• Proceedings of the PSK Conference
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• 2001.04a
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• pp.237.1-237.1
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• 2001

• Restorative Dentistry and Endodontics
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• v.35 no.1
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• pp.13-19
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• 2010

The purpose of this study was to compare the microshear bond strength of a self-etching primer adhesive to dentin prepared with different diamond points, carbide burs and SiC papers, and also to determine which SiC paper yield similar strength to that of dentinal surface prepared with points or burs. Fifty-six human molar were sectioned to expose the occlusal dentinal surfaces of crowns and slabs of 1.2 mm thick were made. Dentinal surfaces were removed with three diamond points, two carbide burs, and three SiC papers. They were divided into one of eight equal groups (n = 7); Group 1: standard diamond point(TF-12), Group 2: fine diamond point (TF-12F), Group 3: extrafine diamond point (TF-12EF), Group 4: plain-cut carbide bur (no. 245), Group 5: cross-cut carbide bur (no. 557), Group 6 : P 120-grade SiC paper, Group 7: P 220-grade SiC paper, Group 8: P 800-grade SiC paper. Clearfil SE Bond was applied on dentinal surface and Clearfil AP-X was placed on dentinal surface using Tygon tubes. After the bonded specimens were subjected to uSBS testing, the mean uSBS (n = 20 for each group) was statistically compared using one-way ANOV A and Tukey HSD test. In conclusion, the use of extrafine diamond point is recommended for improved bonding of Clearfil SE Bond to dentin. Also the use of P 220-grade SiC paper in vitro will be yield the results closer to dentinal surface prepared with fine diamond point or carbide burs in vivo.

• The monthly packaging world
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• s.286
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• pp.42-48
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• 2017

• The monthly packaging world
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• s.286
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• pp.49-53
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• 2017

• The monthly packaging world
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• s.325
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• pp.53-58
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• 2020

• Tribology and Lubricants
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• v.22 no.5
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• pp.243-251
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• 2006

Molecular dynamics simulations of nanoimprint lithography NIL) are performed in order to investigate effects of process parameters, such as stamp shape, imprinting temperature and adhesive energy, on nanoimprint lithography process and pattern transfer. The simulation model consists of an amorphous $SiO_{2}$ stamp with line pattern, an amorphous poly-(methylmethacrylate) (PMMA) film and an Si substrate under periodic boundary condition in horizontal direction to represent a real NIL process imprinting long line patterns. The pattern transfer behavior and its related phenomena are investigated by analyzing polymer deformation characteristics, stress distribution and imprinting force. In addition, their dependency on the process parameters are also discussed by varying stamp pattern shapes, adhesive energy between stamp and polymer film, and imprinting temperature. Simulation results indicate that triangular pattern has advantages of low imprinting force, small elastic recovery after separation, and low pattern failure. Adhesive energy between surface is found to be critical to successful pattern transfer without pattern failure. Finally, high imprinting temperature above glass transition temperature reduces the imprinting force.

• Analytical Science and Technology
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• v.30 no.4
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• pp.213-219
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• 2017

Polyalkylsiloxane has been spotlighted in pressure-sensitive adhesive (PSA) application due to excellent physical properties and good biocompatibility. Thermal behaviour of polyalkylsiloxane mixtures, such as thermal stability and heat flow, were studied using TG-DTA during catalytic hydrosilation. To understand reaction kinetics of cross-linking, catalytic hydrosilation of polyalkylsiloxane was monitored using variable temperature nuclear magnetic resonance (VT-NMR) as increased temperature. The formation of cross-linking bond $Si-CH_2-CH_2-Si$ was directly observed using distortionless enhanced by polarization transfer (DEPT) technique. Successfully polyalkylsiloxane PSA samples exhibited excellent adhesion properties by cross-linking reaction.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.533-537
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• 2003

Compared to sintered polycrystalline diamond (PCD), the deposited thin film diamond has a great advantage on the fabrication of cutting tools with complex geometries such as drills. Because of high performance in high speed machining non-ferrous difficult-to-cut materials in the field of automobiles industry, aeronautics and astronautics industry, diamond-coated drills find large potentialities in commercial applications. However, the poor adhesion of the diamond film on the substrate and high surface roughness of the drill flute adversely affect the tool lift and machining quality and they become the main technical barriers for the successful development and commercialization of diamond-coated drills. In this paper, diamond thin films were deposited on the commercial WC-Co based drills by the electron aided hot filament chemical vapor deposition (EACVD). A new multiple coating technology based on changing gas pressure in different process stages was developed. The large triangular faceted diamond grains may have great contribution to the adhesive strength between the film and the substrate, and the overlapping ball like blocks consisted of nanometer sized diamond crystals may contribute much to the very low roughness of diamond film. Adhesive strength and quality of diamond film were evaluated by scanning electron microscope (SEM), atomic force microscope (AFM), Raman spectrum and drilling experiments. The ring-block tribological experiments were also conducted and the results revealed that the friction coefficient increased with the surface roughness of the diamond film. From a practical viewpoint, the cutting performances of diamond-coated drills were studied by drilling the SiC particles reinforced aluminum-matrix composite. The good adhesive strength and low surface roughness of flute were proved to be beneficial to the good chip evacuation and the decrease of thrust and consequently led to a prolonged tool lift and an improved machining quality. The wear mechanism of diamond-coated drills is the abrasive mechanical attrition.

