Two-step bipolar anodization: Design of titanium with two different faces

Kokubo, Yuuka; Asoh, Hidetaka

doi:10.1016/j.elecom.2022.107376

Cited by 4 publications

(3 citation statements)

References 29 publications

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“…For titanium balls, even if an acidic electrolyte was employed, the formed film (titania) was a barrier-type rather than a porous-type similar to alumina. [37,38] Thus, the part coated with dense titania, having a high refractive index, was characterized by a distinct interference color without dyeing (Figure 10c). This area corresponds to the oxidized region for the DC-bipolar anodization of the titanium ball employed as a BPE.…”

Section: Simultaneous Processing Of Aluminum and Titanium Balls Under...mentioning

confidence: 99%

Design of Multiphase Metal Balls via Maskless Localized Anodization Based on Bipolar Electrochemistry

Asoh

Mizota

Kokubo

2022

Adv Materials Inter

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template-based), direct electrical connection to the workpiece in an electrolyte is indispensable. [1,2] There will be more variation in developing new materials independent of the specimen's shape and size if the need for direct energization is eliminated.Eliminating direct energization is advantageous, especially when processing small objects electrochemically. If the coating is a metal layer rather than an oxide film, a wireless method such as the barrel-plating process can be used industrially. Barrel plating, which involves placing the items in a barrel-shaped cage, is generally used for plating a high volume of smaller metal parts (e.g., bolts, nuts, and screws) at one time. However, in the case of anodization, an approach like barrel-plating cannot be applied because the coating is an insulator (i.e., alumina). Furthermore, the site-selective control of redox reaction on metal objects is not possible in a rotating barrel. Therefore, for anodization, the objects (the metal parts) are physically held by racking (e.g., clamping and bolting) to maintain the position and supply electrical current during the anodization process (Figure S1, Supporting Information). If the racking and unracking processes employed in an industry can be eliminated, the work efficiency of mass production can be enhanced. Furthermore, the electrical contact where the rack touches the metal (so-called rack mark) can also be eliminated. The rack mark's size and position on the metal surface may affect the performance (e.g., corrosion resistance and wear resistance) of the finished product because the contact remains as an exposed metal surface. Thus, developing surface treatment approaches that do not require electrical contact is highly desirable.Novel surface treatment approaches based on bipolar electrochemistry can resolve the above-mentioned issues. Recently, bipolar electrochemistry has attracted renewed interest in material science, bioscience, and related research fields. [11][12][13][14] Unconnected conductive objects, such as bipolar electrodes (BPEs), are placed between the outer electrodes (so-called driving electrodes) in bipolar electrochemistry. The experimental setup of bipolar electrochemistry is different compared to a conventional two-or three-electrode system. Since BPEs do not require a direct electrical connection to the external power supply, they can be prepared using different arrangements. Reduction-oxidation (redox) reactions, driven by the reaction's standard electrode potential, occur on BPEs under a potential gradient.

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Section: Simultaneous Processing Of Aluminum and Titanium Balls Under...mentioning

confidence: 99%

Design of Multiphase Metal Balls via Maskless Localized Anodization Based on Bipolar Electrochemistry

Asoh

Mizota

Kokubo

2022

Adv Materials Inter

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“…This study systematically investigates the regional and temporal changes in anodic oxidation on a BPE under a DC electric field using a spectrophotometer. As previously reported, titanium (Ti) was used as a BPE to visually and simply evaluate the temporal change in the reaction area. The surface of the anodized Ti exhibited specific interference colors due to the high dielectric constant of the oxide films that formed it; − hence, the anodic reaction area can be nondestructively and visually identified using the spectrophotometry technique.…”

Section: Introductionmentioning

confidence: 99%

“…In our previous studies, we adopted bipolar electrochemistry as the surface treatment of light metals (i.e., bipolar anodization) and investigated the effects of electrolytic conditions (e.g., concentration and temperature of the electrolyte, type of electric field, and electrode configuration) on the structures of the formed oxide films. − When aluminum BPE was horizontally positioned at the center of a cell, the area of the anodic reaction (anodic film formation) was much larger than expected, accounting for 90% of the BPE . Although bipolar anodization has a potential for prospective surface treatments due to its design flexibility based on a wireless operation, the change in the area of the region, in which the redox reactions proceed, has not yet been completely clarified.…”

Section: Introductionmentioning

confidence: 99%

Detection of the Oxidation Area by Spectrophotometry: Regional and Temporal Changes in Anodic Oxidation on Titanium in Bipolar Electrochemistry

Kokubo

Asoh

2023

ACS Omega

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This study investigated the temporal change in the oxidation area on a titanium (Ti) bipolar electrode (BPE) subjected to bipolar anodization in a direct current (DC) electric field using a spectrophotometer. The rectangular Ti sheet used as a BPE was horizontally positioned at the center of a cell. After the DC bipolar anodization, the oxidized area was detected nondestructively and visually using a specific interference color that depends on the thickness of the barrier-type oxide film formed on the Ti BPE. The change in the L*a*b* color space corresponding to each interference color revealed that the oxidation area increased along the longitudinal axis of the BPE with the increasing electrolysis time by reflecting the change in the potential distributions on the BPE. As visually demonstrated, the area where the anodic reaction proceeded reached saturation at 90% of the BPE surface area.

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Wirefree electroceuticals: 3D electrical and electrochemical stimulation of biological systems

Forster

2023

Current Opinion in Electrochemistry

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Two-step bipolar anodization: Design of titanium with two different faces

Cited by 4 publications

References 29 publications

Design of Multiphase Metal Balls via Maskless Localized Anodization Based on Bipolar Electrochemistry

Design of Multiphase Metal Balls via Maskless Localized Anodization Based on Bipolar Electrochemistry

Detection of the Oxidation Area by Spectrophotometry: Regional and Temporal Changes in Anodic Oxidation on Titanium in Bipolar Electrochemistry

Wirefree electroceuticals: 3D electrical and electrochemical stimulation of biological systems

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