• 대한기계학회논문집B
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• 제37권4호
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• pp.405-413
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• 2013

4 가지 탄종(Gunvor, Glencore, Noble, ECM)의 촤 산화반응 특성을 $900^{\circ}C$에서 $1300^{\circ}C$까지의 노내온도와 대기압 조건에서 DTF(drop tube furnace)를 이용하여 실험하였다. 촤 반응률은 FT-IR 장비로 측정한 CO, $CO_2$ 농도와 이색온도계로 측정한 입자온도를 통해 계산되었고 고회분탄의 활성화에너지(E)와 pre-exponential 상수(A)는 아레니우스 방정식을 기초로 계산되었다. 실험 결과는 석탄의 회분 함량이 늘어남에 따라, 입자온도와 면적반응성이 감소하였다. 이러한 결과는 회분의 큰 열용량, 회분의 기화잠열과 상대적으로 적은 고정탄소의 함량으로 인한 연소성 저하로 사료된다. 결과적으로 고회분탄은 높은 활성화 에너지(E)를 가진다.

• 열처리공학회지
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• 제33권3호
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• pp.129-134
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• 2020

Due to excellent properties such as high specific strength and low density, application of magnesium alloys have been rapidly increased. However, magnesium alloy has a serious problem that is easily oxidized when exposed to high-temperature. For this reason, magnesium alloys have been generally used for SF6 gas such as protective cover gas in casting and melting, but it has been reported that this gas has a serious influence on global warming. Therefore, many researchers have been studied to improve the oxidation resistance of magnesium alloy. It was reported that addition of Be, Ca and CaO in magnesium alloy can improve the oxidation properties. In this study, the possibility of improving the oxidation resistance by adding CaO extracted from oyster shells was investigated. Oyster shells were completely decomposed into CaO and CO₂ by annealing. With the addition of CaO, a coexistence region of MgO + CaO was formed in the oxide layer and its thickness was also reduced.

• Korean Chemical Engineering Research
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• 제55권2호
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• pp.156-162
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• 2017

CuO의 함량이 반응활성에 미치는 영향을 조사하기 위하여 CuO(x)/0.3Al-0.7Ce (x = 2~20 wt%) 촉매를 함침법으로 제조하고 저온 CO 산화반응을 수행하였다. CuO(10)/0.3Al-0.7Ce 촉매가 반응물 중 수분의 존재 유무에 관계없이 가장 우수한 반응활성을 나타내었다. 수분의 존재는 활성점에 CO와의 경쟁흡착으로 활성점이 감소하여 50% CO 전환율 온도인 $T_{50%}$가 약 $50^{\circ}C$ 고온으로 이동되어 관찰되었다. $N_2O$-적정실험으로 구한 구리 표면적과 CO-펄스 실험으로 계산된 격자산소의 양은 CuO의 함량 증가에 따라 증가하였고, CuO(10)/0.3Al-0.7Ce 촉매에서 최대화되었다. 이러한 특성 분석결과는 사용된 촉매의 CO 산화반응에 대한 $T_{50%}$의 경향과 잘 일치하였다. 위의 특성분석 결과로부터, CuO(x)/0.3Al-0.7Ce 촉매의 CO 산화반응에 대한 반응성은 구리 표면적과 격자산소의 양과 밀접하게 관련된다고 결론지을 수 있다.

• 공업화학
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• 제30권2호
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• pp.151-154
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• 2019

코디어라이트 허니컴 표면에 알루미나 워시코트 지지체를 형성시키고 비교적 단순한 건식 코팅 공정으로 산화철 촉매를 코팅함으로써 실제 환경에 효과적으로 적용이 가능한 모노리스 구조 촉매를 제조하였다. 허니컴 통로 벽 구석으로 형성된 워시코트 알루미나 미세 기공으로 균일하게 코팅된 산화철 촉매를 확인하였으며, 일산화탄소 산화 반응에 적용하기 위하여 산화철 촉매의 열처리 효과를 검증하였다. $350^{\circ}C$ 부근에서 열처리한 산화철 촉매가 가장 우수한 촉매 성능을 발휘하였고, $200^{\circ}C$ 이상의 온도 영역에서 100% 전환율을 나타내었다.

