• 한국응용과학기술학회지
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• 제33권3호
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• pp.483-491
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• 2016

나노실리카가 코팅된 유리 표면은 나노실리카 표면에 존재하는 친수성 수산기로 인해 방담성이 매우 증가하나, 실외에 설치된 유리에 코팅된 경우는 비에 의해 씻겨 나가 방담 특성의 내구성이 급격히 감소한다. 또한 나노실리카가 코팅된 유리 표면의 토폴로지는 광투과율 또는 반사방지 특성을 좌우하는 매우 중요한 인자이다. 이러한 나노실리카 코팅의 특성에 관한 내구성을 향상시키기 위하여 가교제로 테트라에틸오르소실리케이트 (TEOS)를 사용하여 나노실리카 (Ludox) 현탁액으로 친수성 나노실리카피막을 제조하였다. 산성 또는 염기성 수용액 중에서의 TEOS의 가수 분해 최적 조건도 물에 대한 접촉각 측정을 통하여 조사하였다. pH=4의 산성 조건에서 1.5 wt% 나노실리카-TEOS 코팅액으로 얻은 최종 투명한 친수성 코팅층은 매우 향상된 친수성에 대한 내구성뿐만 아니라, 코팅하지 않은 유리에 비해 약 2 % 포인트 정도 높은 가시광투과율을 나타내었다.

• 대한기계학회논문집B
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• 제33권2호
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• pp.85-92
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• 2009

Polymer electrolyte membrane (PEM) fuel cells are a promising technology for short-term power generation required in residential and automobile applications. Proper management of water has been found to be essential for improving the performance and durability of PEM fuel cells. This study investigated the liquid water exhaust capabilities of various flow channels having different geometries and surface properties. Three-pass serpentine flow fields were prepared by patterning channels of 1 mm or 2 mm width onto hydrophilic Acrylic plates or hydrophobic Teflon plates, and the behaviors of liquid water in those flow channels were experimentally visualized. Computational fluid dynamics (CFD) simulations were also conducted to quantitatively assess the liquid water exhaust capabilities of flow channels for PEM fuel cells. Numerical results showed that hydrophobic flow channels have better liquid water exhaust capabilities than hydrophilic flow channels. Flow channels with curved corners showed less droplet stagnation than the channels with sharp corners. It was also found that a smaller width is desirable for hydrophobic flow channels while a larger width is desirable for hydrophilic ones. The above results were explained as being due to the different droplet morphologies in hydrophobic and hydrophilic channels.

• Bulletin of the Korean Chemical Society
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• 제32권11호
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• pp.3991-3995
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• 2011

$TiO_2-SiO_2-In_2O_3$ nanocomposite thin film was deposited on the glass substrates using a dip coating technique. The morphology, surface composition, surface hydroxyl groups, photocatalytic activity and hydrophilic properties of the thin film were investigated by AFM, XPS, methyl orange decoloring rate and water contact angle measurements. The hydroxyl content for $TiO_2$, $TiO_2-SiO_2$ and $TiO_2-SiO_2-In_2O_3$ nanocomposite films was calculated to be 11.6, 17.1 and 20.7%, respectively. $TiO_2-SiO_2-In_2O_3$ film turned superhydrophilic after 180-min irradiation with respect to pure $TiO_2$ and $TiO_2-SiO_2$ thin films. The photocatalytic decomposition of methyl orange for $TiO_2$, $TiO_2-SiO_2$ and $TiO_2-SiO_2-In_2O_3$ thin films was measured as 38.19, 58.71 and 68.02%, respectively. The results indicated that $SiO_2$ and $In_2O_3$ had a significant effect on the hydrophilic, photocatalytic and self-cleaning properties of $TiO_2$ thin film.

• 한국환경보건학회지
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• 제38권4호
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• pp.351-359
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• 2012

Objectives: This study was conducted in order to investigate the specific correlation between physicochemical properties and bioactivity in ecdysteroids found in living organisms. Methods: The examined steroidal compounds were classified into three groups according to their relevance to ecdysone activity. Each compound molecule was completely drawn to automatically calculate its physicochemical parameters and docked against 20-hydroxyecdysone to calculate the total distance. Electronic charge distribution was also observed for each molecule. All procedures were conducted using a computational chemistry program. Results: Ecdysone agonists showed different ranges of parameter values, such as log P, hydrophilic-lipophilic balance (HLB), solubility parameter (SP), hydrophilic surface (HPS), hydrogen bond (HB) and Kappa 2, when compared with antagonists and steroids without ecdysone activity. They also showed a similar electronic charge distribution that is significantly different from the electron charge distribution of antagonists and steroids without ecdysone activity. The total distance values of agonists, estimated by docking them with 20-hydroxyecdysone, were relatively small but showed no correlation with binding affinity with receptor ligand. Conclusions: These results suggest that physicochemical properties such as steric and electronic effects, hydrophobicity and hydrogen bonding may operate in combination to determine the binding activity of ecdysteroids to the receptor protein.

• 한국농공학회논문집
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• 제55권4호
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• pp.29-35
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• 2013

The objective of the current study is to evaluate the effects depending on the types of reinforcing fibers being influential in view of mechanical properties and impact resistance of hybrid fiber reinforced concrete (HFRC) for applications to precast concrete structure. Hybrid fibers applied therefor were three types such as PP/MSF (polypropylene fiber+macro synthetic fiber), PVA/MAF (polyvinyl alcohol fiber+MSF) and JUTE/MSF (natural jute fiber+MSF), where the volume fraction of PP, PVA and natural jute was applied with 0.2 %, respectively, while based on 0.05 % volume fraction of MSF. The HFRC was tested for slump, compressive strength, flexural strength and impact resistance. The test result demonstrated that mixture of such hybrid fibers improve compressive strength, flexural strength and impact resistance of concrete. Moreover, it was found that HFRCs to which hydrophilic fibers, i.e. PVA/MSF and JUTE/MSF, were mixed show more improved features that HFRC to which non-hydrophilic fiber, i.e. PP/MSF was mixed. Meanwhile, the finding that PVA/MSF HFRC exhibited better performance than JUTE/MSF HFRC was attributed from the former having higher aspect ratio than that of the latter.

