The thesis is primarily concerned with the design, construction and preliminary commissioning of a novel polarimeter for full three-dimensional analysis of electron spin polarisation. The polarimeter is described in detail, together with the theoretical basis for its operation. Studies of an amorphous ferromagnetic alloy, Co66Fe4Ni1B14Si15, and its application as a secondary standard are presented. Finally, a design study of a GaAs polarised electron source, capable of providing both longitudinal and transverse polarisations, is detailed.

Plastic deformation of metals and alloys are invariably accompanied by the development of texture. The origin of texture is attributed to the deformation micro-mechanisms associated with processing. The face-centered cubic (FCC) metals and alloys are known to exhibit two distinct types of textures when subjected to large strain rolling deformation, namely, (i) Cu-type texture, commonly seen in high/medium stacking fault energy (SFE) materials, (ii) Bs-type texture in low SFE materials. The circumstances that could result in the formation of Bs-type texture in low SFE materials still remains an open question and no definite mechanism has been uniquely agreed upon. Apart from the SFE, grain size could also influence the deformation mechanism and hence the deformation texture. It is well known that in materials with grain sizes less than 100 nm (referred to as nano-crystalline materials), the microstructures contain large fraction of grain boundaries. This subsequently introduces a variety of deformation mechanisms in the microstructure involving grain boundary-mediated processes such as grain boundary sliding and grain rotation, in addition to slip and twinning. A clear understanding of texture evolution in nano-crystalline materials, particularly at large strains, is a topic that remains largely unexplored. The present work is an attempt to address the aforementioned issues pertaining to the evolution of deformation texture, namely, (i) the effect of SFE and (ii) the effect of grain size, in FCC metals and alloys. Nickel-cobalt alloys are chosen as the model system for the present investigation. The addition of cobalt to nickel leads to a systematic reduction of SFE as a function of cobalt content. In this thesis, three alloys of Ni-Co system have been considered, namely, nickel – 20 wt.% cobalt, nickel – 40 wt.% cobalt and nickel – 60 wt.% cobalt. For a comparison, pure nickel has also been subjected to similar study. Chapter 1 of the thesis presents a detailed survey of literature pertaining to the evolution of rolling textures in FCC metals and alloys, and chapter 2 includes the details of the experimental techniques and characterization procedures, which are commonly employed for the entire work. Chapter 3 addresses the effect of stacking fault energy on the evolution of rolling texture. The materials subjected to study in this chapter are microcrystalline Ni-Co alloys. The texture evolution in Ni-20Co is very similar to pure Ni, and a characteristic Cu-type rolling texture is observed. The evolution of texture in these materials is primarily attributed to the intense dislocation activity throughout the deformation stages. In Ni-40Co, a medium SFE material, the rolling texture was predominantly Cu-type up to a strain of ε = 3 (95% thickness reduction). However, beyond this strain level, namely at ε = 4 (98%), the texture gets transformed to Bs-type with orientations maxima predominantly close to Goss ({110} <001>) position. Simultaneously, the Cu component which was dominant until 95% reduction has completely disappeared. The analysis of microstructures indicate that deformation is mostly accommodated by dislocation slip up to 95%, however, at ε > 3, Cu-type shear bands get initiated, preferably in the Cu-oriented ({112} <111>) grains. The sub-grains within the shear bands show preferred orientation towards Goss, which indicates that the Cu component should have undergone transformation and resulted in high fraction of Goss component. In Ni-60Co alloy, Bs-type texture forms in the early stages of deformation (ε ~ 0.5) itself and further deformation results in strengthening of the texture with an important difference that the maximum in orientation distribution has been observed at a location close to Goss component, rather than at exact Bs-location. The development of Bs-type texture is accompanied by the complete absence of Cu and S components. Extensive EBSD analyses show that the deformation twinning gets initiated beyond 10% reduction and was found extensively in most of the grains up to 50% reduction. At higher strains, tendency for twinning ceases and extensive shear banding is observed. A non-random distribution of orientations close to Goss orientation was found within the shear bands. The near-Goss component in the Ni-60Co alloy can be explained on the basis of deformation twinning and shear banding. Thus, a reasonable understanding of the deformation texture transition in the extreme SFE range has been developed. In chapter 4, the effect of fine grain size on the evolution of rolling texture has been addressed. Nanocrystalline (nc) nickel-cobalt alloys with a mean grain size of ~20 nm have been prepared by pulse electro-deposition method. For a comparison, nc Nickel (without cobalt) with similar grain size has also been deposited. For all the materials, a weakening of the initial fiber texture is observed in the early stage of room temperature rolling (ε ~ 0.22). A combination of equiaxed grain microstructure and texture weakening suggests grain boundary sliding as an operative mechanism in the early stage of rolling. At large strain (ε = 1.2), Ni-20Co develops a Cu-type texture with high fractions of S and Cu components, similar to pure Ni. The texture evolution in Ni-40Co and Ni-60Co alloys is more towards Bs-type. However, the texture maximum occurs at a location 10° away from the Goss. The evolution of Cu and S components in nc Ni-60Co alloy takes place simultaneously along with the α-fiber components during rolling. Microstructural investigation by TEM indicates deformation twinning to be more active in all the materials up to 40% reduction. However, no correlation could be drawn between the texture evolution and the density of twins. The deformation of nc Ni-20Co alloy, is also accompanied by significant grain growth at all the stages of rolling. The increase in grain size, subsequently, renders the texture to be of Cu-type. However, Ni-40Co and Ni-60Co alloys show high grain stability. The absence of strain heterogeneities such as shear bands, and the lack of significant fraction of deformation twins indicate that the observed Bs-type texture could be due to planar slip. The increase in deformation beyond 70% reduction caused a modest reduction in the intensity of deformation texture. The microstructural observation indicates the occurrence of restoration mechanisms such as recovery/ recrystallization at large strains. The overall findings of the investigation have been summarized in chapter 5. The deformation mechanism maps relating stacking fault energy with amount of strain and with grain size are proposed for micro- and nano- crystalline materials respectively.

