• 반도체디스플레이기술학회지
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• 제7권3호
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• pp.35-39
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• 2008

We study the interaction of acetone molecule $[(CH_3)_2CO]$ on Si(001) surface using density functional theory. An acetone molecule is adsorbed on a Si atom of the Si dimer of the Si(001) surface. The adsorption of the acetone molecule on the Si atom at lower height between the two Si atoms of the dimer is more favorable than that on the Si atoms at upper height. Then we calculate an energy variation of dissociation and four-membered ring structures of the acetone molecule adsorbed on the Si surface. Total energy difference between the two structures is about 0.05 eV, indicating that the two structures are almost equally stable. Energy barrier exists when a hydrogen atom is dissociated and adsorbed on the other Si atom of the dimer, while energy barrier does not exist when the adsorbed acetone molecule changes to four-membered ring structure, except for the rotation of the acetone molecule along z-direction. Therefore, four-membered ring structure is kinetically more favorable than the dissociation structure when the acetone molecule is adsorbed on the Si(001) surface.

• 한국진공학회지
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• 제4권2호
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• pp.142-149
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• 1995

본 연구에서는 새로운 장전자 방출법(DOFEC법)으로 W(210)면의 수소 흡착에 의한 일함수의 변화, heat of desorption에 대하여 연구하였다. 텅스텐(210)면에 수소가 흡착될 때 흡착율에 따라 일함수가 증가하다가 다시 감소하는데 이것은 수소가 처음에는(210)면의 step((100)면)에 흡착되고 dose를 증가시킴에 따라 terrace((110)면)에 흡착되기 때문임을 알았다. 즉, terrace보다 step의 sticking coefficient가 더 크며 zero coverage에서의 그 비는 2.57이며 이는 타 연구 결과와 잘 일치한다. (210)면의 step과 terrace의 수소 흡착에 대한 일함수의 정량적인 변화량 그리고 수소 dose량에 대한 각각의 면에 대한 상대적인 흡착율을 얻었으며, 이 결과는 독립된(110)면 또는 (100)면의 결과와 잘 일치됨을 알았다. 또한 이 결과는 흡착 실험에 있어서 dose량을 흡착률로 환산하는데 사용될 수 있다. 텅스텐(210)면에는 4개의 흡착 site가 존재하며 이 site들 중 $\beta$2과 $\beta$4 state는 second order 탈착 과정을 따르며 $\beta$1과 $\beta$3 state는 first order 탈착과정을 따른다. 따라서 텅스텐(210)면에는 수소가 해리적 흡착을 함과 동시에 비해리적 흡착도 함을 알았으며(210)면의 각 흡착 site를 이에 대응되는 (100)면과 (110)면의 흡착 site와 비교 검토하였다.

• ETRI Journal
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• 제16권3호
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• pp.1-10
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• 1994

Undoped GaAs has been successfully grown by chemical beam epitaxy (CBE) via surface decomposition process using arsine $(AsH_3)$ and trimethylgallium (TMG). Three distinct regions of temperature-dependent growth rates were identified in the range of temperatures from 570 to $690^{\circ}C$. The growth rates were found strongly dependent on the V/III ratio between 5 and 30. The growth rate at low V/III ratio seems to be determined by arsenic produced on the surface, whereas at high V/III ratio it shows dependence on the adsorption of TMG. Hall measurement and photoluminescence (PL) analysis show that the films are all p-type and that carbon impurities are primarily responsible for the background doping. Carbon concentrations have been found to be reduced by two orders of magnitude as compared to those of epilayers grown by CBE which employs TMG and arsenic obtained from precracked $AsH_3$ in a high temperature cell. It was also found that hydrogen atoms dissociated from unprecracked $AsH_3$ play an important role in removing hydrocarbon-containing species resulting in a significant reduction of car-bon impurities.

• Carbon letters
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• 제20권
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• pp.19-25
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• 2016

Activated carbon fiber (ACF) surfaces are modified using an electron beam under different aqueous solutions to improve the NO gas sensitivity of a gas sensor based on ACFs. The oxygen functional group on the ACF surface is changed, resulting in an increase of the number of non-carbonyl (-C-O-C-) groups from 32.5% for pristine ACFs to 39.53% and 41.75% for ACFs treated with hydrogen peroxide and potassium hydroxide solutions, respectively. We discover that the NO gas sensitivity of the gas sensor fabricated using the modified ACFs as an electrode material is increased, although the specific surface area of the ACFs is decreased because of the recovery of their crystal structure. This is attributed to the static electric interaction between NO gas and the non-carbonyl groups introduced onto the ACF surfaces.

• Korean Chemical Engineering Research
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• 제49권2호
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• pp.151-154
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• 2011

수열 합성법과 마이크로파 가열법으로 제조한 TS-1의 촉매 성능 평가를 과산화수소수를 이용한 페놀 수산화 반응 에서 수행하였는데 아세톤과 메탄올 및 물의 세 가지 용매를 사용하여 각 용매에서의 페놀 전환율과 생성물의 선택도 변화를 관찰하였다. 수열 합성법으로 제조한 TS-1과 마이크로파 가열법으로 합성한 TS-1의 XRD, EDS, SEM, BET 흡착/탈착 시험을 통해 촉매의 특성을 비교.분석하였고 마이크로파 가열법으로 합성한 TS-1이 수열 합성으로 제조한 TS-1과 상이한 페놀 전환율과 생성물의 선택도를 보이는 이유에 대해서 설명하였다.

