Influence of Film Composition on the Structure and Dielectric Properties of Anodic Films on Ti–W Alloys

Habazaki, H.; Uozumi, M.; Konno, Hidetaka; Shimizu, K.; Nagata, Shinji; Takayama, Koichi; Oda, Y.; Skeldon, P.; Thompson, G.E.

doi:10.1149/1.1940750

Cited by 39 publications

(25 citation statements)

References 34 publications

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“…Where and are the molecular weight (79.866 g mol⁻ ¹) and density (3.1 g cm⁻ ³) [22] of titanium dioxide, is the Faraday constant and 10⁷ is a conversion factor from centimeters to nanometers because of the employed units. This is a simple calculation of the thickness of a compact oxide per unit area per unit charge derived from stoichiometry.…”

Section: Growth Mechanism-mentioning

confidence: 99%

“…In the same paper [19], Berger et al show how the tube wall changes with the expansion factor, from a double shell structure with a porous inner shell when the expansion factor is high, to a compact single wall as the expansion factor goes down. The value of 3.1 g cm⁻ ³ was measured for titanium-tungsten alloys anodized in the presence of ammonium pentaborate or phosphoric acid, and the analysis technique employed in the original paper does not allow for an exact determination of the composition of the oxide in terms of the presence of phosphate or bromide [22], yet it is a widely accepted value for the density of amorphous titania. This observations are a reasonable basis to assert that the density of the oxide depends on the synthesis conditions.…”

Section: Fixed Time Model-mentioning

confidence: 99%

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Empirical kinetics for the growth of titania nanotube arrays by potentiostatic anodization in ethylene glycol

et al. 2016

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Section: Growth Mechanism-mentioning

confidence: 99%

Section: Fixed Time Model-mentioning

confidence: 99%

Empirical kinetics for the growth of titania nanotube arrays by potentiostatic anodization in ethylene glycol

et al. 2016

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“…When the anodic oxides are amorphous, the growth parameters and film properties, such as transport numbers, field strength, density, dielectric properties, of anodic oxide films on binary alloys become a compositional average of those on individual metals [7][8][9][10]. This means that film properties superior to both anodic oxide films on two individual metals cannot be obtained when the anodic oxides are amorphous.…”

Section: Introductionmentioning

confidence: 99%

Formation and dielectric properties of anodic oxide films on Zr–Al alloys

Koyama

Aoki

Nagata

et al. 2010

J Solid State Electrochem

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Zr-Al alloys containing up to 26 at.% aluminum, prepared by magnetron sputtering, have been anodized in 0.1 mol dm -3 ammonium pentaborate electrolyte, and the structure and dielectric properties of the resultant anodic oxide films have been examined by grazing incidence X-ray diffraction, transmission electron microscopy, Rutherford backscattering spectroscopy and AC impedance spectroscopy. The anodic oxide film formed on zirconium consists of monoclinic and tetragonal ZrO 2 with the former being a major phase. Two-layered anodic oxide films, comprising an outer thin amorphous layer and an inner main layer of crystalline tetragonal ZrO 2 phase, are formed on the Zr-Al alloys containing 5 to 16 at.% aluminum. Further increase in the aluminum content to 26 at.% results in the formation of amorphous oxide layer throughout the thickness. The anodic oxide films becomes thin with increasing aluminum content, while the relative permittivity of anodic oxide shows a maximum at the aluminum content of 11 at.%. Due to major contribution of permittivity enhancement, the maximum capacitance of the anodic oxide films is obtained on the Zr-11 at.% Al alloy, being 1.7 times than on zirconium at the formation voltage of 100 V.

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“…It is known that defect-free, high-capacitance composite anodic oxide films can be formed on substrates by anodizing a Ti-62.5 at% Zr alloy [45][46][47][48][49][50][51]. Therefore, a simple fabrication process for creating a micro-porous Ti-Zr alloy with large surface area must be developed to create novel Ti-Zr capacitors.…”

Section: Introductionmentioning

confidence: 99%

Rapid reduction of titanium dioxide nano-particles by reduction with a calcium reductant

Kikuchi

Yoshida

Matsuura

et al. 2014

Journal of Physics and Chemistry of Solids

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Micro-, submicron-, and nano-scale titanium dioxide particles were reduced by reduction with a metallic calcium reductant in calcium chloride molten salt at 1173 K, and the reduction mechanism of the oxides by the calcium reductant was explored. These oxide particles, metallic calcium as a reducing agent, and calcium chloride as a molten salt were placed in a titanium crucible and heated under an argon atmosphere. Titanium dioxide was reduced to metallic titanium through a calcium titanate and lower titanium oxide, and the materials were sintered together to form a micro-porous titanium structure in molten salt at high temperature. The reduction rate of titanium dioxide was observed to increase with decreasing particle size; accordingly, the residual oxygen content in the reduced titanium decreases. The obtained micro-porous titanium appeared dark gray in color because of its low surface reflection. Micro-porous metallic titanium with a low oxygen content (0.42 wt%) and a large surface area (1.794 m 2 g -1 ) can be successfully obtained by reduction under optimal conditions. Key words: Titanium, Calcium, Calciothermic reduction, Nano-particles, Electrolytic capacitor IntroductionMetallic calcium can easily reduce a large number of metal oxides directly to metals because calcium has a strong reducing ability. The reduction of metal oxides with a calcium reductant in calcium chloride molten salt at high temperature, well known as the calciothermic reaction, has long been widely investigated by many researchers. During oxide reduction, calcium chloride molten salt acts as a suitable solvent and has a high solubility for calcium and calcium oxide as a byproduct formed by reduction. [11] are formed via reduction of these oxides with a calcium reductant in calcium chloride molten salt. The residual oxygen in the reduced metal decreases continuously by deoxidation with a calcium reductant [4]. Pure metals, alloys, and intermetallic compounds with a lower residual oxygen content can be successfully fabricated by a one-step reduction technique. Reduction with a calcium reductant is a simpler technique for the production of these metals without complicated processes such as the Kroll process, although reduction is a batch-type production method.In recent years, a method for the successive reduction of metal oxides was developed by electrolysis in calcium chloride and calcium oxide mixture molten salts. Ono and Suzuki reported that calcium oxide in molten calcium chloride becomes the reductant source for the reduction of metal oxides during constant-voltage electrolysis [12]. For example, metallic calcium formed electrochemically at a cathode reacts with metal oxides, and reduced metals with a low residual oxygen content can be formed (OS (Ono and Suzuki) Kyoto process). Metallic titanium [13][14][15], niobium [16], nickel [17], and other alloys and intermetallic compounds [18,19] can be formed via the OS process. In addition, the electrochemical decomposition of carbon dioxide gas by an advanced OS process using ...

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Influence of Film Composition on the Structure and Dielectric Properties of Anodic Films on Ti–W Alloys

Cited by 39 publications

References 34 publications

Empirical kinetics for the growth of titania nanotube arrays by potentiostatic anodization in ethylene glycol

Empirical kinetics for the growth of titania nanotube arrays by potentiostatic anodization in ethylene glycol

Formation and dielectric properties of anodic oxide films on Zr–Al alloys

Rapid reduction of titanium dioxide nano-particles by reduction with a calcium reductant

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