Combinatorial screening of dysprosium-magnesium-zinc alloys for bioresorptive implants
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A thin film dysprosium-magnesium-zinc combinatorial library has been deposited using a thermal co- evaporation technique. Scanning EDX, XRD, SEM and XPS were used to investigate the structure, sur- face morphology and species present. The entire library was found to be amorphous and morphological changes were visible by minor additions of Dy (approximately 1 at.%) and medium to high Zn contents ( > 20 at.%). Open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polar- ization measurements revealed a higher corrosion resistance for Zn-poor alloys ( < 15 at.%), which was demonstrated by downstream ICP-OES analytics. Electrochemical measurements on Zn-rich alloys evi- denced Mg release of up to 200 ng s ?1 cm ?2 . This makes them unsuitable for biomedical applications due to the high H 2 gas evolution. A low Dy content of up to 0.5 at.% was shown to further increase the corrosion resistance with Mg release rates of less than 5 ng s ?1 cm ?2 . Alloys in this region are therefore considered valuable candidates for biomedical implants. The study showed best electrochemical proper- ties, thus the most promising alloy, at a composition range of 0.5 at.% Dy 15.0 at.% Zn and Mg as balance.