전기화학증착법으로 수산화인회석을 코팅한 Ti 합금의 표면특성과 생체적합성

Abstract

Commercial pure titanium (CP-Ti) of 99.5 % purity (grade 4) and Ti-6Al-4V ELI (extra low interstitial) were used as a substrate material for hydroxyapatite coating by electrochemical deposition. The coating process involves two steps ; 1) porous titanium dioxide (TiO2) on Ti alloy was formed at high potential 2) cyclic voltammetry method was carried out in modified simulated body fluid (SBF) for calcium phosphate electrodeposition on anodized Ti. Ti were anodized in solution containing typically calcium and phosphorous ions mixed electrolytes at room temperature. A direct current power source (180～400 V) was used for the process of anodization. HA deposition processing was conducted in an electrochemical cell with three electrodes: anodized Ti as cathode, platinum rod as the anode, and SCE as the reference electrode. A supersaturated solution for Ca-P deposition was prepared by Ca(NO3)2, NH4H2PO4 mixed solution in a liter of distilled water. The cyclic voltammetry method was conducted at cyclic potential (-2.0 V to 0 V) for 85 ℃ and carried out with PARSTAT 2273 (EG & G). Microstructure and chemical composition of coated layer and corrosion properties were characterized by field emission scanning electron microscopy (FE-SEM), energy diffraction spectrospcopy (EDS), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), scanning transmittance electron microscopy (STEM) and electrochemical equipments. In vitro studies were performed with MC3T3-E1 cell to investigate the effect of biological change on different surface conditions.

The results were as follows:

1. From the microstructure analysis, CP-Ti shows the acicular structure of α-phase and Ti-6Al-4V showed the needle-like structure of α+β phase.

2. From the surface properties of anodized layer, as the increasing of input voltages, pore size increased. However, the corrosion resistance of input 260 V anodized layer were higher than those of another conditions.

3. At the relatively low voltage of 180 V, crystal structure of TiO2 showed anatase phase. With increasing voltage, the intensity of anatase TiO2 peak increased until 300 V. However, above 300V, rutile phase began to appeared. After further increasing the voltage, the intensity of rutile phase increased, while that of anatase decreased steadily. The concentration of Ca and P increased with increasing anodization voltage.

4. Calcium phosphate coating on anodized Ti was prepared by electrochemical deposition at 85℃. The phase and morphologies of deposits HA were influenced by the electrolyte concentration, current density and loading cycle numbers.

5. The cell viability test revealed significantly enhanced viability on the HA coated surface of CP-Ti showed a good biocompatibility after anodization compared with another surface