Dissertations / Theses on the topic 'Metal deposition process'
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Byseke, David, and Alexander Thunell. "Automatic monitoring and control of Laser Metal Deposition Process." Thesis, Högskolan Väst, Avdelningen för Industriell ekonomi, Elektro- och Maskinteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-16745.
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Laser metal deposition is an additive manufacturing technique that enables the manufacturing or repair of high-quality metal parts by building fine layers one at a time. To get a stable process with a low number of flaws and irregularities the process needs a fully operational and functioning control system. At PTC in Trollhättan, a production research facility that is a department of University West, several experiments have previously been conducted with an LMD machine. The main objective of this thesis is to deliver input from available methods for automatic control and monitoring of the LMD process. The available methods are explained in the report and previous experiments that have been conducted have been documented in this thesis. Another objective of the thesis is to develop a prototype for monitoring and control of the process. Previous work has mainly used a visual-based control system that has used CMOS-, CCD-, or an infrared camera. Pyrometers and structured light scanning have also been used. Non-optical methods such as acoustical sensors and thermocouples have also been used for monitoring and control. With the gathered information about the available control methods, a prototype has been developed to automatically control the LMD machine located at PTC. The control uses a CMOS camera to gather live imaging from the machine in order to adjust machine parameters, in real-time, to automatically control the process. The different parameters have a strong correlation to the final machine output and are also explained in the thesis. The prototype and the gathering of data from the process have been made using Labview as an image-processing software. An evaluation of the developed prototype has been made and the different control methods have been discussed. The developed prototype measures the melt pool by using an algorithm that counts the number of pixels in the melt pool. However, further research needs to be made to determine if the measured width correlates with the actual width of the cladded string.
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Heralic, Almir. "Towards full Automation of Robotized Laser Metal-wire Deposition." Licentiate thesis, University West, Department of Engineering Science, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-2148.
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Metal wire deposition by means of robotized laser welding offers great saving potentials, i.e. reduced costs and reduced lead times, in many different applications, such as fabrication of complex components, repair or modification of high-value components, rapid prototyping and low volume production, especially if the process can be automated. Metal deposition is a layered manufacturing technique that builds metal structures by melting metal wire into beads which are deposited side by side and layer upon layer. This thesis presents a system for on-line monitoring and control of robotized laser metal wire deposition (RLMwD). The task is to ensure a stable deposition process with correct geometrical profile of the resulting geometry and sound metallurgical properties. Issues regarding sensor calibration, system identification and control design are discussed. The suggested controller maintains a constant bead height and width throughout the deposition process. It is evaluated through real experiments, however, limited to straight line deposition experiments. Solutions towards a more general controller, i.e. one that can handle different deposition paths, are suggested.
A method is also proposed on how an operator can use different sensor information for process understanding, process development and for manual on-line control. The strategies are evaluated through different deposition tasks and considered materials are tool steel and Ti-6Al-4V. The developed monitoring system enables an operator to control the process at a safe distance from the hazardous laser beam.
The results obtained in this work indicate promising steps towards full automation of the RLMwD process, i.e. without human intervention and for arbitrary deposition paths.
RMS
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Denys, Kristof. "Circular motion for robotized metal deposition : verification and implementation." Thesis, Högskolan Väst, Avd för automation och datateknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-5469.
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Metal deposition is an additive layered manufacturing process that deposits molten metal droplets on a substrate and by repeating this process layer by layer, a complex shaped 3D geometry can be manufactured. In this thesis, the metal deposition process is performed by a robot with a wire feeder tool and a laser as energy source to melt the metal wire. The robot programming for robotized metal deposition process can be completely automated by computer aided robotics software. University West is currently developing an add-in application in a computer aided robotics software, Process Simulate, that is capable of programming the robotized metal deposition process. The first goal of this thesis was to verify the up to now developed software and the process from CAD drawing down to robot code. Another goal was to find and implement an algorithm that will reduce the number of locations on a circular arc to three locations. The algorithm to minimize the locations must be capable of changing all the different curvature paths to linear and circular arc motions which are easy to translate to robot code. The user should be able to decide the fitting precision of the approximated motion path to the original path. A real robot cell setup is modelled in Process Simulate. This lets Process Simulate generate the correct robot code for that specific cell. Since each robot cell has its own unique setup, a custom script will be developed that changes the universal robot code, that Process Simulate generates, to the custom robot code required in this specific robot cell. The software is improved and tested from CAD drawing down to robot code but still needs to be debugged more and needs implementation of some non-existing features.
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Yang, Yu. "On-line inspection and thermal properties comparison for laser deposition process." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/Yang_09007dcc803bca12.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 6, 2007) Includes bibliographical references.
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Yarrapareddy, Eswar. "Development of slurry erosion resistant materials by laser-based direct metal deposition process." Ann Arbor, Mich. : ProQuest, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3258777.
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Thesis (Ph.D. in Mechanical Engineering)--S.M.U., 2007.Title from PDF title page (viewed Mar. 18, 2008). Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1898. Adviser: Radovan Kovacevic. Includes bibliographical references.
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Segerstark, Andreas. "Laser Metal Deposition using Alloy 718 Powder : Influence of Process Parameters on Material Characteristics." Doctoral thesis, Högskolan Väst, Avdelningen för svetsteknologi (SV), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-11842.
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Additive manufacturing (AM) is a general name used for manufacturing methods which have the capabilities of producing components directly from 3D computeraided design (CAD) data by adding material layer-by-layer until a final componentis achieved. Included here are powder bed technologies, laminated object manufacturing and deposition technologies. The latter technology is used in this study. Laser Metal Powder Deposition (LMPD) is an AM method which builds components by fusing metallic powder together with a metallic substrate, using a laser as energy source. The powder is supplied to the melt-pool, which is created by the laser, through a powder nozzle which can be lateral or coaxial. Both the powder nozzle and laser are mounted on a guiding system, normally a computer numerical control (CNC) machine or a robot. LMPD has lately gained attentionas a manufacturing method which can add features to semi-finished components or as a repair method. LMPD introduce a low heat input compared to conventional arc welding methods and is therefore well suited in, for instance, repair of sensitive parts where too much heating compromises the integrity of the part. The main part of this study has been focused on correlating the main process parameters to effects found in the material which in this project is the superalloy Alloy 718. It has been found that the most influential process parameters are the laser power, scanning speed, powder feeding rate and powder standoff distance.These process parameters have a significant effect on the temperature history ofthe material which, among others, affects the grain structure, phase transformation, and cracking susceptibility of the material. To further understand the effects found in the material, temperature measurements has been conducted using a temperature measurement method developed and evaluated in this project. This method utilizes a thin stainless steel sheet to shield the thermocouple from the laser light. This has proved to reduce the influence of the laser energy absorbed by the thermocouples.
