• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.429-436
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• 2012

Mg and Mg-based alloys are regarded as strong candidate hydrogen storage materials since their hydrogen capacity exceeds that of known metal hydrides. One of the approaches to improve kinetic is addition of metal oxide. In this paper, we tried to improve the hydrogenation properties of Mg-based hydrogen storage composites. The effect of transition metal oxides, such as $Nb_2O_5$ on the kinetics of the Magnesium hydrogen absorption kinetics was investigated. $MgH_x$-5wt.% $Nb_2O_5$ composites have been synthesized by hydrogen induced mechanical alloying. The powder fabricated was characterized by X-ray diffraction (XRD), Field Emission-Scanning Electron Microscopy (Fe-SEM), Energy Dispersive X-ray (EDX), BET and simultaneous Thermo Gravimetric Analysis / Differential Scanning Calorimetry (TG/DSC) analysis. The Absorption / desorption kinetics of $MgH_x$-5wt.% $Nb_2O_5$ (type I and II) are determined at 423, 473, 523, 573 and 623 K.

• 상하수도학회지
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• 제24권6호
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• pp.775-788
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• 2010

The decomposition of 2,4,6-trinitrotoluene (TNT) and the mass balance of nitrogen (N) species as products were investigated in a UV/H2O2system by varying pH, concentrations of $H_2O_2$, and $O_2$. All experiments were conducted in a semi-batch system employing a 50 mL reaction vessel and a coil-type quartz-tube reactor. In contrast with previous studies employing batch mode, TNT decomposition in the semi-batch mode was proportionally enhanced by increasing $H_2O_2$ concentration to 10 mM (0.034%), indicatingthat an inhibitory effect of excess $H_2O_2$on hydroxyl radical (${\cdot}OH$) can be negligible. N compounds are released as $NO_2^-$ in the early stages of the reaction, but $NO_2^-$ is rapidly oxidized to $NO_3^-$ by means of ${\cdot}OH$. $NH_4^+$ was also detected in this study and showed gradually the increase with increasing reaction time. In this study, $NH_4^+$ production can involve the reduction of nitro group of TNT concurrent with the production of $NO_3^-$. Of the N species originating from TNT decomposition, 12 ~ 72% were inorganic forms (i.e. [$NO_3^-$] + [$NO_2^-$] + [$NH_4^+$]). This result suggests that the large remaining N portions indicate that unidentified N compounds can exist.

• 한국광물학회지
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• 제21권1호
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• pp.37-44
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• 2008

본 연구는 마포소각장에서 발생된 용융슬래그로부터 Na-A형 제올라이트를 합성하여 환경 저감재로 재활용키 위한 목적에서 수행되었다. 초기물질로 사용된 용융슬래그는 용제(flux)로 사용된 Fe 성분(19.6% of $Fe_2O_3$, and 18.9% of FeO)이 비교적 높기는 하지만, 상대적으로 제올라이트의 주요 성분인 $SiO_2$, $Al_2O_3$ 및 $Na_2O$가 각각 26.6%, 10.9% 및 2.7% 함유되어 제올라이트의 합성에 유리한 조성을 가지고 있다. 제올라이트의 수열합성은 $80^{\circ}C$에서 수행되었으며, $SiO_2/Al_2O_3\;=\;0.80{\sim}1.96$인 넓은 범위의 화학조성에서 Na-A형 제올라이트가 합성되는 것을 확인하였다. 제올라이트의 양이온 교환 능력은 10 h 이상의 합성시간에서 일정하게 거의 220 cmol/kg인 것으로 측정되었다. 합성된 제올라이트의 중금속 (As, Cr, Cd, Cu, Mn 및 Pb)에 대한 흡착능을 측정한 결과, As 및 Cr을 제외한 모든 중금속에서 높은 흡착율을 보였다. As와 Cr은 Eh-pH분석을 통해 각각 $HAsO_4^{2-}$와 $CrO_4^{2-}$인 이온상으로 존재하고 있음을 확인하였다. As와 Cr에 대한 제올라이트의 흡착률이 낮은 것은 이들 이온상들의 크기가 Na-A형 제올라이트의 pore size ($4\;{\AA}$)보다 상대적으로 큰 유효 이온반경($4\;{\AA}$, 직경 $8\;{\AA}$)을 가지고 있기 때문인 것으로 결론지었다.

