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Mikrostruktura, její stabilita a únavové vlastnosti ultrajemnozrnné mědi připravené metodou ECAP / Microstructure, it´s Stability and Fatigue Properties of Ultra-Fine Grained Copper Prepared by ECAP MethodNavrátilová, Lucie January 2012 (has links)
This work deals with fatigue properties and stability of microstructure of ultrafine-grained (UFG) copper prepared by severe plastic deformation by means of equal channel angular pressing (ECAP) method. The effect of different fatigue loading regimes and thermal exposition on microstructural changes was investigated and the fatigue lifetime curves were experimentally determined. The research attention was focussed on localization of cyclic plastic deformation and fatigue crack initiation in UFG structure. Experimental results indicate that after stress-controlled fatigue loading (both symmetrical and asymmetrical) the microstructure remains ultrafine; no grain coarsening was observed. Contrary to this, strain-controlled fatigue loading results in formation of bimodal structure. Grain coarsening was observed also after thermal exposition at 250 °C for 30 minutes. Annealing at lower temperatures does not result in grain coarsening or development of bimodal structure. Fatigue loading results in development of surface relief in form of cyclic slip markings. Their density, distribution and shape differ for particular fatigue loading regimes. Differences in crack initiation mechanism in low- and high-cycle fatigue region were found. Nevertheless, the characteristic feature for all loading regimes was stability of UFG microstructure in the region of cyclic slip bands and fatigue cracks.
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Al-3.5Cu-1.5Mg-1Si alloy and related materials produced by selective laser meltingWang, Pei 06 October 2018 (has links)
Selective laser melting (SLM) is an additive manufacturing technology. In this thesis, a heat-treatable Al-3.5Cu-1.5Mg-1Si alloy and related materials (composites and hybrid materials) have been successfully fabricated by selective laser melting and characterized in terms of densification, microstructure, heat treatment, mechanical properties as well as tribological and corrosion behavior. Firstly, the fully dense SLM Al-Cu-Mg-Si alloy was fabricated by SLM successfully. The alloy shows a higher yield strength than SLM Al-12Si alloy, and lower wear resistance and corrosion rate than commercial 2024 alloy before and after T6 heat treatment. Secondly, with the aim of designing new alloy compositions and to examine the phases and microstructures of SLM Al-Cu alloys and to correlate their microstructures with the observed mechanical properties, Al-xCu (x = 4.5, 6, 20, 33 and 40 wt. %) alloys have been synthesized in-situ by SLM from mixtures of Al-4.5Cu and Cu powders. The results indicate that the insufficient Cu solute diffusion during the layer-by-layer processing results in an inhomogeneous microstructure around the introduced Cu powders. With increasing Cu content, the Al2Cu phase in the alloys increases improving the strength of the material. These results show that powder mixtures can be used for the synthesis of SLM composites but the reaction between the matrix and the second-phase should be considered carefully. Thirdly, the TiB2/Al-Cu-Mg-Si composite was also designed and fabricated successfully by SLM and it shows a higher strength than the unreinforced SLM alloy before and after T6 heat treatment. Finally, an Al-12Si/Al-3.5Cu-1.5Mg-1Si hybrid with a good interface was fabricated successfully. This hybrid alloy shows a good yield strength and elongation at room temperature, indicating an effective potential of selective laser melting in the field of hybrid manufacturing.
