• 자원환경지질
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• 제35권5호
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• pp.421-428
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• 2002

계면활성제를 사용하여 지하수의 표면장력을 인위적으로 감소하였을 때, 감소된 표면장력이 지하수 폭기시의 폭기 영향권 및 VOC 제거 효율에 미치는 영향을 실험실 규모의 실험을 통하여 규명하였다. 내경 9.5 cm, 길이 100 cm의 유리 컬럼에 계면활성제(sodium dodecyl sulfate, SDS) 및 toluene 100 ppm 포함하는 물로 채운 후 일정한 속도로 공기를 주입하였을 때의 toluene의 제거 속도를 측정하였다. 또한 같은 컬럼에 토양(모래)이 채워진 상태에서 동일한 실험을 반복하였다. 토양이 존재하지 않는 상태에서의 stripping에 의한 toluene의 제거 속도는 표면장력의 감소(계면 활성제 농도의 증가)에 따라 증가하는 것으로 나타났으며, 토양이 존재하는 경우에도 비슷한 결과를 나타내었다. 2차원 유리 상자에 모래와 SBS를 포함하는 물을 채운 후 일정한 공기 유속을 유지하였을 때, 폭기의 영향권(공기의 침투영역)은 물의 표면장력 감소에 따라 현저히 증가하는 것으로 나타났다. 특히 SDS의 critical micelle concentration(CMC)보다 훨씬 낮은 농도에서 폭기 영향권이 최대화하는 것으로 밝혀졌다. 본 연구결과는 폭기에 의한 지하수 오염물질 중, 특히 휘발성 유기오염물질의 제거 공정의 효율을 증대하는데 기여할 것으로 생각된다.

• Restorative Dentistry and Endodontics
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• 제45권4호
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• pp.47.1-47.11
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• 2020

Objectives: The aim of this study was to assess the physicochemical properties, cytotoxicity and penetration into dentinal tubules of ChlorCid^TM Surf (3% sodium hypochlorite [NaOCl] with surfactant) in comparison to ChlorCid^TM (3% NaOCl without surfactant). Materials and Methods: The physicochemical properties evaluated were pH, surface tension, free available chlorine (FAC) and contact angle. Cytotoxicity was evaluated in L929 fibroblasts exposed to the solutions by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and neutral red assays. Assessment of penetration into dentinal tubules was performed by staining single-rooted permanent human teeth with crystal violet (n = 9), which were irrigated with the solutions and analyzed in cervical, middle and apical segments. Data were analyzed by one-way analysis of variance (ANOVA) and Tukey's post-test, 2-way ANOVA and Bonferroni's post-test or t-test (α = 0.05). Results: ChlorCid^TM Surf and ChlorCid^TM FAC values were close to those indicated by the manufacturer. ChlorCid^TM Surf showed lower surface tension and contact angle on dentin, and higher pH than ChlorCid^TM (p < 0.05). The penetration of ChlorCid^TM Surf was higher in cervical and middle segments, compared with ChlorCid^TM (p < 0.05). There was no difference in irrigant cytotoxicity (p > 0.05). Conclusions: ChlorCid^TM Surf showed lower surface tension, lower contact angle on root canal dentin, higher penetration into dentinal tubules and more alkaline pH, compared with ChlorCid^TM. However, both solutions showed similar cytotoxicity and FAC content.

• 한국세라믹학회지
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• 제51권5호
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• pp.511-515
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• 2014

The thermodynamic instability of bubbles in wet-foam colloidal suspension is due to the substantial area of their gas/liquid interface. Several physical processes lead to gas diffusion from smaller to larger bubbles, resulting in a coarsening and Ostwald ripening of wet foam. This includes a narrowing of the bubble size distribution. The distribution and microstructure of porous ceramics, the adsorption free energy and Laplace pressure of $Al_2O_3$ particle-stabilized colloidal suspension, and $SiO_2$ content were investigated for tailoring the bubble size. Wet-foam stability of more than 80% is related to the degree of hydrophobicity with contact angles of $62-70^{\circ}$ achieved from the surfactant. The contact angle replaces part of the highly energetic interface and lowers the free energy of the system. This leads to an apparent increase in the surface tension (26-33 mN/m) of the colloidal suspension.

