• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.407-414
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• 2017

In this study, a performance evaluation was conducted using a SUS 304 plate applied to low-temperature co-fired coating as a replacement for titanium plates. As a result of computational fluid dynamic analysis, the SUS 304 plate, applied to low-temperature co-fired coating, showed better heat transfer performance than a titanium plate, for 100 micron thickness coating. The result of the experiments using an actual heat exchanger revealed that a coated SUS 304 plate showed better heat transfer performance than a titanium plate. Furthermore, as the degree of corrosion and scale formation of the plate was confirmed through an overhaul inspection, the corrosion resistance of a coated SUS 304 plate was found to be almost the same as that of a titanium plate, and the inhibition effect of scale formation by sea water was better with a coated SUS 304 plate.

• Journal of the Microelectronics and Packaging Society
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• v.2 no.1
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• pp.49-58
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• 1995

출발물질은 cordierite 유리와 borosilicate/Si3N4 복합분말을 사용하였다. Cordierite 유리조성은 무게비로 17.8MgO-23.1Al2O3-48.1ASiO2-5.0ZnO-1.0B2O3를 선택하였다. Borosilicate/Si3N4복합분말은 sol-gel법으로 a-si3N4 core 분말에 borosilicate 겔을 코팅하여 얻었다. 복합분말과 cordierite 유리 분말을 부피비로 0/100, 12.5/87.5 및 25/75의 조성으로 혼합하여 tape casting 에 의해 green sheet를 제작하였다. 이들 sheet들을 800~100$0^{\circ}C$에서 2시간 소성하여 얻은 시편을 SEM, XRD, 밀도, 유전상수 등을 측정하여 저 유전율의 저온 소성 기판재료를 제조하기 위한 조건들을 검토하였다.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.35-41
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• 2016

Ceramic-metal based high power LED array package was developed via thick film LTCC technology using a glass-ceramic insulation layer and a silver conductor patterns directly printed on the aluminum heat sink substrate. The thermal resistance measurement using thermal transient tester revealed that ceramic-metal base LED package exhibited a superior heat dissipation property to compare with the previously known packaging method such as FR-4 based MCPCB. A prototype LED package sub-module with 50 watts power rating was fabricated using a ceramic-metal base chip-on-a board technology with minimized camber deformation during heat treatment by using partially covered glass-ceramic insulation layer design onto the aluminum heat spread substrate. This modified circuit design resulted in a camber-free packaging substrate and an enhanced heat transfer property compared with conventional MCPCB package. In addition, the partially covered design provided a material cost reduction compared with the fully covered one.

• Journal of the Korea Institute of Building Construction
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• v.20 no.5
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• pp.425-432
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• 2020

The appearance of Korean traditional roof tiles is beautiful and excellent in water resistance, fire resistance and durability, but a high sintering temperature of 1,200℃ or higher is required. Therefore, due to the economical and heavy weight problem, the current trend is to use different roof finishing materials than Korean traditional roof tiles. By adding nanoaluminosilicate to clay and kaolin, which are the materials of the clay roof tiles, the sintering temperature is sintered at a low temperature of 1,000℃ or less, and the optimal mixing and material process is designed to satisfy the characteristics required as a Korean traditional roof tile. The results of this study again demonstrate the superiority of Korean traditional tiles with roof finishing materials using nanoaluminate. The properties of Korean traditional roof tiles that satisfy the criteria of KS F 3510 by applying fire resistance of natural minerals and nanoparticle technology to flexural strength of 2800N, Bulk specific gravity of 2.0g/㎤ and absorption rate of less than 10.0%, through which and researched materials development.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.55.2-55.2
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• 2010

기존의 thermal spray coating은 분사시 가스와 입자가 높은 열을 동반하여 상대적으로 차가운 기판과의 충돌되는 과정에서 기판과 입자 사이에 열응력이 발생하게 되고, 이것은 코팅 특성을 저하시킨다. 또한 고온의 가연성 가스등의 사용으로 작업 시 안전문제 등의 단점이 있었다. 이러한 단점을 보완하기 위하여 분사 시 운동에너지를 주로 이용하는 cold spray coating 공정이 개발되었다. 이 공정은 코팅 입자를 임계속도 이상으로 가속시켜 입자와 기판이 충돌시 소성 변형을 통해 적층되는 코팅기술이다. Cold spray coating공정은 상온 코팅이 가능하기 때문에 주입입자의 물성이 비교적 그대로 유지되고, 고온의 열로 인한 기판의 변질을 막을 수 있다. Cold Spray coating에서 주로 원형 노즐을 사용하나 본 연구에서는 분사 효율 향상을 위한 광폭노즐을 사용하여 코팅 시간 단축을 기대하고 있다. 임계속도 이상의 입자 확보를 위하여 노즐의 expansion ratio와 노즐 shape의 변화를 주어 그에 따른 노즐내의 유동장을 수치해석을 통해 계산하였다. 분사되는 출구면과 기판 사이의 입자 속도 분포를 해석하였고, 이를 통해 임계속도 이상의 속도를 갖는 유효 입자들의 분포 및 유효 분사 면적을 예측하였다. 또한, 기존의 원형 노즐과 광폭 노즐과의 유동장 비교 및 각 노즐 분사면을 분석하여 cold spray coating공정에서의 효율적인 노즐 형상을 디자인하였다.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.3 s.40
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• pp.33-38
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• 2006

