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원자간힘 현미경을 이용한 폴리머 박막의 트라이볼로지 특성에 대한 온도의 영향
김광섭(Kwang-Seop Kim),Yasuhisa Ando,김경웅(Kyung-Woong Kim) 한국트라이볼로지학회 2007 한국트라이볼로지학회 학술대회 Vol.2007 No.6
In this study, adhesion and friction tests were carried out in order to investigate the effect of temperature on the tribological characteristics of poly(methyl methacrylate)(PMMA) film using atomic force microscope. The pull-off and friction forces on PMMA film were measured under high vacuum condition (below 1 × 10?⁴ Pa) at various temperatures in the range from 300 K to 420 K. Friction tests also were conducted under high vacuum and atmospheric condition at room temperature. The surface properties of PMMA film was changed suddenly at 420 K, higher 50 K than the Tg of PMMA. Subsequently, the pull-off force increased and was proportional to the maximum applied load at 420 K while it did not depend on the maximum applied load at below 395 K. The friction force started to increase at 370 K and increased greatly at 420 K. In addition, from force-displacement curves, it was observed that the stiffness of PMMA film decreased and the plastic deformation was generated at only 420 K. After the heating of PMMA film up to 420 K, the friction and pull-off forces decreased generally. The RMS roughness was increased and the friction coefficient in atmospheric condition was decreased as well. As a result, it was found that the temperature affected greatly the tribological characteristics of PMMA, especially, at high temperature where PMMA film became soft enough. In addition, the surface property of PMMA film can be changed by the heating and the change affected strongly the tribological characteristics of PMMA film.
탄소와 구리의 마찰 및 마모에 관한 분자 동역학 시뮬레이션
김광섭(Kwang-Seop Kim),강지훈(Ji-Hoon Kang),김경웅(Kyung-Woong Kim) 한국트라이볼로지학회 2003 한국트라이볼로지학회 학술대회 Vol.36 No.-
In this paper, friction and wear behaviors between monocrystalline, defect-free copper and carbon on the atomic scale are investigated by using 2-dimenaional molecular dynamics simulation. It is assumed that all interatomic forces are given by Morse potential. The deformation of carbon is assumed to be neglected and vacuum condition is also assumed. Average friction and normal forces for various surface conditions, various scratch speeds and scratch depths are obtained from simulations. Changes of wear behaviors for various scratch speeds and surface conditions are investigated by observing snapshots in scratch process. The effects of surface conditions, scratch speeds, and scratch depths on the friction force, normal force, and friction coefficient are also investigated.
열가소성 폴리머 필름의 마이크로 점착 및 마찰 거동에 대한 온도의 영향
김광섭(Kwang-Seop Kim),허정철(Jung-Chul Heo),김경웅(Kyung-Woong Kim) 한국트라이볼로지학회 2008 한국트라이볼로지학회 학술대회 Vol.2008 No.6
Adhesion and friction tests were carried out in order to investigate the adhesion and friction behaviors between a PMMA film and a fused silica lens and the effect of temperature on the behaviors in the micro scale. For the tests, a microtribometer system was used. The pull-off and friction forces on the PMMA film were measured under atmospheric condition as the temperature of the PMMA film was increased from 300 K to 443 K (heating) and decreased to 300 K (cooling). The adhesion and friction behaviors were changed with the change of the PMMA surface state as the temperature increased. In glassy state below 363 K, the PMMA film was partially tom out due to adhesive friction during sliding and the transfer layer of the PMMA film was formed in the interface. In rubbery state from 363 K to 423 K, the pull-off and friction forces increased greatly as the temperature increased. In addition, the deformation of the PMMA surface was observed due to ploughing friction. In viscous state above 423 K. the fingering instability was observed when the PMMA film contacted with the lens. It was also found that the adhesion and friction behaviors can be varied with the thermal history of the PMMA film. The residual solvent in the PMMA film could emerge to the PMMA surface due to the heating and reduced the pull-off and friction forces.
분자동역학 시뮬레이션을 이용한 다이아몬드 나노임프린트 리소그라피에서의 점착에 관한 연구
김광섭(Kwang-Seop Kim),강지훈(Ji-Hoon Kang),김경웅(Kyung-Woong Kim) 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.39 No.-
In this paper, molecular dynamics simulations are performed to analyze the adhesion between a diamond mould and a copper substrate in diamond nanoimprint lithography. The diamond nanoimprint lithography process is simplified as punch-type nanoindentation. The copper substrates are assumed to monocrystalline and defect free and consist of 22500~80000 atoms depending on their dimension. The diamond moulds consist of 916 or 2414 atoms, which is assumed to be rigid. The consistent results for the maximum normal force and the adhesion force are obtained regardless of the size of substrates and the adhesion hysteresis is shown in all cases. It is found that the friction acting on the sidewalls of the mould affects the adhesion significantly when the mould is released from the substrate.
열 나노임프린트 리소그래피에서 사용되는 스탬프와 폴리머 재료 사이의 점착 특성
김광섭(Kwang-Seop Kim),강지훈(Ji-Hoon Kang),김경웅(Kyung-Woong Kim) 한국트라이볼로지학회 2006 한국윤활학회지(윤활학회지) Vol.22 No.4
In this paper, the adhesion characteristics between a fused silica without or with an anti-sticking layer and a thermoplastic polymer film used in thermal NIL were investigated experimentally in order to identify the release performance of the anti-sticking layer. The anti-sticking layers were derived from fluoroalkylsilanes, (1H, 1H, 2H, 2H-perfluorooctyl)trichlorosilane (F13-OTS) and (3, 3, 3-trifluoropropyl)trichlorosilane (FPTS), and coated on the silica surface in vapor phase. The commercial polymers, mr-I 7020 and 8020 (micro resist technology, GmbH), for thermal NIL were spin-coated on Si substrate with a rectangular island which was fabricated by conventional microfabrication process to achieve small contact area and easy alignment of flat contact surfaces. Experimental conditions were similar to the process conditions of thermal NIL. When the polymer film on the island was separated from the silica surface after imprint process, the adhesion force between the silica surface and the polym film was measured and the surfaces of the silica and the polymer film after the separation were observed. As a result, the anti-sticking layers remarkably reduced the adhesion force and the surface damage of polymer film and the chain length of silane affects the adhesion characteristics. The anti-sticking layers derived from FPTS and F13-OTS reduced the adhesion force per unit area to 38% and 16% of the silica surfaces without an anti-sticking layer, respectively. The anti-sticking layer derived from F13-OTS was more effective to reduce the adhesion, while both of the anti-sticking layers prevented the surface damages of the polymer film. Finally, it is also found that the adhesion characteristics of mr-I 7020 and mr-I 8020 polymer films were similar with each other.