• 한국분말재료학회지
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• 제13권1호
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• pp.46-51
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• 2006

Through the volume change of Sn in a low-temperature phase transformation, the Sn nanopowder with high, purity, was fabricated by an economic and eco-friendly process. The fine cracks were spontaneously generated. in, Sn ingot, which was reduced to powders in the repetition of phase transformation. The Sn nanopowder with 50 run in size was obtained by the 24th repetitions of phase transformation by low-temperature and ultrasonic treatments. Also, the $SnO_2$ powder was fabricated by the oxidation of the produced Sn powder to the ingot and milled by the ultrasonic milling method. The $SnO_2$ nanopowder of 20 nm in size was fabricated after the milling for 180 h.

• 한국응용과학기술학회지
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• 제30권3호
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• pp.371-379
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• 2013

In order to improve the selective oxidation reaction of gaseous ammonia at a low temperature, various types of metal-impregnated activated alumina were prepared, and also physical and chemical properties of the conversion of ammonia were determined. Both types of metal (Cu, Ag) impregnated activated alumina show high conversion rate of ammonia at high temperature (over $300^{\circ}C$). However, at lower temperature ($200^{\circ}C$), Ag-impregnated catalyst shows the highest conversion rate (93%). In addition, the effects of lattice oxygen of the developed catalyst was studied. Ce-impregnated catalyst showed higher conversion rate than commercial alumina, but also showed lower conversion rate than Ag-impregnated sample. Moreover, 5 vol.% of Ag activation under hydrogen shows the highest conversion rate result. Finally, through high conversion at low temperature, it was considered that the production of NO and $NO_2$, toxic by-products, were effectively inhibited.

• Korean Chemical Engineering Research
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• 제49권6호
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• pp.720-725
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• 2011

금속질산염과 염화금산을 전구체로 사용하여 다양한 금속산화물($$Al_{2}O_{3}$, ZnO, $Fe_{2}O_{3}$, $Cr_{2}O_{3}$, $MnO_{2}$, CuO, NiO, $Co_{3}O_{4}$)에 담지된 금촉매를 공침법을 이용하여 제조한 후, 일산화탄소 산화반응에서 수분첨가의 영향을 검토하였다. 이들 중 $Co_{3}O_{4}$와 ZnO에 담지된 금촉매가 일산화탄소에 대하여 높은 활성을 보여주었다. 반응가스 중에 수분이 첨가될 때 Au/$Co_{3}O_{4}$ 촉매는 활성이 약간 감소하였으나, Au/ZnO 촉매에서는 활성이 크게 증가하여 수분에 의한 일산화탄소 산화 활성은 담체의 종류에 크게 의존함을 알 수 있었다. 반응가스 중에 포함된 수분에 관계없이 반응 전과 후의 Au(5 wt%)/ZnO 촉매의 금입자 크기는 거의 변하지 않아 활성이 감소되는 이유는 금입자들의 소결에 의한 영향보다는 카보네이트와 같은 화학종에 의해 불활성화가 일어남을 알 수 있었으며, 이 화학종은 수분의 첨가에 의해 이산화탄소로 분해되어 활성이 증가한 것으로 생각된다.

• 한국산업융합학회 논문집
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• 제25권6_3호
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• pp.1275-1284
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• 2022

This study provides an investigating the electrolyte reaction characteristics during thermal runaway of a lithium-ion battery(LIB). Dimethyl carbonate(DMC) is known as the main substance that makes up the electrolyte. The mono-molecular decomposition characteristics of DMC were derived through numerical analysis. Cobalt oxide can release oxygen under high temperature conditions. Also, DMC is converted to CH₄, H₂, CO, and CO₂. Especially, it was found that the decomposition of the DMC begins at a temperature range of 340-350℃, which dramatically increases the internal pressure of the LIB. In the by-products gases, the molar ratio of CO and CO₂ changed according to the molecular structure of DMC and temperature conditions. The correlation of the [CO]/[CO₂] ratio according to the temperature during thermal runaway was derived, and the characteristics of the reaction temperature could be estimated using the molar ratio as an indicator. In addition, the oxidation and decomposition characteristics of DMC according to the residence time for each temperature were estimated. When DMC is exposed to low temperature for a long time, both oxidation and decomposition may occur. There is possibility of not only increasing the internal pressure of the LIB, but also promoting thermal runaway. In this study, internal environment of LIB was identified and the reaction characteristics between the active materials of the cathode and electrolyte were investigated.

