• Membrane Journal
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• v.18 no.4
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• pp.274-281
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• 2008

Covalent-crosslinked sulfonated poly(arylene ether sulfone) (SPAES) copolymers were synthesized copolymerization technique and additionally crosslinked with divinylbenzene (DVB). To optimize the reaction condition, a concentration of crosslinking agent and a reaction time were varied in the ranges of $30{\sim}90\;v/v%$ and $30{\sim}720\;min$. The properties of the crosslinked membranes were investigated by SEM, TGA and the measurement of proton conductivity. It was found that the proton conductivity of crosslinked membranes decreased depending on a degree of crosslinking while water uptake and methanol permeability reduced.

• Membrane Journal
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• v.25 no.2
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• pp.144-151
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• 2015

The water-soluble poly(vinyl alcohol) membranes with the addition of sulfosuccinic acid (SSA) were prepared and to assign the ion exchange capacity, poly(4-styrene sulfonic acid-co-maleic acid) (PSSA_MA) was added to PVA according to PSSA_MA contents of 70, 80 and 90 wt%. To characterize the resulting membranes, FT-IR, water contents, ion exchange capacity, proton conductivity and methanol permeability were measured. As PSSA_MA contents increased, water contents, ion exchange capacity, proton conductivity increased, but methanol permeability decreased. From these results, the best preparation component was known as PVA10/SSA9/PSSA_MA80.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.4
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• pp.253-262
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• 2004

Construction of tunnels in a deep crystalline host rock for a potential High-Level Radioactive Waste(HLW) repository inevitably generates an excavation disturbed zone (EDZ). There have been a series of debates on whether a permeability in an EDZ increases or not and what would be the maximum depth of an EDZ. Recent studies show mixed opinions on permeability. However, there has been an international consensus on the thickness of an EDZ; 30 cm for TBM and 1 meter for controlled blast. One of the impacts of an EDZ is on determining the distance between adjacent deposition holes. The void gap by the excavation hinders relaxation of temperature profiles so that the current Korean reference designing distance between holes should be stretched out more to keep the maximum temperature in a buffer region below 100 degrees Celsius. The other impact of an EDZ is on the long-term post closure radiological safety. To estimate the impact, the reference scenario, the well scenario, is chosen. Released nuclides diffuse through a bentonite buffer region experiencing strong sorption and reach a fracture surrounded by a porous medium. Inside a fractured porous region, radionuclides migrate by advection and dispersion with matrix diffusion into a porous medium. Finally, they reach a well assumed to be a source of potable water for local residents. The annual individual dose is assessed on this well scenario to find out the significance of an EDZ. A profound sensitivity study was performed, but all results show that the impact is negligible. Even though the role of an EDZ turns out to be limited on overall safety assessment, still it is worthwhile to study the chemical role of an EDZ, such as a potential source for natural colloids, potential sealing of an open fracture by fine clay particles generated by the process of an EDZ, and alteration of a sorption mechanism by an EDZ in the future.

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.270-278
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• 2007

PEMFC electrodes with various gas diffusion layers (GDL) were characterized to find out the effect of GDL on fuel cell performance. The physical properties of GDL such as electric conductivity, porosity, air permeability, water flux, PTFE content, etc had close relationship each other and affected on the variation of the cell performance. It was observed that the micro-porous layer (MPL) on carbon paper or cloth changed the physical properties of GDL and changed the cell performance. The variation of cell performance as a function of the physical properties of GDL showed different behaviors according to the amount of current density.

• Membrane Journal
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• v.16 no.1
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• pp.9-15
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• 2006

PVA/SSA/HPA composite membranes were prepared by the addition of SSA as a crosslinking agent and HPA such as PWA or SiWA. The water uptake decreased and the IEC increased as the HPA contents increased in PVA/SSA/HPA composite membranes. XRD results showed that HPA distributed well into the composite membranes as the HPA concentration increased, and SiWA dispersed better than PWA in the composite membranes. TGA results showed that PVA/SSA composite membranes were more heat-resistant than PVA due to the crosslinking of PVA, and the heat stability of the composite membranes improved much more as the concentration of HPA increased. The methanol barrier property of PVA/SSA/HPA composite membranes was superior to Nafion, and the methanol permeability of the composite membranes decreased as the concentration of HPA increased.

• Journal of Hydrogen and New Energy
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• v.27 no.3
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• pp.276-282
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• 2016

The effects of conductive additives in a $La_{0.8}Sr_{0.2}MnO_3$ perovskite bifunctional electrode for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were investigated in an alkaline solution. Highly porous carbon black (CB) and Ni powder were added to the bifunctional electrodes as conductive additives. The surface morphologies of electrodes containing CB and Ni were observed by scanning electron microscopy (SEM). The current densities for both ORR and OER were changed by the addition of CB. The conductive additive changed physical properties of bifunctional electrodes such as the sheet conductance, gas permeability and contact angle. It was observed that the air permeability of electrode was most effective to enhance the currents for ORR and OER.

