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Qian, Feng Prorok Barton Charles. "Numerical simulation and mechanical properties of free-standing silver thin films." Auburn, Ala., 2006. http://hdl.handle.net/10415/1301.
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Yang, Wen Fu. "Laser cladding surface treatment for enhancement of mechanical properties." Thesis, Peninsula Technikon, 2003. http://hdl.handle.net/20.500.11838/1267.
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Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 2003Systematic laser cladding experiments were performed using a mixture of a Nickel base alloy powder mixed with tungsten carbide powder (percentage contents of tungsten carbide from 10% to 40%) on EN8 steel substrate with pre-placed powder method. Laser cladding of the Nickel base alloy powder + 50% tungsten carbide powder on EN9 steel substrate was performed with powder injection method as well. A Finite Element Method for calculating the surface temperature distribution was used to help prediction of temperature distribution laser cladding results. Composition of cladding materials was designed; a sticking agent was chosen for the pre-placed powder method. Clad coatings were obtained for different process parameters for laser cladding, and a detailed study of the affects of these parameters has been carried out. The characteristic microstructure and properties of the clad layers and interface were investigated by using an optical microscope, a micro hardness tester and a makeshift wear test. A comprehensive review is presented on the dilution of the coating and the typical problems experienced with the coating substrate interface. The results show that microstructure of clad layers comprise three zones: the cladding layer, bonding zone and heat-affected zone. The results showed that tungsten carbide particles increased the hardness and wear resistance as expected. Wear resistance of laser cladding coating is 3.5 times than that of substrate. The micro hardness range of the cladding layer is from RV 981.5 to RV 1187, which is 2-3 times than that of substrate. The micro hardness varies from cladding coating to transition layer then to heat affected zone and substrate along a gradient.
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Magubane, Siphesihle Siphamandla. "Metal assisted chemically etched silicon nanowires for application in a hybrid solar cell." University of the Western Cape, 2018. http://hdl.handle.net/11394/6733.
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>Magister Scientiae - MScPhotovoltaic (PV) devices based on inorganic-organic hybrid active layers have been extensively studied for over a decade now. However, photoactive hybrid layers of material combinations such as rr-P3HT and SiNWs still require further exploration as candidates for solar cell (SC) fabrication, due to favourable optical absorption and charge carrier mobility associated with them respectively. The ultimate goal of the study is to fabricate ITO/PEDOT:PSS/rr-P3HT:SiNWs/Al SCs with different SiNWs content and investigate the different parameters or factors influencing the performance of these cells. The vertically aligned SiNW arrays on a Si wafer were synthesised via metal assisted chemical etching (MACE) and a method of chemically detaching these wires was developed. The average length and the diameter of the SiNWs obtained were 4.5 μm and 0.2 μm, respectively. Different weight ratios of as-synthesised SiNWs were then incorporated within rr-P3HT to form different hybrid solutions, i.e. rr-P3HT: 0.3 wt% SiNWs, rr-P3HT: 0.7 wt% SiNWs and rr-P3HT: 1.3 wt% SiNWs. In addition, a pure rr- P3HT solution was made for reference purposes. SEM characterisation shows that the SiNWs are randomly distributed across the active area, and that the film becomes progressively inhomogeneous upon addition of SiNWs, whereas the TEM characterisation revealed that there is no chemical interaction between the rr-P3HT and SiNWs. The UV-Vis and PL spectra suggest that there are changes in absorption and emission characteristics upon SiNW incorporation into the rr-P3HT matrix, which may have impacted the charge transfer .The electrical properties of the different hybrid films were probed using Hall Effect measurements, which revealed that the conductivity increases with the increase in the concentration of nanowires (NWs). The increase in conductivity upon the addition of SiNWs in the rr-P3HT matrix was related to an increase of the mobility (μ) of charge carriers in the hybrid films.
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Mallett, Jonathan James. "Electrochemical deposition, characterisation of metal films, and the modification of electrodes by near-field photolithography." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324298.
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Yen, Yung-Chang. "Modeling of metal cutting and ball burnishing prediction of tool wear and surface properties /." Columbus, Ohio : Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1073065455.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xxviii, 254 p.; also includes graphics. Includes abstract and vita. Advisor: Taylan Altan, Dept. of Industrial and Systems Engineering. Includes bibliographical references (p. 240-248).
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Hosoi, A., M. Hamada, A. Fujimoto, and Y. Ju. "Properties of M-AFM probe affected by nanostructural metal coatings." IEEE, 2009. http://hdl.handle.net/2237/13920.
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Jain, Aman Vinay. "Corrosion Inhibitive Properties of Metal-Gluconate Coatings on Al Substrates." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1509983584874447.
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Torrey, Jason Robert. "Antimicrobial Properties Of Metal And Metal-Halide Nanoparticles And Their Potential Applications." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/338682.
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Heavy metals have been known to possess antimicrobial properties against bacterial, fungal, and viral pathogens. Silver and copper in particular have been used for millennia to control bacterial and fungal contamination. Metal nanoparticles (aggregations of metal atoms 1-200 nm in size) have recently become the subject of intensive study for their increased antimicrobial properties due to their increased surface area and localized release of metal ions when attached to pathogens. In the current studies, metal and metalhalide nanoparticles including silver (Ag), silver bromide (AgBr), silver iodide (AgI), and copper iodide (CuI) nanoparticles were evaluated for their antibacterial efficacy against two common bacterial pathogens. All of the nanoparticles significantly reduced bacterial numbers within 24 hours of exposure and were more effective against the Gram-negative Pseudomonas aeruginosa than the Gram-positive Staphylococcus aureus. CuI nanoparticles were found to be highly effective, reducing both organisms by >4.43 log₁₀ within 15 minutes at 60 ppm Cu. CuI nanoparticles were selected for further evaluation against a range of microorganisms to determine their broad spectrum efficacy. CuI nanoparticles formulated with different stabilizers (sodium dodecyl sulfate, SDS; PVP) were tested against representative Gram-positive and Gram-negative bacteria, Mycobacteria, a fungus (Candida albicans), and a non-enveloped virus (poliovirus). Both nanoparticles caused significant reductions in most of the Gram-negative bacteria within five minutes of exposure (>5.09-log₁₀). The Gram-positive bacterial species were more sensitive to the CuI-SDS than the CuI-PVP nanoparticles. Likewise, C. albicans was also more sensitive to the CuI-SDS than the CuI-PVP nanoparticles. In contrast, the acid-fast Mycobacterium smegmatis was more resistant to the CuI-SDS than the CuI-PVP nanoparticle solutions (2.54-log₁₀ vs. 3.80-log₁₀ after 30 minutes). Poliovirus was more resistant than the other organisms tested except for Mycobacterium fortuitum. M. fortuitum was more resistant to both CuI nanoparticle solutions than any of the other organisms tested, requiring longer exposure times to achieve comparable reductions (~4.15 log₁₀ after 24 hours). As an example of a real world antimicrobial application, polymer surface coatings with embedded CuI nanoparticles were investigated to determine their potential use as self-disinfecting surfaces. Brushed polyurethane, spincoated acrylic, and powder coated polyester-epoxy coatings containing various concentrations of CuI nanoparticles were tested for antibacterial efficacy against P. aeruginosa and S. aureus. Polyester-epoxy powder coatings were superior to the other coatings in terms of uniformity and stability under moist conditions and displayed antimicrobial properties against both organisms (>4.92 log₁₀) after six hours at 0.25% Cu. Polyester-epoxy coatings were selected for more rigorous testing under adverse conditions. These surfaces were negatively impacted when tested under dry conditions with high organic content, with organic content appearing to have a greater impact on antimicrobial efficacy. At 0.25% Cu, the antibacterial activity of the powder coatings was not impacted by washing with several commercial cleaners; however, at concentrations of 0.05% Cu, antibacterial activity was reduced by multiple washings with water, Windex®, and Pine Sol®. Additionally, ultrasonic cleaning of the coatings appeared to decrease their antimicrobial efficacy. Despite this, CuI nanoparticles were found in all studies to have great potential as a new class of fast-acting, broad-spectrum antimicrobial.
