• Journal of Powder Materials
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• v.15 no.2
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• pp.95-100
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• 2008

The investigation is to modify the mechanical and chemical properties of Mg alloys using a combination of rapid solidification and surface treatment. As the first approach, $Mg_{95}Zn_{4.3}Y_{0.7}$ was gas atomized and pressure sintered by spark plasma sintering process (SPS), showing much finer microstructure and higher strength than the alloys as cast. Further modification was performed by treating the surface of PM Mg specimen using Plasma electrolytic oxidation (PEO) process. During the PEO processing, MgO layer was initiated to form on the surface of Mg powder compacts, and the thickness and the density of MgO layer were varied with the reaction time. The thickening rate became low with the reaction time due to the limited diffusion rate of Mg ions. The surface morphology, corrosion behavior and wear resistance were also discussed.

• Journal of Microbiology and Biotechnology
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• v.25 no.8
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• pp.1299-1306
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• 2015

This study aims to investigate the mechanism of action of the cinnamon bark essential oil (CB), when used singly and also in combination with piperacillin, for its antimicrobial and synergistic activity against beta-lactamase TEM-1 plasmid-conferred Escherichia coli J53 R1. Viable count of bacteria for this combination of essential oil and antibiotic showed a complete killing profile at 20 h and further confirmed its synergistic effect by reducing the bacteria cell numbers. Analysis on the stability of treated cultures for cell membrane permeability by CB when tested against sodium dodecyl sulfate revealed that the bacterial cell membrane was disrupted by the essential oil. Scanning electron microscopy observation and bacterial surface charge measurement also revealed that CB causes irreversible membrane damage and reduces the bacterial surface charge. In addition, bioluminescence expression of Escherichia coli [pSB1075] and E. coli [pSB401] by CB showed reduction, indicating the possibility of the presence of quorum sensing (QS) inhibitors. Gas-chromatography and mass spectrometry of the essential oil of Cinnamomum verum showed that trans-cinnamaldehyde (72.81%), benzyl alcohol (12.5%), and eugenol (6.57%) were the major components in the essential oil. From this study, CB has the potential to reverse E. coli J53 R1 resistance to piperacillin through two pathways; modification in the permeability of the outer membrane or bacterial QS inhibition.

• Journal of Surface Science and Engineering
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• v.49 no.3
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• pp.286-300
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• 2016

Pd-Ag alloy membranes have attracted a great deal of attention for their use in hydrogen purification and separation due to their high theoretical permeability, infinite selectivity and chemical compatibility with hydro-carbon containing gas streams. For commercial application, Pd-based membranes for hydrogen purification and separation need not only a high perm-selectivity but also a stable long-term durability. However, it has been difficult to fabricate thin, dense Pd-Ag alloy membranes on a porous stainless steel metal support with surface pores free and a stable diffusion barrier for preventing metallic diffusion from the porous stainless steel support. In this study, thin Pd-Ag alloy membranes were prepared by advanced Pd/Ag/Pd/Ag/Pd multi-layer sputter deposition on the modified porous stainless steel support using rough polishing/$ZrO_2$ powder filling and micro-polishing surface treatment, and following Ag up-filling heat treatment. Because the modified Pd-Ag alloy membranes using rough polishing/$ZrO_2$ powder filling method demonstrate high hydrogen permeability as well as diffusion barrier efficiency, it leads to the performance improvement in hydrogen perm-selectivity. Our membranes, therefore, are expected to be applicable to industrial fields for hydrogen purification and separation owing to enhanced functionality, durability and metal support/Pd alloy film integration.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.25-31
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• 2008

Recently risk management based on a quantitative assessment is considered to improve the level of safety in Korea. This paper focuses on the procedure of the quantitative risk assessment for natural gas pipelines. For that purpose, the methods to estimate failure frequency based on failure causes from European Gas Pipeline Incident Data Group and BG Transco, to analyze consequence caused by fire, and to calculate individual risk and societal risk have been proposed systematically in this paper. Risk criteria of individual risk and societal risk have been proposed by considering the environment of pipeline route in Korea. The proposed procedure of quantitative risk assessment may be useful for risk management during the planning and building stages of a new pipeline, and modification of buried pipeline.

