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Добірка наукової літератури з теми "Aluminium contacts"

Автор: Grafiati

Опубліковано: 10 грудня 2022

Оновлено: 28 січня 2023

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Статті в журналах з теми "Aluminium contacts"

Kolaklieva, Lilyana, Roumen Kakanakov, V. Chitanov, Polina Dulgerova, and Volker Cimalla. "Search for a Suitable Ohmic Metallization Scheme to GaN/AlGaN Heterostructures for Sub-Micron Devices." Solid State Phenomena 159 (January 2010): 81–86. http://dx.doi.org/10.4028/www.scientific.net/ssp.159.81.

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Ohmic properties, thermal stability and surface morphology of Al-based and non-aluminium metallizations are investigated in dependence on the annealing temperature and initial composition. Non-aluminium contacts show poor ohmic properties, while contact resistivity of 3.47x10-5 Ω.cm2 is achieved for Ti/Al/Ti/Au metallization with a former-Ti/Al ratio of (30 wt.% /70 wt.%). Thermal properties of the Al-based metallization are improved by application of Mo layer as a barrier under the upper Au film of the contact structure. These contacts show excellent thermal stability at operating temperatures as high as 400oC. The less Al amount in the contact composition and Mo barrier layer contribute to the smoother surface and better edge acuity.

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Schwingenschlögl, U., and C. Schuster. "Geometry effects at atomic-size aluminium contacts." Chemical Physics Letters 439, no. 1-3 (May 2007): 143–47. http://dx.doi.org/10.1016/j.cplett.2007.03.093.

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Ragay, F. W., M. R. Leys, and J. H. Wolter. "Aluminium layers as nonalloyed contacts top‐type GaAs." Applied Physics Letters 63, no. 9 (August 30, 1993): 1234–36. http://dx.doi.org/10.1063/1.109782.

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Spieβ, L., O. Nennewitz, H. Weishart, J. Lindner, W. Skorupa, H. Romanus, F. Erler, and J. Pezoldt. "Aluminium implantation of p-SiC for ohmic contacts." Diamond and Related Materials 6, no. 10 (August 1997): 1414–19. http://dx.doi.org/10.1016/s0925-9635(97)00047-2.

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Meyer, Lennart, Martin Thedens, and Michael Beyer. "Incendivity of aluminium bronze in mechanical friction contacts." Journal of Loss Prevention in the Process Industries 49 (September 2017): 947–52. http://dx.doi.org/10.1016/j.jlp.2017.02.003.

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Böhler, T., A. Edtbauer, and E. Scheer. "Point-contact spectroscopy on aluminium atomic-size contacts: longitudinal and transverse vibronic excitations." New Journal of Physics 11, no. 1 (January 23, 2009): 013036. http://dx.doi.org/10.1088/1367-2630/11/1/013036.

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Raina, Ankush, Mir Irfan Ul Haq, Ankush Anand, Sanjay Mohan, Rajiv Kumar, Subramanian Jayalakshmi, and Ramachandra Arvind Singh. "Nanodiamond Particles as Secondary Additive for Polyalphaolefin Oil Lubrication of Steel–Aluminium Contact." Nanomaterials 11, no. 6 (May 29, 2021): 1438. http://dx.doi.org/10.3390/nano11061438.

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Nanodiamond (ND) particles are effective lubricant additives. Attention of research has shifted towards investigating the particles as secondary additives. ND particles provide more benefits as secondary additives than as the sole lubricant additive for steel–steel contacts. In this work, the influence of ND particles as secondary additives on oil lubrication of steel–aluminium tribopair (hard–soft contact) was examined. AISI 52100 steel balls were slid against AA2024 aluminium alloy discs, in the presence of polyalphaolefin (PAO) base oil, in boundary lubrication regime (applied normal load: 10 N to 50 N). Primary additives were copper oxide (CuO) and hexagonal boron nitride (h-BN) nanoparticles. The addition of ND particles to PAO, with CuO and h-BN as primary additives, at the lowest applied normal load of 10 N: (i) decreased the volumetric wear of the aluminium discs by 28% and 63%, respectively, and (ii) decreased the coefficient of friction by 15% and 33%, respectively. At the highest applied normal load of 50 N, it: (i) decreased the volumetric wear of the aluminium discs by 20% and 38%, respectively, and (ii) decreased the coefficient of friction by 5.4% and 8%, respectively. ND particles as secondary additives significantly reduce energy loss and power loss as a consequence of an effective reduction in friction during sliding. Unique characteristics of ND particles—such as their (a) physicochemical and thermal properties, (b) ball bearing and polishing effects and (c) synergistic interaction with primary additives to form stable tribofilms—enhance the lubrication performance of steel–aluminium contact. ND particles in combination with h-BN nanoparticles showed the best performance, due to better synergy between the primary additive and the secondary additive. Results from the investigation indicate that ND particles taken as secondary additives in small amount (0.2 wt%) can improve oil lubrication performance of hard–soft contacts in engineering systems.

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Yang, Ai Mei, Gui Zhong Li, Shao Ying Zhen, and Lai Jun Liu. "Electrode Interface Polarization in BaTiO₃-Based PTC Ceramics." Key Engineering Materials 697 (July 2016): 248–52. http://dx.doi.org/10.4028/www.scientific.net/kem.697.248.

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Electrodes play a vital role on the electrical properties of positive temperature coefficient (PTC) ceramics. An ohmic contract between ceramics and electrodes is necessary for the PTC effect. In this work, silver mixed aluminium electrode and pure silver electrode were pasted on BaTiO3-based PTC ceramics, which results in an ohmic contact and non-ohmic contact, respectively. Impedance spectroscopy and dielectric and conductivity properties was investigated at different temperature for the two contacts. Small difference of electrical properties was found between the two contacts above the Curie temperature. Below the Curie temperature, however, carriers could pass through the interface of ohmic contract but gather on the interface of non-ohmic contact. The latter resulted in a space charge polarization, which increased low-frequency dielectric permittivity.

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Kopecek, Radovan, Florian Buchholz, Valentin D. Mihailetchi, Joris Libal, Jan Lossen, Ning Chen, Haifeng Chu, et al. "Interdigitated Back Contact Technology as Final Evolution for Industrial Crystalline Single-Junction Silicon Solar Cell." Solar 3, no. 1 (December 22, 2022): 1–14. http://dx.doi.org/10.3390/solar3010001.

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We present our own Interdigitated Back Contact (IBC) technology, which was developed at ISC Konstanz and implemented in mass production with and at SPIC Solar in Xining, China, with production efficiencies of over 24%. To our knowledge, this is the highest efficiency achieved in the mass production of crystalline silicon solar cells without the use of charge-carrier-selective contacts. With an adapted screen-printing sequence, it is possible to achieve open-circuit voltages of over 700 mV. Advanced module technology has been developed for the IBC interconnection, which is ultimately simpler than for conventional double-sided contacted solar cells. In the next step, we will realize low-cost charge-carrier-selective contacts for both polarities in a simple sequence using processes developed and patented at ISC Konstanz. With the industrialisation of this process, it will be possible to achieve efficiencies well above 25% at low cost. We will show that with the replacement of silver screen-printed contacts by copper or aluminium metallisation, future IBC technology will be the end product for the PV market, as it is the best performing c-Si technology, leading to the lowest cost of electricity, even in utility-scale applications.

