Dissertations / Theses on the topic 'Ceramic Additive Manufacturing'

In the last two decades additive manufacturing (AM) has emerged as a highly important and influential technology. A large range of approaches to AM have been developed which give rise to hundreds of distinct techniques. Many of these are specific to one material system, and only a handful have been successful at producing ceramic parts. Robocasting is one such technique, having been used to produce complex ceramic parts with reasonable mechanical properties. In this thesis robocasting is investigated further, firstly by characterising the rheology of the robocasting paste, and then by measuring the strength and reliability of ceramic parts produced by robocasting. The critical defects associated with the process are identified, and efforts have been made to eliminate them. Furthermore, it was possible to produce a new class of ceramic composites consisting of alumina platelets aligned by the shear forces that arise during printing. These platelets themselves and the composites were extensively characterised. A new in-situ double cantilever test was developed in order to study the fracture behaviour of the composites. Lastly, the principle of using the printing process to align platelets was applied to fibres in order to create printed fibre reinforced ceramic matrix composites, and printed carbon fibre reinforced epoxy.

The goal of this work is to develop and characterize a manufacturing process that is able to create metal matrix composites with complex cellular geometries. The novel manufacturing method uses two distinct additive manufacturing processes: i) fabrication of patternless molds for cellular metal castings and ii) printing an advanced cellular ceramic for embedding in a metal matrix. However, while the use of AM greatly improves the freedom in the design of MMCs, it is important to identify the constraints imposed by the process and its process relationships. First, the author investigates potential differences in material properties (microstructure, porosity, mechanical strength) of A356 — T6 castings resulting from two different commercially available Binder Jetting media and traditional 'no-bake' silica sand. It was determined that they yielded statistically equivalent results in four of the seven tests performed: dendrite arm spacing, porosity, surface roughness, and tensile strength. They differed in sand tensile strength, hardness, and density. Additionally, two critical sources of process constraints on part geometry are examined: (i) depowdering unbound material from intricate casting channels and (ii) metal flow and solidification distances through complex mold geometries. A Taguchi Design of Experiments is used to determine the relationships of important independent variables of each constraint. For depowdering, a minimum cleaning diameter of 3 mm was determined along with an equation relating cleaning distance as a function of channel diameter. Furthermore, for metal flow, choke diameter was found to be significantly significant variable. Finally, the author presents methods to process complex ceramic structure from precursor powders via Binder Jetting AM technology to incorporate into a bonded sand mold and the subsequently casted metal matrix. Through sintering experiments, a sintering temperature of 1375 °C was established for the ceramic insert (78% cordierite). Upon printing and sintering the ceramic, three point bend tests showed the MMCs had less strength than the matrix material likely due to the relatively high porosity developed in the body. Additionally, it was found that the ceramic metal interface had minimal mechanical interlocking and chemical bonding limiting the strength of the final MMCs.
Ph. D.

The goal of this work is to develop and characterize a manufacturing process that is able to create metal matrix composites with complex cellular geometries. The novel manufacturing method uses two distinct additive manufacturing processes: i) fabrication of patternless molds for cellular metal castings and ii) printing an advanced cellular ceramic for embedding in a metal matrix. However, while the use of AM greatly improves the freedom in the design of MMCs, it is important to identify the constraints imposed by the process and its process relationships. First, the author investigates potential differences in material properties (microstructure, porosity, mechanical strength) of A356 — T6 castings resulting from two different commercially available Binder Jetting media and traditional 'no-bake' silica sand. It was determined that they yielded statistically equivalent results in four of the seven tests performed: dendrite arm spacing, porosity, surface roughness, and tensile strength. They differed in sand tensile strength, hardness, and density. Additionally, two critical sources of process constraints on part geometry are examined: (i) depowdering unbound material from intricate casting channels and (ii) metal flow and solidification distances through complex mold geometries. A Taguchi Design of Experiments is used to determine the relationships of important independent variables of each constraint. For depowdering, a minimum cleaning diameter of 3 mm was determined along with an equation relating cleaning distance as a function of channel diameter. Furthermore, for metal flow, choke diameter was found to be significantly significant variable. Finally, the author presents methods to process complex ceramic structure from precursor powders via Binder Jetting AM technology to incorporate into a bonded sand mold and the subsequently casted metal matrix. Through sintering experiments, a sintering temperature of 1375 °C was established for the ceramic insert (78% cordierite). Upon printing and sintering the ceramic, three point bend tests showed the MMCs had less strength than the matrix material likely due to the relatively high porosity developed in the body. Additionally, it was found that the ceramic metal interface had minimal mechanical interlocking and chemical bonding limiting the strength of the final MMCs.
Ph. D.

Processing of ceramics has always been difficult due to how hard and brittle the material is. Fused Deposition of Ceramics (FDC) is a method of additive manufacturing which allows ceramic parts to be built layer by layer, abetting more complex geometries and avoiding the potential to fracture seen with processes such as grinding and milling. In the process of FDC, a polymeric binder system is mixed with ceramic powder for the printing of the part and then burned out to leave a fully ceramic part. This experiment investigates a new combination of materials, zirconia and acrylic binder, optimizing the process of making the material into a filament conducive to the printer system and then performing trials with the filament in the printer to assess its feasibility. Statistical analysis was used to determine optimal parameter levels using response surface methodology to pinpoint the material composition and temperature yielding the highest quality filament. It was discovered that although the mixture had adequate melting characteristics to be liquefied and printed into a part, the binder system did not provide the stiffness required to act as a piston to be fed through the printer head. Further studies should be completed continuing the investigation of zirconia and acrylic binder, but with added components to increase strength and rigidity of the filament.

Additive Manufacturing (AM) is beneficial for medical applications in which tissues must be replaced because AM enables the fabrication of highly complex three-dimensional structures. In this study the AM and the post-processing steps of additive manufactured ceramic parts of a specific material for tissue replacement were examined in order to optimize the parts’ quality. Visual inspection and microscopic techniques, weighing, dimensional measurements, and flexural bending tests were used for the result evaluation. Different cleaning agents and methods were tested with the result that the current cleaning agent and method had the best cleaning performance. With changed orientation on the building platform, changed supports during the AM and defined positions in the furnace during sintering, the parts’  quality was clearly improved, i.e. the parts had no longer countless cracks, were not warped anymore and had a smooth surface. Post-curing with UV light was found to have a detrimental impact on the parts’ quality. Tests with different sintering temperatures showed, that the sintering temperature influences the appearance, the degree of shrinkage, the degree of fusion, and the flexural strength of the parts. Hence, depending on the intended application the  sintering parameters must be specified for each part.
Additiv tillverkning är fördelaktigt för medicinska tillämpningar där vävnader måste bytas ut eftersom additiv tillverkning möjliggör tillverkning av högkomplexa tredimensionella strukturer. I denna studie undersöktes additiv tillverkning och efterbehandlingsstegen av tillsatsframställda keramiska delar av ett specifikt material för vävnadsersättning för att optimera delarnas kvalitet. Visuell inspektion och mikroskopiska tekniker, vägning, dimensionella mätningar och böjningsböjningstest användes för resultatutvärderingen. Olika rengöringsmedel och metoder testades med det resultat att det aktuella rengöringsmedlet och metoden hade den bästa rengöringsytan. Med ändrad orientering på byggplattformen och ändrade stöd under additiv tillverkning och definierade positioner i ugnen under sintring förbättrades delarnas kvalitet klart, dvs delarna hade inte längre otaliga sprickor, inte varvade längre och hade en jämn yta. Efterhärdning med UV-ljus har visat sig ha en negativ inverkan på delarnas kvalitet. Test med olika sintringstemperaturer visade att sintringstemperaturen påverkar utseendet, graden av krympning, graden av fusion och böjhållfastheten hos delarna. Därför, beroende på den avsedda tillämpningen, måste sintringsparametrarna anges.

