Papers by Author: Dae Yong Shin

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Authors: Dae Yong Shin, Myung Gi So, Sang Mok Han
Abstract: Thin film photocatalysts of TiO2 coated on the glass were prepared to self-clean and eliminate air pollutants by spin coating process with Ti(OC3H7 i)4, including PEG. The surface structure of TiO2 films changed according to the molecular size of PEG. It was found that NOx was efficiently eliminated by the TiO2 film photocatalyst. The contact angle of water drop on the TiO2 films decreased to less than 10°. It revealed the hydrophilic property of TiO2 films. The morphology and the crystal structure of TiO2 films were affected most.
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Authors: Hyun Jong Lee, Beom Goo Lee, Dae Yong Shin, Heon Park
Abstract: In this study lignocellulosic fibers, such as kenaf bast, kenaf core, sugar cane bagasse, cotton, coconut coir, and spruce, which are environment friendly natural materials, were tested for their ability to remove copper, nickel and zinc ions from aqueous solutions. The fibers were analyzed for Klason lignin content, water sorption capacity and dry volume. The fiber with the highest level of heavy metal removal in the separate and mixed solution was kenaf bast.. In the mixed solution kenaf bast, sugar cane bagasse and cotton removed more copper and nickel ion than in the separate solution, and the amounts of removed heavy metal ions were changed in some lignocellulosic fibers, compared to those of the separate solution. In the mixed solution heavy metal ions may compete with one another for sorption sites on the surface of lignocellusic fiber. In kenaf bast to remove heavy metal ions most, Klason lignin content was the second lowest, and water sorption and dry volume were the lowest in all tested lignocellulosic fibers. It showed that removal of heavy metal ions does not correlate with any chemical and physical factors, but may be affected by the cell wall structure of lignocellulosic fibers and how many free phenolic groups in lignin, which are considered as the heavy metal ion binding site, are exposed on the surface of fibers. Cotton, with about 1% Klason lignin, was very low in heavy metal ion removal, while all other fibers containing greater than about 10% lignin did remove heavy metal ions. It showed that even the lignin content of lignocellulosic fibers does not correlate with heavy metal ion removal but lignin does play a role in heavy metal ion removal.
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Authors: Beom Goo Lee, Hyun Jong Lee, Dae Yong Shin, Yeon Ho Jeong, Jin Chen Wu, Dong Ha Cho, Kang Yol Lee, Dong Eun Kim, Wie Soo Kang, Young Gyun Goh
Abstract: Cotton, a lignocellulosic fiber and environment friendly natural material, was tested for its ability to sorb diesel oil from the pure diesel oil bath and the diesel oil containing water bath. The fiber was ground to disrupt the lumen structure or extracted with diethyl ether to remove wax from cotton. Diethyl ether is an organic solvent and extracts only extractives in the cell wall. Oil sorption capacity was the highest in control as 30.6 g/g in the pure diesel oil bath, and the lowest in ground cotton as 0.8 g/g in the diesel oil containing water bath. Cotton is mainly composed of hydrophilic components and sorb water more easily than oil. As a result diesel oil sorption capacity was much higher in the oil bath than in the water bath. However, after grinding and passing through 20 mesh screen (0.86 cm), wax is preserved but the lumen structure of cotton, of which the fiber length is about 18 mm, is disrupted by grinding and can not hold oil. Therefore, the diesel oil sorption capacity of cotton was decreased significantly to 5.2 g/g in the pure diesel oil bath, and to 0.8 g/g in the water bath, compared to those of control. And because wax is removed but lumen structure is not destroyed after diethyl ether extraction, the diesel oil sorption capacity decreased slightly to 27.7 g/g in the oil bath and to 7.5 g/g in the water. When cotton was presoaked in water, cotton sank during the presoaking process, and so the oil sorption capacity could not be determined. Grinding, extractingand presoaking all contributed to the changes in oil sorption capacity. The most significant change is attributed to the reduction in the particle size of cotton.
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Authors: Beom Goo Lee, Hyun Jong Lee, Dae Yong Shin
Abstract: Kenaf bast, coconut coir, and cotton, which are lignocellulosic fibers and environment friendly natural materials, were tested for their ability to remove copper, nickel, and zinc ions from aqueous solutions according to their physical and chemical changes by solvent extraction. The order of the lignin and xylose content in unextracted fibers is coconut coir>kenaf bast>cotton. The fiber with the highest level of heavy metal removal, however, was kenaft bast. It showed that removal of heavy metals does not correlate with lignin and xylose content. Cotton, with about 1.1% lignin and 0.3% xylose, was very low in heavy metal ion sorption while other two fibers containing lignin and xylose did remove heavy metal ions. It indicates that lignin and xylose play a role in heavy metal ion sorption. Extraction with the various solvents removed different cell wall components and changed the cell wall structure, and thus did change the heavy metal ions removal capacity of lignocellulosic fibers.
