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García-Loera, Antonio Dumon Michel. "Mélanges réactifs Thermodurcissable / Additifs extractibles." Villeurbanne : Doc'INSA, 2005. http://docinsa.insa-lyon.fr/these/pont.php?id=garcia_loera.
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García-Loera, Antonio. "Mélanges réactifs Thermodurcissable / Additifs extractibles : Phénomènes de Séparation de Phase et Morphologies : Application aux matériaux poreux." Lyon, INSA, 2002. http://theses.insa-lyon.fr/publication/2002ISAL0003/these.pdf.
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La stratégie de la séparation de phase induite par une réaction chimique (RIPS) permet de disperser un additif dans un réseau thermodurcissable. Cette stratégie s'avère intéressante car il est possible d'obtenir des morphologies fermées ou ouvertes (bi-continues). L'intérêt de disperser une deuxième phase est très souvent lié à l'amélioration des propriétés mécaniques. Cependant, il est possible d'envisager la fabrication de thermodurcissables poreux, si la phase dispersée peut être facilement extraite (évaporée ou dégradée) du réseau thermodurcissable. Ce travail porte sur l'étude de réseaux thermodurcissables à base de diglycidyl éther du bisphénol A ou de dicyanate fluoré. Ces réseaux ont été modifiés par trois différents types d'additifs extractibles : un additif de faible masse molaire (l'eau), un additif thermoplastique amorphe (Poly(vinyl méthyl éther)) et un thermoplastique semi-cristallin ( Polyoxyméthylène ). La miscibilité de chaque additif, dans les réseaux thermodurcissables, dépend des contributions entropique (augmentation de la masse molaire) et enthalpique ( interactions entre le réseau et l'additif) du système. L'analyse des morphologies finales montre le potentiel de la technique RIPS dans la fabrication de matériaux poreuxThe Reaction Induced Phase Separation (RIPS) technique is an interesting way to blend thermoset networks with diverse additives. Usually, this technique is used to improve the mechanical properties of thermoset networks. An alternative application is the synthesis of porous thermosets. In order to elaborate this kind of thermosets, the dispersed phase must to be easily extracted from the thermoset network. In this work, we investigated the morphology and the phase separation phenomena of thermoset-extractable additives blends. Two thermoset matrices (epoxy-amine and cyanate ester) and three additives (water, polyvinyl ether and polyoxymethylene) were used. The morphologies and the phase separation phenomena of the blends were analysed in order to evaluate the potential of the RIPS technique to synthesizer porous thermosets
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Storck-Gantois, Fanny. "Effet de la compression et de l’ajout d’additifs sur l’amélioration des performances d’un accumulateur au plomb." Paris 6, 2008. http://www.theses.fr/2008PA066370.
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Les travaux de cette thèse visent le développement d’un accumulateur au plomb-acide aux propriétés améliorées en combinant l’utilisation d’additifs et la mise en compression des cellules. L’utilisation d’additifs poreux vise à favoriser la diffusion de l’électrolyte au sein de la matière active positive et l’utilisation d’additifs de conductivité tend à optimiser le réseau de conduction des matériaux actifs. Le maintien de la cohésion des matières en cyclage est assuré par la mise en compression des électrodes. Dans cet objectif, un protocole de fabrication d’électrodes positives a été développé au laboratoire. Un comportement de référence a ensuite été définit en déterminant les performances électriques et les caractéristiques des électrodes témoins soumises à des pressions allant de 0 à 1bar. Puis les effets des additifs ont été évalués lors d’applications en compression. Notre but étant également une meilleure compréhension du système plomb-acide et du mode de fonctionnement des additifs, des mécanismes pour expliquer l’évolution texturale des matériaux actifs positifs en compression et l’interaction entre les additifs et l’application d’une pression ont été proposés
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Lefèvre, Delphine. "Étude expérimentale, modélisation et simulation de la filtration lors de l'écoulement d'une résine chargée de particules à travers un renfort fibreux dans les technologies LCM." Lille 1, 2007. http://www.theses.fr/2007LIL10144.
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La fabrication de pièces composites à matrice organique chargée de particules par un procédé de type LCM (Liquid Composite Molding) soulève le problème de l'écoulement du mélange de la résine avec les charges à travers le renfort fibreux. L'augmentation de la viscosité due aux particules, d'une part, et la filtration éventuelle des charges par le réseau fibreux, d'autre part, sont deux phénomènes à considérer car ils peuvent engendrer d'importants défauts de fabrication. Cette étude, volontairement limitée à une géométrie 1D, comporte une phase expérimentale et une phase de modélisation à l'échelle macroscopique, complémentaires l'une de l'autre, et menées en parallèle. Un moyen simple de mesure de la quantité de charges présentes dans la pièce en fin d'injection a d'abord été mis au point. Des essais d'injection de pièces, menés dans différentes conditions expérimentales, ont mis en évidence l'existence de deux comportements de filtration distincts. La modélisation est basée sur une équation de conservation de la masse et trois équations constitutives. Le modèle de filtration proposé dépend de deux paramètres physiques et d'un seul paramètre numérique, qui ont été identifiés par méthode inverse à partir des résultats expérimentaux. Enfin, la résolution du modèle développé est couplée à celle de l'écoulement d'un fluide à travers un renfort fibreux. Les résultats de la simulation, tant pour le profil de concentration de charges dans la pièce que pour le temps d'injection, sont très satisfaisants et viennent valider la démarche générale de cette étude.
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Kaushik, Swati. "Mécanisme de filtration des suspensions de microgel." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0019/document.
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Les écoulements de suspensions dans des milieux poreux sont particulièrement complexes, notamment à cause du couplage d’écoulements de cisaillement et d’écoulements élongationnels (Herzig, Leclerc et Goff, 1970). On les retrouve fréquemment dans les applications industrielles, l’une des applications principales se trouvant lors des opérations de production de pétrole et de gaz. Lors de la construction d'un puits, des additifs polymères anti perte de fluide empêchent à plusieurs étapes l'écoulement de fluide entre le puits et la formation de roche poreuse environnante. La perte de fluide est un problème grave si elle n’est pas maîtrisée ; elle s’ajoute alors au coût total des opérations et pourrait surtout avoir des conséquences néfastes pour l’environnement et les opérateurs. Parmi les technologies disponibles, des additifs polymères connus sous le nom d'additifs anti perte de fluide, tels que des microgels et des particules de latex, sont ajoutés aux fluides injectés pour limiter les pertes de fluide (généralement de l'eau) via un mécanisme de colmatage / blocage de pores du support poreux.Le comportement de blocage de beaucoup de ces additifs anti perte de fluide a été testé par des méthodes conventionnelles qui impliquent l'application d'une différence de pression élevée (typiquement 35-70 bars) sur le fluide formulé comprenant les additifs contre un filtre représentatif de la taille typique des pores de la formation (une grille métallique, de la céramique ou du papier filtre) et la mesure du volume de filtrat en fonction du temps. Cependant, ces méthodes standard ne permettent pas de comprendre le mécanisme sous-jacent de la dynamique de blocage des supports poreux. Par conséquent, une meilleure compréhension du mécanisme de blocage d’un support poreux par des additifs industriels anti perte de fluide est nécessaire.Dans ce travail, nous utilisons des suspensions de microgels réticulés chimiquement comme additifs anti perte de fluide et nous étudions leur comportement de blocage dans des milieux poreux modèles transparents. Nous utilisons des dispositifs à base de polydiméthylsiloxane (PDMS) comme modèle de support poreux permettant l'observation directe du processus de blocage couplée à des mesures quantitatives. Nous fabriquons des dispositifs microfluidiques de filtration frontale et de filtration latérale avec différentes tailles de pores afin de déterminer comment des paramètres tels que la mouillabilité de la surface, la concentration en particules, la taille des particules et le débit affectent la formation du gâteau de filtration.Nous présentons une méthode de contrôle de la taille des particules constituant les suspensions de microgels. Nous décrivons ensuite une approche pour préparer des suspensions à plus haute concentration et étudions la rhéologie des suspensions en fonction de la concentration en particules. De plus, nous présentons un procédé simple pour former un gâteau de filtration à partir de la suspension de microgels sur une membrane et estimons la perméabilité à l’eau du gâteau de filtration formé selon la loi de DarcyThe flow of suspensions in porous media is a complex phenomenon due to the mechanisms involved such as both shear and extensional flows (Herzig, Leclerc, & Goff, 1970). Their use in industrial applications is quite extensive with one of the major applications being at various stages of oil and gas production operations. At several stages of a well construction, flow of fluid between the well and the surrounding porous rock formation is prevented thanks to the polymeric fluid loss control additives. Fluid loss is a severe problem if not controlled, which would add up to the total cost of operations and more importantly could have hazardous impacts on the environment or operators. Among several technologies industrially available, polymeric additives popularly known as fluid loss additives such as microgels and latex particles are added to the injected fluids to limit the loss of fluid (usually water) via the mechanism of pore clogging/jamming in porous media.Many of these fluid loss additives have been tested for their jamming behaviour by conventional methods which involve the application of a high pressure difference (typically 35-70 bars) on the formulated fluid comprising of the additives against a filter representative of the formation’s typical pore size (either a metallic grid, ceramic or filter paper) and the measurement of the filtrate volume versus time. However, these standard methods do not give any insight in understanding the underlying mechanism of jamming dynamics in porous media, hence, a better understanding of the mechanism of jamming in porous media by industrial fluid loss additives is needed.In this work, we use chemically cross-linked microgel suspensions as the fluid loss additive and study its jamming behaviour in transparent model porous media. We make use of polydimethylsiloxane (PDMS) devices as model porous media which allows direct observation of the jamming process coupled with quantitative measurements. We fabricate microfluidic devices for frontal flow filtration and lateral flow filtration with different pore sizes to see how parameters like surface wettability, particle concentration, particle size and flow rates affect the filter cake formation.We present a method of controlling the size of the microgel suspensions. We then describe an approach for preparing higher concentration suspensions and investigate the rheology of the suspensions as a function of concentration. Furthermore, we present a simple method of forming a filter cake of the microgel suspension on a supporting membrane and estimate the permeability of the filter cake formed for the flow of water using Darcy’s law
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Adam, Jérémy. "Développement, modélisation et caractérisation d'une maille innovante réalisée en fabrication additive pour les grands défauts osseux." Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0068/document.
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Ce travail de thèse traite du développement d’une maille en titane imprimée en 3D pour le comblement des grands défauts osseux. La perte de substance osseuse intervient lors de traumatismes importants ou de chirurgies ablatives (dues à des infections ou à des cancers). Lorsque le défaut atteint un stade critique, la régénération osseuse est impossible et on assiste à une perte de fonction. Il faut alors recourir à des chirurgies reconstructrices comme par exemple la reconstruction mandibulaire. Aujourd’hui, la chirurgie communément pratiquée pour reconstruire la mandibule est la reconstruction par lambeaux libres de fibula, laquelle demande un investissement en temps et en ressource colossale pour des résultats mitigés avoisinant les 10% de taux d’échec. En nous basant sur la littérature internationale, nous avons développé une maille en titane imprimée en 3D pour remplacer l’autogreffe de fibula et ainsi limiter les effets secondaires liés au site donneur tout en offrant aux cellules mésenchymateuses des conditions optimales à la colonisation osseuse. D’un point de vue mécanique, cela consiste à abaisser la rigidité native du titane (110GPa) à une rigidité comprise entre 0,1 et 1 GPa. Pour réaliser cette maille, nous avons mis en place une méthodologie de design qui nous a permis d’innover en mettant au point un système de reprise de charge. Ce système de reprise de charge permet d’adapter la réponse de l’implant en fonction de l’intensité de la sollicitation, ce qui permet de combiner une rigidité faible et une résistance à l’effort élevée. Les différentes itérations de design ont été testées par éléments finis, jusqu’au motif final, lequel a été caractérisée lors de tests mécaniques réels en compression, en traction et en flexion. Remplissant la majorité du cahier des charges, nous avons ensuite mis au point une étude animale, laquelle sera réalisée ultérieurement. Enfin, cette étude a permis de mettre en évidence certaines limitations de l’impression 3D métallique, principalement liés aux surfaces non supportées que nécessitent la reprise de charge. Cette maille très prometteuse est aujourd’hui en cours d’optimisation pour permettre d’être rapidement mise à la disposition des patientsThe work detailed in this thesis is about a titanium 3D printed mesh for large bone defects. Large bone defects are often due to surgical resections, performed after a cancer or an infection. When the defect reach a critical size, bone regeneration is impossible and it often leads to the loss of function. When it happened, the wound need to be cured using reconstructive surgery. The mandibular reconstruction is one of the most performed reconstructive surgery. Nowadays, we reconstruct the mandible with the fibula free flap technique, which require huge amount of time and resources for mixed results (around 10% failure rate). Based on the international literature, we developed a titanium 3D printed mesh to replace the fibula autograft and limit its side effect while offering to mesenchymal cells optimal growing environment. On the mechanical point of view, this environment requires to decrease the titanium initial rigidity from 110GPa to a range between 0.1 and 1GPa. In order to achieve that goal, we have developed a design methodology that lead us to innovation. We developed a load restauration system that allow us to combine low rigidity and high resistance. In order to find the final design, we used finite element modeling. Then, the final design have been tested mechanically in compression, traction and flexion. Because most of the requirements were reached, we designed an animal study which should take place in the next years. Eventually, we discovered some limitation for metallic 3D printing, essentially due to unsupported areas required for the load restauration. This innovative mesh is today optimized in order to be rapidly given to patients in the need
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Boulvert, Jean. "Traitements acoustiques à porosité contrôlée pour atténuation optimale." Thesis, Le Mans, 2020. http://www.theses.fr/2020LEMA1033.
