• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1885-1887
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• 1999

본 연구에서는 $BaTiO_3$를 기본조성으로하는 반도성 세라믹스인 PTC 써미스터에 $Nb_2O_5$을 미량 첨가하여 미세구조 및 PTCR의 전기적 특성에 대해서 연구하였다. 또한 복소 임피던스 측정을 통하여 $Nb_2O_5$ 첨가에 따른 grain, grain boundary 저항변화에 대해서도 고찰하였다. $(Ba_{0.9}Sr_{0.05}Ca_{0.05})TiO_3-0.01SiO_2-0.001MnCO_3$를 기본조성으로 하여 $Nb_2O_5$ 첨가량을 $0.15{\sim}0.2mol%$까지 변화시켰으며 소결조건은 소결온도 $1350^{\circ}C$, 2h 유지하였으며 냉각속도는 $100^{\circ}C/h$로 하였다 첨가된 Nb의 양이 증가할수록 grain의 크기는 점차로 작아졌으며 상온저항과 peak 저항이 함께 증가하였다. 0.15mol% 첨가된 시편의 경우 상온저항은 $19[\Omega]$이었으며 peak 저항은 $5{\times}10^6[{\Omega}]$정도가 되었다.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1437-1442
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• 1994

Self propagating synthesis and thermal explosion of combustion reactions were applied to Al/K2Cr2O7/Al2O3 system as the first stage for a production of magnesia-chromium refractory. Several factors related to products made by two combustion reactions were considered and properties of products were characterised. Two processes were required to preheat upto at least 80$0^{\circ}C$ for the thermal explosion and the self propagating synthesis. These processes were so violent and explosive that alumina as diluent was added to the system in order to absorb the reaction heat and reduce the reaction rate. The products consisted of crystal phases of KAl5O8, Cr2O3, Al2O3, K2CrO4, and K2Al2O4.3H2O. The amount of KAl5O8 and K2Al2O4.3H2O crystal phases of products were decreased with further addition of alumina.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2004.04a
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• pp.42-43
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• 2004

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.5
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• pp.423-430
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• 2015

$Cu/ZnO/Al_2O_3$ catalysts for water gas shift (WGS) reaction were synthesized by co-precipitation method with the fixed molar ratio of Cu/Zn/Al precursors as 45/45/10. Copper and zinc precursor were added into sodium carbonate solution for precipitation and aged for 24h. During the aging period, aluminum precursor was added into the aging solution with different time gap from the precipitation starting point: 6h, 12h, and 18h. The resulting catalysts were characterized with SEM, XRD, BET surface measurement, $N_2O$ chemisorption, TPR, and $NH_3$-TPD analysis. The catalytic activity tests were carried out at a GHSV of $27,986h^{-1}$ and a temperature range of 200 to $400^{\circ}C$. The catalyst morphology and crystalline structures were not affected by aluminum precursor addition time. The Cu dispersion degree, surface area, and pore diameter depended on the aging time of Cu-Zn precipitate without the presence of $Al_2O_3$ precursor. Also, the interaction between the active substance and $Al_2O_3$ became more stronger as aging duration, with Al precursor presented in the solution, increased. Therefore, it was confirmed that aluminum precursor addition time affected the catalytic characteristics and their catalytic activities.

• Korean Journal of Materials Research
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• v.17 no.9
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• pp.480-483
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• 2007

Hydroxyapatites were prepared by the different $SiO_2$ addition at $1450^{\circ}C$ for 2h. With the increase of $SiO_2$ addition, microstructure, bulk density, porosity, mechanical strength of $hydroxyapatite/{\beta}-TCP$ composite were investigated. When the sintered HAp contained 1 wt% $SiO_2$, the each properties of the HAp were increased. But the excess addition of $SiO_2$ content above 1wt% the each property were decreased. This results were due to the ${\beta}-TCP$ phase. The ${\beta}-TCP$ phase appeared at 3 wt% $SiO_2$ addition and the ${\beta}-TCP$ phase was enhanced by the $SiO_2$ increasing.

• Journal of the Korean Ceramic Society
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• v.33 no.3
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• pp.307-312
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• 1996

In following addition of 0.3, -0.6, 0.8, 1.0 and 5 weight percent MgSiF66H2O studies have been made of the setting and hardening characteristics of ordinary portland cement. MgSiF66H2O retarded the setting time of ordinary portland cement and extended the induction pariod of the hydration. In ordinary portland cement the setting characteristics were drastically altered especially at high MgSiF66H2O contents. Evidence was also obtained by the formation of a KSiF6 which was very fine particle. The results wee as follows. 1. Slump was slightly decreased when MgSiF66H2O added. 2. Setting time was retarded depending on the amount of retarding agent 2 to 8 hours 3. Compressive strength was almost same or some increased in comparision with opc. 4. When MgSiF66H2O was added to cement paste K2SiF6 were formed It was fine-sized distributed uniformly in cement grain and caused retardation of cement setting.

