1,721,055 research outputs found
Additive Manufacturing of Ceramics. Printing Beyond the Binder
Full text linkThis research project focuses on the production of ceramics via Additive Manufacturing (AM) techniques, with particular focus on extrusion-based technologies. The main advantage of AM is the ability to produce cellular structures with high complexity and controlled porosity, allowing to manufacture light but efficient stretch-dominated structures. The inspiration comes from nature: bone architectures are a great example, consisting of thin, solid skins attached to highly porous, cellular cores.
Very few commercially available AM systems are suited for ceramic materials, and most of them use ceramic powders as feedstock. Residual pores and cracks are very hard to avoid and result in low strength, poor reliability and loss of unique material properties such as glass optical transparency. AM technologies employing polymers are at a much more advanced stage of development. The goal has been to exploit such advances and to provide alternatives to the ceramic powder-binder approaches. Three different material families were explored: preceramic polymers, geopolymers, and glass.
The same preceramic polymer, a commercial polysilsesquioxane, was employed as a non sacrificial, reactive binder to develop inks for stereolithography (SL) and direct ink writing (DIW).
The first technology allowed for production of dense, crack-free SiOC micro-components with strut size down to ~200 μm and optimal surface quality. No shape limitations were experienced, but porous structures or small dense parts are the best options in order to avoid residual pores and cracks. The second approach was employed for the fabrication of complex biosilicate scaffolds for tissue engineering with a rod diameter of 350 µm and unsupported struts. The preceramic polymer had the double role of source of silica and rheology modifier. Ceramic matrix composites (CMCs) were also fabricated; the preceramic polymer developed the ceramic matrix (SiOC) upon pyrolysis in inert atmosphere, whereas reinforcement was given by chopped carbon fibers.
Geopolymer components with controlled porosity were designed and produced first by negative replica of PLA sacrificial templates and then by DIW. Highly porous ceramic components with features of ~800 μm and unsupported parts with very limited sagging were produced with the latter approach.
A novel extrusion-based AM approach was finally developed for the production of objects starting from molten glass. The system processed glass from the molten state to annealed components of complex, digitally designed forms. Objects possessing draft angles and tight radii were fabricated. Within the design space it was possible to print with high precision and accuracy; parts showed a strong adhesion between layers, and high transparency through the layers
Porous geopolymer components through inverse replica of 3D printed sacrificial templates
No full textAdditive Manufacturing of CO2 sorbents for high-temperature Carbon Capture
Full text linkopenLaureando: Tessarolo Marco
Titolo tesi: Additive Manufacturing of CO2 sorbents for high-temperature Carbon Capture
Corso di Laurea: Ingegneria dei Materiali
Relatrice: Franchin Giorgia
Thermally activated hydrotalcites display great potential for Carbon Capture processes due to their ability to readily adsorb CO2 at temperatures as high as 300°C. Geopolymers are inorganic binders which couple a facile and low-cost synthesis route with excellent mechanical strength and porosity, making them promising matrix candidates for the immobilisation of active fillers. Various formulations of geopolymer-hydrotalcite composite monoliths with a well-defined macroporous structure were 3D printed through the Direct Ink Writing (DIW) technique, then characterized through compression testing, microscopy, FT-IR spectroscopy, XRD and CO2 adsorption tests. The difficult printing of potassium-based geopolymers required the use of carboxymethylcellulose as a rheological additive, whose removal with an appropriate thermal treatment was investigated to avoid performance loss in application. The composites, after thermal activation at 400°C, show high CO2 uptake which increases together with hydrotalcite content, with a better contribution of the K-based geopolymer matrices compared to their Na-based counterparts.Laureando: Tessarolo Marco
Titolo tesi: Additive Manufacturing of CO2 sorbents for high-temperature Carbon Capture
Corso di Laurea: Ingegneria dei Materiali
Relatrice: Franchin Giorgia
