Papers by Author: Dae Yong Shin

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.

Abstract: In this study, mine tailings obtained in a region near to Youngwol Sangdong(Korea) was used to investigate the contamination of heavy metal ions. Some amount of mine tailings and lignin(AE agent) were added in the general cement pastes, of which the compressive strength and leaching rate were investigated. X-ray fluorescence analysis shows that the major constituents of mine tailings are 56.9wt% of SiO2, 10.8wt% of Fe2O3, 11.2wt% of CaO and 11.4wt% of Al2O3, and the major phases are quartz and calcite. In the content of heavy metal ions, the concentration of As ion is the highest as 257.261mg/ℓ. When mine tailings and lignin were added in cement pastes, the compressive strength was higher in the cement pastes adding only lignin. Lignin addition significantly improved the compressive strength of cement pastes by approximately 15% when being cured in distilled water. The compressive strength was lower in the cement pastes adding mine tailings than in the cement pastes not adding. The leaching rates of Cr, Pb and As ion in distilled water were decreased in the cement pastes adding lignin, compared to in the cement pastes not adding. The leaching rates of all heavy metal ions in the cement pastes curing for 28 days were within the maximum permitted limits in KSLT and EPT method. Therefore, it is thought that mine tailings can be used as an ecological material.

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.

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.

Abstract: Kenaf core was tested for its ability to sorb diesel oil from the pure diesel oil bath and the diesel oil containing water bath after extracting with diethyl ether to remove wax from fiber surface, grinding to disrupt lumen structure and presoaking in water. Oil sorption capacity was the highest as 8.0 g/g in diethyl ether extracted fiber in oil bath, and the lowest as 1.3 g/g in water soaked kenaf core in water bath. Diesel oil sorption capacity was much higher in oil bath than in water bath. In diethyl ether extraction the diesel oil sorption capacity was not changed much in kenaf core, compared to that of control. Also, even after grinding and passing through 20 mesh screen (0.86mm) the diesel oil sorption capacity was almost same. When kenaf core was presoaked in water the oil sorption capacity was decreased to about half of control as 1.3g/g in water bath. Grinding, extracting and water presoaking all contributed to the changes in oil sorption capacity. The results show that if in lignocelluloscic fiber like kenaf core the fiber structure is not disrupted during processing and the intact lumen structure can be kept, the oil sorption capacity may not be affected much by physical and chemical changes.

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

Abstract: MgO thin film was deposited on soda lime glass substrate by sol-gel process. MgO thin film with the (200) preferred orientation were prepared by heat-treated at 300~500°C for 10 min. The crystallization, microstructure and electrical properties with various parameters of MgO thin films were investigated. Consequently, it was shows that the (200) preferred orientation of MgO thin film could be obtained as the heating temperature was increased. At heating temperature of 500°C, MgO thin film was composed of columnar crystals with a size of 120 nm. The dielectric constant of the (200) preferred orientation of MgO thin film at 1 kHz without the electric field was 7.2, with a dissipation factor of 4%. When the electric field was increased, the dielectric constant approaches to 7.9 with the dissipation factor of 2.1%. The refractive index of MgO thin film depended on the film thickness. The refractive index of 250 nm thickness was 1.70.

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.

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%.