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Hu, Yi Ran, Mohammad M. Gharbi, Vivian Liang, Yang Zheng, Denis J. Politis, and Li Liang Wang. "The Galling Behavior of Advanced Coating Contacts with Aluminium Alloy during Sliding Wear." Key Engineering Materials 767 (April 2018): 117–23. http://dx.doi.org/10.4028/www.scientific.net/kem.767.117.

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This paper investigates the galling behaviour of a range of hard coatings applied to tooling surfaces during the sheet forming of an aluminium alloy workpiece. A total of three types of tooling materials were investigated, two of which were subject to PVD deposited coatings of AlCrN, CrN and DLC applied to the working surface. The third tooling material had undergone induction heating, plasma-nitriding and polishing. To evaluate the galling behaviour of the applied coatings, a tribological evaluation was conducted using a pin-on-disc test set-up at a constant load and varying temperature. The coated discs, replicating the tooling material, were tested against aluminium alloy pins AA6082 and AA7075 representing the workpiece material. This investigation indicated that the friction and galling behaviour of aluminium is highly dependent on temperature, and the use of two different aluminium pins had no significant effect. At room temperature, it was found that carbon-based coatings provide the lowest friction and the best protection against galling, whilst nitride-based treatments exhibit better performance at high temperature. Moreover, at elevated temperatures, coated tools exhibit superior anti-galling properties compared to uncoated tools.

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Більше джерел

Дисертації з теми "Aluminium contacts"

Ruppert, Christopher. "Thermal fatigue in stationary aluminium contacts." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1125.

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The conductive area of a stationary electrical contact consists of many small contact spots. The contact spots can be described as narrow metal bridges across the interface between two conductors. Deterioration of a contact is closely related to processes occurring in these microscopic areas. The objective of this work is to clarify the basic mechanisms affecting the reliability and degradation of an electrical contact by closely studying the contact spots.

Particular emphasis has been put on examining the contact spots occurring in aluminium-aluminium interfaces when passing AC. Due to the small thermal capacity of a contact spot the temperature in the contact spot cycles with twice the frequency of the applied AC. The minimum temperature attained during one cycle being the bulk temperature of the conductor, the maximum temperature can in heavily stressed contacts be close to the melting point of the conductor material. In the idealized contact used in the present investigation, this thermal cycling may initiate thermal fatigue processes in the contact spot region.

Microscopic cracks appear in the contact spot region as the result of thermal fatigue processes. The cracks not only lower the mechanical strength of the conductor in close vicinity of the contact spot, they also cause a higher electrical resistivity in these areas.

Alloying a tracer metal in one of the electrodes of the contact allows for closer investigation of the crack propagation as it occurred during the experiments. The tracer migrates into the heated contact spot region of the opposite electrode where the cracks constitute a barrier impairing further diffusion into the electrode. Further information on the thermal fatigue processes in the contact spot region is obtained when examining metallographic images of cross sectioned contact spots. Here it can be seen that the repetitive thermal stresses give rise to clearly localized recrystallisation in the contact spot region.

Thermal fatigue is a well known failure mechanism in mechanical structures. It has to the authors knowledge not previously been associated with the deterioration of contact spots. However, the mechanical damage in the contact spot region caused by the temperature cycling also has a detrimental effect on the electrical behaviour of the contact. It is therefore suggested that thermal fatigue is of considerable importance to the reliability and degradation of stationary electrical contacts.

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Boudjelida, Boumedienne. "Metal-aluminium gallium nitride Schottky contacts formation." Thesis, Sheffield Hallam University, 2006. http://shura.shu.ac.uk/19373/.

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X-ray photoelectron spectroscopy (XPS) has been used to investigate the effect of various surface cleaning procedures on Al[x]Ga[1]-[x]N surfaces for x = 0.20 and 0.30. Results show that wet chemical etch in a HF solution followed by a 600°C in-situ annealing under ultra-high vacuum (UHV) is very effective in removing oxygen from the surface. Downward band bending of 0.87 eV and 0.99 eV also occurs between the solvents-treated and the annealed Al[x]Ga[1]-[x]N surfaces for x = 0.20 and 0.30, respectively. Increasing in-situ temperature annealing in increments of 100°C up to 600°C shows a re-ordering at the surface and subsurface with Ga and A1 moving deeper in the surface, whereas N goes to the topsurface. In addition, the Fermi level movement observed when increasing the temperature could be interpreted by the change in surface stoichiometry or by a creation of vacancies due to the ex-situ surface treatment which may, in turn, be activated/deactivated by temperature annealing. Atomic hydrogen clean (AHC) followed by 400°C in-situ UHV annealing is also found effective in removing O and C from Al[x]Ga[1]-[x]N surface (x = 0.20).The formation of Ag/Al[x]Ga[1]-[x]N (x = 0.20) and Ni/Al[x]Ga[1]-[x]N (x = 0.30) interfaces, where the substrate was subjected to HF etch followed by 600°C in-situ UHV anneal, has been studied by a combination of XPS, atomic force microscope (AFM), scanning tunneling microscope (STM) and current-voltage (I-V) measurements. XPS results suggest a layer-by-layer followed by islanding growth mode of Ag and Ni on Al[x]Ga[1]-[x]N. This is confirmed by the presence of metal islands at the metal-covered surfaces using AFM and in-situ STM. XPS investigation shows a more abrupt, well-defined Ag/Al[x]Ga[1]-[x]N interface compared to Ni/Al[x]Ga[1]-[x]N. Ag deposition on Al[x]Ga[1]-[x]N substrates causes upward band bending of 0.30 eV and 0.40 eV between the "clean" surface and the last metal deposition, for x = 0.20 and 0.30, respectively, while Ni induces downward band bending of 0.3 eV for x = 0.20. I-V measurements of Ag/Al[x]Ga[1]-[x]N (x = 0.30), where the substrate was cleaned using N[+] bombardment followed by 600°C annealing, yield a Schottky barrier height of 0.82 eV with ideality factor n = 1.21.XPS and I-V results on Ag/Al[x]Ga[1]-[x]N and Ni/Al[x]Ga[1]-[x]N are compared and discussed in terms of current models of Schottky barrier formation.

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Houle-Paradis, Jean-Philippe. "Modélisation de la flexion libre d'un câble multicouche tenant compte de l'élasticité des contacts." Mémoire, Université de Sherbrooke, 2011. http://savoirs.usherbrooke.ca/handle/11143/1598.

