• Applied Chemistry for Engineering
• /
• v.21 no.5
• /
• pp.514-521
• /
• 2010

A new one-shot process was employed to fabricate proton exchange membranes (PEMs) over conventional solvent-casting process. Here, PEMs containing nano-dispersed silica nanoparticles were fabricated using one-shot process similar to the bulk-molding compounds (BMC). Different components such as reactive dispersant, urethane acrylate nonionmer (UAN), styrene, styrene sulfuric acid and silica nano particles were dissolved in a single solvent dimethyl sulfoxide (DMSO) followed by copolymerization within a mold in the presence of radical initiator. We have successfully studied the water-swelling and proton conductivity of obtained nanocomposite membranes which are strongly depended on the surface property of dispersed silica nano particles. In case of dispersion of hydrophilic silica nanoparticles, the nanocomposite membranes exhibited an increase in water-swelling and a decrease in methanol permeability with almost unchanged proton conductivity compared to neat polymeric membrane. The reverse observations were achieved for hydrophobic silica nanoparticles. Hence, hydrophilic and hydrophobic silica nanoparticles were effectively dispersed in hydrophilic and hydrophobic medium respectively. Hydrophobic silica nanoparticles dispersed in hydrophobic domains of PEMs largely suppressed swelling of hydrophilic domains by absorbing water without interrupting proton conduction occurred in hydrophilic membrane. Consequently, proton conductivity and water-swelling could be freely controlled by simply dispersing silica nanopartilces within the membrane.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.390-390
• /
• 2013

유기물을 이용하여 제작한 비휘발성 메모리 소자는 저전압 구동, 간단한 공정과 플렉서블 모바일에 응용 가능성 때문에 많은 연구가 진행되고 있다. 나노복합체를 사용하여 제작한 비휘발성 메모리 소자의 전기적 특성에 대한 연구가 많이 진행되었으나 고분자를 저장매체로 사용한 메모리 소자의 전기적 특성에 대한 연구는 미흡하다. 본 연구에서 poly (methylmethacrylate) (PMMA)와 poly (3-hexylthiophene) (P3HT) 혼합한 용액을 이용하여 제작한 메모리 소자의 전기적 특성을 연구하였다. P3HT와 PMMA를 같이 클로로벤젠에 용해한 후 초음파 교반기를 사용하여 두 물질을 고르게 섞었다. Indium-tin-oxide가 코팅된 유리 기판 위에 제작한 고분자 용액을 스핀 코팅하고, 열을 가해 용매를 제거하였다. P3HT박막 위에Al을 상부전극으로 열증착하여 소자를 제작하였다. 제작된 소자의 전류-전압(I-V) 측정결과는 같은 전압에서 전도도가 큰 ON 상태와 전도도가 작은 OFF 상태의 큰 ON/OFF 전류비율을 가진 전류의 히스테리시스를 보여주었다. P3HT를 포함하지 않은 소자의 I-V 측정결과는 전류의 히스테리시스 특성이 보이지 않았고 이것은 P3HT 박막이 메모리 특성을 나타내는 저장매체가 됨을 알 수 있었다. 소자의 전류-시간 특성 측정 결과는 전류의 ON/OFF 비율이 시간에 따라 큰 감쇠 현상 없이 오랫동안 지속적으로 유지됨을 보여줌으로 소자의 동작 안정성을 알 수 있었다.

• Journal of the Korean Chemical Society
• /
• v.42 no.5
• /
• pp.519-525
• /
• 1998

The critical micelle concentration $(CMC^{\ast})$ and the counterion binding constant (B) in a micellar state of the mixed surfactant systems of dodecylpyridinium chloride (DPC) with dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), and cetyldimethylethylammonium bromide (CDEAB) were determined at $25^{\circ}C$ as a function of ${\alpha}_1$ (the overall molc fraction of DPC) by the use of electric conductivity method. Various thermodynamic parameters $(X_{i},\;{\gamma}_{I},\;C_{i},\;a^{M}_{i}, \beta,\;{\Delta}H_{mix}, \;and\; {\Delta}G^{o}_{m})$ for the micellization of DPC/DTAB, DPC/TTAB, and DPC/CDEAB mixtures were calculated and analyzed for each system by means of the equations derived from the pseudophase separation model. The results show that the DPC/DTAB mixed system has the greatest deviation and the DPC/CDEAB mixed system has the smallest deviation from the ideal mixed micellar model.