En les darreres dècades, les tecnologies de fabricació additiva han aconseguit una àmplia difusió, evolucionant des dels primers prototips fins a una extensa distribució comercial. Els materials ceràmics són ben coneguts per la seva alta rigidesa, fragilitat i tenacitat, que dificulten la consecució de formes complexes i fa extremadament costosa la seva mecanització (gran consum d’eines o motlles per a ús individual). La fabricació additiva pot reduir el cost de fabricació i obrir nous dissenys, amb llibertat de forma pràcticament total, no realitzables amb tècniques de fabricació tradicional. El primer pas de la recerca en aquest camp és l’aplicació de la fabricació additiva al camp dels materials funcionals, on els requisits de propietats estructurals, microestructurals, òptiques i elèctriques són superiors als de les aplicacions comercials. En particular, l’oportunitat de dissenys complexos és interessant per a aplicacions en les quals l’àrea activa juga un paper important en el rendiment final, com en catàlisi o en dispositius electroquímics. En aquests casos, sovint cal més d’un material ceràmic. Per aquest motiu hi ha un gran interès en la realització una impressió 3D de múltiples materials, que permetria la producció d’aquests dispositius amb passos de fabricació reduïts i, en conseqüència, reduint el cost. Aquesta tesi es centra en la impressió de dispositius de geometries complexes per provar els avantatges exclusius de la fabricació additiva, tant en el camp de la catàlisi com en l’aplicació de piles de combustible i electrolitzadors. Per a això, el treball aborda el desenvolupament de suports imprimibles i la hibridació de dues tecnologies d’impressió diferents per produir tot el dispositiu en un sol pas: estereolitografia i robocasting. La estereolitografia (SLA) es caracteritza per oferir estructures d’alta densitat (> 90%) amb gran resolució espacial, de l’ordre de 25 micres en les tres direccions. S’han produït electròlits per cel·les d’òxid sòlid (SOC) en zircònia estabilitzada amb ítria a el 3% i a l’8% molar. Es produïren piles de botó incorporant materials estàndard d’elèctrode per caracteritzar el rendiment electroquímic. Després d’haver demostrat que la tecnologia SLA produeix electròlits adequats amb propietats comparables a les produïdes per la fabricació tradicional, s’ha mesurat un increment de rendiment, coherent amb l’increment d’àrea activa, realitzat mitjançant la corrugació de l’electròlit. Seguidament, es va explorar en aquesta tesi la possibilitat d’implementar opcions multimaterials, necessàries per imprimir un dispositiu comercial basat en la tecnologia SOCs. Utilitzant SLA com a tecnologia base, es va agregar a la màquina un sistema de robocasting, aconseguint una impressora 3D de cinc materials. Les pastes necessàries per a la impressió per robocasting s’han desenvolupat íntegrament en el marc d’aquesta tesi a partir de pols ceràmics i components orgànics en proporcions adequades, avaluant el seu reologia i capacitat de curat. D’aquesta manera, es van produir materials de càtode, ànode i interconnector. La hibridació de SLA amb robocasting va se assolida satisfactòriament, demostrant la possibilitat d’imprimir piles de capes dels diferents components. El sinteritzat conjunt d’aquests sistemes va ser dut a terme, afrontant les dificultats de la calcinació conjunta de capes composades per diferents materials . Les primeres cel·les obtingudes mitjançant aquest procediment van ser testejades. Tot i que encara serà necessària una optimització per a millorar els rendiments, aquestes cel·les son la demostració de la possibilitat de fabricar dispositius SOC mitjançant impressió 3D multimaterial. Finalment, fent servir la tècnica de SLA es van produir plaques de microcanals, utilitzades com a llit per a la reacció de metanització de CO2, demostrant la seva eficàcia enfront de la tecnologia tradicional basada en acer inoxidable en termes de conversió de CO2. També es va fabricar per primera vegada un reactor d’intercanvi de calor amb col·lectors integrats mitjançant impressió 3D.
En las últimas décadas, las tecnologías de fabricación aditiva han logrado una amplia difusión, evolucionando desde los primeros prototipos hasta conseguir una extensa distribución comercial. Los materiales cerámicos son bien conocidos por su alta rigidez, fragilidad y tenacidad, que dificultan la consecución de formas complejas y hace extremadamente costosa su mecanización (gran consumo de herramientas o moldes para uso individual). La fabricación aditiva puede reducir el coste de fabricación y abrir nuevos diseños, con libertad de forma prácticamente total, no realizables mediante técnicas tradicionales. El primer paso de la investigación en este campo es la aplicación de la fabricación aditiva al campo de los materiales funcionales, donde los requisitos de propiedades estructurales, microestructurales, ópticas y eléctricas son superiores a los de las aplicaciones comerciales. En particular, la oportunidad de diseños complejos es interesante para aplicaciones en las que el área activa juega un papel importante en el rendimiento final, como en catálisis o en dispositivos electroquímicos. En estos casos, a menudo es necesario más de un material cerámico. Por este motivo es de un gran interés la impresión 3D de múltiples materiales, que permitiría la producción de dichos dispositivos con pasos de fabricación reducidos y, en consecuencia, reduciendo el coste. Esta tesis se centra en la impresión de dispositivos de geometrías complejas para probar las ventajas exclusivas de la fabricación aditiva, tanto en el campo de la catálisis como en la aplicación de pilas de combustible y electrolizadores. Para ello, el trabajo aborda el desarrollo de soportes imprimibles y la hibridación de dos tecnologías de impresión diferentes para producir todo el dispositivo en un solo paso: estereolitografía y robocasting. La estereolitografía (SLA) se caracteriza por obtener estructuras de alta densidad (> 90%) con gran resolución espacial, del orden de 25 µm en las tres direcciones. Se han producido electrolitos para celdas de óxido sólido (SOC) en zirconia estabilizada con itria al 3% y al 8% molar. Se produjeron pilas de botón incorporando materiales estándar de cátodo y ánodo sobre los electrolitos imprimidos, para caracterizar el rendimiento electroquímico. Después de haber demostrado que la tecnología SLA produce electrolitos adecuados con propiedades comparables a las producidas por la fabricación tradicional, se ha medido un incremento de rendimiento, coherente con el incremento de área activa, realizado mediante la corrugación del electrolito. Seguidamente, en esta tesis se exploró la posibilidad de implementar opciones multimaterial, necesarias para imprimir un dispositivo comercial basado en tecnología SOCs. Utilizando SLA como tecnología base, se agregó a la máquina un sistema de robocasting, logrando imprimir cinco materiales. Las pastas necesarias para la impresión por robocasting se han desarrollado íntegramente en el marco de esta tesis a partir de polvos cerámicos comerciales y componentes orgánicos, evaluando su reología y capacidad de curado; produciendo materiales de cátodo, ánodo e interconector. La hibridación de SLA con robocasting fue alcanzada satisfactoriamente, demostrando la posibilidad de imprimir apilamientos de capas de los diferentes componentes. El sinterizado conjunto de tales sistemas fue llevado a cabo, afrontando los retos de la calcinación conjunta de capas compuestas por distintos materiales. Las primeras celdas obtenidas utilizando este procedimiento fueron testadas. Aunque será necesaria una optimización para mejorar los rendimientos, estas celdas son la demostración de la posibilidad de fabricar dispositivos SOC mediante impresión 3D multimaterial. Finalmente, usando técnica de SLA se produjeron placas de microcanales, utilizadas como lecho para la reacción de metanización de CO2, demostrando su eficacia frente a la tecnología tradicional basada en acero inoxidable en términos de conversión de CO2. También se fabricó por primera vez un reactor de intercambio de calor con colectores integrados mediante impresión 3D.
In the last decades, additive manufacturing technologies (AM) have obtained a wider spreading, moving from the prototyping scale to the commercial distribution for some types of materials. The ceramic materials are well known for their high stiffness, brittleness and toughness, which make their processing limited in shape and extremely expensive (high consumption of tools or moulds for individual use). Additive manufacturing can reduce the cost of manufacturing and open new designs, near-free to shape, not realizable with subtracting manufacturing. Next step of the research in this field is the application of additive manufacturing to the field of functional materials, where the requirements of structural, microstructural, optical and electric properties are higher than for commercial applications. In particular the near-free design opportunity is particularly interesting for applications in which the area plays an important role on the final performance, such as in catalysis and for electrochemical devices. In these cases, often more than a ceramic material is necessary arising the interest of the scientific community to the multi-material possibility of 3D printing, to enable the production of such devices with reduced manufacturing steps and on consequence, reducing the cost. This thesis focuses on the printing of complex geometries devices to prove the unfair advantage of additive manufacturing, as in the catalysis field, as for fuel cells and electrolysis application. For this purpose, the work addresses on developing of printable media and hybridization of two different printing technologies to produce the entire device in a single step: stereo-lithography and robocasting. Stereo-lithography (SLA) offers the possibility of obtaining high-density structures (>90%) with high spatial resolution, in the order of 25 µm in the three directions. Electrolytes for Solid Oxide Cells (SOCs) have been produced in 3mol% and 8mol% yttria stabilized zirconia. Button cells were realized with state-of-the-art materials to characterize the electrochemical performance. At first, it was demonstrated that SLA technology is suitable to produce electrolytes with properties comparable with the ones produced by traditional manufacturing. The freedom of design, characteristic of the 3D printing, enables the increase of the performance according with the implement of the area. As a further step, the possibility of implementing multi-material options, necessary to print a commercial device based on SOCs technology, was explored in this thesis. Using SLA as a base, a robocasting system was added to the machine. In this way, a five-material 3D printer could be achieved. The required pastes for robocasting were integrally produced, mixing the ceramic commercial powders with organic materials in appropriate proportions and evaluating their rheology performance and curability. In this way, cathode, anode and interconnect layers were produced. The hybridization of SLA with robocasting was satisfactory achieved, demonstrating the possibility of printing stacks of layers of the different components. The co-sintering of such systems was conducted, facing the challenge of the simultaneous annealing of layers of different materials. The first cells using this procedure were obtained and tested. While still requiring optimization to improve their performances, these cells are the first-time demonstration of the feasibility of SOC devices by multi-material 3D printing. Micro-channel plates, used as bed for CO2 methanation reaction were produced with SLA, proving their efficiency compared with stainless steel ones in terms of CO2 conversion. A heat exchange reactor with integrated manifolds was produced by 3D printing for the first time.
Universitat Autònoma de Barcelona. Programa de Doctorat en Ciència de Materials

Metal matrix composites (MMCs) microstructure consists of a metallic alloy and a particular reinforcing component, ceramic in the case of this research. They are of high interest due to their high temperature strength, improved thermal stability, improved friction and wear resistant. Defining a low-cost additive manufacturing process that can fabricate high-quality MMC parts will combine the benefit of additive manufacturing and MMC together, which is highly desirable in today’s manufacturing.

This research introduces a novel method to fabricate MMC by introduction of uniformly distributed and dispersed ultra-fine ceramic particles within a metal substrate to form metal-ceramic composite during bulk sintering and to further develop three dimensional printing for fabrication of MMC structures reinforced by ceramic particles. This novel process is capable to fabricate metal-ceramic composite structures with a lower cost and shorter lead time in manufacturing compared to other existing additive manufacturing processes.

