Дисертації з теми "Aluminum pin"
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Georgeou, Zacharias. "Analysis of material flow around a retractable pin in a friction stir weld." Thesis, Port Elizabeth Technikon, 2003. http://hdl.handle.net/10948/196.
Повний текст джерелаFarjam, Aslan. "Influence of Alumina Addition to Aluminum Fins for Compact Heat Exchangers Produced by Cold Spray Additive Manufacturing." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/33383.
Повний текст джерелаLee, Trevor J. "Investigation of ASTM E 238 Bearing Pin Properties for Various Aerospace Alloys." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1074.
Повний текст джерелаAmara, Holm. "Influence de l'aluminium et des sols acides sur la croissance du sapin de Douglas (Pseudotsuga menziesii, Mirb.) : rôle de la paroi dans les réponses au stress aluminique." Thesis, Limoges, 2020. http://aurore.unilim.fr/theses/nxfile/default/a59ed152-5cd0-4283-8056-5b8950a5f8d5/blobholder:0/2020LIMO0054.pdf.
Повний текст джерелаIn Europe, softwood forests are very abundant and are characterized by an acidic soil profile. In these conditions, when the soil pH drops below 5.5, aluminum is present in soils in a soluble and bioavailable form Al3+. This work was carried out on Douglas fir (Pseudotsuga menziesii), a coniferous tree, widely distributed in France and particularly in the Limousin region. In this study we used different cultivation methods (in vitro cultures with controlled conditions, and semi-controlled conditions in greenhouse on naturally acidic forest soils rich in Al). Plants were analyzed at different stages of development (seedling stage and young tree stage) and for different exposure periods (2 and 11 months). The results have shown that the growth of Douglas fir and its mineral nutrition were disturbed when exposed to high Al concentrations (500 μM AlCl3 in vitro, and about 1 mg Al.g-1 at pH 5 on forest soils). We showed that the roots exhibited severe symptoms of toxicity and accumulated the majority of the Al within the cell wall. It has been shown that, to cope with aluminum toxicity, Douglas fir developed different strategies. On one hand, the chemical characterization of the cell wall revealed quantitative and qualitative modifications in the polysaccharidic composition of the wall, in particular pectins (harboring a higher galacturonic acid content with less ramification) following regulation of pectin methylesterase activity, and hemicelluloses (richer in glucomannans), suggesting a trapping process of Al in the cell wall structures. On the other hand, at the intracellular level, the results showed a stimulation of a key enzyme activity involved in the reduction of oxidative stress induced under aluminum stress, as well as an accumulation of proline, potentially capable of chelating Al inside the cell. Therefore, Douglas fir plantlets showed a relative high tolerance level to Al equivalent to other coniferous species which can be explained at the cellular level by an exclusion process involving retention by the cell wall but also a complexation process in the intracellular compartment
Truog, Adam G. "Bond Improvement of Al/Cu Joints Created by Very High Power Ultrasonic Additive Manufacturing." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337885605.
Повний текст джерелаGomez, Ana Carolina. "Estudo do desgaste de nanocompósitos de alumina-zircônia usando variação de parâmetros no ensaio pino-no-disco." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/74/74133/tde-23022018-084836/.
Повний текст джерелаWear is responsible for a large number of material failures, causing them to be replaced early and consequently shortening their life-time. Therefore, studies are conducted to characterize the limits of use of these materials, thus avoiding catastrophic situations. From the variables and parameters involved in the wear test, it is possible to construct maps that aim to direct the correct choice of material according to the desired application, as well as to identify its behavior against certain conditions of use. In this context, the objective of this work was to know the wear behavior of alumina nanocomposites containing 5% nanometric zirconia inclusions in order to construct a simplified wear transition diagram between the sliding speed and applied load combination limits. For this, test pieces shaped like pins with semi-spherical tips were characterized in terms of hardness and fracture toughness, took to the wear test of the pin-on-disk with ambient temperatures and humidity, varying the speed and load parameters. Slip velocities ranged from 1.2 m/s to 0.1 m/s and loads ranged from 2 N to 100 N. The values of hardness and fracture toughness obtained were 14.08 ± 1.22 GPa and 3.99 ± 0.14 MPa.m1/2, respectively. The results of wear showed that from the characterization and construction of the wear regime transition diagram, with combinations of extrinsic load parameters and slip speed, it was possible to define and reach the boundary conditions between the moderate wear regime and the transition for the severe regime. This diagram helps in the selection and comparison of the transition between the wear limits of the studied material with other types used in engineering.
