Dissertations / Theses on the topic 'Gradient coatings'

The purpose of this study is to investigate the behaviour of functionally graded materials in the coating design through analytical and numerical work. Functionally graded materials are advanced composite materials formed from two or more constituents with a continuously varying composition, which results in a continuous variation of material properties from one surface of the material to the other. The concept of functionally graded material is actively explored in coating design where structural and/or functional failures of the coating can happen due to a mismatch between the material properties of the coating and substrate, particularly at the coating/substrate interface. This work focuses on the performance of coated plates with homogeneous and graded coatings under various types of loading to develop a better understanding of their response. Firstly, the three dimensional elasticity solution for an isotropic coated plate with a stiffness gradient in the coating is extended to cover different types of applied loading and then a three dimensional elasticity solution for transversely isotropic materials with gradients in elastic properties is also developed. Based on the extended/developed solutions, a MATLAB code is created to produce a model that would enable the analysis of coated plates for a range of material, geometric and loading parameters. To test the analytical models, a finite element analysis is performed using the commercial finite element software ABAQUS, in which a user material subroutine is employed to generate a gradient in the material properties within each element and increase the accuracy of the results. All the developed analytical and numerical models are then used to carry out a comparative study of three-dimensional stress and displacement fields in the coated plates with homogeneous and graded coatings and establish the effect of various parameters such as coating thickness, coating position, plate dimensions, stiffness gradient, loading distributions and anisotropy on the coated plate response.

Thermal barrier coatings have been widely used to provide thermal protection to components in the hot section of gas turbines. This research focuses on two influencing factors on coating behavior: thermal gradient and cyclic oxidation. The delamination mechanics under thermal gradient is analyzed, taking thermally grown oxide into consideration. Coatings experience thermal gradients at different stages during actual service flight. One is due to engine power shut down when landing and the other due to internal cooling of the substrate. Thermally grown oxide (TGO) also acts as a critical factor in delamination mechanics. The induced stress gradient and corresponding energy release rate for interface delamination and shallower delamination are presented. Mechanism maps that explain the criteria for preventing delamination from developing and propagating are established. Three cooling trajectories are envisaged to analyze the variation in the possibility of delamination. Multilayer coatings used in components of the hot section of aero turbine engines also experience cyclic temperature variation during flight cycles. As experiment conditions vary and coating performance is improved, the time required to run through the test of coating failure can be both time-consuming and prohibitive. Therefore, protocols providing prediction of quantified coating behavior are in demand to shorten life-time tests. Curves of mass change are obtained from quantifying scale growth and loss by different models such as Cyclic Oxidation Spall Program (COSP). A modification is made by combining COSP and a mechanic based model to obtain critical parameters for lifetime prediction from short time experiment. The time for coatings to reach peak temperature during cycling is discovered to influence prominently on modeling results. Predictions for several coating compositions and cycling conditions are consistent with the data from the existing experiments of the coating system.

Дисертацію присвячено розробленню градієнтних композиційних електролітичних покриттів зміцнених макро- та наночастинками з керованими триботехнічними властивостями. Проведено аналітичні дослідження напружено-деформованого стану одно- та багатошарових градієнтних КЕП, навантажених силами тертя. Експериментально встановлено оптимальні щодо зносостійкості будову та режими нанесення КЕП Ni-SiC. Визначено вплив кількості та розміру частинок наповнювача на триботехнічні властивості покриттів. Проведенням експериментальних досліджень впливу градієнта будови КЕП на триботехнічні властивості встановлено, що більш високою зносостійкістю характеризуються градієнтні КЕП з “прямим” градієнтом будови, що узгоджується з теоретичними розрахунками напружено-деформованого стану. Дослідженнями встановлено, що із введенням одночасно макро- та наночастинок в КЕП значно підвищується зносостійкість таких покриттів. Показано, що оплавленням покриттів Ni-SiC, які містять додатково бор, можна значно підвищити їх фізико-механічні властивості та зносостійкість. При цьому для оплавлення більш ефективним є застосування лазера, а створення дискретно-оплавлених покриттів дозволяє отримати значно вищі триботехнічні властивості порівняно з повністю оплавленими покриттями.<br>Thesis is aim at development of gradient composition electrolytic coatings hardened by macro- and nanoparticles with the guided tribotechnical properties. Analytical researches of the tensely deformed state of single- and multi-layered gradient CEC loaded with forces of friction are conducted. The opti-mum structure and parameters process of CEC Ni-SiC are experimentally established in relation to wear-proofness. Influencing of amount and size of particles of stuff on tribotechnical property of coatings is determined. Experimental researches of influencing of gradient of structure of CEC are conducted on tri-botechnical property. It is established that the higher wearproofness is characterize gradient CEC with the “direct” gradient of structure, that conforms to the theoretical calculations of the tensely deformed state. Researches is established, introduction simultaneously of macro- and nanoparticles into CEC raise wear-proof of such coatings. It is established, meltback of coatings Ni-SiC, which contain the boron additional-ly, it is possible considerably to raise their physical-mechanical properties and wearproofness. Thus for meltback more effective is application of laser, and the creation of discretely meltback coatings allows to get considerably higher tribotechnical properties comparatively with fully meltback coatings

