• Journal of the Korean Chemical Society
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• v.45 no.5
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• pp.429-435
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• 2001

The monomer N,N'-bis(2-pyrrol-1-yl-propyl)-4,4'-bipyridine(bpb) was electrochemically polymerized on the glassy carbon electrode surface, which was modified with 1:1 ratio of erichrome black T(EBT) and glutathione(GSSG) to give a type of GC/poly-bpb, EBT, GSSG electrode for depositing Zn(II). The diffusion coefficients of the incorporated ions were 2.43${\times}10^{-15}$ and 9.14${\times}10^{-15} cm^2s^{-1}$ before taking Zn(II) ions and after them respectively. The modified electrodes are stable at the electrode process. The polymerized poly-bpb of 2.83${\times}10^4gmol^{-1}$ can deposit 2.15${\times}10^4gmol^{-1}$ of Zn(II). The number of pumping ions involving in the redox procedure at 0.77 V was 81.7% of the captured 180 ions into the polymer matrix, which was 3 times larger than that of the electrode modified with EBT alone.

• Journal of Technology Innovation
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• v.8 no.2
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• pp.19-65
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• 2000

This study analyzes the development of technological infrastructure(TI) and technological infrastructure policy(TIP) to enhance the technological capabilities of small and mid-sized manufacturing enterprises(SMEs) in the U.S. and Korea in terms of the technological system(TS) concept, which is composed of technological infrastructure, industrial organization, and institutional infrastructure. In order to analyze the internal dynamics of the system, such as incentive mechanisms, the interaction among economic actors, and the policy implementation process, we compare the MEP(Manufacturing Extension Partnership) system of the U.S. and the Joong-Jin-Gong system of Korea. Among many similarities, contrasts, and insights from each country's effort to construct TI and TS, the main findings are as follows. (1) Both the MEP system and the Joong-Jin-Cong system are TI-led or government-led type TS. However, the nation-wide picture is different: in the U.S., most TSs including the MEP system., are classified as TI-led type; in Korea, many TI-assisted or private sector-led TSs have been developed since the early 1960s. (2) the MEP system, as a representative case of the U.S., is less stable than the Joong-Jin-Gong system of Korea in terms of financing and political cycle. (3) The MEP system is a more complex and cooperative network than the Joong-Jin-Gong system. NIST, as a critical mass, generates the system, bridges various institutions, and influences the development of the system by providing funding. (4) Regarding TI components, TSs in both countries focus on utilizing off-the-shelf technologies rather than advanced technologies. However, the direction of movement is different: in the U.S., TSs have come to emphasize existing technologies to counterbalance an innovation system that has been highly focused toward new technologies; in Korea, TSs have been moving from focusing on a higher diffusion rate of imported process technologies to stressing new technology development. (5) Personnel and staffing, embodying technological capability, is an important concern in both countries. But the human capital infrastructure of the U.S. system is more efficient and industry-oriented than that of the Korean system due to a more flexible labor market. (6) While the U.S. has a strong tradition of state and local autonomy in constructing TI and TS to fit SMEs's specific need, Korea has a centralized and bureaucratically-led policy implementation process.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.5
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• pp.271-277
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• 2004

Zr-xNb alloys (x = 0.2, 0.8, 1.5 wt.%) were prepared to study the characteristics of the phase transformation in Zr-Nb system. The samples were heat treated at ${\beta}$-temperature ($1020^{\circ}C$) for 20 min and then cooled with different cooling rate. The microstructures of the specimens having the same compositions were changed with cooling rate and Nb content. The Widmanst$\ddot{a}$tten structure was observed on the furnace-cooled sample. The relationship between ${\alpha}$-Widmanst$\ddot{a}$tten and ${\beta}$-phase was the {0001}${\alpha}$//{110}${\beta}$, <11$\bar{2}$0>//<111>. The ${\beta}$-phase in Widmanst$\ddot{a}$tten structure of Zr-Nb alloys containing Nb more than solubility limit was identified as ${\beta}_{Zr}$ phase which was a stable phase at high temperature. In the water quenched samples, two kinds of martensite structures were observed depending on the Nb-concentration. The lath martensite was formed in Zr-0.2, 0.8 wt.% Nb alloys and the plate martensite having twins was formed in Zr-1.5 wt.% Nb alloy.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.331-335
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• 1999

