• Carbon letters
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• v.12 no.2
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• pp.90-94
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• 2011

We present the effect of a coupling agent on the optoelectrical properties of few-walled carbon nanotube (FWCNT)/epoxy resin hybrid films fabricated on glass substrates. The FWCNT/epoxy resin mixture solution was successfully prepared by the direct mixing of a $HNO_3$-treated FWCNT solution and epoxy resin. FWCNT/binder hybrid films containing different amounts of the coupling agent were then fabricated on UV-ozone-treated glass substrates. To determine the critical binder content ($X_c$), the effects of varying the binder content in the FWCNT/silane hybrid films on their optoelectrical properties were investigated. In this system, the $X_c$ value was approximately 75 wt%. It was found that above $X_c$, the coupling agent effectively decreased the sheet resistance of the films. From microscopy images, it was observed that by adding the coupling agent, more uniform FWCNT/binder films were formed.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1799-1805
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• 2014

In this article, we described about the preparation and electrochemical properties of a flexible energy storage system based on a plastic polyethylene terephthalate (PET) substrate. The PET treated with UV/ozone was fabricated with multilayer films composed of 30 polyaniline (PANi)/graphene oxide (GO) bilayers using layer-by-layer assembly of positively charged PANi and negatively charged GO. The conversion of GO to the reduced graphene oxide (RGO) in the multilayer film was achieved using hydroiodic acid vapor at $100^{\circ}C$, whereby PANi structure remained nearly unchanged except a little reduction of doping state. Cyclic voltammetry and charge/discharge curves of 30 PANi/RGO bilayers on PET substrate (shorten to PANi-$RGO_{30}$/PET) exhibited an excellent volumetric capacitance, good cycling stability, and rapid charge/discharge rates despite no use of any metal current collectors. The specific capacitance from charge/discharge curve of the PANi-$RGO_{30}$/PET electrode was found to be $529F/cm^3$ at a current density of $3A/cm^3$, which is one of the best values yet achieved among carbon-based materials including conducting polymers. Furthermore, the intrinsic electrical resistance of the PANi-$RGO_{30}$/PET electrodes varied within 20% range during 200 bending cycles at a fixed bend radius of 2.2 mm, indicating the increase in their flexibility by a factor of 225 compared with the ITO/PET electrode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.779-782
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• 2000

Silicone rubbers are first silicone polymers and has named silicone from existence of Si-O bond similar to Keton. Silicon in organic compound has been called silicone, and linear or network polymers. Silicone rubbers have been used as an power insulator because they are well weather proof, ozone proof and have excellent electric characteristics, thermal stability, cold resistance and low surface energy. Especially, it is known that they have very excellent characteristics at 200[$^{\circ}C$]. For this study, we made silicone rubbers as specimens and we measured dielectric loss tangent due to applied voltage at temperature range 25[$^{\circ}C$] to 180[$^{\circ}C$] and frequency range 20[Hz] to 1${\times}$10$\^$6/[Hz] to examine dielectric properties. We measured dielectric loss tangent to study the insulation performance of silicone rubbers.

• Textile Coloration and Finishing
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• v.35 no.1
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• pp.42-65
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• 2023

Leather is widely used in human lives and many industries, and the market size continues to grow. In terms of quality and durability, natural leather is still being used as the most luxurious product. And synthetic leather, made of polyvinyl chloride (PVC) and polyurethane (PU), were developed and being widely have been used as alternative materials for natural leather. Processes, properties and issues of these leather were reviewed. Then silicone leather was reviewed why they can be good candidates for leather. Properties of general silicone polymers and silicone rubber coating agents were reviewed such as eco-friendliness, human-friendliness, stain resistances, resistance to uv light and ozone, heat stability and so on. Papers and patents related to silicone leather were studied to understand current status of development and commercialization of silicone leather. Finally direction of development was described how to improve deficient performances of current silicone leather, such as formulation of silicone, combination with organic materials and manufacturing processes.

