• Transactions of the Korean hydrogen and new energy society
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• v.27 no.1
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• pp.95-105
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• 2016

Spray-dried NiO-based oxygen carriers developed for chemical looping combustion required high calcination temperatures above $1300^{\circ}C$ to obtain high mechanical strength applicable to circulating fluidized-bed process. In this study, the effect of CBB ($CaO{\cdot}BaO{\cdot}B_2O_3$) addition, as a binder, on the physical properties and oxygen transfer reactivity of spray-dried NiO-based oxygen carriers was investigated. CBB addition resulted in several positive effects such as reduction of calcination temperature and increase in oxygen transfer capacity and porosity. However, oxygen transfer rate was considerably decreased. This was more apparent when a higher amount of CBB was added and MgO was added together. From the experimental results, it is concluded that CBB added NiO-based oxygen carriers are not suitable for chemical looping combustion and a new method to reduce calcination temperature while maintaining high oxygen transfer rate of NiO-based oxygen carriers should be found out.

• Microbiology and Biotechnology Letters
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• v.36 no.2
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• pp.165-172
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• 2008

To find the optimum growth and metal removal condition of isolated strain LH2, effects of the environmental factors such as medium pH, growth temperature, and metal concentrations were investigated. Based on the 18S rDNA analysis, the isolated strain was identified to Exophiala sp. with 100% homology. Isolated strain Exophiala sp. LH2 showed maximum removal efficiency of metals at the shaking conditions of pH 7 and $25^{\circ}C$. When the concentration of metal was under 200ppm, the specific metal removal velocity at pH 7 increased from 0.01 to 4.43 mg-metal $L^{-1}{\cdot}d^{-1}{\cdot}mg{\cdot}DCW^{-1}$ as the concentration of metal increased from 10 ppm to 200 ppm. When 200 ppm of each metal was contained in the culture medium adjusted with pH 7, metal removal efficiencies Cr, Cu, Ni, Pb and Zn were 99.28%, 97.67%, 91.94%, 99.77%, 99.61%, respectively.

• Journal of Sensor Science and Technology
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• v.17 no.6
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• pp.418-424
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• 2008

The PZT based piezoelectric thick films prepared by screen printing method have been mainly used as a functional material for MEMS applications due to their compatibility of MEMS process. However the screen printed thick films generally reveal poor electrical and mechanical properties because of their porous microstructure. To improve microstructure we mixed attrition milled powder with ball milled powder of 0.01Pb$(Mg_{1/2}W_{1/2})O_3$-0.41Pb$(Ni_{1/3}Nb_{2/3})O_3$-$0.35PbTiO_3$-$0.23PbZrO_3$+0.1 wt% ${Y_2}{O_3}$+1.5 wt% ZnO composition. By mixing 25 % of attrition milled powder and 75 % of ball milled powder, the broadest particle size distribution was obtained, leading to a dense thick film with crack-free microstructure and improved dielectric properties. The X-ray diffraction analysis revealed that the film was in wellcrystallized perovskite phase. The remanent polarization was increased from $13.7{\mu}C/cm^2$ to $23.3{\mu}C/cm^2$ at the addition of 25 % attrition milled powder.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.7
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• pp.546-551
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• 1998

$Mn{1-X}Fe{2+X}O_4, Mg_{1-X}Fe_{2+X}O_4$ (x=0.0, 0.025, 0.1, 0.2) for negative temperature coefficient (NTC) thermistor was prepared by calcination at $800^{\circ}C$ and sintering at form 1100 to $1250^{\circ}C$ with $50^{\circ}C$ intervals. The best linear property was obtained in the Mn-based sample sintered at $1200^{\circ}C$ with x=0.0 composition. Temperature coefficient of resistance, $\alpha$, was $-5.6%/^{\circ}C$ in the Mn-based sample, $-5.2%/^{\circ}C$ in the MM-based sample, and $-1.6%/^{\circ}C$ in the Mg-based sample. thermistor parameter, B, was in the range of 2665~7780 K. The results show the possibility that Mn-Ni-Co based thermistor could be substituted by the composition used in this study.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.2
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• pp.166-173
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• 2006

Catalytic reforming of $CO_2$ by $CH_4$ over Ni-YSZ based catalysts was investigated to produce syngas as raw material of high valued chemicals and develop high performance catalyst electrode for an internal reforming of $CO_2$ in SOFC system. Ni-YSZ based catalysts were prepared using physical mixing and maleic acid methods to improve catalytic activity and inhibition of carbon deposition. The catalysts before and after the reaction were characterized by $N_2$ physisorption, TPR(temperature programed reduction), XRD and impedance analyzer. The conversions for $CO_2$ and $CH_4$ over Ni-MgO catalyst showed 90% but much amount of carbon deposition was detected on catalyst surface. On the other hand, the conversions for $CO_2$ and $CH_4$ over NiO-YSZ-$CeO_2$ catalyst showed 100% and 85% respectively, and carbon deposition on catalyst surface was inhibited under the tested condition. It was concluded that NiO-YSZ-$CeO_2$ catalyst is a promising candidate for the catalytic reforming of $CO_2$ and the internal reforming in SOFC system.