The transition metal oxides have been of interest as bifunctional electrocatalysts for bifunctional air electrodes. The amorphous citrate precursor (ACP) process has been optimized to prepare perovskite (La0.6Ca0.4CoO3) and pyrochlore (Pb2Ru2O6) powders with high surface area, and consequent improvement of The electrocatalytic performance in an air electrode with thermal treatment. PTFE -bonded gas diffusion electrodes loaded with perovskitc and pyrochlore catalysts showed good bifunctional performances. The electrodes were fairly stable up to 100 hour in the galvanostatic mode at ${\pm}25mA/cm^2$, from which these electrodes offer promise as practical bifunctional air electrodes.

• Membrane Journal
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• v.22 no.6
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• pp.424-434
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• 2012

In this study, a ceramic membrane was prepared by CVD. Tube type alpha alumina support was used for substrate and added the Ga salt in intermediate layer. Synthesized method was counter diffusion CVD method at $650^{\circ}C$ with tetramethylorthosilane (TMOS). Gas permeation was measured at $600^{\circ}C$ using single-component $H_2$, $N_2$, $CO_2$ and $CH_4$. During the steam treatment, $H_2/N_2$ permselectivity of non-Ga silica membrane was decreased 926 to 829 at $600^{\circ}C$. On the other hand $H_2/N_2$ permselectivity of added Ga silica membrane was stable 910 to 904 at $600^{\circ}C$. These results show that the metal-doped membranes improved steam stability for gas separation.

• Korean Journal of Materials Research
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• v.13 no.2
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• pp.126-132
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• 2003

In order to evaluate the corrosion resistance at the anode side separator for molten carbonate fuel cell, STS316 and SACC-STS316 (chromium and aluminum were simultaneously deposited by diffusion into STS316 authentic stainless steel substrate by pack-cementation process) were applied as the separator material. In case of STS316, corrosion proceeded via three steps ; a formation step of corrosion product until stable corrosion product, a protection step against corrosion until breakaway occurs, a advance step of corrosion after breakaway. Especially, STS316 would be impossible to use the separator without suitable surface modification because of rapid corrosion rate after formation of corrosion product, occurs the severe problem on stability of cell during long-time operation. Whereas, SACC-STS316 was showed more effective corrosion resistance than the present separator, STS316 due to the intermetallic compound layer such as NiAl, Ni3Al formed on the surface of STS316 specimen. And it is anticipated that, in order to use SACC-STS316 alternative separator at the anode side, coating process, which can lead to dense coating layer, has to be developed, and by suitable pre-treatment before using it, very effective corrosion resistance will be achieved.

• Journal of Pharmaceutical Investigation
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• v.40 no.2
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• pp.91-100
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• 2010

The objective of this work is to study transdermal delivery of donepezil hydrochloride (DH) using iontophoresis and to evaluate various factors which affect the transdermal transport. After the flux study using 4 kinds of hydrogel, hydrogel containing 8% poly(ethylene oxide) (PEO) was chosen as the hydrogel for further studies. Under experimental condition, DH was stable. We have studied the effect of polarity, current density, drug concentration and current profile on transdermal flux and compared the results. In vitro flux study was performed at $33^{\circ}C$, using side-by-side diffusion cell and full thickness hairless mouse skin. DH is positively charged at pH 7.4, and anodal delivery was much larger than cathodal and passive delivery at all current densities studied (0.2, 0.4 and 0.6 mA/$cm^2$). Cathodal delivery showed higher flux than passive flux. Flux increased as the concentration of DH in hydrogel increased. Pulsatile application of current showed smaller flux value than the application of continuous current. Based on these results, we have evaluated the possibility of delivering enough amount of DH to reach the therapeutic level. The maximum cumulative amount of DH transported for 12 hours was 455 ${\mu}g/cm^2{\cdot}hr$ when the amount of DH in the hydrogel was 3 mg/mL and the current density was 0.4 mA/$cm^2$. If the patch size is 10 $cm^2$, then we can deliver 4.6 mg for 12 hours. Because the daily dosage of DH is 5 mg, it seems possible to deliver clinically effective amount of DH using iontophoresis. This study also provides some information about the role of electrorepulsion and electroosmosis during the transport through skin.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.129-129
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• 2018