• Polymer(Korea)
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• v.24 no.3
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• pp.299-305
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• 2000

In order to increase the thermal stability at high temperatures, new hybrid ceramic percursors were synthesized by chemical modification of polycarbosilane (PCS). The structure of hybrid ceramic percursors were investigated by using FT-IR and $^1$H-NMR spectrometers. The syntheses of hybrid ceramic precursors were confirmed by monitoring the change of the adsorption peaks appearing at 0893, 1092, 609 $cm^{-1}$ / on the FT-IR spectra, and also by the presence of peaks at 3.8, 2.0, 0.6 ppm on the $^1$H-NMR spectra. The conversion of hybrid ceramic percursor was around 74 and 10 wt% higher than that of the pure PCS. After the heat-treatment at 150$0^{\circ}C$, the crystalline peaks for $\beta$-SiC were observed at 2$\theta$=35.7, 42.2, 61.0$^{\circ}$ on the X-ray powder diffractogram. It showed the conversion of hybrid ceramic percursor to crystalline $\beta$-SiC.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.365-365
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• 2010

Similar to the superhydrophobic surfaces of lotus leaf, water strider leg is attributed to hierarchical structure of micro pillar and nano-hair coated with low surface energy materials, by which water strider can run and even jump on the water surface. In order to mimick its leg, many effort, especially, on the fabrication of nanohairs has been made using several methods such as a capillarity-driven molding and lithography using poly(urethane acrylate)(PUA). However most of those effort was not so effective to create the similar structure due to its difficulty in the fabrication of nanoscale hairy structures with hydrophobic surface. In this study, we have selected a low surface energy polymeric material of polytetrafluoroethylene (PTFE, or Teflon) assisted with surface modification of CF4 plasma treatment followed by hydrophobic surface coating with pre-cursor of hexamethyldisiloxane (HMDSO) using a plasma enhanced chemical vapor deposition (PE-CVD). It was found that the plasma energy and duration of CF4 treatment on PTFE polymer could control the aspect ratio of nano-hairy structure, which varying with high aspect ratio of more than 20 to 1, or height of over 1000nm but width of 50nm in average. The water contact angle on pristine PTFE surface was measured as approximately $115^{\circ}$. With nanostructures by CF4 plasma treatment and hydrophobic coating of HMDSO film, we made a superhydrophobic nano-hair structure with the wetting angle of over $160^{\circ}C$. This novel fabrication method of nanohairy structures has been applied not only on 2-D flat substrate but also on 3-D substrates like wire and cylinder, which is similarly mimicked the water strider's leg.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.54-54
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• 2010

Zinc oxide is metal oxide semiconductor with the 3.37 eV bandgap energy. Zinc oxide is very attractive materials for many application fields. Zinc Oxide has many advantages such as high conductivity and good transmittance in visible region. Also it is cheaper than other semiconductor materials such as indium tin oxide (ITO). Therefore, ZnO is alternative material for ITO. ZnO is attracting attention for its application to transparent conductive oxide (TCO) films, surface acoustic wave (SAW), films bulk acoustic resonator (FBAR), piezoelectric materials, gas-sensing, solar cells and photocatalyst. In this study, we synthesized ZnO nanoparticles and defined their physical and chemical properties. Also we studied about the application of ZnO nanoparticles as a photocatalyst and try to find a enhancement photocatalytic activity of ZnO nanorticles.. We synthesized ZnO nanoparticles using spray-pyrolysis method and defined the physical and optical properties of ZnO nanoparticles in experiment I. When the ZnO are exposed to UV light, reduction and oxidation(REDOX) reaction will occur on the ZnO surface and generate ${O_2}^-$ and OH radicals. These powerful oxidizing agents are proven to be effective in decomposition of the harmful organic materials and convert them into $CO_2$ and $H_2O$. Therefore, we investigated that the photocatalytic activity was increased through the surface modification of synthesized ZnO nanoparticles. In experiment II, we studied on the stability of ZnO nanoparticles in water. It is well known that ZnO is unstable in water in comparison with $TiO_2$. $Zn(OH)_2$ was formed at the ZnO surface and ZnO become inactive as a photocatalyst when ZnO is present in the solution. Therefore, we prepared synthesized ZnO nanoparticles that were immersed in the water and dried in the oven. After that, we measured photocatalytic activities of prepared samples and find the cause of their photocatalytic activity changes.

