Thesis (M.S.)--Ohio University, March, 2009. / Title from PDF t.p. Includes bibliographical references.

Thesis (M.S.)--University of Toledo, 2009. / Typescript. "Submitted as partial fulfillments of the requirements for The Master of Science Degree in Mechanical Engineering." "A thesis entitled"--at head of title. Bibliography: leaves 104-110.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (p. 116-121).

Thesis (Ph. D.)--Ohio State University, 2005. / Available online via OhioLINK's ETD Center; full text release delayed at author's request until 2006 Nov 30

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Made available in DSpace on 2014-06-11T19:27:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-11-07Bitstream added on 2014-06-13T19:55:30Z : No. of bitstreams: 1 rocha_tl_me_ilha.pdf: 2209567 bytes, checksum: 0779f425359ed3738d8731ce2f0ae1f2 (MD5) / A metodologia de Sinterização Direta de Metais por Laser (DMLS) é uma das novas tecnologias de manufaturas aditivas, utilizada para fabricação de componentes de geometrias complexas. Dada à possibilidade de obtenção de peças com geometrias complexas, este método possui um grande potencial para a manufatura de implantes personalizados de reconstituição óssea. Dentre os materiais utilizados no processo, o titânio e suas ligas se destacam por possuírem uma combinação de elevada resistência mecânica, alta resistência à corrosão eletroquímica e resposta biológica favorável. Este trabalho visou apresentar um estudo da corrosão eletroquímica em implante de liga Ti-6Al-4V obtido por DMLS. Os ensaios de corrosão eletroquímica foram realizados em temperatura ambiente e na presença do oxigênio atmosférico. Os eletrólitos utilizados foram Soro Fisiológico, Ringer Lactato e Solução de Hanks que simulam os meios fisiológicos, bem como os três meios acrescidos de Peróxido de Hidrogênio até atingirem pH~5,02 e pH~4,33 que simulam respectivamente reações de inflamação e infecção. As curvas de polarização potenciodinâmicas das amostras foram obtidas com uma velocidade de varredura de 1 mV/s e o intervalo de potencial varrido de -1 V a + 1,2 V. A área ensaiada das amostras (eletrodo de trabalho) foi de 0,5 cm2. As correntes de corrosão foram calculadas no intercruzamento das curvas anódica e catódica linearizadas, na região do potencial de corrosão. Os parâmetros eletroquímicos de corrosão obtidos foram: o potencial de corrosão, a densidade de corrente e a resistência à polarização. A análise qualitativa dos ensaios de corrosão foram obtidas mediante Microscopia Eletrônica de Varredura (MEV) e Microscopia Óptica, onde foi possível evidenciar aumento dos poros identificados na superfície após os ensaios / The methodology Direct Metal Laser Sintering (DMLS) is a new additive manufacturing technology, used for the manufacture of components of complex geometries. Given the possibility of obtaining parts with complex geometries, this method has a great potential for the manufacture of customized implants for bone reconstruction. Among the materials used in the process, titanium and its alloys are distinguished by possessing a combination of high mechanical strength, high corrosion resistance and electrochemical favorable biological response. This work aims to present a study of electrochemical corrosion in implant alloy Ti-6Al-4V obtained by DMLS. The electrochemical corrosion tests were performed at room temperature and in the presence of atmospheric oxygen. The electrolytes used were saline solution, Ringer Lactato and Hank´s solution simulating the fluids physiological, and added hydrogen peroxide until reaching pH~5,02 and pH~4,33 respectively which simulate the reactions of inflammation and infection . The potentiodynamic polarization curves of the samples were with a scan speed employed 1 mV/s and the sweep potential range of -1 V to + 1.2 V. The area of the samples tested (working electrode) was 0.5 cm2. The corrosion currents were calculated intercrossing the anode and cathode of the linearized curve in the region of potential corrosion. The electrochemical parameters obtained were: the corrosion potential of corrosion current density and polarization resistance. Qualitative analysis of the corrosion tests were performed by scanning electron microscopy (SEM) and optical microscopy, where it was possible to demonstrate increased presence of pores before corrosion tests