Hard coating application is effective way of cutting tool for hard-to-machine materials such as Inconel, Ti and composite materials focused on high-tech industries which are widely employed in aerospace, automobile and the medical device industry also Information Technology. In cutting tool for hard-to-machine materials, high hardness is one of necessary condition along with high temperature stability and wear resistance. In recent years, high-entropy alloys (HEAs) which consist of five or more principal elements having an equi-atomic percentage were reported by Yeh. The main features of novel HEAs reveal thermodynamically stable, high strength, corrosion resistance and wear resistance by four characteristic features called high entropy, sluggish diffusion, several-lattice distortion and cocktail effect. It can be possible to significantly extend the field of application such as cutting tool for difficult-to-machine materials in extreme conditions. Base on this understanding, surface coatings using HEAs more recently have been developed with considerable interest due to their useful properties such as high hardness and phase transformation stability of high temperature. In present study, the nanocomposite coating layers with high hardness on WC substrate are investigated using high entropy alloy target made a powder metallurgy. Among the many surface coating methods, reactive magnetron sputtering is considered to be a proper process because of homogeneity of microstructure, improvement of productivity and simplicity of independent control for several critical deposition parameters. The N2 is applied to reactive gas to make nitride system with transition metals which is much harder than only alloy systems. The acceleration voltage from 100W to 300W is controlled by direct current power with various deposition times. The coating layers are systemically investigated by structural identification (XRD), evaluation of microstructure (FE-SEM, TEM) and mechanical properties (Nano-indenter).

• Journal of the Korean Ceramic Society
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• v.38 no.9
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• pp.787-793
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• 2001

$La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ membranes were fabricated by solid-state reaction. We investigated sintering behavior and oxygen permeation flux as a function of time-on-stream, temperature and upstream oxygen partial pressure. The oxygen was permeated at temperatures form 750$^{\circ}$C to 950$^{\circ}$C by mixed conducting through oxygen vacancy diffusion in the dense membrane. The oxygen permeation flux through the membrane were about 0.1ml/$cm^3{\cdot}$min at 850$^{\circ}$C. A constant time was required for reaching stable oxygen flux, and oxygen partial pressure affected the oxygen permeation fluxes.

• Journal of the Korean Solar Energy Society
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• v.32 no.4
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• pp.43-50
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• 2012

Metal-metal oxide (M-M oxide) cermet solar selective coatings with a double cermet layer film structure were deposited on the Al-deposited glass substrate by using a directed current (DC) magnetron sputtering technology. M oxide (CrO and ZrO) was used as the ceramic component in the cermets, and Cr and Zr used as the metallic components. In addition, black Cr (Cr-$Cr_2O_3$ cermet) solar selective coatings were deposited on the Ni-plated Cu substrate by using a electroplating method for comparison. The thermal stability tests were carried out for performance evaluation of solar coatings. Reflectance measurements were used to evaluate both solar absorptance(${\alpha}$) and thermal emittance (${\epsilon}$) of the solar coatings before and after thermal testing by using a spectrometer. Optical properties of optimized cermet solar coatings were ${\alpha}{\simeq}0.94-0.96$ and ${\epsilon}{\simeq}0.1$ ($100^{\circ}C$). The results of thermal stability test of M-M oxide solar coatings showed that the Cr-CrO cermet solar selective coatings were more stable than the Zr-ZrO cermet selective coatings at temperature of both $400^{\circ}C$ in air and $450^{\circ}C$ in vacuum. The black Cr solar selective coatings were degraded in air at temperature of $400^{\circ}C$. The main optical degradation modes of these coatings were diffusion of metal atoms, and oxidation.