<br>XXI Ciclo<br>1978

Cette étude se concentre sur les performances hygro-mécaniques de la terre crue compactée comme matériau de construction alternatif aux matériaux de construction classiques à forte empreinte énergétique. Les briques en terre ont été fabriquées en appliquant des pressions de compactage élevées (jusqu’à 100 MPa, d’où la dénomination d’hyper-compactage) pour augmenter la densité du matériau et ainsi obtenir des propriétés mécaniques similaires à celles des matériaux de construction traditionnels tels que les briques cuites, les blocs de béton et la terre stabilisée. Une vaste campagne expérimentale a été menée sur des échantillons constitués de différents mélanges hyper-compactés de terres à leur teneur en eau optimale respective. La rigidité et la résistance mécanique ont été mesurées par des essais de compression non confinés et triaxiaux, tandis que l’adsorption/désorption de vapeur a été évaluée par la valeur de MBV (Moisture Buffering Value). La durabilité à l'érosion hydrique a été étudiée en effectuant des tests de adsorption capillaire, d'immersion et de goutte-à-goutte conformément aux normes DIN 18945 (2013) et NZS 4298 (1998). Les résultats ont confirmé que l'hyper-compactage améliore les performances mécaniques de la terre crue compactée, mais qu'une augmentation sensible de l'humidité ambiante pouvait entraîner une réduction considérable de la résistance. Néanmoins, les tests de durabilité ont révélé que la terre compactée non stabilisée ne pouvait pas être utilisée pour la construction des parties de structures exposées aux intempéries naturelles en raison de sa sensibilité vis-à-vis de l’eau liquide. Les expériences ont démontré la dépendance de la résistance, de la rigidité, du comportement hydrique, de la sensibilité à l’eau liquide et de la durabilité à la taille des particules. En particulier, il a été observé qu'un mélange de terre à faible granulométrie et calibrées présentait des caractéristiques pour les propriétés susmentionnées supérieures à celle d’un sol à la granulométrie grossière et non maîtrisée. Un défi important a été l'amélioration de la durabilité de la terre crue à l'érosion hydrique en adoptant de techniques de stabilisation à faibles impacts environnementaux, ce qui a conduit à la mise au point d’une méthode originale de stabilisation basée sur l’utilisation d’extraits de plantes. Cette méthode était conforme à la précipitation de calcite induite par voie enzymatique via l'action de l'enzyme uréase pour catalyser l'hydrolyse de l'urée. Cette réaction produit des ions carbonates, qui réagissent ensuite avec les ions calcium du sol dissout dans l’eau interstitielle pour précipiter sous forme de carbonate de calcium, liant ainsi les particules du sol<br>The present work investigates the hygro-mechanical performance of compacted earth as an alternative to conventional energy-intensive building materials. Earth bricks were manufactured by applying high compaction pressures up to 100 MPa (hyper-compaction) to increase the density of the earth and hence to obtain mechanical properties that are similar to those of traditional construction materials such as fired bricks, concrete blocks and stabilised earth. A wide campaign of laboratory tests was performed on samples made of different earth mixes that were hyper-compacted at their respective optimum water contents. Stiffness and strength were measured by unconfined and triaxial compression tests while vapour adsorption/desorption was assessed by measuring moisture buffering value (MBV). Durability to water erosion was also evaluated by performing suction, immersion and drip tests according to the norms DIN 18945 (2013) and NZS 4298 (1998), respectively. Results showed that hyper-compaction largely improved the mechanical performance of compacted earth but that a marked increase in ambient humidity could produce a considerable reduction of strength. Durability tests highlighted that the unstabilised compacted earth could not be employed for the construction of structures exposed to natural weathering. The experiments also demonstrated the dependency of strength, stiffness, moisture buffering capacity and water durability on particle grading. In particular, it was shown that a fine and well-graded earth mix exhibited higher levels of strength, stiffness, moisture buffering capacity and durability than a coarse and poorly-graded one. One important challenge lied in the improvement of the earth durability against water erosion by adopting novel stabilisation techniques, which led to the development of an original stabilisation method based on the utilisation of plant extracts. The method was consistent with the principles of Enzymatic Induced Calcite Precipitation (EICP), which utilises the action of the urease enzyme to catalyse the hydrolysis of urea. This reaction produces carbonate ions, which then react with the calcium ions dissolved in the pore water to produce the precipitation of calcium carbonate (i.e. calcite), thus binding the soil together. The novelty of the present work resides in the utilisation of crude plant-derived urease enzyme instead of pure reagent-grade products available from chemical suppliers, which reduces environmental and financial costs. In particular, the urease enzyme was obtained from a liquid soybeans extract, inside which the urea and calcium chloride were subsequently dissolved to induce the precipitation of calcite. Measurements of pH, electrical conductivity and precipitation ratio indicated that the optimum equimolar concentration of urea and calcium chloride (leading to the largest precipitation of calcite) was 2.5 mol/L. An experimental campaign was finally undertaken to implement the proposed bio-stabilisation method into the manufacture of compressed earth bricks. The most promising versions of the proposed bio-stabilisation method were also the object of further investigation to assess the hygro-mechanical behaviour of the stabilised earth by means of unconfined compression and moisture buffering value tests. The findings, although preliminary, suggested that a noticeable improvement of strength and water durability could be achieved by the proposed stabilisation protocol, in spite of the difficulty in replicating exactly quantitative results

