Study of MAO Coatings of Nanostructured Mg-based Bioabsorbable Alloys for Bioactive Ions Delivery in Implant Applications.

Abstract

To determine the effect of grain refinement, down to sub-micrometer range, in mechanical, corrosion and biocompatibility properties of magnesium alloys. There is significant interest in developing better materials for implant applications. Among the biomaterials, metals play a significant role in structural applications where load bearing capacity and toughness are required. Beta Ti alloys appear as an alternative for applications such as implants due to their low modulus of elasticity (E = 50 - 80 GPa), closer to that of bone (E = 30 GPa) and lower than Ti-6Al-4V alloys. (100 GPa) and Stainless Steel (220 GPa). Magnesium is considered the top candidate for biodegradable metallic material due to high biocompatibility and high limit of daily dosage intake. Mg alloys are considered the main candidate system as bioabsorbable alloys due to high biocompatibility, low Young's modulus (45 to 60 GPa) and high limit of daily dose intake. It is of great interest to improve the resistance and reduce the corrosion rate and surface modification through micro-arc oxidation (MAO) of Mg-Zn-(Ca) and Mg-Li-Y alloys give great prospects for this rate control. corrosion for applications such as bioabsorbable implants. However, its mechanical properties (strength and ductility) and corrosion rate needs improvement. Basically, it is of great interest to improve strength, low elastic modulus (45 a 60 GPa) and reduce corrosion rate. Many research groups have focused on evaluating the effect of alloying elements and thermo-mechanical processing in these properties. Recent investigations have shown that severe plastic deformation techniques are able to significantly refine the grain structure of magnesium and its alloys and to improve their strength. However, the effect of such processing on biodegradation is not clear yet. Also, most research has focused on conventional alloys used in structural applications which might contain toxic alloying elements. Thus, the objective of this project is to evaluate the effect of surface modification through micro-arc oxidation (MAO) Mg alloys through extrusion and severe plastic deformation through ECAP (equal chanelling angular pressing) in Mg-Zn-(Ca) and Mg-Li-Y alloys systems as candidates for biodegradable materials. The effect of incorporating Ca, Mg and P ions into the MAO coating will be evaluated using characterization techniques. International cooperation will be deepened with the Charles University group of the current FAPESP-GACR #2021/03756-5 and the FAPESP Thematic #2018/18293-8 coordinated by prof. Rubens Caram, who also cooperates with Charles University.