• Korean Journal of Metals and Materials
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• v.50 no.5
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• pp.383-387
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• 2012

The activation of Mg-10 wt%$Fe_2O_3$ was completed after one hydriding-dehydriding cycle. Activated Mg-10 wt%$Fe_2O_3$ absorbed 5.54 wt% H for 60 min at 593 K under 12 bar $H_2$, and desorbed 1.04 wt% H for 60 min at 593 K under 1.0 bar $H_2$. The effect of the reactive grinding on the hydriding and dehydriding rates of Mg was weak. The reactive grinding of Mg with $Fe_2O_3$ is believed to increase the $H_2$-sorption rates by facilitating nucleation (by creating defects on the surface of the Mg particles and by the additive), by making cracks on the surface of Mg particles and reducing the particle size of Mg and thus by shortening the diffusion distances of hydrogen atoms. The added $Fe_2O_3$ and the $Fe_2O_3$ pulverized during mechanical grinding are considered to help the particles of magnesium become finer. Hydriding-dehydriding cycling is also considered to increase the $H_2$-sorption rates of Mg by creating defects and cracks and by reducing the particle size of Mg.

• Journal of the Korean Vacuum Society
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• v.11 no.1
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• pp.16-21
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• 2002

Selective epitaxial growth(SEG) of silicon were performed at low temperature under an ultraclean environment below $1000^{\circ}C$ using ultraclean $Si_2H_6$ and $H_2$ gases ambient in low pressure chemical vapor deposition(LPCVD). As a result of ultraclean processing, epitaxial Si layers with good quality were obtained for uniform and SEG wafer at temperatures range 600~$710^{\circ}C$ and an incubation period of Si deposition only on $SiO_2$ was found. Low-temperature Si selectivity deposition condition and epitaxy on Si were achieved without addition of HCl. The epitaxial layer was found to be thicker than the poly layer deposited over the oxide. Incubation period prolonged for 20~30 sec can be obtained by $O_2$addition. The surface morphologies & cross sections of the deposited films were observed with SEM, The structure of the Si films was evaluated XRD.

• Journal of the Korea Organic Resources Recycling Association
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• v.14 no.1
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• pp.160-168
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• 2006

This study was performed to evaluate the effect of the addition of vegetable oils on Fenton treatment of PAHs-contaminated soil. Fenton reaction can be proceeded in the soils contaminated with PHAs only in the presence of $H_2O_2$ because of Fe content in the soil. In this case, optimum $H_2O_2$ concentration was 3%. When 17.5 mM $FeSO_4$(III) was added with 3% $H_2O_2$, the removal rate was increased up to 25%, whereas 19% of PAHs was removed with $H_2O_2$ alone. The addition of 1% of olive oil to the contaminated soil before the Fenton reaction or simultaneously increased the removal rate about 15%, compared to the case of Fenton reaction only. There were no significant differences in the removal rates of PAHs, regardless of different kinds and concentration of oils. (olive oil, soybean oil, and used-vegetable oil). The used-vegetable oils were not different from the new, expensive oils in the removal rate, so their use will be desirable in saving the money. In addition of 1% of olive oil after the reaction of 3% $H_2O_2$ and 2.5 mM $FeSO_4$(III), the removal rates of 3~4 and 5~6 ring compounds were increased 13% and 17%, respectively, compared to the case of Fenton reaction only.

• Journal of Microbiology and Biotechnology
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• v.17 no.5
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• pp.868-872
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• 2007

H1N2 influenza viruses are circulating in pigs worldwide and cause considerable economic losses to the pig industry. We genetically analyzed the genes of our isolates from Korean pigs, and compared the antigenicity of our isolates with swine H1N2 viruses isolated from pigs in the U.S.A. In addition, we serologically surveyed the infection rate of swine H1N2 viruses in pigs. We found that H1N2 isolates from Korean pigs are genetically more related to swine H1N2 viruses isolated from pigs in the U.S.A. than those in European countries. When antigenicity was compared, our isolates were weakly reacted to antibodies against swine H1N2 viruses isolated from pigs in the U.S.A. The serological surveillance using sera from pigs in Korea showed that about 46% was positive for H1N2 viruses. Our results suggest that swine H1N2 viruses are widespread in Korean pigs, and the development of a vaccine against H1N2 viruses may help to control their infection in pigs.