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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.
521

Développement de nouvelles membranes céramiques et hybrides de non oxydes pour la séparation de l'hydrogène / Development of new non oxide ceramic and hybrid membranes for the separation of hydrogen

Chareyre, Laetitia 17 December 2012 (has links)
Le développement d'une méthode efficace de séparation/purification d'hydrogène représente une nécessité primordiale pour améliorer les rendements de production des systèmes énergétiques futurs. En effet, le procédé de reformage classique de production d'hydrogène conduit à un mélange complexe de gaz à haute température (au-delà de 523 K) qui limite l'utilisation de H2 dans diverses applications. La réalisation de membranes hautement sélectives à l'hydrogène apparaît alors comme un point essentiel pour augmenter la production d'hydrogène. Les membranes à base de silice ont largement été étudiées en vue de répondre à cette problématique. Malgré leurs excellentes performances, elles ne pourraient être compétitives à l'échelle industrielle qu'après amélioration de leur résistance à la vapeur d'eau en température (lixiviation). Des travaux antérieurs menés à l'IEM ont montré les performances de membranes « SiCN » en termes de perméance et de permsélectivité. Sur la base de ces résultats, nous avons développé des membranes non-oxydes autour du quaternaire « SiZrCN ». L'incorporation de Zr avait pour objectif d'améliorer la tenue en température des membranes et de fait leur sélectivité. Ce projet de thèse a été divisé en trois tâches principales : la première a consisté en la synthèse d'un précurseur moléculaire contenant les éléments Si, Zr, C, N ; la seconde a porté sur la préparation par PECVD de membranes denses non oxydes et la dernière partie a permis d'évaluer les performances de ces membranes en séparation de gaz. Un précurseur moléculaire « single source » a été synthétisé avec succès autour du quaternaire « SiZrCN », de tension de vapeur adéquate pour un dépôt par PECVD. Des films minces ont ainsi été déposés sur des supports variés afin d'obtenir des membranes sans défauts de surface conduisant à une perméance à He de 1,7.10-7 mol.m-2.s-1.Pa -1 et à une sélectivité idéale He/N2 (estimée) de 1300 à T = 423 K et Delta p = 1,105 Pa. / The development of an efficient hydrogen separation/purification method represents a tremendous requirement to enhance the production yields of future energy systems. Indeed, the reforming process commonly used for hydrogen production leads to a complex gas mixture at high temperature (beyond 523 K) that limits the H2 use in various applications. The elaboration of highly hydrogen selective membranes appears to be a determining step to expand hydrogen production. Silica-based membranes have been largely studied to respond this problematics. In spite of their excellent performances, they could only be competitive from an industrial point of view after improvement of their low resistance to water vapor at high temperature (lixiviation). Previous works completed at IEM have demonstrated the good performances of “SiZrCN” membranes in terms of permeance and permselectivity. Based on these results, we developed new non-oxide membranes in the quaternary system “SiZCN”. The incorporation of Zr aimed to enhance the temperature resistance of the membranes and then their selectivity. This thesis project was divided into three major tasks : the first one has consisted in the synthesis of a molecular precursor containing the Si, Zr, C, N elements ; the second one was focused on the preparation by PECVD of dense non-oxide membranes and the last one was meant to evaluate the performances of these membranes in gas separation. A single source molecular precursor was successfully obtained in the system “SiZrCN” usable for PECVD. Thin films were thus deposited over various supports to obtain defect free membranes presenting a He permeance of 1,7.10-7 mol.m-2.s-1.Pa-1 and a (estimated) He/N2 ideal selectivity of 1300 at T = 423 K and Delta p = 1.105 Pa.
522

