O processo de soldagem por resistência de chapas galvanizadas automotivas é parte indispensável na concepção de uma carroceria de automóvel. Utilizado na união das chapas metálicas que formam um veículo, a grande importância deste processo deve-se basicamente ao fato de não agregar peso à carroceria, ter um desempenho satisfatório em relação à qualidade e produtividade nas linhas de montagem e ainda não onerar o custo final do produto, visto que seu custo de operação pode ser considerado baixo de modo geral. As variáveis específicas deste processo demandam atenção permanente quanto aos parâmetros dos equipamentos, a limpeza e a manutenção, a refrigeração dos eletrodos, a dressagem e a eliminação da camada de latão formada na superfície de contato entre o eletrodo e a chapa. A durabilidade e o desgaste do eletrodo estão ligados basicamente a estes cuidados, podendo ainda gerar ganhos em produtividade e qualidade do ponto além de reduzir o nível de problemas durante e após a soldagem da chapa. Durante a realização deste trabalho, procurou-se avaliar o comportamento do eletrodo fabricado através da liga Cu-Zr, o desgaste do eletrodo em relação ao número de pontos soldados, sua relação com a dureza e variação de temperatura durante o processo, os cuidados que podem retardar o desgaste e a microestrutura do material ao longo do número de pontos e do desgaste deste eletrodo. / The resistance welding process of automotive galvanized steel is an indispensable part in the design of a body car. Used in the union of the metal plates that form a vehicle, the great importance of this process is basically due to the fact not add weight to the body, have a satisfactory performance in relation to quality and productivity in assembly lines and still does not burden the final cost the product, the operating cost can be considered low in general. The specific variables this process require constant attention regarding the parameters of the equipment, cleaning and maintenance, cooling the electrodes, the dressing and the elimination of the brass layer formed on the contact surface between the electrode and the plate. The durability and the electrode wear are basically related to such care, and may generate gains in productivity and quality of point and reduce the level of problems during and after welding the plate. During this work, we tried to evaluate the electrode manufactured by Cu-Zr alloy, the electrode wear in relation to the number of welding points, their relationship with the hardness and temperature variation during the process, the care can slow the wear and the microstructure of the material during the number of welding points and the wear of this electrode.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16798号 / 工博第3519号 / 新制||工||1532(附属図書館) / 29473 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 白井 泰治, 教授 酒井 明, 教授 杉村 博之 / 学位規則第4条第1項該当

Philosophiae Doctor - PhD / The domesticated apple (Malus x domestica Borkh.) has been distributed into diverse climatic conditions worldwide for commercial production of fruit. Apple trees need exposure to cold temperatures, referred to as chill unit (CU) accumulation during winter, in order for budbreak to occur promptly and uniformly after winter. In warmer production areas the application of dormancy breaking chemicals has enabled successful production of high chilling requiring apple cultivars in suboptimal environmental conditions. In the Western Cape region of South Africa it is common orchard practice to apply dormancy breaking chemicals after winter in order to stimulate vegetative growth. If this is not done prolonged dormancy symptoms (PDS) are experienced which include extended rest, less synchronised breaking of buds and reduced branching. An increasing awareness of both global warming and the negative effects associated with the use of chemical sprays (for both pest and disease resistance and growth regulation) has resulted in the need to breed cultivars better adapted to current and future environmental conditions. The breeding of new cultivars using conventional breeding methods is a time consuming process, especially in perennial tree species with a long juvenile phase such as apple. The implementation of marker-assistedbreeding (MAB) and selection (MAS) will enable the selection of favourable genotypes at a very early seedling stage. Although markers linked to genes involved in disease resistance for a variety of known apple pathogens have been identified and are already in use in breeding programs, the genetic determinants of dormancy related characteristics residing within the bud itself iii (endodormancy) are poorly understood. This hampers the genetic improvement of such characters. Although this study focused on time of initial vegetative budbreak IVB, there are various other characteristics that can be associated with dormancy, such as position and number of budbreak and budbreak duration.