Les techniques d’élaboration de matériaux par fabrication additive (FA) sont en plein essor [1]. Elles permettent de fabriquer des pièces par ajout de matière, en opposition avec les techniques traditionnelles par soustraction de matière (usinage). Il existe à l’heure actuelle de nombreux procédés de FA, adaptés à différentes applications : fusion ou frittage par faisceau d’électrons ou par laser, dépôt de matière direct ou en lit de poudre… Ces procédés ont été bien développés pour des matériaux polymères puis métalliques. Des techniques de FA de matériaux céramiques via des polymères chargés ont également vu le jour, mais celles-ci nécessitent des traitements postérieurs (cycles de déliantage, frittage) [2]. Les matériaux céramiques denses sont encore peu développés en fabrication additive en raison de la fissuration de ces matériaux lors de leur élaboration.La technologie CLAD (Construction Laser Additive Directe), développée par IREPA-LASER, permet la fabrication de pièces par dépôt de matière fondue. Le matériau sous forme de poudre est acheminé via une buse laser et projeté dans le faisceau. Il est ainsi porté à la température de fusion. La fusion successive de plusieurs couches permet l’obtention de la pièce. Cette technique, en plus de n’utiliser que la matière nécessaire (contrairement aux techniques de fabrication par lit de poudre), permet la fabrication de pièces de grandes dimensions, voire en multi-matériaux. Cette technologie est, pour l’heure, dédiée aux matériaux métalliques.L’objet de ce sujet de thèse, en partenariat entre l’ONERA et IREPA-LASER dans le cadre du projet inter-Carnot CLADIATOR, est d’étudier la FA de matériaux céramiques denses par le procédé CLAD®. Cette étude porte ainsi sur le procédé dans son ensemble, des matières premières aux pièces finales, en passant par l’adaptation du moyen de fabrication aux contraintes spécifiques liées aux matériaux céramiques.Les matières premières exigent d’être adaptées au procédé ; les deux principales difficultés étant la coulabilité de la poudre, nécessaire pour son acheminement dans la buse, et l’absorption de la source laser par le matériau pour sa montée en température. En parallèle de la caractérisation des matières premières (granulométrie, MEB, dilatométrie, DRX…), des essais d’atomisation par séchage seront effectués pour optimiser la coulabilité des poudres [3]. Ce procédé d’atomisation permet d’obtenir des poudres sous forme d’agglomérats sphériques de plus petites particules ; leur forme est régulière, mais elles restent poreuses. L’ajout de dopants sera étudié pour améliorer l’absorption du signal, en adéquation avec une éventuelle adaptation du laser. Les matériaux considérés sont l’alumine, la zircone ainsi que des compositions eutectiques d’alumine-zircone.La principale difficulté de ce sujet réside dans la sensibilité à la fissuration des matériaux céramiques, en raison du fort gradient thermique induit par le chauffage local du laser et le refroidissement de la pièce. Des solutions de chauffage de la pièce et/ou du matériau avant et après le dépôt seront étudiées pour limiter les contraintes thermomécaniques subies par le matériau [3,4].La machine devra également être modifiée pour supporter les températures élevées nécessaires à l’élaboration de céramiques (températures de fusion et dispositif de pré/post chauffage). L’étude et l’optimisation de ces solutions seront effectuées à l’aide de modélisations multi physiques sur le logiciel COMSOL en collaboration avec IREPA-LASER.Enfin, l’influence du procédé d’élaboration sur l’état des pièces réalisées sera étudiée grâce à des caractérisations microscopiques, mécaniques, thermiques…
This work, in partnership between the ONERA Materials and Composite Structure Department (DMSC) and IREPA Laser within the CLADIATOR project, is based on the study of direct additive manufacturing of dense ceramic materials by direct melt deposition (also known as laser cladding) process. This process enables high dimensions or even multi-materials part manufacturing.It will deal with the adaptation of raw materials (ceramic powders) to the existing machine, especially in the case of powder flowability and optical absorption. Indeed, the powder flowability enables its transportation up to the laser nozzle, while the optical absorption of the laser signal is necessary to allow its melting.In parallel, the existing machine also needs to be adapted to ceramic materials : the main difficulty of this work will be the occurence of cracks during the manufacturing. This phenomena is due to the local heating by the laser and the materials brittleness. That’s why some secondary heating solutions, before or after the melt, will have to be defined to decrease the thermal gradient in the material while processing. Those solutions will be discussed between Onera and Irepa Laser, based on FEM simulations established with COMSOL Multiphysics software.Finally, the elaboration process influence on the manufactured ceramics parts will be investigated with microscopy, mechanical and thermal characterization

One of the greatest obstacles to clinical translation of bone tissue engineering is the inability to effectively and efficiently vascularise scaffolds. This limits the size of defects that can be repaired, as blood perfusion is necessary to provide nutrient and waste exchange to tissue at the core of scaffolds. The goal of this work was to systematically explore whether architecture, at a scale of hundreds of microns, can be used to direct the growth of microvessels into the core of scaffolds. A pipeline was developed for the production of hydroxyapatite surfaces with controlled architecture. Three batches of hydroxyapatite were used with two different particle morphologies and size distributions. On sintering, one batch remained phase pure and the other two batches were biphasic mixtures of α-tricalcium phosphate (α-TCP) and hydroxyapatite. Sample production methods based on slip casting of a hydroxyapatite-gelatin slurry were explored. The most successful of these involved the use of curable silicone to produce moulds of high-resolution, three dimensional (3D) printed parts with the desired design. Parts were dried and sintered to produce patterned surfaces with higher resolution than obtainable through conventional 3D printing techniques. Given the difficulties associated with the structural reproducibility of concave pores architectures in 3D reported in the literature, in this work, a 2.5D model has been developed that varies architectural parameters in a controlled manner. Six contrasting architectures consisting of semi-circular ridges and grooves were produced. Grooves and ridges were designed to have widths of 330 μm and 660 μm, with periodicities, respectively, of 1240 μm and 630 μm. Groove depth was varied between 150 μm and 585 μm. Co-cultures of endothelial cells and osteoblasts were optimised and used to grow microcapillary-like structures (referred to as "microvessels") on substrates. Literature shows that these precursors to microcapillaries contain lumina and can produce functional vasculature, demonstrating their clinical promise. The effects of the composition and surface texture of grooved samples on microvessel formation were studied. It was found that surface microtopography and phase purity (α-TCP content) did not affect microvessel formation. However, hydroxyapatite architecture was found to significantly affect microvessel location and orientation. Microvessels were found to form predominantly in grooves or between convexities. Two metrics - the degree of alignment (DOA) and the degree of containment (DOC) - were developed to measure the alignment of endothelial cell structures and their localisation in grooves. For all patterned samples, the CD31 (an endothelial cell marker) signal was at least 2.5 times higher along grooves versus perpendicular to grooves. In addition, the average signal was at least two times higher within grooves than outside grooves for all samples. Small deep grooves had the highest DOA and DOC (6.13 and 4.05 respectively), and individual, highly aligned microvessels were formed. An image analysis method that compares sample X-ray microtomography sections to original designs to quantify architectural distortion was developed. This method will serve as a useful tool for improvements to architectural control for future studies. This body of work shows the crucial influence of architecture on microvessel self-assembly at the hundreds of micron scale. It also highlights that microvessel formation has a relatively low sensitivity to phase composition and microtopography. These findings have important implications for the design of porous scaffolds and the refinement of fabrication technologies. While important results were shown for six preliminary architectures, this work represents a toolkit that can be applied to screen any 2.5D architecture for its angiogenic potential. This work has laid the foundations that will allow elucidating the precise correspondence between architecture and microvessel organisation, ultimately enabling the "engineering" of microvasculature by tuning local scaffold design to achieve desirable microvessel properties.

Ce travail de thèse a pour objectif d'élaborer des pièces céramiques denses mono et multi-matériaux ayant des architectures complexes. Ces architectures sont réalisées à l'aide d'une technologie de fabrication additive d'extrusion de pâtes céramiques à travers une fine seringue (DIW : robocasting). Ce travail de recherche est financé par le projet ANR CERAPIDE qui a pour objectif la réalisation de pièces céramiques plus rapidement et en consommant moins d'énergie, de sa formulation jusqu'aux étapes de post traitements thermiques. Ainsi, les formulations des pâtes sont optimisées en adaptant les additifs et leurs quantités dans le but d'obtenir des pâtes homogènes, sans défauts et ayant les propriétés rhéologiques nécessaires pour l'impression. Une pâte céramique doit entre autres disposer d'un comportement rhéofluidifiant tout en disposant d'une contrainte seuil élevée pour pouvoir être imprimée par empilement successif de couches. La maitrise rhéologique et l'optimisation des formulations permettent d'imprimer des pièces denses avec des propriétés mécaniques améliorées. Le changement d'additif permet de modifier l'état de surface des pièces denses et donc de modifier les propriétés mécaniques des pièces. La définition de l'imprimabilité des pâtes céramiques est étudiée pour comprendre les relations entre les propriétés microstructurales, environnementales et technologiques. Ainsi, les paramètres d'impressions doivent être sélectionnés en fonction des propriétés finales souhaitées pour la pièce imprimée. La compréhension de tous ces paramètres permet d'élaborer des pièces en alumine ayant une moyenne de contrainte à la rupture de 350 MPa sans étapes de polissage
The main goal of this thesis is to elaborate dense single and multi-material ceramic parts with complex architectures. These architectures are realized using an additive manufacturing technology of extrusion of ceramic pastes through a fine syringe (DIW : robocasting). This research work is financed by the ANR CERAPIDE project, which aims to produce ceramic parts more quickly and with less energy consumption, from formulation to post heat treatment stages. Thus, the formulations of the pastes are optimized by adapting the additives and their quantities in order to obtain homogeneous pastes, without defects and having the rheological properties necessary for printing. Among other things, a ceramic paste must have be shear-thinning while having a high yield stress to be able to be printed by successive stacking of layers. The rheological control and the optimization of the formulations allow to print dense parts with improved mechanical properties. The change of additive allows to modify the topography of the dense parts and thus to modify the mechanical properties of the parts. The definition of printability of ceramic pastes is studied to understand the relationships between microstructural, environmental and technological properties. Finally, the printing parameters must be selected according to the final properties desired for the printed part. The understanding of all these parameters allows the development of alumina parts with an average stress at break of 350 MPa without polishing steps

