To see the other types of publications on this topic, follow the link: CVD coatings.
Dissertations / Theses on the topic 'CVD coatings'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'CVD coatings.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Wheeler, David William. "Solid particle erosion of CVD diamond coatings." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342748.
Full text
2
Salgueiredo, Ermelinda da Conceição Portela. "Multilayered micro/nanocrystalline CVD diamond coatings for biotribology." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13465.
Full textAbstract:
Doutoramento em Ciência e Engenharia de MateriaisIn the present work multilayered micro/nanocrystalline (MCD/NCD) diamond coatings were developed by Hot Filament Chemical Vapour Deposition (HFCVD). The aim was to minimize the surface roughness with a top NCD layer, to maximize adhesion onto the Si3N4 ceramic substrates with a starting MCD coating and to improve the mechanical resistance by the presence of MCD/NCD interfaces in these composite coatings. This set of features assures high wear resistance and low friction coefficients which, combined to diamond biocompatibility, set this material as ideal for biotribological applications. The deposition parameters of MCD were optimized using the Taguchi method, and two varieties of NCD were used: NCD-1, grown in a methane rich gas phase, and NCD-2 where a third gas, Argon, was added to the gas mixture. The best combination of surface pre-treatments in the Si3N4 substrates is obtained by polishing the substrates with a 15 μm diamond slurry, further dry etching with CF4 plasma for 10 minutes and final ultrasonic seeding in a diamond powder suspension in ethanol for 1 hour. The interfaces of the multilayered CVD diamond films were characterized with high detail using HRTEM, STEM-EDX and EELS. The results show that at the transition from MCD to NCD a thin precursor graphitic film is formed. On the contrary, the transition of the NCD to MCD grade is free of carbon structures other than diamond, as a result of the richer atomic hydrogen content and of the higher substrate temperature for MCD deposition. At those transitions, WC nanoparticles were found due to contamination from the filament, being also present at the first interface of the MCD layer with the silicon nitride substrate. In order to study the adhesion and mechanical resistance of the diamond coatings, indentation and particle jet blasting tests were conducted, as well as tribological experiments with homologous pairs. Indentation tests proved the superior behaviour of the multilayered coatings that attained a load of 800 N without delamination, when compared to the mono and bilayered ones. The multilayered diamond coatings also reveal the best solid particle erosion resistance, due to the MCD/NCD interfaces that act as crack deflectors. These results were confirmed by an analytical model on the stress field distribution based on the von Mises criterion. Regarding the tribological testing under dry sliding, multilayered coatings also exhibit the highest critical load values (200N for Multilayers with NCD-2). Low friction coefficient values in the range μ=0.02- 0.09 and wear coefficient values in the order of ~10-7 mm3 N-1 m-1 were obtained for the ball and flat specimens indicating a mild wear regime. Under lubrication with physiological fluids (HBSS e FBS), lower wear coefficient values ~10-9-10-8 mm3 N-1 m-1) were achieved, governed by the initial surface roughness and the effective contact pressure.
No presente trabalho desenvolveram-se revestimentos de diamante micro/nanocristalino (MCD/NCD) em multicamadas obtidos por deposição química em fase vapor (CVD) assistida por filamento quente. Pretendeu-se minimizar a rugosidade através de um camada superficial de NCD, maximizar a adesão com um filme inicial de MCD sobre substratos cerâmicos de nitreto de silício (Si3N4) e incrementar a resistência mecânica pela presença de interfaces MCD/NCD nestes revestimentos compósitos. Este conjunto de características garante elevada resistência ao desgaste e baixo coeficiente de atrito, o que somado à biocompatibilidade do diamante, configuram este material como ideal para aplicações em biotribologia. Os parâmetros de deposição do MCD foram otimizados usando o método de Taguchi e utilizaram-se duas variedades de NCD: NCD-1 crescido numa atmosfera com sobressaturação de metano e NCD-2 crescido na presença de árgon. A melhor combinação de pré-tratamentos nos substratos de Si3N4 consiste num polimento com suspensão de diamante (15 μm), seguido de ataque por plasma de CF4 durante 10 minutos e riscagem em suspensão de pó de diamante em etanol durante 1 hora. As interfaces das multicamadas de diamante foram caracterizadas em detalhe por HRTEM, STEM-EDX e EELS. Os resultados mostram que na transição de diamante MCD para NCD ocorre a formação de um filme fino de carbono amorfo, inexistente na transição de NCD para MCD, como resultado da maior percentagem de hidrogénio atómico na mistura de gases e do incremento da temperatura do substrato para a deposição de MCD. Uma característica comum nas interfaces nos dois tipos de NCD é a presença de partículas esféricas de carboneto de tungsténio, devido à contaminação pelos filamentos, estando também presentes na interface entre a camada de MCD e o substrato de nitreto de silício. A adesão e resistência mecânica dos filmes de diamante foram avaliadas por ensaios de indentação, erosão com partículas de carboneto de silício e ensaios tribológicos em movimento recíproco, com pares próprios. Por indentação verificou-se que as multicamadas suportam uma carga de 800N, sem delaminação, valor superior ao atingido pelas mono- e bicamadas. Nos ensaios de erosão, as multicamadas apresentaram igualmente melhor comportamento, devido à ação das interfaces MCD/NCD como defletoras das fissuras, sendo estes resultados confirmados por uma análise de distribuição de tensões de von Mises. As multicamadas apresentam também as cargas críticas de delaminação máximas nos ensaios tribológicos a seco (200 N para multicamadas com NCD-2). Os valores do coeficiente de atrito variam na gama μ=0.02-0.09, para coeficientes de desgaste ~10-7 mm3 N-1 m-1 para a esfera e placa, indicando um regime de desgaste moderado. Sob lubrificação de líquidos fisiológicos (HBSS e FBS) descem para ~10-9-10-8 mm3 N-1 m-1, valores determinados pela rugosidade de partida e pelo regime de pressão de contato efetiva.
3
Bojestig, Eric. "Adhesion of CVD coatings on new cemeted carbides." Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-298648.
Full textAbstract:
Steel turning inserts cemented carbides have a binder phase consisting of cobalt (Co). However, in recent years a study from the United States National Toxicity Program (NTP) found that cobalt powder is carcinogenic upon inhalation. The European Union's REACH have therefore also classified cobalt powder as carcinogenic upon inhalation. The worldwide search to find a replacement has therefore lately intensified. It is important that the alternative binder phase has no negative effects on the properties of the insert. In this thesis the adhesion between a multilayer ceramic chemical vapor deposition (CVD) coating and a cemented carbide with the alternative binder phases consisting of iron (Fe), nickel (Ni) and cobalt (Co) has been studied. First of all, the fracture surfaces showed that the CVD coating was able to grow on all cemented carbides, regardless of which binder phase. To evaluate the adhesion, scratch tests were performed on all samples. The results from the scratch tests were not as expected. No chipping of the coating down to the cemented carbide occurred on any of the samples and the samples with the hardest cemented carbide did not get the highest critical load, which it should according to the literature if all other parameters were the same. Instead the sample with the binder phase consisting of 73 wt% iron and 27 wt% nickel had the highest critical load. This is thought to be due to that during the scratch test the binder phase in this cemented carbide would most likely transform into deformation martensite.
4
Bloyce, David Michael. "Microstructure - property relations in CVD deposited tin dioxide coatings on float glass." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267180.
Full text
5
Shabani, Mohammadmehdi. "Tribosystems based on multilayered micro/nanocrystalline CVD diamond coatings." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/16855.
Full textAbstract:
Doutoramento em Ciência e Engenharia de MateriaisA combinação das características do diamante microcristalino (MCD) e nanocristalino (NCD), tais como elevada adesão do MCD e a baixa rugosidade superficial e baixo coeficiente de atrito do NCD, é ideal para aplicações tribológicas exigentes. Deste modo, o presente trabalho centrou–se no desenvolvimento de revestimentos em multicamada MCD/NCD. Filmes com dez camadas foram depositados em amostras de cerâmicos de Si3N4 pela técnica de deposição química em fase vapor assistida por filamento quente (HFCVD). A microestrutura, qualidade do diamante e adesão foram investigadas usando técnicas como SEM, AFM, espectroscopia Raman, DRX, indentação Brale e perfilometria ótica 3D. Diversas geometrias para aplicações distintas foram revestidas: discos e esferas para testes tribológicos à escala laboratorial, e para testes em serviço, anéis de empanques mecânicos e pastilhas de corte para torneamento. Nos ensaios tribológicos esfera–sobre–plano em movimento recíproco, sob 10–90% de humidade relativa (RH), os valores médios dos coeficientes de atrito máximo e em estado estacionário são de 0,32 e 0,09, respetivamente. Em relação aos coeficientes de desgaste, observou–se um valor mínimo de cerca de 5,2×10–8 mm3N–1m–1 para valores intermédios de 20–25% de RH. A humidade relativa tem um forte efeito sobre o valor da carga crítica que triplica a partir de 40 N a 10% RH para 120 N a 90% de RH. No intervalo de temperaturas 50–100 ° C, as cargas críticas são semelhantes às obtidas em condições de baixa RH (~10–25%). A vida útil das ferramentas com revestimento de dez camadas alternadas MCD/NCD e 24 μm de espessura total no torneamento de um compósito de matriz metálica Al– 15 vol% Al2O3 (Al–MMC) é melhor do que a maioria das ferramentas de diamante CVD encontradas na literatura, e semelhante à maioria das ferramentas de diamante policristalino (PCD). A formação de cratera ocorre por desgaste sucessivo das várias camadas, atrasando a delaminação total do revestimento de diamante do substrato, ao contrário do que acontece com os revestimentos monocamada. Os anéis de empanque testados com biodiesel apresentaram coeficientes de desgaste (4,1x10–10 mm3N–1m–1) duas ordens de grandeza menores do que em ensaios esfera–sobre–plano em movimento recíproco (k = 5,0x10–8 mm3N–1m–1), mas não foi possível obter vedação completa devido a sobreaquecimento do fluido. Esta condição foi obtida com água sob pressão, para condições P.V na gama 0,72–5,3 MPa.ms–1. Um coeficiente de atrito em estado estacionário de ~ 0,04 e um valor de coeficiente de desgaste de 6,0x10–10 mm3N–1m–1, característico de um regime desgaste ultra–suave, revelam o alto desempenho deste tribossistema.
The combination of the characteristics of microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) varieties, such as high adhesion of MCD and low surface roughness and low friction coefficient of NCD, is ideal for highly–demanding tribological applications. The main objective of this study was thus the development of multilayered MCD/NCD coatings for such purpose. Single layer and tenfold multilayer coatings were grown onto Si3N4 ceramic samples by the hot–filament CVD (HFCVD) process and their microstructure, diamond quality and adhesion were investigated using SEM, AFM, Raman spectroscopy, XRD, Brale indentation and 3D optical profilometry. Several geometries for distinct applications were then coated: discs and balls for lab–scale tribological testing, mechanical seal rings and cutting inserts for in–service testing. For the ball–on–flat reciprocating tests in the 10–90% relative humidity (RH) range the average values of the maximum and steady–state friction coefficients are 0.32 and 0.09, respectively. Regarding the wear coefficient of the discs, a valley–shaped evolution is observed within the same RH range, with a minimum of about 5.2×10–8 mm3N–1m–1. Humidity has a strong effect on the value of the critical load that triples from 40 N at 10% RH to 120 N at 90% RH. In the 50–100 °C range the critical loads are similar to those attained under dry conditions ( 25% RH). The tool life of a 24 μm thick tenfold multilayered MCD/NCD coated insert in the turning of an Al–15 vol.% Al2O3 metal matrix composite (Al–MMC) is better than most reported CVD diamond systems, behaving as well as most PCD tools. Crater wear occurs by successive wear of the layers, delaying total delamination of the diamond coating from the substrate, unlike what would happen with monolayer coatings. Under biodiesel lubrication seal rings present wear coefficients (4.1x10–10 mm3N–1m–1) two orders of magnitude lower than the reciprocating sliding ball–on–flat experiments (k = 5.0x10–8 mm3N–1m–1), but no full sealing was possible due to overheating of the fluid. This condition was only attained with pressurized water, for P.V conditions in the range 0.72–5.3 MPa.ms–1. A steady state friction coefficient value of ~0.04 and a wear coefficient value of 6.0x10–10 mm3N–1m–1, characteristic of an ultra–mild wear regime, reveal the high performance of this tribosystem.