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Development of Novel (Cu,Fe)3O4 Coatings for AISI 441 Solid Oxide Cell Interconnects : Coating optimization and long-term studyLarby, Line January 2020 (has links)
As current environmental challenges are gaining increased attention, development of clean energy solutions is becoming one of the essential strategies to keep within the boundaries of established environmental policies. Solid oxide cell (SOC) technology can provide clean energy conversion and storage when hydrogen is the energy carrier. The high total energy conversion efficiency resulting from the high operation temperature of SOCs make the technology promising, but material costs must be reduced to make it commercially viable. Therefore, this thesis aims to study the long- term performance of a novel cost-optimized cell interconnect at 650 and 850 °C. At high temperatures, chromium evaporation from the interconnect result in electrode poisoning, which may be mitigated by application of a protective coating. The studied interconnect is an AISI 441 steel with some different pre-oxidized copper and iron spinel coatings. Sample analysis was made mainly with scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and X-ray diffraction. It was found that the most promising pre-oxidation treatment was 24 h at 750 °C and that chromium migration was restrained at 650 °C long-term treatment but not at 850 °C where it wasfound available for evaporation at the surface. / När samtida milljöutmaningar får ökad uppmärksamhet blir gröna energilösningar en av de viktigaste strategierna för att hålla sig inom satta gränser från etablerade miljöriktlinjer. Teknologin bakom fastoxidceller, eller solid oxide cells (SOCs), kan bidra med grön omvandling och lagring av energi när energibäraren är väte. Den höga totala omvandlingseffektiviteten, som kommer med den höga verkningstemperaturen, gör SOC till en lovande teknologi, men materialkostnaderna måste först reduceras innan den blir komersiellt gångbar. Därför syftar detta examensarbete till att undersöka prestandan av en ny, kostnadsoptimerad cellinterkonnektor på lång sikt i 650 och 850 °C. Vid höga temperaturer förångas krom från interkonnektorn, vilket leder till elektrodförgiftning, men kan mildras genom applicering av en skyddande beläggning. Den undersökta interkonnektorn är ett stål som betäcknas AISI 441 belagt med några olika föroxiderade beläggningar av koppar- och järnspinell. Proverna analyserades i huvudsak genom svepelektronmikroskopi kobinerat med energidispersiv röntgenspektroskopi och röntgendiffraktometri. Det visades att den mest lovande föroxideringsbehandlingen var 24 h i 750 °C och att krom förblev återhållet vid 650 °men inte vid 850 °C då det fanns tillgängligt för förångning vidytan.
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[pt] HIDROGENAÇÃO DE CO2 PARA METANOL: O PAPEL DAS VACÂNCIAS DE OXIGÊNIO NA SÍNTESE DE METANOL EMPREGANDO OS CATALISADORES DE CU/ZNO/AL E AS MISTURAS FÍSICAS A BASE DE IN2O3 / [en] HYDROGENATION OF CO2 TO METHANOL: THE ROLE OF OXYGEN VACANCIES IN METHANOL SYNTHESIS USING CU/ZNO/AL CATALYSTS AND IN2O3-BASED PHYSICAL MIXTURESBRUNA JULIANA DA SILVA BRONSATO 04 January 2024 (has links)
[pt] Esta tese investigou a síntese de metanol via hidrogenação do CO2 empregando dois conjuntos de catalisadores. O primeiro é composto pelos tradicionais catalisadores de Cu/ZnO/Al e o segundo aborda os catalisadores de
In2O3 e ZrO2. Com relação ao Cu/ZnO/Al, foram preparados quatro amostras
via coprecipitação. Os resultados mostraram que há um teor ótimo (3,8 por cento
at.) de Al para a qual se observa uma maior taxa de formação de metanol.
Os catalisadores foram caracterizados por fisissorção de N2, titulação com
N2O,espectroscopia de absorção atômica, ICP, DRX, XPS, TPD-(CO2,NH3
e H2O), TPSR-CO2/H2, TEM/HRTEM/EDS. Uma correlação entre a taxa
de formação de metanol e a quantidade de vacâncias de oxigênio superficiais
do catalisador foi observada. Foi verificado que o Al atua como um promotor
na geração de vacâncias de oxigênio. Com relação aos sistemas de In2O3, foi
realizado um screening e selecionado nove catalisadores. Esses sólidos foram
caracterizados pelas seguintes técnicas: DRX, TPD-NH3, TPD-CO2, TPR-H2
e TPSR-CO2/H2. Foi realizado um estudo em dinâmica molecular clássica investigando os efeitos da dopagem do In2O3 e da interação entre o In2O3 e
o ZrO2 e relacionando os resultados com a performance dos catalisadores. O
melhor desempenho catalítico foi obtido para o inédito catalisador de 0,6Pt-In2O3+6ZnZrO2, sendo esse desempenho associado à presença de vacâncias.