L’hydroxyapatite (HA) de formule Ca10(PO4)6(OH)2 fait partie des matériaux les plus utilisés en reconstruction osseuse. L’amélioration de ses propriétés biologiques, notamment via le dopage par des éléments traces présents dans le corps humain, fait l’objet de récentes études. Cette thèse porte ainsi sur l’élaboration, la caractérisation structurale par spectroscopie et la mise en forme d’hydroxyapatites dopées au cuivre ou au fer. Deux voies de synthèse ont été considérées : les synthèses par coprécipitation en milieu aqueux ont permis d’élaborer des HA pures dopées au cuivre(II) ou au fer(III) stables à basse température (≤ 600°C) tandis que les réactions par voie solide à haute température ont conduit à l’élaboration d’HA pures dopées au cuivre(I), au fer(II) ou au fer(III) stables au-delà de 1100°C. Ces phases ont été caractérisées par DRX ainsi que par diverses techniques spectroscopiques : FTIR, RMN, UV-vis-NIR, XPS, RPE, XANES-EXAFS et Mössbauer afin d’évaluer l’influence de l’incorporation des différents éléments de transition sur la structure apatitique et de déterminer la localisation de l’élément dopant, son degré d’oxydation, sa coordinence, ainsi que son environnement local. L’influence du cuivre et du fer sur la frittabilité et la densification des céramiques obtenues par voie solide ainsi que sur la croissance granulaire a ensuite été établie. Dans le cas des céramiques d’HA dopées au cuivre, la biocompatibilité des matériaux a été vérifiée sur des temps de culture de 5 jours avec la lignée cellulaire MC3T3-E1 et la capacité de ces cellules à se différencier en cellules osseuses à la surface des céramiques semble peu affectée par la présence de cuivre (jusqu’à 5,3% massique). Enfin, des films 2D pré-frittés de la phase d’HA contenant 0,8% massique de cuivre ont pu être mis en forme par frittage laser sélectif
Hydroxyapatite (HA), with formula Ca10(PO4)6(OH)2, is one of the most used material in bone reconstruction. The improvement of its biological properties, in particular by doping with trace elements present in the body, is the subject of recent studies. Therefore, this work deals with the elaboration, structural characterizations from spectroscopy and shaping of copper- or iron-doped hydroxyapatite. Two synthesis routes have been considered: syntheses by aqueous co-precipitation led to the elaboration of pure HA phases doped with copper(II) or iron(III) stable at low temperature (≤ 600°C) while high temperature solid-state reactions led to the elaboration of pure HA phases doped with copper(I), iron(II) or iron(III) stable above 1100°C. These phases have been characterized by XRD and various spectroscopic techniques: FTIR, NMR, UV-vis-NIR, XPS, EPR, XANES-EXAFS and Mössbauer in order to evaluate the influence of the incorporation of the different transition elements into the apatitic structure and to determine the location of the doping element, its degree of oxidation, its coordination, as well as its local environment. The influence of copper and iron on the sinterability and densification of ceramics obtained by solid-state reaction and on the granular growth has been then established. In the case of copper-doped HA ceramics, the biocompatibility of the materials has been verified over a 5-day culture time using MC3T3-E1 cell line and the presence of copper does not seem to affect the cell differentiation onto the ceramic surface (up to 5.3 wt%). Finally, pre-sintered 2D films of the HA phase containing 0.8 wt% of copper have been shaped by selective laser sintering

Les télécommunications sont devenus indispensables dans notre monde actuel. De plus, le volume des données échangées ne cesse de croître. En effet, nous pouvons transmettre nos photos, nos vidéos au monde entier. Nonobstant, nous ne voulons pas attendre pour les avoir, ce qui exige un débit de données très important et par conséquent des signaux avec des bandes passantes plus larges. Les satellites de télécommunications doivent donc s’adapter, c'est pourquoi nous proposons dans ces travaux la recherche de filtre à large bande avec une recherche de compacité et de faibles pertes. Nous nous sommes intéressés à l'utilisation de matériaux céramiques qui permettent d'obtenir de bonnes performances vis à vis de nos besoins. Notre travail est aussi rendu possible par le développement de procédés de fabrication additifs, comme par exemple la stéréolithographie, qui va nous permettre de nous affranchir fortement de règles de dessin contraignantes que nous pourrions avoir en utilisant des procédés classiques. Nous avons développé des filtres avec de larges bandes passantes autour de 4GHz. Une première étude nous a permis de rechercher des concepts qui permettent d'obtenir de forts couplages, conditions sine qua non pour réaliser ces filtres. Plusieurs concepts sont présentés ainsi que leur fabrication et leur mesures. Nous avons ainsi démontré expérimentalement que les concepts proposés, à base de pièces monoblocs céramiques, sont capables de produire des filtres à bandes passantes supérieures à 60 % (voire même 110 % pour une version améliorée)
Every day, the data exchanges increase thanks to the new technologies. We can keep our files, our pictures, our videos online to have an access anywhere on the planet (for now). In this way, the data output of the telecommunication systems has to be increased in order to satisfy the more and more demanding users. One way to allow this is to increase the bandwidths of the different signals, making possible to transmit more data at the same time. In this work, we will develop wide bandpass filters dedicated to space telecommunications. For that purpose, we need them to be compact, with low insertion loss and a limited number of parts to assemble. Consequently, we are interested to use resonators made with ceramic materials that permits to reach such properties. Moreover, these materials are compatible with stereolithography, an additive manufacturing process. Such technology is here very useful for our purpose since its design freedom allows the creation of almost all kind of geometries. To realize such wide bandpass filters, we need strong couplings between the different resonators and also for the accesses, so we will present our studies focused on reaching these specific objectives. Then, we will present different designs of wide bandpass filter around 4GHz. After different generation of ceramic based components, we are be able to experimentally create a 60% bandwidth (even 100% for our last version) very compact bandpass filter filling the objectives of this PhD thesis

The diploma thesis is related to the preparation of hydroxyapatite complex structures by additive manufacturing known as Lithography based ceramics manufacturing – LCM. A photosensitive suspension containing hydroxyapatite particles was used for 3D printing of ceramic complex structures. The influence of printing parameters on the resulting macrostructure, microstructure, density, and dimensional accuracy was evaluated. The aim was to obtain ceramic components without delamination of the layers and optimise following post-processing steps (cleaning and thermal treatment). It was found that the exposure time has a significant effect on the dimensional accuracy of printed parts. During observation microstructure of printed parts, a microporosity at the interface of printed layers, which can cause delamination of several layers was identified. High-temperature dilatometry showed different temperature of beginning densification process in the longitudinal and perpendicular directions to the layers. That could be an initiation mechanism for delamination of the layers. X-ray diffraction analysis determined a single-phase composition of powder in photosensitive suspension and sintered parts. A commercial product LithaSol 20 was suggested as a suitable cleaning agent and efficiency of the ultrasound field for cleaning was demonstrated. Based on the thermogravimetric analysis an optimized cycle of heat treatment was designed. The optimisation led to time saving (49 hours), while maintaining density, dimensional accuracy and macrostructure of the 3D printed structures.

La micro extrusion (ou DIW) est une technique de fabrication additive basée sur le dépôt continu de filaments couche par couche. Utilisée pour l'impression de structures poreuses, le DIW de céramiques denses et résistantes reste un défi. L'avantage du DIW réside dans sa capacité à produire des composites, offrant la possibilité de combiner la mise en forme complexe à un contrôle microstructural et fonctionnel précis de matériaux bioinspirés par exemple.Notre travail se concentre sur l'utilisation de gels de boehmite, un précurseur d'Al2O3, en tant que matrice céramique pour obtenir différentes microstructures. Des légers changements dans la composition des gels conduisent à des microstructures et donc à des propriétés différentes. En combinant la polyvalence microstructurale de ces gels avec une maîtrise rhéologique, on peut imprimer des composites avec des propriétés mécaniques améliorées.L'impression de céramiques denses et résistantes passe par la compréhension des propriétés rhéologiques qui définissent une encre imprimable. Le vieillissement de la boehmite est idéal pour corréler les critères géométriques avec la rhéologie pour fournir un critère universel pour l'imprimabilité. Aussi, l'écoulement à l'intérieur des buses de DIW peut aligner des plaquettes d'alumine pendant l'impression. Ceci fournit à l'objet imprimé une ténacité à la rupture accrue dans la direction souhaitée, avec la possibilité de dévier la propagation de la fracture. Un objet peut ainsi être conçu avec précision, en alternant des couches denses et des couches tenaces pour combiner la complexité de la forme avec l'adaptation du comportement mécanique
Direct Ink Writing is an additive manufacturing technique based on continuous layer-by-layer filament deposition. Mostly used to print porous structures, DIW of dense and strong ceramic objects remains an open challenge. However, the advantage of DIW resides in its ability to print multimaterial objects, offering the possibility to combine complex shaping to precise microstructural and functional control, from bioinspired materials, to novel composite structures.Our work focuses on using boehmite gels for DIW, an Al2O3 precursor, as a ceramic matrix to obtain different microstructures. Very small changes to the gels composition lead to completely different microstructures and hence, functional properties. By combining the microstructural versatility of boehmite gels with an understanding of rheology, we are able to print micro and macrocomposites with enhanced mechanical properties. Printing dense and strong ceramic objects starts with understanding the rheological properties that define a printable ink. Boehmite suspensions were ideal to correlate geometrical criteria with rheology and surface tension effects to provide a universal figure of merit for printability. We take advantage of the flow behavior inside DIW nozzles to align alumina platelets during printing. This provides the printed object with increased fracture toughness in the desired direction, with the ability to deviate the fracture propagation perpendicularly to the printing direction. A single object can thus be precisely designed, alternating between dense, strong layers, and directionally tough, fracture deviating layers, to combine the complexity of the shape with the tailoring of mechanical behavior

