• Korean Journal of Materials Research
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• v.18 no.4
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• pp.187-192
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• 2008

Multi-walled carbon nanotube (MWNT)/$SnO_2$ nano-composite (MSC) for the anode electrode of a Li-ion battery was prepared using a homogeneous precipitation method with $SnCl_2$ precursors in the presence of MWNT. XRD results indicate that when annealed in Ar at $400^{\circ}C$, $Sn_6O_4(OH)_4$ was fully converted to $SnO_2$ phases. TEM observations showed that most of the $SnO_2$ nanoparticles were deposited directly on the outside surface of the MWNT. The electrochemical performance of the MSC electrode showed higher specific capacities than a MWNT and better cycleability than a nano-$SnO_2$ electrode. The electrochemical performance of the MSC electrode improved because the MWNT in the MSC electrode absorbed the mechanical stress induced from a volume change during alloying and de-alloying reactions with lithium, leading to an increase in the electrical conductivity of the composite material.

• Journal of the Korean GEO-environmental Society
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• v.12 no.6
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• pp.5-15
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• 2011

In this study, centrifuge model tests were performed to investigate stress concentration ratio, stress characteristics of soft clay ground improved by granular compaction piles with changes of piles type, loading condition and area replacement ratio. From the results of rigid loading tests, while vertical stresses acting on clay ground is similar, vertical stresses acting on GCP is larger than those acting on SCP with same replacement ratio. Also, average stress concentration ratio is increased proportionally with increasing the area replacement ratio of GCP and SCP. It was evaluated that average stress concentration ratio of soft clay ground improved by GCP is larger than that of SCP. As a result of flexible loading tests, stress concentration ratio is the highest when replacement ratio of GCP and SCP is 40%. Average stress concentration ratio of soft clay ground improved by GCP is a little more higher than is improved by SCP.

• Textile Coloration and Finishing
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• v.34 no.4
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• pp.241-249
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• 2022

As for military backpacks in Korea, utility backpack products equipped with various functions along with comfort and convenience are being developed. As a result, the volume and weight of the backpack increase, and many lightweight studies of the materials forming the backpack are being conducted. This study is a basic study on frame lightweight using fiber-reinforced composites to deal with aluminum, a back frame that maintains the shape of a backpack and provides stability when worn by combatants. As is known, only fiber-reinforced composites have sufficient light weight and mechanical properties, but the mechanical properties were reviewed by drilling holes to maximize the light weight. Tensile strength and flexural strength were measured by drilling 6mm, 12mm, 18mm, and 24mm holes, and the tensile strength and flexural strength were measured when 1, 3, 5, and 7 holes of 12mm were increased. As a result, even when the number of holes was increased, tensile strength did not change significantly, and the flexural strength showed to be higher in the case of 3 holes and 5 holes than in the case of 1 hole.

• The Korea Journal of Herbology
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• v.29 no.2
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• pp.39-45
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• 2014

Objectives : The purpose of this study was to investigate antiaging and antioxidant effects on cultured human skin fibroblast with 80% ethanol extracts of plants including of stem of Dendropanax morbifera, Corni fructus and Lycii Fructus. Methods : An ethanol extract of three medicinal plants including stem of Dendropanax morbifera, Corni fructus and Lycii Fructus. Extracts were assessed to determine the mechanism of antioxidant and antiaging activities. Antioxidant activity of extract was evaluated by two different assays as 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and super oxide dismutase (SOD) like activities. These extracts were tested for cell viability on HS68 skin fibroblast by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. We investigated the effects of Ultraviolet-B irradiation on cytotoxicity, type 1 collagen, elastin level and oxidative damage in cultured human skin fibroblast (HS68). Recently, many studies have reported that elastin is also involved in inhibiting or repairing wrinkle formation, although collagen is a major factor in the skin wrinkle formation. Results : The extracts obtained dose-dependently increased the scavenging activity on DPPH radical scavenging activity and SOD like activity. The extracts of complex herbal medicine showed low cytotoxicity as more than 100% cell viability in 100ppm/ml concentration. HS68 fibroblasts were survived 70% at 120 $mJ/cm^2$ UVB irradiation and treated tumor necrosis factor (TNF)-alpha. The levels of aging factors and cytotoxicity were decreased by ethanol extract of complex herbal medicine. Conclusions : These results suggest that ethanol extracts of complex medicinal plants of including of stem of Dendropanax morbifera, Corni fructus and Lycii Fructus may have value as the potential antioxidant and antiaging medicinal plant.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.3
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• pp.97-103
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• 2023

Barrier films for transparent packaging materials with excellent moisture barrier properties are prepared, utilizing a nanoclay dispersion coating layer formed after a pretreatment process of plasma activation surface treatment process under vacuum at room temperature. Attention is paid on optimizing the coupling additive through the appropriate crosslinking process and optimal dispersion process of the coating process to enhance adhesion. Analysis of the functional coating thin film shows that the water vapor transmission rate is less than 10 g/m²/24 hrs (ASTM F-1249) and the oxygen transmission rate is less than 30 cc/m²/24 hrs (ASTM D3985). It is shown that water barrier properties of coating thin film prepared in this study are greater than conventional untreated films by 10 times or more. The thickness of the transparent gas barrier film is within 0.1 mm, and the transparent gas barrier complex is implemented in two layers. In the study of PET thin film interface characteristics, FT-IR experimental analysis shows the reaction activity was optimized at RDS 1.125 %.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.6
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• pp.459-466
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• 2011

