​Additive Manufacturing (AM) is an emerging part production technology that offers many advantages such as high degree of customization, material savings and design of 3D highly complex structures. However, AM is a complex multiphysics process. Therefore, only a limited number of materials can already be commercially used to produce parts and a handful of others are being studied or developed for such process. Consequently, limited knowledge on this process is available, especially concerning materials that present thermomechanical challenges such as brittle materials.
The research I did during my PhD studies focuses on additive fabrication of silicon pillars on a monocrystalline silicon wafer by Direct Laser Melting (DLM) with a pulsed 1064 nm laser beam. The simple geometry of pillars allowed for the first determining steps into process understanding. Several results were achieved through this PhD work. First, crack-free silicon pillars were successfully built onto monocrystalline silicon wafers. With the help of in-situ process monitoring and sample characterization, wafer substrate temperature and laser repetition rate were found to be the main influential parameters to obtain crack-free samples, as minimum substrate temperature of 730°C and a minimum repetition rate of 100 Hz were necessary to reach this goal (for a feed rate of 15 g/min and a pulse duration of 1 ms). The influence of secondary process parameters such as feed rate and energy per pulse were also discussed. A simple Finite Element Modeling (FEM) model validated by the experiments was used to explain crack propagation in the samples. Then, process monitoring of the DLM process was realized. High-speed camera image analysis re-vealed that vertical stage speed and powder feed rate should match to obtain a constant pillar building rate. As all pillars presented necking at their base, estimations of the thermal characteristics of the pillar during growth were carried out by FEM simulations. They were additionally used to explain the pillar final shape. Finally, the microstructure of the pillars built was characterized by the Electron Back-Scattering Dif-fraction (EBSD) technique. In the conditions presented in this work, the microstructure of the pillar was found to be in the columnar growth mode. The feed rate was identified as the most influential parameter on the microstructure, followed by the stage speed, the impurity content of the powder and the crystallographic orientation of the substrate. Epitaxial growth was achieved on more than 1 mm with a feed rate of 1.0 g/min, a stage speed of 0.1 mm/s, a powder with purity of 4N and a <111> oriented wafer substrate. This work could be further continued by making improvements to the DLM setup, studying the influence of additional process parameters on the thermomechanical behavior and the microstructure control of the pillars, and/or using these results to realize more complicated shapes, either with this setup or by using a powder bed technique.
About
I was born in France and I have grown up in a little town called Beynes, in the department Yvelines, no so far from Paris and Versailles. I am the first of four kids! As a child, I wanted to be a journalist. I have always been interested in digging up into a subject in order to transforming into articles that could be read by others. I had a few friends writing a bunch of articles alongside so we could turn everything into magazines. I spent a lot of time playing with a - now old - layout software in order to make this publication look like my favorite magazines at that time – L’Hebdo, le monde des ados. I even managed to get an internship for a week there!
About
I was born in France and I have grown up in a little town called Beynes, in the department Yvelines, no so far from Paris and Versailles. I am the first of four kids! As a child, I wanted to be a journalist. I have always been interested in digging up into a subject in order to transforming into articles that could be read by others. I had a few friends writing a bunch of articles alongside so we could turn everything into magazines. I spent a lot of time playing with a - now old - layout software in order to make this publication look like my favorite magazines at that time – L’Hebdo, le monde des ados. I even managed to get an internship for a week there!
Crédit photo: Design Days
Bonjour ! Je m'appelle Marie Le Dantec, et je suis la designer et illustratrice multidisciplinaire derrière MLD 😊 Je suis française, basée en Suisse depuis 7 ans. J'ai commencé ma carrière par douze ans d’études en physique et en science des matériaux, puis je choisis ensuite de me former en communication visuelle. En effet, je me rends compte en prenant mes premiers cours que le dessin m’aide à canaliser mes émotions. Et puis, je constate aussi que la recherche scientifique est encore très mal communiquée, et qu’il y a peut-être quelque chose à améliorer là-dedans ! Enfin, des tonnes de choses me fascinent dans la nature et dans les émotions humaines, et j’ai envie de pouvoir partager cela à quelqu’un d’autre que le fond de mon tiroir !
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J’adore les projets multidisciplinaires impliquant l'illustration et j'ai eu la chance de travailler à la croisée de différentes disciplines comme le design, les sciences naturelles et les sciences sociales. Je suis très curieuse, je veux toujours tout comprendre et j’ai besoin de positivité au quotidien pour rester motivée !
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À travers mes illustrations, j'aimerais créer des espaces de réflexion et d'émerveillement sur des sujets variés afin de promouvoir la curiosité et le partage. Mon style se veut sensible et poétique, avec une pointe d’humour occasionnelle, et un accent particulier sur la nature et les émotions. Je peins principalement à l'aquarelle et à l'encre, mais j'aime explorer d'autres techniques comme la craie grasse, le fusain et le dessin numérique sur ma tablette ! Les projets qui promeuvent l'écologie, la nature, les sujets sociaux, l'inclusivité, la curiosité, l'art et l'éducation sont parmi mes préférés !
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N'hésitez pas à me contacter ! Je suis plus toujours heureuse de lire vos messages !