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Ce travail porte sur le développement d'un modèle de câble multicouche permettant la modélisation de son comportement en flexion libre, en tenant compte de l'élasticité des interfaces de contact entre les brins. Le nouveau modèle reprend plusieurs éléments de modèles considérant uniquement un comportement de type stick-slip (non-glissement - glissement) et qui ont déjà fait l'objet de publications. L'influence de l'élasticité des contacts est intégrée dans le modèle en utilisant la théorie des contacts élastiques d'Hertz. Les dimensions des ellipses de contact sont calculées en considérant un comportement élastique-parfaitement plastique. Les forces et les déplacements aux ellipses de contact sont calculés séquentiellement, en débutant par les interfaces entre la couche externe et la couche sous-jacente, pour une valeur de courbure imposée à l'axe central d'un élément de câble de longueur unitaire. La force de traction tangente à chacune des interfaces est calculée en utilisant une fonction continue de la position angulaire du brin, et le déplacement aux interfaces est calculé de manière indépendante pour chacun des brins. Le modèle est validé en comparant les résultats numériques obtenus avec ceux générés par d'autres modèles de câble ayant fait l'objet de publications, pour un conducteur AAC, un conducteur ACSR et un câble en acier. Les résultats montrent que la prise en compte de l'élasticité des contacts réduit considérablement la rigidité initiale du câble et cette valeur devient dépendante de la tension appliquée. Le comportement du câble devient non-linéaire pour de faibles valeurs de courbure, même lorsqu'aucun brin n'est en glissement. À l'aide d'un outil de calcul par éléments finis développé dans le cadre de ce travail, certains essais quasi-statiques sont reproduits numériquement, et les résultats obtenus sont comparés à des résultats expérimentaux publiés dans la littérature.

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Lorrière, Philippe. "Étude numérique du sertissage de contacts électriques aéronautiques sur câbles multibrins." Compiègne, 2004. http://www.theses.fr/2004COMP1499.

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La technologie du sertissage est employée pour assurer la liaison électrique et mécanique entre un câble et un connecteur. Utiliser des câbles en aluminium et des sections de câbles réduites pose de nouveaux problèmes. La modélisation numérique du procédé de sertissage est utile pour comprendre les raisons des difficultés rencontrées notamment grâce à la simulation du retour élastique. Nous avons réalisé une étude analytique et numérique avec un modèle simplifié qui met en évidence l'importance des paramètres matériaux sur le retour élastique. L'étude numérique présente les simulations 2D réalisées avec la méthode des éléments finis, que ce soit en statique implicite avec le code ABAQUS/standard ou dynamique explicite avec ABAQUS/explicit. Les résultats, avec les hypothèses des contraintes planes ou déformations planes, sont comparés aux résultats expérimentaux. Le sertissage est un problème non-linéaire impliquant des grandes déformations élasto-plastique et des conditions de contact multiples avec frottement. Enfin, nous présentons une étude numérique en trois dimensions où l'importance de la géométrie des poinçons est mise en évidence
The crimping technology process to ensure the electrical and the mechanical link between the wire and the connector. The will to use aluminium cables and small sections of table poses new problems. The numerical simulation of the crimping process is usefull to understand the reasons of the difficulties encountered particular with to the simulation of the elastic return. We made an analytical and numerical study with a simplified model winch highlights the importance of the materials parameters on the spring back. The numerical study slows the results of the 2D simulations make with the finite element method, that it is implicit static with the ABAQUS/standard code or explicit dynamics with AQUS/explicit. The results with the hypothesis of the plane strains or plane stress are compared with the experimental results. This nonlinear problem involves large elasto-plastic strains and multiple contact conditions, with friction between the wires and the barrel. Lastly, we present a numerical study inthree dimensions where the importance of the punches geometry is highlighted

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Mercier, David. "Lois de comportement des matériaux utilisés dans les contacts électriques pour application " flip chip "." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI083/document.

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Dans le cadre de l'intégration « 3D », une technologie d'assemblage par report de puces sur tranche de silicium (« flip chip ») reposant sur un procédé de microinsertion a été développée ces dernières années. Cette technologie est basée principalement sur la mise en contact par thermocompression, de réseaux de (micro)inserts en Nickel ECD, avec des plots de connexions métalliques en Al(Cu). Au cours de ce travail, un scénario de formation du contact entre un unique microinsert de Nickel rugueux et un film mince d'Aluminium lisse, prenant en compte la présence d'Alumine native à l'interface de contact, est proposé pour une gamme de pressions allant du MPa au GPa. L'analyse du contact métal-oxyde-métal se base essentiellement sur la fissuration de l'oxyde natif suivie de l'extrusion du métal au travers des fissures, et nécessite d'établir au préalable les lois de comportement des matériaux mis en jeu à partir d'essais de nanoindentation instrumentée couplés à des simulations numériques. Enfin, la mesure de l'évolution de la résistance électrique de contact en fonction de la force appliquée à l'aide de dispositifs expérimentaux originaux, permet de mettre en évidence les différents mécanismes de formation du contact métallique lors du procédé de microinsertion
In the field of « 3D » microelectronic integration, a wafer level technology using flip chip stacking and based on a microinsertion process has been developed recently. This technology is mainly based on the contact realized by thermocompression between a network of microinserts made of Nickel ECD, with connections pads in Al(Cu). In this work, a scenario describing the contact establishment between a unique rough microinsert of Nickel and a smooth thin Aluminum film taking into account the presence of native Alumina at the contact interface, is developed for a range of pressures from MPa to GPa. The analysis of the metal-oxide-metal contact is essentially based on the fracture of the native oxide followd by the metal extrusion through cracks, and requires the knowledge of the behaviour laws of materials, obtained from instrumented nanoindentation tests coupled with numerical modeling. Finally, the measure of the electrical contact resistance evolution in function of applied load, with specific pioneering experimental setup, showcases the mechanisms driving the formation of metallic contact during the microinsertion process

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Pfeifer, Stephanie. "Einfluss intermetallischer Phasen der Systeme Al-Cu und Al-Ag auf den Widerstand stromtragender Verbindungen im Temperaturbereich von 90 °C bis 200 °C." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-211232.