• Membrane Journal
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• v.13 no.2
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• pp.101-109
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• 2003

In the present study, crosslinked poly(vinyl alcohol) (PVA) membranes were prepared at various crosslinking agent content using sulfosuccinic acid (SSA) containing sulfonic acid group ($SO_3H)$. To reduce methanol permeability, silica was introduced to the membrane using sol-gel process. The hybrid membranes were studied in relation to proton conductivity and methanol permeability. It was found that both these properties were very dependent on the effect of SSA content as a crosslinking agent and as a donor of hydrophilic $SO_3H)$ group. The proton conductivities of these PVA/SSA/Silica membranes are in the range from $10^{-3}\;to\;10^{-2}$S/cm and the methanol permeabilities are in the range from $10^{-8}\;to\;10^{-7}\;cm^2/sec$.

• Resources Recycling
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• v.9 no.6
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• pp.23-30
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• 2000

Since most of the waste plastics are incinerated and landfilled for the plastic treatment, the environmental friendly processes must be introduced. The plastic utilization of plastic to the blast furnace as a substitutional fuel was developed as a useful recycling method of waste plastics, and commercialized in several ironmaking company in Europe and Japan. Present study was carried out to understand the effect of plastic injection on blast furnace process continuously by using the foundry blast furnace in POSCO. The coke replacement ratio turned out to be 0.98 with the waste plastic injection up to 13.8 kg/thm of injection rate, and there were no significant effect of the kinds of injection plastics on the replacement ratio in this test operation. The permeability in the furnace became worse and the heat load in the lower part of blast furnace was increased with increasing the injection rate of waste plastics. As the rate of plastic injection were increased, the top gas utilization and shaft efficiency were also decreased from the Rist diagram analysis.

• Membrane Journal
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• v.14 no.2
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• pp.173-184
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• 2004

For the application of direct methanol fuel cell (DMFC), sulfonated polystyrene/teflon (PS/PTFE) composite membranes were developed by changing monomer ratio of styrene and DVB. The composite membranes were prepared as follows: first, the monomer mixtures consisting of styrene, divinyl benzene and AIBN were impregnated in porous PTFE film and then, polymerized under 8$0^{\circ}C$ to give PS/PTFE membranes. Finally, the membranes were reacted with chlorosulfonic acid in 1,2-dichloroethane to give the sulfonated composite membranes. The measurements of ATR-FTIR, SEM, solvent uptake test and ion exchange capacity (IEC) were done for the resulting membranes before or after sulfonation, respectively, which showed the composite membranes with proper crosslinking degree and sulfonic acid content were prepared well as a function of styrene/DVB ratio. ion conductivity and methanol permeability were studied for the sulfonated membranes. It was found that with decreasing the ratio of styrene/DVB, methanol permeability decreased from $6.6{\times}10^{-7}∼1.3{\timas}10^{-7}$ $\textrm{cm}^2$/s, which are much lower values than that of Nafion$^{(R)}$117($1.02{\times}10^{-6}$ $\textrm{cm}^2$/s). Under the same monomer condition, ion conductivity decreased from 0.11 S/cm ($25^{\circ}C$) to 0.08 S/cm ($25^{\circ}C$), which are similar or a little higher values compared with $Nafion^{(R)}117 (1.02{\times}10^{-6}$ $\textrm{cm}^2$/s, 0.0824 S/cm). These two results confirmed the composite membranes prepared could be applied successfully to DMFC.C.

• Membrane Journal
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• v.21 no.4
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• pp.389-397
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• 2011

In this study, polymer composite membranes based on sulfonated poly(arylene ether sulfone) (SPAES) were prepared using a solution casting method with different amount of vermiculite (VMT) content. The dispersion of VMT particles in the SPAES matrix was confirmed by means of a scanning electron microscopy observation. The composite membrane containing less than 1 wt% of VMT has a smooth skin on the top and bottom, which means there is a good dispersion of VMT in the matrix. The water uptake of the composite membranes gradually increases as the temperature increases, and the results confirm that all the adsorbed water is bound water because VMT has a strong water affinity on account of its high cation exchange value. A composite membrane with a VMT content of less than 1 wt% increases the proton conductivity and reduces the methanol permeability. Of all the composite membranes, the membrane SPAES/VMT 1.0 has the best fuel cell performance in terms of membrane selectivity. The performance value of SPAES/VMT 1.0 is double that of Nafion 112, which suggests that SPAES/VMT1.0 could be an excellent candidate for direct methanol fuel cells.