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Field crystallization of anodic niobia

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Title: Field crystallization of anodic niobia
Authors: Habazaki, H. Browse this author →KAKEN DB
Ogasawara, T. Browse this author
Konno, H. Browse this author
Shimizu, K. Browse this author
Nagata, S. Browse this author
Skeldon, P. Browse this author
Thompson, G.E. Browse this author
Keywords: A. Sputtered films
C. Anodic films
Issue Date: Feb-2007
Publisher: Elsevier Ltd.
Journal Title: Corrosion Science
Volume: 49
Issue: 2
Start Page: 580
End Page: 593
Publisher DOI: 10.1016/j.corsci.2006.06.005
Abstract: Influences of electrolyte, pre-thermal treatment and substrate composition have been examined to elucidate the mechanism of field crystallization of anodic niobia formed on magnetron-sputtered niobium. The field crystallization occurs during anodizing at 100 V in 0.1 mol dm−3 ammonium pentaborate electrolyte at 333 K, with the crystalline oxide growing more rapidly than the amorphous oxide, resulting in petal-like defects. The nucleation of crystalline oxide is accelerated by pre-thermal treatment of the niobium at 523 K in air, while vacuum treatment hinders nucleation. Notably field-crystallization is also absent in 0.1 mol dm−3 phosphoric acid electrolyte or when anodizing Nb–10at.%N and Nb–29at.%W alloys in the ammonium pentaborate electrolyte. The behaviour is explained by the role of the air-formed oxide in providing nucleation sites for field crystallization at about 25% of the thickness of the subsequently formed anodic film, the location being due to the growth mechanism of the anodic oxide and the nature of crystal nuclei. Incorporation of tungsten, nitrogen and phosphorus species to this depth suppresses the field crystallization. However, boron species occupy a relatively shallow layer and are unable to affect the nucleation sites.
Type: article (author version)
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 幅崎 浩樹

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