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Nygren, Kristian. "Magnetron Sputtering of Nanocomposite Carbide Coatings for Electrical Contacts." Doctoral thesis, Uppsala universitet, Oorganisk kemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302063.
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Today’s electronic society relies on the functionality of electrical contacts. To achieve good contact properties, surface coatings are normally applied. Such coatings should ideally fulfill a combination of different properties, like high electrical conductivity, high corrosion resistance, high wear resistance and low cost. A common coating strategy is to use noble metals since these do not form insulating surface oxides. However, such coatings are expensive, have poor wear resistance and they are often applied by electroplating, which poses environmental and human health hazards. In this thesis, nanocomposite carbide-based coatings were studied and the aim was to evaluate if they could exhibit properties that were suitable for electrical contacts. Coatings in the Cr-C, Cr-C-Ag and Nb-C systems were deposited by magnetron sputtering using research-based equipment as well as industrial-based equipment designed for high-volume production. To achieve the aim, the microstructure and composition of the coatings were characterized, whereas mechanical, tribological, electrical, electrochemical and optical properties were evaluated. A method to optically measure the amount of carbon was developed. In the Cr-C system, a variety of deposition conditions were explored and amorphous carbide/amorphous carbon (a-C) nanocomposite coatings could be obtained at substrate temperatures up to 500 °C. The amount of a-C was highly dependent on the total carbon content. By co-sputtering with Ag, coatings comprising an amorphous carbide/carbon matrix, with embedded Ag nanoclusters, were obtained. Large numbers of Ag nanoparticles were also found on the surfaces. In the Nb-C system, nanocrystalline carbide/a-C coatings could be deposited. It was found that the nanocomposite coatings formed very thin passive films, consisting of both oxide and a-C. The Cr-C coatings exhibited low hardness and low-friction properties. In electrochemical experiments, the Cr-C coatings exhibited high oxidation resistance. For the Cr-C-Ag coatings, the Ag nanoparticles oxidized at much lower potentials than bulk Ag. Overall, electrical contact resistances for optimized samples were close to noble metal references at low contact load. Thus, the studied coatings were found to have properties that make them suitable for electrical contact applications.
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Millon, Eric. "Étude des mécanismes d'adhérence des émaux sur les aciers." Nancy 1, 1987. http://www.theses.fr/1987NAN10099.
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Caractérisation des propriétés chimiques d'un émail fondu à 800**(O)C par une étude du comportement de ce dernier vis-à-vis des différents composés chimiques intervenant lors de l'émaillage des aciers. Influence de la nature de l'acier. Proposition d'un mécanisme de réactions successives se produisant à l'interface
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Aleksandar, Miletić. "Razvoj nanoslojnih i nanokompozitnih metal-nitridnih prevlaka." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=95438&source=NDLTD&language=en.
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Razvijene su TiAlN/TiSiN i CrAlN/TiSiN nanoslojne prevlake u kojima je napravljen spoj nanoslojnog i nanokompozitnog dizajna. Akcenat je stavljen na proizvodnju prevlaka visoke tvrdoće i visoke otpornosti na lom. Proučavane su i jednoslojne TiAlN, nanokompozitne TiSiN i višeslojne TiAlN/TiSiN prevlake kako bi se utvrdilo kako dizajn utiče na osobine prevlaka. Sve prevlake pripremane su sa jednim, dva i tri stepena rotacije. Pokazano je da dizajn i vid rotacije značajno utiču na mikrostrukturu i teksturu prevlaka, a time na njihove mehaničke osobine, otpornost na lom, adheziju između prevlake i podloge, topografiju površine i tribološko ponašanje. Nanoslojne i nanokompozitne prevlake odlikuju se kompaktnom nanokristalnom mikrostrukturom, dok jednoslojne TiAlN prevlake imaju stubastu strukturu sa kristalnim zrnima veće veličine. Pri prelasku sa jednog na više stepeni rotacije mikrostruktura prevlaka postaje kompaktnija sa kristalnim zrnima manje veličine i manjom poroznošću. U skladu sa tim, najmanju hrapavost, najveću tvrdoću, najveću otpornost na lom i najveću otpornost na habanje imaju nanoslojne i nanokompozitne prevlake pripremane sa dva i tri stepena rotacije.With the aim to develop hard coatings characterized by both, high hardnessand high resistance to cracking, synergy between nanolayered andnanocomposite design was made and nanolayered TiAlN/TiSiN andCrAlN/TiSiN coatings were produced. Monolayer TiAlN, nanocompositeTiSiN and multilayer TiAlN/TiSiN were also studied in order to find therelation between the coating design and their properties. All coatings weredeposited with 1-fold, 2-fold and 3-fold rotation. It is shown that coatingdesign and type of rotation have great influence on coating microstructureand texture, and in this way on their mechanical properties, resistance tocracking, adhesion between coating and substrate, surface topography andtribological behavior. Nanolayered and nanocomposite coatings arecharacterized by compact nanocrystalline microstructure, while monolayerTiAlN coatings have columnar structure with larger crystalline grains. Byincreasing the number of rotational degrees from 1-fold to 3-fold size ofcrystalline grains decreases and microstructure becomes more dense.Therefore, nanolayered and nanocomposite coatings deposited with 2-foldand 3-fold rotation are characterized by the highest hardness, highestresistance to cracking, highest wear resistance and the smoothest surfacetopography.