Гуменюк І.А. Триботехнічні властивості сталі 12Х18Н10Т, поверхнево модифікованої комбінованими покриттями. – На правах рукопису. Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю: 05.02.04 – тертя та зношування в машинах (13 – Механічна інженерія). Національний авіаційний університет, МОН України, Київ, 2018. Дисертаційна робота присвячена вирішенню актуального науково-технічного завдання підвищення зносостійкості поверхневих шарів корозійностійкої сталі 12Х18Н10Т шляхом формування зносостійких комбінованих дифузійних, електроіскрових та композиційних електролітичних покриттів дискретного і градієнтного типу та встановлення закономірностей впливу їх структурно-фазового складу, фізико-механічних властивостей і параметрів структури на триботехнічні характеристики. Дослідженні закономірності формування та механізми зношування багатокомпонентного хромоалітованого покриття в умовах тертя ковзання без змащення в залежності від хімічного і структурно-фазового складу. Представлено та описано результати експериментальних досліджень технологічного процесу азотування попередньо обробленої дискретно лазером сталі 12Х18Н10Т. Встановлено закономірності зношування від параметрів дискретної структури. Досліджено закономірності формування високотемпературним відпалом триботехнічних властивостей електроіскрових і композиційних електролітичних покриттів з евтектичним наповнювачем від ступеня нерівноважності структурно-фазових станів. Теоретично обґрунтовано та експериментально підтверджено вплив дифузійної перехідної зони між твердим наповнювачем і м’якою матрицею на напружено-деформований стан та зносостійкість композиційних електролітичних покриттів. На основі енергетичної моделі трибопроцесу виконано аналітичне дослідження умов утворення частинок зносу в процесі фрикційного руйнування приповерхневих шарів композиційного покриття. Застосовуючи енергетичний підхід до оцінювання зносостійкості поверхневих шарів за умов їх руйнування при терті розроблено технологічний процес формування на сталі 12Х18Н10Т градієнтного покриття з високою припрацьовуваністю і зносостійкістю. Проведено статистичний аналіз та побудовано регресійні моделі залежностей критеріїв оптимізації.<br>Gumenyuk I.A. Tribotechnical properties of steel 12C-18Cr-10Ni-Тi, surface-modified by combined coatings. – Manuscript. Thesis intended for getting scientific degree of Candidate of technical science by specialty: 05.02.04 – Friction and wear in machines (131 – Mechanical Engineering). National Aviation University, Ministry of Education and Science of Ukraine, Kyiv, 2018. The thesis is devoted to solving the actual scientific and technical task of increasing the wear resistance of surface layers of corrosion–resistant steel 12C-18Cr-10Ni-Тi by forming wear resistant combined diffusion, electrospray and composite electrolytic coatings of discrete and gradient type and establishing regularities of influence of their structural-phase composition, physical and mechanical properties and structural parameters on tribotechnical behavior. Investigation of regularities of formation and mechanisms of wear of multi-component chromoalluminized coating in conditions of dry sliding friction, depending on the chemical and structural-phase composition have been done. The results of experimental examinations of technological process of nitriding of selectively laser pre-treated steel 12C-18Cr-10Ni-Тi are presented and described. The regularities of wear on parameters of a discrete structure have been established. The regularities of formation of tribotechnical properties of electrospray and composite electrolytic coatings with eutectic filler by high-temperature annealing on the degree of nonequilibrim of structural-phase states were studied. The influence of the diffusion transition zone between the solid filler and the soft matrix on the stress-strain state and the wear resistance of composite electrolytic coatings was theoretically proved and experimentally confirmed. Based on the energy model of triboprocess, an analytical study of conditions for the formation of wear particles in the process of frictional destruction of near-surface layers of composite coating was carried out. Using the energy approach to evaluation of wear-resistance of surface layers in conditions of their fracture at friction, a technological process of forming gradient coating on the surface of 12C-18Cr-10Ni-Тi steel with high workability and wear resistance was developed. A statistical analysis was carried out. Regression models of dependencies of optimization criteria were constructed.

