• 한국수소및신에너지학회논문집
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• 제26권4호
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• pp.308-317
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• 2015

To investigate the effect of microstructure on the formation of the desorption peak, the volumetric thermal analysis technique (VTA) was applied to the Mg-13.5 wt% Ni hydride system. The sample made by the HCS (hydriding combustion synthesis) process had two kinds of Mg microstructures. Linear heating was started with various constant heating rates. Only one peak was appeared in the case of the small initial hydrogen wt% (0.83 wt%). Yet, two peaks were appeared with increasing initial hydrogen wt% (1.85 and 3.73 wt%) when only Mg was hydrogenated. The first peak was formed through the evolution of hydrogen from $MgH_2$, made by eutectic Mg. The second peak was formed through the evolution of hydrogen from $MgH_2$, made by primary Mg. Therefore, this result shows that the microstructure also has a considerable effect on forming the desorption peak. We have also derived the hydrogen desorption equations by VTA to get apparent activation energy when the rate-controlling step for the desorption of the hydrided system is the diffusion of hydrogen through the ${\alpha}$ phase and the chemical reaction ${\beta}{\rightarrow}{\alpha}$.

• Bulletin of the Korean Chemical Society
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• 제20권9호
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• pp.1061-1066
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• 1999

The adsorption of CO on W(111) surface in the range of adsorption temperature between 300 K and 1000 K has been studied using AES, LEED, and TDS in an UHV system. After CO saturation at 300 K, four desorption peaks are observed at temperatures (K) of about 400, 850, 1000, and 1100 in thermal desorption spectra, called as α, β1, β2, and β3 state, respectively. The state was attributed to molecular species of CO, which is well known. Because the CO in βstates (especially the β3 state) is still debated as to whether it is dissociative or non-dissociative, the β3 state is mainly discussed. By using the variation method of heating rate in the thermal desorption spectrometry, the desorption energy and pre-exponential factor for the β3 state are evaluated to be 280 kJ/mol and 1.5×10 12 s-1 , respectively. A lateral interaction energy of 5.7 kJ/mol can also be estimated by Bragg-Williams approximation. To interpret the thermal desorption spectra for the β3 state, moreover, those for the model of a first order and a second order desorption are simulated using quasi-chemical approximation. In this study, a model of lying-down CO species is proposed for the β3 state of CO adsorption.

• 한국수소및신에너지학회논문집
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• 제30권1호
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• pp.8-13
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• 2019

In order to apply the Sievert's type automatic apparatus to thermal analysis of hydrogen absorbing materials, the Sievert's type automatic apparatus was modified in my laboratory. In this study, an experiment was conducted to see if hydrogen absorption and desorption reactions are possible under near constant pressure (${\pm}0.05atm$) using this device. The hydrogenation and dehydrogenation of the Mg-H system was investigated. And the program was also modified for the kinetics. It was found that it is possible to measure the hydrogen absorption rate under near constant pressure of Mg by using the modified Sievert's type automatic apparatus at 573 K and 598 K. And using this system, the hydrogen desorption rate of Mg hydride under near constant pressure at 623 K was also measurable. However, since the hydrogen desorption rate of Mg hydride is fast at 648 K, the hydrogen desorption reaction did not proceed within a constant pressure range of $0.15{\pm}0.05atm$.

• 한국산업융합학회 논문집
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• 제5권3호
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• pp.209-212
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• 2002

The change of surface structures for the deposition of Sn, In on clean Si(111) surface is investigated as a function of surface coverage by RHEED system. For tin submonolayer films $7{\times}7$, ${\sqrt{3}}{\times}{\sqrt{3}}$ structures are observed depending on the coverage and substrate temperature. For indium submonolayer films $7{\times}7$, ${\sqrt{3}}{\times}{\sqrt{3}}$, ${\sqrt{31}}{\times}{\sqrt{31}}$, $1{\times}1$ structures are observed. We find that at substrate temperature of $500^{\circ}C$, ${\sqrt{3}}{\times}{\sqrt{3}}$ structure is formed at tin coverages of 0.2~0.4 ML and at indium coverages of 0.1~0.3 ML, respectively. From the desorption process, the desorption energies of Sn, In in ${\sqrt{3}}{\times}{\sqrt{3}}$ structure is observed to he 3.25 eV, 2.66eV, respectively.

• 에너지공학
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• 제28권4호
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• pp.8-12
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• 2019

Thermal amine scrubbing is the most advanced CO₂ capture technique but its largescale application is hindered due to the large heat requirement during solvent regeneration step. The addition of a solid metal oxide catalysts can optimize the CO₂ desorption rate and thus minimize the energy consumption. Herein, we evaluate the solvent regeneration performance of Monoethanolamine (MEA) and Diethanolamine (DEA) solvents without and with two metal oxide catalysts (TiO₂ and V₂O₅) within a temperature range of 40-86℃. The solvent regeneration performance was evaluated in terms of CO₂ desorption rate and overall amount of CO₂ desorbed during the experiments. Both catalysts improved the solvent regeneration performance by desorbing greater amounts of CO₂ with higher CO₂ desorption rates at low temperature. Improvements of 86% and 50% in the CO₂ desorption rate were made by the catalysts for MEA and DEA solvents, respectively. The total amount of the desorbed CO₂ also improved by 17% and 13% from MEA and DEA solvents, respectively. The metal oxide catalyst-aided regeneration of amine solutions can be a new approach to minimize the heat requirement during solvent regeneration and thus can remove a primary shortfall of this technology.

