• Journal of the Korean Ceramic Society
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• v.45 no.12
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• pp.827-831
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• 2008

Spark plasma sintering (SPS) of AlN ceramics were carried out with ${Y_2}{O_3}$ as sintering additive at a sintering temperature $1,550{\sim}1,700^{\circ}C$. The effect of ${Y_2}{O_3}$ addition on sintering behavior and thermal conductivity of AlN ceramics was studied. ${Y_2}{O_3}$ added AlN showed higher densification rate than pure AlN noticeably, but the formation of yttrium aluminates phases by the solid-state reaction of ${Y_2}{O_3}$ and ${Al_2}{O_3}$ existed on AlN surface could delay the densification during the sintering process. The thermal conductivity of AlN specimens was promoted by the addition of ${Y_2}{O_3}$ up to 3 wt% in spite of the formation of YAG secondary phase in AlN grain boundaries because ${Y_2}{O_3}$ addition could reduced the oxygen contents in AlN lattice which is primary factor of thermal conductivity. However, the thermal conductivity rather decreased over 3 wt% addition because an immoderate formation of YAG phases in grain boundary could decrease thermal conductivity by a phonon scattering surpassing the contribution of ${Y_2}{O_3}$ addition.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1229-1232
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• 2005

We report the method of preventing the grey color of Bi based glass frits caused by reduction of $Bi_2O_3$. To prevent reduction of $Bi_2O_3$, we controlled the melting temperature. Low melting temperature reduces the reduction of $Bi_2O_3$ and that makes clarity transparent glass cullets. After firing, glass frits that melted at lower temperature showed better transparency. To prevent the browning, we used some additives like CuO, $CeO_2$, CoO and $TiO_2$. The colors of glass cullets were varied according to additives. After firing, dielectric layer contained additives showed better transparency than the one without additives. In the point of reaction between dielectric layer and Ag electrode, CuO was the most effective additive in preventing the yellowing.

• Journal of Power System Engineering
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• v.20 no.4
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• pp.69-74
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• 2016

Recently, in order to meet the stricter emission regulations, the proportion of after-treatments for vehicle and vessel is increasing gradually. The purpose of this study is to investigate the de-$CH_4$ characteristics of NGOC in front of proposed combined system according to additive catalyst and support ratio. In the case of Pd addition, the de-$CH_4$ performance of 2Pt-2Pd-3MgO/$Al_2O_3$ NGOC was improved by approximately 10 to 20% for the HC components. The de-$CH_4$ performance of 2Pt-2Pd-3Cr-3MgO/$Al_2O_3$ NGOC was higher compared to five kinds of NGOC catalysts, because Cr particle was smaller and dispersion of Pd was increased. The NGOC(Zeolite:$Al_2O_3$(80%:20%)｝catalyst according to support ratio, was improved performance at low temperature region on CO and NO conversion rate.

• Elastomers and Composites
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• v.51 no.3
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• pp.175-180
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• 2016

Influence of amino acidic chemical on properties of maleic anhydride-grafted ethylene-propylene-diene terpolymer/zinc oxide (EPDM-g-MAH/ZnO) composites was investigated. 4-Aminosalicylic acid (ASA), 4-amino-2-methoxybenzoic acid (AMBA), 12-aminolauric acid (ALA), and glutamine (Gln) were employed as the amino acidic chemicals. Though small quantity (0.5 phr) of the amino acidic chemical was added to the EPDM-g-MAH/ZnO composite, the properties were notably changed. By adding the amino acidic chemical, the percent crystallinity and apparent crosslink density were reduced. Order of the percent crystallinity was related to that of the $pK_a$ values of amino acidic chemicals. By adding the amino acidic chemical, the basic tensile properties were on the whole improved. The experimental results were explained by the $pK_a$ values of amino acidic chemicals, change of zinc ionomer formation, and interactions between the additive and EPDM-g-MAH chain.

• Journal of Environmental Health Sciences
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• v.34 no.2
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• pp.124-130
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• 2008

This study investigated the age dependencies in ambient air pollution-associated asthma hospitalization from 2003 to 2005 in Seoul. For all ages and the age groups of 0-14, 15-64, and 65+years, the Generalized Additive Model (GAM) was used to estimate the relative risks of daily asthma hospitalization associated with changes in particulate matter and ozone. The time-trends, seasonal variances, day effects, temperature, humidity, and pressure at sea level were controlled in the models. Significant associations were observed between asthma hospitalization and the levels of $PM_{10}$ and $O_3$. The relative risks (RRs) of asthma hospitalization for every 10 unit increases in $PM_{10}({\mu}g/m^3)$ and $O_3$(ppb) were 1.008 (95% CI 1.005-1.012), and 1.012 (95% CI 1.003-1.020), respectively. Evaluated over $10\;{\mu}g/m^3$ increase in $PM_{10}$, we found the relative risks of asthma hospitalization to be 1.009 (95% CI 1.004-1.014) in 0-14 age group, and 1.015 (95% CI 1.008-1.022) in 65+ age group. Considering 10 ppb increase in $O_3$, those were 1.014 (95% CI 1.003-1.024) in 0-14 age group, and 1.025 (95% CI 1.009-1.041) in 65+ age group. It was concluded that current levels of ambient air pollution in Seoul make a significant contribution to the variation in daily asthma hospitalization. Further reduction in air pollution is necessary to protect the health of the community, especially that of the higher risky groups including children and elderly population.