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Melo, Leonardo de. "Powder jet particle density distribution analysis and qualification for the laser metal deposition process." reponame:Repositório Institucional da UFSC, 2015. https://repositorio.ufsc.br/xmlui/handle/123456789/171441.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2015.Made available in DSpace on 2016-12-13T03:03:04Z (GMT). No. of bitstreams: 1 340514.pdf: 4063742 bytes, checksum: 6a2f911982008b177bc31b52c459c372 (MD5) Previous issue date: 2015
Abstract: The quality of the Laser Metal Deposition process depends on several factors and components. One of them and also one of the most important is the powder jet. Regular monitoring of the different variables involved on the powder jet need to be performed in order to assure the demanded high stability and quality standards of the produced coating layers. This monitoring is done through process monitoring techniques, where the powder jet is illuminated from the side, by a laser line, and recorded by a coaxially aligned camera through the powder feed nozzle. Symmetry, geometry and position of different levels of the powder jet can be analyzed through relevant algorithms. They also provide calculations of the particle density distribution the recorded images. The spatial particle density distribution of the powder jet can be calculated by superimposing individual levels along the jet. The measurement and monitoring principle was successfully tested with various nozzles and powder properties, making it possible to fully characterize a powder jet.
A qualidade do processo de deposição de metais a laser depende de diversos fatores e componentes. Um dos componentes mais importantes é o fluxo de pó metálico. É necessário o monitoramento contínuo das diferentes variáveis e parâmetros que influenciam no fluxo de pó para se garantir os altos padrões de qualidade e estabilidade requeridos nas peças produzidas. Este monitoramento é realizado através de técnicas de controle de processos, onde o fluxo de pó metálico é iluminado lateralmente, por um laser de iluminação em formato de linha, e gravado por uma câmera coaxial ao bocal alimentador de pó. Simetria, geometria e posição de diferentes níveis do fluxo de pó podem ser analisados através de algoritmos relevantes. Tais algoritmos tornam possíveis também cálculos da distribuição das partículas no fluxo, através da sobreposição de imagens de todos os frames gravados no vídeo em cada nível do fluxo de pó. O processo de medição e análise foi testado com sucesso em diferentes bocais alimentadores de pó e com diferentes materiais e parâmetros do fluxo, tornando possível sua caracterização e qualificação.
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Kretzschmar, B. S. M., K. Assim, Andrea Preuß, A. Heft, Marcus Korb, Marc Pügner, Thomas Lampke, B. Grünler, and Heinrich Lang. "Cobalt and manganese carboxylates for metal oxide thin film deposition by applying the atmospheric pressure combustion chemical vapour deposition process." Technische Universität Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A21422.
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Coordination complexes [M(O2CCH2OC2H4OMe)2] (M = Co, 4; M = Mn, 5) are accessible by the anion exchange reaction between the corresponding metal acetates [M(OAc)2(H2O)4] (M = Co, 1; M = Mn, 2) and the carboxylic acid HO2CCH2OC2H4OMe (3). IR spectroscopy confirms the chelating or μ-bridging binding mode of the carboxylato ligands to M(II). The molecular structure of 5 in the solid state confirms a distorted octahedral arrangement at Mn(II), setup by the two carboxylato ligands including their α-ether oxygen atoms, resulting in an overall two-dimensional coordination network. The thermal decomposition behavior of 4 and 5 was studied by TG-MS, revealing that decarboxylation occurs initially giving [M(CH2OC2H4OMe)2], which further decomposes by M–C, C–O and C–C bond cleavages. Complexes 4 and 5 were used as CCVD (combustion chemical vapour deposition) precursors for the deposition of Co3O4, crystalline Mn3O4 and amorphous Mn2O3 thin films on silicon and glass substrates. The deposition experiments were carried out using three different precursor solutions (0.4, 0.6 and 0.8 M) at 400 °C. Depending on the precursor concentration, particulated layers were obtained as evidenced by SEM. The layer thicknesses range from 32 to 170 nm. The rms roughness of the respective films was determined by AFM, displaying that the higher the precursor concentration, the rougher the Co3O4 surface is (17.4–43.8 nm), while the manganese oxide films are almost similar (6.2–9.8 nm).
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Segerstark, Andreas. "Additive Manufacturing using Alloy 718 Powder : Influence of Laser Metal Deposition Process Parameters on Microstructural Characteristics." Licentiate thesis, Högskolan Väst, Avd för tillverkningsprocesser, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-8796.
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Additive manufacturing (AM) is a general name used for production methodswhich have the capabilities of producing components directly from 3D computeraided design (CAD) data by adding material layer-by-layer until a final component is achieved. Included here are powder bed technologies, laminated object manufacturing and deposition technologies. The latter technology is used in this study.Laser metal deposition using powder as an additive (LMD-p) is an AM processwhich uses a multi-axis computer numerical control (CNC) machine or robot toguide the laser beam and powder nozzle over the deposition surface. Thecomponent is built by depositing adjacent beads layer by layer until thecomponent is completed. LMD-p has lately gained attention as a manufacturing method which can add features to semi-finished components or as a repair method. LMD-p introduce a low heat input compared to arc welding methods and is therefore well suited in applications where a low heat input is of an essence. For instance, in repair of sensitive parts where too much heating compromises the integrity of the part.The main part of this study has been focused on correlating the main processparameters to effects found in the material which in this project is the superalloy Alloy 718. It has been found that the most influential process parameters are the laser power, scanning speed, powder feeding rate and powder standoff distance and that these parameters has a significant effect on the dimensionalcharacteristics of the material such as height and width of a single deposit as wellas the straightness of the top surface and the penetration depth.To further understand the effects found in the material, temperaturemeasurements has been conducted using a temperature measurement methoddeveloped and evaluated in this project. This method utilizes a thin stainless steel sheet to shield the thermocouple from the laser light. This has proved to reduce the influence of the emitted laser light on the thermocouples.
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Lindell, David. "Process Mapping for Laser Metal Deposition of Wire using Thermal Simulations : A prediction of material transfer stability." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-85474.
