• 접착 및 계면
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• 제12권3호
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• pp.88-93
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• 2011

페놀수지에 함침된 탄소나노튜브 (CNT)의 최적 분산제조공정은 전기저항 측정으로 구해졌으며, 플라즈마 처리된 탄소섬유와 CNT-페놀수지 나노복합재료간의 계면특성이 전기-미세역학시험법에 의해 연구되었다. 탄소섬유의 젖음성은 플라즈마 처리 후에 현격하게 증가되었다. 탄소섬유와 CNT-페놀수지 나노복합재료의 표면에너지는 Wilhelmy 플레이트 시험법으로 측정되었다. 탄소섬유 표면의 활성화로 인하여 플라즈마 처리 후 전진 접촉각은 $65^{\circ}$에서 $28^{\circ}$로 감소되었다. 이는 정적 접촉각과 상호 일치함을 보여 주었다. 플라즈마 처리된 탄소섬유와 CNT-페놀수지 나노복합재료간의 접착일은 플라즈마 처리전보다 증가하였다. 또한, 계면전단강도와 겉보기 강성도 탄소섬유에 대한 플라즈마 처리로 증가하였다.

• Current Photovoltaic Research
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• 제9권3호
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• pp.75-83
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• 2021

The tunnel oxide passivated contact (TOPCon) structure got more consideration for development of high performance solar cells by the introduction of a tunnel oxide layer between the substrate and poly-Si is best for attaining interface passivation. The quality of passivation of the tunnel oxide layer clearly depends on the bond of SiO in the tunnel oxide layer, which is affected by the subsequent annealing and the tunnel oxide layer was formed in the suboxide region (SiO, Si₂O, Si₂O₃) at the interface with the substrate. In the suboxide region, an oxygen-rich bond is formed as a result of subsequent annealing that also improves the quality of passivation. To control the surface morphology, annealing profile, and acceleration rate, an oxide tunnel junction structure with a passivation characteristic of 700 mV or more (V_oc) on a p-type wafer could achieved. The quality of passivation of samples subjected to RTP annealing at temperatures above 900℃ declined rapidly. To improve the quality of passivation of the tunnel oxide layer, the physical properties and thermal stability of the thin layer must be considered. TOPCon silicon solar cell has a boron diffused front emitter, a tunnel-SiO_x/n⁺-poly-Si/SiN_x:H structure at the rear side, and screen-printed electrodes on both sides. The saturation currents J_o of this structure on polished surface is 1.3 fA/cm² and for textured silicon surfaces is 3.7 fA/cm² before printing the silver contacts. After printing the Ag contacts, the J_o of this structure increases to 50.7 fA/cm² on textured silicon surfaces, which is still manageably less for metal contacts. This structure was applied to TOPCon solar cells, resulting in a median efficiency of 23.91%, and a highest efficiency of 24.58%, independently. The conversion efficiency of interdigitated back-contact solar cells has reached up to 26% by enhancing the optoelectrical properties for both-sides-contacted of the cells.

• 접착 및 계면
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• 제21권4호
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• pp.143-155
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• 2020

Sol-Gel 공정을 통해서 제조되는 유-무기 하이브리드 화합물들은 방청 코팅, 방빙 코팅(Anticing), 자가 세정 코팅, 반사 방지 코팅 등과 같은 기능성 코팅 재료로 널리 사용되어져 왔다. 특히 소수성 코팅 표면을 제조하기 위해서는 코팅표면의 표면에너지가 낮고 코팅 표면의 조도를 제어가 요구된다. 표면에너지와 표면 조도를 조절하는 전형적인 공정은 in-situ fabrication 공정, 'Pre-fluorinating/Post-roughening', 'Pre-roughening/ Post-fluorinating이다. 본 연구에서는 in-situ fabrication 공정인 Particle-Binder 공정을 이용해서 소수성 코팅표면을 제조하였다. 3관능기 유기실란화합물과 불소 함유 유기실란 화합물과의 가수분해 및 축합반응을 통해 제조된 불소함유 유-무기 하이브리드를 바인더로 사용하여서 무기물 나노입자와 혼합하여 소수성 코팅액을 제조하고 유리 기재 위에 스핀코팅 후 열건조하여서 코팅막을 제조하였다. 바인더인 유-무기 하이브리드 화합물의 불소 함유 실란화합물의 첨가량, 첨가순서, 무기물 나노입자 첨가량에 따른 코팅막의 물성 변화를 조사하였다. 분석결과 불소 함량이 10 wt%인 유-무기 하이브리드 화합물(GPTi-HF10)을 바인더로 사용하여서 제조된 코팅막이 가장 소수성이 우수하였으며 수접촉각은 (107.52 ± 1.6°), 이 바인더와 무기물 나노입자의 무게비가 1:3인 경우(GPTi-HF10-MS 3.0)에 가장 높은 수접촉각(130.84±1.99°)을 나타내었다.

