The electric Joule heating of solid materials through direct current excitation can be used to generate a temperature profile throughout a powdermetallic (P/M) compact. When recording the surface temperature distribution with an infrared (IR) camera important information regarding the integrity of the sample can be gained. This research will concentrate on the formulation of a mathematical model capable of predicting the temperature distribution and heat flow behavior in P/M parts and its relations to the supplied current, injection method, geometric shape as well as the thermo-physical properties. This theoretical model will subsequently be employed as a tool to aid in the actual measurements of infrared signatures over the sample surface and their correlation with the detection of surface and subsurface flaws. In this work we will develop the theoretical background of IR testing of green-state and sintered P/M compacts in terms of stating the governing equations and boundary conditions, followed by devising analytical and numerical solutions. Our main emphasis is placed on modeling various flaw sizes and orientations in an effort to determine flaw resolution limits as a function of minimally detectable temperature distributions. Preliminary measurements with controlled and industrial samples have shown that this IR testing methodology can successfully be employed to test both green-state and sintered P/M compacts.

Combustion chemical vapor deposition (combustion CVD) is a thin film deposition process that uses a flame created by the ignition of an aerosol containing precursors dissolved in a flammable solvent. Combustion CVD is a relatively new technique for creating thin film oxide coatings. Combustion CVD has been successfully used to deposit high quality thin oxide films for potential applications such as thermal barrier coatings, dielectric thin films, composite interlayer coatings, etc. The present work involved developing the optimum parameters for deposition of thin films of yttria-stabilized zirconia (YSZ), alumina (Al₂O₃), and YSZ-alumina composites followed by a determination of the mechanical properties of the films (measured using nanoindentation) as a function of composition. The optimized parameters for deposition of YSZ, alumina, and YSZ-alumina composites onto single crystal a-plane alumina involved using an organic liquid as the flammable solvent and Y 2-ethylhexanoate, Zr 2-ethylhexanoate and Al acetylacetonate as the metal precursors at a 0.002 M concentration delivered at 4 ml/min at flame temperatures of 155 ℃ and substrate temperatures of 105 ℃. The resulting films were grown with deposition rates of ~ 1.5 μm/hr. Measurement of the mechanical properties (hardness, elastic modulus and fracture toughness) of the films was performed using a mechanical properties microprobe called the Nanoindenter®. In order to obtain valid results from nanoindentation, the combustion CVD films were optimized for minimum surface roughness and grown to a thickness of approximately 0.8 μm. With the penetration depth of the indenter at approximately 150 nm, the 800 nm thickness of the film made influences of the substrate on the measurements negligible. The hardnesses and elastic moduli of the YSZ-alumina films did not vary with the composition of the film. The fracture toughness, however, did show a dependence on the composition. It was found that second phase particles of alumina grown into a YSZ matrix increased the fracture toughness of the films (on average, 1.76 MPa• m⁰.⁵ for 100% YSZ to 2.49 MPa• m⁰.⁵ for 70 mol% YSZ/30 mol% alumina). Similarly, second phase particles of YSZ grown into an alumina matrix also increased the fracture toughness (on average, 2.20 MPa• m⁰.⁵ for 100% alumina to 2.45 MPa• m⁰.⁵ for 37.2 mol% YSZ/62.8 mol% alumina). Modeling of the fracture toughness of the YSZ-alumina films was successfully achieved by using the following toughening mechanisms: crack deflection from the second phase particles, grain bridging around the particles, and residual stress from the CTE mismatch between the film and the substrate and between the second phase particles and the matrix of the film.

No matter how inspection techniques have been advanced, manual visual inspection is currently still the first and fundamental step in assessing civil infrastructure. If no sign of deterioration has been spotted in manual inspection, any future inspection actions is not necessary to take. However, manual inspection has been identified with several limitations including the qualitative nature of inspection results, the time-consuming inspection process, and the heavy reliance on inspectors' and/or engineers' experience. In order to overcome these limitations, automated visual inspection systems have been proposed to enhance and/or replicate the manual inspection process. A number of image processing methods have been developed in detecting defects (i.e. coating rusts) and damage (i.e. cracks) on civil infrastructure. Their effectiveness has been verified in inspecting structures, such as bridges, underground pipes, and tunnels. Although existing methods are effective in finding defects and damage from digital images, missing two important links limits their application for rapid infrastructure assessment and rehabilitation. The first link is the correlation between the defects/damage and the structural members that the defects/damage lie on. The second link is the relationship between the defects/damage and their impacts on the structural members. The purpose of this research is to investigate the way of establishing these two links. It is focused on the retrieval of critical structural members and defects/damage information from images/videos, and then the utilization of this information for automated and rapid assessment and rehabilitation of civil infrastructure. Specifically, a combination of techniques from the areas of visual pattern recognition, digital filtering, and machine vision have been used in order to develop a set of methods for concrete column recognition, crack properties retrieval, and air pockets and discoloration detection and evaluation. The methods proposed in this research were implemented in a Microsoft Visual Studio environment, and tested on the real images/videos of concrete structures inflicted with cracks, air pockets and discoloration. The test results indicated that the methods could automatically recognize concrete columns, correctly measure the properties of the cracks in a crack map, and accurately evaluate the impacts of air pockets and discoloration on the visual quality of concrete surfaces.