Majzlan, Juraj. "Thermodynamics of iron and aluminum oxides /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
Повний текст джерелаWouters, Onne. "Plasticity in aluminum alloys at various length scales." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2006. http://irs.ub.rug.nl/ppn/292535821.
Повний текст джерелаNewlands, Katrina. "The early stage dissolution characteristics of aluminosilicate glasses." Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=227976.
Повний текст джерелаGong, Yuze. "Wear Studies on Silicon Carbide Whisker Reinforced Alumina." Thesis, KTH, Materialvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-35923.
Повний текст джерелаMahmud, Khairil. "Distribution and functional significance of Al in tropical forest plants." Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=235553.
Повний текст джерелаDuncan, Graham Kirk. "Phase diagram studies of the beta-aluminas." Thesis, University of Aberdeen, 1985. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=201758.
Повний текст джерелаAgulló, Pastor Javier. "1-butene isomerisation over amorphous silica-alumina." Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=189659.
Повний текст джерелаMetali, Faizah Haji. "Factors controlling Al accumulation in plants : effects of phylogeny, soil conditions and external nutrient supply." Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=165794.
Повний текст джерелаBrown, Matthew T. "The distribution and behavior of dissolved and particulate aluminum in coastal waters of the northeast Pacific off Oregon and Washington and in the northern Gulf of Alaska /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.
Повний текст джерелаVinceller, Sonia. "Effets de l'extinction thermique de la luminescence sur les phénomènes thermostimulées présentés par le pic dosimétrique de l'alumine alpha." Toulouse 3, 2002. http://www.theses.fr/2002TOU30140.
Повний текст джерелаCorreia, José Carlos Paiva. "Tratamento de efluentes de suinicultura por coagulação/floculação. Estudo comparativo da utilização de biopolímeros versus coagulantes convencionais." Master's thesis, ISA/UTL, 2012. http://hdl.handle.net/10400.5/5332.
Повний текст джерелаGiven the growing food requirements, mainly due to the increase of the world population, the global livestock sector is more intensive. The pig production, an important sector follows this trend yielding large quantities of slurry, rich in nutrients, organic matter and higher amount of metals in the livestock effluents. Physico-chemical processes procedures are effective in the treatment of effluents, which includes coagulation / flocculation. This tecnhology was selected for the development of an experimental study on a raw effluent to simulate reality, where the nutrient removals were analyzed by coagulation / flocculation. In this study the effectiveness of conventional coagulants and polymers was compared, after optimization of the dose, agitation time and speed and volume of sludge produced. The biopolymer used was chitosan, because it is abundant and natural. Aluminum sulphate (Al2(SO4)3) was found to be more effective than ferric chloride (FeCl3), two of the most commonly used coagulant in the treatment of waste water. Comparing the results with the ones obtained by natural sedimentation, it is shown that the coagulation / flocculation is effective in removing turbidity and COD, and especially in the removal of metals analyzed. These removals exceed 60% and reduce the sludge volume by about 38%. The phosphorus, element which can cause eutrophization of the water is removed almost entirely (around 70%-94%).
SUN, CHIEN YUAN. "Analise comparativa do efeito da irradiacao do laser de GaAlAS em 780 nm e 660 nm na hipersensibilidade dentinaria." reponame:Repositório Institucional do IPEN, 2003. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11096.
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Dissertacao (Mestrado Profissionalizante em Lasers em Odontologia)
IPEN/D-MPLO
Instituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP; Faculdade de Odontologia, Universidade de Sao Paulo
FARINA, CASSIUS G. "Terapia laser em baixa intensidade em portadores de disfunção temporomandibular: avaliação eletromiográfica, potência muscular e dor." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11388.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
SANSEVERINO, NELLY T. M. "Avaliacao clinica da acao antialgica do laser em baixa intensidade de arseneto de galio e aluminio (lambda = 785nm) no tratamento das disfuncoes da articulacao temporo-mandibular." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10858.
