• Proceedings of the Materials Research Society of Korea Conference
• /
• 2002.11a
• /
• pp.38-38
• /
• 2002

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2003.05a
• /
• pp.42-42
• /
• 2003

• Proceedings of the Korean Magnestics Society Conference
• /
• 1999.10a
• /
• pp.130-131
• /
• 1999

• Journal of the Korean institute of surface engineering
• /
• v.50 no.6
• /
• pp.427-431
• /
• 2017

Anodic aluminum oxide (AAO) film has recently attracted much attention as a key material for the fabrication of various nanostructures. A control of anodizing voltage (U) was employed to render different anodic aluminum oxide (AAO) nanostructures with pore diameter ($D_p$) and interpore distance ($D_{int}$) in oxalic acid. In this work, we study the effect of stepwise modulation of anodizing voltages on the shape and dimension of porous structures along the vertical direction and demonstrate the fabrication of hierarchical layers of systematically controlled three-dimensional (3D) pore profile.

• Nuclear Engineering and Technology
• /
• v.6 no.1
• /
• pp.14-22
• /
• 1974

Effects of anodization voltage on frequency characteristics of anodic oxide films on tantalum were analyzed based on the following impedance equatious : (equation omitted) Here $R_{f}$, $C_{f}$ and tan $\delta$$_{f}$ are equivalent series resistance in ohm, equivalent Belies capacitance in farad and dielectric loss, of anodic oxide films respectively Parameters P, $\tau$$_{ο}$, $\tau$$_{\omega}$, and Co are defined as follows: P=(d-w)/w, $\tau$$_{ο}$=$textsc{k}$$\rho$$_{ο}$, $\tau$$_{\omega}$=$textsc{k}$$\rho$$_{\omega}$, $C_{ο}$=$textsc{k}$A/d where d is the thickness of oxide film, $\omega$ is the diffusion layer thickness. $\rho$$_{ο}$ is the resistivity of oxide film at the interface of metal and the oxide, $\rho$$_{\omega}$ is the resistivity of oxide film at intrinsic region and A is the area of the film and $textsc{k}$=0.0885$\times$10$^{-12}$ $\times$dielectric constant, (in farad/cm). It was shown that dielectric loss and frequency dependence of equivalent series capacitance decrease as anodization voltage increases. This is a consequence of the fact that the thickness of diffusion layer increases a little with increasing anodization voltage whereas the total oxide thickness is proportional to the anodization voltage. The ngative deviation of measured values from tile relation, tan $\delta$$_{f}$=0.682 $\Delta$ $C_{f}$, was also discussed based on the Impedance equations given above. Here $\Delta$ $C_{f}$ is the change in capacitance between 0.1 and 1 KHZ.KHZ.Z.

• Transactions of the Korean hydrogen and new energy society
• /
• v.29 no.5
• /
• pp.434-441
• /
• 2018

The pore size of nickel (Ni) bottom electrode layer (BEL) for low-temperature solid oxide fuel cells embedded with ultrathin-film electrolyte was controlled by changing the substrate surface morphology and deposition process parameters. For ~150-nm-thick Ni BEL, the upper side of an anodic aluminum oxide (AAO) substrate with ~65-nm-sized pores provided ~1.7 times smaller pore size than the lower side of the AAO substrate. For ~100-nm-thick Ni BEL, the AAO substrate with ~45-nm-sized pores provided ~2.6 times smaller pore size than the AAO substrate with ~95-nm-sized pores, and the deposition pressure of ~4 mTorr provided ~1.3 times smaller pore size than that of ~48 mTorr. On the AAO substrate with ~65-nm-sized pores, the Ni BEL deposited for 400 seconds had ~2 times smaller pore size than the Ni BEL deposited for 100 seconds.

