• Korean Journal of Materials Research
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• v.12 no.5
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• pp.353-358
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• 2002

The microstructure and growth behaviors of anodic oxide layers on titanium were investigated. $TiO_2$ oxide films were prepared by anodizing at constant voltages of 180 and 200V in sulfuric acid electrolyte. The anodic $TiO_2$ layer formed at 200V showed a cell structure with more irregular pore shapes around the interface between the anodic oxide layer and the substrate titanium compared with that formed at 180V. Irregular shape of pores at the initial stage of anodization seemed to be attributed to spark discharge phenomena which heavily occurred during increasing voltages. The thickness of the anodic oxide film increased linearly at a rate of $1.9{\times}10^{ -1}\mu\textrm{m}$/min. The oxide layers formed at 180 and 200V were composed mainly of anatase structure, and the anodizing process could be suggested as one of fabrication methods of photocatalytic $TiO_2$.

• Journal of the Korean institute of surface engineering
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• v.53 no.5
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• pp.249-256
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• 2020

As the size of manufacturing equipment for LCD and OLED displays increases, replacement of existing heavy stainless steel components with light metals, such as aluminum alloys, is being more important in semiconducting and display manufacturing industries. To use aluminum alloys for components in semiconducting and display industries, it is important to develop a new anodization method for improved performance of anodic oxide films than conventional anodization method based on sulfuric acid. In this work, optimum applied current density and the best sealing methods for anodic oxide films in 3% oxalic acid were explored. Experimental results showed 2.5 A/dm2 is the best applied current density for improved hardness and dielectric breakdown voltage. Sealing of the anodic oxide films further improved their hardness, dielectric breakdown voltage and resistance to HCl, by which application of anodic oxide films become applicable for components in semiconducting and display industries.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1047-1052
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• 1998

The porous alumina membrane was prepared from aluminum metal(99.8%) by anodic oxidation using DC power supply of constant current mode in aqueous solution of sulfuric, oxalic, phosphoric and chromic acid. Pore size and distribution, membrane thickness, morphology and crystal structure were examined with several anodizing conditions : reaction temperature, electrolyte concentration, current density and electrolyte type. It was found that ultrafiltration membrane was fabricated in electrolyte of sulfuric, and oxalic acid. On the other hand, microfiltration membrane was fabricated in electrolyte of phosphoric, and chromic acid. Also, it was shown that crystal structure of porous alumina membrane prepared in sulfuric, oxalic, and phosphoric acid was amorphous, whereas porous alumina membrane prepared in chromic acid had ${\gamma}$ type of crystal structure.

• Journal of the Korean institute of surface engineering
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• v.1 no.1
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• pp.14.1-18
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• 1967

The characteristics of sulfuric acid anodized layer was studied under various Conbitions, acid concentration : 5-20%, temperature : 5-25$^{\circ}C$, bath voltate : 16 volts , bath agitain : mech agitation : mechanical . The Al+++ ion increase in anodizing baty, the film thickness under microscope, the comparative porosity and the thickness were determined. It was found that film thickness and the porosithy which are the main factors of determining andoized layet quality, rule the corrosing and abrasiion tesistance of the film, and that the porosity is increasing in the outerlayer. The formation mechanism was assumed as follows : The film thickness -increase is due to OH_ ion diffusion into compact non-conductive layer and Al+ + OH_ \longrightarrowAl(OH), Al(OH)+ + OH_ \longrightarrowAl(OH)+$_2$ , Al(OH)+$_2$ + OH_ \longrightarrowAl(OH)$_3$., the strong adhesion force is alse due to Al(OH) or Al(OH)$_2$ in transtion layer. And the pore-nucleation is produced by volume change between Al and Al$_2$O$_3$ and activated H$_2$O gas created by large reaction heat of Al+(x) +OH_ \longrightarrowAl(OH)x.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.11-15
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• 2018

The parts of equipment for semiconductor are protected by anodic aluminum oxide film to prevent corrosion. This study investigated contamination particle and cracking behavior of anodic oxidation in sulfuric acid containing cerium salt. The insulating properties of the sample were evaluated by measuring the breakdown voltage. It was confirmed that the breakdown voltage was about 50% higher when the cerium salt was added, and that the breakdown voltage after the heat treatment was 55% and 35% higher at $300^{\circ}C$ and $400^{\circ}C$, respectively. After heating at $300^{\circ}C$ and $400^{\circ}C$, cracks were observed in non cerium and cerium 3mM, and more cracks occur at $400^{\circ}C$ than at $30^{\circ}C$. The amount of contamination particles generated in the plasma is about 45% less than that of non-cerium specimens.

