• 한국정밀공학회지
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• 제20권5호
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• pp.189-195
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• 2003

Atomic Force Microscope (AFM) has been widely used in micro/nano-scale studies and applications for. the last few decade. In this work, wear characteristics of silicon-based AFM tip was investigated. AFM tip shape was observed using a high resolution SEM and the wear coefficient was approximately calculated based on Archard's wear equation. It was shown that the wear coefficient of silicon and silicon nitride were in the range of ${10}^{-1}$~${10}^{-3}$ and ${10}^{-3}$~${10}^{-4}$, respectively. Also, the effect of relative humidity and sliding distance on adhesion-induced tip wear was discussed. It was found that the tip wear has more severe for harder test materials. Finally, the probable wear mechanism was analyzed from the adhesive and abrasive interaction point of view.

• 한국재료학회지
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• 제9권4호
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• pp.392-397
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• 1999

The tensile strength and water resistance of ADC12 alloy matrix composites reinforced with saffil/ceraklwool and saffil/Si particle prepared by squeeze casting have been investigated in room temperature and $250^{\circ}C$. Adhesive and scuffing wear phenomena was studied when load was changed to 10~40N and wear velocity was 2.0m/s at room temperature and $250^{\circ}C$. Generally, the morphology of tensile fractured surface revealed dimple pattern which implies ductile fracture of the composites. However, cleavage fracture was also observed in case of ADC12 alloy based saffil/Si particle composite. The maximum tensile strength of 320MPa was obtained in ADC12 alloy based composites reinforced by saffil/cerakwool(5:5) preformed fibers. In the results of dry wear test, it was observed that scuffing was occurred at 40N in room temperature and 30N for $250^{\circ}C$.

• 한국세라믹학회지
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• 제42권2호
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• pp.88-93
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• 2005

아크 이온 플레이팅과 스퍼터로 구성된 하이브리드 시스템을 이용하여 다성분계 Ti-Al-Si-N 코팅막을 WC-Co 기판에 증착하였다. 증착시 Si 함량을 변화시켜 코팅막의 마모특성에 Si 함량이 미치는 영향에 대하여 조사하였다. 마모 특성을 관찰하기 위하여 Ti-Al-Si-N 코팅막이 증착된 WC-Co 원판에 3N의 하중, 0.1 m/s의 속도로 볼 온 디스크(ball-on-disk) 형태의 마모시험기를 이용하여 건식 마모 실험을 하였다. 상대재로는 스틸볼과 지르코니아볼을 사용하였다. 상대재가 스틸볼의 경우 Ti-Al-Si-N 코팅막의 마찰계수가 Ti-Al-N 코팅막의 마찰계수보다 낮게 나타났다 이는 Si가 첨가되어 마모시 상대재와 코팅막 사이에 자기윤활효과(self-lubricant effect)에 의한 것으로 여겨진다. 코팅막과 스틸볼 사이에 응착 마모 거동을 보였으며, Si의 함량이 증가함에 따라 마찰계수는 감소하였다. 한편, 상대재가 지르코니아 볼의 경우 코팅막과 지르코니아 볼 사이에서 연삭마모 거동이 더 지배적이었고, Si 함량이 증가할수록 마찰계수는 증가하였다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.223-224
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• 2002

The mechanisms of formation of transfer film under the condition of wear of Steel AISI1020 by natural rubber were investigated. The transfer film was observed and the formation mechanisms were clarified. The formation process of transfer film on the worn surface of the steel could be divided into two stages. Firstly, the adhesive layer emerged on the worn surface of the steel by adhesion of natural rubber. in which the macromolecular chains of natural rubber joined to the surface of the steel by Van der Waals' force. And then, the iron atom and metal oxide reacted with the macromolecular of natural rubber in the adhesive layer and produced Fe-polymer compound. As a result, the transfer film was formed on the worn surface of the steel. The transfer film was joined to the worn surface of the steel by the chemical bonds and electrostatic force.

• 한국표면공학회지
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• 제44권6호
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• pp.246-249
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• 2011

Surface modification before coating nickel by coupling agents and/or etchant of glass did not provide enough adhesive strength of electroless nickel deposits on glass. Effect of heat treatments on hardness as well as adhesion of nickel deposits was studied by using tape test for adhesion, nanoindenter for hardness and glancing angle x-ray diffractometer (GAXRD) for phase characterization. Heat treatment improved hardness as well as adhesion. XRD results give that the improvements of adhesion and hardness are due to the formation of $NiSiO_4$ around the interface between the nickel deposits and the glass and the precipitation of $Ni_3P$ causing precipitation hardening, respectively. The details in effects of heat treatment on adhesion and hardness are described here.

• Current Photovoltaic Research
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• 제10권1호
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• pp.1-5
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• 2022

Bifacial photovoltaic (PV) technology has received considerable attention in recent years due to the potential to achieve a higher annual energy yield compared to its monofacial PV systems. In this study, we fabricated the bifacial c-Si PV module with a shingled design using the conventional patterned bifacial solar cells. The shingled design PV module has recently attracted attention as a high-power module. Compared to the conventional module, it can have a much more active area due to the busbar-free structure. We employed the transparent backsheet for a light reception at the rear side of the PV module. Finally, we achieved a conversion power of 453.9 W for a 1300 mm × 2000 mm area. Moreover, we perform reliability tests to verify the durability of our Shingled Design Bifacial c-Si Photovoltaic module.

