| Biomedical implants such as artificial heart valves or interventional devices and artificialhip and knee joints have been gaining widespread use with development of medicalengineering. The knee and hip joints are complicatedly loaded parts, implantation materialsbear the comprehensive action of tension–compression, torsion, interface shear andreciprocating fatigue, wear in weight bearing conditions. The implants should withstanddynamical mechanical contact pressures and avoid formation of debris over a desiredlong–term biological interaction with the surrounding biological tissue. With time, mechanicalwear and stress, corrosion and tissue reactions lead either to a mechanical failure or to asepticloosening of the implant, the lifetime of the artificial joint implant is limited. The highlycorrosive environment and the low tolerance of the body to some dissolution productsstrongly restrict the materials available for implants.Some of protective functional film materials being considered for joint applications mayprevent or alleviate production of wear debris. Coating for biomedical materials is thephysical deposition of a ceramic and inert surface onto a medical implant device to improveits performance. In this paper, the F:Si–C–N films coating on Co alloy as bio–mechanicalcoating was put forward. The thickness, phase, composition, morphology andbiocompatibility of the coating were characterized by X–ray diffraction (XRD), atomic forcemicroscope (AFM), scanning electron microscopy (SEM) and Platelet adhesion tests. Thechemical bonding configurations and mechanical properties were characterized by means ofX–ray photoelectron spectroscopy (XPS), and nano–indentation technique and CSMpin–on–disk tribometer. Static contact angle measurements were performed by sessile–dropmethod to determine the wettability and surface free energy of the Si–N–O and F:Si–C–Nfilms.The results are summarized as follow: N2flow rate was the key parameters. On thecondition of keeping other parameter constant, the ratio of N/Si increased with the increasingof the N2flow rate. The Si–N bond gradually became dominant chemical binding state withthe increase of the partial pressure ratio of N2to Ar, the RPN2:PAr=0.3is a critical value to obtain high content of the Si–N bond and high hardness/elastic modulus. With the increase ofsputtering power, the films became smoother and with finer particle growth. The hardnessvaried between6GPa and11.23GPa depending on deposition condition (RPN2:PAr). Duringthe process of film deposition, the increasing N2flow made the bombardment of Ar+decreasewhile the silicon target was poisoned, causing the film to have insufficient density. Asystematic study on the preparation and properties of fluorinated silicon–nitride (Si–N) filmsunder varying different substrate bias voltage was carried out on the matrix of Co–Cr–Moalloy by direct current unbalanced magnetron sputtering techniques. It was found that thedeposition rate decreased linearly when the substrate bias voltage increased. When the biasvoltage exceeded to150V, the deposition rate increased again. It was easily detached by ionbombardment for Si–Si bond during high bias voltage that is less stable than Si–C bond. Theoptimum conditions were observed at substrate negative bias voltage of100–150V. The filmsshowed high hardness and elastic modulus at100V, while the state of samples betweensputtering and the control for Si, C, and N plasma reached to equilibrium at150V to growslow and dense.Significant role of fluorine and carbon–doped on growth characteristics and mechanicalproperties in the film was observed. It was found that CF4flows has a little effect on thecoefficient friction of the films, but large variations took place these films’ deposition rate,composition, microstructure and mechanical properties when CF4flows varied from0to9sccm. At9sccm CF4gas flow, the F:Si–C–N coatings demonstrated a fluorine content of5.95at.%and a maximum nano–hardness of15.3GPa, and a moderate friction coefficient of0.03. It is obvious from the hardness results that the F:Si–C–N coating enhances the hardnessof the Co–Cr–Mo alloy to approximately one time on a smoother surface.Behaviors of silicon nitride films and their relation to blood compatibility andbiomechanical properties have been interesting subjects to researchers. The results of theplatelet adhesion tests shown here have significant difference for the behavior of plateletadhesion between the silicon nitride films with various the ratio of polar component anddispersion component deposited on different N2and CF4flows. Si–N–O coating can be agreat candidate for developing antithrombogenic surfaces in blood contacting materials. Thechemical bonding state made an adjustment in microstructured surfaces, once in the totally wettable configuration, may improve the initial contact between platelet and biomedicalmaterial, due to the appropriate the ratio of and.The tribological characterisation of Co–Cr–Mo alloy with Si–(C)–N coating slidingagainst UHMWPE counter–surface in fetal bovine serum, shows that the wear resistance ofthe Si–(C)–N coated Co–Cr–Mo alloy/UHMWPE sliding pair show much obviouslyimprovement over that of uncoated Co–Cr–Mo alloy/UHMWPE sliding pair. The F:Si–C–Nand Si–N films have potential properties for joint surface modification applications. |
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