An investigation into some aspects for foamed bitumen technology

Namutebi, May January 2016 (has links)
Despite applications of foamed bitumen technology in pavement construction in various places around the world, there are still several aspects about this technology that are not clear. In addition, knowledge on foamed bitumen technology is mainly empirical and lacks scientific basis. This study addresses some of the aspects for foamed bitumen technology such as: Investigation of any effects in binder composition during the production process for foamed bitumen; assessment of the effect of bitumen source on foamed bitumen characteristics; development of a rational method to optimise foamed bitumen characteristics and conditions; evaluation of aggregate particle coating within foamed bitumen mixes; further improvements in the mix design procedure specifically the method of compaction and optimum bitumen content determination stages are suggested.  Fourier transform infrared spectroscopy techniques were used to investigate any changes in bitumen composition after the production process of foamed bitumen. Fourier transform infrared tests were done on foamed bitumen and neat bitumen specimens for two bitumens with similar penetration grades. Foamed bitumen characteristics of three bitumens were established by producing foamed bitumen at temperatures of 150ºC up to 180ºC and foamant water contents of 1, 2, 3, 4 and 5%. From the analysis of variation of foamed bitumen characteristics (maximum expansion ratio and half-life) at different temperatures a new method based on the equi-viscous bitumen temperature to optimize foamed bitumen conditions and characteristics was proposed. Rice density and surface energy concepts were used to evaluate aggregate particle coating with foamed bitumen. A granite aggregate divided into three different size fractions and three sets of foamed bitumen produced from three bitumen penetration grades were used. A gyratory laboratory compaction procedure for laterite gravels treated with foamed bitumen was established using the modified locking concept. Three laterite gravels with different chemical composition were mixed with foamed bitumen produced from one penetration bitumen grade. The resulting mixes were compacted up to 200 gyrations and the corresponding compaction curve defined in terms of height versus number of gyrations noted. In addition, the optimum moisture content requirements at the modified locking point were determined. 3D packing theory concepts, primary aggregate structure porosity and an indirect tensile strength criteria were employed to determine optimum bitumen content for foamed bitumen mixes.  Fourier infrared techniques revealed that foaming did not cause any changes in the bitumen chemistry, implying that the foamed bitumen production process may possibly be a physical process. Characterisation of foamed bitumen produced from three bitumen penetration grades showed that foamed bitumen characteristics (maximum expansion ratio and half-life) were mainly influenced by binder viscosity rather than the source. The equi-viscous temperature seemed to provide a suitable criterion at which foamed bitumen with optimum characteristics could be produced. Rice density results showed that aggregate size fraction, binder expansion ratio and viscosity influenced aggregate particle coating. For the coarser aggregate fraction, results revealed that binder coating seemed to be mainly influenced by temperature. Whilst for fine aggregate fraction the coating was mainly influenced by surface area. Surface energy results revealed that foamed bitumen exhibited better coating attributes than neat bitumen. A new laboratory compaction procedure for laterite gravels treated with foamed bitumen based on the modified locking point was developed. The modified locking point represents the state at which maximum aggregate particle interlock occurs when mixes are compacted in the field. It is based on the iii analysis of the rate of change for the gyratory compaction curve. The compaction curve in this case is defined in terms of compaction height versus number of gyrations. Gradation analysis beyond the modified locking point showed that aggregate particle breakdown occurred. Analysis of the optimum moisture at the modified locking point revealed that the moisture conditions were less than the aggregate optimum moisture conditions. It is recommended that this point be used to determine the optimal compaction characteristics of foamed bitumen mixes.  Aggregate structure porosity and an indirect tensile strength criteria can be used to determine the bitumen content that could be used in design of foamed bitumen mixes. This would reduce the amount of resources required since the bitumen content could be estimated prior to carrying out the actual laboratory work given that the aggregate grading is known. The aggregate structure can be divided (based on 3D packing theory) into oversize, primary, and secondary structures. The primary structure is mostly responsible for carrying loads whilst the secondary structure fills the voids within the primary structure and provides support to the primary structure. The aggregate size particles constituting the primary structure are deduced as a function of standard sieve sizes using the packing theory concepts. The minimum sieve size for the primary structure is proposed as 1 mm. The oversize structure consists of aggregate particles whose size is greater than the maximum size for the primary structure. The secondary structure consists of aggregate particles whose size is below the minimum size for the primary structure. The primary aggregate structure porosity can be used to establish the starting bitumen content; the bitumen content at which this porosity is 50% is chosen as the initial bitumen content. Indirect tensile strength values corresponding to 50% primary porosity are determined as well as the bitumen contents and compared against the recommended minimum values. / <p>QC 20161012</p>
523