The structure of molten Au0.81Si0.19, Au0.72Ge0.28 and Ag0.74Ge0.26 alloys with a composition at or near to the eutectic was investigated by using neutron diffraction (ND). The results suggest that the Au-Au distance in the alloys is similar to that of liquid Au, there is a preference for Au-Si bonds and show that there are pre-peaks in the total structure factors for Au0.72Ge0.28 and Ag0.74Ge0.26 at 1.3(2) and 1.6(3) ˚, A−1 respectively. The asymptotic decay of the pair correlation functions was found to agree both with a theoretical prediction based on simple pair potentials and a fractal model for metallic glasses. The structure of glassy (R2O3)0.2(Al2O3)0.2(SiO2)0.6, where R denotes Dy, Ho or a 50:50 mixture of Dy and Ho, was investigated by using the method of isomorphic substitution in ND, x-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS) spectroscopy. The network is made from SiO4 tetrahedral units with a distribution of AlO4, AlO5 and AlO6 units giving an average coordination number of 4.5(1). There is a distribution of RO5, RO6, RO7, RO8 and RO9 units with an average coordination number of 7.2(3) and an average R-O distance of 2.33(2) ˚ A. The EXAFS results confirmed that Dy and Ho are isomorphic and were used to refine an RMC model of the structure. R-Al and R-Si nearest neighbour shells with average distances of 3.15(3) and 3.6(1) ˚A were required to fit the EXAFS results. The structure of glassy and liquid ZnCl2 was studied by using ND and XRD. The material has a network structure made from ZnCl4 tetrahedra units which is retained in the liquid at temperatures near to the boiling point. An increase of temperature promotes edge sharing connectivity as inferred from a decrease of the Zn-Zn nearest neighbour distance and average Zn-Cl coordination number. An EXAFS study on crystalline ZnCl2 at room temperature shows that Zn remains 4fold coordinated at pressures less than 1 GPa, is 4+2-fold coordinated at 2-4 GPa, and is 6-fold coordinated above 4 GPa. For liquid ZnCl2, Zn is 4-fold coordinated by Cl at a pressure of about 1 GPa and could be 6-fold coordinated at 2-3 GPa.

Nesse trabalho foram estudados os compostos intermetalicos do tipo RAg (R = Nd, Gd e Ho) por calculos teoricos desenvolvidos dentro do formalismo da Teoria do Funcional Densidade (DFT). O metodo APW+lo (Augmented Planes Waves + lo- cal orbitals) foi aplicado para resolver a equacao de Kohn-Sham e a Aproximacao do Gradiente Generalizado (GGA) usada para tratar de forma aproximada o potencial de troca-correlacao. O codigo computacional utilizado foi o WIEN2k. As atividades foram focalizadas em duas frentes. Numa delas, determinou-se a fase magnetica do estado fundamental dos compos- tos HoAg e NdAg. Para isso, simulou-se as 4 estruturas magneticas possiveis (para as celulas cristalinas cubicas) desses dois sistemas (uma ferromagnetica (0,0,0) e as antifer-romagneticas: (0,0,¼), (¼,¼,0) e (¼,¼,¼)) e com a confeccao de gra¯cos de energia das celulas cristalinas dessas estruturas magneticas pela variacao dos volumes de tais celulas, chegou-se na estrutura magnetica (¼,¼,0) como a mais provavel para o estado fundamental magnetico de ambos os compostos. Tambem observou-se que o sistema de NdAg apre- senta uma pequena diferenca entre as energias das estruturas antiferromagnetica (¼,¼,0) e ferromagnetica. Creditou-se a esse efeito a explicacao de encontrar-se na literatura re- sultados experimentais diferentes para a estrutura magnetica do composto de NdAg puro e dopado com o atomo de 140Ce (entrando no sitio do Nd). Acredita-se que a dopagem do NdAg com o atomo de 140Ce (em uma porcao reduzida), gera alteracao no sinal da integral de troca (acoplamento RKKY), mudando-o de positivo para negativo, e isso implica na modficacao da fase magnetica do estado fundamental, passando da estrutura (¼,¼,0) µa 0,0,0). Assim, com a informacao anterior da estrutura magnetica do composto de NdAg quando dopado com o atomo de 140Ce, entrou-se na segunda etapa do estudo. Nela, fez-se os calculos das estruturas eletronicas usando a aproximacao de supercelulas nos compostos de GdAg e NdAg dopados com o atomo de Ce, garantindo que esse substituisse um atomo de terra rara nas supercelulas cristalinas montadas para determinar no Ce o campo hiperfino magnetico e suas componentes geradoras. Os compostos de GdAg e NdAg (dopados com Ce), respectivamente, tiveram suas celulas cristalinas montadas ferromagnetica e antiferromagneticamente. Utilizou-se a polarizacao orbital (DFT+U) nos eletrons da camada 4f das terras raras (excluindo-se o atomo de Gd que nao apresenta momento angular). Dessa forma, em ambos os sistemas foi possivel fazer varias simulacoes, nas quais a camada 4f do atomo de Ce foi populada de maneiras diferentes, afim de se obter varios valores de momento angular e com isso diversos resultados de campo hiperfino orbital foram conseguidos; assim, automaticamente o campo magnetico hiperfino tambem assumiu diferentes valores. Escolheu-se os sub-estados da camada 4f do Ce para serem simulados por meio da regra de Hund. Como esperado o campo hiperfino magnetico orbital gerado na camada 4f e a principal componente do campo hiper¯no total no atomo de Ce e ele apresenta sinal contrario µa componente de contato. Apesar dos resultados teoricos do campo hiperfino magnetico terem consideravel discrepancia dos resultados experimentais, pode-se verificar que o unico eletron da camada 4f do atomo de Ce (nos dois compostos) possivelmente esta em um dos seguintes sub-estados da camada 4f: ml = ¡2, ml = ¡1 ou ainda uma combinacao dos dois.<br>In this work the magnetic hyper¯ne ¯eld acting on Ce atoms substituting the rare-earths in RAg compounds (R = Gd e Nd) was studied by means of ¯rst-principles electronic structure calculations. The employed method was the Augmented Plane Waves plus local orbitals (APW+lo), embodied in the WIEN2k program, within the framework of the Density Functional Theory (DFT) and with the Generalized Gradient Approximation (GGA) for the exchange and correlation potential. The super-cell approach was utilized in order to simulate for the Ce atoms acting as impurities in the RAg matrix. In order to improve for correlation e®ects within the 4f shells, a Hubbard term was added to the DFT hamiltonian, within a procedure called GGA+U. It was found that the magnetic hyper¯ne ¯eld (MHF) generated by the Ce 4f electron is the main component of the total MHF and that the Ce 4f ground state level is probably a combination of the ml = ¡2 and ml = ¡1 sub-levels. In addition, the ground-state magnetic structure was determined for HoAg and NdAg by observing the behavior of the total energy as a function of the lattice volume v for several possible magnetic ordering in these compounds, namelly, ferromagnetic, and the (0,0,¼), (¼,¼,0) and (¼,¼,¼) types of anti-ferromagnetic ordering of rare-earth atoms. It was found that the ground-state magnetic structure is anti-ferromagnetic of type (¼,¼,0) for both, the HoAg and NdAg compounds. The energy di®erence of the ferromag-netic and antiferromagnetic ordering is very small in the case of the NdAg compound.

