• Journal of the Korean Applied Science and Technology
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• v.24 no.1
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• pp.67-73
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• 2007

Methane combustion over perovskite catalysts was investigated. For the preparation of catalysts, Co, Mn, Fe, and Ni were used as B-site components of the perovskite catalysts $(ABO_3)$ and La was used as A-site component. The effect of calcination temperature on methane combustion and perovskite structure was also investigated. The structure of perovskites, surface area, and adsorbed oxygen species were tested with XRD, BET apparatus, and $O_2-TPD$, respectively. The formation of perovskite structure was affected by the calcination temperature. The catalyst desorbing oxygen at a lower temperature showed better activity for the methane combustion, therefore, the oxygen species desorbing at lower temperatures is responsible for the methane combustion.

• Journal of the Korean Ceramic Society
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• v.28 no.11
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• pp.935-941
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• 1991

Effects of calcination process and ZrO2 addition on the electrical properties of [(Ba0.82Sr0.08Ca0.1)O]m(Ti1-$\chi$Zr$\chi$)O2 ceramics have been investigated. With the variation of A/B-site ratio m of the dielectric formulations, sintering behavior and the resistivity after sintering in a reducing atmosphere have been affected by the calcination process. When the dielectric formulations of m=1.01 were sintered in a reducing atmosphere, the room-temperature resitivity of 109 {{{{ OMEGA }}.cm was obtained for samples processed with two-step calcination, which was much lower than 1012 {{{{ OMEGA }}.cm of samples calcined once. It was confirmed that high resistivity of Ca-doped BaTiO3 ceramics, after sintering in a reducing atmosphere, is maintained by acceptor-like behavior of CaTi" which is formed by Ca substitution to Ti-site. It was also found out that the critical amount of B-site Ca substitution for reduction inhibition of BaTiO3 is around 0.005 mol. With the increasing amount of ZrO2 addition to dielectric formulations, Curie peak was depressed and Curie temperature was lowered due to the enhanced diffuse phase transition.tion.

• Journal of environmental and Sanitary engineering
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• v.17 no.3
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• pp.37-45
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• 2002

The Purpose of this study is to reduce environmental problems caused by landfill of bituminous coal fly ash emitted from the power plant and to reuse it. First of all, we experimented that Al and Si elements were extracted from fly ash and investigated that extracted Al and Si elements night use a coagulant. The extraction was carried out under various conditions ; concentration of the extraction solution, calcination temperature and calcination time. As the results, it was found that the optimum conditions of the extraction of Al and Si elements from fly ash were as follows, concentration of NaOH was 5N for both of them, calcination temperature was $700^{\circ}C$ and $600^{\circ}C$ and calcination time was 1hr and 1.5hr, respectively The extracted solution was used as a coagulant to treat the diluted metal-plating solutions which contained Pb and Cu, respectively. As the result of treatment on the diluted Pb-plating solution with 315NTU, the removal efficiency of turbidity was more than 90%, and the removal efficiency of Pb was about 80%. As for treatment of the non-turbid diluted Cu-plating solution, the removal efficiency of Cu was about 98%.

• Journal of Environmental Science International
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• v.7 no.5
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• pp.693-696
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• 1998

We tried to develope a desulfurization sorbent using eggshell for recycling, practicability, and economic development. The calcination character of the eggshell was examined by thermal gravimetric analysis and qualitative-quantitative character by X-ray diffractometer(XRD) and scanning electron microscope(SEM). The calcination was occurred easily in the case of eggshell and its form was changed from calcite($CaCO_3$) to lime(CaO). The grain and pore sizes of the calcined sample after base-treatment were larger and more crystallic. The adsorption ability of the eggshell was two- to six-times in the calcination temperature more than in the grain size. Therefore, the eggshell was thought to be usable as the desulfurization sorbent.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.5
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• pp.371-377
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• 2009

In oxy-fuel combustion, $CO_2$ concentration in the flue gas may be enriched up to 95% owing to the gas recirculation. Under the high $CO_2$ concentration, the calcination characteristic of limestone is different from that of the conventional air combustion system. In this study, three types of limestone taken from different regions in Korea were used as $SO_2$ absorbent and their calcination characteristics depending on calcination temperature were investigated. The experiments were performed to examine the effects of operating variables such as absorbent species, reaction temperatures on the $SO_2$ removal efficiency and reacted limestone particles were captured to examine the sulfur contents. The degree of calcination and the specific surface area increased with calcination temperature and $SO_2$ removal efficiency increased with reaction temperature. The results showed remarkable difference in $SO_2$ removal efficiencies between the limestone types. The sulfur content of the reacted limestone with the highest $SO_2$ removal efficiency was about 10%.

