Titanium has been used in bio-medical implants for decades due to its superior biocompatibility. To improve the osseointegration of dental and orthopaedic implants, various surface modification techniques have been used including laser surface texturing. In particular, short-pulsed lasers, such as femtosecond and picosecond lasers, are widely used for surface modification. In this thesis, commercially pure Ti surfaces are modified by a femtosecond laser to explore the relationship between surface topography, surface chemistry, surface wettability, and biocompatibility with the goal of improving the osseointegration of implants. The laser textured surfaces consist of 1μm wide grooves spaced 10 μm, 4.8 μm, 2.4 μm and 1.2 μm apart. Gradient configurations where the groove spacing varies are also investigated. Surface morphology was characterized using Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). A custom-build contact angle measurement apparatus is used to investigate the wettability of the laser textured surfaces using the sessile drop method. Freshly laser-treated commercially pure Ti surfaces are found to be super-hydrophilic and become hydrophobic over time when exposed to air. The presence of grooves can accelerate the evolution of the contact angle over time, and introduces anisotropy in the wetting behavior (along vs. across the grooves). The hydrophilicity of laser treated surfaces can be retained by storing samples in ethanol. X-ray Photoelectron Spectroscopy (XPS) shows that the relative carbon content increases over time when Ti samples are exposed to air, which results in the subsequent evolution of the contact angle and cell response to laser textured Ti surfaces. Besides, laser treatment promotes the oxidation of pure Ti, and the product, TiO2, is responsible for the better biocompatibility. In vitro experiments using MG 63s osteoblast-like cells are implemented on laser-treated Ti surfaces and polished surfaces (control) with 1 day, 3 days and 7 days of cell culture. The best cell outcome was obtained by storing samples in air for 1 week, where storing for shorter or longer times resulted in the worst outcome, especially in the early stages of cell adhesion. There does not appear to be a direct link between wettability and the fate of cells on Ti surfaces. Indeed, while samples stored in air and ethanol have drastically different contact angle measurements (the former being hydrophobic and the latter hydrophilic), the cell behavior was unaffected. In addition, while wettability and laser treatment can affect the early stages of cell adhesion, they do not have a strong effect on the number of cells at longer incubation times (3 and 7 days). Laser machining does however affect the cell morphology and alignment, where cells preferentially align themselves parallel to the direction of the laser machined grooves with an elongated morphology.

This thesis describes a study of the influence of surface texturing on rolling contact fatigue of non-conformal contacts. The texture depth and density have been considered during experiments. It also presents the methodology and the procedure of creation of micro-dents on sample surfaces. Described results suggested that properly designed surface texturing should not necessarily increase the risk of fatigue failure of rubbing surfaces.

Nonwetting surfaces including superhydrophobic (SHS) and liquid infused surfaces (SLIPS) exhibit diverse exceptional characteristics promoting numerous application opportunities. Engineered textured surfaces demonstrate multiple features including drag reduction, fouling reduction, corrosion resistance, anti-fogging, anti-icing, and condensation enhancement. Integrating these properties, nonwetting surfaces have shown significant potential in improving the efficiency of energy applications. The first part of the thesis work aims at developing a fundamental mathematical understanding of the wetting process on the solid surface followed by presenting fabrication methodologies specifically focused on metallic substrates. The second part of this thesis presents an exhaustive survey on recent advancements and researches about features of nonwetting surfaces that could be implemented in major industrial applications. To establish how realistically these features could enhance the real-life applications, the third part of this work investigates the dynamic performance and economic benefits of using textured surfaces fabricated using an electrodeposition process for condenser tubes in thermoelectric power plants. The textured surfaces are expected to provide enhanced performance by deterring fouling and promoting dropwise condensation of the steam on the shell side. Using a thermal resistance network of a shell and tube condenser, detailed parametric studies are carried out to investigate the effect of various design parameters on the annual condenser performance measured in terms of its electric energy output of a representative 550 MW coal-fired power plant. A cost modeling tool and a new Levelized cost of condenser (LCOC) metric have been developed to evaluate the economic and performance benefits of enhanced condenser designs. The LCOC is defined as the ratio of the lifetime cost of the condenser (and associated costs such as coating, operation and maintenance) to the total electric energy produced by the thermoelectric power plant. The physical model is coupled with a numerical optimization method to identify the optimal design and operating parameters of the textured tubes that minimizes LCOC. Altogether, the study presents the first effort to construct and analyze enhanced condenser design with textured tube surfaces on annual thermoelectric power plant performance and compares it against the baseline condenser design with plain tubes. / Master of Science / Liquid repellant surfaces have attracted lots of attention due to their numerous promising characteristics including promoting condensation, drag reduction, prohibiting fouling/deposition, corrosion, and fog/dew harvesting. These attributes have the potential to inspire a variety of applications for these surfaces in power plants, automotive and aviation industries, oils/organic solvents clean-up, fuel cells, solar panels, membrane distillation, stone/concrete protection, surgical fabrics, and biological applications, to name a few. Some of these applications have reached their potential for real-life implementation and more are still at the research phase needing more experimental and fundamental studies to get them ready. The first part of this study presents the fundamentals of the wetting process. Next, fabrication methods for metallic surfaces have been explored to identify the most scalable and cost-effective approaches which could be administered in large scale industrial applications. A comprehensive review of recent publications on features of nonwetting surfaces has been carried out and presented in the second part of this thesis. To establish how realistically these features could enhance the real-life applications of a thermo-economic a performance model is developed for a powerplant condenser in the third section. Through a simple and cost-effective electrodeposition process, the common condenser tubes are modified to achieve textured tubes with superhydrophobic properties. The influence of using textured tubes on the plant's performance and its economic benefits are investigated to predict the potential promises of nonwetting surfaces.

