| The biocompatibility of medical implants is closely related to their surface properties. Thus it is one of effective methods to improve the biocompatibility of implants by surface modification. Diamond-like carbon, with good biocompatibility, hemocompatibility and elasticity, chemical inertness, has become a kind of bioceramic material which has good future for application. In this study, aimed at 316L stainless steel for implants, diamond-like carbon (DLC) films on 316L stainless steel are prepared by use of PECVD and PS technologies, through twinned microwave ECR plasma source enhanced magnetron sputtering system. Then TiN and Ti/TiN films by arc ion plating technology and anatase TiO2 by liquid phase deposition are deposited, which are used to contrast with DLC films. For potential application as protective film of 316L stainless steel, the DLC film's structure, surface micrograph, mechanical performance, surface tension and corrosion-resistance in Troyde's simulative body liquid have been evaluated in this paper.1. The result of visible Raman spectrum shows that typical diamond-like carbon film can be acquired by PSII, PECVD and PS&PECVD technology. AFM micrographs show DLC film with smooth surface is made up of even and nanocrystal amorphous carbon.2. The Vicker's hardness of diamond-like carbon film is as about 5 times as that of 316L stainless steel substrate, which is 1520.4(HV). And the highest adhesion strength between DLC film and 316L stainless steel substrate, by PSII&PECVD technology, is up to 163.18mN. The DLC film has not been destroyed after friction and wear. Results show mechanical performance has close touch with amorphous carbon structure in DLC film.3. Wetting ability of diamond-like carbon film has been evaluated by measuring static contact angle using different solutions with different pH, and the results show the extent that DLC film is destroyed depends on the pH of solutions. After the surface of 316L stainless steel is modified by DLC film, hydrophobic performance appears and surface tension is smaller than that of 316L stainless steel. There is no great difference on surface tension among DLC films by different technologies, 40mN/m or so, and the polar share of the surface tension is greater than the dispersive share.4. The corrosion-resistance of diamond-like carbon, TiN, Ti/TiN and anatase TiO2 films by different methods in the Troyde's simulative body liquid(pH=7.0) is studied. Corrosion-resistance of coatings is closely related with the structure and components. Compared with others modified films, DLC film by PSII&PECVD technology has the best corrosion-resistance. Analysis shows thatthe defects existing in coatings, such as pinholes or pores, cause the corrosion of films in simulative body liquid, and the film itself does not take part in the electrochemical reactions. The reacting process of electrochemical corrosion in simulative body liquid is as follows: 1) to form the occluded cell; 2) to improve the pitting corrosion of the substrate material by the autocatalytic process; 3) with the breakage of the substrate material, the film is undermined. |
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