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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Lignopoliuretanos: preparação, caracterização e aplicação em compósitos de sisal / Lignopolyurethanes: preparation, characterization and application in sisal composites

Fernando de Oliveira 31 October 2014 (has links)
A valorização racional da lignina e seus derivados é um dos maiores desafios ligado às biorrefinarias em que estas macromoléculas são geradas como subprodutos. Os lignossulfonatos, obtidos através do processo de polpação sulfito da madeira, são produzidos em larga escala e pouco utilizados como reagentes na preparação de compostos macromoleculares. A presença de grupos OH em sua estrutura permite o seu uso como macromonômero na obtenção de poliuretanos (PUs). O presente estudo teve como meta a obtenção de lignopoliuretanos e de compósitos baseados principalmente em matérias primas obtidas a partir de fontes renováveis. O óleo de mamona (OM) e lignossulfonato de sódio (NaLS), ambos oriundos de matérias primas renováveis, foram utilizados, em composições variadas, como substitutos de polióis convencionais, juntamente com difenilmetano diisocianato (MDI), na reação de obtenção de PUs. Inicialmente, PUs foram preparados a partir de NaLS e outros polióis, como dietilenoglicol (DEG), polietilenoglicol (PEG) e OM, assim como a partir destes reagentes, exceto NaLS (amostras controles). Visando aumentar a reatividade das hidroxilas do NaLS frente aos grupos isocianatos na síntese dos lignopoliuretanos, o NaLS foi oxipropilado (reação com óxido de propileno, gerando LS-Oxi) e hidroxialquilado (reações com glutaraldeído e formaldeído, gerando NaLS-Glu e NaLS-For, respectivamente). O uso de aldeídos na modificação do NaLS, até onde se tenha conhecimento, foi uma abordagem inédita no que se refere à síntese de lignopoliuretanos. Os produtos, (LS-Oxi, NaLS-Glu, NaLS-Glu) foram caracterizados por espectroscopia na região do infravermelho (IV) e, associados ou não com OM, foram usados na preparação de lignopoliuretanos (também caracterizados por IV). Fibras lignocelulósicas extraídas de sisal (Agave sisalana), cujo maior produtor mundial é o Brasil, foram utilizadas como reforço dos lignopoliuretanos preparados. Os compósitos lignopoliuretânicos, bem como os lignopoliuretanos não reforçados, foram caracterizados por análise termogravimétrica (TG), resistência ao impacto, resistência à flexão, microscopia eletrônica de varredura (MEV) e análise térmica dinâmico-mecânica (DMA). Os resultados mostraram que as fibras de sisal aumentaram consideravelmente a resistência ao impacto de todos os lignopoliuretanos. Entre os compósitos baseados em NaLS não modificado (Grupo 1), o DEG/NaLS/MDI/Sisal foi o que apresentou melhor resistência ao impacto (472 J m-1) e melhor resistência à flexão (47 MPa). Quando o NaLS oxipropilado foi utilizado (Grupo 2), o compósito LS-Oxi/MDI/Sisal apresentou resistência ao impacto de 459 J m-1 e resistência à flexão de 43 MPa, enquanto que o compósito NaLS-Glu/MDI/Sisal, preparado à partir do NaLS hidroxialquilado (Grupo 3), apresentou resistência ao impacto de 945 J m-1 e resistência à flexão de 23 MPa. As imagens de MEV da superfície de fratura pós-ensaio de impacto revelaram uma forte adesão na interface fibra/matriz, como consequência da presença de ligações hidrogênio entre os grupos uretanos da matriz e os grupos hidroxila das fibras, além das interações entre os domínios hidrofóbicos de ambos, fibra e matriz. Materiais com grau de entrecruzamento diversificados, com características entre elastomérica a termorrígidos, foram obtidos a partir do uso do NaLS e do OM, o que faz com que eles se tornem atrativos para