• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.4
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• pp.123-129
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• 1998

Ceramic and CBN tools are available for the difficult-to -cut-materials such as hardened carbon tool steel. stainless steel and etc. Ceramic tools are suitable for continuous turning cut, not for intermittent milling cut. Ceramic tools are likely to be chipped and abruptly broken before the appearance of normal wear in turning. In this study, TiN coated ceramic tools were found to restrain the chipping, breaking and early fracture and to increase the critical cutting velocity owing to TiN coating in PVD method.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.581-584
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• 2006

The durability of reinforced concrete structures is severely degraded by mainly corrosion due to seawater attack and chloride ion diffusion in concrete. The deterioration of durability causes high repair cost for maintenance of marine concrete structure. In this paper, high-durability materials for prevention of rebar corrosion are investigated to promote the durability in marine concrete structures. For these, the effect of the mineral materials addition(SF, FA and BFS), the modified steel(stainless and coating steel). and corrosion inhibitors are compared.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.109-115
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• 2022

The demand for metal 3D printing technology is increasing in various industries. The materials commonly used for metal 3D printing include aluminum alloys, titanium alloys, and stainless steel. In particular, for applications in the aviation and defense industry, aluminum alloy 3D printing parts are being produced. To improve the corrosion resistance in the 3D printed aluminum alloy outputs, a post-treatment process, such as chromate coating, should be applied. However, powdered materials, such as AlSi7Mg and AlSi10Mg, used for 3D printing, have a high silicon content; therefore, a suitable pretreatment is required for chromate coating. In the desmut step of the pretreatment process, the chromate coating can be formed only when a smut composed of silicon compounds or oxides is effectively removed. In this study, suitable desmut solutions for 3D printed AlSi7Mg and AlSi10Mg materials with high silicon contents were presented, and the chromate coating properties were studied accordingly. The smut removal effect was confirmed using an aqueous desmut solution composed of sulfuric, nitric, and hydrofluoric acids. Thus, a chromate coating was successfully formed. The surfaces of the aluminum alloys after desmut and chromate coating were analyzed using SEM and EDS.

• Membrane Journal
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• v.6 no.2
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• pp.101-108
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• 1996

The oxidation/degradation efficiency of formic acid through the photoelectrochemical reaction has been investigated as a basic research in order to develope the process for degrading toxic organic compounds dissolved in water. A $TiO_{2}$ photoelectro-membrane reactor for purification of water, in which filtration as well as photoelectrocatalytic oxidation of organic compounds could be carried out simultaneously, was developed. Porous $SnO_{2}$ tubes prepared by slip casting and commercial porous stainless steel tubes, being electrically conductive, were used as not only supports but also working electrodes. The UV light with the wavelength of 365 nm was applied as a light source for photocatalytic reactions. The photoelectrocatatytic composite membranes were prepared by coating the support surface with the $TiO_{2}$ sol of pH 1.45. The oxidation efficiency of formic acid increased with the reaction time and the applied voltage, but was almost independent of the solution flux. The results showed that more than 90% of formic acid could he dograded at 27V using the $TiO_{2}$/stainless steel composite membrane, while about 77% in case of the $TiO_{2}/SnO_{2}$ Composite membrane. It was also concluded that the oxidation efficiencies of formic acid could be significantly improved by about 6~7 times by the photoelectrochemical reaction in comparison with those by the photocatalytic reaction only.

• Journal of Welding and Joining
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• v.21 no.4
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• pp.39-45
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• 2003

Nano-TiO$_2$ photocatalytic coatings were deposited on the stainless steel 304(50$\times$70$\times$3mm) by the APS(Atmospheric Plasma Spraying). Photocatlytic reaction was tested in MB(methylene blue) aqueous solution. For applying nano-TiO$_2$ powders by thermal spray, the starting nano-TiO$_2$ powder with 100% anatase crystalline was agglomerated by spray drying. Plasma second gas(H$_2$) flow rate and spraying distance were used as principal process parameters which are known to control heat enthalpy(heat input). The relationship between process parameters and the characteristics of microstructure such as the anatase phase fraction and grain size of the TiO$_2$ coatings were investigated. The photo-decomposition efficiency of TiO$_2$ coatings was evaluated by the kinetics of MB aqueous solution decomposition. It was found that the TiO$_2$ coating with a lower heat input condition had a higher anatase fraction, smaller anatase grain size and a better photo-decomposition efficiency.

