• 제목/요약/키워드: Layer-by-Layer assembly

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Surface Modification of Nafion by Layer-by-Layer Self-Assembled Films of Polyaniline and Sulfonated Poly(ether sulfone) for Direct Methanol Fuel Cell (직접 메탄올 연료전지용 나피온 막의 폴리아닐린/Sulfonated Poly(ether sulfone) 다층 자기조립 박막에 의한 표면 개질)

  • Ok, Jeong-Rim;Kim, Dong-Wook;Lee, Chang-Jin;Kang, Yong-Ku
    • Journal of the Korean Electrochemical Society
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    • v.11 no.4
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    • pp.256-261
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    • 2008
  • In this study, Nafion membrane was modified to prevent methanol crossover by layer-by-layer self assembly using polyaniline (PANi) as a polycation and sulfonated poly(ether sulfone) (SPES) as a polyanion onto the Nafion surface. Since PANi and SPES possess thermal and chemical stability and rigid backbone, their layer-by-layer self-assembled films on the Nafion are expected to reduce methanol permeability and to increase mechanical stability. UV-Vis absorption spectroscopy verified a linear build-up of the multilayers of PANi and SPES. We found that the thickness per bilayer was about 10 nm by TEM measurement. Although modified Nafion membrane exhibited 15% decrease of proton conductivity, it reduceded 67% of methanol permeability compared to that of the pristine Nafion membrane, resulting in 2.5 times larger selectivity. At the performance test of the fuel cell using 5M methanol as a fuel, the modified Nafion membrane showed 2.4 times higher maximum power density at $30^{\circ}C$ and 1.4 times larger at $60^{\circ}C$ than the pristine Nafion.

Polysaccharide-based superhydrophilic coatings with antibacterial and anti-inflammatory agent-delivering capabilities for ophthalmic applications

  • Park, Sohyeon;Park, Joohee;Heo, Jiwoong;Lee, Sang-Eun;Shin, Jong-Wook;Chang, Minwook;Hong, Jinkee
    • Journal of Industrial and Engineering Chemistry
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    • v.68
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    • pp.229-237
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    • 2018
  • Medical silicone tubes are generally used as implants for the treatment of nasolacrimal duct stenosis. However, side effects such as allergic reactions and bacterial infections have been reported following the silicone tube insertion, which cause surgical failure. These drawbacks can be overcome by modifying the silicone tube surface using a functional coating. Here, we report a biocompatible and superhydrophilic surface coating based on a polysaccharide multilayer nanofilm, which can load and release antibacterial and anti-inflammatory agents. The nanofilm is composed of carboxymethylcellulose (CMC) and chitosan (CHI), and fabricated by layer-by-layer (LbL) assembly. The LbL-assembled CMC/CHI multilayer films exhibited superhydrophilic properties, owing to the rough and porous structure obtained by a crosslinking process. The surface coated with the superhydrophilic CMC/CHI multilayer film initially exhibited antibacterial activity by preventing the adhesion of bacteria, followed by further enhanced antibacterial effects upon releasing the loaded antibacterial agent. In addition, inflammatory cytokine assays demonstrated the ability of the coating to deliver anti-inflammatory agents. The versatile nanocoating endows the surface with anti-adhesion and drug-delivery capabilities, with potential applications in the biomedical field. Therefore, we attempted to coat the nanofilm on the surface of an ophthalmic silicone tube to produce a multifunctional tube suitable for patient-specific treatment.

Application of Strain Energy for Determining the Location of Damping Material (스트레인 에너지를 이용한 제진재 위치 결정)

  • Kim, Joong-Bae;Ryu, Kuk-Hyun;Park, Sang-Kyu;Lee, Sang-Jo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.11
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    • pp.1199-1205
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    • 2008
  • The vehicle design engineers have studied the method of applying damping materials to the vehicle bodies by computer simulations and experimental methods in order to improve the vibration and noise characteristics of the vehicles. The unconstrained layer damping, being concerned with this study, has two layers(base layer and damping layer) and proyides vibration control of the base layer through extensional damping. Generally this kind of surface damping method is effectively used in reducing structural vibration at frequencies beyond 150Hz. The most important thing is how to apply damping treatment with respect to location and size of the damping material. To solve these problems, the current experimental methods have technical limits which are cumbersome, time consuming, and expensive. This Paper proposes a method based on finite element method and it employes averaged ESE(element strain energy) percent of total of dash panel assembly for 1/1 octave band frequency range by MSC/NASTRAN. The regions of high ESE percent of total are selected as proposed location of damping treatment. The effect of damping treatment is analyzed by comparing the frequency response function of the SPCC bare Panel and the damping treated panels.

