• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.1-10
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• 1995

Effects of calcination temperature on microstructure and electric-magnetic properties of Mg-ferrite were investigated. As the calcination temperature increase, the green density and the sintered density increase due to the enhancement of densification of calcined powder. The grain size in the sintered ferrite increases with increasing the calcination temperatures from 800 to 100$0^{\circ}C$, but decreases from 1000 to 120$0^{\circ}C$. The resistivity decreases with increasing the calcination temperatures from 800 to 110$0^{\circ}C$, but increases from 1100 to 120$0^{\circ}C$ due to the microstructure which consists of small, uniform grian size and pores at grain boundaries. Magnetization increases slightly due to the increasement of the sintered density while Curie temperature is almost constant regardless of calcination temperatures.

• Journal of Environmental Science International
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• v.14 no.9
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• pp.889-896
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• 2005

The nanosized $TiO_2$ photocatalysts were prepared by the hydrolysis of $TiCl_4$ and calcined at different temperatures. The resulting materials were characterized by TGA, DSC, XRD, and TEM testing techniques. XRD, TEM, and BET measurements indicated that the particle size of $TiO_2$ was increased with rise of calcination temperature and surface area was decreased with rise of it. The prepared $TiO_2$ photocatalysts were used for the photocatalytic degradation of congo red. The effects of calcination temperature, $TiO_2$ loading, the initial concentration of congo red, and usage frequencies were investigated and the rate constants were determined by regressing the experimental data. Calcination is an effective treatment to increase the photo activity of nanosized $TiO_2$ photocatalysts resulting from the improvement of crystallinity. The optimum calcination temperature of the catalyst for the efficient degradation of congo red was found to be $400^{\cric}C$. The rate constant was decreased with increase in the initial concentration of congo red and increased with increase in the $TiO_2$ loading. In the case of $TiO_2$ photocatalysts, the photocatalytic activity wasn't greatly affected by the usage frequencies.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2694-2698
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• 2012

Materials on the scale of nanoscale have widely been used as research topics because of their interesting characteristics and aspects they bring into the field. Out of the many metal oxides, zinc oxide (ZnO) was chosen to be fabricated as nanofibers using the electrospinning method for potential uses of solar cells and sensors. After ZnO nanofibers were obtained, calcination temperature effects on the ZnO nanofibers were studied and reported here. The results of scanning electron microscopy (SEM) revealed that the aggregation of the ZnO nanofibers progressed by calcination. X-ray diffraction (XRD) study showed the hcp ZnO structure was enhanced by calcination at 873 and 1173 K. Transmission electron microscopy (TEM) confirmed the crystallinity of the calcined ZnO nanofibers. X-ray photoelectron spectroscopy (XPS) verified the thermal oxidation of Zn species by calcination in the nanofibers. These techniques have helped us deduce the facts that the diameter of ZnO increases as the calcination temperature was raised; the process of calcination affects the crystallinity of ZnO nanofibers, and the thermal oxidation of Zn species was observed as the calcination temperature was raised.

• Textile Coloration and Finishing
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• v.15 no.3
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• pp.35-35
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• 2003

• 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 the Korean Ceramic Society
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• v.36 no.12
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• pp.1327-1334
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• 1999

Behaviors of abnormal expansion during calcination process of Ba2Ti9O20 ceramics and its related effects on the sintering characteristics were investigated as a function of precursors. When BaCO3 and TiO2 powders were used as starting materials. BaTi4O9 phase which has relatively large molar volume was formed drastically with abnormal ex-pansion during the calcination at 95$0^{\circ}C$ to 115$0^{\circ}C$ ON the contrary using BaTiO3 and TiO2 powders as starting materials led to retardation of the formation of BaTi4O9 phase and concurrently suppressed the abnormal expansion during cal-cination process. Especially the calcined powder of BaTiO3 and TiO2 had advantages in the densification and formation of Ba2Ti9O20 single phase in the sintering process.

