Ju-Seong Lee

Electrochemical characteristics of Pt–WO3/C and Pt–TiO2/C electrocatalysts in a polymer electrolyte fuel cell

Abstract The electrochemical characteristics and the catalytic activity of Pt–tungsten oxide and Pt–titanium oxide catalysts in polymer electrolyte fuel cell were investigated by cyclic voltammetry and in fuel cells. Fuel cell performances for those catalysts at 80°C with humidified hydrogen and oxygen increased with increasing added oxide content in the catalysts up to a certain content. Adsorption characteristics for hydrogen and oxygen on the surface of platinum were greatly influenced by added oxide content in the catalysts. It was also obtained that the electrochemically active surface area of these catalysts was influenced by their oxide content.

Characteristics for electrocatalytic properties and hydrogen–oxygen adsorption of platinum ternary alloy catalysts in polymer electrolyte fuel cell

Abstract The correlation of crystal structure with catalytic activity of Pt ternary alloys prepared by alloying the Pt–Fe alloy with transition metals, using an electrochemical method in a polymer electrolyte fuel cell was investigated. The electrode prepared by Pt alloy catalysts showed higher cell performance than unalloyed Pt. The plots on the correlation of the lattice parameter with specific activity showed volcanic type behavior. The surface area of weakly bonded hydrogen decreased with a decreasing lattice parameter but at a certain point, it increased again. However, the surface area of strongly bonded hydrogen was constant regardless of the variation of the lattice parameter. The specific activity of Pt alloys increased with a decreasing the surface area of weakly bonded hydrogen, but was independent of the surface area of strongly bonded hydrogen. Also, the specific activity increased with a decreasing oxide reduction area but increasing oxide reduction potential. The cell performance of Pt alloy catalysts improved according to alloying with transition metals because the ratio of surface area of strongly bonded hydrogen to total surface area on the Pt surface increased.

Oxygen reduction behavior with silver alloy catalyst in alkaline media

Abstract The electrochemical characteristics of silver catalyst impregnated on carbon black at the oxygen electrode for an alkaline fuel cell were studied. The electrode containing 30 wt.% silver catalyst showed a current density equivalent to that of Pt catalyst. To improve the catalytic activity and electrode performance, silver was bimetallized with Mg and the alloy state was confirmed by X-ray diffraction. When the atomic content of Ag-Mg alloy was 3:1, it showed the highest current density. A decrease in the corrosion potential at the electrode was found by the catalytic effect of silver. The contact of carbon and silver caused a decrease in the reaction sites of silver and the electrolyte, and hence the dissolution potential of silver was increased. Because the fuel cell was operated at an overpotential of 100–300 mV, the dissolution of silver was not important.

Characteristics of Pr1−xMxMnO3 (M = Ca, Sr) as cathode material in solid oxide fuel cells

Abstract Calcium and strontium-doped praseodymium manganite powders were prepared as cathode materials in solid oxide fuel cells. The characteristics of these materials such as particle size distribution, electrical conductivity, cathodic polarization, thermal expansion, and reactivity with electrolyte were investigated. It was found that the optimum doping content of Ca and Sr was 30 mol% and that Ca-doped PrMnO 3 had higher electrical conductivity and lower cathodic overpotential than Sr-doped PrMnO 3 . Further, the 30 mol% Ca-doped PrMnO 3 had not reacted with Y 2 O 3 stabilized ZrO 2 (YSZ) in the temperature range 1000–1200°C for 100 h and it had a thermal expansion coefficient close to that of YSZ. It was found that 30 mol% Ca-doped PrMnO 3 was satisfactory for use as a cathode material in solid oxide fuel cells.

Performance Improvement of Operating Three-Degree-of-Freedom Spherical Permanent-Magnet Motor

This paper describes performance of operating three-degree-of-freedom (3-D.O.F.) spherical permanent-magnet motor with a finite-element-analysis and experimental studies. Torque and efficiency comparison was made for two different models; the pure iron processed stator core model with a Guide-frame structure, and powder formed stator core model with a Guide-frame structure. As a post study to compensate the defect of the guide frame structure, a double-air-gap operating three-degree-of-freedom spherical permanent-magnet motor has been proposed. Double air-gap type has a single stator, double air-gap between the outer rotor and the inner rotor. Moreover, the double air-gap type, which does not have a guide frame, has a higher torque density, better efficiency, and greater applicability. Finally, the estimated performance has been proven via experiment conducted under the proposed efficiency measurement method.