Dans cette thèse, nous avons étudié la conception, le prototypage et la caractérisation de microsystèmes photovoltaïques à concentration à base de cellules solaires Cu(In,Ga)Se2. L'objectif est de réduire l'utilisation de matériaux rares en utilisant la concentration de la lumière, et bénéficier des effets de la miniaturisation, comme la dissipation de la chaleur et des pertes résistives inférieurs. Tout d'abord, la conception optique des systèmes à concentration sur la base des microlentilles sphériques est présentée. À l'aide d'un logiciel de tracés de rayon Zemax OpticStudio, nous avons évalué la meilleure combinaison d'éléments, l'épaisseur et les rayons de courbure des lentilles, ainsi que les tolérances de fabrication et de positionnement du système. Un système optique de 1 mm d'épaisseur avec un rapport géométrique de 100 et une tolérance angulaire de +/- 3,5 ° a été conçu. D'autre part, des procédés de fabrication ont été créés et optimisés pour fabriquer un prototype de 5x5 cm² avec 2500 microcellules. Le meilleur mini-module a montré un facteur de concentration de 72x avec une augmentation en valeur absolue de l'efficacité de + 1,6%. Ensuite, des études numériques et expérimentales ont été réalisées sur des systèmes basés sur des concentrateurs luminescents (LSC) et des concentrateurs paraboliques (CPC). Les LSC ont montré un facteur de concentration faible et souffraient de problèmes de répétabilité tandis que les CPC sont une solution très efficace, mais très difficile à fabriquer à l¿échelle du micron. Enfin, nous avons développé un code MATLAB pour estimer l'énergie produite des systèmes conçus, pour évaluer la pertinence des choix technologiques futurs. / In this thesis, we studied the design, prototyping and characterization of micro-concentrated photovoltaic systems based on Cu(In,Ga)Se2 solar cells. The objective is to reduce the use of rare materials using the concentration of light, and benefit from the effect of miniaturization such as heat dissipation and lower resistive losses. First, the optical design of 1D and 2D concentrating systems based on spherical microlenses is presented. Using a ray-tracing software Zemax OpticStudio, we evaluated the best combination of elements, thickness and radii of curvature of the lenses, as well as the tolerances of fabrication and positioning of the system. An optical system of 1 mm thickness with a geometrical ratio of 100 and an angular tolerance of +/- 3.5° has been designed. Second, fabrication processes have been created and optimized to fabricate a 5x5 cm² prototypes with 2500 microcells. The best mini-module showed a concentration factor of 72x with an absolute increase of the efficiency of +1.6%. Third, numerical and experimental studies have been performed on concentrating systems based on Luminescent Solar Concentrators (LSC) and Compound Parabolic Concentrators (CPC). The LSC showed a low concentration factor and suffered from repeatability issues while the CPC is a very efficient solution but its specific geometry makes it difficult to fabricate at the micron scale. Finally, we developed a MATLAB code to estimate the producible energy of the designed systems, in order to evaluate the relevance of future technological choices that will be made.

No description available.

No description available.

Aluminum was deposited onto both Teflon AF and Parylene AF surfaces by chemical vapor deposition of trimethylaluminum. This work shows that similar thin film (100 Angstroms) aluminum oxide adlayers form on both polymers at the low temperature dosing conditions used in the studies. Upon anneal to room temperature and above, defluorination of the polymer surfaces increased and resulted in fluorinated aluminum oxide adlayers; the adlayers were thermally stable to the highest temperatures tested (600 K). Angle-resolved spectra showed higher levels of fluorination toward the polymer/adlayer interface region. Copper films were also deposited at low temperature onto Teflon AF using a copper hexafluoroacetylacetonate-cyclooctadiene precursor. Annealing up to 600 K resulted in the loss of precursor ligands and a shift to metallic copper. As with aluminum adlayers, some polymer defluorination and resulting metal (copper) fluoride was detected. Parylene AF and polystyrene films surfaces were modified by directly dosing with water vapor passed across a hot tungsten filament. Oxygen incorporation into polystyrene occurred exclusively at aromatic carbon sites, whereas oxygen incorporation into parylene occurred in both aromatic and aliphatic sites. Oxygen x-ray photoelectron spectra of the modified polymers were comparable, indicating that similar reactions occurred. The surface oxygenation of parylene allowed enhanced reactivity toward aluminum chemical vapor deposition. Silicon-carbon (Si-Cx) films were formed by electron beam bombardment of trimethylvinylsilane films which were adsorbed onto metal substrates at low temperatures in ultra-high vacuum. Oxygen was also added to the films by coadsorbing water before electron beam bombardment; the films were stable to more than 700 K, with increasing silicon-oxygen bond formation at elevated temperatures. Copper metal was sputter deposited in small increments onto non-oxygenated films. X-ray photoelectric spectra show three-dimensional copper growth (rather than layer-by-layer growth), indicating only weak interaction between the copper and underlying films. Annealing at elevated temperatures caused coalescence or growth of the copper islands, with spectra indicating metallic copper rather than copper oxide.