This thesis describes the design, manufacture and characterisation of thick vacuum plasma sprayed tungsten (W) coatings on steel substrates. Fusion is a potentially clean, sustainable, energy source in which nuclear energy is generated via the release of internal energy from nuclei. In order to fuse nuclei the Coulomb barrier must be breached - requiring extreme temperatures or pressures – akin to creating a ‘star in a box’. Tungsten is a promising candidate material for future fusion reactors due to a high sputtering threshold and melting temperature. However, the large coefficient of thermal expansion mismatch with reactor structural steels such as the low activation steel Eurofer’97 is a major manufacturing and in-service problem. A vacuum plasma spraying approach for the manufacture of tungsten and tungsten/steel graded coatings has been developed successfully. The use of graded coatings and highly textured 3D interface surfi-sculpt substrates has been investigated to allow the deposition of thick plasma sprayed tungsten coatings on steel substrates. Finite element models have been developed to understand the residual stresses that develop in W/steel systems and made use of experimental measurements of coating thermal history during manufacture and elastic moduli measured by nano-indentation. For both the graded and surfi-sculpt coating, the models have been used to understand the mechanism of residual stress redistribution and relief in comparison with simple W on steel coatings, particularly by consideration of stored strain energy. In the case of surfi-sculpt W coatings, the patterned substrate gave rise to regular stress concentrating features, and allowed 2mm thick W coatings to be produced reproducibly without delamination. Preliminary through thickness residual stress measurements were compared to model predictions and provided tentative evidence of significant W coating stress relief by regulated coating segmentation.

L’introduction des composites à matrice céramique (CMC) dans les turbines haute pression est un des enjeux de la prochaine génération des moteurs d’avion civil. L’environnement thermomécanique et physico-chimique extrême dans lequel évoluent ces pièces nécessite l’ajout d’un revêtement jouant le rôle de barrière thermique et environnementale, en particulier pour éviter les phénomènes de récession de surface du SiC. Dans ce contexte, cette étude a consisté à caractériser et modéliser le comportement thermomécanique du système CMC-revêtement dans un environnement thermique représentatif des conditions d’utilisation afin d’identifier les mécanismes d’endommagement pouvant impacter la durée de vie du système. La première partie du travail propose la mise en place d’un essai avec un laser permettant l’utilisation de différentes instrumentations, à très hautes températures (&gt;1300°C), basées sur des mesures de champs par thermographie infrarouge et corrélation d’images numériques et/ou la détection d’endommagement. La seconde partie du travail présente l’étude du faïençage thermique d’un revêtement grâce aux observations expérimentales et à un modèle par éléments finis du système, alimentée par l’identification du comportement thermomécanique non linéaire du revêtement<br>The introduction of ceramic matrix composites (CMCs) in high pressure turbines is one of the challenges of the next generation of civil aircraft engines. The extreme thermomechanical and physicochemical environment in which these parts evolve requires the addition of a coating acting as a thermal and environmental barrier, in particular to avoid surface recession phenomena of SiC. In this context, this study consisted in characterizing and modeling the thermomechanical behavior of the CMC-coating system in a thermal environment representative of the conditions of use in order to identify the mechanisms of damage that could impact the life of the system. The first part of the work proposes the implementation of a test with a laser allowing for the use of different diagnostics, at very high temperatures (&gt; 1300°C), based on full-field measurements by infrared thermography and digital image correlation, and / or the detection of damage. The second part of the work presents the study of thermal cracking of a coating using experimental observations and a finite element model of the system, using the calibration of the nonlinear thermomechanical behavior of the coating