• 폴리머
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• 제28권2호
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• pp.103-110
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• 2004

토코페롤을 함유하는 폴리($\varepsilon$-카프로락톤)(PCL) 마이크로캡슐은 액중건조법에 의하여 제조하였고, 제조 조건에 따른 마이크로캡슐의 특성과 PCL 필름을 사용하여 PCL의 분해거동을 측정하였다 제조된 마이크로캡슐의 크기 및 형태와 구조적 특성은 각각 SEM과 XRD를 이용하여 관찰하였다. 또한, 접촉각 측정을 통하여 심물질의 농도에 따른 마이크로캡슐의 표면자유에너지를 측정하였다. 실험결과, 마이크로캡슐은 유화제로 폴리(비닐 알코올)을 사용한 경우 안정된 구형의 마이크로캡슐이 형성되었고, 마이크로캡슐의 표면자유에너지와 PCL의 결정성은 감소하고, PCL 필름은 악 21일 후 분해가 시작되었다. 토코페롤의 방출특성은 UV/vis.에 의하여 측정하였으며, 마이크로캡슐의 방출속도는 교반속도의 증가와 함께 증가하였다. 이는 교반속도의 증가와 함께 감소된 마이크로캡슐 입자 크기에 의한 방출용액과 마이크로캡슐 사이의 계면의 증가에 의한 것으로 판단된다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.23.1-23.1
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• 2009

ZnO is of great interest for various technological applications ranging from optoelectronics to chemical sensors because of its superior emission, electronic, and chemical properties. In addition, vertically well-aligned ZnO nanorods on large areas with good optical and structural properties are of special interest for the fabrication of electronic and optical nanodevices. To date, several approaches have been proposed for the growth of one-dimensional (1D) ZnO nanostructunres. Several groups have been reported the MOCVD growth of ZnO nanorods with no metal catalysts at $400^{\circ}C$, and fabricated a well-aligned ZnO nanorod array on a PLD prepared ZnO film by using a catalyst-free method. It has been suggested that the synthesis of ZnO nanowires using a template-less/surfactant-free aqueous method. However, despite being a well-established and cost-effective method of thin film deposition, the use of magnetrons puttering to grow ZnO nanorods has not been reported yet. Additionally,magnetron sputtering has the dvantage of producing highly oriented ZnO film sat a relatively low process temperature. Currently, more effort has been concentrated on the synthesis of 1D ZnO nanostructures doped with various metal elements (Al, In, Ga, etc.) to obtain nanostructures with high quality,improved emission properties, and high conductance in functional oxide semiconductors. Among these dopants, Ga-doped ZnO has demonstrated substantial advantages over Al-doped ZnO, including greater resistant to oxidation. Since the covalent bond length of Ga-O ($1.92\;{\AA}$) is nearly equal to that of Zn-O ($1.97\;{\AA}$), high electron mobility and low electrical resistivity are also expected in the Ga-doped ZnO. In this article, we report the successful growth of Ga-doped ZnO nanorods on c-Sapphire substrate without metal catalysts by magnetrons puttering and our investigations of their structural, optical, and field emission properties.

• 공업화학
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• 제29권5호
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• pp.524-532
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• 2018

본 연구에서는 천연 유래의 코코넛 오일을 원료로 사용하여 2종류의 아미노산계 음이온 생체계면활성제 포타슘 코코일 글루타메이트(potassium cocoyl glutamate, CTK)와 소듐 코코일 글루타메이트(sodium cocoyl glutamate, CTN)를 합성하였으며, 합성한 계면활성제의 구조를 FT-IR, $^1H-NMR$ 및 $^{13}C-NMR$ 분석을 통하여 규명하였다. 합성한 계면활성제에 대하여 정적 및 동적 표면장력과 유화력 등의 계면 물성을 측정한 결과, CTK와 CTN 모두 계면 활성이 우수하고 계면 에너지를 낮추는데 효과적임을 알 수 있었다. 특히, CTK 계면활성제가 CTN 계면활성제와 비교하여 계면 에너지를 낮추는데 보다 효과적이었는데 이는 CTK가 소수성이 더 크고 계면활성제 단분자가 벌크 용액으로부터 공기와 수용액의 계면으로 이동하는 속도가 빨라서 공기와 수용액의 계면이 계면활성제 단분자에 의하여 더 짧은 시간에 포화되기 때문임을 알 수 있었으며, 생활용품이나 화장품 제조에 적용될 수 있을 것으로 기대된다.