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Dissertacao (Mestrado Profissionalizante em Lasers em Odontologia)
IPEN/D-MPLO
Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP; Faculdade de Odontologia, Universidade de Sao Paulo
Barros, Renato Araujo [UNESP]. "Influência da nitretação a plasma e carbonetação a laser nas propriedades tribológicas do par aço AISI/SAE 4340 e liga bronze-alumínio 630." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/148983.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Os aços de ultra alta resistência como o aço 4340 tem sido amplamente utilizados pela indústria aeronáutica e aeroespacial em aplicações como trens de pouso de aeronaves e o veículo lançador de satélite brasileiro (VLS), além de um uso extensivo para diversos setores da indústria em geral. Isso se deve, em grande medida, às suas propriedades mecânicas. Este trabalho se propõe a avaliar as propriedades tribológicas do par aço 4340, inicialmente submetido ao tratamento térmico de têmpera e revenimento, e a liga bronze alumínio 630, utilizados em trens de pouso. Será estudado o comportamento destas estruturas após o aço ser submetido a tratamentos de superfície por nitretação a plasma e carbonetação a laser, como forma de melhorar seu desempenho com relação ao atrito e ao desgaste. Neste estudo foi escolhido o ensaio tipo pino-disco para simular a situação real de desgaste. Os discos foram confeccionados a partir do aço AISI/SAE 4340 e os pinos foram feitos da liga bronze-alumínio 630. Foram realizadas análises microestruturais das estruturas e das camadas de compostos formadas devido ao tratamento de superfície, Após os ensaios de desgaste foram feitas observações das superfícies através de microscopia e perfilometria óptica, microscopia eletrônica de varredura, difratometria de raios-X, testes de riscamento (scratching tests), dureza, observação de rugosidade e pesagem dos corpos de prova. Foram levantados os parâmetros do desgaste e alterações microestuturais devido à interação entre as superfícies de contato durante os ensaios de deslizamento. Foi analisada a perda de massa e levantadas as curvas de desgaste e dos parâmetros relacionados ao atrito em função da distância percorrida e/ou do tempo de ensaio. Nos ensaios foram utilizadas três velocidades de ensaio: 0,5; 1,0 e 1,5 m/s. Foi possível o cálculo da taxa de desgaste para cada par e velocidades estudadas. De uma maneira geral constatou-se que os mecanismos de desgaste detectados são semelhantes para todas as condições de superfície dos discos. As imagens mostram que partículas do pino são deformadas sobre o disco, em forma de camadas, evidenciando o mecanismo de adesão. A carbonetação a laser criou uma camada rica em carbono com a presença de grafite que contribuiu para reduzir o coeficiente de atrito e o desgaste do pino, principalmente, para as velocidades de 0,5 e 1,0 m/s. A nitretação a plasma reduziu a perda de massa do disco e do pino, com indicativos de pequena perda de massa para todas as velocidades estudadas; a rugosidade e o aumento do coeficiente de atrito no par pino-disco para as velocidades de 1,0 e 1,5 m/s podem ter sido induzidas por alteração no tipo de desgaste, de adesivo para uma abrasão a três corpos.
