• Journal of Conservation Science
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• v.27 no.2
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• pp.135-144
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• 2011

When metal artifacts have to undergo conservation treatment, the person in charge of the treatment selects and uses various coating mixtures based on his judgment regarding their condition, material, or environment. Since the kinds of coating mixtures or solvents make a difference in the set time of cyanoacrylate adhesives, they have something to do with the efficiency of the conservation treatment. This study examines the effects and causes that affect the set time of cyanoacrylate adhesives according to the kinds of coating mixtures and solvents and suggests ways to increase the set time. As a result, it is thought that as the surface roughness gets flatter, the wettability of adhesive is improved further, which increases the set time. Moreover, the C-F binding of V-Flon, C-O-C absorption peak, molecular weight of the coating mixtures, and glass transition temperature (Tg) were the factors that significantly affected the set time. According to the result of measuring the set time based on the result of superficial and chemical analysis, relative difference was shown according to the kind and viscosity of adhesive, but all the adhesives indicated the following order of the set time: V-Flon > Paraloid B-72 (in xylene) > Paraloid NAD-10 > Paraloid B-72 (in acetone).

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.5
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• pp.297-305
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• 2006

The thermal ratcheting deformation at the reactor baffle and upper internal structure of the liquid metal reactor (LMR) can occur due to movement of the hot sodium free surface. In in-service inspection of reactor internals of LMR, a new inspection technique should be developed for the detection of the thermal ratcheting damage. In this study, an inspection technique using ultrasonic guided wave is proposed for the detection of the thermal ratcheting damage of cylindrical vessels. A 316L stainless steel cylindrical shell specimen has been prepared. The thermal ratchet structural tests were cyclically performed by heat-up up to $550^{\circ}C$ with steep temperature gradients along the axial direction after cool-down by cooling water. Ultrasonic guided wave propagation has been characterized by analysis of dispersion curve of the stainless steel plate. The zero-order antisymmetric $A_0$ guided wave has been selected as the optimal mode for detection of the ratcheting deformation. It is confirmed that the thermal ratcheting deformation can be detected by the measurement of transit time difference of circumferentially propagated $A_0$ guided waves.

• Clean Technology
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• v.13 no.4
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• pp.266-273
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• 2007

The adsorption properties of the activated carbon-based adsorbents were studied to remove COS emitted from $SO_2$ catalytic reduction process on the integrated gasification combined cycle (IGCC) system in this work. Transition metal supported catalysts and mixed metal oxide catalysts were used for the $SO_2$ catalytic reduction. The mechanism of COS produced from the $SO_2$ reduction and the COS concentration s according to the reaction temperature were investigated. In this study, an activated carbon and a modified activated carbon doped with KOH were used to remove the very low concentration of COS effectively. The adsorption rate and the breakthrough time of COS were measured by a thermo gravity analyzer (TGA, Cahn Balance) and a fixed bed flow reactor equipped with GC-pulsed flammable photometric detector (PFPD), respectively. It was confirmed that the COS breakthrough time of the activated carbon doped with KOH was longer than that of an activated carbon. In conclusion, the modified-activated carbon having a high surface area showed a high adsorption rate of COS produced from the $SO_2$ reduction.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.7-12
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• 2003

The $Bi_{3.3}La_{0.7}O_{12}$(BLT) capacitors with Metal-Ferroelectric-Insulator-Silicon structure were prepared on $SiO_2/Si$ substrates by using sol-gel method. The BLT thin films annealed at $650^{\circ}C$ and $700^{\circ}C$ showed randomly oriented perovskite crystalline structures. The full with at half maximum (FWHM) of the (117) main peak was decreased from $0.65^{\circ}$ to $0.53^{\circ}$ with increasing the annealing temperature from $650^{\circ}C$ to $700^{\circ}C$, indicating the improvement in the crystalline quality of the film. In addition, the grain size and $R_rms$ , values were increased with increasing the annealing temperatures, showing the rough film surface at higher annealing temperatures. From the capacitance-voltage (C-V) measurements, the memory window voltage of the BLT film annealed at $700^{\circ}C$ was found to be about 0.7 V at an applied voltage of 5 V. The leakage current density of the BLT film annealed at $700^{\circ}C$ was about $3.1{\times}10^{-8}A/cm^2$.

• Journal of the Korean Chemical Society
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• v.28 no.6
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• pp.374-383
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• 1984

In order to elucidate the effect of alkali promoter on chemisorption of carbon monoxide on silica supported transition metal catalysts we have investigated the infrared spectra for carbon monoxide chemisorbed on silica supported nickel with and without potassium coating within the frequency range of 1800 ~ 2100cm$^{-1}$ at various nickel concentrations and CO pressures. For the system without potassium coating the IR band intensities are found to greatly depend on the nickel conwgfra concentration although the band positions are scarcely affected. The band positions are nearly coincident with those reported by other people, but we have clarified that the 2057cm$^{-1}$ band arises from Ni(CO)$_4$ molecules physisorbed on silicagel. Besides this, the effect of temperature on CO chemisorption has also been investigated. On coating with potassium we have found that all the bands observed for the system without potassium coating suffer red shifts by 2 ~ 10cm$^{-1}$ and the formation of Ni(CO)$_4$ is inhibited. Furthermore, we have recognized that on the nickel surface with potassium coating a disproportionation may occur to yield carbon dioxide molecules.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.12
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• pp.1063-1069
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• 2012