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Additive manufacturing (AM) is a quickly rising method of manufacturing due to its ability to increase design freedom. This allows the manufacturing of components not possible by traditional subtractive manufacturing. AM can greatly reduce lead time and material waste, therefore decreasing the cost and environmental impact. The adoption of AM in the aerospace industry requires strict control and predictability of the material deposition to ensure safe flights. The method of AM for this thesis is Laser Metal Deposition with wire (LMD-w). Using wire as a feedstock introduces a potential problem, the material transfer from the wire to the substrate. This requires all process parameters to be in balance to produce a stable deposition. The first sign of unbalanced process parameters are the material transfer stabilities; stubbing and dripping. Stubbing occurs when the energy to melt the wire is too low and the wire melts slower than required. Dripping occurs when too much energy is applied and the wire melts earlier than required. These two reduce the predictability and stability that is required for robust manufacturing. Therefore, the use of thermal simulations to predict the material transfer stability for LMD-w using Waspaloy as the deposition material has been studied. It has been shown that it is possible to predict the material transfer stability using thermal simulations and criterions based on preexisting experimental data. The criterion for stubbing checks if the completed simulation result produces a wire that ends below the melt pool. For dripping two criterions shows good results, the dilution ratio is a good predictor if the tool elevation remains constant. If there is a change in tool elevation the dimensionless slenderness number is a better predictor. Using these predictive criterions it is possible to qualitatively map the process window and better understand the influence of tool elevation and the cross-section of the deposited material.Additiv tillverkning (AT) är en kraftigt växande tillverkningsmetod på grund av sin flexibilitet kring design och möjligheten att skapa komponenter som inte är tillverkningsbara med traditionell avverkande bearbetning. AT kan kraftigt minska tid- och materialåtgång och på så sett minskas kostnader och miljöpåverkan. Införandet av AT i flyg- och rymdindustrin kräver strikt kontroll och förutsägbarhet av processen för att försäkra sig om säkra flygningar. Lasermetalldeponering av tråd är den AT metod som hanteras i denna uppsats. Användandet av tråd som tillsatsmaterial skapar ett potentiellt problem, materialöverföringen från tråden till substratet. Detta kräver att alla processparametrar är i balans för att få en jämn materialöverföring. Är processen inte balanserad syns detta genom materialöverföringsstabiliteterna stubbning och droppning. Stubbning uppkommer då energin som tillförs på tråden är för låg och droppning uppkommer då energin som tillförs är för hög jämfört med vad som krävs för en stabil process. Dessa två fenomen minskar möjligheterna för en kontrollerbar och stabil tillverkning. På grund av detta har användandet utav termiska simuleringar för att prediktera materialöverföringsstabiliteten för lasermetalldeponering av tråd med Waspaloy som deponeringsmaterial undersökts. Det har visat sig vara möjligt att prediktera materialöverföringsstabiliteten med användning av termiska simuleringar och kriterier baserat på tidigare experimentell data. Kriteriet för stubbning kontrolleras om en slutförd simulering resulterar i en tråd som når under smältan. För droppning finns två fungerande kriterier, förhållandet mellan svetshöjd och penetrationsdjup om verktygshöjden är konstant, sker förändringar i verktygshöjden är det dimensionslös ”slenderness” talet ett bättre kriterium. Genom att använda dessa kriterier är det möjligt att kvalitativt kartlägga processfönstret och skapa en bättre förståelse för förhållandet mellan verktygshöjden och den deponerade tvärsnittsarean.
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Williams, Joseph James. "Surface reactions of zinc vapour with steel relevant to the Zn-55%Al-1.5%Si hot dip metal coating process." Faculty of Engineering, 2005. http://ro.uow.edu.au/theses/395.
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Zn-55%Al-1.5%Si coated steel strip is manufactured by the continuous hot dipping process. An important difference in the processing of Zn-55%Al-1.5%Si coated steel when compared with galvanised steel is the higher temperature of the molten alloy bath –600ºC for Zn-55%Al-1.5%Si coatings versus 450ºC for galvanised. This increase in temperature leads to an accelerated rate of evaporation of zinc into the pretreatment furnace, leading in turn to various processing difficulties. Zinc vapour in the pre-treatment furnace has long been implicated with defects known within the industry as pinholes and bare patches - uncoated areas where wetting does not occur between the strip and the molten alloy. Despite the association with zinc vapour, the exact mechanisms of pinhole and bare patch formation have not been clearly established. One possible mechanism of pinhole and bare patch formation is the direct reaction of zinc vapour with the strip surface. It has been suggested by industry experts that zinc vapour could condense on the strip, leaving a deposit that prevents wetting by molten Zn-55%Al-1.5%Si alloy. It remains that little is understood of the fundamental nature of the interaction between zinc vapour and a steel substrate. The purpose of this research was to examine the rates and mechanisms of zinc vapour condensation on clean and oxidised steel substrates. Such information is essential for understanding the reactions that occur in the metal coating line furnace. It is intended that this research will strengthen the fundamental knowledge base upon which a solution to the problem can be developed. The experimental work conducted in this study was centred on condensing zinc vapour onto substrates under specific gaseous atmospheres at atmospheric pressure. A major part of the work involved the development of a technique for depositing zinc vapour onto a steel substrate and the design and construction of an experimental apparatus. Preliminary studies were undertaken to define the design criteria for an apparatus in which the rate of condensation of zinc vapour could be measured accurately and the interaction between zinc vapour and clean and oxidised steel substrates could be examined. In this probing exercise, modifications were made to a proven design of an apparatus designed to measure evaporation rates of metals in inert gas atmospheres was used. The preliminary experiments provided a wealth of essential knowledge required to design an experimental facility in which it was possible to accurately measure the rate of condensation of zinc vapour and to study the interaction between zinc vapour and the steel substrate, as well as their potential chemical reactions. This new apparatus was specifically developed for a quantitative assessment of zinc vapour deposition, and allowed the substrate and zinc vapour to be heated in independent, but interconnecting chambers. The exposure of the substrate to the zinc vapour could be controlled with precision, and it was possible to not only measure the zinc vapour condensation rates, but also to assess the effect of using oxidising and reducing gasses during preheating of the substrate. Under conditions of high undercooling, zinc vapour deposited by the island plus continuous thin film mode, while at higher substrate temperatures, close to that expected in the industrial process, the zinc deposited more slowly, and zinc islands did not form on the substrate within the first 60 seconds of exposure. Deposition of zinc vapour on an oxidised substrate occurred at a much higher rate than on a clean steel substrate. This increase in deposition rate has been attributed to a direct reaction occurring between the zinc vapour and the iron oxide without the formation of any liquid condensate. The reaction is: Fe3O4(s) + 4Zn(v) ↔ 4ZnO(s) + 3Fe(s) This reaction will proceed to the right under sufficiently high partial pressures of zinc vapour, and at substrate temperatures both above and below the saturation temperature of the zinc vapour. It was observed that under sufficiently low partial pressures of zinc vapour, the above reaction is driven to the left. Zinc oxide has a determining influence on the wetting of the strip by the molten alloy. Immersion tests, wherein substrates deposited with zinc vapour were dipped into molten Zn-55%Al-1.5%Si alloy, were carried out to examine the effect of various zinc vapour reactions on the quality of the coatings. Deposition of zinc vapour on both clean and oxidised steel surfaces had a detrimental effect on the coating quality. In cases where zinc was deposited onto a clean steel substrate prior to immersion in the coating alloy, pinholes resulted, while zinc vapour deposition on an oxidised surface prior to immersion led to large scale uncoated areas.
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Cho, Soon. "Real-Time In-Situ Chemical Sensing in AlGaN/GaN Metal-Organic Chemical Vapor Deposition Processes for Advanced Process Control." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1798.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2004.Thesis research directed by: Material Science and Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Säger, Florian. "A Feasibility Study of an Automated Repair Process using Laser Metal Deposition (LMD) with a Machine Integrated Component Measuring Solutio." Thesis, KTH, Industriell produktion, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-248022.