Angled curtain coating : an experimental study : an experimental investigation into the effect of die angle on air entrainment velocity in curtain coating under a range of operating conditions

Elgadafi, Mansour Masoud January 2010 (has links)
In all coating applications, a liquid film displaces air in contact with a dry solid substrate. At a low substrate speed a thin uniform wetting line is formed on the substrates surface, but at a high speed the wetting line becomes segmented and unsteady as air becomes entrained between the substrate and the liquid. These air bubbles affect the quality of the coated product and any means to postpone this at higher speeds without changing the specifications of the coating liquid is desirable. This research assesses the validity of a theoretically based concept developed by Blake and Rushack [1] and exploited by Cohu and Benkreira [2] for dip coating. The concept suggests that angling the wetting line by an angle ß would increase the speed at which air is entrained by a factor 1/cos ß. In practice, if achieved this is a significant increase that would result in more economical operation. This concept was tested in a fast coating operation that of curtain coating which is already enhanced by what is known as hydrodynamic assistance [2]. Here we are effectively checking an additional assistance to wetting. The work, performed on a purposed built curtain coater and a rotating die, with a range of fluids showed the concept to hold but provided the data are processed in a way that separate the effect of curtain impingement from the slanting of the wetting line.
524

[en] MACRO-MECHANICAL ANALYSIS OF EARTH AS EXTERNAL FINISHING, WITH OR WITHOUT VEGETABLE FIBERS / [pt] ANÁLISE MACRO-MECÂNICA DO COMPORTAMENTO DA TERRA COMO REVESTIMENTO EXTERNO, COM OU SEM REFORÇO DE FIBRAS VEGETAIS

FERNANDA DE ANDRADE SALGADO 27 January 2011 (has links)
[pt] O objetivo deste trabalho foi a análise macro-mecânica do comportamento da terra como argamassa para revestimentos de terra. Não foram encontradas referências a estudos semelhantes a este, tratando-se portanto de um estudo pioneiro, no Brasil e no exterior. Os revestimentos foram aplicados em um substrato de terra batida de 50 e 30 cm de altura e de largura, respectivamente. Foram analisados revestimentos fabricados com 17,5%, 12%, 9% e 6% em peso de argila em relação ao material seco para dois solos distintos: Tassin (ilítico) e Rochechinard (caulinítico). Como revestimento de referência, foi fabricada uma argamassa de cal e areia (1:3). Além disso, foi avaliado o efeito da inclusão de duas fibras existentes no mercado: fibras curtas de sisal (Agave sisalana), naturais do Brasil, e resíduos de fabricação de fibras curtas de cânhamo (Cannabis sativa), provenientes da França. Tais fibras foram empregadas somente em corpos-deprova de Rochechinard com 17,5% e 12% em peso de argila em relação ao material seco, e adicionadas ao solo em uma porcentagem de 0,5% do peso do solo seco, com as mãos. Sisal possui seção circular com valores médios de 0,15 mm de diâmetro e 40 mm de comprimento; cânhamo é considerado como seção retangular de 2x5 mm de área e comprimento de 20 mm. Para todos os revestimentos foram realizadas observações visuais in situ da retração. Em seguida, os revestimentos foram ensaiados ao cisalhamento através da adição de 250 g, até a ruptura, a cada 30 s em um quadro retangular de madeira, que era pendurado nas amostras. No laboratório, a retração restringida em 4 lados e a resistência à flexão foram testadas em amostras prismáticas. Foi observado que tanto a retração quanto a resistência à flexão aumentam com o teor de argila. Além disso, os compósitos de solo com sisal apresentaram, em geral, maiores resistências àqueles em que houve emprego de cânhamo. / [en] This work analyzes the macro-mechanical behavior of earth when it is used as a raw material for finishing. It is a pioneer study in Brazil and abroad. The finishings were applied on a rammed earth wall of 50 of height and 30 cm of width. Finishings fabricated with four different clay contents (17,5%, 12%, 9% and 6% by weight of clay in relation to the dry material) were analyzed for two different soils. Each one of these soils has a predominant type of clay: Tassin (with illite in greater quantity) and Rochechinard (with kaolinite in greater quantity). As a reference finishing, it was fabricated a mortar of lime and sand (1:3). Furthermore, the behavior of two fibers was evaluated: short sisal fibers (Agave sisalana), natural from Brazil, and residue from the manufacture of short hemp fibers (Cannabis sativa), from France. These fibers were used only in samples of Rochechinard with two clay contents (17.5% and 12% by weight of clay in relation to the dry material). The fibers were added to the soil on a percentage of 0.5% by weight of dry soil, manually. Sisal has circular section with average values of 0.15 mm of diameter and 40 mm long; hemp fiber is considered as a rectangular section with 2 mm of height, 5 mm of width and 20 mm long. For all finishings, visual observations of shrinkage were performed in situ. Those finishings with higher clay content dropped from the support. The finishings which did not fell were tested in shear. For this, a load of 250 g was added, until rupture, in every 30s on a rectangular wood frame (600 g weight), that was hung in the samples. In laboratory, linear shrinkage and flexural strength were tested on prismatic samples. It was observed that both shrinkage and flexural strength increase with clay content. Regarding the addition of fibers, it was found that the composites fabricated with sisal had generally better results than those with hemp.
525

