• Journal of the Korean Society for Precision Engineering
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• v.30 no.8
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• pp.802-808
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• 2013

Thermal barrier coating (TBC) is used to protect substrates and extend the operating life of gas turbines in power plant and aeronautical applications. The major causes of failure of such coatings is spallation, which results from thermal stress due to a thermal expansion coefficient mismatch between the top coating and the bond coating layers. In this paper, the effects of the material properties and the thickness of the top coating layer on thermal stresses were evaluated using the finite element method and the equation for the thermal expansion coefficient mismatch stress. In addition, we investigated a design technique for the top coating whereby thermal resistance is exploited.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.135-136
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• 2011

본 연구에서는 실리콘 기판위의 형성된 AAO (Anodic Aluminum Oxide)의 barrier layer를 $Cl_2/BCl_3$ gas mixture에서 Neutral Beam Etching (NBE)과 Ion Beam Etching (IBE)로 각각 식각한 후 그 결과를 비교하였다. 이온빔의 경우 나노사이즈의 AAO pore의 charging에 의해 pore 아래쪽의 위치한 barrier layer를 어떤 식각조건에서도 제거하지 못하였다. 하지만, charging effect가 없고, 높은 중성화율을 나타내는 low angle forward reflected 방식의 neutral beam etching (NBE)에서는 $BCl_3$-rich $Cl_2/BCl_3$ gas mixture인 식각조건에서 AAO pore에 휘발성 $BO_xCl_y$를 형성하면서 barrier layer를 제거할 수 있었다.

• Korean Journal of Medicinal Crop Science
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• v.28 no.2
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• pp.152-166
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• 2020

Background: Ginsenosides, which have various physiological activities, are known to be abundant in the leaves and roots of ginseng. Ginseng sprouts can be used as a fresh vegetable and roots, stems, and leaves of ginseng can be consumed. This study aimed to investigate the effect of carbon dioxide treatment and the modified atmosphere (MA) packaging method in suppressing quality deterioration during the distribution of ginseng sprouts. Methods and Results: Ginseng sprouts were packed using Styrofoam, barrier film + non gas treatment, barrier film + gas treatment, 15 ㎛ polyamide (PA) double film + non gas treatment, 15 ㎛ PA double film + gas treatment, 25 ㎛ PA film + non gas treatment, or 25 ㎛ PA film + gas treatment. Quality parameters including gas composition, relative humidity, chlorophyll SPAD (Soil Plant Analysis Development) value, firmness, and rate of quality loss in ginseng sprouts were monitored at the following temperatures: 20℃, and 10℃. Ginseng sprouts packaged with 25 ㎛ PA film showed loss in quality because of wilting owing to low relative humidity within the film. Chlorophyll and firmness did not differ between film and gas treatments. The time point at which the combined loss from softening and decay owing to fungal, and bacterial infection and wilt reached 20% was considered the limit of distribution. At 20℃, the packaging not included in the 20% distribution loss rate limit or up to 7 days was 15 ㎛ PA double film + gas treatment. At 10℃, the packaging not included in the 20% distribution loss rate limit for up to 18 days were barrier film + gas treatment and 15 ㎛ PA double film + gas treatment. Conclusions: The film packaging suitable for the distribution of ginseng sprouts was found to be the barrier film and PA film with low gas permeability and maintaining hygroscopicity at 95% relative humidity. To prevent the loss in quality of ginseng sprouts, gas treatment (8% of O₂ and 18% of CO₂) in the film was found to be more suitable than no gas treatment for inhibition of decay.

• Journal of Magnetics
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• v.10 no.2
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• pp.66-70
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• 2005

The junction properties between the ferromagnet (FM) and two-dimensional electron gas (2DEG) system are crucial to develop spin electronic devices. Two types of 2DEG layer, InAs and GaAs channel heterostructures, are fabricated to compare the junction properties of the two systems. InAs-based 2DEG layer with low trans-mission barrier contacts FM and shows ohmic behavior. GaAs-based 2DEG layer with $Al_2O_3$ tunneling layer is also prepared. During heat treatment at the furnace, arsenic gas was evaporated and top AlAs layer was converted to aluminum oxide layer. This new method of forming spin injection barrier on 2DEG system is very efficient to obtain tunneling behavior. In the potentiometric measurement, spin-orbit coupling of 2DEG layer is observed in the interface between FM and InAs channel 2DEG layers, which proves the efficient junction property of spin injection barrier.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.9
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• pp.421-426
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• 2005