• 한국정보통신학회논문지
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• 제18권5호
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• pp.1149-1154
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• 2014

본 연구는 산화물반도체트랜지스터의 터널링 현상을 살펴보기 위해서 게이트 절연막으로서 SiOC 박막을 사용하고 채널층으로 IGZO를 이용하여 트랜지스터를 제작 하였다. SiOC 박막은 분극이 작아질수록 비정질특성이 우수해지면서 절연특성이 좋아진다. SiOC 게이트 절연막과 채널 층 사이의 계면에 존재하는 접합특성은 SiOC의 분극특성에 따라서 달려졌다. 드레인소스 전류($I_{DS}$)와 게이트소스 전압($V_{GS}$)의 전달특성은 분극이 낮은 SiOC를 사용할 경우 양방향성 전달특성이 나타나고 분극이 높은 SiOC 게이트 절연막을 사용할 경우 단방향성 전달 특성이 나타났다. 터널링에 의한 양방향성 트랜지스터의 경우 바이어스 인가 전압이 낮은 ${\pm}1V$의 영역에서 쇼키접합을 나타냈었지만 트래핑효과에 의한 단방향성 트랜지스터의 경우 오믹접합 특성을 나타내었다. 특히 양방향성 트랜지스터의 경우 터널링 현상에 의하여 on/off 스위칭 특성이 개선되었다.

• 한국전기전자재료학회논문지
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• 제30권6호
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• pp.366-371
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• 2017

In this paper, we introduce an electrocardiogram (ECG) system designed to solve problems caused by wetgels and motion artifacts in measuring active movement. The system is called a dry-contact ECG and was designed by considering impedance matching between skin and electrode as well as the frictional electricity between electrode and clothes. In order to create the system, we measured impedance on the skin-electrode interface, and the result was applied to the electronic circuit scheme. Moreover, we added an electrode on the back of the measurement electrode to make a flow path to ground the electrical noise. The final ECG circuit and novel electrode were used to detect real human cardiac signals from a subject who was tested while standing still and walking. The signals obtained from the two activities were nicely shaped, without any motion artifact noise. We took electrode size into account in this study because the impedance depended on the area of the electrode. An electrode of 50 mm diameter showed the best curve for the ECG signal without any electrical noise.

• Corrosion Science and Technology
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• 제17권2호
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• pp.45-53
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• 2018

A new 80Ti-15Ta-5Zr wt% alloy surface was protected by anodic oxidation in phosphoric acid solution. The protective oxide layer (TiO2, ZrO2 and Ta suboxides and thickness of 15.5 nm) incorporated $PO{_4}^{3-}$ ions from the solution, according to high resolution XPS spectra. The AFM analysis determined a high roughness with SEM detected pores (20 - 50 nm). The electrochemical studies of bare and anodically oxidized Ti-15Ta-5Zr alloy in Carter-Brugirard saliva of different pH values and saliva with 0.05M NaF, pointed to a nobler surface for the protected alloy, with a thicker electrodeposited oxide layer acting as a barrier against aggressive ions. The oxidized alloy significantly decreased corrosion current densities and total quantity of ions released into the oral environment in comparison with the bare one, at higher polarisation resistance and protective capacity of the electrodeposited layer. The impedance data revealed a bi-layered oxidation film formed by: a dense, compact, barrier layer in contact with the metallic substrate, decreasing the potential gradient across the metal/oxide layer/solution interface, reducing the anodic dissolution and a more permissive, porous layer in contact with the electrolyte. The open circuit potential for protected alloy shifted to nobler values, with thickening of the oxidation film signifying long-term protection.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.5.1-5.1
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• 2009

Organic photovoltaic (OPV)cells have attracted considerable attention due to their potential for flexible, lightweight, and low-cost application of solar energy conversion. Since a 1% power conversion efficiency (PCE) OPV based on a single donor-acceptor heterojunction was reported by Tang, the PCE has steadily improved around 5%. It is well known that a high parallel (shunt)resistance and a low series resistance are required simultaneously to achieve ideal photovoltaic devices. The device should be free of leakage current through the device to maximize the parallel resistance. The series resistance is attributed to the ohmic loss in the whole device, which includes the bulk resistance and the contact resistance. The bulk resistance originated from the bulk resistance of the organic layer and the electrodes; the contact resistance comes from the interface between the electrodes and the active layer. Furthermore, it has been reported that the bulk resistance of the indium tin oxide (ITO) of the devices dominates the series resistance of OPVs for a large area more than $0.01\;cm^2$. Therefore, in practical application, the large area of ITO may significantly reduce the device performance. In this work, we investigated the effect of sheet resistance ($R_{sh}$) of deposited ITO on the performance of OPVs. It was found that the device performance of polythiophene-fullerene (P3HT:PCBM) bulk heterojunction OPVs was critically dependent on Rsh of the ITO electrode. With decreasing $R_{sh}$ of the ITO from 39 to $8.5\;{\Omega}/{\square}$, the fill factor (FF) of OPVs was dramatically improved from 0.407 to 0.580, resulting in improvement of PCE from $1.63{\pm}0.2$ to $2.5{\pm}0.1%$ underan AM1.5 simulated solar intensity of $100\;mW/cm^2$.

