• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.2
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• pp.93-99
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• 2006

In this paper, we fabricated and evaluated polydimethylsiloxane(PDMS)-based flexible and implantable micro electrodes. The electrode patterning was carried out with the photolithography and chemical etching process after e-beam evaporation of 100 ATi and 1000 A Au. The PDMS substrate was treated by oxygen plasma using reactive ion etching(RIE) system to improve the adhesiveness of PDMS and metal layers. The minimum line width of fabricated micro electrode was 20 $\mu$m. After finished patterning, we did packaging with PDMS and then brought up the electrode's part about 40 $\mu$m with gold electroplating. The Hank's balanced salt solution(HBSS) test was carried out for 6 month for endurance of fabricated micro electrode. We carried out in-vivo test for the evaluation of biocompatibility by implanting electrodes under the ICR mouse skin for 42 days.

• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.177-182
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• 2000

At the porous $La_{0.6}Ca_{0.4}MnO_{3-{\delta}}$(LCM)/YSZ electrodes of solid oxide fuel cells (SOFC), the electrochemical redox reaction of oxygen proceeds via the triple boundary (TPB) of gas/LCM/YSZ. The surface diffusion of adsorbed oxygen on LCM has been proposed as the rate determining process, assuming the gradient of oxygen chemical potential from the outer surface of porous layer to TPB. Along with the formation of this gradient, oxygen nonstoichiometry in the bulk of LCM may varies. In this paper, an electrochemical technique was described precisely to determine the variation of oxygen content in LCM of porous LCM/YSZ under polarization. It was shown that the oxygen potential in LCM layer under large cathodic polarization is much lower than that in the gas phase, being determined from the electrode potential and Nernst equation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1571-1574
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• 2005

Generally, the kerosene or the deionized water has been used for dielectric fluid in the electrical discharge machining. The spark occurs when the voltage is over the breakdown voltage and induces high temperature. In this study, the Oxygen gas is used as the dielectric. The voltage behavior in the dry Micro Electrical discharge machining is compared with that of the conventional Micro Electrical discharge machining. The dry Micro EDM has some advantages. The electrode wear isvery smaller than that of the conventional Micro EDM. The contamination in the dry Micro EDM can be drastically reduced comparing to that of the conventional Micro EDM. The Oxygen gas can be replaced as the dielectric successfully.

• Transactions on Electrical and Electronic Materials
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• v.6 no.5
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• pp.214-220
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• 2005

The ferroelectric properties of the $Pt/PZT(Pb(Zr,Ti)O_3)/Pt$ capacitors are severely degraded when they are annealed in hydrogen-containing environment. Hydrogen atoms created by the catalytic reaction of Pt top electrode during annealing in hydrogen ambient penetrate into PZT films and generate oxygen vacancies by the reduction of the PZT films, which is likely to cause the degradation. The degree of hydrogen-induced degradation and the direction of voltage shift in P-E curves of the pre-poled PZT capacitors after annealing in hydrogen ambient is dependent on the polarity of the pre-poling voltage. This implies that oxygen vacancies causing hydrogen induced degradation are generated by hydrogen ions having a polarity. The degraded ferroelectricity of the PZT capacitors can be effectively recovered by the shift of oxygen vacancies toward the Pt top electrode interface during post-annealing in oxygen environment with applying negative unipolar stressing.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1763-1768
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• 2006

The application of poly(Co(II)-(1,8-diaminonaphthalene))(poly(Co-DAN)) and poly(1,8-diaminonaphthalene) (Poly(1,8-DAN)) to the electrocatalytic reduction of molecular oxygen was investigated, which were electrochemically grown by the potential cycling method on the glassy carbon electrodes. The reduction of oxygen at the polymer and its metal complex polymer coated electrodes were irreversible and diffusion controlled. The Poly(1,8-DAN) and Poly(Co-DAN) films revealed the potential shifts for the oxygen reduction to 30 mV and 110 mV, respectively, in an aqueous solution, compared with that of the bare electrode. Hydrodynamic voltammetry with a rotating ring-disk electrode showed that Poly(1,8-DAN) and Poly(Co-DAN) coated electrodes converted respectively 84% and 22% of $O_2$ to $H_2O$ via a four electron reduction pathway.

• Korean Journal of Food Science and Technology
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• v.28 no.5
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• pp.974-980
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• 1996

A biosensor was prepared with dual cathode electrode and immobilized enzyme membrane. A nylon net was used for the immobilization of glucose oxidase and alcohol oxidase. The immobilized enzymes were placed on the surface of the electrode which was prepared with one anode and two cathodes as an oxygen electrode. The determination of components by the biosensor was based on the consumption of dissolved oxygen. The optimum condition of this system was 0.1 M potassium phosphate buffer solution, pH 7.5 at $35^{\circ}C$. Glucose and ethanol in takju were simultaneously determined by the biosensor. Comparing with UV-spectrophotometer and gas chromatograph for cross checking, there was a good correlation between the biosensor and the conventional methods. Biosensor with dual cathode electrode required no clarification or pretreatments. It was used for simultaneous determination of glucose and ethanol during the fermentation of takju.

• Journal of Sensor Science and Technology
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• v.3 no.2
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• pp.40-49
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• 1994

Potentiometric cell oxygen sensors using $CaF_{2}$ were fabricated for monitering the oxygen partial pressure in the low temperature range ($300^{\circ}C{\sim}$500^{\circ}C). The disk type oxygen sensors consist of a reference electrode: Air($O_{2}:21%$)|Pt, a solid electrolyte $CaF_{2}$, and a sensing metel Pt electrode. And the change in open circuit emf of the disk type cell was about 45mV for the oxygen concentration range, $0.1%{\sim}10%$, at the cell temperature of $400^{\circ}C$. Also, the reference electrode incorporated type sensor showed the change of 40mV for 0.1% to 10% oxygen partial pressure range.

