• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.511-513
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• 2014

$MoS_2$ monolayer에 Au 원자를 흡착시켰을 때 가장 안정한 위치를 찾아 내기위한 연구를 수행하였다. 이를 위하여 $MoS_2$ $1{\times}1$ unit cell 위의 on-top, bridge, hollow 위치에 Au 원자를 놓고 DFT 기반 제일원리 계산을 통하여 최적화된 구조에서의 에너지를 계산, 비교하였다. 그 결과 S 원자 위에 Au 원자가 흡착 되었을 때 가장 안정한 구조를 이루는 것을 알 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.344-344
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• 2011

W(110)면에 흡착원자인 Al원자의 coverage와 annealing과정에서의 온도를 변화시켜, 여러 조건에서의 Al/W(110)계의 흡착구조를 저에너지 전자회절(LEED)과 이온산란분광법(ISS-TOF)을 이용하여 연구하였다. 여러 결과 중, annealing 온도가 900K인 1.0ML Al/W(110)면은 double domain의 p($1{\times}1$)의 흡착구조로 W(110)면의 center of hollow site에서 $0.55{\AA}$ 벗어난 위치에 흡착되었으며, W(110) 표면원자로부터 Al 원자까지의 높이는 $2.13{\pm}0.15{\AA}$이다. 또한 annealing 온도가 1100K인 0.5ML Al/W(110)면은 double domain의 p($2{\times}1$)의 흡착구조로 W(110)면의 center of bridge site에 흡착되었으며, W(110) 표면원자로부터 Al 원자까지의 높이는 $2.18{\pm}0.15{\AA}$이다.

• Journal of the Korean Vacuum Society
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• v.15 no.4
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• pp.360-366
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• 2006

We have performed density functional theory calculations for the surface structure of O/Pd(100)-p($2{\times}2$), formed by the adsorption of oxygen atoms of 0.25 ML. The oxygen atoms adsorb preferentially at the fourfold hollow site, and the calculated O-Pd bond length is $2,15{\AA}$, The first interlayer spacing ($d_{12}$) of Pd(100) expands by +0.8% due to the oxygen adsorption, which differs from the experimental value of +3.6% reported by a previous LEED study. Assuming that the LEED sample was possibly contaminated by hydrogen atoms, we also examined the effect of hydrogen impurities on the surface structure. Hydrogen atoms adsorbed on O/Pd(100)-p($2{\times}2$) are found to result in large expansions of $d_{12}$ of Pd(100). Our analysis estimates the amount of hydrogen atoms remaining on the LEED sample as -0.3 ML.

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.301-308
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• 1996

The heat of desorption and the work function change induced by nitrogen adsorption on the slepped tungstein surface plants, W(210) and W(310), are measured using the Field Electron Emission Microscope(FEM). The adsoption sites are predicted from the Thermal Desortion Spectra(TDS). The wirk function change of both W(210) and W(310) planes increase as increasing the nitrogen dose and saturates at the nitrogen dose about 5 Langmuir to 0.29 eV and 0.20 eV respectively. We find three adsorption site on each plane for the low dose range. The TDS result shows that the intensity of $\alpha_1$ state on W(310) is much stronger than that of $\alpha_1$ state on W(210), and the direction of nitrogen dipole moment adsorbed on the sites correspond to $\alpha_1$ and $\beta_2$ state on W(210) and W(310) planes are in the opposite direction to that of the equivalent states on W(100) plane. From this observation we can predict the relative atomic position in the z-direction (perpendicular direction to the surface) of nitrogen molecules/atoms adsorbed on these sites.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.92-97
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• 2006

A study of the adsorption site of CO in the Ni(111)$(2\times2)$-O/CO coadsorbed phase over different sample preparation temperatures revealed that the atop site is favoured. The Ni-C spacing is given by $1.77\pm0.01\;{\AA}$. A study of the adsorption site of Co in the Ni(111)$(2\times2)$-O/CO coadsorbed phase over different sample preparation temperatures revealed that the atop site is favoured. The Ni-C spacing is given by $1.77\pm0.01\;{\AA}$. The data from the sample prepared at 265 K showed atop sites, which is well consistent with vibrational spectroscopy, whilst the data from the low temperature preparation appears the mixture of atop and hop $(35\%)$. The occupation of hop hollow sites is probably due to an incorrect pre-coverage of atomic oxygen (different from 0.25ml). Similar observation of site mixture also found in recent high resolution XPS measurements using C 1s and O 1s chemical shifts.