• 한국수소및신에너지학회논문집
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• 제14권2호
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• pp.155-170
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• 2003

$Cu-Ce/{\gamma}-Al_2O_3$ based catalysts were prepared and tested for selective oxidation of CO in a $H_2$-rich stream(1% CO, 1% $O_2$, 60% $H_2$, $N_2$ as balance). The effects of Cu loading and weight ratio(=Cu/(Cu+Ce)) upon both activity and selectivity were investigated upon the change in temperatures, It was also examined how the activity and selectivity of catalysts were varied with the presence of $CO_2$ and $H_2O$ in the reactant feed. Among the various Cu-Ce catalysts with different catalytic metal composition, Cu-Ce(4 : 16 wf%) /${\gamma}-Al_2O_3$ catalyst showed the highest activity(>$T_{99}$) and selectivities(50-80%) under wide range of temperatures($175-220^{\circ}C$). However, in the Cu-Ce(4 : 16 wt%)/ ${\gamma}-Al_2O_3$, the presence of $CO_2$ and $H_2O$ in the reactant feed decreased the activity and the maximum activity(>$T_{99}$) in terms of reaction temperature moved by about $25^{\circ}C$ toward higher temperature, the $T_{>99}$ window was seen between $210-230^{\circ}C$ (selectivity 50-75%). From $CO_2-/H_2O-TPD$, it can be concluded that the main cause for the decrease in catalytic activity may be attributed to the blockage of the active sites by competitive adsorption of water vapor and $CO_2$ with the reactant at low temperatures.

• 한국환경과학회지
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• 제17권8호
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• pp.933-941
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• 2008

The formation of $Co_nTiO_{n+2}$ compounds, i.e., $CoTiO_3$ and $CO_2TiO_4$, in a 5wt% $CoO_x/TiO_2$ catalyst after calcination at different temperatures has been characterized via scanning electron microscopy (SEM), Raman and X-ray photoelectron spectroscopy (XPS) measurements to verify our earlier model associated with $CO_3O_4$ nanoparticles present in the catalyst, and laboratory-synthesized $Co_nTiO_{n+2}$ chemicals have been employed to directly measure their activity profiles for CO oxidation at $100^{\circ}C$. SEM measurements with the synthetic $CoTiO_3$ and $CO_2TiO_4$ gave the respective tetragonal and rhombohedral morphology structures, in good agreement with the earlier XRD results. Weak Raman peaks at 239, 267 and 336 $cm^{-1}$ appeared on 5wt% $CoO_x/TiO_2$ after calcination at $570^{\circ}C$ but not on the catalyst calcined at $450^{\circ}C$, and these peaks were observed for the $Co_nTiO_{n+2}$ compounds, particularly $CoTiO_3$. All samples of the two cobalt titanate possessed O ls XPS spectra comprised of strong peaks at $530.0{\pm}0.1$ eV with a shoulder at a 532.2-eV binding energy. The O ls structure at binding energies near 530.0 eV was shown for a sample of 5 wt% $CoO_x/TiO_2$, irrespective to calcination temperature. The noticeable difference between the catalyst calcined at 450 and $570^{\circ}C$ is the 532.2 eV shoulder which was indicative of the formation of the $Co_nTiO_{n+2}$ compounds in the catalyst. No long-life activity maintenance of the synthetic $Co_nTiO_{n+2}$ compounds for CO oxidation at $100^{\circ}C$ was a good vehicle to strongly sup port the reason why the supported $CoO_x$ catalyst after calcination at $570^{\circ}C$ had been practically inactive for the oxidation reaction in our previous study; consequently, the earlier proposed model for the $CO_3O_4$ nanoparticles existing with the catalyst following calcination at different temperatures is very consistent with the characterization results and activity measurements with the cobalt titanates.