This doctoral project combines a performance-led practice with contextual research in order to demonstrate how arts practice can challenge historical perceptions of clay and enhance its material status. The core knowledge deduced from this research is that embodied performance transforms connectivity between artist and clay and produces a unified incarnation of both elements. Through the use of immersive research methods I gained insights which could not have been predicted - particularly that my experiential performances were a process of ‘clay becoming’ in which I ultimately became the clay. In terms of locality, the practice, comprising eight performance-led works and related documentation, focuses on the China Clay and Ball Clay of South West England. Traditionally in the arts, these materials are associated with ceramics, where through heating, clay becomes rigid and fixed. In contrast, my research investigates the textural fluidity and metamorphic potential of these clays in their raw state. The practice encompasses two interrelated groups of work; the In-breath and Out-breath. These terms are significant in three respects. Firstly they define two different modes and moments of practice. Secondly they refer to myself as a living component of these practices. Thirdly they reflect the cultural associations of clay as a metaphor for life. During the initial exploratory ‘In-breath’ phase of my practice, comprising four site-specific pieces, I engaged with clay at sites of historical relevance, building an expansive knowledge of my material. During the later ‘Out-breath’ phase, identification with site was relinquished. These works took place within neutral spaces, allowing the clay to be explored in relation to my body. The introduction of layering, where photographic elements of private clay rituals were situated within the context of a live performance, allowed a texturally dynamic and immersive experience to be created for both artist and viewer. By collecting and preserving clay traces from these live performances (e.g. foot and body prints) additional value was given to the embedded significance of the clay.

In recent years, the United States Departments of Homeland Security (DHS) and Customs and Border Protection (CBP) have been charged with the task of scanning every cargo container crossing domestic borders for illicit radioactive material. This is accomplished by using gamma-ray detection systems capable of discriminating between non-threatening radioisotopes, such as Cs-137, which is often used in nuclear medicine, and fissile material, such as U-238, that can be used to make nuclear weapons or "dirty" bombs. Scintillation detector systems, specifically thallium-doped sodium iodide (NaI(Tl)) single crystals, are by far the most popular choice for this purpose because they are inexpensive relative to other types of detectors, but are still able to identify isotopes with reasonable accuracy. However, increased demand for these systems has served as a catalyst for the research and development of new scintillator materials with potential to surpass NaI(Tl). The focus of a majority of recent scintillator materials research has centered on sintered transparent ceramics, phosphor-doped organic matrices, and the development of novel single crystal compositions. Some of the most promising new materials are glass-ceramic nanocomposites. By precipitating a dense array of nano-scale scintillating crystals rather than growing a single monolith, novel compositions such as LaBr₃(Ce) may be fabricated to useful sizes, and their potential to supersede the energy resolution of NaI(Tl) can be fully explored. Also, because glass-ceramic synthesis begins by casting a homogeneous glass melt, a broad range of geometries beyond the ubiquitous cylinder can be fabricated and characterized. Finally, the glass matrix ensures environmental isolation of the hygroscopic scintillating crystals, and so glass-ceramic scintillators show potential to serve as viable detectors in alpha- and neutron-spectroscopy in addition to gamma-rays. However, for the improvements promised by glass-ceramics to become reality, several material properties must be considered. These include the degree of control over precipitated crystallite size, the solubility limit of the glass matrix with respect to the scintillating compounds, the variation in maximum achievable light yield with composition, and the peak wavelength of emitted photons. Studies will focus on three base glass systems, sodium-aluminosilicate (NAS), sodium-borosilicate (NBS), and alumino-borosilicate (ABS), into which a cerium-doped gadolinium bromide (GdBr₃(Ce)) scintillating phase will be incorporated. Scintillator volumes of 50 cubic centimeters or greater will be fabricated to facilitate comparison with NaI(Tl) crystals currently available.