Made available in DSpace on 2018-07-27T18:26:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-12-04. Added 1 bitstream(s) on 2018-07-27T18:29:49Z : No. of bitstreams: 1 000864680.pdf: 2241907 bytes, checksum: a28a73d650830be8f6e44837bb623ef5 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Neste trabalho, a oxidação eletrolítica assistida por plasma (PEO) foi utilizada para produzir um revestimento cerâmico na superfície de substratos da liga (AA 5052) de alumínio. As propriedades elétricas deste revestimento foram analisadas através da espectroscopia de impedância elétrica (EIE). As espessuras dos revestimentos foram determinadas pelo método de correntes parasitas e microscopia eletrônica de varredura (MEV). O MEV foi empregado também na avaliação da topografia dos revestimentos. Para a determinação da estrutura e composição químicas foram empregadas as espectroscopias de absorção no infravermelho (IRS) e de energia dispersiva de raios x (EDS). As estruturas cristalinas foram determinadas pela técnica da difração de raios x. Os resultados revelaram que as superfícies foram recobertas por um revestimento complexo, contendo principalmente alumínio, oxigênio e silício, que aumento a resistividade elétrica 10-10 vezes em comparação com o alumínio como recebido / In this work, plasma electrolytic oxidation (PEO) has been used to produce ceramic coating on AA 5052 aluminum alloy substrates. The electrical properties of coatings were analyzed using electrical impedance spectroscopy (EIS). The thickness of the coatings was determined by the eddy current method and scanning electron microscopy (SEM). SEM was also used to evaluate the topography of the coatings. Infrared absorption (IRS) and energy dispersive x-ray (EDS) spectroscopy have been employed to determine structural and the chemical composition and the crystalline structures were determined by X-ray diffraction. The results have revealed that the surfaces were covered by complex coatings, composed by aluminum, oxygen and silicon, which increased the electrical resistivity by 1010 times in comparison with the as-recebived aluminum

Orientador: Ruis Camargo Tokimatsu / Coorientador: Carlos Alberto Picone / Banca: Vicente Afonso Ventrella / Banca: Maria Aparecida Larosa / Resumo: A metodologia de Sinterização Direta de Metais por Laser (DMLS) é uma das novas tecnologias de manufaturas aditivas, utilizada para fabricação de componentes de geometrias complexas. Dada à possibilidade de obtenção de peças com geometrias complexas, este método possui um grande potencial para a manufatura de implantes personalizados de reconstituição óssea. Dentre os materiais utilizados no processo, o titânio e suas ligas se destacam por possuírem uma combinação de elevada resistência mecânica, alta resistência à corrosão eletroquímica e resposta biológica favorável. Este trabalho visou apresentar um estudo da corrosão eletroquímica em implante de liga Ti-6Al-4V obtido por DMLS. Os ensaios de corrosão eletroquímica foram realizados em temperatura ambiente e na presença do oxigênio atmosférico. Os eletrólitos utilizados foram Soro Fisiológico, Ringer Lactato e Solução de Hanks que simulam os meios fisiológicos, bem como os três meios acrescidos de Peróxido de Hidrogênio até atingirem pH~5,02 e pH~4,33 que simulam respectivamente reações de inflamação e infecção. As curvas de polarização potenciodinâmicas das amostras foram obtidas com uma velocidade de varredura de 1 mV/s e o intervalo de potencial varrido de -1 V a + 1,2 V. A área ensaiada das amostras (eletrodo de trabalho) foi de 0,5 cm2. As correntes de corrosão foram calculadas no intercruzamento das curvas anódica e catódica linearizadas, na região do potencial de corrosão. Os parâmetros eletroquímicos de corrosão obtidos foram: o potencial de corrosão, a densidade de corrente e a resistência à polarização. A análise qualitativa dos ensaios de corrosão foram obtidas mediante Microscopia Eletrônica de Varredura (MEV) e Microscopia Óptica, onde foi possível evidenciar aumento dos poros identificados na superfície após os ensaios / Abstract: The methodology Direct Metal Laser Sintering (DMLS) is a new additive manufacturing technology, used for the manufacture of components of complex geometries. Given the possibility of obtaining parts with complex geometries, this method has a great potential for the manufacture of customized implants for bone reconstruction. Among the materials used in the process, titanium and its alloys are distinguished by possessing a combination of high mechanical strength, high corrosion resistance and electrochemical favorable biological response. This work aims to present a study of electrochemical corrosion in implant alloy Ti-6Al-4V obtained by DMLS. The electrochemical corrosion tests were performed at room temperature and in the presence of atmospheric oxygen. The electrolytes used were saline solution, Ringer Lactato and Hank's solution simulating the fluids physiological, and added hydrogen peroxide until reaching pH~5,02 and pH~4,33 respectively which simulate the reactions of inflammation and infection . The potentiodynamic polarization curves of the samples were with a scan speed employed 1 mV/s and the sweep potential range of -1 V to + 1.2 V. The area of the samples tested (working electrode) was 0.5 cm2. The corrosion currents were calculated intercrossing the anode and cathode of the linearized curve in the region of potential corrosion. The electrochemical parameters obtained were: the corrosion potential of corrosion current density and polarization resistance. Qualitative analysis of the corrosion tests were performed by scanning electron microscopy (SEM) and optical microscopy, where it was possible to demonstrate increased presence of pores before corrosion tests / Mestre