Ultra high strength steels as 4340 steel has been widely used by the aerospace industry in applications such as aircraft landing gears and the Brazilian satellite launch vehicle (VLS), plus an extensive use for various sectors of the industry in general. This is due largely to their mechanical properties. This work aims to evaluate the tribological properties of 4340 steel pair, initially submitted to heat treatment of quenching and tempering, and aluminum bronze 630 alloy, used in landing gear. The behavior of these structures after the steel be subjected to surface treatment by plasma nitriding and laser carbonetation will be studied, as a way to improve its performance with respect to friction and wear. For this study, pin-on-disc test was chosen in order to simulate the real situation of wear. The discs were made from 4340 steel and pins were made of aluminium bronze 630 alloy. Micro-structural analyses were undertaken of the structures and compound layers formed due to surface treatment. After the wear tests surface observations were made through microscopy and perfilometry optical, scanning electron microscopy, x-ray diffractometry, x-ray tests, scratching tests, hardness, roughness and weighing of the specimens. Parameters of wear and microestuturals changes were raised due to interaction between the contact surfaces during rehearsals. Loss of mass was analyzed and curves of wear and friction related parameters were plotted in function of the slided distance and/or time of test. In the tests three test velocities were used: 0.5; 1.0 and 1.5 m/s. It was possible to calculate the wear rate for each pair and studied velocities. In general it was noted that the mechanisms of wear detected are similar for all conditions of the surface of the discs. The images show that the particles are bent on the disc, in the form of layers, showing the mechanism of adhesion. The laser carbonetation created a carbon-rich layer with the presence of graphite, which contributed to reduce the friction coefficient and pin wear, mainly for the 0.5 and 1.0 m/s velocities. The plasma nitriding reduced the loss in mass of the disk and pin, with indicative of small mass loss for all velocities studied; the roughness and the increase of the coefficient of friction in the couple pin-disc for the velocities of 1.0 and 1.5 m/s may have been induced by changes in the type of wear, from adhesive wear to a three-body abrasion.
CAPES: 99999.002441/2014-04
Moulahoum, Omar. "Dualité du magmatisme d'âge pan-africain : Aspects structuraux et pétrologiques des granites subalcalins et alumineux de la région de Tamanrasset (Hoggar central, Algérie." Nancy 1, 1988. http://www.theses.fr/1988NAN10049.
Повний текст джерелаMoulahoum, Omar. "Dualité du magmatisme d'âge pan-africain aspects structuraux et pétrologiques des granites subalcalins et alumineux de la région de Tamanrasset, Hoggar central, Algérie /." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37616741j.
Повний текст джерелаTedesco, Nadetsa Reginato. "Caracterização do comportamento de desgaste de cerâmicas de alumina densa : efeitos de parâmetros do ensaio do tipo pino no disco." Universidade Federal de São Carlos, 2010. https://repositorio.ufscar.br/handle/ufscar/862.
Повний текст джерелаUniversidade Federal de Sao Carlos
Searching for wear resistant materials, attention has been paid to Si3N4, SiC, Al2O3 and ZrO2 ceramics due to their better properties as compared to other materials. Although ceramic are brittleness, improvements on the processing and by the addition of second phases to the ceramic matrix have lessen this restriction because of microstructure refinement. Therefore, some mechanical proprieties have been optimized e probably the wear resistance also. Among the ceramic composites, greater attention has been given to the alumina nanocomposites due to the improvements on the toughness, hardness and mechanical resistance. Wear research has been made in the literature but, a direct comparison between the many published works regarding this wear improvement is impossible due to the fact that wear resistance is a response of the microstructure, material and testing condition. So the work herein presented aim was to do a systematic study in the alumina wear based on the critical parameters which have to be controlled on a pin-on-disc test concerning about the mild and severe wear regime. Since, it was possible to describe a procedure to evaluate the alumina wear behavior and resistance in terms of applied load, sliding speed and environment. By the use of the study methodology proposed, it was possible to construct a simplify wear transition diagram which allowed to define parameters combination were alumina can be use as a wear resistance material
Na busca por materiais resistente ao desgaste, atenção tem sido dada a cerâmicas como Si3N4, SiC, Al2O3 e ZrO2, por apresentarem melhores características quando comparadas com outros materiais. Apesar da fragilidade destas cerâmicas, pelo melhoramento no processamento e pela introdução de segundas fases nas matrizes cerâmicas, algumas propriedades mecânicas como a de resistência mecânica foram melhoradas pelo refino microestrutural e provavelmente, a resistência ao desgaste. Dentre os compósitos cerâmicos, grande atenção tem sido dada aos nanocompósitos de matriz de alumina pelos seus resultados excepcionais quanto à tenacidade, a resistência mecânica e a dureza. Alguns estudos de resistência ao desgaste destas cerâmicas densas têm sido feito, porém a comparação dos resultados obtidos é difícil, pois a resistência ao desgaste é uma resposta da microestrutura, do material e das condições dos testes. Visando compreender os parâmetros que afetam o valor de desgaste e melhorar a reprodutibilidade dos resultados de desgaste em cerâmicas densas, o objetivo proposto para a presente dissertação foi o estudo sistemático do desgaste da alumina frente às questões dos parâmetros críticos que devem ser controlados em um ensaio de desgaste do tipo pino no disco. Foram verificadas as condições de ensaio que influenciam a determinação dos parâmetros críticos, entre as condições de desgaste moderado e severo. Dessa, forma, foi possível descrever um procedimento para avaliar a resistência e o comportamento de desgaste de alumina quanto aos parâmetros de ensaios de velocidade de deslizamento, carga aplicada e umidade relativa do ar. Esta metodologia permitiu a construção de um diagrama de transição de desgaste simplificado que possibilitou a definição de limites de combinações destes parâmetros que permitem obter bom desempenho da alumina em situações que necessitem de resistência ao desgaste
D'Ans, Pierre. "Contribution à la mise au point d'une démarche rationnelle de sélection des traitements de surface: illustration dans le cas des dispositifs de fonderie de l'aluminium." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210366.
