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Hydroxyapatite-based architectured and nano-structured bioactive coatings fabricated by cold spray

Abstract : Cold spray (CS) is considered as a solid-state coating process by impact. As a result, the harmful effects of high-temperature oxidation, evaporation, melting, crystallization, residual thermal stresses, etc., encountered with traditional thermal spray techniques, are minimized or even eliminated. CS can be of interest in the field of biomedical coatings for Bone Tissue Engineering (BTE), namely hydroxyapatite (HAp) coatings. CS can avoid HAps phase transformation into other calcium phosphates (tricalcium phosphate, tetracalcium phosphate, calcium oxide) during the deposition. Our work here first focuses on CS of HAp-based materials while analyzing in details all the CS processing steps (formation of “splats”, adhesion process and further growth process). More specifically, the influence of the raw powder mechanical properties, substrate surface state (i.e. roughness,hardness), CS pressure and stand-off distance between the gun and the substrate, are investigated. Good quality coatings can be obtained while optimizing the aforementioned parameters. It is shown that the build-up of coatings is mostly due to physical phenomena linked to particles packing ability and mechanical anchor on the roughness of the substrate. No consolidation through chemical phenomena is activated leading to coatings with a poor adhesion. Taking advantage of CS, in a second step we extend the approach to novel functionaly-graded enhanced bio-active hybrid coatings introducing whether collagen, bioglass or antimicrobial silver nanoparticles in the HAp feestocks. The as-obtained coatings are then tested at the microstructural, mechanical and biological (in vitro) levels showing good biocompatibility for BTE.
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https://theses.hal.science/tel-03620872
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Submitted on : Sunday, March 27, 2022 - 1:01:43 AM
Last modification on : Friday, October 21, 2022 - 3:43:58 AM
Long-term archiving on: : Wednesday, June 29, 2022 - 6:09:35 AM

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  • HAL Id : tel-03620872, version 1

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Alberto Ion. Hydroxyapatite-based architectured and nano-structured bioactive coatings fabricated by cold spray. Materials. Université de Limoges, 2021. English. ⟨NNT : 2021LIMO0087⟩. ⟨tel-03620872⟩

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