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Thurber, Casey Ray. "Electrodeposited Metal Matrix Composites for Enhanced Corrosion Protection and Mechanical Properties." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849736/.
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In the oil and gas industry, high corrosion resistance and hardness are needed to extend the lifetime of the coatings due to exposure to high stress and salt environments. Electrodeposition has become a favorable technique in synthesizing coatings because of low cost, convenience, and the ability to work at low temperatures. Electrodeposition of metal matrix composites has become popular for enhanced corrosion resistance and hardness in the oil and gas industry because of the major problems that persist with corrosion. Two major alloys of copper-nickel, 90-10 and 70-30, were evaluated for microbial corrosion protection in marine environments on a stainless steel substrate. Copper and copper alloys are commonly used in marine environments to resist biofouling of materials by inhibiting microbial growth. Literature surveying the electrodeposition of Cu-Ni incorporated with nano- to micro- particles to produce metal matrix composites has been reviewed. Also, a novel flow cell design for the enhanced deposition of metal matrix composites was examined to obtain the optimal oriented structure of the layered silicates in the metal matrix. With the addition of montmorillonite into the Ni and Cu-Ni matrix, an increase in strength, adhesion, wear and fracture toughness of the coating occurs, which leads to an increase corrosion resistance and longevity of the coating. These coatings were evaluated for composition and corrosion using many different types of instrumental and electrochemical techniques. The overall corrosion resistance and mechanical properties were improved with the composite films in comparison to the pure metals, which proves to be advantageous for many economic sectors including the oil and gas industry.
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Weng, Duan. "Corrosion protection of metals by phosphate coatings and ecologically beneficial alternatives : properties and mechanisms /." [S.l.] : [s.n.], 1995. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=11262.
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Baydemir, Tuncay. "Investigations On The Properties And Drug Releases Of Biodegradable Polymer Coatings On Metal Substrates As Drug Carriers." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12611140/index.pdf.
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The use of various biodegradable polymers for the improvement of different controlled and long-lasting drug release systems is an active research area in recent years. The application of different metal prostheses, especially titanium based ones,
to the human body is also very common. A most important disadvantage of these prostheses is the risk of infection at the application areas that necessitates the removing of the prosthesis with a second surgical operation and reapplication of it after recovery. One of the best ways to solve this problem is to render metal prostheses infection free with controlled and sustainable drug (antibiotic) release systems.
The long term sustained release of relevant antibiotics from the various biodegradable polymer coated metal implants is studied in this thesis. Virtual fatigue analysis and drug loading capacities of titanium and stainless steel samples with different surface pattern and modifications were studied. Various biodegradable
polymer and drug combinations were examined and used for coating of metal prosthesis. The aim is to design polymer-drug coated metal implants that are capable of releasing a feasible amount of drug up to a period of at least 1 month. Various
coating techniques and surface modifications were also employed to improve the adhesional properties of the drug containing polymers. Their adhesion abilities on the metal substrates were tested by Lap-shear and T-peel tests. Polymer degradation
kinetics was followed by viscosity studies. Calibration lines for different drugs were obtained and drug releases on different systems were followed by using UV spectroscopy and microbial antibiotic sensitivity tests.
Among the techniques applied to prevent fast release of drugs initially, the coatings of Vancomycin absorbed β
-TCP (&
#946
-tricalcium phosphate) homogeneously distributed in poly(D,L-lactide-co-glycolide) solution in chloroform followed by an inert coating with poly(L-lactide) system proved to be feasible. By this technique, initial burst release was minimized and drug release from implants lasted nearly 2 months. Multiple coatings on polymer plus drug coating layer also gave promising results. In vivo studies on dorsal muscles of native rabbits with antibiotic loaded implants gave no negative effect on the surrounding tissues with high compatibility free of infection.
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Mirhashemihaghighi, Shadi. "Nanometre-thick alumina coatings deposited by ALD on metals : a comparative electrochemical and surface analysis study of corrosion properties." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066349/document.
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La protection contre la corrosion par des films ultramince (≤50 nm) d'alumine déposées par ALD sur le cuivre et l'aluminium à 250°C a été étudiée dans une solution aqueuse 0,5 M de NaCl en combinant méthodes d'analyse électrochimique et de surface. L'étude de l'alumine ALD sur un substrat Cu comprend l'effet de l'épaisseur du revêtement, l'effet de l'oxyde interfacial, l'effet de la préparation de la surface et la durabilité du revêtement. Pour le substrat Al, le travail a porté sur l'examen de l'effet de l'épaisseur du revêtement. Les revêtements ont montré d'excellentes propriétés de corrosion sur des substrats Cu électropoli, tandis qu'ils ont échoué à protéger le substrat recuit, de fait d'une mauvaise adhérence à une surface lissée. L'amélioration de la résistance à la corrosion d'alumine ALD sur le substrat Cu est obtenue en l'absence de vieillissement de l'oxyde natif interfacial, et sa modification par un prétraitement. En dépit de remarquables propriétés d'étanchéité sur un substrat Cu électropoli, la protection contre la corrosion de l'alumine ALD n'est pas durable. Le revêtement du substrat Al avec l'alumine ALD conduit à l'augmentation significative de la résistance à la corrosion. Le potentiel de piqûration est augmenté en présence des revêtements l'épaisseur de 20 et 50 nm, ce qui n'a pas été obtenus avec 10 nm en raison de sa faible épaisseur. Cette étude est une étude préliminaire pour l'application de revêtements d'alumine ALD pour la protection contre la corrosion des alliages Al-Cu en combinaison avec d'autres compositions ALDCorrosion protection by ultrathin (≤ 50 nm) alumina films deposited by atomic layer deposition (ALD) on copper and aluminium at 250°C was studied in 0.5 M NaCl aqueous solution by combining electrochemical and surface analytical methods. The study of ALD Al2O3 on Cu substrate included investigation of the effect of the coating thickness, the effect of an interfacial oxide, the effect of surface preparation and the durability of the coating. For ALD Al2O3 on Al substrate, the work focused on the examination of the effect of the deposited coating thickness. ALD alumina coatings showed excellent corrosion properties on electropolished copper substrates, while they failed to protect the annealed substrate, as a result of poor adhesion to a smoothened surface. Modification of interfacial native copper oxide by its pre-treatment led to better corrosion protection of ALD alumina on copper substrate. Despite its remarkable sealing properties on electropolished Cu substrate, corrosion protection of ALD alumina was not durable. Coating of Al substrate with ALD Al2O3 led to significant increase of polarization resistance. Better performance was obtained for 10 and 20 nm coatings on Al than on Cu. Apart from significant decrease of current, the pitting potential was increased in presence of 20 and 50 nm coatings, which was not achieved with 10 nm due to its low thickness. This study was a preliminary study for application of ALD alumina coatings for corrosion protection of Al-Cu alloys in combination with other ALD compositions
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Wiesing, Martin [Verfasser]. "Interfacial reactivity and adhesive properties of ternary transition metal nitride hard coatings in contact with polymers / Martin Wiesing." Paderborn : Universitätsbibliothek, 2018. http://d-nb.info/1163318957/34.