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Im Netz der Elektroenergieversorgung werden einzelne Netzkomponenten und Betriebsmittel durch Verbindungen elektrisch zusammengeschaltet. Dabei werden häufig Schraubenverbindungen mit Stromschienen eingesetzt. Diese müssen über mehrere Jahrzehnte zuverlässig hohe Ströme tragen können. Abhängig von der sich einstellenden Temperatur an den Verbindungen altern diese mit der Zeit. Die Alterung wird je nach Verbindungssystem von verschiedenen Mechanismen beeinflusst, die alle parallel ablaufen. Bei ruhenden, stationären elektrotechnischen Verbindungen, deren Kontaktpartner aus verschiedenen Materialien bestehen, können abhängig von der Paarung intermetallische Phasen (IMP) entstehen. Die sich bildenden IMP haben schlechtere elektrische und mechanische Eigenschaften als die reinen Metalle. Daraus resultiert ein höherer Verbindungswiderstand. Die erzeugte Verlustleistung sowie die Temperatur der Verbindung steigen an. Dies kann zum Ausfall der Verbindung führen. In der Elektroenergietechnik werden aufgrund ihrer guten elektrischen Leitfähigkeit häufig die Werkstoffe Aluminium und Kupfer sowie das Beschichtungsmetall Silber bei Temperaturen von üblicherweise 90 °C bis 200 °C eingesetzt. Speziell bei Aluminium-Kupfer-Verbindungen, die nicht langzeitstabil sind, wird als maßgebliche Ausfallursache das Bilden von IMP gesehen. Die IMP des Systems Al-Cu wurden in der Vergangenheit bereits vielfach untersucht. Das Übertragen der Ergebnisse auf die Problematik stromtragender Verbindungen der Elektroenergietechnik ist jedoch nicht ohne Weiteres möglich. Der relevante niedrige Temperaturbereich zwischen 90 °C und 200 °C spielt bei vielen Untersuchungen nur eine untergeordnete Rolle. Zusätzlich können die Eigenschaften der IMP bei unterschiedlichen Herstellungsverfahren voneinander abweichen. Zum System Al-Ag ist in der Literatur nur wenig bekannt. Deshalb wurden für diese Arbeit phasenreine IMP der Systeme Al-Cu und Al-Ag mit unterschiedlichen Herstellungsverfahren bei möglichst identischen Randbedingungen hergestellt. Diese wurden mit einer speziell für diese Proben entwickelten Messeinrichtung elektrisch charakterisiert und der ermittelte spezifische elektrische Widerstand der IMP und ihr Temperaturbeiwert mit Werten aus der Literatur verglichen. An verschiedenen Schraubenverbindungen mit Stromschienen aus Aluminium und Kupfer wurden Langzeitversuche von bis zu 3 Jahren durchgeführt. Der Verbindungswiderstand wurde abhängig von der Zeit ermittelt. An ausgewählten Verbindungen wurde zusätzlich in zwei identischen Versuchen der Einfluss der Belastung mit Dauer- und Wechsellast auf das Langzeitverhalten untersucht. Mithilfe der an den IMP ermittelten elektrischen Eigenschaf-ten wurde deren Einfluss auf den Verbindungswiderstand berechnet. Die Ergebnisse dieser Modellrechnung wurden mit den Ergebnissen aus den Langzeitversuchen verglichen. Ausgewählte Verbindungen wurden dazu mikroskopisch untersucht. Es wurde festgestellt, dass die IMP nicht ausschließlich das Langzeitverhalten stromtragender Verbindungen bestimmen. Es muss mindestens ein weiterer Alterungsmechanismus einen signifikanten Einfluss haben. Die Untersuchungen deuten darauf hin, dass dabei Sauerstoff eine zentrale Rolle spielen könnte
In electrical power supply networks a huge number of electrical joints are used to connect transmission lines, conductors, switchgears and other components. During operation these joints are aging due to different aging mechanisms. Depending on the type of the joint several aging mechanisms can take place at the same time. For stationary joints with contact partners made of different materials, the formation of intermetallic compounds (IMC) may be an issue. These IMC have worse electrical and mechanical properties compared to the pure metals. Therefore, the presence of IMC in the contact area results in a higher joint re-sistance and the temperature and the thermal power losses increase. Typical temperatures for high current joints are between 90 °C and 200 °C. Due to their good electrical conductivity aluminum and copper are often used as conductor materials and silver as a coating material. Especially bimetal joints made of aluminum and copper are not long term stable. The formation of Al-Cu IMC is held responsible as a cause of failure. The IMC of the System Al-Cu have already been studied by several authors. However, it is difficult to apply the results directly to electrical joints in power supply networks. In many studies the low temperature range between 90 °C and 200 °C is not regarded. In addition, the properties of the IMC may vary due to different preparation processes. There is only little information about the system Al-Ag in the literature. For this work, phase pure IMC of the systems Al-Cu and Al-Ag were prepared by different preparation processes using similar process parameters. These IMC samples were electrically characterized with a specially developed measuring device. The specific electric resistivity and the temperature coefficient of resistance were determined and compared to values taken from the literature. Various combinations of bus bar joints made of aluminum and copper were investigated in long term tests for up to three years. The joint resistance was determined as a function of time. In addition, for selected joints two identic setups were operated with continuous load and alternating load. The long term behavior was investigated with regard to the load ap-plied. Using the results of the electrical characterization of the IMC their influence on the joint resistance was calculated theoretically. The results of the calculation were compared to the results determined in the long term tests. Selected joints were examined microscopi-cally after termination of the long term tests. It was found, that the long term behavior of bimetal electrical joints with the combination Al-Cu and Al-Ag cannot be exclusively described by the growth of IMC. At least there is one further aging mechanism involved. The studies suggest, that oxygen may have a significant influence

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Filali, Oussama. "Approche multi physique du contact frottant en grande déformation plastique : prédiction numérique du grippage d'alliages d'aluminium en mise en forme à froid." Thesis, Valenciennes, Université Polytechnique Hauts-de-France, 2020. http://www.theses.fr/2020UPHF0035.

