Research on a Crystalline Oxide Film on Ti-Ta Alloy By Anodic Oxidation and Hydrothermal Treatment

Ti-Ta alloys, having low Young’s modulus and high corrosion resistance¹, are expected to be candidates for dental and orthopaedic implants. However, for implant applications, the surface properties of Ti-Ta alloys are needed to be more bioacitve. Anodic oxidation is an efficient surface treatment to modify Ti surfaces because it changes the chemical and physical characteristics of Ti surfaces. According to the report by Sul et al.², an anodically oxidized Ti implant shows a strong response to bone because it surface incorporates P. Therefore, in this study, we attempt to fabricate a P-rich oxide on Ti-Ta alloys by anodic oxidation and hydrothermal treatment. 

In this study, Ti-50Ta plates (ϕ10×1 mm) were abraded to grade 800 silicon carbon paper. Then, the abraded samples were washed with acetone for 5 min followed by ethanol for 3 min in an ultrasonic cleaner, and finally dried at room temperature. Anodic oxidation of Ti-50Ta samples were performed in 30% phosphate acid solution. A high-density graphite plate was used as the cathode. The Ti-50Ta samples were galvanostatically anodized at a constant current density of 50 mA/cm² up to 300 V for 2 min using a direct current power supply. After anodic oxidation, the samples were washed with distilled water and the dries at room temperature. The anodically oxidized samples were hydrothermally treated in a 500 ml Teflon autoclave containing 50% distilled water as a reaction reagent. The samples were treated at 200 ℃ for 6 h.

Results show that after anodic oxidation, an oxide film with rough surface formed on a Ti-50Ta plate. A typical morphology, craters on the surface of oxide film, was observed and it is attributed to sparking occur on the surface. After hydrothermal treatment, crystals with size of ~100 nm formed on the anodic oxide film were observed in Fig. 1. These nano-crystals were suggested as P-O compounds. Sul et al. demonstrated that P-incorporated anodically treated films on Ti implants imparted much stronger bonding with bones than mechanically turned Ti implants. Consequently, this P-rich surface on Ti-Ta alloy is expected to possess a good biological ability.

References

1. D. Mareci, R. Chelariu, D.-M. Gordin, G. Ungureanu, T. Gloriant, Comparative corrosion study of Ti–Ta alloys for dental applications. Acta Biomaterial 2009; 5:3625-3639.

2. Y.T. Sul, C.B. Johansson, Y. Kang, D.G. Jeon, T. Albrektsson, Bone reactions to oxidized titanium implants with electrochemical anion sulphuric acid and phosphoric acid incorporation. Clinical Implant Dentistry and Related Research 2002;4(2):78-87.