In present paper, we used magnesium alloy having a lower density and higher electrical conductivity for bipolar plate to reduce the weight of PEM fuel cell. The silver was coated to prevent corrosion and form passivation film on the metal surface with sputtering. In acid proof evaluation for setting optimal coating conditions, the homogeneity of coating thickness was improved by coating with the thickness of 3 ${\mu}m$ which not indicated any micro cracks and the temperature $180^{\circ}C$. The performance test and evaluation based on the clamping pressure and channel depth to determine the configuration of bipolar plate for assembling single cell was implemented. And then we assembled single cell with this bipolar plate and implemented the performance test to ensure and compare the current-voltage performance followed as several factors such as coating or non-coating, the change of clamping pressure, the change of channel depth, etc. As these results, the maximum power density of single cell with the coated bipolar plate was 192 $mW/cm^2$ and it was confirmed that the power density per unit mass was better than existing metal bipolar plate.

• Korean Journal of Materials Research
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• v.29 no.2
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• pp.92-96
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• 2019

Transition metal oxide is widely used as a water electrolysis catalyst to substitute for a noble metal catalyst such as $IrO_2$ and $RuO_2$. In this study, the sol-gel method is used to synthesize the $Cu_xCo_{3-x}O_4$ catalyst for the oxygen evolution reaction (OER),. The CuxCo3-xO4 is synthesized at various calcination temperatures from $250^{\circ}C$ to $400^{\circ}C$ for 4 h. The $Cu_xCo_{3-x}O_4$ synthesized at $300^{\circ}C$ has a perfect spinel structure without residues of the precursor and secondary phases, such as CuO. The particle size of $Cu_xCo_{3-x}O_4$ increases with an increase in calcination temperature. Amongst all the samples studied, $Cu_xCo_{3-x}O_4$, which is synthesized at 300?, has the highest activity for the OER. Its onset potential for the OER is 370 mV and the overpotential at $10mA/cm^2$ is 438 mV. The tafel slope of $Cu_xCo_{3-x}O_4$ synthesized at $300^{\circ}C$ has a low value of 58 mV/dec. These results are mainly explained by the increase in the available active surface area of the $Cu_xCo_{3-x}O_4$ catalyst.

• Korean Journal of Materials Research
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• v.1 no.3
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• pp.168-174
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• 1991

Ti-silicide was deposited by sputtering the composite target($TiSi_{2.6}$) on single-Si wafers and oxide on them. The heat treatment temperatures by rapid thermal annealing(RTA) have been varied in the range of $600-850^{\circ}C$ for 20seconds. It was not until RTA temperature was $800^{\circ}C$ that a stable $TiSi_2$ was formed, and the value of resistivity of that phase was $27~29{\mu}{\Omega}-cm$, which seems a little higher than that formed by the reactive method. The result of x-ray diffraction peals showed that till $750^{\circ}C$, C49 $TiSi_2$ phase was dominant, but at $800^{\circ}C$, at last, the phase was transformed into a stable C54 $TiSi_2$ phase. And, the result of x-ray photoeletron spectroscopy(XPS) measurements showed that the composition ratio of Ti and Si was 2 1 in the case of specimens treated at $800^{\circ}C$, The surface roughness of $TiSi_2$, which was condidered a weak point, was improved to a superior value of $17{\pm}1nm$, therefore increasing the possibility of applying $TiSi_2$ to semiconductor devices.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.482-489
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• 2020

This study conducted a prototype development and evaluation by performing die-casting mold design, mold manufacturing, and injection condition optimization based on flow and solidification analysis to meet the needs of the coupling parts produced by die casting. Through flow analysis, the injection conditions suitable for 100% filling in the cavity were found to be a molten metal temperature of 670 ℃, injection speed of 1.164 m/s, and filling pressure of 6.324~18.77 MPa. In addition, solidification close to 100 % occurred in all four cavities when the solidification rate was 69.47 %. A defect inspection on the surface and inside the product revealed defects, such as poor molding and pores. In addition, the dimensions of the injected product were within the target tolerance and showed good results. Through the feedback of the results of flow and solidification analysis, it was possible to optimize the mold design, and the injection optimization conditions were confirmed to be a total cycle time of approximately 6.5 seconds. Good quality carrier parts with an average surface hardness of approximately 45 mm from the gate measured at 97.48(Hv) could be produced.

• Journal of Korean Society of Steel Construction
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• v.28 no.5
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• pp.373-382
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• 2016

Painting or thermally sprayed metal coating is often used in corrosion protection of steel structures. In recently, duplex coating system which combines thermally sprayed metals with paint is selected as a new generic type of coatings on steel structures under the highly corrosive environments. In this study, the structural steel specimens were surface treated, thermally sprayed with zinc, zinc-15%aluminum alloy, aluminum and aluminum-5%magnesium alloy, and finally sealing or painted with acrylic urethane. And as a reference specimens, steel specimens were painted with acrylic urethane after surface treatment. Circular defects with 1.0, 3.0 and 5.0 mm in diameters and line defect with 2.0 mm width, which reach the steel substrate were created on all specimens. The specimens were exposed into an environmental testing chamber controlled by the ISO 20340, which is a laboratory cyclic accelerated exposure test condition of spraying/UV/low temperature, for up to 175 days. Based on the corrosion tests, corrosion deterioration from the initial defects were evaluated and weathering performance of the specimens are compared.