• Journal of the Korean Chemical Society
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• v.38 no.5
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• pp.339-344
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• 1994

The crystal structure of a methanol sorption complex of dehydrated partially Co(II)-exchanged zeolite A, $Co_4Na_4-A{\cdot}6.5CH_3OH$ (a = 12.169(1) $\AA)$, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Pm$\bar3$m at $21(1)^{\circ}C. $Co_4Na_4$-A was dehydrated at $360^{\circ}C\;and\;2{\times}10^{-6}$ torr for 2 days, followed by exposure to about 104 torr of methanol vapor at $22(1)^{\circ}C$ for 1 hr. The structure was refined to final error indices, $R_1$ = 0.061 and $R_2$ = 0.060 with 147 reflections, for which I > $3\sigma(I).$ In this structure, four $Co^{2+}$ ions and 1.5 $Na^+$ ions per unit cell lie at 6-ring positions: the $Na^+$ ions are recessed 0.44 $\AA$ into the sodalite unit and the Co(II) ions extend ca. 0.55 $\AA$ into the large cavity. 2.5 $Na^+$ ions lie in an 8-oxygen ring plane. The 6.5 methanol molecules are sorbed per unit cell. The 6.5 methanol oxygens, all in the large cavity, associate with the 4 $Co^{2+}$ ions and 2.5 $Na^+$ ions.

• Journal of the Korean Chemical Society
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• v.35 no.3
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• pp.226-232
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• 1991

Adsorption and oxidation of polychlorinated phenols by suspended ${\sigma}-MnO_2$ in aqueous solution have been studied. Of the proposed mechanism, adsorption reaction of chlorophenols onto ${\sigma}-MnO_2$(s) depended upon the pH of the solution and the concentration of chlorophenol. Adsorption isotherms showed a reasonably good fit to the Langmuir isotherm. From the pH dependence of adsorption partition coefficient and the linear relationship between octanol-water partition coefficient and adsorption partiton coefficient of chlorophenol, it is estimated that adsorption is dominated by its hydrophobicity. The rate of electron transfer reaction evaluated from the rate of reductive dissolution of ${\sigma}-MnO_2$(s) depended linearly upon the concentration of chlorophenol and the pH of medium. Observed rate constants ($K_0$) of the meta-substituted chlorophenol were lower than that of the ortho-or para-chlorophenol because of resonance effect of chlorophenoxy radical. It is indicated that this radical is produced in the adsorption process and the electron transfer reaction is rate determining.

• Journal of the Mineralogical Society of Korea
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• v.21 no.2
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• pp.117-127
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• 2008

The characteristics of phosphate adsorption-desorption on kaolinite was studied by batch adsorption experiments and detailed adsorbed state of phosphate on kaolinite surface was investigated using ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared) spectroscopy. The phosphorous contents were measured using UV-VIS-IR spectrophotometer with 820 nm wavelength. The adsorbed P was generally increased with increasing pH value in the range of pH 4 to pH 9, however it is not distinct. Moreover the adsorbed P was significantly changed with different initial phosphate concentration. The adsorption isotherms were well fitted with the Langmuir equation, Temkin equation, and Freundlich equation in descending order. The maximum Langmuir adsorption capacity of kaolinite KGa-2 is 232.5 ($204.1{\sim}256.5$) mg/kg and has very higher value than that of kaolinite KGa-1b. Most of adsorbed phosphate on kaolinite were not easily desorbed to aqueous solution, but might fixed on kaolinite surface. However it needs further research about the exact desorption experiment. It was impossible to recognize phosphorous adsorption bands on kaolinite in ATR-FTIR spectrum from kaolinite bands themselves, because the absorption peaks of phosphorous have very similar positions with those of kaolinite, and the intensities of the former were very weak in comparison with those of the latter.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.513-513
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• 2012

