Influence of water content on nanotubular anodic titania formed in fluoride/glycerol electrolytes

Valota, Anna T.; LeClere, Darren J.; Skeldon, P.; Curioni, Michele; Hashimoto, Teruo; Berger, Steffen; Kunze, Julia; Schmuki, Patrik; Thompson, G.E.

doi:10.1016/j.electacta.2009.02.098

Cited by 188 publications

(140 citation statements)

References 39 publications

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“…These can be ascribed to evolution of oxygen bubbles at higher voltage. 25,29 As the rings are more exposed to the electrolyte in the gaps among the ATNTs, partial dissolution of the oxide rings due to fluorine ions eventually leads to formation of the ribs around the ATNTs, whereas excessive dissolution over extended anodizing times tends to eliminate the rings and ribs. 29 Eventually ribs on the upper part of the ATNTs are completely dissolved and hybrid morphology of the ATNTs can be observed, with a smooth top and a ribbed bottom.…”

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confidence: 99%

“…[26][27][28] However, there are very few papers involved in the formation mechanism of the ribs around the nanotubes. In 2009, Valota et al 25 proposed that the oxygen gas significantly reduces the efficiency of film growth with increasing water content in the electrolyte. The generation of the ribs is suggested to be a consequence of access of electrolyte between nanotubes, due to chemical dissolution of a fluoride-rich boundary layer, enabling transient formation of films around the external tube walls.…”

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confidence: 99%

“…The generation of the ribs is suggested to be a consequence of access of electrolyte between nanotubes, due to chemical dissolution of a fluoride-rich boundary layer, enabling transient formation of films around the external tube walls. 25 In 2012, Regonini et al 29 also proposed some original and interesting viewpoints about the formation mechanism of ribs on the outer wall of ATNTs. The formation of oxygen bubbles also affects the morphology of the ATNTs.…”

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confidence: 99%

“…A series of useful papers concerning many factors and their influence on the morphologies of ATNTs have been reported, [22][23][24][25][26][27][28] including applied voltages, 22,23 current oscillation and anodizing duration, 24 water content, 25 temperature and electrolyte. [26][27][28] However, there are very few papers involved in the formation mechanism of the ribs around the nanotubes.…”

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confidence: 99%

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Formation Mechanism of Gaps and Ribs Around Anodic TiO₂Nanotubes and Method to Avoid Formation of Ribs

Chong

Gao

et al. 2015

J. Electrochem. Soc.

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Anodic TiO 2 nanotubes (ATNTs) have been studied extensively for many years. However, their mysterious formation mechanism still remains unclear. The formation of gaps and ribs around the nanotubes has not been elucidated. Here, various surface and cross-section morphologies of ATNTs obtained under different anodizing conditions and their evolution process have been investigated in detail. Based on many experimental facts, new explanations for the gaps and ribs are presented. An entire surface layer covered on the nanotubes plays a primary role on the formation of gaps and ribs. The gaps result from the radial distribution of the electric field at the pore bottom. No newly-formed oxide will exist along the gap direction, because the electric filed along the gap is the minimum. The ribs result from the electrolyte entering into the wider gaps among the ATNTs due to the rupture of the entire surface layer. The rings or ribs on the outer wall of ATNTs are formed at the electrolyte/Ti interface due to the discontinuous existence of a small amount of electrolyte within the gap base. The present viewpoint was demonstrated by an original micro-dam, which can block the electrolyte entering into the gaps and avoid the formation of ribs.

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Formation Mechanism of Gaps and Ribs Around Anodic TiO₂Nanotubes and Method to Avoid Formation of Ribs

Chong

Gao

et al. 2015

J. Electrochem. Soc.

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“…The alloys were anodized in a fluoride/glycerol electrolyte with 5 vol.% of added water. This composition of electrolyte has previously been used to form porous or nanotubular anodic films on titanium 25 and barrier films on a magnesium alloy. 19 The anodizing behavior of the alloys is compared with that of sputteringdeposited magnesium.…”

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Behavior of Alloying Elements during Anodizing of Mg-Cu and Mg-W Alloys in a Fluoride/Glycerol Electrolyte

