• 공업화학
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• 제10권8호
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• pp.1161-1168
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• 1999

3주기 전이금속(Cr~Zn)의 산화물 및 V, Mo, W의 산화물에 대하여 temperature-programmed reduction/trmperature-programmed oxidation(TPR/TPO) 실험을 통하여 그 산화-환원 특성을 조사하였다. TPO 곡선의 산화피크는 TPR 곡선의 환원피크와 비슷하거나 약간 낮은 온도에서 나타났으며, 환원피크에 비하여 온도 폭이 넓었다. 3주기 전이금속한화물의 산화 및 환원 과정의 활성화에너지는 33~149 kJ/mol 범위에 있는 반면, V, Mo, W 산화물에서는 더 컸다. 금속산화물의 산화 및 환원 과정의 활성화에너지 변화는 금속-산소 결합세기에 비례하였다. 환원(TPR) 및 산화(TPO) 과정에 대한 활성화에너지 차이(${\Delta}E_a$)가 작을수록 o-자일렌 산화반응에서 금속산화물 촉매의 활성화에너지도 작았다. 금속한화물 촉매에서 o-자일렌 산화반응은 금속산화물 표면의 산화-환원 과정을 반복하는 Mars-van Krevelen 반응 메카니즘으로 설명될 수 있음을 확인하였다.

• 청정기술
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• 제2권1호
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• pp.60-68
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• 1996

고정층 반응기에서 망간광석을 이용하여 저농도의 일산화탄소 산화제어반응에 대하여 고찰하였다. 고려된 실험변수는 일산화탄소 농도 (500ppm~10000ppm), 산소 농도(500ppm~99.8%)와 촉매의 온도($50{\sim}750^{\circ}C$)이다. 또한 망간광석의 특성은 Thermogravimetric Analysis(TGA), 일산화탄소에 의한 환원, Temperature Programmed Reduction(TPR)실험을 이용하여 규명하였다. 망간광석의 일산화탄소 산화력은 순수이산화망간에 비해서 단위 면적당 높은 산화력과 $750^{\circ}C$까지 가열된 후에도 산화력이 유지될 수 있는 안정된 촉매작용을 보였다. Temperature Programmed Desorption(TPD), TPR 실험과 TG 등의 분석결과 산소의 농도가 낮거나 무산소하에서 망간광석의 격자내 산소가 쉽게 제공될 수 있음을 알 수 있었다. 일산화탄소의 농도가 500~3500ppm일 때 일산화탄소의 반응차수는 0.701이며 3500~10000ppm구간에서 일산화탄소의 농도에 무관한 0차 반응이었다.

• Korean Chemical Engineering Research
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• 제50권5호
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• pp.843-849
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• 2012

매체순환식 가스연소기 산소공여입자로 NiO 계열 산소공여입자를 사용할 경우 고온 조건(> $900^{\circ}C$)에서 온도가 증가함에 따라 환원반응 배출기체 중 CO 농도가 증가하게 되며, 이에 의해 연료전환율과 $CO_2$ 선택도가 감소하게 된다. 이러한 고온 환원반응성 저하를 개선하기 위한 방법으로 매체순환 가스연소기에 적용 가능한 금속산화물들에 대해 온도변화에 따른 평형 CO 농도를 계산 및 비교하여 반응성 개선이 가능한 금속산화물을 선정하였다. 선정된 금속산화물을 NiO 계열 산소공여입자와 물리적으로 혼합하는 방법을 적용하여 고온 환원반응성 개선이 가능한지를 회분식 유동층 실험장치를 이용하여 측정 및 해석하였다. $900{\sim}1000^{\circ}C$ 범위에서 기존 NiO 계열 입자(OCN706-1100) 만을 사용한 경우에 비해 $Co_3O_4$ 계열 입자($Co_3O_4/CoAl_2O_4$)를 10% 혼합한 경우가 연료전환율 및 $CO_2$ 선택도가 높게 나타났으며 환원반응 배출기체 중 CO의 농도가 감소하는 경향을 나타내어 $Co_3O_4$ 계열 산소공여입자를 함께 사용하는 방법으로 고온 환원반응성 개선이 가능함을 확인할 수 있었다.

• 한국대기환경학회지
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• 제6권1호
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• pp.31-42
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• 1990

In order to suggest an efficient catalyst systems for NOx reduction of flue gases from industrial boilers, $TiO_2$ supported $WO_3-V_2O_5, V_2O_5$ and $WS_2$ catalysts were tested for the performances of NOx reduction at high reactin temperature range (250-500$^\circ$C) using a simulated flue gas system. It was found that while the proposed $WO_3/TiO_2$ and $WO_3-V_2O_5/TiO_2$ catalysts showed a significant high NOx reduction efficiency at about 350-400$^\circ$C, the conventional commercial catalyst of $V_2O_5/TiO_2$ showed a significant drop in NOx reduction efficiency due to the excessive $NH_3$ oxidation. From the measurement of surface acidities of those catalysts, it was found that the acidity are well correlated with the activities of NOx reduction. The reason of high activity of $WO_3$ series catalysts at high reaction temperature seems due to the low value of surface excess oxygen compared with that of $V_2O_5/TiO_2$ seems equivalent to the acid site of that catalyst.

