Thesis (M.S.)--University of Akron, Dept. of Chemical Engineering, 2006. / "December, 2006." Title from electronic thesis title page (viewed 06/02/2008) Advisor, J. Richard Elliott; Committee members, George G. Chase, Stephanie T. Lopina; Department Chair, Lu Kwang Ju; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

Thesis (M.S.)--University of Iowa, 2009. / Thesis supervisor: Lea-Der Chen. Includes bibliographical references (leaves 94-97).

Neste trabalho realizaram-se varias nitretações e nitrocarbonetações a plasma em um aço AISI 4140 temperado e revenido, com o objetivo de avaliar a magnitude do parâmetro “composição gasosa” nas propriedades metalúrgicas das camadas formadas após a nitretação. Para a realização deste trabalho foram necessárias adaptações do forno e experimentos prévios para verificar a influência do posicionamento das peças na câmara. Todas as superfícies nitretadas para o estudo das misturas gasosas, foram caracterizadas quanto aos seguintes parâmetros: dureza superficial, perfis de dureza e de composição química, fases formadas nas primeiras regiões da superfície, espessura da camada branca, tenacidade superficial, rugosidade e morfologia topográfica. As amostras provenientes do estudo das variáveis térmicas da câmara foram estudadas quanto à espessura da camada branca e perfis de dureza e composição química. Encontrou-se que as variáveis térmicas são determinantes em termos de alterações no processo e que, cuidados com simetria, devem ser levados em consideração em estudos similares em equipamentos sem aquecimento auxiliar nas paredes. Verificou-se também amplas variações nas propriedades microestruturais das amostras tratadas sob as diferentes misturas gasosas postas em uso e, foi possível sugerir com base nos resultados e na literatura, aplicações para alguns dos casos estudados. / In this work various plasma nitriding and plasma nitrocarburizing treatments with hardened and tempered AISI 4140 steel were carried out. The main aim was evaluating the gas mixture influence on metallurgical properties of plasma nitriding and nitrocarburizing layers. For the realization of this study, furnace adaptations and previous experiments in order to verify the parts position influence on final treatments results were necessary. The samples that were nitrided in previous experiments were characterized concerning of compound layer, hardness and chemical composition profiles. All nitride surfaces, were characterized with the parameters: surface hardness, hardness and chemical composition profiles, phases composition on surface, thickness of compound layer, surface toughness, surface roughness and topographical morphology. It was found that thermal parameters are determinants in order to modify the process. Care must be taken about symmetry with this kind of equipment that have no auxiliary heating wall. Later, large variations on microstructural properties in samples under different gas conditions were verified and applications to some cases were proposed.

Neste trabalho realizaram-se varias nitretações e nitrocarbonetações a plasma em um aço AISI 4140 temperado e revenido, com o objetivo de avaliar a magnitude do parâmetro “composição gasosa” nas propriedades metalúrgicas das camadas formadas após a nitretação. Para a realização deste trabalho foram necessárias adaptações do forno e experimentos prévios para verificar a influência do posicionamento das peças na câmara. Todas as superfícies nitretadas para o estudo das misturas gasosas, foram caracterizadas quanto aos seguintes parâmetros: dureza superficial, perfis de dureza e de composição química, fases formadas nas primeiras regiões da superfície, espessura da camada branca, tenacidade superficial, rugosidade e morfologia topográfica. As amostras provenientes do estudo das variáveis térmicas da câmara foram estudadas quanto à espessura da camada branca e perfis de dureza e composição química. Encontrou-se que as variáveis térmicas são determinantes em termos de alterações no processo e que, cuidados com simetria, devem ser levados em consideração em estudos similares em equipamentos sem aquecimento auxiliar nas paredes. Verificou-se também amplas variações nas propriedades microestruturais das amostras tratadas sob as diferentes misturas gasosas postas em uso e, foi possível sugerir com base nos resultados e na literatura, aplicações para alguns dos casos estudados. / In this work various plasma nitriding and plasma nitrocarburizing treatments with hardened and tempered AISI 4140 steel were carried out. The main aim was evaluating the gas mixture influence on metallurgical properties of plasma nitriding and nitrocarburizing layers. For the realization of this study, furnace adaptations and previous experiments in order to verify the parts position influence on final treatments results were necessary. The samples that were nitrided in previous experiments were characterized concerning of compound layer, hardness and chemical composition profiles. All nitride surfaces, were characterized with the parameters: surface hardness, hardness and chemical composition profiles, phases composition on surface, thickness of compound layer, surface toughness, surface roughness and topographical morphology. It was found that thermal parameters are determinants in order to modify the process. Care must be taken about symmetry with this kind of equipment that have no auxiliary heating wall. Later, large variations on microstructural properties in samples under different gas conditions were verified and applications to some cases were proposed.

