• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.143.2-143
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• 2000

• Journal of the Korean Electrochemical Society
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• v.15 no.2
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• pp.95-100
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• 2012

$LiFePO_4$ is an attractive cathode material due to its low cost, good cyclability and safety. But it has low ionic conductivity and working voltage impose a limitation on its application for commercial products. In order to solve these problems, the iron($Fe^{2+}$)site in $LiFePO_4$ can be substituted with other transition metal ions such as $Mn^{2+}$ in pursuance of increase the working voltage. Also, reducing the size of electrode materials to nanometer scale can improve the power density because of a larger electrode-electrolyte contact area and shorter diffusion lengths for Li ions in crystals. Therefore, we chose electrospinning as a general method to prepare $Li[Fe_{0.9}Mn_{0.1}]PO_4$ to increase the surface area. Also, there have been very a few reports on the synthesis of cathode materials by electrospinning method for Lithium ion batteries. The morphology and nanostructure of the obtained $Li[Fe_{0.9}Mn_{0.1}]PO_4$ nanofibers were characterized using scanning electron microscopy(SEM). X-ray diffraction(XRD) measurements were also carried out in order to determine the structure of $Li[Fe_{0.9}Mn_{0.1}]PO_4$ nanofibers. Electrochemical properties of $Li[Fe_{0.9}Mn_{0.1}]PO_4$ were investigated with charge/discharge measurements, electrochemical impedance spectroscopy measurements(EIS).

• Membrane Journal
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• v.13 no.3
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• pp.191-199
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• 2003

Cation exchange polymer electrolyte membrane for the application of direct methanol fuel cell (DMFC) was studied. Poly(vinyl alcohol)(PVA) well known as a methanol barrier in pervaporation separation was used fur the base materials and poly(acrylic acid)(PAA) was used for the crosslinking agent with various concentration. Methanol permeability, ion conductivity, ion exchange capacity, water contents and fixed ion concentration of the membranes were investigated to evaluate the performance of the fuel cell electrolyte membrane. Methanol permeability and ion conductivity of the membranes were decreased with increasing PAA content and were increased over 15% of PAA content. These phenomena would be explained with the introduction of hydrophilic crosslinking agent. The membranes with 15% content of PAA showed methanol permeability of $6.49{\times}10^{-8}/cm^2/s,\; 2.85{\times}10^{-7}CM^2/s$ at $25^{\circ}C,\; 50^{\circ}C$ of operating temperatures, respectively. ion conductivities of the membrane were $2.66{\times}10^{-3}\;S/cm,$ $9.16{\times}10^{-3}\;S/cm$ at $25^{\circ}C,\; 50^{\circ}C$ of operating temperatures, respectively. ion exchange capacity, water content and fixed ion concentration of the membrane were revealed 1.32 meq/g membrane,0.25 g $H_2$O/g membrane and 5.25 meq/g $H_2O$, respectively.

• Membrane Journal
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• v.18 no.4
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• pp.345-353
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• 2008

Organic/inorganic composite electrolyte membranes were prepared for dye sensitized solar cell (DSSC). Polyethylene Glycol (PEG)s with various molecular weight (400, 600, 1,500 and 3,400) was ethoxysilated to fabricate organic/inorganic composite materials through sol-gel processes. The electrolyte membranes were produced by doping the composite materials with NaI and $I_2$, and their ionic conducting behavior was investigated. The ionic conductivity of the composite electrolyte was highly affected by the PEG molecular weight, and the highest conductivity was shown by the composite membrane prepared with PEG with the molecular weight of 1,500. The composite electrolyte membranes showed considerable improvement of ionic conductivity. Compared to PEO electrolyte membranes, the composite electrolyte membrane prepared by PEG, MW 1,500, showed much higher ionic conductivity.

• Membrane Journal
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• v.15 no.1
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• pp.1-7
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• 2005

Polymer electrolyte membranes containing polysilsesquioxane (PSQ) spheres were prepared with the blend of sulfonated poly(ether ether ketone) (SPEEK) (60%) and poly(ether sulfone) (PES) (40%). The amount of PSQ spheres was fixed at 10 wt%. The prepared polymer electrolyte membranes were characterized in terms of methanol permeability, proton conductivity, and ion exchange capacity. In all cases, both methanol permeability and proton conductivity of the polymer electrolyte membranes containing PSQ spheres were lower than the values of Nafion 117 and higher than those of SPEEK/PES (6:4) blend without PSQ spheres. The experimental results indicated that the polymer electrolyte membranes containing MS64 and VTMOS spheres were the best choice in terms of the ratio of proton conductivity to methanol permeability.

