• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.330-334
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• 2013

Mixtures of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and silica nanoparticles are coated on the surface of a silk fabrics separator. The coated separators are finally prepared by injecting an electrolyte solution and then characterized for use of lithium-ion battery separator/electrolyte. In the preparation, various contents of dibutylphthalate (DBP) as a plasticizer are used to enhance the formation of micropores within the coated membrane. The coated silk fabrics separators are characterized in terms of ionic conductivity, drenching rate, and electrochemical stability, and the charge-discharge profiles of lithium-ion batteries adopting the coated separators are also examined. As a result, the coated silk fabrics separator prepared using DBP 40~50 wt% and silica shows the superior separator properties and high-rate capability. This is due to (i) high sustainability of silk fabrics, (ii) the formation of micropores with the coated layer membrane by DBP, (iii) increase in drenching rate by silica nanoparticles to involve great enhancements in specific surface area and ionic conductivity.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.1
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• pp.1-10
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• 2018

Recently, there has been rapid development in the field of flexible electronic devices, such as organic light emitting diodes (OLEDs), organic solar cells and flexible sensors. Encapsulation process is added to protect the flexible electronic devices from exposure to oxygen and moisture in the air. Using numerical simulation, we investigated the effects of the encapsulation layer on mechanical stability of the silicon chip, especially the fracture performance of center crack in multi-layer package for various loading condition. The multi-layer package is categorized in two type - a wide chip model in which the chip has a large width and encapsulation layer covers only the chip, and a narrow chip model in which the chip covers both the substrate and the chip with smaller width than the substrate. In the wide chip model where the external load acts directly on the chip, the encapsulation layer with high stiffness enhanced the crack resistance of the film chip as the thickness of the encapsulation layer increased regardless of loading conditions. In contrast, the encapsulation layer with high stiffness reduced the crack resistance of the film chip in the narrow chip model for the case of external tensile strain loading. This is because the external load is transferred to the chip through the encapsulation layer and the small load acts on the chip for the weak encapsulation layer in the narrow chip model. When the bending moment acts on the narrow model, thin encapsulation layer and thick encapsulation layer show the opposite results since the neutral axis is moving toward the chip with a crack and load acting on chip decreases consequently as the thickness of encapsulation layer increases. The present study is expected to provide practical design guidance to enhance the durability and fracture performance of the silicon chip in the multilayer package with encapsulation layer.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.439-444
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• 2015

Several attempts to design the best-available thermosetting road markings by using MMA to improve the durability and retroreflectivity are presented in this paper. In order to improve field applicability, the components of main materials were designed by means of reducing the hardening time lower than eight minutes. The optimum mixing ratio of thermosetting road marking was TSRM-6 composed of 15.6 wt% of MMA monomer ($Tg=105^{\circ}C$), 6.0 wt% of PMMA (MW = 70,000, $Tg=60^{\circ}C$) and 1.2 wt% of TMPTA (MW = 338, $Tg=27^{\circ}C$). Also the homogeneous mixing of all components was necessary. The use of ceramic glass beads with an optimized TSRM-6 exhibited excellent performance by achieving retroreflectivity coefficients of 431, 354 and $172mcd{\cdot}m^{-2}{\cdot}lux^{-1}$ for dry, wet and rainy test condition, respectively at two hundred thousand cycles.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.141-148
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• 1999

Recently, high performance concrete developed has a good quality at fresh and hardened state, but high binder contents results in spending much money on manufacturing and many cracks by drying and autogenous shrinkage, Therefore, in this paper, not only prevention of cracks caused by drying and autogenous shrinkage, but improvement of quality and accomplishment of economy by applying F.A(fly ash), S.F(silica fume) and CSA(calcium sulfa aluminate) expansive additives as an inorganic admixtures in W/B 35% are discussed. According to the experimental results, when 5% of CSA expansive additives and 15:5(F.A:S.F)are replaced at unit cement content, high performance concrete with both good fluidity at fresh state and high compressive strength, compensation of drying and autogenous shrinkage at hardened state are accomplished.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.6
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• pp.32-37
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• 2006

Micron size Co-alloy(T800) powder was coated on Inconel 718 by HVOF thermal spraying for the studies of the improvement of durability of high speed spindle by using Taguchi program for the parameters of spray distance, flow rates of hydrogen and oxygen and powder feed rate. The optimal coating process was determined by the studies of coating properties such as micro-structure, porosity, surface roughness and micro hardness. Friction and wear behaviors of coatings were investigated by sliding wear test at room temperature and $1000^{\circ}F(538^{\circ}C)$. At both room temperature and $538^{\circ}C$ the sliding wear debris and friction coefficients of the coating were drastically reduced compared with the surface of non-coated parent material. This shows that Co-alloy powder coating is highly recommendable for the durability improvement surface coating of high speed air-bearing spindle. At high temperature wear traces and friction coefficients of both coating and non-coating were drastically reduced compared with those of room temperature since the brittle oxides were formed easily on the surface, and the brittle oxide phases were attrited by the reciprocating sliding wear according to the complicated mixed wear mechanisms These oxide particles, partially melts and the melts play role as lubricant and reduce the wear and friction coefficient. This also shows that Co-alloy powder coating is highly recommendable far the durability improvement surface coating on the surface vulnerable to frictional heat such as high speed spindles.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.176-176
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• 2011

