• Journal of the korean society of oceanography
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• v.35 no.1
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• pp.16-33
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• 2000

In order to measure the vertical fluxes of particles and reactive radionuclides such as thorium and polonium isotopes, Dunbar-type sediment traps were freely deployed at the Ulleung Basin and in warm and cold water masses around the polar front of the East Sea. We estimated the ratios of the catched (F) to the predicted $^234$Th fluxes (P) using natural tracers pair $^234$Th-$^238$U. The F/P ratios are decreased with increasing water depth. Whereas the concentrations of suspended particles are homogeneous in water column, the mass fluxes are also decreased with increasing water depth like the F/P ratios. These facts indicate that organic matters of settling particles are destructed within the euphotic layer due to decomposition. Whereas regenerations of sinking particles are negligible in the cold water mass, about 80% of them are regenerated in the warm water mass during falling of large particles. These downward mass fluxes are closely correlated with their primary productions in euphotic zone. The activities of $^234$Th, $^228$Th and $^210$Po in the sinking material were increased with water depth. Because $^234$Th steadily produced in the water column are cumulatively adsorbed on the surface of sinking particles, vertical $^234$Th fluxes were observed to increase with water depth. Therefore, these sinking particles play important roles in transporting the particle reactive elements like thorium from surface to the deep sea. The scavenging processes including adsorption and settling reactions generate radio-disequilibrium between daughter and parent nuclides in water column. The activity ratios of $^234$Th/$^238$U and $^228$Th/$^228$Ra were observed to be < 1.0 in the surface water and approached to be equilibrium below the thermocline. The extent of the deficiency of daughter nuclides compared to the parents nuclide was highly correlated with the vertical particle flux. Because most of the $^210$Po in the surface water are scavenged on a labile phase and are recycled at sub-surface depths (< 200 m), the $^210$Po are always observed to be excess activities compared to $^226$Ra in surface water.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.226-232
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• 2000

Corrosion mechanisms by molten steel and slag were investigated in the zirconia/graphite composite as a material of submerged entry nozzle (SEN) using for producing high quality steel. Most of corrosions were started by the dissolution of zirconia particles into molten steel and oxidation of graphite, but subsequently three modes of corrosion were observed. Firstly, the penetration of slag into zirconia matrix was induced to the diffusion of stabilizing agent outward cubic zirconia grains, and the destabilization of cubic to fine monoclinic zirconia particles, which is enhanced to the decomposition and dissolution of them into slag. Secondly, molten slag penetrates into large cubic zirconia particles along grain boundary and decomposed them to fine cubic grains, which is also enhanced to the dissolution of zirconia grains into slag. Lastly, reaction between carbon and cubic zirconia was formed porous ZrC and enhanced the dissolution of it into slag.

• Journal of the Korean Society of Safety
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• v.24 no.3
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• pp.54-58
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• 2009

A substitute energy development has been required due to the exhaust of the fossil fuel and an environmental problem. Consequently, possible technologies producing hydrogen from water that does not release carbon is a very promising technology. Also, Iodine-Sulfur(IS) thermochemical water decomposition is one of the promising processes that are used to produce hydrogen efficiently using the high temperature gas-cooled reactor(HTGR) as an energy source that is possible to supply heat over 900$^{\circ}C$. In this study, to make a initiating events identification for the IS process, Master Logic Diagram(MLD) is used and 9 initiating events that cause a leakage of the chemical material are identified. Also, 6 events are identified among 9 initiating events above and are quantified using event tree.

• Korean Journal of Materials Research
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• v.21 no.8
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• pp.450-455
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• 2011

[ $Al_2TiO_5$ ]has a high refractive index and good solubility of the chromophore in the $Al_2TiO_5$ lattice, which allows this structure to be a good candidate for the development of new ceramic pigments. However, pure $Al_2TiO_5$ is well known to decompose on firing at $900{\sim}1100^{\circ}C$. However, this process can be inhibited by the incorporation of certain metal cations into its crystalline lattice. In this study, the synthesis of gray ceramic pigment was performed by doping cobalt on the $Al_2TiO_5$ crystal structure. The $Al_2TiO_5$ was synthesized using $Al_2O_3$ and $TiO_2$, and doped with $Co_3O_4$ as a chromophore material. In order to prevent the thermal decomposition during the cooling procedure, MgO was added to samples by 0.05 mole, 0.1 mole, and 0.15 mole as a stabilizer. The samples were fired at $1500^{\circ}C$ for 2 hours and cooled naturally. The crystal structure, solubility limit, and color of the synthesized pigment were analyzed using XRD, Raman spectroscopy, UV, and UV-vis. $Al_2O_3$ was available for the formation of $CoAl_2O_4$, which should also be considered in order to explain the small amount of this phase detected in the sample with the higher $Co^{2+}$ content (${\geq}$ 0.03 mole). It was found that the solubility limit of $Co^{2+}$ in the $Al_2TiO_5$ crystal was 0.02 mole% through an analysis of Raman spectroscopy. Through the addition of a pigment with 0.02 mole% of $Co^{2+}$ to lime-barium glaze, stabilized gray color pigments with 66.54, -2.35, and 4.68 as CIE-$L^*a^*b^*$ were synthesized.

