Made available in DSpace on 2014-10-09T12:25:36Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:46Z (GMT). No. of bitstreams: 1 06790.pdf: 5752105 bytes, checksum: 9b66a692f462ce07b2dd97fe9220e337 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:43:06Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:46Z (GMT). No. of bitstreams: 1 06210.pdf: 5391897 bytes, checksum: 31d1e55c71f38af31061fa75495c605f (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:48:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:05Z (GMT). No. of bitstreams: 1 09457.pdf: 6812101 bytes, checksum: 35494be3477476dfbf537e0b66e982b7 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Orientadores: Sandra Cristina dos Santos Rocha, Virginia Aparecida da Silva Moris / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-13T14:24:52Z (GMT). No. of bitstreams: 1 Costa_SuzaraSantos_M.pdf: 3149435 bytes, checksum: 4253d824e6807a4d4dabe9f5337e4982 (MD5) Previous issue date: 2009 / Resumo: O leito vibrofluidizado (LVF) consiste na aplicação de vibração mecânica ao leito fluidizado convencional com o objetivo de reduzir a ocorrência de bolhas, canais preferenciais e evitar o fenômeno da de fluidização em processos como recobrimento, granulação, entre outros. A utilização do LVF é diversificada para materiais coesivos, adesivos, aglomerados e pastosos. A granulação consiste no aumento da partícula mediante a incorporação de materiais ativos e/ou inertes e é um importante processo utilizado com o objetivo de melhorar aspecto, manuseio, compactação e transporte de partículas finas. Esse processo é bastante encontrado na literatura com o uso em leitos fluidizados convencionais, contudo, o processamento de materiais que possuem forças interpartículas intensas quando sujeitos a aspersão de ligantes, torna-se difícil e dispendioso. A celulose microcristalina é originada da hidrólise ácida da celulose e utilizada, entre outros usos industriais, como estabilizante e aditivo alimentício. Na indústria farmacêutica, é um dos excipientes mais utilizados em formulações de dosagem oral. Baseado no exposto foi realizado um estudo sobre a granulação da celulose microcristalina em leito vibrofluidizado, utilizando como ligante solução de matodextrina 35%. A solução foi aspergida sobre o leito de partículas através de um sistema de atomização acoplado ao leito vibrofluidizado. Foi desenvolvido um planejamento experimental fatorial fracionário (25-1), cujas variáveis operacionais foram: amplitude (A) e frequência (f) de vibração, pressão de atomização (P), temperatura do ar de entrada (T) e vazão de solução (Q). Os níveis das variáveis de entrada no planejamento foram: 0,01m e 0,02m; 3 Hz e 6 Hz, 5 Psig e 15 Psig, 60ºC e 80ºC e 4 ml/min e 10 ml/min, respectivamente. O planejamento foi desenvolvido com 4 repetições no ponto central. Para avaliar a qualidade do produto foram analisadas três variáveis de resposta, que resultaram nas seguintes faixas: crescimento da partícula - 3,17% a 33,11%, ângulo de repouso - 8,4º a 12º e índice de aglomerados - 0,2% a 5,69%. Com o experimento estatisticamente planejado constatou-se que todas as variáveis independentes influenciaram as variáveis de resposta consideradas e, portanto, não foi possível estabelecer um planejamento completo com um número menor de variáveis. O comportamento fluidodinâmico da celulose microcristalina antes da granulação também foi estudado. As curvas obtidas refletiram um comportamento característico encontrado na literatura de leitos vibrofluidizados. A fluidodinâmica do material permitiu, embora com dificuldade, determinar a velocidade de mínima fluidização (pelo método convencional da interseção das retas em leitos fluidizados) e velocidade de mínima fluidização completa para leitos vibrofluidizados. A velocidade de mínima mistura do material também foi determinada, mas por observação visual durante os experimentos. A velocidade de operação foi estabelecida em 0,30 m/s após os ensaios preliminares de fluidodinâmica e de granulação. O produto final obtido após o processo de granulação apresentou boa escoabilidade e um aumento no seu diâmetro médio de Sauter, confirmando a granulação da celulose microcristalina e revelando o leito vibrofluidizado como equipamento promissor para efetuar o processo de granulação. / Abstract: The vibrofluidized bed (VFB) consists in applying mechanical vibration to the conventional fluidized bed to reduce the occurrence of bubbles, preferential channeling and defluidization phenomena, which are common when fluidizing cohesive, adhesive and paste materials. Granulation is used to increase particle size through incorporation of active materials and/or inert and it is a very important process to improve the appearance, handling and transport of fine particles. Granulation is usually conducted using