Ce travail de thèse concerne l’étude de différents revêtements type « Diamond-Like Carbon » élaborés par un procédé CVD assisté par un plasma basse fréquence (40 kHz). Deux revêtements de référence sont d’abord étudiés : des couches de carbone amorphe hydrogéné (a-C:H) et des couches de carbure de silicium amorphe hydrogéné (a-SiC:H). L’évolution de leurs propriétés mécaniques (dureté, module d’Young) et tribologiques (frottement, usure) est décrite en fonction des paramètres du procédé et corrélée à leur microstructure. Les résultats obtenus pour ces deux couches de référence sont ensuite exploités pour proposer deux systèmes complémentaires : des revêtements a-C:H dopées et des systèmes multicouche a-C:H/a-SiC:H. Ces deux solutions présentent des contraintes résiduelles réduites par rapport à un revêtement a-C:H monocouche ce qui permet d’envisager une augmentation importante des épaisseurs de dépôt tout en conservant des propriétés mécaniques et tribologiques intéressantes. Enfin, en vue d’une application industrielle de ces revêtements sur des pièces de moteur par exemple, l’optimisation de leur adhérence par insertion de sous-couches adaptées ainsi que de leurs performances tribologiques en conditions lubrifiées par l’intermédiaire de texturation de surface est alors envisagée / Hydrogenated amorphous carbon films (a-C:H) and hydrogenated silicon carbide films (a-SiC:H) are deposited by low frequency (40 kHz) plasma enhanced chemical vapour deposition (LF PECVD). Structural, mechanical and tribological properties of those single layers have been first studied in relation with process parameters. Then those results have been used to study two other systems. The first one corresponds to silicon doped a-C:H thin films and the second one to multilayered coatings consisting in a stack of a-C:H and a-SiC:H layers. Those coatings offer potential advantages such as lower residual stress level comparing to that of a-C:H stress level which gives the opportunity to deposit thicker films, and also attractive mechanical and tribological properties. Moreover, in case of applications like car engine parts for example, adhesion and tribological properties under lubrication have to be improved. Solutions as incorporating underlayer or texturing surface are thus also investigated in this study