INVESTIGATION OF BIODEGRADABLE IRON-MANGANESE ALLOYS WITH VARIOUS POROSITY

Sabrina M Huang (6843719) 05 August 2019 (has links)
<p>Bioresorbable iron-manganese (Fe-Mn) alloys are considered as a new class of biomaterials for the development of orthopedic fixation devices due to their promising mechanical properties, comparable to the human cortical bone, and the ability to degrade in the physiological environment and release small quantities of metallic ions/particles that are absorbable by the host. The greatest challenge for developing an ideal resorbable Fe-Mn alloy is to increase the degradation rate of the alloy without compromising the alloy biocompatibility, that is, causing zero or minimal local and systemic toxicity to the tissue. Another challenge is to improve osteo-integration through inducing a cascade of events leading to tissue ingrowth.</p> <p> </p> <p>The incorporation of porosity into the Fe-Mn alloys aimed to increase the corrosion rate and to provide the three-dimensional structure for cellular activity and nutrient transport. The Fe-30wt.%Mn alloys with 0-, 5-, 10-, and 60-volume percent porosity were produced through the space holder technique in powder metallurgy. The space-holder material, ammonium bicarbonate (NH<sub>4</sub>HCO<sub>3</sub>), was sieved to a particle size ranging 355~500 µm. The microstructures and mechanical properties of the alloys, as well as the influence of the degree of porosity on the alloy corrosion rates comparing to the concentrations of the degraded metal ions were investigated. Although the Fe-30Mn alloys containing 60-vol% porosity exhibited the lowest average ultimate compressive strength of 381 MPa among the tested groups, they were still mechanically stronger than a typical human wet compact bone. Furthermore, the alloys had the highest average corrosion rate of 0.98 ± 0.20 mm/year, compared to 0.13 ± 0.07 mm/year for the non-porous Fe-30Mn alloys. Nevertheless, the extract from the 60%-pore group had a cytotoxicity effect to the bone marrow stem cells (BMSCs) at an average normalized cell viability of 58%, which was below the standard viability of 70%, considered as cytotoxic in the indirect cytotoxicity study. The cytotoxicity study also corresponded to the highest level of transition metal ions Mn<sup>2+</sup> released into the media for the 60%-pore group at an average ion released rate of 7 mg/day, compared to the other groups presenting similar Mn<sup>2+</sup> released rates about 4 mg/day after 1 day of incubation. The extreme case of the 60%-pore group demonstrated the tradeoff between the corrosion rates and biocompatibility. On the other hand, the 10%-pore group showed an average ultimate compressive strength of 737 MPa comparable to the stainless steel 316L, an average corrosion rate of 0.260 ± 0.09 mm/year, which was 2-fold higher than the non-porous group, and an average cell viability of 86% close to the non-porous group. It is promising based on the above results, however, the osteo-integration of the 10%-pore group in terms of cell-to-cell and alloy-to-cell interactions was not ideal. </p>
526

Contribution à l'optimisation des propriétés des revêtements utilisés pour la protection des moules en fonderie d'aluminium : Mise en évidence des caractéristiques influant sur la durée de vie et étude de procédés alternatifs pour l'application / Contribution to properties optimization of coatings used to protect dies in aluminium foundry