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Cette thèse exploite certaines possibilités offertes par la fabrication additive pour concevoir et optimiser des traitements pour l'atténuation acoustique à base de matériaux poreux sous un nouvel angle. La fabrication additive permet de contrôler chaque pore d'un matériau individuellement. Le processus de conception de traitement poreux est chamboulé : pour répondre à un problème, au lieu de chercher parmi un catalogue de matériaux existants, il est possible de concevoir directement le matériau adéquat en ajustant sa microstructure. Cette recherche s'inscrit dans une démarche de réduction du bruit des réacteurs d'avion mais s'étend au-delà du domaine aéronautique, aussi bien au niveau théorique qu'à celui de ses possibles applications. Une méthode de prédiction de comportement acoustique de matériaux poreux produits par fabrication additive prenant en compte l'impact des défauts de fabrication est d'abord introduite. Les matériaux poreux à gradient de propriétés contrôlé sont ensuite étudiés. Une méthode d'optimisation des paramètres microstructuraux ou de fabrication est développée. La capacité des matériaux poreux à gradient de propriété à atténuer des fréquences hors de portée des matériaux sans gradient est ainsi prouvée et le gradient optimal pour l'atténuation large bande est défini. L'impact de la taille des parois des pores ainsi que l'impact de possibilité du son de se propager transversalement dans un matériau poreux est étudié. Enfin, un traitement métaporeux permettant l'absorption large bande et sub-longueur d'onde est développé. Les résultats de cette recherche peuvent être mis en application pour créer des traitements poreux à forte capacité d'atténuation du bruit. Cette recherche fait appel à des modèles analytiques et numériques basés sur l'hypothèse selon laquelle le matériau poreux peut être considéré acoustiquement comme un fluide équivalent, à l'analyse physique des comportements et à des validations expérimentales au travers de tests en tube d'impédance de spécimens produits par fabrication additiveThis thesis exploits some of the new possibilities offered by additive manufacturing to design and optimize treatments for sound attenuation consisting in porous materials. Additive manufacturing allows to control individually each pore of a material. The porous treatment design process is turned upside down: instead of searching through a catalogue of existing materials to solve a problem, it is possible to directly design the right material by adjusting its microstructure. This research is part of a plan to reduce aircraft engine noise but extends beyond the aeronautical field, both theoretically and in terms of possible applications. A predicting method of the acoustic behaviour of porous materials produced by additive manufacturing and taking into account the impact of manufacturing defects is first introduced. Porous materials with controlled graded properties are then studied. A method for optimizing microstructural or manufacturing parameters is developed. The ability of graded porous materials to attenuate frequencies too low to be attenuated by non-graded materials is then proven and the optimal gradient for broadband attenuation is defined. The impact of the wall thickness of the pores along with the impact of transverse propagation inside porous materials is studied. Finally, a metaporous treatment allowing broadband and sub-wavelength absorption is developed. The results of this research can be applied to create porous treatments with a high noise attenuation. The analytical and numerical models used in this research are based on the hypothesis of porous materials acoustically behaving as equivalent fluids. The results are physically analyzed and experimentally validated through impedance tube testing of specimens produced by additive manufacturing
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Lambert, Océane. "Solutions architecturées par fabrication additive pour refroidissement de parois de chambres de combustion." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI048/document.
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En vue de leur refroidissement, les parois de chambres de combustion aéronautiques sont perforées de trous à travers lesquels de l’air plus froid est injecté. La paroi est ainsi refroidie par convection et un film isolant est créé en surface chaude (film cooling). Cette thèse a pour objectif d’utiliser les possibilités de la fabrication additive pour proposer de nouvelles solutions architecturées qui permettraient d’augmenter les échanges de chaleur internes et d’obtenir ainsi de meilleures efficacités de refroidissement.La première approche consiste à élaborer de nouveaux designs de plaques multiperforées par Electron Beam Melting (EBM) et Selective Laser Melting (SLM) aux limites de résolution des procédés. Les architectures sont caractérisées en microscopie, en tomographie X et en perméabilité. Des simulations aérothermiques permettent de mettre en évidence l’effet de ces nouveaux designs sur l’écoulement et les échanges de chaleur, et de proposer des voies d’amélioration de la géométrie.La deuxième approche consiste à élaborer de façon simultanée une pièce architecturée par EBM, avec des zones denses et poreuses. A partir d’analyse d’images associée à une cartographie EBSD grand champ, il est possible de remonter aux mécanismes de formation du matériau poreux et de relier la perméabilité et la porosité aux paramètres procédé. Afin de favoriser le film cooling, il pourrait être avantageux que les zones microporeuses soient orientées dans le sens de l’écoulement. Pour ce faire, un nouveau procédé dénommé Magnetic Freezing, où des poudres métalliques forment une structure orientée par un champ magnétique, est mis au point.Les diverses solutions développées durant cette thèse sont testées sur un banc aérothermique. Les essais montrent qu’elles offrent un refroidissement plus efficace et plus homogène que la référence industrielle. Enfin, de premiers tests en combustion sur l’une des structures retenues, plus légère et plus perméable que la référence, montrent qu’il s’agit d’une solution aussi efficace à un débit traversant donné, et donc a priori plus efficace à une surpression donnéeCombustion chamber walls are perforated with holes so that a cooling air flow can be injected through them. The wall is cooled by convection and an insulating film is created on the hot surface (film cooling). This PhD thesis aims to use the possibilities of additive manufacturing to provide new architectured solutions that could enhance the internal heat exchanges, and lead to a higher cooling effectiveness.The first approach is to develop new designs of multiperforated walls by Electron Beam Melting (EBM) and Selective Laser Melting (SLM) used at the resolution limits of the processes. They are characterized by microscopy, X-ray tomography and permeability tests. Some aerothermal simulations help understanding the effects of these new designs on the flow and on heat exchanges. These results lead to a geometry adaptation.The second approach is to simultaneously manufacture an architectured part with dense and porous zones by EBM. Thanks to image analysis combined with large field EBSD, it is possible to investigate the mechanisms leading to the porous zones and to link them to permeability and porosity. The film cooling effect could be favoured by the orientation of pores towards the cooling flow. Therefore, a new powder-based manufacturing process named Magnetic Freezing, where metallic powders organize into an oriented structure thanks to a magnetic field, is developed.The various solutions studied during this thesis are tested on an aerothermal bench. They all show a more efficient and homogeneous cooling than the industrial reference. Some first tests on one of the selected solutions are performed on a combustion bench. This lighter and more permeable structure proves to be a solution as efficient as the industrial reference at a given flow rate. It should therefore be a more efficient solution for a given overpressure
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Taniguchi, Naoya. "Effect of pore size on bone ingrowth into porous titanium implants fabricated by additive manufacturing: An in vivo experiment." Kyoto University, 2016. http://hdl.handle.net/2433/215404.
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Subscription articles: Theses and dissertations which contain embedded PJAs as part of the formal submission can be posted publicly by the awarding institution with DOI links back to the formal publications on ScienceDirect.doi:10.1016/j.msec.2015.10.069Kyoto University (京都大学)
0048
新制・課程博士
博士(医学)
甲第19578号
医博第4085号
新制||医||1013(附属図書館)
32614
京都大学大学院医学研究科医学専攻
(主査)教授 安達 泰治, 教授 開 祐司, 教授 妻木 範行
学位規則第4条第1項該当
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Lacroix, Sébastien. "Solveurs linéaires pour la simulation d'écoulements polyphasiques en milieux poreux, à fortes hétérogénéités et grand nombre de mailles, en modélisation de réservoirs pétroliers." Paris 6, 2004. http://www.theses.fr/2004PA066466.
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Zocca, Andrea [Verfasser]. "Additive manufacturing of porous ceramic structures from preceramic polymers / Andrea Zocca." Clausthal-Zellerfeld : Universitätsbibliothek Clausthal, 2016. http://d-nb.info/1093614021/34.
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Menon, Arun. "sintering Additives for Nanocrystalline Titania and Processing of Porous Bone Tissue Engineering Scaffolds." Master's thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2211.
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Titania (Titanium dioxide, TiO2) has been researched as a promising biomaterial due to its excellent biocompatibility. However, the main limitation of titania is its poor mechanical properties which limit its use in many load-bearing applications. In this thesis report, the properties of titania were improved by doping with small quantities of MgO, ZnO and SiO2 as sintering additives. Nanocrystalline powder was selected, as it possesses outstanding properties over conventional coarse-grained powders due to reduced grain size. Nanocrystalline anatase powder of size 5-15 nm was synthesized via a simple sol-gel technique. Small quantities of dopants were introduced into pure titania powder, through homogeneous mixing. The doped powder compositions were compacted uniaxially and sintered at 1300oC and 1500oC, separately, in air. The effects of sintering cycle and temperature on the microstructure, densification and mechanical properties of the sintered structures were studied. Mg doped structures recorded maximum sintered density of 3.87 g.cm-3. Phase analysis was carried out using powder XRD technique using Cu K[alpha] radiation. Microstructural analysis was performed using Scanning electron microscopy. The mechanical properties were assessed by evaluating hardness and biaxial flexural strength (ASTM F-394) of the structures. Results showed 12% increase in hardness and 18% increase in biaxial flexural strength in structures doped with ZnO and SiO2, respectively. Further, simulated body fluid maintained at 36.5oC was used to study the bioactivity and degradation behavior of the structures. The second part of the work aimed in the processing of porous titania scaffolds using polyethylene glycol as the pore-former. The green structures were sintered at 1400oC and 1500oC, separately in air and their properties have been studied. Microstructural analysis was carried out using Scanning electron microscope (SEM). Porosity was evaluated using the immersion technique. Vickers hardness and biaxial flexural tests were used to carry out the mechanical characterization. Further, the biomechanical/biodegradation behavior of the structures was assessed in simulated body fluid (SBF). Biodegradation and change in biomechanical properties as a function of time were studied in terms of weight change, change in Vickers hardness and biaxial flexural strength. The mechanical properties of porous titania scaffolds doped separately with MgO and ZnO have also been studied to investigate the influence of these additives on the properties of porous structures. The Vickers hardness and biaxial flexural strength were seen to improve with the addition of these sintering additives.M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science & Engr MSMSE
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Walker, Jason M. "Additive Manufacturing towards the Realization of Porous and Stiffness-tailored NiTi Implants." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1396617330.
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Taheri, Andani Mohsen. "Modeling, Simulation, Additive Manufacturing, and Experimental Evaluation of Solid and Porous NiTi." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1438888243.
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Deng, Honghua Materials Science & Engineering Faculty of Science UNSW. "Effect of cation addition on cellular response and bone ingrowth into three dimensional porous bioceramics." Awarded by:University of New South Wales. Materials Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/43733.
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The success of orthopaedic implants fixed in the skeletal system using bone ingrowth into porous surfaces is critically dependent on the extent and quality of the initial bone ingrowth and the subsequent long-term maintenance of the bone within the porous structure. Biologically-significant elements (Ca, Mg, Mn) were incorporated at concentrations up to 5 mol% in solid solution in yttia-stabilised tetragonal zirconia polycrystal (3YTZP), whilst controlling microstructure and phase composition, to investigate the effect of ceramic chemistry on cellular behaviour in vitro and bone ingrowth into porous structures in vivo. Cellular attachment, proliferation, and migration on the ceramics were investigated using in vitro assays using fibroblasts. Cells were able to adhere strongly and proliferate on all ceramic surfaces, exhibiting maximal proliferation and minimal migration on 3YTZP but significantly faster migration on doped-3YTZP. The TZP ceramics were therefore considered to support normal cellular processes and thus were suitable for further study in vivo. A technique based on pressure casting ceramic slurry into a polymer preform of the desire pore structure, followed by polymer burnout and then sintering, was developed for fabricating porous bioceramics containing highly-controlled three-dimensional pore geometries. The ability of a selected pore structure to support bone ingrowth was tested using hydroxyapatite by implanting samples into femoral cortical bone of adult sheep for 4 and 12 weeks. Bone was able to rapidly colonise the porous structure and remodel such that, by 12 weeks implantation time, the majority of the porosity was filled with mature lamellar bone. Porous scaffolds of pure 3YTZP and 3YTZP doped with 1 mol% Mg, 1 mol% Mn, 1 mol% Ca, or 5 mol% Ca were fabricated and tested in the sheep model. Bone ingrowth into the doped compositions was significantly greater than that into pure 3YTZP, and was similar to that into the porous hydroxyapatite, indicating that the dopants significantly promoted osteogenesis within the bioinert scaffolds. This finding has application in clinical applications in that the initial bone ingrowth and, potentially, the long-term maintenance of bone within the porous structure may be improved by the incorporation of small amounts of biologically significant elements.