La mise en forme par fusion laser sélective (LBM) de céramiques oxydes (Al2O3-ZrO2 et Al2O3) a pour objectif l’obtention directe de pièces aux formes complexes et aux microstructures fines et dirigées qui ne peuvent être réalisées par le procédé conventionnel de frittage. Ces pièces légères, possédant une excellente tenue au fluage en température et à l’oxydation, pourront alors répondre aux problématiques d’allègement et d’augmentation de la température de fonctionnement des turboréacteurs, comparativement aux pièces métalliques revêtues de céramiques poreuses. La combinaison matériau/procédé repose sur l’ajout contrôlé d’un absorbant aux poudres céramiques pures, permettant de pallier leur quasi-transparence au rayonnement laser Yb:YAG. A travers la mesure des propriétés optiques, l’étude menée vise à identifier l’impact des paramètres du procédé, de la nature et teneur de l’absorbant, de la compacité du lit de poudre sur la stabilité du bain de fusion. Pour ce faire, des mesures radiatives innovantes en réflexion et en transmission ont été réalisées en cours de fabrication. Ces mesures en dynamique via une sphère intégrante informent sur les mécanismes d’interaction laser-matière des différents milieux traversés, et permettent d’accéder aux propriétés optiques associées. Ces données alimentent un modèle analytique d’interaction laser-matière basé sur l’atténuation du rayonnement par la loi de Beer-Lambert. Ce dernier fait le lien entre les dimensions des bains (largeur, profondeur), les propriétés radiatives des différents milieux concernés (lit de poudre, substrat et bain liquide), les coefficients d’absorption associés, les paramètres du procédé, l’épaisseur et la porosité du lit de poudre. Il constitue un outil pour exprimer analytiquement la forme et la section apparente fondue au sein du lit de poudre, celles de la zone refondue au sein du substrat ainsi que celles de la zone de consolidation au sein du lit de poudre. Certaines de ces données calculées et difficilement mesurables sont utiles pour alimenter un modèle de consolidation du lit de poudre prenant en compte les échanges de matière observés entre une zone dite dénudée (liée à l’éjection de particules du lit de poudre), et une zone dite de consolidation. La quantification de ces flux de matière, impactant fortement la fabrication par LBM de ces céramiques oxydes, a permis le développement d’une stratégie de construction spécifique qui compense la zone dénudée et évite le phénomène de points chauds. L’ensemble de ces données permet alors la mise en forme de pièces avec une porosité réduite et une microfissuration contrôlée
Selective laser melting of oxide ceramics (Al2O3-ZrO2and Al2O3) is identified as a promising way to produce complex shaped parts with oriented fine microstructures, which would not be achievable by conventional sintering. These lightweight parts, presenting excellent resistance to creep at high temperature and oxidation, would appear as the answer to weight reduction and temperature increasing of turbojet engines, as compared to the usual metal parts coated with porous ceramics. The material/process coupling relies on the controlled addition of an absorber to pure ceramic powders, that compensate the quasi-transparency of these materials to Yb:YAG laser radiation. The effect on optical properties of process parameters, absorbent nature and content, compactness of the powder bed and their influence on manufacturing stability are identified. For this purpose, innovative radiative measurements in reflection and in transmission were carried out during manufacturing and for different operating conditions. These dynamic measurements through an integrating sphere provide information on the laser-material interaction mechanisms taking place in each media and they give access to optical material properties. These measurements enrich an analytical laser-matter interaction model based on the radiation attenuation by the Beer-Lambert law. This model gives a relation between melt pool dimensions, radiative propertiesof the different media (powder bed, substrate and liquid) along with the associated absorption coefficients, the process parameters and powder bed porosity. This model expresses also the apparent melted section within the powder bed, the section of the melted zone within the substrate and the consolidation section within the powder bed. Some of these calculated data are not measurable and usefully contribute to a consolidation model of the powder bed. This model takes into account the material exchanges observed between so-called bare zones (linked to the ejection of powder particles) and consolidation zones. Quantification of these particles exchanges, which have a strong impact on the LBM of these oxide ceramics, allows the definition of a specific manufacturing strategy that compensates for the bare zone formation while avoiding the formation of hot spots. These data collection enables the manufacturing of LBM ceramic oxide parts with reduced porosity and controlled micro-cracking

Les technologies de fabrication additive offrent actuellement l’opportunité d’atteindre des géométries complexes pour une offre de matériau relativement large, allant des polymères aux métaux, ainsi que pour certaines céramiques. L’offre commerciale de matériaux de structure est encore limitée par des verrous technologiques généralement associés à la compatibilité entre le procédé de mise en forme et le matériau visé. Dans cette thèse, une nouvelle voie, encore peu explorée dans la littérature, porte sur la fabrication additive de type Digital Light Processing (DLP) de la céramique de type carbure de silicium (SiC), à partir de polymères pré-céramiques. En effet l’utilisation d’une poudre de SiC dans une formulation photosensible, présente des limites en termes de taux de charge, liées à la compatibilité optique entre cette poudre et la longueur d’onde UV utilisée lors de la mise en forme couche par couche. L’utilisation de polymères se convertissant en céramique, avec des traitements thermiques adaptés, apporte la possibilité d’améliorer la compatibilité des constituants à la longueur d’onde de travail et permet l’obtention d’une céramique de type SiC. Trois polymères pré-céramiques commerciaux (deux polysiloxane et un polycarbosilane) ont été sélectionnés et des traitements thermiques de réticulation à 200 °C, suivis d’un traitement de pyrolyse compris entre 1000 et 1700 °C, sous argon, ont été réalisés pour étudier les évolutions microstructurales, les compositions chimiques, ainsi que les propriétés mécaniques. Il en ressort que ces matériaux polymères peuvent être convertis en céramique SiC polycristalline, avec une phase secondaire résiduelle riche en carbone. Des formulations photopolymérisables sous exposition UV, contenant un fort taux de charge en polymère pré-céramique (de 25 à 75 %pds), ont été développées et étudiées afin de pouvoir mettre en forme un objet cru par DLP, qui sera ensuite converti en céramique par traitement thermique. Avant la mise en forme par ce procédé, la réactivité de ces formulations a été caractérisée, en faisant varier les proportions des constituants, en particulier le système amorceur et l’incorporation d’un photoabsorbeur UV. La caractérisation de ces formulations a été principalement réalisée en mesurant l’épaisseur d’une monocouche polymérisée sous exposition UV, ainsi qu’en caractérisant la cinétique de photopolymérisation par spectroscopie infrarouge en temps réel. Pour finir, les objets fabriqués par DLP ont été convertis en céramique et leurs propriétés mécaniques et leur intégrité géométrique ont été caractérisées
Additive manufacturing technologies currently offer the opportunity to achieve complex geometries for a relatively wide material range, from polymers to metals, as well as for certain ceramics. The commercial offer of structural materials is still limited by technological obstacles generally associated with the compatibility between the forming process and the targetted material. In this thesis, a new way of study, still little explored in the literature, concerns the additive manufacturing by Digital Light Processing (DLP) of silicon carbide (SiC) ceramic, from preceramic polymers. In fact, the use of a SiC powder into a photosensitive formulation has limits in terms of charge rate, linked to the optical compatibility between this powder and the UV wavelength used during the layer-by-layer shaping. The use of polymers converting into ceramic, with suitable heat treatments, brings the possibility of improving the compatibility of the constituents at the working wavelength and allows the production of a ceramic of the SiC type. Two commercial preceramic polymers (a polysiloxane and a polycarbosilane) were selected and cross-linked at 200 ° C, followed by a pyrolysis treatment between 1000 and 1700 ° C, under argon. The microstructural changes, chemical compositions, as well as mechanical properties were studied. It appears that these polymer materials can be converted into polycrystalline SiC ceramic, with a residual carbon-rich secondary phase. Photopolymerizable formulations under UV exposure, containing a high load of preceramic polymer (from 25 to 75 wt.%), have been developed and studied in order to be able to shape a green object by DLP, which will then be converted into ceramic by heat treatment. Before additively manufacture parts, the reactivity of these formulations was characterized by varying the proportions of the constituents, including the initiator system and the incorporation of a UV photoabsorbent. The characterization of these formulations was mainly carried out by measuring the thickness of a monolayer polymerized under UV exposure, as well as by characterizing the photopolymerization kinetics by real time infrared spectroscopy. Finally, green parts were produced by DLP and were converted into ceramics and their mechanical properties and geometric integrity were characterized

碩士
國立臺灣大學
材料科學與工程學研究所
104
This research used previous formulation technique of ceramic/polymers, selecting two Al2O3 powders (α- and θ-Al2O3), kneading of several polymers with the ceramic powder, and extruding to produce various feedstocks of wire shape, which was used for 3D additive manufacturing, also known as 3D-printing (3DP). Four tasks were completed. First, the formulation of the feedstocks was conducted using PP as the major binder, replaced with some fractions of EVA, to improve the flexibility of the wires and reduce the chance of the fracture of the wire during 3D printing. The compatibility of PP and EVA was also investigated by grafting maleic acid (MA) on PP chain to reduce polarity difference between PP and EVA. The third task was to study the dispersion condition of the alumina powder in the feedstocks, and quantitatively investigated the influence by kneading sequences, solid content, and other processing parameters. After optimizing the processing conditions, the alumina parts could be densified to a density better than 97% theoretical density (T.D.). Finally, θ-Al2O3 feedstock was used to produce porous catalyst support. Ni-CeO2 nano-particles were evenly coated on the Al2O3 support, used to reform syngas. The CH4 in the syngas, which was gasified from biomass, was reformed to a content less than 1.0 vol% in optimized conditions.

碩士
國立臺北科技大學
製造科技研究所
106
Phononic crystals (PC) are composed of two or more elastic materials arranged periodically. One of the important characteristics of PC is band gap within that frequency range elastic waves are not allowed to transmit. With the band gap, applications of PC include filters for body waves or surface acoustic waves. In recent years, additive manufacturing technique are widely employed to fabricate objects with complicated geometries like PC. In this study, ceramic PC samples are fabricated with additive manufacturing technique. Finite element analysis (FEA) is employed to predict band gaps of PC fabricated with traditional subtracted marching and the newly additive manufacturing technique. Experimental measurements with pulsed ultrasound technique together with fast Fourier Transform (FFT) and tone-bust frequency scanning are employed to measure band gaps. In general, measurement results agree well with the FEA results. Results of the research suggest a new PC fabrication method based on additive manufacturing technique.

碩士
國立臺北科技大學
機電整合研究所
102
Although galvanometer scanner possesses the advantages of fast scanning, the additive manufacturing equipment with a stationary galvanometer scanner can not build the large components is due to the limited working area and less capability of fabricating different component simultaneously. Furthermore, high cost is one of the shortcomings of the galvanometer scanner. Therefore, the aim of this paper is that designing the automation control system for a ceramic slurry-base rapid prototyping apparatus with the X-Y scanning mechanism to make up the deficiency of the galvanometer scanner. A rapid prototyping apparatus is constituted with a laser scanning system and layer coating system. The laser scanning system is based on the X-Y planar scanning, which uses a PC-Based Control Card [MC8141P (M)] with function of 4-axis interpolation, and a 4- axis motion control card [(PMC2)], to control the laser scanning systems and layer coating systems. By setting the parameters through the human –machine- interface, the commands are transmitted to the corresponding devices of the scanning system and coating system via a control panel to carry out the required motion. The laser scanning system is consisted of a 30 W CO2 laser, an optical system, and a X-Y mechanism driven by linear motion screw with two servo motors. The coating system is consisted of a elevating platform moved with a wedge assembly which is driven by a stepper motor to, a slurry feeding device, a coater and a coater cleaning device. In addition, the control panel includes a power supply system and a control signal panel systems. The power supply system supplies the require power. It includes no fuse breakers, power converters, etc. The control signal system will transmit control signals to the servo motor and stepping motor drivers, and feedback the signals to the servo motor control card. Through the human-machine-interface programmed with Microsoft VisualC + +2010, the X-Y scanning mechanism was verified by 2D patterns scanning. Eventually, 3D components were fabricated to verify the function of automation. The experimental results reveal that the constant lowing distance of the elevating platform can be achieved with the wedge mechanism driven by the stepping motor. By calculating the required slurry volume, the coating systems can obtain layers with good quality. The X-Y scanning mechanism not only can scan a larger area but also can achieve the component with high precision. After integrating the laser scanning systems and coating systems, the 3D parts can be built automatically through setting the parameters with the human-machine-interface.

