**1.1 Preface**

It is easy to prepare TiO2 film by electrochemical deposition method technologically. There are some other electrodeposition methods, such as electrophoresis method, anodicelectrodeposition method and cathodic-electrodeposition method.

Tan Xiaochun[1] et al. set up a film formation model by electrophoresis method based on experiments and made an exposition of electrophoresis mechanism. The results showed that colloidal concentration and size, DC bias and time are the major factors to form a film. Hayward[2] et al. made a investigation of electrophoresis method also.

Nanometer TiO2 film prepared by cathodic-electrodeposition is formed in the form of microcrystalline piling up. Kavan[3] et al. took TiCl2 solution as an electrolyte, to get amorphous Titanium (IV) hydrate film on the anode, and the TiO2 film after heat treatment. Cui Xiaoli[4] et al. prepared TiO2 film on the ITO glass substrate with anodicelectrodeposition method, and investigated the effect of the anodic current and deposition time on nano TiO2 structure and adhesive force.

Natarajam[5] et al. used Titanium powder as a raw material, which was dissolved with H2O2 and NH3 to get colloid, so that can accomplish the cathodic-electrodeposition on ITO glass in the aqueous solution. Karuppuchamy[6] et al. took TiOSO4 as a raw material, to prepare TiO2 film by cathodic-electrodeposition, the SEM testing results showed that the TiO2 film is of porous. When a electrode was photosensitized with dyestuff, the incident light current transform rate of TiO2 electrode could reach up to 35%.

Most of cathodic-deposition are accomplished on ITO glass. Chi-Min Lin[7] et al. took TiCl4 ethylbenzene as an electrolyte, and accomplished the cathodic-electrodeposition on pure Ti. But there are few reports on the study of cathodic-electrodeposition on TiNi SMA. In this experiment, a self-prepared aqueous solution of Ti(SO4)2 was taken as the electrolyte, the cathodic-electrodeposition of TiO2 film on TiNi SMA was achieved. This method is with more convenient in operation, lower cost and easier to accomplish technologically.

Ti-O Film Cathodically-Electrodeposited on

Fig. 1-1. Schematic plan of the trielectrode system

**1.2.2.2 Composition analysis of Ti-O film** 

order to analyze the film's depositional effect.

Fig. 1-2. Schematic plan corrosion potential test

the Surface of TiNi SMA and Its Bioactivity and Blood Compatibility 5

The surface of the sample cathodically-electrodeposited for 4 min at 5mA/cm2 was observed with XL30 s-FEG type of scanning electronic microscope (SEM). Ti and Ni contents of Ti-O film were analyzed with Finder 1000 type of energy dispersive spectroscopy (EDS). The elemental composition and valent state of Ti-O film were analyzed with MII type of XPS, in

The deposited sample was put in a muffle furnace to experience crystallization treatment (annealling) for 1h at 300C and 450C respectively, furnace heating and cooling. The phase

**1.2.2.3 Corrosion potential test of the material in simulated physiological environment** 

Corrosion potential was measured with DJS-292 potentiostat. The connecting diagram is as shown in figure 1-2.The reference cathode was saturated calomel electrode (SCE). The sample was connected with copper wire, its working area was 10mm×10mm, and non-working area coated with silica gel. The samples both before and after cathodic-electrodeposition were dipped into Hank's solution (PH7.45) and Fusayama solution (PH6.13) respectively, then recording the electrode potential and time, potential value recorded once every one minute, until the potential no changing basically. Finally a curve of corrosion potential changed with

analysis of Ti-O film was with D/max 2000 type of X-ray diffractormeter (XRD).

time could be charted. The experimental parameters were set as in table 1-1.