Improvement of Fire Resistance and Impact Sound Insulation Performance for Timber Framed Floor by Installation of Isolated Ceiling (분리된 천정의 설치를 통한 목구조 바닥의 내화성능 및 충격음 차단성능 향상)

  • Park, Joo-Saeng;Kim, Se-Jong;Lee, Sang-Joon
    • Journal of the Korea Furniture Society
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    • v.24 no.4
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    • pp.426-432
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    • 2013
  • Fire resistance and impact sound insulation tests were performed for a floor assembly, of which stiffness was reinforced by shortening the span of floor joists by installing glulam beam additionally in the middle or one thirds of the original span, and which an additional ceiling component was installed apart from floor structure. By applying the isolated ceiling, timber framed floor showed 1 hour of fire resistance even in case that dead load was increased by considering cement mortar layer for radiant floor heating. Insulation performance against light and heavy impact sound was improved significantly by applying the sound absorbing layer of big mass and high elasticity in addition to the stiffness improvement and isolated ceiling.

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Characteristics of Fabricated MEA(Membrane Electrode Assembly) on Polymer Electrolyte Membrane Fuel Cell Made by the Screen Printing Method (스크린 프린팅법을 이용하여 제조된 고분자 전해질 연료전지에서 MEA(조합 막 전극)의 특성)

  • 임재욱;최대규;류호진
    • Journal of the Semiconductor & Display Technology
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    • v.2 no.4
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    • pp.27-30
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    • 2003
  • The effect of fabrication method of catalytic layer on electrode performance has been investigated. Brush, spray gun and screen printer were used as fabrication tool and catalytic layers were formed by several methods in screen printing. Direct screen printing on polymer membrane, screen printing on carbon paper, and their combined method were applied. In the electrode fabricated by the screen printing method, Pt loading of Pt/C catalysts could be cut down to 50%, compared with results by the brushing and spraying methods. The best result of electrode was obtained as 0.6 V, at 1 A/$\textrm{cm}^2$ when catalytic layer was formed by the combined way.

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A Study on Optical Properties of Nanocomposite Composed of Au Nanorods and Organic Dyes (금 나노막대와 유기 염료로 구성된 나노복합체의 광학특성 연구)

  • Kim, Ki-Se;Yoo, Seong Il;Sohn, Byeong-Hyeok
    • Clean Technology
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    • v.20 no.2
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    • pp.141-145
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    • 2014
  • In this study, we studied optical properties on the layer-by-layer (LbL) assemblies consisting of Au nanorods and organic dyes. For this purpose, poly (allylamine hydrochloride), PAH and poly (styrene sulfonate), PSS were selected as ionic polymers and rhodamine B isothiocyanate (RB) was utilized as an organic dye based on its spectral overlap with plasmon band of Au nanorods. In the view point of assembling methods, RB was covalently attached to PAH, then, LbL structure of Au [PSS/PAH]2/PSS/PAH-RB was prepared by sequential coating of PAH, PSS, PAH-RB on Au nanorods. Since the prepared LbL assembly exhibits both plasmonic and fluorescent properties, we studied the mutual nanorod-dye properties by dissolving Au nanorods.

Decal Method with High Catalyst Transfer Ratio and Its Performance in PEMFC

  • Park, Hyun-Seo;Cho, Yong-Hun;Cho, Yoon-Hwan;Sung, Yung-Eun
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.06a
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    • pp.169-171
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    • 2007
  • A breaking layer was introduced to conventional decal transfer method in membrane electrolyte assembly fabrication for high catalyst transfer ratio. In this study, the modified decal transfer method with high catalyst transfer ratio was introduced and its performance is studied. The structural features of electrodes made by decal method were investigated using scanning electron microscopy and current-voltage polarization measurement.