• Polymer(Korea)
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• v.33 no.4
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• pp.319-325
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• 2009

The solution polymerization was conducted to synthesize pressure sensitive adhesive for polarizer film using acrylic monomers. 2-Ethylhexylacrylate, butylacrylate, acrylic acid were used as acrylic monomers. The ratio was 2-ethylliexylacrylate:butylacrylate:acrylic acid=25:50:3.6 by reflecting $-40^{\circ}C$ of glass transition temperature in the pressure sensitive adhesive. When 1 wt% of coupling agent was added to the polymerized pressure sensitive adhesive, the light transmissivity was significantly increased. This result is due to the enhancement of adhesive power against liquid crystal cell by Si-O bond of coupling agents. Cross-linking agent was added by 0.5, 1.0, and 1.5 wt% with respect to the synthesized polymer. Initial tackiness decreased, while cohesion increased with increasing crosslinking agent. In the analysis of contact angle, the increase of crosslinking agents yielded the enhancement of surface energy, resulting in the decrease of contact angle. From the measurement of heat resistance, the acrylic pressure sensitive adhesive showed excellent heat resistance regardless of change in temperature and contents in crosslinking agent. In the observation of a cutting plane, the increased crosslinking agent represented a smoother and cleaner section. Comprehensively, the optimum additive amount of crosslinking agent was determined to be 1.0 wt% to monomer.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.325-325
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• 2012

1차원구속 반도체인 nanowires (NWs)는 전기적, 광학적으로 일반 bulk구조와 다른 특성을 가지고 있어서 현재 많은 연구가 되고 있다. 일반적으로 NWs는 Au 등의 금속 촉매를 이용하여 성장을 하게 되는데 이때 촉매가 오염물로 작용을 해서 결함을 만들어서 bandgap내에 defect level을 형성하게 된다. 본 연구는 Si (111) 기판 위에 GaAs NWs 와 InAs NWs를 촉매를 이용하지 않고 성장 하였다. vapour-liquid-solid (VLS)방법으로 성장하는 GaAs NWs는 Ga의 droplet을 이용하게 되는데 Ga이 Si 기판위에 자연 산화막에 존재하는 핀홀(pinhole)로 이동하여 1차적으로 Ga droplet 형성하고 이후 공급되는 Ga과 As은 SiO2 보다 GaAs와 sticking coefficient 가 좋기 때문에 Ga drolept을 중심으로 빠른 선택적 성장을 하게 되면서 NWs로 성장을 하게 된다. 반면에 InAs NWs를 성장 할 시에 droplet 방법으로 성장을 하게 되면 NWs가 아닌 박막 형태로 성장을 하게 되는데 이것으로 InAs과 GaAs의 $SiO_2$와의 sticking coefficient 의 차이를 추측을 할 수 있다. InAs NWs는 GaAs NWs는 달리 native oxide를 이용하지 않고 InAs 과 Si 사이의 11.5%의 큰 lattice mismatch를 이용한다. 이종의 epitaxy 방법에는 크게 3종류 (Frank-van der Merwe mode, Stranski-Krastanov mode, Volmer-Weber mode)가 있는데 각기 다른 adatom 과 surface의 adhesive force로 나누어지게 된다. 이 중 Volmer-Weber mode epitaxy는 adatom 의 cohesive force가 surface와의 adhesive force보다 큰 경우 성장 되는 방식으로 InAs NWs 는 이 방식을 이용한다. 즉 droplet을 이용하지 않는 vapour-solid (VS) 방법으로 성장을 하였다. 이 때 In 의 migration을 억제하기 위해서 VLS mode 의 GaAs NWs 보다 As의 공급을 10배 이상 하였다. FE-SEM 분석 결과 GaAs NWs는 Ga droplet을 확인 할 수 있었고 InAs NWs는 droplet이 존재하지 않았다. GaAs와 InAs NW는 density와 length가 V/III가 높을수록 증가 하였다.