• 한국안광학회지
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• 제18권4호
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• pp.457-463
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• 2013

목적: 본 연구는 하이드로젤 콘택트렌즈에 미치는 카르복시메칠 셀룰로오스나트륨을 포함한 인공누액의 영향을 다양한 조건에서 분석 하였다. 방법: 렌즈 재료로 사용되는 NVP(N-vinyl-2-pyrrolidone) 및 MMA(methyl methacrylate)를 가교제인 Ethylene glycol dimethacrylate를 사용하여 HEMA(2-hydroxyethyl methacrylate)와 공중합 하였으며, 개시제로는 azobisiobutyonitrile을 사용하였다. 또한 제조된 렌즈의 물리적 특성을 평가하기 위해 함수율, 굴절률, 접촉각 그리고 분광투과율 등을 측정하였다. 결과: 제조된 콘택트렌즈의 기본 물성을 측정한 결과, 함수율 26.61% ~ 48.58%, 굴절률 1.422~1.455 그리고 분광투과율의 경우 80.8%~91.4%로 나타났으며 접촉각은 $33.93^{\circ}{\sim}65.70^{\circ}$의 범위로 나타났다. 또한 제조된 콘택트렌즈를 인공누액에 침지시킨 후 측정한 물리적 특성은 함수율 24.46%~48.25%, 굴절률 1.422~1.457 또한 분광투과율의 경우 77.0%~91.0%로 나타났으며 접촉각은 $37.25^{\circ}{\sim}77.33^{\circ}$의 범위로 나타났다. 수화시간에 따른 물성 변화는 굴절률의 증가, 함수율의 감소, 광투과율 감소 및 접촉각의 증가를 나타내었다. 결론: 카르복시메칠 셀룰로오스나트륨을 포함한 인공누액은 친수성 하이드로젤 콘택트렌즈의 함수율, 굴절률, 접촉각 그리고 광투과율에 영향을 주는 것으로 나타났다.

• 대한기계학회논문집B
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• 제37권6호
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• pp.559-566
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• 2013

본 연구에서는 고체의 표면조도가 나노유체 액적의 접촉각에 미치는 영향에 대해 실험적 연구를 수행하였다. 나노유체는 산화구리(CuO) 나노분말을 순수 물과 혼합하여 제조하였으며, 고체는 한 변의 길이가 10 mm 정육면체 구리시편을 실험에 사용하였다. 나노유체 액적의 접촉각은 동일한 표면조도 조건에서 순수 물 액적의 접촉각 보다 다소 낮게 측정되었으며, 구리시편의 표면조도가 증가할수록 순수 물과 나노유체 액적의 접촉각은 모두 증가하고 있음을 실험결과로부터 알 수 있었다. 또한 가열-급냉(quench) 실험을 거친 구리시편 표면에서의 접촉각은 순수 표면에서의 접촉각보다 다소 낮게 측정되었으며, 이는 구리표면의 산화에 기인하는 것으로 판단된다. 그러나 가열-급냉 실험에 있어서 냉각 액체로서 순수 물과 나노유체를 사용한 경우의 액적 접촉각 측정결과들은 큰 차이가 없는 것으로 나타났으며, 이러한 실험결과로부터 냉각과정에 있어서 나노입자가 액적의 접촉각에 영향을 미칠 정도로 구리시편의 표면상태를 변화시키지 못하는 것으로 생각된다.

• 한국염색가공학회지
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• 제21권1호
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• pp.30-37
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• 2009

Studies on plants such as lotus leaf suggested that dual-scale structure could contribute to super-hydrophobicity. We introduced super-hydrophobicity onto poly(ethylene terephthalate)(PET) fabric with dual-scale structure by assembling $TiO_2$ nano sol. PET fabric was treated with $TiO_2$ sol, water-repellent agent using various parameters such as particle size, concentration. Morphological changes by particle size were observed using field emmission scanning electron microscopy(FE-SEM) and AFM measurement, contact angle measurement equipment. The contact angle of water was about 138.5$^{\circ}$, 125.8$^{\circ}$, 125.5$^{\circ}$ and 108.9$^{\circ}$ for PET fabric coated with 60.2nm, 120.1nm, 200nm and 410.5nm $TiO_2$ particles, compared with about 111.5$^{\circ}$ for PET fabric coated with water repellent. When we mixed particle sizes of 60.2nm and 120.1nm by 7:3 volume ratio, the contact angle of water was about 132.5$^{\circ}$. And we mixed particle sizes of 60.2nm and 200nm by 7:3 volume ratio, the contact angle of water was about 141.8$^{\circ}$. Also we mixed particle sizes of 60.2nm and 410.5nm by 7:3 volume ratio, the best super-hydrophobicity was obtained. In this paper, we fabricated various surface structures to the water-repellent surfaces by using four types of $TiO_2$ nano-particles, and we found that the nanoscale structure was very important for the super-hydrophobicity.

• 한국전기전자재료학회논문지
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• 제33권3호
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• pp.245-248
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• 2020

The wettability of silicon carbide (SiC) crystal, which has 6H-SiC and 4H-SiC regions prepared using the physical vapor transport (PVT) method, is quantitatively analyzed using dispensed deionized (DI) water droplets. Regardless of the polytypes in SiC, the average of five contact angle measurements showed a difference of about 6° between the Si-face and C-face. The contact angle on the Si-face (C-face) is measured after the removal of the native oxide using BOE (6:1), and revealed a significant decrease of the contact angle from 74.9° (68.4°) to 47.7° (49.3°) and from 75.8° (70.2°) to 51.6° (49.5°) for the 4H-SiC and 6H-SiC regions, respectively. The contact angle of the Si-face recovered over time during room temperature oxidation in air; in contrast, that of the C-face did not recover to the initial value. This study shows that the contact angle is very sensitive to SiC surface polarity, specific surface conditions, and process time. Contact angle measurements are expected to be a rapid way of determining the surface polarity and wettability of SiC crystals.