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The repair of worn or damaged components is becoming more attractive to manufacturers, since it enables them to save resources, like raw material and energy. With that costs can be reduced, and profit can be maximised. When enabling the re-use of components, the lifetime of a component can be extended, which leads to improved sustainability measures. However, repair is not applied widely, mainly because costs of repairing are overreaching the costs of purchasing a new component. One of the biggest expense factors of repairing a metal component is the labourintense part of identifying and quantifying worn or damages areas with the use of various external measurement systems. An automated measuring process would reduce application cost significantly and allow the applications to less cost intense component. To automate the repair process, in a one-machine solution, it is prerequisite that a measuring device is included in the machine enclosure. For that, different measuring solutions are being assessed towards applicability on the “Trumpf TruLaser Cell 3000 Series”. A machine that uses the Laser Metal Deposition (LMD) technology to print, respectively weld, metal on a target surface. After a theoretical analysis of different solutions, the most sufficient solution is being validated by applying to the machine. During the validation a surface models from a test-component is generated. The result is used to determine the capability of detecting worn areas by doing an automated target-actual comparison with a specialised CAM program. By verifying the capability of detecting worn areas and executing a successful repair, the fundamentals of a fully automated repair process can be proven as possible in a one-machine solution.Tillverkare har börjat se stora möjligheter i att reparera slitna eller skadade komponenter som ett sätt att spara resurser, så som råmaterial och energi. Med den besparingen minskar kostnaderna och vinsten kan således maximeras. Reparation möjliggör även återanvändning av komponenter, vilket förlänger komponentens livslängd och leder till förbättrade hållbarhetsåtgärder. Dock tillämpas reparation inte i någon stor utsträckning i nuläget, främst eftersom kostnaderna för reparation överstiger kostnaderna för att köpa en ny komponent. En av de största kostnaderna för att reparera en metallkomponent är att identifiera och kvantifiera slitna eller skadade områden med hjälp av olika externa mätsystem, som är en väldigt arbetsintensiv process. En automatiserad mätprocess skulle minska avsökningskostnaden avsevärt och således reducera den totala kostnaden för komponenten. För att möjliggöra en automatiserad reparationsprocess i en enda maskinlösning är det en förutsättning att en mätanordning ingår i maskinhöljet. Därför har olika mätningslösningar utvärderats med avseende på användbarhet i "TRUMPF TruLaser Cell 3000 Series", vilket är en maskin som använder Laser Metall Deposition-teknik (LMD-teknik) för att skriva ut och svetsa metall på en definierad yta. En teoretisk analys av olika lösningar har utförts, där den teoretiskt mest lämpliga lösningen validerades genom att appliceras till maskinen. Valideringen genererade en modell av ytan av en testkomponent. Sedan utfördes en automatiserad, målrelaterad jämförelse med ett specialiserat CAM-program baserat på modellresultatet, för att bestämma möjligheten att upptäcka slitna områden. Genom att verifiera förmågan att upptäcka slitna områden samt genomförandet av en lyckad reparation kan grunden för en helt automatiserad reparationsprocess bevisas som möjlig i en enda maskinlösning.
Das reparieren von abgenutzten oder beschädigten Komponenten wird immer attraktiver für Hersteller. Es ermöglicht es Ressourcen einzusparen wie beispielsweise Rohmaterial und Energie, was die Lebenszeit einer Komponente verlängert und damit die Nachhaltigkeit verbessert. Allerdings ist Reparieren nach wie vor nicht weit verbreitet, hauptsächlich dadurch bedingt, dass die Reparaturkosten die Kosten für eine neue Komponente übersteigen. Einer der größten Kostenfaktoren des reparieren einer Metallkomponente ist der Arbeitsintensive Teil der Identifizierung und Quantifizierung des abgenutzten oder beschädigten Bereichs mit verschiedensten externen Vermessung Systemen. Ein automatisierter Vermessungsprozess würde die Kosten signifikant reduzieren und neue Applikationen ermöglichen. Das automatisieren der gesamte Prozesskette – in einer Single-Maschinenlösung – erfordert, dass eine Messeinrichtung im Bearbeitungsraum der Maschine angebracht wird. Dafür werden verschiedene Lösungen nach Anwendbarkeit an der Trumpf Laser Cell 3000 Serie hin beurteilt. Eine Maschine, welche Laser Metal Deposition (LMD) als Technologie anwendet um Material auf Oberflächen aufzubringen. Nach einer theoretischen Analyse verschiedener Lösungen wird die beste Lösung va durch anbringen an die Maschine validiert. Bei der Validierung wird ein Oberflächenmodel erzeugt. Das Ergebnis wird dann genutzt um die Fähigkeit zu belegen, dass beschädigte Stellen, durch einen Soll-Ist-Vergleich in einem speziellen CAM Programm, automatisch detektiert werden können. Basierend auf diesem Beleg und mit dem Ergebnis eine Komponente erfolgreich reparieren zu können, gilt die These eines automatisierten Reparaturprozesses in einer Single-Maschinenlösung als beweisen.
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Ju, Wentao. "Experimental Investigation of the Epitaxial Lateral Overgrowth of Gallium Nitride and Simulation of Gallium Nitride Metalorganic Chemical Vapor Deposition Process." Ohio : Ohio University, 2003. http://www.ohiolink.edu/etd/view.cgi?ohiou1050589636.
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Mascart, Monique. "Mise en suspension de poudres métalliques en vue de leur application par roll-coat analyse structurale des revêtements obtenus." Valenciennes, 1997. https://ged.uphf.fr/nuxeo/site/esupversions/d0ebab09-ade0-42e4-93b2-f4cf273386f9.
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Ce travail présenté un procédé permettant d'obtenir la métallisation d'un substrat d'acier par le biais d'une peinture à base de poudres métalliques. Les revêtements étudiés sont à base d'aluminium et d'alliages aluminium-silicium. Les paramètres de formulation des peintures ainsi que les microstructures obtenues ont été analysés et optimisés. Ce mémoire propose une méthode originale d'obtention d'alliage Al-Si in situ. Divers modèles relatifs aux interactions poudres/organiques, au gradient de composition des revêtements ainsi qu'un diagramme métastable des relations entre phases solides du système Fe-Al-Si sont également développés.
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Apicella, Fernandez Sergio. "Surface energy modification of metal oxide to enhance electron injection in light-emitting devices : charge balance in hybrid OLEDs and OLETs." Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-25097.
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Organic semiconductors (OSCs) present an electron mobility lower by several orders of magnitude than the hole mobility, giving rise to an electron-hole charge imbalance in organic devices such as organic light-emitting diodes (OLEDs) and organic light-emitting transistors (OLETs). In this thesis project, I tried to achieve an efficient electron transport and injection properties in opto-electronic devices, using inorganic n-type metal oxides (MOs) instead of organic n-type materials and a polyethyleneimine ethoxylated (PEIE) thin layer as electron transport (ETLs) and injection layers (EILs), respectively. In the first part of this thesis, inverted OLEDs were fabricated in order to study the effect of the PEIE layer in-between ZnO and two different emissive layers (EMLs): poly(9,9-dioctylfluorene-alt-benzothiadiazole) polymer (F8BT) and tris(8-hydroxyquinolinato) aluminum small molecule (Alq3), based on a solution and thermal evaporation processes, respectively. Different concentrations (0.80 %, 0.40 %) of PEIE layers were used to further study electron injection capability in OLEDs. After a series of optimizations in the fabrication process, the opto-electrical characterization showed high-performance of devices. The inverted OLEDs reported a maximum luminance over 104 cd m-2 and a maximum external quantum efficiency (EQE) around 1.11 %. The results were attributed to the additional PEIE layer which provided a good electron injection from MOs into EMLs. In the last part of the thesis, OLETs were fabricated and discussed by directly transferring the energy modification layer from OLEDs to OLETs. As metal oxide layer, ZnO:N was employed for OLETs since ZnO:N-based thin film transistors (TFTs) showed better performance than ZnO-based TFTs. Finally, due to their short life-time, OLETs were characterized electrically but not optically.
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Hocquette, Disdier Hélène. "Etude structurale de revetement de surface amorphe métallique élaboré par chalumeau plasma." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10016.