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Authors: Beom Goo Lee, Hyun Jong Lee, Dae Yong Shin
Abstract: Kenaf bast, which is lignocellulosic fiber and environment friendly natural material, was tested for its ability to remove copper, nickel and zinc ions from aqueous solutions. The fiber was analyzed for xylose, lignin content, weight loss and dry volume, and extracted with diethyl ether, ethyl alcohol, hot water, or 1% sodium hydroxide to change physical and chemical characteristics of keanf bast. Diethyl ether and ethyl alcohol are organic solvents, which extract only extractives in the cell wall. The weight losses are less than 4.1%, the dry volumes increase up to 0.68 cm3/g, and the changes of lignin content are less than 0.6%. The differences of the heavy metal ions removal capacities are less than 0.05 mg/g, compared to those of control. Hot water and 1% sodium hydroxide remove cell wall components as well as extractives in the cell wall. In addition, during the extraction process the cell wall is swollen by the delamination of cell wall layers, xylose and lignin are exposed. The weight losses increases up to 24.0%, the dry volumes increase up to 1.20 cm3/g, and the changes of lignin content are less than 0.6%. The difference of the heavy metal ions removal capacities of kenaf bast increase up to 0.14 mg/g, and are much higher than those of diethyl ether and ethyl alcohol. The above results show that to increase the heavy metal ions removal capacities, the extraction chemicals may swell the cell wall more than water does and remove the cell wall components as well as extractives to change cell wall chemistry and architecture.
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Authors: Dae Yong Shin, Kyung Nam Kim
Abstract: Thin films of various composition in the system of TiO2•SiO2 have been fabricated by the sol-gel process using Si(OC2H5) and Ti(OC3H7i)4 as precursors. TiO2•SiO2 films were formed on the glass substrate by spin-coating technique and heated at 500°C for 1 h. The relationship between hydrophilicity, photocatalytic properties and self-cleaning property with SiO2 addition and UV light irradiation were investigated. Photocatalytic activity of TiO2•SiO2 films showed decomposition of ~97% of acetaldehyde in 2 h and a water contact angle of ~10°. TiO2•SiO2 films can have more hydrophilic activity and less photocatalytic activity by increasing of SiO2 addition. XPS measurements revealed that the amount of organic compounds adsorbed on the films decreased with the UV light irradiation and SiO2 addition, because of the increased of both OH group contents in films and decomposed organic contaminants of the films surface.
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Authors: Dae Yong Shin, Kyung Nam Kim
Abstract: A green emitting SrAl2O4:Eu2+, Dy3+ phosphor with high brightness and long afterglow was synthesized by the sol-gel method. SrAl2O4: Eu2+, Dy3+ phosphor exhibited broad band extending from 450 to 650 nm and maximum emission spectra peaking at 520 nm. Three excited levels existed, two shoulders were observed at 270 and 330 nm in addition to the maximum at 360 nm on the excitation spectrum. After the removal of excitation light, the excellent after-glow characteristic of the phosphorescence was obtained as a result of low decay time, although the after-glow intensities of phosphor varied exponentially with the time.
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Authors: Kyung Nam Kim, Dae Yong Shin, Hyun Park
Abstract: Sericite has the intermediate nature of the muscovite and illite, which has been used as the additive of the cosmetics, the ceramic industry, welding rods, and other various pigments and the paint. In this study, the characteristics of sericite were examined using XRD(X-ray diffractometer), XRF(X-ray fluorescence spectrometer), TG-DTA(Thermal Analyzer), SEM(Scanning Electron Microscope) and PSA(Particle Size Analyzer). The raw ore is composed of 60.90wt% SiO2, 7.88wt% K2O, 0.36wt% TiO2, 24.80wt% Al2O3, 1.64wt% Fe2O3, 2.39wt% CaO, and 0.83wt% MgO. After sericite was purified, the content of SiO2 decreased from 60.9wt% to 51.4wt%, and in the crystal phase the intensity of quartz decreased significantly. For the high grade purification of sericite, the removal of iron and separation of quartz for the raw ore (sericite), the hydrocyclone were used with the magnetic separator. The content of iron was reduced from 1.64wt% to 0.91wt%.
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Authors: Dae Yong Shin, Kyung Nam Kim, In-Tak Nam, Sang Mok Han
Abstract: ZrO2-SiO2 coatings deposited on 316 L stainless steel were prepared to protect chemically the substrates by sol-gel process using Zr(OC3H7 n)4/Si(OC2H5)4 as precursors. The influence of the ZrO2-SiO2 coatings on the corrosion resistance of the 316 L stainless steel was evaluated with the potentiodynamic polarization curves in deareated 15% H2SO4 solutions at 25, 40 and 50 °C . Comparative test was performed on uncoated one. The values of the electrochemical parameters explain how. ZrO2-SiO2 films increase the resistance of stainless steel against corrosion.
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Authors: Dae Yong Shin, Kyung Nam Kim
Abstract: Municipal incinerator residue (MIR) was used as raw material to replace clay to manufacture bricks. Brick specimens were substituted from 0 to 50 wt% MIR by 10 wt% increment for clay. Clay-MIR brick specimens were fired at 800~1050°C for 2 h. Firing shrinkage, bulk density, water absorption rate and compressive strength were investigated. Leaching procedure tests were also conducted to characterize toxicity. Increasing MIR contents resulted in a decrease in water absorption rate, firing shrinkage and increase in compressive strength of bricks. It was found that when brick specimen with 50 wt% of MIR content was heat-treated at 1000°C for 2 h, a brick specimen could be generated, which was compressive strength of 1256 kg/cm2, water absorption ratio of 6.8% and firing shrinkage of 3.5%. This indicates that MIR is indeed suitable for the partial replacement of clay in bricks
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