• Proceedings of the Membrane Society of Korea Conference
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• 1994.04a
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• pp.57-57
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• 1994

졸-겔 침지코팅 (dipcoating) 또는 가압 졸-겔 코팅 (pressurized coating) 법으로 제조한 $\gamma-Al_2O_3, SiO_2, TiO_2$ 및 aluminosilicate 복합막에 대하여 $CO_2$, He, $N_2$, 및 $O_2$ 기체 투과율과 $CO_2$ 분리계수를 측정하였다. 이들 막을 통한 모든 기체의 이동은 Knudsen 유동이 지배적이었으며 $CO_2/N_2$의 분리계수는 0.9 ~ 1.1 정도로 Knudsen 분리계수 ($CO_2/N_2$의 경우 0.8)보다 약간 높은 값을 보여주었다. $CO_2$ 분리계수를 향상시키기 위하여 silane coupling 및 산화물 도핑법에 의한 복합막의 표면개질을 시도하였으며 분리막의 재질 및 표면개질 조건에 따른 $CO_2/N_2$ 분리계수 변화를 측정 비교하였다. Silane coupling에 의한 표면개질이 $CO_2$의 표면 친화성 (affinity)에 의한 표면확산속도를 증가시키기 때문에 $CO_2$ 분리에 있어서 산화물 도핑에 의한 표면개질보다 더욱 효과적이었다.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.8
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• pp.586-591
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• 2013

This experiment was performed to enhance $CH_4$ purity of landfill gas by applying gas separator membrane for purified nitrogen gas production. 1:6 area ratios of $1^{st}$ to $2^{nd}$ membrane module was suitable for $CH_4$ recovery. After separation membrane system was installed, 249 tries were performed. Average permeability for $CH_4$ was 28.4% and for $CO_2$ was 94.3%. This can explain nitrogen gas separator membrane can be applied to collect $CH_4$ from LFG. However, nitrogen permeability only reached up to 16.5%. Therefore, the final purified landfill gas concentration was rounded up to 69.7% for $CH_4$, 4.3% for $CO_2$ and 26.0% for $N_2$. For the high degree of $CH_4$ purity, $N_2$ should be kept at least under 2.0% by controlling air inflow to landfill.

• Membrane Journal
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• v.31 no.6
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• pp.456-470
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• 2021

In this study, polyetherimide-based hollow fiber membranes were manufactured using the NIPS (nonsolvent induced phase separation) method. THF, Ethanol, and LiNO₃ were used as additives to control the morphology of the PEI-hollow fiber membranes. Furthermore, for the development of a high hydrogen separation membrane, the spinning conditions were optimized through the characterization of SEM and gas permeance. As a result, as the content of THF increased, the hydrogen/carbon dioxide selectivity increased. However, the permeance decreased due to the trade-off relationship. When ethanol was added, a finger-like structure was shown, and when LiNO₃ was added, a sponge structure was shown. In particular, in the case of a hollow fiber membrane with an optimized PDMS coating layer, the permeance was 40 GPU and the hydrogen/carbon dioxide selectivity was 5.6.

• Journal of the Korean Ceramic Society
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• v.41 no.7
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• pp.518-527
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• 2004

In this study, SiC whiskers were grown in porous alumina substrate in order to enhance the filtering efficiency, performance, and durability by controlling pore morphology. This experiment was performed by Chemical Vapor Infiltration (CVI) in order to obtain the whiskers on the inside of pores as well as on the surface of porous the A1$_2$O$_3$ substrate. The deposition behavior was changed remarkably with the deposition position, temperature, and input gas ratio. First, the mean diameter of whisker was decreased as the position of observation moved into the inside of substrate due to the reactant gas depletion effect'. Second, the deposition temperature caused the changes of the deposition type such as debris, whiskers and films and the change in morphology affect the various properties. When SiC films were deposited. the gas permeability and the specific surface area decreased. However, the whisker showed the opposite result. The whiskers increase not only the specific surface area and minimizing pressure drop but also mechanical strength. Therefore it is expected that the porous alumina body which deposited the SiC whisker is the promising material for the filter trapping the particles.

• Journal of Astronomy and Space Sciences
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• v.15 no.1
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• pp.119-138
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• 1998

Recently measurements of atmospheric trace gases from satellite are vigorous. So the development of its data processing algorithm is important. In this study, retrievalof vertical ozone profile from the atmospheric transmittance measured by satellite solar occultation method and its sensitivity to temperature and pressure are investigated. The measured transmittance from satellite is assumed to be given by the limb path transmittance simulated using annual averaged Umkehr data for Seoul. The limb path transmittance between wavelengths $9.89{\mu}m$ and $10.2{\mu}m$ is simulated with respect to tangent heights using the ozone data of HALOE SIDS(Hallogen Occultation Experiment Simulated Instrument Data Set) as an initial profile. Other input data such as pressure and temperature are also from HALOE SIDS. Vertical ozone profile is correctly retrieved from the measured transmittance by onion-peeling method from 50km to 11km tangent heights with the vertical resolution of 3km. The bias error of $\pm0.001$ in measured transmittance, the forced error of $\pm3K$ in each layer temperature, and the forced $\pm3%$ error in each layer pressure are assumed for sensitivity tests. These errors are based on the ADEOS/ILAS error limitation. The error in ozone amount ranges from -6.5% to +6.9% due to transmittance error, from -9.5% to +10.5% due to temperature error, and from -5.1% to +5.4% due to pressure error, respectively. The present study suggests that accurate vertical ozone profile can be retrieved from satellite solar occultation method. Accuracy of vertical temperature profile is especially important in the retrieval of vertical ozone profile.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.5
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• pp.362-368
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• 2021