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Fleming, Steven. "Agro-process intensification using nano-structured micro-porous polymers as soil additives to enhance crop production." Thesis, University of Newcastle upon Tyne, 2012. http://hdl.handle.net/10443/1894.
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Polymerised High Internal Phase Emulsion Polymer (PHP) is a nano-structured microporous polymeric material with a variety of applications. PHPs may have a role to play in sustaining or enhancing crop yields in increasingly alien environments. An elastic hydrophilic version has been developed that has been shown to increase crop yields when used as a soil additive. Soil is a natural carrier of water and nutrients as well as bacteria all of which are widely distributed in the soil and inefficiently maintained and utilised by plants. When polymer is added to the soil, water is attracted to the polymer because of its hydrophilic nature, then roots are attracted to the water and nutrients (if present) in the polymer and they become intimately associated with PHP which therefore brings the plant into close proximity with any fertiliser and bacteria loaded into the polymer. Hence the polymer promotes the interactions between water/nutrients/bacteria/plant roots as well as root exudates within microscopic scale acting as a synthetic rhizosphere which benefits the plant in three ways: (1) Efficient water utilisation and conservation by the plant thus allowing plants to grow in drier environments than would otherwise be possible. The dry weight of soybean shoots with PHP added was increased over 100% compared to plants with no PHP. (2) By adding a fertiliser component to the polymer it can act as a slow release fertiliser, releasing the fertiliser in close proximity to the plant roots, so a larger proportion is utilised by the plant rather than being leached away as normally happens when fertiliser is added direct to the soil. By modifying the production method of PHP so that it contained ammonium sulphate, a major component of many fertilisers, the dry weights of soybean shoots and pea shoots were increased by 66% and 48% respectively after 6 weeks growth. (3) By loading the polymer with beneficial bacteria and fungi, in particular nitrogen fixing bacteria and mycorrhizal fungi, it then offers a protective environment for the organisms which then have a competitive advantage over other soil organisms so their numbers can increase enabling them to make a significant contribution to the nutrient requirements of the plants, in particular nitrogen. The addition of PHP soaked with Azospirillum brasilense broth produced a dry weight increase in grass shoots of 9.6%, 9.5%, 40% and 145% after 3, 6, 9 and 12 weeks growth respectively compared to plants with no PHP or bacteria
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Goel, Archak. "Design of Functionally Graded BCC Type Lattice Structures Using B-spline Surfaces for Additive Manufacturing." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552398559313737.
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Williams, Christopher Bryant. "Design and development of a layer-based additive manufacturing process for the realization of metal parts of designed mesostructure." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22687.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2008.Committee Co-Chair: David Rosen; Committee Co-Chair: Farrokh Mistree; Committee Member: David McDowell; Committee Member: Hamid Garmestani; Committee Member: Joe Cochran; Committee Member: Shreyes Melkote.
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Regmi, Gaurav. "EFFECTS OF ADDITION OF LARGE PERCENTAGES OF FLY ASH ON LIQUEFACTION BEHAVIOR OF SAND." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1461.
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The liquefaction resistance of a saturated medium sand with varying amount of non-plastic type F fly ash was evaluated by conducting cyclic triaxial tests. The test results were used to evaluate the effect of addition of various percentages of fly ash on the liquefaction resistance of Ottawa sand. The effect of cyclic shear stress and confining pressure on liquefaction resistance of the sand-fly ash mixtures was the main scope of this research. In addition, the Young's Modulus and Damping Ratio for sand-fly ash mixtures were also determined. A comprehensive experimental program was conducted in which 50 stress controlled cyclic triaxial tests were performed on a clean sand, sand containing 25%, 30%, 50% and 70% fly ash at a constant relative density of 50%. The results show that sand containing 25% fly ash has the highest liquefaction resistance under cyclic loading in comparison to clean sand and sand containing 30%, 50% and 70% fly ash. The cyclic resistance goes on decreasing as the fly ash content further increases. The test result also shows that the liquefaction resistance of the clean sand and sand containing 70% fly ii ash is almost same. The test results were also examined in terms of the conceptual framework of Thevanayagam (2000). The effects on liquefaction resistance were also measured in terms of pore water pressure generation and deformation of the sample. As the confining pressure increases, shear stress required to cause initial liquefaction of the sample also increases. Modulus of Elasticity was seen to increase with increase in confining pressure and decrease with increase in axial strain for all cases of sand-fly ash mixtures used in these tests. The damping ratio of the sample increases with the increase in axial strain upto about 1% and then it either decreases or remains constant thereafter. There was no clear correlation of damping ratio with confining pressure.
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Caputo, Matthew P. "4-Dimensional Printing and Characterization of Net-Shaped Porous Parts Made from Magnetic Ni-Mn-Ga Shape Memory Alloy Powders." Youngstown State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1525436335401265.
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Brennan, Daniel P. "Small molecule and polymer templating of inorganic materials." Diss., Online access via UMI:, 2006.
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Myers, Eric J. "Finite Element Modeling (FEM) of Porous Additively Manufactured Ferromagnetic Shape Memory Alloy Using Scanning Electron Micrograph (SEM) Based Geometries." Youngstown State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ysu149399154152881.
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Ahsan, AMM Nazmul. "Form and Functionality of Additively Manufactured Parts with Internal Structure." Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/31532.
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The tool-less additive manufacturing (AM) or 3D printing processes (3DP) use incremental consolidation of feed-stock materials to construct part. The layer by layer AM processes can achieve spatial material distribution and desired microstructure pattern with high resolution. This unique characteristics of AM can bring custom-made form and tailored functionality within the same object. However, incorporating form and functionality has their own challenge in both design and manufacturing domain. This research focuses on designing manufacturable topology by marrying form and functionality in additively manufactured part using infill structure. To realize the goal, this thesis presents a systematic design framework that focuses on reducing the gap between design and manufacturing of complex architecture. The objective is to develop a design methodology of lattice infill and thin shell structure suitable for additive manufacturing processes. Particularly, custom algorithmic approaches have been developed to adapt the existing porous structural patterns for both interior and exterior of objects considering application specific functionality requirements. The object segmentation and shell perforation methodology proposed in this work ensures manufacturability of large scale thin shell or hollowed objects and incorporates tailored part functionality. Furthermore, a computational design framework developed for tissue scaffold structures incorporates the actual structural heterogeneity of natural bones obtained from their medical images to facilitate the tissue regeneration process. The manufacturability is considered in the design process and the performances are measured after their fabrication. Thus, the present thesis demonstrates how the form of porous structures can be adapted to mingle with functionality requirements of the application as well as fabrication constraints. Also, this work bridges the design framework (virtual) and the manufacturing platform (realization) through intelligent data management which facilitates smooth transition of information between the two ends.National Science Foundation #OIA-1355466
National Science Foundation-DMR- MRI #1625704
National Institute of Health - COBRE: CDTSPC; Grant # P20GM109024
US-DOT # 693JK31850009CAAP
Dept. of Commerce Research-ND, Award # 17-08-G-191
CSMS, NDEPSCoR
NDSU Grand Challenge and Development Foundation
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Dry, Carolyn Minnetta. "Design of systems for time delayed activated internal release of chemicals in concrete from porous fibers, aggregates of prills, to improve durability." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/37870.
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Incorporation of chemicals into the internal matrix of cement or concrete, with later release occurring upon stimulation, alters the matrix parameters from those at the initial set. Permeability is reduced, for example, and therefore durability enhanced. The advantages of these designs would be the ability to reduce maintenance and repair costs in the initial building configuration and to delay the time of eventual repair. The components and the structure could take greater environmental abuse also.
Permeability is significantly reduced by release of a polymer from wax-coated porous fibers upon heating to temperature of polymerization. Freeze/thaw damage is somewhat reduced by the timed release of linseed oil or antifreeze from porous aggregates due to the freezing action itself. These example designs using timed release mostly gave improved durability performance when compared to conventional treatments for durability or environmental distress. Concerns that significant strength reduction would occur due to heating or fiber loading were shown to be unfounded by our test results; indeed, heating and fiber inclusion increased strength. An adequate amount of wetting of the samples could be obtained with 2.75% volume of fibers; however, above a 2.75% volume of fibers, fibers do reduce the strength. Results were analyzed by the method of comparing results in the samples with factors varied to results in samples without variable factors, that is, by comparing to the controls.
This research shows that timed internal release of chemicals into cement can be accomplished; it appears feasible and is potentially useful.
Long-term tests need to be performed on such factors as chloride ion intrusion/ corrosion tests. Filled fiber, aggregate or prill manufacture, storage, and placement need to be researched and assessed for cost. Design of components using only targeted areas for release in the component and the use of time released fibers in reinforced cement laminates should be evaluated.Ph. D.
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Mercier, Anthony. "Préparation, caractérisation et fonctionnalisation de polymères ultraporeux : les POLYHIPEs." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2001. http://tel.archives-ouvertes.fr/tel-00815119.
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Des supports polymères insolubles, à haute porosité et à cellules ouvertes, appelés polyHIPEs, ont été préparés par polymérisation d'émulsions inverses hautement concentrées (HIPEs). Un polyHIPE précurseur, le (vinyl)polystyrène polyHIPE, a été synthétisé puis caractérisé dans le but d'être fonctionnalisé sous forme de colonne ou de petits dés. Ce précurseur, porteur d'un grand nombre de groupements vinylbenzyle, permet l'addition de petites molécules fonctionnelles, en particulier l'addition régiosélective par voie radicalaire de thiols fonctionnels. Un polyHIPE stannique a également été préparé par copolymérisation de monomères chlorostanniques. Les polyHIPEs fonctionnels se sont révélés efficaces pour l'extraction sélective d'espèces chimiques en solution et pour des réductions et cyclisations radicalaires. Le contrôle de la taille et de la polydispersité des cellules a été étudié.
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Saedi, Soheil. "Shape Memory Behavior of Dense and Porous NiTi Alloys Fabricated by Selective Laser Melting." UKnowledge, 2017. http://uknowledge.uky.edu/me_etds/90.
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Selective Laser Melting (SLM) of Additive Manufacturing is an attractive fabrication method that employs CAD data to selectively melt the metal powder layer by layer via a laser beam and produce a 3D part. This method not only opens a new window in overcoming traditional NiTi fabrication problems but also for producing porous or complex shaped structures. The combination of SLM fabrication advantages with the unique properties of NiTi alloys, such as shape memory effect, superelasticity, high ductility, work output, corrosion, biocompatibility, etc. makes SLM NiTi alloys extremely promising for numerous applications.
The SLM process parameters such as laser power, scanning speed, spacing, and strategy used during the fabrication are determinant factors in composition, microstructural features and functional properties of the SLM NiTi alloy. Therefore, a comprehensive and systematic study has been conducted over Ni50.8 Ti49.2 (at%) alloy to understand the influence of each parameter individually. It was found that a sharp [001] texture is formed as a result of SLM fabrication which leads to improvements in the superelastic response of the alloy. It was perceived that transformation temperatures, microstructure, hardness, the intensity of formed texture and the correlated thermo-mechanical response are changed substantially with alteration of each parameter. The provided knowledge will allow choosing optimized parameters for tailoring the functional features of SLM fabricated NiTi alloys. Without going through any heat treatments, 5.77% superelasticity with more than 95% recovery ratio was obtained in as-fabricated condition only with the selection of right process parameters.
Additionally, thermal treatments can be utilized to form precipitates in Ni-rich SLM NiTi alloys fabricated by low energy density. Precipitation could significantly alter the matrix composition, transformation temperatures and strain, critical stress for transformation, and shape memory response of the alloy. Therefore, a systematic aging study has been performed to reveal the effects of aging time and temperature. It was found that although SLM fabricated samples show lower strength than the initial ingot, heat treatments can be employed to make significant improvements in shape memory response of SLM NiTi. Up to 5.5% superelastic response and perfect shape memory effect at stress levels up to 500 MPa was observed in solutionized Ni-rich SLM NiTi after 18h aging at 350ºC. For practical application, transformation temperatures were even adjusted without solution annealing and superelastic response of 5.5% was achieved at room temperature for 600C-1.5hr aged Ni-rich SLM NiTi.
