Fabrication of tantalum oxide nanotubes by anodization in acid-free electrolytes

Abstract

In this study tantalum oxide nanotubes were fabricated on tantalum foil in acid-free electrolytes by anodization method. Nanotubes morphology, which is dependent on the current, electrolyte concentration, anodization time and the electrolyte temperature were optimized. Concentration of NH4F causes the increase in current density. Current density of the electrolyte also increases with the rise in temperature as graphite is semiconductor. High currents density causes instability in the oxide film and increases the detachment rate of the film. The temperature rise during anodization was controlled by an ice/water bath. Optimized morphology and uniform film of Ta2O5 was in the 70 mg of NH4F in 3 ml deionized water (DI water) and 49 ml ethylyne glycol (EG) electrolyte composition at ice/water cooled eletrochemical bath. The samples annealed at 550 °C show the formation of orthorhombic Ta2O5 crystals.