Palagonia

Němcová

Kuběna

et al. 2015

J. Electrochem. Soc.

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Anodizing of sputtering-deposited magnesium and Mg-0.75at.%Cu and Mg-1.23at.%W alloys has been carried out in a fluoride/glycerol electrolyte. The aims of the study were to investigate the enrichment of alloying elements in the alloy immediately beneath the anodic film and the migration of alloying element species in the film. The specimens were examined by electron microscopy and ion beam analysis. An enrichment of copper is revealed in the Mg-Cu alloy that increases with the anodizing time up to ∼6×10 15 Cu atoms cm −2 . Copper species are then incorporated into the anodic film and migrate outwards. In contrast, no enrichment of tungsten occurs in the Mg-W alloy, and tungsten species are immobile in the film. Anodizing treatments have long been used for the protection of magnesium alloys against corrosion and wear and interest still remains in improving and extending the range of available technologies. [1][2][3][4][5][6] Nevertheless, fundamental knowledge of anodizing of magnesium, 7 for instance relating to the migration rates and transport numbers of film species, is comparatively limited, in part due to the difficulty of forming films of uniform composition and thickness, and also to their reactivity to water. The formation of barrier-type anodic films has been extensively investigated on the valve metals, especially for aluminum, niobium, tantalum, titanium and zirconium.8 These studies have shown that oxide films of uniform thickness are formed under a high electric field that depends upon the film composition and the rate of film growth. [8][9][10] The films on aluminum, tantalum and niobium are usually amorphous, 8 and their formation involves migration of metal ions and oxygen ions, with significant contributions of both types, e.g. the transport numbers of Al 3+ , Nb 5+ and Ta 5+ are ∼0.40, 0.24 and 0.24 respectively. 8 Further, an outer region of the oxide films often contains a low concentration of species derived from the anions of the electrolyte.11 In contrast, the films on zirconium are usually nanocrystalline and form mainly by migration of O 2− ions, 12,13 while films on titanium undergo a transition from amorphous oxide to a mixture of amorphous and crystalline oxide.14 Barrier-type films can also be formed on magnesium, although such films have received much less attention and, consequently, less is known of the details of their composition, structure and growth mechanism. Films formed in aqueous electrolytes are often reported to consist of MgF 2 , MgO and/or Mg(OH) 2 . 5,7,[15][16][17] Barrier-type films can also be formed using non-aqueous electrolytes and the formation of uniform films in such electrolytes provides the opportunity for systematic studies of the anodizing behavior. 18,19 From previous work, anodizing of magnesium alloys can result in the enrichment of alloying elements beneath the anodic film. Such enrichments have been reported for copper, tungsten and zinc beneath oxide/hydroxide films formed on model alloys in an aqueous electrolyte 20,21 and of zinc beneath fluoride-...

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Mathematical Modeling of Self‐Organized Porous Anodic Oxide Films

Hebert

2015

Advances in Electrochemical Sciences and Engineering

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Influence of water content on nanotubular anodic titania formed in fluoride/glycerol electrolytes

Cited by 188 publications

References 39 publications

Formation Mechanism of Gaps and Ribs Around Anodic TiO₂Nanotubes and Method to Avoid Formation of Ribs

Formation Mechanism of Gaps and Ribs Around Anodic TiO₂Nanotubes and Method to Avoid Formation of Ribs

Behavior of Alloying Elements during Anodizing of Mg-Cu and Mg-W Alloys in a Fluoride/Glycerol Electrolyte

Mathematical Modeling of Self‐Organized Porous Anodic Oxide Films

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Influence of water content on nanotubular anodic titania formed in fluoride/glycerol electrolytes

Cited by 188 publications

References 39 publications

Formation Mechanism of Gaps and Ribs Around Anodic TiO2Nanotubes and Method to Avoid Formation of Ribs

Formation Mechanism of Gaps and Ribs Around Anodic TiO2Nanotubes and Method to Avoid Formation of Ribs

Behavior of Alloying Elements during Anodizing of Mg-Cu and Mg-W Alloys in a Fluoride/Glycerol Electrolyte

Mathematical Modeling of Self‐Organized Porous Anodic Oxide Films

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Formation Mechanism of Gaps and Ribs Around Anodic TiO₂Nanotubes and Method to Avoid Formation of Ribs

Formation Mechanism of Gaps and Ribs Around Anodic TiO₂Nanotubes and Method to Avoid Formation of Ribs