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Le but de cette these est l'etude structurale de revetements de surface par un depot amorphe metallique qui ont pour application la protection d'aubes de turbines hydrauliques. Les depots sont elabores par la technique du chalumeau plasma sous atmosphere et temperature controlees. La caracterisation structurale est faite principalement par microscopie electronique en transmission conventionnelle et haute resolution, ainsi que par microanalyse x. Une premiere partie presente les proprietes des verres metalliques et valide le choix de tels materiaux pour l'application industrielle envisagee. La demarche suivie pour le choix de la composition du depot est egalement decrite. Le deuxieme chapitre est consacre a la presentation du procede d'elaboration et des techniques experimentales mises en uvre. Les resultats experimentaux, a partir d'echantillons modeles et industriels obtenus pour differentes conditions d'elaboration, sont presentes dans le troisieme chapitre. Ils mettent l'accent sur certains artefacts produits par la technique d'observation, et mettent en evidence des effets de la methode d'elaboration sur l'etat structural des echantillons. L'analyse et l'interpretation de ces resultats faites dans le dernier chapitre, permettent une approche des mecanismes d'adherence depot/substrat de ces echantillons. Un protocole est enfin propose pour une meilleure qualite des revetements
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Cherkaoui, Mohammed. "Elaboration par electrolyse en courant pulse de revetements d'alliages ni-cu et ni-mo : etude de leurs proprietes." Paris 6, 1987. http://www.theses.fr/1987PA066306.
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Depot electrolytique sous courant pulse de revetements d'alliages base nickel. Etude de l'influence des parametres du courant pulse sur les differentes proprietes des depots ni-cu et ni-mo: composition, structure, contraintes, tenue a la corrosion (nacl a 3%)
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Schunemann, Esteban. "Paste deposition modelling : deconstructing the additive manufacturing process : development of novel multi-material tools and techniques for craft practitioners." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/13803.
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A novel paste deposition process was developed to widen the range of possible materials and applications. This experimental process developed an increasingly complex series of additive manufacturing machines, resulting in new combinations of novel materials and deposition paths without sacrificing many of the design freedoms inherit in the craft process. The investigation made use of open-source software together with an approach to programming user originated infill geometries to form structural parts, differing from the somewhat automated processing by 'closed' commercial RP systems. A series of experimental trials were conducted to test a range of candidate materials and machines which might be suitable for the PDM process. The combination of process and materials were trailed and validated using a series of themed case studies including medical, food industry and jewellery. Some of the object created great interest and even, in the case of the jewellery items, won awards. Further evidence of the commercial validity was evidenced through a collaborative partnership resulting in the development of a commercial version of the experimental system called Newton3D. A number of exciting potential future directions having been opened up by this project including silicone fabrics, bio material deposition and inclusive software development for user originated infills and structures.
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Conti, Alfredo. "Tecniche della manifattura additiva - applicazioni in ambito aeronautico e aerospaziale." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13306/.
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Il potenziale delle nuove tecnologie digitali applicate al settore industriale ha consentito di ridurre enormemente la durata dei cicli produttivi grazie alla rapida gestione di quantità di dati sempre più considerevoli attraverso l’introduzione delle Macchine a Controllo Numerico (Computer Numerical Control – CNC).
Nel corso delle ultime tre decadi, l’industria manifatturiera ha subito notevoli e sostanziali cambiamenti grazie ad una sempre più forte connessione con il mondo dell’informatica.
La più grande rivoluzione in tale ambito è stata segnata dall’avvento della Manifattura Additiva (Additive Manufacturing - AM), conosciuta sotto diversi nomi, tra i quali Prototipazione Rapida (Rapid Prototyping), Manifattura Rapida (Rapid Manufacturing) o Libera Fabbricazione di Forme (Free Form Fabrication).
Materia di ricerca e sviluppo sin dalla fine degli anni ’80, la Manifattura Additiva consente la creazione di elementi fisici tridimensionali partendo da modelli CAD attraverso la sovrapposizione successiva di materiale strato per strato (layer by layer), offrendo i benefici di una elevata flessibilità geometrica degli elaborati, altrimenti irraggiungibile attraverso le tradizionali tecniche di Manifattura Sottrattiva operanti per asportazione di materiale. In seguito ad intensive ricerche, progressi significativi sono stati fatti nello sviluppo e nella commercializzazione di nuovi ed innovativi processi AM.
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Antonysamy, Alphons Anandaraj. "Microstructure, texture and mechanical property evolution during additive manufacturing of Ti6Al4V alloy for aerospace applications." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/microstructure-texture-and-mechanical-property-evolution-during-additive-manufacturing-of-ti6al4v-alloy-for-aerospace-applications(03c4d403-822a-4bfd-a0f8-ef49eb65e7a0).html.
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Additive Manufacturing (AM) is an innovative manufacturing process which offers near-net shape fabrication of complex components, directly from CAD models, without dies or substantial machining, resulting in a reduction in lead-time, waste, and cost. For example, the buy-to-fly ratio for a titanium component machined from forged billet is typically 10-20:1 compared to 5-7:1 when manufactured by AM. However, the production rates for most AM processes are relatively slow and AM is consequently largely of interest to the aerospace, automotive and biomedical industries. In addition, the solidification conditions in AM with the Ti alloy commonly lead to undesirable coarse columnar primary β grain structures in components. The present research is focused on developing a fundamental understanding of the influence of the processing conditions on microstructure and texture evolution and their resulting effect on the mechanical properties during additive manufacturing with a Ti6Al4V alloy, using three different techniques, namely; 1) Selective laser melting (SLM) process, 2) Electron beam selective melting (EBSM) process and, 3) Wire arc additive manufacturing (WAAM) process. The most important finding in this work was that all the AM processes produced columnar β-grain structures which grow by epitaxial re-growth up through each melted layer. By thermal modelling using TS4D (Thermal Simulation in 4 Dimensions), it has been shown that the melt pool size increased and the cooling rate decreased from SLM to EBSM and to the WAAM process. The prior β grain size also increased with melt pool size from a finer size in the SLM to a moderate size in EBSM and to huge grains in WAAM that can be seen by eye. However, despite the large difference in power density between the processes, they all had similar G/R (thermal gradient/growth rate) ratios, which were predicted to lie in the columnar growth region in the solidification diagram. The EBSM process showed a pronounced local heterogeneity in the microstructure in local transition areas, when there was a change in geometry; for e.g. change in wall thickness, thin to thick capping section, cross-over’s, V-transitions, etc. By reconstruction of the high temperature β microstructure, it has been shown that all the AM platforms showed primary columnar β grains with a <001>β.
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陳宜呈. "A Study Defect On Metal Deposition Process." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/5e3sby.
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Olivas, John Daniel. "Surface study of process contamination of plasma spray metal deposition process." Thesis, 1996. http://hdl.handle.net/1911/16985.