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Anancharoenwong, Ekasit. "Synthesis and characterization of cis-1, 4-polyisoprene-based polyurethane coatings ; study of their adhesive properties on metal surface." Phd thesis, Université du Maine, 2011. http://tel.archives-ouvertes.fr/tel-00649080.
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Industriellement, les problématiques d'adhésion polymère/métal se rencontrent dans de nombreux secteurs tels que l'industrie automobile, ou les applications aéronautiques et électroniques. Les polyuréthanes (PU) sont fréquemment utilisés comme adhésifs structuraux, et sont obtenus à partir de polyols provenant de la pétrochimie (polyester et polyéther polyols). Cependant, ces produits ont des inconvénients notables sur le plan écologique car ils sont produits à partir de ressources non renouvelables, ils peuvent également générer une pollution de l'environnement, et leurs matières premières de départ sont d'une part de plus en plus coûteuses et d'autres part amenées à se raréfier dans les années à venir. Le caoutchouc naturel (NR) est une alternative intéressante aux polyols de synthèse car il est issu d'une ressource végétale (hévéa), renouvelable et abondante, et également car il présente des propriétés mécaniques intéressantes. De plus, il peut être facilement modifié chimiquement, afin notamment d'apporter des groupements hydroxyle capables de réagir ensuite avec des fonctions isocyanate pour former un polyuréthane. Dans ce travail, le polyisoprène hydroxytéléchélique (HTPI) ayant une fonctionnalité en hydroxyle de 2 a été synthétisé avec succès par époxydation contrôlée suivie de coupure oxydante de polyisoprène de hautes masses, puis réduction sélective des oligoisoprènes carbonyltéléchéliques obtenus. Ces HTPI de différentes masses molaires (1000-8000 g mol-1) ont été obtenus de façon reproductible. Des modifications chimiques ont été effectuées par époxydation à différents taux (10-60% EHTPI). Les différentes microstructures de ces oligomères ont été mises en évidence par FT-IR, RMN and SEC. Leurs propriétés thermiques ont été déterminées par ATG et DSC. Les propriétés de surface (énergie de surface, microscopie optique) et les propriétés d'adhésion (test de clivage) de différents matériaux ont été caractérisées. Les échantillons à base de HTPI pur (sans époxyde) présentent un niveau d'adhésion élevé. Des taux d'époxydation proches de 30-40% permettent d'obtenir des performances adhésives intéressantes. D'autre part, l'effet de la masse molaire est faible(cependant, une masse molaire plus élevée entraîne globalement une meilleure adhérence). Le niveau d'adhérence observé est similaire à ceux mesurés pour des adhésifs structuraux utilisés dans l'industrie automobile ou aéronautique. Le test de clivage est un test d'adhérence sévère pour un joint adhésif, et les faibles propagations de fissures observées pour certaines formulations permettent d'escompter des développements industriels prometteurs pour ces nouveaux polymères.
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Sanchette, Fredéric. "Synthèse et caractérisation de dépôts Al-Cr-(N) et Al-Ti-(N) obtenus par pulvérisation cathodique magnétron en condition réactive." Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL057N.
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Ce travail porte sur l'élaboration et la caractérisation chimique, structurale, mécanique et électrochimique de revêtements Al-Cr-(N) et Al-Ti-(N) obtenus par pulvérisation cathodique magnétron de cibles composites Al-Cr et Al-Ti dans des plasmas d'argon et d'argon/azote. Les mécanismes de transfert de matière sont d'abord étudiés avec l'aide de l'analyse métallurgique des revêtements, le diagnostic du plasma par spectrométrie d'émission optique et un modèle de pulvérisation adapté à la géométrie des cibles composites. Les revêtements bruts de pulvérisation sont composés de solutions solides microcristallines ou amorphes. L’azote favorise l'amorphisation des revêtements. Les solutions solides amorphes à base d'aluminium qui sont sursaturées en chrome ou en titane et, éventuellement, en azote sont particulièrement étudiées car elles offrent le meilleur compromis entre le renforcement mécanique des revêtements et leurs propriétés électrochimiques. La stabilité thermique de ces revêtements amorphes est aussi discutée
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Torgerson, Tyler B. "Room and Elevated Temperature Sliding Wear Behavior of Cold Sprayed Ni-WC Composite Coatings." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1248400/.
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The tribological properties of cold sprayed Ni-WC metal matrix composite (MMC) coatings were investigated under dry sliding conditions from room temperature (RT) up to 400°C, and during thermal cycling to explore their temperature adaptive friction and wear behavior. Characterization of worn surfaces was conducted using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Raman spectroscopy to determine the chemical and microstructural evolution during friction testing. Data provided insights into tribo-oxide formation mechanisms controlling friction and wear. It was determined that the steady-state coefficient of friction (CoF) decreased from 0.41 at RT to 0.32 at 400˚C, while the wear rate increased from 0.5×10-4 mm3/N·m at RT to 3.7×10-4 mm3/N·m at 400˚C. The friction reduction is attributed primarily to the tribochemical formation of lubricious NiO on both the wear track and transfer film adhered to the counterface. The increase in wear is attributed to a combination of thermal softening of the coating and a change in the wear mechanism from adhesive to more abrasive. In addition, the coating exhibited low friction behavior during thermal cycling by restoring the lubricious NiO phase inside the wear track at high temperature intervals. Therefore, cold sprayed Ni-WC coatings are potential candidates for elevated temperature and thermally self-adaptive sliding wear applications.
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Darbeïda, Abdelhamid. "Mise au point d'une démarche expérimentale de caractérisation de la tenue mécanique des dépôts durs protecteurs de chrome et d'acier inoxydable : mécanismes d'endommagement sous sollicitations avec contact en relation avec les caractéristiques microstructurales." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL006N.
