Made available in DSpace on 2014-12-17T15:41:46Z (GMT). No. of bitstreams: 1 MoisesRCpdf.pdf: 4615723 bytes, checksum: 8e0d75d3465b34a6f59e81df4ba5830e (MD5) Previous issue date: 2009-02-04 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The present work aims the preparation of filmes of strontium-doped lanthanum manganite (perovskita) yttria-stabilized zirconia (LSM-SDC) films deposited on substrate of YSZ by means of spin coating technique having as principal objective their application to solid oxide fuel cells of intermediate temperature. La0,8Sr0,2MnO3 and Ce0,8Sm0,2O1,9 were obtained by modified Pechini method by use of gelatin which act as polymerization agent. The powders obtained were characterized by Xray fluorescence, X ray diffraction, electronic scanning microscopy and the superficial area by BET method. The results obtained by X-ray fluorescence showed that the route adopted for obtention of powders was effective in the obtention of the compositions with close values to the stoichiometrics. Ethyl cellulose was used as pore-forming agent and mixed with the LSM-SDC powders in weight proportions of 1:24, 2:23 and 1:9. The films were sintered at 1150 ?C for 4 h and characterized by X-ray diffraction and scanning electron microscopy technique (SEM) and atomic force. The phases quantification of the precursory powders and of the obtained films was carried through Rietveld method. According with the analysis of SEM, as the content of ethyl cellulose was increased, the pore distribution in films become more uniform and the pore size reduced. The methodology used for the obtention of the films was very efficient, considering a material was obtained with characteristics that were proper to the application as electrolyte/cathode system to solid oxide fuel cells / O trabalho trata da prepara??o de filmes de manganita de lant?nio dopado com estr?ncio (perovskita) c?ria dopada com sam?rio (LSM-SDC) sobre substrato de zirc?nia estabilizada com ?tria (YSZ) pela t?cnica spin coating, para utiliza??o em c?lulas a combust?vel de ?xido s?lido de temperatura intermedi?ria. Neste trabalho, La0,8Sr0,2MnO3 e Ce0,8Sm0,2O1,9 foram obtidos pelo m?todo Pechini modificado pelo uso de gelatina que atua como agente polimerizante e quelante. Os p?s obtidos foram caracterizados por fluoresc?ncia de raios-X, difra??o de raios-X, microscopia eletr?nica de varredura e determina??o da ?rea superficial pelo m?todo BET. Os resultados obtidos por fluoresc?ncia de raios-X mostraram que a rota adotada para obten??o dos p?s foi eficaz na obten??o da composi??o com valores pr?ximos ao estequiom?trico. A etilcelulose foi usada como agente formador de poros e foi misturada ao p?s de LSM-SDC em propor??es m?ssicas de 1:24, 2:23 e 1:9. Os filmes foram tratados termicamente a 1150 ?C por quatro horas e caracterizados estruturalmente pela t?cnica de difra??o de raios X e morfologicamente pelas t?cnicas de microscopia eletr?nica de varredura e for?a at?mica. A quantifica??o das fases dos p?s precursores e dos filmes obtidos foi realizada atrav?s do refinamento Rietveld. De acordo com a an?lise de MEV, quando a quantidade de etilcelulose foi aumentada, a distribui??o dos poros nos filmes tornou-se mais uniformes e o tamanho de poros reduzidos. A metodologia empregada para a obten??o dos filmes mostrou-se satisfat?ria, considerando que foi obtido um material com caracter?sticas apropriadas para a aplica??o como sistema eletrodo/eletr?lito em c?lulas a combust?vel de ?xido s?lido (SOFC)