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Reliability of Fine Pitch Solder Joint with Sn-3.5wt%Ag Lead-Free Solder (Sn-3.5wt%Ag 비납솔더를 이용한 미세피치 솔더접합부의 신뢰성에 관한 연구)

  • 하범용;이준환;신영의;정재필;한현주
    • Journal of Welding and Joining
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    • v.18 no.3
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    • pp.89-96
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    • 2000
  • As solder becomes small and fine, the reliability and solderability of solder joint are the critical issue in present electronic packaging industry. Besides the use of lead(Pb) containing solders for the interconnections of microelectronic subsystem assembly and packaging has enviromental problem. In this study, using Sn/Pb and Sn/Ag eutectic solder paste, in order to obtain decrease of solder joint strength with increasing aging time, initial solder joint strength and aging strength after 1000 hour aging at $100^{\circ}C$ were measured by peel test. And in order to obtain the growth of intermetallic compound(IMC) layer thickness, IMC layer thickness was measured by scanning electron microscope(SEM). As a result, solder joint strength was decreased with increasing aging time. The mean IMC layer thickness was increased linearly with the square root of aging time. The diffusion coefficient(D) of IMC layer was found to $1.29{\times}10^{-13}{\;}cm^2/s$ at using Sn/Pb solder paste, 7.56{\times}10^{-14}{\textrm}{cm}^2/s$ at using Sn/Ag solder paste.

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Improvement of Fouling Resistance with Reverse Osmosis Membrane Using Multi-layer Silane-Epoxy Surface Modification (실란-에폭시 다층 표면개질을 통한 역삼투막의 내오염성 향상)

  • Kwon, Sei;Lee, Yong Taek
    • Membrane Journal
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    • v.25 no.4
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    • pp.332-342
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    • 2015
  • In this study, to solve the major problem of reverse osmosis (RO) membrane, surface of reverse osmosis membrane was modified by silane-epoxy multi layer. Octyltrimethoxysilane (OcTES) was polymerized to membrane surface via cross-linking by Sol-gel method. n = 8 alkylgroup of OcTES formed the branch structure by self assembly. And for improve fouling resistance of RO membrane, Ether group of ethylene glycol diglycidyl ether (EGDE) was given to improve hydrophilicity of RO membrane surface by ring-opening. To analyze structure of RO membrane surface with FE-TEM and AFM. Membrane surface of the ridge and valley structure and the bridge structure was confirmed due to the multi-layer surface modification of OcTES and EGDE. And through the increase of the roughness, the branch structure was formed well on membrane surface. Through the XPS analysis was identified chemical structure of membrane surface. And confirmed that the hydrophilic surface modification is given to the surface of the film through a Contact angle analysis. In optimization of EGDE surface modification condition, was suitable 0.5 wt% EGDE concentraion and $70^{\circ}C$ ring-opening temperature. In result of fouling resistance test and MFI is SUL-H10, $PA-OcTES_{1.0}$, $PA-OcTES_{1.0}-EGDE_{0.5}$ 68.7, 60.4, 5.4 ($10E-8hr/mL^2$), multi-layer surface modified membrane improved fouling resistance.

Effects of Polyamidoamine Dendrimers on the Catalytic Layers of a Membrane Electrode Assembly in Fuel Cells

  • Lee Jin Hwa;Won Jongok;Oh In Hwan;Ha Heung Yong;Cho Eun Ae;Kang Yong Soo
    • Macromolecular Research
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    • v.14 no.1
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    • pp.101-106
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    • 2006
  • The transport of reactant gas, electrons and protons at the three phase interfaces in the catalytic layers of membrane electrode assemblies (MEAs) in proton exchange, membrane fuel cells (PEMFCs) must be optimized to provide efficient transport to and from the electrochemical reactions in the solid polymer electrolyte. The aim of reducing proton transport loss in the catalytic layer by increasing the volume of the conducting medium can be achieved by filling the voids in the layer with small-sized electrolytes, such as dendrimers. Generation 1.5 and 3.5 polyamidoamine (PAMAM) dendrimer electrolytes are well-controlled, nanometer-sized materials with many peripheral ionic exchange, -COOH groups and were used for this purpose in this study. The electrochemically active surface area of the deposited catalyst material was also investigated using cyclic voltammetry, and by analyzing the Pt-H oxidation peak. The performances of the fuel cells with added PAMAM dendrimers were found to be comparable to that of a fuel cell using MEA, although the Pt utilization was reduced by the adsorption of the dendrimers to the catalytic layer.