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On présente une démarche expérimentale de caractérisation de la tenue mécanique des matériaux revêtus. Cette démarche est basée sur les tests de complexité croissante: 1 d'indentation Vickers sous forte charge normale, 2 de rayure monopasse à charge normale croissante et constante, 3 de frottement et d'usure par rayure multipasses à charge normale constante et par usure pion-disque. Appliquée à des revêtements d'acier inoxydable austénitique AISI 316L enrichi en azote et sur des revêtements de chrome (de 5 à 30 [micro]m d'épaisseur), la démarche a permis de dégager les principaux facteurs mécaniques et microstructuraux, intrinsèques et extrinsèques au dépôt, qui influent sur la fragilité et sur la résistance à l'usure du composite. On montre que la tenue mécanique est clairement une propriété du composite. La fragilité du dépôt est intimement liée aux propriétés mécaniques du substrat et de son état de surface initial avant la phase de dépôt. Le rodage et l'augmentation de la dureté du substrat améliorent la résistance à la fissuration du dépôt. La fragilité du dépôt et celle de son interface sont considérées comme les plus importants mécanismes d'endommagement du composite. Dans ce contexte, la charge critique de fissuration fragile, dans le dépôt ou à l'interface entre le dépôt et le substrat, est plus adéquate dans les tests micro mécaniques d'indentation et de rayure et dans les tests de frottement cyclique pour caractériser la fragilité du composite. La fragilité est d'autant plus importante que la densité de défauts et l'intensité des contraintes d'extension sont importantes. Enfin, on établit clairement l'insuffisance de la charge critique de décohésion, en effet, en rayure monopasse à charge croissante, la défaillance interfaciale des dépôts de chrome élaborés par pulvérisation cathodique, à Lc2 = 30N, n'a aucune incidence sur le comportement du dépôt en frottement et usure, sollicitations qui sont représentatives de la réalité d'application de tels revêtements. La dureté s'est avéré la seule variable qui définit l'usure du dépôt
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Bouhouch, Lahoussine. "Élaboration des couches d'alliages NI-FE par voie électrolytique : Études électrique, magnétique et structurale." Nancy 1, 1988. http://www.theses.fr/1988NAN10089.
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Mécanismes, caractéristiques et facteurs influant le dépôt électrolytique. Techniques d'élaboration et de dosage du fer dans les alliages NI-FE déposés. Influence des conditions opératoires sur la nature et composition des alliages élaborés. Étude des propriétés électriques magnétiques et de l'influence des traitements thermiques sur la structure des alliages
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Brodu, Etienne. "Thermal radiative properties and behavior of refractory metals, highly textured metallic coatings and pyrolytic boron nitride on C/C composite for the Solar Probe Plus mission." Thesis, Perpignan, 2014. http://www.theses.fr/2014PERP1203.
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Les travaux menés durant cette thèse s’inscrivent dans le cadre du développement de la mission spatiale Solar Probe Plus (NASA). Cette sonde d’exploration, dont la vocation est l’étude du Soleil, pénétrera la couronne solaire pour y faire des mesures in-situ. Ce travail de thèse a consisté à mener l’étude expérimentale des matériaux constitutifs de la sonde: métaux réfractaires (W, Re, Ta, Mo, Nb, Ti), composite C/C, un revêtement de nitrure de bore pyrolytique (pBN) ainsi que des dépôts métalliques texturés à forte émissivité. L’environnement à l’approche du soleil fut reproduit expérimentalement au sol au laboratoire PROMES-CNRS en associant le four solaire d’1 MW à Odeillo au moyen d’essai MEDIASE (Moyen d’Essai et de Diagnostic en Ambiance Spatiale Extrême). Grâce à ces moyens expérimentaux, ces matériaux candidats ont pu être testés sous formes d’échantillons, à très haute température (1100-2500 K), sous vide (10-4 Pa), ainsi que sous bombardement de protons (1-4 keV, jusqu'à 1018 ions m-2 s-1, pour la simulation du vent solaire). La propriété matériau sur laquelle cette étude expérimentale s’est concentrée est l’émissivité, dans la mesure où celle-ci va conditionner la température des surfaces de la sonde faisant face au Soleil. Celle-ci a été mesurée in-situ dans MEDIASE pendant les différents traitements. Dans le cadre de l’étude des métaux réfractaires, il a s’agit de comprendre la relation entre état de surface et émissivité, ainsi que d’étudier les modifications induites par les traitements. En ce qui concerne les dépôts métalliques texturés ainsi que le dépôt de pBN, leur étude a consisté à évaluer leurs performances radiatives et leurs comportements à haute températureSolar Probe Plus (NASA) will be a historic mission of space exploration as it will consist in the first spacecraft to enter the solar corona. The spacecraft will face harsh environmental conditions that no other spacecraft has ever encountered in the past. One of the most critical technology developments for this mission is thus material science related: the materials constituting all the surfaces directly facing the Sun must be studied and tested in a relevant environment. The study of the candidate materials has been carried out at PROMES-CNRS: refractory metals for the instruments (W, Re, Ta, Mo, Nb, Ti, and their alloys), and refractory ceramics for the thermal protection shield (C/C composite and pyrolytic boron nitride - pBN). Samples of these materials were tested experimentally in a simulated near-Sun environment. This environment was simulated on ground thanks to the association of the 1 MW solar furnace in Odeillo, to the MEDIASE facility. This way materials were tested at very high temperature (1100-2500 K) in high vacuum (10-4 Pa), with the solar wind being reproduced via a proton bombardment (1-4 keV, up to 1018 ions m-2 s-1). The material properties that we have studied the most are the thermal radiative properties as they fully determine the temperature of a free-standing surface exposed to an intense radiative flux in vacuum. For refractory metals, it mainly consisted in studying the relationship between surface state and radiative properties, as well as the effect of the treatments. As for the textured metallic coatings and pBN, it consisted mainly in determining their efficiencies and understanding their behaviors
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Albo, Zieme Louise, and Pontus Bergstedt. "A pre-study for functional coatings evaluated on light metals to be applied on a new HPDC Mg-alloy : Investigating tribological and thermophysical properties, as-cast and coated." Thesis, Jönköping University, JTH, Industriell produktutveckling, produktion och design, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-53096.