The effect of porosity on strength and cyclic response of porous SLM Ni50.1 Ti49.9 (at%) were investigated for potential bone implant applications. It is shown that mechanical properties of samples such as elastic modulus, yield strength, and ductility of samples are highly porosity level and pore structure dependent. It is shown that it is feasible to decrease Young’s modulus of the SLM NiTi up to 86% by adding porosity to reduce the mismatch with that of a bone and still retain the shape memory response of SLM fabricated NiTi. The shape memory effect, as well as superelastic response of porous SLM Ni50.8Ti49.2,were also investigated at body temperature. 32 and 45% porous samples with similar behaviors, recovered 3.5% of 4% deformation at first cycle. The stabilized superelastic response was obtained after clicking experiments.
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Bigarre, Janick. "Effets des impuretés sur la charge d'espace dans l'alumine : application au frottement." Ecully, Ecole centrale de Lyon, 1996. http://www.theses.fr/1996ECDL0007.
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L'effet des impuretés et des dopants dans l'alumine sur le piégeage de charges a été étudié à partir des monocristaux de saphirs purs et impurs, de rubis (saphirs dopés au chrome) et d'alumine polycristalline implantée par des ions zirconium. L'aptitude à former une charge d'espace a été déterminée par la méthode du miroir électrostatique en relation avec la caractérisation des sites de piégeage générés par les impuretés, le chrome et l'implantation ionique. Enfin, les propriétés de charges ont été corrélées avec le comportement tribologique de l'alumine en régime de frottement sans usure.
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Tammas-Williams, Samuel. "XCT analysis of the defect distribution and its effect on the static and dynamic mechanical properties in Ti-6Al-4V components manufactured by electron beam additive manufacture." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/xct-analysis-of-the-defect-distribution-and-its-effect-on-the-static-and-dynamic-mechanical-properties-in-ti6al4v-components-manufactured-by-electron-beam-additive-manufacture(cb034391-b61f-4e16-91cd-7ad3c9ec6312).html.
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Selective electron beam melting (SEBM) is a promising powder bed Additive Manufacturing technique for near-net-shape manufacture of high-value titanium components. An extensive research program has been carried out to characterise in 3D the size, volume fraction, and spatial distribution of the pores in model samples, using X-ray computed tomography (XCT), and correlate them to the SEBM process variables. The average volume fraction of the pores (97.5 %) where fatigue cracks would initiate based on the relative stress intensity factor of all the pores. In contrast, crack growth was found to be insensitive to porosity, which was attributed to the much higher stress concentration generated by the crack in comparison to the pores. Some crack diversion was associated with the local microstructure, with prior β grain boundaries often coincident with crack diversion.
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Bertin, Matthieu. "L’impact du séchage au jeune âge sur la carbonatation des matériaux cimentaires avec additions minérales." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1034/document.
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De nos jours, l’utilisation de liants à faible teneur en clinker est de plus en plus courante. Or la cinétique de réaction des additions minérales utilisées est plus lente que celle du clinker. Si les conditions de cure ne sont pas adaptées, le matériau aura une structure poreuse plus importante, ce qui le rendra plus sensible à la pénétration des agents agressifs extérieurs comme le CO2 ou les Cl-. La carbonatation du béton est l’un des principaux phénomènes pouvant diminuer la durée de vie d’une structure en béton armé. En effet, elle entraine une diminution du pH de la solution interstitielle qui a pour conséquence une dépassivation des armatures, puis la corrosion de ces dernières si les conditions s’y prêtent.L’objectif de cette thèse est d’étudier l’impact de la carbonatation au jeune âge sur des liants à faible teneur en clinker. Pour cela l’étude se compose de deux aspects : le premier est l’étude de l’impact de l’hydratation et de la carbonatation sur les propriétés de transport et les isothermes de sorption hydrique, et le second est l’étude de l’impact du couplage hydratation-séchage-carbonatation sur la microstructure et la structure poreuse. Pour le premier aspect, les propriétés de transport étudiées sont la diffusion de l’O2, la diffusion de la vapeur d’eau, la perméabilité à l’eau liquide qui sont des données d’entrée dans les modèles de carbonatation ainsi que la perméabilité aux gaz qui est un indicateur de durabilité. Pour le second aspect, l’impact du couplage est mesuré par ATG et DRX pour déterminer l’assemblage de phases, de plus de la porosimétrie par intrusion de Mercure et des pesées hydrostatiques sont effectuées pour détecter le changement de la structure poreuse. Les matériaux étudiés sont des pâtes de ciment et des bétons avec un rapport eau/ liant de 0,57 avec l’un des trois liants suivants : CEM I, CEM I +30% de cendres volantes et CEM I +60% de laitiers.Pour le premier aspect, les résultats montrent que pour les pâtes de CEM I le temps de cure a un faible impact sur les isothermes de sorption de vapeur d’eau s’il est compris entre 3 jours et 6 mois. Alors que, pour les pâtes de CEM I + 60% de laitier, l’augmentation du temps de cure accroit significativement la teneur en eau (pour HR=65%, tcure=3 jours et pour tcure=6 mois ) dû à une augmentation de la teneur en C-S-H. D’autre part, la carbonatation entraine une diminution de la teneur en eau de l’échantillon, ainsi que l’amplitude de l’hystérésis. De plus, le gel a une porosité plus grossière. Par ailleurs, la carbonatation entraine une augmentation de la perméabilité aux gaz des matériaux. Pour le second aspect, les résultats montrent que l’utilisation d’additions minérales diminue la résistance à la carbonatation du matériau et que cette résistance augmente avec le temps de cure si l’échantillon contient des additions. La carbonatation de la portlandite, des C-S-H et des aluminates est concomitante. De plus, pour les matériaux aux laitiers, les résultats montrent qu’ils sont plus sensibles à la carbonatation des C-S-H et des aluminates que les CEM I. En effet quand le rapport variation molaire de CaCO3 sur variation molaire de Portlandite est calculé, il vaut 1.8 pour le CEM I et environ 3.5 pour les matériaux aux laitiers. Enfin, la carbonatation entraine une diminution du degré de saturation de l’échantillon. En effet, le degré de saturation à la surface de l’échantillon passe de 50% à 35% après carbonatation pour les échantillons de CEM I et de 50% à 5% pour les échantillons de CEM I + 60% de laitiers. Cette diminution peut s’expliquer par la diminution de la surface spécifique qui est divisée par 2 après carbonatation due à la décalcification des C-S-H. Même si la carbonatation entraine une diminution de porosité cette dernière est trop faible dans ce cas pour contrer cet effetNowaday, low clinker content binders are used more and more often. But the kinetics reactions of the supplementary cementitious materials (SCM) are slower than this one of clinker. If the curing conditions are not adapted, material will have a bigger pore structure and becomes more sensitive to the ingress of aggressive species from the environment like the CO2 or Cl-. Carbonation is one of main phenomena which can lead to decrease the life time of reinforced concrete structure. Indeed, it leads to a decrease of pore solution pH which leads to the depassivation of rebar. Then these rebars can be corroded if the conditions are appropriate.The aim of this thesis is to study the impact of carbonation at early age for binder with a low clinker content. This study was composed of two aspects: the first one is focus on the impact of hydration and carbonation on the transport properties and the water vapour sorption isotherms (WVSI), and the second one is focus on the impact of coupling hydration – drying-carbonation on the microstructure and the pore structure. For the first aspect, the studied transport properties was O2 diffusivity, water vapour diffusivity, water liquid permeability which are inputs for carbonation modelling and the intrinsic gas permeability which is a durability factor. For the second aspect, the coupling impact was measured by TGA and DRX to determine the phase assemblage; moreover Mercury intrusion porosimetry (MIP) and hydrostatic weigh were carried out to measure the change in the pore structure. The studied materials were cement pastes and concretes with water to binder ratio of 0.57 with one of the following binders: CEM I, CEM I +30% PFA and CEM I + 60% GGBS.For the first part, results show that a curing time between 3 days and 6 months has a low impact on the WVSI for the CEM I paste. Whereas, in the CEM I +60% GGBS paste, when the curing time increases, the water content increases (for a RH=65%, tcuring=3 days and for tcuring=6 months ), this is due to the increase of the C-S-H content. Moreover, carbonation leads to decrease the water content and the hysteresis becomes flat. Additionally, carbonation leads to increase the intrinsic gas permeability. For the second part, the results show that the use of SCM decreases the carbonation resistance and this resistance increases with the curing time. Carbonation of Portlandite, C-S-H and aluminates occurs in the same time. Moreover, the CEM I +60% GGBS paste are more sensitive to the carbonation of C-S-H and aluminates than the CEM I paste. Indeed, the molar variation of CaCO3 to the molar variation of Portlandite ratio has a value around 3.5 for the CEM I +60% GGBS and 1.8 for the CEM I. Finally, carbonation leads to decrease the water saturation degree at the surface of sample. Indeed, the degree of saturation at the surface of the sample increases from 50% to 35% after carbonation for the CEM I paste and from 50% to 5% for the CEm I +60% GGBS paste. This decrease can be explained by the decrease of the BET specific surface which is divided by 2 after carbonation. It is due to the decalcification of C-S-H. Although carbonation leads to a decrease of porosity, this one is too small in this case to counter this effect
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Marques, Ana Catarina Fernandes. "Design and processing of porous scaffolds based on calcium phosphates by robocasting for bone tissue engineering." Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22471.
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Doutoramento em Ciência e Engenharia de MateriaisA presente dissertação teve como foco principal o desenvolvimento de estruturas 3D porosas (scaffolds) para regeneração óssea por robocasting. Esta técnica de fabrico aditivo permite a produção de scaffolds com morfologia e estrutura predefinidas e sem a necessidade de maquinagem subsequente, podendo ser usada para o fabrico de implantes personalizados com estrutura interna semelhante à do osso que se pretende substituir. Como materiais de partida, foram utilizados pós de fosfatos de cálcio bifásicos (hidroxiapatite + β-fosfato tricálcico) não dopados, e dopados com diferentes iões (Sr, Ag, Cu, Mg e Zn), obtidos por precipitação em meio aquoso. A substituição parcial de iões Ca pelos iões dopantes induziu alterações na composição de fases cristalinas e resultou em partículas com características morfológicas distintas e em materiais com desempenhos biológicos diferentes. Os pós foram dispersos em meio aquoso com a ajuda de aditivos de processamento adequados (um dispersante e um ligante) de modo a obter suspensões com elevada concentração de sólidos, requisito essencial para o fabrico de componentes por robocasting. O tamanho e a morfologia das partículas e a concentração dos aditivos de processamento desempenharam os papéis cruciais no comportamento reológico das suspensões. A adição de agente floculante modificou drasticamente as propriedades reológicas do sistema e permitiu a obtenção de pastas com comportamento viscoelástico adequado para o processo de extrusão. Os scaffolds com diferentes tamanhos de poro foram produzidos pela deposição de um filamento com 410 μm de diâmetro. A resistência à compressão dos scaffolds sinterizados a 1100°C foi comparável ou mesmo superior à do osso esponjoso. Scaffolds com diferentes tamanhos de poro (120-500 μm) foram testados in vitro usando células estaminais mesenquimais humanas (hMSCs). Pretendeu-se avaliar a influência do tamanho dos poros na adesão celular inicial, na atividade metabólica e no potencial osteogénico. Os resultados obtidos mostraram que os poros com maior dimensão proporcionam condições favoráveis para a diferenciação osteogénica das hMSCs. Além disso, os fosfatos de cálcio co-dopados com Sr e Zn melhoraram o desempenho biológico, incluindo adesão, atividade metabólica e proliferação das hMSC. A última parte da tese foi dedicada à preparação de scaffolds não sinterizados incorporando um fármaco (levofloxacina) de forma a obter componentes com capacidade de regeneração óssea e de tratamento local de infeções. A pasta utilizada foi obtida através da dispersão dos pós de CaP numa solução de quitosano na presença do fármaco e de um agente de reticulação (genipin). Os scaffolds 3D à base de fosfatos de cálcio produzidos por robocasting no âmbito desta tese revelaram-se muito promissores para aplicações na engenharia de tecidos, particularmente regeneração de tecido ósseo e administração de fármacos.
