Formation of self-organized niobium porous oxide on niobium

Anodization of niobium in mixed H2SO4/HF electrolytes was investigated. Under optimized electrochemical conditions the formation of self-organized porous Nb2O5 layers was observed. The porous Nb2O5 layers consist of ordered pore arrays with single pore diameters ranging from 20 to 30 nm. The pore morphology and the layer thickness strongly depend on the HF concentration and the time of anodization. Well-ordered uniform porous layers of up to 500 nm in thickness were formed. The formation of thicker layers is hampered by dissolution process and a tendency to film delamination.