핵 융합로의 대면재질(Plasma Facing Material; PFM)은 고온의 플라즈마와 고 에너지의 이온들에 지속적으로 노출 된다. 특히 PFM은 흡착되는 기체 등에 의한 부식과 변형이 발생할 수 있다. 현재 핵 융합로 내부의 PFM으로 고려되고 있는 재질 중 하나인 고순도 탄소타일의 경우 고온의 수소동위원소 플라즈마에 직접적으로 노출되므로 이에 의한 탄소타일에 흡착되는 수소 등의 기체에 대한 정량적인 분석방법이 필요하다. 본 연구는 고순도 탄소타일 등과 같은 플라즈마 대면재료에 흡착되어 있는 물질의 정량적 분석이 가능한 TDA (Thermal Desorption Analyzer)의 개념 설계에 관한 것이다. TDA는 고온 가열($800^{\circ}C$ 이상) 및 시료 장착부 및 초고진공(~10-9 torr) 및 측정부의 두 부분으로 구성 하였다. TDA 설계시 고온 가열 및 시료 장착부는 시료 내부에 흡착되어 있는 기체의 효과적 탈착을 위한 가열 및 시료의 모양에 영향을 받지 않는 장착방법, 시료 장착부의 outgassing rate를 최소화 하는 재질 선정 등을 고려하였으며, 초고진공(~10-9 torr) 및 측정부는 초고진공 유지방법, 터보펌프 배기속도 실측을 위한 구조, 진공측정 ion 게이지, 잔류가스분석기(Residual Gas Analyzer)의 최적위치 설정 등을 고려하여 설계하였다. 개념 설계된 TDA에 대하여 발표하고자 한다.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.349-356
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• 2006

We have investigated adsorption and desorption properties of CO adsorption on silica supported Ru/Ni alloys at various Ru/Ni mole content ratio as well as CO partial pressures using Fourier transform infrared spectrometer (FT-IR). For Ru-$SiO_{2}$ sample, four bands were observed at $2080.0cm^{-1}$, $2021.0{\sim}2030.7cm^{-1}$, $1778.9{\sim}1799.3cm^{-1}$, $1623.8cm^{-1}$ on adsorption and three bands were observed at $2138.7cm^{-1}$, $2069.3cm^{-1}$, $1988.3{\sim}2030.7cm^{-1}$ on vacumn desorption. For Ni-$SiO_{2}$ sample, four bands were observed at $2057.7cm^{-1}$, $2019.1{\sim}2040.3cm^{-1}$, $1862.9{\sim}1868.7cm^{-1}$, $1625.7cm^{-1}$ on adsorption and two bands were observed at $2009.5{\sim}2040.3cm^{-1}$, $1828.4{\sim}1868.7cm^{-1}$ on vacumn desorption. These absorption bands correspond with those of the previous reports approximately. For Ru/Ni(9/1, 8/2, 7/3, 6/4, 5/5; mole content ratio)-$SiO_{2}$ samples, three bands were observed at $2001.8{\sim}2057.7cm^{-1}$, $1812.8{\sim}1926.5cm^{-1}$, $1623.8{\sim}1625.7cm^{-1}$ on adsorption and three bands were observed at $2140.6cm^{-1}$, $2073.1cm^{-1}$, $1969.0{\sim}2057.7cm^{-1}$ on vacumn desorption. The spectrum pattern observed for Ru/Ni-$SiO_{2}$ sample at 9/1 Ru/Ni mole content ratio on CO adsorption and on vacumn desorption is almost like the spectrum pattern observed for Ru-$SiO_{2}$ sample. But the spectrum patterns observed for Ru/Ni-$SiO_{2}$ samples under 8/2 Ru/Ni mole content ratio on CO adsorption and vacumn desorption are almost like the pattern observed for $Ni-SiO_{2}$ sample. It may be suggested surfaces of alloy clusters on the Ru/Ni-$SiO_{2}$ samples contain more Ni components than the mole content ratio of the sample considering the above phenomena. With Ru/Ni-$SiO_{2}$ samples the absorption band shifts may be ascribed to variations of surface concentration, strain variation due to atomic size difference, variation of bonding energy and electronic densities, and changes of surface geometries according to surface concentration variation. Studies for CO adsorption on Ru/Ni alloy cluster surface by LEED and Auger spectroscopy, interation between Ru/Ni alloy cluster and $SiO_{2}$, and MO calculation for the system would be needed to look into the phenomena.