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The purpose of the present study was to analyze the contamination which resulted from processing steps applied to substrate surfaces for the metal coating process known as plasma spray metal deposition. Additionally, the surface effects resulting from different solvent cleaning steps applied to a Ni based alloy were investigated in detail using incident, angle resolved and thermal desorption x-ray photoelectron spectroscopic methods. In particular, the study focused on contaminant O and C species interactions with the polycrystalline substrate prior to coating deposition. Differences in XPS features were noted between the various solvents used. Each solvent resulted in evaporation and ambient adsorption behavior which produced characteristic contaminants. Combining conventional desorption theory and surface spectroscopic techniques, a method of determining desorption behavior which was independent of weight measurements was developed. By comparing ambient O species to substrate oxides, changes in adsorbate coverage were estimated for the denuding surfaces. Experimental values for desorption behavior and relative desorption energetics were determined for ambient air on a polycrystalline substrate resulting from solvent/substrate interactions. Differences were discriminated between preparation methods and shown to vary as a function of solvent used. The nature of a surface with contamination was explained on this basis.
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Chen, Tin-Chi, and 陳亭棋. "Advanced Process Control of Metal Sputter Deposition Using Time Series Analysis." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/02207222123974896201.
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碩士中華大學
機械與航太工程研究所
93
In this study, we propose a new method to forecast and control the deposition rate of the sputter process by the time series analysis. In order to let the process model consist with the real process anytime, the time series model is fitted by the history data of the sputter process and then the parameters of the process model are updated whenever new measurements are obtained. The simulation results demonstrate that the performance of the proposed method is better than EWMA and DEWMA methods that are adopted in semiconductor processes.
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Chen, Ren-Jie, and 陳仁杰. "Molecular Dynamics Simulation of Sputter-Deposition Metal Films and High Temperature Reflow Process." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/55943194448032856819.
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碩士國立臺灣大學
應用力學研究所
90
The purposes of this thesis are two fold. First, the molecular dynamics (MD) simulation is used to investigate the influence of process parameters on metal thin film morphology and trench-filling morphology in the damascene process. The MD simulation adopts a two dimensional deposition model and uses Lennard-Jones Potential to represent the intermolecular force acting between Cu atoms. The Gear’s predictor-corrector algorithm is used to calculate the trajectories of atoms. A constant substrate temperature is assumed. The rescaling technique is utilized to model the energy absorbed by the substrate due to the impact of incident atoms. The morphologies of films for different physical parameters, such as temperature, incident energy, deposition rate and high temperature reflow process are discussed. It is found that temperature and incident energy effect play a similar role and with increasing temperature or incident energy, the void percentage and root mean square roughness are decreasing. Meanwhile, there exists an optimal region of deposition rate for an incident energy. Reflow process is achieved by the annealing procedure, the heating up and then cooling down the trench rapidly, to drive the copper diffusion and remedy the void defect. Secondary is to improve the computational efficiency of MD simulation. We treat the calculation of interactions which is the most time-consuming part by using distributed computing based on the Message Passing Interface (MPI). In our result, distributed computing is able to reduce the complexity from O(N2) to O(N2/p) on a p-processor system for N particles and achieve a linear speedup result.
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YAO, YING-JU, and 姚映如. "Parametric Optimization of Metal Word Line Tungsten Deposition Process by Using Taguchi Method." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/58062788004606669169.
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碩士逢甲大學
資訊電機工程碩士在職專班
99
This study has successfully applied the Taguchi method by using data produced by L12 orthogonal array experiment; and by applying Taguchi''s analysis of variance in the film deposition process of the tungsten metal word line (mWL W DEP-Metal Word Line Tungsten Deposition), its process parameters are optimized with the best combination of changes to improve the yield and thus the amount of production. Based on the complement table and ANOVA table of defect errors and the thickness variation, it can clearly determine the process parameters to impact tungsten metal word line thin film deposition as the most important nucleation temperature(℃), Silane(SiH4) ventilation temperature(℃), silane(SiH4) ventilation seconds(sec), film thickness uniformity (%), resistance uniformity(%), and the wafer surface defects (> 0.5um). For tungster metal word line thin film deposition, this study choose the best process parameters to run an batch of LOT for observing yield. The results yield significantly and enhance the foundry, The experiment average error combination result of plant A using the Taguchi method is still not as good as the standard wafer of technology parent company. However the number of defects has been controlled within 10, and so, it is still to achieve the purpose of improving the yield.
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Huang, Wen-Yi, and 黃文藝. "An Investigation of the Metal Deposition Process with the Compensation of Substrate Position Effect." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/96146966587384222058.
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碩士正修科技大學
機電工程研究所
97
As study on the density of metal film on substrate is considered in this investigation. There are material characteristic and reaction magnetic field issue during metal films deposition（Sputtering）, and there has stress issue after the metal film deposited upon the substrate surface, to reduce this stress issue can more effectively improve the deformation of substrate and density of metal film. This study is creating a metal film deposition system for substrate application with normal metal material. The sputtering source is 3 inch sputter gun where from Jun-San Tech Co. Ltd. in this system, and cylindrical chamber with CF series flange and expansibility design, thus there has extremely good sealing and repacking capability. To fit for high vacuum pressure and purity of Sputtering system, using Dry Screw Pump for Fore-line Pump to prevent oil vapor pollution, and build up a high vacuum environment by Turbo-molecular Pump. This thesis is studied to utilize the difference parameters in the substrate and target material（Target）. Numerical analysis indicating that the distance between the substrate and target materials may affect the density of metal film significantly.
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Peng, Kang-Tai, and 彭康泰. "Investigation of Mo5Si3/Si3N4 nanocomposites via Metal Organic Chemical Vapor Deposition and Densification Process." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/8x6zbt.
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碩士國立成功大學
材料科學及工程學系碩博士班
90
The metal-organic chemical vapor deposition (MOCVD) conducted in fluidized bed has been employed for the preparation of nano-sized molybdenum silicide and silicon nitride composites. Molybdenum octooxyhydride was decomposed and molybdenum oxide was deposited onto silicon nitride partical surface in the MOCVD process. The MoOx/Si3N4 composite powder was then reduced in H2/N2 and subsequently hot-pressed to be bulk Mo5Si3 composites. XRD, SEM or TEM characterized a series of MoOx/Si3N4 composite powder in order to investigate the crystalline phase and microstructure. The results indicated that the deposition phase was amorphous MoOx and individual deposition and island like deposition were two responsible mechanisms. The Molybdenum oxide phase transformation during reducing process. Heat treatment of composite powder at 1100℃ in H2/N2 produced metallic Mo, and transformed to Mo5Si3/Si3N4 at 1300℃ within 1h. Mo5Si3/Si3N4 composite powders can be sintered by hot pressing at 1850℃ for 1h in 10 atm N2 atmosphere and density of the composites reached to 98.5﹪of theoretical density. The flexural strength, hardness, fracture toughness and microstructure of the dense Mo5Si3/Si3N4 composites were investigated and the results are discussed. Two type Mo5Si3 grain size are proposed. Specimen was tested by 4-point bending method. The strength was 912 MPa. The hardness of the composites was close to that of Si3N4. The fracture toughness increases with the increase of Mo5Si3 content.
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Tsao, Teng-Yueh, and 曹騰躍. "Novel Electrostatic Deposition Method in the Layer Forming Process of Metal-powder-based Additive Manufacturing." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/b938n2.