La projection plasma sous très basse pression (communément désignée par son acronymeanglais VLPPS : « Very Low Pressure Plasma Spraying ») est un procédé émergent de traitement desurface par voie sèche permettant l’élaboration de dépôts métalliques et céramiques (type oxydes),sous des conditions de pression réduite, de l'ordre d'une centaine de Pascal, par utilisation d'un jet deplasma thermique. Un tel niveau de pression permet principalement la formation de dépôts parcondensation de vapeurs résultant de la vaporisation, partielle ou totale, des précurseurshabituellement sous forme solide. C'est principalement en cela que ce procédé diffère des procédésplus conventionnels de projection thermique, conduisant à la formation de dépôts par l'écrasement, lasolidification et l'empilement de particules liquides fondues dans un jet de forte énergie. En fonctiondes conditions de projection employées, les revêtements élaborés par VLPPS peuvent présenterdifférents types de microstructure, de colonnaires à lamellaires, de très denses à poreuses. Le modemixte de construction, caractérisé par la présence de vapeurs condensées et particules fonduesresolidifées peut également être rencontré.L'objectif global de ce travail est d'explorer le potentiel du procédé VLPPS en mode réactif envue de former des dépôts de matériaux présentant une fusion non congruente. Pour ce faire,l'aluminium et le titane ont été considérés comme matériaux métalliques précurseurs et l'azote commeélément réactif. Les matériaux qui pourraient résulter seraient alors des nitrures d'aluminium et detitane. Ces matériaux ont été sélectionnés avant tout comme matériaux démonstrateurs. Desapplications potentielles pourraient cependant rapidement déboucher en cas de performancessatisfaisantes : l'élaboration, sur de grandes surfaces, de couches de nitrures de titane et d'aluminium,présentant de bonnes résistances à l'oxydation ainsi que de bonnes propriétés tribologiques,notamment une résistance élevée à l'usure.Au cours de cette étude, des dépôts métalliques d’aluminium, titane et titane-aluminium et desdépôts composites nitrurés Al-AlN, Ti-TiN et TiAl-TiAlN ont été élaborés par projection VLPPS enmode réactif. Les dépôts composites nitrurés présentent par exemple des duretés moyennes plusimportantes que celles des dépôts métalliques. Ces dépôts renferment jusqu'à 30%at. d'azote et lescomposés TixN, AlN et TixAlN ont été clairement identifiés. / The Very Low Pressure Plasma Spraying (VLPPS) is an emerging deposition process tomanufacture metallic and ceramic coatings, under a very low surrounding pressure, typically about onehundred Pascal, thanks to a thermal plasma jet. Such a pressure range allows principallymanufacturing coatings by condensation of vapors resulting from the vaporization, partial or total, ofsolid precursors, in most of the cases. This is the main difference of this process compared to moreconventional thermal spray processes, which form coatings by spreading, solidification and stacking ofparticles melted in a high energy jet. Depending upon the spray operating conditions, coatingsmanufactured by VLPPS exhibit different types of microstructures, from columnar to lamellar, fromdense to porous. The coating building dual mode, made of condensed vapors and molten particles isalso possible.The aim of this work is to explore in a reactive mode the VLPPS potential to manufacturecoatings made of materials exhibiting a non-congruent melting behavior. Here, for a demonstrationpurpose, Aluminum and Titanium were considered as the metallic precursors and Nitrogen as thereactive element. Therefore, materials which could result would be Aluminum and Titanium nitrides.Some possible applications could result directly from this study: the manufacturing on large surfacesof Aluminum and Titanium nitride layers, exhibiting good oxidation resistance and tribologicalproperties, especially a high wear resistance.In this study, metallic coatings of Aluminum, Titanium and Aluminum-Titanium and Al-AlN,Ti-TiN and TiAl-TiAlN coatings were manufactured by reactive VLPPS. Nitrided composite coatingsexhibit, for example, higher average hardness than metallic coatings, Those coatings embed up to 30at.% of Nitrogen and TixN, AlN and TixAlN compounds were clearly identified.