• Korean Journal of Materials Research
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• v.22 no.7
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• pp.362-367
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• 2012

Magnetite nanoparticles(NPs) have been the subject of much interest by researchers owing to their potential use as magnetic carriers in drug targeting and as a tumor treatment in cases of hyperthermia. However, magnetite nanoparticles with 10 nm in diameter easily aggregate and thus create large secondary particles. To disperse magnetite nanoparticles, this study proposes the infiltration of magnetite nanoparticles into hybrid silica aerogels. The feasible dispersion of magnetite is necessary to target tumor cells and to treat hyperthermia. Magnetite NPs have been synthesized by coprecipitation, hydrothermal and thermal decomposition methods. In particular, monodisperse magnetite NPs are known to be produced by the thermal decomposition of iron oleate. In this study, we thermally decomposed iron acetylacetonate in the presence of oleic acid, oleylamine and 1,2 hexadecanediol. We also attempted to disperse magnetite NPs within a mesoporous aerogels. Methyltriethoxysilicate(MTEOS)-based hybrid silica aerogels were synthesized by a supercritical drying method. To incorporate the magnetite nanoparticles into the hybrid aerogels, we devised two methods: adding the synthesized aerogel into a magnetite precursor solution followed by nucleation and crystal growth within the pores of the aerogels, and the infiltration of magnetite nanoparticles synthesized beforehand into aerogel matrices by immersing the aerogels in a magnetite nanoparticle colloid solution. An analysis using a vibrating sample magnetometer showed that approximately 20% of the magnetite nanoparticles were well dispersed in the aerogels. The composite samples showed that heating under an inductive magnetic field to a temperature of $45^{\circ}C$ is possible.

• Journal of the Korean Institute of Gas
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• v.16 no.4
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• pp.1-7
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• 2012

Systematic safety research by Korea Government has been made to enhance the safety of CNG (compressed natural gas) vehicles since the burst of compressed cylinder of an urban bus in August 9, 2010. This article summarizes some major activities to ensure the safety of CNG vehicles, which covers review of regulation, safety management system including standard of inspection and certification, and training program of inspectors and car mechanics. Specifically, the followings were reviewed; type of CNG cylinder, location of CNG cylinder, material and type of fuel line and vent line, modification of pipeline connection, installation of gas detector, installation of emergency shutdown valve, installation of protecting cover for cylinder, obligations for CNG vehicle filling station. improving periodical inspection, routine test on gas vehicles, training program for engaged in gas vehicles, and designation of safety manager for CNG bus company. This paper suggests how to improve safety of CNG vehicles as a result of review of above mentioned check items.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.26 no.1
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• pp.41-58
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• 2000

Recently the harmfulness of W radiation is in creasing due to encironmental pollution. Environmental population may also play a role in global decrease of ozone layer, A major consequence of ozone depletion is increase in solar ultra violet radiation received at the earth's surface excessive exposure to W radiation cause a lot of problems in our skin. Plant extract that possess antioxidative activities has been reported to retard the oxidation process in product to which they have been added. Plant are alived under solar light. So it is expect the plants have so many protection mechanisms and UV absorbent ingredients against ultra violet radiation such as UVB, UVA. Plant extract which were flavonoids, alkaloids and others could be transformed into UV absorber by chemical modification. Therefore with the aim of finding alternative natural absorber that can safely be used in cosmetic, we have screened various extract for their UV absorbent effect. Thus, the cosmetic safety against human skin, antimicrobial effects and others could be improved by using the silicon.