6
Ryan, David J. "High temperature degradation of combustion CVD coated thermal barrier coatings." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/18909.
Full text
7
Papazoglou, Despina. "CVD of ceramic coatings in a hot wall and fluidised bed reactor." Title page, contents and abstract only, 1994. http://web4.library.adelaide.edu.au/theses/09AS/09asp213.pdf.
Full text
8
Fallqvist, Mikael. "Microstructural, Mechanical and Tribological Characterisation of CVD and PVD Coatings for Metal Cutting Applications." Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-172364.
Full textAbstract:
The present thesis focuses on characterisation of microstructure and the resulting mechanical and tribological properties of CVD and PVD coatings used in metal cutting applications. These thin and hard coatings are designed to improve the tribological performance of cutting tools which in metal cutting operations may result in improved cutting performance, lower energy consumption, lower production costs and lower impact on the environment. In order to increase the understanding of the tribological behaviour of the coating systems a number of friction and wear tests have been performed and evaluated by post-test microscopy and surface analysis. Much of the work has focused on coating cohesive and adhesive strength, surface fatigue resistance, abrasive wear resistance and friction and wear behaviour under sliding contact and metal cutting conditions. The results show that the CVD deposition of accurate crystallographic phases, e.g. α-Al2O3 rather than κ-Al2O3, textures and multilayer structures can increase the wear resistance of Al2O3. However, the characteristics of the interfaces, e.g. topography as well as interfacial porosity, have a strong impact on coating adhesion and consequently on the resulting properties. Through the deposition of well designed bonding and template layer structures the above problems may be eliminated. Also, the presence of macro-particles in PVD coatings may have a significant impact on the interfacial adhesive strength, increasing the tendency to coating spalling and lowering the surface fatigue resistance, as well as increasing the friction in sliding contacts. Finally, the CVD-Al2O3 coating topography influences the contact conditions in sliding as well as in metal cutting. In summary, the work illuminates the importance of understanding the relationships between deposition process parameters, composition and microstructure, resulting properties and tribological performance of CVD and PVD coatings and how this knowledge can be used to develop the coating materials of tomorrow.
9
Hendrick, Michelle Renee. "The effects of combustion CVD-applied alumina coatings on the high temperature oxidation of a Ni-Cr alloy." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/19635.
Full text
10
Longpradit, Panchan. "Effect of substrate pretreatment on CVD diamond coated cemented tungsten carbide tools for wood cutting application." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326525.
Full text
11
Stanton, David. "Coloured, photocatalytic coatings for self-cleaning and architectural glazing applications : precursors and processes for the aerosol-assisted chemical vapour deposition of functional coatings on glass." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681056.
Full textAbstract:
There are a number of “smart” coatings that can be applied to glass. These include self-cleaning coatings based on titanium dioxide, and low-E coatings based on fluorine-doped tin oxide. Products are often more desirable with colour options such as Pilkington Activ BlueTM. There are currently no alternatives to body tinting glass to achieve colour, which is a time-consuming and expensive procedure. The work in this project details a number of coloured coatings via the AACVD or combustion processing of metal nitrate/urea precursors.
12
Karlsson, Dennis. "Residual stress in CVD coatings : Evaluation of XRD and TEM methods for micro and macrostress determination." Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-269050.
Full textAbstract:
Cutting tools are subject to extreme environment during processing, with hightemperatures and pressures. CVD coatings are used to increase lifetime andperformance of the WC/Co composite. Residual stresses in the coatings areinteresting as they may be destructive or constructive for the material duringoperation. Blasting is used to change the as-deposited tensile stress to compressive.The usefulness of X-ray diffraction (XRD) and nanobeam diffraction (NBD) forcharacterization of strains in the different coating layers has been investigated. XRDwith different anode materials has been used to determine the macrostress in thelayers and an attempt was done to calculate the average microstrain and crystallitesize. NBD was used to study the microstrain within single grains of the differentmaterials. A specimen preparation method has been developed for the studiedsamples using the FIB.The XRD analysis shows that the measurement condition is of great importanceduring stress measurements. The macrostress of the different samples show that theZrCN type coating is less stressed than the TiCN type coating after deposition. It isalso shown that the ZrCN type coating is less affected by the blasting. Determinationof microstrain and crystallite size from XRD needs further development.The NBD is a good method to evaluate microstrain within single grains, or betweengrains oriented in the same zone axis. The analyses show more strain within thegrains after blasting. The measurements indicate more strain variation in the Al2O3layer in the TiCN system compared to the ZrCN system.
13
Gomez, Vega Humberto Arturo. "Interface Engineered Diamond Coatings for Dry Machining Applications." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3121.
Full textAbstract:
Several studies have been propose to improve the adhesion of diamond films on cemented carbide tool materials, however a systematic study in identifying the role of the factors that affect the final diamond adhesion and the resulting machining performance of the tool under real manufacturing conditions is still unexplored. CVD diamond film's extraordinary qualities bring little benefit if the film fails to adhere sufficiently to the substrate. Inadequate adhesion undermines tool performance and longevity, causing unpredictable behavior under load and possibly leading to unexpected failure of the tool in the production line. This dissertation investigates the effects of different surface pretreatments on the adhesion and performance of CVD diamond coated WC-Co turning inserts for the dry machining of high silicon aluminum alloys.
Different interfacial characteristics between the diamond coatings and the modified WC-Co substrate were obtained by the use of two different chemical etchings and a CrN/Cr interlayer, with the aim to produce an adherent diamond coating by increasing the interlocking effect of the diamond film, and halting the catalytic effect of the cobalt present on the cemented carbide tool. A systematic study is analyzed in terms of the initial cutting tool surface modifications, the deposition and characterization of microcrystalline diamond coatings deposited by HFCVD synthesis, the estimation of the resulting diamond adhesion by Rockwell indentations and Raman spectroscopy, and finally, the evaluation of the dry machining performance of the diamond coated tools on A390 aluminum alloys. Scanning electron microscopy (SEM), metallographic analysis, and x-ray diffraction techniques were used to characterize the morphology, cobalt content, and nature of the substrate surfaces before and after each pretreatment; optical interferometry was utilized to characterize the surface roughness. After successfully diamond depositions, the films were characterized again using SEM, Raman spectroscopy, XRD, Electron Probe Microscopy Analysis (EPMA), and optical interferometry.
The experiments show that chemical etching methods exceed the effect of the CrN/Cr interlayer in increasing the diamond coating adhesion under dry cutting operations. This dissertation provided new insights about optimizing the surface characteristics of cemented carbides to produce adherent diamond coatings in the dry cutting manufacturing chain of high silicon aluminum alloys. An alternative method to measure the practical adhesion on commercial diamond coatings that can be correlated with the machining performance is proposed to be used when other methods (scratch, nanoindentation, microindentation, pin-on-disk, etc.) are not viable.
This research is the first comprehensive and systematic work that links the surface/subsurface integrity of cutting tools with their ability to produce an adherent diamond coating capable to dry machine high silicon aluminum alloys.
14
Fořt, Tomáš. "Charakterizace nanostruktur deponovaných PVD a CVD technologiemi." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-233449.
Full textAbstract:
The thesis deals with mechanical properties of thin hard wear-resistant coatings. The work presents a method of dynamic testing of thin hard coatings on a newly constructed prototype of impact wear tester. It provides a comparison with standard methods of layer testing and presents new experimental results of dynamic impact wear test of the coatings. Finally, the thesis covers preparation techniques of thin film systems deposited on various substrates and their characterization using optical and electron microscopy.
15
Grandinetti, Giulio. "A study on the deposition of crystalline alpha-alumina and mullite coatings using the combustion CVD process." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/20236.
Full text
16
JAYASEELAN, VIDHYA SAGAR. "STUDY OF POLYCRYSTALLINE DIAMOND THIN FILMS GROWN IN A CUSTOM BUILT ECR PE-CVD SYSTEM." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin975513169.
Full text
17
Varghese, Aneesha Mary. "Relation between structure and properties of TiO2 coatings on metallic substrates." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0026/document.
Full textAbstract:
L'objectif de cette étude était de réaliser des revêtements de TiO2 présentant une large variété de morphologies et d'établir des corrélations entre la structure de ces couches et leurs propriétés fonctionnelles, notamment la photocatalyse. Deux voies de synthèse employant le même précurseur, le tétra-isopropropoxide (TTIP) de titane, ont été utilisées, le procédé sol-gel et le dépôt chimique en phase vapeur (MOCVD). L'emploi de ces deux techniques permet de produire TiO2 sous une large gamme de morphologies mais avec des variétés polymorphiques similaires. Les revêtements synthétisés ont été caractérises afin de déterminer leur composition polymorphique, la taille des cristallites, la surface spécifique, la rugosité et l'épaisseur. Puis leur activité photocalytique pour la dégradation du bleu de méthylène a été déterminée. Par voie sol-gel, des dispersions de nano-cristallites de TiO2 dans l'eau, stables sur une longue durée (plus d'un an) en termes de composition polymorphique, taille d'agglomérats et de cristallites ont été synthétisées. Les revêtements ont été réalisés par tape-casting et dip-coating. Pour la synthèse en MOCVD, un plan d'expérience (PeX) a été utilisé, à notre connaissance pour la première fois. Il a permis de déterminer, d'une manière efficace et économique (avec un nombre minimum de tests expérimentaux), les paramètres les plus importants du procédé contrôlant les diverses propriétés quantifiables du revêtement. Il a aussi permis de mettre en évidence les interactions entre les paramètres de synthèse et leur effet sur la structure du revêtement. Les conclusions tirées du PeX sont en accord avec les résultats obtenus lors des études précédentes. L'analyse en composantes principales (ACP) a été réalisée pour avoir une vue globale de la façon dont les diverses propriétés des revêtements sont reliées entre ellesThe overall objectives of this study was to find an environmental-friendly and simple procedure to synthesize titanium-dioxide, as well as, to determine the relation between the structural and functional properties of titanium dioxide coatings. Both of these objective have been attained in this study. By the sol-gel technique, titanium dioxide sols were synthesized by the hydrolysis of titanium(IV)isopropoxide. Nanocrystalline dispersions of TiO2 in water were prepared that were suitable for coatings and having long-term stability (more than 1 year) in terms of polymorphic composition, crystallite and agglomerate size. A design of experiments (DoE) was utilised, to our knowledge, for the first time in MOCVD for the synthesis of TiO2 coatings. It was employed to determine, in a timely and economical manner, the most significant process parameters for any quantifiable property of the coating and to highlight the interaction between these operating parameters, as well as, the correlation between the structure of the coating and the process. The conclusions drawn from the DoE were compared to results obtained by previous studies and were found to concur. Therefore, the DoE was successful in screening the most important process parameters, with a minimum number of experimental trials. For most of the properties that were under investigation, the DoE showed that, the deposition temperature and reactor pressure were, often-times, the most significant. Therefore, to change the microstructure and composition of MOCVD coatings, changing these process parameters will ensure the highest impact. It has to be stressed that the conclusions drawn from the DoE are restricted to the experimental range that was under investigation. Principal Component Analysis (PCA) was conducted to have an overall view of how the different properties of the coatings related with one another. The interpretations made from this analysis were that the photocatalytic (PC) activity of the coatings produced did not relate strongly to the polymorphic composition, which is contrary to literature review and is explained to be a result of the different morphologies that lead to different porosities and specific surface area. The PC activity did not depend on the mass over a critical mass. With this analysis it appeared to be clear that the porosity and specific surface area played a larger role than polymorphic composition. This hypothesis has to be verified because we did not succeed in determining the specific surface area of our coatings during this study. However, some preliminary tests have been conducted showing that cyclic voltametry could be used to evaluate the surface area of our films
18
Dreiling, Ines [Verfasser], and Thomas [Akademischer Betreuer] Chassé. "Raman Spectroscopy Analysis of CVD Hard Coatings Deposited in the TiC1-xNx, TiBxCyNz and Ti-B-N System / Ines Dreiling ; Betreuer: Thomas Chassé." Tübingen : Universitätsbibliothek Tübingen, 2011. http://d-nb.info/1162627123/34.