conventional fluidized beds; however, the processing of powders having high interparticle forces, when subjected to intense spraying of binders, is difficult and expensive. Microcrystalline cellulose is a fine powder that is originated from acid hydrolysis of cellulose and is used, among other industrial uses, as a stabilizer, food additive and carrier in drugs. This work reports the analysis of wet granulation of microcrystalline cellulose in a vibrofluidized bed using an aqueous maltodextrina solution as binder. A factorial experimental design (25-1) was developed with the independent variables: vibration amplitude (A) and frequency (f), atomization pressure (P), inlet air temperature (T) and maltodextrin solution flow rate (Q). The responses analyzed were in the following levels: particle growth - 3.17% to 33.11%, angle of repose - 8.4º to 12º and percentage of lumps - 0.2% to 5.69%. The statistical analysis of the experimental design was able to determine that all the independent variables showed significant influence on the process and so it was not possible to perform an experimental design with a smaller number of variables. The fluid dynamics of the bed of microcrystalline cellulose before granulation was also analyzed and it presented the behavior of fluid dynamic curves of vibrofluidized beds found in the literature. In spite of the difficulty, the fluid dynamic curves allowed to determine the minimum fluidization velocity (conventional method of intersection of straight lines of fixed and fluidized regions) and complete minimum fluidization for vibrofluidized beds. The velocity of minimum mixture was also determined, by visual observation. The operation velocity was set at 0.30 m/s based on the dynamic tests and preliminary tests of granulation. The final product showed excellent flowability and generated an increase in its mean Sauter diameter, thus confirming the granulation of microcrystalline cellulose and showing the vibrofluidized bed as promising equipment for this process. / Mestrado / Engenharia de Processos / Mestre em Engenharia Química

Orientador: Anselmo Eduardo Diniz / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-23T04:12:20Z (GMT). No. of bitstreams: 1 Carvalho_MartaReginaDelleDonne_M.pdf: 17580883 bytes, checksum: f1ff52988b201685207f750165cbc037 (MD5) Previous issue date: 2013 / Resumo: O resumo poderá ser visualizado no texto completo da tese digital / Abstract: The abstract is available with the full electronic document / Mestrado / Materiais e Processos de Fabricação / Mestra em Engenharia Mecânica

Kafirin, the prolamin protein of sorghum grain, could be extracted from the by-products of the sorghum processing industry and used to make films and coatings for food packaging, in particular to extend the shelf-life of fruits and nuts. Protein-based films can be an environment-friendly alternative to synthetic plastic packaging systems. However, the properties of protein-based films are generally inferior to those of synthetic plastics. Modification can alter the properties of protein-based films. In this project, the interaction between phenolic compounds and kafirin was investigated in relation to their potential to modify kafirin films. A range of phenolic compounds was tested in terms of their ability to bind and complex with kafirin in an in vitro binding assay. The protein-phenolic compound interaction was quantified by haze formation and colorimetric determination of total polyphenol bound. Ferulic acid, catechin and extracted flavonoids from condensed tannin-free sorghum did not complex with kafirin. Tannic acid (TA) and sorghum condensed tannins (SCT) complexed kafirin and formed haze. Thus, T A and SCT were selected as potential modifying agents for kafirin films. TA and SCT were added at up to 20% (w/w tannin to protein basis) during kafirin film casting. Both TA and SCT bound to kafirin in the film. Scanning electron microscopy showed that TA modified films were less porous; and the SCT modified films appeared more globular in structure than unmodified film. Modification with both tannins increased the tensile stress and Young's modulus and decreased the tensile strain of the kafirin films. Oxygen permeability of the modified films was decreased, but no change in the apparent water vapour permeabilty. The T9 of the films increased with increased modification level. SOS-PAGE, FT-IR and Raman spectroscopy were used to study TA and SCT interaction with kafirin. SOS-PAGE revealed a high Mr band for kafirin-SCT complexes which did not enter the separating gel. FT-IR of kafirin complexed tannins and tannin modified films showed a decrease in the absorbance at the frequency of about 1620 cm-1, suggesting a decrease in â-sheet structures. FT-IR results also suggested that the â-sheets of kafirin in dry form were