• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.413-420
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• 2008

Over the past decade, there have been significant advancement in the field of electrospinning area. This study has focused on preparing yarn using polycarbonate (PC) nanofibers including modified multi-walled carbon nanotube (mMWNT) by solution electrospinning process using the mixture of solvents consisting of tretrahydronfuran (THF) and N,N-dimethylformamide (DMF). In order to enhance the dispersion, MWNT was chemically modified. TEM analysis for the prepared PC/mMWNT nanofibers reveals that mMWNT was well-dispersed into the PC nanofiber matrix. Also with increasing contents of mMWNT, thermal stability of PC/mMWNT nanofibers was improved than that of PC nanofibers. Moreover when 3 to 5 wt% of mMWNT was added, the nanofibers showed good electrical properties expecting antistatic effect, ranging 109.1~109.5 ${\Omega}$. It was confirmed that the multi-filament fibers using PC/mMWNT had $60{\sim}100{\mu}m$ in diameter and 4~5 cm in length.

• Membrane Journal
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• v.32 no.5
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• pp.348-356
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• 2022

With the development of the bio industry, membrane chromatography with a high adsorption efficiency is emerging to replace the existing column chromatography used in the downstream processes of pharmaceuticals, food, etc. In this study, through the deacetylation reaction of two commercial cellulose acetate (CA) membranes with different pore sizes, the porous regenerated cellulose (RC) supports for membrane chromatography were obtained to attach the anion exchange ligands. The adsorptive membranes for anion exchange were prepared by attaching an anion exchange ligand ([3-(methacryloylamino) propyl] trimethylammonium chloride) containing quaternary ammonium groups on the RC supports by grafting and UV polymerization. The protein adsorption capacities of the prepared membranes were obtained through both the static binding capacity (SBC) and the dynamic adsorption capacity (DBC) measurement. As a result, the membrane chromatography with the smaller the pore size, the larger the surface area showed the highest protein adsorption capacity. Membrane chromatography which was prepared by using deacetylated commercial CA support with MAPTAC ligand (i.e., RC 0.8 + MAPTAC: 43.69 mg/ml, RC 3.0 + MAPTAC: 36.33 mg/ml) showed a higher adsorption capacity compared to commercial membrane chromatography (28.38 mg/ml).

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.382-387
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• 2018

In this study, the reaction characteristics of combined steam and carbon dioxide reforming of methane (CSCRM) reaction using Pd-Ni-YSZ catalyst were investigated according to types of catalysts and gas compositions. Catalysts were prepared in the form of powder and porous disk. The injected gases were supplied at different ratios of $CH_4/CO_2/H_2O$. As a result, the conversion of $CH_4$ and $CO_2$ was improved as a result of using the porous disc type catalyst as compared with that of the powder type catalyst. When the $CH_4/CO_2/H_2O$ ratio of the feed gas was 1 : 0.5 : 0.5, the $H_2/CO$ ratio was adjusted close to 2. However, after 6 hours of the reaction, $CH_4$ conversion was partially reduced by the carbon deposition and the pressure drop increased from 0.1 to 0.8. This issue was then solved by optimizing the water content. As a result, it was confirmed that the durability was secured by preventing the carbon deposition when the gas was supplied at a $CH_4/CO_2/H_2O$ ratio of 1 : 0.5 : 1, and the conversion rate was maintained at a relatively high level.

• Korean Chemical Engineering Research
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• v.62 no.3
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• pp.238-245
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• 2024

The lactate electrode can be utilized either as an electrode for lactate sensor to monitor the patient's health status, stress level, and athlete's fatigue in real time or lactate fuel cell. In this study, we fabricated a high-performance electrode composed of lactate oxidase, catalase, and mitochondria, and investigated the surface analysis and electrochemical properties of this electrode. Carbon paper modified with single-walled carbon nanotubes (CP-SWCNT) had significantly improved electrical conductivity compared to before modification. The electrode to which lactate oxidase, catalase, and mitochondria were attached (CP-SWCNT-LOx-Cat-Mito) produced a higher current than the electrode to which lactate oxidase and catalase were attached. The amount of reduction current produced by the bilirubin oxidase (BOD)-attached electrode (CP-SWCNT-BOD) was greatly affected by the presence or absence of oxygen in the electrolyte. The fuel cell composed of CP-SWCNT-LOx-Cat-Mito (anode) and CP-SWCNT-BOD (cathode) produced maximum power (29 ㎼/cm²) at a discharge current density of 133 ㎂/cm². From this study, we had proved that mitochondria is essential for improving lactate sensor and fuel cell performance.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.12
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• pp.668-673
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• 2015