• Membrane and Water Treatment
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• 제10권6호
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• pp.461-469
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• 2019

In the present work, we present a new effective hydrophilicity modifier for polysulfone (PSf) membrane. Firstly, amphiphilic nanocellulose (ANC) with different substitution degrees (SD) was synthesized by esterification reaction with nanocellulose (NC) and dodecyl succinic anhydride (DDSA). The SD and morphology of ANC were characterized by titration method and transmission electron microscopy (TEM). Then, the polysulfone (PSf)/ANC blend membranes were prepared via an immersion phase inversion method. The influence of SD on the morphology, structure and performances of PSf/ANC blend membrane were carefully investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), mechanical property test, contact angle measuring instrument and filtration experiment. The results showed that the mechanical property, hydrophilicity and anti-fouling property of all the PSf/ANC blend membranes were higher than those of pure PSf membrane and PSf/NC membrane, and the membrane properties were increased with the increasing of SD values. As ANC-4 has the highest SD value, PSf/ANC-4 membrane exhibited the optimal membrane properties. In conclusion, the prepared ANC can be used as an additive to improve the hydrophilicity and anti-fouling properties of polysulfone (PSf) membrane.

• Composites Research
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• 제25권6호
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• pp.198-204
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• 2012

본 연구에서는 VARTM 공정으로 제조되는 에폭시/아바카 패브릭 복합재의 기계적 특성을 향상 시키고자 하였다. 표면처리를 통하여 패브릭 표면의 미세 거칠기를 증가시키고 친수성을 소수성으로 변화시켜 에폭시-패브릭간 계면결합력을 증가시켜 기계적 특성을 향상 시키고자 하였다. 이를 위해 상온 상압 플라즈마 처리법을 사용하였고 기계적 특성이 향상되는 최적 처리시간을 찾고자 하였다. 플라즈마 처리 특성을 비교하기 위해 NaOH 처리법을 사용하였다. 플라즈마 10초 처리된 패브릭으로 제조된 복합재가 무처리, NaOH 처리 대비 가장 높은 인장강도를 보였으며 20초 이상 처리시 인장강도는 낮아졌다. 미세구조 분석결과 20초 이상 처리시 섬유에 생긴 미세 흠집으로 인해 인장강도가 저하됨을 알 수 있었다. 흡습 시험과 침강 시험을 통해 친수성의 아바카가 소수성의 경향을 보이는 것을 확인하였다.

• 전자공학회논문지 IE
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• 제44권3호
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• pp.6-11
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• 2007

본 연구는 플라즈마 처리한 고분자 복합재료 표면의 접촉각, X-선광전자분광법(XPS) 및 코로나 대전에 의한 표면 정전특성을 분석하여 발생된 화학적 변화와 정전적 특성 변화를 고찰하여 열화 메커니즘을 도출하였다. 플라즈마 처리된 시료의 접촉각 및 표면전위는 표면에 카르복실기 라디칼을 포함하는 다량의 측쇄화가 집중적으로 발생되어 처리시간에 따라 급격한 친수화가 진행되었다. 플라즈마 처리로 인한 화학적 변화에서 표면에 carboxyl 라디칼이 주로 형성되면서 급격히 표면 친수화로 변화하였다. 정전변화를 분석한 전위감쇠 결과에서 미처리 시료는 부극성 표면을 나타내었으나, 친수화 표면은 carboxyl 라디칼(-COO*)을 포함하는 정극성 라디칼로 인해 정극성 표면으로 변화하여 부극성 전하가 빠르게 감소하였다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XIII)
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• pp.655-659
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• 2003

수용성 약물의 캡슐화 효율을 높이기 위하여 eudragit이 코팅된 SLN을 제조하였고 TEM을 이용하여 그 형태가 양호하게 형성된 것을 확인하였다. DLS를 이용하여 형성된 입자의 분포와 크기를 확인하였으며 옥용산을 포함하는 E-SLN은 ${\pm}180$ nm, ascorbic acid는 ${\pm}150$ nm의 크기를 가지는 것으로 확인되었다. 캡슐화 효율은 옥용산을 경우 41%, ascorbic acid는 33%로 나타났으며, 이는 E-SLN이 수용성 약물을 캡슐화하는 데 유용함을 보여준다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1742-1746
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• 2008

An EHD (Electro-Hydro-Dynamic) jet for electrostatic inkjet head shows advantages to print micro-size patterns using various inks because it can generate sub-micron droplets and can use highly viscous inks. Thus, many researchers in industrial fields are concerned about the EHD jet in these days. Since the basic principle of the EHD jet is to form a droplet from an apex of meniscus at the end of the nozzle, the ejection mechanism can be changed by the shape of the meniscus. The stable ejection of the droplet is greatly affected by the shape of the meniscus which is also influenced by surface characteristics of the nozzle, electric potential and ink properties. Experiments have been performed using the nozzles with hydrophilic and hydrophobic coatings in this study. The hydrophobic nozzle forms the stable droplets in wider range of the electric potential than the hydrophilic nozzle does.