• 한국세라믹학회지
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• 제35권12호
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• pp.1329-1336
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• 1998

A twt -step carbothermal reduction scheme has been employed for the synthesis of SiC whiskers in an Ar or a H2 atmosphere via vapor-solid two-stage and vapor-liquid-solid growth mechanism respectively. It has been shown that the whisker growth proceed through the following reaction mechanism in an Ar at-mosphere : SiO2(S)+C(s)-SiO(v)+CO(v) SiO(v)3CO(v)=SiC(s)whisker+2CO2(v) 2C(s)+2CO2(v)=4CO(v) the third reaction appears to be the rate-controlling reaction since the overall reaction rates are dominated by the carbon which is participated in this reaction. The whisker growth proceeded through the following reaction mechaism in a H2 atmosphere : SiO2(s)+C(s)=SiO(v)+CO(v) 2C(s)+4H2(v)=2CH4(v) SiO(v)+2CH4(v)=SiC(s)whisker+CO(v)+4H2(v) The first reaction appears to be the rate-controlling reaction since the overall reaction rates are enhanced byincreasing the SiO vapor generation rate.

• 한국세라믹학회지
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• 제35권12호
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• pp.1336-1336
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• 1998

2단계 열탄소환원법으로 탄화규소 휘스커를 Ar과 H2분위기에서 기상-고상, 2단계, 기상-액상-고상 성장기구를 통해 각각 합성하였다. Ar분위기에서 탄화규소 휘스커는 다음과 같은 반응기구로 성장하였다. SiO2(S)+C(s)-SiO(v)+CO(v) SiO(v)3CO(v)=SiC(s)whisker+2CO2(v) 2C(s)+2CO2(v)=4CO(v) 이때 전체 반응속도는 세번째 반응에 참여하는 탄소에 의해 지배되었다. 따라서 이 반응이 휘스커 합성의 율속반응으로 판단되었다. 한편 H2 분위기에서 탄화규소 휘스커는 다음과 같은 반응기구로 성장하였다.SiO2(s)+C(s)=SiO(v)+CO(v) 2C(s)+4H2(v)=2CH4(v) SiO(v)+2CH4(v)=SiC(s)whisker+CO(v)+4H2(v) 이때 전체 반응속도는 SiO(v) 기체의발생 속도에 의해 지배되었다. 따라서 첫번째 반응이 휘스커 합성의 율속 반응인 것으로 판단되었다.

• Bulletin of the Korean Chemical Society
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• 제35권11호
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• pp.3313-3318
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• 2014

The reaction mechanism of Lead ions catalyzing complexation reactions between TIPP and metal ions was investigated by researching the kinetics of the formation of metalloporphyrins by UV/Vis-spectra, and verified by exploring the formation of metalloporphyrins catalyzed by acetic acid. Kinetics studies suggested that the fluctuations of reaction rate indicated the formation of metalloporphyrin was step-wise, including the pre-equilibrium step (the coordination of the pyrrolenine nitrogens to $Mn^+$) and the rate-controlling step (the deprotonation of the pyrrole proton). In the pre-equalization step, a sitting-atop (SAT) structure formed first with the complexation between larger radius of $Pb^{2+}$ and TIPP, changed the activation, then $Pb^{2+}$ left with the smaller radius of metal ions attacking from the back of the porphyrin ring center. In the rate-controlling step, two pyrrole protons dissociated to restore a stable structure. This was verified by adding acetic acid at different reaction times.

• 한국수소및신에너지학회논문집
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• 제2권1호
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• pp.29-37
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• 1990

The effect of pressure cycling of $Zr_{0.9}Ti_{0.1}Cr_{0.7}Fe_{1.3}$ on the hydrogenation properties was investigated using the P-C-Isotherm curves and hydrogen absorption rate curves in the isotherm condition. The reversible hydrogen absorption capacity was decreased about 45 % after 3300 cycles. In the case of activated sample, the rate controlling steps of hydriding reaction changed from the surface reaction to the hydrogen diffusion process through hydride phase sequentially as reaction proceeded. After 3300 cycles, the sequential change of rate controlling step was same as activated one. However, the hydrogen absorption rate significantly decreased. It is suggested that the degradation of $Zr_{0.9}Ti_{0.1}Cr_{0.7}Fe_{1.3}$ can be interpreted with the formation of $ZrFe_3$ phase at the particle surface.