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La thèse propose une nouvelle approche pour prédire le défaut de grippage rencontré lors de la mise en forme des alliages d’aluminium à froid. De nombreuses études expérimentales montrent que ce défaut de grippage est fortement lié aux conditions de contact et de frottement, et est notamment fonction de la rugosité des outils de fabrication. Les modèles permettant de prédire l’apparition de ce défaut sont rares et reposent généralement sur des observables indirects, tel que les champs de pression ou de température, sans prendre explicitement en compte l’influence des facteurs de premier ordre que sont la lubrification et l’état de surface des matériaux en contact. La méthodologie proposée de nos travaux repose sur l’hypothèse que le défaut apparait lorsque la matière de la pièce au voisinage de sa surface de contact atteint un niveau d’endommagement critique. Toutefois, dans une étude précédente, il a été montré que les modèles d’endommagement reposant exclusivement sur la pression hydrostatique, tels que les modèles GTN ou de Lemaitre, n’étaient capable de prédire l’endommagement qu’à condition de modéliser la rugosité des surfaces. Cela conduit à des simulations numériques multi-échelles très couteuses en temps de calcul et incompatibles avec la modélisation de procédés industriels réels. Pour contourner cette difficulté, la présente étude propose d’utiliser des modèles d’endommagement prenant en compte les effets de cisaillement générés par le contact frottant. L’influence de la rugosité repose alors sur un choix pertinent de la loi de frottement. Dans un premier temps, un chapitre bibliographique traite des modèles d’endommagement. Une attention particulière est portée aux modèles utilisant le paramètre de Lode afin de prendre en compte l’effet des contraintes de cisaillement sur l’évolution des variables d’endommagement. Dans un second temps une revue bibliographique des modèles de frottement et de lubrification est présentée. L’étude met notamment en avant les modèles reposant sur une approche mésoscopique de la lubrification, avec la modélisation de l’écrasement des rugosités lors du contact frottant. A l’issue de ces chapitres, le modèle d’endommagement développé de L. Xue et un modèle de lubrification prenant explicitement en compte la valeur des rugosités des surfaces sont utilisés pour prédire le grippage dans différentes configurations de contact. Dans un premier temps cette méthodologie numérique est appliquée à l’étude du procédé d’étirage plan de plaques en alliage d’aluminium 6082-T4. Puis la méthodologie est appliquée à un contact pion/plan sur des plaques en alliage 6082-T6. Enfin un procédé de filage avant de lopins cylindriques est étudiés avec les mêmes outils numériques. Ces différentes configurations sont testées avec ou sans lubrifiant et avec des outils ayant différentes valeurs de rugosités. Les résultats montrent que la procédure proposée permet dans la majorité des cas testés de prédire l’apparition du défaut, que ce soit dans des configurations avec ou sans lubrifiant. Les prédictions sont néanmoins optimistes, les distances de glissement avant l’apparition du grippage numérique étant généralement supérieure aux distances mesurées expérimentalement. Les résultats sont toutefois prometteurs et un certain nombre de perspectives sont présentées afin d’améliorer la précision de la méthodologie proposée
The thesis proposes a new approach to predict the galling defect encountered during cold forming of aluminum alloys. Numerous experimental studies show that this defect is strongly linked to the conditions of contact and friction and is a function of the roughness of the manufacturing tools. Models to predict the appearance of this defect are rare and are generally based on indirect observables, such as pressure or temperature fields, without explicitly taking into account the influence of first-order factors such as lubrication and 'surface condition of the materials in contact. The proposed methodology of our work assumes that the defect appears when the material of the part near its contact surface reaches a critical level of damage. However, in a previous study, it was shown that damage models based exclusively on hydrostatic pressure, such as GTN or Lemaitre models, were only able to predict damage if they model roughness. surfaces. This leads to multi-scale numerical simulations which are very costly in terms of computation time and incompatible with the modeling of real industrial processes. To get around this difficulty, the present study proposes to use damage models considering the shear effects generated by the friction contact. The influence of roughness is then based on a relevant choice of the friction law. First, a bibliographical chapter deals with damage models. Particular attention is paid to models using the Lode parameter to consider the effect of shear stresses on the evolution of damage variables. Secondly, a bibliographical review of friction and lubrication models is presented. The study notably highlights models based on a mesoscopic approach to lubrication, with the modeling of the crushing of roughness during rubbing contact. At the end of these chapters, the damage model developed by L. Xue and a lubrication model explicitly considering the value of surface roughness is used to predict seizure in different contact configurations. Initially, this numerical methodology is applied to the study of the flat drawing process of 6082-T4 aluminum alloy plates. Then the methodology is applied to a pion / plane contact on 6082-T6 alloy plates. Finally, a process for spinning before cylindrical slips is studied with the same digital tools. These different configurations are tested with or without lubricant and with tools having different roughness values. The results show that the proposed procedure allows in most of the cases tested to predict the appearance of the defect, whether in configurations with or without lubricant. The predictions are nevertheless optimistic, the slip distances before the onset of digital seizure being generally greater than the distances measured experimentally. The results are however promising, and several perspectives are presented to improve the precision of the proposed methodology

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Karbouj, Rim. "Transfert d'aluminium : cas des matériaux pour contact alimentaire." Phd thesis, Grenoble INPG, 2008. http://tel.archives-ouvertes.fr/tel-00294273.

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L'aluminium est le 3ème élément présent à la surface de la terre et le plus utilisé dans l'industrie, ainsi que dans le monde de la fabrication des ustensiles de cuisine et des emballages alimentaires, en particulier pour leur stockage et leur préparation. L'exposition de l'homme est donc inévitable et chaque jour, des taux modérés de ce métal pénètrent dans l'organisme et sont capables de s'accumuler dans certains organes. Longtemps considérée comme inoffensif, l'aluminium est considéré aujourd'hui comme un métal toxique. Le but de notre étude a été de vérifier s'il y avait une migration de l'aluminium dans les aliments, lors de leur stockage ou de leur cuisson, dans des matériaux à base d'aluminium ; d'évaluer la dose libérée d'aluminium, et de la comparer à la dose maximum admissible pour préserver la santé des populations afin d'apprécier si cette utilisation domestique de l'aluminium pouvait présenter un risque toxique potentiel en santé publique. Nous avons confirmé la libération de l'aluminium mise en contact avec des molécules chélatrices, présentes dans les aliments et testées en milieu simple ; et nous avons montré que cette solubilisation pouvait être très importante et était fonction de la nature de la molécule chélatrice, de sa concentration, de sa forme chimique et surtout de la température. Les formes salifiés étudiées (sels de K+, Na+ et Li+ de l'acide citrique, de l'acide oxalique et de l'acide lactique) nous ont permis de comprendre comment la modification d'une molécule pouvait changer la libération de l'aluminium soit par modification du pH, soit par modification de la réactivité. Nous avons également évalué l'impact de la matrice alimentaire sur la quantité d'aluminium relarguée à partir d'ustensiles de cuisine utilisés pour la conservation ou la cuisson. Différents aliments, ont été sélectionnés en fonction de leur composition en molécules chélatrices de l'aluminium. Le relargage de l'aluminium est fonction de l'aliment, de la localisation du prélèvement de l'échantillon, de la température, du temps et du type de contenant. En confrontant nos résultats aux différentes données de la littérature et en les intégrant dans le contexte des apports quotidiens et des limites de sécurité nous avons essayé de modéliser l'implication de l'aluminium, en fonction des quantités relarguées, dans notre nutrition. Ce travail nous a permis d'identifier d'éventuelles habitudes à risque, de proposer des recommandations concernant l'utilisation des ustensiles de cuisine en aluminium, de proposer un modèle cinétique et de découvrir une méthode de prétraitement permettant de réduire le transfert d'aluminium.

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Hamedi, Emilia. "Electrical connection for aluminium conductors in automotive applications : Prestudy of available solutions for electrical connection methods of aluminium cables." Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-212545.