Повний текст джерела- Utiliser des multitraitements de surface peut se faire en scindant les différentes requêtes en sous-ensembles, de manière à ce que chaque traitement réponde à l’un d’eux. Dans quel ordre ces requêtes doivent-elles être introduites par rapport au substrat ?
- Comment sélectionner les traitements de surface répondant à chaque requête individuelle ?
- Comment classer des multitraitements en termes d’adéquation au problème posé ?
Dans ce travail, les première et troisième questions sont abordées, en explorant les requêtes concernant habituellement les dispositifs de moulage de l’aluminium :
- Résistance aux contraintes d’origine thermique.
- Résistance à la corrosion par les métaux fondus.
- Résistance au frottement.
L’analyse de la bibliographie relative aux traitements de surface utilisés dans ces systèmes a été analysée et des « architectures »-types ont été identifiées (chapitre 3). On prévoit, par exemple, un traitement conférant la résistance à la fatigue superficielle, ainsi qu’un revêtement étanche et résistant à l’aluminium fondu. Une barrière thermique est parfois préconisée.
Pour chacune des architectures, des traitements de surface individuels peuvent être sélectionnés. Un « facteur de performance » permettant de classer les solutions par rapport au problème de la fatigue thermique a été construit (chapitre 4) et discuté dans deux situations :
- Lorsqu’un revêtement est présent, et que les contraintes d’origine thermique (différence de dilatation thermique couche-substrat) menacent de le rompre lors de l’immersion dans un milieu corrosif à haute température. Des essais de corrosion dans de l’aluminium fondu ont été réalisés sur un acier revêtu par du nitrure de chrome dopé à l’aluminium, synthétisé par déposition physique en phase vapeur (chapitre 5 – collaboration :Inasmet).
- Lorsque des variations thermiques rapides menacent de rompre le substrat et la (les) couches. Des essais de fatigue thermique ont été réalisés sur de l’acier à outils pour travail à chaud non traité, boruré ou recouvert d’un multitraitements (zircone yttriée / NiCrAlY / boruration / acier). Le revêtement en zircone yttriée a été obtenu par projection par plasma. L’essai de fatigue thermique a été modélisé et le facteur de performance, discuté (chapitre 6).
Au chapitre 7, les architectures-types ont été introduites dans une méthodologie de sélection des multi-traitements de surface, qui a été appliquée dans deux cas :
- Celui des moules de fonderie, devant résister à la fatigue thermique et à la corrosion par l’aluminium fondu. Le facteur de performance a été extrapolé à d’autres situations qu’aux chapitres 5 et 6. Les solutions habituellement proposées pour résoudre ce problème sont retrouvées.
- Celui de deux pièces en acier frottant l’une contre l’autre en présence d’aluminium fondu.
To select surface treatments, one must account for the required functional properties, the substrate features and the solicitations the substrate must endure. Certain combinations of these parameters make it difficult to select a single surface treatment, a reason why several successive treatments are preferred. To select them, one needs to determine:
- How to divide the several requests into groups and how to stack up these groups from the substrate to the outer surface, so that each treatment deals with one specific group of requests/properties.
- How to select individual layers for each group of properties.