• 대한치과보철학회지
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• 제29권3호
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• pp.55-74
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• 1991

The purpose of this study was to investigate the influence of early functional load around osseointegrated titanium implants. 24 titanium plasma spray coated implants (ITI HS-type) were placed into the previously extracted site in the mandible of six adult dogs. The implants were divided into three groups : the control group was the implants without abutment during the experimental period; the experimental group I was loaded by connecting the contoured abutment after 6 weeks of healing; the experimental group II was loaded after 12 weeks of healing: and the mandibular second premolar and surrounding tissues were selected for natural tooth group to compare the implanted group. All dogs were injected intravenously tetracycline, alizarin red S, and calcein for bone labeling. After the experimental period of 18 weeks, the dogs were sacrificed and longitudinal sections of the bone-implant interface were cut and observed using light microscope, scanning electron microscope, and fluorescence microscope. The results of the study were as follows: 1. Light and scanning electron microscopically, all implant surfaces were well contact with bone tissue at the cortical layer, but some areas of cancellous bone were not contact directly. 2. Fluorescence microscopically, number and size of the new secondary osteons around the implant were increased than those of the natural tooth. 3. Fluorescence microscopically, linear and concentrical fluorescence was observed at or near the surface of all implants, and the bone formation and remodeling of the implants loaded after 6 week of healing were great, and unloaded implants were worst. 4. Fluorescence microscopically, endosteal bone formation was greater than periosteal bone formation at or near the implants. 5. Fluorescence microscopically, number and size of linear and concentric fluorescence was increased at the lingual side than the buccal side of the loaded implants. The result of the study indicate the possibility of the early load to the implant via a prosthesis.

• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.1286-1286
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• 2001

Despite extensive theoretical and experimental studies the structure of the protein-solvent interface is subject of many controversy. Understanding the processes that occur in aqueous solution requires understanding of the solvent influence on the structure of protein. The aim of this study is to investigate the applicability of NIR methods in the study of hydration phenomena in protein solutions. Temperature-induced changes in NIR spectra of -lactoglobulin (BLG) in aqueous solutions have been investigated by means of two-dimensional correlation spectroscopy (2DCOS) and principal component analysis (PCA). With the temperature increase the balance of forces between the BLG's interaction with itself and the BLGs interaction with its environment is disrupted leading to BLG unfolding. Significant differences of 2D signals and distinct discrepancies of loading on PC1 and PC2 were observed as a result of temperature increase. In the native folded conformation of BLC, most of the nonpolar amino acids are hidden in the centre of the structure, out of contact with water molecules, while charged groups are outside, in the contact with water. The polar groups promote low density Ih-type structure in the water outside this first hydration shell. When BLG unfolds it assumes a more extended configuration on which the previously buried nonpolar groups are exposed to water and promote the higher density II-type structure outside its first shell. Detailed assignments of bands attributed to the bulk water, different states of the hydrated water and the changed conformation of BLG are proposed.

• 한국주조공학회지
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• 제31권2호
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• pp.66-70
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• 2011

Hot dip aluminizing (HDA) is widely used in industry for improving corrosion resistance of material. The formation of intermetallic compound layers during the contact between dissimilar materials at high temperature is common phenomenon. Generally, intermetallic compound layers of $Fe_2Al_5$ and $FeAl_3$ are formed at the Al alloy and Fe substrate interface. In case of cast iron, high contact angle of graphite existed in the matrix inhibits the formation of intermetallic compound layer, which carry with it the disadvantage of a reduced reaction area and mechanical properties. In present work, the process for the removal of graphite existed on the surface of specimen has been investigated. And also HDA was proceeded at $800^{\circ}C$ for 3 minutes in aluminum alloy melt. The efficiency of graphite removal was increased with the reduction of particle size in sanding process. Graphite appears to be present both in the region of melting followed by re-solidification and in the intermetallic compound layer, which could be attributed to the fact that the surface of cast iron is melted down by the formation of low melting point phase with the diffusion of Al and Si to the cast iron. Intermetallic compound layer consisted of $Fe(Al,Si)_3$ and $Fe_2Al_5Si$, the layer formed at cast iron side contained lower amount of Si.