Mechanical and Tribological Properties of Ag/TiBx Nanocomposite Thin Films with Strong Antibacterial Effect Prepared by Magnetron Co-Sputtering

Abstract

The use of silver-based antimicrobial materials has been growing recently. Considering the threat of developing silver-resistant bacteria, it is essential to address the endurance of such materials and the amount of silver released into the environment. Here we report on a durable, antibacterial Ag/TiBx nanocomposite coating prepared by conventional magnetron sputtering. The coating consists of fine Ag clusters embedded in extremely hard, wear-resistant overstoichiometric TiBx, which serves as a protective matrix. The highest E. coli growth inhibition of 97% is observed for the coating containing 24 at.% of Ag. A strong antibacterial effect is also maintained after 45 days of immersion in the Luria–Bertani + 5% HNO3 solution. Despite a marked hardness decrease from 40 GPa for TiBx to 6.4 GPa for Ag/TiBx with 28 at.% of Ag, the coating maintains a good specific wear rate of 6 × 10−5 mm3/Nm. Moreover, the addition of Ag, which acts as a solid lubricant, decreases the coefficient of friction from 0.77 to 0.35, even at room temperature. Thanks to the combination of antibacterial properties and enhanced wear resistance, such material can find application as a protective coating for cutlery, door handles, water taps, and other daily-used objects in public areas.

Solid Lubrication System and Its Plasma Surface Engineering: A Review

“…Ag has a facecentered cubic structure that is prone to intergranular slip [125][126][127]. Ag can significantly improve the plasticity and toughness of coatings/films by refining grain size, thereby improving the tribological properties of layers [128][129][130]. Ag uses defects and grain boundaries in the internal structure of the coating/film as diffusion channels and uses external temperature and friction as driving forces to diffuse towards the friction surface quickly [131].…”

“…Oxides are potentially the best choice for solid lubrication in harsh conditions, including extreme temperatures, since oxides are often structurally and chemically/thermodynamically stable. These phases, such as PVD, are usually formed in the tribo-oxidation process or used as deposition during synthesis [128]. Significant research focuses on using metal compounds, which lead to developing an oxide lubricious layer in the temperature range.…”