Executive Summary : | Objective: To devlope biodegradable and biocompatible Magnesium based alloys and coatings for temporary implant Summary: Development of Mg based biodegradable implants is a challenging task as controlling the degradation rate with respect to the bone or tissue healing and selection of non toxic alloying elements to meet the required properties are critical. WE43 (Mg-4Y-3Nd) is one of the most widely used Mg alloys for clinical trials. Recently, Mg alloys with heavy RE elements (Y, Gd, Dy etc.) added along with Zn are drawn much attentions as combination of Zn and RE elements provide excellent mechanical and degradation properties. The advantage of Mg-Zn-RE alloys is that the property profiles can be tailored by altering Zn/RE ratio. The mechanical and corrosion properties of materials are depending on grain size. Ultra fine grain structure (ufg) provides not only higher mechanical properties but also enhanced corrosion properties. Due to hcp structure, extrusion is widely used for Mg over rolling to produce fine grain structures. However, sheets with ufg is also needed for the orthopedic applications. Friction stir processing (FSP) is nowadays considered as an effective severe deformation process to produce sheets with ufg. Surface of a biodegradable implant is crucial as it not only facilitates the cell/implant interaction but also prevents the degradation. Moreover, the initial corrosion rate should be controlled to avoid more H2 volume generation from the implant immediately after implantation. Hence development of coatings with better corrosion resistance, mechanical integrity, and biocompatibility is a vital step to realize the temporary metallic implants. Unfortunately, widely used hydroxyapatite (HAp) based calcium phosphate coatings are not completely eliminating the degradation issues. Moreover, chemical conversion techniques which is widely adapted to obtain phosphate coatings is not effective as the coating produce many mud cracks. Hence the present work focuses on to develop Mg-Zn-Y/Nd based alloys with high strength and ductility with good corrosion resistance through hot extrusion and FSP, and to develop a Ce and La based phosphate coatings through electrodeposition technique to tailoring their biodegradation rate. The mechanical properties and their biodegradation and cytotoxicity of the developed alloys and coatings in a cell culture. |
