• 공업화학
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• 제28권3호
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• pp.339-344
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• 2017

다양한 조촉매가 첨가된 $Pt/TiO_2$ 촉매 및 순수 Pt계 촉매의 RWGS 반응에 대한 특성과 성능에 관한 연구를 수행하였다. 지지체 및 활성금속 종류에 의해 RWGS 반응 성능이 크게 영향 받음을 확인하였고, $Pt/TiO_2$ 촉매가 가장 우수한 성능을 보임을 알 수 있었다. $CO_2$ 주입 농도별 실험 및 열역학적 평형 전환율 평가를 통해 $Pt/TiO_2$ 촉매의 성능을 객관적으로 평가할 수 있었고, 상용촉매 대비 우수한 성능을 보임을 관찰하였다. 조촉매로 첨가한 Ca와 Na는 촉매성능을 증진시킬 수 있었으며, XPS 분석을 통해 표면 활성점의 전자밀도가 성능과 밀접한 관련이 있음을 확인하였다.

• 대한화학회지
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• 제30권2호
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• pp.152-158
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• 1986

치환나프톨류(4-Cl-1-naphthol, 6-Br-2-naphthol and $8-NH_2-2-naphthol)$의 해리상수를 온도(25 ~ 40${\circ}C$)와 압력(1~2000bar)을 변화시키면서 분광학적 방법으로 측정했다. 이들의 해리상수는 치환기가 들어가므로서 모두 감소했다. 이것은 치환기의 I-효과로서 설명이 가능했으며 또 온도와 압력이 증가하면 해리상수도 증가하였다. 이들 해리상수로부터 반응의 열역학적 성질을 계산하여 반응의 성질을 알아보았다.

• 대한화학회지
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• 제25권3호
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• pp.152-159
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• 1981

p-니트로벤질클로라이드의 가용매분해 반응속도를 50 와 $60{\circ}C$에서 압력을 1∼1200bar로 변화시키고 에탄올-물 혼합용매의 조성이 0.0∼0.5인 에탄올 몰분율의 범위내에서 전기전도도법으로 측정하였다. 반응의 속도상수로부터 활성화 파라미터, ${\Delta}V_\0^{\neq},\ {\Delta}H^{\neq}$ 및 ${\Delta}S^{\neq}$를 구한결과 ${\Delta}V_\0^{\neq}$는 혼합용매의 몰분율이 0.3부근에서 extremum을 나타내었고 ${\Delta}H^{\neq}$ 와 ${\Delta}S^{\neq}$는 0.1 부근에서 extremum을 나타내었다. 이러한 현상은 용매구조의 변화에 의하여 검토되었고 ${\Delta}V^{\neq}$의 압력의존성도 고찰하였다. ${\Delta}H^{\neq}$와 ${\Delta}S^{\neq}$이 압력의존성은 그 부호에 있어서 고전열역학계에 대한 Maxwell관계의 식과 일치함을 보여주었다.

• 대한화학회지
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• 제31권5호
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• pp.375-381
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• 1987

trans-[Cr(tn)$_2Cl_2]^+$ 및 trans-[Cr(en)(tn)Cl$_2]^+$ 이온의 수화반응속도를 분광광도법을 이용하여 온도의 압력을 변화시켜 가면서 측정하였다. 활성화부피는 모두 음의 값을 가졌으며. 이들 착이온의 경우 그 범위는 -1.7 ∼ -2.9cm$^3$mol$^{-1}$이었다. 활성화엔트로피 및 활성화압축류 계수는 작은 음의 값을 가졌다. 이러한 열역학적 결과로부터 이들 착이온의 수화반응은 교환회합 메카니즘으로 진행됨을 추정할 수 있다. 한편 각중첩모형 체제내에서 가상적 중간체의 총 안정화에너지를 고려하여 반응경로와 전이상태의 구조에 대한 정보를 얻을 수 있는데 추정한 메카니즘과 실험적으로 관찰된 결과가 일치함을 알았다.

• Bulletin of the Korean Chemical Society
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• 제25권5호
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• pp.639-646
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• 2004

Metal treated activated carbons are prepared using various metals. Adsorption behaviors, morphologies, as well as antibacterial effects of metal treated samples are compared before and after solvent washing. Adsorption isotherms are used to characterize the porous structure of metal treated activated carbons before and after the solvent washing with acetone or ethyl alcohol. From these data, it is noticed that the changes in physicochemical properties of metal treated activated carbons depend on the solvents employed. Similar results are observed from BET data obtained from nitrogen adsorption isotherms. From scanning electron microscopy (SEM) studies, the changes in shape and size of metal particles are observed after the samples are washed with solvents. These changes result in different blocking effects, which, in turn, affect the adsorption behavior of metal treated activated carbons. X-ray diffraction (XRD) patterns of the samples treated with different metals are different each other. High intense sharp peaks attributed to metals are observed from silver treated samples, while the peaks are not observed from copper treated samples. To compare thermodynamic behavior of metal treated activated carbons washed with different type of solvents, differential scanning calorimetric (DSC) analysis is carried out. The analysis shows similar endothermic curves for all of the samples. Finally, antibacterial effects of metal treated activated carbon against Escherichia coli are discussed. Comparing the effects among the metals employed, highest effects are obtained from Cd, while lowest effects are obtained from Cu. Antibacterial activity becomes higher with the increase of the amount of metals treated, Optimum concentrations of metals to treat activated carbons, obtained from a shake flask test, are known to be 0.4, 0.1, and 0.6 moles for Ag, Cd, and Cu, respectively.