• 청정기술
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• 제20권2호
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• pp.179-188
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• 2014

본 연구에서는 고정탑 반응기(높이 30 cm, 내경 1 cm)에 서로 다른 4종류의 제올라이트(zeolite) 시료를 충전하여, 탈착압력이 $CO_2$ 흡착파과 및 탈착파과 거동에 미치는 영향을 연구하였다. 흡착제로는 상용물질인 제올라이트 3A, 4A, 5A, 13X 펠렛(pellet)을 사용하였다. 연속조작(cyclic operation)실험은 흡착-탈착 순으로 5회 반복하여 실험하였으며, 흡착 및 탈착 시간은 각각 80분이었다. 탈착압력이 연속조작거동에 미치는 영향을 살펴보기 위해 탈착 압력(혹은 재생 압력)을 진공(0 bar)에서 3 bar까지 변경하며 실험을 진행하였다. 흡착압력(3 bar), 온도(293 K), 농도($CO_2:N_2=10:90$vol%)와 유량(400 ccm) 조건은 고정하였다. 파과시간(breakthrough time), 포화시간(saturation time), 재생시간(regeneration time), 흡착량 그리고 탑 내 온도변화 등을 측정하였다. 상기 변수 실험을 통하여 연소 후 $CO_2$ 포집에 적합한 흡착제 및 운전조건을 찾고자 하였다.

• Bulletin of the Korean Chemical Society
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• 제24권6호
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• pp.691-694
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• 2003

We report a quantum wavepacket study on the characteristic bimodal translational energy distribution of photostimulated desorbed Xe from an oxidized silicon (001) surface observed by Watanabe and Matsumoto, Faraday Discuss. 117 (2000) 203. We have simulated the theoretical translational energy distributions based on wavepacket calculations with a sudden transition and averaging model to reproduce the experiment. We discuss the desorption mechanism and suggest a very strong position dependence of the deexcitation processes for Xe/oxidized Si(001).

• 한국산업융합학회 논문집
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• 제6권3호
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• pp.201-205
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• 2003

The effects of adsorption and desorption of alkali-metals on Si(111) surface were investigated by using AES and RHEED-system. The adsorption system is a fundamental interest because of its unique electronic properties such as measurement of work function change, adatom-core level shift. It was found that the growth node of K on Si(111) surface was layer by layer growth and the saturation coverage was 2.0ML at room temperature. Superstructure changes on Si(111) surface according to the alkali-metal thickness and substrate temperatures were accurately defined. By applying the isothermal desorption method, the desorption energies of Li/Si(111) and K/Si(111) surfaces was measured. On Li/Si(111) and K/Si(111) surfaces, the desorption energies were 3.07 eV, 2.19 eV respectively.

• Journal of Electrochemical Science and Technology
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• 제7권3호
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• pp.185-189
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• 2016

The coupled channel method via the Local Reflection (LORE) matrix is employed to investigate the quantum mechanical behavior of the sticking or adsorption and desorption of hydrogen (H) atom on bilayer graphene via the armchair edge. The sticking and desorption probabilities of H are calculated and are plotted against the initial translational energy of H. The sticking probability plot shows a barrierless reaction indicating that hydrogen is easily adsorbed on the armchair edge of graphene. The desorption probability plot, however, shows that desorption of H from the graphene sheets is an activated process with a barrier height of 4.19 eV suggesting that a strong bond exists between the adsorbed H atom and the edge carbon atom. Thus, temperatures higher than the operating temperatures (300 - 1500 K) of conventional fuel cells are necessary to release the adsorbed H atom from the armchair edge of graphene.

• Bulletin of the Korean Chemical Society
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• 제16권2호
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• pp.143-148
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• 1995

Ketene (CH2CO) adsorption on Ag(111) has been studied in ultrahigh vacuum using electron energy loss spectroscopy and temperature programmed desorption. Ketene adsorbs molecularly on Ag(111) at temperatures below 126 K. The coverage increases linearly with exposure until saturation. No multilayer formation and no shift in desorption temperature with coverage were observed, indicating a lack of attractive interaction between adsorbate molecules. The desorption activation energy is estimated to be 7.8 kcal/mol by assuming first order kinetics and a pre-exponential factor of 1013 sec-1. The adsorption geometry of ketene on the surface is determined from the relative intensities of the vibrational energy loss peaks. The CCO axis of CH2CO is found to be almost parallel to (∼4°away from) the surface and the molecular plane is almost perpendicular to the surface (∼3°tilt).