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Due to increasing weight of electrical component and wiring harnesses in a vehicle contrary to the demand of light constructed vehicles as well as the constantly increasing and fluctuating price of copper compared to aluminium’s stable and far lower price, the use of aluminium conductors as an alternative have been promoted. This thesis work lay theoretical research of the available methods used for electrical connection of aluminium conductors in order to increase the knowledge about the available termination techniques. Due to aluminium’s characteristics such as lower conductivity and strength, tendency to form oxides and relax over time, differences in thermal expansion coefficient and high potential for galvanic corrosion, there is a risk of deterioration and degradation of the connection if the termination of aluminium conductors is not done correctly without being aware of the challenges when it comes to aluminium connection. The founded solutions are different welding and soldering techniques such as friction welding, ultrasonic welding, resistance welding, plasma soldering and many other modifications of conventional crimp. A robust termination system that faces all those challenges and ensure a reliable connection during the entire life length of the vehicle and in order to inhibit corrosion different type of sealing of the contact interface will be required. In order to evaluate the performance of the founded connection method, testing with evaluation of, tensile strength of conductor to contact attachment, tightness demand, corrosion resistance, vibration and heat evolution at the contact attachment have to be conducted.

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Chalfoun, Lynn Louise. "Process optimization of alloyed aluminum backside contacts for silicon solar cells." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10996.

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Книги з теми "Aluminium contacts"

Baghbanan, Mohammad reza. Contact forces and surface characterization of aluminum alloys in a vibratory surface finishing process. Ottawa: National Library of Canada, 2002.

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Kaufman, J. Gilbert, and Elwin L. Rooy. Aluminum Alloy Castings. ASM International, 2004. http://dx.doi.org/10.31399/asm.tb.aacppa.9781627083355.

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Aluminum Alloy Castings: Properties, Processes and Applications is a practical guide to the process, structure, property relationships associated with aluminum alloy castings and casting processes. It covers a wide range of casting methods, including variations of sand casting, permanent mold casting, and pressure die casting, showing how key process variables affect the microstructure, properties, and performance of cast aluminum parts. Other chapters provide similar information on the effects of alloying and heat treating and the influence and control of porosity and inclusions. A significant portion of the book contains curated collections of property and performance data, including many previously unpublished aging response curves, growth curves, and fatigue curves; tensile properties at high and low temperatures and at room temperature after high-temperature exposure; the results of creep rupture tests conducted at temperatures from 212 to 600 °F (100 to 315 °C); and stress-strain curves obtained from casting alloys in various tempers under tensile or compressive loads. The book also discusses the factors that contribute to corrosion and fracture resistance and includes test specimen drawings as well as a glossary of terms. For information on the print version, ISBN 978-0-87170-803-8, follow this link.

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Lampert, William V. A study of aluminum-germanium-nickel ohmic contact metallurgical effects at the gallium arsenide interface. 1992.

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Частини книг з теми "Aluminium contacts"

Lee, Junghoon, Junghoon Lee, and Chang-Hwan Choi. "Superhydrophobic Surfaces for Anti-Corrosion of Aluminum." In Advances in Contact Angle, Wettability and Adhesion, 267–98. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2018. http://dx.doi.org/10.1002/9781119459996.ch12.

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Kaziolas, Dimitrios N., Evangelos Efthymiou, Michael Zygomalas, and Charalambos C. Baniotopoulos. "On the Separation Zones in Aluminium Base-Plate Connections. Numerical Simulation and Laboratory Testing." In Recent Advances in Contact Mechanics, 293–308. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-33968-4_18.

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Wei, Shuguang, Chaiyapat Tangpatjaroen, Hongliang Zhang, and Izabela Szlufarska. "Microstructural Evolution of Ultra-Fine Grained (UFGs) Aluminum in Tribological Contacts." In The Minerals, Metals & Materials Series, 257–62. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-65396-5_38.

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Al-Rifaie, H., R. Studziński, T. Gajewski, M. Malendowski, P. Peksa, W. Sumelka, and P. W. Sielicki. "Full scale field testing of trapezoidal core sandwich panels subjected to adjacent and contact detonations." In Modern Trends in Research on Steel, Aluminium and Composite Structures, 393–99. London: Routledge, 2021. http://dx.doi.org/10.1201/9781003132134-50.

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Benedetti, Angela, Pier Gabriele Molari, and Piero Morelli. "Fracture Initiation and Propagation in Fatigue Contact Loading of AA6082 Aluminium Alloy." In Fracture and Damage Mechanics V, 1091–94. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-413-8.1091.

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Shen, Ping, Lifeng Zhang, and Yi Wang. "Influence of Oxidation on Contact Angle between Liquid Aluminum and Al2O3." In Light Metals 2016, 827–32. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-48251-4_140.

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Beeler, Richard. "Bar to Block Contact Resistance in Aluminum Reduction Cell Cathode Assemblies." In Light Metals 2014, 507–10. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2014. http://dx.doi.org/10.1002/9781118888438.ch86.

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Beeler, Richard. "Bar to Block Contact Resistance in Aluminum Reduction Cell Cathode Assemblies." In Light Metals 2014, 507–10. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-48144-9_86.

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Shen, Ping, Lifeng Zhang, and Yi Wang. "Influence of Oxidation on Contact Angle Between Liquid Aluminum and Al2O3." In Light Metals 2016, 827–32. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119274780.ch140.

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Ziegler, F. L., F. A. de O. Valenzuela, F. Ziegler, and F. Ziegler. "Nanostructured Self-Flow Refractory Castable to Long-Life Melt Aluminum Contact Lining." In Proceedings of the Unified International Technical Conference on Refractories (UNITECR 2013), 1321–24. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2014. http://dx.doi.org/10.1002/9781118837009.ch223.

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Тези доповідей конференцій з теми "Aluminium contacts"

Molenaar, D., D. Gunasegaram, and T. Kilpatrick. "Experimental and numerical studies of surface contamination and degradation of aluminium contacts in primary aluminium smelters." In 26th International Conference on Electrical Contacts (ICEC 2012). IET, 2012. http://dx.doi.org/10.1049/cp.2012.0622.

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Kissling, Stephanie, Wolfgang Schmitt, and Volker Behrens. "Electrochemically Deposited Coating Systems on Aluminium for Contact Applications." In 2012 IEEE 58th Holm Conference on Electrical Contacts (Holm 2012). IEEE, 2012. http://dx.doi.org/10.1109/holm.2012.6336579.

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To, Alexander, Rasmus Schmidt Davidsen, Xinrui An, Alison Lennon, and Allen Barnett. "Inkjet patterned ALD aluminium oxide for rear PERC metal contacts." In 2015 IEEE 42nd Photovoltaic Specialists Conference (PVSC). IEEE, 2015. http://dx.doi.org/10.1109/pvsc.2015.7355871.

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Molenaar, D. "Use of Electrical Contact Fundamentals in the Aluminium Smelting Industry - A Case Study." In 2010 IEEE Holm Conference on Electrical Contacts (Holm 2010). IEEE, 2010. http://dx.doi.org/10.1109/holm.2010.5619457.