• Applied Chemistry for Engineering
• /
• v.16 no.1
• /
• pp.144-149
• /
• 2005

Sulfonated poly(ether ether ketone) (SPEEK) was blended with poly(ether sulfone) (PES) at various compositions. To investigate the possibility of using the blend membranes as polymer electrolyte membranes for direct methanol fuel cell, the blend membranes were characterized in terms of methanol permeability, proton conductivity, ion exchange capacity, and water content. Both proton conductivity and methanol permeability of SPEEK were relatively high. As the amount of PES increased, methanol permeability decreased more rapidly compared to proton conductivity. The experimental results indicated that the blend membrane with 40 wt% PES was the best choice in terms of the ratio of proton conductivity to methanol permeability.

• Journal of the Korean Chemical Society
• /
• v.53 no.5
• /
• pp.491-498
• /
• 2009

The critical micelle concentration (CMC) and the counter ion binding constant (B) for the mixed micellizations of DBS (sodium dodecylbenzenesulfonate) with Brij 30 (polyoxyethylene(4) lauryl ether) and Brij 35 (polyoxyethylene (23) lauryl ehter) at 25 ${^{\circ}C}$ in pure water and in aqueous solutions of n-butanol were determined as a function of $\alpha$1 (the overall mole fraction of DBS) by the use of electric conductivity method. Various thermodynamic parameters (Xi, $\gamma$i, Ci, aiM, $\beta$, and ${\Delta}H_{mix}$) were calculated and compared for each mixed surfactant system by means of the equations derived from the nonideal mixed micellar model. There sults show that the molecules of DBS interact more strongly with Brij 35 than Brij 30 and that the DBS/Brij35 mixed system has greater negative deviation from the ideal mixed micellar model than the DBS/Brij 30mixed system.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.231-231
• /
• 2010

GaN는 상온에서 3.4 eV의 넓은 밴드갭을 갖는 직접천이형 반도체로 우수한 전기적/광학적 특성 및 화학적 안정성으로 발광 다이오드 및 레이저 다이오드 등과 같은 광전소자 응용을 위한 소재로 많은 연구가 진행되어왔다. 특히, GaN 나노구조의 경우 낮은 결함밀도, 빠른 구동 및 고집적 특성 등을 가지기 때문에 효과적으로 소자의 광학적/전기적 특성을 향상시킬 수 있어 나노구조 성장을 위한 연구가 활발히 진행되고 있다. 최근에는 Metal organic vapor deposition (MOCVD), hot filament chemical vapor deposition (CVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE) 등 다양한 방법을 통해 성장된 GaN 나노구조가 보고되고 있다. 하지만 고가 장비 사용 및 높은 공정 온도, 복잡한 공정과정이 요구되며 크기조절, 조성비, 도핑 등과 같은 해결되어야 할 문제가 여전히 남아있다. 본 연구에서는 나노구조를 형성하기 위하여 보다 간단한 방법인 전기화학증착법을 이용하여 GaN 나노구조를 ITO 및 FTO가 증착된 전도성 glass 기판 위에 성장하였고 성장 메커니즘 및 그 특성을 분석하였다. GaN 나노구조는 gallium nitrate와 ammonium nitrate가 혼합된 전해질 용액에 Pt mesh 구조 및 전도성 glass 기판을 1cm의 거리를 유지하도록 담가두고 일정한 전압을 인가하여 성장시켰다. Pt mesh 구조 및 전도성 glass 기판은 각각 상대전극 (counter electrode) 및 작업전극 (working electrode)으로 사용되었고 전해질 용액의 농도, 인가전압, 성장시간 등의 다양한 조건을 통하여 GaN 나노구조를 성장하고 분석하였다. 성장된 GaN 나노구조 및 형태는 field emission scanning electron microscopy (FE-SEM)를 이용하여 분석하였고, energy dispersive X-ray (EDX) 분석을 통하여 정량 및 정성적 분석을 수행하였다. 그리고 성장된 GaN 나노구조의 결정성을 조사하기 위해 X-ray diffraction (XRD)을 측정 및 분석하였다. 또한, photoluminescence (PL) 분석으로부터 GaN 나노구조의 광학적 특성을 분석하였다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 1996.11a
• /
• pp.88-91
• /
• 1996