Full text
19
Tuna, Jaroslav. "Metody povlakování řezných nástrojů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230106.
Full textAbstract:
This diploma thesis is aimed on methods of the coating cutting material (cemented carbide, cermets, cutting ceramic, super hard materials) and evalutation individual method regarding technological posibilities of deposition of hard coatings a their mechanical, thermal and che-mical properties. The task of the work is full elaboration obtained technical knowledges and mainly evalutation a comparison of the work conditions (kind of the cutting materials, cutting conditions) that selected producers recomended for effective turning aplications of the coa-tings cutting materials.
20
Michau, Alexandre. "Dépôts chimiques en phase vapeur de revêtements à base de chrome sur surfaces complexes pour environnements extrêmes : expérimental et simulation." Thesis, Toulouse, INPT, 2016. http://www.theses.fr/2016INPT0088/document.
Full textAbstract:
La protection des gaines de combustible de réacteur nucléaire contre l’oxydation à haute température en conditions accidentelles est essentielle pour garantir leur intégrité, c’est-à-dire celle de la première barrière de confinement. Celle-ci peut s’effectuer par le dépôt d’un revêtement sur leur paroi interne et ce sont les procédés CVD qui sont les plus à même de le faire. Il s’agit plus précisément du procédé DLI-MOCVD qui a été utilisé ici pour déposer des revêtements à base de chrome (chrome métallique Cr(S) cristallisé) et de carbures de chrome (carbures de chrome CrxCy amorphes non recyclés, recyclés et CrxSizCy dopés au Si), réputés pour leur bonne résistance à l’oxydation. Afin d’améliorer la qualité des revêtements, le procédé de dépôt a été optimisé à l’aide de simulations numériques. Après une réflexion sur le mécanisme chimique, un modèle cinétique réactionnel du dépôt d’un revêtement CrxCy amorphe a pu être ajusté et validé. Il a aussi été montré que la solution utilisée de précurseur organométallique bis(arène)chrome et de solvant toluène pouvait être directement recyclée, augmentant ainsi le potentiel d’industrialisation du procédé. Les propriétés physico-chimiques et structurales des revêtements déposés avec ce procédé ont été caractérisées. Une étude des propriétés mécaniques de ces revêtements a par ailleurs été entreprise. Il en ressort que, comparés à des revêtements apparentés déposés par d’autres procédés, ceux déposés par DLIMOCVD possèdent notamment une dureté élevée (jusqu’à une trentaine de GPa), des contraintes résiduelles en compression, une bonne adhérence avec leur substrat et enfin une résistance à l’usure abrasive différente suivant la température. L’évaluation de leur résistance à l’oxydation à 1200 °C a révélé les excellentes performances des revêtements en carbures de chrome amorphes, qui permettent de retarder l’oxydation catastrophique de plus de deux heures pour une épaisseur de 10 µm. Tous les autres revêtements augmentent la tenue en température des substrats en zircaloy mais ne retardent pas autant l’oxydation catastrophiqueNuclear fuel cladding tubes resistance against high temperature oxidation during accident conditions is crucial because it means protecting the first containment barrier. This can be done by coating the inner wall of the cladding tube with CVD processes, which are most likely to do so. More specifically, we used DLI-MOCVD to grow chromium based (Cr(S), metallic crystalline chromium) and chromium carbides based (amorphous chromium carbides CrxCy, recycled CrxCy, silicon doped CrxSizCy) coatings, known for their good oxidation resistance. The coating process was optimized using numerical modelling to improve coatings performance. A reaction kinetics model of the deposition process of amorphous CrxCy coatings was adjusted and validated after the identification of the chemical mechanism. It was also shown that the liquid solution containing organometallic precursor (bis(arene)chromium) and solvent (toluene) could be directly recycled, thereby increasing the industrialization potential of such process. Physical, chemical and structural properties of coatings deposited with this process were characterized. A study of the coatings mechanical properties has also been undertaken. It shows that compared to related coatings grown with other processes, those deposited by DLI-MOCVD exhibit a particularly high hardness (up to 30 GPa), compressive residual stresses, good adhesion with the substrate and finally a different abrasive wear resistance depending on the temperature. The assessment of their oxidation resistance at 1200 °C revealed excellent performances of amorphous chromium carbides coatings, which can delay catastrophic oxidation up to two hours with only a 10 µm thickness. All the other coatings only increase the thermal resistance of zircaloy substrates
21
Lee, Darryl Liang Wee. "Development of a PP-MOCVD System and its Design and Operational Parameters for Uniform Industrial Coatings on 3D Objects." Thesis, University of Canterbury. Dept. of Mechanical Engineering, 2014. http://hdl.handle.net/10092/9644.
Full textAbstract:
Increase in demand for uniform ceramic coatings on larger industrial components have led to a need for a PP-MOCVD coating system scale up. The objective of this thesis is to develop a fully functional coating system operating in the PP-MOCVD regime that is able to deposit thin film ceramic coatings on commercial or industrial components with complex 3D geometries.
This can be achieved by applying engineering and vacuum science theories, coupled with the established fundamentals of PP-MOCVD. A larger system was designed and assembled around the boundaries set by the dimensions and geometry of a stainless steel water pump impellor acting as the base substrate. Most of the components were sourced off the shelf from vacuum and fluid specialists. Components which were unavailable for various reasons were designed, and machined in-house by the departmental workshop.
Initial test depositions were conducted using small stainless steel disk substrates, heated using a resistive heater similar to the one utilised on the research scale system. The test depositions were performed with the heater and substrate combination placed in strategic locations. This is to test the overall uniformity of precursor flux in the chamber volume. The resulting coating uniformity on the disk surfaces were fair but problems such as the large collection of unreacted precursor on the chamber viewport and valve timing issues had to be addressed.
Before making any improvements to the system, each of the process areas leading to a successful deposition needed to be understood. Five process areas were developed: ‘Liquid Delivery’, ‘Atomization’, ‘Evaporation’, ‘Transport and Reactor Geometry’, and ‘Droplet Management’. Each of the process areas were analysed individually and changes were made to push for a maximum evaporation efficiency.
xviii
The improved system provided opportunities to perform depositions that were once not possible for PP-MOCVD. Two sets of deposition tests were designed and conducted. Firstly, the improvements were justified with a series of depositions using flat stainless steel plates with dimensions 65x65x5mm. The other set of 3D case study depositions involve observing the effects of the operational parameters of PP-MOCVD on the uniformity and penetration depths of the coatings into different sized macro blind trenches.
Five geometric setup conditions were used to justify the improvements made to the system. These are: ‘Substrate positioned in the direct line of spray’, ‘Use of an unheated receptor’, ‘Use of a heated receptor’, ‘Use of an unheated receptor with a non-axial substrate setup’, and “Choked Flow’. As expected, the uniformity of the coatings on both sides of the plate varied significantly when the substrate is placed over the line of sight of the precursor spray. Similarly, the coating produced under the induced choked flow condition resulted in low conformality. The introduction of an unheated receptor plate resulted in an increase in uniformity on both sides of the plate. Further prove that PP-MOCVD is geometry independent is provided by the deposition made with the non-axial substrate placement resulting in a coating of similar result to the unheated receptor. The use of a heated receptor provided a source for a secondary evaporation of the larger precursor droplets collected resulting in an increase in coating thickness while maintaining good conformality.
The effects of temperature, pressure, injection volume, and concentration were explored in the final case study. With maximum depths of 50mm, the macro blind trenches has an aspect ratio of 1:1 and cross-sectional areas of 3x3mm, 9x9mm, and 15x15mm. The final results show that as the temperature rises, the depth penetrated into the trench decreases. This could be due to the change in rate limiting steps as homogeneous reactions begin to increase at higher temperatures. Similar trends were observed with increasing pressure. As the pressure difference between the volume of the trenches and the rest of the chamber decreases, the push needed to
xix
force the precursor down the trench also decreases, resulting in less depth penetration. The effects of injection volume and concentration observed, can be explained by how much precursor molecules are present during one pulse cycle. The more that is available at any given time, the more likely a reaction will occur and deeper the penetration will get. Of course a ceiling or a limit exists where the molecules in the chamber will get evacuated without being reacted.
The future work made possible as a result of the scaled up system are proposed. These include a scale up of the operational parameters to suit any given substrate geometry, improvements to the heating source to achieve greater thermal uniformity, further improvements to the overall system accessibility, and performing other depositions using different substrate materials and precursor types.
22
Szwedek, Olivier. "Amélioration du comportement à l’oxydation à très haute température des composites carbone/carbone par des revêtements alternés SiC/HfC." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14184/document.
