Additive manufacturing by stereolithography of tough ceramics for medical application : From the development of specific pastes to suitable compositions and architectures

Le résumé fourni par la source

Additive manufacturing techniques based on the selective photopolymerization of successive layers enable the production of complex ceramic parts with a resolution of a few tens of micrometers. The stereolithography process involves the scraping of a paste that is highly charged with ceramic particles, involving high shear stresses. Following, laser photopolymerization selectively hardens the part before the next layer is applied. At the end of the process, heat treatments are applied to remove the polymer and consolidate the ceramic object. This thesis focuses on the study of the process with a view to its use in the manufacturing of specific implants, tailored to each clinical case Our approach comprehends the fine characterization of the 'ceramic powder-polymer' systems in order to reduce spreading and polymerization defects that can compromise the mechanical properties of ceramic implants. A rheological study involving continuous, oscillatory and multiaxial shear tests allowed us to rationalise the behaviour of the pastes and understand the influence of each compound of the formulation. The flow of the material at high shear rates is disturbed by the roughness of the particles. The adequate dispersion of the particles prevents the paste from shear-thickening. Adding vibration during scraping also helps to reduce viscosity. Measurements of the degree of polymerization by infrared spectroscopy have shown a certain inhomogeneity due to the layer-by-layer manufacturing, which requires controlled thermal debinding to limit crack formation. In a second time, composite powders based on ceria-doped zirconia, which exhibit a certain ductility by phase transformation, are used to limit the impact of manufacturing defects. The printed composites have a more heterogeneous microstructure than those produced by pressing, which tends to increase their transformability, ultimately improving resistance to printing defects.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.