Lors de la polymérisation en suspension du chlorure de vinyle, il se forme sur les parois un dépôt de polychlorure de vinyle (PVC). Ce phénomène, nommé encroûtement, génère des problèmes car il limite la production de PVC et affecte la qualité du produit final. Dans ce contexte, un projet FUI (Fond Unique Interministériel) intitulé «Ecoating», a été financé dans le cadre d’une collaboration entre plusieurs partenaires industriels et universitaires (INEOS ChlorVinyls, Mäder Research, Avenir Group, LPIM, ESPCI-ParisTech). Deux thèses ont vu le jour au LPIM, avec pour but de développer un revêtement (photo)polymère aux propriétés anti-encroûtement durables qui permettrait d’améliorer la qualité du PVC produit, d’augmenter les quantités produites et ainsi d’améliorer la compétitivité des usines de PVC. Cette thèse s’inscrit dans le développement d’un vernis photopolymère répondant au cahier des charges. Pour éviter l’encroûtement des réacteurs, il est nécessaire de stopper une étape du mécanisme d’encroûtement comme l'adsorption sur les parois du réacteur d’un copolymère nommé Acvagen Graft Copolymer (AGC). Ce copolymère est très actif dans le phénomène d’encroûtement (site de nucléation) et se trouve principalement dans la phase aqueuse du milieu réactionnel. La stratégie de recherche élaborée dans ce projet a été basée sur le développement d'un revêtement photopolymère présentant une faible affinité pour l'eau et devant adhérer à la surface des réacteurs pour éviter la formation de croûte. Les polymères à base de fluoroacrylates ont été les premiers candidats choisis dans cette étude du fait que leurs propriétés exceptionnelles (faible énergie de surface, stabilité chimique et haute hydrophobicité...) pouvaient éviter l'adsorption de l'AGC sur les parois du réacteur, et par conséquent le développement de la croûte. Une recherche bibliographique a été réalisée pour comprendre le comportement particulier de ces molécules qui migrent vers la surface du film et s’organisent en surface pour donner des surfaces hydrophobes. Des mélanges de résines fluoroacryliques modèles ont été testés pour évaluer le caractère hydrophobe du revêtement, comprendre la migration des molécules de fluor vers l’interface en fonction de la nature de substrat et aussi déterminer l’influence de l’ajout d’additifs fluorés au mélange sur les propriétés globales du film. Cette étude nous a permis de comprendre l’influence de l’additif fluoré sur les propriétés chimiques et physiques du film. À l’échelle du laboratoire des tests d’immersion de ces revêtements déposés sur l’acier inoxydable ont étés réalisés dans l’eau chaude (80°C) afin de caractériser leur caractère hydrophobe en fonction du vieillissement dans l’eau chaude ainsi que l’adhésion du film au substrat. Nous avons observé une diminution de l'hydrophobicité de la surface du film au cours du temps lors d’une immersion. [...]<br>Our scientific approach has explored different strategies to develop a durable UV-cured coating with antifouling properties to prevent the crust formation. Firstly, the potential of fluoroacrylate photocurable coatings was exhaustively investigated. Indeed, their outstanding properties (low surface energy, chemical stability and high hydrophobicity...) could limit the adsorption of the AGC on the reactor walls and further encrusting. A bibliographic research highlighted the behavior of fluorinated monomers on film surface and the parameters affecting the hydrophobic properties. Different fluorinated monomers were selected. At low concentration, they provide hydrophobic surfaces on 316L stainless steel, the reference substrate. However, a decrease of the films surface hydrophobicity in hot water was observed with time, and was attributed to a disorganization of the fluorinated chains on the coating surface. An optimization of the amount of fluoroacrylate monomer was performed by confocal Raman microscopy (CRM) to promote the fluorinated chains stability on the surface before and after immersion in hot water at 80°C. The beneficial effect was found maximal at a concentration ranging from 1 to 1.8 wt%. However, even after this optimization, a decrease of the film surface hydrophobicity was observed for increased immersion time in hot water. Therefore, optimized fluoroacrylate monomer concentration was combined with alternated thermal/immersion post-treatment and has conducted to more stable photocured films. This result was attributed to a rigidification of the fluorinated chains on the film surface limiting thus, the extent of their disorganization. After this study realized at a laboratory scale, we tested the photocured coating in the VCM pilot reactor. A surface cleaning, an increase of the stainless steel roughness by shot blasting and the use of alkoxysilanes as coupling agents were implemented in order to enhance the adhesion properties of the photopolymer film on stainless steel. In addition, the use of a fluorinated monomer containing a heteroatom improved the rigidification when associated with the alternated thermal/immersion post-treatment. The crust formation was limited during four successive polymerizations in the VCM pilot reactor. A durable anti-fouling UV-coating could be not obtained due to some swelling phenomena resulting from the lack of coating adhesion or some abrasion occurring from small PVC pellets during the PVC polymerization.A second part of this project was dedicated to superhydrophobic coatings. Indeed, reducing interaction with water should lead to a better protection of the substrate. A literature review on the superhydrophobic surfaces has shown that the contact with hot water generally strongly affects their antiwetting properties and induces a large contact angle decrease. [...]

Dans l'industrie du forage pétrolier, les conditions de travail de plus en plus sévères requièrent sans cesse de nouveaux outils plus résistants à l'usure abrasive et à l'impact. Afin de répondre à ce défi, les travaux présentés ici, ont pour but l'élaboration de matériaux en carbure cémenté à gradient de composition par le procédé d'imbibition réactive. Ce procédé peut être décomposé en deux procédés de gradation, à savoir : l'imbibition et le revêtement réactif. L'imbibition a pour rôle d'enrichir graduellement, en phase liante, le coeur d'une pièce en carbure cémenté dense et repose sur le principe de migration de phase liquide dans un corps solide-liquide. Le revêtement réactif est un procédé qui s'applique également sur un carbure cémenté dense sur lequel est déposé un revêtement de nitrure de bore. Après avoir atteint le liquidus de la phase liante du carbure cémenté, une précipitation de borures ternaires prend place à la surface du matériau et s'étend graduellement sur des distances millimétriques. Dans le cas de pièces industrielles (inserts tricône et supports de taillants PDC (Polycrystalline Diamond Compact)), le traitement d'imbibition réactive permet de générer des gradients de dureté pouvant atteindre 450 HV sur 25 mm. L'élaboration de tels gradients a nécessité une meilleure compréhension des cinétiques ainsi que des phénomènes mis en jeu durant l'imbibition et le revêtement réactif. Dans le cas des taillants PDC, l'influence des paramètres du procédé HPHT de synthèse de la plaquette diamantée, sur le gradient de composition présent dans le support WC-Co après imbibition réactive, a été étudiée. Ces travaux se sont également intéressés à l'effet de ces gradients de composition sur les propriétés des plaquettes diamantées ainsi obtenues. A la suite d'essais mécaniques, les inserts WC-Co et taillants PDC gradués montrent une augmentation significative de leur résistance à l'abrasion (de 30 à 100%) et de leur tenue à l'impact (de 20 à 40%)<br>In oil drilling industry, harsher working conditions require ever new and more abrasive wear and impact resistant tools. To meet this challenge, the work presented here, is to develop graded cemented carbide materials by reactive imbibition process. This method can be divided into two gradation processes, namely, reactive coating and imbibition. Imbibition gradually enriches the core of dense cemented carbide with binder phase and is based on the principle of liquid phase migration in a solid-liquid body. Reactive coating also takes place in dense cemented carbide on which a boron nitride coating is deposited. After reaction with the WC-Co liquid binder, some ternary boride precipitations take place from surface to several millimeters deep. For industrial parts (inserts for roller cone bits and PDC (Polycrystalline Diamond Compact) cutters substrates), hardness gradients obtained can reach 450 HV on 25 mm. Such gradients development is passed through a better understanding of kinetics and phenomena occurring during imbibition and reactive coating. In case of PDC cutters, influence of HPHT process parameters, allowing diamond table synthesis, on the WC-Co substrate gradient, generated by reactive imbibition, was studied. This work was also interested in gradient effect on the obtained diamond tables properties. After mechanical tests, graded WC-Co inserts and graded PDC cutters show a significant increase of both wear resistance (from 30 to 100%) and impact resistance (from 20 to 40%)