Além disso, pelos cálculos teóricos de dinâmica molecular foi verificado que
tanto a mistura física quanto a dopagem do In2O3 podem promovem a mobilidade de oxigênio da rede dos óxidos, o que facilita a formação de vacâncias de
oxigênio. Sendo assim, os dois conjuntos de catalisadores estudados mostram
que as vacâncias de oxigênio têm papel central na formação do metanol a partir
da hidrogenação do CO2. As informações geradas neste trabalho contribuirão
para o desenvolvimento de catalisadores promissores para a futura exploração
industrial da geração de metanol a partir de CO2. / [en] This thesis investigated methanol synthesis via CO2 hydrogenation using
two sets of catalysts. The first set consists of the traditional Cu/ZnO/Al
catalysts and the second set involves In2O3 and ZrO2 catalysts. Concerning
Cu/ZnO/Al, four samples were prepared via coprecipitation. The results
showed that there is an optimum Al content (3.8 percent at.) for which a higher
methanol formation rate is observed. The catalysts were characterized by
N2 physisorption, titration with N2O, atomic absorption spectroscopy, ICP,
XRD, XPS (CO2,NH3 and H2O)-TPD, CO2/H2-TPSR, TEM/HRTEM/EDS.
A correlation was observed between the rate of methanol formation and the
amount of surface oxygen vacancies on the catalyst. It was found that Al
acts as a promoter in the generation of oxygen vacancies. Regarding the
In2O3 systems, a screening was carried out and nine catalysts were selected.
These solids were characterized using the following techniques: XRD, NH3-
TPD, CO2-TPD, TPR-H2 and CO2/H2-TPSR. A classical molecular dynamics
study was carried out investigating the effects of doping In2O3 and the
interaction between In2O3 and ZrO2 and relating the results to the performance
of the catalysts. The best catalytic performance was obtained for the new
0,6Pt-In2O3+6ZnZrO2 catalyst, and this performance was associated with the
presence of vacancies. In addition, molecular dynamics calculations showed
that both the physical mixture and the doping of In2O3 can promote the
mobility of oxygen in the oxide lattice, facilitating the formation of oxygen
vacancies. Thus, the two sets of catalysts studied show that oxygen vacancies
play a central role in the formation of methanol from the hydrogenation of CO2.
The information generated in this work will contribute to the development
of promising catalysts for the future industrial exploitation of methanol
generation from CO2.
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The Layered Semiconductor Cu(Sb₂S₃)[AlCl₄]Grasser, Matthias A., Finzel, Kati, Ruck, Michael 04 April 2024 (has links)
Sb₂S₃ and CuCl were reacted in the ionic liquid [BMIm]Cl · 4.4AlCl₃ (BMIm=1-n-butyl-3-methylimidazolium) at 200°C. Upon cooling to room temperature, orange-red colored, air-sensitive crystals of Cu(Sb₂S₃)[AlCl₄] precipitated. X-ray diffraction on a single-crystal revealed an orthorhombic crystal structure, in which cationic [Cu(Sb₂S₃)]⁺ layers are separated by tetrahedral [AlCl₄]⁻ anions. The uncharged Sb₂S₃ partial structure consists of one-dimensional strands with covalent Sb-S single bonds. The copper(I) cation is coordinated by three sulfur atoms and by one of chlorine atoms of the [AlCl₄]⁻ anion. An optical band gap of 2.14 eV was deduced from UV/Vis spectra. In very good agreement, a band gap of 2.07 eV results from DFT-based calculations involving a new implementation of the bifunctional formalism for the exchange energy. By treatment with 0.1 molar hydrochloric acid, AlCl₃ was leached from Cu(Sb₂S₃)[AlCl₄] yielding a compound with the presumed composition Cu(Sb₂S₃)Cl. Hydrolysis at higher pH resulted in Cu₂₋ₓS and Sb₄O₅Cl₂.
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Health status of learners of educational institutions within Selebi Phikwe Ni-Cu mine area, BotswanaEkosse, G.E., De Jager, L., Van Den Heever, D. January 2009 (has links)
Published Article / Health effects associated with Ni-Cu mining on learners living within the mining area at Selebi Phikwe were investigated through the administration of questionnaires. Results depicted learners suffering from a wide range of different symptoms and illnesses. 70% of the learners complained of coughs, 77% had influenza / common cold, and 80% had headaches. The repeated coughing, constant influenza / common cold and persistent headaches from which learners suffered, were very significantly higher than those at the control site; and incidences of their occurrence increased with closeness to the mining area. The unusual high occurrences of these ailments and illnesses coupled with associated diseases among learners were attributed to several environmental factors including contaminated particulate air matter (PAM) (rich in sulphur and heavy metals) linked to the mining and smelting of Ni-Cu.