Scaringella-Guerritat, Yohann 27 May 2015 (has links)
Le groupe Montupet est un spécialiste de la conception et de la production de pièces de fonderie en aluminium usinées pour l’automobile. Les moules métalliques utilisés pour la réalisation de culasses automobiles en aluminium sont protégés par un revêtement appelé le poteyage. La principale fonction du revêtement de poteyage est de protéger l’outillage en acier de la corrosion chimique de l’alliage. Du fait de ses propriétés thermiques, une autre fonction du poteyage est la modulation des échanges thermiques entre le moule et la pièce en cours de solidification dont dépend fortement la microstructure finale de l’alliage. Le procédé utilisé aujourd’hui pour l’application du poteyage sur les parois du moule en acier consiste à projeter manuellement une barbotine au moyen d’un pistolet. Ce procédé ne permet pas d’obtenir la répétabilité des caractéristiques des couches déposées nécessaire au contrôle des gradients de solidification locaux. De plus, les outillages actuels souffrent de l’insuffisance de la protection du poteyage, ce qui conduit à une usure prématurée ayant un coût important et conduisant à des diminutions du rendement de l’outil industriel. Dans le cadre du projet PROOF de robotisation de l’étape de poteyage, les objectifs suivants ont été fixés. Il s’agit de mieux définir ce que devraient être les propriétés physicochimiques du poteyage. L’objectif à long terme est de réaliser une rupture technologique par l’application d’un revêtement permanent ou de longue durée de vie. Dans un premier temps, ces travaux présentent une caractérisation complète de la nature physico-chimique des suspensions des poteyages utilisés actuellement ainsi que l’étude de leur comportement en pulvérisation. Dans un second temps, après que des revêtements aient été produits par projection plasma sous air (APS), il est apparu nécessaire de comparer leurs propriétés thermiques à celles des revêtements de poteyage. Des valeurs de diffusivité thermiques ont été mesurées, les valeurs de conductivités thermiques des revêtements étudiés ont ensuite été calculées puis confirmées expérimentalement. La dernière partie de ces travaux s’attache à présenter les outils mis en place en usine afin de tester les revêtements créés par projection plasma et de vérifier leur adéquation (thermique et chimique notamment) avec la coulée de pièces en alliage d’aluminium. Ces essais en conditions réelles ou semi-réelles permettent la comparaison de l’efficacité de tous les revêtements étudiés. / Montupet is specialized in the manufacture of aluminium foundry components for the automotive industry. The metallic molds used for aluminium cylinder heads are protected by a specific coating called die coating. The main objective of this die coating is to protect the steel tool from chemical corrosion of the liquid alloy. Because of its thermal properties, another of its aims is the adjustment of the thermal exchanges between the mold and the solidifying aluminium, which strongly affects the final microstructure of the alloy. The process used nowadays to coat the die coating on the steel mold walls consists in spraying manually a suspension. However, this process does not allow to obtain reproducible characteristics of the coated layers necessary to control the local solidification gradients. Furthermore, the current tools suffer from the inadequate protection of the die coating, which leads to premature wear resulting in important costs and a decrease of the efficiency of the industrial tool. In the frame of the PROOF project, aiming in the automatisation of the die coating projection, several objectives were set: better know what should be the physico-chemical properties of the die coating and realize a technological jump by creating a long-life or even permanent coating. Firstly, this work shows a complete characterization of the physico-chemical state of the suspensions used nowadays as well as the study of their behavior during spraying. Then, once the coatings were produced by Air Plasma Spraying (APS), it appeared necessary to compare their thermal properties to the ones measured on the die coatings. Hence, thermal diffusivity values have been measured. Afterwards thermal conductivity of the studied coatings have been calculated and finally experimentally checked. Eventually, this work shows the tools developed within the company in order to test the plasma coatings and to check their thermal and chemical compatibility to the process of aluminium casting. These trials in real or semi-real conditions allow the efficiency comparison of the whole studied coatings.
527

Rhéologie des plastisols et leurs procédés d'enduction / Study of spread coating processes and plastisols rheology

