• Restorative Dentistry and Endodontics
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• 제25권4호
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• pp.575-586
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• 2000

In this study, adaptation of compomer to saliva contaminated dentin was evaluated with scanning electron microscope(SEM) and confocal laser scanning microscope(CLSM). For the SEM study, the occulusal surfaces of thirty two molar teeth were grounded to exposure dentin surfaces. The specimen were randomly assigned to control and three experimental groups with four samples in each group. In control group, Dyract and F-2000 compomer were bonded on the specimens according to the manufactures direction. Experimental groups were subdivided into three groups. They were contaminated with saliva on dentin surfaces ; Experimental group 1 : Saliva was dried with compressed air. Experimental group 2 : Saliva was rinsed with air-water spray and dried. Experimental group 3 : After polymerization of an adhesive, they were contaminated with saliva, and then saliva was rinsed with air-water spray and dried. Dyract and F-2000 compomer were bonded on saliva-treated dentin surfaces. The interfaces between dentin and compomer were observed with SEM. For the CLSM study, Class V cavities were prepared in buccal and ligual surfacess of thirty two molars. The specimens were divided into control and experimental groups. Class V cavities in experimental group were contaminated with saliva and those surfaces in each experimental groups received the same treatments as for the SEM study. Cavities were applied Prime & Bond 2.1 and F-2000 compomer primer/adhesive that were mixed with fluorescein, and then were filled with Dyract and F-2000 compomer. Specimens were embedded in transparent acrylic resin and sectioned buccolingual1y with diamond wheel saw, and then mounted on cover slide for CLSM study. The interface between cavity and compomer was observed by fluoresence imaging with a CLSM. The results were as follows : 1. In SEM exammination of Dyract group, control group, experimental group 2, 3 showed close adaptation to dentin and hybrid layer of $3{\sim}4{\mu}m$ diameter. Interfacial gap between compomer and dentin in experimental group 1 was wider than in control group. 2. In SEM examination of F-2000 group, adaptation to dentin of control group was closer than Dytact control group, but hybrid-like layer was not observed. Interfacial gap between compomer and dentin in experimental group 1 was wider than in Dyract experimental group 1. 3. In dissolution specimens of Dyract and F-2000 group, resin tags penetrated through dentinal tubules in control group and experimental group 1 and 3, but the penetration of resin tag was irregular and partial in experimental group 1. 4. In CLSM exammination of Dyract and F-2000 group, adhesive patterns of control and experimental groups showed same as in SEM. This result suggests the treatment methods, rinsing & drying, repeating all adhesive procedures, will produce good effect on adaptation of compomer to dentin if the dentin surface or polymerized adhesive is contaminated by saliva.

• 한국산학기술학회논문지
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• 제17권8호
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• pp.449-455
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• 2016

본 연구에서는 Eurocode에서 제시하는 콘크리트 부재간 계면조건을 고려한 전단강도 설계식을 압축강도가 서로 다른 부재 연결부에 대해서도 적용할 수 있는지를 검토하기 위하여 전단실험을 수행하고 설계 평가식과 비교하였다. Eurocode에서 제시하는 전단강도 평가식의 변수를 고려하여 콘크리트 압축강도, 전단철근 보강비, 요철계면을 변수로 하는 부재를 제작하였고, 콘크리트층 간의 강도 차이와 요철계면의 유무에 따른 전단강도에 주안점을 두고 전단실험을 수행하였다. 실험을 통해 계측한 실제 전단강도를 Eurocode의 전단강도 평가식을 이용한 계산값과 비교하여 실제 전단강도 수준과 평가식과의 차이를 평가하였으며, 이종강도를 갖는 콘크리트 층에서 압축강도가 증가함에 따라 전단강도도 증가하며, 계면요철을 둔 연결부 전단강도는 설계기준의 평가식으로 계산한 값에 비해 20~50%까지 차이를 보이는 것으로 나타났다. 철근보강비가 작은 경우에는 계면요철에 의한 전단저항력이 전단강도에 주로 기여하며, 이 경우에는 계면에서의 급격한 파괴가 일어나는 현상과 전단강도 편차가 크게 나타남에 따라 평가식과 큰 차이를 보였다. 특히, 이종강도를 갖는 콘크리트 층의 전단강도는 압축강도 차이가 클수록 강도 평가식과 큰 차이를 보이는 것으로 판단된다.