La synthèse de textures est une technique qui génère une texture automatiquement grâce à un algorithme. Cette technique permet de réduire le temps de création des textures et le coût mémoire étant donné que seuls les algorithmes et leurs paramètres ont besoin d'être stockés. Cependant, des difficultés sont souvent rencontrées lors de l'utilisation des textures synthétisées. D'abord, les paramètres de ces textures sont difficiles à manipuler. Ensuite, l'algorithme de synthèse génère souvent les textures sous forme de tableaux de pixels nécessitant beaucoup de mémoire. Pour aborder ces difficultés, nous proposons les approches suivantes : pour améliorer la visualisation de l'espace des textures synthétisées, nous proposons de construire un résumé de cet espace: une seule image statique qui résume, dans un espace limité de pixels, les apparences produites par un synthétiseur donné. De plus, pour améliorer la sélection de paramètres, nous augmentons les curseurs qui contrôlent les paramètres avec des bandes visuelles révélant les changements qui se produisent quand l'utilisateur manipule les curseurs. Pour permettre à l'utilisateur d'interagir de manière interactive avec les résumés visuels, nous nous reposons sur un algorithme de synthèse par patch permettant de générer les textures de façon rapide grâce à une implémentation parallèle sur le processeur graphique. Au lieu de générer le résultat de ce synthétiseur sous forme d'un tableau de pixels, nous représentons le résultat dans une structure compacte et nous utilisons une méthode rapide permettant de lire des pixels directement à partir de cette structure / Texture synthesis is a technique that algorithmically generates textures at rendering time. The automatic synthesis reduces authoring time and memory requirements since only the algorithm and its parameters need to be stored or transferred. However, two difficulties often arise when using texture synthesis: First, the visualization and parameters selection of synthesized textures are difficult. Second, most synthesizers generate textures in a bitmap format leading to high memory usage. To address these difficulties we propose the following approaches: First, to improve the visualization of synthesized textures we propose the idea of a procedural texture preview: A single static image summarizing in a limited pixel space the appearances produced by a given synthesizer. The main challenge is to ensure that most appearances are visible, are allotted a similar pixel area, and are ordered in a smooth manner throughout the preview. Furthermore, to improve parameters selection we augment sliders controlling parameters with visual previews revealing the changes that will be introduced upon manipulation. Second, to allow user interactions with these visual previews we rely on a fast patch-based synthesizer. This synthesizer achieves a high degree of parallelism and is implemented entirely on the GPU. Finally, rather than generating the output of the synthesizer as a bitmap texture we encode the result in a compact representation and allow to decoding texels from this representation during rendering

Superfícies anisotrópicas lisas e rugosas foram usadas para avaliar o efeito da rugosidade e da direção de acabamento na formação de MoS2 a partir de MoDTC em ensaios tribologicos lubrificados com óleos de motor completamente formulados. Igualmente foi avaliada a resposta de atrito de lubrificantes de motor usados em carros de passageiros e em testes de dinamômetro abastecidos com etanol (E100) e gasolina (E22). Encontrou-se que tanto a direção de acabamento quanto a rugosidade foram fundamentais na reação MoDTC - MoS2. A direção de acabamento influenciou na medida que carregamentos tangenciais geram respostas diferentes nos ensaios quando são realizados paralelos e perpendiculares às linhas de acabamento, dado que para os últimos apresenta-se maior deformação plástica das asperezas, o qual favorece a obtenção de superfícies livres de óxidos, que tem sido indicada como uma condição necessário para que aconteça a reação MoDTC - MoS2. Por esta razão os valores de coeficiente de atrito próprios da formação de MoS2 foram obtidos somente nas superfícies rugosas ensaiadas perpendiculares às marcas de acabamento. Para superfícies com valores de índice de plasticidade superiores a 1 e nos quais não são formados filmes com boas capacidades redutoras de atrito, como é o caso de ensaios realizados com óleos base (livres de aditivos), o coeficiente de atrito não depende da rugosidade e da direção de acabamento. Nos ensaios lubrificados com óleos usado, encontraram-se valores de coeficiente de atrito similares aos obtidos nas condições de lubrificação com óleo livres de aditivos, devido provavelmente à redução do MoDTC no lubrificante como tem sido identificado por diferentes autores. Quando foram comparados os óleos usados contaminados com etanol com os óleos usados contaminados com gasolina, encontrou-se maior oxidação nestes últimos. Mesmo que estas diferenças de oxidação dos óleos não significaram diferenças em termos de atrito, estas podem ser importantes na medida em que óleos mais oxidados podem favorecer o desgaste oxidativo. / Smooth and rough anisotropic surfaces were used to evaluate the influence of surface roughnesss and lay direction on the in-situ formation of MoS2 from MoDTC in tribological tests. Also, this work evaluated the friction response of engine lubricants which were used in passenger cars and dynamometer tests fueled both with ethanol (E100) and gasoline (E22). It was found that both the lay direction as the surface roughness were critical for the MoDTC -MoS2 reaction. The lay direction influence due to tangential loads generate different responses when tests were conducted along and across the lay, since the latter showed higher asperities plastic deformation , which favors free oxides surfaces, which has been indicated as a condition for the sequence by MoDTC formed MoS2. For this reason the friction coefficient values related to MoS2 were obtained only for tests conducted on rough surfaces and across the lay. For surfaces with plasticity index values greater than 1 and which are not formed films with good friction-reducing capabilities, such as the tests lubricated with base oil (free aditives), the friction coefficient does not depends on the surface roughness and lay direction. For the tests conducted with used engine oils, the friction coefficient values were similar to those obtained on tests lubricated with free additives oils, this could be related by MoDTC depletion in the lubricants as have been identified by different authors. Comparing the used oils contaminated with ethanol with the used oils contaminated with gasoline, higher oxidation was founded in the latter. Even if these differences in oil oxidation not meant differences friction, these may be important as more oxidesed oils can promote oxidative wear.

