Développement et validation des matériaux métalliques pour stents cardiovasculaires biodégradables par dépôt électrolytique
|Advisor:||Mantovani, D.; Fiset, Michel|
|Abstract:||Degradable metallic coronary stents have emerged as possible alternatives for permanent stents fabricated from corrosion-resistant metals such as 316L stainless steel (316L SS). Pure iron has shown to be an interesting candidate for degradable stents in terms of mechanical properties, degradation and biocompatibility. This project is the first to investigate the feasibility of using electroforming process for production of iron for degradable stents where the material is used for a load-bearing application. In this project, firstly, an electroforming process was developed. The produced iron foils showed a fine microstructure and high yield and tensile strength were also obtained comparable to those of 316L SS. Annealing at 550˚C for 1h induced recrystallization in iron and improved its ductility from 8 to 18%. The investigation of the degradation of electroformed iron in Hank’s solution using potentiodynamic polarization, static immersion and dynamic degradation tests showed that it corrodes faster than Armco® iron previously investigated for degradable stents. The effect of current density as an electroforming parameter on the microstructure and thereby the degradation of iron was also studied. Electron backscatter diffraction (EBSD) showed that different microstructures including grain size and texture were produced at different current densities from 1-10 A dm-2. The highest degradation rate was obtained for iron fabricated at 5 A dm-2 since it possesses small grain size and equiaxed grains with random orientations providing more grain boundary volume can be held responsible for its faster degradation rate compared to the other iron samples. Finally, the electroforming process was successfully applied for the fabrication of iron tubes. Iron tubes were electroformed on Sn cylinders which were separated from them by melting after the process. The tubes were then used for the fabrication of iron stents by laser-cutting. Iron stents fabricated from electroformed tubes demonstrated an average grain size of 5 µm after annealing and acid-pickling. This grain size is finer than what usually obtained for 316L SS stents and could potentially provide high mechanical properties and targeted degradation for electroformed iron stents.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||17 April 2018|
|Collection:||Thèses et mémoires|
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