Papers by Author: Hee Soo Lee

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Authors: Hyun Gyu Shin, Yong Nam Kim, Jun Kwang Song, Hee Soo Lee
Abstract: Thermal degradation of indium tin oxide (ITO) thin film has been investigated. ITO thin film was fabricated on glass substrate using RF magnetron sputtering and was characterized. The resistivity of the film which was thermally degraded at high temperatures in air atmosphere was increased highly. Thermally-degraded specimen was analyzed using XPS and Hall measurement to reveal failure mechanism. Result showed that failure mechanism was the decrease in charge carrier concentration and mobility due to oxygen diffusion and chemisorption. Accelerated degradation test (ADT) was performed to predict the lifetime of ITO thin film. The lifetime under normal operating condition could be predicted via statistical analysis and modeling of data acquired from ADT of a short period.
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Authors: Yong Nam Kim, Min Seok Jeon, Sang Mok Lee, Min Chul Shin, Hee Soo Lee
Abstract: The adhesive and wear properties of ITO thin film have been investigated using the scratch and wear tests. ITO thin film was fabricated on glass substrate using RF magnetron sputter and strip lines were formed by selective etching. In the scratch test, the normal load on WC micro-blade was increased and kept constant as it was drawn over the films. In the wear test, sapphire, SUS and WC balls slided repeatedly on the films with the constant normal load. During the scratch and wear, the ESR and the acoustic signal were monitored and recorded. In order to study the adhesive and wear properties of ITO thin films, it was desirable to use the ESR rather than the acoustic signal. From the change in the ESR, it was possible to measure the critical load to cut through ITO film completely and the critical number of sliding to wear ITO film completely.
381
Authors: Young Kil Kim, Yeon Gil Jung, Jun Baek Song, Min Chul Shin, Hee Soo Lee
Abstract: Wall and floor tiles were fabricated by a dry pressing method using waste glass and clay. The properties of the tiles such as absorption, bulk density, porosity, compressive strength, and abrasion loss are investigated with the firing temperature and glass content. The properties are improved with increasing both the firing temperature and glass content. These properties, except the compressive strength, tend to be saturated from the glass contents of 70 wt % in the case of 1050 . The compressive strength shows the maximum values at the glass contents of 70 wt% and then which are decreased with increasing the glass contents. The optimal properties obtained in the tiles are the water absorption of about 0.9 %, the bulk density of about 2.3 g/cm3, the apparent porosity of about 2.1 %, the compressive strength of about 210 MPa, and the abrasion loss of about 0.022 g, when the composition containing the glass of 70 wt% is fired at 1050. These results are better than the properties of commercial clay tiles, due to easy melting and densification of glassy phase in the tiles.
755
Authors: Min Chul Shin, Jin Sun Cha, Jun Han Lee, See Hee Lee, Hee Soo Lee
Abstract: A porous filter was manufactured using cordierite powder by an extrusion method. The filter had an apparent porosity of 58% and a compressive strength of 10 MPa. Pulse cleaning process affected the durability of the filter. We investigated the effect of operating conditions of a hot gas cleaning system using ceramic filter, thermal shock and pressure shock on durability. When pulse cleaning was repeated periodically, the baseline differential pressure was relatively higher. On the other hand, when we repeated pulse cleaning per specific maximum differential pressure we could improve the durability of the filter. In our test conditions, thermal shock is the most important factor decreasing the durability of the filter. Pressure shock didn’t deteriorate the durability of the filter. However thermal shock caused the formation of cracks at the filter surface. This will lead to an increasing of the baseline differential pressure by depth filtration of dust and decrease the durability of the filter.
713
Authors: Jae Won Kim, Seong Hwan Park, Yeon Gil Jung, Hee Soo Lee
Abstract: Layered structures of dense porcelain/porous alumina and dense porcelain/porcelainalumina/ porous alumina are designed and their crack propagation behaviors are investigated. As a substrate, the porous alumina, which is prepared by a gel-casting process using the binary slip of alumina powder and PMMA spherical micro-bead, is dried at room temperature for 24 h and then sintered at 1600 for 2 h. Porcelain is coated on the porous alumina substrate and then re-sintered at 987. Bi- and tri-layered structures are produced by the different dwell times (2 min, 10 min) at re-sintering temperature. There is no delaminating or cracks observed after re-sintering the layered samples. The crack propagation behaviors in the bi- and tri-layered structures are evaluated by micro-indentation. The indentation cracks do not propagate into the porous alumina through interface (porosity; 36~62%) except for another one (porosity; 70%) in the bi-layered samples. In the case of the high porosity bi-layered sample (porosity; 70%), cracks are scattered along the 3-D open-pore channels. However, cracks do not propagate through the interface in the tri-layered samples with a porcelain-alumina buffer layer, because the porcelain-alumina buffer layer plays an important part such as a barrier layer in crack propagation.