• 한국재료학회지
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• 제14권10호
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• pp.725-730
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• 2004

Nickel ultrafine powder have been synthesized by chemical reduction of aqueous $NiSO_4$ with hydrazine at various reaction conditions. The effect of reaction conditions such as the amount of surfactant and reductor, and reaction temperature on the particle size and shape was investigated by the mean of XRD, SEM and SEM-PSA. Experiments showed that the ratio of $N_{2}H_4/Ni$ and the reaction temperature were affected on the particle size of the nickel powder. The average particle size of synthesized nickel powder increased with increasing reaction temperature regardless of the ratio of $N_{2}H_4/Ni$. Also the surfactant could influence the size and agglomeration of ultrafine powder with the reaction temperature.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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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.

• 대한기계학회논문집A
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• 제31권3호
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• pp.295-303
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• 2007

Degradation behaviors of filament-winded composites have been evaluated under the accelerated environmental test of high temperature, water immersion and thermal impact conditions. Two kinds of laminated composites coated by an urethane resin have been used: carbon-fiber reinforced epoxy(T700/Epon-826, CFRP) and glass-fiber reinforced phenolic (E-glass/phenolic, GFRP). For tensile strength of $0^{\circ}$ composites, CFRP showed little degradation while GFRP did high reduction by 25% under the influence of high temperature and water However for water-immersed $90^{\circ}$ composites tensile strength of both CFRP and GFRP showed high reduction. Bending strength and modulus of $90^{\circ}$ composites were largely reduced in water-immersion as well as high temperature environment. Urethane coating on the composite surface improved the bending properties by 20%, however hardly showed such improvement for water-immersed $90^{\circ}$ composites. In case of shear strength and modulus, both CFRP and GFRP showed high reduction by water-Immersion test but did a slight increase by high temperature and thermal impact conditions.

• 한국세라믹학회지
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• 제43권9호
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• pp.582-587
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• 2006

Decomposition behavior of $ferro-Si_3N_4$was investigated with varying temperature and holding time in mud components for high temperature refractory applications. Porosities gradually increased with increasing temperature and holding time due to the carbothermal reduction of $Si_3N_4\;and\;SiO_2$. Silicon monoxide (SiO) as a intermediate resulted from evaporation of $Si_3N_4\;and\;SiO_2$ reacted with C sources to generate needle-like ${\beta}-SiC$ and Fe in $Si_3N_4$ acted as a catalyst in order to enhance growth of SiC grain with the preferred orientation. SiC generation yield increased with increasing holding time, all of the $Si_3N_4\;and\;SiO_2$ affected on SiC formation up to 2h. However, SiC generation was only dependent on residual $SiO_2$ over 2h, because the carbothermal reduction reaction of $Si_3N_4$ was no longer possible at that time.

• 한국세라믹학회지
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• 제43권9호
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• pp.552-557
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• 2006

A low temperature processing route for fabricating porous SiC ceramics by carbothermal reduction has been demonstrated. Effects of expandable microsphere content, sintering temperature, filler content, and carbon source on microstructure, porosity, compressive strength, cell size, and cell density were investigated in the processing of porous silicon carbide ceramics using expandable microspheres as a pore former. A higher microsphere content led to a higher porosity and a higher cell density. A higher sintering temperature resulted in a decreased porosity because of an enhanced densification. The addition of inert filler increased the porosity, but decreased the cell density. The compressive strength of the porous ceramics decreased with increasing the porosity. Typical compressive strength of porous SiC ceramics with ${\sim}70%$ porosity was ${\sim}13 MPa$.

• 한국주거학회논문집
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• 제22권3호
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• pp.25-33
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• 2011

Recently, concerns about conserving proper size of urban green spaces and accessibility are increasing, regarding it as a solution to diverse urban environmental problems including pollution, ecosystem deterioration, urban climate change. Artificial ground greening such as green roofs is regarded as the only alternative that can conserve green spaces which are impossible to be secured on the ground. However, green roofs are not popularized yet and levels are very low in provincial cities despite of related technology development and support systems of related agencies. Based on the background, this study tries to present a theoretical basis of methods for green roofs, conducting green roof simulations Finally, it aims to offer base data which help establish policy direction for activation of green roof technology. As a result of a simulation for verifying temperature reduction effect, it was possible to affirm effect of a plot that green roofs applied. Especially, it was revealed that a green roof method using ground covers such as mixed planting was the most effective way to reduce temperature. Based on precise analysis of the users, actual study for activation of green roofs should be developed in the future, by presenting a standard model for experiments and obtaining information about examples of green roofs on private houses.