• Journal of the Korean Physical Society
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• 제73권11호
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• pp.1708-1711
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• 2018

The polycrystalline sample of $Ba_2Co_{1.5}Mg_{0.5}Fe_{11.88}Ga_{0.12}O_{22}$ Y-type hexaferrite, doped with Ga-cation, was prepared by using the solid-state reaction method. The crystalline structure of sample was investigated by x-ray diffractometer (XRD), and the magnetic properties of sample were measured by vibrating sample magnetometer (VSM), and $M{\ddot{o}}ssbauer$ spectrometer. The crystal structure of prepared sample was determined to be rhombohedral with space group R-3m. From the temperature dependence of the magnetization curves under 100 Oe between 4.2 and 740 K, two temperature-dependent magnetic transitions occurred in the $Ba_2Co_{1.5}Mg_{0.5}Fe_{11.88}Ga_{0.12}O_{22}$ sample. $M{\ddot{o}}ssbauer$ spectra of the sample were analyzed at various temperatures ranging from 4.2 to 620 K, and the $Ba_2Co_{1.5}Mg_{0.5}Fe_{11.88}Ga_{0.12}O_{22}$ sample showed abrupt changes in $H_{hf}$ and $E_Q$ at 200 K, indicating the spin transition effect. We have also determined the magnetic transition temperature $T_C$, in addition to the temperature dependent magnetization and ZVC measurements.

• Bulletin of the Korean Chemical Society
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• 제23권8호
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• pp.1149-1153
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• 2002

CH4/CO2 dry reforming was carried out to make syn gas on the Ni/Al2O3 catalysts calcined at different temperatures. The Ni/Al2O3 (850 $^{\circ}C)$ catalyst gave good activity and stability w hereas the Ni/Al2O3 $(450^{\circ}C)$ catalyst showed lower activity and stability. The NiO/Al2O3 catalyst calcined at $850^{\circ}C$ for 16 h (Ni/Al2O3 $(850^{\circ}C))$ formed the spinel structure of nickel aluminate, which was confirmed by TPR. The carbon formation rate on the Ni/Al2O3 $(850^{\circ}C)$ catalyst was very low till 20 h, and then steeply increased with reaction time without decreasing the activity for CH4 reforming. The Ni/Al2O3 $(450^{\circ}C)$ catalyst showed high carbon formation rate at the initial reaction time and then, the rate nearly stopped with continuous decreasing the activity for CH4 reforming. Even though the amount of carbon deposition on the Ni/Al2O3 $(850^{\circ}C)$ catalyst was higher than that on the Ni/Al2O3 $(450^{\circ}C)$ catalyst, the activity for CH4ing was also high, which could be attributed to the different type of the carbon formed on the catalyst surface.

• Restorative Dentistry and Endodontics
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• 제2권1호
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• pp.11-14
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• 1976

The purpose of this study was to the observe effects of the various bleaching agents on blood clot. Absorbent papers(N9.5) were coated with O type blood and were dried in shadow for 72 hours. Bleaching agents used were 5% NaOCl 30% $H_2O_2$, saturated solutions of $NaBO_3$ $4H_2O$, $Ca(OCl)_2$ and $Na_2O_2$ at $20^{\circ}C$. After the specimens, blood cloted papers were dipped in 10CC of solution for 1 minute, 5 minutes, 30 minutes, 2 hours and 24 hours, specimens were washed with distilled water and dried. Hue Value/Chroma contrived by Munsell was measured in each specimen. The following results were obtained. 1. Superoxol changes 2.5YR 4.5/2 into N9.5 (white) after 24 hours. 2. All bleaching agents except superoxol change YR into Y.

