Electrochemical and Surface Characteristics of Nanotube Formed Ti-xZr Alloy

Nanotube formation on the surface is one of the biocompatibility improvements of titanium and its alloys. This process typically leads to the formation of a disordered oxide structure several hundreds of nanometers thick.

Objective: The electrochemical and surface characteristics of nanotube formation of Ti-Zr alloy have been researched in fluoride containing acid electrolytes at moderate voltages.

Methods: Ti-xZr alloys were prepared by arc melting and homogenized for 24 hr at 1000°C in argon atmosphere. Formation of nanotube on the surface was conducted by anodizing Ti-Zr alloy in H₃PO₄ electrolytes at 30V for 60min with small amounts of fluoride ions at room temperature. Microstructures of the alloys were examined by optical microscopy (OM), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and x-ray diffracto-meter (XRD). The electrochemical properties of the specimens were examined through potentiodynamic test (potential range of -1500 ~ 2000 mV) in 0.9% NaCl solution by potentiostat (EG&G Co, PARSTAT 2273. USA).

Results: Microstructures were changed from lamellar structure to needle-like structure with increasing Zr content from SEM and OM results. The surface morphology showed ordered arrangements of nanotubes consisted of arrays of nanopores with diameter in the 100nm range and thickness up to about 400~500nm. From anodized layer analysis, as Zr content increased, oxide nanotube size decreased in the order of 103nm, 92nm, 60nm, and 28nm, respectively.

From the results of anodic polarization behavior in the Ti-xZr alloys, it was found that the corrosion resistance of nanotube formed alloy increased with increasing Zr content.

Conclusion: Microstructures were changed from lamellar structure to needle-like structure as Zr content increased. As the Zr content increased, nanotube size and number of alloy decreased(Corresponding author:hcchoe@chosun.ac.kr)