probably changed into random coils during kafirin dissolution to make films. Raman spectra showed a shift in the TA peak at about 1710 cm-1 to about 1728 cm-1 in the kafirin- TA complexes, suggesting participation of the carbonyl groups of TA in TA-kafirin interaction. It is proposed that hydroxyl groups of tannin can form hydrogen bonds with carbonyl groups of random coils of kafirin during film casting. Thus, the carbonyl groups are probably not available to be reorganized into â-sheets. The other possible mode of interaction can be hydrophobic interaction between the aromatic rings of tannins and the pyrrolidine rings of proline. Because tannins have numerous aromatic rings with hydroxyl groups, it is also proposed that they can bind with more than one polypeptide chain at the same time to cross-link kafirin. This cross-linking probably produces a high Mr kafirin-tannin complex that leads to haze. The cross-linking would also lead to lower molecular mobility of modified kafirin films. This could decrease oxygen permeability, probably as a result of decreased free volume. Cross-linking could also be responsible for the increased tensile stress and decreased tensile strain of modified kafirin films. The higher tensile stress of modified• kafirin films suggests that they can have the potential to form stronger coatings around fruit such as litchi fruit to possibly reduce pericarp microcracking as an example, and thus may reduce the pericarp browning of litchi. The lower oxygen permeability of the modified films and the potential antioxidant activity of the tannins suggest that these films can be a good coating to prevent rancidity of nuts. / Thesis (PhD (Food Science))--University of Pretoria, 2006. / Food Science / unrestricted

Minimally processed fruits and vegetables are increasingly demanded by local consumers and for export purposes. However, the marketing potential of these produce is limited because of physiological ageing, biochemical changes and microbiological spoilage that lead to a short shelf life. The use of polymeric packaging films to control microbial and metabolic processes and edible coatings to control the white blush formation respectively, have shown potential in improving the quality of minimally processed carrots. In combination they may form a double barrier to gases and water vapour that could provide an interaction effect to enhance the shelf life of minimally processed carrots. The aim of the study was to determine the effects of the polymeric packaging films of different permeability and edible coatings at different levels of concentration, alone and in combination on the physiological and biochemical, microbiological, and sensory quality of minimally processed carrots. A factorial experiment of 3 polymeric packaging films x 3 levels of edible coating was conducted. The three polymeric packaging films were P-Plus®, an oriented polypropylene which were fully permeable to gases and water vapour (pi, control), semi permeable (p160) and least permeable (p90) to gases only. The semi permeable and least permeable packaging had similar water vapour permeability. The coating was Nature Seal®, a cellulose based, at 0% (control), 7.5% and 15% w/w. Carrots were minimally processed into slices, dipped in the edible coating, then packed in the polymeric films and stored for 12 days at 10°C. Four packs were analysed for each combination treatment on d4, d8 and d12, and dO was taken as reference point. With time, the head space in the semi permeable packaging (p160) showed a decrease to about 11.5-13.6% oxygen and an increase to about 7.5-9.6% carbon dioxide. The least permeable pack (p90) showed an oxygen decrease to about 9.8-7.6% and a carbon dioxide increase to about 12.3-13.5%. This change showed the creation of a modified atmosphere that will decrease the metabolic activities. As the coating concentration increased, a slight increase in carbon dioxide and a slight decrease in oxygen were recorded in the head space of the packs. This change was unexpected as the coating was supposed to be a gas barrier. Thus, this change questioned the gas permeability properties of the edible coating. The polymeric packaging and the coating interacted to give lower oxygen and higher carbon dioxide levels in the head space atmosphere. However, packaging had a more pronounced effect in the creation of the modified atmospheres than the coating. A lower white blush formation and a higher retention of chroma values was recorded on the lower surfaces of the carrot slices than on the upper surfaces (upper surfaces refer to those that were facing the packaging material, the lower surfaces was the opposite side of the upper surfaces). This showed that the relative humidity gradient was probably not the same between the surfaces. The coating effectively controlled