The main focus of this thesis was the development of novel 3D porous scaffolds for bone regeneration by robocasting. This additive manufacturing technique allows the production of scaffolds with predefined morphology and structure without the need for subsequent machining and can be used for the manufacture of customized implants with an internal structure similar to that of the bone to be replaced. Biphasic calcium phosphates (hydroxyapatite + β-tricalcium phosphate), undoped and doped (with Sr, Ag, Cu, Mg and Zn), obtained through aqueous precipitation process were used as starting powders. The partial substitution of Ca ions by doping ions induced changes in the crystalline phase assemblages and resulted in particles with distinct morphological characteristics and in materials with different biological outcomes. The powders were dispersed in aqueous medium with the aid of suitable processing additives (a dispersant and a binder) in order to obtain suspensions with high solids loading, an essential requirement for the manufacture of components by robocasting. The size and morphology of the particles and the concentration of the processing additives played crucial roles in the rheological behaviour of the suspensions. The addition of a flocculating agent drastically modified the rheological properties of the systems and allowed obtaining pastes with viscoelastic behaviour suitable for the extrusion process. The scaffolds with different pore sizes were produced by the controlled deposition of filaments with 410 μm in diameter. The compressive strength of scaffolds sintered at 1100 ° C was comparable or even superior to that that of spongy bone. Scaffolds with different pore sizes (120-500 μm) were tested in vitro using human mesenchymal stem cells (hMSCs). The aim was to evaluate the influence of pore size on initial cell adhesion, metabolic activity and osteogenic potential. The results showed that larger pores provide favourable conditions for osteogenic differentiation of hMSCs. In addition, calcium phosphates codoped with Sr and Zn improved the biological performance, including adhesion, metabolic activity and proliferation of hMSC. The last part of the thesis was devoted to the preparation of sintering-free scaffolds incorporating a drug (levofloxacin) in order to obtain components with capacity for bone regeneration and local treatment of infections. The paste used was obtained by dispersing the CaP powders in a solution of chitosan in the presence of the drug and a crosslinking agent (genipin). The 3D scaffolds produced by robocasting in the frame of this thesis program revealed to be very promising for tissue engineering applications, particularly bone tissue regeneration and drug delivery.
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Antonysamy, Alphons Anandaraj. "Microstructure, texture and mechanical property evolution during additive manufacturing of Ti6Al4V alloy for aerospace applications." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/microstructure-texture-and-mechanical-property-evolution-during-additive-manufacturing-of-ti6al4v-alloy-for-aerospace-applications(03c4d403-822a-4bfd-a0f8-ef49eb65e7a0).html.
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Additive Manufacturing (AM) is an innovative manufacturing process which offers near-net shape fabrication of complex components, directly from CAD models, without dies or substantial machining, resulting in a reduction in lead-time, waste, and cost. For example, the buy-to-fly ratio for a titanium component machined from forged billet is typically 10-20:1 compared to 5-7:1 when manufactured by AM. However, the production rates for most AM processes are relatively slow and AM is consequently largely of interest to the aerospace, automotive and biomedical industries. In addition, the solidification conditions in AM with the Ti alloy commonly lead to undesirable coarse columnar primary β grain structures in components. The present research is focused on developing a fundamental understanding of the influence of the processing conditions on microstructure and texture evolution and their resulting effect on the mechanical properties during additive manufacturing with a Ti6Al4V alloy, using three different techniques, namely; 1) Selective laser melting (SLM) process, 2) Electron beam selective melting (EBSM) process and, 3) Wire arc additive manufacturing (WAAM) process. The most important finding in this work was that all the AM processes produced columnar β-grain structures which grow by epitaxial re-growth up through each melted layer. By thermal modelling using TS4D (Thermal Simulation in 4 Dimensions), it has been shown that the melt pool size increased and the cooling rate decreased from SLM to EBSM and to the WAAM process. The prior β grain size also increased with melt pool size from a finer size in the SLM to a moderate size in EBSM and to huge grains in WAAM that can be seen by eye. However, despite the large difference in power density between the processes, they all had similar G/R (thermal gradient/growth rate) ratios, which were predicted to lie in the columnar growth region in the solidification diagram. The EBSM process showed a pronounced local heterogeneity in the microstructure in local transition areas, when there was a change in geometry; for e.g. change in wall thickness, thin to thick capping section, cross-over’s, V-transitions, etc. By reconstruction of the high temperature β microstructure, it has been shown that all the AM platforms showed primary columnar β grains with a <001>β.
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CARVALHO, SABRINA G. de M. "Inclusão e remoção térmica de NaCl, KI e grafite para obtenção de cerâmicas porosas de zircônia estabilizada com ítria." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10553.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Wang, Hao. "The Hot Optimal Transportation Meshfree (HOTM) Method for Extreme Multi-physics Problems." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1607533458323004.
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Pires, Plínio Ferreira. "Estudo da carbonatação avançada em concretos contendo adições minerais." Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/6319.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The carbonation phenomenon consists in a physicochemical process which reduces the alkalinity of concrete. Carbonation can destabilize the protective layer of the steel, leaving it susceptible to corrosion, which is one of the most significant and costly causes of deterioration in reinforced concrete. Accordingly, chemical analysis of the pore solution has been held for about 60 years, but few studies are focused on types of concrete containing mineral additions subjected to carbonation, due to the difficulty of obtaining the pore solution, given its structure densification under these conditions. Depending on the concrete composition, the natural carbonation process can take several years to present sufficient analyzable data, therefore, most of the studies on this topic use accelerated tests to simulate this phenomenon. However, even with full control of the laboratory environment, it is not possible to reproduce the randomness of the variables responsible for the degradation that occur in real situations. This study aims to evaluate the process of natural carbonation in 36 different types of concrete or analysis conditions, which cover a wide range of characteristics and properties of concrete that represent the various service situations of the structures, after about 14 years of exposure, in typical urban environment. The results are presented for types of concrete with and without mineral additions (silica fume, rice husk ash, metakaolin, fly ash and blast furnace slag); three water/binder (0.40, 0.55 and 0.70) and two curing conditions (dry-cured and moist-cured). The study was conducted by the application of simplified models of carbonation and statistical analysis on an extensive experimental database (over 2000 measurements) obtained by eight evaluations of carbonation carried at different ages, through 14 years of natural exposure prototypes of concrete beams. In addition, chemical analysis of pH, ionic strength and conductivity of the pore solution - obtained through innovative method - were conducted in both the carbonated layer and the non-carbonated layer of concrete. The results indicate that the empirically-analytical model proposed by Tuutti, has an excellent representativity of carbonated depth over time. The use of a coefficient of carbonation, from Tuutti’s model, calculated from early ages, can generate mistaken conclusions: underestimating the dry-cured concrete and overestimating the moist-cured concrete. In the overall analysis of the natural carbonation coefficients obtained by ANOVA showed that the water/binder ratio is the most significant factor, followed by curing type and, finally, the type of addition. The best performances as the carbonation are observed to the lower water/binder concretes, subjected to wet cure. Under the method used to obtain the pore solution, it was possible to compare the difference between the chemical properties of non-carbonated and carbonated layers of each type of concrete analyzed.
O fenômeno da carbonatação consiste em um processo físico-químico que leva à redução de alcalinidade do concreto. Isto pode desestabilizar a camada protetora do aço, deixando-o passível de corrosão, que é uma das mais importantes e onerosas causas de deterioração do concreto armado. Nesse sentido, a análise química da solução do poro tem sido realizada há cerca de 60 anos, contudo raros trabalhos focam em concretos submetidos à carbonatação contendo adições minerais, dada a dificuldade de se obter a solução devido à densificação na estrutura porosa nessas condições. Dependendo da composição do concreto, o processo de carbonatação natural pode levar vários anos para apresentar dados passíveis de análise, diante disso, a maioria dos estudos nesse tema utilizam ensaios acelerados para simular tal fenômeno, contudo, mesmo com todo controle do ambiente de laboratório, não se pode reproduzir a aleatoriedade das variáveis que ocorre em situações reais de degradação. Este trabalho tem como objetivo avaliar o processo de carbonatação natural em 36 diferentes concretos ou condições de análise, os quais cobrem uma ampla faixa de características e propriedades dos concretos, representando as mais diversas situações de serviço para as estruturas, após cerca de 14 anos de exposição, em ambiente típico urbano. São, portanto, apresentados resultados de concretos sem e com adições minerais (sílica ativa, cinza de casca de arroz, metacaulim, cinza volante e escória de alto-forno); três relações água/ligante (0,40; 0,55 e 0,70) e duas condições de cura (seca e úmida). O estudo se deu por meio de aplicações de modelos simplificados de carbonatação e análises estatísticas em um extenso banco de dados experimentais (mais de 2000 medidas) obtido por oito avaliações da frente de carbonatação realizadas em diferentes idades, durante 14 anos de exposição natural de protótipos de vigas de concreto. Foram realizadas também análises químicas de pH, força iônica e condutividade da solução do poro, obtida através de método inovador, tanto da camada carbonatada quanto da camada não carbonatada dos concretos. Os resultados indicam que o modelo empírico-analítico, proposto por Tuutti, possui excelente representatividade da profundidade carbonatada ao longo do tempo. A utilização de um coeficiente de carbonatação, do modelo de Tuutti, calculado a partir de idades iniciais pode gerar conclusões equivocadas: subestimando os concretos sem cura e superestimando os de cura úmida. A análise global dos coeficientes de carbonatação, obtidos pela ANOVA, demonstrou que a relação água/ligante é o fator mais significativo, seguido do tipo de cura e, por último, o tipo de adição. Os melhores desempenhos quanto à carbonatação são observados para os concretos de menor relação água/ligante, submetidos à cura úmida. De acordo com o método empregado para obtenção da solução do poro, foi possível comparar a diferença entre as propriedades químicas da camada não carbonatada e a carbonatada, para toda a família de concretos analisada.
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Tabard, Lucie. "Elaboration de céramiques architecturées pour le stockage d'énergie thermique." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI007.
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Ce travail de thèse a pour objectif de développer un matériau composite de haute densité énergétique pour le stockage de chaleur thermochimique. L’objectif principal est de libérer de la chaleur par hydratation exothermique d’un sel hygroscopique, de manière entièrement réversible (stockage sous forme de potentiel chimique), en évitant les pertes de performance systématiques constatées auparavant sur les systèmes à lit de sel, apparaissant avec le temps et dues à l’agglomération du sel. Ainsi, le développement d’un composite de type matériau hôte poreux/sel doit permettre d’éviter l’agglomération du sel et d’augmenter sa réactivité. Dans un premier temps, une méthodologie de cyclage et de caractérisation du sel sélectionné (MgSO4,xH2O) est établie afin d’étudier les évolutions structurales de ce sel (par couplage de résultats obtenus en DRX et en FTIR). Une première voie de mise en forme du sel est également proposée, ne permettant pas de résoudre les problématiques rencontrées en configuration lit de sel. Ainsi, dans un deuxième temps, le développement d’un matériau hôte (zircone cériée) à porosité architecturée est proposé. La zircone est mise en forme par technique de fabrication additive (robocasting) d’une pâte céramique contenant des phases fugitives (amidons) et consolidée par frittage partiel. La porosité multi-échelle résultante est minutieusement caractérisée en termes de volume, de taille et d’interconnexion par des techniques complémentaires. Les propriétés mécaniques sont également caractérisées à travers des essais de compression et de flexion trois points. La pertinence de cette porosité multi-échelle du matériau hôte sur la réactivité du sel et sa stabilité est évaluée dans un troisième temps. Des composites matériau hôtes/sels sont fabriqués par infiltration de solutions salines, puis caractérisés selon la méthodologie développée pour caractériser le sel. La porosité à trois échelles permet d’obtenir des composites de densité énergétique élevée (417 kWh.m-3) et stable au cours du temps, remplissant l’objectif européenThe aim of this thesis work is to develop a composite material with a high energy density for thermochemical heat storage. The main purpose is to produce heat through an exothermic hydration reaction of a hygroscopic salt, entirely reversible (storage as chemical potential), while avoiding the usual loss of performances reported in salt bed configurations. Such issues emerge over time, due to salt agglomeration during its hydration. Thus, the development of a composite made of salt attached onto a host material should prevent the salt agglomeration and enhance its reactivity. First, a protocol to characterize and investigate the salt (MgSO4,xH2O) cyclability behavior was developed to study its structural evolution (through XRD and FTIR). A first method of salt shaping was also proposed, that does not allow resolving the issues encountered in salt bed configurations. Secondly, the development of a host material (ceria zirconia) with a hierarchized porosity is proposed. Zirconia is shaped by additive manufacturing (robocasting) of a paste loaded with fugitive phases (starches) and consolidated by partial sintering. The resulting multi-scale porosity is thoroughly characterized by mean of complementary techniques, focusing on its volume, size and interconnection. Mechanical properties are characterized through compressive and bending tests. The relevance of the multi-scale porosity of the host material for the salt reactivity and stability is finally evaluated. Host material/salt composites are fabricated by liquid impregnation of a saturated saline solution. They are then characterized with the process developed for the characterization of the salt. The three-scale porosity enables the fabrication of composites with high energy density (417 kWh.m-3), that are stable over time, fulfilling the European target
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Kochová, Kateřina. "Studium vlivu přísady XYPEX na reologii čerstvých betonů a trvanlivosti zatvrdlých betonů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-225905.
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This thesis is focused on the study of the influence of crystalline ingredients XYPEX, on the rheology of fresh concrete and durability of hardened concrete. It examines the influence of crystalline additives on the rheology of cement pastes with different types of cement with different temperatures, increasing water tightness and gas tightness and compressive strength. Also assesses pore structure with different bridging cracks.