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Magnesium with two-thirds of the density compared to aluminium and one-quarter of steel, intrigues product developers and material scientists due to the light metal’s excellent combination of strength to weight ratio as well as their capability of being produced as a High Pressure Die Cast component compared to other ferrous or light metal alloys. However, a magnesium alloy inherits some concerning drawbacks, limiting the exploitation in structural applications and mechanical design such as automotive, heavy machinery and aerospace components. The need for a magnesium alloy that could withstand a sufficient amount of wear, temperature and corrosive environment, leads towards the investigation and evaluation of a suitable, functional coating as a solution to exploit the evident advantages a magnesium alloy exhibits. A substantial amount of research is required in order to reduce an existing knowledge gap that is the ongoing development in the search for a sufficient functional coating and adherence capability to the highly reactive substrate that is a magnesium alloy. This industrial master thesis is an early stage investigation to evaluate how the currently used aluminium substrate with an electrodeposited coating relate and compares to a heat-treated electroless deposited coating through tribological and thermophysical induced stresses. These properties are tested with proven industrial standard methods resulted in a comprehensive conclusion and discussion regarding the feasibility of applying the coating onto a commercial magnesium alloy closely related to the Mg-alloy developed by Husqvarna and thereby contributing to technological advances to the highly relevant topic within product development in materials engineering.
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Juškevičius, Kęstutis. "Investigation of optical and physical properties of dielectric thin films and optimisation of their deposition technologies." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140912_140620-35711.
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The main aim of this dissertation was to identify physical causes that limit optical component‘s spectral properties and resistance to laser radiation as well as to optimize the final substrate preparation procedure and coating deposition technology.
In this work we report an experimental investigation of subsurface damage (SSD) in conventionally polished fused silica (FS) substrates, which are widely used in laser applications and directly influence performances of optical elements. Subsurface damages are defined as residual digs and scratches, some of which are filled with polishing slurry and covered with so-called Bielby layer (polished layer). Acid etching procedure of FS substrates was developed, which allows removing polished layer and eliminating SSD. Different durations of acid etching have been used to study laser induces damage threshold (LIDT) of FS substrates. These experiments revealed that the optimal etching time is ~1 min for a given acid concentration. LIDT of etched FS samples increased ~4 times.
The LIDT in LiB3O5 (LBO) crystals coated with different types of (single AR@355 nm and triple AR@355+532+1064 nm wavelength) anti-reflective coatings was also investigated. All these coatings were produced of different oxide materials (ZrO2, Al2O3, and SiO2) and ZrO2-SiO2 mixtures by using the ion beam sputtering (IBS) deposition technique.
Also, we present explorations of reactive magnetron sputtering technology for deposition of ZrO2 and Nb2O5/SiO2 mixture thin... [to full text]Disertacijos tikslas buvo nustatyti fizikines priežastis, ribojančias dielektrinių optinių dangų spektrinius parametrus bei jų atsparumą lazerio spinduliuotei ir pateikti įvairių jų gamybos etapų – optinių pagrindukų paruošimo dengimo procesui, optinių dangų struktūros bei dengimo technologijų optimizavimo rekomendacijas optinių komponentų gamintojams. Šiame darbe buvo atlikta komerciškai poliruotų kvarco pagrindukų visapusiška paviršiaus analize, kuri parodė, kad paviršiuje esama poliravimo medžiagų liekanų įstrigusių įvairiuose rėžiuose bei mikrotrūkiuose ir “paslėptų” po taip vadinamu Bilbio sluoksniu. Siekiant nuėsdinti šį sluoksnį ir pašalinti poliravimo medžiagų liekanas, buvo sukurta cheminio ėsdinimo HF/HNO3 tirpale metodika. Nustatyta, kad ėsdintų kvarco pagrindukų pažaidos lazerio spinduliuotei slenkstis padidėjo apie 4 kartus. Šiame darbe didelis dėmesys buvo skiriamas naujų optinių dangų modelių paieškai ir dangų formavimui, naudojant ZrO2/SiO2 medžiagų mišinius. Panaudojant metalų oksidų mišinių sluoksnius, buvo suformuotos didelio atsparumo skaidrinančios dangos ant netiesinių LBO kristalų bei didelio atspindžio periodiškai kintančio lūžio rodiklio optinės dangos ant kvarco pagrindukų. Šiame darbe buvo pasirinktas magnetroninio dulkinimo technologijos, kuri yra santykinai nauja optinių dangų industrijoje, optimizavimas. Pirma kartą pademonstruota reaktyvaus magnetroninio dulkinimo proceso valdymas, panaudojant kombinuotą reaktyviųjų dujų jutiklį. Jo pagalba buvo... [toliau žr. visą tekstą]
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VASCONCELOS, GETÚLIO de. "Estudo e desenvolvimento de suportes refratários para a fusão e a evaporação de urânio metálico." reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9290.
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Made available in DSpace on 2014-10-09T12:25:46Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:03:34Z (GMT). No. of bitstreams: 1 11318.pdf: 5742692 bytes, checksum: aecd1fffca66bbe1056489e25f5566c9 (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Tigges, Domini. "Nocivité des défauts sous revêtement des cuves de réacteurs à eau sous pressions." Paris, ENMP, 1995. http://www.theses.fr/1995ENMP0588.
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Dans les structures de grandes dimensions réalisées en acier 16mnd5 et revêtues par soudage àa l'arc avec deux couches d'acier austénitique, des décohésions intergranulaires peuvent être présentes dans le métal de base. Pour pouvoir garantir l'intégrité de la structure, p. Ex. De la cuve dans les centrales nucléaires, on cherche à savoir pourquoi ces défauts se forment, et dans quelles conditions accidentelles, une rupture devient possible. Lors d'une rupture déclenchée à partir d'une DIDR, deux mécanismes se superposent. D'une part, la petite taille de ces défauts diminue la température de la transition de la ténacité, et d'autre part, la fragilité intergranulaire est caracterisée par des valeurs de ténacité plus faibles qu'en clivage. Des essais sur des éprouvettes contenant des DIDR confirment avec 36mpam à -90 C la faible ténacité associée à la rupture intergranulaire. En revanche, pour des températures plus élevées, c'est l'effet de taille qui abaisse la température de transition. Pour la rupture en clivage, on observe une diminution de la température de transition de 60 C pour une réduction du rapport A/W de 0. 5 à 0. 1. Dus à la perte de confinement de la plasticité à la pointe de la fissure, le volume plastifié et la ténacité sont augmentes. L'approche locale avec m=29. 8, =0. 5, #u=2460mpa permet de prédire la transition pour des éprouvettes renfermant des petites ou des grandes fissures. Les facies des décohésions intergranulaires provoquées lors du réchauffage (DIDR) sont caracterisés par un taux élevé de soufre qui diminue en s'éloignant de la ligne de fusion. Fragilisant les joints de grains, les contraintes résiduelles sont partiellement relaxées par fissuration. Il en résulte un facies intergranulaire lisse sans aucune trace de déformation. En revanche, la forme finale du défaut est due à un mécanisme combiné de micro-fluage et de fragilisation par du soufre ségrége qui conduit à la formation de facettes intergranulaires cavitées
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Deuis, Robert Leslie. "Aqueous corrosion and tribological properties of metal matrix composite coatings produced by plasma transferred arc surfacing." 1997. http://arrow.unisa.edu.au:8081/1959.8/80086.