the white discolouration and maintained higher chroma values on both surfaces of the carrot discs, but packaging did not affect the colour changes of the upper surfaces. An interaction effect was also observed between the packaging and coating showing a better control of the white blush formation of the lower surfaces of the carrot discs. Yeast and moulds did not prove to be a problem in minimally processed carrots as they were lower than 103 cfu/g carrots throughout the storage period. When the carrots were visibly spoiled, the lactic acid bacteria were over 106 cfu/g and the psychrotrophs were about 107 to 108 cfu/g. Initially, a high growth rate of psychrotrophic bacteria occurred followed by a high growth rate of the lactic acid bacteria. This showed a dynamic relationship between the two microbes. Visible rot was observed by brown discolouration, tissue softening and exudate production. The packaging controlled the microbiological growth and spoilage as compared with the coating that enhanced it. A decrease in pH from d4 to d12 corresponded to an increase in the lactic acid bacteria and visible spoilage. Combination of edible coatings and polymeric packaging films did not show any synergistic or additive effects to enhance the shelf life of minimally processed carrots despite some interactions between these two variables. This was because the polymeric packaging films primarily prevented microbiological growth and spoilage, whereas edible coatings partly controlled white blush formation. White blush formation was the most important shelf life determinant of minimally processed carrots. Research efforts should therefore be focused on overcoming this defect. / Dissertation (MSc (Food Science))--University of Pretoria, 2007. / Food Science / unrestricted

Aluminium alloys are frequently pre-treated by a conversion coating before application of an organic coating in order to improve the corrosion resistance and adhesive properties of the surface and the corrosion resistance provided by the system. Chromate-containing conversion coatings are commonly used for this purpose. However, legislation limits future use of hexavalent chromium compounds due to their toxic and carcinogenic nature. Therefore, alternative, so-called chromium-free conversion coatings are being developed that are more environmentally-compliant.The purpose of the present work has therefore been to contribute to a better understanding of how the aluminium substrate affects the formation and properties of conversion coatings for adhesive bonding. In particular, a chrome-free zirconium-based conversion treatment process has been investigated as a possible replacement for conventional chromate conversion treatment. The influence of the conversion time on the thickness of the formed layer on pure aluminium was investigated using complementary surface analytical techniques. The conversion time was varied between 30 and 600 seconds.In this study, the structure and composition of zirconium-based chromium-free conversion coatings on magnetron sputtered superpure aluminium and a range of aluminium-copper alloys were characterised as a function of immersion time in the aqueous conversion bath to understand the mechanism of coating formation and protection. However, the presence of copper significantly influences the coating development and ultimately the performance of the conversion coatings formed on binary copper-containing aluminium alloys.The morphology and composition of the coatings have been probed using transmission electron microscopy, Rutherford backscattering spectroscopy and glow discharge optical emission spectroscopy, with loss of substrate through growth of the conversion coating also quantified. A comparison of the RBS spectra obtained for the superpure aluminium specimens after different immersion times revealed that zirconium (Zr) and oxygen (O) peaks were wider for longer immersion times, indicating thickening of the coating with increased immersion times. Thus, increasing the immersion time resulted in an increase in coating thickness but little change in coating composition occurred as determined by the RBS RUMP simulations. Alloying decreases the coating thickness, as well as metal consumption. Here, aspects of the corrosion behaviour of superpure aluminium and aluminium-copper alloys were also considered using electronoptical, electrochemical and surface analytical probing. The influence that short and prolonged treatment times exert on the performances of such conversion coating is discussed. The conversion coating formed after 60 s and 180 s of immersion in the zirconium-based conversion coating bath provide good corrosion resistance which can be attributed to the high stability of the compounds that constitute the surface oxide layer, and good adhesion properties.