Full textAbstract:
Les composites C/C sont des matériaux très utilisés dans de nombreuses applications pour leurs propriétés exceptionnelles. Néanmoins, ils présentent l'inconvénient de s'oxyder dès les basses températures. Le travail dans cette thèse a consisté en l'élaboration de dépôts de carbures de silicium (SiC) et d’hafnium (HfC) par dépôt chimique en phase vapeur (CVD) afin de protéger en surface ces composites jusqu’à 2000°C. Cette voie d'élaboration permet l'obtention de dépôts denses et continus. Dans un premier temps, une étude thermodynamique du système chimique Hf-Cl-C-H a permis d’appréhender les conditions de dépôt d’HfC et de tracer des diagrammes de dépôt directement utilisables par l’expérimentateur. Ensuite, après avoir déterminé les conditions expérimentales de chloruration de l’hafnium, étape antérieure à la CVD, et après avoir examiné les compatibilités chimiques des deux carbures par Spark Plasma Sintering (SPS), une étude expérimentale paramétrique de la CVD d’HfC a été proposée. Cela a permis la détermination des conditions optimales de dépôt permettant l’obtention d’une protection multiséquencée HfC/SiC, les conditions de dépôt du SiC étant reprises de la littérature. En plus du procédé de CVD, un autre type de concept portant sur l'enrobage de poudres d'HfC par le SiC, puis frittées par la suite, a également été traité. Enfin, les matériaux fondés sur ces deux concepts ont été testés en oxydation à très haute température. Les résultats obtenus ont permis la validation du matériau multiséquencé à 2000°C et le matériau fritté à 1500°CCarbon/Carbon composites are widely used materials in many fields of application for their outstanding properties. Nevertheless, these materials have the drawback of oxidizing at very low temperatures. The aim of this work consisted in depositing by means of Chemical Vapour Deposition (CVD) coatings made of silicon carbide (SiC) and hafnium carbide (HfC) in order to protect the composite up to 2000°C in an oxidizing atmosphere. This way of manufacturing has allowed reaching dense and continuous coatings. First, a thermodynamic study of the Hf-Cl-C-H chemical system has permitted to study the influence of HfC deposition parameters and to report them into deposition diagrams. Then, after the study of experimental conditions in the metallic hafnium chlorination step and the examination of chemical compatibilities of the two carbides by Spark Plasma Sintering (SPS), a parametric study of the CVD of HfC has been carried out. This has enabled determination of optimal deposition conditions of HfC in order to manufacture an HfC/SiC multilayered protection. SiC experimental conditions were taken from the literature. Besides the materials made by CVD, another kind of material protection made of HfC powder coated with SiC and then sintered has been also studied. Finally, materials based on those two protection concepts have been oxidized at very high temperature. Results have enabled to validate the multilayered protection up to 2000°C and the HfC/SiC sintered powder up to 1500°C
23
Faure, Cyril. "Nouveaux revêtements multicouches diamantés nanograins sur cermets WC-Co : etude des phénomènes microstructuraux intervenant aux interfaces lors de l'élaboration." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14156/document.
Full textAbstract:
Du fait de leurs excellentes propriétés mécaniques et de leurs faibles masses spécifiques, l’utilisation des matériaux composites, au sein des structures mécaniques, est en plein essor. Cependant, leur usinage entraine une usure prématurée et aléatoire des outils de coupes en cermet WC-Co. L’origine de cette étude provient de la nécessité de protéger leur surface par un revêtement dur et résistant comme, par exemple, le diamant NCD. Toutefois, le cobalt présent dans le carbure cémenté favorise la formation de graphite au niveau de l’interface avec le film de diamant, ce qui nuit à son adhérence. La méthode retenue afin d’isoler ce métal de la surface a été de réaliser des systèmes interfaciaux multicouches. Ces derniers sont composés d’une barrière de diffusion au cobalt en nitrure de tantale et/ou en nitrure de zirconium et d’une couche favorisant la germination du diamant en acier inoxydable ou en molybdène. Les protocoles de dépôt élaborés au cours de ce travail ont la particularité d’utiliser une polarisation négative et séquencée du substrat durant l’étape de croissance. Cela induit une morphologie originale au revêtement de diamant breveté sous le nom de PyrNCD (Brevet N° :FR0807181). Les objectifs de cette étude sont la compréhension de l’ensemble des mécanismes (influence de la solubilité du carbone sur la germination du diamant, l’effet de la polarisation sur le substrat revêtu et sur la croissance du diamant,…) intervenant durant le dépôt de diamant et l’optimisation du procédéThe combination of good mechanical properties and low specific mass ensures the increasing use of composite materials to reduce the weight of mechanical structures. However, their machining induces premature and random wear of WC-Co cermet cutting-tools. The origin of this study comes from the necessity to protect cutting-tools surfaces by hard and resistant coatings like NCD diamond. Unfortunately, the cobalt found in these cemented carbides catalyses graphite formation at the interface with the diamond layer and harms the grip of the diamond film. The method used to isolate this metal from the surface has been to form interfacial multilayer systems. These are composed of a tantalum nitride and/or zirconium nitride diffusion barrier for cobalt and a layer promoting the diamond nucleation in molybdenum or stainless steel. The deposit protocols developed during this PhD work have the particularity of using a negative and sequenced substrate bias during the growth stage. This leads to an original morphology of the diamond coating which is patented under the name PyrNCD (International Patent N°: WO/2010/076423). The goal of this study is to understand all the mechanisms (like the impact of the carbon solubility on the diamond nucleation, the effects of negative bias on the coated substrate and the diamond growth,...) occurring during diamond deposition and process optimization
24
Cao, Jie. "Optimized pre-coating of equipment used for CVD." Thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-232480.
Full textAbstract:
In the cutting tool industry, replaceable cutting edge (insert) is often used. As insert support,steel nets are used which are pre-coated before use, since the iron will affect the coatingquality of the inserts. Titanium carbide (TiC) is an ideal material for pre-coating purposes andthe deposition of TiC is performed by chemical vapor deposition (CVD) using a gaseousmixture of TiCl4, CH4 and H2. In order to optimize both the process time and to ensure goodquality, in this master thesis a series of experiments were designed to investigate the influenceof gas flow rates, the CH4/TiCl4 ratio, and the total pressure. The measured parameters werethe coating thickness and the coating quality. The experimental results showed that increasingthe TiCl4 flow rate resulted in an increased coating thickness, but generated HCl has aretarding effect by adsorption. Increasing the CH4/TiCl4 mole ratio led to higher depositionrates, but outgrowth was observed at high ratios. Increasing the total pressure resulted in anincreased deposition rate, but hazardous TiO2 white smoke was observed.The optimal receipt with higher gas flow, CH4/TiCl4 mole ratio, and depositiontemperatures gave a 3.4 μm thick TiC coating after 12.5 h. Compared with the originalprocess, the optimal process obtained in this thesis saved 47 % process time.Surface morphology and grain size were examined using an optical microscope and ascanning electron microscope, and deposited TiC had a grain size of 1-2 μm. Line profileanalysis using energy-dispersive X-ray spectroscopy showed that the coated TiC layerprevented the diffusion of iron and there was no iron on the surface of the coated steel nets.
25
Joly, Damien. "Usinabilité de la fonte à graphite vermiculaire." Thesis, Tours, 2010. http://www.theses.fr/2010TOUR4042/document.
Full textAbstract:
L’étude présentée est consacrée à l’usinabilité de la fonte à graphite vermiculaire. Celle-ci se situe entre la fonte à graphite lamellaire et la fonte à graphite sphéroïdale par rapport à la forme du graphite constituant ce matériau. Elle est utilisée depuis plus de cinq ans dans les blocs moteurs diesel afin d’améliorer les performances et de diminuer les rejets atmosphériques pour respecter les nouvelles normes Européennes. Pour évaluer l’usinabilité d’un matériau, il faut s’étalonner par rapport à un matériau de référence. Dans notre cas, la fonte à graphite vermiculaire a été comparée à la fonte à graphite lamellaire. Des essais de tractions ont permis d’obtenir les propriétés mécaniques du lot de matière utilisé pour la campagne d’essais d’usinage ; ceci, afin de se situer dans la gamme de ce type de fonte. Les plaquettes d’usinage ont été caractérisées par nano-indentation. Les revêtements PVD et CVD ont subit des essais de micro-rayure afin de caractériser leur adhésion sur leurs substrats respectifs. La mise en place d’un plan d’expérience a permis de limiter le nombre de plaquettes d’usinage prototypes à réaliser. Des essais tribologiques de type pion/disque ont révélé des pistes exploitables pour la compréhension des phénomènes de frottement et d’usures mis en jeu lors de l’usinage de la fonte à graphite vermiculaireThis study deals with machinability of compacted graphite iron. This material is in-between grey cast iron and nodular cast iron due to the graphite particle shape. It is used for manufacturing diesel engine blocks so as to increase performances and reduce carbon emissions to comply with Euro 5 norm. It is necessary to compare one material to a reference material to evalute machinability criterium. In our case, compacted graphite iron has been compared to grey cast iron. Tensile tests have given us mechanical properties of our test pieces batch used for machining tests. It helped us to qualify the material in its own material range. Inserts have been characterized by nanoindentation. PVD and CVD coatings were benchmarked in microscratch way to determine their respective adhesion to theirs substrates A design of experiment has been setted up so as to reduce number of inserts protypes to be manufactured. Pin on disk tribologic tests gave few hints to have a better understanding of friction phenomena and wear during compacted graphite iron machining
26
Puneet, Mr. "Computer simulation of hot wall fiber coating CVD reactor." Ohio : Ohio University, 1991. http://www.ohiolink.edu/etd/view.cgi?ohiou1183736234.
Full text
27
Puneet, Vashistha. "Computer simulation of hot wall fiber coating CVD reactor." Ohio University / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1183736234.
Full text
28
Ponton, Simon. "Dépôt chimique en phase vapeur de silice amorphe en tant que revêtement barrière pour flacons pharmaceutiques." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0040.