• 한국기계가공학회지
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• 제18권11호
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• pp.35-40
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• 2019

Laser processing has been used in various fields. In this study, the feasibility of a hydrophobic surface was investigated through the laser cladding technique. A diode laser was used, and the output was set to 600-800 W. Seven different specimens were prepared with different cladding widths and spacings, and the contact angles for water droplets were evaluated. As a result, the contact angle of water droplets measured in the direction parallel to the cladding line was higher than that in the vertical direction. The wider the cladding width and the cladding space, the higher the contact angle in the parallel direction. It is thought that when a higher contact angle is formed in the parallel direction, more air can be placed in the valley between the cladding lines. In addition, for the hydrophobic coating effect, the contact angle of the coated cladding surface was increased by about $5-15^{\circ}$ as a whole compared to the coated smooth surface. It was confirmed that the wetting characteristics were improved through the cladding.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.159-164
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• 2009

The water droplet motion and the interaction between the droplets in a PEMFC air flow channel with multiple pores, through which water emerges, is studied numerically by solving the equations governing the conservation of mass and momentum. The liquid-gas interface is tracked by a level set method which is based on a sharp-interface representation for accurately imposing the matching conditions at the interface. The method is modified to implement the contact angle conditions on the walls and pores. The dynamic interaction between the droplets growing on multiple pores while keeping the total water flow rate through pores constant is investigated by conducting the computations until the droplet motion exhibits a periodic pattern. The numerical results show that the droplet merging caused by increasing the number of pores is not effective for water removal and that the contact angle of channel wall strongly affects water management in the PEMFC air flow channel.

• Advances in concrete construction
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• 제11권4호
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• pp.323-333
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• 2021

The main objective of this study is to characterize and evaluate the hydrophobic performance of polymer-based water-repellent coatings on cementitious mortar surfaces. Different concentrations of poly(vinyl acetate) (PVAc) and poly(1,4-butylene adipate) (PBA) were prepared in the laboratory and their applicability and performance was tested experimentally by water absorption test and analysis of surface contact angles of cementitious mortar specimens. According to the results of this study, it can be stated that incorporation of nano polymer particles on the surface of cementitious mortar specimens can enhance contact angles and reduce water absorption by increasing hydrophobicity. However, a dosage limit exists for polymer materials in coating, and observed hydrophobic improvements decreases when polymer dosage reached beyond the limit. Additionally, it is observed that water absorption of polymer coated cementitious mortars is closely related with the results of surface contact angle.

• 마이크로전자및패키징학회지
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• 제23권1호
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• pp.23-28
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• 2016

본 연구에서는 소수성 구현을 위한 표면 거칠기가 접촉각과 접촉각 이력에 미치는 영향을 평가하였다. 초발수 특성을 극대화하기 위해, 액적이 이동하기 위해 필요한 구름저항력을 제안하였으며, 이에 대한 평가를 통하여 표면에 형성한 패턴이 접촉각 이력 및 구름저항력에 큰 영향을 주는 것을 확인하였다. 초발수 특성이 요구되는 실제 응용을 위해서는 액적의 이동에 필요한 에너지를 최소화하기 위하여 접촉각을 극대화하고 동시에 접촉각 이력을 최소화하기 위한 표면 패턴 형상의 최적화가 요구됨을 확인하였다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권1호
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• pp.78-82
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• 2017

Purpose: The purpose of this study is to evaluate failure characteristic and mechanism of four commercial water-repellent coatings for elevated temperature machinery applications. Method: Thermal degradation was performed for up to 64 thermal cycles. 1 cycle consists of 15 minute holding at 523K under 300rpm revolution and 15 minute-natural cooling. Contact angle was measured and microstructure of the coating layer was observed by using a scanning electron microscope. Results: Four kinds of commercial repellent coating showed hydrophobic or super-hydrophobic property implying that all coatings are suitable for room temperature application. Contact angle of three kinds of commercial coatings decreased rapidly after thermal exposure, while only one specimen having hydrophobic surface showed extremely slow degradation. Conclusion: Observed decrease in contact angle of the coatings were attributed to formation of macro-sized pores and disappearance of micro-protrusion during thermal exposure. Optimum water-repellent coating needs to be selected under the consideration of initial contact angle as sell as service temperature.

• 한국응용과학기술학회지
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• 제21권4호
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• pp.335-344
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• 2004

In this work, the properties as polishing wax for automobile of O/W type microemulsion containing wax, liquid paraffine and quaternaryammonium salt was investigated. The microemulsions were prepared at $96{\sim}97^{\circ}C$ by the phase inversion method, and polyoxyethylene(20) sorbitan monooleate (POE(20)SMO) and distearyl dimethyl ammonium chloride(D.D.A.C) as the emulsifiers were used. The mean particle size of the rnicroemulsions was about 7${\pm}$0.5nm and as the properties of polishing wax, gloss increased degree, water resistant gloss degree, initial and final contact angle after water resistance were tested. The result was that the value of water resistantance and contact angle were decreased with increasing amount of POE(20)SMO and D.D.A.C., while the gloss degree values did not affected. And the rnicroemulsion blended with mono ethylene glycol(MEG) of 5${\sim}$15wt% showed smaller particle size and more stable particle size distribution than without MEG. Finally, this microemulsion showed more excellent values of gloss degree, the water resistant gloss degree and contact angle, than two kinds of commercial polishing wax for automobile.