The environmental issue has recently been central to national and international multidisciplinary debates. The term ecology, has given rise to green culture. Various intellectuals and artists since the first industrial revolution have been palpating the discomfort of what mechanized labor has entailed. Today, both the European Community and the UN set goals for safeguarding the planet and finding answers to the climate and environmental crisis. These issues become central strategies for design disciplines, and as designers we must not underestimate the contemporary condition but rather make it an integral part of what the city of the future will be. Among the changes that can be implemented we identify the need for a paradigm shift in moving from linear production systems to dynamic models that use natural resources and also place attention on processes of disposal or reuse of discarded materials. Thus, a more sustainable doing, thinking, conceiving and designing is also looked at. In the research we set out to imagine a sustainable envelope that is able to meet technical, bureaucratic, administrative, legislative, and also aesthetic regulations. Making design choices fall on local and sustainable materials is one of the most effective solutions. Among the various materials that have come into disuse, in Italy, raw earth has been identified, precisely because of the high potential it possesses. The objective of the research is to study raw earth as a building material, both by analyzing its weaknesses and the dynamics that led to its abandonment, and by identifying the strengths that could promote its recovery. Unfired earth is one of the first materials used by human beings given its ease of processing. Earthen artifacts, in fact, are an integral part of the world's architectural heritage and are identified as powerful expressions of the human ability to create shelter through the resources that were available locally. Ancient artisans, exploited and knew the resources available in the immediate vicinity, an attitude that should be taken today to address the climate crisis currently underway. According to recent studies, earth as a building material has been used for more than eleven millennia, and even today, one-third of humanity lives in earthen buildings. UNESCO, in 2008, with the collaboration of the UN, established the World Heritage Program on Earthen Architecture (WHEAP), an action aimed at the preservation, restoration and enhancement of the properties of earthen architectures. The research took Chinese earthen architecture as paradigmatic of the role earth had and may have in the contemporary condition. In particular the earthen architectures of the Fujian region such as the Tulou, Tubao, and Zhuang Zhai. The comparison takes place with Italian earthen architectures in particular those found in the Lucanian territory, both for scientific interests and to rediscover this material also through cultural comparison with the Chinese context. As the final phase of the work project, the prototyping of an earthen housing module was sought. Freeing ourselves from the restrictive Italian regulations, an attempt was made to find a quick and effective solution to the need for emergency architecture, the research dealt with the study of intuitive and easily replicable construction solutions with dry installation techniques.

A probe for measuring the specific heat of superconductors at low temperatures and in high magnetic fields has been built and commissioned. The probe has been tested using the relaxation method on samples of copper and the accuracy of the data is 1.3 % between 5 K and 30 K, data taken using the long range pulse method has a resolution of 10 mK. Specific heat measurements have been performed on members of the series (Pb(_1)-(_x))Cu(_1.8x)Mo(_6)S(_8), (Sn(_1-x))Eu(_x)Mo(_6)S(_8) and (Pb(_1-x)M(_x))Mo(_6)S(_8) where M = Gd and Eu, from 3 K up to 30 K and in magnetic fields up to 15 T. Additional results from resistivity, susceptibility, magnetisation. X-ray diffraction, transmission electron microscopy and electron dispersive-ray measurements are also presented. These data have been compared to results from other authors and are analysed in terms of the BCS and GLAG theories of superconductivity and the magnetic properties of these materials. The mean field model has been used to calculate numerically the magnetic contribution to the specific heat (cm) of both ferromagnetic and antiferromagnetic systems as a function of temperature and applied field both above and below the ordering temperature. In addition an approximate analytic form for the magnetisation has been used to calculate Cm above the ordering temperature. Expressions have been derived for the saturation value of the peak in C(_m): C(^sat)(_m) = 1.1245n(_cell)RJI(J+1) and the temperature dependence of the peak with applied field ȡ(μ(_o)H(_ext))/ȡT(_peak)=6.540/g(_J)(J+1). They allow the simple calculation of the values of J and g(_J)(J + 1) from specific heat data. The magnetic contribution to the specific heat of the samples (Sn(_0.65)Eu(0.35)Mo(_6)S(_8)) and (Sn(0.50)Eu(_0.50)Mo(_6)S(_8)) have been modelled using these calculations and excellent agreement is found by considering the magnetic ions as free ions. The sample is accurately modelled by including an additional minority phase (Gd(_2)S(_3)). The approximate expressions have also been used to analyse data on high temperature superconductors producing values of J and g(_J)}{J + 1) consistent with a doublet ground state. The properties of Chevrel phase materials have been determined as a function of doping level. The critical temperature is degraded by doping but an increase in the critical current density is observed in the series (Pb(_1-x)Cu(_1-8x)Mo(_6)S(_8) for very low levels of doping. Increases of up to 28 % in the upper critical field, that are probably due to the compensation effect and an increase in the normal state resistivity, are also observed in the series (Sn(_1-x)Eu(_x)Mo(_6)S(_8)) at high levels of doping and in the series (Pb(_1-x)Gd(_x)Mo(_6)s(_8) for low levels of doping.