Owing to an increased risk of aging population and a higher incidence of coronary artery disease (CAD), there is a need for more reliable and safer treatments. Numerous varieties of durable polymer-coated drug eluting stents (DES) are available in the market in order to mitigate in-stent restenosis. However, there are certain issues regarding their usage such as delayed arterial healing, thrombosis, inflammation, toxic corrosion by-products, mechanical stability and degradation. As a result, significant amount of research has to be devoted to the improvement of biodegradable polymer-coated implant materials in an effort to enhance their bioactive response. In this investigation, magneto-electropolished (MEP) and a novel biodegradable polymer coated ternary Nitinol alloys, NiTiTa and NiTiCr were prepared to study their bio and hemocompatibility properties. The initial interaction of a biomaterial with its surroundings is dependent on its surface characteristics such as, composition, corrosion resistance, work of adhesion and morphology. In-vitro corrosion tests such as potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) studies were conducted to determine the coating stability and longevity. In-vitro hemocompatibility studies and HUVEC cell growth was performed to determine their thrombogenic and biocompatibility properties. Critical delamination load of the polymer coated Nitinol alloys was determined using Nano-scratch analysis. Sulforhodamine B (SRB) assays were performed to elucidate the effect of metal ions leached from Nitinol alloys on the viability of HUVEC cells. Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), contact angle meter and X-ray diffraction (XRD) were used to characterize the surface of the alloys. MEP treated and polymer coated (PC) Nitinol alloys displayed a corrosion resistant polymer coating as compared to uncoated alloys. MEP and PC has resulted in reduced Ni and Cr ion leaching from NiTi5Cr and subsequently low cytotoxicity. Thrombogenicity tests revealed significantly less platelet adhesion and confluent endothelial cell growth on polymer coated and uncoated ternary MEP Nitinol alloys. Finally, this research addresses the bio and hemocompatibility of MEP + PC ternary Nitinol alloys that could be used to manufacture blood contacting devices such as stents and vascular implants which can lead to lower U.S. healthcare spending.

Thermal Barrier Coatings (TBC) are used to shield hot sections of gas turbine engines, helping to prevent the melting of metallic surfaces. TBC is a sophisticated layered system that can be divided into top coat, bond coat, and the super-alloy substrate. The highly heterogeneous microstructure of the TBC consists of defects such as pores, voids, and cracks of different sizes, which determine the coating’s final thermal and mechanical properties. The service lives of the coatings are dependent on these parameters. These coatings act as a defensive shield to protect the substrate from oxidation and corrosion caused by elevated temperatures. Yttria Stabilized Zirconia (YSZ) is the preferred thermal barrier coating for gas turbine engine applications. There are a certain number of deposition techniques that are used to deposit the thermal coating layer on the substrate; commonly used techniques are Air Plasma Sprayed (APS) or Electron Beam Physical Vapour Deposition (EB-PVD). The objective of this thesis is to model an optimized TBC that can be used on next-generation turbine engines. Modelling is performed to calculate the effective thermal conductivity of the YSZ coating deposited by EB-PVD by considering the effect of defects, porosities, and cracks. Bruggeman’s asymmetrical model was chosen as it can be extended for various types of porosities present in the material. The model is used as an iterative approach of a two-phase model and is extended up to a five-phase model. The results offer important information about the influence of randomly oriented defects on the overall thermal conductivity. The modelled microstructure can be fabricated with similar composition to have an enhanced thermal insulation. The modelling results are subsequently compared with existing theories published in previous works and experiments. The modelling approach developed in this work could be used as a tool to design the porous microstructure of a coating.