Thick self-organized porous zirconium oxide formed in H2SO4/NH4F electrolytes

We report the formation of self-organized porous layer of ZrO2 by anodization of zirconium in H2SO4 electrolytes containing low concentrations of NH4F. Under optimized electrolyte conditions and polarization in range of several 10 V, ordered sponge-like porous ZrO2 is obtained. The pores typically have a diameter ranged from 10 to 100 nm. Most remarkably the porous ZO(2) layers can reach thickness in the order of several 10 mum. The pore size is almost independent of the applied potential, whereas the amount of well-structured area on the sample surface increases with a higher applied potential. (C) 2004 Elsevier B.V. All rights reserved.