Les traitements antireflets (AR) sont très largement utilisés pour améliorer la transmission de systèmes optiques composés de hublots, lentilles, de lames séparatrices,… Dans cette thèse les gammes spectrales visées sont le visible étendu [400-1800nm] et le moyen infrarouge [3,7-4,8µm]. La méthode de nanostructuration par dépôts de films minces utilisant des techniques PVD en incidence oblique (Oblique Angle Deposition) a été choisie car elle permet d’envisager des AR hautes performances sur une large gamme de longueur d’onde, via un procédé industrialisable. L’introduction de porosité via le contrôle des angles de dépôt est utilisée pour nanostructurer l’architecture de chaque couche et de l’empilement ; méthode permettant de modifier et d’optimiser les propriétés optiques des couches constituantes en vue d’un design complet optimal. Une cartographie des indices effectifs accessibles par OAD a été dégagée concernant les trois matériaux déposés (TiO2, SiO2 et Ge). Mais les propriétés optiques de ces couches nanostructurées diffèrent largement de celles des couches denses du fait de la présence d’anisotropie, de gradient d’indice, de diffusion et d’absorption. A partir de caractérisations microstructurales, chimiques et optiques poussées (AFM, MEB, MET, tomographie FIB, tomographie MET, EDX, EELS, spectrophotométrie et ellipsométrie généralisée) un modèle optique analytique plus complexe et couplé à des analyses par éléments finis (FDTD) est présenté. L’ensemble du travail a permis d’élaborer par OAD de simples antireflet bicouches démontrant déjà de hauts niveaux de transmission, supérieurs aux traitements AR existants (interférentiel) ou en développement (Moth-eyes)<br>Anti-reflective (AR) coatings are widely used to improve the transmission of optical systems composed of window, lenses, separating filters,... In this thesis, the spectral ranges targeted are the extended visible [400-1800nm] and the mid infrared [3.7-4.8µm]. Thin film deposition nanostructuring method using oblique angle deposition (oblique angle deposition) PVD technique was chosen because it allows high performance AR to be considered over a wide wavelength range, by an industrial process. The introduction of porosity with the control of deposition angle is used to nanostructure the architecture of each layer and stack; a method for modifying and optimizing the optical properties of the constituent layers for optimal complete design. A mapping of the effective indices accessible by OAD has been identified for the three materials deposited (TiO2, SiO2 and Ge). However optical properties of these nanostructured layers differ greatly from those of dense layers due to the presence of anisotropy, index gradient, diffusion and absorption. Based on advanced microstructural, chemical and optical characterizations (AFM, SEM, TEM, FIB tomography, TEM tomography, EDX, EELS, spectrophotometry and generalized ellipsometry) a more complex analytical optical model coupled with finite element analyses (FDTD) is presented. All the work has enabled OAD to develop simple two-layer anti-reflective coatings that already demonstrate high levels of transmission, superior to existing (interferential) or work in progress (Moth-eyes) AR treatments

碩士<br>中山醫學大學<br>口腔材料科學研究所<br>95<br>Hydroxyapatite coating have been used as load-bearing implant applications. The aim of this work is to deposit functionally graded HA/Ti layers using plasma spray to improve the coating-substrate interface properties. In addition to the Ti bondcoat and the top HA biolayer, the alternating layers were created by means of changing the feeding rate and input powder of Ti and HA. The stability of the graded coatings such as corrosion resistance and fatigue, and bonding strength of the potential graded coatings without and with post-deposition heat treatment were examined. Results showed that surface chemistry and morphology of the graded coatings were similar to those of monolithic HA coatings. The bonding strength values of the as-sprayed graded coating were much superior to those of monolithic HA coatings. The cyclic fatigue did have a statistically significant effect on bond strength of monolithic HA coatings, with a decrease of 23%. However, the graded coatings were able to survive 1 million cycles of loading in air without significantly reduced bond strength. The in vitro electrochemical measurement results also indicated that the graded coatings had a more beneficial and desired behavior than monolithic HA coatings after fatigue. An appropriate heat treatment resulted in recrystallization of amorphous calcium phosphate of as-sprayed coatings. The enhancement of the resistance to corrosion took place after heat treatment. Consequently, we concluded that the heat treatment at 600℃, endowing with increased crystallinity and the reduced defects as well as enhanced bond strength, may be a suitable post-deposition treatment method to promote the characteristics of graded HA/Ti coatings.