A wire-plate discharge system with a slit barrier has been proposed and investigated experimentally by focusing on the discharges on the slit barrier and ozone generation characteristics. This wire-plate discharge system with a slit barrier can generate an intensive corona discharges, and produce corona discharge twice, once from the corona wire electrode and second time from the surface and the slits of the slit dielectric barrier. As a result this propose wire-plate discharge system with the slit barrier can produce greatly increased ozone than without the slit barrier. This type of wire-plate discharge system with the slit barrier could be used for effective ozone generation as a means with retard to the removal of pollutant gas

• Elastomers and Composites
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• v.46 no.2
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• pp.112-117
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• 2011

Recently, high growth potential of barrier materials industry including high performance packing materials was expected with increasing the national income and well-being culture. As high barrier materials, polymer nanocomposites have considerable attractions due to their excellent physical properties compared to conventional composite materials. In general, polymer nanocomposites were consisted of polymer matrix and inorganic fillers, such as layered silicate, carbon nanotubes, and metal- or inorganic nanoparticles. Among these materials, layered silicate which was called as the clay was usually used as nano-fillers because of naturally abundant and most economical and structural properties. Clay-reinforced polymer nanocomposites have various advantages, such as high strength, flammability, gas barrier property, abrasion resistance, and low shrinkage and used for automotive and packing materials. Therefore, in this paper, we focused on the need of gas barrier materials and materials-related technologies.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.12
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• pp.1028-1032
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• 2009

In this study, the influences of silicon-based gas barrier films fabricated by using a facing target sputtering(FTS) system on the gas permeability for flexible displays have been investigated. Under these optimum conditions on the $SiO_x$ film with oxygen concentration($O_2/Ar+O_2$) of 3.3% and the $SiO_xN_y$ film with nitrogen concentration($N_2/Ar+O_2+N_2$) of 30% deposited by the FTS system, it was found that the films were grown about 4 times higher deposition rate than that of the conventional sputtering system and showed high transmittance about 85% in the visible light range. Particularly, the polyethylene naphthalate(PEN) substrates with the $SiO_x$ and/or $SiO_xN_y$ films showed the enhanced properties of decreased water vapor transmission rate (WVTR) over $10^{-1}\;g/m^2{\cdot}day$ compared with the PEN substrate without any gas barrier films, which was due to high packing density in the Si-based films with high plasma density by FTS process and/or the denser chemical structure of Si-N bond in the $SiO_xN_y$ film.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.271-272
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• 2015

Gas turbine combustors is critical part due to high temperature operating conditions and the optimization of cooling design is required to avoid combustor failure. In gas turbine combustor, effusion cooling, impingement cooling and thermal barrier coating (TBC) are commonly used to improve cooling characteristics. In conceptual design, these cooling schemes are designed by 1D heat transfer calculation. Therefore, these design should be validated ted by nemurical or experiment methods. In this study, Conjugate Heat Transfer (CHT) analysis is performed for validation of gas turbine combustor cooling design.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.6
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• pp.379-383
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• 2015

Some insulating materials are organized and analyzed with variables to obtain the optimized profile of encapsulated three phase of epoxy barrier which is applied to gas compartment and supporting conductors for high voltage GIS (gas insulated switchgear). The high voltage GIS is used in electrical power system and operating reliability. In this paper, optimization possibility of barrier shape including both electrical insulation performance and mechanical strength, premised on that condition minimizing volume and light weight should be kept for high voltage GIS, could be achieved by analysis simulation. As a result, filling material which is lower permittivity such as $SiO_2$ instead of $Al_2O_3$ properly to the epoxy material, can be improved to increase the electrical insulation performance and mechanical strength for an optimized profile barrier of a high voltage GIS.

• Journal of the Korean Institute of Gas
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• v.15 no.5
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• pp.13-18
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• 2011

Experimental studies were carried out to investigate the characteristics of explosion mitigations by varying concentrations of agar gel barriers in an explosion chamber, 1400 mm in length, with a square cross-section of $100{\times}100mm^2$. Another extension chamber, $100{\times}100{\times}300mm^3$, was made to hold a gel barrier. Four different gel concentrations were used in the measurements: 2, 3, 4, 5 %(by weight of gel). Displacement of the gel barrier was measured using a high speed camera, and pressure development was measured using pressure transducers and a data acquisition system. It was found that as the concentrations of the gel barriers increased, the gel rupture time and the time taken to reach the maximum pressure increased. It was also found that the increment of gel concentrations increased the reduction percentage in the maximum pressure between before and after gel barrier.