| Abstract |
| To investigate the effect of anodic oxidation process parameters on TiO2 nanotube formation in Ti-6Al-4V alloys, the composition of NH4F and H2O in the anodic oxidation processes were changed under the conditions of constant DC power ranging from 20 V to 60V and current density ranging from 10 mA to 30 mA. As the amount of NH4F was increased, the surface reaction rate became faster and surface dissolution also became more active. This result can be explained by the fact that TiO2 nanotubes were basically formed in the TiO2 layer located in the front of the Ti matrix by selective dissolution of the oxide layer, due to F - ions existing in the electrolytes. In anodic oxidation in ethylene glycol + 0.2 wt% NH4F with different amounts of water ranging from 0 ~ 8 vol%, the increase in the amount of water resulted in an increase in both the diameter and the length of growing nanotubes. When the voltage increased, the diameter and the length of the nanotubes tended to increase. But no nanotubes were formed at the voltage and the current density lower than a certain critical value. An increase in electrolytic holding time resulted in the diameter of the nanotubes increasing and decreasing repeatedly, but eventually increasing. X-ray analysis indicated that the as-grown nanotubes were amorphous while the anatase phase and the rutile phase were detected after anodic oxidation treatment, followed by annealing at 650 ℃ under Ar atmosphere for 2 hours.
(Received February 14, 2019; Accepted June 13, 2019) |
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| Key Words |
| Ti-6Al-4V alloy, anodic oxidation, TiO2 nanotube, morphology |
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