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碩士國立清華大學
動力機械工程學系
106
Due to many basic expired patents of 3D printing technology, the product of 3D printer had entered a high-growth period. There is lots of competition in 3D printers with 3D printer technology of “fused deposition modeling” (FDM) and “stereolithography” (SLA). Although the technical threshold of metal additive manufacturing and the development funds is relatively high compared to other 3D printer technology, many countries have regarded metal additive manufacturing as an important development project due to its potential in the area of the defense industry and aerospace industry. “Electrostatic deposition method” has the characteristic of forming large-area layers in a short time. We studied the process of using the electrostatic deposition method in the metal-powder additive manufacturing technology in this research. The method we used in the research has the feature of forming the layer through the air without direct contact, making it easy to combine with subtraction processing and the potential in the area of surface repairing. The concept of combining additive and subtractive manufacturing is called hybrid manufacturing. CNC industry in Taiwan can add the function of additive manufacturing into their traditional machine tool to enhance their product value. To verify the feasibility of the method, we should study about the controllability of the layer thickness, coverage rate and the surface roughness of the layer. In the first half of the paper, we studied about the spraying method for even coverage of the dielectric film. In the second half of the paper, we modeled the electrostatic deposition process to predict the deposition thickness of the powder layer, then we verify the created model with experiment and analyze the experimental parameter. According to the results of the experiment, the applied electric field and the geometry of the experiment setup would influence the powder forming rate. We investigated the topic of applying electrostatic deposition method in the powder-based-additive-manufacturing with the feature of forming powder layer in a large area and deposition without direct contact. We did the experiments of the process and studied about the parameter and the results of deposition condition.
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Huang, Wei-Sheng, and 黃惟聖. "Investigation of chromium carbide/alumina Nano-composite via Metal Organic Chemical Vapor Deposition and Densification Process." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/51385421393482413964.
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碩士國立成功大學
材料科學及工程學系碩博士班
91
The metal-organic chemical vapor deposition (MOCVD) conducted in a fluidized bed has been employed for the preparation of nano-sized chromium carbide and alumina composites. Chromium hexacarbonyl(Cr(CO)6) was decomposed and successfully deposited onto alumina particles. The phase and amount of deposition depend on the deposition time and the state of fluid. The crystalline phase and microsturcture of as-deposited powders were characterized by XRD、ESCA and TEM. The result indicated the deposition was amorphous Cr2O3 exastinagas island-like (chain) type or individual type. In order to obtain Cr3C2/Al2O3 composite powder, heat treatment in graphite furnace is required. The Cr7C3/Al2O3 composite was produced from as-deposited powder by hot-pressed at 1400℃ in vacuum for 1h due to carbonization by the of carbon radicals from graphite mould. At high temperature, the conversion of chromium oxide to Cr3C2 or Cr7C3 depends on the activity of carbon. The microstructure of the dense composites was also discussed. The inclusion(Cr7C3) in Cr7C3/Al2O3 composite existed as three types. The matrix Al2O3 transformed into solid solution with a small quantity of Cr2O3. Some pores inside grain induced dislocation cell or low angle grain boundary because of large internal stress generated during cooling from the fabrication temperature 1400℃.
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Chang, Chih-Wei, and 張志維. "A Study For Transparent Metal Oxide Thin Film Transistors By Low Temperature Liquid Phase Deposition Process." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/27657191621224079744.
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碩士明道大學
材料科學與工程學系碩士班
100
The goal of this study is to develop high quality and low cost metal oxide semiconductor fabrication technology. Up to now, there is less study in metal oxide semiconductor TFTs by liquid phase deposition (LPD) process. It has many advantages like low cost, good uniformity and adhesion, easy stoichiometry control, and a potential of large scale batch-type mass production. In preparation of indium titanium oxide thin film transistors, ammonium hexafluoro-titanate and boric acid were used as materials to produce titanium oxide semiconductor films with the liquid phase deposition method. In this process, indium nitrate was doped to improve the mobility. Then, aluminum electrodes were further plated on these films via a shadow mask with the thermal evaporation. The transfer characteristics of TFT device were measured by an HP-4145B semiconductor parameter analyzer. Finally, we proved that, in this preparation of TiO2 by LPD, indium nitrate is an effective doping to the TiO2. This doping made the optical energy gap down to 2.95 eV, and the average transmittance is 74.08 %, the Hall mobility as high as 7.45 cm2/Vs. The final product is a type of inverse staggered, the μsat is 0.799 cm2/Vs, threshold voltage is -5.27 V, subthreshold swing is 0.13 V/dec, and on/off current ratio is 1.39 x 106.
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Chang, Yin-Yu, and 張銀佑. "Synthesis and Characterization of Metal-doped Amorphous Carbon Films Deposited by a Cathodic Arc Activated Deposition Process." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/69369145774616095311.
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博士國立中興大學
材料工程學研究所
92
Diamond-like Carbon (DLC) films containing various metal doping were synthesized by using a cathodic-arc activated deposition (CAAD) process. Metal plasma with intensive ion energies catalyzes the decomposition of hydrocarbon gases (C2H2), and induces the formation of hydrogenated amorphous carbon films with a mixture of sp2 and sp3 carbon bonds. The composite film structure consists of a metal- doped amorphous carbon film on top of a graded metal nitride interlayer, which provides enhanced mechanical and tribological properties. In this study, the plasma characteristics of the CAAD process for the deposition of metal-doped a-C:H was investigated by Langmuir probe measurement and optical emission spectroscopy. The catalysis effect of three common transition metal plasmas, including Cr, Ti, and Zr was investigated. This experiment depicts the advantage of the catalysis effect of Cr plasma in synthesizing DLC films with a higher sp3 carbon bond ratio comparing with that of Ti and Zr plasma. The wear properties were correlated with the metal doping determined by atomic size and electronic configuration. A catalytic ability ranking of transition metals for the deposition of metal-doped amorphous carbon films was suggested. Nitrogen was also introduced to form nitrogen-containing Cr-C:H/N films, which contained a mixture of sp2 and sp3 carbon bonds. The mechanical properties were correlated with the nitrogen doping. When nitrogen atoms occupy the substitutional sites to a large percentage, a donor energy level would be created and induces an increasing electrical conductivity.
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Hsin-YiSun and 孫新怡. "Assessing exposures and health risks associated with the laser metal deposition (LMD) operating process and its control strategy." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/2xqq35.
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Wu, Cheng-Zhang, and 吳承璋. "A Process Development Study on the Making of Dye Synthesized Solar Cells using Low Pressure Chemical Vapor Deposition Metal Doped ZnO as Electrodes." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/18354772027053627475.