Full textAbstract:
L’élaboration de nouvelles solutions médicamenteuses par les laboratoires pharmaceutiques est intimement liée à la maitrise de leurs interactions avec la surface des emballages primaires en verre, afin d’assurer la préservation du principe actif. Sans cet effort, les instances de santé américaine (FDA) et européenne (EMA) ont révélé dès 2007, des altérations irréversibles du médicament et du contenant. Les conséquences sont catastrophiques, les molécules contenues dans le flacon sont dénaturées et deviennent inefficaces, et la surface du verre se délamine en générant des particules insolubles de taille micrométrique en solution. Cette thèse concerne l’étude de revêtements de silice amorphe susceptibles d’être appliqués sur la surface interne de flacons pharmaceutiques pour limiter leur réactivité avec le contenu. Les revêtements ont été élaborés par dépôt chimique en phase gazeuse (CVD), à partir de tétraethylorthosilicate (TEOS) et dioxygène à pression subatmosphérique, entre 350 et 570 °C. Le procédé permet le contrôle des vitesses de dépôt dans la géométrie 3D du flacon, tout en offrant une fenêtre de températures de traitement compatible avec sa tenue mécanique. Une approche pluridisciplinaire qui combine science des matériaux et génie des procédés est mise en œuvre, dans le but de maîtriser les propriétés physico-chimiques et fonctionnelles du revêtement et du procédé d’élaboration. Des dépôts sur substrats plans ont permis d’effectuer une étude croisée de la structure, de la composition et de la densité du film, mettant en œuvre les spectrométries FTIR et ellipsométrique et des techniques d’analyse par faisceau d’ions. Des revêtements peu hydratés, peu poreux et légèrement sous-stœchiométriques en oxygène sont élaborés à 550 °C. Leur valeur de P-etch est 10 Å.s-1 traduisant une bonne résistance à l’érosion. Un modèle cinétique apparent est développé pour la simulation du procédé de dépôt. Il considère deux espèces intermédiaires, impliqués dans deux réactions homogènes et deux hétérogènes. Il reproduit la vitesse de dépôt et sa répartition sur la surface des substrats. Des revêtements de silice amorphe sont déposés dans des flacons en verre et le procédé est simulé numériquement. La prise de masse prédite par la simulation correspond à celle mesurée expérimentalement. Les flacons revêtus sont soumis à un essai de vieillissement hydrothermal lors d’un cycle de stérilisation pendant une heure à 121 °C et 1220 hPa en contact avec de l’eau ultra-pure, suivant la préconisation USP <660>. Ils présentent une excellente résistance hydrolytique, le revêtement empêché le relargage de substances minérales du verre au contact de l’eau. Ce travail ouvre la voie à l’élaboration, par un procédé industrialisable, de revêtements plus denses, susceptibles de remplir les exigences sévères de résistance à l’altération des solutions USP <1660>The development of new pharmaceutical solutions is intimately linked to the control of theirinteractions with the surface of the primary glass packaging, with the aim to ensure thepreservation of the active agent. Already in 2007, the American (FDA) and European (EMA) healthauthorities revealed irreversible alterations between the contained solution and the container. Theconsequences are catastrophic, since the contained active molecules are denatured and becomeineffective, and the surface of the glass delaminates and results in suspension of micrometricsized insoluble particles in the pharmaceutical solution. This thesis focuses on the development ofamorphous silica coatings likely to be applied on the inner surface of pharmaceutical vials to limittheir reactivity with the contained solution. The coatings were processed by chemical vapordeposition (CVD) from tetraethylorthosilicate (TEOS) and dioxygen at subatmospheric pressure,between 350 and 570 °C. The process allows control of the deposition rates in the 3D geometry ofthe vials and at the same time, it operates in a temperature window that is compatible with themechanical integrity of the vial. A multidisciplinary approach, combining materials science andprocess engineering is applied, in order to control the physicochemical and functional properties ofthe coating and its deposition process. Deposition on flat substrates allowed performing a crosslinked investigation of the structure, the composition and the density of the films by FTIR andellipsometric spectroscopies and ion beam analysis techniques. Poorly hydrated, non-porous andslightly lower than SiO2 stoichiometry coatings were processed at 550 °C. Their P-etch value is 10Å.s-1, indicating a good erosion resistance. An apparent kinetic model is developed for thesimulation of the deposition process. It considers two intermediate species, involved in twohomogeneous and two heterogeneous reactions. It reproduces the deposition rate and itsdistribution over the substrates surface. Amorphous silica coatings are deposited on the internalsurface of glass vials and the deposition process is numerically simulated. The simulation predictsa mass gain that corresponds to the one experimentally determined. The coated vials are filledwith ultra-pure water and are subjected to a hydrothermal aging test with a sterilization cycleduring one hour at 121°C and 1220 hPa according to the USP <660> recommendation. Theypresent an excellent hydrolytic resistance, corresponding to the resistance of the glass to therelease of soluble mineral substances into water. This work paves the way towards theprocessing, through an industrial transferrable process, of denser coatings which are expected tomeet severe specifications compatible with the USP <1660> recommendations
29
Roy, Amit Kumar. "Atomic Layer Deposition onto Fibers." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-85451.
Full textAbstract:
The main goal of this dissertation was to show that the principle of atomic layer deposition (ALD) can be applied to “endless” fibers. A reactor of atomic layer deposition has been designed, especially for coating depositions onto meter long bundles of fibers. Aluminum oxide (alumina), titanium oxide (titania), double layers of alumina and titania, as well as aluminium phosphate have been deposited onto bundles of carbon fibers using the home-built reactor. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images indicate that the coatings were uniform and conformal onto fiber surface. There was a good adhesion of the coatings to the fibers. Alumina has been deposited using two separate aluminum sources (aluminum trichloride and trimethylaluminum), and water as a source of oxygen. In case of alumina deposition using aluminum trichloride and water, initial deposition temperature was 500 °C. In these conditions, a part of the fiber bundle has been damaged. Thus, the deposition temperature was decreased to 300 °C and the fibers were unaffected. In addition, during this process hydrochloric acid is formed as a byproduct which is a corrosive substance and affects the reactor and there was a chloride impurity in the coatings. Thus, aluminum trichloride precursor was replaced by trimethylalumium. Alumina deposition onto carbon fibers using trimethylaluminum and water was carried out at a temperature of 77 °C. SEM images revealed that the fibers were unaffected and the coatings were uniform and conformal. Oxidation resistance of the carbon fibers was improved slightly after alumina deposition. Oxidation onset temperature of the uncoated fibers was about 630 °C. The resistance was linearly increased with the coating thickness (up to 660 °C) and getting saturated over a thickness of 120 nm. Titania coatings have been deposited using titanium tetrachloride and water. The physical appearances of the titania coatings were similar to the alumina coatings. The oxidation onset temperature of the titania coated carbon fibers was similar to the uncoated fibers but the rate of oxidation was decreased than the uncoated fibers. Two double layer coatings were deposited, alumina followed by titania (alumina/titania), and titania followed by alumina (titania/alumina). If the fibers were coated with the double layer of alumina/titania, they had almost same oxidation onset as alumina coated fibers but the rate of oxidation was decreased significantly compared to alumina coated fibers. This feature is independent of the thickness of the titania layers, at least in the regime investigated (50 nm alumina followed by 13 nm and 40 nm titania). On the other hand, the oxidation onset temperature of fibers coated with titania/alumina (20 nm titania /30 nm alumina) was approximately 750 °C. The fibers were burned completely when temperature was further increased to 900 °C and held another 60 minutes at 900 °C. This is significantly better than any other coating used in this dissertation. ALD of titania and alumina in principle was known beforehand, this dissertation here applies this knowledge for the first time to endless fibers. Furthermore, this dissertation shows for the first time that one can deposit aluminum phosphate via ALD (planar surface as well as fibers). Aluminum phosphate might be special interest in the fiber coating because it is a rather soft material and thus might be used to obtain a weak coupling between fiber and matrix in composites. Aluminum phosphate was deposited using trimethylaluminum and triethylphosphate as precursors. Energy dispersive X-ray spectroscopy and solid state nuclear magnetic resonance spectra confirmed that the coating comprises aluminum phosphate (orthophosphate as well as other stoichiometries). Scanning electron microscopic images revealed that coatings are uniform and conformal. In cases of alumina and titania, it was observed that the coatings were delaminated from the ends of cut fibers and thus formed of clear steps. On the other hand, for aluminum phosphate coating it was observed that the border between coating and underlying fiber often being smeared out and thus formed an irregular line. It seems in case aluminum phosphate cohesion is weaker than adhesion, thus it might be act a weak interface between fiber and matrix. Alumina, titania, and double layer microtubes have been obtained after selective removal of the underlying carbon fibers. The carbon fibers were selectively removed via thermal oxidation in air at temperatures exceeding 550 °C. SEM and TEM images indicate that the inner side of the tube wall has the same morphology like the fibers. In addition, it was observed that the individual microtubes were separated from their neighbors and they had almost uniform wall thicknesses. The longest tubes had a length of 30 cmDas Hauptziel dieser Dissertation bestand darin nachzuweisen, dass die Atomlagenabscheidung (engl. atomic layer deposition (ALD)) auf „endlose“ Fasern angewendet werden kann. Es wurde ein Reaktor zur Atomlagenabscheidung gestaltet, der speziell für die Beschichtung meterlanger Faserbündel geeignet ist. Aluminiumoxid, Titanoxid, Doppelschichten aus Aluminiumoxid und Titanoxid sowie Aluminiumphosphat wurden mit Hilfe des selbstgebauten Reaktors auf Kohlefaserbündel abgeschieden. Rasterelektronenmikroskopische (REM) und transmissionselektronenmikroskopische (TEM) Aufnahmen zeigten, dass die Beschichtung auf den Fasern einheitlich und oberflächentreu war. Des Weiteren wurde eine gute Adhäsion zwischen Beschichtung und Fasern beobachtet. Das Prinzip der Beschichtung mit Titanoxid und Aluminiumoxid mit Hilfe der ALD war bereits vorher bekannt und im Rahmen dieser Dissertation jedoch erstmals auf "endlose" Fasern angewendet. Des Weiteren wird in dieser Dissertation erstmals gezeigt, dass es möglich ist, Aluminiumphosphat mittels ALD abzuscheiden (sowohl auf planaren Oberflächen als auch auf Fasern). Aluminiumphosphat könnte von besonderem Interesse in der Faserbeschichtung sein, da es ein relativ weiches Material ist und könnte daher als eine Art „schwacher“ Verbindung zwischen Faser und Matrix in Kompositen dienen. Die Oxidationsbeständigkeit von beschichten Kohlefasern wurde im Vergleich zu unbeschichteten Fasern bis zu einem gewissen Grad erhöht. Monoschichten von Aluminiumoxid und Titanoxid waren dafür wenig effektiv. Aluminiumphosphatbeschichtete Fasern waren deutlich besser geeignet als die beiden anderen. Eine Doppelschicht aus Titanoxid gefolgt von Aluminiumoxid verbesserte die Oxidationsbeständigkeit nochmals deutlich gegenüber allen anderen Beschichtungen, die in dieser Dissertation verwendet wurden. Mikroröhren aus Aluminiumoxid, Titanoxid und Doppelschichten wurden durch die selektive Entfernung der zugrunde liegenden Kohlefasern erhalten. Einzelne Mikroröhren waren von benachbarten Röhren getrennt und sie weisen eine nahezu einheitliche Wanddicke auf
30
Siegert, Uwe. "Silber(I)- und Kupfer(I) – Precursoren für CVD, ALD und Spin-Coating Prozesse." Doctoral thesis, Universitätsbibliothek Chemnitz, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-201000265.
Full textAbstract:
Die vorliegende Arbeit beschäftigt sich mit der Synthese von Phosphan-Kupfer(I)- und Silber(I)-Thiocarboxylaten der Art [(nBu3P)mMSC(O)R] (m = 2, 3; M = Cu, Ag; R = Me, Ph). Die Verbindungen wurden in Hinsicht auf ihr Potential zur thermischen Abscheidung dünner Schichten untersucht.
Weiterhin befasst sich diese Arbeit mit der Darstellung von Silber(I)- und Kupfer(I)-Carboxylaten, die im organischen Rest mindestens eine zusätzliche Donorfunktion besitzen ([(nBu3P)mMO2CR]; m = 1, 2; M = Ag, Cu; R = ungesättigter organischer Rest, CH2O(CH2)2OCH3). Das thermische Verhalten und die Anwendbarkeit dieser Komplexe zur Abscheidung dünner Metallschichten mittels CVD-Verfahren wurden untersucht.
Das Verhalten von Phosphan-Silber und -Kupfer-Verbindungen in Lösung wurde mittels dynamischer NMR-Spektroskopie untersucht. Dazu wurden phosphankoordinierte Silber(I)- und Kupfer(I)-Acetate als Modellsystem benutzt und mit einem ausgewählten Vertreter der ungesättigten Carboxylate verglichen.
31
Czok, Gregor Sebastian. "Particle coating by chemical vapor deposition in the fluidized bed." Berlin Pro Business, 2005. http://deposit.ddb.de/cgi-bin/dokserv?id=2689065&prov=M&dok_var=1&dok_ext=htm.
Full text
32
Ćmiel, Milan. "VÝVOJ NÁSTROJŮ S PKD, CVD VRSTVOU A CVD POVLAKEM PRO DOKONČOVÁNÍ DĚR." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228661.
Full textAbstract:
The aim of the thesis is to design, conduct and assess an experiment seeking to look into the utility properties of recent tools manufactured by HAM-FINAL. The tools include polycrystalline diamond (PCD) and CVD diamond cutting edges. In the theoretical part, the attention is devoted to cutting materials with an emphasis on diamond materials, as well as to issues associated with the wearing of the cutting tools, requirements specified for precision of bores and tools used in the manufacture of precision bores. The paper further provides an overview of a selection of world’s leading manufacturers of PCD blanks, CVD diamond coatings, CVD diamond layers and reamers with PCD cutting edges.