diferentes aplicações, como em partes automotivas e painéis de uso arquitetônico. Neste sentido, e atendendo às expectativas atuais, materiais com excelentes propriedades e com elevada proporção de matérias-primas obtidas de fontes renováveis foram desenvolvidos. / The rational valuing of lignin and its derivatives is one of the major challenges in the biorefinery context where these macromolecules are generated as byproducts. Lignosulfonates obtained through the wood sulfite pulping process are produced on a large scale. However, they are rarely used as reagents in the preparation of macromolecular compounds. The presence of OH groups in their structure allows their use as a macromonomer to obtain polyurethanes (PU). This study aimed at obtaining lignopolyurethanes and composites based mainly on raw materials obtained from renewable sources. Castor oil (CO) and sodium lignosulfonate (NaLS), both derived from renewable raw materials, were used in different compositions as replacements for conventional polyols along with diphenylmethane diisocyanate (MDI) in the PU synthesis. Initially, polyurethanes were prepared from NaLS and other polyols such as diethylene glycol (DEG), polyethylene glycol (PEG), and OM, as well as by using these reagents, except for NaLS (control samples). In order to increase the reactivity of the OH groups of NaLS against isocyanates in the lignopolyurethanes synthesis, NaLS was oxypropylated (reaction with propylene oxide, generating LS-Oxy) and hydroxyalkylated (reaction with formaldehyde and glutaraldehyde, generating NaLS-Glu-For NaLS, respectively). The use of aldehydes in the NaLS modification, as far as we know, is a novel approach with regard to the lignopolyurethane synthesis. The products (LS-Oxy, NaLS-Glu, and NaLS-For) were characterized by infrared spectroscopy (IR) and associated or not with CO were also used in lignopolyurethanes preparation (also characterized by IR). Lignocellulosic fibers extracted from sisal (Agave sisalana), which has Brazil as its largest producer in the world, were used as reinforcement for the prepared lignopolyurethanes. Lignopolyurethanic composites and the non-reinforced lignopolyurethanes were characterized by thermogravimetric analysis (TG), impact test, flexural strength, scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). Results showed that sisal fibers substantially increased the impact strength of all lignopolyurethanes. Among the composites based on unmodified NaLS (Group 1), DEG/NaLS/MDI/Sisal showed the best impact strength (472 J m-1) and the best flexural strength (47 MPa). When the oxypropylated NaLS was used (Group 2), the composite <br /> LS-Oxy/MDI/Sisal showed impact strength of 459 J m-1 and flexural strength of 43 MPa, while the composite NaLS-Glu/MDI/Sisal prepared from the hydroxyalkylated NaLS (Group 3) showed impact strength of 945 J m-1 and flexural strength of 23 MPa. The SEM images of the fracture surface after the impact test revealed a strong adhesion in the fiber/matrix interface as a consequence of the presence of hydrogen bonds between the urethane groups of the matrix and the hydroxyl groups of the fibers, in addition to the interactions between the hydrophobic domains of both fiber and matrix. Materials with different degrees of crosslinking and characteristics from elastomeric to thermoset were obtained from the use of NaLS and CO, which makes them attractive for different applications such as automotive parts and panels for architectural use. In general, materials with excellent properties and prepared with a high proportion of renewable raw materials were developed, thus meeting the current expectations concerning biobased materials.
92

