• Journal of the Korean institute of surface engineering
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• v.49 no.1
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• pp.1-13
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• 2016

This review deals with one of the surface modification techniques, chemical conversion coating and particularly cerium-based conversion coatings (CeCC) as a promising substitute for chromium and phosphate conversion coating on magnesium and its alloys. The CeCCs are commonly considered environmentally friendly. The effects of surface preparation, coating thickness, bath composition, and e-paint on the corrosion behavior of CeCCs have been studied on the AZ31 magnesium alloy. This review also correlates the coating microstructural, morphological, and chemical characteristics with the processing parameters and corrosion protection. Results showed that the as-deposited coating system consists of a three layer structure (1) a nanocrystalline MgO transition layer in contact with the Mg substrate, (2) a nanocrystalline CeCC layer, and (3) an outer amorphous CeCC layer. The nanocrystalline CeCC layer thickness is a function of immersion time and cerium salt used. The overall corrosion protection was crucially dependent on the presence of coating defects. The corrosion resistance of AZ31 magnesium alloy was better for thinner CeCCs, which can be explained by the presence of fewer and smaller cracks. On the other hand, maximum corrosion protection was achieved when AZ31 magnesium samples with thin CeCCs are e-painted. The e-paint layer further restricts and hinders the movement of chloride and other aggressive ions present in the environment from reaching the magnesium surface.

• Journal of Environmental Science International
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• v.5 no.4
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• pp.441-451
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• 1996

The surface meteorological and upper layer meteorological observation carried out to investigate influences of sea breeze effect on lower layer atmosphere at Gori nuclear power plant for 29∼30 July, 1996. According to surface meteorological data, the inflow of sea breeze was occurred 11:30 on 29 July, 10:30-on 30 July, respectively, at observation site. And the meteorological tower data showed that wind direction of sea breeze was identified as south-westerly, and wind speed of 58 m was 2 times stronger than that of 10 m. It is notworthy that surface inversion layer which built from the night time to daybreak of next day was not broken off by seab reeze's inflow for daytime, and strong inversion layer observed at 47∼243 m with moderately stable class (F) by URC. It was found that strong stable layer of potential temperature appeared at that layer, maximum relative humidity observed at the bottom of inversion layer and maximum mixing ratio observed in the low of inversion layer.

• Korean Journal of Materials Research
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• v.24 no.12
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• pp.682-688
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• 2014

Physical and chemical changes in a polished wafer and in $2.5{\mu}m$ & $4{\mu}m$ epitaxially grown Si layer wafers (Epilayer wafer) after surface treatment were investigated. We characterized the influence of surface treatment on wafer properties such as surface roughness and the chemical composition and bonds. After each surface treatment, the physical change of the wafer surface was evaluated by atomic force microscopy to confirm the surface morphology and roughness. In addition, chemical changes in the wafer surface were studied by X-ray photoemission spectroscopy measurement. Changes in the chemical composition were confirmed before and after the surface treatment. By combined analysis of the physical and chemical changes, we found that diluted hydrofluoric acid treatment is more effective than buffered oxide etching for $SiO_2$ removal in both polished and Epi-Layer wafers; however, the etch rate and the surface roughness in the given treatment are different among the polished $2.5{\mu}m$ and $4{\mu}m$ Epi-layer wafers in spite of the identical bulk structural properties of these wafers. This study therefore suggests that independent surface treatment optimization is required for each wafer type, $2.5{\mu}m$ and $4{\mu}m$, due to the meaningful differences in the initial surface chemical and physical properties.

• Journal of Environmental Science International
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• v.10 no.6
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• pp.417-422
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• 2001

The vertical structure of atmosphere was observed In investigate the variation of surface ozone concentration by vertical downward mixing of residual ozone in the atmospheric boundary layer at the Busan coastal area. Airsonde and pilot balloon measurements were made at Gamcheondong and the Kimhae airport for April 26~27, 1996. The vertical potential of potential temperature showed a residual layer between 510m and 1800m from 2100LST April 26 to 0900LST April 27. The downward mixing of ozone in the residual layer of the atmospheric boundary layer was confirmed from vertical profile of mixing ratio near 600m in the morning. The thickness of the sea breeze layer was 900m at 1500LST April 26. Thereafter, it become to be lowered with time A low level jet was measured near 900m at 0300LST on April 27 from a pibal measurement. Early morning sharp increase of surface ozone concentration at the Busan coastal area was caused by vertical downward mixing of ozone concentration rather than by photochemical reaction In the atmospheric boundary layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.274-274
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• 2013

