Sputter-deposited TaCuN films: Structure, tribological and biomedical properties

Abstract

Stainless steel is a material that is commonly used in brackets and arch wires during orthodontic treatment. However, the high frictional resistance that occurs between stainless steel/stainless steel can reduce the efficiency of orthodontics. Developing protective films is a simple and effective method that can produce low friction in saliva environment. In this study, we investigated the respective mechanical and tribological behaviors of pure TaN film, TaCuN solid solution film and TaN/Cu nanocomposite film. Hardness tests showed that the hardness of TaN and TaN/Cu are approximately 15.6 and 7.3 GPa, respectively. However, TaCuN film has a higher hardness of about 17.6 GPa, which contributes to its excellent wear resistance. The hydrolysis reaction of TaCuN film during friction process turns the saliva environment into a solution containing oxide colloid particles. Moreover, during friction, a Cu2O-induced hydrophobic surface appears. As a result of the colloidal solution with double electric layer repulsion generated by this process and the saliva-lubricating film absorption of the hydrophobic surface, the TaCuN film achieves outstanding tribological properties, with a friction coefficient and wear rate of 0.045 and 1.18 × 10-9 mm3/Nm, respectively. In addition, biological experiments confirm that the TaCuN film is a material with non-toxic and good biocompatibility and that it demonstrates stronger antibacterial ability than stainless steel. Depositing the TaCuN solid-solution film on the arch wires represents an effective approach for the surface modification of orthodontic appliances. Furthermore, TaCuN film could potentially be applied as a protective film in the field of dental treatment.