This study presents a new approach for nonlinear multi-scale constitutive models using artificial neural networks (ANNs). Three ANN classes are proposed to characterize the nonlinear multi-axial stress-strain behavior of metallic, polymeric, and fiber reinforced polymeric (FRP) materials, respectively. Load-displacement responses from nanoindentation of metallic and polymeric materials are used to train new generation of dimensionless ANN models with different micro-structural properties as additional variables to the load-deflection. The proposed ANN models are effective in inverse-problems set to back-calculate in-situ material parameters from given overall nanoindentation test data with/without time-dependent material behavior. Towards that goal, nanoindentation tests have been performed for silicon (Si) substrate with/without a copper (Cu) film. Nanoindentation creep test data, available in the literature for Polycarbonate substrate, are used in these inverse problems. The predicted properties from the ANN models can also be used to calibrate classical constitutive parameters. The third class of ANN models is used to generate the effective multi-axial stress-strain behavior of FRP composites under plane-stress conditions. The training data are obtained from coupon tests performed in this study using off-axis tension/compression and pure shear tests for pultruded FRP E-glass/polyester composite systems. It is shown that the trained nonlinear ANN model can be directly coupled with finite-element (FE) formulation as a material model at the Gaussian integration points of each layered-shell element. This FE-ANN modeling approach is applied to simulate an FRP plate with an open-hole and compared with experimental results. Micromechanical nonlinear ANN models with damage formulation are also formulated and trained using simulated FE modeling of the periodic microstructure. These new multi-scale ANN constitutive models are effective and can be extended by including more material variables to capture complex material behavior, such as softening due to micro-structural damage or failure.

Modification of the surface chemistry of materials used as implants in biomedical applications affords the ability to control cell adhesion, prevent inflammation and enhance integration with the host. Titanium and its alloys are strong and lightweight thereby making them desirable for applications such as hip and knee replacements, dental implants, and cardiac pacemaker implants. However, the lifetime of these implants is often limited by poor incorporation into the surrounding bone which results in loosening and wear. In order to overcome these limitations we have studied the modification of titanium substrates with a self-assembled monolayer that can be used to perform surface-initiated atom transfer radical polymerization (SI-ATRP) of a monomer to afford polymer brushes that effectively prevent the adhesion of cells. In addition, the polymer brushes afford the ability to tether a peptide sequence. Specific peptides containing adhesion sequences have been tethered to the polymer brushes. The resulting surfaces promote cell adhesion and osteoblast differentiation, thereby increasing bone tissue formation around the implant resulting in better incorporation of the implant.

Thesis (M.S.)--Florida State University, 2006. / Advisor: Piyush Kumar, Florida State University, College of Arts and Sciences, Dept. of Computer Science. Title and description from dissertation home page (viewed June 7, 2006). Document formatted into pages; contains viii, 45 pages. Includes bibliographical references.

This work examines the chemical and physical effects of a material treatment process on the biopolymers PEEK, POM-h, POM-c, PTFE and UHMWPE. The polymers are analyzed physically and chemically using atomic force microscopy, profilometry, scanning electron microscopy, optical microscopy, contact angle measurement, FT infra-red spectroscopy and energy dispersive X-ray spectrometry. PEEK is found to be the most suitable polymer and FT Infra-red spectroscopy an informative analytic tool.