• 접착 및 계면
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• 제23권2호
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• pp.53-58
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• 2022

본 연구는 AlO_x유전체 표면에 유기 자립조립 단분자막 (self-assembled monolayer, SAM) 중간층을 도입함으로써 유전체의 표면특성을 제어하고, 최종적으로 유기전하변조트랜지스터 (Organic charge modulated field-effect transistor, OCMFET)의 전기적 특성을 향상시킨 결과를 제시하였다. 유기 중간층을 적용함으로써, OCMFET의 컨트롤 게이트(CG, Control gate)와 플로팅 게이트 (FG, Floating gate) 사이 커패시터 플레이트로 작용하는 산화알루미늄 게이트 유전체의 표면 에너지를 제어하였으며, FET의 가장 중요한 성능변수인 전계효과 이동도(field-effect transistor, μ_FET)를 향상시켰다. 사용된 SAMs은 네가지의 PA (Octadecylphosphonic acid, Butylphosphonic acid, (3-Bromopropyl)phosphonic acid, (3-Aminopropyl) phosphonic acid)를 사용하여 형성하였으며, 각각 0.73, 0.41, 0.34, 0.15 cm2V^-1s^-1의 μ_OCMFET를 나타내었다. 이 연구를 통해 유기 SAM 중간층의 알킬 체인(Alkyl chain)의 길이 및 말단기의 특성이 소자의 전기적 성능을 제어하는데 중요한 요인임을 확인하였으며, 이 결과를 통해 향후 최적의 센서 플랫폼으로서의 OCMFET 소자성능 최적화에 기여할 수 있을 것으로 기대한다.

• 멤브레인
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• 제33권6호
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• pp.427-438
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• 2023

본 연구에서는 고투과성 및 높은 염 제거율을 가지는 역삼투막의 성능향상을 위하여 다양한 첨가제 및 계면중합 시 경화 온도 및 시간에 따른 특성평가에 대한 연구가 수행되었다. 첨가제가 없는 막과 첨가제를 첨가한 막의 모폴로지는 모두 "ridge-and-valley" 구조를 나타내어, 폴리아미드 층이 다공성 지지층 표면에 성공적으로 중합되었음을 확인하였다. 또한 2-Ethyl-1,3-hexanediol (EHD) 첨가함으로써 향상된 친수성과 수투과율 가졌으며, 이는 접촉각 측정을 통해서 확인되었다. 최종적으로 97.78%와 98.7%의 NaCl 및 MgSO₄ 제거율과 3.31 L/(m²⋅h⋅bar)의 높은 수투과율을 가진 고투과성 계면중합막을 제조하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.154.2-154.2
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• 2016

In this work, we introduce a solution-processed CdS interlayer for use in inverted bulk heterojunction (BHJ) solar cells, and compare this material to a series of standard organic and inorganic cathode interlayers. Different combinations of solution-processed CdS, ZnO and conjugated polyelectrolyte (CPE) layers were compared as cathode interlayers on ITO substrates to construct inverted solar cells based on $PTB7:PC_{71}BM$ and a $P3HT:PC_{61}BM$ as photoactive layers. Introduction of a CdS interlayer significantly improved the power conversion efficiency (PCE) of inverted $PTB7:PC_{71}BM$ devices from 2.0% to 4.9%, however, this efficiency was still fairly low compared to benchmark ZnO or CPE interlayers due to a low open circuit voltage ($V_{OC}$), stemming from the deep conduction band energy of CdS. The $V_{OC}$ was greatly improved by introducing an interfacial dipole (CPE) layer on top of the CdS layer, yielding outstanding diode characteristics and a PCE of 6.8%. The best performing interlayer, however, was a single CPE layer alone, which yielded a $V_{OC}$ of 0.727 V, a FF of 63.2%, and a PCE of 7.89%. Using $P3HT:PC_{61}BM$ as an active layer, similar trends were observed. Solar cells without the cathode interlayer yielded a PCE of 0.46% with a poor $V_{OC}$ of 0.197 V and FF of 34.3%. In contrast, the use of hybrid ZnO/CPE layer as the cathode interlayer considerably improved the $V_{OC}$ of 0.599 V and FF of 53.3%, resulting the PCE of 2.99%. Our results indicate that the CdS layer yields excellent diode characteristics, however, performs slightly worse than benchmark ZnO and CPE layers in solar cell devices due to parasitic absorption below 550 nm. These results suggest that the hybrid inorganic/organic interlayer materials are promising candidates as cathode interlayers for high efficiency inverted solar cells through the modification of interface contacts.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.450-455
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• 2002