33
Costa, Anderson Figueiredo [UNESP]. "Análise comparativa de ferramentas revestidas por PVD e CVD no torneamento do aço ABNT 8620." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/144680.
Full textAbstract:
Submitted by ANDERSON FIGUEIREDO DA COSTA null (and.kairos@hotmail.com) on 2016-11-06T23:21:09Z
No. of bitstreams: 1
Dissertação 20161104.pdf: 2526366 bytes, checksum: 11d77bc71653027d529eb9107a2d4a53 (MD5)Rejected by LUIZA DE MENEZES ROMANETTO null (luizaromanetto@hotmail.com), reason: Solicitamos que realize uma nova submissão seguindo a orientação abaixo: O arquivo submetido está sem a ficha catalográfica. A versão submetida por você é considerada a versão final da dissertação/tese, portanto não poderá ocorrer qualquer alteração em seu conteúdo após a aprovação. Corrija esta informação e realize uma nova submissão com o arquivo correto. Agradecemos a compreensão. on 2016-11-10T15:50:45Z (GMT)
Submitted by ANDERSON FIGUEIREDO DA COSTA null (and.kairos@hotmail.com) on 2016-11-22T17:09:03Z No. of bitstreams: 1 Dissertação 20161104 - Versão Final Corrigida.pdf: 5558976 bytes, checksum: 402eb9e3734833ebc7ccebf113844b8e (MD5)
Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-11-23T17:41:31Z (GMT) No. of bitstreams: 1 costa_af_me_guara.pdf: 5558976 bytes, checksum: 402eb9e3734833ebc7ccebf113844b8e (MD5)
Made available in DSpace on 2016-11-23T17:41:31Z (GMT). No. of bitstreams: 1 costa_af_me_guara.pdf: 5558976 bytes, checksum: 402eb9e3734833ebc7ccebf113844b8e (MD5) Previous issue date: 16-09-08
Com o atual avanço de propriedades dos materiais, novas alternativas estão sendo buscadas para manufaturas desses materiais. Entre os processos, a usinagem se caracteriza por ser um processo que emprega milhões de pessoas. Entretanto para alcançar tais objetivos melhorias nas propriedades das ferramentas se faz necessária. Neste seguimento, os revestimentos vêm apresentando avanços significativos, como pode-se destacar o revestimento por CVD (deposição química a vapor) que permite que a ferramenta seja empregada nas temperaturas em torno de 1200ºC. Nesta mesma linha vale destacar o revestimento por PVD (deposição física a vapor) normalmente em uma única camada, o qual permite que a aresta de corte seja positiva, possa trabalhar com menor esforço de corte, e em temperatura aproximadamente em 700ºC. Este trabalho tem como objetivo analisar comparativamente o desempenho de ferramentas de metal duro revestidas pelo processo CVD e PVD no torneamento do aço ABNT 8620 sem uso de fluido de corte. Foram utilizadas duas pastilhas de metal duro revestidas pelo processo de PVD e CVD, com mesma geometria para efeito comparativo. A pastilha revestida por PVD tem espessura do revestimento de 3µm, enquanto que a pastilha revestida por CVD tem espessura do revestimento de 16µm. As pastilhas revestidas foram caracterizadas quanto a composição química dos elementos de revestimentos utilizando um microscópio eletrônico de varredura pela técnica de linescan e mapping. Posteriormente as ferramentas foram aplicadas ao torneamento nas velocidades de corte (Vc) entre 350 a 500m/min, avanço (f) de 0,20mm/rot e profundidade de corte (ap) de 1,00mm, utilizando um torno da marca ROMI, modelo GL240M. As caracterizações foram realizadas com uso de um microscópio óptico, microscópio eletrônico de varredura e um rugosímetro. Os resultados demonstraram que a ferramenta revestida pelo processo CVD apresenta um melhor rendimento, quando comparado ao processo PVD, este fato ocorreu porque a ferramenta revestida pelo processo CVD apresenta um revestimento multicamadas, possuindo um aporte térmico mais elevado, suportando assim, temperaturas de corte mais elevadas durante a usinagem e promovendo um menor desgaste de flanco e de superfície de saída. Portanto, este trabalho demonstra que para uso em uma indústria que torneia o aço ABNT 8620, as ferramentas revestidas com CVD apresentam melhor desempenho, levando a um menor consumo de pastilhas e uma expressiva redução de custos.
With the current advancement of material properties, new alternatives are being sought for manufacturing these materials. Among the processes, machining is characterized as a process that employs millions of people. However to achieve such goals improvements in the tools properties is necessary. In this follow-up, the coatings have shown significant advances, as can highlight the coating by CVD (chemical vapor deposition) that allows the tool to be used at temperatures around 1200°C. In the same line it is worth highlighting the coating by PVD (physical vapor deposition) usually in a single layer, which allows the cutting edge is positive, can work with less shear stress, and temperature approximately 700°C. This study aims at comparing the performance of carbide tools coated by the CVD process and PVD in the steel turning ABNT 8620 without the use of cutting fluid. We used two carbide inserts coated by the PVD and CVD process, with the same geometry for comparison purposes. The tablet is coated by PVD coating thickness of 3μm, while the tablet is coated by CVD coating thickness of 16μm. The coated tablets were characterized as the chemical composition of coatings elements using a scanning electron microscope for linescan technique and mapping. Subsequently the tools were applied to turning the cutting speed (Vc) between 350 to 500 m/min, feed (f) 0.20 mm/rev and depth of cut (ap) of 1.00mm using a lathe ROMI mark, GL240M model. The characterizations were carried out using an optical microscope, scanning electron microscope and roughness. The results demonstrated that the tool coated by the CVD process has a better performance when compared to PVD this occurred because the tool coated by the CVD process has a multilayer coating having a higher heat input, supporting thus cutting temperatures over high during machining and promote a smaller flank wear and output surface. Therefore, this work shows that for use in an industry that sidesteps steel ABNT 8620, tools coated with CVD have better performance, leading to lower consumption of pellets and a significant cost reduction.
34
Neves, Davi. "Influência da texturização laser na vida de ferramentas de torneamento revestidas por CVD e PVD." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264169.
Full textAbstract:
Orientador: Anselmo Eduardo DinizTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-17T11:44:38Z (GMT). No. of bitstreams: 1 Neves_Davi_D.pdf: 10536142 bytes, checksum: 795991ecdf9cb6dbe266a3307de5386d (MD5) Previous issue date: 2010
Resumo: Uma característica dos revestimentos aplicados nas ferramentas de corte é a adesão. A adesão deficiente libera particulados duros e abrasivos resultantes da fragmentação prematura do revestimento, acelerando o desgaste das superfícies em contato. Na texturização, um laser de pulsos curtos e de alta frequência provoca, na interação com a superfície, uma mudança das propriedades advinda da fusão e ablação de material. Neste processo podem ocorrer a limpeza e a texturização simultâneas da superfície, dependendo da energia do pulso laser. Nesta tese foi avaliada a efetividade da texturização a laser como alternativa ao jateamento na preparação da superfície do substrato de ferramenta de metal duro antes da aplicação do revestimento. Após uma análise prévia dos efeitos do laser sobre o metal duro, dois conjuntos de substratos, um adequado a revestimento CVD e outro adequado a revestimento PVD, foram extraídos do processo produtivo antes do jateamento que antecede a aplicação do revestimento. Texturizados a laser em quatro diferentes condições, os substratos foram posteriormente recobertos com os respectivos filmes de PVD TiAlN e CVD TiCN+Al2O3+TiN. Comparadas com ferramentas convencionais, as ferramentas texturizadas a laser e revestidas por PVD foram superiores em testes de indentação e ensaios de torneamento. As ferramentas texturizadas a laser e revestidas por CVD apresentaram um desempenho inferior nos ensaios de indentação e torneamento. A comparação dos mecanismos de desgaste das ferramentas mostra que a texturização não elimina os mecanismos atuantes na ferramenta, mas altera a relação de importância na formação de seus desgastes. A texturização a laser não eliminou os defeitos produzidos pelo processo CVD na ferramenta, tornou-os mais graves, o que fez com que a ferramenta texturizada a laser apresentasse vida menor que a ferramenta convencional. Por outro lado, em ferramentas PVD, a ancoragem proporcionada pela maior rugosidade da superfície texturizada aumentou a adesão do revestimento com o substrato e, consequentemente, aumentar a vida da ferramenta
Abstract: Adhesion is one of the most important coating characteristics on cutting tools. Poor coating adhesion on the tool makes possible the coating fragmentation and the release of hard and abrasive particles. These particles interact with the tool surfaces accelerating tool wear. In texturing, a high frequency short pulse laser changes surface characteristics generating molten material and ablation. The surface cleaning and texturing can simultaneously occur, depending on the laser pulse energy. This thesis evaluated the effectiveness of laser texturing as an alternative to sand blasting for substrate surface preparation for tool surface coating. After a preliminary examination of laser surface cemented carbide interaction, two sets of substrates, a CVD coating suitable substrate and a PVD coating suitable substrate were taken from production process before blasting to coating application. These substrates were laser textured in four different conditions and then subsequently coated with the respective CVD TiCN+Al2O3+TiN film and PVD TiAlN film. The PVD coated laser texturized tool showed higher performance on indentation tests and turning tests in benchmark with conventional tools. The CVD coated laser-texturized tool was outperformed by conventional tools in the indentation test and turning test. The comparative evaluation of tool wear mechanisms shows that the texturing does not alter the wear mechanisms, but it changes the importance of them in tool wear. Therefore, laser texturizing did not eliminate the defects produced by the CVD process on the tool, instead, it made them more aggressive, what caused the laser texturized tool to have shorter life than the conventional one. On the other hand, in the PVD coated tools the anchoring caused by the higher roughness of the texturized surface could increase the coating adhesion on the substrate and, consequently, to increase tool life
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica
35
Liu, Jiping. "Applications of cellulose acetate phthalate aqueous dispersion (Aquacoat CPD) for enteric coating." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3034932.
Full text
36
Post, Patrick [Verfasser], and Alfred P. [Verfasser] Weber. "Coating of gasborne nanoparticles with silica and silica-organic shells in a post-plasma CVD process / Patrick Post, Alfred P. Weber." Clausthal-Zellerfeld : Technische Universität Clausthal, 2019. http://d-nb.info/1231363363/34.
Full text
37
Swar, Rohan. "Particle Erosion of Gas Turbine Thermal Barrier Coating." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1259075518.
Full text
38
Claudiu, Mortan [Verfasser], Wolfram [Akademischer Betreuer] Jaegermann, and Barbara [Akademischer Betreuer] Albert. "Thin Film Perovskite Solar Cells: Fabrication via Spin Coating, Flash Evaporation and Chemical Vapor Deposition (CVD) / Mortan Claudiu ; Wolfram Jaegermann, Barbara Albert." Darmstadt : Universitäts- und Landesbibliothek, 2020. http://d-nb.info/1224048598/34.
Full text
39
Ibarra, Medina Juansethi Ramses. "Development and application of a CFD model of laser metal deposition." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/development-and-application-of-a-cfd-model-of-laser-metal-deposition(d74829d8-c4b9-40f1-b80f-cbdc456ffaf5).html.