Faisabilité technique et environnementale de l'utilisation dans des matériaux de construction cimentaires de cendres d'incinération de boues de station d'épuration / Technical and environmental feasibility of the utilization of incineration sewage sludge ashes in cementitious materials

Chen, Maozhe 05 June 2012 (has links)
Des quantités importantes de cendres (4,12 million kg en France en 2008) sont issues de l’incinération des boues de station d’épuration. La valorisation de ces cendres comme matière première secondaire pour l’élaboration de matériau dans le domaine du bâtiment et des travaux publics (BTP) a été étudiée dans cette thèse. La caractérisation physique et chimique des cendres et l’étude de leur réactivité ont révélé un comportement intermédiaire entre le ciment et le sable, proche du comportement de matériaux pouzzolaniques. Les tests de lixiviation réalisés sur les cendres ont montré qu’à l’exception du Se et du Mo, les éléments présents dans les cendres sont solubilisés à des concentrations inférieures aux seuils définis règlementairement pour les déchets inertes ou non-dangereux. Les liens entre la solubilisation des éléments et la minéralogie des matériaux ont été étudiés à travers la modélisation géochimique réalisée sous PhreeqC. L’influence du taux de substitution du ciment par les cendres sur les propriétés mécaniques des matériaux a également été étudiée. L’indice d’activité à 28 jours de la cendre est conforme à la spécification de la norme EN 450-1. La résistance du mortier diminue quand le taux de substitution augmente à cause de la faible teneur en CaO dans les cendres et de l’apport supplémentaire d’eau nécessaire. Pour le béton avec un taux de substitution de 10 %, la résistance est comparable à celle du béton témoin. L’essai de durabilité des matériaux cimentaires incorporant les cendres révèle une forte diminution de résistance mécanique sous l’effet de la sollicitation au gel/dégel. Une évaluation environnementale de ces matériaux a été réalisée par l’essai de lixiviation à l’échelle du laboratoire et à l’échelle pilote. Les quantités relarguées cumulées des éléments polluants et des anions sont inférieures aux seuils sans impact environnemental, acceptables en construction aux Pays-Bas et en France. / High quantity (4.12 million kg in France in 2008) of ashes produces from the incineration of sewage sludge. The reutilization of these ashes as secondary raw materials in the building and public works was studied. A physical, chemical, mineral, and behavioral characterization showed that the sewage sludge ash have an intermediate behavior between the cement and sand, near the pozzolan. Most elements had lower release rates than limited value of inert waste or non-hazardous waste, with the exception of the leachable fraction of Se and Mo. A relationship between solubilization of elements and mineralogy of materials were studied by modeling for phase identification of the ashes. A technique part was studied to evaluate the influence of the residue (sewage sludge ash) on the mechanical properties of materials. The activity index of the ash met the specification of EN450-1 in 28 days. The strength of the mortar decreased when the substitution increased due to the high amount of water added and the low CaO content in the ash. For concrete with a substitution of 10%, the compression strength was comparable to the blank sample, and was satisfactory to the threshold of construction projects. However, the durability test showed a strong decrease of mechanical strength for the concrete containing the ashes after a freeze/thaw. An assessment of environmental impacts associates with the observation of the leaching behavior of these materials. The leaching test at laboratory scale and pilot scale were investigated. The cumulative leaching quantities of each pollutant and anions were below the threshold, without significant environmental impact, acceptable for the construction in Netherlands en in France.
93

Variabilité des comportements techniques du Dryas ancien à la fin du Bølling : Analyse techno-économique comparée du matériel lithique de cinq gisements tardiglaciaires du Jura méridional

Bereiziat, Gérald 20 December 2011 (has links)
Ce travail a pour objectif de préciser, à travers la composante lithique de cinq gisements, le cadre chrono-culturel des dernières populations de chasseurs-cueilleurs venues occuper le Jura méridional au sortir de la dernière grande glaciation. Normalisée par une réflexion engagée sur le degré de préservation des ensembles archéologiques, l’étude du matériel lithique, menée sous une double perspective technologique et économique, permet d’éclairer les comportements ayant orienté la conduite technique des individus et de discuter la structuration de ces groupes sur un axe synchronique et diachronique s’étendant du 15ème millénaire au 11ème millénaire avant le présent. Ces nouveaux acquis permettent ainsi de redéfinir la place des assemblages sur l’espace jurassien et de contrôler l’hypothèse d’une région carrefour soumise à de multiples influences. / The present thesis is aimed at defining more closely the chronocultural frame of late glacial populations on the basis of lithic artefacts from five sites in the Southern French Jura. Starting from a taphonomic analysis, a techno-economical approach illuminates the variability of individual technological behaviour and finally discusses the particular humain groups on a synchronic and diachronic axis from 15.000 untill 11.000 yr B.P. These new results permit to redefine the place of these assemblages in the context of the Jura mountains and thus to establish the Southern French Jura within the Rhine-Saone-Rhone area as a crossing point of multiple influences.
94

Effects of calcination and activation conditions on ordered mesoporous carbon supported iron catalysts for production of lower olefins from synthesis gas