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Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Description based on contents viewed June 2, 2008; title from title screen. Includes bibliographical references (p. 36).

Thesis (Ph. D.)--University of Alabama at Birmingham, 2008. / Additional advisors: Yogesh K. Vohra, Xu Feng, Jack E. Lemons, Timothy M. Wick. Description based on contents viewed July 8, 2009; title from PDF t.p. Includes bibliographical references.

Le passage de la technologie au slurry à celle au fil diamanté sur les machines à fils de découpe des blocs de silicium en wafers est motivé par des enjeux économiques et environnementaux. Depuis peu, cette transition de technologie dans l’industrie photovoltaïque s’est accélérée avec la commercialisation d’une nouvelle génération de machines. Afin de profiter de cette transition et de son avenir prometteur, Thermocompact s’est engagé dans le développement de fils diamantés. Le procédé choisi pour le dépôt des particules et du liant métallique enchâssant les particules à la surface du fil est la voie électrochimique. Les premiers essais de fabrication de fils diamantés ont révélé un manque de maîtrise du procédé d’élaboration et un échec pour atteindre les caractéristiques techniques demandées pour la découpe du silicium. Les travaux de cette thèse se sont donc axés dans un premier temps sur la relation entre le bain électrolytique, les conditions de dépôt et ses propriétés, puis sur le comportement des particules à la fois dans le bain jusqu’à leur incorporation à la surface du fil. L’étude s’est poursuivie sur la relation complexe entre les caractéristiques du fil produit, la matière à découper et la machine de découpe utilisée (design, paramètres utilisés). Ce travail a abouti à produire un fil diamanté de diamètre 70µm conforme aux exigences des usineurs pour la découpe à l’échelle industrielle du silicium monocristallin sur des machines de nouvelle génération. Les résultats de découpe vont permettre désormais de démarcher des clients potentiels dans l’industrie photovoltaïque. / The change of technology from slurry to diamond wires in the wafer slicing machines is motivated by economic and environmental issues. Only recently, this transition of technology in the photovoltaic industry has ramped up with the commercialization of a new generation of wafering machines. So as to take advantage of this situation, Thermocompact has launched the development of diamond wires. The selected process is an electrochemical codeposition of metal and diamond particles embedded on the wire surface.The first tests of diamond wire production have shown a lack of process control and a failure to reach the technical characteristics requested by its use. The studies in this thesis are based on the relationship between the electrolytic bath, the coating conditions and the coating properties, then on the behavior of particles both in the bath and up to their incorporation on the wire surface. The researches continued afterwards on the complex link between the characteristics of diamond wire, the material to slice and the machine used for slicing (design, recipe). This work has succeeded in defining a diamond wire with a diameter of 70µm in compliance with customer requirement for the industrial slicing of single crystalline silicon with the new generation of machines. These results will be now used for prospecting new customers in the photovoltaic industry.