Ceria (CeO2), chromia (Cr2O3), yttria-stabilized zirconia (Y2O3-ZrO2), and sodium cerium oxide (Na2CeO3) were used as barrier coatings on Ufala, an alumina-based ceramic refractory, to determine if they were effective at increasing the life of the refractory in a high-temperature black liquor gasification environment. The ceria, chromia, and yttria-stabilized zirconia coatings were applied at atmospheric pressure using a coating applicator at the Institute of Paper Science and Technology at the Georgia Institute of Technology. The sodium cerium oxide coatings in addition to the three other coating types were applied under atmospheric pressure at C3 International Technologies in Alpharetta, GA. The coated refractory, as well as a set of uncoated refractory used for baseline analysis, were tested using molten synthetic smelt at 1000C for 36 hours. Uncoated refractory samples were also tested for 12, 72, 120, and 168 hours in order to make a kinetic reaction rate determination. The refractory were analyzed using gravimetric and dimensional analysis, X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy to determine the severity of the physical changes that occurred after exposure to molten smelt. The data gathered from these experiments were not able to conclude that barrier coatings are sufficient to impede corrosion of the Ufala refractory material in molten smelt.

The effects of edible chitosan coating on quality factors of pomegranate (Punica granatum) arils were investigated in the present research. For that purpose, pomegranate arils were treated with 0% (control) and 1% chitosan (extracted from shrimp shells and deacetylated (.75%)) solutions and stored at 4

Thermal energy storage (TES) is one of the most attractive and cost effective solutions to the intermittent generation systems like solar, wind and other renewable sources, compared to alternatives. It creates a bridge between the power supply and demand during peak hours or at times of emergency to ensure the continuous supply of energy. Among all the TES systems, latent heat thermal energy storage (LHTES) draws lots of interests as it has high energy density and can store or retrieve energy isothermally. Two major technical challenges associated with the LHTES are low thermal conductivity of the phase change materials (PCMs), and corrosion tendency of the containment vessel with the PCMs. Macro-encapsulation of the PCM is one of the techniques to encounter the low thermal conductivity issue as it will maximize the heat transfer area for the given volume of the PCM and restrict the PCMs to get in contact with the containment vessel. However, finding a suitable encapsulation technique that can address the volumetric expansion problem and compatible shell material are significant barriers of this approach. In the present work, an innovative technique to encapsulate PCMs that melt in the 100-350 oC temperature range was developed for industrial and private applications. This technique did not require a sacrificial layer to accommodate the volumetric expansion of the PCMs on melting. The encapsulation consisted of coating a non-reactive polymer over the PCM pellet followed by deposition of a metal layer by a novel non-vacuum metal deposition technique. The fabricated spherical capsules were tested in different heat transfer fluid (HTF) environments like air, oil and molten salt (solar salt). Thermophysical properties of the PCMs were investigated by DSC/TGA, IR and weight change analysis before and after the thermal cycling. Also, the constrained melting and solidification of sodium nitrate PCM inside the spherical capsules of different sizes were compared to explore the charging and discharging time. To accomplish this, three thermocouples were installed vertically inside the capsule at three equidistant positions. Low-density graphene was dispersed in the PCM to increase its conductivity and compared with pure PCM capsules. A laboratory scale packed-bed LHTES system was designed and built to investigate the performance of the capsules. Sodium nitrate (m.p. 306oC) was used as the PCM and air was used as the heat transfer fluid (HTF). The storage system was operated between 286oC and 326oC and the volumetric flow rate of the HTF was varied from 110 m3/h to 151 m3/h. The temperature distribution along the bed (radially and axially) and inside the capsules was monitored continuously during charging and discharging of the system. The effect of the HTF mass flow rate on the charging and discharging time and on the pressure drop across the bed was evaluated. Also, the energy and exergy efficiencies were calculated for three different flow rates. Finally, a step-by-step trial manufacturing process was proposed to produce large number of spherical capsules.

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In order to obtain sustainable engineering systems, this research investigates surface and interface properties of metals and active nanostructured coatings. The goal is to develop new approaches in order to improve the corrosion resistance and obtain knowledge in reconstruction of worn and/or corroded surfaces. The research will focus on high carbon steels as the substrate. These materials are used in most of industries and vehicles like aircrafts and automobiles. For anti-corrosion and self-healing applications, the layer-by-layered (LBL) coatings consisting photo-catalytic materials, the corrosion inhibitor, and the polyelectrolyte will be studied. Potential dynamic tests will be carried out in order to characterize the corrosion potential and current. For wear study, we will develop a metallic composite that has several functions, such as corrosion and wear protection, refresh or reverse worn or corroded surface. Characterization techniques used include optical microscope, surface interferometer, tribometer and the hardness tester. The ultimate goal of this research is to understand several types of problems on metal surface, such as corrosion and wear, and explore the possible ways to reduce those by using active nano-structured composite coating on metal surface.