<p>Cu-zeolites have received renewed attention as catalytic materials that facilitate partial methane oxidation (PMO) to methanol, with a variety of mononuclear, binuclear, and multinuclear Cu active site motifs that have been proposed in prior literature. Our approach to more precisely identify and probe the Cu structures that activate O₂ and reduce in CH₄relies on the synthesis of model supports with varying composition and well-defined Cu speciation, which also facilitates connections between experimental data and theoretical models. Chabazite (CHA) zeolites are high-symmetry frameworks that contain a single lattice tetrahedral site (T-site), in which Cu²⁺ ions exchange at paired Al sites in a six-membered ring (6-MR) while CuOH⁺ species exchange at isolated 6-MR Al sites, the latter of which can react to form binuclear O/O₂-bridged Cu structures. In this work, Cu-CHA zeolites were synthesized to contain predominantly Cu²⁺ (Z₂Cu) or CuOH⁺ (ZCuOH) species of varying density, or a mixture of Z₂Cu and ZCuOH sites. Z₂Cu and ZCuOH sites were quantified by titration of residual Brønsted acid sites with NH₃, which respectively exchange with 2:1 or 1:1 H⁺:Cu²⁺ stoichiometry. Stoichiometric PMO reaction cycles on Cu-zeolites involved high-temperature (723 K) activation in O₂, and then moderate-temperature (473 K) reduction in CH₄ and treatment in H₂O (473 K) to extract CH₃OH. <i>I</i><i>n-situ</i> UV-Visible spectroscopy under oxidizing (O₂, 723 K) and reducing (CO, 523 K; CH₄, 473 K; He, 723 K) conditions detected the presence of mononuclear and binuclear Cu site types, while <i>in-situ</i> Cu K-edge X-ray absorption spectroscopy after such treatments was used to quantify Cu(I) and Cu(II) contents and <i>in situ</i> Raman spectroscopy was used to identify the Cu structures formed. ZCuOH, but not Z₂Cu sites, are precursors to binuclear O/O₂-bridged Cu sites that form upon O₂ activation and subsequently produce methanol after stoichiometric PMO cycles, at yields (per total Cu) that increased systematically with ZCuOH site density. The fraction of Cu(II) sites that undergo auto-reduction in inert at high temperatures (He, 723 K) is identical, within experimental error, to the fraction that reduces in CH₄ at temperatures relevant for PMO (473 K), providing a quantitative link between the binuclear Cu site motifs involved in both reaction pathways and motivating refinement of currently postulated PMO reaction mechanisms. These Cu-CHA zeolites were also studied for other redox chemistries including the selective catalytic reduction (SCR) of NO_x with NH₃. <i>In situ </i>UV-Visible and X-ray absorption spectroscopies were used to monitor and quantify the transient partial reduction of Cu(II) to Cu(I) during exposure to NH₃ (473 K), in concert with titration methods that use NO and NH₃ co-reductants to fully reduce all Cu(II) ions that remain after treatment in NH₃ alone to the Cu(I) state, providing quantitative evidence that both Z₂Cu and ZCuOH sites are able to reduce in NH₃ alone to similar extents as a function of time. These findings provide new insight into the reaction pathways and mechanisms in which NH₃ behaves as a reductant of mononuclear Cu(II) sites in zeolites, which are undesired side-reactions that occur during steady-state NO_x SCR and that often unintendedly result in Cu(II) reduction prior to spectroscopic or titrimetric characterization. Overall, the strategy in this dissertation employs synthetic methods to control framework Al density and arrangement in zeolite supports to emphasize extra-framework Cu site motifs of different structure and at different spatial densities, and to interrogate these model materials using a combination of <i>in situ</i> spectroscopic techniques together with theory, in order to elucidate active site structure and proximity requirements in redox catalysis. This work demonstrates how quantitative reactivity and site titration data, brought together with an arsenal of tools available in contemporary catalysis research, can provide detailed mechanistic insights into transition metal-catalyzed redox cycles on heterogeneous catalysts.</p>

A new materials system of a single layered Co(W) barrier/liner coupled with a Cu(Mn) alloy seed was investigated. Atom probe tomography visualized the sub-nanoscale structure of Cu(Mn)/Co(W) system, and thereby revealed Cu diffusion behavior of Co(W). Grain boundaries of Co were found to be the diffusion path, and successfully stuffed by W. Mn in Cu(Mn) also segregated to stuff the grain boundaries of Co. Combination of these two additives enabled high barrier property against Cu diffusion of Cu(Mn)/Co(W). Foreseeing tiny and high-aspect-ratio Cu interconnect features, Cu(Mn)/Co(W) was fabricated by ALD/CVD processes. To maximize the performance, minor impurities of the film incorporated from the ligand of the precursors were controlled by precursor selection. Thin, conformal, and smooth films were finally demonstrated onto a trench substrate.