Abdesselam, Yamina 14 December 2016 (has links)
L’enduction à la racle est l’un des procédés utilisés pour la fabrication des revêtements de sol. Ce procédé consiste à enduire un substrat de plastisol - une suspension de particules de PVC et de charges minérales dans une phase liquide composée de plastifiant - à l’aide d’une racle fixée au-dessus d’un cylindre entraineur. Les sols type vinyle sont fabriqués par étapes successives d’enduction. Lors de l’enduction à la racle de certains plastisols, un défaut de goutte apparait.L’apparition de ces défauts et fortement dépendante de la nature du plastisol, de la géométrie de la racle et des paramètres procédés tels que la vitesse de ligne, l’entrefer entre la racle et le cylindre etc.Cette étude a tout d’abord pour but de déterminer la rhéologie de différentes formulations de plastisol, modèles et industrielles. L’influence de la taille et la distribution des particules de PVC ainsi que l’adjonction et la taille de charges minérales sur le comportement rhéologique est étudiée.Dans un second temps, une modélisation de l’écoulement est développée afin de calculer les taux de cisaillement rencontrés sous la racle, ainsi que le champ de vitesse et les forces exercées. Ce modèle rend possible l’étude de l’influence des paramètres procédés sur les conditions d’enduction.Une étude de l’influence de ces paramètres procédés sur l’apparition du défaut est alors entreprise, en utilisant une racle pilote, pour des formulations modèles et industrielles.Enfin, des corrélations sont établies, pour ces différentes formulations, entre les conditions d’apparition du défaut, la rhéologie du plastisol et les paramètres thermomécaniques de l’écoulement sous la racle. Différents mécanismes d’apparition des défauts sont proposés. / Spread coating is one of the processes used for the manufacturing of resilient floor coverings. It consists in shearing a plastisol, a suspension of PVC particles and mineral fillers in a liquid phase composed of plasticizer and adjuvants, between a fixed knife and a rotating roll supporting a substrate. Cushion floors are made through successive coating steps. Sometimes defects in the form of droplets appear on some of the successive layers.Defect appearance is strongly dependent on the plastisol nature, on the knife geometry and on the processing parameters such as roll velocity, gap between knife and roll, etc.The study first aims at determining the rheology of several plastisol formulations, model or industrial. The influence of PVC particle size and distribution and the addition and particle size of calcium carbonate filler on the rheological behaviour is studied.In a second step, a model of the flow behaviour is developed to highlight the range of shear rates encountered between the knife and the roll, as well as the velocity field and the coating force. This model then allows the investigation of the coater process parameters influence.Then, in a third step, an investigation of the processing parameters influence on the defect appearance is done using a pilot knife-over-roll coater, with both model and industrial pastes.Finally, correlations are established between defect appearance conditions, plastisol rheology and thermomechanical parameters of the flow between knife and roll for these different plastisol formulations. Different mechanisms of this defect development are proposed.
528

Optimisation du couple revêtement anti-adhérent / matériau de creuset pour la cristallisation du silicium photovoltaïque - Application au moulage direct des wafers de Si / Optimisation of the releasing coating / crucible material couple for photovoltaic silicon crystallisation - Application to direct Si wafers moulding