- How to rank the multi-treatments in terms of relevance for a given application.
In this work, one tries to answer the first and the third questions, by studying the case of aluminium foundry, in which the industrial devices frequently face the following solicitations:
- Thermal stress (thermal fatigue, thermal expansion mismatch).
- Presence of corrosive molten metal.
- Sliding wear.
In the literature, several “standard” architectures are proposed (chapter 3), like a diffusion layer reducing superficial fatigue plus a corrosion barrier layer. A thermal barrier coating is also sometimes proposed.
For each of these architectures, one can select individual treatments. To rank them, one devised a “performance index” for thermal stress (chap.4), which is discussed for two cases:
- For large differences between layer and substrate thermal expansion coefficients, when both are put into contact with a high temperature corrosive medium, the layer may be damaged. One discusses this case by examining the corrosion caused by molten aluminium for a steel substrate coated by anticorrosive chromium nitride doped with aluminium. The layer is produced by physical vapour deposition (chap. 5 – cooperation: Inasmet).
- Repeated fast surface temperature transients can also damage the substrate and/or the layer by thermal fatigue. One conducted thermal fatigue tests with samples of hot work tool steel, respectively untreated, simply borided and protected by a multilayer. In the last case, top coat is yttria stabilised zirconia, followed by a nickel superalloy and then a borided layer (undercoat). One synthesized the zirconia coating by plasma spray and one modelled the thermal fatigue (chap. 6).
In chap. 7, architectures from chap. 2 are introduced in a multi-treatment selection routine, which is applied in two cases:
- Foundry moulds for molten aluminium, withstanding both thermal fatigue and corrosion. The devised performance index is extrapolated beyond the tests of chap. 5 and 6 to treatments for this industrial application, thereby quantifying their respective merits.
- A foundry device exposed to molten metal and sliding wear.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Freire, Eduily Benvindo Vaz. "Estudo estrutural e eletrônico da influência de dopantes em coronenos funcionalizados." Universidade Federal de Juiz de Fora (UFJF), 2017. https://repositorio.ufjf.br/jspui/handle/ufjf/6065.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Recentemente, o óxido de grafeno (GO) tornou-se um material de grande interesse físico e tecnológico e não só um material intermediário na síntese de grafeno, mas também como um produto para aplicações diretas. Na tentativa de tornar o GO mais próximo do grafeno, estruturalmente e tecnologicamente falando, o material passa por um processo de redução dos grupos funcionais oxigenados aderidos. Entretanto esse processo de redução não consegue retirar totalmente os grupos funcionais, e a esse material não completamente livre de grupos baseados no oxigênio damos o nome de óxido de grafeno reduzido (rGO). O rGO ao longo dos últimos anos se tornou alvo de pesquisas e muitas aplicações científicas e tec-nológicas como, por exemplo, em dispositivos eletrônicos orgânicos, como diodos emissores de luz (OLEDs), células solares, entre muitos outros. Para tornar este material ainda mais interessante para a área de eletrônica orgânica, propomos a dopagem das nossas moléculas de óxido de grafeno reduzido (rGOm) com átomos de boro, nitrogênio, alumínio silício, fósforo, gálio, germânio e arsênio, um de cada vez e de forma substitutiva. Nosso objetivo e´ fazer com que nosso material se torne um melhor condutor, mantendo ou melhorando sua transparência, pensando no uso deste material como eletrodos em dispositivos orgânicos. Neste trabalho, objetivamos estudar nossas moléculas de óxido de grafeno reduzido (rGOm) nos seus aspectos estruturais e eletrônicos, utilizando métodos semi-empíricos e ab initio a nível DFT, implementados nos programas GAMESS e MOPAC. Usamos como modelos de rGO estruturas contendo 42, 84 e 154 átomos, derivados da molécula de coroneno com adição de três grupos funcionais oxigenados: hidroxil, carboxil e epoxi. Começamos o trabalho fazendo uma busca conformacional da estrutura das nossas rGOm incluindo cada grupo funcional oxigenado ligado aos carbonos dos coronenos. Estudamos as rGOm juntamente com a dopagem, substituindo carbonos na estrutura pelos seguintes átomos: nitrogênio (N), boro (B), fósforo (P), silício (Si), alumínio (Al), arsênio (As), germânio (Ge) e gálio (Ga). Substituímos um átomo da folha de carbono de cada vez. Analisamos o gap de energia entre os estados eletrônicos de fronteira do material, a fim de encontrar tanto o sítio com menor energia total como o sítio com menor valor de gap. Realizamos os cálculos de energia e valor de gap das dopagens mencionadas acima em diferentes níveis de métodos, utilizamos tanto métodos semiempírico (PM3, PM6), quanto DFT (B3LYP, com base 6-31G), fizemos também comparação entre diferentes tipos de aproximação (UHF e RHF) com o objetivo de saber se essas aproximações eram compatíveis entre sícomparando energia total, gap e geometria. Por fim, um dos principais resultados foi a dopagem da rGOm com alumínio. O alumínio quando colocado em alguns sítios específicos promove a aproximação dos orbitais de fronteira, diminuindo o gap, tornando a rGOm do-pado com alumínio um material com propensão a melhor condução elétrica que a rGOm sem dopagem, o que aumenta o interesse na utilização deste material para eletrônica orgânica.
