Octobre, 2021

01oct14 h 00 min17 h 00 minSoutenance de thèse Pedro Jesus Navarrete Segado



Soutenance en anglais de Pedro Navarrete Segado ( CIRIMAT / LGC )
Titre : Optimisation de poudres de phosphate de calcium à propriétés contrôlées pour la fabrication additive

Résumé : Calcium phosphates ceramics (stoichiometric hydroxyapatite (HA), β-TCP, substituted calcium phosphates, and biphasic compounds) are privileged biomaterials as orthopaedic implants or dental restorations in medical or aesthetics applications. In combination with additive manufacturing technologies, bioceramic parts can be designed with complex shapes with better biocompatibility and bioactivity than metals improving the osseointegration/osseoincorporation of the implant. Powder bed fusion (PBF) and VAT photopolymerization are promising additive manufacturing (AM) groups of techniques allowing the production of functional complex net-shaped or fully dense parts. However, specific tailored ceramic powders for these 3D printing techniques need to be produced. In this context, the challenge here is the evaluation of the characteristics of a suitable feedstock depending of the additive manufacturing technique. HA was chosen
as starting material for the production of scaffolds for bone tissue regeneration. In the course of tailoring the AM feedstock properties, depending on the additive manufacturing technique different processes can be necessary. In the case of the PBF techniques, the processability of the powder feedstock is better achieved when using laser-reactive and flowable dry microspheres. In this regard, this thesis deals with the tailoring of the HA particles morphology through a combination of processes such as, synthesis, wet milling, spray drying, and mixing of the powder with absorption additives. For a second AM group of technologies, like VAT photopolymerization, different characteristics are required for the material feedstock. In this case, the production of slurries composed of stable and low viscosity HA powder-filled photosensitive resins was essential. Their preparation was achieved by a milling step of the powder and a proper homogenization of the different components (photoinitiator, monomers, and diluent). Thus, as part of this PhD work the understanding of the relationships between the powder properties and the processing parameters was of special importance. For this reason, a wide variety of powder and suspension characterization methods was employed to assess the effect of the formulation and the operating parameters on the final product properties. It included the analysis of the chemical composition and structure of the compounds, as well as the physical properties of the particles dispersed in a liquid or in a dry state (morphology, flowability, stability, and rheology of suspensions). Finally, the suitability of the feedstock produced was examined through direct testing on the AM technologies and the quality of the printed parts was evaluated in terms of relative density, porosity, and mechanical properties.

Jury :
M.Eric CHAMPION, Rapporteur,
M.Khashayar SALEH, Rapporteur,
Mme Anne LERICHE, Examinatrice,
M.Liam GROVER, Examinateur,
M.Rodrigo MORENO, Examinateur,
Mme Mallorie TOURBIN, Examinatrice,
Mme Christine FRANCES, Directrice de thèse
M.David GROSSIN, Co-directeur de thèse

Date et heure

(Friday) 14 h 00 min - 17 h 00 min