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Submitted by marcelo capella de campos (kapellla@yahoo.com.br) on 2018-03-16T15:03:39Z No. of bitstreams: 1 Campos_MC - tese corrigida.pdf: 3583190 bytes, checksum: 1db0dbc48ebc01935b750b73717116dc (MD5) / Approved for entry into archive by Maria Marlene Zaniboni null (zaniboni@bauru.unesp.br) on 2018-03-16T19:03:37Z (GMT) No. of bitstreams: 1 campos_mc_dr_bauru.pdf: 3583190 bytes, checksum: 1db0dbc48ebc01935b750b73717116dc (MD5) / Made available in DSpace on 2018-03-16T19:03:37Z (GMT). No. of bitstreams: 1 campos_mc_dr_bauru.pdf: 3583190 bytes, checksum: 1db0dbc48ebc01935b750b73717116dc (MD5) Previous issue date: 2018-01-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os laminados de compósitos poliméricos possuem um valor já consagrado dentro das aplicações mecânicas e industriais. Sua versatilidade aliada a suas propriedades mecânicas, incentivam o aumento das aplicações, devido em partes pela facilidade de construção, tornando-os competitivos com relação a outros materiais. O conhecimento sobre a matriz polimérica, que possui inúmeras variações e aplicações, neste trabalho contou com o estudo de três tipos, sendo duas do grupo bisfenol “a” e uma do grupo bisfenol “f”. A caracterização destas matrizes através das técnicas de TG e DSC, influenciaram na escolha em virtude da aplicação a qual seriam submetidas. E sobre o reforço, que neste estudo, utilizou tecidos de fibra de carbono em trama de tela. O processo de fabricação dos laminados através de infusão a vácuo contribuiu para um resultado satisfatório, demonstrando vantagens com relação à melhor impregnação e minimizando os possíveis vazios na matriz. Os dois tipos de revestimento aplicados nestes laminados, sendo um chamado de revestimento a frio, que é um produto composto por três tipos de materiais distintos, metal, cerâmica e polímeros e o segundo a aspersão térmica, através da técnica de aspersão por chama de arames, contendo carbeto de tungstênio, recobriram o material de forma eficiente, mantendo boa adesão superficial. Estes laminados recobertos tem a finalidade de terem a vida útil aumentada e proporcionar uma maior resistência a abrasão severa. Os ensaios mecânicos aplicados demonstram as boas características destes materiais, juntamente com a caracterização por microscopia óptica e microscopia eletrônica de varredura, revelaram a boa adesão entre laminados e revestimentos, concluindo que existe uma boa identidade para estes materiais, sendo uma das principais conclusões. / The laminates of polymeric composites have an already established value within the mechanical and industrial applications. Its versatility combined with its mechanical properties, encourage the increase the applications, due in part for the ease of construction, making them competitive with respect to other materials. The knowledge about the polymer matrix, which has numerous variations and applications, in this work had the study of three types, two of the bisphenol group "a" and one of the bisphenol "f" group. The characterization of these matrices through TG and DSC techniques influenced the choice by virtue of the application to which they would be submitted. And on the reinforcement, which in this study, used carbon fiber fabrics in screen fabric. The process of manufacturing the laminates through vacuum infusion contributed to a satisfactory result, demonstrating advantages in relation to the better impregnation and minimizing voids in the matrix. The two types of coating applied on these laminates, one called cold coating, which is a product composed of three different types of materials, metal, ceramic and polymers and the second the thermal spray, by the flame spray technique of wires , Containing tungsten carbide, coated the material efficiently, maintaining good surface adhesion. These coated laminates have the purpose of having increased shelf life and providing greater resistance to severe abrasions. The applied mechanical tests demonstrate the good characteristics of these materials, together with the characterization by optical microscopy and scanning electron microscopy, revealed the good adhesion between laminates and coatings, concluding that there is a good identity for these materials.