CNPq / Os aços inoxidáveis são amplamente utilizados nas indústrias químicas, petroquímicas, nucleares, de geração de energia, biomédica e de processamento de alimentos. Em geral os aços inoxidáveis apresentam boa resistência à corrosão, entretanto a aplicabilidade destes aços pode ser restringida pela dureza ou pela resistência a corrosão. Usualmente os aços de alta resistência e dureza apresentam elevados teores de carbono, apresentando uma estrutura martensítica, com consequente redução da resistência à corrosão. Por outro lado os aços com maior resistência a corrosão apresentam menor dureza e consequente menor resistência ao desgaste. Diversas soluções têm sido implementadas no sentido de melhorar a resistência a corrosão e ao desgaste simultaneamente desses materiais. Dentre estas a adição de nitrogênio na superfície através da nitretação a plasma, implantação iônica, tratamento térmico de solubilização após nitretação a plasma (SHTPN – Solution Heat Treatment after Plasma Nitriding). Este trabalho tem como objetivo determinar os parâmetros de SHTPN que possibilite obter martensita de nitrogênio na superfície do aço AISI 409, bem como, a avaliação de sua resistência à corrosão. Foi possível verificar uma melhora na resistência à corrosão das condições tratadas por SHTPN, assim como um aumento na resistência mecânica, avaliado pelo perfil de dureza da camada superficial tratada. / Stainless steels are widely used on chemical, petrochemical, nuclear, energy generation, biomedical and food processing industries. In general, stainless steels present good corrosion resistance. However, the application of these materials can be restrained by the hardness and the corrosion resistance. Usually, high strength steels present high carbon content and martensitic structure, what can consequently cause a reduction on corrosion resistance. On the other hand, high corrosion resistance steels present low hardness and weak wear properties. Thereby, many solutions have been made to improve simultaneously wear properties and corrosion resistance of these materials, specially related to the introduction of nitrogen on the surface, through plasma nitriding, ion implantation and SHTPN (Solution Heat Treatment after Plasma Nitriding) processes. The aim of this paper is to determine SHTPN parameters that can form nitrogen martensite on the surface of AISI 409 stailess steel, as well as the evaluation of its corrosion resistance. It was verified an improve on corrosion resistance conditions of SHTPN treated samples. Aditionally, there was an improve on mechanical resistance showed by hardness profiles.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As plantas naturais da Amazônia vêm instigando o interesse de pesquisadores a extrair os produtos desta região. O intuito destas pesquisas foca no desenvolvimento de novos fármacos a partir dos compostos bioativos de plantas visando o combate de inúmeras doenças associadas ao aumento na produção de espécies reativas de oxigênio. A seiva, folhas e cascas de plantas do gênero Croton são utilizadas pelos povos nativos amazônicos para fins medicinais com ação cicatrizante, anti-inflamatória e antibacteriana. Este estudo teve como objetivo otimizar o processo de extração de produtos naturais de folhas, cascas de extratos de C. lechleri. O delineamento para extração de compostos naturais foi realizado por meio de planejamento fatorial 2³ e análise por metodologia de superfície de resposta (RSM). Três fatores (variáveis independentes); tipo de solvente (água ou etanol), tempo de extração (30 ou 90 min) e temperatura de extração (35°C e 70°C) foram utilizados para o delineamento experimental. Enquanto que as variáveis dependentes; teor de compostos fenólicos, atividade antioxidante por DPPH, e teor de antocianinas foram avaliadas nos extratos de C. lechleri. A composição da diversidade de compostos fenólicos foi investigada por cromatografia líquida de alta eficiência. O conjunto de dados foi submetido à análise de componentes principais (ACP). A melhor condição de extração de compostos fenólicos foi água, a 70 ºC por 30 min, enquanto que para os compostos com atividade antioxidante foi etanol, a 70 ºC por 90 min. A análise por cromatografia revelou a presença majoritariamente de ácido gálico, catequina, epicatequina, ácido siríngico, ácido cumárico e ácido ferrúlico. Por fim, o delineamento fatorial permitiu a redução do número de ensaios realizados sem diminuir a qualidade da informação e dos resultados da análise de variância. Metodologia de superfície de resposta e análise de componentes principais empregadas provaram ser ferramentas eficientes para analisar dados da bioatividade de extratos de C. lechleri. / The natural plants of the Amazon have been instigating the interest of researchers to extract the products of the region. The purpose of this research focuses on no development of new drugs from bioactive plant compounds aimed at fighting numerous diseases associated with increased production of reactive oxygen species. The sap, leaves and barks of plants of the genus Croton are used by native Amazonian peoples for medicinal purposes with healing, anti-inflammatory and antibacterial action. This study aimed to optimize the extraction process of natural products from leaves, bark of C. lechleri extracts. The design for the extraction of natural compounds was performed by 2³ factorial experimental design and analysis using Response Surface Methodology (RSM). Three factors (independent variables); type of solvent (water or ethanol), extraction time (30 or 90 min) and extraction temperature (35 °C and 70 °C) were used for the experimental design. While the dependent variables; content of phenolic compounds, antioxidant activity by DPPH, and anthocyanin content were evaluated in extracts of C. lechleri. The composition of the diversity of phenolic compounds was investigated by high performance liquid chromatography. The data set was submitted to Principal Component Analysis (PCA). The best extraction condition of phenolic compounds was water, at 70 ºC for 30 min, while for the compounds with antioxidant activity was ethanol, at 70 ºC for 90 min. Chromatographic analysis revealed the presence of gallic acid, catechin, epicatechin, syringic acid, coumaric acid and ferulic acid. Finally, the factorial design allowed the reduction of the number of tests carried out without diminishing the quality of information and the results of analysis of variance. Response Surface Methodology and Principal Component Analysis proved to be efficient tools used to analyze data bioactivity of extracts from C. lechleri.

