• Applied Chemistry for Engineering
• /
• v.27 no.5
• /
• pp.516-520
• /
• 2016

Concentrated liquid detergents have 2~3 times higher surfactant contents [35~45% (w/w)] compared to those of normal type detergents. In general, a single surfactant forms a lyotropic liquid crystal (LC) phase when the concentration is in the region of 30~60% (w/w). Whereas the concentrated liquid detergent at about 40% (w/w) concentration in a mixed surfactant system shows an opaque appearance of gel or LC. In order to meet consumer needs and preference for product appearance, we applied hydrotropes and various surfactants systems in concentrated liquid detergents to obtain an opaque gel-phase and also a clear transparent phase at even below zero $^{\circ}C$ temperature. The more effective hydrotropes for making concentrated liquid detergents are 1,6-hexanediol, adipic acid and dipropylene glycol (DPG) which have two hydrophilic groups in both terminated positions. In order to prepare an excellent concentrated liquid detergent, good hydrotropes alongside secondary type surfactants like LAS and SAS were used. The formation of LC phase of concentrated liquid detergents at about 40% (w/w) concentration could be prevented by the use of both hydrotropes and secondary type surfactants. The result indicate that concentrated detergents having excellent low temperature stability and controlled viscosity can be prepared.

• Journal of Korea Soil Environment Society
• /
• v.3 no.1
• /
• pp.65-74
• /
• 1998

To enhance the washing efficiency of soil polluted by hydrophobic organic compounds, the effects of electrolytes and monomeric organic additives on micelle formation and washing efficiency of mixed surfactant solutions were investigated in this study. The surface tensions and critical micelle concentrations(CMCs) of the single and mixed surfactant solutions[$POE_5$/SDS] supplemented by NaCl were measured to investigate the effects on washing efficiency, and the composition ratios of surfactants and NaCl were optimized for the efficient soil washing system. As the mixing ratio of $POE_5$/SDS was increased to 80%, the mixed surfactant with 0.01M NaCl showed more proportional increase of washing efficiency than the mixed surfactant without any salts. The 3% solution of $POE_5$ and SDS(80%/2o%) with 0.01M NaCl showed the washing efficiency of 90%. However, the washing efficiency was not enhanced by NaCl addition to the single surfactant solution of $POE_5$. The CMC of SDS(0.049%) was higher than that of $POE_5$(0.016%), but the CMCs of mixed surfactants were decreased as the mixing ratio of $POE_5$ was increased. Alcohols having longer chain and branched carbon chain were found to be desirable for the soil washing additives.

• Applied Chemistry for Engineering
• /
• v.9 no.7
• /
• pp.1090-1097
• /
• 1998

Lidocaine compounds have widely been used as local anesthetics. Regarding the molecular mechanism for anesthesia by lidocaine, it is proposed that lidocaine molecules penetrate to the hydrophobic region of cell membrane and expand the membrane volume, producing a change in protein conformation that blocks sodium permeability or lidocaine molecules directly adsorb into lidocaine receptor in the protein channel without expanding the cell membrane. But these proposals have never been proven experimentally. In this study, the expansion of cell membrane by lidocaine compounds was investigated by employing lipid monolayer at the air/water interface as the mimetic system of cell membrane. It was found that oil-soluble lidocaine contracted the area/molecule of lipid in the monolayer of phosphatidyl choline, sphingomyelin, DS-PL95E and lipoid, but expanded the monolayer of phosphatidyl ethanolamine only in a certain range of mixing ratios. On the contrary, water-soluble lidocaine-HCl salt expanded the monolayers of all lipids used in this study.

• Journal of the Korean Magnetics Society
• /
• v.6 no.1
• /
• pp.1-6
• /
• 1996

To simulate the characteristics of magnetic exchange coupling at the interface of MR/TbCo thin films, the directions of magnetizations were calculated by minimizing energy in the films. Newton method and Gauss-Seidel method were used. The width of M-H curve increased with TbCo anisotropy constant, and with the thickness of the transition region of TbCo layer. Hysteresis loop width became extremely narrow (less than 10 Oe of coercivity), when the TbCo transition region length was $400\;\AA$. Also the hysteresis loop of films with low interfacial exchange coupling constant was similiar to that of short transition region length. When interfacial exchange coupling constant was 1/100 of perfect coupling, hysteresis loop showed a coercivity of less than 10 Oe. Comparing the measured hysteresis loop of a fabricated sample with that of simulated one, exchange coupling con¬stant could be estimated.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.05a
• /
• pp.32.1-32.1
• /
• 2009

