The development of a Zr-Cu-Al-Ag-N thin film metallic glass coating in pursuit of improved mechanical, corrosion, and antimicrobial property for bio-medical application

The amorphous thin film metallic glass (TFMGs) is a promising material with superior mechanical performance, fatigue properties, corrosion resistance, unique thermal properties, and antimicrobial efficacy. In this study, newly-designed Zr-Cu-Al-Ag-N TFMGs with various nitrogen content were fabricated by adjusting the nitrogen flow rate into the vacuum chamber. The composition of the Zr-Cu-Al-Ag-N thin films were analyzed by field emission electron probe micro-analyzer (FE-EPMA). The amorphous structure of the thin films were examined with grazing angle X-ray diffractometer (GIXRD). The differential scanning calorimetry (DSC) was applied to identify the amorphous characteristics and thermal properties of the thin films. The high resolution transmission electron microscopy (HR-TEM) was used to observe the microstructure and short range order (SRO) structure of the coatings. For a better intrinsic viewpoint, the average interatomic distance was calculated. The calculated distance gets closer with the increasing nitrogen content, which might result from the increase of short range order (SRO) structure. The nano-hardness, elastic modulus were measured with the aid of a nanoindentation tester. A positive relationship between nitrogen content and mechanical properties was acquired. The potentiostat testing and corroded surface observation were executed to quantitatively and qualitatively evaluate the corrosion resistance of the coatings. It is revealed that the corrosion resistance is enhanced as the increasing nitrogen content, which is attributed to the denser-packed structure. To access the antimicrobial performance of the coatings, liquid culture and plate counting method are used under the regulation of Japanese Industrial Standard (JIS Z2801:2000). It is revealed that the antimicrobial rate against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) is over 99.999% for all the TFMG coatings, which is attributed to the ultra-smooth surface roughness and Cu/Ag-containing chemical composition. Finally, the composition of Zr-Cu-Al-Ag-N TFMG with superior mechanical properties, thermal stability, corrosion resistance and antimicrobial efficacy will be revealed and discussed. (C) 2016 Published by Elsevier B.V.