• Journal of environmental and Sanitary engineering
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• v.15 no.1
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• pp.95-101
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• 2000

This study was investigated to the reaction of alumina sintering with alkaline. The soluble $NaAlO_2$ was made after the commercial ${\alpha}-Al_2O_3$ was calcinated with NaOH. The reaction of alumina was carried out to be based on the effects of calcination temperature, time, and the mixing ratio of ${\alpha}-Al_2O_3/NaOH$. The alumina was calcined over $500^{\circ}C$ with NaOH powder after it was sieved with 170/270 mesh. The calcined alumina with NaOH powder was dissolved into $25^{\circ}C$ distilled water and filtrated, and HCI was added to adapt pH 6.5~7.5. The residue was separated with vacuum pump for filtration after it was adapted to proper pH, and aluminum compound was precipitated with $Al(OH)_3$. The investigation was carried out with the variables; the calcination temperature($500-900^{\circ}C$), the calcination time (30~90 min), and the concentration of HCI when leaching(0.5~3.0N) respectively. In this investigation, the main product of ${\alpha}-Al_2O_3$ and NaOH was $NaAlO_2$ and the maximum conversion ratio was 91.4% under the optimum conditions as followed ; the ratio of NaOH/${\alpha}-Al_2O_3$ was 1.5 and the calcination conditions were $800^{\circ}C$ and 90 min.

• Journal of the Mineralogical Society of Korea
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• v.21 no.2
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• pp.209-224
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• 2008

Various types of high-purity limestone, which occurred in the Pungchon Formation, are examined to understand applied-mineralogical factors controlling their calcination characters with respect to the ore characters. To do this work, systematic characterization and determination were carried out for the limestone ores and their calcination products in a fixed heating condition, and the results were correlated and discussed. During the calcination experiment, a phase transition from calcite to quicklime begins to occur selectively in the physical weak zones such as grain boundary, cleavage and twin planes. All the fabrics of original limestones are preserved in the resultant quicklime. In addition, crystallinity of the quicklime was advanced, as the aging time of calcination was increased. Major controlling factors on the calcination effects of the high-purity limestone are elucidated to be the degree of development of cleavage and twin, together with crystallinity and textures in the limestone ore. Especially, lower crystallinity and dense interlocking fabrics obviously play advantageous role in all the calcination characters. But the development of cleavage and twin affects negatively on the calcination characters on account of favoring decrepitaion of quicklime in the lime manufacturing. Thus, the high-purity limestones characteristic of marble fabrics and relatively lower crystallinity are comparatively advantageous for the uses of lime manufacture.

• Journal of the Korean Ceramic Society
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• v.53 no.1
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• pp.34-42
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• 2016

Characteristics of wet flue gas desulfurization and in-furnace desulfurization of domestic and overseas limestone with different crystallinity and crystalline size are studied in this article. Properties of desulfurization were evaluated in relation to physicochemical/ mineralogical characteristics, degree of pore formation for different calcination temperatures and TNC(total neutralizing capability). TNC of domestic high crystalline limestone was lower than that of overseas one. On the other hand, the porosity after calcination was shown to be relatively high for domestic limestone, which had high initial rates of desulfurization reactions in-furnace. Based on low pore formation and porosity with high TNC of crystalline high-Ca limestones compared to macrocrystalline ones, the former are preferred for wet desulfurization processes.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.74-79
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• 2004

[ $CO_3O_4/{\gamma}-Al_2O_3$ ] catalysts were reported high activity on the low temperature CO oxidation. The effects of the calcination temperature, the loaded amount of cobalt and the oxygen concentration on the characteristics of CO oxidation have been investigated for a emergency escape mask cartridge. $Co(NO_3)_2\cdot6H_2O$ was used as cobalt precursor and the catalysts were prepared by incipient wetness impregnation. TGA shows that enough calcination is accomplished at $450^{\circ}C$ and cobalt phase is $Co_3O_4$ after calcination in the temperature range of $300\ ~500^{\circ}C$. The specific surface area and pore volume of catalysts are decreased with increasing of loaded amount of cobalt. And with the increase of loaded amount of cobalt and the oxygen concentration, the catalytic activity is increased.