• 마이크로전자및패키징학회지
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• 제12권1호
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• pp.9-16
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• 2005

This paper presents the development of new anisotropic conductive adhesives with enhanced thermal conductivity for the wide use of adhesive flip chip technology with improved reliability under high current density condition. The continuing downscaling of structural profiles and increase in inter-connection density in flip chip packaging using ACAs has given rise to reliability problem under high current density. In detail, as the bump size is reduced, the current density through bump is also increased. This increased current density also causes new failure mechanism such as interface degradation due to inter-metallic compound formation and adhesive swelling due to high current stressing, especially in high current density interconnection, in which high junction temperature enhances such failure mechanism. Therefore, it is necessary for the ACA to become thermal transfer medium to improve the lifetime of ACA flip chip joint under high current stressing condition. We developed thermally conductive ACA of 0.63 W/m$\cdot$K thermal conductivity using the formulation incorporating $5 {\mu}m$ Ni and $0.2{\mu}m$ SiC-filled epoxy-bated binder system to achieve acceptable viscosity, curing property, and other thermo-mechanical properties such as low CTE and high modulus. The current carrying capability of ACA flip chip joints was improved up to 6.7 A by use of thermally conductive ACA compared to conventional ACA. Electrical reliability of thermally conductive ACA flip chip joint under current stressing condition was also improved showing stable electrical conductivity of flip chip joints. The high current carrying capability and improved electrical reliability of thermally conductive ACA flip chip joint under current stressing test is mainly due to the effective heat dissipation by thermally conductive adhesive around Au stud bumps/ACA/PCB pads structure.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.449-449
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• 2011

We reported the direct effect of intrinsic surface energy of dry adhesive material to the Van der Waals and capillary forces contributions of the total adhesion force in an artificial gecko-inspired adhesion system. To mimic the gecko foot we fabricated tilted nanohairy structures using both lithography and ion beam treatment. The nanohairy structures were replicated from Si wafer mold using UV curable polymeric materials. The control of nanohairs slanting angles was based on the uniform linear argon ion irradiation to the nanohairy polymeric surface. The surface energy was studied utilizing subsequent conventional oxygen ion treatment on the nanohairy structures which resulted in gradient surface energy. Our shear adhesion test results were found in good agreement with the accepted Van der Waals and capillary forces theory in the gecko adhesion system. Surface energy would give a direct impact to the effective Hamaker constant in Van der Waals force and the filling angle (${\varphi}$) of water meniscus in capillary force contributions of gecko inspired adhesion system. With the increasing surface energy, the effective Hamaker constant also increased but the filling angle decreased, resulting in a competition between the two forces. Using a simple mathematical model, we compared our experimental results to show the quantitative contributions of Van der Waals and capillary forces in a single adhesion system on both hydrophobic and hydrophilic surfaces. We found that the Van der Waals force contributes about 82.75% and 89.97% to the total adhesion force on hydrophilic and hydrophobic test surfaces, respectively, while the remaining contribution was occupied by capillary force. We also showed that it is possible to design ultrahigh dry adhesive with adhesion strength of more than 10 times higher than apparent gecko adhesion force by controlling the surface energy and the slanting angle induced-contact line of dry adhesive the materials.

• 대한기계학회논문집
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• 제17권10호
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• pp.2498-2508
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• 1993

$Al/SiC/Al_{2}O_{3}$ hybrid composites are fabricated by squeeze infiltration method. From the misconstructive of $Al/SiC/Al_{2}O_{3}$ hybrid composites fabricated by squeeze infiltration method, uniform distribution of reinforcements and good bondings are found. Hardness value of $Al/SiC/Al_{2}O_{3}$ hybrid composites increases linearly with the volume fraction of reinforcement because SiC whisker and $Al_{2}$O$_{3}$ fiber have an outstanding hardness. Optimal aging conditions are obtained by examining the hardness of $Al/SiC/Al_{2}O_{3}$ hybrid composites with different aging time. Tensile properties such as Young's modulus and ultimate tensile strength are improved up to 30% and 40% by the addition of reinforcements, respectively. Failure mode of $Al/SiC/Al_{2}O_{3}$ hybrid composites is ductile on microstructural level. Through the abrasive wear test and wear surface analysis, wear behaviour and mechanism of 6061 aluminum and $Al/SiC/Al_{2}O_{3}$ hybrid composites are characterized under various testing conditions. The addition of SiC whisker to $Al/SiC/Al_{2}O_{3}$ composites gives rise to improvement of the wear resistance. The wear resistance of $Al/SiC/Al_{2}O_{3}$ hybrid composites is superior to that of Al/SiC composites. The wear mechanism of aluminum alloy is mainly abrasive wear at low speed range and adhesive and melt wear at high speed range. In contrast, that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is abrasive wear at all speed range, but severe wear when counter material is stainless steel. As the testing temperature increases, wear loss of aluminum alloy decreases because the matrix is getting more ductile, but that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is hardly varied. Oil lubricant is more effective to reduce the wear loss of aluminum alloy and $Al/SiC/Al_{2}O_{3}$ hybrid composites at high speed range.

• Current Photovoltaic Research
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• 제11권4호
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• pp.114-117
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• 2023

Transparent Photovoltaic (PV) modules have recently been in the spotlight because they can be applied to buildings and vehicles. However, crystalline silicon (c-Si) solar modules, which account for about 90% of the PV module market, have the disadvantage of applying transparent PV modules due to their unique opacity. Recently, a see-through type PV module using a crystalline silicon solar strap has been developed. However, there is a problem due to a decrease in aesthetics due to the metal ribbon in the center of the see-through type PV module and difficulty bonding the metal ribbon due to the low voltage output of the strap. In this study, to solve this problem, we developed a fabrication process of series connected c-Si solar strap cells using the c-Si solar cells. We succeeded in fabricating a series connected strap with a width of 2-10 mm, and we plan to manufacture an aesthetic see-through type c-Si PV module.