UFR de Physique

Propositions de stages en laboratoire -- M2

Les offres sont actualisées en mai. Par exemple, les offres de stages pour l'année universitaire 2015-2016 seront mises en place en mai 2015, les offres de stages pour l'année universitaire 2016-2017 seront mises en place pour en mai 2016, etc.

MPGM_Surface modification of magnesium based alloys for biomedical applications

  • Option Structure et Propriétés de la Matière Condensée, Générique du parcours Structure et Propriétés de la Matière Condensée
  • Laboratoire: Unité Matériaux et Transformations (UMET)
  • Responsable du stage: SHABADI Rajashekhara (Rajashekhara.Shabadi@univ-lille.fr, 03 20 43 62 24)
  • Mots clés: magnesium, phosphating, biodegradability

The majority of implants currently in use are manufactured from nonresorbable material, especially titanium or steel. A major disadvantage of these implants is that they either have to remain permanently within the body to replace the missing function or need to be explanted, entailing a second surgical procedure. The high rigidity of the implants leads to stress-shielding in bone tissue, which prevents remodeling.

The development of biodegradable implants is extremely captivating, and among the various types of materials used in this regard, magnesium (Mg) and its alloys assume significance. The biodegradable property of Mg in combination of its non-toxic nature makes them potential candidate materials for biodegradable implants. However, the rapid corrosion, accumulation of H2 bubbles in gas pockets adjacent to the implant and unfavorable mechanical properties are the most critical limitations in using Mg and its alloys as implant materials.

Alloying with minimal additions of zinc, calcium and rare earth elements to magnesium were introduced within the toxicity levels to improve the mechanical properties. It was also studied that RE elements were incorporated into the passive film, which can have attendant ramifications on corrosion. But the dynamics of magnesium alloy corrosion rate is non-linear regardless of alloy type. Controlling this initial corrosion spike is therefore necessary and corrosion protection via surface modifications is a feasible option. Potentially, these could offer short term protection to allow the mechanical integrity to remain intact while the magnesium alloy forms its semi-passive reaction layer.

The aim of this thesis is to develop biocompatible and biodegradable coatings for Mg-Zn-Ca-RE alloys, with the intent of reducing and controlling the corrosion rate and increasing their initial biocompatibility. Inorganic chemical conversion coatings like phosphating will be grown with thickness < 10 μm on the metallic substrate surfaces since they have high temperature resistance and chemical stability, and are insoluble in water. Temperature, composition and time will be optimized to control the adhesion of coating to the metallic substrate. Immersion tests and electrochemical tests will be carried out to study its corrosion behavior in different environments. The surface analysis, by means of optical microscopy, XRD, SEM will be performed.