碩士
國立臺北科技大學
機電整合研究所
104
Ceramic additive manufacturing is one of rapid prototyping technologies that can quickly create ceramic components. Previous processes used CO2 laser; the beam energy distribution is the Gaussian distribution. The profile of linear depth of the scanning corresponds to the Gaussian distribution. Due to the energy is concentrated at the center of the laser beam, the scanning depth reveals that the depth at both sides is smaller than that at the center. The scanning layer should be built with adjacent scanning lines with appropriate overlap. Therefore, a high linear overlap is necessary. However, the linear overlap will affect the time-taken of building a scanning layer. The aim of this study is to improve the building rate of the component with decreasing the useless energy to reduce the linear overlap. Eventually, the specimens was fabricated to verify the improvement. Firstly, the mechanism of the existing apparatus and control hardware and software were modified to achieve automatic fabrication. Secondly, transforming laser beam energy distribution from Gaussian distribution to Top-Hat type distribution by using beam shaper to obtain a wider scanning width, the linear overlap then can be reduced. The appropriate parameters for specimens fabrication can be obtained with adjusting the relative laser parameter, such as laser power, scanning speed, scanning hatch. Finally, the building rate was evaluated by specimens fabrication. The results revealed that, building rate of beam shaper isnt better than without beam shaper, when building small workpiece. However, according to the reasoning of results, building rate will significant increase when building large workpiece or increase laser power by using beam shaper.

Indiana University-Purdue University Indianapolis (IUPUI)
Ceramics have been extensively used in aerospace, automotive, medical, and energy industries due to their unique combination of mechanical, thermal, and chemical properties. The objective of this thesis is to develop an extrusion based ceramic 3D printing process to digitally produce a casting mold. To achieve the objective, an in-house designed ceramic 3D printer was developed by converting a filament based plastic 3D printer. For mold making applications, zircon was selected because it is an ultra-high temperature ceramic with high toughness and good refractory properties. Additionally, alumina, bioglass, and zirconia slurries were formulated and used as the feedstock material for the ceramic 3D printer. The developed 3D printing system was used to demonstrate successful printing of special feature parts such as thin-walled high aspect ratio structures and biomimetically inspired complex structures. Also, proof of concept with regard to the application of 3D printing for producing zircon molds and casting of metal parts was also successfully demonstrated. To characterize the printed parts, microhardness test, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses were conducted. The zircon samples showed an increase in hardness value with an initial increase in heat treatment temperature followed by a drop due to the development of porosity in the microstructure, caused by the decomposition of the binder. The peak hardness value for zircon was observed to be 101±10 HV0.2. Similarly, the microhardness values of the other 3D printed ceramic specimens were observed to increase from 37±3 to 112±5 HV0.2 for alumina, 23±5 to 35±1 HV0.2 for bioglass, and 22±5 to 31±3 HV0.2 for zirconia, before and after the heat-treatment process, respectively. Finally, a system model for the ceramic 3D printing system was developed through the application of the model-based systems engineering (MBSE) approach using the MagicGrid framework. Through the system engineering effort, a logical level solution architecture was modeled, which captured the different system requirements, the system behaviors, and the system functionalities. Also, a traceability matrix for the system from a very abstract logical level to the definition of physical requirements for the subsystems was demonstrated.

碩士
國立臺北科技大學
製造科技研究所
104
Ceramic laser sintering (CLS) uses ceramic slurry to fabricate components. The green part is built in a green block after layer casting and selective laser sintering layer by layer. The inherent support is then removed by solution. Because diameter of laser beam is too small, laser scanning is time consuming when building a large component , so the building rate is poor. Study the feasibility of a new process with a modified device to fabricate the large-scale ceramic component is the aim of this research. Based on the process of 3DP, the binder which contains Polyvinyl alcohol (PVA) and phenolic resin, was selective sprayed on the green layer by a nozzle. A green block that contains green part was built after stacking the layers. Outside the sprayed area, the material played as the inherent supporting to support the component with overhang. A part of the existing rapid prototyping apparatus was modified to include the function of binder dispensing. The modified apparatus was employed to selectively spray binder layer by layer. After drying with heat, the green block was then be immersed in the solution. The workpiece was obtained when the supporting which surrounds the workpiece was collapsed. Experimental results revealed that the process is feasible. The workpiece can be completely built up and take out from the green block successfully. However, many details of the new process have to be improved and are worthy to be studied in the future.

Ceramics have been extensively used in aerospace, automotive, medical, and energy industries due to their unique combination of mechanical, thermal, and chemical properties. The objective of this thesis is to develop an extrusion based ceramic 3D printing process to digitally produce a casting mold. To achieve the objective, an in-house designed ceramic 3D printer was developed by converting a filament based plastic 3D printer. For mold making applications, zircon was selected because it is an ultra-high temperature ceramic with high toughness and good refractory properties. Additionally, alumina, bioglass, and zirconia slurries were formulated and used as the feedstock material for the ceramic 3D printer.

The developed 3D printing system was used to demonstrate successful printing of special feature parts such as thin-walled high aspect ratio structures and biomimetically inspired complex structures. Also, proof of concept with regard to the application of 3D printing for producing zircon molds and casting of metal parts was also successfully demonstrated.

To characterize the printed parts, microhardness test, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses were conducted. The zircon samples showed an increase in hardness value with an initial increase in heat treatment temperature followed by a drop due to the development of porosity in the microstructure, caused by the decomposition of the binder. The peak hardness value for zircon was observed to be 101±10 HV0.2. Similarly, the microhardness values of the other 3D printed ceramic specimens were observed to increase from 37±3 to 112±5 HV0.2 for alumina, 23±5 to 35±1 HV0.2 for bioglass, and 22±5 to 31±3 HV0.2 for zirconia, before and after the heat-treatment process, respectively.

Finally, a system model for the ceramic 3D printing system was developed through the application of the model-based systems engineering (MBSE) approach using the MagicGrid framework. Through the system engineering effort, a logical level solution architecture was modeled, which captured the different system requirements, the system behaviors, and the system functionalities. Also, a traceability matrix for the system from a very abstract logical level to the definition of physical requirements for the subsystems was demonstrated.

Dissertação de Mestrado Integrado em Engenharia Química apresentada à Faculdade de Ciências e Tecnologia
O interesse na impressão 3D tem crescido gradualmente de dia para dia, permitindo quer a otimização de muitos processos produtivos, quer a produção de peças com uma geometria cada vez mais complexa num menor espaço de tempo e, em alguns casos, com menores custos. Ao longo dos últimos anos, tem-se observado o desenvolvimento de novas técnicas de impressão 3D ou a otimização das técnicas já existentes. Assim, nesta dissertação pretende-se adaptar uma técnica já existente – robocasting – à produção de peças em alumina.Sendo a alumina um cerâmico técnico com boas propriedades (isolamento, funções químicas e resistência mecânica), neste estudo avalia-se a sua adequabilidade para o processo de impressão e as propriedades do material e das peças finais obtidas por este processo de conformação. Com base na bibliografia encontrada, optou-se por realizar um estudo com várias formulações agrupadas em dois sistemas (S e Z), associados aos diferentes aditivos usados, e com pós de duas granulometrias (0,4 μm e 4 μm). No sistema S elaboraram-se pastas de alumina com os aditivos: sacarose, álcool polivinílico e ácido oleico, enquanto que no sistema Z, as pastas foram preparadas com os aditivos: Zusoplast C92, Zusoplast 126/3, sacarose e ácido cítrico.Para estudar a adequabilidade das pastas elaboradas, avaliaram-se a humidade, a carga de sólidos, o comportamento reológico, a plasticidade, a adesão a superfícies, a dureza e a propensão para o envelhecimento. Por sua vez, para a caracterização dos materiais sinterizados obtidos, optou-se por avaliar a densificação (através da determinação das massas volúmicas e porosidades), a resistência mecânica e observação da sua estrutura interna por microscopia.Verificou-se que pastas adequadas para a impressão têm gamas muito restritas de propriedades, de forma a permitirem a impressão com boa adesão à plataforma e à manutenção da forma da peça durante a impressão. Além disso, verificou-se que a impressora não tem capacidade para imprimir pastas com viscosidades muito elevadas; pastas que apresentem uma viscosidade aparente de 6000 Pa.s a uma taxa de corte de 0,5 s-1 já oferecem muitas dificuldades para impressão às pressões utilizadas (até 7 bar).Ao nível das peças sinterizadas, observou-se que as características obtidas dependem essencialmente da capacidade de união entre os filamentos durante a impressão e da capacidade do pó cerâmico para densificar durante o tratamento térmico. A união dos filamentos é influenciada não só pelos aditivos usados, mas também pelos parâmetros da impressora, sendo que se deve garantir o esmagamento perfeito entre filamentos, nem insuficiente nem excessivo, de forma a evitar a existência de espaços vazios que dificultem a densificação ou a ocorrência de defeitos de forma, respetivamente. Por outro lado, verificou-se que a alumina mais fina permite alcançar densificações maiores e com maior crescimento de grão. Foi ainda possível observar que determinados aditivos podem promover a densificação, verificando-se que a utilização do Zusoplast C92 permite maior ligação entre partículas, originando peças mais densificadas. Os melhores resultados foram obtidos com duas das formulações, uma do sistema S e outra do sistema Z. A do sistema S – 9,9%(m/m) de sacarose, 0,4%(m/m) de álcool polivinílico e 2,0%(m/m) de ácido oleico – permitiu as melhores impressões, graças à sua menor viscosidade, sem que tal não comprometesse demasiado as propriedades finais das peças. A do sistema Z – 0,1%(m/m) de Zusoplast C92, 0,7%(m/m) de Zusoplast 126/3, 4,9%(m/m) de sacarose e 0,1%(m/m) de ácido cítrico, com a qual se alcançou as melhores densificações (Pt≈6%) e resistências (σfs≈150 MPa), tendo, no entanto, apresentado algumas dificuldades de impressão a baixas pressões.
The interest in the 3D printing has been growing every day, allowing not only the optimization of fabrication procedures but also the production of objects with a more complex geometry in less time and sometimes with less costs. In the last years, it was seen the development of new 3D printing technologies or the optimization of the ones that exist. In this way, the purpose of this dissertation is to adapt one of the existent technologies – robocasting – to the production of alumina objects.Being alumina a technical ceramic with good properties (isolation, chemical inertia and mechanical strength/hardness), this study aims to evaluate the printability of the ceramic body and the properties of the material and the final objects designed by this conformation process. According to the literature, different formulations were studied, grouped in two systems (S and Z), associating different additives, and alumina powders, with two different particle sizes (0,4 μm e 4 μm). For system S, the following additives were used: sucrose, polyvinyl alcohol and oleic acid, on the other hand, in system Z, the ceramic bodies were formulated with the additives: Zusoplast C92, Zusoplast 126/3, sucrose and citric acid. In order to analyse the suitability of the ceramic bodies, their humidity, solids content, rheological behaviour, plasticity, surface adhesion, rigidity and aging were evaluated. For the sintered objects characterization, the densification (through the density and porosity), the mechanical strength and internal structure (SEM) were assessed.It was verified that a good ceramic body for printing should fit a small range of properties, in order to allow a good surface adhesion and the shape maintenance during the printing process. Besides that, it was concluded that the 3D printer doesn’t work well with high viscosities; apparent viscosities above 6000 Pa.s at a shear strain of 0,5 s-1 induce printing difficulties at the allowed pressures (7 bar).The final characteristics of the sintered objects depended essentially on the filaments bonding during the printing process and on the capacity of the ceramic powder to densify during the sintering. The filaments bonding is not just influenced by the used additives but also by the 3D printer parameters, that must ensure the perfect crush between filaments, neither insufficient nor excessive, in order to avoid empty spaces that interfere in the densification or the occurrence of shape imperfections in the objects, respectively. On the other hand, it was verified that the alumina with smaller particle size allows higher densifications and grain growth. It was still possible to observe that some additives could enhance the densification, for example the utilization of Zusoplast C92 allows better bonding between the particles, producing more dense objects.The best results were obtained with two formulations, one of the system S and the other of the system Z. For the system S, the formulation with 9,9%wt of sucrose, 0,4%wt of polyvinyl alcohol and 2,0%wt of oleic acid provide the best printing, for its lower viscosity, without compromising too much the properties of the final objects. The one of the system Z, with 0,1%wt of Zusoplast C92, 0,7%wt of Zusoplast 126/3, 4,9%wt of sucrose and 0,1%wt of citric acid, achieved the best densification (Pt≈6%) and mechanical strength (σfs≈150 MPa), leading however to some difficulties during the printing at a low pressure (7 bar).