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Lassalle, Damien. "Les pore forming toxin chez les Lophotrochozoaires : exemple des organismes Biomphalaria glabrata/ Schistosoma mansoni A New Assessment of Thioester-Containing Proteins Diversity of the Freshwater Snail Biomphalaria glabrata Cholesterol-TEG addition at the 5’end of siRNA allows significant increase of its uptake by hemocytes from Biomphalaria glabrata, the schistosomiasis vector snail. Under review in PeeJ. Schistosoma mansoni lysine specific demethylase (SmLSD1) is a druggable target involved in parasite survival, oviposition and stem cell proliferation." Thesis, Perpignan, 2020. https://theses-public.univ-perp.fr/2020PERP0036.pdf.
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La bilharziose est une maladie touchant 230 millions de personnes dans le monde (source OMS). Cette parasitose est provoquée par le schistosome, un vers plat parasite nommé Schistosoma mansoni. Avant de pénétrer dans l’organisme humain par la peau, ce parasite se développe chez un escargot d’eau douce, Biomphalaria glabrata, qui lui sert d’hôte intermédiaire. Nous avons dans ce contexte identifié et étudié deux protéines appartenant à la famille des pore formingtoxins (PFTs), que nous avons appelé Biomphalysine et Glabralysine. Les PFTs sont des effecteurs très connus dans le monde procaryote pour favoriser leurs pathogénicités. Ces protéines sont produites de manière soluble par les organismes, pour se fixer et s’agréger sur les membranes cellulaires cible, ce qui a pour conséquence de créer un pore lytique. Cette super famille de protéine se divise en deux sous familles, alpha et beta, classées en fonction de la modalité de formation du pore. Des études antérieures ont permis de caractériser pour la première fois des ß-PFT chez le mollusque Biomphalaria glabrata, ces protéines ont montré un rôle clef dans l’immunité du mollusque, notamment la capacité de lier au parasite et de le tuer. Cette découverte a pu ouvrir le champ à l’investigation de protéines similaire chez le mollusque et chez le parasite avec lequel il interagie. Ce projet de thèse a pour objectif, au travers d’étude génomique, transcriptomique et protéomique de caractériser et de comprendre la fonction des différentes « pore forming toxins » présentes chez le mollusque Biomphalaria glabrata et chez le parasite Schistosoma mansoni. Grace à des données collectées avant et durant le projet de thèse, nous avons pu caractériser 23 variants apparentés à la famille des Biomphalysines. Cette famille multigénique sans intron, semble avoir été acquise au travers de transfert horizontal de gênes. Par homologie avec les biomphalysines, nous avons pu caractériser 5 gènes codants pour un deuxième groupe de ß-PFT chez Biomphalaria glabrata, que nous avons appelé les Glabralysines. Ces protéines constituent une famille à part entière, proche des toxines cry de Bacillus thuringiensis, et qui d’un point de vue structural partage des homologies avec la Biomphalysine. Elles sont en effet, produites par les cellules immunitaires du mollusque et induites lors de l’infection par le parasite Schistosoma mansoni. Finalement, nous avons aussipu découvrir deux gènes codants pour des toxines, nommées Schistolysines, de la famille des ß-PFT chez le parasite Schistosoma mansoni. Ces protéines semblent être répandues chez les parasites et jouer des rôles essentiels dans leur développement, la reproduction et peut être la nutrition. Nous montrons que ces protéines sont exclusivement retrouvées au stade adulte du parasite et devraient donc jouer un rôle dans l’interaction avec l’hôte humain ou dans l’implantation ou l’exploitation de cet hôte. Ces différentes approches, dans le contexte de l’interaction entre l’hôte et son parasite permettront potentiellement d’identifier de nouvelles stratégies de lutte ou de contrôle de la maladie sur le terrain. Les résultats générés dans ce travail pourront permettre également d’étudier le rôle de ces molécules dans l’interaction avec d’autres pathogènes ou leur lien avec d’autres pathologies et plus particulièrement leur utilisation dans le développement de nouveaux traitements contre le cancer par exempleBilharzia is a disease affecting 230 million people worldwide (source WHO). This parasitosis is caused by schistosome, a parasitic flatworm, and in particular by Schistosoma mansoni, responsible for intestinal bilharzia in Africa and tropical America. Before entering the human body through the skin, this parasite develops in a freshwater snail, Biomphalaria glabrata, which serves as an intermediate host. In this context, we have identified and studied two proteins belonging to the pore forming toxins (PFTs) family, which we have called Biomphalysin and Glabralysin. Pore forming toxins are effectors well known in the prokaryotic world to promote their pathogenicity. These proteins are produced in a soluble way by organisms, to bind and aggregate on the target cell membranes, resulting in the creation of a lytic pore. This protein superfamily is divided into two families, alpha and beta, classified according to the pore formation modality. Previous studies have characterized for the first time §-PFTs in the mollusc Biomphalaria glabrata, these proteins have shown a key role in the immunity of the mollusc, including the ability to bind and kill the parasite. This discovery may have opened the field to the investigation of similar proteins in the mollusc and in the parasite with which it interacts. This thesis project aims, through genomic, transcriptomic and proteomic studies, to characterize and understand the function of different "pore forming toxins" present in the mollusc Biomphalaria glabrata and in the parasite Schistosoma mansoni. Thanks to data collected before and during the thesis project, we were able to characterize 23 variants related to the Biomphalysin family. This multigenic family, without intron, seems to have been acquired through horizontal gene transfer. By homology with the Biomphalysins, we were able to characterize 5 genes coding for a second group of §-PFT in Biomphalaria glabrata, which we called Glabralysins. These proteins constitute a family in their own right, close to the Cry toxins of Bacillus thuringiensis, and which structurally share homologies with the Biomphalysin. They are indeed produced by the immune cells of the mollusc and induced during the infection by the parasite Schistosoma mansoni. Finally, we were also able to discover two genes coding for toxins, called Schistolysins, of the §-PFT family in the parasite Schistosoma mansoni. These proteins seem to be widespread in parasites and play essential roles in their development, in reproduction and hypothetically in nutrition. We show that these proteins are found exclusively in the adult stage of the parasite and should therefore play a role in the interaction with the human host or in the implantation or exploitation of this host. These different approaches, in the context of the interaction between the host and its parasite, will potentially lead to the identification of new strategies for the control or management of the disease in the field. The results generated in this work could also allow to study the role of these molecules in the interaction with other pathogens or their link with other pathologies and more particularly their use in the development of new cancer treatments for example
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Грехов, С. К., and S. K. Grekhov. "Обработка давлением в технологиях производства изделий аддитивными методами 3D печати : магистерская диссертация." Master's thesis, б. и, 2020. http://hdl.handle.net/10995/93991.
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Приведен обзор случаев использования изделий, изготовленных по аддитивной технологии для имплантации. Проанализирован международный стандарт на испытания пористых материалов, изготовленных по аддитивной технологии. Выявлены проблемы и предположительные пути их решения при использовании изделий, изготовленных аддитивным методом из сплавов на основе титана. решена краевая задача определения напряженно-деформированного состояния ячеистого имплантат методом конечных элементов в программном модуле ABAQUS. Рассмотрен вопрос влияния геометрии ячеек испытываемого материала на механические свойства конечного изделия для трех различных форм ячеек. Рассмотрен вопрос влияния трения между испытываемой заготовкой и бойками испытательной машины на свойства конечного изделия при различных уровнях трения.An overview of the cases of using products made using additive technology for implantation is given. The international standard for testing porous materials manufactured by additive technology is analyzed. The problems and possible ways of their solution are revealed when using products manufactured by the additive method from titanium-based alloys. the boundary value problem of determining the stress-strain state of a cellular implant by the finite element method in the ABAQUS software module has been solved. The question of the influence of the geometry of the cells of the test material on the mechanical properties of the final product for three different cell shapes is considered. The question of the influence of friction between the tested workpiece and the strikers of the testing machine on the properties of the final product at various levels of friction is considered.
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Keerthi, Sandeep. "Low Velocity Impact and RF Response of 3D Printed Heterogeneous Structures." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1514392165695378.
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Villoria, del Álamo Beatriz. "Síntesis de catalizadores sólidos orgánicos e híbridos orgánicos-inorgánicos y su aplicación." Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/163789.
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[ES] En este trabajo de tesis doctoral, la investigación se ha centrado en el desarrollo de diferentes procesos catalíticos heterogéneos empleando materiales híbridos orgánico-inorgánicos porosos (MOFs y sílices funcionalizadas) y materiales orgánicos aromáti-cos (PAFs), que se han estudiado en diversas reacciones orgánicas. Tras la preparación de los MOFs en estudio, se han caracterizado sus propiedades estructurales y se han determinado sus centros activos en los clústeres metálicos (circonio, hafnio o cerio). La reactividad de estos MOFs y de los materiales híbridos sílice-aminas se ha estudia-do teniendo en cuenta sus centros catalíticos; estas reacciones se han optimizado lle-vando a cabo un estudio de los mecanismos de reacción. Finalmente, se han preparado sólidos homoquirales de tipo PAF que presentan el sistema binaftilo, cuya reactividad también ha sido probada. Más específicamente, en el capítulo 3 se ha estudiado la esterificación de amidas, que permite convertirlas en ésteres, grupos funcionales más versátiles. Esta transfor-mación se ha abordado desde la catálisis heterogénea via MOFs basados en circonio, hafnio y cerio de las series MOF-808, UiO-66 y MOF-801. El catalizador más eficien-te para la esterificación de amidas ha sido el MOF-808-Zr. Mediante análisis TGA y la adsorción de una molécula sonda básica (CO) estudiada utilizando espectroscopia FT-IR, se han determinado los centros ácidos de Lewis y Brönsted presentes en ellos. De los MOFs preparados en este trabajo, el MOF 808-Zr posee una menor conectividad de los clústeres metálicos y un mayor tamaño de poro mayor que el UiO-66 y el MOF-801; además, tiene el balance adecuado de centros ácidos y básicos de Brönsted y Lewis para activar los sustratos de la reacción. El alcance de la alcoholisis con n-butanol se ha extendido a un gran número de sustratos (amidas primarias, secundarias y terciarias; aromáticas y alifáticas). La reacción también se ha estudiado en condicio-nes no solvolíticas con alcoholes más complejos. El catalizador es estable durante la reacción y puede ser reutilizado fácilmente. El mecanismo de reacción en la esterifica-ción de benzamida con n butanol catalizada por MOF-808-Zr se ha investigado me-diante el análisis cinético empleando el modelo de LHHW y el estudio in situ de las interacciones moleculares por FT-IR. En el capítulo 4, se ha investigado la deuteración por intercambio isotópico deute-rio/hidrógeno catalizada por aminas soportadas en sílice comerciales empleando D2O como fuente de deuterio. Este procedimiento es aplicable a una gran gama de sustra-tos, como compuestos carbonílicos, sales de organofosfonio, nitrocompuestos e, inclu-so, hormonas esteroideas. La estabilidad del catalizador, SiO2-(CH2)3-NH2, se mantie-ne hasta en 10 usos de reacción sin pérdidas significativas de la actividad. Por último, en el capítulo 5, se afronta la síntesis y aplicación de PAFs homoquira-les donde se ha integrado el esqueleto del BINOL (1,1′-binaftil-2,2′-diol) y del BIN-BAM (1,1' binaftil-2,2'-disulfonimida) generando tres nuevos PAFs activos en catáli-sis asimétrica: PAF-3,3'-(S)-BINOL, PAF-6,6'-(R)-BINOL y PAF 3,3'-(S)-BINBAM. En concreto, el PAF-6,6'-(R)-BINOL ha demostrado su actividad catalítica en la reacción de alquilación de aldehídos aromáticos con dietil-zinc y el catalizador PAF-3,3'-(S)-BINBAM es activo en la reacción aldólica de Mukaiyama y la reducción del doble enlace de compuestos carbonílicos a,b-insaturados.[CA] En aquesta tesi doctoral, la investigació s'ha centrat en el desenvolupament de dife-rents processos catalítics heterogenis emprant materials híbrids orgànic-inorgànics porosos (MOFs i sílices funcionalitzades) i materials orgànics aromàtics (PAFs), que s'han estudiat en diverses reaccions orgàniques. Després de la preparació dels MOFs en estudi, s'han caracteritzat les seues propietats estructurals i s'han determinat els seus centres actius en els clústers metàl·lics (zirconi, hafni o ceri). La reactivitat d'aquests MOFs i dels materials híbrids sílice-amines s'ha estudiat tenint en compte els seus cen-tres catalítics; aquestes reaccions s'han optimitzat duent a termini un estudi dels meca-nismes de reacció. Finalment, s'han preparat sòlids homoquirals de tipus PAF que presenten el sistema binaftilo, la reactivitat del qual també ha sigut provada. Més específicament, en el capítol 3 s'ha estudiat l'esterificació d' amides, que per-met convertir-les en èsters, grups funcionals més versàtils. Aquesta transformació s'ha abordat des de la catàlisi heterogènia via *MOFs basats en zirconi, hafni i ceri de les sèries MOF-808, UiO-66 i MOF-801. El catalitzador més eficient per a l'esterificació d'amides ha sigut el MOF-808-Zr. Mitjançant anàlisi TGA i l'adsorció d'una molècula sonda bàsica (CO) estudiada utilitzant espectroscopia FT-IR, s'han determinat els cen-tres àcids de Lewis i Brönsted presents en ells. Dels MOFs preparats en aquest treball, el MOF 808-Zr posseeix una menor connectivitat dels clústers metàl·lics i una major grandària de porus que el UiO-66 i el MOF-801; a més, té el balanç adequat de centres àcids i bàsics de Brönsted i Lewis per a activar els substrats de la reacció. L'abast de l'alcoholisi amb n-butanol s'ha estés a un gran nombre de substrats (amides primàries, secundàries i terciàries; aromàtiques i alifàtiques). La reacció també s'ha estudiat en condicions no solvolítiques amb alcohols més complexos. El catalitzador és estable durant la reacció i pot ser reutilitzat fàcilment. El mecanisme de reacció en l'esterifica-ció de benzamida amb n-butanol catalitzada per MOF-808-Zr s'ha investigat mitja-nçant l'anàlisi cinètica emprant el model de LHHW i l'estudi in situ de les interaccions moleculars per FT-IR. En el capítol 4, s'ha investigat la deuteració per intercanvi isotòpic deuteri/hidrògen catalitzada per amines suportades en sílices comercials emprant D2O com a font de deuteri. Aquest procediment és aplicable a una gran gamma de substrats, com a com-postos carbonílics, sals d'organofosfoni, nitrocompostos i, inclosa, hormones esteroi-dals. L'estabilitat del catalitzador, SiO2-(CH2)3-NH2, es manté fins a 10 usos de reac-ció sense pèrdues significatives de l'activitat. Finalment, en el capítol 5, s'afronta la síntesi i aplicació de PAFs homoquirals on s'ha integrat l'esquelet del BINOL (1,1′-binaftil-2,2′-diol) i del BINBAM (1,1'-binaftil-2,2'-disulfonimida) generant tres nous PAFs actius en catàlisi asimètrica: PAF-3,3'-(S)-BINOL, PAF-6,6'-(R)-BINOL i PAF 3,3'-(S)-BINBAM. En concret, el PAF-6,6'-(R)-BINOL ha demostrat la seua activitat catalítica en la reacció d'alquilació d'aldehids aromàtics amb dietil-zinc i el catalitzador PAF-3,3'-(S)-BINBAM és actiu en la reacció aldólica de Mukaiyama i la reducció del doble enllaç de compostos carbonílics a,b-insaturats.