Made available in DSpace on 2014-10-09T12:51:59Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:07:05Z (GMT). No. of bitstreams: 0<br>Dissertação (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-22T14:03:18Z No. of bitstreams: 0<br>Made available in DSpace on 2017-11-22T14:03:18Z (GMT). No. of bitstreams: 0<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)<br>Nas últimas décadas, o consumo de dispositivos eletrônicos e a alta demanda por armazenamento de dados tem mostrado grandes oportunidades para a criação de novas tecnologias que garantam as necessidades mundiais na área de computação e desenvolvimento. Alguns materiais multiferroicos tem sido amplamente estudados e o BiFeO3, considerado o único material multiferroico em temperatura ambiente, ganhou destaque como candidato para produção de dispositivos lógicos e de memória. O uso de técnicas de crescimento como a deposição por laser pulsado permitiu a produção de filmes finos de BiFeO3 com elevado controle de qualidade. Heteroestruturas de filmes multiferroicos de BiFeO3 e LaBiFeO3 foram crescidas com diferentes espessuras sobre substratos de SrTiO3(100), DyScO3(110) e SrTiO3/Si(100) para avaliação e teste de suas propriedades elétricas e magnéticas. Filmes ferromagnéticos de Co0,9Fe0,1 foram depositados por sputtering sobre os filmes multiferroicos para avaliação da interação interfacial entre ordenamentos magnéticos. Técnicas como fotolitografia foram utilizadas para padronização de microdispositivos gravados sobre as amostras. Tanto os filmes finos de BiFeO3 como os de LaBiFeO3 foram crescidos epitaxialmente sobre os substratos já cobertos com uma camada buffer de SrRuO3 usado como contato elétrico inferior. A estrutura cristalina romboédrica das ferritas de bismuto foi confirmada pelos dados de difração de raios X, bem como a manutenção de tensão estrutural causada pela rede cristalina do substrato para amostras de 20 nm. Os valores de coeficiente do tensor piezelétrico d33 foram da ordem de 0,15 V (&sim; 60 kV.cm-2) para amostras com 20 nm de espessura enquanto que os valores de voltagem coerciva para as análises de histerese elétrica foram da ordem de 0,5 V para as mesmas amostras. A relação de coercividade elétrica com a espessura corresponde ao perfil encontrado na literatura pela relação E&asymp;d-2/3. As amostras de CoFe/BFO e CoFe/LBFO depositadas em diferentes substratos apresentam acoplamento interfacial entre ordenamento ferromagnético e antiferromagnético com momento ferromagnético de rede.<br>Tese (Doutorado em Tecnologia Nuclear)<br>IPEN/T<br>Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP<br>CAPES:99999.009511/2014-08<br>CNPq:146622/2013-2

Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-08-06T15:17:49Z No. of bitstreams: 1 DISSERTAÇÃO-Francisco Maciel de Brito Neto PPGCEM.pdf: 4657821 bytes, checksum: bfb975014ce10e6a646fdd1c54e9758b (MD5)<br>Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-08-06T15:18:13Z (GMT) No. of bitstreams: 1 DISSERTAÇÃO-Francisco Maciel de Brito Neto PPGCEM.pdf: 4657821 bytes, checksum: bfb975014ce10e6a646fdd1c54e9758b (MD5)<br>Made available in DSpace on 2018-08-06T15:18:13Z (GMT). No. of bitstreams: 1 DISSERTAÇÃO-Francisco Maciel de Brito Neto PPGCEM.pdf: 4657821 bytes, checksum: bfb975014ce10e6a646fdd1c54e9758b (MD5) Previous issue date: 2018-05-17<br>CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico<br>Samples of samarium oxide (Sm2O3) and niobium oxide (Nb2O5) were submitted to Mechanical alloying technique and their structural evolution was accompanied by x-ray diffraction (XRD) measurements. In a few hours of milling SmNbO4 crystals were identified with two polymorphisms, one monoclinic and the other tetragonal. The diffractograms were simulated by Rietveld method and all crystallographic parameters were obtained, as well as the respective amounts of phases. The average crystallite sizes were estimated by the single-line method, indicating that both polymorphs have nanosized dimensions, that is, they are nanostructured. Combining calorimetric measurements, thermal treatments and x-ray diffraction the structural stability of the samples was studied. It was observed that the monoclinic structure undergoes phase transition to tetragonal structure in an exothermic process around 850 °C. The energy needed to promote the process was obtained by the Kissinger method and the XRD measurements indicate that the transition is irreversible.<br>Amostras de óxido de samário (Sm2O3) e óxido de nióbio (Nb2O5) foram submetidas à técnica moagem mecânica de alta energia e sua evolução estrutural foi acompanhada por medidas de difração de raios X (DRX). Em poucas horas de moagem foram identificados cristais de SmNbO4 com dois polimorfismos, um monoclínico e outro tetragonal. Os difratogramas foram simulados por método de Rietveld e todos os parâmetros cristalográficos foram obtidos, assim como as respectivas quantidades de fases. Os tamanhos médios de cristalitos foram estimados pelo método da linha única (single-line) indicando que ambos polimorfos possuem dimensões nanométricas, ou seja, são nanoestruturados. Combinando medidas calorimétricas, tratamentos térmicos e difração de raios x a estabilidade estrutural das amostras foi estudada. Foi observado que a estrutura monoclínica sofre transição de fase para estrutura tetragonal em um processo exotérmico em torno de 850°C. A energia necessária para promover o processo foi obtida pelo método de Kissinger e as medidas de DRX indicam que a transição é irreversível.