The Electrochemical Activation (ECA) of water is introduced as a novel refinement of conventional electrochemical processes and the unique features and attributes are evaluated against the universal principles that have described the electrolytic processes to date. While the novel and patented novel reactor design retains the capacity to generate products common to conventional electrolysis, it also manipulates the properties of the reagent solutions to achieve an anomalous Oxidation-Reduction potential (ORP or REDOX) that cannot be replicated by traditional chemical and physical interventions. As a contemporary development in the field, the technology continues to undergo rigorous assessment and while not all of its theoretical aspects have been exhaustively interrogated, its undisputed biocidal efficacy has been widely established. Microbial vitality has been shown to be directly dependent upon the confluence of a diverse variety of physical and chemical environmental conditions. Fundamentally important in this regard is the electronic balance or REDOX potential of the microbial environment. The intricate balance of metabolic pathways that maintain cellular integrity underwrites the measures of irritability required for sustained viability. Aside from the direct effects of the conventional electrolysis products, overt electronic disruption of the immediate microbial environment initiates a cascade of secondary and largely independent autocidal molecular events which compromise the fundamental integrity of the microbe and leads to cell death. The distinctive capacity to impart unique physicochemical attributes to the ECA derived solutions also facilitates the characterisation of the same outside of the conventional physicochemical and gravimetric measures. These adjunct measures display a substantial relationship with the predictability of antimicrobial effect, and the direct relationship between inactivation of a defined microbial bioload and the titratable measures of REDOX capacity have been shown to describe a repeatable benchmark. The use of ultra-microscopy to investigate the impact of the ECA products on bacterial cell structures has shown this tool to have distinctive merit in the imaging and thus refined description of the consequences of exposure to biocidal solutions. The distinctive differences of the ECA solutions relative to conventional antibacterial compounds would suggest a heightened suitability for application in conditions where the efficacy of conventional biocidal compounds had been limited. Aeroslisation of the ECA solutions for the decontamination of airspaces challenged with tuberculosis pathogens revealed that despite initial success, further refinements to the application model will be required to meet the unresolved challenges. The health care benefits associated with the application of the ECA solutions in a medical environment substantiate the merits for the adoption of the technology as a complementary remedy for the management of nosocomial infections. The relative novelty of the technology in the commercial domain will raise questions regarding the potential for resistance development, and it has been proposed that the distinctive mechanism of biocidal action will not contribute to diminished bacterial susceptibility, as it does not reveal any cross- or co-resistance when assessed against multiple antibiotic resistant strains. These benefits are further reinforced by the capacity to install the technology for both onsite and on-demand availability, and being derived from natural ingredients (salt and water) the ECA solutions are regarded as safe and compatible for general in-contact use. Notwithstanding the multiple benefits that the technology may provide, further assessments into materials compatibility as well as potential by-products formation following environmental exposure are imperative before the unfettered adoption of this technology as a cost-effective, safe and reliable alternative to conventional disinfection can be promoted. / Thesis (PhD)--University of Pretoria, 2011. / Microbiology and Plant Pathology / unrestricted

The aim of this work is to quantify the concentration of chromic acid (CA) in a saturated solution of chromium trioxide and sodium dichromate using Artificial Neural Networks (ANNs). A set of titration curves was obtained by automated acid-base titration according to a factorial experimental design that was developed for this purpose. These titration curves were divided into three subsets, a learning, training and test set for use by ANNs. Once trained, ANNs have the ability to recognize, generalize and relate the input to a particular output. Concentration of chromic acid (CA), total chromium(VI) and/or dichromate was used as the outputs and titration curves as the inputs to ANNs. Our aim here was to establish whether ANNs would be able to predict the concentration of chromic acid with an absolute error below 1%. For real world problem, the neural networks are only given the inputs and are expected to produce reasonable outputs corresponding to that inputs without any prior ‘knowledge’ about theory involved – here, no interpretation of titration curves was performed by ANNs. The test set of data that was not used for learning process, was used to validate the performance of the neural networks, to verify whether the ANNs learned the input-output patterns properly and how well trained ANNs were able to predict the concentrations of chromic acid, dichromate and total chromium. A number of ANNs models have been considered by varying the number of neurons in the hidden layer and parameters related to the learning process. It has been shown that ANNs can predict the concentration of chromic acid with required accuracy. A number of factors that affect the performance of the neural networks, such as the number of points in a titration curve, number of test points and their distribution within the training set, has been investigated. This work demonstrates that ANNs can be used for online monitoring of an electrolytic industrial process to manufacture chromic acid. / Dissertation (MSc)--University of Pretoria, 2009. / Chemistry / unrestricted