• 대한화학회지
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• 제19권6호
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• pp.423-427
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• 1975

에탄올의 산화반응중의 칼륨을 dope 한 산화아연의 전기전도의 변화를 250${\sim}350^{\circ}C$에서 측정하였다. 산화아연 상에서는 탈수소 및 탈수반응이 일어난다. 300$^{\circ}C$ 이상에서 $CO_2$의 생성과 이에 따르는 전기전도의 증가를 보였는데 이것은 아세트알데히드의 분해에 의해 생긴 CO의 산화반응에 의한 것이 아닌가 본다. 에탄올에 산소를 가하면 아세트알데히드의 생성은 증가하나 에틸렌의 생성에는 변화가 없었다. 이것은 주로 $O^-$로서 화학흡착 되어있는 산소가 에탄올 흡착과 이에 따른 탈수소 과정에 유리하게 작용하고 있는 것이 아닌가 한다.

• 한국분말재료학회지
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• 제14권2호
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• pp.145-149
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• 2007

Nanocrystalline transient aluminas (${\gamma}$-alumina) were coated on core particles (${\gamma}$-alumina) by a carbonate precipitation and thermal-assisted combustion, which is environmentally friend. The ammonium aluminum carbonate hydroxide (AACH) as a precursor for coating of transient aluminas was produced from precipitation reaction of ammonium aluminum sulfate and ammonium hydrogen carbonate. The crystalline size and morphology of the synthetic, AACH, were greatly dependent on pH and temperature. AACH with a size of 5 nm was coated on the core alumina particle at pH 9. whereas rod shape and large agglomerates were coated at pH 8 and 11, respectively. The AACH was tightly bonded coated on the core particle due to formation of surface complexes by the adsorption of carbonates, hydroxyl and ammonia groups on the surface of the core alumina powder. The synthetic precursor successfully converted to amorphous- and ${\gamma}$-alumina phase at low temperature through decomposition of surface complexes and thermal-assisted phase transformation.

• 한국세라믹학회지
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• 제55권5호
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• pp.473-479
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• 2018

Highly toxic gases such as hydrogen sulfide ($H_2S$), carbon dioxide ($CO_2$), and ammonia ($NH_3$) are generated by both nature and human activities and affect human health. In this research, activated carbon combined with $Ca(OH)_2$ and $CaCO_3$ (AC-CO and AC-CC, respectively) were fabricated and applied in absorbing toxic gases from air pollutants. Activated charcoal powder was compressed in the form of pellets and used in the designated conditions. The optimum operating conditions and material properties, such as adsorption capacity, effect of weight ratio of the mixture, and hardness, have been investigated after combining with the calcium derivative. The good performance exhibited in this study suggests that this material is expected to be an effective and economically viable adsorbent for $NH_3$, $CO_2$, and $H_2S$ removal from the air system.

• Bulletin of the Korean Chemical Society
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• 제34권5호
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• pp.1481-1486
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• 2013

Bifunctional Fe-SBA-15-$SO_3H$ mesoporous materials with different Si/Fe molar ratios (3, 5, and 7) have been synthesized via a simple direct hydrothermal method and characterized by XRD, $N_2$-adsorption/desorption, TG/DTG and FT-IR techniques, and used as solid acid catalysts in the esterification of lactic acid with methanol. XRD and $N_2$ sorption characterizations show successful iron doping within the mesoporous channels of SBA-15-$SO_3H$. The FT-IR and TG/DTG characterizations also reveal the presence of iron. With the incorporation of Fe ions into the SBA-15-$SO_3H$, the acid sites substantially increased because of the self-separated acidity of the hydrolysis of $Fe^{3+}$ solutions. However, in the Si/Fe = 3 molar ratio, the catalytic conversion decreased which is caused by the reduced cooperation effect between the acid pairs due to the weakened hydrogen bonds and collapse of the pore structure. This further suggests that the mesoporous structure decreases with the decrease in Si/Fe ratio.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2011년도 춘계학술대회 및 Fine pattern PCB 표면 처리 기술 워크샵
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• pp.47-48
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• 2011

The effect of solution acidity and organic additives, polyethylene glycol (PEG), on the trivalent chromium electroplating was systematically investigated in the view point of solution stability, electroreduction of trivalent chromium ions and characterization of deposition layer. It was found that, the concentration of fraction chromium complexes in the trivalent chromium bath containing formic acid is strongly depended on pH value. PEG molecules were stable in trivalent chromium bath containing formic acid via studies on electrospray ionization mass spectrometry (ESI-MS) and UV-Vis. However, the presence of PEG molecules decreased the reductive current of hydrogen evolution, increasing of current efficiency higher about 10 % compared with solutions without PEG. Moreover, PEG additives developed the nodular morphology during electroreduction of trivalent chromium ions with the increase of solution acidity and enhanced its current efficiency by maintaining the consumption of complexant, formic acid, at a low speed. In this study, the effect of solution acidity was emphasized important, there, it controlled the formation of complexes in the solution, cathodic film (CF) during deposition, and properties of deposited layer. By electrochemical quartz crystal microbalance (EQCM), studies show that chromium electrodeposition occurs via the formation of intermediate complexes and adsorption on the cathode surface, which hinder the penetration of ions from bulk solution to the cathode surface.