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Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-02-01T18:32:19Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DM Henrique Patriota Alves.pdf: 2961953 bytes, checksum: cd856b581753170ffb1c56ff445144f8 (MD5) / Made available in DSpace on 2017-02-01T18:32:19Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DM Henrique Patriota Alves.pdf: 2961953 bytes, checksum: cd856b581753170ffb1c56ff445144f8 (MD5) Previous issue date: 2016-07-22 / CNPQ / Esta dissertação apresenta uma modelagem computacional da dinâmica de rugosidade de superfície gerada durante o processo de corrosão de um elemento transdutor metálico do sensor à fibra óptica. Tal modelagem é implementada num software dedicado de simulação multifísica que faz uso do Método dos Elementos Finitos. Considerando que a rugosidade de superfície pode ser definida por geometria fractal, que pode ser complexa, é proposta nesta dissertação uma forma alternativa e simples para modelar a superfície rugosa e a sua dinâmica sob corrosão. Para a modelagem computacional, é definida uma função periódica, chamada de função rugosidade, onde seus parâmetros são ajustados com dados experimentais do processo de corrosão. Os resultados da simulação computacional são comparados com um modelo analítico, que faz uso das equações de Fresnel. Nos resultados da simulação, é observado o acoplamento do sinal óptico na superfície rugosa do filme metálico. Esse acoplamento observado é explicado pelo fenômeno de Ressonância de Plásmon de Superfície. A modelagem proposta nesta dissertação apresenta excelente ajuste aos resultados experimentais. / This dissertation presents a computer modeling of the surface roughness dynamics generated during the corrosion process of a metallic element transducer of the fiber-optic sensor. This modeling is implemented in dedicated software that uses the Finite Element Method. Since the surface roughness can be defined by the fractal geometry, which can be complex, it is proposed in this dissertation an alternative and simple way to model the surface roughness and its dynamics under corrosion. The proposed modeling uses a roughness function that is defined by a periodic function, where their parameters are obtained from experimental data of the corrosion process. The computer simulation results are compared to an analytical model, which uses the Fresnel’s equations. In the simulation results, it is observed the optical signal coupling with the rough surface of the metallic film. This observed coupling is explained by the phenomenon of Surface Plasmon Resonance. The proposed modeling and simulations presents excellent fitting to the experimental results.

Superhydrophobic and lubricant-infused porous surfaces are two classes of non-wetting surfaces that are inspired by the adaptation of natural surfaces such as lotus leaves, pond skater legs, butterfly wings, and Nepenthes pitcher plant. This dissertation focuses on fabrication and in depth study of bioinspired functional metallic surfaces for applications such as power plant condensers and marine applications. Toward that, first, facile and scalable methods are developed for the fabrication of superhydrophobic surfaces (SHS) and lubricant-infused surfaces (LIS). Second, the corrosion inhibition mechanism of SHS was systematically studied and modeled via electrochemical methods to elucidate the role of superhydrophobicity and other parameters on corrosion inhibition. The anti-corrosion properties of SHS and LIS were systematically studied over a range of temperatures (23°C–90°C) to simulate an actual condenser environment. Moreover, the environment of application often involves using harsh cleaning chemicals. The fabricated non-wetting surfaces were examined over a wide range of acidity and basicity (pH=1 to pH=14). Third, the durability of SHS and LIS is systematically assessed using a set of testing protocols including water impingement tests, scratch wear tests, and accelerated chemical corrosion tests. Considering that industrial environments of application are often turbulent, in addition to static long term corrosion tests, long term dynamic durability was studied in a simulated turbulent condition. Fourth, the performance of the fabricated nonwetting surfaces was systematically studied against calcium sulfate scaling in turbulent conditions and different temperatures. An analytical relationship based on the Hill-Langmuir model is proposed for the prediction of fouling on nonwetting and conventional surfaces alike in dynamic conditions. Overall 1048 individual samples were studied via over 3000 measurements in this dissertation to establish a comprehensive fundamental knowledge base on fabrication and anti fouling characteristics of metallic nonwetting surfaces, which profoundly helps to design appropriate surfaces and fabrication methods based on the use environment. / Doctor of Philosophy / Metallic surfaces such as copper, brass, and aluminum are everywhere in our daily lives. From tumblers, household pipes to the bank of tubes in power plants condensers. Fouling of these surfaces has significant performance and economic impact. Scaling is a type of crystallization fouling like the familiar limescale everyone is familiar to see around the surface of a house kettle. Corrosion is another type of fouling and is detrimental to metallic surfaces. For example, 50% of water consumption in the U.S. is being used in thermo-electric power plants where fouling of metallic surfaces will impede the flow of working fluid, therefore increasing power needed for pumping, decrease efficiency, and decrease ultimate lifetime. One study in 2019 shows corrosion costs 3% of the gross national products of China and it is already known to be similar for other major economies like the USA, which is a hefty cost. Nature has inspired a lot of solutions for mankind. In this work, inspired by natural surfaces such as lotus leaves, butterfly wings, and pond skater legs, a class of superhydrophobic surfaces (SHS) was fabricated. Moreover, a closer look at how the complex human body puts everything in order exposes one of its most striking and essential characteristics: how wet and lubricated its interfaces are. Our lungs, eyes, joints, intestine, bones; either hairy or porous, all are lined wet surfaces that work as fouling inhibitors and defect free surfaces. This also have been observed elsewhere such as on Nepenthes pitcher plant. Inspired by these, another class of non-wetting surfaces, lubricant-infused surfaces (LIS) was fabricated. This dissertation for the first time investigates a rational methodology in the fabrication of metallic SHS and LIS and their anti-scaling and anti-corrosion properties in different environments of application, including a range of temperature (23°Câ€"90°C), various solutions (pH=1 to pH=14), and long-term static and dynamic (turbulent condition) durability. It is believed that this work would profoundly help to identify appropriate nonwetting metallic surfaces based on the intended use environment.

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Pinhole leaks in copper plumbing pipes are a big concern for the homeowners. The problem is spread across the nation and remains a threat to plumbing systems of all ages. Due to the absence of a single acceptable mechanistic theory no preventive measure is available to date. Most of the present mechanistic theories are based on analysis of failed pipe samples however an objective comparison with other pipes that did not fail is seldom made. The variability in hydraulic and water quality parameters has made the problem complex and unquantifiable in terms of plumbing susceptibility to pinhole leaks. The present work determines the spatial and temporal spread of pinhole leaks across United States. The hotspot communities are identified based on repair histories and surveys. An assessment of variability in water quality is presented based on nationwide water quality data. A synthesis of causal factors is presented and a scoring system for copper pitting is developed using goal programming. A probabilistic model is presented to evaluate optimal replacement time for plumbing systems. Methodologies for mechanistic modeling based on corrosion thermodynamics and kinetics are presented. / Master of Science

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