Cu-cored Sn-Ag solder balls were fabricated by coating pure Sn and Ag on Cu balls. The melting behavior and the solderability of the BGA joint with the Ni/Au coated Cu pad were investigated and were compared with those of the commercial Sn-Ag and Sn-Ag-Cu balls. DSC analyses clarified the melting of Cu-cored solders to start at a rather low temperature, the eutectic temperature of Sn-Ag-Cu. It was ascribed to the diffusion of Cu and Ag into Sn plating during the heating process. After reflow soldering the microstructures of the solder and of the interfacial layer between the solder and the Cu pad were analyzed with SEM and EPMA. By EDX analysis, formation of a eutectic microstructure composing of $\beta$-Sn, Ag$_3$Sn, ad Cu$_{6}$Sn$_{5}$ phases was confirmed in the solder, and the η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer was found to form at the interface between the solder and the Cu pad. By conducting shear tests, it was found that the BGA joint using Cu-cored solder ball could prevent the degradation of joint strength during aging at 423K because of the slower growth me of η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer formed at the solder, pad interface. Furthermore, Cu-cored multi-component Sn-Ag-Bi balls were fabricated by sequentially coating the binary Sn-Ag and Sn-Bi solders on Cu balls. The reflow property of these solder balls was investigated. Melting of these solder balls was clarified to start at the almost same temperature as that of Sn-2Ag-0.75Cu-3Bi solder. A microstructure composing of (Sn), Ag$_3$Sn, Bi and Cu$_{6}$Sn$_{5}$ phases was found to form in the solder ball, and a reaction layer containing primarily η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ was found at the interface with Ni/Au coated Cu pad after reflow soldering. By conducting shear test, it was found that the BGA joints using this Cu-core solder balls hardly degraded their joint shear strength during aging at 423K due to the slower growth rate of the η'-(Au, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer at the solder/pad interface.he solder/pad interface.

• Bulletin of the Korean Chemical Society
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• 제24권11호
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• pp.1659-1663
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• 2003

$Al_2O_3$ thin films were grown on H-terminated Si(001) substrates using dimethylaluminum isopropoxide [DMAl: $(CH_3)_2AlOCH(CH_3)_2$], as a new Al precursor, and water by atomic layer deposition (ALD). The selflimiting ALD process by alternate surface reactions of DMAI and $H_2O$ was confirmed from measured thicknesses of the aluminum oxide films as functions of the DMAI pulse time and the number of DMAI-$H_2O$ cycles. Under optimal reaction conditions, a growth rate of ~1.06 ${\AA}$ per ALD cycle was achieved at the substrate temperature of $150\;^{\circ}C$. From a mass spectrometric study of the DMAI-$D_2O$ ALD process, it was determined that the overall binary reaction for the deposition of $Al_2O_3\;[2\;(CH_3)_2AlOCH(CH_3)_2\;+\;3\;H_2O\;{\rightarrow}\;Al_2O_3\;+\;4\;CH_4\;+\;2\;HOCH(CH_3)_2]$can be separated into the following two half-reactions: where the asterisks designate the surface species. Growth of stoichiometric $Al_2O_3$ thin films with carbon incorporation less than 1.5 atomic % was confirmed by depth profiling Auger electron spectroscopy. Atomic force microscopy images show atomically flat and uniform surfaces. X-ray photoelectron spectroscopy and cross-sectional high resolution transmission electron microscopy of an $Al_2O_3$ film indicate that there is no distinguishable interfacial Si oxide layer except that a very thin layer of aluminum silicate may have been formed between the $Al_2O_3$ film and the Si substrate. C-V measurements of an $Al_2O_3$ film showed capacitance values comparable to previously reported values.