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Shih, Hsiao-Ku, and 施効谷. "Study on the plasma characterization for metal target and the properties of TiN coating by high power impulsed magnetron sputtering." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/54034362867266766868.
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碩士明道大學
材料科學與工程學系碩士班
101
High power impulse magnetron sputtering (HiPIMS) is one of the latest coating technology. A pulsed power with low duty cycle is used to generate the plasma to having a plasma concentrations up to 1019/m3 and an ionization rate of 69 to 99%. In this study, Ti target with high purity was used to deposit TiN thin films on different substrates by HiPIMS deposition technology. The effect of the N2/Ar ratio and the duty cycle on the characterization of the TiN thin film was also investigated. In the study, we use differential carbon rod and current clamp meter to measure the peak voltage and the peak current of the titanium target. The peak power density was therefore calculated. We also use optical excitation spectroscopy (OES) to diagnosis the plasma. Surface and cross-sectional morphology and thickness of the obtained TiN films on Si substrate were measured using SEM. Crystallinity and microstructure were investigated using X-ray diffractometry. The average surface roughness was determined by AFM. Composition and chemical bonding state of the film surface were analyzed using XRD. The hardness and elastic modulus were measured using nanoindenter. The wear behavior was investigated using a ball-on-disk tribometer. The effect of the N2/Ar ratio was first discussed and followed by the duty cycle. The result shows that peak power density increases with decreasing the duty cycle. The highest instantaneous power density of 1019.07 W/cm2 was obtained at the duty cycle of 2%. From the OES analysis, it was found that the ionized Ti (Ti II-334.94nm) increases as the duty cycle decrease. This is resulted from that the high peak current increases the dissociation at low duty cycle. The XRD analysis shows that smaller grain size was observed at low duty cycle. The presented orientation was TiN (111). The surface morphology becomes dense at low duty cycle. The columnar structure also becomes finer with decreasing duty cycle. The deposition rate decreased with decreasing the duty cycle due to the real film deposition time is shorter. The highest hardness of 29.26 GPa was obtained at the duty cycle of 4.5%. The surface roughness decreased from 6.71 to 2.01 nm with decreasing the duty cycle to form a smooth surface structure. The coefficient of friction of 0.5.
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Ng, Evelyn. "Strengthening Mechanisms in Microtruss Metals." Thesis, 2012. http://hdl.handle.net/1807/34825.
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Microtrusses are hybrid materials composed of a three-dimensional array of struts capable of efficiently transmitting an externally applied load. The strut connectivity of microtrusses enables them to behave in a stretch-dominated fashion, allowing higher specific strength and stiffness values to be reached than conventional metal foams. While much attention has been given to the optimization of microtruss architectures, little attention has been given to the strengthening mechanisms inside the materials that make up this architecture. This thesis examines strengthening mechanisms in aluminum alloy and copper alloy microtruss systems with and without a reinforcing structural coating. C11000 microtrusses were stretch-bend fabricated for the first time; varying internal truss angles were selected in order to study the accumulating effects of plastic deformation and it was found that the mechanical performance was significantly enhanced in the presence of work hardening with the peak strength increasing by a factor of three. The C11000 microtrusses could also be significantly reinforced with sleeves of electrodeposited nanocrystalline Ni-53wt%Fe. It was found that the strength increase from work hardening and electrodeposition were additive over the range of structures considered. The AA2024 system allowed the contribution of work hardening, precipitation hardening, and hard anodizing to be considered as interacting strengthening mechanisms. Because of the lower formability of AA2024 compared to C11000, several different perforation geometries in the starting sheet were considered in order to more effectively distribute the plastic strain during stretch-bend fabrication. A T8 condition was selected over a T6 condition because it was shown that the plastic deformation induced during the final step was sufficient to enhance precipitation kinetics allowing higher strengths to be reached, while at the same time eliminating one annealing treatment. When hard anodizing treatments were conducted on O-temper and T8 temper AA2024 truss cores, the strength increase was different for different architectures, but was nearly the same for the two parent material tempers. Finally, the question of how much microtruss strengthening can be obtained for a given amount of parent metal strengthening was addressed by examining the interaction of material and geometric parameters in a model system.
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Heras, I., E. Guillén, M. Krause, A. Pardo, J. L. Endrino, and R. Escobar. "Solar selective coatings based on carbon:transition metal nanocomposites." 2019. https://hzdr.qucosa.de/id/qucosa%3A33927.
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The design of efficient and stable solar selective coatings for Concentrating Solar Power (CSP) central receivers requires a comprehensive knowledge about the incorporated materials. In this work solar selective coatings were grown by filtered cathodic vacuum arc (FCVA) deposition. The complete stacks consist of an infrared reflection layer, an absorber layer of C:ZrC nanocomposites and an antireflection layer. The Carbon-transition metal nanocomposites were studied as absorber materials because they show appropriate optical properties, i.e. high absorption in the solar region and low thermal emittance. Furthermore metal carbides are thermally and mechanically stabile in air at high temperatures. In order to optimize the absorber layer, the metal content was controlled by adjusting the pulse ratio between the two arc sources. The elemental composition of the absorber layers was determined by Ion Beam Analysis. X-Ray diffraction (XRD) measurements show the formation of metal carbides when the metal content is high enough. The optical properties of the deposited coatings were characterized by spectroscopic ellipsometry (SE). The reflectance spectra of the complete selective coating were simulated with the optical software CODE. Bruggeman effective medium approximation (EMA) was employed to average the dielectric functions of the two components which compose the nanocomposite in the absorber layer. Good agreement was found between simulated and measured reflectance spectra of the solar selective multilayer.
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蔡方銘. "Optical properties and residual stress of metal composite films for solar absorbing coatings." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/98667661673261534375.