• Journal of the Korean institute of surface engineering
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• v.26 no.2
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• pp.45-54
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• 1993

In this study, magnetic properties of anodized Al film deposited with ferro-magnetic metals in the capacity of perpendicular magnetic recording media were measured and evaluated to find out the role of structure and morphology of the oxide films on magnetic characteristics. The object of this work was to present the conditions of magnetic thin film formation with more superior magnetic property. Anodizing was carried out under various conditions, and then the anodized film were electro-deposited with Co, Ni, Fe and their alloys. Coercive force and residual magnetization in perpendicular direction increased as the pore length of anodized film increased. It was attributed to the increase of the amount of depoisted metals and the ratio of length/diameter of pores. Morphology of anodized films in phosperic acid was not similar to that of sulfuric acid, and thin films in the former solution had perpendcular magnetic anisostropy because of large diameter, irregular length and distribution of the pores. It was found that magnetic properties of the thin films, which had doubled layer of two metals, were dominated by the metal electrodeposited on the surface of the anodized oxide films.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.152-152
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• 2016

Anodizing is a technology to generate thicker and high-quality films than natural oxide films by treating metals via electrochemical methods. It is a technique to develop metals for various uses, and extensive research on the commercial use has been performed for a long time. Aluminum anodic oxide (AAO) is generate oxide films, whose sizes and characteristics depending on the types of electrolytes, voltages, temperatures and time. Electrochemical manufacturing method of nano structure is an efficient technology in terms of cost reduction, high productivity and complicated shapes, which receives the spotlight in diverse areas. The sulfuric acid was used as an anodizing electrolyte, controlling its temperature to $10^{\circ}C$. The anode was 5083 Al alloy with dimension of $5(t){\times}20{\times}20mm$ while the cathode was the platinum. The distance between the anode and the cathode was maintained at 3 cm. Agitation was introduced by magnetic stirrer at 300 rpm to prevent localized temperature rise that hinders stable growth of oxide layer. In order to observe surface characteristics with applied current density, the electrolyte temperature, concentration was maintained at constant condition for $10^{\circ}C$, 10 vol.%, respectively. To prevent hindrance of stable growth of oxide layer due to local temperature increase during the experiment, stirring was maintained at constant rate. In addition, using galvanostatic method, it was maintained at current density of $10{\sim}30mA/cm^2$ for 40 minutes. The cavitation experiment was carried out with an ultrasonic vibratory apparatus using piezo-electric effect with modified ASTM-G32. The peak-to-peak amplitude was $30{\mu}m$ and the distance between the horn tip and specimen was 1 mm. The specimen after the experiment was cleaned in an ultrasonic, dried in a vacuum oven for more than 24 hours, and weighed with an electric balance. The surface damage morphology was observed with 3D analysis microscope. As a result of the investigation, differences were observed surface hardness and anti-cavitation characteristics depending on the development of oxide film with applied current density.

• Journal of the Korean institute of surface engineering
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• v.35 no.3
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• pp.149-157
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• 2002

Spectral emissivity depends on the surface conditions of the materials. The mechanisms that affect the spectral emissivity in anodic oxide films on aluminum were investigated. The aluminum specimens were anodized in a sulfuric acid solution and the thickness of the resulting oxide film formed changed with the anodizing time. FT-IR spectrum analysis identified the anodic oxide film as boehmite ($Al_2$$O_3$.$H_2$O). Both the infrared emisivity and reflectivity of the anodized aluminum were affected by the structure of the anodic oxide film because Al-OH and Al-O-Al have a pronounced absorption band in the infrared region of the spectrum. The presence of an anodic oxide film on aluminum caused a rapid drop in the infrared reflectivity. An aluminum surface in the clean state had an emissivity of approximately 0.2. However, the infrared emissivity rapidly increased to 0.91 as the thickness of the anodic oxide film increased.

• Journal of the Korean institute of surface engineering
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• v.23 no.1
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• pp.34-43
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• 1990

Al-Si piston alloys such as AlS10CuMg have been anodized to examine apossibility of forming a hard film aat relatively higher temperatures compard with those in conventional sulfuric acid processes. Three types of electrolytes have been employed in this study ; electrolyte A(15% H2SO4, $0^{\circ}C$), electrolyte B(12% H2SO4, 1% oxalic, $10^{\circ}C$), electrolyte C(tartaric acid 125g/L+oxalic 75g/L+aluminum sulfate 225g/L, $25^{\circ}C$). Hard anodisine process in electrolyte B at a current density of 1.54A/dm2 produced a harder film of VHN 396 at a relatibely low film forming voltage compared with those obtained in other electrolyte at equivalent current density. A liner relationship between hardness and abrasion resistance exists for Al-Si piston alloys. The hardness of anodized film decreasees with increasing silicon content in Al-Si alloys and also with bath temperature. The film hardeness of Na-modified alloy os higher than that of P-modified alloy due to its finer microstructre. The film on the silicon phase in Al-Si alloys is observed to be formed by lateral growth of oxide film nucleated at surroundings.

• Korean Journal of Materials Research
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• v.11 no.1
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• pp.48-54
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• 2001

The effects of additives in the HCI etching solution on etching behaviors of aluminum foil as dielectric film for electrolytic capacitors were investigated. The etch pits formed in 1M hydrochloric acid containing ethylene glycol as an additive contain more fine and homogeneous etch tunnels compared to those in 1 M hydrochloric acid only, which led to the increase in the effective internal surface area of aluminum foil. After anodizing of aluminum foil etched in etching solutions, the LCR meter results have shown that the capacitance of dielectric film etched in hydrochloric acid with ethylene glycol was increased remarkably compared to that etched in hydrochloric acid only.