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Cu- and Fe-mediated Atom-Transfer Radical Polymerization in Aqueous SolutionSmolne, Sebastian 06 June 2016 (has links)
No description available.
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Characterization and Process Development of CVD/ALD-based Cu(Mn)/Co(W) Interconnect SystemShima, Kohei, Tu, Yuan, Han, Bin, Takamizawa, Hisashi, Shimizu, Hideharu, Shimizu, Yasuo, Momose, Takeshi, Inoue, Koji, Nagai, Yasuyoshi, Shimogaki, Yukihiro 22 July 2016 (has links) (PDF)
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.
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Behavior of Copper Contamination for Ultra-Thinning of 300 mm Silicon Wafer down to <5 μmMizushima, Yoriko, Kim, Youngsuk, Nakamura, Tomoji, Sugie, Ryuichi, Ohba, Takayuki 22 July 2016 (has links) (PDF)
Bumpless interconnects and ultra-thinning of 300 mm wafers for three-dimensional (3D) stacking technology has been studied [1, 2]. In our previous studies, wafer thinning effect using device wafers less than 10 μm was investigated [3, 4]. There was no change for the retention time before and after thinning even at 4 μm in thickness of DRAM wafer [5]. In this study, the behavior of Cu contamination on an ultra-thin Si stacked structure was investigated. Thinned Si wafers were intentionally contaminated with Cu on the backside and 250 °C of heating was carried out during the adhesive bonding and de-bonding processing. An approximately 200 nm thick damaged layer was formed at the backside of the Si wafer after thinning process and Cu particle precipitates ranged at 20 nm were observed by cross-sectional transmission electron microscopy (X-TEM). With secondary ion mass spectrometry (SIMS) and EDX analyses, Cu diffusion was not detected in the Si substrate, suggesting that the damaged layer prevents Cu diffusion from the backside.
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Étude de l'influence des défauts de soudage sur le comportement plastique et la durée de vie en fatigue de soudures par friction-malaxage d'un alliage Al-Cu-LiLe Jolu, Thomas 08 December 2011 (has links) (PDF)
Dans un but de réduction de poids des avions, un alliage Al-Cu-Li (2198-T8) assemblé par friction-malaxage est envisagé par les avionneurs pour des applications de type fuselage et intrados de l'aile. L'objectif de cette étude est de déterminer le comportement en fatigue des soudures par friction-malaxage et l'influence de certains défauts de soudage pour une durée de vie de l'ordre de 105 cycles. Pour cela le matériau de base, des soudures réalisées pleine tôle (sans défaut), des soudures contenant un résidu de plan de joint (dû à la couche d'oxydes initialement présente sur les chants des tôles avant soudage), un "kissing bond" (dû à un manque de pénétration de l'outil) et un "GAP" (correspondant à un défaut d'accolement des tôles) ont été testés. Pour la durée de vie visée, les soudures sont déformées plastiquement durant la première moitié du premier cycle. Le comportement en traction monotone des soudures n'a montré aucune influence significative des défauts de soudage sur les propriétés des soudures, bien que le kissing bond et le GAP soient le site d'amorçage de la rupture. Des essais de traction in situ au MEB ont permis de déterminer une contrainte seuil au-delà de laquelle on observe l'ouverture du kissing bond. L'étude du comportement en traction des soudures a été complétée par une simulation 3D par éléments finis. Les courbes de Wöhler ont montré que le résidu de plan de joint n'engendrait pas de baisse significative de la durée de vie des soudures, alors que le kissing bond et le GAP conduisaient à une réduction de l'ordre de 17% et 28% respectivement sur la contrainte à 105 cycles. L'étude des mécanismes d'amorçage a révélé que ces deux défauts étaient site d'amorçage de fissures de fatigue uniquement au-delà d'une contrainte seuil. Dans ces cas, la phase d'amorçage était réduite à l'ouverture du défaut durant la première moitié du premier cycle. La rupture finale des soudures a été étudiée au travers d'essais de déchirure ductile montrant une évolution de la nocivité des défauts similaire à celle révélée par les courbes de Wöhler.
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