Full textAbstract:
Laser metal deposition is one of the most versatile methods in the expanding field of additive manufacturing. Its outstanding advantage is its capability to process a variety of metallic materials for the freeform fabrication of objects having sound mechanical properties. The process is used in applications of rapid manufacturing, components repair and surface coating. During recent years, modelling has been increasingly used to study and improve the laser metal deposition process. However, most models have focused on analysing individual stages of the deposition process and thus have not thoroughly dealt with the occurrence of mutually-influencing phenomena. This work presents a new numerical model that, starting from the simulation of powder particles in the deposition head, integrates the important phenomena and interactions that govern the dynamics of a powder stream and a deposition melt pool, within a single model for the first time.The resulting model is comprehensive enough to allow the prediction of the morphology of deposited tracks and structures and the heat flows during their creation; as well as the flexibility to simulate, in principle, any deposition shape. The model has been demonstrated using the settings of an actual laser metal deposition system, and has been applied to study clad formation in the deposition of single tracks, layers, walls and simple three-dimensional structures. Moreover, the model has been used to study the formation of irregularities and excessive mass deposition. A new sensor-less deposition control technique based on the simulation and testing of different deposition strategies prior to actual deposition, is proposed. As a demonstration of this control technique, the model has also been used to study the case where excessive deposition develops at intersecting or cornered tracks. Improved deposition strategies have been tested using the model and applied to real deposits. A two fold improvement in layer height control has been achieved in the case of cornered layers.The outcome of the work presented in this thesis can be applied in further studies and prediction of laser deposited shapes for real applications. Furthermore, it can be potentially used for improvement of the laser metal deposition technology through the simulation of deposition strategies prior to actual processing.
40
Rich, Jared W. "Assessment and Improvement of Wear in Copper Extrusion Dies." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1386080178.
Full text
41
Poozesh, Sadegh. "INKJET PRINTING: FACING CHALLENGES AND ITS NEW APPLICATIONS IN COATING INDUSTRY." UKnowledge, 2015. http://uknowledge.uky.edu/me_etds/72.
Full textAbstract:
This study is devoted to some of the most important issues for advancing inkjet printing for possible application in the coating industry with a focus on piezoelectric droplet on demand (DOD) inkjet technology. Current problems, as embodied in liquid filament breakup along with satellite droplet formation and reduction in droplet sizes, are discussed and then potential solutions identified. For satellite droplets, it is shown that liquid filament break-up behavior can be predicted by using a combination of two pi-numbers, including the Weber number, We and the Ohnesorge number, Oh, or the Reynolds number, Re, and the Weber number, We. All of these are dependent only on the ejected liquid properties and the velocity waveform at the print-head inlet. These new criteria are shown to have merit in comparison to currently used criteria for identifying filament physical features such as length and diameter that control the formation of subsequent droplets. In addition, this study performs scaling analyses for the design and operation of inkjet printing heads. Because droplet sizes from inkjet nozzles are typically on the order of nozzle dimensions, a numerical simulation is carried out to provide insight into how to reduce droplet sizes by employing a novel input waveform impressed on the print-head liquid inflow without changing the nozzle geometry. A regime map for characterizing the generation of small droplets based on We and a non-dimensional frequency, Ω is proposed and discussed. In an attempt to advance inkjet printing technology for coating purposes, a prototype was designed and then tested numerically. The numerical simulation successfully proved that the proposed prototype could be useful for coating purposes by repeatedly producing mono-dispersed droplets with controllable size and spacing. Finally, the influences of two independent piezoelectric characteristics - the maximum head displacement and corresponding frequency, was investigated to examine the quality of filament breakup quality and favorable piezoelectric displacements and frequencies were identified.
42
Štefek, Jaromír. "Moderní řezné nástroje ze slinutých karbidů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-228932.
Full textAbstract:
This thesis deals with modern cutting cemented carbide tools. In the first section are stated several basic innovations already used tools for basic machining operations, which is turning, milling and drilling. It continues with analysis of single materials for production of cemented carbides, non coated as well as coated and with comparing of their properties. There are listed the basic cutting properties of the cutting tools after that. The penultimate point of the work is optimization of the basic machining operations, namely roughing and finishing, for a given application, which is in this case turning on the lamp stand. Finally, everything is summed up and evaluated in the conclusion.
43
Ivchenko, Dmitrii. "Modeling and design of a physical vapor deposition process assisted by thermal plasma (PS-PVD)." Thesis, Limoges, 2018. http://www.theses.fr/2018LIMO0099/document.
Full textAbstract:
Le procédé de dépôt physique en phase vapeur assisté par plasma thermique (PS-PVD) consiste à évaporer le matériau sous forme de poudre à l’aide d’un jet de plasma d’arc soufflé pour produire des dépôts de structures variées obtenus par condensation de la vapeur et/ou dépôt des nano-agrégats. Dans le procédé de PS-PVD classique, l’intégralité du traitement du matériau est réalisée dans une enceinte sous faible pression, ce qui limite les phénomènes d’évaporation ou nécessite d’utiliser des torches de puissance importante. Dans ce travail, une extension du procédé de PS-PVD conventionnel à un procédé à deux enceintes est proposée puis explorée par voie de modélisation et de simulation numérique : la poudre est évaporée dans une enceinte haute pression (105 Pa) reliée par une tuyère de détente à une enceinte de dépôt basse pression (100 ou 1 000 Pa), permettant une évaporation énergétiquement plus efficace de poudre de Zircone Yttriée de granulométrie élevée, tout en utilisant des torches de puissance raisonnable. L’érosion et le colmatage de la tuyère de détente peuvent limiter la faisabilité d’un tel système. Aussi, par la mise en oeuvre de modèles numériques de mécaniquedes fluides et basé sur la théorie cinétique de la nucléation et de la croissance d’agrégats, on montre que, par l’ajustement des dimensions du système et des paramètres opératoires ces deux problèmes peuvent être contournés ou minimisés. En particulier, l’angle de divergence de la tuyère de détente est optimisé pour diminuer le risque de colmatage et obtenir le jet et le dépôt les plus uniformes possibles à l'aide des modèles susmentionnés, associés à un modèle DSMC (Monte-Carlo) du flux de gaz plasmagène raréfié. Pour une pression de 100 Pa, les résultats montrent que la barrière thermique serait formée par condensation de vapeur alors que pour 1 000 Pa, elle serait majoritairement formée par dépôt de nano-agrégatsPlasma Spray Physical Vapor Deposition (PS-PVD) aims to substantially evaporate material in powder form by means of a DC plasma jet to produce coatings with various microstructures built by vapor condensation and/or by deposition of nanoclusters. In the conventional PS-PVD process, all the material treatment takes place in a medium vacuum atmosphere, limiting the evaporation process or requiring very high-power torches. In the present work, an extension of conventional PS-PVD process as a two-chamber process is proposed and investigated by means of numerical modeling: the powder is vaporized in a high pressure chamber (105 Pa) connected to the low pressure (100 or 1,000 Pa) deposition chamber by an expansion nozzle, allowing more energetically efficient evaporation of coarse YSZ powders using relatively low power plasma torches. Expansion nozzle erosion and clogging can obstruct the feasibility of such a system. In the present work, through the use of computational fluid dynamics, kinetic nucleation theory and cluster growth equations it is shown through careful adjustment of system dimensions and operating parameters both problems can be avoided or minimized. Divergence angle of the expansion nozzle is optimized to decrease the clogging risk and to reach the most uniform coating and spray characteristics using the aforementioned approaches linked with a DSMC model of the rarefied plasma gas flow. Results show that for 100 Pa, the thermal barrier coating would be mainly built from vapor deposition unlike 1,000 Pa for which it is mainly built by cluster deposition
44
Vopařil, Josef. "Moderní řezné nástroje ze slinutých karbidů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228549.
Full textAbstract:
This thesis is focused on cutting tools made of cemented carbides. It contains analysis of cemented carbides for uncoated and coated cutting tools. It contains examples of modern tools for turning, milling and drilling. Practical part of this thesis evaluates and compares cutting properties of two types of spiral drills.
45
Nováková, Radana. "Povlakování střižných nástrojů ze slinutých karbidů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231749.
Full textAbstract:
Tato diplomová práce se zabývá problematikou PVD povlakování střižných nástrojů ze slinutých karbidů, se zaměřením na zvýšení životnosti postupových nástrojů. Především poukazuje na využití povlakovaných nástrojů v praxi a procesních kroků před a po procesu povlakování. V teoretické části jsou popsány obě základní metody povlakování, tj. fyzikální metoda PVD a metoda CVD, založena na chemickém procesu. Dále jsou představeny jednotlivé způsoby vlastních procesů povlakování se stručným popisem výhod i nevýhod jejich využití. Praktická část je zaměřena na testování, jehož podstatou byl nejen vhodný výběr samotného povlaku pro daný materiál, ale i úpravy před a po povlakování, které jsou často opomínány. Ty jsou však nezbytnou součástí a mají výrazný vliv nejen na výsledný povlak, ale i na kvalitu pracovního procesu. Vyhodnocením experimentu je souhra určení nejproduktivnějšího povlaku v závislosti na dané úpravě.
46
Brinques, Graziela Brusch. "Otimização da produção de probióticos em biorreatores e suas aplicações em sistemas alimentícios sob a forma imobilizada." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/18601.