현재 ITO를 대체할 재료로 투명 전도성 탄소나노튜브(carbon nanotube, CNT) 필름에 대한 연구가 진행 되고 있다. 이러한 연구에서 특히 CNT 필름의 투과도에 따른 전기저항을 향상시키기 위한 연구가 활발히 진행되고 있다. 본 연구에서는 단일벽 CNT (single-walled CNT)를 여러 가지 계면활성제로 최적 분산시킨 수용액으로부터 제조한 CNT 필름의 투과도에 따른 면 저항 (sheet resistance) 변화를 관찰하였다. 우선 계면활성제로 분산시킨 CNT 수용액을 알루미나 재질의 필터에서 정량적으로 진공 필터링하여 CNT 필름을 제조하였다. 알루미나 필터를 sodium hydroxide (NaOH) 수용액으로 용해시켜 제거함으로써 얻은 CNT 필름을 유리기판 위에 부착시켰다. 필름의 전기저항을 낮추기 위해 유리기판 위에 부착된 CNT 필름을 질산 (HNO3) 용액으로 처리하였다. Scanning electron microscopy, UV-Vis spectroscopy를 이용하여 각각 필름의 형상과 광 투과도를 분석하였고, 4-point probe로 면 저항을 측정하였다. 계면활성제로 분산시킨 CNT 필름 대부분의 면 저항은 질산 처리에 의해 감소하였다. 이는 CNT 표면에 코팅되어 있던 계면활성제가 질산에 의해 제거되었기 때문인 것으로 예상된다. 여러 계면활성제 중 sodium dodecyl benzenesulfonate로 분산시킨 CNT 필름이 산 처리 후에 가장 낮은 면 저항을 보였다. 그리고 Polyvinyl pyrrolidone (PVP)과 cetyltrimethylammonium bromide (CTAB)를 사용하여 제조한 CNT 필름의 면 저항이 가장 뚜렷한 감소를 보였다.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.12
• /
• pp.68-74
• /
• 1998

Improved performance and suppressed short-channel effects of polysilicon thin film transistors (poly-Si TFTs) with very thin electron cyclotron resonance (ECR) $N_2$O-plasma gate oxide have been investigated. Poly-Si TFTs with ECR $N_2$O-plasma oxide ($N_2$O-TFTs) show better performance as well as suppressed short-channel effects than those with conventional thermal oxide. The fabricated $N_2$O-TFTs do not show threshold voltage reduction until the gate length is reduced to 3 ${\mu}{\textrm}{m}$ for n-channel and 1 ${\mu}{\textrm}{m}$ for p-channel, respectively. The improvements are due to the smooth interface, passivation effects, and strong Si ≡ N bonds.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.125.2-125.2
• /
• 2011

CuInGaSe2 (CIGS)을 포함한 Chalcopyrite계 물질은 직접천이형 반도체이면서, ${\sim}1{\times}10^5cm^{-1}$ 이상의 광흡수계수를 보이며, 조성제어를 통한 밴드갭 조절이 가능해 차세대 고효율 박막태양전지재료로 매우 주목받고 있다. 최근, CIGS 박막태양전지 제조를 위해 CIGS 흡수층의 여러 가지 박막제조 공정들이 개발되고 있으나, 동시증착법과 소위 2단계법이라 일컬어지는 금속 전구체 스퍼터링 증착 후 셀렌화 공정을 가장 대표적인 공정이라 말 할 수 있다. 동시증착법은 실험실 수준의 소면적 셀에서 20%에 가까운 높은 효율의 CIGS 박막태양전지 제조에 성공하였음에도 불구하고, 상용화를 위한 대면적 셀 제조를 위해 해결해야 할 문제들이 아직 남아있다. 또한, 2단계법의 경우는 스퍼터링 공정을 기반으로 대면적 셀 제조에는 용이하나, CIGS/Mo 계면에서의 Ga 응집현상의 발생 및 셀렌화 공정에 사용되는 독성가스($H_2Se$)의 문제 등이 남아 있어 새로운 시각에서의 접근 방법이 요구되고 있다. 본 연구에서는 CIGS 4성분계 단일 타겟을 사용, RF 스퍼터링 공정을 통해 $200{\times}200mm^2$ 기판 위에 CIGS 박막을 제조하여 그 특성을 분석하였다. XRD 분석결과, 동시증착법에서 일반적으로 관찰되는 CIGS/Mo 계면에서의 $MoSe_2$ 상의 존재는 관찰되지 않았으며, CIGS 단일상의 다결정 박막이 제조되었음을 알 수 있었다. 또한, CIGS 박막제조 후, RTA 공정을 통해 CIGS 박막의 결정성이 향상됨을 관찰 할 수 있었으며, SIMS 분석결과, Mo층의 공정 조건에 따라 CIGS/Mo 계면에서의 금속원소 (In, Ga, Mo)의 상호확산이 크게 억제됨을 알 수 있었다. 그 외의 특성평가 결과들을 통하여 CIGS 4성분계 단일 타겟을 사용한 CIGS 박막태양전지 제조의 유용성에 대해 논의하고자 한다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.141.1-141.1
• /
• 2016