경사 코팅법은 증발 물질이 기판에 수직으로 입사하는 기존 코팅방법과 다르게 증발물질이 기판과 $90^{\circ}$ 이하의 경사각으로 입사하도록 하여 코팅하는 방법이다. 이러한 경사 코팅법은 각도를 달리함으로 인해 비스듬한 기둥, 나선형, C-형, S-형, zigzag 구조 등의 정교하고 폭넓은 박막을 형성 할 수 있다. 이러한 경사 코팅법은 경사굴절 광학필터, 선형 편광 등의 광 산업계에서 널리 사용되고 있다. 본 연구에서는 경사 코팅법을 이용하여 마그네트론 스퍼터링법으로 Al 박막을 제조하였고 다양한 경사 각도에 따른 조직의 특성과 내식성 등을 평가하고 비교하였다. 기판을 $0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $90^{\circ}$의 다양한 각도로 위치시켜 냉연강판 및 Si 웨이퍼에 단일층 또는 다층으로 Al 박막을 코팅하였다. 박막의 구조를 확인하기 위해 전자현미경(SEM)을 사용하였으며 기판의 위치에 따른 변화를 관찰하기 위해 시편을 좌, 우, 중간으로 구분하여 분석하였다. Al 박막이 단층일 경우 회전각도 $60^{\circ}$에서 치밀한 조직이 관찰되었으며 이것은 표면의 반사도와 표면조도 결과와도 유사하게 나타났다. 다층 박막에서는 회전각도 $45^{\circ}$에서 아주 치밀한 조직이 나타났으며, $3{\mu}m$ 두께로 코팅한 시편의 염수분무 시험 결과 120시간 경과 후에도 적청이 발생하지 않았다. 이것은 기존의 방법이 약 72시간에서 적청이 발생하는 것과 비교할 때 경사 코팅법으로 코팅된 시편의 내식성이 현저히 향상됨을 나타낸다. 따라서 반응성이 높고 쉽게 산화가 일어나는 철강제품의 부식 방지를 위해 경사 코팅법으로 Al 박막을 제조한다면 치밀한 조직으로 인해 얇은 두께에서도 부식이 발생하는 시간을 연장시켜 제품의 내구수명을 연장시킬 수 있을 것으로 기대된다.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.665-668
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• 2008

Recently the city construction and the concrete structures are more becoming extra weight and the efficient use of the space by the population intensively and follow in industrial intensive commerce and the residence commerce composition building which leads the high story of the building. Consequently the high rise of the building which space applies efficiently in objective which will increase continuously. Also with high rise of buildings durability it will be able to increase the life of the structure is emphasized and the concrete structure is demanding the more high strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1013-1016
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• 2008

The demands of urban people for rural natural environments will increase but poor and low level of infrastructure facilities delay the development of green tourism villages as an attractive green tour destination. The objective of this paper are to offered a rural landscape improvement simulation of a aqueduct and designing that to meet the needs of the community.

• Composites Research
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• v.13 no.4
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• pp.33-41
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• 2000

In this research, the mathematical modeling of the formation of SiC layer on the activated carbon was studied to improve the durability and the oxidation resistance of catalyst supports. SiC layer on the activated carbon was formed by permeating SiC from dichlorodimethylsilane(DDS) into pores and depositing while the porous structure was kept. The best conditions of manufacturing the support were found by studying the characteristics of SiC/C which was modelled under various deposition conditions. Changes of the amount of deposition, the pore diameter, the surface area with time were obtained by simulating convection, diffusion and reaction in an isothermal reactor at a steady state. The uniform deposition in the pores of samples was obtained at a lower concentration of the reactant and a lower pressure. Additionally, it was observed that the pore diameter and the surface area have points of inflection at certain times of deposition, because deposition occurred on the inside surface of the pore at first and then on the outside surface of the particle.

• Elastomers and Composites
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• v.44 no.3
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• pp.299-307
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• 2009

The effects of reinforcing materials on durability and mechanical properties of V-rib belt were investigated. Cotton fiber and ZnO were used as a filler for CR, and cotton and aramid fiber were used for EPDM rubber compounds. These materials were prepared as a specimen and V-rib belt for heat resistant and mechanical test. High contents of ZnO give improved wear resistance, and higher contents of cotton fiber showed higher durability in high rotation speed but lower wear resistance for CR rubber compounds. Using the aramid and cotton fiber together in EPDM rubber compounds, thermal and wear resistance were improved simultaneously. The material containing EPDM matrix showed better durability and wear resistance than those of containing CR matrix comparing in the same cotton fiber contents.