Thermally activated hydrotalcites display great potential for Carbon Capture processes due to their ability to readily adsorb CO2 at temperatures as high as 300°C. Geopolymers are inorganic binders which couple a facile and low-cost synthesis route with excellent mechanical strength and porosity, making them promising matrix candidates for the immobilisation of active fillers. Various formulations of geopolymer-hydrotalcite composite monoliths with a well-defined macroporous structure were 3D printed through the Direct Ink Writing (DIW) technique, then characterized through compression testing, microscopy, FT-IR spectroscopy, XRD and CO2 adsorption tests. The difficult printing of potassium-based geopolymers required the use of carboxymethylcellulose as a rheological additive, whose removal with an appropriate thermal treatment was investigated to avoid performance loss in application. The composites, after thermal activation at 400°C, show high CO2 uptake which increases together with hydrotalcite content, with a better contribution of the K-based geopolymer matrices compared to their Na-based counterparts
Volumetric Additive Manufacturing of SiOC by Xolography
Full text link: Additive manufacturing (AM) of ceramics has significantly contributed to advancements in ceramic fabrication, solving some of the difficulties of conventional ceramic processing and providing additional possibilities for the structure and function of components. However, defects induced by the layer-by-layer approach on which traditional AM techniques are based still constitute a challenge to address. This study presents the volumetric AM of a SiOC ceramic from a preceramic polymer using xolography, a linear volumetric AM process that allows to avoid the staircase effect typical of other vat photopolymerization techniques. Besides optimizing the trade-off between preceramic polymer content and transmittance, a pore generator is introduced to create transient channels for gas release before decomposition of the organic constituents and moieties, resulting in crack-free solid ceramic structures even at low ceramic yield. Formulation optimization alleviated sinking of printed parts during printing and prevented shape distortion. Complex solid and porous ceramic structures with a smooth surface and sharp features are fabricated under the optimized parameters. This work provides a new method for the AM of ceramics at μm/mm scale with high surface quality and large geometry variety in an efficient way, opening the possibility for applications in fields such as micromechanical systems and microelectronic components
Improving glass nanostructure fabrication
No full textA new method offers high-resolution three-dimensional printing and low-temperature firing
Additive Manufacturing
No full textAdditive manufacturing is a technology which has the potential not only to change the way of conventional industrial manufacturing processes, adding material instead of subtracting, but also to create entirely new production and business strategies. Ceramic materials are, however, not easy to process by additive manufacturing technologies, as their processing requirements (in terms of feedstock and/or sintering) are very challenging. This article will provide an overview of the different strategies developed so far for additive manufacturing of ceramics, with a special focus on the capability of the respective technologies to produce dense monolithic ceramic parts
Complex SiOC ceramics from 2D structures by 3D printing and origami
No full textManufacturing of ceramic components with a geometrically complex 3D architecture and highly detailed features for use in a variety of practical applications is still a challenge. In our investigation, we adopted a synergistic strategy for fabricating SiOC ceramics with intricate 3D morphologies by additive manufacturing and origami technique or assemblage, taking advantage of the high printability and flexibility of a commercially available silicone elastomer. Secondary shaping using origami of different 2D layers with varied design allowed the manufacturing of spiral, flower-like and polyhedron architectures, which are difficult to fabricate without adding supports or by any conventional ceramic fabrication processes. Produced samples showed no cracks or pores and fully retained the given shape after pyrolysis
3D printing of polymer-derived SiOC with hierarchical and tunable porosity
Full text linkA facile and controllable method for the fabrication of SiOC ceramic components with hierarchical porosity is reported in this work, using additive manufacturing, sacrificial polymeric microbeads and a silicone resin. Particles-containing inks with suitable rheology enabled the fabrication by Direct Ink Writing of scaffolds with mm-scale macropores between filaments, and μm-scale and/or nm pores within the filaments. Isotropic shrinkage and an appropriate pyrolysis program enabled to obtain scaffolds without defects and shape distortions. Total porosity and compression strength depended on the content and size of the PMMA particles in the inks, enabling the fabrication of SiOC ceramic with components possessing a remarkable strength up to 2.92 MPa for a total porosity of 86.5 vol% by the addition of 5 μm PMMA particles
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