• 한국세라믹학회지
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• 제53권6호
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• pp.604-609
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• 2016

This study reports on wet-foam stability with respect to porous ceramics from a particle-stabilized colloidal suspension that is achieved through the addition of polymethyl methacrylate (PMMA) using a wet process. To stabilize the wet foam, an initial colloidal suspension of $Al_2O_3$ was partially hydrophobized by the surfactant propyl gallate (2 wt.%) and $SiO_2$ was added as a stabilizer. The influence of the PMMA content on the bubble size, pore size, and pore distribution in terms of the contact angle, surface tension, adsorption free energy, and Laplace pressure are described in this paper. The results show a wet-foam stability of more than 83%, which corresponds to a particle free energy of $2.7{\times}10^{-12}J$ and a pressure difference of 61.1 mPa for colloidal particles with 20 wt.% of PMMA beads. It was possible to control the uniform distribution of the open/closed pores by increasing the PMMA content and by adding thick struts, leading to the achievement of a higher-stability wet foam for use in porous ceramics.

• 한국안전학회지
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• 제28권6호
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• pp.23-28
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• 2013

In order to improve extinguishing performance of water mist, many studies of additives have been conducted. In this study, viscosity agent which has the ability to improve extinguishing performance by adhering to the surface on fire was used and fluorine-free surfactant was also added to water to enhance water's wetting ability. This study aimed to verify optimal concentration of extinguishing of additives according to fire source and extinguishing performance by comparison with pure water. In case of wood crib fire, the results show that flame suppression and extinguishing time of sodium alginate 0.4 wt.% are 3.4 times and 2.2 times shorter than those of pure water in 0.2 MPa respectively. It seems that large amount of water adhere to surface on fire, thus cooling effect on surface was enhanced. Also water consumption of sodium alginate 0.4wt.% is up to 65% lower than that of pure water. In case of heptane fire, extinguishing time of cocobetaine 0.1 wt.% is 9.7 times shorter than that of pure water in 0.2 MPa. It is thought that because cocobetaine can block oxygen and suppress oil mist by making emulsion film on fire surface due to a low surface tension. On the other hand, water consumption of cocobetaine 0.1 wt.% is 92% lower than that of pure water.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1534-1538
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• 2011

Uniform, hollow nanosilica spheres were prepared by the chemical coating of cationic polystyrene (cPS) with tetraethylorthosilicate (TEOS), followed by calcination at 600 $^{\circ}C$ under air. cPS was synthesized by surfactant-free emulsion polymerization using 2,2'-azobis (2-methyl propionamidine) dihydrochloride as the cationic initiator, and poly(vinyl pyrrolidone) as a stabilizer. The resulting cPS spheres were 280 nm in diameter, and showed monodispersion. After coating, the hollow silica product was spherically shaped, and 330 nm in diameter, with a narrow distribution of sizes. Dispersion was uniform. Wall thickness was 25 nm, and surface area was 96.4 $m^2/g$, as determined by BET. The uniformity of the wall thickness was strongly dependent upon the cPS surface charge. The effects of TEOS and ammonia concentrations on shape, size, wall thickness, and surface roughness of hollow $SiO_2$ spheres were investigated. We observed that the wall thicknesses of hollow $SiO_2$ spheres increased and that silica size was simultaneously enhanced with increases in TEOS concentrations. When ammonia concentrations were increased, the irregularity of rough surfaces and aggregation of spherical particles were more severe because higher concentrations of ammonia result in faster hydrolysis and condensation of TEOS. These changes caused the silica to grow faster, resulting in hollow $SiO_2$ spheres with irregular, rough surfaces.

• Korea-Australia Rheology Journal
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• 제16권1호
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• pp.47-54
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• 2004

Low Reynolds number, dilute, and surfactant-free bubble suspensions are prepared by mechanical mixing after introducing carbon dioxide bubbles into a Newtonian liquid, polyol. The apparent shear viscosity is measured with a wide-gap parallel plate rheometer by imposing a simple shear flow of capillary numbers(Ca) of the order of $10^{-2}$ ~ $10^{-1}$ and for various gas volume fractions ($\phi$). Effects of capillary numbers and gas volume fractions on the viscosity of polyol foam are investigated. At high capillary number, viscosity of the suspension increases as the gas volume fraction increases, while at low capillary number, the viscosity decreases as the gas volume fraction increases. An empirical constitutive equation that is similar to the Frankel and Acrivos equation is proposed by fitting experimental data. A numerical simulation for deformation of a single bubble suspended in a Newtonian fluid is conducted by using a newly developed two-dimensional numerical code using a finite volume method (FVM). Although the bubble is treated by a circular cylinder in the two dimensional analysis, numerical results are in good agreement with experimental results.