abstract: This dissertation aims at developing novel materials and processing routes using alkali activated aluminosilicate binders for porous (lightweight) geopolymer matrices and 3D-printing concrete applications. The major research objectives are executed in different stages. Stage 1 includes developing synthesis routes, microstructural characterization, and performance characterization of a family of economical, multifunctional porous ceramics developed through geopolymerization of an abundant volcanic tuff (aluminosilicate mineral) as the primary source material. Metakaolin, silica fume, alumina powder, and pure silicon powder are also used as additional ingredients when necessary and activated by potassium-based alkaline agents. In Stage 2, a processing route was developed to synthesize lightweight geopolymer matrices from fly ash through carbonate-based activation. Sodium carbonate (Na2CO3) was used in this study to produce controlled pores through the release of CO2 during the low-temperature decomposition of Na2CO3. Stage 3 focuses on 3D printing of binders using geopolymeric binders along with several OPC-based 3D printable binders. In Stage 4, synthesis and characterization of 3D-printable foamed fly ash-based geopolymer matrices for thermal insulation is the focus. A surfactant-based foaming process, multi-step mixing that ensures foam jamming transition and thus a dry foam, and microstructural packing to ensure adequate skeletal density are implemented to develop foamed suspensions amenable to 3D-printing. The last stage of this research develops 3D-printable alkali-activated ground granulated blast furnace slag mixture. Slag is used as the source of aluminosilicate and shows excellent mechanical properties when activated by highly alkaline activator (NaOH + sodium silicate solution). However, alkali activated slag sets and hardens rapidly which is undesirable for 3D printing. Thus, a novel mixing procedure is developed to significantly extend the setting time of slag activated with an alkaline activator to suit 3D printing applications without the use of any retarding admixtures. This dissertation, thus advances the field of sustainable and 3D-printable matrices and opens up a new avenue for faster and economical construction using specialized materials.
Dissertation/Thesis
Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2019

Dissertação de Mestrado Integrado em Engenharia Química apresentada à Faculdade de Ciências e Tecnologia
The present work is framed in the field of additive manufacturing, also known as 3D printing. The Robocasting technology, employed in this work, is one of the categories of additive manufacturing. It allows the processing of several types of materials, giving rise to a wide variety of items with complex geometries.The aim of this dissertation is to develop pastes of Al2O3 to apply in a Robocasting printer, the Wasp Extruder, in order to enable the printing of ceramic pieces at room temperature. The formulations are based on the cold mixture of a solvent, additives and the inorganic powder, being the final purpose the building of ceramic items with good properties, comparable to other objects produced by different AM technologies.Two different types of alumina pastes were selected to be studied. In the pastes of the 1st type, two different types of aluminium oxide with distinct particle size (D50 ≈ 4 µm and 0,7 µm) were tested. Either Zuzoplast C92 or arabic gum were used as a binder and the influence of a lubricant, glycerin, on the pastes was also tested. Water was always used as the solvent.For the 2nd type of pastes, only one type of aluminium oxide was used and water was kept as solvent. The major difference between this type of paste and the previous one is that, in this case, two binders, PVA and powdered sugar, were used in the same formulation. Moreover, an additional additive was used, oleic acid, with high affinity to alumina.The analysis of the rheological behaviour of the alumina pastes was carried out in a capillary rheometer (Thermo Haake Rheoflixer HT). A predominance of the pseudoplastic behaviour (where the viscosity decreases as the shear rate increases) was observed in the two types of formulations analysed. The viscosity increases as the particle size of the inorganic powder decreases. Several properties of sintered samples obtained from these two types of pastes were evaluated, with regard to their density, porosity and mechanical bending strength. Concerning the densification of the fabricated items, it is observed that the finest particles lead to a higher degree of packing, resulting in denser and less porous pieces. The values of the bending strength still are far from those that can be expected for the two types of pastes here studied.After characterizing the best pastes, these were tested in the Robocasting printer. Based on the results, it was observed that the best formulation for printing belongs to the 2nd type of paste. Notably, in spite of presenting good properties for application in the 3D printer, it gives rise to pieces with worse mechanical properties than the pastes of the 1st type.One of the aims of this work was achieved, the printing of Al2O3 pastes in the Robocasting printer. However, the pieces that were built do not exhibit yet the desired properties, namely in terms of densification level and strength. Therefore, further work will be needed for the optimization of conditions and tuning of formulations to achieve improved properties of the sintered items.
O presente trabalho insere-se na temática da fabricação aditiva ou também denominada de impressão 3D. A tecnologia robocasting está contida numa das categorias de fabricação aditiva e apresenta-se capaz de processar diferentes tipos de materiais e de originar uma ampla variedade de peças com geometrias complexas. Esta é a tecnologia usada no presente trabalho.O objetivo desta dissertação passa por desenvolver pastas em Al2O3 para aplicação numa impressora robocasting, a WASP Extruder, de maneira a que seja possível imprimir peças cerâmicas à temperatura ambiente. Estas formulações baseiam-se na mistura a frio de um solvente, aditivos e de um pó inorgânico, e deseja-se construir peças com boas propriedades, podendo ser comparadas com outros objetos originados por diferentes tecnologias AM.De acordo com o estudo prévio realizado optou-se por estudar dois tipos de pastas de alumina.Nas pastas do 1º tipo foram experimentados dois tipos de óxidos de alumínio com granulometrias distintas (D50 ≈ 4 µm e 0,7 µm). Como ligantes usou-se o Zuzoplast C92 ou a goma arábica, testando ainda a influência de um lubrificante nas pastas, a glicerina. Como solvente usou-se a água.Para o segundo tipo de pastas formuladas aplica-se apenas um tipo de óxido de alumínio, mantendo-se a água enquanto solvente. A grande distinção ente este tipo de pastas e o anterior é que, neste caso, são usados dois ligantes na mesma formulação, o PVA e o açúcar em pó, bem como um aditivo adicional, o ácido oleico, caracterizado pela sua grande afinidade com o pó inorgânico, alumina.Um dos principais pontos estudados nas formulações prende-se com a análise do comportamento reológico, tendo-se usado um reómetro capilar (Thermo Haake Rheoflixer HT). Verificou-se que o comportamento pseudoplástico (onde a viscosidade diminui com o aumento da taxa de corte) predomina entre os dois tipos de formulações analisadas. A viscosidade é tanto maior quanto menor a granulometria do pó inorgânico.Avaliaram-se ainda várias propriedades de provetes sinterizados obtidos com estes dois tipos de pastas, ao nível das massas volúmicas, porosidades e resistência mecânica à flexão. Relativamente à densificação das peças, verifica-se que as partículas mais finas conduzem a um maior grau de empacotamento, resultando peças mais densas e menos porosas. Os valores relativos às resistências à flexão alcançados ficam ainda muito aquém do espectável para ambos os tipos de pastas analisadas.Depois de caracterizadas as melhores pastas, testam-se na impressora robocasting. Com base nos resultados, verifica-se que a melhor formulação para impressão resulta do 2º tipo de pastas estudadas (Al1_PVA_A12). É de notar que apesar de apresentar boas propriedades para aplicação na impressora 3D, gera peças com piores propriedades mecânicas que as pastas do 1º tipo.Um dos objetivos do trabalho foi atingido, a impressão de Al2O3 em robocasting. No entanto, as peças construídas não possuem as propriedades desejadas, quer ao nível de densificação, quer ao nível da resistência, havendo ainda um longo caminho a percorrer.