• Journal of the Korean Chemical Society
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• v.22 no.6
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• pp.423-430
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• 1978

The initiation mechanism of trioxane polymerization catalyzed by Ti$Cl_4$ in nitrobenzene was investigated. The kinetic studies revealed that the rate of polymerization was drastically decreased by the addition of a minute amount of water or methanol. A third substance as cocatalyst was not required for the polymerization. Measurements of dielectric constants gave no evidence for the zwitterionic mechanism of the polymerization. The electric conductivity measurements of polymerization system and the initiator solution showed that the initiation was started by Ti$Cl_3^+$ cation, formed by a disproportionation of the initiator in nitrobenzene.

• Journal of the Korean Electrochemical Society
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• v.19 no.2
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• pp.45-49
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• 2016

In order to mitigate oxidative degradation of polymer membrane during fuel cell operation, an organic radical quencher was introduced. Rutin was selected as a radical quencher and mixed with sulfonated poly(arylene ether sulfone) to prepare composite membrane. Physicochemical properties of the composite membranes such as water uptake and proton conductivity were characterized. Hydrogen peroxide exposure experiment, which can mimic accelerated oxidative stability test during fuel cell operation, was adopted to evaluate the oxidative stability of the membranes. The composite membranes containing Rutin showed similar proton conductivity and enhanced oxidative stability compared to pristine ones.

• Electrical & Electronic Materials
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• v.1 no.2
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• pp.126-135
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• 1988

Acrylonitrile-Acrylic acid 공중합체와 이를 amidation시킬 공중합체에 구리착물을 형성시켜 IR spectrum분석, 점도측정, 전자현미경관찰, 열분석, 전기전도성등을 검토하였다. AN-AA 공중합체-Cu(II)와 아미드화 AN-AA 공중합체-Cu(II)착물은 pH9의 범위에서 가장 안정한 값을 가지며 착물이 형성되거나 Cu$_{x}$S가 도입된 공중합체는 그 구조가 ompact해짐을 알 수 있었다. 공중합체에 Cu(II)착물이 형성되면 열안정성이 감소되며 Cu(II)착물은 아세톤 용액에서 요오드로 dope 될 때 저항값이 $10^{5}$-$10^{6}$.OMEGA..cm를 나타냈다. 저항값은 CuCl$_{2}$와 I$_{2}$의 양에 영향을 받으며 20wt% 이상의 CuCl$_{2}$와 1.0wt% I$_{2}$로 처리하였을 때 반도체영역의 저항값을 보였다. 또 Cu$_{x}$S를 도입할 경우 CuSO$_{4}$의 농도가 30g/l로, 3시간 반응시켰을 때 가장 만족스러운 전도도값을 나타냈다. 공중합체-Cu(II)보다 구리이온을 도입한 Cu$_{x}$S공중합체의 전도도값이 $10^{4}$정도로서 공중합체-Cu(II)보다 높은 전도성을 나타냈다.다.

• Clean Technology
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• v.11 no.3
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• pp.141-146
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• 2005

The composite membranes were made by grafting using supercritical carbon dioxide (scCO2) impregnation and polymerization procedures. The membranes were synthesized by changing amount of monomer. The polypropylene grafted polystyrene sulfonic acid (PP-g-pssa) membranes were characterized with various methods. The morphology and structure of PP-g-pssa membranes were analyzed with scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). As amount of monomer was increased, ion conductivity, cell performance was increased and methanol permeability was decreased. However PP-g-pssa membranes with 1.5g monomer and over had similar values of methanol permeability, ion conductivity and cell performance.

• Horticultural Science & Technology
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• v.16 no.3
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• pp.352-354
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• 1998

A soilless culture system with the precise control of nutrient solution was developed and the time changes of ionic contribution to EC reading was analyzed. The measuring device designed was able to wash electrodes cleanly and to measure the pH and EC of nutrient solution stably in the box. The nutrient supply system using metering device was also able to control the EC and pH within ${\pm}0.05mS/cm$ and ${\pm}0.05$, respectively. Under the EC control, activity coefficients of all ions decreased with time as ionic concentrations of $SO_4$, Mg and Ca increased due to the selective nutrient absorption by plants. Time changes of ionic contribution to EC reading could be calculated using equivalent ionic conductivities and activity coefficients obtained by numerical analysis.