• Journal of the Korean Vacuum Society
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• v.7 no.s1
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• pp.171-178
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• 1998

The microstructure and properties of plasma-sprayed coatings depend on a great number of spraying parameters, random factors, which lead to vibration in these spraying parameters, may in some degree influence the microstructure and properties of the coatings. Therefore, the property values appear certain distributions, and the description and comparison of the properties of plasma-sprayed coatings should be performed employing statistical analysis. In this paper, $Cr_3C_2$-Nicr coatings of different thickness were sprayed onto stainless steel using atmosphere plasma system and adopting three kinds of gun translation speeds. Then the microhardness measurements were performed on polished surface of the coatings. Forty readings were taken and statistically analyzed by calculating the characteristic values, estimating and comparing the means, and assessing whether they belonged to the Normal or Weibull Distribution. This study has found that statistical analysis could discriminate influence of spraying parameters and coating design on microhardness of the $Cr_3C_2$-Nicr coatings from random vibration, which showed that the microharness of the $Cr_3C_2$-Nicr coatings were related to gun translation speed coating thickness.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.460-465
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• 2013

Plate-shaped inorganic particles are coated onto a stainless steel substrate by the electrophoretic deposition of a precursor slurry which includes the inorganic particles of $Al_2O_3$ and polymer resin in mixed solvents to mimic the abalone shell structure, which is a composite of plate-shaped inorganic particles and organic interlayer binding materials with a layered orientation. The process parameters of the electrophoretic deposition include the voltage, coating time, and conductivity of the substrate. In addition, the suspension parameters are the particle size, concentration, viscosity, conductivity, and stability. We prepared an organic-inorganic composite coating with a high inorganic solid content by arraying the plate-shaped $Al_2O_3$ particles and electrophoretic resin via an electrophoretic deposition method. We analyzed the effect of the slurry composition and the electrophoretic deposition process parameters on the physical, mechanical and thermal properties of the coating layer, i.e., the thickness, density, particle orientation, Young's modulus and thermogravimetric analysis results.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.937-946
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• 1996

A Far Infrared Ray (FIR) dryer was designed , constructed and tested for red pepper , lycium chinese, and mushroom (Cortiellus shiitake ) drying , and the results were compared to the heated air dryer at the same condition. In the FIR dryer, three different panel materials , galvanized, copper and stainless steel, were used and no ceramic coating and those with ceramic coating (three panels) were 58% , 56%, 64%, and 88% , respectively. The drying times of lycium chinese and mushroom were shortened in FIR dryer by 6 hrs and 4 hrs compared to the heated air drying, respectively. while to remarkable difference in the drying times was found in the red pepper drying . The quality of products was better in FIR dryer where more red color value for red pepper and lycium chinese and more brightness for mushroom . The drying performance of a FIR dryer was superior in terms of total cost of 80,800 WON /100kg of lycium chinese , reduced by 25% compared to the heated air drying.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.6
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• pp.575-580
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• 2023

An electrode was prepared by dip-coating NiFe₂O₄ powder on stainless steel (SUS) support for the application in the alkaline water electrolysis. The prepared electrode was analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS), and was evaluated for the voltage properties with the change of current density in oxygen evolution reaction (OER) and hydrgen evolution reaction (HER) using 1, 3 and 7 M KOH solution. From the SEM and EDXS analysis, it was confirmed that the prepared electrode had NiFe₂O₄ on the SUS support. In OER and HER, the voltage in the 7 M KOH solution had a value of 1.35 and -1.90 V at 0.2 and -0.2 A/cm² of the current density, respectively. It was considered that the prepared electrode could be use as an electrode in the alkaline water electrolysis from the experimental results.

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.75-82
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• 2011

Five different composition UV-cured poly(urethane acrylate-co-acrylic acid) (PU-co-AA) films have been prepared by reacting isophorone diisocyanate(IPDI), polycaprolactone triol(PCLT), 2-hydroxyethyl acrylate(HEA), and different weight ratio trimethylolpropane triacrylate(TMPTA) and acrylic acid(AA) as diluents, and characterized using a Fourier transform infrared spectroscopy(FT-IR). The adhesion properties onto the stainless steel, morphology, mechanical hardness, and electrical property of UV-cured PU-co-AA films were investigated as a function of acrylic acid(AA) content. All the PU-co-AA films are structure-less and the molecular ordering and packing density decreased with increasing content of AA due to the flexible structure and -COOH side chains in AA. The crosscut test showed that PU-co-AA films without AA and with low content of AA showed 0% adhesion(0B) and the adhesion of PU-co-AA films in the range of 40-50% AA increased dramatically as the content of AA increases. The pull-off measurements showed that the adhesion force of PU-co-AA films to stainless steel substrate varied from 6 to 31 kgf /$cm^2$ and increased linearly with increasing AA content. The mechanical hardness also decreased as the content of AA increases. This may come from relatively linear and flexible structure in AA and low crystallinity in PU-co-AA films with higher content of AA. The higher AA-containing PU-co-AA films showed higher dielectric constant due to the increase of polarization by introducing AA monomer. In conclusion, the physical properties of UV-cured PU-co-AA films are strongly dependent upon the content of AA and the incorporation of AA in polyurethane acrylate is very useful way to increase the adhesion strength of UV-curable polymers on the stainless steel substrate.