• Journal of the Korean Magnetics Society
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• v.20 no.4
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• pp.134-142
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• 2010

Barium ferrite ($BaFe_{12}O_{19}$) powders were synthesized by the co-precipitation method. $Fe^{3+}:Ba^{2+}$ mole ratio was fixed 8 and relative amount of $Fe^{3+}$ and $Ba^{2+}$ was controlled. The effects of the pH (= 8, 9, 10), calcination temperature and time on the morphology, structure and magnetic properties of the barium ferrite particles are characterized using XRD, FESEM, and VSM respectively. Coercivity and magnetization value of powders were changed with calcination temperature and time, relative amount of $Fe^{3+}$ and $Ba^{2+}$ and pH. Single-phase barium ferrite was obtained when pH value was 9 in the investigated range of $Fe^{3+}:Ba^{2+}$ relative amount and secondary phases were appeared at $Fe^{3+}:Ba^{2+}$ relative amount of 14.4 : 1.8. The largest value of magnetization (65.7 emu/g) was obtained when $Fe^{3+}:Ba^{2+}$ mole ratio was 12.8 : 1.6 and calcination temperature was $900^{\circ}C$ with air calcination atmosphere. The largest value of coercivity (5280 Oe) was obtained with $O_2$ calcination atmosphere.

• Journal of Hydrogen and New Energy
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• v.24 no.3
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• pp.223-229
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• 2013

Polymer Electrolyte Membrane Fuel Cell (PEMFC) is a power generation system to convert chemical energy of fuels and oxidants to electricity directly by electrochemical reactions. As a catalyst support for PEMFCs, carbon black has been generally used due to its large surface area and high electrical conductivity. However, under certain circumstances (start up/shut down, fuel starvation, ice formation etc.), carbon supports are subjected to serve corrosion in the presence of water. Therefore, it would be desirable to switch carbon supports to corrosion-resistive support materials such as metal oxide. $TiO_2$ has been attractive as a support with its stability in fuel cell operation atmosphere, low cost, commercial availability, and the ease to control size and structure. However, low electrical conductivity of $TiO_2$ still inhibits its application to catalyst support for PEMFCs. In this paper, to explore feasibility of $TiO_2$ as a catalyst support for PEMFCs, $TiO_2$ nanofibers were synthesized by electrospinning and calcinated at 600, 700, 800 and $900^{\circ}C$. Effects of calcination temperature on crystal structure and electrical conductivity of electrospun $TiO_2$ nanofibers were examined. Electrical conductivity of $TiO_2$ nanofibers increased significantly with increasing calcination temperature from $600^{\circ}C$ to $700^{\circ}C$ and then increased gradually with increasing the calcination temperature from $700^{\circ}C$ to $900^{\circ}C$. It was revealed that the remarkable increase in electrical conductivity could be attributed to phase transition of $TiO_2$ nanofibers from anatase to rutile at the temperature range from $600^{\circ}C$ to $700^{\circ}C$.

• Journal of the Korean Applied Science and Technology
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• v.24 no.3
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• pp.272-277
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• 2007

Catalytic activity changes of perovskite catalysts were examined with their A-site substitution. For the preparation of catalysts, Mn was used for B-site component and La, Ce, Sr, Ba, Ca, Ag were used for A-site component of the perovskite $catalysts(ABO_3)$ The effect of calcination temperature on methane combustion and perovskite structure was also investigated. The surface area and adsorbed oxygen species were tested with BET apparatus and $O_2-TPD$, respectively. Perovskite catalysts whose A-site was partially substituted needed higher calcination temperature than un-substituted one to form the perovskite structure. From $O_2-TPD$ experiment, it was found that methane combustion activity was directly related to the oxygen desorbing ability of the catalysts. The prepared catalyst(LM-7) was stable at $600^{\circ}C$ for 72 hours of reaction.

• Journal of the Korean Ceramic Society
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• v.48 no.1
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• pp.106-109
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• 2011

In order to fabricate 8YSZ thick film by silk screen printing, YSZ(yttria-stabilized zirconia) commercial powder was used as starting materials. Paste for screen printing was made by mixing 8YSZ powder and organic vehicles. 8YSZ thick film was formed on $Al_2O_3$ substrate. The crystal structure, and microstructure were investigated. Grain size of 8YSZ was increased with increasing calcination temperature and rapid grain growth was shown after calcination at $1300^{\circ}C$. Microstructure showed the mixture of large and small grain size after $1400^{\circ}C$ sintering. Shrinkage rate of 8YSZ thick film sintered at $1400^{\circ}C$ was more than 40%.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.215-220
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• 2012

ZnO nanoparticles were synthesized through a facile route and were used as ozonation catalysts. With the increase of calcination temperature ($150-300^{\circ}C$), surface hydroxyl groups and catalytic efficiency of asobtained ZnO decreased remarkably, and the ZnO obtained at $150^{\circ}C$ showed the best catalytic activity. Compared with ozonation alone, the degradation efficiency of phenol increased above 50% due to the catalysis of ZnO-150. In the reaction temperatures range from $5^{\circ}C$ to $35^{\circ}C$, ZnO nanocatalyst revealed remarkable catalytic properties, and the catalytic effect of ZnO was better at lower temperature. Through the effect of tertbutanol on degradation of phenol and the catalytic properties of ZnO on degradation of nitrobenzene, it was proposed that the degradation of phenol was ascribed to the direct oxidation by ozone molecules based on solidliquid interface reaction.