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碩士明新科技大學
電子工程研究所
99
The solar absorbing coatings must have high absorptance (α) and a low thermal emittance (ε), and design is multilayer interference stacks because its relatively high operating temperature (T> 400 ℃). The optical constant of metal film is relationship with thickness, and differences of thin metal and bulk of optical constants. First, we have to analyze refractive index (n) and extinction coefficient (k) of pure metallic Nb film, Si film and the Nb-Si mixture film, and measure the dielectric film Nb2O5、SiO2 and metallic film Nb、Si and Nb-Si film’s residual stress. The stress of dielectric film Nb2O5, SiO2 are 0.0309GPa and -0.3088GPa respectively, the stress of pure metallic Nb film and pure Si thin film are -0.586GPa and -0.773GPa respectively, the stress of Si 27.4%,Si 49.2% and Si 75.5% are 0.397GPa,0.5008GPa and -0.166GPa respectively. The foregoing the optical constants and the stress of single-layer are used to coat and design of multilayer solar absorbing coatings. The solar absorbing coatings are plated and designed to use two fabrics, the first fabric is Air / SiO2 / Nb2O5 / Nb / Nb2O5 / Nb / Nb2O5 / Al / Substrate and the second fabric is Air / SiO2 / Nb2O5 / Metal / Nb2O5 / Metal / Nb2O5 / Al / Substrate. Metal is the Si 49.2% with Nb-Si composite, and the design of wavelength range for 400nm ~ 1800nm of the solar spectrum strongest band range. Average reflectance of first fabric below 2.6% and absorptance is 97.4%, and average reflectance of second fabric below 2.8% and absorptance is 97.2%. In this study use of mixing ratio of Si 49.2% of the Nb-Si mixture film with similar refractive index and extinction coefficient and tensile stress characteristic substitute pure metallic Nb film, and the solar absorbing coatings is application.
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HUANG, KUO CHIN, and 黃國晉. "Studying the effects on the mechanical and biological properties of graded porous fluorapatite/titanium composite coatings on titanium metal implant materials by plasma spraying." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/h95gw3.
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碩士南臺科技大學
機械工程系
105
In this study, the fluorapatite (FA), which has higher thermal stability than hydroxyapatite (HA) was mixed as a coating material, and the Ti-6Al-4V substrate was pre-coated with a pure Ti by vacuum plasma spraying (VPS )on the Ti-6Al-4V substrate as bond coat first, and then investgate the mechanical properties and the biological properties of the graded coatings. The results show that In the case of monolayer composite coating, the thickness and porosity of all specimens are decreased with increasing power, and the decreasing proportion of FA / Ti , the coating thickness and porosity increased with the increase of FA / Ti ratio. XRD analysis showed that the thermal decomposition of FA in the coating resulted in CaF2 as the spray power and FA content increased. It was found that on the surface of all samples except that the 2FA /8Ti samples with the lowest spray capacity of 2FA / 8Ti samples were found for 14 days after soaking, three different proportions of the composite coating had been exposed to apatite on the surface of all samples. Increased power and FA / Ti ratio In order to promote the early nucleation of apatite, the apatite size increases with the immersion time gradient. In the coating, the microstructure of the coating shows that the pores of the coating increase with the increase of FA / Ti ratio. The hardness of the sample is the lowest in the pure Ti bond layer, and the FA content decreases with the increase of the FA content. Young's modulus analysis showed that Young's modulus of the sample began to decrease from the matrix to the 8FA / 2Ti coating. The results show that the average bond strength of the coating is 42 ± 3.7MPa, the main failure mode is the cohesion failure of the coating, and the bond between the coating and the substrate is not bonded. In vitro cell test results show that the composite gradient coating has a faster cell adhesion. The results show that the single layer composite coating with FA / Ti composite powder can make the coating have biological and mechanical properties, and the control parameters can keep Young's modulus difference between the coating and the substrate.
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Zhang, Yi. "Atomistic and finite element modeling of zirconia for thermal barrier coating applications." Thesis, 2014. http://hdl.handle.net/1805/6191.
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Indiana University-Purdue University Indianapolis (IUPUI)Zirconia (ZrO2) is an important ceramic material with a broad range of applications. Due to its high melting temperature, low thermal conductivity, and high-temperature stability, zirconia based ceramics have been widely used for thermal barrier coatings (TBCs). When TBC is exposed to thermal cycling during real applications, the TBC may fail due to several mechanisms: (1) phase transformation into yttrium-rich and yttrium-depleted regions, When the yttrium-rich region produces pure zirconia domains that transform between monoclinic and tetragonal phases upon thermal cycling; and (2) cracking of the coating due to stress induced by erosion. The mechanism of erosion involves gross plastic damage within the TBC, often leading to ceramic loss and/or cracks down to the bond coat. The damage mechanisms are related to service parameters, including TBC material properties, temperature, velocity, particle size, and impact angle. The goal of this thesis is to understand the structural and mechanical properties of the thermal barrier coating material, thus increasing the service lifetime of gas turbine engines. To this end, it is critical to study the fundamental properties and potential failure mechanisms of zirconia. This thesis is focused on investigating the structural and mechanical properties of zirconia. There are mainly two parts studied in this paper, (1) ab initio calculations of thermodynamic properties of both monoclinic and tetragonal phase zirconia, and monoclinic-to-tetragonal phase transformation, and (2) image-based finite element simulation of the indentation process of yttria-stabilized zirconia. In the first part of this study, the structural properties, including lattice parameter, band structure, density of state, as well as elastic constants for both monoclinic and tetragonal zirconia have been computed. The pressure-dependent phase transition between tetragonal (t-ZrO2) and cubic zirconia (c-ZrO2) has been calculated using the density function theory (DFT) method. Phase transformation is defined by the band structure and tetragonal distortion changes. The results predict a transition from a monoclinic structure to a fluorite-type cubic structure at the pressure of 37 GPa. Thermodynamic property calculations of monoclinic zirconia (m-ZrO2) were also carried out. Temperature-dependent heat capacity, entropy, free energy, Debye temperature of monoclinic zirconia, from 0 to 1000 K, were computed, and they compared well with those reported in the literature. Moreover, the atomistic simulations correctly predicted the phase transitions of m-ZrO2 under compressive pressures ranging from 0 to 70 GPa. The phase transition pressures of monoclinic to orthorhombic I (3 GPa), orthorhombic I to orthorhombic II (8 GPa), orthorhombic II to tetragonal (37 GPa), and stable tetragonal phases (37-60 GPa) are in excellent agreement with experimental data. In the second part of this study, the mechanical response of yttria-stabilized zirconia under Rockwell superficial indentation was studied. The microstructure image based finite element method was used to validate the model using a composite cermet material. Then, the finite element model of Rockwell indentation of yttria-stabilized zirconia was developed, and the result was compared with experimental hardness data.