Les travaux présentés dans ce manuscrit portent sur la synthèse et la caractérisation de nouveaux matériaux magnétocaloriques à basse de terres rares pour la réfrigération magnétique. Le premier chapitre constitue une introduction aux notions d'effet magnétocalorique et de réfrigération magnétique et dresse un état de l'art des matériaux magnétocaloriques existants. Dans le but d'obtenir des matériaux à forte capacité de réfrigération (RC) et d'identifier des stratégies d'amélioration de ce critère de performance, deux voies de recherche ont été explorées : l'élargissement de la transition magnétique et l'effet de l'élément de transition M et de l'élément p (X) dans les verres métalliques Gd60M30X10 (M = Mn, Fe, Co, Ni, Cu et X = Al, Ga, In) d'une part, et la synthèse de nouveaux siliciures ternaires dans les systèmes R-M-Si (R = Nd, Gd, Tb et M = Co, Ni) à fort potentiel magnétocalorique, d'autre part. Le second chapitre de cette thèse présente les propriétés magnétiques des rubans amorphes à base de gadolinium synthétisés par la technique de melt-spinning, dans lesquels le désordre structural induit un très fort élargissement de la transition magnétique (vis-à-vis de celle du gadolinium par exemple). Il montre dans un premier temps, la faible influence de l'élément p (X) sur les propriétés magnétiques des rubans Gd60Mn30X10 (X = Al, Ga, In). Une seconde partie présente la très forte influence de l'élément de transition M, tant sur la nature de la transition magnétique que sur les propriétés magnétocaloriques des verres métalliques Gd60M30In10 (M = Mn, Fe, Co, Ni, Cu), avec en particulier une température de Curie variant entre 86 (M = Ni) et 220 K (M = Fe) et l'existence d'un phénomène de type cluster-glass en dessous de 35 K lorsque M = Mn. Le chapitre trois de cette thèse se décline en trois parties. La première décrit les conditions de synthèse parfois délicates, notamment dans le choix des températures de recuit, des siliciures R5MSi2, Gd5Si3 et du composé à domaine d'existence Gd3Co2,5 ± xSi1,5 ± y. L'utilisation de la méthode Rietveld pour l'affinement des diffractogrammes de rayons X sur poudre et monocristaux et neutrons a permis de montrer que les composés R5MSi2 adoptent une structure de type Cr5B3 avec la particularité de l'occupation mixte du site 8h par Co et Si à 50 %/50 % et que Gd3Co2,5 ± xSi1,5 ± y adopte une structure de type Er3Ge4 avec des sites mixtes Co/Si en positions 4a et 4c. La seconde partie présente les propriétés magnétiques et magnétocaloriques du siliciure Gd5CoSi2. Ce composé subit une transition ferromagnétique à la température de Curie de 169 K qui s'accompagne d'une variation d'entropie magnétique calculée par l'application de la relation de Maxwell, de -4,7 et 8,7 J kg-1 K-1 pour des variations de champ magnétique respectives de 2 et 5 T. Le troisième volet de ce chapitre décrit les propriétés magnétiques de Nd5CoSi2 et Nd5NiSi2 qui présentent une transition ferromagnétique respectivement à 55 et 44 K. Il décrit également l'affinement de la structure ferromagnétique cantée de Nd5CoSi2 obtenue par des mesures de diffraction neutronique. Il ressort de ces travaux que l'évaluation des matériaux magnétocaloriques par le seul critère de capacité de réfrigération ne mène pas vers les matériaux les plus adaptés à l'application. Il faudrait cibler plus spécifiquement, pour chaque type de cycle de réfrigération envisagé, des critères pragmatiques tels qu'une fenêtre de température d'utilisation autour de la température de Curie ou une valeur de chaleur spécifique optimale afin de mieux guider la recherche de nouveaux matériaux magnétocaloriques.

This thesis draws on David Harvey’s concept of “accumulation by dispossession” and an international political economy (IPE) approach centred on the institutional arrangements and power structures that privilege certain actors and values, in order to critique current capitalist practices of primitive accumulation by the global corporate extractive industry. The thesis examines how accumulation by dispossession by the global extractive industry is facilitated by the “free entry” or “free mining” principle. It does so by focusing on Canada as a leader in the global extractive industry and the spread of this country’s mining laws to other countries – in other words, the transnationalisation of norms in the global extractive industry – so as to maintain a consistent and familiar operating environment for Canadian extractive companies. The transnationalisation of norms is further promoted by key international institutions such as the World Bank, which is also the world’s largest development lender and also plays a key role in shaping the regulations that govern natural resource extraction. The thesis briefly investigates some Canadian examples of resource extraction projects, in order to demonstrate the weaknesses of Canadian mining laws, particularly the lack of protection of landowners’ rights under the free entry system and the subsequent need for “free, prior and informed consent” (FPIC). The thesis also considers some of the challenges to the adoption and implementation of the right to FPIC. These challenges include embedded institutional structures like the free entry mining system, international political economy (IPE) as shaped by international institutions and powerful corporations, as well as concerns regarding ‘local’ power structures or the legitimacy of representatives of communities affected by extractive projects. The thesis concludes that in order for Canada to be truly recognized as a leader in the global extractive industry, it must establish legal norms domestically to ensure that Canadian mining companies and residents can be held accountable when there is evidence of environmental and/or human rights violations associated with the activities of Canadian mining companies abroad. The thesis also concludes that Canada needs to address underlying structural issues such as the free entry mining system and implement FPIC, in order to curb “accumulation by dispossession” by the extractive industry, both domestically and abroad.