Aerosol slurry composed of dielectric materials, distilled water, and deflocculants was sprayed on the substrates, through a high-pressure spray gun as an aerosol. The coated layers were cofired together with $Al_{2}O_{3}$ substrates and green sheets on which the inner connectors were printed. Although the coating rate of coated layers strongly depended on slurry viscosity, spray shape, and the pressure of the spray gun, the coated density was not changed. Buried conductors were maintained as printed by high pressure spray coating method, because the pressing process was not used. At the optimum condition of air controller step 3-4 and slurry viscosity c.p 2000-4000, dense and uniform layers could be achieved. Comparing with conventional lamination process using green sheets, spray coating method enabled thin dielectric layers of $20{\sim}50{\mu}m$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.1
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• pp.38-43
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• 2018

Ceramic membrane has been widely used for water treatment due to its advantages of eco-friendly property and low energy consumption. However, high porosity of ceramic membrane higher than 40 % may cause a problem of strength, when it is applied to a water treatment module. In order to solve this problem, the strength of the membrane edge was improved by using the ceramic glaze. Four different glaze compositions for low temperature sintering was selected to minimize the deformation of the membrane microstructure. After coating with low temperature glaze, cracks were observed due to differences in thermal expansion coefficient between the membrane and glaze. Thus, the thermal expansion coefficient of glaze was controlled by addition of cordierite and petalite. As a results, the compressive strength of the ceramic membrane, which was coated with the optimized glaze composition, was increased from $27N/m^2$ to $117N/m^2$, indicating that the glaze coating can improve the disadvantages of the fragile ceramic membrane.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.298-307
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• 2019

Two types of CaO-Al₂O₃-SiO₂ (CAS) glass powder applied spray coating on the surface of sintered Al₂O₃ were researched for sintering behavior; (1) Si-rich, glass containing high content SiO₂, (2) Ca-rich, containing high content CaO. Foaming of bubbles remaining inside the Ca-rich glass was produced at a viscosity of approximately 10⁷~10⁹ poise, resulting in decreasing shrinkage (interfering with sintering) and increasing surface roughness. In case of Si-rich glass, there was no serious foaming bubbles phenomenon like Ca-rich below 1000℃, however cristobalite crystals with low density occurred at 1200℃ and then produced re-foaming of bubbles, resulting in abnormal sintering behavior. These phenomenon is considered to be a decrease in viscosity due to an increase in the Ca content of the glass according to the formation of low-density cristobalite crystals. Therefore, in case of CAS glass, it is necessary to consider the increase of surface roughness and the sintering interference because of foaming bubbles phenomenon at low temperature sintering. Especially, when containing high SiO₂ content, abnormal foaming phenomenon due to crystallization at high temperature should be predicted.

• Journal of IKEEE
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• v.23 no.3
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• pp.904-909
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• 2019

Using the ion-beam irradiated indium zinc oxide (IZO) films which was cured at $100^{\circ}C$, uniform LC and homogeneous alignment of liquid crystal (LC) molecules was achieved. The IZO film was deposited on the glass substrate at the curing temperature of $100^{\circ}C$ and irradiated by the ion-beam which is an LC alignment method. To verify the LC alignment characteristics, polarizing optical microscope and the crystal rotation method were used. Additionally, it was confirmed that the LC cell with the IZO films had an enough thermal budget for high-quality LC applications. Field emission scanning electron microscope was conducted as a surface analysis to evaluate the effect of the ion-beam irradiation on the IZO films. Through this, it was revealed that the ion-beam irradiation induced rough surface with anisotropic characteristics. Finally, electro-optical (EO) performances of the twisted-nematic cells with the IZO films were collected and it was confirmed that this cell had better EO performances than the conventional rubbed polyimide. Furthermore, the polar anchoring energy was measured and a suitable value for stable LC device operation was achieved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.307-307
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• 2008

전자부품에서 기존에 봉착, 코팅, 결합용 glass frit로 사용되어 왔던 Pb계 glass frit는 낮은 융점을 가지고 있고, 화학적으로도 매우 안정한 특성을 가지고 있다. 그러나 Pb계 glsss frit은 환경에 심각한 문제를 초래하기 때문에 이를 대체하기 위하여 저온에서 소성이 가능한 인산주석계를 기본조성계로 설정하였다. 인산주석계 glass의 취약한 내화학성, 내수성과 SnO의 환원에 의한 결정 석출 등의 문제를 해결하기 위하여 $R_2O_3$, RO 등을 첨가하여 glass frit의 특성을 향상시키고자하였다. 수분에 취약한 $P_2O_5$계 glass의 $R_2O_3$를 첨가하여 항온항습기를 이용하여 흡습성을 측정하고, 내수성에 가장 안정한 특성을 보이는 SnO-$P_2O_5-R_2O_3$ 계 glass 조성에 RO를 첨가하여 RO 첨가량에 따른 내산성과 내알칼리성의 변화를 관찰하였다. SnO-$P_2O_5-R_2O_3$계 glass의 RO첨가량에 따른 melting 특성의 변화를 flow-button test를 통해 관찰하였다. SnO-$P_2O_5-R_2O_3$계는 RO계의 변화에 따라 전이온도가 증가하고, 열팽창계수가 감소하는 결과를 보였다.