Recently, graphene oxide (GO) has become a material of great physical and technological interest and not only an intermediate material in the synthesis of graphene, but also as a product for direct applications. In an attempt to make GO closer to graphene, structurally and technologically speaking, the material undergoes a process of reduction of adhered oxygenated functional groups. Howe-ver, this reduction process does not completely remove the functional groups, and this material which is not completely free of oxygen-based groups, is called redu-ced graphene oxide (rGO). Over the past few years, RGO has become the target of research and many scientific and technological applications, such as organic electronic devices such as light-emitting diodes (OLEDs), solar cells, and many others. To make this material even more interesting to the area of organic elec-tronics, we propose the doping of our reduced graphene oxide molecules (rGO m) with boron, nitrogen, silicon aluminium, phosphorus, gallium, germanium and arsenic, one at a time and in a substitute way. Our goal is to make our material become a better conductor, maintaining or improving its transparency, thinking of using this material as electrodes in organic devices. In this work, we aim to study our reduced graphene oxide molecules (rGOm) in their structural and electronic aspects, using semi-empirical and ab initio methods at the DFT level, implemented in the GAMESS and MOPAC programs. We used as RGO models structures containing 42, 84 and 154 atoms derived from the coronon molecule with addition of three oxygenated functional groups: hidroxyl, carboxyl and epoxy. We begin the work by making a conformational search of the structure of our rGOm including each oxygenated functional group attached to the carbon atoms of the coronenes. We study the rGOm along with doping, replacing carbons in the structure with the following atoms: nitrogen (N), boron (B), phosphorus (P), silicon (Si), aluminium (Al), arsenic, germanium (Ge) and gallium (Ga). We replace one atom of the carbon sheet each time. We analyzed the energy gap between the border electronic states of the material in order to find both the site with the lowest total energy and the site with the least gap value. We performed the energy calculations and gap value of the above-mentioned dops at different levels of methods, we used both semi-empirical methods (PM3, PM6) and DFT (B3LYP, based on 6-31G), we also compared different types of approximations (UHF and RHF) in order to know if these were compatible with each other comparing total energy, gap and geometry. Finally, one of the main results was the doping of rGOm with aluminium. Aluminium when placed at some specific sites promotes the approach of border orbitals by reducing the gap, making aluminium-doped rGOm a material with a propensity for better electrical conduction than rGOm without doping, which increases the interest in using this material for organic electronics.
Wang, Wei-Sheng, and 王威勝. "Study of tool pin shape on the aerospace application aluminum alloy by friction stir welding." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/97096384181544374841.
