Fabrication of Zirconia Nanotube Arrays by Anodization

Highly-ordered and uniform zirconia (ZrO2) nanotube arrays were fabricated by electrochemical anodic oxidation on a pure zirconium sheet in 1 mol/L (NH4)(2)SO4+0.5% (mass fraction) NH4F (20 V, 3 h) inorganic electrolyte and formamide +glycerol (volume ratio 1:1)+ 1% (mass fraction) NH4F (50 V, 24 h) organic electrolyte. SEM and TEM techniques were used to characterize the ZrO2 nanotubes morphology. It is showed that these nanotubes have a length of 19 gm, a diameter of 40nm in inorganic electrolyte and a length of I 10 gm, a diameter of 200 nm in organic electrolyte. XRD diffraction pattern shows that the zirconia nanotubes are orthorhombic phase in inorganic electrolyte. In the organic electrolyte the zirconia nanotubes have amorphous phase structure. The mixed phase of the monoclinic and tetragonal phase appears after annealed in air at 400 degrees C for 3 h; while after annealed in air at 800 degrees C for 3 h, the zirconia crystals in monoclinic phase can be obtained.