Huguet, Charles 14 November 2012 (has links)
Compte tenu de l'utilisation envisagée du graphite comme matériau de creuset à la place de la silice frittée pour la cristallisation dirigée des lingots de silicium multcristallin de qualité photovoltaïque, un objectif majeur de la thèse était de développer un revêtement spécifique au matériau de moule sélectionné. Une première tâche de ce travail a consisté à définir très précisément les conditions de fonctionnement du couple revêtement anti-adhérent / matériau de creuset et les modifications à apporter au procédé afin d'utiliser le revêtement standard à base de poudre de Si3N4 sur graphite, La deuxième tâche de la thèse a consisté à mettre en place le procédé de moulage à partir d'une étude préliminaire basée sur une configuration simplifiée de moulage par écrasement où un morceau de silicium s'étale à l'intérieur du moule au cours de sa fusion. Le but recherché est de mettre en évidence les conséquences de la configuration « moulage » (caractérisée par un rapport élevé surface de contact / volume de Si a priori très défavorable) et des conditions thermiques (gradient et vitesse de solidification) sur l'adhérence (collage), la pollution par le revêtement et la structure cristalline du silicium. / Considering the use of graphite as a crucible material instead of sintered silica for the directional crystallisation process of multicrystalline solar grade silicon, one of the main goals of this PhD program was to develop a dedicated releasing coating to be used with the identified mould material. A first task of this work consisted in a precise definition of the operating conditions for the releasing coating / crucible material couple and consequently modifying the process in order to be able to use the standard silicon nitride powder-based releasing coating on graphite. The second task was to design the moulding process based on a preliminary study of a simplified configuration of squeezing moulding experiments where the silicon piece spreads into the inner space of the mould when melting. The aim of these experiments was to enlighten the consequences of the “moulding” configuration (characterised by a high contact surface / Si volume ratio, a priori very detrimental) and of the thermal conditions (gradient and solidification speed) on adhesion (sticking), pollution coming from the coating, and on the crystalline structure of moulded silicon.
529

Filmes de titânia fotocatalítica sobre polipropileno: correlação entre metodologia de deposição e atividade fotocatalítica da titânia / Photocatalytic titania films on polypropylene: correlation between coating methodology and titania photocatalytic activity

Tafuri, Rodrigo Marques 01 November 2016 (has links)
Neste trabalho, filmes planos de polipropileno (CPP) cobertos com nanopartículas de dióxido de titânio (TiO2) foram feitos a partir da metodologia spray coating, facilmente reproduzida para a imobilização das nanopartículas de titânia nos suportes de polipropileno (PP). O tratamento superficial dos filmes CPP com plasma de nitrogênio (N2) e oxigênio (O2) foi utilizado com sucesso para a produção de polipropileno revestido com TiO2 com excelente estabilidade mecânica do revestimento, assim como atividade fotocatalítica / de autolimpeza como evidenciado pelos testes com corante cristal violeta (CV). Microscopia eletrônica de varredura (MEV) e microscopia confocal à laser de varredura (MCLV) foi utilizada para observar a morfologia de superfície / das fibras e topografia. A presença do revestimento de titânia foi confirmada por espectroscopia de emissão de raios-x com detecção dispersiva de energia (EDX). Tanto o tratamento com plasma como o carregamento significativo de revestimento de titânia resultam em maior hidrofilicidade, como observado pelas medidas de ângulo de contato estático em água. Os filmes CPP revestidos foram testados quanto à sua atividade fotocatalítica contra o corante CV. Os espectros eletrônicos no UV-vis mostraram que a eficiência da atividade fotocatalítica das amostras foi afetada pela quantidade de titânia. A fotoestabilidade do PP revestido com titânia foi medida por ressonância paramagnética eletrônica (RPE), uma vez que esta técnica é capaz de detectar pequena quantidade de radicais livres formados durante a precoce etapa de oxidação do polipropileno. Observa-se a partir das medições de RPE que o polipropileno tratado com plasma gerou as mesmas espécies de radicais livres que foram produzidas durante a radiação UV do polipropileno revestido e não-revestido. Entretanto, aumentando o número de ciclos de deposição da titânia a quantidade relativa de radicais livres diminui, sem perda de atividade fotocatalítica. Portanto, a metodologia empregada se mostrou eficiente para produzir uma superfície fotoativa/autolimpante no polipropileno revestido com dióxido de titânio, levando à diferentes aplicações neste campo, como por exemplo sistemas de filtragem de ar/água, remoção de poluentes orgânicos, produtos termoplásticos com características antibacterianas para uso doméstico e hospitalar, dispositivos de autolimpeza, entre outros. / Cast polypropylene (CPP) films were coated with titanium dioxide (TiO2) nanoparticles by na easily scaled-up spray coating methodology. The O2 and N2 plasma surface treatment of polypropylene was successfully used to produce TiO2-coated polypropylene with outstanding mechanical stability of the coating, as well as photocatalytic/self-cleaning activity toward crystal violet dye. Scanning Electron Microscopy and Confocal Scanning Laser Microscopy were used to observe surface / fibers morphology and topography. The presence of titânia coating was confirmed by X-ray Emission Spectroscopy with Energy Dispersive Detection (EDX). Titania coating results on higher hydrophilicity, as observed by measurements of static water contact angle. The CPP films were tested for their photocatalytic activity against Crystal Violet dye (CV). The UV/Vis electronic spectra showed that the photocatalytic activity efficiency of TiO2-coated CPP film was affected by both the plasma treatment and the titânia amount. The photostability of the titania coated polypropylene was measured by Electron Paramagnetic Resonance (EPR) since this technique is capable to detect tiny amount of free radicals formed during the early oxidation step of the polypropylene. It was observed from EPR measurements that the plasma treated polypropylene generated the same free radicals species that were produced during UV irradiation of the uncoated and TiO2-coated polypropylene. However, by increasing the number of deposition cycles of the titania the relative amount of free radicals decreases without loss of the photocatalytic activity. Therefore, the essayed methodology has been proved efficient to produce photoactive/selfcleaning surface of titania coated polypropylene, leading to different applications in this field, as water/air filtration systems, organic pollutant removal, hospital and domestic thermoplastic goods with antibacterial features, self-cleaning devices and others.
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Protótipo arquitetônico utilizando painéis com inovação tecnológica fabricados com partículas homogêneas de resíduos de madeira / Architectural prototype using technological innovation painels made of homogenous particles of wood waste