저분자 유기태양전지에 사용되는 zinc phthalocyanine(ZnPc)기반의 유기 2층 박막 구조인 ZnPc/C60와 ZnPc/C70에서, 열처리 온도에 따른 유기물층 계면의 변화, ZnPc 층의 격자상수와 응력 변화를 x-ray reflectivity와 GIWAXS 측정을 이용하여 연구하였다. C60 fullerene 층이 있는 ZnPc의 계면은 열처리 온도가 증가하면서 계면의 거칠기가 증가하였으나, C70 fullerene 층이 있을 때는 180도의 고온에서도 계면 거칠기가 증가하지 않고 안정한 상태를 유지하였다. Fullerene층이 있는 ZnPc는 단일 ZnPc 박막에 비해 압축 응력(compressive strain)을 더 받게 되나, 박막의 열처리 온도가 증가함에 따라 응력이 점진적으로 감소하게 된다. 특히 C70 fullerene 층이 있는 경우 ZnPc의 경우 180도에서 응력이 모두 사라진다. 이러한 fullerene 종류에 따른 박막의 응력과 계면의 안정성 특성은 표면 모폴로지에 영향을 주게 되어, ZnPC/C60 박막의 경우 ZnPc/C70에 비해 약 2배 큰 120nm의 grain을 갖게 된다.

• Journal of Adhesion and Interface
• /
• v.9 no.3
• /
• pp.20-26
• /
• 2008

It is well know that the structure of shape memory alloy (SMA) can change from martensite austenite by either temperature or stress. Due to their inherent shape recovery properties, SMA fiber can be used such as for stress or cure-monitoring sensor or actuator, during applied stress or temperature. Incomplete superelasticity was observed as the stress hysteresis at stress-strain curve under cyclic loading test and temperature change. Superelasticity behavior was observed for the single-SMA fiber/epoxy composites under cyclic mechanical loading at stress-strain curve. SMA fiber or epoxy embedded SMA fiber composite exhibited the decreased interfacial properties due to the cyclic loading and thus reduced shape memory performance. Rigid epoxy and the changed interfacial adhesion between SMA fiber and epoxy by the surface treatment on SMA fiber exhibited similar incomplete superelastic trend. Epoxy embedded single SMA fiber exhibited the incomplete recovery during cure process by remaining residual heat and thus occurring residual stress in single SMA fiber/epoxy composite.

• Composites Research
• /
• v.24 no.4
• /
• pp.11-16
• /
• 2011

Retention of interfacial shear strength (IFSS) of polymer composites at cryogenic temperature application is very important. In this work, single carbon tiber reinforced epoxy compositc was used to evaluate IFSS and apparent modulus under room and cryogenic temperatures. The property change of carbon and selected epoxy for particularly cryogenic temperature application were tested in tension and compression. Tensile strength and elongation of carbon fiber decreased at cryogenic temperature, whereas tensile modulus was almost same. On the other hand, epoxy matrix showed the increased tensile strength but decreased elongation. It can be due to maximum thermal contraction existing free volume in cryogenic temperature. IFSS increased up to $-10^{\circ}C$ and then decreased steadily. However, IFSS at cryogenic temperature was still similar to that at room temperature. This result is very useful to cryogenic application since selected epoxy toughness and interfacial adhesion can keep at such low temperature.