• 대한화학회지
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• 제33권1호
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• pp.135-142
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• 1989

HZSM-5를 觸媒로 하여 메탄올과 이소부틸렌으로부터 Methyl tertiary butyl ether(MTBE)의 氣相合成實驗을 하였으며, zeolite 觸媒의 SiO$_2/Al_2O_3$ 比 및 反應條件의 영향을 硏究하였다. 각 觸媒들은 pyridine을 吸着시켜 temperature programmed desorption(TPD) 및 IR法으로 酸點의 세기와 特性을 조사하였으며, 승온탈착실험을 통하여 각 反應物 및 生成物의 吸着特性을 검토하였다. HZSM-5의 SiO$_2/Al_2O_3$比가 증가할수록 强한 酸點의 수는 감소하여 메탄올의 脫水反應은 억제되고 MTBE에 대한 선택도가 증가하였다. MTBE에 대한 전환율과 선택도는 $i-C_4H_8$의 細孔內 확산저항에 의하여 큰 영향을 받음을 알 수 있었다. MTBE合成反應은 發熱的이어서, 전반적으로 80$^{\circ}$C의 반응온도가 合成에 적합하였다. 한편 각 觸媒上에 生成된 coke의 特性을 TG, DTA 및 IR spectrum으로 측정하였다. 침착된 coke의 量은 HY > H-Mordenite > HZSM-5順이었으며, H-Mordenite에 있어서는 누적된 coke의 양이 HZSM-5보다 현저하지는 않았으나, 細孔의 配向이 1方向性이므로 반응시간이 길어짐에 따라 심한 活性減退가 일어났다. HY는 큰 細孔을 가지고 있어 M$i-C_4H_8$의 重合이 쉽게 일어났으며, HZSM-5에 비하여 많은 coke의 참착과 빠른 活性減退를 나타내었다.

• 한국융합학회논문지
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• 제12권4호
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• pp.201-206
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• 2021

고병원성 조류독감 바이러스(H5N1)에 대한 피해가 지속적으로 증가하고 있으나, 이에 대한 항바이러스성 연구는 부족한 상황이다. 본 연구에서는 폴리에틸렌 필름에 Cu/TiO2 광촉매를 코팅하여 H5N1에 대한 항바이러스 특성을 분석하였다. 시료는 광촉매 마스터배치를 제조하여 압출코팅기에서 280℃로 3중 레이어 폴리에틸렌 원단의 양면을 코팅하였다. 그 결과 황색포도상구균과 대장균의 균수가 99.9% 감소되는 것으로 나타났다. 특히 인체감염이 가능한 H5N1형 고병원성 조류인플루엔자는 Cu/TiO2계 필름에 접촉 5분 이내 99.9% 감소하는 것으로 확인되었다. 광촉매를 코팅한 필름의 항균성에 대해서는 알려져 있지만 본 연구를 통해 항바이러스성에 대해서도 확인이 가능하였다.

• 상하수도학회지
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• 제30권5호
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• pp.501-509
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• 2016

In this study, a flat-type photocatalytic reactor is applied under solar irradiation for simultaneous treatment of target pollutants: reduction of Cr(VI) to Cr(III) and oxidation of EDCs (BPA, EE2, E2). An immobilized type of photocatalyst was fabricated to have self-grown nanotubes on its surface in order to overcome limitations of powdery photocatalyst. Moreover, Ti mesh form was chosen as substrate and modified to have both larger surface area and photocatalyst content. Ti mesh was anodized at 50V and $25^{\circ}C$ for 30min in the mixed electrolytes ($NH_4F-H_2O-C_2H_6O_2$) and annealed at $450^{\circ}C$ for 2 hours in ambient oxygen to have anatase structure. Surface characterization was done with SEM and XRD methodologies. Fabricated NTT was applied to water treatment, and coexisting Cr(VI) and organics (EDCs) enhanced each other's reactions by scavenging holes and electrons and thus impeding recombination. Also, several experiments were conducted outdoor under direct sunlight and it was observed that both solar-tracking and applying modified photocatalyst were proven to enhance reaction efficiency.

• 천문학회보
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• 제34권2호
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• pp.37.1-37.1
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• 2009