본 연구에서는 전기화학적 정화방법인 electrokinetic 정화기술을 이용하여 오염된 토양내에서 중금속을 제거하는 방안을 연구하였다. 이를 위하여 납을 혼합하여 오염시킨 점토시료에 대하여 정화가동시간, 공급전류, 오염농도를 다르게 하고 3가지의 향상기법을 적용시켜 정화실험을 실시하였다. 실험결과를 토대로 유입수 및 유출수의 PH, 오염토의 PH, 전기포텐셜, 유출수량, 전기 전도도 등 오염토의 물리화학적 성질변화를 구명하고 정화가동조건 및 향상기법적용에 따른 오염토내의 납 제거효과를 파악하였다. 본 연구를 통하여 electrokinetic 정화기술은 투수성이 낫은 점성토 토양내의 중금속을 제거하는데 매우 효과적인 것으로 판명되었다.

• Journal of the Korean Ceramic Society
• /
• v.42 no.4
• /
• pp.251-259
• /
• 2005

In order to characterize the influence of the reaction-site density on the cathodic polarization property of LSCF, we chose the porosity of LSCF as a main controlling variable, which is supposed to be closely related with active sites for the cathode reaction. To control the porosity of cathodes, we changed the mixing ratio of fine and coarse LSCF powders. The porosity and pore perimeter of cathodes were quantitatively analyzed by image analysis. The electrochemical half cell test for the cathodic polarization was performed via 3-probe AC-impedance spectroscopy. According to the investigation, the reduction of oxygen at LSCF cathode was mainly controlled by following two rate determining steps; i) surface diffusion and/or ionic conduction of ionized oxygen through bulk LSCF phase, ii) charge transfer of oxygen ion at cathode/electrolyte interface. Moreover, the overall cathode polarization was diminished as the cathode porosity increased due to the increase of the active reaction sites in cathode layer.

• Korean Chemical Engineering Research
• /
• v.55 no.3
• /
• pp.379-384
• /
• 2017

An electrochemical reduction of a mixture of NiO and rare earth oxides has been conducted to increase the reduction degree of rare earth oxides. Cyclic voltammetry (CV) measurement was carried out to determine the electrochemical reduction behavior of the mixed oxide in molten LiCl medium. Constant voltage electrolysis was performed with various supplied charges to understand the mechanism of electrochemical reduction of the mixed oxide as a working electrode. After completion of the electrochemical reduction, crystal structure of the reaction intermediates was characterized by using an X-ray diffraction method. The results clearly demonstrate that the rare earth oxide was converted to RE-Ni intermetallics via co-reduction with NiO.

• Journal of the Korean Chemical Society
• /
• v.59 no.4
• /
• pp.271-279
• /
• 2015

The critical micelle concentration (CMC), the counter ion binding constant (B) and the aggregation number (N^* ) for the mixed micellization of sodium dodecanoate and sodium n-octanoate as two anionic surfactants have been investigated by means of electric conductivity and light scattering. As its experimental results are found to be deviated from ideal mixed model, thus two different kinds of regular solution models such as Rubingh and Motomura are used for interpreting our experimental data. The stability of the mixed micelles has been confirmed from the negative values of the standard Gibbs energy of mixed micellization ΔG^micel,0 over all compositions and the measured values of ΔG^micel,0 agreed with the theoretical ones within the experimental error.