• 한국안전학회지
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• 제1권1호
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• pp.27-32
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• 1986

To remove sulfur dioxide from flue gas by the method of metal oxide, copper powder of average diameter $2.4\mu\textrm{m}$and $51\mu\textrm{m}$ were used in a fixed bed reactor over a, temperature range of $300^{\circ}C-500^{\circ}C$. Copper oxide reacts with sulfur dioxide producing cupric sulfate and it can be regenerated from the latter by using hydrogen or methane. Experimental results showed that the reaction rate was increased by the increase of reaction temperature in the range of $300^{\circ}C-422^{\circ}C$ and the removal efficiency of sulfur dioxide was high in case of small size copper particle. However the removal efficiency was decreased at higher temperature due to decomposition of cupric sulfate. The rate controlling step of this reaction was chemical reaction and deactivating catalysts model can be applied to this reaction. The rate constants for this reaction and deactivation are as follows ： k＝8,367exp(-10,298/RT) Kd＝2.23exp(-8,485/RT)

• 한국수소및신에너지학회논문집
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• 제10권1호
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• pp.9-17
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• 1999

기계적인 합금처리된 여러 Mg-Ni 혼합물 중에서 가장 우수한 수소저장 성질을 가지고 있는 Mg-25wt.%Ni 혼합물의 수소화물 형성 및 분해 반응에 대한 반응속도론적 연구를 하였다. 수소화물 형성 및 분해 속도를 측정하여 이론적인 반응 속도식과 비교함으로써 율속 단계를 결정하였다. Mg-25wt.%Ni의 수소화물 형성의 율속단계는 $H_a$ = 4.0 미만의 여러 $H_a$ 범위에서는 입자간 통로 (interparticle channel), 입자의 갈라진 틈(crack) 등을 통한 수소 분자의 이동 단계인 Knudsen 유동과 보통의 기체 확산이고, 4.0 < $H_a{\leq}4.25$ 범위에서는 성장하는 수소화물 층을 통한 수소 원자의 확산으로 생각된다. Mg-25wt.%Ni의 수소화물 분해의 율속 단계는 전 $H_d$ 범위에 걸쳐 수소 분자의 이동 단계인 Knusden 유동과 보통의 기체 확산이다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 창립총회 및 춘계학술발표회
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• pp.52-55
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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 TNT 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.

• 한국세라믹학회지
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• 제35권6호
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• pp.569-574
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• 1998

자체의 반응열에 의해 반응이 자발적으로 진행되는 SHS법을 이용하여 $Ti_3AI$ 금속간 화합물의 생성반응에서의 화염대 두계, 반응속도 그리고 겉보기 활성화에너지에 대하여 고찰하였다. 이 반응에서 화염대 두께는 1.4mm이었고, 반응속도는 $0.4g/\textrm{cm}^2{\cdot}sec$이었다. 또한, 반응물의 상대밀도를 조절하여 얻은 실험 data를 이용하여 구한 반응의 겉보기 활성화에너지는 40kJ/mol이었다.

• 한국대기환경학회지
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• 제10권2호
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• pp.83-89
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• 1994

The reaction of sulfur dioxide with cupric oxide was investigated over a temperature range of 300-50$0^{\circ}C$, and the regenaration reaction was studied using cupric sulfate and hydrogen over a temperature range of 240-35$0^{\circ}C$ in a fixed bed reactor. The experimental results showed that the efficiencies for elimination and regenaration reactions were maximum at 45$0^{\circ}C$ and at 30$0^{\circ}C$ respectively. In both cases the experimental data could be interpreted properly by shrinking unreacted core model while the chemical reaction is rate controlling step. The reaction rate constants were determined to be 24.88 exp(-6724/RT) (cm/min) for elimination reaction, and 0.0165 exp(-2047/RT)(cm/min ) for regeneration reaction.

• 대한금속재료학회지
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• 제47권2호
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• pp.107-113
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• 2009

Molten iron with 2 mass % carbon content was decarbonized at 1823 K~1923 K by bubbling $Ar+O_2$ gas through a submerged nozzle. The reaction rate was significantly influenced by the oxygen partial pressure and the gas flow rate. Little evolution of CO gas was observed in the initial 5 seconds of the oxidation; however, this was followed by a period of high evolution rate of CO gas. The partial pressure of CO gas decreased with further progress of the decarbonization. The overall reaction is decomposed to two elementary reactions: the decarbonization and the dissolution rate of oxygen. The assumptions were made that these reactions are at equilibrium and that the reaction rates are controlled by mass transfer rates within and around the gas bubble. The time variations of carbon and oxygen contents in the melt and the CO partial pressure in the off-gas under various bubbling conditions were well explained by the mathematical model. Based on the present model, it was explained that the decarbonization rate of molten iron was controlled by gas-phase mass transfer at the first stage of reaction, but the rate controlling step was transferred to liquid-phase mass transfer from one third of reaction time.