• Journal of the Korean Ceramic Society
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• v.11 no.2
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• pp.3-10
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• 1974

For the manufacture of the silver-yellow glass, silver nitrate was used as a colorant in the base glass of $K_2O$-CaO-$SiO_2$ system. The latter in which the optimum condition was revealed showing beautiful yellow color had been selected among others after the preparatory studies to choose base glass. Other base glass systems considered were $Na_2O$-CaO-$SiO_2$, $R_2O$-PbO-$SiO_2$ and $R_2O$-PbO-BaO-$SiO_2$. The color developed on the specimen in various conditions was examined, using spectorphotometer, in term of the changes in absorbance with wavelength in the visible range. Experimental variables were the amount of the colorant and the additives, reheating temperature and time. The additives such as ZnO, BaO, $B_2O_3$ and $As_2O_3$ were added to increase the coloring action. It was observed that as the amount of silver increased in the base glass the absorbance around $410{\mu}m$ showed the increasing tendency, but the width of absorption curve was wider. Hence, the optimum amount of silver appeared to be 0.11~0.12%. It was found that ZnO was effective additive when present about 0.1%, while $As_2O_3$ ineffective rather retarding the coloration. Borax and $BaCO_3$ were proved effective when contained separately, but appeared ineffective when coexisted. Proper reheating temperature and time was ranged 550~$580^{\circ}C$ and 50~60 minutes. The higher the reheating temperature and the longer the reheating time, the absorbance was increased, while the width of absorption curve was wider. The colored glass prepared in the present experimental condition was found to have good water-resistance for the decorative purpose.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.4
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• pp.288-292
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• 1998

In this paper, we fabricated $SnO_2$ composite ceramics doped with 0~20mol% $SnO_2$ of bulk type to investigate the CO and $H_2$ gas sensitivity in various composition, temperature, and concentration of CO and $H_2$ gas. At the temperature range from $100^{\circ}C\sim425^{\circ}C$, the measured 1000ppm and 250ppm CO gas sensitivities of $SiO_2-SnO_2$composite ceramics were about 1.0~7.6 and 1.0~5.6, respectively. These values were about 1.0~1.5 times larger than pure $SnO_2$. The maximum 1000ppm CO gas sensitivity of $SiO_2-SnO_2$composites were measured around $325^{\circ}C$. At the temperature range from $270^{\circ}C\sim380^{\circ}C$, the 1000ppm and 500ppm $H_2$gas sensitivities of $SiO_2-SnO_2$ composites were about 2.9~21.2 and 2.1~11.3, respectively. Also the maximum 1000, 500 ppm $H_2$ gas sensitivities of samples were measured around.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.2
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• pp.80-84
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• 2003

The mechanical and electrical properties of the hot-pressed and pressureless annealed SiC-Ti $B_2$electroconductive ceramic composites were investigated as functions of the liquid additives of $Al_2$ $O_3$+ $Y_2$ $O_3$. The result of phase analysis for the SiC-Ti $B_2$ composites by XRD revealed $\alpha$-SiC(6H), Ti $B_2$, and YAG(A $l_{5}$ $Y_3$ $O_{12}$ ) crystal phase. The relative density of SiC-Ti $B_2$ composites was increased with increased $Al_2$ $O_3$+ $Y_2$ $O_3$ contents. The fracture toughness showed the highest value of 6.04 Mpa $m^{\frac{1}{2}}$ for composites added with l2wt% A1$_2$ $O_3$+ $Y_2$ $O_3$ additives at room temperature. The electrical resistivity showed the lowest value of 6.2$\times$10$^{-3}$ $\Omega$ㆍcm for composite added with l6wt% $Al_2$ $O_3$+ $Y_2$ $O_3$ additives at room temperature. The electrical resistivity of the SiC-Ti $B_2$ composites was all positive temperature cofficient resistance(PTCR) in the temperature ranges from $25^{\circ}C$ to $700^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.323-323
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• 2010

PNN-PZT계 세라믹스를 $Pb(Ni_{1/3}Nb_{2/3})_{0.4}(Zr_{0.48}Ti_{0.52})_{0.6}O_3$ 조성으로 설계하고, 이에 낮은 융점의 NiO를 1wt% 첨가하여 저온소결 특성을 평가하였다. 일반적인 세라믹 분말 소결법을 이용하여 시편을 제작하였으며, 이때의 소결온도는 $850{\sim}105^{\circ}C$ 범위에서 변화시켰다. 소결체의 압전 및 유전적 특성을 평가를 하고. SEM 및 XRD를 이용한 미세구조 및 상 분석도 수행하였다. 이러한 실험 결과, PNN-PZT 세라믹은 NiO의 첨가로 $1000^{\circ}C$ 정도에서도 저온소결이 가능한 것을 확인하였다.

• Korean Journal of Materials Research
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• v.13 no.8
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• pp.531-536
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• 2003

The electromagnetic properties and microstructures of the ferrites based on ($Ni_{0.2}$ $Cu_{0.2}$ $Zn_{0.6}$)$_{1.085}$($Fe_2$$O_3$)$_{0.915}$ were investigated by changing the amount of additive SnO$_2$and CaO and the sintering temperatures. Addition of $SnO_2$caused pores in the specimen. There was no variation of grain size by changing the amount of additives. Total loss was reduced when ($Ni_{0.2} $Cu_{0.2}$ $Zn_{ 0.6}$)$_{1.085}$ ($Fe_2$$O_3$)$_{0.915}$ composition was sintered at $1150^{\circ}C$ rather than $1300^{\circ}C$. Addition of CaO was useful to reduce the total loss because it increased the sintering density. The lowest total loss was obtained when 0.06 wt% $SnO_2$and 0.4 wt% CaO were added at the same time.