• Journal of Korea Soil Environment Society
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• v.5 no.2
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• pp.87-97
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• 2000

The effects of environmental conditions, initial dissolved oxygen concentrations, pH, and the presence of electron carrier vitamin $B_{12}$, on the reduction rate of Tn by $Fe^0$ was quantitatively analyzed using a batch reactor In all experiments, TNT reduction was best described with a first order reaction and the reduction rate decreased with the increase in the initial DO concentration. However, the specific reaction rate did not decrease linearly with the increase in the initial DO concentration. In the presence of HEPES buffer 0.2 and 2.0 mM(pH 5.7$\pm$0.2), the specific reaction rate increased more than 5.8 times, which showed reduction rate is rather significantly influenced by the pH of the solution. To test the possibility of reaction rate enhancement, well-known electron carrier(or mediator) , vitamin $B_{12}$, has augmented besides $Fe^0$. In the presence of 8.0 $mu\textrm{g}$/L of vitamin $B_{12}$, the specific reaction rate increased as much as 14.6 times. The results indicate that the addition of trace amount of vitamin $B_{12}$ can be a promising rate controlling option for the removal of organics using a $Fe^0$ filled permeable reactive barrier.

• Journal of the Korean Electrochemical Society
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• v.13 no.2
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• pp.132-137
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• 2010

This study is concerned the electrocatalytic generation of oxygen gas at electrochemically deposited manganese oxide electrode in KOH solution. Manganese oxide nanoparticles electrodeposited onto relatively substrate, e.g glassy carbon, Au, Ti electrode. MnOx is electrodeposited in nanorod structure which cover the overall surface of the substrate. The $\gamma$-MnOOH that is kind of manganese oxide species plays a significant role as a catalytic mediator, which promote 4-electron reduction process. Modified electrodes with electrodeposited manganese oxide structures resulted in significant decrease in the anodic polarization compared with the unmodified electrodes in alkaline media.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.357-362
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• 1998

PWR 정지시 일차계통 수화학 제어의 주요대상은 계통표면에 침적된 부식생성물의 주성분인 비화학양론적 니켈(코발트)페라이트로서, 산성-환원 단계에서 용존수소에 의해 Ni$^{\circ}$ (또는 Co$^{\circ}$)로 환원되고 산성-산화 단계에서 용존산소에 의해 Ni$^{2+}$ (또는 CO$^{2+}$)로 산화되어 이온교환기에 의해 제거된다 본 연구에서는, 니켈 및 코발트 산화물의 25~300 $^{\circ}C$ 환원 또는 산화반응 시 표준자유에너지의 변화 및 용존수소 또는 용존산소의 요구농도를 계산하여, 원자로 정지시 일차계통수 용존 기체의 제어조건을 고찰하였다. 산성-환원 단계의 냉각재 온도인 300~82$^{\circ}C$ 범위에서 용존수소가 충분할 경우 열역학적으로 $^{58}$ Co(또는 $^{60}$Co)Fe$_2$O$_4$$\longrightarrow$Co의 역반응이 억제되므로서 노심외 계통부위 침적이 감소될 수 있기 때문에, 용존수소를 온도에 따라 요구농도 곡선 위로 약간 높게 유지하는 것보다 25~50 cc/kg-$H_2O$로 유지하는 방식이 바람직한 반면, 용존산소를 제공하는 과산화수소 농도가) 2.7 ppm일 때 NiFe$_2$O$_4$$\longrightarrow$Ni$_2$O$_4$(+$\alpha$-Fe$_2$O$_3$) 반응이 일어날 수 있기 때문에, 산성-산화 단계에서는 과산화수소의 냉각재 농도를 이보다 낮게 유지하는 것이 바람직하다.

• Resources Recycling
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• v.28 no.3
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• pp.59-67
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• 2019

This study was conducted to fabrication pig iron containing copper and to reduce sulfur content pig iron. Roasting test was conducted for 1 ~ 9 hours at each temperature of $500^{\circ}C$, $700^{\circ}C$, and $900^{\circ}C$. In addition, the effect of oxygen partial pressure with 0.5, 0.8, and 1 atm was carried out for 30 minutes at $900^{\circ}C$. It was found that there is no effect to reduce sulfure in pig iron through roasting and oxygen partial pressures. The addition of CaO with 15 wt.% was found to reduce sulfur content up to 0.001 wt.%. The suitable temperature and reactive time for carbothermic reduction were $1600^{\circ}C$ and 30 minutes which shows the highest recovery rate of iron from the copper slag.

