Facile fabrication of freestanding through-hole ZrO2 nanotube membranes via two-step anodization methods

Highly ordered freestanding tubular zirconia (ZrO2) membrane was prepared via an electrochemical anodization of zirconium (Zr) substrate in non-aqueous electrolytes (mixture of formamide and glycerol (weight ratio = 1:1) containing 1 wt% NH4F and 3 wt% H2O). Two methods were used to fabricate the two-end opened ZrO2 membranes, one is a potential shock method and another is a reducing potential method. The two-end opened ZrO2 membrane was produced through the detachment of the existing self-organized ZrO2 tubular layer from Zr substrate or sub tubular layer. The microstructures and morphologies of the samples were studied by scanning electron microscopy and the growth mechanisms of the two-end opened ZrO2 nanotube arrays were investigated.