The characteristics of synthesized potassium hexatitanate and the manufacturing process of the matrix

Abstract The characteristics of synthesized potassium hexatitanate (K2O·6TiO2) and the manufacturing process of the matrix for an alkaline fuel cell were studied. Potassium hexatitanate was synthesized by sintering a mixture of K2CO3 and TiO2 at 850 °C, and the thin film type matrix was manufactured with polytetrafluoroethylene (PTFE) as the binder. The highest wettability, 50%, was obtained for the matrix manufactured using 12 h ball-milled powder containing 10 wt.% PTFE, and it also showed good mechanical properties. The matrix made using K2O·6TiO2 whiskers showed 165% wettability. The wettability, bubble pressure and porosity of the matrix made using a 1:2 powder:whisker mixture were 140%, 220 mmHg and 62%, respectively.

Hydrogen oxidation characteristics of Raney nickel electrodes with carbon black in an alkaline fuel cell

The characteristics of hydrogen oxidation of Raney nickel electrodes containing carbon black in an alkaline fuel cell are investigated in 6 M KOH at 80°C. The addition of conductive material to these electrodes is shown to increase both the limiting current density for hydrogen oxidation and the diffusivity of hydroxide ions. The catalytic activity of Raney nickel electrodes containing carbon black is about twice that of an undoped electrode. A Raney nickel electrode with 8 wt.% Vulcan XC-72 exhibits the highest performance due to the high conductivity and high diffusivity of hydroxide ions at the electrode. The pore volume of the micropores increases with increase in the content of carbon black, but the pore volume of the macropores gradually decreases.

Effects of lidocaine–HCl salt and benzocaine on the expansion of lipid monolayers employed as bio-mimicking cell membrane

Effects of lidocaine-HCl salt and benzocaine on the expansion of lipid monolayers employed as bio-mimicking cell membrane were investigated using Langmuir-Blodgett film balance to figure out the molecular mechanism for anesthesia by these local anesthetics. Lidocaine-HCl salt in subphase expanded the monolayer of phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE). Benzocaine was not mixed with lipids in the monolayer, but the monolayer of lipids on the surface of water saturated with benzocaine was expanded same as the case of lidocaine-HCl salt. Even though this study can not explain the whole molecular mechanism for anesthesia by lidocaine-HCl salt and benzocaine, it can be asserted from the results of this study that the expansion of cell membrane by lidocaine-HCl salt and benzocaine contribute, at least partially, to the generation of anesthesia.

The synthrsis of potassium hexatitanate and manufacturing alkaline fuel cell matrix

Summary form only given. The synthesis of potassium hexatitanate has been studied for substitution of asbestos, caused of its severe problem on toxic pollottant. In most of alkaline fuel cell adapted asbestos as the matrial of matrix but it is now prohibited to manufacture because of above reason. For the improvement of alkaline fuel cell performance, developement of matrix with new matrial is required. In this study, the characteristic of synthesized potassium hexatitanate and thin film type matrix for alkaline fuel cell with this material was studied. After ball milled the mixture with 1:4 of K/sub 2/CO/sub 3/ and TiO/sub 2/ Mixture Was sintered at 850/spl deg/C and its product was confirmed with XRD. Adding the PTFE to the obtained potassium hexatitanate according to the various ball-mill time to control its particle size, thin film type matrix was manufactured. The highest wettability of 50/spl deg/ was found powder onlycontaining 10w/o of PTFE and also it had good mechanical properties. But the matrix with K/sub 2/O . 6TiO/sub 2/ whisker had 170/spl deg/% of wettability. To improve its properties, the characteristics of matrix made by whisker and powder mixture were investigated of bubble pressure, pore size distribution and so on. To compared to cell performance according to various mixture ratios of whisker and powder, single cell was assembled Ag oxygen electrode, Raney Ni hydrogen electrode and potassium hexatitanate matrix. Operatibg temperature was at 80/spl deg/C and electrode size was 10 x 10cm/sup 2/.

Effects of lidocaine on the expansion of lipid monolayer at air/water interface in relation to the local anesthesia

Abstract Lidocaine compounds have widely been used as local anesthetics. Regarding the molecular mechanism for anesthesia by local anesthetics, two hypotheses have been proposed. The first one is that molecules of local anesthetics penetrate into the hydrophobic region of cell membrane and expand the membrane volume, resulting in a change of protein conformation that blocks sodium permeability. The second hypothesis is that molecules of local anesthetics are directly adsorbed into the receptors of anesthetics in the protein channel without expanding the cell membrane. However, these proposals have never been examined systematically. In this study, the expansion of cell membrane by lidocaine compounds was investigated by employing lipid monolayer at the air/water interface as the mimetic system for cell membrane. It was found that oil-soluble lidocaine contracted the area/molecule of lipids in the monolayer of phosphatidyl choline, sphingomyelin, DS-PL95E and lipoid, but expand the monolayer of phosphatidyl ethanolamine only in a certain range of mixing ratios. Thus, this study can provide an evidence that lidocaine yields anesthesia effect by adsorbing into receptors in the protein channel rather than expanding the cell membrane.