碩士<br>逢甲大學<br>材料與製造工程所<br>95<br>In order to show that fatigue property of anisotropic microstructure of flat coatings, we deposited functionally graded materials coatings and traditional double layers materials coatings by using atmosphere plasma spray technigue to analysis cohesive property. In oreder to study effect of cohesive property, we define that the direction parallel with the direction of spray gun as out-of-plane coatings and the direction perpendicular to the direction of spray gun as in-plane coatings. We used traditional double layers materials coatings that including NiCrAlY materials and CoCrAlY materials and used functionally graded materials coatings to do tensile strength test and shear strength test and high cycle fatigue test. We also used nonlinear regression method to find the parameter of curves and to understand the cohesive property of microstructure of the out-of-plane coatings and in-plane coatings. Results of high cycle fatigue test show that specimens can tolerate durable property under circulate stress condition. We used nonlinear regression method to analysize data of fatigue test. The results show that the fatigue strength of out-of-plane coatings and in-plane coatings of NiCrAlY and CoCrAlY of traditional double layers materials coatings are all better than functionally graded materials coatings. This study shows that process parameters of APS interact each other and bonding strength between coatings and substrates and cohesive strength of coatings are affected by sprayed process and sprayed particle size and microcrack etc. The curves that we got by nonlinear regression method can use to be the base to predict the relation of melt coatings and life time of fatigue.

碩士<br>逢甲大學<br>材料與製造工程所<br>95<br>As far as application of Atmosphere Plasma Spray (APS) method is concerned, insulation coating on the surface of components is widely used to enhance heat-resistance in high-temperature condition. Nevertheless, thermal fatigue failure often occurs when coating materials undergo a rapid change in temperature. In this proposed study an advanced APS is used to fabricate functionally gradient materials as thermal barrier coatings. Performance of conventional plasma-coating and functionally gradient coating fabricated by APS is compared. In conventional plasma coating, ZrO2/MgO is coated as thermal barrier coatings (TBCs) with MCrAlY (wherein M is Ni, Co or Fe or composite alloy of the three elements) as insertion between substrate and TBCs. Basically conventional coating method uses same materials with advanced but being developed in a different way, the former refers to a method of coating an insertion on a substrate then ceramics layer is coated on, while the latter is to graduated adjust/change the structure and components to produce a ceramics coating layer on insertion. After coating layer being produced, porosity, tensile strength and icro-hardness are measured, and thermal fatigue tests were conducted to compare performance of coatings formed by conventional plasma-coating method and the advanced functionally gradient materials (FGM) approach. The experimental results suggest that FGM better enhances thermal fatigue resistance by showing less cracks on specimens than that by conventional plasma coating. Moreover at 900oC in air, Ni–base functionally gradient thermal barrier coatings demonstrate better thermal fatigue performance than Co-base’s.

碩士<br>國立臺北科技大學<br>光電技術研究所<br>90<br>A new multi-layer bottom anti-reflection coating (BARC) applied to an ArF exposure system with high numerical aperture and modified illumination is proposed and studied. Such a multi-layer BARC has a larger thickness tolerance for different numerical aperture and highly reflective substrates. Besides, it has larger depth of focus (DOF) than single-layer one during exposure. In order to simplify the complication in fabrication of a multi-layer BARC, a new gradient absorption BARC structure that has the advantages of multi-layer BARC is studied. The new BARC films are composed of silicon nitride or silicon oxynitride films, both of which are treated by oxygen plasma to form a gradient absorption optical film. By using the effective medium theory and the results of material analysis, a gradient absorption BARC structure is demonstrated experimentally. Simulation results show that the gradient absorption BARC is capable of providing larger tolerances for thickness than a single layer BARC at different numerical aperture. Additionally, swing effects in the resist and alkaline outgassing from substrate are significantly reduced. Experimental results indicate that the resists have an ideal profile without T-top or footing after development. We experimentally analyzed optical stability, etching rate, surface roughness and other such characteristics of the BARC films with and without plasma treatment. This study shows that the plasma treatment process have great potential for BARC application in both ArF (193 nm wavelength) and F2 (157 nm wavelength) lithography.

