Polycarbonate (PC) possess many commercial applications. However, PC is still limited to non-abrasive and chemical-free environments due to its low hardness, low scratching resistance and high susceptibility to chemical attacks. To overcome this limitation, PC can coat by hydrogenated amorphous carbon layers. The a-C:H layers have very attractive properties such as high hardness, infrared transparency, chemical inertness, low friction coefficients, and biocompatibility. Addition of nitrogen on the structure allows lowering internal stress and improve tribological properties of a-C:H layers.
In this work, a-C:N:H layers were deposited from mixture CH4/N2 gases by Plasma Enhanced Chemical Vapour Deposition (RF CVD 13,56 MHz). Effects of the nitrogen incorporation on structure and tribological properties of deposited layers were investigated. The structure of layers were characterized by X-ray Photoelectron Spectroscopy and Fourier Transform Infrared spectroscopy (FTIR). The friction coefficient, wear resistance as well as the surface topography of a-C:H:N layers were estimated by tribometer in ball-on-disc configuration and atomic force microscopy (AFM), respectively. Results from the measurement indicate that incorporated nitrogen content has considerable effects on film properties. The IR spectra of the obtained layers have demonstrated a presence of nitrogen bonded both to carbon and to hydrogen. A formation of the following bonds has been confirmed: -C≡kN, -NH2, -C-NH2, >C=NH. All they are typical for a-C:N:H layers. The surface roughness of layers estimated by AFM seems to be more smooth with the increase of the N/C fraction. The tribological tests have shown that the layers reduce the friction coefficient of the polycarbonate (up to 50 %) and considerably improve wear resistance. |