Anodic film growth on tantalum in dilute phosphoric acid solution at 20 and 85°C

Lu, Qiongqiong; Mato, S.; Skeldon, P.; Thompson, G.E.; Masheder, D.; Habazaki, H.; Shimizu, K.

doi:10.1016/s0013-4686(02)00141-x

Cited by 42 publications

(36 citation statements)

References 19 publications

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“…An increase in electrolyte temperature resulted in a decrease of the anodic forming voltage and current efficiency. The electric field strength decreases with increasing temperature and decreasing current density, [21] which is confirmed by the present results (Figs 10 and 11). Therefore, microstructural differences are expected in the oxidized film layers formed at different electrolyte temperatures.…”

Section: Resultssupporting

confidence: 90%

Influence of electrolyte temperature on pure titanium modified by electrochemical treatment for implant

Lee

Kim

Park

et al. 2008

Surface & Interface Analysis

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This study examined the effect of electrolyte temperature on the surface characteristics of anodized pure titanium in DL-α-glycerophosphate (DL-α-GP) and calcium acetate (CA). The anodic oxide films contained a large proportion of anatase with some rutile. The relative intensity of the anatase peaks and the surface roughness increased with increasing electrolyte temperature. As the electrolyte temperature was increased, the pore size increased to 1-4 µm, and the apatite crystals became coarser and denser. The amount of calcium and phosphate adsorbed increased with increasing electrolyte temperature. The anodizing voltage reached the onset of constant voltage mode faster with decreasing electrolyte temperature. A higher voltage is essential for the electrolyte at lower temperature to reach the constant voltage mode during this initial period.

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Section: Resultssupporting

confidence: 90%

Influence of electrolyte temperature on pure titanium modified by electrochemical treatment for implant

Lee

Kim

Park

et al. 2008

Surface & Interface Analysis

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“…The incorporated phosphorus species were neglected in the quantitative RBS analysis, due to low sensitivity, but in accord with previous studies [16][17], the phosphorus content in anodic oxide films formed on valve metals in phosphoric acid is usually a few atomic percent. Thus, the similar phosphorus content is presumed also in the present anodic oxide films.…”

Section: Resultsmentioning

confidence: 85%

Thickness dependence of proton conductivity of anodic ZrO2–WO3–SiO2 nanofilms

Aoki

Tsuji

et al. 2012

Journal of Power Sources

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“…The outer layer, which accounts for about 12 % of the film thickness, is composed of ZrO 2 , essentially free from tungsten species, whereas the remaining film region contains both zirconium and tungsten species. In addition, phosphate anions are incorporated in the outer half of the film thickness, similar to the well-studied amorphous anodic oxide films formed on niobium [15] and tantalum [16] in phosphoric acid. The depth distribution of each element was confirmed by depth-profile analysis with glow-discharge Figure 1.…”

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confidence: 84%

High Proton Conductivity in Anodic ZrO₂/WO₃ Nanofilms

2009

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Anodization of the valve metals Al, Ti, Zr, Nb, Hf, Ta, and W leads to formation of barrier-type (compact) or self-organized porous-type anodic oxide films, depending on the electrolytes used. The oxide films formed are dielectrics or semiconductors with useful properties that make them of great interest for many applications, including solid electrolytic capacitors, solar cells, photocatalysis, electrochromic devices, and selfcleaning materials.[1-2] Here we report the first example of an anodic oxide with high proton conductivity below 200 8C. Proton-conducting thin films are promising electrolytes for solid-oxide fuel cells that operate at intermediate temperatures (100-400 8C) and other electrochemical devices. [3] Intermediate-temperature fuel cells have several advantages over polymer electrolyte fuel cells, which operate below 100 8C, under fully hydrated conditions.[4] The former type allows the use of nonprecious-metal electrocatalysts [5] and hydrocarbon fuels [6] and facilitates simpler module assembly by means of anhydrous proton conductors.Inorganic solid acids such as CsHSO 4 , Rb 3 H(SeO 4 ) 2 , and CsH 2 PO 4 exhibit sufficient proton conductivities fuel-cell operation, but their poor processability and low stability limit their practical application.[7] ZrO 2 /WO 3 is a very attractive acid catalyst that displays high catalytic activity and stability in demanding reactions that require strong Brønsted acidity. [8] The acid strength of this material has been reported to be H o À14.5 and is comparable with that of fully anhydrous hydrofluoric acid.[9] The proton-transport properties of this material are therefore of great interest.For practical use of a solid electrolyte in fuel-cell technology, the area-specific resistivity (ASR) of the electrolyte should be below 0.2 W cm 2 .[10] To obtain a sufficiently low ASR value at temperatures below 400 8C, one approach is reducing the thickness of the solid electrolyte to the nanometer scale. Shim et al. reported atomic-layer deposition of yttria-stabilized zirconia nanofilms of 60 nm thickness, which showed high ion conductivity as an electrolyte for solid-oxide fuel cells operated at and below 350 8C.[11] The high proton conductivity of nanofilms below 400 8C has also been reported for amorphous metallosilicate [12] and zirconium pyrophosphate [13] nanofilms prepared by a layer-by-layer sol-gel process. Native protons in these amorphous nanofilms contribute to efficient ionic conduction even in a dry atmosphere. Anodic oxide films formed on valve metals usually contain hydrogen species. [14] It is likely that high proton conductivity occurs in anodic oxide if the oxide is strongly acidic. In addition, the anodizing process is suitable for fabricating nanofilms of a desired thickness, since the thickness of barrier-type anodic oxide films changes linearly with the formation voltage. In this work, we prepared ZrO 2 /WO 3 nanofilms by anodizing magnetron-sputtered Zr/50 atom % W alloy films with flat surfaces. The obtained anodic oxide films showed high pr...

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Anodic film growth on tantalum in dilute phosphoric acid solution at 20 and 85°C

Cited by 42 publications

References 19 publications

Influence of electrolyte temperature on pure titanium modified by electrochemical treatment for implant

Influence of electrolyte temperature on pure titanium modified by electrochemical treatment for implant

Thickness dependence of proton conductivity of anodic ZrO2–WO3–SiO2 nanofilms

High Proton Conductivity in Anodic ZrO₂/WO₃ Nanofilms

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Anodic film growth on tantalum in dilute phosphoric acid solution at 20 and 85°C

Cited by 42 publications

References 19 publications

Influence of electrolyte temperature on pure titanium modified by electrochemical treatment for implant

Influence of electrolyte temperature on pure titanium modified by electrochemical treatment for implant

Thickness dependence of proton conductivity of anodic ZrO2–WO3–SiO2 nanofilms

High Proton Conductivity in Anodic ZrO2/WO3 Nanofilms

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High Proton Conductivity in Anodic ZrO₂/WO₃ Nanofilms