• Korean Journal of Agricultural and Forest Meteorology
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• v.12 no.3
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• pp.207-216
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• 2010

Individual differences of ozone ($O_3$) resistance for seed production, seed germination and seedling development were examined in this study. Five in each healthy and damaged trees of Pinus thunbergii growing in air polluted area for 12 years were chosen based on visible foliar injury and growth. The cones of P. thunbergii, which were collected from healthy and damaged trees, were analyzed for physical characteristics and seeds from the cones were used to test germination percentage under $O_3$ treatment. The germinated seeds were continuously exposed to $O_3$ treatment and the lipid peroxidation and activities of antioxidative enzymes were determined for both seeds and seedlings. The $O_3$ treatment for seed germination and seedling development were conducted at three conditions: control, 150 ppb and 300 ppb of $O_3$. The non-treated seeds from the damaged trees showed 21.6% lower germination than those from the healthy ones. On the $O_3$ treatment of 300 ppb, seed germination decreased approximately 10% for the healthy trees and 19% for the damaged trees compared to that on the control. The seeds from the healthy trees showed significantly higher activities of superoxide dismutase (SOD), glutathione reductase (GR), and catalase (CAT) than those from the damaged trees. The activities of GR, ascorbate peroxidase (APX), and CAT decreased along with the increasing $O_3$ concentration in two tree grades. Malondialdehyde (MDA) content of seeds was not influenced by $O_3$ treatment for two tree grades. In seedling development, there were no significant differences for length and biomass of needle and root of two tree grades at both the control and 150 ppb of $O_3$. At 300 ppb of $O_3$ treatment, however, the length and biomass of needle and stem decreased for two tree grades but no significant differences was detected in root. The seedlings from the damaged trees were more sensitive to the $O_3$ treatment, showing higher activities of SOD, APX, and CAT and content of MDA compared to those from the healthy tree seedlings. Our results indicate that seed germination and seedling development are vulnerable to increasing $O_3$ concentrations and that attention must be paid to the individual selection of tree species for reforestation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.915-922
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• 2017

The study on the thermal and oil resistance rubber composite, 2016. [6] predicted the lifetime of Fluorocarbon Rubber by accelerating aging at high temperature ($150^{\circ}C$, $175^{\circ}C$, $200^{\circ}C$). general rubber products are likely to exhibit different properties depending on the degradation factors such as temperature, humidity, ozone, light, emulsion, mechanical and electrical stress. To solve these problems, We compared the rate of change about tensile strength, elongation rate, volume change rate, weight change rate, thickness change rate, thermal conductivity in low temperature promoting aging on the basis of predictive lifetime of high temperature promoting aging. As a result of the review, the required life expectancy was satisfied, but there was a slight difference in the rate of change between the high-temperature promoted aging life result and the low temperature promoted aging life result. The cause was a reduction in "tensile strength / elongation" and an increase in "volume / weight / thickness" caused by the main chain decomposition of fluorine rubber due to aging at high temperature promoting aging. However, the low temperature promoting aging was caused by the curing reaction of fluorine rubber at $80^{\circ}C$. The tensile strength / elongation and volume / weight / thickness changes were small.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.556-563
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• 2007

We carried out a laboratory scale experiment about the characteristics of chemically active species produced in hybrid gas-liquid discharges. The electrode configuration which had high voltage electrode in the gas phase and ground electrode in the liquid was utilized while high voltage electrode has been typically positioned in the liquid in other studies. Our electrode was configured in such a way as to increase the energy efficiency of chemical reactions by creating a higher electrical field strength and a narrower pulse width than the typical electrode configuration. The highest ozone concentration was obtained at 45 kV which was the medium value in operating voltages. The decrease of solution conductivity increased the resistance of liquid phase and the electric field strength through the gas phase, so ozone gene-ration rate was enhanced. The increase of voltage promoted the production rate of hydrogen peroxide by increasing the electric field strength. In a lower voltage, the increase of solution conductivity increased the degradation rate of $H_2O_2$, so the $H_2O_2$ generation rate decreased. On the other hand, the effects of UV radiation, shock waves etc. increased the $H_2O_2$ generation rate as the solution conductivity increased. A higher rate of $H_2O_2$ generation can be achieved by mixing argon to oxygen which generates a stronger and more stable discharges.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.697-705
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• 2011