Poleto, Sabrina Fernanda Sartório 14 March 2014 (has links)
São vários os fatores que contribuem para o aumento dos resíduos de madeira no Brasil. Dentre eles, a exploração predatória dos recursos naturais, as técnicas rudimentares de desdobro da madeira, como também, a falta de uma política de gerenciamento em empresas que processam madeira em relação aos resíduos e seu destino final. Contudo, a crescente demanda industrial por recursos florestais pode ser de grande valia na construção civil e em indústrias moveleiras, se levados em consideração a otimização do uso dos resíduos do processamento da madeira para o desenvolvimento de produtos alternativos e com valor agregado. Dessa forma, diante do uso de Inovação Tecnológica e a viabilidade técnica constatada em pesquisas recentes para o reaproveitamento desses resíduos na forma de Painel de Partículas Homogêneas, PPH, este trabalho utilizou resíduos de Pinus sp. e Eucalyptus sp. tratados com CCB, para fabricação de Painéis usados na construção de um Protótipo Arquitetônico, em escala real, com o intuito de unir várias pesquisas num só espaço e confirmar os resultados dos trabalhos em que este se baseia visando avaliar a eficiência da aplicabilidade desses painéis como revestimento de pisos e paredes. Os Painéis foram fabricados, em escala de laboratório, a partir de resíduos de madeira provenientes de áreas de reflorestamento na região de São Carlos, SP, e obtidos em serrarias, marcenarias e indústrias locais. A avaliação de seu desempenho ocorreu de acordo com a norma brasileira ABNT NBR 14810:2006 e normas internacionais (EUA e Canadá). A análise dos resultados e desempenho do Protótipo construído evidenciou a viabilidade e a eficiência do emprego destes painéis, possibilitando sua proposição ao mercado de revestimentos. / There are several factors that contribute to the increase of wood waste in Brazil. Among them, the predatory exploitation of natural resources, the rudimentary techniques of wood processing, but also the absence of wood waste management policies. However, the increase of industrial demand for forest resources may be important for construction and furniture industries if considered the optimization of wastes from wood processing, for the development of alternative value-added products. Through the use of technological innovation and the technical feasibility found in researches to recycle these wastes in the form of homogeneous particleboard, HP, this study used Eucalyptus sp. and Pinus sp. wastes treated with Copper Chromium and Boron (CCB), for manufacturing panels used in the construction of an full-scale architectural prototype, that empirically test the efficiency of the applicability of these panels as floor coverings and walls. The panels were manufactured in laboratory using wood waste from reforestation areas in the region of São Carlos, São Paulo State, obtained from sawmills, joinery and local industries according to the Brazilian Standard ABNT NBR 14810:2006 and the international standard (USA and Canada). By monitoring the results and the excellent performance of the prototype built the work proved the feasibility and efficiency of the use of these panels in the coatings market.

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