• Journal of Powder Materials
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• v.24 no.6
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• pp.477-482
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• 2017

Nitrogen-doped titanium dioxide (N-doped $TiO_2$) is attracting continuously increasing attention as a material for environmental photocatalysis. The N-atoms can occupy both interstitial and substitutional positions in the solid, with some evidence of a preference for interstitial sites. In this study, N-doped $TiO_2$ is prepared by the sol-gel method using $NH_4OH$ and $NH_4Cl$ as N ion doping agents, and the physical and photocatalytic properties with changes in the synthesis temperature and amount of agent are analyzed. The photocatalytic activities of the N-doped $TiO_2$ samples are evaluated based on the decomposition of methylene blue (MB) under visible-light irradiation. The addition of 5 wt% $NH_4Cl$ produces the best physical properties. As per the UV-vis analysis results, the N-doped $TiO_2$ exhibits a higher visible-light activity than the undoped $TiO_2$. The wavelength of the N-doped $TiO_2$ shifts to the visible-light region up to 412 nm. In addition, this sample shows MB removal of approximately 81%, with the whiteness increasing to +97 when the synthesis temperature is $600^{\circ}C$. The coloration and phase structure of the N-doped $TiO_2$ are characterized in detail using UV-vis, CIE Lab color parameter measurements, and powder X-ray diffraction (XRD).

• Journal of the Korean Electrochemical Society
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• v.12 no.2
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• pp.162-166
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• 2009

The carbon-coated Si/Cu powders were synthesized by mechanical ball-milling and hydrocarbon gas decomposition methods at high temperature. The carbon-coated Si/Cu powder was used as anode for lithium secondary battery and its electrochemical behavior was investigated. In addition, the carbon-coated Si/Cu/graphite composite anode material was prepared using natural graphite powder and their electrochemical characteristics were compared with natural graphite anode. The specific capacity of carbon-coated Si/Cu anode increased to the initial 10 cycles. The carbon-coated Si/Cu/graphite composite anode exhibited the reversible specific capacity of 450mAh/g and the first cycle efficiency of 81.3% at $0.25mA/cm^2$. The cycling performance of the composite anode was similar to that of pure graphite anode except the reversible specific capacity value.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.423-423
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• 2011

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 O2- and OH radicals. These powerful oxidizing agents are proven to be effective in decomposition of the harmful organic materials and convert them into CO2 and H2O. 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 TiO2. 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.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.77-85
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• 2012

Production process of the flexible ceramic foamed body through the complexation with the fiberous sepiolite and expanded pearlite was researched. The processing of fibrillation of the inorganic mineral fiber sepiolite is the most important whole processing for manufacturing of the ceramic foamed body consisting of the expanded perlite and sepiolite. The fibrous sepiolite and expanded pearlite are blended and becomes the slurry phase. And this slurry phase is converted to a massive foamed body through the low temperature heat treatment process less than $300^{\circ}C$. The heat-treatment process of the slurry phase composite has to be designed to include the evaporation step of the moisture remaining among the slurry composition, foaming step by the decomposition of the foaming agent, and resolution removal step of the organic material which was added in the composite remained after the foaming step. The heat treatment process should be considered as significant factors in design of total process. As to the condition of heat treatment process and foaming agent, there was the a correlation. An organic type foaming agent like DSS (dioctyl sodium sulfosuccinte) was effective in foaming of the slurry compound consisting of the expanded perlite and sepiolite fiber.

• Analytical Science and Technology
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• v.23 no.6
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• pp.560-565
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• 2010

Perchlorate ion ($ClO_4^-$) has been widely used as oxidizing agent in military weapon system such as rocket and missile fuel propellant. So it has been challenging to remove the pollutant of perchlorate ion. nanoscale zero valence iron (nZVI) particles are widely employing reduction catalyst for decomposition of perchlorate ion. nZVI particles has increasingly been utilized in groundwater purification and waste water treatment. But it have strong tendency of aggregation, rapid sedimentation and limited mobility. In this study, we focused on reduction of perchlorate ion using nZVI particles immobilized in alginate polymer bead for stabilization. The stabilized nZVI particles displayed much greater surface area, and much faster reaction rates of reduction of perchlorate ion. In this study, an efficient way to immobilize nZVI particles in a support material, alginate bead, was developed by using $Ca^{2+}$ as the cross-linking cations. The efficiency and reusability of the immobilized Fe-alginate beads on the reduction of perchlorate was tested at various temperature conditions.

• Journal of Fashion Business
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• v.22 no.2
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• pp.51-60
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• 2018

This research focuses on the development of upcycled denim fashion designs, whichis a more specific category within general upcycled fashion design. Characteristics of upcycled fashion design, which has been identified previously by researchers, include the following traits: environmentality, uniqueness, aesthetic appeal, availability, convertibility, and deconstructivity. The expression principles include recycling, substitution, recombination, and reduction. The result of the analysis of the denim fashion design characteristics, which is based on the theoretical analysis, has found. The external expression pattern consists of the deconstruction and reconstitution of materials, the avant-garde style and convertibility, the ability to mix and match materials and techniques, the production of zero waste, and the use of layering. The expression techniques used included decomposition, depaysement, weaving, cut-off, collage, assemblage, overlapping, connecting, attaching, and stitching. The inner meanings were identified as economicality through recycling, convertibility through rearranging, and the rarity and value of hand-made products. The result of the research applying the identified characteristics are as follows. First, developing and creating designs using modified denim and sub-materials with various expression patterns and techniques could provide completely new images unlike existing denim products. Second, modifying the details while maintaining the basic format of denim clothing could provide unique and new possibilities for upcycled denim fashion design. Third, environment-friendly models with creative designs were developed by recycling used denim materials. This reduced waste and energy while maximizing the use of resources. This study expects contribute to upcycled fashion design research by recognizing the unique characteristics and value of denim material.