Master of Science / Department of Biological & Agricultural Engineering / Donghai Wang / Gums are water-soluble polysaccharides used in many industrial and food applications because of their functions such as thickening, gelling, emulsification, adhesion, and encapsulation. Interactions between gums are conducted to enhance functional properties of finished products and reduce processing costs. In this study, camelina gum, from the oil-seed plant Camelina sativa, is characterized by carbohydrate composition and morphological, thermal, and rheological properties. Interactions with xanthan gum, galactomannans guar gum, and locust bean gum (LBG) are also studied. Camelina gum is composed of arabinose, rhamnose, galactose, glucose, xylose and mannose; according to high-performance anion exchange chromatography analysis. Scanning electron microscopy and transmission electron microscopy images showed camelina gum with fibrillar structure and intermeshed network. Camelina gum solutions exhibited a shear thinning flow behavior in a range of concentrations (0.1% to 2.0% w/w) and shear rate (0.001 sˉ¹ to 3000 sˉ¹). Camelina gum is temperature independent at temperature ranges from 4 °C to 90 °C. The apparent viscosity increased as gum concentration increased. Mechanical properties of camelina gum demonstrated viscoelastic behavior with entangled molecular chains. Interaction of camelina gum with monovalent salt NaCl significantly reduced the viscosity of camelina gum solution at 1% when NaCl concentration increased. Camelina gum is soluble in water up to 60% ethanol content, in which the rheological properties do not significantly differ from camelina gum in water solution only. A synergy with xanthan and galactomannans was determined. All mixtures exhibited shear-thinning flow behavior, solid-like behavior at low frequencies, and liquid-like behavior at high frequencies. For camelina-galactomannans mixtures, synergistic interactions occurred in LBG-camelina mixtures at ratios of 1:1 and 3:1. For xanthan-camelina mixture, maximum synergy was observed at the ratio 1:1. Synergistic effects of gum mixtures suggest dependency on the ratios and chemical structures of the gums. The effect of temperature on apparent viscosity of mixtures is not significant. Results showed that camelina gum can be used for commercial applications.

Made available in DSpace on 2014-10-09T12:55:24Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:13Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Neste trabalho realizaram-se varias nitretações e nitrocarbonetações a plasma em um aço AISI 4140 temperado e revenido, com o objetivo de avaliar a magnitude do parâmetro “composição gasosa” nas propriedades metalúrgicas das camadas formadas após a nitretação. Para a realização deste trabalho foram necessárias adaptações do forno e experimentos prévios para verificar a influência do posicionamento das peças na câmara. Todas as superfícies nitretadas para o estudo das misturas gasosas, foram caracterizadas quanto aos seguintes parâmetros: dureza superficial, perfis de dureza e de composição química, fases formadas nas primeiras regiões da superfície, espessura da camada branca, tenacidade superficial, rugosidade e morfologia topográfica. As amostras provenientes do estudo das variáveis térmicas da câmara foram estudadas quanto à espessura da camada branca e perfis de dureza e composição química. Encontrou-se que as variáveis térmicas são determinantes em termos de alterações no processo e que, cuidados com simetria, devem ser levados em consideração em estudos similares em equipamentos sem aquecimento auxiliar nas paredes. Verificou-se também amplas variações nas propriedades microestruturais das amostras tratadas sob as diferentes misturas gasosas postas em uso e, foi possível sugerir com base nos resultados e na literatura, aplicações para alguns dos casos estudados. / In this work various plasma nitriding and plasma nitrocarburizing treatments with hardened and tempered AISI 4140 steel were carried out. The main aim was evaluating the gas mixture influence on metallurgical properties of plasma nitriding and nitrocarburizing layers. For the realization of this study, furnace adaptations and previous experiments in order to verify the parts position influence on final treatments results were necessary. The samples that were nitrided in previous experiments were characterized concerning of compound layer, hardness and chemical composition profiles. All nitride surfaces, were characterized with the parameters: surface hardness, hardness and chemical composition profiles, phases composition on surface, thickness of compound layer, surface toughness, surface roughness and topographical morphology. It was found that thermal parameters are determinants in order to modify the process. Care must be taken about symmetry with this kind of equipment that have no auxiliary heating wall. Later, large variations on microstructural properties in samples under different gas conditions were verified and applications to some cases were proposed.