Oschatz, M., van Deelen, T. W., Weber, J. L., Lamme, W. S., Wang, G., Goderis, B., Verkinderen, O., Dugulan, A. I., de Jong, K. P. 24 July 2017 (has links)
Lower C2–C4 olefins are important commodity chemicals usually produced by steam cracking of naphtha or fluid catalytic cracking of vacuum gas oil. The Fischer–Tropsch synthesis of lower olefins (FTO) with iron-based catalysts uses synthesis gas as an alternative feedstock. Nanostructured carbon materials are widely applied as supports for the iron nanoparticles due to their weak interaction with the metal species, facilitating the formation of catalytically active iron carbide. Numerous synthetic approaches towards carbon-supported FTO catalysts with various structures and properties have been published in recent years but structure-performance relationships remain poorly understood. We apply ordered mesoporous carbon (CMK-3) as a support material with well-defined pore structure to investigate the relationships between calcination/activation conditions and catalytic properties. After loading of iron and sodium/sulfur as the promoters, the structures and properties of the FTO catalysts are varied by using different calcination (300–1000 °C) and activation (350 or 450 °C) temperatures followed by FTO testing at 1 bar, 350 °C, H2/CO = 1. Carbothermal reduction of iron oxides by the support material occurs at calcination temperatures of 800 or 1000 °C, leading to a higher ratio of catalytically active iron(carbide) species but the catalytic activity remains low due to particle growth and blocking of the catalytically active sites with dense graphite layers. For the samples calcined at 300 and 500 °C, the formation of non-blocked iron carbide can be enhanced by activation at higher temperatures, leading to higher catalytic activity. Olefin selectivities of ∼60%C in the formed hydrocarbons with methane of ∼10%C are achieved for all catalysts under FTO conditions at low CO conversion. The influence of the calcination temperature is further investigated under industrially relevant FTO conditions. Promoted CMK-3-supported catalysts obtained at low calcination temperatures of 300–500 °C show stable operation for 140 h of time on stream at 10 bar, 340 °C, H2/CO = 2.
95

Výzkum a vývoj progresivních ochranných prostředků na vodorovné konstrukce s využitím odpadních surovin / Research and development of progressive protective equipments for horizontal construction using waste materials

Hodná, Jana Unknown Date (has links)
Large amount of different types of industrial wastes are still not re-use as secondary raw materials in industry. The work deals with finding a new way how to use secondary raw materials, especially the possibilities of using recycled glass from different sources as a fillers in the polymer protective materials development for horizontal structures. The main task of this work is to develop a material with the desired physic - mechanical properties and further verifying the influence of particle shape on their chemical resistance. Result of this work will find advanced protective materials using secondary raw materials as alternatives to be in terms of economic and ecological efficiency replacement for conventional products.
96

Využití vedlejších produktů z výroby cementotřískových desek pro podkladní vrstvy / Utilization of by-products from cement-bonded particleboards production in base layers

Dobrovolná, Martina January 2019 (has links)
This thesis deals with the use of by–products from the production of cement–bonded particle boards as an alternative raw material for the stabilization of the subsoil or into a ground solid. The theoretical part briefly describes the current status of waste management. A set of alterantive raw materials used to hydraulically cemented mixtures is listed here as well as the recherche of the foreign research is elaborated from this area. The experimental part of the thesis firstly deals with the choice of raw materials and basic recipes. In the advanced stage the laboratory analyses are carried out on the modified formulas. Based on the results of these analyses the posibility of using by–products from the production of cement–bonded boards for the stabilization of the subsoil is evaluated here.
97

Možnosti využití odkalů po vypírce vápence / The possibilities of use of sludges from limestone wash

Švec, Jiří January 2011 (has links)
In modern point of view of waste management is desirable to effectively process the grates possible amount of wastes. Sediments from cleaning of mined lime stones contains a lot of clay components, but there is also indispensable share of soft calcite. This composition makes these sediments a promising material for preparation of hydraulic binders. Production of common hydraulic binders, especially Portland cement, is very energy-intensive plus loads environment with considerable amount of combustion gases, therefore it is necessary to explore possibilities of alternative low - energy binders production and usage.
98

Testování možností využívání druhotných surovin jako náhrady přírodních kameniv / Testing ways of use of secondary raw materials replacing naturals aggregate.

Vašek, Tomáš January 2014 (has links)
Master's thesis consists of two parts, theoretical and practical. In the theoretical section are listed basic information about alternative aggregates used for concrete mixture, like polystyrene, cinder and recycled concrete. Further, the influence of these alternative aggregates, used as secondary raw materials, on the behaviour and properties of fresh respectively hardened concrete. Possibilities of application concrete containing secondary raw materials are mentioned. In the practical part are experimentally verified physical and mechanical properties of concrete containing crushed waste polystyrene beads, furthermore thermal insulation properties and resistance to elevated temperatures is tested. Influence of heating plant cinder powder as active addition to concrete mixture was tested. As a next is prepared concrete with replacement of coarse aggregate by cinder and recycled concrete and tested. The influence of these secondary raw materials on workability, compressive strength, frost resistance and water permeability of concrete is also defined. The last part of research is focused on recycled concrete such as main material used in mixture of aggregates bonded with cement, dispose for base layers in roads. In conclusion are discussed results from experimental research and summary of knowledge’s about using polystyrene, cinder and recycled concrete as aggregates for concrete mixtures.
99