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Liang, Wensheng, Parvathala Narangari, Jingnan Tong, James Bullock, Jesus Ibarra Michel, Hang Cheong Sio, Teng Kho, Stephane Armand, Keith McIntosh, and Kean Chern Fong. "Aluminium electrode induced surface passivation deterioration for dopant free passivated contacts." In 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC). IEEE, 2021. http://dx.doi.org/10.1109/pvsc43889.2021.9518397.

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Molenaar, D., T. Kilpatrick, and D. Gunasegaram. "Experimental and numerical studies of a multi-leaf clamped lap joint design for aluminium bus bar applications." In 26th International Conference on Electrical Contacts (ICEC 2012). IET, 2012. http://dx.doi.org/10.1049/cp.2012.0634.

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Sun, Zhenyu, Chuqi Yi, and Stephen Bremner. "Low-temperature aluminium doped a-Si as hole selective contacts on p-type silicon solar cells." In 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC). IEEE, 2021. http://dx.doi.org/10.1109/pvsc43889.2021.9518591.

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Grewal, Jasmaninder Singh, Buta Singh Sidhu, and Satya Prakash. "Wear Behaviour of Conventional and Nanostructured Thin Films of Titanium Aluminium Nitride." In ITSC2015, edited by A. Agarwal, G. Bolelli, A. Concustell, Y. C. Lau, A. McDonald, F. L. Toma, E. Turunen, and C. A. Widener. ASM International, 2015. http://dx.doi.org/10.31399/asm.cp.itsc2015p1199.

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Abstract Titanium aluminium based nitride (Ti, Al)N coatings possess excellent tribological behaviour with respect to metal cutting and polymer forming contacts. In the present work TiAlN coatings were deposited by plasma spray process. Three coatings of TiAlN were deposited on AISI-347 grade boiler steel substrate out of which two were thin nano coatings deposited at different temperatures of 500°C and 200°C and one conventional coating was deposited by plasma spraying. The as sprayed coatings were characterized with relative to coating thickness, microhardness, porosity and microstructure. The optical microscopy (OM), the XRD analysis and field mission scanning electron microscope (FESEM with EDAX attachment) techniques have been used to identify various phases formed after coating deposited on the surface of the substrate. Subsequently the sliding wear behaviour of uncoated, PVD sprayed nanostructured thin TiAlN coatings deposited at 500°C and 200°C and plasma sprayed conventional coated AISI-347 grade boiler steel were investigated according to ASTM standard G99-03 using pin on disk wear test rig. Cumulative wear volume loss and coefficient of friction, μ were calculated for the coated as well as uncoated specimens for 10, 15 and 20 N normal loads at a constant sliding velocity of 1 m/sec. The worn out samples were analysed with SEM/EDAX. Wear rates in terms of volumetric loss (mm³/g) for uncoated and coated alloys were compared. The nanostructured TiAlN coatings deposited at 500°C and 200°C has shown minimum wear rate as compared to conventional TiAlN coating and uncoated AISI-347 grade boiler steel. Nanostructured TiAlN coatings were found to be successful in retaining surface contact with the substrate after the wear tests.

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Gonzalez Rodriguez, R., J. L. Viesca Rodriguez, A. Hernandez Battez, E. Asedegbega, A. Higuera Garrido, and A. Torres Perez. "1-Hexyl-3-Methylimidazolium Hexafluorophosphate as Oil Additive for the Lubrication of Steel-Steel Contacts and its Influence on the Running-In and Wear-In Periods." In ASME/STLE 2011 International Joint Tribology Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ijtc2011-61039.

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The effectiveness of ionic liquids as lubricants or additives has been recently studied for several tribological pairs: steel-steel, aluminium-steel and steel-titanium [1–2]. Likewise other materials used as engineering surfaces like nanocrystalline nickel coating [3], phosphor bronze [4], PVD coatings [5] and many others, have also been lubricated with ionic liquids in recent years. Most of these research studies are typically focused on the utilization of ionic liquids as neat lubricants. However, in economic terms, the use of ionic liquids as oil additives is more convenient because of its high cost.

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Dwyer-Joyce, R. S., J. Zhang, B. W. Drinkwater, J. Elgoyen, and K. J. Kirk. "Instrumentation of a Rolling Bearing With a Thin Film Piezo Coating for Oil Film Measurement." In ASME/STLE 2007 International Joint Tribology Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ijtc2007-44228.

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This paper describes a novel design of oil-film monitoring sensor capable of measuring oil-film thickness in concentrated contacts. The approach is to use a thin (approx. 4 μm) sputtered coating of piezoelectric material, such as Aluminium Nitride. When correctly electroded this acts as an ultrasonic sensor with a usable bandwidth from 20–350 MHz. This sensor allows the interrogation of the small lubricated region between the ball and raceway without any special focusing requirements. Typically the dimensions of the contact region is less than a millimeter wide. This sensor system is then demonstrated experimentally on a deep groove ball bearing with the piezoelectric thin film on the external surface of the bearing outer raceway. The interaction of ultrasound with the oil-film is modeled using a quasi-static spring model and this allows properties such as film thickness to be extracted. The measured thicknesses are shown to agree well those obtained from classical elastohydrodynamic lubrication theory for the high bearing loads and low speeds where several data points can be collected from the contact during a ball passage. Measurement of oil film thickness in the region of 0.1–1 μm is demonstrated.

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Звіти організацій з теми "Aluminium contacts"

Smith, A. C. Experimental investigation of contact resistance across pressed lead and aluminum. Office of Scientific and Technical Information (OSTI), March 2000. http://dx.doi.org/10.2172/752684.

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Williams, Kevin L., Steven G. Kargl, Eric L. Thorsos, David S. Burnett, Joseph L. Lopes, Mario Zampolli, and Philip L. Marston. Acoustic Scattering from an Aluminum Cylinder in Contact with a Sand Sediment: Measurements, Modeling, and Interpretation. Fort Belvoir, VA: Defense Technical Information Center, August 2009. http://dx.doi.org/10.21236/ada510047.

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Schetselaar, E. M., G. Bellefleur, and P. Hunt. Integrated analyses of density, P-wave velocity, lithogeochemistry, and mineralogy to investigate effects of hydrothermal alteration and metamorphism on seismic reflectivity: a summary of results from the Lalor volcanogenic massive-sulfide deposit, Snow Lake, Manitoba. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/327999.

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We present herein a summary of integrated data analyses aimed at investigating the effects of hydrothermal alteration on seismic reflectivity in the footwall of the Lalor volcanogenic massive-sulfide (VMS) deposit, Manitoba. Multivariate analyses of seismic rock properties, lithofacies, and hydrothermal alteration indices show an increase in P-wave velocity for altered volcanic and volcaniclastic lithofacies with respect to their least-altered equivalents. Scanning electron microscopy-energy dispersive X-ray spectrometry analyses of drill-core samples suggest that this P-wave velocity increase is due to the high abundance of high P-wave velocity aluminous minerals, including cordierite, Fe-Mg amphibole, and garnet, which in volcanic rocks are characteristic of VMS-associated hydrothermal alteration metamorphosed in the amphibolite facies. A seismic synthetic profile computed from a simple amphibolite-facies mineral assemblage model, consisting of mafic-felsic host rock contacts, a sulfide ore lens, and a discordant hydrothermal conduit, show enhanced seismic reflections at conduit-host rock contacts in comparison to the equivalent greenschist facies mineral assemblage model. Collectively our results suggest that VMS footwall hydrothermal alteration zones metamorphosed under middle- to upper-amphibolite facies conditions have enhanced potential for seismic detection.