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Submitted by Kilvya Braga (kilvyabraga@hotmail.com) on 2018-04-23T10:51:37Z No. of bitstreams: 1 EMYDIO CLEMENTE DE SOUSA NETO - DISSERTAÇÃO (PPGEM) 2015.pdf: 5264287 bytes, checksum: 48883828373d3daac0f65ee6e1ef7809 (MD5) / Made available in DSpace on 2018-04-23T10:51:37Z (GMT). No. of bitstreams: 1 EMYDIO CLEMENTE DE SOUSA NETO - DISSERTAÇÃO (PPGEM) 2015.pdf: 5264287 bytes, checksum: 48883828373d3daac0f65ee6e1ef7809 (MD5) Previous issue date: 2015-07-31 / O desgaste prematuro de conjuntos e componentes industriais, bem como de uma infinidade de outros segmentos, representa um grande fator para a redução da eficiência operacional de um equipamento, provocando assim, um aumento das perdas, e consequentemente, em altas despesas com manutenção e reposição de componentes mecânicos. Este trabalho aborda uma análise comparativa entre a resistência ao desgaste de martelos trituradores de baterias recuperados por três ligas a base de cobalto (Stellite 1, 6 e 21), bem como dois processos de deposição: os processos ao Arco Elétrico com Eletrodo Revestido (SMAW) e ao Arco Plasma Transferido com adição de Pó (PTA-P). Os martelos trituradores são originalmente confeccionados em aço inoxidável AISI 316 L sem nenhum recobrimento. Além da avaliação da resistência ao desgaste no próprio meio de trabalho foram realizados ensaios de microdureza, análises microestruturais via microscopia ótica, e eletrônica de varredura e, análise de diluição com o objetivo de caracterizar e consolidar a pesquisa para que se tenha o estudo comparativo da melhor liga e melhor processo de deposição. Os resultados demostraram que a melhor condição testada foi aquela que empregou a liga Stellite 6 depositadas pelo processo PTA-P. Essa condição apresentou a menor perda de massa nos ensaios de resistência ao desgaste, enquanto que a condição menos favorável foi verificada para os depósitos executados com a liga Stellite 1 utilizando o mesmo processo de deposição. A diluição média das ligas depositadas pelo processo SMAW foi 3,7 vezes maior do que a média apresentada utilizando o processo PTA-P. Os maiores valores de microdureza foram aqueles apresentados pelo revestimento executados com a liga Stellite 1 com maior teor de C, e esta liga, proporcionou um maior número de destacamento dos revestimentos. A microestrutura dos depósitos executados pelo processo PTA-P apresentou-se mais refinada quando comparada com aquelas depositadas pelo processo SMAW. / The premature wear sets and industrial components, as well as many of other segments, is a big factor for reducing operational efficiency of equipment, thus causing an increase in losses, and consequently in high cost of maintenance and replacement of mechanical components. This work presents a comparative analysis of the wear resistance of AISI 316 L steel automotive batteries crushers hammers repaired by welding process using three cobalt-based alloys: Stellite 1, 6 and 21, as well as, two welding deposition process: Shielded Metal Arc Welding (SMAW) and Plasma Transferred Arc with addition powder (PTA-P). Crushers hammers are originally made of stainless steel AISI 316 L with no coating. Besides the “in situ” wear resistance evaluation microhardness tests, microstructure and dilution analysis by optical microscopy and scanning electron were done to characterize and consolidate research in order to have a comparative study of best league and better deposition process. The results showed that the best alloy was Stellite 6 using the PTA-P process, which had the lowest mass loss in wear resistance tests, while the less favorable condition was for deposits made with the alloy Stellite 1 using the same deposition welding process. The average dilution of the alloys deposited by the SMAW process was 3.7 times higher than the average using the PTA-P process. The highest microhardness values were presented by Stellite 1 alloy deposit, with higher C content, which also provided a greater number of coating detachment. The deposits made by the process PTAP showed a more refined microstructure when compared to those deposited by the SMAW process