Relative humidity influence strongly the indoor air quality and human comfort. Therefore, the hygrothermal behaviour of building materials is an important parameter and there has been a growing interest in studying passive solutions to regulate the indoor relative humidity. Since earth materials have the ability to absorb and release water vapour, they can be used to moderate the amplitude of indoor relative humidity and therefore to improve the indoor air quality and consequently save energy. Many researchers have been focussed on studying the hygrothermal properties of earth building materials, but it is still a scientific challenge to characterize precisely the hygrothermal coupling of those materials. This dissertation focuses on two main objectives, developed and studied in three different porous materials: compacted earth, earth plaster and hemp concrete. The first one is to analyse the effectiveness and the influence of three different drying-methods (oven-drying at 60°C, oven-drying at 105°C and vacuum-drying), and recommend one standard method, for each material studied, since there is no clear guidance to determine the correct dry mass of biobased and earth materials. Complementary to the first objective, it is evaluated the impact of drying/wetting cycles using the same three drying-methods. The second objective is to study the evolution of sorption curves with temperature, for biobased and raw-earth materials. The analysis of the results showed that the first drying process affects the moisture uptake of all the studied materials, from there forward. Oven-drying at 60ºC and vacuum-drying are the methods that produce less impact in the porous network. More specifically, vacuum-drying is the method that allows less impact in the first drying of compacted earth and hemp concrete, and both, vacuum-drying and oven-drying at 60°C, are suitable for a non-impact drying of earth plaster. However, they are not completely efficient in drying earth materials since hysteresis is observed in drying/wetting cycles. Using oven-drying at 105°C it is not observed hysteresis and therefore, this is the most effective method, but it is the method that most presents impact in the porous network after the first drying. Analysing the influence of temperature on the absorption curves, the results show that temperature cycles have no relevant impact on the hygrothermal behaviour of earth materials. Comparing the sorption curves of the three materials plotted at the same temperature, the influence of temperature is more relevant than the materials itself for compacted earth and earth plaster. The same cannot be stated for the hemp concrete.

This master's report addresses the conceptual and material investigations that were explored within my artistic research made at the University of Texas at Austin between 2011 and 2014. These works are a confluence of adornment, sculpture and installation art. These pieces incorporate ancient and contemporary metalworking techniques with raw, organic material. The notion of elegant ornamentation is expanded beyond the body into the adornment of architecture. The potential for transformation and reinvention within found elements is explored within this work. The natural resources I work with have gone through a cycle, which is interrupted when the objects are removed from the earth. I see my process in relationship to alchemical concepts of transmutation. Through manipulation, common matter evolves into precious material. The refined, meticulous craftsmanship conveys a sense of reverence and honor towards the common material. This intervention with the material is an act of preservation and veneration. This work explores my sense of intrigue about the extraordinary potential of mundane materials, and investigates conventional notions of material value.<br>text

Un-doped, Tb3+ as well as Yb3+ doped ZnO nanocrystals with different concentrations of RE3+ (Tb3+, Yb3+) ions were successfully synthesized via sol-gel method to produce rare earth activated zinc oxide nanophosphors. The phosphor powders were produced by drying the precursor gels at 200˚C in ambient air. Based on the X-ray diffraction results, it was found that the pure and RE3+ doped ZnO nanophosphors were highly polycrystalline in nature regardless of the incorporation of Tb3+ or Yb3+ ions. Moreover, the diffraction patterns were all indexed to the ZnO Hexagonal wurtzite structure and belong to P63mc symmetry group. The Raman spectroscopy confirmed the wurtzitic structure of the prepared samples. Elemental mapping conducted on the as prepared samples using Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDX) revealed homogeneous distribution of Zn, O, and RE3+ ions. The high resolution transmission electron microscope (HR-TEM) analyses indicated that the un-doped and RE3+ doped samples were composed of hexagonal homogeneously dispersed particles of high crystallinity with an average size ranging from 4 to 7 nm in diameter, which was in agreement with X-ray diffraction (XRD) analyses. ZnO:Tb3+ PL study showed that among different Tb3+ concentrations, 0.5 mol% Tb3+ doped ZnO nanoparticles showed clear emission from the dopant originating from the 4f-4f intra-ionic transitions of Tb3+ while the broad defects emission was dominating in the 0.15 and 1 mol% Tb3+doped ZnO. Optical band-gap was extrapolated from the Ultraviolet Visible spectroscopy (UV-Vis) absorption spectra using TAUC‟s method and the widening of the optical band-gap for the doped samples as compared to the un-doped sample was observed. The PL study of ZnO:Yb3+ samples was studied using a 325 nm He-Cd laser line. It was observed that the ZnO exciton peak was enhanced as Yb3+ions were incorporated in ZnO matrix. Furthermore, UV-VIS absorption spectroscopic study revealed the widening of the band-gap in Tb3+ doped ZnO and a narrowing in the case of Yb3+ doped ZnO system. X-ray photoelectron spectroscopy demonstrated that the dopant was present in the doped samples and the result was found to be consistent with PL data from which an energy transfer was evidenced. Energy transfer mechanism was evidenced between RE3+ and ZnO nanocrystals and was discussed in detail.<br>Physics<br>M.Sc. (Physics)