• Journal of the Korean Chemical Society
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• v.37 no.4
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• pp.462-469
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• 1993

The electrocatalytic reduction of dioxygen is investigated by cyclic voltammetry and chronoamperometry at glassy carbon electrode and carbon microelectrode coated with a variety of cobalt phenylporphyrins. The n value obtained at carbon microelectrode is slightly different from that determined at glassy carbon electrode. Dioxygen reduction catalyzed by the monormeric porphyrin Co(II)-TPP mainly occurs through the $2e^-$ reduction pathway resulting in the formation of hydrogen peroxide, electrocatalytic process carries out $4e^-$ reduction pathway of dioxygen to $H_2O$ at the electrodes coated with bis-cobalt phenylporphyrins. The electrocatalytic reduction of dioxygen is irreversible and diffusion controlled.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.843-849
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• 2012

When we use NiO based particle as an oxygen carrier in a chemical looping combustion system, the fuel conversion and the $CO_2$ selectivity decreased with increasing reaction temperature within high temperature range (> $900^{\circ}C$) due to the increment of exhaust CO concentration from reduction reactor. To improve reduction reactivity at high temperature, the applicable metal oxide component was selected by calculation of the equilibrium CO concentration of metal oxide components. After that, feasibility of reduction reactivity improvement at high temperature was checked by using solid mixture of the selected metal oxide particle and NiO based oxygen carrier. The reactivity was measured and investigated using batch type fluidized bed. The solid mixture of $Co_3O_4/CoAl_2O_4$(10%) and OCN706-1100(90%) showed higher fuel conversion, higher $CO_2$ selectivity and lower CO concentration than OCN706-1100(100%) cases. Consequently, we could conclude that improvement of reduction reactivity at high temperature range by adding some $Co_3O_4$ based oxygen carrier was feasible.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.140-144
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• 1996

Trickle bed를 이용하여 고분가 촉매에 의한 용존산소 제거반응을 수행하였다. 고분자 촉매는 폴리스티렌-디비닐 벤젠의 공중합체로 이루어진 담체를 제조하여 백금 용액을 함침시킨 후 수소로 환원하여 제조하였다. trickle bed는 수소 및 산소로 포화되어 있는 물을 향류식으로 접촉할 수 있도록 설계하였다. 이 경우는 액상 실험 장치와 달리 포화기가 없기 때문에 장치는 비교적 단순하였으나 컬럼내에 축적되는 액상의 축적이 중요한 운전변수로 나타났다. trickle bed에서의 용존산소 제거 거동을 semi-empirical relation으로 나타내어 실험치와 비교한 결과 예측된 모델과 매우 잘 일치하는 것으로 나타났다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.86-86
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• 2017

고효율의 에너지 변환 및 친환경적인 이점들을 이유로, 고분자전해질 연료전지(PEMFC)는 차세대 에너지 장치로 이목을 끌어왔다. 반면, 값비싼 백금 촉매의 이용은 연료전지의 상업적 이용에 주요한 결점으로 작용했다. 최근, Zelenay와 연구팀은 폴리아닐린-철-탄소 복합체구조에서 산소환원활성이 백금과 견주어 비슷한 성능을 낼 수 있음을 보고 하였다. Dodelet은 이러한 높은 성능이 전이금속의 영향에 의한 것일 수 있다는 주장을 하였다. 본 연구팀은 지난 연구에서 제일원리전산모사를 통해 니켈, 코발트, 구리등과 같은 전이금속이 질소가 도핑된 탄소 그래핀층에 미치는 거동을 밝혔다. 결론적으로, 금속들은 질소가 도핑된 그래핀의 전자구조를 바꿀 수 있고, 이러한 전자구조의 변화는 산소 환원반응에서 긍정적으로 작용할 수 있음을 확인하였다. 이러한 이론적 연구에 기반하여, 탄소층으로 감싼 금속은 내구성과 활성을 동시에 보유한 향후 전망있는 촉매 물질로 예상되어진다. 특히, 질소가 도핑된 탄소층으로 코팅된 철-코발트 합금은 계산을 통해 산소환원반응에서 우수할 것으로 예측되었다. 본 연구팀은 FeCo@N-C 나노입자를 직접 합성하였고, 이 촉매의 우수한 활성을 전기화학적, 구조적 관점에서 1) 질소의 도핑 효과, 2) 탄소의 두께 효과, 3) 합금효과에 집중하여 분석하였다.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.10a
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• pp.63-67
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• 1997

환원확산법은 저렴한 Nd 산화물을 환원제를 이용하여 환원시키고 환원된 Nd가 Fe, FeB와 확산하여 주상인 Nd$_2$Fe14B가 만들어지는 공정으로 환원제로 사용된 CaO나 미반응 Ca 및 잔존 산소함량을 조절하는데 어려움이 있어 아직까지는 상업되지 못하고 있는 실정이다. 본 연구에서는 환원확산법을 이용하여 Nd-Fe-B계 영구자석에 사용될 미세분말을 제조하고 그 자기적 특성을 관찰하였다.

• Clean Technology
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• v.30 no.1
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• pp.55-61
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• 2024

Efforts are actively underway to address the issues related to the high cost of Pt-based catalysts for oxygen reduction reactions by designing high-performance Pt-based alloys through the control of their nanostructures. In this study, a method was proposed to control the nanostructure of Pt-based alloys, either hollow or core-shell, by adjusting the pH of the solution during the galvanic replacement reaction between the carbon-supported nickel-nickel nitride composite and the Pt ions. The physical characteristics, including the state, quantity, and morphology of the metal particles under different preparation conditions, were evaluated through X-ray diffraction, transmission electron microscopy, and inductively coupled plasma. When the prepared catalysts were employed for the oxygen reduction reaction, they exhibited an improvement in area specific-activity compared to a commercial Pt/C, with a 1.7 and 1.9-fold enhancement for the hollow and core-shell structured catalysts, respectively.