457
Authors: Young Kil Kim, Yeon Gil Jung, Jin Bo Song, Min Chul Shin, Hee Soo Lee
Abstract: Wall and floor tiles were fabricated by a dry pressing method using waste glass and clay. The properties of the tiles such as absorption, bulk density, porosity, compressive strength, and abrasion loss were investigated with the firing temperature and glass contents. The properties were improved by increasing the firing temperature and glass contents. These properties, except the compressive strength, tended to be saturated from the glass contents of 70 wt % in the case of 1050 °C. The compressive strength showed the maximum values at the glass contents of 70 wt% and then decreased with increasing glass contents. The optimal properties obtained in the tiles were the water absorption of about 0.9 %, the bulk density of about 2.3 g/cm3, the apparent porosity of about 2.1 %, the compressive strength of about 210 MPa, and the abrasion loss of about 0.022 g, when the composition containing the glass of 70 wt% was fired at 1050°C. These results are better than the properties of commercial clay tiles for easy melting and densification of glassy phase in the tiles.
395
Authors: Seong Hwan Park, Jae Won Kim, Yeon Gil Jung, Je Hyun Lee, Ung Yu Paik, Hee Soo Lee
Abstract: TiO2 coated open-cell mullite ceramics were fabricated with coating TiO2 sol on pores of mullite, and its processing parameters were investigated. Open-cell mullite ceramics were fabricated through a gel-casting process. Two kinds of mullite precursor powders were prepared by dissolution of two kinds of aluminum salts (Al(NO3)3·9H2O; type I and Al2(SO4)3·16H2O; type II) into colloidal silica sols. To produce porous mullite ceramics, both mullite precursor powders and PMMA beads (≈ 5μm) were co-dispersed by electrosteric stabilized mechanism in an aqueous system and then gel-casted. The green bodies were sintered above 1300°C for 3hrs in air. The PMMA was offered as pores in sintered mullite bodies. The prepared open-cell mullite ceramics were dipped in TiO2 precursor solution. The sintered bodies coated with TiO2 sols were re-sintered below 1000°C for 3hrs after drying at room temperature. The TiO2 was successfully coated into the open-cell mullite ceramics. The characteristics of each TiO2 coated porous mullite ceramics were investigated by XRD, SEM, porosimetry, as functions of aluminum salt and pH of sol. It was found that the synthesis behavior and the porosity of the mullite are strongly dependent upon aluminum salt species, resulting in different grain size, morphology, and pore size.
139
Authors: Yong Nam Kim, Jeong Hyun Park, Hyun Gyu Shin, Jun Kwang Song, Hee Soo Lee
Abstract: Nanosized ITO powder was fabricated by homogeneous precipitation which used formamide as a precipitator. ITO thin film was deposited by RF magnetron sputtering using ITO target which was prepared by sintering of nanosized ITO powder. From the accelerated degradation test with stress factor of temperature, the lifetime estimate, degradation rate/degree, activation energy and etc. were calculated. It was showed that under thermal condition, the prominent failure mechanism of degradation was the decrease of oxygen vacancies due to oxidation of ITO thin film.
285
Authors: Jae Ean Lee, Jae Won Kim, Yeon Gil Jung, Bon Heun Koo, Hee Soo Lee
Abstract: Bilayer with inner layer of ZrO2-3mol% Y2O3 (TZ-3Y) and outer layer of zirconiaalumina (AKP-30) composite is fabricated using gel-casting for the inner layer and dip coating for the outer layer in aqueous system. The processing additives for gel-casting, such as dispersant, monomer, dimmer, and initiator, are adjusted and optimized. From which the solid loading of each starting material is determined. The bilayer structure can be in-situ formed by dip coating, which are verified by the sintered microstructure of the bilayer investigated.
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Authors: Hyung Mi Lim, Hyun-Bae Ji, Youn Seoung Lee, Sun Jae Kim, Hee Soo Lee, Duk-Ho Cho
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