• Journal of the Korean Chemical Society
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• v.31 no.5
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• pp.406-412
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• 1987

The electrical conductivities of ${\alpha}-Fe_2O_3$ containing 2.5 and 5.0mol% of cadmium were measured from 300 to $900^{\circ}C$ under oxygen pressures of 10$^{-7}$ to 10$^{-1}$ atmosphere. Plots of log ${\sigma}$ vs. 10$^3$/T show the extrinsic conductivity at oxygen pressure higher than $5{\times}10$^{-2}$atm. The transition points appear at about 550$^{\circ}$C and the activation energies are 1.34 eV for the intrinsic region and 0.50 eV for the extrinsic region on 5mol% Cd-doped ${\alpha}-Fe_2O_3$. The extrinsic conductivity disappears at oxygen partial pressures lower than $5{\times}10$^{-2}$ atm, and the intrinsic conductivity predominates. The electrical conductivities decrease with increasing mol% of cadmium doped. The predominant defect of ${\alpha}-Fe_2O_3$ doped with Cd is believed to be Fe${2+}$ interstitial for the intrinsic, however, oxygen vacancy predominates for the extrinsic region. The electrical conduction mechanisms are proposed and the conduction band model is suggested for the extrinsic region.

• Journal of the Korean Electrochemical Society
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• v.3 no.2
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• pp.115-120
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• 2000

All solid-state thin film micro-batteries consisting of lithium metal anode, an amorphous LiPON electrolyte and cathode of vanadium oxide have been fabricated and characterized, which were fabricated with cell structure of $Li/LiPON/V_2O_5Pt$. The effect of various oxygen partial pressure on the electrochemical properties of vanadium oxide thin films formed by d.c. reactive sputtering deposition were investigated. The vanadium oxide thin film with deposition condition of $20\%\;O_2/Ar$ ratio showed good cycling behavior. In in-siか process, the LiPON electrolyte was deposited on the $V_2O_5$ films without breaking vacuum by r.f. magnetron sputtering at room temperature. After deposition of the amorphous LiPON, the Li metal films were grown by a thermal evaporator in a dry room. The charge-discharge cycle measurements as a function of current density and voltage variation revealed that the $Li/LiPON/V_2O_5$ thin film had excellent rechargeable properly when current density was $7{\mu}A/cm^2$. and cut-off voltage was between 3.6 and 2.7V In practical experiment, a stopwatch ran on this $Li/LiPON/V_2O_5$ thin film micro-battery. This result means that thin film micro-battery fabricated by in-siか process is a promising for power source for electronic devices.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.3
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• pp.122-126
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• 2012

The properties of Al-doped ZnO (AZO) films were investigated as a function of $H_2/(Ar+H_2)$ gas ratio using an AZO (2 wt% $Al_2O_3$) ceramic target in a radio frequency (RF) magnetron sputtering system. The deposition process was done at $200^{\circ}C$ and in $2{\times}10^{-2}$ Torr working pressure and with various ratios of $H_2/(Ar+H_2)$ gas. During the AZO film deposition process, partial $H_2$ gas affected the AZO film characteristics. The electron resistivity (${\sim}9.21{\times}10^{-4}\;{\Omega}cm$) was lowest and mobility (${\sim}17.8\;cm^2/Vs$) was highest in AZO films when the $H_2/(Ar+H_2)$ gas ratio was 2.5 %. When the $H_2/(Ar+H_2)$ gas ratio was increased above 2.5 %, the electron resistivity increased and mobility decreased with increasing $H_2/(Ar+H_2)$ gas ratio in AZO films. The carrier concentration increased with increasing $H_2/(Ar+H_2)$ gas ratio from 0 % to 7.5 %. This phenomenon was explained by reaction of hydrogen and oxygen and additional formation of oxygen vacancy. The average optical transmission in the visible light wavelength region over 90 % and an orientation of the deposition was [002] orientation for AZO films grown with all $H_2/(Ar+H_2)$ gas ratios.

• Clean Technology
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• v.18 no.2
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• pp.162-169
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• 2012

Pt-Sn/${\theta}-Al_2O_3$ catalyst for n-butane dehydrogenation reaction was prepared by incipient wetness method. To confirm the physicochemical properties of Pt-Sn/${\theta}-Al_2O_3$ catalyst, the characterization was performed using X-ray diffraction (XRD), $N_2$ sorption analysis, temperature programmed desorption of $NH_3$ ($NH_3$-TPD), temperature programmed reduction of $H_2$ ($H_2$-TPR) techniques. Also, the catalytic activities of Pt-Sn/${\theta}-Al_2O_3$ for n-butane dehydrogenation was tested as a function of pretreatment temperature, pretreatment time, reaction temperature, and the partial pressure of n-butane and hydrogen. The sum of selectivities to n-butenes consisting of 1-butene, cis-2-butene, and trans-2-butene was almost constant 95% in the range of conversion of n-butane 5-55%. The activation energy calculated from Arrhenius equation was $82.4kJ\;mol^{-1}$ and the reaction orders of n-butane and hydrogen from Power's law were 0.70 and -0.20, respectively.

• Membrane Journal
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• v.25 no.5
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• pp.415-421
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• 2015

$SrCo_{0.8}Fe_{0.1}Nb_{0.1}O_{3-{\delta}}$ oxide was synthesized by solid state reaction method. Dense ceramic membrane was prepared using as-prepared powder by pressing and sintering at $1250^{\circ}C$. XRD result of membrane showed single perovskite structure. The oxygen permeability were measured under 0.21 atm of oxygen partial pressure ($P_{O_2}$) and between 800 and $950^{\circ}C$. The oxygen permeation flux of $SrCo_{0.8}Fe_{0.1}Nb_{0.1}O_{3-{\delta}}$ membrane was increased with the increasing temperature. The maximum oxygen permeation flux was $1.839mL/min{\cdot}cm^2$ at $950^{\circ}C$. Long period permeability experiment was carried out to confirm the phase stability and $CO_2$-tolerance of membrane containing Nb in the condition of air with $CO_2$ (500 ppm) as feed stream at $900^{\circ}C$. The phase stability and $CO_2$-tolerance of $SrCo_{0.8}Fe_{0.1}Nb_{0.1}O_{3-{\delta}}$ were investigated by XRD and TG analysis. The result of $SrCo_{0.8}Fe_{0.1}Nb_{0.1}O_{3-{\delta}}$ which exposed carbon dioxide for 100 hours indicated 8wt% of $SrCO_3$. But it was known that the level of $SrCO_3$ production dose not have a significant effect on oxygen permeability.

• Korean Membrane Journal
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• v.9 no.1
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• pp.34-42
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• 2007

A perovskite-type ($La_{0.6}Sr_{0.4}Ti_{0.2}Fe_{0.8}O_{3-{\delta}}$) dense ceramic membrane was prepared by polymerized complex method, using citric acid as a chelating agent and ethylene glycol as an organic stabilizer. Effect of Ti addition on lanthanum-strontium ferrite mixed conductor was investigated by evaluating the thermal expansion coefficient, the oxygen flux, the electrical conductivity, and the phase stability. The thermal expansion coefficient in air was $21.19\;{\times}\;10^{-6}/K$ at 473 to 1,223 K. At the oxygen partial pressure of 0.21 atm ($20%\;O_2$), the electrical conductivity increased with temperature and then decreased after 973 K. The decrement in electrical conductivity at high temperatures was explained by a loss of the lattice oxygen. The oxygen flux increased with temperature and was $0.17\;mL/cm^2{\cdot}min$ at 1,223 K. From the temperature-dependent oxygen flux data, the activation energy of oxygen ion conduction was calculated and was 80.5 kJ/mol at 1,073 to 1,223 K. Also, the Ti-added lanthanum-strontium ferrite mixed conductor was structurally and chemically stable after 450 hours long-term test at 1,173 K.

• Korean Journal of Materials Research
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• v.12 no.12
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• pp.941-946
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• 2002

Both Cu and Cu-oxide nanopowders have great potential as conductive paste, solid lubricant, effective catalysts and super conducting materials because of their unique properties compared with those of commercial micro-sized ones. In this study, Cu and Cu-oxide nanopowders were prepared by Pulsed Wire Evaporation (PWE) method which has been very useful for producing nanometer-sized metal, alloy and ceramic powders. In this process, the metal wire is explosively converted into ultrafine particles under high electric pulse current (between $10^4$ and $10^{ 6}$ $A/mm^2$) within a micro second time. To prevent full oxidations of Cu powder, the surface of powder has been slightly passivated with thin CuO layer. X-ray diffraction analysis has shown that pure Cu nanopowders were obtained at $N_2$ atmosphere. As the oxygen partial pressure increased in $N_2$ atmosphere, the gradual phase transformation occurred from Cu to $Cu_2$O and finally CuO nanopowders. The spherical Cu nanopowders had a uniform size distribution of about 100nm in diameter. The Cu-oxide nanopowders were less than 70nm with sphere-like shape and their mean particle size was 54nm. Smaller size of Cu-oxide nanopowders compared with that of the Cu nanopowders results from the secondary explosion of Cu nanopowders at oxygen atmosphere. Thin passivated oxygen layer on the Cu surface has been proved by XPS and HRPD.

• Tuberculosis and Respiratory Diseases
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• v.42 no.3
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• pp.351-360
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• 1995

Background: Pressure support(PS) is becomimg a widely accepted method of mechanical ventilation either for total unloading or for partial unloading of respiratory muscle. The aim of the study was to find out if PS exert different effects on respiratory mechanics in synchronized intermittent mandatory ventilation(SIMV) and continuous positive airway pressure (CPAP) modes. Methods: 5, 10 and 15 cm $H_2O$ of PS were sequentially applied in 14 patients($69{\pm}12$ yrs, M:F=9:5) and respiratory rate (RR), tidal volume($V_T$), work of breathing(WOB), pressure time product(PTP), $P_{0.1}$, and $T_1/T_{TOT}$ were measured using the CP-100 pulmonary monitor(Bicore, USA) in SIMV and CPAP modes respectively. Results: 1) Common effects of PS on respiratory mechanics in both CPAP and SIMV modes As the level of PS was increased(0, 5, 10, 15 cm $H_2O$), $V_T$ was increased in CPAP mode($0.28{\pm}0.09$, $0.29{\pm}0.09$, $0.31{\pm}0.11$, $0.34{\pm}0.12\;L$, respectively, p=0.001), and also in SIMV mode($0.31{\pm}0.15$, $0.32{\pm}0.09$, $0.34{\pm}0.16$, $0.36{\pm}0.15\;L$, respectively, p=0.0215). WOB was decreased in CPAP mode($1.40{\pm}1.02$, $1.01{\pm}0.80$, $0.80{\pm}0.85$, $0.68{\pm}0.76$ joule/L, respectively, p=0.0001), and in SIMV mode($0.97{\pm}0.77$, $0.76{\pm}0.64$, $0.57{\pm}0.55$, $0.49{\pm}0.49$ joule/L, respectively, p=0.0001). PTP was also decreased in CPAP mode($300{\pm}216$, $217{\pm}165$, $179{\pm}187$, $122{\pm}114cm$ $H_2O{\cdot}sec/min$, respectively, p=0.0001), and in SIMV mode($218{\pm}181$, $178{\pm}157$, $130{\pm}147$, $108{\pm}129cm$ $H_2O{\cdot}sec/min$, respectively, p=0.0017). 2) Different effects of PS on respiratory mechanics in CP AP and SIMV modes By application of PS (0, 5, 10, 15 cm $H_2O$), RR was not changed in CPAP mode($27.9{\pm}6.7$, $30.0{\pm}6.6$, $26.1{\pm}9.1$, $27.5{\pm}5.7/min$, respectively, p=0.505), but it was decreased in SIMV mode ($27.4{\pm}5.1$, $27.8{\pm}6.5$, $27.6{\pm}6.2$, $25.1{\pm}5.4/min$, respectively, p=0.0001). $P_{0.1}$ was reduced in CPAP mode($6.2{\pm}3.5$, $4.8{\pm}2.8$, $4.8{\pm}3.8$, $3.9{\pm}2.5\;cm$ $H_2O$, respectively, p=0.0061), but not in SIMV mode($4.3{\pm}2.1$, $4.0{\pm}1.8$, $3.5{\pm}1.6$, $3.5{\pm}1.9\;cm$ $H_2O$, respectively, p=0.054). $T_1/T_{TOT}$ was decreased in CPAP mode($0.40{\pm}0.05$, $0.39{\pm}0.04$, $0.37{\pm}0.04$, $0.35{\pm}0.04$, respectively, p=0.0004), but not in SIMV mode($0.40{\pm}0.08$, $0.35{\pm}0.07$, $0.38{\pm}0.10$, $0.37{\pm}0.10$, respectively, p=0.287). 3) Comparison of respiratory mechanics between CPAP+PS and SIMV alone at same tidal volume. The tidal volume in CPAP+PS 10 cm $H_2O$ was comparable to that of SIMV alone. Under this condition, the RR($26.1{\pm}9.1$, $27.4{\pm}5.1/min$, respectively, p=0.516), WOB($0.80{\pm}0.85$, 0.97+0.77 joule/L, respectively, p=0.485), $P_{0.1}$($3.9{\pm}2.5$, $4.3{\pm}2.1\;cm$ $H_2O$, respectively, p=0.481) were not different between the two methods, but PTP($179{\pm}187$, $218{\pm}181 cmH_2O{\cdot}sec/min$, respectively, p=0.042) and $T_1/T_{TOT}$($0.37{\pm}0.04$, $0.40{\pm}0.08$, respectively, p=0.026) were significantly lower in CPAP+PS than in SIMV alone. Conclusion: PS up to 15 cm $H_2O$ increased tidal volume, decreased work of breathing and pressure time product in both SIMV and CPAP modes. PS decreased respiration rate in SIMV mode but not in CPAP mode, while it reduced central respiratory drive($P_{0.1}$) and shortened duty cycle ($T_1/T_{TOT}$) in CPAP mode but not in SIMV mode. By 10 em $H_2O$ of PS in CPAP mode, same tidal volume was obtained as in SIMV mode, and both methods were comparable in respect to RR, WOB, $P_{0.1}$, but CPAP+PS was superior in respect to the efficiency of the respiratory muscle work (PTP) and duty cycle($T_1/T_{TOT}$).