碩士<br>國立虎尾科技大學<br>機械與電腦輔助工程系碩士班<br>102<br>Titanium and titanium alloys have been used as artificial joints and implants in clinic of orthopedic and dental because of their good properties of biocompatibility and mechanical performance. Recently, surface modification technology has been adopted to improve adhesion and proliferation of cells on implant surface, and a number of studies have confirmed amorphous carbon films can improve biocompatibilities and mechanical properties of titanium. In this study, pure titanium and zirconium targets were used to deposit TiZrN、TiZrCN、TiZr-amorphous Carbon coatings with different chemical contents on titanium substrates using a cathodic arc evaporation system. Staphylococcus aureus (S. a)、Actinobacillus actinomycetemocomitans (A.a ) antibacterial analyses and human skin fibroblast(SKF) biocompatibility of the deposited coatings were conducted. Characterize the composition of coatings was measured by energy dispersive spectrometer(EDS). The crystalline structures and bonding states of coatings were analyzed by X-ray diffraction(XRD), X-ray photoelectron spectroscope(XPS), field emission scanning electron microscope,(FE-SEM),transmission electron microscope(TEM). A surface profilometer was used to measure the surface roughness of the coatings. Potential resistance tests were used to measure the corrosion resistance. In vitro MTT analyses were used for cell activity identification. SKF cell adhesion morphology was also observed by FE-SEM. The results show that the deposited TiZrCN coatings are hydrophilic because of lower contact angles. These TiZrCN coated Ti samples have the best antibacterial performance and SKF compatibility, and they are suitable for biomedical applications.

Dissertação de Mestrado Conjunto Europeu em Tribologia de Superficies e Interfaces apresentada à Faculdade de Ciências e Tecnologia<br>As restrições crescentes na utilização de materiais perniciosos para o meio ambiente tem obrigado as empresas a procurar soluções alternativas aos lubrificantes convencionais. Os revestimentos finos à base de dicalcogenetos de metais de transição (TMD) têm mostrado atributos que lhes permitem ser eficientes como lubrificantes sólidos. A maior desvantagem destes materiais, a sua baixa dureza, pode ser melhorada através da adição de carbono. O revestimento a ser estudado neste trabalho é um W-S-C, um revestimento à base de TMD, que tem um desempenho adequado quando o teor de C é de aproximadamente 50% at. O objetivo deste estudo foi investigar o desempenho tribológico de três tipos diferentes de revestimentos W-S-C, nomeadamente, um W-S-C referência com 50 %at. de C, um W-S-C com teor de C mais reduzido (35 % at.) e um W-S-C com uma estrutura em gradiente. Nesta caso o revestimento tinha uma camada de W-S-C rica em carbono junto ao substrato, reduzindo o teor deste elemento à medida que se aproxima da superfície, terminando com uma camada no topo de WS2 simples. Os revestimentos foram caraterizados no que concerne a sua composição química por espectroscopia por dispersão de comprimentos de onda (WDS), a sua morfologia por microscopia eletrónica de varrimento (SEM), a sua estrutura por espectroscopia Raman e difração de raios-X (XRD), as propriedades mecânicas por nanoindentação e a adesão por indentação deslizante. O desempenho tribológico foi avaliado num tribómetro do tipo bola em disco em movimento alternativo em atmosfera normal, em meio de N2 seco à temperatura ambiente e a temperatura elevada de 200 ºC. Os resultados permitiram concluir que cada um dos revestimentos apresentava um comportamento auto-adaptativo em todas as condições de operação, embora para cada condição, um dos revestimentos comportava-se melhor que os outros. Este estudo mostrou uma perspetiva de melhoria do comportamento tribológico de revestimentos W-S-C em diversos meios de teste através da alteração da composição química e da estrutura.<br>The increasing restriction on the use of environmentally harmful materials pushes industrial needs to shift away from conventional lubricants. Thin film coatings based on transition metal dichalcogenides (TMD) have shown promising attributes to be an effective solid lubricant. The inherent weakness of TMD, its low hardness, can be improved by alloying it with carbon. The coating to be studied in this work is W-S-C, a TMD-based coating which is thought to perform best when it has ~50 at.% of carbon content.The aim of the present study was to investigate the tribological performance of three types of W-S-C coating, namely, a reference W-S-C coating with ~50 at.% carbon, a W-S-C with reduced carbon content at ~35 at.%, and a W-S-C coating with a graded structure. The coating with graded structure had carbon-rich W-S-C on the bottom layers with gradually reducing carbon content on the upper layers and finished with pure WS2 on the top layer. Characterization of the coatings was performed by wavelength-dispersive spectroscopy (WDS) for chemical composition, scanning electron microscopy (SEM) for morphology, Raman spectroscopy and X-ray diffraction (XRD) for crystallinity, nanoindentation for mechanical properties determination, and a scratch test for coating adhesion investigation.The tribological performance was tested by reciprocating ball-on-disk tribometer under ambient air at room temperature, under dry N2 environment at room temperature and under elevated temperature of 200°C. It was found that each coating showed self-adaptive behavior under every operating condition, though for each condition, there was one coating that performed particularly well. This study showed the prospect of improving the tribological performance of W-S-C coatings in a variety of environments through the alteration of the composition and structure.