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碩士龍華科技大學
化工與材料工程系碩士班
103
In this research, low pressure chemical vapor deposition (LPCVD) technique has been employed to prepare metal doped zinc oxide electrodes for dye synthesized solar cells (DSSC). The process parameters are as follow: metal Al as substrate, zinc acetylacetonate as precursor, deposition temperature at 500℃, pressure at 100-250 torrs, and metal acetylacetonates of Mg, Cu, Fe as dopants. FESEM, XRD results point out these LPCVD deposits are mostly poly crystal ZnO with (002) orientation. IV measurements of as assembled DSSC show that cell efficiency around 6-8%, implying these LPCVD doped ZnO can work successfully as the electrodes for solar cells. It is interesting that most LPCVD ZnO deposits on aluminum surface are composed mainly by thin wires (line diameters less than 500 nm) of ZnO crystals. This might be attributed to the eutectic driven vapor liquid solid growth phenomena; as according to the phase diagram of Zn/Al, the melting point for Zn/Al alloy eutectic is 420℃. Therefore, LPCVD ZnO on Al surface might create numerous Zn/Al eutectic tiny droplets densely distributed on the depositing surface. These eutectic droplets work as the ZnO line growing points because of their capability to absorb materials quickly. On the other hand, XRD/IV cross analysis indicate that DSSC will have a better performance, if the Al2O3 diffraction peaks are weak in XRD patterns. It was suggested that the adsorbed dopant molecules such as Mg(acac)2 might inject electrons to aluminum surface, thereby preventing oxidation of Al, and appearance of Al2O3. This leaves substrate has more regimes made by aluminum, rather than high resistivity alumina. Such further improve the efficiency of LPCVD ZnO DSSC. Based on collected data, which confirm the optimum condition to make DSSC is that perform LPCVD at low oxygen concentration, doped Zn(acac)2 with minor amount (< 3 wt %) of Mg(acac)2 or Fe(acac)3, the as assembled DSSC could have a current density of 0.825 mA/cm2, and efficiency of 10.31%.
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Yaddanapudi, G. R. Krishna. "Effect of Process Parameters on the Growth of N-Polar GaN on Sapphire by MOCVD." Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2662.
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Group III-Nitrides (GaN, InN & AlN) are considered one of the most important class of semiconducting materials after Si and GaAs. The excellent optical and electrical properties of these nitrides result in numerous applications in lighting, lasers, and high-power/high-frequency devices. Due to the lack of cheap bulk III- Nitride substrates, GaN based devices have been developed on foreign substrates like Si, sapphire and SiC. These technologies have been predominantly developed on the so called Ga-polarity epitaxial stacks with growth in the [0001] direction of GaN. It is this orientation that grows most easily on sapphire by metal organic chemical vapor deposition (MOCVD), the most common combination of substrate and deposition method used thus far. The opposite [000¯1] or N-polar orientation, very different in properties due to the lack of an inversion centre, offers several ad- vantages that could be exploited for better electronic and optoelectronic devices. However, its growth is more challenging and needs better understanding.
The aim of the work reported in this dissertation was a systematic investigation of the relation between the various growth parameters which control polarity, surface roughness and mosaicity of GaN on non-miscut sapphire (0001) wafers for power electronics and lighting applications, with emphasis on the realization of N-polar epitaxial layers. GaN is grown on sapphire (0001) in a two-step process, which involves the deposition of a thin low temperature GaN nucleation layer (NL) on surface modified sapphire followed by the growth of high temperature device quality GaN epitaxial layer. The processing technique used is MOCVD. Various processing methods for synthesis of GaN layers are described with particular em- phasis on MOCVD method. The effect of ex situ cleaning followed by an in situ cleaning on the surface morphology of sapphire (0001) wafers is discussed. The characterization tools used in this dissertation for studying the chemical bond nature of nitrided sapphire surface and microstructural evolution (morphological and structural) of GaN layers are described in detail.
The effect of nitridation temperature (TN) on structural transformation of non- miscut sapphire (0001) surface has been explored. The structural evolution of nitrided layers at different stages of their process like as grown stage and thermal annealing stage is investigated systematically. The chemical bond environment information of the nitrided layers have been examined by x-ray photoelectron spectroscopy (XPS). It is found that high temperature nitridation (TN ≥ 800oC) results in an Al-N tetrahedral bond environment on sapphire surface. In contrast, low temperature nitridation (TN = 530oC) results in a complex Al-O-N environment on sapphire surfaces. Microstructural evolution of low temperature GaN NLs has been studied at every stage of processing by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Surface roughness evolution and island size distribution of NLs measured from AFM are discussed. It is found that NLs processed on sapphire wafers nitrided at (TN ≥ 800oC) showed strong wurtzite [0002] orientation with sub-nanometre surface roughness. In contrast, NLs processed at (TN = 530oC) showed zinc blende phase in the as grown stage with higher surface roughness, but acquired a greater degree of wurtzite [0002] orientation after thermal annealing prior to high temperature GaN growth.
Polarity, surface quality and crystal quality of subsequently grown high temperature GaN epitaxial layers is described in relation to the structure of the trans- formed nitrided layers. Higher nitridation temperatures (TN ≥ 800oC) consistently yield N-polar GaN whereas lower nitridation temperatures (TN = 530oC) yield Ga-polar GaN. It is found that the relative O atom concentration levels in nitrided layers control the density of inversion domains in N-polar GaN. The effect of various growth parameters (NH3 flow rate, growth temperature, NL thickness) on surface morphology and mosaicity of both Ga & N-polar GaN layers is discussed in detail. We report device quality N-polar GaN epitaxial layers on non-miscut sapphire (0001) wafers by careful optimization of growth temperature. It is found that lower growth temperatures (800oC) are favorable for obtaining smooth N- polar GaN layers. In contrast, N-polar GaN layers grown at higher temperatures (1000 to 1080oC) are rough with hexagonal hillocks.
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Lin, Chi-Ying, and 林奇瑩. "To Recover Heavy Metals from MSWI Fly Ash Liquid after Acid Washing by Electro-deposition Process." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/13816358035050142931.
Full textAbstract:
碩士國立中興大學
環境工程學系所
97
In recent years, because the industry and commerce is fast growing, there''re almost 6 million tons of domestic wastes produced every year. It''s unable to dispose of the domestic wastes effectively by traditional landfill, so the government finished the construction of 24 large-scale incinerators in February 2008. According to EPA statistic in Taiwan, it''s nearly 90% of domestic wastes was treated by Municipal Solid Waste Incinerators (MSWI), but it will produce bottom-ash and fly-ash. The producing amount is 0.044 ton Fly ash/ ton Solid waste. And the MSWI fly ash TCLP (Toxicity Characteristic Leaching Procedure) test results showed that the average concentration of heavy metal lead was about 50 mg/L, which is ten times over the regulation limit 5.0 mg/L, and TCLP disqualification rate is up to 52.9%. If fly ash don’t take treatment through appropriate stability / solidification, it may cause the environmental pollution of heavy metal. The fly ash usually has characteristic of high pH, so that much heavy metal is deposited on the fly ash in the form of hydroxide. This research will dissolve Pb and Cu from fly ash by acid washing, and then utilize electrodeposition technology to deal the acid-washing liquid. The purpose is wanted to discuss the ability of dissolving heavy metal by acid-washing procedure, and the efficiency of electrodeposition technology to recover the heavy metal from acid-washing liquid. The results of study reveal that acid-washing the fly ash by L/S=20/1 with 0.5N HNO3 could cut down the weight by 68.6% after acid-washing. The dissolution rates of Pb and Cu are 55.6% and 83.2% respectively, and then the residue rates of Pb rises from 34% to 66%. By means of electrodeposition experiment, the removing rates of Pb at electric current 5A, 10A, 15A are 54%, 74%, 84% respectively; Cu is differentiated 90%, 80%, 82%. As for rate of recovery, it''s the best to fix electric current at 10A which can recover 25.7% of the Pb and 59.8% of Cu. The results reveal that it can be looked forward to recover heavy metal from MSWI fly ash by the combined procedure with acid-washing and electrodeposition.