Повний текст джерела南台科技大學
機械工程系
97
Both 2024-T3 and 7075-T6 are heat treatable aluminum alloys which have been applied widely in aerospace industry, due to their high specific strength and corrosion resistance. However, if the welding parameters for the aluminum alloy are inappropriately specified during the traditional welding process, defects such as high porosity and solidification cracking can occur easily. Friction stir welding (FSW), which is different from traditional arc welding, is used on welding process conducted under the melting point, and is an emerging solid-state joining process that produces low-distortion and high-quality welds. FSW will effectively better general welding quality. In this study, FSW processes are conducted on 2024-T3 and 7075-T6 aluminum alloys, 3mm thick. The major areas discussed were, the effect of the welding parameters, the microstructures and hardness in different tool pin shapes (threaded cylindrical, threaded triangular). The results show that the grain size of both tool pin shapes was significantly reduced in the fixed rotation speed after welding, but the hardness of the weld increased. This is because the input heat decreases with welding speed increasing. This increasing trend of hardness was not apparent for the threaded triangular pin shape. However, the hardness of the weld in the 2024-T3 alloy increased, and in the 7075-T6 decreased while welding speed was fixed and the rotation speed increased. This can be attributed to the different internal precipitation mechanisms of the two materials. When either fixed rotation speed or welding speed was changed the welding quality for threaded triangular was found to be better than that for the threaded cylindrical tool pin. In addition, the threaded triangular tool pin allows greater plastic flow, with the 2024-T3 specimen having a greater amount of plastic flow than the 7075-T6. The results for the different welding materials indicated that as the rotation speed increased, there was a tendency for weld appearances to become more homogenous and the threaded triangular tool pin was better. In term of hardness, the hardness of specimens using both types of tool pins was improved as the rotation speed and the welding speed were increased. For the hardness of the TMAZ and HAZ located at the two sides of the specimens, the retreating side in 2024-T3 was better than its advancing side. Between the tool pins, the threaded triangular was providing higher hardness than the threaded cylindrical pin. In the specimen AS(2024)-RS(7075), the tensile strength and elongation ratio of the weld increased when the rotation speed and the welding speed were increased for the threaded triangular tool pin. However, in the case of the threaded cylindrical tool pin, both tensile strength and elongation ratio decreased. Furthermore, the tensile strength and elongation of AS(7075)-RS(2024) was generally lower than that of AS(2024)-RS(7075). For the tool pin shape, threaded triangular was better.
Parameswaran, Gopakumar. "Influence of Surface Topography and Tribosystem on Reciprocating Friction in Sparsely Lubricated Contacts." Thesis, 2018. http://etd.iisc.ac.in/handle/2005/4141.
Повний текст джерелаRanganatha, S. "Transfer Layer Formation And Friction In Extrusion Of Aluminum : An Experimental Study Using A High Temperature Vacuum Based Pin-On-Disc Machine." Thesis, 2008. https://etd.iisc.ac.in/handle/2005/871.
Повний текст джерелаRanganatha, S. "Transfer Layer Formation And Friction In Extrusion Of Aluminum : An Experimental Study Using A High Temperature Vacuum Based Pin-On-Disc Machine." Thesis, 2008. http://hdl.handle.net/2005/871.
Повний текст джерелаCauchy, Xavier. "Préparation d'échantillons pour l'étude par GISAXS des mécanismes de déformation des matériaux par faisceaux d'ions lourds de haute énergie." Thèse, 2010. http://hdl.handle.net/1866/4729.
Повний текст джерелаThe machanisms underlying structural deformations following swift heavy ion beam a-Si irradiation are subject of debate. We investigated the hypothesis of the presence of a liquid phase in the wake of the energetic ions in the thermal spike framework. a-Si samples were prepared in order to track a transient liquid phase by implanting Cu or Ag on the a-Si surface and exposing the sample to a 70 MeV Ag12+ beam. Cu and Ag are both very sensitive to segregation in Si and are therefore thought to be capable of keeping track of a molten transient state by concentrating on the ion track. Samples are to be investigated with GISAXS. Nanoscale implantation masks were developed from nanoporous alumina membranes in order to impose a pattern on the ion impact sites and thus improve GISAXS sensitivitity. An alignment method is also developed for the positioning of pores parallel to the ion beam direction. A nearly equidistant impact sites pattern was achieved by irradiating fused silica through these implantation masks.
Laštovková, Andrea. "Diagnostika nových nemocí z povolání - prevence nových poškození z práce." Doctoral thesis, 2018. http://www.nusl.cz/ntk/nusl-386769.
Повний текст джерела