Niobium porous anodizing with glycerin addition

ABSTRACT Niobium is a metal that forms adherent protective oxide in contact with the air, which has the property of self-protection. The method used to accelerate the growth of the oxide is known as anodizing, in which the oxide formed may be barrier or porous. Porous oxide is widely studied and can be used in solar cells, gas sensors, as biomaterial, among others. However, porous oxides in niobium have been obtained with the use of F-, which causes an intense dissolution process of the oxide. In order to minimize this reaction, electrolytes containing glycerine have favored the anodizing process forming uniform porous surfaces. In this sense, the objective of this study is to obtain nanoporous structures in niobium by anodization from known parameters. From (12.73 mA.cm-2, 100 V), times (5 and 30 minutes), HF concentration (2.24%) and platinum cathode use, already used in a previous study, was initially tested the influence of the cathode of stainless steel in substitution to the platinum, aiming to promote a future technological transference. From this, in order to minimize the dissolution process that occurred using HF (2.24%), only HF (1%) was tested. Finally, in order to obtain a more uniform oxide structure, glycerin was added to the HF electrolyte (1%). The use of the stainless steel cathode, although influencing the results of the anodizing transients, due to its probable chemical dissolution, proved effective in the process. Anodized samples with lower concentrations of HF and with addition of glycerine, as expected, presented lower oxide dissolution during oxide formation, originating nanoporous structures, besides microcones.