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Avis, William. Drivers, Barriers and Opportunities of E-waste Management in Africa. Institute of Development Studies (IDS), December 2021. http://dx.doi.org/10.19088/k4d.2022.016.

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Population growth, increasing prosperity and changing consumer habits globally are increasing demand for consumer electronics. Further to this, rapid changes in technology, falling prices and consumer appetite for better products have exacerbated e-waste management challenges and seen millions of tons of electronic devices become obsolete. This rapid literature review collates evidence from academic, policy focussed and grey literature on e-waste management in Africa. This report provides an overview of constitutes e-waste, the environmental and health impacts of e-waste, of the barriers to effective e-waste management, the opportunities associated with effective e-waste management and of the limited literature available that estimate future volumes of e-waste. Africa generated a total of 2.9 million Mt of e-waste, or 2.5 kg per capita, the lowest regional rate in the world. Africa’s e-waste is the product of Local and imported Sources of Used Electronic and Electrical Equipment (UEEE). Challenges in e-waste management in Africa are exacerbated by a lack of awareness, environmental legislation and limited financial resources. Proper disposal of e-waste requires training and investment in recycling and management technology as improper processing can have severe environmental and health effects. In Africa, thirteen countries have been identified as having a national e-waste legislation/policy.. The main barriers to effective e-waste management include: Insufficient legislative frameworks and government agencies’ lack of capacity to enforce regulations, Infrastructure, Operating standards and transparency, illegal imports, Security, Data gaps, Trust, Informality and Costs. Aspirations associated with energy transition and net zero are laudable, products associated with these goals can become major contributors to the e-waste challenge. The necessary wind turbines, solar panels, electric car batteries, and other "green" technologies require vast amounts of resources. Further to this, at the end of their lifetime, they can pose environmental hazards. An example of e-waste associated with energy transitions can be gleaned from the solar power sector. Different types of solar power cells need to undergo different treatments (mechanical, thermal, chemical) depending on type to recover the valuable metals contained. Similar issues apply to waste associated with other energy transition technologies. Although e-waste contains toxic and hazardous metals such as barium and mercury among others, it also contains non-ferrous metals such as copper, aluminium and precious metals such as gold and copper, which if recycled could have a value exceeding 55 billion euros. There thus exists an opportunity to convert existing e-waste challenges into an economic opportunity.

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Bryant, C. A., S. A. Wilks, and C. W. Keevil. Survival of SARS-CoV-2 on the surfaces of food and food packaging materials. Food Standards Agency, November 2022. http://dx.doi.org/10.46756/sci.fsa.kww583.

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COVID-19, caused by the SARS-CoV-2 virus, was first reported in China in December 2019. The virus has spread rapidly around the world and is currently responsible for 500 million reported cases and over 6.4 million deaths. A risk assessment published by the Foods Standards Agency (FSA) in 2020 (Opens in a new window) concluded that it was very unlikely that you could catch coronavirus via food. This assessment included the worst-case assumption that, if food became contaminated during production, no significant inactivation of virus would occur before consumption. However, the rate of inactivation of virus on products sold at various temperatures was identified as a key uncertainty, because if inactivation does occur more rapidly in some situations, then a lower risk may be more appropriate. This project was commissioned to measure the rate of inactivation of virus on the surface of various types of food and food packaging, reducing that uncertainty. The results will be used to consider whether the assumption currently made in the risk assessment remains appropriate for food kept at a range of temperatures, or whether a lower risk is more appropriate for some. We conducted a laboratory-based study, artificially contaminating infectious SARS-CoV-2 virus onto the surfaces of foods and food packaging. We measured how the amount of infectious virus present on those surfaces declined over time, at a range of temperatures and relative humidity levels, reflecting typical storage conditions. We tested broccoli, peppers, apple, raspberry, cheddar cheese, sliced ham, olives, brine from the olives, white and brown bread crusts, croissants and pain au chocolat. The foods tested were selected as they are commonly sold loose on supermarket shelves or uncovered at deli counters or market stalls, they may be difficult to wash, and they are often consumed without any further processing i.e. cooking. The food packaging materials tested were polyethylene terephthalate (PET1) trays and bottles; aluminium cans and composite drinks cartons. These were selected as they are the most commonly used food packaging materials or consumption of the product may involve direct mouth contact with the packaging. Results showed that virus survival varied depending on the foods and food packaging examined. In several cases, infectious virus was detected for several hours and in some cases for several days, under some conditions tested. For a highly infectious agent such as SARS-CoV-2, which is thought to be transmissible by touching contaminated surfaces and then the face, this confirmation is significant. For most foods tested there was a significant drop in levels of virus contamination over the first 24 hours. However, for cheddar cheese and sliced ham, stored in refrigerated conditions and a range of relative humidity, the virus levels remained high up to a week later, when the testing period was stopped. Both cheddar cheese and sliced ham have high moisture, protein and saturated fat content, possibly offering protection to the virus. When apples and olives were tested, the virus was inactivated to the limit of detection very quickly, within an hour, when the first time point was measured. We suggest that chemicals, such as flavonoids, present in the skin of apples and olives inactivate the virus. The rate of viral decrease was rapid, within a few hours, for croissants and pain au chocolat. These pastries are both coated with a liquid egg wash, which may have an inhibitory effect on the virus. Food packaging materials tested had variable virus survival. For all food packaging, there was a significant drop in levels of virus contamination over the first 24 hours, in all relative humidity conditions and at both 6°C and 21°C; these included PET1 bottles and trays, aluminium cans and composite drinks cartons.

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Farm worker electrocuted when aluminum grain tube contacts overhead power line. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, January 1995. http://dx.doi.org/10.26616/nioshsface94wi305.

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Carpenter electrocuted in Pennsylvania when aluminum edging contacts powerline, October 28, 1990. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, June 1990. http://dx.doi.org/10.26616/nioshface9010.

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Insulation installer dies when his aluminum ladder makes contact with overhead power line. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, February 1991. http://dx.doi.org/10.26616/nioshsface90nj013.

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Carpenter dies after falling 22 feet from a ladder when aluminum siding section contacts an overhead power line. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, January 1992. http://dx.doi.org/10.26616/nioshsface91nj017.

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Roofer dies after falling 30 feet from a ladder when an aluminum pole contacts an overhead power line. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, December 1993. http://dx.doi.org/10.26616/nioshsface93nj069.

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