Propuesta de mejora en la cadena de abastecimiento de materias primas de una empresa comercializadora de productos químicos para el sector textil y limpieza mediante el uso del enfoque Lean para la mejora continua / Improvement proposal in the raw materials supply chain of a chemical products’ trading company for the textile and cleaning sector through the use of the Lean approach for continuous improvement

Arias Valdivia, Francisco Fernando, Herrera Moran, Daniel Antonio, Linares Contreras, Diego Antonio, Rodriguez Arqueros, Eder Jhonatan 21 February 2022 (has links)
La empresa seleccionada para la investigación es SOQUITEX ING. SRL., dedicada a la producción y comercialización de productos químicos. Actualmente, los costos operativos de esta organización han aumentado, por lo tanto, la propuesta de solución se basa en la implementación y diseño de un nuevo procedimiento de compras para mejorar la gestión del abastecimiento de materias primas, el cual estará basado en los objetivos de la metodología Lean Management y acompañado de un pronóstico de la demanda más preciso; reduciendo así los costos y el espacio de almacenamiento, cuya capacidad está al máximo. Por lo expuesto, se determina que el giro de negocio de la empresa es la comercialización y producción de insumos, más no la importación y por ello se optará por compras locales de materia prima. Por consiguiente, se tiene la reducción del área operativa de almacenamiento, lo cual permitirá eliminar el uso de un segundo almacén de 100m2 y un ahorro anual de 18,000 dólares, junto con la reducción de casi el 50% del espacio para la materia prima. Además, se tendrá una mejora financiera, ya que las compras locales se realizan mediante créditos, lo que reduce el gasto financiero y aumenta la liquidez. La investigación se divide en cuatro capítulos. El primer capítulo muestra el estado del arte, marco teórico y casos de éxito. El segundo capítulo detalla la descripción, análisis y diagnóstico del problema. El tercer capítulo se enfoca en la propuesta de solución. Finalmente, el cuarto capítulo se centra en las conclusiones y recomendaciones. / The selected company for this research is SOQUITEX ING. SRL., which is dedicated to the production and commercialization of chemical products. Currently, the operating costs of this company have increased, so the solution proposal is about the implementation and design of a new purchasing procedure to improve the supply management of raw materials, which will be based on the Lean Management methodology’s objectives and along with a more accurate demand forecast’s development. And by this way, the costs and the storage space that is working at full capacity will be both reduced. According what is was explained, it is determined that company’s core business is the commercialization and production of inputs and not the importing and that is why local purchases of raw materials will be chosen. Therefore, there is an operational storage area’s reduction, which will allow to eliminate the use of a second warehouse of 100m2 and an annual saving of USD 18,000, along with the reduction of almost 50% of the space for the raw material. In addition, there will be a financial improvement, because local purchases are managed through credits, which means the reduction of financial expenses and the increase of liquidity. This research is divided into four chapters. The first one is about the art state, theory framework and success cases. The second one details the description, analysis and diagnostic of the research’s problem. The third one focuses on the solution proposal. And finally, the last chapter is about conclusions and recommendations. / Trabajo de investigación
100

Nové možnosti využití druhotných surovin pro obnovu tělesa železničního spodku / New possibilities of using secondary raw materials for the renewal of the railway substructure

Buřičová, Karolína January 2022 (has links)
The work is devoted to new possibilities for the recovery of secondary raw materials and track bed waste with a combination of both suitable and unsuitable soils. The aim of the thesis is to develop a new functional sample suitable for the recovery of a substructure of railways based on secondary raw materials. The theoretical part addresses the issue of the use of soil and secondary raw materials as the base layers of railway structures, and is focused on the possibilities of soil adjustments or enhancement. The practical part is focused on the analysis and selection of potentially suitable raw materials, the design of new raw material mixtures containing concrete recyclables, waste from cleaning the auto mixer and waste from cleaning the rail bed. Further, to modify the mixtures designed with fluid ash from biomass combustion to achieve higher toughness. Then they will be experimentally verified and based on the results the optimal formula for use in the solid of the railway bottom will be determined. Final optimal recipe achieving basic required parameters for use in active zone without the requirement for frost resistance and ecology is composed of 30 % of F4-CS, 4 % of portland cement CEM II-B/LL, 3 % of lime hydrate, 70 % of recycled concrete and 10 % of fluid ash from biomass combustion.

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