Tecnologia em Metalurgia, Materiais e Mineração
Tecnologia em Metalurgia, Materiais e Mineração
Artigo Original

Porous structure obtained by anodizing niobium in NaOH

Rafael Martins da Rocha, Leonardo Felix Scheffel, Carlos Leonardo Pandolfo Carone, Fernando Dal Pont Morisso, Sandra Raquel Kunst, Jane Zoppas Ferreira, Cláudia Trindade Oliveira

Downloads: 0
Views: 79


Porous structures can be produced as nanotubes, nanowires and membranes, and they can be used in gas sensors, magnetic and electronic devices, biotechnology, etc. These structures can be obtained by the anodizing process, in which the electrolyte must etch the oxide to occur the pore formation. In the case of niobium, porous oxides have been obtained successfully in electrolytes containing hydrofluoric acid (HF). However, studies have shown that niobium dissolves in electrolytes of NaOH with pH 14, and porous oxides of niobium have already been obtained by the anodizing process with the occurrence of sparking. Thus, the objective of this work is to obtain porous oxides on Nb without HF addition by studying the sparking phenomenon. Therefore, niobium was anodized at different current densities (10, 25, 50, 75 and 100 mA.cm-2). The samples were evaluated concerning morphology by SEM and chemical microanalysis by EDS. It was observed that sparking depends of the oxide barrier thickness and occurs at current densities higher than 50mA.cm-2. However, the increase of the current density, in spite of not increasing the thickness of the barrier layer, caused a greater incidence of sparking. According to the assignment proposed it was possible to obtain a porous structure in niobium with NaOH electrolyte, but this structure got an irregular aspect


Niobium; Anodizing; Porous oxide; Sparking.


1 Centro de Estudos e Debates Estratégicos. Minerais estratégicos e terras-raras. Brasília: Edições Câmara; 2014. 241 p. (Série Estudos Estratégicos; no. 3).

2 Norlin A, Pan J, Leygraf C. Fabrication of porous Nb2O5 by plasma electrolysis anodization and electrochemical characterization of the oxide. Journal of the Electrochemical Society. 2006;153:B225-B230.

3 Xiao-rong L, Qing-feng D, Yuan-yuan C, Xiao-long R, Shu-rui L, Qing-feng W. Effect of Niobium on dynamic recrystallization behavior of 5%Ni steel. Journal of Iron and Steel Research International. 2013;20(6):38-44.

4 Rooke JC, Barakat T, Finol MF, Billemont P, Weireldd G, Li Y, et al. Influence of hierarchically porous niobium doped TiO2 supports in the total catalytic oxidation of model VOCs over noble metal nanoparticles. Applied Catalysis B: Environmental. 2013;142–143:149-160.

5 Borcz C, Lepienski CM, Brunatto SF. Surface modification of pure niobium by plasma nitriding. Surface and Coatings Technology. 2013;224:114-119.

6 D’Alkaine CV, Souza LMM, Nart FC. The anodic behavior of Niobium – I. The state of the art. Corrosion Science. 1993;34:109-115.

7 Gomes MAB, Onofre S, Juanto S, Bulhões LO. Anodization of Niobium in sulphuric acid media. Journal of Applied Electrochemistry. 1991;21:1023-1026.

8 D’Alkaine CV, Souza LMM, Nart FC. The anodic behavior of Niobium – II. General experimental electrochemical aspects. Corrosion Science. 1993;34(1):117-127.

9 Vijayan SM, Göen T, Dennerlein K, Horch RE, Ludolph I, Drexler H, et al. Calcium, magnesium and aluminium ions as decontaminating agents against dermal fluoride absorption following hydrofluoric acid exposure. Toxicology In Vitro. 2021;71:105055. http://dx.doi.org/10.1016/j.tiv.2020.105055.

10 Habazaki H, Oikawa Y, Fushimi K, Aoki Y, Shimizu K, Skeldon P, et al. Importance of water content in formation of porous anodic niobium oxide films in hot phosphate–glycerol electrolyte. Electrochimica Acta. 2009;54:946-951.

11 Kirchgeorg R, Wei W, Lee K, So S, Schmuki P. Through-hole, self-ordered nanoporous oxide layers on titanium, niobium and titanium–niobium alloys in aqueous and organic nitrate electrolytes. ChemistryOpen. 2012;1:21-25.

12 Cavigliasso GE, Esplandiu MJ, Macagno VA. Influence of the forming electrolyte on the electrical properties of tantalum and niobium oxide films: an EIS comparative study. Journal of Applied Electrochemistry. 1998;28:1213-1219.

13 Di Quarto F, Piazza S, Sunseri C. Electrical and mechanical breakdown of anodic films on tungsten in aqueous electrolytes. Journal of Electroanalytical Chemistry. 1988;248:99-115.

14 Hornkjol S. Anodic growth of passive films on niobium and tantalum. Electrochimica Acta. 1991;36:1443-1446.

15 Yahalom J, Zahavi J. Experimental evaluation of some electrolytic breakdown hypotheses. Electrochimica Acta. 1971;16:603-607.

16. Marcolin P, Longhi M, Caio L, Zini LP, Beltrami LVR, Silva JC, et al. Obtaining niobium oxides in acetic acid with addition of HF. Tecnolologia em Metalurgia, Materiais e Mineração. 2018;15(1):35-42.

17 Ikonopisov S. Theory of electrical breakdown during formation of barrier anodic films. Electrochimica Acta. 1977;22:1077-1082.

18 Oliveira, C. T. Caracterização microestrutural e Eletroquimica de óxidos de nióbio crescidos por anodização [tese]. Porto Alegre: Programa de Pós-graduação em Engenharia de Minas, Metalúrgica e de Materiais, Escola de Engenharia, Universidade Federal do Rio Grande do Sul; 2007.

19 Baron-Wiecheć A, Burke MG, Hashimoto T, Liu H, Skeldon P, Thompson GE, et al. Tracer study of pore initiation in anodic alumina formed in phosphoric acid. Electrochimica Acta. 2013;113:302-312. http://dx.doi.org/10.1016/j.electacta.2013.09.060.

20 Ma Y, Wen Y, Li J, Li Y, Zhang Z, Feng C, et al. Fabrication of self-ordered alumina films with large interpore distance by janus anodization in citric acid. Scientific Reports. 2016;6(1):1-8. http://dx.doi.org/10.1038/srep39165.

21 Stella K. Electronic dissipation processes during chemical reactions on surfaces. Duisburgo-essen: Disserta Verlag; 2011. 256 p.

Submetido em:

Aceito em:

611bf17fa953952ced303d54 tmm Articles
Links & Downloads

Tecnol. Metal. Mater. Min.

Share this page
Page Sections