Aços inoxidáveis austeníticos são materiais amplamente utilizados em sistemas que exigem elevadas resistências à oxidação e à corrosão. No entanto, quando em contato com outras superfícies, esses materiais possuem elevado coeficiente de atrito e baixa resistências ao desgaste. Uma alternativa para melhorar suas propriedades tribológicas é a utilização de lubrificantes sólidos adicionados em suas composições pela técnica de metalurgia do pó (M/P). Materiais como itria e boro têm se mostrado eficazes em melhorar as propriedades mecânicas e tribológicas de ligas Fe-Cr-Ni-Mo. Nesse contexto, o objetivo desse estudo foi avaliar o efeito da adição de boro e de itria na microestrutura e nas propriedades tribológicas de aços inoxidáveis austeníticos Fe-Cr-Ni-Mo obtidas por M/P. Foram preparadas amostras de 316L por M/P em quatro condições diferentes. Duas amostras, uma sem aditivo e outra com 0,6% p de boro adicionado à composição do 316L, foram processadas a pressão de compactação de 800 MPa e temperatura de sinterização de 1240°C. Além dessas, duas amostras, uma sem aditivo e outra com 1,0% p de itria adicionada à composição do 316L, foram processadas a pressão de compactação de 400 MPa e temperatura de sinterização de 1280°C. Determinou-se a composição química por espectrometria de emissão óptica, a microdureza Vickers, a microestrutura por MEV e EDS, o comportamento tribológico por ensaio de deslizamento alternado (coeficiente de atrito e coeficiente de desgaste específico) e por MEV e EDS (mecanismos de desgaste). Os resultados mostraram que a adição de boro aumenta significativamente a resistência ao desgaste dos materiais, devido à melhor densificação e à formação de fases duras (como boretos ricos em cromo e molibdênio) na sinterização. A adição de itria, mesmo com o aumento da dureza, diminui a resistência ao desgaste, pois dificultou a densificação devido a sua baixa interação com a matriz austenítica do material. O coeficiente de atrito se manteve em 0,8 para todos os materiais, o que indica que os aditivos não o influenciam e não atuam como lubrificantes sólidos. Os mecanismos de desgaste observados nas superfícies dos materiais desgastado foram os mecanismos por adesão e por reação triboquímica. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-10-06T13:28:30Z No. of bitstreams: 1 Dissertacao Francisco Lanferdini Serafini.pdf: 8038161 bytes, checksum: dcb2bed0b9667682b747c75e0bece6ec (MD5) / Made available in DSpace on 2016-10-06T13:28:30Z (GMT). No. of bitstreams: 1 Dissertacao Francisco Lanferdini Serafini.pdf: 8038161 bytes, checksum: dcb2bed0b9667682b747c75e0bece6ec (MD5) Previous issue date: 2016-10-06 / Austenitic stainless steel materials are widely used in systems that require high oxidation resistance and corrosion resistance. However, in contact with other surfaces, these materials show a high coefficient of friction and a low wear resistance. An alternative to improve their tribological properties is the use of solid lubricants added in their composition by the powder metallurgy technique (P/M). Materials such as yttria and boron have shown an effective role in improving the mechanical and tribological properties of Fe-Cr-Ni-Mo alloys. In this context, this study aims evaluating the effect of boron and yttria additions on the microstructure and tribological properties of austenitic stainless steels Fe-Cr-Ni-Mo obtained by P/M. Samples were prepared with 0.6 wt% boron and 1wt% yttria, using compaction pressures of 400 MPa and 800 MPa, sintering temperature 1240°C and 1280°C, in argon atmosphere. The materials were characterized by chemical analysis (optical emission spectrometry), Vickers hardness and microstructural analysis (SEM and EDS). The coefficient of friction and the wear rate of the materials were obtained by means of reciprocating sliding tests. The wear mechanisms were evaluated by SEM and EDS. The results showed that the boron addition significantly increases the wear resistance of the material, due to the improved densification and the formation of hard phases (such as chromium-rich borides and molybdenum-rich borides) during sintering. However, even though with the increased hardness, the yttria addition decreases the wear resistance, due to the not favouring of the densification and the low interaction of yttria particles with the austenitic matrix. The coefficient of friction for all materials was about 0.8, i.e., and it was not influenced by the presence of additives in the composition. The predominant mechanisms on the worn surfaces of the materials were the adhesive wear and the tribochemical reaction wear (wear by particles oxidation).