O principal objetivo deste trabalho foi estudar a influência do tratamento superficial com laser de femtossegundo em amostras de alumina e compósito de alumina-zircônia estabilizada com ítria para depósito e aderência de apatita. Os resultados obtidos mostraram que houve a formação de apatita sobre as superfícies das amostras que foram texturizadas com laser de femtossegundo e em seguida imersa em 1,5 SBF. Este método biomimético pôde, por conseguinte, tornar estas cerâmicas bioativas. Também houve a formação de apatita na superfície das amostras sem o tratamento a laser. Os efeitos da texturização na superfície para as diferentes cerâmicas e a influência do tempo de imersão em 1,5 SBF são discutidos, a fim de determinar a condição ótima para estimular a deposição e a adesão da apatita na superfície dos materiais. Finalmente, os resultados obtidos das diferentes análises são comparados. A adesão da hidroxiapatita é essencial para interação com o substrato e depende das propriedades das superfícies dos materiais. A qualidade desta adesão influenciará sua morfologia e a capacidade futura de osseointegração. As características de superfície dependem da química de superfície, energia de superfície e topografia de superfície. Geralmente, a reatividade de superfície e energia de superfície pode ser influenciada pelas características de molhabilidade, influenciando o desempenho de biomateriais. A adesão e crescimento da apatita depositada também é função da rugosidade superficial. O tratamento superficial com laser de femtossegundo melhora consideravelmente a adesão da apatita obtida pelo recobrimento biomimético nas superfícies dos materiais. / The main objective of this work was to study the influence of femtosecond laser surface treatment on samples of alumina and composite of zirconia-alumina yttria stabilized for deposit and adhesion of apatite. The results showed that there was apatite formation on the surfaces of the samples that have been textured with femtosecond laser and then immersed in SBF 1.5. This biomimetic method can therefore make these bioactive ceramics. There was also the formation of apatite in the samples without laser treatment. The effects of texturing surface for the different ceramics and the influence of immersion time in SBF 1.5 are discussed in order to determine the optimal conditions to promote the deposition and the adhesion of the apatite in the material`s surface. Finally, the results of the different analyzes are compared. The adhesion of hydroxyapatite is essential for interaction with the substrate and depends on the properties of material´s surface. The quality of this adhesion will influence their morphology and the future ability of osseointegration. The surface characteristics depend on the surface chemical, surface energy and surface topography. Generally, the reactivity of surface and the energy of surface can be affected by wetting characteristics influencing the performance of biomaterials. The adhesion and growth of apatite deposited is also a function of surface roughness. The femtosecond laser surface treatment greatly improves the adhesion of apatite obtained by biomimetic coating on the surfaces of materials.