• Journal of Korean Society for Atmospheric Environment
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• v.5 no.2
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• pp.72-83
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• 1989

Twenty-five atmospheric particulates were collected using a high volume aerosol sampler from Septermber to December, 1988 on a site located on the West coast of Korea and analysed for twelve elements (Na, Mg, Al, Mn, Fe, Cu, Co, Ni, Zn, Ag, Cd, and Pb) by AAS. The particles being mainly crustal minerals, large quantity of spherical fly ashes were also observed. In order to identify the origin of trace metals in atmospheric particulates, enrichment factor, interelemental correlation and factor analysis were performed. Based upon these analysis, the twelve elements can be classified into three groups; the elements dominantly present in soil particles (Al, Mn, Fe, Co, and Ni), those in sea salt aerosols (Na and Mg), and those in air pollution-derived particles (Cu, Cd, Pb, Ag and Zn).

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1757-1762
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• 2006

A solvent sublation using salphen as a ligand was studied and applied for the determination of trace Ni(II), Co(II) and Cu(II) in water samples. The fundamental study was investigated by a solvent extraction process because the solvent sublation was done by extracting the floated analytes into an organic solvent from the aqueous solution. The salphen complexes of Ni(II), Co(II) and Cu(II) ions were formed in an alkaline solution of more than pH 8 and then they were extracted into m-xylene. It was known that the each metallic ion formed 1 : 1 complex with the salphen and the logarithmic values of extraction constants for the complexes were 3.3 5.1 as an average value. Based on the preliminary study, the procedure was fixed for the separation and concentration of the analytes in samples. Various conditions such as the pH of solutions, the influence of $NaClO_4$, the bubbling rate and time of $N_2$ gas, and the type of organic solvent were optimized. The metal-salphen complexes could be extracted into m-xylene from the solution of more than pH 8, but the pH could be shifted to acidic solution of pH 6 by the addition of $NaClO_4$. In addition, the solvent sublation efficiency of the analytes was increased by adding $NaClO_4$. The recovery of 97-115% was obtained in the spiked samples in which given amounts of 0.3 mg/L Ni(II), 0.8 mg/L Co(II) and 0.04 mg/L Cu(II) were added.

• Journal of Environmental Science International
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• v.29 no.7
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• pp.739-748
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• 2020

The characteristics of heavy metal ion (Ni²⁺, Zn²⁺, and Cr³⁺) adsorption by zeolite synthesized from Jeju scoria using the fusion and hydrothermal method, were studied. The synthetic zeolite was identified as a Na-A zeolite by X-ray diffraction analysis and scanning electron microscopy images. The equilibrium of heavy metal ion adsorption by synthetic zeolite was reached within 60 min for Ni²⁺ and Zn²⁺, and 90 min for Cr³⁺. The uptake of heavy metal ions increased with increasing pH in the range of pH 3-6 and the uptake decreased in the order of Cr³⁺ > Zn²⁺ > Ni²⁺. For initial heavy metal concentrations of 20-250 mg/L at nonadjusted pH, the adsoption of heavy metal ions was well described by the pseudo second-order kinetic model and was well fitted by the Langmuir isotherm model. The maximum uptake of heavy metal ions obtained from the Langmuir model, decreased in the order of Zn²⁺ > Ni²⁺ > Cr³⁺, differing from the effect of pH on the uptake, which was mainly based on the different pH of the solutions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.407-410
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• 2000

(M $n_{l-x}$M $g_{l-x}$)F $e_{2+x}$ $O_4$(x=0.0, 0.025, 0.1, 0.2) for NTC(negative temperature coefficient) thermistor was prepared by calcining at 80$0^{\circ}C$ and sintering at from 1100 to 130$0^{\circ}C$ with 5$0^{\circ}C$ intervals while x was varied from 0.0 to 0.025, 0.1 and 0.2. The best linear property was obtained in the based specimen sintered at 120$0^{\circ}C$ with x=0.1 composition. Thermistor parameter, $B_{25~85^{\circ}C}$, was in the range of 5000~ 7300 [K]. Temperature coefficient of resistance, $\alpha$$_{25^{\circ}C}$, was -5.2 %/$^{\circ}C$. The results showed the possibility that Mn-Ni-Co based thermistor could be substituted by the composition used in this study was confirmed.med.d.

• Journal of the Korean Chemical Society
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• v.41 no.7
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• pp.337-342
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• 1997

Acryloylmethylbenzo-15-crown-5 was prepared from the reaction of 4'-hydroxymethylbenzo-15-crown-5 with acryloyl chloride. And, poly(acryloylmethylbenzo-15-crown-5) [poly(AMB15C5)] was synthesized by radical polymerization using AIBN as initiator in benzene. Coated wire lead(II) ion-selective electrodes ($Pb^{2+}$-CWISEs) using either poly(AMB15C5) or B15C5 as neutral carrier were prepared, respectively. $Pb^{2+}$-CWISEs gave linear responses with slopes of 28$\pm$ 1mV per decade within the concentration range of $10^{-5} M{\sim}10^{-1}$ M, respectively. Also, the detection limits were $10^{-6}$ M and response times were either 3 or 5 min. for B15C5 and poly(AMB15C5), respectively. $Pb^{2+}$-CWISE base on B15C5 was rather unstable than poly(AMB15C5)'s due to solubility of the B15C5 in water. The selectivity coefficients of a variety of interfering ions such as $Mg^{2+},\; Ca^{2+},\; Co^{2+},\; Ni^{2+},\; Cu^{2+},\; Zn^{2+}$ and $Cd^{2+}$ were small ($10^{-4}{\sim}10^{-5}$), while those of $Na^+$ and $K^+$ were large (0.1∼0.01). In addition, the electrode responses depended upon the pH of test solution and the composition of the membrane. In the range pH 3∼6 of test solution, potentials of Pb2+-CWISEs were hardly changed. The optimal contents of B15C5 and poly(AMB15C5) were 7.7 wt% and 13.1 wt%, respectively.