Design & Surface Modification Of TiNi Alloy Applied At The Biology Environment

The TiNi shape memory alloy is an attractive material for biology medicine applications, but as material planting into the human body, it exists the issues which phase temperature greatly changes with composition fluctuation and Ni ion release. For solving these problems, the text researcher explores the essence of phase temperature change with composition by the discrete variational Xa method (DVM- Xa). at the same time, the behavior research of hydroxyl (-OH) absorption on TiNi alloy surface is completed by DVM- Xa, it makes theory base of surface modification. At last, diamond-like carbon (DLC) film on TiNi alloy is prepared by PECVD technology, for potential applications as protective film of TiNi alloy, the DLC film' s structure, surface micrograph, mechanical performance and corrosion-resistance in Troyde's simulative body liquid have been evaluated in this paper. The conclusions are as follows:1.Electronic structure is analyzed for the effect of Hf,Zt addition on the Ms of TiNi alloy by DVM- Xa. It is found that the bond order of the strongest bond in the parent and the density of states at the Fermi level for the (110) crystal plane close relate to the Ms temperature, the stronger the parent bond order, the smaller the density of states at the Fermi level for the (110) crystal plane, the lower the Ms temperature.2.The theory calculation of hydroxyl preferential absorption for Ti on TiNi alloy surface is completed by DVM- Xa. The further research on hydroxyl absorption on the (110) plane and (100) plane points out that hydroxyl only interacts with the nearest titanium atom.3.The result of visible Raman spectrum shows that typical diamond-like carbon film can be acquired through the experiment. AFM micrograph shows DLC film with smooth surface is made up of nanocrystal amorphous carbon. FT-IR shows DLC film comprises CH3,CH2, CH, Si-O-Si, Si-O-C and Si-CH3 bond.4.The hardness of diamond-like carbon film is about 5 times as large as that of TiNi alloy substrate, which is 15Gpa, the friction coefficient is 0.124, the adhesion strength between DLC film and TiNi alloy substrate is up to 20N. Results show mechanical performance has close touch with amorphous carbon structure and component in DLC:H film.5. The corrosion-resistance of diamond-like carbon in the Troyde' s simulative body liquid (PH=7.0) is the best when the ion energy is 500v. Analysis shows that the 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.