Alumina-based catalysts with different Ce loadings were studied in the decomposition of $CF_4$ using microwave heating system. Heating material of microwave system used Silicon Carbide. The crystallographic phases of catalysts were investigated by XRD and decomposition rates of $CF_4$ were examined by GC-TCD. The catalysts of 10 wt% Ce modified $Al_2O_3$ showed higher $CF_4$ decomposition rate than un-modified $Al_2O_3$ for $500^{\circ}C$ reaction temperature. The k value of catalysts shows the order of $Ce(20)/Al_2O_3=Ce(0)/Al_2O_3<Ce(5)/Al_2O_3<Ce(10)/Al_2O_3$. XRD patterns of $Ce(0)/Al_2O_3$ were no difference before and after the reaction and showed $Al_2O_3$ phases. With the increase in Ce loadings, $CeO_2$, $AlF_3$ of XRD peaks was observed. The results was indicated that Ce modifed $Al_2O_3$ than un-modifed $Al_2O_3$ was decreased reaction temperature to $200^{\circ}C$ with same decomposition rate. Also the appropriated cerium sulfate loadings on $Al_2O_3$ were 5~10 wt%.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.813-818
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• 2008

Various additives were added in small amounts on Ni/YSZ anode of SOFC (solid oxide fuel cell) in order to improve reactivity and to inhibit deactivation due to coke deposition during methane reforming using a low mole ratio steam ($H_2O/CH_4=1.5$) at $800^{\circ}C$. Ni/YSZ catalysts added with various perovskites did not show any improvement but exhibited a gradual decrease in the methane conversion. K-doped Ni/YSZ showed a steady increase and maintenance of the conversion up to 42 hours, after which there was an abrupt deactivation of catalyst owing to potassium loss by volatilization. Addition of 5% of $K_2Ti_2O_5$ on Ni/YSZ showed a stable maintenance of the conversion without K loss, and was able to prevent coke formation during a long time operation. Deactivation of catalyst during the reaction was mainly caused by the accumulation of graphidic carbon on the catalyst surface.

• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.161-166
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• 2011

The $CO_2$ dry reforming reaction, which converts carbon dioxide to hydrogen and carbon monoxide, is typical endothermic reaction, and also known as adverse reaction owing to thermodynamics. In order to overcome the problem, the development studies of suitable catalyst based on precious metals for high durability of thermal and optimization of life time have been examined but it had economical problem by high cost. In this study, we confirmed optimum contents of Pt and La with such different contents of Pt (0.02~0.2 wt%) or La (2~20 wt%) over $Co/SiO_2$ which prepared for excellent activity and cost-effective catalysts. As a result, the promoted catalysts with 0.04 wt% Pt or 9 wt% La over $Co/SiO_2$ showed the highest activity which is 57% and 55% $CO_2$ conversion respectively. Also, the particle size of cobalt on the promoted catalysts with 0.04 wt% Pt or 9 wt% La by characterization of catalyst could confirm the smallest particle size in this study. Therefore, it could know that particle size of cobalt had effected the stability and reactivity of catalysts due to the contents of Pt and La.

• Composites Research
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• v.29 no.5
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• pp.306-314
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• 2016

In this study, to improve the thermal stabilities of the epoxy composite specimens in addition to the enhanced mechanical properties, those were reinforced with carbon nanotubes and micrometer-sized silica particles. To disperse the filler in matrix relatively simple physical process, specimens were fabricated using shear mixing and sonication. Tensile strength, coefficients of thermal expansion and thermal conductivity of the specimens were measured with varied contents of the two fillers. The mechanical and thermal properties were also discussed, and the experimental results of thermal expansion related to the thermal stability of the specimens were compared with those from several micromechanics models. The hybrid composites specimens incorporating 0.6 wt％ of carbon nanotubes and 50 wt％ of silica particles showed better mechanical properties than the others with increase in tensile strength up to 11％, with respect to those of the baseline specimens. As the silica contents were increased the thermal expansion was reduced down to 36%, and the thermal stability was improved with the decreased thermal deformation. Thermal conductivity of the epoxy composite specimens incorporating 50 wt％ of silica particles was enhanced, which demonstrate improvement of 72%. The mechanical and thermal properties of the hybrid composites specimens incorporating the two fillers were improved simultaneously.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.47-52
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• 2015

To improve both the GOD immobilization capability and sensitivity of MWCNTs-based biosensor electrode, the electrode was prepared by adding different quantities of GO. The addition of GO increased hydrophilicity and the surface free energy of electrodes for glucose sensing as well as the dispersion of MWCNTs. In addition, the GOD immobilization capability was enhanced and the sensitivity was improved up to $121{\mu}A\;mM^{-1}$ even though having a high $K_m$ value (0.105) when adding 0.05 g GO to 0.05 g MWCNTs. These experimental results were attributed to the fact that the improvement in dispersion stability for MWCNTs, hydrophilicity, and surface free energy of electrode surface due to the addition of GO affected GOD immobilization capability.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.286-290
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• 2008

Small amounts of CO in reformate fuel gas effectively block platinum catalysts by strong adsorption on the platinum surface at the operation temperature of $60{\sim}80^{\circ}C$ in PEMFC. To oxidate CO, Ru/C layer (CO filter) was placed between Pt/C layer and GDL (gas diffusion layer) in this study. Ru/C filter provided good CO-tolerant PEMFC anode, but decreased the performance of unit cell about 10% at 0.6 V due to mass transfer resistance from Ru/C filter thickness and increase of charge transfer resistance. Membrane degradation is one of the most important factors limiting the life-time of PEMFCs. Membrane durability would be dependent on the electrode catalyst type. It seemed that Ru catalyst layer would shorten the life time of PEMFC as enhanced the fluoride emission rate of membrane in acceleration test.