Additive Manufacturing (AM) is an area intrinsically linked to industry 4.0 because of its ability to meet some of the most significant challenges in the industry such as production of custom parts, complex geometries and direct processing (through cloud manufacturing). Due to its advantages, the market for functional parts based on inorganic materials via AM is in great development. The present study has focused on the Fused Deposition of Ceramics (FDC) process, which is suitable, in combination with post-processing steps such as debinding and sintering, for the consolidation of ceramic powder particles from filamentary materials. Although the volume content of ceramic powders is very limited, due to the absence of high pressures, the FDC has been of scientific and industrial interest due to its ability to eliminate some limitations imposed by other processes such as Selective Laser Melting (SLM), due to the sources of high energy consumption, and Powder Injection Molding (PIM), due geometric and mold cost limitations. The major challenges of this dissertation involved producing filaments for FDC, based on PIM or powder extrusion (PE) methodologies, joining the filaments of feedstock with optimized ratios of tungsten carbide powder (48.5%vol.) that should withstand the stresses involved in the FDC extrusion, and providing suitable extrusion fluidity. Afterwards, the challenges were overcome and the shaped parts through FDC were debinded and sintered. These processes led to the production of near net shape WC-10Co parts with characteristics and properties close to those resulting from conventional replicative processes of the powders.

Dissertação de mestrado integrado em Arquitectura (área de especialização em Construção e Tecnologia)
Nos dias de hoje não vemos apenas o processo de desenho em arquitetura mediado por ferramentas digitais, assistimos cada vez mais à experimentação e disseminação deste tipo de recursos em todos os estágios da construção, desde a concepção até à manufatura. Neste contexto, a associação de material cerâmico a fabrico aditivo representa, para a arquitetura, uma ampliação daquilo que é possível explorar através deste método e assim, devido às características do material, cria-se a possibilidade de explorar novas ideias e conceitos. O uso combinado de desenho computacional e fabrico digital em arquitetura apresenta um enorme potencial para melhorar e introduzir inovações ao desenho arquitetónico e ao ambiente construído. A associação destas ferramentas, permite não só explorar a produção em série de elementos singulares e personalizáveis, expandindo as potencialidades das técnicas tradicionais, mas também analisar determinados pressupostos, e com base neles, identificar a solução que melhor consegue atender a uma situação específica. A presente investigação procura avaliar a integração destas ferramentas digitais em arquitetura, incidindo especificamente sobre questões relacionadas com a produção de elementos estruturais personalizados, que se definem através de relações paramétricas de inspiração biomórfica, com recurso a fabrico aditivo cerâmico. Neste sentido, o caso de estudo procura desenvolver um sistema de componentes estruturais — um sistema de colunas — reticulados, personalizados e otimizados, com base em pressupostos definidos previamente. O processo de definição deste sistema é mediado por desenho computacional, implementando não só estratégias de análise e otimização estrutural, mas também características formais miméticas da natureza, criando um modelo que adapta os seus atributos formais, consoante os seus pressupostos e as restrições do material, resultando na definição de um conjunto de soluções que respondem ao problema de projeto proposto.
Nowadays, we not only see the design process in architecture mediated by digital tools, we also are increasingly witnessing the experimentation and dissemination of this type of resources at every stage of construction, from design to manufacturing. In this context, the association of ceramic material to additive manufacturing represents, for architecture, an extension of what can be exploited through this method, and thus, due to the characteristics of the material, it is possible to explore new ideas and concepts. The combined use of computational design and digital manufacturing in architecture presents an enormous potential to improve and introduce innovations in architectural design and the built environment. The association of these tools allows not only to explore the concept of standardized production of unique and customizable elements, expanding the potential of traditional techniques, but also allows an analysis of certain assumptions and, based on them, identify the solution that can best meet a specific situation. The present research aims to evaluate the integration of these digital tools in architecture, focusing specifically on issues related to the production of customized structural elements, which are defined through parametric relationships of biomorphic inspiration, using additive ceramic manufacturing. In this sense, the case study seeks to develop a system of reticulated, customized and optimized structural components, — a column system — based on previously defined assumptions. The process of defining this system is mediated by computational design, implementing not only structural and optimization analysis strategies, but also mimetic formal features of nature, creating a model that adapts its formal attributes, depending on its assumptions and the material constraints, resulting in the definition of a set of solutions that respond to the proposed design problem.

Dissertação de mestrado integrado em Arquitectura (área de especialização em Construção e Tecnologia)
O surgimento e disseminação de tecnologias de fabrico aditivo, nomeadamente de impressão tridimensional, contribui para uma mudança de paradigma no processo de conceção e construção do projeto ao permitir que estas duas fases tradicionalmente autónomas se aproximem. Recentemente, tal como muitos outros materiais, a aplicação de cerâmica em tecnologias de fabrico digital expandiu consideravelmente os limites formais, performativos e funcionais que os elementos cerâmicos podem aportar para o contexto da construção e arquitetura. À implementação de processos de fabrico aditivo para a conceção de componentes arquitetónicos, associa-se ainda a possibilidade de produção em série de sistema personalizáveis. Graças a esta tecnologia, e com a integração de processos de desenho paramétrico, na conceção do projeto são criados sistemas que formulam várias soluções, selecionando aquela que melhor responde às necessidades do problema. Deste modo o desenvolvimento de componentes arquitetónicos cerâmicos poderá beneficiar destes dois fatores tendo em vista dar respostas a contextos específicos e objetivos multidisciplinares. Focando-se no desenho e produção de componentes arquitetónicos cerâmicos totalmente personalizados, esta investigação estuda os principais desafios que a integração de ferramentas de desenho e fabrico digital têm na prática da arquitetura. Com base em blocos hexagonais o principal caso de estudo da investigação consiste no desenvolvimento de um sistema de cobertura em abóbada que pretende auxiliar ao controlo da incidência solar. Esta otimização dá-se através da variação geométrica da estrutura interna dos blocos. O processo de projeto é mediado por um modelo paramétrico, considerando os dados climatéricos do local, resultando num sistema que adapta a geometria interna de cada um dos blocos em função da sua posição no conjunto, tornando-os mais ou menos permeáveis dependendo da relação espaço/tempo que se pretende sombrear.
The emergence and dissemination of additive manufacturing technologies, namely three-dimensional printing, contributes to a paradigm shift in the process of project design and construction by allowing these two traditionally autonomous phases to approach. Recently, like many other materials, the application of ceramics to digital manufacturing technologies has considerably expanded the formal, performative, and functional limits that ceramic elements can bring to the context of construction and architecture. The implementation of additive manufacturing processes for the design of architectural components also associates the possibility of serial production of customizable systems. Thanks to this technology, and with the integration of parametric design processes, in the design of the project are created systems that formulate various solutions, helping to select the one that best meets the needs of the problem. In this way the development of ceramic architectural components can benefit from these two factors in order to respond to specific contexts and multidisciplinary objectives. Focusing on the design and production of fully customized ceramic architectural components, this research studies the main challenges that the integration of digital design and manufacturing tools have in architectural practice. Based on hexagonal blocks, the main research case is the development of a dome cover system that aims to help control the solar incidence. This optimization takes place through the geometric variation of the internal structure of the blocks. The design process is mediated by a parametric model, taking into account the climacteric data of the site, resulting in a system that adapts the internal geometry of each one of the blocks by their position in the set, making them more or less permeable depending of the space / time ratio that we want to shade.

Additive manufacturing (AM) represents a set of manufacturing processes that create complex 3D parts out of polymers, metals, and ceramics. AM of metals and ceramics is widely used to produce parts for aerospace, automotive, and medical applications. At the micro- and nano-scales, AM is poised to become the enabling technology for efficient 3D microelectromechanical systems (MEMS), 3D micro-battery electrodes, 3D electrically small antennae, micro-optical components, and photonics. Today, the minimum feature size for most commercially available metal and ceramic AM is limited to ~20-50 μm. Currently, no established processes can reliably produce complex 3D metal and ceramic parts with sub-micron features.

In this thesis, we first demonstrate a nanoscale metal AM process that can produce ~300 nm features out of nanocrystalline, nanoporous nickel using synthesized hybrid organic-inorganic materials, two-photon lithography, and pyrolysis. We study microstructure and mechanical properties of as-fabricated nickel architectures and compare their structural strength to established AM processes. We then show how this process can be extended to other metals and metalloids, including Mg, Ge, Si, and Ti.

This study extends further into nanoscale AM of transparent, high refractive index materials for micro-optics and photonic crystals. We develop an AM process to 3D print fully dense nanocrystalline rutile titanium dioxide (TiO₂) with feature dimensions down to ~120 nm. We carefully study and model the relationship between feature dimensions and process parameters to achieve a <2% variation in critical dimensions. We then use this understanding of the process to fabricate and study 3D dielectric photonic crystals with a full photonic bandgap in the infrared.

Finally, a microscale AM process of titanium dioxide is demonstrated for photocatalytic water treatment. We show how synthesized hybrid organic-inorganic materials can be applied for stereolithography to print TiO₂ architectures with 100 μm features. We use the developed 3D printing process to investigate the effect of 3D architecture on the efficiency of photocatalytic water treatment.

This work establishes a versatile and efficient pathway to create three-dimensional nano-architected metals and ceramics and to investigate their properties for applications in 3D MEMS, micro-optics, photonics, and photocatalysis.

碩士
國立臺北科技大學
製造科技研究所
104
Ceramics have many excellent mechanical properties. But the ceramics are hard and brittle, which result in difficulty of forming and fabricating workpiece with complex shape. Ceramic additive manufacturing improves the drawbacks of the existing ceramic manufacturing processes. It can fabricate the complex ceramic components. The existing slurry-based additive manufacturing of ceramic can cast thinner layer than the layer casted with the powder-based processes to improve the step effect. Original slurry coater had the problem of un-uniform slurry distribution. Un-uniform distribution of water containing of the layer lead to the un-uniform time-taken of the layer drying was one of the disadvantages. The aim of this study is to achieve a proper coater to improve the aforementioned disadvantage through studying the relations of viscosity, slot width, distribution angle of the flow channel of the slot coater. Firstly, mold flow simulation was carried out by Flow-3D. The slurry behavior in the slot coater was simulated with related parameters to find the desirable distribution angle of the flow channel. Eventually, based on the experimental results, the physical coaters were fabricated to conduct slurry distribution and casting experiment, to verify simulation results. Experiment data was analyzed by ANOVA to explain the effect of experimental factor. The results revealed that, the simulation results is reliable. The quantitative slurry could be uniformly delivered to the outlet of the coater to achieve a perfect layer by a proper distribution angle obtained by the simulation. The same method can be employed to rapidly construct the coater for different ceramic slurry.