• Bulletin of the Korean Chemical Society
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• v.22 no.2
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• pp.194-198
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• 2001

In order to look for polymeric materials applicable to the oxygen electrode membranes of biosensors, polyurethanes (PUs) were synthesized from poly(butylene succinate) diol (Mn 1150), poly(ethylene glycol) (Mn 200), and 4,4'-methylenebis(cyclohexyl isocyanate). The PUs (Mn 15000-100000) underwent the crystallization and melting transitions in the temperature range of 20-30 $^{\circ}C$ and 90-110 $^{\circ}C$, respectively. The oxygen permeability for the PU membranes prepared by the solution casting method could not be measured since oxygen simply leaked through the membranes with an audible noise. However, when the PUs were blended with carboxylated poly(vinyl chloride) (CPVC), the permeability could be measured. The oxygen permeability coefficient (Po2) of the PU/CPVC $(96}4)$ membranes (6.4 Barrer) was high enough for the application as the electrode membranes. The Po2 decreased dramatically when the CPVC content increased from 4 to 5 wt%, but decreased very slowly and approached to that of CPVC (~0.26 Barrer) when the CPVC content increased further. The scanning electron micrographs of the membranes revealed that the PU membranes were composed of large crystal grains with many pores, but the size of the PU crystal grains and pores decreased progressively with increasing the CPVC content.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.508-508
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• 1996

;The growth of films have considerable interest in the field of superlattice structured multi-layer epitaxy led to realization of new devices concepts. Molecular beam epitaxy (MBE) with in situ observation by reflection high-energy electron diffraction (RHEED) is a key technology for controlled layered growth on the atomic scale in oxide crystal thin films. Also, the combination of radical oxygen source and MBE will certainly accelerate the progress of applications of oxides. In this study, the growth process of single crystal films using by MBE method is discussed taking the oxide materials of Bi-Sr-Ca-Cu family. Oxidation was provided by a flux density of activated oxygen (oxygen radicals) from an rf-excited discharge. Generation of oxygen radicals is obtained in a specially designed radical sources with different types (coil and electrode types). Molecular oxygen was introduced into a quartz tube through a variable leak valve with mass flowmeter. Corresponding to the oxygen flow rate, the pressure of the system ranged from $1{\;}{\times}{\;}10^{-6}{\;}Torr{\;}to{\;}5{\;}{\times}{\;}10^{-5}$ Torr. The base pressure was $1{\;}{\times}{\;}10^{-10}$ Torr. The growth of Bi-oxides was achieved by coevaporation of metal elements and oxygen. In this way a Bi-oxide multilayer structure was prepared on a basal-plane MgO or $SrTiO_3$ substrate. The grown films compiled using RHEED patterns during and after the growth. Futher, the exact observation of oxygen radicals with MBE is an important technology for a approach of growth conditions on stoichiometry and perfection on the atomic scale in oxide. The oxidization degree, which is determined and controlled by the number of activated oxygen when using radical sources of two types, are utilized by voltage locked loop (VLL) method. Coil type is suitable for oxygen radical source than electrode type. The relationship between the flux of oxygen radical and the rf power or oxygen partial pressure estimated. The flux of radicals increases as the rf power increases, and indicates to the frequency change having the the value of about $2{\times}10^{14}{\;}atoms{\;}{\cdots}{\;}cm^{-2}{\;}{\cdots}{\;}S^{-I}$ when the oxygen flow rate of 2.0 seem and rf power 150 W.150 W.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.4
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• pp.197-210
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• 1999

The hydrogen storage performance and electrochemical properties of $Zr_{1-X}Ti_X(Mn_{0.2}V_{0.2}Ni_{0.6})_{1.8}$(X=0.0, 0.2, 0.4, 0.6) alloys are investigated. The relationship between discharge performance and alloy characteristics such as P-C-T characteristics and crystallographic parameters is also discussed. All of these alloys are found to have mainly a C14-type Laves phase structure by X-ray diffraction analysis. As the mole fraction of Ti in the alloy increases, the reversible hydrogen storage capacity decreases while the equilibrium hydrogen pressure of alloy increases. Furthermore, the discharge capacity shows a maxima behavior and the rate-capability is increased, but the cycling durability is rapidly degraded with increasing Ti content in the alloy. In order to analyze the above phenomena, the phase distribution, surface composition, and dissolution amount of alloy constituting elements are examined by S.E.M., A.E.S. and I.C.P. respectively. The decrease of secondary phase amount with increasing Ti content in the alloy explains that the micro-galvanic corrosion by multiphase formation is little related with the degradation of the alloys. The analysis of surface composition shows that the rapid degradation of Ti-substituted Zr base alloy electrode is due to the growth of oxygen penetration layer. After comparing the radii of atoms and ions in the electrolyte, it is clear that the electrode surface becomes more porous, and that is the source of growth of oxygen penetration layer while accelerating the dissolution of alloy constituting elements with increasing Ti content. Consequently, the rapid degradation (fast growth of the oxygen-penetrated layer) with increasing Ti substitution in Zr-based alloy is ascribed to the formation of porous surface oxide through which the oxygen atom and hydroxyl ion with relatively large radius can easily transport into the electrode surface.