• 멤브레인
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• 제31권6호
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• pp.417-425
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• 2021

고용량 배터리에 대한 요구가 증가에 따라 기존 음극재보다 높은 용량(3,860 mAh/g)과 낮은 전기화학적 전위(-3.040 V)를 갖는 리튬 금속 기반 음극재에 대한 연구가 활발하게 이루어지고 있다. 본 연구에서는 수열 합성을 통해 제작된 아나타제(anatase) 타입의 TiO₂ 나노 입자 기반한 PVdF-HFP/TiO₂ 복합체를 리튬 금속 음극의 계면 보호층으로 적용하였다. 결정구조 및 형상 분석을 통해 유/무기-리튬 나노복합체 박막의 형성을 확인하였다. 또한, 전지화학 테스트(사이클 테스트 및 전압 프로파일)를 통해 리튬 금속 음극의 전기화학 성능 은 복합체 보호막이 TiO₂ 10 wt%, 코팅 두께 1.1 ㎛의 조건에서 가장 개선된 전기화학적 성능(콜롱 효율 유지: 77 사이클 동안 90% 이상) 발현을 확인하였다. 이를 통해, 처리하지 않은 리튬 전극 대비 본 보호층에 의한 리튬 금속 음극의 성능 안정화/개선 효과가 검증되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.160-160
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• 2015

InGaZnO (IGZO) thin-film transistors (TFTs) are very promising due to their potential use in high performance display backplane [1]. However, the stability of IGZO TFTs under the various stresses has been issued for the practical IGZO applications [2]. Up to now, many researchers have studied to understand the sub-gap density of states (DOS) as the root cause of instability [3]. Nomura et al. reported that these deep defects are located in the surface layer of the IGZO channel [4]. Also, Kim et al. reported that the interfacial traps can be affected by different RF-power during RF magnetron sputtering process [5]. It is well known that these trap states can influence on the performances and stabilities of IGZO TFTs. Nevertheless, it has not been reported how these defect states are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOI) can be generated by electron attachment in oxygen atom near target surface and accelerated up to few hundreds eV by self-bias of RF magnetron sputter; the high energy bombardment of NOIs generates bulk defects in oxide thin films [6-10] and can change the defect states of IGZO thin film. In this study, we have confirmed that the NOIs accelerated by the self-bias were one of the dominant causes of instability in IGZO TFTs when the channel layer was deposited by conventional RF magnetron sputtering system. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process [9-10] to eliminate the NOI bombardment effects and present how much to be improved the instability of IGZO TFTs by this new deposition method.

• 한국세라믹학회지
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• 제45권9호
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• pp.561-566
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• 2008

Carbon fiber fabric-silicon carbide composites were fabricated by liquid silicon infiltration (LSI) process. The porous two-dimensional carbon fiber fabric performs were prepared by 13 plies of 2D-plain-weave fabric in a three laminating method, [0/90], [${\pm}45$], [$0/90/{\pm}45$] lay-up, respectively. Before laminating, a thin pyrolytic carbon (PyC) layer deposited on the surface of 2D-plain weave fabric sheets as interfacial layer with $C_3H_8$ and $N_2$ gas at $900^{\circ}C$. A densification of the preforms for $C_f-Si-SiC$ matrix composite was achieved according to the LSI process at $1650^{\circ}C$ for 30 min. in vacuum atmosphere. The bending strength of the each composite were measured and the microstructural consideration was performed by a FE-SEM.