Microstructure And Corrosion Behavior And Hemocompatibility Of DLC Films On The TiNi Alloys

Diamond-like carbon films were deposited successfully on the TiNi alloys by plasma immersion ion implantation and deposition (PIIID). It should be noted that the diamond-like carbon films fabricated using acetylene (C2H2) and graphite acting as plasma source are called DLCa and DLCg films, respectively. The surface characteristics, microstructure, mechanical properties, electrochemical corrosion behavior and hemocompatibility of the DLC films on NiTi alloys have been systematically investigated by Raman spectroscopy, XPS, AES, AFM, nanoindentation tests, scratch tests, electrochemical measurement and hemocompatibility experiments.The results show that technical parameters of preparation have obvious influence on the surface characteristics and structures of DLC films. With the increase of pulsed bias voltage, the RMS values of DLC films are decreased, and the sp~3/sp~2 ratio first increase and then decrease. With inceasing the working pressure, the RMS values of DLC films are increased, whereas the sp~3/sp~2 ratio are decreased. The graded-composition mixing layers are formed between the DLC films and TiNi substrate by PIIID due to the high pulsed bias voltage.With increasing the pulsed bias voltage, the nano-hardness and elastic modulus of DLC films first increase and then decrease. DLCg films with high sp~3/sp~2 ratio have high hardness and elastic modulus, further improve the ability to endure the applied load, consequently, leading to the enhancement of adhesion strength.The DLC films markedly improve the corrosion resistance of TiNi alloys, and effectively suppress the Ni ion released from TiNi alloys. The polarization resistance and breakdown potential of DLC films on NiTi alloys first increase and then decrease with the increase of the pulsed bias voltage, and decrease following the increase of working pressure. Technical parameters of preparation have obvious influence on the corrosion mechanism of DLC films. The pitting corrosion is the main mechanism for DLC films with defects and lower adhesion strength fabricated under the higher working pressure, whereas the uniform...