• 대기
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• 제19권2호
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• pp.127-143
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• 2009

This study investigates characteristics of wintertime simulation conducted by METRI AGCM utilizing new radiation parameterization scheme. New radiation scheme is based on the method of Chou et al., and is utilized in the METRI AGCM recently. In order to analyze characteristics of seasonal simulation in boreal winter, hindcast dataset from 1979 to 2005 is produced in two experiments - control run (CTRL) and new model's run (RADI). Also, changes in performance skill and predictability due to implementation of new radiation scheme are examined. In the wintertime simulation, the RADI experiment tends to reduce warm bias in the upper troposphere probably due to intensification of longwave radiative cooling over the whole troposphere. The radiative cooling effect is related to weakening of longitudinal temperature gradient, leading to weaker tropospheric jet in the upper troposphere. In addition, changes in vertical thermodynamic structure have an influence on reduction of tropical precipitation. Moreover, the RADI case is less sensitive to variation of tropical sea surface temperature than the CTRL case, even though the RADI case simulates the mean climate pattern well. It implies that the RADI run does not have significant improvement in seasonal prediction point of view.

• 대한화학회지
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• 제33권4호
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• pp.343-349
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• 1989

${\omega}$-아미노산인 ${\beta}$-alanine과 ${\gamma}$-aminobutyric acid의 해리상수를 전도도법을 이용하여 온도($20{\sim}40^{\circ}C$)와 압력($1{\sim}2500$ bar)을 변화시키면서 측정하였다. 각각 아미노산의 두 가지 해리상수는 온도가 증가하면 증가하지만 압력이 증가하면 $K_1$은 증가하지만 $K_2$는 감소하였다. 해리상수를 이용하여 여러 가지 열역학적 성질들을 계산하고 이들로부터 해리반응의 특성을 알아보았다. ${\omega}$-아미노산의 해리상수를 해리기와 치환기간의 거리의 상관관계로 알아보았다. 반응특성을 알아보기 위해 Hammett 법칙을 적용하여 반응의 치환기 상수와 압력에 따른 반응상수를 계산하였다. ${\omega}$-아미노산의 특성을 치환기 효과로 설명하고 반응유형을 반응상수로서 알아보았다.

• 한국재료학회지
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• 제25권12호
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• pp.659-665
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• 2015

The self-propagating high temperature synthesis approach was applied to synthesize amorphous boron nano-powders in argon atmospheres. For this purpose, we investigated the characteristics of a thermally induced combustion wave in the $B_2O_3+{\alpha}Mg$ system(${\alpha}=1.0-8.0$) in an argon atmospheres. In this study, the exothermic nature of the $B_2O_3-Mg$ reaction was investigated using thermodynamic calculations. Experimental study was conducted based on the calculation data and the SHS products consisting of crystalline boron and other compounds were obtained starting with a different initial molar ratio of Mg. It was found that the $B_2O_3$ and Mg reaction system produced a high combustion temperature with a rapid combustion reaction. In order to regulate the combustion reaction, NaCl, $Na_2B_4O_7$ and $H_3BO_3$ additives were investigated as diluents. In an experimental study, it was found that all diluents effectively stabilized the reaction regime. The final product of the $B_2O_3+{\alpha}Mg$ system with 0.5 mole $Na_2B_4O_7$ was identified to be amorphous boron nano-powders(< 100 nm).

• 한국주조공학회지
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• 제33권5호
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• pp.215-225
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• 2013

The alloys required for fossil power plants are altered from stainless steel that has been used below $600^{\circ}C$ to Ni-based alloys that can operate at $700^{\circ}C$ for Hyper Super Critical (HSC) steam turbine. The IN740 alloy (Special Metals Co. USA) is proposed for improved rupture strength and corrosion resistance at high temperature. However, previous studies with experiments and simulations on stable phases at about $700^{\circ}C$ indicated the formation of the eta phase with the wasting of a gamma prime phase, which is the most important reinforced phase in precipitation hardened Ni alloys, and this resulted in the formation of precipitation free zones to decrease the strength. On the basis of thermodynamic calculation, the new Ni-based superalloy named LESS 1 (Low Eta Sigma Superalloy) was designed in this study to improve the strengthening effect and structure stability by depressing the formation of topologically close packed phases, especially sigma and eta phases at high temperature. A thermal exposure test was carried out to determine the microstructure stability of LESS 1 in comparison with IN740 at $800^{\circ}C$ for 300 hrs. The experimental results show that a needle-shaped eta phase was formed in the grin boundary and it grew to intragrain, and a precipitation free zone was also observed in IN740, but these defects were entirely controlled in LESS 1.

• 한국분말재료학회지
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• 제24권1호
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• pp.41-45
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• 2017

The effects of the heat treatment temperature and of the atmosphere on the dehydrogenation and hydrogen reduction of ball-milled $TiH_2-WO_3$ powder mixtures are investigated for the synthesis of Ti-W powders with controlled microstructure. Homogeneously mixed powders with refined $TiH_2$ particles are successfully prepared by ball milling for 24h. X-ray diffraction (XRD) analyses show that the powder mixture heat-treated in Ar atmosphere is composed of Ti, $Ti_2O$, and W phases, regardless of the heat treatment temperature. However, XRD results for the powder mixture, heat-treated at $600^{\circ}C$ in a hydrogen atmosphere, show $TiH_2$ and TiH peaks as well as reaction phase peaks of Ti oxides and W, while the powder mixture heat-treated at $900^{\circ}C$ exhibits only XRD peaks attributed to Ti oxides and W. The formation behavior of the reaction phases that are dependent on the heat treatment temperature and on the atmosphere is explained by thermodynamic considerations for the dehydrogenation reaction of $TiH_2$, the hydrogen reduction of $WO_3$ and the partial oxidation of dehydrogenated Ti.