We fabricate encapsulation-layer of OLED panel from organic-inorganic hybrid thin film by atomic layer deposition (ALD) molecular layer deposition (MLD) using Al2O3 as ALD process and Adipoyl Chloride (AC) and 1,4-Butanediamine as MLD process. Ellipsometry was employed to verify self-limiting reaction of MLD. Linear relationship between number of cycle and thickness was obtained. By such investigation, we found that desirable organic thin film fabrication is possible by MLD surface reaction in monolayer scale. Purging was carried out after dosing of each precursor to eliminate physically adsorbed precursor with surface. We also confirmed roughness of the organic thin film by atomic force microscopy (AFM). We deposit AC and 1,4-Butanediamine at $70^{\circ}C$ and investigated surface roughness as a function of increasing thickness of organic thin film. We confirmed precursor's functional group by IR spectrum. We calculated WVTR of organic-inorganic hybrid super-lattice epitaxial layer using Ca test. WVTR indicates super-lattice film can be possibly use as encapsulation in flexible devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.316-316
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• 2014

Two different transparent conducting oxide (TCO) layers of Al-doped ZnO (AZO) and $WO_3$ were prepared by a rf sputtering process. Working pressure, deposition time, and target-to-substrate distance were varied for the sputtering process to improve electrical properties of the resulting layer. Thickness of the TCO layers was measured by a profile meter of ${\alpha}$-step. To evaluate the electrical conductivity, surface resistivity of the TCO layers was measured by a four-point probe technique. Decrease of the working pressure resulted in increase of deposition rate and decrease of surface resistivity of the resulting layer. Increase of the layer thickness due to increased deposition time resulted in decrease of surface resistivity of the resulting layer. The shorter the target-to-substrate distance was, the lower was the surface resistivity of the resulting layer.

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.813-819
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• 2001

The microstructure and the distribution of hardness of Co and A1 alloy powder cladding layer in high carbon 9CrSi alloy steel for roll materials cladded by laser surface cladding were investigated. And, for the evaluation of soundness as the roll materials, we examined the wear resistance of the cladding materials with the wear appratus of pin on disc type. The experimental results showed that the microstructure of laser cladding layer was constituted with the clad surface layer, the alloy layer, the heat treatment layer with base metal. The wear resistance of Ni alloy Powder cladding material was superior to that of Co alloy powder cladding material both at the low speed (0.46m/s) and the high speed(0.92m/s). It seemed that the behavior of wear showed the abrasive wear at the early stage and the adhesive wear at the late stage.

• Journal of the Korean institute of surface engineering
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• v.48 no.6
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• pp.349-353
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• 2015

In this paper, arc thermal spray coating was conducted onto the SS400 steel using Inconel 625 wires in order to improve the durability of marine steel structures, and then investigated cavitation damage behavior of Inconel 625 coating layer in sea water. For the Inconel 625 coating layer, surface hardness appeared similar to that of existing high velocity oxy-fuel coating technology with 380~480 HV, but the porosity of about 6 % was larger relatively. During the cavitation experiment, pit damages were originated and grown at the rough surface and pore defect area of Inconel 625 coating layer. And, after the 72 hours of experimental time, weight loss of Inconel 625 coating layer exhibited gradually increasing tendency due to surface damage effect of the undercut.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.10
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• pp.492-498
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• 2006

A novel surface plasmon resonance(SPR) multisensing method, which does not require imaging apparatus such as CCD, has been proposed and implemented experimentally. The proposed method is based on the multichannel SPR and the separation of signals by use of additional layers whose thickness is controlled. SPR signals are influenced by the thickness of sensing layer as well as the optical condition of sensing surface. As the SPR signals from different ligands are usually positioned closely, the reflected light from sensing surface does not provide us with the clear differences of resonance signal depending on the kinds of ligands. It was found from our experiments that SPR signals from each ligand that is located on the additional layer with different thickness can be separated clearly enough to identify various signals from different ligands. Proposed method with theoretical design and simulation has been verified experimentally by using $SiO_2$ thin film layer as additional layer.

• Journal of Powder Materials
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• v.19 no.3
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• pp.196-203
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• 2012

$TiO_2$ was successfully formed on a Ti specimen by MAO (Micro-Arc-Oxidation) method treated in $Na_3PO_4$ electrolyte. This study deals with the influence of voltage and working time on the change of surface microstructure and phase composition. Voltage affected the forming rate of the oxidized layer and surface microstructure where, a low voltage led to a high surface roughness, more holes and a thin oxidized layer. On the other hand, a high voltage led to more dense surface structure, wider surface holes, a thick layer and fewer holes. Higher voltage increases photocatalytic activity because of better crystallization of the oxidized layer and good phase composition with anatase and rutile $TiO_2$, which is able to effectively separate excited electrons and holes at the surface.