博士<br>國立清華大學<br>工程與系統科學系<br>105<br>For polycrystalline films, X-Ray diffraction (XRD) is the most common nondestructive technique for measuring residual stress because of its excellent phase selective capability and precise interplanar distance determination. However, the measurement of accurate stress and stress gradient on thin films is challenging and critical mainly due to confined thickness and unique microstructure. In this study, we proposed an average X-ray strain (AXS) method by using cos2sin2 XRD technique at several rotational () angles to improve the accuracy of the measurement of X-ray stress (XRS) or X-ray elastic constants (XECs). The major concept was to increase sampling volume by measuring X-ray strain at multiple rotational angles. In addition, by adjusting the grazing incident angle of X-ray the variation of stress with thickness could be measured. Since the resultant stress was an integrated magnitude from the surface to the penetration depth, a layer-by-layer method was adopted to resolve the real layer stress at different penetration depth. TiN hard coating on Si (100) substrate was selected as the model system, where the residual stress was determined by laser curvature, sin2, cos2sin2 and high energy XRD methods, from which the influence of sampling volume was revealed and the corresponding statistical meanings of each method were discussed. When sufficient sampling volume was obtained, the accuracy of AXS method could be reduced to 3% comparing to macrostress acquired from laser curvature method. The thickness limitation of AXS methods was about 350 nm by comparing the XRS and XECs to other techniques and literature data. For ultra-thin film less than 160 nm, a new multiple (hkl) diffraction AXS method was developed. With the correct XRS’s measured at different penetration depths, the stress gradients on TiN coatings with thickness 1.5, 2.7 and 3.9 μm were successfully acquired and the results were correlated to the film structure and fracture morphology in our previous study.

碩士<br>逢甲大學<br>材料科學所<br>99<br>The demands for lightening, slimness and miniaturization of current portable electronic appliances lead extensive usage of lightweight polymeric materials. These portable appliances, especially its touch panel, frequently contacted with human hands easily get fingerprint stains and scratches over the surface, which usually causes visual interference and inconvenience to the handler. Although polymer materials are highly formable, flexible and highly transparent, its insufficient mechanical strength for wear resistance and thermal durability limits their durability and compatibility for processing. To reform above disadvantages, surface modification for improving protectiveness and anti-fingerprint has become an essential in current electronic industry. Unfortunately, the commonly used low surface energy fluorine-carbon-based anti-fingerprint materials exhibit poor mechanical strength. On the contrary, mechanically durable materials usually do not acquire enough low surface energy for satisfactory anti-fingerprint performance. Accordingly, a compositional gradient coating, which combines siloxane-based material as the bottom mechanical support layer and low surface energy fluorine-carbon-based material as the top layer for anti-fingerprint purpose, via a single batch plasma-polymerization process is proposed in this study. In part 1, the tetramethylsiloxane (TMDSO) was used as precursor to plasma-polymerize the mechanical support pp-TMDSO layer on polycarbonate (PC) substrate. RF discharge power was manipulated to obtain a film with optimized mechanical property. Si-OH, Si-O-Si and Si-CH3 function groups were detected in the pp-TMDSO films, where the fraction of Si-OH and Si-O-Si decreases but Si-CH3 increases with increasing discharge power. Ultimately, the film synthesized at higher discharge power (50W) presents the highest pencil hardness and film adhesion of 3H and 5B, respectively with its water and oil contact angle approximately 105° and 20°, respectively. In part 2, tetrafluoromethane (CF4) with different gas flow ratio (CF4/(Ar+TMDSO+CF4)) was added during plasma polymerization of TMDSO to study the influences of fluorine dosage on the hydrophobicity and oleophobicity of plasma-polymerized fluorine-doped TMDSO (pp-F:TMDSO). A low RF discharge power level was used to avoid fluorine ion etching on the grown film. The results show that the obtained pp-F:TMDSO films are still mainly composed of Si-OH, Si-O-Si and Si-CH3 functional groups. The fluorine content in the coatings increases with the flow ratio of CF4 to a maximum of 11.2 at. %. At the same time the Si-(R)4 and (R)2-Si-O2 fraction decreases, while the fraction of (R)1-Si-O3 and Si-O4 increases. Fluorine doping does not affect the water contact angle, which remains at 100°; but increases the oil contact angle to 30°. The drawbacks of fluorine doping are the significant decrease in film hardness and film adhesion to F and 0B, respectively. By combining the optimized conditions for obtaining pp-TMDSO and pp-F:TMDSO, a sequential deposition was carried out in part 3, where modulated RF discharge power and gradient CF4 flow rate were proceeded to create a pp-TMDSO bottom hard layer and compositional gradient pp-F:TMDSO top anti-fingerprint layer. Results show that the gradient pp-F:TMDSO film exhibits water and oil contact angles of 105° and 31.7°, a pencil hardness of 3H, and a film adhesion of 5B. The coated specimens remain an approximate optical transparency of 90%, which is close to the bare PC substrate. The anti-fingerprint performance and mechanical properties of the coating were largely ahead of commercialized iPhone screen protectors.