Innovative Design, Manufacturing and Characterization of Biodegradable Metals for Surgical Implant Applications

Biodegradable Magnesium (Mg) has showed great potential as candidate material for new generation of biodegradable implants, and to replace conventional non-degradable metals and biodegradable polymers. The main problem of current Mg materials is their rather rapid corrosion, which can compromise mechanical integrity during tissue recovery. The goal of this research is to design and manufacture innovate Mg-based and Zinc (Zn)-based alloys and nanocomposites, which possess enhanced corrosion resistance and sufficient mechanical properties. Two types of Mg nanocomposites were manufactured and corrosion-inhibiting nanoparticles were added to enhance corrosion resistance of Mg. Nano-diamond (ND) particles were uniformly dispersed in Mg through Powder Metallurgy (PM) processing, and ultrasonic processing was developed to achieve single particle dispersion of Cerium oxide (CeO2) in Mg. New Zn-based alloy and nanocomposites were designed and developed, and hot extrusion were applied to refine grain structure. Metallurgical, mechanical, electrochemical and corrosion tests were performed to characterize corrosion and mechanical properties of fabricated materials. It was found that corrosion rates of Mg-NDs were still much higher rate than that of commercial pure Mg, although they were much lower than that of PM-processed pure Mg. In contrast, corrosion resistance of Mg-0.1CeO2 is high enough for interference screw application. Zn-based materials had corrosion rates of nearly one-magnitude lower than Mg, thus they are more suitable for coronary stent application. Furthermore, corrosion rates of Zn-based materials are tunable by adjusting material composition, and the rates range from 0.06 to 0.29 mm/ year, for versatile coronary stent designs. In Vitro cytotoxicity test results indicate that Mg, Mg-CeO2, Zn and Zn-Cu-Mg alloys are not toxic since cells growing in contact with corrosion products of these materials maintained high cell viability and healthy morphology.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 201