The electronic and magnetic structure of the colossal magneto resistance material La1-xSrxMnO3, the high-k and strain tailoring compounds REScO3 (Sm, Gd, Dy) and the multiferroic LuFe2O4 was investigated by means of x-ray spectroscopic techniques. SQUID measurements of La1-xSrxMnO3 (x = 0.125, 0.17, 0.36) were compared with XMCD results. The very good agreement between these two experiments proofs the applicability of the correction factor for the spin magnetic moment and the importance of charge transfer. The magnetic moment measured by SQUID and that determined from XMCD proofs that the magnetic moment is completely localized at the Mn ions for different temperatures and magnetic fields. For x = 0.125 the orbital magnetic moment determined from XMCD corresponds to the structural changes in the phase diagram. Additionally the measured orbital moments correspond to anomalies in magnetization versus temperature curves. The magnetic and electronic structure of the rare earth scandates (SmScO3, GdScO3 and DyScO3) were investigated by means of XPS, XES, XAS, SQUID and neutron powder diffraction. The magnetic measurements reveal antiferromagnetic coupling at low temperatures in agreement with neutron diffraction data. With XAS and XES at the O K-edge in comparison with band structure calculations of the unoccupied oxygen states, the band gaps of REScO3 were determined and it was found that these values are corresponding to the Sc-O mean distances. The electronic and magnetic structure of LuFe2O4 was presented. The valence state of Fe ions was determined to 50% divalent and 50% trivalent by XPS of Fe 2p and 3s levels. The big orbital magnetic moment found by XMCD could explain a discrepancy between the magnetic measurements and the spin configuration, which was confirmed by XMCD.

Un-doped, Er3+ doped (TiO2:Er3+) as well as Er3+/Yb3+ co-doped (TiO2:Er3+/Yb3+) nanocrystals with different concentrations of RE3+ (Er3+, Yb3+) were successfully synthesized using the sol-gel method. The powder X-ray diffraction (XRD) spectra revealed that all undoped and doped samples remained in anatase after annealing at 400°C. The presence of RE3+ ions in the TiO2 host lattice was confirmed by conducting elemental mapping on the samples using Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDX), which was in agreement with X-ray photoelectron spectroscopy (XPS) results. Transmission electron microscope (TEM) images approximated particle sizes of the samples to be between 1.5 – 3.5 nm in diameter and this compares well with XRD analyses. Phonon quantification in TiO2 was achieved using Fourier transform infrared (FT-IR) spectroscopy. Optical bandgap from Ultraviolet/Visible/Near-Infrared was extrapolated from Kubelka-Munk relation and the narrowing of the bandgap for the doped samples as compared to the undoped sample was observed. The photoluminescence PL study of the samples revealed two emission peaks attributed to direct band-gap and defect-related emissions. A laser beam with 980 nm wavelength was used to irradiate the samples, and the displayed emission lines of the TiO2: Er3+ in the visible region of the electromagnetic spectrum confirmed up-conversion luminescence. Enhancement of up-conversion luminescence intensity due to Yb3+ co-doping was observed, indicating an efficient energy transfer process from the sensitizer Yb3+ to the activator Er3+.<br>Physics<br>M. Sc. (Physics)

碩士<br>國立東華大學<br>財經法律研究所<br>102<br>China plays an important role of rare earth producer. From the Panel procedure of dispute settlement mechanism, they have not eliminated quantitative restriction regulations, even losing law suit of the Appellate Body procedure. After the Raw Material Case, in fact, dispute settlement mechanism has not solved the similar restrictive measure as result of Rare Earth Cases. From cases of Raw Material and Rare Earth, the issues in action are consisting of two sections: China's Protocol of Accession (Working Party Report included) and GATT. From China's Protocol of Accession, the issue is in Article 11.3," Taxes and Charges Levied on Imports and Exports "; from GATT, the issues are in Article 11.1, " General Elimination of Quantitative Restrictions ," and Article 20," General Exceptions. " Although in Raw Material Case, the Plaintiff raises the issue of Article 10.3(a)," Publication and Administration of Trade Regulations" of GATT, the Rare Earth Case doesn't re-exist. Besides, this paper is going to compare Raw Material Case and Rare Earth Case from the past in order to arrange the using standard of China's Protocol of Accession and GATT. Even though China is losing the suit from Raw Material Case and the Appellate Body procedure of Rare Earth Case, and all quantitative restriction regulations violate China's Protocol of Accession and GATT, there are still various regulations could restrict exporting rare earth productions. This paper is going to examine the legality of regulations and introduce the "Law of the People's Republic of China on Rare Earth Regulations (draft) ". Furthermore, basing "Law of the People's Republic of China on Energy Conservation," China could restrict the exportation of rare earth products or not and examine its legality as well. Finally, it includes predict the Appellate Body ruling on behalf of the conclusions as a result, thereby making the consistency of existing WTO rules and regulations applicable to the relevant standards.