Full textAbstract:
Probióticos são suplementos alimentares de microrganismos vivos com efeitos benéficos no hospedeiro animal pela melhora do balanço intestinal. Dentre os microrganismos considerados probióticos, somente aqueles microrganismos classificados como bactérias ácido lácticas (LAB) são considerados importantes em relação à alimentação. Cultivos de altas densidades de células são cada vez mais importantes do ponto de vista industrial para a obtenção de LABs, pois produtos adicionados com esses suplementos apresentam alto valor agregado. Este trabalho tem por objetivo a produção de Lactobacillus plantarum em cultivo submerso em biorreator, avaliação da sua resistência na forma livre e imobilizada frente às condições de armazenamento sob refrigeração e trânsito gastrointestinal e elaboração de produto fermentado com adição de probióticos. Inicialmente foram realizados experimentos para selecionar Lactobacillus que apresentassem alta produtividade de biomassa. Em seguida foram realizados experimentos para avaliar a utilização de soro de queijo como ingrediente base da formulação do meio de cultivo e sua suplementação com diferentes fontes de nitrogênio. Com o microrganismo selecionado, L. plantarum, realizou-se a seleção de variáveis através do delineamento experimental Plackett Burman (P-B). A otimização das condições de cultivo foi realizada utilizando um delineamento composto central rotacional (DCCR). Paralelamente, foram testadas a sobrevivência de L. plantarum em armazenamento sob refrigeração e à exposição a meios que simulem a passagem pelo aparelho digestivo. Estas avaliações foram realizadas comparativamente entre os microrganismos na forma livre e na forma microencapsulada utilizando como polímeros alginato de sódio e pectina e recobrimentos com alginato de sódio e quitosana. Os resultados mostraram que a temperatura, pH, taxa de aeração, concentração de lactose e peptona foram os parâmetros que mais influenciaram a produção de biomassa. O DCCR para temperatura e taxa de aeração mostraram que o máximo de produção de biomassa predita foi de 14,30 g L-1 de L. plantarum, nas condições otimizadas. No ponto central do DCCR, atingiu-se a produção de biomassa de L. plantarum de 10,2 g L-1, como taxa de conversão de 0,10 g de células g-1 de lactose e 1,08 g de ácido láctico g-1 lactose (m/m) com as seguintes condições de cultivos: 140 g L-1 de lactose; 15 g L-1 peptona; 5 g L-1 extrato de levedura; pH 5,2; velocidade de agitação de 200 rpm; 34 ºC e 3,5 vvm. O meio intestinal simulado não interferiu na viabilidade dos microrganismos em relação ao meio controle. Já o meio gástrico simulado diminui drasticamente a viabilidade dos microrganismos nas condições testadas não havendo diferença significativa entre os diferentes materiais imobilizantes utilizados e o controle sem imobilização. No armazenamento sob refrigeração houve aumento da viabilidade em relação às células não imobilizadas, sendo que os tratamentos em que houve menor perda de viabilidade foram imobilização em 4 % de pectina, 3 % de alginato de sódio recoberto com quitosana e mistura de 2 % de alginato de sódio e 2 % de pectina. Quando testada a viabilidade em iogurte de L. plantarum imobilizados em 3 % de alginato recoberto com quitosana houve perda de viabilidade de 0,55 ciclo logarítmico durante 38 dias de armazenamento. A cepa de L. plantarum estudada se mostra como um microrganismos potencial para utilização como probiótico em alimentos, uma vez que demonstrou alta produtividade de células e boa viabilidade frente às condições de estresse utilizadas.Probiotics are live microorganisms feed supplement, which beneficially affects the host animal by improving its intestinal microbial balance. Among the microorganisms considered probiotics, only those strains classified as latic acid bacteria - LAB are considered of importance regarding to the nutritional effects. High cell density cultivations of LABs are important from the industrial viewpoint, because products added with this supplement are of high value. The aims of this work were to investigate the biomass production of Lactobacillus plantarum in submerged bioreactor cultures, evaluate the resistance of free and immobilized L. plantarum when submitted to refrigerated storage, the viability in simulated gastrointestinal juices and in yoghurt. Initially, experiments were performed to select Lactobacillus that showed high productivity of biomass. Further experiments were performed to evaluate the use of cheese whey as a basic ingredient in the formulation of the medium and its supplementation with different nitrogen sources. The selected microorganism, L. plantarum, was used for the selection of variables of the Plackett Burman (PB) design. The optimization of culture conditions was performed using a central composite rotational (CCD) design. In parallel, it was tested the survival of L. plantarum in refrigerated storage and exposure to media that simulated the passage through the digestive tract. These evaluations were performed comparatively between microorganisms in the free and microencapsulated form using as polymers sodium alginate and pectin, coated with sodium alginate or chitosan. Results have shown that temperature, pH, aeration rate, lactose, and peptone were the most influential over biomass formation. The CCD for temperature and aeration rate showed that the model predicted maximal biomass production of 14.30 g L-1 (dw) of L. plantarum under the optimized conditions. At central point of CCD, it was obtained a biomass production of 10.2 g L-1 (dw), with conversion rates of 0.10 g of cell g-1 lactose and 1.08 g lactic acid g-1 lactose (w/w), with the following conditions: 140 g L-1 of lactose; 15 g L-1 peptone; 5 g L-1 of yeast extract; pH 5.2; stirred agitation of 200 rpm; 34 ºC and 3.5 vvm. The simulated intestinal medium did not affect the viability of microorganisms in relation to the control medium. However, the simulated gastric medium drastically reduces the viability of microorganisms in the conditions tested with no significant difference between the different materials used and the control without immobilization. In refrigerated storage there was an increase in the viability compared to free microorganisms, and the treatments with lower loss of viability were those of 4% pectin, 3% sodium alginate coated with chitosan and a mixture of 2% alginate sodium and 2% pectin. When tested the viability in yogurt of L. plantarum immobilized in 3% alginate coated with chitosan, the viability loss was 0.55 log cycle during 38 days of storage. The strain of L. plantarum studied was shown as a potential organism for use as probiotics in food, since it has shown high yield and good cell viability in the face of stress conditions used.
47
Bégué, Geoffrey. "Etude de l'adhérence de barrière thermique EB-PVD par choc laser (LASAT) pour le développement d'un contrôle non-destructif sur aube de turbine aéronautique." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0093.
Full textAbstract:
L'évaluation de la résistance interfaciale des systèmes barrière thermique EB-PVD est primordiale afin de pouvoir contrôler la production d'aubes de turbine revêtues et d'améliorer la compréhension des phénomènes d'écaillage de la céramique qui se produisent en fonctionnement. L'essai d'adhésion par choc laser LASAT qui s'appuie sur la propagation bidimensionnelle des ondes de choc (le phénomène LASAT-2D) consiste à mesurer le diamètre de fissure interfaciale pour différents tirs effectués à densité de puissance laser croissante. L'application de l'essai LASAT sur une pièce industrielle nécessite d'effectuer le choc du côté revêtu de céramique. Un adhésif vinylique protecteur ainsi qu'un milieu de confinement par adhésif transparent sont utilisés afin de générer un choc en surface de la céramique. La propagation de l'onde de choc est étudiée à travers des expériences spécifiques ainsi qu'une simulation numérique. La fissuration de l'interface est révélée par la présence d'une tache qui est mesurée par observation optique du dessus de la céramique. La reproductibilité de l'essai LASAT appliqué côté céramique est établie. Dans l'optique de valider un protocole de contrôle non destructif, le cyclage thermique est utilisé pour évaluer la nocivité d'une zone choquée présentant ou non des fissures. La présence de fissures à l'interface entre l'alumine et la zircone ne diminue pas la durée de vie à écaillage d'aubes de turbines lors du cyclage thermique. La tenue mécanique initiale de la céramique est comparée de manière qualitative et quantitative pour différents échantillons et qualitativement pour plusieurs aubes de turbine. L'évolution de la résistance interfaciale en fonction du cyclage thermique est étudiée. On démontre également sur plusieurs échantillons une corrélation entre l'adhérence initiale mesurée par LASAT et la durée de vie à écaillage par cyclage thermiqueThe assessment of the interface strength of EB-PVD thermal barrier coating (TBC) is a key issue to control the production and better understand the ceramic spallation that will occur during life duration of coated turbine blades. The Laser Shock Adhesion Test (LASAT) involving bi-dimensional shock wave propagation, namely the LASAT-2D, consists in measuring the interfacial crack diameter when implementing a set of laser shocks with increased laser power densities. Applying the LASAT onto an industrial blade requires implementing the laser shock onto the ceramic side. A protective vinylic adhesive tape and a confinement by transparent adhesive tape are used to generate the shock on the ceramic. Shock wave propagation is studied through specific experiments and a numerical simulation. The interfacial crack is revealed by the presence of a spot that could be measured on a top-view optical image of the ceramic. Reproductibility of the LASAT applied on the coated side of the TBC is thereby established. Harmfulness of a loaded area with and without cracks is investigated thanks to thermal cycling in order to validate a non-destructive protocol. The presence of cracks at the interface between alumina and zirconia does not reduce the life duration of coated turbine blades in thermal cycling. Initial adhesion strength is compared both qualitatively and quantitatively for different samples and qualitatively for some turbine blades. Evolution of the interface strength with thermal cycling is presented. A correlation between initial adhesion and time of spallation of the ceramic is demonstrated on different samples
48
Barutcu, Burcu. "The Design And Production Of Interference Edge Filters With Plasma Ion Assisted Deposition Technique For A Space Camera." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614574/index.pdf.
Full textAbstract:
Interference filters are multilayer thin film devices. They use interference effects between
the incident and reflected radiation waves at each layer interface to select wavelengths. The
production of interference filters depend on the precise deposition of thin material layers on
substrates which have suitable optical properties. In this thesis, the main target is to design
and produce two optical filters (short-pass filter and long-pass filter) for the CCDs that will
be used in the electronics of a space camera. By means of these filters, it is possible to take
image in different bands (RGB and NIR) by identical two CCDs. The filters will be fabricated
by plasma ion-assisted deposition technique.
49
Kianzad, Siamak. "Measurement of Thermal Insulation properties of TBC inside the Combustion chamber." Thesis, Luleå tekniska universitet, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-61917.
Full textAbstract:
This master thesis project was performed in collaboration with Scania CV AB, Engine Materials group. The purpose with the project was to investigate different ceramic TBC (Thermal Barrier Coating) thermal insulation properties inside the combustion chamber. Experimental testing was performed with a Single-Cylinder engine with TBC deposited on selected components. A dummy-valve was developed and manufactured specifically for this test in order to enable a water cooling system and to ease the testing procedure. The dummy-valve consists of a headlock, socket, valve poppet and valve shaft. Additionally, a copper ring is mounted between the cylinder head and the valve poppet to seal the system from combustion gases. Thermocouples attached to the modified valve poppet and valve shaft measured the temperature during engine test to calculate the heat flux. The TBCs consisted of three different materials: 7-8% yttrium-stabilized zirconia (8YSZ), gadolinium zirconia and lanthanum zirconia. The 8YSZ TBC was tested as standard, but also with microstructural modifications. Modifications such as pre-induced segmented cracks, nanostructured zones and sealed porosity were used. The results indicated that the heat flux of 8YSZ-standard, 8YSZ-nano and 8YSZ-segmented cracks was in level with the steel reference. In the case of 8YSZ-sealed porosity the heat flux was measured higher than the steel reference. Since 8YSZ-standard and 8YSZ-sealed porosity are deposited with the same powder it is believed that the high heat flux is caused by radiative heat transfer. The remaining samples have had some microstructural changes during engine testing. 8YSZ-nano had undergone sintering and its nanostructured zones became fewer and almost gone after engine testing leading to less heat barrier in the top coat of the TBC. However, for 8YSZ-segmented cracks and gadolinium zirconia lower heat flux was measured due to the appearance of horizontal cracks. These cracks are believed to act as internal barriers as they are orientated perpendicular to the heat flow. During long-time (5 hour) engine tests the 8YSZ-standard exhibited the same phenomena: a decrease in heat flux due to propagation of horizontal cracks. One-dimensional heat flux was not achieved and the main reason for that was caused by heating and cooling of the shafts outer surface. However, the dummy-valve system has proven to be a quick, easy and stable to perform tests with a Single-Cylinder engine. Both water-cooling and long-time engine tests were conducted with minor issues. The dummy-valve has been further developed for future tests. Changes to the valve shaft are the most remarkable: smaller diameter to reduce heat transfer and smaller pockets to ensure better thermocouple positioning. Another issue was gas leakage from the combustion chamber through the copper ring and valve poppet joint. The copper ring will be designed with a 1 mm thick track to improve sealing, hence better attachment to the valve poppet.
50
Myrillas, Konstantinos. "Experimental and numerical investigation of gas jet and liquid film interaction." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209848.
Full textAbstract:
The topic of this thesis is the interaction between gas jet flow and a liquid film dragged by a solid substrate. This method, known as jet-wiping, is used in several industrial processes. Hot-dip galvanization of steel strips is an important application, where jet wiping is used to control the thickness of the liquid zinc that is applied on a continuous steel substrate. Unsteady phenomena in the process lead to the creation of waves on the liquid film, which is known as undulation. This unwanted phenomenon deteriorates the quality of the final product.The aim of the current study is to identify the causes of the undulation and propose possible solutions to tackle the problem. This is achieved through studying the hydrodynamic interaction between the gas jet flow and the liquid film. Experiments on a laboratory test facility and numerical simulations with 3 different Computational Fluid Dynamics (CFD) codes are employed for that purpose.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished