• Journal of the Korean Electrochemical Society
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• v.4 no.2
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• pp.58-64
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• 2001

YSZ ($8mol\%$ yttria-stabilized zirconia)-modified LSM $(La_{0.85}Sr_{0.15}MnO_3)$ composite cathodes were fabricated by formation of YSZ film on triple phase boundary (TPB) of LSM/YSZ/gas. The YSZ coating film greatly enlarged electrochemical reaction sites from the increase of additional TPB. The composite cathode was formed on thin YSZ electrolyte (about 30 Um thickness) supported on an anode and then I-V characterization and AC impedance analyses were performed at temperature between $700^{\circ}C\;and\;800^{\circ}C$. As results of the impedance analysis on the cell at $800^{\circ}C$ with humidified hydrogen as the fuel and air as the oxidant, R1 around the frequency of 1000 Hz represents the anode Polarization. R2 around the frequency of 100Hz indicates the cathode polarization, and R3 below the frequency of 10 Hz is the resistance of gas phase diffusion through the anode. The cell with the composite cathode produced power density of $0.55\;W/cm^2\;and\;1W/cm^2$ at air and oxygen atmosphere, respectively. The I-V curve could be divided into two parts showing distinctive behavior. At low current density region (part I) the performance decreased steeply and at high current density region (part II) the performance decreased gradually. At the part I the performance decrease was especially resulted from the large cathode polarization, while at the part H the performance decrease related to the electrolyte polarization.

• Journal of the Korean Electrochemical Society
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• v.20 no.1
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• pp.7-12
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• 2017

Using a precursor of $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ as a starting material, a surface-modified cathode material was obtained by coating with KCl, where the added KCl reduces residual Li compounds such as $Li_2CO_3$ and LiOH, on the surface. The resulting electrochemical properties were investigated. The amounts of $Li_2CO_3$ and LiOH decreased from 8,464 ppm to 1,639 ppm and from 8,088 ppm to 6,287 ppm, respectively, with 1 wt% KCl added $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ that had been calcined at $800^{\circ}C$. X-ray diffraction results revealed that 1 wt% of KCl added $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ did not affect the parent structure but enhanced the development of hexagonal crystallites. Additionally, the charge transfer resistance ($R_{ct}$) decreased dramatically from $225{\Omega}$ to $99{\Omega}$, and the discharge capacity increased to 182.73mAh/g. Using atomic force microscopy, we observed that the surface area decreased by half because of the exothermic heat released by the Li residues. The reduced surface area protects the cathode material from reacting with the electrolyte and hinders the development of a solid electrolyte interphase (SEI) film on the surface of the oxide particles. Finally, we found that the introduction of KCl into $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ is a very effective method of enhancing the electrochemical properties of this active material by reducing the residual Li. To the best of our knowledge, this report is the first to demonstrate this phenomenon.

• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.41-47
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• 2003

For the development of low temperature anode-supported planar solid oxide fuel cell, the planar anode supports with the thickness of 0.8 to 1 mm and the area of 25, 100 and $150\;cm^2$ were fabricated by the tape casting method. The strength, porosity, gas permeability and electrical conductivity of the planar anode support were measured. The porosity of anode supports sintered at $1400^{\circ}C$ and then reduced in$H_2$ atmosphere was increased from $45.8\%\;to\;53.9\%$. The electrical conductivity of the anode support was $900 S/cm\;at\; 850^{\circ}C$ and its gas permeability was 6l/min at 1 atm in air atmosphere. The electrolyte layer and cathode layer were fabricated by slurry dip coating method and then had examined the thickness of $10{\mu}m$ and the gas permeability of 2.5 ml/min at 3 atm in air atmosphere. As preliminary experiment, cathode multi-layered structure consists of LSM-YSZ/LSM/LSCF. At single cell test using the electrolyte layer with thickness of 20 to $30{\mu}m$, we achieved $300\;mA/cm^2$ and 0.6V at $750^{\circ}C$

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.7
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• pp.866-873
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• 2007

To analyze and differentiate volatile compounds of 13 extra virgin olive oils from market, solid-phase micro extraction (SPME) GC-MS and electronic nose (EN) equipped with metal oxide sensors were applied. The volatiles identified in extra virgin olive oils include hexanal, 4-hexen-1-ol, (Z)-3-hexen-1-ol, acetic acid, and 2,4-dimethyl-heptane, etc. Response from EN was analysed by the principal component analysis. Proportion of the first Principal component was 99.70%, suggesting that each aroma pattern of the 13 extra virgin olive oils could be discriminated by EN. Fatty acid compositions were oleic (61.1${\sim}$77.9 mole%), palmitic (11.7${\sim}$16.5 mole%), linoleic (4.7${\sim}$9.7 mole%), stearic (2.5${\sim}$2.9 mole%), Palmitoleic (0.8${\sim}$2.4 mole%), and linolenic acid (0.7${\sim}$1.2 mole%). In color study, extra virgin olive oil showed $L^{\ast}$ value of 81.7${\sim}$92.9, $a^{\ast}$ value of -28.3${\sim}$13.5 and $b^{\ast}$ value of 52.2${\sim}$139.0. Total phenol and ${\alpha}-tocopherol$ contents were 6.2${\sim}$24.9 mg/100 g and 5.5${\sim}$12.8 mg/100 g, respectively. In Rancimat test, the induction period of 13 extra virgin olive oils showed 31.76${\sim}$54.04 hr while their POV ranged from 13.5 to 22.9 meq/kg oil.

• Resources Recycling
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• v.30 no.6
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• pp.43-52
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• 2021

In this study, the optimal nitration process for selective lithium leaching from powder of a spent battery cell (LiNi_xCo_yMn_zO₂, LiCoO₂) was studied using Taguchi method. The nitration process is a method of selective lithium leaching that involves converting non-lithium nitric compounds into oxides via nitric acid leaching and roasting. The influence of pretreatment temperature, nitric acid concentration, amount of nitric acid, and roasting temperature were evaluated. The signal-to-noise ratio and analysis of variance of the results were determined using L₁₆(4⁴) orthogonal arrays. The findings indicated that the roasting temperature followed by the nitric acid concentration, pretreatment temperature, and amount of nitric acid used had the greatest impact on the lithium leaching ratio. Following detailed experiments, the optimal conditions were found to be 10 h of pretreatment at 700℃ with 2 ml/g of 10 M nitric acid leaching followed by 10 h of roasting at 275℃. Under these conditions, the overall recovery of lithium exceeded 80%. X-ray diffraction (XRD) analysis of the leaching residue in deionized water after roasting of lithium nitrate and other nitrate compounds was performed. This was done to determine the cause of rapid decrease in lithium leaching rate above a roasting temperature of 400℃. The results confirmed that lithium manganese oxide was formed from lithium nitrate and manganese nitrate at these temperatures, and that it did not leach in deionized water. XRD analysis was also used to confirm the recovery of pure LiNO₃ from the solution that was leached during the nitration process. This was carried out by evaporating and concentrating the leached solution through solid-liquid separation.

• Korean Journal of Heritage: History & Science
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• v.47 no.4
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• pp.210-223
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• 2014

When sarira reliquary was found in stone pagoda of Mireuksa Temple, there were 494 gold artifacts, including inner gold pot, gold plate with inscription for Sarira enshrinement, etc. Most of gold artifacts were crafted, but there were 22 gold plates and 4 gold ingots, which did not have any specific shape. It was considered that they had not been crafted. Since gold exists as a metal rather than a metallic oxide in nature, in general, it can be crafted by melting and shaping. However, gold in nature has impurities so it has to be refined to have malleability. The characteristic features were identified through the analysis of gold artifacts from sarira reliquary found in stone pagoda of Mireuksa Temple. The analysis result showed that there were 3 types of gold; pure gold artifacts, artifacts produced with silver containing gold and natural gold ingots. Inner gold pot, gold earrings and gold small beads were produced with pure gold and they contained less than 1wt.% of copper. It seemed like they were produced as pure gold to be shaped by hammering. Gold plate with inscription, tweezers, gold earrings, ingots, etc. were produced with silver containing gold as they had to be more solid. Gold ingots seemed to be natural gold considering the distribution of silver and copper in them, but it cannot be concluded as there are not enough information on gold ingots in Korea. The comprehensive research on gold ingots from various regions in Korea has to be carried out to confirm the above. Sarira Reliquary showed the very sophisticated gold craftsmanship. Gold ingots with the inscriptions, which say 1 nyang, were approximately 14g. Considering the weight of these ingots as standard, weights of other ingots were half nyang(7g), 2 nyang(28g), etc.