438 Prakt. Met. Sonderband 38 (2006) 
boundary sliding. As a result, the mechanical properties of nanocomposite films are far 2. 
superior to those of bulk material. 
The use of silver as the additional phase in a nitride matrix to produce nanostructures is very Th 
appealing for biomedical tribological applications for the following reasons: (1) silver provides an 
good friction properties, which have the potential to increase the wear resistance® and (2) it 20 
exhibits good anti-bacterial properties, as evidenced by the fact that it has recently been used 
in a variety of medical applications ranging from wound dressings to urinary catheters.'®" 
The antibacterial activity of silver is the result of Ag” ions binding strongly to electron donor 2. 
groups of biological molecules. This activity is dependent on the balance between the activity 
of the Ag” ions and the total amount of silver released from the coating, which, if too high, Pre 
causes cytotoxicity. ph 
In a previous work, our group investigated the structural, chemical, optical, and mechanical mg 
properties of ZrN-Ag nanocomposite films as a function of silver content and substrate bias Th 
voltage.’ In the current study, the tribological, haemocompatibility, antibacterial St 
performance, and cytotoxicity of these coatings will be evaluated. 20 
SO 
fro 
2. EXPERIMENTAL DETAILS 
2.1 Film Deposition ‘ 
ZrN-Ag films were deposited on polished Si (111) wafers and medical grade Ti-Al-V coupons Th 
by unbalanced magnetron dc sputtering using a system that has been described in detail Ne 
elsewhere. The coatings were grown reactively using Zr and Ag targets (99.99% purity) in a an 
mixed Ar (99.999%) and N; (99.999%) discharge. The Ar and N, pressure were set to 0.2 WE 
and 0.01 Pa, respectively. During deposition, the power to the Zr magnetron was fixed at Py Ti- 
= 70 W whereas the power to the Ag magnetron was varied between Pye = 0 and 7 W. trit 
Additionally, a radio frequency power supply was used to apply a bias voltage between V,, = - sa 
70 and -130 V to the substrate. All other deposition conditions for the various samples grown dis 
in this study are listed in Table 1. tel 
de 
| Ag content Young's Hardness el 
Sample (W) (%) Modulus (GPa) (GPa) HASIFIB 
S1 0 0 375415 | 2343 | 0.9401 2. 
a S2 | 3 5+1 3304142 | 3643 1.3401 Tt 
s3 5 p= 250+10 3243 ' 1.2%0.1 SU 
- — — — —-- — — of 
S4 7 10 + 1 180 + 10 22+3 1.1£0.1 Si 
— mre ——————— el} _ — — 
Table 1: Film properties vs. silver concentration i 
u 
i111 
a. 
=