[EN] In this Doctoral Thesis, the research has been focused on the development of different heterogeneous catalytic processes using hybrid porous organic-inorganic materials (MOFs and functionalized silicas) and organic aromatic materials (PAFs), which have been studied in various organic reactions. After the preparation of the MOFs under study, their structural properties have been characterised and their active centres in the metal clusters (zirconium, hafnium or cerium) have been determined. The reactivity of these MOFs and the hybrid silica-mine materials has been studied considering their catalytic centres; these reactions have been optimised by carrying out a study of the reaction mechanisms. Finally, homochiral PAF-type solids have been prepared with the binafil system, whose reactivity has also been tested. More specifically, the esterification of amides has been studied in Chapter 3. This reaction allows to convert the amides into esters, which are more versatile functional groups. This transformation has been approached from the heterogeneous catalysis via MOFs based on zirconium, hafnium and cerium of the MOF-808, UiO-66 and MOF-801 series. The most efficient catalyst for amide esterification has been MOF-808-Zr. Using TGA analysis and the adsorption of a basic probe molecule (CO) studied using FT-IR spectroscopy, the acid centres of Lewis and Brönsted present in them have been determined. Among the MOFs prepared in this work, MOF 808-Zr has a lower metal cluster connectivity and a larger pore size than UiO-66 and MOF-801; it also has the appropriate balance of acid and basic Brönsted and Lewis centres to activate the reaction substrates. The scope of n-butanol alcoholysis has been extended to a large number of substrates (primary, secondary and tertiary amides; aromatic and aliphatic). The reaction has also been studied in non-solvolitic conditions with more complex alco-hols. The catalyst is stable during the reaction and can be easily reused. The reaction mechanism in the esterification of benzamide with n-butanol catalysed by MOF-808-Zr has been investigated through kinetic analysis using the LHHW model and the in situ study of molecular interactions by FT-IR. In Chapter 4, the deuteration by isotopic deuterium/hydrogen exchange catalysed by commercial silica-supported amines using D2O as a source of deuterium has been investigated. This procedure is applicable to a wide range of substrates, such as carbonylic compounds, organophosphonium salts, nitro compounds and, even, steroid hormones. The stability of the catalyst, SiO2-(CH2)3-NH2, is maintained for up to 10 reaction uses without significant loss of activity. Finally, in Chapter 5, the synthesis and application of homochiral PAFs, in which the structure of BINOL (1,1′-binaftil-2,2′-diol) and BIN-BAM (1,1' binaftil-2,2'-disulfonimide) has been integrated, is discussed. Three new PAFs active in asymmetric catalysis has been generated: PAF-3,3'-(S)-BINOL, PAF-6,6'-(R)-BINOL and PAF 3,3'-(S)-BINBAM. In particular, PAF-6,6'-(R)-BINOL has demonstrated its catalytic activity in the alkylation reaction of aromatic aldehydes with diethyl zinc and the catalyst PAF-3,3'-(S)-BINBAM is active in the Mukaiyama aldolic reaction and the reduction of the double bond of carbonylic a,b-unsaturated compounds.
Villoria Del Álamo, B. (2021). Síntesis de catalizadores sólidos orgánicos e híbridos orgánicos-inorgánicos y su aplicación [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/163789
TESIS
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Chen, Cheng-Yu, and 陳承佑. "Development of biomimetic porous Ti6Al4V implant by additive manufacturing." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/kv3yma.
Full textAbstract:
碩士中山醫學大學
口腔科學研究所
106
Porous titanium implants made with 3D printing technology are a new trend in the development of metal orthopedics in recent years. Past studies have also confirmed that porous titanium implants can enhance the stability of implants in vivo. However, such porous titanium scaffolds do not promote bone tissue growth and differentiation autonomously and effectively. Therefore, selective laser melting technique was used in this study. Titanium porous scaffolds were printed on Ti6Al4V ELI powders. Subsequent to the 3D printed porous titanium stent modification, filled with different proportions of chitosan and calcium silicate, prepared by freeze-drying in a metal stent into a fibrous sponge-like polymer scaffold, and analysis of the phase composition and scaffold structure The surface pattern. Followed by human mesenchymal stem cells （hMSCs） biocompatibility and bone differentiation test, the experimental results can be clearly observed with the higher proportion of calcium silicate, the intensity with the stronger. Therefore, such methods should have the opportunity to be used in the future for bone tissue repair.
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Wu, ching-wen, and 吳晴雯. "Micro Porous SiC Ceramics(MPC) prepared with Kaolinate additives." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/23306040805395809079.
Full textAbstract:
碩士國立成功大學
資源工程學系碩博士班
95
The study was putting different quantities of Kaolinite and 10 wt% PVB into six different kinds of particle of powder to produce the micro porous SiC ceramic. We used the binder / pore former PVB, which is 10 wt%，and Kaolinite was add to be the sintering aid. The bulk is covered with Al2O3 in the heating furnace while sintering, we heat at 1300℃ and hold 3 hours. We have then produces the micro porous SiC ceramic successfully within a low constant temperature. At first, we added the PVB and mixed it with the powder of SiC. After drying, we ground it into a powder, and then added Kaolinite as the sintering aid. After pass through 100 mesh, the powder was uniaxially pressed at 50 MPa and the result was green bodies. Cover up the green bodies with Al2O3 powder, burn out the PVB to form pores by 500 ℃, sinter them and heat the temperature to 1300℃ for 3 hours. Therefore, the result was different SiC sintered bodies. We used XRD to identify the produced phase and SEM to observe the fractured surfaces to discover the grain morphology of sintered bodies. By using the Archimedes, we got the apparent density and open pore. We got the compressive strength by the Material Test System as well. The research showed that ： under the condition of sintering at 1300 ℃ for 3 hours, the open pore and the Apparent Density are showing that there is a trend in synchronized variation. They had the same trend in the synchronized variation. The open pore is 26.6 % of the sample of 6S5K is the highest rate. Its Apparent Density is 1.678g/cm3 。
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Wang, Kuang-Chieh, and 王光傑. "The Effects of Porous Material Addition to Anammox’s Nitrogen Removal." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/01706470469729197590.
Full textAbstract:
碩士國立臺灣大學
環境工程學研究所
101
Anaerobic ammonium oxidation process (Anammox) is a novel technology developed for nitrogen removal, especially for wastewater with high organic nitrogen content. However, limitations of its full-scale application include (1) low bacterial growth rate and long doubling time (approximately 7 to 12 day), and (2) requirement of severe operation conditions for bacterial cultivation. The objectives of this study were to establish an anammox reactor from domestic wastewater sludge and investigate the effects of porous material to bacterial aggregation in the reactor. A lab-scale reactor was used to cultivate Anammox bacteria. The results show that the Anammox reactor can achieve over 99% of nitrogen removal efficiencies with the maximum concentrations of nitrite and ammonium of 700 mg/L and 490 mg/L, respectively. The microbial community analysis of this Anammox system revealed that over 99% of bacteria were phylogenetically close to Cadidatus Kuenenia stuttgartiensis. The addition of the porous material increased the sludge settling velocity; the sludge volume index decreased from 175 to 114. However, it significantly decreased the removal efficiencies of ammonia and nitrite (<50%). The removal efficiencies slowly recovered and remained at a steady state (>95%) after 40 days of porous material addition. The results of real-time quantitative PCR using functional-gene-specific primers indicated that the addition of porous material may have adverse effects on Anammox bacteria while it may favor the growth of denitrification bacteria. The study reveals that the addition of porous material may enhance sludge settling and aggregation, however, it tends to lower nitrogen removal efficiency of Anammox system.
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Wei, Lin Chu, and 林鉅幃. "The Properties of Porous Asphalt Containing Warm Mix Asphalt Additives." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/30492521146831624949.
Full textAbstract:
碩士淡江大學
土木工程學系碩士班
99
We are facing more and more global climate anomalies. The emergence of extreme weather including droughts, floods, storms, melting glaciers, heat waves, sea water level rise, and huge cyclones threaten human life and property. These disasters appear mostly because of global warming. Manufacturing of hot mix asphalt (HMA) consumes large amounts of energy resources and energy. Warm mix asphalt (WMA) is a new technology of producing asphalt mixtures using additives or with plant modifications to reduce energy consumption and emissions. The mixing and compacting temperatures of WMA are lower than that of traditional HMA with almost equivalent performance. On the other hand, porous asphalt utilizing highly open aggregate gradations produces very high air voids which can effectively drain the surface runoff and improve roadway safety. This laboratory study was conducted to investigate the performance of the warm mix porous asphalt using WMA additives. In the study, 2 dosage rates (1.5% and 2.5% by weight of binder) of each additive, Sasobit® and Rediset® WMX, were selected to evaluate their effects and to determine the optimum addition rate. Major conclusions of our study were summarized as follows: 1. The viscosity test results showed that the binders containing WMA additives had decreased viscosity at higher temperature, and increased viscosity at lower temperature. The reductions of mixing temperature was found to be 7℃ and 13℃ with the addition of 1.5% and 2.5%, respectively. 2. The laboratory results also showed that the indirect tensile strengths of the warm mix porous asphalt increased with higher WMA additive dosage rate. 3. The resilient modulus test results showed that warm mix additives could increase the resilient modulus with higher WMA additive dosage rate. 4. The wheel tracking test results indicated that the dynamic stability (DS) increased with higher WMA additive dosage rate. 5. The recommended dosage rate of WMA additive was found to be close to 2.5% based on the overall results of performance evaluation from this laboratory study.