Aufgrund von guten Eigenschaften als Kupferdiffusionsbarriere und guter elektrischer Leitfähigkeit könnte sich Ruthenium und Ruthenium basierte Legierungen als Kupferdiffusionsbarriere eignen. Auf eine theoretische Aufarbeitung von Elektromigrationsmechanismen und in der Praxis eingesetzte Elektromigrationsteststrukturen folgen beschleunigte elektrische Elektromigrationstestergebnisse. Es konnte gezeigt werden, dass das System Kupfer, Ruthenium, Tantalnitrid Elektromigrationsstabiler als das konventionelle System Kupfer, Tantal, Tantalnitrid ist.:1 Einleitung 1 2 Stand der Forschung 2 2.1 Migrationsarten 2 2.2 Praktische Formulierung des Mechanismus der Elektromigration 2 2.3 Transportpfade der Elektromigration 3 2.4 Einflüsse auf die Elektromigration 4 2.4.1 Übersicht 4 2.4.2 Quereinfluss des mechanischen Stresses (Blech-Effekt) 5 2.4.3 Quereinfluss durch thermisch induziertem Stress 6 2.4.4 Materialwanderung aufgrund eines Temperaturgradienten 8 2.4.5 Einfluss des Leiterbahnmaterials (Legierung) 8 2.4.6 Einflüsse der Mikrostruktur 8 2.4.7 Einflüsse der Passivierung der Leiterbahnen 9 3 Theoretische Untersuchungen 9 3.1 Untersuchte Elektromigrationsteststrukturen 9 3.1.1 NIST-Struktur 9 3.1.2 Untersuchungen mithilfe der NIST-Struktur 10 3.1.3 Schlitz-Struktur 11 3.1.4 Bestimmung des Flächenwiderstandes RF = r=A der Schlitz-Struktur 12 3.1.5 Schlitzlängenänderungsgeschwindigkeit der Schlitz-Struktur 13 3.1.6 Prinzipielles Vorgehen zur Bestimmung der Schlitzlängenänderungsgeschwindigkeit als Kriterium für Elektromigrationsbeständigkeit 14 3.1.7 Blech-Struktur 15 3.1.8 Untersuchungen mithilfe der Blechstruktur 16 3.2 Vergleich der untersuchten Elektromigrationsteststrukturen 16 4 Experimentelle Untersuchungen 17 4.1 Beschreibung des Versuchsaufbaus 17 4.2 Evaluation der Messvorraussetzungen 18 4.2.1 Temperaturbeständigkeit der Messanordnungen 18 4.2.2 Oxidationsbeständigkeit der Schlitz- & Blechstruktur 19 4.2.3 Vernachlässigung Kupfer- und Leitungswiderstände 21 II 4.2.4 Untersuchungen bei verschiedenen Stromdichten (Schlitzstruktur) 22 4.2.5 Evaluation der günstigsten Schlitzlänge für Klassifikationstests 24 4.3 Untersuchungen an der NIST-Struktur 26 4.3.1 Ergebnisse 26 4.3.2 Probleme beim Versuchsaufbau und mögliche Lösungen 27 4.4 Untersuchungen an der Schlitz-Struktur 28 4.4.1 Bestimmung des Flächenwiderstands RF 28 4.4.2 Bestimmung der Schlitzlängenänderungsgeschwindigkeit 28 4.4.3 Optische Probenauswertung mittels TEM und FIB-Schnitt 30 4.4.4 Vergleich von Ta mit Ru und Ru0;95Mn0;05 31 4.4.5 Probleme beim Messaufbau und mögliche Lösungen 31 4.5 Untersuchungen an der Blechstruktur 33 4.5.1 Untersuchungen bei verschiedenen Stromdichten 33 4.5.2 Untersuchung bei verschiedenen Temperaturen 35 4.5.3 Probleme bei den Messungen und mögliche Lösungen 36 5 Zusammenfassung 37 6 Literaturverzeichnis 38