The aim of this study was to examine ozonation disinfection efficiency for Escherichia coli DH5alpha removal, containing the multi-resistance plasmid pB10 as well as chlorination disinfection efficiency. In addition, plasmid pB10 removal rates were estimated by ozonation and chlorination. The removal efficiency of pB10 via ozonation was about 2 to 4 times higher than chlorination. High removal efficiency of pB10 is likely due to OH radical produced during ozonation. These results suggest that integration of advanced oxidation process such as ozonation (or photocatalytic oxidation) with conventional disinfection such as chlorination may be needed for effective control of antibiotic resistant bacteria and genetic materials.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.3
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• pp.296-301
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• 1999

The concerns on the crop damage by ultraviolet (UV) radiations is increasing owing to the decrease of their absorbing stratospheric ozone in the tropospheric. Cultivar differences on early growth of UV radiation among five Korean rice cultivars, four japonica types and one Tongil type (indica-japonica cross hybrid), were studied. Pot-seeded rice plants were grown under four different radiation conditions, i.e., visible radiation only, visible radiation with supplemented with high or low dose of UV-B (280~320 nm in wavelength) and UV-C (less than 280 nm in wavelength). The inhibitory degree on plant height, shoot and root weight and length of leaf blade and leaf sheath were determined at 40 days after seeding. UV-C showed the most severe inhibitory effect on the degree of biomass gain and leaf growth in most cultivars examined, followed by high UV-B and low UV-B. Among the cultivars used, the Kuemobyeo was the most sensitive cultivar and had not repair or showed resistance ability to continued irradiation of UV radiation. However, Janganbyeo and Jaekeon showed different responses that the elongation of leaf blades was promoted on 2nd and 3rd leaves and inhibited on 4th and 5th leaves but this inhibitory degree was reduced on 6 th and 7th leaves. Such tendency on leaf growth means that both cultivars had low sensitivity and most resistant ability to continued irradiation of UV radiation. While Tongil showed different response to enhanced UV radiation, ie., low UV-B promoted leaf growth but the inhibitory was severely increased by continued irradiation of high UV-B and UV-C, which means that Tongil had high threshold of UV radiation for response as an inhibitory light of plant growth. The results of this study indicate that the differences on sensitivity or resistant to the effects of UV radiation were existed among Korean rice cultivars.

• Tribology and Lubricants
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• v.35 no.4
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• pp.222-228
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• 2019

As rubber products such as O-rings, which are also known as packings or toric joints, come in regular, long term contact with liquid fuel, they can eventually swell, become mechanically weakened, and occasionally crack; this diminishes both their usefulness and intrinsic lifetime and could cause leaks during the steady-state flow condition of the fuel. In this study, we evaluate the lifetime of such products through compression set tests of FKM, a family of fluorocarbon elastomer materials defined by the ASTM international standard D141; these materials have great compression, sunlight, and ozone resistance as well as a low gas absorption rate. In this process, O-rings are immersed in the liquid fuel of airtight containers that can be expressed as a compression set, and the liquid fuel leakage in a flow rig tester at variable temperatures over 12 months is investigated. Using the Power Law model, our study determined a theoretical O-ring lifetime of 2,647 years, i.e. a semi-permanent lifespan, by confirming the absence of liquid fuel leakage around the O-ring assembled fittings. These results indicate that the FKM O-rings are significantly compatible for fuel tests to evaluate long-term sealing conditions.