Purpose: This study evaluated the capability of bone formation with silk fibroin/nano-hydroxyapatite/corn starch composite scaffold as a bone defect replacement matrix when grafted in a calvarial bone defect of rabbits $in$ $vivo$. Methods: Ten New Zealand white rabbits were used for this study and bilateral round-shaped defects were formed in the parietal bone (diameter: 8.0 mm). The silk fibroin 10% nano-hydroxyapatite/30% corn starch/60% composite scaffold was grafted into the right parietal bone (experimental group). The left side (control group) was grafted with a nano-hydroxyapatite (30%)/corn starch (70%) scaffold. The animals were sacrificed at 4 weeks and 8 weeks. A micro-computerized tomography (${\mu}CT$) of each specimen was taken. Subsequently, the specimens were decalcified and stained with Masson's trichrome for histological and histomorphometric analysis. Results: The average ${\mu}CT$ and histomorphometric measures of bone formation were higher in the control group than in the experimental group at 4 weeks and 8 weeks after surgery though not statistically significant ($P$ >0.05). Conclusion: The rabbit calvarial defect was not successfully repaired by silk fibroin/nano-hydroxyapatite/corn starch composite scaffold and may have been due to an inflammatory reaction caused by silk powder. In the future, the development of composite bone graft material based on various components should be performed with caution.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.588-593
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• 2022

Terephthalaldehyde (TPA) is introduced as a cross liker to enhance electron transfer of hemin-based cathodic catalyst consisting of polyethyleneimine (PEI), carbon nanotube (CNT) for hydrogen peroxide reduction reaction (HPRR). In the cyclic voltammetry (CV) test with 10 mM H₂O₂ in phosphate buffer solution (pH 7.4), the current density for HPRR of the suggested catalyst (CNT/PEI/hemin/PEI/TPA) shows 0.2813 mA cm^-2 (at 0.2 V vs. Ag/AgCl), which is 2.43 and 1.87 times of non-cross-linked (CNT/PEI/hemin/PEI) and conventional cross liker (glutaraldehyde, GA) used catalyst (CNT/PEI/hemin/PEI/GA), respectively. In the case of onset potential for HPRR, that of CNT/PEI/hemin/PEI/TPA is observed at 0.544 V, while those of CNT/PEI/hemin/PEI and CNT/PEI/hemin/PEI/GA are 0.511 and 0.471 V, respectively. These results indicate that TPA plays a role in facilitating electron transfer between the electrodes and substrates due to the π-conjugated cross-linking bonds, whereas conventional GA cross-linker increases the overpotential by interrupting electron and mass transfer. Electrochemical impedance spectroscopy (EIS) results also display the same tendency. The charge transfer resistance (R_ct) of CNT/PEI/hemin/PEI/TPA decreases about 6.2% from that of CNT/PEI/hemin/PEI, while CNT/PEI/hemin/PEI/GA shows the highest R_ct. The polarization curve using each catalyst also supports the superiority of TPA cross liker. The maximum power density of CNT/PEI/hemin/PEI/TPA (36.34±1.41 μWcm^-2) is significantly higher than those of CNT/PEI/hemin/PEI (27.87±0.95 μWcm^-2) and CNT/PEI/hemin/PEI/GA (25.57±1.32 μWcm^-2), demonstrating again that the cathode using TPA has the best performance in HPRR.

• Journal of the Speleological Society of Korea
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• no.63
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• pp.1-8
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• 2004

The non-magnetic materials with non-conductive showing high structure dispersity were developed on the base of natural quartz and lava-scoria which was collected from Je-ju island in Korea, and treated by methane-chemical technology those were obtained novel properties of magnetization through the analyzing. Depending on the processing conditions and subsequent applications the materials produced by strong methane-chemical reaction (MCR) in alcohol solution showed concurrently magnetic, dielectric and electrical properties. The obtained magnetic-electrical powders classified by aggregate complex of their features as segnetomagnetics, containing a dielectric material as a carrying nucleus, particularly the quartz on that surface one or more layers of different compounds were synthesized having thickness up to 10～50 nm and showing magnetic, electrical and other properties. It was confirmed in magnetizing process that powders of quartz and lava-scoria produced by MCR were better oil adsorbent as of oleophilic and floating matter on water surface although their specific gravities are comparably more than 1 in quartz or less than unity, as that of water, in lava-scoira. Therefore, it will be Possible and very useful to remove low density and light gravity oil spillage in difficult recovery from sea and inland water contamination spread on water surface, by marine accident and ship sinking accident occurring frequently in recent years, by way of magnetic adsorbent conveyer system in continuous, if it could be built up the mass Production system of water-floating magnetizable oleophilic adsorbent materials with use of iow cost and good Qualify lava-scoria spread on volcano district in Je-ju island. And, there will also be urgent advent of necessity with strong possibility to develop useful applications of various magnetic functional materials include oleophilic adsorbent for removal of sea oil-contaminants and maritime pollutants, and other kinds of various utilities in industrial applications and practical uses of novel functional materials in the fields of environments and health care applications with in deep expectation.