• Clean Technology
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• v.27 no.4
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• pp.367-371
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• 2021

The oxy-combustion system is one of the carbon recovery and storage technologies (CCS: Carbon capture & storage) that performs coal combustion using pure oxygen and recirculated flue gas. This is a technology that facilitates storage of carbon dioxide by generating an exhaust gas consisting of only carbon dioxide without a process of separating carbon dioxide and nitrogen when coal is burned using pure oxygen and recirculated flue gas mixture instead of a conventional air combustion system that produces carbon dioxide and nitrogen mixed exhaust gas. In this study, the characteristics of generated NO and SO₂ as atmospheric pollutants during oxy-combustion were examined using O₂/CO₂ mixed simulation gas. The reaction temperature was varied from 900 ℃ to 1200 ℃ and oxygen partial pressure was varied from 30% to 50%. The results showed that NO and SO₂ concentrations in flue gas increased as the oxygen concentration and the reaction temperature in the furnace increased. The partial pressure of CO₂ in flue gas also increased as the oxygen concentration and the reaction temperature in the furnace increased. As a results of comparing NO production of 30% O₂/CO₂ oxy-combustion with air combustion, NO in flue gas increased with reaction temperature in both experiments and NO of oxy-combustion was 40 ~ 80 ppm lower than that of air combustion.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.70.1-70.1
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• 2012

In-situ X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy studies of SOFC cathode materials will be discussed in this presentation. The mixed conducting perovskites (ABO3) containing rare and alkaline earth metals on the A-site and a transition metal on the B-site are commonly used as cathodes for solid oxide fuel cells (SOFC). However, the details of the oxygen reduction reaction are still not clearly understood. The information about the type of adsorbed oxygen species and their concentration is important for a mechanistic understanding of the oxygen incorporation into these cathode materials. XPS has been widely used for the analysis of adsorbed species and surface structure. However, the conventional XPS experiments have the severe drawback to operate at room temperature and with the sample under ultrahigh vacuum (UHV) conditions, which is far from the relevant conditions of SOFC operation. The disadvantages of conventional XPS can be overcome to a large extent with a "high pressure" XPS setup installed at the BESSY II synchrotron. It allows sample depth profiling over 2 nm without sputtering by variation of the excitation energy, and most importantly measurements under a residual gas pressure in the mbar range. It is also well known that the catalytic activity for the oxygen reduction is very sensitive to their electrical conductivity and oxygen nonstoichiometry. Although the electrical conductivity of perovskite oxides has been intensively studied as a function of temperature or oxygen partial pressure (Po2), in-situ measurements of the conductivity of these materials in contact with the electrolyte as a SOFC configuration have little been reported. In order to measure the in-plane conductivity of an electrode film on the electrolyte, a substrate with high resistance is required for excluding the leakage current of the substrate. It is also hardly possible to measure the conductivity of cracked thin film by electrical methods. In this study, we report the electrical conductivity of perovskite $La_{0.6}Sr_{0.4}CoO_{3-{\delta}}$ (LSC) thin films on yttria-stabilized zirconia (YSZ) electrolyte quantitatively obtained by in-situ IR spectroscopy. This method enables a reliable measurement of the electronic conductivity of the electrodes as part of the SOFC configuration regardless of leakage current to the substrate and cracks in the film.