Made available in DSpace on 2014-10-09T12:55:24Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:13Z (GMT). No. of bitstreams: 0 / Este trabalho trata da avaliação da compressibilidade de misturas de pós de nióbio e alumínio, previamente ativadas por moagem de bolas de alta energia. Foram variados o tempo de moagem e a quantidade de ácido esteárico, adicionado como agente controlador de processo (ACP), assim como o tamanho médio de partícula do pó de alumínio. Os pós de partida e as misturas moídas foram caracterizados por microscopia eletrônica de varredura (forma das partículas) e por difração de raios laser (distribuição granulométrica). Uma máquina universal de ensaios foi utilizada nos testes de compressibilidade mediante compactação das amostras numa matriz cilíndrica de aço-ferramenta. Os dados de compressibilidade foram comparados graficamente segundo curvas de densidade (relativa) versus pressão. As diferenças de comportamento na compactação das amostras foram correlacionadas com as diferentes condições de moagem. Houve um decréscimo da compressibilidade com o aumento do tempo de moagem e da quantidade de ACP. Menos compressíveis foram também as misturas provenientes do pó de alumínio com maior tamanho de partícula. Uma nova equação de compactação foi ainda proposta, cujo ajuste aos dados deste trabalho foi superior aos verificados nas equações de modelos anteriormente publicados. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Species diversity achieved by adding novel functional groups (warm-season grasses and non-leguminous forbs) to pasture land, along with traditional grasses and legumes, could aid in the capture of nutrients and water in pasture systems by offering complementary rooting architecture to aid in water and nitrogen uptake and decrease nitrogen leaching. Because these species may differ from commonly used grasses and legumes in their seasonal pattern of productivity, they could also extend or enhance growing-season productivity. The goal of this project is to better understand the role of plant diversity in 1) nitrogen use and 2) distribution of rooting dynamics and forage production. On a larger scale, this project hopes to identify pasture mixtures with greater diversity and management practices that maintain desirable pasture composition and livestock productivity. Herbage dry mass (DM), root surface area (RSA), and 15N uptake of nine species grown individually in the greenhouse were measured in the first experiment. Species which performed well or which were of particular interest to our study were used in mixtures in the second experiment, which contained varying numbers of functional groups. Individual species grown in monoculture varied in DM production over the course of the experiment, but there were no differences among mixtures, which all increased similarly in DM. Herbage DM of mixtures was 72 to 110% of that predicted by Experiment 1. The RSA of tap-rooted species was low and varied little with depth, while the RSA of cool-season grasses was higher closer to the soil surface. The RSA of mixtures decreased linearly with increased depth, and was between 150 and 350% higher than predicted from the RSA of individual species. Legumes, which have higher foliar protein content than grasses, accumulated more 15N in shoot DM than grasses, but mixtures did not differ from one another. It is concluded that the DM production advantage of mixtures is more consistent yield. Furthermore, increasing the diversity of simple grass-legume mixtures by adding non-leguminous forbs or other functional groups will likely improve water-use efficiency, thus reducing the risk of nitrate leaching compared with low-diversity grass-legume mixtures while fully exploiting biological nitrogen fixation.