A homeotropic liquid crystal (LC) alignment state on rubbed fluorinated self-assembled monolayers (FSAMs) is described according to alkyl chain length. A simple procedure, gas-phase method, for the preparation of FSAM was used. The average optical transmittance in the visible light range of FSAMs were 76.63% to 78.21%, which were superior to the conventional polyimide layer having a transmittance of 75.89%. In addition, the excellent homeotropic LC alignment characteristics of FSAMs were observed through pretilt angle measurement and polarized optical microscope images. By measuring the contact angles and the surface energies of FSAMs, it was confirmed that pretilt angles of LC molecules increased according to the alkyl chain length. High optical transparency and uniform homeotropic LC alignment characteristics of FSAMs showed the possibility of FSAMs as an LC alignment layers.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3114-3119
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• 2008

Relatively high convective flow exists in the under-rib regions of a gas diffusion layer (GDL) when serpentine flow fields are employed in a PEMFC. This under-rib convection is believed to be favorable for the performance of PEMFCs, by enabling more effective use of catalysts in the under-rib regions. From the fact that the under-rib convection in a GDL is directly proportional to the permeability of the GDL, computational fluid dynamics (CFD) simulations were performed to discover the relationship between the GDL permeability and the PEMFC performance. Single-, triple-, and quintuple-path parallel serpentine flow fields for $9\;cm^2$ active cell area were considered while changing the GDL permeability from $1{\times}10^{-12}$ to $5{\times}10^{-11}m^2$. The results showed that higher GDL permeability generally resulted in better performance of PEMFCs, but the degree of performance enhancement became smaller as the parallel path number increased. The effects of the permeability on the local variables were also discussed.

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.659-664
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• 2000

To develop anode-supported tubular cell with proper porosity, we have investigated the anode substrate and t the electrolyte-coated anode tube. The anode substrate was manufactured as a function of carbon content in the range of 20 to 50 vol.%. As the carbon COntent increased, the porosity of the anode substrate increased slightly and the carbon c content with proper porosity is found to be 30 vol.%. The anode-supported tube was fabricated by extrusion process a and the electrolyte layer was coated on the anode tube by slurry coating process. The anode-supported tube was cofired successfully at $^1400{\circ}C$ in air. The porosity of the anode tube was 35%. From the gas permeation test, the anode t tube was found to be porous enough for gas supply. On the other hand, the anode-supported tube with electrolyte layer indicated a very low gas permeation rate. This means that the coated electrolyte was dense.

• Journal of the Korean Ceramic Society
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• v.41 no.7
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• pp.548-554
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• 2004

A sol-gel method was applied to coat TiO$_2$ on porous silica prepared using slurry foaming method from silica. from the results of XRD, SEM, and BET, the anatase phase was firstly observed at the coated supports with the heated of 50$0^{\circ}C$. The coated supports with the heated of $700^{\circ}C$ had the maximum anatase peak, and the particle size of coated TiO$_2$ was about 1 ${\mu}{\textrm}{m}$. Bending strength and gas permeability of the porous silica were measured for the feasibility as a catalytic supports. In case of the uncoated porous materials with the strength of 2.4 MPa, the strength increased to 3.9∼4.3 MPa after the coating process regardless of the heating temperature. On the other hand, the permeability of the uncoated porous materials decreased from 770${\times}$10$^{-13}$ $m^2$ to 363${\times}$10$^{-13}$ $m^2$ after the coating process, and it decreased with the increasing heating temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.4
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• pp.154-158
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• 2021

The optical transmittance of Mn-doped SnO₂ monolayer film increased gradually from 80.9 to 85.4 % at 550 nm wavelengths upon increasing the O₂/Ar+O₂ concentration rate from 0 to 7.9 % and the band gap energy changed from 3.0 to 3.6 eV. The resistivity tended to decrease from 3.21 Ω·cm to 0.03 Ω·cm, reaching a minimum at 2.7 %, and then gradually increased from 0.03 to 52.0 Ω·cm at higher O₂/Ar+O₂ gas concentration ratio. Based on XPS spectra analysis, the Sn 3d_5/2 peak of Mn-doped SnO₂ single layer shifted slightly from 486.40 to 486.58 and O_1s peak also shifted from 530.20 to 530.33 eV with increase the O₂/Ar+O₂ concentration ratio. Therefore, the XPS spectra results indicate that a multiphase with SnO and SnO₂ coexisted in the sputtered Mn-doped SnO₂ monolayer film.