A aplicação de materiais cerâmicos na indústria têxtil, em especial nos processos de produção e modificação de fios é amplamente difundida no mundo. O fator chave para definição da necessidade do uso de um material cerâmico é a abrasividade dos fios associada à velocidade de processamento desse material. Nesse estudo foi focado o processo de texturização por falsa torção, e foi proposto analisar e compreender o impacto da variação de rugosidade de discos de cerâmica (que já tenham sofrido desgaste durante o processamento), sobre as características físicas de um fio de poliamida. Para isso efetuou-se a seleção de discos de cerâmica com diferentes faixas de rugosidade, fixou-se todas demais variáveis da máquina de texturização, e foram produzidos fios em cada uma das faixas. Depois de produzidos, os fios foram submetidos a testes físicos laboratoriais, e os resultados analisados pelo método ANOVA. Foi observado que a variação na rugosidade dos discos afetou principalmente as características de volume do fio (EKB%), não afetando significativamente o alongamento e tenacidade. / Use of ceramic materials in the textile industry, particularly in production and converting processes of yarns is widespread in the world. The key factor which defining the use of a ceramic material is the abrasiveness of the yarns associated by processing speed of the material. This study focused the false twist texturing, and has been proposed to analyze and understand the impact of variation in roughness of ceramic discs (which have already undergone wear during processing) on the physical characteristics of a polyamide yarn. So, the ceramic discs have been selected with different ranges of surface roughness, settled all other variables of the texturing machine, and each yarn were produced in each of the ranges. Once produced, the yarns were subjected to physical testing laboratory, and the results were analyzed by ANOVA. This study indicated that the variation in roughness of the disks mainly affected the characteristics of the yarn crimp (EKB%) not significantly affecting the elongation and tenacity.

Made available in DSpace on 2017-07-21T19:26:08Z (GMT). No. of bitstreams: 1 Yuri Aparecido Opata.pdf: 4954287 bytes, checksum: c870711b60baa7a02a2a9d07afe3f6bd (MD5) Previous issue date: 2014-03-21 / This work presents an experimental study of changes in structural, electrical, magnetic, and mechanical properties / No presente trabalho é apresentado um estudo experimental das mudanças nas propriedades estruturais, elétricas, magnéticas e mecânicas

O principal objetivo deste trabalho foi estudar a influência do tratamento superficial com laser de femtossegundo em amostras de alumina e compósito de alumina-zircônia estabilizada com ítria para depósito e aderência de apatita. Os resultados obtidos mostraram que houve a formação de apatita sobre as superfícies das amostras que foram texturizadas com laser de femtossegundo e em seguida imersa em 1,5 SBF. Este método biomimético pôde, por conseguinte, tornar estas cerâmicas bioativas. Também houve a formação de apatita na superfície das amostras sem o tratamento a laser. Os efeitos da texturização na superfície para as diferentes cerâmicas e a influência do tempo de imersão em 1,5 SBF são discutidos, a fim de determinar a condição ótima para estimular a deposição e a adesão da apatita na superfície dos materiais. Finalmente, os resultados obtidos das diferentes análises são comparados. A adesão da hidroxiapatita é essencial para interação com o substrato e depende das propriedades das superfícies dos materiais. A qualidade desta adesão influenciará sua morfologia e a capacidade futura de osseointegração. As características de superfície dependem da química de superfície, energia de superfície e topografia de superfície. Geralmente, a reatividade de superfície e energia de superfície pode ser influenciada pelas características de molhabilidade, influenciando o desempenho de biomateriais. A adesão e crescimento da apatita depositada também é função da rugosidade superficial. O tratamento superficial com laser de femtossegundo melhora consideravelmente a adesão da apatita obtida pelo recobrimento biomimético nas superfícies dos materiais. / The main objective of this work was to study the influence of femtosecond laser surface treatment on samples of alumina and composite of zirconia-alumina yttria stabilized for deposit and adhesion of apatite. The results showed that there was apatite formation on the surfaces of the samples that have been textured with femtosecond laser and then immersed in SBF 1.5. This biomimetic method can therefore make these bioactive ceramics. There was also the formation of apatite in the samples without laser treatment. The effects of texturing surface for the different ceramics and the influence of immersion time in SBF 1.5 are discussed in order to determine the optimal conditions to promote the deposition and the adhesion of the apatite in the material`s surface. Finally, the results of the different analyzes are compared. The adhesion of hydroxyapatite is essential for interaction with the substrate and depends on the properties of material´s surface. The quality of this adhesion will influence their morphology and the future ability of osseointegration. The surface characteristics depend on the surface chemical, surface energy and surface topography. Generally, the reactivity of surface and the energy of surface can be affected by wetting characteristics influencing the performance of biomaterials. The adhesion and growth of apatite deposited is also a function of surface roughness. The femtosecond laser surface treatment greatly improves the adhesion of apatite obtained by biomimetic coating on the surfaces of materials.