• Journal of Biomedical Engineering Research
• /
• v.21 no.3 s.61
• /
• pp.273-277
• /
• 2000

The galvanostatic anodization of commercially Pure titanium plate (c.p.Ti, grade 2) was investigated in various concentrations of aqueous $H_3PO_4$ from 0.05M to 0.7M. The surfaces of anodic oxide films, formed by the current density in the range between 0.3 and $l.0 A/dm^2$. were analyzed by SEM and XRD. The voltage-time (V-T) curves displayed an initial linear part and a subsequent parabolic part, and the initial slopes increased with an increase in the current density in 0.05M $H_3PO_4$. As the concentration of the electrolyte increased, the V-T corves exhibit no change but the final voltage decreased. The anodic oxide film of titanium developed from fine grains to snowflake-like grains in a layered structure with an increase in the concentration of the electrolyte and current density. Sparking at the interface of the oxide/electrolyte accompanied the local deposition and dissolution of the oxide film through discharging. The crystallinity of the anodic oxide film increased with the anodizing voltage and decreased with an increase in the concentration of the electrolyte.

• Journal of the Korean institute of surface engineering
• /
• v.50 no.5
• /
• pp.308-314
• /
• 2017

Anodic film formation behavior of AZ31 Mg alloy was studied as a function of NaOH concentration in 1 M $Na_2CO_3$ + 0.5 M $Na_2SiO_3$ solution under the application of a constant anodic current density, based on the analyses of voltage-time curves, surface appearances and morphologies of the anodically formed PEO (plasma electrolytic oxidation) films. The anodic film formation voltage and its fluctuations became largely lowered with increasing added NaOH concentration in the solution. Two different types of film defects, large size dark spots indented from the original surface and locally extruded white spots, were observed on the PEO-treated surface, depending on the concentration of added NaOH. The large size dark spots appeared only when added NaOH concentration is less than 0.2 M and they seem to result from the local detachments of porous PEO films. The white spots were observed to be very porous and locally extruded and their size became smaller with increasing added NaOH concentration. The white spot defects disappeared completely when more than 0.8 M NaOH is added in the solution. Concludingly it is suggested that the presence of enough concentration of $OH^-$ ions in the carbonate and silicate ion-containing electrolyte can prevent local thickening and/or detachment of the PEO films on the AZ31 Mg alloy surface and lower the PEO film formation voltage less than 70 V.

• Journal of the Korean institute of surface engineering
• /
• v.54 no.1
• /
• pp.25-29
• /
• 2021

The fabrication of nanopore membrane by deposition of Al2O3 film using electron-beam evaporation, which is fast, cost-effective, and negligible dependency on substance material, is investigated for potential applications in water purification and sensors. The decreased nanopore diameter owing to increased wall thickness is observed when Al2O3 film is deposited on anodic aluminum oxide membrane at higher deposition rate, although the evaporation process is generally known to induce a directional film deposition leading to the negligible change of pore diameter and wall thickness. This behavior can be attributed to the collision of evaporated Al2O3 particles by the decreased mean free path at higher deposition rate condition, resulting in the accumulation of Al2O3 materials on both the surface and the edge of the wall. The reduction of nanopore diameter by Al2O3 film deposition can be applied to the nanopore membrane fabrication with sub-100 nm pore diameter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.545-546
• /
• 2006

This study was performed to investigate the surface properties of electrochemically oxidized pure titanium by anodic spark discharging method. Commercially pure titanium plates of $10{\times}20{\times}1[mm]$ in dimensions were polished sequentially emery paper. Anodizing was performed at current density of $76.2\;[mA/cm^2]$, application voltage of 290, 350, 400 [V] using a regulated DC power supply, which allowed automatic transition constant current when a preset maximum voltage has been reached. The Ti surface oxided films was characterized by scanning electron microscope(SEM). The precipitation of HA(Hydroxyapatite) crystals on anodized surface was greatly accelerated by hydrothermal treatment. The concentrations of DL-$\alpha$-Glycerolphosphate Magnesiurn(DL-$\alpha$-GP-Mg) salt and Ca acetate in an electrolyte was highly affected the precipitation of HA crystals converted by Ti Anodized oxide films by Shape of Impulse Voltage.