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Mu-ChunYang and 楊牧君. "Stress Analysis Application of Additive Manufactured Hip Prosthesis with Porous Structures." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/r43mws.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系
106
For patients recovering from total hip replacement surgery, the stress shielding effect, which is caused by a difference in Young’s modulus between the hip prosthesis and human bone, can lead to prosthesis loosening or dislocation. Additive manufacturing technology, such as electron beam melting (EBM), is mature enough to fabricate porous structures made of Ti6Al4V alloy. This thesis studies the mechanical properties of porous structures and their application to artificial hip prostheses using the finite element method. The study is divided into two parts. The first part establishes the simulation method and the second part discusses the application of the simulation results to hip prostheses. The simulation and experimental results of the Young’s modulus of carbon steel show a very small deviation of about 0.7%. Porous samples with various pore geometries show the trend that higher relative density is accompanied by higher Young’s modulus in both simulation and experiments. Several unit cell structures were chosen for further mechanical simulation. The diagonal unit cell was found to be the most stable. Various compression load, Young’s modulus of cement, hip prosthesis outlook were simulated based on ISO 7206-4. The results show that when the porous structures were applied in a hip prosthesis, the stress concentration value decreased.
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Li, Hao-Ming, and 李晧銘. "The effects of processing and additive on the microstructure of porous glass." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/xh99br.
Full textAbstract:
碩士國立臺北科技大學
資源工程研究所
105
In this study, we used borosilicate commercial powders, CaCO3 and LiF as raw materials, CaCO3 was the foaming agent in the system and adding LiF due to decrease the softening temperature. In order to find the best process conditions for glass abrasive substrates, we used different particle sizes of glass powders and different process parameters to figure out the relationship between the parameters and glass proterties (density, porousity, crystallization, holes sizes and the wall sizes of holes). According to the result, adding LiF can decrease the softening temperature and let the hole become rounded. Using the powders with small partical sizes reduced hole sizes and hole wall thickness at the same time. The specimens were composited with the glass powders (D50=0.804 μm) which was sintered at 720 and 740℃ for 15 minutes had the best hole sizes were 145 and 150 μm and the hole wall thickness were 2.4 and 2.8 μm, respectively. Through the analysis of the mercury porousitymeter we found the pore size range of best specimens were close to the commercially samples, and the structure of specimens were homogeneous. After adding the abrasive materials, the sintering temperature needs increasing to 720℃ to form a uniform structure.
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Chiang, Po-Hsing, and 江柏興. "Mechanical Properties and Fracture Mechanism of Additive Manufactured Porous Ti-6Al-4V Alloy." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/rpra92.
Full textAbstract:
碩士國立臺北科技大學
材料科學與工程研究所
106
Selective laser melting (SLM) technology has extensively manufactured porous metallic materials recently. However, the fracture mechanism of porous metallic material was rarely examined by in-situ mechanical properties test yet. Therefore, this study will study the porous SLM Ti-6Al-4V alloy with the unit cells of TiO and TiZ. The porosity can be modified by changing the diameter of strut. The porosities of the TiO structures are 45 %, 59 %, and 68 %, and those of the TiZ structures are 33 %, 49 %, and 84 %. The uniaxial compression tests and compression fatigue experiments of the porous SLM and HIP Ti-6Al-4V alloys with different unit cells and porosities were executed. Digital image correlation (DIC) technique was also used to investigate the fracture mechanism of strut during loading. The results about uniaxial compression test indicate that the uniaxial compression strengths and the elastic modului of the SLM and HIP specimens with TiO and TiZ unit cells are increased by decreasing the porosity. The fracture mechanisms of the SLM sample with TiO structure are both layer-by-layer and shear fracture. Moreover, the fracture mode of TiO68-HIP sample is shear fracture. The fracture mechanism will be transferred to layer-by-layer by decreasing the porosity from 68 % to 45 % or 59 %. The fracture mechanism of TiZ structure is layer-by-layer in both the SLM and the HIP samples. In the compression fatigue test, the strain is concentrated on the node in all types of specimens. With increasing the fatigue cycles, the strain is gradually expanded from node to the strut and leads to shear fracture. The fatigue cycles of TiO-SLM sample decreases from 29943 cycles to 9907 cycles by increasing the porosity from 45 % to 68 %. The fatigue cycles of TiZ-SLM sample decreased from 31026 cycles to 8371 cycles by increasing the porosity from 33 % to 84 %. The HIP samples can transform the microstructure of the SLM specimens from α′ martensite to α+β mixed phases and eliminate the pore. The fatigue cycles of the HIP specimens can be much increased due to the microstructural change. The fatigue cycles of TiZ-HIP are increased from 85200 cycles to 145433 cycles by increasing the porosity from 33 % to 84 %.
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Vlasea, Mihaela. "Additive Manufacturing Methodology and System for Fabrication of Porous Structures with Functionally Graded Properties." Thesis, 2014. http://hdl.handle.net/10012/8284.
Full textAbstract:
The focus of this dissertation is on the development of an additive manufacturing system and methodology for fabricating structures with functionally graded porous internal properties and complex three-dimensional external characteristics. For this purpose, a multi-scale three-dimensional printing system was developed, with capabilities and fabrication methodologies refined in the context of, but not limited to, manufacturing of porous bone substitutes. Porous bone implants are functionally graded structures, where internally, the design requires a gradient in porosity and mechanical properties matching the functional transition between cortical and cancellous bone regions. Geometrically, the three-dimensional shape of the design must adhere to the anatomical shape of the bone tissue being replaced.
In this work, control over functionally graded porous properties was achieved by integrating specialized modules in a custom-made additive manufacturing system and studying their effect on fabricated constructs. Heterogeneous porous properties were controlled by: (i) using a micro-syringe deposition module capable of embedding sacrificial elements with a controlled feature size within the structure, (ii) controlling the amount of binder dispersed onto the powder substrate using a piezoelectric printhead, (iii) controlling the powder type or size in real-time, and/or (iv) selecting the print layer stacking orientation within the part. Characterization methods included differential scanning calorimetry (DSC)-thermo gravimetric analysis (TGA) to establish the thermal decomposition of sacrificial elements, X-ray diffraction (XRD) and dispersive X-ray spectroscopy (EDAX) to investigate the chemical composition and crystallinity, scanning electron microscopy (SEM) and optical microscopy to investigate the physical and structural properties, uniaxial mechanical loading to establish compressive strength characteristics, and porosity measurements to determine the bulk properties of the material. These studies showed that the developed system was successful in manufacturing embedded interconnected features in the range of 100-500 $ \mu m $, with a significant impact on structural properties resulting in bulk porosities in the range of 30-55% and compressive strength between 2-50 MPa.
In this work, control over the the three-dimensional shape of the construct was established iteratively, by using a silhouette extraction image processing technique to determine the appropriate anisotropic compensation factors necessary to offset the effects of shrinkage in complex-shaped parts during thermal annealing. Overall shape deviations in the range of +/- 5-7 % were achieved in the second iteration for a femoral condyle implant in a sheep model.
The newly developed multi-scale 3DP system and associated fabrication methodology was concluded to have great potential in manufacturing structures with functionally graded properties and complex shape characteristics.
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SUN, Wei-En, and 孫偉恩. "Experimental Studies and Numerical Simulation on Formation of Porous Materials by Combustion Synthesis with TiH2 Addition." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/10886805416757304817.
Full textAbstract:
碩士逢甲大學
航太與系統工程學系
103
The preparation of various porous materials was conducted by self-propagating high-temperature synthesis (SHS) with the use of TiH2 as the pore generator. Materials synthesized by this study included Ti5Si3 in the monolithic and composite forms, Ti3AlC2, and NiAl. Experimental work investigated the effects of the TiH2 content on flame-front velocity, reaction temperature, and phase composition, microstructure and porosity of the final product. A numerical simulation study was performed on the formation of Ti5Si3 and NiAl to realize the influence of porosity on the effective thermal conductivity, reaction enthalpy, and flame velocity. Experimental results showed that due to endothermic decomposition of TiH2, the flame-front velocity and combustion temperature decreased with increasing TiH2 but the product porosity increased. Single-phase Ti5Si3 was synthesized from combustion of Ti, Si, and TiH2. The addition of Al led to formation of the Ti5Si3/TiAl composite containing a minor amount of Ti3Al. With the use of Si3N4 and BN as the nitrogen sources, Ti5Si3/TiN and Ti5Si3/TiN/TiB2 composites were fabricated. In this study, complete decomposition of TiH2 was achieved and as-synthesized Ti5Si3 with a porosity of 42% was obtained from a powder compact with TiH2 of 6.25 mol%. A Ti5Si3/TiAl composite of 45% porosity was produced from a sample with 10 mol% TiH2, a Ti5Si3/TiN composite of 53% porosity from one with 9.41 mol% TiH2, and a Ti5Si3/TiN/TiB2 composite of 41% porosity from one with 6.67 mol% TiH2. Both Ti3AlC2 and NiAl were prepared from elemental powders with addition of TiH2, and there were small amounts of Ti2AlC and Ni3Al, respectively, present in the final products. For the elemental samples with 10 mol% TiH2, the porosities of resultant Ti3AlC2 and NiAl products reached 33% and 57%, respectively. When the TiC-containing sample was adopted, Ti3AlC2 with a porosity of 44% was fabricated from a sample containing 7.27 mol% TiH2. Based upon the numerical simulation, Arrhenius factor of the rate function, A = 3 x 109 s-1, was determined for both 5Ti + 3Si and Ni + Al combustion systems. The effect of product porosity on the SHS process was correlated to the variation of the effective thermal conductivity (keff) of the powder compact. The decrease of keff/kbulk from 0.035 to 0.015 was numerically obtained for the increase of Ti5Si3 porosity from 25.36% to 42.69%. For the case of NiAl, the porosity increase from 37.28% to 57.96% corresponded to a decrease of keff/kbulk from 0.0225 to 0.007.
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Chen, Sheng-Yu, and 陳勝育. "Microstructure and mechanical properties of porous Ti-6Al-4V alloys for bone implants fabricated by additive manufacturing." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/v669qy.
Full textAbstract:
博士國立中山大學
材料與光電科學學系研究所
106
In recent years, additive manufacture (AM), or called as rapid prototyping or 3D printing, has become a flourishing industry suitable to fabricate bio-implants, due to the benefits such as the reduction in process steps, complexity of parts, and customization. Among of them, the application of human bone has been most widely studied. However, the bone is a porous structure, subjected to wide variations as a result of human movement and inevitable changes with age, sex, and location. Therefore, it is important to study the relationship between the porous structure and mechanical properties of various bionic implants. In this study, we used the selective laser melting (SLM) and electron beam melting (EBM) methods to produce porous structures of bone bio-implants. The highly biocompatible Ti-6Al-4V alloy was applied as experimental. For the first part, using Ti-6Al-4V alloy powders, the Ti-6Al-4V porous samples were fabricated by SLM, with the help from computer-aided design (CAD) for different porosities. Compared with the CAD models and porous samples fabricated by SLM, the relevant relationships are characterized with morphology, physical properties and mechanical properties. The difference between the CAD model and porous SLM parts leads to the larger ligament widths and smaller pore sizes for SLM parts, due to the laser beam broadening and laser melting edge effects. Due to the higher porosity samples with a higher pore number density, this difference between the CAD model and porous SLM parts could be more obvious, so that the designed porosity will be greater than that of the actual porosity of porous samples. The difference can be reduced by decreasing the size of laser beam and the used powders. The structure of Ti-6Al-4V prepared by SLM was seen to possess higher hardness favorable for wear resistance and beneficial for the application of human bone implant. The mechanical properties (elastic modulus and yield strength) of porous SLM parts decrease with increasing porosity, matching well with the human bone. In terms of the matched elastic modulus, it can avoid the risk of stress shielding effect. By applying the Gibson and Ashby model, the relationship between porosity and mechanical properties of SLM porous foams can be described and predicted. According to many previous studies, the porous samples with high porosity can effectively reduce the stress shielding problem, but mechanical strength would also be reduced. For the second part, the high porosity of porous Ti-6Al-4V samples are fabricated by EBM, and the physical and mechanical properties are characterized. The results indicate that the porosity of porous parts can be as high as near 80% by increasing the ligament and pore size. The elastic modulus of such EBM porous Ti-6Al-4V structure with high porosity is found to match well with that of the human cancellous bone. However, it can obviously be seen that the higher ligament width of porous samples will enhance the endurance to fracture. Therefore, the relationship between the ligament width and work of fracture is systematically studied. According to the relation, it is concluded that when the ligament width is smaller than 401 μm, the porous structure cannot bear any strength for fracture. However, because the AM is basically a powder metallurgy technique, the porous samples would be inherent with rough surface, prone to cause stress concentration and premature fracture. Therefore, the relationship between the ratio of the ligament width and surface roughness corresponding to the fracture energy is derived in this study. From this relation, the fracture energy of porous samples with the larger ligament width will be less affected by the surface roughness. For an average ligament width of about 650 μm, the maximum acceptable surface roughness cannot be greater than 91 μm; otherwise, the porous sample can barely withstand the energy to fracture. The experimental results are imported into the physical formulae and the relationships between the mechanical properties corresponding to the porous structure prepared by SLM and EBM are deduced. It is expected that these relationships can be used to prepare bionic implants using those processes to estimate its mechanical properties before the implants can be applied, effectively increase the value of their practical application.