The Preparation And Properties Research Of Fluorinated Amorphous Carbon Films On NiTi Alloy

With the rapid development of modern material science and life medical science, different kinds of biomaterials have been widely used in clinical fields. Plasma surface modification of biomaterials has recently become a hot topic in materials design. It is an important way to enhance the corrosion resistance property of the mataerial surface for modern biomaterial design.Amorphous fluorocarbon films (a-C:F) have been proposed as extremely potential biomedical coatings due to their moderate biocompatibility, anti-adherence of the bacterial, chemical inertness, low coefficient of friction, high wear resistance, low dielectric constant, high hydrophobicity and good mechanical properties. Thus it is much importance for development and design of new generation biomaterials to make a detailed study on the film structure and properties.In this paper, the fluorocarobn films were deposited on NiTi alloy surface by radio-frequency plasma magnetron sputtering. Fluorocarbon film composition, structure, surface morphology, mechanical properties and corrosion resistance properties were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), Raman scattering spectroscopy (Raman), X-ray diffraction (XRD), atomic force microscopy (AFM), nano-indentation tests and electrochemical measurement. The influence of deposition parameters such as radio-frequency power, deposition time and Ar flow on the film structure and properties were especially concerned.The result of research showed that the a-C:F film was amorphous structure by magnetron sputtering. Fluorocarbon film was mainly comprised of C-C, -CF, -(CF-CF)n-, -CF₂ and -CF₃ groups; SP²/SP³ hybrid ratio of a-C:F films could be modified by controlling the deposition condition. The surface roughness of the fluorocarbon film decreased with increasing of deposition time and Ra was 3.218 nm at 120 minutes. However, the surface roughness of the fluorocarbon films decreased first and then increased with increasing of radio-frequency powers and Ar fluxes.And the analysis results of nano-indentation tests indicated that a-C:F presented different hardness and modulus with the different deposition parameters. These results indicated that the mechanical properties of a-C:F films were determined by the nature of network and the type of fluorocarbon groups. Electrochemical measurement showed that the corrosion resistance properties of a-C:F films reached a stable level with increasing immersion time and a-C:F film prevented the release of Ni ions effectively.